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Li2Si2O5, M r = 150.05, λ(Mo Kα) = 0.71073 Å, 293 K, orthorhombic, Ccc2, a = 5.807 (2), b = 14.582 (7), c = 4.773 (3) Å, V = 404.2 (3) Å3, μ(Mo Kα) = 0.78 mm−1, Z = 4, D x = 2.466 Mg m−3, R 1 = 0.045 for 249 reflections with I > 2.0σ(I), wR 2 = 0.1138 for all 261 reflections. K2Si2O5, M r = 214.36, λ(Mo Kα) = 0.71073 Å, 150 K, monoclinic, Cc, a = 16.322 (2), b = 11.243 (2), c = 9.919 (1) Å, β = 115.97 (1)°, V = 1636.4 (4) Å3, μ(Mo Kα) = 2.11 mm−1, Z = 12, D x = 2.610 Mg m−3, R 1 = 0.0385 for 2370 reflections with I > 2.0σ(I), wR 2 = 0.0785 for all 2711 reflections. The crystal structures of Li2Si2O5 and K2Si2O5 have been determined and refined. The lithium phyllosilicate sheet topology and structure based on three-dimensional data and refined in the orthorhombic space group Ccc2 confirm the previous determination by Liebau [Acta Cryst. (1961), 14, 389–395] from two-dimensional data, but described in the lower monoclinic Cc space-group symmetry. Potassium disilicate, on the other hand, is not a phyllosilicate but forms a three-dimensional defect cristobalite structure built from Q 3 silica units. In this structure, one Si—O—Si bridge, common to four six-membered T-rings, i.e. rings consisting of six silica tetrahedra in the chair conformation, is missing, resulting in 14-membered T-rings. Continuous sheets built up from these rings form a layer connected to layers above and below by six-membered T-rings in the chair conformation. 29Si MASNMR shows a good correlation between Si—O—Si angle and 29Si chemical shift for K2Si2O5, Li2Si2O5 and KLiSi2O5. The 29Si spin lattice relaxation times, T 1, are 335, 689 and 〈1256〉 s for Li2Si2O5, KLiSi2O5 and K2Si2O5, respectively. The pronounced non-linearity in hygroscopicity in glassy potassium–lithium disilicates is not observed in the osmolality of 0.8M potassium–lithium chloride aqueous solutions.

Thermolysis of bis(tetramethylcyclopentadienyl)-stabilized titanium(III) compounds (C(5)HMe(4))(2)TiR (R = Me (2), Ph (3)) yields, in marked contrast with the bis(pentamethylcyclopentadienyl) analog, the dimeric product [(C(5)HMe(4))(mu-eta(1):eta(5)-C(5)Me(4))Ti](2) (4), With a bridging metalated tetramethylcyclopentadienyl ligand. The hydride (C(5)HMe(4))(2)TiH (5), synthesized by hydrogenolysis of 2 or 3, reacts with N-2 to form the dinuclear Ti(II) dinitrogen compound [(C(5)HMe(4))(2)Ti]N-2(2) (8) Under a dynamic vacuum, the dinitrogen complex 8 loses the N-2 ligand to give the titanocene (C(5)HMe(4))(2)Ti (10). The molecular structures of both 4 and 8 were determined by X-ray diffraction methods.

KLiSi2O5, Mr = 182.21, λ(Mo Kα) = 0.71073 Å, 150 K, monoclinic, P21, a = 5.9803 (6), b = 4.7996 (6), c = 8.1599 (11) Å, β = 93.477 (10)°, V = 233.78 (5) Å3, μ(MoKα) = 15.7 cm−1, Z = 2, F(000) = 180, Dx = 2.5885 (6) Mg m−3, R 1 = 0.0331 for 1023 reflections with I > 2.0σ(I), wR 2 = 0.0864 for all 1064 reflections. The crystal structure of potassium lithium phyllosilicate has been determined and the hygroscopicity of glassy single and mixed alkali disilicates has been measured. The potassium lithium phyllosilicate sheet topology is the same as that of lithium phyllosilicate, consisting of six-membered silica rings in a chair configuration. Li is fourfold oxygen coordinated by three non-bridging O and one bridging O, while K is sixfold oxygen coordinated by five non-bridging O and one bridging O. The K atoms are sandwiched between the LiSi2O5 layer. Crystalline and glassy lithium disilicate are not hygroscopic. Crystalline and glassy potassium disilicate are the most hygroscopic alkali disilicates known to date, whereas the mixed system, crystalline and glassy lithium potassium disilicate, is again not hygroscopic. Calculated valences for lithium potassium phyllosilicate do not provide a rationale for these observations.

The substitution behavior of the organometallic complex cation [Pt{C6H3(CH2NMe2)2-2,6}(OH2)]+ (1) has been studied with a series of nucleophiles (Cl-, Br-, I-, N3-, NCS-, thiourea, N,N‘-dimethylthiourea, N,N,N‘N‘-tetramethylthiourea) as a function of nucleophile concentration ([Nu]), pH, temperature, and pressure. Complex 1 affords pseudo-first-order rate constants, kobs, for the complex-formation reaction given by kobs = k1[Nu] + k-1; the k-1 term is due to the reverse aquation reaction and is insignificant for the stronger, S-donor nucleophiles. The mechanism for the substitution of the coordinated water molecule is associative, as demonstrated by the large negative values of ΔS⧧ and ΔV⧧. The results are compared to those obtained earlier for the geometrically related neutral zwitterionic complex [Pt{C6H4(CH2NMe2)-2}(NC5H4SO3-3)(OH2)] (2). Both cyclometalated complexes 1 and 2 have very high substitution reactivities that can be ascribed to labilization which arises from the σ-bonded carbon atom of the ...

The synthesis of novel magnesium, copper, and metal-free porphyrazines, peripherally substituted with dithia-7-crown-2 (MPz(7)), dithia-15-crown-5 (MPz(15)), and dithia-18-crown-6 (MPz(18)) macrocycles is reported. These compounds are prepared starting from dicyanoethylene containing crown ethers 3, 2(1), and 2(2), respectively, which contain sulfur as well as oxygen heteroatoms. The "crowned" porphyrazines bind silver(I) and mercury(II) perchlorates. UV/vis spectroscopy and electron paramagnetic resonance measurements reveal that addition of the transition-metal ions leads to dimerization of the porphyrazine complexes. In the case of the dithia-18-crown-6-substituted porphyrazines, the dimers break up to form monomeric 6:1 guest-host complexes when more than 2 equiv of the metal ion is added. The single-crystal structures of the crown ether 2(2) and the porphyrazine MgPz(18) are presented. Compound C(14)H(20)N(2)O(4)S(2) (2(2)) crystallizes in the monoclinic space group P2(1)/c with a = 10.9310(13) Å, b = 19.383(3) Å, c = 8.6976(14) Å, beta = 108.898(11) degrees, V = 1743.5(5) Å(3), and Z = 4. The structure refinement converged to R = 0.0366 and R(w) = 0.0504. Compound C(56)H(82)MgN(8)O(17)S(8) (MgPz(18)) crystallizes in the triclinic space group Ponemacr; with a = 9.584(3) Å, b = 17.672(2) Å, c = 19.620(4) Å, alpha = 84.904(14) degrees, beta = 85.21(2) degrees, gamma = 89.29(2) degrees, V = 3298.4(13) Å(3), and Z = 2. The structure refinement converged to R1 = 0.0839 and wR2 = 0.2196. The electrical properties of H(2)Pz(18) have been studied by complex impedance spectroscopy. The bulk electrical conductivity of this compound is approximately 1 order of magnitude higher than that of the corresponding 18-crown-6 phthalocyanine.

Enantioselective Michael additions of α-nitroesters 2a-d with α,β-unsaturated ketones were carried out in the presence of a catalytic amount of chiral Al-Li-(R,R′)-2,2′-dihydroxy-1,1′-binaphthyl (‘AlLiBINOL’) complex prepared in situ from LiAlH 4 and 2.45 equiv. of (R,R′)-BINOL. The enantioselectivity of the Michael addition proved to be extremely temperature dependent: Michael adduct 4a showed 7% e.e when the reaction was performed at RT, whereas 72% e.e. of the opposite enantiomer of 4a was found when the 1,4-addition was performed at −23°C. Solvent variation showed that tetrahydrofuran gave the highest selectivity (up to 80% e.e.), whereas the highest enantioselectivity for the opposite enantiomer was found in methylene chloride (up to 25%). X-Ray structure analysis of the AlLi 3 BINOL 3 complex 6 in combination with 27 Al NMR studies showed that ‘AlLiBINOL’ is a mixture of aluminium complexes in solution.

Thermal decomposition of the carbyl compounds {C5H4(CH2)(2)NR}TiR'(2) proceeds through alpha- and beta-H elimination to give stable aryne, alkylidene, and olefin. complexes in the presence of PMe3. Reaction of the dibenzyl compound {C5H4(CH2)(2)N-t-Bu}Ti(CH2Ph)(2) with B(C6F5)(3) gives the cationic [{C5H4(CH2)(2)N-t-Bu}TiCH2Ph](+), which is an active catalyst for the polymerization of ethene and propene.

A new dinucleating ligand, 1,3-bis[(2-(diphenylphosphino)benzylidene)amino]-propan-2-ol (L1H), has been synthesized from 2-(diphenylphosphino)benzaldehyde and 1,3-diaminopropanol in 85% yield. Complexation with palladium, nickel, and rhodium salts gave the following dinuclear complexes: [M2(L1)(OAc)2](BF4) (6, M = Pd; 7, M = Ni), [Pd2(L1)Me2](BF4) (10), and [Rh2(L1)(CO)2](BF4) (11). In these complexes the two metals are bridged by the secondary alkoxy group of the ligand which keeps them at a fixed distance from each other. X-ray structure determinations of [Pd2(L1)(OAc)2](BF4) (6), [Pd2(L1)Me2](BF4) (10) and [Rh2(L1)(CO)2](BF4) (11) showed that both metals are in a square-planar environment and that the metal−metal distance varies from 3.5 to 3.7 A. The related complex Pd2(L1H)Me2Cl2 (9) has also been characterized crystallographically. In palladium complex 9, the alkoxy group does not bridge the two metal centers and a much longer metal−metal distance of 7.5 A is found. Furthermore, the ligand L1H is c...

We investigated the structural requirements for high 5-HT1A affinity of the agonist flesinoxan and its selectivity versus D2 receptors. For this purpose a series of arylpiperazine congeners of flesinoxan were synthesized and evaluated for their ability to displace [3H]-8-OH-DPAT and [3H]spiperone from their specific binding sites in rat frontal cortex homogenates and rat striatum, respectively. Variations were made in the N4-substituent and the arylpiperazine region. Effects of N4-substitution in the investigated compounds appeared to be quite similar for 5-HT1A- and D2-receptor affinity. Lipophilicity at a distance of four carbon atoms from the piperazine N4 atom seems to be the main contributing factor to affinity for both receptors. Our data show that the amide group in the flesinoxan N4-substituent is unlikely to interact with the 5-HT1A receptor but, instead, acts as a spacer. In contrast to the structure-affinity relationships (SARs) of the N4-substituents, selectivity for 5-HT1A versus D2 receptors was gained by the arylpiperazine substitution pattern of flesinoxan. Restriction of flexibility of the N4-(benzoylamino)ethyl substituent and its effect on 5-HT1A-receptor affinity and activity were also studied. Our data show that in the bioactive conformation, the N4-[(p-fluorobenzoyl)amino]ethyl substituent is probably directed anti-periplanar relative to the HN4 atom. These results were used to dock flesinoxan (1) and two of its congeners (27 and 33) into a model of the 5-HT1A receptor that we previously reported. Amino acid residues surrounding the N4-[(p-fluorobenzoyl)amino]ethyl substituent of flesinoxan and its congeners are also present in D2 receptors. In contrast, several residues that contact the benzodioxane moiety differ from those in D2 receptors. These observations from the 3D model agree with the 5-HT1A SAR data and probably account for the selectivity of flesinoxan versus D2 receptors.

Enantioselective Michael additions of α-nitroesters 2a-d with α,β-unsaturated ketones were carried out in the presence of a catalytic amount of chiral Al-Li-(R,R′)-2,2′-dihydroxy-1,1′-binaphthyl (‘AlLiBINOL’) complex prepared in situ from LiAlH 4 and 2.45 equiv. of (R,R′)-BINOL. The enantioselectivity of the Michael addition proved to be extremely temperature dependent: Michael adduct 4a showed 7% e.e when the reaction was performed at RT, whereas 72% e.e. of the opposite enantiomer of 4a was found when the 1,4-addition was performed at −23°C. Solvent variation showed that tetrahydrofuran gave the highest selectivity (up to 80% e.e.), whereas the highest enantioselectivity for the opposite enantiomer was found in methylene chloride (up to 25%). X-Ray structure analysis of the AlLi 3 BINOL 3 complex 6 in combination with 27 Al NMR studies showed that ‘AlLiBINOL’ is a mixture of aluminium complexes in solution.