Crystal Structures Of 2b Research Articles

2-Amino-2-oxazoline and trialkylisourea Pt(ii) complexes derived from organocyanamides

In the di(organocyanamide) complexes trans-[PtCl2(NCNR2)2] (R = Me 1a, Et 1b), prepared by reaction of PtCl2 with the appropriate NCNR2, the cyanamide ligands, activated by coordination, undergo an unprecedented nucleophilic addition, at room temperature, of an haloalcohol (ClCH2CH2OH/LiBun) or of an alcohol (MeOH) to give the corresponding 2-amino-2-oxazoline cis-[PtCl2{NC(OCH2CH2)NR2}2] (R = Me 2a, Et 2b) or trialkylisourea trans-[PtCl2{NHC(OMe)NR2}2] (R = Me 3a, Et 3b) complexes. The X-ray crystal structure of 2b is also reported, indicating a π-bond delocalization along the NCN group of the aminooxazoline ligands.

Manganese(I) and Rhenium(I) Tricarbonyl (Alkylthio)methyl and Alkylidenesulfonium Complexes

The reactions of Na[M(CO)(3)(bipy)] (M = Mn, Re) compounds with ClCH2SR (R = Me, Ph) afford the (alkylthio)alkyl complexes [Mn(CH2SMe)(CO)(3)(bipy)] (1a), [Mn(CH2SPh)(CO)(3)-(bipy)] (1b), [Re(CH2SMe)(CO)(3)(bipy)] (2a), and [Re(CH2SMe)(CO)(3)(bipy)] (2b). Methylation at sulfur of these compounds with methyl triflate affords the methylidenesulfonium cations [Mn(CH2SMe2)(CO)(3)(bipy)](+) (5a), [Mn(CH2SMePh)(CO)(3)(bipy)](+) (5b), [Re(CH2SMe2)(CO)(3)(bipy)](+) (6a), and [Re(CH2SMePh)(CO)(3)(bipy)](+) (6b) as their triflate salts. These new compounds were characterized by IR and NMR spectroscopy, and the crystal structures of 1b, 2a, 5b, and 6b have been determined by X-ray diffraction. The sulfonium complexes are unreactive toward PPh3 and pyridine. The reactions of 5b and 6b with I-, PPh2-, and SEt(-)anions afford the (phenylthio)methyl complexes 1b and 2b, resulting from nucleophilic attack at the methyl group. 5b and 6b react with styrene to give phenylcyclopropane, free thioanisole, and the corresponding [M(OTf)(CO)(3)(bipy)] complex.

Synthesis and crystal structures of novel 1-aza-2-silacyclobut-3-enes

A crystallographic re-investigation of the structure of the 4-aryl(lithio)amino-1-aza-2-silacyclo-but-3-ene derivative, [Li{N(Ar)CC(R)SiR2NAr}](tmen) F (R = SiMe3, Ar = C6H3Me2-2,6), formed by the treatment of [Li(SiR3)(thf)3] with ArNC in the presence of tmen, revealed the presence of two independent molecules within the unit cell. Its protonolysis with cyclopentadiene monomer gave the 1-aza-2-silacyclobutene, HN(Ar)CC(R)Si(R)2NAr 2b. Replacing tmen with 1,2-bis(dimethylphosphino)ethane (dmpe), in the reaction of [Li(SiR3)(thf)3] with ArNC, gave either [Li{N(Ar)CC(R)Si(R)2NAr}(thf)2] 4 or the dimer [Li{N(Ar)CC(R)Si(R)2NAr}(μ-dmpe)]23, the latter being preferred at low thf concentrations. Each of the compounds F, 2b, 3 and 4 was characterised by multinuclear NMR spectroscopy and (not 4) X-ray diffraction. The single crystal structures of 2b and 3 provide the first examples of a neutral CCSiN compound and a neutral phosphine-bound alkali metal complex, respectively. The NMR spectra revealed that 3 undergoes speciation in solution.

5-Organyl-5-phosphaspiro[4.4]nonanes: a contribution to the structural chemistry of spirocyclic tetraalkylphosphonium salts and pentaalkylphosphoranes.

Spirocyclic phosphonium salts of the type [(CH(2))(4)P(CH(2))(4)](+) X(-) with X = I(3) (1a), I (1b), picrate (1c), benzoate (1d), and Cl (1e) were prepared from 1,4-diiodobutane and elemental phosphorus followed by metathesis reactions. The crystal structures of 1b and 1c and of 1d(H(2)O) have been determined by X-ray diffraction methods. In the cations of these salts the phosphorus atoms are shared by two five-membered rings in envelop conformations. In the picrate 1c the cations show an unsymmetrical ring folding pattern (point group C(1)), while the geometry of the cations of the iodide 1b and the benzoate hydrate [1d(H(2)O)] approaches the symmetry of point group C(2). These structures can be taken as models for the as yet unknown molecular geometries of the corresponding hydrocarbon (CH(2))(4)C(CH(2))(4) and silane (CH(2))(4)Si(CH(2))(4). Treatment of 1e with organolithium reagents RLi affords spirocyclic pentaorganophosphoranes RP[(CH(2))(4)](2) with R = Me, Et, n-Bu, Vi, and Ph (2a-e) in good (R = Me, Et, n-Bu) to low yields (R = Vi, Ph). The products are isolated as colorless liquids, of which only 2a, 2b, and 2d can be distilled without decomposition. Single crystals of 2a were obtained by low-temperature in situ crystal growth. The molecule has a trigonal bipyramidal configuration with the methyl group in an equatorial position and the two five-membered rings spanning axial/equatorial positions of the polyhedron. Deviations from the standard trigonal bipyramidal geometry are small. The compounds 2a-e are fluctional in solution as demonstrated by NMR spectroscopy.

η5-Semiquinone and η4-Quinone Complexes of Manganese Tricarbonyl. Intermolecular Hydrogen Bonding in the Solid State and in Solution

Cationic manganese tricarbonyl complexes containing η6-hydroquinone (1a), η6-catechol (2a), and η6-resorcinol (3a) ligands are readily deprotonated in DMSO with triethylamine or other weak bases to afford stable (η5-semiquinone)Mn(CO)3 (1b−3b) and (η4-quinone)Mn(CO)3- (1c−3c) complexes. The relative acidity in DMSO follows the qualitative order 2a > 3a > 1a. NMR spectra of the semiquinones 1b−3b indicate dynamic, strong hydrogen bonding in solution. The crystal structures of 1b and 2b feature strong intermolecular hydrogen bonding, resulting in polymers with 1b and dimers with 2b. Deprotonation of 1a−3a or 1b−3b with sodium acetate in DMSO allowed the isolation and characterization of the η4-quinone salts Na[1c−3c]·3H2O. The crystal structure of Na[2c]·3H2O shows the sodium cation to be bonded to just one quinone oxygen. IR and crystal structure data of both η5-semiquinone and η4-quinone complexes provide clear evidence of significant contributions to the overall structure from more polar η6-resonance forms.

Homoleptic iron(ii)–diphosphine and –diarsine complexes: syntheses, characterization and redox properties

Treatment of methanol solutions of [Fe(H2O)6](BF4)2 with excess ligand gives low-spin [Fe(L–L)3](BF4)2 where L–L = 1,2-C6H4(AsMe2)2, 1b, Me2PCH2PMe2, 2, Me2PCH2CH2PMe2, 3 and Et2PCH2CH2PEt2, 4. These complexes have been characterized by 31P{1H} and 1H NMR spectroscopy, microanalyses, mass spectrometry, infrared and visible spectroscopy. The crystal structure of 1b·0.5H2O has been determined. Although the Fe–As bond lengths are not significantly longer than the mean for the (very limited) range of other known Fe–1,2-C6H4(AsMe2)2 complexes, there is some evidence, from compressed Me–As–Me and extended Fe–As–Me angles, of steric crowding. Nevertheless, cyclic voltammetry reveals that the complexes have a quasi-reversible Fe(II)/Fe(III) redox process at potentials approximately consistent with the Lever electrochemical ligand parameter (EL) scheme. This is in marked contrast to their Ru(II) analogues. Complex 4 reacts with CH3CN to give trans-[Fe(depe)2(CH3CN)2](BF4)2, 5, in near-quantitative yield.

Reaction of disilagermirenes with phenylacetylene: from a germasilene GeSi to a metalladiene of the type SiGeCC

The reaction of tetrakis[di- tert-butyl(methyl)silyl]-2-disilagermirene ( 1b) with phenylacetylene at room temperature produced highly air- and moisture-sensitive bright orange crystals of 1,1,2,3-tetrakis[di- tert-butyl(methyl)silyl]-4-phenyl-1,2-disila-3-germacyclopenta-2,4-diene ( 2b), which represents a previously unknown metalladiene with one SiGe and one CC double bond. The crystal structure of 2b was determined by X-ray crystallography, which showed a trans-bent configuration around the SiGe double bond with a bond length of 2.250(1) Å. The reaction mechanism to form 2b, the question of conjugation of the two double bonds in a cyclopentadiene ring of 2b, as well as its reactivity are discussed. The reaction of tetrakis[di- tert-butyl(methyl)silyl]-1-disilagermirene ( 1a), which is an isomer of 1b, with phenylacetylene is also examined.

Chelating behaviour of a phosphinoalcohol leading to a stable alcohol palladium complex

Using the enantiopure phosphinoalcohol ligand (P,OH) ( 1) [(P,OH)=[(1 S),(2 S),(4 R)-1-OH-1-Me-2-PPh 2-4-C(Me)CH 2- c-C 6H 7], the stable Pd(II) complexes [(dmba)Pd( P,OH)Cl] ( 2) (dmba= o-C 6H 4CH 2NMe 2), [(dmba)Pd( P, OH)]PF 6 ( 3) and [(dmba)Pd( P, O)] ( 4) have been prepared. Conductivity and NMR measurements showed that complex 2 gives rise to a solvent-dependent equilibrium in solution between the neutral and the cationic species [(dmba)Pd( P,OH)Cl] ( 2a) and [(dmba)Pd( P, OH)]Cl ( 2b), respectively. The crystal structures of 2b and [(dmba)Pd( P, OH)]PF 6 ( 3) have been determined by X-ray diffraction. In the solid state, both cationic complexes display chelating behaviour for the P,OH ligand.

Synthesis, crystal structure, and reactions of the 17-valence-electron rhenium methyl complex [(η 5-C 5Me 5)Re(NO)(P(4-C 6H 4CH 3) 3)(CH 3)] [rad]+ B(3,5-C 6H 3(CF 3) 2) 4−: experimental and computational bonding comparisons with 18-electron methyl and methylidene complexes

Reactions of methyl complex (η 5-C 5Me 5)Re(NO)(P(4-C 6H 4CH 3) 3)(CH 3) ( 2b) and the ferrocenium salt (η 5-C 5H 5) 2Fe + BAr F − (BAr F −=B(3,5-C 6H 3(CF 3) 2) 4 −) or the trityl salt Ph 3C + BAr F − give the very air sensitive title radical cation 2b + BAr F − or the robust methylidene complex [(η 5-C 5Me 5)Re(NO)(P(4-C 6H 4CH 3) 3)(CH 2)] + BAr F − ( 3b + BAr F −) as analytically pure powders in 80% yields. The crystal structures of 2b and 2b + BAr F − are determined. With the aid of high level density functional calculations on model complexes, key structural, bonding, and dynamic properties are compared. Similar quantities are calculated for 3b + BAr F −, which could not be crystallized, and the ReCH 2 rotational barrier is bounded by NMR (Δ G ‡ 383 K>17.5 kcal mol −1). Special attention is given to structural manifestations of backbonding, particularly with the phosphine ligands. Cobaltocene and 2b + BAr F − react to give 2b. However, no phosphine exchange or well-defined thermal decomposition products of 2b + BAr F − are detected.

Synthesis and Ring-Opening Reactions of 1,8-Silanonaphthalenes

1,8-(Di-sec-butylsilano)-, 1,8-{bis[(trimethylsilyl)methyl]silano}-, and 1,8-{bis[(S)-2-methylbutyl]silano}naphthalene (1a−c) were prepared, and their ring-opening reactions were investigated. Reactions of 1a,b with methyllithium afforded products arising from the addition of methyllithium to the Si−C bond of the four-membered ring of 1a,b, followed by rearrangement of the resulting anionic species. Methanolysis of 1a gave 1-(methoxydi-sec-butylsilyl)naphthalene. Heating 1a,b in the presence of a catalytic amount of Pd(PPh3)4 gave the head-to-tail cyclic dimers. Treatment of 1a,c with lithium metal gave ring-opened oligo(silylene-1,8-naphthylenes) in good yield. The optical data of the oligomers indicated the existence of helical structural segments in the backbone. The hole-transporting properties of the oligomer obtained from 1a were examined by the performance of an EL device with the strcture of ITO/oligo(silylene-1,8-naphthylene)/Alq/Mg−Ag, which emitted green luminescence due to the Alq emission. The crystal structures of 1b and its dimer were examined by X-ray diffraction studies.

Trimerization of NaC2N3 to Na3C6N9 in the Solid: Ab Initio Crystal Structure Determination of Two Polymorphs of NaC2N3 and of Na3C6N9 from X-ray Powder Diffractometry

Sodium dicyanamide NaC2N3 was found to undergo two phase transitions. According to thermal analysis and temperature-dependent X-ray powder diffractometry, the transition of alpha-NaC2N3 (1a) to beta-NaC2N3 (1b) occurs at 33 degrees C and is displacive. 1a crystallizes in the monoclinic system, space group P21/n (no. 14), with a = 647.7(1), b = 1494.8(3), c = 357.25(7) pm, beta = 93.496(1) degrees, and Z = 4. The structure was solved from powder diffraction data (Cu Kalpha1, T = 22 degrees C) using direct methods and it was refined by the Rietveld method. The final agreement factors were wRp = 0.072, Rp = 0.053, and RF = 0.074. 1b crystallizes in the orthorhombic system, space group Pbnm (no. 62), with a = 650.15(5), b = 1495.1(2), c = 360.50(3) pm, and Z = 4. The structure was refined by the Rietveld method using the atomic coordinates of 1a as starting values (Mo Kalpha1, T = 150 degrees C). The final agreement factors were wRp = 0.044, Rp = 0.034, RF = 0.140. The crystal structures of both polymorphs contain sheets of Na+ and N(CN)2- ions which are in la nearly and in 1b exactly coplanar. Above 340 degrees C, 1b trimerizes in the solid to Na3C6N9 (2). 2 crystallizes in the monoclinic system, space group P21/n (no. 14), with a = 1104.82(1), b = 2338.06(3), c = 351.616(3) pm, beta = 97.9132(9)degrees, and Z = 4. The structure was solved from synchrotron powder diffraction data (lambda = 59.733 pm) using direct methods and it was refined by the Rietveld method. The final agreement factors were wRp = 0.080, Rp = 0.059, and RF = 0.080. The compound contains Na+ and the planar tricyanomelaminate C6N9(3-). The phase transition from 1b to 2 is reconstructive. It occurs in the solid-state without involvement of other phases or intermediates. The crystal structures of 1b and 2 indicate that there is no preorientation of the N(CN)2- in the solid before their trimerization to C6N9(3-).

Novel η 3-allyl complexes of titanium

Treatment of TiCl 4(dmpe) ( 1a) and TiCl 4(depe) ( 1b) with two equivalents of C 3H 5MgCl in toluene at −30°C affords two novel allyl–titanium complexes: a dinuclear mixed-valent Ti 2 5+ species Ti 2(μ-Cl) 2Cl 2(dmpe) 2(μ 2-η 3-C 3H 5) ( 2) and a mononuclear Ti III complex, TiCl(depe)(η 3-C 3H 5) 2 ( 3). Syntheses and crystal structures of 1b, 2 and 3 are presented. In complex 2, in addition to two bridging chloride ligands a η 3-allyl group spans two titanium atoms with a Ti…Ti separation of 2.908(1) Å. The allyl bridge is symmetrical with each terminal carbon atom having a Ti–C distance of 2.154(6) Å, while the central carbon atom is equidistant from the titanium atoms, Ti–C cent, 2.430(6) Å. Each Ti atom in 2 is further coordinated by a chelating dmpe ligand and a chloride ion. In the mononuclear complex 3 two η 3-allyl groups are bound to the Ti III center and the coordination is completed by a chelating diphosphine ligand and one chloride ion. The Ti–C distances in 3 vary from 2.286(3) to 2.478(3) Å.

Trimerization of NaC2N3 to Na3C6N9 in the Solid

Sodium dicyanamide NaC2N3 was found to undergo two phase transitions. According to thermal analysis and temperature-dependent X-ray powder diffractometry, the transition of α-NaC2N3 (1a) to β-NaC2N3 (1b) occurs at 33°C and is displacive. 1a crystallizes in the monoclinic system, space group P21/n (no. 14), with a = 647.7(1), b = 1494.8(3), c = 357.25(7) pm, β = 93.496(1)°, and Z = 4. The structure was solved from powder diffraction data (Cu Kα1, T = 22°C) using direct methods and it was refined by the Rietveld method. The final agreement factors were wRp = 0.072, Rp = 0.053, and RF = 0.074. 1b crystallizes in the orthorhombic system, space group Pbnm (no. 62), with a = 650.15(5), b = 1495.1(2), c = 360.50(3) pm, and Z = 4. The structure was refined by the Rietveld method using the atomic coordinates of 1a as starting values (Mo Kα1, T = 150°C). The final agreement factors were wRp = 0.044, Rp = 0.034, RF = 0.140. The crystal structures of both polymorphs contain sheets of Na+ and N(CN)2- ions which are in 1a nearly and in 1b exactly coplanar. Above 340°C, 1b trimerizes in the solid to Na3C6N9 (2). 2 crystallizes in the monoclinic system, space group P21/n (no. 14), with a = 1104.82(1), b = 2338.06(3), c = 351.616(3) pm, β = 97.9132(9)°, and Z = 4. The structure was solved from synchrotron powder diffraction data (λ = 59.733 pm) using direct methods and it was refined by the Rietveld method. The final agreement factors were wRp = 0.080, Rp = 0.059, and RF = 0.080. The compound contains Na+ and the planar tricyanomelaminate C6N93-. The phase transition from 1b to 2 is reconstructive. It occurs in the solid-state without involvement of other phases or intermediates. The crystal structures of 1b and 2 indicate that there is no preorientation of the N(CN)2- in the solid before their trimerization to C6N93-.

Proton addition and hydrogen-bond formation in reactions of the dicyano-complex [NBu4][trans-Re(CN)2(dppe)2] with protic reagents

[NBu4][trans-Re(CN)2(dppe)2] (1, dppe = Ph2PCH2CH2PPh2) reacted with protic acids (HA = HBF4, CH3CO2H or [Et3NH][BPh4], added in stoichiometric amounts) to give, on protonation of one of the cyano-ligands, the isocyanide complex trans-[Re(CN)(CNH)(dppe)2] 3a, whereas the hydrogen-bonded cyano-adducts trans-[Re(CN·HO2CCF3)2(dppe)2] 4, trans-[Re(CN·HOMe)2(dppe)2] 5 and trans-[Re(CN·HNEt3)2(dppe)2][BPh4] 6 were obtained on treatment of 3a with an excess of CF3CO2H or of 1 with an excess of MeOH or [Et3NH][BPh4], respectively. However, solvent or other molecules can be trapped in the crystal lattice without hydrogen-bond interaction and trans-[Re(CN)2(dppe)2]·2L (L = MeOH 2a or Me2CO 2b) or trans-[Re(CN)2(dppe)2]·NEt37 are formed on attempted recrystallization of 1 from MeOH or Me2CO, or as a side product in the reaction of 1 with [Et3NH][BPh4], respectively. The crystal structures of 2b, 4, 5 and partially that of 2a were also determined and the anodic cyclic voltammetric behaviour (which is shown to distinguish between the CN–H and the hydrogen-bond CN⋯H formations) of the above complexes is described as well as an interpretative theoretical study (by extended Huckel and ab initio methods) of the CN and CNH complexes.

Double Heterocumulene Metathesis of Cyclic Bis(trimethylsilylamido)stannylenes and Tethered Bimetallic Bisamidinates from the Resulting α,ω-Biscarbodiimides

Reaction of 2 equiv of tert-butylisocyanate with the cyclic bisamidostannylenes, 3a and 3b, provides the α,ω-biscarbodiimides, tBuNCN(CH2)nNCNtBu (2a and 2b; n = 3 and 4, respectively) in high yield. Reaction of 2b with 2 equiv of (η5-C5H5)TiMe3 results in clean formation of the tethered bimetallic bisamidinate represented by meso/rac -1. The crystal structures of 3b and rac-1 are reported.

Photolysis ofcis- andtrans-[FeIII(cyclam)(N3)2]+Complexes: Spectroscopic Characterization of a Nitridoiron(V) Species

Reaction of cis-[FeIII(cyclam)Cl2]Cl in acidic H2O/CH3OH or CH3CN/H2O mixtures with NaN3 at 50 °C produced upon addition of NaClO4 or NaPF6 the complex trans-[FeIII(cyclam)(N3)2]ClO4 (1a) or the hexafluorophosphate salt 1b, whereas at −18 °C the same reaction produced cis-[FeIII(cyclam)(N3)2](ClO4) (2) (cyclam = 1,4,8,11-tetraazacyclotetradecane). The crystal structures of 1b and 2 were determined by single-crystal X-ray crystallography. Complexes 1a, b, contain a low-spin (S = 1/2) and 2, a high-spin ferric ion (S = 5/2) as was established by variable-temperature magnetic susceptibility measurements and Mossbauer and X-band EPR spectroscopy. The low-spin trans-[(cyclam)FeII(N3)2] and high-spin cis-[(cyclam)FeII(N3)2] species were generated electrochemically in CH3CN solution and were characterized by Mossbauer spectroscopy. Photolysis of 1a in CH3CN at −35 °C and 20 °C with a Hg immersion lamp generated within 15 min a yellow solution. EPR and Mossbauer spectra show that a single high-valent species with...

Hydride complexes of platinum(II) containing unsymmetrical di(phosphine) ligands: synthesis, characterization and evidence for pairwise addition of hydrogen based on parahydrogen induced polarization

Unsymmetrical di(phosphine) ligands (dpp) 2Rop ( 1a, b = bis(diphenylphosphino)-2-alkyl-3-oxapropane (alkyl = methyl and ethyl)) and (dpp) 2oCy ( 1c = trans-2-diphenylphosphinocyclohexyl diphenylphosphinite) and their Pt(II) dichloride complexes, PtCl 2((dpp) 2mop) ( 2a), PtCl 2((dpp) 2eop) ( 2b) and PtCl 2((dpp) 2oCy) ( 2c), have been synthesized and characterized by NMR spectroscopy. The crystal structures of 2b and 2c show that the geometry about the platinum centers is square planar. In 2b, the metal and di(phosphine) ligand chelate ring are in a chair conformation, whereas in 2c, the chelate ring conformation is a skewed boat. Initial reaction of sodium borohydride with 2a, b, c yields the monohydride monochloride complexes PtHCl((dpp) 2mop) ( 5a), PtHCl((dpp) 2eop) ( 5b) and PtHCl((dpp) 2oCy) ( 5c). At longer reaction times, fluxional dimeric species are obtained, [PtH((dpp) 2mop)] 2 ( 4a), [PtH((dpp) 2eop)] 2 ( 4b) and [PtH((dpp) 2oCy)] 2 ( 4c),and in the case of 4c two different isomers exist. The dihydride complexes PtH 2((dpp) 2mop) ( 3a), PtH 2((dpp) 2eop) ( 3b) and PtH 2((dpp) 2oCy) ( 3c), are prepared by further reaction of NaBH 4 and 2. Hydrogen cycling is facile in the dihydride complexes 3a, b, c, and oxidative addition of H 2 proceeds in a pairwise manner as determined by the observation of parahydrogen induced polarization (PHIP) in the 1H NMR spectra. The reductive elimination of H 2 is also shown to be concerted by reaction of dihydride complexes with D 2. Crystal data: 2b (C 30H 32Cl 6OP 2Pt), monoclinic, space group P2 1/ c (No. 14), a = 13.7040(1), b = 11.3430(7), c = 21.3880(9) Å, β = 97.923(9)°, V = 3292.9(2) Å 3 and Z = 4; 2c (C 30H 30Cl 2OP 2Pt), monoclinic, space group P2 1 (No. 4), a = 11.7360(2), b = 8.4311(2), c = 14.2789(2) Å, β = 101.290(1)°, V = 1385.52(4) Å 3 and Z = 2.

Condensation of 5-aminothieno[2,3-c]pyridazine-6-carbaldehyde with aliphatic primary amines. Synthesis of new heterocyclic 2,6,9-triazabicyclo[3.3.1]nonane derivatives

5-Amino-3,4-diphenylthieno[2,3-c]pyridazine-6-carbaldehyde (2) undergoes condensation with aliphatic primary amines to give the corresponding 2,6,9-triazabicyclo[3.3.1]nonane derivatives 1 with different substituents at position 14. The molecular and crystal structure of 1b (R = Bu) have been determined by X-ray analysis. A suitable mechanism for the formation of 1 is proposed.

Binuclear pentamethylcyclopentadienyl rhodium(III) compounds with pyrazolate and thiolate bridging ligands

Binuclear thiolato-bridged complexes of general formula [( η 5-C 5Me 5) 2Rh 2( μ-Pz)( μ-SR) 2]BF 4 (Pz=pyrazolate; R=C 6F 5 ( 2a), p-C 6F 4H ( 2b), p-C 6H 4F ( 2c) or C 6H 5 ( 2d)) have been prepared by reacting the hydroxo–pyrazolato-bridged compound [( η 5-C 5Me 5) 2Rh 2( μ-Pz) 2( μ-OH)] BF 4 with the corresponding thiol. Complexes 2a–d show two types of fluxionality: rotation around the thiol C–S bond and isomerization among the three possible isomers in which the thiols occupy axial and/or equatorial positions within the Rh 2S 2 metallacycle. These processes are studied by 1H and 19F NMR spectroscopies. The crystal structures of 2b and 2d were established by X-ray crystallography. Compound 2b crystallises in the monoclinic space group P2 1/n, with lattice parameters a=14.368(2), b=18.252(2), c=15.268(2) Å, β=109.79(1)° and Z=4. Complex 2d crystallises in a monoclinic lattice, space group C2/c, with a=48.723(5), b=8.7503(8), c=40.334(4) Å, β=112.620(5)° and Z=16. Both cationic dinuclear complexes exhibit very similar molecular structures with analogous pseudo-octahedral environments for the rhodium centres. Each metal is bonded to a terminal η 5-C 5Me 5 group and to three bridging ligands: two monodentate thiolates ( p-SC 6F 4H in 2b and SC 6H 5 in 2d) and a bidentate pyrazolate group. The main structural dissimilarity affects the relative configuration of the thiolate phenyl substituents giving rise to syn ( 2b) or anti ( 2d) structures.

Multiple Bonds between Main‐Group Elements and Transition Metals, CLXV. Rhenium(V) Oxo Complexes with Bidentate Schiff Bases: Structures and Catalytic Applications

AbstractReaction of [NBu4][ReOCl4] (1) with bidentate salicylidene amine ligands (salen = HL) (2a‐c) leads to the formation of monomeric octahedral rhenium (V) compounds of formula [ReOCl (L)2] (3a‐c). Spectroscopic date indicate asymmetric arrangement of the ligands in the complexes. This is confirmed by the X‐ray crystal structures of 3b and 3c. Complexes 3a, b have been tested as catalysts for the epoxidation of cyclooctene. No evidence for decomposition for decomposition of the catalysts is observed during the reaction (as in the case for tri‐and tetra‐dentate salen complexes). No undesired byproducts are formed in the catalytic reactions.