Synthesis of cyclic diamino-substituted metal carbene complexes

A series of heterocyclic metal carbene complexes were prepared bg the deoxygenation reaction of M(CO)(6) (M = Cr, Mo, W) with RNH(CH2)(n)N=PPh(3) (R = H, Et, Ph; n = 2, 3, 4) to form the corresponding isocyanide complex, which subsequently underwent intramolecular cyclization to give (CO)(5)M=CN(R)(CH2)(n)NH in good yields. None of the carbene complex reacted further with amine-phosphinimine RNH(CH2)(n)N=PPh(3) to give the bis(carbene) complex. Deprotonation of the N-H of the carbene complex followed by the reaction of alkyl iodides provided the N-alkylated product. In the case of N-allyl-substituted complexes (Co>(5)M=CNR(CH2>N-2(CH2CH=CH2) (M = Cr, Mo, W), the carbon-carbon double bond underwent intramolecular ligand displacement of carbonyl Ligand to yield the corresponding pi-coordinated complex. Unlike the group VI metal carbonyl complexes, treatment of ReBr(CO)(5) with 2 molar equiv of Ph(3)P=N(CH2)(2)NH2 provided a bis(carbene) complex fac-(CO)(3)BrRe(=CNHCH2CH2NH)(2). All complexes are characterized by both spectral and elemental analyses. Complexes (CO)(5)Mo=CNHCH2CH2CH2NH (18) and fac-(CO)(3)BrRe-(=CNHCH2CH2NH)(2) (42) were further characterized by X-ray single-crystal analysis.