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The reaction of the intramolecular frustrated Lewis pair (FLP) tBu2PCH2BPh2 with the amine-boranes NH3 center dot BH3 and Me2NH center dot BH3 leads to the formation of the corresponding FLP-H2 adducts as well as novel five-membered heterocycles that result from capturing the in situ formed amino-borane by a second equivalent of FLP. The sterically more demanding tBu2PCH2BMes2 does not form such a five-membered heterocycle when reacted with Me2NH•BH3 and its H2 adduct liberates dihydrogen at elevated temperatures, promoting the metal-free catalytic dehydrogenation of amine-boranes.

The P-H functionalized Al/P-based frustrated Lewis pair (FLP) Mes(H)P-C[Al{CH(SiMe3)2}2]=C(H)-tBu (3) has the typical functionality of FLPs with Lewis acidic and basic centers in a single molecule and is able to transfer the P bound H atom to activated substrates. Nevertheless, 3 reacted with NH3 only by adduct formation with the N atom coordinated to Al (5). The relatively low basicity of the P atom prevented the for-mation of a hydrogen bridge between P and Al. Similarly, benzil and 3 afforded a simple adduct (6) with only one C=O group bonded to P and Al. The second C=O group and the P-H moiety were unaffected. 6 has two stereogenic centers, and the resulting diastereomers were identified by crystal structure determinations. Migration of the P bound H atom was only observed for substrates containing basic N atoms. Nitriles gave heterocyclic iminophosphine adducts (7) in which the N-H groups were coordinated to the Al at-oms. An isocyanate and two isothiocyanates afforded adducts via Al-X and P-C bond formation (X = O, S), and phosphaurea derivatives (8a to 8c) resulted from H shift to the exocyclic N atoms. A carbodiimide reacted with 3 by the formation of a phosphaguanidine (8d) with the imine N atom coordinated to Al. The latter reactions proceed under mild conditions and represent formally the hydrophosphination of unsaturated substrates.

A series of new homo- and heterometallic lithium and lithium/lanthanide disiloxanediolate complexes were prepared and fully characterized. Three new adducts of dilithium tetraphenyldisiloxanediolate, [(Ph2SiOLi)2O] (2), with simple Lewis bases (Et2O, THF, DME) were prepared by treatment of Ph2Si(OH)OSiPh2(OH) (1) with 2 equiv. of n-butyllithium in the respective donor solvent. This way the adducts [{Ph2SiOLi(Et2O)}2O]2 (3), [{Ph2SiOLi(THF)}2O]2 (4), and [{Ph4Si2O(OLi)2}2(DME)3]∞ (5a) were obtained in a straightforward manner and in nearly quantitative yields. Treatment of anhydrous lanthanide(III) chlorides LnCl3 (Ln = Tb, Lu) with 2 equiv. of 2 in THF afforded the new lanthanide(III) bis(disiloxanediolate) complexes [{(Ph2SiO)2O}2{Li(THF)2}2]TbCl (6) and [{(Ph2SiO)2O}2{Li(THF)2}2]LuCl (7) in high yields. Similar reactions of LnCl3 (Ln = Ce, Nd) with 3 equiv. of 2 provided the heterometallic Li/Ln tris(disiloxanediolate) complexes [{(Ph2SiO)2O}3{Li(DME)}2{Li(THF)}]Ce (8) and [{(Ph2SiO)2O}3{Li(DME)}{Li(Et2O)}{Li(THF)}]Nd (9). All title compounds were structurally characterized through single-crystal X-ray diffraction.

Treatment of the geminal Ga/P-based frustrated Lewis pair (FLP) Mes2P–C(GatBu2)=C(H)–Ph (1) with HX (X = F, Cl, Br, I) afforded the corresponding adducts 2 with the protons bound to the P and the halide anions coordinated to the Ga atoms. Short intramolecular contacts may indicate P–H···X hydrogen bonding interactions. The Br and I compounds (2c, 2d) were accessible in moderate yields even when aqueous solutions of the acids were employed. These unexpected reactions confirm the surprising stability of FLP 1 towards protolysis. Heterocumulenes R–N=C=Y (Y = O, S) and 1 yielded adducts with two different structural motifs. The N=C=Y groups were coordinated to the FLP either via the C=Y (Y = S; Ph–N=C=O) or the C=N bonds (Ph–N=C=O, Et–N=C=O). For phenyl isocyanate the C=O bonded isomer was observed in the solid state, while both isomeric forms were detected in solution. Steric shielding and the hardness of the atoms may influence the formation of the respective isomer. Cleavage of the C=S bonds of isothiocyanates was observed for the first time and afforded a sulfur adduct 9a, in which an S atom (electron sextet) was bound to the lone pair of electrons at phosphorus and to the Lewis acidic Ga atom. Four-membered PCGaY heterocycles resulted, which were also synthesized in high yields by the direct reaction of 1 with propylene sulfide or selenium.

Recently, Bronsted acids, such as phosphoric acids, carboxylic acids, and triflic acid, were found to catalyze the reduction of phosphine oxides to the corresponding phosphines. In this study, we fully characterize the HCl, HOTf, and Me2SiHOTf adducts of triphenylphosphine oxide and find that the thermally stable adduct Ph3POH+OTf– is efficiently converted into triphenylphosphine at 100 °C in the presence of readily available hydrosiloxanes. Under the same reaction conditions, also Ph3POSiMe2H+OTf– selectively affords triphenylphosphine indicating that silylated phosphine oxides are likely intermediates in this process.

The structure, vibrational spectrum, the polymerization and [3+2] cycoaddition reactions of fulminic acid are discussed. In the mass spectra of the solid deposit from gaseous fulminic acid (prepared from sodium fulminate and sulfuric acid) the mass of the adduct of HCNO with hydrogen cyanide was detected, which may be formed by Huisgen 1,3-dipolar cycloaddition. As examples for Heinrich Wieland's experimental mastership the polymerization and his syntheses of fulminic acid and of explosive dinitrosomethanide [HC(NO)(2)](-) are emphasized;the structure of the latter has recently been disclosed by X-ray structure determination.

A series of adducts of LiCN, namely [Li(Me2CO3)CN], [Li(Et2CO3)CN], and [Li(NMP)CN] (NMP = N-methyl-2-pyrrolidone) were prepared by treatment of solvent-free LiCN with the appropriate donor. The starting material for these approaches, donor-free LiCN, was quantitatively prepared from Me3SiCN and Li[Me] in diethyl ether at 0 °C. Alternatively, [Li(NMP)CN] was synthesized by metathesis reaction of LiCl with NaCN in the presence of stoichiometric amounts of NMP. Although [Li(Me2CO3)CN] and [Li(Et2CO3)CN] are water-sensitive compounds and decompose at the exposure to air, [Li(NMP)CN] is stable in air, even at elevated temperatures. The thermal stability of [Li(NMP)CN] was proven by differential thermal analysis (DTA). [Li(NMP)CN] shows thermal stability up to temperatures of about 132 °C. To evaluate the cyanation ability the reactions of 1-bromooctane and 3-bromocyclohexene with unsupported LiCN, [Li(NMP)CN], and a mixture of NaCN/LiCl/NMP were investigated. We found that [Li(NMP)CN] as well as LiCl/NaCN/NMP are efficient cyanation reagents comparable to the expensive and air-sensitive, donor-free LiCN. A product of the chloride-cyanide-bromide exchange could be isolated and structurally characterized by X-ray diffraction.

Syntheses of NHC adducts of bis[tris(trimethylsilyl)silyl]germylene and -stannylene and some structurally related cyclic disilylated stannylenes are reported. Reactions of a cyclic stannylene NHC adduct with gold and silver cyanide led to cationic metal complexes with two cyanostannyl ligands. The Ag complex decomposed further to a cyanostannide. Reactions of bis[tris(trimethylsilyl)silyl]germylene and -stannylene NHC adducts with gold and silver cyanide displayed more unusual coordination chemistry with one silyl group of the ylene unit being transferred to the group 11 metal.

The synthesis of the frustrated carbene-borane 4-(9-borabicyclo[3.3.1]nona-9-yl)-1,3-di-tert-butylimidazolin-2-ylidene (6) was accomplished by deprotonation of the N-heterocyclic carbene (NHC) 1,3-di-tert-butylimidazolin-2-ylidene (1) at the 4-position with n-butyllithium, followed by addition of 9-chloro-9-borabicyclo[3.3.1]nonane (BBN-Cl). The abnormal carbene-borane adduct 5, with the BBN-Cl moiety at the 4-position, was obtained from the reaction of 1 with BBN-Cl; however, its conversion into 6 by treatment with K[N(SiMe3)2] (potassium hexamethyldisilazide, KHMDS) was not achieved. The reactions of 6 with the rhodium(I) complexes [Rh(COD)Cl]2 (COD = 1,4-cyclooctadiene) and [Rh(CO)2Cl]2 afforded the complexes cis-[(6)Rh(COD)Cl] (7) and cis-[(6)Rh(CO)2Cl] (8), with the latter allowing assessment of the σ-donor/π-acceptor properties of 6 by IR spectroscopy. The reactivity of 6 towards carbon dioxide, phenylacetylene and acetonitrile was studied, affording the labile adduct 6·CO2 (9), whereas irreversible deprotonation and formation of the imidazolium phenylalkynylborate 10 and the imidazolium cyanomethylborate 11 was observed for PhCCH and CH3CN. The molecular structures of 5, 7, 8, 10, and 11 were established by X-ray diffraction analyses.

The synthesis and characterization of a novel dimeric N-heterocyclic carbene ligated trimercury hexachloride adduct [(IPr)Hg3Cl6]2 [IPr = (HCNDipp)2C:; Dipp = 2,6-iPr2C6H3] is reported from the disproportionation reaction of IPr with mercury(I) chloride. The molecular structure of this species in the solid state represents a new bonding motif for a mercury halide.

The treatment of N,C,N-chelated antimony(III) and bismuth(III) chlorides [C6H3-2,6-(CH=NR)2]MCl2 [R = tBu and M = Sb (1) or Bi (2); R = Dmp and M = Sb (3) or Bi (4)] (Dmp = 2,6-Me2C6H3) with one molar equivalent of Ag[CB11H12] led to a smooth formation of corresponding ionic pairs {[C6H3-2,6-(CH=NR)2]MCl}+[CB11H12]– [R = tBu and M = Sb (7) or Bi (8), R = Dmp and M = Sb (9) or Bi (10)]. Similarly, the reaction of C,N-chelated analogues [C6H2-2-(CH=NDip)-4,6-(tBu)2]MCl2 [M = Sb (5) or Bi (6), Dip = 2′,6′-iPr2C6H3] gave compounds {[C6H2-2-(CH=NDip)-4,6-(tBu)2]MCl}+[CB11H12]– [M = Sb (11) or Bi (12)]. All compounds 7–12 were characterized with 1H, 11B and 13C{1H} NMR spectroscopy, ESI-mass spectrometry, IR spectroscopy, and molecular structures of 7–9 and 12 were determined by the help of single-crystal X-ray diffraction analysis. In contrast, all attempts to cleave also the second M–Cl bond in 7–12 using another molar equivalent Ag[CB11H12] remained unsuccessful. Nevertheless, the reaction between 7 (or 8) and Ag[CB11H12] produced unprecedented adducts of both reagents namely {[C6H3-2,6-(CH=NtBu)2]SbCl}22+[Ag2(CB11H12)4]2– (13) and {[C6H3-2,6-(CH=NtBu)2]BiCl}+[Ag(CB11H12)2]– (14) in a reproducible manner. The molecular structures of these sparingly soluble compounds were determined by single-crystal X-ray diffraction analysis.

The reaction of 1,3-diisopropylimidazolin-2-ylidene (iPr2Im) with diphenyldichlorostannane and dimethyldichlorostannane, respectively, leads to the formation of the adducts (iPr2Im)·SnPh2Cl2 (1) and (iPr2Im)·SnMe2Cl2 (2). These compounds are stable in solution to temperatures up to 80 °C for several days and rearrangement to backbone-tethered bis(imidazolium) salts or ring expansion reaction to six membered heterocyclic rings was not observed. The reaction of iPr2Im with triphenylstannane Ph3SnH leads to reductive dehydrocoupling of the stannane to yield distannane Sn2Ph6 and iPr2ImH2. Thus, the reactivity of these tin compounds is completely different compared to those of the lighter congener silicon, for which rearrangement (chlorides) and NHC ring expansion (hydrides) was reported earlier.

Addition of N-heterocyclic carbenes [L = 1, 3-di-tert-butylimidazolin-2-ylidene (ItBu), 1, 3-diisopropyl-4, 5-dimethylimidazolin-2-yildene (IiPrMe2), 1, 3-di-mesitylimidazolin-2-yildene (IMes), and 1, 3-bis(2, 6-diisopropylphenyl)imidazolin-2-yildene (IPr)] to manganocene [(C5H5)2Mn] forms the neutral Lewis base adducts [(C5H5)2Mn(L)] (2–5) in moderate yields. Complexes 2–4 were structurally characterized and their solid-state magnetism was investigated between T = 2.6–300 K. In contrast to literature reports, these materials exclusively adopt a high-spin (S = 5/2) ground state.

15N NMR spectra of several aminoboranes (Me2B–NMe2, Cl2B–NMe2, Br2B–NMe2, OCH2CH2OB–NMe2), three N-pyrrolylboranes, and an iminoborane (tBu–B≡N–tBu) was measured. The spin-spin coupling constants 1J(15N, 11B) were resolved at elevated temperatures. In the case of the iminoborane at 105 °C, the coupling constant 1J(14N,11B) = 57 Hz could also be determined from the 11B NMR spectrum [from 15N NMR 1J(15N,11B) = 81 Hz]. Generally, there is no correlation between the magnitude of 1J(15N,11B) and the bond length dBN. The values 1J(15N,11B) indicate that changes in σ bonding affect their magnitude, and the nature of the lone pair of electrons at nitrogen is of great importance. The calculated NMR parameters of an adduct of the iminoborane with an N-heterocyclic carbene, show that the bonding situation around the BN double bond in the adduct is comparable with imines.

The Al/P-based frustrated Lewis pair (FLP)Mes2P–C(=CH–Ph)–Al(CMe3)2 (1) reacted with carboxylic acid chlorides [Cl–C(=O)Me, Cl–C(=O)Et, Cl–C(=O)CH2CMe3] by dehydrochlorination. The released hydrogen chloride molecules were captured by one equivalent of the FLP 1 to yield the previously published HCl adduct, Mes2P(H)+–C(=CH–Ph)–Al(Cl)(CMe3)2– (3). This remarkable reaction resulted in the formal generation of ketenes, R(H)C=C=O, which were trapped by a second equivalent of 1 via the coordination of the C=O groups to the Lewis acidic aluminum and the Lewis basic phosphorus atoms (4 to 6). Five-membered AlC2PO heterocycles were formed, which had an exocyclic C=C double bond. Quantum chemical DFT calculations were performed to study the thermodynamic driving forces of the adduct formation and to identify reactive intermediates with respect to a mutual activation of this process by phosphorus and aluminum atoms.

Reaction of NaPyrtBu2 [PyrtBu2 = 2, 5-(Me3C)2C4H2N] and KPyrtBu2Me2 [PyrtBu2Me2 = 2, 5-(Me3C)2-3, 4-Me2C4N] with MnI2(thf)3 resulted in the isolation of the first bis(pyrrolyl)manganese(II) complexes. However, different coordination modes are realized depending on the identity of the Pyr-ligand. For example, the MnII atom is κN coordinate in [(κN-PyrtBu2)2Mn] (1-Mn), whereas several different species were isolated with the more bulky PyrtBu2Me2 ligand. Depending on the reaction conditions the κN-coordinate complex [(κN-PyrtBu2Me2)2Mn] (2-Mn′) is initially formed, but converts on sublimation to the η3 coordinate isomer [(η3-PyrtBu2Me2)2Mn] (2-Mn′). In some cases we could also identify a THF adduct of 2-Mn to give [(κN-PyrtBu2Me2)(η2-PyrtBu2Me2)Mn(thf)] [2-Mn(thf)], in which one PyrtBu2Me2 ligand binds in a κN coordination mode, while the other is best described as η2-PyrtBu2Me2. These complexes were characterized by elemental analyses and X-ray diffraction studies. Density functional theory (DFT) computations confirm that the potential energy surface between the different hapticities is rather flat for these MnII high-spin species (S = 5/2).

Single crystals of [Fe(η5-C5H4)(η5-C5H5)]2Li2(thf)4 (1) were obtained from a tetrahydrofuran solution containing monolithioferrocene. The title compound crystallizes in the monoclinic space group P21 with a = 9.6589(5) A, b = 17.4285(9) A, c = 30.3116(15) A, β = 91.911(2)° and V = 5099.8(5) A3 with three independent molecules of 1. All individual molecules feature a non- symmetric almost planar Li2C2 four-membered ring with two shorter (2.118–2.215 A) and two longer Li–C distances (2.257–2.309 A). The lithium cations are each coordinated by two carbanionic atoms of two ferrocenyl substituents and two tetrahydrofuran molecules in a distorted tetrahedral fashion. All ferrocenyl moieties display an eclipsed conformation of the C5 rings.

The Al/P-based Frustrated Lewis Pair (FLP) Mes2P-C(=CH-Ph)-Al(CMe3)2 (1) reacted with anhydrous HF and HCl as an ion pair receptor by coordination of the proton to phosphorus and the halide anion to aluminum. Short intramolecular distances and the molecular conformation indicate the presence P–H···X–Al hydrogen bonds (X = F, Cl) and an approach of the phosphorus and halogen atoms with a possible weak P···X interaction.

Polyphosphides composed by late transition metal ions with closed d10 shells are subject of this review. Recent progress has been made during the past years in this field and many new compounds have been discovered. The spectrum of compounds extends from classical binary and ternary compounds, adduct phases of metal halides and molecular species to composites of intermetalloid clusters and molecular anion substructures. Phosphorus is highly reactive to late transition metals forming d10 ions and they entirely react to a plenthora of materials. Only a handful of elements do not form binary compounds with phosphorus and the number is decreasing. This review is focussed on synthetic procedures and the structure property relations of d10 ion polyphosphides. A brief overview is also given to the progress in phosphorus allotrope chemistry and their perspectives and applications. Especially black phosphorus as active material for batteries and its de-laminated form “phosphorene” is added.

The yield of the Lewis acid adducts of a copper-tosylnitrene intermediate and their decay are dependent on the Lewis acidity of the redox innocent metal ions. Surprisingly, however, their spectroscopic properties and reactivity in nitrene transfer reaction with PPh3 are independent of the nature of the Lewis acid used. The result provides some new insights into the structure and reactivity of the Lewis-acid bound copper nitrene complexes.

The complexes [MF4(py)4][MF6], [MF4(2, 2′-bipy)2][MF6] and [MF4(dppe)2][MF6]·½CH3CN (M = Nb, Ta) were obtained from niobium and tantalum pentafluoride by reaction with the donor ligands pyridine (py), 2, 2′-bipyridine (2, 2′-bipy), and bis(diphenylphosphanyl)ethane (dppe) in acetonitrile solution. The complexes were characterized by their vibrational spectra and, in case of the pyridine and dppe adducts, by their crystal structure. The pairs of corresponding niobium and tantalum compounds [NbF4(py)4][NbF6] and [TaF4(py)4][TaF6], as well as [NbF4(dppe)2][NbF6]·½CH3CN and [TaF4(dppe)2][TaF6]·½CH3CN were found to be isostructural and to consist of isolated, distorted square-antiprismatic cations [MF4D4]+ (D = donor atom) and octahedral [MF6]– anions. In all cases, the donor ligands induce self-ionization of these pentafluorides.

The addition of trimethylsilyl trifluoromethanesulfonate TMS-OTf (CF3SO3 = OTf, triflate) to hexaphenyl carbodiphosphorane PPh3=C=PPh3 (1) in toluene yields the silylated carbodiphosphorane [Me3SiC(PPh3)2][OTf] (2). Compound 2 represents the first silylated carbodiphosphorane characterized in solution and in the solid state. 2 is an air-sensitive compound but stable in solution and in the solid state in an inert atmosphere as shown by heteronuclear NMR experiments and also by X-ray diffraction analysis. Compound 2 crystallizes in the monoclinic space group P21/n with the cell dimensions a = 1161.7(1), b = 1714.4(1), c = 1903.3(1) pm; β = 102.74(1)° and Z = 4. Structure, frontier orbitals, and dissociation energies for 2 were determined by density functional theory-based computations highlighting the character of 2 as a Lewis acid adduct of a carbon(0) compound.

The reaction of CrO2Cl2 with 2, 2?-bipyridyl or 1, 10-phenanthroline (diimine) in CCl4 or anhydrous CH3CO2H solution, produces orange-brown diamagnetic [CrO2Cl2(diimine)]. The X-ray structure of [CrO2Cl2(2, 2?-bipy)] shows a six-coordinate central chromium(VI) atom with cis-dioxo groups trans to the diimine. In contrast, the diimines react with CrO3 in CH3CO2H / conc. aqueous HCl to form bright red paramagnetic CrV complexes, [CrOCl3(diimine)]. The X-ray structure of [CrOCl3(2, 2?-bipy)] shows a six-coordinate central chromium atom with mer-chlorines and the diimine trans to O/Cl. The addition of [2, 2-bipyH2]Cl2 to a solution of CrO3 in CH3CO2H saturated with HCl gas, produces the CrV anion [2, 2?-bipyH2][CrOCl4]Cl, which loses HCl on heating in vacuo to form [CrOCl3(2, 2?-bipy)]. IR, UV/Vis, and 1H NMR spectra (CrVI only) are reported for the new complexes. Attempts to extend these routes to oxygen donor ligands, including ethers and phosphine oxides, were unsuccessful. The diimine complexes are the first structurally autheticated adducts of chromium(VI) and (V) oxide-chlorides with neutral ligands.

A great number of binary neutral phosphorus sulfides was discovered and investigated. However all stable representatives of this family of compounds adopt a polycyclic structure in contrast to their lighter homologues, the nitrogen oxides. Acyclic representatives can be stabilized by adduct formation with a nitrogen base. The bis(pyri- dine) adduct py2P2S5 of the unstable acyclic phosphorus sulfide P2S5 is readily obtained stirring P4S10 in pyridine at ambient temperature. X-ray diffraction studies on single crystals of py2P2S5·0.5 py (1b) show a N2O5 like structure for the P2S5 framework. The long P-N distances of 1.86 A indicate only weak coordination of the pyridine

A sulfide-bridged diiron(II) complex bearing a cis-N2H4 (hydrazine) ligand has been prepared by reaction of LFeII(μ-S)FeIIL (1; L = sterically encumbered βdiketiminate ligand) with 2 molar equivalents of N2H4. The metastable diiron(II) hydrazine complex LFeII(μ-S)(μH N-NH2)FeII (3) is formed, as shown by crystallography, and NMR, vibrational, and electronic absorption spectroscopies. Compound 3 has been crystallographically characterized as its DBU (1,8-diazabicyclo[5.4.0]undec-7$ene) adduct, which exhibits weak N-H···DBU hydrogen bonding. The synthetic process evolves roughly 2 equivalents of NH3. The cis-N2H4 bridge in 3 may be relevant to the structure and function of intermediates on the FeMoco of nitrogenase.

This report describes the dimerisation of glutathione, and by extension, other cysteine-containing peptides or protein fragments, with a 5, 5’-disubstituted-2, 2’-bipyridine or 6, 6”-disubstituted-2, 2’:6’,2”-terpyridine unit. The resulting bipy-GS2 and terpy-GS2 were investigated as potential metal ion dependent switches in aqueous solution, and were found to predominantly adopt the transoid conformation at physiological pH. Metal complexation with CuII and ZnII at this pH has been studied by UV/Vis, CD, NMR and ion-mobility mass spectrometry. ZnII titrations are consistent with the formation of a 1:1 ZnII:terpy-GS2 complex at pH 7.4, but bipy-GS2 was shown to form both 1:1 and 1:2 complexes with the former being predominant under dilute micromolar conditions. Formation constants for the resulting 1:1 complexes were determined to be log KM 6.86 (bipy-GS2) and 6.22 (terpy-GS2), consistent with a higher affinity for the unconstrained bipyridine, compared to the strained terpyridine. CuII coordination involves the initial formation of 1:1 complexes, followed by 1.5Cu:1bipy-GS2 and 2Cu:1terpy-GS2 complexes at micromolar concentrations. Binding constants for formation of the 1:1 complexes (log KM 12.5 (bipy-GS2); 8.04 and 7.14 (terpy-GS2)) indicate a higher affinity for CuII than ZnII. Finally, ion-mobility MS studies detected the free ligands in their protonated form, and were consistent with the formation of two different Cu adducts with different conformations in the gas-phase. We illustrate that the bipyridine and terpyridine dimerisation units can behave like conformational switches in response to Cu/Zn complexation, and propose that in future these can be employed in synthetic biology with larger peptide or protein fragments, to control large scale folding and related biological function.

Alanes of the formula HxAlX3–x (x = 0, 1, 2, 3; X = Cl, Br, I) and the mixed halogen species HAlClBr were synthesized as N-methyl-piperidin (nmp) adducts HxAlX3–x·znmp (z = 1, 2) and HAlClBr·2nmp by different routes. The crystal and molecular structures of (H3Al·nmp)2, H2AlBr·2nmp, H2AlI·2nmp, the isotypic and isomorphous HAlBr2·2nmp, HAlI2·2nmp, as well as ACl3·nmp, ABr3·nmp, AI3·nmp, and HAlClBr·2nmp are described. The aluminum atoms in these molecular structures either form a pentagonal bipyramid as coordination sphere with the amine bases in apical positions or are in the center of a distorted tetrahedron (AlCl3·nmp, ABr3·nmp, AI3·nmp). In the nmp adduct of alane, a central Al2H2 ring is formed by dimerisation of AlH3, each aluminum atom displaying a further nmp ligand together with two terminal hydrogen atoms. The influence of the halogen atoms on the hydrogen bonds in the iso-structural compounds were studied by IR spectroscopy, showing in both series H2AlX·2nmp and HAlX2·2nmp (X = Cl, Br, I) a dependence of ν(Al–H) on the substitution pattern: 1770.2–1775.2–(not measured) cm–1 (H2AlX) and 1785.0–1788.0–1791.0 cm–1 (HAlX2). The δ values of the 27Al-NMR spectra in solution show dependences on the halide numbers bonded to aluminum and display a regular growth with heavier element in the H2AlX·2nmp series δ (27Al): 121.2 (Cl), 126.0 (Br), 131.5 (I)], whereas they have an unsteady evolution in the HAlX2·2nmp series [δ (27Al): 118.0 (Cl), 122.0 (Br), 108.0 (I)] and the AlX3·nmp series [δ (27Al): 102.1 (Cl), 104.8 (Br), 61.9 (I)].

Reactions of HC(pz)3 and HC(4-Mepz)3 with MgBu2 and Mg{N(SiMe3)2}2 gave the zwitterionic complexes [Mg{C(pz)3}2] (2) and [Mg{C(4-Mepz)3}2] (4), respectively, containing “free” pyramidal carbanions (pz = pyrazolyl). The solid-state structure of 2 has been determined. Reactions of 2 and 4 as well as the recently reported homo- and heteroleptic complexes [Mg{C(3, 5-Me2pz)3}2] (1) and [Mg{C(3, 5-Me2pz)3}{C(pz)3}] (3) with the Lewis acid AlEt3 furnished the bi- and trimetallic complexes [Mg{C(pz)3}2(AlEt3)2] (5), [Mg{C(pz)3}(AlEt3){C(3, 5-Me2pz)3}] (6), and [Mg{C(4-Mepz)3}2(AlEt3)2] (7). Based on NMR spectroscopic investigations, including an X-ray structural analysis on single crystals of 5, only the parent tris(pyrazolyl)methanide {C(pz)3}– and the 4-methyl-substituted ligand scaffolds form C-bound adducts with the Lewis acid. By quantifying the steric bulk of κ3N-coordinated {C(pz)3}– it could be shown that its steric features are similar to those of bulky phosphine ligands.

4, 4′,5, 5′-Tetranitro-2, 2′-bisimidazole (TNBI) was synthesized by nitration of bisimidazole (BI) and recrystallized from acetone to form a crystalline acetone adduct. Its ammonium salt (1) was obtained by the reaction with gaseous ammonia. In order to explore new explosives or propellants several energetic nitrogen-rich 2:1 salts such as the hydroxylammonium (3), guanidinium (4), aminoguanidinium (5), diaminoguanidinium (6) and triaminoguanidinium 7 4, 4′,5, 5′-tetranitro-2, 2′-bisimidazolate were prepared by facile metathesis reactions. In addition, methylated 1, 1′-dimethyl-4, 4′,5, 5′-tetranitro-2, 2′-bisimidazole (Me2TNBI, 8) was synthesized by the reaction of 2 and dimethyl sulfate. Metal salts of TNBI can also be easily synthesized by using the corresponding metal bases. This was proven by the synthesis of pyrotechnically relevant dipotassium 4, 4′,5, 5′-tetranitro-2, 2′-bisimidazolate (2), which is a brilliant burning component e.g. in near-infrared flares. All compounds were characterized by single crystal X-ray diffraction, NMR and vibrational spectroscopy, elemental analysis and DSC. The sensitivities were determined by BAM methods (drophammer and friction tester). The heats of formation were calculated using CBS-4M electronic enthalpies and the atomization method. With these values and mostly the X-ray densities different detonation parameters were computed by the EXPLO5 computer code. Due to the great thermal stability and calculated energetic properties, especially guanidinium salt 4 could be served as a HNS replacement.

The N, N′-annulated dichlorodiazaphosphole 1 was prepared in 55 % yield by the reaction of cyclohexanone azine (c-HA) with two equivalents of PCl3 in pyridine. Compound 1 revealed one-dimensional chains in crystal with short intermolecular interactions [3.194(1) A] between phosphorus atoms of adjacent molecules. Treatment of c-HA with MeLi (2 equiv. in Et2O) followed by addition of PCl3 gave 1 in 33 % yield. An amount of c-HA isomerizes in these conditions to form corresponding hexahydroindazole derivative 3, which further reacts with 1 to give diazaphosphole 5 as transannulation product. Copper monochloride forms an (1:1) adduct with 5, which was characterized by its X-ray crystal structure. Only one equivalent of PCl3 reacts with c-HA in Et2O/Et3N mixture to form diazaphospholium chloride 2 and hexahydroindazole 3.

The optical spectra of the mono tetrahydrofuran (1), mono triphenylphosphinoxide (2) and bis cyclohexylisocyanide (3) adducts of the tris(bis(trimethylsilyl)amido)samarium(III) (Sm(btmsa)3) moiety as well as those of the bis tetrahydrofuran (4) and partly those of the bis triphenylphosphinoxide (5) of the tris(bis(dimethylsilyl)amido)samarium(III) moiety have been recorded at room and low temperatures. From the spectra obtained, the underlying crystal field splitting patterns could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian. The values of the crystal field parameters B of the OPPh3 adducts are much less negative than those of the remaining adducts or that of the base free compound.

The carbodiphosphorane CO2 adduct (2) reacts slowly with 1, 2-dichloroethane to give (HC{PPh3}2)Cl (5) as result of HCl abstraction along with the ester-like salt (ClCH2CH2O(O)CC{PPh3}2)Cl (4) from nucleophilic substitution of one Cl– by 2. Both compounds could be separated by fractional crystallization. Attempts to dissolve 2 in 1, 2-difluorobenzene leads to small amounts of the hydrolysis product (HC{PPh3}2)(HCO3)·H2O (6·H2O) caused by some humidity in the solvent. All compounds could be crystallized and the structures studied by X-ray analyses and 31P NMR spectroscopy.

Contact with SO2 causes almost immediate dissolution of tetraalkylammonium halides, R4NX, (R = CH3 (Me), X = I; R = C2H5 (Et), X = Cl, Br, I; R = C4H9 (nBu), X = Cl, Br), with the formation of an adduct, [R4N]+[(SO2)nX]– (n = 1–4). Vapor pressure measurements indicate the proclivity for SO2 uptake follows the order N(CH3)4+ < N(C2H5)4+ < N(C4H9)4+. This trend is in accord with the Jenkins–Passmore volume-based thermodynamic model. Born–Haber cycles, incorporating the lattice energy and gas phase energy terms, are used to evaluate the energetic feasibility of reactions. Density functional theory calculations (B3PW91; 6-311+G(3df)) have been used to calculate the energetics of (SO2)nX– (X = Cl and Br) anions in the gas phase. The experimental studies show that tetraalkylammonium halides are feasible sorbents for SO2. In order to correlate the theoretical model, experimental enthalpy, ΔrH° and entropy, ΔrS° changes have been determined by the van't Hoff method for the binding of one SO2 molecule to (C2H5)4NCl, resulting in the liquid adduct (C2H5)4NCl·SO2. The structure of the analogous 1:1 bromide adduct, (C2H5)4NBr·SO2, has been determined by single-crystal X-ray diffraction (monoclinic, P21/c, a = 9.1409(14) A, b = 12.3790(19) A, c = 11.3851(17) A, β = 107.952(2)°, V = 1225.6(3) A3). The structure consists of discrete alkylammonium cations, bromide anions and SO2 molecules with short contacts between the anion and SO2 molecules. The (C2H5)4N+ cationadopts a transoid conformation with D2d symmetry, and represents a rare example of a well-ordered (C2H5)4N+ cation in a crystal structure. The Br– anions and SO2 molecules forms a chain, (SO2Br–)n, with bifurcated contacts. Non-bonding electron pairs on the halide anions engage in electrostatic interactions with the sulfur atoms and charge-transfer interactions with the antibonding S–O orbitals of the bound SO2 moiety. Raman and 17O NMR spectra provide compelling evidence for a charge-transfer interaction between SO2 molecules and the halide ions.

The antimony aminoalkoxide and aminothiolates Sb(ECH 2CH 2NMe 2) 3 [E = O (1), S (2)] were synthesized and their ability to form adducts with other metal moieties investigated. Compound 1 forms 1:1 adducts with NiI 2 (3) and M(acac) 2 [M = Cd (4), Ni (5)], while 2 undergoes ligand exchange with AlMe 3 to afford Me 2AlSCH 2CH 2NMe 2 (6). The structures of 2-4 and 6 were determined. Compound 2 incorporates three S, N-chelating ligands though the interaction with nitrogen is weaker than in analogous alkoxide complexes. Product 3 reveals one iodine has migrated from nickel to antimony, and all three alkoxide ligands bridge the two metals through μ 2-O atoms. In contrast, in 4, only one alkoxide links the antimony and cadmium. Compound 6 adopts the same structure, a chelating S,N ligand generating a tetrahedral center at aluminum, as known tBu 2AlSCH 2CH 2NR 2 species (R = Me, Et).

A novel aza-aromatic base adduct of cadmium(II) thenoyltrifluoroacetonate, [Cd(phen)(ttfa)2] (1), (phen = 1, 10-phenanthroline; ttfa = thenoyltrifluoroacetonate) was synthesized and characterized by elemental analysis, IR, 1H NMR, and 13C NMR spectroscopy, thermal analysis as well as X-ray crystallography. The single-crystal structure of this complex shows that the coordination number of the Cd2+ ions are six with two nitrogen donor atoms from aza-aromatic base ligands and four oxygen donors from two thenoyltrifluoroacetonate ligands. The supramolecular features in these complexes are directed by weak directional intermolecular interactions. The structure of the title complex was optimized by density functional theory calculations. Calculated structural parameters and IR spectra for the title complex are in agreement with the crystal structure. The CdO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant. The average size of the nanoparticles was estimated by the Scherrer equation with the diameter about 45 nm. The morphology and size of the prepared CdO samples were further observed using SEM.

The new Lewis-acid-base adduct of WSF4 and pyridine, WSF4·NC5H5, was prepared by combination of WSF4 and excess pyridine. The WSF4·NC5H5 adduct was characterized by 1H, 13C, 19F NMR, and Raman spectroscopy, and by X-ray crystallography. Calculations of the vibrational frequencies at the DFT level of theory aided in the assignment of the Raman spectrum. In contrast to WOF4, no experimental and theoretical evidence was found for the existence of a WSF4·2NC5H5 adduct.

New crystalline mercury halide adducts with polyetheras ligands were isolated, characterized, and identified as trans-[HgIICl₂(diox)₂]n (1) and trans-[HgIII₂(diox)]n (2). The compounds were obtained from the metal halide salts in solution of 1,4-dioxane and can be considered as “cutting-out” products from the metal halide as they show similarity in the arrangement with starting compounds.

The molecular alumosiloxane (Ph2SiO)8(AlO(OH))4·4Et2O (1) reacts with 4,4′-bipyridine and azobipyridines (4,4′-azobipyridine and 3,3′-azobipyridine) to form polymer adducts. The acidic hydroxygroups of 1 interfere with the pyridine-nitrogen atoms to form O···H···N hydrogen bridges which are the source of one- and two-dimensional networks. As reaction products we have characterized (Ph2SiO)8[AlO(OH)]4·2p-(C5H4N)2 (2), (Ph2SiO)8[AlO(OH)]4·1.5p-(C5H4N)2N2·C4H8O (3) and (Ph2SiO)8[AlO(OH)]4·2m-(C5H4N)2N2 (4). In the crystal structure of 2, the supramolecular adduct forms a one-dimensional connection. In 3 and 4 two-dimensional connections are formed. The azobipyridine ligands in solution show cis-trans-isomerisation by application of light even in the supramolecular state (as base adducts of (Ph2SiO)8[AlO(OH)]4).

The reaction of main group III trimethyls, Me3M, with phenylchalcogenols HEPh leads to dimethyl earthmetal phenylchalcogenolates [(Me2MEPh)n] with M = Ga and E = S (1), Se (2), Te (3), M = In and E = S (4), Se (5), Te (6) and M = Tl and E = S (7), Se (8), Te (9). Alternatively, reaction between Me3M and Me3SiEPh with elimination of SiMe4 is possible for E = Se, Te if a polar solvent is applied, in order to stabilize the initial adduct [Me3M–E(Ph)SiMe3]. Additionally, for M = Tl and E = S the dimeric adduct [{Me2TlSPh(TlMe3)}2] (10) was isolated and structurally characterized. Single crystals and microcrystalline samples of compounds 1 to 9 were examined by X-ray crystallography and polymeric as well as dimeric structures were found. Depending on the size of main group III and VI atoms, sterically shielded polymeric chains or layer-like structures are obtained. The smaller metal atoms M = Ga, In are fourfold coordinated and these compounds exhibit polymorphism. This observation is consistent with quantum chemical calculations that show the syn- and anti-orientation of phenyl groups in a dimer to be energetically nearly equivalent. For M = Tl the coordination number is increased to 5 or 6 by additional coordination of chalcogen atoms with relatively long Tl–E bonds. Variable temperature NMR spectroscopy and molecular weight measurements indicate fast exchange and the presence of several different molecular structures in solution.

Four new copper(II) complexes [Cu(HL)(im)](ClO4)2 (1), [Cu(HL)(py)](ClO4)2 (2), [Cu2(HL)2(bpy)2](ClO4)4·H2O (3), and [Cu2(HL)2(bpy)](ClO4)4·H2O (4) (im = imidazole; py = pyridine; bpy = 4,4′-bipyridine) were synthesized by reactions of tripodal ligandN1-(2-aminoethyl)-N1-(1H-imidazol-4-ylmethyl)-ethane-1,2-diamine(HL) and Cu(ClO4)2·6H2O with different nitrogen-containing aromatic ligands. It was found that the size of the N-containing aromatic ligand, and the ratio of the ligand and metal ion, have great influence on the formation and structure of the complexes.

Five neutral mixed-ligand mononuclear square-pyramidal copper(II) complexes of the type [Cu(cpf)(Ln)Cl] (cpf = ciprofloxacin and Ln = phenanthroline derivatives) (1–5) were synthesized and characterized. The complexes were screened for their antibacterial activity and bactericidal activity against two Gram(+ve) and three Gram(–ve) microorganisms and the results showed that all complexes studied are more potent than the quinolone standard drug ciprofloxacin. Absorption titration, viscosity, and thermal denaturation measurement studies revealed that each of these square-pyramidal complexes moderately interacts with calf thymus DNA. The binding constants for mixed ligand complexes are in order of 1.5 × 104–3.0 × 104 M–1. Based on the data obtained in the DNA binding studies an intercalative mode of binding is suggested for these complexes. The nucleolytic cleavage activity of adducts and gyrase inhibition assay were studied on double stranded pUC19 DNA by gel electrophoresis experiments. From the SOD mimic study; the concentration of complexes ranging from 0.45 μM to 1.45 μM are enough to inhibit the reduction rate of NBT by 50 % (IC50) in NADH/PMS system.