Macromolecules 1987, 20, 904-906
904
perfect system) could be the result of the hydrogenation procedure, about which we know virtually nothing.5 We will be searching for unambiguous methods of cleaving off the polymer chain (e.g., by reactions analogous to that shown in eq 1) and converting it under mild conditions into a soluble, easily characterized polymer. To our knowledge this is the first report of ring-opening polymerization of cyclooctyne. We will be exploring the details of this reaction and will be searching for other catalysts that yield well-behaved living polymers.
Table I
Equilibrium Values for Conversion of Mo(CPr)(0‘Bu)g (la) into Mo{[C(CH2),C],CPr)(OeBu), (lb)1 % la % lb
equiv C8H12 1
2 3
4 8 10 12
40 (336) 23 (186)
60 (674) 77 (826)
156 11
856
89 95
5
20
56
956
4
96 98
2
Acknowledgment. R.R.S. thanks the National Science Foundation for support through Grant DMR 84-17818 and the Materials Research Laboratory for use of the GPC
Cyclooctyne in 0.75 mL of CeDe was added rapidly to a stirred solution of 10 mg of la and p-dichlorobenzene (internal standard) in 1.5 mL of CgDg. The ratio of la to lb was determined by integration after 24 h. In several analogous experiments the equilibrium values did not change after heating the samples at 100 °C for 10 min. 6 These values were obtained in a separate set of analogous experiments.
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1
facility. Registry No.
References and Notes (1) (a) Ivin, K. J. Olefin Metathesis; Academic: New York, 1983. (b) Dragutan, V.; Balaban, A. T.; Dimonie, M. Olefin Metathesis and Ring-Opening Polymerization of Cyclo-Olefins, 2nd ed.; Wiley Interscience: New York, 1985. (2) (a) Gilliom, L. R.; Grubbs, R. H. J. Am. Chem. Soc. 1986,108, 733. (b) Wallace, K. C.; Schrock, R. R. Macromolecules 1987, 20, 448. (c) Kress, J.; Osborn, J.; Greene, R. . E.; Ivin, K. J.; Rooney, J. J. J. Chem. Soc., Chem. Commun. 1985, 874. (d) Schrock, R. R. J. Organometal. Chem. 1986, 300, 249. (3) (a) Schrock, R. R.; Freudenberger, J. H.; Listemann, M. L.; McCullough, L. G. J. Mol. Catal. 1985,28,1. (b) Churchill, M. R.; Ziller, J. W.; Freudenberger, J. H.; Schrock, R. R. Organometallics 1984,3,1554. (c) Freudenberger, J. H.; Schrock, R. R.; Churchill, M. R.; Rheingold, A. L.; Ziller, J. W. Organometallics 1984, 3,1563. (d) McCullough, L. G.; Schrock, R. R.; Dewan, J. C.; Murdzek, J. S. J. Am. Chem. Soc. 1985, 107, 5987. (e) Listemann, M. L.; Schrock, R. R. Organometallics 1985,4, 74. (f) Schrock, R. R. Acc. Chem. Res. 1986, 19, 342. (4) The reaction appears to be extremely clean. Other resonances
Table II Polyethylene Prepared by Hydrogenation of lb1
GPC Studies
equiv
on
Mw/Mn
C8H12
250 350 500
26000 33000 60000
4300 7500 8600
6.1 4.4 7.0
A?n
(theory)
27000 37900 54100
1 la was hydrogenated at 60 psig of H2 overnight in toluene employing Rh(PPha)3Cl as the catalyst. The resulting polyethylene was analyzed at 145 °C in 1,2,4-trichlorobenzene on a Waters 150C instrument equipped with three Styragel columns. A single relatively symmetric peak was observed in each case with a polydispersity from 4.4 to 7.0 and molecular weight as listed. The columns were calibrated with polystyrene standards in the usual way. The usual conversion factor of 4.1 was employed in order to obtain the molecular weight.
I). We also know that if a sample of lb prepared from 15 equiv of cyclooctyne is mixed with an equal amount of la, the amount of la slowly decreases and an equilibrium mixture consisting of ~8% la and 92% lb is established. The most plausible explanation of these findings is that cyclooctyne or some cyclic oligomer comes out of lb and reacts with la until equilibrium is established between lb NMR spectrum of lb (x and la. Examination of an = 15) at 120 °C showed no sign of cyclooctyne (
