57Fe NMR spectroscopy of some sila-[1]ferrocenophanes and a phospha-[1]ferrocenophane

Fe-57 NMR spectra (11.66 MHz) of the 1,1-diorganosila-[1]ferrocenophanes, [Fe(C5H4)(2)]-(SiRR2)-R-1 (1) (R-1 = R-2 = Me) and (2) (R-1 = Me, R-2 Ph), the 1-chloro-1-organosila-[1]ferrocenophanes [Fe(C5H4)(2)]Si(Cl)R-1 3 (R-1 =Me) and 4 (R-1 = Ph), and of 1,1-dichlorosila-[1]ferrocenophane, [Fe(C5H4)(2)]SiCl2 5, were measured. All Fe-57 resonance signals are shifted to lower frequencies with respect to ferrocene, the largest shift being observed for 5 (-147.7 ppm). The influence of chloro substituents at silicon in comparison to organo groups is much more pronounced in the ferrocenophanes than in non-cyclic 1-silyl- or 1,1'-di(silyl)-ferrocene derivatives. In the case of 2,2,6,6-tetramethylpiperidin-1-yl-phospha-[I]ferrocenophane, [Fe(C5H4)(2)]P(tmp) 6, the Fe-57 nucleus is deshielded (129.8 ppm) with respect to ferrocene, and the coupling constant (2)J(Fe-57,P-31) = 3.4 Hz was measured for the first time.