Preparation, properties, and stereochemistry of nitrosyl derivatives of tetracarbonyl[o-phenylenebis(dimethylarsine)]-molybdenum and -tungsten

Abstract

In methanol–toluene [NO][PF₆] and [M(pdma)(CO)₄][pdma =o-phenylenebis(dimethylarsine)] give mer-[M(pdma)(CO)₃(NO)][PF₆](1; M = Mo or W) which reacts with halide ion, [S₂CNMe₂]^–, and Group 5 donor ligands to yield [M(pdma)(CO)₂X(NO)](2: X = Cl, Br, or I), [M(pdma)CO_2–n(NO)(S₂CNMe₂)](3: M = Mo, n= 1), (4; M = W, n= 0), and [M(pdma)(CO)₂L(NO)][PF₆](5; L = phosphine or phosphite) respectively. In the absence of other ligands (1) yields [M(pdma)(CO)₂(NO)(O₂PF₂)](6) in refluxing acetone, but with excess of pdma a mixture of [Mo(pdma)₂(NO)(O₂PF₂)](7) and [Mo(pdma)₂(CO)(NO)][PF₆](8) is formed. The latter reacts with [NO][PF₆] in CH₂Cl₂ to give cis-[Mo(pdma)₂(NO)₂][PF₆]₂(9). In refluxing CHCl₃, (1; M = Mo) gives polymeric [{Mo(pdma)Cl₂(NO)}_n](10). The determination of stereochemistry by i.r. and n.m.r. spectroscopy. and the detection or isolation of reaction intermediates, has allowed comments to be made on the mechanisms of the formation and substitution reactions of (1).