Spectroelectrochemical studies of magnesium deposition by in situ FTIR spectroscopy

Magnesium can be reversibly deposited electrochemically from solutions of ethereal solvents, with Grignard reagents (RMgX) or complexes of Mg(AX_3−nR_n+1)₂ stoichiometry as the electrolytes (A=Al, B; X=Cl, Br; R=alkyl or aryl groups). These processes are far from being simple reactions of the Mg/Mg⁺⁺ couple, since the above electrolytes in solutions have complicated structures in which the ether molecules play an important stabilization role. In addition, Mg deposition processes in all of the above solutions are accompanied by adsorption phenomena. The surface chemistry of magnesium electrodes was studied in situ by FTIR spectroscopy, using an internal reflectance mode. The electrolyte solutions studied included tetrahydrofuran (THF) solutions of the RMgX electrolytes (R=butyl, ethyl, methyl benzyl, and X=Cl, Br); Mg(AlCl₂BuEt)₂; Mg(AlCl₃Bu)₂ and Mg(BPh₂Bu₂); Bu, Et, Ph=butyl, ethyl and phenyl groups, respectively. It was clear from these studies that Mg electrodes do not develop stable passivation in these solutions (i.e. formation of surface films). The nature of the adsorbed species in the above systems is discussed, based on the spectral results.     

Darstellung und spektroskopische Charakterisierung von Di(halogeno)phthalocyaninato(1–)rhodium(III), [RhX2Pc1−] (X = Cl,Br, I)

Synthesis and Spectroscopical Characterization of Di(halo)phthalocyaninato(1–)rhodium(III), [RhX₂Pc^1?] (X = Cl, Br, I) Bronze-coloured di(halo)phthalocyaninato(1–)-rhodium(III), [RhX₂Pc^1?] (X = Cl, Br) and [RhI₂Pc^1?] · I₂ is prepared by oxidation of (ⁿBu₄N)[RhX₂Pc^2?] with the corresponding halogene. Irrespective of the halo ligands, two irreversible electrode reactions due to the first ringreduction (E_R = ?0,90 V) and ringoxidation (E_O = 0,82 V) are present in the cyclovoltammogram of (ⁿBu₄N)[RhX₂Pc^2?]. The optical spectra show typical absorptions of the Pc^1?-ligand at 14.0 kK and 19.1 kK. Characteristic vibrational bands are at 1 366/1 449 cm^?1 (i. r.) and 569/1 132/1 180/1 600 cm^?1 (resonance Raman (r. r.)). The antisym. (Rh? X)-stretching vibration is observed at 294 cm^?1 (X = Cl), 240 cm^?4 (Br) and 200 cm^?1 (I). Only the sym. (Rh? I)-stretching vibration at 133 cm^?1 is r. r. enhanced together with a strong line at 170 cm^?1, which is assigned to the (I? I)-stretching vibration of the incorporated iodine molecule. Both modes show overtones and combinationbands.     

Kinetische und Gleichgewichtsuntersuchungen zur Aquotisierung und Halogenid-Anation an Halogeno-Aquo-Komplexen von Osmium(IV)

Kinetic and Equilibrium Studies on Aquation and Halide-Anation of Osmium(IV)- Halogeno-Aquo Complexes Complexes of type [OsI₅X]^2? (X = Cl, Br, I) undergo hydrolysis in acidic, aqueous solutions already at room temperature according to [OsI₅X]^2? + H₂O ? [OsI₅(H₂O)]^? + X^?. Rate constants of aquation and anation reactions as well as equilibrium constants are determined by spectrophotometrical measurements. The kinetic and equilibrium experimental results are giving similar thermodynamic data. Kinetic stability increases from I over Br to Cl whereas the thermodynamic stability decreases in the same order. The monoaquo complex is less stable than the hexahalo complexes by 2 kcal/mol, and is present as an intermediate product in the halogen exchange reactions carried out in dilute solutions.     

Die Quecksilber(II)-Ionen induzierte Hydrolyse gemischter Hexahalogenoosmate(IV)

Mercury(II)-Induced Hydrolysis of Mixed Hexahalo-Osmates(IV) The strong hydrolytic activity of Hg²⁺ ions on complexes [OsX_nI_6?n]^2?, X = Cl or Br; n = 1 – 5, is due to electrophilic attack at the I ligands. Small amounts of Hg²⁺ remove only one I. The very stable [HgI]⁺ and [HgI₂] are formed along with the corresponding pentahalo-monaquo-osmates(IV). In cis-[OsCl₄I₂]^2? and fac-[OsCl₃I₃]^2? ligands rearrange during hydrolysis giving the thermodynamically favoured I? Os? H₂O axis. Other mono- and bivalent cations have only a slight catalytic effect on the aquation, increasing with the size from Mg²⁺ to Ba²⁺.     

Magnesiumphthalocyanine: Darstellung und Eigenschaften von Halogenophthalocyaninatomagnesat, [Mg(X)Pc2−]− (X = F,Cl, Br); Kristallstruktur von Bis(triphenylphosphin)iminiumchloro(phthalocyaninato)magnesat-Aceton-Solvat

Magnesium Phthalocyanines: Synthesis and Properties of Halophthalocyaninatomagnesate, [Mg(X)Pc^2?]^? (X = F, Cl, Br); Crystal Structure of Bis(triphenylphosphine)iminiumchloro-(phthalocyaninato)magnesate Acetone Solvate Magnesium phthalocyanine reacts with excess tetra(n-butyl)ammonium- or bis(triphenylphosphine)iminiumhalide ((ⁿBu₄N)X or (PNP)X; X = F, Cl, Br) yielding halophthalocyaninatomagnesate ([Mg(X)Pc^2?]^?; X = F, Cl, Br), which crystallizes in part as a scarcely soluble (ⁿBu₄N) or (PNP) complex-salt. Single-crystal X-ray diffraction analysis of ^b(PNP)[Mg(Cl)Pc^2?] · CH₃COCH₃ reveals that the Mg atom has a tetragonal pyramidal coordination geometry with the Mg atom displaced out of the center (Ct) of the inner nitrogen atoms (N_iso) of the nonplanar Pc ligand toward the Cl atom (d(Mg? Ct) = 0.572(3) Å; d(Mg? Cl) = 2.367(2) Å). The average Mg? N_iso distance is 2.058 Å. Pairs of partially overlapping anions are present. The cation adopts a bent conformation (^b(PNP)⁺: d(P1? N(K)) = 1.568(3) Å; d(P2? N(K)) = 1.587(3) Å; ?(P1? N(K)? P2) = 141.3(2)°). Electrochemical and spectroscopic properties are discussed.     

Preparation,infrared, Raman and N.M.R. spectra of N,N′-Diethylthiourea complexes with zinc(II), cadmium(II) and mercury(II) halides

Several complexes of N,N′-diethylthiourea (Dietu) with zinc(II), cadmium(II) and mercury(II) halides were prepared and characterized by i.r. (4000–60 cm^?1), raman (400–60 cm^?1), in the solid state and n.m.r. and conductometric methods in solution. The complexes Zn(Dietu)₂X₂, Cd(Dietu)₂X₂ (X ? Cl, Br, I) and Hg(Dietu)₂X₂ (X ? Br, I) are tetrahedral species in which intramolecular ? NH …? X interactions have been observed. The 1:1 mercury(II) complexes, Hg(Dietu)X₂ (X ? Cl, Br), appear to have a dimeric tetrahedral halide-bridged structure in the solid state. In all these complexes N,N′-diethylthiourea is sulphur-bonded to the metal.     

Osmium(II)-Phthalocyanine: Darstellung und Eigenschaften von Di(acido)phthalocyaninatoosmaten(II)

Osmium(II) Phthalocyanines: Preparation and Properties of Di(acido)phthalocyaninatoosmates(II) “H[Os(X)₂Pc^2?]” (X = Br, Cl) reacts in basic medium or in the melt with (ⁿBu₄N)X forming less stable, diamagnetic, darkgreen (ⁿBu₄N)₂[Os(X)₂Pc^2?]. Similar dicyano and diimidazolido(Im) complexes are formed by the reaction of “H[Os(Cl)₂Pc^2?]” with excess ligand in the presence of [BH₄]^?. The cyclic voltammograms show up to three quasireversible redoxprocesses: E_1/2(I) = 0.13 V (X = CN), ?0.03 V (Im), ?0.13 V (Br) resp. ?0.18 V (Cl) is metal directed (Os^II/III), E_1/2(II) = 0.69 V (Cl), 0.71 V (Br), 0.83 V (CN), 1.02 V (Im) is ligand directed (Pc^2?/?) and E_1/2(III) = 1.17 V (Cl) resp. 1.23 V (Br) is again metal directed (Os^III/IV). Between the typical “B” (～16.2 kK) and “Q” (～29.4 kK), “N regions” (～34.1 kK) up to seven strong “extra bands” of the phthalocyanine dianion (Pc^2?) are observed in the uv-vis spectrum. Within the row CN > Im > Br > Cl, most of the bands are shifted slightly, the “extra bands” considerably more to lower energy in correlation with E_1/2(I). The vibrational spectra are typical for the Pc^2? ligand with D_4h symmetry. M.i.r. bands at 514, 909, 1 173 and 1 331 cm^?1 are specific for hexa-coordinated low spin Os^II phthalocyanines. In the resonance Raman (r.r.) spectra polarized, depolarized or anomalously polarized deformation and stretching vibrations of the Pc^2? ligand will be selectively enhanced, if the excitation frequency coincides with “extra bands”. With excitation at ～19.5 kK the intensity of the symmetrical Os? X stretching vibration at 295 cm^?1 (X = Cl), 252 cm^?1 (X = Im) and 181 cm^?1 (X = Br) is r.r. enhanced, too. The asymmetrical Os? X stretching vibration is observed in the f.i.r. spectrum at 345 cm^?1 (X = CN), 274 cm^?1 (X = Cl), 261 cm^?1 (X = Im) and 200 cm^?1 (X = Br).     

Solid-state vibrational spectroscopy: Part 11. An infrared and raman vibrational spectroscopic study of metal(II) halide aniline complexes

Infrared (4000?200 cm^?1) and Raman (3500?50 cm^?1) spectra are reported for metal(II) halide aniline complexes of the following stoichiometries: (MX₂an₂) (M  Co, Ni or Hg, X  Cl; M  Mn, X  Cl or Br; M  Zn or Cd, X  Cl, Br or I); (MX₂an₃) (M  Mn, X  Cl or Br; M  Ni, X  Cl); (CdCl₂an) and an assignment is proposed for all the observed bands. Low-temperature (83 K) IR spectra are also reported and it is noted that whilst the aniline ring and CH mode values are virtually insensitive to temperature, the NH₂ rocking and metal-ligand stretching mode values increase with decreasing temperature, whilst the NH₂ stretching mode values decrease with decreasing temperature.     

CrIII-Phthalocyaninate: Darstellung und spektroskopische Eigenschaften von Di(halogeno)phthalocyaninatochromaten(III)

Cr^III Phthalocyaninates: Synthesis and Spectroscopical Properties of Di(halo)phthalocyaninato(2 –)chromates(III) [Cr(H₂O)₂Pc^2?]⁺ reacts in acetone with (ⁿBu₄N)X to yield less soluble tetra(n-butyl)ammonium di(halo)phthalocyaninato(2 –)chromate(III), (ⁿBu₄N)[Cr(X)₂Pc^2?] (X = F, Cl, Br, I). In the differential pulse voltammograms the first ring oxidation is observed at 0,80 V, the ring reduction at ?1,48 V and the metal reduction (Cr(III)/Cr(II)) at ?0,80 V (averaged potentials). The last is followed by a partial dissociation of one of the halo ligands. In the UV-VIS-NIR spectra there are three weakly absorbing spin-allowed trip-quarter(TQ) transitions (TQ1 (8,4) < TQ2 (11,5) < TQ3 (20,6); averaged values (av) in 10³ cm^?1), a (Pc + X)-CrCT transition (31,3; av in 10³ cm^?1) and the characteristic π-π* transitions of the Pc^2? ligand (B (14,5) < Q₁ (24,5) < Q₂ (29,2) < N (36,0) < L (41,0); av in 10³ cm^?1). Q₁ and (Pc + X)-CrCT depend strongly on the halo ligands. Prominent luminescence spectra are obtained by excitation within the TQ1 region, in which the spin-forbidden trip-sextet transition (8330 (X = F), 7680 (Cl), 7460 (Br) 7450 cm^?1 (I)) dominates at low temperatures (T < 50 K). The vibrational spectra are discussed. In coincidence of the excitation lines with TQ3, v_s(Cr? X) at 458 (X = F) < 246 (Cl) < 157 (Br) < 107 cm^?1 ( I ) is selectively resonance Raman enhanced. v_as(Cr? X) is observed in the FIR spectrum at 522 (X = F) < 283/326 (Cl) < 227 (Br) < 205 cm^?1 ( I ).     

Photophysical Analysis of 1,10‐Phenanthroline‐Embedded Porphyrin Analogues and Their Magnesium(II) Complexes

The synthesis, characterization, photophysical properties, and theoretical analysis of a series of tetraaza porphyrin analogues ( H? Pn : n=1–4) containing a dipyrrin subunit and an embedded 1,10‐phenanthroline subunit are described. The meso‐phenyl‐substituted derivative ( H? P1 ) interacts with a Mg²⁺ salt (e.g., MgCl₂, MgBr₂, MgI₂, Mg(ClO₄)₂, and Mg(OAc)₂) in MeCN solution, thereby giving rise to a cation‐dependent red‐shift in both the absorbance‐ and emission maxima. In this system, as well as in the other H? Pn porphyrin analogues used in this study, the four nitrogen atoms of the ligand interact with the bound magnesium cation to form Mg²⁺–dipyrrin–phenanthroline complexes of the general structure MgX? Pn (X=counteranion). Both single‐crystal X‐ray diffraction analysis of the corresponding zinc‐chloride derivative ( ZnCl? P1 ) and fluorescence spectroscopy of the Mg‐adducts that are formed from various metal salts provide support for the conclusion that, in complexes such as MgCl? P1 , a distorted square‐pyramidal geometry persists about the metal cation wherein a chloride anion acts as an axial counteranion. Several analogues ( H? Pn ) that contain electron‐donating and/or electron‐withdrawing dipyrrin moieties were prepared in an effort to understand the structure–property relationships and the photophysical attributes of these Mg–dipyrrin complexes. Analysis of various MgX? Pn (X=anion) systems revealed significant substitution effects on their chemical, electrochemical, and photophysical properties, as well as on the Mg²⁺‐cation affinities. The fluorescence properties of MgCl? Pn reflected the effect of donor‐excited photoinduced electron transfer (d‐PET) processes from the dipyrrin subunit (as a donor site) to the 1,10‐phenanthroline acceptor subunit. The proposed d‐PET process was analyzed by electron paramagnetic resonance (EPR) spectroscopy and by femtosecond transient absorption (TA) spectroscopy, as well as by theoretical DFT calculations. Taken together, these studies provide support for the suggestion that a radical species is produced as the result of an intramolecular charge‐transfer process, following photoexcitation. These photophysical effects, combined with a mixed dipyrrin–phenanthroline structure that is capable of effective Mg²⁺‐cation complexation, lead us to suggest that porphyrin‐inspired systems, such as H? Pn , have a role to play as magnesium‐cation sensors.     

Well‐Defined Molecular Magnesium Hydride Clusters: Relationship between Size and Hydrogen‐Elimination Temperature

A new tetranuclear magnesium hydride cluster, [{ NN ‐(MgH)₂}₂], which was based on a N? N‐coupled bis‐β‐diketiminate ligand ( NN ^2?), was obtained from the reaction of [{ NN ‐(MgnBu)₂}₂] with PhSiH₃. Its crystal structure reveals an almost‐tetrahedral arrangement of Mg atoms and two different sets of hydride ions, which give rise to a coupling in the NMR spectrum (J=8.5 Hz). To shed light on the relationship between the cluster size and H₂ release, the thermal decomposition of [{ NN ‐(MgH)₂}₂] and two closely related systems that were based on similar ligands, that is, an octanuclear magnesium hydride cluster and a dimeric magnesium hydride species, have been investigated in detail. A lowering of the H₂‐desorption temperature with decreasing cluster size is observed, in line with previously reported theoretical predictions on (MgH₂)_n model systems. Deuterium‐labeling studies further demonstrate that the released H₂ solely originates from the oxidative coupling of two hydride ligands and not from other hydrogen sources, such as the β‐diketiminate ligands. Analysis of the DFT‐computed electron density in [{ NN ‐(MgH)₂}₂] reveals a counterintuitive interaction between two formally closed‐shell H^? ligands that are separated by 3.106 Å. This weak interaction could play an important role in H₂ desorption. Although the molecular product after H₂ release could not be characterized experimentally, DFT calculations on the proposed decomposition product, that is, the low‐valence tetranuclear Mg(I) cluster [( NN ‐Mg₂)₂], predict a structure with two almost‐parallel, localized Mg? Mg bonds. As in a previously reported β‐diketiminate Mg^I dimer, the Mg? Mg bond is not characterized by a bond critical point, but instead displays a local maximum of electron density midway between the atoms, that is, a non‐nuclear attractor (NNA). Interestingly, both of the NNAs in [( NN ‐Mg₂)₂] are connected through a bond path that suggests that there is bonding between all four Mg^I atoms.     

Über Cyanatverbindungen und deren reaktives Verhalten. XLIII. Darstellung und Eigenschaften von Organomagnesiumthiocyanat- und -selenocyanat-Verbindungen

Cyanates and their Reactive Behaviour. XLIII. Synthesis and Properties of Organomagnesium Thiocyanate and Selenocyanate Compounds RMgX and RMgX · 2 L compounds react with KYCN in tetrahydrofurane via halide pseudohalide exchange reactions to give RMgNCY solutions (R = alkyl or aryl groups; X ? Cl, Br, I; L ? O-donors; Y ? S, Se), from which compounds of the type RMgNCY · 2 THF have been isolated in a crystalline form. The prepared compounds are characterized by analytical data, IR absorption spectra, concentration dependent conductivity measurements and reactive behaviour in relation to classic Grignard reagents.     

Structure and Reaction Chemistry of Magnesium Organocuprates Derived from Magnesiacyclopentadienes and Copper(I) Salts

The chemistry of magnesium organocuprates, including their synthesis, structures, and reactions, remains underexplored. In this work, by taking advantage of the high reactivity and ready availability of magnesiacyclopentadienes, a series of magnesiacyclopentadiene‐based organocuprates were synthesized and structurally characterized. A variety of CuX salts (X=Cl, Br, I, or alkynyl) were successfully applied to react with magnesiacyclopentadienes. Besides CuX salts, AgX salts (X=Cl, alkynyl) also undergwent the above reaction to afford the corresponding magnesium organoargentates. Single‐crystal X‐ray structural analysis and DFT calculations of these butadienyl magnesium organocuprates revealed unique structural characteristics and bonding modes. These results are also very useful to understand the transmetalation process, since the product can be viewed as the resting‐state intermediate of a transmetalation reaction between organomagnesium compounds and coinage‐metal salts. Preliminary information on the reaction chemistry of these magnesium organocuprates is provided by their reactions with allyl bromide, benzoyl chloride, and CO₂.     

Darstellung und Schwingungsspektren von trans-[Pt(acac)2X2] (X  Cl,Br, I,SCN, SeCN,N3)

Preparation and Vibrational Spectra of trans-[Pt(acac)₂X₂] (X ? Cl, Br, I, SCN, SeCN, N₃) By electrolytical oxidation of [Pt(acac)₂] in presence of chloride or bromide, dissolved in dichlormethane, trans-[Pt(acac)₂X₂], X ? Cl, Br, are formed. On treatment of trans-[Pt(acac)₂I₂] with silver pseudohalides trans-[Pt(acac)₂X₂], X ? SCN, SeCN, N₃, are obtained. Beside the nearly persistent bands of coordinated acetylacetonate in the Raman spectra the intensive and sharp symmetric, in the IR spectra the corresponding antisymmetric stretching vibration of the X? Pt? X axis is observed. The observance of the rule of mutual exclusion proves the complexes to belong to point group D_2h. From the resonance Raman spectrum of trans-[Pt(acac)₂I₂] for v_s (Pt? I), A_g, the harmonic frequency ω₁ = 142.45 cm^?1 and the inharmonicity constant x₁₁ = 0.48 cm^?1 is calculated. In the Raman spectrum of trans-[Pt(acac)₂Cl₂] v_s (Pt? Cl) is splitted by the isotops ³⁵Cl/³⁷Cl into the triplet 340, 335, 330 cm^?1 giving the force constant f_PtCl = 2.01 N/cm.     

1,2-Bis-triphenylphosphoranylidenamino-äthan als zweizähniger Ligand in Übergangsmetallkomplexen

1,2-Bis-(triphenylphosphorane-ylidene-amino)ethane as a Bidentate Ligand in Transition Metal Complexes The reactions of Ph₃P?N? C₂H₄? N?PPh₃ with transition metal halogenides MX₂ give according to eq. (1) novel bisiminophosphorane complexes of the type M(Ph₃PNC₂H₄ NPPh₃)X₂ (M ? Co, X ? Cl 1 a , Br 1 b , J 1 c ; M ? Ni, X ? Cl 2 a , Br 2 b , J 2 c , M ? Hg, X ? Cl 3 , M ? Cd, X ? Cl 4 ). The preparation, properties, magnetic moments, and structure of the new complexes are reported     

An η3‐Bound Allyl Ligand on Magnesium in a Mechanochemically Generated Mg/K Allyl Complex

Milling two equivalents of K[1,3‐(SiMe₃)₂C₃H₃] (=K[A′]) with MgX₂ (X=Cl, Br) produces the allyl complex [K₂MgA′₄] ( 1 ). Crystals grown from toluene are of the solvated species [((η⁶‐tol)K)₂MgA′₄] ([ 1 ?2(tol)]), a trimetallic monomer with both bridging and terminal (η¹) allyl ligands. When recrystallized from hexanes, the unsolvated 1 forms a 2D coordination polymer, in which the Mg is surrounded by three allyl ligands. The C?C bond lengths differ by only 0.028 Å, indicating virtually complete electron delocalization. This is an unprecedented coordination mode for an allyl ligand bound to Mg. DFT calculations indicate that in isolation, an η³‐allyl configuration on Mg is energetically preferred over the η¹‐ (σ‐bonded) arrangement, but the Mg must be in a low coordination environment for it to be experimentally realized. Methyl methacrylate is effectively polymerized by 1 , with activities that are comparable to K[A′] and greater than the homometallic magnesium complex [{MgA′₂}₂].     

Magnesium–halobenzene bonding: mapping the halogen sigma-hole with a Lewis-acidic complex

Complexes of the Lewis base-free cations (^MeBDI)Mg⁺ and (^tBuBDI)Mg⁺ with Ph–X ligands (X = F, Cl, Br, I) have been studied (^MeBDI = HC[C(Me)N-DIPP]₂ and ^tBuBDI = HC[C(tBu)N-DIPP]₂; DIPP = 2,6-diisopropylphenyl). For the smaller β-diketiminate ligand (^MeBDI) only complexes with PhF could be isolated. Heavier Ph–X ligands could not compete with bonding of Mg to the weakly coordinating anion B(C₆F₅)₄⁻. For the cations with the bulkier ^tBuBDI ligand, the full series of halobenzene complexes was structurally characterized. Crystal structures show that the Mg⋯X–Ph angle strongly decreases with the size of X: F 139.1°, Cl 101.4°, Br 97.7°, I 95.1°. This trend, which is supported by DFT calculations, can be explained with the σ-hole which increases from F to I. Charge calculation and Atoms-In-Molecules analyses show that Mg⋯F–Ph bonding originates from electrostatic attraction between Mg²⁺ and the very polar C^δ+–F^δ− bond. For the heavier halobenzenes, polarization of the halogen atom becomes increasingly important (Cl < Br < I). Complexation with Mg leads in all cases to significant Ph–X bond activation and elongation. This unusual coordination of halogenated species to early main group metals is therefore relevant to C–X bond breaking.

Complexes of a highly Lewis acidic Mg cation and the full series of Ph–X (X = F, Cl, Br, I) have been structurally characterized. The Mg⋯X–Ph angle decreases with halogen size on account of the growing halogen σ-hole.     

Ruthenium(III)-Phthalocyanine: Darstelllung und Eigenschaften von Di(halogeno)phthalocyaninato(1−)ruthenium(III), [Ru(X)2Pc] (X = Cl,Br, I)

Ruthenium(III) Phthalocyanines: Synthesis and Properties of Di(halo)phthalocyaninato(1?)ruthenium(III) Di(halo)phthalocyaninato(1?)ruthenium(III), [Ru(X)₂Pc^?] (X = Cl, Br, I) is prepared by oxidation of [Ru(X)₂Pc^2?]^? (Cl, Br, OH) with halogene in dichloromethane. The magnetic moment of [Ru(X)₂Pc^?] is 2,48 μ_B (X = Cl) resp. 2,56 μ_B (X = Br) in accordance with a systeme of two independent spins (low spin Ru^III and Pc^?: S = 1/2). The optical spectra of the red violet solution of [Ru(X)₂Pc^?] (Cl, Br) are typical for the Pc^? ligand with the “B” at 13.5 kK, “Q₁” at 19.3 kK and “Q₂ region” at 31.9 kK. Sytematic spectral changes within the iron group are discussed. The presence of the Pc^? ligand is confirmed by the vibrational spectra, too. Characteristic are the metal dependent bands in the m.i.r. spectra at 1 352 and 1 458 cm^?1 and the strong Raman line at 1 600 cm^?1. The antisymmetric Ru? X stretch (v_as(Ru? X)) is observed at 189 cm^?1 (X = I) resp. 234 cm^?1 (X = Br). There are two interdependent bands at 295 and 327 cm^?1 in the region expected for v_as(Ru? Cl) attributed to strong interaction of v_as(Ru? Cl) with an out-of-plane Pc^? tilting mode of the same irreducible representation. Only the symmetric Ru? Br stretch at 183 cm^?1 is selectively enhanced in the resonance-Raman(RR) spectra. The Raman line at 168 cm^?1 of the diiodo complex is assigned to loosely bound iodine. The broad band at 978 cm^?1 in the RR spectra of the dichloro complex is due to an intraconfigurational transition within the electronic ground state of low spin Ru^III split by spin orbit coupling.     

Magnesocene‐Based Electrolytes: A New Class of Electrolytes for Magnesium Batteries

Unlike ferrocene, bis(η⁵‐cyclopentadienyl)magnesium (magnesocene, MgCp₂) is slightly dissociated in solvents, such as ethers, resulting in electrolyte solutions with low conductivity. MgCp₂/tetrahydrofuran solutions make possible reversible magnesium plating and stripping with low over‐potentials for many cycles. The Mg deposits appear with a cauliflower‐like morphology. IR and NMR spectroscopy confirm that the electrolyte is stable and not decomposed during prolonged cycling. The anodic stability limit is in the range of 1.5 V (at platinum) and 1.8 V versus Mg/Mg²⁺ (at stainless steel), which may be sufficient for low‐voltage cathode materials. MgCp₂ is a first example of a completely new class of halide‐free electrolytes, which may open up a new research direction for future magnesium metal and magnesium‐ion batteries.     

Diverse Reactivity of a Ca(I) Synthon

Low-valent Mg^I complexes like (BDI)Mg−Mg(BDI) have found wide-spread application as specialty reducing agents (BDI=β-diketiminate). Also their redox reactivity was extensively investigated. In contrast, attempts to isolate similar Ca^I complexes led to reduction of the aromatic solvents or N₂. Complex (^DIPePBDI)Ca(μ₆,μ₆-C₆H₆)Ca(^DIPePBDI) ( VIII ) should be regarded a Ca^II complex with a bridging C₆H₆²⁻ dianion (^DIPePBDI=HC[C(Me)N-DIPeP]₂, DIPeP=2,6-C(H)Et₂-phenyl). It can react as a Ca^I synthon by releasing benzene and two electrons. Herein we describe the reactivity of VIII with benzene, biphenyl, naphthalene, anthracene, COT, Ph₃SiCl, PhSiH₃, a (BDI)AlI₂ complex, H₂, PhX (X=F, Cl, Br, I), tBuOH and tBuCH₂I. The C₆H₆²⁻ dianion in VIII can react as a 2e⁻ source, a nucleophile or a Brønsted base. In some cases radical reactivity cannot be excluded. Crystal structures of (^DIPePBDI)Ca(μ₈,μ₈-COT)Ca(^DIPePBDI) ( 1 ) and [(^DIPePBDI)CaX ⋅ (THF)]₂ (X=F, Cl, Br, I) ( 2 – 5 ) are described.