Metal-nitrosyl compounds preparative methods

Dichlorodinitrosylmolybdenum and tungsten have been prepared by the reaction of the appropriate hexacarbonyl with nitrosyl chloride in dichloromethane.1 The corresponding dibromo derivatives have been prepared by a similar reaction with nitrosyl bromide.2 These are the only synthetic routes to these compounds they are rapid (3 hours) and convenient. The corresponding chromium compounds are unknown. This method is a general route to transition-metal nitrosyl halide... 

One of the most prominent features of ruthenium chemistry is that the metal forms numerous compounds containing the (RuNO) + fragment. Furthermore, the metal-nitrosyl fragment has in general been of interest to many because of the potential 7r-acceptor ability of NO and its possible existence as NO+, NO , or NO. Explicit details of how to synthesize the ruthenium-NO complexes are virtually nonexistent, and procedures, when available, are laborious. Here we give the preparative descriptions for such compounds by newly developed methods which are explicit and convenient. The information is also valuable in view of the cost of ruthenium. 

Many methods have been used to prepare NO complexes. The reactions of transition metal complexes with gaseous NO or solutions of the dissolved gas have been used to form NO complexes. One example of such a reaction to form, a homoleptic nitrosyl complex is shown in Equation 4.30. Alternatively, the reactions of metal complexes with nitrosonium salts form metal-nitrosyl complexes. (Note Alcohol solvents should be used with caution, because they convert NO " to alkyl nitrites. In addition, tetrahydrofuran should not be used as solvent because it can be polymerized by NO". ) Two examples of such processes are shown in Equations 4.31 and 4.32. A range of organic nitroso compounds release "NO" under appropriate conditions and have been used to introduce NO into transition metal complexes. The generation of a metal-nitrosyl complex from F3CNO is shown in Equation 4.33. ° Inorganic nitrites have also been used to prepare NO complexes, ° as shown in Equation 4.34. ... 

Analogs of the dichloro complex are prepared by a variety of methods, many of which are specific for single compounds. The dibromo complexes can be prepared using nitrosyl bromide or from A-methyl-iV-nitrosotoluene-4-sulfonamide and rhodium tribromide. Replacement of the tribromide by the trichloride and an alkali metal iodide gives diiodo complexes (equations 50 and 51). 

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