Formation of the 1,4-diazabutadien-2-yl complex [Mn(CNPh*)4{C(=NPh*)C(CH3)=N(Ph*)}] through methylation of a manganese(-I) isonitrilate

Article abstract of DOI:10.1021/om970287h

Alkylation of [Mn(CNPh*)₅]^- with CH₃I gives the 1,4-diazabutadien-2-yl complex [Mn-(CNPh*)₄{C(=NPh*)C(CH₃)=N(Ph*)}] (2) in a 30% yield, as established by a single-crystal X-ray diffraction study. The same product can be obtained in poor yield when CH₃OSO₂-CF₃ is used as the alkylating agent, and use of ethyl iodide gives the corresponding ethyl complex [Mn(CNPh*)₄{C(=NPh*)C(CH₂CH ₃)=N(Ph*)}] (3). It is proposed that the first step in the formation of 2 is alkylation at manganese: transient [Mn(CNPh*)₅CH₃] is then converted into an iminoacyl complex by isonitrile/alkyl insertion. Insertion of a second isonitrile into the metal-iminoacyl bond leads to the 1,4-diazabutadien-2-yl complex. The addition of free CNPh* to the reaction solution leads to only a modest increase in the yield of 2, but the importance of exogenous isonitrile is supported by the formation of [Mn(CN^t-Bu)(CNPh*)₃{C(=NPh*)C(CH ₃)=N(Ph*)}] (4), in which 1 equiv of CN^tBu is coordinated to Mn, when CN^tBu is added to a solution of 1^- before reaction with CH₃I.