Tetrubedron Letters ~().54, nl,. 5639-5641, 1968. Perglunon Press. Printed iu Greet Britain.

COMPLEXATION OF OLEFINIC ALCOHOLS WITH AQUEOUS SILVER ION

Donald Gray, Richard A. Wles, and W. 0. Clossonl

Department of Chemistry, State University of New York at Albany Albany, New York I2203

(Received in USA 10 September 1968; received in UK for publication 4 October 1968)

Recently, In the course of some synthetic work In the cyclooctene system, we noted that cls- -

4-cycloocten-l-one was much less easily extracted from ether into aqueous sliver nitrate than the

corresponding alcohol. Measurement of the equlllbrlum constants2 for ccmplex formation for sev-

eral cyclooctene derlvatlves (Table I) showed that while the unsaturated ketone and alcohol were

each better than cis-cyclooctene In coordinating ability, the alcohol was a strikingly superlor -

I Igand. lnvestlgatlon of a series of acycllc, terminally unsaturated alcohols (Table I) indi-

cated that the equilibrium ccnnplex is largest when the double bond is in a A4 relationship to the

hydroxyl group, but a A3 (homoallyllc) or A6 relationship also gives rlse to a relatively stable

complex. Converslon of the hydroxyl group to acetate or methoxyl drastically decreases the sta-

bllity of the ccmplex. Also, secondary hydroxyls appear to have a smaller effect.

Although silver normally does not coordinate strongly wfth oxygen,3 the best explanation for

enhancement In complexation constant (Id- fold In sune cases) would appear to be direct bonding

of the hydroxyl oxygen to silver. The alternatlve, hydrogen bonding of the hydroxyl to a water

molecule coordinated with sliver, seems unlikely In vleu of the small effect of acetate or

methoxy I groups. The decrease in coordlnatlng abfllty on changing the hydroxyl group to methoxyl

Is what one would expect for direct bonding of the oxygen to silver.4 The nmr spectrum (60 MHz)

of the 4-penten-l-al complex ln IO% CC,OD-SO$D,O has the trlplet due to the protons on C-l

shifted IO Hz downfield relative to that of the free alcohol In the same solvent.

The stolchlometry of the complex was shown, by measurement of the equlllbrlum constant at

various concentrations of silver nltrate and 4-pentenol, to be I:I. The usual linear geometry of

5639

5640

Table I

Equillbrlum Constantsa for Silver Ion Complexatlon of Olefln Gerlvatlves at 25

K. l/mole

R=H

NR ___

_R ___

WR ___

-R 0.095b

-R ___

_R

1::

O.G96*

-8 1 O= I.30

0 0 = 0.10 0” <O.I ooH

___

CO.1

-See ref. 2 for definltlon of K. Reproduclbllity Is z. III%. ‘S. Winstein and H.J. Lucas,

J. kner. Chem. Sot., 60,836(1938). ‘F.R. Hartley and L.M. Venanzl, J.Chem.Soc. (A), 333(19671.

This Is the equlllbrium constant for olefin In water solutlon. *J.G. Traynham and J.R.Olechowskl,

J.kner.Chem.Soc., 81, 571(1959). BValue for cyclopentene.

K, l/mole

R = OAc

0.35

0.31

0.44

0.15

co.1

eo.1

0.07

co. I

eo.1

<o. I

K, l/mole

R=ClH

12b , 22=

26

51

29

8.2

so.1

25

I9

38

29

K, l/mole

R = OCH 3

___

___

0.34

0.10

No.54

dlcoordinate Ag(l) species,3 Is clearly not possible In this case. Conceivably, the 6 l/2-

membered ring imposed by the hydroxyolefin ligand forces the sliver Into a roughly tetrahedral

arrangement, similar to its 8-hydroxyquinollne complex, 3

with loosely held water molecules

occypylng the other posltions:

No.5% 5642

The enhancement has obvlous utility. Franzus and coworkers, noting that eyn-7-acetoxy-2-

norbornene formed a IO-fold more stable sliver complex than the ant1 Isomer, were able to use

this small difference to separate efflclently the two I~omers.~ In syntheslzlng the methyl

ethers of 4-penten-l-01 and 5-hexen-l-al (by reactlon of the alkoxldes wlth methyl lodlde) traces

of unreacted alcohol were removed completely from the crude alkenyl ethers by simply washing an

ether solutlon of the crude product once with aqueous silver nltrate.

Acknowledqnents. We would like to thank Professors J.J.

ful conzaents and suggestions. The work was supported In

Zuckerman and L.M. Venanzl for many help-

part by the National Science Foundation.

REFERENCES

I. Fellow of the Alfred P. Sloan Foundatlon, 1968-70.

2. The equlllbrlun constants were measured by equlllbratlng, at 25’ CCl, solutlons of the

olefin wlth 1.0 M aqueous sllver nltrate and detennlnlng the loss of olefln from the Ccl4

phase by gas chromatography. The solublllty of the free olefln In tpa aqueous phase was de-

termlned slmllarly by equlllbratlng Ccl4 solutions of the olefins uTth I.0 fi KNo3 solutlon.

The constant for complexatlon was determined as:

lo=Q?j RzO

K = &=!3Cc!l~ [~+ly 3. MM. Jones, “Elementary Coordlnatlon Chemistry,” Prentice-Hall, Inc., Englewood Cliffs, N.J.,

1964, p 116.

4. R.W. Parry and R.N. Keller, “The Chemistry of The Coordlnatlon Compounds,” (J.C. Baflar, Jr.,

and D.H. Busch. Eds.), Relnhold, New York, New York, 1956, p 123.

5. 6. Franzus, W.C. Baird, Jr., E.I. Snyder, and J.H. Surrldge, J. Org. Chem.,z, 2645(1%7).