Rhodium nitrosyls

Two factors have contributed particularly to the interest in the iridium and rhodium nitrosyl compounds [179] ... 

Figure 2.101 Synthesis of some rhodium nitrosyl complexes.

Table 2.15 Structural data for rhodium nitrosyl complexes...

The crystal structure of the dinitrosyl cation (139) has been determined.1344 This cation can be prepared from other rhodium nitrosyl complexes (equations 323 and 324).1SU304... 

There are a few thionitrosyl complexes of rhodium, many of which contain thionitrosyl bridges. They have been prepared by allowing [NSC1]3 to react with sundry rhodium nitrosyl complexes (equations 327 and 328). 

Both mono and dinitrosyl cations may be prepared. Salts of the tetrahedral dinitrosyl cation can be prepared either from rhodium nitrosyls (equation 56) or by addition of nitric oxide to ionic rhodium(I) complexes (equation 57). Both nitrosyl groups in complex (47) are bent. The action of dppe upon the i)A(triphenylphosphine) complex produces N2O. Penta- and hexacoordinate mononitrosyl cations are more common and are usually prepared by the action of NOPFe or NOBF4 on rhodium(I) complexes in organonitrile solvents (equation 58). The principal reactions of the complexes are substitutions of the nitrile ligands (equations 59-61). A noteworthy feature of (48), [Rh(NO)(MeCN)3(PPh3)2]+, is that the MeCN ligand trans to the bent nitrosyl group is said to be bent. 

The rhodium nitrosyl complex is a deep-red crystalline solid which is moderately stable in the air but decomposes rapidly in solution in the presence of oxygen. It is soluble in chloroform, dichloromethane, and benzene and is insoluble in ether, methanol, and ethanol. The compound is a homogeneous hydrogenation catalyst for unsaturated organic compounds. > ... 

Nitrosyltris(triphenylphosphine)rhodium has previously been prepared by sodium-amalgam reduction of a mixture of rhodium nitrosyl chloride and triphenylphosphine in tetrahydrofuran.32 Preparations from hydridotetrakis(triphenylphosphine)rhodium(I) and nitric oxide,24 and from rhodium trichloride, nitric oxide, triphenylphosphine, and zinc dust have also been reported.35 The following synthesis1 is convenient and rapid. 

When the NO addition was done after the preadsorption of CO on the catalyst surface, absorption bands of linearly adsorbed NO on Pt and Rh were observed. The corresponding bands are seen at 1890 (Rh-NO ) and 1667 cm-1 (Pt-NO or Rh-NO"). The absorption band at 1786 cm" is due to the rhodium nitrosyl band (Rh-NO ) or platinum nitrosyl band (Pt-NO). Strong absorption bands at around 2258 cm" indicate the presence of isocyanate intermediates (Pt-NCO and Rh-NCO) which appeared after the evacuation. If NO was introduced into the chamber before CO the isocyanate complex was formed earlier. NO and CO were also adsorbed strongly on the washcoat giving absorption bands below 1600... 

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