Utilisation of an η3-allyl hydride complex, formed by UV irradiation, as a controlled source of 16-electron (η5-C5Me5)Rh(CH2CHMe)

Sexton, Catherine J.; López‐Serrano, Joaquín; Lledós, Agustı́; Duckett, Simon B.

doi:10.1039/b809321k

Cited by 5 publications

(5 citation statements)

References 25 publications

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“…There are a few other reported iridium allyl hydrides formed through metalation of an olefin upon coordination of a monoanionic tridentate fac -coordinating ligand, and these include {PhB(CH 2 PR 2 ) 3 } (R = Ph, i -C 3 H 7 ), , Tp, and To M . Cp*RhH(C 3 H 5 ) is formed by photolysis of Cp*Rh(η 2 -C 3 H 6 ) 2 , and the iridium analogue is synthesized by reduction of Cp*Ir(η 3 -C 3 H 5 )Cl . The hydride resonance of 11 at −27.49 ppm appeared further upfield than the other iridium allyl hydride compounds following the trend {PhB(CH 2 PPh 2 ) 3 }IrH(η 3 -C 8 H 13 ) (at −12.55 ppm) > {PhB(CH 2 P i Pr 2 ) 3 }IrH(η 3 -C 8 H 13 ) (at −15.3 ppm) > {PhB(CH 2 P i Pr 2 ) 3 }IrH(η 3 -C 3 H 5 ) (at −15.60 ppm) > Cp*IrH(η 3 -C 3 H 5 ) (at −16.7) > TpIrH(η 3 -C 8 H 13 ) (at −18.10 ppm) .…”

Section: Results and Discussionmentioning

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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Section: Results and Discussionmentioning

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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“…Thermal allylic C-H bond activations with iridium(I) tris(pyrazolyl)borate and tris(phosphino)borate compounds had been previously been described, 12,13,14,15 but examples of rhodium(I)-mediated allylic C-H bond activation were limited to photochemical activations. 16,17 Our attempts to develop methods for functionalization of the allyl hydrides have uncovered the first example of (formal) nitrene insertion into rhodium-hydrogen bonds. The mechanism for this insertion may involve either rhodium nitrene or rhodium triazenide intermediates; we are currently investigating reactions of other organoazides with tris(oxazolinyl)borato rhodium compounds to better understand the mechanism and identify intermediates in the formation of rhodium amides.…”

Section: Discussionmentioning

confidence: 99%

“…15 In addition to the thermal allylic C-H bond oxidative additions, photolysis of Tp*Rh(CNCH 2 t Bu)(PhN C NCH 2 t Bu) in liquid propylene generates the allylic C-H bond activation product Tp*RhH(h 1 -CH 2 CH CH 2 )(CNCH t Bu). 16 Irradiation of Cp*Rh(CH 2 CHMe) 2 yields Cp*Rh(h 3 -C 3 H 5 )H. 17 Thus, an allylic C-H bond functionalization scheme might involve a p-allyl Rh(III) or Ir(III) species as a reactive intermediate. While this appears reasonable based on known rhodium-and iridium-catalyzed allylic substitution chemistry, 18,19 examples of nucleophilic attack upon p-allyl compounds obtained from C-H bond activation are uncommon.…”

Section: Introductionmentioning

confidence: 99%

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Allylic C–H bond activation and functionalization mediated by tris(oxazolinyl)borato rhodium(i) and iridium(i) compounds

Gray

Baird

et al. 2011

Dalton Trans.

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Allylic C-H bond oxidative addition reactions, mediated by tris(oxazolinyl)borato rhodium(I) and iridium(I) species, provide the first step in a hydrocarbon functionalization sequence. The bond activation products To M MH(h 3 -C 8 H 13 ) (M = Rh (1), Ir (2)), To M MH(h 3 -C 3 H 5 ) (M = Rh (3), Ir (4)), and To M RhH(h 3 -C 3 H 4 Ph) (5) (To M = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) are synthesized by reaction of Tl[To M ] and the corresponding metal olefin chloride dimers. Characterization of these group 9 allyl hydride complexes includes 1 H-15 N heteronuclear correlation NMR experiments that reveal through-metal magnetization transfer between metal hydride and the trans-coordinated oxazoline nitrogen. Furthermore, the oxazoline 15 N NMR chemical shifts are affected by the trans ligand, with the resonances for the group trans to hydride typically downfield of those trans to h 3 -allyl and tosylamide. These group 9 oxazolinylborate compounds have been studied to develop approaches for allylic functionalization. However, this possibility is generally limited by the tendency of the allyl hydride compounds to undergo olefin reductive elimination. Reductive elimination products are formed upon addition of ligands such as CO and CN t Bu.

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“…52 Similar ΔG ‡ values of ethene rotation have been reported for cyclopentadienyl rhodium complexes: CpRh(CH 2 vCH(CO 2 t Bu)) 2 ΔG ‡ 295 = 72.5 ± 0.1 kJ mol −1 53 and Cp*Rh(CH 2 vCH(Me)) (SiEt 3 )(H) ΔG ‡ 300 = 72.7 ± 0.1 kJ mol −1 . 54 It should be noted that there was no evidence for any CH bond activation of the ethene ligand and upon warming to room temperature 2 was reformed.…”

Section: Photochemical Reaction Of 2 With Ethanementioning

confidence: 98%

Photochemical studies of (η⁵-C₅H₅)Ru(PPh₃)₂Cl and (η⁵-C₅H₅)Ru(PPh₃)₂Me: formation of Si–H and C–H bond activation products

Clark

Duckett

2014

Dalton Trans.

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Studies examining the photochemical reactivity of CpRu(PPh3)2Cl and CpRu(PPh3)2Me towards the two electron donor ligands PEt3, C2H4, DMSO, the CH bond activatable reagents tetrahydrofuran, toluene, and pyridine, and the SiH bond activatable reagents HSiEt3 and HSi(Me)2CH=CH2) are presented. Broadband UV irradiation of CpRu(PPh3)2Cl leads to the formation of mono-substitution products such as CpRu(PPh3)(PEt3)Cl which are inert to further photochemical reaction, although thermally bis-substituted products such as CpRu(PEt3)2Cl can be formed. Room temperature irradiation of the related complex CpRu(PPh3)2Me with L = PEt3, C2H4, and DMSO also produces CpRu(PPh3)(L)Me. However, when these reactions are followed by in situ laser irradiation (325 nm source) at low temperature, three solvent activated isomers (ortho, meta and para) of CpRu(PPh3)2(C6H4Me) are detected in toluene in addition to η(1)- and η(3)-coordinated benzyl species. Furthermore, photolysis in THF leads to both the C-D bond activation product CpRu(PPh3)2(OC4D7) and the labile coordination complex CpRu(PPh3)(THF)Me. Now CH4 rather than CH3D is liberated which suggests the involvement of an orthometallated species. The photochemically driven reaction of CpRu(PPh3)2Me with HSiEt3 at 198 K generates CpRu(κ(2)-2-C6H4PPh2)(SiEt3)H and thereby confirms a role for an orthometallated complex is this process. Irradiation in cyclohexane produces the known orthometallated complex, CpRu(κ(2)-2-C6H4PPh2)(PPh3), and CH4 in accordance with this reactivity.

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Utilisation of an η3-allyl hydride complex, formed by UV irradiation, as a controlled source of 16-electron (η5-C5Me5)Rh(CH2CHMe)

Abstract: Low temperature UV irradiation of solutions of (eta(5)-C(5)Me(5))Rh(CH(2)[double bond, length as m-dash]CHMe)(2) yields (eta(5)-C(5)Me(5))Rh(eta(3)-CH(2)CHCH(2))(H), which provides controlled access to the 16-electron fragment (eta(5)-C(5)Me(5))Rh(CH(2)[double bond, length as m-dash]CHMe).

Cited by 5 publications

References 25 publications

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

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

Allylic C–H bond activation and functionalization mediated by tris(oxazolinyl)borato rhodium(i) and iridium(i) compounds

Photochemical studies of (η⁵-C₅H₅)Ru(PPh₃)₂Cl and (η⁵-C₅H₅)Ru(PPh₃)₂Me: formation of Si–H and C–H bond activation products

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Utilisation of an η3-allyl hydride complex, formed by UV irradiation, as a controlled source of 16-electron (η5-C5Me5)Rh(CH2CHMe)

Cited by 5 publications

References 25 publications

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

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

Allylic C–H bond activation and functionalization mediated by tris(oxazolinyl)borato rhodium(i) and iridium(i) compounds

Photochemical studies of (η5-C5H5)Ru(PPh3)2Cl and (η5-C5H5)Ru(PPh3)2Me: formation of Si–H and C–H bond activation products

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Photochemical studies of (η⁵-C₅H₅)Ru(PPh₃)₂Cl and (η⁵-C₅H₅)Ru(PPh₃)₂Me: formation of Si–H and C–H bond activation products