Another example of carborane based trianionic ligand: Syntheses and catalytic activities of cyclohexylamino tailed ortho-carboranyl zirconium and titanium dicarbollides

In situ reaction of Li[closo-1-Ph-1,2-C2B10H10] with 7-azabicyclo [4.1.0] heptane results in the formation of the disubstituted carborane, closo-1-Ph-2-(2′-aminocyclohexyl)-1,2-C2B10H10 (1), in 63% yield. Decapitation of (1) with potassium hydroxide in refluxing ethanol produces the cage-opened nido-carborane, K[nido-7-Ph-8-(2′-aminocyclohexyl)-7,8-C2B9H10]− (2), in 80% yield. Deprotonation of the above monoanion with two equivalents of n-butyllithium followed by reaction with anhydrous MCl4 · 2THF (M = Zr, Ti) provides d0-half-sandwich metallocarboranes, closo-1-M(Cl)-2-Ph-3-(2′-σ-(H)N-cyclohexyl)-2,3-η5-C2B9H9 (3 M = Zr; 4 M = Ti) in 53% and 42% yields, respectively. The reaction of Li[closo-1,2-C2B10H11] with 7-azabicyclo [4.1.0] heptane in THF affords closo-1-(2′-aminocyclohexyl)-1,2-C2B10H10 (5) in 59% yield. Immobilization of the carboranyl amino ligand (1) to an organic support, Merrifield’s peptide resin (1%), has been achieved by the reaction of the sodium salt of (5) with polystyryl chloride in THF to produce closo-1-(2′-aminocyclohexyl)-2-polystyryl-1,2-C2B10H10 (6) in 87% yield. Further reaction of the dianion derived from (6) with anhydrous ZrCl4 · 2THF led to the formation of the organic polystyryl supported d0-half-sandwich metallocarborane, closo-1-Zr(Cl)-2-(2′-σ-(H)N-cyclohexyl)-3-polystyryl-2,3-η5-C2B9H9 (7), in 38% yield. These new compounds have been characterized by elemental analyses, NMR, and IR spectra. Polymerizations of both ethylene and vinyl chloride with (3) and (7) have been performed in toluene using MMAO-7 (13% ISOPAR-E) as the co-catalyst. Molecular weights up to 32.8 × 103 (Mw/Mn = 1.8) and 9.5 × 103 (Mw/Mn = 2.1) were obtained for PE and PVC, respectively.

C(Cage)-substituted cyclohexylamino-carborane trianionic ligand coordinated Zr and Ti complexes and polymer supported analogues were synthesized and structurally investigated by NMR, IR spectroscopy, and, in the case of polymer supported compounds, by DSC–TGA analysis. The polymerization of vinyl chloride and ethylene catalyzed by the new complexes is discussed.Figure optionsDownload as PowerPoint slide