Antimony and bismuth transition metal

Not all elements in these groups have the same properties and characteristics. For instance, in group 15, nitrogen is a gas, whereas the element just below it in group 15 is phosphorous, anon-metallic solid (semimetal). Just below phosphorous is arsenic (semimetal), followed by antimony and then bismuth, which are more metal-like. These last two, antimony and bismuth, are metals that might be considered an extension of periods 5 and 6 of the transition elements. 

The less common heteroatoms are those other than nitrogen, oxygen and sulfur (arid selenium and tellurium which are treated alongside sulfur), i.e. phosphorus, arsenic, antimony, bismuth, the halogens, silicon, germanium, tin, lead, boron and the transition metals. 

The polyhedral boranes and carboranes discussed above may be regarded as boron clusters in which the single external orbital of each vertex atom helps to bind an external hydrogen or other monovalent atom or group. Post-transition main group elements are known to form clusters without external ligands bound to the vertex atoms. Such species are called bare metal clusters for convenience. Anionic bare metal clusters were first observed by Zintl and co-workers in the 1930s [2-5], The first evidence for anionic clusters of post-transition metals such as tin, lead, antimony, and bismuth was obtained by potentiometric titrations with alkali metals in liquid ammonia. Consequently, such anionic post-transition metal clusters are often called Zintl phases. 

The synthesis of stable complexes with transition metal-phosphorus triple bonds is of fundamental importance and opens a novel chapter of a special field of coordination chemistry. The synthesis of analogous complexes with ligands of the heavier homologues like arsenic has partially been carried out [6], while for antimony and bismuth, the elusive M=Sb and M=Bi systems have now moved within reach. Moreover, the experimental and theoretical... 

Transition Metal Bond Lengths to Antimony and Bismuth... 

S. D. Robinson Transition metal complexes containing phosphorus, arsenic, antimony and bismuth donor ligands. 

Concerning ligands of organoarsenic, -antimony and -bismuth compounds in main group and transition metal complexes, some contributions are cited in the list of references . Thus we fixed our attention to the literature within the last ten years to deal with topics of current interest. 

A125. F. G. Mann, Chemistry of Heterocyclic Compounds, Vol. 1 Heterocyclic Derivatives of Phosphorus, Arsenic, Antimony and Bismuth, 2nd ed. Wiley (Interscience), New York, 1970. A much shorter first edition was published in 1950. A126. C. A. McAuliffe, ed., Transition Metal Complexes of Phosphorus, Arsenic and Antimony ligands. Macmillan, New York, 1973. 

A variety of trivalent phosphorus, arsenic, antimony and bismuth compounds, as well as divalent oxygen, sulfur and selenium compounds, can also give complexes with transition metals. These donor molecules are, of course, quite strong Lewis bases and give complexes with acceptors such as BR3 compounds where d orbitals are not involved. However, the donor atoms do have empty dn orbitals and back-acceptance into these orbitals is possible, as shown in Fig. 22-17. 

The post-transition metals (in their zero formal oxidation states) have a total of 10 + G valence electrons where G is the highest possible oxidation state of the post-transition metal. Thus, germanium, tin, and lead have 10 + 4 = 14 valence electrons arsenic, antimony, and bismuth have 10 + 5 = 15 valence electrons and selenium and tellurium have 10 + 6 = 16 valence electrons. 

Application of this procedure to the post-transition metals forming clusters indicates that bare gallium, indium, and thallium vertices contribute one skeletal electron bare germanium, tin, and lead vertices contribute two skeletal electrons bare arsenic, antimony, and bismuth vertices contribute three skeletal electrons and bare selenium and tellurium vertices contribute four skeletal electrons in 2D and 3D aromatic clusters. Thus, Ge,Sn, and Pb vertices are isoelectronic withBH, Fe(CO)-, andC5H5Co vertices and As, Sb, and Bi vertices are isoelectronic with CH, Co(CO)v and C H Ni vertices in bare metal cluster compounds. 

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