Mono-, Di-, and Trimetallic Complexes of the Nonalternating Polycondensed π-Perimeter Decacyclene, C36H18: Synthesis, Structure, and Spectroelectrochemistry of [{(η5-Me4EtC5)Co}2(μ-η5:η4-C36H18)]

Abstract

Reaction of the half-sandwich complexes [(eta5-Me4RC5)M(eta2:O-acac)] (M = Co, Ni; R = Me or Et) with di- and trianions of the polycondensed pi-hydrocarbon decacyclene results in formation of the first Co and Ni triple-decker complexes of this hydrocarbon. For the title compound NMR spectra as well as a crystal structure analysis reveal an antarafacial coordination of two (eta5-Me4EtC5)Co fragments at the central six-membered ring and one of the neighboring five-membered rings of decacyclene. The bridging pi-perimeter decacyclene displays a bowl-shaped topology. In the case of Ni, coordination of two (eta5-Me5C5)Ni fragments at the central six-membered ring of decacyclene is observed, based on the results of 1H and 13C NMR studies. This coordination mode is without precedent for nickel organometallic compounds reported so far. The cobalt complex shows a rich spectroelectrochemistry. Results of cyclic voltammetry and coupled ESR experiments reveal a strong interaction of both metal centers in the mixed-valent monocation of [(eta5-Me4EtC5)Co2(mu-eta5:eta4-C36H18)]. This categorizes the title compound into Robin Day class III.

Electron Transfer and CO Addition to Polynitrido Cobalt Carbonyl Clusters: Parallel Pathways for Conversion of the [Co10N2(CO)19]4-Anion to the Novel [Co11N2(CO)21]3-Anion

“…The perpendicular peak-to-peak line width, Δ H ⊥ = 218(5) G, allows us to state an upper limit for the magnetic interactions (if any): Δ H ⊥ ≥ a ⊥ (Co, N). This behavior is not surprising in view of the high nuclearity of the paramagnetic species and suggests the fundamental delocalization of the unpaired electron over the whole cobalt frame. , With increase of the temperature at the glassy−fluid transition ( T = 226 K), the anisotropic spectrum quickly drops out and the fluid solution becomes EPR silent, but refreezing the fluid solution quantitatively restores the original anisotropic features, indicating basic stability of the trianion. ,

2 X-band EPR spectrum of a MeCN solution of the trianion [Co 10 N 2 (CO) 19 ] 3- at T = 105 K.

3 X-band EPR spectra of a MeCN solution of the dianion [Co 10 N 2 (CO) 19 ] 2- : top, first derivative; bottom, second derivative. T = 105 K. (---) X-band spectrum of the trianion [Co 10 N 2 (CO) 19 ] 3- under the same experimental conditions.

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“…Infrared spectra were recorded on Nicolet Avatar 360 FT-IR spectrophotometer, using 0.1-mm CaF 2 cells previously purged with nitrogen. Materials and apparatus for electrochemistry and coupled EPR measurements have been described elsewhere 18d. All the potential values are referred to the saturated calomel electrode (SCE).…”

Charge Resonance Excitations in 1,3-Bis[di(4-methoxyphenyl)amino]azulene Radical Cations

“…While electron transfer (ET) through alternant π-electron bridge systems like phenylene, naphthalene, or anthracene derivatives has thoroughly been investigated, only few studies on pure nonalternant hydrocarbons are known. , In order to understand the nature of charge transfer and charge localization in azulene based mixed valence systems, we have already studied 1,2,3-tris-{4-[ N , N -bis(4-methoxyphenyl)amino]phenyl}-6-[ N , N -bis(4-methoxyphenyl)amino]azulene concerning its nonlinear optical and ET properties . Unfortunately, a detailed analysis of the multidimensional ET pathways failed in the latter case because we have not been able to assign the four oxidations to definite redox centers.…”

Cyclopentadienone-like Behavior of Fluorenone and 4,5-Diazafluoren-9-one

“…It is worth addressing the last point in more detail, since it turns out that 4 and 5 are quite unique in this context. All cyclopentadienylcobalt(I) arene complexes known so far belong to one of the following four categories: (A) mononuclear complexes of the electron-poor arenes C 6 (CF 3 ) 6 and C 6 (COOMe) 6 (although crystal structure determinations have not been reported for these types of compounds, there is no doubt that the arene shows η 4 coordination in each case); (B) mononuclear complexes of the electron-rich arene C 6 Me 6 16 (it is generally accepted that this ligand is always η 6 coordinated, although no reliable structural data have been reported); (C) mononuclear complexes of polycyclic aromatic hydrocarbons such as, for example, anthracene,16e decacyclene, and angular [3]phenylene (an η 4 coordination of a single six-membered ring is observed in each case); (D) oligonuclear complexes with bridging arene ligands (an antifacial η 4 :η 4 coordination of an arene ring is commonly observed here) . In view of these facts, an η 4 coordination of a single six-membered ring might have been expected for 4 and 5 .…”

“…Molecular structures of 4 (top) and 5 (bottom). Selected atomic distances (Å): for 4, Co(1)-C(1) ) 2.2326-(14), Co(1)-C(2) ) 2.0916(14), Co(1)-C(7) ) 2.0335(14), Co-(1)-C(8) ) 2.0468(14), Co(1)-C(13) ) 2.0918(14), Co(1)-C(14) ) 2.0442(14), Co(1)-C(15) ) 2.0555(14), Co(1)-C(16) ) 2.0744(14), Co(1)-C(17) ) 2.0326(14), Co(1)-C(18) ) 2.0427(14), C(1)-C(2) ) 1.471(2), C(1)-C(13) ) 1.4723(19), C(2)-C(3) ) 1.427(2), C(2)-C(7) ) 1.440(2), C(3)-C(4) ) 1.356(3), C(4)-C(5) ) 1.424(3), C(5)-C(6) ) 1.361(2), C(6)-C(7) ) 1.422(2), C(7)-C(8) ) 1.4434(19), C(8)-C(9) ) 1.4268(19), C(8)-C(13) ) 1.4372(19), C(9)-C(10) ) 1.363-(2), C(10)-C(11) ) 1.424(2), C(11)-C(12) ) 1.361(2), C(12)-C(13) ) 1.423(2); for 5, Co(1)-C(1) ) 2.0319(15), Co-(1)-C(2) ) 2.0783(15), Co(1)-C(6) ) 2.170(2), Co(1)-C(7) ) 2.0574(16), Co(1)-C(8) ) 2.0526(17), Co(1)-C(9) ) 2.081-(2), C(1)-N(1) ) 1.3776(15), C(1)-C(2) ) 1.4441(16), C(2)-C(3) ) 1.4203(17), C(3)-C(4) ) 1.3667(18), C(4)-C(5) ) 1.4368(17), C(5)-N(1) ) 1.3142(17).…”