PLATINUM METAL-COMPLEXES OF HEXA-AZA MACROCYCLES - SYNTHESIS AND SINGLE-CRYSTAL X-RAY STRUCTURE OF [PD2CL2(ME6[18]ANEN6)](PF6)2 (ME6[18]ANEN6=1,4,7,10,13,16-HEXAMETHYL-1,4,7,10,13,16-HEXAAZACYCLOOCTADECANE)

Reaction of PdCl2(NCPh)2 with 0.5 molar equivalents of Me6[18]aneN6 in refluxing MeCN affords initially the binuclear complex [Pd2Cl2(Me6[18]aneN6)]Cl2. Addition of H2O redissolves this orange precipitate giving a clear orange solution from which the complex [Pd2Cl2(Me6[18]aneN6)](PF6)2 can be isolated in high yield following addition of excess aqueous NH4PF6. A single crystal structure determination of the complex shows the binuclear cation lying across an inversion centre, with each palladium(II) ion coordinated via an N3Cl donor set with Pd-N(1) = 2.113(5), Pd-N(4) = 2.035(5), Pd-N(7) = 2.108(5)angstrom and Pd-Cl = 2.3081(16)angstrom. Thus the hexa-aza macrocycle is bound through a meridional arrangement of three N-donors to each metal ion giving an overall distorted square planar stereochemistry. The restricted bite angle of the five-membered chelate rings within the crown leads to bond angle strain and a significant tetrahedral distortion of the N3Cl donor set away from square planarity. The Pd ... Pd distance of 4.001(1)angstrom indicates that the palladium(II) ions are non-interacting.