Abstract
Bis(benzene-1,2-diolato-κ2 O,O')bis-(dimethyl sulfoxide-κO)titanium(IV), [Ti(C6H4O2)2(C2H6OS)2], crystallizes with two crystallographically independent mol-ecules in the space group P21/c emulating ortho-rhom-bic Pbca symmetry (β = 90.0445 (9)°]. The two mol-ecules are related by pseudo-glide symmetry, broken by modulation of each one catecholate and dimethyl sulfoxide (DMSO) ligand. Twinning by pseudomerohedry was observed [twin ratio 0.5499 (7):0.4401 (7)]. Complex 3 was obtained by heating of diprotonated titanium tris-catecholate precursor 2H in DMSO, by formal displacement of a catechol mol-ecule by two DMSO mol-ecules. Complex 3 is just the second heteroleptic, mono-nuclear, neutral bis-catecholate complex with TiO6 metal coordination, the only other one being its bis-DMF analogue 6. The two mol-ecules of 3 exhibit a distorted octa-hedral geometry. The geometry and distortions from ideal symmetry of 3 are discussed and compared to 6 and to cationic tris-catecholate titanium complexes.
Highlights
The dianion of catechol (1,2-dihydroxybenzene, CatH, 1) is a bidentate, dianionic and non-innocent O,O-chelating agent with a high affinity for HSAB hard-metal ions, i.e., ions of high oxidation states or high charge-to-metal-ionradius ratios (Pierpont & Lange, 1994; Kaim & Schwederski, 2010)
Titanium catecholate complexes have found various uses: Titanium triscatecholate complexes of the alkaline earth metals were utilized as molecular precursors to a number of Published under a CC BY 4.0 licence Acta Cryst. (2022)
One protonated catecholate ligand of the starting triscatcholate complex 2H was exchanged for two DMSO molecules, coordinating through their oxygen atoms in adjacent positions, forming a neutral, heteroleptic, mononuclear octahedral complex
Summary
The dianion of catechol (1,2-dihydroxybenzene, CatH, 1) is a bidentate, dianionic and non-innocent O,O-chelating agent with a high affinity for HSAB hard-metal ions, i.e., ions of high oxidation states or high charge-to-metal-ionradius ratios (Pierpont & Lange, 1994; Kaim & Schwederski, 2010). Structural commentary The title complex 3, having solution C2 symmetry, crystallizes as a racemic mixture with two crystallographically independent molecules in the monoclinic space group P21/c (Fig. 3) For both molecules, the solution C2 symmetry is broken in the solid state, and the Ti atoms are each bonded to two chelating catecholate and two monodentate O-coordinated dimethylsulfoxide ligands. A similar overlay based on only the titanium and oxygen atoms gives a much smaller value of only 0.056 A , indicating that the main differences between the two complexes is rooted in the Figure 6 View of 3 down the c axis, showing the modulation by pseudo-Pbca symmetry. In addition to the variations in molecular geometry seen in the molecule overlay, a very slight rotation of the entire complex is observed
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