Imidazol-2-ylidene-N′-phenylureate ligands in alkali and alkaline earth metal coordination spheres - heterocubane core to polymeric structural motif formation

The synthesis and isolation of two potassium, one lithium and two calcium complexes of imidazol-2-ylidene-N′-phenylureate ligands [ImRNCON(H)Ph] [(R = tBu (1a); Mes (1b) and Dipp (1c); Mes = mesityl, Dipp = 2,6-diisopropylphenyl] are described. Potassium complexes, [{κ2-(ImMesNCONPh)K}4] (2b) and [{κ3-(ImDippNCONPh)K}2{KN(SiMe3)2}2]n (2c), were prepared in good yields by the reactions of 1b and 1c, respectively, with potassium bis(trimethyl)silyl amide at ambient temperature in toluene. Lithium complex [{(2,6-tBu2-4-Me-C6H2O)Li(ImtBuNCON(H)Ph)}2{ImtBuNCON(H)Ph}] (3a) was isolated by a one-pot reaction between 1a and LiCH2SiMe3, followed by the addition of 2,6-tBu2-4-Me-C6H2OH in toluene. Calcium complex [{κ2-(ImtBuNCONPh)Ca{N(SiMe3)2}-{KN(SiMe3)2}]n (4a) was isolated by the one-pot reaction of 1a with [KN(SiMe3)2] and calcium diiodide in THF at ambient temperature. The solid-state structures of ligand 1a and complexes 2b, 2c, 3a and 4a were confirmed by single-crystal X-ray diffraction analysis. It was observed that potassium was coordinated to the oxygen atom of urea group and to the nitrogen atom of the imidazolin-2-imine group, in the solid-state structure of 2b. In complex 4a, the calcium ion was ligated to the monoanionic imidazol-2-ylidene-N′-phenylureate ligand in a bi-dentate (κ2) fashion through the oxygen and nitrogen atoms of the isocyanate building block leaving the imidazolin-2-imine fragment uncoordinated. In the solid state of the potassium complex 2c, tri-dentate (κ3) coordination from the imidazol-2-ylidene-N′-phenylureate ligand was observed through the oxygen and nitrogen atoms of the isocyanate building block and of the imidazolin-2-imine fragment. In contrast, in the dimeric lithium complex 3a, the neutral imidazol-2-ylidene-N′-phenylureate ligand was bound to the lithium centre in a mono-dentate fashion (κ1) through an oxygen atom of the isocyanate moiety. It is to be noted that in each complex thus observed, the elongated carbon-nitrogen bond distances indicate substantial electron delocalisation from the imidazole ring to the ureate group present in ligand 1

Nickel(II) complexes having Imidazol-2-ylidene-N′-phenylurea ligand in the coordination sphere - Syntheses and solid state structures

We report the syntheses and structural studies of two nickel(II) complexes of imidazol-2-ylidene- N′-phenylureate ligand of composition [{Im tBuNCON(H)Ph}2Ni(acac)2](1) and [(C6H5NH2)2Ni(acac)2][ImMes NCON(H)Ph] (2). The nickel complex 1 was readily prepared by the reaction of nickel(II) acetylacetonate [Ni(acac)2] with imidazol-2-ylidene-N′-phenylureate ligand [Im tBuNCON(H)Ph] (L1) in THF under reflux condition for 72 h. The nickel complex 2 was obtained by the reaction of [Ni(acac)2], mesityl derivative of imidazol-2-ylidene-N′-phenylureate ligand [Im MesNCON(H)Ph] (L2) in the presence of aniline as base under reflux condition in THF. Both the paramagnetic complexes have been characterized by FT-IR spectroscopy and elemental analyses. Solid-state structures of both the new complexes were established by single crystal X-ray diffraction analysis. In the molecular structures of complexes 1 and 2, each nickel(II) ion is six fold coordinated and form a distorted octahedral geometry. The optical properties of both complexes have been explored. The Hirshfeld surfaces are used to view and analyze the intermolecular contacts in crystalline state for complex 2

Synthesis and solid state structures of Chalcogenide compounds of Imidazolin-2-ylidene-1,1-Diphenyl-phosphinamine

We report the synthesis and solid state structures of 1,3-di-aryl-imidazolin-2-ylidine-1,1-diphenylphosphinamine [(aryl = mesityl (1a) and aryl = 2,6-diisopripyl (1b)] and their chalcogenide compounds 1, 3-di-aryl-imidazolin-2-ylidine- P,P-diphenylphosphinicamide (2a,b), 1,3-di-aryl-imidazolin-2-ylidine-P,P-diphenyl-phosphinothioicamide (3a,b) and 1,3-diaryl-imidazolin-2-ylidine- P,P-diphenyl-phosphinoselenoic-amide (4a,b). The compounds 1a,b were prepared in good yield by the reaction of 1,3-di-aryl-imidazolin-2-imine and chlorodiphenylphosphine in the presence of triethylamine in toluene. The reactions of 1a,b with elemental sulphur and selenium afforded the corresponding chalcogenide compounds 3a,b and 4a,b respectively. The corresponding oxo- derivative (2a,b) was obtained by reacting compound 1a,b with 30% aqueous hydrogen peroxide in THF. The molecular structures of 1a, 2a, 3a and 4a,b have been established by single crystal X-ray diffraction analyses. The molecular structures reveal that even C1–N1–P1 angle (124.62 ∘) in compound 1a is less obtuse compared to the corresponding C1–N1–Si1 angles (157.8 ∘) observed in related N-silylated 2-iminoimidazolines and trimethylsilyl iminophosphoranes. C1–N1–P1 angles are further widened in compounds 2a, 3a, and 4a,b due to the attachment of chalcogen atoms onto phosphorus atom

Alkali Metal Complexes Having Sterically Bulky Bis-Iminopyrrolyl Ligands – Control of Dimeric to Monomeric Complex

We report the syntheses and structural diversity of three different bis-iminopyrrole ligands and their alkali metal (Li, Na, K) complexes featuring a shift from dimeric to monomeric nature by a simple tuning of the steric control of the imine nitrogen substitutions. The bis-iminopyrrole ligands having molecular formula [(ArN=CH)2C4H2NH] [Ar = CHPh2 (1-H), Ad (2-H), Ad = adamentyl, and CPh3 (3-H)], were prepared through the reaction of 2,5-pyrrole-dicarbaldehyde with corresponding amines (ArNH2) in 1:2 molar ratio and under acidic conditions. Using ligand 1-H, the lithium [{Li(Ph2CHN=CH)2C4H2N}2] (1-Li), sodium [{Na(Ph2CH-N=CH)2C4H2N}2(THF)] (1-Na) and potassium [{3-(Ph2CHN=CH)2C4H2N}-K(THF)2] (1-K) complexes were obtained through either alkane elimination (for Li) or amine elimination (for Na, K). The alkali metal complexes [{2-(Ph3CHN=CH)2C4H2N}M(THF)n] [n = 2, M = Li (3-Li), Na (3-Na); n = 3, M = K (3-K)] were synthesized using the ligand 3-H. Molecular structures of ligands 1-3-H, and alkali metal complexes 1-Li, 1-Na, 1-K, 3-Li, 3-Na and 3-K, in solid state were established. The complexes 1-Li and 1-Na were found to be dimeric in the solid state whereas the complexes 1-K, 3-Li, 3-Na and 3-K were all monomeric – either due to a larger ionic radius (for 1-K) or because of the presence of the bulky triphenylmethyl group in the imine nitrogen

Functionalisation of Imidazolin-2-imine to Corresponding Phosphinamine, Chalcogenide (O, S, Se, Te), and Borane Compounds

1,3-Di-tert-butyl-imidazolin-2-ylidine-1,1-diphenylphosphinamine (2) was prepared from 1,3-di-tert-butyl-imidazolin-2-imine (1) and chlorodiphenylphosphine. Compound 2 was treated further with elemental sulfur, selenium, and tellurium to afford the corresponding chalcogenide derivatives, 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinothioicamide (4), 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinoselenoicamide (5), and 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinotelluroicamide (6) in good yield. 1,3-Di-tert-butyl-imidazolin-2-ylidine-P,P-diphenylphosphinicamide (3) was obtained by dissolving compound 2 in hydrochloric acid solution in THF. The corresponding borane adduct, 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinaminoborane (7) was isolated by the reaction of compound 2 and sodium borohydride in good yield. The molecular structures of compounds 2 and 4–7 were established by X-ray diffraction analyses. To analyse the electronic structure of chalcogenides of imidazolin-2-imine ligands, the protonation energies of the oxygen, sulfur, and selenide derivative of ligand 2 were calculated by means of density functional theory. Finally, the charge distribution in compounds 3, 4, and 5 were determined using natural bond orbital analysis

Heavier Group 2 Metal Complexes with Flexible Scorpionate Ligand based on 2-Mercaptopyridine

We report the synthesis of novel alkaline earth metal complexes [2-SS-(Bmp)2M(THF)n] [M = Ca (2), Sr (3) n = 2; M = Ba (4), n = 3] of flexible dihydrobis(2-thiopyridone)borate (Bmp) ligand based on 2-mercaptopyridine. Complexes 2–4 were isolated in good yield by the reaction between sodium dihydrobis(2-thiopyridone)borate, [{(Bmp)Na(THF)}2]n (1) and corresponding alkaline earth metal diiodides in toluene at ambient temperature. The solid-state structures of strontium and barium complexes, complexes 3 and 4 respectively, were established using single-crystal X-ray diffraction analysis. The solid-state structure of sodium complex 1 was also confirmed using X-ray. The solid-state structures of complexes 3 and 4 revealed that the Bmp ligand coordinates through sulphur atoms to the metal ions in 2 fashion. The strontium ion is attached symmetrically and the barium ion is asymmetrically linked with the Bmp ligand, manifesting the 2-thiopyridone and pyridine-2-thiolate tautomeric form of the Bmp ligand. The strontium ion in complex 3 adopts a distorted octahedral geometry whereas the geometry around the barium ion can best be described as a distorted pentagonal bipyramidal. Both complexes 3 and 4 also have short B...H...M interaction due to the presence of BH2 group in the ligand. In the solid state, sodium complex 1 is polymeric in nature and in the asymmetric unit each sodium ion is bonded to two sulphur atoms through and modes. The adjacent BH2 group is also linked with each sodium ion through hydrogen atoms via 2 and

The Model Analysis of Lower Limb at Ascending from Deep Knee Flexion

A new type of knee prosthesis capable of making deep knee flexion has been long awaited for Asian and Muslim people. Our research group has developed the prosthesis possible to attain even sedentary sitting and designated it as CFK (Complete Flexion Knee). In order to assess the performance of CFK, we have set up various kinds of simulation or experimental projects, such as a cadaveric study, a mathematical model analysis, a photoelastic analysis and FEM analysis. For carrying out the above-mentioned projects, we faced the most fundamental problem; the information about the forces acting on the joints has been limited for ambulatory activities but not for squatting or sedentary sitting. The objective of this study is to introduce the force acting on the knee joint at deep knee flexion through a 2D mathematical model simulation and some experimental measurements. Double leg ascending motion and single leg ascending motion from kneeling position were studied for 10 healthy male subjects. The results demonstrated that for double leg ascending, the maximum knee joint forces were 4.9±0.5 times of body weight, and for single leg ascending, the maximum knee joint forces of dominant leg were 5.0±0.2 times of body weight and those of supporting leg were 3.0±0.5 times of body weight. Ascending speeds did not affect the results much as long as the motion was not strenuous like jumping up/down

Highly Active and Iso-selective Catalysts for ROP of Cyclic Esters Using Group 2 Metal Initiators

A series of alkali and alkaline earth (Ae) metal complexes bearing 1,2 phenylene(bis-diphenylphosphinothioic/selenoic amide) [{Ph2P(E)NH}2C6H4] (E = S (1-H2); Se (2-H2) ligands are reported. Alkali metal complexes [{Ph2P(S)N}2C6H4]Na(THF)4 (3a) [{Ph2P(Se)N}2C6H4]Na(THF)4 (3b), and [{Ph2P(Se)N}2C6H4]K(THF)5 (4b) were obtained in good yield by treating protic ligand 1-H2 or 2-H2 with corresponding metal hexamethyldisilazides [MN(SiMe3)2] (M = Na and K) at ambient temperature. The Ae metal complexes formulated as [{Ph2P(E)N}2C6H4]M(THF)3 [E = S, M = Ca (5a), Sr (6a), Ba (7a); E = Se, M = Ca (5b), Sr (6b), Ba (7b)] can be synthesized using two routes. The molecular structures of the free ligand 1-H2 and metal complexes 5a,b-7a,b in their solid states were established. Complexes 3a and 3b are isostructural; however, in complex 4b, an attachment different from ligand 2 was observed. The complexes 5a,b-7a,b are isostructural and each metal ion exhibits a distorted pentagonal bipyramidal geometry around it. All Ae metal complexes 5a,b-7a,b were tested for the ring-opening polymerization (ROP) of racemic lactide (rac-LA) and - caprolactone (-CL) at room temperature. Calcium complexes 5a and 5b show excellent iso-selectivity, with a Pi value of 0.78-0.87 at 298 K with a high degree of polymerization control, whereas the corresponding strontium complexes 6a and 6b exhibit moderate iso-selectivity, and barium complexes 7a and 7b yield only atactic polylactides (PLAs)

Reaction of sterically congested NHC-Zn(CH 2CH 3) 2 with substituted phenols leading to zincate complexes

We report the reaction of a sterically congested NHC-Zn(CH 2CH3)2 Lewis adduct (1) prepared through reaction of an equimolar ratio of 1,3-di-tert-butylimidazol-2-ylidene and diethyl zinc, with various substituted phenols (4-tert-butyl-phenol, 2,6-di-tert-butyl-4-methyl phenol, and 1-bromo-4,6-di-tert-butyl phenol). The NHC-Zn dative bond was cleaved in each of the reactions with the substituted phenols to afford the corresponding ionic complexes of imidazolium cation and aryloxo-zincate, [{(4-CMe3C6H4O) 2Zn(-OC6H4-4-CMe3)} 2{(1,3-(CMe3)2-ImCH}2] (2), [{(2,6-(CMe3)2-4-Me-C6H3O) 2}Zn{(1,3-(Cme3)2-ImCH}] (3), and [{(1-Br-3,5-(Cme3)2C6H2O) 2}2-Zn{(1,3-(CMe3)2-ImCH}] (4), where 1,3-(CMe3)2-ImCH) is imidazolium carbocation. The molecular structures of 1-4 were established by X-ray diffraction analyses and from the solid-state structures of 2-4, it was confirmed that, in all the compounds, zinc ions are coordinated through substituted phenolate group