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Abstract: Coordination of CoCl2 solutions to the silica polyamine composite, WP-1, made with the branched polymer polyethylenimine (PEI) shows irreversible binding resulting from surface oxidation of the Co2+–Co3+. This is not the case for the silica polyamine composite BP-1 made with the linear polymer polyallylamine where reversible binding and no oxidation is observed. These observations suggested that oxidation of the cobalt was related to the greater coordination number available with the branched polyamine relative to the linear polyamine. A study of the kinetics of cobalt binding to WP-1 indicated initial loading of Co2+ at relatively low coordination number followed by desorption of Co2+ leading to oxidation and irreversible binding. Exclusion of oxygen from the composite-cobalt solution mixtures resulted in irreversible binding at a level that was 14% of the initial experiments. These observations prompted us to undertake a study to elucidate the coordination number around cobalt in the case of the branched polymer PEI. Towards this end, we have synthesized the model complexes [(tren)Co(H2O)2]3+3Cl− (tren=tris(2,2′,2″aminoethyl)amine) and [(dien)Co(H2O)3]3+3Cl− (dien=diethylenetriamine). The UV–Vis spectra of these model complexes were compared with Co3+ coordinated to PEI in solution and it was concluded that the UV–Vis spectrum of the tren complex was closer to that observed for the solution UV–Vis spectrum of Co3+–PEI. These data indicated that coordination of four amines was needed to drive surface oxidation under ambient conditions. In order to further elucidate the coordination number of a metal coordinated to the surfaces of WP-1 and BP-1, we reacted these composites with the probe molecule [Ru(CO)3(TFA)3]−K+ (TFA=trifluoroacetate) (1) where the carbonyl stretching frequencies could be used as a measure of coordination number and geometry of the adsorbed complex. The IR of this complex on WP-1 indicated a monocarbonyl species while the IR of this complex on BP-1 indicated the presence of dicarbonyl species on the surface. These data are consistent with a coordination number of four amines in the case of WP-1 and the coordination of two amines in the case of BP-1 based on our previous studies of the solution coordination chemistry of the 1. Subsequent 13C CPMAS solid-state NMR on 13CO enriched samples of the 1 adsorbed onto BP-1 and WP-1 were consistent with the IR data. [Copyright &y& Elsevier]

The reactions of the electron deficient benzoheterocycle clusters Os3(CO)9(μ3-η2-L&z.sbnd;H)(μ-H) (L=phenanthridine, 2; 5,6-benzoquinoline, 3; quinoxaline, 4; 2-methyl benzimidazole, 5; 2-methyl benzotriazole, 6; 2-methyl benzothiazole, 7; benzothiazole, 8; 2-methyl benzoxazole, 9; benzoxazole, 10) with n-butylamine and with the protic acids HBF4 and CF3CO2H are reported. Complexes 2 and 3 behave very similarly to the analogous quinoline complex (L=quinoline, 1) forming adducts with n-butylamine with similar spectral properties to 1 and undergoing simple protonation at the metal core with both HBF4 and CF3CO2H. Complexes 4–10 on the other hand form an additional amine adduct with different spectral characteristics than 1–3 and in the case of 5 this is the only detectable product. In addition, these compounds also form adducts with acetonitrile while 1–3 do not. Compounds 4–9 also exhibit much more complex behavior in the presence of CF3CO2H than 1–3, giving trifluoroacetate adducts subsequent to initial protonation. Although 4, 5 and 10 behave differently than 1 with n-butylamine and protic acids they form exactly the same triphenyl phosphine adduct as 1 and 3 based on multinuclear NMR data. The solid-state structure for the amine adduct of 2 is reported and suggested structures for the other amine and acid adducts, based on NMR data, are presented. The reasons for the differences in the behavior of the three distinct groups of benzoheterocycles (1–3, 4 and 5–10) are discussed. [Copyright &y& Elsevier]

The electrochemical behavior of the ruthenium(II) diimine complexes [Ru(CO)(CF 3 CO 2 )(dppene)(5-R-phen)][PF 6 ] (dppene = 1,2-diphenylphosphinoethene; phen = 1,10-phenanthroline; R = H, 1 ; R = NH 2 , 2 ; R = cholestoryl carbamate, 3 ; R = 1,2-dihexadecanoyl- sn -glycero-3-phosphoethanolamine, 4 ), [Ru(CO)(H)(4,4′-R-bpy)(R′Ph 2 P) 2 ][PF 6 ] (bpy = 2,2′-bipyridine; R = H, R′ = Ph, 5 ; R = H, R′ = 1,2-dihexadecanoyl- sn -glycero-3-phosphoethanolamine, 6 ; R = 1,2-dihexadecanoyl- sn -glycero-3-phosphoethanolamine, R′ = Ph, 7 ), [Ru(bpy) 2 (5-R-phen)][PF 6 ] 2 (R = NH 2 , 8 ; R = cholestoryl carbamate, 9 ; R = 1,2-dihexadecanoyl- sn -glycero-3-phosphoethanolamine, 10 ) is reported. Complexes 1 – 6 give cyclovoltammetric (CV) responses with multiple ill-defined reduction waves and one oxidation wave, all of which were chemically irreversible. Complexes 5 and 7 , containing axially coordinating phosphines, showed reversible oxidation and reduction CV responses, while 6 showed redox waves similar to 3 . Complexes 8 – 10 show a metal-centered irreversible oxidation around +1.4 V that, in the case of 8 and 9 , is heavily modified by adsorption phenomena. In the negative part of the CV, 9 and 10 show a single chemically and electrochemically reversible 1e − reduction both at E °′ = −1.29 V, about 500 mV cathodically shifted with respect to 8 . The interactions of complexes 1 and 2 with bovine serum albumin (BSA) and double stranded DNA (ds-DNA) were also studied by electrochemical methods. Both complexes showed strong binding to BSA. Evidence for intercalation of both complexes with DNA is presented, with 1 showing a stronger interaction than 2 . [ABSTRACT FROM AUTHOR]

The reaction of the electron-deficient 6-methoxyquinolinate-substituted triosmium cluster [Os 3 (CO) 9 {μ 3 -η 1 ,κ 1 -C 9 H 5 N(6-OMe)}(μ-H)] ( 1 ) with PPh 3 proceeds readily at room temperature to afford the electron-precise adduct [Os 3 (CO) 9 (PPh 3 ){μ-η 1 ,κ 1 -C 9 H 5 N(6-OMe)}(μ-H)] ( 2 ), in which the PPh 3 ligand is bound to the osmium that serves as the coordination site for the hydride and the metallated-carbon atom of the benzoheterocycle. This reaction also leads to a change in the hapticity of the 6-methoxyquinolinate ligand from μ 3 -η 1 ,κ 1 to μ-η 1 ,κ 1 as confirmed by X-ray crystallography. Thermolysis of 2 in boiling toluene furnishes five new triosmium clusters ( 3 – 7 ) as a result of ligand isomerization, decarbonylation and orthometallation of the ancillary PPh 3 ligand. Clusters 3 and 4 are isomers of 2 and the location of the metal-bound hydride and PPh 3 with respect to 6-methoxyquinolinate moiety is the only difference between these isomers. Control experiments show that 5 is a decarbonylation product of 4 which converts into 6 as a result of further decarbonylation with concomitant orthometallation of one of the phenyl rings of the coordinated PPh 3 ligand, whilst 7 is formed from 6 through replacement of an equatorial carbonyl of the nitrogen-bound osmium by PPh 3 ligand. All the new clusters have been characterized by a combination of analytical and spectroscopic methods as well as by X-ray crystallography in the case of 2 , 3 , 6 and 7 . [ABSTRACT FROM AUTHOR]

Abstract: The reactions of 2-amino-anthracene with [Os3(CO)10(CH3CN)2] have been studied and the products structurally characterized by spectroscopic, X-ray diffraction, photophysical and electrochemical techniques. At room temperature in CH2Cl2 two major, isomeric products are obtained [Os3(CO)10(μ-η2-(N-C(1))-NH2C14H8)(μ-H)] (1, 14%) and [Os3(CO)10(μ-η2-(N-C(3))-NHC14H9)(μ-H)] (2, 35%) along with a trace amount of the dihydrido complex [Os3(CO)9(μ-η2-(N-C(3))-NHC14H8)(μ-H)2] (3). In refluxing tetrahydrofuran only complexes 2 and 3 are obtained in 24% and 28%, respectively. A separate experiment shows that complex 1 slowly converts to 2 and that the rearrangement is catalyzed by adventitious water and involves proton transfer to the anthracene ring. Complex 1 is stereochemically non-rigid; exhibiting edge to edge hydride migration while 2 is stereochemically rigid. Complex 3 is also stereochemically non-rigid showing a site exchange process of the magnetically nonequivalent hydrides typical for trinuclear dihydrides. Interestingly, 2 decarbonylates cleanly to the electronically unsaturated 46e− cluster [Os3(CO)9(μ3-η2-(N-C(3))-NHC10H9)(μ-H)] (4, 68%) in refluxing cyclohexane, while photolysis of 2 in CH2Cl2 yields only a small amount of 3 along with considerable decomposition. The mechanism of the conversion of 1 to 2 and the dependence of the product distribution on solvent are discussed. All four compounds are luminescent with compounds 1–3 showing emissions that can be assigned to radiative decay associated with the anthracene ligand. Complexes 1–3 all show irreversible 1e− reductions in the range of −1.85–2.14V while 4 shows a nicely reversible 1e− wave at −1.16V and a quasi-reversible second 1e− wave at −1.62V. Irreversible oxidations are observed in the range from +0.35 to +0.49V. The relationship between the cluster ligand configurations and the observed electrochemical and photochemical behavior is discussed and compared with that of the free ligand. [Copyright &y& Elsevier]