ORGANOPLATINUM(IV) POLYMERS AND MODEL COMPLEXES BY OXIDATIVE ADDITION OF BROMOACETATE ESTERS

The oxidative addition of bromoacetic acid or its derivatives to [PtMe2(bpy)], 1a, bpy = 2,2'-bipyridine, or the new complex [PtMe2(bu2bpy)], 1b, bu2bpy = 4,4'-di-tert-butyl-2,2'-bipyridine, gives the complexes [PtBrMe2(CH2X)(NN)] [(NN = bpy) X = CO2Me (2), X = CO2Et (3), X = CO2H (4), X = C=N (5), X = CONH2 (6); (NN = bu2bpy) X = CO2CH=CH2 (7)]. Similarly, the diester BrCH2CO2CH2CH2O2CCH2Br reacted with [PtMe2(NN)] to give the bridged dimer [{PtBrMe2(NN)}2(mu-CH2CO2CH2CH2O2CCH2)] [8, NN = bpy, 9, NN = bu2-bpy]. Many of the complexes 2-9 were shown by NMR to exist as a mixture of two isomers, the major or sole product corresponding to that of trans oxidative addition. Complexes 2 and 9 were also characterized by X-ray structure determinations, which showed that the preferred conformation has the ester group lying above the flat diimine ligand. This leads to a helical conformation for complex 9. Free radical polymerization of complex 7 gave the polymer [{PtBrMe2(NN)(CH2CO2)}CHCH2]n, 10a, NN = bu2bpy, in which the organoplatinum groups are present as substituents on the acetate groups of the poly(vinyl acetate) chain. A similar polymer, 10b, was prepared by esterification of poly(vinyl alcohol) to poly(vinyl bromoacetate) followed by its oxidative addition to an excess of [PtMe2(bu2bpy)]. The bu2bpy ligand is shown to be useful in giving enhanced solubility to the platinum complexes.