DATIVE COORDINATE BONDING DATIVE COVALENT COORDINATE BONDING A

DATIVE (COORDINATE) BONDING

DATIVE COVALENT (CO-ORDINATE) BONDING A dative covalent bond differs from covalent bond only in its formation Both electrons of the shared pair are provided by one species (donor) and it shares the electrons with the acceptor Donor species will have lone pairs in their outer shells Acceptor species will be short of their “octet” or maximum. Lewis base Lewis acid Ammonium ion, NH 4+ The lone pair on N is used to share with the hydrogen ion which needs two electrons to fill its outer shell. The N now has a +ive charge as - it is now sharing rather than owning two electrons. a lone pair donor a lone pair acceptor

Boron trifluoride-ammonia NH 3 BF 3 Boron has an incomplete shell in BF 3 and can accept a share of a pair of electrons donated by ammonia. The B becomes -ive as it is now shares a pair of electrons (i. e. it is up one electron) it didn’t have before.

1. Ammonium ion : NH 4+ NH 3(g) + HCl(g) NH 4+Cl-(s) H. N. . . H + H+ H. N. H. . H +

2. Hydronium ion : H 3 O+ H 2 O(l) + HCl(g) H 3 O+(aq) + Cl-(aq) . . H. O. . . H + H+ . . H. O. . . H + H H 4 O 2+ unlikely to form via the second lone pair because the second H+ is repelled by H 3 O+

3. Aluminium chloride dimer, Al 2 Cl 6 Cl. . . Cl. Al. . . Cl . . . Al. Cl

4. Carbon monoxide, CO C X X O Isoelectronic with N 2 : N X X X N