Supporting Information

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1 Supporting Information Synthesis and Characterization of Cationic Rhodium Peroxo Complexes Judy Cipot-Wechsler, a Danielle Covelli, b Jeremy M. Praetorius, a igel Hearns, a lena V. Zenkina, Eric C. Keske, Ruiyao Wang, a Pierre Kennepohl*, b and Cathleen M. Crudden* a AUTHR ADDRESS a Department of Chemistry, Queen s University, Chernoff Hall, 90 Bader Lane, Kingston, ntario, Canada K7L 36 and b Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1 cathleen.crudden@chem.queensu.ca; pierre.kennepohl@ubc.ca Figure S1. Crystallographically determined structures of [Rh(IPr) 2( 2)(MeC) 2]BF 4 (11 BF 4) (left) and of [Rh(SIMes) 2( 2)(MeC) 2] CF 3S 3 (12 Tf) (right) displaying thermal ellipsoids drawn at the 50 % confidence level. Hydrogen atoms and counter-anion are omitted for clarity. Selected interatomic distances [Å] and angles [ ] for 11 BF 4: Rh(1) (1), 1.974(2); Rh(1) (2), 1.980(3);

2 Rh(1) C(1), 2.085(3); Rh(1) C(28), 2.097(3); Rh(1) (5), 2.091(3); Rh(1) (6), 2.105(3); (1) (1A), 1.428(3); (1) C(1), 1.379(4); (2) C(1), 1.369(4); C(2) C(3), 1.327(5); (1) Rh(1) C(1), 87.65(12); (1) Rh(1) C(28), 89.15(11); C(1) Rh C(28), (13); (1) Rh(1) (5), (11); (1) Rh(1) (6), (12); C(1) Rh(1) (5), 85.04(12); C(1) Rh(1) (6), 98.34(12); C(28) Rh(1) (5), 97.16(12), C(28) Rh(1) (6), 84.41(12); for 12 Tf: Rh(1) (1), 1.895(5); Rh(1) (2), 1.933(5); Rh(1) C(1), 2.089(7); Rh(1) C(22), 2.094(6); Rh(1) (5), 2.067(5); Rh(1) (6), 2.064(6); (1) (2), 1.439(8); (1) C(1), 1.339(9); (2) C(1), 1.340(9); C(2) C(3), 1.513(11); (1) Rh(1) C(1), 85.4(2); (1) Rh(1) C(22), 84.2(2); C(1) Rh(1) C(22), 167.5(3); (1) Rh(1) (5), 112.5(2); (1) Rh(1) (6), 118.8(2); C(1) Rh(1) (5), 95.9(2); C(1) Rh(1) (6), 94.4(2); C(22) Rh(1) (5), 94.5(2), C(22) Rh(1) (6), 93.6(2). Figure S2. Crystallographically determined structures of [Rh(SIMes) 2( 2)Cl] (4), displaying thermal ellipsoids drawn at the 50 % confidence level. Hydrogen atoms (except for the SIPr backbone hydrogens) are omitted for clarity. Selected interatomic distances [Å] and angles [ ]:Rh(1) (3), 2.090(5); Rh(1) C(1), 2.049(3); ); Rh(1) C(22), 2.058(3), Rh(1) Cl(1), 2.185(3); (3) (4), 1.372(16); (1) C(1), 1.335(4); (2) C(1), 1.339(4); C(2) C(3), 1.521(5); (3) Rh(1) C(1), 88.40(17); (3) Rh(1) C(22), 92.06(17); C(1) Rh(1) C(22), (13); (3) Rh(1) Cl(1), 88.40(17); C(1) Rh(1) Cl(1), 87.32(11); C(22) Rh(1) Cl(1), 93.34(11). Table S1. Crystallographic data for compounds 11 BF 4, 4 and 12 Tf. Formula C 59.5 H 81 6 RhCl 3 BF 4 11 BF 4 C 44 H 56 Cl Rh 4 C 47 H 55 F RhS 12 Tf Fw

3 Crystal dimensions (mm 3 ) 0.20 x 0.18 x x 0.12 x 0.08 mm 0.25 x 0.20 x 0.10 mm Crystal system Monoclinic Monoclinic Monoclinic Space group P2(1)/c C2/c C2/c a (Å) (9) (13) (3) b (Å) (12) (5) (8) c (Å) (2) (9) (3) V (Å 3 ) (8) (6) (15) Z T (K) 180(2) 180(2) K 293(2) K D calcd (g cm -3 ) (mm -1 ) F (000) range (deg) to to Index ranges (h, k, l) ±15, ±20, ±36 ±40, -8+14, ±29 ±39, ±10, ±40 o. of rflns collected o. of independent 8456/ / / rflns/r int o. data/restraints/params 8456/21/ / 36 / / 3 / 462 R1/wR2 (I > 2 (I)) / / / R1/wR2 (all data) / / / GF (on F 2 ) Experimental details. General considerations: All manipulations were carried out in a nitrogen atmosphere in a glovebox (M. Braun) with oxygen and water levels 2 ppm. Solvents were purified on a PureSolv Solvent Purification system, distilled, degassed and stored over 4 Å molecular sieves prior to use. SIMes 1,2 and IPr 2Rh 2Cl 3 were prepared according to previously reported literature procedures. 1 H MR spectra were recorded on a 400 or 500 MHz spectrometer. Chemical shifts are reported in delta (δ) units, expressed in parts per million (ppm) downfield from tetramethylsilane using residual protonated solvent as an internal standard (C 6D 6, 7.15 ppm; CDCl 3, 7.24 ppm; CD 2Cl 2, 5.32 ppm; acetonitrile-d 3, 1.95 ppm). 13 C MR spectra were recorded at 100 or 125 MHz. Chemical shifts are reported as above using the solvent as an internal standard (C 6D 6, ppm; CDCl 3, ppm; CD 2Cl 2, 53.8 ppm; acetonitrile-d 3, ppm). Elemental analyses were performed using a Thermo Scientific Flash 2000 CHS Elemental Analyzer. X-ray data collection was performed on a Bruker SMART APEX II X-ray diffractometer

4 Preparation of [IPr 2Rh 2MeC 2] + [BF 4] - (11 BF 4) BF 4 Rh To a four-dram vial containing IPr 2Rh 2Cl (27.1 mg, mmol) and a stir bar, MeC (3 ml) was added. Magnetic stirring was initiated, despite the starting material s lack of solubility in MeC, AgBF 4 (5.7 mg, mmol) was added as a suspension in MeC (2 x 1 ml). By visual inspection, the reaction was proceeding within a few minutes as the blue starting compound was consumed to yield a grey precipitate and a yellow supernatant. The reaction mixture was allowed to stir for 2 h after which all solvent was removed in vacuo. The product was extracted into DCM (3 ml) and the mixture was passed through a small plug of celite. The solvent was removed from the clear deep yellow-red filtrate to leave a beige solid which was subsequently washed with Et 2 (1 x 2 ml) and dried to leave an analytically pure powder of the title compound (14.4 mg, mmol, 45.8 %). Crystals suitable for X-ray crystallographic analysis were grown from slow diffusion of hexanes into a DCM solution of the title compound. Anal. Calcd. For C58H78BF462Rh: C 64.44, H 7.27, 7.77; found C 64.19, H 7.17, H MR (CD 2Cl 2,400 MHz): δ = 7.42 (t, 3 J HH = 7.5 Hz, 4H, p-arh), 7.24 (d, 3 J HH = 7.8 Hz, 8H, m-arh), 6.83 (s, 4H, -CH=CH-), 2.47 (br m, 8H, - CH(CH 3) 2), 1.88 (br s, 6H, CH 3C), (br m, 48H, -CH(CH 3) 2) ppm. 13 C{ 1 H} MR (CD 2Cl 2): = (-CC(CH(CH 3) 2)CH ach b-), (-CC(CH(CH 3) 2)CH ach b-) or (-

5 CC(CH(CH 3) 2)CH ach b-), (-CC(CH(CH 3) 2)CH ach b-) or (-CC(CH(CH 3) 2)CH ach b-), (-CH=CH-), (-CC(CH(CH 3) 2)CH ach b-), 29.0 (-CH(CH 3) 2), 26.2, 23.2 (- CH(CH 3) 2) ppm. Despite observation of the acetonitrile methyl groups in 1 H MR, they are not observed in the 13 C MR or by 2D MR experiments, likely due to the labile nature of these coordinated solvent molecules at 298 K; low temperature MR of a [IPr 2Rh 2MeC 2][SbF 6] reveals the methyl resonances to sharpen significantly and a 13 C signal at 5.9 ppm is observed for the acetonitrile group. Connectivity and inclusion of the acetonitrile ligands is confirmed by X-ray crystallographic analysis. Preparation of [IPr 2Rh 2MeC 2] + [S 2CF 3] - (11 Tf) S 2 CF 3 Rh To a four-dram vial containing IPr 2Rh 2Cl (27.1 mg, mmol) and a stir bar, MeC (2 ml) and DCE (1.5 ml) were added. Magnetic stirring was initiated, after ~ 3 min and partial dissolution of the starting material, AgS 2CF 3 (10.7 mg, mmol) was added as a solid and the vial from which it came was rinsed with MeC (1 ml). The rinse was added to the reaction mixture. By visual inspection, the reaction was proceeding within a few minutes as a new grey precipitate was noticed and the originally blue solution became yellow. The reaction mixture was allowed to stir for 2 h after which all solvent was removed in vacuo. The product was extracted into fresh DCE (3 ml) and the mixture was passed through a small plug of celite. The solvent was removed from the clear deep yellow-red filtrate to

6 leave a pale dark pink solid which was subsequently washed with Et 2 (1 x 2 ml) and dried to leave an analytically pure powder of the title compound (13.4 mg, mmol, 31.8 %). This reaction was also repeated with full exclusion from halogenated solvents. The same reaction procedure was used but CF 3-Ph was employed instead DCE. This result in isolation of spectroscopically pure compound 11 Tf as a brownish powder in 27% yield. Anal. Calcd. for C 59H 78F 3 6 5RhS: C, 61.98; H, 6.88;, Found: C, 61.71; H, 6.88;, H MR (400 MHz, CD 2Cl 2): = 7.48 (m, 4H, p-arh), 7.27 (d, 3 J HH = 7.7 Hz, 8H, m-arh), 6.90 (s, 4H, - CH=CH-), 2.44 (br m, 8H, -CH(CH 3) 2), 1.92 (br s, 6H, CH 3C), 1.01 (br m, 48H, -CH(CH 3) 2). Confirmation of the acetonitrile methyl proton was achieved by preparing the deuterated acetonitrile version, wherein the resonance at 1.92 ppm was absent in the 1 H MR spectrum and corresponded to a resonance at the same frequency in the 2 D MR spectrum 13C{ 1 H} MR (100 MHz, CD 2Cl 2): = (C-carbene, 1 J RhC=34.7 Hz), (C q), (C q), (-CC(CH(CH 3) 2)CH ach b-), 129.8, (-CH=CH-), 124.2, (- CC(CH(CH 3) 2)CH ach b-), 29.0, 28.5 (-CH(CH 3) 2), 25.4, (-CH(CH 3) 2), 5.40 (CH 3C). At 273K in 13 C MR of a [IPr 2Rh 2MeC 2][Tf] broad signal at 5.40 ppm is observed for the acetonitrile group. Preparation of [IPr 2Rh 2MeC 2][SbF 6] (11 SbF 6) SbF 6 Rh

7 To a four-dram vial containing IPr 2Rh 2Cl (29.8 mg, mmol) and a stir bar, MeC (2 ml) and DCE (1.5 ml) were added. Magnetic stirring was initiated, after ~ 3 min and partial dissolution of the starting material, AgSbF 6 (13.8 mg, mmol) was added as a solid and the vial from which it came was rinsed with MeC (1 ml). The rinse was added to the reaction mixture. By visual inspection, the reaction was proceeding within a few minutes as a new grey precipitate was noticed and the originally blue solution became yellow. The reaction mixture was allowed to stir for 2 h after which all solvent was removed in vacuo. The product was extracted into fresh DCE (3 ml) and the mixture was passed through a small plug of celite. The solvent was removed from the clear deep yellow-red filtrate to leave a beige solid which was subsequently washed with Et 2 (1 x 2 ml) and dried to leave an analytically pure powder of the title compound (37.4 mg, mmol, 98.1 %). Anal. Calcd. for C 58H 78F 6 6 2RhSb: C, 56.64; H, 6.39;, Found: C, 56.82; H, 5.93;, H MR (500 MHz,CD 2Cl 2) reported at 233 K: = 7.37 (t, 3 J HH = 7.4 Hz, 4H, p-arh), 7.20 (d of d, 3J HH = 7.2 Hz, 8H, m-arh), 6.82 (s, 4H, -CH=CH-), 2.41 (m, 8H, -CH(CH 3) 2), 1.76 (s, 6H, CH 3C), 1.09 (br m, 24H, -CH(CH 3) a(ch 3) b), 0.72 (br d, 24H, -CH(CH 3) a(ch 3) b). 13 C{ 1 H} MR (125.6 MHz, CD 2Cl 2) reported at 233 K: = 148.2, 143.4, 141.8, 141.2, 136.8, 129.6, 125.5, 123.9, 123.1, 121.8, 45.2, 28.6, 28.2, 26.0, 25.6, 22.7, 22.1, 5.9 (CH 3C). Preparation of [SIMes 2Rh 2MeC 2][S 2CF 3] (12 Tf) S 2 CF 3 Rh To a four-dram vial containing SIMes 2Rh 2Cl (92 mg, mmol) and a stir bar, MeC (6 ml) and CF 3-Ph (7 ml) were added. Magnetic stirring was initiated, after ~ 3 min and partial dissolution of the starting material, AgS 2CF 3 (32 mg, mmol) was added as a

8 solid and the vial from which it came was rinsed with MeC (2 ml). The rinse was added to the reaction mixture. By visual inspection, the reaction was proceeding within a few minutes as a new white precipitate was noticed and the originally blue solution became yellow. The reaction mixture was allowed to stir for 10 min after which all solvent was removed in vacuo. The product was extracted into CF 3-Ph (7 ml) and the mixture was passed through a small plug of celite. Evaporation of the solvent result in isolation of spectroscopically pure compound 12 Tf as a brownish powder in 44% yield (52 mg). 1 H MR (400 MHz, CDCl 3): δ = 7.70 (s, ArH, 4H), 7.65 (s, ArH, 4H), (m, br, 8H, CH 2), 1.98 (br s, 6H, CH 3C), 1.44 (m. 24H, CH 3), 1.22 (m, 12H, CH 3). Complex 12 Tf is highly unstable in solution and rapidly decomposes. However, some X-ray quality brown plate-like crystals of complex 12 Tf were obtained by slow diffusion of hexane into a concentrated acetonitrile solution of the product. [Rh(SIMes) 2( 2)Cl] (4): Free SIMes carbene (79 mg, mmol) was dissolved in 20 ml of THF and added dropwise to a stirred solution of [Rh(C 2 H 4 )Cl 2 ] 2 (25 mg, mmol) in 10 ml of THF. Afterwards, the reaction mixture was stirred for 12 h under nitrogen atmosphere. Then solution was removed from the glovebox and allowed to stir under air for 48 h. After 12 h the yellow color turned to green. After having been stirred at room temperature for 48 h, the volatiles were removed in vacuo. The resulting green residue was purified by column chromatography with neutral alumina, and benzene as the eluent, to obtain pure complex 4 as a blue powder with 69% yield. X-ray quality blue block-like crystals of complex 4 were obtained after 5 days of slow diffusion of hexane into a concentrated THF solution of the product. 1 H MR (500 MHz, CDCl 3 ): δ = 6.74 (s, ArH, 4H), 6.66 (s, ArH, 4H), 3.71(m, br, 8H, CH 2 ), 1.92 (m, 24H, CH 3 ), 1.83 (m, 12H, CH 3 ). 13 C{ 1 H} MR (125.6 MHz, CD 2 Cl 2 ): δ = (d, 1 J RhC = 35.0 Hz, C-carbene), , , , , , , , 51.57(-CH 2 ), 21.60, Calc m/z for C 42 H 52 Cl 4 Rh (M- 2 ): , found: (M- 2 ) (1) Arduengo, A. J.; Krafczyk, R.; Schmutzler, R.; Craig, H. A.; Goerlich, J. R.; Marshall, W. J.; Unverzagt, M. Tetrahedron 1999, 55, (2) Arduengo, A. J., III; Goerlich, J. R.; Marshall, W. J. J. Am. Chem. Soc. 1995, 117,

9 (3) Praetorius, J. M.; Allen, D. P.; Wang, R.; Webb, J. D.; Grein, F.; Kennepohl, P.; Crudden, C. M. J. Am. Chem. Soc. 2008, 130, Computational Input Files 52> * All calculations were performed using RCA 2.8 using the BP86 functional and TZVP basis set. All calculations were fully converged (all positive frequencies) and performed using ZRA scalar relativistic corrections. Below is an example of an input file used to perform the calculations shown herein: 1> # Rh2HC2(Cl) 2> # singlet RKS geometry optimization 3> # B3LYP + TZVP 4> # ZRA relativistic effects 5> # 6> # umfreq 7> 8>! RKS SP def2-tzvp(-f) def2-tzvp/j B3LYP ZRA PModel DeContractAux 9>! TightSCF Tightpt 10>! PT umfreq 11>! Grid4 ofinalgrid 12>! ormalprint 13> 14> %SCF MaxIter > End 16> 17> * xyz > Rh > Cl > > > C > > C > C > > C > C > C > > C > C > > C > C > H > H > H > H > H > H > H > H > H > H > H > H > H > H > H > H ptimized coordinates Rh 2(IMe 2)Cl Rh C C C H H H H C H H C C H H C C H H H H C H H C C H H C C C H H H H H H Rh 2(IMe 2)(MeC) C C C Rh C C

10 C C C C C C C H H H H H H H H H H H H H H H H H H H Rh 2(IMe 2)(MeC) 2 Rh C C C H H H H C H H C C H H C C H H H H C H H C C H H C C C H H H H H H Rh 2(IMes 2)(MeC) 2 Rh C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C H H H H H

11 H H H H H H C H H C H H C H H C H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H

12