Cr(AA)(C 2O 4) 2] − and [Cu(bpca)] + as building blocks in designing new oxalato-bridged Cr IIICu II compounds [AA=2,2′-bipyridine and 1,10-phenanthroline; bpca=bis(2-pyridylcarbonyl)amide anion

Abstract

The monouclear complex PPh 4[Cr(bipy)(ox) 2]·H 2O ( 1) and the heterodinuclear compounds [Cu(bpca)(H 2O)Cr(bipy)(ox) 2]·2.5H 2O ( 2) and [Cu(bpca)(H 2O)Cr(phen)(ox) 2]·2H 2O ( 3) [PPh 4 +=tetraphenylphosphonium cation, bpca=bis(2-pyridylcarbonyl)amide anion, ox=oxalate dianion, bipy=2,2′-bipyridine and phen=1,10-phenanthroline] have been synthesized and characterized by single-crystal X-ray diffraction. Discrete [Cr(bipy)(ox) 2] − mononuclear anions and tetraphenylphosphonium cations are present in 1 whereas the structures of 2 and 3 are made up neutral oxalato-bridged bimetallic Cr IIICu II units. The chromium environment is distorted octahedral in the three complexes: two nitrogen atoms from a bidentate bipy ( 1 and 2) or phen ( 3) ligand and four oxygen atoms from two oxalate groups ( 1– 3) build the coordination polyhedron around the chromium atom. The CrN(bipy) [2.055(3) and 2.078(3) Å for 1 and and 2.060(3) and 2.066(3) Å for 2] and CrN(phen) bond lengths [2.056(5) and 2.069(5) Å ( 3)] are somewhat longer than the CrO(ox) ones [values in the ranges 1.944(2)–1.955(2) ( 1), 1.948(2)–1.960(2) ( 2) and 1.945(4)–1.953(4) Å ( 3)]. The copper atom in 2 and 3 exhibits a distorted square-pyramidal surrounding: three bpca-nitrogen atoms [values of the CuN(bpca) bonds in the ranges 1.922(3)–2.017(3) ( 2) and 1.918(5)–2.004(6) Å ( 3)] and a water molecule [CuO w=1.952(3) ( 2) and 1.952(5) Å ( 3)] define the equatorial positions whereas an oxalate-oxygen atom occupies the axial site [CuO ox=2.253(2) ( 2) and 2.325(4) Å ( 3)]. The oxalate bridge in 2 and 3 exhibits a unusual bidentate/monodentate coordination mode, the metalmetal separation across this bridge being 5.283(1) ( 2) and 5.407(1) Å ( 3). Magnetic susceptibility measurements of 1– 3 in the temperature range 1.9–290 K reveal a Curie law behavior for the three complexes. The preparation of bimetallic systems by using [Cr(AA)(ox) 2] − (AA=α-diimine type ligand) as a complex ligand towards coordinatively unsaturated metal complexes is analyzed and discussed.