Part 1: I was just reviewing concept of the dative covalent bond in some simple molecules. One of which was carbon monoxide.
Some structures I saw featured the use of formal charges, in which the carbon atom had a negative formal charge while the oxygen atom had positive formal charge. These did not show that a dative bond was involved.
Some I saw claimed the molecule remained neutral and showed a dative bond between the two atoms.
I understand that the formal charge is a theoretical construct and does not refer to actual charges on atoms. Rather, they indicate to the chemists where are the regions of electron-richness and electron-deficiency.
So these two structures do not contradict each other and each are limited in some way.
However, dative bonding in complex metal ions always show dative bonding which is the latter structure, never the former structure, with formal charges. Why is this so?
Part 2: Secondly, what are the differences between a dative covalent bond, where one species donating both electrons, and a typical covalent bond, where each species donates one electron. Other than the process of bond making, is every other characteristic of the two bonds the same?
If you think about it, a lot of covalent bonds are actually "dative". Consider all the bonds between nucleophiles and electrophiles. Isn't it always the case where the nucleophile donates a pair of electrons?
In my opinion, the only difference appears to only be the difference in the bond making process and all else is exactly the same.