Carbosilane Dendrimers with End-Grafted Silacrown- and Crown-Ether Units

Abstract

The synthesis of the vinyl-functionalized silacrown ethers 1-methyl-1-vinylsila-8-crown-3 (3) and 1-methyl-1-vinylsila-1-crown-4 (4) by the reaction of (H 2 C=CH)MeSi(OEt) 2 (1) with HO(CH 2 CH 2 O) n H (2a, n = 2; 2b, n = 3)in presence of catalytic amounts of NaOMe is described. These species can be attached to 1 s t and 2 n d generation carbosilane dendrimers by hydrosilylation. Treatment of Si(CH 2 CH 2 CH 2 SiMe 2 H) 4 (5) or Si(CH 2 CH 2 CH 2 Si-Me(CH 2 CH 2 CH 2 SiMe 2 H) 2 ] 4 (8) with 3 or 4 produces the respective silacrown ether end-grafted carbosilane dendrimers 6, 7, 9 and 10 in nearly quantitative yield. In a similar manner 2-allyloxymethyl-12-crown-4 (11) gives with 5 and 8 the 12-crown-4 end-capped carbosilane dendrimers 12 and 13, respectively. The formation of analytical pure and uniform carbosilane dendrimers with crown ethers at the periphery is based on elemental analysis, IR, 1 H, 1 3 { 1 H} and 2 9 Si{ 1 H} NMR spectroscopy. ESI-TOF MS studies reveal that 7, 10, 12 and 13 form complexes with alkali ions, which enables such species to function as possible ionophores for chemical sensors.