In this review, we highlight the use of organic photoredox catalysts in a myriad of synthetic transformations with a range of applications. This overview is arranged by catalyst class where the photophysics and electrochemical characteristics of each is discussed to underscore the differences and advantages to each type of single electron redox agent. We highlight both net reductive and oxidative as well as redox neutral transformations that can be accomplished using purely organic photoredox-active catalysts. An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.

Organic Photoredox Catalysis

This article sets out to review the chemistry relating to the synthesis of structural and functional analogues of the three classes of hydrogenases. This chemistry has grown explosively over the last 10 or so years since the first X-ray structures of [NiFe]- and [FeFe]-hydrogenase systems were published. There are now some 400 papers covering structural and functional aspects, with the majority of these associated with the di-iron system. As much emphasized in earlier papers

Structural and functional analogues of the active sites of the [Fe]-, [NiFe]-, and [FeFe]-hydrogenases.

π-Bonding and the Lone Pair Effect in Multiple Bonds between Heavier Main Group Elements

This review is essentially an update of one entitled “πBonding and The Lone Pair Effect in Multiple Bonds Between Heavier Main Group Elements” which was published more than 10 years ago in this journal.1 The coverage of that survey was focused on the synthesis, structure, and bonding of stable compounds2 of heavier main group elements that correspond to the skeletal drawings reproduced in Tables 1 and 2. A row of numbers is listed at the bottom of each column in these tables. This refers to the number of stable complexes from each class that are currently known. The numbers in parentheses refer to the number of stable species that were known at the time of the previous review. Clearly, many of the compound classes listed have undergone considerable expansion although some remain stubbornly rare. The most significant developments for each class will be discussed in detail under the respective sections. As will be seen, there are also a limited number of multiple bonded heavier main group species that do not fit neatly in the classifications in Tables 1 and 2. However, to keep the review to a manageable length, the limits and exclusions, which parallel those used earlier, are summarized as follows: (i) discussion is mainly confined to compounds where experimental data on stable, isolated species have been obtained, (ii) stable compounds having multiple bonding between heavier main group elements and transition metals are not generally discussed, (iii) compounds in which a multiple bonded heavier main group element is incorporated within a ring are generally not covered, and (iv) hypervalent main group compounds that may incorporate faux multiple bonding are generally excluded. Such compounds are distinguished from those in Tables 1 and 2 in that they apparently require the use of more than four valence bonding orbitals at one or more of the bonded atoms. The remainder of this review is organized in a similar manner to that of the previous one wherein the compounds to be discussed are classified according to those summarized in Tables 1 and 2. The key unifying feature of almost all molecules discussed in this review is that they are generally stabilized by the use of bulky substituents which block associative or various decomposition pathways.3 Since the previous review was published in 1999, several review articles that cover parts of the subject matter have appeared.4

π-Bonding and the Lone Pair Effect in Multiple Bonds Involving Heavier Main Group Elements: Developments in the New Millennium

Reactions of Hydrosilanes with Transition-Metal Complexes: Formation of Stable Transition-Metal Silyl Compounds.

General strategy for the systematic synthesis of oligosiloxanes. Silicone dendrimers

The tetrasilabicyclo[1.1.0]butane system: preparation and characterization of 1,3-di-tert-butyl-2,2,4,4-tetrakis(2,6-diethylphenyl)tetrasilabicyclo[1.1.0]butane

The heavier group 14 element cation cluster compound, [(tBu3Si)6Ge10I]+·TTFPB- (3+· TTFPB-; TTFPB- = tetrakis(2,3,5,6-tetrafluorophenyl)borate), was unexpectedly obtained by thermolysis of in situ prepared iodocyclotrigermene, (tBu3Si)3Ge3I, in toluene in the presence of KI and K+·TTFPB-. The molecular structure of 3+·TTFPB- has been unambiguously determined by X-ray crystallography, showing that 3+ is a free germyl cation. The three “naked” cationic germanium atoms in the framework constitute a three-center two-electron (3c−2e) bond with a trishomocyclotrigermenylium character, which is well-supported by a theoretical calculation on the model compound Ge10H7+.

Yoshio Kabe

Papers

General strategy for the systematic synthesis of oligosiloxanes. Silicone dendrimers

The tetrasilabicyclo[1.1.0]butane system: preparation and characterization of 1,3-di-tert-butyl-2,2,4,4-tetrakis(2,6-diethylphenyl)tetrasilabicyclo[1.1.0]butane

The cation cluster of heavier group 14 elements: a free germyl cation with trishomoaromaticity.

Oxygenation of digermene derivatives

1,4-Disila(Dewar-benzene) and 1,4-Disilabenzene: Valence Isomerization of Bis(alkylsilacyclopropenyl)s