Diad Phosphorus-Nitrogen Prototropism of Tris(alkylamino)phosphines

Russian Journal of General Chemistry -     

The reactions of alkylamino substituted phosphines with I2 and (Ph2Se2I2)2: structural features of alkylamino phosphonium cations

The reactions of the tris-dialkylamino phosphines (Et2N)3P and (nPr2N)3P, and the pyrrolidinyl substituted phosphines (C4H8N)3P and tBuP(NC4H8)2, with I2 and (Ph2Se2I2)2, have been reported. The reactions with diiodine lead to the formation of [R3PI]I adducts, which are essentially ionic, but show a tendency to display long, soft-soft, II interactions in the solid state. The crystal structures of [(Et2N)3PI]I, (1), [(nPr2N)3PI]I, (2), and [(C4H8N)3PI]I, (3), have all been determined, and display II interactions varying between 3.5170(6) and 3.6389(14) A. The analogous reactions with (Ph2Se2I2)2 lead to the formation of phenylseleno-phosphonium salts, [R3PSePh]I. The structures of [(C4H8N)3PSePh]I, (6) and [(C4H8N)2tBuPSePh] I, (7), have been determined and do not display any soft-soft interactions between the selenium and iodine atoms. All of the phosphonium salts represent examples of structures containing tris-dialkylamino phosphine fragments which show no special nitrogen atom, i.e. all three nitrogen atoms are planar. This type of arrangement is usually observed when a C3 symmetric conformation is observed, (which is the case for 1 and 2), but not for the (C4H8N)3P adducts 3 and 6, where the conformation is closer to Cs, although the nitrogen atoms are still essentially planar. The P-N bonds in all the compounds reported herein are short, ranging between 1.599(12) A and 1.643(12) A, and are consistent with the previously reported short P-N bonds in phosphonium salts featuring tris-dialkylamino substituted phosphines.     

One-electron redox reactions involving chromium(0) and molybdenum(0) bis-1,3,5-trimethylbenzene derivatives

The reaction of M(η⁶-1,3,5-Me₃C₆H₃)₂, M = Cr, Mo, with the tetrahalides of Groups 4 and 5 elements proceeds with the monoelectronic oxidation of the metal bis-arene to the [M(η⁶-Me₃C₆H₃)₂]⁺ cation. In the case of MX₄, M = Ti, X = Cl, Br, M = V, X = Cl, and of Nb₂Cl₁₀ the reduction products are the titanium(III), vanadium(III) halides and the niobium(IV) chloride, isolated as the solvate anions [MCl₄(THF)₂]⁻ and [NbCl₄(CH₃CN)]⁻. The reaction of the tetrachloro complexes MCl₄(THF)₂, M = Zr, Hf, with Cr(η⁶-1,3,5-Me₃C₆H₃)₂ in THF produces the ionic [Cr(η⁶-1,3,5-Me₃C₆H₃)₂][MCl₅(THF)], which has been characterized by single-crystal X-ray diffraction in the case of hafnium.     

Syntheses of copper(I)cis-1,3,5-tri-iminocyclohexane complexes

Copper(I) complexes of the ligand cis-1,3,5-tris(cinnamylideneamino)cyclohexane (L) have been prepared from a versatile precursor complex, [Cu(I)(L)NCMe]BF4, which incorporates a labile acetonitrile ligand that can be exchanged to give a range of new Cu(L)X complexes (where X = Cl, Br, NO2, SPh). 1H NMR spectra and X-ray structures of the Cl, Br and NO2 complexes show L coordinated in a symmetric fashion about the copper centre. The complexes have been further characterised using UV/Visible spectroscopy and cyclic voltammetry. CuLCl shows an electrochemically reversible Cu(I/II) redox couple at 0.51 V (vs. Ag/AgCl) while the CuLNO2 complex shows an analogous quasi-reversible wave at 0.41 V (vs. Ag/AgCl).     

Stereoselective control in the Staudinger reactions involving monosubstituted ketenes with electron acceptor substituents: experimental investigation and theoretical rationalization

The stereoselectivity of the Staudinger reactions involving monosubstituted ketenes with electron acceptor substituents was investigated experimentally by determination of the product stereochemistry and theoretically via DFT calculations. The results indicate that imines preferentially attack the less sterically hindered exo-side of the ketenes to generate zwitterionic intermediates. Subsequently, for cyclic imines, the intermediates undergo a conrotatory ring closure directly to produce β-lactams, while for linear imines, the imine moiety of the intermediates isomerizes to more stable intermediates, which further undergo a conrotatory ring closure to afford trans-β-lactams. The steric hindrance and the isomerization, rather than the torquoelectronic effect, play crucial roles in controlling the stereoselectivity in the practical Staudinger reactions involving monosubstituted ketenes with electron acceptor substituents, although the unaccessible borylketene with a powerful electron acceptor group controls the stereoselectivity torquoelectronically, in theory.     

Oxidative addition reactions of tri(2-methylphenyl)antimony

Bis[??-oxo-tri(2-methylphenyl)antimony] (I) was synthesized via oxidation of tri(2-methylphenyl)antimony by hydrogen peroxide in ether. In the presence of 2-hydroxy-5-bromobenzaldoxime or furfural oxime, the reaction between these reactants (in a 1: 1: 1 molar ratio, respectively) yields (??-oxo)bis[2-hydroxy-5-bromobenzaldoximato-tri(2-methylphenyl)antimony] (II) or (??-oxo)bis[furfural-oximatotri(2-methylphenyl)antimony] (III). The structures of compounds I?CIII was determined by X-ray diffraction. In the centrosymmetric dimeric complex I, the Sb atom has a distorted trigonal-bipyramidal coordination with oxygen atoms in equatorial and axial positions. In II and III, the axial positions are occupied by the bridge oxygen atom and the oxygen atom of the oxime ligand. Bond length values are as follows: Sb-C 2.137(3)?C2.183(3), 2.116(7)?C2.131(7), and 2.105(5)?C2.126(6)?; Sb-O 1.934(2), 2.077(2), 1.973(4)?C2.151(4), and 1.9706(3)?C2.112(6) ? for I, II, and III, respectively. Intramolecular contacts Sb...N (2.953(8), 3.002(9), and 2.951(8) II and III.     

Synthesis and X-ray molecular structure of cis,cis-1,3,5-Tris(diphenylphosphino)- 1,3,5-tris(methoxycarbonyl) cyclohexane

The novel tripodal phosphine ligand cis, cis-1,3,5-tris(diphenylphosphino)-1,3,5-tris(methoxycarbonyl)cyclohexane (tdppcyme) (2) has been synthesized. ¹H, ¹³C and ³¹P NMR spectroscopy shows that in solution the sterically demanding diphenylphosphine groups occupy equatorial positions on the cyclohexane ring. An X-ray crystal investigation confirms this result for the solid state. Treatment of tdppcyme with Mo(η⁶-C₇H₈)(CO)₃ gives Mo(tdppcyme)(CO)₃ (3), with octahedral molybdenum coordination.     

Multiselective enzymatic reactions for the synthesis of protected homochiral cis- and trans-1,3,5-cyclohexanetriols

For the synthesis of the potentially antipsoriatic vitamin D derivative 3 (Ro 65-2299) an efficient and multiselective enzymatic step had been developed in which the easily accessible trans-1,3,5-triacetoxy-cyclohexane 5 was selectively monohydrolyzed in the presence of the cis-isomer 8 to give (1R,3R)-1,3-diacetoxy-5-hydroxy-cyclohexane 6 in high enantiomeric excess (>99%) and yield (84%). Furthermore, for the synthesis of the enantiomer of 3, a simple and efficient enzymatic procedure for the asymmetric acetylation of cis-1,5-dihydroxy-3-(tert-butyldimethylsilanoxy)-cyclohexane 10 in an anhydrous organic solvent providing (1R,3S,5S)-1-acetoxy-3-hydroxy-5-(tert-butyldimethylsilanoxy)-cyclohexane 11 in >99% ee and quantitative yield is described.     

Mixed ligand complexes involving aminoacid dithiocarbamates,substituted phosphines and nickel(II)

Mixed ligand complexes involving four aminoacid dithiocarbamates (RRdtc=glydtc^– (R=H; R=H), methdtc^– (R=H; R=C₃H₇S), sardtc^– (R=Me; R=H), trydtc^– (R=H; R=C₉H₈N), substituted phosphines [PPh₃, Ph₂PCH₂CH₂PPh₂(dppe)] and nickel(II) are reported. All are diamagnetic. Thermal analyses of the complexes are in keeping with the proposed formulae. Thermal decomposition of the dithiocarbamate moiety proceeds through the formation of Ni(SCN)₂. PPh₃ and dppe are lost in the initial decomposition stages.     

Complexing reactions of bis[tri(pentafluorophenyl)germyl]cadmium

Conclusions Several complexes of bis[tri(pentafluorophenyl)germyl]eadmium with ligands of the donor type were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 702–703, March, 1973.     

Reduction of tri(hetero)arylcarbinols to tri(hetero)arylmethanes

Summary A series of seven new tri(hetero)arylmethanes has been prepared by reduction of the corresponding carbinols using a mixture of lithium aluminium hydride/aluminium trichloride. The yields are excellent (77–98%) except in the case of the tri(2-benzothienyl)derivative (41%).¹H NMR spectra are discussed.

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Reduktion von Tri(hetero)arylcarbinolen zu Tri(hetero)arylmethanen

Zusammenfassung Durch die Reduktion der entsprechenden Carbinole mit Lithium-aluminiumhydrid/Aluminiumchlorid wurden sieben neue Tri(hetero)arylmethane in sehr guten Ausbeuten (77–98%) hergestellt. Eine Ausnahme bildet das Tri-(2-benzothienyl)-Derivat mit 41%. Die¹H-NMR-Spektren werden diskutiert.

     

Structures of dibenzocycloheptenylidene- and fluorenylidene-(2,4,6-tri-t-butylphenyl)phosphines and their reactions with sulfur

Dibenzocycloheptenylidene(2,4,6-tri-t-butylphenyl)-phosphine and fluorenylidene(2,4,6-tri-t-butylphenyl)-phosphine were prepared by the reactions of lithium silylphosphide with benzosuberenone and fluorenone, respectively. The reactions of the phosphines with sulfur were carried out to compare the results with those of the corresponding diphenyl derivative, and the new findings are discussed in terms of steric hindrance based on the results of the X-ray crystallographic analyses for dibenzocycloheptenylidenephosphine and its sulfide and the computational structure for the fluorenyl derivative. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 375–382, 1997     

EC(EE) processes in the reduction of some 2-methylthio-4,6-di(alkylamino)-1,3,5-triazines on mercury electrodes

Polarographic (direct current, dc, and differential pulse, DP) studies of the electroreduction of the s-triazine derivatives ametryn (2-methylthio-4-ethylamino-6-isopropylamino)-1,3,5-triazine), dimethametryn (2-methylthio-4-ethylamino-6-(1,2-dimethylpropyl) amino-1,3,5-triazine) and simetryn (2-methylthio-4,6-di(ethylamino)-1,3,5-triazine) were made in the acidity range from 2.25 M H₂SO₄ to pH 6.5. Above this last pH value no signals were obtained. In DP polarography, two main reduction peaks were observed, accompanied by a pre-peak due to the adsorption of the herbicides on the electrode. The main peaks corresponded to two-electron irreversible reduction processes, at pH values higher than the protonation pK of the triazine ring (ca. 4). In this pH range, the protonation of the triazine ring preceding the reduction process is responsible for decrease in limiting current. At pH<pK the herbicides suffer a cleavage of the –SCH₃ group via two different intermediates related by a chemical reaction, whose extension depends on the herbicide.     

Heterofunctionalized phosphines derived from (2-formylphenyl)diphenylphosphine and their reactions with oxorhenium(V) complexes

Reactions of [ReOCl₃(PPh₃)₂] with a potentially tridentate Schiff base derived from (2-formylphenyl)diphenylphosphine and 2-aminophenol, HL¹P, (HL¹P = Ph₂PC₆H₄-2-HCN(C₆H₄-2-OH)) result in a rapid decomposition of the Schiff base and the formation of a large number of hitherto non-identified metal-containing species, while from similar reactions with the analogoue phosphine oxide HL¹PO, (HL¹PO = Ph₂P(O)C₆H₄-2-HCN(C₆H₄-2-OH)) products of the compositions [ReOCl₂(PPh₃)(L¹PO)] (1) and [Re(NC₆H₄-2-OH)Cl₃(PPh₃)₂] (2) could be isolated. The structure of 2 is an experimental proof of the preceding, metal-induced cleavage of the C–N double bond. A subsequent reaction of the released 2-aminophenol forms the final phenylimido ligand.Reduction of HL¹P with NaBH₄ gives the phosphine amine H₂L²P (H₂L² = Ph₂P(C₆H₄-2-CH₂NH(C₆H₄-2-OH))) in good yield. Reactions of H₂L²P with common oxorhenium(V) complexes result in the formation of the stable rhenium(V) complex [ReOCl₂(HL²P)] (3) with a facially coordinated HL²P^? ligand.     

Thiol-ene reactions of 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT): facile access to functional tripodal thioethers

Efficient syntheses of tripodal thioethers have been achieved by ionic thiol-ene reactions of 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT) with a variety of commercially available thiols. The reactions are complete within minutes and give the products in high yields (63−96%) and high purity without a complex workup. The thiol-ene reactions tolerate a wide range of functionality, including hydroxy, amino, carboxylate, and trimethoxylsilyl groups. The amino acid cysteine is also an excellent substrate for this reaction.     

Stereoselective synthesis of cis- and trans-oligo(phenylenevinylene)s via palladium-catalyzed cross-coupling reactions

cis-Oligo(phenylenevinylene)s (OPVs) are synthesized by Suzuki-Miyaura coupling of arylboronic acids with (Z)-bromoalkenes in over 96% geometrical purity. On the other hand, trans-oligo(phenylenevinylene)s can be synthesized by Hiyama coupling of aryl iodide with (E)-alkenylsilanes in almost perfect purities. Effect of pi-conjugation chain length on photoisomerization behavior of OPVs is described.     

Chloride-bridged methylpalladium(II) dimers. Preparation,carbonylation and bridge-splitting reactions with tertiary phosphines

[Pd₂(μ-Cl)₂Cl₂L₂] (L = PEt₃, PBu₃ or PMe₂Ph) reacts with AlMe₃ in ether, THF or a mixture of these solvents depending on L to give [Pd₂(μ-Cl)₂Me₂L₂] in high yield, which has been characterized by IR and NMR spectroscopy as well as elemental analysis. Treatment of [Pd₂(μ-Cl)₂Me₂L₂] with CO yields [Pd₂(μ-Cl)₂(COMe)₂L₂], while its reaction with L leads to trans-[PdClMeL₂]. The preparative method and the characteristic data of these complexes are discussed in comparison with the earlier work on the analogous aryl and aralkyl complexes.