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Reaction of [(IPr)Cu-OtBu] (1) with pinB-SiMe2Ph (2) leads to the Cu-silyl complex [(IPr)Cu-SiMe2Ph] (3). Insertion of CO2 into the Cu-Si bond of 3 is followed by transformation of the resulting silanecarboxy complex [(IPr)Cu-O2CSiMe2Ph] (4) to the silanolate complex [(IPr)Cu-OSiMe2Ph] (5) via extrusion of CO. As 5 reacts readily with 2 to regenerate 3, a catalytic CO2 reduction to CO is feasible. The individual steps were studied by in situ13C NMR spectroscopy of a series of stoichiometric reactions. Complexes 3, 4, and 5 were isolated and fully characterized, including single-crystal X-ray diffraction studies. Interestingly, the catalytic reduction of CO2 using silylborane 2 as a stoichiometric reducing agent leads not only to CO and pinB-O-SiMe2Ph but also to PhMe2Si-CO2-SiMe2Ph as an additional reduction product. [ABSTRACT FROM AUTHOR]

Reactions of the lithium boryl LiB(R′NCHCHNR′) (R′ = 2,6-iPr2C6H3), 1, with organohalides (RX) giving RB(R′NCHCHNR′) and/or XB(R′NCHCHNR′) were studied computationally using density functional theory calculations at the B3LYP level. Our calculations indicate that the boryl anion in the lithium boryl can undergo nucleophilic attack at an organohalide on the halide-bonded carbon atom and/or the halogen atom to form RB(MeNCHCHNMe) (an expected SN2 substitution product) and/or XB(MeNCHCHNMe) (a halogen-abstraction product), respectively. Our energetic calculation results show that an organohalide having a halogen with lower electronegativity and higher ability to engage in hypervalent bonding promotes the halogen-abstraction pathway. Benzyl halides were also found to promote the halogen-abstraction pathway due to conjugation effects that stabilize a benzyl anion in the transition state during the halogen-abstraction process. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented which urges the government to offer incentives to attract dentists to practice in the underserved states and municipalities.