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

Abstract

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 [Li₂(p-tolylform)₂(THF)₃]·2THF (2), [Li(DME)₃][Li₂(p-tolylform)₃] (3) and [{Li₂(p-tolylform)₂(TMEDA)}_∞] (4) respectively. Similar treatment of 1 with NaH or [Na{N(SiMe₃)₂}] in THF or DME yields trinuclear [Na₃(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. μ-η¹:η¹ in 2 and 3 (i.e. bridging mode), μ-η²:η¹ in 4 and 6 (i.e. bridging and chelating) and μ-η²:η² (i.e. bridging and double chelating) and μ₃-η²:η¹:η¹ (i.e. chelating and bridging between three metal centres) in 5.