Dications analogue

A notable utilization of the Hinsberg procedure was executed in the synthesis of a thiophene analogue of porphyrin. A previous synthesis of the tetrathioporphyrin dication of 7 found this material to be unsuitable for chemical exploration as a result of its limited accessibility and solubility. Efforts by Vogel et al. were then directed toward... 

It was Breslow (Breslow, 1982 Breslow et ai., 1982) who first paid attention to this theory. Knowing that the pentachlorocyclopentadienyl cation (Breslow et ai, 1964 Saunders et ai, 1973), the hexachlorobenzene dication (Wasserman et al., 1974) and the 2,3,6,7,10,11-hexamethoxy-triphenylene (HMT, [36]) dication are all ground-state triplets, in good agreement with theory, Breslow and coworkers set out on the synthesis of analogues that should have lower oxidation potentials, be chemically more stable and therefore form CT complexes more readily (Fig. 21c Breslow et al., 1982, 1984 Breslow, 1985, 1989 LePage and Breslow, 1987). 

The tetracyclopropyl analogue, the fra j-cyclopropane-l,2-diylbis(dicyclopropyl-methylium)dication 127, has also been prepared, and showed the following 13C NMR... 

Isoprenoid acyclic polyene carbocations with 6, 14, and 18 tt-electrons were synthesized.138 Considering also previous data for carotenoid dications, an equation correlating /.max (ranging from 400 to 1100 nm) and the number of sp2 hybridized carbon atoms in the dication was developed. Dication (67) and an analogue with a different alkyl substitution pattern were prepared as PF6 salts.139 These dications form... 

The [(tt-C5H5)Co(SR)]2 (R = Me, p-MeC6H4, or p-ClC6H4) complexes undergo voltammetric oxidation to the monocation derivatives, but, unlike the Ni or Fe analogues, they do not form dications.169... 

Since N+ and C are isoelectronic, the simplest and most direct hetero-analogue of benzene 1 is the pyridinium cation 2. Further azonia substitution of this kind gives polycations such as the pyrimidine dication 3. 

Attempted preparation of rr z 5 -a,a -tetramethylcyclopropane-l,2-dimethylium dication 125 resulted in the formation of ring-opened 2,6-dimethylhepta-2-dienyl cation 126 (equation 68) The tetraphenyl substituted dication 122, however, is a stable species, and the charge is significantly delocalized into the aromatic rings ( C 220.9) as compared to its monocation analogue, diphenylcyclopropylmethyl cation ( C 234.4) °. ... 

Cobalt analogues of biferrocene and bis(fulvalene)diiron have not been investigated as extensively as the iron compounds, despite the information on electronic interactions which could be gained from observing cobalt hyperfine splittings by ESR spectroscopy. The bis(fulvalene)dicobalt dication (M = Co) can be reduced in two successive one-electron steps at mild potentials ( = -0.07 V and -0.95 V), and [Co2(tj, t7 -CjoHg)Cp2], [1] " (M = Co), is reduced at -0.53 V and -0.88 V (3i) the preparation of the monocation [3]" (M = Co) has been briefly reported (32, 33). 

Dithiolate- or disulfide-bridged analogues of 29 oxidize reversibly to mono- and dications. The Mo—Mo distance (259.9 pm) in [Mo2(/a-SC3H6S)2Cp2] is very similar to that of [29], (R = Me) preliminary magnetic data on the dications, isolated from the reaction of the neutral species with ceric ion, suggest the presence of two unpaired electrons (67). 

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