CHEMISTRY OF DINUCLEAR FULVALENE COMPLEXES - DIHYDRIDES, ZWITTERIONS,AND RING-SLIPPAGE COMPLEXES DERIVED FROM FVM2(CO)6 (M=MO, W)

Reduction of the metal-metal-bonded complex FvW2(CO)6 generated the di anion FvW2(CO)62-. An X-ray crystallographic analysis of [Et4N+]2[FvW2 (CO)6]2- (monoclinic space group P2(1)/c, a = 7.687(2) angstrom, b = 1 3.752(4) angstrom, c = 16.297(5) angstrom, beta = 94.80(2)-degrees, V = 1716.8(8) angstrom3, Z = 4) showed the dianion to contain a planar F v ring system bonded to the two metal centers in an anti fashion. The dianion reacted with a number of electrophiles to yield the neutral sp ecies FVW2(CO)6E2 (E = H, Me, Et, sigma-C3H5, CH2Ph). The pK(a) values for the two consecutive deproteinations of FvW2(CO)rH2 were determine d as 14.0 and 16.6 by equilibrium measurements in acetonitrile. Thermo lysis and photolysis of FvW2(CO)6H2 yielded FvW2(CO)6 and H-2. Unlike Cp2W2(CO)6, FvW2(CO)6 underwent protonation at the W-W bond by HBF4-Et 2O in acetonitrile. Reactions of FvW2(CO)6 and FvMo2(CO)6 with PMe3 an d Me2PCH2PMe2 (dmpm) resulted in generation of the dinuclear zwitterio ns FvM2(CO)5(PMe3)2 and FvM2(CO)5)(dmpm), respectively. An X-ray cryst allographic analysis of FvMo2(CO)5 (orthorhombic space group P2(1)2(1) 2(1), a = 9.1049(8) angstrom, b = 12.2598(14) angstrom, c = 20.1606(18 ) angstrom, V = 2250.4(7) angstrom3, Z = 4) showed an anti coordinatio n of the MO(CO)3- and Mo(CO)2(dmpm)+ moieties at a planar Fv ligand. E lectrophiles added at the anionic part of the zwitterions, whereas LiA lH4 effected reduction of coordinated CO to CH3 at the cationic center of FvMo2(CO)5(PMe3)2. Excess PMe3 caused the conversion of FvMo2(CO)5 (PMe3)2 and FvMo2(CO)5)(dmpm) to Mo(CO)3(PMe3)3 along with FvMo(CO)2(P Me3)2 and FvMo(CO)2(dmpm), respectively. These reactions constitute th e first ring-slippage reactions that have been observed in fulvalene m etal complexes. When treated with Mo(CO)3(NCMe)3, FvMo(CO)2(PMe3)2 cle anly regenerated FvMo2(CO)5(PMe3)2.