The unique β-diketiminate ligand in aluminum(i) and gallium(i) chemistry.

Mingdong Zhong,Soumen Sinhababu,Herbert W Roesky

doi:10.1039/c9dt04763h

Abstract

Over the past few decades, β-diketiminate ligands have been widely used in coordination chemistry and are capable of stabilizing various metal complexes in multiple oxidation states. Recently, the chemistry of aluminum and gallium in their +1 oxidation state has rapidly emerged. NacNacM(i) (M = Al, Ga; NacNac = β-diketiminate ligand) shows a two coordinate metal center comparable with singlet carbene-like species. The metal center also possesses a formally vacant p-orbital. In this article we present an overview of the last 10 years for aluminum(i) and gallium(i) stabilized by β-diketiminate ligands that have been widely explored in bond breaking and forming species.

Highlights

Complexes containing a low-oxidation metal center is a key topic in modern organometallic chemistry as it leads to the development of new systems
A number of transition metal complexes were synthesized in a broad range of oxidation states to activate small molecules or used as catalysts in organic reactions.[1]
We report monomeric aluminum and gallium carbenoid complexes supported by β-diketiminate ligands which possess a lone pair of electrons and a formally vacant p orbital

Summary

Introduction

Complexes containing a low-oxidation metal center is a key topic in modern organometallic chemistry as it leads to the development of new systems. It is interesting to note that with a redox-inactive metal bound and appropriate substituents, β-diketiminate ligands become redox-active ligands.[19] we present an overview that is of relevance to the corresponding bond aluminum complex containing an aluminum–selenium multiple bond and with 1,3,5,7-cyclooctatetraene (COT) to give the first aluminum complex containing a reduced COT-ligand with a strong aromatic character, respectively.[12] Both aluminyl anion complexes reacted with two abundant greenhouse gases (CO2 and N2O) via cycloaddition to generate a monoalumoxane anion.[13] The first isolable example of a room temperature stable monomeric cyclopentadienylaluminum(I) derivative was reported by Braunschweig and co-workers, which was supported by a bulky 1,2,4-tri-tert-butylcyclopentadienyl (Cp3t) ligand (IV, Fig. 1).14a The same group reported the first example of a monomeric Lewis base stabilized Al(I) hydride that can be isolated and handled under ambient conditions (V, Fig. 1).14b Very recently, Yamashita’s group reported an alkylsubstituted aluminum anion that exhibits very strong basicity and nucleophilicity (VI, Fig. 1).14c These species have been observed to form both covalent and donor–acceptor bonds, revealing both the reducing and nucleophilic properties of these novel complexes. Scheme 2 Carbon chain growth by sequential reactions of CO and CO2 with [W(CO)6] and 1

Small-molecule activation

Cleavage of the M–X single bond

H–X bond activation

Conclusions and perspectives