Phosphorescent complexes of {Mo6I8}4+ with triazolates: [2+3] cycloaddition of alkynes to [Mo6I8(N3)6]2−

Abstract

(Bu₄N)₂[Mo₆I₈(N₃)₆], prepared in a clean high-yield reaction from (Bu₄N)₂[Mo₆I₈(CH₃COO)₆] and Me₃SiN₃, undergoes [3+2] cycloaddition with CH₃O(O)CC(O)OCH₃ with the formation of a novel hexakis(triazolate) complex, (Bu₄N)₂[Mo₆I₈(N₃C₂(COOCH₃)₂)₆] with symmetrically coordinated 4,5-di(carbmethoxy)triazol-2-yl ligands. The product was characterized by X-ray analysis, NMR, IR and ESI-mass spectrometry. It undergoes a quasi reversible oxidation in CH₃CN at E_1/2 = 1.36 V (vs. Ag/AgCl) and is red-light emissive upon UV photoexcitation. Reaction with methylpropiolate also yields a corresponding hexakis(triazolate) complex, [Mo₆I₈(N₃C₂H(COOCH₃))₆]²⁻, which exists as a 1 : 1 mixture of two isomers. Alkynes that lacking strongly electron-withdrawing substituents fail to undergo the cycloaddition reaction.