Hemi-labile coordination

It seemed plausible that if the thiolate sulfur were replaced by neutral thioether sulfur then the latter would be more weakly bound to the metal introducing the possibility of hemi-labile coordination. We have therefore investigated the chemistry of some related phosphinothioether complexes of Ru" and Pd". The new ligand 2-MeSCgH4CH2PPh2 (L) was prepared in reasonable yield in a three stage synthesis starting from 2-bromotoluene by bromination to 2-... 

In the proposed mechanism, the dearomatised pincer ligand deprotonates the alcohol, aromatising the pyridine ring, with no change in oxidation state, to form the ruthenium alkoxide (Figure 12.3). The hemi-labile amine arm dissociates from the Ru metal and allows for the requisite a s-coordination of the alcohol relative to the metal to be adopted, facilitating p-hydride elimination and generating the Ru-bound aldehyde. 

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