Calix[4]arene supported group 5 imido complexes

The reaction of imidoyl chlorides [V(NR)Cl3] (R = Ph 1, Tol 2, tBu 3) and calix[4]arene methyl ether H3Mecalix unexpectedly leads to the formation of the structurally characterized vanadium (IV) complex [VCl(Mecalix)] (4). Calix[4]arene methyl ether stabilized imido complexes of the type [V(NR)(Mecalix)] (R = Ph 7, Tol 8, tBu 9) were afforded from the reaction of [V(NR)Cl3] (R = Ph 1, Tol 2, tBu 3) and the tris(lithium) or tris(sodium) salt of the calix[4]arene ether. The lithium salt [{Li3(Mecalix)}2] (5) is a dimer in the solid state, in which two monomeric trianions are bridged by lithium cations. Imido complexes [M(NR)(Mecalix)] (M = Nb: R = tBu, 12, R = Tol 13, R = Mes 14, R = Dipp 15; M = Ta: R = tBu 16, R = Tol 17) (Tol = 4-C6H4Me, Mes = 2,6-C6H3Me2; Dipp = 2,6-C6H3iPr2) have been prepared from structurally characterized [NbCl2(Mecalix)] (10) and previously known [TaCl2(Mecalix)] (11) via reaction with two equivalents of the appropriately metallated (Li, K) primary amine. The molecular structures of 13 and 15 confirm the mononuclear nature of these complexes.