One-Electron Oxidation of Heterodinuclear Organometallic Compounds Having Polyphosphido Bridges

Abstract

The electrochemical behavior of several heterometallic compounds having polyphosphido bridges has been investigated. Reversible one-electron oxidations were observed for Cp*Fe-(P 5)TaCp′′ (2), Cp*Fe(P 5)[Ir 2 (CO) 2 Cp* 2 ] (3), and Cp′′′ 2 Co 2 (P 2) 2 (4) (Cp*) C 5 M 5 , Cp′′) C 5 H 3 t Bu 2 , Cp′′′) C 5 H 2 t Bu 3). In contrast to the pseudo-sandwich polyphosphido complex Cp*FeP 5 (1), compounds 2-4 undergo very facile oxidations and the corresponding monocations may be generated by bulk electrolysis or by reaction with ferrocenium ion. E 1/2 values (vs Cp 2 Fe 0/+) for the oxidations are-0.24 V for 2,-0.58 V for 3, and-0.33 V for 4 in CH 2 Cl 2 /0.1 M [NBu 4 ][PF 6 ], in contrast to 0.57 V for 1. Although ESR spectra of 2 + display hyperfine coupling to 181 Ta, the SOMO appears to have only minor Ta character. IR spectroelectrochemistry of the 3/3 + couple reveals an increase of ν CO of only 11 cm-1 , indicating that the oxidation of 3 also occurs predominantly at the iron center. The fact that the Fe-based oxidations of 2 and 3 are more negative than that of 1 by ca. 0.8 and 1.15 V, respectively, is ascribed to differences in the iron formal oxidation state which arise from the structural variations of the P 5 bridging groups.

Synthesis, Structural Characterization, and Some Properties of New N-Functionally Substituted Diiron Azadithiolate Complexes as Biomimetic Models of Iron-Only Hydrogenases

“…It is shown that 2 , 3 , 6 , and 7 each display one quasi-reversible reduction process, one irreversible reduction process, and one irreversible oxidation process. All the first quasi-reversible reductions ( E pc = −1.62 to −1.64 V) are one-electron processes, which is supported by the calculated value of 0.9 faraday/equiv (obtained through study of bulk electrolysis of 7 ) and the calculated value of ( i p /ν 1/2 )/( it 1/2 ) = 4.08 (obtained through study of CV and chronoamperometry (CA) of 7 ) . These one-electron processes can be assigned to the reduction of Fe I Fe I to Fe I Fe 0 .…”

Intramolecular Phosphorus–Phosphorus Bond Formation within a Co2P4Core

“…Therefore, the formation of an acyclic P 4 bridge among the three metals in 1a and 1b was initiated by the transfer of one electron from the samarocene to [(Cp‴Co) 2 (μ,η 2:2 -P 2 ) 2 ]. Even though Winter and Geiger examined the quasi-reversible one-electron oxidation process of [{Cp‴Co(μ,η 2:2 -P 2 )} 2 ] to [{Cp‴Co(P 2 )} 2 ] + ( E 0 1/2 = 0.33 V) by cyclic voltammetry, one-electron reduction of this dicobalt μ,η 2:2 -polyphosphide complex has not been reported. For this reason, we performed cyclic voltammetry studies of the one-electron reduction process.…”

Symmetrical P4 cleavage at cobalt half sandwich complexes [(η5-C5H5)Co(L)] (L = CO, NHC) – a computational case study on the mechanism of symmetrical P4 degradation to P2 ligands

“…: 2.737 and 2.705 Å). Compound [{(η 5 -C 5 H 5 )Co-(μ,η 2:2 -P 2 )} 2 ] 9 can be formally considered as a complex in which two P 2 2− ligands bridge two [(η 5 -C 5 H 5 )Co III ] 2+ cations.Geiger et al22 have shown that the analogue complex [{(η 5 -C 5 H 2 t Bu 3 )Co(μ,η 2:2 -P 2 )} 2 ] undergoes reversible oxidation to the monocation at E 1/2 = −0.33 V and a partially reversible oxidation to the dication at E 1/2 = 0.33 V. Geometry optimization of the dication 9 2+ (see Fig.12, right side) leads to a triple decker sandwich complex with a regular cyclo-P4 ligand (P-P bond distances: 2.316 Å, Co-P bond distances: 2.378 Å) in the middle deck. The central Co 2 P 4 unit may also be considered as a heteroatom substituted octahedral cluster with cyclopentadienyl ligands coordinating the cobalt atoms.…”