Bicapped Tetrahedron Research Articles

Microwave-assisted synthesis of mixed ligands organotin(IV) complexes of 1,10-phenanthroline and l-proline: Physicochemical characterization, DFT calculations, chemotherapeutic potential validation by in vitro DNA binding and nuclease activity

Diorganotin(IV) and triphenyltin(IV) derivatives of L-proline (HPro) having general formula R2Sn(Pro)2 (R=n-Bu (1), Ph (2)) and Ph3Sn(Pro) (3), respectively, and the mixed ligands di-/triorganotin(IV) derivatives of L-proline and 1,10-phenanthroline (phen) with general formula [R2Sn(Pro)(Phen)Cl] and [R3Sn(Pro)(Phen)] (where R=Me (4 and 7), n-Bu (5 and 8), Ph (6 and 9)), respectively, have been synthesized by microwave-assisted method and characterized by elemental analysis, IR, NMR (1H, 13C and 119Sn) and DART-mass spectral studies. The results suggest bicapped tetrahedron or a skew trapezoidal-bipyramid geometry for R2Sn(Pro)2, a distorted tetrahedral geometry for Ph3Sn(Pro) and a distorted octahedral geometry for [R2Sn(Pro)(Phen)Cl] and [Ph3Sn(Pro)(Phen)] around the Sn atom, and the same has been validated by density functional theory calculations (DFT). In vitro DNA binding studies of 1–9 have been investigated by UV–Vis, fluorescence and circular dichroism titrations, viscosity and DNA melting experiments. The observed hypochromic shift in UV–Vis and fluorescence studies evidenced a partial intercalative mode of binding of complexes to CT-DNA. The binding affinity and quenching ability have been quantified in terms of intrinsic binding constant (Kb) and Stern-Volmer quenching constant (Ksv). The determined values suggest that di- and triorganotin(IV) derivatives of L-proline possess lesser affinity to bind with CT-DNA in comparison to the mixed ligands di-/triorganotin(IV) derivatives of L-proline and 1,10-phenanthroline. The partial intercalative mode of binding of these complexes with CT DNA has also been supported by a change in the viscosity and melting point of DNA as well as a change in the intensity of positive and negative bands in circular dichroism spectra. The cleavage studies by agarose gel electrophoresis indicate effective cleavage of supercoiled plasmid DNA into its nicked form by all the complexes and even to its linear form in presence of 9.

Novel non-spherical deltahedra in trirhenaborane structures

Low-energy Cp3Re3Bn−3Hn−3 (7 ≤ n ≤ 12) structures are found to be Re3Bn−3 deltahedra with internally bonded Re3 triangles. The rhenium atoms are generally located at degree 6 to 8 vertices and the boron atoms at degree 3 to 5 vertices. Low-energy Cp3Re3B2H2 and Cp3Re3B3H3 structures are found to be trigonal bipyramids and bicapped tetrahedra, respectively.

Structural studies and bioactivity of diorganotin(IV) complexes of pyridin-2-thionato derivatives

A series of diorganotin(IV) derivatives containing the potentially chelating S,N-ligands, 3-trifluoromethyl-pyridine-2-thione (3-CF3-pySH) and 5-trifluoromethyl-pyridine-2-thione (5-CF3-pySH), were prepared by direct reaction between the ligand and the corresponding diorganotin(IV) dichloride R2SnCl2 (R = Me, nBu, Ph) in the presence of triethylamine. The compounds have been characterized by microanalysis, mass spectrometry, IR spectroscopy and by 1H, 13C and 119Sn NMR spectroscopies. The crystal structures of compounds [Ph2Sn(3-CF3-pyS)2] (1) and [nBu2Sn(5-CF3-pyS)2] (2) were analyzed by X-ray diffraction. In both cases, the metal is in a bicapped tetrahedron environment, bound to two carbon atoms of the alkyl or aryl substituents and to the sulfur atoms and the heterocyclic nitrogen atoms of two pyridine-2-thionato ligands, which act as κ2-N,S chelating ligands. The supramolecular structure of 1 consists of chains of complexes parallel to the crystallographic b axis, built up by F⋯F, π-stacking and C–H⋯π intermolecular interactions. In the case of compound 2, the supramolecular structure is mainly determined by CH⋯F(CF3) intermolecular interactions that propagate along the crystallographic b axis. The antimicrobial activities of all complexes against S. aureus (MSSA and MRSA), A. baumanni, Aspergillus fumigates, Bacillus subtilis, E coli and Pseudomonas aeruginosa were also evaluated and in general the complexes derived from 5-trifluoromethylpyridine-2-thionate were found to be more active than the complex derived from 3-trifluoromethylpyridine-2-thionate.

Dihalogen-templated synthesis of dodecanuclear silver dichalcogenophosphate clusters

Dodecanuclear silver clusters, Ag12(μ5-X)2[E2P(OEt)2]10 (X = Br, I; E = S, Se), were isolated from the reaction of [Ag(CH3CN)4](PF6), dichalcogenophosphate ammonium salts and halides in a common organic solvent. The Ag12 ring consists of two identical Ag6 units linked by intermolecular Ag–E bonds. The geometry of a Ag6 motif can be described as a bicapped tetrahedron, which is stabilized by a rare pentacoordinated bromine/iodine atom as well as five 1,1-dichalcogenophosphate ligands.

From Metallaborane to Borylene Complexes: Syntheses and Structures of Triply Bridged Ruthenium and Tantalum Borylene Complexes

Reaction of [1,2-(Cp*RuH)(2)B(3)H(7)] (1; Cp*=η(5)-C(5)Me(5)) with [Mo(CO)(3)(CH(3)CN)(3)] yielded arachno-[(Cp*RuCO)(2)B(2)H(6)] (2), which exhibits a butterfly structure, reminiscent of 7 sep B(4)H(10). Compound 2 was found to be a very good precursor for the generation of bridged borylene species. Mild pyrolysis of 2 with [Fe(2)(CO)(9)] yielded a triply bridged heterotrinuclear borylene complex [(μ(3)-BH)(Cp*RuCO)(2)(μ-CO){Fe(CO)(3)}] (3) and bis-borylene complexes [{(μ(3)-BH)(Cp*Ru)(μ-CO)}(2)Fe(2)(CO)(5)] (4) and [{(μ(3)-BH)(Cp*Ru)Fe(CO)(3)}(2)(μ-CO)] (5). In a similar fashion, pyrolysis of 2 with [Mn(2)(CO)(10)] permits the isolation of μ(3)-borylene complex [(μ(3)-BH)(Cp*RuCO)(2)(μ-H)(μ-CO){Mn(CO)(3)}] (6). Both compounds 3 and 6 have a trigonal-pyramidal geometry with the μ(3)-BH ligand occupying the apical vertex, whereas 4 and 5 can be viewed as bicapped tetrahedra, with two μ(3)-borylene ligands occupying the capping position. The synthesis of tantalum borylene complex [(μ(3)-BH)(Cp*TaCO)(2)(μ-CO){Fe(CO)(3)}] (7) was achieved by the reaction of [(Cp*Ta)(2)B(4)H(9)(μ-BH(4))] [corrected] at ambient temperature with [Fe(2)(CO)(9)]. Compounds 2-7 have been isolated in modest yield as yellow to red crystalline solids. All the new compounds have been characterized in solution by mass spectrometry; IR spectroscopy; and (1)H, (11)B, and (13)C NMR spectroscopy and the structural types were unequivocally established by crystallographic analysis of 2-6.

Chemistry of Vanadaboranes: Synthesis, Structures, and Characterization of Organovanadium Sulfide Clusters with Disulfido Linkage

Vanadaborane, [(CpV)(2)(B(2)H(6))(2)] (Cp = eta(5)-C(5)H(5)), 1 reacts with elemental sulfur to afford the hexasulfide cluster [(CpV)(2)S(4)(mu-eta(1)-S(2))], 2 in high yield. Compound 2 is a notable example of an organovanadium sulfide cluster in which the [V(2)S(4)] atoms define a bicapped tetrahedron framework, with one mu-eta(1)-S(2) ligand bridged the two (CpV) moieties. The sulfur atom in [V(2)S(4)] core in 2 is a four-skeletal-electron donor isoelectronic with the BH(3) unit; therefore, the replacement of boron hydride in 1 by four sulfur atoms necessitates the formation of a bicapped tetrahedron [V(2)S(4)] framework. Furthermore, this is the only reported example of a bimetallic hexasulfide cluster containing vanadium. Pyrolysis of 1 with bis-chalcogenide ligands such as Ph(2)S(2) and Bz(2)Se(2) (Bz = PhCH(2)), results in the formation of substituted vanadahexaboranes [(CpV)(2)B(4)H(12-x)L(x)], 3-5 (3: L = SPh: x = 3; 4: L = SPh, x = 2; 5: L = SeBz: x = 1) in modest yield. All these new compounds have been characterized by mass, (1)H, (11)B, (13)C NMR spectroscopy, and elemental analysis, and the structural types were unequivocally established by crystallographic analysis of compounds 2-5.

High Oxidation State Rhodium and Iridium Bis(silyl)dihydride Complexes Supported by a Chelating Pyridyl-Pyrrolide Ligand

New rhodium and iridium complexes containing the bidentate ligand 3,5-diphenyl-2-(2-pyridyl)pyrrolide (PyPyr) were prepared. The bis(ethylene) complex (PyPyr)Rh(C(2)H(4))(2) (3) reacted with HSiEt(3), HSiPh(3), and HSi(t)BuPh(2) to produce the 16-electron Rh(V) bis(silyl)dihydrides (PyPyr)Rh(H)(2)(SiEt(3))(2) (8), (PyPyr)Rh(H)(2)(SiPh(3))(2) (9), and (PyPyr)Rh(H)(2)(Si(t)BuPh(2))(2) (10), respectively. The analogous Ir(V) bis(silyl)dihyride (PyPyr)Ir(H)(2)(SiPh(3))(2) (11) has also been synthesized. X-ray crystallography reveals that 9-11 adopt a coordination geometry best described as a bicapped tetrahedron. Silane elimination from 9 and 10 occurred in the presence of either HSiEt(3) or PPh(3). Mechanistic studies of the silane exchange process involving 10 and free HSiEt(3) (to give 8) indicate that this process occurs by rate-limiting reductive elimination of HSi(t)BuPh(2) from 10 to generate a 14-electron Rh(III) intermediate of the type (PyPyr)Rh(H)(Si(t)BuPh(2)).

Hexacoordinated spirocyclic germanium(IV) complex: Synthesis and structural characterization

AbstractThe spiro‐dibenzogermocine [O(o‐C6H4S)2]2Ge (1) was prepared in a reaction between O(o‐C6H4SH)2 and Ge(OiPr)4, and its molecular structure was determined by X‐ray diffraction studies. In the solid state, 1 shows the existence of two weak O → Ge transannular interactions, resulting in a hexacoordinated germanium atom that displays the geometry of a distorted bicapped tetrahedron. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:45–49, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20510

Hypercoordinate Silicon Complexes Based on Hydrazide Ligands. A Remarkably Flexible Molecular System

Though only one row apart on the periodic table, silicon greatly differs from carbon in its ability to readily form five- and six-coordinate complexes, termed "hypercoordinate silicon compounds". The assorted chemistry of these compounds is varied in both structures and reactivity and has generated a flurry of innovative research endeavors in recent years. This Account summarizes the latest work done on a specific class of hypercoordinate silicon compounds, specifically those with two hydrazide-derived chelate rings. This family is especially interesting due to the ability to form multiple penta- and hexacoordinate complexes, the chemical reactivity of pentacoordinate complexes, and the observation of intermolecular ligand crossovers in hexacoordinate complexes. Pentacoordinate complexes in this family exhibit marked structural flexibility, as demonstrated by the construction of a complete hypothetical Berry-pseudorotation reaction coordinate generated from individual crystallographic molecular structures. Although hexacoordinate complexes generally crystallize as octahedra, with a decrease in the ligand donor strength the complexes can crystallize as bicapped tetrahedra. Hexacoordinate complexes bearing a halogen ligand undergo a solvent-driven equilibrium ionic dissociation, which is controlled by solvent, temperature, counterion, and chelate structure and has been directly demonstrated by conductivity measurements and temperature-dependent (29)Si NMR. Hexacoordinate silicon complexes can also undergo reversible neutral nonionic dissociation of the N-Si dative bond. Ionic pentacoordinate siliconium salts react readily via methyl halide elimination, initiated by their own counterion acting as a base. Pentacoordinate complexes can also undergo intramolecular aldol condensations of imines, which may find potential as a template for organic synthesis. In addition, these complexes are capable of performing an uncatalyzed intramolecular hydrosilylation of imine double bonds. Perhaps the most striking manifestations of flexibility are the facile and complete intermolecular ligand crossovers. Crossovers have been observed between different hexacoordinate complexes, and between complex molecules and their differently substituted precursors, and take place within minutes. Although the precise mechanisms of these transformations remain elusive, NMR and single-crystal X-ray diffraction measurements have shed light on these interesting phenomena. A profusion of crystallographic data and careful NMR experimentation has led to an improved understanding of penta- and hexacoordinate hydrazide-based silicon dichelates. The diverse chemical reactivity of these complexes demonstrates both the scope and complexity of silicon chemistry. Future exploration into the structures and chemistry of hypercoordinate silicon will continue to enhance our understanding and appreciation of this unique element.

Metallaboranes of the Early Transition Metals: Direct Synthesis and Characterization of [{(η5‐C5Me5)Ta}2BnHm] (n=4, m=10; n=5, m=11), [{(η5‐C5Me5)Ta}2B5H10(C6H4CH3)], and [{(η5‐C5Me5)TaCl}2B5H11

Reaction of [Cp*TaCl4] (Cp*=eta5-C5Me5) with a sixfold excess of LiBH(4)thf followed by BH3thf in toluene at 100 degrees C led to the isolation of hydrogen-rich metallaboranes [(Cp*Ta)2B4H10] (1), [(Cp*Ta)2B5H11] (2), [(Cp*Ta)2B5H10(C6H4CH3)] (3), and [(Cp*TaCl)2B5H11] (4) in modest yield. Compounds 1-3 are air- and moisture-sensitive but 4 is reasonably stable in air. Their structures are predicted by the electron-counting rules to be a bicapped tetrahedron (1), bicapped trigonal bipyramids (2, 3), and a nido structure based on a closo dodecahedron 4. Yellow tantalaborane 1 has a nido geometry with C2v symmetry and is isostructural with [(Cp*M)2B4H8] (M=Cr and Re); whereas 2 and 3 are C3v-symmetric and isostructural with [(Cp*M)2B5H9] (M=Cr, Mo, W) and [(Cp*ReH)2B5Cl5]. The most remarkable feature of 4 is the presence of a hydride ligand bridging the ditantalum center to form a symmetrical tantalaborane cluster with a long Ta--Ta bond (3.22 A). Cluster 4 is a rare example of electronically unsaturated metallaborane containing four TaHB bonds. All these new metallaboranes have been characterized by mass spectrometry, 1H, 11B, and 13C NMR spectroscopy, and elemental analysis, and the structural types were unequivocally established by crystallographic analysis of 1-4.

The shapes of hypoelectronic six-vertex anionic bare boron clusters: Effects of the countercations

RHF/6-31G(d) calculations have been carried out on the hypoelectronic six-vertex boron cluster anions B6 z− (z = 6 and 4) as well as the corresponding alkali metal derivatives B6M z (z = 6 and 4; M = Na and Li) and the isoelectronic B6H6 and B6H6 2+. Using such computational methods, the introduction of alkali metal counterions was found to have relatively little effect on the general structural patterns of the lowest lying structures for these clusters. However, introduction of external hydrogen atoms (i.e., protonation of B6 6− to B6H6 and B6 4− to B6H6 2+) was found to lead to more open structures in the boron network relative to the corresponding alkali metal derivatives because of the need to divert boron valence orbitals from skeletal bonding to covalent bonds to the external hydrogens. The preferred structures of a bicapped tetrahedron for 12 skeletal electron systems derived from B6 6− and a planar network of four fused triangles for 10 skeletal electron systems derived from B6 4− can be rationali...

Diorganotin(IV) derivatives of substituted benzohydroxamic acids with high antitumor activity.

A series of diorganotin(IV) and dichlorotin(IV) derivatives of 4-X-benzohydroxamic acids, [HL(1) (X = Cl) or HL(2) (X = OCH(3))] formulated as [R(2)SnL(2)] (R = Me, Et, nBu, Ph or Cl; L = L(1) or L(2)), along with their corresponding mixed-ligand complexes [R(2)Sn(L(1))(L(2))] have been prepared and characterized by FT-IR, (1)H, (13)C, and (119)Sn NMR spectroscopy, mass spectrometry, elemental analysis, and melting points. In addition, single-crystal X-ray diffraction analyses were carried out for [Me(2)SnL(2)] (L = L(1) or L(2)), which show coordination structures intermediate between distorted octahedra and bicapped tetrahedra. The hydroxamate ligands are asymmetrically coordinated by the oxygen atoms, the carbonyl oxygen atom is further away from the metal center than the other oxygen atom. The complexes are stable monomeric species; most of them are soluble not only in chlorohydrocarbon solvents, but also in alcohols and hydroalcoholic solutions. In polar solvents, the mixed-ligand complexes gradually decompose into the corresponding single-ligand complex couples. The complexes exhibit in vitro antitumor activities (against a series of human tumor cell lines) which, in some cases, are identical to, or even higher than, that of cisplatin. For the dialkyltin complexes, the activity increases with the length of the carbon chain of the alkyl ligand and is higher in the case of the chloro-substituted benzohydroxamato ligand. The [nBu(2)Sn(L(1))(2)] complex displays a high in vivo activity against H22 liver and BGC-823 gastric tumors, and has a relatively low toxicity.

Disproportionation reactions of (methoxy/hydroxy)diorganotin(IV) methanesulfonates with carboxylic acids: Synthesis and structure of new diorganotin(IV) carboxylates

Disproportionation reactions between equimolar quantities of R 2Sn(X)OSO 2Me [X=OMe or OH] and ethylmalonic/maleic acid in acetonitrile under mild conditions afford new diorganotin dicarboxylates, R 2Sn(O 2CR′COOH) 2 [R′=CHEt, R= n-Pr ( 3a), n-Bu ( 3b); R′=CHCH, R= n-Pr ( 3c), n-Bu ( 3d)] along with R 2Sn(OSO 2Me) 2 [R= n-Pr ( 4a), n-Bu ( 4b)]. Similar reactions of the tin precursors with pyridine-2-carboxylic acid provide an access to novel trinuclear tin complexes, R 6Sn 3(O 2CC 5H 4N-2) 3(OSO 2Me) 3 [R= n-Pr ( 5a), n-Bu ( 5b)]. These have been characterized by IR and multinuclear ( 1H, 13C, 119Sn) NMR spectroscopies. The molecular structures of 3b, 4b and 5b have been determined by X-ray crystallography. Compound 3b is monomeric with bicapped tetrahedron geometry by virtue of anisobidentate coordination of one carboxylate group of each ligand, while the other carboxylic acid group remains free. The polymeric structure of 4b features centrosymmetric eight-membered rings comprising bridging methanesulfonate groups and nearly perfect octahedral geometry around each tin atom. Compound 5b crystallizes as 5b·2H 2O·Et 2O. Its molecular structure comprises of mixed ligand tin ester, n-Bu 2Sn(O 2CC 5H 4N-2)OSO 2Me and its disproportionated products, n-Bu 2Sn(O 2CC 5H 4N-2) 2 and n-Bu 2Sn(OSO 2Me) 2 which are coordinatively associated by varying bonding modes of pyridine-2-carboxylate groups. A possible rationalization of these results are discussed in terms of the intermediacy of mixed ligand tin complexes, R 2Sn(L)OSO 2Me (L=carboxylate) formed by the selective substitution of SnOMe group or by the dehydration of SnOH group in the tin precursors with the carboxylic acid.

SrZn(SeO(3))(2) containing novel ZnO(4+2) bicapped tetrahedra.

SrZn(SeO3)2, prepared by hydrothermal methods, contains novel ZnO4+2 bicapped tetrahedra and SeO3 pyramids. These units fuse together by sharing vertices and edges, resulting in a layered structure.

A New Type of Hexaosmium Boride Cluster, H3Os6(CO)16B, That Does Not Conform to Electron Counting Rules

A new type of hexaosmium boride cluster, H3Os6(CO)16B, was produced in the thermolysis of H3Os3(CO)9(BCO). This complex is an 86 valence electron cluster, but the Os6 framework does not possess one of the geometries previously observed for Os6 clusters that have 86 valence electrons. [HOs6(CO)18]- and [Os6(CO)18]2- have octahedral frameworks while that of H2Os6(CO)18 is a face-capped square pyramid. The Os6 framework of H3Os6(CO)16B can be viewed as being derived from a pentagonal bipyramid that is missing one equatorial vertex. It contains an interior boron atom. Alternatively, it can be viewed like the 84 valence cluster Os6(CO)18 as either a bicapped tetrahedron, with a boron atom residing on the edge of the tetrahedron that is common to the capped faces, or a face-capped trigonal bipyramid, with the boron atom on an equatorial edge of the bipyramid that is also an edge of the capped face. H3Os6(CO)16B was characterized by 1H, and 11B, 13C NMR, IR, and mass spectroscopies and single-crystal X-ray diffraction analysis. The molecular structure was determined from two separate crystals. The analysis of each crystal yielded virtually identical structures, but their volumes differed by 36 A3 due to differences in packing in the unit cell. Data for crystal I of H3Os6(CO)16B: monoclinic P2(1/n), a = 9.954(2) A, b = 15.780(4) A, c = 16.448(3) A, beta = 91.07(1) degrees, Z = 4. Data for crystal II of H3Os6(CO)16B: monoclinic P2(1/n), a = 9.927(2) A, beta = 16.623(2) A, b = 16.0233(10) A, beta = 97.78(1) degrees, Z = 4.

Cluster Build-up Reactions using Di-gold Cationic Fragments: Synthesis and Structural Characterization of [Os7(CO)19(Au2dppm)

The reaction of the di-gold cation [Au2(dppx)]2+ with the heptanuclear cluster dianion [Os7(CO)20]2− affords the mixed metal cluster [Os7(CO)20{Au2(dppx)}] (x=m (1), e (2), b (3)). On standing, in solution, this complex undergoes decarbonylation to give the cluster [Os7(CO)19{Au2(dppx)}] (x=m (4), e (5), b (6)). The complexes have been characterised spectroscopically, and an X-ray structure determination of the dppm derivative shows that it contains a metal core based on an Os7 edge-bridged bicapped tetrahedron with the two μ3-Au atoms capping adjacent triangular Os3 faces of the central tetrahedron. In an analogous reaction, the carbido anion [Os7(H)C(CO)19]− affords the neutral cluster [Os7C(CO)19{Au2(dppm)}] (7) when treated with [Au2(dppm)]2+ in the presence of base.

Cluster build-up reactions via the ionic coupling of tetraosmium anions and the [RhCp*(NCMe) 3] 2+ cation; the crystal and molecular structures of [Os 4Rh( μ-H) 3(MeCNH)(CO) 11( η5-Cp*)], [Os 4Rh( μ-H) 2(CO) 13( η5-Cp *)] and [Os 4Rh 2( μ-H) 2(CO) 11( η5-Cp*) 2] (Cp*C 5Me 5)

The reaction of [Os 4H 4(CO) 11] 2− 2, formed by the reduction of [Os 4H 4(CO) 12] 1 with K/Ph 2CO, with the cation [Rh( η 5-Cp*)(MeCN) 3] 2+ (Cp*C 5Me 5) 3, affords a number of penta- and hexanuclear mixed-metal clusters depending on the reaction conditions. If only sufficient K/Ph 2CO is added to dissolve all of 1, and the dication 3 added, a low yield of a blue cluster [Os 4Rh( μ-H) 3(MeCNH)(CO) 11( η 5-Cp*)] (Cp*C 5Me 5) 4 is obtained in addition to large quantities of 1. If an excess of K/Ph 2CO is added so that reduction of 1 is complete, and then the dication 3 added, two new products [Os 4Rh( μ-H) 2(CO) 13( η 5-Cp*)] 5 and [Os 4Rh 2( μ-H) 2(CO) 11( η 5-Cp*) 2] 6 are obtained in low yield. The three new complexes have been characterised spectroscopically and crystallographically. Cluster 4 contains the uncommon MeCNH group coordinated to an edge-bridged tetrahedral metal framework. The metal framework in 5 is also a Rh edge-bridged Os 4 tetrahedron while that of 6 is a bicapped tetrahedron, with two Rh atoms face capping two faces of an Os 4 tetrahedron.

Crystallographic evidence of hexacoordination at phosphorus via intramolecular coordination of donor groups on phosphane and phosphane sulphide

The X-ray structure analysis of bis(8-dimethylamino-l-naphthyl)phenylphosphane ( 3) and of the corresponding sulphide 4 has revealed hexacoordination at phosphorus in both cases, the N … P separations being less than the sum of the van der Waal radii. Furthermore, in both cases the overall geometry corresponds to a distorted bicapped tetrahedron. The optimum geometry calculated for 4 via the Hyperchem program developed by Autodesk (MM + method) suggests that the structure of the molecule is a function not only of steric requirements but also of electronic effects.

Crystal and molecular structures of spiro-bis(trithiastannocane), Sn(SCH 2CH 2SCH 2CH 2S) 2, and spiro-bis(oxadithiastannocane), Sn(SCH 2CH 2OCH 2CH 2S) 2. Distortion of the SnS 4 tetrahedral coordination produced by transannular Sn⋯X (X = S, O) interactions

The title compounds, prepared from X(CH 2CH 2SNa) 2 (X = S, O) and SnCl 4 were investigated by X-ray diffraction. In both compounds transannular secondary Sn⋯X interactions in the eight-membered rings produce a distortion of the SnS 4 tetrahedron. This consists of an enlargement of SSnS angle [to 126.1° when X = S and 118.9° (118.4°) when X = O] with simultaneous decrease of the opposite tetrahedral angle [to 93.2° when X = S and 94.4° (93.2°) when X = O]. The coordination geometry in both compounds can be described as based upon a bicapped tetrahedron.

Cluster build-up using the [Os(η6-C6H6)(MeCN)3]2+cation; synthesis and structural characterisation of some hexa- and hepta-nuclear arene-substituted clusters

Reactions of the cluster dianion [Os5(CO)15]2– with [Os(η6-C6H6)(MeCN)3]2+ and [Os(C6H5Me)(CF3SO3)2] provided [Os6(CO)15(η6-C6H6)]1 and [Os6(CO)15(η6-C6H5Me)]2, respectively, in good yield (≈45%). Reduction of the hexaosmium cluster [Os6(CO)18] with K–Ph2CO gave the cluster dianion [Os6(CO)17]2–3 in quantitative yield. When this dianion was treated with [Os(η6-C6H6)(MeCN)3]2+ the heptanuclear cluster [Os7(CO)17(η6-C6H6)]4 was obtained in fair yield, while the corresponding reaction with [Os(η6-C6H5Me)(CF3SO3)2] gave [Os7(CO)17(η6-C6H5Me)]5 in similar yield (ca. 25%). The four arene clusters have been characterised by spectroscopic techniques, and the molecular geometries of 1, 2 and 4 established by single-crystal X-ray diffraction techniques. In both 1 and 2 the metal framework geometry is best described as a bicapped tetrahedron. In 1 the η6-C6H6 ligand occupies a site on the central Os4 tetrahedron while in 2 in the η6-arene is co-ordinated to one of the capping Os atoms. The metal framework in 4 may be viewed as derived from a bicapped tetrahedron with the seventh metal capping one of the caps to give a chain of four fused tetrahedra. The η6-C6H6 ligand in 4 occupies a similar site to that found in 1.