Reactions of nitrogen mono-oxide with dicyclopentadienyltitanium complexes, including the formation of isocyanate from nitrogen mono-oxide and carbon mono-oxide

Abstract

Nitrogen mono-oxide (NO) rapidly oxidises Ti^III(cp)₂ complexes (cp =η-C₅H₅) according to the equations (i)–(iii) where ‘Ti(cp)₂O’ refers to a polymeric oxide of Ti^IV. The oxidation (iii) is complicated by the formation of small amounts of an NCO complex. Excess of [Ti(cp)₂(CO)₂] and NO react in toluene at 20 (70) or 65 °C (16 h)[{Ti(cp)₂Cl}₂]+ 2NO →[{Ti(cp)₂Cl}₂O]+ N₂O (i), 2[Ti(cp)₂(NCO)]+ 2NO →[{Ti(cp)₂(NCO)}₂O]+ N₂O (ii), [{Ti(cp)₂}₄(CO₃)₂]+ 4NO → 4 ‘Ti(cp)₂O’+ 2N₂O + 2CO₂(iii), to give CO, [Ti(cp)₂(NCO)], and ‘Ti(cp)₂O’, along with traces of Ti^III(cp)₂ products. The NO(reacted) : CO(produced) ratio is between 1 : 2.5 and 1 : 3.0. From e.s.r. and i.r. spectral data and product analyses it is suggested that [Ti(cp)₂(CO)₂] and NO initially give an equilibrium between [Ti(cp)₂(CO)(NO)] and [Ti(cp)₂(NO)], and that subsequent oxygen abstraction from [Ti(cp)₂(NO)]{by CO or [Ti(cp)₂(CO)₂]} or from the coupled intermediate [graphic omitted] {by [Ti(cp)₂(CO)₂]} gives the [Ti(cp)₂(NCO)] product. The compound [Ti(cp)₂] reacts with excess of NO to give a complex of empirical formula [Ti(cp)₂(NO)], which appears to contain Ti^IV and bridging N₂O₂ and cp ligands. The properties of [Ti(cp)₂(NCO)] are reported.