Probing the bonding of phosphines and phosphites to platinum by NMR. Correlations of (1)J(PtP) and Hammett substituent constants for phosphites and phosphines coordinated to platinum(II) and platinum(0)

The values of (1)J(PtP) have been measured for the platinum(II) complexes cis-[PtCl2L2] and cis-[PtMeCiL(2)] and the platinum(0) complexes [PtL(norbornene)(2)] and [PtL2(norbornene)] where L=P(C(6)H(4)Z-4)(3) and [PtL2(norbornene)], [PtL3] and [PtL4] where L=P(OC(6)H(4)Z-4), and Z=NMe2, OMe, Me, H, Cl, CF3. When (1)J(PtP) is plotted against the Hammett substituent constant two distinct trends emerge: for platinum(II) the more electron-withdrawing the substituent the smaller the LJ(PtP), while for platinum(0) the more electron-withdrawing the substituent the larger the (1)J(PtP). These observations are rationalized in terms of the sigma and pi-bonding components of the platinum-phosphorus bonds. (C) 1997 Elsevier Science S.A.