THF Solvent Molecule Research Articles

Two new bulky amido ligands useful for the preparation of metal complexes and examples of their reactivity

The search for new ligands with interesting properties is a quest that can occupy much of a synthetic chemist’s time. We have recently discovered two new ligands based on an adamantyl-substituted, 2,6- i Pr 2-substituted phenyl (Dipp) system. In an attempt to prepare the extremely bulky amine [(ad)(2,6- i Pr 2C 6H 3)NH] (ad = adamantyl) we found instead that the adamantyl group attacks the aromatic ring in the 4-position to form a new primary amine, (4-ad-2,6- i Pr 2C 6H 2)NH 2 ( 1) (ad-Dipp-NH 2), characterized by normal techniques. Compound 1 could be converted into a Li salt by a 1:1 reaction with n BuLi, or converted into a more bulky silylamine, [(ad-Dipp)NH(SiMe 3)] ( 3), by treatment with Me 3SiCl. We have characterized the lithium salt by X-ray crystallography as the dimeric complex, [(ad-Dipp)NHLi(Et 2O)] 2 ( 2). The lithium amide can be used as a reagent towards metal halides, and we have discovered that its reaction with SnCl 2 yields a compound with a tetrameric, [Sn–N] 4 cubane-like cage structure. We have also demonstrated the ligand behavior of 3 by its reaction with Bu 2Mg in THF to form a monomeric Mg-amide with two THF solvent molecules attached. These new ligands can provide advantages over conventional ligands in terms of improved solubility and ease of crystallization.

One-electron oxidation-induced dimerising C–C coupling of a 2,5-diamino-1,4-benzoquinonediimine: a chemical and electrochemical investigation

The one-electron oxidation of N,N′,N″,N‴-tetraneopentyl-2,5-diamino-1,4-benzoquinonediimine 3 has been carried out using Ag(I) as an oxidising agent and led to the formation of the postulated nitrogen-based radical cation B. This unstable species can evolve by following two competing pathways, either a hydrogen atom abstraction from a THF solvent molecule, which leads to the N,N′,N″,N‴-tetraneopentyl-2,5-diamino-1,4-benzoquinonemonoiminemonoiminium triflate 5, or a dimerisation of two carbon-based radical cations C, which affords the new dimer 4. An X-ray diffraction study of the latter established the presence of a centre of symmetry in the middle of the newly formed Csp3–Csp3 bond. Breaking of this bond upon reduction regenerates 3 under mild conditions. This type of chemically induced formation/breaking of a C–C single bond appears to be unprecedented in quinonoid chemistry. Electrochemical studies performed in THF confirm the proposed mechanism for the one-electron oxidation process.

Samarium(III) carbenoid as a competing reactive species in samarium-promoted cyclopropanation reactions.

The trivalent samarium carbenoid I2SmCH2I-promoted cyclopropanation reactions with ethylene have been investigated and are predicted to be highly reactive, similarly to the divalent samarium carbenoid ISmCH2I. The methylene transfer and carbometalation pathways were explored and compared with and without coordination of THF solvent molecules to the carbenoid. The methylene transfer was found to be favored, with the barrier to reaction going from 12.9 to 9.2 kcal/mol compared to barriers of 15.4-17.5 kcal/mol for the carbometalation pathway upon the addition of one THF molecule.

Electronic and Steric Influences on the Rate and Energetics of THF and MenTHF (n= 1, 2) Displacement from LRe(CO)2(L = Tp, Tp*, Cp*) Fragments by Acetonitrile

The dissociative displacement of the THF solvent molecule from LRe(CO)2−THF (L = Tp, Tp*, Cp*) and of MenTHF (n = 1, 2) from TpRe(CO)2−MenTHF by acetonitrile is studied. While the reactivity of the Re−THF bond depends on the electronic properties of the ancillary ligands (Tp, Tp*, Cp*) attached to the metal center, the lability of the Re−MenTHF bond is primarily influenced by the steric demands of the departing solvent.

A Novel Family of Structurally Characterized Lithium Cobalt Double Aryloxides and the Nanoparticles and Thin Films Generated Therefrom

The reaction between LiN(SiMe3)2 and Co(N(SiMe3)2)2 in THF followed by the addition of an aryl alcohol (HOAr) yielded: [Co[(μ-OAr)2Li(THF)x]2 [where x = 2: OAr =: OC6H4Me-2 (oMP, 1), OC6H4(OCHMe2)-2 (oPP, 2), OC6H3(Me)2-2,6 (DMP, 3); where x = 1: OAr = OC6H3(OCHMe2)2-2,6 (DIP, 4)]. Undertaking the same synthesis in pyridine (py) led to the same general structure with py molecules substituted for the THF solvent molecules: [Co[(μ-OAr)2Li(py)2]2 (OAr = oMP (5), oPP (6)]. For 1−6, the tetrahedrally (Td) bound Co atom bridges two OAr ligands to each of the Li atoms. The Li atom adopts a Td or trigonal bipyramidal (TBP) geometry, as determined by the number of bound solvent molecules. For the more sterically demanding ligands with py as the solvent, the mononuclear monometallic species [Co[(μ-OAr)2(py)x]2 (OAr = DMP (7), x = 2; DIP (8), x = 3) were observed adopting a Td or TBP geometry, respectively, based on the number of bound solvent molecules. Increasing the steric bulk of the OAr to OC6H3But2-2,6 (D...

A Comparative Structural and Magnetic Study of Three Compounds Based on the Cluster Unit M4Cl8(THF)6 (M=Mn, Fe, Co)

Treatment of anhydrous MCl2 phases with THF under refluxing conditions leads to excision of the clusters M4Cl8(THF)6 (M=Fe (1), Co (3)) and dimensional reduction to the chain of clusters, {Mn4Cl8(THF)6(Mn(THF)2Cl2}∞, (2). All three compounds were isolated in high yields as crystalline materials and subjected to comprehensive magnetic studies. X-ray structures of the three compounds were performed to verify the nature of the compounds, but only the Mn derivative is discussed in detail due to the fact that the structures of the Fe and Co clusters were reported earlier. The molecular structures of M4Cl8(THF)6 (M=Fe, Co) consist of a rhombic arrrangement of metal ions with two octahedral and two pseudo-five-coordinate metal sites. The four outer edges of the cluster are each spanned by a chloride bridge, while the short diagonal is bridged by two chloride ions. The remainder of the coordination sites are occupied by two terminal chlorides and six THF solvent molecules. The 1D compound {Mn4Cl8(THF)6(Mn(THF)2Cl2}∞, (2), is related to (1) and (3) in that the core of the structure is the same, but in this case the M4Cl8(THF)6 units are linked by MnCl2(THF)2 bridges. The magnetic susceptibility data for Fe4Cl8(THF)6 (1) and Co4Cl8(THF)6 (3) in the high-temperature range are indicative of the presence of ferromagnetic and antiferromagnetic interactions respectively. Fitting of the data to anisotropic exchange models provided information on the intramolecular exchange parameters. In the low-temperature region, cooperative behavior was observed as a consequence of the presence of significant intercluster interactions. The Fe derivative behaves as a metamagnet, while the Co derivative is a weak ferromagnet below 3.5 K. In contrast to (1) and (3), the magnetic properties of {Mn4Cl8(THF)6(Mn(THF)2Cl2}∞, (2), are indicative of the presence of antiferromagnetic exchange interactions within the cluster as well as between the neighboring clusters that lead to a nonmagnetic ground state.

Yttrium and Neodymium Di- and Monohalide Complexes Based on Scorpionate (Poly(pyrazolyl)borate) Ligands

The syntheses of a series of well-characterized complexes of the type TpRYX2(solvent)n (1 and 2, R = H, X = Br, Cl, solvent = THF, n = 2; 4, R = Me, X = Cl, solvent = THF, n = 1; 5, R = Me, X = Cl, solvent = 3,5-dimethylpyrazole, n = 1; 7, R = Ph, X = Cl, solvent = THF, n = 1) and the novel solvent-free bis(poly(pyrazolylborate) complexes [(TpR)(BpR‘)YX] (8, R = R‘ =Me, X = Cl; 9, R = H, R‘ = Ph, X = Br) are presented. The data demonstrate that the steric, dynamic, and coordination behavior of these complexes are heavily influenced by the choice of scorpionate ligand substituents, showing the versatility of this ligand system for catalyst design. The coordinated THF solvent molecules of complexes 1, 2, and 4 are seen to undergo a dynamic solvation/desolvation equilibrium in solution that is fast on the NMR time scale. The position of this equilibrium is solvent-dependent and can be evaluated in complex 4 by observation of the line broadening of the 3-methyl resonance in the 1H NMR spectra taken in differe...

Displacement of the THF solvent molecule from ( η5-C 5H 5)Mn(CO) 2THF by simple two electron donor ligands: evidence for a dissociative mechanism and determination of the Mn–THF bond strength

The reaction between CpMn(CO) 2THF (Cp= η 5-C 5H 5, THF=tetrahydrofuran) and nitrogen containing ligands is studied in THF solution. In all cases the products of the reaction are the known CpMn(CO) 2L complexes (L=piperidine, 4-acetylpyridine). The reaction of the solvated complex with both ligands studied proceeds through a purely dissociative mechanism. In good agreement with previous thermochemical measurements, kinetic analysis yields an average value of 24.0±3.0 kcal mol −1 for the CpMn(CO) 2–THF bond dissociation energy. The results of the present study clarify the relationship between metal–solvent bond strengths obtained by kinetic methods and those obtained by thermochemical measurements.

Bismuth(III) coordination compounds. Synthesis, characterization, and X-ray structures of [Bi(Cl)(μ-Cl) 2(THF) 2] ∞, Bi(O 2CMe) 3(Solv) x (Solv = py, x = 2 or MeIm, x = 4) [1], and [Bi(μ-OCH 2CMe 3)(OCH 2CMe 3) 2(Solv)] 2 (Solv = HOCH 2CMe 3 or py)

We have isolated and structurally characterized several novel bismuth coordination compounds. Dissolution of Bi(NO 3) 3 · 5H 2O in concentrated HCl, followed by crystallization from THF lead to the isolation of [Bi(Cl)(μ-Cl) 2(THF 2] ∞ 1. Each bismuth metal center of 1 adopts a 7-coordinated pentagonal bipyramidal geometry. One THF solvent molecule and one terminal chloride ligand are located in each of the axial positions. A terminal THF solvent molecule and four bridging chlorides reside in the equatorial positions. Dissolution of Bi(O 2CMe) 3 in pyridine (py) or N-methylimidazole (MeIm) results in the isolation of the appropriate amine adduct, either Bi(O 2CMe) 3(py) 2, 2 or Bi(O 2CMe) 3(MeIm) 3 · (MeIm), 3. Compound 2 uses two py molecules to adopt an unusual (for bismuth acetate species) 8-coordinated triangular dodecahedral geometry. In contrast, 3 incorporates three MeIm molecules to adopt the 9-coordinated tricapped trigonal prismatic geometry typically observed for bismuth acetate compounds (a “free” MeIm molecule is located in the lattice). The reaction of Bi[N(SiMe 3) 2] 3 with HOCH 2CMe 3 (HONp) yields [Bi(μ-ONp)(ONp) 2(HONp)] 2, 4. An alternative synthetic route to 4 is the metathical exchange between BiCl 3 and 3 equivalents of NaONp in the presence of HONp. The bismuth atoms of 4 are 5-coordinated and adopt an apical-shared, square base pyramidal (SP) arrangement. Recrystallization of 4 from py yields the dinuclear complex [Bi(μ-ONp)(ONp) 2(py)] 2, 5. The Bi atoms of 5 also adopt a 5-coordinated SP geometry; however, the two metal centers are linked through a basal-shared arrangement. The apical ONp ligands are in an up-down relationship to each other.

Preparation, characterization and crystal structure of Fe((OPPh2)2N)3

White crystals of Fe((OPPh 2 ) 2 N) 3 were obtained from the reaction of a solution of Fe 2 (CO) 9 and excess (PPh 2 ) 2 NH, under an air atmosphere. This product does not form if the solvents are rigorously degassed and the reaction is performed under argon. The structure of the complex, as determined by single crystal X-ray crystallography, is an octahedral tris-chelate arrangement of the oxidized anionic ligand, [(O=PPh 2 ) 2 N] − coordinated to an Fe(III) center. The asymmetric unit of the unit cell also contains a disordered THF solvent molecule. The complex crystallizes in the triclinic space group P 1 , with Z = 2, a = 13.581(3), b = 13.886(8), c = 18.781(7) A ̊ , α = 95.48(4), β = 98.73(2), γ = 97.82(3)°, V = 3444(2) A ̊ 3 , M r = 1377, D x = 1.33 Mg m −3 , F(000) = 1434, T = 298 K and R = 0.086 for 5959 observed reflections. The magnetic moment of the compound Fe((OPPh 2 ) 2 N) 3 was found to be 5.4 BM, using the Gouy method. Reaction of the oxidized ligand, (OPPh 2 ) 2 NH, with Fe(III) salts, such as Fe(NO 3 ) 3 , produces Fe((OPPh 2 ) 2 N) 3 in high yields.

Calixarene complexes of the molybdenum-molybdenum quadruple bond

We report here the first examples of metal-metal quadruple bonds supported by calixarene ligands in the complexes [Mo 2(OAc) 2(H 2-calix[4]arene)] ( 1) and [Mo 2(OAc) 2(H 2- p-tert-butylcalix[4]arene] ( 2). Complexes 1 and 2 were prepared by first deprotonating calix[4]arene and p-tert-butyl-calix[4]arene, respectively, with two equivalents of KH, followed by the addition of [Mo 2(OAc) 2(NCMe) 6][BF 4] 2. X-ray crystallographic analysis revealed the solid state structure of 2(THF)·C 6H 6. A molybdenum-molybdenum quadruple bond (2.1263(6) Å) is spanned by two bridging acetate ligands and a tetradentate, doublydeprotonated calixarene macrocycle. Each MoMo unit is weakly coordinated by an axial THF solvent molecule which is included in the calixarene basket of the neighboring complex.