Two new benzocrown ethers

9 -undecenyloxymethyl - 2

3-benzo- 15 crown- 5 and 18-crown - 6

were synthesized from 1

2 -bis (hydroxyethoxy) benzene bistosylate and corresponding undecenyloxymethylpolyethylene glycol via cyclcondensation in 22 and 20% yield

respectively. The crown ethers were subjected to hydrosilylation by triethoxysilane

followed by immbilization on fumed silica

and then reacting with potassium platinite in acetone under nitrogen atmosphere

sequentially. It was found that the platinum complexes exhibited very high catalytic activity for the hydrosilylation of olefins with triethoxysilane.The hydrosilylation of decene took place even the amount of silica-bound benzo-15-crown-5 platinum complex used was as low as 1×10-5mmol of Pt.In such a case

the decene used was 5.0mmol

the yield of decyltriehoxysilane was about 77% and the turnover number was as high as 380

000.