Insertion of Isocyanides into Group 4 Metal−Carbon and Metal−Nitrogen Bonds. Syntheses and DFT Calculations

The reactions of [Ti(η5-Ind)(NMe2)2Me], [Ti(η5-Ind)(NMe2)Cl2], and [Zr(η5-Ind)(NMe2)2Cl]
with 2,6-dimethylphenyl isocyanide (CN(2,6-Me2Ph)) and tert-butyl isocyanide (CN-t-Bu) have
been investigated. For the first complex, insertion occurs exclusively into the Ti−C bond to
give [Ti(η5-Ind)(NMe2)2{C(Me)N-t-Bu}] (1), which, according to DFT results, is due to the
weakness of the Ti−CH3 bond when compared to Ti−NR2. [Ti(η5-Ind)(NMe2)Cl2] was found
to react with 1 equiv of CN(2,6-Me2Ph) to yield [Ti(η5-Ind){C(NMe2)N(2,6-Me2Ph)}Cl2] (2).
Two equivalents of 2,6-dimethylphenyl isocyanide reacts with [Zr(η5-Ind)(NMe2)2Cl] to give
the double insertion compound [Zr(η5-Ind){C(NMe2)N(2,6-Me2Ph)}2Cl] (3). The same
reaction performed with CN-t-Bu proceeds slowly and enabled the characterization, by NMR,
of [Zr(η5-Ind)(NMe2){C(NMe2)N-t-Bu}Cl] (4) and [Zr(η5-Ind){C(NMe2)N-t-Bu}2Cl] (5). The
molecular structures of 2 and 3 have been determined by X-ray diffraction. DFT calculations
of the insertion of CNH in the zirconium nitrogen bonds of [Zr(η5-Ind)(NR2)2Cl] (R = H, Me)
have been performed and show that the progressive stability of the insertion products
accounts for the experimentally found double insertion product.