Antiferromagnetic Complexes with Metal-metal Bonds ☆: IX. Synthesis and Molecular Structures of Methylcyclopentadienylchromium(III) Sulfide Diamagnetic Tetramer and the Antiferromagnetic Copper(II) Bromide Adduct of the Tetranuclear Cluster (MeC5H4)4Cr4(μ3-O)(μ3-S)3
Journal of Organometallic Chemistry
Reaction of (MeC5H4)2Cr with HSCMe3 gave (MeC5H4)2Cr2S(SCMe3)2 (I) in the form of violet antiferromagnetic crystals ( − 2J = 478 cm−1). Pyrolysis of I in xylene and its reaction with a CuBr2 solution in THF/Et3N (1/1) leads to readily-soluble black diamagnetic crystals of (MeC5H4)4Cr4S4(II). An oxygen-containing antiferromagnetic analog of complex II, (MeC5H4)4Cr4O4(III) was isolated on oxidation of (MeC5H4)2Cr with traces of oxygen in the presence of Ar.
The reaction of I with CuBr2 in the absence of Et3N yielded black-green needle-like crystals of the antiferromagnetic adduct (MeC5H4)4Cr4S3O · CuBr2(IV) (μeff at room temperature is 3.91 BM). The structures of II and IV were established by X-ray crystallography. The molecule of II contains a metallotetrahedral Cr4 skeleton (CrCr 2.822(2) Å) with faces centered at the μ3-bridged S atoms (CrS 2.248(2) Å). Each Cr atom is bonded to a η5-MeC5H4 (CrCaver. 2.241(9) Å). In IV the tetrahedral Cr4 skeleton is distorted owing to the μ3-O bridging ligand (CrCr 2.70(1)–2.78(1) Å, CrSaver. 2.25(2) Å, CrO 2.07(2)–2.12(2) Å) and to CuBr2 coordination to a sulfur atom (CuBr 2.23(2) Å, BrCuBr 163.9(8)°, Cu···S 320 Å).