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UBC Theses and Dissertations

New species of nickel (II) salicylaldimine complexes O'Brien, Ross Joseph 1960

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NEW SPECIES OF NICKEL ( I I ) SALICYLALDIMINE COMPLEXES by ROSS JOSEPH O'BxRIEN B.Sc. U n i v e r s i t y of B r i t i s h Columbia, 1 9 5 8 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of CHEMISTRY We accept t h i s t h e s i s as conforming to the requ i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA October, i 9 6 0 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree th a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n permission. The U n i v e r s i t y of B r i t i s h ' C o l u m b i a Vancouver 8, Canada. Department of Date (Uf 6 i i A b s t r a c t Two new forms of bis-IShmethyl-salicyladimine n i c k e l ( I I ) were prepared. The f i r s t i s a paramagnetic species i s o l a t e d from chloroform s o l u t i o n at - 7 6 ° C . The second species i s an orthorhombic diamagnetic m o d i f i c a t i o n obtained from hot a l c o h o l , and a l s o upon warming the loxv temperature form. A new paramagnetic species was obtained from b is-N^-me thy 1 ^ 5 - c h i or o-s a l i c y l a l d i m i n e n i c k e l ( I I ) upon heating t o l 6 5 ° C . This com-pl e x i s paramagnetic ( 2 . 9 0 B..M.) w i t h a Weiss constant of 6 0 ° . Two other compounds were prepared c o n t a i n i n g both s a l i c y l a l d e h y d e and N-methyl s a l i c y l a l d i m i n e . An apparatus t o measure magnetic s u s c e p t i b i l i t i e s over a temperature range of - 1 7 0 ° C to 2 0 0 ° C i s described. I t i s e s s e n t i a l l y the apparatus r e c e n t l y p ublished by F i g g i s and Nyholm, but some important m o d i f i c a t i o n s are reported. i i i TABLE OP CONTENTS Page L i s t of Figures i v CHAPTER 1 . I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . M 2 . Experimental . . . . . . . . . . . . . . . . . . . . . 1 0 1. « Pre p a r a t i o n and A n a l y s i s 1 0 2 . Magnetic Measurements . . . . . . . . . . . . . 1 9 (a) D e s c r i p t i o n of the Magnetic Balance . . 2 0 •(b) C a l i b r a t i o n of the Apparatus . . . . . . . . 2 2 '(c) Magnetic S u s c e p t i b i l i t y of the Dia-magnetic S o l i d s . . . . . . . . . . . . 2 3 3 . Magnetic Measurements at Low Temperature . . . 2 4 .(a) Cryostat 2 4 .(b) Temperature-Control C i r c u i t . . . . . . . . 2 6 (c) Measurement of Temperatures . 2 8 (d) C a l i b r a t i o n of Gouy Tube 2 8 4 . Magnetic S u s c e p t i b i l i t y of the L i g h t Green Form of B i s - N - M e t h y l - 5 - C h l o r o - S a l i c y l a l d i m i n e N i c k e l ( I I ) 2 9 5 . P r e p a r a t i o n of S o l i d Paramagnetic Species . . 2 9 "(a) I s o l a t i o n of Paramagnetic Species by Cooling of S o l u t i o n . . . . . . . . . . . 2 9 (b) Heating of Complexes 3 1 6 . D i f f u s e Reflectance Spectra of Paramagnetic Species 3 3 3 . D i s c u s s i o n . . . c . . 3 3 4 . Conclusion 3 5 5 . B i b l i o g r a p h y ^ 3 i v L I S T OF FIGURES To F o l l o w Page 1. A Proposed. S t r u c t u r e f o r the B u f f B i s - N -M e t h y l - S a l i c y l a l d i m i n e N i c k e l ( I I ) . . . . . . . 4 2 . A New P o l y m e r i c Compound . . . . . . . . . . . . 17 3 . The C r y o s t a t 23 4 . The O u t s i d e Dewar F l a s k . . . . . . . . . . . . . . 24 5 . The R e f r i g e r a n t L e v e l C o n t r o l C i r c u i t . . . . . . 24 6 . The Temperature C o n t r o l C i r c u i t . 25 7. The Graph of v e r s u s T°K f o r t h e L i g h t Green B i s - N - M e t h y l - 5 - C h l o r o - s a l i c y l a l d i m i n e n i c k e l 28 V ACKNOWLEDGMENTS I would l i k e to express my g r a t i t u d e to Dr. H.C. C l a r k f o r h i s many hours of th o u g h t f u l d i s -cussion and h i s c r i t i c a l a n a l y s i s of the var i o u s ideas I have proposed. I would a l s o l i k e to thank Messrs. S. Rak, L. Stewart, and T. Hawkins f o r t h e i r a s s i s t a n c e i n c o n s t r u c t i o n of apparatus and C. Barnetson f o r h i s many analyses. I n t r o d u c t i o n For the l a s t twenty years, the i n v e s t i g a t i o n of quadricoordinate n i c k e l complexes and i n p a r t i c u l a r the stereo-chemistry of paramagnetic complexes has r e c e i v e d considerable a t t e n t i o n . Of t h i s vast c l a s s , one type of complex has been very a c t i v e l y s t u d i e d . These are the b i s - N - a l k y l - s a l i c y l a l d i m i n e n i c k e l ( I I ) complexes and more s p e c i f i c a l l y the N-methyl d e r i v a t i v e . The reason f o r the i n t e r e s t i n these complexes i s that they are diamagnetic i n the s o l i d s t a t e , but on d i s s o l v i n g the s o l i d i n organic solvents the complex becomes paramagnetic. The problem of determining the stereochemistry of the paramagnetic species has l e d to many r e l a t e d experiments. The f i r s t reported p r e p a r a t i o n of these complexes was by P f e i f f e r and h i s co-workers ( l ) , who prepared the dark green, monoclinic, diamagnetic complex. The f i r s t i n d i c a t i o n that the compounds had unusual p r o p e r t i e s was reported by Klemm and Raddatz ( 2 ) . They pre-pared, by a c c i d e n t , a l i g h t green paramagnetic compound, which on standing r e v e r t e d to a diamagnetic complex. They were unable to d u p l i c a t e t h e i r experiment. W i l l i s and M e l l o r (3)? i n the f i r s t d e t a i l e d magnetic s u s c e p t i b i l i t y study, found that b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( I I ) became paramagnetic i n organic s o l v e n t s . In c o o r d i n a t i n g s o l v e n t s , e.g. p y r i d i n e , the expected value of 2 3 . 1 0 B.M., corresponding to 2 unpaired e l e c t r o n s , was found f o r the magnetic moment, but i n "non-coordinating'- s o l v e n t s , f o r example chloroform, an intermediate value of 2 . 2 B.M. was found at room temperature. W i l l i s and M e l l o r p r e d i c t e d that i n the case of p y r i d i n e the four coordinated complex became s i x coordinated through the c o o r d i n a t i o n of two p y r i d i n e mole-c u l e s . In the case of "non-coordinating" solvents,they postu-l a t e d a t e t r a h e d r a l arrangement f o r the paramagnetic species. C o n d u c t i v i t y measurements were a l s o made,and the r e s u l t s d i s -counted i o n i z a t i o n as a p o s s i b l e cause f o r the paramagnetism. W i l l i s and M e l l o r a l s o showed that the magnetic moment was independent of c o n c e n t r a t i o n . Confirmation of the formation of a d i p y r i d i n e adduct i n p y r i d i n e s o l u t i o n s was obtained by Basolo and Matouch ( 4 ) when they i s o l a t e d such an adduct. C l a r k and O d e l l ( 5 ) a l s o confirmed t h i s . A p o s s i b l e explanation f o r the conversion from a square planar to t e t r a h e d r a l arrangement was given by Nyholm ( 6 ) , who suggested t h a t the t e t r a h e d r a l form was i n h e r e n t l y more st a b l e and that the square planar form was a r e s u l t of the c o n s t r a i n i n g c r y s t a l f i e l d s i n the s o l i d s t a t e . On d i s s o l u t i o n , t h e r e f o r e , conversion to the paramagnetic t e t r a h e d r a l species would occur. The reason f o r the intermediate value of bis-N-methyl-s a l i c y l a l d i m i n e n i c k e l ( i i ) i n "non-coordinating" solvents was reported independently by C l a r k and Odell ( 5 ) and F u j i i and Sumitoni ( 6 ) . I n v e s t i g a t i o n of the magnetic s u s c e p t i b i l i t y 3 over a wide temperature range showed that a temperature depend-ent e q u i l i b r i u m occurred between diamagnetic and paramagnetic forms. In order to determine the importance of the solvent i n the production of a paramagnetic species Sacconi, C l n i and Maggio (7) measured the magnetic s u s c e p t i b i l i t i e s of the molten complexes and showed th a t paramagnetism was e s t a b l i s h e d i n the absence of s o l v e n t . These'experiments were conducted w i t h the N-ethyl to N-decyl d e r i v a t i v e s , and i n the cases where the com-p l e x was molten below 120°C a p l o t of magnetic s u s c e p t i b i l i t y versus temperature shows a minimum i n the magnetic Suscepti-b i l i t y . The f i r s t t h e o r e t i c a l treatment i s due to Maki (8,9, 10), who i n a s e r i e s of quantum mechanical c a l c u l a t i o n s based on a square planar model, showed that only a small a x i a l per-t u r b a t i o n was necessary f o r the s i n g l e t ground s t a t e to be r a i s e d above the next t r i p l e t state g i v i n g r i s e t o para-magnetism. She concluded from these c a l c u l a t i o n s that i n a l l cases solvent i n t e r a c t i o n gives r i s e to the a x i a l p e r t u r b a t i o n s and thus produces paramagnetism. Two main p o i n t s remain unexplained i n Maki fs t r e a t -ment. The f i r s t i s that paramagnetism can occur i n the absence of any s o l v e n t . The second p o i n t f o l l o w s from some r e s u l t s of S a c c o n i , P a o l e t t i and Del Re ( l l ) who d i d magnetic measurements w i t h b i s ^ N - a l k y l - s a l i c y l a l d i m i n e n i c k e l ( I I ) , where the a l k y l group was v a r i e d from N-methyl to N-amyl ?in chloroform, benzene, 4 dioxane and p y r i d i n e s o l v e n t s . The r e s u l t s f o r the Nr-me t h y l d e r i v a t i v e were what one would expect f o r solvent c o o r d i n a t i o n . Chloroform - 1 . 9 2 B.M. Benzene - 2 . 2 2 B.M. Dioxane - 2 . 2 8 B.M. P y r i d i n e - 3 . 1 6 B.M. That i s , i n c r e a s i n g base s t r e n g t h of the solvent produces a l a r g e r a x i a l p e r t u r b a t i o n of the n i c k e l atom and hence a more complete conversion to paramagnetism. The r e s t of the s e r i e s show a completely d i f f e r e n t order. Chloro. Benz. Diox. P y r i d i n e N-ethyl 0 . 9 1 B.M. 0 . 2 9 B.M. 0 . 4 9 B.M. 3 . 1 2 N-propyl 1 . 2 5 B.M. 0 . 7 8 B.M. 0 . 3 9 B.M. 3.16 N-buty 0 . 8 9 B.M. 0 . 4 2 B.M, 0 . 4 5 B.M. 3.14 N-.amyl 0..C-6 B.M. O.65 B.M. 0.84 B.M. 3 . 1 1 Here there seems no r e l a t i o n between base strength and the degree of conversion to paramagnetism. Thus, while Maki-*s r e s u l t s are a p p l i c a b l e to the N-methyl d e r i v a t i v e s , they do not seem c o n s i s t e n t w i t h the magnetic p r o p e r t i e s -of the other members of the s e r i e s . An a l t e r n a t i v e and quite d i f f e r e n t approach would be an attempt to obtain a paramagnetic species of these complexes. The f i r s t such paramagnetic form of bis-N-methyl-s a l i c y l a l d i m i n e n i c k e l ( i i ) was reported by Sacconi, P a o l e t t i and C i n i ( 1 2 ) , but t h e i r complex was l i g h t green i n colour, F I G - I P R O P O S E D P O L Y M E R I C S T R U C T U R E 5 while H a r r i s , Lenzer and Martin [13), who repeated t h i s work a l i t t l e l a t e r , reported that the compound was buff i n col o u r . This paramagnetic form i s prepared by heating at l 8 0 ° f o r about two hours. The discrepancy i n the r e s u l t s seems to be due to the f a c t that Sacconi had impure s t a r t i n g m a t e r i a l and that some b i s - s a l i c y l a l d e h y d e n i c k e l ( I I ) was present, since a graph of magnetic s u s c e p t i b i l i t y versus time at l 8 0 ° shows that at t = 0 the m a t e r i a l was s t i l l paramagnetic. This b u f f compound i s very i n s o l u b l e i n organic solvents,and as a r e s u l t both Sacconi and Martin suggested that the paramagnet-ism arose from the formation of a polymeric species. The l a t t e r workers a l s o suggested that such a species arose from the use of a t r i p l y bonded oxygen, i . e . a lone e l e c t r o n p a i r of the oxygen on one molecule was donated to a n i c k e l atom on another (see F i g . I ) . Due to i t s i n s o l u b i l i t y i n organic s o l v e n t s , t h i s paramagnetic complex i s u n l i k e l y to be the one found i n s o l u t i o n . Further i n f o r m a t i o n on the stereochemistry of the n i c k e l ( i i ) atom i n "non-coordinating" solvents was obtained by Sacconi, P a o l e t t i , and Del Re ( l l , l 4 ) from d i p o l e moment measurements. They showed that i n a l l cases the d i p o l e moment was very low, and hence concluded that the p o s s i b i l i t y of a t e t r a h e d r a l arrangement was very s l i g h t . Another p o s s i b l e mechanism f o r the conversion from diamagnetism to paramagnetism on d i s s o l v i n g i n "non co o r d i n a t i n g " solvents has been suggested by Ballhausen and 6 L i e h r (15). They stat e that the decrease i n the e f f e c t i v e c r y s t a l l i n e f i e l d seen by Nl ( l l ) complexes on melt i n g or on d i s s o l u t i o n i n "non-complexing" solvents may w e l l lower the s p l i t t i n g between the lower s i n g l e t and the upper t r i p l e t such that h i> i s now comparable w i t h thermal energies. In t h i s event the complex w i l l become p a r t i a l l y paramagnetic, and they add that i t i s by t h i s mechanism that the diamagnetic planar n i c k e l ( l l ) complexes a t t a i n p a r t i a l paramagnetic behaviour, r a t h e r than by any e x t e r n a l change i n co n f i g u r a t i o n , s u c h as i s i m p l i e d i n the a l t e r n a t i v e assumption of p l a n a r - t e t r a h e d r a l e q u i l i b r i u m , Ballhausen and Liehr a p p l i e d Van Vleck's equation v _ 2£jfjL ^ + i e x p [g] - % N ^ molar s u s c e p t i b i l i t y the Lande f a c t o r f o r the S,j s t a t e avogadro 1s number temperature i n degrees absolute the boltzman constant the Bohr magnetor the temperature independent part of the s u s c e p t i b i l i t y the energy d i f f e r e n c e between the f i r s t two ground s t a t e s M 3 KT where g = N = T = K = a = N<* = A£ = 7 and s t a t e d t h a t t h i s would be the t r u e d e s c r i p t i o n o f the system. T h i s i s a g e n e r a l e q u a t i o n of s t a t e r e l a t i n g t he t h e r -mal d i s t r i b u t i o n of e l e c t r o n s between two energy l e v e l s . No c o r r e l a t i o n can be drawn f r o m t h i s e l e m e n t a r y d e s c r i p t i o n o f t h i s s t a t e , a n d the c o n d i t i o n s g i v i n g r i s e t o the paramagnetism. S a c c o n i , C i n i , C r a m p o l i n i and Maggio ( l 6 ) have attempted t o "prove" B a l l h a u s e n and L i e h r ' s s u g g e s t i o n by o b t a i n i n g r e a s o n -a b l e v a l u e of from e x p e r i m e n t a l v a l u e s of and T. Van V l e c k l s e q u a t i o n i s a l r e a d y a c c e p t e d as a t r u e d e s c r i p t i o n of paramagnetism a r i s i n g f r om t h e r m a l - d i s t r i b u t i o n of e l e c t r o n s . The r e q u i r e d c o n d i t i o n i n a c c e p t i n g t h i s e q u a t i o n as a d e s c r i p t i o n of thes e n i c k e l ( i i ) complexes i s t h a t a l l of the m o l e c u l e s must be i n t h e same s t a t e , i . e . must have the same environment. I f a s m a l l f r a c t i o n of them i s i n a d i f f -e r e n t environment, then t h i s e q u a t i o n can not be a p p l i e d . T h i s e q u a t i o n would n ot be v a l i d i f a s s o c i a t i o n were p r e s e n t , and the f a c t t h a t a p o l y m e r i c b u f f complex can be o b t a i n e d i n d i c a t e s t h a t a s s o c i a t i o n i s a d e f i n i t e p o s s i -b i l i t y . From v i s c o s i t y measurements on b i s - N - n o n y l -s a l i c y l a l d i m i n e n i c k e l ( i i ) and b i s - N - d e c y l - s a l i c y l a l d i m i n e n i c k e l ( i i ) , S a c c o n i o b t a i n e d an alm o s t l i n e a r r e l a t i o n s h i p between 9 0 ° C and 2 0 0 ° C w h i c h a p p a r e n t l y e l i m i n a t e s the p o s s i -b i l i t y of a s s o c i a t i o n . However, an e x a m i n a t i o n of t h e i r r e s u l t s shows t h a t t h e r e i s n o n l i n e a r i t y between 9 0 ° C and 1 3 0 ° C w h i c h would c e r t a i n l y be e x p e c t e d i f a s s o c i a t i o n were p r e s e n t . 8 Another unexplained f a c t o r i s that i n the case of bis~N~.octyl-s a l i c y l a l d i m i n e n i c k e l ( l l ) i n ddbutyl phthalate, the minimum i n the magnetic s u s c e p t i b i l i t y versus temperature curves moves to higher temperatures as the concentration i n c r e a s e s . This could be explained i f a s s o c i a t i o n occurred. Ferguson (17) has. added f u r t h e r experimental evidence that a s s o c i a t i o n occurs i n "non-coordinating" solvents by showing that the molecular weight of b i s - N - m e t h y l - s a l i c y l -aldimine n i c k e l ( l l ) In benzene increases w i t h I n c r e a s i n g con-c e n t r a t i o n . He has a l s o done considerable s p e c t r a l work on s o l u t i o n s of these complexes,and has shown i n the case of the N-methyl d e r i v a t i v e i n chloroform that two i s o s b e s t i c p o i n t s occur, one at 400 m/* and the other at 3^5 m^w,. This type of behaviour i s f r e q u e n t l y observed w i t h s o l u t i o n s of dyes and i s f a i r l y c l e a r evidence of a s s o c i a t i o n between molecules. In order to c l a r i f y the s i t u a t i o n f u r t h e r , magnetic s u s c e p t i b i l i t y measurements were made on these compounds, but the r e a l object of t h i s experimental work was to t r y to obtain the low temperature paramagnetic "species",and to heat a wide range of s i m i l a r complexes In order to obtain some new paramagnetic species which would give in f o r m a t i o n as to the stereochemistry of the paramagnetic complex i n s o l u t i o n . I f any paramagnetic complexes were .obtained, then magnetic s u s c e p t i b i l i t y measurements over a wide range of temperature were to be conducted to give the Weiss constant and an accurate magnetic moment. 9 The p o s s i b l e magnetic behaviour of the n i c k e l ( i i ) ion i n various c o n f i g u r a t i o n s has been described by G i l l and Nyholm ( l 8 ) . I t should therefore be p o s s i b l e to deter-mine i n favourable cases the c o n f i g u r a t i o n about the n i c k e l atom by using the r e s u l t of magnetic measurements and spectro-scopic observations. No.. Environment of N l ( l l ) atom M e f f (B.M.) ( c a l . ) 1. Free N i ion ( F4) No e l e c t r o s t a t i c f i e l d S = 1, L = 3 assume ^ = 0 4.47 • M = A S(S+l) + L(L+1) 2 . As i n ( l . ) but assume usual value of 7. (-V - 335 cm-1) 5-56 3 . As i n ( l . ) but assume C\ = OC 5.59 +2 4 . N i i o n i n p e r f e c t octahedral f i e l d •of negative charges assume ^ = 0 2.83 M = g / j ( J + i ) 1 o 5. Octahedral N i ( l l ) e.g. [Ni(KpO)5] assum-in g accepted value of s\ ( v a r i e s from . ~ 260 to 324) 3 . 1 - 3 . 2 +2 6 . Ni i n t e t r a h e d r a l f i e l d of negative charges assuming y= 0 and a l a r g e value o f ^ (assume L = l ) , = / 4 s ( S + l ) + L(L+l) 3.16 7. As i n ( 6 . ) but u s i n g same value of as i n octahedral case and assuming ^ i s very .large i . e . only c o n f i g u r a t i o n to be con-sidered i s 3..6 8 . As i n (7 . ) but with. A small enough to per-mit c o n f i g u r a t i o n a l i n t e r a c t i o n ( i . e . weak f i e l d ) 4 .1 A. = energy d i f f e r e n c e between and d e , % = spin o r b i t a l c oupling constant 10 Experimental I . Preparation and, A n a l y s i s The complexes i n v e s t i g a t e d were chelate compounds formed from n i c k e l ( l l ) , s a l i c y l a l d e h y d e , and various amines. The amines used were? methylamine, ethylamine, butylamine, ethylenediamine, o-phenylenediamine, 4 chloro-o-phenylene-diamine and trimethylenediamine. These compounds have been i n v e s t i g a t e d by numerous workers and t h e i r p r e p a r a t i o n i s r e l a t i v e l y simple. There are e s s e n t i a l l y two methods of preparing these compounds. Method I B i s - s a l i c y l a l d e h y d e n i c k e l ( l l ) was prepared by mixing a h a l f saturated s o l u t i o n of n i c k e l acetate i n 5 0 $ aqueous ethanol w i t h the s t o i c h i o m e t r i c amount of pure s a l i c y l a l d e h y d e . A f t e r thorough mixing,the s o l u t i o n was allowed to stand at room temperature. The l i g h t green product was f i l t e r e d o f f , washed and d r i e d . The b i s - s a l i c y l a l d e h y d e was suspended i n methyl alcohol,and sl o w l y added to a s t o i c h i o m e t r i c amount of the amine. The s o l u t i o n was then heated f o r h a l f an hour to ensure completion of the r e a c t i o n . The product was f i l -t e r e d , washed and d r i e d . In view of the l a r g e amounts of m a t e r i a l r e q u i r e d f o r magnetic measurements and i n some cases t h e i r r e l a t i v e i n s o l u b i l i t y i n chloroform, these com-pounds were p u r i f i e d by soxhlet e x t r a c t i o n w i t h chloroform. 11 Method I I The organic imine was prepared by the a d d i t i o n of s t o i c h i o m e t r i c amounts o f ' s a l i c y l a l d e h y d e and the corres-ponding amine i n 95$ ethanol and a l l o w i n g the product to c r y s t a l l i z e . The f i l t e r e d c r y s t a l s were r e d i s s o l v e d i n hot 95$ ethanol,and a s t o i c h i o m e t r i c amount of n i c k e l acetate was d i s s o l v e d i n water and added to the ethanol s o l u t i o n . The s o l u t i o n was then heated f o r h a l f an hour and the f i n a l product f i l t e r e d , washed and d r i e d . Previous investigator's have almost e x c l u s i v e l y used the f i r s t method of p r e p a r a t i o n . Bis-^JST-methyl-salicylaldimine n i c k e l I I Preparation of t h i s compound by the f i r s t method gave the w e l l known diamagnetic dark green s o l i d . The compound was r e c r y s t a l l l z e d from chloroform A n a l y s i s observed c a l c u l a t e d f o r NiC^gH^gOgNg Ni = 17.75$ 17.96 N = 8,45$ 8.57$ C =• 58.54$ 58.75$ N = 4 .72$ 4.93$ Preparation by the second method r e s u l t e d i n the form-a t i o n of a dark brown diamagnetic complex. This was not a r e s u l t of the d i f f e r e n t preparation,but r a t h e r a r e s u l t of c r y s t a l l i z i n g from hot ethanol. This m o d i f i c a t i o n was independently obtained by Ferguson ( 17) . 12 The organic imine was prepared as f o l l o w s : the methyl-amine hydrochloride was weighed 7and d i s s o l v e d i n water,and a s t o i c h i o m e t r i c amount of s a l i c y l a l d e h y d e added. Sodium hydroxide was slow l y added u n t i l the mixture was n e u t r a l , and the r e s u l t i n g s o l u t i o n r e f l u x e d f o r h a l f an hour. The s o l u t i o n was cooled and ex t r a c t e d w i t h chloroform. The e x t r a c t was d r i e d over Mg CIO^ and then d i s t i l l e d . The p o r t i o n d i s t i l l i n g at 220-228°C was used i n the p r e p a r a t i o n of the complex. A n a l y s i s of brown m o d i f i c a t i o n observed c a l c u l a t e d f o r • N i C l 6 H l 6 0 2 N 2 N l 17.82$ 17.96$ N 8.32$ 8.56$ B i s - N - m e t h y l - 5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l ( l l ) Prepared by both methods, and i n both cases the f o r e s t green diamagnetic c r y s t a l s were obtained. These were re-c r y s t a l l i z e d from chloroform. A n a l y s i s observed c a l c u l a t e d f o r N i C l 6 H l 4 0 2 N 2 C l 2 N i 1 4 . 4 6 $ 1 4 . 8 3 $ N 6 .89$ 7.07$ C 48 .51$ 4 8 . 5 1 $ H 3 . 4 1 $ 3 .56$ 13 Bis-N-methyl- 5 ~Promo-salicylaldimine n i c k e l ( I I ) Prepared by Method I . A n a l y s i s observed c a l c u l a t e d f o r N 1 C l 6 H l 4 ° 2 N 2 B r 2 N i 12 .48$ 12.08$ N. . 5.52$ 5.76$ C 39.33$ 39.50$ H 2 .69$ 2 . ' B i s - s a l i c y l a l d e h y d e - e t h y l e n e d i i m i n e n i c k e l ( l l ) Prepared by both Methods I and I I . This complex was p u r i f i e d by soxhlet e x t r a c t i o n w i t h chloroform. B i s - 5 - c h l o r o - s a l i c y l a l d e h y d e - e t h y l e n e d i i m i n e n i c k e l ( l l ) Prepared by both methods. A n a l y s i s observed c a l c u l a t e d f o r N i C l 6 H 1 2 0 2 N 2 C l 2 N i 12,. 90$ 14.91$ N 5.91$ 7.11$ C 44.27$ 48 .77$ H 2 .59$ 3.07$ Bis- 5 -bromo-salicylaldehyde-ethylenediimine n i c k e l ( l l ) This compound was prepared by Method I only^and was p u r i f i e d by soxhlet e x t r a c t i o n w i t h chloroform. 14 A n a l y s i s observed c a l c u l a t e d f o r N 1 C l 6 H 1 2 ° 2 N 2 B r 2 N i 10.91$ 11.95$ N. 5 .09$ 5.79$ C . 3 6 . 9 7 $ 39.69$ H 2.31$ 2.50$ B i s - s a l i c y l a l d e h y d e - o - p h e n y l e n e d i i m i n e n i c k e l ( I I ) Prepared by Methods I and I I . I t was r e c r y s t a l l i z e d from chloroform.. Bis - 5-chl.oro-salicylaldehyde-o-phenylenediimine n i c k e l ( I I ) This compound was prepared by Method I.,and r e c r y s t a l l i z e d from chloroform. A n a l y s i s observed c a l c u l a t e d f o r N i C 2 0 H 1 2 0 2 N 2 C l 2 N i . 13.11$ 1.3.17$ N 6.13$ 6,28$ C 54.11$ 53.< N 2 .72$ 2. ' Bis^ 5-bromo-salicylaldehyde-o-phenylenediimine n i c k e l ( i i ) Prepared by Method I . A n a l y s i s observed c a l c u l a t e d f o r N i C 2 0 H 1 2 0 2 N 2 B r 2 Ni 10.82$ 10.06$ N 5.10$ 5.28$ C 45.40$ 45.03$ N 2 .26$ 2 . 2 8 $ 15 B i s - s a l i c y l a l d e h y d e - 4 - c h l o r o - o - p h e n y l e n e d i i m i n e n i c k e l ( i i ) This compound was prepared v i a b i s - s a l i c y l a l d e h y d e n i c k e l ('II). I t was r e c r y s t a l l i z e d 'by solvent e x t r a c t i o n w i t h a soxhlet e x t r a c t i o n w i t h chloroform. •Analysis observed c a l c u l a t e d f o r N 1 C 2 0 H 1 3 ° 2 N 2 C 1 N i 14.34$ 14.39$ N 6.72 6.87$ c 58.67$ 58.85$ H 3 .39$ 3.21$ S i s - 5 - c h l o r o - salicylaldehyde - 4-chloro-o-phenylenedi.imine  n i c k e l ( i i ) This compound was prepared by Method I . A n a l y s i s N i N C H Bis - 5-bromo-salicylaldehyde - 4-chloro-o-phenylenediimine  n i c k e l ( i i ) P r e p a r a t i o n by Method I was used. A n a l y s i s N i N C H observed 12.06$ 5.68$ 50.20$ 2.27$ calculated f o r N i C 2 0 HllW L 12.22$ 5.83$ 49.97$ 2.31$ observed 10.12$ 4.87$ 42.61$ 2.15$ calculated f o r N 1 C 2 0 H l l ° 2 N ? C 1 B r 2 10.38$ 4 . 9 5 $ 4 2 .46$ 1 .96$ Attempts were made to prepare a n i l i n e , P-chloro a n i l i n e , P - n i t r o a n i l i n e d e r i v a t i v e of b i s - s a l i c y l a l d e h y d e n i c k e l ( l l ) , b i s - 5 - c h l o r o - s a l i c y l a l d e h y d e n i c k e l ( I I ) , bis -5-bromo-s a l i c y l a l d e h y d e n i c k e l ( l l ) and b i s - 5 - n i t r o - s a l i c y l a l d e h y d e n i c k e l ( I I ) . The object of preparing t h i s s e r i e s was to obtain a w e l l defined product and measure i t s magnetic moment. In the s e r i e s , o n l y one w e l l defined product was obtained. Bis-P-chloro-phenylimine- 5 -bromo-salicylaldehyde n i c k e l ( l l ) This compound was prepared from the organic imine according to Method I I . The w e l l defined b l a c k c r y s t a l s were r e c r y s t a l l l z e d from chloroform. A n a l y s i s observed c a l c u l a t e d f o r N 1 C 2 6 H l 6 0 2 K 2 B r 2 C 1 2 N i 8 .40$ 8 N 3 -99$ 4 . 13$ C 4 5 . 9 4 $ ' 46 . 0 3 $ H 2 .33$ 2.; These analyses were done by A l f r e d Bernhardt of Mikro-a n a l y t i s h e s Laboratorium i n Max-Plank-Institute, Germany. B i s - N ~ e t h y l - s a l i c y l a l d i m i n e n i c k e l ( l l ) P r e p a r a t i o n of t h i s compound from b i s - s a l i c y l a l d e h y d e n i c k e l ( I I ) gave f i n e dark green c r y s t a l s . Preparation v i a the imine gave a l i g h t green p r e c i p i t a t e , p o s s i b l y a dihydrate, that q u i c k l y changed to the dark green m o d i f i c a t i o n , Bis-N-ethyls 5~ chloro- s a l i c y l a l d i m i n e n i c k e i ^ _ ( j l l ) _ This compound was prepared by both methods,and the r e s u l t i n g compounds were i d e n t i c a l . B i s - N - b u t y l - s a l i c y l a l d i m i n e n i c k e l ( l l ) This compound was only prepared v i a b i s -s a l i c y l a l d e h y d e n i c k e l ( l l ) , and r e c r y s t a l l l z e d from chloroform. B i s - N - b u t y l - 5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l ( l l ) P r e p a r a t i o n by Method I was used to give a dark green. product. Mercurous C o b a l t i t e t r a t h i o c y a n a t e This compound was prepared as described by Figgs and Nyholm (19), and was used as a s o l i d to c a l i b r a t e the magnetic balance. N-methyl- salicylald_imine-_salicylaldehyde n i c k e l ( I I ) This complex was prepared by mixing equlmolar quanti-t i e s of N - m e t h y l - s a l i c y l a l d i m i n e and s a l i c y l a l d e h y d e i n a l c o h o l then the s t o i c h i o m e t r i c amount of n i c k e l acetate was added. The volume of a l c o h o l was reduced to about 15 ml,and the com-plex was p r e c i p i t a t e d by the a d d i t i o n of water to the hot alcohol.. This complex i s probably the dihydrate, but i t i s u n l i k e l y t o be a mixture of b i s - s a l i c y l a l d e h y d e n i c k e l ( l l ) , and b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( l l ) as the complex i s h i g h l y s o l u b l e i n a l c o h o l , while b i s - s a l i c y l a l d e h y d e n i c k e l i s only very s l i g h t l y s o l u b l e . The complex i s paramagnetic. The p r e p a r a t i o n of the anhydrous complex would y i e l d F I G - H A P R O P O S E D P O L Y M E R I C S T R U C T U R E / / H O-Ni-0 CH,\ \ ,CH,\ H .c = o 18 I n t e r e s t i n g information, as anhydrous h i s - s a l i c y l a l d e h y d e n i c k e l ( l l ) i s paramagnetic, while b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( l l ) i s diamagnetic. This complex has not been p r e v i o u s l y r e p o r t e d . A n a l y s i s observed c a l c u l a t e d f o r NiH 1 3C 1 5N0 2.2H 20 N i 17.19$ 17.38$ N 4.18$ 4.16$ A New, P o s s i b l y Polymeric Complex In the pre p a r a t i o n by Method I I of bis-N-methyl-s a l i c y l a l d i m i n e n i c k e l ( l l ) , a completely pure l i g a n d was d i f f i c u l t to obtain,.as the b o i l i n g p o i n t s of s a l i c y l -aldehyde and N - m e t h y l - s a l i c y l a l d i m i n e were s i m i l a r . In an a l c o h o l s o l u t i o n c o n t a i n i n g predominantly N-methyl-s a l i c y l a l d i m i n e , but w i t h s a l i c y l a l d e h y d e as an impur i t y , the gradual a d d i t i o n of n i c k e l acetate at f i r s t p r e c i p i -t a t e d the f a m i l i a r b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( l l ) , but a f t e r the amount of N - m e t h y l - s a l i c y l a l d i m i n e had been s u b s t a n t i a l l y reduced, a second product could be i s o l a t e d (M.P. 2 1 0 ° - 2 1 1 ° ), This paramagnetic complex was then r e c r y s t a l l l z e d from a l c o h o l . A n a l y s i s gave 5 .82$ n i t r o g e n . The only p o s s i b l e complex c o n s i s t e n t w i t h t h i s a n a l y s i s con-t a i n s : 3 n i c k e l atoms, 4 N - m e t h y l - s a l i c y l a l d i m i n e molecules, and 2 s a l i c y l a l d e h y d e molecules. One p o s s i b l e arrangement of these molecules i s given i n P i g . I I , but only complete x-ray a n a l y s i s w i l l give the true arrangement. Regardless of the true arrangement, t h i s must be an ass o c i a t e d molecule,and may provide information concerning the a s s o c i a t i o n i n benzene reported by Ferguson. This i s u n l i k e l y to be a mixture,as the complex i s extremely sol u b l e i n a l c o h o l , but i t i s p o s s i b l y a di h y d r a t e . A n a l y s i s observed c a l c u l a t e d f o r N i 3 C 4 6 H 4 2 0 8 N v 2 H 2 0 N i 1 7 . 4 0 $ 1 7 . ' N 5 . 8 2 $ 5 . ' C 5 5 . 9 7 $ 5 7 . 1 ^ $ H 4 . 2 8 $ 4 . 3 7 $ X-Ray Powder Photographs A General E l e c t r i c model XRP - 5 F I I x-ray d i f f r a c t i o n u n i t was used to obtain powder photographs of the compounds prepared. The powder photographs were used to d i s t i n g u i s h v a r i o u s species of the complexes obtained, and no attempt was made to index these photographs. I I . Magnetic Measurements The determination of the magnetic s u s c e p t i b i l i t y provides the f i r s t means of i n v e s t i g a t i n g the stereochemistry of these n i c k e l compounds. The experimental value f o r the magnetic moment of a paramagnetic substance can be c a l c u l a t e d 2 0 from the e q u a t i o n 2 3k(T+/J ) where %„- molar s u s c e p t i b i l i t y M- magnetic moment T = a b s o l u t e temperature A = m o l e c u l a r f i e l d c o n s t a n t o r Weiss c o n s t a n t The m o l e c u l a r f i e l d c o n s t a n t & may have v a l u e s of 1 0 0 ° or more, and t h e r e f o r e can e x e r t a c o n s i d e r a b l e e f f e c t on the magnetic moment. I t i s t h e r e f o r e n e c e s s a r y t o measure magnetic s u s c e p t i b i l i t i e s o v er as wide a temperature range as p o s s i b l e . (a) D e s c r i p t i o n of t h e magnetic B a l a n c e The magnetic b a l a n c e c o n s i s t e d o f a m i c r o - b a l a n c e s t a n d i n g on a s l a t e - t o p p e d t a b l e . The \ i n c h s l a t e t o p was mounted on a n t i v i b r a t i o n mountings t o s t a b i l i z e the m i c r o -b a l a n c e . A Spaerhase Model 1 0 M m i c r o - b a l a n c e w i t h a s e n s i t i v i t y o f + 0 . 0 0 0 0 1 gm was used t o determine the f o r c e e x e r t e d by the' magnetic f i e l d on the sample. The magnet used was a V a r i a n 4 i n c h e l e c t r o m a g n e t Model V 4 0 8 4 with. 2 i n c h t a p e r e d p o l e c a p s . The p o l e gap was s e t a t 1 I n c h and a f i e l d of a p p r o x i m a t e l y 1 5 k i l o g a u s s was o b t a i n e d w i t h a c u r r e n t of 2 amps/winding s e c t i o n . The magnet was c o o l e d by c i r c u l a t i o n of water t h r o u g h j a c k e t s 21 surrounding the magnet core. The current and hence f i e l d r e g u l a t i o n was main-t a i n e d constant by a Model U 2300A Power Supply and a Model 2301A Current Regulator. The Power Supply u t i l i z e s convention c i r c u i t s to produce a h i g h output c u r r e n t . Control of the output voltage i s provided by means of a tapped secondary winding on the power transformer i n conjunction w i t h a s e r i e s v a r i a b l e t r a n s -former. R e c t i f i c a t i o n i s obtained w i t h selenium r e c t i f i e r s i n a f u l l wave bridge c i r c u i t . No f i l t e r i n g i s provided,as - 3 the magnet load reduces the f i e l d r i p p l e to below 10 . Reversal of the magnetic f i e l d i s accomplished w i t h a multiple-contact-cam-operated s w i t c h . When the switch i s r o t a t e d from the normal f i e l d p o s i t i o n , the primary l i n e power i s disconnected from the transformer. As the switch i s r o t a t e d f u r t h e r , the magnet c o i l s are shorted, u s i n g the i n t e r n a l r e s i s t a n c e of the magnet c o i l s to d i s s i p a t e the stored power. A d d i t i o n a l r o t a t i o n of the switch removes the short across the magnet but w i t h the current feed reversed. In the reversed p o s i t i o n , the l i n e power i s reconnected to the transformer,primary. The Current Regulator u t i l i z e s a saturable r e a c t o r to s t a b i l i z e the a.c. current feed to the r e c t i f i e r c i r c u i t of the power supply. The current output from the supply passes through a low r e s i s t a n c e current viewing r e s i s t o r which derives a voltage p r o p o r t i o n a l to the c u r r e n t . This voltage i s a l g e b r a i c a l l y added to the voltage from a reference c e l l , 22 and the net e r r o r voltage i s chopped f o r p r e s e n t a t i o n to a.c. a m p l i f i e r s . The output from the a m p l i f i e r s i s phase detected f o r d r i v i n g a balanced d.c, power a m p l i f i e r connected to the saturable r e a c t o r . Thus, a change i n the magnet supply current causes an impedence change i n the secondary c i r c u i t of the power supply h o l d i n g the d.c. output current constant. (b) C a l i b r a t i o n of the Apparatus For the determination of magnetic s u s c e p t i b i l i t i e s by the Gouy method, the specimen tube i s so placed that the bottom of the sample i s i n the centre of the homogeneous p o r t i o n of the magnetic f i e l d . A l s o , the l e n g t h of the sample i s such that i t s top i s i n a region of n e g l i g i b l e f i e l d . The f o r c e exerted on the sample on the a p p l i c a t i o n of the f i e l d i s then given by f = -g A w = i K-j^  H 1 2 A where &w = change i n weight of sample on a p p l i c a t i o n of f i e l d . g = g r a v i t a t i o n a l constant. = volume s u s c e p t i b i l i t y of sample. H-^  = maximum f i e l d to which the sample i s subjected, A = c r o s s - s e c t i o n a l area of the sample. Hence the gram s u s c e p t i b i l i t y i s given by the expression The constant C i s defined as the apparatus constant^ and i s given by where h = the leng t h of the specimen. The apparatus constant can be determined a c c u r a t e l y by usi n g standard substances of known s u s c e p t i b i l i t y . Dry benzene of Analar grade was used as one standard, and mercurous c o b a l t i t e t r a t h i o c y a n a t e as the second standard. Benzene = 0.702 x 10" c.g.s. (20) Co Hg (SCN)^ y. = 16.44 x l o " 6 c.g.s. (19) (c) Magnetic S u s c e p t i b i l i t y of Diamagnetic S o l i d s Magnetic measurements of s o l i d s e n t a i l s one d i f f i c u l t y . This i s the packing of the sample. When the c r y s t a l s are of uniform s i z e and they are about 0 .01 cm diameter, then the packing may be accomplished by dropping the sample from about three f e e t down a gl a s s tube. The tube i s f i l l e d i n stages,and the number of times the sample i s dropped i s u s u a l l y 100. But i f the sample must be ground i n a p e s t l e and mortar, then numerous d i f f i c u l t i e s a r i s e when t h i s method i s used. The major d i f f i c u l t y i s that the small p a r t i c l e s acquire a s t a t i c charge, making a re p r o d u c i b l e packing very d i f f i c u l t . This method was used f o r these measurements,and the accuracy i s not extremely good. A much b e t t e r method i s to use a v i b r a t o r . The type used f o r F I G 3DL 24 p r e p a r a t i o n of I.R. Potassium biomide d i s c s i s r e a d i l y adapt-ab l e . The f o l l o w i n g t a b l e gives the diamagnetic s u s c e p t i b i l i t y 6 ( x 10 cgs) of the complexes prepared. Amine methyl- ethylene-amine diamine o-phenylene- 4-chloro-o-diamine phenylene-diamine aldehyde s a l i c y i a l d e h y d e - . 3 0 7 '-..376 5-chloro-s a l i c y l a l d e h y d e - . 2 6 7 - . 3 7 6 5-bromo-s a l i c y l a l d e h y d e - .312 - . 3 2 4 .313 .372 .291 - . 3 3 1 - . 3 2 3 - . 2 6 4 bis-P-chloro-phenylimine - 5-bromo-salicyialdehyde n i c k e l ( I I ; - - 0 . 3 7 1 3• Magnetic Measurements at Low Temperature The equipment used i s b a s i c a l l y that described by F i g g i s and Nyholm (21) , w i t h a few m o d i f i c a t i o n s . The apparatus c o n s i s t s of a c r y o s t a t and the temperature c o n t r o l e l e c t r o n i c equipment. (a) Cryostat This ( F i g . I l l ) c o n s i s t s of a chamber 1.2 cm i n s i d e diameter and 20 cm i n length, i n which a t h i n w a l l e d glass Gouy F I G m FIG-3C CONSTANT REFRIGERANT LEVEL MECHANISM C - CRYOSTAT D - 2 5 LITRE STORAGE DEWAR VESSEL T - THERISTMOR T.-TRANSFORMER, 2 4 0 - 6 0 V. S-SUNVIC 6 0 2 HOT WIRE SWITCH A-AIR MAIN V-SOLENOID VALVE 25 tube (0 .55 cm outside diameter and 8 .0 cm long) i s hung. This chamber i s i n s u l a t e d by a v a r i a b l e vacuum from a bath of l i q u i d n i t r o g e n . In Nyholm's apparatus, the outside Dewar was c y l i n d r i c a l i n shape and had an outside diameter of 1 cm, but by p l a c i n g a l i q u i d n i trogen r e s e r v o i r above and below a con-s t r i c t i o n at the c o n i c a l pole p i e c e s , i t was p o s s i b l e to have an outside diameter-(of the Dewar) of 2,6 cm between the pole pieces (see P i g . I V ) . I t i s therefore unnecessary to have a very large electromagnet while the very t h i n w a l l e d Gouy tube : i s comparable to that used by Nyholm. In the i n s i d e chamber, a heating c o i l , s p i r a l l i n g around a grooved polyethylene tube and capable of d i s s i p a t i n g 15 w, counterbalances the heat l o s s across the vacuum. A platinum wire wound between the s p i r a l s of the heating c o i l serves as a r e s i s t a n c e thermometer f o r temperature c o n t r o l ; i t s room-temperature r e s i s t a n c e i s about 10 ohms. A Cenco "Hyvac" model 91105 high-vacuum pump produced the vacuum i n the inner Dewar f l a s k , which was u n s i l v e r e d . For operation at , and f o r about 40° above, the l i q u i d n i t r o g e n temperature, a i r at atmospheric pressure was allowed to remain i n the Inner Dewar f l a s k ; f o r temperature above t h i s the Gouy vacuum of the pump was employed... The r e f r i g e r a n t l e v e l was kept constant i n the outer Dewar v e s s e l by means of the device set out i n F i g . V. A the r m i s t e r , of room-temperature r e s i s t a n c e of 500 ohms, was FIG- YL TEMPERATURE-CONTROL CIRCUIT 4 E C-P-H-Rr Rr Rs-E-M-M r M3-A -I-Tr CRVOSTAT PLATINUM- RESISTANCE WINDING HEATER WINDING 5 DECADE RESISTANCE BOX 10 OHMS 3 0 0 O H M S 6 V . ERROR-SIGNAL METER, 0- IOO>uV. AMPLIFIER - OUTPUT METER, 0-200 V. A.C. HEATER-CURRENT METER, 0-I AMR A.C. D.C; AMPLIFIER OUTPUT TRANSFORMER, 5000-15 OHMS "VARIAC" CONTINUOUSLY VARIABLE AUTOTRANSFORMER TRANSFORMER, 240-17V. 26 held s l i g h t l y above the d e s i r e d r e f r i g e r a n t l e v e l and was heated by a c o i l d i s s i p a t i n g 5 w. The t h e r m i s t e r and the heater c o i l were encased i n an asbestos-sodium s i l i c a t e s h e l l which had a small hole to allow entrance of the l i q u i d n i t r o g e n . A Sunvic model 60Z high vacuum switch was i n s e r i e s w i t h the t h e r m i s t e r and the combination was e x c i t e d ..with 60 v. A.C. At room temperature s u f f i c i e n t current was passed by the t h e r m i s t e r to close the switch, which then operated a General Controls s o l e n o i d valve model M 8 C which allowed a i r from a compressed a i r l i n e to f o r c e a i r i n t o a 25 1. l i q u i d a i r storage v e s s e l . R e f r i g e r a n t was thus e j e c t e d i n t o the outer Dewar v e s s e l . When the r e f r i g e r a n t l e v e l had r i s e n s u f f i c i e n t l y to c o ol the t h e r m i s t e r , i t s increased r e s i s t a n c e reduced the current and so switched o f f the s o l e n o i d v a l v e . A small l e a k d i s s i p a t e d the pressure i n the storage v e s s e l , and the e j e c t i o n of r e f r i g e r a n t ceased. (b) Temperature-Control C i r c u i t The c i r c u i t s f o r automatic c o n t r o l at any d e s i r e d temperature are shown i n F i g . V I . A p l a t i n u m - r e s i s t a n c e thermometer, comprising of 12 f e e t of '29 AWG platinum w i r e , was wound on the outside of the s p i r a l grooved t a f l o n tube between the windings of the heating c o i l . No p a r t i c u l a r care t o avoid s t r a i n i n the wire was e x e r c i s e d i n winding the platinum as t h i s thermometer was not used as a primary stands a r d . The ends of the thermometer were s i l v e r soldered to a copper wire which was brought out of the inner Dewar to a t e r m i n a l b lock. The r e s i s t a n c e thermometer formed one arm of a Wheatstone bridge, whose other v a r i a b l e arm was a 5 decade r e s i s t a n c e box of maximum r e s i s t a n c e of 111.1 ohms. This bridge was e x c i t e d by 6 v. D.C. The "out-of-balance" of the bridge was a m p l i f i e d by means of a Leads and Northrop model R-820-1 D.C. a m p l i f i e r which d e l i v e r e d about 150 v. A.C. at 7 w to an output transformer of 15 ohms output impedence. The secondary winding of t h i s transformer was i n s e r i e s w i t h the primary of a c o n t i n u i n g v a r i a b l e auto-transformer; t h i s arrangement was fed from 17 v. A.C. The output of the var-i a b l e transformer was the supply f o r the heating c o i l of the c r y o s t a t . The phase of the voltage s u p p l i e d by the output transformer was determined by the sign of the out-of-balance s i g n a l to the a m p l i f i e r . A c c o r d i n g l y , as t h i s voltage was i n or out of phase w i t h the 17 v. A.C. supply, i t increases or decreases the power su p p l i e d to the heating c o i l . The phase r e l a t i o n s h i p was arranged so that the change of power was i n the d i r e c t i o n r e q u i r e d to reduce the e r r o r s i g n a l . Meters, f o r reading the e r r o r s i g n a l , the a m p l i f i e r output v o l t a g e , and the heater current were provided. Operation of the temperature c o n t r o l was as f o l l o w s . With the a m p l i f i e r output voltage s h o r t - c i r c u i t e d by a condenser, the heater current was adjusted to maintain the r e q u i r e d temperature w i t h a s u i t a b l e vacuum i n the inner Dewar f l a s k . The Wheatstone bridge was balanced, and the short c i r c u i t removed from the a m p l i f i e r output; the temperature was then c o n t r o l l e d at the r e q u i r e d v a l u e . (c) Measurement of Temperatures The temperatures of the specimen were measured w i t h constantan-copper thermo couple so i n s e r t e d that i t s "hot" j u n c t i o n was beside the mid-point of the Gouy tube; w i t h t h i s tube i n p o s i t i o n . When temperature e q u i l i b r i u m had been a t t a i n e d , the thermocouple was withdrawn and the s u s c e p t i -b i l i t y immediately measured; The thermocouple was c a l i b r a t e d against the standard values given i n the I n t e r n a t i o n a l C r i t i c a l Tables f o r the p o t e n t i a l drop between "hot" j u n c t i o n and the c o l d j u n c t i o n held at i c e temperature. The thermo-couple was c a l i b r a t e d at the l i q u i d n i t r o g e n p o i n t , the i c e p o i n t , and the f r e e z i n g p o i n t of 1,2-dichloro-ethane and showed agreement w i t h 0.2° of the standard v a l u e s . The p o t e n t i a l drop was measured by a Rhodes model PV p o t e n t i o -meter . ( d) C a l i b r a t i o n of Gouy Tube The c a l i b r a t i o n of the Gouy tube i n temperature-dependence measurements presents d i f f i c u l t y i n the assign-ment of the constants <x and O i n the usual formula x u 7 \ ? ~ w where c< allows f o r the medium ( u s u a l l y a i r ) occupying the tube subsequently d i s p l a c e d by the specimen j (3 i s dependent only on the geometry of the tube and the magnetic f i e l d ; S i s the fo r c e exerted on the tube alone, and P that on the tube + specimen; w i s the weight of the specimen. FIG VII LIGHT GREEN HEATED SPECIES OF BIS-N-METHYL- 5 CHLORO- SALICYALDIMINE NICKEL 2 9 Whereas i s e s s e n t i a l l y independent of temperature, o r and 6 are l i k e l y to he f u n c t i o n s of i t . I t i s p o s s i b l e to e l i m i n a t e the c o r r e c t i o n o < - by performing measurements i n an open tube. The c o r r e c t i o n b was found by measuring the fo r c e .. developed on the Gouy tube over the temperature range. For a t y p i c a l tube, 6 decreased from 2 . 0 mg at 3 5 0 ° K to 1 . 0 mg at 9 0 ° K apparently owing to the paramagnetic i m p u r i t i e s i n the (diamagnetic) g l a s s . 4 . Magnetic S u s c e p t i b i l i t y of the L i g h t Green Form of Bis-N- M e t h y l - 5 - C h l o r o - S a l i c y l a l d i m i n e The magnetic moment of the l i g h t green form of b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( l l ) was found to be 2 . 9 0 B.M. at 2 5 ° C . The Weiss constant was found to be 6 0 ° . The r e l a t i o n s h i p between the magnetic moment and temperature i s shown i n F i g . V I I . 5 • P r e p a r a t i o n of S o l i d Paramagnetic Species (a) I s o l a t i o n of Paramagnetic Species by Cooling_of S o l u t i o n Previous i n v e s t i g a t o r s ( C l a r k , F u j i ! ) of these complexes had shown that i n the case of bis-N-methyl-s a l i c y l a l d i m i n e n i c k e l ( l l ) the paramagnetism of the s o l u t i o n increased as the temperature was lowered. Thus, i f a para-magnetic "species" e x i s t e d as such, then a p o s s i b l e means of i s o l a t i o n would be to cool a s o l u t i o n of the complex to a p o i n t where there i s almost t o t a l conversion to the para-magnetic "species" and then remove the solvent, or i n some way p r e c i p i t a t e the paramagnetic complex. E s s e n t i a l l y there are three experimental ways to. isolve t h i s problem. Chloro-form was used i n most cases,as i t was the only common solvent w i t h a low f r e e z i n g point,and i n which the complexes had high, s o l u b i l i t y , 1-2 d i c h l o r o ethane was a l s o used i n one case. The f i r s t method c o n s i s t e d of d i s s o l v i n g the com-pl e x i n chloroform and then p l a c i n g t e s t tubes of the s o l u t i o n i n a dry i c e - e t h a n o l mixture and a l l o w i n g the chloroform to p a r t i a l l y f r e e z e . The concentrated s o l u t i o n from s e v e r a l t e s t tubes was placed In a new t e s t tube and the process repeated u n t i l the paramagnetic "species" p r e c i p i t a t e d . In the case of. b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( i i ) , the l a s t of the chloroform was removed under vacuum and the t h i c k syrupy l i q u i d then poured o f f . The complex then s o l i d i f i e d . With. b i s - N - m e t h y l - 5 - c h l o r o - s a l i c y i a l d e h y d e n i c k e l ( I I ) the paramagnetic "species" p r e c i p i t a t e d from s o l u t i o n long before a l l the solvent had been removed. The second method of o b t a i n i n g the d e s i r e d product c o n s i s t e d of removing the solvent of a. cooled chloroform s o l u t i o n under vacuum. The t h i r d method c o n s i s t e d of p r e c i p i t a t i n g the complex from a cooled chloroform s o l u t i o n w i t h l i g r o i n . A paramagnetic "species" (2.8 B.M.) was obtained w i t h chloroform s o l u t i o n s of bis-N-methyl-5-chloro-s a l i c y l a l d i m i n e n i c k e l ( I I ) by a l l three methods. The product w i t h 1-2 d i c h l o r o ethane by method three gave a s l i g h t l y d i f f e r e n t powder x-ray than the chloroform s o l u t i o n , but the d i f f e r e n c e in. solvent may have s l i g h t l y changed the pa in g of the molecule. With b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( l l ) , only the f i r s t method was used t o obtain a paramagnetic product. (b) Heating of Complexes In view of the c o n f l i c t i n g r e s u l t s by Sacconi (12) and Martin (13) > i t was decided t o repeat the experiment as w e l l as extend i t to other complexes. Heating the dark green diamagnetic bis-N-methyl-s a l i c y l a l d i m i n e n i c k e l ( l l ) to 200°C f o r 2 hours converted the dark green complex i n t o a buff coloured paramagnetic compound. The o r i g i n a l complex was so l u b l e In organic s o l -vents, but the f i n a l product was not. These r e s u l t s are c o n s i s t e n t w i t h those obtained by M a r t i n . In the case of the dark brown m o d i f i c a t i o n obtained from hot a l c o h o l , the complex must melt before the buff m o d i f i c a t i o n i s obtained. With the paramagnetic species obtained from s o l u t i o n , l e t t i n g i t stand at room temperature i s s u f f i c i e n t to convert i t to the dark brown diamagnetic m o d i f i c a t i o n . On heating b i s - N - m e t h y l - 5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l ( l l ) , two products were obtained. The f i r s t para-magnetic species (2.9 . 0 B.M.) was obtained by heating t o l65°C f o r h a l f an hour. This compound was l i g h t green i n colour and s o l u b l e i n organic s o l v e n t s , and from these s o l u t i o n s the o r i g i n a l diamagnetic complex could be obtained. On f u r t h e r heating to 205° Q f o r four hours a buff coloured compound 32 was obtained. The compound was paramagnetic (3 .38 B.M.), and was i n s o l u b l e i n organic s o l v e n t s . B i s-N-methyl-5-bromo-s a l i c y l a l d i m i n e n i c k e l ( l l ) gave product s i m i l a r to bis-N-m e t h y l - 5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l ( l l ) . With the complex obtained at low temperature from chloroform s o l u t i o n of b i s -N - m e t h y l - 5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l ( l l ) , heating to 100°C converted i t to the diamagnetic complex. Heating of the f o l l o w i n g compounds was c a r r i e d out, but no n o t i c e a b l e conversion took p l a c e . B i s - N - - e t h y l - s a l i c y l a l d i m i n e n i c k e l ( l l ) B i s - N - e t h y l - 5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l ( l l ) B i s - N - b u t y l - s a l i c y l a l d i m i n e n i c k e l ( l l ) B i s - N - b u t y l - 5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l ( l l ) Ethylenediimine b i s - s a l i c y l a l d e h y d e n i c k e l ( l l ) Ethylenediimine b i s - 5 - c h l o r o - s a l i c y l a l d e h y d e n i c k e l ( l l ) Ethylenediimine b i s - 5 - c h l o r o - s a l i c y l a l d e h y d e n i c k e l ( l l ) o-phenylenediimine b i s - s a l i c y l a l d e h y d e n i c k e l ( l l ) o-phenylenediimine-bis- 5 -chloro-salicylaldehyde n i c k e l ( l l ) o-phenylenediimine bis- 5 -bromo-salicylaldehyde n i c k e l l ( l l ) 4 -chloro-o-phenylenediimine b i s - s a l i c y l a l d e h y d e n i c k e l ( l l ) 4 -chloro-o-phenylene diimine b i s - 5 - c h l o r o - s a l i c y l a l d e h y d e n i c k e l ( l l ) 4 -chloro-o-phenylenediimine bis- 5 -bromo-salicylaldehyde n i c k e l ( l l ) Bis-P-chloro-phylimine- 5 -bromo-salicylaldehyde n i c k e l ( l l ) In order to determine whether the o r i g i n a l l i g a n d had- been changed by heating, the c e n t r a l n i c k e l atom was removed w i t h dimethylglyoxine,and the yellow colour of the imine taken as evidence f o r i t s presence. In the case of the s o l u b l e complexes, the experiment was conducted i n a l c o h o l , while w i t h the buff complexes were f i r s t d i s s o l v e d i n 6N HC1. In no case was any change found. 6. D i f f u s e Reflectance Spectra of Paramagnetic Species These measurements were k i n d l y done by Dr. M.C.R. Symons, who r e c e n t l y described t h i s method of o b t a i n i n g the u.v. and v i s i b l e spectra of s o l i d s (22). The absorption spectra a r i s e because m u l t i p l e r e f l e c t i o n s of the i n c i d e n t l i g h t are accompanied by l i m i t e d t r a n s m i t t a n c e . They are measured by c o l l e c t i n g monochromated l i g h t d i f f u s e l y r e f l e c t e d from the powdered s o l i d w i t h a t o r o i d a l m i r r o r which focuses the l i g h t onto the d e t e c t o r . This i s compared w i t h l i g h t r e f l e c t e d from a reference sur-f a c e . When spectra of compounds with, high e x t i n c t i o n c o e f f i c i e n t s were measured i n the u l t r a v i o l e t r e g i o n , even u n d i l u t e d specimens d i d not appear to be o p t i c a l l y black, and i t was sometimes p o s s i b l e to describe peaks which subsequently were found to be spurious. Such peaks had an absorbance greater than 0.8, and d i d not decrease on i n i t i a l d i l u t i o n . The procedure, t h e r e f o r e , was to d i l u t e ( w i t h L i P ) u n t i l f u r t h e r d i l u t i o n r e s u l t e d i n the expected decrease i n absorbance. Peaks that could be reproduced w i t h d i f f e r i n g d i l u t i o n s of the compound w i t h l i t h i u m f l u o r i d e (normally between 1 :5 and 1:15 by volume) were regarded as r e a l and a l l others as spurious. 35 D i s c u s s i o n E s s e n t i a l l y there have been four t h e o r i e s advanced to e x p l a i n the appearance of paramagnetism i n the b i s - N - a l k y l -s a l i c y l a l d i m i n e n i c k e l ( I I ) complexes on d i s s o l u t i o n i n organic solvents or upon m e l t i n g . These are;.the formation of a t e t r a h e d r a l complex, the i n t e r a c t i o n of s o l v e n t s , the removal of the c r y s t a l l i n e f i e l d , and the formation of an a s s o c i a t e d product. The p o s s i b i l i t y of the formation of a t e t r a h e d r a l com-pl e x on d i s s o l u t i o n i s u n l i k e l y , as the d i p o l e moment of the complex i n organic solvents i s low. Maki's suggestion that the paramagnetism r e s u l t e d from solvent i n t e r a c t i o n and the formation of a d i s t o r t e d octa-hedral c o n f i g u r a t i o n leaves- s e v e r a l f a c t s unexplained. The f i r s t i s the existence of the paramagnetism i n the molten st a t e where there i s no p o s s i b i l i t y of solvent i n t e r a c t i o n . Another p o i n t i s that although the degree of paramagnetism descreses w i t h decreasing b a s i c i t y f o r the N-methyl d e r i v a t i v e i n the s e r i e s : p y r i d i n e , dioxane, benzene, and chloroform, the trend i s not maintained f o r the other N - a l k y l d e r i v a t i v e s . A second set of r e s u l t s that do not show the c o r r e c t s h i f t i n paramagnetism demanded by Maki*s theory are the magnetic measurements on b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( I I ) i n methylbenzene solvents ( 5 ) . There was no c o r r e l a t i o n between base strength, and the amount of paramagnetism; indeed, i t seems probable that the decrease i n paramagnetism 36 as the solvent i s changed from benzene to toluene to m xylene i s r a t h e r an e f f e c t of the increase asymmetry of the solvent molecule. The f i n a l p o i n t that t h i s theory does not e x p l a i n i s the existence of the low temperature form, which contains no solvent, i r r e s p e c t i v e of i t s true c o n f i g u r a t i o n . One p o i n t that Maki s t r e s s e s i n her p r e s e n t a t i o n of t h i s theory i s that there i s no p o i n t i n a s e r i e s of s o l -vents where one solvent i s c o o r d i n a t i n g and the next i s non-coordinating and as the c o o r d i n a t i o n of p y r i d i n e has been proved then t h i s mechanism could be extended to the r e s t of the s o l v e n t s . This argument, however, does not consider the p o s s i b i l i t y of solvent c o o r d i n a t i o n being superseded by a second mechanism. The t h i r d theory advanced to e x p l a i n the paramagnetism was that removal of the c r y s t a l f i e l d on d i s s o l u t i o n or melting decreased the s p l i t t i n g between the lower s i n g l e t and the nexd t r i p l e t state so that h i s of the order of KT. This suggestion may be c o r r e c t f o r temperatures above 120°C as Sacconi (l6) has shown that above t h i s temperature the magnetic s u s c e p t i b i l i t y of molten complexes increase, and that the v i s c o s i t y measurements of the Nr-nonyl and N-decyl d e r i v a t i v e s are p e r f e c t l y l i n e a r , but below t h i s temperature there i s evidence that t h i s suggestion i s not v a l i d , as the molten complexes show a minimum about 120°C i n a p l o t of magnetic s u s c e p t i b i l i t y versus temperature, and the v i s c o s i t y measurements show n o n - l i n e a r i t y . In a d d i t i o n 37 t o this,, b i s - N - m e t h y l - 5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l ( l l ) forms a s o l u b l e paramagnetic (2...90 B.M.) species without the removal of the c r y s t a l f i e l d , i . e . by heating. A l s o , the existence of a low temperature paramagnetic species i s not explained by t h i s theory. The most recent suggestion to e x p l a i n the paramagnetism of these complexes on d i s s o l u t i o n Is that a s s o c i a t i o n of the molecules occurs ( 2 3 , 1 7 ) . Ferguson has shown that the molecular weight of the N-methyl d e r i v a t i v e increased w i t h i n c r e a s i n g concentration i n benzene, i n d i c a t i n g that a s s o c i a t i o n occurs. S p e c t r a l work i n chloroform showed th a t i s o s b e s t i c p o i n t s are present and Ferguson st a t e d that these are a l s o observed w i t h dye molecules where a s s o c i a t i o n i s known to occur. A s s o c i a t i o n of .nickel ('II) complex molecules may not prove to be uncommon as p r e l i m i n a r y x-ray studies (24,25) have i n d i c a t e d that anhydrous b i s (acetylacetanato) n i c k e l ( l l ) and anhydrous b i s - s a l i c y l -aldehyde n i c k e l ( I I ) may have a t r i m e r i c s t r u c t u r e i n the s o l i d s t a t e . Many p r e v i o u s l y unexplained f a c t s can be explained i n terms of a s s o c i a t i o n . F i r s t l y , Sacconi i n h i s most recent paper reported that the N - o c t y l d e r i v a t i v e when d i s s o l v e d i n d i b u t y l p h t h a l a t e , showed a minimum In the p l o t of magnetic s u s c e p t i b i l i t y versus temperature which moved to higher temper-ature w i t h higher c o n c e n t r a t i o n . This can now be explained by c o n s i d e r i n g a s s o c i a t i o n , as the degree of a s s o c i a t i o n w i l l be g r e a t e r w i t h Increased c o n c e n t r a t i o n . S e c o n d l y , r a d i o a c t i v e exchange e x p e r i m e n t s with' the n i c k e l atom (26) and w i t h the l i g a n d (27) where exchange was n o t e d whenever paramagnetism a r o s e I n s o l u t i o n are r e a d i l y e x p l a i n e d by a s s o c i a t i o n . . I n p a r t i c u l a r , the d i f f i c u l t y of h a v i n g t o p o s t u l a t e a c i s d i p y r i d i n e adduct t o e x p l a i n l i g a n d exchange i n p y r i d i n e i s removed s i n c e exchange c o u l d w e l l p r o -ceed t h r o u g h an a s s o c i a t e d form p r e s e n t i n v e r y s m a l l amounts. T h i r d , the i s o l a t i o n of a low t e m p e r a t u r e p a r a m a g n e t i f o r m can be e x p l a i n e d by a s s o c i a t i o n as the l o w e r i n g of. the t e m p e r a t u r e w i l l i n c r e a s e the degree of a s s o c i a t i o n u n t i l a u n i f o r m s p e c i e s e x i s t s t h r o u g h o u t the s o l u t i o n and removal of t s o l v e n t p r e c i p i t a t e s t h e s p e c i e s . I n the case of b i s - N - m e t h y l s a l i c y l a l d i m i n e n i c k e l ('II), almost a l l o f the s o l v e n t must be removed b e f o r e the low t e m p e r a t u r e s p e c i e s i s o b t a i n e d . A s p e c i a l p o i n t t o note t h a t i f the square p l a n a r monomeric con-f i g u r a t i o n i s m a i n t a i n e d i n s o l u t i o n as i n d i c a t e d by B a l l h a s e n and L i e h r , then the s o l u b i l i t y of the complex s h o u l d decrease as t h e t e m p e r a t u r e d e c r e a s e s , b u t , as p r e v i o u s l y s t a t e d , the s o l u b i l i t y of b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( i i ) i n c h l o r o f o r m a t -76°G i s almo.st i n f i n i t e . T h i s h i g h s o l u b i l i t y can a l s o be found i n the new s p e c i e s g i v e n i n P i g . I I w h i c h may i n d i c a t e t h a t the same type a s s o c i a t i o n i s p r e s e n t i n b o t h c a s e s . Warming of the low t e m p e r a t u r e s p e c i e s changes i t t o the square p l a n a r form, but i n the case of b i s - N - m e t h y l -s a l i c y l a l d i m i n e n i c k e l , the d i a m a g n e t i c form i s the new o r t h o -rhombic m o d i f i c a t i o n where the N i - N i d i s t a n c e i s 3.10 r a t h e r t h a n t h e o r d i n a r y m o n o c l i n i c f orm w h i c h has a N i - N i d i s t a n c e of '5.32 S. The c o n v e r s i o n t a k e s p l a c e a t room t e m p e r a t u r e , c o n s e q u e n t l y the N i - N i d i s t a n c e can not have changed c o n s i d e r a b l y f r o m t h a t o r i g i n a l l y p r e s e n t i n the low t emperature form. T h i s c l o s e N i - N i d i s t a n c e l e n d s f u r t h e r credence t o the s u g g e s t i o n t h a t an a s s o c i a t e d p r o d u c t i s i s o l a t e d . F o u r t h , a n o t h e r s p e c i e s t h a t almost c e r t a i n l y i s a s s o c i a t e d i s the l i g h t green p a r a m a g n e t i c form of B i s ^ N - m e t h y l -5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l ( l l ) o b t a i n e d by h e a t i n g t o 1 6 5 ° -The c o r r e c t e d magnetic moment i s 2.90 b.m. w h i c h . i n d i c a t e s an o c t a h e d r a l arrangement about the n i c k e l atom. The l a r g e v a l u e o f 60° f o r the Weiss Constant can be e x p l a i n e d as d i s t o r t i o n f r o m a r e g u l a r o c t a h e d r a l arrangement, and a l s o by the f a c t t h a t t h e s p l i t t i n g between the l o w e r t r i p l e t and the n e x t s i n g l e t s t a t e i s not l a r g e compared t o KT. T h i s p r o d u c t may not be e x a c t l y the same as the low t emperature form s i n c e on h e a t i n g t h e l a t t e r s p e c i e s t h e d i a m a g n e t i c s p e c i e s i s o b t a i n e d . How-e v e r , the method of a s s o c i a t i o n i s u n l i k e l y t o be c o m p l e t e l y d i f f e r e n t , as t h e y a r e b o t h s o l u b l e i n o r g a n i c s o l v e n t s w h i l e a t h i r d b u f f complex ( F i g . I ) i s i n s o l u b l e i n o r g a n i c solvents.. I t i s i m p r o b a b l e t h a t t h r e e d i s t i n c t t y p e s of a s s o c i a t i o n a r e p r e s e n t f o r one m o l e c u l e . W i t h th e s e complexes, i t i s d i f f i c u l t t o i r r e v o c a b l y e s t a b l i s h whether the p r o d u c t i s o l a t e d i s r e l a t e d t o the p a r a -magnetic s p e c i e s i n s o l u t i o n . One method of r e l a t i n g the s o l i d s p e c i e s t o the s p e c i e s i n s o l u t i o n i s t o compare t h e i r u.v. and v i s i b l e s p e c t r a . The s p e c t r a of f o u r compounds were o b t a i n e d . These were: the d a r k green d l a m a g n e t i c form ( i ) , the l i g h t green p a r a m a g n e t i c form ( i i ) , the low temperature p a r a -magnetic form ( i l l ) , and the b u f f f orm ( IV) of b i s - N - m e t h y l - 5 -c h l o r o - s a l i c y l a l d i m i n e n i c k e l ('II). The f o l l o w i n g maxima's were observed.. 1 - 4 4 0 m/<(P), 6 2 0 m/<('P) I I - 4 8 0 m/rf(-sh), 6 3 0 m><(p), 8 2 0 m > ( s h ) , (Ca) 1 0 0 0 mx<(P). I l l - 4 3 0 m/<(sh), 6 1 0 m/<('P), 78O m//(-sh), Ca 9 3 0 m / ^ ( P ) . IV - 4 2 0 m/x(sh), 56.O m/x(p), 7 8 0 m/* ( s h ) , 9 0 0 m//(.P) . The s p e c t r a of I I I show a c l o s e resemblance t o t h e s p e c t r a r e p o r t e d by Maki ( 1 0 ) f o r b i s - N - m e t h y l - s a l i c y l a l d i m i n e n i c k e l ( i i ) i n c h l o r o f o r m , w h i l e the b u f f complex ( IV) resembles t h a t g i v e n f o r the complex i n p y r i d i n e . The p a r t i a l s h i f t of almost a l l of the maxima of the l i g h t green h e a t e d form ( i i ) may i n d i c a t e t h a t t h i s compound i s i n an i n t e r m e d i a t e stage of development. The maxima r e p o r t e d by Maki were: Complex i n c h l o r o f o r m 4 9 0 m>u ( s h ) , 6 1 0 m/v (P) 1 1 5 0 (P) . Complex i n P y r i d i n e 5 7 0 mju (P) 7 ^ 5 m/^  ( s h ) , 96O m/* (P) . The maxima about 8 0 0 mjufqv the c h l o r o f o r m s o l u t i o n may be hid d e n under the broad 1 1 5 0 mju peak. Not o n l y are the p o s i t i o n s o f the maxima of the s o l i d s s i m i l a r t o those found i n the s p e c t r a o f . t h e complexes i n o r g a n i c s o l v e n t s , but a l s o the r e l a t i v e h e i g h t s of the peaks are unchanged. I t i s not u n r e a s o n a b l e t o suggest t h a t the•environment of the n i c k e l atom f o r I I I i s s i m i l a r t o t h a t found i n c h l o r o f o r m s o l u t i o n . W h i l e the b u f f complex w h i c h may have an o c t a h e d r a l arrangement has a s i m i l a r environment t o the complex i n p y r i d i n e where a d i p y r i d i n e adduct i s known t o e x i s t . I f a r a d i c a l l y d i f f e r e n t s t r u c t u r e ( e . g . t e t r a h e d r a l ) were p r e s e n t i n the s o l i d s , then new peaks s h o u l d be observed or a t l e a s t a major s h i f t of the peaks a l r e a d y p r e s e n t . An i m p o r t a n t q u e s t i o n now i s the p o s s i b l e c o n f i g u r a t i o n of the a s s o c i a t e d species.. One type of a s s o c i a t i o n has been proposed by M a r t i n t o e x p l a i n the paramagnetism of the b u f f complex o b t a i n e d on heat-i n g ( P i g . I ) . They proposed t h a t a t r i v a l e n t oxygen atom p r o -v i d e d the means of o b t a i n i n g , an o c t a h e d r a l arrangement. T h i s s p e c i e s i s not r e l a t e d t o the p a ramagnetic complex o b t a i n e d i n s o l u t i o n , as i t i s i n s o l u b l e i n o r g a n i c solvents,, F o r the p a r amagnetic s p e c i e s i n s o l u t i o n and the low temperature s p e c i e s , the method of a s s o c i a t i o n i s p o s s i b l y v i a the n i t r o -gen atom where the l o n e p a i r of e l e c t r o n s of the n i t r o g e n from one m o l e c u l e i s donated t o the n i c k e l atom of a n o t h e r m o l e c u l e . T h i s I s shown i n F i g . I I . C o n c l u s i o n The two c u r r e n t t h e o r i e s a t t e m p t i n g t o e x p l a i n the r i s e of paramagnetism of b i s - N - a l k y l s a l i c y l a l d i m i n e n i c k e l ( l l ) , i . e . , s o l v e n t i n t e r a c t i o n , and removal of c r y s t a l f i e l d , have d i f f i c u l t y i n e x p l a i n i n g the e x i s t e n c e of a low temperature form. The low t emperature form can be e x p l a i n e d i f a s s o c i a -t i o n i s p r e s e n t i n s o l u t i o n . The proposed method of a s s o c i a t i o n I s v i a the n i t r o g e n atom where the n i t r o g e n atom donates i t s 42 l o n e p a i r of e l e c t r o n s t o a n i c k e l atom i n a d i f f e r e n t m o l e c u l e and the paramagnetism a r i s e s f r o m t h i s d i s t o r t e d arrangement. ' A l t h o u g h the l i g h t green heated form of b i s - N - m e t h y l -5 - c h l o r o - s a l i c y l a l d i m i n e n i c k e l (I.I) and the low temperature form show s i m i l a r s o l u b i l i t y , s p e c t r a , and x - r a y p a t t e r n , t h e y are p r o b a b l y s l i g h t l y d i f f e r e n t . T h i s d i f f e r e n c e i s m a n i f e s t e d i n the f a c t t h a t warming of the low temperature form produces the square p l a n a r d i a m a g n e t i c s p e c i e s . Another p o i n t i s t h a t i t i s u n l i k e l y t h a t t h r e e t o t a l l y d i f f e r e n t t y p e s of a s s o c i a t i o n a re p r e s e n t f o r one m o l e c u l e . The paramagnetic s p e c i e s i n " n o n - c o o r d i n a t i n g " s o l v e n t s and i n the molten complexes t o 120°C i s proposed t o be an a s s o c i a t e d f o rm w h i l e the paramagnetism above 120°C may a r i s e f r om the prom-o t i o n of e l e c t r o n s f rom the lo w e r s i n g l e t t o the nex t t r i p l e t s t a t e as d e s c r i b e d by B a l l h a u s e n and L i e h r ( 1 5 ) . However, t h e i r s u g g e s t i o n t h a t t h e i r p roposed e q u a t i o n c o u l d be v e r i f i e d by magnetic measurements o f t h e s e complexes over a wide temperature range i s not v a l i d . BIBLIOGRAPHY 1. P. P f e i f f e r , E, B r e i t h , E. Lubbe, T. T u i m a k i , Ann. 502, 8o4 (1933). 2. W. Klem and N. Raddatz, Z_. A n o r g a n i A l l g e m . Chem., 250, 207 (1942). 3 . J.B. W i l l i s and D.P. M e l l o r , J_. o f Am. Chem. S o c , 69, 1237 (1947). 4 . P. B a s s l o and W. Matouch, J_. o f Amer. Chem. Soc., 75., 5663 (1952). 5. H.C. C l a r k and A.L. O d e l l , J . o f Chem. S o c , 3431 (1955). 6. R.S. Nyholm, Chem, Review, 53., 263 (1953) . 7. L. S a c c o n i , R. C i n i and F. Maggio, J_. of Amer. Chem. Soc., 79, 3933 (1957). 8 . G. Maki, J . of Chem. Phys., 28, 651 (1958). 9 . G. Maki, J . of Chem. Phys., 2£, 162 (1958) . 10. G. M a k i , - J . of Chem. Phys.,2 9 , 1129 (1958) . 11. L. S a c c o n i , P. P a o l e t t i and G. D e l Re, J_. of Amer. Chem. S o c , 79, 4062 (1957). 12. L. S a c c o n i , P. P a o l e t t i , and R. C i n i , J . of Amer, Chem, S o c , 80, 3583 (1958) . 13. C.H. H a r r i s , S.H. L e n z e r and R.L. M a r t i n , A u s t . J . of Chem., 11, 331 (1958) . 14. L. S a c c o n i , M. C i a m p o n i n i , P. Maggio and G. D e l Re, J . of Amer. Chem. S o c , 82, 815 ( i960) . 15. G.J. B a l l h a s e n and A.D. L i e h r , J_. of Amer. Chem. Sac., 8l_, 538 (1959). 16. L. S a c c o n i , R. C i n i , M. C r a m p o l i n i , and P. Maggio, J . of Amer. Chem. Soc., 82, 348 ( i 9 6 0 ) . 17. J . Ferguson, i n P r e s s . 18. N. G i l l and R.S. Nyholm, J', of Amer. Chem. Soc., 8 l , 3996, 1959. 4 4 1 9 . B.N. F i g g i s , and R.S. Nyholm, J . of Chem. S o c , 4 1 9 0 ( 1 9 5 8 ) . 2 0 . C M . F r e n c h , and V.C. G. Trew, T r a n s . F a r a . Soc., 4 l , 4 3 9 ( 1 9 4 5 ) . 2 1 . B.N. F i g g i s and R.S. Nyholm, J . of Chem. S o c , 3 3 1 ( 1 9 5 9 ) . 2 2 . T.R. G r i f f i t h s , K.A.K. L o t t , and M..C.R. Symons, A n a l . Chem.,31, 1 3 3 8 ( 1 9 5 9 ) . 2 3 . R.J. 0 l B r i e n , B.Sc. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, 1 9 5 8 : 2 4 . G.J. B u l l e n , N a t u r e , 1 7 7 , 5 3 7 ( 1 9 5 6 ) . 2 5 . E.K.C. L y l e , B. M o r o s i n , and E.C. L i n g a f e l t e r , A c t a . C r y s t . , 1 2 , 9 3 8 ( 1 9 5 9 ) . 2 6 . N.F. H a l l , and B.R. W i l l e f o r d , J . o f Amer. Chem. S o c , 7 3 , 5 4 1 9 ( 1 9 5 1 ) . 2 7 . H.C. C l a r k , and A.L. O d e l l , J . of Chem. S o c , 5 2 0 ( 1 9 5 6 ) . 

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