N- vs O-Coordination in cyclomanganation of 1,5-diaryl-3-(2-pyridyl)pentane-1,5-diones and 3-(2-pyridyl)chalcones; cyclomanganation at saturated carbon and the crystal structure of [1,5-diphenyl-κC-3-(2-pyridyl- κN)pentan-2-yl-κC-1,5-dione-κOκO]tetracarbonylmanganesetricarbonylmanganese

Reaction of 1,5-diphenyl-3-(2-pyridyl)pentane-1,5-dione (5a) with 2.5 moles of benzylpentacarbonylmanganese in petroleum spirit under reflux gives a small amount of the symmetric di-aryl-manganated product [1,5-diphenyl-κC²-3-(2-pyridyl)pentane-1,5-dione-κO¹κO⁵]bis-(tetracarbonylmanganese) (7a), but mostly [1,5-diphenyl-κC²-3-(2-pyridyl-κN)pentan-2-yl- κC²-1,5-dione-κO¹κO⁵]tetracarbonylmanganesetricarbonylmanganese (6a) which is manganated at only one aryl carbon [by Mn(CO)₄] but also [by Mn(CO)₃ with N and O coordination] at the methylene carbon adjacent to the Mn(CO)₄-coordinated ketone carbonyl. The latter is a rare example of direct cyclomanganation at a saturated carbon and the only known case adjacent to a carbonyl group; the X-ray crystal structure of 6a is reported. With 3 moles of benzylpentacarbonylmanganese the yield of 6a remains unchanged but some trimanganation product [1,5-diphenyl-κC^2′κC^2?-3-(2-pyridyl-κN)pentan-2-yl-κC²-1,5-dione-κO¹κO⁵]tris-(tetracarbonylmanganese) (8a) is formed, presumably from 7a. Routes to products are proposed and activating factors considered. 1,5-Di-(2-thienyl)-3-(2-pyridyl)pentane-1,5-dione (5b) and its 3-thienyl isomer (5c) similarly give 6a analogues [1,5-di-(2-thienyl-κC³)-3-(2-pyridyl-κN)pentan-2-yl-κC²-1,5-dione-κO¹κO⁵]tetracarbonylmanganesetricarbonylmanganese (6b) and [1,5-di-(3-thienyl-κC²)-3-(2-pyridyl-κN)pentan-2-yl-κC²-1,5-dione-κO¹κO⁵]tetracarbonylmanganesetricarbonylmanganese (6c).Also reported are the mono-cyclomanganation product [1-(2,6-dimethoxyphenyl)-3-(2-pyridyl-κN)prop-2-en-2-yl-κC²-1-one]tetracarbonylmanganese (16) and dicyclomanganation product [1-(2,5-dimethyl-3-thienyl-κC⁴)-3-(2-pyridyl-κN)prop-2-en-2-yl- κC²-1-one-κO ]bis-(tetracarbonylmanganese) (17) from reaction of the respective (E)-1-aryl-3-(2-pyridyl)prop-2-en-1-ones (3-(2-pyridyl)chalcones), the first reported examples of enone metallation at the α-carbon via N-coordination by a β-2-pyridyl group.     

Synthesis and X-ray diffraction analysis/crystal structure of new germatranes containing methyl substituents in three five-membered chelating rings

Three monomeric germatranes, 1-isopropoxy-3,3,7,7,10,10-hexamethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.0^1,5]undecane (1), 1-isopropoxy-3,3,7,7-tetramethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.0^1,5]undecane (2), and 1-isopropoxy-3,3-dimethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.0^1,5]undecane (3) have been synthesized by the reaction of Ge(O-i-Pr)₄ in refluxing toluene with corresponding triethanolamines, (HOCH₂CH₂)_nN(CH₂CMe₂OH)_3−n (n = 0, L1H₃; n = 1, L2H₃; n = 2, L3H₃), where the number of CMe₂ groups adjacent to a OH functionality varied from 3 (L1H₃) to 2 (L2H₃), and to 1 (L3H₃). These germatranes 1-3 have been characterized by solution ¹H and ¹³C{¹H} NMR and the solid state structure of 2 has been determined by single crystal X-ray diffraction.     

Platinum(IV) complexes with purine analogs. Studies of molecular structure and antiproliferative activity in vitro

A series of tetrachloride platinum(IV) compounds of the general formulae PtCl₄L₂, where L = 1,2,4-triazolo[1,5-a]pyrimidine (tp) (1), 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp) (2), 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) (3) and 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) (4) have been prepared and characterized by thermal analysis, ¹H, ¹³C, ¹⁵N, ¹⁹⁵Pt NMR and IR spectroscopy. Spectral data suggest that the triazolopyrimidines act as a monodentate ligand via the nitrogen atom N(3). The preliminary assessments of antitumor properties of the four complexes were evaluated as in vitro antiproliferative activity against three cell lines: HL-60 human acute promyelocytic leukemia, SW707 rectal adenocarcinoma and HCV29T bladder cancer. PtCl₄(dbtp)₂ exhibits high cytotoxic activity against all human cell lines, whereas the other complexes are only moderately active.     

η1-Alkynylplatinum(II) complexes with cycloocta-1,5-diene and tri(1-cyclohepta-2,4,6-trienyl)phosphane ligands

η¹-Alkynylplatinum(II) complexes of the type (cod)Pt(CCR)₂ (1, cod=η⁴-cycloocta-1,5-diene; R=Me (a), ^tBu (b), Ph (c), Fc (d), SiMe₃ (e)) were prepared in good yields from the reaction of (cod)PtCl₂ with either HCCR and NaOEt (R=^tBu, Ph, Fc) or di(1-alkynyl)dimethyltin, Me₂Sn(CCR)₂ (R=Me, SiMe₃). The analogous reaction of [P]PtCl₂ ([P]=tri(1-cyclohepta-2,4,6-trienyl)phosphane, {P(C₇H₇)₂(η²-C₇H₇)}) with Me₂Sn(CCR)₂ (R=Me, ^tBu, Ph, Fc, SiMe₃), afforded selectively the complexes [P]PtCl(CCR) 2a–e in high yield, in which the 1-alkynyl group is in cis position with respect to the phosphorus atom, and one of the C₇H₇ rings is η²-coordinated to platinum through the central CC bond. Complexes 3a–e of the type [P]Pt(CCR)₂ could not be prepared by the reaction of 2 with an excess of the 1-alkynyltin reagents. However, the reaction of 1 with the phosphane P(C₇H₇)₃ gave compounds 3a–e in quantitative yield by substitution of the cod ligand. The molecular structures of 2b and 3d were determined by X-ray structure analysis, and complexes 1–3 were characterised in solution by multinuclear magnetic resonance spectroscopy (¹H-, ¹³C-, ²⁹Si-, ³¹P-, ¹⁹⁵Pt-NMR). The structures of 2 and 3 in solution were found to be fluxional with respect to coordination of the C₇H₇ rings to platinum.     

Long-range nuclear spin-spin coupling between 11B and 13C, 29Si or 119Sn: a promising tool for structural assignment

The influence of unresolved long-range nuclear spin-spin coupling [ⁿJ(¹¹BX) (n > 1; X = ¹³C, ²⁹Si or ¹¹⁹Sn)] on X resonances has been studied for aminoboranes (1 and 2), haloboration (2 and 4), hydroboration (5) and organoboration products of alkynes (6 and 7). The differential broadening of X resonances in the X NMR spectra arising from ⁿJ(¹¹BX) (most obvious for X= ¹¹⁹Sn) shows a qualitatively useful pattern of various coupling pathways. |²J(¹³CN-¹¹B)| in 1 and 2 appears to be sensitive to the nature of the trans-ligand and to the ring rize. In many alkenylboranes (3, 4, 5b and d, 6 and 7) the magnitude of the coupling constants across the CC double bond follows the trend |²J(¹¹BX)| ∼ |³J(¹¹BX)|_cis < |³J(¹¹BX)|_trans. An increasing number of electropositive substituents at the CC double bond causes an increase in the magnitude of |³J(¹¹BX)|_cis,trans. If there are only organyl groups of hydrogen attached to the CC double bond, as in the hydroboration products of alkynes (5a and c) |ⁿJ(¹³C-¹¹B)| appears to be too small with respect to [T_Q(¹¹B)]⁻¹, and the differential broadening was neglibible under the experimental conditions used.     

Réactivité du bromure de 5-thioxylopyranosyle et du 1,5-dithioxylopyranoside vis-à-vis d’anions thiolate

Reactivity of 5-thioxylopyranosyl bromide and 1,5-dithioxylopyranoside towards thiolate anions. Reactivity of thiolate anion RS^– 2′ (C₆H₅–S^–) and 3′ (p-CH₃–C₆H₄–S^–) towards 5-thioxylopyranosyl bromide Xyl–Br yields to the corresponding 1,5-dithioxylopyranoside Xyl–SR 7 R = C₆H₅– and 8 R = p-CH₃–C₆H₄, respectively. In the presence of 4′ (C₆H₅–CH₂–S^–) or 5′ (CH₃–S^–), the reaction gives the 5-thioxylopyranose 9. Anions 5′ and 4′ react with 1,5-dithioxylopyranoside 10 Xyl–SR′ (R′ = –C₆H₄–CO–C₆H₄–CN) to give sulphide derivative 11 (CH₃–S–C₆H₄–CO–C₆H₄– CN) and 13 (C₆H₅–CH₂–S–C₆H₄–CO–C₆H₄–CN), respectively, and the 1,5–dithioxylose 12. These differences in terms of reactivity could be explained by the nucleophilic behaviour of the formed thiolate anion. To cite this article: D. Brevet et al., C. R. Chimie 6 (2003).     

Rhodauricanol A,an analgesic diterpenoid with an unprecedented 5/6/5/7 tetracyclic system featuring a unique 16-oxa-tetracyclo[11.2.1.01,5.07,13]hexadecane core from Rhododendron dauricum

A novel diterpenoid with an unprecedented 5/6/5/7 tetracyclic system, rhodauricanol A (1), five new grayanane-derived diterpenoids, dauricanols A?E (2?6), and five known ones (7?11) were isolated from the flowers of Rhododendron dauricum. Rhodauricanol A (1) possesses a unique 5/6/5/7 tetracyclic ring system featuring a 16-oxa-tetracyclo[11.2.1.0^1,5.0^7,13]hexadecane core. Dauricanols A?C (2?4) are the first 1,3-dioxolane conjugates of grayanane diterpenoids and 5-hydroxymethylfurfural and vanillin, respectively, and dauricanols D (5) and E (6) represent the first examples of 6-deoxy-1,5-seco-grayanane diterpenoids. Their structures were determined by spectroscopic methods, quantum chemical calculation including ¹³C NMR-DP4+ analysis and ECD calculation, and single-crystal X-ray diffraction analysis. Plausible biosynthetic pathways for 1?4 were proposed. All the isolates showed significant analgesic activities, and dauricanols B (3) and C (4) showed more potent analgesic activities than the positive control, morphine.     

Synthesis and structural characterization of the first trialkylguanidinate and hexahydropyramidopyramidinate complexes of tin

The first guanidinate complexes of tin have been prepared using N,N′,N′′-trialkylguanidinates ([(RN)₂C(NRH)]⁻; R=cyclohexyl; isopropyl) and 1,3,4,6,7,8-hexahydro-2H-pyramido[1,2-a]pyramidinate (hpp⁻) as ligands. The direct reaction between triisopropylguanidine and SnCl₄ provided the complex {[ⁱPrN]₂C[NHⁱPr]}SnCl₃ (1) along with concomitant formation of the guanidinium salt {C[NHⁱPr]₃}⁺[SnCl₅(THF)]⁻ (2). The Sn(II) guanidinate complexes {(C₆H₁₁N)₂C[NH(C₆H₁₁)]}₂Sn (3) and {CN[N(CH₂)₃]₂}₂Sn (4) were prepared through metathesis reactions between 0.5 equiv. SnCl₂ and (C₆H₁₁N)₂C[NH(C₆H₁₁)]Li or hppLi, respectively. Complex 4 is the first reported mononuclear complex of this ligand. In contrast, the reaction of hppLi with 1 equiv. SnCl₂ afforded a bridging dinuclear species, {CN[N(CH₂)₃]₂SnCl}₂ (5). A second mononuclear complex of the hpp⁻ ligand, {CN[N(CH₂)₃]₂}₂SnCl₂ (6), was the product obtained from the reaction of 2 equiv. of hppLi with SnCl₄. The full structural details of compounds 1 and 3–6 are reported. In the case of compounds 1 and 3 these results revealed a distinctly unsymmetrical bonding mode for the bidentate guanidinate ligand and suggest variable degrees of π delocalization with the ligand. The geometries of the Sn centers in 3, 4 are derived from distorted trigonal bipyramidal coordination with a stereochemically active lone pair occupying one coordination site. In contrast, complex 5 displayed a geometry derived from a tetrahedral ligand array with one vertex occupied by a lone pair of electrons. Complex 6 is six coordinate and possesses 2 equiv. chelating bidentate hpp⁻ ligands and two cis-chloro groups.     

Catechol oxidation: activity studies using electron-rich nitrogen-based ligands

We have studied the oxidation of catechol to o-quinone with atmospheric dioxygen at ambient conditions by in situ generated copper (II) complexes of five electron-rich nitrogen ligands: (3,5-dimethyl-pyrazol-1-yl)-methanol L1; 3-benzylamino-propionitrile L2; 3-[benzyl-(3,5-dimethyl-pyrazol-1-ylmethyl)-amino]-propionitrile L3; {3-[(2-cyano-ethyl)-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propyl}-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propionitrile L4 and 3-[{2-[(2-cyano-ethyl)-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-ethyl}-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propionitrile L5. We found that all complexes catalyze the oxidation reaction with different rates depending on three parameters: the nature of the ligand, the nature of ion salts, and the concentration of the complex. The combination of L3(CuSO₄) gave the highest rate of this activity about 8.71 μmol¹/L¹/min¹.     

Unprecedented triphosphinine iron interactions: Intramolecular electron transfer,reactivity round a corner,and a low-activated ring element exchange reaction

2,4,6-Tri-tert-butyl-1,3,5-triphosphinine (7) was combined with 1,5-COD or 2,4-di-tert-butyl-1,3-diphosphete to form iron π-complexes. The ligands of highly reactive [(2,4-di-tert-butyl-1,3-diphosphete)(2,4,6-tri-tert-butyl-1,3,5-triphosphinine)Fe] (8) are formed by cyclooligomerization of tert-butylphosphaalkyne (3) under the influence of the iron atom. 8 rearranges spontaneously to yield penta-tert-butyl-pentaphosphaferrocene (9) as the isolable product. An intramolecular electron transfer product [(1,5-COD)(η⁶-1,3,5-triphosphacyclohexa-2,5-dine-1,4-diyl)Fe⁽²⁺⁾] (12) is obtained with 1,5-COD. Addition of [(CO)₅Cr(THF)] initiates an interligand hydrogen transfer to form [(η⁵-trihydropentalenyl)Fe(μ,1-3-η-4,5,6-trihydro-1,3,5-triphosphinine)Cr(CO)₅] (13) Extensive DFT calculations of isolated and reactive species, and several possible intermediates agree with the experimental observations and revealed for the first time a possible reaction sequence, which allows a low-activated exchange of ring elements between the ligands of sandwich complex 8 to form 9. The process is based on the specific combination of the metal and its heterocyclic π-ligands. Both, singlet and triplet spin states play an important role in the process.     

Chiral arene ruthenium complexes: Part 3. [Ruthenium(η6-arene)(η4-1,5-cyclooctadiene)] complexes with N or O donor functions in the arene side chain

Arene ruthenium(0) complexes with carbonyl side chain functionalities like [Ru(η⁶-C₆H₅COR)(η⁴-COD)] or [Ru(η⁶-o-C₆H₄{R¹}COR)(η⁴-COD)] (COD=1,5-cyclooctadiene; R=H, CH₃; R¹=H, CH₃, OCH₃) are easily accessible by replacing the naphthalene ligand of [Ru(η⁶-naphthalene)(η⁴-COD)] (1) through an arene exchange reaction. These carbonyl species are susceptible to standard organic reactions of the carbonyl function, thus allowing the introduction of dangling side chains bearing highly polar functions like hydroxyl or amino groups. Aldol reaction of [Ru(o-C₆H₄{CH₃}COCH₃)(COD)] (3) with (−)-menthylchloroformate in the presence of LDA (LDA=lithium diisopropylamide) leads to a diastereomeric mixture of [Ru(menthyl-{3-oxo-3-η⁶-o-tolyl}propionate)(COD)] (10). However, treatment of 3 with LDA and o-tolylaldehyde or benzaldehyde affords the unexpected products [Ru(1-η⁶-o-tolyl-3-o-tolylpropan-1-one)(COD)] (11) and [Ru(1-η⁶-o-tolyl-1-phenylpropan-1-one)(COD)] (12). A diastereoselective addition (88% de) of deprotonated menthylacetate to [Ru(o-tolylaldehyde)(COD)] (4) results in the formation of [Ru(menthyl 3-η⁶-o-tolyl-3-hydroxypropionate)(COD)] (13). Racemic planar-chiral aldehyde complexes 2 and 4 react with amines giving the imination products in good yield. In case of reaction between 2 and (R)-N-amino-2-(methoxymethyl)-pyrrolidine (RAMP), diastereomeric [Ru(N-[[η⁶-(2-methylphenyl]methylene]-(R)-2-(methoxymethyl)-1-pyrrolidinamine)(COD)] (17) is formed. The diastereomers (R,R)-17 and (S,R)-17 have been separated by fractional crystallisation. Asymmetric arene ruthenium complexes with a defined planar-chiral configuration are thus accessible. Reduction of [Ru(3-η⁶-phenyl-(R)-methylbutyrate)(COD)] (7) with LiAlH₄ yields the chiral γ-alcohol [Ru(3-η⁶-phenyl-(R)-1-butanol)(COD)] (18). A Wittig olefination converts the aldehyde complex 4 into a mixture of E- and Z-isomeric [Ru(1-η⁶-o-tolyl-2-phenylethylene)(COD)] 21a and 21b, which were separated again by fractional crystallisation.     

Syntheses, crystal structures and fluorescent properties of two d 10-metal coordination polymers based on 1,5-naphthalenedisulfonic acid

The first examples of two d ¹⁰ metal coordination polymers based on 1,5-naphthalenedisulfonic acid and benzimidazole, namely, [Cd(bim)₄(1,5-nds)] 1 and [Ag(bim)₂]·½1,5-nds 2 (bim = benzimidazole, 1,5-nds = 1,5-naphthalenedisulfonic acid) were synthesized successfully under solvothermal conditions. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR, TG-DSC, PXRD, UV–Vis, and DFT. 1 exhibits a 3D supramolecular structure which started from 1D helical chain. 2 also shows a 3D architecture which was assembled via π–π interactions and hydrogen bonds. The hydrogen bonds formed by 1,5-nds play an important role in increasing the dimensionality of architectures of 1 (from 1D to 3D) and 2 (from 0D to 1D). Moreover, both 1 and 2 show excellent luminescent properties, 335 nm for 1 (λ _ex = 286 nm) and 341 nm and 389 nm for 2 (λ _ex = 234 nm), and may be the suitable candidates of fluorescent materials. From UV–Vis spectra, the remarkable absorption peaks can be found at 276 nm for 1 and 271 nm for 2. The simulated UV–Vis spectra (290.30 nm for 1 and 271.64 nm for 2) by Gaussian 09 DFT correspond well with the experimental results. From the electron density distribution of frontier molecular orbitals, it is known that the two absorption bands are attributed to the intra-ligand electron transition from HOMO?26 to LUMO and from HOMO?3 to LUMO+1 for 1, from HOMO?1 to LUMO+18 and LUMO+19 for 2.     

Synthesis,conformational preferences in gas and solution,and molecular gear rotation in 1-(dimethylamino)-1-phenyl-1-silacyclohexane by gas phase electron diffraction (GED), LT NMR and theoretical calculations

1-(Dimethylamino)-1-phenyl-1-silacyclohexane 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED), low temperature ¹³C NMR spectroscopy and quantum-chemical calculations. The predominance of the 1-Ph_ax conformer (1-Ph_eq:1-Ph_ax ratio of 20:80%, ΔG°(317?K)?=??0.87?kcal/mol) in the gas phase is close to the theoretically estimated conformational equilibrium. In solution, low temperature NMR spectroscopy showed analyzable decoalescence of C_ipso and C(1,5) carbon signals in ¹³C NMR spectra at 103?K. Opposite to the gas state in the freon solution employed (CD₂Cl₂/CHFCl₂/CHFCl₂?=?1:1:3), which is still liquid at 100?K, the 1-Ph_eq conformer was found to be the preferred one [(1-Ph_eq: 1-Ph_ax?=?77%: 23%, K?=?77/23?=?2.8; ?ΔG°?=??RT ln K (at 103?K)?=?0.44?±?0.1?kcal/mol]. When comparing 1 with 1-phenyl-1-(X)silacylohexanes (X?=?H, Me, OMe, F, Cl), studied so far, the trend of predominance of the Ph_ax conformer in the gas phase and of the Ph_eq conformer in solution is confirmed.     

Total synthesis of the sesquiterpene (±)-hirsutene using an organoselenium-mediated cyclization reaction

Cyclization of 2-carbomethoxy-3-(4',4'-dimethylcyclopent-2-enylmethyl)cyclopentanone (4) with N-phenylselenophthalimide and tin(IV) chloride affords cis-syn-cis-1β-carbomethoxy-4,4-dimethyl-3β-phenylselenotricyclo [6.3.0.0^2,6]undecan-11-one (8) and cis-anti-cis-1β-carbomethoxy-4,4-dimethyl-3α-phenylselenotricyclo [6.3.0.0^2,6]undecan-11-one (9). Both of these selenides can be elaborated to cis-anti-cis-4,4-dimethyl-1β-methyltricyclo [6.3.0.0^2,6]undecan-11-one (13) which upon treatment with CH₂Br₂/ TiCl₄/Zn affords the sesquiterpene (±)-hirsutene (1) in 20% overall yield.     

A hexanuclear discrete assembly and a two dimensional coordination polymer constructed from heterotrinuclear [(CuL)2Zn]2+ nodes and dicyanamide spacer (H2L = salen type Schiff base ligands)

Two new Cu(II)–Zn(II) complexes as a discrete hexanuclear cluster [{(CuL¹)₂Zn}₂(μ_1,5-N(CN)₂)₂](ClO₄)₂ (1) and a two dimensional (2D) coordination polymer [(CuL²)₂Zn(μ_1,5-N(CN)₂)₂]_n (2) have been isolated by mixing two similar tetradentate Schiff bases H₂L¹ (N,N′-bis(ɑ-ethylsalicylidene)-1,3-propanediamine) and H₂L² (N,N′-bis(salicylidene)-1,3-pentanediamine) separately with Cu(ClO₄)₂·6H₂O, Zn(ClO₄)₂·6H₂O and NaN(CN)₂ ?at same reaction condition. The heterometallic complexes have been structurally characterized by single crystal X-ray analyses showing that both are formed by angular trinuclear nodes and μ_1,5-dicyanamide spacers. The trinuclear nodes ([(CuL¹)₂Zn]²⁺ in 1 and [(CuL²)₂Zn]²⁺ in 2 are produced in situ from their corresponding reactants. The two Schiff base ligands coordinating the Cu(II) ions through the N₂O₂ donor set are additionally bonded to a Zn(II) ion with the four phenoxido oxygen atoms that act as bridging atoms. The zinc ion completes its coordination geometry with two terminal nitrogen atoms of two different dicyanamide spacers. The orientation of spacers from zinc ion are convergent in 1 whereas divergent in 2. Thus, two [(CuL¹)₂Zn]²⁺ nodes are interconnected by double μ_1,5-dicyanamide bridges via Zn(II) centres to form discrete hexanuclear assembly of complex 1. On the other hand, [(CuL²)₂Zn]²⁺ nodes in 2 are joined by μ_l,5-dicyanamide that bridge Zn(II) to Cu(II) centres of symmetry related units in order to construct a 2D coordination polymer. Consequently, the final coordination environment around Zn(II) is octahedral in both complexes whereas that around Cu(II) are square planar and square pyramidal in 1 and 2 respectively.     

Mössbauer and NMR studies of intramolecular coordination in thienyltetraorganotin(IV) compounds,and the x-ray crystal structure of {C,N-[3-(2-pyridyl)-2-thienyl]} tri(p-tolyl)tin(IV)

Tetraorganotin(IV) compounds containing the [3-(2-pyridyl)-2-thienyl] group (L), of formula R₃SnL (1: R = p-tolyl; 2: R = Ph; 3: R = p-ClC₆H₄; 4: R = cyclo-C₅H₉; 5; R = cyclo-C₆H₁₁) have been synthesized and their structures examined by ^119mSn Mössbauer and NMR (¹¹⁹Sn and ¹³C modes) spectroscopic techniques, and in the case of compound 1 by X-ray analysis.Compound 1 crystallises in the space group C2/c with a 20.85(1), b 9.521(1), c 26.69(1) Å; β 95.37(3)°; V 5274(3) ų; Z = 8. Its structure was solved by the heavy-atom method from 4251 observed MO-K_α data and refined to R = 0.068. The coordination environment at tin in the compound is best described as a pseudo-trigonal bipyramid, involving a waek intramolecular SnN bond of distance 2.841(7) Å. This view is supported by the observation of partially-resolved Mössbauer spectra for compounds 1–5 (QS 0.57–0.96 mm s⁻¹) which is not evidenced, on the other hand, for (2-thienyl)SnR₃ compounds (7: R = p-tolyl; 8: R = Ph), as well as by similar comparisons of data on ¹¹⁹Sn chemical shifts (−176.3 ppm for 1 relative to −135.5 ppm fr 8) and one-bond coupling constants, ¹J(¹¹⁹Sn-¹³C(1)), where C(1) = ipso-carbon of the aryl group or α-carbon of the cycloalkyl group (647.5 Hz for 1, 726.6 Hz for 2 and 786.2 Hz for 3 relative to 536.9 Hz for 7).     

Nucleophilic substitution reactions of acetylides on substituted tricarbonyl(η6-fluoroarene)chromium and reactions of tricarbonyl[η6-(2-trimethylsilylethynyl)toluene]chromium and tricarbonyl[η6-(p-ethynyl-phenylethynyl)benzene]chromium with dicobalt octacarbonyl

Nucleophilic substitution reactions of various acetylides on substituted tricarbonyl(η⁶-fluoroarene)chromiums were pursued. The reaction presumably underwent a more complicated mechanism rather than the direct substitution on the fluorine-bearing carbon. The organometallic compounds (η⁶-C₆H₃R¹R²R³)Cr(CO)₃ (R¹: CC–C₆H₄CH₃, R²: o-Me, R³: H (5a), R¹: CC–C₆H₄CH₃, R²: o-OMe, R³: H (6a), R¹: CC–C₆H₄CH₃, R²: m-OMe, R³: H (6b), R¹: CCPh, R²: o-Me, R³: o-OMe (8b), R¹: CCPh, R²: m-Me, R³: m-OMe (8c), R¹: CCSiMe₃, R²: o-Me, R³: H (9a), R¹: CC–C₆H₄CCH, R²: H, R³: H (12), R¹: CC–C₆H₄CCH, R²: o-Me, R³: H (13)) as well as the organometallic dimmer [{(η⁶-o-Me-C₆H₄)Cr(CO)₃(di-ethynyl)] (di-ethynyl: CC–C₆H₄CC (14)) have been synthesized from nucleophilic substitution reactions of tricarbonyl(η⁶-fluoroarene)(chromium) compounds with suitable acetylides. The products have been characterized by spectroscopic means. In addition, (8b) and (8c) were characterized by X-ray diffraction studies. Further reactions of (9a) and (12) with appropriate amount of Co₂(CO)₈ yielded μ-alkyne bridged bimetallic complexes, Co₂(CO)₆{μ-Me₃SiCC–(o-tolueneCr(CO)₃} (10) and (Co₂(CO)₆)₂{μ-HCC–C₆H₄–CC–(benzene)Cr(CO)₃)}(15), respectively. Both (10) and (15) were characterized by spectroscopic means as well as single crystal X-ray crystallography. The core of these molecules is quasi-tetrahedron containing a Co₂C₂ unit. A two-dicobalt-fragments coordinated di-enyls complex, (Co₂(CO)₆)₂{μ-HCC–C₆H₄–CC–H} (17), was synthesized from the reaction of 1,3-diethynylbenzene with Co₂(CO)₈. Crystallographic studies of (17) also show that it exhibits a distorted Co₂C₂ quasi-tetrahedral geometry.     

Synthesis of bis N-heterocyclic carbenes,derivatives and metal complexes

A method for the synthesis and isolation of 1,1′-methylene-bis-(3-aryl-imidazol-2-ylidene) ligands, aryl = 2,6-diisopropyl-phenyl (DiPP), L^DiPP, mesityl (mes), L^mes, is reported, which provides synthetically useful quantities of high purity. Derivatisation of L^DiPP with chalcogenides gave the adducts L^DiPPE₂, E = S, Se, Te. Reaction of L^DiPP with [Pd(tmeda)Me₂], [Pt(μ-SMe₂)Me₂]₂, [Ir(1,5-COD)(μ-Cl)]₂/KPF₆ and [NiBr₂(dme)] gave [Pd(L^DiPP)Me₂] (1), [Pt(L^DiPP)Me₂] (2), [Ir(L^DiPP)(1,5-COD)](PF₆) (3) and [Ni(L^DiPP)Br₂] (4), respectively. The latter was reduced in the presence of CO to [Ni(L^DiPP)(CO)₂] (5). The structures of L^mes, L^DiPPTe₂, and 1–5 are also reported.     

Triferrocenyl-komplexe von wolfram(VI): Molekülstruktur im festkörper und dynamisches verhalten in Lösung von triferrocenyl-ferrocenoxy-oxo-wolfram,WO(OFc)Fc3

Triferrocenyltungsten complexes of the type WO(X)Fc₃ (X = Cl, (1), OMe (2), OFc (3) and OⁿBu (4)) were obtained by treating WOCl₄ with ferrocenyllithium, FcLi, in tetrahydrofuran solution¹. Reaction of WOCl₄ with a threefold excess of FcLi gives 1, which may be converted into 2 using KOCH₃. Reaction of WOCl₄ with a sixfold excess of FcLi gives a mixture containing 3 und 4 in addition to ferrocene and biferrocene. According to the X-ray crystallographic analysis, WO(OFc)Fc₃ (3) has a trigonal-bipyramidal structure with three ferrocenyl ligands occupying the equatorial positions and an axial ferrocenoxy group coordinated trans to the oxo ligand. The three WC(ferrocenyl) (average 2.092 Å) and the OC(ferrocenyl) (1.33(1) Å) bond distances are remarkably short. The axial tungsten—oxygen distances correspond to a WO double and a WO single bond (1.705(5) and 1.945(5) Å), respectively. The ¹H and ¹³C NMR spectra of WO(OFc)Fc₃ (3) are temperature-dependent. This is ascribed to a hindered rotation of the ferrocenyl ligands around the WC(ferrocenyl) bonds; the free activation enthalpy ΔG^≠(T_c) of this intramolecular dynamic process is 62.5 ± 0.5 kJ mol⁻¹.     

Hydrogen transfer processes in the formation of cationic η5 -dienyl complexes of ruthenium(II): X-ray structure of [Ru(1-5-η-cyclooctadienyl)(PMe2Ph)3][PF6]

The cations [Ru(1—3:5—6-η-C₈H₁₁)(η⁶ -1,3,5-cyclooctatriene)]⁺ (2) and [RuH(COD)L₃]⁺ (5) (COD = cycloocta-1,5-diene, L = PMe₂Ph, AsMePh₂) are convenient precursors to a range of η⁵ -dienyl complexes of ruthenium(II); evidence for hydrogen transfer processes is presented.