Synthesis, characterization, and crystal structure of a quadruply bonded dimolybdenum(II) complex containing the water-soluble phosphine 1,3,5-triaza-7-phosphaadamantane (PTA)

The quadruply bonded molybdenum(II)-molybdenum(II) complex, tetrachlorotetrakis(1,3,5-triaza-7-phosphaadamantane) dimolybdenum(H), Mo2Cl4(PTA)(4), was synthesized by reaction of 1,3,5-triaza-7-phosphaadamantane (PTA) with K-4[Mo2Cl8] in refluxing methanol. The complex was characterized using H-1 and P-31 NMR, and UV-Vis spectroscopy, X-ray crystallography, and cyclic voltammetry. The Mo-Mo separation in the solid state structure is 2.13 angstrom, with the PTA and chloride ligands in an eclipsed arrangement with a P-Mo-Mo-Cl twist angle of 1.75(3)degrees. The P-31 NMR spectrum contains a single peak at -62.8 ppm, and the H-1 NMR spectrum exhibits two singlets of equal height at 4.60 and 4.33 ppm. The UV-Vis spectrum contains three absorbance features at 615, 363, and 231 run, with the absorbance at 615 nm due to the delta -> delta* transition. The one electron oxidation Of Mo2Cl4(PTA)(4) is reported at E-1/2 = 0.91 V relative to Ag/Ag+ in CH2Cl2. Also discussed is the reactivity of the molybdenum complex with CN-, H2O, and HCl. (c) 2005 Elsevier B.V. All rights reserved.