The Road Travelled: After Main‐Group Elements as Transition Metals

Abstract

Since the latter quarter of the twentieth century, main group chemistry has undergone significant advances. Power's timely review in 2010 highlighted the inherent differences between the lighter and heavier main group elements, and that the heavier analogues resemble transition metals as shown by their reactivity towards small molecules. In this concept article, we present an overview of the last 10 years since Power's seminal review, and the progress made for catalytic application. This examines the use of low oxidation state and/or low coordinate group 13 and 14 complexes towards small molecule activation (oxidative addition step in a redox based cycle) and how ligand design plays a crucial role in influencing subsequent reactivity. The challenge in these redox based catalytic cycles still centres on the main group complexes’ ability to undergo reductive elimination, however considerable progress in this field has been reported via reversible oxidative addition reactions. Within the last 5 years the first examples of well‐defined low valent main group catalysts have begun to emerge, representing a bright future ahead for main group chemistry.

Aluminium‐Mediated Carbon Dioxide Reduction by an Isolated Monoalumoxane Anion

“…Reactivity traditionally associated with transition-metals is now accessible by compounds of the p-block elements. [6] In this context, Stephan and co-workers demonstrated that phosphine/AlX 3 frustrated Lewis-pairs (FLPs) can stoichiometrically reduce CO 2 . [7] Unsaturated compounds of silicon and germanium also accomplish this reaction under mild conditions.T his is illustrated for homodiatomic multiple bonds of group 14 (E-E, E = Si, Ge) by ab ase-stabilized disilyne that generates the m-oxo/m-carbonate species I (Figure 1), [8] and the disilicon species (L)DSi = SiD(L) (L = Nheterocyclic carbene) that affords heterocycle II.…”

Lithium‐Aluminate‐Catalyzed Hydrophosphination Applications

“…[7b,8] Attractive indus-trially owing to its high natural abundance and low toxicity, aluminum is gaining prominence in this main group catalysis enlightenment. [9] Work by Roesky,W right, Cowley/Thomas, Harder,Stephan, and others,have successfully employed Albased catalysts in hydroboration and hydrogenation. [10] Uhl has also demonstrated that aP/Al geminal FLP can stoichiometrically hydrophosphinate heteroatom substituted nitriles, generating imines incorporated into 5-atom AlCPCN heterocycles.…”

CO2Fixation and Catalytic Reduction by a Neutral Aluminum Double Bond

“…[1,2] In this regard, use of CO 2 to form C 1 feedstocks for the production of value-added products has been ar apidly expanding area of research. [4][5][6] Whilst transition metals have dominated this field, the development of main group complexes that can act as transition metals [7,8] has begun to emerge as ac heaper and more environmentally benign alternative for CO 2 activation. [4][5][6] Whilst transition metals have dominated this field, the development of main group complexes that can act as transition metals [7,8] has begun to emerge as ac heaper and more environmentally benign alternative for CO 2 activation.…”

“…[3] Conversion of CO 2 to carbon monoxide (CO), methanol, formic acid, and cyclic/polycarbonates has been shown to be possible by several homogeneous catalytic systems. [4][5][6] Whilst transition metals have dominated this field, the development of main group complexes that can act as transition metals [7,8] has begun to emerge as ac heaper and more environmentally benign alternative for CO 2 activation. Frustrated Lewis pairs (FLPs) [9][10][11] and polar main-group multiple bonds have proven to be efficient methods for CO 2 activation.…”