(BB)-Carboryne Complex of Ruthenium: Synthesis by Double B–H Activation at a Single Metal Center

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.