화학공학소재연구정보센터
Inorganic Chemistry, Vol.49, No.24, 11606-11618, 2010
High-Nuclearity Pt-Tl-Fe Complexes: Structural, Electrochemistry, and Spectroelectrochemistry Studies
A series of heteropolynuclear Pt-Tl-Fe complexes have been synthesized and structurally characterized. The final structures strongly depend on the geometry of the precursor and the PO ratio used. Thus, the anionic heteroleptic cis-configured [cis-Pt(C6F5)(2)(C CFc)(2)](2-) and [Pt(bzq)(C CFc)(2)](-) (Fc = ferrocenyl) complexes react with Tl+ to form discrete octanuclear (PPh3Me)(2)[{trans,cis,cis-PtTl(C6F5)(2)(C CFc)(2)}(2)] (1), [PtTl(bzq)(C CFc)(2)](2) (5; bzq = benzoquinolate), and decanuclear [trans,cis,cis-PtTl2(C6F5)(2)(C CFc)(2)](2) (3) derivatives, stabilized by both Pt-II center dot center dot center dot Tl-I and Tl-I center dot center dot center dot eta(2)(alkynyl) bonds. By contrast, Q(2)[trans-Pt(C6F5)(2)(C CFc)(2)] (Q = NBu4) reacts with Tl+ to give the one-dimensional (1-D) anionic [(NBu4){trans,trans,trans-PtTl(C6F5)(2)(C CFc)(2)}](n) (2) and neutral [trans,trans,trans-PtTl2(C6F5)(2)(C CFc)(2)](n) (4) polymeric chains based on [PtFc(2)](2-) platinate fragments and Tl+ (2) or [Tl center dot center dot center dot Tl](2+) (4) units, respectively, connected by Pt-II center dot center dot center dot Tl-I and secondary weak kappa-eta(1) (2) or eta(2) (4) alkryl center dot center dot center dot Tl-1 bonding. The formation of 1-4 is reversible, and thus treatment of neutral 3 and 4 with PPh3MeBr causes the precipitation of TlBr, returning toward the formation of the anionic 1 and 2' (Q = PPh3Me). Two slightly different pseudopobtmorphs were found for 2', depending on the crystallization solvent. Finally, the reaction of the homoleptic [Pt(C Fc)(4)](2-) with 2 equiv of Tl+ affords the tetradecanuclear sandwich type complex [Pt2Tl4(C CFc)(8)] (6). Electrochemical, spectroelectrochemical, and theoretical studies have been carried out to elucidate the effect produced by the interaction of the Tl+ with the Pt-C Cfc fragments. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) of 1-5 reveal that, in general, neutralization of the anionic fragments increases the stability of the fully oxidized species and gives higher E-1/2 (Fc) values than those observed in their precursors, increasing with the number of Pt-Tl bonding interactions. However, the electronic communication between Fc groups is reduced or even lost upon Tl+ coordination, as confirmed by electrochemical (CVs and DPVs voltammograms, 1-5) and spectroelectrochemical (UV-vis-NIR, 2-4) studies. Complexes 2 and 4 still display some electronic interaction between the Fc groups, supported by the presence of an IVCT band in their UV-vis-NIR spectra of oxidized species and additional comparative DFT calculations with the precursor [trans-Pt(C6F5)(2)(C CFc)(2)](2-) and complex 3.