The use of differential photoionization cross sections as a function of excitation energy in assigning photoelectron spectra

A criterion for spectral assignments employing the variation in the differential photoionization cross section as a function of the incident photon energy is described. The He I and He II photoelectron spectra of N₂, CO, CH₃SH, ClHCCHCH₃, H₂CCBrCH₃, and transClHCCHCl are presented and discussed in terms of this criterion.     

Metal—azo and metal—imine compounds : IV. Chemical properties of cyclometallated compounds

The reactions of some cyclometallated azo and imino compounds have been studied. Treatment of [IrHX(PhCCHCHNC₃H₇)(PCy₃)₂] with X₂ (X = Cl, Br) yields substitution products [IrHX(PhCCXCHNC₃H₇)(PCy₃)₂] without rupture of the IrC bond. Treatment of [IrHCl(5-CH₃ · C₆H₃CHNCH₃) (PPh₃)₂] with AgClO₄ and then with CNC₆H₁₁ or CO (= L) leads to the formation of the complexes [IrHL(5-CH₃ · C₆H₃CHNCH₃)(PPh₃)₂]ClO₄, the metallocyclic ring remaining intact. Rupture of the metallocyclic ring is observed when [PdCl(C₆H₄NNPh)]₂ is treated under mild conditions with CNC₆H₁₁, and the insertion product [PdCl(CNC₆H₁₁)₂ {(CNC₆H₁₁)₂C₆H₄NNPh} ] is obtained.Possible mechanisms for the reactions are discussed.     

Influence des interactions attractives non liees sur les stabilites relatives d'ethers et d'acetates d'enol renfermant un groupe styryle

The measure of relative stabilities of β-alcoxystyrene isomers I: C₆H₅-CHCH-OR shows that the trans compound is the most stable when RCH₃ and C₂H₅ and the cis compound is the most stable when Ri-C₃H₇ and t-C₄H₉. The orientation of the OR group can be determined by RMN ¹³C. The stabilities of these molecules are discussed in terms of non bounded attractive interactions. This interpretation is confirmed by the measure of relative stabilities of α-methyl β-alcoxy (and acetoxy)-styrene isomers II: C₆H₅-C(CH3)CH-OR. (RCH₃, C₂H₅ et COCH₃).     

A study of gaseous 3-membered ring oxonium and sulphonium ions

The 1-methyl-1-thionia cyclopropane 3 and 1-phenyl-1-thionia cyclopropane 4 ions are stable, with lifetimes greater than 10^?5 sec, and can be identified from their collisional activation spectra. Their metastable counterparts (lifetime window 10^?6–10^?5 sec) have undergone ring opening to the isomeric structures CH₃S⁺CHCH₃9 and C₆H₅S⁺CHCH₃11 prior to decomposition. The 1-methyl-1-oxonia cyclopropane 1 and 1-phenyl-1-oxonia cyclopropane 2 ions could not be generated: instead acyclic structures CH₃O⁺CHCH₃5 and C₆H₅O⁺CHCH₃7 were found for both metastable and long living species. Loss of a phenoxy radical from C₆H₅OCH₂CH₂OCH₃ is shown to be preceded by a reciprocal hydrogen transfer and is not due to a SN_i-type reaction.     

The addition of small molecules to (η-C5H5)2Rh2(CO)(CF3C2CF3): IV. The sunlight assisted making and breaking of alkene CH bonds on the dirhodium centre; the crystal and molecular structures of (η-C5H5)2Rh2(CHCHCN){C(CF3)CF3)H} · H2O and (η-C5H5)2Rh2(CHCF2){C(CF3)C(CF3)H}

Bis-alkenyl complexes of the type (η-C₅H₅)₂RH₂(alkene − H)(alkyne + H) are obtained when the alkyne complex (η-C₅H₅)₂Rh₂(CO)(CF₃C₂CF₃) is treated with the following alkenes: H₂CCH₂, H₂CCHR (R = Me, Bu^t, Ph, CN), H₂CCF₂, RHCCHR′ (R = R′ = Me, Ph, Cl; R = Me, R′ = Et), cyclooctene and norbornene. An approximately equimolar amount of (η-C₅H₅)₂Rh₂(CO)₂(CF₃C₂CF₃) is also formed. The reactions are greatly accelerated when the reaction mixtures are exposed to sunlight. There is some regioselectivity in the reactions with H₂CCHR and MeHCCHet, with a preference for CH bond cleavage at the least crowded alkene-carbon. When the reaction with acrylonitrile is performed in the absence of sunlight, the complex (η-C₅H₅)₂(CO){(H₂CCHCN)(CF₃C₂CF₃)} can be isolated; upon exposure to sunlight, there is loss of CO and H-transfer to form two isomers of the appropriate bis-alkenyl complex.The molecular geometries of (η-C₅H₅)₂Rh₂(CHCHCN){C(CF₃)C(CF₃)H} and (η-C₅H₅)₂Rh₂(CHCF₂){C(CF₃)C(CF₃)H} have been ascertained by X-ray structure determination. Each molecule has two bridging alkenyl units spanning a RhRh single bond; the dihedral angle between the two RhRhCC planes is just above 90°. There is a cyclopentadienyl ring η⁵-attached to each metal. Crystal data: C₁₇H₁₃F₆NRh₂·H₂O, M 569.1, monoclinic, P2₁/n, a 15.014(7), b 14.882(7), c 8.590(5) Å, β 94.57(9)°, Z = 4, final R 0.056 for 2493 observed reflections; C₁₆H₁₂F₈Rh₂, M 562.1, monoclinic, P2₁/c, a 13.037(6), b 8.765(2), c 14.873(3) Å, β 103.16(3)°, Z = 4, final R 0.062 for 1820 observed reflections.     

Reaktionen an komplexgebundenen liganden: XXIX. Ein einfacher weg zu azomethin-komplexen: Kondensation von chrom—, molybdän—, wolfram—, mangan— und eisen—ammoniak-komplexen und ketonen zu ketimin-komplexen

Treatment of transition-metal—ammonia complexes with ketones yields complexes with RR′CNH ligands. Of particular interest is the stabilization of dialkylketimines such as e.g. (CH₃)₂CNH and C₆H₁₀NH in [M(CO)₅{NHC(CH₃)₂}] or [M(CO)₅ {NHC₆H₁₀}] (M = Cr, Mo, W). The principle of synthesis may be applied to a wide range of different metals and types of complexes, as can be shown by the synthesis of [C₅H₅Mn(CO)₂ {NHC(CH₃)₂}], [C₅H₅Fe(CO)₂{NHC(CH₃)₂}]PF₆, [M(CO)₄L₂] (M = Cr, Mo, W; L = (CH₃)₂CNH, C₆H₁₀NH) and [W(CO)₃(diphos){NHC(CH₃)}₂]. Treatment of [Cr(CO)₅NH₃] with urotropine gives [Cr(CO)₅ {N₄(CH₂)₆}] which is also obtained from [Cr(CO)₅THF] and urotropine. The methods of preparation, reactions and spectroscopic properties of the complexes are reported.     

1-Alkoxy-2-azaallenyl-komplexe von chrom und wolfram

The successive reaction of (CO)₆M with Na[NCR₂¹] and [Et₃O]BF₄ yields (CO)₅M[C(NCR₂¹)OEt] (II: M = Cr; III: M = W; CR₂¹ = C(C₆H₄Br-p)₂ (a), CPh₂ (b), C(C₆H₄OMe-p)₂ (c), C(C₆H₄)₂O (d), CBu₂^tt (e)). Hexacarbonyltungsten, (CO)₆W, reacts with Na[NCPh₂] and MeOSO₂F to give (CO)₅W[C(NCPh₂) OMe] (IV). X-Ray analysis of IIe shows that: (1) the CNC fragment is almost linear (171.7°); (2) the two NC bond lengths are equal within experimental error; and (3) the O,C,Cr,N plane is perpendicular to the C(Me₃),C,N,C(Me₃) plane (90.0°). Therefore compounds II–IV are best described as 1-alkoxy-2-azaallenyl complexes.     

Cleavage of iron2-alkenyl and iron2-alkynyl bonds by mercury(II) chloride

Reactions of HgCl₂ with η⁵-C₅H₅Fe(CO)₂R (R  CH₂CHCH₂ and CH₂C(CH₃)CH₂) in THF at 25°C rapidly afford $\text{1}\text{1}$ adducts of the two reactants. These adducts were converted to the corresponding PF₆^? salts, [η⁵-C₅H₅Fe(CO)₂(η²-CH₂C(R)CH₂HgCl)]⁺ PF₆^? (R  H and CH₃), for characterization. Slower reactions with cleavage of the ironcarbon σ bond and elimination of the R group from η⁵-C₅H₅Fe(CO)₂R occur for R  CH₂CHC(CH₃)₂, CH₂CHCHC₆H₅, and CH₂CCC₆H₅. Both elimination and $\text{1}\text{1}$ adduct formation are observed when R  CH₂CHCHCH₃. The kinetics of the cleavage reactions are presented and possible mechanisms for both cleavage and $\text{1}\text{1}$ adduct formation are discussed.     

Preparation of η2-acetylene- and η1-vinylidene-manganese complexes from p-diethynylbenzene and cymantrene. X-ray crystal and molecular structure of Cp(OC)2MnCCHC6H4CBrCH2

Cp(OC)₂Mn(THF) reacts with p-diethynylbenzene (Deb), yielding Cp(OC)₂Mn(Deb) (I) and [Cp(OC)₂Mn]₂(Deb) (II) with the η²-acetylene coordination of Deb (to both Mn atoms in II). Under the action of PhLi, I and II are isomerized into Cp(OC)₂MnCCHC₆H₄CCH (III) and [Cp(OC)₂MnCCH]₂C₆H₄ (VI). Treatment of I with PhLi, LiBr and an excess of HCl in ether, as well as direct interaction of III with LiBr and HCl/Et₂O, gives Cp(OC)₂MnCCHC₆H₄CBrCH₂ (IV), which has been characterized by an X-ray single-crystal diffraction study. III adds PPh₃, yielding a zwitterionic complex, Cp(OC)₂Mn⁻C(P⁺Ph₃)CHC₆H₄CCH (V).     

Dicyclopentadienyl-niobium(iii) and -niobium(iv) complexes

The reduction of (η-C₅H₅)₂NbCl₂ (I) under various conditions gives the dimer (η-C₅H₅)₄Nb₂Cl₃ (II) containing niobium(III) and niobium(IV). Reaction of II with AgClO₄ gives [(η-C₅H₅)₄Nb₂Cl₂]⁺ ClO₄^- (III). FeCl₃ and (C₆F₅)₂ TlBr displace I from II to give (η-C₅H₅)₂Nb(μ-Cl)(μ-X)MY₂, where MFe, XYCl(IV) and MTl, XBr, YC₆F₅ (V). Reactions of I with metal halides MXY₂ give (η-C₅H₅)₂ClNb(μ-Cl)MXY₂ where XYCl, MAl (VI), Fe (VII), Tl (VIII) and XBr, YC₆F₅, MTl (IX). The chemical behaviour of all these compounds is described.     

σ-Cumulenic transition metal compounds. Remarkably stable cobaloxime complexes; (R)2CCCHCo(dmg)2py

Interaction of NaCo(dmg)₂py with (R)₂CC(OSO₂CF₃)CCH in methanol provides a simple route to novel, stable cumulenyl complexes (R)₂CCCCHCo(dmg)₂py, where R = CH₃ or C₆H₅. In the case of R = H the stable ene-yne complex H₂CC(CCH)Co(dmg)₂py was isolated. The formation and properties of these complexes are discussed.     

Reactions of pentafluorosulfanyliminodihalosulfanes,SF5NSX2, with nucleophiles. Preparation and characterization of pentafluorosulfanylsulfinylamine,SF5NSO.

Reactions of SF₅NSF₂ with sodium alkoxides and aryloxides have produced both the mono- and disubstituted derivatives SF₅NS(F)OR and SF₅NS(OR)₂, where RCH₃, CH₂CHCH₂, C₆H₅, p-C₆H₄NO₂, p-C₆H₄Br, p-C₆H₄CN. The reaction of SF₅NSCl₂ with AgNCO produced SF₅NS(NCO)₂. This diisocyanate can also be prepared from the reaction of SF₅NSCl₂ with KOCN in liquid SO₂. The proposed intermediate, SF₅NSO, in the hydrolysis of SF₅NSF₂ was prepared from the low temperature reaction of SF₅NSCl₂ and Ag₂O in C₆H₅NO₂. The new pentafluorosulfanyl derivatives were characterized by IR, ¹H and ¹⁹F NMR, mass spectrometry and where possible ¹³C NMR and elemental analysis.     

Asymmetrically substituted ferrocene derivatives showing redox switching of optical properties

The electrochemical and spectroelectrochemical behaviors of three ferrocene derivatives, (1) (C₁₈H₃₇)₂NC₆H₄CHCHFcCH₂OH, (2) (C₁₈H₃₇)₂NC₆H₄CHCHFcCHO, (3) (C₁₈H₃₇)₂NC₆H₄CHCHFcCHC(CN)₂, were studied and analyzed on basis of frontier orbital interactions. It was shown that all the three derivatives show two oxidation steps. The first oxidized states of 1 and 2 are stable and show strong LMCT (ligand-to-metal charge transfer) bands. This suggests that they may serve as redox switching of optical properties. In contrast, the first oxidized state of 3 becomes unstable due to strong electron-withdrawing effect of the acceptor substitute.     

A dipole moment study of n-trimethyl-ammoniobenzamidates and n-benzoyliminodimethylsulphur(iv)

Analysis of the dipole moments of N-trimethylammoniobenzamidates Me₃N⁺-N^?COC₆H₄X, with X = H, p-F, p-Cl or p-NO₂, and of N-aroyliminodimethylsulphur(IV) Me₂SNCOC₆H₄X (X = H and p-NO₂) shows that, as solutes, these compounds exist in the syn conformation. Models are proposed for N-trimethylammonio-orthochloroben-zamidate and N-orthocyanobenzoyliminodimethylsulphur(IV). The (Me₃N⁺-N^t-) and (SN) dipole moments, and the (N-CO) and (SN-CO) mesomeric moments, are derived and discussed.     

Effect of macromolecular chemical structure and isomerism on the stability of poly(vinyl chloride)

Calculations of the relative stabilities of various structures contained in PVC macrochains, performed by the MO LCAO method in the CNDO/2 approach, have shown that it is the carbonylallyl C(O)CHCHCHCl and polyenyl (CHCH)_n groups which are primarily responsible for the low thermal stability of the polymer.The formation of short polyene sequences, C(O)(CHCH)_nCHCl (n = 2,3), is initiated by the carbonylallyl groups even at relatively low temperatures (353–413 K).     

On the reaction of metallated acetylenes and allenes with carbon disulfide. Influence of the alkali metal counter-ion and the substituents in the acetylene and allene on the course of the reaction

Addition at low temperatures of carbon disulfide to a solution of the lithium compound

(R¹ = CH₃, C₃H₇, Ph, OCH₃, SCH₃) results in the initial formation of an allenic carbodithioate H₂CCC(R¹)CSSLi, while for R¹ = t-C₄H₉ or SiMe₃ acetylenic carbodithioates R¹CCCH₂CSSLi are formed. The initial products undergo very rapid subsequent reactions. For R¹ = CH₃ or C₃H₇ the lithium compound adds (in the allenic form) in a conjugated fashion to the CCCS system of the allenic carbodithioate. The acetylenic dithioates are deprotonated to give the geminal dithiolates R¹CCCHC(SLi)₂. For R¹ = Ph, OCH₃ or SCH₃, subsequent deprotonation at the terminal carbon atom of the initial allenic dithioate gives enyne dithiolates HCCC(R¹)C(SCH₃)₂; this reaction proceeds more satisfactorily with the potassium compounds.     

Cyclometallation reactions of N-(benzylidene)benzylamines with palladium compounds

The cyclometallation of p-RC₆H₄CHNCH₂C₆H₂, (R = H, Cl, NO₂) by PdX₂ (X = Cl, AcO) has been studied.In every case the cyclometallation occurs with formation of a five-membered ring containing the methine group. The structure of these compounds [$\text{PdX(}\text{p}\text{-RC}{}_6\text{H}{}_3\text{CHN}$CH₂C₆H₅)]₂, derived from ¹H NMR spectra, are different from those reported previously. Reaction of these compounds with PEt₃ gives the compounds [PdX(p-RC₆H₃CHNCH₂C₆H₅)(PEt₃)₂] but with an excess of PPh₃ only the complexes [$\text{PdX(}\text{p}\text{-RC}{}_6\text{H}{}_3\text{CHN}$CH₂C₆H₅)(PPh₃)] are formed.     

Reaktionen an komplexgebundenen liganden: XXXVI. Synthese und oxidationsverhalten von M(CO)5-komplexen (M = Cr,Mo, W) mit amin- und benzochinondiimin-liganden

The oxidation of yellow Cr(CO)₅NH₂R complexes (NH₂R = aniline, m-toluidine, 3,5-xylidine, m-anisidine) with Pbac₄ gives deep blue to deep purple coloured compounds, which have been identified as the respective [Cr(CO)₅(N-phenyl-1,4-benzochinon-diimine)] complexes. Oxidation of the p-phenylenediamine complex yields [(OC)₅CrHNC₆H₄NHCr(CO)₅], which is also deep blue. The binuclear blue complex [{Cr(CO)₅}₂HNC₆H₄NC₆H₅] is obtained by treating Cr(CO)₅THF with the free ligand in THF/hexane; it dissociates rapidly in acetone to form [Cr(CO)₅HNC₆H₄NC₆H₅] and Cr(CO)₅. Analogous Mo(CO)₅ and W(CO)₅ complexes could not be obtained. The oxidation of [W(CO)₅(m-anisidine)] by I₂ yields [W(CO)₄I]₂. All the compounds were characterized by spectroscopic methods as well as by elemental analysis.     

Vinyliden-Übergangsmetallkomplexe: II. Die Protonierung der Vinyliden-Komplexe C5H5Rh(CCHR)(PPri3) und ihre stufenweise Umwandlung in Vinyl- und α-Halogenalkyl-Rhodiumverbindungen

The protonation ofC₅H₅Rh(CCH₂)(PPrⁱ₃) (I) by CF₃CO₂H, HCl and HI gives the vinylrhodium compounds C₅H₅Rh(CHCH₂)(PPrⁱ₃)X (II-IV). The reaction of III (X = Cl) and IV (X = I) with a second molecule of HCl leads to the formation of the α-chloroethyl complexes C₅H₅Rh(CHClCH₃)(PPrⁱ₃)X (VII, VIII). The stereochemistry of these products allows us to propose a mechanism for HCl addition to the CC double bond of the vinyl ligand. C₅H₅Rh(CCHPh)(PPrⁱ₃) (XII) reacts with CF₃CO₂H and HI to give the kinetically preferred compounds C₅H₅Rh(Z-CHCHPh)(PPrⁱ₃)X (XIVa, XVa) of which XIVa (X = CF₃CO₂) in4bpolar solvents rearranges smoothly to form the thermodynamically more stable E isomer C₅H₅Rh(E-CHCHPh)(PPrⁱ₃)OCOCF₃ (XIVb). C₅H₅Rh(E-CHCHPh)(PPrⁱ₃)I (XVb) is obtained from XIVb and NaI. The protonation reactions of C₅H₅Rh(CCHMe)(PPrⁱ₃) (XIII) with CF₃CO₂H, HCl and HI always produce mixtures of isomers of the complexes C₅H₅Rh(CHCHMe)(PPrⁱ₃)X (XVI-XVIII). The ratio of Z to E isomers (≈ 62/38) is not dependent on the anion X and is also not influenced by the polarity of the solvent.     

Reaction of a phosphaketene with diiron enneacarbonyl: Possible intermediacy of a terminal phosphinidene complex

Evidence is presented for the intermediacy of a terminal phosphinidene complex, [2,4,6-(t-Bu)₃C₆H₂]PFe(CO)₄, in the reaction of [2,4,6-(t-Bu)₃C₆H₂]PCO with Fe₂(CO)₉.