Chemical bonding in oblatonido ditantalaboranes and related compounds

Bruce King, R. ; Ghosh, Sundargopal (2012) Chemical bonding in oblatonido ditantalaboranes and related compounds Theoretical Chemistry Accounts, 131 (2). Article ID 1087. ISSN 1432-881X

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The recently discovered ditantalaboranes Cp2Ta2BnHn+6 (n = 4, 5) are isoelectronic with the previously discovered dimetallaboranes Cp2M2BnHn+4 of the group 6 metals Cr, Mo, and W where Cp = η5-cyclopentadienyl or substituted cyclopentadienyl. Their oblatonido polyhedral structures can be derived from the oblate (flattened) deltahedra of the oblatocloso dirhenaboranes Cp2Re2Bn+1Hn+1 by removal of an equatorial BH vertex with adjustment of the skeletal electron count by changing the metal atoms and adding hydrogen atoms. In these oblatocloso dirhenaborane deltahedra, the approximately antipodal rhenium atoms are close enough together to form a formal Re=Re double bond with lengths in the range 2.69–2.82 Å. Similarly, short M=M distances are maintained in the related oblatonido derivatives Cp2Ta2BnHn+6 (n = 4, 5) and Cp2M2BnHn+4 (M=Cr, Mo, W). However, the synthesis of Cp2Ta2BnHn+6 (n = 4, 5) from CpTaCl4 + LiBH4/BH3 also gives a less-reduced product Cp2Ta2Cl2B5H11 with a longer Ta–Ta distance of ~3.2 Å. This may be regarded as a formal single bond bridged by one of the hydrogen atoms. Vertices of degree 5 (excluding terminal atoms/groups but not edge-bridging hydrogens) are sites of highest stability/lowest chemical reactivity not only in metal-free boranes but also in the dimetallaboranes discussed in this paper. For example, all four boron vertices in Cp2Ta2B4H10 have the favorable degree or 5.

Item Type:Article
Source:Copyright of this article belongs to Springer Verlag.
Keywords:Dimetallaboranes; Boranes; Tantalum; Oblate Polyhedral; Chemical Bonding
ID Code:110984
Deposited On:31 Jan 2018 12:31
Last Modified:31 Jan 2018 12:31

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