Aromaticity-Driven Molecular Structural Variation and Electronic Configuration Alternation: An Example of Cyclic π Conjugation Involving a Mo–Mo δ Bond

We have synthesized and characterized the mixed-ligand dimolybdenum paddlewheel complex Na[(DAniF)3Mo2(C3S5)] (Na[1]; DAniF = N,N′-di-p-anisylformamidinate, dmit = 1,3-dithiole-2-thione-4,5-dithiolate), which has a six-membered chelating [Mo2S2C2] ring created by equatorial coordination of the dmit (C3S5) ligand to the Mo2 unit. One-electron oxidation of Na[1] using Cp2FePF6 yields the neutral complex [(DAniF)3Mo2(C3S5)] ([1]), and removal of two electrons from Na[1] using AgBPh4 gives [(DAniF)3Mo2(C3S5)]BPh4 ([1]BPh4). In the crystal structures, [1]− and [1] present dihedral angles of 118.9 and 142.3° between the plane defined by the Mo–Mo bond vector and the dmit ligand, respectively, while DFT calculations show that in [1]+ the Mo–Mo bond and the dmit ligand are coplanar. Complex [1] is paramagnetic with a g value of 1.961 in the EPR spectrum and has a Mo–Mo bond distance of 2.133(1) A, increased from 2.0963(9) A for [1]−. Consistently, a broad absorption band is observed for [1] in the near-IR region,...