NN Bond Cleavage by a Low-Coordinate Iron(II) Hydride Complex

Switchable catalysis offers opportunities to control the rate or selectivity of a reaction via a stimulus such as pH or light. However, few examples of switchable catalytic systems that can facilitate multiple processes exist. Here we report a rare example of such dual-functional, switchable catalysis. Featuring an easily prepared, bench-stable cobalt(I) hydride complex in conjunction with pinacolborane, we can completely alter the reaction outcome between two widely employed transformations – olefin migration and hydroboration – with visible light as the sole trigger. This dichotomy arises from ligand photodissociation which leads to metamorphosis of the active catalytic site, resulting in divergent mechanistic pathways.

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Metal-Metal Cooperative Bond Activation by Heterobimetallic Alkyl, Aryl, and Acetylide PtII/CuI Complexes

10.26434/chemrxiv.11742687 ◽

2020 ◽

Author(s):

Shubham Deolka ◽

Orestes Rivada Wheelaghan ◽

Sandra Aristizábal ◽

Robert Fayzullin ◽

Shrinwantu Pal ◽

...

Keyword(s):

Alkyl Group ◽

Bond Activation ◽

Bond Cleavage ◽

Terminal Alkyne ◽

Alkyl Aryl ◽

Metal Metal ◽

The Stability ◽

Selective Formation ◽

Organoplatinum Compounds

We report selective formation of heterobimetallic PtII/CuI complexes that demonstrate how facile bond activation processes can be achieved by altering reactivity of common organoplatinum compounds through their interaction with another metal center. The interaction of the Cu center with Pt center and with a Pt-bound alkyl group increases the stability of PtMe2 towards undesired rollover cyclometalation. The presence of the CuI center also enables facile transmetalation from electron-deficient tetraarylborate [B(ArF)4]- anion and mild C-H bond cleavage of a terminal alkyne, which was not observed in the absence of an electrophilic Cu center. The DFT study indicates that the role of Cu center acts as a binding site for alkyne substrate, while activating its terminal C-H bond.

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Room Temperature Alkali Metal Reduction of Carbon Dioxide

10.26434/chemrxiv.12665336 ◽

2020 ◽

Author(s):

Lucas A. Freeman ◽

Akachukwu D. Obi ◽

Haleigh R. Machost ◽

Andrew Molino ◽

Asa W. Nichols ◽

...

Keyword(s):

Alkali Metal ◽

Alkali Metals ◽

Room Temperature ◽

Chemical Reduction ◽

Bond Cleavage ◽

Open Shell ◽

Metal Reduction ◽

One Pot ◽

Earth Abundant ◽

Electron Reduction

The reduction of the relatively inert carbon–oxygen bonds of CO2 to access useful CO2-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Facilitating this bond-cleavage using earth-abundant, non-toxic main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere interactions between CO2 and the MGE. Herein we report the first successful chemical reduction of CO2 at room temperature by alkali metals, promoted by a cyclic(alkyl)(amino) carbene (CAAC). One-electron reduction of CAAC-CO2 adduct (1) with lithium, sodium or potassium metal yields stable monoanionic radicals clusters [M(CAAC–CO2)]n(M = Li, Na, K, 2-4) and two-electron alkali metal reduction affords open-shell, dianionic clusters of the general formula [M2(CAAC–CO2)]n (5-8). It is notable that these crystalline clusters of reduced CO2 may also be isolated via the “one-pot” reaction of free CO2 with free CAAC followed by the addition of alkali metals – a reductive process which does not occur in the absence of carbene. Each of the products 2-8 were investigated using a combination of experimental and theoretical methods.

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