R₁,R₂-C=Se

R₁

R₂

N_f

C=Se

C–N

N

N

261

1.841 (0.022)

1.352 (0.018)

N³

N³

252

1.841 (0.022)

1.352 (0.018)

N

C

97

1.830 (0.018)

1.323 (0.025)

N³

C³

71

1.832 (0.017)

1.322 (0.026)

N³

C⁴

23

1.819 (0.019)

1.329 (0.016)

C

C

3

1.796 (0.026)

–

C³

C³

2

1.808 (0.024)

–

C⁴

C⁴

1

1.773

–