Three-Coordinate [CuIIX3]− (X=Cl, Br), Trapped in a Molecular Crystal

Abstract

Mixtures of [Ph3PNPPh3]+Cl− with CuBr2 (or CuBr2+CuCl2) in ethanol/dichloromethane yield crystals containing three‐coordinate copper(II) with mixed chloride and bromide ligands, namely [Ph3PNPPh3]+[CuCl0.9Br2.1]− (1) and [Ph3PNPPh3]+[CuCl2.4Br0.6]− (2). The trigonal‐planar coordination of copper(II) is angularly distorted but unambiguous, as there is no other halide ligand within 6.7 Å of the copper atom. Density functional theory (DFT) calculations on planar [CuClBr2]− show that the energy surface for angle bending is very soft. Crystallisation in the presence of CH3CN yields [Ph3PNPPh3]+[CuCl0.7Br2.3(NCCH3)]− (3), in which there is additional secondary coordination by NCCH3 (Cu−N 2.44 Å). DFT calculations of the potential energy surface for this secondary coordination show that it is remarkably flat (<3 kcal mol−1 for a variation of Cu−N by 0.8 Å). The crystal packing in 1, 2 and 3, which involves multiple phenyl embraces between [Ph3PNPPh3]+ ions and numerous C−H⋅⋅⋅Cl and C−H⋅⋅⋅Br motifs, is associated with intermolecular energies that are larger than the variations in intramolecular energies. For reference, the crystal structures of [Ph3PNPPh3+]2[Cu2Cl6]2− (4) and [Ph3PNPPh3+]2[Cu2Br6]2− (5) are described. We conclude 1) that three‐coordinate copper(II) with monatomic halide ligands, although uncommon, can be regarded as normal, 2) that steric control by ligands is not necessary to enforce three‐coordination, 3) that a hydrophobic aryl environment stabilises [Cu(Cl/Br)3]−, and 4) that the energy change in the transition from three‐ to four‐coordinate copper(II) is very small (ca 5 kcal mol−1).

Role of Bis(triphenylphosphine)iminium Cation [PNP]+ on the Crystal Packing of [PNP]+[HSeO3]− Solvate Salt

“…The compound is isostructural with the analogous bis(triphenylphosphine)iminium hexachlorocuprate [30]. The geometrical parameters of the bis(triphenylphosphine)iminium cation is consistent with those observed in the literature.…”

Questions for crystal engineering of halocuprate complexes: concepts for a difficult system

“…28 We discovered that crystallisation of mixtures of copper(II) with chloride and bromide ligands, and the Ph 3 28 The crystal packing follows the general principles described above. We further showed that solvent is influential in this crystallisation, because crystallisations from ethanol without dichloromethane yielded instead the more familiar compounds (Ph 3 PNPPh 3 …”

Orthogonally Bimetallized Phosphane‐ene Photopolymer Networks

“…Network 2[Cu]Ge was swelled with acetonitrile in a cuvette to form a gel that could be analysed by UV/Vis spectroscopy. The spectrum of the purple gel revealed a maximum absorption wavelength in the yellow region ( λ max =549 nm), which corresponded to the purple [CuBr 4 ] 2− anion and a shoulder in the red region ( λ =628 nm), which corresponded to the green [CuBr 3 (MeCN)] − anion (Figure ) . Despite the paramagnetic anions, the 31 P NMR chemical shift was observed and did not change from that of 2[Br]Ge , and the IR spectrum confirmed that the aryl groups on the germanium centres were still present.…”