Isolated Ir(V) Boryl Complexes and Their Reactions with Hydrocarbons

Kawamura, Kohei; Hartwig, John F.

doi:10.1021/ja015975d

Cited by 93 publications

(66 citation statements)

References 30 publications

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“…[17,[26][27][28] Our NMR spectroscopic data imply that the BÀH interactions in 2 a,b remain intact in solution, though the two hydride positions are averaged on the NMR time scale and the small magnitude of the scalar coupling suggests a weak interaction.…”

Section: Methodsmentioning

confidence: 69%

“…1 H NMR spectra of compounds containing discrete, cis-disposed boryl and hydride ligands contain sharp hydride signals that remain unchanged upon 11 B decoupling. [17,[26][27][28] Our NMR spectroscopic data imply that the BÀH interactions in 2 a,b remain intact in solution, though the two hydride positions are averaged on the NMR time scale and the small magnitude of the scalar coupling suggests a weak interaction.…”

Section: Methodsmentioning

confidence: 99%

“…Several rhodium products are formed from these thermolysis reactions, and these materials have not yet been fully characterized. Because borane dissociates from 2 a and 2 b more readily than H 2 or silane, and the borylation of arenes and alkanes typically occurs through metal boryl complexes, [16,27,30,31] the mechanism of the reactions of 2 a and 2 b with hydrocarbons is likely to be complex.…”

Section: Methodsmentioning

confidence: 99%

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Rhodium Silyl Boryl Hydride Complexes: Comparison of Bonding and the Rates of Elimination of Borane, Silane, and Dihydrogen

et al. 2004

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Transition-metal "s complexes" [1] of dihydrogen [2] and of silanes [3] are common, and transition-metal s-borane complexes are now known. [4][5][6][7][8][9][10][11] Dihydrogen complexes are intermediates in the oxidative addition that occurs during hydrogenation, and they are intermediates of the reductive elimination that occurs during dehydrogenation. Similarly, silane complexes are probably intermediates in the oxidative additions of silanes that occur during hydrosilylation, [12] and borane complexes have been shown to be intermediates in catalytic hydroboration.[5] Borane complexes are also likely intermediates [13] in the borylation of alkanes [14,15] and arenes. [15][16][17][18][19] A complex with hydride, silyl, and boryl groups bound to the metal center of the same complex could adopt a structure with a s-dihydrogen, -silane, or -borane ligand. No complexes of this type have been isolated in pure form, but compounds with this collection of ligands would allow direct assessment of the similarities and differences between the three types of s complexes. Herein, we report the synthesis, experimental and calculated structures, as well as the reaction chemistry of [Cp*RhH 2 (Bpin)(SiR 3 )] (Cp* = C 5 Me 5 , Bpin = (pinacolato)-boryl) complexes, which contain two hydrides, one silyl and one boryl group. Our data suggests that this complex contains partial BÀH bonding and that borane eliminates from this complex faster than dihydrogen or silane.Reaction of the known bis(silyl) dihydride 1 a [20] with a large excess of HBpin in refluxing cyclohexane formed [Cp*RhH 2 (SiEt 3 )(Bpin)] (2 a) in 90 % yield, as determined by NMR spectroscopy with an internal standard [Eq. (1)]. In addition to a single pinacol methyl resonance at d = 1.09 ppm[*] Dr.

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Section: Methodsmentioning

confidence: 69%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Rhodium Silyl Boryl Hydride Complexes: Comparison of Bonding and the Rates of Elimination of Borane, Silane, and Dihydrogen

et al. 2004

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“…Additional mechanistic studies have led to the generation of Cp*Ir(V)-boryl complexes that are potential intermediates in the iridium catalyzed borylation of alkanes and that are analogs of intermediates in the rhodium catalyzed borylation of alkanes (62). Reaction of Cp*IrH 4 with excess pinacolborane generated Cp*IrH 2 (Bpin) 2 , and lithiation of Cp*IrH 4 ,(tfi).…”

Section: Single-turnover Studies Of the Borylation Of Alkanesmentioning

confidence: 99%

Catalytic, Thermal, Regioselective Functionalization of Alkanes and Arenes with Borane Reagents

Hartwig

2004

ACS Symposium Series

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“…In the case of Ir, however, some intriguing reactivity is associated with high-valent intermediates. For example, complexes of Ir IV and Ir V have been proposed as key intermediates in C-H bond activation, [1][2][3][4] oxygen atom transfer reactions, 5 and water oxidation chemistry. [6][7][8][9][10] Simple complexes of Ir IV are also known as strong one-electron oxidants.…”

Section: Introductionmentioning

confidence: 99%

Tris(guanidinato)complexes of iridium and rhodium in the oxidation states +III and +IV

Lee¹

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Mononuclear [Ir{ArNC(NR 2)NAr}(C 8 H 14) 2 ] complexes (where R = Me or Et; Ar = Ph or 4-MeC 6 H 4 ; and C 8 H 14 = cis-cyclooctene) were synthesized from the neutral N,Ndialkyl-N′,N′′-diarylguanidines via deprotonation and transmetalation. As confirmed by single-crystal structure determination, the guanidinato(1−) ligands coordinate the lowvalent d 8 Ir I center in an N,N′-chelating binding mode, and the C−N distances of the CN 3 core suggest that these ligands function as stronger donors than related monoanionic, bidentate nitrogen-based ligands. In the reaction of the complexes with O 2 , new [Ir{ArNC(NR 2)NAr}] 3 complexes were identified among the products, suggesting a new route for their synthesis. Tris(guanidinato) complexes of Ir III , [Ir{ArNC(NR 2)NAr} 3 ] (R = Me or Et; Ar = Ph or 4-MeC 6 H 4), were synthesized and, as revealed by electrochemical measurements, can be oxidized reversibly at unusually low potentials. These potentials are even lower than those of other Ir III complexes with very electron-rich, trianonic ligand sets as, for example, in cyclometalated tris(2-pyridylphenyl), corrolato and tris(dithiocarbamato) complexes. Chemical oxidation by [FeCp 2 ]PF 6 afforded isolable, paramagnetic Ir IV compounds, [Ir{ArNC(NR 2)NAr} 3 ]PF 6 , which were characterized by elemental analysis, mass spectrometry, electronic absorption and EPR spectroscopy and X-ray crystallography. The reactivity of these Ir IV complexes toward mild inorganic and organic reductants and substrates with O−H bonds was investigated. Similar tris(guanidinato) complexes of Rh III , [Rh{ArNC(NR 2)NAr} 3 ] (R = Me or Et; Ar = Ph, 4-MeC 6 H 4 or 4-MeOC 6 H 4), were synthesized. These complexes also were oxidized reversibly at low potentials, as compared to the corresponding tris(amidinato) and tris(triazenido) complexes. Chemical oxidation by [FeCp 2 ]PF 6 afforded thermally unstable, paramagnetic Rh IV compounds, [Rh{ArNC(NR 2)NAr} 3 ]PF 6 , which were characterized by mass spectrometry and electronic absorption spectroscopy.

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Isolated Ir(V) Boryl Complexes and Their Reactions with Hydrocarbons

Cited by 93 publications

References 30 publications

Rhodium Silyl Boryl Hydride Complexes: Comparison of Bonding and the Rates of Elimination of Borane, Silane, and Dihydrogen

Rhodium Silyl Boryl Hydride Complexes: Comparison of Bonding and the Rates of Elimination of Borane, Silane, and Dihydrogen

Catalytic, Thermal, Regioselective Functionalization of Alkanes and Arenes with Borane Reagents

Tris(guanidinato)complexes of iridium and rhodium in the oxidation states +III and +IV

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