Photochemistry of metal-metal bonds

Meyer, Thomas J.; Caspar, Jonathan V.

doi:10.1021/cr00067a002

Cited by 323 publications

(200 citation statements)

References 54 publications

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“…Homobinuclear complexes such as Mn 2 (CO)io w fth a direct metal-metal bond are split homolytically by GO* (M-M) excitation [4,7]. In heteronuclear complexes which are characterized by a polar metal-metal bond this GG* excitation involves a CT from the donor to the acceptor metal.…”

Section: Ligand Dissociation/substitutionmentioning

confidence: 99%

“…Metal carbonyl radicals which are usually obtained by oa*(M-M) excitation of dimeric metal carbonyls [4,7] may be also generated by MMCT excitation of heteronuclear complexes with a polar metal-metal bond. The radical Co(CO) 4 can thus be generated upon light absorption into MMCT bands of Ph 3 PAu I -Co-I (CO) 4 [64] or (OC) 4 Co-I -M II -Co-I (CO) 4 with M = Zn, Cd, and Hg [65].…”

Section: Metal-based Radicalsmentioning

confidence: 99%

“…Binuclear complexes with a covalent metal-metal bond can be split homolytically by a b M . M -> a*M-M excitation [4,7]. For example, the photolysis of Mn 2 (CO)io yields Mn(CO)5 radicals which recombine or engage in secondary reactions [4,7].…”

mentioning

confidence: 99%

“…M -> a*M-M excitation [4,7]. For example, the photolysis of Mn 2 (CO)io yields Mn(CO)5 radicals which recombine or engage in secondary reactions [4,7]. Much less is known on the photochemistry of MC excited states of the sp [8], pp [8], ds [9], dp or ff [2,10] type.…”

mentioning

confidence: 99%

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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: Ligand Dissociation/substitutionmentioning

confidence: 99%

Section: Metal-based Radicalsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Charge Transfer Excitation of Coordination Compounds. Generation of Reactive Intermediates

Vogler

Kunkely

1993

Catalysis by Metal Complexes

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“…The fluorenyl ligand in these structures exhibits a variety of bonding modes, including v3 in fluorenylbis(quinuclidine)lithium,2 q5 in fluorenyl(tetramethylethylenediamine)pota~sium,~ and v6 in cyclopentadienylfluorenyliron. 4 Until very recently, when Struchkov et al published the structure of fluorenyl(triphenylphosphine)gold(I),5 no +bonded fluorenyl ring was structurally characterized.…”

Section: Introductionmentioning

confidence: 99%

Structural investigations of benzocyclopentadienylzinc compounds. Crystal structure of the bis(tetrahydrofuran) complex of difluorenylzinc

Koten¹,

Fisher²,

Boersma³

et al. 1989

Organometallics

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Crystals of difluorenylzinc-bis(tetrahydr0furan) are monoclinic, space group Pc, with unit cell dimensions a = 9.680 (2) A, b = 9.315 (3) A, c = 16.061 (4) A, fl = 106.35 (2)O, and 2 = 2. The structure refinement converged at RF = 0.0426. The crystal structure of the difluorenylzinc-tetrahydrofuran complex shows one of the first examples of a structurally characterized, q1 metal-bonded fluorenyl group. Solution NMR data of the complex suggest a covalent bonding mode of the fluorenyl ligands and show the presence of two conformational isomers. From the crystal data it can be concluded that one of the two fluorenyl ligands is covalently bonded. The other ligand, however, shows some unexpected bonding features that probably do not result from crystal packing effects alone but may arise from electrostatic interactions that are also present in solid benzene and other aromatic compounds.

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Nucleophilic addition versus electron transfer in carbonylmetallate salts. Donor-acceptor interactions in the precursor ion pairs

Bockman¹,

Kochi²

1997

J. Phys. Org. Chem.

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The isostructural pentacarbonylmetallate anions M(CO)ϪϪ 5 ] is identified as the critical precursor for both electron transfer and nucleophilic coupling. Based on these observations, it is proposed that the rates and mechanisms of these interionic reactions are controlled by donor-acceptor bonding in the transition states, which in turn is directly related to the charge-transfer interactions extant in the ion-pair intermediate. ©

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Photochemistry of metal-metal bonds

Cited by 323 publications

References 54 publications

Charge Transfer Excitation of Coordination Compounds. Generation of Reactive Intermediates

Charge Transfer Excitation of Coordination Compounds. Generation of Reactive Intermediates

Structural investigations of benzocyclopentadienylzinc compounds. Crystal structure of the bis(tetrahydrofuran) complex of difluorenylzinc

Nucleophilic addition versus electron transfer in carbonylmetallate salts. Donor-acceptor interactions in the precursor ion pairs

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