Multinuclear and dynamic NMR study of trans-[Pt(Cl)(PHCy2)2(PCy2)], [Pt(Cl)(PHCy2)3][BF4], [Pt(Cl)(PHCy2)3][Cl], trans-[Pt(Cl)(PHCy2)2[P(S)Cy(2)]], and trans-[Pt(Cl)(PHCy2)2[P(O)Cy2]]. Influence of intramolecular P=O...H-P and Cl...H-P interactions on restricted rotation about Pt-P bond. X-ray structure of trans-[Pt(Cl)(PHCy2)2[P(O)Cy2]

Dynamic NMR experiments on trans-[Pt(Cl)(PHCy2)2[P(X)Cy2]]z where X is a lone pair (1, z = 0), H (2, z = +1), S (3, z = 0), or O (4, z = 0) show that the rotation around the P(X)-Pt bond is hindered for all molecules studied, with deltaG++ ranging from 8.2 to 11.0 kcal/mol. The highest value of the series was calculated for trans-[Pt(Cl)(PHCy2)2[P(O)Cy2]] (4) where intramolecular P=O...H-P interactions act as a molecular brake at room temperature. Single-crystal X-ray diffraction confirms the presence of both intra and intermolecular P=O...H interactions in solid 4. In the case of [Pt(Cl)(PHCy2)3]Cl, multinuclear NMR analysis indicates the presence of a P-H...Cl- interaction in aromatic or halogenated solvents which could have also a minor effect on the rotational barrier around the P(X)-Pt bond.     

N,N-Dialkylcarbamato Complexes of the d10 cations of copper,silver, and gold

The reaction of CuO'Bu with CO₂, and ⁱPr₂NH in the presence of PPh₃, gives the dialkylcarbamato complex [Cu(O₂CNⁱPr₂)(PPh₃)₂] ( 1 ). The CO₂/R₂NH system (R = Me, Et) in an appropriate organic medium reacts with Ag₂O giving the corresponding N,N-dialkylcarbamato complexes of analytical formula [Ag(C₂CNR₂)] (R = Me, 2 ; R = Et, 3 ). The methyl derivative 2 was characterized by X-ray diffraction methods. Crystal data of 2 : for [Ag₂(O₂CNMe₂)₂], C₆H₁₂Ag₂N₂O₄, mol. wt. 391.9; monoclinic, space group P2₁/c, a = 12.08(1), b = 3.797(2), c = 11.316(7) Å, β = 113.37(6)°, V = 476.3 ų, Z = 2, D_c = 2.732 g cm^?3; μ(MoK_α) = 40.64 cm^?1, F(000) = 376.0; R = 0.059, R_w = 0.067; g.o.f. 1.27. The structure consists of dinuclear [(Ag₂OCNMe₂)₂] units with slightly distorted linearly two-coordinated Ag-atoms containing bridging carbamato groups to form a substantially planar eight-membered ring with an intra-annular Ag? Ag distance of 2.837(2) Å; the dinuclear units are further joined by Ag? O bonds to form an infinite array. Compound 3 , which is presumably dinuclear, as suggested by cryoscopic measurements in benzene, undergoes a structural fission with PPh₃, giving the mononuclear triphenylphosphine derivative [Ag(O₂CNEt₂)(PPh₃)₂] ( 4 ). The amine-catalyzed conversion of Ag₂O into Ag₂CO₃, in the presence of the ⁱPr₂NH/CO₂ system, is also reported. Cl-Exchange from [AuCl(PPh₃)] with [Ag(O₂CNEt₂)] ( 3 ) gives the first N,N-dialkylcarbamato complex of gold, namely [Au(O₂CNEt₂)(PPh₃)] ( 5 ), which crystallizes in the monoclinic system: C₂₃H₂₅AuNO₂P · 0.5 C₇H₁₆, mol. wt. 625.5, space group P2₁/c; a = 13.212(5), b = 12.25(1), c = 16.795(6) Å, β = 109.09(2)°, V = 2568(2) Å₃, Z = 4, D_c, = 1.618 g cm^?3; μ(AgK_α) = 31.40 cm^?1, F(000) = 1236.0; R = 0.058; R_w = 0.064; g.o.f. 2.121. The compound contains two-coordinated Au-atom, namely to the P-atom and to the O-atom of the monodentate carbamato group, the P? Au? O bond angle being 174.7(3)°. The reaction with MeI showed these compounds to react predominantly at the carbamato O-atom giving the corresponding urethanes R₂NCO₂Me. Evidence was gathered for the transient coordination of CO to Ag in 3 .     

Citrus-Carotinoide. 1. Mitteilung. Synthese von Apocarotinoiden mit einer anders gelagerten Methylgruppe; Strukturaufklärung von Citrus-Carotinoiden

Synthesis of Apocarotenoides with a Shifted Methyl Group; Structure Elucidation of Citrus-Carotenoides With regard to the investigation of the biosynthesis of the C₃₀-carotenoids in citrus fruits apocarotenoids with a methyl group shifted by one position (diapocarotenoids) were synthesized. Characteristical differences, especially in the 270-MHz-¹H-NMR. spectra between the apo- and the diapocarotenoids are reported. The comparison of the natural pigments with the synthetic compounds proves that the natural products belong to the apocarotenoids as has been postulated earlier.     

Ammonothermal Synthesis,X-Ray and Time-of-Flight Neutron Crystal-Structure Determination,and Vibrational Properties of Barium Guanidinate,Ba(CN3H4)2

We report the crystal structure of Ba(CN₃H₄)₂ as synthesized from liquid ammonia. Structure solution based on X-ray diffraction data suffers from a severe pseudo-tetragonal problem due to extreme scattering contrast, so the true monoclinic symmetry is detectable only from neutron powder diffraction patterns, and structure solution and refinement was greatly aided by density-functional theory. The symmetry lowering is due to slight deviations of the guanidinate anion from the mirror plane in space group P b2, a necessity of hydrogen bonding. At 300 K, barium guanidinate crystallizes in P2₁/c with a=6.26439(2) Å, b=16.58527(5) Å, c=6.25960(2) Å, and a monoclinic angle of β=90.000(1)°. To improve the data-to-parameter ratio, anisotropic displacement parameters from first-principles theory were incorporated in the neutron refinement. Given the correct structural model, the positional parameters of the heavy atoms were also refinable from X-ray diffraction of a twinned crystal. The two independent guanidinate anions adopt the all-trans- and the anti-shape. The Ba cation is coordinated by eight imino nitrogens in a square antiprism with Ba−N contacts between 2.81 and 3.04 Å. The IR and Raman spectra of barium guanidinate were compared with DFT-calculated phonon spectra to identify the vibrational modes.     

Ordered binary crystals via cocrystallisation of quasiracemic Pd(II) complexes in a borderline regime between inertness and lability

Square planar complexes of the type [2-(1-aminoethyl)phenyl-kappa(2)C(1),N]chloro(py-kappaN)palladium(II)(py = pyridine derivative) have been prepared by cyclopalladation of 1-phenylethylamine. When opposite enantiomers of the chiral amine and different pyridine ligands were coordinated to the metal, quasiracemic complexes were obtained. The racemisation speed of solutions containing equimolar amounts of such quasiracemic complexes was used to test the compounds for inertness: slow ligand exchange was found for methylated pyridines. Enantiomerically pure complexes of opposite chirality with the electron rich ligands 2,6-collidine and 2,4,6-lutidine were successfully cocrystallised: they form a well-ordered binary solid in which four independent molecules, two of each constituent, are related by pseudo symmetry operations. This quasiracemate as well as its components and the true racemates of the latter were characterised by single crystal X-ray diffraction. The heterochiral crystals, both the cocrystal as well as the racemates, show better space filling than the homochiral solids.     

Gamma-ray production cross section from energetic neutron inelastic scattering for methodical improvements in planetary gamma-ray spectroscopy

Planetary gamma-ray spectroscopy can be used to chemically analyze the top soil from planets in future planetary missions. The production from inelastic neutron interaction plays an effective role in the determination on the C and H at the surface. The gamma-ray production cross section from the strongest lines excited in the neutron bombardment of Fe have been measured by the use of a time analyzed quasi-mono-energetic neutron beam and a high purity germanium detector. The results from En=6.5, 32, 43, and 65 MeV are presented.