Crystal structure of tris(quinoxaline-2,3-dithiolato)molybdate(V); a distorted trigonal prismatic complex

Synthesis and Structures of Bis(dithiolene)molybdenum Complexes Related to the Active Sites of the DMSO Reductase Enzyme Family

“…Coordination geometries ranging between octahedral and trigonal prismatic are, of course, a common structural feature of tris(dithiolene) complexes. Pertinent examples include [Mo(S 2 C 2 H 2 ) 3 ], [Mo(bdt) 3 ], [Mo(S 2 C 2 (COOMe) 2 ) 3 ] 2- , [Mo(qdt) 3 ], -,-,, and [Mo(mnt) 3 ] 2- …”

Synthesis, characterization, and crystal structures of molybdenum complexes of unsymmetrical electron-poor dithiolene ligands

“…Moreover, the monoanion spectra show multiple absorption peaks and much less closely resemble those of the corresponding dianions than is the case for the olefinic species [7,9]. The qualitative differences in monoanion spectra between these alkyl-substituted olefinic and aromatic classes of compounds are paralleled by differences in structure, with approximately D 3h ( ~ 0 for dt = S 2 C 2 Me 2 [14]) and D 3 ( > 30° for dt = S 2 C 6 H 4-x R x [7,68,82]; 14.6° for S 2 C 8 H 4 N 2 [83]) geometries, respectively, being found in crystal structures, in electron-spin resonance (ESR) spectra [9], and in sulfur K-edge X-ray absorption spectroscopy; DFT calculations suggest these differences are related to a difference in the ordering of the frontier orbitals, resulting in primarily ligand-and metal-based semi-occupied molecular orbitals (SOMOs) for Mo(dt) 3 complexes with olefinic and aromatic ligands, respectively [8,9]. The Mo(S 2 C 2 Ph 2 ) 3 n series shows somewhat intermediate behavior in that the monoanion absorption and ESR spectra are qualitatively similar to that of other olefinic Mo(dt) 3 spectra, but absorptivities, especially for the neutral compound, are much higher, and the main low-energy dianion peak is slightly blue-shifted from that of the neutral compound; moreover, a crystal structure shows an anion significantly twisted from ideal trigonal prismatic geometry ( = 18.0°) [9].…”

The Electronic Structure and Spectroscopy of Metallo‐Dithiolene Complexes

“…Interestingly, variable-temperature absorption data for the oxo-molybdenum(dithiolene) complex [MoO-(quinoxaline-2,3-dithiolate) 2 ] À reveals the highly thermochromic nature of this compound. Although the observed thermochromism may be explained within the context of valence tautomerism, a more general description has recently been put forth, namely, thermally driven intramolecular CT, as this more accurately reflects the highly covalent nature of the MoÀ ÀS bonds and extreme noninnocence of the quinoxaline-2,3-dithiolate ligand (110,250,(329)(330)(331)405 À is highly thermochromic, and turns dark orange almost instantaneously upon lowering the temperature. The observed thermochromism is readily evident in the variable temperature electronic absorption spectra presented in Fig.…”

“…In particular, Kirk and co-workers (23) showed that RR spectroscopy is an extremely useful tool in making band assignments in oxo-molybdenum-mono(-dithiolenes). Specifically, the important c xy in-plane covalency in oxo-metal-mono(dithiolenes) suggests that this interaction, in concert with ligand p-delocalization, plays a fundamental role in the unusual ability of these ligands to support multiple redox states (86,87,110,281,(327)(328)(329)(330)(331) and to electronically buffer (16) metal centers to the large changes in charge that accompany these redox changes. Another role hypothesized for this in-plane covalency is to facilitate electron transfer in pyranopterin molybdenum and tungsten enzymes (20-24, 106, 110).…”