The preparation and characterization of six rare earth 2-methyl-3-furoate (2m3fur) complexes are reported. All compounds belong to two structural groups: {[RE₂(2m3fur)₆(EtOH)] ⋅ H₂O}_n (RE=La, Ce, Pr) and [RE₃(2m3fur)₉]_n (RE=Y, Er, Yb). In corrosion inhibition tests on mild steel in 0.01 M NaCl solution, the maximum efficiency was observed with [Y₃(2m3fur)₉]_n. The results suggest that the steric effect of the methyl group adversely affects corrosion inhibition.

Abstract

The preparation and characterization of six rare earth 2-methyl-3-furoate (2m3fur) complexes are detailed in this study. Analysis through single-crystal X-ray diffraction, as well as powder XRD, reveals that all six compounds belong to one of two structural groups: {[RE₂(2m3fur)₆(EtOH)] ⋅ H₂O}_n (RE=La, Ce, Pr) and [RE₃(2m3fur)₉]_n (RE=Y, Er, Yb). These structural groups feature carboxylate coordinated linear polymers. The former complexes have two distinct metal centers, one ten coordinate and one nine, with lattice water participating in a hydrogen bond with coordinated ethanol. The latter structures, involving erbium, ytterbium, and yttrium, have three unique metal centers: two eight coordinate, and one seven-coordinated. In corrosion inhibition tests on mild steel in 0.01 M NaCl solution, the maximum efficiency was observed with [Y₃(2m3fur)₉]_n at 59 %, which is less effective than yttrium 3-furoate (90 % efficiency). The results suggest that the steric effect of the methyl group adversely affects corrosion inhibition.

Three novel metal-phosphonate frameworks, namely, rod-shaped one-dimensional [{Cu(terpy)}(H₆-MTPPA)(H₂O)]⋅2H₂O, three-dimensional [{Cu₅(2,2’-bpy)₂}(H₂-MTPPA)(H₄-MTPPA)] and one-dimensional [{Cu₂(phen)₂)}(H₄-MTPPA)]⋅4H₂O, constructed from tetrahedral shaped methane-p-tetraphenylphosphonic acid (MTPPA) and N-ancillary organoimine ligands were synthesized and characterized by X-ray crystallography. Magnetic analysis of [{Cu₅(2,2’-bpy)₂)}(H₂-MTPPA)(H₄-MTPPA)] exhibited paramagnetic behavior.

A heterocycle containing phosphorus, known as dialkyl-2H-1,2-phosphasiliren-3-olate is synthesized through the reaction of dialkylsilylene and sodium phosphaethynolate (NaOCP). The theoretical studies are identified two nucleophilic centres located on the phosphorus (P) and oxygen (O) atoms, respectively. The electrophilic reactivities involving R₃SiCl, Me₂SO₄ and acyl chlorides are also conducted occurring at the oxygen atom.

Abstract

A heterocycle containing phosphorus, known as dialkyl-2H-1,2-phosphasiliren-3-olate 2, is synthesized through the reaction of dialkylsilylene 1 and sodium phosphaethynolate (NaOCP) in a high yield at ambient conditions. The structure of 2 is determined by single-crystal X-ray diffraction and multinuclear NMR spectroscopy. The theoretical studies are identified two nucleophilic centres located on the phosphorus (P) and oxygen (O) atoms, respectively. According to WBIs and the crystal characterization analyses, both the C−P and C−O bonds in the C−Si-P three-membered ring have significant double bond character. Reactions involving R₃SiCl and Me₂SO₄ with 2 at room temperature are also conducted at room temperature. The nucleophilic substitution reaction can also occur on oxygen atom of 2, and yield ring-retaining products 3 and 4 a–4 c, respectively. When acyl chlorides are employed as electrophiles, the derivatives of (silylmethylidyne)phosphane, 6 a–6 c, are produced as a result of the substitution of the oxygen atom.

Solid-state reactions between SiI₄ (or GeI₄) and Li₂(CN₂) pass through amorphous stages to finally yield the unprecedented Li₄[Si(CN₂)₄] (or Li₄[Ge(CN₂)₄]). Tetracyanamidometallate anions may be combined with various cations of the PSE.

Abstract

The tetracyanamidometallates Li₄[T(CN₂)₄] with T=Si, Ge were prepared by solid-state metathesis (SSM) reactions between TI₄ and Li₂(CN₂). The new compounds Li₄[T(CN₂)₄] are obtained as crystalline phases in high yields and represent the most basic examples of the family of tetracyanamidometallates. The formation of these compounds, via SiI₄ and Li₂(CN₂), is analyzed by means of differential scanning calorimetry (DSC). The [Si(CN₂)₄]⁴⁻ ion in the structure of Li₄[Si(CN₂)₄] can be considered an analogue to the [SiO₄]⁴⁻ ion in Li₄SiO₄. The crystal structures of Li₄[T(CN₂)₄] were solved and refined isotypically on the basis of single-crystal X-ray diffraction data in the space group C2/c, and further characterized by infrared and solid-state NMR techniques.

Despite long time assumed as direct intramolecular migratory insertions, the two last of the three alkyl group migrations after alkylborane carbonylation with carbon monoxide are shown to proceed either through activated dimeric species or catalyzed by the final product, as the only low barrier possible pathways, the latter leading to scarcely aromatic boroxines.

Abstract

The classical simple picture of stepwise B-to-C migratory insertion of all three alkyl groups in the carbonylation reaction of trialkyl boranes with CO was shown not to be correct, except for the first alkyl group shift affording an acyl borane. The second and third direct alkyl shifts turned out to be kinetically hampered due to the non-activated character of the B−C bond in electron-poor B atoms. The latter can only be achieved by either the autocatalytic action of the final alkyl boron oxide or by formation of dimeric species with weakened B-alkyl bonds at borate centres. Both thermodynamic and several NICS-related parameters pointed to scarce, even “negative”, aromatic character for boroxines, the final cyclotrimerization products of alkyl-boron oxides.

A zwitterionic tetrastanna(II) cyclic compound comprising of two stannate (II) and two stannyliumylidene in alternating positions of the macrocycle has been synthesized which represents the Sn analogue of 12-crown-4. This has been achieved by the simple deprotonation from a bis(imidazole) using Sn[N(SiMe₃)₂].

Abstract

A 12-membered zwitterionic tetrastanna(II) cycle 1 having a crown ether-like topology has been isolated from the deprotonation of 1,1′-methylenediimidazole (B) with two equivalents of Sn[N(SiMe₃)₂]₂ (A). The solid-state structure and NMR analysis confirms the tetrastanna(II) cycle 1 to be comprised of two stannate(II) and two stannyliumylidene ion pairs in alternating positions of the heterocycle. Computational analysis shows greater nucleophilicity at the proximally located stannate(II) centers. Nonetheless, the tetrastanna(II) cycle 1 remains poorly reactive due to engagement of Sn^II lone pair electrons in intramolecular donor-acceptor interactions. Simple deprotonation reaction between Sn[N(SiMe₃)₂]₂ (A) and N-(diisopropylphenyl)imidazole (C) in equimolar ratio has led to a stannylene 2, involving the formation of a Sn−C covalent bond with the anionic imidazol-2-yl carbon center along with the release of NH(SiMe₃)₂. Compound 2 exists as a dimer, where the unsubstituted ring nitrogen atom coordinated intermolecularly to the other stannylene center.

The reaction of GeCl₂ ⋅ 1,4-dioxane with Fe₂(CO)₉ gives [Cl₂GeFe(CO)₄]₂, Cl₂Ge[Fe₂(CO)₈]Ge[Fe₂(CO)₈] or Ge[Fe₂(CO)₈]₂, depending on the educt ratio. [Cl₂GeFe(CO)₄]_2, Ge[Fe₂(CO)₈]₂ and ^Me₂iPr₂NHC ⋅ GeCl₂ ⋅ Fe(CO)₄ were characterized in their thermal decomposition behavior and applied as single source precursors in chemical vapor deposition, resulting in Fe_xGe_1-x thin films.

Abstract

Binary iron-germanium phases are promising materials in magnetoelectric, spintronic or data storage applications due to their unique magnetic properties. Previous protocols for preparation of Fe_xGe_y thin films and nanostructures typically involve harsh conditions and are challenging in terms of phase composition and homogeneity. Herein, we report the first example of single source chemical vapor deposition (CVD) of Fe_xGe_y films. The appreciable volatility of [Ge[Fe₂(CO)₈]₂], [Cl₂GeFe(CO)₄]₂ and ^Me₂iPr₂NHC ⋅ GeCl₂ ⋅ Fe(CO)₄ allowed for their application as precursors under standard CVD conditions (^Me₂iPr₂NHC=1,3-diisopropoyl-4,5-dimethylimidazol-2-ylidene). The thermal decomposition products of the precursors were characterized by TGA and powder XRD. Deposition experiments in a cold-wall CVD reactor resulted in dense films of Fe_xGe_y. During the optimization of synthetic conditions for precursor preparation the new iron-germanium cluster Cl₂Ge[Fe₂(CO)₈]Ge[Fe₂(CO)₈] was obtained in experiments with a higher stoichiometric ratio of GeCl₂ ⋅ 1,4-dioxane vs. Fe₂(CO)₉.

A cubic metal-sulfur cluster, [Cp^SiEt3 ₃Mo₃S₄Pd]Cl (Mo₃Pd, Cp^SiEt3=C₅Me₄SiEt₃), was synthesized by the incorporation of the Pd ion into a Mo₃S₄ cluster [Cp^SiEt3 ₃Mo₃S₄] (Mo₃ ). Mo₃Pd promoted a two-electron reduction process and was utilized for the hydrogen evolution reaction (HER). The mechanism of the HER was determined by density functional theory (DFT) calculations.

Abstract

A cubic metal-sulfur cluster containing three Mo ions and a Pd ion, [Cp^SiEt3 ₃Mo₃S₄Pd]Cl (Mo₃Pd, Cp^SiEt3=C₅Me₄SiEt₃), was synthesized by the incorporation of the Pd ion into a Mo₃S₄ cluster [Cp^SiEt3 ₃Mo₃S₄] (Mo₃ ). Mo₃Pd was characterized by ¹H NMR, UV-vis, X-ray crystallography, and cyclic voltammetry measurements. The electrochemical measurements demonstrated reversible one- and two-electron reduction processes for Mo₃Pd, which suggested potential catalytic activity for two-electron substrate reductions such as hydrogen evolution reaction. Controlled potential electrolysis in the presence of Mo₃Pd and trifluoroethanol in THF solvent displayed H₂ formation with a constant current over 60 min. The amount of generated H₂ by Mo₃Pd was two times higher than Mo₃ , indicating the catalytic activity facilitated by the Pd center. The mechanism of the catalytic cycle was determined by density functional theory.

The crystalline complexes were obtained by the interaction of [Sn^II(Pc⁽ⁿ⁺²⁾⁻)]ⁿ⁻ (n=1, 2) anions with {(COD)RhCl}₂. Heterometallic anionic assemblies [(COD)Rh(Cl)⋅Sn^II(Pc⁽ⁿ⁺²⁾⁻)]⁻ with tin-rhodium bonds based on paramagnetic Pc⋅³⁻ or diamagnetic Pc⁴⁻ species were formed.

Abstract

Crystalline {Cryptand(Na⁺)}[(COD)Rh^ICl⋅Sn^II(Pc³⁻)]⁻⋅2C₆H₄Cl₂ (1) and {Cryptand(Cs⁺)}[(COD)Rh^I⋅Sn^II(Pc⁴⁻)]⁻⋅C₆H₅CH₃ (2) complexes were obtained via the interaction of [Sn^II(Pc³⁻)]⁻ and [Sn^II(Pc⁴⁻)]²⁻, respectively, with organometallic {(COD)RhCl}₂ dimer (COD is 1,5-cyclooctadiene). Dissociation of {(COD)RhCl}₂ followed by the Rh−Sn binding is observed at the formation of 1. Elimination of the chlorine atom at the rhodium atom is observed in 2, and rhodium is additionally coordinated to the imine nitrogen atom of Pc⁴⁻. The complexes contain mono- Pc⋅³⁻ and doubly reduced Pc⁴⁻ species, respectively, that is supported by the data of XRD analysis as well as optical and magnetic properties of 1 and 2. There is an alternation of C-N_imine bonds in the macrocycles, which gradually increases with increasing negative charge on the macrocycle. The difference between shorter and longer bonds increases from 0.051 Å in Pc³⁻ to 0.075 Å in Pc⁴⁻. The formation of 1 is accompanied by an essential blue shift of the Q-band of starting SnPc and the appearance of a new intense band at 1031 nm. The even stronger shift of the Q-band is observed in the spectrum of 2, but the band in the near-IR range becomes weaker. The value of effective magnetic moment of 1 is 1.76 μ _B at 300 K corresponding the contribution of the Pc³⁻ radical trianions (S=1/2). Only weak magnetic coupling with the Weise temperature of −3 K is observed in 1 due to weak π–π interaction between the macrocycles in the chains. Paramagnetic Pc³⁻ species additionally monitored by EPR spectroscopy show a strong temperature dependence of g-factor and linewidth of the EPR signal. Complex 2 is diamagnetic and EPR silent.