Binuclear Cyclopentadienylmetal Methylene Sulfur Dioxide Complexes of Rhodium and Iridium Related to a Photochromic Metal Dithionite Complex

Abstract

The photochromic dithionite complex Cp*Rh(μ-CH)(μ-OSSO) (Cp* = η-MeC) is of interest because it undergoes an unusual fully reversible unimolecular photochemical rearrangement to the isodithionite complex Cp*Rh(μ-CH)(μ-OSOSO). In order to obtain more insight into these systems, a comprehensive density functional theory study has been carried out on isomeric CpM(CH)(SO) (M = Rh, Ir) derivatives. The experimentally observed rhodium complexes with coupled sulfur dioxide (SO) units to give dithionite or isodithionite ligands are surprisingly high-energy kinetic isomers in our analysis, reflecting the need for dithionite rather than SO for their synthesis. Many isomeric structures containing two separate SO ligands are found to lie at lower energies than these dithionite and isodithionite complexes. In the lowest-energy CpM(CH)(SO) isomers, the two methylene groups couple to form an ethylene ligand that can be either terminal or bridging. In slightly higher energy structures, a formal hydrogen shift is predicted to occur within the ethylene ligand to give a methylcarbene CHCH ligand. Isomers with a bridging methylcarbene ligand are energetically preferred over isomers with a terminal methylcarbene ligand. Generation of the lower-energy CpRh(CH)(SO) isomers containing separate SO ligands should be achievable through reactions of SO with more highly reduced cyclopentadienylrhodium methylene complexes such as Cp*Rh(μ-CH).

Immobilization of PdCl2 on a Natural Asphalt Sulfonic Acid Network for C−N and C−O bonds Formation

“…Actually, it plays as a network in which holes aim at trapping PdCl 2 via coordination of Pd(II) by sulfur. [24,25] The FT-IR spectra of natural asphalt, natural asphalt sulfonic acid (NAS) and NAS@PdCl 2 network, were demonstrated in the range of 400-4000 cm À 1 . Figure 1 (b) shows a symmetric and asymmetric stretching vibrations of S=O in the SO 3 H at 615 cm À 1 and 900-1200 cm À 1 in natural asphalt sulfonic acid(NAS).…”

“…As shown in shceme 1, we believe that sulfonic acid branches form many holes by hydrogen bonding and dipolar interactions. Actually, it plays as a network in which holes aim at trapping PdCl 2 via coordination of Pd(II) by sulfur [24,25] …”

Schematic Design of Metal-Free NHC-Mediated Sequestering and Complete Conversion of SO2 to Thiocarbonyl S-Oxide Derivatives at Room Temperature

“…The toxic SO 2 easily reacts with the transition metal to form stable coordination complexes through the oxygen atom, sulfur atom, or the π bond of SO acting as a Lewis base. − On the other hand, SO 2 acts as a Lewis acid when it reacts with carbene as it is amphoteric in nature . Due to its affluent reactivity, SO 2 is also activated by complexes of the f-block elements .…”

“…16−18 On the other hand, SO 2 acts as a Lewis acid when it reacts with carbene as it is amphoteric in nature. 17 Due to its affluent reactivity, SO 2 is also activated by complexes of the f-block elements. 18 When SO 2 reacts with metals, in most cases it is inserted into M−C or M−O bonds.…”

Quenching of the phosphorescence of thermally reversible photochromic naphthopyran Re(i) complexes initiated by either visible or ultraviolet radiation

“…2 Additionally, the photochromic reaction has been reported to modulate and/or switch the luminescence of the transition metal complexes. Photoresponsive ligands, activated by UV irradiation, employed to date include dithienylethenes, 3 azobenzenes, 4 spirooxazines, 5 viologens 6 and a selection of metal centres including Co, 7 Zn, 8 Mo, 9 Ru, 10 Rh, 11 Pd/Pt, 12 Ag, 13 Cd, 14 Re, 15 Ir, 16 Au, 17 have been investigated. Thermally reversible, UV activated photochromic naphthopyrans, whilst established in ophthalmic sunlenses and variable transmission filters, 18 remain unexplored as photoresponsive ligands to modulate the luminescence of TM complexes.…”