Crystal Structures and Melting Behaviors of 2D and 3D Anionic Coordination Polymers Containing Organometallic Ionic Liquid Components

Although coordination polymers generally do not melt, several that do melt have been synthesized recently and have drawn much attention. In this study, two- and three-dimensional coordination polymers that melt were synthesized, [Ru(Cp)(C₆H₅R)][M{C(CN)₃}₂] (R=H, Me, Et; M=K, Rb; Cp=C₅H₅), which are complex salts comprising M[C(CN)₃] and organometallic ionic liquids [Ru(Cp)(C₆H₅R)][C(CN)₃]. They have anionic [M{C(CN)₃}₂]_n⁻ coordination polymer frameworks, whose dimensionalities depend on the size of the organometallic cation inside. Their melting points decreased with increasing cation substituent length and size of the alkali metal ion (T_m=102–239 °C), and these low-melting-point coordination polymers exhibited incongruent melting, forming mixtures of solid M[C(CN)₃] and ionic liquid upon melting. Using the same method, coordination polymers were synthesized with various bridging ligands, [Co(Cp)₂][MX₂] (X=B(CN)₄, C(CN)₃, N(CN)₂; M=K, Na), as well as a paramagnetic coordination polymer, [Fe(Cp)₂][K{C(CN)₃}₂].     

Further Evidence for ‘Extended’ Cumulene Complexes: Derivatives from Reactions with Halide Anions and Water

Reactions of [Ru{C=C(H)-1,4-C₆H₄C≡CH}(PPh₃)₂Cp]BF₄ ([ 1 a ]BF₄) with hydrohalic acids, HX, results in the formation of [Ru{C≡C-1,4-C₆H₄-C(X)=CH₂}(PPh₃)₂Cp] [X=Cl ( 2 a-Cl ), Br ( 2 a-Br )], arising from facile Markovnikov addition of halide anions to the putative quinoidal cumulene cation [Ru(=C=C=C₆H₄=C=CH₂)(PPh₃)₂Cp]⁺. Similarly, [M{C=C(H)-1,4-C₆H₄-C≡CH}(LL)Cp ]BF₄ [M(LL)Cp’=Ru(PPh₃)₂Cp ([ 1 a ]BF₄); Ru(dppe)Cp* ([ 1 b ]BF₄); Fe(dppe)Cp ([ 1 c ]BF₄); Fe(dppe)Cp* ([ 1 d ]BF₄)] react with H⁺/H₂O to give the acyl-functionalised phenylacetylide complexes [M{C≡C-1,4-C₆H₄-C(=O)CH₃}(LL)Cp’] ( 3 a – d ) after workup. The Markovnikov addition of the nucleophile to the remote alkyne in the cations [ 1 a–d ]⁺ is difficult to rationalise from the vinylidene form of the precursor and is much more satisfactorily explained from initial isomerisation to the quinoidal cumulene complexes [M(=C=C=C₆H₄=C=CH₂)(LL)Cp’]⁺ prior to attack at the more exposed, remote quaternary carbon. Thus, whilst representative acetylide complexes [Ru(C≡C-1,4-C₆H₄-C≡CH)(PPh₃)₂Cp] ( 4 a ) and [Ru(C≡C-1,4-C₆H₄-C≡CH)(dppe)Cp*] ( 4 b ) reacted with the relatively small electrophiles [CN]⁺ and [C₇H₇]⁺ at the β-carbon to give the expected vinylidene complexes, the bulky trityl ([CPh₃]⁺) electrophile reacted with [M(C≡C-1,4-C₆H₄-C≡CH)(LL)Cp’] [M(LL)Cp’=Ru(PPh₃)₂Cp ( 4 a ); Ru(dppe)Cp* ( 4 b ); Fe(dppe)Cp ( 4 c ); Fe(dppe)Cp* ( 4 d )] at the more exposed remote end of the carbon-rich ligand to give the putative quinoidal cumulene complexes [M{C=C=C₆H₄=C=C(H)CPh₃}(LL)Cp’]⁺, which were isolated as the water adducts [M{C≡C-1,4-C₆H₄-C(=O)CH₂CPh₃}(LL)Cp’] ( 6 a–d ). Evincing the scope of the formation of such extended cumulenes from ethynyl-substituted arylvinylene precursors, the rather reactive half-sandwich (5-ethynyl-2-thienyl)vinylidene complexes [M{C=C(H)-2,5-^cC₄H₂S-C≡CH}(LL)Cp’]BF₄ ([ 7 a – d ]BF₄ add water readily to give [M{C≡C-2,5-^cC₄H₂S-C(=O)CH₃}(LL)Cp’] ( 8 a – d )].     

Cationic arenechromium-nitrosyls and -hydrides

Complexes Cr(CO)₂L(C₆Me_6-nH_n), n = 0-3, L = CO and PPh₃, react with NOPF₆ in methanol/toluene to give [Cr(CO)L(NO)(C₆Me_6-nH_n)] PF₆, n = 0-3, L = CO; n = 0, L = PPh₃, and these react with nucleophiles (X^-) to give cyclohexadienyl derivatives Cr(CO)₂(NO)(C₆Me_6-nH_nX); the compounds Cr(CO)₂(PhCCPh)(C₆Me_6-nH_n) react with NOPF₆ to yield [Cr(H)(CO)₂(PhCCPh)(C₆Me_6-nH_n)] PF₆, n = 0 and 1.     

Spectroscopic Evidence of in situ Formation of a Novel Tetrakis(Tetrazolato)Iron Compound

In an attempt to synthesize the complex [Fe(CN)₅(N₂)]^3- by reaction of Na[Fe(CN)₅(NO)]·2H₂O with azide followed by treatment with NO[SbCl₆], a similar method to that used by Feltham to obtain trans-[RuCl(N₂)(das)₂]Cl₂ from trans-[RuCl(NO)(das)₂]Cl₂, we found spectroscopic evidence that excess azide reacts with the CN^- ligands to generate tetrazolato groups C-coordinated to Fe. Initial results suggest that the obtained compound is sodium azidotris(2H-tetrazolato)(5H-tetrazolato)iron(0). The spectroscopic evidence also indicates that these heterocycles are destroyed by reaction with NO[SbCl₆], and the CN^- groups are regenerated. Here we present the characterization of these complexes by IR, ¹³C NMR, conductivity measurements, elemental analysis and magnetic susceptibility.     

Synthesis and coordination chemistry of perfluoroalkylated dithiophosphate ligands

Dithiophosphoric acids [HS₂P(OC₂H₄C_nF_2n+1)₂] (n = 4, 6) have been prepared in high yields. Deprotonation and reaction with transition metal substrates affords fluorous metal complexes which have been characterised by elemental analysis, mass spectrometry, IR and NMR spectroscopies. The structures of [Cu{S₂P(OC₂H₄C_nF_2n+1)₂}(PPh₃)₂] (n = 4, 6) and [Cu{-S₂P(OC₂H₄C₄F₉)₂}(PPh₃)]₂ have been determined by single crystal X-ray diffraction.     

Metal-Assisted Opening of Intact P4 Tetrahedra

The reactivity of ruthenium and manganese complexes bearing intact white phosphorus in the coordination sphere was investigated towards the low-valent transition-metal species [Cp′′′Co] (Cp′′′=η⁵-C₅H₂-1,2,4-tBu₃) and [L⁰M] (L⁰=CH[CHN(2,6-Me₂C₆H₃)]₂; M=Fe, Co). Remarkably, and irrespective of the metal species, the reaction proceeds by the selective cleavage of two P–P edges and the formation of a square-planar cyclo-P₄ ligand. The reaction products [{CpRu(PPh₃)₂}{CoCp′′′}(μ,η^1:4-P₄)][CF₃SO₃] ( 5 ), [{Cp^BIGMn(CO)₂}₂{CoCp′′′}(μ,η^1:1:4-P₄)] ( 6 ) and [{Cp^BIGMn(CO)₂}₂{ML⁰}(μ,η^1:1:4-P₄)] (Cp^BIG=C₅(C₆H₄nBu)₅; L⁰=CH[CHN(2,6-Me₂C₆H₃)]₂; M=Fe ( 7 a ), Co ( 7 b )), respectively, were fully characterized by single-crystal X-ray diffraction and spectroscopic methods. The electronic structure of the cyclo-P₄ ligand in the complexes 5 – 7 is best described as a π-delocalized P₄²⁻ system, which is further stabilized by two and three metal moieties, respectively. DFT calculations envisaged a potential intermediate in the reaction to form 5 , in which a quasi-butterfly-shaped P₄ moiety bridges the two metals and behaves as an η³-coordinated ligand towards the cobalt center.     

Synthesis,spectral and thermal characterization of 6-hydroxymethyl pyridine-2-carboxylic acid methyl ester and its complexes

New pincer ligand, 6-hydroxymethylpyridine-2-carboxylic acid methyl ester, HL, and its bipositive, tripositive and uranyl metal complexes have been synthesized and characterized by elemental and thermal analyses, IR, diffuse reflectance and ¹H NMR spectra, molar conductance and magnetic moment measurements. The downfield shift of the aliphatic OH signal (from 3.87 vs. 2.96 ppm in the ligand) upon complexation indicates the coordination by protonated aliphatic OH group. Zn(II) and UO2(II) complexes are found to be diamagnetic as expected. The low molar conductance values indicate that Ni(II) and Zn(II) complexes are non electrolytes; Fe(II), Co(II), Cu(II) and UO₂(II) complexes are 1:2  electrolytes while Fe(III) complex is a 1:3 electrolyte. The general compositions of the complexes are found to be [M(HL)X₂]·nH₂O where M=Ni(II) (X=Cl, n=1) and Zn(II) (X=Br, n=0); and [M(HL)₂]X_m·nH₂O where M=Fe(II) (X=Cl, m=2, n=0), Fe(III) (X=Cl, m=3, n=4), Co(II) (X=Cl, m=2, n=0), Cu(II) (X=Cl, m=2, n=0) and UO₂(II) (X=NO₃, m=2, n=0). The thermal behaviour of the complexes has been studied and different thermodynamic parameters are calculated using Coats-Redfern method.     

Poly[μ‐2‐aminopyrazine‐κ2N1:N4‐μ‐cyanido‐copper(I)]: a three‐dimensional network from laboratory powder diffraction data

In the title compound, [Cu(CN)(C₄H₅N₃)]_n or [Cu(μ‐CN)(μ‐PyzNH₂)]_n (PyzNH₂ is 2‐aminopyrazine), the Cu^I center is tetrahedrally coordinated by two cyanide and two PyzNH₂ ligands. The Cu^I–cyano links give rise to [Cu–CN]_∞ chains running along the c axis, which are bridged by bidentate PyzNH₂ ligands. The three‐dimensional framework can be described as being formed by two interpenetrated three‐dimensional honeycomb‐like networks, both made of 26‐membered rings of composition [Cu₆(μ‐CN)₂(μ‐PyzNH₂)₄].     

The HNO donor ability of hydroxamic acids upon oxidation with cyanoferrates(III)

The hydroxamic acids (RC(O)NHOH, HA) exhibit diverse biological activity, including hypotensive properties associated with formation of nitroxyl (HNO) or nitric oxide (NO). Oxidation of two HAs, benzohydroxamic and acetohydroxamic acids (BHA, AHA) by [Fe(CN)₅NH₃]^2? or [Fe(CN)₆]^3? was analyzed by spectroscopic, mass spectrometric techniques, and flow EPR measurements. Mixing BHA with both Fe(III) reactants at pH 11 allowed detecting the hydroxamate radical, (C₆H₅)C(O)NO˙^?, as a one-electron oxidation product, as well as N₂O as a final product. Successive UV–vis spectra of mixtures containing [Fe(CN)₅NH₃]^2? (though not [Fe(CN)₆]^3?) at pH 11 and 7 revealed an intermediate acylnitroso-complex, [Fe(CN)₅NOC(O)(C₆H₅)]^3? (λ_max, 465 nm, very stable at pH 7), formed through ligand interchange in the initially formed reduction product, [Fe(CN)₅NH₃]^3?, and characterized by FTIR spectra through the stretching vibrations ν_(CN), ν_(CO), and ν_(NO). Free acylnitroso derivatives, formed by alternative reaction paths of the hydroxamate radicals, hydrolyze forming RC(O)OH and HNO, postulated as precursor of N₂O. Minor quantities of NO are formed only with an excess of oxidant. The intermediacy of HNO was confirmed through its identification as [Fe(CN)₅(HNO)]^3? (λ_max, 445 nm) as a result of hydrolysis of [Fe(CN)₅(NOC(O)(C₆H₅)]^3? at pH 11. The results demonstrate that hydroxamic acids behave predominantly as HNO donors.     

Transition metal chemistry of oxime-containing ligands,IX

The vibrational (conventional and far-infrared) and diffuse-reflectance spectra in conjunction with magnetic susceptibility measurements over a temperature range down to liquid nitrogen temperature are reported and discussed for the complexes; [Mn(HPOX)₂ X ₂]; [Mn(HMPX)₂ X ₂]; [Fe(HPOX)(POX) X ₂] and [Fe(HMPX)(MPX) X ₂](whereHPOX=pyridine-2-aldoxime (C₆H₆N₂O);POX=C₆H₅N₂O;HMPX=6-Methylpyridine-2-aldoxime (C₇H₈N₂O);MPX=C₇H₇N₂O;X=Cl, Br, I, NO₃, NCS, or OA c andX ₂=SO₄). On the basis of these physical studies a six-coordinated structure is suggested for the manganese(II) and iron(III) complexes.Mössbauer spectra, measured at room-temperature and liquid nitrogen temperature also indicated a six-coordinate geometry for iron(III) complexes.

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Übergangsmetallkomplexe mit Oxim-enthaltenden Liganden, IX. Spektroskopische und magnetische Untersuchungen von Mn(II)- und Fe(II)-Komplexen mit Pyridin-2-aldoxim und 6-Methylpyridin-2-aldoxim

Zusammenfassung Es wurden Komplexe von Pyridin-2-aldoxim (HPOX) und 6-Methylpyridin-2-aldoxim (HMPX) vom Typ [Mn(HPOX)₂ X ₂], [Mn(HMPX)₂ X ₂], [Fe(HPOX)(POX)X ₂] und [Fe(HMPX)(MPX)X ₂] (X=Cl, Br, I, NO₃, NCS, OA c;X ₂=SO₄) dargestellt. Die Diskussion erfolgt basierend auf Infrarot-spektroskopie (inklusive fernes IR), Messungen der magnetischen Suszeptibilität (Temp. bis zu fl. N₂) undMössbauer-Spektroskopie.

     

Zum Koordinationsverhalten der Phenylhydrazonpropandinitrile: Darstellung und strukturelle Charakterisierung von Silber(I)‐Komplexen

On the Coordination Behaviour of Phenylhydrazonepropanedinitriles: Preparation and Structural Characterization of Silver(I) Complexes The preparation of novel silver(I) complexes with anions of phenylhydrazonepropanedinitriles [XC₆H₄NNC(CN)₂]^— (X = H or NO₂) is described. The structures of the following complex compounds are determined by X‐ray diffraction on single crystals: [Ag{O₂NC₆H₄NNC(CN)₂}] ( 2 ), [Ag{C₆H₅NNC(CN)₂}(PPh₃)] · CH₂Cl₂ ( 3 · CH₂Cl₂), [Ag{C₆H₅NNC(CN)₂}(PPh₃)₂] · 0, 5 CH₂Cl₂ ( 4 · 0, 5 CH₂Cl₂) and [Ag(PPh₃)₄][C₆H₅NNC(CN)₂] ( 5 ). In these complexes a variety of coordination modes of the phenylhydrazonepropanedinitrile anions are observed. In 3 and 4 the phenylhydrazonide anion is coordinated via the hydrazone nitrogen atom N(2). 2 shows the structure of a coordination polymer, where the phenylhydrazone coordinates as a tridentate ligand through both nitrile nitrogen atoms and the hydrazone nitrogen atom N(2). In 5 appears a free, non coordinated phenylhydrazonide anion.     

Structural investigations on new iron-acyl derivatives of B(C6F5)3

Reactions between [Fe(η-C₅H₅)(MeCO)(CO)(L)], L = PPh₃ (1), PMe₃ (2), PPhMe₂ (3), PCy₃ (4), CO (5), and B(C₆F₅)₃ give new complexes [Fe(η-C₅H₅){MeCOB(C₆F₅)₃}(CO)(L)] L = PPh₃ (7), PMe₃ (8), PPhMe₂ (9), PCy₃ (10), CO (11), where B(C₆F₅)₃ coordinates selectively to the O-acyl groups. Hydrolysis of 7 gives [Fe(η-C₅H₅){HOB(C₆F₅)₃}(CO)(PPh₃)] (6). The X-ray structures of 6, 8 and 11 have been determined. Calculations, using density functional theory, demonstrate that the charge transfer to the acyl group on Lewis acid coordination is more significant in the σ than the π system. Both effects lead to a lengthening of the acyl C-O bond thus π populations cannot be inferred from the distance changes.     

Addition Reactions of Me3SiCN with Aldehydes Catalyzed by Aluminum Complexes Containing in their Coordination Sphere O,S, and N Ligands

The reaction of one equivalent of LAlH₂ ( 1 ; L=HC(CMeNAr)₂, Ar=2,6‐iPr₂C₆H₃, β‐diketiminate ligand) with two equivalents of 2‐mercapto‐4,6‐dimethylpyrimidine hydrate resulted in LAl[(μ‐S)(m‐C₄N₂H)(CH₂)₂]₂ ( 2 ) in good yield. Similarly, when N‐2‐pyridylsalicylideneamine, N‐(2,6‐diisopropylphenyl)salicylaldimine, and ethyl 3‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐2‐carboxylate were used as starting materials, the corresponding products LAl[(μ‐O)(o‐C₆H₄)CN(C₅NH₄)]₂ ( 3 ), LAlH[(μ‐O)(o‐C₄H₄)CN(2,6‐iPr₂C₆H₃)] ( 4 ), and LAl[(μ‐NH)(o‐C₈SH₈)(COOC₂H₅)]₂ ( 5 ) were isolated. Compounds 2 – 5 were characterized by ¹H and ¹³C NMR spectroscopy as well as by single‐crystal X‐ray structural analysis. Surprisingly, compounds 2 – 5 exhibit good catalytic activity in addition reactions of aldehydes with trimethylsilyl cyanide (TMSCN).     

Four (2,2′‐bipyridyl)(ferrocenyl)boronium derivatives

Crystal structures are reported for four (2,2′‐bipyridyl)(ferrocenyl)boronium derivatives, namely (2,2′‐bipyridyl)(ethenyl)(ferrocenyl)boronium hexafluoridophosphate, [Fe(C₅H₅)(C₁₇H₁₅BN₂)]PF₆, (Ib), (2,2′‐bipyridyl)(tert‐butylamino)(ferrocenyl)boronium bromide, [Fe(C₅H₅)(C₁₉H₂₂BN₃)]Br, (IIa), (2,2′‐bipyridyl)(ferrocenyl)(4‐methoxyphenylamino)boronium hexafluoridophosphate acetonitrile hemisolvate, [Fe(C₅H₅)(C₂₂H₂₀BN₃O)]PF₆·0.5CH₃CN, (IIIb), and 1,1′‐bis[(2,2′‐bipyridyl)(cyanomethyl)boronium]ferrocene bis(hexafluoridophosphate), [Fe(C₁₇H₁₄BN₃)₂](PF₆)₂, (IVb). The asymmetric unit of (IIIb) contains two independent cations with very similar conformations. The B atom has a distorted tetrahedral coordination in all four structures. The cyclopentadienyl rings of (Ib), (IIa) and (IIIb) are approximately eclipsed, while a bisecting conformation is found for (IVb). The N—H groups of (IIa) and (IIIb) are shielded by the ferrocenyl and tert‐butyl or phenyl groups and are therefore not involved in hydrogen bonding. The B—N(amine) bond lengths are shortened by delocalization of π‐electrons. In the cations with an amine substituent at boron, the B—N(bipyridyl) bonds are 0.035 (3) Å longer than in the cations with a methylene C atom bonded to boron. A similar lengthening of the B—N(bipyridyl) bonds is found in a survey of related cations with an oxy group attached to the B atom.     

m-Ferrocenylbenzoate-bridged lanthanide coordination polymers: Syntheses, structures, electrochemical and magnetic properties

A series of m-ferrocenylbenzoate [m-ferrocenylbenzoate = m-NaOOCH₄C₆Fc, Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄)] lanthanide coordination polymers, namely [Ln(μ₂-OOCH₄C₆Fc)(η²-OOCH₄C₆Fc)(μ₂-η²-OOCH₄C₆Fc)(CH₃OH)₂]_n [Ln = La (1), Pr (2), Nd (3), Sm (4) and Gd (5)], have been synthesized by reactions of m-ferrocenylbenzoate with Ln(NO₃)₃·nH₂O. X-ray crystallographic analyses reveal that 1, 2 and 5 are essentially isostructural with unique one-dimensional linear chain structure. Three types of coordination modes for m-ferrocenylbenzoate are observed in the unit structure which consists of the eight-membered metallacycle Ln₂(COO)₂ and the rhomboid Ln₂O₂. Electrochemical studies indicate that 1-5 exhibit a reversible redox wave of Fe^II/Fe^III and the half-wave potentials of 1-5 are slightly more positive than that of m-ferrocenylbenzoic acid. Magnetic investigations show that an antiferromagnetic interaction between Gd(III) ions exists in 5.     

Rare-earth metal allyl and hydrido complexes supported by an (NNNN)-type macrocyclic ligand: synthesis, structure, and reactivity toward biomass-derived furanics

The preparation and characterization of a series of neutral rare‐earth metal complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane anion (Me₃TACD^?) are reported. Upon treatment of the neutral allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] with Brønsted acids, monocationic allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)(thf)₂][B(C₆X₅)₄] (Ln=La, Ce, Nd, X=H, F) were isolated and characterized. Hydrogenolysis gave the hydride complexes [Ln(Me₃TACD)H₂]_n (Ln=Y, n=3; La, n=4; Sm). X‐ray crystallography showed the lanthanum hydride to be tetranuclear. Reactivity studies of [Ln(Me₃TACD)R₂]_n (R=η³‐C₃H₅, n=0; R=H, n=3,4) towards furan derivatives includes hydrosilylation and deoxygenation under ring‐opening conditions.     

Syntheses, structures and reactivities of diindenyl-coordinated diiron bridging carbene complexes

Compound [Fe₂(μ-CO)₂(CO)₂(η⁵-C₉H₇)₂] (1) reacts with aryllithium reagents, ArLi (Ar = C₆H₅, p-CH₃C₆H₄, p-CF₃C₆H₄) followed by alkylation with Et₃OBF₄ to give the diindenyl-coordinated diiron bridging alkoxycarbene complexes [Fe₂{μ-C(OC₂H₅)Ar}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (2, Ar = C₆H₅; 3, Ar = p-CH₃C₆H₄, 4, Ar = p-CF₃C₆H₄). Complex 4 reacts with HBF₄ · Et₂O at low temperature to yield cationic bridging carbyne complex [Fe₂(μ-CC₆H₄CF₃-p)(μ-CO)(CO)₂(η⁵-C₉H₇)₂]BF₄ (5). Cationic 5 reacts with NaBH₄ in THF at low temperature to afford diiron bridging arylcarbene complex [Fe₂{μ-C(H)C₆H₄CF₃-p}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (6). The reaction of 5 with NaSC₆H₄CH₃-p under the similar conditions gave the bridging arylthiocarbene complex [Fe₂{μ-C(C₆H₄CF₃-p)SC₆H₄CH₃-p}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (7). Complex 5 can also react with carbonylmetal anionic compounds Na[M(CO)₅(CN)] (M = Cr, Mo, W) to produce the diiron bridging aryl(penta-carbonylcyanometal)carbene complexes [Fe₂{μ-C(C₆H₄CF₃-p)NCM(CO)₅}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (8, M = Cr; 9, M = Mo; 10, M = W). The structures of complexes 4, 6, 7, and 10 have been established by X-ray diffraction studies.     

The effect of olefinic terminal chains on the mesomorphic properties of 4,4′-disubstituted diphenyldiacetylenes

New diphenyldiacetylenes of the type with A, B = H and/or F; m = 0, 1; n = 1–4; and X = C _n H_2n+1, F, CF₃ or CN were synthesized and their mesomorphic properties determined by hot stage polarizing microscopy and DSC. When m = 0, all of these compounds showed only a nematic phase except when X = CF₃ when both nematic and smectic A phases were seen. Both clearing and melting temperatures were higher than those reported for substitution with the corresponding alkyl chains but the much larger increase in clearing temperatures produced considerably wider nematic phases. Eutectic mixtures of a few of these olefins yielded nematic materials also having much wider temperature ranges and higher clearing temperatures than the eutectic mixtures of the alkyl compounds, while retaining their high birefringence and low viscosities. Such materials are of interest for beam-steering devices. Four of the diacetylenes with m = 1 (A, B = H) were also prepared (X = C₆H₁₃, F, n= 2, 3). When X was C₆H₁₃ (n=2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X=F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X=C₆H₁₃ and n=2 had a melting temperature below room temperature.     

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Achiral P‐donor pincer‐aryl ruthenium complexes ([RuCl(PCP)(PPh₃)]) 4c , d were synthesized via transcyclometalation reactions by mixing equivalent amounts of [1,3‐phenylenebis(methylene)]bis[diisopropylphosphine] ( 2c ) or [1,3‐phenylenebis(methylene)]bis[diphenylphosphine] ( 2d ) and the N‐donor pincer‐aryl complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 2). The same synthetic procedure was successfully applied for the preparation of novel chiral P‐donor pincer‐aryl ruthenium complexes [RuCl(P*CP*)(PPh₃)] 4a , b by reacting P‐stereogenic pincer‐arenes (S,S)‐[1,3‐phenylenebis(methylene)]bis[(alkyl)(phenyl)phosphines] 2a , b (alkyl=ⁱPr or ^tBu, P*CHP*) and the complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 3). The crystal structures of achiral [RuCl(equation/tex2gif-sup-3.gifPCP)(PPh₃)] 4c and of chiral (S,S)‐[RuCl(equation/tex2gif-sup-6.gifPCP)(PPh₃)] 4a were determined by X‐ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh₃)] complexes and chiral [RuCl(P*CP*)(PPh₃)] complexes were tested as catalyst in the H‐transfer reduction of acetophenone with propan‐2‐ol. With the chiral complexes, a modest enantioselectivity was obtained.     

Studies on interaction of isocyanide with transition metal complexes : XI. Photochemical reactions of isocyanide complexes of iron

The photochemical reaction of π-C₅H₅Fe(CO)(CNC₆H₁₁)COCH₃ (I) gave the heterocyclic compound π-C₅H₅Fe(CO)[(C=NC₆H₁₁)₂(CH₃)] (II) involving N-coordination to the iron atom. The analogous complex is obtained by the photo-induced reaction of π-C₅H₅Fe(CO)₂CH₃ with C₆H₁₁NC. A similar reaction of π-C₅H₅Fe(CO)[CNC(CH₃)₃]CH₃ with C₆H₁₁NC gave π-C₅H₅Fe(CO)[(C=NC₆H₁₁) {C=N(CH₃)₃}(CH₃)] (IV) involving different N-substituted imino groups. The possible pathways leading to formation of II are discussed. The mass spectra of these complexes were also investigated.