Metal cluster and Boranes

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* Metal Clusters and Boranes -
Metal clusters are of two types.......

1.High Nuclearity carbonyl complexes (n >4).
2.Low Nuclearity carbonyl complexes (n<4)........(n=4 is border line)

A.Determination of structure for HNCC
Step1.Calculated TEC-( total electron count)
Step2.add the value of valances electron
Step3.Polyhedral electron count (PEC=TEC-nx12)......n=metals in the given clusters.
Step4.PEC/2   =n-1=Super closo
                           n=Hyper closo
                            n+1=Closo
                            n+2=Nido
                            n+3=Arachano
                            n+4=Hypo

eg.     Rh6(CO)16                                                             
             TEC=9x6+2x16=86
          PEC=86-72
          PEC/2=14/2=7
           n+1=Closo......n=metal
           6+1=7

No. of frame
 work
 metal atoms.               Cluster types.                Shapes                      Example

           7.               Monocapped  closo    capped octahedral.     Rh7(CO)16]3-                                                                                                               [Os7(CO)21]
           6.                        Closo.                     Octahedral.                  Rh6(CO)16],                                                                                                               [Ru6(CO)17]

           6.              Monocapped nido.         Capped square

                                                                     pyramidal.                    H2Os6(CO)18

           5.                       Nido.                     Square pyramidal.        Ru5C(CO)15

           4.                  Arachano.                    Butterfly.                     [Fe4(CO)3H-


*Similar analogy for Boranes:-
 (BnHn)2+               Super closo

(BnHn)n.                 Hyper closo

(BnHn)2-                 Closo

(BnHn)4-                 Nido

(BnHn)6-                 Arachano

(BnHn)8-                 Hypo


eg.(B6H6)2-=Closo
      (B5H9)=(B5H5)4-=Nido
      (B4H10)=(B4H4)6-=Arachano

eg.    1CH=BH    ( for carbon family also)
          N =BH2      (for nitrogen family also)
C2B10H12=carborane
(BH)2B10H12=
 (B2H2B10H12)
 (B12H14)
  (B12H12)2-=Closo

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