4-Phenyl-1,2,4-triazoline-3,5-dione: A Prosthesis for the μ-η1-S2 Ligand in Organovanadium Sulfide Chemistry

Article abstract of DOI:10.1021/ja00337a025

4-Phenyl-1,2,4-triazoline-3,5-dione (PTD) reacts with (CH3C5H4)2V2(μ-S)2(μ-η¹S2) (1) to yield primarily (CH3C5H4)2V2(μ-S)(μ-η²-S2)(μ-η¹-PTD) (2) along with other minor products.The structure of 2 was inferred from the structure of its Pt(PPh3)2 adduct (CH3C5H4)2V2S3(PTD)Pt(PPh3)2 (5), which was determined by single-crystal X-ray diffraction techniques.The crystal of 5 belong to space group P2₁/c with a=22.181(7) Angstroem, b=13.176(4) Angstroem, c=19.303(5) Angstroem, β=111.10(2) deg, Z=4.Conventional full-matrix least-squares refinement with non-carbon atoms anisotropic , carbon atoms independently isotropic, and hydrogen atoms identically isotropic gave R=0.059 and R_w=0.065 for 6934 reflections having 2θ<55 deg and I>3?(I).The structure consists of an isosceles triangle of metal atoms capped by two μ₃-S ligands, with the V-V edge spanned by a μ-S and a μ-η¹-PTD ligand.An evaluation of the V-S and V-Pt distances indicates that formation of the Pt(PPh3)2 adduct effects only minor perturbations on the electronic structure of 2.Compound 2 is efficiently desulfurised by tri-n-butylphosphine to yield (CH3C5H4)2V2(ν-S)2(ν-η¹-PTD) (3).Compound 3 reacts further with PTD to yield (CH3C5H4)2V2S2(PTD)2 (4).Both 3 and 4 are minor products of the reaction of 1 with PTD.The high symmetry of 3 and 4 is supported by spectroscopic measurements.Compound 4 forms a stable Pt(PPh3)2 adduct, (CH3C5H4)2V2S2(PTD)2Pt(PPh3)2 (6), whose properties indicate a structure consisting of a <(CH3C5H4)V>2 moiety bridged by two μ-η¹-PTD ligands and a μ-η²-S2Pt(PPh3)2 ligand.The structure of 4 thus arises from oxidative coupling of the two μ-S ligands in 3.Comparison of 2 and 3 with (CH3C5H4)2V2(μ-S)(μ-η¹²-S2) (μ-η²-S2) and (CH3C5H4)2V2(μ-S)2(μ-η¹-S2) illustrates that the μ-η¹-PTD ligand functions as prosthesis for the μ-η¹-S2 ligand in these cyclopentadienylvanadium dimers.