PUB - Publikationen an der Universität Bielefeld

Reaction of (dibromoboryl)ferrocene (1) with 1 equiv. of the diazabutadiene tBuN=CH-CH=NtBu, and subsequent reduction of the obtained borolium salt 2 with sodium amalgam, affords the first ferrocenyl-functionalized 1,3,2-diazaborole (3). Similarly, 1,1'-bis(dibromoboryl)ferrocene (4) can be transformed into compound 6, which contains two diazaborolyl substituents at the ferrocene core. Treatment of precursors I and 4 with 1, 2 -bis(tert-butylamino) ethane in the presence of Et3N gives rise to the formation of the diazaborolidine derivatives 13 and 14.1-Dibromoboryl-3-methylcymantrene (7) was also treated with tBuN=CH-CH=NtBu to give the borolium salt 8, which was subsequently reduced to the 2-cymantrenyl-diazaborole 9. Treatment of 7 with tBuN(H)-CH2CH2N(H)tBu in the presence of Et3N furnished the corresponding 2-cymantrenyl-diazaborolidine 15. The novel compounds were characterized by elemental analyses and various spectroscopic techniques (IR; H-1, C-13, and B-11 NMR; MS). The molecular structures of 3, 6, and 15 were elucidated by X-ray diffraction analyses. Cyclovoltammetric studies of the ferrocene derivatives at high scan rates show features of a quasireversible oxidation at the iron center. The heterocyclic groups serve as electron donors, considerably lowering the oxidation potential of the central iron atoms when compared to the parent compound ferrocene. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).