Why does [Co(NO2)6]4- ion have 3 unpaired electron as opposed to 1?

Why does $\ce{[Co(NO2)6]^4-}$ ion have 3 unpaired electron as opposed to 1?


The book says that it has 3 unpaired electrons. I thought $\ce{NO2-}$ was a strong field ligand, making $\ce{Co^2+}$ a $\ce{d^7}$ low spin ion. Six electrons go in the $\mathrm{t\_{2g}}$ orbital and 1 in the $\mathrm{e\_g}$ orbital.


Please explain the bonding in this compound (preferably with a suitable MO diagram to go with it).




According to Elliot, Hathaway & Slade (1966) cited by [this paper](http://scripts.iucr.org/cgi-bin/paper?S0567740880005535), Co(II) with nitrite ligands is low spin.


[![enter image description here](https://i.stack.imgur.com/ir2ram.jpg)](https://i.stack.imgur.com/ir2ram.jpg)


So maybe it is just a typo. For d7 low spin, you would expect one unpaired electron.


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