Identify the anionic sphere complex from following.

An anionic sphere complex is a coordination compound in which the complex ion (coordination sphere) carries a net negative charge.

Triamminetrinitrocobalt(III) is $[Co(NH_3)_3(NO_2)_3]$. The net charge on the complex is $+3 + 3(0) + 3(-1) = 0$. It is a neutral complex.

Tetramminecopper(II) ion is $[Cu(NH_3)_4]^{2+}$. The net charge on the complex is $+2 + 4(0) = +2$. It is a cationic complex.

Sodium hexanitrocobaltate(III) is $Na_3[Co(NO_2)_6]$. The complex ion is $[Co(NO_2)_6]^{3-}$. The net charge on the complex sphere is $+3 + 6(-1) = -3$. It is an anionic complex.

Pentacarbonyliron(0) is $[Fe(CO)_5]$. The net charge on the complex is $0 + 5(0) = 0$. It is a neutral complex.

Therefore, Sodium hexanitrocobaltate(III) contains an anionic coordination sphere.

Answer: Sodium hexanitrocobaltate(III)