With 20 valence electrons, nickelocene, [Ni(η⁵-C₅H₅)₂], has the highest electron count of the transition metal metallocenes.

[CoF₆]^3- is an outer orbital complex with octahedral geometry (sp³d² hybridisation). [Zn(H₂O)₆]²⁺ is an outer orbital complex with square planar geometry (sp³d² hybridisation).

Osmium is in +6 oxidation state in given complex. Hence, the correct IUPAC name of K₂[OsCl₅N] is potassium pentachloronitridoosmate(VI).

[Ti(H₂O)₆]³⁺: (t_2g)¹ has one unpaired electron. [Cu(H₂O)₆]²⁺: (t_2g)⁶(e_g)³ has one unpaired electron.

The nephelauxetic effect not only depends upon the ligand type, but also upon the central metal ion. These too can be arranged in order of increasing nephelauxetic effect as follows: Mn(II) < Ni(II) ≈ Co(II) < Mo(II) < Re(IV) < Fe(III) < Ir(III) < Co(III) < Mn(IV).

Ziegler-Natta catalysts are used to polymerise terminal-1 alkenes (ethylene and alkenes with the vinyl double bond). Cisplatin, cis-PtCl₂(NH₃)₂, is an anti-cancer drug that is used to treat various types of cancers. On moderate heating, Ni(CO)₄ decomposes to form carbon monoxide and nickel metal. Combined with the easy formation from CO and even impure nickel, this decomposition is the basis of Mond's process for the purification of nickel. Wilkinson's catalyst, (RhCl(PPh₃)₃, catalyses the hydrogenation of alkenes.

This is the correct option. Vaska's complex is the common name for trans-chlorocarbonylbis(triphenylphosphine)iridium(I). Wilkinson's catalyst is the common name for chlorotris(triphenylphosphine)rhodium(I). Jacobsen's catalyst is the common name for N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese chloride.

[Cr(NH₃)₆]³⁺: t_2g³ e_g⁰; 3 unpaired electrons; paramagnetic [Fe(CN)₆]^3-: t_2g5 e_g⁰; one unpaired electron; paramagnetic

Correct order of nephelauxetic effect is F⁻ < H₂O < NH₃ < en < NCS⁻ < Cl⁻ < CN⁻ < Br⁻ < N³⁻ < I⁻.

[Pt(NH₃)₂Cl₂] is a heteroleptic square planar complex of Ma₂b₂ type. In a square planar complex of formula [Ma₂b₂], the two similar ligands may be arranged adjacent to each other in a cis isomer or opposite to each other in a trans isomer.

Chlorophylls are green pigments in plants and contain Mg. Haemoglobin is the red pigment or colour of blood and contains iron (Fe). Vitamin B₁₂ is a cyanide ion substituted cobalamin derivative (cyanocobalamin) with the presence of cobalt mineral at 6 position. Carboxypeptidase A is a zinc metalloenzyme that breaks peptide linkages in the digestion of proteins.

Increase in the extent of back donation causes the stretching frequencies to be found at lower wavenumbers. In [V(CO)₆]^-, vanadium has a -1 charge and with the addition of six C-O ligands, there is a tendency to relieve part of the negative charge by extensive back donation. The tendency is less in [Cr(CO)₆] and even less when the metal has a positive charge as in [Mn(CO)₆]⁺. Thus, the correct order of decreasing C-O stretching frequency is Mn(CO)₆]⁺, 2090 cm^-1 > [Cr(CO)₆], 1981 cm^-1 > [V(CO)₆]^-, 1859 cm^-1.

The metal ions can be arranged in order of increasing Δ, and this order is largely independent of the identity of the ligand. Mn²⁺ < Ni²⁺ < Co²⁺ < Fe²⁺ < V²⁺ < Fe³⁺ < Cr³⁺ < V³⁺ < Co³⁺

All the three given ligands will show linkage isomerism. The sulphito group (SO₃^2-), an ambidentate ligand, can be coordinated to metal ions through either the oxygen or the sulphur. So, it will show linkage isomerism. NO₂^- is an ambidentate ligand. It can attach at either the nitrogen atom or the oxygen atom. Hence, it will show linkage isomerism. SCN⁻ is an ambidentate ligand. Since it can attach at either the sulphur atom or the nitrogen atom, it will show linkage isomerism.

Correct Answer: [Mn(CN)₆]^3-, [Fe(CN)₆]^3- and [Co(C₂O₄)₃]^3- are diamagnetic inner orbital complexes that involve d²sp³ hybridisation.