[Cr(dmbipy)(ox)2]−: a new bis-oxalato building block for metal assembling. Crystal structures and magnetic properties of XPh4[Cr(dmbipy)(ox)2]·5H2O (X = P and As), {Ba(H2O)2[Cr(dmbipy)(ox)2]2}n·17/2nH2O and {Ag(H2O)[Cr(dmbipy)(ox)2]}n·3nH2O

The synthesis, X-ray structure and variable-temperature magnetic study of new compounds of formula PPh4 [Cr(dmbipy)(ox)2 ]$5H2O (1), AsPh4 [Cr(dmbipy)(ox)2 ]$5H2O (2), {Ba(H2O)2[Cr(dmbipy)(ox)2]2}n$17/2nH2O (3) and {Ag(H2O)[Cr(dmbipy)(ox)2]}n$3nH2O (4) (PPh4 + ¼ tetraphenylphosphonium cation; AsPh4 + ¼ tetraphenylarsonium cation; dmbipy ¼ 4,4 0 -dimethyl- 2,2 0 -bipyridine; ox 2 ¼ oxalate dianion) are reported herein. The isomorphous compounds 1 and 2 are made up of discrete [Cr(dmbipy)(ox)2] anions, XPh4 + cations [X ¼ P (1) and As (2)] and uncoordinated water molecules. The chromium environment in 1 and 2 is distorted octahedral with Cr–O and Cr–N bond distances varying in the ranges 1.950(2)–1.9782(12) and 2.047(3)–2.0567(14) A˚ , respectively. The angles subtended at the chromium atom by the two bidentate oxalate ligands cover the range 82.58(10)– 83.11(5) , and they are somewhat greater than those concerning the chelating dmbipy [79.04(10) (1) and 79.24(5) (2)]. The [Cr(dmbipy)(ox)2] unit of 1 and 2 also occurs in 3 and 4 but it adopts different coordination modes. It acts as a chelating ligand through its two oxalate groups towards the divalent barium cations in 3 affording neutral chains with diamond-shaped units sharing the barium atoms, while the two other corners are occupied by two crystallographically independent chromium atoms. The barium atom in 3 is coordinated by eight oxygen atoms from four oxalate groups and two aqua ligands. The structure of 4 consists of neutral bimetallic layers where the [Cr(dmbipy)(ox)2] unit acts as a ligand towards the univalent silver(I) cation through its two oxalate groups, one of them being bidentate and the other bidentate/monodentate (outer). Each silver atom is six-coordinated with a water molecule and five oxygen atoms from three oxalate groups building a highly distorted octahedral environment. Magnetic susceptibility measurements for 1–4 in the temperature range 1.9– 300 K show the occurrence of weak ferro- (1 and 2) and antiferromagnetic (3 and 4) interactions which are mediated by p–p stacking between dmbipy ligands through the spin polarization mechanism. A comparative study of the potentiality of the [Cr(AA)(ox)2] unit (AA ¼ bidentate nitrogen donor) as a building bl

Cubane-type Mo3FeS44+,5+ complexes containing outer diphosphane ligands: ligand substitution reactions, spectroscopic studies, and electronic structure

A general protocol to access Mo3FeS44+ clusters selectively modified at the Fe coordination site is presented starting from the all-chlorine Mo3(FeCl)S4(dmpe)3Cl3 (1) [dmpe = 1,2-bis(dimethylphosphane-ethane)] cluster and tetrabutylammonium salts (n-Bu4NX) (X = CN–, N3–, and PhS–). Clusters Mo3(FeX)S4(dmpe)3Cl3 [X = CN– (2), N3– (3), and PhS– (4)] are prepared in high yield, and comparison of geometric and redox features upon modification of the coordination environment at the Fe site at parity of ligands at the Mo sites is also presented. The existence of the cubane-type Mo3FeS44+,5+ redox couple is demonstrated by cyclic voltammetry and for compound 1 by cluster synthesis and X-ray structure determinations. Ground states for the 1/1+ redox couple are evaluated on the basis of magnetic susceptibility measurements, electron paramagnetic resonance, and 57Fe Mössbauer spectroscopy aimed at providing an input of experimental data for electronic structure determination based on density functional theory calculations