Ruthenium complexes sulfoxides

Sava, G. Alessio, E. Bergamo, A. Mestroni, G. Sulfoxide Ruthenium Complexes Non Toxic Tools for the Selective Treatment of Solid Tumor Metastases In Metallopharmaceuticals l DNA Interactions, Clarke, M. J. and Sadler, P. J., Ed. Springer-Verlag Berlin, 1999 Vol.l, pp 143-170. 

Several ruthenium complexes bearing chiral Schiff s base ligands have been published. RuL(PPh3)(H20)2], complex C (Fig. 11), with PhIO produced (S)-styrene oxide in 80% ee [61]. Chiral Schiff s base complex D was examined using molecular oxygen with aldehyde, with or without 2,6-dichloropyridine N-oxide as an axial ligand. Styrene oxide was produced in up to 24% ee[62]. A chiral bis(oxazolinyl)pyridine ruthenium complex E with iodosylbenzene diacetate PhI(OAc)2 produced (lS,2S)-fra s-stilbene oxide in 74% ee [63]. Similarly, chiral ruthenium bis(bipyridine) sulfoxide complex F [64] was effective in combination with PhI(OAc)2 as an oxidant and resulted in in 33% ee for (R,R) trans-stilbene oxide and 94% ee for (R,R) trans-/i-Me-styrene (after 75 h at 25 °C). 

The main methodologies developed until now for enantioselective oxidation of sulfides are effective only in the oxidation of alkyl aryl sulfoxides. Dialkyl sulfoxides on the other hand are generally oxidized with only poor selectivity. In an attempt to solve this problem, Schenk s group69 recently reported a stereoselective oxidation of metal-coordinated thioethers with DMD. The prochiral thioether is first coordinated to a chiral ruthenium complex by reaction with the chloride complexes [CpRu[(S,S)-chiraphos]Cl], 36. Diastereoselective oxygen transfer from DMD produces the corresponding sulfoxides in high yield and selectivity. The chiral sulfoxides 37 are liberated from the complexes by treatment with sodium iodide. Several o.p. aryl methyl sulfoxides have been obtained by this method in moderate to high ee (Scheme 12). 

A variety of other oxidants that produce sulfoxides from sulfides are known, such as nitric acid, acyl nitrates, nitronium salts,N204, oxygen with ruthenium complex catalysts, - pressurized oxygen with CAN as a catalyst, ozone, - TTN, Ce salts, - and potas-... 

In our application to molecular hysteresis accompanying a change in oxidation state, we have exploited linkage isomerization of ruthenium and osmium complexes (oxidation states 2+ and 3+). An early example in this circumscribed field is the linkage isomerization observed for the pentammine ruthenium complex with dimethyl sulfoxide when the oxidation state changes from 2+ (heteroligand attached at S) to 3+ (relocation to oxygen) (Fig. 3A) [13, 14]. The points of attachment have been confirmed by X-ray diffraction... 

Kinetic and Equilibrium Parameters for Linkage Isomerizations of Sulfoxide/Ruthenium Complexes [14]... 

Examples of sulfur oxidation constitute the sulfone of the ruthenium complex and the sulfoxide of the tungsten derivative [37]. In the latter, an excess of dioxirane effected the oxidation to the corresponding sulfone. Oxyfunctionalizations of this type are unprecedented. 

These interpretations await definitive structural confirmation. Certainly, DMSO as ligand in the ruthenium complexes dictates a different behaviour than that observed by Clark and Taube in their study of the [Ru(NH3)5C1] system (7). Further, depending on the structure, displacement of chloride and both S-and 0-bound sulfoxide has been observed in these reactions with the simple nucleic acid bases. 

Sulfoxide ruthenium complexes have received attention in part from the fact that they are useful starting materials for new organometallic and coordination compounds and in part from their role in biology and catalytic processes see Metal-related Diseases of Genetic Origin). Potential applications are found in medicinal chemistry. 

The preparation of ruthenium bis(diimine)sulfoxide complexes by reaction of cis-[Ru(bipyridine)2(Cl)2] (165) with enantiomerically pure chiral sulfoxides 166 was described by Ait-Haddou [94] as a new concept in the preparation of optically active octahedral ruthenium complexes (Scheme 5.47). The reaction produces two dia-stereomeric complexes 167 and 168 and the microwave-irradiated reactions resulted in excellent yields and high reaction rates with a notable increase in the observed diastereomeric excess. 

Ruthenium complexes containing atropoisomeric diphosphines related to BINAP, such as MeO-BIPHEP (see Fig. 40), employed in the hydrogenation of jS-keto esters, j8-keto sulfoxides, sulfones, and jS-diketones also follow the inner coordination sphere mechanism (234,235). 

James, B. R., R. S. MacMillan, and K. J. Reimer Catalytic Asymmetric Synthesis Using Ruthenium Complexes Containing Sulfoxide Ligands. J. Mol. Catal. 1, 439 (1975/76). 

No sulfoxide complexes of osmium have been reported. Unsymmetri-cal dialkyl sulfoxides have been utilized in extraction studies, and methyl-4,8-dimethylnonyl sulfoxide has found application in the extraction of iron (266). Extraction of ruthenium from hydrochloric acid solutions by sulfoxides has been studied (470) and comparisons of sul-fones, sulfoxides, and thioethers as extractants for nitrosoruthenium species reported (441, 443). Similar studies on the extraction of nitro-soosmium species have been reported (442). 

---