Dative Covalent Bonds

Could anyone give me a bit more information about Dative Covalent Bonds?

I'm quite unsure about them, and my text book (which i wont name) isn't too good at explaining...

Thanks.

Reply 1

username68316

All I can tell you from what I remember, is that it's a covalent bond between two atoms sharing 2 electrons, as you would expect in any single bond. Except the two electrons that make up that single bond come from one of the atoms in the bond. So one atom offers 2 electrons for the bond, and the other atom offers nothing, but shares them.

Reply 2

charco

Study Forum Helper

yeah, what Nat says
Dative means 'giving' or 'donating' as in the dative case in Latin. A dative covalent bond has both of the electrons donated by the same atom. This has ABSOLUTELY NO consequences in terms of the actual bond. There are still two electrons between the two nuclear centres and the bond is exactly the same as a normal covalent bond, it's just that we like to give it a different name to indicate that the pair of electrons originated from the same atom that's all.

Reply 3

t-a-r-online

Thank you both for your replies.

How do we know whether two atoms are bonded using the dative bond? How can we tell?

Reply 4

firestone

In some cases you can't really tell just by looking at the molecule - which atom provided the electron pair to form the dative covalent bond as the electrons are identical. But I think that you could sort of tell if one of the atoms is forming more bonds than usual (than bonding to the required number of electrons to complete its outer quantum shell). Like say for H₃O⁺ or NH₄⁺ oxygen is forming three bonds instead of two, nitrogen is forming four instead of three so you could sort of tell that one of them isn't a normal covalent bond as oxygen would otherwise be unable to form three, nitrogen four since they would already have a full outer quantum shell. They do not need any more electrons or to form any more bonds to attain a stable electronic structure. Therefore one of the covalent bonds must be dative with the bonding electron pair being provided by the oxygen / nitrogen without sharing any more electrons from the hydrogen into its outer shell since O/N no longer has any unpaired electrons to share (no singly occupied orbital to interact).

Dative covalent bonds are sometimes (sometimes because I only know of cases where this is true) formed during nucleophilic reactions with the nucleophile providing the lone pair of electrons to form a dative covalent bond to the electron deficient positive charge. These are also formed in electrophilic additions where the negative charge provides a bonding pair of electrons to the positive electron-deficient attacking species; for example with the electrophilic addition of bromine to alkenes another dative covalent bond is formed in the last stage when the negative bromide ion provides a lone pair of electrons to the positive carbocation to the forming of a new covalent bond. So if you know the mechanism, you'd know whether it was a dative covalent bond.

Dative Covalent Bonds

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