"Nido"series -formula BH+4) .Total valence electrons(VEC)=3n (B)+ n(H)+4 (extra H and/or negative charges) =4n+4 Number of skeletal electrons to make the structure stable: .Framework electrons (NFE)=2n+4(n+2 pairs). 2n+2 where n=the number of surface Closo ,The structure of the“nido”compound is atoms present in the cluster,i.e.n =N based on the“closo”polyhedron with one more vertex than the“nido”compound, missing surface atom on cluster 2n+4 Now N=n+l(so the number of elec- trons 2n'+2 where Nido “Arachno”series-formula B,Ha+6 n'=n+) .Total valence electrons(VEC)=4n +6 .Framework electrons(NFE)=2n+4(n+2 pairs) Arachno 2n+6 Now N=n+2 (so ,The structure of the“nido”compound is the number of elec- trons is still 2n"+2 based on the“closo”polyhedron with two whwere n"=n+2) more vertex than the“nido”compound. Electron-deficient multi-center bonds Electron-deficient multi-center bonds 6.1.4 other deficient electron compounds Boron group B、AI、Ga、In、TI Gaseity:monomer H3C CH3. 120A214A 70° A Solid state:polymer H3C CH3 H3 CH: CHy CH;“Nido” series – formula BnH(n+4) •Total valence electrons(VEC) = 3n (B) + n(H) + 4 (extra H and/or negative charges) = 4n +4 •Framework electrons (NFE) =2n+4 (n+2 pairs). •The structure of the “nido” compound is based on the “closo” polyhedron with one more vertex than the “nido” compound. “Arachno” series – formula BnH(n+6) •Total valence electrons(VEC) = 4n +6 •Framework electrons (NFE) =2n+4 (n+2 pairs). •The structure of the “nido” compound is based on the “closo” polyhedron with two more vertex than the “nido” compound. Electron-deficient multi-center bonds 6.1.4 other deficient electron compounds Electron-deficient multi-center bonds 1.94Å 2.14 Å 120º 70º B、Al、Ga、In、Tl Gaseity: monomer Solid state: polymer Boron group H3C Al H3C Al C CH3 H3 CH3 CH3