Preparation and Crystal Structure of 1,2-Bis(2,5-Dimethylthiophen-3-Yl)ethane-1,2-Dione

Abstract

Preparation, crystal structure and <sup>1</sup>H NMR spectrum of 1,2-bis(2,5-dimethylthiophen-3-yl)ethane-1,2-dione is reported. The title compound is a convenient starting material for the preparation of photochromic diarylethenes with various backbones.<br>

Hexacoordinated MIV (M=Ti, Zr, Hf) Tetrachlorido Complexes with Chelating Dithienylethane Based 1,2 Diketone Ligand – π‐Conjugation as Decisive Factor for Axial Chirality Mode

“…ally elongated with respect to the free ligand (1.224(2) Å in 1) [35] and a C7À C8 interatomic distance of 1.541(3) Å, which is in good agreement for a typical CÀ C single bond. The coordinated carbonyl groups exhibit a OÀ CÀ CÀ O torsion angle of 19.2°.…”

“…The thiophene rings in the coordinated ligand 1 reside in mutual syn alignment with respect to the CÀ H moiety and remain only slightly shifted from coplanarity with respect to the adjacent carbonyl group (torsion angles in 2: O2À C8À C9À C10 = 17.9°; O1À C7À C1À C2 = 26.6°). This remarkable structural feature may imply that the π-conjugation in ligand 1 is effective and gives rise to coplanarity (which can be also observed in the structure of the free ligand) [35] resulting in one possible chiral axis along the C7À C8 bond (Figure 1, Scheme 2 F, G). Consequently, two enantiomers (R and S) exist for complex 2 (Scheme 2 G).…”

“…The 1 H NMR chemical shifts of complex 2 remained similar with respect to free ligand 1 except for the methyl group adjacent to the 2-position of the thiophene ring (see SI, CH 3 group label a), which displays a more significant shift from 2.70 ppm to 2.96 ppm upon coordination of 1 to the titanium i P. Pakulski, D. Pinkowicz. [35] Figure In contrast, 13 C{ 1 H}-NMR spectra of 3 and 4 reveal 28 resonances indicating significantly reduced symmetry with respect to 2. Such an observation might be caused by partial dissociation [36] or a non-centrosymmetric arrangement of the diketone ligand in solution.…”