Synthesis and characterization of sodium, potassium, zinc and aluminium formamidinate complexes

Abstract

The metalation reactions of N,N’-bis-(2,4-dimethylphenyl)formamidine (DMFormH) and N,N’-bis-(phenyl)formamidine (PhFormH) with KN(SiMe3)2 or NaN(SiMe3)2 in toluene/1,2-dimethoxyethane (dme) resulted in the formation of [K(DMForm)(dme)]n (K1), [K2(PhForm)(N(SiMe3)2)]n (K2), [Na(DMForm)(dme)2] (Na1), and [Na(PhForm)(dme)]2 (Na2). Treatment of PhFormH with ZnEt2 or AlMe3 in toluene/tetrahydrofuran (thf) yielded [Zn4(PhForm)6O]·2.5thf (Zn1) and [Al(PhForm)3] (Al1), respectively. The potassium-formamidinate compounds (K1 and K2) are polymeric. K1 has six-coordinate potassium with additional C…K interactions. Reducing the steric effect of the formamidinate changes the formamidinate bonding mode. Thus, for potassium complexes, it led to both inter- and intra-molecular η6-arene-K binding in K2. With the sodium complexes, the structure changed from a six-coordinate monomer in [Na(DMForm)(dme)2] to a five-coordinate dimer in [Na(PhForm)(dme)]2 in which there is a μ 2-1κ(N,N’): 2κ (N) formamidinate binding mode. Zn1 has a pseudo-cubane oxide centered cage like structure, whereas Al1 is monomeric with six-coordinate aluminium and chelating formamidinate ligands.