Constructing homo- and hetero-metallic molecular topologies using pyridylcarboxylates as spacers: preparation of a half-ring complex with active coordination sites

Abstract

Addition of isonicotinic acid NC₅H₄CO₂H (or isonicH) to [Pt(dppf)(MeCN)₂]²⁺2OTf⁻ (dppf = 1,1′-bis(diphenylphosphino)ferrocene, OTf = triflate) affords a mixture of the homometallic molecular square [Pt₄(dppf)₄(μ-O₂CC₅H₄N)₄]⁴⁺4OTf⁻, 1 and its precursor intermediate [Pt(dppf)(η¹-NC₅H₄CO₂H)₂]²⁺2OTf⁻, 2. The latter captures [Pd(dppf)(MeCN)₂]²⁺2OTf⁻ to give a heterometallic square, [Pt₂Pd₂(dppf)₄(μ-O₂CC₅H₄N)₄]⁴⁺4OTf⁻, 3. Slight skeletal modification of the ligand leads to different assemblies. This is illustrated by the addition of NC₅H₄CH₂CO₂H·HCl to [Pt(dppf)(MeCN)₂]²⁺2OTf⁻ to give [PtCl(dppf)(NC₅H₄CH₂CO₂H)]⁺OTf⁻, 4, which reacts with another equivalent of AgOTf to yield the dibridged complex [Pt₂(dppf)₂(μ-NC₅H₄CH₂CO₂)₂]²⁺2OTf⁻, 5. All complexes, with the exception of 3, have been structurally characterized by single-crystal X-ray crystallography. Complexes 2 and 4 are potential precursors to further molecular topologies.