Derivatization of surfaces via reaction of strained silicon-carbon bonds. Characterization by photoacoustic spectroscopy

Ferrocene-centered reagents can be bound to the surface of high surface area (400 m/sup 2//g) silica by reaction of the silica with alkane solutions of (1,1'-ferrocenediyl)dichlorosilane (Ia), (1,1'-ferrocenediyl)dimethylsilane (Ib), or (1,1'-ferrocenediyl)diphenylsilane (Ic). Derivatization is not found when ferrocene itself is used as the derivatization reagent; ferrocene is easily washed from the silica powder by solvents which do not affect the ferrocene centers bound upon reaction of the silica with Ia-c. As determined by photoacoustic spectroscopy, derivatization with Ia-c results in ring opening of the strained C-Si-C linkage bridging the two cyclopentadienyl rings to yield a simple, monosubstituted ferrocene center attached to the surface. Surface -OH functionality apparently reacts in a manner analogous to homogeneous solution sources of -OH such as MeOH. Reaction of Ib with MeOD yields (Fe(eta/sup 5/-C/sub 5/H/sub 4/D)(eta/sup 5/-C/sub 5/H/sub 4/Si(OMe)Me/sub 2/)). Optical absorption spectral changes accompanying reaction of Ia-c with solution sources of -OH are consistent with the differences found in the photoacoustic spectra of the pure powders of Ia-c compared to the silica powders derivatized with these reagents. Reaction of silica powders derivatized with Ia-c with acidic solutions of benzoquinone results in the oxidation of the surface-confined ferrocene centers to ferricenium centers giving photoacoustic spectramore » nearly the same as that from an authentic sample of a pure ferricenium salt. The surface-confined ferricenium can be used to oxidize N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) to TMPD/sup +/. in solution; this reaction allows an estimate of the surface coverage at 10/sup -11/ mol/cm/sup 2/. 3 figures, 2 tables.« less