A New, Flexible N,N,NTripodal Facially Capping Ligand System: Synthesis and Structural Characterization of βTriketimines and Their MCO3Complexes M = Cr, Mo, WDedicated to the memory of Swiatoslaw Jerry TrofimenkoPioneer of scorpionate chemistry

Reaction of imidoyl chlorides ArN=CClR Ar = 2iPrC6H4, 2,6iPr2C6H3, 2MeOC6H4; R = Me, Ph, tBu with [Linacnac] [nacnac = ArNCMe2CH] gives βtriketimines L, most of which exist in solution in equilibrium with their imineenamine tautomers. The route is highly modular, allowing independent variation of at least five parameters. The solution equilibria are very sensitive to such substituent pattern variation. Singlecrystal Xray diffraction analyses of examples of both tautomers and a geometric isomer in the solid state are presented, alongside solution NMR studies of the tautomerism. All examples revert exclusively to the βtriimine form on complexation with MCO3fragments M = Cr, Mo, W. Facial isomers result. The ligands are weak σdonors, as adjudged by CO IR stretching frequencies in [LMCO3]. Crystalstructure determination on the isostructural pair [HC2iPrC6H4N=CMe3MCO3] M = Cr, Mo revealed a hexagonal packing arrangement composed of aryl–aryl and carbonyl CO–H–C interactions which generates pseudocylindrical voids accounting for 6–9  of the crystal volume. In only one case were these occupied by solvent molecules. This family of facially capping N,N,Nligands with finely tunable bulk have wide potential in coordination chemistry.© WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009