Nucleophilic Substitutions of N-Acyl-4-Chloro-3-Thiazolidines with the Organometallic Selenolates LiSeMcp(CO)3, M = Mo,W. Crystal Structure of (RS)-3-Acetyl-4-[(η5-cyclopentadienyl)(tricarbonyl)selenolato-tungsten(II)]-2,2,5,5-tetramethyl-3-thiazolidine

Selenolato complexes of molybdenum(II) and tungsten(II) with biologically important thiazolidine N/S-heterocycles have been prepared via nucleophilic attack of LiSeMocp(CO)₃ or LiSeWcp(CO)₃ on N-acyl-4-chloro-thiazolidines, easily accessible by reaction of acyl chlorides with 3-thiazolines. The resulting complexes represent the first examples of organometallic derivatives of this class of heterocycles. They are stable under nitrogen in the solid state, but decompose in solution when exposed to air. An X-ray structure analysis of (RS)-3-acetyl-4-[(η⁵-cyclopentadienyl)(tricarbonyl)(selenolato)tungsten(II)]-2,2,5,5-tetramethyl-3-thiazolidine ( 2 a ) has been performed (C₁₇H₂₁NO₄SSeW, orthorhombic, Pbca, a = 1579.5(3) pm, b = 1138.7(2) pm, c = 2209.4(3) pm, Z = 8). It revealed a monomeric structure with a non-planar heterocyclic substituent in an envelope conformation and a W–Se bond length of 264.96(10) pm. ⁷⁷Se-NMR spectra displayed chemical shifts in the range –280 to –350 ppm. These values are consistent with earlier results on related complexes.