Spectroscopic and crystallographic characterisation of cadmium complexes incorporating a bidentate phosphine ligand

Abstract

The 1∶1 stoichiometric addition of the bidentate phosphine ligand 2,2-dimethyl-2-sila-1,3-bis(diphenylphosphino)propane (L2) to a range of cadmium(II) salts produced a series of moisture-sensitive complexes of general formula [CdX2(L2)] (X = Cl 1, Br, I, SCN or NO3). These complexes have been investigated by vibrational and multinuclear (31P and 113Cd) NMR spectroscopy and by X-ray crystallography. Complex 1 crystallises in the orthorhombic space group P212121, with a = 9.2862(10), b = 15.386(2), c = 20.724(3) Å, U = 2960.9(6) Å3 and Z = 4. The metal centre exhibits four-co-ordinate, tetrahedral geometry, with the ligand bound in a bidentate manner. Both the solution- and solid-state cross-polarisation magic angle spinning 31P NMR spectra of the complexes show clearly resolved 113Cd–31P and 111Cd–31P one bond couplings in a 113Cd∶111Cd ratio of 1.044∶1.046 as expected. Vibrational spectroscopy indicates that each complex is mononuclear, with no evidence for bridging species; [Cd(NO3)2(L2)] features monodentate nitrate groups. The addition of 2 equivalents of the ligand to cadmium perchlorate yields a complex which has been established as [Cd(L2)2][ClO4]2 by spectroscopic and conductance studies.