Dehydrogenative Boron Homocoupling of an Amine‐Borane

Johnson, Heather C.; McMullin, Claire L.; Pike, Sebastian D.; Macgregor, Stuart A.; Weller, Andrew S.

doi:10.1002/anie.201304382

Cited by 67 publications

(69 citation statements)

References 42 publications

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“…Examples have also been isolated in which multiple amine-borane moieties are bound to a metal centre, similar to intermediates often invoked for dimerisation and polymerisation mechanisms (vide infra) [12,62,[68][69][70] [72]. In 2013, Weller and MacGregor reported the first well-characterised example of the B-B homocoupling of an amine-borane to yield the diborane (4) Me 3 N · BH 2 BH 2 · NMe 3 ligand sigma bound to rhodium [62].…”

Section: Sigma Complexes Of Amine-boranesmentioning

confidence: 94%

“…In 2013, Weller and MacGregor reported the first well-characterised example of the B-B homocoupling of an amine-borane to yield the diborane (4) Me 3 N · BH 2 BH 2 · NMe 3 ligand sigma bound to rhodium [62]. B-B homocoupling of boranes has been otherwise limited to B-B bond formation in polyhedral boranes [73,74], guanidine bases [75] and catechol-and pinacolboranes [76][77][78] Sigma complexes of aminoboranes have also been isolated, where donation from the B-H bonds into a vacant metal orbital is reinforced by π back-donation from the metal into the π* B-N orbital of the aminoborane [80].…”

Section: Sigma Complexes Of Amine-boranesmentioning

confidence: 99%

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The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

Johnson

Hooper

Weller

2015

Topics in Organometallic Chemistry

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127

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Section: Sigma Complexes Of Amine-boranesmentioning

confidence: 94%

Section: Sigma Complexes Of Amine-boranesmentioning

confidence: 99%

The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

Johnson

Hooper

Weller

2015

Topics in Organometallic Chemistry

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127

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“…9 Recently there has been significant interest in the chemistry associated with Xantphos acting as a POP-pincer ligand to the group 9 metals (Figure 2), for example in carbonylation (A), 9 activation of H 2 /alkenes (B− D), 10−12 silylation (E), 13 hydroamination (F), 14 hydroacylation (G), 15 and amine−borane dehydrocoupling and hydroboration processes (H). 16 −18 We have recently reported the use of the [Rh(Xantphos)] + catalyst fragment in carbothiolation reactions between alkynes and ketone-bearing aryl sulfides to produce alkenyl sulfide products (Scheme 1). 19 These catalyst systems operate best at elevated temperatures, e.g.…”

Section: Introductionmentioning

confidence: 99%

Rh–POP Pincer Xantphos Complexes for C–S and C–H Activation. Implications for Carbothiolation Catalysis

et al. 2015

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The neutral Rh(I)–Xantphos complex [Rh(κ3-P,O,P-Xantphos)Cl] n , 4, and cationic Rh(III) [Rh(κ3-P,O,P-Xantphos)(H)2][BArF 4], 2a, and [Rh(κ3-P,O,P-Xantphos-3,5-C6H3(CF3)2)(H)2][BArF 4], 2b, are described [ArF = 3,5-(CF3)2C6H3; Xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; Xantphos-3,5-C6H3(CF3)2 = 9,9-dimethylxanthene-4,5-bis(bis(3,5-bis(trifluoromethyl)phenyl)phosphine]. A solid-state structure of 2b isolated from C6H5Cl solution shows a κ1-chlorobenzene adduct, [Rh(κ3-P,O,P-Xantphos-3,5-C6H3(CF3)2)(H)2(κ1-ClC6H5)][BArF 4], 3. Addition of H2 to 4 affords, crystallographically characterized, [Rh(κ3-P,O,P-Xantphos)(H)2Cl], 5. Addition of diphenyl acetylene to 2a results in the formation of the C–H activated metallacyclopentadiene [Rh(κ3-P,O,P-Xantphos)(ClCH2Cl)(σ,σ-(C6H4)C(H)CPh)][BArF 4], 7, a rare example of a crystallographically characterized Rh–dichloromethane complex, alongside the Rh(I) complex mer-[Rh(κ3-P,O,P-Xantphos)(η2-PhCCPh)][BArF 4], 6. Halide abstraction from [Rh(κ3-P,O,P-Xantphos)Cl] n in the presence of diphenylacetylene affords 6 as the only product, which in the solid state shows that the alkyne binds perpendicular to the κ3-POP Xantphos ligand plane. This complex acts as a latent source of the [Rh(κ3-P,O,P-Xantphos)]+ fragment and facilitates ortho-directed C–S activation in a number of 2-arylsulfides to give mer-[Rh(κ3-P,O,P-Xantphos)(σ,κ1-Ar)(SMe)][BArF 4] (Ar = C6H4COMe, 8; C6H4(CO)OMe, 9; C6H4NO2, 10; C6H4CNCH2CH2O, 11; C6H4C5H4N, 12). Similar C–S bond cleavage is observed with allyl sulfide, to give fac-[Rh(κ3-P,O,P-Xantphos)(η3-C3H5)(SPh)][BArF 4], 13. These products of C–S activation have been crystallographically characterized. For 8 in situ monitoring of the reaction by NMR spectroscopy reveals the initial formation of fac-κ3-8, which then proceeds to isomerize to the mer-isomer. With the para-ketone aryl sulfide, 4-SMeC 6H4COMe, C–H activation ortho to the ketone occurs to give mer-[Rh(κ3-P,O,P-Xantphos)(σ,κ1-4-(COMe)C6H3SMe)(H)][BArF 4], 14. The temporal evolution of carbothiolation catalysis using mer-κ3-8, and phenyl acetylene and 2-(methylthio)acetophenone substrates shows initial fast catalysis and then a considerably slower evolution of the product. We suggest that the initially formed fac-isomer of the C–S activation product is considerably more active than the mer-isomer (i.e., mer-8), the latter of which is formed rapidly by isomerization, and this accounts for the observed difference in rates. A likely mechanism is proposed based upon these data.

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“…reported the catalytic dehydrocoupling of catechol and pinacol borane . Weller and co‐workers reported the dehydrogenative boron‐homocoupling reaction of amine‐borane at a Rh atom . Fontaine and co‐workers reported an elegant diborane(4) synthesis by thermal H 2 elimination from a diborane(6) precursor .…”

Section: Introductionmentioning

confidence: 99%

Boron−Boron Dehydrocoupling of Boranes Initiated by Reaction with Iodine

Elias

Kaifer

Himmel

2019

Chemistry A European J

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A new boron–boron dehydrocoupling strategy was established, providing convenient access to some diborane(4) compounds starting from simple borane adducts under mild conditions. In contrast to the traditional pathway using a reducing reagent, the reduction from BIII to BII was paradoxically initiated by the addition of the oxidation‐reagent iodine. A reaction pathway for this unusual reaction was proposed based on quantum‐chemical calculations.

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Dehydrogenative Boron Homocoupling of an Amine‐Borane

Cited by 67 publications

References 42 publications

The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

Rh–POP Pincer Xantphos Complexes for C–S and C–H Activation. Implications for Carbothiolation Catalysis

Boron−Boron Dehydrocoupling of Boranes Initiated by Reaction with Iodine

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