Monomere Komplexe NiL mit vierzähnigen Liganden [R2P(S)N–R'–NP(S)R2]2– (= L) [1]

Monomeric Complexes NiL with Tetradentate Ligands [R₂P(S)N–R'–NP(S)R₂]^2– (= L) Metathesis of [NiCl₂(PPh₃)₂] with Li salts of the potentially tetradentate ligands [R₂P(S)N–R'–NP(S)R₂]^2– (= L) affords monomeric complexes NiL containing the chromophore NiN₂S₂ ( 1 : R = Et; a , b : R' = Me₂C–(CH₂)₂–CMe₂, o-Phenylen; 2 : R = t-Bu, R' = (CH₂)_n; a – c : n = 2, 3, 4). According to the results of magnetic measurements and VIS as well as NMR spectroscopy (¹H, ³¹P) these complexes are planar except 1 a that is tetrahedral. In case of 1 a and 2 c this was confirmed by the results of crystal structure analyses. In toluene, however, 1 a and 2 c form an equilibrium of planar (diamagnetic) and tetrahedral (paramagnetic) conformers. VT-¹H-NMR including ¹H,¹H-COSY showed a hindered Δ,Λ-inversion of 1 a below 330 K. Only with 1 b a pentacoordinate adduct 1 b · PPh₃ was obtained that completely dissociates in its components on dissolving in benzene. 1 a and 2 c crystallize in the monoclinic space group P2₁/c containing 4 molecules in the unit cell of the dimensions 1 a : a = 8.774(1), b = 12.335(2), c = 21.339(3) Å, β = 92.33(1)° and 2 c : a = 13.374(8), b = 16.197(8), c = 12.814(6) Å, β = 109.20(4)°. The coordination of the Ni atom yields in 1 a a dihedral angle ϵ of 41.7(1)° and thus a geometry intermediate between planar and tetrahedral while in 2 c the angle of 4.5(1)° reveals a nearly planar chromophore NiN₂S₂.     

[NiL2X2] oder [HL][NiLX3] – Reaktion sterisch anspruchsvoller Trialkylphosphine L mit NiX2 (X = Cl,Br) in Ethanol

[NiL₂X₂] or [HL][NiLX₃] – Reaction of Sterically Demanding Trialkylphosphines L with NiX₂ (X = Cl, Br) in Ethanol The reaction of some sterically demanding trialkylphosphines L = PR₂R′ (R = ⁱPr, R′ = ^tBu; R = ^tBu, R′ = ⁱPr, Me) with NiX₂ (X = Cl, Br) in ethanol affords instead of the expected non-electrolytes [NiL₂X₂] tertiary phosphonium nickelates [HL][NiLX₃] due to participation of the solvent. In case of the less bulky P^tBu₂Me both complex types were obtained. [Ni(P^tBu₂Me)₂Cl₂] is tetrahedral and therefore one of the two examples of paramagnetic bis(trialkylphosphine)dihalogenonickel(II) complexes known so far. In solution the latter compound undergoes an equilibrium of tetrahedral (paramagnetic) and planar (diamagnetic) conformer. Vis spectra as well as the results of magnetic measurements and ¹H and ³¹P NMR investigations are reported.     

Synthesis and spectroscopic characterization of bis(N-alkyldithiocarbamato)nickel(II) complexes: crystal structures of [Ni(S2CNH(n-Pr))2] and [Ni(S2CNH(i-Pr))2]

Bis(N-alkyldithiocarbamato)nickel(II) complexes (1–5) [Ni(S₂CNHR)₂] (where R?=?Me, Et, n-Pr, i-Pr, n-Bu) were synthesized by the reaction of NiCl₂?·?6H₂O and the corresponding sodium salt of N-alkyldithiocarbamate in 1?:?2 molar ratio in aqueous medium. These bis(N-alkyldithiocarbamato)nickel(II) complexes (1–5) were characterized by elemental analysis, UV-Visible, IR, and ¹H/¹³C-NMR spectroscopy. The crystallographic investigation of [Ni(S₂CNH(n-Pr))₂] (3) and [Ni(S₂CNH(i-Pr))₂] (4) revealed distorted square-planar geometry around nickel(II). The dithiocarbamates have anisobidentate coordination with nickel and the dithiocarbamates are trans.     

Monomere Dialkylmetallkomplexe des Typs R2M(NR′)2XR mit M = Al,Ga, In,TI; X = S,C und R,R′ = Alkyl und Silyl

Monomeric Dialkyl Metal Complexes of the R₂M(NR′)₂XR Type with M = Al, Ga, In, Tl; X = S, C and R, R′ = Alkyl and Silyl N,N′-Bis(trimethylsilyl)sulfurdiimide reacts with the trimethyl derivatives of aluminium, gallium, and indium within insertion. Hereby monomeric sulfinic acid imidamidates Me₂M(NSiMe₃)₂SMe (Me = CH₃) are formed. The lithium amidinates Li(NR′)₂CMe (R′ = i-C₃H₇ and SiMe₃) are formed likewise by insertion reactions with LiMe and the corresponding carbodiimides R′N?C?NR′ and were used in reactions with R₂MCl (M = Al to Tl) to synthesize dialkyl metal amidinates R₂M(NR′)₂CMe. The NMR (¹H and ¹³C) and the vibrational spectra (IR and Raman) are discussed and applied to describe the structure of these chelat complexes.     

Hypervalent Organoselenium(II) Compounds with Organophosphorus Ligands. Crystal and Molecular Structure of [2‐(iPr2NCH2)C6H4]Se[S2PR′2] (R′ = Ph,OiPr)

Redistribution reactions between diorganodiselenides of type [2‐(R₂NCH₂)C₆H₄]₂Se₂ [R = Et, iPr] and bis(diorganophosphinothioyl disulfanes of type [R′₂P(S)S]₂ (R = Ph, OiPr) resulted in the hypervalent [2‐(R₂NCH₂)C₆H₄]SeSP(S)R′₂ [R = Et, R′ = Ph ( 1 ), OiPr ( 2 ); R = iPr, R′ = Ph ( 3 ), OiPr ( 4 )] species. All new compounds were characterized by solution multinuclear NMR spectroscopy (¹H, ¹³C, ³¹P, ⁷⁷Se) and the solid compounds 1 , 3 , and 4 also by FT‐IR spectroscopy. The crystal and molecular structures of 3 and 4 were determined by single‐crystal X‐ray diffraction. In both compounds the N(1) atom is intramolecularly coordinated to the selenium atom, resulting in T‐shaped coordination arrangements of type (C,N)SeS. The dithio organophosphorus ligands act monodentate in both complexes, which can be described as essentially monomeric species. Weak intermolecular S ··· H contacts could be considered in the crystal of 3 , thus resulting in polymeric zig‐zag chains of R and S isomers, respectively.     

Palladium(II) complexes with R2edda-derived ligands

Four palladium(II) complexes with R₂edda ligands, dichlorido(O,O′-dialkylethylenediamine-N,N′-diacetate)palladium(II) monohydrates, [PdCl₂(R₂edda)]?H₂O, R = Me, Et, n-Pr, i-Bu, and the new ligand precursor i-Bu₂edda?2HCl?H₂O, O,O′-diisobutylethylenediamine-N,N′-diacetate dihydrochloride monohydrate, were synthesized and characterized by IR, ¹H and ¹³C NMR spectroscopy, and elemental analysis. DFT calculations were performed for the palladium(II) complexes and a high possibility for isomer formation due to stereogenic N ligand atoms was confirmed. Moreover, DFT simulations revealed energetic profile of isomer formation. Computational outcomes are in agreement with spectroscopic instrumental findings, both strongly indicating a non-stereoselective reaction between selected esters and K₂[PdCl₄], forming isomers.     

Übergangsmetallkomplexe [Et2P(S)NR]M/n,Vierringchelate mit Thiophosphinsäure-Organylamidato-Liganden [1]

Transition Metal Complexes [Et₂P(S)NR]M/n, Chelates containing 4-membered Rings and Phosphinothioic-organylamidato Ligands Phosphinothioic-organylamidato complexes [Et₂P(S)NR]M/n (R = Me, Et, tBu, cHex, Ph; M = Ti^III, V^III, Cr^III, Co^II, Zn^II) are obtained by reaction of metal halides with [Et₂P(S)NR]Li or from ZnEt₂ and Et₂P(S)NHR. In contrast to the analogous phosphinothioic complexes [R′₂P(S)X]M/n (X = O, S, Se) they are extremely hydrolyzable. The ligand field parameters Δ and β of Et₂P(S)NR^? are found to be similar to those of R′₂P(S)S^? indicating a low ligand field strength and a strong nephelauxetic effect. In contrast to [R′₂P(S)O]₂M (M = Co, Zn), which are highly polymerised, there is only a weak tendency of the corresponding tetrahedral phosphinothioicorganylamidato complexes to form ligand bridges.     

Preparation of complexes formed in the reaction between diironnanocarbonyl and tetraalkyl(phenyl)diphosphine disulfides,R2P(S)P(S)R2 (R=Et,n -Pr,n -Bu,Ph)

Fe₂(CO)₉ and R₂P(S)P(S)R₂ (R = Et, n-Pr, n-Bu, Ph) react to form two types of cluster complexes Fe₃(CO)₉(μ₃-S)₂ (1), Fe₂(CO)₆(μ-SPR₂)₂ (2A)–(2D), [2A, R = Et; 2B, R = n-Pr; 2C, R = n-Bu; 2D, R = Ph]. The complexes result from phosphorus–phosphorus bond scission; in the former sulfur abstraction has also occurred. The complexes have been characterized by elemental analyses, FT-IR and ³¹P-[¹H]-NMR spectroscopy and mass spectrometry.     

Isomere η2-Acyl- und σ-Alkyl(carbonyl)-Komplexe von Molybdän und Wolfram. Eine Studie zum Bildungs-mechanismus,zur Isomerisierungsgeschwindigkeit und zur Steuerung der Gleichgewichtslage

η²-Acyl and σ-Alkyl(carbonyl) Coordination in Molybdenum and Tungsten Complexes: Synthesis and Studies of the Isomerization Equilibria and Kinetics The anionic molybdenum and tungsten complexes [L_RM(CO)₃]^? (L_R^? = [(C₅H₅)Co{P(O)R₂}₃]^?, R = OCH₃, OC₂H₅, O-i-C₃H₇; M = Mo, W) have been alkylated with the iodides R′ I, R′ = CH₃, C₂H₅, i-C₃H₇, and CH₂C₆H₅. The reactivity pattern of the alkylation is in accord with a S_N2 mechanism. Depending on M, R′, reaction temperature, and time the η-alkyl (carbonyl) compounds [L_RM(CO)₃R′] and/or the isomeric η²-acyl compounds [L_RM(CO)₂(η²-COR′)] can be obtained. 8 new σ-alkyl(carbonyl) compounds and 15 new η²-acyl compounds have been isolated and characterized. The ¹H NMR and the IR spectra give conclusive evidence that the σ-alkyl(carbonyl) compounds [L_RM(CO)₃R′] are formed as the primary products of the alkylation and that they isomerize partly or completely to give the η²-acyl compounds [L_RM(CO)₂(η²-COR′)]. The position of the equilibrium σ-alkyl(carbonyl)/η²-acyl is controlled by the steric demands of the groups R′ and the ligands L_R^?. The molybdenum compounds isomerize much more readily than the tungsten compounds. The rate constants of the isomerization processes [L_RMo(CO)₃CH₃] → [L_RMo(CO)₂(η²-COCH₃)], R = OCH₃, OC₂H₅, and O-i-C₃H₇, measured at 305 K in acetone-d₆, are 6–8 x 10^?3 s^?1.     

A new synthesis and the electrochemical behaviour of nickel(II) dithiophosphate and dithiophosphinate complexes

Summary The [Ni(S₂PR₂)₂] complexes (R=i-PrO, PhO, or Et) can be conveniently prepared by reaction of [Ni{P(OPh)₃}₄] with [R₂P(S)S]₂ (R=i-PrO, PhO, or Et) in refluxing CHCl₃. The electrochemical behaviour of the complexes in CH₂Cl₂ and MeCN has been studied by cyclic voltammetry and coulometry. The oxidation of complexes at a glassy carbon reveals an e.c. mechanism. The [Ni(S₂PR₂)₂] complexes undergo a one-electron irreversible reduction.     

Regioselectivity in the amination of azines: Reaction of pyrazine derivatives with <Emphasis Type="Italic">O</Emphasis>-mesitylenesulfonylhydroxylamine

Treatment of 2-X-substituted pyrazines [X = H, Me, Et, Pr, i-Pr, t-Bu, MeCH(OH), H₂N, AcNH] with O-mesitylenesulfonylhydroxylamine gave the corresponding 2-X- and 3-X-(1-amino)pyrazin-1-ium mesitylenesulfonates. 2-Alkylpyrazines (X = Me, Et, Pr, i-Pr) displayed a correlation between the logarithms of the concentration ratio of 2- and 3-substituted cations and substituent steric constants. Wider series of substituted pyrazines [X = H, Me, Et, Pr, i-Pr, MeCH(OH), H₂N, AcNH] conformed to a multiparameter correlation between the logarithms of the concentration ratio of 2- and 3-substituted cations, on the one hand, and substituent constants σ_I, σ_R^o, and E _s^o, on the other. The obtained data on the regioselectivity of amination of pyrazines were interpreted in terms of DFT/PBE/3Z quantum-chemical calculations.     

P(RNCH2CH2)3N: AN EFFICIENT PROMOTER FOR THE SYNTHESIS OF 3-SUBSTITUTED COUMARINS

ABSTRACT

The title compounds wherein R = Me or i-Pr function as efficient promoters for the formation of coumarins in good to excellent yields (80–95%) from salicylaldehydes and di-activated methylene compounds of the type R′CH₂CO₂Et (R′ = CO₂Et, COMe, CN). Although the yields are not generally superior to those reported in the literature, our methodology is more convenient in that milder conditions and shorter reaction times are facilitated by the use of the aforementioned commercially available catalysts.     

Synthesis and characterization of methylpalladium(II) dithiolate complexes of the type [PdMe(SS)(ER3)] (SS = S2CNR 2, S2COEt, S2P(OR)2, S2 PPh2; ER3 = PMePh2, PPh3, AsPh3)

Methylpalladium(II) dithiolate complexes of the type [PdMe(SS)(ER₃] (SS = S₂ CNR₂ (R = Me or Et), S₂COEt, S₂P(OR)₂ (R = Et, ⁿPr, ⁱPr), S₂PPh₂; ER₃ = PMePh₂, PPh₃, AsPh₃) have been synthesized by the reaction of [Pd₂Me₂(μ-Cl)₂(PMePh₂)₂] with sodium/potassium/ammonium salts of the dithio acid or by treatment of [PdMeCl(cod)] with ER₃ followed by sodium/potassium/ammonium salts of the dithio ligand. All the complexes were characterized by elemental analysis, IR and nuclear magnetic resonance (¹H, ³¹P) data.     

Stabilization of a Silaaldehyde by its η2 Coordination to Tungsten

Treatment of pyridine‐stabilized silylene complexes [(η⁵‐C₅Me₄R)(CO)₂(H)W?SiH(py)(Tsi)] (R=Me, Et; py=pyridine; Tsi=C(SiMe₃)₃) with an N‐heterocyclic carbene ^MeIⁱPr (1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) caused deprotonation to afford anionic silylene complexes [(η⁵‐C₅Me₄R)(CO)₂W?SiH(Tsi)][H^MeIⁱPr] (R=Me ( 1‐Me ); R=Et ( 1‐Et )). Subsequent oxidation of 1‐Me and 1‐Et with pyridine‐N‐oxide (1 equiv) gave anionic η²‐silaaldehydetungsten complexes [(η⁵‐C₅Me₄R)(CO)₂W{η²‐O?SiH(Tsi)}][H^MeIⁱPr] (R=Me ( 2‐Me ); R=Et ( 2‐Et )). The formation of an unprecedented W‐Si‐O three‐membered ring was confirmed by X‐ray crystal structure analysis.     

Insertion Reactions of Carbon Disulfide into Mg‐C and Mg‐N Bonds: Syntheses and Structural Determinations of Mg(S2CY)2(THF)n(Y=NEt2, NiPr2, iPr,Ph) and BrMg(S2CZ)(THF)3(Z=Ph,iPr)

The insertion reaction of CS₂ with Mg(NR₂)₂ (R= Et, ⁱPr), MgR′₂ (R′= Et, Ph) and R″MgBr (R″= ⁱPr, Ph) respectively lead solid products, Mg(S₂CNR₂)₂(THF)_n ( 1 : R= Et, n=2; 2 : R= ⁱPr, n=1), Mg(S₂C′R)₂(THF)₂ ( 3 : ′R= Et, 4 : ′R= Ph), BrMg(S₂C″R) (THF)₃ ( 5 : ″R= ⁱPr, 6 : ″R= Ph) in which the inserted carbon disulfides act as terminal chelating ligands. These compounds were characterized with ¹H, ¹³C NMR, IR spectroscopy, mass spectrometry, elemental analyses, and X‐ray crystallography.     

Hydrogenation of β-Keto Sulfones to β-Hydroxy Sulfones with Alkyl Aluminum Compounds: Structure of Intermediate Hydroalumination Products

β-Hydroxy sulfones are important in organic synthesis. The simplest method of β-hydroxy sulfones synthesis is the hydrogenation of β-keto sulfones. Herein, we report the reducing properties of alkyl aluminum compounds R₃Al (R = Et, i-Bu, n-Bu, t-Bu and n-Hex); i-Bu₂AlH; Et₂AlCl and EtAlCl₂ in the hydrogenation of β-keto sulfones. The compounds i-Bu₂AlH, i-Bu₃Al and Et₃Al are the at best reducing agents of β-keto sulfones to β-hydroxy sulfones. In reactions of β-keto sulfones with aluminum trialkyls, hydroalumination products with β-hydroxy sulfone ligands [R₂AlOC(C₆H₅)CH₂S(O)₂(p-R¹C₆H₄]_n [where n = 1,2; 2aa: R = i-Bu, R¹ = CH₃; 2ab: R = i-Bu, R¹ = Cl; 2ba: R = Et, R¹ = CH₃; 2bb: R = Et, R¹ = Cl] and {[Et₂AlOC(C₆H₅)CH₂S(O)₂(p-ClC₆H₄]∙Et₃Al}_n 3bb were obtained. These complexes in the solid state have a dimeric structure, while in solutions, they appear as equilibrium monomer–dimer mixtures. The hydrolysis of both the isolated 2aa, 2ab, 2ba, 2bb and 3bb and the postreaction mixtures quantitatively leads to pure racemic β-hydroxy sulfones. Hydroalumination reaction of β-keto sulfones with alkyl aluminum compounds and subsequent hydrolysis of the complexes is a simple and very efficient method of β-hydroxy sulfones synthesis.     

Rhodium(I) and platinum(II) complexes of aminomethylphosphines as hydrogenation and hydroformylation catalysts

Hydrogenation of α-acetamidocinnamic acid with chiral aminomethylphosphine complexes of rhodium(I), [Rh(cyclo-octa-1, 5-diene) {(R₂PCH₂)₂NR¹}]-PF₆ (R = Ph or Cy, R¹ = D(+)-CHMePh, L-CHMeCO₂Et, (R)(+)-bornyl) shows no asymmetric induction. The hydroformylation of styrene using the catalyst mixture [PtCl₂(P–P)]/SnCl₂ shows asymmetric induction with up to 31% enantiomeric excess of 2-phenyl-propanol being observed.     

The crystal structure,equilibrium and spectroscopic studies of bis(dialkyldithiocarbamate) copper(II) complexes [Cu2(R2dtc)4] (dtc=dithiocarbamate)

Four copper(II) complexes of bis(dialkyldithiocarbamate) [Cd(R₂dtc)₂] (R=Me, Et, Pr, i-Pr; dtc=dithiocarbamate) have been prepared and characterized by elemental analysis, IR and ESR spectra studies. Their equilibrium constants (K), determined by a UV–vis spectrometry in EtOH, were influenced by the alkyl groups in the following order: i-Pr>n-Pr≈Et>Me. The single crystal structures of complex [Cu₂(R₂dtc)₄] have been determined using X-ray diffraction methods. The compounds [Cu₂(Et₂dtc)₄] and [Cu₂(Pr₂dtc)₄] are built of centrosymmetric neutral dimeric [Cu₂(R₂dtc)₄] entities. The copper atom lies in a distorted square–pyramidal environment. The four equatorial donors are two bidentate chelate sulfur atoms from two dtc ligands. One of the sulfur atoms from the third dtc ligand acts as a bridging ligand occupying the apical position of the symmetry-related copper atom in the dimer structure, which is viewed as two edge-sharing distorted square–pyramids. The structure of [Cu₂(i-Pr₂dtc)₄] is square planar with an exactly planar CuS₄ unit and nearly planar NCS₂ moieties. The Cu–S distances shows small decreases along the series n-Pr>Et>i-Pr, the biggest change being for the diisopropyl complex. The alkyl substituents at the nitrogen atom affect their coordination number and Cu⋯Cu distance. In the solid, [Cu₂(n-Pr₂dtc)₄] has the shortest Cu⋯Cu distance and [Cu(i-Pr₂dtc)₂] has the longest one.     

Metallkomplexe der Phosphinsäuren. XVIII. Ansa- und Oligokomplexe bifunktioneller Dithiophosphinsäuren

Metal Complexes of Phosphinic Acids. XVIII. Ansa- and Oligo-Complexes of Bifunctional Dithiophosphinic Acids The influence of R′ in the bifunctionell chelate ligands ^?S(S)P(R)? R′? (R)P(S)S^? on the association of their planar Ni^II and tetrahedral Co^II complexes is investigated by vapour pressure osmometry and in the case of diamagnetic Ni^II compounds also by ³¹P-NMR spectroscopy. While insoluble coordination polymers [S₂P(R)? R′? (R)PS₂M]_x (M = Ni^II, Co^II) are formed with R′ = p-(C₂H₄)₂C₆H₄ it can be shown, that in solutions of the complexes with R′ = o-(C₂H₄)₂C₆H₄ and R′ = o-(C₃H₆)₂C₆H₄ there exists an association equilibrium comprehending oligomers with n ? x. Above all in the latter case steric conditions seem to favour intramolecular chelating and thus formation of ansa-type complexes. Synthesis of the ligands and the complexes is described.     

Die Kristallstruktur von Bis(N,N-diethyl-N′ -benzoylselenoureato)nickel(II)

The Crystal Structure of Bis(N,N-diethyl-N′ -benzoylselenoureato)nickel(II) Ni(C₁₂H₁₅N₂OSe)₂ crystallizes in the monoclinic space group P2₁/c. The cell parameters are a = 11.399(3), b = 16.016(4), c = 14.910(6) Å, β = 104.64(3)° and Z = 4. The structure was solved with Patterson and direct methods and was refined to a final R-value of 5.43%. Nickel is coordinated to two N,N-diethyl-N′ -benzoylselenourea molecules to form a bidentally coordinated chelate complex with cis arrangement of the donor atoms. Coordinaton around the nickel atom is planar while the chelate rings diverge from planarity. The ethyl groups of one diethylamino group are disordered. The Ni? Se bond lengths are 2.244(1) and 2.264(1) Å, the Ni? O bond lengths are 1.871(4) and 1.883(4) Å, respectively.