Derek A. Tocher

Synthesis and structure of a binuclear ruthenium 4-chlorobenzamidato complex

Abstract The compound Ru2Cl(4-Cl-C6H4CONH)4 was prepared by reaction of Ru2Cl(O2CCH3)4 with 4-Cl-C6H4CONH2 at 180°C. Crystals of the composition Ru2Cl(4-Cl-C6H4CONH)4CH3OH were obtained by slow diffusion of CH3OH containing Et4NCl into a Me2SO solution of the compound. The structure of the crystalline product, which loses solvent of crystallization on removal from the mother liquor, was solved by X-ray crystallography by mounting a single crystal in a capillary containing the mother liquor. The crystals belong to the space group P1 (triclinic crystal system) with a = 12.731(3) A, b = 14.389(3) A, c = 12.604(3) A, α = 103.41(2)°, β = 106.43(2)°, γ = 64.90(2)°, V = 1988.6(8) A3 and Z = 2. There are two half ruthenium dimers linked by a Cl atom and an uncoordinated solvent CH3OH molecule per asymmetric unit. The ruthenium dimers lie on two centers of inversion at 0, 0, 0 and 1/2, 0, 0. The chloride ions bridge dinuclear cations in the crystal, forming infinite zigzag chains. The average Ru-Ru distance is 2.296[1] A and each ruthenium atom has a RuClN2O2 coordination sphere where the average Ru′-Ru-Cl angle is virtually linear (175.68[6]°). The metal oxidation states in the complex are + 2 and + 3, giving an average value of + 2.5. The arrangement of four bridging 4-Cl-benzamidato ligands is of the 2 : 2 type. The average Ru-N, Ru-O, Ru-Cl distances and Ru(1)-Cl(1)-Ru(2) angle are 2.036[6] A, 2.044[5] A, 2.583[2] A and 117.26(8)°, respectively. The IR spectrum of the compound shows two N-H stretches at 3380 and 3340 cm−1. The electronic spectrum of the compound in Me2SO exhibits bands at 558 nm (e = 340 M−1 cm−1), 425 nm (1000) and 320 nm (22,700).

STRUCTURAL AND MASS-SPECTRAL STUDIES ON SOME MULTIPLY BONDED DIOSMIUM TETRACARBOXYLATE COMPOUNDS

Abstract The compounds Os 2 (O 2 CCH 3 ) 4 Cl 2 ,1 and Os(O 2 CC 2 H 5 ) 4 Cl 2 , 2, have been structurally characterized. Both compounds crystallize in space group P2 1 /n. For 1 the unit cell parameters are a = 6.546(1) A, b = 8.950(1) A, c = 12.533(1) A, β = 90.17(1)° and Z = 2; for 2 they are a = 6.792(2) A, b = 10.519(3) A, c = 13.372(4) A, β = 89.27(3)° and Z = 2. Both molecules have approximate D 4th symmetry with important dimensions as follows: for 1, Os≡Os 2.314(1) A, OsCl 2.448(2) A; for 2, Os≡Os 2.316(2) A, OsCl 2.430(5) A. The mass spectra of these compounds as well as that of Os 2 (O 2 CC 3 H 7 ) 4 Cl 2 ,3, are reported and discussed.

Syntheses, structures and redox properties of tetrakis-(μ-benzamidato)dirhodium(II) complexes

Abstract The reaction of Rh2(O2CCh3)4 with an excess of molten PhCONH2 gave Rh2(PhCONH)4(PhCONH2)2 (1) which contains a dirhodium unit having four bridging benzamidato anions and two axial, neutral benzamide ligands. The compound has been characterized by elemental analysis and infrared spectroscopic data. Reactions of (1) with SbPh3 and pyridine in CH2Cl2 (2) and Rh2(PhCONH)4(py)2 (3), respectively, The structures (2) and (3) were determined from single-crystal X-ray diffraction data. Compound (2) crystallizes in the triclinic space group P1 with half of the dinner and half of the CH2Cl2 molecule constituting the asymmetric unit. The cell dimensions for (2) are: a = 12.927(7) A, b = 13.661(5) A, c = 10.242(6) A α = 103.45(4)°, β = 99363(4)°, γ = 67.44(4)°, V = 1622(1) A3, and Z = 1. The molecule, which has a crystallographic center of inversion, consists of a dirhodium unit bridged by four benzamidato ligands. Each rhodium has one axial ligand, SbPh3. The RhRh distance is 2.463(1) A and the RhSb bond length is 2.681(1) A. The mean RhO and RhN distances are 2.029[4] A and 2.056[3] A, respectively. The RhRhSb angle is essentially linear having a value of 176.40(2)°. The compound (3) crystallizes in the orthorhombic space group Pbca with the following unit cell dimensions: a = 16.395(2) A, b = 18.250(2) A, c = 11.754(1) A, α = β = γ = 90.0°, V = 3517(1) A3, and Z = 4. Half of the molecule has two pyridine ligands in the axial positions. The equatorial positions are occupied by four anionic benzamidato ligands as in (2). The RhRh distance is 2.437(1) A. The distance between the rhodium and the axial pyridine nitrogen atoms is 2.227(7) A and the angle RhRhN(3) is 175.5(2)°. The averages of the RhO and RhN bond lengths are 2.059[6] A and 2.050[7] A, respectively. Electron transfer behavior of (1) in different solvents and in the presence of strong neutral donor ligands has been investigated. The compound (1) in THF, DMF and CH3CN exhibits a prominent oxidation wave at E1/2 = 0.42 Λ (ΔEp = 100 m V), = 0.23 V (58 mV), and +0.36 V (65 mV), respectively. The pyridine, dithiane, PPh3 adducts of (1) in CH2Cl2 show the first oxidation at +0.39 V (60 m V), +0.48 V (90 mV), +0.46 V (65 mV) and +0.47 V (200 mV), respectively. The PPh3 adduct displays another quasireversible oxidation at +1.1 V (90 mV). In the THF, the pyridine and PPh3 adducts undergo oxidation at +0.35 V and +0.60 V, respectively. In DMF, the PPh3 adduct show oxidation at +0.50 V. In most of the cases, a second, less prominent oxidation wave was observed at slightly higher potential than the prominent oxidation peak. The electronic spectra of the pyridine, PPh3 and SbPh3 adducts show low energy absorption at 460 nm (shoulder), 445 nm (shoulder), and 508 nm (ϵ = 1520 M−1 cm−1, respectively. The electronic spectra of (1) studied in several polar solvents display bands in the range 440–563 nm.