Date of Award
Doctor of Philosophy
John D. Corbett
The chemistry of clusters of post-transition main-group elements has been extended to group 3 elements, indium in particular. The bonding in the known "naked" cluster ions Sn[subscript]9[superscript]4-, Pb[subscript]5[superscript]2- and Bi[subscript]4[superscript]2- as examples, is analogous to that in borane clusters like B[subscript]nH[subscript]n[superscript]2- where a minimum of 2n + 2 bonding electrons is always required within the cluster. Similar clusters of the electron-poorer boron family (Al, Ga, In, Tl) have never been reported perhaps because unusually high charges would be required to meet the 2n + 2 "rule", i.e., M[subscript]n[superscript]-n-2. Different, sometimes surprising, means to avoid this are observed for the indium clusters;A hypoelectronic "naked" cluster In[subscript]11[superscript]7- is present in K[subscript]8In[subscript]11. Its geometry of a distorted pentacapped trigonal prism has not been observed for the analogous 11-atom borane. Extended-Huckel calculations show that it requires 2n - 4 skeletal electrons and has a charge of -7 instead of the otherwise -13. Mercury has been successfully substituted for one indium in the cluster, In[subscript]10Hg[superscript]8-. Similar distortions of a bicapped square antiprism and a tetracapped trigonal prism lead to a requirement of 2n bonding electrons for In[subscript]10Zn[superscript]8- and In[subscript]10Z[superscript]10- (Z = Ni, Pd or Pt), respectively. Both clusters receive additional bonding from the central hetero-element, and the former gains two additional electrons from the zinc;Another, by far more frequently observed way of reducing the charge of a cluster is through a formation of exo bonds to other clusters or isolated indium atoms. Each exo bond reduces the charge of the cluster by one through oxidation of the otherwise lone pair on that vertex. First-of-a-kind clusters with more than 12 atoms have been achieved by utilizing this option. 8-, 12- and 16-bonded closo-In[subscript]16 in Na[subscript]7In[subscript]11.8, Na[subscript]15In[subscript]27.4 and Na[subscript]9In[subscript]16.8Zn[subscript]2.3, respectively, 15-bonded closo-In[subscript]15 in Na[subscript]23In[subscript]38.4Zn[subscript]4.6, 12-bonded closo-In[subscript]18 in Na[subscript]49In[subscript]80.9Sn[subscript]9.1 and 12-bonded arachno-In[subscript]12 in K[subscript]3Na[subscript]26In[subscript]48 are some of the examples. Although extremely complex, many of these structures of networks of indium clusters are very close to electronically balanced, that is, the number of available electrons barely exceeds the number of electrons needed for the bonding. Most of them are metals but poor ones;Another surprise in indium chemistry came with the discovery that in presence of the right ingredients this element forms fullerene-type cages of different sizes, analogous to the well known carbon fullerenes. Fused cages of 70, 74 and 78 indium atoms contain isolated, Ni(Pd, Pt)-centered indium clusters at their centers. Spherical layers of sodium cations shield the inside surface of the cage from the indium atoms of the central cluster. The whole formation can be compared with an onion bulb with layers of In, Na, In and Ni inward from the surface. ftn*This work was performed at Ames Laboratory under contract no. W-7405-eng-82 with the U.S. Department of Energy. The United States government has assigned the DOE Report number IS-T 1648 to this thesis.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Slavi Christov Sevov
Sevov, Slavi Christov, "Solid state chemistry of alkali-metal-indium systems: synthesis, characterization and bonding of indium cluster phases " (1993). Retrospective Theses and Dissertations. 10270.