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 = PPh 2 (CH 2 ) 4 PPh 2 ) have been prepared and characterized spectroscopically. The X‐ray crystal structure of RuCl 2 (nbd)(dppb) (crystal data at 22°C: space group P 1, 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 H 2 , in presence of Proton Sponge (PS, 1,8‐bis(dimethylamino)naphthalene) as base, is complicated by initial dissociation of nbd, and [Ru 2 Cl 5 (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)(PPh 3 ) 2 , 1 , and dppb, or (b) reaction of RuCl 2 (dppb)‐(PPh 3 ) with H 2 in presence of nbd and PS. Complex 5 is unreactive toward H 2 or CO while 1 has been shown previously to give η 2 ‐H 2 and norbornenoyl derivatives, respectively; the differences in reactivity are discussed.