Silver(I) ferrocenylcarboxylate: Reactivity and reaction behavior toward phosphines and phosphites

Silver(I) ferrocenylcarboxylate [Fe(η5-C5H4CO2Ag)(η5-C5H5)] (1) subsequently decarboxylates either in boiling dichloromethane or tetrahydrofuran to give biferrocene [Fe(η5-C5H4)(η5-C5H5)]2 (2) and elemental silver. Phosphine silver(I) ferrocenylcarboxylates of type [Fe(η5-C5H4CO2Ag(PR3)n)(η5-C5H5)] (R = Ph: 4a, n = 1; 4b, n = 2; 4c, n = 3. R = n-Bu: 5a, n = 1; 5b, n = 2; 5c, n = 3. R = OMe: 6a, n = 1; 6b, n = 2; 6c, n = 3) are accessible by treatment of 1 with PR3 (3a, R = Ph; 3b, R = n-Bu; 3c, R = OMe) in the ratio of 1:n. With dppe (7) tetrametallic [Fe(η5-C5H4CO2Ag(μ-dppe))(η5-C5H5)]2 (8) (dppe = Ph2PCH2CH2PPh2) was formed. The structures of 4b and 8 in the solid state have been determined by single X-ray structure determination. In 4b the silver(I) ion possesses a pseudo-tetrahedral environment, whereby the four coordination sites are occupied by the chelated FcCO2 unit and two datively-bonded PPh3 ligands. Compound 8 forms in the solid state a dimer setup by a [Ag(μ-dppe)]2 central building block. The FcCO2 groups are chelated to Ag(I) thus resulting in a pseudo-tetrahedral coordination sphere at silver. The solution behavior of 4–6 was analyzed by temperature-dependent 31P{1H} NMR studies indicating ligand exchange processes.

The thermal behavior and reaction chemistry of [Fe(η5-C5H4CO2Ag)(η5-C5H5)] toward phosphines and phosphites is discussed. The structures of two compounds in the solid state are reported.Figure optionsDownload as PowerPoint slideHighlights
► Silver(I) and phosphine/phosphite silver(I) carboxylates in the synthesis of silver ferrocenylcarboxylates.
► Biferrocene formation by thermal treatment of silver ferrocenylcarboxylate.
► Formation of heterobimetallic complexes.
► Dimeric, tetrametallic Fe2Ag2 complex formation.
► Solid-state structure of a FeAg and Fe2Ag2 ferrocene phosphine carboxylate.