Procedures for the synthesis of carboxysilanes and -germanes of the type Me,Phs-nMC02H, where M = Si and Ge and n = 0--3, and (XCeHa)sGeCOzH, where X = m-CH3, p-CH3, m-OCH3, p-OCH3, m-F, p-F, and p-CF3, by carbonation of the corresponding triorganosilyl-and triorganogermyllithium reagents are given. The spectral properties, uv, ir, and pmr, of a number of these acids and their carbon analogs are listed and discussed. The uv spectra of Me3MC02H and MeaMCOz-, n + T * transition, are interpreted in terms of inductive release by the metalloid and T ( T * --+ d ) bonding between the functional group and the metalloid.

Ionization constants of the following carboxylic acids have been determined by a spectrophotometric method: MenPh3 -"MC02H, where M = C, Si and Ge, = 0-3, in ethanol-water media and where M = C and Ge, in dimethyl sulfoxide; (XCeH4)3GeC02H, where X = H, p-Me, m-Me, p-OMe, m-OMe, p-F, m-F, and p-CFs, in ethanol-water media and X = H, p-Me, m-Me, p-OMe, in dimethyl sulfoxide. The relative order of acidity, R3Si-C02H » RsGeCOaH > R3CC02H, is explained in terms of ( -d) bonding between the orbitals of the C02_ group and the vacant nd orbitals of the metalloid with steric hindrance to anion solvation playing a smaller role. The transmission of substituent effects through the phenyl group and germanium also are discussed.

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Ausgehend von den Lithio‐Verbindungen (I) werden durch Behandlung mit Kohlendioxid die Carbonsäuren (II) erhalten, deren Spektren sowie deren Ionisationskonstanten untersucht und diskutiert werden.