Posts Tagged ‘CHs’

It’s Hexa-coordinate carbon Spock – but not as we know it!

Friday, October 2nd, 2009
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Science is about making connections. And these can often be made between the most unlikely concepts. Thus in the posts I have made about pentavalent carbon, one can identify a series of conceptual connections. The first, by  Matthias Bickelhaupt and co, resulted in the suggestion of a possible frozen SN2 transition state. They used astatine, and this enabled a connection to be made between another good nucleophile/nucleofuge, cyclopentadienyl anion. This too seems to lead to a frozen Sn2 transition state.  The cyclopentadienyl theme then asks whether this anion can coordinate a much simpler unit, a C2+ dication (rather than Bickelhaupt’s suggestion of a (NC)3C+ cation/radical) and indeed that complex is also frozen, again with 5-coordinate carbon, and this time with five equal C-C bonds. So here, the perhaps inevitable progression of ideas moves on to examining the properties of this complex, the outcome being a quite counter-intuitive suggestion which moves us into new territory.