Observation and Characterization of the Hg-O Diatomic Molecule: A Matrix-Isolation and Quantum-Chemical Investigation.

Mercuric oxide is a well-known and stable solid, but the diatomic molecule Hg-O is very fragile and does not survive detection in the gas phase. However, laser ablation of Hg atoms from a dental amalgam alloy target into argon or neon containing about 0.3 % of O or of O during their condensation into a cryogenic matrix at 4 K allows the formation of O atoms which react on annealing to make ozone and new IR absorptions in solid argon at 521.

(Noble Gas) -NC Molecular Ions in Noble Gas Matrices: Matrix Infrared Spectra and Electronic Structure Calculations.

An investigation of pulsed-laser-ablated Zn, Cd and Hg metal atom reactions with HCN under excess argon during co-deposition with laser-ablated Hg atoms from a dental amalgam target also provided Hg emissions capable of photoionization of the CN photo-dissociation product. A new band at 1933.4 cm in the region of the CN and CN gas-phase fundamental absorptions that appeared upon annealing the matrix to 20 K after sample deposition, and disappeared upon UV photolysis is assigned to (Ar) CN , our key finding.

M←NCCH, M-η-(NC)-CH, and CN-M-CH Prepared by Reactions of Ce, Sm, Eu, and Lu Atoms with Acetonitrile: Matrix Infrared Spectra and Theoretical Calculations.

The reactions of laser-ablated Ce, Sm, Eu, and Lu atoms with acetonitrile were studied by matrix infrared spectra in a neon matrix, and M←NCCH, M-η-(NC)-CH, and CN-M-CH were identified with isotopic substitution and quantum chemical calculations. The major product is the insertion complex (CN-M-CH), while the end-on and side-on complexes (M←NCCH and M-η-(NC)-CH) are also trapped in the matrix. The CCN antisymmetric stretching mode for Ce-η-(NC)-CH was observed at 1536.

Cyanides, Isocyanides, and Hydrides of Zn, Cd and Hg from Metal Atom and HCN Reactions: Matrix Infrared Spectra and Electronic Structure Calculations.

Zinc and cadmium atoms from laser ablation of the metals and mercury atoms ablated from a dental amalgam target react with HCN in excess argon during deposition at 5 K to form the MCN and MNC molecules and CN radicals. UV irradiation decreases the higher energy ZnNC isomer in favor of the lower energy ZnCN product. Cadmium and mercury atoms produce analogous MCN primary molecules.

Matrix Infrared Spectroscopic Studies of B-NCCN, B--(NC)-CN, NCBCN, CNBCN, CNBNC, and High-Order Products Produced in Reactions of Boron Atoms with Cyanogen.

The products in reactions of laser-ablated boron atoms with cyanogen in excess argon have been identified via investigation of the matrix spectra and their variation on photolysis, annealing, and isotopic substitutions. DFT calculations have been performed for the plausible products and reaction paths, providing helpful guides. B-NCCN and B-η-(NC)-CN were observed in the original deposition spectra, but they disappear on photolysis with λ > 220 nm while more stable NCBCN, CNBCN, and CNBNC were produced.

Matrix Infrared Spectroscopic and Theoretical Investigations of M···NCCN, M···CNCN, M···C()CN, NCMCN, CNMNC, CNMCN, and [M···NCCN] Produced in the Reactions of Group 11 Metal Atoms with Cyanogen.

Reactions of group 11 metals with cyanogen, N≡C-C≡N, in excess argon and neon have been carried out, and the products were identified via examination of the matrix spectra and their variation upon photolysis, annealing, and isotopic substitutions. Density functional theory calculations provided helpful information for the plausible products and reaction paths. While M···NCCN and M···CNCN were observed in all three metal systems, the cyanide and isocyanide products (NCMCN, NCMNC, and CNMNC) were identified only in the Cu reactions, and M···C(N)CN was identified in the Cu and Au spectra.

Cyanides and Isocyanides of Zinc, Cadmium and Mercury: Matrix Infrared Spectra and Electronic Structure Calculations for the Linear MNC, NCMCN, CNMNC, NCMMCN, and CNMMNC Molecules.

Cadmium atoms from laser ablation react with cyanogen, NC=CN, in excess argon during co-deposition at 4 K, and even more on UV irradiation of the cold samples. Final annealing to 35 K increases bands at 2187.3 and 2089.

Matrix Infrared Spectroscopic and Theoretical Investigations of XCX···MX and CX-MX Provided in Reactions of Ag and Au with Tetrahalomethanes.

Reactions of laser-ablated silver atoms with tetrahalomethanes have been carried out in excess argon, and the products were identified via examination of the matrix spectra and their variation on photolysis and annealing. While production of the insertion products (CX-AgX) was evident in all Ag reactions, different sets of product absorptions were also observed in the higher frequency region (1260-720 cm). They increased on photolysis but decreased on annealing, opposite to the absorptions of the insertion products.

Formation of Short Zn-Zn Bonds Stabilized by Simple Cyanide and Isocyanide Ligands.

Cyanogen diluted in argon was reacted with laser ablated Zn atoms to produce the NCZnCN and NCZnZnCN cyanides and higher energy isocyanides ZnNC, CNZnNC, and CNZnZnNC, which were isolated in excess argon at 4 K. These reaction products, identified from the matrix infrared spectra of their -CN and -NC chromophore ligand stretching modes, were confirmed by C and N isotopic substitution and comparison with frequencies calculated by the B3LYP and CCSD(T) methods using the all electron aug-cc-pVTZ basis sets. The cyanide and isocyanide products were increased markedly by mercury arc UV photolysis, which covers the zinc atomic absorption.

Infrared Spectra of CHCN→M, M-η-(NC)-CH, CH-MNC Prepared by Reactions of Laser-Ablated Fe, Ru, and Pt Atoms with Acetonitrile in Excess Argon.

Reactions of laser-ablated Fe, Ru, and Pt atoms with acetonitrile have been carried out in excess argon, and the products identified in the matrix spectra. CHCN→Fe and Fe-η-(NC)-CH observed in the original deposition spectra converted to CH-FeNC on uv irradiation. CHCN→Ru, the only product detected in the Ru system, dissociated on uv irradiation, but was partly reproduced on subsequent visible irradiation and annealing.

Matrix Infrared Spectroscopic and Theoretical Studies for Products Provided in Reactions of Sn with Ethane and Halomethanes.

Tin insertion products (oxidation state 2+) were observed in reactions of laser-ablated Sn atoms with ethane, and halomethanes in excess argon, parallel to the Pb reactions. The CSnX bond angles of the observed Sn complexes are close to right angles, and natural bond orbital calculations show that Sn also utilizes mostly its p-orbitals to make chemical bonds. Bridged Sn complexes [CX(X)-SnX] were also provided in reactions of tetrahalomethanes via photo-isomerization of the insertion products, showing that the p-orbitals of Sn are more accessible than those of Pb.

Mercury Cyanides and Isocyanides: NCHgCN and CNHgNC as well as NCHgHgCN and CNHgHgNC: Simple Molecules with Short, Strong Hg-Hg Bonds.

Mercury atoms, laser-ablated from an amalgam dental filling target, react with cyanogen in excess argon during condensation at 4 K to form two major products in the 2200 cyanide M-C-N stretching region of the IR spectrum, which were assigned to NCHgCN and NCHgHgCN from their antisymmetric C-N stretching mode absorptions at 2213.8 and 2180.1 cm .

Matrix Infrared Spectra and Electronic Structure Calculations of Linear Alkaline Earth Metal Di-isocyanides CNMNC, Ionic (NC)M(NC) Bowties, and Ionic (MNC) Rings.

Laser-ablated group 2 metal atoms exhibit different reactivities with (CN) in excess argon and neon during condensation at 4 K. UV irradiation (220-290 nm) is required to activate Be to produce the linear CNBeNC di-isocyanide molecule with a strong antisymmetric C-N stretching band at 2104.3 cm and a C-N-Be-N-C stretching mode at 1265.

Matrix Infrared Spectra, Photochemistry and Density Functional Calculations of Cl-HCCl, ClHCl, Cl-ClCCl, and Cl-HCHCl Produced from CHCl and CHCl Exposed to Irradiation from Laser Ablation.

Strong absorptions for Cl-HCCl with D and C isotopes were observed in the spectra of CHCl codeposited with laser-ablated metal atoms, cations, electrons, and vacuum ultraviolet radiation, which shows that the precursor is an effective electron scavenger. The IR spectra, isotopic shifts, and DFT calculations identified the major product as Cl-HCCl, which is characterized by a strong, broad C-H stretching mode interacting with the overtone of the H-C-Cl bending fundamental. These absorptions decreased on subsequent annealing and photolysis treatments while the ClHCl absorptions increased, suggesting that dissociation of the chloroform anion generates the stable symmetrical hydrogen dichloride anion as does the reaction of HCl and Cl.

Matrix Infrared Spectroscopic and Theoretical Studies for the Products of Lead Atom Reactions with Ethane and Halomethanes.

The insertion products of laser-ablated Pb atom reactions with ethane and mono-, di-, tri-, and tetrahalomethanes in excess argon were prepared and identified from their matrix infrared spectra on the basis of DFT computed frequencies and observed isotopic shifts. Unlike the lighter elements in group 14, the heaviest member lead exists primarily in the oxidation state 2+ using 6p orbitals in reaction products due to relativistic contraction of the 6s orbital. The C-Pb-X (X = H, F, Cl) bond is close to a right angle, indicating that Pb contributes mostly p-character to the C-Pb and Pb-X bonds.

Reactions of Laser-Ablated Aluminum Atoms with Cyanogen: Matrix Infrared Spectra and Electronic Structure Calculations for Aluminum Isocyanides Al(NC) and Their Novel Dimers.

Laser-ablated Al atoms react with (CN) in excess argon during condensation at 4 K to produce AlNC, Al(NC), and Al(NC), which were computed (B3LYP) to be 27, 16, and 28 kJ/mol lower in energy, respectively, than their cyanide counterparts. Irradiation at 220-580 nm increased absorptions for the above molecules and the very stable Al(NC) anion. Annealing to 30, 35, and 40 K allowed for diffusion and reaction of trapped species and produced new bands for the Al(NC) dimers including a rhombic ring core (C)(AlN)(C) with C's attached to the N's, a (NC)Al(II)-Al(II)(NC) dimer with a computed Al-Al length of 2.

Tungsten Hydride Phosphorus- and Arsenic-Bearing Molecules with Double and Triple W-P and W-As Bonds.

Laser ablation of tungsten metal provides W atoms which react with phosphine and arsine during condensation in excess argon and neon, leading to major new infrared (IR) absorptions. Annealing, UV irradiation, and deuterium substitution experiments coupled with electronic structure calculations at the density functional theory level led to the assignment of the observed IR absorptions to the E≡WH and HE═WH molecules for E = P and As. The potential energy surfaces for hydrogen transfer from PH to the W were calculated at the coupled-cluster CCSD(T)/complete basis set level.

Matrix Infrared Spectra of Insertion and Metallacyclopropane Complexes [CHCH-MH and (CH)-MH] Prepared in Reactions of Laser-Ablated Group 3 Metal Atoms with Ethane.

CHCH-MH and (CH)-MH were identified in the matrix IR spectra from reactions of laser-ablated group 3 metal atoms with ethane, and they were characterized via theoretical investigations. The observed products are the most stable in the proposed reaction path. Because of the small number of valence electrons, the group 3 metal high oxidation-state complexes are less stable.

Observation and Characterization of CHCH-MH, (CH)-MH, CH═CH-MH, and CH-C≡MH Produced by Reactions of Group 5 Metal Atoms with Ethane.

The primary products in reactions of laser-ablated group 5 metal atoms with ethane were identified in argon matrix IR spectra and characterized via density functional theory computations. The second- and third-row transition metals Nb and Ta produced insertion, metallacyclopropane, vinyl trihydrido, and anionic ethylidyne complexes (CHCH-MH, (CH)-MH, CH═CH-MH, and CHC≡MH), while the first-row transition metal V yielded only the insertion and metallacyclopropane products. The energetically higher ethylidenes and neutral ethylidynes (CHCH═MH and CHC[Formula: see text]MH) were not detected.

Thorium and Uranium Hydride Phosphorus and Arsenic Bearing Molecules with Single and Double Actinide-Pnictogen and Bridged Agostic Hydrogen Bonds.

Thorium atoms from laser ablation react with phosphine during condensation in excess argon to produce two new infrared absorptions at 1467.2 and 1436.6 cm near weak bands for ThH and ThH, which increase on annealing to 25 and 30 K, indicating spontaneous reactions.

Matrix Infrared Spectra and Quantum Chemical Calculations of Ti, Zr, and Hf Dihydride Phosphinidene and Arsinidene Molecules.

Laser ablated Ti, Zr, and Hf atoms react with phosphine during condensation in excess argon or neon at 4 K to form metal hydride insertion phosphides (H2P-MH) and metal dihydride phosphinidenes (HP═MH2) with metal phosphorus double bonds, which are characterized by their intense metal-hydride stretching frequencies. Both products are formed spontaneously on annealing the solid matrix samples, which suggests that both products are relaxed from the initial higher energy M-PH3 intermediate complex, which is not observed. B3LYP (DFT) calculations show that these phosphinidenes are strongly agostic with acute H-P═M angles in the 60° range, even smaller than those for the analogous methylidenes (carbenes) (CH2═MH2) and in contrast to the almost linear H-N═Ti subunit in the imines (H-N═TiH2).

Infrared Spectra and Density Functional Calculations for Singlet CH2═SiX2 and Triplet HC-SiX3 and XC-SiX3 Intermediates in Reactions of Laser-Ablated Silicon Atoms with Di-, Tri-, and Tetrahalomethanes.

Reactions of laser-ablated silicon atoms with di-, tri-, and tetrahalomethanes in excess argon were investigated, and the products were identified from the matrix infrared spectra, isotopic shifts, and density functional theory energy, bond length, and frequency calculations. Dihalomethanes produce planar singlet silenes (CH2═SiX2), and tri- and tetrahalomethanes form triplet halosilyl carbenes (HC-SiX3 and XC-SiX3). The Si-bearing molecules identified are the most stable, lowest-energy product in the reaction systems.

Matrix Infrared Spectroscopic and Quantum Chemical Investigations of the Group 5 Transition Metal Atom and CX4 Molecule (X = H, F, and Cl) Reaction Products.

Laser-ablated vanadium, niobium, and tantalum atoms were reacted with CH2X2, CHX3, and CX4 (X = F and Cl) molecules in condensing argon, and the products were investigated by matrix isolation infrared spectroscopy. The major reaction products are new CH2-MX2, CHX-MX2, HC-MX3, and XC-MX3 complexes. These reactive species were identified by comparing their matrix infrared spectra with frequencies, intensities, and isotopic shifts from density functional theory calculations.

Methane activation by laser-ablated Th atoms: matrix infrared spectra and theoretical investigations of CH₃-Th-H and CH₂═ThH₂.

Methane activation by laser-ablated Th atoms on the triplet potential energy surface produces the methylthorium hydride, CH3-Th-H, that converts smoothly by α-H transfer to CH2-ThH2, which relaxes in the matrix to the more stable singlet methylidene, CH2═ThH2. This first actinide methylidene was characterized from argon matrix infrared spectra and B3LYP calculations in our laboratory. We now report neon matrix investigations, which include the methylthorium hydride and the Th-D stretching modes of CD2═ThD2 that are blue-shifted in neon from under the intense CD4 precursor absorption, and reactions with CH2D2 that give rise to the CHD═ThHD modifications and their α-H and α-D transfer counterparts CD2═ThH2 and CH2═ThD2.

Matrix infrared spectra and density functional calculations for new iso-halomethanes: CHCl2-Cl, CHFCl-Cl, CFCl2-Cl, CHBr2-Br, and CBr3-Br in solid argon.

Laser ablation of transition metals for reactions with halocarbons to produce new metal bearing molecules also exposed these samples to laser plume radiation and its resulting photochemistry. Investigations with CCl4 also produced several known neutral and charged intermediate species, including the iso-tetrachloromethane CCl3-Cl observed in previous work and identified by the Maier group. CHCl2-Cl, CHFCl-Cl, and CFCl2-Cl, photoisomers of CHCl3, CHFCl2, and CFCl3, were also identified in matrix IR spectra.