Syntheses and catalytic activities of Group 4 metal complexes derived from C(cage)-appended cyclohexyloxocarborane trianion

The reaction of Li[closo-1-Me-1,2-C2B10H10] with cyclohexene oxide produced closo-1-Me-2-(2′-hydroxycyclohexyl)-1,2-C2B10H10 (1) in 86% yield. Decapitation of (1) with potassium hydroxide in refluxing ethanol gave the corresponding cage-opened potassium salt of the carborane anion, [nido-1-Me-2-(2′-hydroxycyclohexyl)-1,2-C2B9H10]− (2) in 82% yield. Deprotonation of (2) with two equivalents of n-butyllithium in THF at −78 °C, followed by its further reaction with anhydrous MCl4 · 2THF (M = Ti, Zr) produced the corresponding d0-half-sandwich metallacarboranes, closo-1-M(Cl)-2-Me-3-(2′-σ-O-cyclohexyl)-η5-2,3-C2B9H9 (3 M = Zr; 4 M = Ti), in 59% and 51% yields, respectively. Reaction of Li[closo-1,2-C2B10H11] with Merrifield’s peptide resin (1%) in refluxing THF gave the ortho-carborane-functionalized polymer (5) in 88% yield. The corresponding closo-1-polystyryl-2-(2′-hydroxycyclohexyl)-1,2-C2B10H10 (6) was produced in 94% yield by refluxing a mixture of the lithium salt of (5) and cyclohexene oxide in THF for 2 days. Compound (6) was decapitated, deprotonated and then reacted with ZrCl4 · 2THF to produce a polymer-supported d0-half-sandwich metallacarborane closo-1-Zr(Cl)-2-polystyryl-3-(2′-σ-O-cyclohexyl)-η5-2,3-C2B9H9 (7) in 41% yield. Compounds (3) and (7), in the presence of MMAO-7 (13% ISOPAR-E), were found to catalyze the polymerization of ethylene and vinyl chloride in toluene to give high molecular weight PE (9.4 × 103 (Mw/Mn = 1.8)) and PVC (2.1 × 103 (Mw/Mn = 1.6)), respectively.

Constrained-geometry half-sandwich titana- and zirconacarborane complexes, derived from the trianionic C(cage)-appended cyclohexyloxocarborane ligand, and the corresponding polymer-supported species were synthesized, spectroscopically characterized, and their catalytic activities in polymerization of ethylene and vinyl chloride have been explored.Figure optionsDownload as PowerPoint slide