A BIMETALLIC TANTALUM ZINC COMPLEX WITH AN ANCILLARY ARYLDIAMINE LIGAND AS PRECURSOR FOR A REACTIVE ALKYLIDYNE SPECIES - ALKYLIDYNE-MEDIATED C-H ACTIVATION AND A PALLADIUM-MEDIATED ALKYLIDYNE FUNCTIONALIZATION

The 1:1 reaction of TaCl2{C6H3(CH2NMe2)2-2,6}(=CH-t-Bu) with neopentyl zinc chloride affords the bimetallic complex TaCl2{C6H3(CH2NMe2)2-2,6} (mu-C-t-Bu) (mu-ZnCI) (2) in high yield. Crystals of 2 belong to the s pace group P2(1)2(1)2(1) with a = 9.725(2) angstrom, b = 10.436(2) ang strom, c = 20.766(3) angstrom, Z = 4, M(r) = 613.11, V = 2107.5(7) ang strom3, p(calcd) = 1.932 g.cm-3. The pentacoordinate tantalum center h as a coordination geometry between trigonal bipyramidal and square pyr amidal while the zinc center has a distorted tetrahedral ligand array; the alkylidyne functionality and the aryl ipso-carbon bridge between the zinc and tantalum centers. The p-orbital at C(ipso) of the aryldia mine ligand forms a 2-electron bond to the zinc center, and this aryld iamine ancillary thus functions as an 8-electron donor. The reaction o f 2 with tmeda at 60-degrees-C leads to elimination of zinc chloride a nd formation of the alkylidene complex TaCl{C6H3(CH2N(Me)CH2)-2-(CH2-N Me2)-6}(=CH-t-Bu); this is an alkylidyne-mediated activation reaction of a methyl C-H bond in a NMe2 group. In the presence of [Pd(C6H4CH2NM e2-2)(mu-X)]2 (X = Cl, I) the reaction of bimetallic 2 with tmeda [Me2 N(CH2)2NMe2] appears to generate TaCl2(C6H4CH2NMe2-2)[=C(t-Bu){C6H3(CH 2NMe2)2-2,6}] and, as such, is an unanticipated, new palladium-mediate d alkylidyne functionalization reaction.