Preparation and Properties of Bis[μ‐ S ‐(2‐tiolatoethyl)‐diphenylphosphine][(2‐thiolatoethyl)diphenyl‐phosphine]dinickel(+1) Ion, a Novel Unsymmetrical Thiolate‐bridged complex

The title cation ( = Ni 2 L   + 3 ) is formed in a variety of reactions ( Schemes 1 and 2 ) in systems containing Ni 2+ and (2‐thiolatoethyl)‐diphenylphosphine (= L − ) in the absence of coordinating anions at Ni 2+ /L − ratios > 0.5 in apolar or moderately polar media. Solid [Ni 2 L 3 ]CIO 4 and [Ni 2 L 3 ]BPh 4 have been isolated. Job 's plots confirm the Ni 2 L   + 3 ‐ stoichiometry in solution. 31 P‐NMR data are consistent with ≥ 97% Ni 2 L   + 3( vs. ⩽ 3% of hypothetical Ni 3 L   2+ 4 ) at equilibrium and support the suggested configuration ( Fig. 2 ). The equilibrium between NiL 2 + NiL 2 Br 2 and Ni 2 L   + 3+ Br − varies with the solvent composition in CH 23 Cl 2 /EtOH mixtures. The rate of formation of Ni 2 L 2 Br 2 from Ni 2 L   + 3and bromide (in high excess) in CH 2 Cl 2 is first‐order in [Ni 2 L   + 3 ] tot but depends on the ratio [Bu 4 NBr] tot /[Ni 2 L 3 · ClO 4 ]tot, even at a high excess of bromide. This is interpreted by efficient competition in ion‐aggregate formation between the small perchlorate concentration introduced as the counterion of Ni 2 L   + 3 , and the large excess of bromide.