Synthesis of new η6-(arene) chromium tricarbonyl complexes of isoxazolidines by 1,3-dipolar cycloaddition

The 1,3-dipolar cycloaddition products of C,N-disubstituted nitrones and different in situ prepared mono-N-substituted nitrones to η⁶-(styrene) chromium tricarbonyl and η⁶-(ethyl cynnamate) chromium tricarbonyl were synthesized and characterized by HPLC, IR, ¹H NMR spectroscopy, and mass spectrometry. The resulted isoxazolidines were produced with a full regioselectivity and high stereoselectivity reached 100% in most cases.     

Insertion d'une phosphine acétylénique dans un complexe μ-alkylidénique du tungstène suivie de la rupture d'une liaison CP

The diphosphinoalkyne Ph₂PCCPPh₂ (2) reacts with the μ-alkylidene complex (CO)₉W₂[CHCHC(CH₃)₂] (1) to give, upon insertion of the alkyne into one of the CW bonds of the bridging carbene followed by rupture of a CP bond, a phosphido complex (CO)₈W₂[C(PPh₂)CCHCHC(CH₃)₂] PPh₂ (3). An unexpected long-range ¹H³¹P coupling, through five bonds, is observed in complex 3.     

Hydroborierung von 3-methyl-1,3-butadien mit 1,2:1,2-bis(tetramethylen)diboran(6)

The nature of the hydroboration product obtained from 3-methyl-1,3-butadiene and 1,2 : 1,2-bis(tetramethylene)diborane(6) (1) allows for the discussion of the reaction mechanism. The hydroboration proceedsby retention of the cyclic structure in the first step, followed by exchange of BH and BC bonds and final cyclic hydroboration to give 1-(boracyclopentyl)-4-(3-methylboracyclopentyl)butane (5). The structural assignment of 5 is based on ¹H, ¹¹B and ¹³C NMR data.     

Synthesis and crystal structure of a heterodinuclear complex with a bridged ethenyl ligand FeCo(CO)7(μ-CH=CPhH)

[Fe₂(CO)₆(μ-CO)(μ-CHCPhH)]⁻ reacts with Co₂(CO)₈ at room temperature to give the neutral heterodinuclear complex FeCo(CO)₇(μ-CHCPhH), which has been characterized by elemental analysis and spectroscopic (mass, IR and ¹H NMR) methods and by determination of its structure by X-ray diffraction.     

Group 6 metal carbonyl complexes of 3′H-spiro[indole-3,2′-[1,3]benzothiazole-2(1H)]-one

The spiro-compound 3′H-spiro[indole-3,2′-[1,3]benzothiazole-2(1H)-one (IBTH₂) was synthesized and its structure was determined using spectroscopic techniques (FTIR, ¹H NMR and mass) and X-ray crystallography. This ligand possesses different centers for coordination. Reactions of [M(CO)₆], M = Cr, Mo or W with IBTH₂ in THF under reduced pressure were studied. For chromium a complex with molecular formula [Cr(ITP)₂] was isolated; where ITP is the opened form of the ligand which occurred through C_spiro–S bond, while [Mo(CO)₅(IBTH₂)] and [W(CO)₅(IBTH₂)] were isolated from the reaction of IBTH₂ with molybdenum and tungsten carbonyls, respectively. All complexes were characterized by elemental analysis, IR, mass and ¹H NMR spectroscopy. The biological activity of the ligand and its complexes were studied and compared with the parent compound isatin.     

Low temperature spectroscopic observation of oxygen-protonated troponeiron tricarbonyl complexes

Troponeiron tricarbonyl and 7-methyltroponeiron tricarbonyl undergo kinetically controlled oxygen protonation at low temperatures to give the corresponding hydroxytropyliumiron tricarbonyl cations, observable by ¹C and ¹H NMR spectroscopy. At higher temperatures, the oxygen-protonated species isomerize to yield the thermodynamically more stable carbon-protonated pentadienyliron tricarbonyl cations.     

Photochemical reactions of W(CO)6 with hydrosilanes: synthesis, spectroscopic characteristic, and crystal structure of W(CO)3(η-PhSiHPh2)

Photolysis of W(CO)₆ in the presence of Ph₃SiH in n-heptane leads to the formation of the first tricarbonyl(η⁶-triphenylhydrosilane)tungsten complex W(CO)₃(η⁶-PhSiHPh₂) (1) in good yield (ca. 70%). The molecular structure of the new tungsten-silane compound was established by single-crystal X-ray diffraction studies and characterized by IR, UV-Vis, ¹H, ¹³C{¹H}, and ²⁹Si{¹H} NMR spectroscopy.     

Group 6 metal carbonyl complexes containing 3,5-dimethyl-4-ferrocenylmethylpyrazole: synthesis,structure and electrochemical properties

Reaction of M(CO)₆ with 3,5-dimethyl-4-ferrocenylmethylpyrazole under UV irradiation yields monosubstituted group 6 metal carbonyl complexes M(CO)₅L (M?=?Cr, Mo or W; L?=?3,5-dimethyl-4-ferrocenylmethylpyrazole). Their electrochemical behaviour, investigated by cyclic voltammetry, indicates that chromium and tungsten complexes exhibit two one-electron quasi-reversible couples corresponding to the ferrocenyl group and the chromium or tungsten centre, respectively, while the molybdenum complex has one quasi-reversible couple corresponding to the ferrocenyl group and one irreversible oxidation process for molybdenum. The crystal structure of W(CO)₅L, determined by X-ray diffraction methods, shows that ferrocenylpyrazole acts as a monodentate ligand, and W is six-coordinate with quasi-octahedral coordination geometry. The complex is linked into a one-dimensional chain in the lattice through weak intermolecular hydrogen bonds with metal carbonyls acting as acceptors.     

Synthèse de complexes du tungstène,du chrome et du rhénium contenant un ligand 1,4-bidenté carbéne-alcéne

A general synthesis of alkene-carbene complexes of tungsten, chromium and rhenium, containing a six-membered ring system, is outlined and the crystal structure of two new complexes of this type, (CO)₄WC(OEt)(CH)(η²-CH₂CHCH₂) (CH₂CHCH₂) and (CO)₉Re₂(OCH₂CH₃(CH₂(CH₂(CH₂CHCH₂), is described.     

Syntheèse et étude structurale de complexes aminocarbéniques contenant un ligand 1,4 bidenté

The synthesis of aminocarbene complexes of tungsten, containing either a free or a coordinated double bond is described. The crystal structure of complex (CO)₅W[(NCH₃)(CH₂(CHCH₂)][Ph], in which the geometry of the double bond does not permit coordination and of complex (CO)₄WC(NCH₂CHCH₂)(η²-CH₂CHCH₂) in which the unsaturated alkyl chain is coordinated to the metal, is outlined.     

1H NMR conformational analysis of disubstituted arene tricarbonyl chromium complexes

The positions of conformational equilibrium in disubstituted arene chromium tricarbonyl complexes, i.e. alkylanisole chromium tricarbonyl complexes and alkylbenzoate chromium tricarbonyl complexes, have been determined by ¹H NMR spectroscopy. It has been found that the donor effect is the dominant factor in determining the preferred conformation.     

Benzo-1,2,3,6-diazadiborine als liganden in d6-(CO)3M-metallkomplexen

Benzo-1,2,3,6-diazadiborines (III) react with hexacarbonyls of chromium, molybdenum and tungsten to yield the corresponding tricarbonyl-(benzo[d]-1,2,3,6-diazadiborine)metal complexes. From ¹H, ¹¹B and ¹³C NMR results it is concluded that complexation of the (CO)₃M-group occurs at the benzo ring. The ligands IIIa–IIIc exhibit better π donor properties than benzene.     

Synthesis and crystal structure of 2-{5-[2-(2,6-dichlorophenylamino)benzyl]-4-p-tolyl-4H-1,2,4-triazol-3-ylthio}acetate

The compound 2-{5-[2-(2,6-dichlorophenylamino)benzyl]-4-p-tolyl-4H-1,2,4-triazol-3-ylthio}acetate has been prepared and characterized by IR, ¹H NMR, ¹³C NMR and mass spectra. The crystal and molecular structure were further confirmed using single crystal X-ray diffraction. The crystal structure has been found to be stabilized by intermolecular C–H···O interaction generating bifurcated hydrogen bonds whereas the C–H···N interactions generate chain of molecules. The intramolecular N–H···N hydrogen bond forms a ring with S(7) graph-set motif.     

[2+4] Cycloaddition of η6-(styrene)chromium tricarbonyl and conjugated dienes

Cycloaddition of η⁶-(styrene)chromium tricarbonyl to hexa-2,4-diene or cyclopentadiene afford the Diels-Alder adducts with retention of the Cr(CO)₃ group, whereas cyclohexa-1,3-diene undergoes aromatization to give η⁶-(benzene)chromium tricarbonyl. The counter synthesis of these (arene)chromium tricarbonyl derivatives from uncoordinated adducts of the Diels-Alder reaction and chromium hexacarbonyl was carried out.     

η6-苊烯三羰基铬配合物的合成、结构及光谱性质研究

采用苊烯配体与三胺基三羰基铬在四氢呋喃中回流反应,合成了η6-苊烯三羰基铬配合物.通过元素分析、IR、1HNMR、13CNMR、MS和X射线单晶衍射对其结构进行了表征,比较了标题配合物与其自由配体的光物理行为.晶体结构分析表明,标题配合物属单斜晶系,空间群P21/c,Z=4,a=0.8719(7)nm,b=1.2436(10)nm,c=1.1504(9)nm,β=111.835(13)°,Cr(CO)3基团可与苊烯配体中的2个苯环中的任意一个配位,形成2个异构体(R,S),并以1:1的比例在其晶胞单元中反向面对面堆积,这种异构体共存于晶体中归属于Cr(CO)3基团在配体芳环之间的配位移动重排(IRHRs).     

Bis(acetylacetonato)tricarbonyl tungsten(II): a convenient precursor to chiral bis(acac) tungsten(II) complexes

Two equivalents of acetylacetonate (acac) have been successfully introduced into a monomeric tungsten(II) coordination sphere. With the tetracarbonyltriiodotungsten(II) anion as a precursor, the formation of a tungsten(II) bis(acac) tricarbonyl complex, W(CO)3(acac)2, 1, has been accomplished. The addition of PMe3 or PMe2Ph to tricarbonyl complex 1 formed tungsten(II)bis(acac)dicarbonylphosphine complexes 2a and 2b, respectively. Single-crystal X-ray diffraction studies of the parent tricarbonyl complex, 1, and dicarbonyl trimethylphosphine complex 2a confirmed seven-coordinate geometries for both complexes. Variable-temperature 1H and 13C{1H} NMR spectroscopy revealed fluxional behavior for these seven-coordinate molecules: rapid exchange of the three carbon monoxide ligands in 1 was observed, and movement of the phosphine ligand through a mirror plane in a C(S) intermediate species was observed for both 2a and 2b. Tricarbonyl complex 1 reacted readily with alkyne reagents to form bis(acac)monocarbonylmonoalkynetungsten(II) complexes 3a (PhC(triple bond)CH) and 3b (MeC(triple bond)CMe). Variable-temperature 1H NMR spectroscopy was used to probe rotation of the alkyne ligand in 3a and 3b. The introduction of two alkyne ligands was accomplished thermally using excess PhC(triple bond)CPh to form bis(alkyne) complex 4 which was characterized crystallographically, as well as by 1H and 13C NMR spectroscopy. The availability of W(CO)3(acac)2 as a source of the W(acac)2 d4 moiety lies at the heart of the chemistry reported here.     

Determination of the conformation in thioester compounds containing the NSO group through pre-resonance Raman study: Spectroscopic properties of S(N-sulphinylimine)-fluorocarbonylsulphane,FC(O)SNSO

Starting from fluorocarbonylsulphenyl chloride, FC(O)SCl, and N-trimethylsilysulphinylimine, (CH₃)₃SiNSO, the compound S(N-sulphinylimine)-fluorocarbonylsulphane, FC(O)SNSO, has been prepared. The IR, pre-resonant Raman, ¹³C NMR, mass, and UV spectra have been obtained and interpreted.The two bands appearing in the CO stretching fundamental mode region of the vibrational spectra were specially investigated to probe the existence of conformational isomerism in the molecule. From the analysis of the bands and their contours in the vapour-IR spectra, and the depolarization ratios together with the pre-resonant behaviour in the Raman spectrum of the liquid (whose extension is also evaluated), two planar forms can be determined for the molecule.The study of the CO envelope in the IR spectrum of the vapour phase reveals syn conformation (with respect to the CO and SN bonds) as the most stable structure for the molecule, and the anti conformation as the second structure.     

Quantum chemical study of the structures and dynamic behavior of tricarbonyl complexes of Group 6 metals (Cr,Mo, W) with polyaromatic hydrocarbons using the density functional theory

The quantum chemical study of the mechanism was performed for tricarbonyl η⁶-complexes of coronene I-M and kekulene II-M (M = Cr, Mo, W) by the density functional method. The activation barriers of η⁶,η⁶-interring haptotropic rearrangements (IHR), being the migration of the metaltricarbonyl group M(CO)₃ from one six-membered aromatic ring to another, were determined. The processes of η⁶,η⁶-IHR in the metal tricarbonyl complexes with relatively high polycyclic aromatic hydrocarbons (PAH) I and II occur with close energy barriers (ΔG^≠ ≈ 20—25 kcal mol^–1), which are lower than the barriers (ΔG^≠ ~ 30 kcal mol^–1) of similar transformations measured or calculated earlier for the chromium tricarbonyl complexes of naphthalene and its derivatives and other PAH. For the molybdenum tricarbonyl complexes the activation barriers of η⁶,η⁶-IHR decrease additionally by ~ 5 kcal mol^–1 compared to those for the chromium tricarbonyl complexes, whereas for the tungsten tricarbonyl complexes they increase again and become approximately equal to the activation barriers of similar chromium tricarbonyl complexes. All stationary states on the potential energy surface determining the mechanism of η⁶,η⁶-IHR are characterized by a decrease in hapticity compared to the initial and final complexes.     

The diastereoselectivity of the addition of tricarbonyl-(η6-2-lithiothiophene) chromium(O) complexes on aldehydes

It has been shown that the reactions of tricarbonyl(η⁶ -2-lithiothiophene)chromium(O) with various arene carboxaldehydes yields mixtures of unequal amounts of diastereoisomers, which can be separated by flash chromatography. The structures of the products have been established by ¹H NMR spectroscopy and by independent synthesis. A novel synthesis of tricarbonyl(η⁶-thiophene)-chromium(O) (1) is described.     

Tricarbonyl(η6-cyclophane)molybdenum complexes and their geometry-dependent 13C NMR behavior

In the ¹³C NMR spectra of tricarbonyl(η⁶-cyclophane)molybdenum complexes, where the cyclophane moiety is [8]–[15]paracyclophanes, [2.2]paracyclophane, or [2.2]metacyclophane, the complexation shifts for the complexed-ring carbons are dependent on both the degree and the direction of the ring bending. The magnitude of the complexation effect on the one-bond aromatic ¹³C¹H coupling correlates with the magnitude of the complexation shift.