Metal-centered oxidations facilitate the removal of ruthenium-based olefin metathesis catalysts

Accepted Manuscript Metal-Centered Oxidations Facilitate the Removal of Ruthenium-Based Olefin Metathesis Catalysts Evelyn L. Rosen, C. Daniel Varnado, Kuppuswamy Arumugam, Christopher W. Bielawski PII:

S0022-328X(13)00570-6

DOI:

10.1016/j.jorganchem.2013.07.063

Reference:

JOM 18180

To appear in:

Journal of Organometallic Chemistry

Received Date: 20 June 2013 Revised Date:

24 July 2013

Accepted Date: 24 July 2013

Please cite this article as: E.L. Rosen, C. Daniel Varnado Jr., K. Arumugam, C.W. Bielawski, MetalCentered Oxidations Facilitate the Removal of Ruthenium-Based Olefin Metathesis Catalysts, Journal of Organometallic Chemistry (2013), doi: 10.1016/j.jorganchem.2013.07.063. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

Synopsis

AC C

EP

TE D

M AN U

SC

RI PT

The redox processes intrinsic to commercially-available Ru-based olefin metathesis catalysts were used to switch between two different states of activity in ring opening metathesis polymerizations and ring closing metathesis reactions, and also used to facilitate the precipitation and isolation of the catalysts.

ACCEPTED MANUSCRIPT

Highlights 1.) The activities displayed by olefin metathesis catalysts may be modulated by adding oxidants or reductants;

RI PT

2.) The solubility and recoverability of olefin metathesis catalysts may be controlled via metal centered oxidation processes;

AC C

EP

TE D

M AN U

SC

3.) A new approach for recovering commercially available olefin metathesis catalysts using redox-driven processes has been established.

ACCEPTED MANUSCRIPT

RI PT

Metal-Centered Oxidations Facilitate the Removal of Ruthenium-Based Olefin Metathesis Catalysts

SC

Evelyn L. Rosen, C. Daniel Varnado, Jr., Kuppuswamy Arumugam and

M AN U

Christopher W. Bielawski*

Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712 * To whom correspondence should be addressed.

TE D

[email protected]

Commercially available catalysts (SIMes)(PCy3)Cl2Ru(=CHPh) (2) and (SIMes)Cl2Ru(=CH-o-OiPrC6H4) (3) (SIMes = 1,3-dimesitylimidazolin-2-ylidene) were found to display reversible Ru

EP

oxidations via a series of electrochemical measurements. The redox processes enabled the catalysts to be switched between two different states of activity in ring opening metathesis polymerizations and ring

AC C

closing metathesis reactions, primarily through changes in catalyst solubility. Moreover, treating a solution of 2 dissolved in C6H6/CH2Cl2/[BMI][PF6] (6:1:1.1 v/v/v) with 2,3-dichloro-5,6-dicyano-1,4benzoquinone was found to remove >99.9% of the catalyst, as determined by UV/vis spectroscopy. The methodology described herein establishes a new approach for controlling the activities displayed by commercially available olefin metathesis catalysts and for removing residual Ru species using redox processes.

1

ACCEPTED MANUSCRIPT

1. Introduction The removal and reuse of precious metal based catalysts from reaction media has been a long-standing challenge in the field of homogeneous catalysis. Indeed, catalysts have been attached to various types of phase tags

RI PT

[1, 2] including fluorine containing derivatives [3-5], photoresponsive groups [6, 7], redox active groups [8, 9], and ionic liquids [10] to facilitate separation. The use of redox active phase tags to recover and reuse catalysts is a

particularly attractive approach as redox processes are often diffusion controlled and operate in a manner that is orthogonal to other stimuli, such as light or heat. One area where redox active phase tags [8, 9, 11] have found

SC

utility is in the recovery of ruthenium-based olefin metathesis catalysts [12-21]. For example, Plenio and co-

workers [9] elegantly designed a Ru-based olefin metathesis catalyst featuring two ferrocene groups attached to an

M AN U

N-heterocyclic carbene ligand [22-29]. Upon the addition of two equivalents of [FcCOCH3][CF3SO3], the ferrocene moieties underwent oxidation to their ferrocenium derivatives and caused the catalyst to precipitate from solution. The oxidized catalyst could then be recovered via filtration and reused upon reduction to its neutral form. A related catalyst which featured a ferrocene group appended to the 2-isopropoxybenzylidene moiety of a Hoveyda-Grubbs type catalyst was recently reported by Wang and co-workers [11]. Similar to the above mentioned system, exposing the catalyst to iodine resulted in oxidation of the ferrocene group and facilitated extraction of the corresponding

TE D

complex from non-polar media into an ionic liquid; subsequent reduction with decamethylferrocene (Fc*) restored the complex’s solubility as well as its catalytic activity [11]. Alternatively, a number of other approaches have been employed to remove ruthenium residues upon completion of metathesis reactions [30-55], including

EP

attachment to silica gel [30-36] or other heterogeneous supports [37-42], selective chemical degradation [43-46], conversion to water soluble derivatives through ligand exchange [47, 48] or quarternization of a pendant amino

AC C

groups [49], and selective extraction [50-53].

The primary drawbacks to the aforementioned redox-based approaches are that either specially designed redox-active ligands are needed or the metal is recovered in a form that is not easily reusable. Since Ru-based olefin metathesis catalysts contain redox active metal centers, we envisioned finding suitable conditions that utilizes the RuII/III couple to induce solubility changes and facilitate catalyst removal. An ability to selectively oxidize the metal center without irreversible chemical degradation of the complex should also facilitate reuse upon subsequent recovery and reduction, or enable external control over polymerizations [56] and other types of redoxmediated reactions [57].

2

ACCEPTED MANUSCRIPT

2. Experimental 2.1 General comments Toluene and CH2Cl2 were dried and degassed using a Vacuum Atmospheres Company solvent purification

RI PT

system and then subsequently stored over 3 Å molecular sieves. Benzene-d6 was distilled from sodium and benzophenone ketyl under an atmosphere of nitrogen then degassed by three, consecutive freeze-pump-thaw

cycles. CD2Cl2 and toluene-d8 (99.9%) were purchased from Cambridge Isotope Laboratories and stored over 3 Å molecular sieves. (PCy3)2Cl2Ru=CHPh (Cy = cyclohexyl) (1), (SIMes)(PCy3)Cl2Ru(=CHPh) (2) and

SC

(SIMes)Cl2Ru(=CH-o-O-i-PrC6H4) (3) are commercially available from Sigma-Aldrich. Diethyl diallylmalonate (DDM) was dried by stirring over 3 Å molecular sieves then degassed by three consecutive freeze-pump-thaw

M AN U

cycles. Cis,cis-1,5-cyclooctadiene was distilled from CaH2 under an atmosphere of N2 then degassed by three consecutive freeze-pump-thaw cycles. All other materials and solvents were of reagent quality and were used as received. Unless otherwise noted, all manipulations were performed under an atmosphere of nitrogen using standard drybox or Schlenk techniques. 2.2 Instrumentation 1

H and 13C NMR spectra were recorded using a Varian 300, 400, 500 or 600 MHz spectrometer. Chemical

TE D

shifts δ (in ppm) were referenced to tetramethylsilane using the residual solvent as an internal standard. For 1H NMR: C6D6, 7.15 ppm; toluene-d8, 2.09 ppm; CD2Cl2, 5.32 ppm. UV-visible absorption spectra were recorded on a Perkin-Elmer Lambda 35 spectrometer. All measurements were made using matched 6Q Spectrosil quartz cuvettes

EP

(Starna) with 1 cm path lengths and 3.0 mL sample solution volumes. Electrochemical experiments were conducted on Series 660D CH Instruments Electrochemical Workstation using a gastight, three-electrode cell under an

AC C

atmosphere of dry nitrogen. The cell was equipped with platinum working and platinum counter electrodes, as well as a silver wire quasi-reference electrode. Measurements were performed in dry CH2Cl2 with 0.1 M [nBu4N][PF6] as the electrolyte and (Me5Cp)2Fe (Fc*) (Cp = cyclopentadienyl) as the internal standard. All potentials were determined by differential pulse voltammetry and were referenced to the saturated calomel electrode (SCE) by shifting (Fc*)0/+ to –0.057 V (CH2Cl2) [58].

2.3 Redox-switchable metathesis reactions catalyzed by 2 or 3. Stock solutions of Ru catalysts 2 or 3, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and Fc* were made in CD2Cl2, toluene-D8, or C6D6. The reactions were performed in screw-cap NMR tubes so that the chemical 3

ACCEPTED MANUSCRIPT

oxidant or reductant could be added at a later point in time and the reaction progress was monitored by 1H NMR spectroscopy. 2.4 Chemical precipitation of [2][DDQ].

RI PT

A 20 mL glass vial equipped with a stir bar was charged with 2 (34.4 mg, 0.0405 mmol) and toluene (20.25 mL). DDQ (9.6 mg, 0.0425 mmol) was then added and the vial was sealed with a Teflon-lined cap. The reaction mixture was stirred for 15 min at room temperature. A black precipitate formed which was isolated by filtration and dissolved in CH2Cl2. Evaporation of the solvent under reduced pressure afforded the desired compound in 92%

2.5 Ring-closing metathesis catalyzed by 2 in organic/IL biphasic media.

SC

yield based on the initial masses of 2 and DDQ.

M AN U

A glass vial was charged with 2 (4.6 mg, 0.0054 mmol), 0.5 mL CH2Cl2, 3 mL C6H6, and 0.5 mL [1-butyl-3methylimidazolium][PF6]. Diethyl diallylmalonate (50 µL, 0.21 mmol) was then added and the reaction was stirred at ambient temperature for 30 min, at which point the reaction was determined to be complete by NMR spectroscopy. An aliquot of the benzene/dichloromethane solution was removed and analyzed by UV/vis spectroscopy. DDQ (1.2 mg, 0.0054 mmol) was then added and the resulting mixture was stirred for 5 min. A separate aliquot of the nonpolar fraction was removed and analyzed by UV/vis spectroscopy.

TE D

3. Results and Discussion

3.1 Electrochemistry

The electrochemical properties of three commercially available catalysts (1 – 3; Figure 1)

EP

were studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). While the bisphosphine complex 1 was found to display a quasi-reversible redox couple (at E1/2 = 0.63

AC C

V; scan rate = 100 mVs-1) in CH2Cl2 containing [(nBu)4N][PF6] as the electrolyte, the redox couples of 2 (E1/2 = 0.51 V) and 3 (E1/2 = 0.91 V) were reversible (Figure 2 and Figure S1 in the Supporting Information) and dependent on the donor properties of their respective ligands [59-61]. 3.2 Catalysis

4

ACCEPTED MANUSCRIPT

Upon verification of reversibility of the RuII/III couples for 2 and 3, subsequent efforts were directed toward exploring how redox chemistry influences the catalytic activities displayed by the aforementioned catalysts. Since 2,3-dichloro-5,6-dicyanoquinone (DDQ) (E1/2 = 0.58 V

RI PT

versus SCE in CH2Cl2/[Et4N][ClO4]) [13] was previously shown to oxidize the Ru center in 2, it was used as an oxidant [62]. Fc* was selected as the reductant (E1/2 = –0.057 V versus SCE in CH2Cl2/[Bu4N][PF6]) [58] as this compound has been reported as a spectator in olefin

SC

metathesis reactions catalyzed by Ru-based catalysts [9, 63]. As summarized in Scheme 1, two representative olefin metathesis reactions were explored under standardized conditions [64]: the

M AN U

ROMP of cis,cis-1,5-cyclooctadiene (COD) (Eq. 1) and the RCM of diethyl diallylmalonate (DDM) (Eq. 2).

As summarized in Figure 3 (left), complex 2 quantitatively converted COD to poly(1,3butadiene) within 40 min (kobs = 4.8 × 10-3 s-1), as determined by 1H NMR spectroscopy in C6D6.

TE D

However, in a separate experiment, the addition of DDQ shortly after the polymerization was initiated resulted in a significant decrease in the observed reaction rate (kobs = 6.0 × 10-5 s-1) and attributed to the formation of [2][DDQ] [62]. The subsequent addition of Fc* caused the rate

EP

constant of polymerization to increase (kobs = 1.3 × 10-3 s-1), consistent with an increase in concentration of the catalytically active RuII complex formed upon reduction of the RuIII

AC C

precursor (see below). Similarly, pre-oxidation of 2 through the addition of excess DDQ (7.7 equiv. relative to catalyst) prior to the addition of COD resulted in a relatively slow reaction (kobs = 5.2 × 10-5 s-1) whereas the subsequent addition of Fc* significantly increased the rate of the reaction (kobs = 1.0 × 10-3 s-1). The ability to modulate the RCM of DDM with catalyst 3 was also examined by 1H NMR spectroscopy in CD2Cl2 using DDQ as the oxidant and Fc* as the reductant [65]. As summarized in Figure 3 (right), complex 3 catalyzed the conversion of DDM to its ring-closed product within 40 min (kobs = 1.2 × 10-3 s-1). However, in a

5

ACCEPTED MANUSCRIPT

separate experiment, the addition of DDQ after the aforementioned reaction was initiated resulted in a significant decrease in the observed rate constant (kobs = 2.0 × 10-6 s-1) whereas the subsequent addition of Fc* restored the rate of the reaction (kobs = 3.7 × 10-4 s-1). Moreover, through the sequential addition of oxidant followed by reductant,

RI PT

the catalytic activity was effectively toggled between two states of activity multiple times over the course of a single reaction. Finally, as demonstrated with the ROMP reaction described above, oxidizing 3 prior to the addition of DDM resulted in a relatively low catalytic activity which was later increased upon the addition of Fc*.

As noted above, the addition of oxidants to the aforementioned reactions significantly reduced catalytic

SC

activity, which we surmised was due to precipitation of the oxidized catalyst. Thus, subsequent efforts were

directed toward verifying this hypothesis and recovering the oxidized species. Treating a toluene solution of 2 ([2]0

M AN U

= 2 mM) with DDQ (1.05 equiv) resulted in the formation of a dark green precipitate, which was collected by filtration in 92% yield (assuming the complex formed was [2][DDQ]). Unfortunately, only limited quantities of precipitate were observed when 3 was treated to otherwise identical conditions and recovery of 3 was not further pursued. To facilitate catalyst recovery, a biphasic organic-ionic liquid mixture analogous to that reported by Wang was employed [11]. The RCM of DDM catalyzed by 2 was set up in C6H6/CH2Cl2/[BMI][PF6] (6:1:1.1 v/v/v) (BMI = 1-butyl-3-methylimidazolium) using otherwise identical conditions to those described above. After conversion to

TE D

the desired product was complete, the reaction mixture was analyzed by UV/vis spectroscopy which revealed a strong λmax at 339 nm, attributed to a Ru centered absorption (see Figure 4). After the addition of DDQ (1 equiv. relative to catalyst), the solution was stirred for 5 min and then re-analyzed by UV/vis spectroscopy. The

EP

absorption at 339 nm was significantly reduced with no local λmax observed. Moreover, the lack of absorption bands in the range of 500–600 nm indicated that the concentration of DDQ • – was not significant, consistent with the

AC C

formation of the charge transfer complex [2][DDQ]. Based on the absorbance at 429 nm, which is the λmax attributed to a Ru-centered transition for [2][DDQ], >99.9% of Ru was effectively removed from the organic layer. While the removal of Ru from the organic layer appeared successful, the subsequent addition of Fc* to the reaction mixture did not result in the restoration of any absorbance that could be attributed to the reformation of a Ru(II) species, presumably due to decomposition of the coordinatively unsaturated methylidene complex formed during the course of the RCM reaction [66].

4. Conclusions

6

ACCEPTED MANUSCRIPT

In summary, the ability to use metal centered oxidation processes to recover commercially available olefin metathesis catalysts was explored. The addition of DDQ to 2 or 3 was shown to significantly reduce catalytic activity in representative RCM and ROMP reactions, a result that

RI PT

was attributed to a RuII → RuIII oxidation process concomitant with precipitation of the catalyst; activity was subsequently restored through the addition of Fc*. The removal of the residual Ru species from solution was facilitated through the use of DDQ in conjunction with a biphasic

SC

organic/IL mixture. Collectively, the results described herein demonstrate that metal centered oxidations may be used to modulate the activities of Ru-based olefin metathesis catalysts and,

M AN U

under some conditions, may be used to facilitate their removal.

Acknowledgment

We are grateful to the U. S. Army Research Laboratory under grant number W911NF-09-1-0446 and the

EP

TE D

National Science Foundation (CHE- 1266323) for their generous financial support.

AC C

Figure 1. Commercially available Ru olefin metathesis catalysts. Cy = cyclohexyl. Mes = 2,4,6trimethylphenyl.

7

RI PT

ACCEPTED MANUSCRIPT

Figure 2. Cyclic voltammograms for (A) Ru complex 1 (E1/2 = 0.63 V at 100 mV s-1; quasi-

SC

reversible), (B) Ru complex 2 (E1/2 = 0.51 V at 100 mV s-1; reversible), and (C) Ru complex 3 (E1/2 = 0.91 V at 100 mV s-1; reversible) at scan rates of 25, 50, 100, 250, and 500 mVs-1.

M AN U

Conditions: CH2Cl2, 1 mM analyte, 0.1 M [nBu4N][PF6]. The data were referenced to a saturated calomel electrode (SCE) by shifting decamethylferrocene0/+ to –0.057 V (CH2Cl2)

TE D

[58].

Scheme 1. Metathesis reactions studied using 2 and 3.

EP

(i)

AC C

E E

(ii)

(1) n E E +

H2C=CH2

(2)

E = CO2Et

(i) 0.003 mol% [Ru], [COD]0 = 0.5 M, C6D6, 27 °C. (ii) 1 mol% [Ru], [DDM]0 = 0.1 M, CD2Cl2,

8

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Figure 3. (left) Redox-switchable ROMP reactions catalyzed by 2 as monitored by 1H NMR spectroscopy (C6D6). The conditions are given in Scheme 1. Curve A refers to a control experiment in which no oxidant or reductant was added. Curve B refers to an experiment in

TE D

which the catalyst was oxidized and subsequently reduced. Curve C refers to an experiment in which the pre-oxidized 2 was reduced after the ROMP was in progress. The letter O refers to when 7.7 equiv. of DDQ (relative to catalyst) was added. The letter R refers to when 12.5 equiv.

EP

of Fc* (relative to catalyst) was added. For the reaction to which only Fc* was added, 7.7 equiv. of DDQ was added 2 h prior to the addition of substrate. (right) Redox-switchable RCM

AC C

reactions catalyzed by 3 as monitored by 1H NMR spectroscopy (CD2Cl2). The conditions are given in Scheme 1. Curve A refers to the control experiment in which no oxidant or reductant was added. Curve B refers to the experiment in which the catalyst was oxidized and subsequently reduced. Curve C refers to the experiment in which the pre-oxidized 2 was reduced after the RCM reaction was in progress. The letter O refers to when 1.1 equiv of DDQ (relative to catalyst) was added. The letter R refers to when 1.2 equiv of Fc* (relative to

9

ACCEPTED MANUSCRIPT

catalyst) was added. For the reaction to which only Fc* was added, 1.1 equiv of DDQ was

M AN U

SC

RI PT

added 15 min prior to the addition of substrate.

Figure 4. UV/vis spectra (CH2Cl2) of aliquots taken from the RCM of diethyl diallylmalonate

TE D

catalyzed by 2 in a biphasic solution: (A) before and (B) after the addition of DDQ. References

AC C

EP

[1] D.P. Curran, Angew. Chem. 110 (1998) 1230-1255. [2] D.P. Curran, Angew. Chem. Int. Ed. 37 (1998) 1174-1196. [3] I.T. Horváth, Acc. Chem. Res. 31 (1998) 641-650. [4] A. Studer, S. Hadida, R. Ferritto, S.-Y. Kim, P. Jeger, P. Wipf, D.P. Curran, Science 275 (1997) 823-826. [5] M. Matsugi, Y. Kobayashi, N. Suzumura, Y. Tsuchiya, T. Shioiri, J. Org. Chem. 75 (2010) 7905-7908. [6] G. Liu, J. Wang, Angew. Chem. Int. Ed. 49 (2010) 4425-4429. [7] G. Liu, J. Wang, Angew. Chem. 122 (2010) 4527-4531. [8] C.A. Fleckenstein, H. Plenio, Adv. Synth. Catal. 348 (2006) 1058-1062. [9] M. Süßner, H. Plenio, Angew. Chem. Int. Ed. 44 (2005) 6885-6888. [10] B. Ni, A.D. Headley, Chem. Eur. J. 16 (2010) 4426-4436. [11] G. Liu, H. He, J. Wang, Adv. Synth. Catal. 351 (2009) 1610-1620. [12] M.R. Buchmeiser, Chem. Rev. 100 (2000) 1565-1604. [13] A. Fürstner, Angew. Chem. 112 (2000) 3140-3172. [14] R.H. Grubbs, Tetrahedron 60 (2004) 7117-7140. [15] R.H. Grubbs, S. Chang, Tetrahedron 54 (1998) 4413-4450. [16] K. Ivin, H. Mol, Preface, in: Olefin Metathesis and Metathesis Polymerization (2), Academic Press, London, 1997, pp. xiii-xiv. 10

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

[17] K.J. Ivin, J. Mol. Catal. A: Chem. 133 (1998) 1-16. [18] T.M. Trnka, R.H. Grubbs, Acc. Chem. Res. 34 (2000) 18-29. [19] C. Fraser, R.H. Grubbs, Macromolecules 28 (1995) 7248-7255. [20] P. Schwab, M.B. France, J.W. Ziller, R.H. Grubbs, Angew. Chem. 107 (1995) 21792181. [21] P. Schwab, R.H. Grubbs, J.W. Ziller, J. Am. Chem. Soc. 118 (1996) 100-110. [22] A. Briot, M. Bujard, V. Gouverneur, S.P. Nolan, C. Mioskowski, Org. Lett. 2 (2000) 1517-1519. [23] A. Fürstner, O.R. Thiel, L. Ackermann, H.-J. Schanz, S.P. Nolan, J. Org. Chem. 65 (2000) 2204-2207. [24] W.A. Herrmann, C. Köcher, Angew. Chem. Int. Ed. 36 (1997) 2162-2187. [25] J. Huang, E.D. Stevens, S.P. Nolan, J.L. Petersen, J. Am. Chem. Soc. 121 (1999) 26742678. [26] J.P. Morgan, R.H. Grubbs, Org. Lett. 2 (2000) 3153-3155. [27] M. Scholl, T.M. Trnka, J.P. Morgan, R.H. Grubbs, Tetrahedron Lett. 40 (1999) 22472250. [28] B.F. Straub, Angew. Chem. Int. Ed. 44 (2005) 5974-5978. [29] T. Weskamp, F.J. Kohl, W. Hieringer, D. Gleich, W.A. Herrmann, Angew. Chem. Int. Ed. 38 (1999) 2416-2419. [30] J.H. Cho, B.M. Kim, Org. Lett. 5 (2003) 531-533. [31] E. Borré, M. Rouen, I. Laurent, M. Magrez, F. Caijo, C. Crévisy, W. Solodenko, L. Toupet, R. Frankfurter, C. Vogt, A. Kirschning, M. Mauduit, Chemistry – A European Journal 18 (2012) 16369-16382. [32] D. Fischer, S. Blechert, Adv. Synth. Catal. 347 (2005) 1329-1332. [33] J.r.A. Schachner, J. Cabrera, R. Padilla, C. Fischer, P.A. van der Schaaf, R. Pretot, F. Rominger, M. Limbach, ACS Catalysis 1 (2011) 872-876. [34] K. Skowerski, P. Kasprzycki, M. Bieniek, T.K. Olszewski, Tetrahedron 69 (2013) 74087415. [35] A. Michrowska, L. Gulajski, K. Grela, Chem. Commun. (2006) 841-843. [36] M. Kluciar, K. Grela, M. Mauduit, Dalton Transactions 42 (2013) 7354-7358. [37] L. Jafarpour, S.P. Nolan, Org. Lett. 2 (2000) 4075-4078. [38] K. McEleney, D.P. Allen, A.E. Holliday, C.M. Crudden, Org. Lett. 8 (2006) 2663-2666. [39] P. Nieczypor, W. Buchowicz, W.J.N. Meester, F.P.J.T. Rutjes, J.C. Mol, Tetrahedron Lett. 42 (2001) 7103-7105. [40] S.C. Schürer, S. Gessler, N. Buschmann, S. Blechert, Angew. Chem. Int. Ed. 39 (2000) 3898-3901. [41] Z. Yinghuai, L. Kuijin, N. Huimin, L. Chuanzhao, L.P. Stubbs, C.F. Siong, T. Muihua, S.C. Peng, Adv. Synth. Catal. 351 (2009) 2650-2656. [42] J. Dowden, J. Savovic, Chem. Commun. (2001) 37-38. [43] B.R. Galan, K.P. Kalbarczyk, S. Szczepankiewicz, J.B. Keister, S.T. Diver, Org. Lett. 9 (2007) 1203-1206. [44] D.W. Knight, I.R. Morgan, A.J. Proctor, Tetrahedron Lett. 51 (2010) 638-640. [45] L.A. Paquette, J.D. Schloss, I. Efremov, F. Fabris, F. Gallou, J. Méndez-Andino, J. Yang, Org. Lett. 2 (2000) 1259-1261. [46] R.H. Lambeth, S.J. Pederson, M. Baranoski, A.M. Rawlett, J. Polym. Sci., Part A: Polym. Chem. 48 (2010) 5752-5757.

11

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

[47] H.D. Maynard, R.H. Grubbs, Tetrahedron Lett. 40 (1999) 4137-4140. [48] R.L. Pederson, I.M. Fellows, T.A. Ung, H. Ishihara, S.P. Hajela, Adv. Synth. Catal. 344 (2002) 728-735. [49] K. Skowerski, C. Wierzbicka, G. Szczepaniak, L. Gulajski, M. Bieniek, K. Grela, Green Chemistry 14 (2012) 3264-3268. [50] H. Wang, H. Matsuhashi, B.D. Doan, S.N. Goodman, X. Ouyang, W.M. Clark Jr, Tetrahedron 65 (2009) 6291-6303. [51] R.C. Buijsman, E. van Vuuren, J.G. Sterrenburg, Org. Lett. 3 (2001) 3785-3787. [52] K. Skowerski, C. Wierzbicka, G. Szczepaniak, L. Gulajski, M. Bieniek, K. Grela, Green Chemistry 14 (2012) 3264-3268. [53] D. Rix, H. Clavier, Y. Coutard, L. Gulajski, K. Grela, M. Mauduit, J. Organomet. Chem. 691 (2006) 5397-5405. [54] H. Clavier, K. Grela, A. Kirschning, M. Mauduit, S.P. Nolan, Angew. Chem. Int. Ed. 46 (2007) 6786-6801 and references therein. [55] G.C. Vougioukalakis, Chem. Eur. J. 18 (2012) 8868-8880 and references therein. [56] F.A. Leibfarth, K.M. Mattson, B.P. Fors, H.A. Collins, C.J. Hawker, Angew. Chem. Int. Ed. 52 (2013) 199-210. [57] A.M. Allgeier, C.A. Mirkin, Angew. Chem. Int. Ed. 37 (1998) 894-908. [58] I. Noviandri, K.N. Brown, D.S. Fleming, P.T. Gulyas, P.A. Lay, A.F. Masters, L. Phillips, J. Phys. Chem. B 103 (1999) 6713-6722. [59] S. Leuthäußer, V. Schmidts, C.M. Thiele, H. Plenio, Chem. Eur. J. 14 (2008) 54655481. [60] M. Sussner, H. Plenio, Chem. Commun. (2005) 5417-5419. [61] V. Thiel, M. Hendann, K.-J. Wannowius, H. Plenio, J. Am. Chem. Soc. 134 (2011) 1104-1114. [62] V. Amir-Ebrahimi, J. G. Hamilton, J. Nelson, J. J. Rooney, J. M. Thompson, A. J. Beaumont, A. Denise Rooney, C. J. Harding, Chem. Commun. (1999) 1621-1622. [63] K. Arumugam, C.D. Varnado Jr, S. Sproules, V.M. Lynch, C.W. Bielawski, Chem. Eur. J. in press (2013). [64] T. Ritter, A. Hejl, A.G. Wenzel, T.W. Funk, R.H. Grubbs, Organometallics 25 (2006) 5740-5745. [65] The use of a stronger oxidant, [FcCOCH3][BF4], effectively stopped catalytic activity but the process was determined to be irreversible. [66] S.H. Hong, A.G. Wenzel, T.T. Salguero, M.W. Day, R.H. Grubbs, J. Am. Chem. Soc. 129 (2007) 7961-7968.

12

ACCEPTED MANUSCRIPT

Electronic Supporting Information

RI PT

Metal-Centered Oxidations Facilitate the Removal of Ruthenium-Based Olefin Metathesis Catalysts

Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A1590, Austin, Texas 78712

M AN U

†

SC

Evelyn L. Rosen, C. Daniel Varnado, Jr., Kuppuswamy Arumugam and Christopher W. Bielawski*

E-mail: [email protected]

TE D

Table of Contents

Differential Pulse Voltammograms

S2

Redox Switchable RCM Kinetic Data

S3 S3 – S8

AC C

EP

Log Plots of Ln [substrate] vs. Time

S1

ACCEPTED MANUSCRIPT

RI PT

a)

M AN U

SC

b)

AC C

EP

TE D

c)

Figure S1. Differential pulse voltammograms (50 mV pulse amplitude) for (a) Ru complex 1 (E1/2 = 0.63 V at 100 mV s-1; quasi-reversible), (b) Ru complex 2 (E1/2 = 0.51 V at 100 mV s-1; reversible), and (c) Ru complex 3 (E1/2 = 0.91 V at 100 mV s-1; reversible). Conditions: CH2Cl2, 1 mM analyte, 0.1 M [nBu4N][PF6].

S2

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

Figure S2. Redox-switchable RCM of DDM catalyzed by 2 and monitored by 1H NMR spectroscopy (CD2Cl2). Conditions: 1 mol% 2, [DDM]0 = 0.1 M, 27 °C. The letter O refers to when 1.1 equiv of DDQ (relative to catalyst) was added. The letter R refers to when 1.2 equiv of Fc* (relative to catalyst) was added.

Figure S3. Plot of ln [DDM] versus time. Conditions: [DDM]0 = 0.1 M, [2]0 = 1.0 mM, CD2Cl2, 27 °C. The equation for the best fit line shown in red is as follows: y = mx + b, where m = –0.04399 ± 3.522 × 10-4 min-1 and b = –0.6972 ± 0.00332 (R2 = 0.999).

S3

ACCEPTED MANUSCRIPT

b)

RI PT

a)

TE D

M AN U

SC

c)

AC C

EP

Figure S4. (a) Plot of ln [DDM] versus time. Conditions: [DDM]0 = 0.1 M, [2]0 = 1.0 mM, CD2Cl2, 27 °C. The equation for the best fit line shown in red is as follows: y = mx + b, where m = –0.0427 ± 6.114 × 10-4 min-1 and b = –7.0993 ± 0.00461 (R2 = 0.999). (b) Plot of ln [DDM] versus time after the addition of DDQ. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.0077 ± 3.605 × 10-4 min-1 and c = – 1.10823 ± 0.0146 (R2 = 0.97853). (c) Plot of ln [DDM] versus time after the addition of Fc*. The equation for the best fit line shown in red is as follows: y = mx + c, where m = – 0.04066 ± 0.00114 min-1 and c = 0.90659 ± 0.09713 (R2 = 0.98841).

S4

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

Figure S5. Plot of ln [COD] versus time. Conditions: [COD]0 = 0.5 M, [2] = 0.003 mol%, C6D6, 27 °C. The equation for the best-fit line shown in red is as follows: y = mx + c, where m = –0.29691 ± 0.05596 min-1 and c = 0.73245 ± 0.02043 (R2 = 0.98592).

S5

ACCEPTED MANUSCRIPT

b)

SC

RI PT

a)

TE D

M AN U

c)

AC C

EP

Figure S6. (a) Plot of ln [COD] versus time. Conditions: [COD]0 = 0.5 M, [2]0 = 0.003 mol%, C6D6, 27 °C. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.18377 ± 0.03301 min-1 and c = –0.75032 ± 0.07858 (R2 = 0.93749). (b) Plot of ln [COD] versus time after the addition of DDQ. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.00358 ± 5.92895 × 10-4 min-1 and c = –1.71693± 0.02401 (R2 = 0.77989). (c) Plot of ln [COD] versus time after the addition of Fc*. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.07596 ± 0.00188 min-1 and c = 3.13704 ± 0.16275 (R2 = 0.99028).

S6

ACCEPTED MANUSCRIPT

b)

SC

RI PT

a)

AC C

EP

TE D

M AN U

Figure S7. (a) Plots of ln [COD] versus time. Conditions: [COD]0 = 0.5 M, [2][DDQ] = 0.003 mol%, C6D6, 27 °C. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.00309 ± 2.56868 × 10-4 min-1 and c = –0.76796± 0.00995 (R2 = 0.92288). (b) Plot of ln [COD] versus time after the addition of Fc*. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.06064 ± 0.0014 min-1 and c = –2.98215 ± 0.11316 (R2 = 0.99149).

Figure S8. Plot of ln [DDM] versus time. Conditions: [DDM]0 = 0.1 M, [3] = 1 mol%, CD2Cl2, 27 °C. The equation for the best-fit line shown in red is as follows: y = mx + c, where m = –0.07308 ± 0.00128 min-1 and c = –2.34963 ± 0.01034 (R2 = 0.99815).

S7

ACCEPTED MANUSCRIPT

b)

c)

d)

TE D

M AN U

SC

RI PT

a)

AC C

EP

e)

Figure S9. (a) Plots of ln[DDM] versus time. Conditions: [DDM]0 = 0.1 M, [3]0 = 1 mol%, CD2Cl2, 27 °C. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.05248 ± 0.00845 min-1 and c = –2.33287 ± 0.02681 (R2 = 0.92601). (b) Plot of ln [DDM] versus time after the addition of DDQ. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –1.21892 10-4 ± 2.6143 × 10-4 min-1 and c = –2.61468 ± 0.00368. (c) Plot of ln [DDM] versus time after the S8

ACCEPTED MANUSCRIPT

M AN U

SC

RI PT

addition of Fc*. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.02264 ± 3.54856 × 10-4 min-1 and c = -2.18324 ± 0.01019 (R2 = 0.99877). (d) Plot of ln [DDM] versus time after the addition of DDQ. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –5.23585 × 10-17 ± 2.9981 × 10-17 min-1 and c = –2.97593 ± 1.41356 × 10-15. (e) Plot of ln [DDM] versus time after the addition of Fc*. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.0079 ± 1.82281 × 10-4 min-1 and c = –2.55079 ± 0.01585 (R2 = 0.99523).

AC C

EP

TE D

Figure S10. (a) Plots of ln [DDM] versus time. Conditions: [DDM]0 = 0.1 M, [3][DDQ] = 1 mol%, CD2Cl2, 27 °C. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.0018 ± 4.49253 × 10-5 min-1 and c = –2.30008 ± 6.21962 × 10-4 (R2 = 0.99321). (b) Plot of ln [DDM] versus time after the addition of Fc*. The equation for the best fit line shown in red is as follows: y = mx + c, where m = –0.02033 ± 2.87567 × 10-4 min-1 and c = –1.88889 ± 0.01239 (R2 = 0.99701).

S9