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Free keywords:
platinum; platinum trihalides; crystal structure; electronic structure; periodic nodal surface
Abstract:
The isotypical crystal structures of the mixed valent trihalides PtCl3
and PtBr3 were redetermined by single crystal methods (space group R
(3) over bar, trigonal setting; PtCl3: a = 21.213 Angstrom, c = 8.600
Angstrom, cla = 0.4054; Z = 36: 1719 hkl; R = 0.035; PtBr3: a = 22.318
Angstrom. c = 9.034 Angstrom; cla = 0.4048; Z = 36; 1606 hkl; R =
0.027). A cubic closest packing of X- anions forms the basis of an
optimized arrangement of cuboctahedrally [Pt6X12] cluster molecules
with Pt-II and enantiomers of helical chains of edge-condensed
[PtX2X4/2] octahedra with Pt-IV in cis-Delta- and
cis-Lambda-configuration, respectively The bond lengths vary with the
function of the X- ligands ((d) over bar (Pt-II-X) = 2.315 and 2.445
Angstrom; (d) over bar (Pt-II-Pt-II) = 3.336 and 3.492 Angstrom;
d(Pt-IV-X) = 2.286 - 2.417 Angstrom and 2.437 - 2.563 Angstrom). The
P-II atoms are shifted outwards the X-12 cuboctahedra by 0.045 Angstrom
and 0.024 Angstrom, respectively. The symmetry governed Periodic Nodal
Surface, PNS, perfectly separates the regions of different valencies.
Quantum chemical calculations exclude the possible additional
interactions between P-II and one of the exo-ligands of Pt-IV.
