Treatment of the cisoid-capped complex [Pt(4)(micro-OCOCH(3))(6)(kappa(4)-N(4)-DAr'Bp)] (), which was obtained from the reaction of [Pt(4)(micro-OCOCH(3))(8)] (1) with Na(2)D(t)BuPhBp (D(t)BuPhBp = 1,3-bis(para-tert-butylphenylbenzamidinate)propane), with an equimolar amount of 1,1'-ferrocenedicarboxylic acid undergoes a stereoselective self-assembly to afford an indented-quadrangle tetramer [Pt(4)(micro-OCOCH(3))(4)(kappa(4)-N(4)-D(t)BuPhBp){Fe(C(5)H(4)COO)(2)}](4) as a single diastereomer.
Reaction of [Pt4(μ-OCOCH3)8] (1) with 1 equiv of acrylic acid led to the selective monosubstitution of one of the four in-plane acetates in 1, affording [Pt4(μ-OCOCH3)7(μ-OCOCH=CH2)] (2a), whereas treatment with excess amounts of acrylic acid resulted in a full-substitution of four in-plane acetates, yielding [Pt4(μ-OCOCH3)4(μ-OCOCH=CH2)4] (3). Similarly, monosubstituted heptaacetate complexes [Pt4(μ-OCOCH3)7{μ-OCO(CH)nCH=CH2}] (2b–2d: n = 1–3) were prepared. Catalytic intermolecular coupling reactions of 2c and 2d assisted by Grubbs’ catalysts gave the desired dimers [{Pt4(μ-OCOCH3)7}2{μ-OCO(CH2)nCH=CH(CH2)n(μ-OCO)}] (6c: n = 2; 6d: n = 3).
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.
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