Dihapto-coordinated arene

Phosphine and phosphite ligands react with arene tricarbonyl complexes of Cr, Mo, and W yielding complexes of the type /ac-(PRg)3M-(CO)3 32, 261, 341-343, 466). Kinetic studies reveal that the reaction proceeds by an 8 2 mechanism 341-343, 466) which is thought to involve the stepwise displacement of the arene via tetrahapto- and dihapto-coordinated arene intermediates 466) ... 

Reduction of /rcMr-RuCl2[Me2PCH2)2]2 by arene radical anions such as sodium naphthalide has been shown to lead to a series of hydridoaryl complexes of the type Ru(H)(aryl)[(Me2PCH2)2]2 63). The hydride structure of the napthalene derivative has been shown in solution (63) and in the solid state 232). However, on the basis of the chemistry of the complexes, the following equilibrium was proposed 63), between a hydride and a small amount of a dihapto-coordinated arene-Ru(O) complex ... 

Conformational and linkage isomerizations for dihapto-coordinated arenes and aromatic heterocycles controlling the stereochemistry of ligand transformations 04CCR(248)853. 

This chapter will initially cover several aspects of dihapto-coordination of aromatic molecules, including the scope of the dearomatization agent and the aromatic substrate. The primary focus of this work, however, will be the fundamental organic reactions of these complexes with electrophiles and the subsequent reactions of those products. Several applications of this methodology will also be illustrated. Owing largely to its earlier discovery, the majority of the organic transformations reviewed will be with osmium(II), however, recent arene transformations promoted with rhenium(I) and molybdenum(O) will also be discussed, with an emphasis on differences in reactivity compared to those of osmium. 

Harman D (2004) Dearomatization of Arenes by Dihapto-Coordination. 7 95-128 Hatano M, see MikamiM (2005) 14 279-322... 

Figure 7.43 Dihapto arene coordination synthetic implications L = NH3 Tf = S02CF3...

This precursor is well known to very easily give, with aromatics, complexes of the type [RuCp (r -arene)]+, even when the aromatic bears a double bond in a substituent. Thus, this reaction is a good example of the inability of Ceo to coordinate to the metal in a hexahapto fashion, and on the contrary of its strong tendency to give dihapto complexes. " ... 

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