Reactions of M{N(SiMe3)2}2 (M = Mn, Fe or Co) with pyridine and 4,4′-bipyridyl:: structural and magnetic studies

The reactions of the aromatic nitrogen donor ligands pyridine (py) and 4,4'-bipyridyl (4,4-bipy) with the transition metal silylamides M{N(SiMe3)(2)}(2) (M = Mn, Fe or Cc) were investigated. Treatment of the metal amides with pyridine afforded the bispyridine complexes M{N(SiMe3)(2)}(py)(2) (M = Mn, 1a; Fe, 2a; Co, 3a). Distillation or sublimation of 2a or 3a afforded the monopyridine complexes M{N(SiMe3)(2)}(2)(py) (M = Fe, 2b; Co, 3b). The addition of pyrazine (prz) to Mn{N(SiMe3)(2)}(2) also yielded the bispyrazine adduct Mn{N(SiMe3)(2)}(2)(prz)(2), 1b. However, the reaction of 4,4'-bipyridyl with Fe{N(SiMe3)(2)}(2) or Co{N(SiMe3)(2)}(2) afforded the polymeric chain-like complexes {M{N(SiMe3)(2)}(2)(4,4'-bipy)}(infinity) (M = Fe, 4; Co, 5). With the exception of 2b, all complexes were characterized by X-ray crystallography. The complexes la, 1b, 2a and 3a displayed monomeric structures and metal geometries that are based on a tetrahedron with interligand angles that deviate markedly from idealized values. Complex 3b was found to have a distorted trigonal planar geometry. In contrast, complexes 4 and 5 displayed polymeric zig-zag chain structures which have four coordinate metal centers connected by 4,4'-bipyridyl ligands. Magnetic studies indicated that complexes 1-3b have high-spin electron configurations and that the paramagnetic centers in 4 and 5 did not interact with each other through the 4,4'-bipyridyl ligands. (C) 2002 Elsevier Science Ltd. All rights reserved.