Ligand substitution reactions of the nickel–sulphur cluster [Ni3S2(PEt3)6]2+. Phosphorus-31 nuclear magnetic resonance characterization of mono- and di-substituted species and X-ray crystal structure of [Ni3(μ3-S)2(PEt3)5Cl]BPh4

Abstract

The complexes [Ni₃Y₂(PEt₃)₆]²⁺, Y = S or Se, undergo metathetical reactions with halides and pseudohalides yielding both asymmetric, monosubstituted [Ni₃Y₂(PEt₃)₅X]⁺ and disubstituted [Ni₃Y₂(PEt₃)₄X₂] derivatives. The cationic trimetallic species react with donor molecules, such as CO and H₂S, only when the halide group is appropriately removed. All of the complexes have been characterized by ³¹P-{¹H} n.m.r. spectroscopy. Computer simulation of the complicated second-order spectra allowed determination of the spectral parameters. The refined values of the coupling constants between phosphorus atoms in geminal, trans-vicinal, or cis-vicinal positions are quite similar within the two series of compounds. In contrast, the values of the ³¹P chemical shifts depend remarkably on the nature of the substituting group. The molecular structure of [Ni₃(μ₃-S)₂(PEt₃)₅Cl] BPh₄ has been established by a single-crystal X-ray diffraction study. Crystal data are: a = 17.496(12), b = 17.087(12), c = 11.027(9) Å, α = 98.95(8), β = 90.58(8), γ = 102.70(9)°, space group P, Z = 2. Substitution of chloride ion for phosphine leaves unchanged the trigonal-bipyramidal skeleton, the only difference being some shortening of the M–S bond trans to the chlorine atom.