Infrared Photodissociation Spectroscopic and Theoretical Study of [Co(CO2)n]+ Clusters

The mass-selected infrared photodissociation (IRPD) spectroscopy was utilized to investigate the interactions of cationic cobalt with carbon dioxide molecules. Quantum chemical calculations were performed on the [Co(CO₂)_n]⁺ clusters to identify the structures of the low-lying isomers and to assign the observed spectral features. All the [Co(CO₂)_n]⁺(n=2-6) clusters studied here show resonances near the CO₂ asymmetric stretch of free CO₂ molecule. Experimental and calculated results indicate that the CO₂ molecules are weakly bound to the Co⁺ cations in an end-on con guration via a charge-quadrupole electrostatic interaction. The present IRPD spectra of [Co(CO₂)_n]⁺ clusters have been compared to those of Ar-tagged species ([Co(CO₂)_n]⁺-Ar), which would provide insights into the tagging effect of rare gas on the weakly-bounded clusters.     

Magic cluster ion distributions: (NO)3+ (N2O)n and (NO)3+ (CO2)n

Supersonic jet expansions of mixtures of nitric oxide with either nitrous oxide or carbon dioxide have been investigated over a wide range of relative concentrations. Mixed molecular cluster ions of the form (NO) _m ⁺ (N₂O)_n and (NO) _m ⁺ (CO₂)_n are detected following non-resonant two-photon ionization. Over a wide range of intermediate concentrations, the cluster ion distributions (NO) ₃ ⁺ (N₂O)_n and (NO) ₃ ⁺ (CO₂)_n with n30 are significantly more intense than clusters containing other numbers of nitric oxide molecules. The extra abundance of these species is attributed to their especially stable structures and several possible forms are discussed. An intriguing possibility involves a stable cyclic nitric oxide trimer (or ion) when combined with nitrous oxide or carbon dioxide clusters.     

Early Stage Solvation of Protonated Methanol by Carbon Dioxide (cited: 1)

The solvation of protonated methanol by carbon dioxide has been studied via a cluster model. Quantum chemical calculations of the H⁺(CH₃OH)(CO₂)_n⁺(n=1-7) clusters indicate that the rst solvation shell of the OH groups is completed at n=3 or 4. Besides hydrogen-bond interaction, the C_CO2…O_CO2 intermolecular interaction is also responsible for the stabilization of the larger clusters. The transfer of the proton from methanol onto CO₂ with the formation of the OCOH⁺ moiety might be unfavorable in the early stage of solvation process. Simulated IR spectra reveal that vibrational frequencies of free O-H stretching, hydrogen-bonded O-H stretching, and O-C-O stretching of CO₂ unit a ord the sensitive probe for exploring the solvation of protonated methanol by carbon dioxide. IR spectra for the H⁺(CH₃OH)(CO₂)_n⁺(n=1-7) clusters could be readily measured by the infrared photodissociation technique and thus provide useful information for the understanding of solvation processes.     

Fluorescence quantum yields and cascade-free lifetimes of state selected CO+2, COS+, CS+2 and N2O+ determined by photoelectron—photon coincidence spectroscopy

The details and principles of an apparatus built for measurements of fluorescence quantum yields and cascade-free lifetimes of open-shell cations are reported. These rely on the detection of coincidences between energy selected photoelectrons and undispersed photons. The results of such measurements for CO⁺₂, COS⁺, CS⁺₂ and N₂O⁺ in selected vibrational levels of their excited states are presented. Non-unity fluorescence quantum yields are found for some vibronic levels of CO⁺₂($\text{B}$), COS⁺ ($\text{A}$), N₂OP⁺($\text{A}$) and a non-exponential decay is observed for CS⁺₂($\text{A}$). The data yield the following values for the radiative lifetimes: CO⁺₂($\text{A}$) 124 ± 6 ns, CO⁺₂($\text{B}$) 140 ± 7 ns, COS⁺($\text{A}$) 550 ± 50 ns and N₂O⁺($\text{A}$) 240 ± 12 ns.     

Some transesterification reactions of [Ir(CO2Me)(CO)2(PPh3)2]

The iridium(I) complex [Ir(CO₂Me)(CO)₂(PPh₃)₂] undergoes a transesterification reaction with the alcohols CH₂C(R)CH₂OH (R = H, Me), MeCCCH₂CH₂OH, and HOCH₂CH₂OH to afford the complexes

[Ir(CO₂CH₂CH₂CMe)(CO)₂(PPh₃)₂] and [Ir(CO₂CH₂CH₂OH)(CO)₂(PPh₃)₂], respectively. In contrast the acetylenic alcohol HCCCH₂CH₂OH gives [Ir(CCCH₂CH₂OH)(CO)PPh₃)₂]. Some reactions of the new complexes are described.     

Synthesis and infrared study of (C6H5)nPX3-nCr(CO)5 (X = Cl,Br, I,H; n = 0–3) and (C6H5)2 PRCr(CO)5 (R = Methyl,Ethyl, i-Propyl, t-Butyl) compounds

A method for the preparation of (C₆H₅)_nPX_3-nCr(CO)₅ complexes in the crystalline state is described. The carbon-oxygen stretching vibration, ^v_CO(A, eq.), of the complexes with X = Cl, Br, I is mainly determined by the inductive effect of the (C₆H₅)_nPX_3-n group. For X = H, the ^v_CO band is defined by the concomitant influence of the σ, π and steric effects.     

Infrared Photodissociation Spectroscopic and Theoretical Study of the HC2nO+ (n=3-6) Cations

The carbon chain cations, HC_2nO⁺ (n=3-6) are produced via a pulsed laser vaporization supersonic expansion ion source in the gas phase. Their infrared spectra are measured via mass-selected infrared photodissociation spectroscopy of the CO “tagged” [HC_2nO·CO]⁺ cation complexes in 1600-3500 cm^-1 frequency range. The geometric and electronic structures of the [HC_2nO·CO]⁺ complexes and the core HC_2nO⁺ (n=3-6) cations are determined with the aid of density functional theory calculations. These HC_2nO⁺(n=3-6) ions are identified to be linear carbon chain derivatives terminally capped by hydrogen and oxygen. The triplet ground states are 10-15 kcal/mol lower in energy than the singlet states, indicating cumulene-like carbon chain structures.     

Photodissociation of the dimer ions Ar+2, Ne+2, and (CO2)+2

The tandem quadrupole photodissociation mass spectrometer has been used to study photodissociation reactions of Ar⁺₂, Ne⁺₂, and (CO₂)⁺₂. The cross sections for photodissociation of Ar⁺₂ exhibited a strong dependence on ion source pressure, varying from 2 × 10 ^?18cm² at 0.1 torr to 6 × 10^?19cm² at 0.5 torr. A large photodissociation cross section (2 × 10^?17cm² for the reaction (CO₂)⁺₂ → CO⁺₂+ CO₂ was observed at the red end of the visible spectrum (580–620 nm) suggesting that this may be an important reaction in CO₂ rich planetary ionspheres such as that of Mars.     

Electron transfer reactions of (C5R5)2(CO)2Ti (R=H or Me) with TCNE or TCNQ: Spectroelectrochemical assignment of metal and ligand oxidation states in [(C5Me5)2(CO)Ti(TCNX)]

The TCNX ligands TCNE (tetracyanoethene) and TCNQ (7,7,8,8-tetracyano-p-quinodimethane) react instantaneously with (C₅R₅)₂(CO)₂Ti, R=H or Me, to yield highly air-sensitive mononuclear complexes (C₅R₅)₂(CO)Ti(TCNX) of which the soluble species (R=Me) were characterized also in the oxidized and reduced forms through cyclic voltammetry, EPR, IR and UV-vis spectroelectrochemistry. While oxidation at rather low potentials yields labile carbonyltitanium(IV) species of the TCNX⁻ ligands, the reduction occurs stepwise at unusually negative potentials, first on the ligand (to yield coordinated TCNX²⁻) and then on the metal (to form Ti^II). For the neutral complexes (C₅R₅)₂(CO)Ti^2+q(TCNX^−q) the results support a rather large amount of charge transfer 1<q<2 from the metal to the acceptors TCNX. Evidence for the previously formulated {(μ-TCNE²⁻)[(C₅H₅)₂Ti^IV(CO)]₂}(TCNE²⁻) could not be found. The complexes (C₅R₅)₂(CO)Ti(TCNE) are compared with related compounds (C₅R₅)₂BrV(TCNE), (C₆R₆)(CO)₂Cr(TCNE) and (C₅R₅)(CO)₂Mn(TCNE).     

Computational modeling of environmental plutonyl mono-, di- and tricarbonate complexes with Ca counterions: Structures and spectra: , PuO2(CO3)2Ca, and PuO2(CO3)3Ca3

We have computed the structures, and select vibrational spectra, electron density and molecular orbital contour plots of plutonium(VI) complexes of environmental importance such as [PuO₂(CO₃)₂]²⁻ and [PuO₂(CO₃)₃]⁴⁻. We show that Ca²⁺ is efficacious in gas-phase modeling of electronic and spectroscopic properties of multiply charged plutonyl di and tricarbonate anions through complexes such as PuO₂(CO₃)₂Ca and [PuO₂(CO₃)₃Ca₃]²⁺.     

Exploring the nitrosyl-approach: “Re(CO)2(NO)”- and “Tc(CO)2(NO)”-complexes provide new pathways for bioorganometallic chemistry

Nitrosylation reactions are rare in the context of low valent Re(I)- and Tc(I)-tricarbonyl complexes so far. We herein describe a method for the conversion of a “M(CO)₃-moiety” (M = Re, Tc) into a dicarbonyl-nitrosyl moiety “M(CO)₂NO”, the synthesis of important precursor complexes and intermediates and possible applications for this new kind of Re- and Tc-chemistry.The behavior of the complex [ReCl₃(CO)₂(NO)]⁻ in water was studied in detail and compared to that of [ReCl₃(CO)₃]²⁻. Contrary to the conversion of [ReCl₃(CO)₃]²⁻ to the mixed aquo-carbonyl complex [Re(OH₂)₃(CO)₃]⁺ in water, one chloride remains initially bound to the metal center in the dicarbonyl-nitrosyl complex, making [ReCl(OH₂)₂(CO)₂(NO)]⁺ the main species for further reactions. In this context, we isolated and characterized the complex [Re(μ₃-O)(CO)₂(NO)]₄. Examples of complexes with different bi- and tridentate ligands based on ReCl₃(CO)₂(NO)]⁻ are discussed.For the development of potential new radiopharmaceuticals we also adapted the nitrosylation technique to the n.c.a. level with ^99mTc. [^99mTc(OH₂)₃(CO)₃]⁺ served as starting material to form a ^99mTc(CO)₂(NO)-core. Labelling reactions with ligands such as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA) and diethylenetriamine pentaacetic acid (DTPA) were performed, resulting in the complexes [^99mTc(IDA)(CO)₂(NO)], [^99mTc(NTA)(CO)₂(NO)] and [^99mTc(DTPA)(CO)₂(NO)]. In this way, the “nitrosyl-approach” adds a new and challenging synthetic tool to the already established organometallic chemistry of Re- and Tc-tricarbonyl complexes.     

Double electron transfer reactions of CO22+ ions

Time-of-flight techniques have been used to measure fast neutral CO₂ products from double electron transfer reactions of CO₂²⁺ ions with 4.0–7.0 keV impact energies. Double electron transfer cross sections have been determined to be in the range of (1.1–12.5) × 10^?16 cm² for reactions of CO₂²⁺ ions with CO₂, CO, N₂, Ar and O₂.     

Synthesis and characterization of the [Cu(Cin2bda)2]ClO4 and [Cu(Ncin2bda)2]ClO4 complexes: Crystal structure of [Cu(Ncin2bda)2]ClO4

Two copper(I) complexes [Cu(Cin₂bda)₂]ClO₄ (I) and [Cu(Ncin₂bda)₂]ClO₄ (II) have been prepared by the reaction of the ligands N²,N²′-bis(3-phenylallylidene)biphenyl-2,2′-diamine (L¹) and N²,N²′-bis[3-(2-nitrophenyl)allylidene]biphenyl-2,2′-diamine (L²) and copper(I) salt. These compounds were characterized by CHN analyses, ¹H NMR, IR, and UV-Vis spectroscopy. The C=N stretching frequency in the copper(I) complexes shows a shift to a lower frequency relative to the free ligand due to the coordination of the nitrogen atoms. The crystal and molecular structure of II was determined by X-ray single-crystal crystallography. The coordination polyhedron about the copper(I) center in the complex is best described as a distorted tetrahedron. A quasireversible redox behavior was observed for complexes I and II. The article is published in the original.     

以[M(DETA)2)]n+(M=Cu2+, Ni2+, Co3+)为客体的MnPS3夹层化合物的合成、结构表征与磁性研究

将过渡金属配合物阳离子([M(DETA)₂]ⁿ⁺(M=Cu²⁺,Ni²⁺,Co³⁺;DETA=Diethylenetriamine,二乙烯三胺)作为客体插入层状MnPS₃层间得到了相应的3个夹层化合物。通过X-射线粉末衍射、元素分析和红外光谱对夹层化合物的结构进行了表征。结果表明,与主体MnPS₃ 0.65 nm的层间距相比较,夹层化合物(Mn_0.88PS₃[Cu(DETA)₂]_0.12)的层间距扩大了0.32 nm,由此推测客体[Cu(DETA)₂]²⁺在层间以平面四方的配位形式存在,而另2个夹层化合物(Mn_0.79PS₃[Ni(DETA)₂]_0.21和Mn_0.74PS₃[Co(DETA)₂]_0.17)的层间距扩大了0.48 nm,说明客体[(M(DETA)₂]ⁿ⁺,M=Co³⁺,Ni²⁺) 在主体层间以八面体配位形式存在。磁性测试结果表明过渡金属离子[(M(DETA)₂]ⁿ⁺(M=Cu²⁺,Co³⁺)的插入能引起主体MnPS₃的磁性在35~40 K发生由顺磁向亚铁磁性的转变并表现自发磁化,而客体[Ni(DETA)₂]²⁺却使夹层化合物的反铁磁相互作用增强,抑制了自发磁化的发生。     

Isocyanide addition to MN2(CO)5(Ph2PCH2PPh2)2 and the formation of a four-electron doubly-bridging isocyanide

The reactions of Fe(CO)₅, Fe(CO)₄P(C₆H₅)₃, M(CO)₆ (M  W, Mo, Cr), and (CH₃C₅H₄Mn(CO)₃ with KH and several boron and aluminium hydrides were investigated. Iron pentacarbonyl was converted quantitatively to K⁺Fe(CO)₄-(CHO) by hydride transfer from KBH(OCH₃)₃ allowing isolation of [P(C₆H₅)₃]₂-Nⁿ⁺Fe(CO)₄(CHO)^? in 50% yield. Lower yields were obtained with LiBH(C₂H₅)₃, and other hydride sources gave little or no formyl product. The stability of Fe(CO)₄(CHO)^? in THP was found to depend on the cation, decreasing in the order [P(C₆H₅)₃]₂N⁺ > K⁺ > Na⁺ > Li⁺. No formyl complexes were isolated and no spectroscopic evidence for formyl formation was observed in the reactions of the other transition metal carbonyls with several hydride sources. Fe(CO)₄-P(C₆H₅)₃ gave K₂Fe(CO)₄ when treated with KHB(OCH₃)₃. When treated with LiBH(C₂H₅)₃, W(CO)₆ gave a mixture of HW₂(CO)₁₀^?and (OC)₅W(COC₂H₅)^?; the latter was methylated to give the carbene complex (OC)₅WC(OCH₃)C₂H₅.     

Preparation and characterization of mono-cyclopentadienylvanadium dihalide bis-phosphine complexes; crystal structure of (η5-C5H5)VCL2(PMe3)2

Mono-cyclopentadienyl complexes CpVX₂(PR₃)₂ and Cp′VX₂ (PR₃)₂ (Cp = η⁵- C₅H₅; Cp′ = η⁵-C₅H₄Me; R = Me, Et; X = Cl, Br) have been prepared by reaction of VX₃(PR₃)₂ with CpM (M = Na, T1, SnBuⁿ3, 1/2 Mg) or Cp′Na. Attempts to prepare analogous complexes with other phosphine ligands, PPh₃, PPh₂ Me, PPhMe₂, Pcy₃, DMPE and DPPE failed. Reduction of CpVCl₂(PEt₃)₂ with zinc or aluminium under CO (1 bar) offers a simple method for the preparation of CpV(CO)₃(PEt₃). The crystal structure of the trimethylphosphine complex CpVCl₂(PMe₃)₂ is reported.     

CS+(B2Σ+ → A 2Πi) fluorescence from penning excitation of CS

The energy transfer reation of He(2³S) + CS was studied spectroscopically in a flowing afterglow apparatus. The CS⁺(B²Σ⁺ → A ²Π_i) transition is identified via three members of the Δν = 0 sequence (406–415 nm). The spin-orbit splitting of the (0, 0) band of CS⁺(A ²Π_i) is 301 ± 5 cm^?1. A weak emitting system (280–340 nm) is tentatively identified as CS⁺(B²Σ⁺→ X²Σ⁺).     

Synthesis and x-ray crystallographic structural determination of the acetylene complex (η5−C5H5)2W2(CO)4(C2H2)

Reaction of photogenerated (η⁵?C₅H₅)₂W₂(CO)₄ with acetylene at 25°C yields a complex of the formula (η⁵-C₅H₅)₂W₂(CO)₄(C₂H₂). The crystal structure of the complex shows it to have a tetrahedrane-like W₂C₂ core. The C—C bond distance of the C₂H₂ unit is 1.33 Å which is close to that of ethylene, considerably longer than the 1.20 Å for acetylenes. The W—W distance is 2.987 Å which is ～0.25 Å shorter than the W—W distance in (η⁵-C₅H₅)₂W₂(CO)₆ but longer than that expected for (η⁵-C₅H₅)₂W₂(CO)₄. By analogy to the parent (η⁵-C₅H₅)₂M₂(CO)₆ species, the near-UV absorption in (η⁵-C₅H₅)₂M₂(CO)₄(C₂H₂) is assigned to a σ_b → σ^* transition. Owing to the shorter M—M bond in the C₂H₂ adducts, the σ_b → σ^* absorption is at higher energy than in the (η⁵-C₅H₅)₂M₂(CO)₆ complexes.     

Studies on the reaction N + N3 → N2(B 3Πg) + N2(X 1Σ+g)

Strongly enhanced N₂ first positive emission N₂(B ³Π_g → A ³Σ⁺_u) has been observed on addition of N atoms into a flowing mixture of Cl and HN₃. The dependence of the emission intensity on N atom concentration gave a rate constant for the reaction N + N₃ → N₂(B ³Π_g) + N₂(X ¹Σ⁺_g) of _i(1.6 ± 1.1) × 10^?11 cm³ molecule^?1 s^?1. That for the reaction Cl + HN₃ → HCl + N₃ is (8.9 ± 1.0) × 10^?13 cm³ molecule^?1 s^?1 from the decay of the emission. Comparison of the emission intensity in ClHN₃ with that in ClHN₃N gave the rate constant of the reaction N₃ + N₃ → N₂(B ³Π_g) + 2N₂(X ¹Σ⁺_g) as 1.4 × 10^?12 cm³ molecule^?1 s^?1 on the assumption that N + N₃ yields only N₂(B ³Π_g) + N₂(X ¹Σ⁺_g).     

Synthesis and reactivity of [ReBr2(NCCH3)2(CO)2]: A new precursor for bioorganometallic chemistry

We have synthesised (Et₄N)[ReBr₂(NCCH₃)₂(CO)₂] 1 in two steps from [ReBr₃(CO)₃]²⁻. Complex 1 is water and air stable and the two Br⁻ ligands are easily exchanged for coordinating solvent molecules such as water. The reactivity of 1 with several ligands such as imidazole (imz) and 2-picolinic acid (2-pic) are easily possible with substitution exclusively occurring in trans-position to the carbonyl groups. The resulting complexes [Re(imz)₂(NCCH₃)₂(CO)₂]⁺ and [Re(2-pic)(NCCH₃)₂(CO)₂] have been isolated and structurally characterised. The two acetonitrile ligands are strongly bound and are not substituted under any conditions. Complex 1 represents therefore the new moiety “trans,cis-[Re(NCCH₃)₂(CO)₂]⁺” which can be considered as a further building block in organometallic chemistry.