Element misidentification in X-ray crystallography: a reassessment of the [MCl2(diazadiene)] (M = Cr, Mo, W) series

Rhenium versus cadmium: an alternative structure for a thermally stable cadmium carbonyl compound

An alternative description is provided for the previously reported novel tetranuclear cadmium carbonyl compound, [Cd(CO)3(C6H3Cl)]4. Specifically, consideration of single crystal X-ray diffraction data indicates that the compound is better formulated as the rhenium compound, [Re(CO)3(C4N2H3S)]4. Furthermore, density functional theory calculations predict that, if it were to exist, [Cd(CO)3(C6H3Cl)]4 would have a very different structure to that reported. While it is well known that X-ray diffraction may not reliably distinguish between atoms of similar atomic number (e.g. N/C and Cl/S), it is not generally recognized that two atoms with very different atomic numbers could be misassigned. The misidentification of two elements as diverse as Re and Cd (ΔZ = 27) is unexpected and serves as an important caveat for structure determinations.

Electronic and Geometric Structures of Paramagnetic Diazadiene Complexes of Lithium and Sodium

The electronic and molecular structures of the lithium and sodium complexes of 1,4-bis(2,6-diisopropylphenyl)-2,3-dimethyl-1,4-diazabutadiene (Me2DADDipp) were fully characterized by using a multi-frequency electron paramagnetic resonance (EPR) spectroscopy approach and crystallography, together with density functional theory (DFT) calculations. EPR measurements, using T1 relaxation-time-filtered pulse EPR spectroscopy, revealed the diagonal elements of the A and g tensors for the metal and ligand sites. It was found that the central metals in the lithium complexes had sizable contributions to the SOMO, whereas this contribution was less strongly observed for the sodium complex. Such strong contributions were attributed to structural specifications (e.g. geometrical data and atomic size) rather than electronic effects.

Playing with Pearson's concept: orthogonally functionalized 1,4-diaza-1,3-butadienes leading to heterobinuclear complexes

By reacting 1,2-diketones and ortho- diphenylphosphinoyl aniline in the presence of zinc(ii) as a templating agent, cationic zinc(ii) complexes of novel phosphine oxide functionalized 1,4-diaza-1,3-butadiene ligands are acessible. Herein the zinc(ii) site is bound to all four donor atoms of the ligand. Depending on the flexibility of the 1,4-diaza-1,3-butadiene backbone, the bonds to zinc(ii) from the 1,4-diaza-1,3-butadiene donors can be broken. Reaction with oxalate cleaves the zinc(ii) coordination completely and makes accessible the free ligands possessing orthogonal (N,N: soft; O,O: hard) sets of donor sites. This allows for the specific coordination of soft and hard Lewis acids and thus for the generation of heterobimetallic complexes, here exemplarily shown for the combination of palladium(ii) (soft) and zinc(ii) (hard) centres.

Crystal structure of unsymmetrical α-di-imine palladium(II) complex cis-[{ArN=C(Me)-(Et)C=NAr}PdCl2] [Ar = 2,6-(iPr)2C6H3]

The unsymmetrical α-di-imine ligand N-{2-[2,6-bis-(propan-2-yl)phenylimino]pentan-3-yl-idene}-2,6-bis-(propan-2-yl)aniline, [ArN=C(Me)-(Et)C=NAr] [Ar = 2,6-(iPr)2C6H3], (I), and the corresponding palladium complex, cis-(N-{2-[2,6-bis-(propan-2-yl)phenylimino]pentan-3-yl-idene}-2,6-bis-(propan-2-yl)aniline)di-chlor-ido-palladium(II) 1,2-di-chloro-ethane monosolvate, [PdCl2(C29H42N2)]·C2H4Cl2 or cis[PdCl2{I}], (II), have been synthesized and characterized. The crystal and mol-ecular structure of the palladium(II) complex have been established by single-crystal X-ray diffraction. The compound crystallized along with a 1,2-di-chloro-ethane solvent of crystallization. The coordination plane of the PdII atom shows a slight tetra-hedral distortion from square-planar, as indicated by the dihedral angle between the PdCl2 and PdN2 planes of 4.19 (8)°. The chelate ring is folded along the N⋯N vector by 7.1 (1)°.