Bulky Polyfluorinated Terphenyldiphenylboranes: Water Tolerant Lewis Acids

Protocols for the synthesis of the bulky polyfluorinated triarylboranes 2,6-(C₆F₅)₂C₆F₃B(C₆F₅)₂ ( 1 ), 2,6-(C₆F₅)₂C₆F₃B[3,5-(CF₃)₂C₆H₃] ( 2 ), 2,4,6-(C₆F₅)₃C₆H₂B(C₆F₅)₂ ( 3 ), 2,4,6-(C₆F₅)₃C₆H₂B[3,5-(CF₃)₂C₆H₃] ( 4 ) were developed. All boranes are water tolerant and according to the Gutmann-Beckett method, 1 – 3 display Lewis acidities larger than that of the prominent B(C₆F₅)₃.     

Crystal structures and thermal behavior of complexes of group 13 metal halides with pyridine-type ligands

Complexes of group 13 metal halides with pyridine-type ligands (pyridine, pyrazine, and 4, 4´-bipyridine) have molecular, polymeric, or ionic structures containing metal atoms with a coordination number of 4, 5, or 6 depending on the component ratio, the acceptor ability of the halide, the donor ability and the coordination mode of the ligand. The strongest donor-acceptor bond is formed in the 1 : 1 molecular complexes, and their transition to the gas phase is energetically most favorable. The acceptor ability of Lewis acids in the complexes decreases in the series AlCl₃ > AlBr₃ > GaCl₃ > GaBr₃ > GaI₃. The stability of the complexes with respect to homogeneous dissociation correlates with the donor proton affinity. Group 13 metal trihalides act as catalysts for the pyrolysis of ligands.     

Complexes of borazine and its analogs with Lewis acids and bases

The author’s review summarizes the results of B3LYP/TZVP quantum chemical calculations of complexes of borazine, substituted borazines, polyborazines, alumazine, and boraphosphabenzene with Lewis acids and bases. The effects of the nature of the heterocycle, substituents, and the donor and acceptor properties of the molecules on the thermodynamic characteristics of complex formation are considered. The reactivity of the complexes of heterocycles in hydrogenation and electrophilic substitution reactions was studied.     

Reaction of Tungsten–Phosphinidene and –Arsinidene Complexes with Carbodiimides and Alkyl Azides: A Straightforward Way to Four‐Membered Heterocycles

The reaction of the phosphinidene and arsinidene complexes [Cp*E{W(CO)₅}₂] (E=P ( 1 a ), As ( 1 b ); Cp*=C₅Me₅) with carbodiimides leads to the new four‐membered heterocycles of the type [Cp*C(NR)₂E{W(CO)₅}₂] (E=P: R=iPr ( 2 a ), Cy ( 3 a ); E=As: R=iPr ( 2 b ), Cy ( 3 b )). The reaction of phosphinidene complex 1 a with alkyl azides yields the triazaphosphete derivatives [Cp*P{W(CO)₅}N(R)NN{W(CO)₅}] (R=Hex, Cy) ( 4 ). These unprecedented N₃P four‐membered triazaphosphete complexes can be regarded as stabilized intermediates of the Staudinger reaction, which have not been previously isolated. All of the isolated products were characterized by NMR, IR spectroscopy, mass spectrometry, and by single‐crystal X‐ray diffraction analysis.     

Isolation and Characterization of Lewis Base Stabilized Monomeric Parent Stibanylboranes

The synthesis of the Lewis base stabilized monomeric parent compound of stibanylboranes, “H₂Sb? BH₂”, is reported. Through a salt metathesis route, the silyl‐substituted compounds (Me₃Si)₂Sb? BH₂?LB (LB=NMe₃, NHC^Me) were synthesized as representatives of derivatives with a Sb? B σ bond. Under very mild conditions, they could be transformed into the target compounds Me₃N?H₂B? HSb? BH₂?NMe₃ and H₂Sb? BH₂?NHC^Me, respectively. The products were characterized by X‐ray structure analysis, NMR spectroscopy, IR spectroscopy, and mass spectrometry. DFT calculations give further insight into the stability and bonding of these unique compounds.     

Fast H/D exchange of B,B',B'-tribromoborazine in C6D6 in the presence of aluminum tribromide: first evidence for an electrophilic substitution reaction of borazines in solution

A solution of B,B',B'-tribromoborazine (BrBNH)(3) in excess C(6)D(6) in a sealed NMR tube shows no changes for over 14 months at room temperature but undergoes fast (within minutes) H/D exchange in the presence of AlBr(3) as a Lewis acid, as evidenced by (1)H, (2)H, (11)B, and (27)Al NMR spectroscopy. The proposed electrophilic exchange mechanism is in agreement with the results of DFT computations. To our knowledge, this is the first example of the electrophilic substitution reaction of borazines in solution.     

Calculations of microconstants and equilibrium formation constants for platinum(II) and palladium(II) halide complexes in solution

Distribution diagrams and formation functions for halide complexes [M(H₂O)_{4 ? n} Cl _n ]^{2 ? n} (M = Pt(II) or Pd(II)) and [PdCl_{4 ? n} Br _n ]^2? (n = 0?C4) in solution are analyzed in terms of the matrix model. Equilibrium constants for binding the first ligand $\left( {\bar K} \right)$ and corrections for the mutual influence between ligands (??) in the course of complex formation in solution are calculated. In examples analyzed, the substitution of chloride ion for water in the coordination sphere of platinum(II) and palladium(II) is an anti-cooperative process. The substitution of bromide ion for chloride ion in the coordination sphere of [PdCl₄]^2? is weakly cooperative. Quantum-chemical calculations show that platinum(II) and palladium(II) cis-bisaquadichloro complexes in the gas phase are thermodynamically less stable than trans-isomers. The cis-trans isomerization constants in the gas phase calculated by the DFT method and those found for solutions using the matrix model have the same order of magnitude.