Dications X-ray studies

Aurated dications of a different type, bissulfonium salts 100 formed from dithiols, have been reported265,266 including the systematic study by Sladek and Schmidbaur.267 Single-crystal X-ray diffraction study indicated that they form complicated aggregated structures. 

It was reported that arylpinacols (48a) can undergo a superacid-catalyzed dehydrative cyclization to give the aryl-substituted phenan-threnes (eq 27).23 Superelectrophilic intermediates were proposed in the conversion. Tetraarylethylene dications have been studied by several methods and were observed directly by NMR as well as by UV-vis spectroscopy and X-ray crystallography.28 The low temperature oxidation of tetraaiylethylenes gives the dicationic species (50, eq 28). 

Related classes of gitonic superelectrophiles are the previously mentioned protoacetyl dications and activated acyl cationic electrophiles. The acyl cations themselves have been extensively studied by theoretical and experimental methods,22 as they are intermediates in many Friedel-Crafts reactions. Several types of acyl cations have been directly observed by spectroscopic methods and even were characterized by X-ray crystal structure analysis. Acyl cations are relative weak electrophiles as they are effectively stabilized by resonance. They are capable of reacting with aromatics such as benzene and activated arenes, but do not generally react with weaker nucleophiles such as deactivated arenes or saturated alkanes. 

There have been several types of gitonic superelectrophiles having acyl cationic groups as part of a 1,3-dicationic system. Monocationic acyl cations (168) can be prepared as persistent species in superacidic media and salts have even been studied by X-ray crystallography.113 Much of the interest in superelectrophilic species from acyl cations has focused on the protioacyl dications (169, vide supra).61... 

More highly stabilized l,8-bis(diarylmethyl)naphthalene dications have been prepared, including the p -methoxyphenyl derivative 53.20 This dication is generated from ionization of the diol in HBF4 and (CF3CO)2O.20a Dication 53 has been characterized by experimental studies (single crystal X-ray analysis and NMR) and theoretical calculations. The carbenium ion centers are found to be separated by just 3.076 A (X-ray and ab initio results) and show 13C NMR resonances at A3C 191.8. Two electron reduction is also shown to give the acenaphthene derivative 54. 

In a serendipitous fashion, a novel mixed valence tetranuclear copper(II)/copper(III) dithiocarbamate [2]catenane was prepared in near quantitative yield by partial chemical oxidation of a preformed dinuclear copper(II) naphthyl dtc macrocycle (Scheme 6).49 X-ray structure, magnetic susceptibility, ESMS and electrochemical studies all support the tetranuclear catenane dication formulation. The combination of the lability of copper(II) dtc coordinate bonds and favourable copper(II) dtc-copper(III) dtc charge transfer stabilisation effects are responsible for the high yielding formation of the interlocked... 

---