J O U R N A L OF T H E AMERICAN CHEMICAL SOCIETY (Registered in
VOLUMES1
U.S. P a t e n t
Oflice)
(0 Copyright, 1959, by t h e American Chemical Society)
AUGUST 17, 1959
YUMBER 15
PHYSICAL, A N D INORGANIC CHEMISTRY [ C O N T R I B U T I O N FROM THE CHEXZISTRY
LABORATORIES O F NORTIIWESTERN
UNIVERSITY]
Mechanism of Racemization of Complex Ions. V. The Dissociation and Racemization of Tris-(2,Z '-bipyridine)-iron(I1) and Tris-( 1,lo-phenanthro1ine)-iron(I1) Ions in WaterMethanol and Methanol Solutions1x2 BY LESTERs E I D E N , 3 FREDBASOLOAND H. 11.N E U X A N N RECEIVED OCTOBER 27, 1958 T h e rates of racemization of tris-(2,Z'-bipyridine)-iron( 11)and of tris-( 1,lO-phenanthro1ine)-iron( 11) increase continuously with increasing methanol content of water-methanol mixtures, while the rates of dissociation display a maximum. T h e differences in the two rates suggest that in alcohol rich solvents racemization takes place essentially by a n intramolecular process. There is a specific anion catalysis on the rates of dissociation. The observed results are discussed in terms of ionpair formation a n d solvation of the complexes.
Detailed kinetic studies have been carried out on the rates of dissociation and racemization of the complexes of nickel(I1) and iron(I1) with 2,2'bipyridine and 1,lO-phenanthroline, respectively, e.g., M(bipy)a2+ and M(phen)3*+. In aqueous solution nickel(I1) complexes were' found to racemize by a dissociation mechanism4 whereas the iron(I1) complexes racemize largely by an intramolecular process and only in part by dissociation? Davies and Dwyer6 have investigated the racemization of these complexes in several non-aqueous solvents and in water-organic solvent mixtures. Recently Lx'ilkins and Williams7 studied the exchange of 1,lO-phenanthroline in the system Ni(phen)32+-*phen in various solvents. They observed that the dissociative path for racemization also persists in these solvents. Except for a few preliminary observations6 on the rates of racemization, the iron(I1) complexes had not previously been studied in non-aqueous (1) Previous paper in this series, A. Jensen, F. Basolo and H. M. i i e u m a n n , THIS]OURN.4L, 80, 2354 (1F)Sg); presented in part a t t h e Chicago Meeting of the American Chemical Society, September, 1958. (2) This investigation was supported by a Grant-in-Aid from t h e National Institutes for Health, Grant iio. RG-4335(C). (3) Taken from a dissertation submitted by L. Seiden in partial fulfillment of t h e requirements for the Ph.D. at Northwestern University, Evanston, Illinois, 1957. (4) F. Basolo, J. c. Hayes and H. ?iI. Nelimann, THISJ O U R N A L . 75, 5102 (1953). ( 5 ) F. Basolo, J. C . Hayes a n d H. ?VI. Neumann, ibid., 76, 3807 (195l). (6) N. R. Davies and F. P. Dwyer, Trans. Favadny Sac., 60, 1326 ( 1984). (7) I
