Joachim Heinicke

Synthesis, structures and reactions of new thermally stable silylenes

Two representatives 1a and 1b of a new series of stable but reactive bis(amino)silylenes, derived from the N,N′-dineopentyl-1,2-phenylenediamido ligand RC6H3[(CH2But)]2, have been prepared by reductive elimination from RC6H3[[graphic omitted]SiCl2 and characterised by NMR spectroscopy and for 1a X-ray crystallography; the silyienes [graphic omitted](CH2But)]2C6H3-1,2-R (R = H 1a or 4-Me 1b) readily undergo oxidative addition with EtOH or Mel.

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.

Synthesis of 1H-1,3-benzazaphospholes: substituent influence and mechanistical aspects

Abstract Various substituted carboxylic acid 2-chloro- and 2-bromoanilides 1a–j react with triethylphosphite in the presence of anhydrous NiCl2 or NiBr2 to give o-acylamido-benzenephosphonic acid esters 2a–g and 2j. Yields depend strongly on the substituents. 2-Fluoro-4,6-dibromoacetanilide 1g reacts only at 6-position, indicating an o-directed process. Based on substituent effects, we infer a mechanism via Ni(0) intermediates that insert into the carbon–halogen bond. The N-tertiary 2-bromoformanilide 4 does not undergo phosphonylation to 5 in the presence of the Ni-catalyst but reacts in the presence of Pd-catalysts. The subsequent reduction of the N-secondary o-acylamido-benzenephosphonic acid esters 2 with excess LiAlH4 is coupled with an intramolecular cyclisation to the 1H-1,3-benzazaphospholes 6 whereas the N-tertiary derivative 5 does not undergo cyclisation upon reduction. NMR data and the crystal structure of 6d are reported.

Sterically and Polarity-Controlled Reactions of tBuLi with P=CH-NR Heterocycles : Novel Heterocyclic P-and P,O-Ligands and Preliminary Tests in Transition-Metal Catalysis

(1R)-1,3-Benzazaphospholes 1 a-c, P=CH-NR heterocycles of the indole type, react with tBuLi in two ways, depending on the steric demand of the N-substituent and the polarity of the medium. The presence of small N-alkyl groups induces CH-deprotonation in the 2-position to give hetaryllithium reagents 2 a and 2 b, whereas bulky N-substituents and nonpolar solvents change the reactivity towards addition at the P=C bond. The preferred regioselectivity is tert-butylation at phosphorus, occurring with excellent diastereoselectivity for trans-adducts 3 b and 3 c, but the inverse tert-butylation at C2 to 5 b was also observed. N-Neopentyl groups, with intermediate steric demand, give rise to formation of mixtures in ethers but allow switching either to selective CH lithiation in THF/KOtBu or to addition in pentane. Bulkier N-adamantyl groups always cause preferred addition. Protonation, silylation, and carboxylation were used to convert the P=CLi-NR, (E)-tBuP-CHLi-NR, and LiP-CH(tBu)-NR species into the corresponding sigma(2)-P or sigma(3)-P compounds 4 b and 6 a,b, 7 b,c, or 8 b-10 b with additional N and/or O donor sites. Slow diffusion-controlled air oxidation of 10 b led to the meso-diphosphine 11 b. Preferred eta(1)-P coordination was shown for an [Rh(cod)Cl] complex 12 b, and the potential of the new ligands 4 b and 7 b in catalysis was demonstrated by examples of Pd-catalyzed C-N coupling and Ni-catalyzed ethylene oligomerization (TON>6300). Crystal structures of 6 b, 11 b, and 12 b are presented.

Synthesis of novel water-soluble linear and heterocyclic phosphino amino acids from 2-phosphinophenols or 2-phosphinophenolethers, formaldehyde and amino acids

Acyclic and cyclic amino acid derivatives of 2-phosphinophenols have been synthesised by reaction of primary phosphinophenols (4-R-2-H2PC6H3OH; R=H, Me, OMe) 1a–c with formaldehyde and amino acids (o- and p-aminobenzoic acid, l-lysine) via in situ formed hydroxymethyl species 2a–c. Condensation reactions with glycine did not afford defined products except when the methoxymethyl and tetrahydropyranyl ethers of 1d,e were used instead of the hydroxy compounds. o-Aminobenzoic acid gives rise to linear bis(o-carboxyphenylaminomethyl)phosphines 3a–e. p-Aminobenzoic acid, dependent on the molar ratio, affords bis(p-carboxyphenylaminomethyl)phosphines 4a,d as well as eight-membered heterocyclic 1,5,3,7-diazadiphosphacyclooctanes 5a–e. The aliphatic amino acids glycine and l-lysine form six-membered heterocyclic 1,3,5-diazaphosphorinanes 6d and 7a–e, respectively, in presence of excess formaldehyde. l-lysine differs from glycine by reaction at the terminal amino group. The structures of the compounds have been elucidated by multinuclear NMR spectroscopy. The salts of the phosphino amino acids are soluble in water. Water solubility increases with the number of hydrophilic groups, i.e. free phenols are more soluble than their ethers. Ligand concentrations in water from 0.1 to 1 M were observed.

Nickel Chelate Complexes of 2-Alkylphenylphosphanylphenolates: Synthesis, Structural Investigation and Use in Ethylene Polymerization

2-Diphenylphosphanyl- and 2-alkylphenylphosphanyl-4-methylphenols 1 or their silyl ethers 2 and equimolar amounts of nickelocene react in benzene preferably to give orange-brown diamagnetic cyclopentadienylnickel chelate complexes [η-CpNi(P∩O)] (3). Addition of a second equivalent of 1 or 2 affords (RR) and (SS) diastereoisomers of cis-bis(P∩O-chelates) 4a–c (R = Ph, Me, iPr) or the unsymmetrical cis-bis(P∩O-chelate) 5, whereas with bulkier substituted derivatives 1d or 2d (R = tBu) the second step is hindered or retarded. The reactivity of 1d remains high towards nickel salts in polar solvents, but in contrast to 1a–c, yielding 4, a sparingly soluble green trans-bis(P–O-chelate) nickel complex 6d is formed. Complexes formed in situ from 1 or 2 and Ni(COD)2 in toluene catalyze the polymerization of ethylene. The cyclopentadienyl (P∩O) complexes 3, however, are too stable to be active in this process. The crystal and molecular structure of 3c and 4c are described.

Metalated 1, 3-Azaphospholes: η1-(1H-1, 3-Benzazaphosphole-P)M(CO)5 and μ2-[(1, 3-Benzazaphospholide-P)(cyclopentadienide)nickel] Complexes†

1H-1, 3-Benzazaphospholes react with M(CO)5(THF) (M = Cr, Mo, W) to give thermally and relatively air stable η1-(1H-1, 3-Benzazaphosphole-P)M(CO)5 complexes. The 1H- and 13C-NMR-data are in accordance with the preservation of the phosphaaromatic π-system of the ligand. The strong upfield 31P coordination shift, particularly of the Mo and W complexes, forms a contrast to the downfield-shifts of phosphine-M(CO)5 complexes and classifies benzazaphospholes as weak donor but efficient acceptor ligands. Nickelocene reacts as organometallic species with metalation of the NH-function. The resulting ambident 1, 3-benzazaphospholide anions prefer a μ2-coordination of the η5-CpNi-fragment at phosphorus to coordination at nitrogen or a η3-heteroallyl-η5-CpNi-semisandwich structure. This is shown by characteristic NMR data and the crystal structure analysis of a η5-CpNi-benzazaphospholide. The latter is a P-bridging dimer with a planar Ni2P2 ring and trans-configuration of the two planar heterocyclic phosphido ligands arranged perpendicular to the four-membered ring. Metallierte 1, 3-Azaphosphole: η1-(1H-1, 3-Benzazaphosphol-P)M(CO)5 und μ2-[(1, 3-Benzazaphospholid-P)(cyclopentadienid)nickel] Komplexe 1H-1, 3-Benzazaphosphole reagieren mit M(CO)5(THF) (M = Cr, Mo, W) zu thermisch und zumindest kurzzeitig luftstabilen η1-(1H-1, 3-Benzazaphosphol-P)M(CO)5-Komplexen. Die 1H- und 13C-NMR-Daten sind mit dem Erhalt des phosphaaromatischen π-Systems im Liganden im Einklang. Die starke 31P-Koordinationsverschiebung zu hohem Feld, vor allem der Mo- und W-Komplexe, steht im Gegensatz zur Koordinationsverschiebung zu tiefem Feld, beobachtet bei Phosphin-M(CO)5 Komplexen, und verweist auf schwache Donator-, aber gute Akzeptoreigenschaften der Liganden. Nickelocen reagiert als Ubergangsmetallorganyl unter Metallierung der NH-Funktion. Die resultierenden ambidenten 1, 3-Benzazaphospholid-Anionen bevorzugen eine μ2-Koordination des η5-CpNi-Fragments am Phosphor gegenuber N-Koordination oder einer η3-Heteroallyl-η5-CpNi-Semisandwich-Struktur. Dies wird durch charakteristische NMR-Daten und die Ergebnisse der Strukturuntersuchung an Einkristallen eines η5-CpNi-benzazaphospholids belegt. Letzteres kristallisiert mit Benzol und bildet ein P-Bruckendimer mit planarem Ni2P2 Ring und trans-Konfiguration der beiden senkrecht zum Vierring angeordneten planaren heterocyclischen Phosphidoliganden.

Zur chemie der silylene: Cycloadditionen von methoxymethylsilylen mit heterodienen

Abstract Methoxymethylsilylene, generated thermally from 1,2-dimethyltetramethoxydisilane, was reacted with benzil, some benzil monoimines and 1,4-diazabutadienes to furnish in medium to good yields 1,3-dioxa-, 1,3-oxaza- and 1,3-diaza-2-sila-4-cyclopentenes via formal 1,4-cycloadditions. With unsaturated ketones and 1-azabutadienes, respectively, analogously 1-oxa- and 1-aza-2-sila-4-cyclopentenes are obtained. These are, however, accompanied by the 3-en isomers. The heterocycles are thermally very stable but sensitive to hydrolysis and oxidation. They are characterized by NMR data.

A new promising application for highly cytotoxic metal compounds: η6-areneruthenium(II) phosphite complexes for the treatment of alveolar echinococcosis.

Two series of η(6)-areneruthenium(II) phosphite complexes were prepared, characterized, and evaluated in vitro for their toxic potential against Echinococcus multilocularis metacestodes. Neutral complexes of general formula [(η(6)-p-cymene)RuCl(2){P(OR)(3)}] (R = Et, (i)Pr, Ph) with two easily exchangable chloride ligands showed only minor toxicity, whereas the substitution of these moieties against a β-diketonate (2,2,6,6-tetramethylheptanedionate) ligand led to hydrolytically stable complex salts of type [(η(6)-p-cymene)Ru(β-diketonate){P(OR)(3)}][BF(4)] (R = Et, (i)Pr, Ph) with comparable in vitro toxicity (50% PGI release at c = 1.4 - 4.7 μM) to the reference drug nitazoxanide (50% PGI release at c = 1.2 μM). In addition, the latter complexes were highly toxic against rat hepatoma cells (IC(50) = 0.40-2.0 μM) and less toxic against human foreskin fibroblasts (IC(50) = 1.1-2.9 μM) and Vero cells (IC(50) = 1.2-8.9 μM). The measured cytotoxicities against mammalian cells are, to the best of our knowledge, among the highest ever observed for ruthenium-based complexes. In conclusion, complex salts of type [(η(6)-p-cymene)Ru(β-diketonate){P(OR)(3)}][BF(4)] might be interesting candidates for further development toward anthelmintic drugs and/or highly cytotoxic metal compounds.

Metalated 1,3-azaphospholes: synthesis of lithium-1,3-benzazaphospholides and reactivity towards organoelement and organometal halides

Abstract Metalation of benzazaphospholes 1a – e with t -BuLi provided the ambident anions 1a – e Li in high selectivity. A crystal structure analysis of 1b Li ·3THF reveals monomers and coordination of lithium at nitrogen. The tungsten pentacarbonyl complexes also react preferably at nitrogen as shown by the reaction of 2a and 2d with t -BuLi. Addition at the PC bond is a minor process in the case of 2a . Compounds 1a , c Li as well as 2d Li react with alkyl halides at phosphorus to give the 3-alkyl-1,3-benzazaphospholes 3a and 3d or the respective W(CO) 5 complex 4d . Even acetyl and pivaloyl chloride attack 1e Li at phosphorus affording the P -acyl derivatives 5e and 6e . Silylation can occur at nitrogen or phosphorus to give 7 and/or 8 depending on steric and electronic effects exerted by the substituent in position 2. The different effect of 2- t -butyl groups on the steric hindrance at N and P is illustrated by the molecular geometry of 1d determined by crystal structure analysis. Soft organometallic halides such as Me 3 SnCl, CpFe(CO) 2 I and CpW(CO) 3 Cl react with 1 Li preferably at phosphorus affording the stannyl or monomer organo-transition metal derivatives 9 – 11 . The products are characterized by multinuclear NMR data of all new compounds.