Mapping the Interactions of I2, I., I−, and I+ with Alkynes and Their Roles in Iodocyclizations

A combination of experiment and theory has been used to explore the mechanisms by which molecular iodine (I₂) and iodonium ions (I⁺) activate alkynes towards iodocyclization. Also included in the analysis are the roles of atomic iodine (I ^. ) and iodide ion (I^?) in mediating the competing addition of I₂ to the alkyne. These studies show that I₂ forms a bridged I₂–alkyne complex, in which both alkyne carbons are activated towards nucleophilic attack, even for quite polarized alkynes. By contrast, I⁺ gives unsymmetrical, open iodovinyl cations, in which only one carbon is activated toward nucleophilic attack, especially for polarized alkynes. Addition of I₂ to alkynes competes with iodocyclization, but is reversible. This fact, together with the capacity of I₂ to activate both alkyne carbons towards nucleophilic attack, makes I₂ the reagent of choice (superior to iodonium reagents) for iodocyclizations of resistant substrates. The differences in the nature of the activated intermediate formed with I₂ versus I⁺ can also be exploited to accomplish reagent‐controlled 5‐exo/6‐endo‐divergent iodocyclizations.     

5‐(Pyren‐1‐yl)uracil as a Base‐Discriminating Fluorescent Nucleobase in Pyrrolidinyl Peptide Nucleic Acids

A pyrene‐labeled uridine (U^Py) monomer for a pyrrolidinyl peptide nucleic acid with an alternating proline/2‐aminocyclopentanecarboxylic acid backbone (acpcPNA) was synthesized and incorporated into the PNA. The U^Py base in acpcPNA could specifically recognize the base A in its complementary DNA strand as determined by thermal denaturation (T_m) experiments. The fluorescence of the U^Py‐containing single‐stranded acpcPNA was very weak in aqueous buffer. In the presence of a complementary DNA target, the fluorescence was enhanced significantly (2.7–41.9 folds, depending on sequences). The fluorescence enhancement was specific to the pairing between U^Py and dA, making the U^Py‐modified acpcPNA useful as a hybridization‐responsive fluorescence probe for DNA‐sequence determination.     

Post-Nickelation of a Crystalline Trinuclear Copper Organic Framework for Synergistic Photocatalytic Carbon Dioxide Conversion

Rational regulation of electronic structures and functionalities of framework materials still remains challenging. Herein, reaction of 4,4′,4′′-nitrilo-tribenzhydrazide with tris(μ₂-4-carboxaldehyde-pyrazolato-N,N′)-tricopper (Cu₃Py₃) generates the crystalline copper organic framework USTB-11(Cu). Post-modification with divalent nickel ions affords the heterometallic framework USTB-11(Cu,Ni). Powder X-ray diffraction and theoretical simulations reveal their two-dimensional hexagonal structure geometry. A series of advanced spectroscopic techniques disclose the mixed Cu^I/Cu^II state nature of Cu₃Py₃ in USTB-11(Cu,Ni) with a uniform bistable Cu₃⁴⁺(Cu^I₂Cu^II) : Cu₃⁵⁺(Cu^ICu^II₂) (ca. 1 : 3) oxidation state, resulting in a significantly improved formation efficiency of the charge-separation state. This endows the Ni sites with enhanced activity and USTB-11(Cu,Ni) with outstanding photocatalytic CO₂ to CO performance with a conversion rate of 22 130 μmol g⁻¹ h⁻¹ and selectivity of 98 %.     

Spectroscopic,Electrochemical and Computational Characterisation of Ru Species Involved in Catalytic Water Oxidation: Evidence for a [RuV(O)(Py2Metacn)] Intermediate

A new family of ruthenium complexes based on the N‐pentadentate ligand Py₂^Metacn (N‐methyl‐N′,N′′‐bis(2‐picolyl)‐1,4,7‐triazacyclononane) has been synthesised and its catalytic activity has been studied in the water‐oxidation (WO) reaction. We have used chemical oxidants (ceric ammonium nitrate and NaIO₄) to generate the WO intermediates [Ru^II(OH₂)(Py₂^Metacn)]²⁺, [Ru^III(OH₂)(Py₂^Metacn)]³⁺, [Ru^III(OH)(Py₂^Metacn)]²⁺ and [Ru^IV(O)(Py₂^Metacn)]²⁺, which have been characterised spectroscopically. Their relative redox and pH stability in water has been studied by using UV/Vis and NMR spectroscopies, HRMS and spectroelectrochemistry. [Ru^IV(O)(Py₂^Metacn)]²⁺ has a long half‐life (>48 h) in water. The catalytic cycle of WO has been elucidated by using kinetic, spectroscopic, ¹⁸O‐labelling and theoretical studies, and the conclusion is that the rate‐determining step is a single‐site water nucleophilic attack on a metal‐oxo species. Moreover, [Ru^IV(O)(Py₂^Metacn)]²⁺ is proposed to be the resting state under catalytic conditions. By monitoring Ce^IV consumption, we found that the O₂ evolution rate is redox‐controlled and independent of the initial concentration of Ce^IV. Based on these facts, we propose herein that [Ru^IV(O)(Py₂^Metacn)]²⁺ is oxidised to [Ru^V(O)(Py₂^Metacn)]²⁺ prior to attack by a water molecule to give [Ru^III(OOH)(Py₂^Metacn)]²⁺. Finally, it is shown that the difference in WO reactivity between the homologous iron and ruthenium [M(OH₂)(Py₂^Metacn)]²⁺ (M=Ru, Fe) complexes is due to the difference in the redox stability of the key M^V(O) intermediate. These results contribute to a better understanding of the WO mechanism and the differences between iron and ruthenium complexes in WO reactions.     

2:2 Complexes from Diphenylpyridiniums and Cucurbit[8]uril: Encapsulation‐Promoted Dimerization of Electrostatically Repulsing Pyridiniums

Rigid linear compounds G1 and G2 , which contained two 4‐phenylpyridinium (PhPy⁺) units, have been prepared to investigate their binding with cucurbit[8]uril (CB[8]). X‐ray crystallographic structures revealed that in the solid state both compounds were included by CB[8], through antiparallel stacking, to form 2:2 quaternary complexes ( G1 )₂@(CB[8])₂ and ( G2 )₂@(CB[8])₂. For the former complex, CB[8] entrapped G1 by holding two heterodimers of its Py⁺ and benzyl units, which were at opposite ends of the backbone. In contrast, for the first time, the second complex disclosed parallel stacking of two cationic Py⁺ units of G2 in the cavity of CB[8] in the solid state, despite the generation of important electrostatic repulsion. Isothermal titrations in water afforded high apparent association constants of 4.36×10⁶ and 6.43×10⁶ m ^?1 for 1:1 complexes G1 @CB[8] and G2 @CB[8], respectively, and ¹H NMR spectroscopy experiments in D₂O confirmed a similar stacking pattern to that observed in the solid state. A previous study and crystal structures of the 2:1 complexes formed between three new controls, G3–5 , and CB[8] did not display such unusual stacking of the cationic Py⁺ unit; this may be attributed to the multivalency of the two CB[8] encapsulation interactions.     

Dorzolamide hydro­chloride: an anti­glaucoma agent

Dorzolamide hydro­chloride [systematic name: (4S)‐trans‐4‐ethyl­ammonio‐6‐methyl‐5,6‐dihydro‐4H‐thieno[2,3‐b]thio­pyran‐2‐sulfonamide 7,7‐dioxide chloride], C₁₀H₁₇N₂O₄S₂⁺·Cl⁻, belongs to a class of drugs called carbonic anhydrase inhibitors. The ethyl­ammonio side chain is in an extended conformation and is protonated at the N atom, which is hydrogen bonded to the Cl⁻ anion. The dihedral angle between the planes of the thio­phene ring and the sulfonamide group is 80.7 (1)°. A comparison is made with the dorzolamide bound in human carbonic anhydrase in the solid state. Hydrogen bonding is mediated by Cl⁻ anions, resulting in indirect connectivity between the mol­ecules.     

Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag+/X2 (X=Cl,Br, I) System

The synergistic Ag⁺/X₂ system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X₂ or Ag⁺ alone. Intermediates for its action may include [Ag_m(X₂)_n]^m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I₂‐Ag( A ), [Ag₂(I₂)₄]²⁺( A ⁻)₂ and [Ag₂(I₂)₆]²⁺( A ⁻)₂⋅(I₂)_x≈0.65 form by reaction of Ag( A ) ( A =Al(OR^F)₄; R^F=C(CF₃)₃) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I₂‐Ag( A ) is ideally set up to act as a 2 e⁻ oxidant with stoichiometric formation of 2 AgI and 2 A ⁻. Preliminary reactivity tests proved this ( A )Ag‐I₂‐Ag( A ) starting material to oxidize n‐C₅H₁₂, C₃H₈, CH₂Cl₂, P₄ or S₈ at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF₆ (M=4d metals). This suggests that ( A )Ag‐I₂‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.     

Darstellung,Kristallstruktur und Schwingungsspektren von cis‐(CH2Py2)[ReBr4Py2]2 · (CH3)2CO

Synthesis, Crystal Structure, and Vibrational Spectra of cis ‐(CH₂Py₂)[ReBr₄Py₂]₂ · (CH₃)₂CO By reaction of (n‐Bu₄N)₂[ReBr₆] with pyridine and (n‐Bu₄N)BH₄ in dichloromethane halogeno‐pyridine‐rhenium(III)complexes are formed and purified by chromatography. X‐ray structure determination on a single crystal has been performed of cis‐(CH₂Py₂)[ReBr₄Py₂]₂ · (CH₃)₂CO (monoclinic, space group P2₁/c, a = 15.0690(9), b = 8.3337(8), c = 35.588(4) Å, β = 96.409(7), Z = 4). Based on the molecular parameters of the X‐ray structure determination and assuming C₂ point symmetry for the anion cis‐[ReBr₄Py₂]^– the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants are in the Br–Re–Br axis f_d(ReBr) = 1.49, in the asymmetrically coordinated N′–Re–Br ^· axes f_d(ReBr ^· ) = 1.03 und f_d(ReN′) = 2.52 mdyn/Å.     

l‐Methioninium chloride and l‐seleno­methioninium chloride at 103 K

The crystal structures of the title compounds, (S)‐1‐carboxy‐3‐(methyl­sulfanyl)­propanaminium chloride, C₅H₁₂NO₂S⁺·Cl⁻, and (S)‐1‐carboxy‐3‐(methyl­selanyl)­propanaminium chloride, C₅H₁₂NO₂Se⁺·Cl⁻, are isomorphous. The proton­ated l ‐methionine and l ‐seleno­methionine mol­ecules have almost identical conformations and create very similar contacts with the Cl⁻ anions in the crystal structures of both compounds. The amino acid cations and the Cl⁻ anions are linked viaN—H⋯Cl⁻ and O—H⋯Cl⁻ hydrogen bonds.     

Structural diversity in imidazolidinone organocatalysts: a synchrotron and computational study

(S)‐1‐(Methylaminocarbonyl)‐3‐phenylpropanaminium chloride (S2·HCl), C₁₀H₁₅N₂O⁺·Cl⁻, crystallizes in the orthorhombic space group P2₁2₁2₁ with a single formula unit per asymmetric unit. (5R/S)‐5‐Benzyl‐2,2,3‐trimethyl‐4‐oxoimidazolidin‐1‐ium chloride (R3 and S3), C₁₃H₁₉N₂O⁺·Cl⁻, crystallize in the same space group as S2·HCl but contain three symmetry‐independent formula units. (R/S)‐5‐Benzyl‐2,2,3‐trimethyl‐4‐oxoimidazolidin‐1‐ium chloride monohydrate (R4 and S4), C₁₃H₁₉N₂O⁺·Cl⁻·H₂O, crystallize in the space group P2₁ with a single formula unit per asymmetric unit. Calculations at the B3LYP/6–31G(d,p) and B3LYP/6–311G(d,p) levels of the conformational energies of the cation in R3, S3, R4 and S4 indicate that the ideal gas‐phase global energy minimum conformation is not observed in the solid state. Rather, the effects of hydrogen‐bonding and van der Waals interactions in the crystal structure cause the molecules to adopt higher‐energy conformations, which correspond to local minima in the molecular potential energy surface.     

4‐Carboxypiperidinium 1‐carboxycyclobutane‐1‐carboxylate

The title salt, C₆H₁₂NO₂⁺·C₆H₇O₄⁻ or ISO⁺·CBDC⁻, is an ionic ensemble assisted by hydrogen bonds. The amino acid moiety (ISO or piperidine‐4‐carboxylic acid) has a protonated ring N atom (ISO⁺ or 4‐carboxypiperidinium), while the semi‐protonated acid (CBDC⁻ or 1‐carboxycyclobutane‐1‐carboxylate) has the negative charge residing on one carboxylate group, leaving the other as a neutral –COOH group. The –⁺NH₂– state of protonation allows the formation of a two‐dimensional crystal packing consisting of zigzag layers stacked along a separated by van der Waals distances. The layers extend in the bc plane connected by a complex network of N—H...O and O—H...O hydrogen bonds. Wave‐like ribbons, constructed from ISO⁺ and CBDC⁻ units and described by the graph‐set symbols C₃³(10) and R₃³(14), run alternately in opposite directions along c. Intercalated between the ribbons are ISO⁺ cations linked by hydrogen bonds, forming rings described by the graph‐set symbols R₆⁶(30) and R₄²(18). A detailed analysis of the structures of the individual components and the intricate hydrogen‐bond network of the crystal structure is given.     

Two Distinct Thermal Stabilities of DNA and Enzymatic Activities of DNase I in a Multistep Assembly with Carbazole Ligands: Different Binding Characteristics for Duplex and Quadruplex DNA

A partially hydrophobic carbazole ligand ((Im⁺)₂Cz: 2,2′‐(9‐ethyl‐9 H‐carbazole‐3,6‐diyl)bis(ethyne‐2,1‐diyl)bis(1,3‐dimethyl‐1 H‐imidazol‐3‐ium)) adopts two different binding states (binding states I and II) in its interactions with calf‐thymus (ct‐) DNA. Two distinct binding states were identified by biphasic UV/Vis and circular dichroism (CD) spectral changes during the titration of DNA into the carbazole ligand. At low concentrations of ct‐DNA, (Im⁺)₂Cz binds to nearly every part of ct‐DNA (binding state I). By contrast, an increased concentration of ct‐DNA results in a switch in the DNA‐binding state, so that the ligands are bound per five DNA base pairs. Similarly, a monocationic carbazole ligand (Im⁺Cz: 2‐((6‐bromo‐9‐ethyl‐9 H‐carbazol‐3‐yl)ethynyl)‐1,3‐dimethyl‐1 H‐imidazol‐3‐ium) also shows biphasic UV/Vis spectral changes during the titration of ct‐DNA into Im⁺Cz, which suggests two different binding states of the Im⁺Cz ligand with ct‐DNA. The stepwise equilibrium of the ligand–DNA‐complex formation is capable of switching the thermal stability of ct‐DNA, as well as the enzymatic activity of deoxyribonuclease (DNase I). In binding state I, the (Im⁺)₂Cz ligands interact with nearly every base pair in ct‐DNA and stabilize the double‐helix structure, which results in a larger increase in the melting temperature of the ct‐DNA than that observed with binding state II. On the other hand, the (Im⁺)₂Cz ligand significantly reduces the enzymatic activity of DNase I in binding state I, although the enzymatic activity is recovered once the binding state of the ligand–DNA complex is changed to binding state II. The (Im⁺)₂Cz ligand was also employed as a binder for G‐quadruplex DNA. In contrast to the stepwise complex formation between (Im⁺)₂Cz and ct‐DNA, (Im⁺)₂Cz shows a monotonous UV/Vis spectral response during the titration of G‐quadruplex DNA into (Im⁺)₂Cz, which suggests a single binding state for (Im⁺)₂Cz with G‐quadruplex DNA.     

Unusual hydrogen bonding in L‐cysteine hydrogen fluoride

L‐Cysteine hydrogen fluoride, or bis(L‐cysteinium) difluoride–L‐cysteine–hydrogen fluoride (1/1/1), 2C₃H₈NO₂S⁺·2F⁻·C₃H₇NO₂S·HF or L‐Cys⁺(L‐Cys...L‐Cys⁺)F⁻(F⁻...H—F), provides the first example of a structure with cations of the `triglycine sulfate' type, i.e.A⁺(A...A⁺) (where A and A⁺ are the zwitterionic and cationic states of an amino acid, respectively), without a doubly charged counter‐ion. The salt crystallizes in the monoclinic system with the space group P2₁. The dimeric (L‐Cys...L‐Cys⁺) cation and the dimeric (F⁻...H—F) anion are formed via strong O—H...O or F—H...F hydrogen bonds, respectively, with very short O...O [2.4438 (19) Å] and F...F distances [2.2676 (17) Å]. The F...F distance is significantly shorter than in solid hydrogen fluoride. Additionally, there is another very short hydrogen bond, of O—H...F type, formed by a L‐cysteinium cation and a fluoride ion. The corresponding O...F distance of 2.3412 (19) Å seems to be the shortest among O—H...F and F—H...O hydrogen bonds known to date. The single‐crystal X‐ray diffraction study was complemented by IR spectroscopy. Of special interest was the spectral region of vibrations related to the above‐mentioned hydrogen bonds.     

Gas‐phase dissociation of ionic liquid aggregates studied by electrospray ionisation mass spectrometry and energy‐variable collision induced dissociation

Positive singly charged ionic liquid aggregates [(C_nmim)_m+1(BF₄)_m]⁺ (mim = 3‐methylimidazolium; n = 2, 4, 8 and 10) and [(C₄mim)_m+1(A)_m]⁺ (A = Cl⁻, BF₄⁻, PF₆⁻, CF₃SO₃⁻ and (CF₃SO₂)₂N⁻) were investigated by electrospray ionisation mass spectrometry and energy‐variable collision induced dissociation. The electrospray ionisation mass spectra (ESI‐MS) showed the formation of an aggregate with extra stability for m = 4 for all the ionic liquids with the exception of [C₄mim][CF₃SO₃]. ESI‐MS‐MS and breakdown curves of aggregate ions showed that their dissociation occurred by loss of neutral species ([C_nmim][A])_a with a ≥ 1. Variable‐energy collision induced dissociation of each aggregate from m = 1 to m = 8 for all the ionic liquids studied enabled the determination of E_{cm, 1/2} values, whose variation with m showed that the monomers were always kinetically much more stable than the larger aggregates, independently of the nature of cation and anion. The centre‐of‐mass energy values correlate well with literature data on ionic volumes and interaction and hydrogen bond energies. Copyright © 2008 John Wiley & Sons, Ltd.     

Solution Synthesis,Structure, and CO2 Reduction Reactivity of a Scandium(II) Complex, {Sc[N(SiMe3)2]3}−

The first crystallographically characterizable complex of Sc²⁺, [Sc(NR₂)₃]⁻ (R=SiMe₃), has been obtained by LnA₃/M reactions (Ln=rare earth metal; A=anionic ligand; M=alkali metal) involving reduction of Sc(NR₂)₃ with K in the presence of 2.2.2‐cryptand (crypt) and 18‐crown‐6 (18‐c‐6) and with Cs in the presence of crypt. Dark maroon [K(crypt)]⁺, [K(18‐c‐6)]⁺, and [Cs(crypt)]⁺ salts of the [Sc(NR₂)₃]⁻ anion are formed, respectively. The formation of this oxidation state of Sc is also indicated by the eight‐line EPR spectra arising from the I =7/2 ⁴⁵Sc nucleus. The Sc(NR₂)₃ reduction differs from Ln(NR₂)₃ reactions (Ln=Y and lanthanides) in that it occurs under N₂ without formation of isolable reduced dinitrogen species. [K(18‐c‐6)][Sc(NR₂)₃] reacts with CO₂ to produce an oxalate complex, {K₂(18‐c‐6)₃}{[(R₂N)₃Sc]₂(μ‐C₂O₄‐κ ¹O:κ ¹O′′)}, and a CO₂⁻ radical anion complex, [(R₂N)₃Sc(μ‐OCO‐κ ¹O:κ ¹O′)K(18‐c‐6)]_n .     

Syntheses and structures of lanthanide(III) complexes with some bis(pyrazolyl)borate and tris(pyrazolyl)borate podand ligands

Two new poly(pyrazolyl)borate ligands have been prepared: potassium tris[3-{(4-^tbutyl)-pyrid-2-yl}-pyrazol-1-yl]hydroborate (KTp^BuPy) which has three bidentate arms and is therefore hexadentate; and potassium bis[3-(2-pyridyl)-5-(methoxymethyl)pyrazol-1-yl]-dihydroborate (KBp^(COC)Py) which has two bidentate arms and is therefore tetradentate. The crystal structures of their lanthanide complexes [La(Tp^BuPy)(NO₃)₂] and [La(Bp^(COC)Py)₂X] (X=nitrate or triflate) have been determined. In [La(Tp^BuPy)(NO₃)₂] the metal ion is ten-coordinate, from the hexadentate N-donor podand ligand and two bidentate nitrates. [La(Bp^(COC)Py)₂(NO₃)] is also ten-coordinate, from two tetradentate ligands and a bidentate nitrate, but in [La(Bp^(COC)Py)₂(CF₃SO₃)] the metal ion is nine-coordinate because the triflate anion is monodentate. Two unexpected new complexes which arose from partial decomposition of the poly(pyrazolyl)borate ligands have also been characterised structurally. In [La(^BuPypzH)₃(O₃SCF₃)₃] the metal ion is nine-coordinate from three bidentate pyrazolyl-pyridine arms (liberated by decomposition of KTp^BuPy) and three triflate anions; there is extensive NH· · · O hydrogen-bonding between the pyrazolyl and triflate ligands. [Nd(Tp^Py)(Bp^Py)][Nd(PypzH)(NO₃)₄] was isolated from the reaction of hexadentate tris[3-(2-pyridyl)-pyrazol-1-yl]hydroborate (Tp^Py) with Nd(NO₃)₃. One of the Tp^Py ligands has lost one bidentate pyrazolyl-pyridine ‘arm’ (PypzH) to leave tetradentate tris[3-(2-pyridyl)-pyrazol-1-yl]dihydroborate (Bp^Py). In this structure, the cation [Nd(Tp^Py)(Bp^Py)]⁺ is ten-coordinate from inter-leaved hexadentate and tetradentate ligands, and the anion [Nd(PypzH)(NO₃)₄]⁻ is also ten-coordinate from the bidentate N-donor ligand PypzH and four bidentate nitrates.     

Similarity in structures of racemic and enantiomeric ibuprofen sodium dihydrates

The crystal structures of two ibuprofen sodium dihydrates, racemic sodium (RS)‐2‐(4‐isobutylphenyl)propanoate dihydrate or (RS)‐NaIBDH, Na⁺·C₁₃H₁₇O₂⁻·2H₂O, and enantiomeric sodium (S)‐2‐(4‐isobutylphenyl)propanoate dihydrate or (S)‐NaIBDH, Na⁺·C₁₃H₁₇O₂⁻·2H₂O, have been determined in the space groups P and P1, respectively. The unit cells of the two triclinic structures have similar lattice parameters and cell volumes. The constituent ions have similar coordination environments, but differ slightly in their hydrogen‐bonding inter­actions. The dominance of the inter­actions between the O atoms and the Na⁺ cations explains the structural similarity of these two structures, despite the fact that one is heterochiral while the other is homochiral.     

Solution Synthesis,Structure, and CO2 Reduction Reactivity of a Scandium(II) Complex, {Sc[N(SiMe3)2]3}−

The first crystallographically characterizable complex of Sc²⁺, [Sc(NR₂)₃]⁻ (R=SiMe₃), has been obtained by LnA₃/M reactions (Ln=rare earth metal; A=anionic ligand; M=alkali metal) involving reduction of Sc(NR₂)₃ with K in the presence of 2.2.2‐cryptand (crypt) and 18‐crown‐6 (18‐c‐6) and with Cs in the presence of crypt. Dark maroon [K(crypt)]⁺, [K(18‐c‐6)]⁺, and [Cs(crypt)]⁺ salts of the [Sc(NR₂)₃]⁻ anion are formed, respectively. The formation of this oxidation state of Sc is also indicated by the eight‐line EPR spectra arising from the I =7/2 ⁴⁵Sc nucleus. The Sc(NR₂)₃ reduction differs from Ln(NR₂)₃ reactions (Ln=Y and lanthanides) in that it occurs under N₂ without formation of isolable reduced dinitrogen species. [K(18‐c‐6)][Sc(NR₂)₃] reacts with CO₂ to produce an oxalate complex, {K₂(18‐c‐6)₃}{[(R₂N)₃Sc]₂(μ‐C₂O₄‐κ ¹O:κ ¹O′′)}, and a CO₂⁻ radical anion complex, [(R₂N)₃Sc(μ‐OCO‐κ ¹O:κ ¹O′)K(18‐c‐6)]_n .     

New rhodium(I) water‐soluble complexes with 1‐alkyl‐1‐azonia‐3,5‐diaza‐7‐phospha‐adamantane iodides and their catalytic activity

The water‐soluble phosphine ligands, 1,3,5‐triaza‐7‐phosphatricyclo[3.3.1.1^3,7]decane (tpa) and 1‐alkyl‐1‐azonia‐3,5‐diaza‐7‐phosphatricyclo[3.3.1.1^3,7]decane iodides (Rtpa⁺I⁻), with alkyl=methyl(mtpa⁺I⁻), ethyl (etpa⁺I⁻) and n‐propyl, (ptpa⁺I⁻), and mtpa⁺Cl⁻ react with [Rh₂Cl₂(CO)₄] giving the rhodium(I) complexes [RhCl(CO)(tpa)₂], [RhI(CO)(Rtpa⁺I⁻)₂], [RhCl‐­(CO)(mtpa⁺Cl⁻)₃] and [RhI(CO)(Rtpa⁺I⁻)₃]. The properties and reactivities of the complexes have been investigated using ¹H and ³¹PNMR and IR spectroscopies. The five‐coordinate complexes in solutions show dynamic properties. The complexes are catalysts of the water‐gas shift reaction, the hydrogenation of CC and CO bonds, the hydroformylation of alkenes and the isomerization of unsaturated compounds. Copyright © 1999 John Wiley & Sons, Ltd.     

Darstellung,Kristallstrukturen, Schwingungsspektren und Normalkoordinatenanalysen der mer‐Trihalogeno‐tris‐Pyridin‐Osmium(III)Komplexe mer‐[OsX3Py3], X = Cl,Br, I

Synthesis, Crystal Structures, Vibrational Spectra, and Normal Coordinate Analyses of the mer ‐Trihalogeno‐tris‐Pyridine‐Osmium(III) Complexes mer‐[OsX₃Py₃], X = Cl, Br, I By reaction of the hexahalogenoosmates(IV) with pyridine and iso‐amylalcohol mer‐trihalogeno‐tris‐pyridine‐osmium(III) complexes are formed and purified by chromatography. X‐ray structure determinations on single crystals have been performed of mer‐[OsBr₃Py₃] (monoclinic, space group P2₁/n, a = 9.098(5), b = 12.864(5), c = 15.632(5) Å, β = 90.216(5)°, Z = 4) and mer‐[OsI₃Py₃] (monoclinic, space group P2₁/n, a = 9.0952(17), b = 13.461(4), c = 15.891(10), β = 91.569(5)°, Z = 4). The pyridine rings are twisted propeller‐like against the N₃ meridional plane with mean angles of 49° (Cl), 46° (Br), 44° (I). Based on the molecular parameters of the X‐ray structure determinations and assuming C₂ point symmetry, the IR and Raman spectra are assigned by normal coordinate analysis. Due to the stronger trans influence of pyridine as compared with the halide ligands for N'–Os–X ^· axes significantly different valence force constants are observed in comparison with symmetrically coordinated octahedron axes: f_d(OsCl) = 1.74, f_d(OsCl^·) = 1.49, f_d(OsBr) = 1.43, f_d(OsBr ^· ) = 1.18, f_d(OsI) = 0.99, f_d(OsI ^· ) = 0.96, f_d(OsN) between 1.96 and 2.07 and f_d(OsN') between 2.13 and 2.32 mdyn/Å.