Structures of one-dimensional PdII–PdIV mixed-valence complexes, [PdII L][PdIVCl2 L]Y 4 (Y= ClO4 and PF6), and their parent PdII and PdIV complexes, [PdII L](ClO4)2 and [PdIVCl2 L](NO3)2.HNO3.H2O, with 1,4,8,11-tetraazacyclotetradecane (L)

Unusual bridging of three nitrates with two bridgehead protons in an octaprotonated azacryptand

Structural analysis of the nitrate complex of a thiophene-based azacryptand suggests that three nitrates are bridged with two bridgehead protons which play the topological role of two transition metal ions in a classical Werner type coordination complex bridging three anions.

"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.