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An approach towards the synthesis of lithium and beryllium diphenylphosphinites

  • Chantsalmaa Berthold , Lewis R. Thomas-Hargreaves , Sergei I. Ivlev and Magnus R. Buchner EMAIL logo
Published/Copyright: September 29, 2021
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Zeitschrift für Naturforschung B
From the journal Zeitschrift für Naturforschung B Volume 76 Issue 10-12

Abstract

The diphenylphosphinites [(THF)Li(OPPh2)]4 and [(THF)2Be(OPPh2)2] have been synthesized via direct deprotonation of diphenylphosphine oxide with n BuLi and BePh2, respectively, as well as via salt metathesis. These compounds were characterized by multinuclear NMR spectroscopy, and the side-products of the reactions obtained under various reaction conditions have been identified. The beryllium derivative could not be isolated and decomposed into diphosphine oxide Ph2PP(O)Ph2. The solid-state structure of this final product together with that of [(THF)Li(OPPh2)]4 have been determined by single-crystal X-ray diffraction.

Keywords: beryllium; coordination chemistry; frustrated Lewis pair; lithium; phosphinous acid

1 Introduction

The concept of frustrated Lewis acid base pairs (FLPs) has attracted considerable attention in the chemistry community in the last decade [1]. One highlight is the ability of mixtures of electron deficient boranes and sterically demanding phosphines to reversibly cleave dihydrogen, as depicted in Figure 1 [2]. This initiated extensive research into FLPs which comprise of a borane acting as the Lewis acid and a phosphine acting as the Lewis base [3].

Figure 1: Reversible activation of H2 by a phosphine borane Lewis acid base pair [2].
Figure 1:

Reversible activation of H2 by a phosphine borane Lewis acid base pair [2].

More recently it was shown by the group of Uhl that FLPs comprising of a phosphine and an organo-aluminum function, which are separated by a linking carbon atom (Figure 2 left), are versatile compounds for the activation of small molecules [4, 5]. This molecular geometry was generalized and could be employed also for gallium and magnesium as shown in Figure 2 in the center and on the right, respectively [6].

Figure 2: Phosphorus-based group 13/15 Lewis pairs with a C1 linker [4], [5], [6].
Figure 2:

Phosphorus-based group 13/15 Lewis pairs with a C1 linker [4], [5], [6].

While Lewis acid base pairs with boron or aluminum have been widely studied, hardly any research has been devoted to Lewis acids of the s-block [1]. We have shown that the combination of beryllium chloride and tricyclohexylphosphine readily activates C–Cl bonds [7]. More recently we demonstrated that this could also be achieved with amine adducts to beryllium halides [8]. Additionally, the acidity of carboxylic acids [9] and ammonia [10] is significantly increased by beryllium coordination. Furthermore, we frequently observe transformations of functional groups, like alcohols [11], aldehydes [12] or nitriles [13], which all are induced by the Lewis acidity of the beryllium atom.

Intrigued by these observations we decided to venture into s-block metal systems, which are tethered to a Lewis base. Since most of these metals form highly ionic compounds, we restricted our study to the second period of the Periodic Table of the elements. Considering the high basicity of lithium organic compounds and the little knowledge on beryllium organyles [14, 15] we decided to use oxygen linkers between the s-block Lewis acid and the phosphine. The intention was to utilize the equilibrium between the diorganophosphine oxides and their corresponding diorganophosphinous acid tautomers as depicted in Figure 3. This decision was also driven by the high oxophilicity of beryllium, which suggested stable compounds [16, 17].

Figure 3: Intended reactions to form lithium and beryllium diphenylphosphinites.
Figure 3:

Intended reactions to form lithium and beryllium diphenylphosphinites.

To our surprise, there is virtually no research on simple metal diorganophosphinites. The only available studies deal with sodium [18, 19] and magnesium [20] derivatives and are mainly limited to NMR spectroscopic studies [21]. However, since harder metals – according to the Pearson concept [22] – should be better for Lewis acid base pair chemistry, we limited our research to the lithium and beryllium compounds described in Figure 3.

2 Discussion

2.1 Lithium compounds

Reaction of diphenylphosphine oxide with n butyllithium at 0 °C in THF leads to an orange solution upon warming to ambient temperature. From this solution, colorless crystals suitable for single-crystal X-ray diffractometry could be grown. These crystals comprise of [(THF)Li(OPPh2)]4 (1), which crystallizes in the tetragonal space group I 4 ‾ with two formula units per unit cell. Compound 1 is a tetranuclear molecule consisting of four (THF)Li(OPPh2) subunits. In this tetranuclear complex the four lithium and the four oxygen atoms of the phosphinous acid build a heterocubane structure, in which lithium and oxygen are sitting alternately at the corners of the cube as depicted in Figure 4. The lithium atoms are capped by THF molecules, which coordinate via their oxygen atoms. The corners occupied by the oxygen atoms are capped by the phosphorus atoms. The lithium atoms are only coordinated by oxygen atoms and exhibit a distorted tetrahedral coordination environment, while the phosphorus atoms are only three-coordinated with no indication of interaction of their lone pairs with other atoms. The solid-state structure of a different polymorph of 1, which crystallizes in the triclinic space group P 1 ‾ , has been described previously by Hoskin and Stephan [23]. However, they obtained 1 in a significantly more complicated synthetic procedure.

Figure 4: Molecular structure of [(THF)Li(OPPh2)]4 (1) in the solid state at T = 100 K. Ellipsoids are depicted at the 70% probability level. Hydrogen atoms are omitted and carbon atoms depicted as wireframe for clarity.
Figure 4:

Molecular structure of [(THF)Li(OPPh2)]4 (1) in the solid state at T = 100 K. Ellipsoids are depicted at the 70% probability level. Hydrogen atoms are omitted and carbon atoms depicted as wireframe for clarity.

The Li–O distances within the heterocubane structure of 1 are in the range of 1.973(3) to 2.011(3) Å. The Li–O bond lengths to the oxygen atoms of the THF molecules are with 1.958(3) Å slightly shorter. The P–O separations are with 1.5908(12) Å significantly shorter, which would be expected due to the covalent nature of this bond. The O–Li–O angles within the heterocubane moiety range from 94.50(13)° to 97.66(13)°, while the corresponding Li–O–Li angles are 82.29(13)°–84.97(13)°. These values all compare very well with the ones found for the other polymorph [23].

Complex 1 is insoluble in aliphatic and aromatic solvents, but moderately soluble in THF and reasonably soluble in pyridine. The 31P NMR signal is shifted considerably downfield in 1 compared to diphenylphosphine oxide. This is indicative of the formation of the lithium diphenylphosphinite. The deprotonation is also confirmed by the lack of 1 J PH coupling in 1, while in the starting material this coupling is clearly observed (Figure 5 spectra at top and bottom). The 7Li NMR signal of 1 is observed at 0.2 ppm in THF-d 8 and at 2.6 ppm in pyridine-d 5, with line widths of 11.6 and 3.7 Hz, respectively. The small line width indicates a highly symmetric coordination environment around the quadrupolar 7Li nuclei, which is evidence for the retention of the heterocubane structure in solution. The coordination of one THF molecule per lithium atom was confirmed via comparison of the integrals of the phenyl and the THF signals in a pyridine-d 5 solution of 1.

Figure 5: Proton coupled 31P NMR spectra of Ph2P(O)H in C6D6, of the reaction mixture of n BuLi with Ph2P(O)H in C6D6, of the products formed from the reaction of n BuLi with Ph2P(O)H in C6D6 re-dissolved in THF-d 8, and of [(THF)Li(OPPh2)]4 in THF-d 8 (from top to bottom).
Figure 5:

Proton coupled 31P NMR spectra of Ph2P(O)H in C6D6, of the reaction mixture of n BuLi with Ph2P(O)H in C6D6, of the products formed from the reaction of n BuLi with Ph2P(O)H in C6D6 re-dissolved in THF-d 8, and of [(THF)Li(OPPh2)]4 in THF-d 8 (from top to bottom).

Complex 1 can be prepared in reasonable yield in THF. However since both starting materials are soluble in aromatic solvents and product 1 is not, we tested if the synthesis in benzene was advantageous. But, to our surprise, we observed the formation of the tertiary phosphines Ph2P n Bu, PhP n Bu2 and PPh3, as evident from their respective 31P NMR signals at −16.3, −25.5 and −5.3 ppm (Figure 5) [24, 25]. These phosphines are the only species present in benzene solution, while large amounts of colorless precipitate are present. Removal of the solvent in vacuo and re-dissolution in THF proves this solid to be compound 1 (Figure 5).

Based on these observations we propose the mechanism depicted in Figure 6 for the formation of compound 1 and Ph2P n Bu in aromatic reaction media. The lithium atom is coordinated by the oxygen atom of the diphenylphosphinous acid. In the major reaction pathway this leads to deprotonation of the OH function under formation of n-butane and 1. In the minor reaction pathway the n-butyl group is transferred to the phosphorus atom and consecutively the P–O bond is broken with formation of lithium hydroxide. We assume that this is only feasible if the lithium atom is not coordinated by other donor solvents, since this pathway is completely suppressed in the O-donor solvent THF. Scrambling of the organic substituents at the phosphine is accountable for the presence of PhP n Bu2 and PPh3. However, no information on the mechanism for this was obtained.

Figure 6: Proposed reaction mechanism for the reaction of n BuLi with Ph2P(O)H in aromatic solvent.
Figure 6:

Proposed reaction mechanism for the reaction of n BuLi with Ph2P(O)H in aromatic solvent.

2.2 Beryllium compounds

For the synthesis of the corresponding beryllium bis(diphenylphosphinite), two routes were tested. The first is the salt metathesis of BeBr2 with 1 in THF, while the second one is the direct deprotonation of diphenylphosphinous acid with BePh2. Both reactions are depicted in Figure 7.

Figure 7: Synthesis of [(THF)2Be(OPPh2)2] (2) in THF.
Figure 7:

Synthesis of [(THF)2Be(OPPh2)2] (2) in THF.

The salt metathesis reaction leads to the formation of one defined species (2) according to 1H, 13C, 9Be and 31P NMR spectroscopy. Compound 2 exhibits one signal in the 9Be NMR spectrum at 2.2 ppm (ω 1/2 = 48.4 Hz). This is in the typical region for tetrahedrally coordinated 9Be nuclei [26, 27]. The 31P NMR signal is observed at 83.4 ppm (Figure 8 top), which is very close to the one observed for 1. In the 1H and 13C NMR spectra of 2, only one set of signals is observed for the phenyl groups. Based on these data, we propose [(THF)2Be(OPPh2)2] to be the structure of 2 (Figure 7). However, further characterization of 2 was impossible due to decomposition upon removal of the solvent. This is discussed further below in more detail.

Figure 8: 31P{1H} NMR spectra the reaction mixture of [(THF)Li(OPPh2)]4 with BeBr2 in THF-d 8, of the reaction mixture of BePh2 with Ph2P(O)H in THF-d 8, of the product of the reaction of BePh2 with Ph2P(O)H in THF re-dissolved in C6D6, and of the reaction mixture of [(THF)Li(OPPh2)]4 with BeBr2 in THF-d 8 after heating to 90 °C (from top to bottom).
Figure 8:

31P{1H} NMR spectra the reaction mixture of [(THF)Li(OPPh2)]4 with BeBr2 in THF-d 8, of the reaction mixture of BePh2 with Ph2P(O)H in THF-d 8, of the product of the reaction of BePh2 with Ph2P(O)H in THF re-dissolved in C6D6, and of the reaction mixture of [(THF)Li(OPPh2)]4 with BeBr2 in THF-d 8 after heating to 90 °C (from top to bottom).

The direct deprotonation of Ph2P(O)H with BePh2 in THF also results in the formation of 2. However, substantial amounts of diphenylphosphine are formed as well. This is evident from the characteristic 31P and 1H NMR chemical shift of Ph2PH at −40.7 and 5.41 ppm, respectively, as well as of its typical 1 J PH and 3 J PH coupling constants of 215.5 and 7.4 Hz (Figure 8) [28]. The presence of a hydrogen atom directly bound to the phosphorus atom was additionally proven via proton coupled 31P NMR spectroscopy. Considering that Ph2PH is only formed if Ph2P(O)H is used as starting material, we conclude that this is the origin of the hydrogen atom directly bound to the phosphorus atom. However, this is only feasible if Ph2P(O)H is reduced. We assume BeO is formed in this process, since small amounts of colorless precipitate, which is neither soluble in organic solvents nor in water, is formed. However, attempts to verify the presence of BeO via Raman spectroscopy failed [29]. Due to the small amounts of precipitate no further characterization was possible. Therefore, no further insights into the reaction mechanism were obtained.

In an attempt to verify that two THF molecules are coordinated in 2, the solvent from the reaction mixture of BePh2 with Ph2P(O)H in THF was removed in vacuo and C6D6 was added. However, no 9Be NMR signals could be detected in the resulting suspension. The 31P NMR spectrum revealed the presence of 1,1,2,2-tetraphenyl-diphosphine 1-oxide (Ph2PP(O)Ph2, 3), as evident from the characteristic two NMR signals at −23.8 and 33.9 ppm with a 1 J PP coupling of 218.8 Hz [30, 31]. Compound 3 is also formed directly if BePh2 is reacted with Ph2P(O)H in benzene. From this reaction mixture single crystals suitable for X-ray crystallography were obtained.

The diphosphine monoxide 3·C6H6 crystallizes in the triclinic space group P 1 ‾ with one formula unit per unit cell and its solid-state structure is depicted in Figure 9. Compound 3 comprises of two PPh2 subunits, which are connected by a P–P bond. The Ph2PP(O)Ph2 molecule is disordered with a 50% occupancy of the oxygen atom at each phosphorus atom, both of which are tetrahedrally surrounded. The P–P and P–O distances are 2.2047(8) and 1.371(2) Å, respectively, while the P–C separations range from 1.8226(13) to 1.8247(15) Å. The C–P–C angle is 105.21(7)°, the C–P–P angles are 100.68(6)° and 102.70(6)°, the O–P–P angle is 118.62(10)° and the C–P–O angles are 113.72(11)° and 114.12(11)°. These angles are all reasonably close to the ideal tetrahedral angle as would be expected. The interatomic distances and bond angles compare very well to the ones found in the solid-state structure of 3·C7H8 [32].

Figure 9: Molecular structure of Ph2PP(O)Ph2 (3) in the solid state at T = 100 K. Ellipsoids are depicted at the 70% probability level. Hydrogen atoms are omitted for clarity.
Figure 9:

Molecular structure of Ph2PP(O)Ph2 (3) in the solid state at T = 100 K. Ellipsoids are depicted at the 70% probability level. Hydrogen atoms are omitted for clarity.

Based on the observations described above, we deduct the following mechanism for the formation of 3 from diphenylphosphine oxide. Diphenylphosphinous acid is deprotonated by BePh2 under the formation of beryllium bis(diphenylphosphinite). This is stable if an excess Lewis bases like THF is present, as evident from the stability of 2 in THF solutions. However, if no additional electron donor is present or if the coordinated THF is removed, the electron density at the beryllium center is reduced to an extent, that one of the P–O bonds is broken. This results in the formation of highly stable BeO, which is presumably the driving force for the reaction. Additionally, the two phosphorus atoms disproportionate from oxidation state +III into +II and +IV under formation of the P–P bond in 3. This is exemplified in Figure 10 for the generation of 3 from 2.

Figure 10: Hypothesis for the formation of Ph2PP(O)Ph2 (3).
Figure 10:

Hypothesis for the formation of Ph2PP(O)Ph2 (3).

Decomposition of 2 into 3 was also observed when a THF solution of 2, which had been prepared in situ from 1 and BeBr2, was heated to 90 °C. However, in this case two more signal sets (two doublets each) were observed in the 31P NMR spectrum. These are assigned to compound 3 coordinated to Li+ and Be2+ ions, as similar coordination was described to other hard metal ions like Ga3+ [33] and Zr4+ [34]. The presence of lithium and beryllium nuclei in solution was proven via 7Li and 9Be NMR spectroscopy. The fact that lithium and beryllium coordination are present indicates that the salt metathesis reaction between 1 and BeBr2 does not proceed to completion.

3 Conclusions

We could generate the diphenylphosphinites of lithium and beryllium in the form of their THF adducts [(THF)Li(OPPh2)]4 (1) and [(THF)2Be(OPPh2)2] (2). While 1 is stable in solution and the solid state, 2 is only stable in the presence of excess THF. The insolubility of 1 in non-coordinating solvents and the instability of 2 renders their use in FLP chemistry rather limited. The high reactivity of 2, which is presumably induced by the extreme oxophilicity of beryllium, demonstrates the potential of beryllium based FLPs. However, this reactivity needs to be “tamed” through the use of other atoms than oxygen, linking the Lewis acid to the Lewis base, which is currently under investigation.

4 Experimental section

Caution! Beryllium and its compounds are regarded as toxic and carcinogenic. As the biochemical mechanisms that cause beryllium-associated diseases are still unknown [35, 36], special (safety) precautions are strongly advised [37].

4.1 Methods

4.1.1 General experimental techniques

All manipulations were performed under an inert gas atmosphere of argon either by working in a glove box or by using Schlenk techniques. THF and benzene were dried by refluxing over sodium and subsequent distillation under argon. THF-d 8 and C6D6 were dried over Na/K-alloy, while pyridine-d 5 was dried over 3 Å molecular sieves. All NMR solvents were freshly distilled before use and all NMR spectra were recorded in J. Young NMR tubes. Ph2P(O)H and n BuLi (2.5 [M] in hexane) were purchased from ABCR and Aldrich, respectively, and used as received. BeBr2 and BePh2 were prepared according to the literature [38], [39], [40]. Due to the health hazards associated with the beryllium compounds, no mass spectrometry or elemental analysis could be performed on these compounds.

4.1.2 X-ray structure determinations

Suitable single crystals were selected under a stream of pre-dried argon in perfluorinated polyether (Fomblin YR 1800, Solvay Solexis) and mounted using the MiTeGen MicroLoop system at ambient temperature. X-ray diffraction data was collected using the monochromated CuKα (λ = 1.54186 Å) radiation of a STOE StadiVari diffractometer equipped with a Xenocs Microfocus Source and a Dectris Pilatus 300 K Detector. Evaluation, integration and reduction of the diffraction data was carried out using the X-Area software suite [41]. Multi-scan absorption correction was applied with the LANA module of the X-Area software suite. The structures were solved with dual-space methods (Shelxt-2018/2) and refined against F 2 (Shelxl-2018/3) using the ShelXle software package [42], [43], [44]. All atoms were located by Difference Fourier synthesis and non-hydrogen atoms refined anisotropically. Hydrogen atoms were refined using the “riding model” approach with isotropic displacement parameters 1.2 times of that of the carbon atom. For the crystal data and details of the structure determination see Table 1.

Table 1:

Crystal data and details of the structure determination of compounds 1 and 3.

1 3
Empirical formula C64H72Li4O8P4 C24H20OP2·C6H6
Relative molecular mass 1120.85 464.45
Crystal system Tetragonal Triclinic
Space group I 4 ‾ (no. 82) P 1 ‾ (no. 2)
Radiation wavelength λ (Å) 1.54186 1.54186
A (Å) 12.8740(10) 8.1586(3)
B (Å) a 9.0694(3)
C (Å) 17.9970(4) 9.3578(4)
α (°) 90 84.246(4)
β (°) 90 65.050(2)
γ (°) 90 72.917(3)
V (Å3) 2982.82(8) 599.88(4)
Z 2 1
F(000)/ e 1184.0 244.0
ρ calcd. (g cm−3) 1.25 1.29
µ (mm−1) 1.6 1.8
θ range (°) 4.22–75.77 5.10–75.97
Range of Miller indices hkl −11 ≤ h ≤ 16 −7 ≤ h ≤ 10
−16 ≤ k ≤ 15 −7 ≤ k ≤ 11
−22 ≤ l ≤ 21 −11 ≤ l ≤ 11
Reflections collected; unique 28314; 3026 11014; 2433
Restraints; parameters 0; 183 0; 155
R int 0.016 0.018
R1 (I > 2σ(I)) 0.021 0.038
R1 (all data) 0.021 0.040
wR2 (I > 2σ(I)) 0.056 0.094
wR2 (all data) 0.056 0.095
S (GoF) 1.078 1.034
Δρ min; Δρ max (e·Å−3) −0.17; 0.19 −0.31; 0.47
Volume fraction of the inversion twin component 0.086(17) –

CCDC 2098818 (1) and 2098819 (3) contain the supplementary crystallographic data for this paper. This data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

4.1.3 NMR spectroscopy

1H, 7Li, 9Be, 13C, and 31P NMR spectra were recorded on Bruker Avance III HD300 and Avance III AV500 spectrometers. The latter was equipped with a Prodigy Cryo-Probe. 1H (300/500 MHz) and 13C (76/126 MHz) NMR chemical shifts are given relative to the solvent signal for C6D6 (7.16 and 128.1 ppm), THF-d 8 (1.73/3.58 and 25.4/67.6 ppm) and pyridine-d 5 (7.22/7.58/8.74 and 123.9/135.9/150.4 ppm). 7Li (194 MHz), 9Be (42 MHz) and 31P (122 and 202 MHz) NMR used 9.7 [M] LiCl or 0.43 [M] BeSO4 in D2O and 85% H3PO4 as an external standard, respectively. NMR spectra were processed with the MestReNova software package [45].

4.1.4 IR spectroscopy

IR spectra were recorded on a Bruker alpha FTIR spectrometer equipped with a diamond ATR unit in an argon-filled glovebox. Processing of the spectra was performed with the Opus [46] software package and OriginPro 2017 [47].

4.1.5 Raman spectroscopy

The Raman spectra were recorded on a S&I Confocal Raman Microscope MonoVista CRS+ at ambient temperature. The Raman spectrometer was equipped with four laser diodes with excitation lines of 488, 532, 633 and 785 nm.

4.2 Synthesis and characterization

4.2.1 [(THF)Li(OPPh2)]4 (1)

In a Schlenk flask 500 mg (2.47 mmol, 1 eq.) diphenylphosphine oxide was dissolved in approximately 3 mL of THF and cooled to 0 °C. To this solution 981 μL (2.45 mmol, 1 eq.) of 2.5 m n-butyl lithium in hexane was added and the orange solution was stirred overnight. The solvent was removed in vacuo and the residue was washed with 5 mL of n-pentane. After drying under reduced pressure 419 mg (2.01 mmol, 81%) of [(THF)Li(OPPh2)]4 were received as an orange solid. Single crystals suitable for X-ray crystallography were obtained from an oversaturated THF solution at ambient temperature. – 1H NMR (500 MHz, pyridine-d 5): δ = 1.57–1.68 (m, 4H, CH 2), 3.62–3.72 (m, 4H, CH 2), 7.14 (t, J = 7.4, 2H, H Ph), 7.21 (t, J = 7.3, 4H, H Ph), 7.94 (t, J = 6.5, 4H, H Ph). – 1H NMR (500 MHz, THF-d 8): δ = 7.01 (t, J = 7.2, 2H, H Ph), 7.12 (t, J = 7.4, 4H, H Ph), 7.52 (t, J = 6.1, 4H, H Ph). – 7Li{1H} NMR (194 MHz, pyridine-d 5): δ = 2.6 (s, ω 1/2 = 3.7 Hz). – 7Li{1H} NMR (194 MHz, THF-d 8): δ = 0.2 (s, ω 1/2 = 11.6 Hz). – 13C{1H} NMR (126 MHz, pyridine-d 5): δ = 26.3 (s, CH2), 68.3 (s, CH2), 127.0 (s, C Ph), 128.1 (d, 3 J PC = 5.7, C Ph), 130.1 (d, 2 J PC = 19.4, C Ph), 156.3 (d, 1 J PC = 33.1, C Ph). – 13C{1H} NMR (126 MHz, THF-d 8): δ = 126.8 (s, C Ph), 127.8 (s, C Ph), 129.8 (d, 2 J PC = 20.9, C Ph), 156.7 (d, 1 J PC = 37.4, C Ph). – 31P{1H} NMR (202 MHz, pyridine-d 5): δ = 86.4 (s). – 31P{1H} NMR (202 MHz, THF-d 8): δ = 85.5 (s). – IR (cm−1): 3050 (br, w), 2979 (br, w), 2880 (br, w), 1595 (w), 1474 (m), 1433 (m), 1293 (w), 1095 (m), 1036 (s), 914 (s), 739 (s), 692 (s), 523 (s). – Elemental analysis for C64H72Li4O8P4 (1120.92 g mol−1): calculated: C 68.58, H 6.47; found C 68.32, H 6.58%.

4.2.2 [(THF)2Be(OPPh2)2] (2)

Method 1: A J. Young NMR tube was charged with 4.2 mg (0.025 mmol, 2 eq.) BeBr2 and 14.0 mg (0.013 mmol, 1 eq.) of [(THF)Li(OPPh2)]4 and subsequently 500 μL of THF-d8 was added. The received suspension was sonicated for several hours before NMR spectra were recorded.

Method 2: A J. Young NMR tube was charged with 4.1 mg (0.025 mmol, 1 eq.) BePh2 and 10.1 mg (0.050 mmol, 2 eq.) of diphenylphosphine oxide and subsequently 500 μL of THF-d 8 was added. The received suspension was sonicated for several hours before NMR spectra were recorded. – 1H NMR (300 MHz, THF-d 8): δ = 6.94–7.19 (m, 6H, H Ph), 7.33–7.43 (m, 6H, H Ph), 7.46–7.58 (m, 4H, H Ph), 7.66–7.83 (m, 4H, H Ph). – 9Be NMR (42 MHz, THF-d 8): δ = 2.2 (s, ω 1/2 = 48.4 Hz). – 13C NMR (126 MHz, THF): δ = 127.2 (bs, C Ph), 128.1 (bs, C Ph), 129.5 (bs, C Ph), 133.6 (bs, C Ph). – 31P NMR (122 MHz, THF-d 8): δ = 83.4.

4.2.3 Ph2PP(O)Ph2 (3)

Method 1: Heating of a THF solution of a (THF)2Be(OPPh2)2 (prepared according to method 1) results in the formation of Ph2PP(O)Ph2.

Method 2: Removal of the solvent from a THF solution of (THF)2Be(OPPh2)2 (prepared according to method 2) and re-dissolving the residue in C6D6 leads to the formation of Ph2PP(O)Ph2.

Method 3: A J. Young NMR tube was charged with 4.1 mg (0.025 mmol, 1 eq.) BePh2 and 10.1 mg (0.050 mmol, 2 eq.) of diphenylphosphine oxide and subsequently 500 μL of C6D6 was added. From this reaction mixture single crystals suitable for X-ray crystallography were obtained at ambient temperature. – 1H NMR (300 MHz, C6D6): δ = 7.11–7.38 (m, 13H, H Ph), 7.52–7.65 (m, 1H), 7.90–8.03 (m, 2H, H Ph), 8.06–8.14 (m, 2H, H Ph), 8.17–8.35 (m, 2H, H Ph). – 31P NMR (122 MHz, C6D6): δ = −23.8 (d, 1 J PP = 218.8 Hz), 33.8 (d, 1 J PP = 218.8 Hz). – Raman (cm−1): 3057 (s), 2294 (s), 2268 (m), 1591 (m), 1003 (s), 951 (s).

Dedicated to: Professor Richard Dronskowski of the RWTH Aachen on the Occasion of his 60th Birthday.

Corresponding author: Magnus R. Buchner, Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany, E-mail:

Funding source: DFG

Award Identifier / Grant number: BU2725/8-1

Acknowledgments

M. R. B. thanks Prof. F. Kraus for moral and financial support as well as the provision of laboratory space.

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: The DFG is gratefully acknowledged for financial support (BU2725/8-1).

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.

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Received: 2021-07-29
Accepted: 2021-08-18
Published Online: 2021-09-29
Published in Print: 2021-11-25

© 2021 Walter de Gruyter GmbH, Berlin/Boston

Articles in the same Issue

  1. Frontmatter
  2. In this issue
  3. Laudatio/Preface
  4. Celebrating the 60th birthday of Richard Dronskowski
  5. Review
  6. Orbital-selective electronic excitation in phase-change memory materials: a brief review
  7. Research Articles
  8. Solving the puzzle of the dielectric nature of tantalum oxynitride perovskites
  9. d- and s-orbital populations in the d block: unbound atoms in physical vacuum versus chemical elements in condensed matter. A Dronskowski-population analysis
  10. Single-crystal structures of A 2SiF6 (A = Tl, Rb, Cs), a better structure model for Tl3[SiF6]F, and its novel tetragonal polymorph
  11. Na2La4(NH2)14·NH3, a lanthanum-rich intermediate in the ammonothermal synthesis of LaN and the effect of ammonia loss on the crystal structure
  12. Linarite from Cap Garonne
  13. Salts of octabismuth(2+) polycations crystallized from Lewis-acidic ionic liquids
  14. High-temperature diffraction experiments and phase diagram of ZrO2 and ZrSiO4
  15. Thermal conversion of the hydrous aluminosilicate LiAlSiO3(OH)2 into γ-eucryptite
  16. Crystal structure of mechanochemically prepared Ag2FeGeS4
  17. Effect of nanostructured Al2O3 on poly(ethylene oxide)-based solid polymer electrolytes
  18. Sr7N2Sn3: a layered antiperovskite-type nitride stannide containing zigzag chains of Sn4 polyanions
  19. Exploring the frontier between polar intermetallics and Zintl phases for the examples of the prolific ALnTnTe3-type alkali metal (A) lanthanide (Ln) late transition metal (Tn) tellurides
  20. Zwitterion coordination to configurationally flexible d 10 cations: synthesis and characterization of tetrakis(betaine) complexes of divalent Zn, Cd, and Hg
  21. An approach towards the synthesis of lithium and beryllium diphenylphosphinites
  22. Synthesis, crystal and electronic structure of CaNi2Al8
  23. Crystal and electronic structure of the new ternary phosphide Ho5Pd19P12
  24. Synthesis, structure, and magnetic properties of the quaternary oxysulfides Ln 5V3O7S6 (Ln = La, Ce)
  25. Synthesis, crystal and electronic structure of BaLi2Cd2Ge2
  26. Structural variations of trinitrato(terpyridine)lanthanoid complexes
  27. Preparation of CoGe2-type NiSn2 at 10 GPa
  28. Controlled exposure of CuO thin films through corrosion-protecting, ALD-deposited TiO2 overlayers
  29. Experimental and computational investigations of TiIrB: a new ternary boride with Ti1+x Rh2−x+y Ir3−y B3-type structure
  30. Synthesis and crystal structure of the lanthanum cyanurate complex La[H2N3C3O3]3 · 8.5 H2O
  31. Cd additive effect on self-flux growth of Cs-intercalated NbS2 superconducting single crystals
  32. 14N, 13C, and 119Sn solid-state NMR characterization of tin(II) carbodiimide Sn(NCN)
  33. Superexchange interactions in AgMF4 (M = Co, Ni, Cu) polymorphs
  34. Copper(I) iodide-based organic–inorganic hybrid compounds as phosphor materials
  35. On iodido bismuthates, bismuth complexes and polyiodides with bismuth in the system BiI3/18-crown-6/I2
  36. Synthesis, crystal structure and selected properties of K2[Ni(dien)2]{[Ni(dien)]2Ta6O19}·11 H2O
  37. First low-spin carbodiimide, Fe2(NCN)3, predicted from first-principles investigations
  38. A novel ternary bismuthide, NaMgBi: crystal and electronic structure and electrical properties
  39. Magnetic properties of 1D spin systems with compositional disorder of three-spin structural units
  40. Amine-based synthesis of Fe3C nanomaterials: mechanism and impact of synthetic conditions
  41. Enhanced phosphorescence of Pd(II) and Pt(II) complexes adsorbed onto Laponite for optical sensing of triplet molecular dioxygen in water
  42. Theoretical investigations of hydrogen absorption in the A15 intermetallics Ti3Sb and Ti3Ir
  43. Assembly of cobalt-p-sulfonatothiacalix[4]arene frameworks with phosphate, phosphite and phenylphosphonate ligands
  44. Chiral bis(pyrazolyl)methane copper(I) complexes and their application in nitrene transfer reactions
  45. UoC-6: a first MOF based on a perfluorinated trimesate ligand
  46. PbCN2 – an elucidation of its modifications and morphologies
  47. Flux synthesis, crystal structure and electronic properties of the layered rare earth metal boride silicide Er3Si5–x B. An example of a boron/silicon-ordered structure derived from the AlB2 structure type
https://doi.org/10.1515/znb-2021-0104
Keywords for this article
beryllium; coordination chemistry; frustrated Lewis pair; lithium; phosphinous acid

Articles in the same Issue

  1. Frontmatter
  2. In this issue
  3. Laudatio/Preface
  4. Celebrating the 60th birthday of Richard Dronskowski
  5. Review
  6. Orbital-selective electronic excitation in phase-change memory materials: a brief review
  7. Research Articles
  8. Solving the puzzle of the dielectric nature of tantalum oxynitride perovskites
  9. d- and s-orbital populations in the d block: unbound atoms in physical vacuum versus chemical elements in condensed matter. A Dronskowski-population analysis
  10. Single-crystal structures of A 2SiF6 (A = Tl, Rb, Cs), a better structure model for Tl3[SiF6]F, and its novel tetragonal polymorph
  11. Na2La4(NH2)14·NH3, a lanthanum-rich intermediate in the ammonothermal synthesis of LaN and the effect of ammonia loss on the crystal structure
  12. Linarite from Cap Garonne
  13. Salts of octabismuth(2+) polycations crystallized from Lewis-acidic ionic liquids
  14. High-temperature diffraction experiments and phase diagram of ZrO2 and ZrSiO4
  15. Thermal conversion of the hydrous aluminosilicate LiAlSiO3(OH)2 into γ-eucryptite
  16. Crystal structure of mechanochemically prepared Ag2FeGeS4
  17. Effect of nanostructured Al2O3 on poly(ethylene oxide)-based solid polymer electrolytes
  18. Sr7N2Sn3: a layered antiperovskite-type nitride stannide containing zigzag chains of Sn4 polyanions
  19. Exploring the frontier between polar intermetallics and Zintl phases for the examples of the prolific ALnTnTe3-type alkali metal (A) lanthanide (Ln) late transition metal (Tn) tellurides
  20. Zwitterion coordination to configurationally flexible d 10 cations: synthesis and characterization of tetrakis(betaine) complexes of divalent Zn, Cd, and Hg
  21. An approach towards the synthesis of lithium and beryllium diphenylphosphinites
  22. Synthesis, crystal and electronic structure of CaNi2Al8
  23. Crystal and electronic structure of the new ternary phosphide Ho5Pd19P12
  24. Synthesis, structure, and magnetic properties of the quaternary oxysulfides Ln 5V3O7S6 (Ln = La, Ce)
  25. Synthesis, crystal and electronic structure of BaLi2Cd2Ge2
  26. Structural variations of trinitrato(terpyridine)lanthanoid complexes
  27. Preparation of CoGe2-type NiSn2 at 10 GPa
  28. Controlled exposure of CuO thin films through corrosion-protecting, ALD-deposited TiO2 overlayers
  29. Experimental and computational investigations of TiIrB: a new ternary boride with Ti1+x Rh2−x+y Ir3−y B3-type structure
  30. Synthesis and crystal structure of the lanthanum cyanurate complex La[H2N3C3O3]3 · 8.5 H2O
  31. Cd additive effect on self-flux growth of Cs-intercalated NbS2 superconducting single crystals
  32. 14N, 13C, and 119Sn solid-state NMR characterization of tin(II) carbodiimide Sn(NCN)
  33. Superexchange interactions in AgMF4 (M = Co, Ni, Cu) polymorphs
  34. Copper(I) iodide-based organic–inorganic hybrid compounds as phosphor materials
  35. On iodido bismuthates, bismuth complexes and polyiodides with bismuth in the system BiI3/18-crown-6/I2
  36. Synthesis, crystal structure and selected properties of K2[Ni(dien)2]{[Ni(dien)]2Ta6O19}·11 H2O
  37. First low-spin carbodiimide, Fe2(NCN)3, predicted from first-principles investigations
  38. A novel ternary bismuthide, NaMgBi: crystal and electronic structure and electrical properties
  39. Magnetic properties of 1D spin systems with compositional disorder of three-spin structural units
  40. Amine-based synthesis of Fe3C nanomaterials: mechanism and impact of synthetic conditions
  41. Enhanced phosphorescence of Pd(II) and Pt(II) complexes adsorbed onto Laponite for optical sensing of triplet molecular dioxygen in water
  42. Theoretical investigations of hydrogen absorption in the A15 intermetallics Ti3Sb and Ti3Ir
  43. Assembly of cobalt-p-sulfonatothiacalix[4]arene frameworks with phosphate, phosphite and phenylphosphonate ligands
  44. Chiral bis(pyrazolyl)methane copper(I) complexes and their application in nitrene transfer reactions
  45. UoC-6: a first MOF based on a perfluorinated trimesate ligand
  46. PbCN2 – an elucidation of its modifications and morphologies
  47. Flux synthesis, crystal structure and electronic properties of the layered rare earth metal boride silicide Er3Si5–x B. An example of a boron/silicon-ordered structure derived from the AlB2 structure type
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