Nuclear magnetic resonance spectroscopic characterisation and the crystal and molecular structures of Ph₃PSe·AlCl₃and Ph₃PSe·AlCl₃: a classification of the co-ordinative bonding modes of the phosphine chalcogenides

Abstract

A series of compounds with the general formula R,PE*AICI, (R = Ph or NMe,, E = S or Se) has been examined by n.m.r. spectroscopy as a contribution toward the characterisation of the P-E bond and of the co-ordinate bond. Two derivatives, Ph,PS=AICI, and Ph,PSe*AICI,, have been studied by X-ray crystallography. [Crystal data: C,8H15AIC13PS, monoclinic, space group, P2,/n, a = 9.710(2), b = 9.464(1), c = 21.893(5) A, p = 95.15(2)", Z = 4, R = 0.042; C,,H,,AICI,PSe, triclinic, space group, P i , a = 8.967(2), b = 12.626(4), c = 18.242(4) A, a = 84.83(2), p = 89.02(2), y = 85.67(2)", Z = 4, R = 0.044.1 In hontrast to the oxygen analogues, the sulphur and selenium derivatives exhibit bent geometries [P-S-AI 109.62(8), P-Se-A1 (mean) = 107.0(1 )"I. The structures are maintained in solution, as demonstrated by the 27AI n.m.r. spectra. The 31P and 13C n.m.r. spectra are informative of the changes associated with adduct formation, and show the oxygen derivatives (E = 0) to be unique. Disruption of the P-E formation is more dramatic for the sulphur and selenium than for the oxygen derivatives. The extensive information available in the literature is re-evaluated in the light of the present results, and a classification for the co-ordinative bonding modes of the phosphine chalcogenides is proposed.interaction due to adduct Spectroscopic and structural studies on complexes of phosphine chalcogenides (R3PE; E = 0, S, or Se) have played an important role in the development of a model for the phosphoryl bond.' Nevertheless, the phosphoryl systems continue to attract attention and the nature of the P-E bond is a point of much discussion by theoreticians' and experi-mentalist~.~-' We have recently discovered that aluminium halide (AlCl, and AlBr,) adducts of phosphine oxides adopt a rare linear P-0-A1 geometry in both the solid state and in solution.6 Here we report a comparative investigation of the sulphide and selenide analogues and show them to be severely bent in the solid state. Moreover, the n.m.r. data are consistent with a bent structure in solution. The unique behaviour of the phosphine oxides is supported by extensive information available in the literature,6 and is further emphasised by the new data, culminating in a proposal for a classification of complexes of the type R,PE.M (M = Lewis acid, e.g. AlC13, BF3, or transition-metal complex). ExperimentalGeneral Procedures.-The compounds Ph3PS (Pflatz and Bauer) and Ph3PSe (Aldrich) were obtained commercially and used without purification; (Me,N),PS was prepared by reaction of (Me,N),P with S8 in Et,O at 0°C. Anhydrous aluminium chloride (Aldrich) was sublimed under vacuum. Dichloromethane was dried over P,O, and CaH,, carbon disulphide over CaH,, and these were stored in evacuated bulbs. Solids were manipulated in a Vacuum/Atmospheres nitrogenfilled glove-box. Infrared spectra were recorded as Nujol mulls on CsI plates using a Perkin-Elmer 283B spectrophotometer and n.m.r. spectra on a Nicolet NT-360 spectrometer in CH,C12. Chemical shifts are reported in p.p.m. relativ...

Tris(dialkylamino)phosphine Chalcogenide Complexes of Tin(IV) Chloride: A Multinuclear (31P,77Se, and119Sn) NMR Characterization

“…10,12,28,29 Interestingly, the P-E distance is identical to that obtained by the crystal structure for related complexes. 10,28 In complex 1, the coordination mode is confirmed by a lengthening (0.1 Å) of the P Se bond compared with that of the free ligand (2.111 Å) calculated at the same level of theory. This lengthening is consistent with the low stretching frequency observed in the IR spectra and also explains the differences observed in the 1 J PSe coupling constant and in the 31 P NMR chemical shifts between the free and bound ligands in solution.…”

“…The comparable changes in geometry have also been observed in related complexes. 28,30,31 In addition, the large solution 77 Se NMR shift toward higher frequency for 1 and 2 could be explained by the decrease in the calculated Mulliken charge and/or the change in the geometry at the Se atom in the complex as compared with the free ligand (Table 3).…”

Uncommon Coordination Behaviour of P(S) and P(Se) Units when Bonded to Carboranyl Clusters: Experimental and Computational Studies on the Oxidation of Carboranyl Phosphine Ligands

“…Three P=E bond resonance structures (Figure 8) are proposed in the literature. [24,34,35] Calculations of the natural hybrid orbitals (NHOs) of the P=E (E= S, Se) bonds in 9 and 15 yielded the following composition: s PS = 0.7097(sp …”

Structure of the ambient temperature alkali metal molten salt AlCl3/LiSCN

“…The peak at 1.9 Å, assigned to the Al-N bond distance, indicates that the thiocyanate anion is coordinated to the AlCl 3 molecule through the N instead of the S. Atwood et al 15,16 investigated a series of adducts made of Al͑CH 3 ͒ 3 and the thiocyanate ion and they concluded that the Al͑CH 3 ͒ 3 molecule coordinates to the N end with an Al-N bond distance around 1.94 Å. The Al-S bond distances reported in the literature 17,18 are longer ͑about 2.32 Å͒. These observations are in accord with the concept of hard and soft acids and bases ͑HSAB͒.…”