Reactions of titanocene-bis(trimethylsilyl)ethyne complexes with diethynylsilane derivatives

Titanocene complexes [Ti(η5-C5H5−nMen)2(η2-Me3SiCCSiMe3)] (n=0, 4 and 5) react uniformly with siladiynes R22Si(CCR1)2, where R1=Ph, and R2=Ph or Me, at elevated temperature in hydrocarbon solvents to give the corresponding silacyclobutene-annelated titanacyclobutene complexes, 3-bis(η5-cyclopentadienyl)titana-6-diorganylsilabicyclo[2.2.0]hexa-1(2),4(5)-dienes, [(η5-C5H5−nMen)2Ti{R12C4(SiR22)}]. Products arising from [Ti(η5-C5H5−nMen)2(η2-Me3SiCCSiMe3)] (n=0, 2 (1,3-isomer), 4 and 5) and Me2Si(CCCMe3)2 vary with n: the non-methylated titanocene complex affords a mixture of an analogous silacyclobutene-annelated titanacyclobutene and [{Ti(η5-C5H5)2}2{μ-η(3–5):η(4–6)-Me3CCCCCCMe3}], the permethylated titanocene precursor gives mainly the allyldiene complex [Ti(η5-C5Me5)(η3:η4-C5Me3(CH2)2)] while no titanium-containing product could be isolated for n=4. The reaction of [Ti(η5-1,3-C5H3Me2)2(η2-Me3SiCCSiMe3)] with Me2Si(CCCMe3)2, however, cleanly affords the expected silacyclobutene–titanacyclobutene complex. All complexes were studied by spectral methods and solid-state structure of two representatives, [(η5-C5Me5)2Ti{Ph2C4(SiMe2)}] and [(η5-1,3-C5H3Me2)2Ti{(Me3C)2C4(SiMe2)}] was determined by single-crystal X-ray diffraction.