Redox chemistry of a pair of complexes that contain the bridging bis(diphenylphosphino)methane ligand and the Re26+ and Re24+ cores: Re2(.mu.-Cl)2(.mu.-dppm)2Cl4 and [Re2(.mu.-dppm)2Cl3(NCR)2]PF6 (R = CH3, C2H5, C6H5) Academic Article uri icon

abstract

  • The oxidant NOPF6 has been used to prepare the new paramagnetic dirhenium complexes [Re2(μ-dppm)2Cl3(NCR)2](PF6)2 (dppm = bis(diphenylphosphino)methane; R = CH3, C2H5, C6H5) from the monocationic precursors. The compounds are derivatives of the Re25+ core. The doubly bonded dirhenium(III) complex Re2Cl6(dppm)2 undergoes a one-electron oxidation with NOX (X = BF4-, PF6-), and a one-electron reduction with cobaltocene, to yield paramagnetic ions with bond orders of 1.5. The resulting monocation and monoanion provide examples of previously unknown types of metal-metal bonds of order 1.5 (σ2π2δ∗2δ1 and σ2π2δ∗2δ2π∗1, respectively). The structural identity of the monocation, a rare example of a Re27+ core complex, has been established through an X-ray crystal structure determination on the salt [Re2(μ-C1)2(μ-dppm)2Cl4]H2PO4-H3PO4-4H2O. This compound crystallizes in the monoclinic space group C2/c with cell dimensions a = 23.524 (4) Å, b = 13.354 (3) Å, c = 19.717 (5) Å, β = 93.60 (2)°, and Z = 4. The cation possesses crystallographic inversion symmetry. The phosphate groups (also related by inversion symmetry) and the waters are disordered. From 5418 unique data collected with use of Mo Kα radiation on an Enraf-Nonius CAD-4 diffractometer (2θ < 50°; ω-2θ scans), 3967 data were considered observed (I > 2σ(I)). The data were refined by block-diagonal least-squares minimizing Σw(|Fo|-|Fc|)2 with w = 1/σ2(F) to an R of 0.051. The Re-Re distance in this complex (2.6823 (6) Å) is appreciably longer than that in the parent neutral complex Re2(μ-Cl)2(μ-dppm)2Cl4 (2.616 (1) Å). © 1985, American Chemical Society. All rights reserved.

author list (cited authors)

  • Dunbar, K. R., Powell, D., & Walton, R. A.

citation count

  • 11

publication date

  • August 1985