N,N′-Di( tolyl) formamidinate complexes of potassium:: studies of ancillary donor imposed molecular and supramolecular structure

Treatment of N,N'-di(tolyl) formamidines ((Tol)NC(H)N(H)(Tol))HFTolP (TolP = para-tolyl) and HFTolM (TolM = meta-tolyl) with potassium hydride affords the colourless crystalline formamidinate complexes [{K-2(FTolP)(2)(THF)(3)}(infinity)], 1, and [{(K-2(FTolM)(2)(THF)(3)).THF}(infinity)], 2 when conducted in THF. An analogous HFTolP preparation in 1,2-dimethoxyethane yields the DME analogue of 1; [{K(FTolP)(DME)}(infinity)], 3, whilst treatment of HFTolP with potassium hydride in toluene followed by stoichiometric addition of 18-crown-6 gives monomeric [K(FTolP)(18-crown-6)], 4. Compounds 1-4 have been characterised by spectroscopy (H-1 NMR, C-13 NMR and FTIR) and single crystal XRD. In the solid-state 1-3 display one-dimensional polymeric structures that exhibit mu-eta(2):eta(2)-coordinated formamidinates. These approach eta(3)-diazaallyl contact by virtue of dinuclear bridging. Compound 4, the first example of a poly-ether crown adducted monomeric Group 1 amidinate, exhibits both inter- and intra-molecular C-H ... O hydrogen bonding in the solid-state. Supramolecularly, this renders 4 a two-dimensional hydrogen-bonded polymer. Complexes 1-4 are discussed with respect to known potassium benzamidinate/guanidinate complexes and related amido-2-pyridyl ligand species.