Synthesis and structural characterisation of some novel lithium and sodium N,N′-di(para-tolyl)formamidinate complexes

Treatment of N,N'-di(para-tolyl)formamidine (p-tolylformH) (1) with LiBun in THF, DME or hexane/TMEDA leads to deprotonation of the amidine affording [Li-2(p-tolylform)(2)(THF)(3)].2THF (2), [Li(DME)(3)][Li-2(p-tolylform)(3)] (3) and [{Li-2(p-tolylform)(2)(TMEDA)}(infinity)] (4) respectively. Similar treatment of 1 with NaH or [Na{N(SiMe3)(2)}] in THF or DME yields trinuclear [Na-3(p-tolylform)(3)(THF)(4)] (5) and dinuclear [{Na(p-tolylform)(DME)}(2)] (6). All complexes were characterised by spectroscopy (NMR and IR) and X-ray crystallography. These show p-tolylform to be a versatile ligand for alkali metals, exhibiting a wide variety of binding modes, viz. mu-eta(1):eta(1) in 2 and 3 (i.e. bridging mode), mu-eta(2):eta(1) in 4 and 6 (i.e. bridging and chelating) and mu-eta(2):eta(2) (i.e. bridging and double chelating) and mu(3)-eta(2):eta(1):eta(1) (i.e. chelating and bridging between three metal centres) in 5.