Low‐Coordinate Barium Boryloxides: Synthesis and Dehydrocoupling Catalysis for the Production of Borasiloxanes

Coz, Erwann Le; Dorcet, Vincent; Roisnel, Thierry; Tobisch, Sven; Carpentier, Jean‐François; Sarazin, Yann

doi:10.1002/ange.201807297

Cited by 12 publications

(3 citation statements)

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“…Although a number of heterobimetallic barium alkoxide species are also known, homometallic Ba alkoxides are scarce and form aggregates, for example, [Ba 5 (Omesityl) 5 (OMe) 5 (dme) 4 ]⋅dme . Some other derivatives of Ba‐alkoxides of low nuclearity have also been reported, for example, two‐coordinate Ba‐boryloxides that catalyse the dehydrocoupling of hydrosilanes and borinic acids . Some Ba siloxides also exist.…”

Section: Methodsmentioning

confidence: 99%

“…Ae complexes provide effective catalysts for these reactions . They also enable the formation of silazanes through N−H/H−Si heterodehydrocoupling, and that of borasiloxanes from BO−H/H−Si coupling . Yet, metal catalysts, and a fortiori Ae‐based ones, have seldom been implemented in the controlled production of siloxanes, despite the commercial importance of oligo‐ and polysiloxanes .…”

Section: Methodsmentioning

confidence: 99%

“…The kinetic data gathered so far agree with a mechanism involving nucleophilic attack of the Ba‐bound O siloxide atom onto the incoming hydrosilane, thus generating a pentavalent hydrosilicate. Such a scenario is akin to that established for the Ba‐catalysed formation of silazanes and borasiloxanes, but further investigations are required to support this working hypothesis.…”

Section: Methodsmentioning

confidence: 99%

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Barium Siloxides and Catalysed Formation of Si−O−Si' Motifs

Coz

Kahlal

Saillard

et al. 2019

Chemistry A European J

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The first unsupported barium siloxide, the homoleptic dimer [Ba 2 {m 2 -OSi(SiMe 3 ) 3 } 3 {OSi(SiMe 3 ) 3 }],i sp resented,a nd its structural features are discussed in the light of DFT computations. This complex, together with the related [Ba{m 2 -OSi(SiMe 3 ) 3 }{N(SiMe 3 ) 2 }] 2 and their parent [Ba{N(SiMe 3 ) 2 } 2 ] 2 ,m ediates the formation of asymmetric si-loxanesR 3 SiÀOÀSiR' 3 through the first case of main group metal-mediated dehydrocoupling of silanols and hydrosilanes. Early kinetic analysish ighlights an unusual catalytic manifold.Molecular alkaline-earth (Ae = Ca, Sr,B a) alkoxides and fluoroalkoxides have been employeda su seful precursors for the deposition of metal oxide or fluoridet hin films. [1,2] More recently,t hey have also been used as effective ring-opening polymerisation catalysts. [3] Yet, the p-donating ability of alkoxides combinedt ot he hard, oxophilic nature of Ae metals often leads to the formation of multinuclear or ill-defined alkoxides of limited solubility or volatility.T he propensity to producea ggregates increases upon descending group 2, and is particularly pronounced for the very large (1.35 )B a 2 + cation.I tg enerates complexes in whichb onding is essentiallyi onic, and in which coordination numberso ften reach eight or more. Althoughanumbero fh eterobimetallic barium alkoxide species are also known, [4] homometallic Ba alkoxides are scarce and form aggregates, fore xample, [Ba 5 (Omesityl) 5 -(OMe) 5 (dme) 4 ]·dme. [5] Some other derivatives of Ba-alkoxides of low nuclearity have also been reported, for example, two-coordinate Ba-boryloxides that catalyse the dehydrocoupling of hydrosilanes and borinic acids. [6] Some Ba siloxides also exist. Yet, they are either stabilized by solvento rm acrocyclic donors, as in [Ba 3 (OSiPh 3 ) 6 .thf]·(thf) 1/2 , [7] [Ba(OSiPh 3 ) 2 (15-crown-5)·thf] [8] [Ba 2 (OSitBu 3 ) 4 ·thf], [9] and [Ba 3 (OSiPh 2 OSiPh 2 O) 3 (tetraglyme) 2 ], [10] or the siloxide is the anionic part of am ultidentate ligand. [11,12] To our knowledge, no occurrence of solvent-free, unsupported Ba-siloxidei sk nown to date.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Barium Siloxides and Catalysed Formation of Si−O−Si' Motifs

Coz

Kahlal

Saillard

et al. 2019

Chemistry A European J

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Ruthenium‐Photocatalyzed Synthesis of Borasiloxanes in a One‐Pot Manner from Readily Available Silanes and Pinacolborane

Fan

Chen

et al. 2021

Asian J Org Chem

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An N‐Heterocyclic Boryloxy Ligand Isoelectronic with N‐Heterocyclic Imines: Access to an Acyclic Dioxysilylene and its Heavier Congeners

et al. 2019

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Introduced here is an ew type of strongly donating N-heterocyclic boryloxy (NHBO) ligand, [(HCDippN) 2 BO] À (Dipp = 2,6-diisopropylphenyl), which is isoelectronic with the well-known N-heterocyclic iminato (NHI) donor class.T his 1,3,2-diazaborole functionalized oxyl igand has been used to stabilizet he first acyclic two-coordinate dioxysilylene and its Ge,Sn, and Pb congeners,thereby presenting the first complete series of heavier group 14 dioxycarbene analogues.A ll four compounds have been characterized by X-raycrystallography and density-functional theory,e nabling analysis of periodic trends:t he potential for the [(HCDippN) 2 BO] À ligand to subtly vary its electronic-donor capabilities is revealed by snapshots showing the gradual evolution of arene p coordination on going from Si to Pb.Anionic oxygen-based ligands constitute af amily of donors prevalent in the coordination chemistry of harder metal centers. [1] Among the most common are alkoxy (RO À ) ligands,w hich stand out in having only one pendant substituent, thereby giving them the potential to donate 2s + 4p electrons to ametal center-the maximum for any h 1 ligand system. Thes ingle substituent, however, offers only limited steric protection at the metal center, meaning that Obridged oligomeric structures are commonly encountered. [1b] This tendency towards aggregation is problematic for applications which involve low-coordinate metal centres,f or example ambiphilic main-group species (such as carbenes and their heavier group 14 analogues) of interest in smallmolecule activation chemistry. [2] An approach used to counter this problem exploits aryloxy (ArO À )l igands featuring bulky ortho substituents, thereby extending steric protection towards the metal center. Thus,m onomeric species of the type (ArO) 2 E( E= Ge,S n, Pb) have been reported by Lappert and by Power using this approach. [1c-e] That said, further chemistry with these systems typically involves the ArO À unit acting as aleaving group (cf. pK a of phenol % 9), and being substituted by as tronger donor. [1f] Apotential strategy to circumvent this problem is to replace the O-bound aryl substituent with afunctional group based on amore electro-positive element such as boron (e.g., by employing boryloxy ligands,R 2 BO À ). As mall number of ligands of this type have been reported, although for R = alkyl or aryl these are typically considered as electron-deficient alkoxide variants:t he formally empty p-orbital at boron renders the R 2 BO À system aweak p donor. [3] Applications in main-group chemistry are thus rare (limited primarily to groups 1, 2a nd 13 complexes), [3b-d] although very recently Sarazin and co-workers isolated monomeric species of the type (R 2 BO) 2 E( E = Sn, Pb,B a) by employing the bulky (Me 3 Si) 2 HC group to inhibit dimerization. [3e-f] With aview to targeting an isolable dioxysilylene,wesaw an eed for more strongly p-donating boryloxy ligands which would potentially lead to awide HOMO-LUMO gap on the basis of LUMO destabilization (O-to-Si p donation) and...

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Low‐Coordinate Barium Boryloxides: Synthesis and Dehydrocoupling Catalysis for the Production of Borasiloxanes

Cited by 12 publications

References 56 publications

Barium Siloxides and Catalysed Formation of Si−O−Si' Motifs

Barium Siloxides and Catalysed Formation of Si−O−Si' Motifs

Ruthenium‐Photocatalyzed Synthesis of Borasiloxanes in a One‐Pot Manner from Readily Available Silanes and Pinacolborane

An N‐Heterocyclic Boryloxy Ligand Isoelectronic with N‐Heterocyclic Imines: Access to an Acyclic Dioxysilylene and its Heavier Congeners

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