Reductive Reactivity of the 4f5d Gd(II) Ion in {Gd[N(SiMe)]}: Structural Characterization of Products of Coupling, Bond Cleavage, Insertion, and Radical Reactions.

The reductive reactivity of a Ln(II) ion with a nontraditional 4f5d electron configuration has been investigated by studying reactions of the {Gd(N(SiMe))]} anion with a variety of reagents that survey the many reaction pathways available to this ion. The chemistry of both [K(18-c-6)] and [K(crypt)] salts (18-c-6 = 18-crown-6; crypt = 2.2.

Formation of the End-on Bound Lanthanide Dinitrogen Complexes [(RN)Ln-N═N-Ln(NR)] from Divalent [(RN)Ln] Salts (R = SiMe).

Lanthanide-based dinitrogen reduction chemistry has been expanded by the discovery of the first end-on Ln(μ-η:η-N) complexes, whose synthesis and reactivity help explain the reduction of N by the combination of trivalent Ln(NR) complexes (R = SiMe) and potassium. The formation of end-on versus the more common side-on Ln(μ-η:η-N) complexes is possible by using recently discovered Ln(II) complexes ligated by three NR amide ligands (R = SiMe). The isolated Ln(II) tris(amide) complex [K(crypt)][Tb(NR)] (crypt = 2.

The importance of the counter-cation in reductive rare-earth metal chemistry: 18-crown-6 instead of 2,2,2-cryptand allows isolation of [Y(NR)] and ynediolate and enediolate complexes from CO reactions.

The use of 18-crown-6 (18-c-6) in place of 2.2.2-cryptand (crypt) in rare earth amide reduction reactions involving potassium has proven to be crucial in the synthesis of Ln(ii) complexes and isolation of their CO reduction products.

Isolation of U(ii) compounds using strong donor ligands, CMeH and N(SiMe), including a three-coordinate U(ii) complex.

New examples of uranium in the formal +2 oxidation state have been isolated by reduction of Cptet3U (Cptet = C5Me4H) and U(NR2)3 (R = SiMe3) in the presence of 2.2.2-cryptand (crypt) to produce [K(crypt)][Cptet3U] and [K(crypt)][U(NR2)3], respectively.

Synthesis, Structure, and Magnetism of Tris(amide) [Ln{N(SiMe ) } ] Complexes of the Non-traditional +2 Lanthanide Ions.

A new series of Ln complexes has been synthesized that overturns two previous generalizations in rare-earth metal reduction chemistry: that amide ligands do not form isolable complexes of the highly reducing non-traditional Ln ions, and that yttrium is a good model for the late lanthanides in these reductive reactions. Reduction of Ln(NR ) (R=SiMe ) complexes in THF under Ar with M=K or Rb in the presence of 2.2.

Evaluating the electronic structure of formal Ln ions in Ln(CHSiMe) using XANES spectroscopy and DFT calculations.

The isolation of [K(2.2.2-cryptand)][Ln(CHSiMe)], formally containing Ln, for all lanthanides (excluding ) was surprising given that +2 oxidation states are typically regarded as inaccessible for most 4f-elements.

Redox Potential and Electronic Structure Effects of Proximal Nonredox Active Cations in Cobalt Schiff Base Complexes.

Redox inactive Lewis acidic cations are thought to facilitate the reactivity of metalloenzymes and their synthetic analogues by tuning the redox potential and electronic structure of the redox active site. To explore and quantify this effect, we report the synthesis and characterization of a series of tetradentate Schiff base ligands appended with a crown-like cavity incorporating a series of alkali and alkaline earth Lewis acidic cations (1M, where M = Na, K, Ca, Sr, and Ba) and their corresponding Co(II) complexes (2M). Cyclic voltammetry of the 2M complexes revealed that the Co(II/I) redox potentials are 130 mV more positive for M = Na and K and 230-270 mV more positive for M = Ca, Sr, and Bacompared to Co(salen-OMe) (salen-OMe = N,N'-bis(3-methoxysalicylidene)-1,2-diaminoethane), which lacks a proximal cation.