The Tetracyanopyridinide Dimer Dianion, σ‐[TCNPy]₂²⁻

Abstract

The reaction of 2,3,5,6-tetracyanopyridine (TCNPy) and Cr(C6 H6 )2 forms diamagnetic σ-[TCNPy]2 (2-) possessing a 1.572(3) Å intrafragment sp(3) -sp(3) bond. This is in contrast to the structurally related 1,2,4,5-tetracyanobenzene and 1,2,4,5-tetracyanopyrazine that form π-dimer dianions possessing long, multicenter bonds.

Characterization of Tetracyanopyridine (TCNPy)‐Based Magnets: V[TCNPy]2⋅z (CH2Cl2) (Tc=111 K) and V[TCNPy]3⋅z (CH2Cl2) (Tc=90 K)

“…TCNPyu ndergoes aq uasi-reversible one-electronr eduction at À0.51 V( vs. SCE in MeCN) [17,21] that is % 0.85 Vh arder to reducet han TCNE, but easier to reduce than TCNB (À0.64 V) albeit more difficult to reduce than TCNP (À0.31 V), [22] and areaction, as occurs with TCNB [16] and TCNP, [12] with V(CO) 6 was expected. Reaction of TCNPy with V(CO) 6 in CH 2 Cl 2 rapidlyo ccurs and turns black with CO evolution, and adark insoluble precipitate forms,i ndicating formation of an extendedn etwork structured materials imilar to V[TCNE] x ,T CNB, and TCNP.T he compositiono ft he initial precipitate after allowing the reaction to proceedf or two hours, wasd etermined to be V[TCNPy] 2 ·z (CH 2 Cl 2 )f rom the observed elemental composition as well as the thermogravimetrica nalysis.…”

“…This is attributed to the instability of [TCNPy]C À as it does not undergo ar eversible oxidation, [17] and can form the diamagnetic s-[TCNPy] 2 2À dimer. [21] However,t his gradualr earrangementp rocess can be suppressed by keeping the sample at extremely low temperature, such as 5K.…”