Annulation of an Iridabenzene through Formal Cycloaddition Reactions with Organonitriles

Abstract

The cationic iridacyclopentadiene complex [Ir(C4H4)(CS)(MeCN)(PPh3)2][CF3SO3] (2), which is derived from the reaction between [Ir(CS)(MeCN)(PPh3)2][CF3SO3] (1) and ethyne, undergoes a thermally induced migratory insertion reaction involving the thiocarbonyl ligand to form the cationic iridabenzene [Ir(C5H4{S-1})(MeCN)(PPh3)2][CF3SO3] (3) in very high yield. The addition of methyl triflate to this iridabenzene in the presence of NCMe results in methylation of the sulfur atom, and the red dicationic iridabenzene [Ir(C5H4{SMe-1})(MeCN)2(PPh3)2][PF6]2 (4) is obtained after the addition of NH4PF6. Upon treatment of 3 with RCN (R = Me or p-tolyl) and acid, a cyclization reaction ensues between the organonitrile and the η2-C(S)Ir function of the iridabenzene to give the corresponding iridabenzothiazolium complexes [Ir(C5H4{NH═C(R)S-1})(RCN)(PPh3)2][PF6]2 [R = Me (6a); p-tolyl (6b)], where the iridium occupies a ring junction position.