SODIUM OXIMATES AS STARTING MATERIALS FOR THE SYNTHESIS OF HALF-SANDWICH-TYPE ARENE(OXIMATO) AND ARENE(AZAVINYLIDENE) OSMIUM COMPLEXES

The reaction of [C6H6OsI2((PPr3)-Pr-i)] (1) with Na[ON=CR(2)](R(2)=Ph( 2), Me(2), C(CH2)(5)) in the presence of KPF6 leads to the formation o f the oximato osmium(II) complexes [C6H6Os(eta(2)-ON=CR(2))((PPr3)-Pr- i)]PF6 (6, 7, 8b) in almost quantitative yield. The mesitylene compoun ds [(mes)Os(eta(2)-ON=CR'R '')(PR(3))]PF6 (9-14) have been prepared si milarly using [(mes)OsCl2(PR(3))] (3-5) as starting materials. The syn thesis of [C6H6Os(eta(2)-ON=CMe(t)Bu)((PPr3)-Pr-i)]PF6 (17) has been a chieved from [C6H6OsCl2((PPr3)-Pr-i)] (16) which in turn is prepared f rom [C6H6Os(eta(2)-O2C=O)((PPr3)-Pr-i)] (15) and excess Me(3)SiCl. Rea ction of 1, [C6H6OsI2(PMe(t)Bu(2))] (2) and 3 (PR(3) = (PPr3)-Pr-i) wi th Na[ON=CMe(t)Bu] in the presence of KPF6, in methanol as solvent, un expectedly yields the azavinylidene complexes [(arene)Os(=N=CMe(t)Bu)( PR(3))]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 '')(PR(3))] PF6 (21-26) have been obtained on treatment of the corresponding oxima to complexes 7, 10 or 14 with either HN=CR'R '' or, for R'=H and R ''= Ph, the trimethylsilyl derivative.