The comparative catalytic activities of iron phosphides, Fe x P (x = 1-3), have been established with phase-pure material grown by Chemical Vapor Deposition (CVD) from single-source organometallic precursors. This is the first report of the preparation of phase-pure thin films of FeP and Fe 2 P and their identity was established with scanning-electron microscopy, X-ray photoelectron spectroscopy, and powder X-ray diffraction. All materials were deposited on fluorine-doped tin oxide (FTO) for evaluation of their activities towards the hydrogen evolution reaction (HER) of water splitting in 0.5 M H 2 SO 4. HER activity follows the trend Fe 3 P > Fe 2 P > FeP, with Fe 3 P having the lowest overpotential of 49 mV at a current density of 10 mA cm-2. Density functional theory (DFT) calculations are congruent with the observed activity trend with hydrogen binding favoring the iron-rich terminating surfaces of Fe 3 P and Fe 2 P over the iron-poor terminating surfaces of FeP. The results present a clear trend of activity with iron-rich phosphide phases outperforming phosphorus rich phases for hydrogen evolution. The films of Fe 2 P were grown using Fe(CO) 4 PH 3 (1), while the films of FeP were prepared using either Fe(CO) 4 P t BuH 2 (2) or the new molecule {Fe(CO) 4 P(H) t Bu} 2 (3) on quartz and FTO. Compound 3 was prepared from the reaction of PCl 2 t Bu with a mixture of Na[HFe(CO) 4 ] and Na 2 [Fe(CO) 4 ] and characterized by single-crystal X-Ray diffraction, ESI-MS, elemental analysis, and 31 P/ 1 H NMR spectroscopies. Films of Fe 3 P were prepared as previously described from H 2 Fe 3 (CO) 9 P t Bu (4).
Six new anionic bismuth-oxido clusters containing trifluoroacetate ligands were prepared. These include two new BiO clusters: [M(NCMe)(HO)][Bi(μ-O)(μ-OH)(CFCO)] with an octahedral BiO(OH) core (M = Ni, 1a; Co, 1b) and four BiO clusters, {[Co(NCMe)][Bi(μ-O)(CFCO)]} (2a), {[Co{HC(MeCO)(MeCNH)}][Bi(μ-O)(CFCO)]·2[CFCO]·2[CFCOH]·2[HO]} (2b), {[Cu(NCMe)][Bi(μ-O)(CFCO)]·2[CFCOH]} (2c), and {[MeN][Bi(μ-O)(CFCO)]·2[CFCOH]} (2d). These are among the first bismuth-oxido anionic clusters synthesized, and the first to have transition metal countercations. The BiO anion in 1a and 1b is a high-symmetry octahedron. Additionally, two of the new BiO clusters are arranged in 1D polymeric structures via bridging carboxylate ligands. The cation in compound 2c had not been previously characterized and was also observed in the synthesis of [Co{HC(MeCO)(MeCNH)}][Bi(NO)] (3). The new compounds were characterized using single crystal X-ray crystallography and elemental analysis.
BiPh3 and trifluoroacetic acid (TFAH) react in toluene in the presence of Ag2O to form {[Bi4(µ3‐O)2(TFA)9Ag(tol)2]2} (1; tol = PhMe). Similarly, BiPh3, TFAH, PPh3, and Ag2O react in hexane to form [Bi4(µ3‐O)2(TFA)10(AgPPh3)2]n (2). Both contain {Bi4(µ3‐O)2} units, which have been previously observed with a variety of carboxylate ligands in neutral compounds and anionic compounds. In contrast to other anionic [Bi4(µ3‐O)2(TFA)N](N–8)– with metal‐based countercations, the Ag+ ions in 1 and 2 are directly attached to oxygen atoms of the TFA– ligands bonded to the bismuth core. A crystallographic evolution was observed for 1. Solvent‐rich orthorhombic crystals grew initially on standing. However, by three weeks all crystals had converted to a triclinic unit cell that contained no free solvent. The molecular volume decreased from 3146.11 Å3 (orthorhombic) to 2954.06 Å3 (triclinic). The latter had an intermolecular π–π stacking system between silver‐ and bismuth‐bound toluene molecules, which explains the reorganization to a nonsolvated morphology. Compound 2 crystallizes in the triclinic space group P1 as a coordination polymer through bridging carboxylate ligands. The presence of the PPh3 ligands on Ag+ results in a higher Ag/Bi ratio than in 1. The importance of Ag2O in generating the oxido ligands was confirmed by the isolation of {[Bi2(TFA)6(TFAH)(tol)]2}n (3) from the reaction of BiPh3 with TFAH in toluene in the absence of the metal oxide.
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