Dimeric Copper and Lithium Thiolates: Comparison of Copper Thiolates with Their Lithium Congeners

Abstract

The direct reactions of the large terphenyl thiols HSAr iPr4 (Ar iPr4 = −C 6 H 3 -2,6-(C 6 H 3 -2,6-iPr 2 ) 2 ) and HSAr iPr6 (Ar iPr6 = −C 6 H 3 -2,6-(C 6 H 2 -2,4,6-iPr 3 ) 2 ) with stoichiometric amounts of mesitylcopper(I) in THF at ca. 80 °C afforded the first well-characterized dimeric copper thiolato species {CuSAr iPr4 } 2 (1) and {CuSAr iPr6 } 2 (2) with elimination of mesitylene. The complexes 1 and 2 were characterized by NMR and electronic spectroscopy as well as by X-ray crystallography. They have dimeric Cu 2 S 2 core structures in which the two copper atoms are bridged by the sulfurs from the thiolato ligands and feature short Cu--Cu distances near 2.4 Å as well as a weak copper-flanking aryl ring interaction from a terphenyl substituent. The structures of the planar Cu 2 S 2 cores bear a resemblance to the Cu A site in nitrous oxide reductase in which two cysteines also bridge two copper atoms. The related dimeric Li 2 S 2 structural motif was also observed in the lithium congeners {LiSAr iPr4 } 2 (3) and {LiSAr iPr6 } 2 (4) which were synthesized directly from the thiols and n-BuLi in hexanes. However, despite the very similar effective ionic radii of the Li + (0.59 Å) and Cu + (0.60 Å) ions, the Li--Li structures display very much longer (by more than ca. 0.5 Å) separations than the corresponding Cu--Cu distances in 1 and 2, which may be due to weaker dispersion interactions.

Coordination Assemblies Based on a Methylthio Carboxylic Ligand: Syntheses, Structures and Luminescent Properties

“…All the bond lengths and bond angles are in the range of previously reported data in related coordination polymers. [28][29][30] Furthermore, the Cu• • • Cu distance is 2.788(6) Å which is slightly shorter than the van der Waals radii sum of 2.80 Å suggesting a Cu-Cu bonding interaction. [31] MBA linker is coordinated to four Cu + ions through a μ2-η 1 η 1 carboxylic group and a μ2-methylthio group (Figure 1b).…”

The Unusual Structural Behavior of Heteroleptic Aryl Copper(I) Thiolato Molecules: Cis vs Trans Structures and London Dispersion Effects

“…The Cu1−Cu2 distance is 2.45(5) Å, which is in the normal range for aryl copper species. 14,20 However, the Cu2−Cu2′ distance was determined to be 2.37(8) Å, which is at the shorter end of the range for Cu(I) thiolates, 13,21 aryl copper complexes 14,20 or even copper amides. 22−24 The Cu1− Cu1′ distance is 3.21(8) Å, which is considerably greater than the sum of the van der Waals radii (2.8 Å), 17 suggesting no significant interaction between these two copper centers.…”

“…The signals for methyl groups of the isopropyls resonate at 1.77, 1.23, and 1.08 ppm, which are comparable to those of complexes 2 and 3 . The UV–vis spectra of complexes 1 – 4 show broad absorption bands in the range of 273 to 303 nm with the molar extinction coefficient in the range of 1700 to 3000 M –1 cm –1 , featuring a charge transfer process which is also seen in some related species. , …”

“…In pursuit of further examples of low coordinate copper­(II) species, we investigated the use of large terphenyl substituted thiolato ligands where dispersion effects had been noted earlier by Ziegler . The use of the terphenyl thiolato ligands has recently afforded the first dimeric copper­(I) thiolato derivatives {CuSAr iPr4 } 2 and {CuSAr iPr6 } 2 from the reaction of the thiol with a mesitylcopper­(I) precursor. Upon further investigation we found that adjustment of the ratio of the thiolate ligand to copper yielded unknown types of heteroleptic organo/thiolato copper molecules {Cu 2 (SAr)­Mes} 2 (Mes = −C 6 H 2 -2,4,6-Me 3 ; Ar = −C 6 H 3 -2,6-(C 6 H 2 -2,4,6-Me 3 ) 2 (Ar Me6 ), 1 ; −C 6 H 3 -2,6-(C 6 H 3 -2,6-iPr 2 ) 2 (Ar iPr4 ), 2 ; −C 6 H 3 -2,6-(C 6 H 2 -2,4,6-iPr 3 ) 2 (Ar iPr6 ), 3 ) and {Cu 4 (SAr)­Mes 3 } (Ar = C 6 H-2,6-(C 6 H 2 -2,4,6-Me 3 ) 2 -3,5-iPr 2 (Ar iPr8 ), 4 ).…”

“…12 In pursuit of further examples of low coordinate copper(II) species, we investigated the use of large terphenyl substituted thiolato ligands where dispersion effects had been noted earlier by Ziegler. 5 The use of the terphenyl thiolato ligands has recently afforded the first dimeric copper(I) thiolato derivatives 13 {CuSAr iPr4 } 2 and {CuSAr iPr6 } 2 from the reaction of the thiol with a mesitylcopper(I) 14 precursor. Upon further investigation we found that adjustment of the ratio of the thiolate ligand to copper yielded unknown types of heteroleptic organo/thiolato copper molecules {Cu 2 (SAr)Mes} different arrangements relative to the Cu 4 core, Thus, whereas 1 and 2 have symmetrical structures and alternating aryl and thiolate ligands (Figure 1), 3 has a unique cis disposition of these ligands.…”