Search for: All records

Sulfur K-edge XAS data provide a unique tool to examine oxidation states and covalency in electronically complex S-based ligands. We present sulfur K-edge X-ray absorption spectroscopy on a discrete redox-series of Ni-based tetrathiafulvalene tetrathiolate (TTFtt) complexes as well as on a 1D coordination polymer (CP), NiTTFtt. Experiment and theory suggest that Ni–S covalency decreases with oxidation which has implications for charge transport pathways. 

The molecular tetravalent oxidation state for praseodymium is observed in solution via oxidation of the anionic trivalent precursor [K][Pr 3+ (NP(1,2-bis- t Bu-diamidoethane)(NEt 2 )) 4 ] (1-Pr(NP*)) with AgI at −35 °C. The Pr 4+ complex is characterized in solution via cyclic voltammetry, UV-vis-NIR electronic absorption spectroscopy, and EPR spectroscopy. Electrochemical analyses of [K][Ln 3+ (NP(1,2-bis- t Bu-diamidoethane)(NEt 2 )) 4 ] (Ln = Nd and Dy) by cyclic voltammetry are reported and, in conjunction with theoretical modeling of electronic structure and oxidation potential, are indicative of principal ligand oxidations in contrast to the metal-centered oxidation observed for 1-Pr(NP*). The identification of a tetravalent praseodymium complex in in situ UV-vis and EPR experiments is further validated by theoretical modeling of the redox chemistry and the UV-vis spectrum. The latter study was performed by extended multistate pair-density functional theory (XMS-PDFT) and implicates a multiconfigurational ground state for the tetravalent praseodymium complex. 

Reaction of the complexes [Fe 2 (μ 2 -NP(pip) 3 ) 2 (NP(pip) 3 ) 2 ] ( 1-Fe ) and [Co 2 (μ 2 -NP(pip) 3 ) 2 (NP(pip) 3 ) 2 ] ( 1-Co ), where [NP(pip) 3 ] 1− is tris(piperidinyl)imidophosphorane, with nitrous oxide, S 8 , or Se 0 results in divergent reactivity. With nitrous oxide, 1-Fe forms [Fe 2 (μ 2 -O)(μ 2 -NP(pip) 3 ) 2 (NP(pip) 3 ) 2 ] ( 2-Fe ), with a very short Fe 3+ –Fe 3+ distance. Reactions of 1-Fe with S 8 or Se 0 result in the bridging, side-on coordination (μ-κ 1 :κ 1 -E 2 2− ) of the heavy chalcogens in complexes [Fe 2 (μ-κ 1 :κ 1 -E 2 )(μ 2 -NP(pip) 3 ) 2 (NP(pip) 3 ) 2 ] (E = S, 3-Fe , or Se, 4-Fe ). In all cases, the complex 1-Co is inert.