OCH, I
31.0 ppm. Students need only interpret the NMR information on the basis of the number of different kinds of carbon to confirm the structure (I).
f-n
(I) Reaction of the yellow product (I) with sodium methoxide
-
2C~H12PdCls+ 2NaOCH3
(C6H120CH3PdC1)2 + 2NaCI
gives a white, air-stable, compound. Coordination t o the palladium activates the olefin toward nucleophilic attack and results in the addition of methoxide and palladium across one of the double bonds. Formation of a metal-carbon sigma hond requires the loss of one chloride per palladium fur charge balanre. The loss of one chloride per palladium results in the formation of a dimer tomaintain square planar coordination (1-3) with a structure similar to that of [Pt (OMe) (C8Hl20Me) 12 (5).The weight of product (11) typically obtained by students is slightly less than the weight of the treated starting material (I), and their spectrophotometric determinations also indicate only a small change in molecular weight per palladium due to reaction with methoxide. The proton decoupled '3C NMR spectrum of (11) in chloroform-d shows nine well-resolved peaks a t 105.2,100.9, 81.4,56.5,51.6, 34.4,30.9,28.2, and 26.6 ppm. The presence of nine different carbon peaks in the 13C NMR of (II), when (I) has only eight carbon atoms, confirms methoxide addition and the structure (11). We have found this experiment to be a useful and stimulating laboratory introduction to organometallic chemistry, as well as an excellent application of chemical deduction. Students were generally capable of proposing reasonable
structures for (I) and (II), especially when given a few leading hints, such as if a methoxide has been added with little change to the weight percent of palladium, then something of similar weight (i.e., chloride) must have been lost. At the end of the experiment all palladium containing solids can be collected and the palladium chloride recovered for later re-use (see experimental). The recovered palladium chloride reacts identically to the original commercially ohtained material. Acknowledgmen! The authors acknowledge Lawrence F. Dahl and Richard Porter from the Chemistry Department, University of Wisconsin-Madison, for their help in obtaining 13C NMR spectra.
Literature Cited (I) Chstl, J., Vallarino, L. M..and VenanzLL. M., J. Cham. Soc., 3413 (1957) (2) Schultz, R. G., J. Orgcnomelol. Chem. (Amsterdam), 6,435 (1966). 131 HerUeu. F. a . Chem. Re". 69.799 11969). (4) Drew.D.. and'~oyle,J. R.:I~&. ~ynfh.; 13.52 (1972). (5) Giordsno, F.,and Vitagliano, A,, lnorg. Chem., 20,63311981). 16) Ayres, G. H..and Tufny. B. L.. A n d Chem.. 24.949 11952). 171 Treadwell. F. P.. and Hall. W. T.. ,"Anal*eai Chemistry," 9th ed., John Wiley and Sons. New York. 1946. Vol. 1.p. 525.
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Volume 82 Number 10 October 1985
897
