Formation and Characterization of Homoleptic Thorium Isocyanide

Article pubs.acs.org/IC

Formation and Characterization of Homoleptic Thorium Isocyanide Complexes Xiuting Chen,†,‡ Qingnuan Li,† Yu Gong,*,†,§ Lester Andrews,§ Benjamin K. Liebov,§ Zongtang Fang,∥ and David A. Dixon*,∥ †

Department of Radiochemistry, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China University of Chinese Academy of Sciences, Beijing 100049, China § Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, United States ∥ Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487-0336, United States ‡

S Supporting Information *

ABSTRACT: Homoleptic thorium isocyanide complexes have been prepared via the reactions of laser-ablated thorium atoms and (CN)2 in a cryogenic matrix, and the structures of the products were characterized by infrared spectroscopy and theoretical calculations. Thorium atoms reacted with (CN)2 under UV irradiation to form the oxidative addition product Th(NC)2, which was calculated to have closed-shell singlet ground state with a bent geometry. Further reaction of Th(NC)2 and (CN)2 resulted in the formation of Th(NC)4, a molecule with a tetrahedral geometry. Minor products such as ThNC and Th(NC)3 were produced upon association reactions of CN with Th and Th(NC)2. Homoleptic thorium cyanide isomers Th(CN)x (x = 1−4) are predicted to be less stable than the corresponding isocyanides. The C−N stretches of thorium cyanides were calculated to be between 2170 and 2230 cm−1 at the B3LYP level, more than 120 cm−1 higher than the N−C stretches of isocyanides and with much weaker intensities. No experimental absorptions appeared where Th(CN)x should be observed.

■

INTRODUCTION The coordination chemistry of transition metal cyanides is wellunderstood, and both carbon-bound terminal and bridging coordination modes have been identified for the CN− ligand in a number of complexes.1−4 For the actinides, a series of thorium and uranium cyanide complexes have been synthesized and structurally characterized, where ligated complexes of thorium and uranium are always coordinated by the cyano group at the carbon center.5,6 Although the diatomic cyano ligand can bind to a transition metal center via nitrogen to form isocyanide complexes,7 such structures are only identified in the bulk for the actinides of polynuclear cyanide complexes with U−CN−U and Th−CN−Th bridging linkages.5,6 Examples of actinide isocyanides with terminal −NC coordination are uncommon. A thorium complex with a terminal isocyano ligand can be obtained via the reaction of imido thorium metallocene and Me3SiCN/Ph2CO.8 Other examples of thorium isocyanides are limited to the HThNC and CH3ThNC molecules prepared from the reactions of laser-ablated thorium atoms with HCN and CH3CN in solid argon.9,10 Both complexes were characterized to be isocyanides based on infrared spectroscopy and density functional calculations. The formation of a IVU complex with two axial U−NC linkages via the reaction of IVU precursor and cyanide salts in nonaqueous solution has been reported.11 Straka et al.12 have studied the bonding in UF4(CN)2 and UF4(NC)2 using density functional theory © 2017 American Chemical Society

with single-point CCSD(T) energies and showed that the isocyanide formed a stronger interaction with U(VI) than does the cyanide. They also showed that the cyano group is a strong σ donor and moderate π acceptor so that it does not interact well with U(VI) at the carbon end. In addition, they noted that the nitrogen end is a better π donor so it interacts with the d0f0 U(VI) better than does the carbon end. Dicyanogen13 (CN)2 is an ideal oxidative addition reagent for the preparation of CN-coordinated metal complexes.14 Recently, we were able to prepare a series of binary uranium isocyanide complexes by reactions of laser-ablated uranium and (CN)2 in solid argon.15 Three major products, UNC, U(NC)2, and U(NC)4, were identified via matrix infrared spectroscopy and electronic structure calculations. Insertion of the NC−CN bond to form binary U−NC complexes is facilitated under UV irradiation. In the current work, we expand on the reactions of cyanogen by reacting laser-ablated thorium atoms with (CN)2 and observing the products by matrix infrared spectroscopy. Binary complexes in the form of Th(NC)x were identified via their characteristic infrared absorptions with the help of vibrational frequencies obtained from electronic structure calculations. Received: January 22, 2017 Published: April 19, 2017 5060

DOI: 10.1021/acs.inorgchem.7b00196 Inorg. Chem. 2017, 56, 5060−5068

Article

Inorganic Chemistry

■

EXPERIMENTAL AND COMPUTATIONAL METHODS

The experimental apparatus and procedure for investigating laserablated thorium atom reactions with (CN)2 during condensation in excess argon or neon at 4 K have been described previously.16,17 The Nd:YAG laser fundamental (Continuum II, 1064 nm, 10 Hz repetition rate with 10 ns pulse width) was focused onto a freshly cleaned thorium target mounted on a rotating rod. Laser-ablated thorium atoms were codeposited with argon or neon (research grade) containing 0.1%, 0.5%, or 1% (CN)2 gas prepared in this laboratory. We employed thermal decomposition of AgCN at 360−380 °C in the bottom of a stainless steel finger (0.5 in. o.d.) until a constant pressure was reached in a stainless steel vacuum line to generate the cyanogen.14 The product gas was condensed at 77 K, and the system was evacuated before use. Isotopic reagents were synthesized using K13CN and KC15N (99% enriched, Cambridge Isotopic Laboratories) and silver nitrate to prepare Ag13CN and AgC15N as reagents, which were dried by ethanol rinses and heating to 100 °C under vacuum. Fourier transform infrared (FTIR) spectra were recorded at 0.5 cm−1 resolution on a Nicolet 750 FTIR instrument with a HgCdTe range B detector. Matrix samples were annealed at different temperatures and cooled back to 4 K for spectral acquisition. Selected samples were subjected to broad-band photolysis by a medium-pressure mercury arc street lamp (Philips, 175W) with the outer globe removed. Geometry optimization of the Th(NC)n and Th(CN)n (n = 1−4) complexes was performed at the density functional theory (DFT)18 level with the B3LYP19,20 hybrid exchange-correlation functional and with the aug-cc-pVTZ basis set21 on C and N and the cc-pVTZ-PP basis set on Th.22 Vibrational frequencies were calculated to characterize the global minimum on the potential energy surface and to obtain the zero-point energy corrections (ZPEs). The unscaled calculated frequencies are reported. We do not use scaling factors from (CN)2 because this species differs from thorium isocyanide complexes and because of the different effects of the matrix on the different species. Multiple spin states were tried to obtain the spin state with the lowest energy. As a test of the functional, calculations were also performed with the PBE23,24 and PW9125,26 functionals which gave the same energy ordering and similar frequencies. The optimized geometries with the B3LYP functional were used for single-point calculations at the CCSD(T)27−30 level with the aug-cc-pVXZ basis set on C and N and the cc-pVXZ-PP basis set on Th (X = D, T, Q), and the energies were extrapolated to the complete basis set (CBS) limit.31 These basis sets are denoted as aX. The open-shell calculations were calculated with the R/UCCSD(T) approach where a restricted openshell Hartree−Fock (ROHF) calculation was initially performed and the spin constraint was then relaxed in the coupled cluster calculation.32,33 The DFT calculations were done with the program Gaussian0934 and the CCSD(T) calculations were done with the program MOLPRO.35,36

■

Figure 1. Infrared spectra in the product absorption regions from reaction of the laser-ablated thorium atom with (CN)2 in excess argon at 4 K: (a) Th and 1% (CN)2 codeposited for 1 h, (b) after annealing to 20 K, (c) after full arc (λ > 220 nm) irradiation, (d) after annealing to 25 K, (e) after annealing to 30 K, and (f) Th and 0.1% (CN)2 codeposited for 1 h followed by full arc irradiation and annealing to 30 K. The asterisk denotes Th(NC)3 tentatively assigned. The intensity of the CNCN absorption in the 0.1% (CN)2 experiment is twice as much as that in the 1% (CN)2 experiment, most likely due to the differences in the laser energy.

addition to these peaks, a weak feature at 1995.6 cm−1 also appeared after sample annealing. To investigate the concentration dependence of the product absorptions, experiments were repeated by using 0.1% (CN)2 in Ar. The infrared spectrum from 30 K annealing after broadband irradiation is shown in Figure 1, trace f. Despite the absence of the feature at 2014.6 cm−1 and dramatic decrease of the 2000.8 cm−1 peak, new absorptions at 1995.6, 1991.5, 1979.3, and 1977.8 cm−1 were observed but with much lower intensities than those observed with 1% (CN)2 in Ar. Experiments with pure and mixed isotopic samples (13CN)2, 12 ( CN)2 + (13CN)2, (12CN)2 + NC13CN + (13CN)2, (C14N)2 + NCC15N + (C15N)2, and (C15N)2 samples were performed to help identify the reaction products. Mixed 1:1 (12CN)2 + (13CN)2 samples enable the identification of the products resulting from multiple (CN)2 molecules, while scrambled (12CN)2 + NC13CN + (13CN)2 and (C14N)2 + NCC15N + (C15N)2 samples are crucial for the identification of products with one or two CN ligands. The infrared spectra from the reaction products of thorium atoms with isotopically substituted (CN)2 samples in an argon matrix are shown in Figure 2 with all the frequencies observed in the experiments listed in Table 1. Complementary experiments in a neon matrix were also performed as shown in Figure S1. In addition to the weak common absorptions due to CNCN,42 ThO (887.1 cm−1), and ThO2 (756.8 cm−1),43 three new product bands were observed at 2009.0, 1998.4, and 1979.1 cm−1. Annealing to 8 K produced satellites at 2007.4 and 1976.1 cm−1. Next, broad-band irradiation (λ > 220 nm) increased the 1998.4 cm−1 band more than the others as did its argon matrix counterpart at 2000.8 cm−1. Annealing to 11 K sharpened these bands and markedly increased the 1976.1 cm−1 band. Infrared spectra from the reactions of thorium and (12CN)2 + (13CN)2, (12CN)2 + NC13CN + (13CN)2, (C14N)2 + (C15N)2, and (C14N)2 + NCC15N + (C15N)2 samples are also shown in Figure S1, and the band positions are listed in Table 2.

RESULTS AND DISCUSSION

Summary of IR Experiments. Figure 1 illustrates Th and (CN)2 reaction products in solid argon using samples with 1.0% and 0.1% (CN)2. Products common to previous U/(CN)2 experiment are the strong CNCN parent isomer band at 2054.2 cm−1,37 the weak CN radical absorption at 2044.2 cm−1,38 and a weak CNNC peak at 1997.0 cm−1.39 Weak absorptions due to ThO2 (787.1 and 735.1 cm−1) were also observed.40,41 With 1% (CN)2 in Ar, new thorium product absorptions appeared at 2014, 2001, 1991, and 1978 cm−1, which slightly sharpened upon annealing to 20 K. The intensity of the 2014 cm−1 peak remained unchanged upon broad-band irradiation (λ > 220), while the other three bands increased significantly. The 2014, 2001, and 1991 cm−1 absorptions sharpened and shifted to 2014.6, 2000.8, and 1991.5 cm−1 when the sample was further annealed to 25 and 30 K. The 1978 cm−1 band split into two peaks at 1979.3 and 1977.8 cm−1 upon sample annealing. In 5061


Article

Inorganic Chemistry

when scrambled (12CN)2 + NC13CN + (13CN)2 reagent was used (Figure 2, traces c and d). A similar intermediate peak was observed at 1960.1 cm−1 in the (C14N)2 + NCC15N + (C15N)2 experiment (Figure 2, trace e). Note that a weak peak at 1995.6 cm−1 tracked with the 1977.8 cm−1 band throughout the experiments, and it shifted to 1956.7 and 1965.4 cm−1 with 12 C/13C and 14N/15N ratios of 1.0199 and 1.0154. Intermediate peaks at 1981.4 and 1983.0 cm−1 were observed with (12CN)2 + NC13CN + (13CN)2 and (C14N)2 + NCC15N + (C15N)2 samples. The isotopic ratios as well as the single intermediate peak for both 1977.8 and 1995.6 cm−1 bands confirm the involvement of two equivalent C−N ligands in the absorber, and they can be assigned to the antisymmetric and symmetric mix of the two CN stretching modes of Th(NC)2. These values are close to where the CN groups absorb in U(NC)2 at 2028.5 and 2020.0 cm−1.15 Analogous triplets at 1976.1, 1941.5, 1935.8 and 1976.1, 1950.2, 1945.3 cm−1 were observed when thorium reacted with (12CN)2 + NC13CN + (13CN)2 and (C14N)2 + NCC15N + (C15N)2 in a neon matrix (Figure S1), suggesting that the 1976.1 cm−1 band corresponds with the 1977.8 cm−1 band in an argon matrix. The neon counterpart of the 1995.6 cm−1 band is too weak to be observed. As shown in Figure S1, the 1979.1 cm−1 band favored at 8 K is probably a less stable matrix trapping site of the 1976.1 cm−1 band which dramatically increased after annealing to 11 K. Th(NC)3. The weak band at 2014.6 cm−1 in argon is tentatively assigned to Th(NC)3. The 12C/13C and 14N/15N isotopic ratios for this band are very close to what we observed for the other binary thorium isocyanide complexes. The intermediate absorptions with mixed and scrambled experiments were not well-resolved due to their weak intensities and band overlaps. In the neon matrix, the counterpart for the 2014.6 cm−1 band was observed at 2009.0 cm−1. Th(NC)4. The 2000.8 cm−1 absorption shifted to 1960.8 and 1971.2 cm−1 upon 13C and 15N substitutions. The isotopic ratios of 1.0204 and 1.0150 indicate it is due to a CN stretching mode. Experiments with mixed 1:1 (12CN)2 + (13CN)2 sample revealed a triplet at 2000.8, 1970.4, and 1960.8 cm−1 with the intensity of the intermediate band being lower than those of the pure isotopomers (Figure 2, trace c). The spectra from the reactions of thorium and scrambled 1:2:1 (12CN)2 + NC13CN + (13CN)2 and (C14N)2 + NCC15N + (C15N)2 samples are complicated due to band overlaps as well as the low intensities of the intermediate peaks. The isotopic patterns indicate the absorber should involve four equivalent CN ligands, as demonstrated in some transition metal oxide complexes with tetrahedral geometries.46,47 Since U(NC)4 absorbs at 1989.4 cm−1,15 the 2000.8 cm−1 absorption in the

Figure 2. Infrared spectra in the product absorption regions from reaction of the laser-ablated thorium atoms with isotopically substituted (CN)2 in excess argon at 4 K. Spectra were taken after full arc (λ > 220 nm) irradiation followed by annealing to 25 K (a) 1% (12CN)2, (b) 1% (13CN)2, (c) 1% (12CN)2 + 1% (13CN)2, (d) 0.25% (12CN)2 + 0.5% NC13CN + 0.25% (13CN)2, (e) 0.25% (C14N)2 + 0.5% NCC15N + 0.25% (C15N)2, and (f) 1% (C15N)2.

ThNC. The triatomic ThNC molecule absorbs at 1991.5 cm−1 in Ar. The isotopic frequency ratios for this band are characteristic of a CN stretch. No intermediate absorption (the term intermediate absorption means a mixed isotopic product absorption between two pure isotopic product absorptions) was observed in any mixed and scrambled experiments (Figure 2), suggesting the involvement of only one CN ligand in the product molecule. As shown in Figure 1, the survival of more ThNC and Th(NC)2 when (CN)2 was lowered from 1% to 0.1% further supports the assignment of these complexes resulting from a single (CN)2 molecule. The corresponding neon counterpart was not observed experimentally most likely due to the low trapping efficiency of simple molecules in a softer matrix such as neon, as observed in other systems.44 Th(NC)2. The broad peak around 1978 cm−1 became more intense and split into two peaks at 1977.8 and 1979.3 cm−1 (the molecule is found in two local different matrix environments known as trapping sites)45 after annealing to 25 K following broad-band irradiation. The 1977.8 cm−1 band shifted to 1937.7 and 1947.2 cm−1 upon 13C and 15N substitutions with isotopic shifts of 1.0207 and 1.0157, suggesting it should be due to a CN stretching vibration. No intermediate absorptions were observed when thorium reacted with a mixed (12CN)2 + (13CN)2 sample while a new peak appeared at 1951.6 cm−1

Table 1. Infrared Absorptions (cm−1) Observed for Products from the Reactions of Th with (CN)2 in Excess Argon molecule

a

(12CN)2

(13CN)2

(12CN)2 + (13CN)2

(12CN)2 + NC13CN + (13CN)2 a

ThNC

1991.5

1951.4

1991.5, 1951.5

1991.5, 1951.6

Th(NC)2

1995.6, 1977.8 (1979.3)b

1956.7, 1937.7 (1939.2)b

1995.6, 1956.9, 1977.9, 1937.8

Th(NC)3 Th(NC)4

2014.6 2000.8

1974.0 1960.8

b 2000.8, 1970.4, 1960.8

1995.6, 1981.4, 1956.9a 1977.8, 1951.6a 1937.8 b b

(C15N)2

(C14N)2 + NCC15N + (C15N)2

1960.2

1991.5, 1960.2a 1995.6, 1983.0, 1965.4a 1977.8, 1960.1a 1947.2 b b

1965.4, 1947.2 (1948.5)b 1983.8 1971.2

Overlap with other absorptions. bNot well-resolved. Absorptions due to different trapping sites are listed in parentheses. 5062


Article

Inorganic Chemistry

Table 2. Infrared Absorptions (cm−1) Observed for Products from the Reactions of Th with (CN)2 in Excess Neon after Annealing to 11 K molecule Th(NC)2 Th(NC)3 Th(NC)4 a

(12CN)2 1976.1 2009.0 1998.4

(12CN)2 + (13CN)2 1976.1, 1935.8 b 1998.4, 1968.8, 1958.5

(12CN)2 + NC13CN + (13CN)2 1976.1, 1941.5, 1935.8 b 1998.4, 1973.4, 1968.8, 1963.6, 1958.5

(C14N)2 + (C15N)2 a

1976.1, 1945.3 b 1998.4, 1975.4,a 1966.6

(C14N)2 + NCC15N + (C15N)2 1976.1,a 1950.2, 1945.3 b 1998.4, 1981.7, 1975.4,a 1970.7, 1966.6

Overlap with other absorptions. bNot well-resolved.

argon matrix is assigned to the homoleptic Th(NC)4 complex based on the band positions. This is also consistent with the CN stretching frequencies for other neutral thorium isocyanide complexes.8−10 Note that the intensity of the 2000.8 cm−1 band is significantly reduced in the experiment with 0.1% (CN)2 (Figure 1, trace f), suggesting the involvement of multiple (CN)2 during the formation of the absorber, consistent with the results from mixed and scrambled isotopic experiments. The neon counterpart of the 2000.8 cm−1 band was observed at 1998.4 cm−1 with 12C/13C and 14N/15N shifts of 1.0204 and 1.0162. Well-resolved triple and quintuple splittings were observed in the experiments with mixed (12CN)2 + (13CN)2, (C14N)2 + (C15N)2 and scrambled (12CN)2 + NC13CN + (13CN)2, (C14N)2 + NCC15N + (C15N)2 samples (Figure S1), which further supports the assignment of Th(NC)4 with tetrahedrally coordinated CN ligands. Electronic Structure Calculations: Energies. To support the experimental assignments, frequency calculations at the density functional theory level using different exchangecorrelation functionals were performed for binary Th(CN)1−4 complexes. The thorium isocyanide Th(NC)1−4 and cyanide Th(CN)1−4 isomers were both calculated. The ground states of all of the thorium isocyanide isomers are predicted to be more stable than the ground-state cyanide isomers with the energy differences increasing from ThNC/ThCN to Th(NC)4/Th(CN)4 as shown in Figure 3. The triatomic ThNC and ThCN molecules have linear, doublet ground states with ThNC more stable by 9 kcal/mol than ThCN. Both quartets are about 20 kcal/mol higher in energy than 2ThNC. Both Th(NC)2 and Th(CN)2 complexes are predicted to be singlets with C2v symmetry with Th(CN)2 less stable by 16 kcal/mol. The triplet state for Th(NC)2 is about 6 kcal/mol higher in energy than the singlet, and the triplet for Th(CN)2 is about 12 kcal/mol higher in energy than the corresponding singlet. With ligands like F, Cl, and NC, the singlet ground state has been predicted to be lower than the triplet for a series of two-coordinate thorium(II) complexes, some of which have been identified in a cryogenic matrix.48−51 Both Th(NC)3 and Th(CN)3 are predicted to have doublet ground states with D3h symmetry for the former and C3v symmetry for the latter. Th(NC)3 is more stable than Th(CN)3 by 22 kcal/mol. The computations for Th(NC)4 and Th(CN)4 predict a closed-shell singlet ground state with a tetrahedral geometry. Th(NC)4 is more stable than Th(CN)4 by 30 kcal/ mol. The experimental NC−CN bond energy is 136.7 ± 1.6 kcal/ mol, significantly higher than that in other hydrocarbons with C−C bonds,52 due to the presence of some double-bond character in the NC−CN bond.14 The individual Th−NC bond dissociation energies are about 120 kcal/mol, ranging from 117 to 124 kcal/mol (Table 3). Thus, formation of ThNC can only occur on UV irradiation from the lamp or the plume from laser ablation of the metal target during sample deposition, which also involves UV and vacuum UV irradiation,53,54 as its bond

Figure 3. Predicted structures for Th(NC)x and Th(CN)x for x = 1− 4. The cyano compounds are all higher in energy than the isocyano compounds. The Th atoms are in light blue, N atoms in dark blue, and C atoms in gray. The numerical value after the cyano compound is the energy difference (kcal/mol) between the cyano and isocyano compounds at the CCSD(T)/CBS level.

dissociation energy is less than that of cyanogen. The reaction of cyanogen to form Th(NC)2 is highly exothermic, −106 kcal/ mol. The reaction of Th(NC)2 with a second (CN)2 to form Th(NC)4 has a high comparable exothermicity of −105 kcal/ mol. This reaction is then favored at high (CN)2 concentration. Th(NC)3 can be formed by addition of (CN)2 to ThNC in a similar highly exothermic reaction. Th(NC)3 can also be formed by UV irradiation of Th(NC)4. Due to the low concentration of CN versus (CN)2 or the need to generate the Th(NC)2 and Th(NC)4 followed by photolysis, the yield of both ThNC and Th(NC)3 is expected to be much lower than that of Th(NC)2 and Th(NC)4. Electronic Structure Calculations: Frequencies. Calculations at the B3LYP level predict a higher CN stretch at 2170.5 cm−1 with low IR intensity for ThCN, whereas the corresponding absorption for ThNC was predicted at 2071.5 cm−1 with a much higher intensity of 555 km/mol (Table 4). The experimentally observed band at 1991.5 cm−1 fits the computed results for ThNC better than ThCN, supporting our assignment of ThNC. The difference in the calculated and experimental frequency is due in part to matrix effects and to the neglect of anharmonicity in the harmonic frequency calculations. The respective computed 12C/13C and 14N/15N 5063


Article

Inorganic Chemistry

Table 3. Calculated Reaction Energies (kcal/mol) for NC Bonded to Th at the CCSD(T), B3LYP, PBE, and PW91 Levels

a

molecule

CCSD(T)/CBS

CCSD(T)/aQ

CCSD(T)/aT

CCSD(T)/aD

B3LYP

PBE

PW91

2CN → (CN)2a Th + (CN)2 → Th(NC)2 ThNC + (CN)2 → Th(NC)3 Th(NC)2 + (CN)2 → Th(NC)4 Th + CN → Th(NC) Th(NC)2 + CN → Th(NC)3 Th(NC) + CN → Th(NC)2 Th(NC)3 + CN → Th(NC)4

−135.1 −106.2 −107.9 −104.8 −117.3 −119.0 −124.0 −121.0

−134.7 −106.3 −107.7 −104.6 −117.1 −118.6 −123.8 −120.7

−133.8 −106.5 −107.6 −104.3 −116.8 −117.8 −123.5 −120.3

−127.6 −108.8 −108.5 −104.5 −114.9 −114.6 −121.6 −117.5

−140.6 −106.6 −106.0 −103.0 −123.4 −122.8 −123.8 −120.8

−140.1 −102.3 −100.4 −96.9 −121.9 −120.0 −120.5 −117.0

−140.6 −103.9 −101.8 −98.0 −122.9 −120.8 −121.6 −117.8

The reaction energy is −136.4 kcal/mol at CCSD(T)/CBS level with core−valence electrons correlated.

Table 4. Calculated DFT Isocyanide N−C Stretches (cm−1, Unscaled) and Intensities (km/mol) for NC Bonded to Tha molecule

PG

B3LYP, asym

Th(NC) 2 Th(N13C) 2 Th(15NC) 1 Th(NC)2 1 Th(N13C)2 1 Th(15NC)2 2 Th(NC)3 2 Th(N13C)3 2 Th(15NC)3 1 Th(NC)4 1 Th(N13C)4 1 Th(15NC)4 1 Th(N13C)2(N12C)2

C∞v

2071.5 (555) σ 2030.1(549) σ 2037.9(524) σ 2039.0 (813) b2 1997.3 (804) b2 2006.7 (767) b2 2061.4 (1886) e′ 2019.6(1870) e′ 2028.4(1773) e′ 2057.4 (2674) t2 2015.8 (2655) t2 2024.4 (2514) t2 2015.8 (885) b2 2027.2 (734) a1 2057.4 (891) b1

2

a

C2v

D3h

Td

C2v

B3LYP, sym

PBE, asym

2057.0 (51) a1 2015.8 (51) a1 2023.6 (48) a1 2086.9 (0) a1′ 2045.7(0) a1′ 2052.5(0) a1′ 2092.8 (0) a1 2052.0 (0) a1 2057.9 (0) a1 2081.8 (154) a1

1995.6 1956.0 1963.0 1929.6 1889.3 1899.6 1984.4 1944.2 1952.5 1982.8 1942.8 1950.8 1942.8 1953.8 1982.8

(530) (524) (501) (425) (419) (403) (1882) (1796) (1705) (2549) (2532) (2397) (844) (702) (850)

PBE, sym

1948.1 1908.4 1917.0 2010.0 1970.5 1976.7 2017.3 1978.0 1983.5 2006.6

(4) (4) (3) (0) (0) (0) (0) (0) (0) (145)

PW91, asym 1946.1 1906.4 1915.3 1941.0 1900.8 1910.6 1989.7 1949.5 1957.7 1986.8 1946.7 1954.7 1946.7 1957.8 1986.8

(215) (215) (202) (469) (462) (444) (1809) (1793) (1702) (2551) (2532) (2400) (844) (703) (850)

PW91, sym

1959.3 (12) 1919.7 (12) 1927.9 (11) 2015.4 (0) 1975.8 (0) 1982.0 (0) 2021.4 (0) 1982.1 (0) 1987.5(0) 2010.7 (145)

asym = asymmetric stretch; sym = symmetric stretch.

cm−1, consistent with the 2000.8 cm−1 absorption observed experimentally. Frequency calculations on the Th(N12C)2(N13C)2 isotopomer predict four absorptions at 2015.8 (b2), 2027.2 (a1), 2057.4 (b1), and 2081.8 (a1) cm−1, with the first three being the splitting of the triply degenerate stretch due to the isotopic substitution. The higher frequency a1 band derived from the symmetric stretch is predicted to be substantially weaker. These absorptions are almost the same as those of Th(N12C)4 and Th(13CN)4; three absorptions with relative intensities of approximately 5:2:5 should be observed.46,55 A similar pattern was observed in the mixed isotopic experiments, which further supports the assignment of Th(NC)4. The less stable Th(CN)4 isomer possesses a Td symmetry and singlet ground state as well with an infrared active absorption calculated at 2227.2 cm−1 and an intensity lower by a factor of 3. We have recently reported the formation of UNC, U(NC)2, and U(NC)4;15 the structures of these uranium isocyanides are very similar to those of the Th(NC)x complexes characterized here. For both uranium and thorium, the isocyanide complexes are always more stable than the cyanide isomers. The N−C bond lengths for the isocyanides are slightly longer than the C− N bonds for cyanides. Computed frequencies at the B3LYP level of theory revealed that the N−C stretches for U(NC)x and Th(NC)x (x = 1−4) appear below 2100 cm−1 while the C−N stretches for U(CN)x and Th(CN)x (x = 2−4) are predicted to be significantly higher and weaker, mostly above 2200 cm−1. Ground-state UCN and ThCN complexes were predicted to absorb at 2169 and 2170.5 cm−1 with negligible

isotopic ratios of 1.020 and 1.016 (Supporting Information) also agree well with the experimental values. The antisymmetric and symmetric N−C stretching vibrational frequencies for singlet Th(NC)2 were predicted to be at 2039.0 and 2057.0 cm−1 with a relative intensity of 16:1, in reasonable agreement with the experimental values of 1977.8 and 1995.6 cm−1. The differences in the calculated and experimental frequencies are consistent with the values for ThNC. The respective computed 12C/13C and 14N/15N frequency ratios for the asymmetric combination stretch are 1.020 and 1.016 and for the symmetric combination stretch are 1.020 and 1.017, consistent with the experimental values (Tables 1, 2, and 4). In addition, frequency calculations of Th(NC)(N13C) revealed two C−N stretching modes at 2004.6 and 2050.0 cm−1 with 2:1 relative intensity, which fit nicely with the 1951.6 and 1981.4 cm−1 absorptions produced when thorium reacted with (12CN)2 + NC13CN + (13CN)2. Compared with the frequencies of Th(NC)2, the two C−N stretching modes of singlet Th(CN)2 are predicted to be 2200.3 and 2201.7 cm−1, which are too high to match the experimental values. Frequency calculations revealed a doubly degenerate C−N stretching mode at 2061.4 cm−1 for the isocyanide Th(NC)3 and 2219.5 cm−1 for the cyanide isomer Th(CN)3. The experimental absorption at 2014.6 cm−1 is much closer to where Th(NC)3 absorbs. For Th(NC)4, a very intense triply degenerate antisymmetric N−C stretching vibration was predicted at 2057.4 cm−1 together with an infrared inactive symmetric stretch at 2092.8 5064


Article

Inorganic Chemistry Table 5. NBO6 Population Analysis (B3LYP) for the Lowest Energy States of Th(NC)n for n = 1−4 molecule 2

ThNC ThNC 1 Th(NC)2 3 Th(NC)2 2 Th(NC)3 1 Th(NC)4

(C2v) (C2v) (D3h) (Td)

1 3 0 2 1 0

(C2v) (C2v) (C3v) (Td)

1 3 0 2 1 0

4

2

ThCN ThCN 1 Th(CN)2 3 Th(CN)2 2 Th(CN)3 1 Th(CN)4

spin, excess electron config

4

(7s26d1) (7s16d2) (7s0.76d1.2) (7s0.56d0.5)

(7s26d1) (7s16d2) (7s0.656d1.1) (7s0.56d0.5)

7s total pop spin (α, β) Isocyano Derivatives 1.85 (0.91, 0.94) 0.92 (0.89, 0.02) 1.63 0.80 (0.76, 0.04) 0.60 (0.54, 0.06) 0.13 Cyano Derivatives 1.60 (0.86, 0.75) 0.95 (0.92, 0.05) 1.56 0.86 (0.75, 0.10) 0.60 (0.52, 0.08) 0.31

5f total pop spin (α, β) 0.26 0.20 0.18 0.17 0.21 0.28

(0.20, 0.05) (0.18, 0.02)

0.18 0.11 0.13 0.23 0.18 0.23

(0.15, 0.03) (0.08, 0.02)

(0.11, 0.06) (0.12, 0.09)

(0.19, 0.04) (0.11, 0.07)

6d total pop spin (α, β) 1.13 2.00 0.72 1.53 1.07 0.90

(1.01, 0.12) (1.92, 0.08)

1.49 2.14 0.99 1.58 1.31 1.15

(1.09, 0.40) (2.03, 0.11)

(1.36, 0.17) (0.78, 0.29)

(1.34, 0.24) (0.93, 0.21)

be expected, 4ThNC has a 7s16d2 electron configuration and has slightly less 5f orbital population. 1Th(NC)2 has 1.6 electrons spin-paired in the Th 7s orbital and 0.7 electrons spin-paired on the 6d, so the formal +II oxidation state is mostly 7s2. There are only 0.2 e in the 5f orbitals on Th. For 1 Th(CN)2, the 7s and 5f populations decrease and the 6d population increases relative to the diisocyano isomer. On the other hand, 2Th(NC)3 splits the single excess spin between the 7s and the 6d due to the presence of some spin pairing in the 6d. Again, the tricyano isomer has more 6d character than does the triisocyano isomer. For 1Th(NC)4, in the formal +IV oxidation state, the Th has very little 7s character, about 0.9 e in the 6d and 0.28 e in the 5f due to back-bonding. The tetracyano isomer has more 7s and 6d character than does the tetraisocyano isomer. The NPA charge for the isocyano compounds show that the charge on the Th is always more positive than that for the cyano compounds and that the difference in the charge increases with increasing the number of CN ligands. The CN bond distance is shorter in the cyanide compounds and longer in the isocyanides consistent with the higher CN stretch in the former. Coupled with this is the fact that the Th− C bond distance is 0.14 Å longer than the Th−N bond distance showing that the Th is interacting more strongly with the isocyanide than with the cyanide. In addition, the positive charge on the Th (Supporting Information) in the isocyanides is larger than on the cyanides. Thus, there is more negative charge on the NC in the isocyanides than on the CN in the cyanides. The isocyanides are highly polarized with a charge of about −1.1 e on the N and a positive charge of ∼0.35 e on the C. In contrast, the charges on the C and N are both about equal and negative in ThCN. Thus, the electrostatic and dipolar interactions are larger in the isocyanides than in the cyanides. As a consequence, the isocyanide bonding interactions are larger than in the cyanides and the isocyanides are more stable with shorter Th−N bond lengths and longer NC bond distances. These results are essentially the same as found for the uranium cyano/isocyano species.15

intensities. Such differences in the vibrational frequencies for both isomers are consistent with the computational results on the first row transition metal cyanides and isocyanides, where the C−N stretching frequencies for isocyanides were predicted to be 100 cm−1 lower than those of cyanides.7 On the basis of the good agreement between experimental and computed frequencies of isocyanides as well as the absence of cyanide isomers in the experiments, the band positions of cyanide/ isocyanide species can serve as fingerprints in identifying the coordination mode of the CN ligand in a neutral complex. A series of ligated thorium cyanide complexes has been synthesized and characterized by crystallography.5,6 The experimentally determined C−N bond lengths in these ligated thorium cyanide complexes are usually around 1.16 Å, close to our computed values of 1.181−1.183 Å for the N−C bonds in Th(NC)x complexes. It is interesting to note that the observed C−N stretching vibrational frequencies for compounds with ThIV−CN or ThIV−CN−ThIV moieties fall between 2070 and 2110 cm−1,6,56 which are close to those of structurally characterized CeIII and UIV isocyanides.11,57 In contrast, the C−N stretches of neutral Th(NC)x and Th(CN)x complexes are predicted to be different by at least 100 cm−1 higher at the B3LYP level. If the cyanide molecules were formed in these experiments, they would appear over 2100 cm−1 (2115 cm−1 for ThCN and >2150 cm−1 for the others), where no new product absorption was detected. In addition to the homoleptic complexes identified in our experiments, the N−C vibrational frequencies of actinide bearing molecules such as HThNC (1999 cm−1) and CH3ThNC (2035 cm−1) are lower than those computed for HThCN and CH3ThCN as well,9,10 suggesting that the large frequency difference is common between neutral cyanide and isocyanide. Since the reported ligated complexes containing ThCN moieties are all negative anions,5,6,56 it appears that the charge of the whole complexes not only plays a role on the C−N vibrational frequencies, but affects the coordination mode of the CN ligand as well. Electronic Structures. The results of the natural bond orbital/natural population analysis (NBO/NPA)58−61 are given in Table 5 and show that the electron configuration of the 2 ThNC ground state has a 7s26d1. (See the Supporting Information for the NBO populations. The NBO6 program was used.62,63) The 2ThCN has basically the same electron configuration, but there is more 6d orbital character and less 7s orbital character on the Th as well as less 5f character. As would

■

CONCLUSIONS

A series of homoleptic thorium isocyanide complexes has been prepared via the reactions of laser-ablated thorium atoms and (CN)2 in a cryogenic matrix, and the products were identified by infrared spectroscopy with isotopic labeling. Theoretical 5065


Article

Inorganic Chemistry calculations at the density functional theory level aided in the assignment of the vibrational spectra and prediction of the molecular geometries and electronic properties. Initially, thorium atoms react with (CN)2 under UV irradiation leading to the formation of the oxidative addition product Th(NC)2 with Th in the formal +II oxidation state in a highly exothermic reaction. The diisocyanide is predicted to have a closed-shell singlet ground state with both the NThN and ThNC bond angles being nonlinear. The dicyano isomer is 16 kcal/mol higher in energy. The reaction of Th(NC)2 with another (CN)2 leads to the formation of tetrahedral Th(NC)4 with the Th in the formal +IV oxidation in a highly exothermic reaction; the tetracyano isomer is 30 kcal/mol higher in energy. Dissociation of (CN)2 leads to the formation of the CN radical which can react with Th and Th(CN)2 leading to the respective formation of the minor products ThNC and Th(NC)3, again by highly exothermic reactions. No experimental absorptions appeared where Th(CN)x are predicted to be observed, and the CN stretches in the cyano compounds are predicted to be significantly weaker in terms of the infrared intensity than those of the isocyano compounds. The NPA charges show that the first electron to be lost for Th(I) is a 6d for ThNC, and that the Th(II) in Th(NC)2 is mostly in the 7s2 state. In Th(NC)3, the excess spin is split between the 7s and the 6d with more on the 6d, so Th(III) has more like an s0.5d0.5 configuration. The Th in Th(NC)4 has back-bonding into the 6d and is clearly in the +IV oxidation state. There is always 0.2−0.3 e back-bonding into the 5f orbitals independent of the oxidation state. The isocyanides have a more ionic interaction between the Th and the NC than in the cyanides leading to stronger Th−N bonds in the isocyanides than the Th−C in the cyanides. The Th−NC bond dissociation energies are all similar and quite strong, 120 ± 4 kcal/mol. The results for these isolated isocyano Th compounds are very similar to what was found previously for the corresponding uranium isocyanides. The fact that isocyanides are formed over cyanides for Th is consistent with predictions of the energy difference between UF4(CN)2 and UF4(NC)2 which favors the isocyanide.12 We note that, for both the Th and U compounds, the preference for isocyanide or cyanide bonding to the metal is dependent on the charge on the metal which is governed in part by the nature of any other ligands that are present.

■

David A. Dixon: 0000-0002-9492-0056 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by the “Strategic Priority Research Program” and “Frontier Science Key Program” of the Chinese Academy of Science (Grant No. XDA02030000 and QYZDYSSW-JSC016) (X.C., Q.L., Y.G.), “Young Thousand Talented Program” (Y.G.), and retirement funds from TIAA (L.A.). D.A.D. acknowledges the Department of Energy, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences, Heavy Element Program via a subcontract from Argonne National Laboratory for support of the computational work. D.A.D. also thanks the Robert Ramsay Chair Endowment of The University of Alabama for support.

■

(1) Pike, R. D. Structure and Bonding in Copper (I) Carbonyl and Cyanide Complexes. Organometallics 2012, 31, 7647−7660. (2) Vahrenkamp, H.; Gei, A.; Richardson, G. N. Cyanide-Bridged Oligonuclear Complexes: Features and Attractions. J. Chem. Soc., Dalton Trans. 1997, 3643−3652. (3) Tanase, S.; Reedijk, J. Chemistry and Magnetism of Cyanidobridged d-f Assemblies. Coord. Chem. Rev. 2006, 250, 2501−2510. (4) Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochmann, M. Advanced Inorganic Chemistry, 6th ed.; John Wiley & Sons: New York, 1999. (5) Berthet, J. C.; Thuéry, P.; Ephritikhine, M. Advances in f-Element Cyanide Chemistry. Dalton Trans. 2015, 44, 7727−7742. (6) Herve, A.; Thuery, P.; Ephritikhine, M.; Berthet, J.-C. Structural Diversity in Cyanido Thorocene Complexes. Organometallics 2014, 33, 2088−2098. (7) Rayón, V. M.; Redondo, P.; Valdés, H.; Barrientos, C.; Largo, A. Cyanides and Isocyanides of First-Row Transition Metals: Molecular Structure, Bonding, and Isomerization Barriers. J. Phys. Chem. A 2007, 111, 6334−6344. (8) Ren, W.; Zi, G.; Fang, D. C.; Walter, M. D. Thorium Oxo and Sulfido Metallocenes: Synthesis, Structure, Reactivity, and Computational Studies. J. Am. Chem. Soc. 2011, 133, 13183−13196. (9) Gong, Y.; Cho, H.-G.; Andrews, L. Reactions of Laser-Ablated U Atoms with HCN: Infrared Spectra in Solid Argon and Quantum Chemical Calculations for HUNC. Eur. J. Inorg. Chem. 2015, 2015, 2974−2981. (10) Cho, H.-G.; Andrews, L. Infrared Spectra of the η2-M(NC)CH3, CH3-MNC, and CH2:M(H)NC Complexes Prepared by Reactions of Thorium and Uranium Atoms with Acetonitrile. Organometallics 2012, 31, 535−544. (11) Hervé, A.; Bouzidi, Y.; Berthet, J. C.; Belkhiri, L.; Thuéry, P.; Boucekkine, A.; Ephritikhine, M. UIII−CN versus UIV−NC Coordination in Tris(silylamide) Complexes. Inorg. Chem. 2015, 54, 2474−2490. (12) Straka, M.; Patzschke, M.; Pyykkö, P. Why Are Hexavalent Uranium Cyanides Rare While U−F and U−O bonds Are Common and Short? Theor. Chem. Acc. 2003, 109, 332−340. (13) Dewar, J.; Jones, J. O. XXVI. The Chemical Reactions of Nickel Carbonyl. Part I. Reactions with the Halogens and Other Inorganic Substances. J. Chem. Soc., Trans. 1904, 85, 203−212. (14) Corain, B. The Coordination Chemistry of Hydrogen Cyanide, Cyanogen, and Cyanogen Halides. Coord. Chem. Rev. 1982, 47, 165− 200. (15) Gong, Y.; Andrews, L.; Liebov, B. K.; Fang, Z.; Garner, E. B., III; Dixon, D. A. Reactions of Laser-ablated U atoms with (CN)2: Infrared Spectra and Electronic Structure Calculations of UNC, U(NC)2, and U(NC)4 in Solid Argon. Chem. Commun. 2015, 51, 3899−3902. (16) Andrews, L.; Citra, A. Infrared Spectra and Density Functional Theory Calculations on Transition Metal Nitrosyls. Vibrational

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.7b00196. Complete citations for refs 34 and 36, infrared spectra from reactions of thorium and (CN)2 in neon, NBO population analysis, relative energies of the different isomers, complete sets of calculated vibrational frequencies, total energies, and geometries (x, y, z Cartesian coordinates in angstroms) (PDF)

■

REFERENCES

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Yu Gong: 0000-0002-8847-1047 Lester Andrews: 0000-0001-6306-0340 5066


Article

Inorganic Chemistry Frequencies of Unsaturated Transition Metal Nitrosyls. Chem. Rev. 2002, 102, 885−911. (17) Andrews, L. Matrix Infrared Spectra and Density Functional Calculations of Transition Metal Hydrides and Dihydrogen Complexes. Chem. Soc. Rev. 2004, 33, 123−132. (18) Parr, R. G.; Yang, W. Density Functional Theory of Atoms and Molecules; Oxford University Press: New York, 1989. (19) Becke, A. D. Density-functional Thermochemistry. III. The Role of Exact Exchange. J. Chem. Phys. 1993, 98, 5648−5652. (20) Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti Correlation-Energy Formula into a Functional of the Electron Density. Phys. Rev. B: Condens. Matter Mater. Phys. 1988, 37, 785−789. (21) Kendall, R. A.; Dunning, T. H., Jr.; Harrison, R. J. Electron Affinities of the First-Row Atoms Revisited. Systematic Basis Sets and Wave Functions. J. Chem. Phys. 1992, 96, 6796−6806. (22) Peterson, K. A. Correlation consistent basis sets for actinides. I. The Th and U atoms. J. Chem. Phys. 2015, 142, 074105. (23) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865−3868. (24) Errata to reference 23. Phys. Rev. Lett. 1997, 78, 1396. (25) Perdew, J. P.; Wang, Y. Accurate and Simple Analytic Representation of the Electron Gas Correlation Energy. Phys. Rev. B: Condens. Matter Mater. Phys. 1992, 45, 13244−13249. (26) Burke, K.; Perdew, J. P.; Wang, Y. Derivation of a Generalized Gradient Approximation: The PW91 Density Functional. In Electronic Density Functional Theory: Recent Progress and New Directions; Dobson, J. F., Vignale, G., Das, M. P., Eds.; Plenum Press: New York, 1998; pp 81−111. (27) Purvis, G. D., III; Bartlett, R. J. A Full Coupled-Cluster Singles and Doubles Model: The Inclusion of Disconnected Triples. J. Chem. Phys. 1982, 76, 1910−1918. (28) Raghavachari, K.; Trucks, G. W.; Pople, J. A.; Head-Gordon, M. A Fifth-Order Perturbation Comparison of Electron Correlation Theories. Chem. Phys. Lett. 1989, 157, 479−483. (29) Watts, J. D.; Gauss, J.; Bartlett, R. J. Coupled-Cluster Methods with Non-iterative Triple Excitations for Restricted Open-Shell Hartree-Fock and Other General Single-Determinant Reference Functions. Energies and Analytical Gradients. J. Chem. Phys. 1993, 98, 8718−8733. (30) Bartlett, R. J.; Musial, M. Coupled-Cluster Theory in Quantum Chemistry. Rev. Mod. Phys. 2007, 79, 291−352. (31) Peterson, K. A.; Woon, D. E.; Dunning, T. H., Jr. Benchmark Calculations with Correlated Molecular Wave Functions. IV. The Classical Barrier Height of the H + H2 → H2 + H Reaction. J. Chem. Phys. 1994, 100, 7410−7415. (32) Deegan, M. J. O.; Knowles, P. J. Perturbative Corrections to Account for Triple Excitations in Closed and Open Shell Coupled Cluster Theories. Chem. Phys. Lett. 1994, 227, 321−326. (33) Rittby, M.; Bartlett, R. J. An Open-Shell Spin-Restricted Coupled Cluster Method: Application to Ionization Potentials in N2. J. Phys. Chem. 1988, 92, 3033−3036. (34) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; et al. Gaussian 09, revision B.01; Gaussian, Inc.: Wallingford, CT, 2009. (35) Werner, H.-J.; Knowles, P. J.; Knizia, G.; Manby, F. R.; Schütz, M. Molpro: a General-Purpose Quantum Chemistry Program Package. WIREs Comput. Mol. Sci. 2012, 2, 242−253. (36) Knowles, P. J.; Manby, F. R.; Schütz, M.; Celani, P.; Knizia, G.; Korona, T.; Lindh, R.; Mitrushenkov, A.; Rauhut, G.; Adler, T. B.; et al. MOLPRO, version 2010.1, a package of ab initio programs. (37) Maier, G.; Reisenauer, H. P.; Eckwert, J.; Sierakowski, C.; Stumpf, T. Matrix Isolation of Diisocyanogen, CNNC. Angew. Chem., Int. Ed. Engl. 1992, 31, 1218−1220. (38) Lanzisera, D. V.; Andrews, L. Reactions of Laser-Ablated Beryllium Atoms with Hydrogen Cyanide in Excess Argon. FTIR Spectra and Quantum Chemical Calculations on BeCN, BeNC, HBeCN, and HBeNC. J. Am. Chem. Soc. 1997, 119, 6392−6398.

(39) Stroh, F.; Winnewisser, B. P.; Winnewisser, M.; Reisenauer, H. P.; Maier, G.; Goede, S. J.; Bickelhaupt, F. Matrix-Isolation Infrared Investigation of the Flash Vacuum Thermolysis of Norbornadienone Azine. Chem. Phys. Lett. 1989, 160, 105−112. (40) Gabelnick, S. D.; Reedy, G. T.; Chasanov, M. G. Infrared Spectra and Structure of Some Matrix-Isolated Lanthanide and Actinide Oxides. J. Chem. Phys. 1974, 60, 1167−1171. (41) Andrews, L.; Gong, Y.; Liang, B.; Jackson, V. E.; Flamerich, R.; Li, S.; Dixon, D. A. Matrix Infrared Spectra and Theoretical Studies of Thorium Oxide Species: ThOx and Th2Oy. J. Phys. Chem. A 2011, 115, 14407−14416. (42) Jacox, M. E.; Thompson, W. E. Infrared Spectroscopy and Photochemistry of NCCN+ and CNCN+ Trapped in Solid Neon. J. Chem. Phys. 2007, 126, 244311. (43) Gong, Y.; Zhou, M.; Andrews, L. Spectroscopic and Theoretical Studies of Transition Metal Oxides and Dioxygen Complexes. Chem. Rev. 2009, 109, 6765−808. (44) Wang, X.; Andrews, L.; Gagliardi, L. Infrared Spectra of ThH2, ThH4, and the Hydride Bridging ThH4(H2)x (x = 1−4) Complexes in Solid Neon and Hydrogen. J. Phys. Chem. A 2008, 112, 1754−1761. (45) Ning, X. J.; Qin, Q. Z. Trapping Site Structures of O3 Isolated in Argon Matrices. J. Chem. Phys. 1999, 111, 7047−7052. (46) Gong, Y.; Zhou, M. Formation and Characterization of the Oxygen-Rich Hafnium Dioxygen Complexes: OHf(η2-O2)(η2-O3), Hf(η2-O2)3, and Hf(η2-O2)4. J. Phys. Chem. A 2007, 111, 8973−8979. (47) Gong, Y.; Zhou, M.; Kaupp, M.; Riedel, S. Formation and Characterization of the Iridium Tetroxide Molecule with Iridium in the Oxidation State + VIII. Angew. Chem., Int. Ed. 2009, 48, 7879−7883. (48) Gong, Y.; Andrews, L. Matrix Infrared Spectroscopic and Density Functional Theoretical Investigations on Thorium and Uranium Atom Reactions with Dimethyl Ether. Dalton Trans. 2011, 40, 11106−11114. (49) Thanthiriwatte, K. S.; Wang, X.; Andrews, L.; Dixon, D. A.; Metzger, J.; Vent-Schmidt, T.; Riedel, S. Properties of ThFx from Infrared Spectra in Solid Argon and Neon with Supporting Electronic Structure and Thermochemical Calculations. J. Phys. Chem. A 2014, 118, 2107−2119. (50) Vent-Schmidt, T.; Metzger, J.; Andrews, L.; Riedel, S. Investigation of Thorium Hydride Fluorides by Matrix-Isolation Spectroscopy. J. Fluorine Chem. 2015, 174, 2−7. (51) Thanthiriwatte, K. S.; Vasiliu, M.; Battey, S. R.; Lu, Q.; Peterson, K. A.; Andrews, L.; Dixon, D. A. Gas Phase Properties of MX2 and MX4 (X = F, Cl) for M = Group 4, Group 14, Ce, and Th. J. Phys. Chem. A 2015, 119, 5790−5803. (52) Luo, Y.-R. Comprehensive Handbook of Chemical Bond Energies; CRC Press, Taylor and Francis Group: Boca Raton, FL, 2007. (53) Flesch, R.; Schurmann, M. C.; Hunnekuhl, M.; Meiss, H.; Plenge, J.; Ruhl, E. A Pump-Probe Photoionization Mass Spectrometer Utilizing Tunable Extreme Ultraviolet Laser-Produced-Plasma Radiation. Rev. Sci. Instrum. 2000, 71, 1319−1324. (54) Gong, Y.; Andrews, L. Infrared Spectrum of the CH3OCH2 Radical in Solid Ar. J. Phys. Chem. A 2011, 115, 3029−3033. (55) Gong, Y.; Zhao, Y. Y.; Zhou, M.-F. Formation and Characterization of the Tetranuclear Scandium Nitride: Sc4N4. J. Phys. Chem. A 2007, 111, 6204−6207. (56) Hervé, A.; Garin, N.; Thuéry, P.; Ephritikhine, M.; Berthet, J. C. Bent Thorocene Complexes with the Cyanide, Azide and Hydride Lligands. Chem. Commun. 2013, 49, 6304−6306. (57) Hervé, A.; Bouzidi, Y.; Berthet, J. C.; Belkhiri, L.; Thuéry, P.; Boucekkine, A.; Ephritikhine, M. U−CN versus Ce−NC Coordination in Trivalent Complexes Derived from M[N(SiMe3)2]3 (M = Ce, U). Inorg. Chem. 2014, 53, 6995−7013. (58) Weinhold, F. Natural Bond Orbital Methods. In Encyclopedia of Computational Chemistry; Schleyer, P. v. R., Ed.; John Wiley & Sons: Chichester, U.K., 1998; Vol. 3, pp 1792−1811. (59) Weinhold, F.; Landis, C. R. Valency and Bonding: A Natural Bond Orbital Donor−Acceptor Perspective; University Press: Cambridge, U.K., 2003. 5067


Article

Inorganic Chemistry (60) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Intermolecular Interactions from a Natural Bond Orbital, Donor-Acceptor Viewpoint. Chem. Rev. 1988, 88, 899−926. (61) Reed, A. E.; Weinstock, R. B.; Weinhold, F. Natural Population Analysis. J. Chem. Phys. 1985, 83, 735−746. (62) Glendening, E. D.; Badenhoop, J. K.; Reed, A. E.; Carpenter, J. E.; Bohmann, J. A; Morales, C. M.; Landis, C. R.; Weinhold, F. Natural Bond Order 6.0 Homepage, Theoretical Chemistry Institute, University of Wisconsin, Madison, WI, 2013. http://nbo6.chem.wisc. edu/. (63) Glendening, E. D.; Landis, C. R.; Weinhold, F. NBO 6.0: Natural Bond Orbital Analysis Program. J. Comput. Chem. 2013, 34, 1429−1437.

5068


Formation and Characterization of Homoleptic Thorium Isocyanide

Recommend Documents