Inorganic Chemistry, Vol.43, No.21, 6786-6792, 2004
Terminal titanium-ligand multiple bonds. Cleavages of C = O and C = S double bonds with Ti imido complexes
Treatment of t-BuN=TiCl2Py3 with 2 equiv lithium ketiminate compound, Li[OCMeCHCMeN(Ar)] (where Ar = 2,6-diisopropylphenyl), in toluene at room temperature gave t-BuN=Ti[OCMeCHCMeN(Ar)](2) (1) in high yield. The reaction of 1 with phenyl isocyanate at room-temperature resulted in imido ligand exchange producing PhN=Ti[OCMeCHCMeN(Ar)](2) (2). Compound 1 decomposed at 90 degreesC to form a terminal titanium oxo compound O=Ti[OCMeCHCMeN(Ar)](2) (3) and t-BuNHCMeCHCMeNAr (4). Also, the compound 3 could be obtained by reacting 1 with CO2 under mild condition. Similarly, while 1 reacts with an excess of carbon disulfide, a novel terminal titanium sulfido compound S=Ti[OCMeCHCMeN(Ar)](2) (5) was formed via a C=S bond breaking reaction. A novel titanium isocyanate compound Ti[OCMeCHCMeN(Ar)](2)(NCO)(OEt) (6) was formed on heating 1 with 1 equiv of urethane, H2NCOOEt. Compounds 1-6 have been characterized by H-1 and C-13 NMR spectroscopies. The molecular structures of 1, 3, 5, and 6 were determined by single-crystal X-ray diffraction. A theoretical calculation predicted that the cleavage of the C-S double bonds for carbon disulfide with the Ti=N bond of compound 1 was estimated at ca. 21.8 kcal(.)mol(-1) exothermic.