Reversible carbon–boron bond formation at platinum centers through σ-BH complexes

Ríos, Pablo; Calle, Rocío Martín-de la; Vidossich, Pietro; Fernández-de-Córdova, Francisco José; Lledós, Agustı́; Conejero, Salvador

doi:10.1039/d0sc05522k

Cited by 11 publications

(23 citation statements)

References 59 publications

(51 reference statements)

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“…In our previous contribution we explored the reactivity of complex [Pt(I t Bu i Pr')(I t Bu i Pr)[BAr F ] (1.1) [11] toward HBpin (pinacolborane), HBcat (catecholborane) and HBdab (1,3,2benzodiazaborolane). [10] The reaction proceeded with the initial formation of the corresponding σ-BH complexes that are stable at temperatures ranging from À 15 to + 10°C, being the diamino borane HBdab derivative (2.1 c) the most stable (Scheme 2). Similarly, the reaction of HBMedab (1-methyl-1,3,2benzodiazaborolane) or HBMe 2 dab (1,3-dimethyl-1,3,2-benzodiazaborolane) with complex [Pt(I t Bu i Pr')(I t Bu i Pr) [BAr F ] at low temperature leads to the initial formation of the corresponding σ-BH complexes 2.1 d, e (Scheme 3).…”

Section: Reactions Of Complex 11 With Diaminoboranesmentioning

confidence: 99%

“…2200-2500 Hz). [10] These signals sharpen upon 11 B decoupling (See ESI Figure S12 and Figure S17). The 11 B{ 1 H} NMR spectra for 2.1 d, e show a very broad signal at 19.5 and 20.3 ppm, respectively.…”

Section: Reactions Of Complex 11 With Diaminoboranesmentioning

confidence: 99%

“…The Pt•••B distances are 2.243(2) Å (2.1 d) and 2.272(3) Å (2.1 e), above of the sum of covalent radii for Pt and B (2.2 Å) and longer than those observed for Pt-boryl complexes. [10,12] The BÀ H bond distances of 1.22(3) Å (2.1 d) and 1.21(3) Å (2.1 e) are only marginally different to that in complex 2.1 c (1. 19(3) Å) and are slightly elongated with respect to those in free boranes.…”

Section: Reactions Of Complex 11 With Diaminoboranesmentioning

confidence: 99%

“…[13] These structural parameters indicate that the replacement of the NH groups by NCH 3 fragments has not an important steric effect in the interaction of the borane with the Scheme 2. Reversible CÀ B/CÀ H process observed for complexes 2.1 a-c. [10] Scheme 3. Reaction of complex 1.1 with diamino boranes HBMedab and HBMe 2 dab at low temperature.…”

Section: Reactions Of Complex 11 With Diaminoboranesmentioning

confidence: 99%

“…[1h,9] Very recently, we have been able to isolate and characterize some rare platinum examples of this kind (Scheme 2, complexes 2.1 a-c). [10] Intriguingly, these compounds were unexpectedly involved in a reversible carbon-boron bond formation/cleavage process in which the formation of the carbonÀ boron bond (and a platinum hydride bond) was kinetically preferred whereas generation of a carbonÀ hydrogen bond (together with a platinumÀ boron bond) was thermodynamically favored, according to DFT calculations and low temperature NMR experiments. Thus, we set out to explore how the nature of the borane and NHC substituents influence the CÀ H/CÀ B bond forming reactions.…”

Section: Introductionmentioning

confidence: 99%

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Ligand Effects in Carbon−Boron Coupling Processes Mediated by σ‐BH Platinum Complexes

et al. 2021

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The reaction of tri-coordinated boranes (derived from dioxaborolanes and diazaborolanes) with cyclometalated low-electron count platinum complexes [Pt(NHC')(NHC)][BAr F ] (NHC = I t Bu i Pr, IMes, IMes*) led, at low temperature, to the formation of the corresponding σ-BH species. Some of these species have been characterized by X-Ray diffraction methods showing a rare η 1coordination mode. These compounds are thermally unstable and undergo a carbon-boron coupling process whose reversibility depends on the NHC ligand. DFT calculations indicate that the energy barriers required for CÀ B bond formation events (together with PtÀ H bonds) are lower than the competitive reactions leading to CÀ H bond formation (and PtÀ B bonds). However, the CÀ B coupling products appear to be formed under kinetic control with I t Bu i Pr ligands, whereas the relative low energy barrier leading to CÀ H bond formation is sufficiently low to form the thermodynamically more stable platinum boryl complexes at rt. The latter energy barrier is, nevertheless, too high for the systems bearing IMes and IMes* ligands.

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Section: Reactions Of Complex 11 With Diaminoboranesmentioning

confidence: 99%

Section: Reactions Of Complex 11 With Diaminoboranesmentioning

confidence: 99%

Section: Reactions Of Complex 11 With Diaminoboranesmentioning

confidence: 99%

Section: Reactions Of Complex 11 With Diaminoboranesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ligand Effects in Carbon−Boron Coupling Processes Mediated by σ‐BH Platinum Complexes

et al. 2021

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Metathesis by Partner Interchange in σ‐Bond Ligands: Expanding Applications of the σ‐CAM Mechanism

2021

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Metathesis by Partner Interchange in σ‐Bond Ligands: Expanding Applications of the σ‐CAM Mechanism

2021

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In 2007 two of us defined the σ‐Complex Assisted Metathesis mechanism (Perutz and Sabo‐Etienne, Angew. Chem. Int. Ed. 2007, 46, 2578–2592), that is, the σ‐CAM concept. This new approach to reaction mechanisms brought together metathesis reactions involving the formation of a variety of metal–element bonds through partner‐interchange of σ‐bond complexes. The key concept that defines a σ‐CAM process is a single transition state for metathesis that is connected by two intermediates that are σ‐bond complexes while the oxidation state of the metal remains constant in precursor, intermediates and product. This mechanism is appropriate in situations where σ‐bond complexes have been isolated or computed as well‐defined minima. Unlike several other mechanisms, it does not define the nature of the transition state. In this review, we highlight advances in the characterization and dynamic rearrangements of σ‐bond complexes, most notably alkane and zincane complexes, but also different geometries of silane and borane complexes. We set out a selection of catalytic and stoichiometric examples of the σ‐CAM mechanism that are supported by strong experimental and/or computational evidence. We then draw on these examples to demonstrate that the scope of the σ‐CAM mechanism has expanded to classes of reaction not envisaged in 2007 (additional σ‐bond ligands, agostic complexes, sp2‐carbon, surfaces). Finally, we provide a critical comparison to alternative mechanisms for metathesis of metal–element bonds.

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Reversible carbon–boron bond formation at platinum centers through σ-BH complexes

Abstract: A reversible carbon-boron bond formation has been observed in the reaction of the coordinatively unsaturated, cyclometalated, Pt(II) complex [Pt(ItBuiPr’)(ItBuiPr)][BArF], 1, with tricoordinated boranes HBR2. X-ray diffraction studies provided structural snap-shots...

Cited by 11 publications

References 59 publications

Ligand Effects in Carbon−Boron Coupling Processes Mediated by σ‐BH Platinum Complexes

Ligand Effects in Carbon−Boron Coupling Processes Mediated by σ‐BH Platinum Complexes

Metathesis by Partner Interchange in σ‐Bond Ligands: Expanding Applications of the σ‐CAM Mechanism

Metathesis by Partner Interchange in σ‐Bond Ligands: Expanding Applications of the σ‐CAM Mechanism

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