Organoplatinum(IV) complexes with hydrogen bonds: From monomers to polymers

A series of organoplatinum(IV) complexes has been prepared, in which one of the alkyl groups contains a functional group that is capable of taking part in hydrogen bonding. These complexes are formed by oxidative addition of reagents RCH2X to [PtMe2(bu(2)bipy)] (1; bu(2)-bipy = 4,4'-di-tert-butyl-2,2'-bipyridine) and have the formula [PtXMe2(CH2R)(bu(2)bipy)] (2, R = CO2H, X = Br; 3, R = 4-C6H4CO2H, X = Br; 4, R = 4-C6H4CH2CO2H, X = Br; 6, R = C4N2H3O2, X = Cl; 6, R = 4-C6H4NHCO2Me, X = Cl; 7, R = 2,4-C6H3(NHCO2Me)(2), X = Cl). These complexes may form dimers through OH ... O or NH ... O hydrogen bonding or polymers through NH ... X hydrogen bonding. Further derivatives were prepared by reaction of the above complexes with AgBF4 in the presence of nicotinic acid or 4,4'-bipyridyl (bipy): namely, [PtMe2(CH2C6H4CO2H)(4-NC5H4CO2H)(bu(2)bipy)][BF4] (8) and [{PtMe2(CH2R)(bu(2)bipy)}(2)(mu-bipy)][BF4](2) (9a, R = C6H4CO2H; 10a, R = C6H4CH2CO2H) Complex 9a forms a polymer by OH ... O-hydrogen bonding, whereas 8 and 10a undergo hydrogen bonding with the solvent and/or the counterion. This work shows that extended structures can be designed with hydrogen bonding in organoplatinum compounds and that there is a fine balance between formation of dimers or polymers through OH ... O, NH ... O, or NH ... Cl bonding forms and formation of simpler structures arising from hydrogen bonding to solvent molecules or counterions.