Activation of Carbon Dioxide and Carbon Disulfide by a Scandium N- Heterocyclic Carbene Complex

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1 Activation of Carbon Dioxide and Carbon Disulfide by a Scandium N- Heterocyclic Carbene Complex Polly L. Arnold,* a Isobel A. Marr, a Sergey Zlatogorsky, a,b Ronan Bellabarba, c and Robert P. Tooze c Supplementary Data Experimental General Procedures All manipulations were carried out under a dry, oxygen-free dinitrogen atmosphere using standard Schlenk techniques or in a glovebox unless otherwise stated. Solvents (toluene, hexane and THF) were dried by passage activated 4 Å molecular sieve towers, stored over activated 4 Å molecular sieves and degassed three times prior to use. Deuterated solvents were refluxed over potassium, vacuum transferred and free-pumpthaw degassed three times prior to use. 1 H NMR spectra were recorded at 298 K unless otherwise stated on a Bruker AVA400 at MHz. 13 C and 13 C{ 1 H} NMR spectra were recorded at 298 K on a Bruker AVA500 at MHz. The 1 H, 13 C and 13 C{ 1 H} NMR spectra were referenced internally to residual protio solvent ( 1 H) or solvent ( 13 C) and are reported to tetramethylsilane ( = 0 ppm). Chemical shifts are quoted in (ppm) and coupling constants in Hz. Solid-state 13 C NMR spectra were obtained using a Bruker Avance III spectrometer, equipped with a 9.4 T wide-bore superconducting magnet ( 1 H Larmor frequency of MHz). The sample was packed into a conventional 4 mm rotor, and rotated at a MAS rate of 12.5 khz. Cross polarisation from 1 H was employed, with a spin-lock pulse (ramped from % for 1 H) of 5 ms and two pulse phase modulation (TPPM) decoupling of 1 H ( khz) applied during acquisition. Signal averaging was carried out for 1688 transients with a repeat interval of 5 s. Dipolar dephasing experiments were carried out with a dephasing interval of up to 1.5 ms. The transverse 13 C magnetisation was then refocused by a 180 pulse, and the signal was recorded from the top of the resulting echo. Signal averaging was carried out for 3584 transients with a repeat interval of 5 s. Solid-state 45 Sc NMR spectra were obtained using a Bruker Avance III spectrometer, equipped with a 14.1 T wide-bore superconducting magnet ( 1 H Larmor frequency of MHz). The sample was packed into a conventional 4 mm rotor, and rotated at a MAS rate of 14 khz. For the one-dimensional spectrum, a spinecho pulse sequence with a rotor-synchronised echo period of s was used, with signal averaging carried out for 640 transients with a repeat interval of 1 s. Two-dimensional triple-quantum MAS experiments were recorded using an amplitude-modulated z-filtered pulse sequence, with the pulses used during the z filter chosen to be selective for the central transition. 1 Signal averaging was carried out for 336 transients with a repeat interval of 0.5 s for each of 50 t 1 increments of 10.2 s. After recording, spectra were sheared and referenced. 2 Elemental analyses were determined by Mr Stephen Boyer at London Metropolitan University. Infrared spectra were recorded on a Jasco 410 spectrophotometer. Crystallographic data were collected at 170 K on an Oxford Diffraction Excalibur diffractometer using Cu- K radiation ( = Å) or at 120 K on an Agilent Technologies SuperNova diffractometer with Cu-K radiation and X-ray mirror optics. ScCl 3 (thf) 3 3 and KL 4 were synthesised according to literature procedures. CS 2 was freeze-pump-thaw degassed three times prior to use. All other reagents were used as purchased. 1

2 Preparations Sc(L) 3 (1) ScCl 3 (thf) 3 (2.00 g, 5.44 mmol) and KL (3.60 g, 16.3 mmol) were combined in a Schlenk and thf (50 ml) was added at room temperature. The reaction was stirred for 2 h to afford a yellow suspension. The volatiles were then removed under reduced pressure and the solid dried overnight. The product was extracted into toluene (2 x 40 ml) and subsequent removal of volatiles under reduced pressure afforded Sc(L) 3 as yellow solid which was washed with hexane (2 x 10 ml) and dried under vacuum. A second crop of product was yielded by precipitation from the hexane washings at room temperature. Yield: 2.15 g (67 %). Diffraction quality crystals were grown from slow diffusion of hexane into a concentrated solution of Sc(L) 3 in benzene. 1 H NMR (C 6 D 6, 400 MHz, 298 K): 6.35 (3 H, d, 3 J HH = 2 Hz, NCHCHN), 6.32 (3 H, d, 3 J HH = 2 Hz, NCHCHN), 5.36 (br. m, 3 J HH = 6 Hz, HCMe 2, 4.00 (6 H, br. s, OCMe 2 CH 2 ), 1.28 (18 H, s, OCMe 2 CH 2 ), 1.03 (18 H, d, 3 J HH = 6 Hz, HCMe 2 ) ppm. 13 C{ 1 H} NMR (C 6 D 6, 500 MHz, 298 K): (NCN), and (NCHCHN), 71.5 (OCMe 2 CH 2 ), 63.6 (OCMe 2 CH 2 ), 49.7 (CMe 2 ), 30.5 (OCMe 2 CH 2 ), 23.6 (CMe 2 ) ppm. 1 H NMR (d 8 -tol, 600 MHz, 203K): 6.75 (1 H, br. m, HCMe 3 ), 6.20 (1 H, s, NCHCHN), 6.16 (1 H, s, NCHCHN), 6.14 (3 H, br. m. NCHCHN), 6.02 (1 H, s, NCHCHN), 5.46 (1 H, br. m, HCMe 3 ), 5.41 (1 H, br. m, HCMe 3 ), 5.33 (1H, d,, 3 J HH = 11 Hz, OCMe 2 CHH), 4.84 (1 H, d, 3 J HH = 11 Hz, OCMe 2 CHH), 3.64 (1 H, d, 3 J HH = 11 Hz, OCMe 2 CHH), 3.35 (2 H, m, OCMe 2 CHH), 3.10 (1 H, d, 3 J HH = 11 Hz, OCMe 2 CHH), 1.67 (3 H, Me), 1.63 (3 H, Me), 1.55 (3 H, Me), 1.31 (3 H, Me), 1.13 (6 H, Me) 1.08 (3 H, Me), 1.02 (3 H, Me), 0.86 (3 H, Me), 0.76 (3 H, Me), 0.66 (3 H, Me), 0.62 (3 H, Me) ppm. Anal. Found (calcd for C 30 H 51 N 6 O 3 Sc): C, (61.20) H, 8.65 (8.73), N, (14.28). Figure1:Low,VariableTemperature 1 HNMRspectraforScL 3 1intoluened 8 solution Sc(L) 2 (L CS2 ) (2) 2

3 To a saturated solution of Sc(L) 3 (0.20 g, 0.34 mmol) in toluene was added CS 2 (0.026 g, 0.34 mmol), immediately forming a bright red solution. The solution was cooled to -30 C, affording Sc(L) 2 (L CS2 ) 2 as a red microcrystalline product. The supernatant was removed by filtration and the product dried under reduced pressure. Yield: 0.12 g (51 %). Diffraction quality crystals were grown from slow diffusion of hexane into a concentrated solution of Sc(L) 2 (L CS2 ) in benzene. 1 H NMR (C 6 D 6, 400 MHz): 8.25 (1 H, d, 3 J HH = 2 Hz, NCHCHN), 6.43 (2 H, d, 3 J HH = 2 Hz, NCHCHN), 6.30 (2 H, d, 3 J HH = 2 Hz, NCHCHN), 6.28 (1 H, d, 3 J HH = 2 Hz, 3 J HH = 2 Hz, NCHCHN), 5.75 (1 H, sept, 3 J HH = 7 Hz, HCMe 2 ), 4.92 (2 H, sept, 3 J HH = 7 Hz, HCMe 2 ), 4.08 (1 H, br. s, OCMe 2 CHH), 4.02 (1 H, br. s, OCMe 2 CHH), 3.77 (2 H, br. d, OCMe 2 CHH), 3.44 (2 H, br. d, OCMe 2 CHH) (36 H, m, OCMe 2 CH 2, HCMe 2 ) ppm. 13 C{ 1 H} NMR (C 6 D 6, 500 MHz): (CCS 2 ), (NCN), (CCS 2 ), (NCHCHN), (NCHCHN), (NCHCHN), (NCHCHN), 72.8 (OCMe 2 CH 2 ), 72.2 (OCMe 2 CH 2 ), 64.3(OCMe 2 CH 2 ), 60.0 (OCMe 2 CH 2 ), 50.8 (HCMe 2 ), 49.8 (HCMe 2 ), 31.6, 30.8, 29.1, 23.9, 22.2 (HCMe 2 and OCMe 2 CH 2 ) ppm. Anal. Found (calcd for C 31 H 51 N 6 O 3 S 2 Sc): C, (56.00), 7.82 (7.72), (12.64) Sc(L)(L CS2 ) 2 (3) in toluene To a solution of Sc(L) 3 (0.20 g, 0.34 mmol) in toluene (10 ml) was added CS 2 (0.26 g, 3.41 mmol) forming a bright red solution and an oily red solid. The reaction mixture was stirred overnight at room temperature. This oily solid was then isolated by filtration and washed with toluene (2 x 5 ml). The product was then titrated with hexane (3 x 5 ml) to produce a red powder. The product was then dried under vacuum to afford Sc(L)(L CS2 ) 2 as a red powder. Yield: 0.18 g, (68) % Diffraction quality crystals were grown by adding a few drops of thf to a solution of 1 in toluene before addition of 3 equivalents of CS 2 and allowing the reaction mixture to stand for 4 days. Sc(L)(L CS2 ) 2 (3) in CS 2 CS 2 (1 ml) was added to ScL 3 (30 mg, mmol) to afford a red solid and red solution. The red solution was decanted and upon leaving to stand overnight, crystals of Sc(L)(L CS2 ) 2 formed and all colour was lost from solution. 1 H NMR (CS 2 with few drops of C 6 D 6, 400 MHz): 7.98 (1 H, d, 3 J HH = 2 Hz, NCHCHN), 6.72 (2 H, d, 3 J HH = 1 Hz, NCHCHN), 6.60 (2 H, d, 3 J HH = 1 Hz, NCHCHN), 6.41 (1 H, d, 3 J HH = 2 Hz, NCHCHN), 5.58 (2 H, sept., 3 J HH = 7 Hz, HCMe 2 ), 4.67 (1 H, sept., 3 J HH = 7 Hz, HCMe 2 ), 3.74 (2H, m, (OCMe 2 CHH), 3.57 (2H, m, (OCMe 2 CHH), (36 H, m, OCMe 2 CH 2, HCMe 2 ) ppm. Anal. Found (calcd for C 31 H 51 N 6 O 3 S 2 Sc): C, (51.87), 7.02 (6.94), (11.34) Sc(L CO2 ) 3 (4) An ampoule containing a solution of ScL 3 (0.50 g, 0.85 mmol) in benzene (30 ml) was charged with an atmosphere of CO 2 whilst stirring vigorously. A colourless precipitate began to form immediately. After allowing to stir for 5 minutes, the solid was isolated by filtration and washed with benzene (3 x 10 ml). The product was then dried under vacuum to afford Sc(L CO2 ) 3 as a colourless powder. Yield: 0.52 g (85%). 13 C MAS NMR: (CCO 2 ), (CCO 2 ), (NCHCHN), (NCHCHN), 72.1 (OCMe 2 CH 2 ), 61.6 (OCMe 2 CH 2 or CHMe 3 ), 51.3 (OCMe 2 CH 2 or CHMe 3 ), 30.3 (CH 3 ), 22.9 (CH 3 ) ppm. Sc MAS NMR 128, 45 ppm. IR (nujol mull): 1672, 1492, 1321, 1223 cm -1. Anal. Found (calcd for C 33 H 51 N 6 O 9 Sc): C, (54.99), (7.13), (11.66). HL.CS 2 3

4 (1) In a Teflon-valved valve NMR tube, excess CS 2 was added to a solution of HL (20 mg, mmol) in thf causing the quantitative formation of a deep red precipitate, eq. 1. The volatiles were removed under reduced pressure and the solid dried under vacuum to afford HL.CS 2 in quantitative yield. Diffraction quality crystals were grown by slow diffusion of CS 2 into a solution of HL in thf. 1 H NMR (d 5 -pyridine, 400 MHz): 9.86 (1 H, br s, OH), 8.93 (1H, d, NCHCHN), 8.64 (1H. d. NCHCHN), 6.22 (1H, sept, Me 2 CH), 5.59 (2H, s, OCMe 2 CH 2 ) 2.49 (6 H, s, OCMe 2 CH 2 ), 2.40 (6 H, d, Me 2 CH) ppm. 13 C{ 1 H} NMR (d 5 -pyridine, 500 MHz): (CCS 2 ), (CCS 2 ), (NCHCHN), (NCHCHN), 69.6 and 57.8 (OCMe 2 CH 2 and OCMe 2 CH 2 ), 50.6 (HCMe 2 ), 28.0 (CH 3 ), 22.2 (CH 3 ) ppm. 4

5 XrayCrystalStructures Figure2:TheXraycrystalstructuresofthemer(left)andmer(right)enantiomersofSc(L) 3 1.All hydrogenatomsandfreesolventmoleculesareomittedforclarity;ellipsoidsaredrawnat50% %probability. Figure3:TheXraycrystalstructuresofbothenantiomersofSc(L) 2 (L CS2 )2.Allhydrogenatomsandfreesolventmolecules areomittedforclarity;ellipsoidsaredrawnat50%probability. 5

6 Figure4:TheXraycrystalstructureofSc(L)(L CS2 ) 2 3.Allhydrogenatomsandfreesolventmoleculesareomittedfor clarity;ellipsoidsaredrawnat50%probability. Figure 5: The Xray crystal structureof HL.CS 2 4. All hydrogen atoms except H1 and free solvent molecules are omittedforclarity;ellipsoidsaredrawnat50%probability. 6

7 Table1:Selectedexperimentalcrystallographicdatafor(1)ScL 3,(2)Sc(L) 2 (L CS2 ),(3)Sc(L)(L CS2 ) 2,(4)HL.CS 2 Crystal data Sc(L) 3 1 (p12032b-sr) Sc(L) 2 (L CS2 ) 2 (po3005_refinalized) Sc(L)(L CS2 ) 2 3 (po2003) HL.CS 2 4 (po9039) Chemical formula C 30 H 51 N 6 O 3 Sc C 74 H 114 N 12 O 6 S 4 Sc 2 C 106 H 168 N 12 O 12 S 8 Sc 2 C11H18N2S2O M r Crystal system, Orthorhombic, Monoclinic, P2 space group 1 /c Monoclinic, P2 1 /n Triclinic, P1 P Temperature (K) a, b, c (Å) (3), (2), (7),, ( ) 90, (2), (5), (5), (5) (5), (5), (5) (14), (11), (13) (7), (9), (7) (5), (7), (8) 90, 90, 90 V (Å 3 ) (2) 8673 (4) (4) (14) Z Radiation type Mo K Cu K Cu K Mo K μ (mm 1 ) Crystal size (mm) Data collection Diffractometer Absorption correction Xcalibur, diffractometer Bruker SMART SuperNova, Dual, Cu at SuperNova, Dual, Cu at Eos APEX CCD area zero, Atlas zero, Atlas detector diffractometer diffractometer diffractometer Analytical CrysAlis PRO, Agilent Gaussian Technologies, Version Multi-scan CrysAlis PRO, Agilent (release 27- CrysAlis PRO, Agilent Technologies, Version CrysAlis171 Technologies, Version (release NET) (compiled Oct (release CrysAlis171.NET) 2011,15:02:11) Analytical CrysAlis171.NET) (compiled Oct (compiled Feb 1 numeric absorption ,15:02:11) Empirical 2013,16:14:44) Numerical absorption correction using absorption correction based spherical harmonics, implemented on gaussian integration in SCALE3 ABSPACK scaling over a multifaceted crystal algorithm. model correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, ) Multi-scan SADABS T min, T max 0.827, , , , No. of measured, independent and 68199, 13441, observed [I > 71477, 17775, , 10330, , 4154, (I)] reflections R int (sin /) max (Å 1 ) Refinement R[F 2 > 2(F 2 )], wr(f 2 ), S 0.064, 0.168, , 0.375, , 0.243, , 0.115, 1.16 No. of reflections No. of parameters No. of restraints H-atom treatment max, min (e Å 3 ) Riding H atoms treated by a mixture of independent and constrained refinement H atoms treated by a mixture of independent and constrained refinement H-atom parameters constrained 0.33, , , ,

8 Computer programs: CrysAlis PRO, Agilent Technologies, Version (release CrysAlis171.NET) (compiled Oct ,15:02:11), CrysAlis PRO, Agilent Technologies, Version (release CrysAlis171.NET) (compiled Feb ,16:14:44), SMART (Siemens, 1993), SAINT (Siemens, 1995), SIR92 (Giacovazzo, 1994), SHELXL97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 1997), ORTEP (Farrugia, 1997), Mercury, encifer (Allen et al., 2004). Table2:BonddistancecomparisonsbetweenY(L) 3,Ti(L) 3 andsc(l) 3 fromxraycrystallographicstudies Bond Ligand trans Observed Distance Bond Ligand trans Observed Distance Y1-O1 C 2.118(3) Y1-C27 O 2.644(4) Y2-O4 C 2.115(3) Y2-C57 O 2.594(4) Y1-O2 O 2.179(3) Y1-C7 C 2.594(4) Y1-O3 O 2.143(3) Y1-C17 C 2.570(4) Y2-O5 O 2.177(3) Y2-C37 C 2.562(4) Y2-O6 O 2.161(3) Y2-C47 C 2.561(4) Ti1-O1 C 1.994(3) Ti1-C27 O 2.299(4) Ti2-O4 C 1.972(3) Ti2-C57 O 2.300(5) Ti1-O2 O 1.948(3) Ti1-C7 C 2.263(5) Ti1-O3 O 1.958(3) Ti1-C17 C 2.252(4) Ti2-O4 O 2.014(3) Ti2-C47 C 2.274(4) Ti2-O5 O 1.954(3) Ti2-C37 C 2.286(4) Sc1-O3 C 1.989(2) Sc1-C6 O 2.451(3) Sc2-O6 C 1.992(2) Sc2-C46 O 2.495(3) Sc1-O1 O 2.036(2) Sc1-C16 C 2.411(3) Sc1-O2 O 2.047(2) Sc1-C26 C 2.402(3) Sc2-O4 O 2.050(2) Sc2-C36 C 2.418(3) Sc2-O5 O 2.017(2) Sc2-C56 C 2.439(3) 8

9 Table3:LongestMC carbene BondDistancesandAverageBondMC carbene Distances(CorrectedfortheCovalentRadii ofthesixcoordinatemetalcation) Bond Covalent M(III) radii Longest distance Corrected longest distance Average distance Corrected average distance Y-C 1.04A 2.644(4) Ti-C 0.81A 2.300(5) Sc-C 0.885A 2.495(3) References 1. C. Fernandez and J.-P. Amoureux, Solid State Nucl. Magn. Reson., 1996, 5, K. J. Pike, R. P. Malde, S. E. Ashbrook, J. McManus and S. Wimperis, Solid State Nucl. Magn. Reson., 2000, 16, L. E. Manzer, Inorganic Syntheses, 1982, 21, P. L. Arnold, M. Rodden and C. Wilson, Chem. Commun., 2005,