Rhodium complexes mixed bridge

For both the dipalladium and palladium-platinum complexes the metal-metal bond is unusually reactive and a number of small molecules undergo an insertion reaction with (9) to give (10 equation 8). The corresponding sulfide-bridged dipalladium dimer can be prepared from the reaction of S8 or MeCHCH2S with (9).83 A mixed rhodium-palladium dimer can also be prepared from (9) (see Scheme 6).84... 

Recently, Severin reported the Kharasch addition of several mixed rhodium(I)-ruthenium(II) and rhodium(III)-ruthenium(II) catalysts (see Part 3, Sect. 8.5). It was also demonstrated that 0.5 mol% of dinuclear rhodium(I) complex 434 having a bridging THDP ligand is an active catalyst for the Kharasch addition of BrCCl3 to simple olefins 433 in water [228]. The yields of adducts 435 ranged from 81 to 92%. 

Ruthenium, osmium, rhodium, and iridium form octahedral MClj" chloro complexes which, in aqueous solution, usually exist as chloro-aquo mixed species of the general composition [MCl6 ,(H20)J ( c = 1-6). Ruthenium and osmium also form complexes of the type [MCl6 t(H2P),] (jr = 1-6) and oxygen-bridged complexes such as [(RuCl5)20] . In many cases, complexes of the PGM are kinetically inert [4]. 

Although the general rule for mixed cyclopentadienyl carbonyl complexes is that metals with odd atomic number form mononuclear complexes whilst those of even atomic number form binuclear complexes, it has been reported that mononuclear cyclopentadienyl rhodium dicarbonyl polymerises to a binuclear complex. The structure of a binuclear complex with an unusual carbonyl bridging group is reported. 

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