A series of Pd complexes of 3'-diphenylphosphino-2,2':5'2' '-terthiophene (1a, dppterth) in which the metal is coordinated in three different modes have been prepared and electropolymerized, resulting in the formation of conductive thin films. In [Pd2(mu-Cl2)(dppterth-P,C3)2] (3a) the metal is P,C-coordinated, in [PdCl2(dppterth-P)2] (4a) the coordination is monodentate via the phosphine, and in [Pd(dppterth-P,C3)(dppterth-P,S1)][PF6] (5a) both P,C- and P,S-coordination modes are found. In 5a, the coordinated thiophene is hemilabile and may be displaced by reaction with more strongly coordinating ligands such as isocyanides. To probe the effect of blocking the alpha-position of the terthienyl moiety with methyl groups, 3'-diphenylphosphino-5-methyl-2,2':5'2' '-terthiophene (1b, Me-dppterth) and 3'-diphenylphosphino-5,5' '-dimethyl-2,2':5'2' '-terthiophene (1c, Me2-dppterth) were prepared, and the corresponding series of Pd complexes was synthesized. One of these complexes, [Pd(Me2-dppterth-P,C3)(Me2-dppterth-P,S1)][PF6] (5c), has been crystallographically characterized. The electropolymerized films prepared from 5a react with isonitriles, and shifts in the absorption spectra of the electropolymerized materials are observed upon reaction. A Pd complex has also been prepared from 5-diphenylphosphino-2,2':5'2' '-terthiophene (2, 5dppterth), and this complex has been electropolymerized. All the electropolymerized thin films have been characterized using EDX analysis, which demonstrates good correspondence with the elemental analysis of the respective monomers, and the maximum conductivities of the films are near 10(-4) S x cm(-1). Comparing the electropolymerization behavior of the complexes, along with their electrochemical and spectroscopic data, allows conclusions to be drawn regarding the involvement of pi-delocalization and the metal group in the conductivity of the materials.
The synthesis and properties of [cis-Ru(dppm)2(C⋮CFc)2]CuI (dppm = Ph2PCH2PPh2, Fc = ferrocenyl) (1) and trans,trans,trans-Ru(PBu3)2(CO)(L)(C⋮CFc)2 (3, L = CO; 4, L = pyridine; 5, L = P(OMe)3) are reported. The ruthenium bisacetylide bridges in these complexes allow electronic interaction between the terminal ferrocenyl groups. The interaction is enhanced when the ancillary ligands on the ruthenium center are electron donors and lessened when the ligands are acceptors. Complex 1 was prepared in 70% yield by the coupling of FcC⋮CSn(n-Bu)3 and cis- or trans-RuCl2(dppm)2 in the presence of excess CuI and was crystallographically characterized. Removal of the coordinated CuI from 1 with excess P(OMe)3 yields trans-Ru(dppm)2(C⋮CFc)2 (2). Reaction of 2 with CuI yields 1. trans,trans,trans-Ru(PBu3)2(CO)2(C⋮CFc)2 (3) was synthesized from RuCl2(CO)2(PBu3)2 and FcC⋮CSn(n-Bu)3 using a CuI catalyst and was crystallographically characterized. Reaction of 3 with excess pyridine yields trans,trans,trans-Ru(PBu3)2(CO)(py)(C⋮CFc)2 (4). The reaction is reversible; 3 may be obtained by reacting 4 with excess carbon monoxide. Reaction of 4 with P(OMe)3 yields trans,trans,trans-Ru(PBu3)2(CO)(P(OMe)3)(C⋮CFc)2 (5). Dications of all the complexes were prepared by oxidation with 2 equiv of FcPF6, and monocations were prepared in solution by reaction of the neutral complexes with the dications. The difference between the first and second ferrocenyl oxidations (ΔE 1/2) in the cyclic voltammograms of 1, 3, 4, and 5 are 0.14, 0.09, 0.13, and 0.15 V, respectively. Characterization of the complexes by visible, IR, and near-IR spectroscopy supports the conclusion that the ligand environment of the ruthenium center affects the extent of electronic delocalization between the ferrocenyl groups.
The preparations of two new phosphinothiophene ligands, 3,3'-bis(diphenylphosphino)-2,2'-bithiophene (dppbt; 1) and 3,3' "-dihexyl-3',3' '-bis(diphenylphosphino)-2,5':2',2' ':5' ',2' "-quaterthiophene (hdppqt; 2) are reported. Oxidation of 1 gives 3,3'-bis(diphenylphosphine oxide)-2,2'-bithiophene (3), and the crystal structure of this compound was determined. Pd(II) and Au(I) complexes of these ligands have been synthesized and characterized. Crystal structures of [(dppbt)PdCl(2)] (1-Pd), [(hdppqt)PdCl(2)] (2-Pd), [(dppbt)(AuCl)(2)] (1-Au), and [(hdppqt)(AuCl)(2)] (2-Au) were obtained. [(dppbt)(AuCl)(2)] crystallized in two solid-state forms; crystals grown from CH(2)Cl(2)/Et(2)O show a gold-gold interaction of 3.3221(4) A, but from CH(2)Cl(2)/toluene, the molecule crystallizes as a toluene adduct (1-Au-tol) and does not show any gold-gold interaction. All the complexes were characterized via UV-vis spectroscopy and cyclic voltammetry, and the effect of the metal on the energy of the pi-pi transition and oxidation potential was determined. These data are correlated to the interannular torsion angles in the oligothienyl groups from the crystal structure studies.
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