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

The reactions of [Ti(η 5 -Ind)(NMe 2 ) 2 Me], [Ti(η 6 -Ind)(NMe 2 )Cl 2 ], and [Zr(η 5 -Ind)(NMe 2 ) 2 Cl] with 2,6-dimethylphenyl isocyanide (CN(2,6-Me 2 Ph)) 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(η 5 -Ind)(NMe 2 ) 2 {C(Me)=N-t-Bu}] (1), which, according to DFT results, is due to the weakness of the Ti-CH 3 bond when compared to Ti-NR 2 . [Ti(η 5 -Ind)(NMe 2 )Cl 2 ] was found to react with 1 equiv of CN(2,6-Me 2 Ph) to yield [Ti(η 5 -Ind){C(NMe 2 )=N(2,6-Me 2 Ph)}Cl 2 ] (2). Two equivalents of 2,6-dimethylphenyl isocyanide reacts with [Zr(η 5 -Ind)(NMe 2 ) 2 Cl] to give the double insertion compound [Zr(η 5 -Ind){C(NMe 2 )=N(2,6-Me 2 Ph)} 2 Cl] (3). The same reaction performed with CN-t-Bu proceeds slowly and enabled the characterization, by NMR, of [Zr(η 5 -Ind)(NMe 2 ){C(NMe 2 )=N-t-Bu}Cl] (4) and [Zr(η 5 -Ind){C(NMe 2 )=N-t-Bu} 2 Cl] (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(η 5 -Ind)(NR 2 ) 2 Cl] (R = H, Me) have been performed and show that the progressive stability of the insertion products accounts for the experimentally found double insertion product.