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Ring-whizzing in polyene-PtL 2 complexes revisited

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ABSTRACT

Ring-whizzing was investigated by hybrid DFT methods in a number of polyene–Pt(diphosphinylethane) complexes. The polyenes included cyclopropenium+, cyclobutadiene, cyclopentadienyl+, hexafluorobenzene, cycloheptatrienyl+, cyclooctatetraene, octafluorooctatetraene, 6-radialene, pentalene, phenalenium+, naphthalene and octafluoronaphthalene. The HOMO of a d10 ML2 group (with b2 symmetry) interacting with the LUMO of the polyene was used as a model to explain the occurrence of minima and maxima on the potential energy surface.

No MeSH data available.


The four coordination geometries for d10 polyene-ML2 complexes along with their hapto numbers and electron count.
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Figure 1: The four coordination geometries for d10 polyene-ML2 complexes along with their hapto numbers and electron count.

Mentions: Polyene–transition metal complexes were found to undergo fluxional rearrangements as early as 1956 with the preparation of Cp2Fe(CO)2 [1]. The migration of an MLn unit around the periphery of a cyclic polyene is commonly called ring-whizzing, purportedly ascribed to Rowland Pettit [2]. A more inclusive term is haptotropic rearrangement [3] wherein a metal atom changes its hapticity along the reaction path. Haptotropic rearrangements in ML3 and MCp complexes are numerous [4–9] and have found use in synthetic strategies [10], switching devices [11–13] and energy storage [14–15]. Much less is known about the polyene–ML2 analogs. There are two classes of compounds; one set consists of d8 ML2 compounds [16–19] and the other, which we will be concerned with, are the d10 ML2 class. There is ample precedent for four basic coordination geometries exhibited by these compounds. These are shown in Fig. 1. Notice that in each case the orientation of the ML2 unit is tied to the coordination number of the polyene and total electron count. One of us undertook a theoretical survey of these compounds at the extended Hückel level a number of years ago [20–21]. In the present contribution we shall revisit some of these rearrangements using DFT theory, as well as, investigate some new compounds.


Ring-whizzing in polyene-PtL 2 complexes revisited
The four coordination geometries for d10 polyene-ML2 complexes along with their hapto numbers and electron count.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4979650&req=5

Figure 1: The four coordination geometries for d10 polyene-ML2 complexes along with their hapto numbers and electron count.
Mentions: Polyene–transition metal complexes were found to undergo fluxional rearrangements as early as 1956 with the preparation of Cp2Fe(CO)2 [1]. The migration of an MLn unit around the periphery of a cyclic polyene is commonly called ring-whizzing, purportedly ascribed to Rowland Pettit [2]. A more inclusive term is haptotropic rearrangement [3] wherein a metal atom changes its hapticity along the reaction path. Haptotropic rearrangements in ML3 and MCp complexes are numerous [4–9] and have found use in synthetic strategies [10], switching devices [11–13] and energy storage [14–15]. Much less is known about the polyene–ML2 analogs. There are two classes of compounds; one set consists of d8 ML2 compounds [16–19] and the other, which we will be concerned with, are the d10 ML2 class. There is ample precedent for four basic coordination geometries exhibited by these compounds. These are shown in Fig. 1. Notice that in each case the orientation of the ML2 unit is tied to the coordination number of the polyene and total electron count. One of us undertook a theoretical survey of these compounds at the extended Hückel level a number of years ago [20–21]. In the present contribution we shall revisit some of these rearrangements using DFT theory, as well as, investigate some new compounds.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Ring-whizzing was investigated by hybrid DFT methods in a number of polyene–Pt(diphosphinylethane) complexes. The polyenes included cyclopropenium+, cyclobutadiene, cyclopentadienyl+, hexafluorobenzene, cycloheptatrienyl+, cyclooctatetraene, octafluorooctatetraene, 6-radialene, pentalene, phenalenium+, naphthalene and octafluoronaphthalene. The HOMO of a d10 ML2 group (with b2 symmetry) interacting with the LUMO of the polyene was used as a model to explain the occurrence of minima and maxima on the potential energy surface.

No MeSH data available.