Multimetallic catalysis based on heterometallic complexes and clusters.

Publisher Summary This chapter focuses on the organometallic chemistry and new aspects of arene ruthenium and osmium complexes. It explores that arene ruthenium and osmium complexes play an increasingly important role in organometallic chemistry. They appear to be good starting materials for access to reactive arene metal hydrides or 16-electron metal (0) intermediates that have been used recently for carbon-hydrogen bond activation. Various methods of access to cyclopentadienyl, borane, and carborane arene ruthenium and osmium complexes have been reported. Recently, from classic organometallic arene ruthenium and osmium chemistry has grown an area making significant contributions to the chemistry of cyclophanes. These compounds are potential precursors of organometallic polymers, which show interesting electrical properties and conductivity. The possibility of coordination of a two-electron ligand, in addition to arene, to the ruthenium or osmium atom provides a route to mixed metal or cluster compounds. Cocondensation of arene with ruthenium or osmium vapors has recently allowed access to new types of arene metal complexes and clusters. It reviews that arene ruthenium and osmium appear to be useful and specific catalyst precursors, apart from classic hydrogenation, for carbon–hydrogen bond activation and activation of alkynes; such compounds may become valuable reagents for organic syntheses.

Organometallic Chemistry of Arene Ruthenium and Osmium Complexes

https://escholarship.org/content/qt6rj7h8dv/qt6rj7h8dv.pdf?t=p0lnso

A diffuse LEED study of the adsorption structure of disordered benzene on Pt(111)

In biological reduction processes the dihydronicotinamides NAD(P)H often transfer hydride to an unsaturated substrate bound within an enzyme active site. In many cases, metal ions in the active site bind, polarize and thereby activate the substrate to direct attack by hydride from NAD(P)H cofactor. This review looks more widely at the metal coordination chemistry of organic donors of hydride ion – organo-hydrides – such as dihydronicotinamides, other dihydropyridines including Hantzsch's ester and dihydroacridine derivatives, those derived from five-membered heterocycles including the benzimidazolines and benzoxazolines, and all-aliphatic hydride donors such as hexadiene and hexadienyl anion derivatives. The hydride donor properties – hydricities – of organo-hydrides and how these are affected by metal ions are discussed. The coordination chemistry of organo-hydrides is critically surveyed and the use of metal–organo-hydride systems in electrochemically-, photochemically- and chemically-driven reductions of unsaturated organic and inorganic (e.g. carbon dioxide) substrates is highlighted. The sustainable electrocatalytic, photochemical or chemical regeneration of organo-hydrides such as NAD(P)H, including for driving enzyme-catalysed reactions, is summarised and opportunities for development are indicated. Finally, new prospects are identified for metal–organo-hydride systems as catalysts for organic transformations involving ‘hydride-borrowing’ and for sustainable multi-electron reductions of unsaturated organic and inorganic substrates directly driven by electricity or light or by renewable reductants such as formate/formic acid.

The coordination chemistry of organo-hydride donors: new prospects for efficient multi-electron reduction

Publisher Summary This chapter discusses the electron-transfer reactions of polynuclear organotransition metal complexes The chemistry of polynuclear organometallic complexes has become increasingly important, particularly in aiding the understanding of the relationship among structure, bonding, and reactivity A great deal of effort has been devoted to the study of linked metallocene units to probe the redox properties of compounds containing two or more identical electron-transfer sites The imido-bridged complexes are reduced in a reversible one-electron process The monoanion (E = P), prepared by sodium naphthalenide reduction of the neutral compound and isolable as a sodium salt, has an electron spin resonance (ESR) spectrum consisting of 15 triplets There is very little information available on the redox properties of organometallic clusters of the early transition metals The trinuclear carbonyls and the mixed metal clusters undergo one-electron reduction Theoretical studies have shown that the monocations of both biferrocene and bis(fulvalene)diiron show some delocalization; the latter is much more delocalized than the former

The Electron-Transfer Reactions of Polynuclear Organotransition Metal Complexes

A new co-ordination mode for benzene ligands in cluster complexes, in which the ring is symmetrically placed above a metal triangle has been crystallographically established in the carbonyl complexes [Ru6C(CO)11(µ3-η2: η2:η2-C6H6)(η6-C6H6)] and [Os3(CO)9(µ3-η2: η2:η2-C6H6)].

Benzene in a new face-capping bonding mode: molecular structures of [Ru6C(CO)11(µ3-η2: η2:η2-C6H6)(η6-C6H6)] and [Os3(CO)9(µ3-η2: η2:η2-C6H6)]

This paper describes the synthesis of trinuclear metal complexes containing benzene in a new face-capping bonding mode, (μ 3 :η 2 :η 2 :η 2 -C 6 H 6 ), that accurately models the coordination geometry of benzene chemisorbed non surface of a close-packed metal lattice. [Os 3 (CO) 9 (μ 3 :η 2 :η 2 :η 2 -C 6 H 6 )]

M. Pilar Gómez-Sal

Papers

Benzene in a new face-capping bonding mode: molecular structures of [Ru6C(CO)11(µ3-η2: η2:η2-C6H6)(η6-C6H6)] and [Os3(CO)9(µ3-η2: η2:η2-C6H6)]

A face-capping bonding mode for benzene in triosmium carbonyl cluster complexes

Structural and chemical aspects of electron deficient pentamethylcyclopentadienyltitanium halides, alkyls, and oxides

The electrochemical reduction of an unsaturated mixed-metal cluster anion: Synthesis and x-ray crystal structure of [(Ph3P)2N][{Os3H(CO)10}2Ag]

Allyl derivatives of [{Ti(η5-C5Me5)(μ-O)Cl)}3]: X-ray crystal structure of [{Ti(η5-C5Me5)(μ-O)(CH2CH=CHMe)}3]