Synthesis and coordination chemistry of silver(I), gold(I) and gold(III) complexes with picoline-functionalized benzimidazolin-2-ylidene ligands
-
Mareike C. Jahnke
Abstract
The reactions of N-alkyl-N′-picolyl-benzimidazolium bromides or N,N′-dipicolyl-benzimidazolium bromide with silver oxide yielded the silver dicarbene complexes of the type [Ag(NHC)2][AgBr2] 1–4 (NHC = picoline-functionalized benzimidazolin-2-ylidene). The silver complexes 1–4 have been used in carbene transfer reactions to yield the gold(I) complexes of the type [AuCl(NHC)] 5–8 in good yields. A halide exchange at the metal center of complexes 5–8 with lithium bromide yielded the gold bromide complexes 9–12. Finally, the oxidation of the gold(I) centers in complexes 9–12 with elemental bromine gave the gold(III) complexes of the type [AuBr3(NHC)] 13–16. Molecular structures of selected Au(I) and Au(III) complexes have been determined by X-ray diffraction studies.
1 Introduction
N-heterocyclic carbenes (NHCs) are well established ligands in organometallic chemistry [1], [2], [3], [4]. Most of the known NHCs have been obtained from five-membered dinitrogenheterocycles such as imidazole, imidazoline or benzimidazole [1], [2], [3], [4]. However, some extended analogs derived from six- [5], [6], [7], [8], [9], [10], seven- [7], [8], [9], [10], or even eight-membered dinitrogenheterocycles [11, 12] have also been prepared. Due to the strong σ-donor properties of the NHC ligands and, when compared to their phosphine counterparts, to the superior stability of the NHC complexes against air, moisture, heat and oxidizing conditions, NHC complexes have found multiple applications as catalysts for chemical transformations [13], [14], [15], as building blocks for supramolecular architectures [16], [17], [18], in metallodrugs [19, 20], and for the generation of OLED devices [21, 22].
Access to NHC complexes is conveniently provided by several protocols. The most common method is the reaction of a free NHC or its enetetraamine dimer with a coordinatively unsaturated metal precursor. The free NHC is normally generated in situ by deprotonation of a suitable azolium salt [1], [2], [3], [4]. Less common synthetic procedures for NHC complexes are the template-controlled cyclization of functionalized isocyanide ligands [23, 24] or, more recently developed, the oxidative addition of azoles or azolium cations to low-valent metal centers [25], [26], [27]. A rather facile procedure for the preparation of NHC complexes has been described by Lin and Wang in 1998 [28], who reacted azolium salts with Ag2O followed by transmetallation, i. e. a transfer of the NHC ligand from the silver complex to various transition metals [28]. Currently, the Ag2O method constitutes a standard route for the preparation of NHC complexes [29], [30], [31].
Recently, gold NHC complexes have become a focus of research [31], [32], [33], due to their potential applications as pharmaceuticals [20, 34], [35], [36] or as homogeneous catalysts for several transformations [37], [38], [39]. In combination with poly-NHC ligands, gold(I) ions are also known to form supramolecular assemblies featuring molecular rectangles [40] or cylinders-like structures [41, 42].
We have previously reported the synthesis of palladium and platinum complexes bearing picoline-functionalized benzimidazolin-2-ylidene ligands [43, 44]. Related work on gold complexes with pyridine-functionalized imidazolin-2-ylidene ligands [45], [46], [47] initiated our interest in further modifications of such complexes. We became particularly interested in the exchange of the co-ligands in complexes of the type [AuX(NHC)] (X = halogen) and in the oxidation of their gold(I) atoms with elemental bromine. A related study involving the oxidation of the gold atom in gold(I) NHC complexes using PhICl2 as oxidizing agent has recently been published [48, 49].
Here we report the synthesis of a series of silver(I) NHC complexes bearing picoline-functionalized benzimidazolin-2-ylidene ligands. These compounds were utilized as agents for the transfer of the NHC ligand to gold(I). The obtained gold(I) carbene complexes of the type [AuCl(NHC)] were subsequently transformed via a halide exchange reaction to complexes of the type [AuBr(NHC)], followed by an oxidation with elemental bromine to give square planar gold(III) complexes featuring a picoline-functionalized benzimidazolin-2-ylidene ligand. Molecular structures were obtained for selected silver(I), gold(I) and gold(III) carbene complexes bearing picoline-functionalized NHC ligands.
2 Results and discussion
2.1 Silver complexes with picoline-functionalized benzimidazolin-2-ylidene ligands
The preparation of several picoline-functionalized benzimidazolium salts has been described [43]. These salts were reacted with silver oxide in dichloromethane under exclusion of light (Scheme 1) following the Ag2O method of Wang and Lin [28] to give the silver NHC complexes 1–4 as colorless compounds in yields of 74–84%. The preparation and analytical data for the silver complex 3 have been previously reported [44]. Complexes 1–4 are readily soluble in dichloromethane and DMSO, but they are insoluble in protic solvents.
Synthesis of the silver dicarbene complexes 1–4.
As expected, the 1H NMR spectra of complexes 1–4 do not exhibit the characteristic downfield resonance for the NCHN proton anymore, which was detected for the parent benzimidazolium salts at δ = 10.11–11.50 ppm [43]. This indicates the deprotonation of the benzimidazolium salts. The 13C{1H} NMR spectra of complexes 1–4 exhibit the characteristic resonance for the NCN carbene carbon atom in the narrow range of δ = 190.0–191.3 ppm. These values fall in the typical range for the chemical shift of the carbene carbon atoms observed for [Ag(NHC)2]+ complexes (NHC = benzimidazolin-2-ylidene) [50, 51]. A very similar chemical shift for the carbene carbon atom (δ = 190.9 ppm) was also observed for the mononuclear silver complex bearing a dipicolyl-substituted benzimidazolin-2-ylidene and a chloride ligand [52]. Positive ion MALDI mass spectrometry showed the strongest peaks for complexes of the type [Ag(NHC)2]+ (NHC = benzimidazolin-2-ylidene).
Single crystals suitable for X-ray diffraction studies were obtained by slow evaporation of the dichloromethane solvent from solutions of 1 and 2. Surprisingly, both molecular structures 1a and 2a (Figures 1 and 2) differ from the structures depicted in Scheme 1 assigned on the basis of mass spectrometric and NMR spectroscopic data.
Molecular structure of complex 1a in the crystal. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (°): Ag⋯Cl 2.8066(10), Ag–C1 2.134(3), N1–C1 1.362(4), N1–C1 1.353(4); C1*–Ag–C1 153.20(15), Cl–Ag–Cl 103.40(8), N1–C1–N2 105.6(2).
Molecular structure of complex 2a (top) and the intermolecular interactions between the molecules in the crystal (bottom). Displacement ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (°): Ag–Br 2.6387(5), Ag–Br* 2.8951(5), Ag–N3* 2.617(2), Ag–C1 2.144(3), N1–C1 1.363(4), N2–C1 1.356(3); Br–Ag–Br* 97.824(12), Br–Ag–C1 143.03(7), Br–Ag–N3* 87.86(5), Br*–Ag–N3* 92.31(6), Ag–Br–Ag* 82.176(13), N3*–Ag–C1 114.57(9), N1–C1–N2 104.6(2).
In the case of 1a, the structure analysis revealed the formation of a mononuclear silver dicarbene cation residing on a crystallographic twofold axis along with one chloride anion instead of the expected salt [Ag(NHC)2][AgBr2]. However, this observation is not completely surprising, since related halide exchange reactions have been observed for silver carbene complexes in solvents such as dichloromethane or 1,2-dichloroethane in the presence of silver cations [29, 53]. The rather long Ag⋯Cl separation of 2.8066(10) Å indicates an only weak interaction between the silver and the chlorine atoms, similar to a previously reported Ag⋯Cl distance of 2.981(1) Å in a complex where a chlorido ligand bridges three [Ag(NHC)2]+ units [54]. The Ag–CNHC bond length in 1a measures 2.134(3) Å and thus falls in the typical range observed for Ag–CNHC bond lengths for [Ag(NHC)2]+ complex cations (NHC = benzimidazolin-2-ylidene) [28, 29]. The deprotonation of the benzimidazolium salt and the subsequent coordination of the NHC leads to a reduction of the N1–C1–N2 bond angle (105.6(2)°) compared to the corresponding angle found in a picoline-substituted benzimidazolium salt (110.4(2)°) [43].
Contrary to the expected nearly linear ligand arrangement of the NHC donors for a dicarbene silver complex of the type [Ag(NHC)2]+ the CNHC–Ag–CNHC bond angle in 1a measures 153.20(15)° caused by the influence of the chlorido ligand. A similar distortion has been reported for a related dicarbene silver complex with an additional bromido ligand enforcing an CNHC–Ag–CNHC bond angle of 157.04(14)° [55]. An even smaller CNHC–Ag–CNHC bond angle (152.6(3)°) was observed for the disilver complexes of a macrocyclic tetracarbene ligand [56], where steric constraints of the macrocycle cause the observed distortion.
The X-ray diffraction analysis of crystals obtained from a dichloromethane solution of compound 2 revealed the formation of the dinuclear silver dicarbene complex 2a residing on a crystallographic inversion center (Figure 2, top). This complex represents the dinuclear structural isomer of the expected complex 2 depicted in Scheme 1. In dinuclear 2a, each silver atom is coordinated by one carbene ligand and two bromido ligands bridging the two silver atoms. This type of rearrangement has been described previously [28, 29], [30], [31, 57] and a mechanism has been proposed [58] based on the lability of the Ag–CNHC bond. The proposed rearrangement process for complex 2 → 2a is depicted in Scheme 2. The similarity of comparable NMR data of 1–4 indicates that the rearrangement to give 2a (and 1a) occurs upon crystallization, while the mononuclear complexes 1–4 are the dominant species in solution.
Proposed mechanism for the rearrangement 2 to 2a.
The Ag–CNHC bond length in 2a has been determined as 2.144(3) Å and compares well to the Ag–CNHC separation found in similar bromido-bridged dinuclear disilver NHC complexes (2.131(5) Å) [57] and is also close to the value found in 1a (2.134(3) Å). The two bridging Ag–Br bonds measure 2.6387(5) Å for Ag–Br and 2.8951(5) Å for Ag–Br*. The crystal structure revealed the formation of intermolecular Ag–Npicoline contacts between the dinuclear silver complexes leading to indefinite polymeric chains (Figure 2, bottom).
The formation of polymeric chains has previously been reported for silver carbene complex bearing picoline-functionalized imidazolin-2-ylidene ligands [59]. The N1–C1–N2 bond angle of 104.6(2)° in 2a is comparable to the N1–C2–N2 angle found in 1a (105.6(2)°). The four-coordinate silver atoms features a large Br–Ag–C1 angle (143.03(7)°) and three smaller ones (Br–Ag–Br* 97.824(12)°, Br–Ag–N3* 87.86(5)°, Br*–Ag–N3* 92.31(6)°).
2.2 Synthesis of gold NHC complexes with picoline-functionalized benzimidazolin-2-ylidene ligands
NHC ligand transfer from the silver(I) complexes to [AuCl(SMe2)] yielded gold(I) complexes 5–8 bearing the picoline-functionalized benzimidazolin-2-ylidene ligands (Scheme 3). The gold complexes 5–8 were obtained as colorless solids in yields of 97–98%. Although compound 8 has already been described [52], it is still included here since it was used for further reactions in this study.
Synthesis of gold(I) NHC complexes 5–8 by NHC transfer from their silver precursors.
13C{1H} NMR spectroscopy revealed CNHC resonances in a narrow range between δ = 178.3 and 179.3 ppm, well within the range reported for CNHC atoms of benzimidazolin-2-ylidene ligands coordinated to gold (δ = 177.4–179.2 ppm) [50, 52]. Thus the transfer of the NHC ligand from silver(I) to gold(I) causes an up-field shift of the respective CNHC resonance by about 11 ppm (δ(CNHC) for 1–4 ≈ 190 ppm).
Crystals suitable for X-ray diffraction studies of the gold(I) complexes 5–8 were obtained upon slow diffusion of diethyl ether or pentane into chloroform solutions of the complexes. Interestingly, complex 6 crystallized from a chloroform-diethyl ether solution as the salt [H-6]Cl·CHCl3 featuring a complex cation [H-6]+ with a protonated picoline nitrogen atom and a chloride counter anion. 1H NMR spectroscopy did not indicate protonation of the picoline nitrogen atom in 6. Therefore it must be assumed that the N-protonation of complex 6 occurred during crystallization with acid or water obtained from the CHCl3–Et2O solvent mixture used for crystallization. This type of N-protonation is in principle also possible for complexes 5 and 7–8 but was only observed for 6, apparently due to the specific impurities in the solvent mixture used for crystallization of this specific complex.
The molecular structures of complexes 5–8 are depicted in Figure 3. Selected bond lengths and angles are summarized in Table 1. The molecular structure of another polymorph of complex 8 has already been reported, which crystallizes in a different space group (triclinic
Molecular structures of complexes 5–8 in the crystal. C–H hydrogen atoms, counterions and solvent molecules have been omitted for clarity.
Selected bond lengths (Å) and angles (°) for gold complexes 5–8.
| Parameter | 5 | [H-6]Cl·CHCl3 | 7 | 8 |
|---|---|---|---|---|
| Au–Cl | 2.2719(12) | 2.2943(8) | 2.2840(14) | 2.3037(7) |
| Au–C1 | 1.985(4) | 1.973(3) | 1.988(5) | 1.977(3) |
| N1–C1 | 1.345(5) | 1.361(4) | 1.352(6) | 1.356(4) |
| N2–C1 | 1.341(5) | 1.350(4) | 1.337(7) | 1.354(4) |
| Cl–Au–C1 | 179.52(11) | 177.12(10) | 178.30(15) | 176.31(7) |
| N1–C1–N2 | 107.7(4) | 106.1(3) | 107.4(5) | 106.8(2) |
All four gold complexes feature the expected, almost linear coordination geometry at the gold atoms (angles Cl–Au–CNHC 176.31(7)–179.52(11)°). The Au–CNHC (1.973(3)–1.988(5) Å) and the Au–Cl bond lengths (2.2719(12)–2.3037(7) Å) fall in the reported range for monocarbene gold(I) complexes of the type [AuCl(NHC)] (NHC = benzimidazolin-2-ylidene) [50, 52, 60]. The protonation status of the picoline nitrogen atom (protonated in cation [H-6]+ and non-protonated in the remaining [AuCl(NHC)] complexes) has no significant influence on the bond parameters at the gold atom. No intermolecular Au⋯Au interactions [61] have been observed in the crystal structures of 5–7, while a weak aurophilic interaction (Au⋯Au 3.3578(2) Å) between the molecules was observed in the crystal structure of 8.
We have described the oxidation of gold(I) NHC complexes of type [AuBr(NHC)] to their gold(III) analogs of type [AuBr3(NHC)] using bromine as the oxidation agent [62]. These complexes bear N,N′-dialkylated benzimidazolin-2-ylidene ligands, which were not affected by the oxidation reaction. We now became interested to learn if the picoline-functionalized benzimidazolin-2-ylidene ligands would also be inert towards oxidation with bromine, since a recent report on the bromine-oxidation of gold(I) complexes bearing N-allyl substituted benzothiazolin-2-ylidene ligands demonstrated an attack of the bromine oxidation agent at the allyl group with formation of a cyclometallated reaction product [63].
In order to avoid halogen scrambling in the bromine oxidation step, the chlorido ligands in complexes 5–8 had to be substituted for bromido ligands. Similar to the halogen exchange in gold(I) complexes with the N,N′-dialkylated benzimidazolin-2-ylidene ligands [62], the chlorido ligands in complexes 5–8 were substituted for bromido ligands by stirring the complexes with a 10-fold excess of lithium bromide in acetone. This procedure yielded the gold(I) bromido complexes 9–12 (Scheme 4).
Synthesis of gold(I) bromido complexes 9–12.
Complexes 9–12 were obtained in yields of 80–93%. The halogen exchange did not produce significant changes in the NMR spectra of the products. Only a slight downfield shift of ≈ 3 ppm for the resonance of the CNHC carbon atom from δ = 178.3–179.3 ppm (for 5–8) to δ = 180.7–182.4 ppm (for 9–12) was observed. As an example, complex 12 was crystallized by slow diffusion of diethyl ether into a saturated solution of the complex and its molecular structure was determined by X-ray diffraction (Figure 4).
Molecular structure of complex 12 in the crystal. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (°): Au–Br 2.4039(7), Au–C1 2.004(4), N1–C1 1.342(3); Br–Au–C1 180, N1–C1–N1* 108.1(4).
Complex 12 resides on a crystallographic twofold axis. This leads to a perfectly linear coordination geometry at the gold atom. The halogen exchange from 8 to 12 leads to slightly elongated bonds to the gold atom from 2.3037(7) to 2.4039(7) Å for the Au–X bond and from 1.977(3) to 2.004(4) Å for the Au–C bond.
Finally, elemental bromine was added at T = −78 °C to dichloromethane solutions of 9–12 to give the gold(III) complexes of the type [AuBr3(NHC)] 13–16 (Scheme 5). In accord with previous reports on gold(I) complexes bearing NHC ligands with N,N′-alkyl substituents [62, 64], [65], [66], the oxidation reaction produced no by-products and gave the gold(III) complexes in good (13–15, 90%) to moderate (16, 60%) yields.
Oxidation of gold(I) bromide 9–12 to gold(III) tribromide complexes 13–16.
The 13C{1H} NMR spectra of the gold(III) complexes exhibit a significant high-field shift of the CNHC resonances (Table 2). The comparison of the CNHC chemical shifts in Table 2 indicates an influence of both the type of halogenido ligand present and of the oxidation state of the gold centre. While the halide exchange leads only to a small downfield shift of the CNHC resonance of ≈3 ppm, a significant highfield shift of ≈30 ppm was observed upon oxidation from gold(I) to gold(III). Contrary to a previous study, reporting only small differences for the chemical shifts of the CNHC resonances in gold(III) complexes compared to the NCN resonances in the parent imidazolium salts (Δδ = 0.9–2.3 ppm) [65], we observed a more significant difference for the same parameters (Δδ ≈ 6–8 ppm) in complexes 13–16 (δ = 148.8–150.8 ppm) and their benzimidazolium salts (δ = 143.1–143.8 ppm) [43].
Chemical shifts (δ in ppm) of the CNHC resonances of gold(I) and gold(III) complexes.
| Complex | R = Et | R = Pr | R = Bu | R = –CH2–pyr |
|---|---|---|---|---|
| [AuICl(NHC)] | 178.3 | 178.5 | 178.5 | 179.3 |
| [AuIBr(NHC)] | 180.7 | 181.8 | 181.5 | 182.4 |
| [AuIIIBr3(NHC)] | 150.0 | 150.8 | 148.8 | 149.8 |
Two examples of the gold(III) complexes (13 and 15) were crystallized from dichloromethane solutions. This procedure yielded, similarly to complex 6, the salts [H-13]Br·CH2Cl2 and [H-15]Br, composed of a complex cation bearing an NHC protonated at the picoline substituent and a bromide anion. As in the case of compound 6, we believe that the protonation of the picoline group in these complexes occurs during crystallization with acid or water from the dichloromethane solvent used for crystallization. The molecular structures of the complex cations [H-13]+ and [H-15]+ are depicted in Figure 5.
![Figure 5:
Molecular structures of complex cations [H-13]+ (left) and [H-15]+ (right) in [H-13]Br·CH2Cl2 and [H-15]Br. Displacement ellipsoids are drawn at the 50% probability level. C–H Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (°) in [H-13]+ (values for [H-15]+ are given in square brackets […]): Au–Br1 2.4337(4) [2.4299(6)], Au–Br2 2.4151(4) [2.4221(6)], Au–Br3 2.4099(4) [2.4170(6)], Au–C1 2.010(3) [2.014(5)], N1–C1 1.343(4) [1.346(6)], N2–C1 1.338(4) [1.343(6)]; Br1–Au–Br2 92.406(13) [90.90(2)], Br1–Au–Br3 91.335(12) [91.05(2)], Br1–Au–C1 178.67(9) [174.97(15)], Br2–Au–Br3 176.228(13) [174.64(3)], Br2–Au–C1 86.48(9) [88.92(14)], Br3–Au–C1 89.79(9) [89.57(14)], N1–C1–N2 108.6(3) [108.1(4)].](/document/doi/10.1515/znb-2021-0087/asset/graphic/j_znb-2021-0087_fig_005.jpg)
Molecular structures of complex cations [H-13]+ (left) and [H-15]+ (right) in [H-13]Br·CH2Cl2 and [H-15]Br. Displacement ellipsoids are drawn at the 50% probability level. C–H Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (°) in [H-13]+ (values for [H-15]+ are given in square brackets […]): Au–Br1 2.4337(4) [2.4299(6)], Au–Br2 2.4151(4) [2.4221(6)], Au–Br3 2.4099(4) [2.4170(6)], Au–C1 2.010(3) [2.014(5)], N1–C1 1.343(4) [1.346(6)], N2–C1 1.338(4) [1.343(6)]; Br1–Au–Br2 92.406(13) [90.90(2)], Br1–Au–Br3 91.335(12) [91.05(2)], Br1–Au–C1 178.67(9) [174.97(15)], Br2–Au–Br3 176.228(13) [174.64(3)], Br2–Au–C1 86.48(9) [88.92(14)], Br3–Au–C1 89.79(9) [89.57(14)], N1–C1–N2 108.6(3) [108.1(4)].
Both complex cations exhibit an almost perfect square-planar coordination geometry. The Au–CNHC bond lengths in [H-13]+ and [H-15]+ measure 2.010(3) Å and 2.014(5) Å, respectively, which is in good agreement with the values previously observed for gold(III) complexes bearing N,N′-dialkylated benzimidazolin-2-ylidene ligands (Au–CNHC = 2.003(4)–2.009(4) Å) [62, 64]. Interestingly, the oxidation of the gold(I) complexes to the gold(III) derivatives does not influence the Au–CNHC bond length as can be seen from a comparison of this parameter in gold(I) complex 12 (2.004(4) Å) and the complex cations [H-13]+ and [H-15]+ (2.010(3) and 2.014(5) Å). As expected, the Au–Br bond lengths in [H-13]+ and [H-15]+ are significantly different with the longer values observed for the Au–Br bonds in trans-positions to the NHC donor (2.4337(4) and 2.4299(6) Å), while the other Au–Br bonds are significantly shorter (range 2.4099(4)–2.4221(6) Å). The N1–C1–N2 bond angles (108.6(3)° and 108.1(4)°) are remarkably large for coordinated benzimidazolin-2-ylidenes, where normally values around 104° are observed [1]. The expansion of the N1–C1–N2 angles can be attributed to the high oxidation state of the gold(III) atoms causing an enhanced electron donation from the NHC to the metal centre.
3 Conclusion
Silver complexes of the type [Ag(NHC)2][AgBr2] (1–4) have been prepared from N-picoline-N′-alkylbenzimidazolium bromides and Ag2O. The silver complexes were used as carbene transfer agents for the preparation of gold(I) complexes of the type [AuCl(NHC)] (5–8). Halogen exchange with LiBr yielded complexes [AuBr(NHC)] (9–12). Complexes 9–12 were oxidized with elemental bromine to give the square-planar gold(III) complexes [AuBr3(NHC)] (13–16). The oxidation reaction did not affect the picoline-functionalized NHC ligands but protonation of the picoline nitrogen atoms was observed under the conditions employed for the crystallization of the complexes. The oxidation of gold(I) to gold(III) leads to a significant upfield shift (≈30 ppm) of the CNHC resonances. A comparison of the Au–CNHC bond lengths in gold(I) and gold(III) complexes has indicated that this parameter is not affected by the oxidation AuI → AuIII. However, the N1–C1–N2 angles within the benzimidazolin-2-ylidene ligands are significantly enlarged to ≈108° in the gold(III) complexes.
4 Experimental section
4.1 General remarks
All manipulations were carried out in purified solvents using Schlenk techniques. NMR spectra were recorded on Bruker AC 200, Bruker AVANCE I 400 or Bruker AVANCE III 400 spectrometers. Chemical shifts (δ) are expressed in ppm using the residual protonated solvent signal as internal standard. Coupling constants are expressed in Hertz. MALDI mass spectra were measured on a Reflex IV MALDI TOF instrument (Bruker Daltonics, Bremen). HR Mass spectra were measured on an Orbitrap LTQ XL (Thermo Fisher Scientific) and EI mass spectra were recorded on a Finnigan MAT95 instrument. The picoline-functionalized benzimidazolium salts [43] and the silver complex 3 [44] were prepared following the published procedures. Silver oxide, [AuCl(SMe2)], lithium bromide and bromine were purchased from Fisher Scientific or Sigma-Aldrich.
4.2 General procedure for the synthesis of the silver(I) complexes 1–2 and 4
One of the picoline-functionalized benzimidazolium salts [43] (1.0 mmol) and an excess of silver oxide (1.1 mmol, 0.255 g) were suspended in dichloromethane (60 mL). The reaction mixture was stirred under exclusion of light for 12 h at ambient temperature. Subsequently, the suspension was filtered through Celite and the filtrate was brought to dryness in vacuo. The solid residue was dissolved in dichloromethane (5 mL) and the solution was added dropwise under stirring to diethyl ether (200 mL). The formed precipitate was collected by filtration and dried in vacuo.
4.2.1 Analytical data for [bis(N-ethyl-N′-picolylbenzimidazolin-2-ylidene)silver] [dibromoargentate] (1)
Yield: 82% (0.351 g, 0.41 mmol). – 1H NMR (200 MHz, DMSO-d 6, ppm): δ = 8.50 (d, 3 J = 4.7 Hz, 2H, pyridine-H), 7.89–7.79 (m, 6H, Ar–H), 7.49–7.40 (m, 4H, Ar–H, pyridine-H), 7.38–7.29 (m, 4H, pyridine-H), 5.85 (br s, 4H, NCH2-pyridine), 4.56 (q, 3 J = 7.2 Hz, 4H, NCH2CH3), 1.46 (t, 3 J = 7.2 Hz, 6H, NCH2CH3). – 13C{1H} NMR (50.3 MHz, DMSO-d 6, ppm): δ = 190.0 (NCN), 155.2, 149.2, 137.0 (pyridine-C), 133.4, 133.1 (Ar–C), 123.6, 123.4 (pyridine-C), 122.9, 121.9, 112.1, 111.5 (Ar–C), 53.6 (NCH2-pyridine), 50.9 (NCH2CH3), 14.1 (NCH2CH3). – MS ((+)-MALDI): m/z = 583, 581 [1–AgBr2]+.
4.2.2 Analytical data for [bis(N-propyl-N′-picolylbenzimidazolin-2-ylidene)silver] [dibromoargentate] (2)
Yield: 84% (0.370 g, 0.42 mmol). – 1H NMR (200 MHz, DMSO-d 6, ppm): δ = 8.49 (d, 3 J = 4.7 Hz, 2H, pyridine-H), 7.89–7.72 (m, 6H, Ar–H), 7.47–7.39 (m, 4H, Ar–H, pyridine-H), 7.36–7.27 (m, 4H, pyridine-H), 5.87 (br s, 4H, NCH2-pyridine), 4.49 (t, 3 J = 7.2 Hz, 4H, NCH2CH2CH3), 1.95–1.84 (m, 4H, NCH2CH2CH3), 0.88 (t, 3 J = 7.2 Hz, 6H, NCH2CH2CH3). – 13C{1H} NMR (50.3 MHz, DMSO-d 6, ppm): δ = 190.1 (NCN), 155.3, 149.4, 137.2 (pyridine-C), 133.5, 133.2 (Ar–C), 123.9, 123.8 (pyridine-C), 123.1, 122.0, 112.2, 112.0 (Ar–C), 53.2 (NCH2-pyridine), 50.0 (NCH2CH2CH3), 23.2 (NCH2CH2CH3), 11.0 (NCH2CH2CH3). – MS ((+)-MALDI): m/z = 611, 609 [2–AgBr2]+.
4.2.3 Analytical data for [bis-(N,N′-dipicolylbenzimidazolin-2-ylidene)silver] [dibromoargentate] (4)
Yield: 74% (0.366 g, 0.37 mmol). – 1H NMR (200 MHz, DMSO-d 6, ppm): δ = 8.44 (d, 3 J = 4.5 Hz, 4H, pyridine-H), 7.82–7.67 (m, 8H, Ar–H), 7.45–7.34 (m, 8H, pyridine-H), 7.32–7.24 (m, 4H, pyridine–H), 5.86 (s, 8H, NCH2-pyridine). – 13C{1H} NMR (50.3 MHz, DMSO-d 6, ppm): δ = 191.3 (NCN), 155.3, 149.5, 137.3 (pyridine-C), 133.7 (Ar–C), 124.0, 123.2 (pyridine-C), 122.2, 112.4 (Ar–C), 53.4 (NCH2-pyridine). – MS ((+)-MALDI): m/z = 709, 707 [4–AgBr2]+.
4.3 General procedure for the synthesis of the gold(I) complexes 5–8
One equivalent of one of the silver-dicarbene complexes 1–4 (0.15 mmol) and two equivalents of the complex [AuCl(SMe2)] (0.3 mmol, 0.088 g) were dissolved in dichloromethane (50 mL) under exclusion of light. The reaction mixture was stirred for 12 h at ambient temperature. The mixture was then filtered through Celite and the solvent was removed in vacuo. The colorless residue was dissolved in dichloromethane (2 mL) and this solution was added dropwise into diethyl ether (50 mL). The formed white precipitate was collected by filtration and dried in vacuo.
4.3.1 Analytical data for [(N-ethyl-N′-picolylbenzimidazolin-2-ylidene)gold chloride] (5)
Yield: 97% (0.135 g, 0.29 mmol). – 1H NMR (400.0 MHz, CDCl3, ppm): δ = 8.58 (d, 3 J = 4.5 Hz, 1H, pyridine-H), 7.69 (td, 3 J = 7.7 Hz, 4 J = 1.8 Hz, 1H, Ar–H), 7.62 (d, 3 J = 7.7 Hz, 1H, Ar–H), 7.50–7.47 (m, 2H, Ar–H), 7.44–7.34 (m, 2H, pyridine-H), 7.29–7.24 (m, 1H, pyridine-H), 5.84 (s, 2H, NCH2-pyridine), 4.58 (q, 3 J = 7.3 Hz, 2H, NCH2CH3), 1.57 (t, 3 J = 7.3 Hz, 3H, NCH2CH3). – 13C{1H} NMR (100.6 MHz, CDCl3, ppm): δ = 178.3 (NCN), 154.3, 149.2, 137.8 (pyridine-C), 133.4, 132.8 (Ar–C), 124.73, 124.70 (pyridine-C), 123.6, 122.6, 112.9, 111.2 (Ar–C), 54.2 (NCH2-pyridine), 44.1 (NCH2CH3), 15.5 (NCH2CH3). – MS ((+)-EI): m/z = 469 [5]+. – HRMS ((+)-ESI): m/z = 470.0712 (calcd. 470.0698 for C15H16N3AuCl, [5 + H]+), 434.0942 (calcd. 434.0932 for C15H15N3Au, [5–Cl]+).
4.3.2 Analytical data for [(N-propyl-N′-picolylbenzimidazolin-2-ylidene)gold chloride] (6)
Yield: 97% (0.142 g, 0.29 mmol). – 1H NMR (400.0 MHz, CDCl3, ppm): δ = 8.55 (d, 3 J = 4.8 Hz, 1H, pyridine-H), 7.65 (td, 3 J = 7.7 Hz, 4 J = 1.7 Hz, 1H, Ar–H), 7.57 (d, 3 J = 7.7 Hz, 1H, Ar–H), 7.47 (d, 3 J = 7.7 Hz, 1H, Ar–H), 7.43–7.31 (m, 3H, Ar–H, pyridine-H), 7.25–7.21 (m, 1H, pyridine-H), 5.81 (s, 2H, NCH2-pyridine), 4.47 (t, 3 J = 7.4 Hz, 2H, NCH2CH2CH3), 2.01 (sext, 3 J = 7.4 Hz, 2H, NCH2CH2CH3), 1.02 (t, 3 J = 7.4 Hz, 3H, NCH2CH2CH3). – 13C{1H} NMR (100.6 MHz, CDCl3, ppm): δ = 178.5 (NCN), 154.4, 149.4, 137.4 (pyridine-C), 133.3, 133.2 (Ar–C), 124.63, 124.60 (pyridine-C), 123.4, 122.3, 112.8, 111.3 (Ar–C), 54.4 (NCH2-pyridine), 50.5 (NCH2CH2CH3), 23.3 (NCH2CH2CH3), 11.4 (NCH2CH2CH3). – MS ((+)-EI): m/z = 483 [6]+. – HRMS ((+)-ESI): m/z = 484.0848 (calcd. 484.0855 for C16H18N3AuCl, [6 + H]+), 448.1080 (calcd. 448.1088 for C16H17N3Au, [6–Cl]+).
4.3.3 Analytical data for [(N-butyl-N′-picolylbenzimidazolin-2-ylidene)gold chloride] (7)
Yield: 98% (0.147 g, 0.295 mmol). – 1H NMR (400.0 MHz, CDCl3, ppm): δ = 8.57–8.53 (m, 1H, pyridine-H), 7.64 (dt, 3 J = 7.7 Hz, 4 J = 1.7 Hz, 1H, Ar–H), 7.57 (d, 3 J = 7.7 Hz, 1H, Ar–H), 7.46 (d, 3 J = 7.7 Hz, 1H, Ar–H), 7.43–7.31 (m, 3H, Ar–H, pyridine-H), 7.23 (dd, 3 J = 6.7 Hz, 3 J = 5.0 Hz, 1H, pyridine-H), 5.80 (s, 2H, NCH2-pyridine), 4.50 (t, 3 J = 7.3 Hz, 2H, NCH2CH2CH2CH3), 1.99–1.88 (m, 2H, NCH2CH2CH2CH3), 1.50–1.38 (m, 2H, NCH2CH2CH2CH3), 0.97 (t, 3 J = 7.4 Hz, 3H, NCH2CH2CH2CH3). – 13C{1H} NMR (100.6 MHz, CDCl3, ppm): δ = 178.5 (NCN), 154.4, 149.3, 137.4 (pyridine-C), 133.3, 133.1 (Ar–C), 124.63, 124.59 (pyridine-C), 123.4, 122.4, 112.8, 111.3 (Ar–C), 54.4 (NCH2-pyridine), 48.8 (NCH2CH2CH2CH3), 32.0 (NCH2CH2CH2CH3), 20.1 (NCH2CH2CH2CH3), 13.7 (NCH2CH2CH2CH3). – MS ((+)-EI): m/z = 497 [7]+. – HRMS ((+)-ESI): m/z = 498.1004 (calcd. 498.1011 for C17H20N3AuCl, [7 + H]+), 462.1237 (calcd. 462.1245 for C17H19N3Au, [7–Cl]+).
4.3.4 Analytical data for [(N,N′-dipicolylbenzimidazolin-2-ylidene)gold chloride] (8)
Yield: 97% (0.153 g, 0.29 mmol). – 1H NMR (400.0 MHz, CDCl3, ppm): δ = 8.59–8.55 (m, 2H, pyridine-H), 7.68 (dt, 3 J = 7.7 Hz, 4 J = 1.8 Hz, 2H, Ar–H), 7.58 (dd, 3 J = 6.1 Hz, 3 J = 3.1 Hz, 2H, pyridine-H), 7.47 (d, 3 J = 7.7 Hz, 2H, Ar–H), 7.33 (dd, 3 J = 6.1 Hz, 3 J = 3.1 Hz, 2H, pyridine-H), 7.28–7.23 (m, 2H, pyridine-H), 5.86 (s, 4H, NCH2-pyridine). – 13C{1H} NMR (100.6 MHz, CDCl3, ppm): δ = 179.3 (NCN), 154.2, 149.4, 137.6 (pyridine-C), 133.4 (Ar–C), 124.9, 123.5 (pyridine-C), 122.5, 112.6 (Ar–C), 54.4 (NCH2-pyridine). – MS ((+)-EI): m/z = 532 [8]+, 497 [8–Cl]+. – HRMS ((+)-ESI): m/z = 533.0811 (calcd. 533.0807 for C19H17N4AuCl, [8 + H]+), 497.1043 (calcd. 497.1040 for C19H16N4Au, [8–Cl]+).
4.4 General procedure for the synthesis of gold(I) complexes 9–12
A sample of one of the complexes 5–8 (0.15 mmol) was dissolved in acetone (10 mL). To this was added an excess of lithium bromide (1.5 mmol, 0.130 g) and the resulting suspension was stirred for 24 h. The solvent was removed in vacuo and the residue was extracted with dichloromethane. The extract was filtered through Celite® and the solvent was removed in vacuo to give the bromide complexes as pale yellow powders.
4.4.1 Analytical data for [(N-ethyl-N′-picolylbenzimidazolin-2-ylidene)gold bromide] (9)
Yield: 93% (0.071 g, 0.14 mmol). – 1H NMR (400.0 MHz, CD2Cl2-DMSO-d 6, ppm): δ = 8.51–8.48 (m, 1H, pyridine-H), 7.67 (td, 3 J = 7.7 Hz, 4 J = 1.8 Hz, 1H, Ar–H), 7.60 (d, 3 J = 8.0 Hz, 1H, Ar–H), 7.53 (d, 3 J = 8.0 Hz, 1H, Ar–H), 7.44–7.38 (m, 1H, Ar–H), 7.37–7.32 (m, 2H, pyridine-H), 7.23 (dd, 3 J = 6.8 Hz, 3 J = 5.0 Hz, 1H, pyridine-H), 5.78 (s, 2H, NCH2-pyridine), 4.55 (q, 3 J = 7.3 Hz, 2H, NCH2CH3), 1.51 (t, 3 J = 7.3 Hz, 3H, NCH2CH3). – 13C{1H} NMR (100.6 MHz, CD2Cl2-DMSO-d 6, ppm): δ = 180.7 (NCN), 154.2, 149.0, 136.6 (pyridine-C), 132.8, 132.1 (Ar–C), 124.04, 124.01 (pyridine-C), 122.7, 121.5, 112.1, 111.1 (Ar–C), 53.5 (NCH2-pyridine), 43.3 (NCH2CH3), 14.8 (NCH2CH3). – MS ((+)-EI): m/z = 515, 513 [9]+, 434 [9–Br]+.
4.4.2 Analytical data for [(N-propyl-N′-picolylbenzimidazolin-2-ylidene)gold bromide] (10)
Yield: 93% (0.075 g, 0.14 mmol). – 1H NMR (400.0 MHz, CDCl3, ppm): δ = 8.58 (d, 3 J = 4.8 Hz, 1H, pyridine-H), 7.71 (td, 3 J = 7.7 Hz, 4 J = 1.7 Hz, 1H, Ar–H), 7.65–7.61 (m, 1H, Ar–H), 7.51–7.45 (m, 2H, Ar–H), 7.44–7.34 (m, 2H, pyridine-H), 7.29 (dd, 3 J = 7.0 Hz, 3 J = 5.2 Hz, 1H, pyridine-H), 5.87 (s, 2H, NCH2-pyridine), 4.49 (t, 3 J = 7.3 Hz, 2H, NCH2CH2CH3), 2.08–1.97 (m, 2H, NCH2CH2CH3), 1.04 (t, 3 J = 7.4 Hz, 3H, NCH2CH2CH3). – 13C{1H} NMR (100.6 MHz, CDCl3, ppm): δ = 181.8 (NCN), 154.2, 148.9, 138.1 (pyridine-C), 133.24, 133.17 (Ar–C), 124.7, 123.7 (pyridine-C), 123.7, 122.7, 112.8, 111.4 (Ar–C), 53.9 (NCH2-pyridine), 50.4 (NCH2CH2CH3), 23.3 (NCH2CH2CH3), 11.4 (NCH2CH2CH3). – MS ((+)-EI): m/z = 529, 527 [10]+.
4.4.3 Analytical data for [(N-butyl-N′-picolylbenzimidazolin-2-ylidene)gold bromide] (11)
Yield: 93% (0.076 g, 0.14 mmol). – 1H NMR (400.0 MHz, CDCl3, ppm): δ = 8.52 (br s, 1H, pyridine-H), 7.61 (t, 3 J = 7.9 Hz, 1H, Ar–H), 7.52 (d, 3 J = 7.9 Hz, 1H, Ar–H), 7.44 (d, 3 J = 7.9 Hz, 1H, Ar–H), 7.39–7.28 (m, 3H, Ar–H, pyridine-H), 7.22–7.17 (m, 1H, pyridine-H), 5.77 (s, 2H, NCH2-pyridine), 4.47 (t, 3 J = 7.3 Hz, 2H, NCH2CH2CH2CH3), 1.94–1.85 (m, 2H, NCH2CH2CH2CH3), 1.45–1.37 (m, 2H, NCH2CH2CH2CH3), 0.92 (t, 3 J = 7.3 Hz, 3H, NCH2CH2CH2CH3). – 13C{1H} NMR (100.6 MHz, CDCl3, ppm): δ = 181.5 (NCN), 154.3, 149.3, 137.4 (pyridine-C), 133.1, 133.0 (Ar–C), 124.6, 124.5 (pyridine-C), 123.4, 122.2, 112.6, 111.3 (Ar–C), 54.1 (NCH2-pyridine), 48.6 (NCH2CH2CH2CH3), 32.1 (NCH2CH2CH2CH3), 19.9 (NCH2CH2CH2CH3), 13.6 (NCH2CH2CH2CH3). – MS ((+)-EI): m/z = 543, 541 [11]+.
4.4.4 Analytical data for [(N,N′-dipicolylbenzimidazolin-2-ylidene)gold bromide] (12)
Yield: 80% (0.072 g, 0.12 mmol). – 1H NMR (400.0 MHz, CDCl3, ppm): δ = 8.60–8.54 (m, 2H, pyridine-H), 7.71–7.63 (m, 2H, pyridine-H), 7.59–7.53 (m, 2H, Ar–H), 7.45 (d, 3 J = 7.8 Hz, 2H, Ar–H), 7.36–7.30 (m, 2H, pyridine-H), 7.24–7.20 (m, 2H, pyridine-H), 5.86 (s, 4H, NCH2-pyridine). – 13C{1H} NMR (100.6 MHz, CDCl3, ppm): δ = 182.4 (NCN), 154.5, 149.6, 137.6 (pyridine-C), 133.4 (Ar–C), 124.9, 123.6 (pyridine-C), 122.5, 112.7 (Ar–C), 54.3 (NCH2-pyridine). – MS ((+)-EI): m/z = 578, 576 [12]+, 497 [12–Br]+.
4.5 General procedure for the synthesis of gold(III) complexes 13–16
A sample of one of the gold complexes 9–12 (0.1 mmol) was dissolved in dichloromethane (10 mL). The solution was cooled to −78 °C and three drops of elemental bromine were added. The reaction mixture was then stirred for 3 h at −78 °C. Subsequently, the solvent and unreacted bromine were removed in vacuo. The orange residue was dissolved in dichloromethane (5 mL) and the solvent was removed in vacuo to remove residual bromine. This procedure was repeated twice and the resulting orange residue was dissolved in dichloromethane (3 mL). This solution was added dropwise into diethyl ether (50 mL). The formed orange precipitate was collected by filtration and dried in vacuo.
4.5.1 Analytical data for [(N-ethyl-N′-picolylbenzimidazolin-2-ylidene)gold(III) tribromide] (13)
Yield: 90% (0.059 g, 0.09 mmol). – 1H NMR (400.0 MHz, CD2Cl2, ppm): δ = 8.68 (br s, 1H, pyridine-H), 7.93–7.87 (m, 1H, Ar–H), 7.77–7.72 (m, 1H, Ar–H), 7.70–7.62 (m, 2H, Ar–H), 7.60–7.46 (m, 3H, pyridine-H), 6.00 (s, 2H, NCH2-pyridine), 4.65 (q, 3 J = 7.3 Hz, 2H, NCH2CH3), 1.64 (t, 3 J = 7.3 Hz, 3H, NCH2CH3). – 13C{1H} NMR (100.6 MHz, CD2Cl2, ppm): δ = 151.5, (pyridine-C), 150.0 (NCN), 148.1, 139.1 (pyridine-C), 134.5, 133.7, 126.0 (Ar–C), 125.9 (Ar–C and pyridine-C), 125.5 (pyridine-C), 113.2, 112.1 (Ar–C), 52.4 (NCH2-pyridine), 44.3 (NCH2CH3), 14.1 (NCH2CH3). – MS ((+)-MALDI): m/z = 674 [H-13]+, 594 [13–Br]+.
4.5.2 Analytical data for [(N-propyl-N′-picolylbenzimidazolin-2-ylidene)gold(III) tribromide] (14)
Yield: 90% (0.062 g, 0.09 mmol). – 1H NMR (400.0 MHz, CDCl3, ppm): δ = 8.74 (br s, 1H, pyridine-H), 7.98–7.92 (m, 1H, Ar–H), 7.84–7.79 (m, 1H, Ar–H), 7.75–7.70 (m, 1H, Ar–H), 7.64–7.58 (m, 1H, Ar–H), 7.57–7.47 (m, 3H, pyridine-H), 6.06 (s, 2H, NCH2-pyridine), 4.52 (t, 3 J = 7.6 Hz, 2H, NCH2CH2CH3), 2.21–2.10 (m, 2H, NCH2CH2CH3), 1.10 (t, 3 J = 7.3 Hz, 3H, NCH2CH2CH3). – 13C{1H} NMR (100.6 MHz, CDCl3, ppm): δ = 151.4 (pyridine-C), 150.8 (NCN), 147.3, 140.9 (pyridine-C), 134.2, 133.9, 126.2, 126.0 (Ar–C), 125.9, 125.2 (pyridine-C), 113.4, 112.1 (Ar–C), 51.9 (NCH2-pyridine), 50.7 (NCH2CH2CH3), 22.6 (NCH2CH2CH3), 11.4 (NCH2CH2CH3). – MS ((+)-EI): m/z = 529, 527 [14–2Br]+. – MS ((+)-MALDI): m/z = 530, 528 [H-14−2Br]+.
4.5.3 Analytical data for [(N-butyl-N′-picolylbenzimidazolin-2-ylidene)gold(III) tribromide] (15)
Yield: 90% (0.062 g, 0.09 mmol). – 1H NMR (400.0 MHz, DMSO-d 6, ppm): δ = 8.55 (d, 3J = 4.7 Hz, 1H, pyridine-H), 8.07–8.00 (m, 2H, Ar–H), 7.93–7.89 (m, 1H, Ar–H), 7.60–7.56 (m, 2H, Ar–H, pyridine-H), 7.55–7.50 (m, 1H, pyridine-H), 7.46–7.41 (m, 1H, pyridine-H), 6.00 (s, 2H, NCH2-pyridine), 4.63–4.58 (m, 2H, NCH2CH2CH2CH3), 2.03–1.93 (m, 2H, NCH2CH2CH2CH3), 1.44–1.33 (m, 2H, NCH2CH2CH2CH3), 0.92 (t, 3 J = 7.3 Hz, 3H, NCH2CH2CH2CH3). – 13C{1H} NMR (100.6 MHz, DMSO-d 6, ppm): δ = 152.4 (pyridine-C), 148.8 (NCN), 147.9, 138.3 (pyridine-C), 134.1, 133.2, 125.7, 125.6 (Ar–Ar–C), 124.0, 123.3 (pyridine-C), 113.3, 112.9 (Ar–C), 51.8 (NCH2-pyridine), 47.9 (NCH2CH2CH2CH3), 30.7 (NCH2CH2CH2CH3), 19.1 (NCH2CH2CH2CH3), 13.4 (NCH2CH2CH2CH3). – MS ((+)-EI): m/z = 621 [H-15–Br]+.
4.5.4 Analytical data for [(N,N′-dipicolylbenzimidazolin-2-ylidene)gold(III) tribromide] (16)
Yield: 60% (0.042 g, 0.06 mmol). – 1H NMR (400.0 MHz, DMSO-d 6, ppm): δ = 8.52–8.48 (m, 2H, pyridine-H), 8.02–7.98 (m, 2H, Ar–H), 7.88–7.82 (m, 2H, pyridine-H), 7.59–7.54 (m, 2H, Ar–H), 7.51–7.48 (m, 2H, pyridine-H), 7.41–7.36 (m, 2H, pyridine-H), 5.97 (s, 4H, NCH2-pyridine). – 13C{1H} NMR (100.6 MHz, DMSO-d 6, ppm): δ = 152.9 (pyridine-C), 149.8 (NCN), 149.4, 137.9 (pyridine-C), 134.1, 125.8 (Ar–C), 123.9, 123.3 (pyridine-C), 113.3 (Ar–C), 52.5 (NCH2-pyridine).
4.6 X-ray structure determinations
X-ray diffraction data for compound 1a data was obtained with a Bruker AXS APEX diffractometer equipped a rotating anode using CuKα radiation (λ = 1.54184 Å) at T = 100(2) K. Diffraction data for all other compounds were obtained on a AXS 2000 CCD diffractometer equipped with a rotating anode using MoKα radiation (λ = 0.71073 Å). Data collections were performed at T = 153(2) K over the full sphere. Structure solutions were found with the Shelxt [67] package using Direct Methods and were refined with Shelxl [68] against all |F 2| using first isotropic and later anisotropic displacement parameters (for exceptions see description of the individual molecular structures). Hydrogen atoms were added to the structure models on calculated positions if not noted otherwise.
4.6.1 Selected crystallographic details for 1a
Formula C30H30N6AgCl, M = 617.92 g mol−1, colorless prism, 0.29 × 0.21 × 0.15 mm3, monoclinic, space group C2/c, Z = 4, a = 11.47200(10), b = 12.62770(10), c = 18.4668(2) Å, β = 102.5190(10)°, V = 2611.59(4) Å3, ρ calcd = 1.57 g cm−1, μ = 7.4 mm−1, ω and φ scans, 7399 measured intensities (9.8 ≤ 2θ ≤ 143.2°), semiempirical absorption correction (0.223 ≤ T ≤ 0.404), 2391 independent intensities (R int = 0.0597) and 2323 observed intensities (I ≥ 2 σ(I)), refinement of 174 parameters against |F 2| of all independent intensities with hydrogen atoms on calculated positions. R = 0.0387, R w = 0.1037, R all = 0.0394, R w,all = 0.1045. The asymmetric unit contains ½ formula unit of 1a linked to the other half by a crystallographic twofold axis.
4.6.2 Selected crystallographic details for 2a
Formula C32H34N6Ag2Br2, M = 878.20 g mol−1, colorless prism, 0.22 × 0.15 × 0.06 mm3, monoclinic, space group P21/c, Z = 2, a = 9.0685(14), b = 8.4086(12), c = 20.089(3) Å, β = 95.488(3)°, V = 1524.9(4) Å3, ρ calcd = 1.91 g cm−1, μ = 3.9 mm−1, ω and φ scans, 17,320 measured intensities (4.1 ≤ 2θ ≤ 60.1°), semiempirical absorption correction (0.478 ≤ T ≤ 0.798), 4436 independent intensities (R int = 0.0512) and 3573 observed intensities (I ≥ 2 σ(I)), refinement of 191 parameters against |F 2| of all independent intensities with hydrogen atoms on calculated positions. R = 0.0347, R w = 0.0728, R all = 0.0492, R w,all = 0.0773. The asymmetric unit contains ½ formula unit of 2a linked to the other half by a crystallographic inversion center.
4.6.3 Selected crystallographic details for 5
Formula C15H15N3AuCl, M = 469.72 g mol−1, colorless plate, 0.27 × 0.08 × 0.04 mm3, monoclinic, space group P21/c, Z = 4, a = 10.4506(6), b = 7.6849(40), c = 18.9956(10) Å, β = 98.4150(10)°, V = 1509.15(14) Å3, ρ calcd = 2.07 g cm−1, μ = 9.9 mm−1, ω and φ scans, 17960 measured intensities (3.9 ≤ 2θ ≤ 63.6°), semiempirical absorption correction (0.175 ≤ T ≤ 0.692), 4856 independent intensities (R int = 0.0364) and 3201 observed intensities (I ≥ 2 σ(I)), refinement of 182 parameters against |F 2| of all independent intensities with hydrogen atoms on calculated positions. R = 0.0285, R w = 0.0620, R all = 0.0535, R w,all = 0.0714. The asymmetric unit contains one formula unit of 5.
4.6.4 Selected crystallographic details for 6·HCl·CHCl3
Formula C17H19N3AuCl5, M = 639.57 g mol−1, colorless prism, 0.06 × 0.03 × 0.03 mm3, monoclinic, space group P21/c, Z = 4, a = 15.0277(9), b = 8.7598(5), c = 16.5927(10) Å, β = 96.8820(10)°, V = 2168.5(2) Å3, ρ calcd = 1.96 g cm−1, μ = 7.4 mm−1, ω and φ scans, 26252 measured intensities (2.7 ≤ 2θ ≤ 64.0°), semiempirical absorption correction (0.665 = T ≤ 0.808), 7061 independent intensities (R int = 0.0324) and 5925 observed intensities (I ≥ 2 σ(I)), refinement of 236 parameters against |F 2| of all independent intensities with hydrogen atoms on calculated positions. R = 0.0291, R w = 0.0665, R all = 0.0390, R w,all = 0.0702. The asymmetric unit contains one formula unit of 6, protonated at N3 by HCl and one molecule of CHCl3.
4.6.5 Selected crystallographic details for 7
C17H19N3AuCl, M = 497.77 g mol−1, colorless stick, 0.07 × 0.03 × 0.02 mm3, monoclinic, space group P21/c, Z = 4, a = 10.0296(8), b = 9.9236(8), c = 16.8415(13) Å, β = 95.0080(10)°, V = 1669.8(2) Å3, ρ calcd = 1.98 g cm−1, μ = 9.0 mm−1, ω and φ scans, 17704 measured intensities (4.1 ≤ 2θ ≤ 57.7°), semiempirical absorption correction (0.572 ≤ T ≤ 0.841), 4392 independent intensities (R int = 0.0437) and 3287 observed intensities (I ≥ 2 σ(I)), refinement of 200 parameters against |F 2| of all independent intensities with hydrogen atoms on calculated positions. R = 0.0329, R w = 0.0680, R all = 0.0542, R w,all = 0.0748. The asymmetric unit contains one formula unit of 7.
4.6.6 Selected crystallographic details for 8
C19H16N4AuCl, M = 532.77 g mol−1, colorless block, 0.15 × 0.13 × 0.09 mm3, monoclinic, space group P21/n, Z = 4, a = 9.7067(3), b = 11.0119(4), c = 17.2971(6) Å, β = 104.93(1)°, V = 1786.42(11) Å3, ρ calcd = 1.98 g cm−1, μ = 8.4 mm−1, ω and φ scans, 21,601 measured intensities (4.4 ≤ 2θ ≤ 63.8°), semiempirical absorption correction (0.366 ≤ T ≤ 0.519), 5792 independent intensities (R int = 0.0307) and 4917 observed intensities (I ≥ 2 σ(I)), refinement of 226 parameters against |F 2| of all independent intensities with hydrogen atoms on calculated positions. R = 0.0230, R w = 0.0509, R all = 0.0307, R w,all = 0.0530. The asymmetric unit contains one formula unit of 8.
4.6.7 Selected crystallographic details for 12
C19H16N4AuBr, M = 577.23 g mol−1, colorless stick, 0.34 × 0.12 × 0.10 mm3, monoclinic, space group C2/c, Z = 4, a = 17.897(4), b = 13.456(3), c = 7.3500(15) Å, β = 96.85(3)°, V = 1757.4(6) Å3, ρ calcd = 2.18 g cm−1, μ = 10.7 mm−1, ω and φ scans, 10396 measured intensities (3.8 ≤ 2θ ≤ 61.0°), semiempirical absorption correction (0.122 ≤ T ≤ 0.416), 2683 independent intensities (R int = 0.0395) and 2507 observed intensities (I ≥ 2 σ(I)), refinement of 115 parameters against |F 2| of all independent intensities with hydrogen atoms on calculated positions. R = 0.0255, R w = 0.0623, R all = 0.0279, R w,all = 0.0633. The asymmetric unit contains ½ formula unit of 12 linked to the other half by a crystallographic twofold axis.
4.6.8 Selected crystallographic details for 13·HBr·CH2Cl2
C16H18N3AuBr4Cl2, M = 839.84 g mol−1, orange plate, 0.13 × 0.11 × 0.04 mm3, monoclinic, space group P21/c, Z = 4, a = 11.2208(8), b = 9.4166(7), c = 23.0711(17) Å, β = 99.2650(10)°, V = 2405.9(9) Å3, ρ calcd = 2.32 g cm−1, μ = 13.0 mm−1, ω and φ scans, 26084 measured intensities (3.6 ≤ 2θ ≤ 58.3°), semiempirical absorption correction (0.199 ≤ T ≤ 0.595), 6468 independent intensities (R int = 0.0382) and 5641 observed intensities (I ≥ 2 σ(I)), refinement of 235 parameters against |F 2| of all independent intensities with hydrogen atoms on calculated positions. R = 0.0239, R w = 0.0495, R all = 0.0308, R w,all = 0.0514. The asymmetric unit contains one formula unit of 13 protonated at N3 by HBr and one molecule of CH2Cl2.
4.6.9 Selected crystallographic details for 15·HBr
C17H20N3AuBr4, M = 782.97 g mol−1, orange stick, 0.10 × 0.03 × 0.02 mm3, monoclinic, space group P21/n, Z = 4, a = 12.6613(10), b = 8.2075(7), c = 23.779(2) Å, β = 102.0150(10)°, V = 2416.9(3) Å3, ρ calcd = 2.15 g cm−1, μ = 12.7 mm−1, ω and φ scans, 24039 measured intensities (3.4 ≤ 2θ ≤ 55.7°), semiempirical absorption correction (0.358 = T ≤ 0.782), 5764 independent intensities (R int = 0.0471) and 4404 observed intensities (I ≥ 2 σ(I)), refinement of 236 parameters against |F 2| of all independent intensities with hydrogen atoms on calculated positions. R = 0.0306, R w = 0.0670, R all = 0.0467, R w,all = 0.0723. The asymmetric unit contains one formula unit of 13 protonated at N3 by HBr and one molecule of CH2Cl2. The nBu group is disordered. The asymmetric unit contains a strongly disordered CH2Cl2 molecule. Since the disorder could not be resolved, the CH2Cl2 molecule was removed using the SQEEZE procedure [69] as incorporated in Platon [70].
CCDC 2088809 (1a), 2088810 (2a), 2088811 (5), 2088812 (6·HCl·CHCl3), 2088813 (7), 2088814 (8), 2088816 (12), 2088817 (13·HBr·CH2Cl2) and 2088818 (15·HBr) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
-
Author contributions: All authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
-
Research funding: This research was funded by the Deutsche Forschungsgemeinschaft /SFB 858 and IRTG 2027).
-
Conflict of interest statement: The authors declare no conflicts of interest regarding this article.
References
1. Hahn, F. E., Jahnke, M. C. Angew. Chem. Int. Ed. 2008, 47, 3122–3172; https://doi.org/10.1002/anie.200703883.Search in Google Scholar PubMed
2. Jahnke, M. C., Hahn, F. E. Top. Organomet. Chem. 2010, 30, 95–129; https://doi.org/10.1007/978-3-642-04722-0_4.Search in Google Scholar
3. Martin, D., Melaimi, M., Soleilhavoup, M., Bertrand, G. Organometallics 2011, 30, 5304–5313; https://doi.org/10.1021/om200650x.Search in Google Scholar PubMed PubMed Central
4. Hopkinson, M. N., Richter, C., Schedler, M., Glorius, F. Nature 2014, 510, 485–496; https://doi.org/10.1038/nature13384.Search in Google Scholar PubMed
5. Bazinet, P., Ong, T.-G., O'Brien, J. S., Lavoie, N., Bell, E., Yap, G. P. A., Korobkov, I., Richeson, D. S. Organometallics 2007, 26, 2885–2895; https://doi.org/10.1021/om0701827.Search in Google Scholar
6. Otto, M., Conejero, S., Canac, Y., Romanenko, V. D., Rudzevitch, V., Bertrand, G. J. Am. Chem. Soc. 2004, 126, 1016–1017; https://doi.org/10.1021/ja0393325.Search in Google Scholar PubMed
7. Sampford, K. R., Carden, J. L., Kidner, E. B., Berry, A., Cavell, K. J., Murphy, D. M., Kariuki, B. M., Newman, P. D. Dalton Trans. 2019, 48, 1850–1858; https://doi.org/10.1039/c8dt04462g.Search in Google Scholar PubMed
8. Iglesias, M., Beetstra, D. J., Stasch, A., Horton, P. N., Hursthouse, M. B., Coles, S. J., Cavell, K. J., Dervisi, A., Fallis, I. A. Organometallics 2007, 26, 4800–4809; https://doi.org/10.1021/om7004904.Search in Google Scholar
9. Iglesias, M., Beetstra, D. J., Knight, J. C., Ooi, L.-L., Stasch, A., Coles, S., Male, L., Hursthouse, M. B., Cavell, K. J., Dervisi, A., Fallis, I. A. Organometallics 2008, 27, 3279–3289; https://doi.org/10.1021/om800179t.Search in Google Scholar
10. Newman, P. D., Cavell, K. J., Kariuki, B. M. Organometallics 2010, 29, 2724–2734; https://doi.org/10.1021/om1002107.Search in Google Scholar
11. Lu, W. Y., Cavell, K. J., Wixey, J. S., Kariuki, B. Organometallics 2011, 30, 5649–5655; https://doi.org/10.1021/om200467x.Search in Google Scholar
12. Cervantes-Reyes, A., Rominger, F., Rudolph, M., Hashmi, A. S. K. Adv. Synth. Catal. 2020, 362, 2523–2533.10.1002/adsc.202000281Search in Google Scholar
13. Janssen-Müller, D., Schlepphorst, C., Glorius, F. Chem. Soc. Rev. 2017, 46, 4845–4854; https://doi.org/10.1039/c7cs00200a.Search in Google Scholar PubMed
14. Mata, J. A., Hahn, F. E., Peris, E. Chem. Sci. 2014, 5, 1723–1732; https://doi.org/10.1039/c3sc53126k.Search in Google Scholar
15. Peris, E. Chem. Rev. 2018, 118, 9988–10031; https://doi.org/10.1021/acs.chemrev.6b00695.Search in Google Scholar PubMed
16. Sinha, N., Hahn, F. E. Acc. Chem. Res. 2017, 50, 2167–2184; https://doi.org/10.1021/acs.accounts.7b00158.Search in Google Scholar PubMed
17. Gan, M.-M., Liu, J.-Q., Zhang, L., Wang, Y.-Y., Hahn, F. E., Han, Y.-F. Chem. Rev. 2018, 118, 9587–9641; https://doi.org/10.1021/acs.chemrev.8b00119.Search in Google Scholar PubMed
18. Sinha, N., Tan, T. T. Y., Peris, E., Hahn, F. E. Angew. Chem. Int. Ed. 2017, 56, 7393–7397; https://doi.org/10.1002/anie.201702637.Search in Google Scholar PubMed
19. Liu, W., Gust, R. Coord. Chem. Rev. 2016, 329, 191–213; https://doi.org/10.1016/j.ccr.2016.09.004.Search in Google Scholar
20. Mora, M., Gimeno, M. C., Visbal, R. Chem. Soc. Rev. 2019, 48, 447–462; https://doi.org/10.1039/c8cs00570b.Search in Google Scholar PubMed
21. Strassner, T. Acc. Chem. Res. 2016, 49, 2680–2689; https://doi.org/10.1021/acs.accounts.6b00240.Search in Google Scholar PubMed
22. Visbal, R., Gimeno, M. C. Chem. Soc. Rev. 2014, 43, 3551–3574; https://doi.org/10.1039/c3cs60466g.Search in Google Scholar PubMed
23. Edwards, P. G., Hahn, F. E. Dalton Trans. 2011, 40, 10278–10288; https://doi.org/10.1039/c1dt10864f.Search in Google Scholar PubMed
24. Basato, M., Michelin, R. A., Mozzon, M., Sgarbossa, P., Tassan, A. J. Organomet. Chem. 2005, 690, 5414–5420; https://doi.org/10.1016/j.jorganchem.2005.07.021.Search in Google Scholar
25. Jahnke, M. C., Hahn, F. E. Coord. Chem. Rev. 2015, 293–294, 95–115; https://doi.org/10.1016/j.ccr.2015.01.014.Search in Google Scholar
26. Jahnke, M. C., Hahn, F. E. Chem. Lett. 2015, 44, 226–237; https://doi.org/10.1246/cl.141052.Search in Google Scholar
27. Kuwata, S., Hahn, F. E. Chem. Rev. 2018, 118, 9642–9677; https://doi.org/10.1021/acs.chemrev.8b00176.Search in Google Scholar PubMed
28. Wang, H. M. J., Lin, I. J. B. Organometallics 1998, 17, 972–975; https://doi.org/10.1021/om9709704.Search in Google Scholar
29. Garrison, J. C., Youngs, W. J. Chem. Rev. 2005, 105, 3978–4008; https://doi.org/10.1021/cr050004s.Search in Google Scholar PubMed
30. Lin, I. J. B., Vasam, C. S. Coord. Chem. Rev. 2007, 251, 642–670; https://doi.org/10.1016/j.ccr.2006.09.004.Search in Google Scholar
31. Lin, J. C. Y., Huang, R. T. W., Lee, C. S., Bhattacharyya, A., Hwang, W. S., Lin, I. J. B. Chem. Rev. 2009, 109, 3561–3598; https://doi.org/10.1021/cr8005153.Search in Google Scholar PubMed
32. Lin, I. J. B., Vasam, C. S. Can. J. Chem. 2005, 83, 812–825; https://doi.org/10.1139/v05-087.Search in Google Scholar
33. Raubenheimer, H. R., Cronje, S. Chem. Soc. Rev. 2008, 37, 1998–2011; https://doi.org/10.1039/b708636a.Search in Google Scholar PubMed
34. Bertrand, B., Williams, M. R. M., Bochmann, M. Chem. Eur J. 2018, 24, 11840–11851; https://doi.org/10.1002/chem.201800981.Search in Google Scholar PubMed
35. Rubbiani, R., Can, S., Kitanovic, I., Alborzinia, H., Stefanopoulou, M., Kokoschka, M., Mönchgesang, S., Sheldrick, W. S., Wölfl, S., Ott, I. J. Med. Chem. 2011, 54, 8646–8657; https://doi.org/10.1021/jm201220n.Search in Google Scholar PubMed
36. Hickey, J. L., Ruhayel, R. A., Barnard, P. J., Baker, M. V., Berners-Price, S. J., Filipovska, A. J. Am. Chem. Soc. 2008, 130, 12570–12571; https://doi.org/10.1021/ja804027j.Search in Google Scholar PubMed
37. Marion, N., Nolan, S. P. Chem. Soc. Rev. 2008, 37, 1776–1782; https://doi.org/10.1039/b711132k.Search in Google Scholar PubMed
38. de Frémont, P., Marion, N., Nolan, S. P. J. Organomet. Chem. 2009, 694, 551–560; https://doi.org/10.1016/j.jorganchem.2008.10.047.Search in Google Scholar
39. Gaillard, S., Cazin, C. S. J., Nolan, S. P. Acc. Chem. Res. 2012, 45, 778–787; https://doi.org/10.1021/ar200188f.Search in Google Scholar PubMed
40. Radloff, C., Weigand, J. J., Hahn, F. E. Dalton Trans. 2009, 9392–9394; https://doi.org/10.1039/b916651c.Search in Google Scholar PubMed
41. Sinha, N., Roelfes, F., Hepp, A., Mejuto, C., Peris, E., Hahn, F. E. Organometallics 2014, 33, 6898–6904; https://doi.org/10.1021/om500973b.Search in Google Scholar
42. Rit, A., Pape, T., Hahn, F. E. J. Am. Soc. Chem. 2010, 132, 4572–4573; https://doi.org/10.1021/ja101490d.Search in Google Scholar PubMed
43. Jahnke, M. C., Pape, T., Hahn, F. E. Eur. J. Inorg. Chem. 2009, 1960–1969; https://doi.org/10.1002/ejic.200801214.Search in Google Scholar
44. Jahnke, M. C., Pape, T., Hahn, F. E. Z. Naturforsch. 2010, 65b, 341–346; https://doi.org/10.1515/znb-2010-0318.Search in Google Scholar
45. Catalano, V. J., Malwitz, M. A., Etogo, A. O. Inorg. Chem. 2004, 43, 5714–5724; https://doi.org/10.1021/ic049604k.Search in Google Scholar PubMed
46. Catalano, V. J., Moore, A. L. Inorg. Chem. 2005, 44, 6558–6566; https://doi.org/10.1021/ic050604+.10.1021/ic050604+Search in Google Scholar PubMed
47. Catalano, V. J., Etogo, A. O. J. Organomet. Chem. 2005, 690, 6041–6050; https://doi.org/10.1016/j.jorganchem.2005.07.109.Search in Google Scholar
48. Muuronen, M., Perea-Buceta, J. E., Nieger, M., Patzschke, M., Helaja, J. Organometallics 2012, 31, 4320–4330; https://doi.org/10.1021/om3003027.Search in Google Scholar
49. Pažický, M., Loos, A., Ferreira, M. J., Serra, D., Vinokurov, N., Rominger, F., Jäkel, C., Hashmi, A. S. K., Limbach, M. Organometallics 2010, 29, 4448–4458.10.1021/om1005484Search in Google Scholar
50. Jahnke, M. C., Paley, J., Hupka, F., Weigand, J. J., Hahn, F. E. Z. Naturforsch. 2009, 64b, 1458–1462; https://doi.org/10.1515/znb-2009-11-1228.Search in Google Scholar
51. Hahn, F. E., Jahnke, M. C., Pape, T. Organometallics 2006, 25, 5927–5936; https://doi.org/10.1021/om060741u.Search in Google Scholar
52. Zhang, X., Gu, S., Xia, Q., Chen, W. J. Organomet. Chem. 2009, 694, 2359–2367; https://doi.org/10.1016/j.jorganchem.2009.03.031.Search in Google Scholar
53. Tulloch, A. A. D., Danopoulos, A. A., Winston, S., Kleinhenz, S., Eastham, G. J. Chem. Soc. Dalton Trans. 2000, 4499–4506; https://doi.org/10.1039/b007504n.Search in Google Scholar
54. Topf, C., Leitner, S., Monkowius, U. Acta Crystallogr. 2012, E68, m272; https://doi.org/10.1107/s1600536812004473.Search in Google Scholar
55. Newman, C. P., Clarkson, G. J., Rourke, J. P. J. Organomet. Chem. 2007, 692, 4962–4968; https://doi.org/10.1016/j.jorganchem.2007.07.041.Search in Google Scholar
56. Schulte to Brinke, C., Pape, T., Hahn, F. E. Dalton Trans. 2013, 42, 7330–7337; https://doi.org/10.1039/c2dt32905k.Search in Google Scholar PubMed
57. Lee, K. M., Wang, H. M. J., Lin, I. J. B. Dalton Trans. 2002, 2852–2856; https://doi.org/10.1039/b201957d.Search in Google Scholar
58. Schneider, S. K., Herrmann, W. A., Herdtweck, E. Z. Anorg. Allg. Chem. 2003, 629, 2363–2370; https://doi.org/10.1002/zaac.200300247.Search in Google Scholar
59. Liu, Q.-X., Li, H.-L., Zhao, X.-J., Ge, S.-S., Shi, M.-C., Shen, G., Zang, Y., Wang, X.-G. Inorg. Chim. Acta. 2011, 376, 437–445; https://doi.org/10.1016/j.ica.2011.07.007.Search in Google Scholar
60. Das Adhikary, S., Bose, D., Mitra, P., Das Saha, K., Bertolasi, V., Dinda, J. New J. Chem. 2012, 36, 759–767; https://doi.org/10.1039/c2nj20928d.Search in Google Scholar
61. Schmidbaur, H., Schier, A. Chem. Soc. Rev. 2008, 37, 1931–1951; https://doi.org/10.1039/b708845k.Search in Google Scholar PubMed
62. Jahnke, M. C., Pape, T., Hahn, F. E. Z. Anorg. Allg. Chem. 2010, 636, 2309–2314; https://doi.org/10.1002/zaac.201000234.Search in Google Scholar
63. Han, X., Koh, L. L., Weng, Z., Hor, T. S. A. Dalton Trans. 2009, 7248–7252; https://doi.org/10.1039/b909661b.Search in Google Scholar PubMed
64. Huynh, H. V., Guo, S., Wu, W. Organometallics 2013, 32, 4591–4600; https://doi.org/10.1021/om400563e.Search in Google Scholar
65. de Frémont, P., Singh, R., Stevens, E. D., Petersen, J. L., Nolan, S. P. Organometallics 2007, 26, 1376–1385; https://doi.org/10.1021/om060887t.Search in Google Scholar
66. Hirtenlehner, C., Krims, C., Hölbling, J., List, M., Zabel, M., Fleck, M., Berger, R. J. F., Schoefberger, W., Monkowius, U. Dalton Trans. 2011, 40, 9899–9910; https://doi.org/10.1039/c1dt11175b.Search in Google Scholar PubMed
67. Sheldrick, G. M. Acta Crystallogr. 2015, A71, 3–8; https://doi.org/10.1107/s2053273314026370.Search in Google Scholar PubMed PubMed Central
68. Sheldrick, G. M. Acta Crystallogr. 2015, C71, 3–8.Search in Google Scholar
69. Spek, A. L. Acta Crystallogr. 2015, C71, 9–18.10.1107/S2053229614024929Search in Google Scholar
70. Spek, A. L. Acta Crystallogr. 2009, D65, 148–155; https://doi.org/10.1107/s090744490804362x.Search in Google Scholar
© 2021 Walter de Gruyter GmbH, Berlin/Boston
Articles in the same Issue
- Frontmatter
- In this issue
- Research Articles
- Orthoamide und Iminiumsalze, CIV. Umsetzungen von Orthoamiden der Alkincarbonsäuren mit enolisierbaren Carbonylverbindungen – Cyclisierung der Kondensationsprodukte zu Pyran-Derivaten
- 1,3-Dimethyl-tetrakis(2-triphenylsilylethyl)dimethyldisiloxane: a new carbosilane for the preparation of high-refractive-index films
- Antibacterial activity of some chemical constituents from Trichilia prieuriana (Meliaceae)
- A cobalt-based coordination polymer with a tripodal carboxylate ligand: synthese, structure and properties
- The stannides Ca1.692Pt2Sn3.308, SrPtSn2 and EuAuSn2
- Synthesis and coordination chemistry of silver(I), gold(I) and gold(III) complexes with picoline-functionalized benzimidazolin-2-ylidene ligands
Articles in the same Issue
- Frontmatter
- In this issue
- Research Articles
- Orthoamide und Iminiumsalze, CIV. Umsetzungen von Orthoamiden der Alkincarbonsäuren mit enolisierbaren Carbonylverbindungen – Cyclisierung der Kondensationsprodukte zu Pyran-Derivaten
- 1,3-Dimethyl-tetrakis(2-triphenylsilylethyl)dimethyldisiloxane: a new carbosilane for the preparation of high-refractive-index films
- Antibacterial activity of some chemical constituents from Trichilia prieuriana (Meliaceae)
- A cobalt-based coordination polymer with a tripodal carboxylate ligand: synthese, structure and properties
- The stannides Ca1.692Pt2Sn3.308, SrPtSn2 and EuAuSn2
- Synthesis and coordination chemistry of silver(I), gold(I) and gold(III) complexes with picoline-functionalized benzimidazolin-2-ylidene ligands
