Synthesis, crystal, and molecular structure of paramagnetic tri-t-butylphosphonium tribromo(tri-t-butylphosphine)nickelate(II)

Abstract

Reaction of tri-t-butylphosphine with nickel(II) bromide in alcoholic solution yielcs green [Bu^t₃PH][(Bu^t₃P)NiBr₃]. Conductivity, magnetic-susceptibility, and electronic spectral measurements, and X-ray single-crystal analysis indicated the structure to be the same in solution as in the solid state. Crystals are monoclinic, space group Cc. with cell dimensions a= 24·069(3), b= 13·896(4), c= 18·739(2)Å, β= 14891(1)°, Z= 4. The structure was solved by conventional heavy-atom methods and refined to R 0·088 for 1 839 observed reflexions. Structural data for the paramagnetic anion, which has nearly C_3v symmetry (excluding the butyl groups), particularly reflect the bulkiness of the Bu^t₃P ligand; mean dimensions: Br–Ni–Br 108·7°, P–C 2·02(10) and Ni–Br 2·38(2)Å, and a Ni–P bond length of 2·48(1)Å. The calculated Ni–PBu^t₃ cone angle is 180 ± 2°. The P(2)–H bond of the cation lies near the pseudo C₃ axis of the anion so that Ni⋯P(2) is 4·48 Å, with P(2)⋯Br 4·27–4-31 Å. These interion contacts indicate strong ion-pairing interaction in the solid-state structure.