Transformation of 5-chloro- and 5-bromo-2-cyanopyridine to amides and iminonitriles at the Mo(IV) center

Jurowska, Anna, Koprowska, Martyna, Bogdał, Weronika, Hodorowicz, Maciej, Szklarzewicz, Janusz

molybdenum  nitriles  cyanides  structure  ligand modification 

The reaction of $K_{3}Na[Mo(CN)_{4}O_{2}]·6H_{2}O$ complex with 5-chloro-2-cyanopyridine (5cl2py) and 5-bromo-2-cyanopyridine (5br2py), results in isolation of 4 new compounds, which were characterized by single X-ray crystal structure measurements, elemental analyses, IR and UV-Vis spectroscopy methods. Dimeric complex with the formula $(PPh_{4})_{4}[Mo(CN)_{3}O(μ-CN)Mo(CN)_{4}(H_{2}O)]·5cl2py·5H_{2}O·EtOH$ was isolated for the first time. The exchange of cyanido ligands for bidentate organic ligands, in this type of complexes, is largely pH dependent. Careful control of the reaction environment made it possible to obtain a modified organic ligand in which the nitrile group was hydrolyzed to the amide group (pH ca 8), or transformed, due to presence of cyanides in solution, to imino(5-chloropyridin-2-yl)acetonitrile (5cl2pya) or imino(5-bromopyridin-2-yl)acetonitrile (5br2pya), respectively. Two complexes with the formulas $(PPh_{4})_{2}[Mo(CN)_{3}O(5cl2pya)]·5cl2py$ and $(PPh_{4})_{2}[Mo(CN)_{3}O(5br2pya)]·5br2py$ (pH ca 10) were isolated. In these compounds, the 5cl2pya (or 5br2pya) was coordinated to the metal center as N,N-donating ligand, in which the modification of the nitrile group is discussed in detail in the paper.