Synthesis and Stereoselective Interconversion of Chiral 1-Aza-3,6-diphosphacycloheptanes

Deep-Blue Emissive Copper(I) Complexes Based on P-Thiophenylethyl-Substituted Cyclic Bisphosphines Displaying Photoinduced Structural Transformations of the Excited States

A synthetic method for a primary 2-(thiophen-2'-yl)ethylphosphine was developed. The reaction of thiophenylethylphosphine with paraformaldehyde and primary arylamines leads to the formation of cyclic bisphosphines, namely, 1,5-di(aryl)-3,7-bis(thiophenylethyl)-1,5-diaza-3,7-diphosphacyclooctane (aryl = phenyl, p-tolyl). The obtained bisphosphines form cationic bis-P,P-chelate complexes with copper(I) tetrafluoroborate, which were structurally characterized by NMR spectroscopy, mass spectrometry, and elemental and XRD analyses. Surprisingly, the copper(I) complexes display a multiband emission in the solid state with maxima at 355-360, 425-430, and 480-490 nm and nanosecond lifetimes (1.2-1.4 ns) upon a 335 nm excitation. The excitation of the complexes at 360 nm at room temperature results in a deep-blue emission at 425-430 nm and a tail at 460-490 nm. A temperature decrease leads to an increased intensity of the emission band at 480 nm, while the luminescence lifetimes insignificantly increased up to 14 ns. Quantum chemical calculations explain the observed unusual luminescent behavior by the existence of "undistorted" and "flattened" singlet excited states of copper(I) complexes at room temperature and at 77 K, respectively.

Synthesis and Structure of Iron (II) Complexes of Functionalized 1,5-Diaza-3,7-Diphosphacyclooctanes

In order to synthesize new iron (II) complexes of 1,5-diaza-3,7-diphosphacyclooctanes with a wider variety of the substituents on ligands heteroatoms (including functionalized ones, namely, pyridyl groups) and co-ligands, it was found that these ligands with relatively small phenyl, benzyl, and pyridin-2-yl substituents on phosphorus atoms in acetonitrile formed bis-P,P-chelate cis-complexes [L₂Fe(CH₃CN)₂]²⁺ (BF₄)₂⁻, whereas P-mesityl-substituted ligand formed only monoligand P,P-complex [LFe(CH₃CN)₄]²⁺ (BF₄)₂⁻. 3,7-dibenzyl-1,5-di(1′-(R)-phenylethyl)-1,5-diaza-3,7-diphosphacyclooctane reacted with hexahydrate of iron (II) tetrafluoroborate in acetone to give an unusual bis-ligand cationic complex of the composition [L₂Fe(BF₄)]⁺ BF₄⁻, where two fluorine atoms of the tetrafluoroborate unit occupied two pseudo-equatorial positions at roughly octahedral iron ion, according to X-ray diffraction data. 1,5-diaza-3,7-diphosphacyclooctanes replaced tetrahydrofurane and one of the carbonyl ligands of cyclopentadienyldicarbonyl(tetrahydrofuran)iron (II) tetrafluoroborate to form heteroligand complexes [CpFeL(CO)]⁺BF₄⁻. The structural studies in the solid phase and in solutions showed that diazadiphosphacyclooctane ligands of all complexes adopted chair-boat conformations so that their nitrogen atoms were in close proximity to the central iron ion. The redox properties of the obtained complexes were performed by the cyclic voltammetry method.

Chiral [16]-ane P4N2 macrocycles: stereoselective synthesis and unexpected intermolecular exchange of endocyclic fragments

Chiral 1,9-diaza-3,7,11,15-tetraphosphacyclohexadecanes were stereoselectively synthesized as pure RPSPSPRP isomers via a one-pot Mannich-type condensation reaction of 1,3-bis(arylphosphino)propane, formaldehyde and optically active, as well as racemic, primary amines. An unprecedented intermolecular exchange of endocyclic amino fragments of 1,9-diaza-3,7,11,15-tetraphosphacyclohexadecanes was observed. The lability of the P-CH2-N fragment in macrocyclic aminomethylphosphines is the reason of the stereoisomerization, formation of products with medium-sized cycles as well as the exchange of endocyclic amino fragments. The mechanism of these transformations involving the formation of a methylenephosphonium intermediate and further intra- and intermolecular nucleophilic substitution is discussed.

Synthesis of platinum, palladium and rhodium complexes of α-aminophosphine ligands

α-Aminophosphine-type ligands are of interest as building blocks of transition metal complexes. This review focuses on the utilization of α-aminophosphines as monodentate and bidentate ligands in platinum, palladium and rhodium complexes. Besides the linear derivatives, the applications of cyclic α-aminophosphines as ligands are also summarized. Various aspects, such as synthesis, structure and applications, as well as the catalytic activity of these complexes are discussed.

Covalent self-assembly of the specific RSSR isomer of 14-membered tetrakisphosphine

The first representative of the specific RSSR isomer of 14-membered tetrakisphosphine has been obtained instead of the RRRR/SSSS isomer predicted according to the empirical rule formulated recently. The geometry of the obtained 14-P₄N₂ is preorganized for the dicopper complex formation with the unique coordination mode in the row of P₄N₂ corands.

Cyclic aminomethylphosphines as ligands. Rational design and unpredicted findings

Rational design of title ligands and their transition metal complexes gave the high effective catalysts for hydrogen economy and perspective “stimuli-responsive” luminescent materials. Together with the above novel cyclic aminomehtylphospine ligands have showed a row of unpredicted properties like spontaneous formation of macrocyclic molecules, unique reversible slitting of macrocycles on to the smaller cycles, rapid interconversion of the isomers catalyzed by both acids and transitional metals, bridging behavior of usually chelating ligands and unexpected high influence of handling substituents on N-atoms on to the catalytic and luminescent properties of P-complexes.

Synthesis and unique reversible splitting of 14-membered cyclic aminomethylphosphines on to 7-membered heterocycles

A novel type of 14-membered cyclic polyphosphine, namely 1,8-diaza-3,6,10,13-tetraphosphacyclotetradecanes 2a–4ahas been synthesized by the condensation of 1,2-bis(phenylphosphino)ethane, formaldehyde and alkylamines (isopropylamine, ethylamine and cyclohexylamine) as a RRRR/SSSS-stereoisomer. The structure of macrocycle 2a was investigated by NMR-spectroscopy and X-ray crystal structure analysis. The unique reversible processes of macrocycles 2a–4a splitting onto the corresponding rac- (2b–4b) and meso- (2c–4c) stereoisomers of 1-aza-3,6-diphosphacycloheptanes were discovered.

Alternating stereoselective self-assembly of SSSS/RRRR or RSSR isomers of tetrakisphosphines in the row of 14-, 16-, 18- and 20-membered macrocycles

Covalent self-assembly of novel 18- and 20-membered P,N-corands as single stereoisomer is described.