Crystal structure of [1,3-bis(dimethylarsino)-2-chloro-1,1,3,3-tetrafluoropropane]tetracarbonylchromium (Me2AsCF2·CHCL·CF2AsMe2)Cr(CO)4

Abstract

Crystals of [1,3-bis(dimethylarsino)-2-chloro-1,1,3,3-tetrafluoropropane]tetracarbonylchromium, (Me₂AsCF₂·-CHCI·CF₂AsMe₂)Cr(CO)₄, are monoclinic, a= 8·55, b= 13·98, c= 16·00 Å, β= 105·61°, Z= 4, space group P2₁/c. The structure was determined from diffractometer data by Patterson, electron-density, and full-matrix least-squares methods, the final R being 0·065 for 1475 observed reflexions. The six-membered ring has a chair conformation, with chlorine occupying the less sterically hindered equatorial position. The chromium atom is surrounded by a distorted octahedral arrangement of four carbonyl groups and two arsenic atoms, with Cr–As 2·423(3) and 2·439(3)Å, and As–Cr–As 86·6(1)°. The remaining angles within the ring, mean 116°, are all significantly larger than the regular tetrahedral value. The C–F distances, mean 1·38(2)Å, and the C–Cl bond length of 1·81(2)Å lie close to normal single-bond values.