An electronically unsaturated trinickel complex containing triply

J. Am. Chem. SOC.1990, I 1 2,1047-1048

7041

Communications to the Editor An Electronically Unsaturated Trinickel Complex Containing Triply Bridging Benzyne and 2,2'-Biphenylyl Groups

81I

2*208-

Martin A. Bennett,* K. David Griffiths, Tamon Okano, Viraraghavan Parthasarathi, and Glen B. Robertson

n

The Research School of Chemistry Australian National University GPO Box 4 , Canberra, ACT 2601, Australia W

Received March 27, 1990 Revised Manuscript Received July 9, 1990

2.1

NI

Benzyne (o-phenylene, C6H4)and its derivatives can act as v2 ligands donating between two and four electrons in monomeric transition-metal complexes,' e.g., TaCp*Me3(v2-C6H4),2s3 ZrCpz(v2-C6H4)(PMe,),' Re(v2-3-MeC6H3)(t,1-2-MeC6H4)2L2 (L = PMe3, PMe2Ph),' R u ( ~ ~ - C ~ H ~ ) ( Pand M ~Ni~)~,~ (v2-C6H4)(Cy2PCH2CH2PCy2) ( l).7 They can also behave as bridging ligands in polynuclear metal complexes and are often generated when aromatic derivatives are heated with O S ~ ( C O ) ~ ~ or R U ~ ( C O )A~ common ~. structural type contains a four-electron donor C6H4group lying over a triangle of osmium or ruthenium atoms, e.g., Os,(C0)9(p-H)2(p3-C6H4) (2),8 M3(C0)7(PPPh2)2(p3-C6H4) [M = Os (3)? Ru (4)],1°and Os3(CO),(p1.208 H)(p-AsMe2)(p3-C6H4)(5)." In the course of preparing analogues of l containing monodentate tertiary phosphines, we have isolated and structurally characterized a trinickel complex containing both p3-C6H4and a novel bridging 2,2'-biphenylyl group, 1.955 C6H&H4. 1.419 1.391 Reduction of NiC1(2-C1C6H4)(P-i-Pr3)2 (6)12with 1% sodium amalgam in THF gives two products in variable proportions that 1.404 1.372 can be separated by fractional crystallization from diethyl ether. The main product, isolated in 3 0 4 0 % yield, is the yellow, crystalline, q2 benzyne complex Ni(v2-C6H4)(P-i-Pr3)2(7), identified ~NCNI.QW