Reaction of Cp*2Zr(2,3-dimethylbutadiene) with Isonitriles and CO

We have investigated the reaction of isonitriles with a permethylzirconocene complex of 2,3-dimethylbutadiene. Cp*2Zr­(2,3-dimethylbutadiene) (1) reacts with tert-alkyl isonitriles to give η2-iminoacyl complexes Cp*2Zr­[CH2C­(CH3)­C­(CH3)­CH2C­(NR)] 2 (R = tBu) and 3 (R = 1-adamantyl). Treatment of 2 with excess isopropyl isonitrile gives the η1,η2-bis­(iminoacyl) complex Cp*2Zr­[C­(NiPr)­CH2C­(CH3)­C­(CH3)­CH2C­(­(NiPr)] (4) and free tert-butyl isonitrile. The reaction of 1 with 2 equiv of isopropyl isonitrile also affords 4, through the intermediate Cp*2Zr­[CH2C­(CH3)­C­(CH3)­CH2C­(NiPr)] (5). Carbonylation of 2 affords the Zr formimidoyl cyclopentadienolate 6. Treatment of a Zr hydride cyclopentadienolate (7), obtained from the carbonylation of 1, with tert-butyl isonitrile also affords 6. Isotopic labeling shows that the insertion of tert-butyl isonitrile into 1 and 7 is reversible. All complexes were characterized by spectroscopic and crystallographic methods.