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.

Graphical abstractSynthesis and characterization of calix[4]arene methyl ether stabilized imido complexes of the type [M(NR)(Mecalix)] (M = V, Nb, Ta; R = alkyl, aryl) were prepared by reacting [V(NR)Cl3] (R = Ph, Tol, tBu) with the tris(lithium) or tris(sodium) salt of the calix[4]arene ether H3Mecalix or from the reaction of [MCl2(Mecalix)] (M = Nb, Ta) with two equivalents of the appropriately metallated primary amine.Figure optionsDownload full-size imageDownload as PowerPoint slide