Bond dissociation energies of diatomic transition metal selenides: ScSe, YSe, RuSe, OsSe, CoSe, RhSe, IrSe, and PtSe

Abstract

The diatomic transition metal selenides, MSe (M = Sc, Y, Ru, Os, Co, Rh, Ir, and Pt), were studied by resonant two-photon ionization spectroscopy near their respective bond dissociation energies. As these molecules exhibit high densities of vibronic states near their dissociation limits, the spectra typically appear quasicontinuously at these energies. Spin–orbit and nonadiabatic couplings among the multitudes of potential curves allow predissociation to occur on a rapid timescale when the molecule is excited to states lying above the ground separated atom limit. This dissociation process occurs so rapidly that the molecules are dissociated before they can be ionized by the absorption of a second photon. This results in an abrupt drop in the ion signal that is assigned as the 0 K bond dissociation energy for the molecule, giving bond dissociation energies of 4.152(3) eV (ScSe), 4.723(3) eV (YSe), 3.482(3) eV (RuSe), 3.613(3) eV (OsSe), 2.971(6) eV (CoSe), 3.039(9) eV (RhSe), 3.591(3) eV (IrSe), and 3.790(31) eV (PtSe). The enthalpies of formation, ΔfH0K° (g), for each diatomic metal selenide were calculated using thermochemical cycles, yielding ΔfH0K° (g) values of 210.9(4.5) kJ mol−1 (ScSe), 203.5(4.5) kJ mol−1 (YSe), 549.2(4.5) kJ mol−1 (RuSe), 675.9(6.5) kJ mol−1 (OsSe), 373.9(2.6) kJ mol−1 (CoSe), 497.4(2.7) kJ mol−1 (RhSe), 557.4(6.5) kJ mol−1 (IrSe), and 433.7(3.6) kJ mol−1 (PtSe). Utilizing a thermochemical cycle, the ionization energy for ScSe is estimated to be about 7.07 eV. The bonding trends of the transition metal selenides are discussed.

Chemical Bonding and Electronic Structure of the Early Transition Metal Borides: ScB, TiB, VB, YB, ZrB, NbB, LaB, HfB, TaB, and WB

“…This trend mimics what is observed for the late transition metal borides (see Table ), where the bond energies of the 4d and 5d borides are greatly enhanced . It has also been observed in the transition metal carbides, , silicides, ,, sulfides, , and selenides , that the 3d series gives much weaker bonds than are found in the congeners from the subsequent periods. This observation may be rationalized by the fact that the 3d orbitals are much smaller than the 4d and 5d orbitals, and the ratio ⟨ r ⟩ n d /⟨ r ⟩ ( n +1)s is much smaller for the 3d orbitals than the 4d and 5d orbitals as well .…”

“…Thus, the observation of a sharp predissociation threshold can be used to assign the BDE for a molecule with R2PI spectroscopy. This technique has been previously employed to precisely measure the BDEs for transition metal boride, aluminide, , carbide, ,− silicide, ,,, nitride, oxide, sulfide, − ,− selenide, ,,− and chloride diatomics. In this article, we report ten highly precise BDEs for early transition metal borides using the same spectroscopic method.…”

Early Transition Metals Strengthen the B2Bond in MB2Complexes

“…In previous work, − we have demonstrated that for small d- and f-block molecules, the high density of electronic states in the vicinity of the ground separated fragment limit allows the molecule to dissociate via spin–orbit and nonadiabatic couplings as soon as this limit is exceeded in energy, leading to a sharp drop in the ion signal obtained in a resonant two-photon ionization (R2PI) spectroscopy experiment. As illustrated in Figures and S1–S5, this method has allowed us to measure the predissociation thresholds of ScB 2 , TiB 2 , VB 2 , YB 2 , and MoB 2 .…”

Electronic Structure of Heteronuclear Cerium-Platinum Clusters

“…Both have triple bonds formed through σ 5d‑5d and π 5d‑5d orbitals, but the CePt molecule has a significant ionic character. The Morse group has measured the bond dissociation energies of related diatomics, − and perhaps this study will inspire additional measurements on the CePt diatomic.…”