Anionic Tris Research Articles

Syntheses and Spectroscopic and Structural Characterization of Silver(I) Complexes Containing Tertiary Phosphines and Hydrotris(pyrazol-1-yl)-, Hydrotris(4-bromopyrazol-1-yl)-, Hydrotris(3,5-dimethypyrazol-1-yl)-, and Hydrotris(3-methyl-2-thioxo-1-imidazolyl)borates

(Trialkyl- and (triarylphosphine)silver(I) derivatives containing anionic tris(1H-pyrazol-1-yl)borates were prepared from AgX (X = CF3SO3 or NO3), PR3 (R = phenyl, benzyl, cyclohexyl, 2,4,6-trimethylphenyl, or o-, m-, and p-tolyl) or PMePh2, and M[HB(pz)3] [M = K or Na; pzH = pyrazole in general; in detail, pyrazole (PzH), 3,5-dimethylpyrazole (3,5-Me2PzH), or 4-bromopyrazole (4-BrPzH)] and characterized through analytical and spectral (IR; 1H, 13C, and 31P NMR) measurements. These air stable, light-sensitive complexes are not electrolytes in CH2Cl2 and acetone. In these solvents they decompose even with strict exclusion of oxygen and light. The solid-state structures show that the silver atom adopts a distorted tetrahedral geometry. Crystal data with Mo Kα (λ = 0.710 70 Å) at 293 K: [HB(Pz)3]Ag(PPh3), C54H50Ag2B2N12P2, a = 15.082(2) Å, b = 19.728(2) Å, c = 9.432(1) Å, α = 94.8(1)°, β = 107.4(1)°, γ = 87.8(1)°, triclinic, P1̄, Z = 2; [HB(Pz)3]Ag[P(o-tolyl)3], C30H31AgBN6P, a = 14.461(2) Å, b = 14.461(2) Å, c = 30.473(2) Å, α = 90°, β = 90°, γ = 120°, trigonal, R3̄, Z = 6; [HB(Pz)3]AgP(Bz)3, C30H31AgBN6P, a = 12.183(2) Å, b = 18.596(2) Å, c = 13.804(2) Å, β = 100.8(1)°, monoclinic, P21/n, Z = 4; [HB(3,5-Me2Pz)3]Ag[P(p-tolyl)3], C36H41AgBN6P, a = 34.839(3) Å, b = 10.375(2) Å, c = 10.203(2) Å, β = 90.8(1)°, monoclinic, P21/n, Z = 4. Crystal data with Cu Kα (λ = 1.5418 Å): [HB(4-BrPz)3]AgPPh3, C27H22AgBBr3N6P2, a = 10.306(2) Å, b = 11.425(2) Å, c = 13.571(2) Å, α = 90.3(1)°, β = 107.0(1)°, γ = 91.4(1)°, triclinic, P1̄, Z = 2. The anionic soft S3-donor hydrotris(3-methyl-2-thioxo-1-imidazolyl)borate (Tm) was synthesized as its potassium salt from the corresponding imidazole and KBH4 in high yield. The potassium complex KTm was used as ligand transfer agent in the preparation of the silver(I) derivatives [(Tm)Ag]n and (Tm)Ag(PPh3). The S-donor 1-methylimidazolyl-2-thione (Hmimt) reacts with [HB(3,5-Me2Pz)3]Ag(PPh3), yielding the derivative [HB(3,5-Me2Pz)3](Hmimt)AgPPh3 in which the [HB(3,5-Me2Pz)3]- acts likely as bidentate N2-donor.

Synthesis and characterization of copper(I) derivatives with N-donor ligands—III. Hydridotris (1H-pyrazol-1-yl)borate. The X-ray crystal structure of [HB-(μ-pz) 3-Cu(PPh 3)

(Triarylphosphine)copper(I) derivatives containing anionic tris(1 H-pyrazol-1-yl)borato have been prepared from (Ar 3P) 2CuNO 3 and KTp, KTp ∗, KTp Me and KTp ∗Cl and characterized through IR and 1H, 13C and 31P NMR spectra. The complexes contain tetrahedral Cu I and a tridentate ligand. The X-ray single crystal analysis of the (PPh 3)CuTp complex is reported. Four-coordinate Cu 1 is present in a distorted tetrahedral configuration owing to the bulky PPh 3 and Tp groups: NCuN angles range from 88.4(2) to 91.8(2)°; NCuP angles range from 120.6(2) to 127.3(1)°. The CuN distances are 2.081(5), 2.065(5) and 2.083(5) Å and the CuP distance is 2.153(2) Å.

Studies on the retention behaviour of α-hydroxyisobutyric acid complexes of thorium(IV) and uranyl ion in reversed-phase high-performance liquid chromatography

The retention behaviour of complexes of thorium(IV) and uranyl ion with α-hydroxyisobutyric acid (HIBA) on a C 18 reversed-phase column is investigated. Using a mobile phase comprising 400 m M HIBA at pH 4.0 in 10:90 (v/v) methanol—water, the thorium(IV) peak was eluted before the uranyl peak, despite the fact that calculations based on formation constants suggested that the thorium(IV) was present as the neutral tetra(HIBA) complex, whilst uranyl was present as the anionic tris(HIBA) complex. Hydrolysis of the thorium-(IV) complex (with subsequent inclusion of hydroxyl in the coordination sphere of the metal ion and formation of an overall negative charge) is proposed as a likely explanation for the early elution of this complex. When the percentage of methanol in the mobile phase was varied, both thorium(IV) and uranyl complexes exhibited reversed-phase behaviour. The retention times of both complexes decreased when the concentration of HIBA in the mobile phase was increased over the range 50–600 m M, despite the fact that increased complexation should be favoured. This effect was attributed to competition for the adsorption sites on the stationary phase by neutral, protonated HIBA in the mobile phase. A retention mechanism based on hydrophobic adsorption (rather than cation-exchange) is suggested.

Structural Properties of S‐alkylated Dithiolene Chelates (II). Crystal and Molecular Structure of Tris‐(S‐methylethene‐1,2‐dithiolato)cobalt

AbstractThe crystal and molecular structure of tris(S‐methyl‐ethene‐1,2‐dithiolato)cobalt has been determined by X‐ray structure analysis. The substance crystallizes in the cubic space group Pa3 with a = 14.545 Å and 8 formula units per unit cell. The structure was solved by heavy‐atom technique and refined to a final R value of R = 0.11. The co‐ordination polyhedron of this trischelate is a slightly distorted octahedron. The distances from the cobalt atom to thioether‐sulphur atoms and to mercaptide‐sulphur atoms differ significantly. The methyl groups are arranged in a facial (cis) manner. The molecule has the symmetry C3. The substance shows great structural similarity to anionic tris(dithiolene) chelates.

Zum Bindungszustand des fünf- und sechsbindigen Siliciums in kationischen und anionischen o-Arylendioxychelaten / (d ← n) π-Bonding in Anionic and Cationic o-Arylenedioxy Chelates of Hexacoordinate and Pentacoordinate Silicon Studied by Means of ESCA

The “Si-2s- and Si-2p-binding energies” of 5 o-arylenedioxy complexes containing penta- and hexacoordinate silicon have been obtained from their ESCA-spectra. The data have been compared to those of tetracovalent silicon compounds. A linear correlation between calculated Pauling charges and binding energies has been found for compounds where no (d ← n) -interaction should exist. Characteristic deviations from the linear relation were found both in tetravalent silicon compounds containing Si-O-bonds, the (d ← n)π-interaction of which is well established, and in the anionic tris(o-phenylenedioxy) siliconate and in the bis(o-phenylenedioxy) organosiliconates. No deviations were observed in case of the cationic 6-coordinate complexes of silicon with acetylacetone and 2-hydroxypyridine-N-oxide. We conclude that an additional back donation from the free electron pair (dSi ← nOo) only exists to a considerable extent in tetracovalent silicic ester derivatives, in the hexa- and pentacoordinate tris(o-phenylendioxy) siliconate and in the bis(o-phenylenedioxy) organosiliconates. A method is given to obtain crystalline tris(2-oxypyridine-N-oxy) siliconium chloride in good yield.