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A combination of experimental and theoretical studies on the synthesis, structures, and reactivity of two rhodium boryl complexes that are likely intermediates in the catalytic borylation of alkanes are described. The results show that the C-H bond cleavage process occurs by a metal-assisted O-bond metathesis mechanism that generates a borane complex that isomerizes if needed to place the alkyl group cis to the boryl group.

The asymmetric synthesis of axially chiral 2-arylpyridines by a cobalt-catalyzed [2+2+2] cycloadition reaction is presented. The utility of planar chiral (1-neomenthylindenyl)cobalt (CAD) complex under photochemical conditions is very important for reacting the 1-naphthyldiynes with a range of differently functionalized nitriles, providing the enantiomeric atropoisomers with high chemical yields.

The functionalization of primary C-H bonds in alkanes is examined with one of the well-defined systems that have reacted under photochemical conditions by using both density functional theory calculations and pico- through microsecond time-resolved IR spectroscopy. The studies have shown that the cis-Cp*W[(CO).sub.2](Bpin)(pentane) complex has undergone C-H bond activation by a [sigma]-bond metathesis mechanism.

The robust CoI precatalyst [CpCo(P{OEt}3)(trans‐MeO2CHC=CHCO2Me)] was investigated in cyclotrimerizations, furnishing benzenes and pyridines from triynes, diynes and nitriles, comparing the influence of different ways of energy supply; namely, irradiation and conventional (thermal) or microwave heating. The precatalyst was found to work under all conditions, including the possibility to catalyze cyclotrimerizations at room temperature under photochemical conditions at longer reaction times. Performance of the reactions in a microwave reactor proved to be the most time‐efficient way to rapidly assemble the expected reaction products; however, careful selection of reaction conditions can be required. The synthesis of pyridines and isoquinolines successfully involved the utilization of versatile functionalized nitriles, affording structurally interesting reaction products. Comparison with the known and often applied precatalyst CpCo(CO)2 demonstrated the significantly higher reactivity of the CpCoI–phosphite–olefin precatalyst. [ABSTRACT FROM AUTHOR]

We report a detailed study concerning the efficient generation of highly active chiral rhodium complexes of the general structure [Rh(diphosphine)(solvent)2]+ as well as their exemplary successful utilization as catalysts for cyclotrimerizations. Such solvent complexes could likewise be prepared from novel ammonia complexes of the type [Rh(diphosphine)(NH3)2]+. A valuable, feasible approach to generate novel chiral RhI complexes was found by in situ generation from Wilkinson's catalyst [RhCl(PPh3)3] with chiral P,N ligands. The generated catalysts led to moderate to good enantioselectivities and excellent yields in the cyclotrimerizations of triynes, showcasing their usefulness in the synthesis of axially chiral benzene derivatives. [ABSTRACT FROM AUTHOR]