Ruthenium sulfoxide ligands

Ruthenium and Rhodium Hydrides Containing Chiral Phosphine or Chiral Sulfoxide Ligands, and Catalytic Asymmetric Hydrogenation... 

This chapter reports principally on studies with ruthenium chiral phosphine and chiral sulfoxide complexes and their use for catalytic hydrogenation. We have used the familiar diop ligand, [2R,3R-(—)-2,3-Oisopropylidene-2,3-dihydroxy-l,4-bis(diphenylphosphino) butane] (7) a related chiral chelating sulfoxide ligand dios, the bis(methyl sulfinyl)butane analog (21) (S,R S,S)-(+)-2-meth-ylbutyl methyl sulfoxide(MBMSO), chiral in the alkyl group and R-(+)-methyl para-tolyl sulfoxide(MPTSO), chiral at sulfur. Preliminary data on some corresponding Rh(I) complexes are presented also. 

In 2008-2009, Grela and co-workers disclosed the synthesis of NHC Ru complexes bearing chelating sulfoxide ligands (25) that showed no catalytic activity in RCM or enyne metathesis reactions at room temperature, but became active upon heating to 40 110 °C. Concomitantly, Lemcoff et al. prepared a closely related series of sulfur-chelated latent ruthenium alkene... 

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). 

On the other hand, James reported, in 1976, the use of a chiral sulfoxide as a ligand of ruthenium for the asymmetric hydrogenation of itaconic acid, providing a low enantioselectivity of 12% ee (Scheme 8.23). ... 

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). 

Smith MK, Gibson JA, Young CG, Broomhead JA, Junk PC, Keene FR. Photoinduced ligand isomerization in dimethyl sulfoxide complexes of ruthenium(II). Eur J Inorg Chem 2000 1365-70. 

Dimethyl sulfoxide solutions of [(CgHe)RuCl2]2 were shown to react with nucleophiles such as H , OH , or CN . Nuclear magnetic resonance studies showed the presence of cyclohexadienyl complexes, but the compounds were too unstable to be isolated, and the identity of the other ligands coordinated to the ruthenium atom is uncertain (462, 464). 

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. 

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