Dimetallaborane analogues of the octaboranes of the type Cp sub(2)M sub(2)B sub(6)H sub(10): structural variations with changes in the skeletal electron count

The structures and energetics of the complete series of hydrogen-rich dimetallaboranes Cp sub(2)M sub(2)B sub(6)H sub(10) and Cp* sub(2)M sub(2)B sub(6) H sub(10) (Cp = eta super(5)-C sub(5)H sub(5); Cp* = eta super(5)-Me sub(5)C sub(5); M = Pd, Pt; Rh, Ir; Ru, Os; Re; Mo, W; Ta), including the expe...

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Bibliographic Details
Published in:Dalton transactions : an international journal of inorganic chemistry 2016-05, Vol.45 (22), p.9354-9362
Main Authors: Branzanic, Adrian MV, Lupan, Alexandru, King, RBruce
Format: Article
Language:English
Subjects:
Atomic structure
Bonding
Counting
Density functional theory
Hydrogen atoms
Palladium
Platinum
Tantalum
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Summary:The structures and energetics of the complete series of hydrogen-rich dimetallaboranes Cp sub(2)M sub(2)B sub(6)H sub(10) and Cp* sub(2)M sub(2)B sub(6) H sub(10) (Cp = eta super(5)-C sub(5)H sub(5); Cp* = eta super(5)-Me sub(5)C sub(5); M = Pd, Pt; Rh, Ir; Ru, Os; Re; Mo, W; Ta), including the experimentally known Cp* sub(2)Rh sub(2)B sub(6)H sub(10) and Cp* sub(2)W sub(2)B sub(6)H sub(10) (Cp* = eta super(5)-Me sub(5)C sub(5)), have been investigated by density functional theory. The lowest energy structures of the hyperelectronic Cp sub(2)M sub(2)B sub(6)H sub(10) (M = Pd, Pt; Rh, Ir) systems have central M sub(2)B sub(6) frameworks with a hexagonal open face similar to the B sub(8) networks in arachno-B sub(8)H sub(14) and nido-B sub(8)H sub(12). The two lowest energy structures for Cp sub(2)Rh sub(2)B sub(6)H sub(10) and Cp* sub(2)Rh sub(2)B sub(6)H sub(10), lying within 1 kcal mol super(-1) of energy, differ only in the locations of the bridging hydrogen atoms around the hexagonal hole consistent with the experimentally observed fluxionality of the hydrogen atoms in Cp* sub(2)Rh sub(2)B sub(6)H sub(10). Most of the lowest energy Cp sub(2)M sub(2)B sub(6)H sub(10) (M = Ru, Os) structures also have a central M sub(2)B sub(6) framework similar to B sub(8)H sub(12), typically with such additional features as an additional metal-metal bond or a formal metal-metal double bond. A common motif for the low-energy structures of the hypoelectronic Cp sub(2)M sub(2)B sub(6)H sub(10) (M = Re; Mo, W; Ta) systems, including the experimentally known Cp* sub(2)W sub(2)B sub(6)H sub(10), is a central M sub(2)B sub(4) octahedron with its two M sub(2)B faces capped by the remaining boron atoms and with four M-B edges bridged by hydrogen atoms. Such structures can also be considered as oblatonidostructures derived from the experimentally known 9-vertex oblatoclosoCp* sub(2)Re sub(2)B sub(7)H sub(7) structure by removal of the unique degree 4 vertex atom.
ISSN:1477-9226
1477-9234
DOI:10.1039/c6dt00985a