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Why are the Homoleptic Diyl Complexes M(InR) 4 with M = Ni and Pt Stable Compounds while only Ni(CO) 4 but not Pt(CO) 4 can become Isolated? A Theoretical Study of M(EMe)4 4 and M(CO) 4 (M = Ni, Pd, Pt; E = B, Al, Ga, In, Tl)
Author(s) -
Doerr Markus,
Frenking Gernot
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(200205)628:4<843::aid-zaac843>3.0.co;2-q
Subject(s) - homoleptic , bond energy , bond dissociation energy , sextuple bond , covalent bond , chemistry , crystallography , single bond , dissociation (chemistry) , bent bond , metal , bond order , ligand (biochemistry) , chemical bond , bond length , computational chemistry , molecule , alkyl , crystal structure , organic chemistry , biochemistry , receptor
The equilibrium geometries and first bond dissociation energies of the homoleptic complexes M(EMe) 4 and M(CO) 4 with M = Ni, Pd, Pt and E = B, Al, Ga, In, Tl have been calculated at the gradient corrected DFT level using the BP86 functionals. The electronic structure of the metal‐ligand bonds has been examined with the topologial analysis of the electron density distribution. The nature of the bonding is revealed by partitioning the metal‐ligand interaction energies into contributions by electrostatic attraction, covalent bonding and Pauli repulsion. The calculated data show that the M‐CO and M‐EMe bonding is very similar. However, the M‐EMe bonds of the lighter elements E are much stronger than the M‐CO bonds. The bond energies of the latter are as low or even lower than the M‐TlMe bonds. The main reason why Pd(CO) 4 and Pt(CO) 4 are unstable at room temperature in a condensed phase can be traced back to the already rather weak bond energy of the Ni‐CO bond. The Pd‐L bond energies of the complexes with L = CO and L = EMe are always 10 — 20 kcal/mol lower than the Ni‐L bond energies. The calculated bond energy of Ni(CO) 4 is only D o = 27 kcal/mol. Thus, the bond energy of Pd(CO) 4 is only D o = 12 kcal/mol. The first bond dissociation energy of Pt(CO) 4 is low because the relaxation energy of the Pt(CO) 3 fragment is rather high. The low bond energies of the M‐CO bonds are mainly caused by the relatively weak electrostatic attraction and by the comparatively large Pauli repulsion. The σ and π contributions to the covalent M‐CO interactions have about the same strength. The π bonding in the M‐EMe bonds is less than in the M‐CO bonds but it remains an important part of the bond energy. The trends of the electrostatic and covalent contributions to the bond energies and the σ and π bonding in the metal‐ligand bonds are discussed.