Metal complexes derived from o-carboranes : synthesis, structures and versatile properties

Abstract

In accordance with the recent needs for the development of new type of ancillary ligands particularly in metallocene chemistry, a set of new isopropyl bridged cyclopentadienyl ο-carboranyl ligands $CpHCMe_2CB_{10}H_{10}CR$ (R = H; 1, Me; 2) was prepared and their lithiation property was determined. Reaction systems of mono- or di-lithium salts of 1 and mono-lithiated 2 with group 4 halides or mono-$Cp^*$ Ti halides were investigated, leading to the preparation of several group 4 metal complexes including $rac-M(η^5:η^1-CpHCMe_2CB_{10}H_{10}C)_2$ (M = Ti; 3 Zr; 4, and Hf; 5), $Zr(η^5-CpHCMe_2CB_{10}H_{10}CR)_2$ (R=H; 6, Me; 7), $Zr(η^5:^1-CpHCMe_2CB_{10}H_{10}C)Cl_2$ (8), $Cp^*Ti(η^5-CpCMe_2CB_{10}H_{10}CR)Cl_2$(R = H; 9, Me; 11), $Cp^{*}Ti(η^5: ^1-CpCMe_2CB_{10}H_{10}C)Cl_2$ (10). For a given single crystals of 3, 4, and 5, the X-ray analysis reveals that only one form of racemic conformer exists. The variable temperature $^{11}B{^1H$} NMR Spectra of 4, reveal that this complex goes through the racemization, moving from one racemic conformer to the other by flipping the ligands in THF solution. Complex 4 is active for the polymerization of methyl methacrylate (MMA) without the presence of co-catalyst in THF solution. Complex 4, 6, and 7 with MMAO produced low molecular weight products in ethylene or propylene polymerization. Complex 5 showed photoluminescence (PL) at 420 nm. A new optical analysis system for the detection of mechanoluminescence (ML) determined the wavelength of complex 5 at 435 nm. The electroluminescence (EL) of green light was observed in the complex 5 blended with poly (N-vinylcabazole) (PVH) system. Maximum luminescence of 47 Cd/㎠ was achieved at 30 V at 530 nm. Complex 9 and 11 is active for the polymerization of ethylene and propylene with MMAO in Toluene. In the polymerization of ethylene, these system act like conventional metallocene catalysts, from a point of view of molecular weight(MW) and molecular weight distribution(MWD), and p...