A “Conjugal” Consanguineous Family of Butadiynediyl-Derived Complexes:  Synthesis and Electronic Ground States of Neutral, Radical Cationic, and Dicationic Iron/Rhenium C₄Species

Abstract

The reaction of (η5-C5Me5)Re(NO)(PPh3)(C⋮CC⋮CSiMe3) and (η5-C5Me5)Fe(η2-dppe)(Cl) with KF, KPF6, and 18-crown-6 in MeOH/THF gives the heterobimetallic butadiynediyl complex (η5-C5Me5)Re(NO)(PPh3)(C⋮CC⋮C)(η2-dppe)Fe(η5-C5Me5) (9, 65%). This can be oxidized with [(η5-C5H5)2Fe]+ PF6 - to the isolable radical cation 9 + PF6 - and dication 9 2+ 2PF6 -, which constitute the first conjugal consanguineous family of C x complexes. The crystal structure of 9 is determined, and 9 n + nPF6 - are characterized in detail by cyclic voltammetry (CV) and IR, NMR, near-IR, ESR, and 57Fe Mössbauer spectroscopies. The bond lengths/angles suggest some bridge polarization in 9, and CV data show that the iron and rhenium endgroups communicate strongly. The odd electron in 9 + PF6 - is delocalized between the endgroups. In 9 2+ 2PF6 -, both electronic and magnetic interactions are found between remote unpaired spins on the rhenium and iron endgroups. This antiferromagnetic coupling stabilizes the singlet cumulenic over the triplet butadiynediyl state. At room temperature, however, both isomers of 9 2+ 2PF6 - are simultaneously present. Data are carefully compared to those of the analogous consanguineous diiron and dirhenium complexes.

Oligoalkyne-Bridged (η4-Cyclobutadiene)(η5-cyclopentadienyl)cobalt Fragments − Syntheses and Properties

“…This can be attributed to the librational shortening caused by the strong anisotropic motion of this molecular tail, which cannot be modeled correctly by an ellipsoid-shaped description. The distances found for the other triple bonds (C10ϪC11 and C12ϪC13) vary between 1.20 Å (15, 16) and 1.28 Å (17). The angles at the triple bonds deviate slightly from 180°, as reported for other long alkyne chains.…”

Facile Access to Redox‐Active C2‐Bridged Complexes with Half‐Sandwich Manganese End Groups

“…The UV-visible spectra of the series of complexes 6 ] did not reveal an extra broad absorption at long wavelength that could be assigned to a mixed-valence band, [6,11,15,18,43,48,74,[102][103][104][105][106] as expected for class II systems according to the Robin-Day classification. In accord with the CV results, this would allow one to conclude that the manganese end groups of 1, [1] + [PF 6 ], and [1] 2 + [PF 6 ] 2 are electronically strongly coupled and that these complexes belong to class III.…”

“…A similar behavior was observed in complexes with longer carbon chains between the metal centers. [43,44,[48][49][50][51][52][53][54][55][56][57][58][59][67][68][69][70][71][72][73][74] According to the resonance forms of Equation (3) the MnÀC bonds shorten with increasing degree of oxidation, while the internal CÀC bond elongates. This indicates that the cumulenic resonance form is transformed into the bis-carbyne type with a C À C single bond (Table 1).…”

Bis‐alkynyl Diruthenium Compounds with Built‐in Electronic Asymmetry: Toward an Organometallic Aviram–Ratner Diode

“…[9,10] Notably, prototypes of single-molecule transistor have been realized based on mono-, [11] di-, [12] and trimetallic complexes. [13] In a broader scope, facile electron/hole transfer within metal-s-alkynyl scaffolds have been demonstrated in bulk with metal centers including Fe, [14] Re, [15] Fe/Re, [16] Mn, [17] and Ru, [18] revealing the potential of metal-s-alkynyl molecules in molecular electronics. Further demonstrating the potential of organometallics in molecular electronics, a recent report revealed that [HSA C H T U N G T R E N N U N G (C 6 H 4 C C) 2 -Fc-(C CC 6 H 4 ) 2 SH] exhibits the near quantum conductance, which is two orders of magnitude higher than that of the corresponding OPE (OPE = oligo(phenyleneethynylene)) without ferrocene, namely HSA C H T U N G T R E N N U N G (C 6 H 4 CC) 4 A C H T U N G T R E N N U N G (C 6 H 4 )SH.…”