3.2. General Methods
1H and 13C{1H}, 31P{1H} NMR spectra were recorded on Bruker Avance 360 MHz and Bruker DRX 400 NMR spectrometers (Bruker, Billerica, MA, USA) and were referenced to residual solvent peaks and to 85% phosphoric acid. A Bruker maXis II MicroTOF-Q type Qq-TOF-MS instrument (Bruker Daltonik, Bremen, Germany) was used to obtain high-resolution electrospray ionization mass spectra (HR ESI-MS) in positive ion mode, and controlled by Compass Data Analysis 4.4 software from Bruker.
The X-ray intensity data were measured on an Enraf Nonius TurboCAD4 diffractometer. The structure was solved by ShelXT [
63], refined with ShelXL [
64], using Olex
2 [
65] and WinGX [
66] graphical interfaces. Publication materials were prepared by Mercury [
67] and Platon [
68]. The crystallographic data (including structure factors) for
5 were deposited in the Cambridge Crystallographic Data Centre (CCDC) with the No. CCDC 2023158.
Gas chromatographic analyses were performed with the use of an Agilent Technologies 7890 A instrument (HP-5, 0.25 µm × 30 m × 0.32 mm, FID 300 °C, (Agilent Technologies, Santa Clara, CA, USA); carrier gas: nitrogen 1.9 mL/min). The products were identified by comparison of their retention time with well-known standard compounds.
3.2.1. Preparation of [RhC(cod)(sSIMes)] (1)
In 7 mL MeOH 0.122 g (0.22 mmol) [sSIMesH]Cl was dissolved in a Schlenk tube equipped with a reflux condenser. To this solution at room temperature, 0.055 g (0.11 mmol) [RhCl(cod)]2 and 0.307 g (2.22 mmol) K2CO3 were added in one portion. The resulting yellow solution was refluxed for four hours under argon atmosphere. The reaction mixture was cooled to room temperature and filtered through a Celite Hyflo Supercel pad, and the solvent was evaporated under vacuum. The product, a hygroscopic sticky solid was dissolved in 5 mL dry MeOH. Aliquots of this stock solution were used for further experiments.
1H-NMR (360 MHz, MeOD) δ/ppm: 7.42 (s, 2H, CHAr) 4.74–4.49 (br, 2H, -CH2-, cod), 4.17 (s, 4H, N-CH2-CH2-N), 3.69–3.60 (br, 2H, -CH2-, cod), 2.96 (s, 12H, CH3), 2.63 (s, 6H, CH3), 2.24–2.15 (m, 4H, =CH-CH2-, cod), 1.80–1.78 (m, 4H, =CH-CH2-);
13C-NMR (90 MHz, MeOD) δ/ppm: 142.8; 139.8; 137.8; 137.2; 135.4; 132.7; 97.8 (d, 1JRh–C = 7.9 Hz); 69.1 (d, 1JRh–C = 13.2 Hz); 51.7; 32.0; 27.2; 22.5; 17.7; 16.7.
MS(ESI), positive mode, in MeOH, m/z for 1, [M-Cl]+ (C29H36N2Na2O6RhS2), Calculated: 721.0860,Found: 721.0859.
3.2.2. Synthesis of [RhCl(bmim)(cod)] (3)
In an argon-filled Schlenk tube in 20 mL distilled CH2Cl2 0.327 g (0.717 mmol) [Rh(OH)(cod)]2 was dissolved, and then 5 mL CH2Cl2 0.25 g (1.434 mmol) [bmimH]Cl was added. The solution was stirred for 6 h at reflux temperature, and then the solvent was removed under vacuum yielding a dark yellow sticky residue. This residue was cooled in liquid N2, and triturated several times with small portions of cold diethyl ether, yielding 3 as a light yellow powder. Yield: 0.413 g (1.08 mmol), 75%.
1H NMR (360 MHz, CD2Cl2) δ/ppm: 6.90 (s, 2H, -N-CH=CH-N-) δ: 4.98–4.89 (m, 2H, N-CH2CH2CH2CH3), 4.56–4.42 (m, 2H, -CH2-, cod), 4.10 (s, 3H, N-CH3), 3.40–3.26 (m, 2H, -CH2-, cod), 2.54–2.33 (m, 4H, =CH-CH2-, cod), 2.07–1.79 (m, 4H, =CH-CH2-, cod + 2H, N-CH2CH2CH2CH3), 1.5 (m, 2H. N-CH2CH2CH2CH3) 1.07 (t, 3H, N-CH2CH2CH2CH3);
13C{1H} NMR (90 MHz, CD2Cl2) δ/ppm: 182.11 (d, 1JRh–C = 45.79 Hz, NCN), 121.95 (-NCH=CHN-), 120.14 (-N-CH=CH-N-), 97.83 (d, 1JRh–C = 7.4 Hz, =CH-CH2-, cod), 97.72 (d, 1JRh–C = 7.4 Hz, =CH-CH2-, cod), 68.08 (d, 1JRh–C = 14.8 Hz, -CH=CH-, cod) 67.28 (d, 1JRh–C = 14.82 Hz, -CH=CH-, cod), 50.39 (-N-CH2CH2CH2CH3), 37.55 (CH3-N-), 33.29, 32.99 (-CH2-, cod), 33.52 (-N-CH2CH2CH2CH3), 29.18, 28.52 (-CH2-, cod), 20.05 (-N-CH2CH2CH2CH3), 13.60 (-N-CH2CH2CH2CH3);
MS(ESI), positive mode, in MeOH, m/z for 3, [M]+ (C16H26N2Rh), Calculated: 349.1146 Found: 349.1145.
3.2.3. Synthesis of Na2[Rh(bmim)(cod)(mtppts)] (4)
In an argon-filled Schlenk tube, 0.200 g (0.520 mmol) [RhCl(bmim)(cod)] (3) was dissolved in 20 mL acetone. To the resulting clear yellow solution 0.323 g (0.520 mmol) mtppts-Na3 was added followed by 3.5 mL deoxygenated water, upon which the colour of the solution became dark yellow. After 5 min stirring the solvent was evaporated in vacuum, and the resulting sticky residue, cooled in liquid N2, was triturated with small portions of cold diethyl ether, yielding 4 as a yellow solid. Yield: 0.212 g (0.210 mmol), 40%.
1H NMR (400 MHz, MeOD) δ/ppm: 8.53–7.20 (m, 12H, Ar–CH-, mtppts), 7.00 (s, 2H, -N-CH=CH-N-), 4.81–4.44 (m, 4H, -CH2-, cod), 4.27 (m, 2H, N-CH2CH2CH2CH3), 3.78 (s, 3H, N-CH3), 2.61–2.27 (m, 8H. =CH-CH2-, cod), 1.64–1.59 (m, 2H, N-CH2CH2CH2CH3), 1.46–1.43 (m, 2H, N-CH2CH2CH2CH3), 0.99 (t, 3H, N-CH2CH2CH2CH3);
13C{1H} NMR (100 MHz, MeOD) δ/ppm: 174.62 (dd, 1JRh–C = 49.2 Hz, 2JC-P = 15.5 Hz. NCN), 146.08–128.89 (m, Ar-CP), 124.54, 121.78 (-N-CH=CH-N-), 98.71 (dd, 1JRh–C = 9.2 Hz, 3JC–P = 9.9 Hz =CH-CH2-, =CH-CH2-, cod), 97.5 (dd, 1JRh–C = 7.9 Hz, 3JC–P = 9.9 Hz, =CH-CH2-, cod), 94.55 (dd, 1JRh–C = 13.9 Hz, 3JC–P = 7.3 Hz, -CH=CH-, cod), 50.52 (N-CH2CH2CH2CH3), 36.99 (CH3-N-), 33.33, 31.99(-CH2-, cod), 30.38 (-N-CH2CH2CH2CH3), 29.77, 29.25 (-CH2-, cod), 19.76 (-N-CH2CH2CH2CH3), 12.97 (N-CH2CH2CH2CH3);
31P {1H} NMR (146 MHz, MeOD): δ/ppm 27.31 (d, 1JRh–P = 160.4 Hz)
MS(ESI), positive mode, in MeOH, m/z for 4, [M]+ (C34H38N2Na3O9PRh), Calculated: 917.0220, Found: 917.0220.
3.2.4. Synthesis of [Rh(bmim)(cod)(pta)]BF4 (5)
Method A: In a Schlenk tube under argon atmosphere in 50 mL distilled CH2Cl2, 0.200 g (0.44 mmol) [Rh(OH)(cod)]2 and 0.199 g (0.88 mmol) [bmimH]BF4 were dissolved. The solution was stirred at reflux temperature for 4 h, followed by filtering under argon. A portion of 0.137 g (0.88 mmol) pta was added and stirred for another 2 h at reflux temperature. Then it was filtered again and the solvent was removed by evaporation under vacuum. The sticky residue was cooled in liquid N2 and triturated with small portions (5 mL) of cold diethyl ether yielding 0.332 g (0.559 mmol), 64%, product.
Method B: In a Schlenk tube, 0.050 g (0.129 mmol) [RhCl(bmim)(cod)] (3) was dissolved in 4 mL dry MeOH, and 0.014 g (0.129 mmol) NaBF4 was added and stirred at room temperature for 3 h. The NaCl was filtered under argon and 0.020 g (0.13 mmol) pta was added and the mixture was stirred for 3 h at room temperature. Then it was filtered again and the solvent was removed by evaporation under vacuum, the sticky residue was triturated with small portions (5 mL) of cold diethyl ether yielding 0.063 g (0.106 mmol), 82%, product.
1H NMR (360 MHz, MeOD) δ/ppm: 7.37, 7.32 (2H, -N-CH=CH-N-), 4.84–4.80 (m, 2H, -CH2-, cod), 4.52–4.44 (m, 2H, -CH2-, cod + 6H, N-CH2-N, pta), 4.17-4.09 (m, 2H, N-CH2CH2CH2CH3), 3.95-3.92 (m, 3H, N-CH3 + 6H, P-CH2-N, pta), 2.41–2.29 (m, 8H. = CH-CH2-, cod), 2.03–1.79 (m, 2H, N-CH2CH2CH2CH3), 1.57–1.49 (m, 2H, N-CH2CH2CH2CH3), 1.06 (t, 3H, N-CH2CH2CH2CH3);
13C{1H}NMR (100 MHz, MeOD) δ/ppm: 175.71 (dd, 1JRh–C = 48.5 Hz, 2JC–P = 18.5 Hz. NCN), 124.14, 121.76 (-N-CH=CH-N-), 100.13 (dd, 1JRh–C = 8.6 Hz, 3JC–P = 9.9 Hz =CH-CH2-, =CH-CH2-, cod), 98.73 (dd, 1JRh–C = 7.3 Hz, 3JC–P = 9.9 Hz, =CH-CH2-, cod), 89.12 (dd, 1JRh–C = 13.9 Hz, 3JC–P = 6.6 Hz, -CH=CH-, cod), 71.93 (d, 3JC–P = 6.6 Hz, N-CH2-N, pta), 50.53(d, 3JC–P = 13,4 Hz, -CH2-P, pta), 50.51 (N-CH2CH2CH2CH3), 36.95 (CH3-N-), 32.72, 31.27 (-CH2-, cod), 30.33 (-N-CH2CH2CH2CH3), 30.23, 29.29 (-CH2-, cod), 20.07 (-N-CH2CH2CH2CH3), 12.98 (N-CH2CH2CH2CH3);
31P{1H} NMR (146 MHz, MeOD) δ/ppm: -54.90 (d, 1JRh–P = 125.6 Hz);
MS(ESI), positive mode, in MeOH, m/z for 5, [M]+ (C22H38N5PRh), Calculated: 506.1914, Found: 506.1915.
3.2.5. General Procedure Redox Isomerization of Allylic Alcohols
Catalytic isomerization of allylic alcohols was performed in Schlenk tubes, into which 1× 10−3 mol allylic alcohol and 1 × 10−5 mol 1, 3, 4, 5, or 2 × 10−5 mol 1 together with 2 × 10−5 mol mtppms-Na (in 450 μL MeOH) were dissolved in 3 mL deoxygenated water or aqueous phosphate buffer. All reactions were carried out under oxygen-free atmosphere using argon or nitrogen gas. The reaction mixtures were heated (80 °C) in a thermostated bath and stirred for the desired reaction time, then cooled to room temperature. In the case of water-insoluble substrates, the product mixtures were extracted twice with 1 mL of chloroform, the extracts were dried over MgSO4, and the conversions were determined by gas chromatography or by 1H NMR (CDCl3). In the case of water-soluble allylic alcohols, the conversions were determined by 1H NMR (D2O). The presented yields are averages of 3–5 measurements, with a reproducibility of ±3%.
In the catalyst recycling experiments, the reaction mixtures was cooled down to room temperature (r.t.). The extraction was done under argon with 2 mL of hexane. Traces of hexane were removed from the aqueous phase by stirring under vacuum for 20 min at r.t., and the resulting aqueous solution of the catalyst was used in the next catalytic cycle.