P‐bis(trifluoromethyl) ylides: Synthesis and reactions

Bis(trifluoromethyl)phosphines RP(CF₃)₂ (R = Me, NEt₂) were methylated by MeOSO₂CF₃, yielding the respective phosphonium salts [RP(CF₃)₂Me]⁺ and CF₃SO₃⁻. Deprotonation using MeNP(NEt₂)₃ led to the phosphorus ylides RP(CF₃)₂CH₂, stable in solution at ambient temperature, which could be converted into 1,2λ⁵σ⁵‐oxaphosphetanes by adding hexafluoroacetone. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:650–653, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10061     

Synthesis and Crystal Structure of {(NH4)xCo((3–x)/2)}(H2O)2[BP2O8] · (1 – x) H2O (x ≈ 0.5)

A borophosphate hydrate with general composition {(NH₄)_xCo_((3–x)/2)}(H₂O)₂[BP₂O₈] · (1 – x) H₂O (x ≈ 0.5) was prepared under mild hydrothermal conditions (T = 170 °C). The crystal structure of the purple title compound was refined in space group P6₅ (no. 170) as a merohedric twin (a = 949.14 pm, c = 1558.25 pm, R₁ = 0.037, wR₂ = 0.092 for all data). According to preliminary X‐ray investigations, vis‐spectra, and magnetic susceptibility measurements, a second blue coloured variant exhibits a superstructure of the title compound with a change in coordination numbers around cobalt from six and five to six and four. Both phases show reversible de‐/rehydration properties.     

Two Dieneplatinum Synthetic Reagents,Pt(C6H2F3‐2,4,6)2(cod) and Pt(C6HF4‐2,3,4,5)2(cod)

Reactions of PtCl₂(cod) (cod = cycloocta‐1,5‐diene) with 2,4,6‐trifluoro‐ and 2,3,4,5‐tetrafluoro‐phenyllithium in diethyl ether gives Pt(C₆H₂F₃‐2,4,6)₂(cod) ( 1 ) (monoclinic, P2₁/n, Z = 4, a = 7.141(1), b = 15.002(2), c = 17.071(3) Å, β = 91.37(2)°) and Pt(C₆HF₄‐2,3,4,5)₂(cod) ( 2 ) (triclinic, P 1, Z = 2, a = 10.150(2), b = 10.762(2), c = 10.812(2) Å, α = 63.606(3), β = 63.327(3), γ = 76.496(3)°) respectively, which have two ipso carbon atoms and two double bond midpoint centres in a square planar arrangement, and aromatic rings angled near perpendicular to the coordination plane.     

Ein neues Chloropalladat(II): BaPdCl4

A New Chloropalladate(II): BaPdCl₄ BaPdCl₄ was prepared through reaction of barium chloride and palladium dichloride (molar ratio 2:1) with the aid of the Bridgman technique. According to a X‐ray single crystal investigation, BaPdCl₄ crystallizes with the orthorhombic crystal system (space group Pbcn (No. 60), Z = 4, a = 686.7(1), b = 1258.8(2) pm, c = 750.2(2), R_all = 0.0383). The crystal structure is built up from square planar [PdCl₄] units which are linked together by Ba²⁺ ions in an eightfold coordination.     

[Ag(NH3)2]ClO4: Kristallstrukturen,Phasenumwandlung, Schwingungsspektren

[Ag(NH₃)₂]ClO₄: Crystal Structures, Phase Transition, and Vibrational Spectra [Ag(NH₃)₂](ClO₄) is obtained from a solution of AgClO₄ in conc. ammonia as colourless single crystals (orthorhombic, Pnmn, Z = 4, a = 795.2(1) pm, b = 617.7(1) pm, c = 1298.2(2) pm, R_all = 0.0494). The structure consists of linearly coordinated cations, [Ag(NH₃)₂]⁺, stacked in a staggered conformation and of tetrahedral (ClO₄)^‐ anions. A first order phase transition was observed between 210 and 200 K and the crystal structure of the low‐temperature modification (monoclinic, P2/m, Z = 4, a = 789.9(5) pm, b = 604.1(5) pm, c = 1290.4(5) pm, β = 97.436(5)°, at 170 K, R_all = 0.0636) has also been solved. Spectroscopic investigations (IR/Raman) have been carried out and the assignment of the spectra is discussed.     

Design of a Heterogeneous Catalyst Based on Cellulose Nanocrystals for Cyclopropanation: Synthesis and Solid‐State NMR Characterization

Heterogeneous dirhodium(II) catalysts based on environmentally benign and biocompatible cellulose nanocrystals (CNC‐Rh₂) as support material were obtained by ligand exchange between carboxyl groups on the CNC surface and Rh₂(OOCCF₃)₄, as was confirmed by solid‐state ¹⁹F and ¹³C NMR spectroscopy. On average, two CF₃COO^? groups are replaced during ligand exchange, which is consistent with quantitative analysis by a combination of ¹⁹F NMR spectroscopy and thermogravimetry. CNC‐Rh₂ catalysts performed well in a model cyclopropanation reaction, in spite of the low dirhodium(II) content on the CNC surface (0.23 mmol g^?1). The immobilization through covalent bonding combined with the separate locations of binding positions and active sites of CNC‐Rh₂ guarantees a high stability against leaching and allows the recovery and reuse of the catalyst during the cyclopropanation reaction.