Pyridine-based SNS-iridium and -rhodium sulfide complexes, including d8–d8 metal–metal interactions in the solid state

Abstract

The cationic, pincer-type complexes [(SNS)Ir(COE)][BF4] (1) and [(SNS)Rh(COE)][BF4] (2) (SNS = 2,6-bis(t-butylthiomethy1)pyridine; COE = cyclooctene) complexes were prepared, and their structure and reactivity were studied. They are fluxional at room temperature as a result of "arm" hemilability, which can be frozen at low temperatures. Reaction of complex 1 with H2 resulted in a dimeric dihydride complex [(SNS)Ir(H2)]2[BF4]2 (3) in which the sulfur atoms bridge between two metal centers. The Rh complex 2 did not react with H2. Both the carbonyl complexes [(SNS)Ir(CO)][BF4] (5) and [(SNS)Rh(CO)][BF4] (6) show differences in the IR stretching frequencies in solution vs. solid states, which are a result of uncommon metal-metal interactions between square planar d8 systems in the solid state. Complexes 1, 3, 5 and 6 were structurally characterized by X-ray crystallography. A network of hydrogen bonds involving the BF4(-) counter anion and hydrogen atoms of complex 5 was observed.

Cationic mono and dicarbonyl pincer complexes of rhodium and iridium to assess the donor properties of PCcarbeneP ligands

“…A related PNP system containing phosphinato donor arms is significantly less donating, with a n CO stretch of 2010 cm −1 found for its monocarbonyl cation. 44 Other systems, including SNS, 42 NNS, 45 and NNN 46,47 pincer complexes are all less donating than the ligands in compounds 3 and 5 by this criterion.…”

Iron(II) Complexes of a Hemilabile SNS Amido Ligand: Synthesis, Characterization, and Reactivity

“…In this work, reduction of a similar [S Me NS Me ] ligand affords an amine derivative that is used to prepare new iron amido complexes containing hemilabile thioether donors. Thioether ligands usually bind weakly to first row transition metals, ,,,− and their hemilability has been demonstrated previously. ,− Amido groups typically form strong bonds to metals, may serve as terminal or bridging ligands, and can thus form mononuclear or multimetallic compounds. Additionally, late-metal-bound amido groups have reactive lone-pair electrons available for bifunctional substrate activation.…”

“…The proliferation of bifunctional catalysts has been largely due to the popularity of pincer ligands that allow for tight binding and a variety of donors including P, S, N, and C. − In our efforts to develop new bifunctional iron catalysts, we are investigating sterically svelte tridentate ligands with a mixture of hard nitrogen and soft sulfur donors capable of stabilizing a range of metal oxidation states, − and hemilabile arms that allow for substrate coordination . Recently, we reported a series of mono-, di- and trinuclear iron­(II) complexes containing an easily prepared tridentate thiolate ligand with thioether and imine donors, [S Me NS – ] .…”

Coordination chemistry of Co complexes containing tridentate SNS ligands and their application as catalysts for the oxidation of n-octane

“…Relatively weak metal-metal interactions were observed between the two octahedral centers of 1 separated through space by a Co⋯Co distance of 3.684 Å, which in perspective is weaker than similar interactions in reported square-planar SNS metal complexes bearing t-butyl groups on the S-donor atoms, having dimeric centers (respectively, 3.223 and 3.255 Å for Ir⋯Ir and Rh⋯Rh). 36 Complex 2 crystallizes in the monoclinic Cc space group with four twins (two independent molecules, Fig. 2) in the asymmetric unit cell.…”

“…One of the key features of the SNS pincer ligand relevant to its application in catalysis is that it may be designed to adopt a hemilabile binding mode. 36 This is usually achieved by exploiting the relative difference in binding abilities between the hard nitrogen donor and the soft sulfur donor atoms to metal centers. 37 Being hemilabile also affords the metal complex with greater flexibility and balance between stability and reactivity.…”