D. de Montauzon

A comprehensive study of the system μ-dichlorotetra-carbonyldirhodium-phosphines and evidence of oxidative addition involving new dinuclear complexes☆

Abstract An infrared study has established that the [Rh(CO) 2 Cl] 2 -phosphine (L) systems are composed of two series of complexes, mononuclear complexes X n of formula RhCl(CO) 3- n L n ( n = 1, 2, 3) and dinuclear complexes Y m of formula Rh 2 Cl 2 (CO) 4- m -L m ( m =0,1,2,3,4). The new compounds Y 2 and Y 3 are sufficiently stable to allow elemental analysis but for the compounds X 1 and Y 1 proof of their structures has been obtained by chemical methods and by mass spectrometric investigations. Preliminary PMR studies indicate that quite fast and complex exchanges occur in the system. Reactions of Cl 2 , HCl and CH 3 I molecules on dinuclear complexes are examples of oxidative additions to two coordinative metal centers.

Automatic ir drop correction for studies of electrochemical systems

Abstract The interest of automatic ir drop correction by the interrupt method is evaluated by carrying out electrochemical studies on ferrocene in various non-aqueous solvents, using a home-made microcomputer-controlled potentiostat. Special attention is devoted to voltammetry and cyclic voltammetry.

Electrochemical investigation of coordination compounds: II. Phosphine derivatives of Co0 and Ni0. Correlations between E12, ΔHNP and v(CO) in these complexes☆

Abstract The complexes [Co(CO) 3 L] 2 , Hg[Co(CO) 3 L] 2 , HgCo 2 (CO) 8− n L n and Ni(CO) 4− n L n (L = PR 3 , P(OR) 3 ) have been reduced electrochemically. The E 1 2 values of the reduction processes are dependent on L and n . These values can be related to the ΔHNP values of the ligands and to the CO stretching frequency of the molecules. The results can be interpreted in terms of either kinetic or thermodynamic factors.

A new example of ligand-to-metal electron-transfer process : one-electron reduction products of nickel(II)-tetradentate schiff base complexes

Abstract The reduction of three nickel(III) complexes involving two symmetrical N,N′-ethylenebis (acetylacetoneiminato) and N,N′-ethylenebis (salicylideneiminato) and one non-symmetrical N,N′-ethylene (acetylacetoneiminatosalicylideneiminato) and Schiff bases has been investigated by electrochemistry and ESR spectroscopy. In all cases, exhaustive reduction results in the formation of nickel(I) complexes. However, ESR data support the formation of a nickel(II)-stabilized ligand radical species at the early stage of the reduction of the non-symmetrical Schiff base complex.

Synthesis and characterization of neutral oxorhenium(V) and nitridotechnetium(V) complexes with a tetradentate N2S2 unsaturated ligand derived from dithiocarboxylic acid

Abstract Neutral complexes of technetium(V) and rhenium(V) of the type TcN(L2) and ReO(L2)CI, where L2 corresponds to the dianionic form of the tetradentate N 2 S 2 ligand N , N ′-ethylene bis(methyl 2-aminocyclopentane-l-dithiocarboxylate), were prepared by substitution reaction on the starting materials 99 TcNCl 2 (PPh 3 ) 2 and ReOCl 3 (PPh 3 ) 2 , respectively. The complexes were characterized by elemental analysis, IR, NMR spectroscopy and conductimetry. The molecular and crystal structure of the nitrido complex TcN(L2) was determined by single-crystal X-ray diffraction technique (monoclinic P 2 1 / c , a = 13.380(6), b = 9.945(2), c = 15.839 A, β = 113.91(3)°). The electrochemical behaviour of the nitrido complex was investigated.

Electrochemical Studies of the Formation Mechanism of (cation) x [Ni(dmit)2 Conductive Compounds and of their Non-Integer Oxidation State

Abstract The mechanism of electrocrystallization of (cation) x [Ni(dmit)2 (cation = NHMe+ 3, NMe+ 4) conductive compounds is studied under non-stationary conditions by cyclic voltammetry using ultramicroelectrodes at high potential-scan rates. It is shown that the formation of non-integer oxidation state compounds proceeds through one-electron transfers combined with chemical reaction between [Ni(dmit)2 − and [Ni(dmit)2 0 electrogenerated species exhibiting integer charges. The non-integer oxidation state in (cation) x [Ni(dmit)2 compounds (cation = NBu+ 4, AsPh+ 4, NH2Me+ 2, NH3Me+), measured by the non-integer value of x, is determined under stationary conditions by use of the carbon paste electrode at very low potential-scan rates.

Electrochemical studies of Iron(III) Schiff base complexes—I. The monomeric FeIII(N2O2)Cl complexes

Abstract The electrochemical reduction of Fe III (L)Cl, where L is a Schiff base, has been investigated in aprotic solvents by cyclic voltammetry and coulometry with UV-vis spectroscopy. Six complexes derived from Schiff base ligands with N 2 O 2 environments are described. The reduction of Fe III (L)Cl into Fe II (L)Cl occurs at a potential around −0.5 V vs S.C.E. through an EC mechanism where the following reaction concerns the decomposition of iron(II), a highly reactive complex. A high electronic delocalization of the Schiff base, such as in SALOPH, stabilizes the oxidation state II of iron and shifts the redox potential anodically. The study reveals the extreme reactivity of iron(II) towards dioxygen. Traces of dioxygen with Fe II (L)Cl yield the μ-oxo bridged Fe III dimers (L)FeOFe(L), whose reduction potentials lie around −1 V vs S.C.E. The redox couple Fe II (L)/Fe III (L) is potentially a good electrochemical mediator for redox catalysis.

Synthesis, UV-visible and electrochemical studies of lipophilic and hydrophilic lanthanide(III) bis(porphyrinates)☆

Abstract In a recent work we described the synthesis and some physicochemical properties of lanthanide(III) monoporphyrinate complexes. The increasing interest in cationic and/or anionic metalloporphyrins due to their biocompatibility with human tissues, their application as intercalating agents or as photochemical probes and NMR imaging agents, prompted us to extend our research to the synthesis and physico-chemical study of hydrophilic lanthanide double-deckers. We present herein the synthesis of four new lanthanide(III) lipophilic 5,10,15,20-tetrapyridyl-bis (porphyrinates) and their easy conversion (upon methylation) to the corresponding water soluble double-deckers. Electrochemical studies were carried out using different polarity media while the optical properties of the complexes were studied in organic and aqueous media.

Electrochemistry of trimetallic ‘crown-like’ iridium(I) complexes

Abstract The electrochemistry of trimetallic ‘crown-like’ iridium(I) complexes of the type Ir 3 (μS- t Bu) 3 (μX)(CO) 6 [X = F 3 CCCCF 3 (1), H 3 COOCCCCOOCH 3 (2)] and substituted analogues Ir 3 (μS- t Bu) 3 (μX)(CO) 5 L [X = F 3 CCCCF 3 , L = C 4 F 6 (3), CH 3 CN (4)] has been studied in CH 3 CN and CH 2 Cl 2 solvents on mercury, platinum and glassy carbon electrodes. These complexes undergo an irreversible one-electron reduction leading to the destruction of the trimetallic units. An irreversible one-electron oxidation step is also observed. A redox mechanism is proposed on the basis of electrochemical and IR spectroscopic results by comparison with the electrochemical behavior of the analogous dimetallic [Ir(μS- t Bu)(CO) 2 ] 2 (5).

ELECTROCHEMICAL STUDIES OF PROTONATED AND DEPROTONATED FORMS OF HETEROLEPTIC AND HOMOLEPTIC EUROPIUM(III) AND DYSPROSIUM(III) PORPHYRIN DOUBLE-DECKERS

Abstract The cyclic voltammetric oxidation, of heteroleptic and homoleptic lanthanide porphyrin double-deckers demonstrates the presence of equilibrium protonated/deprotonated species present in CH2Cl2, DMF, and THF.