Organometallic chemistry on periodic mesoporous organosilicas: generation of surface-confined zinc and yttrium centres.
Periodic mesoporous ethylenesilicas with hexagonal P6mm and cubic Fm3m/Pm3n symmetry were prepared by using divalent surfactant C(16-3-1) and binary surfactant mixtures C(18-3-1) and C(18)TABr as structure-directing agents, respectively, under basic conditions. A tetramethyldisilazane-based surface silylation was carried out under mild conditions affording hybrid materials SiHMe(2)@PMO[MCM-41], SiHMe(2)@PMO[KIT-5] and SiHMe(2)@PMO[SBA-1], corresponding to silanol group populations of ca. 1.46, 0.67 and 1.63 mmol g(-1), respectively. New molecular zinc precursor compounds Zn[N(SiHMe(2))(2)](2) and EtZn(OSiH(t)Bu(2)) were synthesized via salt metathesis and alkane elimination procedures from ZnCl(2) and LiN[SiH(CH(3))(2)](2), HOSiH(t)Bu(2) and ZnEt(2), respectively. Organozinc and organoyttrium complexes were reacted with the surface silanol groups according to a heterogeneously performed silylamide route, aswell as an alkane elimination reaction, yielding Zn[N(SiHMe(2))(2)]@PMO[MCM-41], Zn[N(SiHMe(2))(2)]@PMO[KIT-5], Zn[N(SiHMe(2))(2)]@PMO[SBA-1], Zn[N(SiMe(3))(2)]@PMO[MCM-41], Zn[N(SiMe(3))(2)]@PMO[KIT-5], Zn[N(SiMe(3))(2)]@PMO[SBA-1], Y[N(SiHMe(2))(2)](x)(THF)(y)@PMO[MCM-41], Y[N(SiHMe(2))(2)](x)(THF)(y)@PMO[KIT-5], Y[N(SiHMe(2))(2)](x)(THF)(y)@PMO[SBA-1] and Zn(OSiH(t)Bu(2))@PMO[MCM-41]. The metal loading mainly depended on the surface silanol group population, size and shape of metal-coordinated ligand, and reaction time as shown for Zn contents in the range of 4.2 to 10.6 wt%. In addition, a preferred N(SiHMe(2))(2)/OC(6)H(2)(t)Bu(2)-2,6-Me-4 ligand exchangeability was found for the large yttrium surface centres. The parent and functionalized materials were characterized by powder X-ray diffraction, elemental analysis, N(2) physisorption, FTIR, (13)C CP and (1)H MAS NMR spectroscopy.[1]References
- Organometallic chemistry on periodic mesoporous organosilicas: generation of surface-confined zinc and yttrium centres. Liang, Y., Anwander, R. Dalton transactions (Cambridge, England : 2003) (2006) [Pubmed]
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