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The addition compound Cl(3)SiSiCl(3)·TMEDA was formed quantitatively by treatment of Cl(3)SiSiCl(3) with tetramethylethylenediamine (TMEDA) in pentane at room temperature. The crystal structure of Cl(3)SiSiCl(3)·TMEDA displays one tetrahedrally and one octahedrally bonded Si atom (monoclinic, P2(1)/n). (29)Si CP/MAS NMR spectroscopy confirms this structure. Density functional theory (DFT) calculations have shown that the structure of the meridional isomer of Cl(3)SiSiCl(3)·TMEDA is 6.3 kcal lower in energy than that of facial coordinate species. Dissolving of Cl(3)SiSiCl(3)·TMEDA in CH(2)Cl(2) resulted in an immediate reaction by which oligochlorosilanes Si(n)Cl(2n) (n = 4, 6, 8, 10; precipitate) and the Cl(-)-complexed dianions [Si(n)Cl(2n+2)](2-) (n = 6, 8, 10, 12; CH(2)Cl(2) extract) were formed. The constitutions of these compounds were confirmed by MALDI mass spectrometry. Additionally, single crystals of [Me(3)NCH(2)CH(2)NMe(2)](2)[Si(6)Cl(14)] and [Me(3)NCH(2)CH(2)NMe(2)](2)[Si(8)Cl(18)] were obtained from the CH(2)Cl(2) extract. We found that Cl(3)SiSiCl(3)·TMEDA reacts with MeCl, forming MeSiCl(3) and the products that had been formed in the reaction of Cl(3)SiSiCl(3)·TMEDA with CH(2)Cl(2). X-ray structure analysis indicates that the structures of [Me(3)NCH(2)CH(2)NMe(2)](2)[Si(6)Cl(14)] (monoclinic, P2(1)/n) and [Me(3)NCH(2)CH(2)NMe(2)](2)[Si(8)Cl(18)] (monoclinic, P2(1)/n) contain dianions adopting an "inverse sandwich" structure with inverse polarity and [Me(3)NCH(2)CH(2)NMe(2)](+) as countercations. Single crystals of SiCl(4)·TMEDA (monoclinic, Cc) could be isolated by thermolysis reaction of Cl(3)SiSiCl(3)·TMEDA (50 °C) in tetrahydrofuran (THF).

The crystal structure of the title compound, [Fe(C(5)H(5))(CH(3)CN)(CO)(2)]BF(4), of which only the coordinates of the non-H atoms of the cation have previously been reported [Fadel et al. (1979 ▶). Z. Anorg. Allg. Chem.453, 98-106] has been redetermined. The Fe(II) atom in the complex cation is coordinated by a cyclo-penta-dienyl ring, two carbonyl ligands and an acetonitrile mol-ecule displaying a three-legged piano stool structure. Three of the four F atoms of the BF(4) (-) anion are disordered over two sets of sites, with a site-occupancy factor of 0.709 (10) for the major occupied site.

The dimeric iron carbonyl [CpFe(CO)(2)](2) and the iodosilanes tBu(2)RSiI were obtained from the reaction of [CpFe(CO)(2)]I with the silanides Na[SiRtBu(2)] (R = Me, tBu) in THF. By the reactions of [CpFe(CO)(2)]I and Na[SiRtBu(2)] (R = Me, tBu) the disilanes tBu(2)RSiSiRtBu(2) (R = Me, tBu) were additionally formed using more than one equivalent of the silanide. In this context it should be noted that reduction of [CpFe(CO)(2)](2) with Na[SitBu(3)] gives the disilanes tBu(3)SiSitBu(3) along with the sodium ferrate [(Na(18-crown-6))(2)Cp][CpFe(CO)(2)]. The potassium analogue [(K(18-crown-6))(2)Cp][CpFe(CO)(2)] (orthorhombic, space group Pmc2(1)), however, could be isolated as a minor product from the reaction of [CpFe(CO)(2)]I with [K(18-crown-6)][PtBu(2)BH(3)]. The reaction of [CpFe(CO)(2)](2) with the potassium benzophenone ketyl radical and subsequent treatment with 18-crown-6 yielded the ferrate [K(18-crown-6)][CpFe(CO)(2)] in THF at room temperature. The crown ether complex [K(18-crown-6)][CpFe(CO)(2)] was analyzed using X-ray crystallography (orthorhombic, space group Pna2(1)) and its thermal behaviour was investigated.

9,10-Dihydroanthracene-9,10-diyl-bridged B(2)(NMe(2))(2) readily adds [H(2)NMe(2)](+), HCl and F(3)CCOOH across its partial B=N double bond(s), thereby forming mono- or diadducts; treatment with 1-iso-propyl-2-mercaptoimidazole leads to a triply B-B-bridged propellane-like structure.

A new polymorph of the title compound, [Pd(2)(C(8)H(18)P)(2)(C(8)H(19)P)(2)], has been found. It belongs to the triclinic P-1 space group, whereas the known form [Leoni, Sommovigo, Pasquali, Sabatino & Braga (1992 ▶), J. Organo-met. Chem.423, 263-270] crystallizes in the monoclinic C2/c space group. The title compound features a dinuclear palladium complex with a planar central Pd(2)(μ-P)(2) core (r.m.s. deviation = 0.003 Å). The Pd-Pd distance of 2.5988 (5) Å is within the range of a Pd(I)-Pd(I) bond. The mol-ecules of both polymorphs are located on a crystallographic centre of inversion. The mol-ecular conformations of the two polymorphs are essentially identical. The crystal packing patterns, on the other hand, are slightly different.

The crystal structures of five dibromobenzene derivatives, namely dibromoborylbenzene, C(6)H(5)BBr(2), (I), 1-dibromoboryl-4-(trimethylsilyl)benzene, C(9)H(13)BBr(2)Si, (II), 4-bromo-1-(dibromoboryl)benzene, C(6)H(4)BBr(3), (III), dibromo(dimethylamino)(phenyl)borane, C(8)H(12)BBr(2)N, (IV), and dibromo(dimethylsulfanyl)[4-(trimethylsilyl)phenyl]borane, C(11)H(19)BBr(2)SSi, (V), have been determined. Compounds (I)-(IV) crystallize with one molecule in the asymmetric unit, but the molecule of (V) is located on a crystallographic mirror plane, implying twofold disorder of the central aromatic ring, the S atom and one of the methyl groups bonded to the S atom. In (I), (II) and (III), the B atom is three-coordinated, and in (IV) and (V) it is four-coordinated. The geometric parameters of the -BBr(2) group in these five structures agree well with those of comparable structures retrieved from the Cambridge Structural Database. The C-B and B-Br bond lengths in the molecules with a three-coordinated B atom are significantly shorter than those in the molecules with a four-coordinated B atom. In the compounds with a three-coordinated B atom, the -BBr(2) group tends to be coplanar with the aromatic ring to which it is attached.

Molecules of the title compound [systematic name: 2,4,6-(pentafluorophenyl)-1,3,5,2,4,6-trioxatriborinane], C(18)B(3)F(15)O(3), are located on crystallographic twofold rotation axes which run through the boroxine and one of the pentafluorophenyl rings. The boroxine ring (r.m.s. deviation = 0.027 Å) and the pentafluorophenyl rings (r.m.s. deviations = 0.004 and 0.001 Å) are essentially planar. The dihedral angles between the boroxine and the two symmetry-independent benzene rings are 8.64 (10) and 8.74 (12)°. The two benzene rings are mutually coparallel [dihedral angle = 0.80 (11)°]. The packing shows planes of molecules parallel to ( ̅201), with an interplanar spacing of 2.99 Å. Within these planes, all the molecules are oriented in the same direction, whereas in neighbouring planes the direction is inverted. Short B···F contacts of 3.040 (2) and 3.1624 (12) Å occur between planes. The geometric parameters of the boroxine ring in the title compound agree well with those of comparable boroxine structures, while the packing reveals some striking similarities and differences.

The Au(I) atom of the title compound, [AuI(C(12)H(27)P)], shows an almost linear coordination, with a P-Au-I angle of 178.52 (3)° [Au-P = 2.2723 (14) Å and Au-I = 2.5626 (6) Å].

1,2-Bis(trimethylsilyl)benzenes are key starting materials for the synthesis of benzyne precursors, Lewis acid catalysts, and certain luminophores. We have developed efficient, high-yield routes to functionalized 4-R-1,2-bis(trimethylsilyl)benzenes, starting from either 1,2-bis(trimethylsilyl)acetylene/5-bromopyran-2-one (2) or 1,2-bis(trimethylsilyl)benzene (1)/bis(pinacolato)diborane. In the first reaction, 5 (R = Br) is obtained through a cobalt-catalyzed Diels-Alder cycloaddition. The second reaction proceeds via iridium-mediated C-H activation and provides 8 (R = Bpin). Besides its use as a Suzuki reagent, compound 8 can be converted into 5 with CuBr(2) in i-PrOH/MeOH/H(2)O. Lithium-bromine exchange on 5, followed by the addition of Me(3)SnCl, gives 10 (R = SnMe(3)), which we have applied for Stille coupling reactions. A Pd-catalyzed C-C coupling reaction between 5 and 8 leads to the corresponding tetrasilylbiphenyl derivative. The bromo derivative 5 cleanly undergoes Suzuki reactions with electron-rich as well as electron-poor phenylboronic acids.

Mol-ecules of the title compound, [HgBr(C(9)H(11))], are located on a crystallographic twofold rotation axis. Due to the mol-ecular symmetry, the Hg(II) atom is linearly coordinated by the ipso-C of the mesityl group and the Br atom. In the crystal, mol-ecules lie in planes parallel to (001).

The title complex, [PdCl(2)(C(18)H(15)P)(2)]·0.5C(6)H(6), has the Pd(II) ion in a square-planar coordination mode (r.m.s. deviation for Pd, P and Cl atoms = 0.024 Å) with the PPh(3) and Cl ligands mutually trans. The benzene solvent mol-ecule is located about a crystallographic inversion centre. The title complex is isostructural with trans-dichloridobis(triphenyl-phosphane)-palladium(II) 1,4-dichloro-benzene sesquisolvate [Kitano et al. (1983 ▶). Acta Cryst. C39, 1015-1017].

The Ir(III) atom of the title compound, [Ir(C(11)H(8)N)(2)Cl(CH(3)CN)], displays a distorted octa-hedral coordination. The pyridyl groups are in trans positions [N-Ir-N = 173.07 (10)°], while the phenyl groups are trans with respect to the acetonitrile and chloride groups [C-Ir-N = 178.13 (11) and C-Ir-Cl = 176.22 (9)°]. The pyridyl-phenyl groups only show a small deviation from planarity, with the dihedral angle between the planes of the two six-membered rings in each pyridyl-phenyl group being 5.6 (2) and 5.8 (1)°. The crystal packing shows inter-molecular C-H⋯Cl, C-H⋯π(acetonitrile) and C-H⋯π(pyridyl-phen-yl) contacts.

The targeted hydrolysis of the 9,10-dihydro-9,10-diboraanthracene adduct (Me(2)S)HB(C(6)H(4))(2)BH(SMe(2)) (1) with 0.5 equiv of H(2)O leads to formation of the borinic acid anhydride [(Me(2)S)HB(C(6)H(4))(2)B](2)O (2) and thereby provides access to the field of unsymmetrically substituted 9,10-dihydro-9,10-diboraanthracenes. Compound 2 reacts with tBuC≡CH to give the corresponding vinyl derivative in an essentially quantitative conversion. Subsequent cleavage of the B-O-B bridge by LiAlH(4) with formation of hydridoborate functionalities is possible but is accompanied by partial B-C(vinyl) bond degradation. This situation changes when the related mesityl derivative [MesB(C(6)H(4))(2)B](2)O (7) is employed, which can be synthesized from BrB(C(6)H(4))(2)BBr (6) by treatment with 1 equiv of MesMgBr and subsequent hydrolysis. The reaction of 7 with LiAlH(4) in tetrahydrofuran (THF) furnishes Li[MesB(C(6)H(4))(2)BH(2)] (8); hydride elimination with Me(3)SiCl leads to formation of the THF adduct MesB(C(6)H(4))(2)BH(THF) (9·THF). Alternatively, 7 can be transformed into the bromoborane MesB(C(6)H(4))(2)BBr (10) by treatment with BBr(3). A Br/H-exchange reaction between 10 and Et(3)SiH yields the donor-free borane MesB(C(6)H(4))(2)BH (9), which forms B-H-B bridged dimers (9)(2) in the solid state. The vinyl borane MesB(C(6)H(4))(2)BC(H)=C(H)Mes (14) is accessible from MesC≡CH and either 9·THF or 9. Compared with the related compound Mes(2)BC(H)=C(H)Mes, the electronic absorption and emission spectra of 14 reveal bathochromic shifts of Δλ(abs)=17 nm and Δλ(em)=74 nm, which can be attributed to the rigid, fully delocalized π framework of the [MesB(C(6)H(4))(2)B] chromophore., (Copyright © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.)

The crystal structure of the title compound, hexa-μ(2)-bromido-μ(4)-oxido-tetra-kis-[(diethyl ether)magnesium], [Mg(4)Br(6)O(C(4)H(10)O)(4)], determined from data measured at 173 K, differs from the previously known structure of diethyl ether magnesium oxybromide, which was determined from room-temperature data [Stucky & Rundle (1964 ▶). J. Am. Chem. Soc. 86, 4821-4825]. The title compound crystallizes in the tetra-gonal space group I[Formula: see text], whereas the previously known structure crystallizes in a different tetra-gonal space group, namely P[Formula: see text]2(1)c. Both molecules have crystallographic [Formula: see text] symmetry and show almost identical geometric parameters for the Mg, Br and O atoms. The crystal of the title compound turned out to be a merohedral twin emulating a structure with apparent Laue symmetry 4/mmm, whereas the correct Laue group is just 4/m. The fractional contribution of the minor twin component converged to 0.462 (1).

The title compound, [Li(4)O(4)(C(12)H(8)BO)(4)(C(4)H(10)O)(4)], features a Li(4)O(4) cube. Each Li atom in the cube is additionally coordinated by a diethyl ether mol-ecule and each O atom in the cube carries a 9-oxa-10-boraanthracene residue. The crystal studied was a non-merohedral twin [twin law (-1 0 0 / 0 0 1 / 0 1 0); the contribution of the major twin component refined to 0.553 (3)] emulating apparent tetra-gonal symmetry, whereas the actual crystal system is just ortho-rhom-bic.

The dimethyl sulfide adduct 2(DMS) is a crystalline storage form of the unstable hydroboration reagent 9-H-9-borafluorene (2); 2(DMS) is available by the addition of DMS to either in situ generated [2](2) or 1,2-(2,2'-biphenylylene)diborane(6) (7)., (This journal is © The Royal Society of Chemistry 2011)

The title compound, C(25)H(20)N(4)O(2), is a ditopic ortho-hydro-quinone-based bis-(pyrazol-1-yl)methane ligand. The dihedral angles between the planes of the pyrazole rings and their attached phenyl rings are 17.4 (3) and 5.9 (4)°. The pyrazole rings make a dihedral angle of 87.84 (16)°. One of the two hy-droxy groups forms an intra-molecular hydrogen bond to the other hy-droxy group, whereas the second is involved in an inter-molecular O-H⋯N hydrogen bond. As a result of these inter-molecular hydrogen bonds, helical chains running along the b axis are formed.

Mol-ecules of the title compound, [Zn(8)(C(6)F(5))(8)O(4)(C(4)H(10)O)(4)], are located on a special position of site symmetry [Formula: see text]. As a result, there is just one quarter-mol-ecule in the asymmetric unit. The title compound features a Zn(4)O(4) cube. Each Zn atom in the cube carries a pentafluorophenyl substituent. Each O atom is bonded to a further Zn atom, which is connected to a pentafluorophenyl substituent and the O atom of a diethyl ether mol-ecule. All ether C atoms are disordered over two sets of sites with a site occupation factor of 0.51 (2) for the major occupied site.

9-H-9-Borafluorene (H(8)C(12)BH; 5) can be generated in situ from 9-Br-9-borafluorene and Et(3)SiH in benzene or hexane. Monitoring of the reaction by NMR spectroscopy at rt in C(6)D(6) reveals that 5 forms C(1)-symmetric dimers (5)(2) under these conditions. DFT calculations on conceivable isomers of (5)(2) and a comparison of calculated and experimentally determined (1)H, (13)C, and (11)B NMR shift values lead to the conclusion that (5)(2) is not a classical dimer H(8)C(12)B(μ-H)(2)BC(12)H(8), but contains one B-H-B three-center, two-electron bond together with a boron-bridging phenyl ring. Addition of 1 equiv of pyridine to (5)(2) leads to the clean formation of the pyridine adduct H(8)C(12)BH(py) (5·py). Likewise, (5)(2) can be employed in hydroboration reactions, as evidenced by its transformation with 0.5 equiv of tert-butylacetylene, which gives the hydroboration products tBuC(H)(2)C(H)(BC(12)H(8))(2) (9) and tBuC(H)C(H)BC(12)H(8) in almost quantitative yield. (5)(2) is not long-term stable in benzene solution. Addition of pyridine to aged reaction mixtures allowed the isolation of the adduct (py)H(2)B-C(6)H(4)-C(6)H(4)-(py)BC(12)H(8) (10·py(2)) of a ring-opened dimer of 5. Storage of a hexane solution of 9-Br-9-borafluorene and Et(3)SiH for 1-2 weeks at rt leads to the formation of crystals of a ring-opened pentamer H[-(H)B-(C(6)H(4))(2)-](4)BC(12)H(8) (11) of 5 (preparative yields are obtained after 1-4 months). The polymer main chain of 11 is reinforced by four intrastrand B-H-B three-center, two-electron bonds. Apart from the main product 11, we have also isolated minor amounts of closely related oligomers carrying different chain ends, i.e., H(8)C(12)B-(C(6)H(4))(2)[-(H)B-(C(6)H(4))(2)-](2)BC(12)H(8) (12) and H[-(H)B-(C(6)H(4))(2)-](5)BH(2) (13). When the reaction between 9-Br-9-borafluorene and Et(3)SiH is carried out in refluxing toluene, the cyclic dimer [-(μ-H)B-(C(6)H(4))(2)-](2) (14) can be obtained in a crystalline yield of 25%. The compounds 9, 10·py(2), 11, 12, 13, and 14 have been structurally characterized by X-ray crystallography. The entire reaction pathway leading from 5 to 10, 11, 12, 13, and 14 has been thoroughly elucidated by DFT calculations and we propose a general mechanistic scenario applicable for ring-opening polymerization reactions of 9-borafluorenes.

Single crystals of the meta- and para-phenylene-bridged ditopic trihydridoborates (Li(THF)(2))(2)[m-C(6)H(4)(BH(3))(2)] and (Li(THF)(2))(2)[p-C(6)H(4)(BH(3))(2)] have been prepared and investigated by X-ray crystallography. The compounds turned out to be coordination polymers in which each trihydridoborate substituent is connected with one trihydridoborate substituent of a neighbouring monomer via two bridging Li(THF)(2)(+) ions. (Li(THF)(2))(2)[m-C(6)H(4)(BH(3))(2)] and (Li(THF)(2))(2)[p-C(6)H(4)(BH(3))(2)] suffer from poor solubility in all common non-protic solvents. Thus, a more soluble derivative of (Li(THF)(2))(2)[p-C(6)H(4)(BH(3))(2)], equipped with n-hexyl groups at the positions 2 and 5 of the phenylene ring, has been used for all further investigations (i.e., compound Li(2)[6]). Treatment of Li(2)[6] with Me(3)SiCl in the presence of excess N(Me)(2)Et leads to the abstraction of one hydride ion per boron atom under formation of the ditopic amine-borane adduct p-C(6)H(2)(n-hexyl)(2)(BH(2)-N(Me)(2)Et)(2) (7). The compound turned out to be an efficient hydroboration reagent both for internal olefins (i.e., 1,5-cyclooctadiene) and terminal alkynes (i.e., tert-butyl acetylene) to give p-C(6)H(2)(n-hexyl)(2)(9-BBN)(2) (8; 9-BBN = 9-borabicyclo[3.3.1]nonyl) and p-C(6)H(2)(n-hexyl)(2)(B(C(H)=C(H)tBu)(2))(2) (9), respectively.

The title compound, [Tl(4)(C(4)H(9)O)(4)], featuring a (Tl-O)(4) cube, crystallizes with a quarter-mol-ecule (located on a special position of site symmetry ..) and a half-mol-ecule (located on a special position of site symmetry 23.) in the asymmetric unit. The Tl-O bond distances range from 2.463 (12) to 2.506 (12) Å. All O-Tl-O bond angles are smaller than 90° whereas the Tl-O-Tl angles are wider than a recta-ngular angle.

The title compound, [Li(3)(C(4)F(9)O)(3)(C(3)H(6)O)(3)], features an open Li/O cube with an Li ion missing at one corner. Three of the four bridging O atoms of the cube carry a fluorinated tert-butyl residue, whereas the fourth is part of an acetone mol-ecule. Two of the Li atoms are further bonded to a non-bridging acetone mol-ecule. Two of the lithium ion coordination geometries are very distorted LiO(4) tetra-hedra; the third could be described as a very distorted LiO(3) T-shape with two distant F-atom neighbours. The Li⋯Li contact distances for the three-coordinate Li(+) ion [2.608 (14) and 2.631 (12) Å] are much shorter that the contact distance [2.940 (13) Å] between the tetra-hedrally coordinated species.

The donor-free mesityllithium was prepared from the reaction of MesBr with n-BuLi in diethyl ether at -78 degrees C. The solid-state structure of unsupported mesityllithium consists of C(2)Li(2)-rings composed of two LiMes units, which interact with adjacent dimers [LiMes](2), forming a polymeric infinite chain along the crystallographic c-axis (monoclinic space group, P2(1)/n). The structure of donor-free mesityllithium reveals short contacts between the C atoms of the mesityl rings and the lithium atoms of neighbouring [LiMes](2) units. The structure determination of LiMes was performed by X-ray powder diffraction. In addition we have investigated the reaction of LiMes with Me(3)SnCl and P(4) for our understanding of the reactivity of donor-free mesityllithium. The heterogeneous reaction of donor-free mesityllithium with Me(3)SnCl produces conveniently the stannylated mesitylene Me(3)SnMes (triclinic, space group P1). White phosphorus reacts with three equivalents of unsupported mesityllithium in benzene to give Li(3)P(4)Mes(3). In this context it should be noted that a tetraphosphide with an identical LiP-core as in Li(3)P(4)Mes(3) had been formed in the 1:3 reaction of P(4) with the silanide Li[SitBu(3)]. The tetraphosphide Li(3)P(4)Mes(3) was analyzed using X-ray crystallography (monoclinic, space group C2/c).

Two series of sterically demanding para-dimethoxyphenyl-substituted bis(pyrazol-1-yl)methane ligands have been synthesized, i.e., L2(R,R') = ((MeO)(2)C(6)H(3))C(H)(pz(R,R'))(2) and L3(R,R') = ((MeO)(2)C(6)H(3))C(Me)(pz(R,R'))(2) (R,R' = 3-Me,5-Me; 3-Ph,5-H; 3-tBu,5-H). In the solid state, already the sterically least encumbered derivative L2(Me2) is able to stabilize Co(II) complexes of the form [X(2)Co(L2(Me2))] (X = Cl, NO(3)); in solution, these complexes are at an equilibrium with the 1:2 species [Co(L2(Me2))(2)](2+). Oxidative demethylation of L3(Ph) and L3((t)Bu) with [Ce(NH(4))(2)(NO(3))(6)] leads to the corresponding para-benzoquinonyl-substituted bis(pyrazol-1-yl)methane ligands L4(Ph) and L4((t)Bu). Contrary to that, the methyl derivative L3(Me2) is transformed into the ortho-benzoquinone species L5(Me2), which still contains one methoxy substituent while one oxygen atom has been newly introduced. The formation of L5(Me2) requires (i) the admission of air, (ii) the presence of both methoxy substituents of L3(Me2), and (iii) the presence of (methyl) substituents both at the exocyclic carbon atom and at the 5- positions of the pyrazolyl rings. The parent ortho-hydroquinonyl-substituted bis(pyrazol-1-yl)methane ligand ((HO)(2)C(6)H(3))C(H)(pz(H,H))(2) is readily available from 3,4-dihydroxybenzaldehyde and (pz(H,H))(2)SO/pyridine.

The asymmetric unit of the title compound, [K(C(5)HF(6)N(2))(H(2)O)(2)](n), is composed of two 3,5-bis-(trifluoro-meth-yl)pyrazol-ide anions, two potassium cations and four water mol-ecules. The water mol-ecules and 3,5-bis-(trifluoro-meth-yl)pyrazolide anions act as bridges between the potassium cations. Each potassium cation is surrounded by four O atoms [K-O = 2.705 (3)-2.767 (3) Å] and four F atoms [K-F = 2.870 (7)-3.215 (13) Å]. The water mol-ecules and the 3,5-bis-(trifluoro-meth-yl)pyrazolide anions are connected by O-H⋯N hydrogen bonds, forming layers in the ab plane. All -CF(3) groups show rotational disorder between two orientations each.

The title compound, [Na(CF(3)O(3)S)(C(12)H(24)O(6))], features a sodium cation that is coordinated by eight O atoms in an irregular hexa-gonal bipyramidal environment. The equatorial positions are occupied by the six O atoms of an 18-crown-6 ether ring. In the axial positions, there is one O atom of a trifluoro-methane-sulfonate anion and an ether O atom of a symmetry-equivalent crown ether ring. In this way, centrosymmetric dimers are formed.

2-{1-[(4-Chloroanilino)methylidene]ethyl}pyridinium chloride methanol solvate, C(13)H(13)ClN(3)(+) x Cl(-) x CH(3)OH, (I), crystallizes as discrete cations and anions, with one molecule of methanol as solvent in the asymmetric unit. The N-C-C-N torsion angle in the cation indicates a cis conformation. The cations are located parallel to the (\overline{2}02) plane and are connected through hydrogen bonds by a methanol solvent molecule and a chloride anion, forming zigzag chains in the direction of the b axis. The crystal structure of 2-{1-[(4-fluoroanilino)methylidene]ethyl}pyridinium chloride, C(13)H(13)FN(3)(+) x Cl(-), (II), contains just one anion and one cation in the asymmetric unit but no solvent. In contrast with (I), the N-C-C-N torsion angle in the cation corresponds with a trans conformation. The cations are located parallel to the (100) plane and are connected by hydrogen bonds to the chloride anions, forming zigzag chains in the direction of the b axis. In addition, the crystal packing is stabilized by weak pi-pi interactions between the pyridinium and benzene rings. The crystal of (II) is a nonmerohedral monoclinic twin which emulates an orthorhombic diffraction pattern. Twinning occurs via a twofold rotation about the c axis and the fractional contribution of the minor twin component refined to 0.324 (3). 2-{1-[(4-Fluoroanilino)methylidene]ethyl}pyridinium chloride methanol disolvate, C(13)H(13)FN(3)(+) x Cl(-) x 2 CH(3)OH, (III), is a pseudopolymorph of (II). It crystallizes with two anions, two cations and four molecules of methanol in the asymmetric unit. Two symmetry-equivalent cations are connected by hydrogen bonds to a chloride anion and a methanol solvent molecule, forming a centrosymmetric dimer. A further methanol molecule is hydrogen bonded to each chloride anion. These aggregates are connected by C-H...O contacts to form infinite chains. It is remarkable that the geometric structures of two compounds having two different formula units in their asymmetric units are essentially the same.

The title compound, 3K(+).C(6)H(3)B(3)F(9)(3-), crystallizes as discrete anions and cations which are connected by K...F and K...pi interactions. Two of the -BF(3) residues attached to the aromatic ring adopt a conformation with all F atoms out of the plane of the aromatic ring, whereas the third residue has an almost synperiplanar conformation for one of the F-B-C-C torsion angles. It is remarkable that only one of the K(+) cations interacts with the arene ring and that only one side of the aromatic ring coordinates to a K(+) cation. As a result, a sandwich structure does not occur. All K(+) ions show a coordination mode that cannot be conveniently described with a polyhedron. The anions are located in the (102) planes with the K(+) cations located between these planes. The investigated crystal was a nonmerohedral twin with the fractional contribution of the minor twin component being 0.405 (4). The title compound is the first example of a structure containing a benzene ring substituted with three -BF(3) groups. Only eight other structures have been reported in which a benzene ring carries at least one -BF(3) group. Just five of these contain a K(+) ion, but in none of these is the K(+) ion coordinated to the aromatic ring.

The dimethyl sulfide, pyridazine, or pyrazolide adducts of 9,10-dihydro-9,10-diboraanthracene are potent hydroboration reagents for terminal alkynes; the 1,2-diazene derivatives possess a paddle-wheel structure and are stabilised towards hydrolysis.

The coordination behavior, the conformational flexibility, and the stability of the novel (pyrazol-1-yl)borate ligands [Ph(pz)B(mu-N(Me))(mu-pz)B(pz)Ph](-) ([L(1)](-)), [Ph(pz)B(mu-O)(mu-pz)B(pz)Ph](-) ([L(2)](-)), and [Ph(pz)B(mu-O)(mu-OB(Ph)O)B(pz)Ph](2-) ([L(3)](2-)) have been experimentally assessed by investigating the following compounds: [Li(thf)L(1)], [Li(thf)L(2)], [Mg(Cl)(thf)(x)L(1)], [Mg(Cl)(thf)(2)L(2)], [Mn(CO)(3)L(2)], K(thf)[Mn(CO)(3)L(3)], [CoCl(2)(HL(1))], [L(1)Co(mu-Cl)(2)CoL(1)], [Zn(Br)L(1)], [Cu(Cl)L(1)], [Cu(Cl)L(2)]. The L(1)-complexes were prepared from a mixture of HL(1) and the appropriate metal salt by addition of a base. HCl elimination from [CoCl(2)(HL(1))], which gives [L(1)Co(mu-Cl)(2)CoL(1)], does not necessarily require the assistance of a base, but happens spontaneously when a solution of the complex is stored at room temperature for several days. K(thf)[Mn(CO)(3)L(3)] was obtained via in situ hydrolysis of HL(1)/[Mn(CO)(5)Br] in the presence of K(2)CO(3). In some other cases, formation of the coordination compounds proceeded with decomposition of a part of the ligand molecules and yielded pyrazole (e.g., [Zn(Cl)(Hpz)L(2)]) or pyrazolide (e.g., [L(2)Co(mu-Cl)(mu-pz)CoL(2)]) complexes. As evidenced by the crystal structure analyses of [Zn(Br)L(1)]/[Mg(Cl)(thf)(2)L(2)]/[Mn(CO)(3)L(2)] on the one hand and [L(1)Mg(mu-Cl)(2)Mg(thf)L(1)]/[Cu(Cl)L(1)]/[Cu(Cl)L(2)](2) on the other, [L(1)](-) and [L(2)](-) are able to adopt both a facial and a meridional conformation. Moreover, while many of the established design principles of scorpionate chemistry are still valid for [L(1)](-), [L(2)](-), and [L(3)](2-), the bonding situation of the central donor moiety (N(Me) in [L(1)](-); O in [L(2)](-), [L(3)](2-)) is distinctly different from the way the pyrazolyl rings are attached to the molecule, so that donor scrambling is not an issue in these [N,N,N] and [N,O,N] mixed-donor ligands.

We present here the crystal structures of two acetylene derivatives cocrystallized with benzene, namely bis(trimethylsilyl)acetylene benzene solvate, C(8)H(18)Si(2).C(6)H(6), (I), and diphenylacetylene benzene solvate, C(14)H(10).C(6)H(6), (II). In (I), both molecules belong to the symmetry point group C(2h) and are located about special positions with site symmetry 2/m. In (II), both molecules show crystallographic inversion symmetry. In both structures, there are C-H...pi contacts between aromatic H atoms and the pi-electrons of the triple bond. In addition to these, in (II) there are C-H...pi contacts between aromatic H atoms and the pi-electron cloud of the benzene molecules.

In contrast to the previous structure determinations of the title structure, (NH(4))(2)[MoS(4)], the present determination at 173 K localized the positions of the H atoms. The title structure belongs to the β-K(2)SO(4) family and all the ions are located on crystallographic mirror planes. The ions are held together by N-H⋯S hydrogen bonds (some of which are bifurcated), forming a three-dimensional network. One of the N atoms has nine contacts to the S atoms shorter than 4 Å, and the other has ten.

The title compound, C(12)H(8)BBr, crystallizes with three essentially planar mol-ecules (r.m.s. deviations = 0.018, 0.020 and 0.021Å) in the asymmetric unit: since the title compound is rigid, there are no conformational differences between these three mol-ecules. The crystal packing resembles a herringbone pattern.

In the title molecular salt, C(16)H(36)N(+)·C(12)H(20)BS(3) (-), three of the four n-butyl chains show a trans conformation, whereas the fourth has the C-C-C-C torsion angle in a gauche conformation [-77.8 (5)°]. In the crystal, mol-ecules are packed in layers parallel to the (101) plane.

Mono- and ditopic lithium ferrocenylhydridoborates Li[FcBH(3)] (2) and Li(2)[H(3)B-fc-BH(3)] (4) have been synthesized from FcB(OMe)(2)/(MeO)(2)B-fc-B(OMe)(2) and Li[AlH(4)] (Fc = ferrocenyl; fc = 1,1'-ferrocenylene). X-ray quality crystals were grown from OEt(2). Depending on the amount of Li(+)-coordinated solvent molecules, dimeric (2(OEt(2))(2)) or tetrameric (2(OEt(2))) aggregates are observed in the solid state. The ditopic derivative 4 crystallizes as two different macrocyclic dimers (4(OEt(2))(5) and 4(OEt(2))(6)) in the unit cell. Each of the four aggregates is held together mainly by RBH(3)-eta(2)-Li bonds. Addition of Me(3)SiCl to 2 or 4 generates the corresponding boranes FcBH(2) (5) and H(2)B-fc-BH(2) (6), which can be trapped by adduct formation with NMe(2)Et or SMe(2). In contrast, when OEt(2) is present as the sole Lewis basic donor, no stable ether adducts are obtained, but condensation takes place leading to Fc(2)BH (10) and the novel borane polymer [-fcB(H)-](n) (9), respectively. In situ generation of FcBH(2) (5) in the presence of cyclohexene gives Fc(2)BCy and BCy(3) but no FcBCy(2), thereby indicating that 5 undergoes condensation to 10 more quickly than hydroboration of an internal olefin can occur (Cy = cyclohexyl). Fc(2)BH (10) was further studied as a model system for the optimization of modification reactions of polymer [-fcB(H)-](n) (9). Hydroboration of PhCCH or tBuCCH with 10 proceeds smoothly and quantitatively to give the corresponding vinylboranes Fc(2)B(CH horizontal lineCHR) (11(Ph), R = Ph; 11(tBu), R = tBu), which were fully characterized. In a similar manner, the polymeric borane 9 was successfully transformed into ferrocenylborane polymers [-fcB(CH horizontal lineCHR)-](n) (12(Ph), R = Ph; 12(tBu), R = tBu) that contain vinyl groups attached to boron. The structures of polymers 12 were confirmed by NMR and IR spectroscopy and mass spectrometry. The MALDI-TOF spectra of 12(Ph) and 12(tBu) showed patterns of equidistant peaks with peak separations that are consistent with the masses of the expected repeating units of each of the polymers. The absorption maxima in the UV-vis spectra of polymers 12 are significantly red-shifted in comparison to the dimeric model systems 11.

A 1,4-naphthoquinone-substituted bis(pyrazol-1-yl)methane ligand (N--N) has been synthesized and transformed into its corresponding Pd(II) chelate complex [(N--N)PdCl(2)]. Both N--N and [(N--N)PdCl(2)] have been fully characterized by NMR spectroscopy, spectro-electrochemistry, and X-ray crystallography. After treatment of [(N--N)PdCl(2)] with NEt(3), the signature of a 1,4-naphthosemiquinonate radical is visible in the UV-vis- and electron paramagnetic resonance (EPR) spectrum of the reaction mixture; the free ligand N--N does not react with NEt(3) under the conditions applied. It is therefore concluded that NEt(3) first reduces the Pd(II)-ion of [(N--N)PdCl(2)] to the zero-valent state and that this reaction is followed by a single-electron transfer from the metal atom to the 1,4-naphthoquinone moiety. The complex has been specifically designed to disfavor any direct Pd-to-naphthoquinone coordination. Electron transfer thus proceeds through space or, less likely, via sigma-bonds of the ligand framework.

The Mg centre in the title compound, [MgBr(2)(C(2)H(7)N)(3)], is penta-coordinated in a trigonal-bipyramidal mode with the two Br atoms in axial positions and the N atoms of the dimethyl-amine ligands in equatorial positions. The Mg(II) centre is located on a crystallographic twofold rotation axis. The crystal structure is stabilized by N-H⋯Br hydrogen bonds. The N atom and H atoms of one dimethylamine ligand are disordered over two equally occupied positions.

The di- and trinuclear ferrocene species Li[Fc-BPh(2)-Fc] (Li[]) and Li(2)[Fc-BPh(2)-fc-BPh(2)-Fc] (Li(2)[]) have been investigated with regard to their electrochemical properties and the degree of intervalence charge-transfer after partial oxidation. Li[] shows two distinct one-electron redox waves for its chemically equivalent ferrocenyl substituents in the cyclic voltammogram (E(1/2) = -0.38 V, -0.64 V; vs. FcH/FcH(+)). The corresponding values of Li(2)[] are E(1/2) = -0.45 V (two-electron process) and -1.18 V. All these redox events are reversible at r. t. on the time scale of cyclic voltammetry. X-ray crystallography on the mixed-valent Fe(II)(2)Fe(III) complex Li(12-c-4)(2)[] reveals the centroid-centroid distance between the cyclopentadienyl rings of each of the terminal ferrocenyl substituents (3.329 A) to be significantly smaller than in the central 1,1'-ferrocenediyl fragment (3.420 A). This points towards a charge-localized structure (on the time scale of X-ray crystallography) with the central iron atom being in the Fe(III) state. Mössbauer spectroscopic measurements on Li(12-c-4)(2)[] lend further support to this interpretation. Spectroelectrochemical measurements on Li[] and Li(2)[] in the wavelength range between 300-2800 nm do not show bands interpretable as intervalence charge-transfer absorptions for the mixed-valent states. All data accumulated so far lead to the conclusion that electronic interaction between the individual Fe atoms in Li[] and Li(2)[] occurs via a through-space pathway and/or is electrostatic in nature.

The title compound, C(14)H(14)Si, crystallizes with two almost identical mol-ecules (r.m.s. deviation = 0.080 Å for all non-H atoms) in the asymmetric unit. All atoms of the silafluorene moiety lie in a common plane (r.m.s. deviations = 0.049 and 0.035 Å for the two mol-ecules in the asymmetric unit). The Si-C(meth-yl) bonds are significantly shorter [1.865 (4)-1.868 (4) Å] than the Si-C(aromatic) bonds [1.882 (3)-1.892 (3) Å]. Owing to strain in the five-membered ring, the endocyclic C-Si-C angles are reduced to 91.05 (14) and 91.21 (14)°.

The tetraphosphenediides M2[t-Bu3SiPPPPSi-t-Bu3] (M = Li, Na, K) were accessible by the reaction of P4 with the silanides M[Si-t-Bu3] (M = Li, Na, K), whereas M2[t-Bu3SiPPPPSi-t-Bu3] (M = Rb, Cs) were obtained from the reaction of RbCl and CsF with Na2[t-Bu3SiPPPPSi-t-Bu3]. 31P NMR experiments revealed that, in tetrahydrofuran, Na2[t-Bu3SiPPPPSi-t-Bu3] adopts a cis configuration. However, treatment of Na2[t-Bu3SiPPPPSi-t-Bu3] with 18-crown-6 led to the formation of [Na(18-crown-6)(thf)2]2[t-Bu3SiPPPPSi-t-Bu3] that possesses a trans configuration in the solid state. The ion-separated tetraphosphenediide [Na(18-crown-6)(thf)2]2[t-Bu3SiPPPPSi-t-Bu3] was analyzed using X-ray crystallography (monoclinic, space group P2(1)/n). The reaction of Na2[t-Bu3SiPPPPSi-t-Bu3] with BaI2 gave, conveniently, the corresponding barium derivative Ba[t-Bu3SiPPPPSi-t-Bu3]. However, addition of AuI to the tetraphosphenediide Na2[t-Bu3SiPPPPSi-t-Bu3] yielded 1,3-diiodo-2,4-disupersilyl-cyclotetraphosphane (monoclinic, space group C2/c), which is an isomer of disupersilylated diiodotetraphosphene. A further isomeric derivative of disupersilylated tetraphosphene, the 3,5-disupersilyl-2,2-di-tert-butyl-2-stanna-bicyclo[2.1.0(1,4)]pentaphosphane, which possesses a phosphanylcyclotriphosphane structure, was obtained by the reaction of Na2[t-Bu3SiPPPPSi-t-Bu3] with t-Bu2SnCl2. Calculations revealed that the acyclic cis and trans isomers of the dianions [HPPPPH]2- and [H3SiPPPPSiH3]2- are thermodynamically more stable than the cyclic isomers with a phosphanylcyclotriphosphane or a cyclotetraphosphane structure. However, the neutral cyclic isomers of H4P4 and H2(H3Si)2P4 represent more stable structures than the cis- and trans-tetraphosphenes H2P-P=P-PH2 and (H3Si)HP-P=P-PH(SiH3), respectively. In addition, the molecular orbitals (MOs) of the silylated cis- and trans-tetraphosphene dianions of [H3SiPPPPSiH3]2-, which are comparable with those of the ion-separated supersilylated tetraphosphenediide [t-Bu3SiPPPPSi-t-Bu3]2-, show the highest occupied antibonding pi*MO (HOMO). The HOMO is represented by the (p(z)-p(z)+p(z)-p(z)) pi* MO.

A P2(1)2(1)2(1) polymorph of the title compound, [Cu(CH(3)CN)(4)]BF(4), is reported. The crystal structure is very similar to the structure of the Pna2(1) polymorph reported by Jones & Crespo [Acta Cryst. (1998), C54, 18-20]. The anions and one of the three independent cations occupy similar positions in both polymorphs. Two of the four symmetry-related positions of the other two cations are also identical in the two polymorphs, and the other two positions are related by mirror symmetry. The crystal used for the structure determination contained a volume fraction of 0.088 (7) of the Pna2(1) polymorph.

The asymmetric unit of the title compound, [K(C(3)H(3)N(2))(C(12)H(24)O(6))], is composed of a potassium cation bonded to the six O atoms of a crown ether mol-ecule and the two N atoms of a pyrazolate anion. The K⋯O distances range from 2.8416 (8) to 3.0025 (8) Å, and the two K⋯N distances are 2.7441 (11) and 2.7654 (11) Å. The K cation is displaced by 0.8437 (4) Å from the best plane through the six O atoms. The latter plane is almost perpendicular to the plane of the pyrazolate ring [dihedral angle 83.93 (3)°].

Building bridges: The title compound forms an unprecedented polymeric structure with bridging B-H-B three-center two-electron bonds in the solid state. This organoborane serves as an efficient precursor for the preparation of boron-doped pi-conjugated polymers by hydroboration polymerization with a functionalized 1,4-diethynylbenzene (see picture). These polymers form thin films that show intense green luminescence.

In the title compound, C(12)H(14)N(2) (2+)·2Cl(-), the 4,4'-dimethyl-2,2'-bipyridinium cation is essentially planar (r.m.s. deviation for all non-H atoms = 0.004 Å) and is located on a crystallographic inversion centre. The cations and chloride anions lie in planes parallel to (111) and are connected by N-H⋯Cl and C-H⋯Cl hydrogen bonds.

The title compound, [Fe(2)(C(5)H(5))(2)(C(24)H(22)BP(2))(CO)(4)][FeCl(4)]·CHCl(3), is an oxidation product of CpFe(CO)(2)PPh(2)BH(3). One pair of phenyl rings attached to the two different P atoms are almost parallel, as are the other pair [dihedral angles = 8.7 (5) and 8.9 (5)°]. The planes of the two cyclo-penta-dienyl rings are inclined by 26.8 (7)° with respect to each other. The carbonyl groups at each Fe atom are almost perpendicular [C-Fe-C = 92.6 (6) and 94.3 (5)°].

The complete mol-ecule of the title compound, [Sn(C(6)H(5))(2)Cl(2)(C(9)H(21)OP)(2)], is generated by crystallographic inversion symmetry, the Sn atom is located on a special position of site symmetry . The Sn atom adopts an all-trans SnC(2)O(2)Cl(2) octa-hedral geometry. As a consequence of the bulky substituents at the O atom, the P-O-Sn bond angle is 163.9 (3)°.

The title compound, C(18)H(15)BrSi, crystallizes with two almost identical mol-ecules (r.m.s. deviation for all non-H atoms = 0.074 Å) in the asymmetric unit. It is isomorphous with chloro-triphenyl-silane.

The title compound, [Re(2)(OH)(C(10)H(8)N(2))(2)(CO)(6)][ReO(4)], is a mixed-valence rhenium compound containing discrete anions and cations. The Re(I) atoms are in a slightly distorted octa-hedral environment, whereas the Re(VII) atoms show the typical tetra-hedral coordination mode. The dihedral angle between the two bipyridine groups is 34.3 (7)°.

The caesium triphosphenide Cs[tBu3SiPPPSitBu3] was accessible from the reaction of CsF with the sodium triphosphenide Na[tBu3SiPPPSitBu3] in tetrahydrofuran at room temperature. In contrast to the preparation of tetrahydrofuran-solvated silanides M[SitBu3] (M = Li, Na, K), our efforts to synthesize the caesium silanide Cs[SitBu3] as a tetrahydrofuran complex failed. When tBu3SiBr was treated with an excess of caesium metal in tetrahydrofuran at room temperature, the caesium enolate Cs[OCH=CH2] and the supersilane tBu3SiH formed rather than the silanide Cs[SitBu3]. X-Ray quality crystals of the enolate Cs[OCH=CH2] (orthorhombic, Pnma) were obtained from tetrahydrofuran at ambient temperature. In contrast to the structures of its homologues M[tBu3SiPPPSitBu3] (M = Na, K), the caesium triphosphenide Cs[tBu3SiPPPSitBu3] features a polymer in the solid state (orthorhombic, Cmcm).