TRANSITION-METAL STANNYL COMPLEXES .3. METAL, HYDROGEN, TIN 3-CENTER BONDING IN GROUP-VI HYDRIDO STANNYL COMPLEXES

The hydrido stannyl complex (pi-1,3,5-Me3C6H3)(CO)2Cr(H)-SnPh3 (1) is prepared by photochemical reaction of (pi-1,3,5-Me3C6H3)(CO)3Cr with HSnPh3. The (SnHCr)-Sn-119 coupling constant (327.6 Hz) and an X-ray structure analysis [Sn-H 202(4), Cr-H 159(4), Cr-Sn 270.16(6) pm] show that the Sn-H bond is coordinated in an eta-2 fashion. The complexes (CO)4(R3P)W(H)SnPh3 (R3P = Ph3P, MePh2P) (2) and (CO)3(dppe)M(H)-SnR3 (M = Cr, SnR3 = SnPh3; M = Mo, SnR3 = SnMe3, SnPh3; M = W, SnR3 = SnMe3, SnPh2Me, SnPh3) (4-6) are obtained either by thermal reaction of (CO)4(R3P)W(THF) or (CO)3(dppe)ML (L = THF, acetone) with HSiR3, or by photochemical reaction of (CO)4(dppe)M with HSnPh3. Reaction of (CO)4(Ph3P)W(THF) with HSnMe3 yields (CO)4(Ph3P)W(SnMe3)2 (3). The Sn,M,H coupling constants in the complexes 2 and (CO)3(dppe)M(H)SnR3 (M = Cr, Mo) are in the range of 250-315 Hz and therefore these complexes seem to contain an eta-2-coordinated stannane. Contrary to this, the SnWH coupling constants in (CO)3(dppe)W(H)SnR3 are considerably lower (70-90 Hz), suggesting complete oxidative addition of the H-Sn bond. The complexes (CO)3(dppe)M(H)SnPh3 decompose in benzene solution at room temperature to give, inter alia, hexaphenyldistannane. Ph6Sn2 . 2 C6H6 crystallizes in the space group R3BAR (Z = 1); in the crystal lattice the benzene molecules are perpendicular to the three-fold axis of symmetry of the distannane molecule.