Derivatisation of boryl substituted titanium half-sandwich complexes – Molecular structures of [Ti{(η5-C5H4)B(NiPr2)N(H)tBu}Cl2(NMe2)] and [{TiCl2(μ-{OB(NHMe2)-η5-C5H4})}2-μ-O]

The half-sandwich complex [Ti{(η5-C5H4)B(NiPr2)N(H)iPr}(NMe2)3] (6) was prepared from (η1-C5H5)B(NiPr2)N(H)iPr (5) and [Ti(NMe2)4] with cleavage of one equivalent of HNMe2 and further converted into the corresponding constrained geometry complex [Ti{(η5-C5H4)B(NiPr2)NiPr}(NMe2)2] (7) by elimination of a second equivalent of HNMe2. Reaction of the half-sandwich complexes [Ti{(η5-C5H4)B(NiPr2)N(H)R}(NMe2)3] (R = iPr, tBu) with excess Me3SiCl yielded the corresponding dichloro complexes [Ti{(η5-C5H4)B(NiPr2)N(H)R}Cl2(NMe2)] (R = tBu (10), iPr (11)). The intermediate species [Ti{(η5-C5H4)B(NiPr2)N(H)iPr}Cl(NMe2)2] (9) could also be spectroscopically characterised. Partial hydrolysis of 10 and 11, respectively, resulted in formation of [{TiCl2(μ-{OB(NHMe2)-η5-C5H4})}2-μ-O] (12). The molecular structures of 10 and 12 have been determined by X-ray crystallographic analyses. Complex 10, when activated with MAO, was found to be a highly active styrene polymerisation catalyst while being inactive towards the polymerisation of ethylene.