TETRAAZA MACROCYCLES AS ANCILLARY LIGANDS IN EARLY METAL ALKYL CHEMISTRY - SYNTHESIS AND CHARACTERIZATION OF OUT-OF-PLANE (ME(4)TAEN)ZRX(2) (X=ALKYL, BENZYL, NME(2), CL) AND (ME(4)TAEN)ZRX(2)(NHME(2)) (X=CL, CCPH) COMPLEXES

The synthesis, properties, and structures of a series of out-of-plane (Ne-macrocycle)ZrX(2) complexes incorporating the tetraaza macrocycle Me(4)taen(2-) are described ((Me(4)taen)H-2 = 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraene). Alkane elimination reactions of (Me(4)taen)H-2 (1) with ZrR(4) yield (Me(4)taen)ZrR(2) (2, R = CH(2)Ph; 3, R = CH(2)SiMe(3)). The amine elimination reaction of 1 with Zr(NMe(2))(4) yields (Me(4)taen)Zr(NMe(2))(2) (4). Protonolysis of 4 with [HNHMe(2)]Cl yields the seven-coordinate amine adduct (Me(4)taen)ZrC1(2)(NHMe(2)) (5), which loses amine under vacuum (120 degrees C, 10 h) to afford base-free (Me(4)taen)ZrCl2 (6). The reaction of 4 with phenylacetylene yields the seven-coordinate bisacetylide complex (Me(4)taen)Zr(CCPh)(2)(NHMe(2)) (7). The reaction of 6 with RLi reagents in toluene yields (Me(4)taen)ZrR(2) (8, R = CH(2)CMe(3); 9, R = CH3). Halide displacement does not provide facile access to 6. Deprotonation of 1 yields [Li(THF)](2)[Me(4)taen] (10), which readily loses THF to yield Li-2[Me(4)taen] (11); however, the reaction of 11 with ZrCl4(THF)(2) yields mixtures of 6 and (Me(4)taen)(2)Zr (12). Bismacrocycle complex 12 is formed in good yield via reaction of Zr(NMe(2))(4) with 2 equiv of 1. Dialkyls 2 and 9 rearrange thermally by migration of an alkyl group from Zr to a macrocycle imine carbon. The solid state structures of 1, 2, 4-6, and 10 have been determined. Compounds 1 and 10 exhibit rather planar Me(4)taen conformations. Dichloride 6 adopts a trigonal prismatic structure in which the chlorides occupy adjacent edge sites, and the Me(4)taen(2-) conformation is similar to that in 1 and 10. Dibenzyl complex 2 adopts a similar but. more twisted trigonal prismatic structure. Bisamide complex 4 adopts a distorted octahedral structure in which the Me(4)taen(2-) ligand is significantly folded. These structural differences are rationalized in terms of the conformational preference of the Me(4)taen(2-) ligand, as deduced from the structures of 1 and 10, and the pi-donating ability of the X group. Seven-coordinate complex 5 adopts a side-capped trigonal prismatic structure with a tripodal arrangement of chloride and amine ligands. The structures and properties of these new compounds are compared to those of Cp(2)MX(2) and other early metal analogues.