Organometallic Zirconium Compounds in an Oxygen-Rich Coordination Environment: Synthesis and Structural Characterization of Tris(oxoimidazolyl)hydroboratozirconium Compounds

Abstract

A series of tris(oxoimidazolyl)hydroborato ligands, which serve as LX [O] donors, have been employed to obtain organometallic zirconium compounds in an uncommon oxygen-rich coordination environment. For example, Cp[To]ZrCl has been synthesized via the reaction of [To]Na with CpZrCl and bears a structural resemblance to the bent metallocene dichloride derivative CpZrCl. In addition, the half-sandwich counterparts [To]ZrCl and [To]ZrCl have been obtained by metathesis of ZrCl with [To]Na and [To]Na, respectively. The structurally related zirconium benzyl compounds [To]Zr(CHPh) (R = Me, Bu, 1-Ad) have also been synthesized via the reactions of [To]Tl with Zr(CHPh), and X-ray diffraction studies demonstrate that the benzyl ligands in these compounds are conformationally flexible and exhibit a large range of Zr-CH-Ph bond angles (94.7-131.7°). Protolytic cleavage of one of the benzyl ligands of [To]Zr(CHPh) (R = Bu, 1-Ad) may be achieved by treatment with [PhNHMe][B(CF)] to generate {[To]Zr(CHPh)}[B(CF)], which are catalysts for the polymerization of ethylene. The molecular structure of the ether adduct, {[To]Zr(CHPh)(OEt)}[B(CF)], has been determined by X-ray diffraction. In addition to the use of tris(oxoimidazolyl)hydroborato ligands, bis(oxoimidazolyl)hydroborato ligands have also been used to obtain zirconium benzyl compounds in oxygen-rich environments, namely, [Bo]Zr(CHPh) and [Bo]Zr(CHPh).

Synthesis and Structural Characterization of Tris(isopropylbenzimidazol-2-ylthio)methyl Zinc Complexes, [TitmPriBenz]ZnX: Modulation of Transannular Zn–C Interactions

“…Specifically, several tetradentate tripodal ligands that incorporate a central carbon atom, namely tris­(2-pyridylthio)­methyl ([Tptm]), , tris­(1-methylimidazol-2-ylthio)­methyl ([Titm Me ]), and tris­[(1-isopropylbenzimidazol-2-yl)­dimethylsilyl]­methyl ([Tism Pr i Benz ]), allow for the construction of metallacarbatranes, as illustrated in Figure . , Although [Tptm] and [Titm Me ] differ by the presence of six-membered pyridyl and five-membered imidazolyl rings, respectively, a common aspect is that the carbon atoms that are adjacent to the nitrogen atom donors possess only hydrogen atom substituents; as such, the ligands do not possess much steric bulk. Therefore, we report here a more sterically demanding counterpart of [Titm Me ] which features benzannulated rings …”