[NiBr2(PPh3)2] is monoclinic, a= 9·828 ± 0·002, b= 37·178 ± 0·009, c= 10·024 ± 0·003 Å, β= 114·65 ± 0·02°, space group P21/n with four molecules in the unit cell. The co-ordination round nickel is tetrahedral, distorted by repulsion of the bromine atoms to give an enlarged Br–Ni–Br angle of 126°. The bond lengths Ni–Br = 2·34 and Ni–P = 2·33 Å indicate that these are single bonds, with no π bonding, and that the bonding radius of tetrahedral nickel(II) is 1·21 ± 0·01 Å. Comparison with un-co-ordinated triphenylphosphine shows that the formation of the co-ordinate link Ni–P has no effect on the P–C bond lengths or the C–P–C bond angles, and hence on the hybridisation of the phosphorus atoms.