Structure and reactivity of titanium-platinum and -palladium heterobinuclear complexes with .mu.-methylene ligands

A series of titanium/platinum and palladium heterobinuclear {mu}-methylene complexes Cp{sub 2} TiCH{sub 2}MX(Me)L has been prepared: M = Pt, X = Cl, L = PMe{sub 3} (2b), PMe{sub 2}Ph (2c), PMePh{sub 2} (2d); M = Pt, X = Me, L = PMe{sub 2}Ph (2e, 2f); M = Pd, X = Cl, L = PMe{sub 3} (2g). The {mu}-CH{sub 2}/{mu}-Cl complex 2c crystallizes in the monoclinic system in space group P2{sub 1}/n (No. 14), with a = 13.249 (3) {angstrom}, b = 11.646 (3) {angstrom}, c = 14.542 (5) {angstrom}, {beta} = 114.45 (2){degree}, V = 2042.6 (10) {angstrom}{sup 3}, Z = 4, and density = 1.87 g cm{sup {minus}3}. The {mu}-CH{sub 2}/{mu}-CH{sub 3} analogue 2e is isostructural to 2c and also crystallizes in space group P2{sub 1}/n (No. 14) with a = 13.333 (4) {angstrom}, b = 11.686 (2) {angstrom}, c = 14.351 (2) {angstrom}, {beta} = 115.03 (2){degree}, V = 2026.0 (8) {angstrom}{sup 3}, Z = 4, and density = 1.82 g cm{sup {minus}3}. structural studies indicate the following: (1) the Ti-CH{sub 2} bond possesses residual double-bond character, (2) there is a dative Pt {yields} Ti interaction, which may be regarded as {pi} back-donation from the platinum atom to the Ti{double bond}CH{sub 2} group, and (3) the {mu}-CH{sub 3} group in 2e is bound to the titanium atom through a three-center, two-electron agostic bond. Complexes 2c and 2d react with tertiary phosphines to give Cp{sub 2}(Cl)TiCH{sub 2}Pt(Me)L{sub 2} species, which form {mu}-(C,O)-ketene complexes Cp{sub 2}(Cl)TiOC({double bond}CH{sub 2})Pt(Me)L{sub 2} upon carbonylation. The palladium complex 2g undergoes a reductive elimination reaction to give Cp{sub 2}Ti(Et)Cl and Pd{sup 0}PMe{sub 3} complexes. 31 refs., 3 figs., 5 tabs.