Crystal structure of bis(octamethylcyclotetraphosphonitrilium) tetrachlorocobaltate(II), [(NPMe2)4H]2CoCl4

Abstract

Crystals of [(NPMe₂)₄H⁺]₂CoCl₄^2– are monoclinic, a= 10·43₅, b= 32·83₇, c= 11·17₄Å, β= 102·29°, Z= 4, space group P2₁/n. The structure was determined with Mo-K_α counter data by Patterson, electron-density, and least-squares methods, to R 0·077 for 1324 observed reflexions. The structure consists of a tetrahedral CoCl₄^2– ion and two protonated eight-membered phosphonitrilic rings, one with a tub and one with a saddle conformation. Each ring contains four distinct pairs of NP bonds: commencing at the protonated nitrogen, 1·70, 1·54, 1·61, and 1·58 Å. These differences, and corresponding valency-angle variations, can be interpreted in terms of π-bonding theories. The CoCl₄^2– ion is tetrahedral with mean Co–Cl 2·29 Å. A feature of the interionic contacts is the presence of two N–H ⋯ Cl hydrogen bonds (each 3·21 Å).