Sodium oximates as starting materials for the synthesis of half-sandwich-type arene( oximato) and arene( azavinylidene) osmium complexes

Article abstract of DOI:10.1016/0022-328X(95)06010-T

The reaction of [C₆H₆OsI₂(PⁱPr₃)] (1) with Na[ON=CR₂] (R₂ = Ph₂, Me₂, C(CH₂)₅) in the presence of KPF₆ leads to the formation of the oximato osmium(II) complexes [C₆H₆Os(η²-ON=CR₂)(PⁱPr₃)]PF₆ (6, 7, 8b) in almost quantitative yield. The mesitylene compounds [(mes)Os(η²-ON=CR′R″)(PR₃)]PF₆ (9-14) have been prepared similarly using [(mes)OsCl₂(PR₃)] (3-5) as starting materials. The synthesis of [C₆H₆Os(η²-ON=CMe^tBu)(PⁱPr₃)]PF₆ (17) has been achieved from [C₆H₆OsCl₂(PⁱPr₃)] (16) which in turn is prepared from [C₆H₆Os(η²-O₂C=O)(PⁱPr₃)] (15) and excess Me₃SiCl. Reaction of 1, [C₆H₆OsI₂(PMe^tBu₂)] (2) and 3 (PR₃ = PⁱPr₃) with Na[ON = CMe^tBu] in the presence of KPF₆, in methanol as solvent, unexpectedly yields the azavinylidene complexes [(arene)Os(=N=CMe^tBu)(PR₃)]PF₆ (18b, 19, 20). The X-ray structural analysis of 18b reveals the presence of a nearly linear Os-N-C fragment with an Os-N distance that is in agreement with typical osmium-nitrogen double bond lengths. Related azavinylideneosmium compounds [(arene)Os(=N=CR′R″)(PR₃)]PF₆ (21-26) have been obtained on treatment of the corresponding oximato complexes 7, 10 or 14 with either HN=CR′R″ or, for R′ = H and R″ = Ph, the trimethylsilyl derivative.