Manganese–Tin Triple Bonds: A New Synthetic Route to the Manganese Stannylidyne Complex Cation trans-[H(dmpe)2MnSn(C6H3‑2,6-Mes2)]+ (dmpe = Me2PCH2CH2PMe2, Mes = 2,4,6-Trimethylphenyl)

A new approach to the first complex featuring a manganese–tin triple bond that takes advantage of the propensity of dihydrogen complexes to eliminate H2 is reported. Reaction of the 18-valence-electron manganese dihydrogen hydride complex [MnH­(η2-H2)­(dmpe)2] (1) (dmpe = Me2PCH2CH2PMe2) with the organotin­(II) chloride SnCl­(C6H3-2,6-Mes2) (Mes = 2,4,6-trimethylphenyl) selectively afforded by H2 elimination the chlorostannylidene complex trans-[H­(dmpe)2MnSn­(Cl)­(C6H3-2,6-Mes2)] (2), which upon treatment with Na­[B­(C6H3-3,5-(CF3)2)4] and Li­[Al­(OC­(CF3)3)4] was transformed quantitatively into the stannylidyne complex salts trans-[H­(dmpe)2MnSn­(C6H3-2,6-Mes2)]­A [A = B­(C6H3-3,5-(CF3)2)4 (3a), Al­(OC­(CF3)3)4 (3b)]. Complexes 2 and 3a/3b were fully characterized, and the structures of 2 and 3a were determined by single-crystal X-ray diffraction. Complex 2 features the shortest Mn–Sn double bond reported to date, a large Mn–Sn–Caryl bond angle, and a long Sn–Cl bond of the trigonal-planar-coordinated tin center. These bonding features can be rationalized in valence-bond terms by a strong contribution of the triply bonded resonance structure [LnMnSnR]Cl and were verified by a natural resonance theory (NRT) analysis of the electron density of the DFT-minimized structure of 2. Complex 3a features the shortest Mn–Sn bond reported to date and a linearly coordinated tin atom. Natural bond order and NRT analyses of the electronic structure of the complex cation in 3a/3b suggested a highly polar Mn–Sn triple bond with a 65% ionic contribution to the NRT Mn–Sn bond order of 2.25. Complex 3a undergoes reversible one-electron reduction, suggesting that open-shell stannylidyne complexes might be accessible using strong reducing agents.