Nickel(0) stilbene complexes and the structure of bis(tri-p-tolylphosphine)(trans-stilbene)nickel(0) hemitetrahydrofuranate

A series of nickel(0)-stilbene complexes has been prepared by the reaction of triarylphosphines or tert-butyl isocyanide with bis(1,5-cyclooctadiene)nickel(0) in hexane. The structure of the complex bis(tri-p-tolylphosphine)(trans-stilbene)nickel(0) hemitetrahydrofuranate, Ni[P(C₆H₄CH₃)₃]₂[(C₆H₅)HCCH(C₆H₅)] · 0.5(C₄H₈O), has been determined at room temperature from three-dimensional X-ray data collected by counter methods. The structure has been refined by least-squares techniques to a final R index (on F) of 0.092 based on 2417 observations above background. The material crystallizes in the orthorhombic space group D¹⁰_2h-Pccn, with eight molecules of complex and four molecules of solvent in a cell of dimensions a = 19.548(8), b = 26.145(12), c = 19.718(9) ». The Ni atom has trigonal coordination if the olefin is regarded as a monodentate ligand. The five atoms of the inner coordination sphere are distorted planar and the two olefinic carbon atoms are essentially equidistant from the nickel atom. The structure is compared with that of bis(tri-p-tolylphosphine)(azobenzene)nickel(0) determined previously. Observed differences in the bonding of the olefin and the isoelectronic azo complex are discussed.