Search Results (6)

The so far unattended version of the Hirao reaction involving the coupling of the less reactive chloroarenes with >P(O)H reagents, such as diarylphosphine oxides, diethyl phosphite, and ethyl phenyl-H-phosphinate, was investigated in detail using Pd(OAc)₂ as the catalyst precursor, and applying some excess of the P-reagent to provide the ligand via its trivalent tautomeric (>P-OH) form. In the presence of triethylamine, no P–C coupling took place, meaning that there was a need for a stronger base, an alkali carbonate. The solvent had a significant effect on the efficiency of the Hirao reaction. The optimum conditions (10% of the Pd(OAc)₂, 1.3 equiv. of the P-reagent, 1.1 equiv. of the alkali carbonate, 135–150 °C) explored herein were applied in the synthesis of diaryl-phenylphosphine oxides, aryl-diphenylphosphine oxides, diethyl arylphosphonates, and ethyl diphenylphosphinate. Theoretical calculations performed at the M06-2X/6-31G(d,p)[PCM(MeCN)] level also justified coupling with the chloroarenes under appropriate conditions, and were in accord with the experimental results revealing the unsuitability of triethylamine as a base and the need for an alkali carbonate. The new protocol elaborated herein is more practical and “greener” than the version with bromoarenes, and embraces a wide substrate scope. Full article

Two substituted phosphonium tetrahydoxidohexaoxidopentaborate(1-) salts, [ⁱPrPPh₃][B₅O₆(OH)₄]·3.5H₂O (1) and [MePPh₃][B₅O₆(OH)₄]·B(OH)₃·0.5H₂O (2), were prepared by templated self-assembly processes with good yields by crystallization from basic methanolic aqueous solutions primed with B(OH)₃ and the appropriate phosphonium cation. Salts 1 and 2 were characterized by spectroscopic (NMR and IR) and thermal (TGA/DSC) analysis. Salts 1 and 2 were thermally decomposed in air at 800 °C to glassy solids via the anhydrous phosphonium polyborates that are formed at lower temperatures (<300 °C). BET analysis of the anhydrous and pyrolysed materials indicated they were non-porous with surface areas of 0.2–2.75 m²/g. Rhe recrystallization of 1 and 2 from aqueous solution afforded crystals suitable for single-crystal XRD analyses. The structure of 1 comprises alternating cationic/anionic layers with the H₂O/pentaborate(1-) planes held together by H-bonds. The cationic planes have offset face-to-face (off) and vertex-to-face (vf) aromatic ring interactions with the ⁱPr groups oriented towards the pentaborate(1-)/H₂O layers. The anionic lattice in 2 is expanded by the inclusion of B(OH)₃ molecules to accommodate the large cations; this results in the formation of a stacked pentaborate(1-)/B(OH)₃ structure with channels occupied by the cations. The cations within the channels have vf, ef (edge-to-face), and off phenyl embraces. Both H-bonding and phenyl embrace interactions are important in stabilizing these two solid-state structures. Full article

A series of [Cu(POP)(N^N][PF₆] and [Cu(xantphos)(N^N][PF₆] compounds has been prepared and characterized in which POP = bis[2-(diphenylphosphanyl)phenyl]ether (IUPAC PIN oxydi(2,1-phenylene)bis(diphenylphosphane), xantphos = 4,5-bis(diphenylphosphanyl)-9,9-dimethyl-9H-xanthene (IUPAC PIN (9,9-dimethyl-9H-xanthene- 4,5-diyl)bis(diphenylphosphane)) and the N^N ligands are 4-(4-bromophenyl)-6,6′-dimethyl-2,2′- bipyridine (1), 5,5′-bis(3-methoxyphenyl)-6-methyl-2,2′-bipyridine (2), and 6-benzyl-2,2′-bipyridine (3). The single crystal structures of [Cu(xantphos)(1)][PF₆]·CH₂Cl₂, [Cu(xantphos)(2)][PF₆]·CH₂Cl₂ and [Cu(POP)(3)][PF₆]·0.5H₂O were determined by X-ray diffraction. Each complex contains a copper(I) ion in a distorted tetrahedral environment with chelating N^N and P^P ligands. In the [Cu(xantphos)(1)]⁺ and [Cu(xantphos)(2)]⁺ cations, there are face-to-face π-stackings of bpy and PPh₂ phenyl rings (i.e., between the ligands); in addition in [Cu(xantphos)(2)][PF₆]·CH₂Cl₂, inter-cation π-embraces lead to the formation of infinite chains as a primary packing motif. In [Cu(POP)(3)][PF₆]·0.5H₂O, centrosymmetric pairs of [Cu(POP)(3)]⁺ cations engage in C–H…π (phenyl to bpy) and offset face-to-face (bpy…bpy) contacts. The electrochemical and photophysical properties of the compounds containing ligands 1 and 2 are reported. They are green or yellow emitters in the solid-state (λ_em in the range 535–577 nm) with values for the photoluminescence quantum yield (PLQY) in the range 19%–41%. Full article

A mononuclear iron(II) complex bearing the linear pentadentate N₅ Schiff-base ligand containing two 1,2,3-triazole moieties and the MeCN monodentate ligand, [Fe^IIMeCN(L_3-Me-3^Ph)](BPh₄)₂·MeCN·H₂O (1), have been prepared (L_3-Me-3^Ph = bis(N,N′-1-Phenyl-1H-1,2,3-triazol-4-yl-methylideneaminopropyl)methylamine). Variable-temperature magnetic susceptibility measurements revealed an incomplete one-step spin crossover (SCO) from the room-temperature low-spin (LS, S = 0) state to a mixture of the LS and high-spin (HS, S = 2) species at the higher temperature of around 400 K upon first heating, which is irreversible on the consecutive cooling mode. The magnetic modulation at around 400 K was induced by the crystal-to-amorphous transformation accompanied by the loss of lattice MeCN solvent, which was evident from powder X-ray diffraction (PXRD) studies and themogravimetry. The single-crystal X-ray diffraction studies showed that the complex is in the LS state (S = 0) between 296 and 387 K. In the crystal lattice, the complex-cations and B(1)Ph₄⁻ ions are alternately connected by intermolecular CH···π interactions between the methyl group of the MeCN ligand and phenyl groups of B(1)Ph₄⁻ ions, forming a 1D chain structure. The 1D chains are further connected by P4AE (parallel fourfold aryl embrace) interactions between two neighboring complex-cations, constructing a 2D extended structure. B(2)Ph₄⁻ ions and MeCN lattice solvents exist in the spaces of the 2D layer. DFT calculations verified that the 1,2,3-triazole-containing ligand L_3-Me-3^Ph gives a stronger ligand field around the octahedral coordination environment of the iron(II) ion than the analogous imidazole-containing ligand H₂L^2Me (= bis(N,N′-2-methylimidazol-4-yl-methylideneaminopropyl)methylamine) of the known compound [Fe^IIMeCN(H₂L^2Me)](BPh₄)_1.5·Cl_0.5·0.5MeCN (2) reported by Matsumoto et al. (Nishi, K.; Fujinami, T.; Kitabayashi, A.; Matsumoto, N. Tetrameric spin crossover iron(II) complex constructed by imidazole⋯chloride hydrogen bonds. Inorg. Chem. Commun. 2011, 14, 1073–1076), resulting in the much higher spin transition temperature of 1 than that of 2. Full article

Herein, we describe the preparation of heteronuclear dirhodium-silver complexes by reaction between molecular Rh(II)-Rh(II) compounds [Rh₂(μ-O₂CR)₄L₂] (R = Me, Ph (1), CH₂OEt (2); L = solvent molecules) with paddlewheel structure and PPh₄[Ag(CN)₂]. One-dimensional coordination polymers of (PPh₄)_n[Rh₂(μ-O₂CR)₄Ag(CN)₂]_n (R = Me (3), Ph (4), CH₂OEt (5)) formula have been obtained by replacement of the two labile molecules in the axial positions of the paddlewheel structures by a [Ag(CN)₂]⁻ bridging unit. The crystal structures of 3–5 display a similar arrangement, having anionic chains with a wavy structure and bulky (PPh₄)⁺ cations placed between the chains. The presence of the (PPh₄)⁺ cations hinders the existence of intermolecular Ag-Ag interactions although several C-H····π interactions have been observed. A similar reaction between [Rh₂(μ-O₂CCMe₃)₄(HO₂CCMe₃)₂] and PPh₄[Ag(CN)₂] led to the molecular compound (PPh₄)₂{Rh₂(μ-O₂CCMe₃)₄[Ag(CN)₂]₂} (6) by replacement of the axial HO₂CCMe₃ ligands by two [Ag(CN)₂]⁻ units. The trimethylacetate ligand increases the solubility of the complex during the crystallization favouring the formation of discrete heteronuclear species. Full article

In this paper, the bromo- and phosphonate-ester-functionalized complexes [Zn(1)₂][CF₃SO₃]₂ and [Zn(2)₂][CF₃SO₃]₂ (1 = 4′-(4-bromophenyl)-2,2′:6′,2″-terpyridine, 2 = diethyl (4-([2,2′:6′,2″-terpyridin]-4′-yl)phenyl)phosphonate) are reported. The complexes have been characterized by electrospray mass spectrometry, IR and absorption spectroscopies, and multinuclear NMR spectroscopy. The single-crystal structures of [Zn(1)₂][CF₃SO₃]₂^.MeCN^.1/₂Et₂O and [Zn(2)₂][CF₃SO₃]₂ have been determined and they confirm {Zn(tpy)₂}²⁺ cores (tpy = 2,2′:6′,2″-terpyridine). Ongoing from X = Br to P(O)(OEt)₂, the {Zn(4′-XC₆H₄tpy)₂}²⁺ unit exhibits significant “bowing” of the backbone, which is associated with changes in packing interactions. The [Zn(1)₂]²⁺ cations engage in head-to-tail 4′-Phtpy...4′-Phtpy embraces with efficient pyridine...phenylene π-stacking interactions. The [Zn(2)₂]²⁺ cations pack with one of the two ligands involved in pyridine...pyridine π-stacking; steric hindrance between one C₆H₄PO(OEt)₂ group and an adjacent pair of π-stacked pyridine rings results in distortion of backbone of the ligand. This report is the first crystallographic determination of a salt of a homoleptic [M{4′-(RO)₂OPC₆H₄tpy}₂]ⁿ⁺ cation. Full article