Electronic Interactions in Dinuclear Platinum and Palladium Ethynylferrocene and Ferrocenylvinylidene Complexes

Abstract

The complex [Pd2(dppm)2(μ‐η1:η1‐H−C=C−Fc)Cl2] (2) and its vinylidene isomer [Pd2(dppm)2(μ‐C=CH−Fc)Cl2] (3) [dppm = bis(diphenylphosphanyl)methane, Fc = ferrocenyl unit, CpFeC5H4] have been synthesized and characterized by single‐crystal X‐ray diffraction. Both 2 and 3 are A‐frame structures with long Pd−Pd distances of 3.2055(9) Å (2) and 3.1002(2) Å (3), respectively, and square‐planar metal coordination. The cyclic voltammograms (CV) of the complexes are measured and compared with that of [Pt2(dppm)2(μ‐η1:η1‐H−C=C−Fc)Cl2] (1). The CV of 2 and 3 consist of a nearly reversible Fc‐oxidation, an irreversible oxidation and a small reversible couple. The E1/2 values (vs. Cp2Fe+/Cp2Fe) of the Fc‐groups in complexes 1−3 follow the order 2 (−75±8 mV) > 1 (−108±10 mV) > 3 (−124±8 mV). The difference in the E1/2 values is explained by the orbital interactions between the acetylene and vinylidene groups with Pt2 and Pd2 cores. Our analysis shows that the metal‐to‐ligand π back‐bonding and ligand‐to‐metal σ‐donation have determining effects on the electronic interactions between the dimetallic centers and the bridgehead ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Strong Electronic Couplings between Ferrocenyl Centers Mediated by Bis-Ethynyl/Butadiynyl Diruthenium Bridges

“… Very recently, Cotton et al reported a novel linear trimetallic species, trans- Co 3 (dpa) 4 (C⋮CFc) 2 , for which a Δ E c of 70 mV was indirectly estimated from CV data . It is also worth noting that many compounds containing two σ-FcC⋮C ligands have been reported for which either electrochemistry was not interrogated or no discernible Δ E c was observed. − …”

“…48 It is also worth noting that many compounds containing two σ-FcCtC ligands have been reported for which either electrochemistry was not interrogated or no discernible ∆E c was observed. [49][50][51][52][53][54][55][56][57][58][59][60] In the preceding communication, we established through both voltammetric and spectroelectrochemical measurements that two Fc moieties are strongly coupled in the trans-Ru 2 (Y-DMBA) 4 -(C 2 Fc) 2 type compounds (Y-DMBA are m-substituted dimethylbenzamidinates, 1a/2a in Scheme 2). 34 Described in this contribution are, in addition to the details about compounds 1a/2a, the syntheses and structural characterizations of both the symmetric bis-ferrocenylbutadiynyl (FcC 4 , 1c/2c in Scheme 2) and unsymmetric FcC 2 /FcC 4 adducts (1b/2b) of the Ru 2 (Y-DMBA) 4 core, the detailed voltammetric and spectroelectrochemical investigation of charge transport properties within these compounds, and a time-dependent density functional (TD-DFT) calculation of the model compound trans-Ru 2 (NHCHNH) 4 -(CtCFc) 2 (3) that provides insights on spectral assignment for compounds 1 and 2.…”

15 Noble metals

“…240 The complexes [M 2 (dppm) 2 (m-g 1 :g 1 -CHLC-Fc)Cl 2 ] and [M 2 (dppm) 2 (m-CLCH-Fc)Cl 2 ] (M = Pd, Pt), with ethynylferrocene and ferrocenylvinylidine bridges Pt units and the ferrocenyl units. 241 The anion of 1-methyl-2,6-bis(trimethylsilyl)-3,5-diphenylphosphinine (a phosphabenzene derivative) coordinates to Pd(II) in a p-type manner via a side-on PLC bond. 242 The interest in coordinating metals to C 60 continues, with the isolation and X-ray characterization of [M(g 2 -C 60 ){Ph 2 PCH 2 (CH 2 OCH 2 )CH 2 PPh 2 }] (M = Pd, Pt).…”