Electrochemical Investigation of the Kinetics of Chloride Substitution upon Reduction of [Ru(porphyrin)(NO)Cl] Complexes in Tetrahydrofuran

Abstract

The electrochemistry of several ruthenium porphyrin nitrosyl chloride complexes [Ru(por)(NO)Cl] have been examined in tetrahydrofuran (THF). The complexes undergo one‐electron irreversible reductions, which result in diffusion‐limited substitutions of the chloride ligands for THF. This chloride metathesis is reversible in the presence of added NBu4Cl, and equilibrium constants and rate constants for chloride loss have been estimated. These parameters correlate with the NO stretching frequencies of the parent complexes, with more electron‐donating porphyrin ligands favoring chloride loss from the reduced complexes. The [Ru(por)(NO)(THF)] products of the reductions can be detected by IR, EPR, and visible spectroscopies. These species undergo three further reductions, with good reversibility at scan rates >0.40 V s−1. The [Ru(por) (NO)(THF)]+/0 couples have also been determined, and the rate constants and equilibrium constants for recombination with chloride have been estimated. One‐electron reductions of the [Ru(por)(NO)Cl] complexes result in approximately 1018 enhancement of the rates of chloride loss.

NO Releasing and Anticancer Properties of Octahedral Ruthenium–Nitrosyl Complexes with Equatorial 1H-Indazole Ligands

“…It is unlikely that this band would correspond to the double reduced Ru II –NO – , {Ru­(NO)} 8 type, [3] 0 species. A similar behavior was recently reported for a porphyrin complex [Ru­(OEP)­(NO)­Cl] …”

“…The EPR spectra obtained by chemical reduction in MeCN/ n Bu 4 NPF 6 solutions (black lines in Figure S13A and B) perfectly matched the records of electrogenerated [3] + . The X-band EPR signal of [3] + resembles well the spectra of several {Ru­(NO)} 7 systems known from the literature, for example, the extensively studied porphyrin complexes [Ru­(OEP)­(NO)­(THF)], [Ru­(OEP)­(NO)­(py)], or [Ru(TPP)(NO)­(py)] . The reduction with Fc* was also successfully used to generate the one electron reduced {Ru­(NO)} 7 species from [4] 2+ , [5] 0 , and [6] 0 .…”

Rare and Nonexistent Nitrosyls: Periodic Trends and Relativistic Effects in Ruthenium and Osmium Porphyrin-Based {MNO}7 Complexes

“…The sixth ligand plays a critically important role in determining the stability of the species in question: the {MNO} 7 state may spontaneously lose NO or otherwise decompose in the presence of strong-field trans ligands such as alkoxide, thiolate, or aryl. The equatorial ligand is also important; thus, whereas electroreduction of certain {RuNO} 6 porphyrins occurs reversibly and yields {RuNO} 7 species in solution, − electroreduction of {RuNO} 6 corroles occurs irreversibly, with concomitant loss of NO . Last but not least, the fact that the BP86-D3 and B3LYP-D3 methods afford radically different electronic descriptions for the six-coordinate {OsNO} 7 model complex underscores the need for further methodological investigations for heavy-element–containing compounds, especially for open-shell 4d and 5d transition-metal complexes.…”

“…According to this notation, nitrosylheme is an {FeNO} 7 complex, which may be formally thought of as derived from Fe­(II), a d 6 ion, and NO • . Unlike nitrosylhemes, which are stable and widespread in both biology and coordination chemistry, analogous {RuNO} 7 porphyrin species have only been characterized in solution as electrogenerated species − and genuine {OsNO} 7 porphyrins, to our knowledge, remain unknown . In a similar vein, only a small handful of nonporphyrin {RuNO} 7 and {OsNO} 7 species have been reported, generally only as solution-state species. − Presented herein is a density functional theory (DFT) study aimed at explaining the rarity and instability of {RuNO} 7 and {OsNO} 7 porphyrins.…”

Proton activation in the presence of a weak acid facilitated via second coordination effects in iron porphyrins

“…During the electrocatalytic investigations, the glassy carbon electrode was polished with 0.05 μm deagglomerated alumina oxide suspension, sonicated and dried after each incremental proton source addition. A platinum wire was used as the counter electrode and an Ag/AgCl wire was used as a pseudoreference electrode, with all E values reported against the Fc +/0 couple at 0 V. Ohmic drop was compensated for post data collection using techniques reported elsewhere 61,62 discussed further in the supporting information (Figure S17, equation S4, SI section (II)).…”