Oxidative Addition of α-Glycosyl Halides to a Platinum(0) Olefin Complex: Stereochemistry of Pt−C Bond Formation

The oxidative addition of α-glucosyl and α-galactosyl halides to the platinum(0) complex [Pt(2,9-dimethyl-1,10-phenanthroline)(ethene)] has been investigated. In all cases the main reaction product is the five-coordinate Pt(II) complex containing in axial position an α-glycosyl fragment in the unusual 1C4 conformation. In the case of glucose, a minor product could be identified as the β isomer, which retains the typical 4C1 chair. The single crystal structures of two diastereomers are compared. The outcome of the reaction does not depend on the nature of the halide and is only slightly affected by the solvent. The addition mechanism is discussed, also in the light of literature data. Experimental data, along with DFT calculations, point towards a radical chain mechanism.