ИСТИНА

Transition metal σ-ethynylpyridyl complexes attract considerable research interest since they can act as precursors for pyridylvinylidene complexes and as buildings blocks for supramolecular assemblies in molecular electronics, as well as materials for nonlinear optics. Aiming at the development of a convenient route to the iron σ-pyridylethynyl complex Cp(CO)2Fe-C≡С-(2-C5H4N) (Ia), we studied the Pd/Cu-catalyzed reaction of Cp(CO)2FeI with 2-ethynylpyridine. The reaction was found to afford a binuclear FePd µ-pyridylvinylidene complex [Cp(CO)Fe{μ2-η1(Cα):η1(Cα)-κ1(N)-Cα=Cβ(H)(2-C5H4N)}(μ-CO)PdI] (II) (in slight yield of 2%), rather than the expected Sonogashira product Ia. The molecular structure of complex II was determined by X-ray diffraction [1]. While optimizing the synthesis of the FePd complex, the conditions for high-yield isolation of II were found and the factors resulting in the“abnormal” reaction pathway were revealed. An alternative synthetic approach to the σ-pyridylethynyl complex Ia and its analogue Ib was developed. Possible reasons for the coupling reaction to proceed along the “abnormal” and “expected” pathways are proposed. [1] V.V. Verpekin, A.Z. Kreindlin, O.V. Semeikin, A.F. Smol’yakov, F.M. Dolgushin, O.S. Chudin, N.A. Ustynyuk, Acta Crystallographica, section E. 2017, 73, 68-71.