Synthesis and reactions of do imido aryl derivatives of chromium, molybdenum, and tungsten. Crystal structures of Cr(NBut)2(C6H2Me3-2,4,6)2, Mo(NBut)2(C6H3Me2-2,6)2, and Cr(NBut)2[C(C6H2Me3-2,4,6)NBut](C6H2Me3-2,4,6)
Abstract
The compounds M(NBut)2R′2(M = Cr, Mo, or W, R′= C6H2Me3-2,4,6 or C6H3Me2-2,6; M = Mo, R′= C6H4Me-o) have been prepared form M(NBut)2(OSiR3)2(M = Cr or Mo, R = Me; M = W, R = Ph) and appropriate Grignard reagents. Cr(NBut)2(C6H2Me3-2,4,6)2 reacts with CO to give a thermally unstable bis(acyl) complex Cr(NBut)2(COC6H2Me3-2,4,6)2 which eliminates the amide HN(But)(COC6H2Me3-2,4,6) possibly via acyl migration to the imido nitrogen. Cyclic voltammetry on Cr(NBut)2(C6H2Me3-2,4,6)2 shows a quasi-reversible one-electron reduction, E½red=–1.31 V. Reaction of compounds M(NBut)2R′2(M = Cr, Mo, or W, R′= C6H2Me3-2,4,6; M = Mo, R′= C6H3Me2-2,6) with t-butyl isocyanide gives the corresponding η2-iminoacyls M(NBut)2[C(R′)NBut]R′. The X-ray crystal structures of Cr(NBut)2(C6H2Me3-2,4,6)2, Mo(NBut)2(C6H3Me2-2,6)2, and Cr(NBut)2[C(C6H2Me3-2,4,6)NBut](C6H2Me3-2,4,6) have been determined. The first two consist of monomeric distorted tetrahedra in which one o-methyl group on each aryl ligand is positioned close to the metal atom. In the latter compound the structure is best described in terms of a distorted tetrahedron, with the η2-iminoacyl occupying one split site.