Ines Starke

Homologous series of the PdCl2 and PtCl2 complexes of maleonitrile-dithiacrown ethers: synthesis, crystal structures, NMR spectroscopy and mass spectrometry

Abstract The chelate complexes of maleonitrile-dithiacrown ethers mn-12S 2 O 2 –mn-21S 2 O 5 (mn=maleonitrile) and of the acyclic ligand mn-S 2 with salts, respectively, of Pd(II) and Pt(II) were studied in the solid state, in solution and in the gas phase. The structures of [MCl 2 (mn-S 2 O n )] ( n =2–5) (M=Pd, Pt) were investigated experimentally by X-ray analysis, mass spectrometry and 1D and 2D NMR spectroscopy in solution; the complex formation was studied by 1 H, 13 C and 195 Pt NMR titration experiments. As techniques the fast atom bombardment (FAB), desorption ionization (DEI) and electrospray mass spectrometry (ESMS) have been applied. The results of the extraction investigations of the maleonitrile-dithiacrown ethers prove the stability of the complex [PdCl 2 (mn-S 2 O 2 )] to be much higher than that of the other ligands with the same metal ion (H.-J. Holdt, K. Gloe, H. Bukowsky, H. Stephan, Chem. Eur. J. in preparation). The explanation for the preferred complexation of mn-S 2 O 2 regarding the salts PdCl 2 and PtCl 2 is given. For the ligands with smaller ring sizes, mn-12S 2 O 2 and mn-15S 2 O 3 , one sulfur atom was found in R and the second sulfur atom in S -configuration. In the complexes of the larger macrocycle ligands as well as that of the acyclic ligand mn-S 2 , both sulfur donor atoms have the same configuration. These differences in the configuration at the S-donor atoms of the complexes and the free ligands depending on the ring size have been never described before.

NMR spectroscopic study of solution structure and complexational behaviour of bis-benzo crown ethers

Abstract The 1 H, 13 C and 15 N NMR spectra of a series of polymethylene-bridged carbonylhydrazone bis(benzo-15-crown-5 ethers) 1–9 ( n = 0−8) and bis(benzo-18-crown-6 ethers) 10–11 ( n = 1,5) were recorded and assigned by COSY, HMQC and HMBC 2D NMR experiments. The stereoisomerism of the bridging RCHNNHC(O)(CH 2 ) n moieties was studied by various useful NMR parameters ( δ CO , 3 J C,H , 1 J NH , 1 J CH , 2 J C(O)NH and intramolecular NOEs. Three isomers (E/E), E/Z and Z/Z, respectively) with respect to the amide bond proved to exist, NH and the imine lone pair were found in anti position. The OCH 2 CH 2 O fragments occur as rapidly interconver gauche conformations and the α-CH 2 groups more or less in-plane with the adjacent phenyl ring moiety as concluded from the corresponding 13 C chemical shifts and NOEs, respectively. The solvent dependence of the amide isomerism was studied and the complexation of the bis-benzo crown ethers to Na + and K + cations carefully investigated. The conformation of the free and complexed bis-crown ethers was obtained. Both the complexation mechanism (sandwich, double-sandwich, inclusion and addition complex) and the conformational equilibrium about the CHPh bond proved to be strongly dependent on the bis-benzo crown ethers 1–11 studied. The conformational study is accompanied and corroborated by molecular dynamics and quantum-chemical calculations.

Quinoxalines XV. Convenient synthesis and structural study of pyrazolo[1,5-a]quinoxalines.

A series of aryloxymethylquinoxaline oximes, hitherto unknown and synthesized from the corresponding aldehydes, afforded in only one step pyrazolo[1,5-a]quinoxalines in the presence of acetic anhydride at high temperatures. A formal [3,5]-sigmatropic rearrangement was proposed as the mechanistic rationale for this unprecedented transformation. Saponification with potassium hydroxide furnished the free phenol derivatives which were studied by NMR spectroscopy and accompanying theoretical DFT calculations, establishing intramolecular hydrogen bonding and the spatial magnetic properties. Additionally, mass spectrometric fragmentation was investigated by B/E-linked scans and collision-induced dissociation experiments. The fragmentation pattern devoted a new gas phase rearrangement process, which proved to be unique and characteristic for pyrazolo[1,5-a]quinoxalines.

1H, 13C and 15N NMR study of the solution structure of meta-bridged bis(benzo-15-crown-5 ether)s

Abstract The 1 H and 13 C NMR spectra of the three isomers of the bis(benzo-15-crown-5 ether) studied and their complexes with K + and Na + cations were recorded and assigned by H,H-COSY and HMQC 2D-NMR experiments. The three isomers with respect to the amide C(O)NH bonds could be assigned by 15 N NMR spectroscopy and heteronuclear coupling constants. Relevant conclusions about the isomerism were deduced from the 1 J 15N,1H coupling constants of the various NH amide groups and the 1 J 13C,1H coupling constants of C 3 H and C α H 2 C(O) groups, respectively. From 2D-ROESY NMR experiments, further stereochemical information about the preferred conformation of the free and complexed bis(benzo-15-crown-5 ether) was obtained. The conformational study is accompanied and corroborated by molecular dynamics and quantum chemical calculations. In the case of the K + complex, a “sandwich”-like complex could be determined. This structure clearly proved to be already preorganized in the non-complexed host molecule. For the corresponding Na + complex, the “usual” 2:1 host-guest complex was detected.

Host–guest complexation of imine-type meta-bridged bis(benzo crown ether)s with alkali cations in the gas phase under fast atom bombardment conditions

The complexation of a series of bis(benzo crown ether)s of variable ring size and length of the linking chain with Na+, K+ and Cs+ was studied in the gas phase by fast atom bombardment mass spectrometry in nitrobenzyl alcohol/glycerol as a matrix. Both 2:1 (conventionally within the cavity of the crown ether units) and 1:1 complexes (a sandwich-like structure) were found depending on the cavity size of the crown units, the outer diameter of the complexing cations and the length and flexibility of the linking chain.

Ligand exchange reactions of ReCl4(PPh3)2 with tridentate diacidic ligands with the donor set ONO(S). Molecular structures of the resulting oxo-rhenium(V) complexes

Abstract Ligand exchange reactions of ReCl4(PPh3)2 with tridentate diacidic ligands with the donor set ONO(S) were studied. The reaction course was cleared up by mass spectrometric and X-ray structural analysis of intermediate and final products. The rhenium (IV chelates formed first react further to give oxo-rhenium(V) chelates via aerial oxidation. To clarify the structural properties of these rhenium(V) chelates, X-ray analyses were carried out. The crystal structures were determined for salicylaldehyde thiobenzoylhydrazonato (2−) salicylaldehyde thiobenzoylhydrazonato oxo-rhenium(V) (1) C28H21N4O3Re: monoclinic P2 1 /c, a=9.9183(13), b=12.721(2), c=20.802(3) A , β = 96.416(13)°, Z = 4, R1 = 0.0513; benzoylacetone thiobenzoylhydrazonato (2−) benzoylacetone thiobenzoylhydrazonato oxo-rhenium(V) (2) C34H29N4S2Re: triclinic P 1 , a = 10.811(4), b = 11.364(9), c = 14.878(16) A , α = 67.56(4), β = 71.54(3) , γ = 79.50(3)°, Z = 2, R1 = 0.0354. Benzoylacetonato-dichloro-triphenylphosphane-oxo-rhenium(V) (3b) is characterized as a decomposition product resulting from oxidation of rhenium(IV) to oxo-rhenium(V) and hydrolysis of the ligand benzoylacetone benzoylhydrazone. Crystal data for 3b. C28H24O3PCl2Re: monoclinic P2 1 /c, a = 15.904(2), b = 11.021(5), c = 17.227(2) A , β = 115.476(11)°, Z=4, R 1 = 0.0394 .

Mass spectra of tetrahydroisoquinoline-fused 1,3,2-O,N,P-and 1,2,3-O,S,N-heterocycles : influence of ring size and fusion, of present heteroatoms, substituent effects and of the stereochemistry on fragmentation

The electron ionization (EI) mass spectra of a variety of stereoisomeric tricyclic 1,3,2-oxazaphosphino[4,3-a]isoquinolines (1-4), 1,2,3-oxathiazino[4,3-a]isoquinoline-4-oxides (5-7) and the -4,4-dioxides (8-10) of oxazaphospholo- and oxathiazolo[4,3-a]- (11, 12, 15 and 16) and -[3,4-b]isoquinolines (13, 14 and 17) were recorded. Ring size and fusion, the different heteroatoms (P and S) and substituents on the ring systems strongly influence the mass spectra. In addition, mass spectra of the stereoisomers of compounds 1, 2 and 13, 14 revealed stereochemically relevant differences which are not observed for the other pairs of isomers.

SbCI3, BiCl3 and Na+ Complexes of Maleonitrile-Dithiacrown Ethers: Synthesis, Crystal Structures and DEP-MS Experiments

The reactions of MlC3 (M = Sb, Bi) with maleonitrile-dithia-15-crown-5 (mn-15S2O3) and maleonitrile-dithia-18-crown-6 (mn-18S2O4) in MeCN yielded the complexes [MCl3(mn-15S2O3)] {M = S b (l), Bi(2)} and [MCl3(mn-18S2O4)] {M = Sb(3), Bi(4)}, respectively. The pyramidal MCl3 units are coordinated very weakly to the three oxygen and two sulphur donor atoms of mn-15S2O3 in 1 and 2, and to the four oxygen donor atoms of mn- 18S2O4 in 3 and 4. Both mn-15S2O3 complexes, 1 and 2, crystallize isotypically in the m onoclinic space group P2(1)/n with four formula units per unit cell, while the isotypic mn-18S2O4 complexes, 3 and 4, are triclinic, space group P-1, with two formula units per unit cell. In the SbCl3 complexes, 1 and 3, the mean contact distances between the Sb centres and the macrocyclic donor atoms are longer than the corresponding distances in their isostructural BiCl3 analogues, 2 and 4, which may reflect a stereochemical activity of the Sb111 lone pair. Under the conditions of DEP-M S experiments with 1 and 3 the monocationic SbCl2+ complexes [SbCl2(L)]+ (L = mn-15S2O3, mn-18S2O4) were detected. NaSbCl6 and mn-18S2O4 in MeCN furnished the 2:1 complex [Na(mn-18S2O4)2]SbCl6 {(5)SbCl6). In the complex cation 5 the sodium atom is coordinated sandwich-like through the eight oxygen atoms of two mn-18S2O4 molecules. Compound (5)SbCl6 crystallize in the triclinic space group P -1 with two formula units per unit cell

Fragmentation of imine‐type meta‐bridged bis(benzo crown ethers) under electron impact

Electron impact (EI) spectra of polymethylene-bridged carbonylhydrazones of 4′-formylbis(benzo-15-crown-5 ether)s, their 18-crown-6 analogs, and their complexes with alkali cations (Na+, K+, and Cs+) were studied. Evidently, there are three main routes of fragmentation, including two types of McLafferty rearrangements and the formation of an azine species. The products of the McLafferty rearrangements fragment further to two ions both with the mass number (m/z 105) but different elemental compositions (C6H5N2 and C6H3NO). No loss of ammonia was detected, in contrast to earlier observations. The ring size of the crown moieties had no influence on their decomposition behavior, but the length of the methylene bridges affected the fragmentation patterns of these compounds mainly due to increasing flexibility. The EI technique could not be used to estimate complexation tendencies or to obtain information on the stoichiometry of the bis(benzo crown ether) complexes. Copyright

Nuclear magnetic resonance studies and molecular modelling of the solution structure of some dibenzo crown ethers and their complexes

Abstract The 1 H and 13 C NMR spectra of the structurally related crown ethers 1 – 7 with further potential coordination groups (OH, COOH) and the alkali metal complexes of the latter were recorded. Structural information was deduced especially from 13 C NMR chemical shifts, the salt-induced 13 C chemical shifts (as a measure of both the in-plane interactions HC 2 C 1 OC 8 H 2 and HC 5 C 6 OC 7 H 2 ), vicinal H,H coupling constants and spin-lattice relaxation times, T 1 , of protonated 13 C nuclei. The complex stability constants ( K A ) for the complexes of 1 – 7 with LiI were determined by 7 Li NMR spectroscopy. Accompanying quantum-mechanical calculations corroborate the spectroscopical conclusions about the preferred conformers of the studied crown ethers both in the free and in the complexed state. New insights into the complexation behaviour of the crown ether carboxylic acids 3 – 5 were obtained which are in contrast to the generally discussed “cavity effects”. The results of NMR spectroscopy and molecular modelling prove the complexation of the crown ether carboxylic acid to take place first at the carboxyl group. In a second step, the bound cation is folded over the cavity of the same crown ether or over one of another crown ether ring system.