Reduction of Rhodium(III) Porphyrin Hydroxide to Rhodium(II) Porphyrin

Abstract

Highly reactive rhodium(III) porphyrin hydroxides were formed from the ligand substitution of rhodium porphyrin halides in benzene and were rapidly reduced to rhodium(II) porphyrins and hydrogen peroxide. Thus hydroxide acted as the reducing agent. Oxidative addition of rhodium(II) porphyrin with hydrogen peroxide proceeded rapidly at room temperature to give back rhodium(III) porphyrin hydroxides. Rhodium(II) porphyrins and H2O2 therefore were thermally reversible with rhodium porphyrin hydroxides.

Solution Catalytic Cycle of Incompatible Steps for Ambient Air Oxidation of Methane to Methanol

“…This suggests that reactive oxygen species other than hydroperoxide, such as superoxide, likely contribute to the oxidation of 1b and the formation of CH 3 OH. As hydroperoxide is known to react reversibly with 1a in a similar fashion as O 2 , 30 a spatial distribution of reactive oxygen species generated by the O 2 also contributes to the observed reactivity. Interestingly, no other C 1 or C 2 liquid products were observed, and the generation of CO or CO 2 was not detectable in the outgas by GC-MS (Figure S14).…”

Alkylation of Rhodium Porphyrin Complexes with Primary Alcohols under Basic Conditions

“…Then, (PhCN)­Rh I (ttp) − attacks the carbonyl carbon of benzaldehyde, which leads to the α-hydroxyalkyl complex Rh III (ttp)­CH­(OH)­Ph upon protonation. , Rh III (ttp)­CH­(OH)­Ph is then reduced by Rh III (ttp)H to afford the final product Rh III (ttp)­CH 2 Ph ( 3a ) and Rh III (ttp)­OH, likely via σ-bond metathesis. Rh III (ttp)­OH then undergoes rapid reductive dimerization to produce [Rh II (ttp)] 2 and H 2 O 2 at 120 °C . Under basic conditions and polar medium, K 2 CO 3 promotes the conversion of [Rh II (ttp)] 2 to Rh I (ttp) − K + anion and Rh III (ttp)­CO 3 K, which can participate in the C–O cleavage reaction.…”

“…Organometallics Article DOI: 10.1021/acs.organomet.9b00454 Organometallics 2019, 38, 3662−3670Rh III (ttp)OH, likely via σ-bond metathesis. Rh III (ttp)OH then undergoes rapid reductive dimerization to produce [Rh II (ttp)] 2 and H 2 O 2 at 120 °C 23. Under basic conditions and polar medium, K 2 CO 3 promotes the conversion of [Rh II (ttp)] 2 to Rh I (ttp) − K + anion and Rh III (ttp)CO 3 K,24 which can participate in the C−O cleavage reaction.…”

Synthesis of RhIII Anilido, Hydroxide, and Methoxide Complexes

“…For instance, Milstein and co‐workers reported the stoichiometric generation of H 2 and O 2 from H 2 O by successive thermal and photochemical activation using a bis‐hydroxide Ru II pincer complex [(pnp)Ru(CO)(OH) 2 ] [pnp = 2‐(di‐ tert ‐butylphosphinomethyl)‐6‐(diethylaminomethyl)pyridine] 13. Heating the Rh III porphyrin complex [(tpp)RhCl] (tpp = tetratolylporphyrinato dianion) in the presence of KOH led to the formation of the reactive Rh hydroxide intermediate [(tpp)Rh(OH)] 14…”