Evaluation of dispersion type metal···π arene interaction in arylbismuth compounds - an experimental and theoretical study.

The dispersion type Bi···π arene interaction is one of the important structural features in the assembly process of arylbismuth compounds. Several triarylbismuth compounds and polymorphs are discussed and compared based on the analysis of single crystal X-ray diffraction data and computational studies. First, the crystal structures of polymorphs of Ph3Bi (1) are described emphasizing on the description of London dispersion type bismuth···π arene interactions and other van der Waals interactions in the solid state and the effect of it on polymorphism. For comparison we have chosen the substituted arylbismuth compounds (C6H4-CH═CH2-4)3Bi (2), (C6H4-OMe-4)3Bi (3), (C6H3-t-Bu2-3,5)3Bi (4) and (C6H3-t-Bu2-3,5)2BiCl (5). The structural analyses revealed that only two of them show London dispersion type bismuth···π arene interactions. One of them is the styryl derivative 2, for which two polymorphs were isolated. Polymorph 2a crystallizes in the orthorhombic space group P212121, while polymorph 2b exhibits the monoclinic space group P21/c. The general structure of 2a is similar to the monoclinic C2/c modification of Ph3Bi (1a), which leads to the formation of zig-zag Bi-arenecentroid ribbons formed as a result of bismuth···π arene interactions and π···π intermolecular contacts. In the crystal structures of the polymorph 2b as well as for 4 bismuth···π arene interactions are not observed, but both compounds revealed C-HPh···π intermolecular contacts, as likewise observed in all of the three described polymorphs of Ph3Bi. For compound 3 intermolecular contacts as a result of coordination of the methoxy group to neighboring bismuth atoms are observed overruling Bi···π arene contacts. Compound 5 shows a combination of donor acceptor Bi···Cl and Bi···π arene interactions, resulting in an intermolecular pincer-type coordination at the bismuth atom. A detailed analysis of three polymorphs of Ph3Bi (1), which were chosen as model systems, at the DFT-D level of theory supported by DLPNO-CCSD(T) calculations reveals how van der Waals interactions between different structural features balance in order to stabilize molecular arrangements present in the crystal structure. Furthermore, the computational results allow to group this class of compounds into the range of heavy main group element compounds which have been characterized as dispersion energy donors in previous work.

Iron-bismuth halido compounds: molecules, clusters, and polymers.

The pentamethylcyclopentadienyl substituted iron-bismuth halides [Bi{FeCp*(CO)2}X2] [X = Cl (1), Br (2), I (3); Cp* = η(5)-C5Me5] were synthesized starting from [FeCp*(CO)2]2 and BiX3 (X = Cl, Br), followed by halogen exchange reaction with KI in case of 3. From a reaction mixture of [FeCp*(CO)2]2 with BiCl3 in CH2Cl2 to which CH3CN had been added, a novel coordination polymer of the formula [FeCp*(CO)2(CH3CN)]2n[Bi4Cl14]n (4) was isolated. The change of the molar ratio from 1:1 to 1:2 in the reaction of [FeCp*(CO)2]2 with BiBr3 afforded the novel ionic complex [{FeCp*(CO)2Br]2[Bi6Br22{FeCp*(CO)2}]·CH2Cl2 (5·CH2Cl2). It is demonstrated that treatment of [FeCp*(CO)2X] (X = Cl, Br) with BiCl3 and BiBr3, respectively, is a more convenient route to synthesize the new halido bismuthates 4 and 5.

Synthesis of Mg and Zn diolates and their use in metal oxide deposition.

The synthesis of complexes [M(OCHMeCH2NMeCH2)2] (5, M = Mg; 7, M = Zn) is described. Treatment of MeHNCH2CH2NMeH (1) with 2-methyloxirane (2) gave diol (HOCHMeCH2NMeCH2)2 (3), which upon reaction with equimolar amounts of MR2 (4, M = Mg, R = Bu; 6, M = Zn, R = Et) gave 5 and 7. The thermal behavior and vapor pressure of 5 and 7 were investigated to show whether they are suited as CVD (= chemical vapor deposition) and/or spin-coating precursors for MgO or ZnO layer formation. Thermogravimetric (TG) studies revealed that 5 and 7 decompose between 80-530 °C forming MgO and ZnO as evidenced by PXRD studies. In addition, TG-MS-coupled experiments were carried out with 7 proving that decomposition occurs by M-O, C-O, C-N and C-C bond cleavages, as evidenced from the detection of fragments such as CH4N+, C2H4N+, C2H5N+, CH2O+, C2H2O+ and C2H3O+. The vapor pressure of 7 was measured at 10.4 mbar at 160 °C, while 5 is non-volatile. The layers obtained by CVD are dense and conformal with a somewhat granulated surface morphology as evidenced by SEM studies. In addition, spin-coating experiments using 5 and 7 as precursors were applied. The corresponding MO layer thicknesses are between 7-140 nm (CVD) or 80 nm and 65 nm (5, 7; spin-coating). EDX and XPS measurements confirm the formation of MgO and ZnO films, however, containing 12-24 mol% (CVD) or 5-9 mol% (spin-coating) carbon. GIXRD studies verify the crystalline character of the deposited layers obtained by CVD and the spin-coating processes.

Magnesium ß-ketoiminates as CVD precursors for MgO formation.

The synthesis and characterization of bis(ketoiminato)magnesium(ii) complexes of composition [Mg(OCR2CH2CHR1NCH2CH2X)2] (X = NMe2: 3a, R1 = R2 = Me; 3b, R1 = Me, R2 = Ph. X = OMe: 3c, R1 = R2 = Me) are reported. Complexes 3a-c are accessible by the reaction of C(O)R2CH2CHR1N(H)CH2CH2X (X = NMe2: 1a, R1 = R2 = Me; 1b, R1 = Me, R2 = Ph. X = OMe: 1c, R1 = R2 = Me) with Mg n Bu2. The structure of 3b in the solid state was determined by a single crystal X-ray diffraction study, confirming that the Mg(ii) ion is hexa-coordinated by two ketoiminato ligands, while each of the latter coordinates with its two N- and one O-donor atom in an octahedral MgN6O2 coordination environment in the OC-6-33 stereo-isomeric form. The thermal behavior of 3a-c was studied by TG and DSC under an atmosphere of Ar and O2 respectively. The respective Me-substituted complexes 3a,c decompose at lower temperatures (3a, 166 °C; 3c, 233 °C) than the phenyl derivative 3b (243 °C). PXRD studies indicate the formation of MgO. Additionally, TG-MS studies were exemplarily carried out for 3a, indicating the release of the ketoiminato ligands. Vapor pressure measurements were conducted at 80 °C, whereby 3a,c possess with 5.6 mbar (3a) and 2.0 mbar (3c) significantly higher volatilities than 3b (0.07 mbar). Complexes 3a-c were used as MOCVD precursors for the deposition of thin MgO films on silicon substrates. It was found that only with 3a,c thin, dense and rather granulated MgO layers of thicknesses between 28-147 nm were produced. The as-deposited MgO layers were characterized by SEM, EDX, and XPS measurements and the thicknesses of the as-deposited layers were measured by Ellipsometry and SEM cross-section images. Apart from magnesium and oxygen a carbon content between 3-4 mol% was determined.

Zirconium and Hafnium Twin Monomers for Mixed Oxides.

The synthesis of Zr and Hf twin monomers of type [M(2-OCH2 c C4 H3 O)4 (x HOCH2 c C4 H3 O)] (3, M=Zr, x=0; 4, M=Hf, x=1) and M[(2-OCH2 -C6 H4 O)2 (2-HOCH2 -C6 H4 OH)] (5, M=Zr; 6, M=Hf) by reacting M(OR)4 (M=Zr, R=n C3 H7 , 1; M=Hf, R=n C4 H9 , 2) with 2-furylmethanol or 2-hydroxybenzyl alcohol is discussed. Complexes 3-6 were homopolymerized under acidic conditions. Additionally, 5 and 6 were copolymerized with 2,2'-spirobi[4 H-1,3,2-benzodioxasiline] (SBS). Under acidic conditions SBS forms a phenolic resin/SiO2 nanostructured material. The resulting hybrid materials from the homopolymerization of 3-6 and the copolymerized materials from 5 and 6 were characterized by standard solid-state analytics. The inorganic lattice of the MO2 materials from the homopolymerized complexes 3-6 and SiO2 /MO2 from the copolymerization of 5 and 6 with SBS was obtained by air oxidation. The oxide materials were characterized by X-ray powder diffraction (XRPD) and energy-dispersive X-ray analysis, which proved their identity. The inner surface area was determined by N2 adsorption/desorption studies, which revealed surface areas of 100 m2 g-1 for MO2 . The mixed oxides SiO2 /MO2 were additionally investigated by differential scanning calorimetry and variable-temperature XRPD to study the thermal behavior. It was found that crystallization of tetragonal MO2 nanoparticles is characteristic within the SiO2 matrix, but higher sintering temperatures caused crystallization of the SiO2 lattice.

Copper(II) and triphenylphosphine copper(I) ethylene glycol carboxylates: synthesis, characterisation and copper nanoparticle generation.

Ethylene glycol-functionalised copper(II) carboxylates Cu[O2CCR2(OC2H4)nOCH3]2 (n = 0-3; R = H, Me) (2a-e) have been prepared by the reaction of [Cu2(OAc)4·2H2O] with CH3O(C2H4O)nCR2CO2H (1a-e). Upon reduction of 2a-e with triphenylphosphine, the corresponding tris(triphenylphosphine)copper(I) complexes 3a-e were obtained, which could be converted to the bis(triphenylphosphine)copper(I) complexes 4a-e by removal of one phosphine ligand. Based on IR spectroscopy and single crystal X-ray structure analysis the binding motif of the carboxylato group on the copper ion is discussed. DSC, TG and TG-MS experiments were performed to analyse the thermal decomposition mechanism of 2-4. Complex 4c was used as a precursor for the generation of copper nanoparticles by thermal decomposition in hexadecylamine without the need of any further reactants. Depending on the precursor concentration, spherical copper nanoparticles with a mean diameter ranging from 10 to 85 nm as well as nanorods with a length of up to 1.3 µm (aspect ratios ranging between 2 and 32) were obtained. Electron diffraction analysis of the rods suggested that they consist of five domains which are arranged around a fivefold rotational axis.