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Mission accomplished: More than 100 years after first attempts at isolating a stable silanone, this task has finally been completed with the isolation of a metallosilanone complex. The elusive bare Si=O bond was made accessible by utilizing the coordination sphere of an electron-rich chromium fragment in combination with a sterically demanding saturated N-heterocyclic carbene (NHC) to protect the reactive site.

This review discusses the use of multidentate actor ligands as new inroads to small molecule activation and catalysis. Bio-inspired strategies such as the use of redox-active ligands, metal–ligand cooperation, and hemilabile ligands will be examined as they relate to functional actor ligands and their design. The application of new concepts of reactivity such as the use of frustrated Lewis pairs (FLPs) in actor ligand design will also be discussed. The focus of the discussion of metal–ligand cooperation will be on long-range cooperation between the metal and a remote reactive site on the ligand. In addition to metal–ligand cooperation, ligand-based reactivity in the presence of a spectator metal centre will be examined. Small molecules of particular interest in this review will include but not be limited to H2, O2, CO2, alcohols, silanes, and alkenes/alkynes.

Two possible reaction intermediates of the ortho-lithiation of 1-phenyl-2-N,N-dimethylcubane carboxamide were investigated using an ab-initio SCF molecular orbital approach at STO-5G level. The molecular electrostatic potential was used to analyze the reactivity of these intermediates. The geometry of the key intermediates is discussed. Based on the relative stability and the strength of the negative electrostatic potential near the reactive site criteria, it is quite clear that this reaction proceeds via a five-membered ring intermediate. The results agree well with experimental findings.

The photophysical and photochemical properties of exciplexes are summarized considering the electronic structure and role of energetics and kinetics in the formation and stabilization of these molecular entities. Exciplexes involving transition metal complexes, are known as transition metal complex exciplexes (TMCEs) and are classified on the basis of the reactive site of the excited metal complex and the properties of the ground state reactant. There are two main groups; ligand-centered exciplexes and metal-centered exciplexes. A survey of the literature of TMCEs is presented. Common features of exciplexes classified into different groups are revealed. A strategy for searching for new TMCEs is suggested.

Silicon is a truly exceptional element as it serves as a reactive site for an almost infinite number of transformations pertinent to synthetic organic chemistry. Importantly, the intertwined relationship of the valency atsilicon and its chemical reactivity represents the key to a profound understanding and the design of novel reactions. Thus, these so-called hypervalent silanes are crucial intermediates in silicon-based carbon-carbon bond-forming reactions, whereby tetravalent silanes are conventionally employed in carbon-silicon bond-forming processes. This review aims at a detailed discussion of these mechanistic aspects illustrated with some synthetically significant developments in modern organosilicon chemistry. Recent advances in silicon-mediated, organocatalytic C(sp 3 )-C(sp 3 ) bond formation directed towards the preparation of aldol and aldol-like products are covered. Silicon-based transition-metal-catalyzed C(sp n )-C(sp 2 ) bond formations involving hypervalent silicon intermediates are also included. These seemingly dissimilar reactions will be comparatively juxtaposed.

Polymer-bound lithium amides were used in an aldol reaction. The introduction of a spacer between the polymer backbone and the reactive site was important to enhance yields of the aldol products. The polymer-bound reagent was repeatedly used in the same reaction after the conversion to the lithium amide.

The 3,4-double bond of photoexcited furocoumarin shows a higher reactivity than the 4′,5′-double bond toward simple olefins, leading to the formation of cyclobutane derivatives.