Dimethylsulfoxide as a Ligand for RhI and IrI Complexes—Isolation, Structure, and Reactivity Towards XH Bonds (X=H, OH, OCH3)
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Dickson R. S., 1983, Organometallic Chemistry of Rhodium and Iridium
Collman J. P., 1987, Principles and Applications of Organotransition Metal Chemistry
A RhI–DMSO dimer [RhCl(DMSO)2]2was characterized based only on its IR spectrum see:
Parshall G. W., 1992, Homogeneous Catalysis
Cole‐Hamilton D. J., 1977, Nouv. J. Chim., 1, 141
The reported dimer [Rh2Cl2(DMSO)4] may actually be complex1 see reference [3].
It has been shown for other transition‐metal complexes that thetransarrangement of S‐bound DMSO is not very favorable see reference [2].
Quite surprisingly a data search showed that complexes of the type [IrCl(PR3)3] have never been characterized by X‐ray crystallography and thus structural comparison of complex2with its phosphine analogues was not possible.
Complex10reacts with benzyl chloride in much the same way as complex9; R. Dorta D. Milstein unpublished results.
Kuc M. Green T. A., 1972, J. Chem. Soc. Dalton Trans., 832
For details see the data deposited at the CCDC.
In this context it is interesting to note that sulfoxides can be forced to bind through their sulfur atoms to such cationic RhI–COD complexes. Chelating ethylene‐bridged bis(sulfoxides) of this kind have been characterized based on spectroscopic data see:
For the preparation of [Rh(coe)2(OCMe2)2]PF6 see:
Irtrans‐dihydride complexes give rise to1H NMR signals at a significantly lower field thancis‐dihydride ones see for example:
Analysis of the rate is approximate as the DMSO molecules of the starting complex exchange rapidly with the deuterated solvent. Thus completion of the reaction was observed by comparing the integration of the hydride peak with the signal for one of the free non‐deuterated DMSO molecules.
It has been shown that oxidative addition of OH bonds to neutral electron‐rich iridium phosphine complexes occurs by nucleophilic attack of 16‐electron species of the type [IrCl(PR3)3] (R=methyl ethyl) on the OH proton (see reference [6 o]). The fact that the 16‐electron complexes7and8do not undergo water oxidative addition is probably a result of their not being nucleophilic enough on the one hand and capable of forming a reactive 14‐electron species on the other.
The NMR spectrum of a mixture of these two compounds did not give clear results because of the low solubility of these complexes and possibly because exchange processes rendered analysis difficult (see also the discussion of complexes17and18).
Protonation of the PF6−counterion was also observed during the reaction of complex [Ir(coe)2(OCMe2)2]PF6with water: R. Dorta D. Milstein unpublished results.
G. M. Sheldrick SHELX‐97 Program for Crystal Structure Refinement University of Göttingen Göttingen (Germany) 1997.