MONODENTATE AND BIDENTATE COORDINATION OF N,N-DIALKYLATED 1,3-PROPANEDIAMINES TO COBALT(III) - A STRUCTURAL AND SPECTROSCOPIC STUDY

Cationic bis-pentane-2,4-dionato (acac(-)) complexes [Co(acac)(2)(L)]C lO4, where L=1,3-propanediamine (tn), N,N-dimethyl-1,3-propanediamine (dmp) or N,N'-diethyl-1,3-propanediamine (bep) were prepared. Coordina tion of the nitrogen mustard N,N-bis(2-chloroethyl)-1,3-propanediamine (dcp) was not successful. Reaction of the steric-mimicking but non-al kylating diamine N,N-diethyl-1,3-propanediamine (dep) gave three produ cts: [Co(acac)(2)(dep)]ClO4.H2O (4), trans-[Co(acac)(2)(Hdep)(2)](ClO4 )(3) (5) and cis-[Co(acac)(2)(Hdep)(2)](ClO4)(3) (6); the latter two c omplexes contain two monodentate protonated dep ligands. Comparison of product yields with those of complexes based on the related 1,2-ethyl enediamine ligands indicate significant effects of six- versus five-me mbered chelate ring stability and pendant alkyl chain length at one ni trogen. The complexes were characterised by UV-Vis, H-1 and C-13{H-1} NMR and high-resolution (FAB(+)) mass spectroscopy. The crystal struct ures of complexes 4 and 5 were determined by single crystal X-ray diff raction studies. Complex 4 crystallises in the monoclinic system, spac e group P2(1)/c, formula C17H32ClCoN2O8, M=486.83, a=12.0270(10), b=12 .113(6), c=15.618(2) Angstrom, beta=104.460(10)degrees, Z=4, D-c=1.468 g cm(-3). Complex 5 crystallises in the monoclinic system, space grou p P2(1)/c, formula C24H52Cl3CoN4O16, M=817.98, a=12.922(4), b=13.039(3 ), c=22.641(2) Angstrom, beta=101.33(2)degrees, Z=4, D-c=1.447 g cm(-3 ).