η3-Allyl carbonyl complexes of group 6 metals: Structural aspects, isomerism, dynamic behaviour and reactivity
| Autor: | David J. Cardin, František Hartl, David E. Ryan |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Agostic interaction
Denticity Coordination sphere 010405 organic chemistry Chemistry Ligand Stereochemistry 010402 general chemistry 01 natural sciences Non-innocent ligand 0104 chemical sciences Inorganic Chemistry chemistry.chemical_compound Cyclopentadienyl complex Diphosphines Materials Chemistry Physical and Theoretical Chemistry Organometallic chemistry |
| Zdroj: | Coordination Chemistry Reviews. 335:103-149 |
| ISSN: | 0010-8545 |
| DOI: | 10.1016/j.ccr.2016.12.018 |
| Popis: | Transition metal complexes with π-allylic ligands remain an attractive topic in organometallic chemistry, given the numerous reports of a wide variety of synthetic routes, dynamic behaviour and reactivity, structural (including isomerism), spectroscopic and redox properties, and applications in organic synthesis and catalysis. Surprisingly, despite the considerable interest in the rich and varied chemistry of this family of organometallic compounds, there is no recent review. This review is focused on π-allylic representatives of low-cost Group-6 metals bearing one or more carbonyl ligand, the coordination sphere being complemented with η 5 -cyclopentadienyl (Section 2), chelating ligands, including redox-active α-diimines and various complementary diphosphines (Section 3), and novel anionic amidinate or pyrazolate ligands (Section 4). In Section 1, particular attention is paid to rearrangements of the π-allylic ligand, namely exo and endo isomerism, interconversion mechanisms, fluxionality, and agostic interactions. In addition, the application of multinuclear NMR spectroscopy to the elucidation of such isomerism, and the effect of the metal-centre oxidation state on the bonding, dynamic behaviour and reactivity of the π-allylic ligand are described. The detailed mechanistic description of the synthetic routes and dynamic behaviour of selected representatives of α-diimine complexes in Section 2 is followed by a description of the [M(CO) 2 (η 3 -allyl-H,R)(α-diimine)] 0/+ fragment as a convenient scaffold for diverse monodentate ligands participating in a range of substitution, insertion, intramolecular migration and C–C coupling reactions – frequently involving also the π-allylic ligand, such as allylic alkylation. Special attention is devoted to selected examples of redox and acid-base reactivity of the α-diimine complexes with emphasis on prospects in electrocatalysis. The amidinate (and related pyrazolate) ligands treated in Section 4 may directly replace the π-allylic ligand in some cyclopentadienyl complexes (Section 2) or the α-diimine ligand in some dicarbonyl π-allylic complexes (Section 3). The brief description of their synthetic routes is complemented by intriguing examples of fluxionality and characteristic reactivity encountered for these unusual four-electron donor ligands. |
| Databáze: | OpenAIRE |
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