Synthesis,Characterization, and Reactivity of trans-Ru(X)(Cl)(nbd)(dppb) (X = H,Cl; nbd = 2,5-norbornadiene; dppb = 1,4-bis(diphenylphosphino)butane), Including the X-ray Crystal Structure of the Dichloride

The ruthenium (II) diene complexes Ru(X)(Cl)(nbd)(dppb)] (X = Cl, H; nbd = 2,5-norbornadiene; dppb = PPh₂(CH₂)₄PPh₂) have been prepared and characterized spectroscopically. The X-ray crystal structure of RuCl₂(nbd)(dppb) (crystal data at 22°C: space group P1, a = 10.896 (1) Å, b = 15.168(2) Å, c = 10.829 (1) Å, α = 103.02(1)°, β = 107.08(1)°, γ = 81.65(1)°, Z = 2, R = 0.054 for 6420 reflections) shows an octahedral geometry at Ru, with the chloro ligands slightly distorted from a trans configuration (Cl)(1)-Ru-C1(2) = 168.4°); the unit cell contains two molecules of the complex and one molecule of benzene. Reaction of this complex with H₂, in presence of Proton Sponge (PS, 1,8-bis(dimethylamino)naphthalene) as base, is complicated by initial dissociation of nbd, and Ru₂Cl₅(dppb)₂]⁻-PSH⁺ is the major product. A minor product, the hydrido(diene) complex trans-RuCl(nbd)(dppb) 5 , characterized spectroscopically, is more effectively synthesized from (a) trans-Ru(H)Cl(nbd)(PPh₃)₂, 1 , and dppb, or (b) reaction of RuCl₂(dppb)-(PPh₃) with H₂ in presence of nbd and PS. Complex 5 is unreactive toward H₂ or CO while 1 has been shown previously to give η²-H₂ and norbornenoyl derivatives, respectively; the differences in reactivity are discussed.