Chemo- and Stereoselective Coordination of 5,6-Dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene by d8- and d6-Metal Carbonyls. Diels-Alder reactivity of Dienes Perturbed by Remote Olefin Complexation

The endocyclic double bond C(2), C(3) in 5,6-dimethylidene-7-oxabicyclo[2.2.1]-hept-2-ene ( 1 ) can he coordinated selectively on its exo-face before complexation of the exocyclic s-cis-butadiene moiety. Irradiation of Ru₃(CO)₁₂ or Os₃(CO)₁₂ in the presence of 1 gave tetracarbonyl [(1R,2R, 3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]-hept-2-ene)]ruthenium ( 6 ) or -osmium ( 8 ). Similarly, irradiation of Cr(CO)₆ or W(CO)₆ in the presence of 1 gave pentacarbonyl[(1R, 2R, 3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]chromium (10) or -tungsten (11) . Irradiation of complexes 6 and 11 in the presence of 1 led to further CO substitution giving bed-tricarbonyl-ae-bis[(1R,2R,3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]ruthenium ( 7 ) and trans-tetracarbonyl[(1R,2R,3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo-[2.2.1]hept-2-ene)]tungsten (12) , respectively. The diosmacyclobutane derivative cis-m?-[(1R,3R,3S,4S)-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hepta-2,3-diyl)]bis(tetracarbonyl-osmium) (Os-Os) (9) wa also obtained. The Diels-Alder reactivity of the exocyclic s-cis-butadiene moiety in complexs 7 and 8 was found to be significantly higher than that of the free triene 1 .     

Yttrium pyrogermanate,Y2Ge2O7

The structure of diyttrium digermanate, Y₂Ge₂O₇, has been determined in the tetragonal space group P4₃2₁2. It contains one Y, one Ge (both site symmetry 1 on general position 8b) and four O atoms [one on special position 4a (site symmetry ..2) and the remaining three on general positions 8b]. The basic units of the structure are isolated Ge₂O₇ groups, sharing one common O atom and displaying a Ge—O—Ge angle of 134.9 (3)°, and infinite helical chains of pentagonal YO₇ dipyramids, parallel to the 4₃ screw axis. The crystal investigated here represents the left‐handed form of the tetragonal R₂Ge₂O₇ compounds (R = Eu³⁺, Tb³⁺, Er³⁺, Tm³⁺ and Lu³⁺).     

Compounds containing layers of composition [(SbF)XO4] (X = P, As). Crystal structures of Na(SbF)PO4 · 1.5H2O, Na(SbF)AsO4, NH4(SbF)PO4 · H2O, and NH4(SbF)AsO4 · 3H2O

The title compounds have been prepared in water by reaction of SbF₃ with dihydrogen phosphates or arsenates and characterized by single crystal X-ray work, IR, Raman, and Mössbauer spectroscopy. They have identical layer structures. Layers of composition [(SbF)XO₄]⁻ (X = P, As) were formed by sharing four corners between XO₄ tetrahedra and SbFO₄ pseudooctahedra. The lengths of the terminal Sb---F bond (with the lone pair in a trans-position) and the Sb---O bonds are 192 and 219 pm, respectively. The stacking of the layers and the interlayer distance depend on the cations and the number of intercalated water molecules. In Na(SbF)AsO₄ the Na⁺ ion is coordinated by only two oxygen atoms within 300 pm. Crystal data: Na(SbF)PO₄ · 5H₂O, monoclinic, P2₁/m, A = 656.2(5), B = 654.1(5), C = 867.9(3) pm, β = 92.43(1)°, 889 reflections, 81 parameters, R = 0.044, R_w = 0.046. NH₄(SbF)PO₄ · H₂O, tetragonal, I4/m, A = 656.6(3), C = 1439.8(5) pm, 680 reflections, 31 parameters, R = 0.023, R_w = 0.021. Na(SbF)AsO₄, tetragonal, P4/ncc, A = 671.8(1), C = 1756.4(4) pm, 1056 reflections, 28 parameters, R = 0.052, R_w = 0.065. NH₄(SbF)AsO₄ · 3H₂O, tetragonal, P4/ncc, A = 683.8(2), C = 1873.0(7) pm, 1194 reflections, 30 parameters, R = 0.042, R_w = 0.050.     

Cyclodimerization of 1-(Dimethoxyniethyl)-5,6-dimethylidene-7-oxa-bicyclo[2.2.1]hept-2-ene Induced by Nonacarbonyldiiron. Crystal Structure of (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)- Tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl)-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)]iron

The transition-metal-carbonyl-induced cyclodimerization of 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene is strongly affected by substitution at C(1) While 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept–2-ene-l-methanol ( 7 ) refused to undergo [4 + 2]-cyclodimerization in the presence of [Fe₂(CO)⁹] in MeOH, 1-(dimethoxymethyl)-5,6-di-methylidene-7-oxabicyclo[2.2.1]hept-2-ene ( 8 ) led to the formation of a 1.7:1 mixture of ‘trans’ ( 19, 21, 22 ) vs. ‘cis’ ( 20, 23, 24 ) products of cyclodimerization together with tricarbonyl[C, 5,6, C-η-(l-(dimethoxymethyl)-5,6-di-methylidenecyclohexa-1,3-diene)]iron ( 25 ) and tricarbonyl[C,3,4, C-η-(methyl 5-(dimethoxymethyl)-3,4-di-methylidenecyclohexa-1,5-diene-l-carboxylate)]iron ( 26 ). The structures of products 19 and of its exo ( 21 ) and endo ( 22 ) [Fe(CO)₃(1,3-diene)]complexes) and 20 (and of its exo ( 23 ) and endo (24) (Fe(CO)₃(1,3-diene)complexes) were confirmed by X-ray diffraction studies of crystalline (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)-tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl])-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)iron ( 21 ). In the latter, the Fe(CO)₃(1,3-diene) moiety deviates significantly from the usual local C_s symmetry. Complex 21 corresponds to a ‘frozen equilibrium’ of rotamers with η-alkyl, η³-allyl bonding mode due to the acetal unit at the bridgehead centre C(1).     

From Isolated Polyanions to 1‐D Structure: Synthesis and Crystal Structure of Hybrid Fluorides {[(C2H4NH3)3NH]4+}2 · (H3O)+ · [Al7F30]9– and {[(C2H4NH3)3NH]4+}2 · [Al7F29]8– · (H2O)2

Two new hybrid fluorides, {[(C₂H₄NH₃)₃NH]⁴⁺}₂ · (H₃O)⁺ · [Al₇F₃₀]^9– ( I ) and {[(C₂H₄NH₃)₃NH]⁴⁺}₂ · [Al₇F₂₉]^8– · (H₂O)₂ ( II ), are synthesized by solvothermal method. The structure determinations are performed by single crystal technique. The symmetry of both crystals is triclinic, sp. gr. P 1, I : a = 9.1111(6) Å, b = 10.2652(8) Å, c = 11.3302(8) Å, α = 110.746(7)°, β = 102.02(1)°, γ = 103.035(4)°, V = 915.9(3) ų, Z = 1, R = 0.0489, R_w = 0.0654 for 2659 reflections, II : a = 8.438(2) Å, b = 10.125(2) Å, c = 10.853(4) Å, α = 106.56(2)°, β = 96.48(4)°, γ = 94.02(2)°, V = 877.9(9) ų, Z = 1, R = 0.0327, R_w = 0.0411 for 3185 reflections. In I , seven corner‐sharing AlF₆ octahedra form a [Al₇F₃₀]^9– anion with pseudo 3 symmetry; such units are found in the pyrochlore structure. The aluminum atoms lie at the corners of two tetrahedra, linked by a common vertex. In II , similar heptamers are linked in order to build infinite (Al₇F₂₉)_n^8– chains oriented along a axis. In both compounds, organic moieties are tetra protonated and establish a system of hydrogen bonds N–H…F with four Al₇F₃₀^9– heptamers in I and with three inorganic chains in II .     

Synthesis,crystal structure and magnetic properties of the binuclear copper (II) complex of a new bis (1, 4, 7, 10‐tetraazacyclododecane) ligand

A new binucleating macrocyclic ligand 2,6‐bis (1,4,7,10‐tetraazacyclododecan‐10‐ylmethyl) methoxy‐benzene (L) and its binuclear copper (II) complex, [Cu₂LBr₂] (CIO₄ )₂ · 3H₂O (1), was prepared and the structure was determined by X‐ray crystallography. Complex 1 crystallizes in monoclinic crystal system, P2₁/n space group with a = 0.8206(3), b =2.0892(8), c = 2.3053(7) mn, β = 95.83(2)°, V = 3.932 nm³, Mr=1017.57, Z = 4, D_c =1.692 g/cm³, and R= 0.0489, R_w 0.0552 for 6571 observed reflections with I ≥ 2σ (1). Both of the copper(II) centers are coordinated by four amine nitrogen donors of cyclen subunits and a bromide anion, and each copper(II) ion is in a square‐pyramidal coordination environment. Variable temperature magnetic susceptibility studies indicate that there exists weak intramolecular antiferro‐magnetic coupling ( ?2J = 2.06 cm^?1) between the two copper (II) centers.     

Crystal Structure of C-(n-propyl)calix[4]resorcinarene and its Complex with Caffeine

Abstract

The crystal structures of the all-cis epimer of C-(n-propyl)calix[4]resorcinarene (1) and its caffeine complex are reported. 1 · CH₃CN · H₂O (2) crystallizes in the tetragonal space group P4, a = 14.3645(9), c = 9.3344(8) Å, V = 1926(2) ų. Refinement led to a final conventional R ₁ value of 0.047 for 3406 reflections and 236 parameters. The caffeine complex 1 · C₈H₁₀N₄O₂ · CH₃OH · H₂O (3) crystallizes in the triclinic space group P1, a = 11.2892(4), b = 13.0367(8), c = 16.9700(11) Å, α = 82.902(2), β = 79.713(3), γ = 88.053(2)°, V = 2438(2) ų. Refinement led to a final conventional R ₁ value of 0.067 for 6393 reflections and 641 parameters. The resorcinarene displays the usual bowl shape in both compounds. The caffeine molecule in 3 is hydrogen bonded to two resorcinarene and one water molecules and one of its methyl groups is included in the cavity of a third macrocycle, suggesting CH₃…π interactions. Extended hydrogen bonding patterns involving phenolic protons and solvent molecules are also present in both compounds.     

Unimolecular reactions of the isolated immonium ions CH3CH = NH+C4H9, CH3CH2Ch = NH+C4H9 and (CH3)2C = NH+C4H9

The reactions of ten metastable immonium ions of general structure R¹R²C?NH⁺C₄H₉ (R¹ = H, R² = CH₃, C₂H₅; R¹ = R² = CH₃) are reported and discussed. Elimination of C₄H₈ is usually the dominant fragmentation pathway. This process gives rise to a Gaussian metastable peak; it is interpreted in terms of a mechanism involving ion-neutral complexes containing incipient butyl) cations. Metastable immonium ions ontaining an isobutyl group are unique in undergoing a minor amount of imine (R¹R²C?NH) loss. This decomposition route, which also produces a Gaussian metastable peak, decreases in importance as the basicity of the imine increases. The correlation between imine loss and the presence of an isobutyl group is rationalized by the rearrangement of the appropriate ion-neutral complexes in which there are isobutyl cations to the isomeric complexes containing the thermodynamically more stable tert-butyl cations. A sizeable amount of a third reaction, expulsion of C₃H₆, is observed for metastable n-C₄H₉ ⁺NH?CR¹R² ions; in contrast to C₄H₈ and R¹R²C?NH loss, C₃H₆ elimination occurs with a large kinetic energy release (40–48 kJ mol^?1) and is evidenced by a dish-topped metastable peak. This process is explained using a two-step mechanism involving a 1,5-hydride shift, followed by cleavage of the resultant secondary open-chain cations, CH₃CH⁺ CH₂CH₂NHCHR¹R².     

Aurivillius Phases in the Bi4Ti3O12/BiFeO3 System: Thermal Behaviour and Crystal Structure

Four compounds of the Bi₄Ti₃O₁₂/BiFeO₃ system with the formula Bi₂Bi_n?1(Ti,Fe)_nO_3n+3, n = 3, 4, 4.5 and 6 were studied using high‐temperature X‐ray powder diffraction and differential thermoanalysis methods. The crystal structure of the n = 6 phase was refined by the Rietveld method. An unusual behaviour of thermal expansion attributed to an orthorhombic‐to‐tetragonal transformation was revealed. For all the compounds, the lattice parameter c vs temperature T dependence has three regions in the range of T = 20 –750 °C interpreted as (1) expansion of the initial orthorhombic phase, (2) a pronounced structure reconstruction to the tetragonal phase, (3) an expansion of the tetragonal phase. The crystal structure of Bi₇Ti₃Fe₃O₂₁ based on 6‐layer‐perovskite blocks is proposed from X‐ray powder diffraction data. The Rietveld refinement of the structure in the orthorhombic space group F2mm with lattice parameters a = 5.4699(3), b = 5.4924(3), c = 57.551(3) Å (R_p = 9.4, R_wp = 11.9, R_exp = 4.7, R_B = 4.4 %) shows that a distorted 6‐layer model fits the data of Bi₇Ti₃Fe₃O₂₁.     

Coordination Chemistry of Sulfonyl Amides. 2 The Crystal Structure of Copper(II) and Silver(I) Complexes of N,N-4-Toluenesulfonyl-2-Pyridylaminato Ligand

Three structures containing the N,N-4-toluenesulfonyl-2-pyridylaminato ligand are presented. The brown crystal of Cu₂L₄ (L =N,N-4-toluenesulfonyl-2-pyridylaminato) was found to crystallize in the monoclinic space group P2,/c with a = 15.762(12), b = 15.552(5), c = 20.505(11) Å, β = 104.14(7)°; V = 4874(5) Å^3;Z = 4; the final R_F = 0.050, R_WF = 0.049 for 5142 observed reflections and 612 variables. The Cu-Cu distance is small, 2.516(2) Å and the complex is diamagnetic at room temperature. The colorless crystal of Ag₂L was found to crystallize in the monoclinic space group P2_t/n with a = 9.620(2), b = 5.625(2), c ? 23.250(3) Å, Å = 94.72(1)°; V = 1254.0(5) ų; Z = 2; the final R_F = 0.027; R_WF = 0.028 for 1929 observed reflections and 164 variables. The Ag-Ag distance is 2.739(1) Å The green crystal of CuL₂ (py)₂was found to crystallize in the monoclinic space group P2₁ with a = 9.366(2), b = 20.615(7), c = 9.862(2) Å,β = 116.73(2)°; V = 1700.5(8) ų; Z = 2; the final R_F = 0.037; R_WF = 0.038 for 1636 observed reflections and 423 variables. A reversible transformation between Cu₂L₄ and CuL₂(py)₂ is reported.     

4‐Carboxyanilinium (2R,3R)‐tartrate and a redetermination of the α‐polymorph of 4‐aminobenzoic acid

In the title compounds, 4‐carboxyanilinium (2R,3R)‐tartrate, C₇H₈NO₂⁺·C₄H₅O₆⁻, (I), and 4‐aminobenzoic acid, C₇H₇NO₂, (II), the carboxyl planes of the 4‐carboxyanilinium cations/4‐aminobenzoic acid are twisted from the aromatic plane. In (I), the characteristic head‐to‐tail interactions are observed through the tartrate anions, forming two C₂²(7) chain motifs propagating parallel to the a and c axes of the unit cell. Also, the tartrate anions are connected through two primary C₁¹(6) and C₁¹(7) chain motifs, leading to a secondary R₄⁴(22) ring motif. In (II), head‐to‐tail interaction is seen through a discrete D₁¹(2) motif and carboxyl group dimerization is observed through centrosymmetrically related R₂²(8) motifs around the inversion centres of the unit cell. The crystal structures of both compounds are stabilized by intricate three‐dimensional hydrogen‐bonding networks. Alternate hydrophobic and hydrophilic layers are observed in (I) as a result of a column‐like arrangement of the anions and the aromatic rings of the cations.     

Synthesis and Crystal Structures of Novel Copper(I) Clusters with Bridging Silyl Amide Ligands

Treatment of copper(I) chloride with R₂Si(NLiPh)₂ (R = Me, Ph) in thf led to the formation of the octanuclear cluster compounds [Cu₈{(R₂Si(NPh)₂}₄] [R = Me ( 1 ), Ph ( 2 ).] Compound 1 crystallizes in the tetragonal space group P4/n, with a = 1505.41(5) and c = 1911.32(7) pm. The X‐ray crystal structure determination revealed a cube shaped Cu₈ cluster core with μ₄ bridging Me₂Si(NPh)₂^2– ligands. The copper atoms display an almost linear coordination with Cu–N distances in the range of 191.1(3)–191.4(3) pm. The Cu–Cu distances are 265.7(1)–267.3(1) pm. Compound 2 forms monoclinic crystals, space group P2₁/n, with a = 1461.87(4), b = 2483.77(6), c = 2725.49(8) pm, β = 100.77(1)°. The cluster core of compound 2 consists formally of two mutually perpendicular arranged trigonal prisms, which share a common square face. Like in the case of compound 1 the square faces of the cluster core are capped by μ₄ bridging Ph₂Si(NPh)₂^2– ligands. The copper atoms adopt a nearly linear N–Cu–N coordination with Cu–N distances of 190.0(4)–195.1(4) pm. The Cu–Cu distances are 252.3(1)–305.6(1) pm.     

Zu Oxoiridaten mit quadratisch-planaren [IrO4]4−-Gruppen: Na4IrO4, eine MgO-Ersetzungsvariante mit geordneten Lücken im Anionenteilgitter

On Oxoiridates(IV) with Square-planar Groups [IrO₄]^4?: Na₄IrO₄, a Substitution-variant of MgO with Ordered Vacancies in the Anionic Part of Structure . For the first time we prepared transparent red single crystals of Na₄[IrO₄] by an “exchange reaction” (Li₂IrO₃ + 2.20 Na₂O; Ag, 800°C, 71 days): tetragonal, space group I4/m (No. 87), a = 716.70(4) pm and c = 471.32(4) pm; Z = 2. The structure determination via four circle diffractometer data (Mo? Kα , graphite; 2 138 I₀(hkl), R = 0.0179; R_w = 0.0184) was carried out with all 296 independent reflexions. Therefore Na₄IrO₄ crystallizes in a defect-variant of MgO which can be derived from Na₄UO₅. Ir⁴⁺ is surrounded square-like by four O^2? with two vacancies completing the octahedron. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed. Furthermore the mean value for MAPLE(“IrO₂”) of all alkaline- and alkaline-earth-oxoiridates(IV) is given.     

Crystal structure of 2-butylamino-3-(4-fluorophenyl) benzofuro[3,2-d]pyrimidin-4(3H)-one

The title compound (C₂₀H₁₈FN₃O₂, Mr = 351.37) is prepared and its crystal structure is determined by single crystal X-ray diffraction. The crystal is tetragonal, the P-42(1)c space group with a = 11.0922(6) ?, b = 11.0922(6) ?, c = 28.6271(15) ?, V = 3522.2(3) ?³, Z = 8, d _x = 1.325 g/cm³, F(000) = 1472, μ = 0.095 mm⁻¹, MoK _α radiation (λ = 0.71073), R = 0.0505, wR = 0.1090 for 2433 observed reflections with I > 2σ(I). The X-ray diffraction analysis reveals that all ring atoms in the benzo[4,5]furo[3,2-d]pyrimidinone moieties are almost coplanar.     

Zur struktur von CaPdF4, CdPdF4, HgPdF4 und HpPdF2

Single crystals of CaPdF₄ (purple) and CdPdF₄ (dark blue) have been obtained by heating CaF₂ (CdF₂) with PdF₂ at 820°C (900°C) for ca. 20–30 d in sealed Pd (Pt) tubes. CaPdF₄ crystallizes tetragonal (KBrF₄-Type) with a = 5.52₁, c = 10.57₀ Å (space group I4/mcm ? D^18_4h, No. 140) Z = 4, 283 unique reflexions, R = 0.083; R_w = 0.079, CdPdF₄ cubic (CaF₂-variant) with a = 5.40₃ Å (space group Pa3 ? T^6_h, No. 205) Z = 4, 165 unique reflexions, R = 0.047, R_w = 0.032. The high pressure modification of PdF₂, obtained by heating PdF₂ in closed Pt-tubes under a pressure of ≈ 60 kbar and ‘HgPdF₄’, both black, a = 5.32₇ Å and a = 5.43 Å are isotypic. CaPdF₄ is diamagnetic, CdPdF₄ and HPPdF₂ are antiferromegnetic.     

Regioselectivity of the Diels-Alder Additions of 2-Substituted 5,6 Dimethylidenenorbornanes and-bicyclo[2.2.2]octanes

The cycloadditions of methyl propynoate and methyl vinyl ketone to 5,6-dimethylidene-2-norbornanone ( 6 ) are para′-regioselective

1 “Para” (p) designs in this paper the 4, 9-disubstituted tricclo[6.2.1.0^{2, 7}] undecane- and 4, 9-disubsstituted tricycle[6.2.20^2,7] dodecane derivatives, “meta” (m) design the corresponding 4, 10-disubstituted compounds.

. A smaller para -regioselectivity is observed for the addition of methyl propynoate to 5,6-dimethylidene-2bicyclo[2.2.2]octanone ( 10 ). No regioselectivity is observed with 5,6-dimethylidene-2exo-norbornyl alcohol ( 3 ), acetate ( 5 ) and 5,6-dimethylidene-2exo-bicyclo[2.2.2]octanol ( 9 ). PMO arguments based on the shape of the HOMO's and subHOMO's of the dienes allow to rationalize these observations. Unpredictable para′- or ‘meta’regioselectivities are found for the Diels,-Alder additions of 5,6-dimethylidene-2endo-norbornyl alcohol ( 2 ), acetate ( 4 ) and 5,6-dimethylidene-2endo-bicyclo[2.2.2]octanol ( 8 ). The carbonyl group of β,γ unsaturated ketones such as 6 and 10 can act as an electron donating homoconjugated substituent. The n(CO) ? σ[C(1), C(2)] ? π[C(5), C(6)] hyperconjugative interaction can override the usual electron-withdrawing effect of this function.     

Synthesis,Crystal Structures,and Nonlinear Optical Properties of Two Cubane‐Like Cluster Compounds [(n‐Bu)4N]3[MoS4Ag3Cl4] and [Et4N]3[WOS3Cu3I4]

The compounds [(n‐Bu)₄N]₃[MoS₄Ag₃Cl₄] ( 1 ) and [Et₄N]₃[WOS₃Cu₃I₄] ( 2 ) were synthesized and characterized. Compound 1 crystallizes in the rhombohedral system, space group R3c with a = 17.194(1), b = 17.194(1), c = 39.194(3)Å, Z = 6, V = 10034.7(11)ų. Compound 2 crystallizes in the rhombohedral system, space group R3c with a = 14.461(2), b = 14.461(2), c = 34.952(2)Å, Z = 6, V = 6329.9(13)ų. The X‐ray crystallographic structure determinations show that these two cluster compounds consist of a slightly distorted cubic core. Nonlinear optical (NLO) properties of these two clusters were investigated by using Z‐scan techniques with an 8 ns pulsed laser at 532 nm; both clusters exhibit strong nonlinear optical absorption effect (effective α₂ = 1.18 × 10^—10 m · W^—1 for 1 and 1.0 × 10^—10 m · W^—1 for 2 ).     

Subgroup 4 (Ti,Zr, Hf) derivatives of Cobalt Carbonyls

Bimetallic and trimetallic compounds containing unsupported bonds of subgroup 4 metals (M = Ti, Zr, Hf) and Co were prepared by hydride elimination (A) from RM derivatives (R¹ = PhCH₂; RN; R² = Me, Et)) and by salt elimination (B) from RMX (X = Cl, Br; R.¹ = PhCH₂, RN and R³O; R³= i-Pr, n-Bu)) by reaction with HCo(CO)₄ and Na[Co(CO)₄], respectively. Compounds RMCo(CO)₄ with R¹ = PhCH₂, RM[Co(CO)₄]₂ R.¹ = PhCH₂, were prepared both by methods A and B, while (R³O)₄-n Ti[Co(Co)₄]n (n = 1, 2) compounds were obtained by reaction B. Several tertiary phosphine and phosphite derivatives of the former two types were obtained by substitution of a carbonyl group by PR ligand or by A type reaction of HCo(CO)³(PR with RM compounds.     

The Acetolysis of exo- and endo-5,6-Dimethylidene-2-Norbornyl p-Bromobenzenesulfonates and of their Optically Active and Deuterium-Labelled Derivatives

The buffered (AcOK) acetolyses of exo, (11) and endo-5, 6-dimethylidene-2-norbornyl brosylate (12) yielded exo5, 6-dimethylidene-2-norbornyl (16) and (3-methylidene-2-nortricyclyl)methyl acetates (18) . Endo-5, 6-dimethylidene-2-norbornyl (17) and 2-methylidene-3-tricyclo [3.2.1.0^3,6]octyl acetates (20) could not be detected. The titrimetric rate constants of the acetolysis of 11 (k_t(exo)=4.49 ± 0.02) · 10^?5 s^?1 at 25°, ΔH^≠=23.6 ±0.7 kcal mol^?1, ΔS^≠=0.7 ±2 calmol^?1 K^?1 and 12 (k_t(endo)=1.9 ±0.08) · 10^?9 s^?1 at 25°, ΔH^≠=27 ±1 kcal mol^?1, ΔS^≠=-8 ±2.5 calmol^?1 K^?1) were measured and compared with the polarimetric rate constants (k_α/k_(exo)=6.8 at 25°,(k_α/k_(exo)=1.0 at 121°) of the buffered acetolyses of the optically active brosylates (+)- 11 and (+)- 12 . Neither a common-ion (KOBs) nor a special ion effect (LiClO₄) on k_t(endo) could be detected, although external return might well intervene as some exo-5,6-dimethylidene-2-norbornyl tosylate (21) was formed upon solvolysis in the presence of KOTs. Acetolysis of (+)- 11 yielded completely racemized products, whereas (+)- 12 led to incomplete racemization. The buffered acetolysis of exo-(3exo-D)-5,6-dimethylidene-2-norbornyl brosylate (24) furnished (3exo-D)-( 26 :37.5%), exo-(7syn-D)-5,6-dimethylidene-2-norbornyl brosylate (27 : 37.5%) and [(5anti-D)-3-methylidene-2-nortricyclyl]methyl acetates (28 : 25 %). The acetolysis of endo-(2exo-D)-5,6-dimethylidene-2-norbornyl brosylate (25) yielded (2endo-D)-( 29 : 54%), exo-(1-D)-5,6-dimethylidene-2-norbornyl ( 30 : 36%) and [(6-D)-3-methylidene-2-nortricyclyl]methyl acetates ( 31 : 10%). Product analysis and deuterium label distribution was established by a combination of GC., ¹H-NMR., ²H-{¹H}-NMR. and MS. techniques. The results are rationalized by invoking anchimerically assisted ionization of the exo-brosylate 11 to symmetrical ion-pairs (cyclopropylcarbinyl cation intermediates) which undergo internal (and probably also external) return. Acetolysis of the endo-brosylate 12 is not anchimerically assisted and leads initially to non-symmetrical ion pairs. These evolve to symmetrical ion pair intermediates or, to a minor extent, are intercepted by solvent.     

Bis(arylimido) Molybdenum(VI) Amidinate and Guanidinate Complexes; Molecular Structures of [(ArN)2MoMe{N(Cy)C[N(i‐Pr)2]N(Cy)}] (Ar = 2,6‐i‐Pr2C6H3; Cy = Cyclohexyl) and [(2,6‐i‐Pr2C6H3N)2MoCl2] · [NH=C(C6H5)CH(SiMe3)2]

The reaction of [(ArN)₂MoCl₂] · DME (Ar = 2,6‐i‐Pr₂C₆H₃) ( 1 ) with lithium amidinates or guanidinates resulted in molybdenum(VI) complexes [(ArN)₂MoCl{N(R¹)C(R²)N(R¹)}] (R¹ = Cy (cyclohexyl), R² = Me ( 2 ); R¹ = Cy, R² = N(i‐Pr)₂ ( 3 ); R¹ = Cy, R² = N(SiMe₃)₂ ( 4 ); R¹ = SiMe₃, R² = C₆H₅ ( 5 )) with five coordinated molybdenum atoms. Methylation of these compounds was exemplified by the reactions of 2 and 3 with MeLi affording the corresponding methylates [(ArN)₂MoMe{N(R¹)C(R²)N(R¹)}] (R¹ = Cy, R² = Me ( 6 ); R¹ = Cy, R² = N(i‐Pr)₂ ( 7 )). The analogous reaction of 1 with bulky [N(SiMe₃)C(C₆H₅)C(SiMe₃)₂]Li · THF did not give the corresponding metathesis product, but a Schiff base adduct [(ArN)₂MoCl₂] · [NH=C(C₆H₅)CH(SiMe₃)₂] ( 8 ) in low yield. The molecular structures of 7 and 8 are established by the X‐ray single crystal structural analysis.