Nitrosyls of Iridium and Rhodium

Two factors have contributed particularly to the interest in the iridiiun and 

The report in 1968 of the first crystallographically characterized bent metal-nitrosyl linkage in [IrCl(NO)(CO)(PPh3)2] BF4 [180]. 

The discovery that [Ir(NO)2(PPh3)2] reacts with CO forming the carbonyl Ir(CO)3(PPh3)2, which then regenerates the starting material in reacting with NO [181] 

This has obvious potential for removing undesirable NO and CO from automobile exhaust gases. 

Bent metal-NO bonding is traditionally associated with NO bonding as NO , whereas linear coordination is associated with NO. The latter is predicted to involve shorter M—N bonds as both a- and 7r-donation can be involved. 

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COMPLEXES OF RUTHENIUM, OSMIUM, RHODIUM, AND IRIDIUM CONTAINING HYDRIDE CARBONYL, OR NITROSYL LIGANDS... 

It is remarkable that not a single example of a rhodium or iridium nitrosyl with a Tp ligand has been reported. In a similar manner, analogues based on arenediazenido and thionitrosyl ligands have yet to appear for group 9 metals, despite such compounds being reported for earlier transition metal centres. 

Ruthenium(III), d, is ruthenium s most stable oxidation state and resembles rhodium(III) and iridium(III) more than osmium(III). The salts inelude the halides, hydroxides, and oxides RuCls SHaO is most important because it is a good starting material for other compounds and reacts readily with olefins and phosphines. Complexes of this oxidation state are known with water, eyanide, oxygenated organies, sueh as diketones and earboxylates, pyridines, earbonyls, ey-elopentadienyls, phosphine, and arsine ligands. A notable differenee between ruthenium(II) and ruthenium(III) is the absenee of ruthenium(III) nitrosyl complexes. 

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