The central atoms in these compounds usually possess the d8 electron configuration, and, as in octahedral compounds, the kinetics of substitution reactions in compounds with this type of geometry are strongly influenced by the trans ligand.
A common feature of hydration-promoting catalysts, such as chlorotris(triphenylphosphine)rhodium, Wilkinson's catalyst, is the adoption of this molecular structure.  Hoogsteen pairing gives rise to complexes with this configuration which are composed of hydrogen-bonded guanines stabilized around a potassium cation.  The central atoms in these compounds usually possess the d8 electron configuration, and, as in octahedral compounds, the kinetics of substitution reactions in compounds with this type of geometry are strongly influenced by the trans ligand. An exemplary compound exhibiting this geometry is cisplatin.  For 10 points, name this type of molecular geometry characterized by two nonbonding and four bonding electron pairs, in which the four substituents are situated ninety degrees apart on the same plane as the central atom.
A common feature of hydration-promoting catalysts, such as chlorotris(triphenylphosphine)rhodium, Wilkinson's catalyst, is the adoption of this molecular structure.  
square planar