The cis-Re(Ph2PCH2CH2PPh2)2)+ metal centre. Synthesis and molecular structure of the dinitrile complex cis-[Re(NCC6H4Me-4 2(Ph 2 PCH 2 CH 2 PPh 2 2 ][BF4]

Reaction of NCC₆H₄X-4 (X  Me, OMe, or Cl) with trans-[ReCl(N₂)(dppe)₂] (dppe  Ph₂PCH₂CH₂PPh₂), at room temperature, in the presence of Tl[BF₄], gives the corresponding complexes cis-[Re(NCC₆H₄X-4)₂(dppe)₂][BF₄] (1); the crystal structure of 1 (X  Me) has been determined by single crystal X-ray diffraction analysis.     

Catalytic activity of Mn(III) and Fe(III) complexes of meso-tetra(n-propyl)porphyrin in oxidation of olefins: Meso-alkyl substituent in comparison with the alkenyl and aryl ones

Catalytic activity of Mn(III) and Fe(III) complexes of meso-tetra(n-propyl)porphyrin, MnT(n-Pr)P(X) and FeT(n-Pr)P(X) (X = Cl, SCN, OAc) in oxidation of olefins with tetra-n-butylammonium periodate at room temperature has been studied. The influence of different parameters including the molar ratio of catalyst to imidazole, type of counter ion (X) and oxidative stability of metalloporphyrins on the efficiency of the catalysts was investigated. The results of competitive oxidation of cis- and trans-stilbene suggest the presence of a high-valent Mn-oxo as the predominant oxidant species in equilibrium with a six coordinate complex, MnT(n-Pr)P(ImH)(IO₄) in the case of MnT(n-Pr)P(OAc). An unusual preference for trans-stilbene over cis-stilbene was observed in the reaction catalyzed by FeT(n-Pr)P(OAc). Control reaction indicated a significant cis- to trans-isomerization (81%) in oxidation of cis-stilbene catalyzed by FeT(n-Pr)P(OAc) which may explain the observed unusual cis to trans-stilbene oxide ratio. While oxidation of cyclooctene and styrene led to the exclusive formation of the corresponding epoxides, oxidation of cyclohexene gave 2-cyclohexe-1-ol and cyclohexene oxide as the products. However, the results of this study clearly demonstrate the key role played by the group substituted at the meso positions of metalloporphyrins on their catalytic activity, apart from the electron-donating or electron-withdrawing properties of the substituents.     

Selective reduction of tertiary alkyl,benzyl, and allyl halides to hydrocarbons using lithium 9,9-di-n-butyl-9-borabicyclo[3.3.1]nonanate

The title 9-borabicyclo[3.3.1]nonane(9-BBN) ate complex (1) brings about selective removal of tertiary alkyl, benzyl and allyl halides to give the corresponding hydrocarbons in excellent yields without concomitant attack on secondary, primary and aryl derivatives. The reduction of cis- and trans - 4 - t - butyl - 1 - methylcyclohexyl chlorides (2) with 1 gives 4 - t - butyl - 1 - methylcyclohexanes (3) with partial inversion of configuration in cyclohexane, while that in benzene gives thermodynamically stable trans-3 predominantly. The reactions of 1,1 - dimethyl - 5 - hexenyl chloride (4) and 1,7,7 - trimethylbicyclo[2.2.1]hept - 2 - yl chloride (8) with 1 proceed with the rearrangements characteristic to a carbonium ion intermediate. The reduction of 1 - ethyl - 1 - methylpentyl chloride with 1 follows a second-order rate equation.     

Cyanoalkyl Complexes of Platinum (II). I. Preparation and Spectroscopic Properties

The oxidative addition of XRCN to PtL₄ yields cis-and/or trans-PtX(RCN)L₂ (X = Cl, Br; R = (CH₂)_n, n = 1, 2, 3; L = PPh₃, PPh₂CH₃, AsPh₃). L is readily displaced by more basic phosphines or by a diphosphine. In each case the trans complex is the thermodynamically more stable isomer and cis-trans isomerization catalyzed by free L occurs in dichloromethane. Insertion of CO in the σ Pt? C bond takes place quantitatively in the case of cyanoethyl and cyanopropyl. Abstraction of X by AgBF₄ gives cis or trans cationic complexes with N-bonded CN group.     

Phosphinsubstituierte chelatliganden I. Mangan- und rheniumcarbonyl-komplexe mit phosphino-(thio)formamid- und -dithioformiat-liganden

A series of new tetracarbonyl and tricarbonyl complexes of manganese and rhenium with heteroallylic phosphine chelate ligands L  [XC(Y)PPh₂]^? and HXC-(Y)PPh₂ (X, Y  NR, O, S) were prepared by reaction of the appropriate metal carbonyl halides with the free ligands or their silyl intermediates. The silyl method yields both cis-(CO)₄ML and fac-(CO)₃M(X)L (X  Cl, Br) complexes by controlled addition of water. Analytical, spectroscopic and crystallographic data of the ambidentate thioformamide ligands result in a P,S-coordination in all complexes. The ¹³C NMR spectra of several selected compounds were recorded and reveal some unexpected features.     

Cumulated double bond systems as ligands : IV. 1H and 13C NMR studies of the intra- and inter-molecular exchange processes of cationic dialkylsulfurdiimine compounds of RhI,IrI and PtII

The preparation and properties are described of trans-[(Ph₃P)₂(CO)M(RNSNR)] [ClO₄] (M  Rh^I, Ir^I; R  Me, Et, i-Pr, t-Bu) and of cis- or trans-[L₂Pt(RNSNR)X] [ClO₄] (X  Cl^?, L  Et₂S, PhMe₂As, PhMe₂P, R  Me, t-Bu; X  CH₃, L  PhMe₂P, R  Me).¹H and ¹³C NMR data show the existence of various isomers in solution which may interconvert via intra- and inter-molecular exchange processes. A general reaction scheme for the intramolecular exchange processes is discussed.     

Syntheses of chiral 1,3-disubstituted tetrahydro-β-carbolines via CIAT process: highly stereoselective Pictet–Spengler reaction of d-tryptophan ester hydrochlorides with various aldehydes

A highly stereoselective Pictet–Spengler reaction of d-tryptophan methyl ester hydrochloride 1-HCl with various aldehydes via a CIAT (crystallization-induced asymmetric transformation) process is described. It was revealed that the CIAT process should be performed in a mixed solvent of nitromethane and toluene, and a fine tuning of the ratio of nitromethane and toluene for each epimer mixture of 2-HCl was necessary in order to get as high yields and stereoselectivities as possible. Enantiomerically pure cis (or trans) 1,3-disubstituted tetrahydro-β-carbolines 2a–2v were obtained by recrystallization or flash chromatography after neutralization of the corresponding hydrochloride salts cis-2-HCl or trans-2-HCl.     

Synthesis of 1,4-disilacyclohexa-2,5-dienes

Title compounds of the type 2,3,5,6-tetraphenyl-1,4-di-X-1,4-di-Y-1,4-disilacyclohexa-2,5-diene wherein X=Y=NMe₂ (4); X=NMe₂, Y=Cl (cis, trans-5); X=NMe₂, Y=Me [(trans)-6] and X=t-Bu, Y=Cl (trans-8) were synthesized from Si₂(NMe₂)₅Cl, sym-Si₂(NMe₂)₄Cl₂, sym-Si₂(NMe₂)₄Me₂, and sym-Si₂Cl₄(t-Bu)₂, respectively, in the presence of diphenylacetylene at 200 °C. Similarly the analogous title compound from the combination of 1-phenyl-1-propyne and Si₂(NMe₂)₅Cl [X=Y=NMe₂ (cis and trans-7) was synthesized. In all cases where cis/trans diastereomers could arise from two different silicon substituents (5, 6, 8) the trans isomer was the sole or dominant product. Evidence for the intermediacy of the silylene Si(NMe₂)₂ in these reactions was gained from a trapping experiment. Compound 4 upon treatment with SiCl₄, SiBr₄ or PI₃ provided the corresponding 1,1,4,4-tetrahalo derivatives 9a-c, respectively. Treatment of 4 with MeOH or PhOH gave the 1,1,4,4-tetramethoxy and tetraphenoxy analogues 9d and 9e, respectively. The tetrachloro derivative 9a upon LAH reduction led to the corresponding tetrahydro compound 10, while the reaction of 9a with H₂O gave the tetrahydroxy derivative 11. Allowing (trans)-6 to react with SiCl₄ provided a ca. 1:1 cis/trans ratio of the derivative 12 in which X=Cl, Y=Me, and possible pathways that rationalize this loss of stereochemistry are proposed. Synthesis of trans-13 in which X=t-Bu, Y=H was achieved by LAH reduction of 8. All of the title compounds except 8 experience free phenyl rotation at room temperature. At −30 °C this rotation in 8 is essentially halted. The molecular structures of 4, 8, 9c, 9e, 10 and 13 were determined by X-ray crystallography.     

PhP-PPh group bound to 1,8-positions of naphthalene: Preparation of cis isomer and synthesis of binuclear complex

A thermodynamically less stable cis isomer of 1,2-diphosphacycle was prepared from the corresponding trans isomer. Diphosphine, in which a PhP-PPh bond bridges the 1,8-positions of naphthalene, 1,2-diphenyl-1,2-dihydronaphtho[1,8-cd][1,2]diphosphole (1), was first prepared according to a previously reported method, and the trans isomer of 1 was irradiated in tetrahydrofuran with UV-vis light to reach equilibrium with cis-1 in a trans:cis ratio of 1:2. When a similar photochemical conversion was carried out using a saturated hexane solution of trans-1, cis-1 was precipitated in a good yield of 94%. The configuration of cis-1 was confirmed by X-ray analysis. Both cis- and trans-1 diphosphine ligands were used for the preparation of binuclear gold complexes. The crystal structure of (μ-cis-1)-[AuCl]₂ demonstrated that the two lone pairs of cis-1 are suitably directed for arrangement of the two gold centers in close proximity to each other. The two independent (μ-cis-1)-[AuCl]₂ molecules in the crystal were found to form a dimer through the multiple intermolecular interaction among the gold centers.     

δ-lactones from grignard reactions : Their isolation and structure characterization

Grignard reactions on methyl 4-methyl, 5-oxo, 5-phenyl (pX substituted) pentanoates 1-6 (X = H, Me, F, Cl, Br, OMe) produced mixtures of cis-(7-11) and trans-(12-16) tetrahydro 5,6 dimethyl-6-phenyl -2H-pyran-2-ones. They were isolated by HPLC and characterized by ¹H and ¹³C techniques. The stereochemistry of Grignard reactions in THF with CH₃MgCl was determined at 0° and 60°.     

Synthesis and structure of some cis-and trans-myrtanylstannanes

Enantiomerically pure cis- and trans-myrtanylstannanes cis-MyrSnPh₃ (1), trans-MyrSnPh₃ (2), cis-MyrSnPh₂Cl (3), trans-MyrSnPh₂Cl (4), cis-MyrSnPhCl₂ (5), trans-MyrSnPhCl₂ (6), cis-MyrSnCl₃ (7), trans-MyrSnCl₃ (8) were synthesized and fully characterized by ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. The molecular structures of 1, 3, 6, 7, and [trans-MyrSn(OH)Cl₂ · H₂O]₂ (8a) a hydrolysis product of 8, were determined by X-ray crystallography.     

Übergangsmetall-Carbin-Komplexe: CIII. Aktivierung von Ethylisocyanid an elektronenreichen Metallzentren; Synthese von einkernigen Wolfram-Aminocarbin-Komplexen des Typs Tp′(CO)2 WCN(R)Et (R  Me,Et)

A large-scale, high-yield synthesis of the aminocarbyne complexes Tp′(CO)₂WCN(R)Et (5: R  Me; 6: R  Et) [Tp′ = hydridotris(3,5-dimethylpyrazol-1-yl)borate] is reported, starting from Tp′W(CO)₃I (2). The first step of the synthetic procedure involves thermal decarbonylation of 2 with EtNC to give cis-Tp′W(CO)₂(CNEt)I (3). Complex 3 is then reduced with Na/Hg to give the metallate Na[Tp′W(CO)₂(CNEt)] (4). Finally, complex 4 is alkylated with RI (R  Me, Et) exclusively at the isocyanide nitrogen to give the aminocarbyne complexes 5 and 6. In contrast, the metallates Na[(η⁵-C₅R′₅)W(CO)₂(CNEt)] (R′  H, Me) undergo alkylation with RI at the metal centre to afford the W^II alkyl complexes cis/trans-(η-C₅R′₅)W(CO)₂(CNEt)R. This difference in reactivity is ascribed to the steric demands of the Tp′ ligand, which shields the metal centre from the incoming electrophile.     

Solid-state vibrational spectroscopy: Part 11. An infrared and raman vibrational spectroscopic study of metal(II) halide aniline complexes

Infrared (4000?200 cm^?1) and Raman (3500?50 cm^?1) spectra are reported for metal(II) halide aniline complexes of the following stoichiometries: (MX₂an₂) (M  Co, Ni or Hg, X  Cl; M  Mn, X  Cl or Br; M  Zn or Cd, X  Cl, Br or I); (MX₂an₃) (M  Mn, X  Cl or Br; M  Ni, X  Cl); (CdCl₂an) and an assignment is proposed for all the observed bands. Low-temperature (83 K) IR spectra are also reported and it is noted that whilst the aniline ring and CH mode values are virtually insensitive to temperature, the NH₂ rocking and metal-ligand stretching mode values increase with decreasing temperature, whilst the NH₂ stretching mode values decrease with decreasing temperature.     

Synthesis and characterization of some trans-hydridomethylbis(phosphine)-platinum(II) and -palladium(II) complexes

Several trans-hydridomethylbis(phosphine)-platinum(II) and -palladium(II) complexes have been made by the reaction: trans-M(H)Cl(PR₃)₂ + CH₃MgBr → trans-M(CH₃)(PR₃)₂ + MgClBr and their structures determined by ¹H NMR and IR spectroscopy. The complexes in which M  Pt and R  Cy (cyclohexyl) or i-Pr (isopropyl) are very stable in the solid state and in solution, while the compounds in which M  Pt, R  Et (ethyl) and M  Pd, R  i-Pr slowly decompose either in the solid state or in solution. The compound in which M  Pd and R  Cy was not isolated but was identified in solution.     

Heterocyclic polyfluoro-compounds. Part 36 [1]. The reaction of 2,2-bis(trifluoromethyl)-3,4-difluoro-oxetan with aluminium trichloride

2,2-Bis(trifluoromethyl)-3,4-difluoro-oxetan, when treated with aluminium trichloride at 30 to 90 °C, undergoes $\text{cis}$ to $\text{trans}$ isomerisation, non-stereospecific exchange of the 4-fluorine by chlorine, and more slowly of the 3-fluorine, and ring opening to give preferentially the alcohols (CF₃)₂C(OH)CXCHCl (X  F or Cl), together with the aldehydes (CF₃)₂CClCHXCHO and acid chlorides (CF₃)₂CClCHXCClO (X  F or Cl). A large number of unidentified minor products were also obtained from the reactions carried out at the higher temperatures.     

Template synthesis of a macrocycle with a mixed NHC/phosphine donor set

Reaction of cis-[ReCl(NHC)(CO)₄] cis-[1] (NHC = NH,NH-substituted saturated cyclic diaminocarbene) with diphosphine (2-F-C₆H₄)₂P-CH₂CH₂-P(C₆H₄-2-F)₂2 yields complex fac-[Re(NHC)(2)(CO)₃]Cl fac-[3]Cl. Deprotonation of the NH,NH-NHC ligand in fac-[3]Cl with KOtBu leads to an intramolecular nucleophilic aromatic substitution of one fluorine atom from each -P(C₆H₄-2-F) group by the NHC ring nitrogen atoms with formation of complex fac-[4]Cl bearing a facially coordinated [11]ane-P₂C^NHC ligand. Reaction of cis-[MnBr(NHC)(CO)₄] cis-[5] (NHC = NH,NH-substituted saturated cyclic diaminocarbene) with diphosphine 2 yields complex [MnBr(NHC)(2)(CO)₂] [6] without substitution of the bromo ligand and with the phosphine donors from the bidentate diphosphine occupying one cis and one trans position to the NHC donor.     

Synthesis and applications of a new palladacycle as a high active catalyst in the Suzuki couplings

The reaction of biphenyl-based phosphine P(o-C₆H₄Me)Ph₂ (1) with Pd(OAc)₂ in toluene affords the air and water stable palladacycle (2) as a binuclear compound which has been characterized by multi-nuclear NMR spectroscopy and elemental analysis as a mixture of cis and trans isomers with relative intensity of 1:3, respectively. This palladacycle is a highly efficient catalyst precursor for the coupling of aryl boronic acids and aryl halides. Both activated and deactivated aryl bromides and chlorides are efficiently coupled in the presence of 2 to furnish the corresponding cross-coupled products in excellent yields, and a wide variety of functional groups are tolerated in aryl halides. This methodology has also been extended for the coupling of bromoarylphosphines and bromoarylphosphine oxides with aryl boronic acids for the generation of hindered corresponding products.     

A new route to the benzazepines and a general synthesis of rhoeadanes

Treatment of immonium salt 4 under Schotten-Baumann conditions yielded aldehydo amide 5 which was cyclized in base to benzazepine 6. In an extension of this new benzazepine synthesis, immonium salt 7 was converted to the aldehydo amide 8 which was cyclized in base to the B/D-trans rhoedane 9. Red-al reduction of 9 yielded hemiacetal 12, and further Red-al reduction of methyl acetal 13 followed by HCOH-NaBH₄ N-methylation afforded the B/D-trans rhoeadane 16.     

Octahedral bis(acetylide) and bis(diacetylide) complexes of ruthenium(II) with linear C2MC2 and C4MC4 chains: The first X-ray structures of the all trans bis(acetylides) Ru(CO)2(CCPh)2(PEt3)2 and Ru(CO)2(CCH)2(PEt3)2

Bis(acetylides) and bis(diacetylides) of ruthenium(II), trans-Ru(CO)₂(PEt₃)₂(CCR)₂ (1) (1a, R  Ph; 1b, R  ^tBu; 1c, R  SiMe₃; 1d, R  H) and trans-Ru(CO)₂(PEt₃)₂(CCC CR)₂ (2) (2a, R  SiMe₃; 2b, R  H) have been synthesized and characterised. The first single crystal X-ray analyses of these all trans-acetylides have revealed linear C₂RuC₂ chains in 1a and 1d.     

Reactions of nitrilium triflate salts with trans-[IrCl(CO)(PPh3)2

Low yields of the ionic carbene complexes [Ir(RCNHMe)Cl(CO)(PPh₃)₂-(O₃SCF₃)]O₃SCF₃]O₃SCF₃ (R  Ph or PhCH₂) have been isolated from the reactions of trans-[IrCl(CO)(PPh₃)₂] with the nitrilium triflate salts, [RCNMe]O₃SCF₃. The major products from these, and the similar reactions of the nitrilium salts where R  Me or Bu^t, are amorphous, yellow complexes [Ir(RCNHMe)Cl(CO)(PPh₃)₂O₃SCF₃.