Cryoscopic Molecular Weight Research Articles

Molecular precursors for the preparation of homogenous zirconia–silica materials by hydrolytic sol–gel process in organic media. Crystal structures of [Zr{OSi(OtBu)3}4(H2O)2]·2H2O and [Ti(OtBu){OSi(OtBu)3}3

[Zr(OPr(i))(4)·Pr(i)OH] reacts with [HOSi(O(t)Bu)(3)] in anhydrous benzene in 1:1 and 1:2 molar ratios to afford alkoxy zirconosiloxane precursors of the types [Zr(OPr(i))(3){OSi(O(t)Bu)(3)}] (A) and [Zr(OPr(i))(2){OSi(O(t)Bu)(3)}(2)] (B), respectively. Further reactions of A or B with glycols in 1:1 molar ratio afforded six chemically modified precursors of the types [Zr(OPr(i))(OGO){OSi(O(t)Bu)(3)}] (1A-3A) and [Zr(OGO){OSi(O(t)Bu)(3)}(2)] (1B-3B), respectively [where G = (-CH(2)-)(2) (1A, 1B); (-CH(2)-)(3) (2A, 2B) and (-CH(2)CH(2)CH(CH(3)-)} (3A, 3B)]. The precursors A and B are viscous liquids, which solidify on ageing whereas the other products are all solids, soluble in common organic solvents. These were characterized by elemental analyses, molecular weight measurements, FAB mass, FTIR, (1)H, (13)C and (29)Si-NMR studies. Cryoscopic molecular weight measurements of all the products, as well as the FAB mass studies of 3A and 3B, indicate their monomeric nature. However, FAB mass spectrum of the solidified B suggests that it exists in dimeric form. Single crystal structure analysis of [Zr{OSi(O(t)Bu)(3)}(4)(H(2)O)(2)]·2H(2)O (3b) (R(fac) = 11.9%) as well as that of corresponding better quality crystals of [Ti(O(t)Bu){OSi(O(t)Bu)(3)}(3)] (4) (R(fac) = 5.97%) indicate the presence of a M-O-Si bond. TG analyses of 3A, B, and 3B indicate the formation of zirconia-silica materials of the type ZrO(2)·SiO(2) from 3A and ZrO(2)·2SiO(2) from B or 3B at low decomposition temperatures (≤200 °C). The desired homogenous nano-sized zirconia-silica materials [ZrO(2)·nSiO(2)] have been obtained easily from the precursors A and B as well as from the glycol modified precursors 3A and 3B by hydrolytic sol-gel process in organic media without using any acid or base catalyst, and these were characterized by powder XRD patterns, SEM images, EDX analyses and IR spectroscopy.

Glycol modified titanosiloxane as molecular precursor for homogenous titania–silica material: synthesis and characterization

Ti(OPri)4 reacts with HOSi(OtBu)3 in anhydrous benzene in 1:1 and 1:2 molar ratios to afford alkoxy titanosiloxane precursors, [Ti(OPri)3{OSi(OtBu)3}] (A) and [Ti(OPri)2{OSi(OtBu)3}2] (B), respectively. Further reactions of (A) or (B) with glycols in 1:1 molar ratio afforded six complexes of the types [Ti(OPri)(O–G–O){OSi(OtBu)3}] (1A–3A) and [Ti(O–G–O){OSi(OtBu)3}2] (1B–3B), respectively [where G = (CH2)2 (1A, 1B); (CH2)3 (2A, 2B) and {CH2CH2CH(CH3)} (3A, 3B)]. Both (A) and (B) are liquids while all the other products are viscous liquids which get solidified on ageing. Cryoscopic molecular weight measurements of the fresh products indicate their monomeric nature. FAB mass studies of (A) and (B) also indicate monomeric nature. However, FAB mass spectra of the two representative solids (1A) and (2B) suggest dimeric behavior of the glycolato derivatives. (A) distills at 85 °C/5 mm while other products get decomposed even under reduced pressure. TG analyses of (A), (B), (1A), and (1B) suggest formation of titania–silica materials at 200 °C for (A) and (B) and 350 °C for (1A) and (1B). The products have been characterized by elemental analyses, FTIR and 1H, 13C & 29Si-NMR techniques. All these products are soluble in common organic solvents indicating a homogenous distribution of the components on the molecular scale. The Si/Ti ratio of the oxide may be controlled easily by the composition of the starting precursors. Hydrolysis of the glycol modified derivative, (1A) by the Sol–Gel technique affords the desired homogenous titania–silica material, TiO2·SiO2 in nano-size while, the precursor (A) yields a non-stiochiometric silica doped titania material. However, pyrolysis of (A) yields nano-sized crystallites of TiO2·SiO2. All these materials were characterized by FTIR, powder XRD patterns, SEM images, and EDX analyses.

Diorganomorpholinometallane von Gallium und Indium - Monomer-Dimer-Gleichgewichte in Lösung

Diorganomorpholinometalates of Gallium and Indium – Monomer-Dimer-Equilibrium in Solution The reaction of Li[N(CH2CH2)2O] (LiMorpholinate; Li(Morph)) with Me2GaCl and Me2InCl gives by salt-elimination the diorganoamidometalates Me2M(Morph) ( M = Ga: 1; M = In: 2), respectively. 1 and 2 were characterized by NMR and vibrational spectroscopy as well as by X-ray structure determinations. According to this, centrosymmetrical dimers are present in the solid state while a monomer-dimer equilibrium was assumed for the THF-solution. Cryoscopic molecular weight determinations confirmed our assumptions.

Structure Investigations of Group 13 Derivatives of N-Phenylsalicylideneimine

The reaction of MMe3 with 1 molar equiv of N-phenylsalicylideneimine (HsaldPh) yields the O,N-chelate complexes Me2M(saldPh) (where M = Al (1), Ga (2), In (3)) in high yields. The reaction of 1 with γ-picoline results in a ligand redistribution reaction and the formation of the five-coordinate complex MeAl(saldPh)2 (4), while the gallium and indium compounds are stable in the presence of γ-picoline. The resulting compounds have been characterized in a solution by NMR and IR spectroscopy and cryoscopic molecular weight measurements, and their molecular and crystal structure have been determined by X-ray crystallography. Compounds 1 and 2 exist as monomeric tetrahedral complexes, while the indium analogue 3 is dimeric with the In2(μ-O)2 bridges and five-coordinate metal centers. The five-coordinate methylaluminum compound 4 exhibits trigonal-bipyramidal geometry of the metal center. The obtained results show that a Schiff base acts as a strongly coordinating chelate ligand and, in this regard, it resembles ...

Chemistry of Some Dihalogallium(III) β-Diketonate Derivatives. Crystal and Molecular Structures of GaCl2(acac), GaCl2(tmhd), and [trans-Ga(acac)2(THF)2+][GaCl4-

The dichlorogallium(III) β-diketonato derivatives GaCl2(bdk) [bdk = acac (2,4-pentanedionato) and tmhd (2,2,6,6-tetramethylheptanedionato)] have been prepared and characterized in hydrocarbon solutions by NMR spectral studies and cryoscopic molecular weight measurements and in the solid state by X-ray structural studies. These compounds, which have chelated β-diketonato ligands and four-coordinate gallium, react with THF to form species of composition GaCl2(bdk)·THF. A single-crystal X-ray diffraction study identified GaCl2(acac)·THF as the ion-pair [trans-Ga(acac)2(THF)2+][GaCl4-]. The gallium atom in the cation is six-coordinate, whereas in the anion it is four-coordinate. Variable-temperature 1H NMR spectral studies in CD2Cl2 solution suggest that multiple processes including (i) a stereochemical rearrangement, (ii) THF exchange, and (iii) equilibria between [Ga(bdk)2(THF)2+][GaCl4-], GaCl2(bdk), and at least one other species such as [Ga(bdk)2(THF)+][GaCl4-] are occurring in solution. In contrast, GaX...

Tert-butylaluminium complex of 2,2 ′-di(hydroxymethyl)biphenyl: intra-molecular hydrogen bonding

The reaction of 2,2 ′-di(hydroxymethyl)biphenyl with ( t-Bu) 3Al leads to the formation of the bimetallic compound [( t-Bu) 4Al 2(HOCH 2C 12H 8CH 2O) 2] ( 1) with two hydroxyl groups. The compound 1 has been characterized by 1H and 13C NMR spectroscopy, cryoscopic molecular weight measurements and elemental analysis and molecular structure has been confirmed by X-ray crystallography. The 18 membered cycle (Al 2O 4C 12) of 1 adopts a configuration with endocyclic oxygen atoms that allow for the intra-molecular hydrogen bonding formation.

Homoleptic and Heteroleptic Gallium(III) Compounds Containing Monosubstituted Cyclopentadienyl Ligands: Ga(C5H4Me)3, Ga(C5H4SiMe3)3, and R2Ga(C5H4Me) (R = Me, Et)

The new gallium(III) cyclopentadienyl derivatives Ga(C5H4Me)3 and Ga(C5H4SiMe3)3 have been synthesized by metathetical reactions. Subsequent stoichiometric ligand redistribution reactions with GaR3 (R = Me, Et) were used to prepare R2Ga(C5H4Me) as pure single compounds. However, when the syntheses of RGa(C5H4Me)2 (R = Me, Et) and MenGa(C5H4SiMe3)3-n (n =1, 2) by analogous stoichiometric ligand redistribution reactions were investigated, mixtures of compounds were the isolated products. The heteroleptic organogallium compound Me2Ga(C5H4Me) has also been prepared in high yields by using metathetical reactions between Me2GaCl and Li(C5H4Me) in pentane and between Cl2Ga(C5H4Me), formed in-situ from Ga(C5H4Me)3 and GaCl3 in diethyl ether, and LiMe. All pure compounds have been characterized by their physical properties, elemental analyses, NMR spectra, and cryoscopic molecular weight studies.

Synthesis and structural characterization of polymeric dimethylaluminum phenylthiolate

The reaction of trimethylaluminum with thiophenol forms the compound [Me 2Al(μ-SPh)] n in good yield. The compound has been characterized by 1H, 13C and variable-temperature NMR (VT-NMR) spectroscopy, mass spectroscopy, and by cryoscopic molecular-weight determination. The solid-state structure has been determined by single-crystal X-ray crystallography and was assigned to the monoclinic space group Pc (no. 7) with cell constants a=9.2499(12), b=7.1344(10), c=7.1947(11) Å, β=100.328(3)° and Z=2. The refinement converged with R 1=7.24% ( wR 2=15.4%) for 581 ( I≥2 σ( I)) observed reflections and was described in terms of an infinite chain polymer with phenyl thiol groups and dimethylaluminum groups alternating. The average Al–S distance is 2.36 Å. VT-NMR shows that the compound exhibits some fluxional behavior, which affects the ortho protons of the phenyl ring. Cryoscopic molecular-weight measurements show that the aggregation state is a function of concentration, and it has been proposed that two species, dimer and trimer, exist in solution.

High oxidation state imido metallasiloxanes: synthesis and structural characterisation of novel bis-imido chromium(VI) and molybdenum(VI) compounds †

For reactions between [M(NBut)2Cl2] (M = Cr or Mo) or [Mo(NAr)2Cl2]·dme, Ar = 2,6-Pri2C6H3, dme = 1,2-dimethoxyethane, and tetraphenyldisiloxanediol, [O(Ph2SiOH)2] (2∶1), in the presence of a nitrogen donor base, changing the nitrogen donor from pyridine, py, to triethylamine, NEt3, inhibited the protonation of imido groups and facilitated the formation of bis-imido compounds. Thus the compounds [Cr(NBut)2(O(Ph2SiO)2)]21, [Mo(NBut)2(O(Ph2SiO)2)2] 2 and [Mo(NAr)2(O(Ph2SiO)2)]23 were isolated when NEt3 was used as base. Compound 3 was also formed when the dilithium reagent [O(Ph2SiOLi)2] was used. The pyridine adduct [Mo(NAr)2Cl2]·2py 4 was isolated from the reaction between [Mo(NAr)2Cl2] and O(Ph2SiOH)2 and py (1∶1∶2 molar ratio). Compounds 2, 3·C6H6 and 4·0.5C6H5Me have been characterised by X-ray crystallography. The dimeric composition of 1 in the gas phase and in benzene was confirmed by mass spectroscopy and cryoscopic molecular weight determination respectively. All compounds were characterised by NMR spectroscopy.

Evidence for the trans-influence of axial substituents as a significant factor determining the structure and stability of five-coordinate complexes: molecular structure of the first simple five-coordinate dialkylaluminum O,O′-chelate complex

The addition of 4-methylpyridine to Me 2Al[OC(Me)C 6H 4-2-O] produced the relatively stable five-coordinate Lewis acid–base adduct Me 2Al[OC(Me)C 6H 4-2-O]·( γ-picoline). The resulting compound has been characterized by 1H and 27Al NMR spectroscopy and cryoscopic molecular weight measurements and the molecular structure has been confirmed by X-ray crystallography. X-ray structure analysis of this simple five-coordinate complex reveals that the trans-influence of axial substituents is a significant factor controlling the structure and stability of five-coordinate aluminum compounds.

Monomeric Organogallium−Nitrogen Compounds. Chemistry of Et2GaNH[C6H2(2,4,6-t-Bu)3] with Decomposition to the Metallacycle {EtGaNH[C6H2(4,6-t-Bu)2CMe2CH2-2]}2 and of EtGa{NH[C6H2(2,4,6-t-Bu)3]}2

Two monomeric gallium−nitrogen compounds, Et2GaNH[C6H2(2,4,6-t-Bu)3] and EtGa{NH[C6H2(2,4,6-t-Bu)3]}2, have been prepared by metathetical reactions between either Et2GaCl or EtGaCl2, as appropriate, and LiNH[C6H2(2,4,6-t-Bu)3] and have been characterized fully. Cryoscopic molecular weight studies demonstrated both compounds to be monomeric in benzene solution, whereas an X-ray structural study of the latter identified a monomer. The compound Et2GaNH[C6H2(2,4,6-t-Bu)3] decomposes at room temperature to form a new metallacyclic derivative GaEt3, and H2N[C6H2(2,4,6-t-Bu)3]. A 1H NMR spectral study and an X-ray structural study were used to elucidate its structure. The compound EtGa{NH[C6H2(2,4,6-t-Bu)3]}2 does not decompose to the metallacycle, but it reacts readily with GaEt3 to form Et2GaNH[C6H2(2,4,6-t-Bu)3].

Reactivity of triethylaluminum with a series of secondary amines.: Adduct and aminoalane dimer synthesis and characterization; the crystal structures of [Et 2AlN( c-C 6H 11) 2] 2 and [Et 2AlNC 4H 8NCH 3] 2

The reactions of triethylaluminum with a series of 13 secondary amines (RH=HNMe 2, HNEt 2, HNPr 2 n, HNPr 2 i, HNBu 2 n, HNBu 2 i, HNBu 2 s, HNC 4H 8, HNC 5H 10, HNC 6H 12, HN( c-C 6H 11) 2, HN(CH 2Ph) 2, and HNC 4H 8NMe) afford room-temperature stable, clear, colorless liquid complexes. These complexes were characterized by 1H and 13C NMR, IR and elemental analyses. Trends in the NMR chemical shift data are compared with data previously reported for the analogous trimethylaluminum, -gallium, and -indium compounds in terms of the steric properties of the amines. Subsequent thermolysis of these complexes yields dimeric aminoalanes via 1,2-elimination of ethane in all cases. The dimers were characterized by 1H and 13C NMR, IR, melting point, cryoscopic molecular weight determinations, and elemental analyses. The NMR chemical shift data are compared with known data for the [Me 2AlR] 2 and [Me 2GaR] 2 series. The molecular structures of [Et 2AlN( c-C 6H 11) 2] 2 and [Et 2AlNC 4H 8NCH 3] 2, obtained from X-ray crystal data, are presented and discussed in terms of the correlations between the structural parameters of the Al 2N 2 ring and the nature of the Al and N substituents.

Diorganogallium β-Diketonates and Their Lewis Acid−Base Adducts. Crystal and Molecular Structures of Mes2Ga(hfac) and Me2Ga(hfac)·NC5H5

Compounds of the type R2Ga(bdk) (R = Me, Et, Mes (mesityl); bdk = 2,4-pentanedionato (acac), 1,1,1-trifluoro-2,4-pentanedionato (tfac), 1,1,1,5,5,5-hexafluoro-2,4-penatedionato (hfac), 2,2,6,6-tetramethyl-3,5-heptanedionato (tmhd)) have been prepared by multiple routes, including hydrocarbon elimination, metathesis, and ligand redistribution reactions, and fully characterized by elemental analyses, cryoscopic molecular weight studies in benzene, and IR and multinuclear NMR spectroscopic studies. An X-ray structural study of Mes2Ga(hfac) demonstrated four-coordinate gallium with σ bonds to the two mesityl rings and to the two oxygen atoms of the β-diketonate ligand. The Lewis acidities of the diorganogallium β-diketonate derivatives toward NMe3 and/or pyridine were also investigated. Two adducts, Me2Ga(hfac)·NMe and Me2Ga(hfac)·py, were stable to dissociation at room temperature and thus were fully characterized by elemental analysis, cryoscopic molecular weight studies in benzene, vapor pressure−temperature studies, and IR and multinuclear NMR (including variable temperature) spectroscopic studies. The compound Me2Ga(hfac)·py was also characterized by an X-ray structural study. The structure involved five-coordinate gallium with one Ga−N, two (inequivalent) Ga−O, and two Ga−C bonds.

Simple synthesis of organogallium azides: structural characterization of [Mes2GaN3

Salt elimination reactions between R2GaCl [R = n-Bu, s-Bu, Mes (C6H2Me3-2,4,6)] and NaN3 leads to the bisorganogallium azides R2GaN3 (R = n-Bu 1, s-Bu 2, Mes 3) in good yields. The compounds have been characterized by NMR, IR spectroscopy and mass spectrometry, elemental analyses and cryoscopic molecular weight determinations. While 1 and 2 are liquids at room temperature, 3 is a solid. Its solid state structure was determined by single crystal X-ray analysis.

Synthesis and characterization of rings with the atom combination Ga/As and In/As

The organogallium arsenide [Pr i(Cl)GaAsBu 2 t] 2 ( 1) and the organoindium arsenide [(PhCH 2) 2 InAsBu 2 t] 2 ( 2) have been prepared by the reaction of the corresponding halides Pr iGaCl 2 and (PhCH 2) 2InCl with Bu 2 tAsLi in THF and Et 2O, respectively. 1 and 2 have been fully characterized by elemental analysis and IR, NMR, and MS techniques as well as by X-ray diffraction. According to cryoscopic molecular weight determinations in benzene, 1 and 2 are present as dimers in solution. The structures of 1 and 2 display rhombic distorted four-membered rings M 2As 2 (M = Ga, In).

Electronic Factors Determining the Rearrangement of Dialkylaluminum O,O‘-Chelate Compounds from Dimeric Five- to Monomeric Four-Coordinated Complexes on Dissolution. Structure Investigations of Dialkylaluminum Chelate Derivatives of α- and β-Hydroxy Carbonyl Compounds

The synthesis and the structure characterization of dialkylaluminum O,O‘-chelate complexes derived from α- and β-hydroxy carbonyl compounds: α-tropolone (tropH), ethyl rac-lactate (elacH), and 2-acetyl-4-chlorophenol (Cl-acphH), with saturated and conjugated unsaturated bond systems, are reported. The reaction of R3Al with an equimolar amount of the hydroxy carbonyl compound leads to the formation of [R2Al(O,O‘)]n chelate complexes [where O,O‘ = Cl-acph, R = Me (1a); trop, R = Et (2b); elac, R = Me (3)]. According to the X-ray study these compounds are dimeric in the solid state. The aluminum atoms adopt a distorted trigonal bipyramidal geometry with a long internal (in 1a and 2b) or external (in 3) Al−O axial bond. In addition, complex 3 posseses a C2 symmetry, which indicates that the five-coordinated [R2Al(O,O‘)]2-type adduct is formed in a highly stereoselective manner. In solution 1a and 2b adducts rearrange to the monomeric four-coordinated chelate complexes, while 3 remains a dimeric structure found in the solid state, as confirmed by cryoscopic molecular weight determination and 1H and 27Al NMR and IR spectroscopy. The influence of the nature of the O,O‘-bifunctional ligand on the structure of dialkylaluminum chelate complexes in the solid state and in solution and the geometry of the aluminum coordination sphere are discussed on the basis of the results reported and structural data of related compounds.

Lewis Acid−Base Studies of Triorganogallium Compounds with Organophosphines

The relative Lewis acidities of the series of triorganogallium compounds GaR3 (R = Me, Et, CH2CMe3, CH2SiMe3, CH2CMe2Ph, C6H2Me3) toward the common Lewis base HPPh2 and the relative Lewis basicities of a series of organophosphines which incorporate an acidic hydrogen HPRR‘ (PRR‘ = PPh2, P(C6H11)2, PEt2, P(H)(C6H11)) toward the common Lewis acid Ga(CH2CMe3)3 have been investigated and compared. Cryoscopic molecular weight data permitted an evaluation of the equilibrium constant for the dissociation of each of the adducts. The 31P NMR spectral data, which were consistent with the molecular weight data, were also used to study the relative rates of hydrocarbon elimination reactions to form (R2GaPRR‘)2.

Mesitylcopper: Tetrameric and Pentameric

New phases containing tetrameric and pentameric mesitylcopper have been isolated from ether solvents and characterized with single-crystal X-ray diffraction. Mesitylcopper crystallized from toluene, which is a widely used reagent, has been found to contain one lattice solvent molecule. On the basis of these findings and cryoscopic molecular weight determinations, an equilibrium between a tetramer and pentamer in both etheral and aromatic solutions is proposed.

Carbonylation of a Tetrameric Aryloxocopper(I) Cluster.

Carbonylation of 2,6-diphenylphenoxocopper(I), tetrameric [(CuOC(6)H(3)Ph(2))(4)] (1, Ph = C(6)H(5)), has been shown to result in a [{Cu(OC(6)H(3)Ph(2))(CO)}(2)] dimer (2). The parent aryl oxide, [(CuOC(6)H(3)Ph(2))(4)], which has been prepared from mesitylcopper(I) and 2,6-diphenylphenol, has an approximately planar Cu(4)O(4) core, in which copper(I) is two-coordinated and Cu-O bonds range from 1.834(7) to 1.865(7) Å. Its carbonylation product 2 is a &mgr;(2)-phenoxo-bridged dimer, containing three-coordinated copper(I), with longer Cu-O bonds, viz. 1.953(7)-1.995(7) Å. Cu-C bond lengths in [{Cu(OC(6)H(3)Ph(2))(CO)}(2)] are 1.78(1) and 1.79(1) Å, respectively, with both carbonyl C-O distances equal to 1.12(1) Å, and Cu-C-O angles of 174(1) and 179(1) degrees, respectively. Carbonyl stretching frequencies in the infrared are 2099, 2103, and 2112 cm(-)(1) for the solid and 2102 cm(-)(1) in toluene solution, and the (13)C NMR signal (toluene solution) is at 168 ppm. From comparison with other carbonyl complexes of copper(I), the Cu-C bond is judged to be predominantly of sigma character, with minimal metal --> ligand pi contribution. Both [(CuOC(6)H(3)Ph(2))(4)] and [{Cu(OC(6)H(3)Ph(2))(CO)}(2)] retain their aggregation states on dissolution in nonpolar solvents, as ascertained by cryoscopic molecular weight determinations of the compounds in benzene. Crystal data: 1, triclinic, space group P&onemacr; (No. 2), a = 12.738(9), b = 22.426(5), and c = 9.984(3) Å, alpha = 101.62(2), beta = 91.02(4), and gamma = 85.93(3) degrees, Z = 2, R = 0.052 (R(w) = 0.058) for 721 parameters and 3843 reflections; 2, triclinic, space group P&onemacr; (No. 2), a = 10.67(3), b = 15.72(1), and c = 10.05(1) Å, alpha = 96.99(8), beta = 104.66(16), and gamma = 101.46(12) degrees, Z = 2, R = 0.049 (R(w) = 0.054) for 397 parameters and 2152 reflections.

SUBSTITUTIONS OF COPPER(II) CARBOXYLATES WITH SCHIFF BASES

Substitutions of anhydrous copper(II) acetate with higher carboxylic acids in an equimolar ratio in refluxing toluene yield monosubstituted soluble derivatives, which undergo substitutions with Schiff bases (derived from salicylaldehyde and aniline or p-chloroaniline) to give mixed complexes of the general formula [Cu(OOCR)- (SB)] (HSB = Schiff base and R = C13H27, C15H31, C17H35 and C21H43). The products have been characterized by elemental analyses, electrical conductance, magnetic moment and spectral (i.r. and electronic) data. Cryoscopic molecular weight determinations indicate that the derivatives are dimers. The complexes are e.p.r. silent.