Ligation kinetics as a probe for gas-phase ligand field effects: Ligation of atomic transition metal cations with ammonia at room temperature

Abstract

The kinetics of ammonia ligation to atomic first and second row transition metal cations were measured in an attempt to assess the role of ligand field effects in gas-phase ion-molecule reaction kinetics. Measurements were performed at 295 AE 2 K in helium bath gas at 0.35 Torr using an inductively coupled plasma/selected-ion flow tube tandem mass spectrometer. The atomic cations were produced at ca. 5500 K in an inductively coupled plasma source and were allowed to decay radiatively and to thermalize by collisions with argon and helium atoms prior to reaction. A strong correlation was observed across the periodic table between the measured rate coefficients for ammonia ligation and measured/calculated bond dissociation energies. A similar strong correlation is seen with the ligand field stabilization energy. So ligand field stabilization energies should provide a useful predictor of relative rates of ligation of atomic metal ions.

Toward ICP‐SIFT mass spectrometry and atomic cation ligation as a probe of relativistic effects—A personal journey

“…Indeed, the observed trends in reaction efficiencies for ammonia addition to first‐ and second‐row atomic transition metal cations are seen to track the values of octahedral LFSE for ammonia ligation across the periodic table (see Figure 6) (Blagojevic et al, 2019b). The LFSE that arises from the interaction of the d‐orbitals of a transition metal ion with the ligand field contributes to the ion/ligand binding energy which in turn determines the kinetics of ion/ligand bond formation.…”

“…Comparison of measured reaction efficiencies (open squares) at 295 ± 2 K in He bath gas at 0.35 ± 0.01 Torr with experimental (full squares) and theoretical (full circles) binding energies (BE) for the ligation of first‐row atomic transition metal cations with ammonia (Blagojevic et al, 2019b)…”

“…In our experiments, atomic transition metal cations with no LFSE exhibit lower reaction efficiencies, up to a full order of magnitude, compared to the observed maxima in measured efficiencies for ligand addition across the periodic table. This implies that relative LFSE values may be (Blagojevic et al, 2019b) useful, especially when experimental or theoretical binding energies are unavailable, in the prediction of the relative reactivity of gas-phase metal cations in ligand addition reactions.…”

“…With the ICP as an atomic ion source, we now have surveyed reactions of up to 61 atomic cations each with 16 different molecules including O 2 (Koyanagi et al, 2002), NO (Blagojevic et al, 2005), D 2 O (Cheng et al, 2007), CO 2 (Koyanagi & Bohme, 2006), NO 2 (Jarvis et al, 2013), N 2 O (Lavrov et al, 2004), OCS (Blagojevic et al, 2018), CS 2 (Cheng et al, 2006a), NH 3 (Koyanagi, Kapishon, et al, 2010; Blagojevic et al, 2019b), CH 4 (Shayesteh et al, 2009), CH 3 F (Zhao et al, 2006), CH 3 Cl (Blagojevic et al, 2018), C 6 H 6 (Koyanagi & Bohme, 2003), C 6 F 6 (Caraiman et al, 2004), SF 6 (Cheng et al, 2009), and C 5 H 5 N (Blagojevic & Bohme, 2015). Surveys of lanthanide ions have been reported separately for N 2 O and O 2 (Koyanagi & Bohme, 2001), CO 2 and CS 2 (Cheng et al, 2006b), CH 3 Cl (Zhao et al, 2005), SF 6 (Cheng & Bohme, 2006), NO 2 (Jarvis et al, 2010), NH 3 (Koyanagi, Cheng, et al, 2010), and C 6 H 6 (Koyanagi et al, 2015).…”

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

“…A convenient summary of this study can be found at http://www.yorku.ca/dkbohme/research/selection_table.html. It includes studies of the cations of main group, transition metal, and lanthanide elements with O 2 (Koyanagi & Bohme, 2001; Koyanagi et al, 2002), CO 2 (Cheng et al, 2006a; Koyanagi & Bohme, 2006), OCS and CS 2 (Cheng et al, 2006a, 2006b), NO (Blagojevic et al, 2005, 2006), N 2 O (Koyanagi & Bohme, 2001; Lavrov et al, 2004), NO 2 (Jarvis et al, 2010, 2013), CH 4 (Shayesteh et al, 2009), NH 3 (Blagojevic et al, 2019a, 2019b; Koyanagi et al, 2010), D 2 O (Cheng et al, 2006c, 2007), CH 3 F (Koyanagi et al, 2005; Zhao et al, 2006), CH 3 Cl (Zhao et al, 2005), SF 6 (Cheng & Bohme, 2006; Cheng et al, 2009), C 6 H 6 (Blagojevic et al, 2015), C 6 F 6 (Caraiman et al, 2004), and C 5 H 5 N (Blagojevic & Bohme, 2015). In all cases, quantitative rate constants at 295 K and 0.35 Torr of He were obtained for metal cations generated by an inductively coupled plasma (ICP).…”