Robinson's theory does not do so; in fact, he explicitly brushes it aside.B The idea that 2,2'linking without 2,2'-hydrogen-loss might produce an intermediate for all forms of rearranged linking does meet the stereochemical challenge; however, it was never developed into a theory because it received no support from studies of hydrogen-isotope effects on rates and products (cf. Section lo), and because it seemed difficult thus to accommodate all that we knew about products in their dependence on structure (cf. Sections 12-14).

The large-scale synthesis of two highly methylated fluorene ligands is reported, and the synthesis and characterization of three organometallic derivatives are reported. Starting with 1,2,3,4-tetramethylbenzene, 1,2,3,4,5,6,7,8-octa- and 1,2,3,4,5,6,7,8,9-nonamethylfluorene (Flu‘ ‘H and Flu*H) have been synthesized in overall yields of above 50%. Both fluorenes may be deprotonated at the 9 position to yield useful organometallic synthons; the Sn derivative, Flu*SnMe3, is synthesized using this reagent, and its molecular structure has been elucidated. The Fe bimetallics [(FeCp)2Flu*H][PF6]2 and [(FeCp)2Flu‘ ‘H][PF6]2 have been isolated, and their electrochemical properties ascertained. Electrochemical measurements on these complexes show the methylated fluorene ligand acts as a strong electron donor and acts to increase the electronic communication between the metal centers, in comparison with the nonmethylated analogues. The solid-state structure of [(FeCp)2Flu‘ ‘H][PF6]2 has been determined and, unlike the Sn complex, does not show a significantly twisted fluorenyl core.

No abstract

The acid-catalysed rearrangements of the above-mentioned compounds have bcen studied at various aciditics in the presence of l5N-label1ed nitric and nitrous acids. The rearrangement products contained no detectable tracer. These observations, together with the results of experiments with added scavengers, exclude mechanisms involving fission to ionic or radical species followed by intermolecular recombination of the counter-fragments.THE formation of C-nitro-products from the acid-promoted rearrangement of N-nitroarylamines is generally considered to be intramole~ular,~-~ but few substrates have been adequately studied over a range of reaction conditions, and in one example an intermolecular component of rearrangement has been claimed.5 Various methods can give information on this point, but each has its limitations if taken as an isolated criterion.We have studied the rearrangements of N-methyl-N-nitro-l-naphthylamine and Nnitro-l-naphthylamine, using a combination of methods to enable a decision concerning the intra-or inter-molecularity to be reached. Analogies with previous work l s 5 suggest that intermolecular mechanisms may be especially favoured for these substrates. RESULTSTracer E=cperimeizts.-Reactions were carried out in the presence of 15N-labelled nitric and nitrous acids a t different acidities. The only rearrangement products were the 2and 4-nitroderivatives, and a dinitro-derivative under one set of conditions. These products were isolated, purified, and examined for tracer-uptake by mass spectrometry. Results are in the Table . The error in the abundance measurements was & @ l o in the units quoted for experiments 1-3, and f0-15 for experiment 4.Attempts to simulate the condition of experiment 1 f a i l d for N-rdro-l-naphthylamine ; rearrangement was negligible but much tar was formed. This seems a characteristic fate if

Banthorpe nnd Thomas '7149 1318. The Rearrangement of Aromatic N-Nitroamines. Part V.l The Acid-catalysed Rearrangements of N-Nitro-1 -naphthylarnine and its N-Methyl Homologue