Joachim Bruckmann

BIDENTATE PHOSPHINES OF HETEROARENES : 9,9-DIMETHYL-4,5-BIS(DIPHENYLPHOSPHINO)XANTHENE

Twofold lithiation of 9,9-dimethylxanthene with n-butyllithium and N,N,N′,N′-tetrametylethylenediamine (TMEDA) in boiling n-heptane followed by reaction with chlorodiphenylphosphine (Ph2PCl) yielded the title compound 4. The phosphine ligand was characterised by 1H NMR, 13C NMR, 31P NMR spectroscopy and single crystal X-ray structure analysis. The folded and deformed xanthene unit causes a remarkably short P…P distance of 4.1 A which in turn results in a large coupling 6JPP′ = 27.3 Hz.

HOMO-DIELS-ALDER REACTIONS OF 2,4,6-TRI-TERT-BUTYL-1,3,5-TRIPHOSPHA-DEWAR-BENZENE

Homo-Diels—Alder reactions take place under very mild conditions when the 1,3,5-triphospha-Dewar-benzene derivative 4 is allowed to react with electron-deficient alkynes, such as dimethyl acetylenedicarboxylate or methyl propyonate, or with tert-butylphosphaacetylene. The resultant [2 + 2 + 2]-cycloadducts 5, 6, and 8 can be isolated in excellent yields and are formed regioselectively. Moreover, the first example of a [4 + 2 + 2]-cycloaddition has been realized by the reaction of 4 with tri-tert-butylazacyclobutadiene 10 which yields the two exo-cycloadducts 11 and 12. The cycloadduct 12 is unstable under the conditions of column chromatography on silica gel and undergoes rearrangement to the isomer 13.

4,5-bis(diphenylphosphino)acridine: A new type of tridentate phosphorus-nitrogen-phosphorus ligands

Abstract Reaction of 4,5-difluoroacridine (8) with two equivalents of potassium diphenylphosphide (Ph2PK) yielded the title compound 3. Contrarily, diphenylphosphine (Ph2PH) reacted with 8 under addition, and 4,5-difluoro-9-diphenyl-9,10-dihydroacridine (12) was obtained. Compound 8 was prepared from 2-amino-3-fluorobenzoic acid (13) in a four step synthesis. As it is shown by the preparation of the metal complexes 4,5-bis(diphenylphosphino)-acridine-palladium dichloride (16) and 4,5-bis(diphenylphosphino)acridine-molybdenum tricarbonyl (17), compound 3 is capable of acting as a tridentate PNP ligand which coordinates transition metals in an approximately “T-shaped” planar coordination geometry. Single crystal X-ray structure analyses are reported for 3 and 17.

Structure of 2,4,6-Tri-tert-butyl-1,3,5-triphosphabenzene and of 2,4-Di-tert-butyl-1,3-diphosphabenzene: X-ray Analysis, Photoelectron Spectra and Molecular Orbital Calculations

The structure of 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene (1) as well as the He(I) photoelectron spectra of 1 and 2,4-di-tert-butyl-1,3-diphosphabenzene (2) have been investigated. It was found that 1 is planar with average C–P–C angles of 109.3° (±0.3°) and P–C–P angles of 130.7° (± 0.4°). All P–C bond lengths amount to 1.727 (± 0.008) A. The PE spectra were interpreted by comparison with the results of ab initio calculations (RHF/ 6-31G*). They reveal a splitting of the lone pairs on P in 2 of 0.7 eV.

Bidentate phosphines of heteroarenes: effective stabilization of the Co2(CO)6 fragment by 4,6-bis(diphenylphosphino) dibenzofuran☆

Reaction of Co2(CO)8 with 4,6-bis(diphenylphosphino)dibenzofuran (1) in diethylether gives the dinuclear complex 4,6-bis(diphenylphosphino)dibenzofurandicobalthexacarbonyl (2). The solid state structures of 1 and 2 have been established by X-ray crystallography. Low temperature 13C-NMR spectroscopy was used to analyse 2 in solution.

Synthesis and characterization of organometallic precursors for the preparation of Sn/chalcogenide heterostructures

Abstract Synthesis, spectroscopic and structural characterization as well as thermal behavior of a series of molecular organometallic Sn/chalcogenide complexes, which present valuable complexes for the MOCVD process, is reported. These compounds are obtained from a reaction of the stannylene complex [{{(CH3)3Si}2(CH)}2Sn]2]] with elemental O2, S8, Se8 or metallic Te in high yields at RT in an organic solvent. These compounds are crystalline solids which are soluble in common organic solvents and are stable in air over extended periods of time, which make their handling easy.

NOVEL TETRAPHOSPHABARRELENE AND -SEMIBULLVALENE DERIVATIVES BY REACTIONS OF 2,4,6-TRI-TERT-BUTYL-1,3,5-TRIPHOSPHABENZENE WITH PHOSPHAALKYNES

2,4,6-Tri-tert-butyl-1,3,5-triphosphabenzene 4 reacts with phosphaalkynes P≡C–R [R = tBu (5a), tPen (5b)] at room temperature in a formal [4 + 2] cycloaddition to yield the corresponding 1,3,5,7-tetraphosphabarrelene derivatives 8a and 8b, respectively. The analogous reaction of 4 with the aminophosphaethyne P≡C–N(iPr)2 (9) unexpectedly leads to the 1,3,4,7-tetraphosphasemibullvalene derivative 10 as the only product. The single-crystal X-ray analysis of 10 exhibits a diphosphirane unit with a very long PP distance of 2.274(1) A together with a large extension of the PCP angle in the three-membered ring to 75.3(1)°.

New Phosphorus−Carbon Cage Compounds by Diels−Alder and Homo Diels−Alder Reactions of 1,3,5‐Triphosphabenzenes with Alkenes

Ethylene, various monosubstituted alkenes (acrylic acid derivatives, styrene), as well as some selected disubstituted alkenes (maleic acid derivatives, fumaric acid derivatives, norbornene, cyclopentadiene) undergo Diels−Alder reactions with the 1,3,5-triphosphabenzenes 1 under mild conditions to furnish the dihydrotriphosphabarrelenes 9, 11a−c, 13a−e, 15a−d, 17a,b, and 24. The monoadduct 26 as well as the diadducts 27 and 28 are isolated following the reaction with norbornadiene. Cyclopropene is the only alkene to undergo a Diels−Alder/homo Diels−Alder reaction sequence to afford the hexacyclic system 20.

Syntheses of benzocyclooctenedione derivatives, cyclopenta[a]indanones and a benzo-anellated tetraquinane via sequential transformations of tricarbonyl(η6-1,2-dioxobenzocyclobutene)chromium(0)

Tricarbonyl(η6-1,2-dioxobenzocyclobutene)chromium(0)1 can be converted into benzocyclooctenedione derivatives 3, 7 and 8 as well as fused five-membered ring systems 2, 4 and 6 by addition of vinyl lithium derivatives and following double anionic oxy-Cope rearrangement under very mild reaction conditions (–78 °C); product ratios depend on the method of hydrolysis.

1,3,5‐Triphosphabicyclo[3.1.0]hexene‐η3,η1‐diyl Hafnium Complexes: Structure and Reactivity

It is shown that the (P≡C–tBu)3 ligand found in the hafnium complex (COT)Hf(P≡C–tBu)35 (COT = cyclooctatetraene), which we reported recently,[3] is also present in the new hafnium complex 12, prepared by reaction of hexachloroethane with complex 5 in pentane, as well as in its trimethylphosphane adduct 14. The structures of complexes 12 and 14 have been determined by X-ray crystallography and that of 5by comparing its 1H-, 13C-, and 31P-NMR spectra with those of the complexes 12and 14. The organophosphorus ligand in all three complexes is a 2,4,6-tri-tert-butyl-1,3,5-triphosphabicyclo[3.1.0]hexene-η3,η1-diyl. Hydrolysis of complexes 5 and 12 with water gives the new phosphorus heterocycle 15, whereas the new heterocycles 16 and 17 are formed in an approximately 1:1 mixture using either silica gel containing 2% H2O or Na2SO4 · 10 H2O.