Metal-induced B-H bond activation: reactions between half-sandwich Ir and Rh complexes with carboranylthioamide

Synthesis of Bis(Carboranyl)amides 1,1'-μ-(CH2NH(O)C(CH2)n-1,2-C2B10H11)2 (n = 0, 1) and Attempt of Synthesis of Gadolinium Bis(Dicarbollide)

Bis(carboranyl)amides 1,1'-μ-(CH2NH(O)C(CH2)n-1,2-C2B10H11)2 (n = 0, 1) were prepared by the reactions of the corresponding carboranyl acyl chlorides with ethylenediamine. Crystal molecular structure of 1,1'-μ-(CH2NH(O)C-1,2-C2B10H11)2 was determined by single crystal X-ray diffraction. Treatment of bis(carboranyl)amides 1,1'-μ-(CH2NH(O)C(CH2)n-1,2-C2B10H11)2 with ammonium or cesium fluoride results in partial deboronation of the ortho-carborane cages to the nido-carborane ones with formation of [7,7'(8')-μ-(CH2NH(O)C(CH2)n-7,8-C2B9H11)2]2-. The attempted reaction of [7,7'(8')-μ-(CH2NH(O)CCH2-7,8-C2B9H11)2]2- with GdCl3 in 1,2-dimethoxy- ethane did not give the expected metallacarborane. The stability of different conformations of Gd-containing metallacarboranes has been estimated by quantum-chemical calculations using [3,3-μ-DME-3,3'-Gd(1,2-C2B9H11)2]- as a model. It was found that in the most stable conformation the CH groups of the dicarbollide ligands are in anti,anti-orientation with respect to the DME ligand, while any rotation of the dicarbollide ligand reduces the stability of the system. This makes it possible to rationalize the design of carborane ligands for the synthesis of gadolinium metallacarboranes on their base.

Regioselective B(3)-H bond activation based on an o-carboranyl dithiocarboxylate ligand and its derivatives

Herein, we describe the synthesis of tetraphenylphosphonium o-carboranyl dithiocarboxylate (Ligand 1) and methyldithiocarboxyl-o-carborane (Ligand 2). The complexes [Cp*M(o-C₂B₁₀H₁₁CS₂)Cl] (M = Ir (3); Rh (4)) and [Cp*M(o-C₂B₁₀H₁₁CS₂)₂] (M = Ir (5); Rh (6)) have been synthesized based on Ligand 1. The selective B-H bond activation of Ligand 2 has also been explored, leading to the synthesis of the B-H activated complex [Cp*Ir(o-C₂B₁₀H₁₀CS₂CH₃)Cl] (7) and four of its substituted derivatives (8, 9, 10 and 11). All of these compounds have been characterised through single-crystal X-ray diffraction, NMR, IR spectroscopy and elemental analysis.

Iridium-induced regioselective B–H and C–H activations at azo-substitutedm-carboranes: facile access to polynuclear complexes

Iridium-induced selective C–H and B(2,3)–H bond activations have been achieved atm-carboranes featuring azobenzene directing groups. A series of mononuclear, dinuclear and trinuclear complexes have been obtained.

Regioselective B-H/C-H activation and metal-metal bond formation induced by half-sandwich metals complexes at hydroxy-substituted o-carboranes

A binuclear iridium complex, (Cp2*Ir2(CH2O)C2B10H8) (6), with a unique metal-metal bond has been synthesized and fully characterized. Importantly, this complex is constructed via selective C-H and B(3)-H bond activation on the carborane precursor. Additionally, when the proligand (2-pyridine)(o-carboranyl)methanol ligand was combined with a half-sandwich iridium complex, selective B(6)-H bond activation or metal-carbon bond formation can be induced by the use of different bases. And the rhodium complex constructed from (2-pyridine)(o-carboranyl)methanol ligand containing a metal-carbon bond has been obtained and fully characterized.

Triazole vs. triazolium carbene ligands in the site-selective cyclometallation of o-carboranes by M(iii) (M = Ir, Rh) complexes

M(iii)-mediated (M = Ir, Rh) site-selective cage B–H and C–H bond activation in o-carboranylmethyl derivatives has been achieved by switching the electron donating properties of the 1,2,3-triazole ligand.

The synthesis and reactivity of 16-electron half-sandwich iridium complexes bearing a carboranylthioamide ligand

The 16-electron complex 2 has been synthesized. It can react with different donor ligands and undergoes M–S bond insertion reactions with DMAD. Complex 2 is shown to react with [Cp*Ir] unit to form a M–M-bound binuclear complex. Interestingly, the metal–metal bond could be broken by HCl to produce the selective B(6)–H activation species.

B–H functionalization of the monocarba-closo-dodecaborate anion by rhodium and iridium catalysis

The regioselective derivatization of the monocarba-closo-dodecaborate anion via catalytic B–H bond activation is reported.

Efficient synthesis of carborane azo derivatives and their reactivity

An iridium(iii)-catalyzed C–N-bond-forming direct synthesis of carborane azo derivatives was developed.

Luminescent Metal Complexes Featuring Photophysically Innocent Boron Cluster Ligands

We report the synthesis and characterization of a series of d8 metal complexes featuring robust and photophysically innocent strong-field chelating 1,1'-bis(o-carborane) (bc) ligand frameworks. A combination of UV-Vis spectroscopy, single crystal X-ray structural analysis, and DFT calculations of these species suggest that the dianionic bc ligand does not contribute to any visible metal-to-ligand charge transfer (MLCT) transitions, yet it provides a strong ligand field in these complexes. Furthermore, a bc-based Pt(II) complex containing a 4,4'-di-tert-butyl-2,2'-bipyridine ligand (dtb-bpy) has been prepared and was found to display blue phosphorescent emission dominated by MLCT from the Pt(II) center to the dtb-bpy ligand. Importantly, the bulky three-dimensional nature of the bc ligand precludes intermolecular Pt(II)⋯Pt(II) interactions in the solid state where the resulting compounds retain their emission properties. This study opens a potentially new avenue for designing organic light-emitting diode (OLED) materials with tunable properties featuring photophysically innocent boron-rich cluster ligands.