Electronic Supplementary Material (ESI) for ChemComm. This journal is © The Royal Society of Chemistry 2018 ESI Synthetic Details General Procedures. Solvents were purified by standard methods.1 Palladium(II) acetate, (p- NH2C6H4)2SO2, 2,3,4−(MeO)3C6H2CHO, (p-NH2C6H4)2O and the phosphine Ph2PCH2PPh2 (dppm) were purchased from Sigma-Aldrich. All preparations were carried out under dry dinitrogen. Elemental analyses were performed with a Fisons elemental analyzer, Model 1108. IR espectra were recorded as Nujol mulls or polythene discs on Perking-Elmer 1330, Mattson Model Cygnus-100, and Bruker Model IFS-66V spectrophotometers. 1H NMR spectra in solution were recorded in CDCl3, DMSO-d6 or Acetone-d6 at room temperature on Bruker DPX 250 and Varian Mercury 300 spectrometer operating at 250.13MHz and 300.14 MHz respectively using 5 mm o.d. tubes; chemical shifts, in ppm, are reported downfield relative to TMS using the solvent 1 1 1 signal (CDCl3, H = 7.26 ppm; DMSO-d6, H = 2.46ppm; MeCOMe-d6 H = 2.05ppm) as reference. 31P NMR spectra were recorded at 161.91 MHz and 202.46 MHz on a Varian Inova 400 and Bruker AMX 500 spectrometer respectively using 5 mm o.d. tubes and are reported in ppm relative to external H3PO4 (85%). Coupling constants are reported in Hz. All chemical shifts are reported downfield from standard OMe OMe OMe OMe MeO MeO MeO OMe 5 Ac O 6 X MeO MeO MeO OMe Pd Pd Pd N N N X N Pd(OAc)2 NaX Toluene Acetone/Water or CH2Cl2/Water Ac N N O N X N Pd Pd Pd MeO MeO MeO OMe X MeO MeO MeO OMe OMe OMe OMe OMe 2 IIa, IIb a, b Ia, Ib X = Cl IIIa, IIIb X = Br = SO2 a IIa, IIb, IIIb = O b 1:4 Ph2PCH2PPh2 / NH4PF6 Acetone 2+ OMe MeO OMe MeO OMe 2+ MeO Ph Ph 2 Ph2 2 MeO P P OMe P MeO Pd Pd Pd N N N P X P P Ph2 Ph2 Ph2 Acetone-d 2 PF - 6 - 6 2 PF6 Ph2 Ph2 Ph N P X P N 2 N P Pd Pd Pd MeO MeO P P OMe Ph2 Ph2 P Ph2 MeO OMe MeO OMe MeO OMe 2a X = Cl 1a, 1b(IIb), 1b(IIIb) 2b X = Cl 3b X = Br Scheme 1ESI Reaction sequence leading to the synthesis of the double A−frame complexes. Synthesis of [2,3,4-(MeO)3C6H2(CH)=NC6H4]2SO2 (a) 1 Perrin, D.D., Armarego, W.L.F. Purification of Laboratory Chemicals, Butterworth-Heinemann, London, 4th ed., 1996 A 1:2 mixture of (p-NH2C6H4)2SO2 (2.57 g, 10.33 mmol) and 2,3,4−(MeO)3C6H2CHO (4.0 g, 20.39 mmol) in chloroform (50 cm3) was refluxed for 3 h. After cooling to room temperature, the solvent was removed under reduced pressure to give a yellow oil. Addition of diethyl ether and stirring for 24 h gave a pale-yellow solid, which was filtered and dried under vacuum. Yield: 4.891 g, 80%. Anal. Found: C: 63.4, H: 5.2, N: 4.6, S: 5.3 %; C32H32N2O8S (604.67 g/mol); −1 1 requires C: 63.6, H: 5.3, N: 4.6, S: 5.3 %. IR(cm ): (C=N) 1621. H NMR (DMSO-d6, δ/ppm, J/Hz): 8.58 (s, 2H, HC=N), 7.94 (d, 4H, H7H8, N = 8.2), 7.74 (d, 2H, H6, 3JH6H5 = 8.9), 7.33 (d, 4H, H9H10, N = 8.2), 6.94 (d, 2H, H5, 3JH5H6 = 8.9), 3.90 (s, 6H, MeO), 3.84 (s, 6H, MeO), 3.74 (s, 6H, MeO). Synthesis of [{Pd{2,3,4-(MeO)3C6H(CH)=NC6H4}(2−O2CMe)}2SO2]2 (Ia) The ligand a (0.475 g, 0.785 mmol) and palladium(II) acetate (0.355 g, 1.580 mmol) were added in toluene (50 cm3) and the resulting mixture was stirred at 60° C for 24 h under argon. After cooling to r. t. the orange-brown solid formed was filtered off and dried under vacuum, to afford the final product as a dark orange solid. Yield: 0.70 g, 98%. Anal. Found: C 46.4, H 4.2, N 3.2, −1 S 3.3 %; C72H72N4O24Pd4S2 (1867.16 g/mol) requires C 46.3, H 3.9, N 3.0, S 3.4%. IR(cm ): 1 (C=N) 1566. H NMR (DMSO−d6, δ ppm, J Hz): 8.26 (s, 4H, HC=N), 7.94 (m, 8H, H7H8), 7.52 (m, 8H, H9H10), 6.16 (s, 4H, H5), 3.83 (s, 12H, MeO), 3.77 (s, 12H, MeO), 3.65 (s, 12H, MeO), 1.91 (s, 12H, MeCO2). Synthesis of [{Pd{2,3,4-(MeO)3C6H(CH)=NC6H4}(2−Cl)}2SO2]2 (IIa) A solution of Ia (0.407 g, 0.218 mmol) in 20 cm3 of acetone was treated with a saturated solution of NaCl in ca. 20 cm3 of water. The yellow precipitate formed was filtered off, washed with water and dried under vacuum. Yield: 393 mg, 88%. Anal. Found: C, 43.5, H, 3.2, N, 3.2, S −1 3.4 %; C64H60Cl4N4O16Pd4S2 (1772.80 g/mol) requires C, 43.4, H, 3.4, N, 3.2, S, 3.6%. IR(cm ): 1 (C=N) 1570, (Pd−Cl) 309,284. H NMR (DMSO−d6, δ ppm, J Hz): 8.28 (s, 4H, HC=N), 7.96 (m, 8H, H7H8, N = 8.5), 7.54 (m, 8H, H9H10, N = 8.4), 6.16 (s, 4H, H5), 3.85 (s, 12H, MeO), 3.79 (s, 12H, MeO), 3.67 (s, 12H, MeO). Synthesis of [{Pd{2,3,4-(MeO)3C6H(CH)=NC6H4}(2−Br)}2SO2]2 (IIIa) A solution of Ia (0.224 g, 0.120 mmol) in 20 cm3 of acetone was treated with a saturated solution of LiBr in ca. 20 cm3 of water. The yellow precipitate formed was filtered off, washed with water and dried under vacuum. Yield: 350 mg, 95.6%. Anal. Found: C, 39.4, H, 3.2, N, 3.0, S, 3.1 %; C64H60Br4N4O16Pd4S2 (1950.61 g/mol) requires C, 39.4, H, 3.1, N, 2.9, S, 3.3%. −1 1 IR(cm ): (C=N) 1621. H NMR (DMSO−d6, δ ppm, J Hz): 8.52 (m, 8H, H7H8, N = 8.5), 8.28 (s, 4H, HC=N), 7.95 (m, 8H, H9H10, N = 8.4), 7.38 (s, 4H, H5), 3.83 (s, 12H, MeO), 3.78 (s, 12H, MeO), 3.65 (s, 12H, MeO). Synthesis of [Pd{2,3,4-(MeO)3C6H(CH)=NC6H4}(Ph2PCH2PPh2−P,P)]2SO2 · 2PF6 (1a) Ph2PCH2PPh2 (0.029 g, 0.075 mmol) was added to a suspension of IIa (0.033 g, 0.019 mmol) in acetone (10 cm3). The mixture was stirred for 30 min, after which an excess of ammonium hexafluorophosphate was added. The mixture was stirred for a further 1 h, the complex precipitated out by addition of water, filtered off and dried in vacuo. IR(cm−1): C=N: 1568. 1 4 H NMR (MeCOMe−d6, δ ppm, J Hz): 8.53 (d, 2H, HC=N, JHPtrans = 5.9), 6.04 (dd, 2H, H5, 4 4 JH5P = 10.5, JH5P = 7.9), 4.65 (m, 4H, PCH2P), 3.98 (s, 6H, MeO), 3.71 (s, 6H, MeO), 3.20 31 1 2 (s, 6H, MeO). P-{ H} NMR (MeCOMe−d6, δ ppm, J Hz): -37.2 (d, PtransC , JPP =72.1), -12.9 (d, 2 1 PtransN , JPP = 72.1), -149.9 (sept, PF6 JPF = 709.5). Synthesis of {[Pd{2,3,4-(MeO)3C6H(CH)=NC6H4}(−Ph2PCH2PPh2−P,P)]2(−Cl)SO2}2 · 2PF6 (2a) Ph2PCH2PPh2 (8.5 mg, 0.022 mmol) and ammonium hexafluorophosphate (0.004 g, 0.024 3 mmol) were added to a solution of IIa (8.5 mg, 0.005 mmol) in acetone-d6 (0.6 cm ) and left to stand until complete conversion. Yield: 16 mg, 93% related to IIa. Anal. Found: %; C, 55.3, H, 4.4, N, 1.6, S, 1.8 %; C164H148Cl2F12N4O16P10Pd4S2 (3529.42 g/mol) requires C, 55.8, H, 4.2, N, −1 1 1.6, S, 1.8 % IR(cm ): C=N: 1597, Pd−Cl: 280m. H NMR (MeCOMe−d6, δ ppm, J Hz): 8.10 (s, 4H, HC=N), 7.02 (m, 4H, H5), 4.25 (s, 12H, MeO), 3.58 (s, 12H, MeO), 3.48 (s, 12H, MeO). 31 1 1 P-{ H} NMR (MeCOMe−d6, δ ppm): 1.48 (s), -150.0 (sept, PF6, JPF 707.7). Synthesis of [2,3,4-(MeO)3C6H2(CH)=NC6H4]2O (b) A 1:2 mixture of (p-NH2C6H4)2O (1.0 g, 4.99 mmol) and 2,3,4−(MeO)3C6H2CHO (2.0 g, 9.98 mmol) in ethanol (50 cm3) was stirred at room temperature for 24 h. The white precipitate formed was filtered off, washed with water and dried under vacuum. Yield: 2.273 g, 82%. Anal. Found: C: 68.8, H: 5.9, N: 5.1 %; C32H32N2O7 (556.61 g/mol) requires C: 69.0, H: 5.8, N: 5.0 %. −1 1 IR(cm ): (C=N) 1609. H NMR (DMSO-d6, δ/ppm, J/Hz): 8.64 (s, 2H, HC=N); 7.75 (d, 2H, H6, 3JH6H5 = 8.7); 7.25 (d, 4H, H9H10, N = 8.3); 7.03 (d, 4H, H7H8, N = 8.3); 6.93 (d, 2H, H5, 3JH5H6 = 8.7); 3.86 (s, 6H, MeO); 3.84 (s, 6H, MeO); 3.75 (s, 6H, MeO). Synthesis of [{Pd{2,3,4-(MeO)3C6H(CH)=NC6H4}(−O2CMe)}2O]2 (Ib) The ligand b (0.500 g, 0.898 mmol) and palladium(II) acetate (0.403 g, 1.795 mmol) were added in toluene (30 cm3) and the resulting mixture was stirred at 55° C for 24 h.