Hybrid Organic/Inorganic Complexes Based on Electroactive Tetrathiafulvalene-Functionalized Diphosphanes Tethered to C3-Symmetrized Mo3Q4 (Q = S, Se) Clusters

A two-step procedure for the preparation of hybrid complexes based on electroactive tetrathiafulvalene (TTF)- functionalized o-P2 diphosphanes (o-P2 = 3,4-dimethyl-3,4-bis(diphenylphosphino)tetrathiafulvalene) and inorganic C3-symmetrized Mo3Q4 (Q = S, Se) clusters, namely, [Mo3S4Cl3(o-P2)3]PF6 ([1]PF6) and [Mo3Se4Cl3(o-P2)3]PF6 ([2]PF6), is reported. Their molecular and electronic structures are also described on the basis of X-ray diffraction experiments and density functional theory (DFT) calculations aimed at understanding the interactions established between both the organic and the inorganic parts. Cyclic voltammograms of compounds [1]PF6 and [2]PF6 display reduction features associated to the Mo3Q4 core and oxidation characteristics due to the TTF skeleton. The oxidation chemistry of [1]PF6 and [2]PF6 in solution is also investigated by means of ̈in situ electrospray ionization (ESI) mass spectrometry, UV−vis, and, electron paramagnetic resonance (EPR) measurements. Upon addition of increasing amounts of NOPF6 (less than 3 equiv), the sequential formation of 1n+ (n = 1−4) species was observed whereas addition of a 3-fold excess of NOPF6 allows to access the three-electron oxidized [Mo3S4Cl3(o-P2)3]4+ (14+) and [Mo3Se4Cl3(o-P2)3]4+ (24+) cations. These 14+ and 24+ cations represent still rare examples of complexes with oxidized TTF-ligands that are remarkably stable either toward diphosphane dissociation or phosphane oxidation. Polycrystalline samples of compound [1](PF6)4 were obtained by oxidation of compound [1]PF6 using NOPF6 which were analyzed by solid state absorption, UV−vis, and Raman spectroscopies