DIVALENT MANGANESE, IRON, AND COBALT BIS(TRIMETHYLSILYL)AMIDO DERIVATIVES AND THEIR TETRAHYDROFURAN COMPLEXES

Abstract

The intention of this chapter is to describe in detail reliable synthetic procedures for the uncomplexed metal bissilylamides M{N(SiMe3)2}2 (M =Mn, Fe, or Co) as well as those of their mono-tetrahydrofuran complexes M{N(SiMe3)2}2(THF). In addition, a synthesis for the bis(THF) complex Mn{N(SiMe3)2}2(THF)2 is given. The bis(trimethylsilyl)amido group {N(SiMe3)2} −1, 2 is one of the simplest, most versatile, and inexpensive bulky monodentate ligands. Its steric properties were first demonstrated by Bürger and Wannagat via the synthesis of several low(i.e. twoor three-) coordinate transition metal derivatives in the early 1960s. They were prepared by the simple reaction of an alkali metal salt of the amide {N(SiMe3)2} − with chromium, manganese, iron, cobalt, nickel, or copper halides. The list of new compounds 4 included the trivalent complexes M{N(SiMe3)2}3 (M = Cr and Fe), the divalent species M{N(SiMe3)2}2 (M =Mn, Co, and Ni (unstable)), and the monovalent Cu{N(SiMe3)2}. 4 The volatility of M(II) and M(III) derivatives supported the notion that the compounds had unassociated molecular structures and were therefore the first stable examples of open-shell (i.e. d–d) transition metal complexes with coordination numbers less than four. The closed-shell (d) Cu(I) derivative, although volatile, proved to be tetrameric {CuN(SiMe3)2}4 with four coppers arranged in a planar array and bridged by silylamido ligands. The trigonal planar coordination of the M(III) species was proven for Fe{N(SiMe3)2}3 via a determination of its crystal