Direct Observation of a Bent Carbonyl Ligand in a 19-Electron Transition Metal Complex

Lomont, Justin P.; Nguyen, Son C.; Harris, Charles B.

doi:10.1021/jp311732t

Cited by 9 publications

(17 citation statements)

References 73 publications

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“…Formation of a 19e adduct occurred to a significant extent upon reaction of P(OMe) 3 with the 17e iron and ruthenium radical products, but no electron transfer was observed; this is due to the fact that the 19e iron and ruthenium adducts localize their excess electron density at a ligand away from the metal center. 49 For the manganese and rhenium species, no formation of a 19e adduct was observed.…”

Section: Photochemical Disproportionationmentioning

confidence: 98%

“…57,58 Solution-phase photolysis at 400 nm again leads to efficient formation of the corresponding 17e radicals, with significant depletion observed for the bridging CO band of the parent species, indicating photochemical dissociation of the bridged parent complex. 49 Likewise, the photochemistry of Co 2 (CO) 8 , which is characterized by a dibridged structure of C 2v symmetry, [59][60][61] has been studied on the microsecond time scale following 355 nm excitation, and this too leads to efficient formation of the corresponding 17e Co(CO) 4 radicals. 62 It appears that bridging CO ligands do not significantly hinder cleavage of the M-M bond of a dimer to yield the corresponding radical halves.…”

Section: Influence Of Bridging Ligands On M-m Bond Cleavagementioning

confidence: 99%

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Primary photochemical dynamics of metal carbonyl dimers and clusters in solution: Insights into the results of metal–metal bond cleavage from ultrafast spectroscopic studies

Lomont

Harris

2015

Inorganica Chimica Acta

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Supporting Information PlaceholderABSTRACT: Metal carbonyl dimers and clusters constitute a diverse class of organometallic reagents and catalysts. The photochemistry of these complexes is a topic of significant and long-standing interest, as preparative-scale photolyses constitute many of the most synthetically powerful reactions in organometallic chemistry. The metal-metal bonding present in dimers and clusters is varied and significantly influences their overall reactivity. In this review we discuss the primary photochemical dynamics of transition metal carbonyl metal dimers and clusters, with a focus on the changes in metal-metal bonding that occur upon visible and/or ultraviolet photochemical excitation. The bulk of the results discussed here were obtained using ultrafast time-resolved infrared spectroscopy, a technique with high structural sensitivity afforded by the carbonyl reporter ligands of the complexes studied. Picosecond time resolution allows detailed monitoring of the photochemical reaction dynamics, including observation of initially excited complexes and short-lived transient metal-metal bond cleavage intermediates, as well as formation of the longer-lived, yet reactive, intermediates responsible for reactivity occurring on diffusion-limited time scales and beyond.

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Section: Photochemical Disproportionationmentioning

confidence: 98%

Section: Influence Of Bridging Ligands On M-m Bond Cleavagementioning

confidence: 99%

Primary photochemical dynamics of metal carbonyl dimers and clusters in solution: Insights into the results of metal–metal bond cleavage from ultrafast spectroscopic studies

Lomont

Harris

2015

Inorganica Chimica Acta

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“…The carbonyl ligand hence assumes a bent geometry, avoiding a 19 valence electron metal centre. However, this phenomenon remains to be substantiated, and whilst not entirely unprecedented, [245] previously reported bent carbonyl ligands in crystal structures [246] have often been shown to be due to erroneous measurements. [247]…”

Section: Scheme 22mentioning

confidence: 99%

η3-Allyl carbonyl complexes of group 6 metals: Structural aspects, isomerism, dynamic behaviour and reactivity

Ryan

Cardin

Hartl

2017

Coordination Chemistry Reviews

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Contents 1. Introduction 2. Complexes [CpM(CO)2(η 3 -allyl)] and related compounds 2.1. Synthetic strategies 2.2. Exo ⇌ endo isomerism 2.3. 95 Mo and 183 W NMR spectroscopy 2.4. Oxidized cationic complexes -reactivity, fluxionality, structural features 2.5. Mixed nitrosyl carbonyl complexes [CpM(CO)(NO)(η 3 -allyl)] + (M = Mo, W) 3. Complexes [M(CO)2(η 3 -allyl)(α-diimine)X] (X = anionic monodentate ligand) and related compounds 3.1. Synthetic strategies 3.2. Mechanistic features, structural aspects, and dynamic behaviour 3.3. Monodentate ligands bound to M(CO)2(η 3 -allyl)(L⏜L): reactivity and intermediacy in allylic alkylations 3.4. Redox Properties and Electrocatalysis 4. Amidinato and pyrazolato complexes related to [M(CO)2(η 3 -allyl)(α-diimine)X] 4.1. Synthesis and dynamic behaviour 4.2. Coordinatively unsaturated species and their reactivity 5. Summary and outlook Acknowledgement References 2 ABSTRACTTransition 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 5cyclopentadienyl (Section 2), chelating ligands, including redox active α-diimines and various complementary diphosphine (Section 3) and novel anionic amidinate or pyrazolate (Section 4) ligands. 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 αdiimine complexes in Section 2 is followed by a description of the [M(CO)2(η 3 -allyl-H,R)(αdiimine)] 0/+ fragment as a convenient scaffold for diverse monodentate ligands participating in a range of substitution, insertion, intramolecular migration and C-C coupling reactionsfrequently 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...

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“… 14 , 15 Noteworthy, persistent 19-e Mo-centered radicals that are perhaps better described as 18-e complexes with reduced ligands (so-called “18 + δ” complexes) were synthesized previously; however, the spin density on the metal center in these complexes was negligible (<1%). 16 − 19 …”

Section: Introductionmentioning

confidence: 99%

Carborane Stabilized “19-Electron” Molybdenum Metalloradical

et al. 2021

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Paramagnetic metal complexes gained a lot of attention due to their participation in a number of important chemical reactions. In most cases, these complexes are dominated by 17-e metalloradicals that are associatively activated with highly reactive paramagnetic 19-e species. Molybdenum paramagnetic complexes are among the most investigated ones. While some examples of persistent 17-e Mo-centered radicals have been reported, in contrast, 19-e Mo-centered radicals are illusive species and as such could rarely be detected. In this work, the photodissociation of the [Cp(CO) 3 Mo] 2 dimer ( 1 ) in the presence of phosphines was revisited. As a result, the first persistent, formally 19-e Mo radical with significant electron density on the Mo center (22%), Cp(CO) 3 Mo • PPh 2 ( o -C 2 B 10 H 11 ) ( 5b ), was generated and characterized by EPR spectroscopy and MS as well as studied by DFT calculations. The stabilization of 5b was likely achieved due to a unique electron-withdrawing effect of the o -carboranyl substituent at the phosphorus center.

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Direct Observation of a Bent Carbonyl Ligand in a 19-Electron Transition Metal Complex

Cited by 9 publications

References 73 publications

Primary photochemical dynamics of metal carbonyl dimers and clusters in solution: Insights into the results of metal–metal bond cleavage from ultrafast spectroscopic studies

Primary photochemical dynamics of metal carbonyl dimers and clusters in solution: Insights into the results of metal–metal bond cleavage from ultrafast spectroscopic studies

η3-Allyl carbonyl complexes of group 6 metals: Structural aspects, isomerism, dynamic behaviour and reactivity

Carborane Stabilized “19-Electron” Molybdenum Metalloradical

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