Substitution reactions of tetrahydrofuran in [Cr(thf)3Cl3] with mono and bidentate N-donor ligands: X-ray crystal structures of [Cr(bipy)(OH2)Cl3] and [HpyNH2][Cr(bipy)Cl4]

Substitution of thf ligands in [Cr(thf)3Cl3] and [Cr(thf)2(OH2)Cl3] was investigated. 2,2′-Bipyridine (bipy) was reacted with [Cr(thf)3Cl3] to form [Cr(bipy)(thf)Cl3] (1), which was subsequently reacted with water to give [Cr(bipy)(OH2)Cl3] (2). Reaction of 1 with acetonitrile (CH3CN), pyridine (py) and pyridine derivatives to form [Cr(bipy)(L)Cl3] (L = CH3CN 3, py 4 and 4-pyR with R = NH25, But6 and Ph 7). In addition, the substitution of bipy in [Cr(thf)3Cl3] was followed by 1H NMR spectroscopy at room temperature, which showed completion of the reaction in ca. 100 min. Complex 2 was characterised by single crystal X-ray diffraction. The theoretical powder diffraction pattern of 2 was compared to the experimentally obtained powder X-ray diffraction pattern, and shows excellent agreement. The dimer [Cr2(bipy)2Cl4(μ-Cl)2] was cleaved asymmetrically to give the anionic complex [Cr(bipy)Cl4]− (8) and [Cr(bipy)2Cl2]+ (9). Complexes 8 and 9 were characterised by single crystal X-ray diffraction.

Graphical abstractSubstitution of thf ligands in [Cr(thf)3Cl3] and [Cr(thf)2(OH2)Cl3] by pyridine derivatives was investigated. Cleaving of the dimeric dichromium(III) intermediate containing bridging chloro ligands can lead to symmetrical (type A) or asymmetrical (type B) cleaved products. Examples of both these types of complexes have been isolated and structurally characterized.Figure optionsDownload full-size imageDownload as PowerPoint slide