The numbei of isoelectronic species among $$Sc^{3+},Cr^{2+},Mn^{3+},Co^{3+}\text{ and }Fe^{3+}$$ is 'n'. If 'n' moles of AgCl is formed during the reaction of complex with formula $$CoCl_{3}(en)_{2}NH_{3}$$ with excess of $$AgNO_{3}$$ solution, then the number of electrons present in the $$t_{2g}$$ orbital of the complex is ________.

To determine the number n of isoelectronic species among $$Sc^{3+}, Cr^{2+}, Mn^{3+}, Co^{3+}, Fe^{3+}$$ and then to find the number of electrons in the $$t_{2g}$$ orbitals of the complex $$[CoCl_n(en)_2(NH_3)]$$ reacting with excess $$AgNO_3$$, we first calculate the electron counts for each ion.

Sc has 21 electrons so $$Sc^{3+}$$ has $$21-3=18$$ electrons (configuration $$[Ar]$$), Cr has 24 electrons so $$Cr^{2+}$$ has $$24-2=22$$ electrons (configuration $$[Ar]3d^4$$), Mn has 25 electrons so $$Mn^{3+}$$ has $$25-3=22$$ electrons (configuration $$[Ar]3d^4$$), Co has 27 electrons so $$Co^{3+}$$ has $$27-3=24$$ electrons (configuration $$[Ar]3d^6$$), and Fe has 26 electrons so $$Fe^{3+}$$ has $$26-3=23$$ electrons (configuration $$[Ar]3d^5$$).

Since isoelectronic species share the same total electron count, we find one species with 18 electrons ($$Sc^{3+}$$), two species with 22 electrons ($$Cr^{2+}$$ and $$Mn^{3+}$$), one species with 23 electrons ($$Fe^{3+}$$), and one species with 24 electrons ($$Co^{3+}$$). Thus the number of isoelectronic species is 2, giving $$n=2$$.

Next, we analyze the complex given as $$CoCl_3(en)_2(NH_3)$$ for Co(III), which has a coordination number of 6. The two en ligands are bidentate and contribute four donor atoms, while $$NH_3$$ contributes one donor atom, so only one chloride remains in the coordination sphere.

Therefore the complex can be written as $$[CoCl(en)_2(NH_3)]Cl_2$$, where the two outer‐sphere chlorides precipitate as AgCl when the complex reacts with excess $$AgNO_3$$, yielding 2 moles of AgCl, consistent with $$n=2$$.

Finally, since $$Co^{3+}$$ has a $$3d^6$$ configuration and the ligands en and $$NH_3$$ are strong-field, the complex is low-spin octahedral with a $$t_{2g}^6 e_g^0$$ electron distribution. Hence the number of electrons in the $$t_{2g}$$ orbitals is $$\boxed{6}$$.