Trialkoxysilyl‐Functionalized Silver(I) Carboxylates: New Building Blocks for the Synthesis of Immobilizable and Immobilized Homogeneous Catalysts

Abstract

AbstractPartly fluorinated trialkoxysilyl‐substituted carboxylic acids (RO)3Si(CH2)3N(R')C(O)(CF2)3COOH (3a: R = Et, R' = H; 3b: R = R' = Me) have been prepared in a straightforward synthesis from the respective trialkoxysilyl‐substituted primary and secondary amines and hexafluoroglutaric anhydride. Treatment with silver(I) oxide yields the corresponding silver carboxylates 4a,b which have been thoroughly characterized in solution and in the solid state, including an X‐ray crystallographic analysis of 4a. The molecular structure of 4a consists of archetypal carboxylate‐bridged disilver(I) pairs with a strong closed‐shell Ag–Ag (d10–d10) interaction and a unique intramolecular bond between a silyl ether group and the metal ion. In addition the amide oxygen atoms are involved in H‐bonding and in intermolecular silver coordination, giving rise to an unusual two‐dimensional network structure. Silyl‐free acid iPr2NC(O)(CF2)3COOH (5) and its silver salt 6 have been prepared and structurally characterized for comparison. It is shown that the trialkoxysilyl tail in 4a,b allows for convenient attachment of these silver complexes to silica surfaces, as is corroborated by DRIFT measurements. The immobilized silver carboxylates 7a,b exhibit remarkable stability and are expected to open an easy access to a wide variety of SiO2‐grafted transition metal catalysts via transfer of the carboxylate ligand in simple exchange reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)