Synthesis, Structure, and Reactivity of Ruthenium and Osmium Nitrido Complexes with 1,2-Benzenedithiolate Ligands:  N- versus S-Alkylation

The reactivity of the nitrido complexes (NⁿBu₄)[Ru(N)(S₂C₆H₄)₂] (1) and (NⁿBu₄)[Os(N)(S₂C₆H₄)₂] (2) (C₆H₄(SH)₂ = 1,2-benzenedithiol) toward electrophiles, R⁺ (R = Me, Et, Ph₃C), is described. While 1 yielded intractable mixtures of products, 2 could be cleanly alkylated. The synthesis of 1 has been reported previously (Z. Naturforsch. 1987, 42B, 341); complex 2 can be synthesized by treating (NⁿBu₄)[Os(N)Cl₄] with deprotonated 1,2-benzenedithiol in acetone/MeOH at 0 °C. Complexes 1 and 2 are isostructural and crystallize in the orthorhombic space group Pna2₁, Z = 8, with a = 36.881(6) Å, b = 9.402(2) Å, and c = 17.652(2) Å for 1 and a = 37.042(4) Å, b = 9.375(2) Å, and c = 17.671(2) Å for 2. The anions of both compounds consist of a five-coordinate mononuclear center with a distorted square-pyramidal geometry; a terminal nitrido ligand occupies the apical position and two chelating (S₂C₆H₄)^2- ligands form the basal plane. Treatment of 2 with R₃OBF₄ in CH₂Cl₂ yields [Os(N)(S₂C₆H₄)(SC₆H₄SR)] (R = Me, 3; R = Et, 4) where one thiolate donor is alkylated. Alkylation of the sulfur of the 1,2-benzenedithiolate ligand was confirmed by NMR spectroscopy and X-ray crystallography (for 3). Complex 3·CH₂Cl₂ crystallizes in the orthorhombic space group P2₁2₁2₁, Z = 4, with a = 8.551(1) Å, b = 10.772(2) Å, and c = 19.716(3) Å. In contrast, treatment of 2 with Ph₃CPF₆ in CH₂Cl₂ yields [Os(NCPh₃)(S₂C₆H₄)₂] (5), whose ¹H and ¹³C NMR spectra indicate that the terminal nitride is the site of electrophilic attack. X-ray crystallography further confirms the alkylation at the nitrogen atom; complex 5 crystallizes in the triclinic space group P1̄, Z = 2, with a = 9.338(8) Å, b = 10.001(3) Å, c = 16.280(6) Å, α = 75.88(3)°, β = 74.29(6)°, and γ = 69.55(5)°.