INIFTA   05425
INSTITUTO DE INVESTIGACIONES FISICO-QUIMICAS TEORICAS Y APLICADAS
Unidad Ejecutora - UE
artículos
Título:
Potential Unusual Chemical Bonding in Mixed Structures of the 3rd Transition Series Containing the Element Ni
Autor/es:
M.J. BUCKNUM; EDUARDO ALBERTO CASTRO
Revista:
J Theor Comp Chem
Referencias:
Año: 2007 vol. 6 p. 165 - 175
Resumen:
A heuristic proposal is made in this communication that involves potentially unusual
chemical bonding between the 3d transition series element Ni and the 3d transition series
metals preceding it in the Periodic Table. The bonding in such mixed metal dimers, and
their potential realizations as some simple three-dimensional (3D) extended structures
in a one-to-one stoichiometry, as sphaelerite, rocksalt or CsCl structure-types, is proposed
to include two principal components that involve either covalent or ionic contributions.
Ordinary covalent contributions from a ó bond (or band) formed from overlap of
singly occupied 4s atomic orbitals on each metal center are proposed to be operative in
these molecules (or their extended realizations). However, in addition to this 4s4s ó bond
(band), an unprecedented transfer of a d electron from the incomplete, open 3d9 subshell
of the transition metal involved in the bonding that precedes Ni in the Periodic Table, into
the 3d9 subshell on the Ni center, which results in completion of this 3d subshell in Ni, is
here implicated as a further driving force for the formation of these species. The resulting
molecular and extended structures MNi, where M is a 3d transition metal preceding Ni
in the Periodic Table (i.e. M = Sc, Ti, V, Cr, Mn, Fe and Co), are therefore proposed to
be bonded together by a combination of covalent and ionic forces, such that the Ni center
acts as an anion of charge 1−, a so-called nickelide anion Ni−, while its counterpart is a
univalent cation M+. This proposal is consistent with commonly employed electronegativity
scales of chemical bonding, and with considerations of the relative orbital energies
of the 3d subshells of the elements across the 3d transition series period, as well as with
known trends in covalent and ionic bonding in the Periodic Table of the elements. It is also
found to be in agreement with the spin multiplicities calculated in the nickel dimers MNi
(M = Sc, Ti, V, Cr, Mn, Fe and Co) if Hunds rule is assumed to be operative.
Keywords: Intermetallic bonding theory; quantum theory of metals; transition series
elements; ionization transition; covalentionic bonding.