Halogenation of alkenes in five-coordinate platinum(II) complexes - A route to stable (beta-haloalkyl)platinum(IV) species

Five-coordinate complexes [PtX2(olefin) (2,9-Me-2-phen)] (1; 2,9-Me-2-phen = 2,9-dimethyl-1,10-phenanthroline; olefin = ethene denoted by a, propene b y b, 1-butene by c; X = Cl denoted by x, Br by y) undergo photoactivated re actions with Cl-2 and Br, to give the (beta-haloalkyl)platinum(IV) complexe s [Pt(CH2CHRX)(2,9-Me-2-phen)X-3] (2). Bromination of the chloro species la x leads to the formation of the Pt-IV species 2axy containing the bromide, the bromoalkyl, and the phenanthroline Ligands in the equatorial plane and two chloride ions in axial positions. The iodo complexes 1(a-c)z are not ox idized by iodine even under UV irradiation but react readily with Cl-2 or B r-2 to give 2(a-c)x and 2(a-c)y. The structure of 2ay, the first structural ly characterized (beta-haloalkyl)platinum(IV) complexes has been determined by X-ray diffraction methods. The stereochemistry of the (beta-haloalkyl)p latinum(IV) complexes is in accord with a simultaneous addition of two halo gen atoms to the coordinated olefin and to the metal center.