Alkyne-gold iridium

In the field of homogeneous catalysis, electrophilic metals [palladium(II), plati-num(II), rhodium(II), iridium (I), ruthenium(II), cobalt(I), titanium(II) and gold(I)] activate alkynes under mild conditions [2-8]. When an alkyne behaves as a ligand, there are four orbitals that can participate in the bonding (Fig. 1.1) [4]. The in-plane orbitals, Try and n, are responsible for a donor interaction (M <- L donation) and a 7r-acceptor interaction (M L back-donation) respectively. The orthogonal, out-of-plane orbitals, and n , are engaged in the M <- L 7t donation and the d symmetry M L back-donation respectively. This latter interaction can be neglected, due to the weak overlap of the orbitals. 

Scheme 19 Gold catalyst and iridium catalyst for hydrothiolation of alkynes...

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