C–H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C–H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C–H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C–H activation until summer 2018.

3d Transition Metals for C-H Activation.

N-heterocyclic carbene analogues with low-valent group 13 and group 14 elements: syntheses, structures, and reactivities of a new generation of multitalented ligands.

London dispersion, which constitutes the attractive part of the famous van der Waals potential, has long been underappreciated in molecular chemistry as an important element of structural stability, and thus affects chemical reactivity and catalysis. This negligence is due to the common notion that dispersion is weak, which is only true for one pair of interacting atoms. For increasingly larger structures, the overall dispersion contribution grows rapidly and can amount to tens of kcal mol(-1) . This Review collects and emphasizes the importance of inter- and intramolecular dispersion for molecules consisting mostly of first row atoms. The synergy of experiment and theory has now reached a stage where dispersion effects can be examined in fine detail. This forces us to reconsider our perception of steric hindrance and stereoelectronic effects. The quantitation of dispersion energy donors will improve our ability to design sophisticated molecular structures and much better catalysts.

London Dispersion in Molecular Chemistry—Reconsidering Steric Effects

Since the discovery of the first stable N-heterocyclic carbene (NHC) in the beginning of the 1990s, these divalent carbon species have become a common and available class of compounds, which have found numerous applications in academic and industrial research. Their important role as two-electron donor ligands, especially in transition metal chemistry and catalysis, is difficult to overestimate. In the past decade, there has been tremendous research attention given to the chemistry of low-coordinate main group element compounds. Significant progress has been achieved in stabilization and isolation of such species as Lewis acid/base adducts with highly tunable NHC ligands. This has allowed investigation of numerous novel types of compounds with unique electronic structures and opened new opportunities in the rational design of novel organic catalysts and materials. This Review gives a general overview of this research, basic synthetic approaches, key features of NHC–main group element adducts, and might be...

NHCs in Main Group Chemistry.

N‐Heterocyclic Carbene Ligands: Coordination Chemistry, Reactivity, and Applications Steṕhane Bellemin-Laponnaz*,†,‡ and Samuel Dagorne* †IPCMS (Institut de Physique et Chimie des Mateŕiaux de Strasbourg), CNRS-Universite ́ de Strasbourg, 23 rue du Loess BP 43, F-67034 Strasbourg, France ‡University of Strasbourg Institute for Advanced Study (USIAS), 5 alleé du Geńeŕal Rouvillois, F-67083 Strasbourg, France Institut de Chimie de Strasbourg, CNRS-Universite ́ de Strasbourg, 1 rue Blaise Pascal, F-67000 Strasbourg, France

Group 1 and 2 and Early Transition Metal Complexes Bearing N-Heterocyclic Carbene Ligands: Coordination Chemistry, Reactivity, and Applications

Catalytic C H bond activation reactions at sp centers in the a position to nitrogen atoms have recently attracted much attention because they offer new and promising synthetic approaches for the functionalization of simple amines. Particularly important in this context are studies dealing with the development of methods for the hydroaminoalkylation of alkenes. This highly atom efficient reaction, which does not lead to the formation of any side products, allows the addition of a-C H bonds of primary or secondary amines to C C double bonds in a single step (Scheme 1). The signifi-

The Mechanism of the Titanium‐Catalyzed Hydroaminoalkylation of Alkenes

Synthesis and reactivity of N-aryl substituted N-heterocyclic silylenes

By reaction of 1,4-dipotassio-1,1,4,4-tetrakis(trimethylsilyl)tetramethyltetrasilane with PbBr2 in the presence of triethylphosphine a base adduct of a cyclic disilylated plumbylene could be obtained. Phosphine abstraction with B(C6F5)3 led to formation of a base-free plumbylene dimer, which features an unexpected single donor–acceptor PbPb bond. The results of density functional computations at the M06-2X and B3LYP level of theory indicate that the dominating interactions which hold the plumbylene subunits together and which define its actual molecular structure are attracting van der Waals forces between the two large and polarizable plumbylene subunits.

https://pubs.acs.org/doi/pdf/10.1021/ja300654t

Dispersion energy enforced dimerization of a cyclic disilylated plumbylene.

Reduction of group 4 metallocene dichlorides with magnesium in the presence of cyclic disilylated stannylene or plumbylene phosphine adducts yielded the respective metallocene tetrylene phosphine complexes. Under the same conditions the use of the respective dimerized stannylene or plumbylene gave metallocene ditetrylene complexes. A computational analysis of these reactions revealed for all investigated compounds multiple-bonded character for the M–E(II) linkage, which can be rationalized in the case of the monotetrylene complex with the classical σ-donor/π-acceptor interaction. The strength of the M–E(II) bond increases descending group 4 and decreases going from Sn to its heavier congener Pb. The weakness of the Ti–E(II) bonds is caused by the significantly reduced ability of the titanium atom for d–p π-back-bonding.

https://pubs.acs.org/doi/pdf/10.1021/ja301547x

Patrick Zark

Papers

The Mechanism of the Titanium‐Catalyzed Hydroaminoalkylation of Alkenes

Synthesis and reactivity of N-aryl substituted N-heterocyclic silylenes

Dispersion energy enforced dimerization of a cyclic disilylated plumbylene.

Coordination chemistry of cyclic disilylated stannylenes and plumbylenes to group 4 metallocenes.

Cardiac glycosides from Yellow Oleander (Thevetia peruviana) seeds