Platinum metal complexes of hexa-aza macrocycles: Synthesis and single crystal X-ray structure of [Pd 2Cl 2(Me 6[18]aneN 6)](PF 6) 2 (Me 6[18]aneN 6  1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane)

Abstract

Reaction of PdCl 2(NCPh) 2 with 0.5 molar equivalents of Me 6[18]aneN 6 in refluxing MeCN affords initially the binuclear complex [Pd 2Cl 2(Me 6[18]aneN 6)]Cl 2. Addition of H 2O redissolves this orange precipitate giving a clear orange solution from which the complex [Pd 2Cl 2(Me 6[18]aneN 6)](PF 6) 2 can be isolated in high yield following addition of excess aqueous NH 4PF 6. 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 N 3Cl donor set with PdN(1) = 2.113(5), PdN(4) = 2.035(5), PdN(7) = 2.105(5) Å and PdCl = 2.3081 (16) Å. 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 N 3Cl donor set away from square planarity. The Pd ⋯ Pd distance of 4.001(1) Å indicates that the palladium(II) ions are non-interacting.