Insertion of isocyanides into Re---C bonds

Isocyanide-substituted Re alkyl complexes cis-p-XC₆H₄CH₂Re(CO)₄(CN-p-tolyl) (X = Cl, OMe) were prepared from the PdO-catalyzed reaction of p-XC₆H₄CH₂Re(CO)₅ (X = Cl, OMe) with p-tolyl isocyanide. On heating in toluene these complexes undergo isocyanide insertion into the Re---C bond to afford iminoacyl complexes which further react to orthometallate the p-tolyl ring. An X-ray crystal structure determination on (CO)₄

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(3a) revealed that C₁₉H₁₃ClO₄NRe crystallizes in the monoclinic space group P2₁/c with 4 formulas per unit cell. Unit cell parameters are a = 9.799 (1), B = 15.252 (2), C = 13.569 (2) Å and β = 110.788 (8)°. The structure shows Re---C bond distances indicative of substantial carbenoid character.