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Infraredspectra of mass-selected mononuclear iron nitrosyl cations Fe(NO)n+with n= 1–5and their argon tagged complexes are measured via infrared photodissociationspectroscopy in the nitrosyl stretching frequency region in the gasphase. The structures are established by comparison of the experimentalspectra with the simulated spectra derived from density functionalcalculations. Two IR active bands were observed for the argon-taggedFe(NO)2+and Fe(NO)3+complexes,consistent with theoretical predictions that these complexes havebent C2vand nonplanar C3vsymmetry, respectively.The Fe(NO)4+complex was characterized to havea completed coordination sphere with 17 electrons containing a bentone-electron NO ligand and three three-electron NO ligands. The Fe(NO)5+complex was determined to involve a Fe(NO)4+core ion that is solvated by an external NO molecule. [ABSTRACT FROM AUTHOR]

Gold cation–water complexes with attached argonatoms areproduced via a laser vaporization supersonic cluster source. The [Au(H2O)nArx]+(n= 1–8; x= 1 or 2) complexes are each mass selected and studied by infraredphotodissociation spectroscopy in the OH stretching frequency regionto explore the coordination and solvation structures of the Au+cation. Density functional calculations have been performed,and the calculated vibrational spectra are compared to the experimentalspectra to identify the gas-phase structures of the Au(H2O)n+complexes. Confirmingprevious theoretical predications, the first coordination shell ofthe Au+cation contains two water molecules forming a linearO–Au+–O arrangement; subsequent water moleculesbind to the two H2O ligands of the Au(H2O)2+core ion via hydrogen bond forming of the secondhydration shell, which is complete at n= 6. Forthe complexes with n≤ 7, the experimentalspectrum can in general be assigned to the predicted global minimumstructure. However, the spectrum suggests that two or more conformerscoexist for the n= 8 complex, indicating that theidentification of a single global minimum becomes less important uponincreasing the number of solvating water molecules. [ABSTRACT FROM AUTHOR]

The infrared photodissociation spectroscopy of mass-selectedmononucleariron carbonyl anions Fe(CO)n–(n= 2–8) were studied in the carbonyl stretchingfrequency region. The FeCO–anion does not fragmentwhen excited with infrared light. Only a single IR active band wasobserved for the Fe(CO)2–and Fe(CO)3–anions, consistent with theoretical predictionsthat these complexes have linear D∞hand planar D3hsymmetry, respectively. The Fe(CO)4–anion is the most intense peak in the mass spectra and was characterizedto have a completed coordination sphere with high stability. Anionclusters larger than n= 4 were determined to involvea Fe(CO)4–core anion that is progressivelysolvated by external CO molecules. Three CO stretching vibrationalfundamentals were observed for the Fe(CO)4–core anion, indicating that the Fe(CO)4–anion has a C3vstructure.All the carbonyl stretching frequencies of the Fe(CO)n–anion complexes are red-shiftedwith respect to those of the corresponding neutrals. [ABSTRACT FROM AUTHOR]

The combination of matrix isolation infrared spectroscopic and density functional calculation results provides strong evidence that the transition metal monoxide cation, ScO+, coordinates five noble gas atoms in forming the [ScO(Ng)5]+ (Ng = Ar, Kr, or Xe) complexes in noble gas matrixes. [ABSTRACT FROM AUTHOR]

Cationic complexes of heavy alkaline earth metal and carbon dioxide [M(CO 2 ) n ] + (M = Ca, Sr, and Ba) are produced by a laser vaporization-supersonic expansion ion source in the gas phase and are studied by infrared photodissociation spectroscopy in conjunction with quantum chemistry calculations. For the n = 1 complexes, the metal-ligand binding arises primarily from the electrostatic interaction with the CO 2 ligand bound to the metal (+I) center in an end-on η 1 -O fashion. The more highly coordinated complexes [M(CO 2 ) n ] + with n ≥ 2 are characterized to involve a [M 2+ (CO 2 - )] core ion with the CO 2 - ligand bound to the metal (+II) center in a bidentate η 2 -O, O manner. The activation of CO 2 in forming a bent CO 2 - moiety occurs via solvation-induced metal cation-ligand electron transfer reactions. Bonding analyses reveal that the attractive forces between M 2+ and CO 2 - in the core cation come mainly from electrostatic attraction, but the contribution of covalent orbital interactions should not be underestimated. The atomic orbitals of metal dications that are engaged in the orbital interactions are ns and ( n - 1)d orbitals.

Heteronuclear magnesium-iron carbonyl cation complexes MgFe(CO) n + ( n = 4-9) are prepared in the gas phase and are detected by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The geometric structures and the metal-metal bonding are discussed with the aid of quantum chemical calculations. The MgFe(CO) 9 + cation is a coordinatively saturated complex. Each complex is characterized to contain more than one isomer. The small complexes ( n = 4-6) possess the Mg-Fe bonded [(OC) n -4 Mg-Fe(CO) 4 ] + and/or [(OC) n -5 Mg-Fe(CO) 5 ] + structures with all the carbonyl ligands terminally bonded. For the larger complexes with n = 7-9, the [(OC) n -4 Mg-Fe(CO) 4 ] + structure is the major isomer experimentally observed. In addition, the [(OC) n -5 Mg-OC-Fe(CO) 4 ] + isomer involving a linear bridging carbonyl ligand is also characterized. Bonding analyses indicate that each [(OC) n -4 Mg-Fe(CO) 4 ] + complex contains a Mg-Fe electron-sharing σ bond. The metal-metal bond is described as a Mg(+I)-Fe(0) bond in MgFe(CO) 4 + and as a Mg(+II)-Fe(-I) bond in the larger n = 5-9 complexes.

The reactions of alkaline-earth metal atoms (Ca, Sr, and Ba) with carbon dioxide are investigated using matrix isolation infrared spectroscopy in solid neon. The ground-state metal atoms react with two carbon dioxide molecules to produce the oxalate complexes MC 2 O 4 and the carbonate-carbonyl complexes OCMCO 3 (M = Ca, Sr, Ba) spontaneously on annealing. The species are identified by the effects of isotopic substitution on their infrared spectra as well as density functional calculations. Bonding analyses reveal that the attractive forces between M 2+ and (CO 3 ) 2 - or (C 2 O 4 ) 2 - in the OCMCO 3 and MC 2 O 4 complexes come mainly from electrostatic attraction, but covalent orbital interactions also play an important role, which are dominated by the ligand-to-metal donation bonding. The calcium, strontium, and barium metal centers in these complexes use their ns and predominately ( n - 1)d atomic orbitals for covalent bonding that mimic transition metals.

The boron-dinitrogen cation complexes B(NN) 3 + and B 2 (NN) 3,4 + are produced in the gas phase and are studied by infrared photodissociation spectroscopy in the N-N stretching vibrational frequency region. The geometric and electronic structures are determined by comparison of the experimental spectra with density functional theory calculations. The B(NN) 3 + cation is characterized to have a closed-shell singlet ground state with planar D 3 h symmetry. The B 2 (NN) 3 + cation is determined to have a B═B bonded (NN) 2 BBNN structure with C 2 v symmetry. Two isomers of the B 2 (NN) 4 + cation contribute to the experimental spectrum. One is a N 2 -tagged complex involving a B 2 (NN) 3 + core ion. Another one is a B-B bonded B 2 (NN) 4 + complex with a planar D 2 h structure. Bonding analyses reveal that the B-NN interactions in these complexes come mainly from covalent orbital interactions, with the NN → B σ donation being stronger than the B → NN π back-donation.

The solvent effect of the TaO 2 + reaction with water molecules in the gas phase is examined. Stoichiometric TaO 2 (H 2 O) n + cations are generated by the laser vaporization of a tantalum metal target in the pulsed supersonic expansion of H 2 O/He mixed gas. The infrared photodissociation spectra of TaO 2 (H 2 O) n + cations are measured using the argon-tagging technology in the 2800-3850 cm -1 region. Density functional theory calculations are carried out to identify the observed infrared bands and elucidate the reaction mechanism. In the TaO 2 + reaction with one H 2 O molecule, both the hydrated adduct H 2 O-TaO 2 + and dihydroxide TaO(OH) 2 + are generated. The coexistence of tetrahydroxide Ta(OH) 4 + and hydrated dihydroxide H 2 O-TaO(OH) 2 + is seen when the second H 2 O molecule is involved. However, only the hydrated H 2 O-Ta(OH) 4 + product is obtained in the TaO 2 reaction with three H 2 O molecules. Theoretical calculations indicate that in the reaction, the formation of a six-membered cyclic transition state through the hydrogen bond lowers the energy barrier significantly, which promotes the transfer of the hydrogen of hydrated adducts to generate di- and tetrahydroxides.

Stoichiometric Cu 2 O 2 (CO) n + ( n = 3-7) clusters were generated via a laser vaporization supersonic cluster source in the gas phase and identified by infrared photodissociation spectroscopy in the C-O stretching region. The infrared spectra were interpreted, and the cluster structures were determined by density functional calculations. The ground states of the Cu 2 O 2 (CO) n + complexes were formed by a dicopper superoxide carbonyl with [(OC) x CuOOCu(CO) y ] + ( x + y = n ) structures in which the CO ligands coordinate a zigzag Cu(OO)Cu + core. The structural characterization for the Cu(OO)Cu + core-based clusters is crucial in order to correctly understand the associated reactions catalyzed by metal clusters.

The reactions of iridium- and osmium-carbyne hydride cations [HIrCH] + and [HOsCH] + with ethylene have been studied using mass spectrometry with isotopic-labeling in the gas phase. The carbyne reactivity is compared with that of the rhodium, cobalt, and iron analogues [TMCH 2 ] + (TM = Fe, Co, and Rh), which were determined to have the carbene structures. Besides the cycloaddition/dehydrogenation reaction in forming the [TMC 3 H 4 ] + + H 2 (TM = Ir and Os) products, a second reaction pathway producing the [TMC 2 H 2 ] + ion and CH 4 via triple hydrogen atom transfer reactions to the carbyne carbon is observed to be the major channel. The latter channel is not observed in the rhodium, cobalt, and iron carbene cation reactions. Quantum-chemical calculations indicate that the distinct reactivity is not due to different initial structures of the reactants. Both reaction channels are predicted to be thermodynamically exothermic and kinetically facile for the carbyne cations, and the reactions proceed with the initial formation of a carbene intermediate via hydride-carbyne coupling. The latter channel is also exothermic but kinetically unfavorable for the rhodium, cobalt, and iron carbene cations.

The boron carbonyl cluster cations in the form of B 3 (CO) n + ( n = 4-6) are produced and studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region in the gas phase. Their geometric structures are determined with the aid of density functional theory calculations. The B 3 (CO) 4 + cation is characterized to have a D 2 d (OC) 2 B═B═B(CO) 2 structure and 1 A 1 electronic ground state with a linear boron skeleton. The B 3 (CO) 5 + cation is determined to have a chain boron framework with C 2 v symmetry. The B 3 (CO) 6 + cation is a weakly bound CO-tagged complex involving a B 3 (CO) 5 + ion core. Bonding analysis reveals that B 3 (CO) 4 + has a chemical bonding pattern similar to allene, while bonding in B 3 (CO) 5 + is similar to that in allyl anion.

Fe-Zn and Co-Zn heteronuclear carbonyl cation complexes are produced via a laser vaporization supersonic cluster source in the gas phase. The dinuclear FeZn(CO) 5 + and CoZn(CO) 7 + cation complexes are observed to be the most intense heterodinuclear carbonyl cation species in the mass spectra. The infrared spectra are obtained via mass selection and infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Their geometric and electronic structures are assigned with the support of density functional calculations. The FeZn(CO) 5 + complex is determined to have a (OC) 5 Fe-Zn structure with a Fe-Zn half bond. The CoZn(CO) 7 + ion is established to have a staggered (OC) 4 Co-Zn(CO) 3 structure involving a Co-Zn σ single bond.

Heteronuclear transition metal carbonyl cluster cations FeM(CO)8(+) (M = Co, Ni and Cu) and MCu(CO)7(+) (M = Co and Ni) are produced via a laser vaporization supersonic cluster ion source in the gas phase, which are each mass-selected and studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Their geometric and electronic structures are established by comparison of the experimental spectra with those derived from density functional theoretical calculations. The FeM(CO)8(+) (M = Co, Ni, Cu) complexes are determined to have eclipsed (CO)5Fe-M(CO)3(+) structures, and the MCu(CO)7(+) (M = Co, Ni) ions are characterized to have staggered (CO)4M-Cu(CO)3(+) structures. Natural bonding orbital analysis indicates that the positive charge is mainly distributed on the M(CO)3 fragment. The metal-metal interaction involves an σ-type (OC)4,5M→M(CO)3(+) dative bonding.

Infrared photodissociation spectra are measured for mass-selected cation complexes with a chemical formula [MC7O6](+) (M = Fe, Co, Ni) formed via pulsed laser evaporation of metal target in expansions of helium gas seeded by CO. The geometries of the complexes are determined by comparison of the experimental spectra with the simulated spectra from density functional calculations. All of these complexes are identified to have [M(CO)4(C3O2)](+) structures involving a carbon suboxide ligand, which binds the metal center in an η(1) fashion. The antisymmetric CO stretching vibration of C3O2 is slightly red-shifted upon coordination. The donor-acceptor bonding interactions between C3O2 and the metal centers are analyzed using the EDA-NOCV method. The results show that M ← C3O2 σ donation is stronger than the M → C3O2 π back-donation in these cation complexes.

The infrared spectra of mass-selected Ni(O2)n(+) (n = 2-4) and their argon-tagged complexes are measured by infrared photodissociation spectroscopy in the gas phase. The experimental spectra provide distinctive patterns allowing the determination of their geometric and electronic structures by comparison with the simulated vibrational spectra from density functional theory calculations. The [Ni(O2)2Ar2](+) cation complex was determined to have D2h symmetry involving a Ni(O2)2(+) core ion with two equivalent superoxide ligands side-on bound to a Ni(3+) cation center. The higher Ni(O2)3(+) and Ni(O2)4(+) cation complexes were determined to have structures with a chemically bound Ni(O2)2(+) core ion that is weakly coordinated by neutral O2 molecule(s).

Mass-selected heteronuclear iron-copper carbonyl cluster anions CuFe(CO)n(-) (n = 4-7) are studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region in the gas phase. The cluster anions are produced via a laser vaporization supersonic cluster ion source. Their geometric structures are determined by comparison of the experimental spectra with those calculated by density functional theory. The experimentally observed CuFe(CO)n(-) (n = 4-7) cluster anions are characterized to have (OC)4Fe-Cu(CO)n-4 structures, each involving a C3v symmetry Fe(CO)4(-) building block. Bonding analysis indicates that the Fe-Cu bond in the CuFe(CO)n(-) (n = 4-7) cluster anions is a σ type single bond with the iron center possessing the most favored 18-electron configuration. The results provide important new insight into the structure and bonding of hetronuclear transition metal carbonyl cluster anions.

The [M(NO)n](+) cation complexes (M = Au and Ag) are studied for exploring the coordination and bonding between nitric oxide and noble metal cations. These species are produced in a laser vaporization supersonic ion source and probed by infrared photodissociation spectroscopy in the NO stretching frequency region using a collinear tandem time-of-flight mass spectrometer. The geometric and electronic structures of these complexes are determined by comparison of the distinctive experimental spectra with simulated spectra derived from density functional theory calculations. All of these noble metal nitrosyl cation complexes are characterized to have bent NO ligands serving as one-electron donors. The spectrum of [Au(NO)2Ar](+) is consistent with 2-fold coordination with a near linear N-Au-N arrangement for this ion. The [Au(NO)n](+) (n = 3-4) cations are determined to be a mixture of 2-fold coordinated form and 3- or 4-fold coordinated form. In contrast, the spectra of [Ag(NO)n](+) (n = 3-6) provide evidence for the completion of the first coordination shell at n = 5. The high [Au(NO)n](+) and [Ag(NO)n](+) (n ≥ 3 for Au, n ≥ 4 for Ag) complexes each involve one or more (NO)2 dimer ligands, as observed in the copper nitrosyl cation complexes, indicating that ligand-ligand coupling plays an important role in the structure and bonding of noble metal nitrosyl cation complexes.

Infrared spectra of mass-selected oxygen-rich iron dioxygen complexes Fe(O2)n(+) with n = 3-5 are measured via infrared photodissociation spectroscopy in the gas phase. These cation complexes are produced via a laser vaporization supersonic ion source. The structures are established by comparison of the experimental spectra with the simulated spectra derived from density functional calculations. All of the Fe(O2)n(+) complexes studied have a single IR-active band in the 1050-1100 cm(-1) region, arising from the O-O stretching vibration of the superoxo ligand(s). These complexes are determined to have structures with a chemically bound Fe(O2)2(+) core ion that is weakly coordinated by neutral O2 molecules. The Fe(O2)2(+) core ion has a planar D2h symmetry with two equivalent side-on superoxo ligands bound to an Fe(3+) cation center.

Infrared spectra of mass-selected homoleptic cobalt carbonyl cluster cations including dinuclear Co2(CO)8(+) and Co2(CO)9(+), trinuclear Co3(CO)10(+) and Co3(CO)11(+), as well as tetranuclear Co4(CO)12(+) are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The geometric structures of these complexes are determined by comparison of the experimental spectra with those calculated by density functional theory. The Co2(CO)8(+) cation is characterized to have a Co-Co bonded structure with Cs symmetry involving a bridging CO ligand. The Co2(CO)9(+) cation is determined to be a mixture of the CO-tagged Co2(CO)8(+)-CO complex and the Co(CO)5(+)-Co(CO)4 ion-molecular complex. The Co3(CO)10(+) cation is the coordination-saturated trinuclear cluster, which is characterized to have a triangle Co3 core with C2 symmetry involving two edge-bridging and eight terminal CO ligands. The Co3(CO)11(+) cation is a weakly bound complex involving a Co3(CO)10(+) core ion. The Co4(CO)12(+) cluster cation is deduced to have a tetrahedral Co4(+) core structure with three edge-bridging and nine terminal carbonyls.

Infrared spectra of mass-selected homoleptic copper carbonyl cluster cations including dinuclear Cu2(CO)6(+) and Cu2(CO)7(+), trinuclear Cu3(CO)7(+), Cu3(CO)8(+), and Cu3(CO)9(+), and tetranuclear Cu4(CO)8(+) are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The structures are established by comparison of the experimental spectra with simulated spectra derived from density functional calculations. The Cu2(CO)6(+) cation is characterized to have an unbridged D3d structure with a Cu-Cu half bond. The Cu2(CO)7(+) cation is determined to be a weakly bound complex involving a Cu2(CO)6(+) core ion. The trinuclear Cu3(CO)7(+) and Cu3(CO)8(+) cluster cations are determined to have triangle Cu3 core structures with C2 symmetry involving two Cu(CO)3 groups and one Cu(CO)x group (x = 1 or 2). In contrast, the trinuclear Cu3(CO)9(+) cluster cation is determined to have an open chain-like (OC)3Cu-Cu(CO)3-Cu(CO)3 structure. The tetranuclear Cu4(CO)8(+) cluster cation is characterized to have a tetrahedral Cu4(+) core structure with all carbonyl groups terminally bonded.

Mononuclear and dinuclear titanium carbonyl cation complexes including Ti(CO)(6)(+), Ti(CO)(7)(+), TiO(CO)(5)(+), Ti(2)(CO)(9)(+) and Ti(2)O(CO)(9)(+) are produced via a laser vaporization supersonic cluster source. The ions are mass selected in a tandem time-of-flight mass spectrometer and studied with infrared photodissociation spectroscopy in the CO stretching frequency region. The structures are established by comparison of the experimental spectra with simulated spectra derived from density functional calculations. Only one IR band is observed for the 15-electron Ti(CO)(6)(+) cation, which is characterized to have an octahedral O(h) structure. The Ti(CO)(7)(+) cation is determined to be a weakly bound complex involving a Ti(CO)(6)(+) core ion instead of the seventh coordinated ion. The TiO(CO)(5)(+) cation has a completed coordination sphere with a C(4v) structure. The Ti(2)(CO)(9)(+) cation is determined to have a doublet C(s) structure with two four-electron donor side-on bridging CO groups and one semibridging CO group. The Ti(2)O(CO)(9)(+) cation has a doublet C(s) structure involving a planar cyclic Ti(2)O(η(2)-μ-CO) core with a four electron donor side-on bridging CO. Bonding analysis indicates that the Ti(2)(CO)(9)(+) and Ti(2)O(CO)(9)(+) cations each have a Ti-Ti single bond. The results suggest that metal-metal multiple bonding is not favorable, and the oxophilic titanium centers failed to satisfy the 18-electron configuration in these metal carbonyl complexes.

Infrared spectra of mass-selected homoleptic dinuclear chromium carbonyl cluster cations Cr(2)(CO)(n)(+) with n = 7-9 are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region in the gas phase. The structures are established by comparison of the experimental spectra with the simulated spectra derived from density functional calculations. The Cr(2)(CO)(n)(+) cluster cations are characterized to have the (OC)(5)Cr-C-O-Cr(CO)(n-6)(+) structures with a linear bridging carbonyl group bonded to one chromium atom through its carbon atom and to the other chromium atom through its oxygen atom. The cluster cations all have a sextet ground state with the positive charge and the unpaired electrons located on the Cr(CO)(n-6) moiety. The formation of the linear bridging structures without Cr-Cr bonding can be rationalized that chromium forms strong Cr-CO bonds but weak Cr-Cr bonds.

The reactions of beryllium atoms with dioxygen were reinvestigated by matrix isolation infrared absorption spectroscopy. Besides the previously reported linear OBeO and cyclic Be(2)O(2) molecules, two interconvertible beryllium ozonide complexes were prepared and characterized. The BeOBe(η(2)-O(3)) complex was formed on annealing, which is characterized to be a side-on bonded ozonide complex with a planar C(2v) structure. The BeOBe(η(2)-O(3)) complex isomerized to the BeOBe(η(1)-O(3)) isomer under visible light excitation, which is an end-on bonded ozonide complex with planar C(s) symmetry. These two isomers are interconvertible; that is, visible light induces the conversion of the side-on bonded complex to the end-on bonded isomer, and vice versa on annealing. In addition, evidence is also presented for the linear BeOBeOBe cluster.

The reactions of tantalum monoxide (TaO) and dioxide (TaO(2)) molecules with methanol in solid neon were investigated by infrared absorption spectroscopy. The ground-state TaO molecule reacted with CH(3)OH in forming the CH(3)OTa(O)H molecule via the hydroxylic hydrogen atom transfer from methanol to the metal center spontaneously on annealing. The observation of the spontaneous reaction is consistent with theoretical predictions that the OH bond activation process is both thermodynamically exothermic and kinetically facile. In contrast, the TaO(2) molecule reacted with CH(3)OH to give primarily the TaO(2)(CH(3)OH) complex, which further rearranged to the CH(3)OTa(O)OH isomer via the hydroxylic hydrogen atom transfer from methanol to one of oxygen atom of metal dioxide upon visible light excitation.

The reactions of molecular tantalum and niobium monoxides and dioxides with water were investigated by matrix isolation infrared spectroscopy. In solid neon, the metal monoxide and dioxide molecules reacted with water to form the MO(H(2)O) and MO(2)(H(2)O) (M = Ta, Nb) complexes spontaneously on annealing. The MO(H(2)O) complexes photochemically rearranged to the more stable HMO(OH) isomers via one hydrogen atom transfer from water to the metal center under visible light excitation. In contrast, the MO(2)(H(2)O) complexes isomerized to the more stable MO(OH)(2) molecules via a hydrogen atom transfer from water to one of the oxygen atoms of metal dioxide upon visible light irradiation. The aforementioned species were identified by isotopic-substituted experiments as well as density functional calculations.

The reactions of magnesium atoms with dioxygen and dioxygen/carbon monoxide mixture have been investigated by matrix isolation infrared absorption spectroscopy. Magnesium atoms react with dioxygen in solid argon to form the inserted MgO(2) molecules under UV excitation, which were previously characterized. Annealing allows the dioxygen molecules to diffuse and to react with MgO(2) and form the magnesium bisozonide complex, Mg(O(3))(2), which is proposed to be coordinated by two argon atoms in solid argon matrix. The Mg(O(3))(2)(Ar)(2) complex is characterized to have two equivalent side-on bonded ozonide ligands with a D(2h) symmetry. The coordinated argon atoms can be replaced by carbon monoxide to give the magnesium bisozonide dicarbonyl complex, Mg(O(3))(2)(CO)(2), a neutral magnesium carbonyl complex with CO binding to the Mg(2+) center.

The reaction of tantalum dioxide molecule with dinitrogen has been studied by matrix isolation infrared spectroscopy. The tantalum dioxide molecules produced from laser evaporation of bulk Ta(2)O(5) target reacted with dinitrogen to form the TaO(2)(eta(1)-NN)(x) (x = 1-3) complexes on annealing, in which the N(2) ligands are end-on bonded to the tantalum metal center. The TaO(2)(eta(1)-NN)(3) complex decomposed to TaO(2)(eta(1)-NN)(2) under infrared irradiation. The TaO(2)(eta(1)-NN)(2) and TaO(2)(eta(1)-NN)(3) complexes rearranged to the less stable TaO(2)(eta(1)-NN)(eta(2)-N(2)) and TaO(2)((eta(1)-NN)(2)(eta(2)-N(2)) isomers under visible light excitation. Both the mono- and bis-dinitrogen complexes were predicted to have (2)A' or (2)A(1) ground states arising from the (2)A(1) ground state of TaO(2), whereas the two tridinitrogen complexes were predicted to have (2)B(2) ground states with C(2v) symmetry, which are derived from the (2)B(1) excited state of TaO(2).

The copper atom reacts with dioxygen in solid argon to form a mononuclear copper dioxygen complex Cu(eta(2)-O(2))(eta(1)-O(2))(2) bearing both side-on and end-on bonded O(2) ligands. The complex is characterized as being a trisuperoxide species with the copper center in its unusual +3 oxidation state. The Cu(III) trisuperoxide complex loses an end-on bonded superoxo ligand in forming the copper bisdioxygen complex under infrared irradiation.

A manganese atom reacts with dioxygen to form the previously characterized MnO 2 molecule in solid argon under UV-visible light irradiation. Subsequent sample annealing allows the dioxygen molecules to diffuse and to react with MnO 2 to give the (eta (2)-O 2)MnO 2 complex, which is characterized to be a side-on bonded peroxo manganese dioxide complex. The manganese tetraoxide MnO 4, which was predicted to be less stable than the (eta (2)-O 2)MnO 2 isomer, was not observed. However, the (eta (2)-O 2)MnO 2 complex reacts with another weakly coordinated dioxygen to give the (eta (2)-O 2)MnO 4 complex via visible light irradiation, in which the manganese tetraoxide is coordinated and stabilized by a side-on bonded O 2 molecule. Manganese dimer reacts with dioxygen to form the cyclic Mn(mu-O) 2Mn cluster spontaneously upon annealing, which further reacts with dioxygen to give the (eta (2)-O 2) 2Mn(mu-O) 2Mn cluster, a side-on bonded disuperoxide complex with a planar D 2 h structure.

Binary nickel, palladium, and platinum nitrous oxide complexes Ni(NNO)x, Pd(NNO)x (x = 1, 2), and PtNNO have been produced by the reactions of laser-evaporated metal atoms with nitrous oxide in solid argon. The complexes were identified on the basis of isotopically substituted infrared absorptions as well as theoretical frequency calculations. These complexes were characterized to have structures with the terminal N atom of N(2)O bound to the metal atoms. The MNNO complexes are photosensitive and rearrange to OMNN or MO + N(2) upon ultraviolet-visible irradiation.

The reactions of niobium and tantalum monoxides and dioxides with methane have been investigated using matrix isolation infrared spectroscopic and theoretical calculations. The niobium and tantalum oxide molecules were prepared by laser evaporation of Nb(2)O(5) and Ta(2)O(5) bulk targets. The niobium monoxide molecule interacted with methane to form the ONb(CH(4)) complex, which was predicted to have C(3)(v)() symmetry with the metal atom coordinated to three hydrogen atoms of the methane molecule. The ONb(CH(4)) complex rearranged to the CH(3)Nb(O)H isomer upon 300 nm < lambda < 580 nm irradiation. The analogous OTa(CH(4)) complex was not observed, but the CH(3)Ta(O)H molecule was produced upon UV irradiation. The niobium and tantalum dioxide molecules reacted with methane to form the O(2)Nb(CH(4)) and O(2)Ta(CH(4)) complexes with C(s)() symmetry, which underwent photochemical rearrangement to the CH(3)Nb(O)OH and CH(3)Ta(O)OH isomers upon ultraviolet irradiation.

Scandium monoxide-dinitrogen complexes-OSc(N2), OScNN, and OScNN+-have been prepared by the reactions of laser-evaporated scandium monoxide with N2 or scandium atoms with N2O in solid argon. The ground-state scandium monoxide molecule reacted with N2 to form the side-bonded OSc(N2) complex spontaneously on annealing. This complex rearranged to the end-on bonded OScNN complex upon UV irradiation. Both the OSc(N2) and OScNN complexes in solid argon can be assigned to have 2A' ' electronic ground state with Cs symmetry arising from the 2Delta first excited-state ScO. The neutral complexes can also be photoionized to the OScNN+ cation complex upon UV irradiation.

Hydrido scandium hydroxide dinitrogen complexes, (eta2-N2)Sc(H)OH and (eta1-NN)xSc(H)OH (x = 1, 2), have been prepared by the reactions of laser-ablated scandium atoms with H2O/N2 mixtures in solid argon. The end-on bonded (eta1-NN)xSc(H)OH (x = 1, 2) complexes were formed spontaneously on annealing, whereas the side-bonded (eta2-N2)Sc(H)OH complex was generated on broad-band irradiation. These complexes were characterized by infrared absorption spectroscopy as well as density functional theoretical calculations.