A Combined Theoretical and Experimental Study of the Reaction Products of Laser-Ablated Thorium Atoms with CO:  First Identification of the CThO, CThO^-, OThCCO, OTh(η³-CCO), and Th(CO)_n (n = 1−6) Molecules

Abstract

Laser-ablated thorium atoms have been reacted with CO molecules during condensation in excess neon. Absorptions at 617.7 and 812.2 cm(-1) are assigned to Th-C and Th-O stretching vibrations of the CThO molecule. Absorptions at 2048.6, 1353.6, and 822.5 cm(-1) are assigned to the OThCCO molecule, which is formed by CO addition to CThO and photochemical rearrangement of Th(CO)(2). The OThCCO molecule undergoes further photoinduced rearrangement to OTh(eta(3)-CCO), which is characterized by C-C, C-O, and Th-O stretching vibrations at 1810.8, 1139.2, and 831.6 cm(-1). The Th(CO)(n) (n = 1-6) complexes are formed on deposition or on annealing. Evidence is also presented for the CThO(-) and Th(CO)(2)(-) anions, which are formed by electron capture of neutral molecules. Relativistic density functional theory (DFT) calculations of the geometry structures, vibrational frequencies, and infrared intensities strongly support the experimental assignments. It is found that CThO is an unprecedented actinide-containing carbene molecule with a triplet ground state and an unusual bent structure ( angleCThO = 109 degrees ). The OThCCO molecule has a bent structure while its rearranged product OTh(eta(3)-CCO) is found to have a unique exocyclic structure with side-bonded CCO group. We also find that both Th(CO)(2) and Th(CO)(2)(-) are, surprisingly, highly bent, with the angleC-Th-C bond angle being close to 50 degrees; the unusual geometries are the result of extremely strong Th-to-CO back-bonding, which causes significant three-centered bonding among the Th atom and the two C atoms.

Modeling intermediates in carbon monoxide coupling reactions using cyclooctatetraene thorium derivatives

“…Table 7 lists the CO dissociation energies for both the mononuclear derivatives (C 8 H 8 )Th(CO) n and the binuclear derivatives (C 8 H 8 ) 2 Th 2 (CO) n . For the mononuclear derivatives the CO dissociation energy from (C 8 H 8 )Th(CO) 5 to give (C 8 H 8 )Th(CO) 4 is rather low at B5 kcal mol À1 , whereas the CO dissociation energy from (C 8 H 8 )Th(CO) 4 to give (C 8 H 8 )Th(CO) 3 is much higher at B20 kcal mol À1 . This suggests that (C 8 H 8 )Th(CO) 4 is the favored species among the mononuclear cyclooctatetraene thorium carbonyls (C 8 H 8 )Th(CO) n .…”

“…The tetracarbonyl (C 8 H 8 ) 2 Th 2 (CO) 4 and the pentacarbonyl (C 8 H 8 ) 2 Th 2 (CO) 5 The chemically relevant energy surfaces of the dicarbonyl (C 8 H 8 ) 2 Th 2 (CO) 2 and the tricarbonyl (C 8 H 8 ) 2 Th 2 (CO) 3 are relatively simple since the CO groups either couple to form bridging m-C 2 O 2 ligands or remain as terminal CO groups. The energy surfaces of the carbonyl-richer structures (C 8 H 8 ) 2 Th 2 (CO) n (n = 4, 5) become more complicated.…”

Functionalization of Carbon Monoxide and tert‐Butyl Nitrile by Intramolecular Proton Transfer in a Bis(Phosphido) Thorium Complex

“…The reaction of (C 5 Me 5 ) 2 Th[PH(Mes)] 2 ,M es = 2,4,6-Me 3 C 6 H 2 ,w ith 1atm of CO yields (C 5 Me 5 ) 2 Th(k 2 -(O,O)-OCH 2 PMes-C(O)PMes),i n which one CO molecule is inserted into each thoriumphosphorus bond. [3][4][5][6][7][8][9] However,t hese characteristics make actinides well-suited for small molecule activation of oxygenated substrates. DFT calculations were employed to determine the lowest energy pathway.…”

“…[3][4][5][6][7][8][9] However,t hese characteristics make actinides well-suited for small molecule activation of oxygenated substrates. In contrast, the actinides are large,h ighly electropositive metals with minimal metal-ligand bonding interaction, and their valence orbitals have little need for p-acceptor ligands.T herefore,C Oi sapoor ligand for felements,w ith few examples.…”

“…In contrast, the actinides are large,h ighly electropositive metals with minimal metal-ligand bonding interaction, and their valence orbitals have little need for p-acceptor ligands.T herefore,C Oi sapoor ligand for felements,w ith few examples. [3][4][5][6][7][8][9] However,t hese characteristics make actinides well-suited for small molecule activation of oxygenated substrates. [10,11] While reductive coupling of CO is readily accomplished by low-valent f-element complexes such as U III , [12][13][14][15][16][17][18][19][20] Sm II , [21] and aL a III dinitrogen complex, [22] the most common reaction with CO is migratory insertion and CÀC bond formation.…”