1,4-Diaza-1,3-diene (DAD) complexes of early transition metals. Synthesis and structural characterization of (t-Bu-DAD)ZrCl(μ-Cl)3Zr(t-Bu-DAD)(THF) and its reaction with benzophenone

The reaction of ZrCl4(THF)2 with one equivalent of [{Li(THF)2}2(t-Bu-DAD)] (1), t-Bu-DAD(t-Bu)NCHCHN(t-Bu), in THF produces the pale-yellow zirconium complex [(t-Bu-DAD)ZrCl2(THF)] which dimerizes in the solid state to [(t-Bu-DAD)ZrCl(μ-Cl)3Zr(t-Bu-DAD)(THF)] (2) using three chlorine atoms as bridging ligands. Treatment of 2 with two equivalents of benzophenone in ether affords the novel zirconium complex [Zr{OCPh2CH(CHNt-Bu)N(t-Bu)}Cl2(THF)] (3) which is formed by a cycloaddition reaction of the Zr−NC unit to the CO carbonyl group of benzophenone. In complex 3 the zirconium is octahedrally coordinated by the new tripodal α-aminoalkoxy ligand {OCPh2CH(CHNt-Bu)N(t-Bu)}, two Cl− ligands and one molecule of THF.