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Structural studies on iminophosphine ligands and their palladium complexes
No full textThe crystal and molecular structures of the iminophosphine o-(Ph2P)C6H4CH=NC6H4OMe-4 (1) and its palladium complexes [Pd(3-C3H5){o-(Ph2P)C6H4CH=NC6H4OMe-p}]BF4 (2) and [Pd(2-fn){o-(Ph2P)C6H4CH=NC6H4OMe-4}] [fn=fumaronitrile, (3)] have been determined by X-ray analysis. In the free ligand (1), the planar imino group of E configuration is oriented, relative to the PPh2 unit, so that the CH=N hydrogen atom points towards phosphorus, with the nitrogen atom on the opposite side. In (2) and (3) the iminophosphine behaves as a P,N-chelate ligand, this coordination mode being achieved by the imino group rotation of 169.3° and 145.3°, respectively, around its bond with the ortho disubstituted phenyl ring. Complex (2) shows a structural disorder with two different orientations of the allyl ligand. The trigonal planar coordination around the central metal in complex (3) involves the P- and N-donor atoms of (1) and the 2-bound olefin, with a marked lengthening of the olefinic carbon-carbon bond. In both the complexes, the chelate six-membered ring of the iminophosphine with palladium is not coplanar with the N-Pd-P coordination plane, the imino carbon atom and the ortho disubstituted phenyl group lying on the same side out of the N-Pd-P plane, whereas the N-substituent and one of the PPh2 groups are on the opposite side. The 1H-n.m.r. spectra at low temperatures of (2) and (3), and of [Pd(2-tmetc){o-(Ph2P)C6H4CH=NCMe3}] [tmetc=tetramethyl ethylenetetracarboxylate, (4)] are interpreted on the basis of a non-rigid conformation of the chelate iminophosphine, which undergoes a fast dynamic process whereby the N- and P-substituents move above and below the coordination plane
New organometallic palladium(II) complexes containing PN ligands. Synthesis, characterization and X-ray structure.
No full textNew neutral organometallic palladium(II) complexes, [PdPhI(PNMe2)] (1), [PdPhI(PC=NMe)] (2), [PdPhI(PC=NEt)] (3), and [PdMeCl(PNMe2)] (4), {PNMe2 means N,N-dimethyl2-(diphenylphosphanyl)aniline; PC=NMe means N-[2-(diphenylphosphanyl) benzylidene]-N-methylamine; PC=NEt means N-[2- (diphenylphosphanyl)benzylidene]-N-ethylamine} have been synthesized by oxidative addition of PhI to [Pd(dba)(2)] in the presence of the (PN)-N-boolean AND ligand (1-3), or by substitution reaction on [PdMeCl(COD)] with PNMe2 (4). Cationic sigma-organometallic species [PdR(PPh3)((PN)-N-boolean AND)](+) are obtained upon treating complexes of the type [PdRX((PN)-N-boolean AND)] with PPh3 and AgCF3SO3 and consist predominantly of the trans-P,P isomer in CDC13 solution, as shown by NMR spectroscopic studies. The cationic eta(3)-allyl complex [Pd(eta(3)-all)(PNMe2)]PF6 has also been prepared and characterized, both in solution and in the solid state. Compounds [PdPhI(PNMe2)] (P2(1)/n), [PdPhI(PC=NMe)] (P (1) over bar), [PdPhI(PC=NEt)] (P (1) over bar), and [Pd(eta(3)-all) (PNMe2)]PF6 (P (1) over bar) have been authenticated by X-ray analysi
Chemical communication induced by intermolecular electron transfer in heterobimetallic ferrocenyl-indenyl-Cr(CO)3 complexes
No full textMixed Valence Properties in Ferrocenyl-Based Bimetallic FeCp−Indenyl-MLn Complexes: Effect of the MLn Group
No full textA series of ferrocenyl-based complexes of general structure [eta(5)-(2-ferrocenyl)indenyI]ML(n) [ML(n) = RuCp*, FeCp, IrCOD, Mn(CO)(3), and Cr(CO)(2)NO] were synthesized with the aim of tuning the effect of the nature of the second metal group ML(n) on the magnitude of the metal-metal electronic coupling in their mixed valence ions generated by electrochemical oxidation. The electronic interaction was probed by determining different and independent physical properties, the potential splitting in the cyclic voltammograms, and the IT bands in the near-IR spectra, which were rationalized in the framework of Marcus-Hush theory and at the quantum chemistry level by the density functional theory and TD density functional theory methods. On the basis of the obtained results, we were able to establish a trend based on the magnitude of the Fe-M electron transfer parameters H(ab) and alpha ranging from weakly to moderately coupled mixed valence ions
Heterobimetallic (ferrocenyl)-indenyl iridium complexes. Synthesis, Crystal Structure and Oxidative Activation
No full textThe reaction of (1-ferrocenyl)indenyl lithium, generated from (3-ferrocenyl)-indene (1) and n-butyl lithium in THF, with the dimers [Ir(mu-Cl)(cod)](2) and [Ir(mu-Cl)(coe)(2)](2) afforded the heterobimetallic [eta(5)-(1-ferrocenyl)indenyl]-Ir(cod) (2) and [eta(5)-(1-ferrocenyl)indenyl]-Ir(coe)(2) (3) (cod=cycloocta-1,5-diene; coe=cyclooctene). The complex [eta(5)-(1-ferrocenyl)indenyl]-Ir(CO)(2) (4) was obtained from 3 by exchange reaction with CO at room temperature. In contrast, the carbonylation of 2 at low temperature produces the eta(1)-(1-ferrocenyl)indenyl]-Ir(cod)(CO)(2) intermediate stable up to room temperature. The elimination of COD to give 4 occurs at higher temperature than in the corresponding monometallic eta(1)-indenyl-Ir(cod)(CO)(2). The crystal structure of 4 showed that iron and iridium are disposed in a cisoid configuration favoured by a stabilising weak bond interaction between the hydrogens of the cyclopentadienyl (Cp) ring and iridium and its carbonyls. The results of the electrochemical oxidation of 4 support the existence of a significant chemical interaction between the two metals. The comparison with the voltammetric results of the isomorphous rhodium complex 6 evidences for 4 a slowing down of the kinetic of the metal-metal interaction, and the absence of the radical cation oxidation even at high potential
Heterobimetallic Iron-Rhodium Complexes. The Synthesis and Characteristics of CpFe-(mu-eta:eta-as-Indacene-diide)-RhL2 [L2 = COD, NBD, (Ethylene)2]
No full textThe heterobimetallic CpFe(mu-eta(5): eta(5)-as-indacenediide)RhL2 complexes (L-2 = COD (2), NBD (3), (ethylene)2 (4)) have been obtained from metalation of the mononuclear lithium CpFe(eta(5)-as-indacenediide) with [Rh(mu-Cl)L-2](2). Mixtures of syn and anti heterobimetallic complexes were formed and fully characterized by 2D NMR spectroscopy. The reactivity at the rhodium center is greatly influenced by the presence of the ferrocenyl moiety. The voltammetric behavior and the optical spectra are in favor of the existence of significant electronic interactions between the two metals
Designing molecules for metal-metal electronic communication: Synthesis and molecular structure of the couple of heterobimetallic isomers [eta(6)-(2-ferrocenyl)indenel-Cr(CO)(3) and [eta(6)-(3-ferrocenyl)indenel-Cr(CO)(3)
No full textThe heterobinuclear isomers [eta(6)-(2-ferrocenybindene]-Cr(CO)(3) (1) and [eta(6)-(3-/errocenyl)indene]-Cr(CO)(3) (2) have been prepared and the crystal structure determination showed that the Fe(C5H5) and Cr(CO)(3) groups in the two molecules are disposed in different conformations with respect to the Cp-indene bridging ligand, cisoid in 1 and transoid in 2. Preliminary electrochemical (CV) and spectroscopic (IR and near-IR) results obtained for the corresponding monooxidized 1(+) and 2(+) demonstrate the existence of stronger electronic coupling in 1(+) than in 2(+)
Crystal structures of neutral trigonal bipyramidal [NiCl2(PMePh2)(PNMe2)] · 1⁄2 CH2Cl2 and cationic square planar [NiCl(PMePh2)(PNMe2)][PF6] complexes
No full textThe crystal structures of [NiCl2(PMePh2) . (PNMe2)] . 1/2 CH2Cl2 (1), C33H33Cl2NNiP2 . 1/2 CH2Cl2, and [NiCl(PMePh2) (PNMe2)][PF6] (2), C33H34ClF6NNiP3, have been determined by X-ray diffraction. Complex 1 crystallises in the monoclinic space group P2(1)/n, a = 11.305(6) Angstrom, b = 17.620(9) Angstrom, c = 18.061(9) Angstrom, beta = 90.48(4)degrees, V = 3597(3) Angstrom(3) and Z = 4. Refinement of 2508 observed reflections and 275 parameters converges to a conventional R of 0.051. The coordination around the Ni(II) centre is distorted trigonal bipyramidal with the two axial positions occupied by the phosphorus atom of the monodentate phosphine and the tertiary amine nitrogen of the bidentate PNMe2 chelate. The equatorial sites accommodate the remaining phosphorus of the amino-phosphine and two chlorine donors. Complex 2 crystallites in the orthorhombic space group Pbca, a = 18.61(1) Angstrom, b = 15.42(1) Angstrom, c = 23.25(2) Angstrom, V = 6673(7) Angstrom(3) and = 8. Refinement of 2351 observed reflections and 347 parameters yields R = 0.051. A square planar geometry de scribes the coordination around the metal with the two phosphorus donors located in a mutual cis-arrangement. As expected on the basis of the different coordination number, all of the metal-donor distances decrease on going from 1 to 2, as evidenced, in particular, by the Ni-N bond which contracts from 2.325(8) Angstrom to 2.056(8) Angstrom
Heterobimetallic (Ferrocenyl)-Indenyl Rhodium Complexes. Synthesis, Crystal Structure and Oxidative Activation of [eta5-(1-Ferrocenyl)-Indenyl]-RhL2 [L2 = COD, NBD, (CO)2]
No full textThe binuclear [eta(5)-(1-ferrocenyl)indenyl]Rh(NBD) (1), [eta(5)-(1-ferrocenyl)indenyl]Rh(COD) (1a), and [eta(5)-(1-ferrocenyl)indenyl]Rh(CO)2 (2) complexes have been synthesized (NBD = norbornadiene; COD = cyclooeta-1,5-diene). The crystal structure determination showed that the iron and rhodium nuclei are disposed in a transoid configuration in 1 probably to avoid steric repulsions. On the contrary, in 2 the metals are in a cisoid configuration due to the presence of stabilizing pi-hydrogen bonds between the CO's and the hydrogens of the unsubstituted cyclopentadienyl ring. The results of the chemical and electrochemical oxidation of 2 are in favor of the existence of an effective interaction between the two metals
Tuning the electronic communication in heterobimetallic mixed-valence ions of (1-ferrocenyl)- and (2-ferrocenyl)indenyl rhodium isomers
No full textA series of heterobimetallic complexes of general structure [RhL2-{eta(5)-(2-ferrocenyl)indenyl}] (L-2 = cod, nbd, L = CO; cod = cyclooctadiene; nbd = norbornadiene) has been synthesised with the aim of tuning the metal-metal interaction in their mixed-valence ions generated both by chemical and electrochemical oxidation, and the results are compared with those obtained for [RhL2{eta(5)-(1-ferrocenyl)indenyl}] isomers. Crystallographic studies and DFT calculations provide a detailed description of the structural and electronic features of these complexes evidencing a significant difference in the extent of planarity of the flexible bridging ligand between the 1- and 2-ferrocenyl isomers. Independent experimental probes, in particular the potential splitting in the cyclic voltammograms and the IT bands in the near-IR spectra, are rationalised in the framework of Marcus-Hush theory and at quantum chemistry level by DFT and TD-DFT methods. These methods allow us to establish a trend based on the magnitude of iron-rhodium electronic coupling H-ab ranging from valence trapped to almost delocalised ions. The quasi planar bridge and the olefin ancillary ligands make [Rh(nbd)-{eta(5)-(2-ferrocenyl)indenyl}](+) and [Rh(cod){eta(5)-(2-ferrocenyl)indenyl}](+) rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species
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