Synthesis, Structure, and Reactions of a (η<sup>3</sup>-α-silabenzyl)molybdenum Complex: A Synthetic Equivalent of a Coordinatively Unsaturated Silyl Complex

Komuro, Takashi; Kanno, Yuto; Tobita, Hiromi

doi:10.1021/om400225j

Cited by 9 publications

(7 citation statements)

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“…Further diversity is introduced by the incorporation of heteroatoms into the allyl ligand. While such compounds remain beyond the scope of the present article, the interested reader will find notable examples of such species in the following references: η 3 -azaallyl [58][59][60][61][62][63][64], η 3 -silaallyl [343][344][345], and silabenzyl [346][347][348][349] complexes, while the related η 3 -bound benzyl species are detailed in [350][351][352][353][354][355][356][357]. The benzyl and related complexes offer an alternative route to coordinative unsaturation, via a relatively facile η 3 → η 1 haptotropic shift.…”

Section: Discussionmentioning

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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Section: Discussionmentioning

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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“…As a first step to demonstrating migration with larger groups, the Tobita group investigated 1,2‐methyl and 1,2‐aryl migration from W to Si in a range of silylenes. [ 62 , 63 , 64 , 65 ] Work on reversible aryl migrations, which is summarised in Scheme 9 , resulted in the isolation of the aryl migration intermediate – a silicon analogue of an η 3 ‐benzyl complex ( 26 ) – for both W and Mo. [ 64 , 65 ]…”

Section: Elementary Reactions and Cooperativitymentioning

confidence: 99%

“…[ 62 , 63 , 64 , 65 ] Work on reversible aryl migrations, which is summarised in Scheme 9 , resulted in the isolation of the aryl migration intermediate – a silicon analogue of an η 3 ‐benzyl complex ( 26 ) – for both W and Mo. [ 64 , 65 ]…”

Section: Elementary Reactions and Cooperativitymentioning

confidence: 99%

Cooperativity in Transition Metal Tetrylene Complexes

Somerville

Campos

2021

Eur J Inorg Chem

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Cooperative reactivity between transition metals and ligands, or between two metals, has created significant opportunities for the development of new transformations that would be difficult to carry out with a single metal. Here we explore cooperativity between transition metals and divalent heavier group 14 elements (tetrylenes), a less‐explored facet of the field of cooperativity. Tetrylenes combine their strong σ‐donor properties with an empty p‐orbital that can accept electron density. This ambiphilicity has allowed them to form metal tetrylene and metallotetrylene complexes that place a reactive site adjacent to the metal. We have selected examples to demonstrate what has been achieved so far regarding cooperative reactivity, as this already spans metal‐, tetrylene‐ or multi‐site‐centred bond cleavage, cycloaddition, migration, metathesis, and insertion. We also highlight some challenges that need to be overcome for this cooperativity to make it to catalysis.

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“…2b, 3 We have recently found a reversible 1,2-aryl migration in tungsten−silicon complexes 4 and finally succeeded in isolation of key intermediates of this migration reaction, i.e. η 3 -α-silabenzyl complexes Cp*W(CO) 2 {η 3 (Si,C,C)-Si(p-Tol) 2 R} (R = p-Tol (1-W), Me), the first silicon analogues of η 3 -benzyl complexes.…”

Section: ■ Introductionmentioning

confidence: 98%

Direct Conversion of a Si–C(aryl) Bond to Si–Heteroatom Bonds in the Reactions of η³-α-Silabenzyl Molybdenum and Tungsten Complexes with 2-Substituted Pyridines

2015

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η 3 -α-Silabenzyl complexes Cp*M(CO) 2 -{η 3 (Si,C,C)-Si(p-Tol) 3 } (M = Mo (1-Mo), W (1-W)) reacted with 2-substituted pyridines NC 5 H 4 (2-EH n ) (E = O, S (n = 1); N (n = 2)) under mild conditions to give M−Si−E−C−N (E = O, N), W−Si−N−C−S, and M−E−C−N (E = S, N)metallacycles depending on the metal M or heteroatom E. These three kinds of metallacycles were characterized by spectroscopy, elemental analysis, and X-ray crystallography. The first two silametallacycles take on some silylene complex character and are considered to form via (aryl)silylene complex intermediates generated by cleavage of the Si−C(aryl) bond in the η 3 -α-silabenzyl ligand of 1-Mo and 1-W. ■ INTRODUCTIONActivation of robust Si−C(aryl) bonds induced by transitionmetal complexes is of considerable interest because this can be applied to the direct functionalization of arylsilanes. 1 Many catalytic and stoichiometric reactions via Si−C(aryl) bond activation have been developed using late-transition-metal complexes. 1,2 In these reactions, oxidative addition of Si−C(aryl) bonds to low-valent metal centers plays a crucial role. 2 In contrast, the counterparts using early-transition-metal complexes have received less attention.In addition to the oxidative addition, 1,2-migration of aryl substituents on silicon to metal in coordinatively unsaturated arylsilyl complexes producing (aryl)silylene complexes has been proposed as a crucial process for a few Si−C(aryl) bond activation reactions. 2b,3 We have recently found a reversible 1,2-aryl migration in tungsten−silicon complexes 4 and finally succeeded in isolation of key intermediates of this migration reaction, i.e. η 3 -α-silabenzyl complexes Cp*W(CO) 2 {η 3 (Si,C,C)-Si(p-Tol) 2 R} (R = p-Tol (1-W), Me), the first silicon analogues of η 3 -benzyl complexes. 5a We also found that the reaction of these complexes with 4-(dimethylamino)pyridine (DMAP) gave DMAP-stabilized (aryl)silylene complexes Cp*W(CO) 2 (pTol){Si(p-Tol)R·DMAP} via Si−C(aryl) bond cleavage (1,2-aryl migration) (Scheme 1). This result prompted us to examine the reactions of the η 3 -α-silabenzyl tungsten complex 1-W and its molybdenum analogue 1-Mo 5b with 2-substituted pyridines NC 5 H 4 (2-EH n ) (E = O, S (n = 1); E = N (n = 2)). These substrates bear multiple nucleophilic heteroatoms (N and E) that can attack the electrophilic silicon atom as well as protic hydrogen(s) on E that can protonate the metal center. As a result, we developed unique conversion reactions via Si−C(aryl) bond cleavage and arene elimination to give silametallacycles. We report here the direct conversion of a Si−C(aryl) bond to Si−heteroatom bonds starting from 1-W and 1-Mo. ■ RESULTS AND DISCUSSIONReactions of η 3 -α-Silabenzyl Complexes 1-Mo and 1-W with 2-Substituted Pyridines. 1-Mo and 1-W reacted with 2-substituted pyridines (2-hydroxypyridine, 2-mercaptopyridine, and 2-aminopyridine) to give three kinds of metallacycles 2−6 depending on the metal and the 2-EH n substituent (routes A−C in Scheme 2). Complexes 1-Mo and 1-W reacted with 2-hydroxypy...

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Synthesis, Structure, and Reactions of a (η³-α-silabenzyl)molybdenum Complex: A Synthetic Equivalent of a Coordinatively Unsaturated Silyl Complex

Cited by 9 publications

References 49 publications

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

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

Cooperativity in Transition Metal Tetrylene Complexes

Direct Conversion of a Si–C(aryl) Bond to Si–Heteroatom Bonds in the Reactions of η³-α-Silabenzyl Molybdenum and Tungsten Complexes with 2-Substituted Pyridines

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Synthesis, Structure, and Reactions of a (η3-α-silabenzyl)molybdenum Complex: A Synthetic Equivalent of a Coordinatively Unsaturated Silyl Complex

Cited by 9 publications

References 49 publications

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

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

Cooperativity in Transition Metal Tetrylene Complexes

Direct Conversion of a Si–C(aryl) Bond to Si–Heteroatom Bonds in the Reactions of η3-α-Silabenzyl Molybdenum and Tungsten Complexes with 2-Substituted Pyridines

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Synthesis, Structure, and Reactions of a (η³-α-silabenzyl)molybdenum Complex: A Synthetic Equivalent of a Coordinatively Unsaturated Silyl Complex

Direct Conversion of a Si–C(aryl) Bond to Si–Heteroatom Bonds in the Reactions of η³-α-Silabenzyl Molybdenum and Tungsten Complexes with 2-Substituted Pyridines