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concentration.10 In accord with these observations, we have noted large proton shifts for this compound that are concentration dependent. Finally, we have observed large changes in the n.m.r. spectra of several nickel chelates of salicylaldimines on the addition of pyridine together with corresponding shifts in the proton resonances of pyridine. Such effects are consistent with a coordination of pyridine to nickel and studies are being continued. The chelates prepared for this study were obtained either by treating the Schiff base phenolate ion with nickel acetate or, more conveniently, by treating a suspension of the bis-(salicylaldehyde)nickel(I1) in boiling ethanol with an excess of the substituted aniline.11,12 The chelates were obtained as anhydrous solids and had satisfactory C, H, N and Ni analyses.
crystallizes in a packing arrangement similar to that of the diester. It was therefore of interest to test its photo-behavior, which had not been reported by Griffin. Ultraviolet irradiation of a powdered sample of monomethyl fumarate produced a progressive change in the X-ray powder pattern. After several days of exposure the irradiated sample was washed free from starting material with diethyl ether; the less soluble residue showed no hydrogen uptake on attempted catalytic hydrogenation. After recrystallization from din-butyl ether this material melted a t 153-154' ; elemental analysis gave: C, 46.5; H, 4.4; (0) CH3, 11.5. Calcd. for C1~HI2O8:C, 46.2; H, 4.7; (0)CH3,11.6. A convenient method of isolation of the dimeric material treats the irradiated sample with excess boiling thionyl chloride which removes the monomer a t the water pump as the volatile p-(chloro(10) R . H. Holm, J . A m . Chem. SOL., 83, 4683 (1961). (11) F. Basolo and W. R. Matoush, ibid., 76, 5663 (1953). formyl) methylacrylate. The anhydride of the (12) L. Sacconi, P. Paoletti and G. Del Re, ibid., 79, 4062 (1957). dimer (m.p. 144' from chloroform) gives an COXTRIBUTION No. 808 E . A. LALANCETTE infrared spectrum characteristic of a five-membered CENTRAL RESEARCH DEPARTMENT D. R. EATON cyclic anhydride. Hydrolysis with hot water EXPERIMESTAL STATION R . E. BENSON regenerates the diacid diester of m.p. 153-154'. E . I. DZi POST D E h-EMOURS AND COMPANY WILMISGTOS,DELAWARE W. D PHILLIPS The photodimer as well as its anhydride were AUGUST6, 1962 converted by methanolic hydrogen chloride to a RECEIVED compound identical with cyclobutane 1,2,3,4tetracarboxylic acid tetramethyl ester of n1.p. 144145' obtained by Grifin and co-workers by the THE PHOTODIMERIZATION OF MONOMETHYL photodimerization of dimethyl fumarate.2 The FUMARATE conformation of the dimer of monomethyl fumaSir: Through the courtesy of Dr. G. W. Griffin we rate is therefore established as I. Thus, the crystal have had access to his work (since published1$2) structures of the three monomers have in common on the photodimerization in the solid state of a shortest axis of 4 A. and dimerization to dimers HOgC fumaric acid derivatives to the corresponding cyclobutanes. Following our own interest in the photodimerization of cinnamic acids to a-truxillic and @-truxinic acids and the dependence of the stereochemical course of this reaction on the lattice geometry of the m ~ n o m e r ,we ~ have extended TABLE I fyans-Compound
hIe02CCH=CHC0&e4 SCCH=CHCS6 Me02CCH=CHC02H $PhCH=CHCO2H Me02C(CH=CH)2C02Me MeO?CfCH=CH)rC02ble
a,.&.
3.92 3.89 14.14 6.05 T .74 7.60
b,A.
c,A.
9.24 3.60 3.99 4.04 5.81
5,93 11.34 5.60 31.3 5.82 13.06
.i.RR
OL
101'47' ...
72.6" ... 88 0"
81.1"
B
1120 49' 121.9' 98.8" 90.3" 121.Xo
1n.i.;"
Y
109' 20' ... 83.8" ... 106.1" 105.9"
Space group
Pi P21/n Pi P2,/c
Pi Pi
n
1
2 3
I
4 1
-
1
Griffin's work on the fumaric derivatives by crystallographic studies. As Griffin, et al., have already noted the packing arrangements of dimethyl fumarate4 and of fumaronitrile5 (see Table I) favor the formation of dimers of symmetry 2/m through the contact of parallel omoleculesalong the shortest translation period of 4 A. A crystallographic survey of other fumaric acid derivatives shows that monomethyl fumarate
of symmetry m; they are completely analogous to the @-modification of substituted ci;namic 0.1 A . and acids defined by shortest axes of 4.0 photodimerization to p-truxinic acids. The next higher homologs, dimethyl trans,transmuconate and dimethyl all-trans-hexatriene dicarboxylate, do not belong to this structure type (see Table I); work on their photochemical behavior is under way.
(1) G. W. Griffin, G. E. Basinski and A. F. Vellturo, Telvahedvon Lelters, S o . S , 18 (1960). ( 2 ) G. W. Griffiu, A. F. L'ellturo and K. Furukawa, J . A m . Chem. S o i . , 83, 2725 (1961). (3) G. ?VI.J. Schmidt, Acfa C v y s f . , 10, 783 (1967); M. D. Cohen and G. M . J. Schmidt in J. H. de Boer, Ed., "Reactivity of Solids," Elsevier Publishiug Co., .4rnstrrdum, 1961, p. 556. ( 4 1 I. E. Knagys and K. Lonsdale, J . C h e w . Sa.,417 (1942). ( 2 ) B. peal, private cururuunication.
Acknowledgment.-\i?e wish to thank N r . L. Leiserowitz and h4r. D. Rabinovich for measuring some of the crystallographic constants reported here.
*
DEPARTMEST OF X-RAYCRYSTALLOGRAPHY INSTITCTE OF SCIENCE .r.SADEH WEIZMANN G. IT.J. SCHMIDT KEHOVOTH,ISRAEL K E C E I V U u d U G L J b r 16, 1962
