Preparation and Properties of Bis[μ-S-(2-tiolatoethyl)-diphenylphosphine][(2-thiolatoethyl)diphenyl-phosphine]dinickel(+1) Ion,a Novel Unsymmetrical Thiolate-bridged complex |
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Authors: | Ernst Pfeiffer Maurice L Pasquier Werner Marty |
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Abstract: | The title cation ( = Ni2L ) is formed in a variety of reactions (Schemes 1 and 2) in systems containing Ni2+ and (2-thiolatoethyl)-diphenylphosphine (= L?) in the absence of coordinating anions at Ni2+/L? ratios > 0.5 in apolar or moderately polar media. Solid Ni2L3]CIO4 and Ni2L3]BPh4 have been isolated. Job's plots confirm the Ni2L - stoichiometry in solution. 31P-NMR data are consistent with ≥ 97% Ni2L (vs. ? 3% of hypothetical Ni3L ) at equilibrium and support the suggested configuration (Fig. 2). The equilibrium between NiL2 + NiL2Br2 and Ni2L + Br? varies with the solvent composition in CH23Cl2/EtOH mixtures. The rate of formation of Ni2L2Br2 from Ni2L and bromide (in high excess) in CH2Cl2 is first-order in Ni2L ]tot but depends on the ratio Bu4NBr]tot/Ni2L3 · ClO4]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 Ni2L , and the large excess of bromide. |
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