Reactions dinitrosyl complexes with

Molybdenum dinitrosyl complexes with the general formula Mo(NO)2(CHR) (0R )2(A1C12)2 have been found to be active in a variety of metathesis reactions [110]. New alkylidenes could be identified. Variations such as Mo(NO)2(CHMe) (RC02)2 also are known [111]. Complexes of this type are believed to be more reduced than typical d° species discussed here, although they appear to be much more active as metathesis catalysts than typical Fischer-type carbene complexes. 

Fig. 25. Possible mechanism for the reaction of dinitrosyl complexes with carbon monoxide to give N2O and COj.

An important use of dinitrosyl complexes of molybdenum has been as catalyst precursors in the alkene disproportionation reaction. Thus [MoCl2(NO)2L2] (L = PPh3 or py) together with AlCl2Et forms an active homogeneous catalyst for alkene disproportionation. The catalysis appears to require loss of NO from the metal and the field has been reviewed.19,31... 

In addition, when cts-[MoCl2(NO)2(diars)] is allowed to stand in methanol, [ MoCl2diars(NO) 2(/i,2-N202)] is isolated (253), this is an example of the conversion from a d -dinitrosyl complex to a d -hyponi-trite complex. A binuclear hyponitrite complex, [Pt2(/u,-N202)-(PPh3)4]2, has also been reported as the product of the reaction of (54) with NO (254). 

Dinitrosyl complexes of the type [Mo°(NO)2X2] were obtained by reduction of [Mo04] by hydroxylamine in the presence of added anionic ligands X, where X = dithiocarbamate, dithiocarboxylate, alkoxide, 2-NH2C6H4E (E = O or S), hydroxamic acids. Reaction of [Mo(NO)2 (dttd)] (dttd = (22)) with hydrazine or NaBH4 gave the k -hydroxylamide, [Mo(NO) (ONH2) (dttd)]. 

Grundy KR, Laing KR, Roper WR (1970) Dinitrosyl complexes of ruthenium and osmium and their reaction with oxygen. J Chem Soc D 1500-1501... 

Hexacoordinated mixed-ligand dinitrosyl complexes of molybdenum(O) of the composition [Mo(NO)2(L)(OH)] with a variety of Schiff base ligands have been reported [3]. Such complexes are readily obtained by a single-step reaction between molybdate(VI) and the ligand in presence of hydroxylaminehydrochloride in a dimethylformamide solvent. A ds-octahedral structure has been observed in these complexes, as shown in Figure 12. 

This reaction has been reexamined using optical, IR and NMR spectroscopic methods to probe NO reactions with Fe(TPP)(NO) and the more soluble Fe(TmTP)(NO) (92). These studies confirmed the formation of Fe(Por)(NO)2 in toluene-dg at low temperature (Eq. (43)). NMR line shape analysis was used to calculate K43 = 23 M-1 at 253 K (3100 M-1 at 179 K, AH° = —28kJmol 1) (92). The failure of the Fen(Por) complexes to promote NO disproportionation, in contrast to the behavior of the respective Ru(II) and Os(II) analogs, may find its origin partly in the relatively low stability of the dinitrosyl intermediate (K52 estimated to be 2.8 M-1 at 298 K) and unfavorable kinetics of subsequent reaction of this species with NO. 

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