A series of mono- and dihydrido- as well as mono- and dimethylosmium(II) complexes containing [(mes)Os(CNR)] as a building block
摘要:
The dihydridoosmium(II) complexes [(mes)OsH2(CNR)] (7-10) were prepared in excellent yield from the dichloroosmium(II) precursors [(mes)OsCl2(CNR)] upon treatment with 10% magnesium amalgam in THF in the presence of ethanol. Under similar conditions, the methylisocyanide derivative [(mes)OsH2(CNMe)] (6) as well as the monohydrido compounds [(mes)OsH(X)(CNMe)] (11, 13) were obtained. The same methodology using [(mes)OsCl(C6H5)(CNR)] as the starting material was applied for the preparation of the hydrido(phenyl)osmium(II) complexes [(mes)OsH(C6H5)(CNR)] (19-23) which were also isolated in almost quantitative yield. Treatment of these complexes with HCl in CH2Cl2 at -78 degrees C led to the cleavage of the osmium-phenyl but not the osmium-hydride bond. Reactions of [(mes)OsCl2(CNR)] with MeLi/LiCl gave exclusively the dimethylosmium(II) compounds [(mes)Os(CH3)(2)(CNR)] (29-32) while the corresponding reactions with MeLi/LiI afforded a mixture of 29-32 and the monomethyl derivatives [(mes)OsI(Me)(CNR)] (26, 33-35). A cyclic carbeneosmium(II) complex 37 was obtained from [(mes)OsCl2(CNPh)] and MeLi/LiI followed by treatment with deactivated Al2O3. The etheneosmium(0) compound [(mes)Os(C2H4)(CNMe)] (38) was prepared from the dimethylosmium(II) precursor 29 and briefly investigated as starting material for photochemical C-H activation reactions. (C) 2000 Elsevier Science S.A. All rights reserved.
The isocyanide complexes [(mes)Os(CNR)Cl2] (2-4) are prepared almost quantitatively from [(mes)OsCl2]n (1) and CNR in dichloromethane. Reactions of 2 (R = CH3) with CH3Li and C6H5Li in hydrocarbon-ether give the dimethyl and diphenyl derivates [(mes)OsR2(CNCH3)] (5, 6) in excellent yields. Treatment of 2 with CH3MgI leads to the formation of a mixture of [(mes)OsCH3(CNCH3)I] (7) and [(mes)Os(CNCH3)I2] (9), which can be separated by column chromatography. Analogously, from 2 and C6H5MgI, both [(mes)OsC6H5(CNCH3)I] (8) and 9 have been obtained. In contrast, reaction of 2 with C6H5MgBr gives, besides [(mes)OsC6H5(CNCH3)Br] (11), the carbene complex [(mes)Os(= C(NHCH3)C6H5)(C6H5)2] (10) as the main product. The X-ray crystal structure of 10 has been determined (monoclinic space group P2(1)/n with a = 12.402 (3) angstrom, b = 14.237 (2) angstrom, c = 13.622 (2) angstrom, beta = 91.54 (1)-degrees). The molecule possesses a piano-stool configuration with an Os-C(carbene) distance of 1.992 (5) angstrom.