Revisiting the coordination chemistry of molybdenum(V)

Reactions of (pyH)$_5$[MoOCl$_4$(H$_2$O)]$_3$Cl$_2$ with picolinic and pyrazinoic acids yielded three new dinuclear molybdenum(V) complexes: (pyH)$_2$[Mo$_2$O$_4$Cl$_2$(pic)$_2$]·CH$_3$CN (1), (pyH)$_2$[Mo$_2$O$_4$Cl$_2$(pic)$_2$]·CH$_3$CH$_2$CN (2) and (pyH)$_2$[Mo$_2$O$_4$Cl$_2$(pyraz)$_2$]·CH$_3$CN (3) (pic$^−$ = picolinate, pyraz$^−$ = pyrazinoate and pyH$^+$ = protonated pyridine). The compounds were characterized by single-crystal X-ray diffraction, infrared and $^1$H NMR spectroscopy, elemental analysis, and TG/DSC measurements. All display a robust {Mo$^V_2$O$_4$}$^{2+}$ core with the heteroaromatic ligands bound in a N,O-bidentate chelating manner.