Cooperative Bond Activation Reactions with Ruthenium Carbene

Article pubs.acs.org/Organometallics

Cooperative Bond Activation Reactions with Ruthenium Carbene Complex PhSO2(Ph2PNSiMe3)CRu(p‑cymene): RuC and N−Si Bond Reactivity Kai-Stephan Feichtner, Thorsten Scherpf, and Viktoria H. Gessner* Lehrstuhl für Anorganische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany S Supporting Information *

ABSTRACT: The synthesis of ruthenium carbene complex PhSO2(Ph2PNSiMe3)CRu(p-cymene) (3) and its application in cooperative bond activation reactions were studied. Compound 3 is accessible via salt metathesis using the dilithium methandiide ligand or alternatively via dehydrohalogenation of the corresponding chlorido complex 2. The carbene complex was studied by Xray crystallography, multielement NMR spectroscopy, and DFT studies, all of which confirm the presence of a RuC double bond. The polarization of the RuC bond is less pronounced than in an analogous carbene complex with a thiophosphoryl instead of the iminophosphoryl moiety. This should be beneficial for realizing reversible activation processes by the addition of element-hydrogen bonds across the RuC double bond. Accordingly, 3 is more stable and the RuC linkage less reactive in the activation of aromatic alcohols and elemental dihydrogen, showing reversible processes and longer reaction times. Despite the selective addition of dihydrogen across the Ru− C bond, the activation of O−H bonds was accompanied by hydrolysis of the N−Si linkage. The reaction of 3 with water led to the hydrolysis of the N−Si bond as well as protonative cleavage of the central P−C bond in the ligand backbone, thus resulting in the formation of an unusual dinuclear ruthenium−imido complex.

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INTRODUCTION Metal−ligand cooperation has become a powerful tool in organometallic chemistry to allow for bond activation reactions and catalytic transformations via mechanistic pathways circumventing classical oxidative addition and reductive elimination steps.1,2 Most ligand systems capable of supporting metal− ligand cooperation rely on the intrinsic Brønsted basicity of the cooperating ligand. Here, the ligand usually serves as a proton acceptor, particularly facilitating the activation of polar E−H bonds as a basic center. In the past few years, a series of different functional groups have been reported that support this type of activation chemistry. In particular, transitions between ketone/alcohol (CO → C−OH),3,4 amido/amino (M-NR2 → M-NR2H),5 or imido/amido (MNR → M-N(H)R) units have been documented.6 However, one of the most elegant and also efficient examples is the methylpyridine-based system pioneered by the Milstein group.7,8 This system is applicable in a variety of bond activation reactions and catalytic transformations, including the splitting of water or dihydrogen as well as acceptorless dehydrogenation reactions.9 In these PNN and PNP pincer complexes (e.g., A/B in Figure 1a), the metal− ligand cooperation relies on an aromatization-dearomatization mechanism based on the high acidity of the pyridine-bound methylene moiety. Comparable to imido systems, several carbene complexes have been reported to be active in cooperative bond activation © XXXX American Chemical Society

Figure 1. Examples of complexes used in cooperative bond activation reactions.

reactions, although their number is still rather limited. Here, the activation step relies on the transition between a carbene and an alkyl complex.10 This has been demonstrated, for example, by means of PCP-type pincer ligands with group 9 and 10 metals reported by the Piers11 and Iluc group12 as well as with Special Issue: Organometallic Chemistry in Europe Received: April 5, 2017

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DOI: 10.1021/acs.organomet.7b00254 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics methandiide-derived complexes13 such as C reported by our group.14 Ruthenium complex C showed remarkable activity toward a series of different E−H bonds of different polarities. Some reactions were found to be reversible, which is especially important in terms of a later transfer of the activated species and catalytic transformations. However, no efficient application in catalysis has been established to date with C or any other carbene system. Because the electronics of the MC bond play an important role in the activity of the carbene complex, we have become interested in the effects of different substituents on cooperative bond activation reactions. In case of the Milstein ligands, replacement of the amine “arm” in PNN complex A by a phosphine moiety also showed remarkable changes in the reactivity. For example, although complex A is an excellent catalyst for the coupling of alcohols with amines to form amides, its PNP derivative catalyzes dehydrogenative coupling to form imines rather than amides.15 Thus, we became interested in substitution effects in complex C on its reactivity. To this end, we addressed the corresponding iminophosphoryl system of C to examine its impact on cooperative bond activation reactions in comparison to that of its thiophosphoryl analogue. We hypothesized that exchange of the thiophosphoryl moiety by other donors should change the electron density at the metal and thus the nature of the MC bond. Here, we report our findings.

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H NMR spectrum, no splitting of the signals of the cymene protons was observed, thus being in line with the free rotation of the aromatic ligand. The carbenic carbon atom resonates as a doublet at δC = 140.8 ppm with a coupling constant of 1JCP = 69.0 Hz, which is considerably downfield-shifted compared to known alkyl complexes, indicating a metal carbon double bond. This is also in agreement with other reported ruthenium carbene complexes. For example, the carbenic carbon atom in the thiophosphoryl system C appeared at δC = 140.0 ppm with a coupling constant of 1JCP = 30.2 Hz.14 The considerably larger coupling constant in 3 suggests a higher s-character in the P−C bond, which is well in line with the higher electronegativity of the nitrogen moiety compared to that of sulfur. Despite the selective formation of carbene complex 3 from methandiide 1-Li2, isolation of pure 3 was found to be complicated. As such, elemental analyses repeatedly gave low C, H, N, and S values, yet with the correct ratio relative to each other. Because the NMR spectra showed no impurities, we attributed the failed purification to still present lithium chloride, which may coordinate to carbene complex 3; therefore, it could not be removed by filtration as in the case of the synthesis of thiophosphoryl-stabilized carbene complex C.14 This is most likely due to the stronger coordinating ability of the iminophosphoryl moiety to lithium compared to the sulfur system. Thus, we attempted the synthesis of the carbene complex in a stepwise fashion, starting from the monoanionic compound 1-K and subsequent dehydrohalogenation with KOtBu. We envisioned that the potassium chloride formed as a byproduct in this reaction would be less strongly coordinated by the imino moiety compared to that of the lithium salt. The reaction of methanide 1-K with [(p-cymene)RuCl2]2 led to the formation of a single new species characterized by a signal at δP = 45.3 ppm in the 31P{1H} NMR spectrum. After filtration and washing with a hot mixture of toluene and hexane, chlorido complex 2 could be isolated as an orange solid in 66% yield. No complexation of KCl was observed in this case; thus, purification was easily accomplished. The 1H NMR spectrum shows four independent signals for the aromatic hydrogen atoms of the cymene ligand. The signal of the methanide hydrogen atom appears as a characteristic doublet at δH = 4.81 ppm with a coupling constant of 2JPH = 9.06 Hz and the corresponding carbon atom as a doublet in the 13C{1H} NMR spectrum at δC = 31.9 ppm with a coupling constant of 1JCP = 59.0 Hz. Single crystals suitable for X-ray diffraction analysis were obtained by slow diffusion of pentane into a saturated solution of 2 in THF. The molecular structure of complex 2 is shown in Figure 2. Chlorido complex 2 crystallizes in the monoclinic space group P21/n. The methanide serves as a bidentate ligand coordinating to the metal center via the methylene carbon and the nitrogen atom of the iminophosphoryl moiety. The chlorido ligand and the (freely refined) hydrogen atom of the methylene bridge adopt a cis configuration. The Ru−Cl bond length of 2.4336(5) Å is comparable to other ruthenium chlorido complexes, whereas the Ru−C bond of 2.159(2) Å is slightly shorter than in comparable methanide complexes.18 With chlorido complex 2 in hand, we attempted the dehydrohalogenation using various bases, from which KOtBu was found to be the base of choice. As such, treatment of chlorido complex 2 with one equimolar amount of KOtBu in toluene at room temperature selectively led to the formation of carbene complex 3, which could be successfully isolated as a pure dark-purple solid in 89% yield. This was evidenced by

RESULTS AND DISCUSSION

Synthesis of Carbene Complex 3. Recently, we reported on the synthesis of the dimetalated species 1-Li2, which seemed to be a good precursor for studying ligand influence on the reactivity of the corresponding carbene complex 3.16 1-Li2 is conveniently available in gram-scale from the protonated precursor by direct double lithiation. For the synthesis of carbene complex 3, we first attempted a direct double salt elimination using methandiide 1-Li2 and [(p-cymene)RuCl2]2, analogous to the procedure previously reported for the synthesis of the thiophosphoryl-substituted carbene complex C (Scheme 1).14,17 During the reaction, a gradual color change from red to intense purple was observed over a period of 24 h. The 31P{1H} NMR spectrum showed the formation of a single new species exhibiting a low field shifted signal at δP = 54.6 ppm. The 1H and 13C NMR data were all consistent with successful formation of the desired carbene complex 3. In the Scheme 1. Synthesis of Carbene Complex 3 by Dehydrohalogenation of 2 and via Dilithium Methandiide 1Li2

B


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Organometallics

shorter compared to that of 2 or analogous compounds.19 The C−P and C−S bond lengths in the ligand backbone are (with values of 1.722(2) and 1.697(2) Å, respectively) elongated compared to those in monoanion 1-K and especially compared to those in methandiide 1-Li2 (e.g., C−S 1.608(3) Å).16 This indicates an efficient charge transfer from the methandiide carbon atom to the metal center, which leads to reduced electrostatic interactions within the P−C−S linkage. An important proof for the existence of a metal carbon double bond in 3 is the planar coordination environment of the central carbon atom (sum of angles of 359.6(1)°). In contrast, complexes with an ylidic metal carbon interaction have been shown to exhibit pyramidalized carbon environments.20 Compared to the thiophosphoryl system C, the introduction of the imino function only results in small changes in the structural properties of the carbene moiety. The Ru−C bond lengths (1.955(2) Å in 3 vs 1.965(2) Å in C) as well as the 13C NMR shifts of the carbenic carbon atom (140.8 vs 140.8 ppm in C) are almost identical in both complexes, suggesting similar electronics of the Ru−C bond. Additional density functional theory (DFT) studies were performed to gain further insights into the electronic structure of both complexes. As shown in Figure 4, the calculations confirm the double bond character of

Figure 2. Molecular structure of chlorido complex 2 with ellipsoids drawn at the 50% probability level. Hydrogen atoms (except for the methylene bridge) are omitted for clarity. Selected bond lengths [Å] and angles [°]: C1−S1 1.736(2), C1−P1 1.776(2), C1−Ru1 2.159(2), P1−N1 1.5848(17), P1−C2 1.800(2), P1−C8 1.792(2), N1−Si1 1.7161(18), N1−Ru1 2.1630(17), S1−O1 1.4408(16), S1−O2 1.4342(16), S1−C14 1.777(2), Ru1−Cl1 2.4336(5), S1−C1−P1 121.00(12), P1−N1−Si1 133.40(11).

NMR spectroscopy as well as elemental analysis. Single crystals suitable for X-ray diffraction analysis could be obtained by cooling of a saturated solution of 3 in toluene to −40 °C. Carbene complex 3 crystallizes in the triclinic space group P1̅ with half of a toluene molecule in the asymmetric unit (Figure 3). The Ru−C distance of 1.955(2) Å is comparable to other ruthenium carbon double bonds and distinctly shorter than in precursor 2. The Ru−N contact of 2.145(2) Å is only slightly

Figure 4. (top) Results of the NBO analysis [(B3LYP/6-311+G(d,p)/ LanL2TZ(f)] of complex 3 (left) and C (right) and (bottom) displays of the HOMO and LUMO of 3 (isosurface value 0.02).

the MC linkage. This is demonstrated by the highest occupied and lowest unoccupied molecular orbitals, which reflect the bonding and antibonding π-interaction, respectively. The Wiberg bond index (WBI), the natural charge calculated at the carbene carbon atom and the results of the natural bond orbital (NBO) analysis indicate that the RuC bond in the iminophosphoryl system is somewhat less polar and thus presumably less reactive than in the corresponding thiophosphoryl system. As such, the WBI in 3 is slightly higher and the negative charge at the carbon atom slightly lower than in complex C. The less polarized MC bond suggests a higher stability of the MC bond and a thermodynamically lessfavored protonation of the carbene ligand. Both should be particularly beneficial for realizing reversible activation processes.

Figure 3. Molecular structure of carbene complex 3. Ellipsoids are drawn at the 50% probability level. Hydrogen atoms and solvent molecules are omitted for clarity. Selected bond lengths [Å] and angles [°]: C1−S1 1.697(2), C1−P1 1.722(2), C1−Ru1 1.955(2), P1−N1 1.607(2), P1−C2 1.817(2), P1−C8 1.807(2), S1−O1 1.4556(17), S1−O2 1.4540(17), S1−C14 1.785(2), N1−Ru1 2.1452(19), S1− C1−P1 125.90(14), S1−C1−Ru1 137.91(14), P1−C1−Ru1 95.74(11), P1−N1−Si1 133.86(12). C


Article

Organometallics Activation of Aromatic Alcohols. Next, we addressed the activity of carbene complex 3 in cooperative bond activation reactions, particularly in comparison with the thiophosphoryl congener C. At first, the reactivity toward a series of aromatic alcohols was examined. Treatment of 3 with an equivalent amount of alcohol instantaneously led to a color change from purple to brown and the formation of the corresponding O−H activation products, which could be isolated in 51−85% yield (see Scheme 2 and the Supporting Information (SI)).21 The Scheme 2. Reversible Activation of Aromatic Alcohols

nature of the activation products could unambiguously be confirmed by multinuclear NMR spectroscopy as well as X-ray diffraction analysis. All methods confirmed the activation of the O−H bond via cis-addition across the RuC double bond, resulting in a transition from a carbene to an alkyl complex. In the 31P{1H} NMR spectrum, the signals of the activation products resonate somewhat high-field-shifted compared to those of carbene complex 3 (e.g., δP = 44.6 ppm for R = Ph). Furthermore, a characteristic doublet for the proton at the methylene bridge can be detected in the 1H NMR spectra between 3.60 and 4.10 ppm (e.g., δH = 4.02 ppm with a coupling constant of 2JHP = 7.92 Hz for R = Ph), whereas the methanide carbon atom appears at considerably higher field (δC = ∼34 ppm) compared to that of the carbene complex. Most interestingly, in the case of phenol and 4-tertbutylphenol, the activation reaction resulted in an equilibrium between the corresponding 1,2-addition product and carbene complex 3 at room temperature. With the electron-poor dichloro-substituted derivative, no equilibrium, but quantitative activation to complex 4c was observed. This is well in line with the observations made with the thiophosphoryl-substituted carbene complex C. C also only showed quantitative activation at room temperature when reacted with electron-poor aromatic alcohols.14 To illustrate the reversibility of the activation reactions, we performed VT-NMR studies for the activation of p-tert-butyl phenol (see SI for spectra). An 11:1 mixture between 4b and 3 could be observed at 30 °C, whereas a 1:1.6 ratio was found at 70 °C. Recooling of the reaction mixture to 30 °C again led to reformation of the activation product. This reversibility confirms the efficient charge transfer from the methandiide ligand to the ruthenium center and the stability of carbene complex 3. The reversibility of the O−H activation and the different stabilities of the activation products were further confirmed by an exchange experiment. To this end, carbene complex 3 was first treated with 4-tert-butyl phenol to generate activation product 4b and subsequently treated with 3,5dichlorophenol. This lead to the consumption of 4b and the formation of 4c with no carbene complex present in the reaction mixture (see the SI for NMR spectra). Despite the reversible nature of the reactions, we were able to obtain crystals of 4a and 4b suitable for X-ray diffraction analysis (see Figure 5) by diffusion of pentane into saturated THF solutions of the complexes. Compound 4a crystallizes in

Figure 5. Molecular structures of 4a (top) and 4b (bottom). Ellipsoids are drawn at the 50% probability level. Hydrogen atoms (except for the methylene bridge) are omitted for clarity. Selected bond lengths [Å] and angles [°] for 4a C1−S1 1.734(3), C1−P1 1.781(3), C1−Ru1 2.188(3), P1−N1 1.596(3), P1−C2 1.813(3), P1−C8 1.814(3), N1− Si1 1.739(3), N1−Ru1 2.174(3), S1−O1 1.443(2), S1−O2 1.435(2), S1−C14 1.775(3), Ru1−O3 2.083(2), S1−C1−P1 122.95(18), P1− N1−Si1 130.26(17) and 4b: C1−S1 1.7394(15), C1−P1 1.7873(16), C1−Ru1 2.1649(15), P1−N1 1.5890(12), P1−C2 1.8079(15), P1− C8 1.8167(15), N1−Si1 1.7278(13), N1−Ru1 2.1667(12), S1−O1 1.4426(11), S1−O2 1.4482(11), S1−C14 1.7803(15), Ru1−O3 2.0687(11), S1−C1−P1 126.15(9), P1−N1−Si1 134.91(8).

the orthorhombic space group P212121, and 4b crystallizes in the orthorhombic space group Pbca. Both compounds show similar bond lengths and angles. The alcoholato ligand and the proton at the methylene bridge are attached to the same side of the former RuC double bond, indicating a concerted cisaddition reaction, as it was also observed for the thiophosphoryl-substituted system. The O−H distances in both complexes (2.389(13) Å for R = Ph and 2.437(16) for R = p-C6H4-tBu) are still rather short due to the small C1−Ru1− O3 and Ru−C1−H1 angles of approximately 80°. This is well in line with the facile elimination of the corresponding aromatic alcohols at elevated temperatures and the reversibility of the reaction. The Ru1−C1 bonds with values of 2.188(3) and 2.1649(15) Å, respectively, are in the expected range of D


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Organometallics

in toluene at room temperature was exposed to 1 atm of hydrogen gas, resulting in the slow consumption of the carbene complex (Scheme 4). Complete conversion was only observed

ruthenium carbon single bonds and elongated compared to those of carbene complex 3. Compared to the thiophosphoryl system, the O−H activation processes with 3 were revealed to be less selective. In all activation reactions, traces of a further byproduct were observed in the 31P{1H} NMR spectra, which could not be removed during the work-up procedures. This side product features a signal at around 57.0 ppm with slowly increasing intensity over time. This increase can nicely be followed in the VT-NMR experiments, showing the increasing amount of the new compound together with consumption of the free alcohol in the course of the experiment. To our delight, we were able to obtain crystals of the corresponding side product for the activation of phenol, which could thus be identified as the corresponding activation product with the TMS group at the nitrogen replaced by a hydrogen atom (Scheme 3, Figure 6).

Scheme 4. Activation of Elemental Hydrogen with 3

after stirring at room temperature for 1 week, leading to a color change from intense purple to light brown and the formation of a new species exhibiting a signal in the 31P{1H} NMR spectrum at δP = 26.8 ppm. Removal of the solvent under reduced pressure and washing with pentane afforded hydrido complex 5 as a yellow solid in 82% yield. The reaction time could be decreased by performing the hydrogen activation at elevated temperatures. Temperature-dependent studies showed that, after 24 h at 40 °C, 55% conversion to 5 could already be observed. After the same period of time, 75% conversion was reached at 50 °C, whereas at 65 °C, complete consumption of the carbene complex was observed in the NMR spectra. However, performing the hydrogen activation at elevated temperatures led to less-selective product formation. At 65 °C in particular, only 58% yield of activation product 5 was detected in the NMR spectra. Overall, compared to thiophosphoryl-substituted carbene complex C, a drastically increased reaction time was found to be necessary for full conversion of 3 to 5. This is well in line with the DFT studies and the proposed lower reactivity of the iminophosphorylsubstituted carbene complex 3. Interestingly, despite the slow formation of 5, no equilibrium between the carbene and hydrido complex was observed. This was experimentally confirmed by VT NMR studies, showing no release of H2 even upon heating to 75 °C. Treatment of the hydrido complex with deuterium also resulted in no H/D exchange. Hydrido complex 5 was characterized by multinuclear NMR spectroscopy, elemental as well as XRD analysis. In the 1H NMR spectrum, the hydridic hydrogen in 5 appears at δH = −5.34 ppm, and the proton at the methylene bridge appears as a doublet at δH = 3.63 ppm with a coupling constant of 2JHP = 1.92 Hz. The methanide carbon atom is characterized by a doublet at δC = 30.4 ppm with a coupling constant of 1JCP = 67.7 Hz. Crystals suitable for X-ray diffraction analysis were obtained by slow evaporation of a saturated solution of 5 in DCM at −40 °C. The molecular structure of 5 is displayed in Figure 7. Compound 5 crystallizes in the triclinic space group P1̅. The asymmetric unit contains one molecule of 5 and an additional DCM molecule. The hydrogen atom of the PCS bridge and the hydridic hydrogen at the ruthenium center adopt a cis configuration. The Ru1−C1 bond length is well in line with other Ru−C single bonds and longer than the one found in carbene precursor 3. It is noteworthy that hydrogenation to 5 must be carried out very carefully under absolute exclusion of traces of water because already small amounts of water led to the formation of a new, intensely blue colored product. This product is characterized by a signal at δP = 34.5 ppm in the 31P{1H} NMR spectrum, whereas no signal indicative for protonation of the PCS linkage can be found in the 1H NMR spectrum. The nature of the complex could be unambigously identified by

Scheme 3. Alcoholysis of 4a to 4a-TMS

Figure 6. Molecular structure of 4a-TMS with ellipsoids drawn at the 50% probability level. Hydrogen atoms (except for the methylene bridge and the nitrogen) are omitted for clarity. Selected bond lengths [Å] and angles [°]: C1−S1 1.735(2), C1−P1 1.789(2), C1−Ru1 2.208(2), P1−N1 1.584(2), P1−C2 1.806(2), P1−C8 1.812(2), N1− Ru1 2.109(2), S1−O1 1.4410(17), S1−O2 1.4482(17), S1−C14 1.777(2), Ru1−O3 2.0986(15), S1−C1−P1 121.87(12).

Such a N−Si bond cleavage with alcohols is well-known for “free” phosphine imides but has not been reported for group 4 metal complexes with a bis(iminophosphoryl)methandiide ligand.22 Compound 4a-TMS crystallizes in the monoclinic space group P21/c. All bond lengths and angles are comparable to those of the TMS-substituted congener 4a. Activation of Elemental Hydrogen. Overall, the activation of alcohols proceeds similarly facilely compared to that of thiophosphoryl system C, yet the reactivity of the N−Si bond prevented any further applications. Thus, we next addressed the more challenging activation of the nonpolar H−H bond in elemental hydrogen to form the corresponding hydrido complex. To this end, a vigorously stirred solution of 3 E


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Organometallics

with two bridging phosphinoylimido ligands. Compound 6 can be described as the product of the reaction of two molecules of carbene complex 3 with three equivalents of water and elimination of hexamethyldisiloxane and phenyl methyl sulfone (Scheme 5). This hydrolysis reaction of 3 can be reproduced by Scheme 5. Hydrolysis of Carbene Complex 3 to Dinuclear Complex 6

Figure 7. Molecular structure of hydrido complex 5. Ellipsoids are drawn at the 50% probability level. Hydrogen atoms (except for the methylene bridge and hydridic hydrogen) and solvent molecules are omitted for clarity. Selected bond lengths [Å] and angles [°]: C1−P1 1.782(2), C1−S1 1.741(2), C1−Ru1 2.182(2), S1−O1 1.4394(16), S1−O2 1.4489(16), S1−C14 1.779(2), P1−N1 1.5854(18), P1−C2 1.820(2), P1−C8 1.814(2), N1−Si1 1.7255(18), N1−Ru1 2.1937(17), Ru1−H33 1.54(2), S1−C1−P1 119.78(12), P1−N1− Si1 132.15(11).

adding 1.5 equiv of degassed water directly to a solution of carbene complex 3. Within 5 h of reaction time at room temperature, a color change from purple to dark blue could be observed. Monitoring of the reaction via NMR spectroscopy revealed the nearly selective formation of dimeric complex 6. Purification to remove the formed phenyl methyl sulfone gave complex 6 as a blue solid in 62% yield. Complex 6 crystallizes in the triclinic space group P1̅. The asymmetric unit contains one dimeric complex and an additional molecule of THF. The dimer features pseudo-C2 symmetry, which is broken by the solvent molecule in the asymmetric unit. The central structural motif of the complex consists of a nonplanar Ru−N−Ru−N four-membered ring with a Ru1−Ru2 distance of 2.7225(3) Å). The Ru−N bonds of approximately 2.0 Å are in the range of a single bond. Electron counting together with the short Ru−Ru bond and the nonplanar structure of the (RuN)2 core thus suggest the presence of a RuRu double bond.23 The N−P bond lengths are (with an average value of 1.6408(18) Å) in the range of single bonds,24 whereas the P−O bond lengths (with an average length of 1.4915(2) Å) argue for typical PO double bonds.25 Overall, the hydrolysis of 3 results in a N−Si as well as in a complete P−C bond cleavage. To the best of our knowledge, only a few examples of such a reaction have been reported in the literature.18 Interestingly, an analogous reaction has not been observed with the thiophosphoryl compound, thus suggesting that the imino group is also responsible for the higher sensitivity of carbene complex 3 toward hydrolysis. Mechanistically, one can assume that the reaction first proceeds via the O−H activation of water across the RuC bond to form a hydroxy complex, followed by oxygenative cleavage of the N−Si bond and protonative cleavage of the P−C bond. The activation of water with amido-substituted group 4 methandiide-derived carbene complexes was reported by So and coworkers.26 In their case, activation of water took place via hydrolysis of one of the amido ligands. Thus, formation of an intermediate hydroxy complex was proposed, which in contrast to our system further reacts to a dimeric oxo-bridged species due to the oxophilicity of the group 4 metals. The hydroxo species formed after H2O activation with 3 is presumably less stable than that of analogous group 4 systems. We propose that it further reacts under the formation of an oxo-species and protonation of the methanide ligand. The oxo complex then results in N−Si bond cleavage and O−Si bond formation, which has for example also been observed by Caulton and coworkers in the case of an osmium complex with a PNP ligand.27

single-crystal X-ray diffraction analysis (Figure 8). Suitable single crystals could be obtained by diffusion of pentane into a THF solution. The new compound 6 is a diruthenium complex

Figure 8. Molecular structure (top) and central structure motif (bottom) of 6. Ellipsoids drawn at the 50% probability level. Hydrogen atoms and solvent molecule omitted for clarity. Selected bond lengths [Å] and angles [°]: Ru1−Ru2 2.7225(3), Ru1−N1 1.9945(17), Ru1− N2 2.0030(17), Ru2−N1 1.9964(17), Ru2−N2 2.0002(17), N1−P1 1.6419(18), N2−P2 1.6396(18), P1−O1 1.4879(18), P1−C1 1.818(2), P1−C7 1.819(2), P2−O2 1.4931(15), P2−C13 1.822(2), P2−C19 1.818(2), N1−Ru1−N2 76.41(7), N1−Ru2−N2 76.43(7), N1−P1−O1 120.29(9), N2−P2−O2 120.70(9). F


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Organometallics

toluene and hexane (4:1) and dried in vacuo, giving chlorido complex 2 as an orange solid (901 mg, 1.29 mmol, 66%). 1H NMR (300.2 MHz, C6D6): δ 0.16 (9H; Si(CH3)3), 1.17 (d, 3JHH = 6.99 Hz, 3H; CH(CH3)2), 1.19 (d, 3JHH = 7.1 Hz, 3H; CH(CH3)2), 1.98 (s, 3H; CCH3), 3.10 (sept, 3JHH = 6.7 Hz, 1H; CH(CH3)2), 4.81 (d, 2JHP = 9.06 Hz, 1H; SCHP), 5.16 (m, 1H; CHCym), 5.22 (m, 1H; CHCym), 5.36 (m, 1H; CHCym), 6.00 (m, 1H; CHCym), 6.73−6.91 (m, 6H; CHPPh,meta,para/CHSPh,meta,para), 7.13−7.23 (m, 3H; CHPPh,meta,para/ CHSPh,meta,para), 7.57−7.67 (m, 4H; CHPPh,ortho + CHSPh,ortho), 7.75− 7.83 (m, 2H; CHPPh,ortho). 13C{1H} NMR (75.5 MHz, C6D6): δ 4.87 (d, 3JCP = 3.37 Hz; Si(CH3)3), 18.8 (CCH3), 21.7 (CH(CH3)2), 23.0 (CH(CH3)2), 31.1 (CH(CH3)2), 31.9 (d, 1JCP = 59.0 Hz; SCHP), 74.8 (CHCym), 82.5 (CHCym), 83.7 (CHCym), 85.3 (CHCym), 89.8 (CCym), 107.4 (CCym), 126.5 (CHSPh,meta), 127.5 (d, 3JCP = 12.14 Hz; CHPPh,meta), 128.0 (d, 3JCP = 11.4 Hz; CHPPh,meta), 128.5 (CHSPh,ortho), 129.7 (d, 1JCP = 87.3 Hz; CPPh,ipso), 131.4 (CHSPh,para), 131.5 (d, 4JCP = 2.86 Hz; CHPPh,para), 132.5 (d, 4JCP = 3.09 Hz; CHPPh,para), 132.6 (d, 2 JCP = 10.7 Hz; CHPPh,ortho), 134.5 (d, 2JCP = 10.7 Hz; CHPPh,ortho), 136.0 (d, 1JCP = 71.4 Hz; CPPh,ipso), 146.0 (d, 3JCP = 1.51 Hz; CSPh,ipso). 31 P{1H}-NMR (121.5 MHz, C6D6): δ 45.3. Anal. Calcd for C32H41ClNO2PRuSSi: C, 55.12; H, 5.64; N, 2.01; S, 4.60. Found: C, 54.74; H, 5.50; N, 2.22; S, 4.21. Synthesis of Carbene Complex 3. First, 700 mg (1.00 mmol) of chloro complex 2 and 113 mg (1.00 mmol) of KOtBu were dissolved in 17.5 mL of toluene, and the reaction mixture was stirred at room temperature overnight. The resulting purple solution was filtered; the solvent was removed in vacuo, and the residue was washed three times with 3 mL of pentane to give carbene complex 3 as a purple solid (590 mg, 893 μmol, 89%). 1H NMR (500.1 MHz, CD2Cl2): δ −0.04 (9H; Si(CH3)3), 1.18 (d, 3JHH = 6.9 Hz, 6H; CH(CH3)2), 2.15 (s, 3H; CCH3), 2.35 (sept, 3JHH = 6.9 Hz, 1H; CH(CH3)2), 5.32−5.39 (m, 4H; CHCym), 7.15−7.18 (m, 2H; CHPPh,para), 7.28−7.31 (m, 1H; CHSPh,para), 7.34−7.38 (m, 6H; CHSPh,meta/CHPPh,meta), 7.47−7.50 (m, 2H; CHSPh,ortho), 7.60−7.64 (m, 4H; CHPPh,ortho). 13C{1H}-NMR (125.8 MHz, C6D6): δ 3.21 (d, 3JCP = 3.21 Hz; Si(CH3)3), 20.6 (CCH3), 24.2 (CH(CH3)2), 32.1 (CH(CH3)2), 79.0 (CHCym), 81.2 (CHCym), 85.4 (CCym), 97.2 (CCym), 126.1 (CHSPh,meta), 128.3 (CHSPh,para), 128.3 (CHPPh,meta), 130.4 (CHSPh,ortho), 131.6 (d, 4JCP = 2.76 Hz; CHPPh,para), 132.0 (d, 2JCP = 10.9 Hz; CHPPh,ortho), 132.4 (d, 1 JCP = 75.2 Hz; CPPh,ipso), 140.8 (d, 1JCP = 69.0 Hz; SCP), 147.7 (d, 3JCP = 3.17 Hz; CSPh,ipso). 31P{1H} NMR (202.5 MHz, C6D6): δ 54.6. Anal. Calcd for C32H38NO2PRuSSi: C, 58.16; H, 5.80; N, 2.12; S, 4.85. Found: C, 58.21; H, 5.79; N, 2.43; S, 4.54. Activation of Phenol. First, 150 mg (227 μmol) of carbene complex 3 was dissolved in 5 mL of toluene. Then, 21.4 mg (227 μmol) of phenol was added, which resulted in a color change to dark brown. The reaction was stirred overnight, and the solvent was removed under reduced pressure. The residue was washed three times with pentane (3 mL). Drying in vacuo gave slightly impure activation product 4a (due to constant decomposition to 4a-TMS) as a light brown solid in 54% yield (93.0 mg, 123 μmol). 1H NMR (400.1 MHz, C6D6): δ 0.17 (s, 9H; Si(CH3)3), 0.93 (d, 3JHH = 7.03 Hz, 3H; CH(CH3)2), 1.29 (d, 3JHH = 6.75 Hz, 3H; CH(CH3)2), 2.09 (s, 3H; CCH3), 2.74 (sept, 3JHH = 6.91 Hz, 1H; CH(CH3)2), 4.02 (d, 2JHP = 7.92 Hz, 1H; SCHP), 5.11 (d, 3JHH = 5.52 Hz, 1H; CHCym), 5.26 (d, 3 JHH = 5.72 Hz, 1H; CHCym), 5.54 (d, 3JHH = 5.76 Hz, 1H; CHCym), 6.43 (d, 3JHH = 5.60 Hz, 1H; CHCym), 6.62−6.91 (m, 8H; CHPPh,meta,para + CHSPh,para + CHOPh,para), 7.13−7.24 (m, 4H; CHPPh,ortho + CHSPh,meta), 7.31−7.33 (m, 2H; CHOPh,meta), 7.41−7.46 (m, 2H; CHSPh,ortho), 7.57−7.62 (m, 4H; CHPPh,ortho + CHOPh,ortho). 13C{1H} NMR (100.6 MHz, C6D6): δ 4.38 (d, 3JCP = 3.34 Hz; Si(CH3)3), 18.6 (CCH3), 20.5 (CH(CH3)2), 24.3 (CH(CH3)2), 31.1 (CH(CH3)2), 32.6 (d, 1JCP = 62.9 Hz; SCHP), 74.3 (CHCym), 76.2 (CHCym), 84.9 (CH Cym ), 85.4 (CH Cym ), 87.6 (C Cym ), 112.0 (C Cym ), 113.8 (CHOPh,para), 120.8 (CHOPh,meta), 126.5 (CHOPh,ortho), 127.6 (d, 3JCP = 11.9 Hz; CHPPh,meta), 127.8 (CHPPh,meta), 128.2 (CHSPh,para), 129.4 (d, 1 JCP = 91.3 Hz; CPPh,ipso), 129.6 (CHSPh,ortho), 131.3 (CHSPh,meta), 131.3 (d, 4JCP = 2.64 Hz; CHPPh,para), 131.6 (d, 2JCP = 10.6 Hz; CHPPh,ortho), 132.5 (d, 4JCP = 2.84 Hz; CHPPh,para), 134.3 (d, 2JCP = 10.4 Hz;

To gain insights into the mechanism, NMR spectroscopic studies were carried out with different amounts of water. Unfortunately, no intermediates along the reaction pathway could be identified. The use of one equivalent of H2O only led to 60% conversion to 6 with no intermediates being identifiable in the NMR spectra. This further supports the suggested 2:3 ratio of the carbene complex and water necessary for the reaction. The monitoring of the reaction over time also only revealed immediate formation of 6 without any substantial intermediates observable in the NMR spectra (see SI for NMR spectra).

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SUMMARY AND CONCLUSIONS In summary, we reported on the synthesis of sulfonyl- and iminophosphoryl-substituted carbene complex 3 via salt metathesis using the corresponding methandiide ligand and via dehydrohalogenation of chlorido complex 2. Carbene complex 3 was studied by various analytical as well as theoretical methods showing similar properties compared to its known thiophosphoryl congener, however with a slightly less polar RuC bond. This results in lower reactivity of the Ru−C linkage in cooperative E−H activation reactions. For example, O−H bond activation reactions of aromatic alcohols resulted in the formation of equilibria between the carbene complex and the corresponding activation products, which was demonstrated by VT NMR experiments. The lower reactivity also resulted in longer reaction times, as was found for the activation of dihydrogen. Despite the lower activity of the Ru−C bond, activation chemistry was interfered by the higher reactivity of the N−TMS moiety. Excessive alcohol or traces of water always led to hydrolysis of the N−Si bond. In the case of the reaction with water, hydrolysis also resulted in the cleavage of the central P−C bond in the ligand backbone and the formation of an unusual dinuclear ruthenium imido complex. Overall, these results demonstrate the sensitivity of methandiide-derived carbene complexes to changes in the ligand framework. E−H bond activation reactions can thus be triggered by changes in the ligand design. On-going studies are now focusing on the replacement of the silyl group by aryl and alkyl groups to prevent byproduct formation due to the reactivity of the N−Si linkage.

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EXPERIMENTAL SECTION

General Procedures. All experiments were carried out under a dry, oxygen-free argon atmosphere using standard Schlenk techniques. Involved solvents were dried over sodium or potassium (or over P4O10 in case of CH2Cl2) and distilled prior to use. H2O is distilled water. 1H, 7 Li, 13C, and 31P NMR spectra were recorded on Avance-500, Avance400, Avance-300 or DPX-250 spectrometers at 22 or 30 °C if not stated otherwise. All values of the chemical shift are in ppm regarding the δ-scale. All spin−spin coupling constants (J) are printed in hertz (Hz). For multiplicities and signal forms to be displayed correctly, the following abbreviations were used: s = singlet, d = doublet, sept = septet, m = multiplet, and br = broad signal. Signal assignment was supported by DEPT and HMQC experiments. Elemental analyses were performed on an Elementar vario MICRO-cube elemental analyzer. All reagents were purchased from Sigma-Aldrich, ABCR, Rockwood Lithium, or Acros Organics and used without further purification. Synthesis of Chlorido Complex 2. First, 900 mg (1.97 mmol) of methanide 1-K and 603 mg (985 μmol) of [(p-cymene)RuCl2]2 were dissolved in 8 mL of THF. The solution was stirred at room temperature overnight. The reaction mixture was filtered to remove the formed potassium chloride, and the solvent was removed under reduced pressure. The crude product was washed with a hot mixture of G


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Organometallics CHPPh,ortho), 135.4 (d, 1JCP = 73.0 Hz; CPPh,ipso), 146.1 (COPh,ipso), 168.2 (CSPh,ipso). 31P{1H} NMR (101.2 MHz, C6D6): δ 44.6 ppm. Activation of 4-tert-Butyl Phenol. First, 150 mg (227 μmol) of carbene complex 3 was dissolved in 3 mL of toluene, and the resulting solution was cooled to −78 °C. A solution of 34.1 mg (227 μmol) of 4-tert-butyl phenol in 3 mL of toluene was added dropwise, and the reaction mixture was slowly warmed to RT. After stirring overnight, the solvent was removed under reduced pressure. The residue was washed with 2 mL of pentane, giving slightly impure activation product 4b (due to constant decomposition) as a light brown solid in 85% yield (156 mg, 193 μmol). 1H NMR (400.3 MHz, C6D6): δ 0.18 (s, 9H; Si(CH3)3), 0.92 (d, 3JHH = 7.01 Hz, 3H; CH(CH3)2), 1.29 (d, 3 JHH = 6.77 Hz, 3H; CH(CH3)2), 1.42 (s, 9H; CH(CH3)3), 2.06 (s, 3H; CCH3), 2.75 (sept, 3JHH = 6.92 Hz, 1H; CH(CH3)2), 4.10 (d, 2JHP = 8.13 Hz, 1H; SCHP), 5.16 (d, 3JHH = 5.60 Hz, 1H; CHCym), 5.22 (d, 3 JHH = 5.52 Hz, 1H; CHCym), 5.57 (d, 3JHH = 5.68, 1H; CHCym), 6.43 (d, 3JHH = 5.60 Hz, 1H; CHCym), 6.66−6.82 (m, 6H; CHPPh,meta,para + CHSPh,meta,para), 7.16−7.20 (m, 4H; CHPPh,ortho,meta), 7.22−7.25 (m, 1H; CHPPh,para), 7.29−7.33 (m, 2H; CHOPh), 7.44−7.48 (m, 2H; CHOPh), 7.58−7.64 (m, 4H; CHPPh,ortho + CHSPh,ortho). 13C{1H} APT-NMR (100.7 MHz, C6D6): δ 4.40 (d, 3JCP = 3.50 Hz; Si(CH3)3), 18.7 (CCH3), 20.6 (CH(CH3)2), 24.2 (CH(CH3)2), 31.1 (CH(CH3)2), 32.3 (d, 1JCP = 61.2 Hz; SCHP), 32.4 (C(CH3)3), 74.3 (CHCym), 76.4 (CHCym), 84.5 (CHCym), 85.0 (CHCym), 87.9 (CCym), 112.0 (CCym), 120.2 (CHOPh), 126.2 (CHOPh), 126.5 (CHSPh,ortho), 127.5 (d, 3JCP = 11.9 Hz; CHPPh,meta), 128.2 (CHPPh,meta), 128.4 (CHSPh,meta), 129.2 (d, 1 JCP = 87.3 Hz; CPPh,ipso), 131.2 (CHSPh,para), 131.2 (d, 4JCP = 2.79 Hz; CHPPh,para), 131.7 (d, 2JCP = 10.5 Hz; CHPPh,ortho), 132.5 (d, 4JCP = 2.75 Hz; CHPPh,para), 134.3 (d, 2JCP = 10.3 Hz; CHPPh,ortho), 135.4 (COPh,para), 135.5 (d, 1JCP = 72.3 Hz; CPPh,ipso), 146.2 (COPh,ipso), 167.0 (CSPh,ipso). 31 1 P{ H} NMR (101.3 MHz, C6D6): δ 43.6 ppm. Activation of 3,5-Dichlorophenol. First, 150 mg (227 μmol) of carbene complex 3 was dissolved in 3 mL of toluene, and the resulting mixture was cooled to −78 °C. A solution of 37.0 mg (227 μmol) of 3,5-dichlorophenol in 3 mL of toluene was added dropwise. The reaction mixture was slowly warmed to RT and stirred overnight, whereupon the color changed from purple to brown. The solvent was removed in vacuo, and the residue was washed with 2 mL of pentane, giving slightly impure activation product 4c (due to constant decomposition) as light brown solid in 51% yield (95.8 mg, 116 μmol). 1H NMR (400.3 MHz, C6D6): δ 0.12 (s, 9H; Si(CH3)3), 0.91 (d, 3JHH= 6.96 Hz, 3H; CH(CH3)2), 1.14 (d, 3JHH = 6.81 Hz, 3H; CH(CH3)2), 2.09 (s, 3H; CCH3), 2.62 (sept, 3JHH = 6.72, 1H; CH(CH3)2), 3.67 (d, 2JHP = 7.24 Hz, 1H; SCHP), 5.11 (d, 3JHH = 5.65 Hz, 1H; CHCym), 5.27 (d, 3JHH = 5.88 Hz, 1H; CHCym), 5.44 (d, 3JHH = 5.81 Hz, 1H; CHCym), 6.48 (d, 3JHH = 5.51 Hz, 1H; CHCym), 6.68− 6.79 (m, 6H; CHSPh,meta,para + CHPPh,meta + CHOPh,para), 6.86−6.93 (m, 3H; CHPPh,ortho,para), 7.03−7.08 (m, 4H; CHPPh,meta + CHOPh,ortho), 7.11−7.16 (m, 1H; CHPPh,para), 7.50−7.55 (m, 4H; CHPPh,ortho + CHSPh,ortho). 13C{1H} APT-NMR (100.7 MHz, C6D6): δ 4.43 (d, 3JCP = 3.49 Hz; Si(CH3)3), 18.4 (CCH3), 20.7 (CH(CH3)2), 23.8 (CH(CH3)2), 31.3 (CH(CH3)2), 35.1 (d, 1JCP = 62.6 Hz; SCHP), 73.5 (CHCym), 77.0 (CHCym), 85.2 (CHCym), 85.9 (CHCym), 86.6 (CCym), 111.4 (CCym), 113.5 (CHOPh,para), 119.1 (CHOPh,ortho), 126.7 (CHSPh,ortho), 127.7 (d, 3JCP = 11.8 Hz; CHPPh,meta), 128.0 (CHPPh,meta), 128.6 (CHSPh,meta), 130.1 (d, 1JCP = 82.4 Hz; CPPh,ipso), 131.1 (d, 2JCP = 10.5 Hz; CHPPh,ortho), 131.3 (d, 4JCP = 2.80 Hz; CHPPh,para), 131.5 (CHSPh,para), 132.6 (d, 4JCP = 2.74 Hz; CHPPh,para), 134.1 (d, 2JCP = 10.3 Hz; CHPPh,ortho), 134.1 (d, 1JCP = 77.7 Hz; CPPh,ipso), 135.1 (COPh,meta), 145.6 (COPh,ipso), 170.6 (CSPh,ipso). 31P{1H} NMR (162.1 MHz, C6D6): δ 46.5 ppm. Activation of Elemental Hydrogen. First, 100 mg (151 μmol) of carbene complex 3 was dissolved in 5 mL of toluene. Three freeze− thaw cycles with H2 were performed, and the reaction was stirred at room temperature for 7 days during which the color changed to a light brown. Removal of the solvent under reduced pressure afforded the crude product, which was washed three times with pentane (2 mL) to give hydrido complex 5 in 80% yield (80.2 mg, 121 μmol). 1H NMR (400.1 MHz, C6D6): δ −5.43 (s, 1H; RuH), 0.01 (s, 9H; Si(CH3)3),

1.25 (d, 3JHH = 6.84 Hz, 3H; CH(CH3)2), 1.30 (d, 3JHH = 6.88 Hz, 3H; CH(CH3)2), 2.64 (s, 3H; CCH3), 2.70 (sept, 3JHH = 6.86 Hz, 1H; CH(CH3)2), 3.63 (d, 2JHP = 1.91 Hz, 1H; SCHP), 4.56 (d, 3JHH = 5.58 Hz, 1H; CHCym), 5.11 (s, 2H; CHCym), 6.20 (d, 3JHH = 5.44 Hz, 1H; CHCym), 6.64−6.68 (m, 2H; CHPPh,meta), 6.77−6.84 (m, 3H; CHSPh,meta,para), 6.94−6.98 (m, 1H; CHPPh,para), 7.00−7.05 (m, 3H; CHPPh,meta,para), 7.26−7.28 (m, 2H; CHSPh,ortho), 7.39−7.44 (m, 2H, CHPPh,ortho), 7.47−7.52 (m, 2H; CHPPh,ortho). 13C{1H} NMR (125.8 MHz, C6D6): δ 4.03 (d, 3JCP = 3.39 Hz, Si(CH3)3)), 19.8 (CCH3), 24.1 (CH(CH3)2), 24.4 (CH(CH3)2), 30.4 (d, 1JCP = 67.3 Hz; SCHP), 33.1 (CH(CH3)2), 69.7 (CHCym), 75.0 (CHCym), 85.0 (CHCym), 88.7(CHCym), 101.5 (CCym), 107.8 (CCym), 126.4 (CHSPPh,ortho), 128.3 (CHPPh,meta), 130.2 (CHSPh,meta ), 130.7 (d, 2 JCP = 10.0 Hz; CHPPh,ortho),130.9 (d, 4JCP = 2.46 Hz; CHPPh,para), 131.3 (d, 4JCP = 2.68 Hz; CHPPh,para), 133.2 (d, 2JCP = 9.87 Hz, CHPPh,ortho), 134.3 (d, 1 JCP = 19.7 Hz; CPPh,ipso), 135.1 (CHSPh,para), 146.6 (CSPPh,ipso). 31P{1H NMR (101.5 MHz, C6D6): δ 26.8. Anal. Calcd for C32H40NO2PRuSSi: C, 57.98; H, 6.08; N, 2.11; S, 4.84. Found: C, 57.30; H, 6.14; N, 2.48; S, 4.47. Reaction of Carbene Complex 3 with Water. First, 200 mg (303 μmol) of carbene complex 3 was dissolved in 3 mL of toluene. Then, 8.18 mg (453 μmol) of water was added, and the reaction mixture was stirred overnight during which the color changed from dark purple to dark blue. The reaction mixture was filtered; the solvent was evaporated, and the resulting residue was washed three times with 3 mL of Et2O, thus giving complex 6 as a blue solid in 62% yield (85.3 mg, 94.7 mmol). 1H NMR (400.1 MHz, C6D6): δ 0.75 (d, 3JHH = 6.60 Hz, 12H; CH(CH3)2), 0.89 (sept, 3JHH = 6.60 Hz, 2H; CH(CH3)2), 1.81 (s, 6H; CCH3), 4.97 (d, 3JHH = 6.00 Hz, 4H; CHCym), 5.14 (d, 3 JHH = 6.00 Hz, 4H; CHCym), 7.04−7.08 (m, 4H; CHPPh,para), 7.13− 7.18 (m, 8H; CHPPh,meta), 8.34−8.38 (m, 8H; CHPPh,ortho). 13C{1H} APT-NMR (100.6 MHz, C6D6): δ 19.7 (CCH3), 23.6 (CH(CH3)2), 30.0 (CH(CH3)2), 81.8 (CHCym), 82.6 (CHCym), 90.7 (CCym), 103.7 (CCym), 127.9 (CHPPh,meta), 129.6 (d, 4JCP = 2.60 Hz; CHPPh,para), 132.8 (d, 2JCP = 7.91 Hz; CHPPh,ortho), 144.1 (d, 1JCP = 114.5 Hz; CPPh,ipso). 31 1 P{ H} NMR (101.3 MHz, C6D6): δ 34.5. Anal. Calcd for C44H48N2O2P2Ru2·0.5THF: C, 58.96; H, 5.59; N, 2.99. Found: C, 58.69; H, 5.45; N, 3.27. X-ray Crystallography. Data collection of the compounds was conducted with a Bruker APEX2-CCD (D8 three-circle goniometer), an Oxford XCalibur 2 (Sapphire 2 detector), or Oxford SuperNova (Cu-μsource, Atlas). The structures were solved using direct methods, refined with the Shelx software package, and expanded using Fourier techniques.28 The crystals of all compounds were mounted in an inert oil (perfluoropolyalkylether). Crystal structure determinations were effected at 100 or 170 K. Crystallographic data (excluding structure factors) have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC 1541854− 1541860. Copies of the data can be obtained free of charge upon application to the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK [fax: (+44) 1223-336-033; e-mail: [email protected]]. Crystal Data for Complex 2. Single crystals suitable for X-ray diffraction analysis were obtained by slow diffusion of pentane into a saturated solution of 2 in THF. C32H39ClNO2PRuSSi: Mr = 697.28 g mol−1; orange block; 0.10 × 0.05 × 0.05 mm3; monoclinic; space group P21/n; a = 11.9339(8), b = 17.8371(12), c = 15.1322(10) Å; V = 3076.4(4) Å3; Z = 4; ρcalcd = 1.505 g cm−3; μ = 0.786 mm−1; F(000) = 1440; T = 100(2) K; R1 = 0.0224 and wR2= 0.0547; 5413 unique reflections (θ < 25.00); and 408 parameters. Crystal Data for Complex 3. Single crystals were obtained by cooling of a saturated solution of 3 in toluene to −40 °C. The asymmetric unit contains half a molecule of toluene placed on an inversion center. C29H38NO2PRuSSi: Mr = 624.79 g mol−1; purple plate; 0.10 × 0.09 × 0.03 mm3; triclinic; space group P1;̅ a = 9.4718(8), b = 11.9668(10), c = 16.4426(13) Å; V = 1680.8(2) Å3; Z = 2; ρcalcd = 1.235 g cm−3; μ = 0.635 mm−1; F(000) = 648; T = 100(2) K; R1 = 0.0263 and wR2 = 0.0938; 5922 unique reflections (θ < 25.00); and 394 parameters. H


Article

Organometallics Crystal Data for Complex 4a. Single crystals were obtained by diffusion of pentane into a saturated THF solution of the complex. C38H44NO3PRuSSi: Mr = 754.93 g mol−1; orange block; 0.20 × 0.20 × 0.40 mm3; orthorhombic; space group P212121; a = 9.99508(16) Å, b = 18.8476(3) Å, c = 19.1935(3) Å; V = 3615.74(10) Å3; Z = 4; ρcalcd = 1.384 g cm−3; μ = 0.606 mm−1; F(000) = 1568; T = 173(2) K; R1 = 0.0218 and wR2 = 0.0521; 6352 unique reflections (θ < 25.00); and 425 parameters. Crystal Data for Complex 4a-TMS. Single crystals suitable for Xray diffraction analysis were obtained by slow diffusion of pentane into a saturated solution of 4a in THF. C35H36NO3PRuS: Mr = 682.75 g mol−1; orange block; 0.40 × 0.15 × 0.20 mm3; monoclinic; space group P21/c; a = 12.5006(3) Å, b = 16.4807(3) Å, c = 15.7356(3) Å; V = 3149.67(11) Å3; Z = 4; ρcalcd = 1.440 g cm−3; μ = 0.651 mm−1; F(000) = 1408; T = 170(2) K; R1 = 0.0260 and wR2 = 0.0667; 5544 unique reflections (θ < 25.00); and 390 parameters. Crystal Data for Complex 4b. Single crystals were obtained by diffusion of pentane into a saturated THF solution of the complex. C42H52NO3PRuSSi: Mr = 811.04 g mol−1; orange block; 0.41 × 0.32 × 0.09 mm3; orthorhombic; space group Pbca; a = 21.51012(15) Å, b = 17.23853(12) Å, c = 21.60793(16) Å; V = 8012.28(10) Å3; Z = 8; ρcalcd = 1.345 gcm−3; μ = 4.614 mm−1; F(000) = 3392; T = 100(2) K; R1 = 0.0266 and wR 2= 0.0695; 8254 unique reflections (θ < 75.00); and 463 parameters. Crystal Data for Complex 5. Single crystals were obtained by slow evaporation of a saturated solution of 5 in DCM at −40 °C. The asymmetric unit contains an additional DCM molecule. C33H42Cl2NO2PRuSSi: Mr = 747.76 g mol−1; yellow block; 0.25 × 0.23 × 0.30 mm3; triclinic; space group P1̅; a = 9.7418(2) Å, b = 12.0970(3) Å, c = 15.9001(4) Å; V = 1730.99(8) Å3; Z = 2; ρcalcd = 1.435 g cm−3; μ = 0.779 mm−1; F(000) = 772; T = 170(2) K; R1 = 0.0252 and wR2 = 0.0621; 6096 unique reflections (θ < 25.00); and 393 parameters. Crystal Data for Complex 6. Single crystals suitable for X-ray diffraction analysis were obtained by slow diffusion of pentane into a saturated solution of 6 in THF. The asymmetric unit contains one dimeric complex and an additional molecule of THF. C24H28NO1.50PRu: Mr = 973.02 g mol−1; blue block; 0.27 × 0.23 × 0.23 mm3; triclinic; space group P1̅; a = 12.6771(8) Å, b = 13.2511(8) Å, c = 13.7984(8) Å; V = 2168.9(2) Å3; Z = 2; ρcalcd = 1.490 g cm−3; μ = 0.814 mm−1; F(000) = 1000; T = 100(2) K; R1 = 0.0224 and wR2 = 0.0558; 7628 unique reflections (θ < 25.00); and 520 parameters. Computational Studies. All calculations were performed without symmetry restrictions. Starting coordinates were obtained directly from the crystal structures or with GaussView 5.0. All calculations were performed with the Gaussian 09 (revision D.01) program package29 using the hybrid functional B3LYP or M062X of Truhlar and Zhao.30 The 6-311++G** basis set was employed for all nonmetal atoms and the LANL2TZ basis set for ruthenium augmented with an f polarization function of exponent 0.938. Frequency calculations, to establish the nature of the stationary point, were carried out using the same level of theory. Cartesian coordinates for all optimized structures and additional details are given in the Supporting Information. NBO analyses were carried out on the optimized systems using the NBO 5.0 program as implemented in the Gaussian 03 package and the same level of theory.31 Cartesian coordinates of the energy-optimized structures of 3 and C are given in the Supporting Information.

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Accession Codes

CCDC 1541854−1541860 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Viktoria H. Gessner: 0000-0001-6557-2366 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the German Research Foundation (Emmy-Noether grant DA1402/1-1) and the Fonds der Chemischen Industrie. We further acknowledge the German Research Foundation for support within the Cluster of Excellence RESOLV EXC1069.

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REFERENCES

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.7b00254. Complete experimental procedures, analytical data, and NMR spectra for all new compounds with crystallographic and computational details (PDF) 3D structure of complex 3 (XYZ) 3D structure of complex C (XYZ) I


Article

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Cooperative Bond Activation Reactions with Ruthenium Carbene

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