Planar carbon propellanes

The carbon atoms not at the ends of the stack have a half-planar or bntterfly-type disposition of their fonr bonds (Fig. 12.2). This makes them members of the unconventional non-tetrahedral assortment of tetracoordinate carbons to which also belong planar, pyramidal, and propellane (umbrella) carbon (Fig. 12.2 references to these carbon stereochemistries and to half-planar carbon in organometallic compounds, are given in [1]). Thns they excite the same kind of curiosity as that engendered by the planar carbon of Chapter 1 and the pyramidal carbon of Chapter 2. 

Fig. 2.1 Planar- (a), pyramidal- (b) and propellane-type (c) carbon atoms...

Fig. 12.2 The half-planar or butterfly stereochemistry of carbon atoms in polyprismanes. Besides this and the normal tetrahedral, other conceivable stereochemistries for carbon are the planar (Chapter 1), pyramidal (Chapter 2), and propellane. See refs, in [1]...

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