The bond energy of ReO+: Guided ion-beam and theoretical studies of the reaction of Re+ (7S) with O2

Abstract

The kinetic-energy dependence of the Re(+) + O2 reaction is examined using guided ion-beam mass spectrometry. The cross section for ReO(+) formation from ground state Re(+) ((7)S) is unusual, exhibiting two endothermic features. The kinetic energy dependence for ReO(+) formation is analyzed to determine D0(Re(+)-O) = 4.82 ± 0.05 eV, with the higher energy feature having a threshold 1.35 ± 0.28 eV higher in energy. This bond energy is consistent with much less precise values determined in the literature. Formation of ReO2(+) is also observed with a pressure dependent cross section, establishing that it is formed in an exothermic reaction of ReO(+) with O2. The nature of the bonding for ReO(+) and ReO2(+) is discussed and analyzed primarily using theoretical calculations at the B3LYP/def2-TZVPPD level of theory. The ground state of ReO(+) is identified as either (5)Π or (3)Δ, with the latter favored once estimates of spin-orbit splitting are included. Bond energies for ground state ReO(+) are calculated at this level as well as BP86 and CCSD(T,full) levels using several different basis sets. BP86 theoretical bond energies are higher than the experimental value, whereas B3LYP and CCSD(T,full) values are lower, although estimated spin-orbit corrections increase the latter close to experiment. Potential energy surfaces for the reaction of Re(+) with O2 are also calculated at the B3LYP/def2-TZVPPD level of theory and reveal that ground state Re(+) ((7)S) inserts into O2 by forming a Re(+)(O2) ((5)A") complex which can then couple with additional surfaces to form ground state ReO2(+) ((3)B1). Several explanations for the unusual dual endothermic features are explored, with no unambiguous explanation being evident. As such, this heavy metal system provides a very interesting experimental phenomenon of both adiabatic and nonadiabatic behavior.

Reactions of Th+ + H2, D2, and HD Studied by Guided Ion Beam Tandem Mass Spectrometry and Quantum Chemical Calculations

“…30 Similarly, CBS limit extrapolations using correlation consistent basis sets are also lower than the experimental value by 0.2 eV for several transition metal oxide cation BDEs. 91,92 For calculations involving several other ThL + species, it was found that high levels of theory, CCSDT(Q) and multireference configuration interaction (MRCI+Q) calculations, were necessary to reproduce experimental relative energies of the ground and excited states. Specific errors relative to the experimental difference between the ground and first excited state (0.08 eV) were 0.06 eV for CCSD(T), 0.03 eV for CCSDT(Q), and 0.01 5 eV for MRCI+Q.…”

Periodic trends in gas‐phase oxidation and hydrogenation reactions of lanthanides and 5d transition metal cations

“…These results are consistent with GIBMS studies of the 3d (Fisher et al, 1990) and 4d (Chen & Armentrout, 1995; Sievers, Chen, & Armentrout, 1996a) TM + (including the much lower reactivity of Mo + ). Comparable GIBMS results for the 5d TM + , Hf + –Au + , reacting with O 2 are collected in Figure 1 (Armentrout, 2013; Armentrout & Li, 2013; Hinton et al, 2009, 2013; Li et al, 2010; Zhang & Armentrout, 2003a). The results are consistent with those of Bohme in all cases.…”

“…Cross sections for reactions of O 2 with Hf + (red triangles), Ta + (black circles), W + (green inverted triangles) (Hinton et al, 2009), Re + (blue squares) (Armentrout, 2013), Os + (pink diamonds) (Hinton et al, 2013), Ir + (purple triangles) (Armentrout & Li, 2013), Pt + (red inverted triangles) (Zhang & Armentrout, 2003a), Au + ( 1 S) (yellow circles), and Au + ( 3 D) (yellow triangles) (Li et al, 2010) as measured using GIBMS. The arrow indicates the BDE of O 2 at 5.117 eV.…”

“…Thus, A′ and A″ surfaces do not mix efficiently and could lead to different reaction paths. Indeed, calculations of the potential energy surfaces for these reactions showed that surfaces of A′ and A″ symmetry are qualitatively different in the entrance channels for all three metals (Armentrout, 2013; Armentrout & Li, 2013; Hinton et al, 2013). For Re + , no low‐energy pathways are available along the A′ surfaces, whereas for Os + and Ir + , A″ surfaces have barriers in the entrance channels.…”

“…Low‐lying orbitals are the metal 5d nonbonding 1δ MO s, followed by the antibonding 2π and 3σ MO s. For TaO + and WO + , the additional electrons are placed in the 1δ MO leading to 3 Δ (1σ 2 1π 4 2σ 1 1δ 1 ) and 4 Σ − (1σ 2 1π 4 2σ 1 1δ 2 ) ground states that require no promotion (Hinton et al, 2009). For ReO + , the additional electron can be added to the 2σ, 1δ, or 2π MO s. Calculations indicate that both the 3 Δ (1σ 2 1π 4 2σ 1 1δ 3 ) and 5 Π (1σ 2 1π 4 2σ 1 1δ 2 2π 1 ) states are low‐lying, with corrections for spin‐orbit effects suggesting the former is the true ground state (by 0.16 eV at the CCSD(T)/CBS level) (Armentrout, 2013). In either case, the BDE is reduced either by the loss of exchange energy ( 3 Δ) or the occupation of the antibonding MO ( 5 Π).…”