New organometallic chemistry of ruthenium and osmium

The reaction of Schiff monobases of 2,6-diformyl-4-methylphenol with ruthenium(II) and osmium(II) has afforded a new family of orthometalated organometallics. Synthesis, characterization and reactivity are briefly discussed in this article

Electroprotic reactions

Reactions involving the coupled transfer of electrons and protons are called electroprotic reactions. In this article we briefly describe some of our experiences with electroprotic reaction as a tool for executing interesting chemical transformations

A triad of rhenium-mediated transformations

The title transformations are oxygen atom transfer, twin isomerization and regiospecific imine oxidation.Bispyridyldiazole ligands have furnished new oxygen atom transfer reagents of coordination type ReVOCl3(NN) which undergo a slower transfer to PPh3 than the corresponding azole reagents. The rate of twin isomerization (linkage and geometrical) of meridional azole complexes of coordination type ReIII(OPnP)Cl3(NN) to facial ReIII(PnPO)Cl3(NN) decreases rapidly asn increases in the interval 1-4 (PnP is Ph2P(CH2)nPPh2). An α-diimine chelate of type ReV(NPh)Cl3(NN) is shown to undergo facile oxidation to the corresponding iminoamide complex ReVI(NPh)Cl3(NN) upon treating with dilute nitric acid. The reaction proceeds via regiospecific nucleophilic addition of waterto the more polarized imine function

Structure and reactivity of palladium and platinum arylazooximates

The structure and selected reactions of the title compounds are reviewed. Some highlights are as follows (L = conjugate base of phenylazoacetaldoxime). While PtL<SUB>2</SUB> exist in cis and trans forms, PdL<SUB>2</SUB> occurs only in thetrans form. In the crystalline state cis-PtL<SUB>2</SUB> consists of weakly held dimers (Pt. Pt 3.151 &#197;) buttrans-PtL<SUB>2</SUB> consists of stacks of discrete molecules in the solid state.Trans- PdL<SUB>2</SUB> displays a surprisingly large tetrahedral distorsion. The different metal-ligand bonds undergo selective cleavage by different reagents. Thus HCl and tertiary phosphines respectively cleave the M-N (oxime) and M-N (azo) bonds. Phosphine cleavage leads to interesting situations such as cone angle-dependent equilibria and fluxional behaviour. A rich redox chemistry consisting of successive reductions of the azo groups and of the metal are revealed electrochemically.Cis-PtL<SUB>2</SUB> unliketrans- PtL<SUB>2</SUB> undergoes a facile one-electron oxidation at low potentials. Another very curious reaction of cis-PtL<SUB>2</SUB> is the process in which an aromatic ring is thermally hydroxylated at the expense of an oximato oxygen atom. The meaning and significance of the observations are discussed

Comments on the colour of alkyl-gold(III) complexes

This article does not have an abstract

Variable-valent rhenium chemistry of conjugated nitrogenous ligands: structure and reactivity

The valence states of particular concern in this review are VI–I and the ligand types are diimine, azoimine, imineamide and azooximeall bidentate and N,N-coordinating. Metal reduction potentials and stability of oxidation states are subject to control via variation of the nature and extent of N,N-chelation and coligation. Back-bonding plays a major role in determining stability and isomer specificity, particularly in the valence domain III–I. Three types of mediated oxygen atom transfer processes have been scrutinized and modeled: from Re^VO to tertiary phosphanes and variable-spacer diphosphanes, from water to diimine and from oxime to metal/coligand. Other reactivity topics include isomerizations associated with ligand substitution, stable azo anion radical generation and azo cleavage

Electroprotic phenomena and metal oxidation states

A ubiquitous reaction in transition metal chemistry is electron transfer deriving from the variable valence capability of the metal center. When the coordinated ligand has one or more potentially labile protons, electron transfer at the metal (M) may proceed with symbiotic proton transfer at the ligand (L), Such a coupled transfer will be called an electroprotic reaction. An important extension of Fig. 1 can be the transfer of externally added redox equivalents to the ligand via the metal thereby effecting a metal-catalyzed electroprotic transformation of the ligand. The scope of electroprotic phenomena is obviously wide and spans many reactions in chemistry and biology. This Comment has the limited objective of recounting some of our personal experiences in this fascinating field which we gained in the course of our dealing with the synthetic chemistry and redox activity of multiple oxidation states of copper, nickel, ruthenium, and molybdenum