Sulfoxide coordination

Cases where sulfoxides coordinate to soft metals via oxygen are now known, and these require some comment. The first reports of such a complex concerned the [Pd(Me2SO)4]2+ cation (475, 476), shown to be cis-[Pd(0-Me2SO)2(S-Me2SO)2]2+ by a variety of techniques. Since that time, many other similar complexes have beeiyreported, including [Pd(0-diisoamylsulfoxide)4]2+ (447-449), [Ru(0-Me2S0)(S-... 

Of particular note is the complex [Fe(CN)5(Me2SO)]3 (226), where the positive shift in i (S=0) upon sulfoxide coordination [Ai>(S=0) = +15 cm-1] is taken as indicative of coordination via sulfur. No structural data appear to be available for confirmation. 

It has recently been shown that alkyl sulfoxides are good solvents for transition metal halides, and many adducts can be isolated 42, 84, 167, 227, 231). Nickel perchlorate takes up six dimethyl sulfoxide ligands, but the chloride apparently only three. It has been shown from the reflectance spectrum and from the high magnetic moment 42) that this compound should be formulated as [Ni(DMSO)6][NiCl4], in which the anion is tetrahedral. Infrared spectra 43, 127) show that the dimethyl sulfoxide coordination is through oxygen. Similar compounds are found with tetrahydro-thiophenoxide 84) ... 

An enantiopure cyanohydrin of 2-p-tolylsulfinylbenzaldehyde has been prepared (g) using various metallic cyanating agents in the presence of Yb(in) or Y(III) triflate.264 Sulfoxide coordination with the metal is implicated, supported by DFT calculations. 

The intermediate 139 formed following the addition of z-butylmagnesium chloride to the nitrile 138 was then treated with sulfoxide 137 to afford the sulfinyl ketimine 140. " Diastereoselective addition of hydride to the chiral imine 140 in the presence of Ti(0 Pr)4 afforded the chiral amine 142. This reaction may proceed via a closed-transition state (e.g., 141) in which the sulfoxide coordinates to the metal center and directs the stereoselective addition of hydride, as has been proposed for related reactions.Treatment of the sulfoxide 142 with acid and base effected removal of the auxiliary. 

In general, the higher the fra s-effect of a ligand, the lower is its cis-effect. However, the series are not completely reversible. For example, dimethyl sulfoxide, coordinated to platinum(II) through sulfur, exhibits both a very high frans-effect (comparable with that of ethylene) and also a high cis-effect. A cis-effect series based upon comparable data is ... 

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