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Two sigma-bonded Rh 2 5+ complexes, Rh 2 (ap) 4 (C 6 H 5 ) and Rh 2 (ap) 4 (CH 3 ), where ap = 2-anilinopyridinate anion were synthesized and examined as to their electrochemical and spectroscopic properties in nonaqueous media. Rh 2 (ap) 4 (C 6 H 5 ) was also structurally characterized. The presence of the phenyl axial ligand on Rh 2 (ap) 4 (C 6 H 5 ) does not bring about a significant structural effect on the ap framework as compared to Rh 2 (ap) 4 Cl or Rh 2 (ap) 4 (C CH) but the Rh–Rh and Rh–C axial bond lengths are both elongated due to the strong electron-donating effect of the phenyl group. The two sigma-bonded dirhodium compounds each undergo a single reversible one-electron reduction to in situ generate a stable Rh 2 4 + complex and two reversible one-electron oxidations to give stable compounds in Rh 2 6 + and Rh 2 7 + oxidation states. These redox reactions occur at E 1/2 = −0.79, 0.28 and 0.93 V for R = CH 3 and −0.71, 0.35 and 0.95 V for R = C 6 H 5 . The ESR spectrum of Rh 2 (ap) 4 (CH 3 ) has g ⊥ and g || values of 2.17 and 1.89 while Rh 2 (ap) 4 (C 6 H 5 ) has an ESR spectrum with signals at 2.17 ( g ⊥ ) and 2.00 (g || ), consistent with the odd electron in each dimetal unit being localized on only one of the two metal centers in Rh 2 5 + .

Three related diruthenium complexes containing four symmetrical anionic bridging ligands were synthesized and characterized as to their electrochemical and spectroscopic properties. The examined compounds are represented as Ru2(dpb)4Cl, Ru2(dpb)4(CO), and Ru2(dpb)4(NO) in the solid state, where dpb = diphenylbenzamidinate anion. Different forms of Ru2(dpb)4Cl are observed in solution depending on the utilized solvent and the counteranion added to solution. Each Ru2(5+) form of the compound undergoes multiple redox processes involving the dimetal unit. The reversibility as well as potentials of these diruthenium-centered electrode reactions depends upon the solvent and the bound axial ligand. The Ru2(5+/4+) and Ru2(5+/6+) processes of Ru2(dpb)4Cl were monitored by UV-vis spectroscopy in both CH2Cl2 and PhCN. A conversion of Ru2(dpb)4Cl to [Ru2(dpb)4(CO)](+) was also carried out by simply bubbling CO gas through a CH2Cl2 solution of Ru2(dpb)4Cl at room temperature. The chemically generated [Ru2(dpb)4(CO)](+) complex undergoes several electron transfer processes in CH2Cl2 containing 0.1 M TBAClO4 under a CO atmosphere, and the same reactions were seen for a chemically synthesized sample of Ru2(dpf)4(CO) in CH2Cl2, 0.1 M TBAClO4 under a N2 atmosphere, where dpf = N,N'-diphenylformamidinate anion. Ru2(dpb)4(NO) undergoes two successive one-electron reductions and a single one-electron oxidation, all of which involve the diruthenium unit. The CO and NO adducts of Ru2(dpb)4 were further characterized by FTIR spectroelectrochemistry, and the IR spectral data of these compounds are discussed in light of results for previously characterized Ru2(dpf)4(CO) and Ru2(dpf)4(NO) derivatives under similar solution conditions.

The syntheses and characterization of the (4,0), (3,1), and (2,2) trans isomers of Ru2(F5ap)4Cl and Ru2(F5ap)4(C⋮CC6H5)2 are reported where F5ap is the 2-(2,3,4,5,6-pentafluoroanilino)pyridinate an...

The synthesis and characterization of the first paramagnetic diruthenium(III) complex containing two unpaired electrons is described. The investigated compound, represented as Ru2(hpp)4Cl2, where hpp is 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate ion, was obtained from the reaction of Ru2(CH3COO)4Cl with excess molten Hhpp under Ar (150 °C, 10 h). It was characterized by X-ray single-crystal diffraction, electrochemistry, ESR, and UV−visible spectroscopy and the data compared to that for other Ru26+ derivatives containing either four unpaired electrons (in the case of a bis-H2O complex) or zero unpaired electrons (in the case of a bis-C⋮CC6H5 derivative).

The effect of axial ligands on the structure, oxidation state, and electronic configuration of two diruthenium(II,III) and two diruthenium(III,III) complexes is reported. The investigated compounds are represented by Ru2(dpf)4Cl (1), Ru2(dpf)4(C⋮CC6H5) (2), Ru2(dpf)4(C⋮CC6H5)2 (3), and Ru2(dpf)4(CN)2 (4), where dpf is the N,N‘-diphenylformamidinate ion. The chloro and mono(phenylacetylide) complexes, which contain a Ru25+ core, are paramagnetic and contain three unpaired electrons, while the bis(phenylacetylide) and bis(cyano) species, which contain a Ru26+ core, are diamagnetic. Compound 1, Ru2(dpf)4Cl, was prepared by heating Ru2(CH3COO)4Cl and excess molten N,N‘-diphenylformamidine (Hdpf) for 10 h at 130 °C under an argon atmosphere. Compound 2, Ru2(dpf)4(C⋮CC6H5), was prepared by reaction of purified Ru2(dpf)4Cl with LiC⋮CC6H5 (in a 1:5 ratio) in THF at room temperature (2 h). Compound 3, Ru2(dpf)4(C⋮CC6H5)2, was also obtained from Ru2(dpf)4Cl by using excess LiC⋮CC6H5. A related diruthenium(III,III) ...

The relationship between half-wave potential, the site of electron transfer, and the catalytic activity of a given [(P)Ni] - complex toward CH 3 I reduction was investigated for seven nickel(II) porphyrins.

The synthesis, physicochemical properties, and electrochemistry of a new series of metal metal σ-bonded metalloporphyrins are reported. The investigated compounds are represented as (P)MRe(CO)5 where P is the dianion of octaethylporphyrin (OEP) or tetraphenylporphyrin (TPP) and M = Al, Ga, In, or Tl. These compounds provide the first examples of Al and Ga metalloporphyrins with covalent metalmetal bonds as well as give the first series of compounds in which the same metalate anion is covalently bonded to four different group 13 metalloporphyrins. Each synthesized complex was characterized by 1H NMR, IR, and UV-visible spectroscopy as well as by electrochemistry. Graham Δσ and Δπ parameters, and calculated residual charges on the rhenium atom of (P)MRe(CO)5 demonstrate that the covalency of the metalmetal bond decreases in the order: Tl > In > Ga > Al. The thallium derivative is stable upon electrooxidation by either one or two electrons. However, the In, Ga, and Al complexes undergo rapid cleavage of the metalrhenium bond after formation of a [(P)MRe(CO)5]+· cation radical. The chemical reactivity and physical properties, as well as the electrochemistry, of each (P)MRe(CO)5 species were analyzed as a function of the central metal ion or porphyrin ring basicity. The spectroscopic properties and electrochemistry of these metalmetal σ-bonded species are compared with data for other metal metal bonded metalloporphyrins of the type (P)MM′(L) as well as with data for related metalcarbon bonded porphyrins of the type (P)M(R).

The synthesis and characterization of 10 different ionic and σ-bonded aluminum(III) porphyrins are reported. These compounds were studied by mass spectroscopy and IR, UV-visible, and 1 H NMR spectroscopy as well as by electrochemistry. The spectroscopically investigated compounds are represented by (P)AlCl an (P)Al(R), where P is the dianion of tetraphenylporphyrin (TPP) or octaethylporphyrin (OEP) and R is CH 3 , n-C 4 H 9 , C 6 H 5 , or C 6 F 4 H. The molecular structure of (OEP)Al(CH 3 ) was determined by X-ray diffraction

The synthesis and characterization of a new structural type of diruthenium(III) complex is reported. The investigated compound is represented by Ru2(F4Oap)(F5ap)3Cl where F5ap is the 2-(2,3,4,5,6-pentafluoroanilino)pyridinate ion and F4Oap is 2-(3,4,5,6-tetrafluoro-2-oxoanilino)pyridinate dianion, a ligand which derives from F5ap by substitution of an oxygen for a fluorine atom at the ortho position of the pentafluorophenyl ring. Ru2(F4Oap)(F5ap)3Cl was characterized by room temperature magnetic susceptibility, X-ray single-crystal diffraction, electrochemistry, and mass spectrometry and is the first example of a diruthenium(III) derivative having a tridentate dianionic ligand bound to the two metal centers.

Two neutral diruthenium complexes and one anionic diruthenium complex, Ru2(dpf)4(NO), Ru2(dpf)4(NO)2, and [Ru2(dpf)4(NO)]-, where dpf is diphenylformamidinate anion, were synthesized and characterized as to their electrochemical and spectroscopic properties. Two of the compounds, Ru2(dpf)4(NO) and Ru2(dpf)4(NO)2, were also structurally characterized. Ru2(dpf)4(NO) undergoes reversible one-electron reductions under N2 at E1/2=0.06 and -1.24 V in CH2Cl2, 0.1 M TBABr. These processes are shifted to E1/2=0.18 and -0.78 V under CO due to the trans-coordination of a CO molecule which stabilizes the singly and doubly reduced forms of the metal-metal bonded complexes, thus leading to easier reductions. CO does not coordinate to Ru2(dpf)4(NO), but it does bind to the singly reduced species to generate [Ru2(dpf)4(NO)(CO)]- under a CO atmosphere in solution; characteristic NO and CO bands are seen for this compound at nuNO=1674 cm(-1) and nuCO=1954 cm(-1). Ru2(dpf)4(NO)2 displays a reversible one-electron reduction at E1/2=-1.24 V versus SCE and an irreversible reduction at Epc=-1.96 V in CH2Cl2, 0.1 M TBAP under N2. There are also two reversible one-electron oxidations at E1/2=0.24 and 1.15 V. Spectroelectrochemical monitoring of the Ru2(dpf)4(NO)2 oxidation processes in a thin-layer cell shows only a single NO vibration for each electrogenerated product and nuNO is located at 1726 (neutral), 1788 (singly oxidized), or 1834 (doubly oxidized) cm(-1). Finally, a labile CO complex, [Ru2(dpf)4(NO)(CO)]-, could be generated by passing CO into a solution of [Ru2(dpf)4(NO)]-. Formation of the mixed CO/NO adduct was confirmed by electrochemistry and infrared spectroscopy. Analysis of the NO and CO stretching vibration frequencies for [Ru2(dpf)4(NO)(CO)]- by in-situ FTIR spectroelectrochemistry and comparisons with data for Ru2(dpf)4(NO) and Ru2(dpf)4(CO) reveal the presence of a strong interaction between NO and CO across the Ru-Ru bond.

A monocarbonyl diruthenium(II,II) complex of the type (dpf)4Ru2(CO), where dpf is N,N‘-diphenylformamidinate, was characterized as to its electrochemical and spectroscopic properties (UV−vis, FTIR, and ESR) under a N2 or CO atmosphere. The synthesis and X-ray structural characterization of (dpf)4Ru2(CO) are also presented.