Multifaceted behavior of a doubly reduced arylborane in B-H-bond activation and hydroboration catalysis

Unique Double and Triple Decker Arrangements of Rare-Earth 9,10-Diborataanthracene Complexes Featuring Single-Molecule Magnet Characteristics

Herein, we present the first report on the synthesis of rare-earth complexes featuring a 9,10-diborataanthracene ligand. This 14-π-electron ligand is highly reductive and was previously used in small-molecule activation. Salt elimination reactions between dipotassium 9,10-diethyl-9,10-diborataanthracene [K2(DEDBA)] and [LnIII(η8-CotTIPS)(BH4)(thf)x] (CotTIPS=1,4-(iPr3Si)2C8H6) in a 1 : 1 ratio yielded heteroleptic sandwich complexes [K(η8-CotTIPS)LnIII(η6-DEDBA)] (Ln=Y, Dy, Er). These compounds form Lewis-base-free one-dimensional coordination polymers when crystallised from toluene. In contrast, reaction of [K2(DEDBA)] and [LnIII(η8-CotTIPS)(BH4)(thf)x] in a 1 : 2 ratio led to the formation of heteroleptic triple-decker complexes [(η8-CotTIPS)LnIII(μ-η6:η6-DEDBA)LnIII(η8-CotTIPS)] (Ln=Y, Dy, Er). Notably, these are not only the first lanthanide triple-decker compounds featuring a six-membered ring as a deck but also the first trivalent lanthanide triple-decker featuring a heterocycle in the coordination sphere. Magnetic investigations reveal that [K(η8-CotTIPS)LnIII(η6-DEDBA)] (Ln=Dy, Er) and [(η8-CotTIPS)ErIII(μ-η6:η6-DEDBA)ErIII(η8-CotTIPS)] exhibit Single-Molecule Magnet (SMM) behaviour. In the case of [(η8-CotTIPS)LnIII(μ-η6:η6-DEDBA)LnIII(η8-CotTIPS)] (Ln=Dy, Er), the introduction of a second near lanthanide ion results in strong antiferromagnetic interactions, allowing the enhancement of the magnetic characteristic of the system, compared to the quasi isolated counterpart. This research renews the overlooked coordination chemistry of the DBA ligand and expands it to encompass rare-earth elements.

Juggling Optoelectronics and Catalysis: The Dual Talents of Bench Stable 1,4-Azaborinines

Boron- and nitrogen-doped polycyclic aromatic hydrocarbons (B-PAHs) have established a strong foothold in the realm of organic electronics. However, their catalytic potential remains largely untapped. In this study, we synthesise and characterise two bench stable B,N-doped PAH derivatives based on a 1,4-azaborinine motif. Most importantly, the anthracene derived structure is an efficient catalyst in the reduction of various carbonyls and imines. These results underscore the potential of B,N-PAHs in catalytic transformations, setting the stage for deeper exploration in this chemical space.

Carbodiimide and Isocyanate Hydroboration by a Cyclic Carbodiphosphorane Catalyst

We report hydroboration of carbodiimide and isocyanate substrates catalyzed by a cyclic carbodiphosphorane catalyst. The cyclic carbodiphosphorane outperformed the other Lewis basic carbon species tested, including other zerovalent carbon compounds, phosphorus ylides, an N-heterocyclic carbene, and an N-heterocyclic olefin. Hydroborations of seven carbodiimides and nine isocyanates were performed at room temperature to form N-boryl formamidine and N-boryl formamide products. Intermolecular competition experiments demonstrated the selective hydroboration of alkyl isocyanates over carbodiimide and ketone substrates. DFT calculations support a proposed mechanism involving activation of pinacolborane by the carbodiphosphorane catalyst, followed by hydride transfer and B-N bond formation.

Vicinal Vinylation of Boron-Doped Acenes via Heck Coupling

Silylated and halogenated benzenes 1,2-(Me3Si)2-4,5-X2-C6H2 [X = Br (3), I (4)] are versatile synthetic building blocks. 3 was prepared from known 1,2-(Me3Si)2-4,5-Cl2-C6H2 via C-Cl borylation/bromodeboronation; CuI-catalyzed Br/I exchange on 3 affords 4. 3 or 4 and BBr3 yield 9,10-dibromo-9,10-dihydro-9,10-diboraanthracenes (DBAs) 7 or 8. The B centers were protected with mesityl (Mes; 9, 10) or 2,4,6-tris(trifluoromethyl)phenyl (FMes; 11, 12) groups. Heck coupling of 9 and styrene/2,3,4,5,6-pentafluorostyrene furnishes the two tetravinyl-substituted green/blue emitters 13/14.

Synthesis, bridgehead functionalization, and photoisomerization of 9,10-diboratatriptycene dianions

9,10-Diboratatriptycene salts M2[RB(μ-C6H4)3BR] (R = H, Me; M+ = Li+, K+, [n-Bu4N]+) have been synthesized via [4 + 2] cycloaddition between doubly reduced 9,10-dihydro-9,10-diboraanthracenes M2[DBA] and benzyne, generated in situ from C6H5F and C6H5Li or LiN(i-Pr)2. [HB(μ-C6H4)3BH]2- reacts with CH2Cl2 to form quantitatively the bridgehead-derivatized [ClB(μ-C6H4)3BCl]2-, while twofold H- abstraction with B(C6F5)3 in the presence of SMe2 leads cleanly to the diadduct (Me2S)B(μ-C6H4)3B(SMe2). Photoisomerization of K2[HB(μ-C6H4)3BH] (THF, medium-pressure Hg lamp) provides facile access to diborabenzo[a]fluoranthenes, a little explored form of boron-doped polycyclic aromatic hydrocarbons. According to DFT calculations, the underlying reaction mechanism consists of three main steps: (i) photoinduced di-π-borate rearrangement, (ii) "walk reaction" of a BH unit, and (iii) boryl anion-like C-H activation.