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(eta(5)-C5Me5)R-2}(2)(mu-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 eta(2)-iminoacyl species [{Ti(eta(5)-C5Me5)(R'NCR)R}(2)(mu-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 [Ti-2(eta(5)-C5Me5)(2)(mu-O)(mu-NiPr) {N(iPr)CMe=CMe2}Me] (7), whereas the reaction of complex 2 with XylNC rendered the N-C bond cleavage product [{Ti(eta(5)-C5Me5)(CH=CHPh)}(mu-O)(mu-kappa(2)-N,C-N(MeC6H3)CH2){Ti(eta(5)-C5Me5)}] (8). The reactions of 1 with nitriles tBuCN and iPrCN gave the ketimido products [{Ti(eta(5)-C5Me5)Me(CN(Me)R')}(2) (mu-O)] (R' = tBu 9, iPr 10), whereas the analogous processes with 2 gave the alkenyl-imido complexes [{Ti(eta(5)-C5Me5)(CH2Ph)(2)}(mu-O){Ti(eta(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(eta(5)-C5Me5)Me-2}(mu-O){Ti(eta(5)-C5Me5)(kappa(2)-C,N-Me-2 CNSiMe3 )(CNSiMe3)] (13).