Ruthenium triarylphosphine complex

In common with other platinum metals, an important area of ruthenium chemistry involves trialkyl- and triarylphosphines, and the corresponding phosphites. An extremely wide range of complexes is known, mainly of the II state, although compounds in the 0, III, and less commonly, IV state are known other ligands commonly associated with the PR3 group are halogens, alkyl and aryl groups, CO, NO, and alkenes as well as H and H2. Similar chemistry is found for osmium. 

Orthometallation of triarylphosphine and triarylphosphite at mthenium has long been knovm as intramolecular C-H bond activation in ruthenium chemistry [2], but did not receive attention from organic chemists. In 1965, Chatt and Davidson documented that a Ru(0) complex, which was formed by two-electron reduction of Ru(II) by use of sodium naphthalene is capable of reversible cleavage of sp C-H bonds of naphthalene by oxidative addition/reductive elimination processes (Scheme 14.1) [3]. 

In 2007, Trost and McClory reported the rhodium-catalyzed cycloaromatization of terminal alkynes bearing an amino or a hydroxy group (61 and 63) into the corresponding indoles and benzofurans (62 and 64) (Scheme 21.27) [36]. As described in the preceding section, McDonald et al. reported a similar transformation catalyzed by molybdenum carbonyl complex as a catalyst [10] (see Schemes 21.23 and 21.25). Use of rhodium catalyst provided some advantages in terms of the catalyst turnover and the selectivity. The combination of [RhCl(cod)]2 and a fluorinated triarylphosphine promoted the cyclization efficiently. Later, a ruthenium version of this cyclization was reported, as shown in Scheme 21.22 [31]. 

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