Sulfur Monoxide as 4-Electron Bridge-Ligand in the Complex [{(η5-C5H5)(CO)2Mn}2SO]

Stepwise Sulfite Reduction on a Dinuclear Ruthenium Complex Leading to Hydrogen Sulfide

Sulfite reduction by dissimilatory sulfite reductases is a key process in the global sulfur cycle. Sulfite reductases catalyze the 6e- reduction of SO32- to H2S using eight protons (SO32- + 8H+ + 6e- → H2S + 3H2O). However, detailed research into the reductive conversion of sulfite on transition-metal-based complexes remains unexplored. As part of our ongoing research into reproducing the function of reductases using dinuclear ruthenium complex {(TpRu)2(μ-Cl)(μ-pz)} (Tp = HB(pyrazolyl)3), we have targeted the function of sulfite reductase. The isolation of a key SO-bridged complex, followed by a sulfite-bridged complex, eventually resulted in a stepwise sulfite reduction. The reduction of a sulfite to a sulfur monoxide using 4H+ and 4e-, which was followed by conversion of the sulfur monoxide to a disulfide with concomitant consumption of 2H+ and 2e-, proceeded on the same platform. Finally, the production of H2S from the disulfide-bridged complex was achieved.

A sulfur monoxide complex of platinum fluoride with a positively charged ligand

A sulfur monoxide complex of platinum fluoride in the form of PtF₂(η¹-SO) was generated via the isomerization of a molecular complex Pt(SOF₂) in cryogenic matrixes under UV-vis irradiation. The infrared absorptions observed at 1205.4, 619.8 and 594.9 cm^-1 are assigned to the S-O, antisymmetric and symmetric F-Pt-F stretching vibrations of the PtF₂(η¹-SO) complex, which possesses nonplanar C_s symmetry with a singlet ground state according to density functional theory calculations. The experimental vibrational frequency and computed distance (1.449 Å) of the SO ligand indicate that the SO ligand features a positively charged character, which is further confirmed by natural bond orbital analysis and Mayer bond order. Such character is completely different from that for early transition metal-SO complexes and dioxygen complexes of platinum. Formation of the PtF₂(η¹-SO) complex was found to occur via the consecutive transfer of the two fluorine atoms from SOF₂ to Pt in the sulfur bound Pt(SOF₂) complex, which involves a series of intermediates on the basis of the mechanism study at the B3LYP level. Although the whole process is hindered by the large energy barrier encountered during the transfer of the first fluorine atom, UV-vis irradiation can provide sufficient energy to surmount this barrier and facilitates the formation of the nonplanar PtF₂(η¹-SO) complex stabilized in matrix.

Strong Be-Be bonds in double-aromatic bridged Be2(μ-SO) molecules

A bridged Be2(μ-SO) molecule is formed by stabilizing the Be2 dimer using a SO ligand. In this molecule, which is thermodynamically stable, the Be2 moiety behaves as an efficient electron donor toward the SO fragment. The ionic character of Be2δ+ and SOδ- in this molecule is confirmed by NBO analysis. Energy decomposition analysis shows that the strongest attractive interactions in this molecule are the polarization and exchange interactions. Also, Adaptive Natural Density Partitioning (AdNDP) analysis indicates the stability of this molecule, which could be due to the double-aromatic character of this system. Therefore, it seems that the title molecule could be experimentally detected.