The crystal and molecular structure of tris( trans-dichloro( μ-(1,2-bis(3,5-dimethylpyrazol-1-yl)ethane- N, N′)) palladium( II)): a ‘molecular tricorn’

• Published in: Inorganica Chimica Acta 1995-03, Vol.230 (1), p.225-229
• Main Authors: Baker, Anthony T., Crass, Jeffrey K., Maniska, Mina, Craig, Donald C.
• Format: Article
• Language: English
• Subjects: Crystal structures; Palladium complexes; Polydentate ligand complexes; Pyrazolyl complexes; Trimeric complexes; Trimetallic macrocycle
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/0020-1693(94)04295-7

The ligand 1,2-bis(3,5-dimethylpyrazol-1-yl)ethane has been synthesized by the direct reaction of 1,2-dibromoethane and 3,5-dimethylpyrazole. The complex of this ligand with palladium(II) chloride has been prepared and the structure of its toluene solvate has been determined by X-ray crystallography. The compound crystallises in the triclinic space group P 1 , a = 11.088(5), b = 13.786(5), c = 21.169(9) A ̊ , α = 86.96(3), β = 81.02(3), γ = 73.32(3)° with Z = 2. Final residuals after least-squares refinement: R = 0.030, R w = 0.039. The compound has a trimeric structure which may be described as a ‘molecular tricorn’: the ligand bridges adjacent palladium centres, giving rise to a 21-membered trimetallic macrocycle. The overall structure closely approximates D 3 symmetry with approximate two-fold axes passing through each palladium atom and the centre of the 1,2-ethanediyl moiety opposite. An interesting feature of the structure is the close approach of several hydrogen atoms from the 1,2-ethanediyl groups to each palladium centre; these interactions are thought to be close-packing rather than agostic bonds.