Acylphosphido and η2-phosphaalkenyl complexes of osmium

Article abstract of DOI:10.1016/0022-328X(88)80325-5

Acylphosphido complexes, OsClR)>(CO)2(PPH3)2; (R = t-Bu, CH3, CO2Et, Ph, p-C6H4NO2, CF3; 2a-e, 3) are formed when OsCl(PH2)(CO)2(PPh3)2 is treated with the appropriate acid chloride or anhydride.Related complexes, MXCF3)>(CO)L'(PPh3)2, (M = Ru, X = Cl, L' = CO; 7; M = Os, X = H, L' = CO; 8; M = Os, X = Cl, L' = PMe3; 9) are also prepared from the related PH2 complexes and trifluoroacetic anhydride.The structure of a representative example of one of these with a pivaloylphosphido ligand, 2a, has been determined.The pale yellow crystals are triclinic, space group P1<*>, a 10.691(1), b 12.565(3), c 17.291(2) Angstroem, α 97.39(1), β 103.871(9), γ 102.72(1) deg with Z = 2 and V 2159 Angstroem³.When 3 is treated with sodium hydride in THF at reflux for 1.5 h, HCl is lost and a η²-phospha-alkenyl complex Os<*>(P=C<*>CF3)(CO)2(PPh3)2 (10) is formed.The two-coordinate phosphorus atom in 10 is nucleophilic, and with Fe2(CO)9 forms the adduct Os<*><*>CF3>(CO)2(PPh3)2 (12), and with methyl iodide gives a methyltrifluoroacylphosphido complex, OsICF3)>(CO)2(PPh3)2 (11b).Both 10 and 12 have been structurally characterized.Bright orange crystals of 12 crystallize in the monoclinic space group P2₁/c, with a 12.168(3), b 18.135(3), c 21.804(3) Angstroem and β 103.11(2) deg, Z = 4, V 4686 Angstroem³.Complete details of the structure of 10 are also reported.The bonding in 10 and 12 is discussed in terms of two canonical forms, one with phospha-alkene like character, the other with phosphinidene character.