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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: AhmedEzatAlzawalaty on March 18, 2007, 11:56:24 AM

Title: DMG vs 8-Hydroxyquinoline
Post by: AhmedEzatAlzawalaty on March 18, 2007, 11:56:24 AM

Why 8-hydroxy quinoline [benzo(2,3-b)azine] is bidentate ligand?(my answer : this is due to the N and -OH ) and DMG is bidentate due to N and N, shouldnt DMG be Tetradentate ligand as it contains also two OH groups.(as OH is considered to have lone pair)
do u get it?

Title: Re: DMG vs 8-Hydroxyquinoline
Post by: AWK on March 19, 2007, 11:21:55 AM

8-hydroxyquinoline complexes throuhh N and O^-
DMG complexes through O^- and nonbonded electron pair of the second oxygen atom.

Title: Re: DMG vs 8-Hydroxyquinoline
Post by: AhmedEzatAlzawalaty on March 19, 2007, 01:10:48 PM

u answer the wrong question.i say either why the two N in DMG not share in complexing?

Title: Re: DMG vs 8-Hydroxyquinoline
Post by: AWK on March 19, 2007, 01:19:37 PM

DMG structure is different from that you drew

Title: Re: DMG vs 8-Hydroxyquinoline
Post by: AhmedEzatAlzawalaty on March 19, 2007, 03:00:50 PM

ok i draw it wrong,here it is
but the question stills the same.

Title: Re: DMG vs 8-Hydroxyquinoline
Post by: AWK on March 20, 2007, 03:11:55 AM

OK read this link
http://www2.truman.edu/~blamp/chem222/manual/pdf/nickelgrav.pdf

Title: Re: DMG vs 8-Hydroxyquinoline
Post by: AhmedEzatAlzawalaty on March 20, 2007, 08:08:17 AM

i figure out from the file that Oxygen of DMG are already involved in H bond so they dont share in the coordinate bonds of the chelate. right?

Title: Re: DMG vs 8-Hydroxyquinoline
Post by: AWK on March 20, 2007, 11:16:12 AM

Two possible coordinations are known, though for (DMG)2Ni only one is found so far.
See below. Molecules are taken from below two real crystal structures (codes are from CSD)