31P and 195Pt NMR characteristics of new binuclear complexes of [Pt 2X 4](PR 3) 2] cis/trans isomers and of mononuclear analogs

Abstract

The 31P and 195Pt chemical shifts are reported for the first time for complexes of binuclear platinum(II) of the type [Pt 2(μ-X) 2(X) 2(PR 3) 2]. These were identified as intermediate from the reaction of the [PtX 2COD)] complex with different tertiary phosphines (where X may be Cl or I and PR 3 may be PBz 3, PCy 3, PCyPh 2, PCy 2Ph or PPh 2C 6F 5). In addition, cis and trans-[PtX 2(PR 3) 2] were produced in the final step, and their 31P and 195Pt are also described (X = Cl or I; PR 3 = PBz 3, PCy 3, PPhCy 2, PPh 2Cy, PPh 2 iPr, PPh 2C 6F 5, PPh 3, P( m-tolyl) 3, P( p-tolyl) 3, PBu 3, PPhMe 2, PPh 2Me, (bis-1,2-Ph 2P)- C 6H 4, Ph 2PCH 2PPh 2 or Ph 2PCH 2CH 2PPh 2). The platinum-195 chemical shift is shown to be relatively sensitive to the nature of complex geometry. The unsymmetrical (unsym.) cis isomer absorbs at a lower frequency (upfield) than the symmetrical (sym.) trans isomer and in a somewhat higher platinum chemical shift than in the equivalent terminal complexes [PtX 2(PR 3) 2], The 1 J(Pt-P) couplings are consistent and related to the cone-angle data of the ligand and the 1 J value of sym. trans form is 1.26 times that for the unsym, cis form and shows some solvent dependency. Interestingly, two isomers of the unsym. cis dimer were identified, and then one of the isomers isomerized to the sym. trans dimer. The nature of the reaction intermediate and products was found to be very dependent on both the reactants and conditions.