**3. Materials and Methods**

With the exception of the salan ligands and their Pd complexes, all chemicals and solvents were high-quality commercial products purchased from Sigma-Aldrich/Merck, St. Louis, Missouri, USA; VVR International, West Chester, Pennsylvania, USA; and Molar Chemicals Kft., Halásztelek, Hungary and were used without further purification. Good quality ion-exchanged water was used throughout (S ≤ 2 μS). Gases (Ar and N2) were supplied by Linde Gáz Magyarország Zrt., Répcelak, Hungary.

## *3.1. Synthesis of the Sulfosalan Ligands*

HSS [44], PrHSS [45], BuHSS [46] and *rac*-CyHSS [46] were synthesized according to published methods. Synthetic procedures for dPhHSS as well as for *cis*- and *trans*-CyHSS are described below.

3.1.1. 1,2-Diphenyl-*N*,*N*'-*bis*(2-hydroxy-5-sulfonatobenzyl)-1,2-diaminoethane-dPhHSS

This was prepared from the appropriate salen derivative (dPhS) by hydrogenation to afford the benzylamino intermediate (dPhHS) followed by sulfonation to yield dPhHSS.

Synthesis of dPhS:

*meso*-1,2-Diphenyl-ethylenediamine (4.0 g, 18.80 mol) was added into a round-bottom flask containing 50 mL ethanol. To this solution, salicylaldehyde (3.70 mL, 37.60 mmol) was added and the mixture was stirred at 25 ◦C for 1 h, resulting in formation of a yellow precipitate. The reaction mixture was filtered, and the product was washed with ethanol to obtain dPhS as a yellow crystalline solid. Yield was 7.58 g (17.93 mmol), 95%, yellow crystalline solid.

1H-NMR (*d*6-DMSO, 360 MHz, δ): 5.06 (s, 2H, –CH–CH–), 6.85 (d, *J* = 8.0 Hz, 4H, CHarom), 7.20–7.32 (m, 12H, CHarom), 8.43 (s, 2H, CH=N–), 13.17 (s, 2H, –OH).

13C{1H} NMR (*d*6-DMSO, 90 MHz, δ): 166.17, 160.11, 139.93, 132.53, 131.75, 128.23, 127.86, 127.44, 118.69, 118.50, 116.34, 77.70.

Synthesis of dPhHS

dPhS (4.00 g, 6.87 mmol) was dissolved in methanol (300 mL) followed by the addition of 4 equivalents (1.04 g, 27.48 mmol) of sodium borohydride in 100 mL of methanol under constant stirring at room temperature. The mixture was then stirred at reflux for 30 min. The hot reaction mixture was added dropwise into 600 mL of water with continuous stirring. The white precipitate was filtered, washed with water and dried under vacuum. Yield was 3.90 g (6.67 mmol), 97%, white solid.

1H-NMR (*d*6-DMSO, 360 MHz, δ): 3.00 (d, 14.0 Hz, 2H, CH2–NH) and 3.11 (d, 14.0 Hz, CH2–NH), 3.49 (s, 2H, –CH–CH–), 6.28–6.32 (m, 4H, CHarom), 6.46 (d, *J* = 7.2 Hz, 2H, CHarom), 6.68 (t, *J* = 7.3 Hz, 2H, CHarom), 6.94–7.04 (m, 10H, CHarom).

13C{1H} NMR (*d*6-DMSO, 90 MHz, δ: 156.51, 140.81, 128.41, 128.04, 127.98, 127.65, 127.13, 124.60, 118.32, 115.07, 66.82, 47.75.

Synthesis of dPhHSS

In a round-bottom flask, dPhHS (1.00 g, 2.34 mmol) was added in small portions to a mixture of 4 mL of 20% fuming sulfuric acid (oleum) and 1 mL of concentrated sulfuric acid. The flask was cooled in ice water, and the mixture was stirred for 60 min. Then, the content of the flask was carefully added to 25 mL of cold water. The pH of the reaction mixture was set to 4 with a concentrated NaOH solution. Then, the mixture was cooled for 24 h, during which a white precipitate formed. The solid was collected by filtration, washed with cold water and dried under vacuum. The compound thus obtained is the zwitterionic free acid form of the ligand, which is slightly soluble in water.

Yield was 825.05 mg (1.41 mmol), 60%, white solid.

1H-NMR (D2O, 360 MHz, δ): 3.14 (d, *J* = 14.0 Hz, 2H, CH2–NH), 3.27 (d, *J* = 14.0 Hz, 2H, CH2–NH), 3.89 (s, 2H, –CH–CH–), 6.43 (d, *J* = 8.4 Hz, 2H, CHarom), 7.05 (s, 2H, CHarom), 7.36–7.54 (m, 12H, CHarom).

13C{1H} NMR (D2O, 90 MHz, δ): 169.22, 139.50, 129.10, 128.28, 127.26, 126.64, 126.29, 125.56, 118.33, 66.02, 46.27.

IR (ATR), ν/cm<sup>−</sup>1: 594.7, 697.8, 759.0, 1033.6, 1101.7, 1181.0, 1285.9, 1590.8. ESI-MS for C28H28N2O8S2 (*m*/*z*): calcd for [M − H]<sup>−</sup> 583.121, found 583.121.

3.1.2. *N*,*N*'-*bis*(2-Hydroxy-5-sulfonatobenzyl)-*cis*-1,2-diaminocyclohexane-*cis*-CyHSS

This was prepared from the appropriate salen derivative (*cis*-CyS) by hydrogenation to afford the benzylamino intermediate (*cis*-CyHS) followed by sulfonation to yield *cis*-CyHSS.

Synthesis of *cis*-CyS

According to Section 3.1.1, 1.05 mL (8.76 mmol) of *cis*-1,2-diaminocyclohexane and 1.83 mL (17.51 mmol) of salicylaldehyde yielded 2.50 g (7.71 mmol), 88%, yellow crystalline solid.

1H-NMR (*d*6-DMSO, 360 MHz, δ): 1.54–1.87 (m, 8H, –CH2–CH2–), 3.67 (s, 2H, CH–CH), 6.82–6.9 (m, 4H, CHarom), 7.31 (t, *J* = 7.4 Hz, 2H, CHarom), 7.41 (d, *J* = 7.3, 2H, CHarom), 8.56 (s, 2H, –CH=N–), 13.66 (s, 2H, –OH).

13C{1H} NMR (*d*6-DMSO, 90 MHz, δ): 165.05, 160.76, 132.25, 131.72, 118.66, 118.42, 116.45, 68.12, 30.42, 21.95.

Synthesis of *cis*-CyHS

According to Section 3.1.1, 2.50 g (7.71 mmol) of *cis*-CyS and 1.17 g (30.84 mmol) of sodium borohydride yielded 2.23 g (6.79 mmol), 88%, white crystalline solid.

1H-NMR (*d*6-DMSO, 360 MHz, δ): 1.25–1.36 (m, 4H, –CH2–CH2–), 1.54–1.65 (m, 4H, –CH2–CH2–), 2.72 (s, 2H, –CH–CH–), 3.69 (d, *J* =13.9 Hz, CH2–NH), 3.78 (d, *J* =13.9 Hz, CH2–NH), 6.72 (s, 2H, CHarom), 7.07 (d, *J* = 7. 6 Hz, 2H, CHarom).

13C{1H} NMR (*d*6-DMSO, 90 MHz, δ): 157.02, 128.74, 127.79, 125.07, 118.50, 115.30, 55.32, 47.58, 27.11, 21.97.

Synthesis of *cis*-CyH*SS*

According to Section 3.1.1, 1 g (3.06 mmol) CyHS, 4 mL of 20% fuming sulfuric acid (oleum) and 1 mL of concentrated sulfuric acid yielded 821 mg (1.68 mmol), 55%, white crystalline solid.

1H-NMR (D2O, 360 MHz, δ): 1.33–1.69 (m, 8H, –CH2–CH2–), 2.83 (s, 2H, –CH–CH–), 3.59 (d, *J* = 13 Hz, CH2–NH), 3.69 (d, *J* = 13 Hz, CH2–NH), 6.60 (d, *J* = 8.7 Hz, 2H, CHarom), 7.43–7.47 (m, 4H, CHarom).

13C{1H} NMR (D2O, 90 MHz, δ): 169.31, 127.79, 127.39, 126.46, 126.18, 118.57, 55.69, 46.69, 26.81, 21.81.

IR (ATR), ν/cm<sup>−</sup>1: 588.8, 6923.0, 846.2, 1039.3, 1101.6, 1138,2, 1435.8, 1604.7.

ESI-MS for C20H26N2O8S2 (*m*/*z*): calcd for [M + H]<sup>+</sup> 487.120, found 487.122 and [M + Na+] + 509.102, found 509.104.

3.1.3. *N*,*N*'-*bis*(2-Hydroxy-5-sulfonatobenzyl)-*trans*-1,2-diaminocyclohexane - *trans*-CyHSS

This was prepared from the appropriate salen derivative (*trans*-CyS) by hydrogenation to afford the benzylamino intermediate (*trans*-CyHS) followed by sulfonation to yield *trans*-CyHSS. Synthesis of *trans*-CyS

According to Section 3.1.1, 3.06 mL (25.50 mmol) of *trans*-1,2-diaminocyclohexane and 5.0 mL

(51.00 mmol) of salicylaldehyde yielded 7.89 g (24.32 mmol), 95%, yellow crystalline solid. 1H-NMR (*d*6-DMSO, 360 MHz, δ): 1.39–1.45 (m, 2H, –CH2–CH2–), 1.59–1.62 (m, 2H, –CH2–CH2–),

1.76–1.88 (m, 4H, –CH2–CH2–), 3.36 (s, 2H, CH–CH), 6.81 (d, *J* = 8.0 Hz, 4H, CHarom), 7.24–7.29 (t, *J* = 8.1 Hz, 2H, CHarom), 7.32–7.35 (d, *J* = 7.3, 2H, CHarom), 8.47 (s, 2H, –CH=N–), 13.32 (s, 2H, –OH).

13C{1H} NMR (*d*6-DMSO, 90 MHz, δ): 165.00, 160.33, 132.16, 131.54, 118.48, 116.29, 71.29, 32.48, 23.67.

Synthesis of *trans*-CyHS

According to Section 3.1.1, 7.90 g (24.04 mmol) of *trans*-CyS and 3.64 g (61.65 mmol) of sodium borohydride yielded 7.11 g (21.65 mmol), 90%, white crystalline solid.

1H-NMR (*d*6-DMSO, 360 MHz, δ): 1.08–1.23 (m, 4H, –CH2–CH2–), 1.67 (s, 2H, –CH2–), 2.07–2.10 (m, 2H, –CH2–), 2.51 (s, 2H, –CH–CH–), 3.79 (d, *J* = 13.7 Hz, 2H, CH2–NH), 3.92 (d, *J* = 13.7 Hz, 2H, CH2–NH), 6.74–6.78 (t, *J* = 7.2 Hz, 2H, CHarom), 6.86 (d, *J* = 7.9 Hz, 2H, CHarom), 7.08–7.12 (t, *J* = 7.7 Hz, 2H, CHarom), 7.24 (d, *J* = 7.2 Hz, 2H, CHarom).

13C{1H} NMR (*d*6-DMSO, 90 MHz, δ): 156.04, 129.63, 128.53, 123.28, 118.80, 115.15, 58.91, 44.95, 28.73, 24.01.

Synthesis of *trans*-CyHSS

According to Section 3.1.1, 1 g (3.06 mmol) *trans*-CyHS, 4 mL of 20% fuming sulfuric acid (oleum) and 1 mL of concentrated sulfuric acid yielded 868 mg (1.78 mmol), 58%, white crystalline solid.

1H-NMR (D2O, 360 MHz, δ): 1.05–1.17 (m, 4H, –CH2–CH2–), 1.57–1.60 (m, 2H, –CH2–), 1.89–1.92 (m, 2H, –CH2–), 2.34–2.37 (m, 2H, –CH2–NH–), 3.59–3.67 (m, 4H, CH2–NH), 6.55 (d, *J* = 8.1 Hz, 2H, CHarom), 7.38–7.45 (m, 4H, CHarom).

13C{1H} NMR (D2O, 90 MHz), δ: 169.13, 128.13, 127.18, 126.34, 126.10, 118.51, 59.47, 46.48, 29.68, 24.06.

IR (ATR), ν/cm<sup>−</sup>1: 587.5, 694.4, 840.3, 1033.3, 1165.4, 1207.3, 1281.3, 1598.1

ESI-MS for C20H26N2O8S2 (*m*/*z*): calcd for [M + H]<sup>+</sup> 487.119, found 487.121 and [M + Na+] + 509.102, found 509.104.
