[CarbeneGirl]

I ran Gaussian twice- once on a singlet dichlorocarbene and once on the triplet state. I am trying to explain (or can you confirm my theory- or perhaps add to it) why the singlet shows lower energy in comparison to its triplet state, and yet the triplet shows shorter bond length and a bond angle of 120 (with the singlet having 109)- both suggesting greater stability. And I was thinking the bond angle closer to 120 would be more stable because of the sp2 hybridization. (is that right?) Actually, I am still unclear if the triplet is sp2 or not. So anyway, I was thinking this contradiction was due to the paired electrons of the singlet in the s orbital- and the unpaired single e- in the s and p of the triplet. So, triplet could be more stable and stick around longer b/c the symmetry of the species could be more difficult to match up with another- resulting in the more relaxed angle and shorter bond? seems like something that hangs around longer would have stronger bonds? But the empty p orbitals of the singlet make it easier to match up with another molecule. (right?) Hmmm.... but it still blows my mind that the triplet isn't lower in energy! It just seems odd that the unpaired electrons of the triplet are enough to make the energy lower, despite its strong reactivity.

[Sepelio]

I just recently finished my dissertation, which was largely about carbene/radical chemistry. Theres a lot of useful literature on these compounds from the research group I was working in. Largely I was looking at the dimerisation. Lets see if I can dig up some papers for you.

DOI: 10.1002/anie.200700554  - neutral organic electron donors

A lot of publications by the John A Murphy group are involving these kinds of molecules/carbenes. I have no doubt some of it will be of use to you.