Synthesis, Characterization, and the Effect of Lewis Bases on the Nuclearity of Iron Alkoxide Complexes.

Inspired by the potential of alkoxides as weak-field ligands and their ability to bridge, we report herein a series of high-spin iron complexes supported by a bis-alkoxide framework PhDbf. A diiron complex [Fe2(PhDbf)2] (1a) is obtained upon metalation of the ligand, whereas addition of substituted pyridines affords five-coordinate mononuclear iron complexes [(R-Py)2Fe(PhDbf)] (2a-4a, R = H, p-tBu, p-CF3). The potential for nuclearity control of the metal complexes via auxiliary ligands is highlighted by the formation of asymmetric diiron species [(p-CF3-Py)Fe2(PhDbf)2] (5a) and [(m-CF3-Py)Fe2(PhDbf)2] (6a) with trifluoromethyl substituted pyridines, while electron-rich pyridines only produced monomeric species. Electronic properties analysis via UV-vis, electron paramagnetic resonance, 57Fe Mössbauer spectroscopy, and time-dependent density functional theory, along with redox capabilities of these complexes are reported to illustrate the effect of nuclearity on reactivity and the potential of these complexes to access higher oxidation states relevant in oxidative chemistry. Species 1a-5a, [(THF)2Fe(PhDbf)][PF6] (7), [PyFe(PhDbf)Cl] (2b), and [Py2Fe(PhDbf)][PF6] (2c) were characterized via SCXRD. Indirect evidence for the formation of dimeric Fe(III) species (1b, 5b, and 6b) is discussed.

Synthesis of disubstituted furans catalysed by [(AuCl)2(µ-bis(phosphino)metallocene)] and Na[BArF24].

The catalytic activity of a series of [(AuCl)2(µ-PP)] (PP = 1,1'-bis(phosphino)metallocene ligands) compounds in the presence of Na[BArF24] (BArF24 = tetrakis(3,5-bis(trifluoromethyl)phenyl borate)) was examined in the formation of disubstituted furans from pyridine-N-oxide and terminal alkynes. The products of these reactions were typically the 2,5-disubstituted furans, but in the case of using 2-ethynylpyridene, the 2,4-disubstituted furan formed. The catalytic efficiency was dependent upon both the nature of the terminal alkyne and the 1,1'-bis(phosphino)metallocene ligands. During the course of this study, two new compounds, [(AuCl)2(µ-dppr)] and [(AuCl)2(µ-dppo)] (dppr = 1,1'-bis(diphenylphosphino)ruthenocene; dppo = 1,1'-bis(diphenylphosphino)osmocene), were prepared and characterized by NMR. X-ray crystal structures of both compounds were determined and the oxidative electrochemistry of these new compounds was examined.