Allenyliden-komplexe als synthone zur darstellung von hydroxylaminocarben- und isoxazolidinyliden-komplexen

Abstract

The diarylallenylidene complexes (CO) 5MCCC(C 6H 4NMe 2- p) 2 [M  W ( 1), Cr ( 2)] and N-alkyl-substituted hydroxylamines, RNH—OH, to form the hitherto unknown isoxazolidinylidene complexes (CO) 5M= ▪ [M  W ( 3), Cr ( 4); R  Me ( a), Bn ( b), iPr ( c), cHex ( d)]. Thestructure of these heterocyclic carbene complexes is established by X-ray analysis of compound 3a. Only in the synthesis of 4d could by-products [ E/Z-( CO) 5 CrC[ N( H) c Hex] C( H) C( C 6 H 4 NMe 2-p) 2(E/Z- 5) ] isolated. The reaction of 1 with the sterically strongly hindered N-alkyl-substituted hydroxylamine tBuNH—OH or with the only weakly nucleophilic N-aryl-substituted hydroxylamine p-TolNH—OH does not afford isoxazolidinylidene complexes. Instead the alkenyl(amino)carbene complexes ( CO) 5 W C[ N( H) t Bu] C( H) C( C 6H 4NMe 2-p) 2 ( 6) and E/Z-( CO) 5 W C[ N(H)p- Tol] C( H) C( C( C 6 H 4- NMe 2-p) 2 (E/Z- 7 ) are formed by the addition of amines which arise via dismutation of the hydroxylamines. From the reaction of 1 with the N, N-distributed hydroxylamine, Me 2N—OH, only the alkenyl(amino)carbene complex (CO) 5WC[C(H)C(C 6H 6NMe 2- p) 2 ( 8) is isolated. Hence, formation of 3 and 4 must proceed by initial attack of thy hydroxylamine N-atom at the C α-atom of 1 and 2. Similarly, 1 also adds the N, O-disubstituted hydroxylamine MeNH—OMe to give the alkenyl(hydroxylamino)carbene complexes E− and Z(CO) 5WC[N(Me)OMe]C(H)C(C 6H 4NMe 2- p) 2 ( E- 9 and Z- 9 ) in the ratio E/ Z = 1 : 3.2. Both conformers were investigated by X-ray analysis. On warming in solution, E-bd9 isomerizes to form Z- 9 .