Transition metal configurations

Scerri, E. R. [1989] Transition Metal Configurations and Limitations of the Orbital Approximation , Journal of Chemical Education, 66(6), p. 481. 

Ionizations are evident before ligand ionizations with early transition metals Ti(m), V(III), or Cr(III), not evident at all or masked under ligand ionization bands with late transition metals such as Cu(ll) or Zn(II), and highly intermixed with the first ligand ionizations for intermediate transition metal configurations such as d6 of Co(III) or d6 of Ni(H). (Fig. 11). This type of behavior is probably of general occurrence and is in fact found also in other classes of coordination compounds, especially with sulfur ligands. 

Table 3 Transition Metal Configuration Energies and Electronegativities (Pauling Units) i ...

Copper differs in its chemistry from the earlier members of the first transition series. The outer electronic configuration contains a completely-filled set of d-orbitals and. as expected, copper forms compounds where it has the oxidation state -)-l. losing the outer (4s) electron and retaining all the 3d electrons. However, like the transition metals preceding it, it also shows the oxidation state +2 oxidation states other than -l-l and - -2 are unimportant. 

Olefin Isomerization- a variety of transition metal (RhCl3 H20) catalyst will isomerize doubles bonds to more thermodynamically favorable configurations (i.e. more substituted, trans, conjugated)... 

Not all ligands use just two electrons to bond to transition metals Chromium has the electron configuration [Ar]4s 3rf (6 valence electrons) and needs 12 more to satisfy the 18 electron rule In the compound (benzene)tricarbonylchromium 6 of these 12 are the tt elec Irons of the benzene ring the remammg 6 are from the three carbonyl ligands... 

Tacticity of products. Most solid catalysts produce isotactic products. This is probably because of the highly orienting effect of the solid surface, as noted in item (1). The preferred isotactic configuration produced at these surfaces is largely governed by steric and electrostatic interactions between the monomer and the ligands of the transition metal. Syndiotacticity is mostly produced by soluble catalysts. Syndiotactic polymerizations are carried out at low temperatures, and even the catalyst must be prepared at low temperatures otherwise specificity is lost. With polar monomers syndiotacticity is also promoted by polar reaction media. Apparently the polar solvent molecules compete with monomer for coordination sites, and thus indicate more loosely coordinated reactive species. 

Polyatomic molecules cover such a wide range of different types that it is not possible here to discuss the MOs and electron configurations of more than a very few. The molecules that we shall discuss are those of the general type AFI2, where A is a first-row element, formaldehyde (FI2CO), benzene and some regular octahedral transition metal complexes. 

In general, octahedral complexes of transition-metal ions possessing 0, 1, or 2 electrons beyond the electronic configuration of the preceding noble gas, ie, i/, (P configurations, are labile. The (P systems are usually inert the relative lability of vanadium(II) may be charge and/or redox related. 

The next major commodity plastic worth discussing is polypropylene. Polypropylene is a thermoplastic, crystalline resin. Its production technology is based on Ziegler s discovery in 1953 of metal alkyl-transition metal halide olefin polymerization catalysts. These are heterogeneous coordination systems that produce resin by stereo specific polymerization of propylene. Stereoregular polymers characteristically have monomeric units arranged in orderly periodic steric configuration. 

With an atomic number of 28, nickel has the electron configuration [Ar]45 34f (ten valence electrons). The 18-electron rule is satisfied by adding to these ten the eight electrons from four carbon monoxide ligands. A useful point to remember about the 18-electron rule when we discuss some reactions of transition-metal complexes is that if the number is less than 18, the metal is considered coordinatively unsaturated and can accept additional ligands. 

Not all ligands use just two elections to bond to transition metals. Chiomium has the election configuration (6 valence electrons) and needs 12 more to satisfy the 18-... 

Superoxo complexes having a nonlinear M-O-O configuration are known at present only for Fe, Co, Rh and perhaps a few other transition metals, whereas the Vaska-type (Ila) complexes are known for almost all the transition metals... 

Figure 19.16 The possible high-spin and low-spin configurations arising as a result of the imposition of an octahedral crystal field on a transition metal ion.

Here, we address the more general question of the relative stability of monomers, dimers and triangular trimers on the (111) surface of FCC transition metals of the same chemical species as a function of the d band filling Nd. All possible atomic configurations of the systems are considered monomers and dimers at sites N and F, triangles with A and B borders at sites N and F (Fig. 4). The d band-filling includes the range of stability of the FCC phase (Nd > 7.5e /atom). The densities of states are obtained from... 

Give the electron configuration and/or orbital diagram of a transition metal cation. 

---