Synthesis, Structure, and Reactions of Stable Titanacyclopentanes

Article abstract of DOI:10.1246/bcsj.64.2475

Titanacyclic compounds of the formula Cp^*2Ti<*>(CH2CH2C<*>(CH2C<*>HR)C<*>H2) (5a; R=H and 5b; R=C6H5, Cp*=pentamethylcyclopentadienyl), the first stable titanacyclopentanes, have been prepared by the reaction of bis(pentamethylcyclopentadienyl)titanium-ethylene complex (3) with methylenecyclopropanes (4), and their structures were determined based on both spectroscopic data and X-ray crystallography.Complex 5b crystallized in space group P2₁/a (Z=4) with cell constants, a=21.832(3), b=8.580(1), c=14.759(2) Angstroem, β=96.81(1) deg, U=2744.9(6) Angstroem³ (4261 reflections, R=0.053).The reaction of 5 with carbon monoxide afforded spiro<2.4>heptan-5-ones in 98percent yield.The thermal decomposition of 5 has been investigated, and possible mechanisms of the reactions have been proposed based on deuterium-labeled experiments.A novel formal reductive elimination of organic ligands giving 1-phenylspiro<2.4>hexane has been observed in the thermolysis of 5b.A structure-reactivity relationship has been discussed.