Incorporation of coinage metal-NHC complexes into heptaphosphide clusters.

Cu(i) and Au(i) ions, capped with an N-heterocyclic carbene (NHC), react with (TMS)3P7 (TMS = trimethyl-silyl) to afford an η4-coordinated anion [NHCDippCu-P7(TMS)]- and a neutral trinuclear complex (NHCDippAu)3P7. Protecting the P7 cage with the TMS groups is instrumental in controlling the course of these reactions.

Homoleptic mono-, di-, and tetra-iron complexes featuring phosphido ligands: a synthetic, structural, and spectroscopic study.

We report the first series of homoleptic phosphido iron complexes synthesized by treating either the β-diketiminato complex [(Dippnacnac)FeClLi(dme)] (Dippnacnac = HC[(CMe)N(CH-2,6-iPr)]) or [FeBr(thf)] with an excess of phosphides RPLi (R = tBu, tBuPh, Cy, iPr). Reaction outcomes depend strongly on the bulkiness of the phosphido ligands. The use of tBuPLi precursor led to an anionic diiron complex 1 encompassing a planar FeP core with two bridging and two terminal phosphido ligands.

Nucleophilic Activation of Red Phosphorus for Controlled Synthesis of Polyphosphides.

Reactions between red phosphorus (P) and potassium ethoxide in various organic solvents under reflux convert this rather inert form of the element to soluble polyphosphides. The activation is hypothesized to proceed via a nucleophilic attack by ethoxide on the polymeric structure of P, leading to disproportionation of the latter, as judged from observation of P(OEt) in the reaction products. A range of solvents has been probed, revealing that different polyphosphide anions (P, P, P, and P) can be stabilized depending on the combination of the boiling point and dielectric constant (polarity) of the solvent.

Radical Dimerization in a Plastic Organic Crystal Leads to Structural and Magnetic Bistability with Wide Thermal Hysteresis.

The nitroxyl radical 1-methyl-2-azaadamantane -oxyl (Me-AZADO) exhibits magnetic bistability arising from a radical/dimer interconversion. The transition from the rotationally disordered paramagnetic plastic crystal, Me-AZADO, to the ordered diamagnetic crystalline phase, (Me-AZADO), has been conclusively demonstrated by crystal structure determination from high-resolution powder diffraction data and by solid-state NMR spectroscopy. The phase change is characterized by a wide thermal hysteresis with high sensitivity to even small applied pressures.

Dicyanometalates as Building Blocks for Multinuclear Iron(II) Spin-Crossover Complexes.

A synthetic strategy featuring dicyanometalates [M(CN)] (M = Ag, Au) as N-coordinating ditopic linkers connecting partially blocked Fe centers has been employed to produce heterometallic hexanuclear complexes, which exhibit spin-crossover (SCO) behavior at the Fe sites. The reaction between tris(2-pyridylmethyl)amine (tpma)-capped Fe ions and [Ag(CN)] proceeded with partial decomposition of the dicyanoargentate and led to the formation of {[Fe(tpma)](μ-CN)[μ-Ag(CN)]}(ClO)·3HO (), in which both [Ag(CN)] and CN act as bridging ligands, and the opposite [Ag(CN)] bridges are engaged in a pronounced argentophilic d-d interaction. In an analogous synthesis, the more stable [Au(CN)] species remained intact and furnished the complex {[Fe(tpma)][μ-Au(CN)]} (), which features two Fe centers bridged by two [Au(CN)] dimers.

Square-planar Co(iii) in {O} coordination: large ZFS and reactivity with ROS.

Oxidation of distorted square-planar perfluoropinacolate Co compound [CoII(pinF)2]2-, 1, to [CoIII(pinF)2]1-, 2, is reported. Rigidly square-planar 2 has an intermediate-spin, S = 1, ground state and very large zero-field splitting (ZFS) with D = 67.2 cm-1; |E| = 18.

Heteroleptic Fe(II) Complexes with NS Coordination as a Platform for Designing Spin-Crossover Materials.

Heteroleptic complexes [Fe(bpte)(bim)]X and [Fe(bpte)(xbim)]X (bpte = S,S'-bis(2-pyridylmethyl)-1,2-thioethane, bim = 2,2'-biimidazole, xbim = 1,1'-(α,α'-o-xylyl)-2,2'-biimidazole, X = ClO, BF, OTf) were prepared by reacting the corresponding Fe(II) salts with a 1:1 mixture of the ligands. All mononuclear complexes exhibit temperature-induced spin crossover (SCO) with the onset above room temperature. The SCO is rather gradual, due to low cooperativity of interactions between the cationic complexes, as revealed by crystal structure analyses.

Synthetic, Structural, and Spectroscopic Characterization of a Novel Family of High-Spin Iron(II) [(β-Diketiminate)(phosphanylphosphido)] Complexes.

This work describes a series of iron(II) phosphanylphosphido complexes. These compounds were obtained by reacting lithiated diphosphanes RPP(SiMe)Li (R = t-Bu, i-Pr) with an iron(II) β-diketiminate complex, [LFe(μ-Cl)Li(DME)] (1), where DME = 1,2-dimethoxyethane and L = Dippnacnac (β-diketiminate). While the reaction of 1 with t-BuPP(SiMe)Li yields [LFe(η-MeSiPP-t-Bu)] (2), that of 1 with equimolar amounts of i-PrPP(SiMe)Li, in DME, leads to [LFe(η-i-PrPPSiMe)] (3).

Spin Crossover in Fe(II) Complexes with N4S2 Coordination.

Reactions of Fe(II) precursors with the tetradentate ligand S,S'-bis(2-pyridylmethyl)-1,2-thioethane (bpte) and monodentate NCE(-) coligands afforded mononuclear complexes [Fe(bpte)(NCE)2] (1, E = S; 2, E = Se; 3, E = BH3) that exhibit temperature-induced spin crossover (SCO). As the ligand field strength increases from NCS(-) to NCSe(-) to NCBH3(-), the SCO shifts to higher temperatures. Complex 1 exhibits only a partial (15%) conversion from the high-spin (HS) to the low-spin (LS) state, with an onset around 100 K.

Facile Conversion of Red Phosphorus into Soluble Polyphosphide Anions by Reaction with Potassium Ethoxide.

Soluble polyphosphide anions were successfully generated in a number of organic solvents by the reaction between shelf-stable red phosphorus and potassium ethoxide. The species were identified by (31)P NMR spectroscopy in solution and by X-ray crystal-structure determination of (Bu4N)2P16 in the solid state. The reaction was scaled up to gram quantities by using a flow-chemistry process.

Properties of Prussian blue materials manifested in molecular complexes: observation of cyanide linkage isomerism and spin-crossover behavior in pentanuclear cyanide clusters.

Pentanuclear, cyanide-bridged clusters [M(tmphen)2]3[M'(CN)6]2 (M/M' = Zn/Cr (1), Zn/Fe (2), Fe/Fe (3), Fe/Co (4), and Fe/Cr (5); tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) were prepared by combining [M'III(CN)6]3- anions with mononuclear complexes of MII ions with two capping tmphen ligands. The clusters consist of a trigonal bipyramidal (TBP) core with three MII ions in the equatorial positions and two M'III ions in the axial positions. Compounds 1-4 are isostructural and crystallize in the monoclinic space group P21/c.

A charge-transfer-induced spin transition in a discrete complex: the role of extrinsic factors in stabilizing three electronic isomeric forms of a cyanide-bridged co/fe cluster.

A series of bimetallic, trigonal bipyramidal clusters of type {[Co(N-N)(2)](3)[Fe(CN)(6)](2)} are reported. The reaction of {Co(tmphen)(2)}(2+) with [Fe(CN)(6)](3)(-) in MeCN affords {[Co(tmphen)(2)](3)[Fe(CN)(6)](2)} (1). The cluster can exist in three different solid-state phases: a red crystalline phase, a blue solid phase obtained by exposure of the red crystals to moisture, and a red solid phase obtained by desolvation of the blue solid phase in vacuo.

A charge-transfer-induced spin transition in the discrete cyanide-bridged complex [[Co(tmphen)2]3[Fe(CN)6]2].

A charge-transfer-induced spin transition (CTIST) is observed in the discrete cyanide-bridged complex, {[Co(tmphen)2]3[Fe(CN)6]2}. Single-crystal X-ray diffraction, 57Fe Mössbauer spectroscopy, and magnetic susceptibility were used collectively to describe the oxidation states of the Co and Fe ions in this cluster as a function of temperature. This pentanuclear complex represents the first example of a CTIST at the discrete molecular level.