211247-67-5Relevant articles and documents
New cyclopentadienylosmium compounds containing unsaturated carbon donor coligands: Synthesis, structure, and reactivity of Os(η5-C5H5)Cl(=C=C=CPh2)(P iPr3)
Crochet, Pascale,Esteruelas, Miguel A.,López, Ana M.,Ruiz, Natividad,Tolosa, José I.
, p. 3479 - 3486 (1998)
The addition of 1,1-diphenyl-2-propyn-1-ol to pentane solutions of the cyclopentadienyl compound Os(η5-C5H5)Cl(PiPr 3)2 (1) produces the displacement of a phosphine ligand from 1 and the formation of the π-alkyne complex Os(η5-C5H5)Cl{η 5-HC≡C-C(OH)Ph2}(PiPr3) (2), which affords the allenylidene derivative Os(η5-C5H5)Cl(=C=C=CPh2)(P iPr3) (3) in toluene at 85°C. The structure of 3 has been determined by X-ray diffraction. The Os-Cα, Cα-Cβ and Cβ-Cγ bond lengths are 1.875(6), 1.222(9), and 1.344(9) A?, respectively, while the Os-Cα-Cβ and Cα-Cβ-Cγ angles are 171.6(6)° and 172.0(7)°, respectively. Protonation of 3 with HBF4·OEt2 leads to the α,β-unsaturated carbyne [Os(η5-C5H5)Cl(≡C-CH-CPh 2)-(PiPr3)]BF4 (4), as a result of the attack of the proton from the acid at the Cβ carbon atom of the allenylidene. The nucleophilicity of this atom is also revealed by the reaction of 3 with dimethyl acetylenedicarboxylate, which leads to the allenylvinylidene Os(η5-C5H5)Cl-{=C=C(CO 2Me)C(CO2Me)=C=CPh2}(PiPr 3) (5). A second C3 + C2 coupling process is the formation of the pentatrienyl complex Os(η5-C5H5){(3-5-η)CH 2CHC=C=CPh2}(PiPr3) (6) by reaction of 3 with CH2=CHMgBr. Complex 3 also reacts with KI to give Os(η5-C5H5)I(=C=C=CPh2)(P iPr3)(7). The reduction of the Cβ-Cγ double bond of the allenylidene ligand of 3, to form the vinylidene complex Os(η5-C5H5)Cl(=C=CH-CHPh 2)(PiPr3) (8), has been carried out in the presence of NaBH4 and methanol.
