Peter Lönnecke

Influence of anellation in unsaturated heterocyclic diaminogermylenes

Abstract The influence of anellation on the properties and structures of heterocyclic diaminogermylenes was studied. Benzo- and pyrido-anellated cyclic germylenes 1,2-C6H4[N(CH2tBu)]2Ge (1) and 2,3-C5H3N[N(CH2tBu)]2Ge (2) were synthesised by dilithiation of aromatic ortho-diamino compounds C5H3X[N(CH2tBu)]2 (X=CH, N) with BuLi and subsequent reaction with GeCl2(dioxane), the non-anellated but analogously N,N′-disubstituted C2H2[N(CH2tBu)]2Ge (3) was obtained by reductive metalation of N,N′-dineopentyl-glyoxal diimine with lithium and cyclisation with GeCl2(dioxane). Crystal structure determinations on 1–3 give evidence on their monomer nature and lack of interactions between Ge(II) and the basic pyridine N-atom in 2. Spectroscopic data and structures of anellated and non-anellated compounds were compared. The sensitivity to distortions of bond lengths in the germylene 3 as compared to 1 and 2 may hint to a lower stability of the non-anellated diazagermoline-2-ylidene π-system as compared with the 10π-system in the anellated compounds 1 and 2, which are favoured by the intrinsic stability of the o-arenediimine fragment.

Aminoalkylferrocenyldichlorophosphanes: facile synthesis of versatile chiral starting materials

A series of racemic and optically pure aminoalkylferrocenyldichlorophosphanes has been prepared by reaction of phosphorus trichloride with the corresponding lithiated aminoalkylferrocene precursors. Crystal structures of racemic 1-dichlorophosphanyl-2-N,N-dimethylaminomethylferrocene, racemic 1-dichlorophosphanyl-2-N,N-dimethylaminomethyl-3-triphenylsilylferrocene and (S)-N,N-dimethyl-1-[(R)-2-(dichlorophosphanyl)ferrocenyl]ethylamine reveal short intramolecular N[dot dot dot]P distances, which are suggestive of weak N --> P dative bonds. The aminoalkylferrocenyldichlorophosphanes can be used for the preparation of the corresponding primary phosphanes, one of which was characterised by X-ray crystallography. Optically pure (R)-N,N-dimethyl-1-[(S)-2-(phosphanyl)ferrocenyl]ethylamine can easily be lithiated twice to give the first enantiomerically pure lithium-phosphorus closo cluster compound, which was also structurally characterised.

Antiproliferative effect of novel platinum(II) and palladium(II) complexes on hepatic tumor stem cells in vitro

Novel platinum and palladium complexes with (2-isopropoxyphenyl)dicyclohexylarsine and (2-methoxyphenyl)dicyclohexylarsine ligands were synthesized and tested on different tumor cells. Adducts with general formula MX(2)L(2) (M = Pt(II), Pd(II); X = Cl or I; L = organoarsenic ligand) were fully characterized. According to the crystallographic data, in all complexes the organoarsenic ligands coordinate the metal center through the arsenic atom only, in a trans arrangement with the halogen atoms. The antiproliferative potential of complexes 1-4 was evaluated in vitro on human tumor cell lines. A markedly biological activity was observed against the chemoresistant hepatic tumor stem cell line, the normal hepatic stem cells and towards the hepatocellular carcinoma (non-stem) cells. The new compounds toxicity is selectively limited in normal liver cells, unlikeness with the oxaliplatin, which displays a more intense effect in normal cells, compared with the two tumor cell lines. The stem cells treatment with compounds 1-4 causes DNA damages; the antimitotic effect of these compounds is based on their genotoxicity and on the capacity to form crosslinks with the DNA interstrand. In the case of platinum complexes 1 and 3 this mechanism gives rise to specific lesions on DNA that induces apoptosis in stem cells, influencing their selectivity in tumor cell growth inhibition. Compounds 1, 2 and 4 display higher activity against tumor stem cells. The novel platinum complexes 1 and 3 are more efficient against tumor stem cells than oxaliplatin, and if used in combination with sorafenib-based monoclonal anticancer therapy, complexes 1, 3 and 4 have the ability to induce superior chemosensitivity relative to sorafenib than the standard platinum-based drug, making them promising candidates for prodrug development.

New Functional Cyclic Aminomethylphosphine Ligands for the Construction of Catalysts for Electrochemical Hydrogen Transformations

Eight-membered cyclic functional bisphosphines, namely 1,5-di-aryl-3,7-di(2-pyridyl)-1,5-diaza-3,7-diphosphacyclooctanes (aryl=2-pyridyl, m-tolyl, p-tolyl, diphenylmethyl, benzyl, (R)-(+)-(α-methyl)benzyl), with 2-pyridyl substituents on the phosphorus atoms have been synthesized by condensation of 2-pyridylphosphine, formaldehyde, and the corresponding primary amine. The structures of some of these bisphosphines have been investigated by X-ray crystallography. The bisphosphines readily form neutral P,P-chelate complexes [(κ(2)-P,P-L)MCl2], cationic bis-P,P-chelate complexes [(κ(2)-P,P-L)2 M](2+), or a five-coordinate complex [(κ(2)-P,P-L)2 NiBr]Br. The electrochemical behavior of two of the nickel complexes, and their catalytic activities in electrochemical hydrogen evolution and hydrogen oxidation, including the fuel-cell test, have been studied.

Synthesis and Reactivity of ortho-Carbaborane-Containing Chiral Aminohalophosphines

The synthesis of chiral ortho-carbaboranyl bis(aminohalophosphines) is presented, and spectroscopic and crystallographic data of these compounds are discussed. Furthermore, their reactivity toward alcoholysis was investigated. Quantum chemical calculations showed that the inhibition of methanolysis is of kinetic and not of thermodynamic origin. The disubstitution of the carbaboranes leads to P...P interactions as strong as a hydrogen bond that extremely lower the rate of the methanolysis.

Coordination Chemistry of the cyclo‐(P5tBu4)− Ion: Monomeric and Oligomeric Copper(I), Silver(I) and Gold(I) Complexes

[Na{cyclo-(P(5)tBu(4))}] (1) reacts with [CuCl(PCyp(3))(2)] (Cyp=cyclo-C(5)H(9)) and [CuCl(PPh(3))(3)] (1:1) to give the corresponding copper(I) complexes with a tetra-tert-butylcyclopentaphosphanide ligand, [Cu{cyclo- (P(5)tBu(4))}(PCyp(3))(2)] (2) and [Cu{cyclo-(P(5)tBu(4))}(PPh(3))(2)] (3). The CuCl adduct of 2, [Cu(2)(mu-Cl){cyclo-(P(5)tBu(4))}(PCyp(3))(2)] (4), was obtained from the reaction of 1 with [CuCl(PCyp(3))(2)] (1:2). Compounds 2 and 3 rearrange, even at -27 degrees C, to give [Cu(4){cyclo- (P(4)tBu(3))PtBu}(4)] (5), in which ring contraction of the [cyclo-(P(5)tBu(4))](-) anion has occurred. The reaction of 1 with [AgCl(PCyp(3))](4) or [AgCl(PPh(3))(2)] (1:1) leads to the formation of [Ag(4){cyclo-(P(4)tBu(3))PtBu}(4)] (6). Intermediates, which are most probably mononuclear, [Ag{cyclo-(P(5)tBu(4))}(PR(3))(2)] (R=Cyp, Ph) could be detected in the reaction mixtures, but not isolated. Finally, the reaction of 1 with [AuCl(PCyp(3))] (1:1) yielded [Au{cyclo-(P(5)tBu(4))}(PCyp(3))] (7), whereas an inseparable mixture of [Au(3){cyclo-(P(5)tBu(4))}(3)] (8) and [Au(4){cyclo-(P(4)tBu(3))PtBu}(4)] (9) was obtained from the analogous reaction with [AuCl(PPh(3))]. Complexes 3-7 were characterised by (31)P NMR spectroscopy, and X-ray crystal structures were determined for 3-9.

Sodium Tetra‐tert‐butylcyclopentaphosphanide: Synthesis, Structure, and Unexpected Formation of a Nickel(0) Tri‐tert‐butylcyclopentaphosphene Complex

Forming a phosphorus envelope: The first structurally characterized cyclooligophosphanide ion [cyclo-(P5 tBu4 )]- to be obtained by a targeted synthesis reacts with [NiCl2 (PEt3 )2 ] by loss of a tBu group to give (η2 -3,4,5-tri-tert-butylcyclopentaphosphene)bis(triethylphosphane)nickel(0) (1). The previously unknown cyclopentaphosphene ring in 1 has an envelope conformation in solution and in the solid state, and the tBu groups adopt an all-trans configuration.

Ruthenium(II) polypyridyl complexes as carriers for DNA delivery

Two novel water soluble ruthenium(II) complexes [Ru(bpy)(2)(bqbg)](2+) and [Ru(phen)(2)(bqbg)](2+) have been structurally characterized and their DNA condensation activity, cytotoxicity, and cellular uptake studies of DNA condensates as potential non-viral DNA carriers were evaluated.

Copper(ii) halogenopropionates: low-temperature crystal and molecular structure of bis(2,2-dichloropropionato)-di(methyl-3-pyridylcarbamate)copper(ii) and bis(2-bromopropionato)-di (2-pyridylmethanol)copper(ii)

The synthesis and characterization of [Cu(CH3CCl2CO2)2(3-mpyc)2] (1) (3-mpyc = methyl-3-pyridylcarbamate) and [Cu(CH3CHBrCO2)2(2-pyme)2] (2) (2-pyme = 2-pyridylmethanol) are reported. The compounds under study were characterized by IR, electronic spectroscopy and X-ray analysis. The molecular structure of both Complexes 1 and 2 is mononuclear. The coordination environment around each copper(II) atom is a distorted tetragonal bipyramid.

Novel chiral 1,5-diaza-3,7-diphosphacyclooctane ligands and their transition metal complexes

Reaction of bis(hydroxymethyl)phenylphosphine with (R)- or (S)-α-methylbenzylamine leads to the novel cyclic chiral bisphosphine ligands 1,5-(R,R)- and 1,5-(S,S)-bis(α-methylbenzyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane (1r or 1s). Novel chiral chelate complexes of PtII (2r, 3r and 3s), PdII (4s, 5s) and ReI (6r) have been obtained by reaction of 1r or 1s with [MCl2(cod)] (M = Pt, Pd; cod = 1,5-cyclooctadiene) and [{ReBr(CO)3(thf)}2]. Compounds 1–6 were characterised by multinuclear NMR (1H, 13C, 31P) and IR spectroscopy. The former technique revealed the presence of two inequivalent phosphorus atoms in 6r. The molecular structure of 1r confirmed the absolute configuration of the chiral centers and a chair-chair conformation of the heterocycle with equatorial orientation of the substituents on phosphorus and axial on nitrogen atoms. Compound 1s was used to form a palladium catalyst for the co-polymerisation of carbon monoxide and norbornadiene. The structures of the co-polymers obtained were characterised by GPC, 1H and 13C NMR spectroscopy and elemental analysis.