Synthesis and crystal structure of trichromium metal string complex

Abstract

The synthesis, crystal structures and molecular packing of the three trichromium metal string complexes [Cr 3(dpa) 4Cl(OC 2H 5)]OH·C 2H 5OC 2H 5·2.5H 2O ( 1), [Cr 3(dpa) 4(OH) 2]ClO 4·3H 2O ( 2) and [Cr 3(dpa) 4F 2Na(H 2O)BF 4]BF 4·CH 3OH ( 3) (dpa −=bis(2-pyridyl)amido) have been studied. The crystal structure data for 1: C 46H 54ClCr 3N 12O 5.5, monoclinic, P2 1 / c, a=19.9998(4) Å, b=15.9756(3) Å, c=16.9943(3) Å, β=114.0548(8)°, Z=4, R 1=0.0791, wR 2=0.1927; for 2: C 40H 40ClCr 3N 12O 9, orthogonal, Pna2 1 , a=18.3373(2) Å, b=16.8220(2) Å, c=14.0268(2) Å, Z=4, R 1=0.0683, wR 2=0.1804; for 3: C 41H 38B 2Cr 3F 10N 12NaO 2, monoclinic, P2 1/n , a=12.3902(1) Å, b=16.2081(2) Å, c=23.4119(3) Å, β=98.8725(6)°, Z=4, R 1=0.0670, wR 2=0.1568. The structure data were collected using graphite monochromated molybdenum Kα radiation and refined using full-matrix least square techniques on F 2. The magnetic property of complex 1 was carried out on polycrystalline samples with a SQUID magnetometer. The IR, FAB-MS mass spectra of all complexes were also measured. In the three complexes, trichromium metal string complexes can be considered as mini-1D asymmetrically chains since the distance between the two axial ligands is around 1 nm. The types of hydrogen bonding in three complexes are C–H⋯O, C–H⋯Cl, C–H⋯F and O–H⋯O). 1 and 2 have a one-dimensional double-chain structures. 1 is a rare example of three-dimensional novel sandwich structure. In 3, one of the axial ligand, F − acts as a bridge ligand to link the sodium ion to the Cr 3 axis with a bond angle of Cr(1)–F(1)–Na in 169.90(13)°. It can be considered as a metal string complex with an extra long axis.