"Swollen" Macrocycles: Palladium(II)-Directed Template Syntheses of Pendant-Arm 14-, 16-, and 18-Membered Macrocycles.
The bis(diamine)palladium(II) cations (diamine = ethane-1,2-diamine, propane-1,3-diamine, or butane-1,4-diamine) all undergo condensation reactions with formaldehyde and nitroethane to produce macromonocycles where each pair of cis-disposed primary amines has been converted to a -NH-CH(2)-C(CH(3))(NO(2))-CH(2)-NH- strap. The 14-membered-ring macrocycle has been previously prepared by condensation around copper(II) and nickel(II), but this does not permit synthesis of the larger ring macrocycles. The macrocyclic complex (6,13-dimethyl-6, 13-dinitro-1,4,8,11-tetraazacyclotetradecane)palladium(II) perchlorate crystallizes in the triclinic space group P&onemacr;, a = 8.105(3) Å, b = 8.370(2) Å, c = 9.437(4) Å, alpha = 69.04(3) degrees, beta = 68.60(3), gamma = 71.53(3) degrees. Complexes of the 16- and 18-membered macrocycles (3,11-dimethyl-3,11-dinitro-1,5,9,13-tetraazacyclohexadecane)palladium(II) perchlorate and (3,12-dimethyl-3,12-dinitro-1,5,10,14-tetraaazacyclooctadecane)palladium(II) perchlorate crystallize in the monoclinic space group P2(1)/c, with a = 8.391(2) Å, b = 12.816(3) Å, c = 23.925(9) Å, and beta = 93.18(2) degrees, and the triclinic space group P&onemacr;, with a = 7.746(5) Å, b = 9.912(5) Å, c = 18.96(2) Å, alpha = 91.76(6) degrees, beta = 101.73(7) degrees, and gamma = 112.83(5) degrees respectively. The larger macrocycles are "swollen" by incorporating longer methylene chains, "swelling" leading to an increase in Pd-N distance and in tetrahedral distortion, with the dominant geometric isomer apparently changing with macrocycle size from anti-disposed nitro pendants (14-membered) to the syn isomer (16-, 18-membered). An irreversible Pd(II/IV) oxidation occurs at ca +1 V (vs Ag/AgCl), varying slightly with ring size, with a multi-electron nitro group reduction observed near -0.8 V in each case. Electronic spectra also vary slightly with ring size.
Rossignoli
Monica
M
Department of Chemistry, The University of Newcastle, Callaghan, NSW 2308, Australia, and School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.
Allen
Christine C.
CC
Hambley
Trevor W.
TW
Lawrance
Geoffrey A.
GA
Maeder
Marcel
M