Structure and magnetic properties of (meso-tetraphenylporphinato)manganese(III) bis(dithiolato)nickelates

The crystal structures of [MnTPP]{Ni[S2C2H(CN)]2} [MnTPP = (meso-tetraphenylporphinato)manganese(III)] and [MnTPP]{Ni[S2C2(CN)2]2} have been determined. These salts possess trans-mu-coordination of S = 1/2 {Ni[S2C2H(CN)]2}*- and {Ni[S(2)C(2)(CN)(2)](2)}*- to Mn(III) and form parallel 1-D coordination polymer chains exhibiting nu(CN) at 2210 and 2200 and 2220 and 2212 cm(-1), respectively. The bis(dithiolato) monoanions are planar and bridge two cations with MnN distances of 2.339(16), and 2.394(3) A, respectively, which are comparable to related MnN distances observed for [MnTPP][TCNE].x(solvates). In addition, [MnTP'P]{Ni[S2C2(CN)2]2} {H2TP'P = meso-tetrakis[3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin] and [MnTP'P(OH2)]{Ni[S2C2(CN)2]2} were prepared. The latter forms isolated paramagnetic ions. The room-temperature values of chiT for 1-D [MnTPP]{Ni[S2C2H(CN)]2}, [MnTPP]{Ni[S2C2(CN)2]2}, and [MnTP'P]{Ni[S2C2(CN)2]2} are 2.55, 3.28, and 2.86 emu K/mol, respectively. Susceptibility (chi) measurements between 2 and 300 K reveal weak antiferromagnetic interactions with theta= -5.9 and -0.2 K for [MnTPP]{Ni[S(2)C(2)H(CN)](2)} and [MnTPP]{Ni[S2C2(CN)2]2}, respectively, and stronger antiferromagnetic coupling of -50 K for [MnTP'P]{Ni[S2C2(CN)2]2} from fits of chi(T) to the Curie-Weiss law. The 1-D intrachain coupling, J(intra), of [MnTPP]{Ni[S2C2H(CN)]2} and [MnTPP]{Ni[S2C2(CN)2]2} was determined from modeling chiT(T) by the Seiden expression (H = -2JSi.Sj) with J/kB = -8.00 K (-5.55 cm(-1); -0.65 meV) for [MnTPP]{Ni[S2C2H(CN)]2}, J/kB = -3.00 K (-2.08 cm(-1); -0.25 meV) for [MnTP'P]{Ni[S2C2(CN)2]2}, and J/kB = -122 K (-85 cm(-1)) for [MnTP'P]{Ni[S2C2(CN)2]2}. These observed negative J(intra)/kB values are indicative of antiferromagnetic coupling. These materials order as ferrimagnets at 5.5, 2.3, and 8.0 K, for [MnTPP]{Ni[S2C2H(CN)]2}, [MnTPP]{Ni[S2C2(CN)2]2}, and [MnTP'P]{Ni[S2C2(CN)2]2}, respectively, based upon the temperature at which maximum in the 10 Hz chi'(T) data occurs. [MnTP'P]{Ni[S2C2(CN)2]2} has a coercivity of 17,700 Oe and remanent magnetizations of 7250 emu Oe/mol at 2 K and 17 Oe and 850 emu Oe/mol at 5 K; hence, upon cooling it goes from being a soft magnet to being a very hard magnet.     

Molecular Structure of ortho-Fluoronitrobenzene Studied by Gas Electron Diffraction and Ab Initio MO Calculations

The molecular structure of ortho-fluoronitrobenzene (o-FNB) has been investigated by gas-phase electron diffraction and ab initio MO calculations. The geometrical parameters and force fields of o-FNB were calculated by ab initio and DFT methods. The obtained force fields were used to calculate vibrational amplitudes required as input parameters in an electron diffraction analysis. Within the experimental error limits, the geometrical parameters obtained from the gas-phase electron diffraction analysis are mostly in agreement with the results obtained from the ab initio calculations. The main results are: the molecular geometry of o-FNB is nonplanar with a dihedral angle about C–N of 38(3)°. The r _g (C–F) bond is shortened to 1.307(13) Å in comparison with r _g (C–F) = 1.356(4) Å in C₆H₅F.     

Functionalizations of [6]- and [7]helicenes at their most sterically hindered positions

Although the reactions of enol ethers of aryl methyl ketones with benzoquinone make it easy to prepare nonracemic helicenes that are substituted by hydroxyl groups at their 1,omega-positions, the hydroxyl groups fail to facilitate the introduction of electrophiles ortho to them. However, ethers of [6]- and [7]helicenols prepared in this way, seemingly because of the activation by the alkoxyl groups at the 6-positions, combine with electrophilic reagents to introduce bromines and acyl groups exactly into these positions. Moreover, these bromine and acyl groups can be transformed into other functional groups (including phosphine oxides and acetylenes), the ether functions adjacent to these functional groups can then be removed, and the phenols can be oxidized to quinone-acetals. An alternative way to introduce functional groups next to the phenols is to rearrange their phosphate esters. Two reactions that differentiate the ends of the helicenes are also described.     

Ammonium and caesium carbonate peroxosolvates: supramolecular networks formed by hydrogen bonds

Diammonium carbonate hydrogen peroxide monosolvate, 2NH₄⁺·CO₃²⁻·H₂O₂, (I), and dicaesium carbonate hydrogen peroxide trisolvate, 2Cs⁺·CO₃²⁻·3H₂O₂, (II), were crystallized from 98% hydrogen peroxide. In (I), the carbonate anions and peroxide solvent molecules are arranged on twofold axes. The peroxide molecules act as donors in only two hydrogen bonds with carbonate groups, forming chains along the a and c axes. In the structure of (II), there are three independent Cs⁺ ions, two of them residing on twofold axes, as are two of the four peroxide molecules, one of which is disordered. Both structures comprise complicated three‐dimensional hydrogen‐bonded networks.     

Phosphinohydrazines and phosphinohydrazides M(-N(R)-N(R)-PPh2)n of some transition and main group metals: synthesis and characterization: Rearrangement of Ph2P-NR-NR- ligands into aminoiminophosphorane, RNPPh2-NR-, and related chemistry

The reactions of phosphinohydrazines ArNH-N(Ar)-PPh₂ {Ar = Ph (2a), p-Bu^t-C₆H₄- (2b)} with metal silylamides M[N(SiMe₃)₂]_n, {M = Fe(II), Fe(III), Co(II), Ni(I), Cu(I)} or the reactions of lithium salts ArN(Li)-N(Ar)-PPh₂ with metal halides (GeCl₂, ZnCl₂, FeBr₂, CoCl₂, NiBr₂, CrCl₃, MnCl₂) are strongly dependent on nature of a metal and its ligand environment.Early transition metals or non-transition metals form stable phosphinohydrazides M[N(Ar)N(Ar)PPh₂]_n {M = Li, Zn, Ge(II), Mn(II), Cr(III), Fe(II)}.Starting ligand 2a and germylene Ge(NPhNPhPPh₂)₂ (7) were characterized by X-ray analysis.Germanium is coordinated additionally with a phosphorus atom of one of the diphenylphosphine groups.The distance Ge?P was found to be 2.563(1) Å.This coordination leads to an appreciable increase in a pyramidal geometry of nitrogen atoms relatively to a non-coordinated fragment.Late transition metals (Co, Ni, Cu) and metals with enhanced oxidation state (Fe³⁺) cause transformation of a phosphinohydrazide ligand.For Co(II), Ni(II), Fe(III) this leads quantitatively to aminoiminophosphoranates M(NAr-PPh₂NAr)_n.Complex Co[N(C₆H₄Bu^t)-PPh₂N-C₆H₄Bu^t]₂ (11) was characterized by X-ray analysis.Nickel(I) silylamide, (Ph₃P)₂NiN(SiMe₃)₂, being reacted with 2a yields azobenzene complex, (Ph₃P)₂Ni(PhNNPh), while copper(I) silylamide originally forms (PhNH-NPh-PPh₂)₂CuN(SiMe₃)₂ (18).Heating of the latter in toluene solution yields insoluble copper(I) diphenylphosphide, azobenzene, 2a and hexamethyldisilazane.The reaction of hydrazobenzene with Ph₂PCl (1:1) in methylene chloride for three days gives aminoiminophosphorane dihydrochloride[PhNH-PPh₂NPh] · 2HCl (3) in quantitative yield.     

Binuclear copper(I) macrocycles synthesized via the weak-link approach

The weak-link approach has been employed to synthesize a series of bimetallic Cu(I) macrocycles in high yield. Addition of phosphinoalkylether or -thioether ligands to [Cu(MeCN)4]PF6 produces "condensed" intermediates, [mu-(1,4-(PPh2CH2CH2X)2Y)2Cu2][PF6]2 (X = S, O; Y = C6H4, C6F4), containing strong P-Cu bonds and weaker O-Cu or S-Cu bonds. The weak bonds of these intermediates can be cleaved through ligand substitution reactions to generate macrocyclic structures, [mu-(1,4-(PPh2CH2CH2X)2Y)2(Z)nCu2][PF6]2 (X = S, O; Y = C6H4, C6F4; Z = pyridine, acetonitrile, diimines, isocyanide) in nearly quantitative yields. The incorporation of tetrahedral Cu(I) metal centers into these macrocycles provides a pathway to complexes that differ from analogous d8 square planar macrocycles generated via this approach in their increased air stability, small molecule reactivity, and ability to form multiple structural isomers. Solid-state structures, as determined by single-crystal X-ray diffraction studies, are presented for condensed intermediates and an open macrocycle     

Synthesis and magnetic properties of wheel-shaped [Mn12] and [Fe6] complexes

The reactions of the ligands N-methyldiethanol amine and N-ethyldiethanol amine (abbreviated H(2)mdea and H(2)edea, respectively) with [Mn(12)O(12)(O(2)CCH(3))(16)(H(2)O)(4)] yield novel dodecanuclear wheel-shaped products. The capability of the ligands H(2)mdea and H(2)edea to support wheel structures in metals other than Mn is demonstrated with the crystal structure of a new hexanuclear ferric wheel.     

A general bifunctional catalyst for the anti-Markovnikov hydration of terminal alkynes to aldehydes gives enzyme-like rate and selectivity enhancements

A new, bifunctional catalyst for anti-Markovnikov hydration of terminal alkynes to aldehydes (6) allows practical room-temperature hydration of alkyl-substituted alkynes. Other outstanding features include near-quantitative aldehyde yields from both alkyl- and aryl-substituted alkynes and wide functional group tolerance. The uncatalyzed rate of alkyne hydration is measured for the first time, showing the enzyme-like rate and selectivity enhancements of aldehyde formation by 6. For aldehyde formation, an uncatalyzed rate <1 x 10-10 mol h-1 means a half-life >600 000 years. The catalyzed rate is up to 23.8 mol (mol 6)-1 h-1 and 10 000:1 ratio in favor of aldehyde. Changes in rate and selectivity induced by 6 are thus >2.4 x 1011 and 300 000, respectively.     

Potassium peroxostannate nanoparticles

Stable amorphous potassium peroxostannate nanoparticles with controlled sizes (10–100 nm), morphology, and hydrogen peroxide percentage (19–30 wt %) were synthesized for the first time. The compounds were characterized by vibrational spectroscopy, ¹¹⁹Sn MAS NMR spectroscopy, powder X-ray diffraction, and thermogravimetry. These characteristics were compared to those for K₂Sn(OH)₆ and K₂Sn(OOH)₆. Potassium peroxostannate particles are mainly built of peroxo-bridged polymer chains. The particles are stable when stored in a dry state or suspended in nonaqueous solvents; in contact with water, they release hydrogen peroxide.     

Strategic Capture of the {Nb7} Polyoxometalate

Group V Nb-polyoxometalate (Nb-POM) chemistry generally lacks the elegant pH-controlled speciation exhibited by group VI (Mo, W) POM chemistry. Here three Nb-POM clusters were isolated and structurally characterized; [Nb₁₄O₄₀(O₂)₂H₃]¹⁴⁻, [((UO₂)(H₂O))₃Nb₄₆(UO₂)₂O₁₃₆H₈(H₂O)₄]²⁴⁻, and [(Nb₇O₂₂H₂)₄(UO₂)₇(H₂O)₆]²²⁻, that effectively capture the aqueous Nb-POM species from pH 7 to pH 10. These Nb-POMs illustrate a reaction pathway for control over speciation that is driven by counter-cations (Li⁺) rather than pH. The two reported heterometallic POMs (with UO₂²⁺ moieties) are stabilized by replacing labile H₂O/HO−Nb=O with very stable O=U=O. The third isolated Nb-POM features cis-yl-oxos, prior observed only in group VI POM chemistry. Moreover, with these actinide-heterometal contributions to the burgeoning Nb-POM family, it now transects all major metal groups of the periodic table.