Linked C7 Carbon-Rich Bridges: A New Dimension for Ruthenium

Sep 28, 2009 - of two linked bimetallic units bearing a W-shaped C7 carbon-rich bridge was ... obtain bimetallic species bearing original W-shaped C7...
0 downloads 0 Views 835KB Size
Download PDF
6096

Organometallics 2009, 28, 6096–6100 DOI: 10.1021/om9006449

Linked C7 Carbon-Rich Bridges: A New Dimension for Ruthenium Redox-Active Organometallics Antoine Vacher, Ahmed Benameur, Cheikh Mbacke Ndiaye, Daniel Touchard, and Stephane Rigaut* UMR 6226 CNRS-Universit e de Rennes 1, Sciences Chimiques de Rennes, Campus de Beaulieu, F-35042 Rennes Cedex, France Received July 21, 2009

The synthesis of the tetrametallic complexes trans-[(Cl(dppe)2RudCdCdC(CH3)CHdC(-CtC-Ru(dppe)2Cl)(p-C6H4))2][OTf]2 (7b; dppe=1,2-bis(diphenylphosphino)ethane) composed of two linked bimetallic units bearing a W-shaped C7 carbon-rich bridge was achieved by modification of the unsaturated ligand precursor. This complex represents a novel example of the connection of two organometallic redox-active molecular wires via a carbon-rich chain for access to larger redoxactive multicomponent assemblies. UV-visible and cyclic voltammetry studies show that the properties of the building blocks are retained in the new adduct, providing two conduits of approximately 12 A˚ for electron transfer in either an oxidation or a reduction process. Over the past decade, coordination complexes in which rigid linear π-conjugated organic chains span transitionmetal centers have been proposed as models for molecular wires in molecular-scale electronics.1,4 Binuclear organometallic σ-arylacetylide complexes with direct connection *To whom correspondence should be addressed. E-mail: stephane. [email protected]. (1) (a) Joachim, C.; Ratner, M. A. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 8801–8808. (b) Nitzan, A.; Ratner, M. A. Science 2003, 300, 1384– 1389. (c) Carroll, R. L.; Gorman, C. B. Angew. Chem., Int. Ed. 2002, 41, 4378. (d) James, D. K.; Tour, J. Chem. Mater. 2004, 15, 4423–4435. (2) (a) Brunschwig, B. S.; Creutz, C.; Sutin, N. Chem. Soc. Rev. 2002, 31, 168–184. (b) Nelsen S. F. In Electron Transfer in Chemistry; Balzani, V., Ed.; Wiley-VCH: Weinheim, Germany, 2001; Vol. 1, Chapter 10. (c) Launay, J.-P. Chem. Soc. Rev. 2001, 30, 386–397. (d) Demadis, K. D.; Hartshorn, C. M.; Meyer, T. J. Chem. Rev. 2001, 101, 2655–2685. (e) Ceccon, A.; Santi, S.; Orian, L.; Bisello, A. Coord. Chem. Rev. 2004, 248, 683–724. (f) Alessandro, D. M.; Keene, F. R. Dalton Trans. 2006, 424–440. (g) Chisholm, M. H.; Patmore, N. J. Acc. Chem. Res. 2007, 40, 19–27. (h) Kaim, W.; Lahiri, G. K. Angew. Chem., Int. Ed. 2007, 46, 1778–1796. (3) For reviews on organometallic complexes see: (a) Ren, T. Organometallics 2005, 24, 4854–4870. (b) Bruce, M. I.; Low, P. J. Adv. Organomet. Chem. 2004, 50, 179–444. (c) Rigaut, S.; Touchard, D.; Dixneuf, P. H. Coord. Chem. Rev. 2004, 1586–16501. (d) Powell, C. E.; Humphrey, M. G. Coord. Chem. Rev. 2004, 248, 725–756. (e) Paul, F.; Lapinte, C. Coord. Chem. Rev. 1998, 178-180, 431–509. (f) Venkatesan, K.; Blacque, O.; Berke, H. Dalton Trans. 2007, 1091–1100. (g) Szafert, S.; Gladysz, J. A. Chem. Rev. 2006, 106, 1–33. (h) Akita, M.; Koike, T. Dalton Trans. 2008, 3523–3530. (i) Long, N. J.; Willimas, C. K. Angew. Chem., Int. Ed. 2003, 42, 2586–2617. (4) For recent organometallic examples see: (a) Hamon, P.; Justaud, F.; Cador, O.; Hapiot, P.; Rigaut, S.; Toupet, L.; Ouahab, L.; Stueger, H.; Hamon, J.-R.; Lapinte, C. J. Am. Chem. Soc. 2008, 130, 17372– 17383. (b) Ghazala, S. I.; Paul, F.; Toupet, L.; Roisnel, T.; Hapiot, P.; Lapinte, C. J. Am. Chem. Soc. 2006, 128, 2463–2476. (c) Fox, M. A.; Roberts, R. A.; Baines, T. E.; Le Guennic, B.; Halet, J.-F.; Hartl, F.; Yufit, D. S.; Albesa-Jove, D.; Hward, J. A. K.; Low, P. J. J. Am. Chem. Soc. 2008, 130, 3566–3578. (d) Pichlmaier, M.; Winter, R. F.; Zabel, M.; Zalis, S. J. Am. Chem. Soc. 2009, 131, 4895–4903. (e) Motoyama, K.; Koike, T.; Akita, M. Chem. Commun. 2008, 5812–5814. (f) Olivier, C.; Kim, B.-S.; Touchard, D.; Rigaut, S. Organometallics 2008, 27, 509–518. (g) Lagrost, C.; Costuas, K.; Tchouar, N.; Bozec, H. L.; Rigaut, S. Chem. Commun. 2008, 6117–6119. (h) Bruce, M. I.; Karine, C.; Ellis, B. G.; Halet, J.-F.; Low, P. J.; Moubaraki, B.; Murray, K. S.; Ouddaie, N.; Perkins, G. J.; Skelton, B. W.; White, A. H. Organometallics 2007, 26, 3735–3745. (i) Fan, Y.; Liu, I. P.-C.; Fanwick, P. E.; Ren, T. Organometallics 2009, 28, 3959–3962. pubs.acs.org/Organometallics

Published on Web 09/28/2009

of a carbon-rich bridge and the metal atoms are particularly well suited models for investigations of electron transfer under carefully controlled conditions.3,4 Electronic cooperation was also established in larger organometallic complexes including more than two redox centers, such as star-shaped, square, and linear assemblies, in which electrons can be transported over nanometric distances.3,5 In order to bring these individual units together within higher dimensional organometallic networks designed for a specific task, it is essential to be able to link several wires in another dimension. This connection should be possible via the metal unit by incorporation of functionalized remote ligands3a,6 or via the carbon-rich chains if functionalization of this ligand is possible. Ruthenium systems present opportunities for the synthesis of novel organometallic compounds as models for electron conduction with unusual and stable topologies.3a-d Especially, the ruthenium [RuCl(dppe)2]þ (dppe = 1,2-bis(diphenylphosphino)ethane) species offers the possibility to obtain bimetallic species bearing original W-shaped C7 carbon-rich bridges (Scheme 1).7 The exceptional ability of this ruthenium trans ditopic structure to operate as a connector allowing electron flow to occur between different elements in carbon-rich systems8 also allowed the achievement (5) Alessandro, D. M.; Keene, F. R. Chem. Rev. 2006, 106, 2270–2298. (6) (a) Chen, W. Z.; Ren, T. Organometallics 2005, 24, 2660–2669. (b) Ren, T. Chem. Rev. 2008, 108, 4185–4207. (7) (a) Rigaut, S.; Massue, J.; Touchard, D.; Fillaut, J.-L.; Golhen, S.; Dixneuf, P. H. Angew. Chem., Int. Ed. 2002, 41, 4513. (b) Rigaut, S.; Olivier, C.; Costuas, K.; Choua, S.; Fadhel, O.; Massue, J.; Turek, P.; Saillard, J. Y.; Dixneuf, P. H.; Touchard, D. J. Am. Chem. Soc. 2006, 128, 5859–5878. (c) Bruce, M. I.; Ellis, B. G.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 2005, 690, 1772–1783. (8) (a) Rigaut, S.; Costuas, K.; Touchard, D.; Saillard, J.-Y.; Golhen, S.; Dixneuf, P. H. J. Am. Chem. Soc. 2004, 126, 4072–4073. (b) Xu, G.-L.; De Rosa, M. C.; Crutchley, R. J.; Ren, T. J. Am. Chem. Soc. 2004, 126, 3728–3729. (c) Zhu, Y.; Clot, O.; Wolf, M. O.; Yap, G. P. A. J. Am. Chem. Soc. 1998, 120, 1812–1821. (d) Lebreton, C.; Touchard, D.; Le Pichon, L.; Daridor, A.; Toupet, L.; Dixneuf, P. H. Inorg. Chem. Acta 1998, 272, 188– 196. (e) Colbert, M. C. B.; Lewis, J.; Raithby, P. R.; White, J. P.; Williams, D. J. Dalton Trans. 1997, 99–104. r 2009 American Chemical Society

Article

Organometallics, Vol. 28, No. 20, 2009

6097

Scheme 1

Scheme 2. Synthetic Pathway for the Allenylidene Precursor 3c

of very efficient electronic communication along 24 A˚ in the trimetallic oligomeric analogue trans-[Cl(dppe)2Ru-CtCC(Ph)dCHC(CH3)dCdCdRu(dppe)2Cl-CtCC(CH3)dCHC(Ph)dCdCdRu(dppe)2Cl][OTf]2 (D), in either an oxidation or a reduction process.9 These bridged systems are particularly interesting alternatives to the classical metal polyynediyls [M]-(CtC)n-[M], since they can be potentially functionnalized on two regions of the chain (Scheme 1). In this work, we have taken advantage of the nature of this type of bridging ligand to realize a novel redoxactive complex, with higher dimensionality, by modifying the allenylidene precursor in order to link two wires via the unsaturated chain. In addition, we illustrate the influence of the linker structure on the formation of the complex, as well as on its electronic properties in the light of UV-visible and electrochemical results.

a classical procedure,12 activation of 4-ethynylacetophenone with the ruthenium precursor 1 led to the neutral bis-alkynyl ruthenium derivatives 2 in good yield. The carbonyl groups are further converted into propargylic alcohol functions by the action of lithium acetylide to obtain 3c. This complex displays FTIR characteristic vibration stretches at 3051 (νCH), 2144 (νCtCH), and 2065 (νCtC), cm-1. The 31P NMR spectrum shows a single signal at δ 54.5 ppm characteristic of trans bis-acetylide species. Further, reaction of 3a-c with the 16-electron precursor [RuCl(dppe)2]OTf (4) led to the bis-allenylidene complexes 5a-c bearing the methyl groups in ca. 80% yield (Scheme 3). The three complexes were fully characterized by means of IR, NMR, mass spectrometry, and elemental analysis. The FTIR spectra of 5a-c show characteristic features for such compounds at 1915-1940 cm-1 (νCdCdC) and, additionally, at 2014 cm-1 (νCtC) for 3c. The two allenylidene groups are equivalent, and therefore the NMR spectra show only one set of signals for both sides with a relative trans disposition of the chlorine atom and the allenylidene ligand. As expected, the characteristic allenylidene low-field 13C signals for the CR carbon nucleus appear as a quintet above δ 300 ppm, with 2 JPC ≈ 14 Hz. In the last step, 2 equiv of the neutral diynyl compound 6 was slowly added to 1 equiv of the cationic allenylidene complexes 5a-c over a period of 3 days, at room temperature. While the reaction proceeds smoothly with 5b, attempts to obtain tetrametallic complexes by activation of the bisallenylidene complexes 5a,c unfortunately failed, probably for steric reasons. Indeed, for example, tris-allenylidene ruthenium species could be obtained only when the propargylic alcohol functionalities were separated by a large tripodal core.10b,13 Complex 7b was isolated in good yields (72%) as stable poor-quality dark green crystals and fully characterized. The FTIR spectrum presents an intense absorption around 1900 cm-1, characteristic of the cumulenic character of the chains. NMR analysis evidences the equivalency of the two chains but with an unsymmetrical structure intermediate between the two possible mesomeric forms for each chain, as observed for the bimetallic analogue B (Scheme 1). For example, the 31P NMR spectrum displays only two singlets at δ 46.9 and 49.2 ppm, and the 1H NMR spectrum presents a single signal for the methyl groups and for the protons on the two chains at δ 1.08 and 5.90 ppm, respectively. The spectroscopic characteristics of 7b are very close to those of B.

Results and Discussion Following the route we described to obtain the W-shaped bimetallic species with C7 carbon-rich bridges from metal allenylidenes and from a neutral diynyl compound (Scheme 1), the strategy to obtain new tetrametallic species composed of two W-shaped units linked by the carbon-rich bridge consists of coupling the same neutral diynyl compound after an in situ desilylation7 with the key bimetallic species bearing two allenylidene termini with a methyl group (Scheme 3). Bis-allenylidene complexes are obtained via the double activation of molecules containing two propargylic alcohol functions.10,11 Therefore, in addition to the wellestablished bis-propargylic alcohols 3a,11 we targeted the two new bis-propargylic alcohols 3b,c in order to (i) modulate the length of the linker between the allenylidene functions and thus between the future C7 chains and (ii) try to introduce a supplementary redox-active unit in the linker. The bis-alcohol 3b was readily obtained by the action of lithium acetylide on the corresponding bis-ketone 1-(40 -acetyl-1,10 -biphenyl-4-yl)ethan-1-one, while the bisacetylide complex 3c was achieved using a step-by-step organometallic synthesis: i.e., by modification of the carbon-rich ligands of a bis-acetylide to introduce the propargylic alcohol functions (Scheme 2). More precisely, following (9) Olivier, C.; Choua, S.; Turek, P.; Touchard, D.; Rigaut, S. Chem. Commun. 2007, 3100–3102. (10) (a) Guesmi, S.; Touchard, D.; Dixneuf, P. H. Chem. Commun. 1996, 2773–2774. (b) Rigaut, S.; Perruchon, J.; Guesmi, S.; Fave, C.; Touchard, D.; Dixneuf, P. H. Eur. J. Inorg. Chem. 2005, 447–460. (c) Castellas-Gaspar, B.; Laubender, M.; Werner, H. J. Organomet. Chem. 2003, 684, 144–152. (d) Mantovani, N.; Brugnati, M.; Gonsalvi, L.; Grigiotti, E.; Laschi, F.; Marvelli, L.; Peruzzini, M.; Reginato, G.; Rossi, R.; Zanello, P. Organometallics 2005, 24, 405–418. (11) Rigaut, S.; Touchard, D.; Dixneuf, P. H. Organometallics 2003, 22, 3980–3984.

(12) Touchard, D.; Haquette, P.; Guesmi, S.; Le Pichon, L.; Daridor, A.; Toupet, L.; Dixneuf, P. H. Organometallics 1997, 16, 3640–3648. (13) (a) Weiss, D.; Dixneuf, P. H. Organometallics 2003, 22, 2209. (b) Uno, M.; Dixneuf, P. H. Angew. Chem., Int. Ed. 1998, 37, 1714–1717.

6098

Organometallics, Vol. 28, No. 20, 2009

Vacher et al.

Scheme 3. Synthetic Pathway for the Tetrametallic Species

Table 1. Electrochemical (CV) and UV-Vis Data electrochemistrya

5a 5b 5c 7b Bf

E°red2(V)

E°red1(V)

-0.841

-0.631 -0.981b -1.191b,d -1.160 b,d -1.24

E°ox1(V)

0.214 0.281b 0.32

E° ox2 (V)

1.030b,c 0.97c

UV-vise λmax/nm (ε/mol-1 L cm-1) 232 (83 100), 269 (789 000), 582 (29 00) 232 (84 800), 272 (90 300), 563 (45 000) 233 (137 700), 265 (118 200), 766 (83 000) 233 (179 400), 261 (180 600), 538 (15 900), 754 (142 000) 226 (122 800), 258 (95 700), 494 (4700), 746 (98 000)

a Conditions and details: sample 1 mM in CH2Cl2, [NBu4]PF6 (0.1 M), v = 100 mV s-1, potentials reported in V vs ferrocene as an internal standard, reversible oxidation process, ΔEp ≈ 60 mV. b Two overlapping one-electron processes. c Peak potential of a chemically irreversible process. d ΔEp ≈ 120 mV. e In CH2Cl2. f From ref 7b.

In addition to the classical intense short-wavelength absorption bands for the ligand-centered π-π* and n-π* type transitions originating from the dppe and the carbon-rich ligands, the UV-visible absorption spectrum of complex 7b shows a strong and broad absorption band at λmax 764 nm with a weaker absorption at higher energy (Table 1, Figure 1). The broad band is red-shifted by comparison to the RuII(dπ) f π*(allenylidene) MLCT of the allenylidene precursor (Table 1)10b,14 and looks similar to that of the bimetallic analogue B. As already discussed, the MO diagram of B suggests that these intense and broad bands include several transitions close in energy with an MLCT character.7b,15 (14) Winter, R. F.; Klinkhammer, K. W. Organometallics 2001, 20, 1317–1333. (15) The broad bands of B and 7b look similar, but they do not match. Thus, the frontier orbital levels (and probably the oscillator strengths of the transitions) are not the same for the two molecules. A simple comparison of the extinction coefficients of the envelopes considering two independent W-shaped moieties in 7b (vide infra) is then meaningless.

Figure 1. UV-vis absorption spectra for compounds 7b and B in CH2Cl2 solutions.

Cyclic voltammetry (CV) was used to study the electrochemical behavior of 5a,b and 7b (CH2Cl2, 0.1 M Bu4NPF6). The values of the potentials for all compounds are reported in Table 1. Complex 7b undergoes a well-defined reversible

Article

Organometallics, Vol. 28, No. 20, 2009

6099

This is not surprising, since the biphenyl linker is known to decrease the communication with other systems,4b owing to the free rotation between the two aromatic rings. With regard to 7b, this breaking of the conjugation is probably amplified for steric reasons, the ruthenium moieties being very bulky. Therefore, it is likely that the two phenyl groups of the linker in 7b do not stand in the same plane; rather, their planes are perpendicular, giving rise to a connection of the two C7 conduits in three dimensions.

Conclusion Figure 2. CV for 7b (Bu4NPF6 (0.1 M) in CH2Cl2; v=100 mV s-1). The inset shows the full reversibility of the first oxidation process.

oxidation wave followed by an almost irreversible second oxidation (Figure 2). This is consistent with an ongoing chemical reaction of the second oxidized species, producing a new wave on the return scan around 1.0 V. A well-defined one-electron reversible reduction wave at rather negative potential was also observed. This behavior is similar to that of B, for which the reduction process was mainly ascribed to the reduction of the carbon chain with the single electron delocalized over the bridge, while the first oxidation processes pointed out the delocalized nature of the single electron involving the two metallic centers with about half of the unpaired electron on the Ru atoms and with an almost equal participation of the carbon bridge. Therefore, the redox processes in 7b are ascribed to the simultaneous reduction of the two independent chains and to the concomitant oxidation processes of the two independent “RuC7Ru” moieties, in which the C7 bridge is a noninnocent redox ligand that cannot be decoupled from the metal in the redox processes. It is worth noting that the rate of the reduction process is somewhat slower (ΔEp ≈ 120 mV), probably because of the influence of the bulky substituent on the reorganization of the chains upon reduction. These results also establish that the first oxidized and first reduced species are unstable in solution with respect to disproportionation.16 Overall, the different spectroscopic and electrochemical studies pointed out the resemblance of the behavior of 7b and B. This behavior sharply contrasts with that of the linear trimetallic analogue D, in which the presence of a second chain and a third metallic center has the effect of extending the communication along the all-conjugated path by comparison with B.9 In the present case, the apparent independent behavior of the two chains may be the result of the lack of electronic communication between these two parts of the molecule, due to the nature of the biphenyl bridge. The bis-allenylidene complex 5a, which shows two consecutive one-electron reductions (Table 1), is composed of two redoxactive allenylidene units separated by only one ring that allows for electronic communication, as previously described for a very similar complex.10b In contrast, complex 5b displays only one reduction wave for the two overlapping processes, probably because of a less efficient communication.17 (16) (a) Barriere, F.; Camire, N.; Geiger, W. E.; Mueller-Westerhoff, U. T.; Sanders, R. J. Am. Chem. Soc. 2002, 124, 7262–7263. (b) Lapinte, C. J. Organomet. Chem. 2008, 693, 793–801. (17) Other phenomena such as Coulombic repulsion, structural distortion through the oxidations, and ion pairing in addition to delocalization also contribute to Kc, and one must therefore be careful in interpreting the meaning of Kc (or ΔE°) trends.15 Meanwhile, we are confident in the proposed tendency for this bis-allenylidene series.10b

In conclusion, complex 7b represents an original example of the connection of two organometallic redox-active molecular wires via a carbon-rich chain to obtain a tetrametallic complex. In such a complex, the metals and the intervening bridging ligands provide two linear conduits for electron transfer of approximately 12 A˚, in either an oxidation or a reduction process. Importantly, the optical and electrochemical properties of the building blocks are retained in the new adduct, with no apparent significant electronic cooperation between the moieties on the basis of electrochemical and optical results. As a proof of concept, this work shows that, with an accurate choice of the spacer avoiding steric hindrance between the metal units, access to novel nanoscaled organometallic assemblies should be possible, especially with this ruthenium system allowing trans chlorine atom substitutions with carbon-rich chains. It is noteworthy that these results also open the door to the realization of novel magnetic assemblies, since each moiety exhibits a similar spin distribution in each redox process.

Experimental Section The reactions were carried out under an inert atmosphere using Schlenk techniques. Solvents were freshly distilled under argon using standard procedures. Chromatography and filtration were performed using alumina (Acros, actived neutral 50-200 μm). Electrochemical studies were carried out under argon using an Eco Chemie Autolab PGSTAT 30 potentiostat (CH2Cl2, 0.1 M Bu4NPF6). The working electrode was a Pt disk, and ferrocene was the internal reference. High-resolution mass spectra (HRMS) were recorded in Rennes at the CRMPO (Centre Regional de Mesures Physiques de l’Ouest) on a ZabSpecTOF (LSIMS at 4 kV) spectrometer. [RuCl2(dppe)2] (1),18 HCtC(OH)C(CH3)-p-C6H4-(CH3)C(OH)CtCH (3a),11 and [RuCl(dppe)2][OTf] (4)19 were prepared as previously reported. trans-[(dppe)2Ru(-CtC(p-C6H4)COCH3)2] (2). In a Schlenk tube, 968 mg (1 mmol) of cis-[RuCl2(dppe)2] (1), 432 mg (3 mmol) of HCtC-p-C6H4COCH3, and 672 mg (4 mmol) of NaPF6 were dissolved in 100 mL of dry dichloromethane, and 1 mL of Et3N was added. The solution was stirred for 24 h at room temperature. After evaporation, the residue was washed with diethyl ether (3  20 mL). The compound was extracted with CHCl3 (3  20 mL). Evaporation of the solvent led to 911 mg of 2 (77%). 31P{1H} NMR (CDCl3): δ 54.5 (s, PPh2). 1H NMR (CDCl3): δ 7.80-6.70 (m, 48H, Ph), 2.64 (m, 8H, CH2), 2.60 (s, 6H, CH3). 13C{1H} NMR (CD2Cl2): δ 136.7-127.1 (Ph), 118.4 (Ru-CtC), 31.3 (m, |1JPC þ 3JPC|=23 Hz, CH2), 26.17 (CH3). IR (KBr, cm-1): 2049 (νCtC), 1674 (νCdO). HR-MS FABþ (m/z): 1185.2837 ([M þ Hþ]þ, calcd 1185.2822). Anal. Found for C72H62P4RuO2: C, 73.57, H, 5.11. Calcd: C, 73.82; H, 5.28. (18) Chaudret, B.; Commengues, G.; Poilblanc, R. J. Chem. Soc., Dalton Trans. 1984, 1635–1639. (19) Higgins, S. J.; La Pensee, A.; Stuart, C. A.; Charnock, J. M. Dalton Trans. 2001, 902–910.

6100

Organometallics, Vol. 28, No. 20, 2009

HCtC(OH)C(CH3)(p-C6H4)2(CH3)C(OH)CtCH (3b). In a Schlenk tube, THF (20 mL) was cooled to -78 °C before addition of acetylene, measured with a gas buret (8 mmol), and nBuLi (4 mmol, 8 mL of 1.6 M solution in hexane). The mixture was stirred for 15 min at -78 °C before addition of a suspension of 476 mg of CH3CO(p-C6H4)2COCH3 (2 mmol) in THF (20 mL). The resulting mixture was further stirred for 1 h at -78 °C and 18 h at room temperature before being hydrolyzed with a saturated NH4Cl solution. The crude product was extracted with CH2Cl2 (4  50 mL), washed with water (3  20 mL), and dried, and the solvent was evaporated. Further purification was achieved by chromatography over silica gel (10% diethyl ether in n-pentane) to afford 470 mg of 3b (81%). 1 H NMR (CDCl3): δ 7.76 (d, 3JHH =8.5 Hz, 4H, Har), 7.62 (d, 3 JHH = 8.5 Hz, 4H, Har), 2.73 (s, 2H, CtCH), 2.52 (s br, 2H, OH), 1.86 (s, 6H, CH3). 13C{1H} NMR (CDCl3): δ 145.6, 145.5, 129.4, 122.5 (CAr), 87.6 (CtCH), 73.7 (CtCH), 70.1 (COH), 33.5 (CH3). IR (cm-1, KBr): 2112 (νCtC). MS ESIþ (m/z): 313.1204 ([M þ Na] þ, calcd 313.1205). trans-[HCtCC(OH)(CH3)(p-C6H4)CtC-Ru(dppe)2CtC(p-C6H4)(CH3)(OH)CCtCH](OTf)2 (3c). In a Schlenk tube, 10 mmol of acetylene 3b was dissolved in 60 mL of dry THF cooled to -78 °C, and 2.5 mL of n-butyllithium (4 mmol, solution 1.6 M in hexane) was added slowly. The mixture was stirred for 1 h at -78 °C. Then, 335 mg of 2 (0.3 mmol) was dissolved in 5 mL of dry THF and added dropwise to the mixture. The solution was stirred for 1 h at -78 °C and 24 h at room temperature. The solvent was then evaporated. The crude product was dissolved in 40 mL of dichloromethane and washed with water (2  30 mL). After drying and washing with pentane (2  30 mL), 297 mg of 3c was recovered as a yellow solid in 80% yield. 31P{1H} NMR (CDCl3): δ 55.1 (s, PPh2). 1H NMR (CDCl3): δ 7.53-6.75 (m, 48H, Ph), 2.73 (s, 2H, CtCH), 2.62 (m, 8H, CH2), 2.35 (s, 2H, OH), 1.85 (s, 6H, CH3). 13C{1H} NMR (CD2Cl2): δ 139.2-124.1 (Ph), 132.6 8 (quint, 2JPC =15 Hz, Ru-CtC), 116.1 (Ru-CtC), 87.8 (CtCH), 72.47 (CtCH), 69.6 (COH), 32.6 (CH3), 31.3 (m, |1JPC þ 3JPC| = 24 Hz, CH2). IR (KBr, cm-1): 3051 (νCH), 2144 (νCtCH), 2058 (νCtC). HR-MS FABþ (m/z): 1236.3080 ([M]þ, calcd 1236.3057). Anal. Found for C76H66P4RuO2: C, 74.07; H, 5.27. Calcd: C, 73.83; H, 5.38. trans-[Cl(dppe)2RudCdCdC(CH3)(p-C6H 4)(CH 3)CdCd CdRu(dppe)2Cl](OTf)2 (5a). In a Schlenk tube containing 500 mg of [(dppe)2RuCl]OTf (4; 0.5 mmol) and 54 mg of HCtC(OH)C(CH3)(p-C6H4)(CH3)C(OH)CtCH (3a; 0.25 mmol) was added 35 mL of CH2Cl2. The solution was stirred for 10 days at room temperature. After evaporation, the residue was washed with diethyl ether (3  20 mL). Further crystallization in a dichloromethane/pentane mixture led to 310 mg of dark blue crystals (80%) of 5a. 31P{1H} NMR (CDCl3): δ 42.0 (s, PPh2). 1 H NMR (CDCl3): δ 7.28-6.89 (m, 84H, Ph), 3.14 (m, 8H, CH2), 2.93 (m, 8H, CH2), 1.55 (s, 6H, CH3). 13C{1H} NMR (CD2Cl2): δ 329.0 (quint., RudC, 2JPC =14 Hz), 224.2 (Rud CdC), 161.0 (RudCdCdC), 135.1-127.8 (Ph), 32.5 (CH3), 29.4 (m, |1JPC þ 3JPC| = 23 Hz, CH2). IR (KBr, cm-1): 1940 (νdCdCdC). Anal. Found for C120H106P8Cl2Ru2F6O2S2: C, 61.27; H, 4.67. Calcd: C, 61.51; H, 4.56. trans-[Cl(dppe)2RudCdCdC(CH3)(p-C6H4)2(CH3)CdCd CdRu(dppe)2Cl](OTf)2 (5b). In a Schlenk tube containing 541

Vacher et al. mg of [(dppe)2RuCl]OTf (4; 0.5 mmol) and 72.5 mg of HCtC(OH)C(CH3)(p-C6H4)(CH3)C(OH)CtCH (3b; 0.25 mmol) was added 30 mL of CH2Cl2. The solution was stirred for 7 days at room temperature. After evaporation, the residue was washed with diethyl ether (3  20 mL). Further crystallization in a dichloromethane/pentane mixture led to 467 mg of dark blue crystals (77%) of 5b. 31P{1H} NMR (CDCl3): δ 41.5 (s, PPh2). 1 H NMR (CDCl3): δ 7.57-6.95 (m, 88H, Ph), 3.13 (m, 8H, CH2), 2.91 (m, 8H, CH2), 1.72 (s, 6H, CH3). 13C{1H} NMR (CD2Cl2): δ 308.4 (quint, RudC, 2JPC = 14 Hz), 211.2 (RudCdC), 160.6 (RudCdCdC), 142.9-123.3 (Ph), 121.1 (q, 1JCF =321 Hz, OTf-), 31.4 (CH3), 28.8 (m, |1JPC þ 3JPC|= 23 Hz, CH2). IR (KBr, cm-1): 1926 (νdCdCdC). HR-MS FABþ (m/z): 2119.4057 ([M2þ - Hþ]þ, calcd 2119.3936). Anal. Found for C120H106P8Cl2Ru2F6O2S2: C, 62.22; H, 4.62. Calcd: C, 62.56; H, 4.58. trans-[Cl(dppe)2RudCdCdC(CH3)(p-C6H4)CtC-Ru(dppe)2CtC(CH3)CdCdCdRu(dppe)2Cl](OTf)2 (5c). In a Schlenk tube containing 443 mg of [(dppe)2RuCl]OTf (4; 0.41 mmol) and 247 mg of HCtC(OH)C(CH3)(p-C6H4)CtC-Ru(dppe)2CtC(p-C6H4)(CH3)C(OH)CtCH (3c; 0.20 mmol) was added 40 mL of CH2Cl2. The solution was stirred for 10 days at room temperature. After evaporation, the residue was washed with diethyl ether (3  20 mL). Further crystallization in a dichloromethane/pentane mixture led to 329 mg of dark blue crystals (49%) of 5c. 31P{1H} NMR (CDCl3): δ 53.3 (s, PPh2), 43.7 (s, PPh2). 1H NMR (CDCl3): δ 7.39-6.32 (m, 128H, Ph), 3.07 (m, 8H, CH2), 2.77 (m, 8H, CH2), 3.68 (m, 8H, CH2), 1.74 (s, 6H, CH3). 13C{1H} NMR (CD2Cl2): δ 350.8 (quint, RudC, 2 JPC = 13 Hz), 191.6 (RudCdC), 159.9 (RudCdCdC), 136.7-127.3 (Ph), 136.1 (Ru-CtC), 121.1 (q. OTf-, 1JCF = 321 Hz), 31.3 (m, |1JPC þ 3JPC|=23 Hz, CH2), 29.7 (CH3), 28.9 (m, |1JPC þ 3JPC|=24 Hz, CH2). IR (KBr, cm-1): 2014 (νCtC), 1915 (νdCdCdC). HR-MS FABþ (m/z): 1533.7905 ([M2þ], calcd 1533.7897). trans-[(Cl(dppe)2RudCdCdC(CH3)CHdC(-CtC-Ru(dppe)2Cl) (p-C6H4) 2][OTf]2 (7b). In a Schlenk tube, 3b (263 mg, 0.15 mmol) was dissolved in CH2Cl2 (30 mL). In another tube, 6 (316 mg, 0.3 mmol) was dissolved in CH2Cl2 (100 mL). This solution was slowly added to the first one over 3 days using a dropping funnel. This mixture was further stirred for 11 days at room temperature. After filtration, the solution was evaporated, and then the residue was washed with diethyl ether (2  40 mL). Crystallizations in a CH2Cl2/pentane mixture yielded 477 mg of dark green crystals (72%). 31P{1H} NMR (CDCl3): δ 49.2 (s, PPh2), 46.9 (s, PPh2). 1H NMR (CDCl3): δ 7.66-6.69 (m, 168H, Ph), 5.90 (s., 2H, CdCH), 2.84 (m, 16H, CH2), 2.35 (s, 2H, OH), 1.08 (s, 6H, CH3). 13C{1H} NMR (75 MHz, CD2Cl2, 297 K): δ 228.8 (br, CR or CR0 ), 163.3 (Cβ0 methyl side), 161.5 (Cβ phenyl side), 152.9 (Cγ0 methyl side), 144.7 (Cγ phenyl side), 137.3 (CH), 152.4-126.9 (Ph), 30.38 and 29.4 (m, |1JPC þ 3JPC| = 24 Hz, CH2), 25.68 (CH3). IR (KBr, cm-1): 1896 (νdCdCdC), 1984. HRMS FABþ (m/z): 2043.3566 ([M]2þ, calcd 2043.3547). Anal. Found for C238H208P16Cl4Ru4F6S2O3: C, 64.92; H, 4.81. Calcd: C, 65.20; H, 4.78.

Acknowledgment. We thank the CNRS, the University of Rennes 1 for support, the AUF for a grant to C.M.N., and the Algerian MESRS for a grant to A.B.