bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production of intracellular IL‐2, TNF‐α, and IFN‐γ by T cells in B‐CLL
Authors: Gallego A. , Vargas J. A. , Castejón R. , Citores M. J. , Romero Y. , Millán I. , Durántez A. 
Published: October 2003

AbstractBackgroundRecent evidence indicates that the slowly expanding population of CD5+ B cells that characterizes B‐cell chronic lymphocytic leukemia (B‐CLL) could be related to defects in the response to cytokine produced by T cells that regulate apoptosis. We studied the intracellular expressions of interleukin‐2 (IL‐2), tumor necrosis factor‐α (TNF‐α), and interferon‐γ (IFN‐γ) in T‐helper 1 cells (Th1 response) of B‐CLL.MethodsPeripheral blood mononuclear cells from 21 healthy individuals and purified T cells from 21 early‐stage and 15 late‐stage B‐CLL patients were activated with phorbol myristate acetate and ionomycin. The Th1 cytoplasmic cytokines were evaluated in CD4+ and CD8+ T cells by flow cytometry.ResultsThe percentages of CD4+ and CD8+ T cells positive for IL‐2 were significantly lower in B‐CLL patients than in healthy individuals (P = 0.030 and 0.049, respectively). No significant differences in TNF‐α or IFN‐γ intracellular expressions were found between patients and healthy individuals. TNF‐α‐ and IFN‐γ–expressing CD8 T cells were disease stage dependent, being significantly higher in late‐stage patients (P < 0.001 for both cytokines).ConclusionsOur present observations suggested that Th1 cytokines may be of major importance in the pathogenesis of B‐CLL. Cytometry Part B (Clin. Cytometry) 56B:23–29, 2003. © 2003 Wiley‐Liss, Inc.
Measurement of proliferation marker Ki67 in breast tumour FNAs using laser scanning cytometry in comparison to conventional immunocytochemistry
Authors: Zabaglo Lila , Ormerod Michael G. , Dowsett Mitch 
Published: October 2003

AbstractBackgroundA variety of markers, including Ki67, estrogen receptors (ER), and progesterone receptors (PgR), are frequently measured in fine needle aspirates from human breast carcinomas. Previously, we demonstrated the use of laser scanning cytometry (LSC) for the measurement of Ki67, ER, and PgR in a human breast carcinoma cell line, MCF7 (21). In the present study, we investigated the expression of Ki67 in breast tumour fine needle aspirates (FNAs) using LSC and compared the results to the data obtained using conventional immunocytochemistry (ICC).MethodsA total of 11 sets of cytospins of FNAs taken from breast tumours at various stages of tamoxifen treatment were used. For LSC, the cytospins were stained for Ki67 with fluorescein using immunofluorescence; the nuclei were counterstained with propidium iodide. A parallel set of cytospins was stained using horseradish peroxidase and diaminobenzidine and scored manually by conventional light microscopy.ResultsValues for Ki67 obtained using the LSC were generally lower than ICC scores. The changes in Ki67 measured by the LSC were almost all parallel to those obtained by manual scoring of immunocytochemical stains.ConclusionsIt should be possible to use LSC for the routine measurement of Ki67 marker in FNAs from human breast carcinomas. Cytometry Part B (Clin. Cytometry) 56B:55–61, 2003. © 2003 Wiley‐Liss, Inc.
Comparative measurement of spontaneous apoptosis in pediatric acute leukemia by different techniques
Authors: Savitskiy Valery P. , Shman Tatiana V. , Potapnev Michael P. 
Published: October 2003

AbstractBackgroundTo distinguish between subgroups of patients with acute leukemia, the rate of spontaneous (culture‐induced) apoptosis of leukemic cells was evaluated using five methods.MethodsLeukemic cells (cells) from the bone marrow of children with acute lymphoblastic leukemia (ALL, n = 112) and acute myeloid leukemia (AML, n = 30) were cultured for 20 h in vitro. The level of apoptosis was detected by fluorescent microscopy after staining with acridine orange (AO) or by flow cytometry after staining using PI, JC‐1, the APO‐BRDU kit, or the AnnexinV‐FITC kit.ResultsALL cells were significantly more sensitive to spontaneous apoptosis versus AML cells, as was detected by all methods. The least sensitive technique was apoptosis detection by sub‐G1‐peak/PI‐staining. No difference in the rate of apoptosis in cells was determined between T‐ and B‐lineage ALL patients. In patients with B‐lineage ALL, strong positive correlation existed between the level of cells with loss of mitochondrial membrane potential (JC‐1), chromatin condensation (AO), and externalization of phosphatidylserine (AnnexinV+PI+). The proportion of AnnexinV+PI– cells had no correlative link with any other apoptotic cell subpopulation.ConclusionsWe found different sensitivities of ALL and AML cells to undergoing spontaneous apoptosis in vitro. Detection of the early/intermediate, but not the late stage of apoptosis is of preferable for correct assignment of spontaneous apoptosis in pediatric acute leukemia. Cytometry Part B (Clin. Cytometry) 56B:16–22, 2003. © 2003 Wiley‐Liss, Inc.
Investigating Actinyl Oxo Cations by X‐ray Absorption Spectroscopy
Authors: Den Auwer Christophe , Simoni Eric , Conradson Steven , Madic Charles 
Published: October 2003

AbstractEarly actinide elements (from U to Am) have the ability to form lineartrans‐dioxo complexes with formal valence of the actinide being equal to (V) or (VI). For instance, the ubiquity of the uranyl cation in uranium aqueous chemistry is the basis for its very important industrial and environmental concerns. As a result, the physical chemistry of the actinyl moieties has been the subject of constantly growing investigations. Among all the spectroscopic probes, X‐ray absorption spectroscopy is a particularly useful element and energy‐selective technique. This article reviews the investigation of molecular actinyl complexes using both XANES and EXAFS tools. The absorption edge features have long been used to characterize the frontier orbitals of the absorbing atom. In the case of actinide cations, the LIIIedge, located in the hard X‐ray region, provides a useful fingerprint of the cation polyhedron. Tentatively, simple molecular orbital considerations together with full multiple scattering simulation codes have provided significant interpretations of the edge features. Various examples involving a distortion of the actinyl coordination sphere, starting from the aqueous species are given. Complementary structural data can be obtained in the EXAFS region of the absorption spectrum. In the literature, such molecular systems have been well documented from uranyl aqueous chemistry to neptunyl or plutonyl coordination complexes with oxygen donor ligands. Furthermore, complexation mechanisms upon absorption onto mineral surfaces have been increasingly investigated over the past few years. Overall, contribution of the XAS technique to a better understanding of the actinide bonding is demonstrated from various examples of the literature and the authors’ data. Importance of the simulation codes in order to better describe the absorption features is also strongly underlined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis, Characterisation of (Arene)tricarbonylchromium Complexes Linked to Cationic Fe and Ru Derivatives and Studies of First Hyperpolarisabilities by Hyper‐Rayleigh Scattering
Authors: Garcia Maria Helena , Royer Sophie , Robalo Maria Paula , Dias Alberto Romão , Tranchier Jean‐Philippe , Chavignon René , Prim Damien , Auffrant Audrey , Rose‐Munch Françoise , Rose Eric , Vaissermann Jacqueline , Persoons André , Asselberghs Inge 
Published: October 2003

AbstractIn order to investigate the non‐linear optical properties, in particular second‐order effects of binuclear organometallic complexes, a series of new cationic binuclear [MCp(DPPE)N≡C−(spacer)−C≡C−C6H5Cr(CO)3]+[PF6]− compounds and mononuclear precursors [N≡C−(spacer)−C≡ C−C6H5Cr(CO)3] have been synthesised [where M = FeII or RuII; Cp = η5‐C5H5 and spacer = phenyl ring (C6H4), thiophene, (C4H2S), or bithiophene (C4H2S)2]. The Fe or Ru organometallic π‐donor fragments were linked by an extended π system to the acceptor Cr(CO)3 fragment. The effect of π back‐donation involving the second Fe or Ru metal centre and the π* orbitals of the N≡C‐coordinated group, was probed by the ν(N≡C) stretching bands on the IR spectra and also by NMR spectroscopic data. The planarity, largely due to the π‐electron resonance, found on the solid state structure of the mononuclear complex [N≡C−C6H5−C≡C−(η6‐C6H5)Cr(CO)3] (1Cr) determined by X‐ray diffraction [monoclinic system, P21/c space group, with a = 10.326(2) Å, b = 13.209(5) Å, c = 11.799(2) Å and Z = 4] emphasises the electronic effect of this building block. The significant values of first hyperpolarisability β determined by hyper‐Rayleigh scattering (HRS) indicate that the Fe containing compounds were more efficient on second‐order non‐linear optical properties than the ruthenium analogues and the parent mononuclear chromium compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Novel Water‐Soluble Tripodal Imidazolyl Ligand as a Model for the Tris(histidine) Motif of Zinc Enzymes: Nickel, Cobalt and Zinc Complexes and a Comparison with Metal Binding in Carbonic Anhydrase
Authors: Kunz Peter C. , Reiß Guido J. , Frank Walter , Kläui Wolfgang 
Published: October 2003

AbstractTris[2‐isopropylimidazol‐4(5)‐yl]phosphane (4‐TIPiPr), a novel model ligand for the tris(histidine) motif of many zinc enzymes, has been prepared. 4‐TIPiPr is hydrolytically stable and soluble in protic solvents. It readily forms chloro‐ and nitratocobalt, ‐nickel and ‐zinc complexes in aqueous methanol. The crystal structures of the solvates [(4‐TIPiPr)Co(MeOH)(NO3)]NO3·2Et2O (3·2Et2O), [(4‐TIPiPr)Ni(MeOH)(NO3)]NO3·Et2O·MeOH (4·Et2O·MeOH), [(4‐TIPiPr)CoCl]Cl·MeOH·2.5H2O (5·MeOH·2.5H2O), and [(4‐TIPiPr)ZnCl]Cl·MeOH·2.5H2O (6·MeOH·2.5H2O) have been determined. The complex 3 shows striking structural similarities to the hydrogencarbonate complex of cobalt‐substituted human carbonic anhydrase II (HCA II). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of New PdII Complexes Containing a Thioether‐Pyrazole Hemilabile Ligand − Structural Analysis by 1H, 13C NMR Spectroscopy and Crystal Structure of [PdCl(bdtp)]BF4 [bdtp = 1,5‐Bis(3,5‐dimethyl‐1‐pyrazolyl)‐3‐thiapentane]
Authors: García‐Antón Jordi , Pons Josefina , Solans Xavier , Font‐Bardia Mercè , Ros Josep 
Published: October 2003

AbstractTreatment of the ligand 1,5‐bis(3,5‐dimethyl‐1‐pyrazolyl)‐3‐thiapentane (bdtp) with [PdCl2(CH3CN)2] led to a [PdCl2(bdtp)] complex. Subsequent treatment of this complex with AgBF4 gave [PdCl(bdtp)](BF4). These PdII complexes were characterised by elemental analysis, conductivity measurements, IR spectroscopy, and 1H and 13C NMR spectroscopy. Complex [PdCl2(bdtp)] was again obtained when the complex [PdCl(bdtp)](BF4) was heated under reflux in a solution of NEt4Cl in CH2Cl2/MeOH (1:1). Ligand bdtp in complexes 1 and 2 exhibited a hemilabile character. The X‐ray structure of the complex [PdCl(bdtp)](BF4) was determined. The metal atom is tricoordinated by the two azine nitrogen atoms and one thioether sulfur atom of the thioether‐pyrazole ligand, its coordination (distorted square planar) being completed with one chloride ion. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Binuclear Hydridoplatinum(II): One‐Pot Synthesis, INS Spectra and X‐ray Crystal Structure of [Pt2(dcype)2(H)3][BPh4] {dcype = 1,2‐Bis(dicyclohexylphosphanyl)ethane}
Authors: Bandini Anna Laura , Banditelli Guido , Manassero Mario , Albinati Alberto , Colognesi Daniele , Eckert Juergen 
Published: October 2003

AbstractThe binuclear platinum(II) hydride [Pt2(dcype)2(H)3][Cl] (1b) has been isolated in high yields by treatment of Pt(dcype)Cl2 with NaBH4 (molar ratio 1:2) in ethanol solution at room temperature. This one‐pot synthesis is not straightforward when starting from diphenylphosphanylalkane complexes. The compounds [Pt2(dppp)2(H)3][OH] (3b) and [Pt2(dppb)2(H)3][OH] (4) were isolated by starting from the mononuclear hydrides {cis‐[Pt(P‐P)(H)2]} while mixtures of both binuclear {[Pt2(dppe)2(H)3]+, 5} and trinuclear {[Pt3(dppe)3(H)3]+, 6} trihydrides were obtained with the dppe ligand. Various salts of the cation 1, [Pt2(dcype)2(H)3][X] (X = BF4, 1a; OH, 1c; BPh4, 1d), were isolated either from [Pt(dcype)(μ‐OH)]2[BF4]2 (2) by a general procedure (1a), or by decomposition of the complex cis‐[Pt(dcype)(H)2] in solution (1c), as well as by metathesis reactions (1a, 1c, and 1d). Compounds 1a, 1b, and 1d react with CO under mild conditions to afford the corresponding PtI binuclear hydrides [Pt2(dcype)2(μ‐CO)(μ‐H)][X] (X = Cl, 7a; BF4, 7b; BPh4, 7c). The binuclear core of cation 1 is broken by KCN in methanol solution, yielding the mononuclear complex cis‐[Pt(dcype)(CN)(H)] (8). The complexes 1a−d, 2, 7a−c, and 8 have been characterised by FAB MS, IR, and NMR (1H, 31P, and 195Pt) spectroscopic techniques; the 1 and 7 cations show fluxional behaviour on the NMR timescale. The structure of compound 1d was determined, at 200 K, by single‐crystal X‐ray diffraction. All the hydrido ligands were located. The Pt−Pt separation is 2.696(1) Å and the coordination geometry around each platinum centre can be regarded as distorted square planar. Incoherent Inelastic Neutron Scattering (INS) spectra were obtained for 1a and [Pt2(dppe)2(H)3][BF4] (5a); the spectra reflect the different geometries of the two “P4Pt2(H)3” cores as found by single‐crystal structure determinations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis, Crystal Structure, and Optical Properties of a New Molecular Complex of C60 with a Covalently Linked (FeIIITPP)2O Dimer
Authors: Litvinov Aleksey L. , Konarev Dmitri V. , Kovalevsky Andrey Yu. , Lapshin Alexander N. , Yudanova Evgeniya I. , Drichko Natalia V. , Coppens Philip , Lyubovskaya Rimma N. 
Published: October 2003

AbstractA new molecular complex of C60 with covalently linked μ‐oxo dimer (FeIIITPP)2O are (TPP = tetraphenylporphyrin) was obtained. The complex has a neutral ground state and is formed mainly by van der Waals forces. The X‐ray analysis of the crystal structure of the complex showed it to have isolated packing of fullerenes in which each fullerene molecule is embraced in a pocket built by porphyrins. Optical properties and EPR behavior of the complex are described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Stepwise Assembly of Mixed Metal Dinuclear Carbonyl Complexes
Authors: Heinze Katja , Jacob Volker 
Published: October 2003

AbstractThe one‐pot/three‐step solution synthesis of a library of nine directional, dinuclear mixed‐metal complexes composed of different metal‐carbonyl units (M = Cr, Mo, W) and a bifunctional bridging isocyanide Schiff‐base ligand is described. The well‐defined metal sequence in these complexes with Cr, Mo, and W in two positions can be determined post‐synthesis by a combination of spectroscopic methods. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Group 10 Metal Complexes of SPS‐Based Pincer Ligands: Syntheses, X‐ray Structures, and DFT Calculations
Authors: Doux Marjolaine , Mézailles Nicolas , Ricard Louis , Le Floch Pascal 
Published: October 2003

AbstractThe 2,6‐bis(diphenylphosphanylsulfide)phosphinine (1) reacts with water to afford a 1,2‐dihydrophosphinine oxide 5 featuring a P−H bond. Reaction of 5 with one equivalent of [Pd(COD)Cl2] yields the SPS pincer‐based complex 6 with a P(OH) λ5‐phosphinine central ligand. Complex 6 has been structurally characterized. Two possible mechanisms account for the formation of 5: an intramolecular P−H to P−Pd metathesis or one based on the P=O to POH equilibrium. Methanol, ethanol or diethylamine also react with 1 to afford the corresponding P(H)(OMe) 7, P(H)(OEt) 8, and P(H)(NEt2) 9 λ5‐phosphinines. No definitive mechanism for the formation of 7−9 can be proposed since no intermediates were detected in situ by 31P NMR spectroscopy. However, DFT calculations (at the B3LYP 6‐311+G(d,p) level of theory) suggest that the conversion of 1,2‐dihydrophosphinines into λ5‐phosphinines is not viable because it involves a high activation energy. Like 5, λ5‐phosphinines 7 and 8 react with [Pd(COD)Cl2] to afford the expected palladium complexes 10 and 11. An alternative method relies on the reactivity of nucleophiles with a SPS pincer‐based complex 2 featuring a P−Cl bond. (−)‐Menthol and lithium diethylamide react with 2 to yield the expected P‐OMen 13 and P‐NEt2 14 complexes. Both complexes have been structurally characterized. Bromonickel 18 and chloroplatinum 19 complexes of the SPS ligand, featuring a P−Br or P−Cl bond, have also been prepared by reacting 1 with [NiBr2(DME)] and [Pt(COD)Cl2], respectively. Like their palladium congener, both species react with ethanol to afford the corresponding P−OEt derivatives 20 [M = Ni] and 21 [M = Pt]. nButyl derivatives of these SPS ligands also bind to Ni−Br (complex 22) and Pt−Cl (complex 23) fragments. Both complexes were straightforwardly prepared by reacting anion 3, resulting from the reaction of nBuLi with 1, with the [NiBr2(DME)] and [Pt(COD)Cl2] precursors. The chloride ligand is readily substituted by acetonitrile in complexes 4, 11, 20, and 21 upon treatment with AgBF4 in dichloromethane. Reaction of AgOTf with the palladium complex 4 affords complex 28 via substitution of the chloride ligand by TfO−. The X‐ray crystal structures of the dimethyl‐λ5 derivative 29 of 1, and that of its P‐OMe anion 30, have been recorded. Anion 30 can be regarded as a phosphanyl‐substituted pentadienyl anion. DFT calculations and a charge decomposition analysis (CDA) show that the phosphorus atom in these SPS‐pincer structures is a classical tertiary phosphane ligand in terms of donation and acceptance. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Lithium [Bis{benzoyl‐W(CO)5}(μ2‐hydrogen)] − A Charge‐Assisted H+‐Bridged Organometallic Complex Prepared by Selective Li+ Ion Replacement
Authors: Esterhuysen Matthias W. , Raubenheimer Helgard G. 
Published: October 2003

AbstractEfficient syntheses and isolation procedures of two closely related benzoyl−W(CO)5 compounds, [{Li(diglyme)}{Ph(O)CW(CO)5}] (1) and [Li(diglyme)2][(μ2‐H){Ph(O)CW(CO)5}2] (2) are reported. The empirical formulae of 1 and 2 differ only in that the latter contains half the number of Li+ ions, with the balance of cations replaced by protons through an acidic silica gel filtration procedure. X‐ray structural investigations of both compounds revealed a self‐assembled polymeric Li+‐bridged structure for 1, and a strikingly dissimilar H+‐bridged structure for 2, thereby emphasising the important influences of strong, charge‐assisted hydrogen bonds on solid‐state structures. Possible implications of this novel route to charge‐assisted hydrogen bonds for crystal engineering are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cover Picture: Lithium [Bis{benzoyl‐W(CO)5}(μ2‐hydrogen)] − A Charge‐Assisted H+‐Bridged Organometallic Complex Prepared by Selective Li+ Ion Replacement (Eur. J. Inorg. Chem. 21/2003)
Authors: Esterhuysen Matthias W. , Raubenheimer Helgard G. 
Published: October 2003

AbstractThe cover picture shows the crystal structure of lithium bis[benzoyl‐W(CO)5][μ2‐hydrogen] (orange: tungsten; red: oxygen; blue: lithium; grey: carbon), a new class of hydrogen‐bridged organometallic complexes exhibiting strong, charge assisted hydrogen bonds between anionic metal−acyl moieties in Fischer‐type carbene precursors. The novel cation‐exchange procedure used here could find application in future organometallic crystal engineering studies involving carbonylmetal fragments. Details are discussed in the article by H. G. Raubenheimer et al. on p. 3861 ff. Dedicated to E. O. Fischer on the occasion of his 85th birthday
Regioselective Reduction of 2‐(Arylideneamino)isoindole‐1,3‐diones − Synthesis of Alkaloid Analogues by N‐Acylhydrazonium Ion Aromatic π‐Cyclization
Authors: Fogain‐Ninkam Alain , Daïch Adam , Decroix Bernard , Netchitaïlo Pierre 
Published: October 2003

AbstractHydroxylactams 6a−c and 7a−c were synthesized by successive regioselective reductions of arylideneaminophthalimides 3a−c, which were easily available from aminophthalimide 1 and benzaldehyde (2a) or thiophenecarboxaldehydes 2b and 2c. N‐Acylhydrazonium ions III, generated in the presence of Lewis acid from acetoxy derivatives 8a and 9a of hydroxylactams 6a and 7a, or in organic acid medium directly from hydroxylactams 6b and 6c, induced the expected isoindolo‐phthalazines 10a and 11a and thienopyridazino‐isoindolones 12b and 12c. On the other hand, hydroxylactams 7b and 7c under acidic conditions gave the unexpected N‐thienylmethyl‐substituted thienopyridazino‐isoindolones 13b and 13c. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Star‐Shaped Compounds Having 1,3,5‐Triazine Cores
Authors: Meier Herbert , Holst Hans Christof , Oehlhof Annette 
Published: October 2003

AbstractThe 1,3,5‐triazine derivatives 1−4 having styryl or higher oligo(phenylenevinylene) chains in the 2‐, 4‐, and 6‐positions represent star‐shaped push‐pull compounds. Alkoxy or dimethylamino groups on the peripheral benzene rings, which act as electron donors, and the central 1,3,5‐triazine ring, which acts as an electron acceptor, cause intramolecular charge transfer (ICT) to occur in the absorption S0⇄S1. Protonation of the 1,3,5‐triazine core enhances the effect, as demonstrated by a bathochromic shift; a secondary protonation on the dimethylamino groups, however, leads to the breakdown of the ICT. Thus, the yellow compound 1d first becomes violet and then colorless upon the addition of trifluoroacetic acid. In neutral solution, the long‐wavelength absorption of the series 1f, 2b, 3, and 4 converges to λ∞ = 427 nm (with an effective conjugation length nECL = 7). The absorption of the corresponding protonated compounds approaches λ∞ = 515 nm (nECL = 6). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Thermal Rearrangement of 1,5,8‐Triphosphaisolumibullvalenes (1,5,8‐Triphosphatetracyclo[4.4.0.02,8.05,7]deca‐3,9‐dienes)
Authors: Disteldorf Hendrik , Renner Jens , Heydt Heinrich , Binger Paul , Regitz Manfred 
Published: October 2003

Abstract1,5,8‐Triphosphaisolumibullvalenes (1,5,8‐triphosphatetracyclo[4.4.0.02,8.05,7]deca‐3,9‐dienes) 3, when suitably substituted, undergo thermal rearrangement to afford the 1,1b,2a‐triphosphahomoquadricyclanes (tetrahydro‐1H‐1,1b,2a‐triphosphadicyclopropa[cd,gh]‐pentalenes) 6. The structure of the rearranged compound 6d was elucidated by X‐ray crystallography. The newly synthesized compound 6a undergoes addition of oxygen or sulfur with an increase in the coordination at the phosphorus atom P‐1 to yield the products 10a/b; it also undergoes complexation with Co2(CO)8 at the newly formed P−C≡C− unit to afford product 11. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A REKS Assessment of the Face‐Diagonal Bond in 1,3‐Didehydrocubane and a Comparison with Benzyne Biradicals
Authors: de Visser Sam P. , Filatov Michael , Schreiner Peter R. , Shaik Sason 
Published: October 2003

AbstractThe three isomeric cubane biradicals were studied using spin‐restricted ensemble‐referenced Kohn−Sham (REKS) density functional calculations at the B3LYP/6‐31G(d) level of theory. The most stable biradical was found to be ortho‐cubene with the meta‐cubene and para‐cubene biradicals 4.7 kcal mol−1 and 17.8 kcal mol−1 higher in energy, respectively. The singlet ground states are well separated from their lowest lying triplet states. These singlet‐triplet energy differences mostly originate from through‐space interactions for the ortho and meta isomers, whereas these interactions are rather weak for the para isomer. In contrast to para‐benzyne, which was also considered for comparison with an unsaturated system, the singlet‐triplet energy gap remains large in para‐cubadiyl, mainly as a result of its much stronger through‐bond interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)