The unique β-diketiminate ligand in aluminum(i) and gallium(i) chemistry

Herein we present an overview of the last 10 years for aluminum(i) and gallium(i) stabilized by β-diketiminate ligands that undergo a series of oxidative addition reactions with molecules containing single and multiple bonds.

The synthesis of cyclometalated platinum(II) complexes with benzoaryl-pyridines as C^N ligands for investigating their photophysical, electrochemical and electroluminescent properties

A series of (C^N)Pt(acac)-type complexes has been successfully synthesized with a benzo[b]furan, benzo[b]thiophene, benzo[b]selenophene, or benzo[b]tellurophene group in the benzoaryl-pyridine ligand. Using X-ray crystallography, the chemical structures of the complexes with benzo[b]selenophene and benzo[b]tellurophene groups have been clearly revealed. The photophysical, electrochemical, and electroluminescent (EL) behaviors of these (C^N)Pt(acac)-type complexes have been fully characterized. Furthermore, both time-dependent functional theory (TD-DFT) and natural transition orbital (NTO) theoretical results have been obtained to gain insight into the absorption and emission features. It has been shown that both the absorption bands with the lowest energy and the phosphorescence emission behaviors are dominated by the benzoaryl-pyridine cyclometalating ligand. Importantly, the effects of the group VIA atoms on the properties of these (C^N)Pt(acac)-type complexes have been revealed. Owing to the rareness of (C^N)Pt(acac)-type complexes with benzo[b]selenophene and benzo[b]tellurophene groups, their EL abilities have been characterized using solution-processed organic light-emitting diodes (OLEDs). The optimized red OLEDs with the complex bearing a benzo[b]selenophene unit show a maximum external quantum efficiency (ηext) of 6.3%, current efficiency (ηL) of 10.5 cd A-1, and power efficiency (ηP) of 9.1 lm W-1, while the EL device with the complex bearing a benzo[b]tellurophene unit can give deep-red emission at ca. 636 nm with ηext of 6.3%, ηL of 6.5 cd A-1, and ηP of 5.8 lm W-1. This research not only provides novel (C^N)Pt(acac)-type complexes, but also furnishes critical information regarding the photophysical and EL behavior of these new complexes.

Facile oxidative addition of O2 and S8 by an indium bis(carbene) analogue

The oxidative addition of oxygen towards an indium bis(carbenoid) yields an almost planar In₄O₂ ring, an isovalence-electronic analogue of dioxane, in which the indium is in the formal oxidation state +ii. The weaker oxidant sulfur, however, yields an eight-membered ring in a deck-chair conformation containing four indium(iii) centres and four sulfides in an alternating fashion. According to DFT calculations, this reactivity difference originates from kinetic rather than thermodynamic reasons. When the reaction with S₈ is performed with the in situ generated bis(carbenoid), a β-diketimine (NacNac) incorporating an S₄-chain bridging the two γ-carbon atoms of each NacNac unit is derived.

7-Metalla-1,4-diphosphanorbornadienes: cycloaddition of monovalent group 13 NacNac complexes to a stable 1,4-diphosphinine

Monovalent group 13 NacNac complexes reacted as dienophiles with a tricyclic 1,4-diphosphinine to furnish first examples of 7-metalla-1,4-diphosphanorbornadienes via reversible [4 + 1]-cycloaddition reactions.

Cycloaddition versus Cleavage of the C=S Bond of Isothiocyanates Promoted by Digallane Compounds with Noninnocent α-Diimine Ligands

Whereas the chemistry of single-bond activation by compounds of the main group elements has undergone some development in recent years, the cleavage of multiple bonds remains underexplored. Herein, the reactions of two digallanes bearing α-diimine ligands, namely, [L¹ Ga-GaL¹ ] (1, L¹ =dpp-dad=[(2,6-iPr₂ C₆ H₃ )NC(CH₃ )]₂ ) and [L² Ga-GaL² ] (2, L² =dpp-bian=1,2-[(2,6-iPr₂ C₆ H₃ )NC]₂ C₁₀ H₆ ), with isothiocyanates are reported. Reactions of 1 or 2 with isothiocyanates in 1:2 molar ratio proceeded with [2+4] cycloaddition of the C=S bond across the C₂ N₂ Ga metallacycle with formation of C-C and S-Ga single bonds to afford [L¹ (RN=C-S)Ga-Ga(S-C=NR)L¹ ] (3, R=Me; 4, R=Ph) and [L² (RN=C-S)Ga-Ga(S-C=NR)L² ] (8, R=allyl; 9, R=Ph). In the cases of 8 and 9, this cycloaddition is reversible. The digallanes reacted with 2 equiv of PhNCS in the presence of Na metal or at high temperatures through a unique reductive cleavage of the C=S bond to yield the disulfide-bridged digallium species [Na(THF)₃ ]₂ [L¹ Ga(μ-S)₂ GaL¹ ] (5), [L² Ga(μ-S)₂ GaL² ] (10), and [Na(DME)₃ ][L² Ga(μ-S)₂ GaL² ] (11). Moreover, products 4 and 5 can further react with an excess of isothiocyanate, through cleavage of the C=S bond or cycloaddition, to give the bis- or mono-S-bridged complexes [Na(THF)₂ ]₂ [L¹ (PhN=C-S)Ga(μ-S)₂ Ga(S-C=NPh)L¹ ] (6) and [L¹ (PhN=C-S)Ga(μ-S)Ga(S-C=NPh)L¹ ] (7). All the newly prepared compounds were characterized by elemental analysis, single-crystal X-ray diffraction, IR spectroscopy, NMR (3-9) or ESR spectroscopy (11), and DFT calculations.

Lewis acid–base adducts of group 13 elements: synthesis, structure and reactivity toward benzaldehyde

[LGa-M(C₆F₅)₃] (M = B 1, Al 2, Ga 3) reacts with benzaldehyde in different ways including the formation of the zwitterionic species [LGa(C₆F₅){CH(Ph)(OAl(C₆F₅)₂)}] (5).

A Gallium-Substituted Distibene and an Antimony-Analogue Bicyclo[1.1.0]butane: Synthesis and Solid-State Structures

RGa {R=HC[C(Me)N(2,6-iPr2C6H3)]2} reacts with Sb(NMe2)3 with insertion into the Sb-N bond and elimination of RGa(NMe2)2 (2), yielding the Ga-substituted distibene R(Me2N)GaSb=SbGa(NMe2 )R (1). Thermolysis of 1 proceeded with elimination of RGa and 2 and subsequent formation of the bicyclo[1.1.0]butane analogue [R(Me2N)Ga]2Sb4 (3).