Reactions of coordinated ligands. Part 47. Synthesis, structure, and reactivity of [.eta.4(5e)-butadienyl]ruthenium complexes: crystal structures of CpRu:C(Ph)-.eta.3-[C(Ph)C(Ph)CH(Ph)], CpRuC(Ph):C(Ph)-.eta.2-[C(Ph):CH(Ph)]P(OMe)3, and CpRu2[.mu.-(Z)-C(Ph):CH(Ph)](CO)2(.eta.4-C4Ph4)

Abstract

The chemistry of the first example of a {eta}{sup 4}(5e)-butadienyl complex is described. Reaction of (CpRu(NCMe)({eta}{sup 4}-C{sub 4}Ph{sub 4}))(BF{sub 4}) with K(BHBu{sub 3}{sup a}) affords CpRu{double bond}C(Ph)-{eta}{sup 3}-(C(Ph)C(Ph)CH(Ph)) (5), which was structurally identified by single-crystal X-ray crystallography. Compound 5 is triclinic, space group P{anti 1} (No. 2); a = 10.156 (5), b = 10.996 (5), c = 13.145 (6) {angstrom}, {alpha} = 112.12 (4), {beta} = 101.20 (4), {gamma} = 103.76 (4){degree}. The molecule contains an open-chain {eta}{sup 4}(5e)-butadienyl system, in which the CpRu fragment is double bonded to C(1) (Ru-C(1) = 1.896 (5) {angstrom}), the remaining three carbon ruthenium distances Ru-C(2) (2.204 (5) {angstrom}), Ru-C(3) (2.152 (4) {angstrom}), and Ru-C(4) (2.154 (6) {angstrom}) being appropriate for an {eta}{sup 3}-allyl system. A mechanism is proposed for the formation of 5 involving conrotatory ring-opening of an {eta}{sup 3}-cyclobutenyl intermediate carrying an endo hydrogen, which becomes a pseudo-syn hydrogen on the terminus of the C{sub 4} chain.