Dinuclear and mononuclear chromium acetylide complexes

Abstract

Reaction of trans-Cl2Cr(dmpe)2 (1) dmpe = 1,2-bis(dimethylphosphanyl)ethane] with 0.5 equiv. of Me3SnC=CC=CSnMe3 or Me3SnC=CC6H4C=CSnMe3 afforded the dinuclear complexes trans-Cl(dmpe)2Cr=CC=CC=Cr(dmpe)2Cl] (2), trans-Cl(dmpe)2CrC=CC=CCr(dmpe)2Cl]SnMe3Cl2]2 (2SnMe3Cl2]2), and trans-Cl(dmpe)2CrC=CC6H4C=CCr(dmpe)2Cl]SnMe3Cl2]2 (3SnMe3Cl2]2), which could be transformed to the 2PF6]2 and 3BPh4]2 salts. Substitutions of the chloride groups in 2 were carried out to achieve the corresponding iodo (4) and (trimethylsilyl)alkynyl (5) complexes. Utilizing similar reactions and treatment with only 1 equiv. of the corresponding alkynyl ligand Me3SnC=CR (R = SnMe3, C6H5), Me3SnC=CC=CR (R = SiMe3, SnMe3), and Me3SnC=CC6H4C=CSnMe3] allowed us to prepare a series of mononuclear monoacetylide complexes: trans-Cl(dmpe)2CrC=CR] R = SnMe3(6),C6H5(7)], trans-Cl(dmpe)2CrC=CC=CR] R = SiMe3(8),SnMe3(9)], and trans-Cl(dmpe)2CrC=CC6H4C=CSnMe3] (10), respectively. The complexes 2, 2SnMe3Cl2]2, 2PF6]2, 3SnMe3Cl2]2, 3BPh4]2, and 610 displayed paramagnetic behavior. Electrochemical studies performed on the dinuclear complexes (2), (2SnMe3Cl2]2), (3SnMe3Cl2]2), and (5) showed one two-electron redox wave revealing a class-I type behavior based on the RobinDay classification, which is untypical for dinuclear complexes bridged by a butadiyne ligand. The complexes were characterized by NMR, ESIMS, cyclic voltammetry, EPR spectroscopy, magnetic measurements, and exemplary single-crystal X-ray diffraction studies for 2, 2SnMe3Cl2]2, 8, 9, and 10.