Homo- and Heterometallic Complexes of Tetra-(Di-Substituted Hydroxybenzyl)-N,N′-Ethylenediamine Derivatives

The coordination behavior of a series of group 4 metal alkoxides [M(OR)(4)] modified by a set of novel substituted hydroxybenzyl ethylene diamine (H(4)-ED-L(4)) ligands {[tetra(3,5-di-t-butyl-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DBP(4) (1), [tetra(3,5-di-t-amyl-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DAP(4) (1a), and [tetra(3,5-dichloro-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DCP(4) (2)} was elucidated. The reaction of 1 or 1a with the M(OR)(4) precursor led to the isolation of the structural similar species M(ED-L(4)) where L = DBP, M = Ti (3), Zr (4), Hf (5); L = DAP, M = Zr (4a), Hf (5a). In contrast, the reaction of 2 with the M(OR)(4) precursors yielded Ti(ED-DCP(4)) (6), (py)(2)Zr(ED-DCP(4)) (7), and (HOBu(t))Hf(ED-DCP(4)) (8) where py = pyridine and HOBu(t) = HOC(CH(3))(3). For 3-6, the cations of the monomeric species were completely encapsulated by all available heteroatoms (four O and two N) of the ED-L(4) ligands, yielding an octahedral geometry for each metal center. For 7 and 8, an identical binding by the ED-DCP(4) ligand was observed with the additional coordination of Lewis basic adducts, forming 8- and 7-coordinated metal centers, respectively. Switching to +2 cations led to the isolation of [(THF)Ca](2)(ED-DBP(4)) (9a) where THF = tetrahydrofuran, {[(py)Ca](4)(ED-(mu-DBP-eta(6))(4))(2)}(n) (9b), and [(py)Zn](ED-DBP(4))[Zn(py)(2)] (10) *5py and [(py)Sn](2)(ED-DBP(4)) (11). The structures of these species were significantly different in arrangement compared to the Group 4 derivatives. Further attempts to produce a mixed +4/+2 cationic species yielded [(py)(ONep)(2)Ti(ED-DBP(4))Zn(py)] (12). Reacting the single-source precursor Co[mu-OC(6)H(4)(CHMe(2))(2)-2)(2)Li(py)(2)](2) with 1, led to the isolation of (py)Li[ED-DBP(3)(H-DBP)]Co (13), with one of the phenol protons remaining unreacted. The synthesis and characterization of these compounds are presented in detail.