Volume 74, Issue 4

The ZrBeSi type is a superstructure variant of the aristotype AlB 2 with an ordering of the beryllium and silicon atoms on the boron network. Every other layer of Be 3 Si 3 hexagons is rotated by 60°, leading to an ABAB stacking sequence and a sandwich-like coordination of zirconium by two Be 3 Si 3 hexagons. The ZrBeSi type shows a pronounced coloring on its three crystallographic sites. Among the numerous compounds are electron-precise Zintl phases in the field of tetrelides, pnictides and chalcogenides, selenide hydrides and fluorides as well as intermetallic compounds. A variety of element combinations leads to distinctly differing c / a ratios and different bonding patterns. Several compounds are rather isopointal than isotypic. The present work focuses on a crystal chemical description of selected ZrBeSi related compounds and the results of theoretical studies for evaluating the bonding peculiarities. From quantum theory (DFT) based investigations, the trends of charge transfer according to Bader’s AIM theory have been established. These are in general agreement with the course of the electronegativities. For the prototype ZrBeSi, the main characteristics are illustrated through the electron localization function, manifesting the sp 2 -like planar hybridization for the silicon atoms. The site-projected densities of states PDOS of a series of compounds underline a continuous trend from metallic (e.g. ZrBeSi) to semi-conducting (e.g. LiBC) compounds in agreement with the observed electron exchanges.

The crystal structures and Hirshfeld surface analyses are reported for four aldoximes, ( E )-X–C 6 H 4 CH=N–OH [X = 3-Cl ( 1 ), 4-F ( 2 ), 2-O 2 N ( 3 ) and 4-O 2 N ( 4 )]. The strong classical O–H · · · N hydrogen bonds involving the oxime group generate C(3) chains in compound 1 , in contrast to the R 2 2 (6) dimers formed in compounds 2–4 ; such arrangements have been shown to be the most frequently found for oximes other than salicylaldoximes (2-hydroxybenzaldehyde oximes). In general, weaker intermolecular interactions involving the X substituents, as well as C–H · · · O and π · · · π interactions have significant effects on the supramolecular arrays generated in the aggegation. A further important interaction in compound 1 , and to a lesser extent in compound 4 , is a π(C=N) · · · π(phenyl) molecular stacking. A data base search has indicated that short Cg(C=N) · · · Cg(phenyl) distances, <3.3 Å (Cg = centre of gravity), have been found in various compounds, including other oximes. A theoretical study was carried out starting from the crystal structure data of compound 1 , with optimisation at the BLYP-D3/def2-DZVP level, as well as at the higher PBE0/ma-def2-TZVP level. Breakdown of the interaction energy into separate contributions was achieved using SAPT (using the jun-cc-pvdz basis set). Overall, the calculations indicate that the π(C=N) ·· · π(phenyl) interaction is attractive, with a magnitude of 14–18 kJ mol −1 .

A new multicage compound [(Me) 2 EtNH][Mn(N 3 ) 3 ] (Me = methyl, Et = ethyl) with a perovskite-related structure has been synthesized. The manganese(II) cations are bridged by end-to-end ( EE ) azide anions to form three-dimensional cages with the N,N -dimethylethylammonium cations residing in the cavities of the [Mn(N 3 ) 3 ] n n − cages. The compound has been characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis, second-harmonic generation, and magnetic measurements. The second-harmonic generation results support its noncentrosymmetric polar crystal structure. Magnetic susceptibility measurements show antiferromagnetic interactions among the Mn II ions.

A new coordination polymer [Cd(C 10 H 8 N 2 ) 2 (C 10 H 4 O 8 )] n (C 10 H 8 N 2  = 2,2′-bipyridine and C 10 H 4 O 8  = 2,5-dicarboxybenzene-1,4-dicarboxylate) has been hydrothermally synthesized and characterized by elemental analysis, infrared spectroscopy, thermal gravimetric analysis and single-crystal X-ray diffraction. Crystal structural analysis reveals that the Cd II cation is coordinated by two 2,5-dicarboxybenzene-1,4-dicarboxylate ligands and two 2,2′-bipyridine molecules, forming a distorted octahedral CdN 4 O 2 coordination geometry. The 2,5-dicarboxybenzene-1,4-dicarboxylate ligands link the Cd II cations to generate a one-dimensional metal-organic structure running along the [0 1 0] direction. Adjacent chains are further connected by carboxyl-carboxyl O–H···O hydrogen bonds, resulting in a two-dimensional supermolecular architecture running parallel to the (1 0 0) plane in the solid state. The fluorescence properties of the complex were investigated.

Acetylenic iminium triflates with the general formula [R–C≡ C–C(Ar)=N + R 2 TfO − ] were found to be excellent dipolarophiles in [3+ 2] cycloaddition reactions with diazoacetates leading to (1 H -pyrazol-3(5)-yl)methanaminium triflates in high yields. The terminal acetylenic iminium salt (propyne iminium salt) [HC≡C–C(Ph)=N + Me 2 TfO − ] reacted with an equimolar amount of methyl diazoacetate instantaneously at 20°C to form the expected pyrazole in almost quantitative yield. When a 2:1 stoichiometry was applied, subsequent Michael addition of the pyrazole at the alkyne occurred and the bis(iminium) ditriflate 4 was obtained in high yield. By hydride reduction or hydrolysis of the iminium group, some of the highly hygroscopic pyrazole iminium salts were converted into neutral, twofold functionalized, di- and tri- C -substitued 1 H -pyrazoles.

The mixed cation triel borate Ga 4 In 4 B 15 O 33 (OH) 3 was synthesized in a Walker-type multianvil apparatus at high-pressure/high-temperature conditions of 12.5 GPa and 1300°C. Although the product could not be reproduced in further experiments, its crystal structure could be reliably determined via single-crystal X-ray diffraction data. Ga 4 In 4 B 15 O 33 (OH) 3 crystallizes in the tetragonal space group I 4 1 / a (origin choice 2) with the lattice parameters a  = 11.382(2), c  = 15.244(2) Å, and V  = 1974.9(4) Å 3 . The structure of the quaternary triel borate consists of a complex network of BO 4 tetrahedra, edge-sharing InO 6 octahedra in dinuclear units, and very dense edge-sharing GaO 6 octahedra in tetranuclear units.

The reaction of [ i Pr 2 N=CHCl]Cl with 2-phenylbenzthiazolidine (Ph-BtzH) and subsequent anion metathesis afforded the formamidinium salt [(Ph-Btz)CH(N i Pr 2 )][PF 6 ] ([ 1a H][PF 6 ]). The reaction of [ 1a H][PF 6 ] with (Me 3 Si) 2 NNa in the presence of grey selenium furnished the selenourea derivative 1a Se as trapping product of the acyclic diaminocarbene 1a . In the absence of selenium, a 2 H -1,4-benzothiazine derivative ( 2 ) was obtained, which is an isomer of 1a , whose formation is plausibly initiated by deprotonation of [ 1a H] + not at the cationic N 2 CH unit, but at the neighbouring PhCH position. CO was ineffective as trapping reagent for 1a . [ 1a H][PF 6 ], 1a Se and 2 have been structurally characterised by X-ray diffraction.

Metathesis reactions of [PNP]Cl ([PNP] +  ≡ bis(triphenyl- λ 5 -phosphanylidene)ammonium) with Na 2 [SO 4 ] or K[HSO 4 ] in water yield [PNP] 2 [SO 4 ] and [PNP][HSO 4 ], respectively, as colorless solids. Reactions under basic conditions lead to a partial decomposition of the weakly coordinating [PNP] + cation. N -Diphenylphosphine-triphenylphosphazene, triphenylphosphinimine, and benzene were identified as decomposition products by NMR spectroscopy. The compounds [PNP] 2 [SO 4 ] and [PNP][HSO 4 ] were characterized by multinuclear NMR and vibrational spectroscopy. [PNP][HSO 4 ] could be crystallized from acetonitrile-diethyl ether giving single crystals with and without additional acetonitrile solvate molecules. The [HSO 4 ] − anions form dimers in the solid state in both structures, which are held together by O–H⋯O hydrogen bonds. At T  = 127 K the [HSO 4 ] − anions in the crystal structure of solvate free [PNP][HSO 4 ] are ordered, while at T  = 300 K and in the structure containing additional acetonitrile solvate molecules a disorder of the [HSO 4 ] − anions over two positions is observed, for the latter even at 150 K.

A potassium tetranitratopalladate(II) with the composition K 2 [Pd(NO 3 ) 4 ] · 2HNO 3 was synthesized by a simple solvothermal process in a glass ampoule. The new compound crystallizes in the monoclinic space group P 2 1 /c (no. 14) with the lattice parameters a  = 1017.15(4), b  = 892.94(3), c  = 880.55(3) Å, and β  = 98.13(1)° ( Z  = 2). The crystal structure of K 2 [Pd(NO 3 ) 4 ] · 2HNO 3 reveals isolated complex [Pd(NO 3 ) 4 ] 2− anions, which are surrounded by eight potassium cations and four HNO 3 molecules. The complex anions and the cations are associated in layers which are separated by HNO 3 molecules. K 2 [Pd(NO 3 ) 4 ] · 2HNO 3 can thus be regarded as a HNO 3 intercalation variant of β -K 2 [Pd(NO 3 ) 4 ]. The characterization is based on single-crystal X-ray and powder X-ray diffraction.

The known compound diphenyl([2.2]paracyclophanyl)phosphane 1 reacted smoothly with elemental sulfur or selenium to give the phosphane chalcogenides 3 and 4 . The corresponding chlorido- or bromido-gold(I) complexes were however not obtained by the usual reaction with (tht)AuCl or (tht)AuBr. For the latter, direct oxidation of the reaction mixture with elemental bromine led to small quantities of {(PCP)PPh 2 Br} + [AuBr 4 ] − 5 (PCP = [2.2]paracyclophanyl). Attempts to obtain the alkyl phosphane di-isopropyl([2.2]paracyclophanyl)phosphane 2 were at first unsuccessful because of contamination by the phosphonium derivatives [ i Pr 2 (PCP)PH] + X − (X = Cl 6 , X = Br 7 ), but the mixture was found to react with elemental sulfur or selenium to give the phosphane chalcogenides 8 and 9 . The gold(I) complexes (PCP) i Pr 2 P E Au X [ E  = S, X  = Cl ( 10 ), Br ( 11 ); E  = Se, X  = Cl ( 12 ), Br ( 13 )] were obtained by the reactions of 8 and 9 with (tht)AuX. The chlorido complexes 10 and 12 were oxidized by PhICl 2 to the gold(III) complexes (PCP) i Pr 2 P E AuCl 3 14 ( E  = S) and 15 ( E  = Se). An excess of PhICl 2 led to the fully oxidized compound {(PCP) i Pr 2 PSeCl} + [AuCl 4 ] − 16 . The bromido complexes 11 and 13 were oxidized by elemental bromine to (PCP) i Pr 2 P E AuBr 3 17 ( E  = S) und 18 ( E  = Se), the latter however with a poor yield. Further oxidation was not achieved. The reactions of the chalcogenides 3 , 4 , 8 and 9 with elemental iodine led to the products 19 , 20 , 21 (1:1 adducts) and 22 (1:1 adduct with additional disordered diiodine), respectively.