Reactions of [Ru(CO)ClH(Me2Hpz)(PR3)2] (Me2Hpz = 3,5-dimethylpyrazole; R = Ph, p-tolyl) with acetylenes. The crystal structure of [Ru(CO)Cl(HC=CHCMe3)(Me2Hpz)(PPh3)2] and [Ru(CO)(MeO2CC=CHCO2Me)(HCO3)(PPh 3)2]

Article abstract of DOI:10.1021/om00099a014

Monosubstituted acetylenes R′C≡CH (R′ = n-C₃H₇, CMe₃, Ph, CO₂Me) react with the pyrazole hydrido complexes [Ru(CO)ClH(Me₂Hpz)(PR₃)₂] (R = Ph, p-tolyl) in CH₂Cl₂ to yield alkenylpyrazole complexes [Ru(CO)Cl(HC=CHR′)(Me₂Hpz)(PR₃)₂] resulting from a cis insertion of the alkyne into the Ru-H bond. The X-ray crystal structure determination of the complex with R = Ph and R′ = CMe₃ [monoclinic, P2₁/n, a = 10.413 (1) ?, b = 18.262 (1) ?, c = 23.861 (2) ?, β = 96.29 (1)°] shows a distorted octahedral geometry, with the ligands CO and Cl, alkenyl and pyrazole, and both phosphine molecules mutually trans. Bis-insertion derivatives [RU(CO)Cl{MeO₂CC=C(CO₂Me)C(CO₂Me)=CHCO ₂Me}PR₃)] (R = Ph, p-tolyl) are formed in the reactions of both starting complexes with dimethyl acetylenedicarboxylate, and no reactions were observed with (trimethylsilyl)acetylene and diphenylacetylene. A secondary unexpected product of composition [Ru(CO)(MeO₂CC=CHCO₂Me)(HCO₃)(PPh ₃)₂] was isolated, along with the major alkenyl product, from the reaction of [Ru(CO)ClH(Me₂Hpz)(PPh₃)₂] with methyl propiolate in CH₂Cl₂. The crystal structure of this compound has been determined by X-ray crystallography [monoclinic, P2₁/n, a = 11.556 (1) ?, b = 35.707 (2) ?, c = 10.386 (1) ?, β = 111.01 (2)°]. Reaction of the ruthenium hydrides with PhC≡CH in EtOH yielded the unusual metallacycles [Ru{NH=C(Ph)OC=CHPh} (CO)Cl(PR₃)₂] (R = Ph, p-tolyl). The metallacycle with R = p-tolyl was also isolated from the reaction of the corresponding pyrazole alkenyl complex with PhC≡CH in EtOH. However, the reaction of [Ru(CO)Cl(HC=CHPh)(Me₂Hpz)(PPh₃)₂] with PhC≡CH in EtOH affords an alkynyl complex, [Ru(CO)Cl(C≡CPh)(Me₂Hpz)(PPh₃)₂]. A similar product was obtained in the reaction of the alkenyl complex (R = Ph, R′ = CMe₃) with Me₃CC≡CH in EtOH. Mixtures of both pyrazole alkenyl and alkynyl complexes are formed in the reactions of [Ru-(CO)ClH(Me₂Hpz)(PPh₃)₂] with Me₃CC≡CH and pent-1-yne in EtOH.