Solution 31P and 113Cd NMR studies of phosphine adducts of monomeric cadmium (bisphenoxide) complexes and the solid-state structures of (2,6-di-tert-butylphenoxide)2Cd(PCy3) and (2,6-di-tert-butylphenoxide)2Cd(PMe3)2

Monomeric phosphine derivatives of cadmium phenoxides, (phenoxide)(2)CdLn, where the phenoxide ligands contain sterically demanding substituents in the 2,6-positions (2,6-di-tert-butylphenoxide and 2,6-diphenylphenoxide) are described. These derivatives were synthesized from the reaction of Cd[N(SiMe3)(2)](2) and the corresponding phenol followed by the addition of the phosphine. For the large PCy3 ligand (Tolman's cone angle (theta) = 170 degrees) n = 1, whereas for the smaller Me3P (theta = 118 degrees) and n-Bu3P (theta = 132 degrees) ligands both mono- and bis(phosphine) derivatives (n = 1 and 2) were prepared. The (2,6-di-tert-butylphenoxide)(2)Cd(PCy3) and (2,6-di-terr-butylphenoxide)(2)Cd(PMe3)(2) were characterized in the solid-state by X-ray crystallography. The structure of the monophosphine adduct of PCy3 consists of a near trigonal planar geometry about the cadmium center, where the average P-Cd-O angle of 131.4 degrees is larger than the O-Cd-O angle of 96.72 degrees with a Cd-P bond length of 2.5247(12) Angstrom. On the other hand, the bis(phosphine) adduct, Cd(O-2,6-(BuC6H3)-Bu-t-C-2)(2)(PMe3)(2) is a distorted tetrahedral structure with O-Cd-O and P-Cd-P bond angles of 116.7(6)degrees and 104.3(2)degrees, respectively. The average Cd-P bond length in this derivative was determined to be 2.737[5] Angstrom. The monotricyclohexylphosphine derivatives of these cadmium bisphenoxides were shown by P-31 NMR spectroscopy not to be undergoing facile exchange with free phosphine in solution at ambient temperature. On the contrary, the corresponding Me3P and n-Bu3P analogues readily undergo self-exchange with free phosphine in solution via a rapid equilibrium between monophosphine adduct plus free phosphine and the bis(phosphine) adduct. The Cd-113 chemical shifts in the CdO2P moieties shift downfield and the Cd-113-P-31 coupling constants decrease by about 900 Hz upon binding an additional phosphine ligand.