Triborirane dianions

Next, let us have a closer look at the 3c2e BBB bond in the series of triborirane dianion [6] and its homo forms [7]. The parent, cyclic B3H32-, M, has a true n MO occupied by two electrons and composed of pure p orbitals from the three boron atoms (see Figure 3.2-2). Inserting a methylene group into one 2c2e BB... 

Fig. 3.2-2. Molecular formula (top view) and plot [9a] of the 3c BBB natural bonding orbital (NBO) [9b] (side view) for the triborirane dianion (M) as well as homo- (N), bishomo-...

In Section 3.2.1 the prototype O of the bishomo form of the triborirane dianion was discussed (see Figure 3.2-2). Experimentally, bishomotriborirane dianions were obtained by reduction of 1,2,4-triboracyclopentanes or by addition of nucleophiles to 12a (see Scheme 3.2-7) [22], However, these species do not exist as free dianions, but as contact ion pairs and will be presented together with derivatives of N and P (see Figure 3.2-2) in Section 3.3.8. 

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). 

On the other hand, the mono-, bis- and trishomoaromatic (N, O, P) species are formally derived from the triborirane dianion M by successive incorporation of methylene bridges into the ring. 

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See also in sourсe #XX -- [ ]

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