Platinum-group metal cyclodextrin complexes and their use as command-cure catalysts in silicones

The Command-Cure concept is defined for a curable formulation as one with long work-life at ambient temperature and rapid cure time at elevated temperature. This concept is explored for a curable silicone system, cured via hydrosilylation. CODMCl(2), complexes (COD = 1,5-cyclo-octadiene; M = Pt. Pd) are reacted with beta-cyclodextrin (beta-CD) to make 1:1 inclusion compounds, M = Pd. 2; M = Pt, 4. Compounds 2 and 4 were analyzed by H-1 NMR and X-ray powder diffraction. Their catalytic ability was evaluated in a model system as well as a polymeric system that gels upon cure. Surprisingly, the Pd analog 2 was a good command-cure catalyst whereas the guest compound CODPdCl2, 1, was not active in the hydrosilylation reaction. The Pt analog, 4, was an effective command-cure catalyst while the corresponding guest, CODPtCl2, 3, was too active at low temperature in the hydrosilylation reaction. Additional Pt compounds and one Rh inclusion compound were evaluated as command cure catalysts. These inclusion compounds were: 1:1 beta-CD:[CODRhCl](2), 5; 1:1 beta-CD:CpPtMe(3), 6 (Cp = cyclopentadienyl); 1:2 beta-CD:MeCpPtMe(3), 7; 1:2 beta-CD:CODPtMe(2), 8. The effectiveness of 4-8 was evaluated in a number of silicone systems.