The First Crystallographically Characterized (Perfluoroaryl)lanthanoid(II) Complex, Eu(C₆F₅)₂(OC₄H₈)₅

Reaction of europium metal with Hg(C6F5)2 in thf (thf = tetrahydrofuran) followed by crystallization from thf/light petroleum affords the organoeuropium(II) complex Eu(C6F5)2(thf)5 (1). The X-ray crystal structure reveals axial C6F5 and equatorial thf ligands bound to a pentagonal-bipyramidal europium center

A Half-Sandwich Perfluoroorganoytterbium(II) Complex from a Simple Redox Transmetalation/Ligand Exchange Synthesis

Reaction of ytterbium metal with HgPh(C6F5) and HC5Me5 in THF (THF = tetrahydrofuran) affords seven-coordinate, monomeric [Yb(C5Me5)(C6F5)(THF)3] (1), which is presumed to be formed by protolysis of a transitory “YbPh(C6F5)” species with HC5Me5. In the absence of the latter, reaction of ytterbium metal and HgPh(C6F5) gave a mixture of products, including the structurally characterized [Yb(C6F5)2(THF)4] (2) and the ytterbium(III) complex [YbPh3(THF)3] (3)

Stabilization of Copper(II) Thiosulfonate Coordination Complexes Through Cooperative Hydrogen Bonding Interactions

A series of copper(II) thiosulfonate complexes have been prepared via the reaction of [Cu(Me3tren)(OH2)](ClO4)2 (Me3tren = tris(2-methylaminoethyl)amine) with three thiosulfonate ligands (RSO2S−, where R = Me, Ph, and MePh) and characterized by microanalysis, FTIR spectroscopy, and X-ray crystallography. In these complexes, the distorted trigonal bipyramidal copper(II) coordination sphere is occupied by four amine nitrogen atoms from the tripodal tetramine ligand and an apically bound sulfur atom from the thiosulfonate ligand. By using the tripodal tetramine ligand the oxidation of the thiosulfonate has been restricted, allowing the isolation of the complexes. The Cu−S distances were found to be similar to those in related thiosulfate complexes, indicating coordinative interactions of similar strength. Two types of intramolecular hydrogen bonding interactions were evident which enhance the binding of the thiosulfonate to the copper(II) center. These interactions, which involve two amine N−H groups and either one or two thiosulfonate oxygens, were found to be weaker than in the corresponding thiosulfate complexes. The complex formation constants for the thiosulfonate complexes (log Kf = 0.3−0.7) were found to be two orders of magnitude lower than compared to the thiosulfate analogues. This correlates well with a lower strength of intramolecular hydrogen bonding

Stabilization of Copper(II) Thiosulfonate Coordination Complexes Through Cooperative Hydrogen Bonding Interactions

A series of copper(II) thiosulfonate complexes have been prepared via the reaction of [Cu(Me3tren)(OH2)](ClO4)2 (Me3tren = tris(2-methylaminoethyl)amine) with three thiosulfonate ligands (RSO2S−, where R = Me, Ph, and MePh) and characterized by microanalysis, FTIR spectroscopy, and X-ray crystallography. In these complexes, the distorted trigonal bipyramidal copper(II) coordination sphere is occupied by four amine nitrogen atoms from the tripodal tetramine ligand and an apically bound sulfur atom from the thiosulfonate ligand. By using the tripodal tetramine ligand the oxidation of the thiosulfonate has been restricted, allowing the isolation of the complexes. The Cu−S distances were found to be similar to those in related thiosulfate complexes, indicating coordinative interactions of similar strength. Two types of intramolecular hydrogen bonding interactions were evident which enhance the binding of the thiosulfonate to the copper(II) center. These interactions, which involve two amine N−H groups and either one or two thiosulfonate oxygens, were found to be weaker than in the corresponding thiosulfate complexes. The complex formation constants for the thiosulfonate complexes (log Kf = 0.3−0.7) were found to be two orders of magnitude lower than compared to the thiosulfate analogues. This correlates well with a lower strength of intramolecular hydrogen bonding

Lewis Acid Catalyzed Diels−Alder Reactions of 1,2-Naphthoquinones

The use of BF3·OEt2 catalysis in Diels−Alder reactions of 3,4-unsubstituted 1,2-naphthoquinones provides direct access to cis-tetrahydrophenanthrene derivatives in good to excellent yields (66−99%) without rapid adduct aromatization commonly associated with corresponding thermal processes

Stabilization of Copper(II) Thiosulfonate Coordination Complexes Through Cooperative Hydrogen Bonding Interactions

A series of copper(II) thiosulfonate complexes have been prepared via the reaction of [Cu(Me3tren)(OH2)](ClO4)2 (Me3tren = tris(2-methylaminoethyl)amine) with three thiosulfonate ligands (RSO2S−, where R = Me, Ph, and MePh) and characterized by microanalysis, FTIR spectroscopy, and X-ray crystallography. In these complexes, the distorted trigonal bipyramidal copper(II) coordination sphere is occupied by four amine nitrogen atoms from the tripodal tetramine ligand and an apically bound sulfur atom from the thiosulfonate ligand. By using the tripodal tetramine ligand the oxidation of the thiosulfonate has been restricted, allowing the isolation of the complexes. The Cu−S distances were found to be similar to those in related thiosulfate complexes, indicating coordinative interactions of similar strength. Two types of intramolecular hydrogen bonding interactions were evident which enhance the binding of the thiosulfonate to the copper(II) center. These interactions, which involve two amine N−H groups and either one or two thiosulfonate oxygens, were found to be weaker than in the corresponding thiosulfate complexes. The complex formation constants for the thiosulfonate complexes (log Kf = 0.3−0.7) were found to be two orders of magnitude lower than compared to the thiosulfate analogues. This correlates well with a lower strength of intramolecular hydrogen bonding

Stabilization of Copper(II) Thiosulfonate Coordination Complexes Through Cooperative Hydrogen Bonding Interactions

A series of copper(II) thiosulfonate complexes have been prepared via the reaction of [Cu(Me3tren)(OH2)](ClO4)2 (Me3tren = tris(2-methylaminoethyl)amine) with three thiosulfonate ligands (RSO2S−, where R = Me, Ph, and MePh) and characterized by microanalysis, FTIR spectroscopy, and X-ray crystallography. In these complexes, the distorted trigonal bipyramidal copper(II) coordination sphere is occupied by four amine nitrogen atoms from the tripodal tetramine ligand and an apically bound sulfur atom from the thiosulfonate ligand. By using the tripodal tetramine ligand the oxidation of the thiosulfonate has been restricted, allowing the isolation of the complexes. The Cu−S distances were found to be similar to those in related thiosulfate complexes, indicating coordinative interactions of similar strength. Two types of intramolecular hydrogen bonding interactions were evident which enhance the binding of the thiosulfonate to the copper(II) center. These interactions, which involve two amine N−H groups and either one or two thiosulfonate oxygens, were found to be weaker than in the corresponding thiosulfate complexes. The complex formation constants for the thiosulfonate complexes (log Kf = 0.3−0.7) were found to be two orders of magnitude lower than compared to the thiosulfate analogues. This correlates well with a lower strength of intramolecular hydrogen bonding

Synthesis of the Proposed Structures of Prevezol C

The first enantioselective synthesis of the proposed relative structures of Prevezol C is reported in 11 linear steps from readily available materials. The unusual <i>syn</i> bromohydrin was installed via a multistep sequence culminating in a diastereoselective geminal dibromide reduction. Discrepancies in the spectral data of the synthetic materials and the natural sample have led to the conclusion that the proposed structures are incorrect

Reduction of Carbodiimides by Samarium(II) Bis(trimethylsilyl)amidesFormation of Oxalamidinates and Amidinates through C−C Coupling or C−H Activation

The reaction of [Sm{N(SiMe3)2}2(THF)2] (THF = tetrahydrofuran) with carbodiimides RNCNR (R = Cy, C6H3-2,6-iPr2) led to the formation of dinuclear SmIII complexes via differing C−C coupling processes. For R = Cy, the product [{(Me3Si)2N}2Sm(μ-C2N4Cy4)Sm{N(SiMe3)2}2] (1) has an oxalamidinate [C2N4Cy4]2- ligand resulting from coupling at the central C atoms of two CyNCNCy moieties. In contrast, for R = C6H3-2,6-iPr2, H transfer and an unusual coupling of two iPr methine C atoms resulted in a linked formamidinate complex, [{(Me3Si)2N}2Sm{μ-(RNC(H)N(Ar−Ar)NC(H)NR)}Sm{N(SiMe3)2}2] (2) (Ar−Ar = C6H3-2-iPr-6-C(CH3)2C(CH3)2-6‘-C6H3-2‘-iPr). Analogous reactions of RNCNR (R = Cy, C6H3-2,6-iPr2) with the SmII “ate” complex [Sm{N(SiMe2)3Na] gave 1 for R = Cy, but a novel C-substituted amidinate complex, [(THF)Na{N(R)C(NR)CH2Si(Me2)N(SiMe3)}Sm{N(SiMe3)2}2] (3), for R = C6H3-2,6-iPr2, via γ C−H activation of a N(SiMe3)2 ligand

Synthesis of the Proposed Structures of Prevezol C

The first enantioselective synthesis of the proposed relative structures of Prevezol C is reported in 11 linear steps from readily available materials. The unusual <i>syn</i> bromohydrin was installed via a multistep sequence culminating in a diastereoselective geminal dibromide reduction. Discrepancies in the spectral data of the synthetic materials and the natural sample have led to the conclusion that the proposed structures are incorrect