Crystallographic report: Crystal structure of bis(2,4,6‐tri‐tert‐butylphenolato‐O) bis(tetrahydrofuran‐O) samarium (N,N‐η2‐azobenzene) diethyl ether solvate

Reaction of divalent Sm(OAr)₂(THF)₃ (Ar = C₆H₂‐tert‐Bu₃‐2,4,6; THF = tetrahydrofuran) with one equivalent of azobenzene in THF and crystallization of the product in diethyl ether afforded the title complex (ArO)₂(THF)₂Sm(η²‐N₂Ph₂)·Et₂O in good yield. In the complex, the N? N bond length for the azobenzene species is lengthened. The two Sm? N bonds are equivalent, and their bond lengths are intermediate between the donor bond and the single bond. Copyright © 2005 John Wiley & Sons, Ltd.     

Transfer hydrogenation of ketones catalyzed by nickel complexes bearing an NHC [CNN] pincer ligand

Four NHC [CNN] pincer nickel (II) complexes, [^iPrCNN (CH₂)₄‐Ni‐Br] ( 5a ), [^nBuCNN (CH₂)₄‐Ni‐Br] ( 5b ), [^iPrCNN (Me)₂‐Ni‐Br] ( 6a ) and [^nBuCNN (Me)₂‐Ni‐Br] ( 6b ), bearing unsymmetrical [C (carbene)N (amino)N (amine)] ligands were synthesized by the reactions of [CNN] pincer ligand precursors 4 with Ni (DME)Cl₂ in the presence of Et₃N. Complexes 5a and 5b are new and were completely characterized. The transfer hydrogenation of ketones catalyzed by the four pincer nickel complexes were explored. Complexes 5a and 6a have better catalytic activity than 5b and 6b . With a combination of NaO^tBu/ⁱPrOH/80 °C and 2% catalyst loading of 5a , 77–98% yields of aromatic alcohols could be obtained.     

Ruthenium(II)-Phthalocyaninate(2–): Darstellung und Eigenschaften von Acido(carbonyl)phthalocyaninato(2–)ruthenat(II), [Ru(X)(CO)Pc2−]− (X = Cl,Br, I,NCO, NCS,N3)

Ruthenium(II) Phthalocyaninates(2–): Synthesis and Properties of (Acido)(carbonyl)phthalocyaninato(2–)ruthenate(II), [Ru(X)(CO)Pc^2?]^? (X = Cl, Br, I, NCO, NCS, N₃) (ⁿBu₄N)[Ru(OH)₂Pc^2?] is reduced in acetone with carbonmonoxid to blue-violet [Ru(H₂O)(CO)Pc^2?], which yields in tetrahydrofurane with excess (ⁿBu₄N)X acido(carbonyl)phthalocyaninato(2–)ruthenate(II), [Ru(X)(CO)Pc^2?]^? (X = Cl, Br, I, NCO, NCS, N₃) isolated as red-violet, diamagnetic (ⁿBu₄N) complex salt. The UV-Vis spectra are dominated by the typical π-π* transitions of the Pc^2? ligand at approximately 15100 (B), 28300 (Q₁) und 33500 cm^?1 (Q₂), only fairly dependent of the axial ligands. v(C? O) is observed at 1927 (X = I), 1930 (Cl, Br), 1936 (N₃, NCO) 1948 cm^?1 (NCS), v(C? N) at 2208 cm^?1 (NCO), 2093 cm^?1 (NCS) and v(N? N) at 2030 cm^?1 only in the MIR spectrum. v(Ru? C) coincides in the FIR spectrum with a deformation vibration of the Pc ligand, but is detected in the resonance Raman(RR) spectrum at 516 (X = Cl), 512 (Br), 510 (N₃), 504 (I), 499 (NCO), 498 cm^?1 (NCS). v(Ru? X) is observed in the FIR spectrum at 257 (X = Cl), 191 (Br), 166 (I), 349 (N₃), 336 (NCO) and 224 cm^?1 (NCS). Only v(Ru? I) is RR-enhanced.     

Magnesium(I) Halide versus Magnesium Metal: Differences in Reaction Energy and Reactivity Monitored in Reduction Processes of P−Cl Bonds

Magnesium(I) halides (Mg^IX; X=Cl, Br, I), as high temperature molecules, are trapped and finally stored at ?80 °C in toluene/donor solutions. These solutions provide insights into the fundamental mechanism of reduction reactions using activated magnesium metal as a prototype for every base metal. The most important example of such a reaction is the preparation of Grignard reagents (RMgX). The details of this highly complex mechanism especially of intermediates between Mg metal and Mg^II (RMgX) remain unknown until today. The same is true for the reaction of bulk magnesium with Group 15 halide compounds that give biradicaloid species. We investigate the reduction of P?Cl bonds with solutions of [Mg^IBr(NⁿBu₃)]₂ ( 1 ). The phosphanes [ClP(μ‐NTer)]₂ ( 2 ) and (Me₃Si)₂N‐PCl₂ ( 3 ), were chosen as they had successfully been reduced by Mg metal before. Furthermore, reactions of both 1 and Mg metal are compared with an Mg^I chelate complex L¹Mg?MgL¹ containing a strong Mg?Mg σ‐bond.     

A rare octacoordinated mononuclear iron(III) spin‐crossover compound: synthesis,crystal structure and magnetic properties

The chemistry of transition‐metal complexes with unusually high coordination numbers has been of interest because of their application in catalytic and biological systems. Deprotonation of the ionogenic tetradentate ligand 6,6′‐bis(1H‐tetrazol‐5‐yl)‐2,2′‐bipyridine [H₂bipy(ttr)₂] in the presence of iron(III) and tetra‐n‐butylammonium bromide, [n‐Bu₄N]Br, in solution resulted in the synthesis of a rare octacoordinated anionic mononuclear complex, tetra‐n‐butylammonium bis[6,6′‐bis(tetrazol‐1‐id‐5‐yl)‐2,2′‐bipyridine]iron(III) methanol hemisolvate dihydrate, (C₁₆H₃₆N)[Fe(C₁₂H₆N₁₀)₂]·0.5CH₃OH·2H₂O or [n‐Bu₄N][Fe{bipy(ttr)₂}₂]·0.5CH₃OH·2H₂O ( 1 ), which has been structurally characterized by elemental analysis, powder X‐ray diffraction (PXRD) and single‐crystal X‐ray diffraction. In 1 , the coordination sphere of the iron(III) ion is a distorted bis‐disphenoid dodecahedron, in which the eight coordination positions are occupied by eight N atoms from two independent tetradentate [bipy(ttr)₂]^2? anionic ligands, therefore forming the anionic [Fe{bipy(ttr)₂}₂]^? unit, with the negative charge balanced by a free [n‐Bu₄N]⁺ cation. An investigation of the magnetic properties of 1 revealed a gradual incomplete spin‐crossover behaviour below 150 K.     

Conformational Heterogeneity in Diphthalocyaninato(2–)metallates(III) of Sc,Y, In,Sb, Bi,La, Ce,Pr, and Sm

Potassium diphthalocyaninato(2–)metallate(III), K[M(pc^2–)₂] (M = Bi, La, Ce, Pr, Sm, Sb, In) has been prepared by melting the metal chloride, iodide or acetate with 1,2‐dicyanobenzene in the presence of potassium methylate. Crystallisation with tetra(n‐butyl)ammonium bromide or hydroxide ((ⁿBu₄N)Br/OH), tetra(n‐pentyl)ammonium chloride ((ⁿPe₄N)Cl) or bis(triphenylphosphine)iminium halide ((PNP)X; X = Br, I) yields the corresponding red‐purple complex salt (ⁿBu₄N)[M(pc^2–)₂] (M = Bi ( 1 ), La ( 3 ), Ce ( 2 )), (ⁿBu₄N)[M(pc^2–)₂] · x CH₃OH (M = Bi ( 5 ), Pr ( 6 ), Sm ( 7 ); 0 9 x 9 1), (ⁿPe₄N)[La(pc^2–)₂] ( 4 ), (ⁿBu₄N)[Pr(pc^2–)₂] · 2 py ( 10 ), (ⁿBu₄N)[Sb(pc^2–)₂] · 2 thf ( 11 ), (PNP)₂[M(pc^2–)₂]Br · 2 Et₂O (M = Sb ( 12 ), Bi ( 13 )), and (PNP)₂[In(pc^2–)₂]I · 2 Et₂O ( 14 ). Bronze coloured diphthalocyaninato(1–)metal(III) polyiodide, [M(pc^–)₂]I₂ (M = Sc, Y) has been prepared similarly in the presence of ammonium iodide. Reduction with (ⁿBu₄N)OH provides (ⁿBu₄N)[M(pc^2–)₂] · x CH₃OH (M = Y ( 8 ), Sc ( 9 ); 0 9 x 9 1). Spectral properties (UV/VIS/NIR; IR; resonance Raman) of diphthalocyaninates in their different ring oxidation states (2–/2–; 2–/1–; 1–/1–) are discussed. 1 – 3 crystallise in the tetragonal (P4/ncc), 5 – 9 in the orthorhombic (Pna2₁), 10 , 11 in the triclinic (P‐1), and 4 , 12 – 14 in the monoclinic crystal system ( 4 : P2₁/m; 12 : C2/c; 13 , 14 : P2/c). Ecliptic rotamers with skew angles ranging from 4.1° to 6.0° are found in 1 – 3 , and staggered rotamers with skew angles ranging from 35.8° to 45.0° are found in 4 – 14 . The mean M–N_i bond lengths and interplanar distances increase monotonically with the ionic radius of the metal ion. Both distances deviate notably from this linear correlation in the Sb^III and Bi^III derivatives. The discrepancy is presumably due to the sterical dominance of the ns² lone‐pair character. The actual size of eight co‐ordinated Sb^III and Bi^III is estimated to be R₈ ≈ 1.02(Sb)/1.11(Bi) Å. In every complex salt, the pc ligand is severely distorted from planarity and can adopt domed, saddled, waved and mixed non‐planar conformations; the crystal symmetry is the most important factor for the conformational heterogeneity.     

Reactivity of the Latent 12‐Electron Fragment [Rh(PiBu3)2]+ with Aryl Bromides: Aryl?Br and Phosphine Ligand C?H Activation

Oxidative addition of aryl bromides to 12‐electron [Rh(PiBu₃)₂][BAr^F₄] (Ar^F=3,5‐(CF₃)₂C₆H₃) forms a variety of products. With p‐tolyl bromides, Rh^III dimeric complexes result [Rh(PiBu₃)₂(o/p‐MeC₆H₄)(μ‐Br)]₂[BAr^F₄]₂. Similarly, reaction with p‐ClC₆H₄Br gives [Rh(PiBu₃)₂(p‐ClC₆H₄)(μ‐Br)]₂[BAr^F₄]₂. In contrast, the use of o‐BrC₆H₄Me leads to a product in which toluene has been eliminated and an isobutyl phosphine has undergone C? H activation: [Rh{PiBu₂(CH₂CHCH₃C H₂)}(PiBu₃)(μ‐Br)]₂[BAr^F₄]₂. Trapping experiments with ortho‐bromo anisole or ortho‐bromo thioanisole indicate that a possible intermediate for this process is a low‐coordinate Rh^III complex that then undergoes C? H activation. The anisole and thioanisole complexes have been isolated and their structures show OMe or SMe interactions with the metal centre alongside supporting agostic interactions, [Rh(PiBu₃)₂(C₆H₄O Me)Br][BAr^F₄] (the solid‐state structure of the 5‐methyl substituted analogue is reported) and [Rh(PiBu₃)₂(C₆H₄S Me)Br][BAr^F₄]. The anisole‐derived complex proceeds to give [Rh{PiBu₂(CH₂CHCH₃C H₂)}(PiBu₃)(μ‐Br)]₂[BAr^F₄]₂, whereas the thioanisole complex is unreactive. The isolation of [Rh(PiBu₃)₂(C₆H₄O Me)Br][BAr^F₄] and its onward reactivity to give the products of C? H activation and aryl elimination suggest that it is implicated on the pathway of a σ‐bond metathesis reaction, a hypothesis strengthened by DFT calculations. Calculations also suggest that C? H bond cleavage through phosphine‐assisted deprotonation of a non‐agostic bond is also competitive, although the subsequent protonation of the aryl ligand is too high in energy to account for product formation. C? H activation through oxidative addition is also ruled out on the basis of these calculations. These new complexes have been characterised by solution NMR/ESIMS techniques and in the solid‐state by X‐ray crystallography.     

Review: Chemistry of the phosphinophosphinidene tBu2P?P,a novel π‐electron ligand

In reactions with transition metal compounds, ^tBu₂P? P?P(X)^tBu₂ (X = Br, Me) acts mainly as a precursor of the ^tBu₂P? P ligand, whereas ^tBu(Me₃Si)P? P?P(Me)^tBu₂ acts as a precursor of the (Me₃Si)P?P^tBu ligand. Up to now, only Pt(0) d¹⁰ ML₂ metal centres were found to be able to stabilize the ^tBu₂P? P group in ‘pure form’ by means of η²‐coordination (side on). Several compounds of the [{η² ? ^tBu₂P? P}Pt(PR₃)₂] type were sufficiently stable to be isolated and characterized; however, not all of them gave single crystals suitable for X‐ray structure determinations. The X‐ray structures of these compounds and of [{µ ? (1,2:2 ? η ? ^tBu₂P? P)Pt(PR₃)₂} {M(CO)₅}] strongly suggest the ethene‐like form of 1,1‐di‐tert‐butyldiphosphene in these complexes. Such a form is also in agreement with RI DFT calculations with SVP basis for free ^tBu₂P? P. However, in trapping experiments with cyclic olefins and cyclic dienes ^tBu₂P? P exhibits, to some extent, electrophilic ‘singlet carbene’ properties. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis,structural characterization and cytotoxic activity of diorganotin(IV) complexes of N‐(5‐halosalicylidene)‐α‐amino acid

Fourteen new diorganotin(IV) complexes of N‐(5‐halosalicylidene)‐α‐amino acid, R′₂Sn(5‐X‐2‐OC₆H₃CH?NCHRCOO) (where X = Cl, Br; R = H, Me, i‐Pr; R′ = n‐Bu, Ph, Cy), were synthesized by the reactions of diorganotin halides with potassium salt of N‐(5‐halosalicylidene)‐α‐amino acid and characterized by elemental analysis, IR and NMR (¹H, ¹³C and ¹¹⁹Sn) spectra. The crystal structures of Bu₂Sn(5‐Cl‐2‐OC₆H₃CH?NCH(i‐Pr)COO) and Ph₂Sn(5‐Br‐2‐OC₆H₃CH?NCH(i‐Pr)COO) were determined by X‐ray single‐crystal diffraction and showed that the tin atoms are in a distorted trigonal bipyramidal geometry and form five‐ and six‐membered chelate rings with the tridentate ligand. Bioassay results of a few compounds indicated that the compounds have strong cytotoxic activity against three human tumour cell lines, i.e. HeLa, CoLo205 and MCF‐7, and the activity decreased in the order Cy>n‐Bu>Ph for the R′ group bound to tin. Copyright © 2005 John Wiley & Sons, Ltd.     

Homoleptic Zincate‐Promoted Room‐Temperature Halogen–Metal Exchange of Bromopyridines

Homoleptic lithium tri‐ and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine–metal exchanges were realized at room temperature with a substoichiometric amount of nBu₄ZnLi₂?TMEDA reagent (1/3 equiv; TMEDA=N,N,N′,N′‐tetramethylethylenediamine). This reactivity contrasted with that of tBu₄ZnLi₂?TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N???Li stabilized polypyridyl zincates in the reaction. The one‐pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C? Zn bonds in bromopyridines enabled us to perform efficient Negishi‐type cross‐couplings.     

Molecular Polyarsenides of the Rare‐Earth Elements

Reduction of [Cp*Fe(η⁵‐As₅)] with [Cp′′₂Sm(thf)] (Cp′′=η⁵‐1,3‐(tBu)₂C₅H₃) under various conditions led to [(Cp′′₂Sm)(μ,η⁴:η⁴‐As₄)(Cp*Fe)] and [(Cp′′₂Sm)₂As₇(Cp*Fe)]. Both compounds are the first polyarsenides of the rare‐earth metals. [(Cp′′₂Sm)(μ,η⁴:η⁴‐As₄)(Cp*Fe)] is also the first d/f‐triple decker sandwich complex with a purely inorganic planar middle deck. The central As₄^2? unit is isolobal with the 6π‐aromatic cyclobutadiene dianion (CH)₄^2?. [(Cp′′₂Sm)₂As₇(Cp*Fe)] contains an As₇^3? cage, which has a norbornadiene‐like structure with two short As?As bonds in the scaffold. DFT calculations confirm all the structural observations. The As?As bond order inside the cyclo As₄ ligand in [(Cp′′₂Sm)(μ,η⁴:η⁴‐As₄)(Cp*Fe)] was estimated to be in between an As?As single bond and a formally aromatic As₄^2? system.     

Attenuated Organomagnesium Activation of White Phosphorus

Sequential reactions between a 2,6‐diisopropylphenyl‐substituted β‐diketiminato magnesium n‐butyl derivative and P₄ allow the highly discriminating synthesis of unusual [nBu₂P₄]^2? and [nBu₂P₈]^2? cluster dianions.     

Hydrogels Composed of Organic Amphiphiles and α‐Cyclodextrin: Supramolecular Networks of Their Pseudorotaxanes in Aqueous Media

Mixtures of N‐alkyl pyridinium compounds [py‐N‐(CH₂)_nOC₆H₃‐3,5‐(OMe)₂]⁺(X^?) ( 1b Cl: n=10, X=Cl; 1c Br: n=12, X=Br) and α‐cyclodextrin (α‐CD) form supramolecular hydrogels in aqueous media. The concentrations of the two components influences the sol–gel transition temperature, which ranges from 7 to 67 °C. Washing the hydrogel with acetone or evaporation of water left the xerogel, and ¹³C CP/MAS NMR measurements, powder X‐ray diffraction (XRD), and scanning electron microscopy (SEM) revealed that the xerogel of 1b Cl (or 1c Br) and α‐CD was composed of pseudorotaxanes with high crystallinity. ¹³C{¹H} and ¹H NMR spectra of the gel revealed the detailed composition of the components. The gel from 1b Cl and α‐CD contains the corresponding [2]‐ and [3]pseudorotaxanes, [ 1b? (α‐CD)]Br and [ 1b? (α‐CD)₂]Br, while that from 1c Br and α‐CD consists mainly of [3]pseudorotaxane [ 1c? (α‐CD)₂]Br. 2D ROESY ¹H NMR measurements suggested intermolecular contact of 3,5‐dimethoxyphenyl and pyridyl end groups of the axle component. The presence of the [3]pseudorotaxane is indispensable for gel formation. Thus, intermolecular interaction between the end groups of the axle component and that between α‐CDs of the [3]pseudorotaxane contribute to formation of the network. The supramolecular gels were transformed into sols by adding denaturing agents such as urea, C₆H₃‐1,3,5‐(OH)₃, and [py‐N‐nBu]⁺(Cl^?).     

1,3 Dichloro- and 1,3 dibromotetra-n-butyldistannoxane mixtures: ligand redistribution and fluxional dynamics in distannoxanes

The halogen redistribution reaction in the binary [ⁿBu₂SnCl]₂O/[ⁿBu₂SnBr]₂O system is examined by ¹¹⁹Sn- and ¹³C-NMR spectroscopy. Binary mixtures of [ⁿBu₂SnCl]₂O and [ⁿBu₂SnBr]₂O reach equilibrium rapidly at room temperature. The reactant dimers are found to be in equilibrium with all five possible mixed distannoxane dimers in the equimolar mixture. These mixed distannoxane dimers differ in the ratio of Cl and Br as well as the relative positioning of the halogens. The mechanism responsible for the rapid formation of the mixed Cl:Br distannoxane dimers is found to proceed via bimolecular collisions producing a four-centered transition state, which in turn undergoes a concerted exchange of the halogens. The equilibrium concentrations of the reactant and product dimers are well represented by a statistical distribution, indicating that Cl and Br exhibit equivalent donor abilities. At 298 K, the NMR spectral data are consistent with time-averaged structures arising from rapidly interconverting rigid ladder pairs. Lowering the temperature to 173 K failed to freeze out this fluxional process. A reversible configurational rearrangement is also observed in which rotation about the oxygen---exocyclic tin bond results in the mutual exchange of halogens associated with the same exocyclic tin atom.     

Lanthanide(II) Complexes of the Dihydrotriazinido Ligand [N{C(Ph)=N}2C(tBu)Ph]−

The potassium dihydrotriazinide K(L^Ph,tBu) ( 1 ) was obtained by a metal exchange route from [Li(L^Ph,tBu)(THF)₃] and KOtBu (L^Ph,tBu = [N{C(Ph)=N}₂C(tBu)Ph]). Reaction of 1 with 1 or 0.5 equivalents of SmI₂(thf)₂ yielded the monosubstituted Sm^II complex [Sm(L^Ph,tBu)I(THF)₄] ( 2 ) or the disubstituted [Sm(L^Ph,tBu)₂(THF)₂] ( 3 ), respectively. Attempted synthesis of a heteroleptic Sm^II amido‐alkyl complex by the reaction of 2 with KCH₂Ph produced compound 3 due to ligand redistribution. The Yb^II bis(dihydrotriazinide) [Yb(L^Ph,tBu)₂(THF)₂] ( 4 ) was isolated from the 1:1 reaction of YbI₂(THF)₂ and 1 . Molecular structures of the crystalline compounds 2 , 3· 2C₆H₆ and 4· PhMe were determined by X‐ray crystallography.     

Improving the Halogen–Magnesium Exchange by using New Turbo-Grignard Reagents

This Minireview describes the scope of the halogen–magnesium exchange. It shows that the use of the turbo-Grignard reagent (iPrMgCl⋅LiCl) greatly enhances the rate of the Br– and I–Mg exchange. Furthermore, this magnesium reagent allows the performance of a fast sulfoxide–magnesium exchange. Also, the use of sBuMgOR⋅LiOR (R=2-ethylhexyl) enables a Br–Mg exchange in toluene leading to various Grignard reagents in toluene. Additionally, the new exchange reagent sBu₂Mg⋅2 LiOR (R=2-ethylhexyl) further increases the rate of the halogen–magnesium exchange allowing one to perform a chlorine–magnesium exchange for aromatic chlorides bearing an ortho-methoxy substituent in toluene.     

Effect of variation of [PMDETA]0/[Cu(I)Br]0 ratio on atom transfer radical polymerization of n‐butyl acrylate

A kinetic study was conducted to examine the effect of varying the ratio of ligand to transition metal in a Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) catalyst system for atom transfer radical polymerization (ATRP) of n‐butyl acrylate (nBA) using methyl 2‐bromopropionate as the initiator. Experimental molecular weights were higher than theoretical when low molecular weight polymers were targeted at low ratios of [PMDETA]₀/[Cu(I)Br]₀ (< 1), indicating inefficient initiation/deactivation. A downward curvature in the plot of M_n versus conversion was observed at high monomer conversion when targeting high molecular weight polymers. This deviation became more significant when an excess of ligand was used, indicating a contribution of chain transfer to ligand. The maximum rate of polymerization was obtained at [PMDETA]₀/[Cu(I)Br]₀ ≈ 0.5 for bulk ATRP of nBA; however for polymerization in the presence of 10 vol% DMF, the maximum appeared at the ratio ≈ 1:1. Addition of acetone or DMF improved solubility of Cu(II) complex, which consequently improved the level of control over the polymerization at low ratios of [PMDETA]₀/[Cu(I)Br]₀, but also reduced the reaction rate. The polymerization rate increased with temperature, but at the expense of increased polydispersities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3285–3292, 2004     

Electrochemical methylation of a chelate anionic NiI complex with methylcobaloxime. Partial modeling of the action mechanism of the active center of acetyl-CoA synthase

Electrochemically generated anions of Co and Ni chelate complexes can be alkylated with BuⁿBr, BuⁿI, and (dmgH)₂CoMe (dmgH is the dimethylglyoximate anion). Unlike the anionic Co complexes, the anionic Ni complex cannot be alkylated with BuⁿBr; however, it reacts with stronger alkylating agents (BuⁿI and (dmgH)₂CoMe). It is assumed that the electrochemical alkylation of the Ni complex with (dmgH)₂CoMe can serve as a model for alkylation occurring in biological synthesis of acetyl coenzyme A. Reactions of some Co chelate anions with BuⁿI can proceedvia the reduction of the latter. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 55–58, January, 2000.     

Darstellung,Kristallstrukturen und Schwingungsspektren von trans‐[Pt(N3)4X2]2–, X = Cl,Br, I

Synthesis, Crystal Structures, and Vibrational Spectra of trans ‐[Pt(N₃)₄X₂]^2–, X = Cl, Br, I By oxidative addition to (n‐Bu₄N)₂[Pt(N₃)₄] with the elemental halogens in dichloromethane trans‐(n‐Bu₄N)₂[Pt(N₃)₄X₂], X = Cl, Br, I are formed. X‐ray structure determinations on single crystals of trans‐(Ph₄P)₂[Pt(N₃)₄Cl₂] (triclinic, space group P1, a = 10.352(1), b = 10.438(2), c = 11.890(2) Å, α = 91.808(12), β = 100.676(12), γ = 113.980(10)°, Z = 1), trans‐(Ph₄P)₂[Pt(N₃)₄Br₂] (triclinic, space group P1, a = 10.336(1), b = 10.536(1), c = 12.119(2) Å, α = 91.762(12), β = 101.135(12), γ = 112.867(10)°, Z = 1) and trans‐(Ph₄P)₂[Pt(N₃)₄I₂] (triclinic, space group P1, a = 10.186(2), b = 10.506(2), c = 12.219(2) Å, α = 91.847(16), β = 101.385(14), γ = 111.965(18)°, Z = 1) reveal, that the compounds crystallize isotypically with octahedral centrosymmetric complex anions. The bond lengths are Pt–Cl = 2.324, Pt–Br = 2.472, Pt–I = 2.619 and Pt–N = 2.052–2.122 Å. The approximate linear Azidoligands with N^α–N^β–N^γ‐angles = 172.1–176.8° are bonded with Pt–N^α–N^β‐angles = 116.2–121.9°. In the vibrational spectra the platinum halogen stretching vibrations of trans‐(n‐Bu₄N)₂[Pt(N₃)₄X₂] are observed in the range of 327–337 (X = Cl), at 202 (Br) and in the range of 145–165 cm^–1 (I), respectively. The platinum azide stretching modes of the three complex salts are in the range of 401–421 cm^–1. Based on the molecular parameters of the X‐ray determinations the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants are f_d(PtCl) = 1.90, f_d(PtBr) = 1.64, f_d(PtI) = 1.22, f_d(PtN^α) = 2.20–2.27 and f_d(N^αN^β, N^βN^γ) = 12.44 mdyn/Å.     

Electrochemical methylation of a chelate anionic NiI complex with methylcobaloxime. Partial modeling of the action mechanism of the active center of acetyl-CoA synthase

Electrochemically generated anions of Co and Ni chelate complexes can be alkylated with BuⁿBr, BuⁿI, and (dmgH)₂CoMe (dmgH is the dimethylglyoximate anion). Unlike the anionic Co complexes, the anionic Ni complex cannot be alkylated with BuⁿBr; however, it reacts with stronger alkylating agents (BuⁿI and (dmgH)₂CoMe). It is assumed that the electrochemical alkylation of the Ni complex with (dmgH)₂CoMe can serve as a model for alkylation occurring in biological synthesis of acetyl coenzyme A. Reactions of some Co chelate anions with BuⁿI can proceedvia the reduction of the latter. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 55–58, January, 2000.