Abstract
The fragments fOs(NH 3 ) 5g2þ and fTpRe(CO)(L)g (where L ¼ 1-methylimidazole, pyridine,
PMe3 , or tert-butylisonitrile) form stable h2 -coordinate complexes with a wide variety of are-
nes. The act of coordination greatly reduces the aromatic character of these ligands and, as a
consequence, activates them towards various organic reactions. In particular, the addition of
carbon-based electrophiles to arenes is notably enhanced relative to the free aromatic mole-
cules. The resulting arenium intermediates are stabilized by metal backbonding to the point
that they may be isolated and subsequently subjected to a variety of carbon-based nucleo-
philes. The overall vicinal difunctionalization of two ring carbons may be accomplished with
excellent stereo- and regiocontrol.
