In an effort to prepare molecular components for the construction of larger aggregates - from nanostructures to multidimensional arrays - of gallium sulfide, the chemistry of the (chloro)gallium hydrides GaHnCl3-n has been developed further and employed for selective substitution reaction. The synthetic pathways to [HGaCl2](2) have been optimized and the structure of the crystalline product determined. The dinuclear compound was converted into mononuclear 1:1 complexes with series of both tertiary phosphines and substituted pyridines. The complexes are stable and soluble in common organic solvents to allow efficient purification. The crystal structures of selected examples have been determined including those of coordination compounds of ditertiary phosphines. Reference compounds with GaCl3 and GaH3 have also been prepared and fully characterized. On controlled thermal decomposition, the HGaCl2 complexes undergo dehydrogenative coupling to give almost quantitative yields of GaCl2 complexes which are diamagnetic dinuclear species with a Ga-Ga single bond, as demonstrated for phosphine and pyridine adducts. The 2:1 complex of GaH3 with 2,4-dimethylpyridine undergoes an internal 1,4-hydrogallation reaction to afford the 4-hydro-pyridyl-(pyridine)gallium dihydride. (HGaCl2)(2) can be readily converted into ternary compounds [GaYX] which are soluble in pyridines (L) as the trinucleai complexes [GaYX(L)](3) with X = Cl, Br and Y = S, Se. Their molecular structures (six-membered rings) and conformations have been determined. With excess ligand L, these trinuclear compounds can be transformed into bicyclic tetranuclear dications of the type [Ga4Y5(L)(6)](2+) and finally into molecular species [Ga4Y6(L)(4)] containing e.g. molecular gallium sulfide Ga4S6 as a soluble pyridine complex.

Tri(2-thienyl)phosphine (1) has been transformed into chlorotri(2-thienyl)phosphonium chloride (3) in the reaction with hexachloroethane, into tetra(2-thienyl)phosphonium bromide (4) in a NiBr2-catalyzed quaternization with 2-bromothiophene, and into the p-tolylsulfonyliminotri(2-thienyl)phosphorane (6) using "chloramine T". Attempts to generate the homoleptic penta(2-thienyl)phosphorane (2-C4H3S)5P (5) by treating 3, 4, 6 or the known (PhO)3P=NSO2C6H4-2-Me (9) with 2-thienyllithium were unsuccessful. Tri(2-furyl)phosphine (2) was converted into the related imine 7, but the reaction of 7 or of 9 with 2-furyllithium failed to give (2-C4H3O)5P (8). It was only with the strained phosphorane Ph(C12H8)P=NSO2C6H4-4-Me (C12H8= 2,2'-biphenylylene) (10) that with 2-C4H3OLi the corresponding phosphorane Ph(C12H8)P(C4H3O-2)2 (11) could be obtained (31P NMR: delta-106.7 ppm). In the arsenic series, tri(2-thienyl)- and tri(2-furyl)arsine (12, 13) were converted into the tosylimino compounds (14, 15) and successfully transformed into the homoleptic arsoranes with 2-C4H3E-Li: penta(2-thienyl)- (16) and penta(2-furyl)-arsorane (17) are stable colourless crystalline solids, the NMR spectra of which indicate rapid pseudo-rotation in solution. The single crystal structure analysis of 17 shows an only slightly distorted trigonal-bipyramidal configuration. In crystals of the phosphine 2 and the arsine 13 the molecules have a propeller configuration with approximate C3v symmetry for the former, but Cs symmetry for the latter. The crystal structures of the precursors or intermediates 3, 4, 6, 9, and 10 have also been determined.

The crystal and molecular structures of 2,4-dibromo-1-iodo-benzene (1) and 1,3-dibromo-2-iodobenzene (2) have been determined by single crystal X-ray diffraction. The proximity of two or three large halogen substituents (Br/I) induces only minor distortions of the C-C-Br/I angles (ca. 2°) and the halogen atoms remain in the plane of the molecules. These undistorted structures lead to short intramolecular, sub-van-der-Waals Br-I contacts [in the range 3.465(4) to 3.530(4) Å ]. The results suggest that the peripheral Br-I interactions have an attractive component which alleviates the repulsion out of steric crowding. The influence is associated with an absorption in the visible region and is possibly responsible for the enhanced reactivity of the 1,2-dihalobenzene molecules

Triethoxysilane HSi(OEt)3, tetraethoxysilane Si(OEt)4 and hexaethoxydisiloxane Si2O(OEt)6 have been probed as reagents for the synthesis of hydrogen-rich silyl-arenes Ar(SiH3)n. A large set of new silyl-arenes, varying in their substitution patterns and grades, have been prepared. The results establish the two new silylating agents HSi(OEt)3 and Si2O(OEt)6 as particularly useful alternatives to Si(OEt)4. The products, which include trihydrosilyl-substituted methylbenzenes, naphthalenes and ferrocenes, have been characterized by NMR and IR spectroscopy, mass spectrometry and single crystal X-ray diffraction.

High-yield syntheses of the bromide (1a) and picrate salts (1b) of the 5-azonia-spiro[4]nonane cation [(CH2)4N(CH2)4]+ are reported. In the single crystal X-ray diffraction analyses of the two salts the spirocyclic quaternary ammonium cations have their five-membered rings in envelop and twist conformations modified by packing forces. The conformation found experimentally for 1a has C2-symmetry as predicted for the gas phase by quantum-chemical calculations (RI-DFT, RI-MP2), but the five-membered rings are intermediate between the expected envelop and the twist form. For 1b, both of the two independent cations can be described as a combination of rings in an envelop and a twist conformation. According to the NMR spectra, in solution the cations are highly flexible and pseudosymmetrical (point group D2d)

The weak base pyridine has been found to deprotonate trichlorogermane HGeCl3 with quantitative formation of pyridinium trichlorogermanate(II), Py-H+GeCl3-, the pyramidal structure of the anion resembling that of the isoelectronic AsCl3 molecule. This course of the reaction supports the assignment of an inverse polarization (-)Ge-H(+) of the bond in HGeCl3 as compared to the (+)Si-H(-) bond in trichlorosilane HSiCl3, which is known to form a 1:2 adduct with pyridine instead. Germanium tetrachloride also undergoes simple addition reactions with pyridine leading ultimately e.g. to GeCl4L2 with L = 4-ethyl-pyridine. Dichlorogallane gives 1:1 addition compounds (HGaCl2L) with L = pyridine, 4-dimethylamino-pyridine, 4-cyano-pyridine, and 3,5-dimethylpyridine, the molecular structures of which have been determined by single crystal X-ray diffraction. Simple tetrahedral arrays of substituents around the gallium center with only minor distortions, and characteristic Ga-H stretching vibrations in the IR spectra, show that the Ga-H bond is untouched in the addition reactions. The addition of two equivalents of 3,5-dimethyl-pyridine to HGaCl2 affords the 1:2 complex which was shown to have a trigonal-bipyramidal geometry with the hydride ligand in an equatorial position. In order to provide benchmark data, the 1:1 adducts GaCl3(L) and GaH3(L) with L = 3,5-dimethyl-pyridine were also prepared and structurally characterized. Pyridinium tetrachlorogallate(III) takes up pyridine, but the extra ligand is attached to the cation via hydrogen bonding leaving the anion unchanged: [Py-H...Py](+)[GaCl4](-).

In an investigation of the vinyl-activation in trivinylphosphine by acceptor molecules the 1 ∶ 1 addition compounds with BH3, BCl3, BBr3, and BI3 have been prepared. The reaction of Vi3P with BF3 led to polymerization of the phosphine and its adduct. While the complexes (Vi3P)BX3 with X = Cl, Br and I are air-stable colorless crystalline solids, (Vi3P)BH3 is a colorless, distillable liquid. The NMR spectra show little variation in the chemical shifts and coupling constants of the nuclei of the vinyl groups with the nature of the halogen, but there are large differences as compared to the borane complex (X = H). The crystal structures of the three boron trihalide complexes are also very similar. The components Vi3P and BX3 have a staggered conformation and the vinyl groups are in an all-trans propeller orientation. The variations in the bond distances and angles are very small and do not indicate major trends within the series. As shown by the successful preparation and structure elucidation of the reference compound (Et3P)BF3, the instability of (Vi3P)BF3 is not due to an intrinsically low affinity of BF3 to tertiary phosphines or a steric effect of the phosphine. (Et3P)BF3 has an exceedingly long P–B donor–acceptor bond. It appears that BF3 forms a weak complex, but is most effective in activating the vinyl groups for polymerization. In (Vi3P)BH3 the three vinyl groups and the three B–H function would match for an intermolecular triple-hydroboration to give a three-dimensional polymer with C–C and P–B structural units, but neither of the two functionalities appears to be sufficiently activated to accomplish this reaction.

Complexes of the type (R3P)AuSCN and (R3P)AuSeCN have been prepared in high yields from the corresponding chlorides (R3P)AuCl by treatment with KSCN or KSeCN, respectively, in a two-phase water/dichloromethane system. Crystal structure determinations revealed discrete monomeric molecules for the isomorphous thiocyanate and selenocyanate compounds with R=2-MeC6H4. For R=iPro there is only weak association into dimers via long AuS contacts, but for R3=Me2PhP chain-like polymers are formed via short aurophilic interactions [AuAu, 3.2334(2) and 3.2533(2) Å]. A monoclinic modification of (Ph3P)AuSCN was found, which shows a standard geometry of the molecules. An orthorhombic modification published previously featured a doubtful strongly distorted molecular geometry. All compounds of the type (R3P)AuS/SeCN can be converted into salts with dinuclear cations {[(R3P)Au]2S/SeCN}+Y− on reaction with equimolar quantities of [(R3P)Au]+Y− (Y=BF4, SbF6) as confirmed by analytical and spectroscopic data. The S/SeCN units are found to be bridging the two metal atoms via the S/Se atoms. The tetrafluoroborates are less stable than the hexafluoroantimonates, and all selenocyanate complexes are markedly less stable thermally and more sensitive towards air and moisture than their sulfur counterparts.

Treatment of the disulfones RSO2CH2SO2R (R = Me, Ph) with 1 or 2 equiv of organolithium reagents, followed by metathesis with a (phosphine/arsine)gold(I) halide, afforded high yields of mono- or diaurated sulfones of the types [(R'P-3)Au]CH(SO2R)(2) (R = R' = Ph) and [(R'P-3/As)Au](2){mu-C(SO2R)(2)} (R = Me, R'P-3 = Ph3P, Ph2MeP, Ph3As; R = Ph, R'P-3 = PPh3, Ph2MeP). Using the same procedure, PhSO2CH2CN was transformed into [(Ph3P)Au](2){mu-C(CN)SO2Ph}. The products are stable to air and moisture and decompose at temperatures well above 150 degreesC. The crystal structure analysis of the diaurated compounds reveals compact A-frame core units in which the central carbon atom forms a CAu2 triangle with an exceedingly small Au-C-Au angle and, consequently, a short aurophilic Au- - -Au contact. The corresponding angles S-C-S (or SAuC(N)) are widened in an overall distorted-tetrahedral environment. Attempted triauration using [(R'P-3)Au]+BF4- reagents was unsuccessful with the disulfones but gave the adduct {[(Ph3P)Au](2)C(SO2Ph)CN[Au(PPh3)]}+BF4-, in which the third gold atom is attached to the nitrile nitrogen atom. Benzyl phenyl sulfone was monoaurated to give the chiral product [(Ph3P)Au]CH(Ph)SO2Ph. 3-[(Triphenylphosphine)gold]pentane-2,4-dione was found to undergo a redistribution reaction induced by tri-tert-butoxyaluminum in benzene solution to give the diaurated diketone [(Ph3P)Au](2){mu-C{C(O)Me}(2)]. Its crystal structure shows a core unit with bonding characteristics similar to those of keto instead of sulfone/cyano substituents.

Abstract The reaction of anhydrous beryllium chloride with nitrogen donors L in diethylether as a solvent under mild conditions affords 1:2 complexes of the type L2BeCl2 [L = benzonitrile (1), pyridine (2), 3,5-dimethylpyridine, pyrrolidine, piperidine (8), and diethylamine (10)]. Structural studies of compounds 1, 2, 8 (CHCl3), and 10 have shown that the complexes have the beryllium centers N2Cl2- tetracoordinated with a distorted tetrahedral geometry of the core unit. In crystals of 8 and 10 these molecules are associated to form helical strings via distinct N-H-Cl hydrogen bonding. The reaction of the weak donor pyrazole (pyz) with (Et2O)2BeCl2 at low temperature gives the mixed complex [(Et2O)(pyz)BeCl2] (4), in which one diethylether molecule is retained in the inner coordination sphere of the metal. In tetrahydrofuran (thf) solution, no reaction is observed with pyrazole, indicating that tetrahydrofuran is the stronger donor as compared to pyrazole, and the (thf)2BeCl2 solvate remains intact. By contrast, with the strong base pyrrolidine (pyrr) the same reaction leads to substitution of one chloride ligand to give the ionic product [(pyrr)3BeCl]+Cl−, (7). Both products (4, 7) have been structurally characterized. At room temperature the reactions with pyrazole or piperidine lead to ether cleavage as a side-reaction which may even become dominant at long reaction times and more forcing conditions. Dinuclear complexes of the type [LBeCl(μ2-OR)]2 are formed, the structures of which have also been determined. The results suggest that hydrogen bonding may assist in the ether cleavage process, since this reaction is not observed for ligands devoid of N-H functions.

Tri(2-thienyl)- and tri(2-furyl)phosphine and -arsine (L) have been introduced as ligands to gold(I) chloride and acetate (AuX). Structural studies have shown that in the 1:1 complexes of the type L-Au-X the gold atoms are bound exclusively to the phosphorus/arsenic centers without any intraor intermolecular approach of the donor atoms of the three heterocycles towards the metal atoms. Intermolecular aurophilic bonding is found in the crystals of the [tri(thienyl)phosphine]gold acetate complex, but is absent in crystals of the chloride complexes. The phosphines L have been quaternized with methyl iodide and the resulting phosphonium salts [LMe]I structurally characterized to provide reference data as to the preferred configurational and conformational motifs. The mass spectra of the gold complexes indicate a high stability of the dinuclear cationic species [(LAu)2X]+ with X = Cl, OAc for all ligands L.

Treatment of gold(I) halide complexes of the type L-Au-X [where L = PPh3, PEt3 with X = Cl, Br, I, or L = 2,6-(MeO)2C6H3PPh2 with X = Cl] with AgSbF6 in the molar ratio 2:1 in dichloromethane/tetrahydrofuran at −78°C affords high yields of di[gold(I)]halonium salts of the formula {X[Au(PR3)]2}+ SbF\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{6}^{-}}}\end{equation*}\end{document} (2-8). A determination of the crystal structures of the four triarylphosphine complexes (2-4, 8) revealed the presence of novel tetranuclear dications with a highly symmetrical structure (point group S4) that arises from self-assembly of the dinuclear monocations through a set of four equivalent aurophilic Au–Au interactions. A comparison with two reference structures of corresponding chloronium perchlorate and bromonium tetrafluoroborate salts with monomeric, dinuclear cations shows that the geometry of the latter is greatly altered on dimerization to optimize the interactions between the closed-shell metal centers (Au: 5d10). Weak metallophilic bonding clearly becomes significant only in crystal lattices where anions with a larger ionic radius (SbF\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{6}^{-}}}\end{equation*}\end{document} vs. BF\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{4}^{-}}}\end{equation*}\end{document}, ClO\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{4}^{-}}}\end{equation*}\end{document}) reduce the otherwise dominant role of strong interionic Coulomb forces. The results indicate that aurophilic bonding is indeed an ubiquitous, quite dependable mode of intermetallic interactions provided that the right environment is chosen to allow the weak forces to become operative.

Dichlorogallane (HGaCl(2))(2) is readily prepared from gallium trichloride and triethylsilane in quantitative yield. Its crystal structure has been determined by single crystal X-ray diffraction. In the chlorine-bridged dimers of crystallographically imposed C(2h) symmetry, the terminal hydrogen atoms are in trans positions. In the reaction with 2 equiv of triethylphosphine, the mononuclear complex (Et(3)P)GaHCl(2) is formed. Thermal decomposition of (HGaCl(2))(2) affords hydrogen gas and quantitative yields of "GaCl(2)" as mixed-valent Ga[GaCl(4)]. Treatment of this product with triethylphosphine gives the symmetrical, Ga-Ga-bonded gallium(II) complex [GaCl(2)(PEt(3))](2) with an ethane-type structure and with the phosphine ligands in a single-trans conformation. The corresponding [GaBr(2)(PEt(3))](2) complex is prepared from Ga[GaBr(4)] and has an analogous structure. (Et(3)P)GaCl(3) has been synthesized and structurally characterized as a reference compound.

[GaCl2(pyrazole)4]+Cl- and [GaCl2(pyrazole)4]+GaCl4- are formed in the reaction of pyrazole and anhydrous gallium trichloride in toluene/diethyl ether. The crystal structure of the chloride salt shows cations in a trans-conufiguration which are associated with the chloride counterions through N-H- -Cl hydrogen bonds.

Treatment of the gold(I) halide complexes LAuCl (where L=PMe3, PEt3, PPh3, PPh2Py) and PP(AuCl)2 [where PP=bis(diphenylphosphino)methane; 1,1′-bis(diphenylphosphino)ferrocene] with 4-amino-2-pyrimidine-thiol (2-SPym-4-NH2) (one or two equivalents as required) in the presence of sodium methoxide provides the corresponding (phosphine)gold(I) thiolate complexes LAu(2-SPym-4-NH2) and PP[Au(2-SPym-4-NH2)]2, respectively. A polyaurated product [(Ph3PAu)2(2-SPym-4-NH2)]BF4 is obtained on treating the thiol with the oxonium complex [(Ph3PAu)3O]BF4. The compounds LAu(2-SPym-4-NH2) (L=PPh3, PPh2Py, PEt3) and [(dppm)Au2(2-SPym-4-NH2)2] have been investigated crystallographically.

Trivinylphosphine has been prepared via an improved synthetic method (from triphenyl phosphite). Vi(3)P undergoes standard quaternization only with methyl iodide to give high yields of [MeVi(3)P]I. The reactions with ethyl iodide, ethyl trifluoromethanesulfonate, benzyl bromide, and vinyl bromide failed to give the analogous phosphonium salts, and insoluble polymeric products were obtained instead. Polymerization also occurs upon attempted halogenation using hexachloroethane or elemental iodine. By contrast, trivinylarsine gives the corresponding arsonium salts with MeI, EtI, and BzBr without complications. A mechanism is proposed for the observed differences in reaction behavior taking into account complementary observations from previous investigations. The activation of the vinyl functions upon quaternization Of Vi(3)P is also evident from the propensity of [MeVi(3)P]I to the spontaneous (or base-catalyzed) addition of up to 3 equiv of methanol to give the three salts [MeVi(n)P(CH2CH2OMe)(3-n)]I (n = 1-3). The three chalkogenides Vi(3)PE (E = O, S, Se) can be prepared by addition of E to Vi(3)P without polymerization, and coordination to AuCl also leads to a stable complex (Vi(3)P)AuCl. No reaction was observed between Vi3P and elemental tellurium. The crystal and molecular structures of [MeVi(3)P]I(CHCl3), [MeVi(2)PCH(2)CH(2)OMe]I, [MeVi(3)As]I, [BzVi(3)As]Br, Vi(3)PO, Vi(3)PSe, and (Vi(3)P)AuCl have been determined, and their conformational characteristics are discussed.

The dissociation equilibria of aqueous solutions of beta-glutamic acid were studied by potentiometric titration and the three pK values determined under standard conditions. The hydrogen beta-glutamate anion beta-GluH(-) was found to be the dominating species in the physiologically relevant pH range 4.0-9.4. Neutralization of beta-glutamic acid by magnesium oxide affords magnesium bis(hydrogen beta-glutamate) Mg (beta-GluH)(2), which crystallizes as the hexahydrate from dilute aqueous solution. A single-crystal X-ray study showed that the beta-GluH(-) anions are not part of the coordination sphere of the magnesium ion. Instead hexahydrated dications [Mg(H2O)(6)](2+) are intimately associated with free beta-GluH(-) anions through a three-dimensional network of H-bonds. This study provides the first structural and conformational reference data for the beta-GluH(-) anion.