A 12-Vertex Metallacarborane of Silver(I)

The
discovery of ferrocene in 1951 was a significant landmark in
the field of organometallic chemistry, and since then, numerous sandwich-
or half-sandwich metallic complexes have been reported. However, silver
stands as an intriguing exception in this regard, and knowledge of
its bonding situation has remained undisclosed. Herein, unprecedented
12-vertex metallacarboranes of Ag­(I) (2a and 2b) were synthesized through the reaction of sodium hexamethyldisilazide
(NaHMDS) with the mixture of nido-C2B9 carborane anion-supported N-heterocyclic
carbene precursors (1a and 1b) and [Ag­(PPh3)­Cl]4. The X-ray structural analysis of the resulting
metallacarboranes revealed a unique “slipped” half-sandwich
structure, which is a rarity among cyclopentadienyl analogues. DFT
calculations provided insights into the asymmetric π-interactions
between the pentagonal C2B3 face and the silver
ion.