First Row Transition Metal Aminopyridinates - the Missing Complexes

Lithiated 4-methyl-2-[(trimethylsilyl)amino]pyridine (Ap(TMS)H) undergoes a salt metathesis reaction with [SCCl3(thf)(3)] and FeCl3, at low temperature in thf, to yield the homoleptic complexes [Sc(Ap(TMS))(3)] (1) and [Fe(Ap(TMS))(3)] (2). An analogous reaction with MnCl2, CoCl2 and FeCl2 using two equivalents of 4-tert-butylpyridine (tBuPy) as additional donor ligand affords the structurally analogous cis complexes [Mn(Ap(TMS))(2)(tBuPy)(2)] (3), [Co(Ap(TMS))(2)(tBuPy)(2)] (4) and [Fe(Ap(TMS))(2)(tBuPy)(2)] (5). If FeCl3, is used without tBuPy, the highly symmetric trinuclear complex [Fe-3(Ap(TMS))(6Li2O] (6) is obtained. Furthermore, the use of ZnCl2 in a reaction with lithiated Ap(TMS)H yields the dimeric complex [Zn(Ap(TMS))(4)] (7) in which two Ap(TMS) ligands bridge the two metals. All complexes have been characterised by X-ray crystal structure analysis. To the best of our knowledge, complexes 1 and 2 and 5 are the first scandium and iron aminopyridinates, respectively, and complex 3 is the first manganese aminopyridinate complex which contains no additional anionic ligand. Complexes 4 and 7 are rare examples of cobalt and zinc aminopyridinates. This study proves that aminopyridinato ligands are highly universal ligands since they are able to stabilize early and late transition metals. Aminopyridinates of every first row transition metal are now available. The magnetic properties of all paramagnetic complexes were investigated. All complexes are high-spin complexes and the trinuclear iron complex 6 exhibits a weak antiferromagnetic coupling. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)