Tetraphenylantimony(V) O,O′-dialkyl dithiophosphates [Sb(C6H5)4{S2P(OR)2}] (R = s-C4H9, c-C6H11): Synthesis, structures, and 13C and 31P CP/MAS NMR spectra

Tetraphenylantimony(V) O,O′-di-sec-butyl dithiophosphate (I) and tetraphenylantimony(V) O,O′-dicyclohexyl dithiophosphate (II) [Sb(C₆H₅)₄{S₂P(OR)₂}] (R = sec-C₄H₉ or cyclo-C₆H₁₁) were obtained. Their structures and spectroscopic properties were studied by X-ray diffraction analysis and ¹³C and ³¹P CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in complexes I and II were found to be coordinated in S-monodentate and S,S′-bidentate fashions, respectively (MAS NMR data). According to X-ray diffraction data, the coordination polyhedron of antimony in molecular structure I is a trigonal bipyramid with unusual monodentate coordination of the Dtph group in the axial position.     

Photocatalytic reduction of CO2 using cis,trans-[Re(dmbpy)(CO)2(PR3)(PR’3)]+ (dmbpy=4,4′-dimethyl-2,2′-bipyridine)

Photocatalysis of biscarbonylrhenium complexes cis,trans-[Re(dmbpy)(CO)₂(PR₃) (PR′₃)]⁺ (dmbpy=4,4′-dimethyl-2,2′-bipyridine: R, R′=Ph (1a ⁺); p-FPh (1b ⁺); R=Ph, R′=OEt (1c ⁺); R, R′=O-i-Pr (1d ⁺)) is reported for the first time. The rhenium complexes with two triarylphosphine ligands (1a ⁺, 1b ⁺) efficiently photocatalyzed CO₂ reduction with triethanolamine as a sacrificial donor. On the other hand, the complexes with one or two trialkylphosphite ligand(s) (1c ⁺, 1d ⁺) had low photocatalytic abilities under the same reaction conditions.     

Competitive Binding Sites of a Ruthenium Arene Anticancer Complex on Oligonucleotides Studied by Mass Spectrometry: Ladder-Sequencing versus Top-Down

We report identification of the binding sites for an organometallic ruthenium anticancer complex [(η ⁶-biphenyl)Ru(en)Cl][PF₆] (1; en = ethylenediamine) on the 15-mer single-stranded oligodeoxynucleotides (ODNs), 5′-CTCTCTX₇G₈Y₉CTTCTC-3′ [X = Y = T (I); X = C and Y = A (II); X = A and Y = T (III); X = T and Y = A (IV)] by electrospray ionization mass spectrometry (ESI-MS) in conjunction with enzymatic digestion or tandem mass spectrometry (top-down MS). ESI-MS combined with enzymatic digestion (termed MS-based ladder-sequencing), is effective for identification of the thermodynamically-favored G-binding sites, but not applicable to determine the thermodynamically unstable T-binding sites because the T-bound adducts dissociate during enzymatic digestion. In contrast, top-down MS is efficient for localization of the T binding sites, but not suitable for mapping ruthenated G bases, due to the facile fragmentation of G bases from ODN backbones prior to the dissociation of the phosphodiester bonds. The combination of the two MS approaches reveals that G₈ in each ODN is the preferred binding site for 1, and that the T binding sites of 1 are either T₇ or T₁₁ on I and IV, and either T₆ or T₁₁ on II and III, respectively. These findings not only demonstrate for the first time that T-bases in single-stranded oligonucleotides are kinetically competitive with guanine for such organoruthenium complexes, but also illustrate the relative merits of the combination of ladder-sequencing and top-down MS approaches to elucidate the interactions of metal anticancer complexes with DNA.      

New copper(II) 2-(alkylamino)troponates

The copper aminotropones Cu[ON(R′)C₇H₄R-4]₂ [R = H, R′ = Me (13), Et (14), n-Pr (15), n-Bu (16), Bz (17), MenOCH₂CH₂ (20); R = i-Pr, R′ = Me (18), n-Pr (19), MenOCH₂CH₂ (21)] have been prepared from the corresponding aminotropones HN(R′)OC₇H₄R-4 (1–7) by reacting with copper(II) acetate in aqueous ethanol. 20, 21 contain the flavourant, menthol, as part of the ligand. The structures of 5 (R = H, R′ = Bz), a hydrogen-bonded dimer, 14 and 20, both incorporating square-planar, four-coordinate copper centres, have been determined by X-ray crystallography. The antibacterial activities of complexes 13, 17, 20 and 21 have been assayed against Staphylococcus waneri, an in vitro model of plaque inhibition effects, and found to be more active than a commercial toothpaste formulation, but less active than the O,O-chelated copper(II) complex of ethylmaltol.     

Analysis of the metal–ligand bonds in [Mo(X)(NH2)3] (X = P, N, PO, and NO), [Mo(CO)5(NO)]+, and [Mo(CO)5(PO)]+

Quantum chemical calculations at the DFT level have been carried out for model complexes [Mo(P)(NH₂)₃] (1), [Mo(N)(NH₂)₃] (2), [Mo(PO)(NH₂)₃] (3), [Mo(NO)(NH₂)₃] (4), [Mo(CO)₅(PO)]⁺ (5), and [Mo(CO)₅(NO)]⁺ (6). The equilibrium geometries and the vibration frequencies are in good agreement with experimental and previous theoretical results. The nature of the Mo–PO, Mo–NO, Mo–PO⁺, Mo–NO⁺, Mo–P, and Mo–N bond has been investigated by means of the AIM, NBO and EDA methods. The NBO and EDA data complement each other in the interpretation of the interatomic interactions while the numerical AIM results must be interpreted with caution. The terminal Mo–P and Mo–N bonds in 1 and 2 are clearly electron-sharing triple bonds. The terminal Mo–PO and Mo–NO bonds in 3 and 4 have also three bonding contributions from a σ and a degenerate π orbital where the σ components are more polarized toward the ligand end and the π orbitals are more polarized toward the metal end than in 1 and 2. The EDA calculations show that the π bonding contributions to the Mo–PO and Mo–NO bonds in 3 and 4 are much more important than the σ contributions while σ and π bonding have nearly equal strength in the terminal Mo–P and Mo–N bonds in 1 and 2. The total (NH₂)₃Mo–PO binding interactions are stronger than for (NH₂)₃Mo–P which is in agreement with the shorter Mo–PO bond. The calculated bond orders suggest that there are only (NH₂)₃Mo–PO and (NH₂)₃Mo–NO double bonds which comes from the larger polarization of the σ and π contributions but a closer inspection of the bonding shows that these bonds should also be considered as electron-sharing triple bonds. The bonding situation in the positively charged complexes [(CO)₅Mo–(PO)]⁺ and [(CO)₅Mo–(NO)]⁺ is best described in terms of (CO)₅Mo → XO⁺ donation and (CO)₅Mo ← XO⁺ backdonation (X = P, N) using the Dewar–Chatt–Duncanson model. The latter bonds are stronger and have a larger π character than the Mo-CO bonds.     

New aryl ethynylene substituted silicon-centered molecules

The reactions of substituted dichlorosilane monomers,Cl₂SiRR′, with two equivalents of lithium aryl acetylide(1), LiC ≡ C-4-C₆H₄-Ph, afford RR′Si(C ≡ C-4-C₆H₄-Ph)₂ (6: R,R′ =CH₃; 7: R = CH₃, R′ = CH=CH₂; 8: R,R′ = Ph). An isomeric mixture of meso, (R,R)- and (S,S)-Bis[2-(N,N-dimethylaminomethyl)ferrocenyl]dichlorosilane (5) was used as starting chlorosilyl compound for reaction with LiC ≡ C-4-C₆H₄-Ph to give (FcN)₂Si(C ≡ C-4-C₆H₄-Ph)₂ (9). A detailedcharacterization of 6, 7, 8 and 9 has been carried out by ¹H-NMR, ¹³C-NMR, ²⁹Si-NMR, IR and UV-VIS spectroscopy. The crystal structure of 9 has been determined by X-ray diffraction analysis.     

Carbene complexes of molybdenum and tungsten Et3E-CH=M(NAr)(OR)2 (M = Mo, W; E = Si, Ge) and π-complex of molybdenum (RO)2(ArN)Mo(CH2=CH-GeEt3). Synthesis and catalytic properties

The heteroelement-containing alkylidene imide complexes with molybdenum and tungsten Et₃SiCH=Mo(NAr)(OR)₂ (I), Et₃ ECH=W(NAr)(OR)₂ (E = Si (II), Ge (III); Ar = 2,6-i-Pr₂C₆H₃; R=CMe₂ CF₃) and π-complex (RO)₂(ArN)Mo(CH₂=CH-GeEt₃) (IV) were synthesized by the reaction of Alkyl-CH=M(NAr) (OR)₂ (M=Mo, W; Alkyl = t-Bu, PhMe₂C) with organosilicon and organogermanium vinyl reagents Et₃ECH=CH₂ (E = Si, Ge). The structure of compounds I–III was determined by X-ray diffraction (XRD). The complexes I–IV are active initiators of metathesis polymerization of cycloolefins.     

Cis-Cycloprolylprolin-Anion-ein konfigurationsstabiles Carbanion

The racemisation ofcyclo-(l-Pro?l-Pro) (2) with metal amides in liq. ammonia was examined. The K-kation causes more extensive racemisation than Na-kation, which in turn is more effective than Li⁺. This, the racemisation of2 int-butyl alcohol with K⁺C₆H₅O^? and the data gained from corresponding deuterated medium show that the racemisation of2 proceeds in two steps: in the first, the less stabletrans-cyclo-(l-Pro?d-Pro) (3) is formed, followed by the rapid conversion of3 to a mixture ofcyclo-(l-Pro?l-Pro) andcyclo-(d-Pro?d-Pro) in the second step.     

Formation of carbon-carbon bonds between activated alkynes and diimine ligands in the aluminum complexes

The gallium and aluminum complexes containing the redox-active ligand (dpp-bian)Ga-Ga(dpp-bian) (1), (dpp-bian)Al-Al(dpp-bian) (2), or (dpp-bian)AlI(Et₂O) (3) (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) react with alkyl butynoates Me-C≡C-CO₂R (R = Me, Et) to form C-C bonds between the dpp-bian ligand and alkyne. The reaction of complex 1 with methyl 2-butynoate and 4-chloroaniline in a molar ratio of 1: 2: 2 affords 7-(2,6-diisopropylphenyl)-10-methylacenaphtho[1,2-b]pyridin-8(7H)-one (4) containing no gallium. In the reaction of complex 2 with methyl 2-butynoate, alkyne is inserted into the skeleton of the dpp-bian ligand to form 4-(dpp-AIE)-9-(2,6-diisopropylphenyl)-8-(1,3-dpp-2MBIDP)-3,7-dimethoxy-1,5-dialuma-9-aza-2,6-dioxabicyclo[3.3.1]nonadiene-3,7 (5) (dpp-AIE is 1-[2-(2,6-diisopropylphenylimino)acenaphthen-1(2H)-ylidene]ethyl; 1,3-dpp-2MBIDP is 1,3-bis(2,6-diisopropylphenylimino)-2-methyl-2,3-dihydro-1H-phenalen-2-yl). The reactions of complex 3 with methyl and ethyl 2-butynoates afford dimeric derivatives [-OC(OR)=C(2,3-dpp-1MBIDP)Al(I)-]₂ (2,3-dpp-1MBIDP is 2,3-bis(2,6-diisopropylphenylimino)-1-methyl-2,3-dihydro-1H-phenalen-2-yl; R = Me (6), Et (7)). The reaction of complex 3 with methyl 2-butynoate gives the product isomeric to compound 6: [-OC(OCH₃)=C(1,3-dpp-2MBIDP)Al(I)-]₂ (8), which cleaves THF resulting in complex [-OC(OCH₃)=C(1,3-dpp-2MBIDP)Al(OC₄H₈I)-]₂ (9). Complex (dpp-bian)Al(acac) (10), obtained by the reduction of dpp-bian with aluminum in the presence of Al(acac)₃ in diethyl ether at ambient temperature, is inert towards acetylene, phenylacetylene, and alkyl butynoates. Compounds 4–7 and 10 were characterized using IR spectroscopy, and compounds 4, 7, and 10 were additionally characterized by ¹H NMR spectroscopy. The structures of compounds 4–7, 9, and 10 were determined by X-ray diffraction analysis.     

Further studies of the reactions of PtRu5(μ6-C)(CO)16 with alkynes: The preparation and structural characterizations of PtRu5(CO)13(μ-EtC2Et)(μ3-EtC2Et)(μ5-C) and Pt2Ru6(CO)17(μ-η5-Et4C5)(μ3-EtC2Et) (μ6-C)

The reaction of PtRu₅(CO)₁₆(μ₆-C),1 with 3-hexyne in the presence of UV irradiation produced two new electron-rich platinum-ruthenium cluster complexes PtRu₅(CO)₁₃(μ-EtC₂Et)(μ₃-EtC₂Et)(μ₅-C),2 (20% yield) and Pt₂Ru₆(CO)₁₇(μ-η⁵-Et₄C₅)(μ₃-EtC₂Et) (μ₆-C),3 (7% yield). Both compounds were characterized by single-crystal X-ray diffraction analyses. Compound2 contains of a platinum capped square pyramidal cluster of five ruthenium atoms with the carbido ligand located in the center of the square pyramid. A EtC₂Et ligand bridges one of the PtRu₂ triangles and the Ru-Pt bond between the apical ruthenium atom and the platinum cap. The structure of compound3 consists of an octahedral PtRu₅ cluster with an interstitial carbido ligand and a platinum atom capping one of the PtRu₂ triangles. There is an additional Ru(CO)₂ group extending from the platinum atom in the PtRu₅ cluster that contains a metallated tetraethylcyclopentadienyl ligand that bridges to the platinum capping group. There is also a EtC₂Et ligand bridging one of the PtRu₂ triangular faces to the capping platinum atom. Compounds2 and3 both contain two valence electrons more than the number predicted by conventional electron counting theories, and both also possess unusually long metal-metal bonds that may be related to these anomalous electron configurations. Crystal data for2, space group Pna2₁,a=19.951(3) Å,b=9.905(2) Å,c=17.180(2) Å,Z=2, 1844 reflections,R=0.036; for3, space group Pna2₁,α=13.339(1) Å,b=14.671(2) Å,c=11.748(2) Å, α=100.18(1)°, β=95.79(1)°, γ=83.671(9)°,Z=2, 3127 reflections,R=0.026.     

Hydrothermal synthesis, crystal structure, and properties of two novel binuclear complexes based on Zaltoprofen and 2,2′-bipyridine ligands

Two novel binuclear metal-organic coordination complexes [M₂(Zaltoprofen)₂(Bipy)₂] [M = Cd (I), Zn (II); Zaltoprofen = 5-(1-carboxyethyl)-2-(phenylthio)phenylacetic acid, Bipy = 2,2′-bipyridine) have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR and electronic spectroscopy, powder X-ray diffraction, and fluorescent properties. Complexes I, II crystallize isomorphously in the monoclinic space group P2₁/c. Structural analysis shows that the M(II) atom of I and II is coordinated with four oxygen atoms from the carboxyl group of the Zaltoprofen together with two nitrogen atoms from the Bipy. The 3D structures of the complexes are stabilized by π-π stacking interactions.     

Selektive Darstellung zweifach diorganophosphido-verbrückter Metallatetrahedrane [Re2(MPR3)2(μ-PR2)2(CO)6] mit Re2M2-Metallgerüst (M = Au,Ag)

Selective Preparation of Twofold Diorganophosphido-bridged Metallatetrahedranes [Re₂(MPR₃)₂(μ-PR₂)₂(CO)₆] with Re₂M₂ Metal Core (M = Au, Ag) The reaction of the in situ prepared salt Li[Re₂(AuPR)(μ-PR₂)(CO)₇Cl] (R = R′ = Cy ( 1 a ), R = Cy, R′ = Ph ( 1 b ), R = Ph, R′ = Cy ( 1 c ), R = Ph, R′ = Et ( 1 d ), R = Ph, R′ = Ph ( 1 e )) with one equivalent HPR in methanolic solution at room temperature yields the neutral cluster complexes [Re₂(AuPR)(μ-PR₂)(CO)₇(ax-HPR) (R = R′ = R″ = Cy ( 2 a ), Ph ( 2 b ), R = R′ = Cy, R″ = Et ( 2 c ), R = Cy, R′ = R″ = Ph ( 2 d ), R = Cy, R′ = Ph, R″ = Et ( 2 e ), R = R″ = Ph, R′ = Et ( 2 f ), R = Ph, R′ = Cy, R″ = Et (2 g)). Photochemically induced these complexes react in the presence of the organic base DBU in THF solution to give the doubly phosphido bridged anions Li[Re₂(AuPR)(μ-PR₂)(μ-PR)(CO)₆], which were characterized as salts PPh₄[Re₂(AuPR)(μ-PR₂)(μ-PR)(CO)₆] (R = R′ = R″ = Ph ( 3 a ), R = R′ = Ph, R″ = Cy ( 3 b ), R = Ph, R′ = Cy, R″ = Et ( 3 c ), R = R″ = Ph, R′ = Et ( 3 d )). These precursor complexes 3 then react with one equivalent of ClMPR (M = Au, Ag) to doubly phosphido bridged metallatetrahedranes [Re₂(MPR₃)₂(μ-PR₂)(μ-PR)(CO)₆] (M = Au, R = R′ = R″ = Ph ( 4 a ), M = Au, R′ = Et, R = R″ = Ph ( 4 b ), M = Au, R = R′ = Ph, R″ = Cy ( 4 c ), M = Au, R = Cy, R′ = Ph, R″ = Et ( 4 d ), M = Ag, R = R′ = R″ = Ph ( 4 e )). All isolated cluster complexes were characterized and identified by the following analytical methods: NMR- (¹H, ³¹P) and ν(CO) IR-spectroscopy and, additionally, complexes 2 b , 4 a and 4 e by X-ray structure analysis.     

Syntheses and characterizations of group 6 metal cyanotrihydroborate complexes

The anions, [M(CO)_6-n(NCBH₃)_n]ⁿ⁻ (n=2, M=Cr(1); n=3, M=Cr(2), Mo(3), W(4)), were prepared either from the reactions of sodium cyanotrihydroborate with group 6 transition metal hexacarbonyls, M(CO)₆ (M=Cr, Mo, W), or through the reactions of M(CO)₃(CH₃CN)₃ (M=Cr, W) with sodium cyanotrihydroborate. The cyanotrihydroborate ligand bonds to the metal through a nitrogen atom, which was confirmed by the Infrared, proton and boron NMR spectroscopies. Crystal structures of the above complexes were determined by single crystal X-ray diffraction analyses. A cis configuration is found in 1. Molecular structures of 2, 3, and 4 are similar and a facial configuration is observed.     

Germylenes and stannylenes based on aminobisphenolate ligands: insertion into the C—Br bond

A reaction of previously synthesized germylenes and stannylenes based on aminobisphenols RN{CH₂[(5-R´)(3-But)C₆H₂(2-O—)]}₂M^II, M = Ge, R = CH²(2-Py), R´ = But (1); M = Ge, R = Et, R´ = Me (2); M = Sn, R = CH₂(2-Py), R´ = But (3); M = Sn, R = Et, R´ = Me (4), containing (tetrylenes 1 and 3) or not containing (tetrylenes 2 and 4) a group capable of additional donation, with allyl bromide leads to the products of the insertion of tetrylenes into the C—Br bond: RN{CH₂[(5-R´)(3-Bu^t)C₆H₂(2-O—)]}₂M(Br)All, M = Ge, R = CH₂(2-Py), R´ = But (5); M = Ge, R = Et, R´ = Me (6); M = Sn, R = CH₂(2-Py), R´ = But (7); M = Sn, R = Et, R´ = Me (8). The structures of obtained derivatives were confirmed by NMR spectroscopy and elemental analysis. The structures of compounds 4, 5, and 7 were studied by X-ray crystallography. Stannylene 4 was found to be monomeric in the solid phase: the coordination number of the Sn atom is 3. The insertion products 5 and 7 are characterized by the coordination number 6 for the central atom.     

The use of Pearlman's catalyst for the oxidation of Si–H bonds. Synthesis, structures and acid-catalysed condensation of novel α, ω-oligosiloxanediols HOSiMe2O(SiPh2O)nSiMe2OH (n = 1−4)

The preparation of α , ω-oligosiloxanediolsHOSiMe₂O(SiPh₂O)_nSiMe₂OH(5–8; n=1–4) by the mild oxidation of thecorresponding organo-H-siloxaneHSiMe₂O(SiPh₂O)_nSiMe₂H(1–4; n = 1–4) using Pearlman's catalyst,Pd(OH₂)/C, is reported. Compounds 5–7 possessnew hydrogen bonding modes, whose influences on the Si–O chainconformation are discussed and compared with the published analoguesHOSiPh₂OSiPh₂OSiPh₂OH (9),HOSit-Bu₂OSiMe₂OSit-Bu₂OH (10) andHOSiPh₂OSiPh₂OSiPh₂OSiPh₂OH(11), whereas compound 8 appears to be polycrystalline.Preliminary results of the HCl-catalysed condensation of5–8 are also reported, which provided complex mixtures ofoligomeric products in the case of 5 and 8, and (almost)exclusivelycyclo-(Me₂SiO)₂(Ph₂SiO)₂(12) andcyclo-(Me₂SiO)₂(Ph₂SiO)₃(13) in the case of 6 and 7, respectively. Compounds5–7 and 13 were investigated by X-raycrystallography.     

Synthesis and molecular structures of dinuclear complexes with 1,2-dihydro-1,2-diphenyl-naphtho[1,8-c,d]1,2-diphosphole as a bridging ligand

A bisphosphine in which a PhP-PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole (1), was used as a bridging ligand for the preparation of dinuclear group 6 metal complexes. Free trans-1, a more stable isomer having two phenyl groups on phosphorus centers mutually trans with respect to a naphthalene plane, was allowed to react with two equivalents of M(CO)₅(thf) (M = W, Mo, Cr) at room temperature to give dinuclear complexes (OC)₅M(μ-trans-1)M(CO)₅ (M = W (2a), Mo (2b), Cr (2c)). The preparation of the corresponding dinuclear complexes bridged by the cis isomer of 1 was also carried out starting from the free trans-1 in the following way. Mono-nuclear complexes M(trans-1)(CO)₅ (M = W (3a), Mo (3b), Cr (3c)) which had been prepared by a reaction of trans-1 with one equivalent of the corresponding M(CO)₅(thf) (M = W, Mo, Cr) complex, were heated in toluene, wherein a part of the trans-3a-c was converted to their respective cis isomer M(cis-1)(CO)₅. Each cis trans mixture of the mono-nuclear complexes 3a-c was treated with the corresponding M(CO)₅(thf) to give a cis trans mixture of the respective dinuclear complexes 2a-c. The cis isomer of the ditungsten complex 2a was isolated, and its molecular structure was confirmed by X-ray analysis, showing a shorter W?W distance of 5.1661(3) Å than that of 5.8317(2) Å in trans-2a.     

DFT, NBO, and NRT analysis of alkyl and benzyl β-silyl substituted cations: carbenium ion vs. silylium ion

The effect of β-trimethylsilyl (TMS) substituent on the structure, stability, natural charges, electrostatic potential map, natural bond orders, rotational energy barrier, and hyperconjugative interactions of five acyclic β-silyl carbocation derivatives of RR′C⁺–CH₂Si(Me)₃ including α-dimethyl 1 (R,R′ = Me), α-methyl phenyl 2 (R = Me, R′ = Ph), α-methyl para-aminophenyl 3 (R = Me, R′ = p-NH₂Ph), α-methyl para-nitrophenyl 4 (R = Me, R′ = p-NO₂Ph) and diphenyl 5 (R,R′ = Ph) was investigated in the gas phase and in solution using polarized continuum model (PCM) at B3LYP/6-311 ++G** level of theory. The resonance structures weighting of cations 1–5 were determined using natural resonance theory (NRT). The contribution of carbenium ion (RR′C⁺–CH₂Si(Me)₃) and silylium ion (RR′C=CH₂ Si(Me) ₃ ⁺ ) to the stability depend upon substituents. The former form dominants when R,R′ = Ph, but the latter is major the contributor when R,R′ = Me. The weighting of carbocation forms of β-silyl benzyl cation overwhelms silylium cation due to the delocalization of positive charge on the phenyl ring. The calculated molecular orbital (MO) diagrams, energy decomposition analysis (EDA) and ²⁹Si and ¹³C nuclear magnetic resonance (NMR) chemical shifts complement these predictions.     

Helix-sense-selective radical polymerization of bulky styrenic monomers: chiral induction and liquid crystallinity

Eight chiral vinylterphenyl monomers,(+)-2,5-bis{4′-[(S)-1″-methylpropyloxy]phenyl}styrene(Ia),(+)-2,5-bis{4′-[(S)-2″-methylbutyloxy]phenyl}styrene(Ib),(+)-2,5-bis{4′-[(S)-3″-methylpentyloxy]phenyl}styrene(Ic),(+)-2,5-bis{4′-[(S)-4″-methylhexyloxy]phenyl}styrene(Id),(?)-2,5-bis{4′-[(R)-1″-methylpropyloxy]phenyl}styrene(Ie),(+)-2-{4′-[(S)-1″-methylpropyloxy]phenyl}-5-{4′-[(R)-1″-methylpropyloxy]phenyl}styrene(IIa),(?)-2-{4′-[(R)-1″-methylpropyloxy]phenyl}-5-{4′-[(S)-1″-methylpropyloxy]phenyl}styrene(IIb),and(+)-2-{4′-[(S)-2′′-methylbutyloxy]phenyl}-5-{4′-[(S)-1″-methylpropyloxy]phenyl}styrene(III),were synthesized and radically polymerized.These molecules were designed to further understand long-range chirality transfer in radical polymerization and to possibly tune the chiroptical properties of the polymers by varying the spatial configuration,position,and various combination of the stereogenic centers at the ends of p-terphenyl pendants.The resultant polymers adopted helical conformations with a predominant screw sense.When the stereogenic centers ran away from the terphenyl group as in Ib?d,the corresponding polymers changed the direction of optical rotation in an alternative way and showed no obvious stereomutation upon annealing in tetrahydrofuran.The two stereogenic centers of IIa,IIb,and III acted concertedly in chiral induction,whereas those of Ia and Ie played a counteractive role.The five polymers derived from Ia,Ie,IIa,IIb,and III underwent stereomutation when annealed in tetrahydrofuran.The polymers PIa?e had good thermal stability and high glass transition temperatures(Tgs).They generated liquid crystalline phases at above Tgs that could be kept upon cooling,with the exception of PIe.This result was consistent with the extended helical structures.     

Dicarbonylcyclopentadienyltellurophenyliron complexes as ligands

The reaction of CpFe(CO)₂TePh (I) with ferricinium hexafluorophosphate as an oxidant affords ionic complex {[CpFe(CO)₂]₂(μ-TePh)}⁺PF ₆ ^? (II) with the simultaneous formation of diphenylditellurium. The decarbonylation of compound II by Me₃NO followed by the addition of complex I affords trinuclear complex {[CpFe(CO)₂(μ-TePh)]₂Fe(CO)Cp}PF₆ (III). The corresponding tetrafluoroborate (IV) is synthesized similarly. The heating of compound I with PPh₃ gives CpFe(CO)(PPh₃)TePh (V) that reacts with ionic complex [CpMn(CO)₂(NO)]PF₆ (VI) to form binuclear heterometallic ionic complex [CpFe(CO)(PPh₃)(μ-TePh)Mn(CO)(NO)Cp]PF₆ (VII). A similar reaction of Cp′Fe(CO)₂TePh (Cp′ is methylcyclopentadienyl) with compound VI affords heterometallic [Cp′Fe(CO)₂(μ-TePh)Mn(CO)(NO)Cp]PF₆ (VIII). The structures of compounds II, IV, VII, and VIII are determined by X-ray diffraction analysis (CIF files CCDC 963285, 963286, 963288, and 963289, respectively).     

First Examples of Electrophilic Addition to a Fe2Q Face of [Fe3(μ3-Q)(CO)9]2− (Q=Se, Te)—Synthesis and Characterisation of [MFe3(μ4-Q)(CO)9Cp*] and [IrFe2(μ3-Q)(CO)7Cp*] (M=Rh, Ir; Cp*=η5-C5(CH3)5)

The reaction of [Et₄N]₂[Fe₃(μ ₃-Q)(CO)₉] (Q=Se ([Et₄N]₂[1b]), Te ([Et₄N]₂[1c])) with [Cp*M(CH₃CN)₃][CF₃SO₃]₂ (M=Rh, Ir) leads to the addition of a Cp*M²⁺ unit to a Fe₂Q face of the initial cluster. In this way four new heteronuclear clusters [MFe₃(μ ₄-Q)(CO)₉Cp*] (M=Rh (2b, c); M=Ir (3b, c)) were obtained possessing a butterfly-shaped cluster core bridged by a μ ₄-Q unit. Furthermore, reaction with the Ir starting complex leads to the metal-substituted derivatives [IrFe₂(μ ₃-Q)(CO)₇Cp*] (4b, c) in lower yields, whose structures consist of a triangular metal core capped by a μ ₃-Q ligand. The products were comprehensively characterised by spectroscopic methods and the molecular structures of 2b, 3c, and 4c were established by single crystal X-ray diffraction measurements.