Square-planar complexes molecular orbital bonding

In the structure of Zeise s salt, the ethylene occupies the fourth coordination site of the square planar complex with the CC axis perpendicular to the platinum-ligand plane. In this compound, the dsp2 hybridised s orbital of Pt overlaps with / -bonding molecular orbitals of ethylene. Simultaneously, the filled dp orbital of Pt overlaps with p orbital of C2H4. 

We have seen in Chapter 11 that the square planar configuration is particularly stable because Tour of the mostly metal nd molecular orbitals are stabilized relative to the dxj.yS-derived orbital. IW> Three of the four orbitals (metal-ligand it bonding, but to a first approximation, the interact with any other orbitals in an isolated square planar complex.147 Suppose, however, we configure the complex so that the is farced into interaction. By bridging two square planar complexes, the two systems are forced to lie parallel (face-to-face) at a fixed distance ... 

Dissociative mechanisms for square-planar substitutions are discussed in a review. A molecular orbital study of insertion of ethene into Pt—H bonds concludes that the reaction can be best described by a series of, preferably, dissociative steps. Rearrangements of three-co-ordinate ML3 T- or Y-shaped i -structures are discussed in this context. Three-co-ordinate intermediates are also suggested in the mechanisms for palladium(ii)-catalysed oxidations of olefins, and for electrophilic cleavage of platinum-carbon ff-bonds by protons. Parallel associative and dissociative processes have been proposed for a substitution reaction of a square-planar rhodium(i) complex in benzene solution. Especially, sterically crowded complexes have been thought to stabilize three-co-ordinate intermediates more easily. Recently determined activation volumes for sterically hindered square-planar complexes both of platinumand palladium are not compatible with dissociative activation, however. 

Divalent late transition metals like cobalt (d ), nickel (d ), and copper (d ) in the first row of the d-block can use five 3d orbitals, one 4s orbital, and three 4p orbitals to form 4-, 5-, or 6-coordinate complexes. As a general rule, if there are N ligands in the first-shell coordination sphere of a transition metal complex, then there should be N bonding molecular orbitals, N anti-bonding molecular orbitals, and 9-N nonbonding molecular orbitals. Exceptions to this rule occur in some square-planar complexes in which three orbitals with the same symmetry properties overlap and form chemical bonds. Usually, some coordination sites in the first-shell of the... 

Construct the molecular-orbital and valence-bond wave functions for the (T bonding in a square-planar complex. When are the molecular-orbital and valence-bond descriptions the same ... 

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