Ene-Type Reactions between an α-Alkenylphosphine and Terminal Alkynes Promoted by Osmium-Cyclopentadienyl Fragments

Abstract

Complex Os(η 5 -C 5 H 5 )Cl{[η 2 -CH 2 =C(CH 3 )]P i Pr 2 } (1) reacts with phenylacetylene to give the dienylphosphine derivative Os(η 5 -C 5 H 5 )Cl{[η 2 -(E)-PhCH=CHCH 2 C(=CH 2 )]P i Pr 2 } (2). The reaction of 1 with PhC≡CD leads tothe monodeuterated compound Os(η 5 -C 5 H 5 )Cl{[η 2 -(E)-PhCH=CDCH 2 C(=CH 2 )]P i Pr 2 } (2-d 1 ). The position of the deuterium atom in 2-d 1 is consistent with the participation of π-alkyne intermediates in the formation of 2 and 2-d 1 . In agreement with this, complex 1 reacts with 1,1-diphenyl-2-propyn-1-ol to give initially Os(η 5 -C 5 H 5 )Cl-{η 2 -HC≡CC(OH)Ph 2 }{P i Pr 2 [C(CH 3 )=CH 2 ]} (3), which in toluene under reflux evolves into Os(η 5 -C 5 H 5 )Cl{[η 2 -(E)-{Ph 2 (OH)C}CH=CHCH 2 C(=CH 2 )]P i Pr 2 } (4). Treatment of 1 with lithium phenylacetylide affords the alkynyl derivative Os(η 5 -C 5 H 5 )(C≡CPh){[η 2 -CH 2 =C(CH 3 )]P i -Pr 2 } (5). Complex 5 also reacts with 1,1-diphenyl-2-propyn-1-ol. The reaction initially gives Os(η 5 -C 5 H 5 )(C≡CPh){η 2 -HC≡CC(OH)Ph 2 }{P i Pr 2 [C(CH 3 )=CH 2 ]} (6), which subsequently affords Os(η 5 -C 5 H 5 )(C≡CPh){[η 2 -(E)-{Ph 2 (OH)C}CH=CHCH 2 C(=CH 2 )]P i Pr 2 } (7). Triethylamine inhibits the coupling between the isopropenyl group of 1 and phenylacetylene. In the presence of this base, the addition of phenylacetylene to 1 leads to the vinylidene derivative Os(η 5 -C 5 H 5 )Cl(=C=CHPh){P i Pr 2 [C(CH 3 )=CH 2 ]} (8). The X-ray structures of 2 and 8 are also reported.