Molybdenum complexes 1,10-phenanthroline

The reaction of [MoO(H20)(CN)4] with 1,10-phenanthroline (211) and 2,2 -dipyridyl (215) has also been studied by means of reaction kinetics. It is clear that there are still uncertainties and questions regarding the mechanism of the reaction of these bidentate ligands For example, why is the reaction of the molybdenum complex faster at high pH values at which there is less of the aqua and more of the hydroxo) complex in solution (211) Scheme 5 was proposed for reaction with 2,2 -bipyridyl (215). 

The catalytic activity of co-ordination compounds in oxidations continues to be examined and, together with the Faraday Society Discussion, other aspects of this area of investigation have been the subject of recent reviews. Redox reactions involving bipyridyl and u-phenanthroline complexes of transition metals have been discussed and catalytic oxidations of complexes of manganese, cobalt, copper, and palladium have also been surveyed. Reviews are also available of ruthenium ammine chemistry, and redox reactions involving molybdenum complexes, together with an account of catalase and peroxidase reactivity of copper(ii) complexes. ... 

In the electron spectrum of the molybdenum complex, there is an intense metal-ligand charge transfer band (MLCT) from the d orbital on the 71 orbital of phenanthroline. After the formation of the adduct with triethylaluminum, the MLCT band becomes shifted to higher energies. This constitutes evidence for stronger back-bonding in the adduct than in the [Mo(CO)2 (phen)(PPh3)2] complex. 

Numerous experimental systems verified the theory of surface electrode reactions. Reductions of methylene blue [92], azobenzene [79, 82] alizarine red S [93], probucol [94], molybdenum(V)-fulvic acid complex [95], molybdeniun(VI)-1,10 phenanthroline-fulvic acid complex [96], indigo [97], and reduction of vana-dium(V) [98] at a mercury electrode are some of the examples for surface electrode... 

Applications for the 1,10-phenanthroline nucleus are widespread for example, they have been used as chelating agents (see Section 10.23.5.2), ligands for catalysis (see Section 10.23.5.2), as cytotoxic drugs <2002T9095>, and, when complexed with molybdenum, as cancer therapeutics <2005W0087783>. 

Many methods for sulphide and H2S are based on the reducing properties of S(-II). Hydrogen sulphide reduces molybdate in acid medium to molybdenum blue, and the molybdophosphate to phosphomolybdenum blue [52]. Iron(III) reduced by H2S in the presence of 1,10-phenanthroline gives the orange Fe(phen)3 complex [2,53], Hydrogen sulphide may be determined after conversion into thiocyanate by the reaction with Fe(III) [54]. Sulphide has been determined also by a colour redox reaction with nitroprusside [55-57], In another sensitive reaction the sulphide ions decompose the Ag complex with Cadion 2B and Triton X-100 (e = 2.5-10 ) [58], In another indirect method sulphide releases the chloranilate ion from the Hg(Il) chloranilate [59]. Sulphide has also been determined by a method based on its reaction with bromate, followed by bromination of 2 ,7 -dichlorofluorescein by the bromine released [60]. 

The results of CNDO/2 calculations on relative bond strengths in mono-1,10-phenanthroline, mono-2,2 -bipyridyl, and monoaliphatic diimine complexes of cobalt(III) should prove useful in discussion of rates of substitution and aquation of cobalt(III)-diimine complexesPresumably these authors will shortly turn their attention to the much more studied iron(II) analogs they do mention the molybdenum(O) analog [Mo(CO)4(bipy)]. 

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