Supramolecular Organoplatinum(IV) Chemistry: Dimers and Polymers Formed by Intermolecular Hydrogen Bonding

The reaction of [PtMe2(6-dppd)], 1, where 6-dppd is a 1,4-bis(2-pyridyl)pyridazine derivative, with bromoalkanes BrCH2R, having a hydrogen-bond donor group R, gave the corresponding chiral products of trans oxidative addition [PtBrMe2(CH2R)(6-dppd)], 2a, R = CO2H; 3, R = 4-C6H4CO2H; 4, R = 4-C6H4CH2CO2H; 7, R = 2-C6H4CH2OH; 8, R = 4-C6H4B(OH)(2); 9, R = 3-C6H4B(OH)(2); and 10, R = 2-C6H4B(OH)(2). Complex 2a was formed in equilibrium with two isomers formed by cis oxidative addition, while the reaction of 1 with BrCH2CH2CO2H gave mostly [PtBrMe(6-dppd)], 6. The supramolecular chemistry was studied by structure determination of six of the platinum(IV) complexes, with emphasis on the preference of the hydrogen bond acceptor (O, pyridyl N, or Br atom), formation of monomer, dimer, or polymer, and self-recognition or self-discrimination in self-assembly. Complex 7 formed a monomer with the OH center dot center dot center dot N hydrogen bond, and complexes 2a and 10 formed racemic dimers by complementary hydrogen bonding with self-discrimination between CO2H or B(OH)(2) groups, respectively. Complexes 3, 4, and 9 formed polymers by intermolecular hydrogen bonding with self-recognition, with 4 containing OH center dot center dot center dot N and 3 and 9 containing OH center dot center dot center dot Br hydrogen bonds. It is concluded that there is no clear preference for the hydrogen bond acceptor group, and that the observed product depends also on the orientation of the hydrogen bond donor group