Cationic magnesium hydride [MgH]+ stabilized by an NNNN-type macrocycle

A magnesium hydride cation [(L)MgH]⁺ supported by a macrocyclic ligand (L = Me₄TACD; 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) has been shown to react with Lewis acids as well as with unsaturated substrates including pyridine.

Highly Active Dinuclear Titanium(IV) Complexes for the Catalytic Formation of a Carbon-Heteroatom Bond

A series of mononuclear titanium(IV) complexes with the general composition κ³-[R{NHPh₂P(X)}₂Ti(NMe₂)₂] [R = C₆H₄, X = Se (3b); R = trans-C₆H₁₀, X = S (4a), Se (4b)] and [{κ²-N(PPh₂Se)₂}₂Ti(NMe₂)₂] (6b) and two dinuclear titanium(IV) complexes, [C₆H₄{(NPh₂PS)(N)}Ti(NMe₂)]₂ (3c) and [{κ²-N(PPh₂Se)}Ti(NMe₂)₂]₂ (6c), are reported. Dinuclear titanium(IV) complex 6c acts as an efficient catalyst for the chemoselective addition of an E-H bond (E = N, O, S, P, C) to heterocumulenes under mild conditions. The catalytic addition of aliphatic and aromatic amines, alcohol, thiol, phosphine oxide, and acetylene to the carbodiimides afforded the corresponding hydroelemented products in high yield at mild conditions with a broader substrate scope. The catalytic efficiency of the dinuclear complex depends on the cooperative effect of the Ti^IV ions, the systematic variation of the intermetallic distance, and the ligand's steric properties of the complex, which enhances the reaction rate. Most interestingly, this is the first example of catalytic insertion of various E-H bonds into the carbodiimides using a single-site catalyst because only the titanium-mediated insertion of E-H into a C═N unsaturated bond is reported to date. The amine and alcohol insertion reaction with the carbodiimides showed first-order kinetics with respect to the titanium(IV) catalyst as well as substrates. A most plausible mechanism for hydroelementation reaction is also proposed, based on the spectroscopic data of the controlled reaction, a time-course study, and the Hammett plot.

Carbodiimides as catalysts for the reduction of CO2 with boranes

Carbodiimides catalyse the reduction of CO2 with H-BBN or BH3·SMe2 to give either mixtures of CH2(OBBN)2 and CH3OBBN or (MeOBO)3 and B(OMe)3 under mild conditions (25-60 °C, 1 atm CO2). Stoichiometric reactions and theoretical calculations were performed to unveil the mechanism of these catalytic processes.

Hydroboration of alkynes and nitriles using an α-diimine cobalt hydride catalyst

Addition of NaEt₃BH to (^Ph2PPrDI)CoCl₂ affords the corresponding monohydride, (^Ph2PPrDI)CoH. X-ray diffraction and DFT calculations indicate that this compound possesses a radical monoanion α-DI chelate and a Co(ii) centre. Notably, (^Ph2PPrDI)CoH catalyzes the hydroboration of alkynes and dihydroboration of nitriles under mild conditions.

Carbodiimides as catalysts for the reduction of a cadmium hydride complex

A rare terminal cadmium hydride complex has been synthesised. Reduction to the cadmium(i) dimer complex was achieved upon treatment with carbodiimides.

Magnesium Boryl Reactivity with 9-BBN and Ph3 B: Rational B-B' Bond Formation and Diborane Isomerization

Reactions of a magnesium‐based pinacolatoboryl nucleophile with the electrophilic organoboranes, 9‐BBN and Ph₃B, provide facile B−B′ single bond formation. Although the Ph₃B derivative is thermally stable, when heated, the unsymmetrical diborane(5) anion derived from 9‐BBN is found to isomerize to two regioisomeric species via a proposed mechanism involving dehydroboration of the borabicyclo[3.3.1]nonane and syn‐diboration of the resultant alkenyl carbocycle.

Synthesis, Structure, and Reactivity of a Terminal Magnesium Hydride Compound with a Carbatrane Motif, [TismPriBenz]MgH: A Multifunctional Catalyst for Hydrosilylation and Hydroboration

The tris[(1-isopropylbenzimidazol-2-yl)dimethylsilyl)]methyl ligand, [Tism^PriBenz], has been employed to form the magnesium carbatrane compound, [Tism^PriBenz]MgH, which possesses a terminal hydride ligand. Specifically, [Tism^PriBenz]MgH is obtained via the reaction of [Tism^PriBenz]MgMe with PhSiH₃. The reactivity of [Tism^PriBenz]MgMe and [Tism^PriBenz]MgH allows access to a variety of other structurally characterized carbatrane derivatives, including [Tism^PriBenz]MgX [X = F, Cl, Br, I, SH, N(H)Ph, CH(Me)Ph, O₂CMe, S₂CMe]. In addition, [Tism^PriBenz]MgH is a catalyst for (i) hydrosilylation and hydroboration of styrene to afford the Markovnikov products, Ph(Me)C(H)SiH₂Ph and Ph(Me)C(H)Bpin, and (ii) hydroboration of carbodiimides and pyridine to form N-boryl formamidines and N-boryl 1,4- and 1,2-dihydropyridines, respectively.

Tris(2,4,6-trifluorophenyl)borane: An Efficient Hydroboration Catalyst

The metal-free catalyst tris(2,4,6-trifluorophenyl)borane has demonstrated its extensive applications in the 1,2-hydroboration of numerous unsaturated reagents, namely alkynes, aldehydes and imines, consisting of a wide array of electron-withdrawing and donating functionalities. A range of over 50 borylated products are reported, with many reactions proceeding with low catalyst loading under ambient conditions. These pinacol boronate esters, in the case of aldehydes and imines, can be readily hydrolyzed to leave the respective alcohol and amine, whereas alkynyl substrates result in vinyl boranes. This is of great synthetic use to the organic chemist.

Hydrodeoxygenation of isocyanates: snapshots of a magnesium-mediated C[double bond, length as m-dash]O bond cleavage

Organic isocyanates are readily converted to methyl amine products through their hydroboration with HBpin in the presence of a β-diketiminato magnesium catalyst.

Organic isocyanates are readily converted to methyl amine products through their hydroboration with HBpin in the presence of a β-diketiminato magnesium catalyst. Although borylated amide and N-,O-bis(boryl)hemiaminal species have been identified as intermediates during the reductive catalysis, the overall reduction and C–O activation is metal-mediated and proposed to occur through the further intermediacy of well-defined magnesium formamidato, formamidatoborate and magnesium boryloxide derivatives. Examples of all these species have been identified and fully characterised through stoichiometric reactivity studies and the stability of the borate species leads us to suggest that, under catalytic conditions, the onward progress of the deoxygenation reaction is crucially dependent on the further activation provided by the Lewis acidic HBpin substrate. These deductions have been explored and ratified through a DFT study.

Sterically bulky amido magnesium methyl complexes: syntheses, structures and catalysis

The synthesis, crystal structure and catalysis of a series of sterically bulky amidomagnesium methyl complexes are described.

The phosphinoboration of carbodiimides, isocyanates, isothiocyanates and CO2

The transition metal-free addition of phosphinoboronate ester Ph₂PBpin (pin = 1,2-O₂C₂Me₄) to heterocumulenes including carbodiimides, isocyanates, isothiocyanates and carbon dioxide proceeds with remarkable selectivity to give products in high yield.

Magnesium hydridotriphenylborate [Mg(thf)6][HBPh3]2: a versatile hydroboration catalyst

Magnesium bis(hydridotriphenylborate), isolated as a solvent-separated ion pair [Mg(thf)₆][HBPh₃]₂, effectively catalyzed the hydroboration of several unsaturated substrates including CO₂.