Four-electron reduction of CO: from formaldehyde and acetal synthesis to complex transformations.

The expansive and dynamic field of the CO Reduction Reaction (CORR) seeks to harness CO as a sustainable carbon source or energy carrier. While significant progress has been made in two, six, and eight-electron reductions of CO, the four-electron reduction remains understudied. This review fills this gap, comprehensively exploring CO reduction into formaldehyde (HCHO) or acetal-type compounds (EOCHOE, with E = [Si], [B], [Zr], [U], [Y], [Nb], [Ta] or -R) using various CORR systems.

Borohydride Compounds Catalyze the Selective 4e Reduction of CO with 9-BBN.

The selective double hydroboration of CO into bis(boryl)acetal (BBA) is a challenging yet appealing reduction process since BBA can be used as a versatile C and C sources for the synthesis of value-added products. In the present study, we demonstrate that simple borohydride compounds are efficient and selective catalysts for the synthesis of BBA when using 9-borabicyclo(3.3.

Single electron reduction of NHC-CO-borane compounds.

The carbon dioxide radical anion [CO˙] is a highly reactive species of fundamental and synthetic interest. However, the direct one-electron reduction of CO to generate [CO˙] occurs at very negative reduction potentials, which is often a limiting factor for applications. Here, we show that NHC-CO-BR species - generated from the Frustrated Lewis Pair (FLP)-type activation of CO by N-heterocyclic carbenes (NHCs) and boranes (BR) - undergo single electron reduction at a less negative potential than free CO.

Doubly Base-Stabilized Diborane(4) and Borato-Boronium Species and Their Chemistry with Chalcogens.

In an effort to isolate diborane(4) derivatives, we have developed an efficient and uncatalyzed approach using [BH·THF] and the mercaptopyridine ligand. Thermolysis of 2-mercaptopyridine, in the presence of [BH·THF], afforded a doubly base-stabilized diborane(4) species , [HB(μ-CHNS)], along with the formation of its isomeric species , [HB(μ-CHNS)], albeit in less yield. Based on the coordination of the boron with the mercaptopyridine ligand in and its spectroscopic data, compound has been designated as a borato-boronium species, in which the anionic borate and cationic boronium units are covalently bonded to each other.

Group IV Complexes with Sterically Congested -Aryl-adamantylcarbamidate Ligands.

Metalation of -(2,6-dibenzhydryl-4-tolyl)adamantane-1-carboxamide (, Ar*N(H)-C(O)-Ad) with M(NMe) (M = Ti, Zr, Hf) yields amidate complexes Ar*N=C(Ad)-O-Ti(NMe) () as well as bis(amidate) compounds (Ar*N=C(Ad)-O)M(NMe) (M = Zr (), Hf ()). In , the amidate ligand acts as a monodentate base via the oxygen atom with the Ti center in a slightly distorted tetrahedral environment. The steric requirement of the amidate ligand stabilizes the small coordination number of four of the Ti atom.