Cyclization of Thiocarbonyl Groups in Binuclear Homoleptic Nickel Thiocarbonyls To Give Ligands Derived from Sulfur Analogues of Croconic and Rhodizonic Acids

• Published in: Inorganic chemistry 2015-01, Vol.54 (1), p.132-142
• Main Authors: Gong, Hejing, Luo, Qiong, Li, Qian-shu, Xie, Yaoming, King, R. Bruce, Schaefer, Henry F
• Format: Article
• Language: English
• Subjects: Bonding; Bridges (structures); Carbon oxides; Carbon-carbon composites; Joining; Ligands; Nickel; Sulfur
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic501924p

The sulfur analogue of the well-known Ni(CO)4, namely, Ni(CS)4, has been observed spectroscopically in low temperature matrices but is not known as a stable species under ambient conditions. Theoretical studies show that Ni(CS)4 with monomeric CS ligands and tetrahedrally coordinated nickel is disfavored by ∼17 kcal/mol relative to unusual isomeric Ni(C2S2)2 structures. In the latter structures the CS ligands couple pairwise through C–C bond formation to give dimeric SCCS ligands, which bond preferentially to the nickel atom through their CS bonds rather than their CC bonds. Coupling of CS ligands in the lowest energy binuclear Ni2(CS) n (n = 7, 6, 5) structures results in cyclization to give remarkable C n S n (n = 5, 6) ligands containing five- and six-membered carbocyclic rings. Such ligands, which are the sulfur analogues of the well-known croconate (n = 5) and rhodizonate (n = 6) oxocarbon ligands, function as bidentate ligands to the central Ni2 unit. Higher energy Ni2(CS) n (n = 7, 6, 5) structures contain dimeric C2S2 ligands, which can bridge the central Ni2 unit. Dimeric C2S2 ligands rather than tetrathiosquare C4S4 ligands are found in the lowest energy Ni2(CS)4 structures.