Formation of azabutadienyl fragments by addition of the isopropenyl substituent of a phosphine to benzonitriles, promoted by an osmium center

Article abstract of DOI:10.1021/om049178a

Complex Os(η⁵-C₅H₅) Cl{[η²-CH₂=C(CH₃)]PⁱPr ₂} (1) reacts with ρ-tolunitrile, benzonitrile, and ρ-chlorobenzonitrile to give the corresponding iminophosphine derivatives Os(η⁵-C₅H₅)-Cl{NH=C(ρ-C ₆H₄R)CH=C(CH₃)PⁱPr₂} (R = CH₃ (2), H (3), Cl (4)), as a result of the insertion of the carbon-nitrogen triple bond of the nitriles into one of the C(sp²)-H bonds of the phosphine of 1. Treatment of 2-4 with NaBH₄ and methanol produces the rupture of the P - C(CH₃) bond of the iminophosphine ligands and the formation of the respective osmapyrrole derivatives Os(η⁵-C₅H₅){NH-C(ρ-C₆H ₄R)-CH-C(CH₃)}(PHⁱPr₂) (R = CH ₃ (5), H (6), Cl (7)). The addition of HBF₄-Et ₂O to the diethyl ether solutions of 5-7 leads to the hydride-azabutadienyl-osmium(IV) complexes [OsH(η⁵-C ₅H₅){NH=C(ρ-C₆H₄R)CH=C-(CH ₃)}(PHⁱPr₂)]BF₄ (R = CH₃ (8), H (9), Cl (10)), as a consequence of the protonation of the metallic center of 5-7. Complexes 3 and 10 have been characterized by X-ray diffraction analysis.