title: Rational synthesis of supramolecular assemblies based on tetraplatinum units: synthesis, characterization, and selective substitution reactions of four different Pt4 clusters.
abstract: Four different types of square-planar Pt(4) clusters, trans-[Pt(4)(μ-OCOCH(3))(6)(μ-ArNCHNAr)(2)] (2: ArNCHNAr = N,N'-diarylformamidinate), [Pt(4)(μ-OCOCH(3))(7)(μ-ArNCHNAr)] (8), cis-[Pt(4)(μ-OCOCH(3))(6)(κ(4)-N(4)-DArBp)] (9: DArBp = 1,3-bis(arylbenzamidinate)propane), and [Pt(4)Cl(2)(μ-OCOCH(3))(5)(κ(4)-N(2),P(2)-dpfam)] (13: dpfam = N,N'-bis[(2-diphenylphosphino)phenyl]formamidinate), were successfully prepared by using selective substitution reactions of in-plane acetate ligands of [Pt(4)(μ-OCOCH(3))(8)] (1), which has four in-plane and four out-plane acetate ligands, with appropriate capping ligands. Fundamental substitution reactions of the remaining in-plane acetates with benzoic acid derivatives were also investigated. All newly prepared complexes were characterized from spectral and physical data and combustion analysis. X-ray crystallographic studies of some of the clusters were also performed. Electrochemical measurements of amidinate-modified Pt(4) clusters revealed stepwise oxidation processes of the Pt(4) core due to Pt(4)(9+)/Pt(4)(8+) and Pt(4)(10+)/Pt(4)(9+). Based on the lability of the in-plane acetate ligands of the modified Pt(4) clusters, reactions of cis-[Pt(4)(μ-OCOCH(3))(6)(κ(4)-N(4)-DArBp)] (9 c: Ar = C(6)H(4)tBu-4) with ferrocenedicarboxylic acid and p-phenylenedipropionic acid resulted in the selective formation of cyclic dimers 17 and 18 and the reaction of 13 with 4,4'-biphenyldicarboxylic acid afforded a linear dimer 20. The dimers were characterized by spectral data, as well as X-ray analyses for 17 and 18. The finding of two Fe(3+)/Fe(2+) redox couples in the electrochemical measurement of dimer 17 indicated that two ferrocenyl units in dimer 17 communicated electronically.
authors.affiliation: Department of Chemistry, Graduate School of Engineering Science, Osaka University, and CREST, JST, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Tanaka
authors.forename: Akihiro
authors.initials: A
authors.lastname: Yagyu
authors.forename: Masashi
authors.initials: M
authors.lastname: Kikugawa
authors.forename: Masato
authors.initials: M
authors.lastname: Ohashi
authors.forename: Tsuneaki
authors.initials: T
authors.lastname: Yamagata
authors.forename: Kazushi
authors.initials: K
authors.lastname: Mashima