Inorganic Chemistry, Vol.51, No.11, 6020-6031, 2012
(Ni,Mg)(3)Si2O5(OH)(4) Solid-Solution Nanotubes Supported by Sub-0.06 wt % Palladium as a Robust High-Efficiency Catalyst for Suzuki-Miyaura Cross-Coupling Reactions
(Ni1-x,Mg-x)(3)Si2O5(OH)(4) solid-solution nanotubes (NTs) with tunable compositions were hydrothermally synthesized by altering the molar ratio of Mg2+ to Ni2+. The as-synthesized NTs were loaded with sub-0.06 wt % palladium (Pd; similar to 0.045 wt %) for Suzuki-Miyaura (SM) coupling reactions between iodobenzene or 4-iodotoluene and phenylboronic acid. The (Ni,Mg)(3)Si2O5(OH)(4) (Mg2+:Ni2+ = 1.0:1.0) NTs supported by 0.045 wt % Pd promoted the iodobenzene-participated coupling reaction with a high yield of >99%, an excellent recycling catalytic performance during 10 cycles of catalysis with yields of similar to 99%, and also an extremely low Pd releasing level of similar to 0.02 ppm. High-activity Pd and PdO clusters, multitudes of dislocations, and defects and terraces contained within the NTs should contribute to the (Ni,Mg)(3)Si2O5(OH)(4) (Mg2+:Ni2+ = 1.0:1.0) NTs supported by 0.045 wt % Pd as a robust, reusable, and high-efficiency catalyst for SM coupling reactions with an extremely low Pd releasing level. The present hydrothermally stable (Ni,Mg)(3)Si2O5(OH)(4) (Mg2+:Ni2+ = 1.0:1.0) solid-solution silicate NTs provided an ideal alternative tubular-structured support for noble- or transition-metal catalysts with low Pd loading, good recycling, and extremely low ppb levels of Pd release, which could also be extended to some other SM coupling reactions.