Preparation and structural characterization of Os2Cl4(chp)2(L) (chp = 6-chloro-2-hydroxypridinato; L = water, pyridine): a new class of M2X4(LL)2 complexes possessing an eclipsed conformation where LL is a substituted hydroxypyridinato ligand Academic Article uri icon

abstract

  • The melt reaction of 6-chloro-2-hydroxypyridine with Os2(O2CCH3)4Cl2at 145 °C affords two products. A polar compound, Os2(chp)4Cl, was recently characterized, and details of the X-ray structure and spectroscopic data are fully described in the preceding paper.1We now wish to report the identification of the second product, Os2Cl4(chp)2, which has been isolated as two different adducts: Os2Cl4(chp)2(py) (1) and Os2Cl4(chp)2(H2O)-(CH3)2CO (2). Crystals of 1 were grown by vapor diffusion of hexane into a solution of the compound in acetone—pyridine (40:1). The crystallographic data for 1 are as follows: monoclinic, space group C2/c, a = 14.718 (2) Å, b = 12.860 (3) Å, c = 11.553 (2) Å, β = 100.5 (1)°, V= 2150 (1) Å3, Z = 4. The structure was refined to R = 0.027 (Rw= 0.033). The molecule has crystallographically imposed C2symmetry with a twofold axis lying along the Os-Os bond axis. The Os-Os distance is 2.322 (1) Å, Os(1)-N(axial) = 2.238 (14) Å, Os-Cl(av) = 2.29 (3) Å, Os(1)-N(1) = 2.095 (9) Å, Os(2)-O(1) = 1.980 (8) Å. Crystals of 2 were grown by slow evaporation in air of an acetone solution of the complex. Pertinent crystallographic data are as follows: triclinic, space group P1*, a = 9.445 (2) Å, b = 15.148 (3) Å, c = 7.855 (2) Å, α = 94.92 (2)°, β = 98.50 (2)°, γ = 75.73 (1)°, V = 1075.7 (4) Å3, Z = 2. The structure was refined to R = 0.039 (Rw= 0.065). The molecule possesses virtual C2vsymmetry although there is a lack of crystallographically imposed symmetry. The interstitial acetone molecule interacts significantly with the diosmium unit via hydrogen bonding to the axial water molecule. The hydrogen atoms were not located during the crystallographic refinement, but the distance between the oxygen atoms of acetone and water is only 2.726 Å, clearly indicating the presence of hydrogen bonds. The title compounds are formally derivatives of [Os2Cl8]2-, a species that has only recently been prepared and structurally characterized.2aIn addition, 1 and 2 are the first examples of an Os2X4(LL)2class of compounds, a type unknown for platinum metals. Furthermore, there are no reported examples of M2X4(LL)2complexes with an overall eclipsed conformation that contain a substituted hydroxypyridinate anion as the trans bidentate ligand. The electrochemistry of 1 and 2, as determined by cyclic voltammetry, reveals a reversible reduction process located at E1/2= +0.15 V vs. Ag/AgCl for 1 and E1/2= +0.46 V vs. Ag/AgCl for 2. A solution of Os2Cl4-(chp)2(py) in dichloromethane exhibits a band at 555 nm (ε = 2815 M-1 cm-1), and an acetone solution of Os2Cl4(chp)2(H2O) displays an absorption maximum at 549 nm (ε = 3440 M-1 cm-1). © 1986, American Chemical Society. All rights reserved.

author list (cited authors)

  • Cotton, F. A., Dunbar, K. R., & Matusz, M.

citation count

  • 12

publication date

  • May 1986