Double deboronation and homometalation of 1,1'-bis(ortho-carborane)

• Published in: Dalton transactions : an international journal of inorganic chemistry 2017-02, Vol.46 (6), p.1811-1821
• Main Authors: Thiripuranathar, Gobika, Chan, Antony P Y, Mandal, Dipendu, Man, Wing Y, Argentari, Mario, Rosair, Georgina M, Welch, Alan J
• Format: Article
• Language: English
• Subjects: Bonding; Cage; Displays; Isomerization; Isomers; Links; Reduction (metal working); Reduction-Oxidation
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c6dt04457c

Double deboronation of 1,1'-bis(ortho-carborane) results in a mixture of racemic and meso diastereoisomers which are sources of the [7-(7'-7',8'-nido-C B H )-7,8-nido-C B H ] tetraanion. Consistent with this, metalation of the mixture with {Ru(p-cymene)} affords the diastereoisomers α-[1-(8'-2'-(p-cymene)-2',1',8'-closo-RuC B H )-3-(p-cymene)-3,1,2-closo-RuC B H ] (3α) and β-[1-(8'-2'-(p-cymene)-2',1',8'-closo-RuC B H )-3-(p-cymene)-3,1,2-closo-RuC B H ] (3β) in which the primed cage has undergone a spontaneous 3',1',2' to 2',1',8'-RuC B isomerisation. Analogous cobaltacarboranes α-[1-(8'-2'-Cp-2',1',8'-closo-CoC B H )-3-Cp-3,1,2-closo-CoC B H ] (4α) and β-[1-(8'-2'-Cp-2',1',8'-closo-CoC B H )-3-Cp-3,1,2-closo-CoC B H ] (4β) are formed by metalation with CoCl /NaCp followed by oxidation, along with a small amount of the unique species [8-(8'-2'-Cp-2',1',8'-closo-CoC B H )-2-Cp-2,1,8-closo-CoC B H ] (5) if the source of the tetraanion is [HNMe ] [7-(7'-7',8'-nido-C B H )-7,8-nido-C B H ]. Two-electron reduction and subsequent reoxidation of 4α and 4β afford species indistinguishable from 5. The reaction between [Tl] [1-(1'-3',1',2'-closo-TlC B H )-3,1,2-closo-TlC B H ] and [CoCpI (CO)] leads to the isolation of a further isomer of (CpCoC B H ) , rac-[1-(1'-3'-Cp-3',1',2'-closo-CoC B H )-3-Cp-3,1,2-closo-CoC B H ] (6), which displays intramolecular dihydrogen bonding. Thermolysis of 6 yields 4α, allowing a link to be established between the α and β forms of 3 and 4 and racemic and meso forms of the [7-(7'-7',8'-nido-C B H )-7,8-nido-C B H ] tetraanion, whilst reduction-oxidation of 6 again results in a product indistinguishable from 5.