Borinium Cations as σ-B−H Ligands in Osmium Complexes

Esteruelas, Miguel A.; Fernández-Álvarez, Francisco J.; López, Ana M.; Mora, Malka; Oñate, Enrique

doi:10.1021/ja101806x

Cited by 40 publications

(39 citation statements)

References 44 publications

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“…Hydride ligands were located by single‐crystal X‐ray diffraction of 3 b and 3 c and were refined freely (Figure 1). These ligands are clearly interacting with the borylene ligand, the BH distances ( 3 b 1.33(3), 3 c 1.29(9) Å) being either slightly longer or statistically equivalent to those in the aforementioned borinium (1.32(5) Å) and unsymmetrical bis(σ‐borane) complexes4b (1.17(2), 1.22(6) Å) 4a. It is also noteworthy that the MB distances are both about 7 % shorter in the hydridoborylene complexes ( 3 b : 2.020(3); 3 c : 2.025(9) Å) than in the starting materials ( 1 b : 2.152(2); 1 c : 2.151(7) Å), and the MBN axes remain effectively linear, despite their decreased borylene character and increased coordination number.…”

Section: Resultsmentioning

confidence: 96%

“…Two interesting examples of this variability in bonding have been published in recent years concerning ligands of the form [HBR] 4. In 2010, Esteruelas and co‐workers published three complexes with σ‐borinium ligands bound adjacent to a hydride ligand (Scheme , bottom left) 4a. The difference between the two BH distances (Δ≈0.9 Å) was sufficient to confirm that the two ligands were effectively independent.…”

Section: Introductionmentioning

confidence: 99%

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Hydridoborylene Complexes and Di‐, Tri‐, and Tetranuclear Borido Complexes with Hydride Ligands

Bauer

Bertsch

Braunschweig

et al. 2013

Chemistry A European J

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Mono‐ and dinuclear hydridoborylene complexes were prepared by intermetallic borylene transfer from Group VI borylene or metalloborylene reagents. The hydride and borylene ligands were found to interact with each other significantly, although the boron ligand retains much of its former borylene character. Zero‐valent platinum fragments were successively added to the dinuclear hydridoborylene complexes, resulting in tri‐ and tetranuclear borido complexes, in which the BH interaction has been lost, and the hydride ligands now bridge two metal centers. The complexes were studied spectroscopically, crystallographically, and by DFT methods, and the unusual bonding situation in the MBH triangles of hydridoborylene complexes were evaluated.

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Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Hydridoborylene Complexes and Di‐, Tri‐, and Tetranuclear Borido Complexes with Hydride Ligands

Bauer

Bertsch

Braunschweig

et al. 2013

Chemistry A European J

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“…[45] Using 3 as a latent source of H 2 B-NMe 2 : dimerisation of H 2 B-NMe 2 : The isolation of 3 as a pure material in useful amounts allows its use as a latent source of B. This aminoborane is often observed in low relative concentrations during dehydrocoupling reactions of A, [15,21,26,42] but due to the dimerisation to form D its reaction chemistry with regard to dehydrocoupling has not been directly explored, although there are early reports by Burg and Rudolph on the vapour-phase reactivity of B.…”

Section: This Is the Case And Reaction Ofmentioning

confidence: 99%

[Ir(PCy₃)₂(H)₂(H₂BNMe₂)]⁺ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H₃B⋅NMe₂H and Retrodimerisation of [H₂BNMe₂]₂

Stevens

Dallanegra

Chaplin

et al. 2011

Chemistry A European J

116

167

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The Ir(III) fragment {Ir(PCy(3))(2)(H)(2)}(+) has been used to probe the role of the metal centre in the catalytic dehydrocoupling of H(3)B⋅NMe(2)H (A) to ultimately give dimeric aminoborane [H(2)BNMe(2)](2) (D). Addition of A to [Ir(PCy(3))(2)(H)(2)(H(2))(2)][BAr(F)(4)] (1; Ar(F) = (C(6)H(3)(CF(3))(2)), gives the amine-borane complex [Ir(PCy(3))(2)(H)(2)(H(3)B⋅NMe(2)H)][BAr(F)(4)] (2 a), which slowly dehydrogenates to afford the aminoborane complex [Ir(PCy(3))(2)(H)(2)(H(2)B-NMe(2))][BAr(F)(4)] (3). DFT calculations have been used to probe the mechanism of dehydrogenation and show a pathway featuring sequential BH activation/H(2) loss/NH activation. Addition of D to 1 results in retrodimerisation of D to afford 3. DFT calculations indicate that this involves metal trapping of the monomer-dimer equilibrium, 2 H(2)BNMe(2) ⇌ [H(2)BNMe(2)](2). Ruthenium and rhodium analogues also promote this reaction. Addition of MeCN to 3 affords [Ir(PCy(3))(2)(H)(2)(NCMe)(2)][BAr(F)(4)] (6) liberating H(2)B-NMe(2) (B), which then dimerises to give D. This is shown to be a second-order process. It also allows on- and off-metal coupling processes to be probed. Addition of MeCN to 3 followed by A gives D with no amine-borane intermediates observed. Addition of A to 3 results in the formation of significant amounts of oligomeric H(3)B⋅NMe(2)BH(2)⋅NMe(2)H (C), which ultimately was converted to D. These results indicate that the metal is involved in both the dehydrogenation of A, to give B, and the oligomerisation reaction to afford C. A mechanism is suggested for this latter process. The reactivity of oligomer C with the Ir complexes is also reported. Addition of excess C to 1 promotes its transformation into D, with 3 observed as the final organometallic product, suggesting a B-N bond cleavage mechanism. Complex 6 does not react with C, but in combination with B oligomer C is consumed to eventually give D, suggesting an additional role for free aminoborane in the formation of D from C.

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“…The current work appears to be the first detection of an osmium(II) hydride NMR peak for an osmium hydride in an aqueous solution. [56][57][58][59][60][61][62][63][64] These findings suggest that osmium arene complexes can modulate the redox balance in cells by a novel mechanism. 95 1 H NMR studies show that complexes 6 and 14 are more effective in oxidising NADH than 8 and 16 after 24 h incubation at 310K ( Figure S5).…”

Section: Accumulation Of Ros In Cancer Cellsmentioning

confidence: 99%

The contrasting chemical reactivity of potent isoelectronic iminopyridine and azopyridine osmium(ii) arene anticancer complexes

Romero

Habtemariam

et al. 2012

Chem. Sci.

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A wide variety of steric and electronic features can be incorporated into transition metal coordination complexes, offering the prospect of rationally-designed therapeutic agents with novel mechanisms of action. Here we compare the chemical reactivity and anticancer activity of organometallic Os II complexes [Os(h 6 -arene)(XY)Z]PF 6 where arene ¼ p-cymene or biphenyl, XY ¼ N,N 0 -chelated phenyliminopyridine or phenylazopyridine derivatives, and Z ¼ Cl or I. The X-ray crystal structure of [Os(h 6 -p-cym)(Impy-OHLike the azopyridine complexes we reported recently (Dalton Trans., 2011, 40, 10553-10562), some iminopyridine complexes are also potently active towards cancer cells (nanomolar IC 50 values). However we show that, unlike the azopyridine complexes, the iminopyridine complexes can undergo aquation, bind to the nucleobase guanine, and oxidize coenzyme nicotine adenine dinucleotide (NADH). We report the first detection of an Os-hydride adduct in aqueous solution by 1 H NMR (À4.2 ppm). Active iminopyridine complexes induced a dramatic increase in the levels of reactive oxygen species (ROS) in A549 lung cancer cells. The anticancer activity may therefore involve interference in the redox signalling pathways in cancer cells by a novel mechanism.

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Borinium Cations as σ-B−H Ligands in Osmium Complexes

Cited by 40 publications

References 44 publications

Hydridoborylene Complexes and Di‐, Tri‐, and Tetranuclear Borido Complexes with Hydride Ligands

Hydridoborylene Complexes and Di‐, Tri‐, and Tetranuclear Borido Complexes with Hydride Ligands

[Ir(PCy₃)₂(H)₂(H₂BNMe₂)]⁺ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H₃B⋅NMe₂H and Retrodimerisation of [H₂BNMe₂]₂

The contrasting chemical reactivity of potent isoelectronic iminopyridine and azopyridine osmium(ii) arene anticancer complexes

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Borinium Cations as σ-B−H Ligands in Osmium Complexes

Cited by 40 publications

References 44 publications

Hydridoborylene Complexes and Di‐, Tri‐, and Tetranuclear Borido Complexes with Hydride Ligands

Hydridoborylene Complexes and Di‐, Tri‐, and Tetranuclear Borido Complexes with Hydride Ligands

[Ir(PCy3)2(H)2(H2BNMe2)]+ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H3B⋅NMe2H and Retrodimerisation of [H2BNMe2]2

The contrasting chemical reactivity of potent isoelectronic iminopyridine and azopyridine osmium(ii) arene anticancer complexes

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[Ir(PCy₃)₂(H)₂(H₂BNMe₂)]⁺ as a Latent Source of Aminoborane: Probing the Role of Metal in the Dehydrocoupling of H₃B⋅NMe₂H and Retrodimerisation of [H₂BNMe₂]₂