Among $[B_{12}H_{12}]^{2-}$, $[Ni_5(CO)_{12}]^{2-}$, $[C_2B_9H_{11}]^{2-}$, $Rh_6(CO)_{16}$, $Os_6(CO)_{20}$, $B_5H_{11}$ and $B_6H_{10}$, how many have nido structures? Atomic numbers H,B,C,O,Ni,Rh,Os are 1,5,6,8,28,45,76.
Wade counting identifies nido clusters by n+2 skeletal electron pairs. The carborane $[C_2B_9H_{11}]^{2-}$ has 26 skeletal electrons for 11 vertices, hence nido. B₆H₁₀ has 16 skeletal electrons for 6 vertices, also nido. For the metal carbonyls, Os₆(CO)₂₀ has 88 cluster valence electrons, the 14n+4 nido count; Ni₅(CO)₁₂²⁻ has 76 = 14n+6 (arachno), and Rh₆(CO)₁₆ has 86 = 14n+2 (closo). B₁₂H₁₂²⁻ is closo and B₅H₁₁ arachno. There are three nido species.
More Main Group Elements: Shapes and structures of molecules using VSEPR postulates, Hydrides, halides, oxides, oxoacids, nitrides, sulfides - shapes and reactivity. Structure and bonding of boranes, carboranes, silicones, silicates, boron nitride, borazine and phosphazenes: electron counting in polyhedral boranes, isolobal analogy. Allotropes of carbon, phosphorus and sulfur. Industrial synthesis of compounds of main group elements such as NH3, H2SO4 and HNO3. Chemistry of noble gases and interhalogen compounds. Acid-base concepts and principles (Lewis, Brønsted, HSAB and acid-base catalysis). questions