Aldehyde and ketone ligands in organometallic complexes and catalysis

Abstract

Aldehydes and ketones are two of the most important functional groups in organic chemistry. Their synthetic and mechanistic chemistry has been studied in detail (1). It has also been known for some time that aldehydes and ketones can serve as ligands in transition metal complexes (2-33). However, this area has not received a great deal of systematic study. Indeed, the frequent use of acetone as a reaction or recrystallization solvent has likely led to the occasional serendipitous synthesis of acetone complexes-or at least it has once in the authors' laboratory.There are numerous transition metal catalyzed reactions that involve aldehyde or ketone starting materials or intermediates (34-37). Two industrially important examples are given in Figure 1. Clearly, the systematic study of stable aldehyde and ketone complexes is necesary to provide in-Volume 65 Number 4

Gas‐Phase Reactivity of Metavanadate [VO3]− towards Methanol and Ethanol: Experiment and Theory

“…[59][60][61] Such complexes are relevant to the catalytic reduction of carbon monoxide, for which coordinated h 2 -O,C-OCH 2 ligands are possible intermediates. [54,56,58] The present work demonstrates the formation of a h 2 -O,C-OCH 2 ligand at a vanadium centre by hydrogen-atom transfer from a methoxo ligand.…”

“…[54] For example, the complex Cp 2 V(h 2 -O,C-OCH 2 ) (Cp: h 5 -C 5 H 5 ) was prepared by reaction of paraformaldehyde with vanadocene Cp 2 V. [55,56] Equivalent ligands have been observed for the heavier congeners niobium and tantalum, [57,58] as well as for siloxide-supported centres, for example, [(tBu 3 SiO) 3 Ta(h 2 -O,C-OCH 2 )]. [59][60][61] Such complexes are relevant to the catalytic reduction of carbon monoxide, for which coordinated h 2 -O,C-OCH 2 ligands are possible intermediates.…”

Mechanistic studies on reaction of [ReH4(η2-H2)(Cyttp)]+ with ketones to give the hydrido-oxo complex [ReH2(O)(Cyttp)]+ (Cyttp=PhP(CH2CH2CH2PCy2)2)

“…Both modes of attachment are known for a large number of reported transition-metal ketone complexes [9,20], and, in some cases, equilibrium exists between the two [21]. Owing to the robust nature of the Cyttp ligand, it is assumed here that the ketone is coordinated to rhenium in an g 1 fashion.…”

Lewis Acid Catalysis by Ruthenium Complexes

“…Yamamoto has been a major contributor to the development of chiral main group Lewis acid catalysts [1,8]. Organometallic Lewis acids of late transition metals have been extensively studied by Beck [9], but the potential for stoichiometric asymmetric reactions on coordinated ligands was largely developed by others, particularly with rhenium [10,11] and molybdenum reagents [12]. These studies of stoichiometric reactions provided valuable information regarding mechanistic aspects and control of nucleophilic attack on coordinated substrates.…”