Structure, bonding, and ligand-based reactions of zwitterionic boratoiridium(I) complexes with oxazolinyl scorpionate ligands

Pawlikowski, Andrew V.; Gray, Tristan S.; Schoendorff, George; Baird, Benjamin; Ellern, Arkady; Windus, Theresa L.; Sadow, Aaron D.

doi:10.1016/j.ica.2009.06.017

Cited by 15 publications

(21 citation statements)

References 34 publications

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“…2 ] react with strong acids (such as HOTf) to afford oxazoline protonation rather than formation of a metal hydride. 17, 29 The exclusive reaction at the pendent oxazoline described here, however, is unexpected given the relatively strong nucleophilic character of Al-Me groups. Additionally, we expected that intra-or intermolecular proton transfer from the oxazolinium to an aluminum methyl would occur over time.…”

Section: Comparisons Between Bis(oxazolinyl)borate and Tris(oxazolinymentioning

confidence: 73%

“…We have crystallographically characterized several (k 2 -To M )IrL 2 compounds (L 2 = h 4 -C 8 H 12 or (CO) 2 ), and in all cases the six-membered BC 2 N 2 Ir rings form a boat conformation. 29 Thus, planar bis(oxazolinyl)borato chelate rings are formed in the absence of unfavorable interligand steric effects.…”

Section: Aluminum Methyl Group Abstraction By [Phb(ox Me2 ) 2 ]mentioning

confidence: 99%

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Bis(oxazolinyl)phenylborane: A Lewis acid-containing ligand for methide abstraction-based coordination to aluminum(III)

et al. 2010

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A compound that contains a Lewis acidic boron center and coordinating oxazoline groups, bis(4,4-dimethyl-2-oxazolinyl)phenylborane (PhB(Ox(Me2))2; 1), has been prepared and spectroscopically characterized. Solvent dependent 15N and 11B NMR spectroscopic properties and solid-state 11B NMR measurements provide support for intermolecular interactions involving Lewis acid and base sites. The bifunctional nature of oxazolinylborane 1 is demonstrated by its reaction with (AlMe3)2, which proceeds via methide abstraction by the boron and oxazoline coordination to aluminum to yield [(kappa(2)-PhMeB(Ox(Me2))2AlMe2] (2). Compound 2 contains a planar six-membered chelate ring, in contrast to related bis(pyrazolyl)boratoaluminum compounds that are puckered. Additionally, compound 2 and related bidentate tris(oxazolinyl)phenylborato dimethylaluminum are inert toward aluminum-methyl bond protonolysis. This robust nature suggested the possibility of using these oxazolinylboratoaluminum compounds in catalytic reactions, as is demonstrated by lactide ring-opening polymerization.

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Section: Comparisons Between Bis(oxazolinyl)borate and Tris(oxazolinymentioning

confidence: 73%

Section: Aluminum Methyl Group Abstraction By [Phb(ox Me2 ) 2 ]mentioning

confidence: 99%

Bis(oxazolinyl)phenylborane: A Lewis acid-containing ligand for methide abstraction-based coordination to aluminum(III)

et al. 2010

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“…Thus, {HTo M }CoCl 2 differs from 1 and 2 by its zwitterionic nature. Related iridium and rhodium compounds of protonated or methylated tris(oxazolinyl)borate complexes have been reported, as have zwitterionic cobalt(II) complexes stabilized by bulky tris(carbene)borate ligands , . Compared with 1 , compound 3 features slightly longer Co–Cl bonds (by more than 0.034 Å) and shorter Co–N bonds (by more than 0.025 Å).…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Oxidation Catalysis of [Tris(oxazolinyl)borato]cobalt(II) Scorpionates

Reinig¹,

Mukherjee

Weinstein

et al. 2016

Eur J Inorg Chem

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The reaction of CoCl 2 ·THF and thallium tris(4,4-dimethyl-2-oxazolinyl)phenylborate (TlTo M ) in tetrahydrofuran (THF) provides To M CoCl (1) in 95 % yield; however, appropriate solvents and starting materials are required to favor 1 over two other readily formed side-products, (To M ) 2 Co (2) and {HTo M }CoCl 2 (3). ESR, NMR, FTIR, and UV/Vis spectroscopies were used to distinguish these cobalt(II) products and probe their electronic and structural properties. Even after the structures indicated by these methods were confirmed by X-ray crystallography, the spectroscopic identification of trace contaminants in the material was challenging. The recognition of possible contaminants in the synthesis of To M CoCl in combination [a]

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“…The reaction of K [2] with 0.5 equiv of the rhodium starting material gives a red-brown solid that is difficult to purify. Recrystallization of the reaction product provides an interesting asymmetric dimer, {κ 4 (10), in which only one PhB(Ox Me2 ) 2 Im Mes ligand is present per two rhodium centers even though 2 equiv of K [2] were allowed to react with [Rh(μ-Cl)(η 2 -C 8 H 14 ) 2 ] 2 in the initial exploratory experiments. An upfield signal in the 1 H NMR spectrum at −21.70 ppm revealed that a rhodium hydride formed, and the doublet of doublets splitting pattern indicated that the hydride interacts inequivalently with two rhodium centers ( 1 J RhH = 30 and 18 Hz).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Rendered thermal ellipsoid plot of {κ 4 -PhB(Ox Me2 ) 2 Im Mes ′ -CH 2 }Rh(μ-H)(μ-Cl)Rh(η 2 -C 8 H 14 )2 (10) with ellipsoids depicted at 35% probability. A disordered pentane and hydrogen atoms are not included in the representation, with the exception of the rhodium hydride, which was located in the Fourier difference map and refined isotropically.…”

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confidence: 99%

Mixed N-Heterocyclic Carbene–Bis(oxazolinyl)borato Rhodium and Iridium Complexes in Photochemical and Thermal Oxidative Addition Reactions

Manna

Ellern

et al. 2014

Organometallics

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In order to facilitate oxidative addition chemistry of fac-coordinated rhodium(I) and iridium(I) compounds, carbene−bis(oxazolinyl)phenylborate proligands have been synthesized and reacted with organometallic precursors. Two proligands, PhB(Ox Me2 ) 2 (Im tBu H) (H[1]; Ox Me2 = 4,4-dimethyl-2-oxazoline; Im tBu H = 1-tertbutylimidazole) and PhB(Ox Me2 ) 2 (Im Mes H) (H[2]; Im Mes H = 1-mesitylimidazole), are deprotonated with potassium benzyl to generate K[1] and K[2], and these potassium compounds serve as reagents for the synthesis of a series of rhodium and iridium complexes. Cyclooctadiene and dicarbonyl compounds {PhB(Ox Me2 ) 2 Im tBu }Rh(Mes }Ir(CO) 2 (7) are synthesized along with To M M(η 4 -C 8 H 12 ) (M = Rh (8); M = Ir (9); To M = tris(4,4-dimethyl-2-oxazolinyl)phenylborate). The spectroscopic and structural properties and reactivity of this series of compounds show electronic and steric effects of substituents on the imidazole (tert-butyl vs mesityl), effects of replacing an oxazoline in To M with a carbene donor, and the influence of the donor ligand (CO vs C 8 H 12 ). The reactions of K[2] and [M(μ-Cl)(η 2 -C 8 H 14 ) 2 ] 2 (M = Rh, Ir) provide {κ 4 -PhB(Ox Me2 ) 2 Im Mes ′ CH 2 }Rh(μ-H)(μ-Cl)Rh(η 2 -C 8 H 14 ) 2 (10) and {PhB(Ox Me2 ) 2 Im Mes }IrH(η 3 -C 8 H 13 ) (11). In the former compound, a spontaneous oxidative addition of a mesityl ortho-methyl to give a mixed-valent dirhodium species is observed, while the iridium compound forms a monometallic allyl hydride. Photochemical reactions of dicarbonyl compounds 5 and 7 result in C−H bond oxidative addition providing the compounds {κ 4 -PhB(Ox Me2 ) 2 Im Mes ′ CH 2 }RhH(CO) (12) and {PhB(Ox Me2 ) 2 Im Mes }IrH(Ph)CO (13). In 12, oxidative addition results in cyclometalation of the mesityl ortho-methyl similar to 10, whereas the iridium compound reacts with the benzene solvent to give a rare crystallographically characterized cis-[Ir](H)(Ph) complex. Alternatively, the rhodium carbonyl 5 or iridium isocyanide {PhB(Ox Me2 ) 2 Im Mes }Ir(CO)CN t Bu (15) reacts with PhSiH 3 in the dark to form the silyl compound {PhB(Ox Me2 ) 2 Im Mes }RhH(SiH 2 Ph)CO (14) or {PhB(Ox Me2 ) 2 Im Mes }IrH(SiH 2 Ph)CN t Bu (17). These examples demonstrate the enhanced thermal reactivity of {PhB(Ox Me2 ) 2 Im Mes }-supported iridium and rhodium carbonyl compounds in comparison to tris(oxazolinyl)borate, tris(pyrazolyl)borate, and cyclopentadienyl-supported compounds. ■ INTRODUCTIONOxidative addition is an essential part of the rich chemistry of low-valent rhodium and iridium compounds, playing a central role in C−H bond activation chemistry 1 and a large range of catalytic chemistry including hydrogenation, 2 hydrosilylation, 3 hydroformylation, 4 and hydroacylation. 5 Decarbonylation of aldehydes also involves oxidative addition of formyl C−H bonds. 6 Recently, we described a rhodium(I)-catalyzed alcohol and aldehyde decarbonylation reaction that involves oxidative addition of formyl C−H bonds. 7 The To M Rh(CO) 2 or To M Rh(H) 2 CO (To M = tris(4,4-dimethyl-2-oxazolinyl...

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Structure, bonding, and ligand-based reactions of zwitterionic boratoiridium(I) complexes with oxazolinyl scorpionate ligands

Cited by 15 publications

References 34 publications

Bis(oxazolinyl)phenylborane: A Lewis acid-containing ligand for methide abstraction-based coordination to aluminum(III)

Bis(oxazolinyl)phenylborane: A Lewis acid-containing ligand for methide abstraction-based coordination to aluminum(III)

Synthesis and Oxidation Catalysis of [Tris(oxazolinyl)borato]cobalt(II) Scorpionates

Mixed N-Heterocyclic Carbene–Bis(oxazolinyl)borato Rhodium and Iridium Complexes in Photochemical and Thermal Oxidative Addition Reactions

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