The first example of a transition
metal (BB)-carboryne complex
containing two boron atoms of the icosahedral cage connected to a
single exohedral metal center (POBBOP)Ru(CO)2 (POBBOP =
1,7-OP(i-Pr)2-2,6-dehydro-m-carborane) was synthesized by double B–H activation within
the strained m-carboranyl pincer framework. Theoretical
calculations revealed that the unique three-membered (BB)>Ru metalacycle
is formed by two bent B–Ru σ-bonds with the concomitant
increase of the bond order between the two metalated boron atoms.
The reactivity of the highly strained electron-rich (BB)-carboryne
fragment with small molecules was probed by reactions with electrophiles.
The carboryne–carboranyl transformations reported herein represent
a new mode of cooperative metal–ligand reactivity of boron-based
complexes.
The kinetics of RAFT inverse miniemulsion polymerization of acrylamide are presented. The polymerizations exhibit typical behavior of controlled polymerizations under conditions where the hydrolytic degradation of the RAFT agent is less favorable. The effects of different reaction parameters such as temperature, initiator concentration, pH of the aqueous phase, RAFT agent, and surfactant concentration on RAFT inverse miniemulsion polymerization are presented. The particle nucleation process in the inverse miniemulsion polymerizations is evaluated by the use of radical scavengers. The presence of RAFT agent was found to have a significant impact on the particle nucleation process. The fate of desorbed monomeric radicals in inverse miniemulsion polymerizations is evaluated by the comparison of the rates of propagation, re-entry, and termination. One of the potential reasons for the induction time observed in the RAFT inverse miniemulsion polymerizations is suggested to be associated with desorption of monomeric and oligomeric radicals from the particles to the continuous oil phase.
The ruthenium carboranyl pincer complex featuring fluxional ”cage-walking“ of the metal center is an efficient catalyst for cyclooctane transfer dehydrogenation.
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