Synthesis and Reactivity Studies of the Stable Bimetallic Formyl Complexes -. Crystal and Molecular Structure of a Methylation Product Which Derives by Coupling of Phosphido and Carbene Ligands

Article abstract of DOI:10.1021/ja00332a030

The binuclear complex has been prepared by the reaction of Li2 with Os(CO)4Br2.It reacts with L=PMe3 and PMePh2 to give the adduct complexes (CO)4W(μ-PPh2)2Os(CO)3L.These in turn react with ^- to give the binuclear formyl complexes <(CO)4W(μ-PPh2)2Os(CHO)(CO)2L>^-.These are stable at elevated temperatures with the PMe3 derivative decomposing at 78 deg C with t_1/2=4.3 h by loss of CO to give the hydride complex <(CO)4W(μ-PPh2)2OsH(CO)2(PMe3)>^-.The PMePh2 derivative decomposes at 110 deg C via competing CO and PMePh2 loss to yield a mixture of <(CO)4W(μ-PPh2)2OsH(CO)2L>^- with L=CO and PMePh2.Protonation of the formyl complexes leads to conversion of one μ-PPh2 ligand into a PPh2H ligand and migration of hydride to Os to give complexes of the type (CO)5W(μ-PPh2)OsH(CO)2(PR3)(PPh2H).Reaction of the formyl complexes with <(CH3)3O>BF4 gives the derivatives in wich the μ-PPh2CHOMe ligand derives by coupling of carbene and phosphido ligands.The PMePh2 derivative has been characterized by a complete single-crystal X-ray diffraction study.It crystallizes in the space group P2₁/n with a=13.907(3) Angstroem, b=13.367(2) Angstroem, c=24.344(5) Angstroem, β=90.60(2)^o, V=4525(3) Angstroem³, and Z=4.The structure has been refined for the 4967 reflections with I > 2.5?(I) to R₁=0.037 and R₂=0.042.The W and Os atoms are joined by a direct single metal-metal bond (3.022(1) Angstroem) and bridged by μ-PPh2 and η²(P,C)-μ-PPh2CHOMe ligands.The W is further coordinated by four CO's and the Os by two CO's and a PMePh2 ligand.Complexes similar to the methylation products with η²(P,C)-μ-PPh2CHOC(O)Me ligands derive from treatment of the formyl complexes with acetyl chloride.