Structural Diversity in the Reactions of Dimetallic Alkyl Titanium Oxides with Isonitriles and Nitriles

Abstract

A detailed study of the reaction of the dinuclear [{Ti­(η5-C5Me5)­R2}2(μ-O)] (R = Me 1, CH2Ph 2) compounds with a series of organic isonitriles (R′NC, R′ = tBu, iPr, CH2SiMe3, Xyl) (Xyl = 2,6-Me2C6H3) and nitriles (R′CN, R′ = tBu, iPr, SiMe3) has been carried out. Single-crystal X-ray structural studies revealed a variety of reactivity and structural moieties. Theoretical calculations (density functional theory, DFT) were used to understand the mechanism of some uncommon reactions observed experimentally. Reactions of 1 and 2 with isocyanides tBuNC, iPrNC, and Me3SiCH2NC led to the formation of dimetallic η2-iminoacyl species [{Ti­(η5-C5Me5)­(R′NCR)­R}2(μ-O)] (R = Me, R′ = tBu 3, iPr 4, CH2SiMe3 5; R = CH2Ph, R′ = CH2SiMe3 6). Complex 4 underwent net rearrangements at room temperature to give the imido-vinylamido derivative [Ti2(η5-C5Me5)2(μ-O)­(μ-NiPr) {N­(iPr)­CMeCMe2}­Me] (7), whereas the reaction of complex 2 with XylNC rendered the NC bond cleavage product [{Ti­(η 5 -C5Me5)­(CHCHPh)}­(μ-O)­(μ-κ 2 -N,CN­(MeC6H3)­CH2)­{Ti­(η 5 -C5Me5)}] (8). The reactions of 1 with nitriles tBuCN and iPrCN gave the ketimido products [{Ti­(η 5 -C5Me5)­Me­(CN­(Me)­R′)}2(μ-O)] (R′ = tBu 9, iPr 10), whereas the analogous processes with 2 gave the alkenyl-imido complexes [{Ti­(η 5 -C5Me5)­(CH2Ph)2}­(μ-O)­{Ti­(η 5 -C5Me5)­(NC­(R′)C­(H)­Ph)­(NCR′)}] (R′ = tBu 11, iPr 12) with the concomitant coordination of a nitrile molecule. Complex 1 reacts with Me3SiCN to afford the nitrile–isonitrile isomerization product [{Ti­(η 5 -C5Me5)­Me2}­(μ-O)­{Ti­(η5-C5Me5)­(κ 2 -C,N-Me2CNSiMe3)­(CNSiMe3)] (13).