Zwitterionic amidinates as effective ligands for platinum nanoparticle hydrogenation catalysts

Pt NPs covered with zwitterionic amidinates as ligands exhibit an exciting ligand effect in the hydrogenation of carbonyl groups when electron donor/acceptor groups are introduced in the N-substituents.


S3
Wide-angle X-ray scattering (WAXS). WAXS was performed at CEMES-CNRS. Samples were sealed in 1.0 mm diameter Lindemann glass capillaries. The samples were irradiated with graphite monochromatized molybdenum Kα (0.071069 nm) radiation and the X-ray intensity scattered measurements were performed using a dedicated two-axis diffractometer. Radial distribution functions (RDF) were obtained after Fourier transformation of the reduced intensity functions.
Nuclear Magnetic Resonance (NMR). 1 H spectra were recorded on a Bruker Avance 400 spectrometer.
Solid state NMR (MAS-NMR). Solid-state NMR experiments were recorded at the LCC (Toulouse) on a Bruker Avance 400 spectrometer equipped with 3.2 mm probes. Samples were spun between 14 to 20 kHz at the magic angle using ZrO 2 rotors. 13 C MAS experiments were performed with a recycle delay of 20 s. 13  Infrared spectroscopy (IR). ATR IR-FT spectra were recorded on a Thermo Scientific Nicolet 6700 spectrometer in the range 4000-600 cm -1 .

X-Ray Photoelectron Spectroscopy (XPS). XPS analyses were performed at CIRIMAT Laboratory
(Toulouse) using a Thermoelectron Kalpha device. The photoelectron emission spectra were recorded using Al-Kα radiation (hν= 1486.6 eV) from a monochromatized source. The analyzed area was about 0.15 mm 2 . The pass energy was fixed at 40 eV. The spectrometer energy calibration was made using the Au 4f 7/2 (83.9 ± 0.1 eV) and Cu2p 3/2 (932.8 ± 0.1 eV) photoelectron lines. XPS spectra were recorded in direct mode N(Ec). The background signal was removed using the Shirley method. The atomic S4 concentrations were determined from photoelectron peak areas using the atomic sensitivity factors reported by Scofield, taking into account the transmission function of the analyzer. The photoelectron peaks were analyzed by Gaussian/ Lorentzian (G/L=50) peak fitting.
DFT calculations. All DFT calculations on the [Ru 6 ] clusters were performed with Gaussian09. 3 Geometries were fully optimized in gas phase without symmetry constraints, employing the B3PW91 functional 4 and the Stuttgart effective core potential for Ru, 5 augmented with a polarization function (ζ f =1.235). For the other elements (H, C, O, and P), Pople's double-ζ basis set 6-31G(d,p )6 was used.
Calculations of vibrational frequencies were systematically done in order to characterize the nature of stationary points. Among the various theories available to compute chemical shielding tensors, the Gauge Including Atomic Orbital (GIAO) method has been adopted for the numerous advantages it presents. Calculating a theoretical chemical shift requires the knowledge of the chemical shielding of a reference, since it is explicitly calculated as δ = (σ ref -σ), in ppm. We have shown in previous studies on ruthenium clusters that DFT-GIAO provides 1 H and 13 C chemical shifts in excellent agreement with experiments. 7 The experimental reference chemical shift for 15 N corresponds to ammoniac in its liquid phase. The theoretical magnetic shielding for NH 3 has been calculated using the same strategy as in Ref.
[ 8 ] (ab initio molecular dynamic simulations combined with the calculations of magnetic shielding on extracted cluster's structures from molecular dynamics). We have also used the Natural Population Analysis (NPA) 9 included in the Natural Bond Orbital (NBO) 10 routines available in Gaussian09, yielding the often called "NBO charges".

S5
DFT calculations on the [Ru 55 ] hcp nanoparticles were performed with the Vienna ab initio simulation package, VASP 11 within the framework of density functional theory. Projector augmented waves (PAW) 12 were used, with a plane-wave kinetic energy cutoff of 500 eV. All the calculations used the Perdew-Burke-Ernzerhof form of the generalized gradient approximation. 13 The supercell used was 27 x 27.5 x 28 Å large, ensuring at least 16 Å of vacuum between to successive images of ligand-covered Ru 55 . Γ-centered 14 calculations were performed with a Gaussian smearing (σ) of 0.02 eV, the energies being therefore extrapolated for σ=0.00 eV. The atoms positions were optimized until the criterion of the residual forces on any direction being less than 0.02 eV/Å was met. Also Reliable atom-projected density of states (pDOS), directly based on plane-wave DFT output as given by the VASP package, were computed with the Lobster package. 15
Carbodiimides RC 6 H 4 N=C=NC 6 H 4 R were obtained from the corresponding thioureas according to the procedure reported by Patel. 16 The synthesis of diphenylurea (from phenylisocyanate and aniline) and diphenylcarbodiimide is described in ref. 3. Bis-p-methoxythiourea was synthesized from thiophosgene and p-anisidine. 17 We also prepared bis pchlorophenylthiourea using the latter procedure, albeit a synthesis from CS 2 has been described recently. 18 Phenyl isothiocyanate, anilines and 98% aniline-15 N were purchased from Aldrich and used without further purification. 1,3-Dicyclohexylimidazolium tetrafluoborate was prepared by a literature method. 19 The synthesis of imidazolium-amidinate ligands was carried out under inert argon atmosphere using standard Schlenk techniques.
Synthesis of ICy .(Ph) NCN: 16.2 mL of a 0.5 M solution of t BuOK in THF (8.1 mmol) were slowly added to a stirred suspension of 2.56 g (8.1 mmol) of N,N-dicyclohexylimidazolium tetrafluoborate in 20 mL of the same solvent, cooled to -80 ºC. The cooling bath was removed and the stirring was continued for 30 min at r.t. The mixture was cooled again to -80 ºC and a solution of diphenylcarbodiimide (1.58 g, carbene, a yellow color develops. The mixture was allowed to stir at the r.t. for 2h, and then was taken to dryness under reduced pressure. Extraction in dichloromethane, and filtration through a celite pad afforded a clear yellow solution, which was evaporated. The solid residue was washed with 20 mL of diethyl ether, leaving the product as a yellow powder (1.90 g, 4.5 mmol, 55.0 % yield

Synthesis of ICy .(Ph) NC 15 N:
The labeled ligand was prepared as shown in Scheme S1, starting from 1 g (10.7 mmol) of 98% aniline-15N. The final yield was 2.03 g (4.9 mmol, 69.9 % yield from the labeled thiourea). The product was recrystallized from a dichloromethane/hexane mixture. The IR spectrum (nujol) and solution 1 H and 13 C{ 1 H} NMR spectra showed no significant differences with the non-labeled compound, except for the slight broadening of the quaternary C atoms directly bound to the "amidinate" N atoms due to unresolved 15 N- 13      in 15 mL of the same solvent. As the acid was added, the yellow color of the starting imidazolium-

Catalytic hydrogenation reactions.
Catalytic experiments were performed in a HEL 24-multireactor (volume of the tubes 1.5 mL). In a typical experiment, Pt NPs (0.0025 mmol of Pt assuming % of Pt from ICP analysis) in 0.75 mL of THF (as a standard solution, prepared immediately prior to use) was mixed with 0.5 mmol of substrate in 1.5 mL vials and the reactor was sealed under nitrogen before pressurization. The reactor was then pressurized with 3 bars of hydrogen and depressurized three times to purge and finally pressurized to 5 bars. The reactor was stirred during 20h at room temperature. After that, the reactor was slowly depressurized and samples from each reaction were passed through silica and analyzed by 1 H NMR.

Surfaces studies of Pt and Ru NPs through coordination of CO and 13 CO
For CO coordination studies, metal NPs were introduced in a Fischer-Porter bottle and were              S22 Figure S22. ATR FT-IR spectra registered for Pt/ICy .(p-tol) NCN 0.2 before (blue) and after (red) bubbling CO during 5 min. Figure S23. ATR FT-IR spectra registered for Pt/ICy .(p-tol) NCN 0.5 before (blue) and after (red) bubbling CO during 5 min.