Covalency in metal-oxygen multiple bonds evaluated using oxygen K-edge spectroscopy and electronic structure theory.
Advancing theories of how metal-oxygen bonding influences metal oxo properties can expose new avenues for innovation in materials science, catalysis, and biochemistry. Historically, spectroscopic analyses of the transition metal MO(4)(x-) anions have formed the basis for new M-O bonding theories. Herein, relative changes in M-O orbital mixing in MO(4)(2-)  (M = Cr, Mo, W) and MO(4)(-)  (M = Mn, Tc, Re) are evaluated for the first time by nonresonant inelastic X-ray scattering, X-ray absorption spectroscopy using fluorescence and transmission (via a scanning transmission X-ray microscope), and time-dependent density functional theory. The results suggest that moving from Group 6 to Group 7 or down the triads increases M-O e* (π*) mixing; for example, it more than doubles in ReO(4)(-) relative to CrO(4)(2-). Mixing in the t(2)* orbitals (σ* + π*) remains relatively constant within the same Group, but increases on moving from Group 6 to Group 7. These unexpected changes in orbital energy and composition for formally isoelectronic tetraoxometalates are evaluated in terms of periodic trends in d orbital energy and radial extension.
Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
Stefan G
SG
Minasian
Jason M
JM
Keith
Enrique R
ER
Batista
Kevin S
KS
Boland
Joseph A
JA
Bradley
Scott R
SR
Daly
Stosh A
SA
Kozimor
Wayne W
WW
Lukens
Richard L
RL
Martin
Dennis
D
Nordlund
Gerald T
GT
Seidler
David K
DK
Shuh
Dimosthenis
D
Sokaras
Tolek
T
Tyliszczak
Gregory L
GL
Wagner
Tsu-Chein
TC
Weng
Ping
P
Yang
D004583:Electrons; D019216:Metals, Heavy / Q000737:chemistry*; D017348:Microscopy, Electron, Scanning Transmission; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D011789:Quantum Theory; D056928:X-Ray Absorption Spectroscopy; D014965:X-Rays
D019216:Metals, Heavy; D010100:Oxygen