Interactions of cis-P2PtX2 Complexes (X = H, Me) with Bis(pentamethylcyclopentadienyl)ytterbium

Abstract

The interactions formed in solution between the bent lanthanide metallocene Cp{sup *}{sub 2}Yb (1) and cis-P{sub 2}PtX{sub 2} complexes (P{sub 2} = a chelating phosphine; X = H, CH{sub 3}) have been investigated using NMR spectroscopy. We have found that 1 forms interactions of significant strength with cis dihydride complexes of platinum(II). The nature of this interaction is not affected by a change in the P-Pt-P bite angle, a somewhat surprising result. While intermolecular exchange can be stopped only at very low temperature for the dimethyl platinum derivative 9, the solid-state structure of this adduct shows a rare agostic bonding mode for the bridging methyl groups. The methyl hydride derivative, 11, undergoes slow exchange in solution at 25{degree}C and, in contrast to 9, shows a Pt-C-Yb bonding mode in the solid state. The solution-state Yb-methyl interaction likely arises mainly as a result of the strong Yb-hydride interaction holding the Yb center near the methyl group (i.e., it results from conformational constraints) and appears to involve both Yb-C and C-H- -Yb interactions, although the exact nature of this interaction cannot be unequivocally determined from the solution-state data. 63 refs., 9 figs., 10 tabs.