Stanisław Wołowiec

Physicochemical structural characterization of ambers from deposits in Poland

Abstract The physical and chemical properties of 8 samples of amber from different localities in Poland (Baltic Coast, Belchatow Tertiary brown coal, and Jaroszow clay mine) were investigated by N 2 sorption at 77 K, positron annihilation spectroscopy for chemical analysis (PASCA) and by organic geochemical methods (FT-IR, 1 H and 13 C NMR, GC, and GC-MS). The porosity of the ambers as determined by PASCA consists of narrow micropores with diameters ranging from 0.8 to 0.9 nm and a volume 0.025 cm 3 g −1 . In the external eroded part of the amber samples (rind) the concentration of pores where positronium atoms can form is lower and consists of approximately12 the concentration as in their interior. Values of pore parameters determined from sorption of N 2 are comparable with those found by the PASCA method. The average diameter of pores ranges from 2 to 12 nm, while their volume varies from 0.018 to 0.048 cm 3 g −1 .. The chemical character of the ambers is similar based on FT-IR spectroscopy. However, noticeable differences in concentrations of ester and hydroxyl groups are observed in both exterior and interior regions, where the abundances of the ester groups are lower in the exterior rind. The proportion of organic material extractable with chloroform-methanol (1:1, v/v) ranges from 15 to 50% and correlates inversely to the average reflectances (R r ) of polished amber surfaces which range from 1.7 to 0.1 %. These variations are attributed to differing concentrations of oxygenated groups in the respective amber samples. The FT-IR spectra of the non-polar fractions (NP) from the extracts resemble the spectra of the source ambers. However, the intensities of the absorbance for the hdroxyl group are much lower, while absorbances for exomethylene groups are not present. The 1 H and 13 C NMR data of NP fractions showed a complex diversity of components in mixtures with different relative concentrations but predominantly aliphatic in character for the respective samples. GC and GC-MS analyses of these fractions revealed that they are comprised of a mixture of compounds typical for Baltic amber but with variable relative concentrations. Two groups of compounds are found to be common to all NP fractions. The first is a minor concentration of homologous n -alkanes with a characteristic Gaussian distribution in the range from C 22 to C 32 and maximizing at C 26 –C 27 . In addition C 22 is characteristically slightly higher in concentration compared to C 23 . The second group of compounds is comprised of succinates with methyl, fenchyl, bomyl and isobornyl alcohols. The composition of these diesters revealed the same equilibrium ratio between compounds with fenchyl, bornyl and isobornyl alcohols in all NP fractions. We suggest an early enzymatically controlled (bacterial) process in the formation of succinates during resin diagenesis from the biotic precursors, yielding the same characteristic ratio of the respective succinates in these ambers. These results show that all the ambers analyzed here fall into a common class of fossil resin, succinite (class Ia) independent of the sample location in Poland.

Synthesis and characterization of nickel(II), copper(II), manganese(III) and iron(III) complexes with new chiral salen-type ligand |N,N′-bis(3,5-di-tert-butylsalicylidene)-(1R,3S)-1,3-diamine-1,2,2-trimethylcyclopentane|

Abstract The title Schiff base (tBuSalcamH2) obtained by condensation of enantiomerically pure (1R,3S)-1,2,2-trimethyl-1,3-cyclopentanediamine with 3,5-di-tert-butylsalicylic aldehyde was used as a ligand to prepare Ni(II), Cu(II), Mn(III), and Fe(III) 1 : 1 complexes. The compounds were characterized by physicochemical methods. Catalytic activity of (tBuSalcam)MnCl complex was tested in the reactions of single oxygen atom transfer.

Complexes of heteroscorpionate trispyrazolylborate anionic ligands: Part I. The crystal structure and reactivity of thiocyanato[hydrobis(3-phenylpyrazolyl)(3-tert-butylpyrazolyl)borato]cobalt(II) complex

Abstract The high-spin cobalt(II) complexes with homoscorpionate hydrotris(3-phenylpyrazolyl)borate (Tp Ph ) and heteroscorpionate hydrobis(3-phenylpyrazolyl)(3- tert -butylpyrazolyl)borate {HB(3-Phpz) 2 (3- t -Bupz)} anionic ligands (Tp′) of the general formula Tp′Co(X) were studied. The former tripodal ligand provides intermediate steric hindrance for the central metal ion, which is able to adopt two additional donors from thiocyanate and neutral ligands like pyrazole (pzH) and methanol, or two oxygen donors from the lactate anion. Replacement of one of three 3-phenyl substituents in Tp Ph by the tert -butyl one produces a ligand of high steric hindrance which gave tetracoordinate Tp′Co(X) complexes, where X=thiocyanate or monodentate lactate. The complexes were studied by the 1 H NMR spectroscopic method in solution and two of them, Tp Ph Co(NCS)(pzH) and [HB(3-Phpz) 2 (3- t -Bupz)]Co(NCS), were characterized structurally by X-ray crystallography.

Palladium(0) Deposited on PAMAM Dendrimers as a Catalyst for C-C Cross Coupling Reactions

PAMAM dendrimers of generations G2–G3 as well as a partially substituted derivative of generation G4 and a low-molecular-weight tricyclic ligand 4 were used to bind Pd(0) nanoparticles. The obtained adducts were tested as catalysts for C–C cross-coupling reactions, such as the Suzuki-Miyaura, Hiyama, Heck and Sonogashira reaction. The highest yields of the coupling product, diphenylacetylene, were obtained with all the catalysts studied in the Sonogashira coupling performed in ethanol with K2CO3 as base. Very good results, 85–100%, were also found in the Suzuki-Miyaura cross-coupling, while the efficiency of the Hiyama coupling appeared lower, with 38–52% of 2-Methylbiphenyl formed. In all reactions, the G2–Pd(0) catalyst, containing an unmodified dendrimer, afforded the highest yields of the cross-coupling products.

Complexes of heteroscorpionate trispyrazolylborate anionic ligands. Part III. X-ray crystallographic and NMR studies on cobalt(II) complexes with tris(pyrazolyl)borate anionic ligands obtained from 3,5-di-methylpyrazole and 3(5)-methyl,5(3)-phenylpyrazole

Abstract Condensation of 2 equiv. of 5(3)-methyl,3(5)-phenylpyrazole and 1 equiv. of 3,5-di-methylpyrazole with NaBH4 resulted in the formation of sodium [hydrobis(3-phenyl,5-methylpyrazolyl)(3,5-di-methylpyrazolyl)borate]. The ligand was converted into the pentacoordinate [HB(3,5-di-Mepz)(3-Ph,5-Mepz)2]Co(NCS)(THF)·THF complex for which the molecular structure was determined by the X-ray crystallographic method. The geometry of the ligand in the cobalt(II) complex was compared with that of the homoscorpionate ligand in [HB(3-Ph,5-Mepz)3]Co(NCS)(THF)·0.5THF on the basis of X-ray structural data. The condition for the thermal conversion of the ligands in the studied Tp′Co(NCS) was established. The heating of the mentioned complexes at 428 K in propylbenzene resulted in a borotropic shift of 3-phenyl,5-methylpyrazolyl moieties resulting in the formation of new heteroscorpionates: the chiral [HB(3,5-di-Mepz)(3-Ph,5-Mepz)(3-Me,5-Phpz)]Co(NCS) and [HB(3-Me,5-Phpz)2(3-Ph,5-Mepz)]Co(NCS), which were characterized in solution by 1H NMR spectroscopy.

Anionic Poly(pyrazolyl)borate Ligands Obtained from 3,5-Dimethylpyrazole and 3,5-Diphenylpyrazole and Their Cobalt(II) Complexes − X-ray Crystallographic and1H NMR Studies

Synthesis of poly(pyrazolyl)borate anionic ligands composed of 3,5-dimethyl- and 3,5-diphenylpyrazoles and their bis(ligand) high-spin cobalt(II) complexes are described. The molecular structures of [dihydrobis(3,5-diphenylpyrazolyl)borato][hydrobis(3,5-dimethylpyrazolyl)(3,5-diphenylpyrazolyl)borato]cobalt(II) and bis[dihydro(3,5-dimethylpyrazolyl)(3,5-diphenylpyrazolyl)borato]cobalt(II) complexes were established by X-ray crystallography. The cobalt center is hexacoordinate in the former with five Co−N2(pyrazolyl) bonds and short Co−H [attached to the boron atom of bis(pyrazolyl)borate] bond (2.03 A), whereas a distorted tetrahedral geometry was found for the latter due to four Co−N2(pyrazolyl) bonds. Additionally, the pentacoordinate homoscorpionate [tris(3,5-diphenylpyrazolyl)borato]cobalt(II) nitrate side product was obtained from the reaction and characterized structurally. It contains a κ3-coordinated Tp′ ligand and a κ2-bound nitrate anion.

Complexes of heteroscorpionate trispyrazolylborate ligands. Part VI. Carboxylate induced conversion of mono-ligand Tp′M(L) into bis-ligand Tp′2M complexes (M=Co(II) and Cu(II))

Abstract A series of homoleptic complexes of hexacoordinate cobalt(II) and copper(II) complexes with 3,5-disubstituted homo- and heteroscorpionate tris(pyrazolyl)borate anionic ligands (Tp′) were synthesized, i.e. bis[hydrotris(3-phenyl,5-methylpyrazol-1-yl)borato]cobalt(II), bis[hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3-methyl,5-phenylpyrazol-1-yl)borato]cobalt(II) and bis[hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3-methyl,5-phenylpyrazol-1-yl)borato]copper(II) and their structures were elucidated crystallographically. The complexes were also formed spontaneously during attempted metathesis of the corresponding Tp′M(NCS) complexes into Tp′M(OOCCH(OH)CH3) complexes. In the case of the analogous conversion applied for the thiocyanato [hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3,5-dimethylpyrazol-1-yl)boratocobalt(II) complex with sodium carboxylates (lactate, pyruvate and 2-hydroxybutyrate), the cross-transfer of pyrazolyl residues between starting anionic ligands was observed resulting in formation of bis-ligand homo- and heteroleptic Tp′CoTp″ complexes, where Tp′, Tp″ were tris(pyrazolyl)borates composed of n 3(5)-phenyl,5(3)-methylpyrazolyl and (3−n) 3,5-dimethylpyrazolyl residues (n=0–3) identified by mass spectrometry. Metathesis of thiocyanate in thiocyanato hydrotris(3-phenyl,5-methylpyrazol-1-yl)boratocobalt(II) into pyruvate led to the isolation of stable the pyruvato hydrotris(3-phenyl,5-methylpyrazol-1-yl)boratocobalt(II) complex, the structure of which was determined crystallographically. The Tp′ ligands are η3 coordinated to metal ions in every case, whereas the pyruvate anion is coordinated through carboxylate and carbonyl oxygen atoms to the cobalt center. Two rotational isomers distinguishable by 1H NMR spectroscopy for the hexacoordinate bis[hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3-methyl,5-phenylpyrazol-1-yl)borato]cobalt(II) complex were detected in solution.

Complexes of heteroscorpionate trispyrazolylborate anionic ligands: Part II. The X-ray crystallographic and 1H NMR studies on thiocyanato[hydrobis(3-phenylpyrazolyl)(3,5-di-tert-butylpyrazolyl)borato]cobalt(II) and thiocyanato[hydrobis(3-phenyl,5-methylpyrazolyl)(3-methyl,5-phenylylpyrazolyl)borato]cobalt(II) complexes

Abstract Synthesis of two heteroscorpionate tris(pyrazolyl)borate anionic ligands (Tp′) was described; the sterically demanding [hydrobis(3-phenylpyrazolyl)(3,5-di-tert-butylpyrazolyl)borate]− obtained by condensation of KBH4 with 3-phenylpyrazole and 3,5-di-tert-butylpyrazole and [hydrobis(3-phenyl,5-methylpyrazolyl)(3-methyl, 5-phenylylpyrazolyl)borate]− formed in similar reaction between NaBH4 and 3(5)-methyl,5(3)-phenylpyrazole. The ligands were converted into tetracoordinate [HB(3,5-di-tBupz)(3-Phpz)2]Co(NCS) and pentacoordinate [HB(3-Me,5-Phpz)(3-Ph,5-Mepz)2]Co(NCS)(THF)·THF complexes, which molecular structures were determined by X-ray crystallographic method. The reactivity of high-spin cobalt(II) complexes was studied by the 1H NMR spectroscopy in solution. The reactive [HB(3-Me,5-Phpz)(3-Ph,5-Mepz)2]Co(NCS) complex readily underwent conversions into pentacoordinate [HB(3-Me,5-Phpz)(3-Ph,5-Mepz)2]Co(OOCCH(OH)CH3) and hexacoordinate [HB(3-Me,5-Phpz)(3-Ph,5-Mepz)2]Co[HB(pz)3] complexes.

Synthesis and structure of Rh(I) tris(pyrazolyl)borate complexes of the type TpPh,MeRhL1L2

The complex Tp Ph,Me Rh(CO) 2 ( 1 ) was prepared from the reaction of the appropriate potassium pyrazolyl borate, Tp Ph,Me K, with Rh(acac)(CO) 2 in warm benzene. Reaction of Rh(acac)(CO) 2 with Tp Ph,Me K and PPh 3 gave the compound Tp Ph,Me Rh(CO)(PPh 3 ) ( 2 ). The complexes 1 and 2 were characterized by elemental analysis and IR, 1 H-, 13 C-, and 31 P-NMR spectroscopies. The structures of both compounds were determined by X-ray crystallography. The complex 1 crystallizes in the triclinic space group P 1 with a =11.227(2), b =12.219(2), c =12.262(2) A, α =63.61(3), β =87.67(3), γ =88.17(3)°, V =1505.4(4) A 3 , and Z =2. Crystals of 2 are triclinic, space group P 1, with a =11.114(2), b =11.913(2), c =18.071(4) A, α =82.69(3), β =82.02(3), γ =64.01°, V =2123.9(7) A 3 , Z =2. The fluxional behavior of 1 and 2 was studied by variable-temperature 1 H-NMR spectroscopy. In the case of 1 the κ 2 ↔ κ 3 conversion is fast on the NMR time-scale even at −90°C, whereas complex 2 is a unique example of two well-separated κ 2 ↔ κ 3 equilibria (by 21 kJ mol −1 Δ G ≠ gap).

Cobalt(II) triazene 1-oxide bis(chelates). A case of planar (low spin)–tetrahedral (high spin) isomerism

High- and low-spin cobalt(II) trizene 1-oxide bis(chelates) have been isolated. The low-spin complexes possess square-planar structure whilst the high-spin complexes are tetrahedral. The molecular structure of high-spin [Co(OMeN3C6H4Me-4)2] has been determined: triclinic, space group P, Z= 2, a= 7.970(5), b= 10.174(5), c= 11.676(5)A, α= 87.18(4), β= 74.31(4) and γ= 74.06(4)°. For some complexes the isolation of both planar (low-spin) and tetrahedral (high-spin) isomers or of their conglomerates is possible depending on the synthesis conditions. The crystal structure of square-planar [Ni(OMeN3C6H4-Me-4)2], which is isomorphous with the low-spin isomer of [Co(OMeN3C6H4Me-4)2], has been determined: triclinic, space group P, Z= 1, with a= 7.495(2), b= 7.694(5), c= 8.612(3)A, α= 64.64(5), β= 87.84(2) and γ= 78.64(3)°. The complexes exhibit a planar-tetrahedral equilibrium in non-co-ordinating solvents, the ΔH⊖ and ΔS⊖ values of which, determined from solution magnetic susceptibility measurements, are in the range 1–15 kJ mol–1 and 5–30 J K–1 mol–1, respectively. The electrochemical properties of the complexes are given.