Excited-state reactivity patterns of hexakisarylisocyano complexes of chromium(0), molybdenum(0), and tungsten(0)

Mann, Kent R.; Gray, Harry B.; Hammond, George S.

doi:10.1021/ja00443a083

Cited by 99 publications

(111 citation statements)

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“…W(CO) 2 (diphos)(CPh)Cl (A^ax = 639 nm) [82], isocyanide (e.g. W(CNPh) 6 (Vax = 638 nm [83] and orthometalated complexes (e.g. Pt(thpy) 2 with thpy = 2-(2-thienyl)pyridine anion, (Vax = 580 nm) [84][85][86] …”

Section: Mlctmentioning

confidence: 99%

Charge Transfer Excitation of Coordination Compounds. Generation of Reactive Intermediates

Vogler

Kunkely

1993

Catalysis by Metal Complexes

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Reactive compounds exhibit frequently catalytic properties. Particularly, many reactive metal complexes are characterized by their catalytic activity. Photochemistry presents one of the most important and versatile methods for the generation of reactive compounds. The design of photochemically generated catalysts requires a deeper insight in the photochemistry in general. The choice of appropriate light-sensitive precursors can be guided by several considerations. A straight-forward approach involves the selection of compounds according to the type of electronic excitation which often predetermines the nature of the photoproducts.In a metal complex the metal-ligand bonds are generally polar. The molecular orbitals are then not equally delocalized between metal and ligands but predominantly located at the metal or the ligands. The electronic transitions are classified according to this localization [1]. In simple homoleptic mononuclear complexes three types of electronic excitations can be distinguished. Electronic transitions are localized at the metal (metalcentered, MC), at the ligand (ligand-centered, LC or intraligand, IL) or they take place between MOs at the metal and the ligand. The latter transitions are associated with a spatial redistribution of electrons and therefore are termed charge transfer (CT) transitions. While this review deals with CT excited states let us first have a short look at MC and LC states and their significance for the generation of reactive species which might be catalytically active.Since the valence orbitals of metals may be of the s, p, d, and f type all these orbitals can be involved in MC transitions. Ligand field (LF) or dd excited states have been investigated in great detail [2][3][4][5][6]. In many cases LF (or dd) excitation leads to a weakening of metal-ligand bonds. As a result a ligand may be released without any change of the oxidation state of the metal. This process is very important for the generation of catalysts because the product is a coordinatively unsaturated complex which provides an

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Section: Mlctmentioning

confidence: 99%

Charge Transfer Excitation of Coordination Compounds. Generation of Reactive Intermediates

Vogler

Kunkely

1993

Catalysis by Metal Complexes

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“…As an example, electron transfer from the MLCT states of the hexakisarylisocyano complexes, M(CNPh) 6 (M is Mo or W), to CHC1 3 resulted in formation of the seven-coordinate products [M(CNPh) 6 Cl]+[Cl]" by a net 2-e" oxidation process (8). Transfer via CTTS states is somewhat more common and is exemplified by the pho tooxidation of (rç 5 -C 5 H 5 ) 2 Fe in CC1 4 (9).…”

Section: Photooxidation Of Organometallic Complexesmentioning

confidence: 99%

“…In the photooxidation of M(CNPh) 6 (M is Mo or W) just discussed, the M(CNPh) 6 radical cation is postulated to abstract a CI atom within the caged ion pair to yield the final product, [M(CNPh) 6 Cl] + CP (8). Similar atom-abstraction reactions are also observed for the photochemically generated radicals *Mn(CO) 5 and (η 5 -C 5 H 5 )Fe(CO) 2 - (12,13).…”

Section: Photooxidation Of Organometallic Complexesmentioning

confidence: 99%

Photooxidation of Metal Carbynes

McElwee‐White

Kingsbury

Carter

1993

Photosensitive Metal—Organic Systems

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Radical cations formed upon photooxidation of the metal carbyne complexes (n 5 -C 5 H 5 )L 1 L 2 M≡CR (M is Mo or W; L 1 and L 2 are CO or P(OMe) 3 ; and R is alkyl or aryl) were found to be extremely reactive. Depending on the reaction conditions, either the radical cations exhibited the ligand-exchange and atom--abstraction processes that are typical of metal radicals, or the carbyne ligands underwent a series of highly unusual rearrangements to yield organic products. When organic products were generated, they were formed with good stereochemical and regiochemical control.REACTIVE ORGANIC FRAGMENTS CAN BE STABILIZED with transi tion metals so that they can be used for synthesis under ordinary reaction conditions. One example is the extensive utilization of metal carbenes in organic synthesis (2). It is thus somewhat surprising that there are so few reported cases of generation of organic products from the closely related metal carbynes. Although the chemistry of metal carbynes has been explored (2), most of the reported reactions involve conversion into other carbyne complexes by exchange of ancillary ligands; interconversion of car byne, carbene, and vinylidene complexes; or [2 + 2] cycloaddition with alkenes and alkynes followed by metathesis or polymerization. With the exception of polymers and metathesis products, organic species derived from the carbyne ligand are almost never generated.One method for inducing new modes of reactivity in metal complexes is one-electron (l-e~) oxidation. The differences in reaction rates between 18-e~ complexes and their 17-e~ counterparts can be quite dramatic (3-5). Reaction manifolds that are not available to an 18-e~ complex can thus become accessible to its corresponding 17-e~ radical cation. This chapter

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“…Photooxidation of six-coordinate isocyanide complexes of Cr, Mo, and W has indeed been observed in chlorocarbon solvents [48], but experiments more directly related to energy storage have not been successful.…”

Section: Photoionizationmentioning

confidence: 99%

Solar energy storage reactions involving metal complexes

Maverick¹,

Gray²

1980

Pure and Applied Chemistry

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-Photochemical properties of transition metal complexes are discussed as they relate to possible schemes for energy storage. Complexes of copper(I) with r-acceptor ligamds have been used to sensitize isomerizations of organic molecules, and there is room for considerable further investigation in this area. Electron transfer reactions have been more intensively studied. These reactions fall into three broad categories: ionization, oxidative addition/reductive elimination, and excited state electron transfer. Experiments in the first two categories have ierally led to rather poor storage efficiency and have required ultraviolet light. But long-lived excited states of coordination compounds can participate in chemical reactions with high efficiency, and such systems are promising for solar energy storage. Specific systems of this type that are discussed in detail involve electron transfer quenching of the lowest emissive excited states of Ru(2,2'_bipyridine), M (diisocyanoalkane) (M=Rh,Ir), and Mo6Cl.

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Excited-state reactivity patterns of hexakisarylisocyano complexes of chromium(0), molybdenum(0), and tungsten(0)

Cited by 99 publications

References 1 publication

Charge Transfer Excitation of Coordination Compounds. Generation of Reactive Intermediates

Charge Transfer Excitation of Coordination Compounds. Generation of Reactive Intermediates

Photooxidation of Metal Carbynes

Solar energy storage reactions involving metal complexes

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