A series of monomeric (NHC)Cu(SR) (R = Ph or CH2Ph; NHC = N-heterocyclic carbene) complexes have been synthesized and fully characterized including single-crystal X-ray diffraction studies. These complexes catalyze the addition of S-H bonds across electron-deficient olefins to regioselectively produce "anti-Markovnikov" products.

The Ru(II) hydride complex (IMes) 2 Ru(Cl)(H)(CO) (1) {IMes ) 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene} was synthesized from [Ru(CO) 2 Cl 2 ] n and free IMes. Complex 1 rapidly reacts with CO to produce the cis-dicarbonyl Ru(II) complex (IMes) 2 Ru(Cl)(H)(CO) 2 (2). The reaction of 1 with NaBAr′ 4 {Ar′ ) 3,5-(CF 3 )C 6 H 3 } produces the four-coordinate Ru (