YLIDE AND ALLYL COMPLEXES OF NICKEL DERIVED FROM THE TETRANUCLEAR ALKYLIDENE [NI2(MU)2-CHCME2-O-C6H4)CL(PME3)2]2

The bridging alkylidene complexes [Ni2(mu2-CHCMe2-o-C6H4)Cl(PMe3)2]2, 1 and Ni2(mu2-CHCMe2-o-C6H4)Cl(PMe3)3, 2, react with an excess of PMe3 with formation of the ylide Ni[CH(PMe3)CMe2-o-C6H4]Cl(PMe3), 3 and Ni (PMe3)4. In the presence of PMe3, water readily protonates the ylide 3 to furnish the phosphonium compound trans-[Ni(C6H4-o-CMe2CH2PMe3)Cl(P Me3)2]OH, 4, while treatment of 3 with the PMe3 abstracting reagent Ni (cod)2 (cod = 1,5-cyclooctadiene) affords a binuclear, chloride bridge , complex of composition [Ni{CH(PMe3)CMe2-o-C6H4}]2(mu-Cl)2, 6. Two ot her ylide derivatives have been prepared, namely the cyclopentadienyl species CpNi[CH(PMe3)CMe2-o-C6H4], 5 and the isocyanide complex Ni[CH( PMe3)CMe2-o-C6H4]Cl(CNBu(t)), 7. When alkylidene 1 is treated with Mg( CH = CH2)Br, an unusual reaction ensues that yields the pi-allyl compo und Ni(eta3-CH2CHCHCMe2C6H5)Br(PMe3), 8, as a result of the coupling o f the alkylidiene and vinyl fragments. Complexes 3 and 8 have been cha racterized by X-ray crystallography. 3 crystallizes in the triclinic s pace group P-1 with unit cell constants a = 8.058(3); b = 10.961(3); c = 11.904(3) angstrom; alpha = 110.70(2); beta = 94.74(2); gamma = 99. 89(2)-degrees; Z = 2. Crystals of 8 are monoclinic, C2/c, with a = 22. 890(9); b = 10.634(9); c = 15.164(14) angstrom; beta = 113.19(4)-degre es; Z = 8. The structures were refined to R values of 0.041 and 0.066, respectively(a).