*3.3. General Procedure*

1H and 13C{1H} NMR spectra were recorded on a Bruker Avance 360 MHz spectrometer (Bruker, Billerica, MA, USA) and were referenced to residual solvent peaks. Single crystal X-ray diffraction (SC-XRD) measurements were performed using a Bruker D8 Venture diffractometer, SuperNova X-ray diffractometer system, and the methods and software described in [53–60]. The crystallographic data for all compounds were deposited in the Cambridge Crystallographic Data Centre (CCDC) with the No. CCDC 2020275–2020282 and 2020437. Details of the structure determinations are found in the Supplementary Material.

Infrared spectra were recorded on a Perkin Elmer Spectrum Two FT-IR Spectrometer in attenuated total reflectance (ATR) mode.

Gas chromatographic measurements were done with the use of an Agilent Technologies 7890A instrument (Agilent Technologies, Santa Clara, CA, USA) equipped with a HP-5, 0.25 μm × 30 m × 0.32 mm or an OPTIMA (30 m × 0.32 mm × 1.25 μm) column, and a flame ionization detector 300 ◦C; the carrier gas was nitrogen 1.9 mL/min.

ESI-TOF-MS measurements were carried out on a BRUKER BioTOF II ESI-TOF spectrometer in positive ion mode or on a Bruker maXis II MicroTOF-Q type Qq-TOF-MS instrument (Bruker Daltonik, Bremen, Germany) both in positive and negative ion modes. The mass spectra were calibrated internally using the exact masses of sodium formate clusters. The spectra were evaluated using Compass Data Analysis 4.4 software from Bruker.

All catalytic Suzuki–Miyaura cross-coupling reactions were carried out under air. The reaction temperatures were kept constant by using a thermostated circulator (set to 80.0 ± 0.1 ◦C). The products were identified by comparison of their retention time with those of known standard compounds.

#### **4. Conclusions**

All investigated Pd (II)–sulfosalan complexes 6–10 showed high catalytic activities in the Suzuki–Miyaura reactions of aryl halides and phenylboronic acid derivatives in water and air at 80 ◦C. The catalytic activity of a particular complex depended on the length of the linker group between the secondary N-atoms of the sulfosalan ligand and/or on the steric congestion around these donor atoms. With the most active catalyst, Na2[Pd(dPhHSS)] (9), a TOF = 40,000 h−<sup>1</sup> was achieved in the reaction of iodobenzene and phenylboronic acid.

**Supplementary Materials:** The following are available online, ORTEP views of ligands and Pd complexes (9), crystal lattice packing views with indication of π–π interactions and H-bond networks (17), tables of hydrogen bonds in ligands and complexes (7), calculated and experimental powder diffraction patterns for the crystals of **1** × 2 H2O and **3**, comparison (superposition) of known and newly determined structures of the ligands (7), table of crystal data and diffraction measurements, 1H and 13C NMR spectra (Figures S37–S111) of ligands **1**–**5**, Pd(II)-complexes **6**–**10**, starting materials (salens **11**–**15**) and synthetic intermediates (salans **21**–**25**).

**Author Contributions:** Conceptualization, all authors (S.B., K.V., Á.K., A.U., F.J.); methodology, S.B and A.U.; investigation, S.B. and A.U.; discussion of experimental results, all authors; writing—original draft preparation, S.B., A.U. and F.J.; writing—review and editing, all authors; visualization, S.B. and A.U.; supervision, F.J. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research was supported by the EU and cofinanced by the European Regional Development Fund (under the projects GINOP-2.3.2-15-2016-00008 and GINOP-2.3.3-15-2016-00004). Support was also provided by the Thematic Excellence Programme of the Ministry for Innovation and Technology of Hungary (ED-18-1-2019-0028), within the framework of the Vehicle Industry thematic programme of the University of Debrecen. The financial support of the Hungarian National Research, Development and Innovation Office (FK-128333) is gratefully acknowledged.

**Acknowledgments:** Dedicated to P.H. Dixneuf for his outstanding contributions to organometallic chemistry and catalysis, and for his invaluable services to the scientific community. The authors thank Attila Bényei (University of Debrecen) for his generous recording of diffraction data and for his most useful advices. The authors are also grateful to Éva Kováts for her invaluable help in collecting diffraction data for the highly sensitive **8** and to the Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, for the courteous allowance to use the diffraction equipment.

**Conflicts of Interest:** The authors declare no conflict of interest.
