The complexes Fe2(OCHPh2)6 and L2FeOR (R = Et or CHPh2, L = N,N‘-bis(trimethylsilyl)benzamidinate) were structurally characterized, and comparative studies of the behavior of those compounds comprising the same alkoxide (Ph2HCO-) in polymerizations of e-caprolactone (CL) and d,l-lactide (LA) were performed. Both Fe2(OCHPh2)6 and L2FeOCHPh2 are effective polymerization catalysts, as reflected by molecular weight control, polydispersities, and end group analysis, but the diiron complex generally exhibits greater polymerization control, particularly for CL. Kinetic investigations of the polymerization of CL revealed the same first-order dependence on [CL] for both catalysts, but different orders in [catalyst] that signified a distinct contrast in mechanism. Analysis that invoked the presence of a termination-causing impurity at low concentration yielded a first-order dependence on [Fe2(OCHPh2)6], but the order in [L2FeOCHPh2] was found to be one-half. This fractional dependence was interpreted by using a mod...

Mechanistic comparison of cyclic ester polymerizations by novel iron(III)-alkoxide complexes: Single vs multiple site catalysis

Rapid and controlled polymerization of lactide by structurally characterized ferric alkoxides.

The synthesis and properties of several complexes of Ru(II) containing 4,4‘-dicarboxy-2,2‘-bipyridine (dcbpyH2), 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (bmipy), or 2,6-bis(1-methylbenzimidazol-2-yl)-4-phenylpyridine (ph-bmipy), and monodentate ligands (X- = Cl-, I-, NCS-, NCSe-, CN-) are reported. The introduction of the ambident ligands X- = NCS-, NCSe-, and CN- into the coordination sphere of [Ru(bmipy)(dcbpy)I]- and cis-Ru(dcbpyH2)2Cl2 has been studied in situ via 1H and 13C NMR spectroscopy using 13C-enriched ligands X-. Introduction of thiocyanate and selenocyanate initially yields the two possible linkage isomers in comparable amounts; prolonged reaction time converts the S-bound isomer and the Se-bound isomer to the N-bound isomers. The isoselenocyanate complex decomposes rapidly, yielding the cyano complex under loss of Se. The N-bound isothiocyanato complex K[Ru(bmipy)(dcbpy)(NCS)] was found to be an efficient sensitizer for nanocrystalline TiO2; the incident monochromatic photon-to-current e...

Ruthenium(II) Charge-Transfer Sensitizers Containing 4,4‘-Dicarboxy-2,2‘-bipyridine. Synthesis, Properties, and Bonding Mode of Coordinated Thio- and Selenocyanates

Stereochemistry and polymetallic ligand-bridged molecular assemblies

ctc-Ru(L)2(Cl)2, 1 [L = pyridine-2-azobenzene], reacts with EtOCS2K to give an unusual product, 3, where the ortho-carbon atom of the pendant phenyl ring of each L is selectively thiolated. Crystal structure and spectra of compound 3 are reported.

A Novel Example of Metal-Mediated Aromatic Thiolation in a Ruthenium Complex. Crystal Structure of RuII(SC6H4NNC6H4N)2†

The chemistry of tris(2,2{prime}-bipyridine)ruthenium(II) and -rhodium(III) complexes and complexes of related ligands has had an extensive literature in recent years. The reason for this is primarily the relevance of this chemistry to photophysical, photochemical, and redox phenomena. But until now, no simple and general synthetic route has been available for the synthesis of such compounds. For example, the tris complex of 2,2{prime}-bipyridine (L{sup 1}) is commonly synthesized by fusion of MCl{sub 3} with the ligand at a very high temperature, whereas the syntheses of the tris complexes of 1,10-phenanthroline (L{sup 2}) and 2-(m-tolyazo)pyridine (L{sup 3}) involve several steps which need extra purification at every stage to eliminate contaminated products. The standard reported synthetic routes are not only lengthy but also cumbersome, and in most of the cases the routes are inefficient. Therefore, there is an obvious need to develop new and direct procedures, of general application, for the synthesis of the important title compounds. In the present report, the authors describe high-yield, single-pot, and general synthetic routes to ML{sub 3}{sup n+} from either hydrated MCl{sub 3} or MCl{sub 2}L{sub 2} (M = Ru(II), Rh(III); L = L{sup 1}-L{sup 3}) and the silver bis complex of the corresponding ligand.

A novel and generalized approach to the synthesis of ML sub 3 sup n+ (M = Ru(II), Rh(III); L = 2,2 prime -bipyridine, 1,10-phenanthroline, 2-(arylazo)pyridine; n = 2, 3)

Isomeric complexes of ruthenium(II) with neutral heterocyclic schiff base ligands. High resolution proton resonance spectra of trans-cis isomeric pairs of RuX2L2 (L 2-arylpyridinecarboxaldimine, X Cl, Br) and comparison of their physical properties

http://repository.ias.ac.in/12836/1/347.pdf

Monovalent copper complexes of N-aryl-pyridine-2-aldimine. synthesis, characterization and structure

Isomeric dithiocyanate complexes of ruthenium(II), synthesis, characterization of all possible bond isomers of trans,cis-Ru(CNS)2L2 [L = 2-(arylazo)pyridine] and studies of isomerization

The title reaction is exemplified by the high yield conversions 1→2 and 3→4 by H2O2, and the X-ray structures of 2 and 4 are reported; the species 1+ and 3+ afford 2 and 4 respectively when treated with water.

Alok K. Deb

Papers

A novel and generalized approach to the synthesis of ML sub 3 sup n+ (M = Ru(II), Rh(III); L = 2,2 prime -bipyridine, 1,10-phenanthroline, 2-(arylazo)pyridine; n = 2, 3)

Isomeric complexes of ruthenium(II) with neutral heterocyclic schiff base ligands. High resolution proton resonance spectra of trans-cis isomeric pairs of RuX2L2 (L 2-arylpyridinecarboxaldimine, X Cl, Br) and comparison of their physical properties

Monovalent copper complexes of N-aryl-pyridine-2-aldimine. synthesis, characterization and structure

Isomeric dithiocyanate complexes of ruthenium(II), synthesis, characterization of all possible bond isomers of trans,cis-Ru(CNS)2L2 [L = 2-(arylazo)pyridine] and studies of isomerization

Oxidation of coordinated azomethine to amide. Synthetic and structural studies on a rhenium and a ruthenium system