Synthesis, Crystal Structures, and Electrochemical Behavior of FeâRu

Article pubs.acs.org/Organometallics

Synthesis, Crystal Structures, and Electrochemical Behavior of Fe−Ru Heterobimetallic Complexes with Bridged Metallocene Units Jiří Schulz,† Filip Uhlík,‡ J. Matthaü s Speck,§ Ivana Císařová,† Heinrich Lang,§ and Petr Štěpnička*,† †

Department of Inorganic Chemistry, Faculty of Science, and ‡Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, 12840 Prague 2, Czech Republic § Institute of Chemistry, Inorganic Chemistry, Faculty of Natural Sciences, Technische Universität Chemnitz, D-09107 Chemnitz, Germany S Supporting Information *

ABSTRACT: A series of Fe−Ru complexes was prepared by reactions of (2-phenylethyl)ferrocene (1), (E)-(2-phenylethenyl)ferrocene (2), and (phenylethynyl)ferrocene (3) with [Ru(η5-C5R5)(MeCN)3][PF6] (R = H, Me) salts. These heterobimetallic complexes of the general formula [Fc-spacer-(η6-C6H5)Ru(η5-C5R5)][PF6] (Fc = ferrocenyl, spacer = CH2CH2 (4), CHCH (5), CC (6)) were isolated as hexafluorophosphate salts and characterized by elemental analysis, multinuclear NMR spectroscopy, and electrospray ionization mass spectrometry. The solid-state structures of the complete series of [Fcspacer-(η6-C6H5)Ru(η5-C5Me5)]Cl (resulting via anion exchange upon recrystallization from a halogenated solvent) and of [FcCCRu(η6-C6H5)(η5-C5H5)][PF6] were determined by single-crystal Xray diffraction analysis. In addition, a η4-butadiene complex [Ru(η5-C5H5)(η4-1,2-Fc2-3,4-Ph2C4)][PF6] (7[PF6]), obtained along with some unidentified alkyne oligomers and 6a[PF6] upon the treatment of 3 with [Ru(η5-C5H5)(MeCN)3][PF6], was characterized similarly, including structure determination. Cyclic voltammetry measurements performed on 1−3 revealed that these compounds undergo a single reversible one-electron oxidation, which can be attributed to the ferrocene/ferrocenium redox couple. Their redox potential increases with increasing electron-withdrawing nature of the ferrocenyl substituent (E°′: 1 < 2 < 3). The cationic Fe−Ru complexes show similar redox waves that are shifted to more positive potential due to coordination of the positively charged Ru(η5-C5R5) fragment and are only marginally influenced by the substitution at the Ru-bonded cyclopentadienyl ring (C5H5 vs C5Me5). Furthermore, the metal−organic Fe−Ru dyads exert an irreversible reduction event below 2 V presumably due to reduction of the Ru center. Spectroelectrochemical measurements in the UV−vis−NIR region and DFT computations confirmed the anticipated nature of the observed oxidative redox processes and further suggested electronic communication between the metal centers in compounds possessing the conjugated linking groups.

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INTRODUCTION

Chart 1

Because of its defined and tunable redox activity, the ferrocene moiety has been extensively employed in the preparation of various functional materials and molecular devices, such as electrochemical sensors,1 redox-controlled catalytic systems,2 redox-tagged biomolecules and their supramolecular assemblies,3 organometallic polymers,4 ferrocenyl-modified dendrimers,5 metal surfaces and nanoparticles,6 and other materials.7 Along with these developments, many fundamental studies into the nature of electron transfer processes in various ferrocenylcontaining compounds have been performed, with the main emphasis put onto the redox behavior of singly and multiply ferrocenylated organic conjugated molecules, including heterocycles,8 and of multinuclear coordination compounds containing ferrocene-based ligands.9 Recently, we decided to prepare and study a series of hitherto unknown, simple ligand-bridged bimetallocene complexes comprising the congeneric (3d and 4d) FeII and RuII metal ions ligated by bridging π ligands (denoted as 4−6 in Chart 1). © 2014 American Chemical Society

Special Issue: Organometallic Electrochemistry Received: May 13, 2014 Published: July 28, 2014 5020

dx.doi.org/10.1021/om500505n | Organometallics 2014, 33, 5020−5032

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Investigation of the redox chemistry of these compounds, which can be regarded as prototypical examples of the so-called push−pull (or dipolar) bimetallic systems,10 combining the electron-rich ferrocenyl moiety and the cationic RuII(η6-arene) fragment as the electron donor and acceptor parts, respectively, represent a new entry into the field of electrochemical studies on Fe−Ru complexes dominated so far by those performed with simple or organometallic Ru complexes bearing typically Pcoordinated phosphinoferrocene11,12 and σ-bonded unsaturated ω-ferrocenylorganyl ligands.13 Compounds that are at least vaguely similar to the compounds reported in this study include analogous complexes with aldimine linking groups, [Ru(η6FcCHNHC6H5−nRn)(η5-C5Me5)](CF3SO3)14 (Fc = ferrocenyl), [Ru(η5-C5R5)]+ complexes with η6-bonded triferrocenylbenzene, i.e. [Ru(η6-1,3,5-Fc3C6H3)(η5-C5R5)][PF6] (R = H, Me), and [Ru(η5-(8-ferrocenylnaphth-1-yl)C5H4)(η6-C6H6)][PF6],15 which were studied mainly for their nonlinear optical properties.16 Further, less similar compounds include trimetallic complexes in which metalloligands FcC(O)CHC(CH3)N(1,2-C6H4)NCH(2-O−,5-R-C6H3) coordinate simultaneously in a η6 fashion to a Ru(η5-C5Me5) fragment and as a O2N2 donor to CuII or NiII ions.17 Also noteworthy are some ruthenocene analogues with ferrocenyl-substituted indenyl and fluorenyl ligands: viz., [Ru(η5-C5Me5)(η5-2-FcC9H6)] and [Ru(η5C5Me5)(η5-9-FcC13H8)].18 We herein describe the preparation of a series of [Fc-spacer(η6-C6H5)Ru(η5-C5R5)]X (spacer = CH2CH2, CHCH, C C; R = H, Me, X = simple anion) complexes differing in the spacer groups connecting the two iso-π-electronic metallocene units and in the substitution at the Ru-bonded cyclopentadienyl ring and their detailed structural characterization. Furthermore, we report the results of our electrochemical and spectroelectrochemical measurements and DFT computations aimed at an explanation of the redox behavior of these compounds.

Scheme 1. Preparation of the Fe−Ru Complexes 4[PF6]− 6[PF6]

Scheme 2. Reaction of 3 with [Ru(η5-C5H5)(MeCN)3][PF6], Affording 6a[PF6] and the η4-Cyclobutadiene Complex 7[PF6]

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RESULTS AND DISCUSSION Synthesis and Characterization. The heterobimetallic Ru−Fe complexes 4a[PF6]−6a[PF6] and 4b[PF6]−6b[PF6] resulted19 upon gentle heating of the respective mixtures of the commercially available [Ru(η5-C5R5)(MeCN)3][PF6] salts and the ferrocenyl-substituted benzenes 1−3 in 1,2-dichloroethane (Scheme 1). These complexes readily undergo anion exchange when recrystallized from solvent mixtures containing dichloromethane to afford the corresponding chloride salts. This halogen exchange can be rationalized in terms of a selective separation of the less soluble and/or better crystallizing salts from solutions containing two different anions, namely the hexafluorophosphate originating from the Ru precursors and chloride ions resulting by decomposition of the halogenated solvent, which may well be aided photochemically. The Fe−Ru complexes were isolated in good yields (60−93%) in all but one case. The exception was the reaction of [Ru(η5C5H5)(MeCN)3][PF6] with alkyne 3 (Scheme 2), which gave rise to a mixture of unidentified alkyne oligomers20 along with the expected product 6a[PF6] (19%) and the rather unstable η4cyclobutadiene complex 7[PF6] (34%). It is noteworthy that the latter compound was detected and isolated in one of the two possible isomeric forms possessing η4-coordinated 1,2-differocenyl-3,4-diphenylcyclobuta-1,3-diene that results from a formal [2 + 2] cycloaddition of two molecules of alkyne 3 in a head-to-head/tail-to-tail manner. Previously, complexes of the type [Ru(η5-C5R5)(η4-C4R′4)(L)]q (q = 0 and 1+ for anionic and neutral ligands L, respectively) were identified among the

products arising from interactions of alkynes with RuII(η5-C5R5) precursors such as [Ru(η5-C5H5)(CO)2]2/Ag+,21 [RuCl(η5C 5 Me 5 )] 4 , 2 2 [RuCl(η 5 -C 5 Me 5 )(Me 2 NCH 2 CH 2 NMe 2 κ2N,N′)],23 [RuCl(η5-C5Me5)(cod)] (cod = η2:η2-cycloocta1,5-diene),24 [Ru(η5-C5H5)(MeCN)2(PMe3)]+,25 and even [RuCl(η5-C5Me5)(i-Pr2PCH2CO2Me-κ2O,P)].22b The formation of the η4-C4R4 ring was suggested26 to proceed via a ruthenacyclopentatriene intermediate (sic!),27 resulting from the metal precursor and two alkyne molecules and its subsequent rearrangement, which appears to be facilitated by bulky substituents at the (original) triple bond. Compounds 4[PF6]−6[PF6] were characterized by multinuclear NMR spectroscopy, electrospray ionization (ESI) mass spectrometry, and elemental analysis. The ESI mass spectra show intense signals due to the complex cations (see the Experimental Section). In their 1H and 13C{1H} NMR spectra, compounds 4[PF6]−6[PF6] display characteristic signals of the ferrocenyl and phenyl moieties, the Ru-bonded cyclopentadienyl ligands, and the aliphatic linking groups, whereas the 31P{1H} NMR spectra uniformly show a septet at ca. δP −144 with the typical 1 JPF coupling constant of 711 Hz (note: tabular summaries of the NMR data are available in the Supporting Information, Tables S1 and S2). The rather unstable complex 7[PF6] was characterized similarly, except that high-resolution mass spectra were recorded in place of the conventional elemental analysis, which could not 5021


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be performed because of an easy decomposition of this compound. Molecular Structures. The crystal structures of the respective solvated chloride salts 4bCl·CH2Cl2, 5bCl·CH2Cl2, and 6bCl·CH2Cl2, obtained upon recrystallization of the hexafluorophosphate salts from dichloromethane (vide supra), as well as of 6a[PF 6]·CHCl 3 and 7[PF 6 ]·CHCl 3 were determined by single-crystal X-ray diffraction analysis. The structures of the complex cations in these salts are presented in Figures 1−5, and selected geometric data are summarized in Tables 1 and 2. Figure 3. PLATON plot of the complex cation in the structure of 6bCl· CH2Cl2 with displacement ellipsoids at the 30% probability level. The cation resides on the crystallographic mirror plane, the atoms in positions “b” being generated by the x, 1/2 − y, z symmetry operation.

Figure 1. PLATON plot of the complex cation in the structure of 4bCl· CH2Cl2 with the atomic labeling scheme and displacement ellipsoids at the 30% probability level.

Figure 4. PLATON plot of the complex cation in the structure of 6a[PF6]·CHCl3 with displacement ellipsoids at the 30% probability level.

The main difference between the complex cation in 6a[PF6]· CHCl3 and its Ru(η5-C5Me5) counterpart is seen in the overall molecular conformation. Although the conjugated C6H5 and C5H4 planes in cation 6a+ remain coplanar (dihedral angle ca. 3°), their associated metallocene units assume mutually opposite positions (anti) with respect to the bridge. This conformational change, which may appear rather surprising if one considers lower steric demands of the unsubstituted cyclopentadiene ligand, may be the consequence of the crystal-packing effects. On the other hand, all other differences in the molecular geometry are rather minor. The ompound 7[PF6]·CHCl3 crystallizes with two complex cations per asymmetric unit of the triclinic unit cell (space group P1̅). A view of cation 1 is shown in Figure 5, and relevant geometric data for both complex cations are given in Table 2 for a comparison. An overlap of the two independent cations demonstrating the differences in their molecular geometry is available in the Supporting Information (Figure S1). The cations in the structure of 7[PF6]·CHCl3 adopt a pseudotrigonal geometry, albeit angularly distorted owing to the different steric demands of the Ru-bound ligands.29 The π ligands are mutually tilted (ca. 36°) and coordinate markedly asymmetrically. The Ru−C bond lengths for the cyclopentadienyl carbons are in the ranges 2.184(3)−2.259(3) Å and 2.186(3)−2.248(3) Å in cations 1 and 2, respectively, the shortest being the distances to C(37/87) located opposite the

Figure 2. PLATON plot of the complex cation in the structure of 5bCl· CH2Cl2 with displacement ellipsoids scaled to the 30% probability level.

In the crystal state, the metallocene units in the Ru(η5-C5Me5) complexes 4bCl, 5bCl, and 6bCl are arranged in a syn fashion: i.e., with both metal centers located at the same side with respect to the C6H5-spacer-C5H4 moiety. Whereas the C6H5 and C5H4 planes in the cations containing the ethene-1,2-diyl and ethyndiyl bridges are nearly coplanar (see φ angle in Table 1), those in 4bCl are mutually rotated by 40° owing to the presence of the flexible ethane-1,2-diyl linker that disrupts possible conjugation. The distance between the metal atoms in these cations progressively increases as the spacer group straightens out (the Ru···Fe distances are 6.6219(3) Å in 4bCl, 6.6410(4) Å in 5bCl, and 6.7959(8) Å in 6bCl). Otherwise, however, the geometry around the π-coordinated metal centers does not vary significantly upon changing the linking groups, which themselves exert the expected geometries.28 5022


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Figure 5. (a) View of cation 1 in the structure of 7[PF6]·CHCl3. Note that the atom labeling scheme used for cation 2 is strictly analogous. Atomic labels for the carbon atoms are obtained by adding 50 to the numerical part of the respective label in cation 2, while the heavy atoms are labeled as follows: Ru2, Fe3, Fe4, and N2. (b) Detailed view of the coordination environment of the Ru atom. Only the pivotal atoms from the phenyl and ferrocenyl substituents are shown to avoid complicating the figure. The hydrogen atoms in parts a and b are omitted for clarity, and the displacement ellipsoids are scaled to the 30% probability level.

Table 1. Selected Geometric Data for 4bCl·CH2Cl2, 5bCl·CH2Cl2, 6a[PF6]·CHCl3, and 6bCl·CH2Cl2 (in Å and deg)a param Ru−C6H5b b

Ru−Cp φRuc Fe−C5H4b Fe−C5H5b φFec Fe···Ru φRuFec C1−C11 C11−C12 C12−C13 C1−C11−C12 C11−C12−C13 C1−C11−C12−C13

4bCl·CH2Cl2

5bCl·CH2Cl2

6a[PF6]·CHCl3

6bCl·CH2Cl2

1.6964(8) 1.8073(8) 2.29(9) 1.646(1) 1.646(1) 3.2(1) 6.6219(3) 40.1(1) 1.498(3) 1.531(3) 1.505(3) 113.9(2) 111.3(2) −172.1(2)

1.709(1) 1.809(1) 1.6(2) 1.648(1) 1.651(1) 4.4(2) 6.6410(4) 7.1(2) 1.454(3) 1.332(4) 1.469(4) 125.9(3) 126.3(3) −176.5(3)

1.695(1) 1.816(1) 1.3(1) 1.663(1) 1.666(1) 1.1(1) 7.4448(4) 9.6(1) 1.423(3) 1.194(3) 1.431(3) 178.7(3) 177.9(2) −

1.704(2) 1.809(2) 0.3(2) 1.641(2) 1.647(2) 0.1(2) 6.7959(8) 3.1(2) 1.434(7) 1.186(8) 1.443(7) 179.7(6) 177.1(6) −

a

The ring planes are defined as follows: C6H5 = C(13−18) (C13, C14, C15, C16, C15b, and C14b for 6bCl·CH2Cl2), Cp = C(19−23) (C19, C20, C21, C20b, and C19b for 6bCl·CH2Cl2), C5H4 = C(1−5) (C1, C2, C3, C3b, and C2b for 6bCl·CH2Cl2), C5H5 = C(6−10) (C6, C7, C8, C8b, and C7b for 6bCl·CH2Cl2). bDistance between the metal center and the centroid of the π-coordinated aromatic ring. cφRu and φFe denote the dihedral angles subtended by the planes C6H5/Cp and C5H4/C5H5, respectively; φRuFe stands for the dihedral angle of the planes C6H5/C5H4.

Bu4N[B(C6F5)4] (0.1 M) as the base electrolyte. The UV−vis− NIR and IR spectroelectrochemical measurements were carried out using an OTTLE (optically transparent thin-layer electrochemistry) cell30 and 10 mM solutions in dichloromethane containing the same supporting electrolyte (see the Experimental Section for details). Representative cyclic voltammograms are shown in Figure 6, and the pertinent data are summarized in Table 3. The starting ferrocene derivates 1−3 displayed a single reversible redox change attributable to the ferrocene/ferrocenium redox couple. The formal redox potentials increased from 1 to 3 following the increase in the electron-withdrawing character of the substituent at the ferrocenyl unit (cf. the Hammett σp constants: −0.12, −0.07, and 0.16 for CH2CH2Ph, CHCHPh, and CCPh, respectively).31 Complexation of 1−3 with Ru(η5C5R5)+ to give the cationic species 4a+−6a+ and 4b+−6b+ was manifested by an anodic shift (100−150 mV) of the ferrocene/ ferrocenium wave. The less easy oxidation of the iron center in

MeCN ligand. In the cyclobutadiene rings, the Ru−C distances toward the carbon atoms bearing the ferrocenyl substituents (C1/2 and C51/52), which reside at the apparently more crowded hinge position of the pseudometallocene unit, are significantly longer than those to the phenyl-substituted carbons (C3/4 and C53/54) facing the more open side that accommodates the Ru-bonded acetonitrile. The cyclobutadiene ring is somewhat rectangular, maintaining a partially localized character, while the in-ring angles remain close to the ideal 90° (Table 2). The CFc−CPh distances in 7[PF6] corresponding to triple bonds in the starting alkyne are slightly but statistically significantly shorter (ca. 1.44 Å) that the remaining C−C bonds (ca. 1.49 Å). Such bond asymmetry was previously explained in terms of orbital interactions between the d6 Ru metal fragment and the cyclobutadiene ligand.21a Electrochemistry. The electrochemical studies on 1−3 and the Ru−Fe complexes 4[PF6]−[PF6] were performed under an argon atmosphere in dichloromethane solutions containing 5023


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Table 2. Selected Distances and Angles for the Cations in the Structure of 7[PF6]·CHCl3 (in Å and deg)a cation 1 Ru1−Cp1b Ru1−Cbd1b φ(Ru1)c Ru1−C1 Ru1−C2 Ru1−C3 Ru1−C4 C1−C2 C2−C3 C3−C4 C4−C1 C−C−C(Cbd1)d Ru1−N1 N1−C42 Ru1−N1−C42 Cp1−Ru1−N1e Cbd1−Ru1−N1e Fe1−C5H4b Fe1−C5H5b φ(Fe1)f Fe2−C5H4b Fe2−C5H5b φ(Fe2)f

cation 2 Ru2−Cp2b Ru2−Cbd2b φ(Ru2)c Ru2−C51 Ru2−C52 Ru2−C53 Ru2−C54 C51−C52 C52−C53 C53−C54 C54−C51 C−C−C(Cbd1)d Ru2−N2 N2−C92 Ru2−N2−C92 Cp2−Ru2−N2e Cbd2−Ru2−N2e Fe3−C5H4b Fe3−C5H5b φ(Fe3)f Fe4−C5H4b Fe4−C5H5b φ(Fe4)f

1.868(1) 1.908(1) 36.1(2) 2.208(2) 2.189(3) 2.149(3) 2.141(2) 1.482(4) 1.445(4) 1.501(4) 1.443(4) 89.5(2)−90.6(2) 2.062(2) 1.133(4) 172.0(2) 113.59(8) 103.89(8) 1.647(1) 1.659(1) 1.3(2) 1.638(1) 1.646(2) 2.2(2)

1.878(2) 1.909(1) 35.5(2) 2.190(3) 2.189(3) 2.147(3) 2.163(3) 1.480(3) 1.444(4) 1.496(4) 1.443(4) 89.1(2)−90.8(2) 2.048(3) 1.124(5) 171.3(3) 112.27(9) 103.92(9) 1.637(2) 1.642(2) 0.7(2) 1.645(1) 1.658(2) 1.7(2)

a Definition of the ring planes: Cp1 = C(37−41), Cp2 = C(87−91), Cbd1 = C(1−4), Cbd2 = C(51−54). bDistance of the metal atom from the centroid of the π-coordinated ring. cDihedral angle of the planes of the cyclobutadiene (Cbd) and cyclopentadienyl (Cp) rings π-coordinated to Ru. d The range of the in-ring angles for the η4-cyclobutadiene ring. eAngles among the centroid of the respective π-coordinated ring, the ruthenium atom, and Ru-bound nitrogen. fDihedral angle of the cyclopentadienyl planes in ferrocene units.

with a higher intensity in comparison to those of 1−3, especially for the compounds possessing the unsaturated bridges (5a,b+ and 6a,b+), which represent conjugated donor−acceptor (DA) systems.35 No further absorptions due to metal−metal charge transfer interactions were observed. During the electrochemical generation of 3+, CC stretching bands with increasing intensities could be detected at 2220 (shoulder) and 2211 cm−1 (Fermi coupling) in the IR region.36 The spectra of the corresponding Ru complexes 6a[PF6] and 6b[PF6] showed similar bands in the same range (2224 and 2209 cm−1), whose intensity decreased upon the oxidation (i.e., during the generation of the dicationic species) (Figure 9). DFT Studies. In order to rationalize the redox and spectroelectrochemical behavior of the Fe−Ru complexes and their precursors, we have studied the series of all nine compounds in their native form (1−3 and cations 4a+−6a+/4b+−6b+) and as the respective ferrocenium species also theoretically using the well-established B3LYP density-functional theory method with the standard basis sets 6-31G* for geometry optimizations and 6311G** for energy refinements (except for Ru, where the LanL2DZ basis set with the corresponding effective core potential was employed). The solvent effects were estimated using the polarizable continuum model (PCM). Likewise the experiments, the theoretical results for 4b+−6b+ were always very similar to those for 4a+−6a+ and, hence, the discussion can be simplified by focusing on 1−3 and 4a+−6a+ only. Indeed, this similarity is quite plausible, as the complex cations 4b+−6b+ differ from 4a+−6a+ only by permethylation of the Ru-bound cyclopentadienyl ring. The calculated bond lengths and angles obtained after the geometry optimization in their native state (i.e., nonoxidized)

the Ru−Fe complexes can be rationalized by a decrease of the electron density at the ferrocene unit due to the coordination and by the overall positive charge of the resulting species that renders the electron removal more difficult. Permethylation of the Rubonded cyclopentadienyl ring in 4b+−6b+ had virtually no influence on the potential of the iron-based redox transitions. Apart from the ferrocene/ferrocenium waves, no further anodic redox events could be detected in the accessible potential range. On the other hand, an irreversible one-electron reduction was observed for all Ru−Fe complexes, except for 4a+ at the very cathodic end of the accessible potential window. The exact nature of this redox process, tentatively ascribed to a reduction located at the Ru,32 remains unclear. During the oxidation of 1−3 typical absorptions could be detected in the UV−vis range (Figure 7). The absorption close to the NIR edge (between 600 and 800 nm) was attributed to a ligand-to-metal charge transfer (LMCT) from the phenylcontaining substituent to the ferrocenium moiety.33 This transition was most intense and most bathochromically shifted for the styryl ferrocene monocation 2+. Furthermore, weak lowenergy NIR absorptions around 2500 nm could be detected for the electrochemically generated cations, which were assigned to the formally forbidden ligand-field (LF) transitions located at the ferrocenium units.34 Complexation of the Ru(η5-C5R5)+ fragment onto 1−3 resulted in a decrease of the intensity of the bands due to LMCT and LF transitions, likely due to the acceptor−acceptor nature of the electrogenerated dications, and further caused a significant hypsochromic shift of the LMCT bands (Figure 8). On the other hand, the characteristic absorptions of the ferrocenyl unit at 400−500 nm (d−d bands) were observed 5024


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Figure 6. Cyclic voltammograms for 1−3 and 4+−6+ as recorded at a scan rate of 100 mV s−1 at 25 °C in dichloromethane solutions (1.0 mM) containing Bu4N[B(C6F5)4] (0.1 M) as the electrolyte.

render the possible difference relatively large in absolute values but chemically meaningless (for a full listing, see the Supporting Information, Tables S3−S6). As for the energies, the experimental information comes mainly from the electrochemical measurements (Figure 6). The redox potential of the ferrocene/ferrocenium couple with respect to the standard hydrogen electrode is about 4.4 V.37 Although the observed changes (range about 200 mV) are rather small, a steady increase of the redox potential by ca. 100 mV upon increasing conjugation in the molecules of 1−3 could be observed (i.e., from CH2CH2 through CHCH to CC), except for an irregularity between 1 and 2, where the step change is less than half of this amount. As the oxidation involves predominantly the ferrocene unit, the difference between the series 1−3 and 4a+−6a+ (or 4b+−6b+) can be tentatively attributed to an increased electron-withdrawing effect of the substituent associated with the coordination of the positively charged Ru(η5-C5R5) fragment, whose influence is better relayed to the ferrocene/ferrocenium electrochemical probe in compounds with a more extensive conjugation. For this reason we tried to estimate the redox potentials using calculated differences of the electronic energies (corrected for the presence of the solvent) and adjusted by the corresponding vibrational zero-point energies (ZPE). To some extent the ZPEs are also influenced by the solvent, but their differences are already rather small, and for this reason their contribution to the redox potentials can usually be neglected.38 The estimated and experimentally measured redox potentials (with respect to the ferrocene/ferrocenium reference) are given in Table 3, while the

Table 3. Summary of Cyclic Voltammetry Data and Calculated Redox Potentialsa wave I compd

E°′/V (ΔEp/mV)a

E°′(calcd)/V

wave II Epc/Va

1 2 3 4a[PF6] 5a[PF6] 6a[PF6] 4b[PF6] 5b[PF6] 6b[PF6]

−0.055 (65) −0.020 (65) 0.100 (65) 0.060 (70) 0.155 (65) 0.255 (65) 0.050 (65) 0.150 (70) 0.255 (67)

−0.046 −0.039 0.079 0.152 0.366 0.467 0.132 0.331 0.358

n.a. n.a. n.a. −2.450 −2.095 −2.090 n.o. −2.305 −2.360

a

The potentials are given relative to ferrocene/ferrocenium reference. Conditions: 1.0 mM analyte in 0.1 M Bu4N[B(C6F5)4]/dichloromethane, glassy-carbon-disk electrode, 25 °C. bE°′ was calculated as the arithmetic mean of the anodic (Epa) and cathodic (Epc) peak potentials from cyclic voltammetry. ΔEp = Epa − Epc. n.a. = not applicable, n.o. = not observed.

agree quite well with the experimental values obtained from Xray structural analysis of the solid-state samples (compounds 4bCl, 5bCl, 6a[PF6], and 6bCl; vide supra) with an average deviation of 0.025 Å (maximum 0.15 Å) for the bond distances. The comparison of the calculated and experimentally determined bond angles is less straightforward because of a practically unhindered rotation of the cyclopentadienyl rings that may 5025


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changes are observed. For 1−3, the LUMO is located primarily at the phenyl group with antibonding character, and for 2 and 3 it reaches to the linker (Supporting Information, Figure S2). After oxidation, the LUMO is located back on Fe, giving rise to the ligand-to-metal charge transfer (LMCT) absorption bands observed in the UV−vis−NIR spectra of the oxidized species. Similar observations were made for 4a+−6a+ (Supporting Information, Figure S3), except that the situation on the phenyl group is now significantly influenced by the coordination of the Ru(η5-C5R5)+ fragment. In order to confirm that the oxidation takes place predominantly on the ferrocenyl unit, differences of the electron densities ρ(M) − ρ(M+) were mapped at the equilibrium geometry of the particular species in its native form (denoted as M). Although the resulting difference density maps are rather warped (Figures 10 and 11), it is obvious that the main changes are indeed located on Fe and their bonding cyclopentadienyl ring and only in the case of the conjugated species possessing the CHCH and CC bridges does the change in the electron distribution extend further to the linker and, for 4a+−6a+, even to the Ru atom. On the other hand, there are no visible changes occurring on the phenyl rings. This is in accordance with the anticipated increase in delocalization upon going from CH2CH2 to CC and the experimentally observed trend in the redox potentials. A similar picture could be also less directly obtained from various population analyses of the wave function or by a simple examination of the HOMO. Nonetheless, we prefer to use the difference electron maps for their unambiguous physical interpretation. DFT computations have been also used to rationalize the changes observed in the UV−vis−NIR and IR spectra upon the electrochemical oxidation. The recorded UV−vis−NIR spectra (Figures 7 and 8) show similarities. In all cases the oxidation is manifested by a formation of an absorption band at the red end of the UV−vis spectrum. Whereas this band is at ca. 600 nm for 1, it is considerably more intense, broadened, and red-shifted (to about 900 nm) in the case of the conjugated derivatives 2 and 3. The situation is similar for the molecules with the coordinated Ru(η5-C5R5)+ moiety, except that the shift is relatively smaller (to about 750 nm). The same features are reproduced also by the calculated spectra shown in Figure 7 by vertical lines. For 1+ the major contribution to this band can be indentified as the transition from the HOMO (located mainly on Fe) to the LUMO (located mainly on Ph for compounds based on 1 or in the PhCHCHC5H5 and PhCCC5H5 moieties in compounds bearing the conjugated ligands 2 and 3) (Figure 7). This also explains why the transition is weaker in the case of the compound featuring the CH2CH2 linker and more red-shifted upon increasing conjugation. As for the IR spectra, the most interesting feature is the antagonistic change in intensities of the CC stretching bands upon oxidation (Figure 9). For 3 the intensity increases upon oxidation, while in the case of 6a+ or 6b+ the opposite trend is seen. These results are reproduced by the DFT calculations. Because the IR absorption intensities depend on the derivative of the dipole moment with respect to the involved normal mode coordinate, the full explanation is less intuitive. Equivalently, the IR intensities can be obtained by using the atomic polar tensor (APT) charges40 (calculated or derived from the experimental intensities). While the calculated APT charges on the C atoms forming the triple bond in 3 are initially small (0.08 for Fc-C and −0.23 for C-Ph), upon oxidation they reverse polarity and rise to −1.00 and 0.85, respectively. For species containing the Ru(η5-

Figure 7. UV−vis−NIR spectra of 1−3 as recoded at increasing potentials. Conditions: 10 mM analyte, 0.1 M Bu4N[B(C6F5)4] in dichloromethane at 25 °C. Arrows indicate the observed trends, and the blue (M) and red (M+) lines represent the calculated transitions (see the results in DFT Studies).

calculated electronic energies and their PCM corrections and ZPEs are presented in the Supporting Information (Table S7). Although the predicted values are not accurate enough for a direct quantitative comparison, evident trends can be seen that fully correspond with the experimental observations. Thus, there is a systematic increase of the redox potential within all series (except between 1 and 2) and between the series 1−3 and 4a+− 6a+, while the differences between 4a+−6a+ and 4b+−6b+ are practically negligible. The highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) for 1−3 and their corresponding ferrocenium cations (Supporting Information, Figure S2) indicate that the HOMO of 1−3 is located mostly on the iron atom and only in the case of conjugated 2 and 3 does it extend also to the linker and the phenyl group. For the oxidized species 1+−3+, the HOMO essentially disappears from the Fe atom and is located on the phenyl group and, in the case of conjugated systems 2+ and 3+, also on the organic linker. This can be interpreted as the oxidation occurring mostly at the iron.39 With respect to the UV−vis−NIR spectra it is interesting to investigate also the corresponding LUMOs, where the opposite 5026


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Figure 8. UV−vis−NIR spectra of the Ru−Fe complexes as recorded at increasing potentials. Arrows indicate the observed trends. Conditions: 10 mM analyte, 0.1 M Bu4N[B(C6F5)4] in dichloromethane at 25 °C.

C5H5)+ moiety the reverse holds true. Initially, the APT charges are large (0.92 for Fc-C and −1.10 for C-Ph in 6a+) and, after oxidation, the polarity is reversed and the charges are reduced in magnitude (to −0.21 and −0.09, respectively, in 6a2+). The decrease of the APT charges corresponds with the decrease of the intensities of the CC stretching vibrations. The same trends can be seen in the difference electron densities.

ligand upon going from the native species to their oxidized forms. The same comparison also reflects an electronic communication between both metal centers in complex cations possessing 2 and 3 as the conjugated spacers, whereas the redox change in cations based on 1 remain localized on the particular metallocene unit (Fc group). Furthermore, the DFT computations confirm the observed trends in the redox potentials, reflecting an increase in the electron-withdrawing nature of the ferrocenyl substituents in 1−3 that renders the electrochemical oxidation more difficult and, for the Fe−Ru complexes, also the anodic shift reflecting electron donation to the coordinated Ru atom and the overall positive charge of the formed Fe−Ru complexes.

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CONCLUSION Heterobimetallic cations [Fc-spacer-(η6-C6H5)Ru(η5-C5R5)]+ and their precursors Fc-spacer-Ph (spacer = CH2CH2, CH CH, CC; R = H, Me) undergo one-electron reversible oxidation localized at the ferrocenyl unit to afford the corresponding ferrocenium cations. The originally rather intuitive assignment of this redox transition is fully supported by spectroelectrochemical measurements that reveal the gradual appearance of characteristic ferrocenium bands upon oxidation. DFT computations are in also in line with the spectroscopic data, showing that the HOMO orbitals from which electron removal can be expected to occur are localized predominantly at the ferrocene moieties. Another proof for the assignment of the redox processes comes from an inspection of the differences in the chemically unambiguous electron densities, indicating that major changes occur on Fe and their bonding cyclopentadienyl

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EXPERIMENTAL SECTION

Materials and Methods. The syntheses were carried out under an argon atmosphere and with the exclusion of direct daylight. Compound 3 was prepared according to a literature procedure.41 The complexes [Ru(η5-C5R5)(MeCN)3][PF6] (R = H, Me) and anhydrous 1,2dichloroethane were purchased from Strem and Sigma-Aldrich, respectively. Tetrahydrofuran (THF) was distilled from potassium/ benzophenone ketyl under argon. Solvents utilized for workup and chromatography (Lachner, Czech Republic) were used without any further purification. NMR spectra were recorded with a Varian Unity Inova 400 spectrometer at 25 °C (1H, 399.95 MHz; 13C{1H}, 100.583 MHz; 5027


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Figure 10. Contours of difference electron densities ρ(M) − ρ(M+) (+0.005 au in blue, −0.005 au in red) mapped at the equilibrium geometry of the native species (i.e., the neutral molecules) for 1−3.

Figure 9. IR spectra of 3, 6a[PF6], and 6b[PF6] as recorded at increasing potentials. Arrows indicate the trends. Conditions: 10 mM analyte, 0.1 M Bu4N[B(C6F5)4] in dichloromethane at 25 °C. 31

P{1H}, 161.90 MHz). Chemical shifts (δ/ppm) are given relative to internal SiMe4 (13C and 1H) and to external 85% aqueous H3PO4 (31P). In addition to the usual notation of the signal multiplicity, vt is used to denote apparent triplets arising from the AA′BB′ spin of the substituted ferrocene cyclopentadienyls (C5H4). Electrospray ionization (ESI) mass spectra were recorded on an Esquire 3000 (Bruker) spectrometer using dilute methanolic solutions. High-resolution (HR) ESI mass spectra were obtained with a Q-Tof Micro spectrometer (Waters). Preparation of [(1E)-2-Phenylethenyl]ferrocene (2). Butyllithium (22 mL of 1.6 M in hexanes, 35 mmol) was added dropwise to a solution of PhCH2PO3Et2 (8.4 mL, 40 mmol) in dry THF (50 mL) with stirring and cooling to −75 °C. The resulting brownish mixture was stirred at −75 °C for 10 min before a solution of ferrocenecarboxaldehyde (4.28 g, 20 mmol) in THF (25 mL) was introduced, and the resultant mixture was transferred to an oil bath and warmed to 60 °C. After it was stirred at this temperature for 6 h, the reaction solution was cooled to room temperature and washed with brine. The organic layer was dried over MgSO4 and filtered through a pad of silica gel (diethyl ether was used to elute the product). The crude product obtained after evaporation of all volatiles was dissolved in hot heptane (50 mL) and crystallized by slow cooling to 4 °C. The separated crystalline solid was filtered off, washed with a small amount of pentane, and dried under vacuum. Yield: 3.72 g (82%), burgundy red needles. The compound was isolated as the pure E isomer. Mp 122−123.5 °C (heptane) (lit.42 mp 120−122 °C (methanol), lit.43 mp 123−125 °C). 1H NMR (CDCl3): δ 4.13 (s, 5 H, C5H5Fe), 4.27 (vt, J = 1.8 Hz, 1 H, C5H4Fe), 4.46 (vt, J = 1.8 Hz, 1 H, C5H4Fe),

Figure 11. Contours of difference electron densities ρ(M+) − ρ(M2+) (+0.005 au in blue, −0.005 au in red) mapped at the equilibrium geometry of the starting monocations 4a+−6a+. 6.70 and 6.87 (2 × d, 3JHH = 16.2 Hz, 1 H, CHCH), 7.18−7.45 (m, 5 H, Ph). 13C{1H} NMR (CDCl3): δ 66.86 (2 C, CH of C5H4Fe), 69.01 (2 C, CH of C5H4Fe), 69.19 (5 C, C5H5Fe), 83.33 (1 C, Cipso of C5H4Fe), 125.77 (2 C, CH of Ph), 126.05, 126.77, and 126.90 (3 × 1 C, CHpara of Ph and CHCH), 128.64 (2 C, CH of Ph), 137.90 (1 C, Cipso of Ph). The NMR data are in agreement with those in the literature.44 Preparation of 2-(Phenylethyl)ferrocene (1). Platinum(IV) oxide (Adams’ catalyst; 65 mg) was added to a solution of compound 5028


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2 (4.04 g, 14 mmol) in absolute ethanol (150 mL). The mixture was degassed by three vacuum−hydrogen cycles and then stirred under hydrogen (1 atm), while it was heated to 60 °C (the starting alkene separates from the mixture at lower temperatures) for 15 h. During this time, the reaction mixture changed gradually from burgundy-red to orange-red. The reaction mixture was filtered and evaporated, leaving a rusty brown residue, which was taken up with chloroform. The solution was passed through a silica gel plug and evaporated. Because 1H NMR analysis revealed the reduction to be incomplete (FcCH2CH2Ph:(E)FcCHCHPh ratio ca. 85:15), the residue was redissolved in absolute ethanol (10 mL) and the reduction was continued with fresh catalyst (65 mg PtO2) overnight. Then, the reaction mixture was filtered and evaporated, and the residue was dissolved in hot heptane (12 mL). Slow cooling to room temperature and then down to −18 °C afforded large, rusty brown crystals of pure 1, which were isolated by suction, washed with pentane, and dried under vacuum. Yield: 3.38 g (83% based on the starting alkyne). Mp 58−59 °C (heptane) (lit.45 mp 55−57 °C, lit.46 mp 57−58 °C). 1 H NMR (CDCl3): δ 2.61−2.67 and 2.79−2.85 (2 × m, 2 H, CH2), 4.04−4.07 (m, 4 H, C5H4Fe), 4.10 (s, 5 H, C5H5Fe), 7.16−7.31 (m, 5 H, Ph). 13C{1H} NMR (CDCl3): δ 31.78 and 38.57 (2 × 1 C, CH2), 67.16 (1 C, CH of C5H4Fe), 68.07 (1 C, CH of C5H4Fe), 68.49 (5 C, C5H5Fe), 88.60 (1 C, Cipso of C5H4Fe), 125.84 (1 C, CHpara of Ph), 128.31 and 128.37 (2 × 2 C, CH of Ph), 142.18 (1 C, Cipso of Ph). General Procedure for the Preparation of 4[PF6]−6[PF6]. A solution of the appropriate ferrocene derivative 1−3 (0.13 mmol) in 1,2dichloroethane (3 mL) was added to the solid ruthenium(II) precursor [Ru(η5-C5R5)(MeCN)3][PF6] (R = H, Me; 0.1 mmol). The resulting mixture was heated at 40 °C for 3 h, filtered through a PTFE syringe filter, and evaporated under vacuum. The solid residue was purified by column chromatography over neutral alumina. The first band containing unreacted 1−3 was removed with a CH2Cl2/MeOH mixture (100/1, v/ v). Subsequently, the polarity of the eluent was increased (see details below) to elute a second band due to the product, which was collected and evaporated under vacuum to afford pure 4[PF6]−6[PF6]. The yields given below are based on the Ru precursor. Preparation of 4a[PF6]. Complex 4a[PF6] was obtained as described above starting from 1 (38 mg, 0.13 mmol) and [Ru(η5C5H5)(MeCN)3][PF6] (43 mg, 0.1 mmol). CH2Cl2/MeOH (10/1) was employed during the chromatographic purification. Yield: 42 mg (70%), yellow solid. 1H NMR (CD2Cl2): δ 2.62−2.71 (m, 4 H, CH2CH2), 4.01 (vt, J = 1.7 Hz, 2 H), 4.09 (vt, J = 1.7 Hz, 2 H) and 4.11 (s, 5 H) (3 × CH of Fc); 5.29 (s, 5 H, C5H5Ru), 5.92−6.08 (m, 5 H, C6H5). 13C{1H} NMR (CD2Cl2): δ 31.96 and 37.08 (2 × CH2); 68.24 (2 C), 68.81 (2 C) and 69.13 (5 C) (3 × CH of Fc); 80.90 (5 C, CH of C5H5Ru), 85.20 and 85.71 (2 C) (2 × CH of C6H5), 86.39 (Cipso of Fc), 86.96 (2 C, CH of C6H5), 106.36 (Cipso of C6H5). 31P{1H} NMR (CD2Cl2): δ −143.9 (septet, 1JPF = 711 Hz). MS (ESI+): m/z 457 ([Ru(C5H5)(FcCH2CH2Ph)]+). Anal. Calcd for C23H23PF6FeRu: C, 45.94; H, 3.86. Found: C, 45.66; H, 3.65. Preparation of 5a[PF6]. The general method described above was followed using 2 (38 mg, 0.13 mmol), [Ru(η5-C5H5)(MeCN)3][PF6] (43 mg, 0.1 mmol), and a CH2Cl2/MeOH (10/1) mixture for the chromatographic purification to afford 5a[PF6] as a maroon red solid. Yield: 54 mg (90%). 1H NMR (CD2Cl2): δ 4.16 (s, 5 H), 4.41 (vt, J = 1.8 Hz, 2 H) and 4.54 (vt, J = 1.8 Hz, 2 H) (3 × CH of Fc); 5.36 (s, 5 H, C5H5Ru), 6.16−6.49 (m, 5 H, C6H5), 6.40 and 7.14 (2 × d, 3JHH = 16.0 Hz, 1 H, CH). 13C{1H} NMR (CD2Cl2): δ 68.35 (2 C), 70.00 (5 C) and 70.96 (2 C) (3 × CH of Fc); 80.68 (Cipso of Fc), 81.47 (5 C, CH of C5H5Ru), 83.26 (2 C), 85.43 and 86.41 (2 C) (3 × CH of C6H5), 102.73 (Cipso of C6H5), 118.89 and 136.33 (CHCH). 31P{1H} NMR (CD2Cl2): δ −143.8 (septet, 1JPF = 711 Hz). MS (ESI+): m/z 455 ([Ru(C5H5)(FcCHCHPh)]+). Anal. Calcd for C23H21PF6FeRu: C, 46.09; H, 3.53. Found: C, 45.63; H, 3.45. Preparation of 6a[PF6]. Compound 6a was obtained using a slightly modified procedure. Thus, 3 (186 mg, 0.65 mmol) and [Ru(η5C5H5)(MeCN)3][PF6] (217 mg, 0.5 mmol) were reacted in dry 1,2dichloroethane (10 mL) at 60 °C for 3 h, whereupon the originally green reaction mixture turned pale brown. Two poorly resolved bands were obtained during the subsequent chromatographic purification over

neutral alumina with CH2Cl2/MeOH (50/1) as the eluent. Following evaporation, the first reddish brown band afforded complex 7[PF6], and the second orange band furnished the expected product 6a[PF6]. No starting alkyne 3 was recovered. Note: Compounds 6a[PF6] and 7[PF6] are rather difficult to fully separate, as they tend to coelute during the column chromatography. In addition, the chromatography (and purification in general) is complicated by an easy decomposition of complex 7[PF6], particularly in solution. Data for 6a[PF6]. Yield: 56 mg (19%), red solid. 1H NMR (CD2Cl2): δ 4.27 (s, 5 H), 4.38 (br s, 2 H) and 4.58 (br s, 2 H) (3 × CH of Fc); 5.41 (s, 5 H, C5H5Ru), 6.11−6.35 (m, 5 H, C6H5). 13C{1H} NMR (CD2Cl2): δ 62.17 (C), 70.71 (2 C), 70.84 (5 C) and 72.70 (2 C) (3 × CH of Fc); 79.71 (C), 82.16 (5 C, CH of C5H5Ru), 85.27, 86.07 (2 C) and 87.87 (2 C) (3 × CH of C6H5); 88.52 (Cipso of Fc), 94.42 (Cipso of C6H5). 31P{1H} NMR (CD2Cl2): δ −143.9 (septet, 1JPF = 711 Hz). MS (ESI+): m/z 453 ([Ru(C5H5)(FcCCPh)]+). Anal. Calcd for C23H21PF6FeRu: C, 46.25; H, 3.21. Found: C, 46.62; H, 3.43. Data for 7[PF6]. Yield: 151 mg (34%), reddish brown solid. 1H NMR (CD2Cl2): δ 1.96 (s, 3 H, MeCN), 4.13 (dt, J = 2.6, 1.3 Hz, 2 H, C5H4Fe), 4.21 (s, 10 H, C5H5Fe), 4.40 (td, J = 2.6, 1.3 Hz, 2 H, C5H4Fe), 4.50 (td, J = 2.6, 1.3 Hz, 2 H, C5H4Fe), 4.79 (dt, J = 2.6, 1.3 Hz, 2 H, C5H4Fe), 4.94 (s, 5 H, C5H5Ru), 7.42−7.73 (m, 10 H, Ph). 31P{1H} NMR (CD2Cl2): δ −144.4 (septet, 1JPF = 711 Hz). HR MS (ESI+): calcd for C41H43Fe2Ru ([Ru(C5H5)(Ph2Fc2C4)]+) 739.0319, found 739.0326. Preparation of 4b[PF6]. Compound 4b[PF6] was obtained by the general synthetic procedure given above starting from 1 (38 mg, 0.13 mmol) and [Ru(η5-C5Me5)(MeCN)3][PF6] (50 mg, 0.1 mmol). CH2Cl2/MeOH (50/1 v/v) was used as the more polar mobile phase during the chromatographic purification. Yield: 42 mg (63%), yellow solid. 1H NMR (CD2Cl2): δ 1.93 (s, 5 H, C5Me5), 2.39 (t, 3JHH = 7.4 Hz, 2 H, CH2), 2.66 (t, 3JHH = 7.4 Hz, 2 H, CH2), 3.98 (br s, 2 H), 4.08 (br s, 2 H) and 4.11 (s, 5 H) (3 × CH of Fc); 5.41−5.45 (m, 2 H) and 5.63− 5.69 (m, 3 H, C6H5). 13C{1H} NMR (CD2Cl2): δ 16.58 (5 C, C5Me5), 37.92 and 41.75 (2 × CH2); 74.12 (2 C), 74.85 (2 C) and 75.05 (5 C) (3 × CH of Fc); 92.26 (Cipso of Fc), 92.56, 93.14 (2 C) and 93.65 (2 C) (3 × CH of C6H5); 102.59 (5 C, C5Me5), 109.38 (Cipso of C6H5). 31P{1H} NMR (CD2Cl2): δ −143.8 (septet, 1JPF = 711 Hz). MS (ESI+): m/z 527 ([Ru(C5Me5)(FcCH2CH2Ph)]+). Anal. Calcd for C28H33PF6FeRu: C, 50.08; H, 4.95. Found: C, 49.75; H, 4.82. Preparation of 5b[PF6]. Complex 5b[PF6] was obtained by the general procedure using 2 (38 mg, 0.13 mmol) and [Ru(η5C5Me5)(MeCN)3][PF6] (50 mg, 0.1 mmol). CH2Cl2/MeOH (20/1 v/v) was used for the chromatographic purification. Yield: 62 mg (93%), red solid. 1H NMR (CD2Cl2): δ 1.93 (s, 5 H, C5Me5), 4.20 (s, 5 H), 4.43 (vt, J = 1.7 Hz, 2 H) and 4.54 (vt, J = 1.7 Hz, 2 H) (3 × CH of Fc); 5.69− 5.83 (m, 5 H, C6H5), 6.15 and 7.04 (2 × d, 3JHH = 16.0 Hz, 1 H) (2 ×  CH). 13C{1H} NMR (CD2Cl2): δ 10.79 (5 C, C5Me5), 68.14 (2 C), 69.94 (5 C) and 70.92 (2 C) (3 × CH of Fc); 81.39 (Cipso of Fc), 84.15 (2 C), 86.76 and 87.32 (2 C) (3 × CH of C6H5); 96.94 (5 C, C5Me5), 100.73 (Cipso of C6H5). 31P{1H} NMR (CD2Cl2): δ −143.8 (septet, 1JPF = 711 Hz). MS (ESI+): m/z 525 ([Ru(C5Me5)(FcCHCHPh)]+). Anal. Calcd for C28H31PF6FeRu: C, 50.23; H, 4.67. Found: C, 50.09; H, 4.67. Preparation of 6b[PF6]. Compound 3 (37 mg, 0.13 mmol) and [(η5-C5Me5)Ru(MeCN)3][PF6] (50 mg, 0.1 mmol) were reacted according to the general procedure to afford 6b[PF6]. CH2Cl2/MeOH (50/1) was used for chromatographic purification. Yield: 52 mg (78%); red solid. 1H NMR (CD2Cl2): δ 1.99 (s, 5 H, C5Me5), 4.28 (s, 5 H), 4.37 (vt, JHH = 1.8 Hz, 2 H) and 4.57 (vt, JHH = 1.8 Hz, 2 H) (3 × CH of Fc); 5.78−5.85 (m, 5 H, C6H5). 13C{1H} NMR (CD2Cl2): δ 10.49 (5 C, C5Me5), 62.40 (C), 70.41 (2 C), 70.61 (5 C) and 72.47 (2 C) (3 × CH of Fc); 79.01 (C), 86.76 and 87.32 (2 C) (2 × CH of C6H5); 87.38 (Cipso of Fc), 89.32 (2 C, CH of C6H5), 94.14 (Cipso of C6H5), 97.69 (5 C, C5Me5). 31P{1H} NMR (CD2Cl2): δ −143.8 (septet, 1JPF = 711 Hz). MS (ESI+): m/z 523 ([Ru(C5Me5)(FcCCPh)]+). Anal. Calcd for C28H29PF6FeRu: C, 50.39; H, 4.38. Found: C, 50.39; H, 4.35. X-ray Crystallography. Single crystals used for the X-ray diffraction analyses were grown by liquid-phase diffusion of diethyl ether into solutions in dichloromethane (4bCl·CH2Cl2, yellow block, 0.20 × 0.33 × 0.43 mm3; 5bCl·CH2Cl2, 0.04 × 0.19 × 0.22 mm3, red plate) or 5029


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similarly from dichloromethane/pentane (6bCl·CH2Cl2, orange-red plate; 0.08 × 0.10× 0.52 mm3) and chloroform/pentane (6a[PF6]· CHCl3, red plate, 0.14 × 0.35 × 0.56 mm3; 7[PF6]·CHCl3, red prism, 0.26 × 0.28 × 0.43 mm3). The X-ray diffraction data (2θmax = 52.0° for 5bCl·CH2Cl2 and 55.0° for all other compounds; data completeness ≥99.8%) were recorded on a Nonius KappaCCD diffractometer equipped with a Bruker Apex-II CCD detector and a Cryostream Cooler (Oxford Instruments) using graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). The crystal structures were solved by direct methods (SHELXS97), and the structure models were refined by least-squares routines based on F2 (SHELXL97).47 All non-hydrogen atoms were refined anisotropically, and the hydrogen atoms were placed in their calculated positions and refined using the riding model. Selected crystallographic data and structure refinement parameters are given in the Supporting Information (Table S8). Particular details of structure refinement are as follows. The disordered solvent molecule in 4bCl·CH2Cl2 was modeled over two positions with occupancies of 75% and 25%. Compound 6bCl· CH2Cl2 crystallizes as a twin (space group P21/m), and the diffraction data were corrected for nonmerohedral twinning (twin matrix: (−1,0,0; 0,−1,0; 0.416,0,1)) with the refined fractional contributions from the twin components being 88:12. The correction was applied on 877 diffractions, decreasing the R index from 6.2% to 4.1%. In addition, all discrete moieties constituting the crystals of 6bCl·CH2Cl2 reside on or around crystallographic mirror planes, which renders only their halves structurally independent (in the case of the complex cation, the mirror plane passes through the atoms C1, C6, C11−C13, C16, and C23 and through midpoints of the C3−C3b and C19−C19b bonds). Finally, the asymmetric unit of the unit cell of 7[PF6]·CHCl3 contains two complex cations, two molecules of solvating CHCl3, one complete PF6− anion in a general position, and two halves of PF6− ions residing on the inversion centers. A recent version of the PLATON program48 was used to prepare all structural drawings and perform geometric calculations. The numerical values given in the main text are rounded with respect to their estimated standard deviations (esd’s) given in one decimal place. CCDC reference numbers: 1002374−1002378. Electrochemical Measurements. Cyclic voltammograms were recorded with a Voltalab 10 instrument (Radiometer Analytical) under an argon atmosphere using 1.0 mM solutions of the analyte in dichloromethane containing 0.1 M Bu4N[B(C6F5)4] as the supporting electrolyte.49 A standard three-electrode cell was used, equipped with a platinum auxiliary electrode, a glassy-carbon working electrode, and an Ag/Ag+ reference electrode. The working electrode was polished with a Bühler micro cloth and Bühler diamond pastes with decreasing particle sizes (1−0.25 μm). The reference electrode was constructed from a silver wire inserted into a Luggin capillary with a Vycor tip containing 0.01 M AgNO3 and 0.1 M Bu4N[B(C6F5)4] in acetonitrile. This Luggin capillary was inserted into another Luggin capillary with a Vycor tip filled with 0.1 M Bu4N[B(C6F5)4] in dichloromethane. Repeated measurements showed the potentials to be reproducible within 5 mV. Potentials presented in this paper are given relative to the ferrocene/ferrocenium couple.50 When decamethylferrocene was used as an internal standard, the experimentally measured potential was converted to the ferrocene/ ferrocenium scale by subtracting 0.61 V.51 The spectroelectrochemical measurements were performed in an OTTLE (optically transparent thin-layer electrochemistry) cell30 placed in a Varian Cary 5000 UV− vis−NIR spectrometer or in a Thermo Nicolet 200 FT-IR spectrometer in. DFT Calculations. All calculations were done within density functional theory (DFT) using Becke’s three-parameter functional52 with the nonlocal Lee−Yang−Parr correlation functional (B3LYP).53 For the geometry optimization, starting from the experimentally determined solid-state structures where available, the standard basisset 6-31G* (for all atoms except Ru for which LanL2DZ with the corresponding effective core potential (ECP)) was used. After the stationary points on the potential energy surface (PES) were located, the harmonic vibrational analysis was carried out using the analytically calculated force-constant matrix to verify that the points are minima and

the vibrational frequencies as well as IR intensities were calculated. The energies were further refined using a larger 6-311G** basis set. The solvent effects were estimated using the polarizable continuum model (PCM).54 The solvent dielectric constant and volume were set corresponding to dichloromethane used in the experiments. The oxidized (doublet electronic) states were described using separate α and β orbitals. The calculated geometries are available in the Supporting Information. All calculations were performed using the Gaussian program package.55

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ASSOCIATED CONTENT

* Supporting Information S

Tables, figures, and CIF and xyz files giving a summary of 1H and 13 C NMR data, overlap of the two independent molecules in the structure of 7[PF6]·CHCl3, comparison of calculated and computed bond distances and angles for cations 6a+ and 4b+− 6b+, contours of the frontier molecular orbitals, summary of calculated energetic parameters and relevant crystallographic parameters, and NMR spectra. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail address for P.S.: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Financial support from the Czech Science Foundation (grant no. P207/11/0705) and the Fonds der Chemischen Industrie are gratefully acknowledged. J.M.S. is grateful to the Fonds der Chemischen Industrie for a Ph.D. fellowship.

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REFERENCES

(1) (a) Sun, R.; Wang, L.; Yu, H.; Abdin, Z.; Chen, Y.; Huang, J.; Tong, R. Organometallics 2014, DOI: 10.1021/om5000453. (b) Bayly, S. R.; Beer, P. D.; Chen, G. Z. In Ferrocenes: Ligands, Materials and Biomolecules; Štěpnička, P., Ed.; Wiley: Chichester, U.K., 2008; Chapter 8, pp 281−318. (2) (a) Arumugam, K.; Varnado, C. D.; Sproules, S.; Lynch, V. M.; Bielawski, C. W. Chem. Eur. J. 2013, 19, 10866. (b) Broderick, E. M.; Guo, N.; Vogel, C. S.; Xu, C.; Sutter, J.; Miller, J. T.; Meyer, K.; Mehrkhodavandi, P.; Diaconescu, P. L. J. Am. Chem. Soc. 2011, 133, 9278. (c) Liu, G.; He, H.; Wang, J. Adv. Synth. Catal. 2009, 351, 1610. (d) Gregson, C. K. A.; Gibson, V. C.; Long, N. J.; Marshall, E. L.; Oxford, P. J.; White, A. J. P. J. Am. Chem. Soc. 2006, 128, 7410. (e) Lorkovic, I. M.; Duff, R. R.; Wrighton, M. S. J. Am. Chem. Soc. 1995, 117, 3617. (3) (a) Metzler-Nolte, N.; Salmain, M. In Ferrocenes: Ligands, Materials and Biomolecules; Štěpnička, P., Ed.; Wiley: Chichester, U.K., 2008; Chapter 13, pp 499−639. (b) Moriuchi, T.; Hirao, T. Top. Organomet. Chem. 2006, 17, 143. (c) van Staveren, D. R.; Metzler-Nolte, N. Chem. Rev. 2004, 104, 5931. (d) Kraatz, H.-B. J. Inorg. Organomet. Polym. 2005, 15, 83. (4) (a) Amer, W. A.; Wang, L.; Amin, A. M.; Ma, L.; Yu, H. J. Inorg. Organomet. Polym. 2010, 20, 605. (b) Whittell, G. R.; Manners, I. Adv. Mater. 2007, 19, 3439. (c) Abd-El-Aziz, A. S.; Manners, I. J. Inorg. Organomet. Polym. Mater. 2005, 15, 157. (d) Hudson, R. D. A. J. Organomet. Chem. 2001, 637−639, 47. (5) (a) Caminade, A.-M.; Laurent, R.; Ouali, A.; Majoral, J.-P. Inorg. Chim. Acta 2014, 409A, 68. (b) Rapakousiou, A.; Wang, Y.; Nzulu, F.; Djeda, R.; Pinaud, N.; Ruiz, J.; Astruc, D. Organometallics 2013, 32, 6079. (c) Astruc, A.; Ornelas, C.; Ruiz Aranzaes, J. J. Inorg. Organomet. Polym. Mater. 2008, 18, 4. (6) Representative examples: (a) Grelaud, G.; Gauthier, N.; Luo, Y.; Paul, F.; Fabre, B.; Barrière, F.; Ababou-Girard, S.; Roisnel, T.; Humphrey, M. G. J. Phys. Chem. C 2014, 118, 3680. (b) Kitagawa, T.; 5030


Organometallics

Article

Matsubara, H.; Komatsu, K.; Hirai, K.; Okazaki, T.; Hase, T. Langmuir 2013, 29, 4275. (c) MacDonald, D. G.; Kübel, C.; Corrigan, J. F. Inorg. Chem. 2011, 50, 3252. (d) Eckermann, A. L.; Feld, D. J.; Shaw, J. A.; Meade, T. J. Coord. Chem. Rev. 2010, 254, 1769 (review). (e) Ling, X. Y.; Reinhoudt, D. N.; Huskens, J. Langmuir 2006, 22, 8777. (7) (a) Takahashi, S.; Anzai, J. Materials 2013, 6, 5742. (b) Heck, J.; Dede, M. In Ferrocenes: Ligands, Materials and Biomolecules; Štěpnička, P., Ed.; Wiley: Chichester, U.K., 2008; Chapter 9, pp 319−392. (c) Togni, A. In Ferrocenes: Homogenous Catalysis, Organic Synthesis, Materials Science; Togni, A., Hayashi, T., Eds.; Wiley-VCH: Weinheim, Germany, 1995; Chapter 8, pp 433−469. (8) Reviews: (a) Hildebrandt, A.; Lang, H. Organometallics 2013, 32, 5640. (b) Hildebrandt, A.; Pfaff, U.; Lang, H. Rev. Inorg. Chem. 2011, 31, 111. Representative examples: (c) Tauchman, J.; Hladíková, K.; Uhlík, F.; Císařová, I.; Štěpnička, P. New J. Chem. 2013, 37, 2019. (d) Wang, Y.; Rapakousiou, A.; Chastanet, G.; Salmon, L.; Ruiz, J.; Astruc, D. Organometallics 2013, 32, 6136. (e) Wright, J. R.; Shaffer, K. J.; McAdam, C. J.; Crowley, J. D. Polyhedron 2012, 36, 73. (f) Tauchman, J.; Trnka, J.; Císařová, I.; Štěpnička, P. Collect. Czech. Chem. Commun. 2010, 75, 1023. (g) Wang, M. C. P.; Li, Y.; Merbouh, N.; Yu, H.-Z. Electrochim. Acta 2008, 53, 7720. (h) Gong, Y.-H.; Audebert, P.; Yang, F.; Miomandre, F.; Lian, X.-C.; Tang, J. J. Electroanal. Chem. 2007, 606, 8. (i) Zhang, W.-W.; Yu, Y.-G.; Lu, Z.-D.; Mao, W.-L.; Li, Y.-Z.; Meng, Q.-J. Organometallics 2007, 26, 865. (j) Thomas, K. R. J.; Lin, J. T. J. Organomet. Chem. 2001, 637−639, 139. (k) Burrell, A. K.; Campbell, W. M.; Officer, D. L.; Scott, S. M.; Gordon, K. C.; McDonald, M. R. J. Chem. Soc., Dalton Trans. 1999, 3349. (l) McAdam, C. J.; Brunton, J. J.; Robinson, B. H.; Simpson, J. J. Chem. Soc., Dalton Trans. 1999, 2487. (9) Reviews: (a) Geiger, W. E. Organometallics 2011, 30, 28. (b) Zanello, P. In Ferrocenes: Homogenous Catalysis, Organic Synthesis, Materials Science; Togni, A., Hayashi, T., Eds.; Wiley-VCH: Weinheim, Germany, 1995; Chapter 7, pp 317−430. Selected recent examples:. (c) Nkoana, W.; Nyoni, D.; Chellan, P.; Stringer, T.; Taylor, D.; Smith, P. J.; Hutton, A. T.; Smith, G. S. J. Organomet. Chem. 2014, 752, 67. (d) Talancón, D.; López, C.; Font-Bardı ́a, M.; Calvet, T.; Roubeau, O. Eur. J. Inorg. Chem. 2014, 213. (e) Gramigna, K. M.; Oria, J. V.; Mandell, C. L.; Tiedemann, M. A.; Dougherty, W. G.; Piro, N. A.; Kassel, W. S.; Chan, B. C.; Diaconescu, P. L.; Nataro, C. Organometallics 2013, 32, 5966. (f) Lohan, M.; Justaud, F.; Lang, H.; Lapinte, C. Organometallics 2012, 31, 3565. (g) Lohan, M.; Milde, B.; Heider, S.; Speck, M.; Krausse, S.; Schaarschmidt, D.; Rüffer, T.; Lang, H. Organometallics 2012, 31, 2310. (h) Berstler, J.; Lopez, A.; Ménard, D.; Dougherty, W. G.; Kassel, W. S.; Hansen, A.; Daryaei, A.; Ashitey, P.; Shaw, M. J.; Fey, N.; Nataro, C. J. Organomet. Chem. 2012, 712, 37. (i) Tanaka, S.; Mashima, K. Inorg. Chem. 2011, 50, 11384. (j) Berenguer, J.; Bernechea, M.; Fernández, J.; Gil, B.; Lalinde, E.; Moreno, M. T.; Ruiz, S.; Sánchez, S. Organometallics 2011, 30, 4665. (k) Mandell, C. L.; Kleinbach, S. S.; Dougherty, W. G.; Kassel, W. S.; Nataro, C. Inorg. Chem. 2010, 49, 9718. (l) Siemeling, U.; Färber, C.; Leibold, M.; Bruhn, C.; Mücke, P.; Winter, R. F.; Sarkar, B.; von Hopffgarten, M.; Frenking, G. Eur. J. Inorg. Chem. 2009, 4607. (m) Khan, S. L.; Breheney, M. K.; Martinak, S. L.; Fosbenner, S. M.; Seibert, A. R.; Kassel, W. S.; Dougherty, W. G.; Nataro, C. Organometallics 2009, 28, 2119. (n) Štěpnička, P.; Císařová, I. Collect. Czech. Chem. Commun. 2009, 74, 799. (o) Sadhukhan, N.; Bera, J. K. Inorg. Chem. 2009, 48, 978. (p) Ghent, B. L.; Martinak, S. L.; Sites, L. A.; Golen, J. A.; Rheingold, A. L.; Nataro, C. J. Organomet. Chem. 2007, 692, 2365. (q) Maishal, T. K.; Mondal, B.; Puranik, V. G.; Wadgaonkar, P. P.; Lahiri, G. K.; Sarkar, A. J. Organomet. Chem. 2005, 690, 1018. (10) Lang, H.; Packheiser, R.; Walfort, B. Organometallics 2006, 25, 1836. (11) (η6-arene)RuII complexes: (a) Štěpnička, P.; Gyepes, R.; Lavastre, O.; Dixneuf, P. H. Organometallics 1997, 16, 5089. (b) Mai, J.-F.; Yamamoto, Y. J. Organomet. Chem. 1998, 560, 223. (c) Therrien, B.; Vieille-Petit, L.; Jeanneret-Gris, J.; Štěpnička, P.; Süss-Fink, G. J. Organomet. Chem. 2004, 689, 2456. (d) Elsegood, M. R. J.; Lake, A. J.; Mortimer, R. J.; Smith, M. B.; Weaver, G. W. J. Organomet. Chem. 2010, 695, 1838. (e) Sixt, T.; Sieger, M.; Krafft, M. J.; Bubrin, D.; Fiedler, J.; Kaim, W. Organometallics 1020, 29, 5511. (f) Tauchman, J.; Therrien, B.; Süss-Fink, G.; Štěpnička, P. Organometallics 2012, 31, 3985.

(g) Paim, L. A.; Dias, F. M.; Siebald, H. G. L.; Ellena, J.; Ardisson, J. D.; da Silva, M. D.; Batista, A. A. Polyhedron 2012, 42, 110. (h) Tauchman, J.; Süss-Fink, G.; Štěpnička, P.; Zava, O.; Dyson, P. J. J. Organomet. Chem. 2013, 723, 233. (η6-cyclopentadienyl)RuII and (η6indenyl)RuII complexes: (i) Ng, S. Y.; Leong, W. K.; Goh, L. Y.; Webster, R. D. Eur. J. Inorg. Chem. 2007, 463. (j) Ng, S. Y.; Leong, W. K.; Goh, L. Y.; Webster, R. D. Eur. J. Inorg. Chem. 2008, 144. (k) Shaw, A. P.; Norton, J. R.; Buccella, D.; Sites, L. A.; Kleinbach, S. S.; Jarem, D. A.; Bocage, K. M.; Nataro, C. Organometallics 2009, 28, 3804. (l) Dong, T.Y.; Chen, C.-P.; Kuo, C.-T.; Lin, S.-F.; Chen, C.-N.; Hsu, S.-C.; Wen, Y.S. Inorg. Chim. Acta 2010, 363, 1741. (12) Ru complexes with other ferrocene-based ligands: Auzias, M.; Therrien, B.; Süss-Fink, G.; Štěpnička, P.; Ang, W. H.; Dyson, P. J. Inorg. Chem. 2008, 47, 578. (13) (a) Lebreton, C.; Touchard, D.; Le Pichon, L.; Daridor, A.; Toupet, L.; Dixneuf, P. H. Inorg. Chim. Acta 1998, 272, 188. (b) Tschan, M. J.-L.; Therrien, B.; Ludvík, J.; Štěpnička, P.; Süss-Fink, G. J. Organomet. Chem. 2006, 691, 4304. (c) Dong, T.-Y.; Lin, H.-Y.; Lin, S.F.; Huang, C.-C.; Wen, Y.-S.; Lee, L. Organometallics 2008, 27, 555. (d) Liu, F.; Wu, X. H.; Xia, J.-L.; Jin, S.; Yu, G.-A.; Liu, S. H. J. Organomet. Chem. 2010, 695, 809. (e) Vacher, A.; Barrière, F.; Lorcy, D. Organometallics 2013, 32, 6130. (14) Mewborn, C. L.; Britt, R. L.; Baetz, N. W.; Heinrich, J. E.; Wheeler, D. E. J. Undergrad. Chem. Res. 2011, 10, 25; SciFinder Scholar 2011, 438705. (15) Malessa, M.; Heck, J.; Kopf, J.; Garcia, M. H. Eur. J. Inorg. Chem. 2006, 857. (16) Steffens, S.; Prosenc, M. H.; Heck, J.; Asselberghs, I.; Clays, K. Eur. J. Inorg. Chem. 2008, 1999. (17) (a) Trujillo, A.; Justaud, F.; Toupet, L.; Cador, O.; Carrillo, D.; Manzur, C.; Hamon, J.-R. New J. Chem. 2011, 35, 2027. (b) Trujillo, A.; Fuentealba, M.; Carrillo, D.; Manzur, C.; Ledoux-Rak, I.; Hamon, J.-R.; Saillard, J.-Y. Inorg. Chem. 2010, 49, 2750. (c) Trujillo, A.; Sinbandhit, S.; Toupet, L.; Carrillo, D.; Manzur, C.; Hamon, J.-R. J. Inorg. Organomet. Polym. Mater. 2008, 18, 81. (d) Fuentealba, M.; Hamon, J.-R.; Carrillo, D.; Manzur, C. New J. Chem. 2007, 31, 1815. (18) (a) Santi, S.; Durante, C.; Donoli, A.; Bisello, A.; Orian, L.; Ceccon, A.; Crociani, L.; Benetollo, F. Organometallics 2009, 28, 3319. (b) Buchmeiser, M.; Schottenberger, H. Organometallics 1993, 12, 2472. (19) (a) Garcia, M. H.; Valente, A.; Florindo, P.; Morais, T. S.; Piedade, F. M.; Duarte, M. T.; Moreno, V.; Avilés, F. X.; Loreno, J. Inorg. Chim. Acta 2010, 363, 3765. (b) Janková, Š.; Schulz, J.; Hybelbauerová, S.; Císařová, I.; Štěpnička, P.; Kotora, M. Eur. J. Org. Chem. 2013, 44. (20) These oligomers (either cyclic or linear) can result from Rumediated reactions of the starting alkynes: Trost, B. M.; Toste, F. D.; Pinkerton, A. B. Chem. Rev. 2001, 101, 2067. (21) (a) Crocker, M.; Green, M.; Orpen, A. G.; Thomas, D. M. J. Chem. Soc., Chem. Commun. 1984, 1141. (b) Crocker, M.; Froom, S. F. T.; Green, M.; Nagle, K. R.; Orpen, A. G.; Thomas, D. M. J. Chem. Soc., Dalton Trans. 1987, 2803. (22) (a) Campion, B. K.; Heyn, R. H.; Tilley, T. D. Organometallics 1990, 9, 1106. (b) Braun, T.; Steinert, P.; Werner, H. J. Organomet. Chem. 1995, 488, 169. (23) Gemel, C.; LaPensée, A.; Mauthner, K.; Mereiter, K.; Schmid, R.; Kirchner, K. Monatsh. Chem. 1997, 128, 1189. (24) (a) Le Paih, J.; Dérien, S.; Bruneau, C.; Demerseman, B.; Toupet, L.; Dixneuf, P. H. Angew. Chem. 2001, 113, 2996. (b) Le Paih, J.; Dérien, S.; Demerseman, B.; Bruneau, C.; Dixneuf, P. H.; Toupet, L.; Dazinger, G.; Kirchner, K. Chem. Eur. J. 2005, 11, 1312. (c) Yamamoto, Y.; Arakawa, T.; Itoh, K. Organometallics 2004, 23, 3610. (25) Rüba, E.; Mereiter, K.; Schmid, R.; Sapunov, V. N.; Kirchner, K.; Shottenberger, H.; Calhorda, M. J.; Veiros, L. F. Chem. Eur. J. 2002, 8, 3948. (26) Veiros, L. F.; Dazinger, G.; Kirchner, K.; Calhorda, M. J.; Schmid, R. Chem. Eur. J. 2004, 10, 5860. (27) DFT computations suggested a ruthenacyclopentatriene rather than a ruthenacyclopentadiene structure for these intermediates. For a review, see: Varela, J. A.; Saá, C. J. Organomet. Chem. 2009, 694, 143. 5031


Organometallics

Article

(28) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A. G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1. (29) Compare the angles (in deg) around the Ru center for cation 1 [cation 2]: Cp−Ru−Cbd 142.50(6) [143.76(6)], Cp−Ru−N 113.59(8) [112.27(9)], and Cbd−Ru−N 103.89(8) [103.92(9)]. (30) Krejčík, M.; Daněk, M.; Hartl, F. J. Electroanal. Chem. 1991, 317, 179. (31) Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165. (32) This assumption is supported by the fact that the LUMO in the cations 4+−6+ is localized predominantly at the ruthenocene moiety (see the results of the DFT calculations in DFT Studies). (33) (a) Mücke, P.; Winter, R. F.; Novak, I.; Kowalski, K. J. Organomet. Chem. 2012, 717, 14. (b) Flood, A. H.; McAdam, C. J.; Gordon, K. C.; Kjaergaard, H. G.; Manning, A. M.; Robinson, B. H.; Simpson, J. Polyhedron 2007, 26, 448. (34) (a) Atwood, C. G.; Geiger, W. E. J. Am. Chem. Soc. 1994, 116, 10849. (b) Paul, F.; Toupet, L.; Thépot, J.-Y.; Costuas, K.; Halet, J.-F.; Lapinte, C. Organometallics 2005, 24, 5464. (c) Lohan, M.; Ecorchard, P.; Rüffer, T.; Justaud, F.; Lapinte, C.; Lang, H. Organometallics 2009, 28, 1878. (d) Speck, J. M.; Schaarschmidt, D.; Lang, H. Organometallics 2012, 31, 1975. (35) Zanello, P.; Opromolla, G.; Fabrizi de Biani, F.; Ceccanti, A.; Giorgi, G. Inorg. Chim. Acta 1997, 255, 47. (36) (a) Paul, F.; Mevellec, J.-Y.; Lapinte, C. J. Chem. Soc., Dalton Trans. 2002, 1783. (b) Cuffe, L.; Hudson, R. D. A.; Gallagher, J. F.; Jennings, S.; McAdam, C. J.; Connelly, R. B. T.; Manning, A. R.; Robinson, B. H.; Simpson, J. Organometallics 2005, 24, 2051. (37) Reiss, H.; Heller, A. J. Phys. Chem. 1985, 89, 4207. (38) Baik, M.-H.; Friesner, R. A. J. Phys. Chem. A 2002, 106, 7407. (39) For previous calculations on FcCHCH, FcCHCH2, and FcCH2CH3, see: Boccia, A.; Marrani, A. G.; Stranges, S.; Zanoni, R.; Alagia, M.; Cossi, M.; Iozzi, M. F. J. Chem. Phys. 2008, 128, No. 154315. (40) Milani, A.; Tommasini, M.; Castiglioni, C. Theor. Chem. Acc. 2012, 131, No. 1139. (41) Dyadchenko, V. P.; Dyadchenko, M. A.; Okulov, V. N.; Lemenovskii, D. A. J. Organomet. Chem. 2012, 696, 468. (42) Chen, S. C.; Lee, C. C.; Sutherland, R. G. Synth. React. Inorg. Met.Org. Chem. 1977, 7, 565. (43) Sonogashira, K.; Hagihara, N. Kogyo Kagaku Zasshi 1963, 66, 1090; SciFinder Scholar 1965, 44020. (44) (a) Plazuk, D.; Zakrzewski, J. J. Organomet. Chem. 2006, 691, 287. (b) Solčań iová, E.; Toma, Š.; Liptaj, T. Collect. Czech. Chem. Commun. 1986, 51, 670. (45) Hoh, G. L. K.; McEwen, W. E.; Kleinberg, J. J. Am. Chem. Soc. 1961, 83, 3949. (46) Nesmeyanov, A. N.; Perevalova, E. G.; Shilovtseva, L. S. Izv. Akad. Nauk SSSR, Ser. Khim. 1961, 1982. (47) Sheldrick, G. M. Acta Crystallogr., Sect. A: Fundam. Crystallogr. 2008, 64, 112. (48) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7. (49) LeSuer, R. J.; Buttolph, C.; Geiger, W. E. Anal. Chem. 2004, 76, 6395. (50) Gritzner, G.; Kuta, J. Pure Appl. Chem. 1984, 56, 461. (51) Nafady, A.; Geiger, W. E. Organometallics 2008, 27, 5624. (52) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (53) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785. (54) Tomasi, J.; Mennucci, B.; Cammi, R. Chem. Rev. 2005, 105, 2999. (55) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Keith, T.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.;

Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision D.01; Gaussian, Inc., Wallingford, CT, 2013.

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