Novel Asymmetric and Stereospecific Aziridination of Alkenes with a Chiral Nitridomanganese Complex

The addition of pyridine N -oxide is necessary to obtain high enantioselectivities in the asymmetric aziridination of styrene derivatives through transfer of a nitrogen atom from chiral, toluenesulfonic anhydride activated nitridomanganese complex 1 [Eq. (a)]. Remarkably, high stereospecificity was observed in all the aziridinations of trans- and cis-1,2-disubstituted alkenes. R¹=H, Me, nPr, iPr; R²=H, Me; Ts=p-toluenesulfonyl.     

The interplay of solvation,molecular conformation and supramolecular assembly in 1,1′‐({[(ethane‐1,2‐diyl)dioxy](1,2‐phenylene)}bis(methanylylidene))bis(thiosemicarbazide) and its N,N‐dimethylformamide disolvate

The wide diversity of applications of thiosemicarbazones and bis(thiosemicarbazones) has seen them used as anticancer and antitubercular agents, and as ligands in metal complexes designed to act as site‐specific radiopharmaceuticals. Molecules of 1,1′‐({[(ethane‐1,2‐diyl)dioxy](1,2‐phenylene)}bis(methanylylidene))bis(thiosemicarbazide) {alternative name: 2,2′‐[ethane‐1,2‐diylbis(oxy)]dibenzaldehyde bis(thiosemicarbazide)}, C₁₈H₂₀N₆O₂S₂, (I), lie across twofold rotation axes in the space group C2/c, with an O—C—C—O torsion angle of −59.62 (13)° and a trans‐planar arrangement of the thiosemicarbazide fragments relative to the adjacent aryl rings. The molecules of (I) are linked by N—H...S hydrogen bonds to form sheets containing R²₄(38) rings and two types of R²₂(8) ring. In the N,N‐dimethylformamide disolvate, C₁₈H₂₀N₆O₂S₂·2C₃H₇NO, (II), the independent molecular components all lie in general positions, but one of the solvent molecules is disordered over two sets of atomic sites having occupancies of 0.839 (3) and 0.161 (3). The O—C—C—O torsion angle in the ArOCH₂CH₂OAr component is −75.91 (14)° and the independent thiosemicarbazide fragments both adopt a cis‐planar arrangement relative to the adjacent aryl rings. The ArOCH₂CH₂OAr components in (II) are linked by N—H...S hydrogen bonds to form deeply puckered sheets containing R²₂(8), R²₄(8) and two types of R²₂(38) rings, and which contain cavities which accommodate all of the solvent molecules in the interior of the sheets. Comparisons are made with some related compounds.     

Chiral Salan Aluminium Ethyl Complexes and Their Application in Lactide Polymerization

Synthetic routes to aluminium ethyl complexes supported by chiral tetradentate phenoxyamine (salan‐type) ligands [Al(OC₆H₂(R‐6‐R‐4)CH₂)₂{CH₃N(C₆H₁₀)NCH₃}‐C₂H₅] ( 4 , 7 : R=H; 5 , 8 : R=Cl; 6 , 9 : R=CH₃) are reported. Enantiomerically pure salan ligands 1–3 with (R,R) configurations at their cyclohexane rings afforded the complexes 4 , 5 , and 6 as mixtures of two diastereoisomers ( a and b ). Each diastereoisomer a was, as determined by X‐ray analysis, monomeric with a five‐coordinated aluminium central core in the solid state, adopting a cis‐(O,O) and cis‐(Me,Me) ligand geometry. From the results of variable‐temperature (VT) ¹H NMR in the temperature range of 220–335 K, ¹H–¹H NOESY at 220 K, and diffusion‐ordered spectroscopy (DOSY), it is concluded that each diastereoisomer b is also monomeric with a five‐coordinated aluminium central core. The geometry is intermediate between square pyramidal with a cis‐(O,O), trans‐(Me,Me) ligand disposition and trigonal bipyramidal with a trans‐(O,O) and trans‐(Me,Me) disposition. A slow exchange between these two geometries at 220 K was indicated by ¹H–¹H NOESY NMR. In the presence of propan‐2‐ol as an initiator, enantiomerically pure (R,R) complexes 4 – 6 and their racemic mixtures 7 – 9 were efficient catalysts in the ring‐opening polymerization of lactide (LA). Polylactide materials ranging from isotactically biased (P_m up to 0.66) to medium heterotactic (P_r up to 0.73) were obtained from rac‐lactide, and syndiotactically biased polylactide (P_r up to 0.70) from meso‐lactide. Kinetic studies revealed that the polymerization of (S,S)‐LA in the presence of 4 /propan‐2‐ol had a much higher polymerization rate than (R,R)‐LA polymerization (k_SS/k_RR=10.1).     

Synthesis of amidine complexes by metal-mediated addition of amino acid esters to coordinated nitriles

The reaction of the nitrile platinum(IV) complex trans-[PtCl₄(EtCN)₂] with amino acid esters H₂NC(R¹)(R²)CO₂Me (R¹ = R² = H, H-Me, Me-Me, H-Ph) and H₂NCH₂CH₂CO₂Me in CH₂Cl₂ produces the amidine complexes trans-[PtCl₄{ Z-NH=C(Et)NHC(R¹)(R²)CO₂Me}₂] and trans-[PtCl₄{ Z-NH=C(Et)NHCH₂CH₂CO₂Me}₂], which were isolated in 70–80% yields and characterized by elemental analysis, mass spectrometry, IR spectroscopy, and ¹H and ¹³C{¹H} NMR spectroscopy. The structures of the complexes with R¹ = R² = H (1), R¹ = H, R² = Me (2), and R¹ = H, R² = Ph (4) were established by X-ray diffraction analysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 601–605, March, 2005.     

Chiral and Nonchiral [OsX2(diphosphane)(diamine)] (X: Cl,OCH2CF3) Complexes for Fast Hydrogenation of Carbonyl Compounds

The osmium complexes trans‐[OsCl₂(dppf)(diamine)] (dppf: 1,1′‐bis(diphenylphosphino)ferrocene; diamine: ethylenediamine in 3 , propylenediamine in 4 ) were prepared by the reaction of [OsCl₂(PPh₃)₃] ( 1 ) with the ferrocenyl diphosphane, dppf and the corresponding diamine in dichloromethane. The reaction of derivative 3 with NaOCH₂CF₃ in toluene afforded the alkoxide cis‐[Os(OCH₂CF₃)₂(dppf)(ethylenediamine)] ( 5 ). The novel precursor [Os₂Cl₄(P(m‐tolyl)₃)₅] ( 2 ) allows the synthesis of the chiral complexes trans‐[OsCl₂(diphosphane)(1,2‐diamine)] ( 6 – 9 ; diphosphane: (R)‐[6,6′‐dimethoxy(1,1′‐biphenyl)‐2,2′‐diyl]bis[1,1‐bis(3,5‐dimethylphenyl)phosphane] (xylMeObiphep) or (R)‐(1,1′‐binaphthalene)‐2,2′‐diylbis[1,1‐bis(3,5‐dimethylphenyl)phosphane] (xylbinap); diamine=(R,R)‐1,2‐diphenylethylenediamine (dpen) or (R,R)‐1,2‐diaminocyclohexane (dach)), obtained by the treatment of 2 with the diphosphane and the 1,2‐diamine in toluene at reflux temperature. Compounds 3 – 5 in ethanol and in the presence of NaOEt catalyze the reduction of methyl aryl, dialkyl, and diaryl ketones and aldehydes with H₂ at low pressure (5 atm), with substrate/catalyst (S/C) ratios of 10 000–200 000 and achieving turnover frequencies (TOFs) of up to 3.0×10⁵ h^?1 at 70 °C. By employment of the chiral compounds 6 – 9 , different ketones, including alkyl aryl, bulky tert‐butyl, and cyclic ketones, have successfully been hydrogenated with enantioselectivities up to 99 % and with S/C ratios of 5000–100 000 and TOFs of up to 4.1×10⁴ h^?1 at 60 °C.     

Reactivity of an N,N‐Chelated Germylene Toward Substituted Alkynes,Alkenes, and Allenes

Treatment of N,N‐chelated germylene [(iPr)₂NB(N‐2,6‐Me₂C₆H₃)₂]Ge ( 1 ) with ferrocenyl alkynes containing carbonyl functionalities, FcC≡CC(O)R, resulted in [2+2+2] cyclization and formation of the respective ferrocenylated 3‐Fc‐4‐C(O)R‐1,2‐digermacyclobut‐3‐enes 2 – 4 [R = Me ( 2 ), OEt ( 3 ) and NMe₂ ( 4 )] bearing intact carbonyl substituents. In contrast, the reaction between 1 and PhC(O)C≡CC(O)Ph led to activation of both C≡C and C=O bonds producing bicyclic compound containing two five‐membered 1‐germa‐2‐oxacyclopent‐3‐ene rings sharing one C–C bond, 4,8‐diphenyl‐3,7‐dioxa‐2,6‐digermabicyclo[3.3.0]octa‐4,8‐diene ( 5 ). With N‐methylmaleimide containing an analogous C(O)CH=CHC(O) fragment, germylene 1 reacted under [2+2+2] cyclization involving the C=C double bond, producing 1,2‐digermacyclobutane 6 with unchanged carbonyl moieties. Finally, 1 selectively added to the terminal double bond in allenes CH₂=C=CRR′ giving rise to 3‐(=CRR′)‐1,2‐digermacyclobutanes [R/R′ = Me/Me ( 7 ), H/OMe ( 8 )] bearing an exo‐C=C double bond. All compounds were characterized by ¹H, ¹³C{¹H} NMR, IR and Raman spectroscopy and the molecular structures of 3 , 4 , 5 , and 8 were established by single‐crystal X‐ray diffraction analysis. The redox behavior of ferrocenylated derivatives 2 – 4 was studied by cyclic voltammetry.     

Synthesis and Characterization of Ruthenium Complexes with Substituted Pyrazino[2,3‐f][1,10]‐phenanthroline (=Rppl; R=Me,COOH, COOMe)

A series of substituted pyrazino[2,3‐f][1,10]‐phenanthroline (Rppl) ligands (with R=Me, COOH, COOMe) were synthetized (see 1 – 4 in Scheme 1). The ligands can be visualized as formed by a bipyridine and a quinoxaline fragment (see A and B ). Homoleptic [Ru(R¹ppl)₃](PF₆)₂ and heteropleptic [Ru(R¹ppl){(R²)₂bpy}₂](PF₆)₂ (R¹=H, Me, COOMe and R²=H, Me) metal complexes 5 – 7 and 8 – 13 , respectively, based on these ligands were also synthesized and characterized by conventional techniques (Schemes 2 and 3, resp.). In the heteroleptic complexes, the R¹‐ppl ligand reduces at a less‐negative potential than the bpy ligand, reflecting the acceptor property conferred by the quinoxaline moiety. The potentiality of some of these complexes as solar‐cell dyes is discussed.     

Isomerism of copper(II) coordination compounds with hydroxamic acids

The structure of Cu^II complexes with hydroxamic acids Cu[R¹N(O)−(O)CR²]₂, where R¹=Ph, R²=Me; R¹=Me, R²=Ph, was studied by ESR spectroscopy. In toluene solutions and low-temperature glasses, the complexes exist as two forms, which were identified ascis-andtrans-isomers. The proportions of the isomers were determined. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 726–729, April, 1999.     

Transition-Metal Complexes with Bidentate Ligands Spanning trans-Positions. Part XVII. Some platinum(II) complexes with anionic ligands such as methoxide,formate, carboxylate,hydride, and borohydride,and the X-ray crystal structure of [PtHCl( )] (PP = 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene)

The complexes trans-[PtXY( 2 ] (X = H or Me; Y = OMe, OCHO, CO₂H, and BH₄; 2 = 2,11-bis{bis[3-(trifluoromethyl)phenyl]phosphinomethyl}benzo[c]phenanthrene) were prepared, and their decompositions to trans[PtHX( 2 )] were studied. Some binuclear hydrido-bridged complexes, e.g.[( 2 )HPt(μ-H)PtH( 2 )]⁺, were also obtained. The preparation of complexes trans-[PtHX( 28 )₂] (X = H or Me, 28 = bis[3-(trifluoromethyl)phenyl]benzylphosphine) is also reported. The X-ray crystal structure of trans-[PtHCl 1 )] ( 1 = 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene) was carried out.     

New nickel(II) diimine complexes bearing phenyl and sec‐phenethyl groups: synthesis,characterization and ethylene polymerization behaviour

A series of nickel(II) catalysts containing phenyl and chiral sec‐phenethyl groups, {[(4‐R₁‐2‐R₂C₆H₂N?C)₂Nap]NiBr₂} (Nap: 1,8‐naphthdiyl, R₁ = Me, R₂ = Ph ( 3a ); R₁ = Me, R₂ = sec‐phenethyl ( 3b ); R₁ = Cl, R₂ = sec‐phenethyl ( 3c ); R₁ = Me, R₂ = Me ( 3d ) were synthesized and characterized. All organic compounds were fully characterized by FT‐IR and NMR spectroscopy and elemental analysis. The single crystal for X‐ray crystallography was isolated from 3a in CH₂Cl₂/n‐hexane under air; the crystal structure showed a binuclear complex 3a ′, in which each nickel atom was six‐coordinate. The two nickel atoms together with two bromine atoms form a planar four‐membered ring, with a bromine and H₂O axial ligands. These complexes, activated by diethylaluminum chloride and chiral nickel pre‐catalysts rac‐ 3c , exhibited good activities (up to 2.85 × 10⁶ g PE (mol Ni h bar)^?1) for ethylene polymerization, and produced polyethylene products with a high degree of branching (up to 117 branched per 1000 carbons) at high temperature. The type and amount of branches of the polyethylenes obtained were determined by ¹H and ¹³C NMR spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd.     

Unprecedented Reaction Pathway of Sterically Crowded Calcium Complexes: Sequential C−N Bond Cleavage Reactions Induced by C−H Bond Activations

Five bis(quinolylmethyl)‐(1H ‐indolylmethyl)amine (BQIA) compounds, that is, {(quinol‐8‐yl‐CH₂)₂NCH₂(3‐Br‐1H ‐indol‐2‐yl)} ( L¹H ) and {[(8‐R³‐quinol‐2‐yl)CH₂]₂NCH(R²)[3‐R¹‐1H ‐indol‐2‐yl]} ( L^2–5H ) ( L²H : R¹=Br, R²=H, R³=H; L³H : R¹=Br, R²=H, R³=i Pr; L⁴H : R¹=H, R²=CH₃, R³=i Pr; L⁵H : R¹=H, R²=n Bu, R³=i Pr) were synthesized and used to prepare calcium complexes. The reactions of L^1–5H with silylamido calcium precursors (Ca[N(SiMe₂R)₂]₂(THF)₂, R=Me or H) at room temperature gave heteroleptic products ( L^{1, 2} )CaN(SiMe₃)₂ ( 1 , 2 ), ( L^{3, 4} )CaN(SiHMe₂)₂ ( 3 a , 4 a ) and homoleptic complexes ( L^{3, 5} )₂Ca ( D3 , D5 ). NMR and X‐ray analyses proved that these calcium complexes were stabilized through Ca⋅⋅⋅C−Si, Ca⋅⋅⋅H−Si or Ca⋅⋅⋅H−C agostic interactions. Unexpectedly, calcium complexes (( L^3–5 )CaN(SiMe₃)₂) bearing more sterically encumbered ligands of the same type were extremely unstable and underwent C−N bond cleavage processes as a consequence of intramolecular C−H bond activation, leading to the exclusive formation of (E )‐1,2‐bis(8‐isopropylquinol‐2‐yl)ethane.     

Structural properties of trans‐cyclohexane‐1,2‐diamine complexes of copper(II) and zinc(II) acesulfamates

The title compounds, trans‐bis(trans‐cyclohexane‐1,2‐diamine)bis(6‐methyl‐2,2,4‐trioxo‐3,4‐dihydro‐1,2,3‐oxathiazin‐3‐ido)copper(II), [Cu(C₄H₄NO₄S)₂(C₆H₁₄N₂)₂], (I), and trans‐diaquabis(cyclohexane‐1,2‐diamine)zinc(II) 6‐methyl‐2,2,4‐trioxo‐3,4‐dihydro‐1,2,3‐oxathiazin‐3‐ide dihydrate, [Zn(C₆H₁₄N₂)₂(H₂O)₂](C₄H₄NO₄S)₂·2H₂O, (II), are two‐dimensional hydrogen‐bonded supramolecular complexes. In (I), the Cu^II ion resides on a centre of symmetry in a neutral complex, in a tetragonally distorted octahedral coordination environment comprising four amine N atoms from cyclohexane‐1,2‐diamine ligands and two N atoms of two acesulfamate ligands. Intermolecular N—H...O and C—H...O hydrogen bonds produce R₂²(12) motif rings which lead to two‐dimensional polymeric networks. In contrast, the Zn^II ion in (II) resides on a centre of symmetry in a complex dication with a less distorted octahedral coordination environment comprising four amine N atoms from cyclohexane‐1,2‐diamine ligands and two O atoms from aqua ligands. In (II), an extensive two‐dimensional network of N—H...O, O—H...O and C—H...O hydrogen bonds includes R₂¹(6) and R₄⁴(16) motif rings.     

Rhodium/tris-binaphthyl chiral monophosphite complexes: Efficient catalysts for the hydroformylation of disubstituted aryl olefins

A family of threefold symmetry phosphite ligands, P(O–BIN–OR)₃ (BIN = 2,2′-binaphthyl; R = Me, Bn, CHPh₂, 1-adamantyl), derived from enantiomerically pure (R)-BINOL, was developed. Cone angles within the range 240–270° were calculated for the phosphite ligands, using the computational PM6 Hamiltonian. Their rhodium complexes formed in situ showed remarkable catalytic activity in the hydroformylation of hindered phenylpropenes, under relatively mild reaction conditions, with full chemoselectivity for aldehydes, high regioselectivity, however with low enantioselectivity. The ether substituents at the ligand affected considerably the catalytic activity on the hydroformylation of 1,1- and 1,2-disubstituted aryl olefins. The kinetics of the hydroformylation of trans-1-phenyl-1-propene, using tris[(R)-2′-benzyloxy-1,1′-binaphthyl-2-yl]phosphite as model ligand, was investigated. A first order dependence in the hydroformylation initial rate with respect to substrate and catalyst concentrations was found, as well as a positive order with respect to the partial pressure of H₂, and a slightly negative order with respect to phosphite concentration and CO partial pressure.     

1,2-dihydro-1,2,4,3-triazaphospholo[4,5-a]quinolines as electron carriers in the electrochemical reduction of 1,1-dichloro-2-methoxycarbonyl-2-methylcyclopropane

Electrochemical reduction of 1-X-1-R¹-5-methyl-2-phenyl-7-R²-1,2-dihydro-1,2,4,3-tri-azaphospholo[4,5-a]quinolines1–5 (1: X is the lone electron pair (LEP), R¹=Et₂N, R²=Me;2: X=LEP, R¹=Ph, R²=H;3: X=S, R¹=Et₂N, R²=H;4: X=LEP, R¹=Et₂N, R²=H;5: X=LEP, R¹=MeO, R²=H) in DMF with 0.1M Bu₄NI as supporting electrolyte is reversible and results in metastable radical anions. Radical anions of compounds1–3 efficiently reduce 1,2-dichloro-2-methoxycarbonyl-2-methylcyclopropane both in the presence and in absence of Ni¹¹ ions. Effective reduction rate constants have been evaluated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2088–2091, November, 1999.     

Disilene R*RSi=SiRR* (R* = SitBu3) mit siliciumgebundenen Me‐ und Ph‐Gruppen R: Bildung,Nachweis, Thermolyse,Struktur: Verbindungen des Siliciums. 154 [1]. Ungesättigte Siliciumverbindungen. 61 [1]

Compounds of Silicon. 154 [1]. Unsaturated Silicon Compounds. 61 [1] Disilenes R*RSi=SiRR* (R* = SitBu₃) with Silicon‐Bound Me and Ph Groups R: Formation, Identification, Thermolysis, Structure Dehalogenations of the 1, 2‐disupersilylsilanes R*MeBrSi—SiBrMeR* (gauche : trans 1.15 : 1.00) and R*PhClSi—SiBrPhR* (gauche : trans = 2.7 : 1.0) in THF with equimolar amounts of NaR* (R* = SitBu₃ = Supersilyl) lead at —78 °C under exchange of bromine for sodium to the disilanides R*MeBrSi—SiNaMeR* and R*PhClSi—SiNaPhR* which are identified by protonation and bromination (formation of R*RXSi—SiX′RR* with R = Me, X/X′ = Br/H, Br/Br: gauche : trans = 1.15 : 1.00, and R = Ph, X/X′ = Cl/H, Cl/Br: gauche : trans = 2.7 : 10, respectively). These eliminate at about —55 °C NaHal with formation of non‐isolable trans‐R*MeSi=SiMeR* and isolable trans‐R*PhSi=SiPhR*. The intermediate existence of the disilene R*MeSi=SiMeR* could be proved by trapping it with PhC≡CPh (formation of a [2+2] cycloadduct; X‐ray structure analysis). In the absence of trapping agents, R*MeSi=SiMeR* decomposes into a mixture of substances, the main product of which is R*MeHSi—SiMeR*—SiHMeR*. The light yellow disilene R*PhSi=SiPhR* has been characterized by spectroscopy (Raman: ν(Si=Si) = 592 cm^—1; UV/VIS: λ_max = 398 nm with ∈ = 1560; ²⁹Si‐NMR: δ(>Si=) = 128 ppm) and by X‐ray structure analysis (planar central framework >Si=Si<; Si=Si distance 2.182Å). R*PhSi=SiPhR* is reduced by lithium in THF with formation of a red radical anion which decomposes at room temperature into hitherto non‐identified products. At about 70 °C, R*PhSi=SiPhR* decomposes with intramolecular insertion of the Si=Si group into a C—H bond of a Ph group and with change of configuration of the R* groups, which at first are trans then cis‐positioned (X‐ray structure analysis of the thermolysis product).     

Iron-Catalyzed Highly Enantioselective cis-Dihydroxylation of Trisubstituted Alkenes with Aqueous H2O2

Reliable methods for enantioselective cis-dihydroxylation of trisubstituted alkenes are scarce. The iron(II) complex cis-α-[Fe^II(2-Me₂-BQPN)(OTf)₂], which bears a tetradentate N₄ ligand (Me₂-BQPN=(R,R)-N,N′-dimethyl-N,N′-bis(2-methylquinolin-8-yl)-1,2-diphenylethane-1,2-diamine), was prepared and characterized. With this complex as the catalyst, a broad range of trisubstituted electron-deficient alkenes were efficiently oxidized to chiral cis-diols in yields of up to 98 % and up to 99.9 % ee when using hydrogen peroxide (H₂O₂) as oxidant under mild conditions. Experimental studies (including ¹⁸O-labeling, ESI-MS, NMR, EPR, and UV/Vis analyses) and DFT calculations were performed to gain mechanistic insight, which suggested possible involvement of a chiral cis-Fe^V(O)₂ reaction intermediate as an active oxidant. This cis-[Fe^II(chiral N₄ ligand)]²⁺/H₂O₂ method could be a viable green alternative/complement to the existing OsO₄-based methods for asymmetric alkene dihydroxylation reactions.     

Chiral Ruthenium-Oxo Complexes for Enantioselective Epoxidation of trans-Stilbene

Two oxoruthenium(IV) complexes containing C₂ symmetric 1,1′-biisoquinoline (biqn) and (R,R)-3,3′-(1,2-dimethylethylenedioxy)-2,2′-bipyridine (diopy*) were prepared, and both are active oxidants for alkene epoxidations. The oxidation of styrene and cis- and trans-β-methylstyrenes by [(Cn)(diopy*)-Ru^IV(O)](ClO₄)₂ did not proceed enantioselectively, but the same oxidant can attain a moderate enantioselectivity of 33%ee for the trans-stilbene oxidation to trans-stilbene oxide. A head-on approach model, where the C=C is directed from the top to the O=Ru moiety, is proposed to account for the facial differentiation of the trans-stilbene oxidation.     

Separation of racemiccloso-3,3-(η3,2-norbornadienyl)rhodacarboranes into enantiomers by HPLC on chiral stationary phasesinto enantiomers by HPLC on chiral stationary phases

Racemiccloso-rhodacarboranes,vis. closo-(η^3,2-C₇H₃-2-CR ₂ ¹ )-1-R²-2-R³-3,1,2-RhC₂B₉H₉ (R¹=R²=R³=H; R¹=H, R²=R³=Me; R¹=R²=R³=Me) and (closo-2,2-(η^3,2-C₇H₇-2-CH₂)-2,1,7-RhC₂B₉H₁₁), were successfully separated into enantiomers by high-performance liquid chromatography (HPLC). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 759–761, April, 2000.     

Cleavage of the carbon-silicon bonds in trimethylsilylacetylenes by trans[(PR3)2PtX(R′OH)]PF6 cations and formation of cationic alkoxycarbene complexes of platinum(II)

Cationic alkoxycarbene complexes of platinum(II) have been isolated in the reactions of trans-[(PR₃)₂PtX(R′OH)]PF₆ (X  H or Me; R′  Me or Et) with Me₃SiCCR′′ (R′′  H, Me or SiMe₃). In these reactions cleavage of the carbon-silicon bond by the nucleophilic attack of alcohol has been observed. These carbene complexes have been characterized by elemental analyses and by IR, ¹H and ¹³C NMR spectral data. ¹³C NMR chemical shift data for carbene carbon atoms suggest that the carbene carbon may be very positively charged.     

Transition metalcarbon bonds XXXVII. platinum acetylide complexes formed from ethynyl alcohols or ethers

Several new platinum(II) acetylide complexes, trans-{Pt[CCCR₁R₂(OR₃)]₂-L₂} (R₁, R₂  H, Me, Et; CR₁R₂  cyclohexylidene; R₃  H, Me or Ph), trans-[Pt(CCCH₂CH₂OH)₂L₂], trans-[Pt(p-tolylacetylide)₂L₂] and trans-[PtX(p-tolylacetylide)L₂] (L  PMe₂Ph or in one case, AsMe₂Ph) have been prepared. Platinum(II) acetylide complexes with tertiary hydroxyl groups are easily dehydrated by acetic anhydride/pyridine to give platinum-enyne complexes. Analogous compounds with primary hydroxyl groups do not dehydrate but give acetates. ¹H and ¹³C NMR data are given and the shift reagent Eu(fod)₃ was used to analyse the ¹H NMR spectrum of trans-[Pt(CCCH₂CH₂OH)₂(PMe₂Ph)₂].