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Syntheses and magnetic studies of manganese(II) monophenylphosphinates and some cadmium(II) doped compounds Du, Jing-Long 1987

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SYNTHESES AND MAGNETIC STUDIES OF M A N G A N E S E ( 11) MONOPHENYLPHOSPHINATES AND SOME C A D M I U M ( l l ) DOPED COMPOUNDS by JING-LONG DU B . S c , Nankai U n i v e r s i t y , People's Republic of China, 1975 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department of Chemistry We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA September 1987 © JING-LONG DU, 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of C h e m i s t r y  The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date September 18, 1987  DE-6 (3/81) ABSTRACT Anhydrous monophenylphosphinates of manganese(II), M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I, Form II and Form 1(B)) and cadmium(II), C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I and Form II) were s y n t h e s i z e d and c h a r a c t e r i z e d by s o l u b i l i t y t e s t s , D i f f e r e n t i a l Scanning C a l o r i m e t r y (DSC), I n f r a r e d Spectroscopy, X-ray Powder D i f f r a c t o m e t r y , E l e c t r o n Spin Resonance (ESR) spectroscopy, magnetic s u s c e p t i b i l i t y measurements and E l e c t r o n Spectroscopy f o r Chemical A n a l y s i s (ESCA). These m a t e r i a l s are c o n s i d e r e d to be polymeric with metal ions connected i n c h a i n s by double b r i d g i n g phosphinate groups with c r o s s - l i n k a g e forming sheets and o c t a h e d r a l metal c e n t e r s . Magnetic s u s c e p t i b i l i t y s t u d i e s showed that M n [ H ( C 6 H s ) P 0 2 ] 2 (Form I) e x h i b i t s r e l a t i v e l y s trong a n t i f e r r o m a g n e t i c exchange i n t e r a c t i o n s ( J i s about -4.50 cm - 1) and the e f f e c t s on t h i s magnetic exchange of doping diamagnetic cadmium ions i n t o the m a t e r i a l have been i n v e s t i g a t e d . A s e r i e s of mixed metal phosphinates of the form Mn. Cd [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) where x=0 to 1.00 were prepared and i n v e s t i g a t e d . The e f f e c t of doping with cadmium i s to break the i n f i n i t e manganese(II) monophenylphosphinate ch a i n i n t o f i n i t e segments and to generate monomer i i i m p u r i t i e s i n odd numbered segments. As the extent of doping i s i n c r e a s e d the average c h a i n l e n g t h decreases and the f r a c t i o n of monomer i n c r e a s e s . In a d d i t i o n , the exchange c o u p l i n g constant, J , was found to decrease (from -4.50 to -2.70 cm - 1) as the average c h a i n l e n g t h decreases. M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form 1 ( B ) ) , which i s p r e c i p i t a t e d from c o n c e n t r a t e d s o l u t i o n s , c o n t a i n s much s h o r t e r c h a i n fragments than the pure Form I m a t e r i a l . Mn [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I I ) has a d i s t i n c t i n f r a r e d spectrum and X-ray powder d i f f r a c t i o n p a t t e r n and shows much weaker a n t i f e r r o m a g n e t i c behavior ( J i s about -2.40 cm" 1) than the Form I compound. Magnetic s t u d i e s suggest that i n t h i s compound the average c h a i n l e n g t h i s s i g n i f i c a n t l y s m a l l e r than i n M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) . The hydrated monophenylphosphinates of manganese(II), M n [ H ( C s H 5 ) P 0 2 ] 2 - H 2 0 and Mn[H(C 6H 5)P0 23 2*2H 20, were s y n t h e s i z e d and c h a r a c t e r i z e d i n t h i s work. The s t r u c t u r e s of these compounds are c o n s i d e r e d to be s i m i l a r to those of the anhydrous m a t e r i a l s except i n the hydrated compounds one or two of the metal c o o r d i n a t i o n s i t e s are occupied by water molecules. The d i h y d r a t e shows only very weak a n t i f e r r o m a g n e t i c p r o p e r t i e s ( J i s about -0.50 cm" 1). The diphenylphosphinates of manganese(II) and cadmium(II) were a l s o prepared and c h a r a c t e r i z e d . The i n f r a r e d s p e c t r a and X-ray powder d i f f r a c t i o n p a t t e r n s f o r these m a t e r i a l s are d i s t i n c t from each other,which i n d i c a t e s the compounds are not isomorphous. Only r a t h e r weak magnetic exchange was observed i n the manganese compound. Zn[H(C 6H 5 ) P 0 2 ] 2 has a l s o been s y n t h e s i z e d and p a r t i a l l y c h a r a c t e r i z e d i n t h i s work. The i n f r a r e d spectrum and X-ray powder d i f f r a c t i o n p a t t e r n o btained f o r t h i s compound are unique among a l l the metal phosphinates s t u d i e d i n t h i s work. iv TABLE OF CONTENTS A b s t r a c t i i L i s t of T a b l e s i x L i s t of F i g u r e s x i i Acknowledgements x v i Chapter 1. I n t r o d u c t i o n 1 1.1. H i s t o r i c a l Remarks 1 1.2. O b j e c t i v e s and O u t l i n e of t h i s Work ... 7 Chapter 2. Monophenylphosphinates of Manganese(11) and Cadmium ( I I ) , M [ H ( C 6 H 5 ) P 0 2 ] 2 10 2.1. S y n t h e s e s , S o l u b i l i t i e s and Thermal P r o p e r t i e s 10 2.2. I n f r a r e d S p e c t r o s c o p y 17 2.3. X-ray Powder D i f f r a c t i o n P a t t e r n s .... 3 1 2 . 4 . E l e c t r o n S p i n Resonance S p e c t r o s c o p y . 36 2.5. M a g n e t i c P r o p e r t i e s of M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I , Form I I , and Form 1(B)) ... 39 2 . 6 . Summary 4 9 Chapter 3. Mixed M e t a l Systems M a t e r i a l s of C o m p o s i t i o n M n 1 _ x C d x [ H ( C s H 5 ) P 0 2 ] 2 51 3 . 1 . I n t r o d u c t i o n 51 3 . 2 . S y n t h e s e s , S o l u b i l i t i e s and Thermal P r o p e r t i e s 52 3 . 3 . I n f r a r e d S p e c t r o s c o p y 56 3 . 4 . X-ray Powder D i f f r a c t i o n 58 3.5. M a g n e t i c P r o p e r t i e s 61 3 . 6 . E l e c t r o n S p i n Resonance (ESR) S p e c t r o s c o p y 76 v 3.7. E l e c t r o n Spectroscopy f o r Chemical A n a l y s i s (ESCA) 82 Chapter 4. M i s c e l l a n e o u s Compounds 89 4.1. M a nganesedl) and Cadmium(II) Diphenylphosphinate 89 4.2. Monohydrates of Manganesedl) and Cadmium(Il) Monophenylphosphinate . 101 4.3. The D i h y d r a t e of Manganesedl) Monophenylphosphinate 107 4.4. Z i n c ( I I ) Monophenylphosphinate 110 Chapter 5. Summary,and Suggestions f o r F u r t h e r Study ... 113 5.1. Summary 113 5.2. Suggestions f o r Furt h e r S t u d i e s 115 Chapter 6. Experimental 117 6.1. P h y s i c a l methods 117 6.1.1. I n f r a r e d Spectroscopy 117 6.1.2. D i f f e r e n t i a l Scanning C a l o r i m e t r y (DSC) 117 6.1.3. Magnetic S u s c e p t i b i l i t y Measurements 118 6.1.4. E l e c t r o n Spin Resonance (ESR) Spectroscopy 119 6.1.5. X-Ray Powder D i f f r a c t o m e t r y 120 6.1.6. E l e c t r o n Spectroscopy f o r Chemical A n a l y s i s (ESCA) 120 6.1.7. Elemental Analyses 121 6.2. Compound Syntheses 123 v i 6.2.1. P r e p a r a t i o n of Manganese(II) Monophenylphosphinate (Form I ) , M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) 124 6.2.2. P r e p a r a t i o n of Manganese(II) Monophenylphosphinate (Form I I ) , M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form II) 125 6.2.3. P r e p a r a t i o n of Manganesedl) Monophenylphosphinate (Form I ( B ) ) , M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form 1(B)) 125 6.2.4. P r e p a r a t i o n of Manganesedl) monophenylphosphinate Monohydrate, M n [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 126 6.2.5. P r e p a r a t i o n of Manganese(II) Monophenylphosphinate D i h y d r a t e , M n [ H ( C 6 H 5 ) P 0 2 ) ] 2 - 2 H 2 0 ... 127 6.2.6. P r a p a r a t i o n of Cadmium(II) monophenylphosphinate (Form I ) , C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) 127 6.2.7. P r e p a r a t i o n of Cadmium(II) Monophenylphosphinate (Form I I ) , C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form II) 128 6.2.8. P r e p a r a t i o n of Cadmium(II) Monophenylphosphinate Monohydrate, C d [ H ( C 6 H s ) P 0 2 ] 2 « H 2 0 128 v i i 6.2.9. P r e p a r a t i o n of Z i n c ( I I ) Monophenylphosphinate, Z n [ H ( C 6 H 5 ) P 0 2 ] 2 129 6.2.10. P r e p a r a t i o n of Mixed M a n g a n e s e d l ) , Cadmium(II) Monophenylphosphinate (Form I ) , M n 1 _ x C d x [ H ( C s H 5 ) P 0 2 ] 2 (Form I) 129 6.2.11. P r e p a r a t i o n of Mixed M a n g a n e s e d l ) , Cadmium(II) Monophenylphosphinate (Form 1 ( B ) ) , M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I (B)) 131 6.2.12. Preparaton of Manganesedl) Diphenylphosphinate, M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 131 6.2.13. P r e p a r a t i o n of Cadmium(Il) Diphenylphosphinate, C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 132 References 133 Appendix 143 v i i i List of Tab I es Table 2.1 S o l u b i l i t i e s of Monophenylphosphinates of Manganesedl) and Cadmiumdl) 11 Table 2.2 DSC Studi e s on the Monophenylphosphinates of Manganesedl) and Cadmiumdl) 15 Table 2.3 I n f r a r e d Bands A s s o c i a t e d With P-0 s t r e t c h i n g f o r the Monophenylphosphinates of Manganesedl) and Cadimium(II) 26 Table 2.4 I n f r a r e d Bands A s s o c i a t e d with M-0 S t r e t c h i n g f o r the Monophenylphosphinates of Manganesedl) and Cadmiumdl) 27 Table 2.5 I n f r a r e d Bands A s s o c i a t e d with P-H S t r e t c h i n g f o r the Monophenylphosphinates of Manganesedl) and r Cadmiumdl) 28 Table 2.6 I n f r a r e d Bands A s s o c i a t e d with P-C S t r e t c h i n g f o r the Monophenylphosphinates of Manganesedl) and Cadmiumdl) 29 Table 2.7 I n f r a r e d Bands A s s o c i a t e d with (C)(H)P0 2 Bending f o r the Monophenylphosphinates of Manganesedl) and Cadmiumdl) 30 Table 2.8 X-ray Powder D i f f r a c t i o n P a t t e r n s f o r the Monophenylphosphinates of Manganesedl) and Cadmiumdl) 34 Table 2.9 X-ray Powder D i f f r a c t i o n P a t t e r n s f o r the Monophenylphosphinates of Manganesedl) and Cadmiumdl) 35 ix Table 2.10 Magnetic Parameters f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 48 Table 3.1 DSC S t u d i e s on the M n , _ v C d v [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) . I A A 55 Table 3.2 X-ray Powder D i f f r a c t i o n Data f o r M n 1 _ x C d x [ H ( C s H 5 ) P 0 2 ] 2 (Form I ) , where x=0.005, 0.01, 0.09 58 Table 3.3 X-ray Powder D i f f r a c t i o n Data f o r M n 1 _ x C d x [ H ( C 6 H s ) P 0 2 ] 2 (Form I ) , where x=0.27 and 0.47 59 Table 3.4 Magnetic Parameters f o r M n 1 _ x C d x [ H ( C 6 H S ) P 0 2 ] 2 (Form I) 71 Table 3.5 Magnetic Parameters f o r Mn. Cd [ H ( C 6 H 5 ) P 0 2 ] 2 I A A (Form I (B) ) 72 Table 3.6 ESR Linewidth of M n . _ v C d v [ H ( C 6 H 5 ) P 0 2 ] 2 (Form 1(B)) 1 A A 81 Table 3.7 Binding Energy (eV) From ESCA S t u d i e s 84 Table 4.1 I n f r a r e d A b s o r p t i o n s f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and C d [ ( C 6 H s ) 2 P 0 2 ] 2 91 Table 4.2 X-ray Powder D i f f r a c t i o n Data f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 94 Table 4.3 I n f r a r e d A b s o r p t i o n s f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 « H 2 0 and C d [ H ( C s H 5 ) P 0 2 ] 2 . H 2 0 104 Table 4.4 X-ray Powder D i f f r a c t i o n Data f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 a n d C d [ H ( C 6 H 5 ) P 0 2 ] 2 « H 2 0 106 Table 4.5 I n f r a r e d A b s o r p t i o n s f o r M n [H(C 6H 5)P0 2] 2•2H 20 .110 x Table 6.1 Elemental Analyses 122 x i List of Fi gur es F i g u r e 1.1 Polymeric S t r u c t u r e of Cu[ ( C 6 H , 3 ) 2 P 0 2 ] 2 ( A P o r t i o n of the Chain) 5 F i g u r e 2.1 Thermograms of a) M n [ H ( C 6 H s ) P 0 2 ] 2 (Form I ) , and b) Cd[H(C 6H 5 )P0 2 ] 2 (Form I) 16 F i g u r e 2.2(1) RR'P0 2* Bonding Modes and P o s s i b l e Polymeric S t r u c t u r e s 20 F i g u r e 2.2(2) RR'P0 2~ Bonding Modes and P o s s i b l e Polymeric S t r u c t u r e s 21 F i g u r e 2.3 I n f r a r e d Spectra of M n [ H ( C 6 H 5 ) P 0 2 ] 2 a) Form I; b) Form 1(B)? and c) Form II 24 F i g u r e 2.4 I n f r a r e d Spectra of C d [ H ( C 6 H 5 ) P 0 2 ] 2 a) Form I; b) Form II 25 F i g u r e 2.5 X-ray Powder D i f f r a c t i o n P a t t e r n s of a) C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) and b) M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) 32 F i g u r e 2.6 ESR Powder Spectra of M n [ H ( C 6 H 5 ) P 0 2 ] 2 a) Form I; b) Form II 38 F i g u r e 2.7 Magnetic S u s c e p t i b i l i t y and Magnetic Moment versus Temperature P l o t f o r Mn[H(C 6H 5)P0 2 3 2 ( Form I) 42 F i g u r e 2.8 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r Mn[H(C 6H 5 )P0 2 ] 2 ( Form I I ) 43 F i g u r e 2.9 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r Mn[H(C sH 5 )P0 2 ] 2 ( Form 1(B)) 44 x i i F i g u r e 3.1 Thermograms of a) Mn Q g i C d Q n g [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) and b) Mn Q 5 3 C d 0 4 7 [ H ( C 6 H 5 ) P 0 2 3 2 (Form I) ..54 F i g u r e 3.2 I n f r a r e d Spectrum of M n 0 5 3 C d 0 > 4 7 [ H ( C s H 5 ) P O 2 3 2 (Form I) 57 F i g u r e 3.3 X-ray Powder D i f f r a c t i o n P a t t e r n of M n 0 > 5 3 C d 0 i 4 7 [ H ( C 6 H 5 ) P O 2 ] 2 (Form I) 60 F i g u r e 3.4 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) 63 F i g u r e 3.5 Magnetic Moment versus Temperature P l o t f o r M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 3 2 (Form I) 64 F i g u r e 3.6 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r a) M n 0 > g g C d 0 < 0 l [ H ( C 6 H 5 ) P 0 2 3 2 and b) M n 0 . 9 9 5 C d 0 . 0 0 5 [ H ( C 6 H s ^ P ° 2 ] 2 ( F o r m l ) 6 5 F i g u r e 3.7 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r a) M n ( K 9 l C d C L n g [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) and b) M n 0 > 7 3 C d 0 < 2 7 i H ( C 6 H s ) P O 2 3 2 (Form I) 66 F i g u r e 3.8 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r M n 0 > 5 3 C d 0 > 4 7 [ H ( C 6 H 5 ) P O 2 3 2 (Form I) 67 F i g u r e 3.9 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r M n 0 > g g C d 0 > 0 l [ H ( C s H 5 ) P O 2 ] 2 (Form 1(B)) 68 F i g u r e 3.10 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r a) M n 0 > g 2 C d n > 0 8 [ H ( C 6 H 5 ) P O 2 ] 2 and b) M n 0 . 9 5 C d 0 . 0 5 [ H ( ^ s H s ) P ° 2 ] 2 ( F o r m I ( B ) ) 6 9 F i g u r e 3.11 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r a) M n 0 8 5 C d 0 > l 5 [ H ( C 6 H 5 ) P 0 2 3 2 a n d b) M n 0 . 5 2 C d 0 . 4 8 [ H ( C s H s ) P ° 2 1 2 ( F o r m I ( B ) ) 7 0 x i i i F i g u r e 3.12 P l o t of Exchange C o u p l i n g Constant J versus x (Mole F r a c t i o n of Cadmium) i n M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 76 F i g u r e 3.13 ESR Powder Spectrum of Mn Q 0 i c d o 9 g f H ( c 6 H 5 ) P 0 2 ] 2 a) at Room Temperature, and b) at L i q u i d Nitrogen Temperature 78 F i g u r e 3.14 Energy L e v e l Diagram f o r Octahedral M anganesedl) 79 F i g u r e 3.15 ESR Powder Spectrum of Mn. Cd [ H ( C 6 H 5 ) P 0 2 ] I A A (Form 1( B ) ) ; a) x=0.08; b) x=0.02; c) X=0.01 80 F i g u r e 3.16 ESCA Bindi n g Energy of M n ( 2 p 3 y 2 ) i a ^ Form I I ; b) Form I; c) M n n > 5 3 C d 0 4 7 f H ( C 6 H 5 ) P 0 2 ] 2 (Form I) 85 F i g u r e 3.17 ESCA Bindi n g Energy of C X l s ^ j ) : a) Form I I ; b) Form I; c) Mn n coCd n . 7 [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) 86 F i g u r e 3.18 ESCA Bindi n g Energy of P ( 2 p 3 y 2 ) : a) Form I I ; b)Form I; c ) M n Q ^ 5 3 C d 0 > 4 ? [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) 87 F i g u r e 4.1 I n f r a r e d Spectra of a) M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and b) C d [ ( C s H 5 ) 2 P 0 2 ] 2 90 F i g u r e 4.2 X-ray Powder D i f f r a c t i o n P a t t e r n s of a) M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and b) C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 93 F i g u r e 4.3 ESR Spectra of Mn Q 0 l C d n g g [ ( C S H 5 ) 2 P 0 2 ] 2 a) at Room Temperature, and b) a t L i q u i d N itrogen Temperature 96 F i g u r e 4.4 Magnetic Moment versus Temperature P l o t f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 9 9 x i v F i g u r e 4.5 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r Mn[ ( C 6 H 5 ) 2 P 0 2 ] 2 100 F i g u r e 4.6 Thermograms of a) M n [ H ( C 6 H 5 ) P 0 2 ] 2 « H 2 0 and b) C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 103 F i g u r e 4.7 X-ray Powder D i f f r a c t i o n P a t t e r n s of a) M n [ H ( C 6 H 5 ) P 0 2 ] 2 * H 2 0 and b) C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 105 F i g u r e 4.8 I n f r a r e d Spectrum of M n [ H ( C 6 H 5 ) P 0 2 ] 2 • 2 H 2 0 109 F i g u r e 4.9 X-ray Powder D i f f r a c t i o n P a t t e r n of Z n [ H ( C 6 H 5 ) P 0 2 ] 2 112 xv ACKNOWLEDGEMENTS I would l i k e to express s i n c e r e s t thanks t o my s u p e r v i s o r , Dr. R.C. Thompson f o r the support, encouragement and guidance he p r o v i d e d d u r i n g the course of t h i s work. I am extremely g r a t e f u l to Dr. Hong-liang Hu f o r running many of my samples on the X-ray E l e c t r o n Spectrophotometer. I am a l s o indebted to Mr. J . Peers f o r h i s a s s i s t a n c e i n t h i s work and f o r h i s p r o o f - r e a d i n g of t h i s t h e s i s . I would l i k e to express a s p e c i a l thanks t o my wi f e , Jiuxue Song, whose many words of encouragement d u r i n g the l a s t three years have made t h i s t h e s i s p o s s i b l e . x v i CHAPTER 1. INTRODUCTION 1.1. HISTORICAL REMARKS There has been an i n c r e a s i n g i n t e r e s t shown by chemists and p h y s i c i s t s a l i k e i n the p r o p e r t i e s of t r a n s i t i o n metal c o o r d i n a t i o n polymers [ 1 ] . Research has been d i r e c t e d to the formation of t h e r m a l l y s t a b l e polymers with p l a s t i c p r o p e r t i e s that might be of some commercial use. Compounds which have r e c e i v e d c o n s i d e r a b l e a t t e n t i o n i n t h i s regard are the p o l y ( m e t a l phosphinates), compounds of the type M ( R 2 P 0 2 ) 2 , i n which metal ions are b r i d g e d by a r y l -or a l k y l - s u b s t i t u t e d phosphinate anions (or mixed RR'P0 2 _ anions) [ 2 ] . There are s e v e r a l reasons f o r choosing the phosphinate d e r i v a t i v e s : i ) the three atom bridge i s c o n s i d e r e d to have p o t e n t i a l i n the formation of f l e x i b l e polymers, i i ) the phosphorus atom i s p r o t e c t e d from chemical a t t a c k by the organic s u b s t i t u e n t s which a l s o give good h y d r o l y t i c s t a b i l i t y , i i i ) the donor atoms are oxygen, r e s u l t i n g i n g r e a t e r o x i d a t i v e s t a b i l i t y , i v ) there are only two donor atoms per b r i d g e , p r e v e n t i n g branching, and v) the charge on the anion i s -1, p e r m i t t i n g the ready design of n e u t r a l c h a i n s . 1 2 The f i r s t metal phosphinate compound, U 0 2 [ ( n - C „ H 9 ) 2 P 0 2 ] 2 , was r e p o r t e d i n l a t e 1800's [ 3 ] , but no c h a r a c t e r i z a t i o n of the m a t e r i a l was repo r t e d u n t i l 1959 when v i s c o s i t y data were p u b l i s h e d [ 4 ] . In the 1960's, r e s e a r c h e r s began to c o n c e n t r a t e on modifying the p r o p e r t i e s of phosphinate polymers. By changing the s u b s t i t u e n t s on the phosphorus and by employing d i f f e r e n t metals, i t was p o s s i b l e to a l t e r p r o p e r t i e s such as the c r y s t a l l i z a b i l i t y , the g l a s s t r a n s i t i o n temperature, m e l t i n g and decomposition temperatures, the v i s c o s i t y , t e n s i l e s t r e n g t h , percent e l o n g a t i o n , s o l u b i l i t y and molecular weight [5, 6 ] . At the same time, the c l a s s i f i c a t i o n of these compounds by s t r u c t u r a l type and the c o r r e l a t i o n of these types with the R groups on phosphorus were a l s o undertaken [7-13], A knowledge of molecular s t r u c t u r e was expected to a i d i n the understanding of the polymeric p r o p e r t i e s of these m a t e r i a l s and thus enable r e s e a r c h e r s to design and s y n t h e s i z e polymers with s p e c i f i c p r o p e r t i e s . I n i t i a l l y , s t r u c t u r a l c h a r a c t e r i z a t i o n was achieved s o l e l y by i n d i r e c t methods i n v o l v i n g s o l u b i l i t y , v i s c o s i t y , thermal a n a l y s i s , s p e c t r a l techniques and, at times, magnetic s u s c e p t i b i l i t y measurements [9-12, 14-16]. The f i r s t s i n g l e c r y s t a l s t r u c t u r e d eterminations were c a r r i e d out by Giordano el a l . [17] i n 1967 on two z i n c ( l l ) 3 phosphinates: Z n [ ( n - C 0 H 9 ) 2 P 0 2 ] 2 and Z n [ ( C 6 H 5 ) ( n - C 4 H g ) P 0 2 ] 2 . These authors found a l i n e a r s t r u c t u r e i n v o l v i n g a b r i d g i n g system i n which chains of z i n c ions are l i n k e d a l t e r n a t e l y by s i n g l e and t r i p l e phosphinate anion b r i d g e s . In 1976, C o l a m i r i n o et a l . [18] f i r s t confirmed the e x i s t e n c e of the double phosphinate b r i d g e d s t r u c t u r e among phosphinate compounds with t h e i r r e p o r t of the c r y s t a l s t r u c t u r e of P b [ ( C 6 H 5 ) 2 P 0 2 ] 2 . A number of c o p p e r ( I I ) phosphinates have been s y n t h e s i z e d and c h a r a c t e r i z e d i n t h i s l a b o r a t o r y [1, 19-21] and elsewhere [3, 10-13, 22-23]. Gillman [10] examined the d i - n - o c t y l d e r i v a t i v e and i n t e r p r e t e d the data as being " c o n s i s t e n t with a v a r i e t y of s t r u c t u r e s i n c l u d i n g square p l a n a r , d i s t o r t e d o c t a h e d r a l and e i g h t - c o o r d i n a t e . " For the d i - n - b u t y l compound [11], he proposed d i s t o r t e d t e t r a h e d r a l metal c e n t e r s with c r o s s l i n k i n g phosphinate b r i d g e s . T h i s was based on the i n s o l u b i l i t y of the compound and i t s isomorphism with the c o b a l t ( I I ) and z i n c ( I I ) analogs. However, a c r y s t a l s t r u c t u r e d e t e r m i n a t i o n [24] of c o p p e r ( I I ) d i - n - b u t y l p h o s p h i n a t e has shown that i t i s a ch a i n polymer c o n t a i n i n g d i s t o r t e d t e t r a h e d r a l copper c e n t e r s and symmetric double b r i d g i n g phosphinate groups. In order to i n v e s t i g a t e the magnetic p r o p e r t i e s of these c o o r d i n a t i o n polymers of c o p p e r ( l l ) , p a r t i c u l a r l y t h e i r 4 p o t e n t i a l as systems which e x h i b i t magnetic exchange e f f e c t s , and to study how such p r o p e r t i e s are a f f e c t e d by molecular s t r u c t u r e (magneto-structural c o r r e l a t i o n s ) , a number of mono- and d i - s u b s t i t u t e d c o p p e r ( I I ) phophinate compounds were s y n t h e s i z e d and c h a r a c t e r i z e d by O l i v e r [ 1 ] . Two polymorphic forms, l a b e l l e d a and 0, were found f o r the c o pper(II) compounds c o n t a i n i n g s t r a i g h t c h a i n a l k y l groups. In some cases, the same compound c o u l d be i s o l a t e d i n both forms. X-ray c r y s t a l l o g r a p h y showed that the s t r u c t u r e s of both forms c o n s i s t of i n f i n i t e l i n e a r chains of eight-membered r i n g s , formed by two copper atoms in f l a t t e n e d t e t r a h e d r a l environments, j o i n e d by two b r i d g i n g phosphinate l i g a n d s . A p o r t i o n of the chain s t r u c t u r e of c o p p e r ( I I ) di-n-hexylphosphinate [1] i s shown in F i g . 1.1. S t r u c t u r a l d i f f e r e n c e s between the a and /3 forms were found to be a s s o c i a t e d with d i f f e r e n t degrees of d i s t o r t i o n of the CuOj, chromophore from r e g u l a r t e t r a h e d r a l geometry, and with d i f f e r e n t o r i e n t a t i o n s of the a l k y l groups on the phosphorus. Moreover, both forms were found to be m a g n e t i c a l l y c o n c e n t r a t e d . The a isomers e x h i b i t ant i f e r r o m a g n e t i c exchange with v a l u e s of the exchange parameter, J , ranging from c a . -1 to -30 cm - 1 i n d i f f e r e n t compounds, while the 0 isomers show weak ferromagnetic c o u p l i n g with J approximately 2 cm" 1. On the b a s i s of i t s e l e c t r o n i c spectrum O l i v e r , suggested that C u [ ( C 6 H 5 ) 2 P 0 2 ] 2 F i g u r e 1.1 Polymeric S t r u c t u r e of C u [ ( C 6 H , 3 ) 2 P 0 2 ] 2 ( A P o r t i o n of the Chain) probably has a unique s t r u c t u r e among the c o p p e r ( I I ) phosphinates. She s p e c u l a t e d that the compound had a c r o s s l i n k e d s t r u c t u r e with r e l a t i v e l y f l a t t e n e d CuO« chromophores. Recently, Bino and Sisman [23] prepared the 6 compound in a c r y s t a l l i n e form and determined i t s structure by X-ray d i f f r a c t i o n . The compound has the same basic double phosphinate bridged i n f i n i t e chain structure as the other copper(II) phosphinates; however, in this case the CuOft chromophore i s square planar. Magnetic s u s c e p t i b i l i t y studies down to 2.0 K were made on t h i s compound soon after i t s structure was reported and t h i s work confirmed the presence of weak ferromagnetic exchange in the compound [25]. Relatively few manganesedl) phosphinate compounds have been prepared and characterization of these materials has been very cursory. Scott et al. [26-27] f i r s t characterized a series of Mn(RR'P0 2)2 compounds by variable temperature magnetic s u s c e p t i b i l i t y measurements and found generally that the structures and properties of these materials were dependent upon the substituents on phosphorus. In 1978, Cookson and his coworkers [28J synthesized a series of manganesedl) dialkylphosphinates, diarylphosphinates and phosphates, and characterized them using electron spin resonance (ESR) spectroscopy. The d i v e r s i t y of the ESR spectra of the compounds studied indicated that the manganese(11) ion is sensitive to the st r u c t u r a l changes resulting from the e f f e c t s of the d i f f e r e n t organic substituents on the phosphate or 7 phosphinate l i g a n d s . R ecently, C i c h a et al. [29] r e p o r t e d the s y n t h e s i s and magnetic p r o p e r t i e s of the dimethylphosphinate of m a n g a n e s e d l ) , M n [ ( C H 3 ) 2 P 0 2 ] 2 / and i t s d i h y d r a t e . Magnetic s u s c e p t i b i l i t y s t u d i e s on the d i h y d r a t e a t temperatures from 300 to 4.2 K r e v e a l e d a magnetic moment of ca . 5.9 B.M. over most of the range s t u d i e d and gave no evidence f o r s i g n i f i c a n t magnetic exchange. Conversely, the anhydrous compound showed r e l a t i v e l y s trong a n t i f e r r o m a g n e t i c exchange e f f e c t s . An X-ray s t r u c t u r e d e t e r m i n a t i o n of the d i h y d r a t e r e v e a l e d a double phosphinate bri d g e d c h a i n s t r u c t u r e with a s t r o n g hydrogen-bonding network l i n k i n g the cha i n s t o g e t h e r . I t was suggested that the i n t e r c h a i n i n t e r a c t i o n e f f e c t i v e l y dampens the magnetic exchange i n t h i s m a t e r i a l . 1.2. OBJECTIVES AND OUTLINE OF THIS WORK The main o b j e c t i v e of t h i s work was to focus on the e f f e c t s of doping diamagnetic metal atoms i n t o m a g n e t i c a l l y c o n c e n t r a t e d phosphinate systems. We chose to i n v e s t i g a t e manganesedl) systems because of the r e l a t i v e s i m p l i c i t y of the i n t e r p r e t a t i o n of magnetic data i n these cases. S p i n - f r e e manganesedl) complexes have a 6A, e l e c t r o n i c ground s t a t e . Here, i n a m a g n e t i c a l l y d i l u t e system, the magnetic moment i s the s p i n - o n l y value of 5.92 B.M., and i s 8 independent of temperature. Any d e v i a t i o n from t h i s (except p o s s i b l y at very low temperature) i s i n d i c a t i v e of magnetic c o u p l i n g . Moreover, the q u a n t i t a t i v e treatment of the magnetic data f o r a n t i f e r r o m a g n e t i c manganesedl) systems i s r e l a t i v e l y s t r a i g h t f o r w a r d as has been demonstrated r e c e n t l y by Cicha et al. [29]. The l i g a n d s that were used i n t h i s work were mono- and diphen y l p h o s p h i n a t e . We chose these l i g a n d s p a r t l y because we a n t i c i p a t e d having to prepare a l a r g e number of samples and the commercial a v a i l a b i l i t y of the corresponding ph o s p h i n i c a c i d s made them a p p r o p r i a t e f o r such s t u d i e s . We prepared M n [ H ( C 6 H s ) P 0 2 ] 2 i n t w o forms, one of which (denoted Form I) shows much str o n g e r a n t i f e r r o m a g n e t i c exchange than e i t h e r the second form (Form II) or the diphenylphosphinate d e r i v a t i v e , M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 . In a d d i t i o n , we were able to ob t a i n two forms of Cadmium(II) monophenylphosphinate, one of which i s isomorphous with M n [ H ( C 6 K 5 ) P 0 2 ] 2 (Form I ) . Hence, most of the work r e p o r t e d here concerns the monophenylphosphinates of manganesedl) and cadmium(II) and the mixed metal system M n , _ v C d v [ H ( C e H 5 ) P 0 2 ] 2 (Form I ) . 1 A X In the course of t h i s work we a l s o prepared, and at l e a s t p a r t i a l l y c h a r a c t e r i z e d , hydrates of cadmium(II) and manganesedl) monophenylphosphinate, z i n c ( II) 9 monophenylphosphinate and hydrates of both cadmiumdl) and manganese(II) diphenylphosphinate. CHAPTER 2. MONOPHENYLPHOSPHINATES OF MANGANESE(11) AND CADMIUM ( I I ) , M[H(C 6H 5 ) P 0 2 ] 2 2.1. SYNTHESES, SOLUBILITIES AND THERMAL PROPERTIES Complete d e s c r i p t i o n s of the experimental procedures i n v o l v e d i n the syntheses o f " t h e manganesedl) and cadmiumdl) monophenylphosphinates are given i n chapter 6. Depending on the s o l v e n t used i n the s y n t h e s i s , two d i f f e r e n t forms or isomers of both the manganese and the cadmium compounds were o b t a i n e d . Each has a d i s t i n c t i n f r a r e d spectrum and X-ray powder d i f f r a c t i o n p a t t e r n (see below). We have a r b i t a r i l y l a b e l l e d the m a t e r i a l obtained from e t h a n o l as Form I and the m a t e r i a l from methanol as Form I I . In a d d i t i o n , we observed (vide infra) that depending on the c o n d i t i o n s under which p r e c i p i t a t i o n was c a r r i e d out, the magnetic p r o p e r t i e s of d i f f e r e n t samples of Mn [ H ( C 6 H 5 ) P 0 2 1 2 (Form I) are d i f f e r e n t . Samples prepared from d i l u t e s o l u t i o n s ( c o n c e n t r a t i o n c a . 4 x 10" 2 M of acet a t e ) g i v e r e p r o d u c i b l e magnetic r e s u l t s and are l a b e l l e d as Form I i n t h i s t h e s i s . A n a l y s i s of the magnetic data of samples prepared from more c o n c e n t r a t e d s o l u t i o n s i n d i c a t e they c o n t a i n paramagnetic i m p u r i t i e s (probably s t r u c t u r a l i m p u r i t i e s - see l a t e r ) and we have l a b e l l e d such samples as 10 11 Form 1(B). The q u a l i t a t i v e s o l u b i l i t i e s and thermal properties of these Mn[H(C 6H 5)P0 2 ]2 compounds were investigated and the results of the s o l u b i l i t y tests, for a number of common solvents, are given in Table 2 . 1 . Table 2.1 S o l u b i l i t i e s 1 of Monophenylphosphinates of Manganesedl) and Cadmiumdl). Compound Solvent 2 Metal Form A B c D E F G H I Mn I s S S S S i S S i S S SS SS Mn II s s S S S S S S i S S S S SS Mn I (B) s s SS i S S i i i i Cd I s s S S i S S i i i i Cd II s s i i S S i i i i *s = s o l u b l e , ^ 0 . 1 g / 1 0 0 m l ; s s = s l i g h t l y soluble, ca. 0 . 0 1 g / l 0 0 ml; i = insoluble. 2A = Water; B = methanol; C = ethanol; D = acetone; E = benzene; F = petroleum ether; G = carbon tetrachloride; H dichloromethane; I = chloroform. 12 A l l compounds are i n s o l u b l e or only very s l i g h t l y s o l u b l e in. the non-polar or s l i g h t l y p o l a r s o l v e n t s (CHC1 3, C 6H 6, CCli,, C H 2C1 2), i n d i c a t i n g , perhaps, the presence of c r o s s l i n k e d two- or thr e e - d i m e n s i o n a l s t r u c t u r e s . A l l m a t e r i a l s under d i s c u s s i o n were found to be s o l u b l e in water and had v a r i o u s s o l u b i l i t i e s i n the more p o l a r s o l v e n t s ( e t h a n o l , methanol and acet o n e ) . The s o l u b i l i t i e s of metal phosphinate polymers i n p o l a r s o l v e n t s have been a t t r i b u t e d by o t hers to the r e l a t i v e a b i l i t i e s of d i f f e r e n t s u b s t i t u e n t s on phosphorus to s h i e l d the i n o r g a n i c polymer backbone [31-34], The process of d i s s o l u t i o n can be viewed as i n v o l v i n g , p r i m a r i l y , the breakdown of the thre e - d i m e n s i o n a l s t r u c t u r e a r i s i n g through i n t e r c h a i n a s s o c i a t i o n . The a s s o c i a t i o n a r i s e s from a combination of d i p o l e - d i p o l e i n t e r a c t i o n s i n v o l v i n g the i n o r g a n i c backbone, expected to be maximized when s u b s t i t u e n t s are small (and hence unable to s h i e l d the backbone), and of induced d i p o l e - d i p o l e i n t e r a c t i o n s i n v o l v i n g i n t e r l e a v e d s u b s t i t u e n t s , expected to be maximized when the s u b s t i t u e n t s are l a r g e . In p o l a r s o l v e n t s such as water, methanol, ethanol and acetone, t h e r e f o r e , s i g n i f i c a n t s o l u b i l i t y i s expected on l y i n those cases where the p o l a r i n o r g a n i c backbone i s a c c e s s i b l e , that i s , where the s u b s t i t u e n t i s s m a l l . In the present case, both the hydrogen atom and to some extent the phenyl group, are small compared to most 13 a l k y l groups. Hence, the compounds are s o l u b l e i n the most p o l a r s o l v e n t t e s t e d , water. D i f f e r e n t i a l scanning c a l o r i m e t r y (DSC) has played an important r o l e i n i n v e s t i g a t i n g the thermal p r o p e r t i e s of metal phosphinate polymers. Such s t u d i e s y i e l d i n f o r m a t i o n on the r e v e r s i b i l i t y and en e r g i e s of melting and phase t r a n s i t i o n s , and on decomposition p a t t e r n s and energie s [7-9, 11, 18, 32-36]. V a r i a t i o n s i n those p r o p e r t i e s , f o r a given metal with d i f f e r e n t s u b s t i t u e n t s on the phosphorus atom have been a t t r i b u t e d p a r t i a l l y to v a r y i n g a b i l i t i e s of d i f f e r e n t s u b s t i t u e n t groups to s h i e l d the backbone from p o l a r i n t e r c h a i n i n t e r a c t i o n s [30-31, 34, 37-38]. Another i n t e r e s t i n g p r o p e r t y that can be i n v e s t i g a t e d u s ing DSC i s the polymorphism that i s common i n many of the b i v a l e n t metal phosphinate polymers [9-11, 32-35, 37, 39]. The r e s u l t s of the DSC an a l y s e s are given i n Table 2.2 f o r both forms of M n [ H ( C 6 H 5 ) P 0 2 ] 2 and C d [ H ( C 6 H 5 ) P 0 2 ] 2 . A l l f i v e compounds e x h i b i t an event corresponding to exothermic, o x i d a t i v e , decomposition i n the range 220 - 290°C. There i s no evidence f o r phase t r a n s i t i o n s over the range from room temperature to the decomposition temperature f o r any of the compounds. The cadmium compounds decompose at s i g n i f i c a n t l y h igher temperatures than the manganese d e r i v a t i v e s 1 4 (see F i g . 2.1) and f o r both metals r e l a t i v e l y small but s i g n i f i c a n t d i f f e r e n c e s are seen i n the thermal p r o p e r t i e s of the two forms. The DSC thermal diagrams show that i t i s not p o s s i b l e to convert from one form to the other by h e a t i n g above room temperature. t Table 2.2 DSC Studi e s on the Monophenylphosphinates of Manganesedl) and Cadmiumdl) 15 Compound Metal Form Peak Temperature(K) AH(KJ/mol) Mn I 220.5 160 Mn II 241.6 270 Mn 1(B) 223.6 90 Cd I 290.8 240 Cd II 285.0 270 16 10 B u 9) JZ o X u * o 0) X * E o o o 50 100 150 200 250 300 Temperature (°C) F i g u r e 2.1 Thermograms of a) Mn[H(C 6H 5)P0 2 3 2 (Form I ) , and b) Cd[H(C 6H 5)P0 2 3 2 (Form I) 17 2 . 2 . INFRARED SPECTROSCOPY I n f r a r e d s p e c t r o s c o p y c a n p r o v i d e i n f o r m a t i o n a b o u t t h e c o o r d i n a t i o n mode(s) o f t h e l i g a n d s i n a complex ( f r o m t h e numbers and p o s i t i o n s of b a n d s ) , t h e s t e r e o c h e m i s t r y a r o u n d t h e m e t a l , and s t r e n g t h o f t h e m e t a l - l i g a n d i n t e r a c t i o n [ 4 0 - 4 2 ] , F o r l i g a n d s w i t h h i g h e r symmetry i n t h e n o n - c o o r d i n a t e d ( " f r e e " ) s t a t e t h a n i n t h e c o o r d i n a t e d s t a t e , i n f r a r e d s p e c t r o s c o p y c a n , i n some c a s e s , d i s t i n g u i s h between p o s s i b l e c o o r d i n a t i o n mode(s) t h r o u g h t h e a p p e a r a n c e o f i n f r a r e d i n a c t i v e bands a n d / o r t h e s p l i t t i n g o f d e g e n e r a t e v i b r a t i o n s , due t o t h e l o w e r i n g o f t h e l i g a n d ' s symmetry upon c o o r d i n a t i o n . I n f o r m a t i o n on t h e s t r e n g t h o f c o o r d i n a t i o n , i . e . n o n - c o o r d i n a t e d ( " f r e e s t a t e " ) , s e m i - c o o r d i n a t e d (weak m e t a l - l i g a n d i n t e r a c t i o n ) , o r c o o r d i n a t e d ( s t r o n g m e t a l - l i g a n d i n t e r a c t i o n ) c a n a l s o be o b t a i n e d by c o m p a r i n g t h e number and t h e f r e q u e n c i e s o f i n f r a r e d a b s o r p t i o n s of t h e l i g a n d i n t h e " f r e e " s t a t e a n d i n a complex [ 4 3 - 4 5 ] . F o r a l i g a n d w h i c h has a r e l a t i v e l y low " f r e e s t a t e " symmetry, t h e i n f r a r e d s p e c t r a o f i t s c o m p l e x e s do n o t g e n e r a l l y y i e l d a s much i n f o r m a t i o n s i n c e t h e r e may be no d e g e n e r a t e modes and, henc e , no band s p l i t t i n g upon c o o r d i n a t i o n . T h i s i s t h e c a s e w i t h , f o r example, w i t h c a r b o x y l a t e and p h o s p h i n a t e l i g a n d s , where t h e maximum f r e e i o n symmetry i s C 2 V o r C g , and s t r u c t u r a l 18 i n f e r e n c e s must come from the p o s i t i o n s , r a t h e r than the number of bands. In a d d i t i o n , f a c t o r s such as v i b r a t i o n a l c o u p l i n g between groups i n the same molecule and the c o u p l i n g of l a t t i c e modes with i n t e r n a l modes [15] serve to incr e a s e the complexity of the s p e c t r a of such complexes. The phosphinate l i g a n d s c o n s i d e r e d i n t h i s work have a maximum f r e e ion symmetry of C g or C-2v' F o r R R ' P 0 2 ~ ( C 2 v ' when R=R'), nine fundamentals are expected ( 4 A 1 f 1A 2, 2B 2, 2B 2 ) , none of which are degenerate and only one of which, the A 2 ( t o r s i o n ) mode, i s i n f r a r e d i n a c t i v e . In the case of HRP0 2" ( C g symmetry, when R=C 6H 5-, monophenylphosphinate l i g a n d ) , nine fundamentals are again expected, 6A' and 3A"), of which none are degenerate, and a l l are i n f r a r e d a c t i v e . C l e a r l y , i f any s t r u c t u r a l i n f o r m a t i o n can be obtained from the i n f r a r e d s p e c t r a of the metal phosphinates, i t must come from an a n a l y s i s of band p o s i t i o n s . Oldham [46] compared the s h i f t s of C0 2 s t r e t c h i n g f r e q u e n c i e s in c a r b o x y l a t e s upon c o o r d i n a t i o n and, with r e f e r e n c e t o t h i s work, Gillman [10] c o r r e l a t e d the frequency d i f f e r e n c e between the asymmetric and symmetric P0 2 s t r e t c h e s i n phosphinates, , with the c o o r d i n a t i o n mode of the phosphinate and hence with the geometry about the metal. The manner in which the phosphinate binds w i l l depend 19 on a number of f a c t o r s such as: i ) the p r e f e r r e d c o o r d i n a t i o n number and s t e r e o c h e m i s t r y of the metal i n v o l v e d and, i i ) the s u b s t i t u e n t s on phosphorus. The s u b s t i t u e n t s can int r o d u c e s t e r i c r e s t r i c t i o n s on the type of phosphinate bonding p o s s i b l e . Some of the p o s s i b l e symmetric and unsymmetric c o o r d i n a t i o n modes are shown i n F i g . 2.2 [1, 10, 47]. Types I-IV are symmetric bonding types (each oxygen of the phosphinate bonded to the metal i n an e q u i v a l e n t manner r e s u l t i n g i n two e q u i v a l e n t PO bonds). These are expected to have s m a l l e r Ai> values than the unsymmetric bonding types (types V-VIII) which i n v o l v e non-equivalent PO bonds. S t r u c t u r e s IX, X, XII and XIV show p o s s i b l e c h a i n polymer s t r u c t u r e s i n v o l v i n g symmetric (IX, X, XII) and unsymmetric bonding (XIV) modes with t e t r a h e d r a l or o c t a h e d r a l metal c e n t e r s . Types XI, X I I I , XV and XVI show p o s s i b l e sheet polymer s t r u c t u r e s i n v o l v i n g symmetric (XI, XIII) and unsymmetric (XV, XVI) b r i d g i n g c o o r d i n a t i o n . In types XII and XIII there are two d i s t i n c t RR'P0 2~ groups, suggesting the p o s s i b i l i t y of four PO s t r e t c h e s f o r both of these s t r u c t u r a l types. 2 0 Examples of symmetric P02 bonding^ o; 9 ^ 9 pC PX A ' P % A M M M M M M M M M M I II III I V Examples of unsymmetric P02 bonding•• V V V o'p*o yo' o o'p^o o'p*o M M M M M M M M V VI VII VIII Possible polymer structures : Symmetric--p Xp' I X X F i g u r e 2 . 2 ( 1 ) R R ' P 0 2 " Bonding Modes and P o s s i b l e Polymeric S t r u c t u r e s . 21 XIII Unsymmetric t XIV VfclfL V & l C \ & C M ' l •» XV X V I F i g u r e 2 . 2 ( 2 ) RR'PO 2- Bonding Modes and P o s s i b l e Polyme r i c S t r u c t u r e s . The i n f r a r e d s p e c t r a of both forms of the manganesedl) and cadmium(II) phosphinates are shown in F i g s . 2.3 and 2.4. The s p e c t r a f o r both the manganesedl) (Form I) and cadmium(II) (Form I) compounds are almost i d e n t i c a l , i n d i c a t i v e of these compounds having the same s t r u c t u r e . The bands observed f o r both compounds are l i s t e d i n Tables 2.3 to 2.7. Four bands are a s s i g n e d to P-0 s t r e t c h i n g v i b r a t i o n s ; two bands are a s s i g n e d as asymmetric s t r e t c h e s and two as symmetric s t r e t c h e s . The small s p l i t t i n g of the bands might a r i s e from the presence of two s l i g h t l y d i f f e r e n t phosphinate l i g a n d s i n the compounds. T h i s i s c o n s i s t e n t with the o b s e r v a t i o n of a small s p l i t t i n g i n the band assi g n e d to the P-H s t r e t c h i n g value (see Table 2.5). Averaging the two asymmetric and the two symmetric bands g i v e s a Av value of ca. 107 cm"1 f o r the manganese compound and 114 cm - 1 f o r the cadmium compound. A c c o r d i n g l y , the compounds may be a s s i g n e d s t r u c t u r e s of type XIV or XVI. Such s t r u c t u r e s would be expected to have Av value of ca. 100 cm - 1 or g r e a t e r because they i n v o l v e unsymmetric P0 2 b r i d g e s [10]. The i n f r a r e d s p e c t r a of both the manganese and the cadmium Form II compounds are d i f f e r e n t from each other and from the s p e c t r a of the Form I compounds. The a b s o r p t i o n f r e q u e n c i e s and i n t e n s i t i e s are l i s t e d i n Table 2.3 to 2.7. 23 Based on the complexity of the s p e c t r a and Av v a l u e s of more than 120 cm - 1, i t i s suggested that two d i s t i n c t phosphinate l i g a n d s are i n v o l v e d i n these Form II compounds. The i n f r a r e d spectrum of Mn[H(C 6H 5)P0 2] 2 (Form 1(B)) i s given i n F i g . 2.3 and the a b s o r p t i o n s bands are recorded i n Tables 2.3 to 2.7. The spectrum f o r t h i s m a t e r i a l i s v i r t u a l l y i d e n t i c a l with those of both Form I m a t e r i a l s , i n d i c a t i n g t h a t they have the same b a s i c s t r u c t u r e s . The only s i g n i f i c a n t d i f f e r e n c e between Form I and Form 1(B) of Mn[H(C 6H 5)P0 2] 2 observed i n t h i s work was i n t h e i r magnetic p r o p e r t i e s (vide infra). Form 1(B) appears to have some s t r u c t u r a l impurity which a f f e c t s the magnetic behavior to a measurable e x t e n t . 24 WAVENUMBER /cm* 1 F i g u r e 2.3 I n f r a r e d S p e c t r a of M n [ H ( C 6 H 5 ) P 0 2 ] 2 a) Form I; b) Form 1(B); and c) Form I I . WAVENUMBER /cm-1 F i g u r e 2.4 I n f r a r e d Spectra of C d [ H ( C 6 H 5 ) P 0 2 ] 2 a) Form I Form I I . 26 Table 2.3 I n f r a r e d B a n d s 1 ' 2 A s s o c i a t e d With P-0 S t r e t c h i n g for the Monophenylphosphinates of Manganesedl) and Cadmium(II) Compound Metal Form V asy ( c m " 1 ) 3 • V sym, ( c m " 1 ) 3 t A K c n r 1 ) * Mn I 1 1 47 s 1073 w 1121 vs 1 034 ms 1018 s 107 Mn II 1 186 s 1098 ms 1 162 s. sh 1070 ms 1 149 s 1 039 s 1021 ms 1 25 Mn 1(B) 1 147 s 1071 w 1 122 vs 1034 ms 1018 s 109 Cd I 1 1 47 s 1072 w 1 129 s. sh 1033 ms 1 120 s. sh 1015 vs 1 14 Cd II 1 164 vs 1071 w 1 1 52 s. sh 1038 m 1 1 25 s 1013 ms 1 08 ^ h e s e data were taken on P e r k i n - E l m e r 1 7 1 0 . 2w = weak; vs=very s t r o n g ; s = strong; s.sh = str o n g shoulder; m = medium ms = medium strong 3Band assignments here and i n Tables 2.4 to 2.7 are as given in Reference [ 1 ] . "The v a l u e s here are the d i f f e r e n c e of two averaged asymmetric and two averaged symmetric s t r e t c h i n g frequenc i e s . 27 Table 2.4 I n f r a r e d Bands 1 A s s o c i a t e d with M-0 S t r e t c h i n g f o r the Monophenylphosphinates of Manganesedl and Cadmiumdl) Compound Metal Form Frequency ( c m - 1 ) 2 Mn I 421 m 366 mw Mn II 444 w 361 w Mn K B ) 421 w 366 mw Cd I 416 w 360 w Cd II 41?[D5 w 355 w ^ h e s e data were taken on Perkin-Elmer 598. 2w = weak; mw = medium weak; m = medium 28 Table 2.5 I n f r a r e d Bands 1 A s s o c i a t e d with P-H s t r e t c h i n g f o r the Monophenylphosphinates of Manganesedl) and Cadmiumdl) Compound Metal Form Frequency ( c m - 1 ) 2 Mn I 2346 m 2336 m Mn II 2370 m 2356 m 2342 m Mn K B ) 2338 m Cd I 2342 m 2331 m Cd II 2420 w 2352 w ^ h e s e data 2w = weak; m were taken = medium on Perkin-Elmer 1710. 29 Table 2.6 I n f r a r e d Bands 1 A s s o c i a t e d with P-C S t r e t c h i n g f o r the Monophenylphosphinates of Manganesedl) and Cadmium(II) Compound Metal Form Frequency ( c m " 1 ) 2 Mn I 758 w. sh 751 w 710 m Mn II 745 m 708 m Mn I (B) 758 w. sh 750 w 710 m Cd I 757 w 751 w 709 m Cd II 748 m 707 m 'These data were taken on P e r k i n - E l m e r 1 7 1 0 . 2w = weak; w.sh = weak shoulder; m = medium 30 Table 2.7 I n f r a r e d Bands 1 A s s o c i a t e d with (C)(H)P0 2 Bending f o r the Monophenylphosphinates of Manganesedl) and Cadmium(II) Compound Metal Form Frequency ( c m - 1 ) 2 Mn I 559 vs 504 w.sh 490 m Mn II 566 m.sh; 552 543 s; 515 mw 506 mw; 482 m Mn K B ) 559 s 504 w.sh 490 m Cd I 556 s 486 m Cd II 556 vs 493 w 472 w 'These data were taken on P e r k i n - E l m e r 1 7 1 0 . 2w = weak; w.sh = weak shoulder; vs = very s t r o n g ; s = stron g ; m = medium; mw = medium weak 31 2.3. X-RAY POWDER DIFFRACTION PATTERNS X-ray powder d i f f r a c t i o n s t u d i e s have, i n the past, p r o v i d e d u s e f u l s t r u c t u r a l i n f o r m a t i o n on metal phosphinates [14, 17, 31-34, 36, 48]. With polymeric m a t e r i a l s , the g e n e r a l l y amorphous or s e m i c r y s t a l l i n e nature of the system can preclude the i s o l a t i o n of s i n g l e c r y s t a l s s u i t a b l e f o r X-ray a n a l y s i s . T h i s has been the case i n the study of metal phosphinates, where r e l a t i v e l y few c r y s t a l s t r u c t u r e d e t e r m i n a t i o n s have been accomplished employing s i n g l e c r y s t a l X-ray d i f f r a c t i o n methods [1, 17-21, 29, 49-50]. Gillman f i r s t determined that Mn [ ( C 8 H , 7 ) 2 P 0 2 ] 2 and F e [ ( C 8 H , 7 ) 2 P 0 2 ] 2 are isomorphous with one another, as w e l l as with one form of C o [ ( C 8 H , 7 ) 2 P 0 2 ] 2 , based on t h e i r X-ray powder d i f f r a c t i o n p a t t e r n s [9-10]. The i n f r a r e d s p e c t r a of these three m a t e r i a l s are a l s o v i r t u a l l y i d e n t i c a l . These f i n d i n g s have been confirmed i n our l a b [51J. The same case can be made f o r the M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) and C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) . The d i f f r a c t i o n p a t t e r n s are shown in F i g . 2.5 and the d spacing and the i n t e n s i t i e s are given i n Table 2.8. These m a t e r i a l s are a l s o observed to form a complete s e r i e s of s o l i d s o l u t i o n s (vide infra). The compounds are m i c r o - c r y s t a l l i n e , judging from the sharpness of the peaks in d i f f r a c t i o n p a t t e r n s . In c o n t r a s t , the a ) 1 1 1 1 »~ 5 10 15 20 25 26(DEGREES) F i g u r e 2.5 X-ray Powder D i f f r a c t i o n P a t t e r n s of a) C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) and b) M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) d i f f r a c t i o n p a t t e r n s of the Form II compounds are d i f f e r e n t from those of the Form I compounds (see Tables 2.8 and 2.9), demonstrating c l e a r l y the lack of isomorphism between the Form I and Form II m a t e r i a l s . 34 Table 2.8 X-ray Powder D i f f r a c t i o n P a t t e r n s f o r the Monophenylphosphinates of Manganesedl) and Cadmium(II) M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) d I / I . d I / I . 15.56 7 10.78 100 10.78 100 8.02 6 6.27 8 6.29 8 6.09 8 5.37 7 5.39 10 5.20 7 5.25 6 4.66 25 4.67 2 4.49 5 4.24 2 4.00 20 4.01 5 3.28 5 3.27 3 3.33 6 3.23 3 3.10 2 35 Table 2.9 X-ray Powder D i f f r a c t i o n P a t t e r n s f o r the Monophenylphosphinates of Manganesedl) and Cadmiumdl) M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form II) C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I I ) d I / I . d I / I . 15.50 62 15.78 100 14.73 100 10.81 5 7.63 12 7.78 26 6.89 9 5.44 9 5.38 4 5.02 18 5.18 31 4.62 8 4.51 10 4.35 12 4.33 5 4.23 10 3.71 26 3.42 8 2.4. ELECTRON SPIN RESONANCE SPECTROSCOPY 36 The manganesedl) ion has a d 5 c o n f i g u r a t i o n . For a weak c r y s t a l f i e l d the 6S s t a t e of d 5 has no nearby c r y s t a l - f i e l d s t a t e s , and thus the ESR spectrum i s r e a d i l y d e t e c t e d over a l a r g e range of temperatures i n any c r y s t a l - f i e l d symmetry [52], Furthermore, a resonance i s r e a d i l y d e t e c t e d even f o r l a r g e z e r o - f i e l d s p l i t t i n g , because d 5 i s an o d d - e l e c t r o n system whose ground s t a t e i s a Kramer's doublet and whose degeneracy i s completely removed by a magnetic f i e l d . Normally, the g f a c t o r s are always near the f r e e s p i n value of 2.0023. Wickman et al. [53] have c o r r e l a t e d c e r t a i n f e a t u r e s of the ESR s p e c t r a of some d 5 systems with the z e r o - f i e l d s p l i t t i n g parameters D and E of the s p i n Hamiltonian. Here D i s a measure of a x i a l d i s t o r t i o n from c u b i c symmetry, and E of rhombic d i s t o r t i o n . They d e f i n e d X=(E/D) as a parameter i n p l a c e of E, and symmetry c o n s i d e r a t i o n s show that the only meaningful values of X l i e between 0 ( a x i a l symmetry) and 1/3 (rhombic symmetry). Dowsing et al. [54] have re p o r t e d the ESR s p e c t r a of some pure p o l y c r y s t a l l i n e manganesedl) complexes s t u d i e d at X-band frequency, and measured D and X from these s p e c t r a . They found that any compound with r e g u l a r c u b i c symmetry, such as o c t a h e d r a l 37 MnL 6 or t e t r a h e d r a l MnLfl, g i v e s o n l y a s i n g l e l i n e at g=2.00, but as the z e r o - f i e l d s p l i t t i n g i s i n c r e a s e d e i t h e r by g e o m e t r i c a l d i s t o r t i o n or by the presence of d i f f e r e n t types of l i g a n d s , the l i n e at g=2.00 becomes s p l i t , and components may be observed at higher and lower f i e l d . In the present work, at X-band frequency, powdered samples of M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) and M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form II) give a s i n g l e l i n e at g=2.00, even though the s t r u c t u r e s of the compounds cannot be r e g u l a r and an a p p r e c i a b l e z e r o - f i e l d s p l i t t i n g i s expected. These compounds are poly m e r i c , and i t i s l i k e l y that the pr o x i m i t y of neighbouring manganese ions r e s u l t s i n magnetic i n t e r a c t i o n s , c a using a s i n g l e l i n e to be observed. The ESR s p e c t r a of the compounds at room temperature are shown i n F i g . 2.6. 38 / / / s EL a. Q • > 1 b) ^ / 500 Gauss ' 0 1000 2000 3000 4000 5000 MAGNETIC FIELD (GAUSS) F i g u r e 2.6 ESR Powder Spectra of M n [ H ( C 6 H 5 ) P 0 2 ] 2 a) Form I; b) Form I I . 39 2.5. MAGNETIC PROPERTIES OF M n [ H ( C 6 H 5 ) P 0 2 ] 2 (FORM I, FORM II , AND FORM I(B)) The su b j e c t of magnetic i n t e r a c t i o n s i n s o l i d s has been of t e c h n i c a l importance and academic i n t e r e s t f o r s e v e r a l decades [54-61]. The concept of superexchange was i n t r o d u c e d i n s o l i d s t a t e p h y s i c s i n order to c o r r e l a t e observed magnetic behavior with e l e c t r o n i c and c r y s t a l s t r u c t u r e i n simple i n o r g a n i c systems l i k e f e r r i t e s . These ideas were u s u a l l y c a s t i n terms of valence bond arguments and a p p l i e d to high symmetry s i t u a t i o n s [62]. In the l a s t decade, i n o r g a n i c chemists have been a c t i v e i n the i n v e s t i g a t i o n of the magnetic behavior of a wide range of t r a n s i t i o n metal polymers and c l u s t e r s . In a few i n s t a n c e s , i t has been p o s s i b l e to deduce simple m a g n e t o - s t r u c t u r a l c o r r e l a t i o n s f o r changes i n v o l v i n g v a r i a t i o n of a s t r u c t u r a l parameter over a r a t h e r l i m i t e d range. Simultaneously, superexchange arguments have been r e c a s t i n the language of chemistry and have p r o v i d e d the b a s i s f o r the i n t e r p r e t a t i o n of these c o r r e l a t i o n s on a molecular l e v e l [61, 63-64], At the same time, there has been a renewed i n t e r e s t i n the chemical and p h y s i c a l p r o p e r t i e s of low-dimensional magnetic systems, many asp e c t s of the dynamics of which remain to be u n r a v e l l e d [65-66]. With the proper understanding and a p p l i c a t i o n of m a g n e t o - s t r u c t u r a l c o r r e l a t i o n s , i n o r g a n i c 40 chemists can provide an extremely v a l u a b l e s e r v i c e by s y n t h e s i z i n g systems which w i l l p r ovide examples f o r t e s t i n g s p e c i f i c , models important i n low-dimensional p h y s i c s . A l a r g e number of cha i n compounds of manganesedl) have been c h a r a c t e r i z e d s i n c e the 1960's [65]. A l l of these e x h i b i t ant i f e r r o m a g n e t i c i n t r a c h a i n i n t e r a c t i o n s , and many of the compounds undergo long-range o r d e r i n g at low temperatures. T y p i c a l l y , the manganesedl) ion occupies an oc t a h e d r a l s i t e with a 6A, ground s t a t e . As a r e s u l t , the magnetic p r o p e r t i e s are expected, and found, to be l a r g e l y i s o t r o p i c with a g tensor that i s c l o s e to the f r e e - e l e c t r o n g value ( g g = 2.0023). The analyses of magnetic s u s c e p t i b i l i t y data of such compounds have i n v o l v e d two approaches, both of which use the i s o t r o p i c Heisenberg h a m i l t o n i a n . These are ( i ) the s c a l e d i n f i n i t e c h a i n method of Wagner and F r i e d b e r g [66] and ( i i ) the i n t e r p o l a t i o n method of Weng [67]. A t y p i c a l i s o t r o p i c a n t i f e r r o m a g n e t i c l i n e a r chain compound i s TMMC (Tetramethylammonium manganesedl) c h l o r i d e ) [68-74]. The compound i s a chain with t r i c h l o r o - b r i d g e s , running p a r a l l e l to the c - a x i s . The i n t r a c h a i n exchange constant J i s about -4.38 cm"1 and the exchange i s strong enough to be observed i n s p e c i f i c heat measurements [75]. Recently i n t h i s l a b [29], the dimethylphosphinate of m a n g a n e s e d l ) , M n [ ( C H 3 ) 2 P 0 2 ] 2 was sy n t h e s i z e d and i t s magnetic p r o p e r t i e s measured . The compound i s a n t i f e r r o m a g n e t i c and the best f i t value of the exchange c o u p l i n g constant as determined using the Weng model i s -2.69 cm - 1 (using Wagner-Friedberg, J=-2.9 c m - 1 ) . Comparing these r e s u l t s with those f o r TMMC (J=-4.38 cm" 1) and those f o r CsMnCl 3•2H 20, (a compound with monochloro-bridge c h a i n , J=-2.16 c m - 1 ) i t was concluded that the magnetic i n t e r a c t i o n i n the phosphinate compound i s at l e a s t comparable to that i n v o l v i n g a monochloro-bridge but l e s s than t h a t i n v o l v i n g a t r i c h l o r o - b r i d g e . Magnetic s u s c e p t i b i l i t i e s measured over the temperature range 82 K to 4.2 K f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I, Form II and Form 1(B)) are given i n the Appendix. P l o t s of magnetic s u s c e p t i b i l i t y , x M , versus temperature f o r a l l these m a t e r i a l s are shown i n F i g s . 2.7 to 2.9 and magnetic moment f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) , M e f £ , versus temperature i s given i n F i g . 2.7. A l l these m a t e r i a l s e x h i b i t a n t i f e r r o m a g n e t i c behavior ( i ^ f f decreases with d e c r e a s i n g temperature) but only Form I shows a maximum i n i t s x M versus T p l o t (Neel p o i n t ) . a ° g R Ul 3 (A W a g n e r - F r i e d b e r g Model Weng Model o . o ?o o « : o 60 o Temperature (K) e o . o F i g u r e 2.7 Magnetic S u s c e p t i b i l i t y and Magnetic Moment versus Temperature P l o t f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 ( Form I) 43 Temperature (K) F i g u r e 2.8 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r M n [ H ( C 6 H s ) P 0 2 ] 2 ( Form II) 44 o ° I I I I I I I I I 1 0.0 20.0 40.0 60.0 80.0 T e m p e r a t u r e ( K ) F i g u r e 2.9 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 ( Form 1(B)) 45 As the magnetic p r o p e r t i e s of these compounds e x h i b i t the type of behavior d i s p l a y e d by other l i n e a r c h a i n . manganesedl) polymers, the magnetic data c o u l d be analyzed a c c o r d i n g to the same models which p r o v i d e d s a t i s f a c t o r y r e s u l t s f o r the other systems. As mentioned e a r l i e r , two models are a v a i l a b l e f o r the t h e o r e t i c a l a n a l y s i s of a n t i f e r r o m a g n e t i c exchange i n l i n e a r - c h a i n manganesedl) compounds. Ac c o r d i n g to the Wagner-Friedberg model, the magnetic s u s c e p t i b i l i t y , xM , i s given by the f o l l o w i n g equation Ng 2^S(S+1 ) 1+U  XM ~ 3kT 1-U U ) In t h i s equation, U=coth(K-1/ K ) and K=2JS(S+1)/kT. M b i s the Bohr Magneton, k i s Boltzman's constant, T i s the temperature i n degrees K e l v i n , g i s the Lande s p l i t t i n g f a c t o r , J i s the c o u p l i n g constant and S i s 5/2 f o r m a n g a n e s e d l ) . H i l l e r et al . [76] have generated a s e r i e s of c o e f f i c i e n t s to reproduce Weng's numerical r e s u l t s [69] f o r the magnetic s u s c e p t i b i l i t i e s . According to t h i s model: _ N g ^ [A+BXil . XM kT [1+CX+DX3] In t h i s equation, f o r S=5/2, A=2.9167, B=208.04, C=15.543, D=2707.2 and X=J/kT. 46 Our experimental r e s u l t s were analyzed u s i n g both models with f i t s made to the s u s c e p t i b i l i t y data with J and g as w e l l as % monomer as f i t t i n g parameters. I t i s assumed that f r a c t i o n s of the manganese atoms are behaving as normal paramagnets, uncoupled to other metal c e n t e r s i n the c h a i n . These atoms are behaving then as monomers and the percentage of these i s c a l l e d the % monomer. The monomers are assumed to f o l l o w C u r i e Law given by = Ng»g»S(S+1) mono. 3kT where g i s assumed to have the same value as i n the bulk of the polymer. Then, *obs. = (]-K)XChain + xxmono. U ) where 100X=% monomer and X c h a ^ n i s the s u s c e p t i b i l i t y c a l c u l a t e d employing one or other of the t h e o r e t i c a l models. The best f i t to the experimental s u s c e p t i b i l i t y data i s obtained by a d j u s t i n g g, J and % monomer u n t i l the f u n c t i o n F, d e f i n e d below, i s minimized. n x calc._ obs. F = [" Z -rr-1 ) 2 1 1 / 2 (5) n i X;cbs. In equation (5), x^ca^c' i s the molar s u s c e p t i b i l i t y c a l c u l a t e d , x^°^s' i s the molar s u s c e p t i b i l i t y observed and n i s the number of data p o i n t s . 47 In Figures 2.7 and 2.8, showing the magnetic s u s c e p t i b i l i t y and magnetic moment versus temperature plots, the points are experimental and the l i n e s are t h e o r e t i c a l , calculated using the best f i t values of J , g and % monomer. These parameters are l i s t e d in Table 2.10. Both th e o r e t i c a l models reproduce the experimental magnetic data reasonably well, although only the Wagner-Friedberg model reproduces the temperature of the s u s c e p t i b i l i t y maximum for Form I s a t i s f a c t o r i l y . Either or both of the following factors could account for the discrepancies observed between experiment and theory. Zer o - f i e l d s p l i t t i n g may have a s i g n i f i c a n t effect [65]. In most cases, magnetic phenomena are determined to the f i r s t order by the properties of the thermally occupied energy levels derived from the lowest electronic ground state of the constituent single ion. The z e r o - f i e l d s p l i t t i n g in a pa r t i c u l a r compound determines the electronic ground state, which i s the state involved in magnetic ordering at low temperatures. Both models ignore these ef f e c t s and although these should be small in the case of manganesedl), they may have a measurable contribution at low temperatures. Also, interchain interactions are ignored in both models. The p o s s i b i l i t y of some weak association between chains to raise the coordination number of manganese to six was discussed 48 Table 2.10 Magnetic Parameters 1 ' 2 f o r Mn[H(C 6 H 5 ) P 0 2 ] 2 Form J(cm~ 1) % monomer F I -4.50 0.00 0.0333 (-4.00) (0.00) (0.1100) II -2.40 4.70 0.0273 (-2.25) (4.95) (0.0353) K B ) -3.65 3.15 0.0246 (-3.45) (3.45) (0.0371) ]The data i n s i d e the b r a c k e t s are obtained by using the Weng model and those o u t s i d e the b r a c k e t s are obtained by using the Wagner-Friedberg model. 2We f i x e d g=2.00 in f i t t i n g the experimental d a t a . e a r l i e r (see F i g . 2.2). As the data i n Table 2.10 show, the exchange parameter J (as c a l c u l a t e d by e i t h e r model) i s s i g n i f i c a n t l y g r e a t e r f o r the Form I compound than f o r e i t h e r the Form 1(B) or the Form II m a t e r i a l s . C o n s i d e r i n g the parameters as determined using the Wagner-Friedberg model, J i s -4.50 cm"1 f o r Form I compared to -3.65 f o r Form 1(B) and -2.40 f o r Form I I . These d i f f e r e n c e s appear to be connected to the c a l c u l a t e d 49 % monomer i n the sample. The 3.15% monomer in Form 1(B) and 4.7% monomer i n Form II probably r e f l e c t s the fragmentation of the i n f i n i t e c h a i n i n the compounds i n t o segments and t h i s i n t u r n appears to dampen the magnetic exchange i n t e r a c t i o n between the magnetic c e n t e r s . T h i s phenomenon i s d i s c u s s e d i n more d e t a i l i n chapter 3 where experiments are d e s c r i b e d i n which the chains are fragmented e x p e r i m e n t a l l y by i n c o r p o r a t i o n of diamagnetic metal ions i n t o them. 2.6. SUMMARY Both M n [ H ( C 6 H 5 ) P 0 2 ] 2 and C d [ H ( C 6 H 5 ) P 0 2 ] 2 have been prepared i n isomorphous forms (see F i g s . 2.3 to 2.5). The s t r u c t u r e of M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) i s not known with c e r t a i n t y , but the c o l o r of the m a t e r i a l (pale pink) suggests o c t a h e d r a l manganese [41] and the i n f r a r e d spectrum supports a s t r u c t u r e with unsymmetric b r i d g i n g phosphinates and t h e r e f o r e a s t r u c t u r e as r e p r e s e n t e d of type XIV, XV or XVI i n F i g . 2.2(2). The l a t t e r s t r u c t u r e was suggested p r e v i o u s l y f o r M n [ ( C H 3 ) 2 P 0 2 ] 2 [29] and i s the p r e f e r r e d s t r u c t u r e here. The i n f r a r e d s p e c t r a and X-ray powder d i f f r a c t i o n p a t t e r n s show that Form II i s a d i s t i n c t s t r u c t u r a l form although the complexity of i n f r a r e d s p e c t r a makes i t d i f f i c u l t to s p e c u l a t e on i t s s t r u c t u r e . The magnetic s t u d i e s have confirmed the presence of magnetic 50 exchange i n M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) . Reasonable agreement with theory f o r i n f i n i t e c hains suggests that the manganese atoms i n the phosphinate b r i d g e d chains are a n t i f e r r o m a g n e t i c a l l y coupled with l i t t l e c h a i n fragmentation. The p o s s i b i l i t y e x i s t s that some weaker i n t e r c h a i n i n t e r a c t i o n s may be p r e s e n t . Samples of M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) prepared from c o n c e n t r a t e d s o l u t i o n s ( c a l l e d Form 1(B)) d i f f e r mainly i n t h e i r magnetic p r o p e r t i e s , the analyses of which i n d i c a t e c o n s i d e r a b l e c h a i n fragmentation. The Form II m a t e r i a l a l s o appears to have measurable chain fragmentation p r e s e n t . CHAPTER 3. MIXED METAL SYSTEMS MATERIALS OF COMPOSITION M n 1 _ x C d x [ H ( C « H 5 ) P 0 2 ] 2 3.1. INTRODUCTION In recent y e a r s , random or d i s o r d e r e d magnetic systems have a t t r a c t e d the i n t e r e s t of t h e o r e t i c a l and experimental p h y s i c i s t s and i n o r g a n i c chemists [77-84]. Very l i t t l e of t h i s type of study has, however, been done on metal phosphinates. Quite r e c e n t l y i n our l a b , Peers [85] c h a r a c t e r i z e d a mixed metal phosphinate system of composition C u 1 _ x N i x f ( n - C 8 H , 7 ) 2 P 0 2 ] 2 > with x=0.1. The whole system was found to adopt the s t r u c t u r e of pure copper ( I I) d i - n - o c t y l p h o s p h i n a t e (ferromagnetic form) with about 10% of the metal s i t e s occupied by s p i n - p a i r e d n i c k e l ( I I ) i o n s . A major o b j e c t i v e of the work d e s c r i b e d i n the present t h e s i s was to i n v e s t i g a t e f u r t h e r the phenomenon of magnetic exchange i n metal phosphinates by s t u d y i n g the e f f e c t of doping diamagnetic metal ions i n t o the l a t t i c e , i n e f f e c t randomly r e p l a c i n g paramagnetic metal ions by diamagnetic ones. To t h i s end we s y n t h e s i z e d a s e r i e s of M n j _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I and Form 1 (B)) compounds and measured and analyzed t h e i r magnetic p r o p e r t i e s over the temperature range from 80 to 4.2 K. T h i s work r e p r e s e n t s the f i r s t s ystematic and e x t e n s i v e study on such systems. 51 52 In the previous chapter we showed that manganese(II) and cadmium(11) monophenylphosphinate (Form I) are isomorphous. In order to be sure that the mixed metal M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 systems are not p h y s i c a l mixtures and to ensure that they are isomorphous with the pure manganese and cadmium (Form I) systems, we c a r e f u l l y examined t h e i r thermal p r o p e r t i e s , i n f r a r e d s p e c t r a and X-ray powder d i f f r a c t i o n p a t t e r n s . T h i s work i s d e s c r i b e d below i n s e c t i o n s 3.2, 3.3 and 3.4. The magnetic p r o p e r t i e s are d e s c r i b e d i n s e c t i o n 3.5. We have a l s o examined the ESR and X-ray p h o t o e l e c t r o n s p e c t r a of some of these mixed metal systems and t h i s work i s presented i n s e c t i o n s 3.6 and 3.7. 3 . 2 . S Y N T H E S E S , S O L U B I L I T I E S A N D T H E R M A L P R O P E R T I E S D e t a i l e d procedures f o r the p r e p a r a t i o n of the mixed metal Mn. Cd [ H ( C s H 5 ) P 0 2 ] 2 compounds are given in Chapter 6. An important aspect of t h i s work was to determine as a c c u r a t e l y as p o s s i b l e the metal composition of the samples. For t h i s purpose we used atomic a b s o r p t i o n spectroscopy ( f o r compositions where x>0.1) and t h i s work i s a l s o d e s c r i b e d i n Chapter 6. The only s o l u b i l i t y t e s t s that have been done on these m a t e r i a l s were on M n 0 53C<^0 4 7 [ H ( C 6 H 5 ) P 0 2 ] 2 . T h i s m a t e r i a l shows the same s o l u b i l i t y trends as e x h i b i t e d by pure M n [ H ( C 6 H 5 ) P 0 2 ] 2 and 53 C d [ H ( C 6 H 5 ) P 0 2 ] 2 . DSC thermal diagrams are shown i n F i g . 3.1 and the DSC parameters are recorded i n Table 3.1. The thermal diagrams show that a l l of the systems s t u d i e d (except where x=0.47) undergo exothermic decomposition with peak temperatures around 220°C. T h i s compares with the pure Mn and Cd systems which e x h i b i t peak temperatures of 220°C and 290°C r e s p e c t i v e l y . The sample of composition M n 0 5 3 C d 0 4 7 ^ H ( C s H s ) P 0 2 ] 2 shows the onset of decomposition at 240°C. Small exothermic events p r i o r t o decomposition which are observed i n some samples may be due to minor s t r u c t u r a l adjustments. 54 e u «l -C o X u o a> s Temperature ( ° C ) Figure 3.1 Thermograms of a) Mn I) and b) M n 0 > 5 3 C d 0 > 4 7 ?Q 9 1 C < 3 0 ngfH(C 6H 5 ) P 0 2 ] [H(CIH 5 7P02] 2 (Form I) (Form 55 Table 3.1 DSC S t u d i e s on the Mn._ C d v [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) , where x=0.005, 0.01, 0.09, 0.27, 0.47 Compound Peak Temperature (K) AH (KJ/mol) M n 0 . 9 9 5 C d 0 . 0 0 5 2 2 1 ' 4 M n 0 . 9 9 C d 0 . 0 l 2 2 3 * 7 M n 0 . 9 l C d 0 . 0 9 2 1 6 M n 0 . 7 3 C d 0 . 2 7 2 2 2 ' 6 M n 0 . 5 3 C d 0 . 4 7 2 3 6 ' 9 150 1 70 230 180 190 56 3.3. INFRARED SPECTROSCOPY The i n f r a r e d s p e c t r a of the Mn, Cd [ H ( C 6 H 5 ) P 0 2 ] 2 I A A (Form I) m a t e r i a l s (x=0.005, 0.01, 0.09, 0.27, 0.47) are a l l v i r t u a l l y i d e n t i c a l . The spectrum of the compound with x=0.47 i s given i n F i g . 3.2. To w i t h i n ±1 cm" 1, a l l samples show a strong band at 1147 and a very s t r o n g band at 1112 cm"1 [ J> „ ( P 0 2 ) ] ; very strong bands at 1034 and 1018 cm"1 3 sy • [^ _,,_ ( P 0 2 ) ] ; a medium to medium strong band at 2336 cm"1 [ f ( P H ) ] ; medium shoulder to medium bands at 758 and 710 cm"1 [v(PC)]j a medium to strong band at 558 cm"1 and a weak to medium band at 489 cm"1 [ ( C ) ( H ) P 0 2 bending]. Some of the samples showed a s p l i t t i n g of the band a s s i g n e d to viPH). S p e c i f i c a l l y , the samples where x=0.005, 0.01 and 0.09 show a medium band of 2346 cm"1 i n a d d i t i o n to the one at 2336 cm " 1 . 57 F i g u r e 3.2 I n f r a r e d Spectrum of Mn n c , C d n A1[H(CeHs)P02]2 (Form !) U - D J u - 4 / 58 3 . 4 . X-RAY POWDER DIFFRACTION X-ray powder d i f f r a c t i o n data are recorded i n Tables 3.2 and 3.3; the d i f f r a c t i o n p a t t e r n of the x=0.47 m a t e r i a l i s shown i n F i g . 3.3. Both the i n f r a r e d s t u d i e s and these data i n d i c a t e isomorphism f o r the d i f f e r e n t samples. Table 3.2 X-Ray Powder D i f f r a c t i o n Data For M n 1 - x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I),where x=0.005, 0.01, 0.09 M n 0 . 9 9 5 C d0.005 M n 0 . 9 9 C d 0.01 M n o . 91 C d0.09 d I / I . d I / I . d I / I . 14.61 6 1 0.60 1 00 1 0.67 100 10.61 100 6.24 7 6.25 7 • 6.24 4 6.03 8 6.07 8 6.07 5 5.31 9 5.34 6 5.34 6 5.18 6 5.21 6 5.17 3 4.63 34 4.64 31 4.64 28 3.98 26 3.99 23 3.99 17 3.44 4 3.46 4 3.28 4 3.27 4 59 Table 3.3 X-Ray Powder D i f f r a c t i o n Data f o r M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) , where x=0.27 and 0.47 M n 0 . 7 3 C d 0 . 2 7 M n 0 . 5 3 C d 0 . 4 7 d I / I . d I / I . 10.58 100 10.70 100 6.24 9 6.24 8 6.07 9 6.07 1 0 5.34 8 5.34 8 5.16 8 5.1 9 6 4.64 23 4.64 5 4.49 8 3.99 1 4 3.99 10 3.45 7 3.46 5 3.29 10 3.29 9 60 1 1 1 1 1 1 5 10 15 20 25 30 26(DEGREES) F i g u r e 3.3 X-ray Powder D i f f r a c t i o n P a t t e r n of M n 0 5 3 C d o . 4 7 [ H ( C 6 H 5 ) P ° 2 ] 2 ( F o r m J ) 3 . 5 . MAGNETIC PROPERTIES 61 In the l a s t few years s e v e r a l experimental and t h e o r e t i c a l s t u d i e s have been devoted to the i n f l u e n c e of non-magnetic i m p u r i t i e s on the behavior of pseudo one-dimensional a n t i f e r r o m a g n e t i c systems [81, 86-90]. The strong r e d u c t i o n of the three- d i m e n s i o n a l o r d e r i n g temperature, T c, has e s p e c i a l l y caught the a t t e n t i o n of r e s e a r c h e r s . In systems l i k e TMMC (Se c t i o n 2.5), a l a r g e i n t r a c h a i n i n t e r a c t i o n , J , causes the development of strong magnetic c o r r e l a t i o n along the i n d i v i d u a l c h a i n s . Hence, even a very small i n t e r c h a i n i n t e r a c t i o n , J ' , may t r i g g e r a t r a n s i t i o n to 3D long-range order at low temperatures. The s u b s t i t u t i o n of i m p u r i t i e s has been found to break the cha i n i n t o more or l e s s independent segments and reduces the development of strong 1D c o r r e l a t i o n s and hence lowers the 3D o r d e r i n g temperature [88, 89]. As mentioned i n Chapter 2, Mn[H(C 6H 5)P0 2] 2 i s m a g n e t i c a l l y concentrated, e x h i b i t i n g a maximum i n i t s s u s c e p t i b i l i t y versus temperature behavior at 33 K. Although t h i s system does not undergo long-range magnetic o r d e r i n g above 4.2 K (the lowest temperature i n v e s t i g a t e d ) i t i s c l e a r l y an a n t i f e r r o m a g n e t i c a l l y coupled system, the magnetic p r o p e r t i e s of which may be analyzed a c c o r d i n g t o a 62 Heisenberg model f o r l i n e a r c hains of S=5/2 metal c e n t e r s (as shown i n Chapter 2). The e f f e c t of doping with diamagnetic metal ions on the magnetic p r o p e r t i e s of t h i s system and thereby breaking the magnetic c h a i n i s c l e a r l y seen i n the p l o t s of s u s c e p t i b i l i t y versus temperature and magnetic moment versus temperature shown i n F i g u r e s 3.4 and 3.5. As the f r a c t i o n of Cd i n c r e a s e s , both the s u s c e p t i b i l i t y and the magnetic moment i n c r e a s e at a l l temperatures. Moreover, as the f r a c t i o n of Cd i s in c r e a s e d , the maximum i n the s u s c e p t i b i l i t y i s l o s t , s i n c e the s u s c e p t i b i l i t y i n c r e a s e s more at lower temperatures than at higher ones. T h i s i s an important o b s e r v a t i o n as i t i n d i c a t e s that not only i s the c o u p l i n g (as determined by J) d e c r e a s i n g but another e f f e c t i s t a k i n g p l a c e , i n a l l p r o b a b i l i t y an i n c r e a s e i n some paramagnetic component of the system. We have chosen to analyze our data with the Wagner-Friedberg and Weng models as d e s c r i b e d i n Chapter 2. In the f i t s to these mixed metal systems we set g=2.00 and allowed J and % monomer to vary. The f i t s to the s u s c e p t i b i l i t y are shown i n F i g s . 3.6 to 3.11 and the parameters f o r both Wagner-Friedberg and Weng model f i t t i n g s are g iven i n Tables 3.4 to 3.5. 63 CO INl i n . O _ ° e -u o o ^ m w u £ • co in 0 o + X • • O M n[H(C 6H s ) P 0 2 l 2 * M n 0 . 9 1 C d O . 0 9 ' H ( C 6 H S ) P O 2 ^ D % . 7 3 C d 0 . 2 7 t H W P 0 2 l 2 * M n 0 . S J C d 0 . 4 7 l HW P 0 2 ) 2 • • • X X X X • * • X • * • • • i 1 1 1—i 1 1 1 1 1 1 r — i 1— 0 0 16.0 32.0 -36.0 64.0 BO.O 96 .0 ] ) 2 0 TEMPERATURE (K) F i g u r e 3.4 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) 6 4 O c + X • O H n [ H ( C 6 H s ) P 0 2 l j ° M n 0 . 9 9 5 C < , 0 . 0 0 5 t H ( C 6 H 5 ) P 0 2 J 2 + % . 9 9 C d 0 . 0 l l H ( W P O 2 > 2 * M n 0 . 9 1 C d 0 . 0 9 l H l C 6 H 5 ) P 0 2 1 2 C M n 0 . 7 3 C d 0 . 2 7 < H ( W P O j ) 2 * M n 0 . S J C d 0 . 4 7 [ H W 0 2 > 2 ~ G ~ • * CJ- x • X «ry, X ^ • x to ) r X —1 1 1 1 1 1 1 1 r 0.0 16.0 32.0 48.0 6^.0 Temperature (K) 80.0 96.0 112J) F i g u r e 3 . 5 Magnetic Moment versus Temperature P l o t f o r M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 (form I) 65 Temperature (K) F i g u r e 3.6 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r a) M n n > g g C d 0 > 0 l [ H ( C 6 H 5 ) P 0 2 ] 2 and b) M n 0 . 9 9 5 C d 0 . 0 0 5 [ H ( C 6 H 5 ) P ° 2 ] 2 { F o r m J ) 66 8 S J . J3 a <v u ui 3 W a ) o o J3 * J c . a ~ a u in 3 0.0 W a g n e r - F r i e d b e r g M o d e l W e n g M o d e l T e m p e r a t u r e ( K ) F: .0 W a g n e r - F r i e d b e r g M o d e l W e n g M o d e l —i 1 1 1 1 r 20 .0 ao 0 6 n 0 T e m p e r a t u r e ( K ) F i g u r e 3.7 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r a) M n 0 t 9 l C d 0 o g [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) and b) M n 0 > 7 3 C d n > 2 7 [ H ( C 6 H 5 ) P O 2 ] 2 (Form I) 67 F i g u r e 3.8 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f 0 r M n 0 . 5 3 C d 0 . 4 7 [ H ( C 6 H s ) P ° 2 ] z ( F o r m J ) 68 F i g u r e 3.9 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r Mn n Q Q C d n n . [ H ( C 6 H 5 ) P 0 2 ] 2 (Form 1(B)) 69 -« ° o (?. E " E U o to t- S i w o in 3 C/l o a a) Wagner-Friedberg Model Weng Model -i 1 1 1 Temperature (K) 8C o o £ E-E-o. u o a 9-r b) Wagner-Friedberg Model . Weng Model PC 0 40 0 60 0 Temperature (K) F i g u r e 3.10 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r a) M n 0 > g 2 C d n > 0 8 [ H ( C 6 H 5 ) P O 2 ] 2 and b) Mn 0 > 9 5 C d 0 > 0 5 [ H ( C 6 H 5 ) P 0 2 ] 2 (Form 1(B)) 70 C C ?C c a; : t; 5 Temperature (K) Temperature (K) F i g u r e 3.11 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r a) M n 0 > 8 5 C d 0 > l 5 i H ( C 6 H 5 ) P 0 2 ] 2 a n d b) Mn Q 5 2 C d n > 4 8 [ H ( C 6 H 5 ) P 0 2 ] 2 (Form 1(B)) Table 3.4 Magnetic P a r a m e t e r s 1 ' 2 f o r Mn, Cd [ H ( C 6 H 5 ) P 0 2 ] 2 I A A (Form I ) , where x=0.005, 0.01, 0.09, 0.27, 0.47 Compound J (cm" 1) % monomer M n 0 . 9 9 5 C d 0 . 0 0 5 M n 0 . 9 9 C d 0 . 0 l M n 0 . 9 l C d 0 . 0 9 M n 0 . 7 3 C d 0 . 2 7 M n 0 . 5 3 C d 0 . 4 7 -4.00 (-3.81) -3.50 (-3.80) -3.50 (-3.40) -3.30 (-3.18) -2.70 (-2.60) 0.38 (0.78) 1.10 (1.50) 6.00 (6.40) 1 6.30 (16.83) 25.50 (25.90) 0.013 (0.026) 0.011 (0.026) 0.028 (0.039) 0.030 (0.028) 0.026 (0.028) 1 The data i n s i d e the br a c k e t s are obtained by using the Weng model and those o u t s i d e the brackets are obtained by usi n g the Wagner-Friedberg model. 2We f i x e d g = 2.00 in f i t t i n g the experimental data. 72 Table 3.5 Magnetic P a r a m e t e r s 1 ' 2 f o r Mn. v C d v [ H ( C 6 H 5 ) P 0 2 ] 2 I A A (Form 1 ( B ) ) , where x=0.01, 0.05, 0.08, 0.15, 0.48 Compound J (cm - 1) % monomer F M n o . 99 C d0.01 -3.40 6.50 0.028 (-3.30) (7.05) (0.038) M n 0 . 95 C d0.05 -2.20 21 .20 0.064 (-2.10) (21.55) (0.067) M n o . 92 C d0.08 -3.30 10.60 0.028 (-3.20) (11.15) (0.037) M n o . 85 C d0.15 -3.35 1 1 .40 0.024 (-3.25) (11.40) (0.033) M n 0 . 52 C d 0 . 4 8 -1 .60 45.30 0.010 (-1.50) (45.10) (0.020) ^ h e data i n s i d e the bracke t s are obtained by using the V/eng model and those o u t s i d e the bracke t s are ob t a i n e d by using the Wagner-Friedberg model. 2We f i x e d g=2.00 i n f i t t i n g the experimental data. 73 I n t e r e s t i n g e f f e c t s are observed. As the f r a c t i o n of Cd i n c r e a s e s , J decreases, and at the same time, the % monomer i n c r e a s e s . Such e f f e c t s had been r a t i o n a l i z e d by De Jonge [91] by what he c a l l e d the "random d e f e c t " model based on h i s study of C u ( p y r a z i n e ) ( N 0 3 ) 2 • With t h i s model, any experimental chain system w i l l s u f f e r from a c e r t a i n c o n c e n t r a t i o n of d e f e c t s . These w i l l break the magnetic cha i n i n t o f i n i t e segments. Half of these f i n i t e segments w i l l c o n t a i n an odd number of magnetic atoms and, coupled ant i f e r r o m a g n e t i c a l l y , these odd numbered segments w i l l have a net s p i n at low temperatures. T h i s net s p i n w i l l be very weakly coupled along the c h a i n , s i n c e the e f f e c t i v e magnetic i n t e r a c t i o n w i l l have to t r a v e r s e the d e f e c t s , and w i l l t h e r e f o r e be much smal l e r than the nearest neighbour i n t r a c h a i n i n t e r a c t i o n . In our case, Cd breaks up the chain and c r e a t e s i s o l a t e d f i n i t e c h a i n s . For example, c o n s i d e r the case where x=0.09. For a random d i s t r i b u t i o n of Cd atoms we might expect the average c h a i n of Mn atoms to be ~ 9 atoms lo n g . T h i s w i l l r e s u l t i n a d i s t r i b u t i o n of chain lengths about t h i s average and one h a l f of the c h a i n s w i l l be odd numbered and e f f e c t i v e l y c o n t a i n one Mn atom which i s uncoupled (the net s p i n r e f e r r e d to i n the random d e f e c t model). If we assume that these uncoupled c e n t e r s behave as m a g n e t i c a l l y d i l u t e Mn, then one out of ~ 18 - 20 Mn atoms are m a g n e t i c a l l y d i l u t e (monomer i m p u r i t y ) . Hence, we expect 74 about 5% monomer impurity versus the observed 6% (see Table 3.4). T h i s a n a l y s i s works p r e t t y w e l l f o r a l l systems although i t i s probably r e a l i s t i c only f o r the systems with small values of x, s i n c e as x i n c r e a s e s the p r o b a b i l i t y of the formation of c l u s t e r s of Cd atoms i n c r e a s e s . For example, i t i s u n l i k e l y that f o r the x=0.47 system there i s complete a l t e r n a t i o n of Cd and Mn atoms along the c h a i n . Indeed, i f t h i s were the case the value of J should be ~ 0 and the % monomer 100%. I t i s l i k e l y there are c l u s t e r s of Mn and Cd u n i t s along the chain i n t h i s system. Another important o b s e r v a t i o n here i s that the value of J decreases as x i n c r e a s e s (see Tables 3.4, 3.5 and F i g . 3.12). The s t r e n g t h of the c o u p l i n g between nearest magnetic c e n t e r s decreases as the average ch a i n l e n g t h gets s h o r t e r ! Put i n the p o s i t i v e sense, the s t r e n g t h of the c o u p l i n g between the magnetic c e n t e r s i n c r e a s e s as the average number of coupled s p i n s i n the c h a i n i n c r e a s e s . Doping l e v e l s as low as 0.5% Cd i n these M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 systems s i g n i f i c a n t l y a f f e c t the c o u p l i n g constant and g i v e a measurable % impurity as shown by the a n a l y s i s of the magnetic data (Table 3.4). T h i s i n d i c a t e s that i n pure M n [ H ( C 6 H 5 ) P 0 2 ]2 systems the number of d e f e c t s i n the chain i s probably l e s s than 0.5% and/or the average l e n g t h of chain i s i n excess of 200 Mn atoms. T h i s i s f i r s t time an estimate of the average c h a i n l e n g t h i n a pol y ( m e t a l phosphinate) has been made by t h i s method. We a l s o note that a n a l y s i s of the magnetic data f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form 1(B)) (Table 2.10) shows that the % monomer i s 3.5 and the J i s -3.45 cm - 1. T h i s suggests an average c h a i n l e n g t h of only about 13 atoms f o r t h i s "pure" system. As expected f o r t h i s a n a l y s i s , the Form 1(B) mixed metal systems a l l show higher % monomer and lower J valu e s (Table 3.5) than f o r mixed metal Form I systems. 76 _ IO E u c ra _ w * c o cn a o H u a) e cn • c m u • Form 1 * Form K B ) 0.00 T T i r 0.24 i r 0.32 0.08 0.16 x ( F r a c t i o n of Cadmium) i r 0.40 0.48 F i g u r e 3.12 P l o t of Exchange Coupling Constant J versus x (Mole F r a c t i o n of Cadmium) in M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 3 . 6 . ELECTRON SPIN RESONANCE (ESR) SPECTROSCOPY We have examined the ESR sp e c t r a of s e v e r a l mixed metal systems, s p e c i f i c a l l y samples of composition Mn. Cd [ H ( C 6 H 5 ) P 0 2 ] 2 where x i s 0.99, 0.98, 0.08, 0.02 and I X X 0.01. In the case of the f i r s t two we have, i n e f f e c t , m a t e r i a l s i n which a small amount of manganese i s doped i n t o 77 C d [ H ( C 6 H 5 ) P 0 2 ] 2 • Here the Mn ions are d i l u t e d , exchange e f f e c t s minimized, and ESR s p e c t r a show h y p e r f i n e s t r u c t u r e ( F i g 3.13). There i s no s i g n i f i c a n t d i f f e r e n c e i n the x=0.99 and x=0.98 s p e c t r a and, except f o r a small decrease i n i n t e n s i t y at the lower temperature, no s i g n i f i c a n t dependence on temperature. We have not attempted to analyze these s p e c t r a i n any d e t a i l but note that the major a b s o r p t i o n observed i s due to the M = + l/2«-*M =-1/2 t r a n s i t i o n s p l i t by h y p e r f i n e c o u p l i n g i n t o 6 l i n e s by the 1=5/2 s p i n of the Mn n u c l e i ( F i g . 3.14) [92-93]. Other minor f e a t u r e s seen i n these s p e c t r a may a r i s e from some of the other t r a n s i t i o n s -5/2<-^-3/2, -3/2^-1/2, +1 /2-«-*+3/2 , +3/2-*-> +5/2. These t r a n s i t i o n s are not normally observed i n the s p e c t r a of powders. The samples with x=0.08, 0.02 and 0.01 are e f f e c t i v e l y samples of M n [ H ( C 6 H 5 ) P 0 2 ] 2 doped with cadmium. Here exchange e f f e c t s broaden the M =+1/2«-»--l/2 t r a n s i t i o n to the po i n t that only a s i n g l e broad l i n e i s observed ( F i g . 3.15 and Table 3.6) [94], We note ( F i g . 3.15) however, that as the Cd c o n c e n t r a t i o n i n c r e a s e s (x ranging from X=0.01 to 0.08) the l i n e broadens due to a decrease i n exchange e f f e c t s and the presence of unresolved h y p e r f i n e s t r u c t u r e (Table 3.6). 78 0 1000 2000 3000 4000 5000 MAGNETIC FIELD (GAUSS) F i g u r e 3.13 ESR Powder Spectrum of M n Q ^ n ^ d Q ^ g 9 [ H ( C 6 H 5 ) P 0 2 ] 2 a) at Room Temperature, and b) at L i q u i d N i t r o g e n Temperature 79 «5-2D _ 40 r / / /y \ \ \ -1 / \ * / \ Zero field levels Applied Nuclear field splitting Fine structure transitions F i g u r e 3.14 Energy L e v e l Diagram f o r Octahedral Manganese(II) 80 i I 1 | i 1 0 0 0 2 0 0 0 3 0 0 0 4 0 0 0 5 0 0 0 MAGNETIC F IELD (GAUSS) F i g u r e 3.15 ESR Powder Spectrum of M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] (Form K B ) ) ? a) x=0.08; b) x=0.02; c) X=0.01 81 Table 3.6 ESR Linewid t h of Mn, Cd [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I A A 1 ( B ) ) , where X=0.01, 0.02, 0.05, 0.08. Compound Linewid t h (Gauss) M n 0 . 9 9 C d 0 . 0 l 1 2 0 M n 0 . 9 8 C d 0 . 0 2 1 2 5 M n 0 . 9 5 C d 0 . 0 5 1 6 5 M n 0 . 9 2 C d 0.08 1 6 5 82 3 . 7 . ELECTRON SPECTROSCOPY FOR CHEMICAL ANALYSIS (ESCA) T h i s b a s i c p h o t o e l e c t r o n s p e c t r o s c o p i c technique i n v o l v e s the i o n i z a t i o n of the sample atom or molecule by a beam of monoenergetic photons and the measurement of the k i n e t i c energy of the e j e c t e d e l e c t r o n . The energy c o n s e r v a t i o n f o r the photoemission process r e q u i r e s that E h, = E B E + E K E + 0 S P ' where E ^ i s the X-ray energy, E f i E i s the b i n d i n g energy of the e l e c t r o n i n a p a r t i c u l a r l e v e l of the compound, E R E i s the p h o t o e l e c t r o n k i n e t i c energy, and 0<,p i s the work f u n c t i o n of the instrument. The value of 0gp i s e i t h e r known or assumed to be constant f o r a given system. Because the source energy has to be h i g h i n comparison to the b i n d i n g energy, A l K q or Mg K q r a d i a t i o n i s used. A f t e r p h o t o i o n i z a t i o n of inner l e v e l e l e c t r o n s , the vacant hole c r e a t e d can t r i g g e r a t w o -electron p r o c e s s . When one e l e c t r o n from a higher l e v e l f a l l s i n t o t h i s hole and l o s e s energy and another e l e c t r o n gains e x a c t l y the same energy and becomes i o n i z e d , the process i s c a l l e d the Auger p r o c e s s . ESCA measurements f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 (both Form I and Form II) and C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) , as w e l l as f o r some mixed metal compounds, have been made and the r e s u l t s recorded i n Table 3.7. Some s p e c t r a are a l s o shown i n F i g s . 3.16 to 3.18. For the purpose of comparison, ESCA measurements have a l s o been made on monophenylphosphinic a c i d , manganesedl) a c e t a t e t e t r a h y d r a t e and cadmiumdl) a c e t a t e d i h y d r a t e . The two forms of the manganese compound show very l i t t l e d i f f e r e n c e i n t h e i r ESCA s p e c t r a although the b i n d i n g energy f o r Mn(2p^y2^ seems higher i n the Form I case. The 0 ( 1 s 1 / 9 ) and P ( 2 p , / 9 ) b i n d i n g e n e r g i e s are both higher i n the Cd compound than i n e i t h e r of the Mn compounds, i n d i c a t i n g a g r e a t e r d e l o c a l i z a t i o n of charge from the l i g a n d onto the metal i n the cadmium case. C o n s i s t e n t with t h i s , i n the a c e t a t e s the b i n d i n g energy of ^ 1 s 1 / 2 ^ * s n^-9^ e r ^ n the Cd than i n the Mn compound. In the doped compounds the b i n d i n g energy f o r Mn(2p2/ 2) i n c r e a s e s while the b i n d i n g energy f o r Cd(3dgy 2) decreases as the percent Cd i s i n c r e a s e d (Table 3.7). T h i s suggests an i n c r e a s e d t r a n s f e r of e l e c t r o n d e n s i t y onto Cd as the percentage of t h i s metal i n c r e a s e s . I n t e r e s t i n g l y enough, the b i n d i n g energy f o r O d s ^ j ) a n ^ p ^ P 3 / 2 ^ a r e a l s o about the same for the d i f f e r e n t doped samples and are almost i d e n t i c a l to those observed i n pure C d [ H ( C 6 H 5 ) P 0 2 ] 2 . I t appears that when Cd i s doped i n t o 84 Table 3.7 Bi n d i n g Energy (eV) from ESCA S t u d i e s . Compound Mn(2p 3 / 2 ) C d ( 3 d 5 y 2 ) 0 ( 1 s 1 y 2 ) P ( 2 p 3 / 2 ) H ( C 6 H 5 ) P 0 2 H 529 .7 1 30 .8 Mn(CH 3COO) 2 *4H 20 641 .5 531 .0 Cd(CH 3COO) 2'2H 20 405. 4 531 .8 M n [ H ( C 6 H 5 ) P 0 2 ] 2 Form I 641 .4 529 .9 131 .6 C d [ H ( C 6 H 5 ) P 0 2 ] 2 Form I 405. 8 531 .3 1 32 .6 M n 0 . 9 1 C d 0 . o 9 [ H ( C 6 H 5 ) P 0 2 ] 2641 .7 405. 4 530 .9 132 .6 M n 0 . 7 3 C d 0 . 2 7 [ H ( C 6 H 5 ) P 0 2 ] 2641 .7 405. 4 531 . 1 132 .5 M n 0 . 5 3 C d 0 . „ 7 [ H ( C 6 H 5 ) P 0 2 ] 2 64 1 .9 405. 1 531 .2 1 32 .6 M n [ H ( C 6 H 5 ) P 0 2 ] 2 ] Form II 641 .0 529 .8 131 .8 M n [ ( C H 3 ) 2 P 0 2 ] 2 -2H 20 641 . 1 529 .7 131 .5 M n [ ( C H 3 ) 2 P 0 2 ] 2 641 . 1 530 .5 132 .2 8 5 636^00 638^500 ' 64l!00 643i50 ' 64 6'.00 646.50 Binding Energy (eV) F i g u r e 3.16 ESCA Bindi n g Energy of Mn(2p 3 /, 2): a) Form I I ; b) Form I; c) M n Q ^ 5 3 C d 0 ^ 4 ? [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) 8 6 F i g u r e 3.17 ESCA Bindi n g Energy of O f l s ^ ) : a) Form I I ; b) Form I; c) M n Q ^ 5 3 C d Q ^ 4 ? [ H ( C 6 H S ) P 0 2 ] 2 (Form I) 00 Binding Energy (eV) F i g u r e 3.18 ESCA Bindi n g Energy of P ( 2 p 3 ^ 2 ) : a) Form II b)Form I; c ) M n n > 5 3 C d 0 > 4 7 [ H ( C 6 H 5 ) P O 2 ] 2 (Form I) Mn[H(C 6H 5 ) P 0 2 ] 2 i e l e c t r o n d e n s i t y moves from the b r i d g i n g phosphinates and from the manganese atoms onto the cadmium atoms. T h i s no doubt a f f e c t s the e f f i c i e n c y of the magnetic superexchange between Mn c e n t e r s and may account f o r the observed r e d u c t i o n i n the exchange c o u p l i n g constant J as the f r a c t i o n of Cd atoms i n c r e a s e s . CHAPTER 4. MISCELLANEOUS COMPOUNDS 4.1. MANGANESE(11) AND CADMIUM(II) DIPHENYLPHOSPHINATE The syntheses of the di p h e n y l p h o s p h i n a t e s of manganesedl) and cadmium(II) are gi v e n i n d e t a i l i n Chapter 6. Only one form of each compound has been obtained in t h i s study. S o l u b i l i t y t e s t s show that both compounds are i n s o l u b l e or only very s l i g h t l y s o l u b l e i n p o l a r s o l v e n t s (water, e t h a n o l , methanol and a c e t o n e ) . T h i s can be understood i n terms of the i n a c c e s s i b i l i t y of p o l a r s o l v e n t molecules t o the i n o r g a n i c backbone, s i n c e the backbone i s s h i e l d e d by the two phenyl groups. DSC s t u d i e s show both compounds to be t h e r m a l l y s t a b l e up to 450°C. The i n f r a r e d s p e c t r a f o r both M n [ ( C e H 5 ) 2 P 0 2 ] 2 and C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 are shown i n F i g . 4.1. The a b s o r p t i o n bands are l i s t e d i n Table 4.1. The s i m i l a r i t y i n the s p e c t r a suggest the compounds may have s i m i l a r s t r u c t u r e . Averaging the f r e q u e n c i e s of the bands a s s i g n e d to ^ a S y (P0 2) and doing the same f o r those a s s i g n e d t o f s y m (P0 2) g i v e Au v a l u e s f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and C d f ( C 6 H 5 ) 2 P 0 2 ] 2 of 107 cm"1 and 101 cm - 1, r e s p e c t i v e l y . F o l l o w i n g the d i s c u s s i o n of the r e l a t i o n between Af and s t r u c t u r e i n s e c t i o n 2.2, these diphenylphosphinate compounds probably have unsymmetrical 8 9 90 b r i d g i n g groups and may be a s s i g n e d s t r u c t u r a l type XIV, XV or XVI. A medium str o n g band around 1200 cm - 1 i s observed f o r these d i p h e n y l p h o s p h i n a t e s . T h i s band i s not seen i n the s p e c t r a of the monophenylphosphinate and i t s o r i g i n i s u n c e r t a i n . u 1 i i i | i_ UOO UOO UOO 1000 tOO tOO 400 VAVENUMBER / c m - ' F i g u r e 4.1 I n f r a r e d Spectra of a) M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and b) C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 91 Table 4.1 I n f r a r e d A b s o r p t i o n s 1 f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 Frequency ( c m - 1 ) 2 Assignment 3  M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 v C-C i n - p l a n e 1594 vw 1595 vw P-C 6H 5 v i b . 1440 m.sh 1440 m.sh 1208 w 1201 w P0 2 asy. s t r . 1 145 vs 1 1 34 vs P0 2 sym. s t r . 1051 s 1045 s 1024 m 1022 m P-C 6H 5 bending 1000 w 999 w (C ) ( C ) P 0 2 a s y . s t r . 753 w 754 w C-C out-plane r i n g 700 m 698 m deformat ion ( C ) ( C ) P 0 2 bending 564 s 562 s (C ) ( C ) P 0 2 bending 541 m 542 m 'The data were taken on P e r k i n - E l m e r 1 7 1 0 . 2w = weak; vs = very s t r o n g ; s = st r o n g ; m.sh = medium st r o n g ; m = medium 3 R e f e r e n c e [ 1 ]. 92 The X-ray powder d i f f r a c t i o n p a t t e r n s f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 are shown i n F i g . 4.2. and the data are recorded i n Table 4.2. While there are obvious s i m i l a r i t i e s i n the p a t t e r n s they do not provide c o n c l u s i v e evidence f o r isomorphism i n t h i s case. The white c o l o r of M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 i n d i c a t e s o c t a h e d r a l c o o r d i n a t i o n [41]. I t i s important to note that Korshak et al . [95] prepared the white M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and assig n e d i t a t e t r a h e d r a l s t r u c t u r e with double phosphinate b r i d g e s without any s t r u c t u r a l evidence to support t h i s . I t seems u n l i k e l y that t h i s compound i s t e t r a h e d r a l s i n c e t e t r a h e d r a l manganesedl) compounds are u s u a l l y yellow-green while o c t a h e d r a l manganese(11) compounds are pink or white [41]. to z w 2 b) r -S I 10 IS 30 2 6(DEGREES) as 30 F i g u r e 4.2 X-ray Powder D i f f r a c t i o n P a t t e r n s of M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and b) C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 94 Table 4.2 X-ray Powder D i f f r a c t i o n Data f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 C d [ ( C 6 H 5 ) 2 P 0 2 ] 2 d I / I . d I / I . 12.1425 100 12.1425 96 10.7690 46 10.7169 100 6.6669 2 6.6819 9 6.0096 3 6.0505 9 4.4439 3 4.4616 6 4.1908 4 4.2144 8 3.9954 12 4.1032 2 3.7777 9 3.7936 5 95 The X-band ESR spectrum of M n [ H ( C 6 H 5 ) P 0 2 ] 2 shows one s i n g l e broad l i n e at g around 2, t y p i c a l of r e g u l a r o c t a h e d r a l manganesedl) compounds. The ESR spectrum (room temperature and l i q u i d n i t r o g e n temperature) of a powdered sample of Mn Q 0 i c d n g g t ( c e H 5 ) 2 P 0 2 ] 2 i s given i n F i g . 4.3. These s p e c t r a show c h a r a c t e r i s t i c groups of s i x l i n e s due to h y p e r f i n e s t r u c t u r e . Since the main group of l i n e s i s around 3300 Gauss, the o v e r a l l symmetry may be c l o s e to a x i a l (strong resonance near g=2). Besides, there are weaker groups of l i n e s more or l e s s symmetrically d i s p o s e d about the main group which may be a t t r i b u t e d to some other allowed t r a n s i t i o n s (e.g. AM =± 1 ) other than the M =+1/2-*—»M = -1 /2 5 S S t r a n s i t i o n . Cookson et al. [28] analysed the powder spectrum of M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and concluded that the " o r i g i n of s t r u c t u r e i n the main groups of l i n e s at about g=2 i s probably due to small a n i s o t r o p i c G and A t e n s o r s . " They compared the spectrum of M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 with that of M n [ ( C 6 H 5 0 ) 2 P 0 2 ] 2 ( p y r i d i n e ) 2 and assigned both d i s t o r t e d o c t a h e d r a l s t r u c t u r e s with, i n the l a t t e r case, the oxygen atoms from the phosphate groups l y i n g approximately at the c o r n e r s of a r e c t a n g l e i n the x-y plane, and the two p y r i d i n e s along the z - a x i s . 96 KAGHTTJC F I E L D (GAUSS) F i g u r e 4.3 ESR Spectra of M n 0 ^ Q y C d Q ^ g g [ ( C 6 H 5 ) 2 P 0 2 ] 2 a) at Room Temperature, and b) at L i q u i d Nitrogen Temperature 97 T h i s i s c o n s i s t e n t with the assignment of c o o r d i n a t i o n modes of type XIV, XV or XVI to the phosphinates compounds s t u d i e d i n t h i s work. Another important o b s e r v a t i o n i s that peak i n t e n s i t i e s are almost the same at both room and l i q u i d n i t r o g e n temperatures. T h i s c o n t r a s t s with the o b s e r v a t i o n that peak i n t e n s i t i e s v a r i e d s l i g h t l y with temperature in the monophenylphosphinate system (Chapter 3). The s i m i l a r i t y of peak i n t e n s i t i e s at room and low temperature may be i n t e r p e r a t e d i n terms of the presence of only very weak magnetic exchange i n t e r a c t i o n s i n the diphenylphosphinate system [96]. The magnetic moment and magnetic s u s c e p t i b i l i t y data f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 are p l o t t e d versus temperature i n F i g . 4.4 and F i g . 4.5. The decrease i n magnetic moment with d e c r e a s i n g temperature suggests a n t i f e r r o m a g n e t i c exchange as found, f o r example, in M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Chapter 2). The magnetic data were analyzed as i n Chapter 2. By f i x i n g g a t 2.00, the best f i t values f o r J and % monomer are -0.30 cm - 1 and 12.0(±0.8) r e s p e c t i v e l y u s i n g the Weng model and -0.30 and 9.30(±0.40) u s i n g the Wagner-Friedberg model. Both models f i t the data very w e l l . I t i s important to n o t i c e that the c o u p l i n g constant, J , i s s i g n i f i c a n t l y s maller than that observed f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Chapter 2). The presence of only very weak magnetic c o u p l i n g i n t h i s compound makes i t a poor candidate f o r the type of study i n v o l v i n g mixed metal systems as d e s c r i b e d i n Chapter 3. 99 20.0 40.0 60.0 Temperature (K) 80.0 100.0 F i g u r e 4.4 Magnetic Moment versus Temperature P l o t f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 100 F i g u r e 4 . 5 Magnetic S u s c e p t i b i l i t y versus Temperature P l o t f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 101 4.2. MONOHYDRATES OF MANGANESE(11) AND CADMIUM(11) MONOPHENYLPHOSPHINATE The syntheses of these compounds are d e s c r i b e d i n chapter 6. These compounds are s o l u b l e i n str o n g p o l a r s o l v e n t s such as water, methanol and ethanol but are not s o l u b l e i n the weakly p o l a r s o l v e n t , acetone. They are a l s o i n s o l u b l e i n non-polar or weakly p o l a r organic s o l v e n t s (petroleum e t h e r , chloroform, benzene, carbon t e t r a c h l o r i d e , dichloromethane). Thermal diagrams f o r both M n [ H ( C 6 H 5 ) P 0 2 ] 2 * H 2 0 and C d [ H ( C 6 H 5 ) P 0 2 ] « H 2 0 are given i n F i g 4.6. There are two thermal events shown f o r each of these compounds: one endothermic event occurs at around 120°C f o r Mn [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 and 140 °C f o r C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 , and has been a s s i g n e d as d e h y d r a t i o n . Another exothermic event occurs near 230°C f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 « H 2 0 and 290°C for C d [ H ( C 6 H 5 ) P 0 2 ] 2 *H20, and i s as s i g n e d as o x i d a t i v e decomposition. The decomposition temperatures f o r the hydrated compounds are almost the same as those of the corresponding anhydrous compounds. T h i s suggests, f o r example, that M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) i s the thermodynamically s t a b l e form of the compound no matter which method has been u t i l i z e d to prepare i t . 1 02 The i n f r a r e d s p e c t r a of M n [ H ( C 6 H 5 ) P 0 2 ] 2 * H 2 0 and C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 (data given i n Table 4.3) d i f f e r s i g n i f i c a n t l y , suggesting these compounds may have d i f f e r e n t s t r u c t u r e s . The X-ray powder d i f f r a c t i o n p a t t e r n s f o r these compounds are given i n F i g . 4.7 and the d i f f r a c t i o n data are t a b u l a t e d i n Table 4.4. The d i f f r a c t i o n p a t t e r n s are d i s t i n c t from each other, showing these compounds are not isomorphous. 1 03 F i g u r e 4 . 6 Thermograms of a) M n [ H ( C 6 H 5 ) P 0 2 ] 2 . H 2 0 and b) C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 1 04 Table 4.3 I n f r a r e d A b s o r p t i o n s 1 f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 * H 2 0 and C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 Frequency ( c m - 1 ) 2 Assignment 3  M n [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 O-H v i b . 3311 w.br 3421 w.br P-H s t r . 2359 m 2390 vw 2347 vw O-H bending 1703 w 1673 w P0 2 asy. s t r . 1165 m.sh 1147 s.sh 1141 vs 1113 vs P0 2 sym. s t r . 1056 w 1057 m 1024 m 1030 w P-C 6H 5 s t r . 744 m 743 w C-C out-plane r i n g 709 m 708 w deformation (H)(C)P0 2 554 m 556 m deformation 480 vw 486 vs 'These data were taken on P e r k i n - E l m e r 1 7 1 0 . 2w.br = weak broad; w = weak; vw = very weak; vs = very st r o n g ; s.sh = str o n g shoulder; m.sh = medium shoulder; m = medium. 3 R e f e r e n c e [ 1 ]. b) T — I I I—I—| I I—I—I—I—I I I—I | I I I I—I—I—I—I—I—J 5 10 15 20 25 30 26(decrees) F i g u r e 4.7 X-ray Powder D i f f r a c t i o n P a t t e r n s of a) Mn[H ( C 6 H 5 ) P 0 2 ] 2 . H 2 0 and b) C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 1 06 Table 4.4 X-ray Powder D i f f r a c t i o n Data f o r M n [ H ( C 6 H 5 ) P 0 2 ] 2 ' H 2 0 and C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 M n [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 d I / I . d I / I . 15.6653 100 14.6081 79 14.8784 100 10.9150 80 7.3324 12 7.3750 11 5.7135 12 5.1405 15 5.0108 8 4.9900 21 4.8849 5 107 4.3. THE DIHYDRATE OF MANGANESE(11) MONOPHENYLPHOSPHINATE. The s y n t h e s i s of Mn[H(C 6H 5)P0 2J•2H 20 i s d e s c r i b e d i n Chapter 6. S o l u b i l i t y t e s t s show that i t has s i m i l a r s o l u b i l i t y p r o p e r t i e s to the monohydrated d e r i v a t i v e . I t only d i s s o l v e s i n strong p o l a r s o l v e n t s such as water and methanol and does not d i s s o l v e i n non-polar s o l v e n t s (petroleum e ther, benzene, c h l o r o f o r m , dichloromethane, carbon t e t r a c h l o r i d e ) . S i m i l a r l y , i t s DSC t r a c e shows two thermal events very s i m i l a r to those observed f o r the monohydrates. One endothermic dehydration peak occur at 130°C and one exothermic o x i d a t i v e decomposition peak occurs at 240°C. The i n f r a r e d spectrum of M n [ H ( C 6 H 5 ) P 0 2 ] « 2 H 2 0 i s given in F i g . 4.8 and a l l a b s o r p t i o n s are l i s t e d i n Table 4.5. The value of Av f o r t h i s compound (obtained by t a k i n g the d i f f e r e n c e between the averaged values of the f r e q u e n c i e s a s s i g n e d to asymmetric and symmetric P0 2 s t r e t c h i n g v i b r a t i o n s ) i s 96 cm - 1. T h i s v a l u e , although s m a l l e r than that observed f o r anhydrous compound, i s s t i l l r e l a t i v e l y l a r g e and suggests the phosphinate b r i d g i n g i s r e l a t i v e l y unsymmetric here too. The s t r u c t u r e of t h i s compound probably i n v o l v e s double phosphinate bridges forming square pla n a r MnOi, chromophores with a x i a l l y c o o r d i n a t e d water 108 molecules, as observed f o r M n [ ( C H 3 ) 2 P 0 2 ] 2 * 2 H 2 0 [29]. The X-ray powder d i f f r a c t i o n p a t t e r n i s almost the same as f o r the monohydrated compound except that the peak at d=14 i s a s i n g l e t . In the case of the monohydrated compound the peak at d=14 i s s p l i t . The magnetic s u s c e p t i b i l i t y of M n [ H ( C 6 H 5 ) P 0 2 ] 2 • 2 H 2 0 was p r e v i o u s l y measured i n t h i s l a b [97]. By f i x i n g g=2.00, the best f i t v a l u e s found f o r J and % monomer were -0.50 cm"1 and 6.1(±0.40) r e s p e c t i v e l y using the Weng model and -0.50 cm"1 and 3.80(±0.30) r e s p e c t i v e l y u s i n g the Wagner-Friedberg model. T h i s r e s u l t i s very s i m i l a r to that obtained f o r M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 and although the magnitude of the exchange i s very weak compared to that i n the anhydrous monophenylphosphinate compound i t i s s i g n i f i c a n t l y g r e a t e r than that observed i n the r e l a t e d compound, M n [ ( C H 3 ) 2 P 0 2 ] 2 • 2 H 2 0 , where the value of J was shown to be <0.02 cm"1 [29]. 109 T 1 1 1 1 1 r 1600 U00 1200 1000 800 600 400 WAVENUMBER / c n r * F i g u r e 4.8 I n f r a r e d Spectrum of Mn[H(C 6H 5)P0 2] 2•2H 20 110 Table 4.5 Infrared Absorptions 1 for Mn[H(C 6H 5)P0 2] 2•2H 20 Frequency ( c m - 1 ) 2 Assignment 3 3432 s.br O-H s t r . 2357 s P-H s t r . 1701 s O-H bending 1592 w C-C in-plane 1137 vs P0 2 asy. s t r . 1057 vs P0 2 sym. s t r . 1024 s 984 s 744 s 708 s P-C 6H 5 s t r . C-C out-plane ring deformation 554 vs (H)(C)P0 2 deformation 479 s ^hese data were taken on Perkin-Elmer1710. 2w = weak; vs = very strong; s.br = strong broad; s = strong. 3Reference [1]. 4.4. Z I N C ( I I ) MONOPHENYLPHOSPHINATE We prepared and investigated Zn[H(C 6H 5)P0 2] 2 in order to see whether i t is isomorphous with the manganese analogue and therefore a potential candidate for doping studies. The detailed procedure for the synthesis of the compound i s given in Chapter 6. Zn[H(C GH 5)P0 2] 2 dissolves in neither polar nor non-polar solvents. DSC shows i t has only one endothermic peak near 290°C and no oxidative decomposition u n t i l 320°C. The infrared spectrum of this compound shows that i t i s similar to that of Mn[H(C 6H 5)P0 2] 2 (Form II) in the P0 2 stretching region. 111 The X-ray powder d i f f r a c t i o n p a t t e r n of Z n [ ( C 6 H 5 ) ( n - C „ H 9 ) P 0 2 ] 2 ( F i g 4.9) i s unique among a l l the metal phosphinates s t u d i e d and t h i s l a c k of isomorphism with the manganese analogue makes i t a poor candidate f o r doping experiments. T h i s z i n c compound, l i k e Z n [ ( C 6 H 5 ) ( n - C t t H 9 ) P 0 2 ] 2 and Z n [ ( n - C « H 9 ) 2 P 0 2 ] 2 [17], may adopt a l i n e a r s t r u c t u r e with a s i n g l e - t r i p l e a l t e r n a t i n g phosphinate b r i d g i n g system. Normally, i f the phosphinate l i g a n d s c o o r d i n a t e to the z i n c c e n t e r i n t h i s way, the b r i d g i n g groups are symmetrical and the i n f r a r e d spectrum gi v e s a value of about 60 cm - 1. However, here a Ap value of about 100 cm"1 i s observed, i n d i c a t i n g that whether or not the b r i d g i n g i s of the a l t e r n a t i n g s i n g l e - t r i p l e type, the br i d g e s are l i k e l y unsymmetric. 112 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 » 1 1 \ i 1 1 5 10 15 20 25 30 20(DECREES) F i g u r e 4 . 9 X-ray Powder D i f f r a c t i o n P a t t e r n of Z n [ H ( C 6 H 5 ) P 0 2 ] 2 CHAPTER 5. SUMMARY,AND SUGGESTIONS FOR FURTHER STUDY The work d e s c r i b e d in t h i s t h e s i s has u t i l i z e d s e v e r a l experimental techniques to c h a r a c t e r i z e metal phosphinates of the type M .M' [ R ( C 6 H 5 ) P 0 2 ] 2 - y H 2 0 , i n which R=H, C 6H 5-, I A . A M=Mn or Zn, M'=Cd, x ranges from 0 to 100 and y=0, 1 or 2. T h i s chapter presents a summary and suggests d i r e c t i o n s that f u r t h e r s t u d i e s may take. 5.1. SUMMARY In t h i s r e s e a r c h , anhydrous monophenylphosphinates of manganesedl) and cadmiumdl) were s y n t h e s i z e d , each one i n two d i s t i n c t forms ( l a b e l l e d Form I and Form II i n t h i s t h e s i s ) , as shown by i n f r a r e d s p e c t r o s c o p i c and X-ray powder d i f f r a c t i o n s t u d i e s . Magnetic s u s c e p t i b i l i t y s t u d i e s showed that M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) e x h i b i t s r e l a t i v e l y strong a n t i f e r r o m a g n e t i c exchange i n t e r a c t i o n s and the e f f e c t s on t h i s magnetic exchange of doping diamagnetic cadmium atoms i n t o the m a t e r i a l have been i n v e s t i g a t e d . To t h i s end, a s e r i e s of mixed metal phosphinates of the form M n 1 C d [ H ( C 6 H 5 ) P 0 2 ] 2 , where x=0 to 100, were prepared and I A A s t u d i e d . The e f f e c t of doping with cadmium i s to break the i n f i n i t e c h a i n i n t o f i n i t e segments and to generate monomer i m p u r i t i e s i n odd numbered segments. As the extent of doping 1 1 3 1 14 i s i n c r e a s e d the average chain l e n g t h decreases and the f r a c t i o n of monomer i n c r e a s e s . In a d d i t i o n , the exchange c o u p l i n g c o n s t a n t , J , was found to decrease as the average ch a i n l e n g t h decreased. P r e c i p i t a t i o n of samples of M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I) from con c e n t r a t e d s o l u t i o n s gave specimens which have s i g n i f i c a n t l y a l t e r e d magnetic p r o p e r t i e s . A n a l y s i s of the data i n d i c a t e that these samples ( l a b e l l e d Form 1(B)) c o n t a i n much sh o r t e r c h a i n fragments than the pure Form I m a t e r i a l . A second form of M n [ H ( C 6 H 5 ) P 0 2 ] 2 was s y n t h e s i z e d i n t h i s work ( r e f e r r e d to here as Form I I ) . T h i s compound has a d i s t i n c t i n f r a r e d spectrum and X-ray powder d i f f r a c t i o n p a t t e r n and shows much weaker a n t i f e r r o m a g n e t i c behavior than the Form I compound. A n a l y s i s of the magnetic data suggest that i n t h i s compound the average c h a i n length i s s i g n i f i c a n t l y s m a l l e r than i n M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) . The hydrated monophenylphosphinates of m a n g a n e s e d l ) , M n [ H ( C 6 H 5 ) P 0 2 ] 2 * H 2 0 and Mn[H(C 6H 5)P0 2] 2*2H 20, were a l s o prepared and c h a r a c t e r i z e d i n t h i s work. The s t r u c t u r e s of these compounds are con s i d e r e d to be s i m i l a r to those of the anhydrous m a t e r i a l s , except that i n the hydrated compounds one or two of the a x i a l p o s i t i o n s are occupied by water molecules. The d i h y d r a t e shows only very weak a n t i f e r r o m a g n e t i c p r o p e r t i e s (J i s about -0.50 c m - 1 ) . F i n a l l y , the diphenylphosphinates of manganesedl) and 1 1 5 cadmium(II) were also prepared. Some characterization of these materials was undertaken and both the infrared spectra and powder d i f f r a c t i o n patterns were found to be d i s t i n c t from each other, indicating the compounds are not isomorphous. The rather weak magnetic exchange observed in the manganese compounds, however, rendered these compounds poor candidates for extensive mixed metal studies as were undertaken with the monophenylphosphinates. 5.2. SUGGESTIONS FOR FURTHER STUDIES. It would be very useful to obtain single c r y s t a l s of manganesedl) or cadmium(ll) monophenylphosphinate. A single c r y s t a l X-ray d i f f r a c t i o n study would greatly a s s i s t in the understanding of the magnetic properties of Mn[H(C 6H 5)P0 2]z and the cadmium doped samples. The p o s s i b i l i t y of interchain magnetic interactions (as well as intrachain interactions) in t h i s polymeric manganese phosphinate system was raised in t h i s thesis. An attempt to analyze the magnetic data on th i s basis may prove f r u i t f u l . It might permit the determination of the r a t i o of interchain to intrachain coupling, information that would give a hint about the onset of long-range ordering as has been done in related studies [ 8 6 , 9 8 ] . 1 16 F i n a l l y , a d e t a i l e d a n a l y s i s of the powder ESR s p e c t r a of the Mn. Cd [ H ( C 6 H 5 ) P 0 2 ] 2 systems should be undertaken as i t would l i k e l y provide more i n f o r m a t i o n about the manganesedl) environment i n these systems [28]. CHAPTER 6. EXPERIMENTAL 6.1. PHYSICAL METHODS 6.1.1. I n f r a r e d Spectroscopy I n f r a r e d s p e c t r a were recorded on a Perkin-Elmer 1710 F o u r i e r transform i n f r a r e d spectrophotometer, c o v e r i n g the range from 4000 to 450 cm - 1 and on a Perkin-Elmer 598 g r a t i n g spectrophotometer i n the region of 4000-250 cm" 1. A l l the a b s o r p t i o n s a s s i g n e d are assumed ac c u r a t e to ca. ±1 cm - 1 on the Perkin-Elmer 1710 and ca. ±3 cm'1 on the Perkin-Elmer 598. C a l i b r a t i o n was achieved by using the 1601 and 907 cm - 1 bands of p o l y s t y r e n e . The c e l l windows used were KRS-5 p l a t e s (42% T l B r + 58% T i l , Harshaw Chemical Co.). A l l samples were mulled i n N u j o l . 6.1.2. D i f f e r e n t i a l Scanning C a l o r i m e t r y (DSC) DSC s t u d i e s were made us i n g a M e t t l e r DSC 20 c e l l i n t e r f a c e d with a M e t t l e r TC 10 TA processor and a P r i n t Swiss Matrix Ro-80 p r i n t e r / p l o t t e r . In a t y p i c a l experiment, a f i n e l y powdered sample of approximately 3 to 12 mg was a c c u r a t e l y weighed i n t o an aluminium c r u c i b l e (with a small p i n h o l e on the l i d a l l o w i n g atmospheric access) and the 1 17 118 sample was heated from c a . 308 to 598 K at a r a t e of 4 K per minute. The temperature c a l i b r a t i o n of the platinum sensor was achieved u s i n g the known f u s i o n temperature of indium. The heat flow was c a l i b r a t e d u sing an e x a c t l y known q u a n t i t y of indium. The peak temperature and enthalpy of a p a r t i c u l a r thermal event were o b t a i n e d r e s p e c t i v e l y from the maximum in the DSC curve and the i n t e g r a t e d area beneath the curve. 6.1.3. Magnetic S u s c e p t i b i l i t y Measurements Routine temperature-dependent s t u d i e s from 4.2 K to 82 K were made using a P r i n c e t o n A p p l i e d Research Model 155 V i b r a t i n g Sample Magnetometer [20]. A magnetic f i e l d of 7501 Gauss was employed f o r the s t u d i e s . The f i e l d s t r e n g t h was set to a accuracy of 0.5% and measured u s i n g an F.W. B e l l Model 620 Gaussmeter. A c c u r a t e l y weighed samples of approximately 90 to 120 mg, c o n t a i n e d i n g e l a t i n c a p s u l e s , were a t t a c h e d to a Kel-F holder with epoxy r e s i n . C o r r e c t i o n s were made f o r the diamagnetic background produced by the h o l d e r . Temperature measurement was achieved with a chromel versus Au - 0.02% Fe thermocouple [99] l o c a t e d i n the sample holder immediately above the sample. The thermocouple was c a l i b r a t e d u sing the known s u s c e p t i b i l i t y versus temperature behavior of tetramethylenediammonium t e t r a c h l o r o c u p r a t e ( I I ) and checked 119 with m e r c u r y ( l l ) t e t r a t h i o c y a n a t o c o b a l t a t e ( I I ) [100]. The temperatures were estimated to be accurate to ±1% over the range s t u d i e d , 4.2 K-82 K. The accuracy of the magnetic s u s c e p t i b i l i t y values as measured by t h i s technique i s estimated t o be ±1%. Molar magnetic s u s c e p t i b i l i t i e s were c o r r e c t e d f o r the diamagnetism of the metal ions and the l i g a n d s . The diamagnetic c o r r e c t i o n s ( u n i t s of 10" 6 cm 3 mol." 1) are: Mn(-14), Cd(-22), ( C 6 H 5 ) 2 P 0 2 - ( - 1 2 7 ) , and H ( C 6 H 5 ) P 0 2 " ( - 7 8 ) . 6.1.4. E l e c t r o n Spin Resonance (ESR) Spectroscopy A V a r i a n A s s o c i a t e s E-3 ESR Spectrometer equipped with a 100 KHz f i e l d modulation was used to r e c o r d s p e c t r a at both room and l i q u i d n i t r o g e n temperatures. The X-band microwave frequency and the magnetic f i e l d were c a l i b r a t e d using a Hewlett-Packard 5245 E l e c t r o n i c Frequency Counter i n the range of 8 to 18 KHz. For the "pure" manganese samples, DPPH ( 2 , 2 - d i p h e n y l - i - p i c r y l h y d r a z y l f r e e r a d i c a l ) was used as the i n t e r n a l standard (g=2.0023). Samples were s t u d i e d as f i n e l y ground powders c o n t a i n e d i n 3 mm i . d . s i l i c a tubes. 1 20 6.1.5. X-Ray Powder Diffractometry Powder d i f f r a c t i o n p a t t e r n s were obtained on a P h i l i p s X-Ray D i f f r a c t i o n (XRD) u n i t using Cu Ka as the r a d i a t i o n source. The measurements were done with a d i f f r a c t o m e t e r 29 (where 26 i s the r e f l e c t i o n angle) s e t t i n g of 2° per minute and c h a r t speed of 2 c e n t i m e t e r s per minute. Samples were prepared by d i s p e r s i n g the specimen by g r i n d i n g under a l c o h o l i n an agate mortar. The sample s l u r r y was mounted on a g l a s s s l i d e and allowed to dry. The d i f f r a c t i o n p a t t e r n s were c a l i b r a t e d by using S i as an i n t e r n a l standard. S i has a simple c u b i c u n i t c e l l and has only one peak between 5-30° at 20=28.457°. 6.1.6. Electron Spectroscopy for Chemical Analysis (ESCA) ESCA s t u d i e s were done on a V a r i a n IEE-15 Spectrometer, using Mg Ka r a d i a t i o n (1253.60 eV) at 280 Watts, at a pressure of 10" 7 T o r r , and an a n a l y s e r pass energy of 100 eV. Instrumental r e s o l u t i o n was found to be 1.5 eV using the Au ( 4 f 7 y 2 ) standard peak. The work f u n c t i o n 0 Sp of the spectrometer was e f f e c t i v e l y e l i m i n a t e d from the energy balance by use of a s p e c t r a l energy c a l i b r a t i o n , u s u a l l y the carbon 1s peak at 284 eV [101]. B i n d i n g Energies are c o n s i d e r e d a c c u r a t e to ±0.1 eV. 121 6.1.7. Elemental Analyses The q u a n t i t a t i v e d e t e r m i n a t i o n of metal content i n the phosphinate samples was c a r r i e d out using V a r i a n AA5 ( f o r Mn) and Perkin-Elmer 305 ( f o r Cd) Atomic A b s o r p t i o n Spectrophotometers. The sample s o l u t i o n was prepared by d i s s o l v i n g a known amount (20 to 70 mg) of the metal phosphinate i n 15 ml of 37% HCI. T h i s s o l u t i o n was then heated g e n t l y u n t i l a l l the s o l i d s were d i s s o l v e d , and was d i l u t e d with d i s t i l l e d water to about 3 ppm i n c o n c e n t r a t i o n . Mn and Cd standard s o l u t i o n (1-5 ppm) were made using spectrum grade manganese or cadmium n i t r i t e s . C and H microanalyses were performed by P. Borda of t h i s Department. The a n a l y t i c a l r e s u l t s are recorded i n Table Table 6.1 Elemental A n a l y s e s 1 122 Compound-Elements H Mn Cd M n l H ( C 6 H s ) P 0 2 J 2 ( F o r m I) 42.90 3.70 (42.76) (3.59) M n [ H ( C 6 H 5 ) P 0 2 ] 2 ( F o r m I I ) 42.62 3.71 (42.76) (3.59) M n [ H ( C s H 5 ) P 0 2 ] 2 ( F o r m I ( B ) 42.29 3.66 (42.76) (3.59) C d [ H ( C e H , ) P 0 2 ] 2 ( F o r m I ) 36.64 3.10 (36.53 (3.07) C d [ H ( C s H s ) P 0 2 ] 2 ( F o r m I I ) 36.40 3.04 28.26 (36.53 (3.07) (28.47) Mn 0 9 9 5 Cd o . o o 5 [ H ( C 6 H s ) P 0 2 42.62 3.71 (42.72 (3.58) Mn 0 9 9Cd 0 . o , [ H ( C 6 H 5 ) P 0 2 ] 2 I 42.78 3.77 (42.68 (3.58) Mn 0 9 i C d 0 . 0 9 [ H ( C s H 5 ) P 0 2 ] 2 I 41 .96 3.55 13.68 2.89 (42.04 (3.53) ( 1 4 . 4 2 ) ( 3 . 2 8 ) Mn 0 7 3 C d 0 . 2 7 [ H ( C 6 H s ) P 0 2 ] 2 I 40.93 3. 56 10.89 8.62 (40.67 (3.41 ) (10.85)(9.52) Mn 0 5 3 C d 0 . , , [ H ( C 6 H 5 ) P 0 2 ] 2 I 39.63 3.36 7.57 14.08 (39.40 (3.31) (7.51) (15.36) Mn 0 9 9 C d 0 .o , [ H ( C $ H 5 ) P 0 2 ] 2 K B ) 42.62 3.59 16.45 0.25 (42.68 (3.58) ( 16. 11 ) (0.33) Mn 0 9 5 C d 0 . 0 5 [ H ( C 6 H S ) P 0 2 ] 2 I (B) 42.41 3.68 15.55 1.55 (42.41 > (3.56) ( 15.42) (1.57) Mn 0 9 2Cd 0 . O B [ H ( C 6 H 5 ) P 0 2 ] 2 I (B) 41 .57 3.66 14.83 2.58 (41 .96 >(3.52) (14.59)(2.99) Mn 0 e $ C d 0 . , s [ H ( C 6 H 5 ) P 0 2 ] 2 1 ( B ) 41 .60 3.51 13.63 4.69 (41.57 I (3.49) (13.21)(5.40) Mn 0 5 j C d 0 . « 8 [ H ( C 6 H 5 ) P 0 2 ] 2 K B ) 39. 23 3.39 8.09 6.97 (39.40 ) (3.31) (7.51) (8.00) M n [ H ( C s H 5 ) P 0 2 ] 2 - H 2 0 40.76 3.88 15.10 (40.53 )(3.97) (15.47) M n [ H ( C 6 H 5 ) P 0 2 ] 2 - 2 H 2 0 38.55 4.30 (38.63 1 (4.32) C d [ H ( C s H 5 ) P 0 2 ] 2 - H 2 0 35.09 3.60 25.81 (34.93 ) (3.42) (27.24) Z n [ H ( C s H . ) P O 2 ] 2 41 .49 3.46 (41.47 1 (3.48) M n [ ( C c H 5 ) 2 P 0 2 3 2 58.99 4.11 9.51 (58.91 K4.12) (11.23) C d [ ( C c H . ) 2 P O 2 ] 2 52.64 3.65 (52.72 (3.69) ^ h e data i n s i d e the b r a c k e t s are c a l c u l a t e d and those o u t s i d e the bra c k e t s are ex p e r i m e n t a l . 2Here I r e f e r s to Form I and 1(B) to Form 1 ( B ) . 123 6.2. COMPOUND SYNTHESES Most of the s y n t h e s i s work was undertaken u s i n g c o n v e n t i o n a l Pyrex glassware and bench-top t e c h n i q u e s . A l l chemicals and s o l v e n t s were reagent or chemical grade and were used without f u r t h e r p u r i f i c a t i o n . Two g e n e r a l methods were u t i l i z e d f o r the p r e p a r a t i o n of the metal phosphinates. One method i n v o l v e d the r e a c t i o n between a hydrated metal a c e t a t e and monophenylphosphinic a c i d employing methanol or ethanol as s o l v e n t . T h i s gave products of the type M [H(C 6H 5)P0 2] 2>yH 20 where y=0, 1 or 2, and M i s Mn or Cd. M(CH 3C0 2) 2•xH 20+2H(C 6H 5)P0 2H * M[H(C 6H 5)P0 2] 2.yH 20+2CH 3C0 2H+(x-y)H 20 The other method i n v o l v e d the r e a c t i o n between a hydrated metal s u l f a t e and the potassium s a l t of monophenylphosphinic a c i d employing aqueous methanol as the s o l v e n t . K 2C03 + 2 H ( C 6 H 5 ) P 0 2 H *2H(C 6H 5)P0 2K+H 2C0 3 1 24 MSO„ • H 2 0 + 2 H ( C 6 H 5 ) P 0 2 K «-M[ H ( C 6 H 5 ) P 0 2 ] 2 • 2 H 2 0 + K 2 S O „ A l l the compounds prepared are moisture and a i r s t a b l e . Both methods of p r e p a r a t i o n give about 85% y i e l d of the product. 6 . 2 . 1 . P r e p a r a t i o n o f M a n g a n e s e ( 1 1 ) M o n o p h e n y l p h o s p h i n a t e ( F o r m I ) , M n [ H ( C 6 H 5 ) P 0 2 ] 2 ( F o r m I) Monophenylphosphinic a c i d (1.9891 g, 14.00 mmol) was d i s s o l v e d i n 200 ml e t h a n o l . A manganesedl) a c e t a t e t e t r a h y d r a t e s o l u t i o n was prepared by d i s s o l v i n g 1.4717 g (6.01 mmol) of s a l t i n 150 ml e t h a n o l . The s a l t s o l u t i o n was added dropwise to the s t i r r i n g a c i d s o l u t i o n . The r e a c t i o n mixture became cloudy a f t e r about 1/6 of the s a l t s o l u t i o n has been added. The r e a c t i o n mixture was t o t a l l y opaque and pink i n c o l o r once the a d d i t i o n was completed. The s o l u t i o n was l e f t s t i r r i n g f o r a f u r t h e r 24 h r s , then allowed to stand f o r another 5 days. The p r e c i p i t a t e was c o l l e c t e d on a s i n t e r e d g l a s s f i l t e r , washed with ethanol and set a s i d e to a i r - d r y between p i e c e s of f i l t e r paper. The dry product i s a pink, f i n e - g r a i n e d powder. 1 25 6 . 2 . 2 . P r e p a r a t i o n o f M a n g a n e s e ( 1 1 ) M o n o p h e n y l p h o s p h i n a t e ( F o r m I I ) , M n [ H ( C 6 H 5 ) P 0 2 ] 2 ( F o r m I I ) Monophenylphosphinic a c i d (1.7643 g, 12.42 mmol) was d i s s o l v e d i n 75 ml methanol and c o o l e d to a temperature of 0°C i n an i c e - b a t h . Manganese(II) a c e t a t e t e t r a h y d r a t e (1.2252 g, 5.00 mmol) was d i s s o l v e d i n 75 ml methanol, then added dropwise to the s t i r r i n g a c i d s o l u t i o n . Upon completion of the a d d i t i o n , the r e a c t i o n mixture was pink i n c o l o r with no sign of p r e c i p i t a t i o n . The s o l u t i o n was allowed to warm to room temperature with the f l a s k open to the atmosphere. Three days l a t e r the product, which had formed slowly as a pale purple p r e c i p i t a t e , was c o l l e c t e d by f i l t r a t i o n and a i r - d r i e d between p i e c e s of f i l t e r paper. 6 . 2 . 3 . P r e p a r a t i o n o f M a n g a n e s e ( 1 1 ) M o n o p h e n y l p h o s p h i n a t e (Form K B ) ) , M n [ H ( C 6 H 5 ) P 0 2 ] 2 ( F o r m 1 ( B ) ) Manganesedl) a c e t a t e t e t r a h y d r a t e (1.2274 g, 5.01 mmol) was d i s s o l v e d i n 60 ml e t h a n o l . T h i s s o l u t i o n was added dropwise to a s t i r r i n g a c i d s o l u t i o n which was prepared by d i s s o l v i n g 1.4222 g (10.01 mmol) of monophenylphosphinic a c i d in 55 ml e t h a n o l . The a d d i t i o n was over a p e r i o d of about 70 minutes. The p r e c i p i t a t e s t a r t e d forming almost immediately and was c o l l e c t e d on s i n t e r e d 1 26 g l a s s and a i r - d r i e d o v e r n i g h t . 6.2.4. Preparation of Manganesedl) monophenylphosphinate Monohydrate, Mn[H(C 6H 5)P0 2] 2-H 20 Manganesedl) a c e t a t e t e t r a h y d r a t e (1.2262 g, 5.06 mmol) was d i s s o l v e d i n 55 ml methanol. T h i s s o l u t i o n was added dropwise to a s t i r r i n g a c i d s o l u t i o n which was prepared by d i s s o l v i n g 1.4219 g (10.02 mmol) of monophenylphosphinic a c i d i n 55 ml methanol. Both the s a l t and a c i d s o l u t i o n s were maintained under a atmosphere of ni t r o g e n gas and kept i n an i c e - b a t h . The r e a c t i o n mixture was p a l e - p i n k i n c o l o r and there was no si g n of p r e c i p i t a t i o n a f t e r the a d d i t i o n had been completed. A p i n k i s h p r e c i p i t a t e appeared one hour l a t e r . The s o l u t i o n was kept s t i r r i n g f o r a f u r t h e r 17 h r s . , then c o l l e c t e d on a s i n t e r e d g l a s s f i l t e r . The pink c o l o r e d f i n e powder was a i r - d r i e d f o r 3 days. Compared with the p r e p a r a t i o n of M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I I ) , the s o l u t i o n of manganesedl) a c e t a t e t e t r a h y d r a t e was more c o n c e n t r a t e d (5.00 mmol i n 75 ml f o r Form II versus 5.00 mmol i n 55 ml i n t h i s c a s e ) . The f l u s h of n i t r o g e n gas over the s u r f a c e of the s o l u t i o n i n t h i s case made the s o l u t i o n even more co n c e n t r a t e d . T h e r e f o r e , water was trapped and monohydrated m a t e r i a l was produced. 1 27 6 . 2 . 5 . P r e p a r a t i o n o f M a n g a n e s e ( 1 1 ) M o n o p h e n y l p h o s p h i n a t e D i h y d r a t e , M n [ H ( C 6 H 5 ) P 0 2 ) ] 2 • 2 H 2 0 Monophenylphosphinic a c i d (2.8420 g, 20.00 mmol) was n e u t r a l i z e d with 1.3855 g (10.00 mmol) of potassium carbonate i n 50 ml of aqueous methanol s o l u t i o n (50:50 by volume). Manganesedl) s u l f a t e monohydrate (1.6900 g, 10.00 mmol) was d i s s o l v e d i n 50 ml d i s t i l l e d water, then added dropwise to the s t i r r i n g potassium monophenylphosphinate s o l u t i o n . The r e a c t i o n mixture became cloudy a f t e r about 6 ml of the s u l f a t e s o l u t i o n had been added, but with continued a d d i t i o n , the p r e c i p i t a t e r e d i s s o l v e d . The mixture was s t i r r e d f o r another 50 minutes and d u r i n g that p e r i o d of time the s o l u t i o n became cloudy a g a i n . The white p r e c i p i t a t e was i s o l a t e d by f i l t r a t i o n on s i n t e r e d g l a s s , washed with aqueous methanol, and then l e f t t o a i r - d r y between p i e c e s of f i l t e r paper. 6 . 2 . 6 . P r a p a r a t i o n o f C a d m i u m d l ) m o n o p h e n y l p h o s p h i n a t e ( F o r m I ) , C d [ H ( C 6 H 5 ) P 0 2 ] 2 ( F o r m I) Monophenylphosphinic a c i d (1.4213 g, 10.00 mmol) was d i s s o l v e d i n 55 ml e t h a n o l . Cadmiumdl) a c e t a t e d i h y d r a t e (1.3324 g, 5.00 mmol) was d i s s o l v e d i n 150 ml e t h a n o l , then added dropwise to the a c i d s o l u t i o n . A white product began 1 28 to p r e c i p i t a t e a f t e r about 10 ml of cadmium a c e t a t e s o l u t i o n had been added. The p r e c i p i t a t e was c o l l e c t e d , l e f t to a i r - d r y o v e r n i g h t , then d r i e d i n vacuum at 85°C f o r 12 h r s . 6.2.7. P r e p a r a t i o n of Cadmium(II) Monophenylphosphinate (Form I I ) , C d [ H ( C 6 H 5 ) P 0 2 ] 2 (Form II) A cadmium a c e t a t e d i h y d r a t e s o l u t i o n , prepared from 1.3385 g (5.00 mmol) of the s a l t i n 60 ml methanol was added dropwise with s t i r r i n g to a s o l u t i o n of 1.444 g (10.1 mmol) monophenylphosphinic a c i d i n 55 ml methanol. A white p r e c i p i t a t e appeared a f t e r 10 to 15 ml of the s a l t s o l u t i o n had been added. A f t e r the a d d i t i o n had been completed the mixture was s t i r r e d f o r another 20 minutes. The p r e c i p i t a t e was c o l l e c t e d on s i n t e r e d g l a s s , washed with methanol and then set a s i d e to a i r - d r y between p i e c e s of f i l t e r paper. The white powder was f i n a l l y d r i e d i n vacuum at 118°C f o r 20 hr s . 6.2.8. P r e p a r a t i o n of Cadmium(II) Monophenylphosphinate Monohydrate, C d [ H ( C 6 H 5 ) P 0 2 ] 2 - H 2 0 Monophenylphosphinic a c i d (2.8229 g, 19.87 mmol) was d i s s o l v e d i n 50 ml aqueous methanol s o l u t i o n (50:50 by volume), then n e u t r a l i z e d with 1.3815 g (9.98 mmol) of 129 potassium carbonate. Cadmium s u l f a t e octahydrate (2.329 g, 19.2 mmol), d i s s o l v e d i n 50 ml d i s t i l l e d water, was added dropwise to the phosphinate s a l t s o l u t i o n . As soon as the cadmiumdl) a c e t a t e s o l u t i o n had been added, the mixture became cloudy. The mixture was s t i r r e d f o r another 40 minutes. The p r e c i p i t a t e was then removed by f i l t r a t i o n and a i r - d r i e d o vernight between p i e c e s of f i l t e r paper. 6 . 2 . 9 . P r e p a r a t i o n o f Z i n c ( I I ) M o n o p h e n y l p h o s p h i n a t e , Z n [ H ( C 6 H 5 ) P 0 2 ] 2 Z i n c ( I I ) a c e t a t e d i h y d r a t e (1.1018 g, 5.00 mmol) was d i s s o l v e d i n 60 ml e t h a n o l . T h i s s o l u t i o n was added dropwise to a s t i r r i n g a c i d s o l u t i o n which was prepared by d i s s o l v i n g 1.5225 g (10.00 mmol) of monophenylphosphinic a c i d i n 60 ml e t h a n o l . The s o l u t i o n was added over a p e r i o d of about 70 minutes. The white c o l o r e d p r e c i p i t a t e was c o l l e c t e d on a s i n t e r e d g l a s s f i l t e r and a i r - d r i e d o v e r n i g h t . 6 . 2 . 1 0 . P r e p a r a t i o n o f M i x e d M a n g a n e s e ( 1 1 ) , C a d m i u m d l ) M o n o p h e n y l p h o s p h i n a t e ( F o r m I ) , M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 ( F o r m I) Monophenylphosphinic a c i d (1.98 g, 14.00 mmol) was d i s s o l v e d i n 200 ml e t h a n o l . A manganesedl) a c e t a t e 130 t e t r a h y d r a t e s o l u t i o n was prepared by d i s s o l v i n g [ 0 - x ) * 1 . 7 l 5 g, (1-X)*7 mmol] of s a l t i n (1-x)*150 ml e t h a n o l . S i m i l a r l y , a cadmium(II) a c e t a t e d i h y d r a t e s o l u t i o n was prepared by d i s s o l v i n g 1.866x g (7x mmol) of s a l t i n x*150 ml e t h a n o l . Two s a l t s o l u t i o n s were separated i n two funnels and added to the s t i r r i n g a c i d s o l u t i o n . The p r e c i p i t a t e was c o l l e c t e d on a s i n t e r e d g l a s s and a i r - d r i e d between p i e c e s of f i l t e r paper. Consider the p r e p a r a t i o n of M n 0 5 3 C d 0 4 7 [ H ( C 6 H 5 ) P 0 2 ] 2 J monophenylphosphinic a c i d 1.9985 g (14.00 mmol) was d i s s o l v e d i n 200 ml e t h a n o l . A manganesedl) a c e t a t e t e t r a h y d r a t e s o l u t i o n was prepared by d i s s o l v i n g 0.7344 g (3.00 mmol) of the s a l t i n 75 ml et h a n o l . S i m i l a r l y , a cadmium(II) a c e t a t e d i h y d r a t e s o l u t i o n was prepared by d i s s o l v i n g 0.7995 g (3.00 mmol) of the s a l t i n 75 ml e t h a n o l . The two s a l t s were added to the s t i r r i n g a c i d s o l u t i o n from separate f u n n e l s . The r e s t of the procedures f o r t h i s and other mixed metal systems of the type M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) , where x=0.27, 0.09, 0.01, 0.005, were i d e n t i c a l to that f o r the p r e p a r a t i o n of M n [ H ( C 6 H 5 ) P 0 2 ] 2 (Form I ) . 131 6.2.11. P r e p a r a t i o n of Mixed Manganese(11), Cadmium(ll) Monophenylphosphinate (Form 1(B)), Mn, Cd [ H ( C 6 H 5 ) P 0 2 ] 2 (Form K B ) ) Manganesedl) a c e t a t e t e t r a h y d r a t e (1-x mmol) and cadmium a c e t a t e d i h y d r a t e (x mmol) were d i s s o l v e d i n 60 ml e t h a n o l . T h i s s o l u t i o n was added to a s t i r r i n g a c i d s o l u t i o n which was prepared by d i s s o l v i n g (ca. 1.42 g, 10.00 mmol) of monophenylphosphinic a c i d i n 55 ml e t h a n o l . Consider the p r e p a r a t i o n of Mn Q 5 2 c d n 4 8 [ H ( C 6 H 5 ) P 0 2 ] 2 (Form 1 ( B ) ) : monophenylphosphinic a c i d (1.4225 g, 10.00 mmol) was d i s s o l v e d i n 55 ml e t h a n o l . Manganesedl) a c e t a t e t e t r a h y d r a t e (0.6189 g, 2.50 mmol) and cadmiumdl) a c e t a t e d i h y d r a t e (0.6663 g, 2.50 mmol) were d i s s o l v e d i n 60 ml e t h a n o l , then added dropwise to the s t i r r i n g a c i d s o l u t i o n . The remaining procedures f o r t h i s and other mixed metal compounds of the type M n 1 _ x C d x [ H ( C 6 H 5 ) P 0 2 ] 2 (Form 1 ( B ) ) , where x=0.15, 0.08, 0.05, 0.01, were i d e n t i c a l to that f o r the p r e p a r a t i o n of M n [ H ( 6 H 5 ) P 0 2 ] 2 (Form 1 ( B ) ) . 6.2.12. Preparaton of Manganese(11) Diphenylphosphinate, M n [ ( C 6 H 5 ) 2 P 0 2 ] 2 Manganesedl) s u l f a t e Monohydrate (0.8453 g, 5.00 mmol) was d i s s o l v e d i n 35 ml d i s t i l l e d water, then added 1 32 dropwise to the s t i r r i n g a c i d s o l u t i o n which was prepared by d i s s o l v i n g 2.8122 g (10.00 mmol) of d i p h e n y l p h o s p h i n i c a c i d i n t o 40 ml 25% methanol-aqueous s o l u t i o n f o l l o w i n g n e u t r a l i z a t i o n with 0.6916 g (5.00 mmol) of potassium carbonate. A white p r e c i p i t a t e was obtained at the end of the a d d i t i o n . The r e a c t i o n mixture was s t i r r e d f o r another 45 minutes, then c o l l e c t e d on a s i n t e r e d g l a s s f i l t e r , washed with 50% methanol-aqueous s o l u t i o n , l e f t t o a i r - d r y and e v e n t u a l l y d r i e d i n vacuum at 105°C f o r 18 hours. 6.2.13. P r e p a r a t i o n of Cadmium(II) Diphenylphosphinate, C d f ( C 6 H 5 ) 2 P 0 2 ] 2 Diphenylphosphinic a c i d (4.3602 g, 20.00 mmol) was d i s s o l v e d i n 80 ml 25% methanol-aqueous s o l u t i o n , then n e u t r a l i z e d by 1.3800 g (10.00 mmol) of potassium carbonate. Cadmium(II) s u l f a t e octahydrate (7.6875 g, 10.00 mmol) was d i s s o l v e d i n 70 ml d i s t i l l e d water, then added dropwise to the s t i r r i n g a c i d s o l u t i o n . At the same time, the s o l u t i o n was heated g e n t l y and kept s t i r r i n g f o r a f u r t h e r 20 minutes a f t e r the a d d i t i o n was completed. The white p r e c i p i t a t e was c o l l e c t e d , a i r - d r i e d and f u r t h e r d r i e d i n vacuum at 118°C fo r 18 hours. REFERENCES 1. K.W. O l i v e r , Ph.D. D i s s e r t a t i o n , The U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r , B.C., ( 1 9 8 4 ) . 2. B.P. B l o c k , I n o r g a n i c . M a c r o m o l . 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APPENDIX : Magnetic S u s c e p t i b i l i t y R e s u l t s 1 f o r M n 1 _ x C d x [ H ( C 6 H S ) P 0 2 ] 2 PART A: Mn 1_ xCd J t[H(C,H,)PO , ] , (Form I) MnfHfC.H.JPO,], M n 0 . 9 9 5 C d 0 . 0 0 5 [ H ( C » H » ) P O * J » 3 6 . 0 3 3 3 6 . 0 3 3 3 5 . 8 2 9 3 5 . 8 2 9 3 5 . 8 6 3 3 5 . 9 6 4 3 6 . 2 7 0 3 7 . 0 8 4 3 7 . 6 6 0 3 7 . 8 2 9 3 7 . 8 3 0 3 7 . 8 3 0 J 7 . 8 3 0 3 7 . 8 3 0 3 7 . 6 6 0 3 7 . 8 9 7 3 7 . 6 6 0 3 7 . 2 5 3 3 6 . 5 7 5 3 5 . 5 5 8 34 . 71 1 3 3 . 9 6 5 3 3 . 0 4 9 3 2 . 2 0 1 31 .455 3 0 . 7 8 6 3 0 . 0 3 1 T(K) *. " t i t . T(K) 4.40 27 . 6 5 7 1 . oo • 5 . 0 2 6 . 4 4 28 . 2 9 8 1 . 21 5 . 3 3 7 . 4 7 28 . 6 6 8 1 . 31 6 . 8 2 8 . 7 1 2 9 . 2 0 8 1 , . 43 7 . 8 0 9 . 8 0 2 9 . 7 4 7 1 .53 9 . 6 4 1 0 . 6 8 3 0 . 152 1 . 6 0 1 0 . 9 2 1 2 . 8 1 31 . 0 9 6 1 . 7 8 1 2 . 9 0 1 4 . 7 0 31 . 9 3 8 1 . 9 4 1 8 . 5 7 1 8 . 2 0 33 . 186 2 . 2 0 2 3 . 15 2 3 . 0 6 34 . 66fc 2 . 5 3 24 . 24 2 8 . 15 35 . 6 1 3 2 . 8 3 2 5 . 0 5 32 . 6 5 36 . 0 8 5 3 . 0 7 2 6 . 0 6 3 3 . 3 0 36 . 0 1 7 3 . 10 26 . 8 6 3 5 . 4 1 36 . 0 8 5 3 . 2 0 27 68 3 7 . 2 0 36 . 0 8 5 3 . 2 8 3 2 . 6 1 3 8 . 9 5 35 . 9 5 0 3 . 3 3 3 3 . 5 5 4 1 . 9 2 35 . 7 8 2 3 .46 3 6 . 12 4 6 . 2 0 35 . 4 7 8 3 6 2 4 0 . 6 0 5 2 . 4 0 34 . 6 6 9 3 .81 4 6 . 12 5 6 . 6 9 33 .961 3 9 2 52 . 38 6 1 . 1 4 33 . 186 4 0 3 5 6 . 8 7 6 6 . 11 32 . 3 4 3 4 . 14 6 1 . 1 4 7 0 . 4 0 31 . 5 6 8 4 . .22 6 6 . 3 4 74 . 7 0 3 0 . 8 6 0 4 . . 2 9 7 0 . 6 8 7 6 . 7 1 3 0 . 4 8 9 4 . .32 74 . 8 6 7 8 . 4 5 3 0 . . 152 4 35 7 B . 5 5 8 2 . 0 5 2 9 511 4 . . 4 0 82 . 33 U • f f . 1 . 2 0 1 . 2 4 1 . 4 0 1 . 5 0 1 . 6 6 1 . 7 7 1 . 9 3 2 . 3 5 2 . 6 4 2 .71 2 . 7 5 2 .81 2 . 8 5 2 . 8 9 3. . 13 3 . 19 3 . 3 0 3 . 4 8 3. 6 7 3 . 8 6 3 . 9 7 4 . 0 8 4 . 19 4 . 2 7 4 . 34 4 . 4 0 4 . 45 V 9 g C d 0 . 0 1 ^ H ' C ' H 5 T(K) " e f t . 5 . 8 8 3 9 . 5 5 5 1 . 36 6 . 6 0 3 9 . 4 1 8 i . 4 4 7 . 8 0 3 9 . 1 1 1 1 . 5 6 9 . 9 4 38 . 7 3 5 i . 7 5 10 . 9 0 38 . 6 3 3 1 . 8 4 13 . 0 0 38 5 9 9 2 . 0 0 18 . 3 0 38 . 7 7 0 2 . 3 8 2 3 . 1 1 38 . 9 7 5 2 . 6 8 25 . 3 0 3 9 0 0 8 2 .81 26 . 0 5 3 9 . 0 7 7 2 8 5 2 7 . 16 3 9 0 7 7 2 .91 2 7 . 8 4 3 9 0 0 8 2 . 9 5 32 . 7 0 38 7 3 5 3 . 18 3 3 . 3 0 38 8 7 2 3 . 2 2 3 6 . 7 0 38 5 9 9 3 . 3 7 4 0 .64 38 0 1 9 3 .52 46 0 0 3 7 . 201 3 7 0 52 4 0 36 0 7 5 3. 8 9 5 6 8 7 3 5 . 154 4 . 0 0 6 1 . 2 6 34 . 3 3 5 4 . 10 6 6 . 2 8 3 3 . 4 14 4 . 21 7 0 6 2 3 2 . S 9 6 4 . 2 9 74 . 98 31 . B 11 4 . 3 7 78 9 4 31 . 0 9 5 4 . 4 3 82 2 8 3 0 . 481 4 . 48 M"0.91 C d 0 0 9 [ H ( C i>P0. T(K) *« U e f t . 4 . 4 0 88 . 6 3 4 1 . 7 7 4 . 6 4 8 7 . 4 5 4 1 . 8 2 6 .OO 7 9 . 188 1 . 9 5 7 . 2 3 7 3 . 6 2 6 2 . 0 6 9 . 35 6 7 . 2 2 6 2 .24 1 0 . 3 0 6 5 . 0 9 2 2 . 3 2 1 2 . 6 5 6 0 . 9 7 8 2 . 4 8 1 7 . 8 0 5 5 . 4 1 6 2 .81 2 2 . 6 1 5 2 . 2 9 2 3 0 8 2 7 . 5 2 5 0 . 0 8 2 3 . 32 3 2 . 3 3 4 7 . 7 2 1 3 .51 3 3 . 2 5 48 140 3 . 58 3 5 . 9 3 4 8 . 2 6 0 3 . 72 4 0 . 5 0 4 5 . 4 3 4 3. 8 4 45 9 3 4 3 . 5 3 0 4 . 0 0 5 2 . 2 5 4 1 . 5 1 1 4. 16 5 6 . 6 9 3 9 8 7 3 4 . 2 5 6 0 . 9 7 38 6 16 4 . 34 6 6 . 1 1 3 7 . 2 0 7 4 . 44 7 0 . 6 8 36 101 4 . 52 7 4 . 8 6 3 5 . 0 7 3 4 . 58 7 8 . 6 1 3 4 . 159 4 . 6 3 8 2 . 11 3 3 . 2 4 4 4 . 6 7 PART A, Continued 0 . 7 3 C d 0 . 2 7 [ H ( c « H » 5 p ° i ) » T(K) *» V C f f . 6 . 12 149 .914 2 .71 6 .90 137 .917 2 .76 7 .70 125 . 869 2 .78 9 .94 106 .886 2 .91 10 .99 101 .216 2 98 13 . 10 91 .396 3 .09 18 .24 77 .271 3 .36 23 02 69 .577 3 58 27 .95 64 .4 14 3 .79 32 . 79 60 .263 3 .98 32 93 60 .466 3 .99 35 79 58 .289 4 08 40 22 55 301 4 22 45. 55 52. 214 4 . 36 51 . 90 48 873 4 . 50 56. 75 46. 646 4 . 60 61 . 08 44 . 773 4 . 68 66. 11 42. 748 4. 79 70. 62 4 1 . 077 4.. 82 74 . 86 39. 559 4 . 87 78. 33 38. 394 4 . 90 82 . 28 36 . 977 4 . 93 0 . 5 3 C d 0 . 4 7 [ H ( c » H » > p ° j ] i T(K) *. "•If. 4 . 23 39 .759 1 . 16 4 . 48 39 759 1 . 19 6 14 39 486 1 .39 T. 59 39 .008 1 .54 9. 42 38 .701 1 .71 10 62 38 .668 1 .81 17 95 38 .872 2 36 22 50 39 . 179 2 67 27 .77 39 .213 2 95 32 80 38 .940 3 20 33 .22 38 .975 3 22 35 .97 38 .701 3 34 40 .62 38 . 156 3 52 46 . 15 37 .337 3. 71 52 .42 36 . 245 3. 90 56 .81 35 . 324 4 . 01 66 .28 33 .483 4 . 21 74 .86 31 .947 4 . 37 78 .56 31 . 164 4 . 47 82 .33 10 .446 4 . 48 PART B. M n [ H ( C « H s ) P O , ] 2 (Form II) 145 T(K) *» .4. 56 88. 752 1. 80 6. 45 85. 653 2 . 10 7. 72 83. 663 2 .27 B . 58 82 . 213 2 .38 8. 75 80. 798 2 .57 10. 61 79. 349 2 .59 12. 95 76. 787 2 82 14 . 95 74. 63 2 99 18. 34 71 . 732 3 24 22 98 68 . 126 3 54 28 38 64. .52 3 83 32 57 62 329 4 03 33 29 61 992 4 . 06 35 .90 60 . 172 4. . 16 40 .37 57 .645 4 .31 45 .83 54 .376 4 .46 51 .64 51 . 140 4 .59 56 .78 48 612 4 .70 61 .02 46 .422 4 . 76 66 .00 44 .636 4 .85 70 .62 42 .816 4 .92 76 .71 40 .659 4 .99 82 . 17 38 .839 5 .05 PART C . H n ^ C c y H C C H j P O j j [ F o r m 1(B)] Mn[H(C,Hj)PO,], T(K) *» V e f f . 4 42 6 1 .03 1 1 . 47 6 . 2 1 56 .649 1 68 7 . 59 54 .693 1 82 8 . 58 53 . 244 1 91 9 . 35 52 .266 1 93 10 .68 50 .817 2 08 12 . 70 49 738 2 . 25 14 .90 48 . 524 2 . 4 18 . 20 47 . 2 1 2 .62 22 .90 45 . 827 2 . 90 27 .88 44 . 782 3 . 16 32 . 50 43 . 906 3 . 38 33 40 43 . 737 3 .42 3S .00 43 .029 3 . 52 40 . 40 42 . 052 3 .69 46 . OO 40 . 670 3 .87 52 . 25 39 254 4 .05 56 . 58 38 . 108 4 . 15 60 44 37 . 164 4 . 24 65 . 94 36 . 085 4 . 36 70. 34 35 074 I . 44 74 . 02 34 . 332 4 5 1 76 . 60 33 . 86 4 . 55 82 . 1 1 32 . 68 4 . 63 0 . 9 9 C d 0 . 0 1 [ H ( C i H » ' P O j j TOO *• U • It. 4 .62 89 528 1 . 82 6 . 18 81 .752 2 .01 7 . 16 77 04 4 2 . 10 7 .95 73 .429 2 . 16 8 .97 71 .745 2 .27 10 01 68 .210 2 .34 12 .02 64 .083 2 .48 13 95 61 .467 2 .62 16 65 56 .332 2 .74 19 .37 56 .272 2 .95 21 68 54 .703 3 .08 26 87 51 .906 3 . 34 30 62 50 .098 3 50 35. 18 48 .052 3 68 39. 62 46 .4 14 3. 83 45. 04 44 .333 4 . 00 50. 61 42 .287 4 . 14 56. 40 40 .855 4 . 29 60. 60 39 .490 4 . 37 65. 90 38 .092 4 . 48 70. 10 36 .898 4 . 55 76. 10 35 499 4 . 65 81. 60 34. . 203 4 . 72 PART C, Continued M n 0 i 9 5 C d 0 > 0 5 [ H ( C , H , ) P O , ) , T(K) 1 hn "elf. 4 . 22 136 .188 2 . 14 5 . 00 123 I.820 2 . 23 6 . 13 110.4 12 2 33 7. 22 102 ! . 166 2 43 7. 97 9 6 . 521 2 48 8. 95 91 . 358 2 56 9 .95 8 7 . 235 2 .63 I t , .73 8 1 . 070 2 76 13 .37 75 907 2 85 16 .73 6 9 . 704 3 .05 19 .56 6 5 . 099 3 . 19 21 .38 6 3 . OB 4 3 .28 26 .70 57 . 855 3 .51 30 .68 5 5 . 292 3 .68 35 .20 52 . 396 3 .84 39 .56 50 . 093 3 .98 44 .70 4 7 . 567 4. . 12 51 .27 44 . 893 4 .29 56 .60 42 . 999 4 .41 60 .90 4 1 . 476 4 .49 65 .80 3 9 . 841 4 .58 70 25 38 . 467 4 .65 76 .38 36 . 685 4 .73 81 .78 35 . 273 4 .80 M n 0 9 2 C d 0 . 0 8 l H t c « H ' , P O j J ' T(K) *» " • f l . 4 .47 139 498 2 23 4 .55 137 .341 2. 24 5 .48 122 .699 2. .32 6 .58 11 1 .311 2 42 7 40 104 .632 2 .48 8 . 17 98 059 2 .53 9 32 92 356 2 .62 10 . 12 88 .556 2 .68 12 .21 60 .398 2 .80 13 89 75 .558 2 .90 16 40 70 .676 3 .04 19 23 66 325 3 . 19 21 80 62 . 542 3 .30 26 75 58 . 189 3 53 30. 70 55 465 3 69 35 56 52 .536 3 87 39. 51 . 50, .258 3 .99 44 . 88 47. 574 4 . 13 51 . 21 44 931 4 , .29 56 . 63 43 018 4 . 41 60 . 91 41 . .513 4 , ,50 65 88 39 886 4 58 70. 34 38 .504 4 , 65 76. 49 36 632 4. 73 81 . 78 35 208 4 . 80 0 . 8 5 C d 0 . 1 5 [ H ( C , Hj J P O , ] , M n 0 . 5 2 C d 0 . 4 8 ^ H ( C « H s ) P O , T(K) "elf. T(K) * B "•!!. 3 54 260 .477 2 .72 4 .21 491.346 4.07 4 . 9 0 227 .329 2 .98 6 .50 351 .89 4 . 28 6 . 10 206 .539 3 . 17 7 . 40 314.321 4.31 7 . 2 5 187 .7 16 3 .30 8 . 37 289.86 4 . 40 7 .88 177 .768 3 .35 9 . 18 2 70.304 4 . 45 9 . 0 6 165 .458 3 .46 10 .06 251 .519 4 . 50 9 . 9 5 156 .440 3 .53 1 1 . 88 222 . 15 4 . 59 11.81 140 .802 3 .65 12 . 33 214.86 4 . 68 13.71 129 . 459 3 .77 14 .21 192.781 4 .68 16.32 115 .717 3 .89 17 .22 165.856 4 . 78 19.26 105 .304 4 . 0 3 19 .62 150.375 4 . 86 2 1 . 18 99 .078 4 . 10 21 . 13 149.096 5 .02 26 46 91 .026 4 .39 26 .75 1 17 .783 5.02 30.31 79 .217 4 .38 30 .57 105.515 5.08 34 .81 72 .597 4 .50 35 . 17 94.07 1 5.14 3 9 . 3 6 67 .838 4 .62 39 .45 85 . 96 5.21 44 .65 61 .682 4 .69 44 .88 77.829 5. 29 5 0 . 8 0 56 .494 4 .79 51 , .03 70.469 5.36 5 5 . 9 8 52 . 7O0 4 .86 56 . 4 1 64.723 5 . 40 6 0 . 16 49 . 874 4 . 90 60. 60 61 .498 5 .46 6 5 . 5 0 4 7 . 440 4 .99 65. 80 57.433 5.50 6 8 . 8 5 4 5 . 509 5 .01 70. 3 54.138 5.52 7 3 . 8 2 43 . 039 9 .04 76. 3 50.913 5.57 S O . 92 4 0 . 462 S . 12 81 . 4 47 .619 5.57 90. 32 43.554 5.61 98 . 82 40. 26 5.64 1 Molar S u s c e p t i b i l i t y ( x m ) are i n 1 0 3 cm 3 mol" 1 ; Magnetic moments U e f f > are i n B.M.. S u s c e p t i b i l i t i e s are per mole manganese. 

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