A versatile synthetic route for cyclopentadienyl-amido titanium(IV) compounds. NMR spectroscopy study and X-ray molecular structure of [Ti{eta(5)-C5H4SiMe2NMe(CH2)(2)-eta-NMe}Cl-2]

The reaction of the chlorosilyl-substituted cyclopentadienyltitanium compou nd [Ti(eta (5)-C5H4-SiMe2Cl)Cl-3] with N,N ' -dimethylethylenediamine in th e presence of 2 equiv of NEt3 gave a mixture of two complexes, [Ti{eta (5)- C5H4SiMe2NMe(CH2)(2)-eta -NMe}Cl-2] (1) and [Ti{eta (5)-C(5)H(4)SiMe(2)eta -N(CH2)(2)-eta -NHMe}Cl-2] (2), in a molar ratio of 3:1. However, a similar reaction with N-methylethylenediamine afforded complex 2 regiospecifically . The dialkyl derivatives [Ti-{eta (5)-C5H4SiMe2NMe(CH2)(2)-eta -NMe}R-2] ( R = Me (3), CH2Ph (4)) were prepared by reacting the dichloride complex 1 w ith 2 equiv of MgClMe or 1 equiv of Mg(CH2Ph)(2). 2THF, respectively. The a nalogous reaction with LiNMe2 afforded the diamido derivative [Ti{eta (5)-C 5H4SiMe2NMe(CH2)(2)-eta -NMe}(NMe2)(2)] (5) in high yield. Complex 1 reacts with dry CO2 via insertion of a molecule of CO2 into each of the Ti-N and Si-N bonds to yield the dicarbamate compound [Ti{(eta (5)-C5H4SiMe2OC(O)NMe (CH2)(2)NMe(eta (2)-CO2)}Cl-2] (6), in which the carbamate groups are bound in eta (2)- and eta (1)-fashion. Thermal decomposition of complex 6 afford ed the known oxo derivatives [Ti{mu-(eta (5)-C5H4SiMe2-eta -O)}Cl-2](2) and [(TiCl2)(2)(mu -O)-[mu-{(eta (5)-C5H4SiMe2)(2)-(mu -O)}] with elimination of CO2 and 1,3-dimethyl-2-imidazolidinone. The conformational interconversi on of 1 and 6 and the reversible coordination of the terminal "NHMe" group to the metal center in 2 were studied in solution by DNMR spectroscopy. The crystal structure of 1 was determined by X-ray diffraction methods.