Synthesis, spectroscopic and electrochemical properties of manganese, nickel and iron octakis-(2-diethylaminoethanethiol)-phthalocyanine

The syntheses, spectroscopic and electrochemical properties of manganese (3), nickel (4) and iron (5) phthalocyanine complexes, octa-substituted at the peripheral positions with diethlyaminoethanethiol substituent, are reported. The electrochemistry of these complexes and the corresponding cobalt complex (6) are reported. Complex 3 showed two reversible reduction couples attributed to the Mn^IIIPc⁻²/Mn^IIPc⁻² (E_½ = −0.12 V versus Ag|AgCl) and Mn^IIPc⁻²/Mn^IIPc⁻³ (E_½ = −0.82 V versus Ag|AgCl) species. Two ring-based reduction couples were also observed for complex 4. Two reduction couples, assigned to the Fe^IIPc⁻²/Fe^IPc⁻² (E_½ = −0.35 V versus Ag|AgCl) and Fe^IPc⁻²/Fe^IPc⁻³ (E_½ = −0.96 V versus Ag|AgCl) species, and an oxidation couple, attributed to Fe^IIIPc⁻²/Fe^IIPc⁻² (E_½ = 0.26 V versus Ag|AgCl) species, were observed. For complex 6, two reductions and one oxidation were also observed with the potential range of 1.2 to −1.8 V versus Ag|AgCl Spectroelectrochemical studies were used to confirm some of the assigned processes.     

Synthesis and structures of the dinuclear tin(II) complexes [R = Ph, X(Z) = CPh; R = SiMe3, X(Z) = PPh2] and of related compounds

Tin(II) compounds containing the ligands [CH(C₆H₃Me₂-2,5)C(Bu^t)NSiMe₃]⁻ (≡ L¹), [CH(Ph)C(Ph)NSiMe₃]⁻ (≡L²), [CH(SiMe₃)P(Ph)₂NSiMe₃]⁻ (≡ L³),

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(≡ L⁴), [C(Ph)C(Ph)NSiMe₃]²⁻ (≡ L⁵), and [C(SiMe₃)P(Ph)₂NSiMe₃]²⁻ (≡ L⁶) are reported: the transient SnBr(L¹) (1) and SnBr(L²) (2), Sn(L¹)₂ (3) [P.B. Hitchcock, J. Hu, M.F. Lappert, M. Layh, J.R. Severn, J. Chem. Soc., Chem. Commun. (1997) 1189], the labile Sn(L²)₂ (4), [Sn(L⁵)]₂ (5), SnCl(L³) (6), Sn(L³)₂ (7), [Sn(L⁶)]₂ (8), Sn(L⁴)₂ (9) and Pb(L⁴)₂ (10). They were prepared from (i) SnBr₂ and K(L¹) (1, 3) or K(L²) (2, 4, 5); (ii) SnCl₂ and Li(L³) (6–9); or (iii) PbCl₂ and Li(L⁴) (10). Each of 1, 3 and 5–10 has been characterised by multinuclear NMR spectra; 3, 5, 6, 8, 9 and 10 by EI-mass spectra, but only 3, 5, 8, 9 and 10 were isolated pure and furnished X-ray quality crystals. Of greatest novelty are the title binuclear fused tricyclic ladder-like compounds 5 and 8. Quantum chemical calculations, on alternative pathways to 5 from 2 and to 8 from 7, are reported.     

Synthesis of bis N-heterocyclic carbenes,derivatives and metal complexes

A method for the synthesis and isolation of 1,1′-methylene-bis-(3-aryl-imidazol-2-ylidene) ligands, aryl = 2,6-diisopropyl-phenyl (DiPP), L^DiPP, mesityl (mes), L^mes, is reported, which provides synthetically useful quantities of high purity. Derivatisation of L^DiPP with chalcogenides gave the adducts L^DiPPE₂, E = S, Se, Te. Reaction of L^DiPP with [Pd(tmeda)Me₂], [Pt(μ-SMe₂)Me₂]₂, [Ir(1,5-COD)(μ-Cl)]₂/KPF₆ and [NiBr₂(dme)] gave [Pd(L^DiPP)Me₂] (1), [Pt(L^DiPP)Me₂] (2), [Ir(L^DiPP)(1,5-COD)](PF₆) (3) and [Ni(L^DiPP)Br₂] (4), respectively. The latter was reduced in the presence of CO to [Ni(L^DiPP)(CO)₂] (5). The structures of L^mes, L^DiPPTe₂, and 1–5 are also reported.     

Synthesis,structure, and photoluminescence of ZnII and CdII coordination complexes constructed by structurally related 5,6-substituted pyrazine-2,3-dicarboxylate ligands

Aiming at exploring the effect of substituting groups of three structurally related ligands, 5,6-diethyl-pyrazine-2,3-dicarboxylic acid (H₂L¹), 5,6-diphenyl-pyrazine-2,3-dicarboxylic acid (H₂L²), and dibenzo[f,h]quinoxaline-2,3-dicarboxylic acid (H₂L³), seven new coordination polymers constructed from these three substituted dicarboxylate ligands, {[Zn(L¹)(H₂O)₃]·2H₂O}_∞ (1), {[Cd₂(L^2ʹ)₄(H₂O)]·3H₂O}_∞ (2), [Zn(L²)(CH₃OH)]_∞ (3), {[Zn(L²)(H₂O)₂]·H₂O}_∞ (4), {[Zn(L^2ʹ)]·H₂O}_∞ (5), [Zn₂(L³)(DMF)₄]_∞ (6), [Zn(L³)(2,2ʹ-bipy)(H₂O)]_∞ (7), have been prepared and structurally characterized. 1 is a 1D chain structure in which Zn^II ion is six-coordinated with octahedron geometry. 2 is also a 1D chain structure in which there are two crystallographically independent Cd^II ions in the asymmetric unit and exist transformative L^2ʹ ligands in the resulting complex. 3 and 4 both possess 2D layer network with the same (4, 8²) topology, while the two complexes take different coordination modes during the forming of the compounds. 5 has a 1D chain structure based on the transformative L^2ʹ ligand in which Zn^II ion is five-coordinated with bipyramidal geometry. 6 and 7 both have 1D chain structure constructed from L³ ligand. Thereinto, Zn^II ion in 6 is five-coordinated by three oxygen atoms from two individual L³ ligands and two oxygen atoms from two DMF molecules. While in 7 there are also five coordination sites occupied by two carboxylate oxygen atoms from two L³ ligands. In addition, the compounds are characterized by elemental analysis, IR spectra. The luminescent properties of the compounds are also discussed and exhibit strong fluorescent emissions in the solid state.     

Crystal structures of two syn bent tetraalkylhydrazines,their radical cations,and a dication

The crystal structures of 2,7-diazatetracyclo[6.2.2.2^3,6.0^2.7]tetradec-4-ene, 2, its cation radical nitrate salt 2⁺, NO₃^-, 2,7-diazatetracyclo[6.2.2.2^3,6.0^3,7]tetradecane, 3, its dication dihexafluorophosphate salt 3²⁺(PF₆^-)₂, and a low quality structure of the monocation radical tosylate salt of 3 are reported and compared with MNDO calculations of these structures. Cations 2⁺ and 3⁺ are found to be significantly syn bent at nitrogen, and the dication 3²⁺ has a longer N-N distance than its azo analogue, 2,3-diazabicyclo [2.2.2]oct-2-ene (11).     

Synthesis and characterization of germanium (IV) and silicon (IV) complexes derived from 9-hydroxyphenalenone: X-ray crystal and molecular structure of tris-(9-oxophenalenone)-germanium (IV) and silicon (IV) salts

The germanium (IV) and silicon (IV) complexes, tris-(9-oxophenalenone)-germanium (IV) tetrakis[3,5-bis(trifluoromethyl) phenyl] borate (7⁺TFPB⁻) and tris-(9-oxophenalenone)-silicon (IV) tetrakis[3,5-bis(trifluoromethyl) phenyl] borate (8⁺TFPB⁻), derived from 9-hydroxyphenalenone have been synthesized and characterized by elemental analyses, infrared spectra and as well as by single crystal X-ray study. The crystal structure of 7⁺TFPB⁻ and 8⁺TFPB⁻ shows a one-dimensional chain like structure and π-overlap between the neighbouring phenalenyl planes. The cyclic voltammograms of 7⁺TFPB⁻ and 8⁺TFPB⁻ show three reversible one-electron reduction steps due to the formation of the radical, anion and dianion as each phenalenyl moiety accepts an electron.     

Interconversion of acetyl- and terminal-carbonyl groups on labeled (η5-indenyl)(CO)2Fe13C(O)CH3

The ¹³C-labeled (95–99%) acetyl complex (η⁵-In)(CO)₃Fe¹³C(O)CH₃ (8) (In = indenyl) has been prepared by acylating In(CO)₂Fe⁻ Na⁺ (1) with CH₃ ¹³C(O)Cl. All of the starting 1 must be consumed in this reaction (at −78°C), or 45% of the product results as In(CO)(¹³CO)FeC(O)CH₃ (9). Once isolated, neither 8 nor mixtures of 8 and 9 further redistribute or lose this label after pressurizing under 800 atm CO, or after heating in heptane, THF, or acetonitrile solution. Treating 8 with even trace amounts of 1 or of Cp(CO)₂Fe⁻ Na⁺ (5) rapidly interconverts the acetyl and terminal carbonyls, thus transforming 8 into mixtures of 8 and 9. A mechanism is proposed that involves a labile metalla-β-diketonate In(CO)Fe(Fp-CO)(CH₃¹³CO)⁻ Na⁺.     

Metal complexes of anionic 3-borane-1-alkylimidazol-2-ylidene derivatives

Addition of BH₃·thf to 1-alkylimidazoles (alkyl=methyl, butyl) and 1-methylbenzimidazole leads to BH₃ adducts, which are deprotonated by BuLi to yield the organolithium compounds (L)Li⁺(1b–d)⁻. In the solid state (thf)Li⁺1b⁻ is dimeric. The acyl–iron complexes (thf)₃Li⁺(3b,d)⁻ are formed from (thf)Li⁺(1b,d)⁻ and Fe(CO)₅. (L)Li⁺(1a–c)⁻ react with [CpFe(CO)₂X], however, the only complex obtained is [CpFe(CO)₂1a] (5a). The analogous reaction of (L)Li⁺1a⁻ with the pentadienyl complex [(C₇H₁₁)Fe(CO)₂Br] yields the corresponding iron compound 6a. Their compositions follow from spectroscopic data. Treatment of Cp₂TiCl with (L)Li⁺1a⁻ leads to [Cp₂Ti1a] (7a), which could not be oxidized with PbCl₂ to give the corresponding Ti(IV) complex. The compounds [Li(py)₄]⁺9a⁻ and [Li(L)₄]⁺(10b–d)⁻ are obtained when (L)Li⁺1⁻ are reacted with VCl₃ and ScCl₃. The X-ray structure analysis of the vanadium complex reveals a distorted tetrahedron of the anion [V(1a)₄]⁻ with two smaller and four larger CVC angles. The scandium compound [Li(dme)₂⁺10c⁻] has a different structure: the distorted tetrahedron of the anion [Sc(1c)₄]⁻ contains two larger (140.2 and 142.9°) and four smaller CScC angles (93.9–98.7°). This arrangement allows the formation of four bridging BHSc 3c,2e bonds to give an eight-fold coordination. The anion 10c⁻ is formally a 16e complex.     

Alkaloids of NIRAM,natural dye from Polygonum tinctorium,and their anti-inflammatory activities

Phytochemical investigation of EtOH extract of NIRAM, natural dye from Polygonum tinctorium, resulted in the purification of nine alkaloid compounds (1–9) including four new compounds (1–4). Structures of these new compounds were elucidated by 1D and 2D NMR (¹H and ¹³C NMR, ¹H–¹H COSY, ¹H–¹³C HSQC, ¹H–¹³C HMBC), IR, UV, HR-ESI-MS, and ECD spectra. Isolated compounds (1–9) were tested for their inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 cells. Compounds 1–3, 5, and 7 showed potent NO production inhibitory activities, with IC₅₀ values of 3.88–22.87 μM.     

Tributyltin hydride-mediated free radical cyclization of allene-tethered oxime ethers,oxime esters and hydrazones. Influence of the substituents borne by the C=N double bond on the course of the reaction

A set of allenic derivatives 1 bearing a C=N bond in β position and diversely substituted in R³ and Z was prepared. The behaviour of compounds 1 towards the Bu₃Sn^• radical was then studied. Depending on the nature of R³ and Z, products 2, 3, and 4 were obtained in diverse ratios. When the steric hindrance on the C-atom of the C=N bond was low (R³ = H), the product ‘normally’ obtained was 2. When the steric hindrance of R³ was higher, the formation of 3 and 4 became competitive. In this case, the ratio between 2, 3, and 4 can be explained on the basis of the polarity of R³ and Z. The higher the electroattractive effect of R³ and Z, the higher the quantity of 2 and 4 in comparison with 3.     

Base-promoted rearrangement of cage α-haloketones—II : 12-oxa-3,5,9,10-tetrachlorohexacyclo[5.4.1.02,6.03,10.05,9.08,11]-dodecane-4-one

A synthesis of 12-oxa-3,5,9,10-tetrachlorohexacyclo[5.4.1.0^2,6.0^3,10.0^5,9.0^8,11]dodecane-4-one (6) from 4,4-dimethoxy-2,3,5,6-tetrachloropentacyclo [[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8,11-dione (1) is described. Reaction of 6 with sodium hydroxide in refluxing benzene, toluene, or tetrahydrofuran affords 11-oxa-3,4,5-exo-6-tetrachloropentacyclo [[6.2.1.0^2,7.0^4,10.0^5,9]undecane-endo-3-carboxylic acid (7a, 80·2% yield). The corresponding reaction of 6 with refluxing aqueous sodium hydroxide solution affords 4,12-dioxa-8,11-dichlorohexacyclo-[5.4.1.0^2,6.0^3,10.0^5,9.0^8,11]dodecane-1-carboxylic acid (8a, 66·5% yield). A mechanism which accounts for the formation of 7a and 8a from 6 is presented.     

Synthesis,structural characterisation and reactivity of molybdenum half-sandwich complexes containing keto- and amido-phosphines

The keto-functionalised N-pyrrolyl phosphine ligand PPh₂NC₄H₃{C(O)CH₃-2} L¹ reacts with [MoCl(CO)₃(η⁵-C₅R₅)] (R=H, Me) to give [MoCl(CO)₂(L¹-κ¹P)(η⁵-C₅R₅)] (R=H 1a; Me 1b). The phosphine ligands PPh₂CH₂C(O)Ph (L²) and PPh₂CH₂C(O)NPh₂ (L³) react with [MoCl(CO)₃(η⁵-C₅R₅)] in an analogous manner to give the compounds [MoCl(CO)₂(L-κ¹P)(η⁵-C₅R₅)] (L=L², R=H 2a, Me 2b; L=L³, R=H 3a, Me 3b). Compounds 1–3 react with AgBF₄ to give [Mo(CO)₂(L-κ²P,O)(η⁵-C₅R₅)]BF₄ (L=L¹, R=H 4a, Me 4b; L=L², R=H 5a, Me 5b; L=L³, R=H 6a, Me 6b) following displacement of chloride. The X-ray crystal structure of 4a revealed a lengthening of both Mo–P and CO bonds on co-ordination of the keto group. The lability of the co-ordinated keto or amido group has been assessed by addition of a range of phosphines to compounds 4–6. Compound 4a reacts with PMe₃, PMe₂Ph and PMePh₂ to give [Mo(CO)₂(L¹-κ¹P)(L)(η⁵-C₅H₅)]BF₄ (L=PMe₃ 7a; PMe₂Ph 7b; PMePh₂ 7c) but does not react with PPh₃, 5a reacts with PMe₂Ph, PMePh₂ and PPh₃ to give [Mo(CO)₂(L²-κ¹P)(L)(η⁵-C₅H₅)]BF₄ (L=PMe₂Ph 8b; PMePh₂ 8c; PPh₃ 8d), and 6a reacts with PMe₃, PMe₂Ph, PMePh₂ and PPh₃ to give [Mo(CO)₂(L³-κ¹P)(L)(η⁵-C₅H₅)]BF₄ (L=PMe₃ 10a; PMe₂Ph 10b; PMePh₂ 10c; PPh₃ 10d). No reaction was observed for the pentamethylcyclopentadienyl compounds 4b–6b with PMe₃, PMe₂Ph, PMePh₂ or PPh₃. These results are consistent with the displacement of the co-ordinated oxygen atom being influenced by the steric properties of the P,O-ligand, with PPh₃ displacing the keto group from L² but not from the bulkier L¹. In the reaction of [Mo(CO)₂(L²-κ²P,O)(η⁵-C₅H₅)]BF₄ (5a) with PMe₃ the phosphine does not displace the keto group, instead it acts as a base, with the only observed molybdenum-containing product being the enolate compound [Mo(CO)₂{PPh₂CHC(O)Ph-κ²P,O}(η⁵-C₅H₅)] 9. Compound 9 can also be formed from the reaction of 2a with BuLi or NEt₃, and a single crystal X-ray analysis has confirmed the enolate structure.     

Long-range nuclear spin-spin coupling between 11B and 13C, 29Si or 119Sn: a promising tool for structural assignment

The influence of unresolved long-range nuclear spin-spin coupling [ⁿJ(¹¹BX) (n > 1; X = ¹³C, ²⁹Si or ¹¹⁹Sn)] on X resonances has been studied for aminoboranes (1 and 2), haloboration (2 and 4), hydroboration (5) and organoboration products of alkynes (6 and 7). The differential broadening of X resonances in the X NMR spectra arising from ⁿJ(¹¹BX) (most obvious for X= ¹¹⁹Sn) shows a qualitatively useful pattern of various coupling pathways. |²J(¹³CN-¹¹B)| in 1 and 2 appears to be sensitive to the nature of the trans-ligand and to the ring rize. In many alkenylboranes (3, 4, 5b and d, 6 and 7) the magnitude of the coupling constants across the CC double bond follows the trend |²J(¹¹BX)| ∼ |³J(¹¹BX)|_cis < |³J(¹¹BX)|_trans. An increasing number of electropositive substituents at the CC double bond causes an increase in the magnitude of |³J(¹¹BX)|_cis,trans. If there are only organyl groups of hydrogen attached to the CC double bond, as in the hydroboration products of alkynes (5a and c) |ⁿJ(¹³C-¹¹B)| appears to be too small with respect to [T_Q(¹¹B)]⁻¹, and the differential broadening was neglibible under the experimental conditions used.     

Silver(I) complexes with (1-pyrazolyl)pyridazine ligands: Synthesis,crystal structures and luminescent properties

Four Ag(I) coordination complexes formulated as {[Ag(L¹)(ClO₄)]}_n (1), {[Ag(L¹)(NO₃)]}_n (2), {[Ag(L¹)(PF₆)]}₂ (3) and {[Ag(L²)](ClO₄)·CH₃OH}_n (4), (L¹ = 3,6-bis(1-pyrazolyl)pyridazine, L² = 3,6-bis(3,5-dimethyl-1-pyrazolyl)pyridazine) have been synthesized in the presence of different anions [ClO₄^? (1) and (4), NO₃^? (2), PF₆^? (3)] and structurally characterized by FT-IR spectra, elemental analysis and X-ray diffraction. Studies of X-ray diffraction reveal that complexes 1, 2 and 4 show infinite helical chains, which are the alternate left- and right-handed helical chains. Furthermore, helical chains are arranged to 2D sheet via C–H?O (from anion O atoms) hydrogen bonds. As the anion changed to PF₆^?, a dinuclear molecule is formed in complex 3, further constructing a 2D sheets by C–H?F hydrogen bonds. The photoluminescence properties of all the complexes 1–4 have been investigated in the solid state at room temperature.     

Synthesis,structure, electrochemistry,and Mössbauer effect studies of (ring)Fe complexes (ring = Cp,Cp1, and C6H7). Photochemical replacement of benzene in the cyclohexadienyl complex [(η5-C6H7)Fe(η-C6H6)]+

Visible light irradiation of cation [(η⁵-C₆H₇)Fe(η-C₆H₆)]⁺ (1⁺) in acetonitrile results in substitution of the benzene ligand giving the labile acetonitrile derivative [(η⁵-C₆H₇)Fe(MeCN)₃]⁺ (2a⁺). The stable isonitrile and phosphite complexes [(η⁵-C₆H₇)FeL₃]⁺ [L = ^tBuNC (2b⁺), P(OMe)₃ (2c⁺), P(OEt)₃ (2d⁺)] were obtained by reaction of 1 with L in MeCN. The structures of 2cPF₆, [CpFe(η-C₆H₆)]PF₆ (3PF₆), and Cp¹Fe(η-C₆H₆)]PF₆ (4PF₆) were determined by X-ray diffraction.The redox activity of the cyclohexadienyl complexes 1⁺, 2b⁺?2d⁺ has been investigated by electrochemical techniques and compared with that of the related cyclopentadienyl complexes 3⁺ and 4⁺. DFT calculations of the redox potentials and the respective geometrical changes were performed.Variable temperature Mössbauer (ME) spectroscopy has elucidated the relationship between structure and formal oxidation state of the iron atom in these complexes. In the case of 3⁺ an unexpected pair of crystallographic changes has been observed and interpreted in terms of both a second and first order phase transition. The mean-square-amplitude-of-vibration of the metal atom has been compared between the ME and X-ray data. ME measurements in a magnetic field have shown that in 4⁺ the quadrupole splitting is positive as it is in ferrocene.     

Isomere n-aryltetrazole—IV: 1H und 13c NMR-untersuchungen zur struktur von tetrazoliumkationen

¹H and ¹³C NMR spectra of protonated N-phenyltetrazoles 1⁺ and 2⁺ and of tetrazole 3⁺ have been measured in sulphuric acid. The structures of the cations 1⁺–3⁺ were unequivocally derived from a comparison of the data obtained with spectral parameters (chemical shifts and ¹J(¹³C,H) coupling constants) of the tetrazolium salts 4 and 5 used as model compounds. Protonation occurs always exclusively at ring nitrogen N-4. Changes of the spectral parameters due to protonation were briefly discussed and the protonation site is compared with the results of quantum chemical calculations.     

A new mode of formation of the phosphorus—phosphorus bond: Synthesis and crystal structure determination of 1,5-dichloro-2,4-dimethyl-2,4- diaza-1,5-diphospha-1,5-diphenylpentan-3-one and of 1,4-dimethyl-2,3-diphenyl-1,4,3,2- diazadiphospholidin-5-one-2-oxide and its oxidation with tetrachloroorthobenzoquinone

Reaction of phenyldichlorophosphine, 2b, with N,N′-dimethyl-N,N′-bis(trimethylsilyl)urea, 1, leads to a symmetrical diphosphorylation product, 3b. A mechanism for the formation of 3b, on the basis of ³¹P NMR-data, is proposed. 3b reacts with oxalic acid bis(trimethylsilyl)ester, 5, with intramolecular P—P-coupling and formation of the λ³P–λ⁴P-mixed-valence diphosphorus compound, 1,4-dimethyl-2,3-diphenyl-1,4,3,2- diazadiphospholidin-5-one-2-oxide, 6, which has been oxidized by means of tetrachloroorthobenzoquinone (TOB), 7, to the λ⁴P–λ⁵P-compound, 8. The structures of 3b, 6 and 8 have been elucidated by ¹H- and ³¹P-NMR-spectroscopy; single crystal X-ray diffraction studies of 3b and of 6 have been conducted. The identity of both compounds has been confirmed. In the acyclic diphosphorus compound, 3b, a remarkably short non-bonding PP distance of 280.6 pm has been found while the PP bond length in the cyclic compound 6 is of the usual order of magnitude (221.1 and 221.8 pm, respectively).     

A N,N′-diacetate benzodioxotetraazamacrocycle and its transition metal complexes

Reaction of 2,9-dioxo-1,4,7,10-tetraazabicyclo[1.10.1]hexadeca-1(11),13,15-triene-4,7-diacetic acid (H₂L1) with CuCl₂ · 2H₂O in ethanol at pH 6 led to the monomeric benzodioxochlorocomplex [Cu(L′1)Cl] (1) (HL′1 = monoethylesther of H₂L1). X-ray structural analysis has shown that in complex 1 the Cu is five-coordinated by two nitrogen and two oxygen atoms of the macrocycle and by a chloride, displaying a square pyramidal coordination geometry. One of the acetate arms does not coordinate to the Cu and has suffered an in situ ethanolic esterification reaction. The protonation constants of H₂L1 and the stability constants of its complexes with Cu²⁺, Ni²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ were determined by potentiometric methods and in some cases by ¹H NMR spectroscopy. The stability constants of the complexes follow the trend [Ni(H₋₁L1)]⁻ > [Cu(H₋₁L1)]⁻ ≫ [Pb(H₋₁L1)]⁻ > [Zn(H₋₁L1)]⁻ > [Cd(H₋₁L1)]⁻, probably due to steric requirements. Spectroscopic measurements (absorption and EPR) at different pH values have shown the effect of the pH on the coordination sphere of the Cu complexes.     

Addition reactions of the trichlorocyclopropenylium ion with alkenes: A novel access to cyclopropene and cyclopropenone derivatives

Trichlorocyclopropenylium tetrachloroaluminate 1⁺-AlCl⁻₄ reacts with alkenes in nitromethane at −35°C to give the 1:1 addition products 2⁺-AlCl⁻₄, which can be converted into the 2-chlorocyclopropenones 5 or the ä,β-acetylenic carboxylates 6.     

Schmidt reaction of 4-substituted adamantanones

The Schmidt reaction of various 4^a - and 4^e -substituted adamantanones has been investigated. It is shown that the direction of the nitrogen insertion is not dominated by inductive substituent influences. The main reaction pathway involves the diazoiminium ion 3 and the intermediates 4 and 5 which prefer different reactions: 4 undergoes mainly fragmentation (8 and 9) whereas 5 gives mainly water addition products (7). The recyclisation of 8 and 9 is highly regloselective. The structure determinations of the products are based on their ¹H and ¹³C NMR data.