TY - JOUR
T1 - Fe(CH4)n+ and Ni(CH4)n+ clusters
T2 - Experimental and theoretical bond energies for n=1-6
AU - Zhang, Qiang
AU - Kemper, Paul R.
AU - Bowers, Michael T.
N1 - Funding Information:
The support of the National Science Foundation under grant no. CHE-9729146 is gratefully acknowledged. One of the authors (M.T.B.) also wishes to thank Nico for 30 years of productive and enjoyable interactions, and for the inspiration his insight and boundless energy have given.
PY - 2001/9/14
Y1 - 2001/9/14
N2 - Measurements are reported for sequential clustering of CH4 to Fe+ and Ni+ ions under equilibrium conditions. Detailed density functional theory calculations were performed to provide structural and electronic configuration information and to help analyse and interpret the experimental data. The calculations indicate that the first two CH4 ligands add on opposite sides of the Fe+ core ion in an η3 configuration, in an η2 configuration for Ni+, and induce significant s/d hybridization on both of the metal centers. This hybridization both reduces Pauli repulsion and fosters sigma donation from the ligands into the 4s orbital on M+. Another major covalent interaction is the donation from CH4 into the singly occupied d orbital(s) on M+ for both η2 and η3 configurations. For Fe+, the change of spin state, from 6D (3d64s1) to 4F (3d7), takes place during the clustering of the first methane ligand. The clustering of the third CH4 to Fe+ and Ni+, unlike Co+(CH4)3, is not impeded by the s/d hybridization present for n=1 and 2. The interactions of all three CH4 ligands with the Fe+ and Ni+ core are essentially the same. The m/z 120 peak [nominally Fe+(CH4)4] and the m/z 122 peak [nominally Ni+(CH4)4] were formed irreversible in the temperature range from 270 to 170 K, probably due to the persistent impurity we reported earlier for the Co+ system. The n=5 and 6 ligands are very weakly bound and begin a second solvation shell. Calculations suggest the n=6 cluster forms a pseudo octahedral complex.
AB - Measurements are reported for sequential clustering of CH4 to Fe+ and Ni+ ions under equilibrium conditions. Detailed density functional theory calculations were performed to provide structural and electronic configuration information and to help analyse and interpret the experimental data. The calculations indicate that the first two CH4 ligands add on opposite sides of the Fe+ core ion in an η3 configuration, in an η2 configuration for Ni+, and induce significant s/d hybridization on both of the metal centers. This hybridization both reduces Pauli repulsion and fosters sigma donation from the ligands into the 4s orbital on M+. Another major covalent interaction is the donation from CH4 into the singly occupied d orbital(s) on M+ for both η2 and η3 configurations. For Fe+, the change of spin state, from 6D (3d64s1) to 4F (3d7), takes place during the clustering of the first methane ligand. The clustering of the third CH4 to Fe+ and Ni+, unlike Co+(CH4)3, is not impeded by the s/d hybridization present for n=1 and 2. The interactions of all three CH4 ligands with the Fe+ and Ni+ core are essentially the same. The m/z 120 peak [nominally Fe+(CH4)4] and the m/z 122 peak [nominally Ni+(CH4)4] were formed irreversible in the temperature range from 270 to 170 K, probably due to the persistent impurity we reported earlier for the Co+ system. The n=5 and 6 ligands are very weakly bound and begin a second solvation shell. Calculations suggest the n=6 cluster forms a pseudo octahedral complex.
UR - http://www.scopus.com/inward/record.url?scp=0035860248&partnerID=8YFLogxK
U2 - 10.1016/S1387-3806(01)00402-X
DO - 10.1016/S1387-3806(01)00402-X
M3 - Article
AN - SCOPUS:0035860248
VL - 210-211
SP - 265
EP - 281
JO - International Journal of Mass Spectrometry
JF - International Journal of Mass Spectrometry
SN - 1387-3806
ER -