Osmiumkomplexe vom Halbsandwichtyp mit Oximen, Iminen und Azavinylidenen als Liganden

Abstract

Osmium Complexes of the Half‐Sandwich Type with Oximes, Imines, and Azavinylidenes as Ligand Azavinylideneosmium complexes of the general composition [(arene)Os(NCRR)(L)]X (L = PMe 3 , PMe t Bu 2 , P i Pr 3 ) have been prepared by two methods. The first one uses the hydrido compound [C 6 H 6 OsHI(PMe t Bu 2 )] ( 2 ) and oximes HONCRR as starting materials and proceeds via the oxime complexes [C 6 H 6 OsH{N(OH)CRR}(PMe t Bu 2 )]PF 6 ( 10, 11 ) as intermediates. They react with Al 2 O 3 with elimination of water to give the final products 6–9 . The second method starts with the dichloro‐ or diiodoosmium(II) compounds [(arene)OxX 2 (PR 3 )] ( 14, 16, 19, 21 ; arene = C 6 H 6 , 1,3,5‐Me 3 C 6 H 3i R = Me, i Pr) which upon treatment with HN = CPh 2 or imine derivatives XNC(R)Ph (X = Li, SiMe 3 ) afford the azavinylidene complexes 13b, 18, 23, 33 . In the reactions with HNCPh 2 , the corresponding imine complexes [(arene)OsX(NHCPh 2 )‐(PR 3 )]X ( 15, 17, 20, 22 ) are formed as the primary products. Whereas nucleophilic addition of H – and CH 3 — to the N=C carbon atom of [C 6 H 6 Os(NCPh 2 )(PMe t Bu 2 )] + ( 6 ) gives the imidoosmium(II) compounds [C 6 H 6 Os(NCRPh 2 )(PMe t Bu 2 )] ( 24, 25 ), the reaction of [C 6 H 6 Os(NCPh 2 )(P i Pr 3 )]PF 6 ( 13 b ) with LiAlH(O t Bu) 3 yields the hydrido(imino) derivative [C 6 H 6 OsH(NHCPh 2 )(P i Pr 3 )]PF 6 ( 26 ). The bis(azido) complex [C 6 H 6 Os(N 3 ) 2 (P i Pr 3 )] ( 27 ), which is prepared either from 13 b or [C 6 H 6 OsI 2 (P i Pr 3 )] ( 14 ) and NaN 3 , undergoes a [3 + 2] cycloaddition reaction with C 2 (CO 2 Me) 2 . Two isomeric (triazole)osmium compounds 28, 29 have been isolated. Treatment of [C 6 H 6 Os(NCRPh)(P i Pr 3 )]PF 6 with HX (X = O 2 CCF 3 ) leads to addition of the acid to the OsN bond and, for R = Ph ( 13 b ), by subsequent elimination of HX to the formation of a five‐membered metallaheterocycle 31 . The X‐ray structural analysis of [C 6 H 6 Os(NCPh 2 )(PMe t Bu 2 )]PF 6 ( 6 ) reveals an allene‐like arrangement of the ligands and substituents around the OsNC unit.