Über Tris[(trialkylphosphan)gold(I)]oxonium-tetrafluoroborate und Tris[(triphenylphosphan)gold(I)]sulfonium-tetrafluoroborat

On Tris[(trialkylphosphine)gold(I)]oxonium Tetrafluoroborates and Tris[(triphenylphosphine)gold(I)]sulfonium Tetrafluoroborate [Et₃PAu]⁺BF, obtained from Et₃PAuCl and AgBF₄ in tetrahydrofuran, reacts with KOH (molar ratio 3:1) to give the oxonium salt [(Et₃P)Au]₃O⁺BF ( 1 ). The homologous [^t(Bu₃P)Au]₃O⁺BF ( 2 ) is generated similarly from ^tBu₃PAuCl and Ag₂O in the presence of NaBF₄ in THF. The composition and identity of these two first tris[(tri alkyl phosphine)gold(I)]oxonium salts have been confirmed by analytical and spectroscopic data. The compounds are useful aurating agents. From the corresponding triphenylphosphine complex and (Me₃Si)₂S quantitative yields of the sulfonium salt [(Ph₃P)Au]₃S⁺BF ( 3 ) are obtained. Its crystal structure features monomeric cations, and in these small Au? S? Au angles indicate significant metal-metal bonding.     

X-RAY STRUCTURES OF BIS[(2-AMINOPHENYL)DIPHENYLPHOSPHINE]BIS-(ETHANOL)SILVER(I) NITRATE AND TRIS[(2-AMINOPHENYL)DIPHENYLPHOSPHINE] SILVER(I) NITRATE MONOHYDRATE

Abstract

The crystal structures of two Ag(I) salts, [Ag(LH)₂(EtOH)₂](NO₃) (1) and [Ag(LH)₃](NO₃).H₂O (2) where LH is (2-aminophenyl)diphenylphosphine, have been determined at room temperature. In 1 the Ag atom is coordinated by two P atoms derived from the phosphine ligands (Ag-P(1) 2.433(3) and Ag-P(2) 2.439(3) Å and P(1)-Ag-P(2) 160.1(1)°) and two O atoms derived from two weakly coordinating ethanol molecules (Ag-O(1a) 2.49(1) and Ag-O(2a) 2.75(1) Å). In 2 the three phosphine ligands coordinate via the P atoms (Ag-P 2.455(2), 2.462(2) and 2.484(2) Å) which define a trigonal planar geometry about the Ag atom. In neither case was any evidence found for a bonding interaction between the amino-N atom and the Ag atom. Crystals of 1 are monoclinic, space group P2₁/n with unit cell dimensions: a=10.272(4), b=16.358(2), c=23.709(3) Å, β=101.01(2)° and Z=4 and crystals of 2 are triclinic, space group P 1 with a=11.857(2), b=21.285(2), c=11.190(4) Å, α=91.77(1), β=104.50(2), γ=97.93(1)° and Z=2. The structures were each refined by a full-matrix least-squares procedure to final R=0.058 using 2433 reflections for 1 and to R=0.069 using 4428 reflections for 2.     

Isomeric mono- and bis[(phosphane)gold(I)] thiocyanate complexes

The solid-state IR spectrum of Me(3)PAuSCN shows two signals in the range of the C-N stretching vibrations at 2075 and 2113 cm(-1). On the basis of thoroughly tested quantum chemical ab initio calculations (MP2 level of theory) these signals have been assigned to the two isomeric forms Me(3)PAuNCS and Me(3)PAuSCN. The molecular structures, the vibrational frequencies, and the relative energies of the two species have been calculated and the results compared with the experimental IR data. Treatment of Me(3)PAuSCN with equimolar quantities of [(Me(3)P)Au](+)[SbF(6)](-) in CH(2)Cl(2) at -78 degrees C gives the dinuclear reaction product [C(7)H(9)Au(2)NP(2)S](+)[SbF(6)](-) in high yields. A comparison of results of ab initio calculations and IR data suggest that at least three isomeric cationic species [(R(3)PAu)(2)NCS](+), [(R(3)PAu)(2)SCN](+) and [(R(3)PAu)SCN(AuPR(3))](+) are present, the second and third being the predominant components. The structures and vibrational frequencies of all three species have been calculated. The relative energies in the gas phase and in solution are discussed and compared with the corresponding data of the experimental IR spectra.     

Ring-Expanded N-Heterocyclic Copper(I) Boryl Complexes: The Structures of [(6-Dipp)CuBcat], [(6-Dipp)CuBneop], and [(6-Dipp)CuBhex]

σ-Bond metathesis reactions between [(6-Dipp)CuOtBu] (6-Dipp=:C({Dipp}NCH₂)₂CH₂, Dipp=2,6-iPr₂−C₆H₃) and three diboranes gave access to three new copper(I) boryl complexes [(6-Dipp)CuBcat], [(6-Dipp)CuBneop], and [(6-Dipp)CuBhex] (cat=1,2-O₂C₆H₄; neop=(OCH₂)₂C(CH₃)₂; hex=OC(CH₃)HCH₂C(CH₃)₂O). Whilst [(6-Dipp)CuBcat] and [(6-Dipp)CuBneop] formed rapidly in toluene, access to [(6-Dipp)CuBhex] required heating to 60 °C for days. The complexes were characterised by single-crystal X-ray crystallography which showed in all three cases that the systems were monomers and distorted-linear at the copper atom. The stability of [(6-Dipp)CuBneop] was found to be comparable to that of [(IPr*)Cu-Bneop] (IPr*=1,3-bis(2,6-(diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene); it persisted in solution for days with no sign of decomposition. [(6-Dipp)CuBhex] is a rare crystallographically characterised example of a complex containing a boryl anion supported by the hexylene glycolato ligand.     

Crystallization and interconversions of vapor-sensitive, luminescent polymorphs of [(C6H11NC)2Au(I)](AsF6) and [(C6H11NC)2Au(I)](PF6)

The remarkable, vapor-induced transformation of the yellow polymorphs of [(C(6)H(11)NC)(2)Au(I)](AsF(6)) and [(C(6)H(11)NC)(2)Au(I)](PF(6)) into the colorless forms are reported along with related studies of the crystallization of these polymorphs. Although the interconversion of these polymorphs is produced by vapor exposure, molecules of the vapor are not incorporated into the crystals. Thus, our observations may have broad implications regarding the formation and persistence of other crystal polymorphs where issues of stability and reproducibility of formation exist. Crystallographic studies show that the colorless polymorphs, which display blue luminescence, are isostructural and consist of linear chains of gold(I) cations that self-associate through aurophilic interactions. Significantly, the yellow polymorph of [(C(6)H(11)NC)(2)Au(I)](AsF(6)) is not isostructural with the yellow polymorph of [(C(6)H(11)NC)(2)Au(I)](PF(6)). Both yellow polymorphs exhibit green emission and have the gold cations arranged into somewhat bent chains with significantly closer Au···Au separations than are seen in the colorless counterparts. Luminescence differences in these polymorphs clearly enhance the ability to detect and monitor their phase stability.     

Some Tris[(triorganophosphine)gold(I)]-oxonium and -Organoimonium Tetrafluoroborates with Bulky Substituents

Tris{[tri(2-methylphenyl)phosphine]gold(I)}-, tris{[tri(2,4,6-trimethylphenyl)phosphine]gold(I)}- and tris{[tri(cyclohexyl)phosphine]gold(I)}-oxonium tetra-fluoroborate ( 1?3 ) have been prepared from the corresponding (phosphine)gold(I) chlorides, silver oxide, and sodium tetrafluoroborate in acetone. These oxonium salts are excellent aurating agents for primary amines. Thus in the reaction with 1, t -butylamine ^tBuNH₂ and aniline PhNH₂ are readily converted into the tri nuclear imino complexes {[(2-MeC₆H₄)₃P]Au}₃N^tBu⁺BF₄^? ( 4 ) and {[(2-MeC₆H₄)₃P]Au}₃NPh⁺BF ( 5 ) in high yields. With 3 , both aniline and 8-amino-quinoline also give the tri nuclear complexes, i.e. {[(c-C₆H₁₁)₃P]Au}₃ NPh⁺BF ( 6 ) and {[(c-C₆H₁₁)₃P]Au}₃N(C₉H₆N)⁺BF ( 7 ). Auration of aniline with the most sterically hindered reagent 2 yields only the bi nuclear complex {[2,4,6-Me₃C₆H₂)₃P] · Au}₂N(Ph)H⁺BF ( 8 ). The reagents 1?3 and the Products 4 – 8 have been characterized by analytical and NMR spectroscopic data, and the crystal structures of compounds 4 and 6 have been determined by single crystal x-ray diffraction. In the cations of 4 , a triangle of gold atoms with short Au — Au contacts [3.036(1), 3.107(1), and 3.214(1) Å] forms a steep pyramid with the nitrogen atom, in which the angles Au? N? Au are all much smaller than the tetrahedral standard of 109.7°: 94.8(4), 98.1(4), and 103.0(4)°. This triangular Au₃ unit is staggered relative to the three methyl groups of the ^tBu substituent at nitrogen. The results for 6 are similar [Au — Au: 3.037(1), 3.071(1), and 3.222(1) Å; Au? N? Au: 95.3(3), 96.5(3), and 103.6(3)°]. Variable temperature NMR studies of compounds 3 and 8 show hindered rotation of the mesityl groups about the P? C bonds of the ligands originating from the steric congestion within each tertiary phosphine.     

Copper(I)alkyl bonding in the dinuclear copper(I) compound [(CH3)2P(CH2)2]2Cu2

The complex of empirical formula Cu^I[(CH₃)₂(CH₂)₂P] has been found to be dimeric with two digonal copper(I) atoms bridged by two ligand molecules through coppercarbon σ-bonds, resulting in a centrosymmetric eight-membered heterocycle.     

Synthesis of (--)-lasubine(I) via a planar chiral [(eta6-arene)Cr(CO)3] complex

Key steps of the synthesis of the Lythracaea alkaloid (--)-lasubine(I) are the formation of an enantiopure planar chiral arylaldehyde tricarbonylchromium complex and highly diastereoselective aza-Diels-Alder cycloaddition and intramolecular radical cyclization reactions to afford a quinolizidinone intermediate. Ketone reduction, desilylation, and decomplexation yield the enantiomerically pure product.