Non-classical Triboretanes

4c bonding MO) after reaction with the to a three- or two-dime 6 onc expands electrophile E+. To allow for the new 2c2e endo-13 and exo-13 res l0na 5ond like in 

Compounds of type 13 are species at the borderline between classical aromatics and three-dimensional rx-aromatic clusters (see also Section 3.2.2.4). 

Oxidation of the anion 15a with C2C16 leads to the blue radical 15a characterized by g = 2.0039, which is reminiscent of the blue radical CBuMei2 (S 2.0037) obtained by oxidation of the corresponding anion CB 1 Me [23]. 

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Isomeric with non-classical triboretanes of type 3 (Schemes 3.2-3 and 3.2-5) are triboraficyclo] 1.1,0 butanes of type 13 (Scheme 3.2-8). The first derivative 13a was obtained when 4b was reacted with dichloro(trimethylsilylmethyl)borane [19]. 

In Section 3.2.1 the 3c2e BBB bonds in the series of triborirane dianions (M) and its homo forms N, O and P were described and the NBOs (natural bonding orbitals) are displayed in Figure 3.2-2. The chemistry of derivatives of N (10A2- in Scheme 3.2-6) was reported in Section 3.2.2 (non-classical triboretanes), and several derivatives of the bishomotriborirane dianion (O) are known [22] (see Section 3.2.8). 

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