Rational synthesis of supramolecular assemblies based on tetraplatinum units: synthesis, characterization, and selective substitution reactions of four different Pt4 clusters

Four different types of square‐planar Pt₄ clusters, trans‐[Pt₄(μ‐OCOCH₃)₆(μ‐ArNCHNAr)₂] ( 2 : ArNCHNAr=N,N′‐diarylformamidinate), [Pt₄(μ‐OCOCH₃)₇(μ‐ArNCHNAr)] ( 8 ), cis‐[Pt₄(μ‐OCOCH₃)₆(κ⁴‐N₄‐DArBp)] ( 9 : DArBp=1,3‐bis(arylbenzamidinate)propane), and [Pt₄Cl₂(μ‐OCOCH₃)₅(κ⁴‐N₂,P₂‐dpfam)] ( 13 : dpfam=N,N′‐bis[(2‐diphenylphosphino)phenyl]formamidinate), were successfully prepared by using selective substitution reactions of in‐plane acetate ligands of [Pt₄(μ‐OCOCH₃)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 Pt₄ clusters revealed stepwise oxidation processes of the Pt₄ core due to Pt₄⁹⁺/Pt₄⁸⁺ and Pt₄¹⁰⁺/Pt₄⁹⁺. Based on the lability of the in‐plane acetate ligands of the modified Pt₄ clusters, reactions of cis‐[Pt₄(μ‐OCOCH₃)₆(κ⁴‐N₄‐DArBp)] ( 9 c : Ar=C₆H₄tBu‐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 Fe³⁺/Fe²⁺ redox couples in the electrochemical measurement of dimer 17 indicated that two ferrocenyl units in dimer 17 communicated electronically.     

Synthesis of a large functional cage compound based on four Ga-Ga single bonds and its application as an oligoacceptor: on the way to bio-organogallium hybrid molecules

The digallium compound R(2)Ga-GaR(2) (1; R=CH(SiMe(3))(2)) reacts with citracinic acid by the release of two equivalents of bis(trimethylsilyl)methane and the formation of a unique oligofunctional cage compound (2). Four Ga-Ga bonds in a tetrahedral arrangement are bridged by four spacer ligands that are located on the faces of the tetrahedron and bridge the gallium atoms of three different Ga-Ga bonds. Four pyridinium groups result from the shift of one of the three acidic protons of four citracinic acid molecules to the nitrogen atoms of the aromatic rings. The N-H groups are arranged in pairs and are capable of acting as chelating acceptors for the coordination of THF molecules (2(THF)(2)) or the nitrogen atoms of 1-deazapurine (3(OEt(2))(4)). In particular, the last reaction verifies the potential applicability of this relatively water- and air-resistant acceptor compound for the generation of bioorganometallic hybrid molecules.