Reversible double insertion of aryl isocyanates into the Ti-O bond of titanium(IV) isopropoxide

The insertion of phenyl isocyanate into titanium isopropoxide leads to the formation of a dimeric complex $[Ti(O^iPr)_2(\mu -O^iPr){C_6H_5N(O^iPr)CO}]_2$ (1) which has been structurally characterized. Reaction of titanium isopropoxide with two and more than 2 equiv. of phenyl isocyanate is complicated by competitive, reversible insertion between the titanium carbamate and titanium isopropoxide. The ligand formed by insertion of phenyl isocyanate into the titanium carbamate has been structurally characterized in its protonated form $C_6H_5N{C(O^iPr)O}C(O)N(H)C_6H_5 (3aH)$. Insertion into the carbamate is kinetically favored whereas insertion into isopropoxide gives the thermodynamically favored product