Volume 54, Issue 2

Three diorganotin(IV) chelates with a tetradentate Schiff base, H 2 Vanophen, [H 2 Vanophen = N,N′-1,2-phenylen-bis(3-methoxysalicylideneimine)] of the type R 2 Sn(Vanophen) (R = Ph: 1; R = n-Bu: 2; R = Me: 3) have been synthesized by the reaction of R 2 SnCl 2 (R = Ph, n-Bu, Me) and H 2 Vanophen in the presence of triethylamine in benzene. The complexes have been characterised by IR and NMR spectroscopy and by elemental analysis. The δ( 119 Sn) values for the complexes 1 - 3 are -543.0, -414.2 and -398.2 ppm respectively, indicating hexacoordinated Sn centers. These have been ascertained by X-ray crystal structure determinations of 1 and 3. The distances between tin and the two axial carbon atoms in each complex differ not significantly [2.17(1) Å in 1, and 2.100(3) and 2.115(3) Å in 3). The C-Sn-C angles for 1 and 3 are 165.9(4)° and 159.96(9)°, respectively. The solution NMR spectra ( 1 H , 13 C, 119 Sn) show clearly that the solid state structures are retained in solution.

The hydrolysis of functional trialkoxysilanes was studied under various conditions by 1 H NMR spectroscopy. The silane concentration was 1 - 2% by weight in a water/acetonesystem. Under these conditions, the reaction was found to be first order. In detail, influence of pH, grade of stirring, and size and structure of functional groups of the alkyltrialkoxysilanes were investigated in order to compare the relative reaction rates of the different compounds.

The molecular structure and EPR studies of bis(tetraphenylphosphonium)bis( 1,2- dithiosquarato)oxovanadate(IV) are reported. (Ph 4 P) 2 [VO(dtsq) 2 ] crystallizes in the monoclinic space group P2 1 /n with the unit cell parameters a = 10,9820(2), b = 15,4620(3), c = 14,5050(3) Å, β = 95,700(8)°, Z = 2. The g and hyperfine coupling tensors A v obtained from the EPR spectra in liquid and frozen solution are used to characterize the properties of the molecular orbital containing the unpaired electron and are compared to those obtained from EHT-MO calculations.

Treatment of [Ml 2 (CO) 3 (NCMe) 2 ] (M = Mo, W) with two equivalents of EtC 2 Et in CH 2 CI 2 at 0°C yields the bis(3-hexyne) complexes [MI 2 (CO)(NCMe)(η 2 -EtC 2 Et) 2 ] (1 and 2). Complexes 1 and 2 react with two equivalents of PPh 3 in CH 2 CI 2 to give the complexes [Ml 2 (CO)(PPh 3 ) 2 (η 2 -EtC 2 Et)] (3 and 4). The molecular structure of 4 (M = W) has been crystallographically determined and has a pseudo-octahedral geometry with the two PPh3 ligands trans to each other with the two cis-iodo-ligands, which together with the carbonyl and 3-hexyne ligand are occupying the equatorial plane. Reaction of 1 and 2 with an equimolar amount of Ph 2 P(CH 2 ) n PPh 2 (for M = Mo, n =1; for M = W, n = 1 to 6 ) in CH 2 CI 2 affords the mono(3-hexyne) complexes [Ml 2 (CO){Ph 2 P(CH 2 ) n PPh 2 }(η2-EtC 2 Et)] (5 - 11). The tungsten complex [Wl 2 (CO){Ph 2 P(CH 2 ) 3 PPh 2 }(η 2 -EtC 2 Et)] (8 ) has also been crystallographically characterised and has cis-phosphorus atoms in the equatorial plane with the carbonyl and one of the iodo-ligands, with the other iodo-ligand and the 3-hexyne occupying the axial sites.

Reaction of dimethyl 1,3-acetonedicarboxylate 8 with oxalylchloride 2 and magnesium chloride as catalyst yielded 2,3-dioxo-2,3-dihydrofuran 9, which is in equilibrium with tautomer 10 (9:10 = 1:2). Addition of thionyl chloride to a mixture of 9/10 afforded 3-chloro-2(5H)-furanone 11. The structure of 11 was unequivocally established by X-ray diffraction, which indirectly proved the structure of 10 as well. Ring opening of 11 by nucleophilic attack with benzylamine 14 in C2-position and subsequent recyclization led to racemic 3-chloro-5-hydroxy-2-oxo-2,5-dihydropyrrole 15. According to a single crystal X-ray analysis, 15 aggregates via stereospecific self selection through hydrogen bonds to give chiroselectively the one-dimensional strands ∞ 1 [(S)-15] and ∞ 1 [( R)-15]

Among the large family of azaphospholes 1,2,4-diazaphospholes feature a particularly stable ring system. 3,5-Unsubstituted and 3,5-equally substituted 1,2,4-diazaphospholes and -diazaarsoles are best made from 1,3-bis(dimethylamino)-2-phospha/arsaallyl chlorides and hydrazines. This way four examples for single crystal X-ray structure investigations were prepared: The unsubstituted 1,2,4-diazaphosphole 2 and -diazaarsole 4, the N-substituted 1 -(2-pyridyl) 1.2.4-diazaphosphole 1, and the C-substituted 3,5-di-tert-butyl 1,2,4-diazaphosphole 3. They all possess planar rings with small angles at P (86°) and As (81°). The N-unsubstituted molecules are connected to each other by NH···N hydrogen bonds forming in case of the isotypic compounds 2 and 4 a helix along a crystallographic axis and in case of compound 3 for steric reasons a dimer. The structures of the aggregates found are compared to those of pyrazoles.

The structure parameters around the Cu(I) ion in pyridine (PY), 4-methylpyridine (4MPY), 2-methylpyridine (2MPY), 2,6-dimethylpyridine (26DMPY), and acetonitrile (AN) were determined by the extended X-ray absorption fine structure (EXAFS) method. The solvation structures of the Cu(I) ion in PY, 4MPY, and AN are 4-coordinate tetrahedral with Cu-N bond lengths of 205, 205, and 200 pm, respectively. In the case of 2MPY and 26DMPY, the Cu(I) ion has a 3-coordinate triangular structure with a Cu-N bond length of 201 pm. Such a decrease in the coordination number was interpreted in terms of the bulkiness of the solvent molecules. In order to clarify the most stable solvation structure of the Cu(I) ion, we carried out ab initio molecular orbital calculations for the solvation system of [Cu(NCH) n ] + (n = 1 - 6 ) where the steric effect is negligible. The Gibbs free energy of solvation was the smallest in the case of n = 4 and the 4-coordinate tetrahedral solvation of the Cu(I) ion was theoretically evaluated as most stable. The enthalpy of solvation monotonously decreases with increasing n, while the entropy of solvation proportionally increases. Although a larger gain of enthalpy is observed for the octahedral structure rather than the tetrahedral one, the entropic loss for the former overcomes the enthalpic gain.

The reactions of the dibromosilanes Et 2 SiBr 2 , Ph 2 SiBr 2 , EtHSiBr 2 , PhHSiBr 2 and MeHSiBr 2 with N-methylimidazole (NMI) led to white powders stable at room temperature (with Et 2 SiBr 2 an 1:2 adduct, with EtHSiBr 2 and Ph 2 SiBr 2 1:3 adducts, and with PhHSiBr 2 and MeHSiBr 2 1:4 adducts). The compounds crystallize from solutions in chloroforme and acetonitrile. The X-ray single crystal investigations show in all five cases dicationic complexes.

Cis-Dichloro-bis(2 ,6 -dimethyl-4 -phenyl-η 1 -phosphinine)platinum (3) has been prepared by ligand substitution from cis -dichloro(2,5-cyclooctadiene)platinum and characterized by spectroscopy ( 1 H , 13 C, 31 P NMR, IR, UV-Vis), CV and X-ray diffraction (space group P2 1 /c, a = 14.998, b = 16.540, c - 11.506 Å, α = γ = 90°, β = 92.46°, Z = 4). In line with findings for similar P hybridization states, the Pt-P bond length (221 pm) in 3 equals that in η 1 -phosphaalkene Pt complexes and falls short of the respective parameters in Pt phosphane species. The stretching frequencies ν PtCl and the bond length Pt-Cl indicate that phosphinines and phosphaalkenes, relative to phosphanes, adopt a lower position on the trans-influence scale. This gradation is also suggested by the coupling constants 1 J( 195 Pt, 31 P).

The mercury-edta dehydrogenation of the 4′-aminosubstituted-acetophenones 1, 8a and 9a produced the ring cleavaged derivatives 7 ,11a and 12a, while the piperidine and its derivatives 10a - 10e gave rise to tetracyclic compounds 16a - 16e and to methylenedi-enamines 19a - 19d, the additionally C-1-fragment in 19a - 19d probably coming from mercury edta. With addition of m-nitrobenzaldehyde to the mercury-edta dehydrogenation of substituted phenylpiperidines another route only generated the di-enamines 22.

N-(Nitrophenyl) substituted isoquinolinium salts reacted with nucleophiles of the hydroxylamine type to different products depending on the electron withdrawing strength of the substituent. Mononitro compound 8 produced only the cyclic hydroxylamine 9a, the trinitroderivative 5 solely the ring cleaved oximes. The dinitro substance 1 held an intermediate position and gave rise to a labile cyclic hydroxylamine and a more stable ring opened Z-enamine; hydroxylamine ethers generated cyclic products which showed in dimethylsulfoxide ring chain isomerism with the tautomers.

The phase diagram of the pseudobinary sytem Bi 2 Te 3 /BiCl 3 was investigated by DTA, total pressure measurements, and X-ray phase analysis. Only BiTeCl exists as a ternary phase in this system. The compound melts incongruently at 430 °C. The heat of formation and the standard entropy of BiTeCl were calculated from vapor pressure data: ΔH° B (BiTeCl, f, 298) = (-39,5 ± 1,6) kcal/mol; S° (BiTeCl, f, 298) = (34,4 ± 2,7) cal/K· mol. The heat of formation of BiCl 3 was determined on the basis of the heat of solution of BiCl 3 and Bi 2 O 3 , and the heat of formation of Bi 2 O 3 : ΔH° B (BiCl 3 , f, 298) = (-95,9 ± 0,9) kcal/mol.

We describe the existence of six thermodynamically stable phases on the binary line Bi 2 O 3 - SeO 2 at room temperature: Bi 12 SeO 20 , Bi 10 Se 2 O 19 , Bi 16 Se 5 O 34 , Bi 2 SeO 5 , Bi 2 Se 3 O 9 and Bi 2 Se 4 O 11 . At higher temperature we optained evidence for Bi 20 Se 3 O 36 and Bi 4 SeO 8 . The decomposition pressures were measured for all phases in a membrane zero manometer and the enthalpy of formation and the standard entropy was determined. The phase barogram and phase diagram followed from total pressure measurements and differential thermoanalysis. The standard enthalpies of formation of all phases were also derived from solution calorimetry. The necessary data of transitions on molar enthalpies were obtained by DSC- and Cp-measurements.

The phase relations in the ternary system Bi/Te/O have been determined in previous studies by solid state reactions. Thermodynamical data have now been obtained for the pertinent equilibria. The heats of solution of Bi 2 O 3 , Bi 12 TeO 20 , Bi 10 Te 2 O 19 , Bi 16 Te 5 O 34 , Bi 2 TeO 5 , Bi 2 Te 2 O 7 , Bi 2 Te 4 O 11 and TeCl 4 were determined in 4N HCl. From these the enthalpies of formation of bismuth tellurites at 298 K have been derived: ⊿H°b (Bi 12 TeO 20 , f, 298) = -901,6 ± 8 kcal/mol, ⊿H°b (Bi 10 Te 2 O 19 , f, 298) = -856,1 ± 9 kcal/mol, ⊿H°b (Bi 16 Te 5 O 34 , f, 298) = -1519,5 ± 17 kcal/mol, ⊿H°b (Bi 2 TeO 5 , f, 298)= -222,8 ± 3 kcal/mol, ⊿H°b (Bi 2 Te 2 O 7 , f, 298)= -299,4 ± 4 kcal/mol, ⊿H°b (Bi 2 Te 4 O 11 , f, 298)= -448,2 ± 7 kcal/mol.

Only the ternary phase Bi 2 O 2 Se is shown to exists in the thermodynamical equilibrium in the investigated ternary system on the binary line Bi 2 O 3- Bi 2 Se 3 . Its thermal decomposition was measured in a quartz membrane zero manometer. The enthalpy of formation and the standard entropy were derived from the temperature function of the decomposition equilibrium: ⊿H° f (Bi 2 O 2 Se s,298 ) = -104,6 ±4,0 kcal/mol S°(Bi 2 O 2 Se s,298 ) = 43 ± 3 cal/K·mol. The coexistence ranges in the ternary region Bi 2 O 3 - SeO 2 - Bi 2 O 2 Se-Se were followed by X-ray diffraction, IR spectroscopy and total pressure measurements of binary and ternary compositions.

Organosilicon polymers containing (SiH 2 ) or (SiH 2 ) 2 units have been prepared via silyltriflate intermediates. Two methods of the formation of silicon-hydrogen bonds are described. Polysilaethylene [SiH 2 -CH 2 - ] n has been prepared by ring-opening polymerization of tetraphenyl-1,3-disilacyclobutane followed by a protodesilylation reaction with triflic acid and reduction with LiAlH 4 . The reaction of H 2 Si(OTf) 2 or (TfO )H 2 Si- SiH 2 (OTf) with organolithium or organomagnesium compounds gave poly(silyleneethyne)s [(SiH 2 ) n -C≡C] n and poly(silylenephenylene)s [(SiH 2)n -C 6 H 4 -] n . These polymers may serve as suitable precursors for ceramic materials. The TGA studies gave remarkably high ceramic yields. NMR measurements ( 29 Si, 13 C, 1 H) indicate an regular alternating arrangement of silicon atoms and organic groups in the polymer backbone.

Stannyloligosilanes 1 and 2 with terminal organotin groups are available by reacting alkali metal tri- or diorganostannides with α,ω-dichloro- or difluorosilanes, or by treatment of organochlorostannanes with α,ω-difluorosilanes in the presence of magnesium . Attempts to functionalize the triorganotin derivatives 2 by halogenation reagents did not result in the halogen compounds 5; instead cleavage of silicon-tin bonds is observed. In contrast, reactions of the hydridotin derivatives 1 with CHX 3 (X = Cl, Br) lead to the quantitative formation of the bis(chloro- or bromostannyl)oligosilanes 5. A ll compounds were characterized by NMR, IR, MS and elemental analysis. In addition, the triorganotin compound 2i and the hydridotin species 1b have been characterized by X-ray crystallography.

(PPh 4 ) 2 [As 2 Cl 8 ] · CH 3 CN was obtained from PPh 4 Cl and S 2 Cl 2 with As or As 4 S 4 or AsCl 3 in acetonitrile. PPh 4 Cl, S 2 Cl 2 and Sb 2 S 3 yielded (PPh 4 )[Sb 2 Cl 8 ] CH 3 CN. PPh 4 Br and AsBr 3 gave (PPh 4 ) 2 [Sb 2 Br 8 ]-CH 3 CN. AsCl 2 OPh (from AsCl 3 and NaOPh) reacted with Ph 4 Br in acetonitrile in the presence of Na 2 Se, selenium, and HCl, affording (PPh 4 ) 2 [As 2 Br 4,2 Cl 3,8 ] · CH 3 CN. According to their X-ray crystal structure determinations, all products are isotypic (space group C2/c, Z=4). The centrosymmetric anions consist of two ψ octahedra sharing an edge. In the [As 2 Br 4,2 Cl 3,8 ] 2- ion the bridging positions are taken solely by bromine atoms, whereas Br and Cl atoms occupy the other halogen positions randomly.