Synthesis and crystal structures of silver(I) and copper(II) complexes with p-xylylene-bridged bipyrazolyl ligands

Abstract

Two semi-rigid bipyrazolyl ligands, namely 2,3,5,6-tetramethyl-1,4-bis[(3 0 ,5 0 -dimethyl-1H -pyrazol-4 0 -yl)methylene]benzene (H 2 L) and 2,3,5,6-tetramethyl-1,4-bis[(3 0 ,5 0 -diphenyl-1H -pyrazol-4 0 -yl)methylene]benzene (H 2 L 0 ), and their Ag(I) and Cu(II) complexes have been prepared and structurally characterized by means of X-ray analysis. In the structures of the metal complexes, namely [Ag 2 (H 2 L) 2 ](BF 4 ) 2 Á2H 2 O (1), [Ag(H 2 L)(NO 3 )] n (2), [Cu 2 (H 2 L) 4 (SO 4 ) 2 ]Á11H 2 O (3), and {[Ag(H 2 L 0 )]BF 4 } n (4), the bipyrazoles act as bridging ligands to connect two metal atoms. Complexes 2 and 4 exhibit 1-D polymeric structures, while 1 and 3 are discrete molecules with a rectangular dimer or tetragonal prismatic shapes, respectively. Two different conformations, namely cis and trans, have been observed for these bipyrazolyl ligands.

Investigating the Structural Features and Spectroscopic Properties of Bis(tetrazolato)-Based Coordination Polymers

“…By comparing the geometrical features of the ligand in the crystal structure of the three CPs, ,, a certain similarity of the conformational parameters can be observed. Together with H 2 BDMPX and H 2 DMPMB, also 4,4′-((2,3,5,6-tetramethyl-1,4-phenylene)­bis­(methylene))­bis­(3,5-dimethyl-1 H -pyrazole) (Scheme S1 of the Supporting Information) and 4,4′-((2,3,5,6-tetramethyl-1,4-phenylene)­bis­(methylene))­bis­(3,5-diphenyl-1 H -pyrazole) (Scheme S1) show an anti conformation of the pyrazolyl substituents in position para on the central hexa-atomic ring. Moreover, a search in the Cambridge Structural Database (v 1.18) for organics containing fragments of the kind depicted in Scheme S2 (Supporting Information) revealed that, when the fragment is not involved in extended fused rings or cyclic oligomers, an (ideal or not) anti conformation is adopted in all of the cases.…”