Synthetic and structural study of cyclopentadienylchromium dithiocarbamate complexes and their thermolytic derivatives

Abstract

The reaction of [CpCr(CO)3]2 (1) with the tetraalkylthiuram disulfides [R2NC(S)S]2 (R = Me, Et, i-Pr) has been investigated. At ambient temperature, CpCr(CO)2(η2-S2CNR2) (3) was obtained as air-stable dark red crystals in 81-87% yields from reactions in solution and in quantitative yield from a reaction in the solid state (3a, R = Me); the precursor complex CpCr(CO)3(η1-S2CNMe2) (2a) crystallized out in a 1:1 admixture with 3a from a product solution after 3 days at -29 °C. At 90 °C for 2 h, the same reaction or the thermal degradation of 3 led to the isolation of the thiocarbenoid complex CpCr(CO)2(η2-SCNR2) (4) as dark red crystals (ca. 10%), double cubanes Cp6Cr8S8(η2:4-SCNR 2)2 (5a, R = Me; 5b, R = Et) as dark brown crystals (3-7%), Cp6Cr6S8(η1:η?2-S 2CNR) (6) as dark crystals (7-14%), Cr(η2-S2CNR2)3 (7) as dark blue crystals (16-21%), Cp2Cr2(CO)4S as dark green crystals (1-3%), and Cp4Cr4S4 (12-22%) as dark green solids. The crystal structures of 2-6 were reported. Unprecedented bridging modes were found in the double cubanes: in 5, two Cr4S4 cubane clusters were linked by a μ-η2:η4-dithiooxamide ligand as well as a Cr - Cr bridge with bond distances of 3.101 and 3.118 Å in the two independent molecules of the compound, and in 6, the cubanes were linked by two μ-η1:η2-dithiocarbamate ligands.