Hapticity is often required to describe their binding, and decrease in the parameter B due to the binding of these compounds is known as the nephelauxetic effect.  
The Tolman cone angle describes the space that one of these objects occupies, and those with unclear oxidation states are referred to as non-innocent ones. Sometimes divided into inner-sphere and outer-sphere varieties, those that bind to each other across the long axis of a compound are referred to as trans-spanning ones. Hapticity is often required to describe their binding, and decrease in the parameter B due to the binding of these compounds is known as the nephelauxetic effect.  The spectrochemical series arranges them ? in terms of their ability to split energy between two sets of d-orbitals; this is described by a modification of crystal field theory named for these compounds. For 10 points, name these compounds with can be mono- or polydentate, a term used to describe the groups bound around a central metal atom in a coordination compound.
The Tolman cone angle describes the space that one of these objects occupies, and those with unclear oxidation states are referred to as non-innocent ones.
{Ligand}