No abstract

The metal atom dynamics of four triferrocenylmethane derivatives have been elucidated, using temperature-dependent 57Fe Mössbauer effect (ME) spectroscopy. The hyperfine parameters (IS and QS) at 90 K are compared to each other and those of related ferrocenoids. The metal atom vibrational amplitudes as a function of temperature have been extracted from the ME recoil-free fraction data, and are compared to the X-ray U(i,j) values for two of the compounds. The single crystal structural data for triferrocenylmethanol have been determined at 173 and 295 K. The vibrational anisotropy of the metal atom for all of the compounds is negligibly small over the accessible temperature range.

The reaction of some 1,1'-dialkynylferrocenes with a variety of phenols in the presence as well as in the absence of [Mo(CO)(6)] yields good to high yields of phenoxy[4]ferrocenophanedienes. Similar reactivity was observed with a thiophenol and with acetic acid. Reaction under basic reaction conditions led to the formation of the [4]ferrocenophanone 17. The phenoxy[4]ferrocenophanedienes obtained show dynamic behavior as a result of a torsional twist of the carbon bridge as indicated by the (1)H and (13)C NMR spectra. The reaction mechanism is discussed in view of recent related results of Sato et al. as well as of Pudelski et al. A vinyl cation intermediate is postulated in this context, whose relative stability is evident from the mass spectra of the compounds prepared.

Alkynylferrocenes react with tetracyanoethylene (TCNE) to form 2-ferrocenyl-1,1,4,4-tetracyanobutadienes. These reactions occur under mild reaction conditions in almost quantitative yields if the triple bond is electron-rich. Systems with more than one triple bond, namely, 1,1Ј-dialkynylferrocenes or diynylferrocenes, react once at the more electron-rich triple bond, and the second reaction cannot be achieved, even under more-forcing reaction conditions. For a diyne with the [a]

In situ generated acetone pyrrolidine enamine undergoes [6 + 2] cycloadditions with fulvenes to give 1,2-dihydropentalenes. This ring annulation method works particularly well with 6-monosubstituted fulvenes and is subject to steric hindrance at C-6 of the fulvene. On the basis of mechanistic studies, optimal conditions have been developed for a one-pot synthesis of 1,2-dihydropentalenes using catalytic amounts of pyrrolidine.