Syntheses and structural characterizations of di-substituted alkylimido hexamolybdates: an insight on bi-alkylimido functionalization

Abstract

Bi-alkylimido functionalization of hexamolybdates has been developed and several novel di-substituted alkylimido hexamolybdates with n-butyl, cyclohexyl and tert-butylamines as the imido-releasing reagents have been synthesized in reasonable yields. Their structures have been characterized by elemental analysis, IR, UV-Vis, and ESI mass spectrometry. Moreover, the structures of [Mo₆O₁₇(NCy)₂]²⁻ and [Mo₆O₁₇(NCMe₃)₂]² have been determined by single-crystal X-ray diffraction techniques. It is notable that the compound (Bu₄N)₂[Mo₆O₁₇(NCy)₂] crystallizes in polar space group Fdd2 with potential ferroelectricity. In addition, theoretical investigation of the reactivity and regioselectivity of bi-alkylimido functionalization has also been conducted. The calculation results show that more energy is required for the bi-functionalization process than for the mono-substitution process, and that the cis-bi-functionalization is the kinetically favored process while trans-[Mo₆O₁₇(NR)₂]²⁻ is the thermodynamically favored product.