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Photoinduced organometallics

This review illustrates the above delineated characteristics of electron-transfer activated reactions by analyzing some representative thermal and photoinduced organometallic reactions. Kinetic studies of thermal reactions, time-resolved spectroscopic studies of photoinduced reactions, and free-energy correlations are presented to underscore the unifying role of ion-radical intermediates [29] in—at first glance—unrelated reactions such as additions, insertions, eliminations, redox reactions, etc. (Photoinduced electron-transfer reactions of metal porphyrin and polypyridine complexes are not included here since they are reviewed separately in Chapters 2.2.16 and 2.2.17, respectively.)... [Pg.1283]

Considerable progress has been made on C02 fixation in photochemical reduction. The use of Re complexes as photosensitizers gave the best results the reduction product was CO or HCOOH. The catalysts developed in this field are applicable to both the electrochemical and photoelectrochemical reduction of C02. Basic concepts developed in the gas phase reduction of C02 with H2 can also be used. Furthermore, electrochemical carboxyla-tion of organic molecules such as olefins, aromatic hydrocarbons, and alkyl halides in the presence of C02 is also an attractive research subject. Photoinduced and thermal insertion of C02 using organometallic complexes has also been extensively examined in recent years. [Pg.392]

The importance of tertiary amines in the photochemically induced electron transfer reactions has also been addressed5. Direct irradiation of aromatic or aliphatic amines often leads to the scission of C—N, N—H or C—H bonds that lead to the subsequent chemical reactions by radical pathways6. In this section, photochemical reactions of amines reported since 1978 will be considered with emphasis on photoinduced electron transfer. Photochemical reactions of inorganic and organometallic compounds will not be included unless photochemistry of amine moieties is the primary interest. [Pg.684]

It has been demonstrated that visible light irradiation of the absorption band of AcrH + in the presence of organometallic compounds and alkenes and alkylbenzenes in MeCN results in efficient C-C bond formation between these electron donors and AcrH+ via photoinduced electron transfer from the donors to the singlet excited state of AcrH+ to yield the alkylated or allylated adducts selectively [89-91], The AcrH+ is also photoreduced by ethylbenzene and other alkylbenzenes to yield the corresponding 9-substituted-10-methyl-9,10-dihydroacridine [92] ... [Pg.131]

We have organized this review of the photochemistry of organometallic compounds of the heavier group 14 elements by compound class, with the exception of photoinduced electron transfer processes which we treat under a separate heading. This review describes the recent literature which has appeared since the publication in 1995 of an earlier review of this topic1. [Pg.1522]

The photoinduced activation of organometallic ion pairs as presented in Section II has its counterpart in the purely thermal (adiabatic) processes for metal-metal bond formation. Thus, the dimeric metal carbonyls can be... [Pg.72]

While the propensity of organometallics to undergo photoinduced electron transfer reactions can lead to (often unwanted) polymerization reactions e.g. of substrates or solvents, there lies an opportunity in the controlled photopolymerization [142] via organometallics. [Pg.247]

These results illustrate the utility of photochemical methods for preparing and characterizing thermally unstable organometallic intermediates via low-temperature irradiation. In many cases, photoinduced ligand loss can occur at temperatures low enough that intermediates thus formed do not have enough internal energy to further react so that they can be characterized. The subsequent thermal decomposition of such compounds can then be monitored upon warm-up of the solutions. [Pg.333]

Table 3. Free energy change, AG°ct, and rate constants, of photoinduced electron transfer from group 14 organometallic electron donors to C, observed rate constants, obs, triplet quenching rate constants, kq, and limiting quantum yields, Oco, in the photoaddition of the donors to in benzonitrile at 298 K [212]. Table 3. Free energy change, AG°ct, and rate constants, of photoinduced electron transfer from group 14 organometallic electron donors to C, observed rate constants, obs, triplet quenching rate constants, kq, and limiting quantum yields, Oco, in the photoaddition of the donors to in benzonitrile at 298 K [212].
In the absence of a strong acid, photoinduced electron transfer from RH (alkyl-benzenes [276] and alkenes [277]) to the singlet excited state of AcrH+ ( AcrH+ ) is reported to lead to formation of the alkylated or ally la ted adducts, 9-R-lO-methyl-9,10-dihydroacridine (AcrHR). Photoinduced electron transfer form a variety of organometallic compounds (RM) also gave the same type of adduct, AcrHR [278-282]. In the presence of HCIO4 (l.2 M), however, the photooxygenation of ethylbenzene to 1-phenylethanol occurs as shown in Eq. 26 ... [Pg.2417]

Photoinduced reductive elimination of is synthetically important because it can lead to the generation of reactive organometallic complexes not obtained under thermal conditions, e.g., in the photochemistry " of (h -C5H5)jWH2, which leads to the smooth elimination of Hj and generation of tungstenocene, (h -C5H5>jW ... [Pg.324]


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