The life, death, and ROMP activity of ruthenium complexes containing the basic, chelating diphosphine bis(dicyclohexyl)-1,4-phosphinobutane

Abstract

Reaction of RuCl2(PPh3)3 with bis(dicyclohexyl)-1,4-phosphinobutane (dcypb) under N2 affords access to a formerly elusive family of dcypb complexes based on the RuCl2(PP) core. Under Ar or vacuum atmosphere, decomposition occurs via Ru-promoted dehydrogenation of the dcypb ligand. While the N2-stabilized species [RuCl2(dcypb)]2(N2) (4a) is easily handled under N2 in nonchlorinated solvents, reaction with chlorinated solvents rapidly yields paramagnetic Ru2Cl5(dcypb)2 (5). The N2 ligand within 4a is readily displaced under H2 or CO atmosphere, yielding Ru2Cl4(dcypb)2(H2) (6) or RuCl2(dcypb)(CO)2, the latter as a mixture of ccc-(7) and tcc-(8) isomers. Benzylidene derivative RuCl2(dcypb)(CHPh) (1a), prepared in situ by reaction of 4a with PhCHN2, proves exceptionally active in ring-opening metathesis polymerization (ROMP) of norbornene. The X-ray crystal structure of 5 is reported: triclinic, a = 13.390(2), b = 15.726(2), c = 19.524(2) Å, α = 77.325(2), β = 70.964(2), γ = 73.478(2)°, with space group P and Z = 2.Key words: ruthenium, alkylphosphine, dehydrogenation, carbene, metathesis, crystal structure.