Q45. Which one of the following complexes will exhibit the least paramagnetic behaviour? [Atomic number, $\mathrm { Cr } = 24 , \mathrm { Mn } = 25 , \mathrm { Fe } = 26 , \mathrm { Co } = 27 ]$\\
(1) $\left[ \mathrm { Cr } \left( \mathrm { H } _ { 2 } \mathrm { O } \right) _ { 6 } \right] ^ { 2 + }$\\
(2) $\left[ \mathrm { Fe } \left( \mathrm { H } _ { 2 } \mathrm { O } \right) _ { 6 } \right] ^ { 2 + }$\\
(3) $\left[ \mathrm { Co } \left( \mathrm { H } _ { 2 } \mathrm { O } \right) _ { 6 } \right] ^ { 2 + }$\\
(4) $\left[ \mathrm { Mn } \left( \mathrm { H } _ { 2 } \mathrm { O } \right) _ { 6 } \right] ^ { 2 + }$