Pentacoordinated Tin(IV) chloride complexes

Preparation and I.R. spectra of tin(IV) chloride complexes with acridine and piperazine have been described and their structures have been suggested.     

Pentacoordinated iridium(I) complexes incorporating azopyridine chelation. Synthesis,structure and bonding

The reaction of [Ir(COD)Cl]₂ with 2-(arylazo)pyridine (L) in dichloromethane solution has afforded the nonelectrolytic pentacoordinated species of type Ir(L)(COD)(Cl) from which the corresponding bromides and iodides have been synthesised by metathesis (COD=1,5-cyclooctadiene). L ligands used are: 2-(phenylazo)pyridine (L¹); 2-(m-tolylazo)pyridine (L²) and 2-(p-chlorophenylazo)pyridine (L³). The X-ray structures of Ir(L²)(COD)(Cl)·0.5 CH₂Cl₂ and Ir(L³)(COD)(I) have been determined revealing square-pyramidal geometry. The relatively short IrN(azo) lengths (∼2.00 Å) and the relatively long NN bond distance (∼1.30 Å) are consistent with significant dππ* (azo) back-bonding. The HOMO (50% Ir and 15% azo character) and LUMO (50% azo and 30% Ir character) are primarily localised in the IrL fragment and the absorption bands near 600 nm is assigned tentatively to the HOMO→LUMO transition. The stability of the pentacoordinated structures and the inertness to oxidative addition of the present complexes in contrast to the behaviour of corresponding 2,2′-bipyridine species (tetracoordinated, reactive) is rationalised in terms of π-acidity order L≫bpy.     

Synthesis and Reactivity of New Pentacoordinated Phosphoenolpyruvate Derivatives

Abstract

Pentaoxyphosphoranes are closely related as intermediates to the biologically important phosphate ester reactions. Thus, the hydrolysis of phosphoenolpyruvate 1, a strong phosphorylating agent, proceeds most probably via the formation of the cyclic acyloxyphosphorane 2.     

Synthesis of Hexa- and Pentacoordinated Phosphorus Compounds from White Phosphorus

Abstract

A new method is developed for the synthesis of phosphoranes (IIIa-d) and phosphorates (IVa-d) starting from substituted o-benzoquinones(Ia-d), catechols(IIa-d) and white phosphorus.     

A Pentacoordinated Di-N-carboxamido-dithiolato-O-sulfinato-iron(III) Complex Related to the Metal Site of Nitrile Hydratase

Postcoordination oxidation by dioxygen of one of the thiolate groups in a pentadentate N(2)S(3) ligand results in an iron(III) complex with two N-carboxamido, two thiolato, and one O-sulfinato ligands (see the CAMERON representation). This novel mixed coordination is similar to that determined for the inactive form of the nitrile hydratase from Rhodococcus sp. N-771, but differs by the O versus S binding of the sulfinato ligand.     

三齿配体杂环五配位有机锡化合物的合成与生物活性

邻氨基苯酚与邻羟基芳香醛(酮)反应,合成了4个三齿Schiff碱配体(2a,2d,2g和2j),2分别与二苄基二氯化锡,二苯基二氯化锡,二正丁基二氯化锡反应合成了12个未见文献报道的三齿配体杂环五配位有机锡配合物(3a~3l),其结构经1HNMR,IR和元素分析确证。体外抗菌和抗癌活性测试结果表明,3b,3c,3f,3i和3k具有较强的抑菌活性;3c和3l具有较好的抗癌活性。     

Synthesis and reactivity of bis-pentamethylcyclopentadienyl diiododialane (Cp*AlI)2: an aluminium(II) precursor to (Cp*Al)4

Use of an alternative aluminium(iii) starting material has led to the isolation of a new aluminium(ii) diiododialane, which functions as an intermediate in the synthesis of (Cp*Al)(4), reacts oxidatively with methyllithium, and undergoes oxidative cleavage of the Al-Al bond with an aryl azide.     

Synthesis of U(IV) imidos from Tp*2U(CH2Ph) (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) by extrusion of bibenzyl

Addition of organic azides, N(3)R (R = 2,4,6-trimethylphenyl (Mes), phenyl (Ph), 1-adamantyl (Ad)), to a solution of the uranium(III) alkyl complex, Tp*(2)U(CH(2)Ph) (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) (1), results in the formation of a family of uranium(iv) imido derivatives, Tp*(2)U(NR) (2-R). Notably, these complexes were synthesized in high yields by coupling of the benzyl groups to form bibenzyl. The uranium(IV) imido derivatives, 2-Mes, 2-Ph, and 2-Ad, were all characterized by both (1)H NMR and IR spectroscopy, and 2-Mes and 2-Ad were also characterized by X-ray crystallography. In the molecular structure of 2-Mes, typical κ(3)-coordination of the Tp* ligands was observed; however in the case of 2-Ad, one pyrazole ring of a Tp* ligand has rotated away from the metal centre, forcing a κ(2)-coordination of the pyrazoles. This results in a uranium-hydrogen interaction with the Tp* B-H. Treating these imido complexes with para-tolualdehyde results in multiple bond metathesis, forming the terminal uranium(IV) oxo complex, Tp*(2)U(O), and the corresponding imine.     

Synthesis and properties of pyrazole carbaldehyde bis(2-hydroxyethyl)-dithioacetal hydrochlorides*

A simple method has been developed for the synthesis of water-soluble pyrazole derivatives, namely 4-[bis(2-hydroxyethylsulfanyl)methyl]pyrazoles hydrochlorides, by the reaction of a series of pyrazole carbaldehydes with 2-mercaptoethanol in the presence of trimethylchlorosilane. When treated with aqueous ammonia solution the pyrazole-4-carbaldehydes bis(2-hydroxyethyl)dithioacetal hydro-chlorides are converted to the 4-[bis(2-hydroxyethylsulfanyl)methyl]pyrazole free bases.     

ESR. Study of the Pentacoordinated Arsenic Radical Anion [(OH)3(O)AsCH2As(O)(OH)2]=

The anion [(OH)₃(O)AsCH₂As(O)(OH)₂] has been trapped in an X-irradiated single crystal of methylene diarsonic acid. The g -tensor and the hyperfine coupling tensors of the two ⁷⁵As-nuclei have been obtained and the spin densities in the arsenic 4s- and 4p-orbitals determined.     

Synthesis,Crystal Structure,and Diastereomeric Transfer of Pentacoordinated Phosphoranes Containing Valine or Iso-Leucine Residue

Pentacoordinated phosphoranes containing valine or iso-leucine residue (2-phenyl-2,7⁵-spiro[1,3,2-phenanthrodioxaphosphole-2,2′-1,3,2-oxazaphospholan]-5′-one) were synthesized through sequential two-step reactions, whereby the reaction products of phenyldichlorophosphine with N,O-bis(trimethylsilyl)valine or iso-leucine were followed by the addition of phenanthrenequione, and the crystals of 4a and 4b were obtained from benzene and hexane mixed solution. The x-ray structure of the crystals 4a and 4b revealed that they are distorted TBP, exhibiting R_P absolute configuration. The ³¹P NMR spectra showed that the S_P diastereomer could transfer into the other one R_P that came out from the solution during crystallization. Correspondingly, when it was dissolved in solvents the R_P diastereomer transferred into the other one S_P, and the pair of diastereomers changed each other in solution at room temperature through a phosphonium carboxylate zwitterions intermediate.