Premium
Vibrational Properties of [FeH(N 2 )(depe) 2 ] + and [FeCl(N 2 )(depe) 2 ] + ]: Dinitrogen Bonding in the Low Activation Limit
Author(s) -
Franke Oliver,
Wiesler Beatrix E.,
Lehnert Nicolai,
Tuczek Felix
Publication year - 2002
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200211)628:11<2395::aid-zaac2395>3.0.co;2-m
Subject(s) - chemistry , raman spectroscopy , force constant , bond length , octahedron , crystallography , stereochemistry , computational chemistry , molecule , crystal structure , organic chemistry , physics , optics
The vibrational properties of the two octahedral Fe II dinitrogen complexes [FeH(N 2 )(depe) 2 ] + ( 1 ) and [FeCl(N 2 )(depe) 2 ] + ( 2 , depe = 1, 2‐bis(diethylphosphino)ethane) are investigated with the help of infrared and Raman spectroscopies. Vibrational data are evaluated with a Quantum Chemistry Assisted Normal Coordinate Analysis (QCA‐NCA; N. Lehnert, F. Tuczek, Inorg. Chem. 1999 , 38 , 1659). In agreement with high values found for ν(NN) and the corresponding force constants f(NN), the N 2 ligands in compounds 1 and 2 are non‐activated which corresponds to the observation that N 2 is not protonable in Fe II systems. Taking into account the short Fe‐N bond lengths, the values of the Fe‐N stretching force constants (2.55mdyn/Å for 1 and 2.58mdyn/Å for 2 ) are found to be compatible with those of other Fe II low‐spin compounds coordinated to backbonding N‐coordinating ligands. The force fields obtained for the Fe‐N 2 units of 1 and 2 are almost identical although the thermal stability of 1 and 2 with respect to loss of N 2 is different. This indicates that the zero‐point vibrational levels are unaffected by possible ground‐state level crossing processes occuring at larger Fe‐N bond lengths, as observed for 2 (O. Franke, B. E. Wiesler, N. Lehnert, C. Näther, V. Ksenofontov, J. Neuhausen, F. Tuczek, Inorg. Chem. 2002 , 41 , 3491).