Bridged and Unbridged M2L10 Complexes

Sason Shaik, Roald Hoffmann*, C. Richard Fisel, Richard H. Summerville

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

240 Scopus citations

Abstract

Remarkably there are several structural alternatives to quadruple-bonded d4-d4 complexes of the Cotton type Re2Cl8L21 2-, namely, the bridged, double-bonded edge-sharing bioctahedral Vahrenkamp complex V2(CO)8(m-PR2)2, and metal-metal nonbonded, high-spin, bridged complexes of the Walton type, Re2Cl4(dppe)2(µ-Cl)2. This observation leads to a general theoretical analysis of M2L10 structures. Walsh diagrams for 4 (µ-x)2 4 bioctahedral geometries with X, Y = donor, acceptor are constructed. The M-X-M angle is taken as the measure of deformation. The total energy is a sum of the d-block contributions and a core d°-d° potential which has steep walls and limits sharply the ability of the d electrons to control the geometry. For instance, it forces the Walton complexes to be high spin. The energy wall at low in the biooctahedral complexes is dominated by repulsions among the axial substituents, while the precise location of the minima is governed by the bridging atoms. Superimposed on the d°-d° energy there is a variable contribution due to metal-metal interaction, which may be attractive or repulsive, depending on electron count. After a brief analysis of the unsupported dimers the interconversions of the two types of geometries are studied. The transformation of d4-d4 Cotton and Vahrenkamp complexes is forbidden while that of d7-d7 M2(CO)10 compounds is allowed.

Original languageEnglish
Pages (from-to)4555-4572
Number of pages18
JournalJournal of the American Chemical Society
Volume102
Issue number14
DOIs
StatePublished - Jul 1980
Externally publishedYes

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