Reactions of the unsaturated alkyne cluster [Os3(CO)7{µ3-η2(⊥)-PhC2Ph}(dppm)] with P-donors; crystal structures of [Os3(CO)6(PhC2Ph)(dppm){P(OMe)3}] and two isomers of [Os3(CO)7(PhC2Ph)(dppm)(PBu3)](dppm = Ph2PCH2PPh2)

Abstract

Treatment of the unsaturated cluster [Os₃(CO)₇(PhC₂Ph)(dppm)]1(dppm = Ph₂PCH₂PPh₂) with P-donors gave the saturated monoadducts [Os₃(CO)₇(PhC₂Ph)(dppm)L][L = PBu₃2, PPh₃3, PMe₂Ph 4 or P(OMe)₃5]. Spectroscopic studies have established that these adducts exist in three isomeric forms the ratio of which depends on the polarity of the solvent used in the reaction. X-Ray crystallographic determinations of two isomers of the PBu₃ adduct, 2a and 2c, showed the phosphine to be co-ordinated to different metal centres in the two isomers. The P(OMe)₃ adducts 5b and 5c underwent a facile decarbonylation reaction to give the unsaturated cluster [Os₃(CO)₆(PhC₂Ph)(dppm){P(OMe)₃}]6, which has been structurally characterised by X-ray crystallography. Attempts to decarbonylate the monoadducts 2–4 have been unsuccessful.