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On the kinetics and chemistry of some reactions of phosphonitrilic derivatives Stewart, Charles John 1970-12-31

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ON THE KINETICS AND CHEMISTRY OF SOME REACTIONS OF PHOSPHONITRILIC DERIVATIVES  by CJ.  Stewart  B.ScfHons.), U n i v e r s i t y of B r i t i s h Columbia, 1967  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE  i n the Department of Chemistry  We accept t h i s t h e s i s as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA October, 1970  In p r e s e n t i n g t h i s t h e s i s  in p a r t i a l  f u l f i l m e n t o f the requirements  an advanced degree at the U n i v e r s i t y of B r i t i s h C o l u m b i a , I agree the L i b r a r y  s h a l l make i t f r e e l y  available for  I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e  r e f e r e n c e and copying o f t h i s  It  i s understood that copying o r  thesis  permission.  Depa rtment The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada  or  publication  o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my written  that  study.  f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department by h i s r e p r e s e n t a t i v e s .  for  ABSTRACT  The k i n e t i c parameters i n a c e t o n i t r i l e of the n u c l e o p h i l i c substitution reaction: N_P_C1. + KCNS  -> N_P_C1 NCS + KC1  5 6 b  have been determined. mole"  1  5  C 5 b  Tlie Arrhenius a c t i v a t i o n energy i s 15.5 ± 5 Kcal  and the common logarithm of the pre-exponential factor i s 10.2 ± 3.  The r e a c t i o n i s f i r s t order i n each reagent and i s probably b i m o l e c u l a r . Comparison with s i m i l a r r e a c t i o n s i n d i c a t e s a lone p a i r e l e c t r o n donation from the nitrogen to the phosphorus atoms of the r i n g . The compound, N^P^(NMe )gHCuClg was prepared by the r e a c t i o n 2  of tetrameric p h o s p h o n i t r i l i c dimethylamide with copper (II) c h l o r i d e i n butanone.  The i n f r a - r e d spectrum i n d i c a t e s that the copper atom i s  bound to one r i n g nitrogen atom, and the proton to the opposite nitrogen atom.  The r i n g i s found to be too small to allow c h e l a t i o n of the  copper atom. The s a l t , N P ( N M e ) C u C l C u C l " was prepared by the dehydro+  6  6  2  12  2  halogenation of N ^ P ^ ( N M e ) H C l C ^ C l g . 2  The hydrochloride was prepared  by the r e a c t i o n of hexameric p h o s p h o n i t r i l i c dimethylamide (H.P.D.) with ' copper (II) c h l o r i d e i n the reducing solvent butanone.  The s a l t was  also produced by the r e a c t i o n of H.P.D. with an equimolar mixture of copper (I) c h l o r i d e and copper (II) c h l o r i d e i n a c e t o n i t r i l e . Chemical and magnetic studies on the s a l t showed i t to have one copper (II) atom per molecule.  The x-ray c r y s t a l s t r u c t u r e showed the  copper (II) atom to be i n a d i s t o r t e d square pyramidal environment, bonded  to four r i n g n i t r o g e n and one c h l o r i n e atom. The s a l t contains the f i r s t known example of the C u C ^ " anion. o  This i s l i n e a r with a Cu-Cl bond length of 2.11A.  The anion i s also  one of the few examples of a f i n i t e species containing a two co-ordinate copper (I) atom. The i n f r a - r e d spectrum o f the s a l t was very s i m i l a r to that of the parent H.P.D.  The main difference was i n the frequencies of the  s t r e t c h i n g modes of the phosphorus nitrogen r i n g bonds; which i s consistent with copper c h e l a t i o n . Conductiometric and a n a l y t i c a l studies showed that the s a l t does not r e t a i n the form N..P,.(NMe„), CuCl CuCl„ +  0  O  O  I. 1/  <i  the l i m i t i n g molecular conductance 377 ± 10 Ohms consistent with a 1:1 e l e c t r o l y t e .  in acetonitrile solution; -1  being too large to be  - i i i -  TABLE OF CONTENTS  T i t l e Page Abstract  i  Table of Contents  i i i  L i s t of Tables  v  L i s t of Figures  vi  Acknowledgement  vii  Chapter One - General Introduction  1  Chapter Two - K i n e t i c Studies of N u c l e o p h i l i c S u b s t i t u t i o n i n Phosphonitriles  3  - Materials  6  - Preparation  7  - Apparatus  -  7  - Procedure  10  - Kinetics  11  - Discussion  28  Chapter Three - Metal Halide D e r i v a t i v e s o f Phosphonitriles  36  - Introduction  36  - The Reaction of Tetrameric P h o s p h o n i t r i l i c Dimethylamide (T.P.D.) with Copper (II) C h l o r i d e  41  - The Preparation of T . P . D .  41  - The Preparation of N P ( N M e ) H C u C l 4  - Discussion  4  2  g  3  48 49  - iv -  Chapter Four - The Preparation of a P h o s p h o n i t r i l i c Complex Containing a Chelated Copper  52  - The Preparation of Hexameric P h o s p h o n i t r i l i c Dimethylamide (H.P.D.)  52  - The Reaction of H.P.D. with Copper (II) Chloride  53  - Reactions i n Butanone  53  - Reactions i n A c e t o n i t r i l e  60  - Reaction of Copper (II) Chloride with H.P.D.  60  - Reaction of Copper (I) C h l o r i d e with H.P.D.  61  - Reaction of Copper (I) C h l o r i d e and Copper (II) Chloride w i t h H.P.D.  64  - Discussion  65  Chapter Five - - P h y s i c a l Studies of N P ( N M e ) C u C l f i  6  2  1 2  2  69  3  -....Introduction, and Summary  . . .  - The C r y s t a l Structure of N P ( N M e ) C u C l 6  &  2  1 2  2  6  6  2  1 2  2  - Studies on N,P,(NMe_),„Cu_Cl, i n S o l u t i o n D O  - Quantitative  Z  1Z  3  79 81  J  Z  Ionic A n a l y s i s  82  - Conductance Studies  . 8 2  - Magnetic Measurements of N,P,(NMe_),„Cu_Cl„ O  References  70  3  - The Infra-Red Spectrum of N P ( N M e ) C u C l  69  0  l  lz  I  86  Z> 90  - V -  LIST OF TABLES  I  K i n e t i c Parameters of S u b s t i t u t i o n Reactions of  4  Phosphonitriles II  The Second Order Rate Constants at Various Temperatures  28  III  P h o s p h o n i t r i l i c A d d i t i o n Compounds  37  IV  pKa Values for Some Phosphonitriles  V  Infra-Red Spectra of N ^ f N M e ^ g and  VI  Infra-Res Spectra of  VII  Elemental A n a l y s i s of H.P.D. Copper Complex  N  p 6  6  (NMe ) 2  1 2  39-40 (NMe ) HCuCl 2  g  and N P (NMe ) C u C l fi  6  2  1 2  2  43  3  3  54 58  o  VIII  Bond Length (A) and Valency Angles (Degrees), with Standard Deviations i n Parenthesis  73  IX  Actual and Predicted Bond Lengths  74  X  I n t r a Molecular Distances  XI  L i m i t i n g Conductance of Some S a l t s i n A c e t o n i t r i l e at 25°C  84  XII  Diamagnetic S u s c e p t i b i l i t i e s  88  . 7 8  - vi LIST OF FIGURES 1.  Conductivity C e l l  2.  Graph of Temporary Thermal Effect at 8.8°C  12  3.  Graph for C a l c u l a t i o n of S u b s t i t u t i o n Rate Constant at 25°C  14  4-11  9  P l o t s of Isothiocyanate  S u b s t i t u t i o n Reactions at 8.8°C  15-22  12.  Graph for C a l c u l a t i o n of S u b s t i t u t i o n Rate Constant at 8.8°C  23  13.  Graph for C a l c u l a t i o n of S u b s t i t u t i o n Rate Constant at 0.9°C  24  14.  Graph for C a l c u l a t i o n of S u b s t i t u t i o n Rate Constant at 40.2°C  25  15.  Arrhenius A c t i v a t i o n Energy Graph  16.  The Structure of P^MegHCuClg (Exocyclic Groups Omitted)  38  The Infra-Red Spectrum of N.P.(NMe„)  44 - 45  17(a).  .  .26  z  4 4  '  0  o  17(b).  The Infra-Red Spectrum of N^P^(NMe^)gHCuCl^  46-47  18(a).  The Infra-Red Spectrum of N , P . ( N M e _ )  55-56  DO  18(b).  The Infra-Red Spectrum o f  (NMe ) 2  10  1/  £.  C u 1 2  2  19.  P h o s p h o n i t r i l i c Ring of N P ( N M e ) C u C l  20.  General View of the N P ( N M e ) C u C l  21.  6  6  6  6  2  2  1 2  +  1 2  C 1  +  3 Anion  5 7  71  i o n , Showing the  Copper (II) Atom Co-Ordination  72  Conductance P l o t of N.P,(NMe„),„Cu„Cl_  85  "  5 8  - V l l -  ACKNOWLEDGEMENT  I wish to record my gratitude  to  Professor N . L . Paddock under whose guidance and i n s t r u c t i o n I completed t h i s work.  C HA P TE  R O N E  GENERAL INTRODUCTION  P h o s p h o n i t r i l i c d e r i v a t i v e s contain the formally unsaturated II  repeating, u n i t - ^ P ^ ) are p o s s i b l e .  f o r which several types of chemical reactions  Among these are n u c l e o p h i l i c s u b s t i t u t i o n of the ligands (X)  which has been e x t e n s i v e l y s t u d i e d , mainly from a preparative point of view.  A d d i t i o n reactions e i t h e r to the double bond or of a donor-acceptor  type have also been s t u d i e d , but not so e x t e n s i v e l y . Since n i t r o g e n i s more electronegative than phosphorus, binding electrons tend to accumulate near i t .  This causes the phosphorus and  nitrogen atoms to be r e s p e c t i v e l y e l e c t r o p h i l i c and n u c l e o p h i l i c . Of the various types of reactions at the phosphorus and nitrogen centres which could occur, two are studied i n t h i s t h e s i s : (1)  acceptor p r o p e r t i e s t y p i f i e d by n u c l e o p h i l i c s u b s t i t u t i o n ' at phosphorus by the thiocyanate anion,  (2)  and donor p r o p e r t i e s , through the c h e l a t i o n o f copper (II) by n i t r o g e n .  L i t t l e information e x i s t s about the k i n e t i c s o f n u c l e o p h i l i c s u b s t i t u t i o n at phosphorus i n p h o s p h o n i t r i l e s .  This may, i n p a r t , be due  to the d i f f i c u l t y of studying r e a c t i o n rates with a molecule having many  -  p o t e n t i a l attack s i t e s .  2  -  Therefore, i t was f e l t that a k i n e t i c study  would be worthwhile, because i t would give some information i n a f i e l d where few facts are known.  A l s o , i t might throw some further  l i g h t on  the nature o f the ir-bonding systems i n p h o s p h o n i t r i l i c compounds. For t h i s work the i n i t i a l r e a c t i o n of potassium  thiocyanate  with t r i m e r i c p h o s p h o n i t r i l i c c h l o r i d e was s t u d i e d . N,P_C1, + KCNS -> KC1 + N_P_C1_NCS 5 5 o 5 5 b The r e a c t i o n was found to be bimolecular and i t s r a t e constant and a c t i v a t i o n energy were determined. The study of the preparation o f t r a n s i t i o n metal complexes of p h o s p h o n i t r i l e s i s also a f i e l d i n which very l i t t l e information i s available.  Metal halides have been made to react with p h o s p h o n i t r i l e s ,  but the r e s u l t i n g complexes have, at most, one r i n g nitrogen bonded to the metal. In t h i s work, two copper complexes have been prepared; '"N P (NMe ) HCuCl 4  4  2  8  s  and N P ( N M e ) 6  6  2  probably has a s t r u c t u r e s i m i l a r to  1 2  Cu(II)Cl C u ( I ) C l . 2  The former  N P (Me)gH CuCl^ with one nitrogen 4  4  bound to a proton and one bound to the C u C l ^  -  group.  Determination of  the c r y s t a l s t r u c t u r e of the complex o f the hexameric dimethylamide showed i t to contain a unique p o r p h y r i n - l i k e framework i n which copper  (II)  i s co-ordinated to four endocyclic nitrogen atoms i n the same molecule with the p h o s p h o n i t r i l e a c t i n g as a macrocyclic l i g a n d .  The d e t a i l e d  geometry shows evidence o f competitive donor-acceptor i n t e r a c t i o n s which are compatible with i r - e l e c t r o n theory.  - 3 -  C HAP TE R T W 0 KINETIC STUDIES OF NUCLEOPHILIC SUBSTITUTION IN PHOSPHONITRILES  P h o s p h o n i t r i l i c h a l i d e s undergo many n u c l e o p h i l i c s u b s t i t u t i o n reactions.  T h e i r reactions with primary and secondary amines, a l c o h o l s ,  phenols, h a l i d e i o n s , and the thiocyanate i o n have a l l been reported. These r e a c t i o n s are among the most important and i n t e r e s t i n g i n phosphon i t r i l i c chemistry, and i t i s therefore  s u r p r i s i n g that there e x i s t s  almost no q u a n t i t a t i v e information concerning t h e i r k i n e t i c s .  Since  the rates of s u b s t i t u t i o n reactions would be expected, as a f i r s t approximation, to depend on ir-electron density at the phosphorus atom, an increase i n k i n e t i c information should therefore understanding of the ir-molecular o r b i t a l s . already been d o n e ^ ^ \  lead to a greater  Some q u a n t i t a t i v e work has  and the r e s u l t s are summarized i n Table I .  However  the mass of k i n e t i c information i s q u a l i t a t i v e , dealing mainly with the types of observed o r i e n t a t i o n p a t t e r n s . The object of t h i s work has been to obtain q u a n t i t a t i v e k i n e t i c data on n u c l e o p h i l i c s u b s t i t u t i o n i n t r i m e r i c p h o s p h o n i t r i l i c c h l o r i d e . The r e a c t i o n studied was that producing the mono-substituted d e r i v a t i v e . I t should be n o t i c e d that p h o s p h o n i t r i l i c h a l i d e s o f f e r many d i f f e r e n t r e a c t i o n s i t e s to s u b s t i t u t i o n and therefore,  f o r any r e a c t i o n there e x i s t  s e v e r a l steps. A t t e n t i o n was concentrated on the f i r s t step, because a l t e r n a t i v e paths are open to the second s u b s t i t u e n t .  Because of the  Table I Compound  Reagent  (NPC1 )  3  Cl~  (NPC1 )  4  CNPC1 )  S  (NPC1 )  6  (NPC1 )  3  2  2  2  2  2  Aniline  K i n e t i c Parameters of S u b s t i t u t i o n Reactions of Solvent  Temp.  Acetonitrile  0-35°C  Ethanol-Benzene  Ethanol Piperidine  Parameters log A E •(Kcal/mole)"  Ref  1  1 Q  18.3  12.1  (3)  II  16.3  12.0  it  it  17.0  11.9  ti  it  16.3  11.2  ti  34.5°C it  Toluene  Phosphonitriles  0°C  k  2  = 148 x 10" t o o l e " s e c "  k  2  = 0.01 x 10 ~ £ m o l e ~ s e c ~  k  2  = 2.2 x 10" Jlmole" sec~  3  1  3  3  1  1  1  1  (1) 1  it  (2)  I  I  - 5 -  equivalence of the c h l o r i n e atoms i n the parent p h o s p h o n i t r i l e , the f i r s t step can only go to form one d e r i v a t i v e .  P J  + N \  However, the mono-substituted d e r i v a t i v e has three non-equivalent  sites  for n u c l e o p h i l i c attack which cannot be d i s c r i m i n a t e d i n a s i n g l e experiment.  N P  N  Geminal  N  C i s non-geminal  Trans non-geminal  The r e a c t i o n used was the n u c l e o p h i l i c displacement of a c h l o r i n e atom on phosphorus by a thiocyanate i o n . P_N,C1, + NCS" + p N C1 NCS + C I ' C  The thiocyanate i o n was chosen because i t reacts more r a p i d l y than many other n u c l e o p h i l e s .  A l s o , w h i l e the mono-substituted d e r i v a t i v e has not  - 6 -  been i s o l a t e d , the  r e a c t i o n does go  N^P^CNCS)^ which has  been p r e p a r e d and  experiments showed t h a t there  i s a possible  completely  characterized  .  thiocyanate  Preliminary  a c o n v e n i e n t method o f f o l l o w i n g  p o s s i b l e because o f the c o n d u c t i v i t y o f the  Also,  group because i t has  i n t e r a c t w i t h t h a t o f the r i n g and  Finally,  substituted  the r e a c t i o n p r o c e e d s a t a s u i t a b l e r a t e .  i n t e r e s t i n the  ir-system which c o u l d of r e a c t i o n .  to produce the  thiocyanate  modify the  a  rate  the r e a c t i o n i s ion.  Materials:  T r i m e r i c p h o s p h o n i t r i l i c c h l o r i d e was c r y s t a l l i z a t i o n from benzene f o l l o w e d to a constant melting The  r e a g e n t was  c o n t a i n no  point.  examined by  tetrameric  by  sublimation  (113.5°C, l i t e r a t u r e i n f r a - r e d and  chloride.  p h o s p h o n i t r i l i c c h l o r i d e was  s t o r e d at  B e f o r e the  ethanol  and  d i s t i l l a t i o n s o v e r the t o a dry-box.  I t was  s o l u t i o n s as w e l l by  and  114°C - - ) . (  r e a c t i o n s , the  10  )  found t o  trimeric  was  p u r i f i e d by  repeated 100°C^^.  d r i e d by r e p e a t e d washings w i t h r e a g e n t  150°C. d r i e d over calcium  i t under r e f l u x f o r s e v e r a l h o u r s .  d i s t i l l a t i o n under n i t r o g e n  112.8 ^  then d r i e d i n vacuo at  Reagent grade a c e t o n i t r i l e was heating  recrystallization  d r i e d i n vacuo f o r t h r e e hours a t 50°C.  Potassium c h l o r i d e was grade acetone and  and  re-  mass s p e c t r o m e t r y and  Reagent grade p o t a s s i u m t h i o c y a n a t e r e c r y s t a l l i z a t i o n from 95%  p u r i f i e d by  T h i s was  followed  on to p h o s p h o r i c a n h y d r i d e .  found important to e x c l u d e oxygen from At  t h i s s t a g e , i t was  by  by  After  a c i d a n h y d r i d e , the a c e t o n i t r i l e was  as m o i s t u r e .  oxide  two  transferred the  checked f o r dryness  e l e c t r o c o n d u c t i v i t y measurement on a Wayne K e r r U n i v e r s a l  Bridge  B221A.  I f the s p e c i f i c conductance was above the a r b i t r a r i l y set  of 1.9 x 10~ Ohm 6  -1  limit  ( l i t e r a t u r e s p e c i f i c conductance I O " O h m " ^ - ' ) , 8  1  12  i t was r e d i s t i l l e d . (7*) Due to the warnings of A u d r i e t h  v  ' about the i n s t a b i l i t y of  the isothiocyanate d e r i v a t i v e s , a l l the p u r i f i e d materials and d r i e d apparatus were handled i n the dry box. Preparation: The preparation of the r e a c t i o n s o l u t i o n s was done by clean dry p i p e t t e s i n the dry box.  A quantity of reagent was placed i n a  weighing b o t t l e which was then removed from the box and weighed.  This  was returned to the box and a s u i t a b l e quantity of the reagent was added to a c o n i c a l f l a s k .  Both the f l a s k and b o t t l e were weighed, and  the f l a s k was returned to the dry box. f l a s k was removed and weighed again.  A c e t o n i t r i l e was added and the The concentration was then c a l c u l a t e d  i n u n i t s of moles per gram of s o l u t i o n . This procedure was used because the pipettes d i d not d e l i v e r reproducible volumes.  A l s o , i t was more accurate to use weight measure-  ments which do not vary with temperature.  The r e s u l t s were changed l a t e r  i n t o moles per l i t r e using the d e n s i t i e s of solvent and s o l u t e .  ' Apparatus:  1  Two constant temperature baths were used during the experiment. The one for 25°G v a r i e d no more than ± 0 . 0 1 C , and the other by 0  ± 0.02C° .  - 8 -  An e l e c t r o c o n d u c t i v i t y c e l l was constructed of the type shown i n Figure 1.  Because the electrodes were held i n place only by  t h e i r connecting w i r e s , utmost caution had to be exercised so as not to a l t e r the c e l l  constant.  The c e l l was c a l i b r a t e d with potassium thiocyanate at 25°C. F i r s t the background conductance due to potassium c h l o r i d e and a c e t o n i t r i l e was measured.  Next, an amount of thiocyanate s o l u t i o n with a known  concentration was added to the tared c e l l with a s y r i n g e , (a p i p e t t e gave non-reproducible r e s u l t s ) .  The t o t a l conductance was measured and the  background conductance was subtracted from i t .  The c e l l was then weighed  and the concentration was c a l c u l a t e d . The p l o t of thiocyanate concentration against thiocyanate conductance gave a curve upon which three e x c e l l e n t s t r a i g h t l i n e s could be f i t t e d :  = " 0.5307  C  C  s  k  'o.4497  8  ^ r k = 1.8 - 6 . 4  6 3  f o r k = 6.4 - 10.8  .'-  (2-1)  (2-2)  _ k - 2.974 0.3733  for k = 10.8 - 14.5  C = concentration KCNS x 1 0 - g m o l e " 6  ,  (2-3)  1  k = conductance x 10 *0hms 3  No s i g n i f i c a n c e i s attached to these l i n e s other than that they made the c a l c u l a t i o n of the concentration of thiocyanate easier and more accurate. The background conductance was small and never exceeded 1% of the lowest measured conductance.  I t was none the l e s s , not q u i t e steady  Figure 1 .  Conductivity C e l l  - 10 -  and a c o r r e c t i o n for i t was always a p p l i e d .  Procedure: The d i f f e r e n t k i n e t i c runs were c a r r i e d out using the same chemical procedures.  For a l l of them t h i s meant making reagent s o l u t i o n s  with known concentrations, e q u i l i b r a t i n g these s o l u t i o n s , mixing them, and then f o l l o w i n g the decrease i n thiocyanate concentration as a function of time. The reactant s o l u t i o n s were prepared i n the dry-box.  A few  m l . o f one stock s o l u t i o n were added to the c e l l which was then weighed. A 50 m l . f l a s k was treated i n the same way, using the other s o l u t i o n . The f l a s k was then replaced i n the dry-box and pure a c e t o n i t r i l e was added. A l l reactions were c a r r i e d out with 30 m l . of s o l u t i o n , and the f i n a l concentrations were v a r i e d by varying the amount of stock solutions.  Once the c e l l had been f i l l e d ,  i n t o the dry-box  i t could not be put back  because i t could not be sealed w e l l enough.  The two reactant s o l u t i o n s were then e q u i l i b r a t e d i n the constant temperature bath,  (usually 30 minutes).  The f l a s k was then  removed from the bath and i t s contents poured i n t o the c e l l . p o i n t , the clock and c o n d u c t i v i t y runs were s t a r t e d .  At t h i s  In a l l cases the  r e a c t i o n was followed u n t i l 20% of the thiocyanate had been used. the r e a c t i o n was f i n i s h e d , the f u l l c e l l was weighed.  Once  This gave the  amount of both r e a c t i o n s o l u t i o n s present, and from t h i s the concentrations could be c a l c u l a t e d .  11 -  When the two s o l u t i o n s were mixed, there was an unavoidable increase i n the temperature of one of the s o l u t i o n s which was caused by removing the s o l u t i o n from the bath by hand i n order to pour the solution.  This caused the i l l u s i o n of a sharp decrease i n thiocyanate  ion concentration.  That t h i s was an i l l u s i o n was i l l u s t r a t e d by  taking the conductance of an e q u i l i b r a t e d KCNS s o l u t i o n then pouring the s o l u t i o n i n t o an e q u i l i b r a t e d f l a s k .  A f t e r t h i s had e q u i l i b r a t e d , i t  was poured back i n t o the c e l l and conductance was measured as a function of time (Figure 2 ) .  A downward curye l e v e l i n g o f f at the o r i g i n a l value  w i t h i n one or two minutes, showed that what appeared to be a decrease i n concentration was i n fact a temperature e f f e c t .  Because many of the  experiments have concentration readings w i t h i n one minute of a d d i t i o n , t h i s curve i s superimposed on t h e i r concentration graphs.  Kinetics: The r e a c t i o n :  —  P N C1 3  3  6  + 6KCNS -> 6KC1 + P N ( N C S ) 3  3  6  f71  has been reported by R . J . A . Otto and L . F . A u d r i e t h  v  .  It has been  assumed for the present work that the r e a c t i o n takes place by a s e r i e s of i n d i v i d u a l and separate s u b s t i t u t i o n steps, therefore, the f i r s t r e a c t i o n w i l l be: P,N_C1 '+ KCNS -* P_N_C1 NCS + KC1 C  I f t h i s r e a c t i o n i s f i r s t order i n each reagent, then:  76.6  7 6.5O > >-t CO 3 rt  n co  n o  7 6.4  O  76 5  3  o  CD 3 rt >-i ja rt  o  7 6.2  H'  o  o 3  O  O  I  76 7 o  3  o  - 76.6  0  o o o ° o  o  o  o  o  o  o  o  75.9 0  2  4  5  6  7  8  9  Time*(Minutes ) -1  Figure 2.  Graph of the Temporary Thermal Effect at 8.8°C  70  77  12  -  -d[KCNS]  The  initial  rate,  the product  r"d[KCNS] ^  of the i n i t i a l  [ P „ N . C l J . and 3 3 6 1  L  If  J  L  t  J  will  when  [P^NgClg]  (2-4)  to  c o n c e n t r a t i o n s o f t h e two r e a c t a n t s ,  -d[KCNS3^  s  k  rp3N5Cl6].[KCNS].  be omitted  against  a l s o be true  [P,N,ClJ  ...^^j  for a plot  i s constant.  from a l l f u t u r e  with  [KCNS]  equations.) then a p l o t  constant w i l l  -d[KCNSj o f " d [ ^ N S ^ [p  [ K C N S  ]-1  -d[KCNS]  equations  (2-5)  N  of be l i n e a r .  ci6]-1 against  [KCNS]  T h i s r e s u l t s i n two e q u a t i o n s w h i c h m u s t  -d[KCNS]  order.  =  k  [P3N3Cl6]  a  (2-6) and (2-7)  will  (2-6)  k [ K C N g ]  ( 2  _  y )  p r o d u c e two c o i n c i d e n t a l  l i n e s with s l o p e . k o r i g i n a t i n g at the o r i g i n . The r e a c t i o n r a t e  [KCNS]  Cl6]  then be d i r e c t l y p r o p o r t i o n a l  m  w  be s a t i s f i e d f o r a r e a c t i o n o f second  straight  3 N 5  the r e a c t i o n i s of the second o r d e r ,  This  Therefore,  p  k [ K C N S ] [  1  * i *w i l l  "d^KCNS^-[KCNS]~1 d  -  [KCNS]..  r  (The s u b s c r i p t  =  13  against  of a s t r a i g h t The  time. line  ^^t^^—  This plot  at small  initial  knowing t h e q u a n t i t i e s has been determined  1  C a n  ^  e  d e t e r m :  should r e s u l t  '-  from a p l o t  n e d  i n a good  of  approximation  time.  concentrations of both reagents  can be c a l c u l a t e d  of reagents used i n t h e i r p r e p a r a t i o n .  for several temperatures,  then the  Once k  Arrhenius  ( c o n t i n u e d on page  27)  73  Time-(minutes)~ Figure 5.  1  P l o t of isothiocyanate s u b s t i t u t i o n r e a c t i o n at 8.8°C  O 13 O I n i t i a l KCNS cone. 14.314 x 10" moles-g" 6  Initial P N C1 3  3  1  cone. 13.32(5 x 1 0 " moles-g' b  6  00 I  12  o  o  11 0  3  8 Time-(minutes)"  Figure 7.  1  P l o t o f isothiocyanate s u b s t i t u t i o n r e a c t i o n at 8.8°C  10  11  12  Time.(minutes)~ Figure 8.  P l o t of isothiocyanate s u b s t i t u t i o n r e a c t i o n at 8.8°C  Figure 9.  P l o t of i s o t h i o c / a n a t e s u b s t i t u t i o n r e a c t i o n at 8.8°C  Time-(minutes) Figure 10.  _1  P l o t of isothiocyanate s u b s t i t u t i o n r e a c t i o n at 8.8°C  Figure 12.  Graph for c a l c u l a t i o n of s u b s t i t u t i o n  rate constant at 8.8°C  - 27 -  a c t i v a t i o n energy, E , can be c a l c u l a t e d from equation  (2-8).  Si  ln k = -  E  + ln A  where A i s the frequency or pre-exponential  ( 2  " ^ 8  factor.  Equations (2-6) and (2-7) were thoroughly checked at 25°C (Figure 3 ) .  This graph gave a good approximation to a s t r a i g h t l i n e  beginning at the o r i g i n .  This proves that the r e a c t i o n :  KCNS + P,NC1, -> P,N,Cl NCS + KC1 6 o 6 5 b r  i s second order i n both reagents and, therefore,  "  ^  d [ K  S ]  that:  = k[KCNS] [ P N C 1 ] 3  3  (2-4)  6  C h a r a c t e r i s t i c p l o t s of thiocyanate i o n concentration against time i n minutes are shown i n Figures 4 - 11.  At small time, a s t r a i g h t  l i n e approximation was found which was used to c a l c u l a t e —ft{rcCNS]—, A p l o t of - £ ^ l d  K  s  against  Figure 12 for the r e a c t i o n at 8.8°C. equations  [ P N C 1 ] [KCNS] i s shown on 3  3  6  Figures 3, 13 and 14 are p l o t s o f  (2-6) and (2-7) for 2 5 ° , 0.9° and 40.2°C. The study showed the r e a c t i o n to be second order, being f i r s t  order i n each reagent.  Its second order r a t e constant  temperatures i s given i n Table I I .  (k)  at various  The Arrhenius a c t i v a t i o n energy  was 15.5 ± 0.5 Kcal/mole and the log^g of the pre-exponential factor was 10.2 ± 0 . 3 (Figure 15).  - 28 -  TABLE II  THE SECOND ORDER RATE  CONSTANTS AT VARIOUS TEMPERATURES Temperature ° C  k • [fc/mole-sec.]  _ 1  1  0.9  6.1 ± 0.3 x 10"  3  8.8  11.9 ± 0.4 x I O "  3  67  ± 5  x IO"  3  191  ± 10  x IO"  3  25 40.2  Discussion: The thiocyanate group i s an ambidentate ligand and can bond to an e l e c t r o p h i l e through e i t h e r o f i t s n u c l e o p h i l i c ends; i n f a c t , the thiocyanate anion reacts with t r i m e r i c p h o s p h o n i t r i l i c c h l o r i d e to produce the f u l l y s u b s t i t u t e d isothiocyanato d e r i v a t i v e . Several factors c h a r a c t e r i s t i c of the e l e c t r o p h i l e determine which atom w i l l bond.  These factors are mainly determined by the  e l e c t r o n i c environment of the e l e c t r o p h i l e , and i t s  stereochemistry.  Two sets of antibonding TT o r b i t a l s are l o c a l i z e d on the (131 sulphur atom  , and these can accept electrons from the e l e c t r o p h i l e .  This r e s u l t s i n a d d i t i o n a l s t a b i l i t y o f the s u l p h u r - e l e c t r o p h i l e bond. The thiocyanate d e r i v a t i v e i s formed i n groups that are able to back bond i n t h i s manner.  With the metals, the second h a l f of the second and  t h i r d t r a n s i t i o n s e r i e s such as Rh, Pd, Ag, Cd, I r , P t , Au, Hg, Te and (14") Pb a l l form metal-sulphur bonds  .  However, with smaller atoms such  as the metals o f the f i r s t t r a n s i t i o n s e r i e s :  C r , Mn, Fe, N i , Cu and  Zn, the b a s i c i t y of the n u c l e o p h i l e becomes i n c r e a s i n g l y important, and  - 29 -  they form metal-nitrogen bonds. No n u c l e o p h i l i c s u b s t i t u t i o n r e a c t i o n of an a l k y l h a l i d e with a thiocyanate has apparently ever produced an isothiocyanato d e r i v a t i v e and so r e l a t i v e l y small atoms can f i n d the p o l a r i z a b i l i t y of sulphur more a t t r a c t i v e than the high b a s i c i t y of n i t r o g e n .  However, with perita-  valent phosphorus, the bonding does occur through the  P 0 C1 2  3  4  + KSCN  C  S  l4  nitrogen.  P0C1 (NCS) 2  Knowing the element and i t s o x i d a t i o n number i s not i n i t s e l f s u f f i c i e n t information for p r e d i c t i o n of the type of bond which w i l l be formed.  The nature of the surrounding ligands has been shown to be a (17)  determining factor  j ir-electron withdrawing ligands reduce the e l e c t r o n  density at the e l e c t r o p h i l e , thus making i t a weaker nr-electron donor. The next determining factor has been shown to be s t e r i c .  The  +  isothiocyanato group can become l i n e a r by assuming the form (-NsC-S~). The thiocyanate on the other hand, i s always bent/S-C=N .  An example  of t h i s i s found when the non u-bonding l i g a n d d i e t h y l e n e t r i a m i n e , NH C H NHC H NH , gives the S-bonded complex [Pd(dien)SCN] . +  2  2  4  2  4  2  extremely bulky t e t r a e t h y l substituted  ligand,  gives the N-bonded complex [ P d ( E t d i e n ) ( N C S ) ]  The  (C H ) NC H NHC H N(C H ) , 2  +  4  5  .  2  2  4  2  4  2  5  2  For the phosphoryl  d e r i v a t i v e s i t seems u n l i k e l y that s t e r i c factors could have any effect. on the s u b s t i t u t i o n , and i n the f u l l y s u b s t i t u t e d  isothiocyanato-  (23) phosphonitrile  the substituent  groups are w e l l separated.  K i n e t i c studies have been done on phosphoryl compounds, but none have been reported which use the thiocyanate anion as the n u c l e o p h i l e . This l i m i t s the extent to which v a l i d comparisons can be made between  -. 30 -  the k i n e t i c s of the phosphoryl and the p h o s p h o n i t r i l i c series of compounds.  However, i t i s s t i l l p o s s i b l e to compare the base strength  preferences  of the phosphoryl groups with that of the p h o s p h o n i t r i l e .  S i m i l a r l y , for the p h o s p h o n i t r i l e s only very l i m i t e d information i s a v a i l a b l e which can be used as a comparison w i t h t h i s work. N u c l e o p h i l i c r e a c t i v i t i e s are mainly determined by the e l e c t r o n i c , s t e r i c , and s o l v a t i o n c h a r a c t e r i s t i c s of the r e a c t a n t s . I f s t e r i c and solvent effects  are ignored, then the r e a c t i v i t y of a  s e r i e s of s i m i l a r nucleophiles w i t h one e l e c t r o p h i l e can be c o r r e l a t e d from the equation:  log  Ji_ -  a  H + BP  (2-9)  o where:  k  = r a t e constant for s u b s t i t u t i o n with water  o  k  = r a t e constant for s u b s t i t u t i o n w i t h the nucleophile  P . = a function of the p o l a r i z a b i l i t y of the nucleophile H  = a function of the pKa o f the conjugate a c i d of the n u c l e o p h i l e ;  a and g are parameters associated e n t i r e l y w i t h the e l e c t r o p h i l i c sub(19) strate  v  .  I f , as i n the case of saturated carbon, p o l a r i z a b i l i t y i s  more important than b a s i c i t y , then the value of B w i l l be higher than that of a.  The r e a c t i v i t y w i l l then follow the p o l a r i z a b i l i t y f u n c t i o n ,  P, o f the n u c l e o p h i l e . The opposite has been found for the phosphorochloridates  where:'- '' 20  F" > HO" > C\.H 0" > EtOH > C H S " > CH_C0 " 6 5 6 5 3 2 c  £  r  Here r e a c t i v i t y follows the b a s i c i t y of the n u c l e o p h i l e , and g can be assumed to be s m a l l .  The base preference of the phosphorochloridates  is  - 31 -  a l s o evident i n the formation of the isothiocyanato d e r i v a t i v e , C^PCCONCS, i n preference to the corresponding thiocyanato d e r i v a t i v e . This allows equation (2-9) to be expressed i n the form: log k = apKa + constant  (2-10)  Therefore, where the r e a c t i v i t y of the e l e c t r o p h i l e follows the p o l a r i z a b i l i t y o f the nucleophile 3 i s predominant i n equation (2-9). On the other hand, where the base strength i s followed a i s predominant and equation (2-10) i s the r e s u l t .  Furthermore, i n compounds with  saturated carbon, where $ i s important, the thiocyanato d e r i v a t i v e i s formed.  Conversely, with the phosphorochloridates, where a i s important,  the i s o t h i o c y a n a t o d e r i v a t i v e i s formed. The formation of the isothiocyanato p h o s p h o n i t r i l i c d e r i v a t i v e i s then s t r o n g l y suggestive of a r e a c t i v i t y dependent upon a.  This can  be shown by a comparison of the rate constant, k ^ , for the r e a c t i o n ^ N„P C1, + C l " * -r N P C1 C1* + C l " 7  7  C  with the r a t e constant k • k  for the thiocyanate s u b s t i t u t i o n r e a c t i o n . * * i s lower, 5.01 x 1 0 " than k, 6.7 x 1 0 " . Therefore, 2  c l  2  the r e a c t i v i t y does follow the b a s i c i t y .  These two r a t e constants  allow a value of a to be c a l c u l a t e d :  HCl log k i n  = c l  log k 1 Q  i n u n i t s of £ m o l e s e c _i  a  P  K a  = ctpKa  +  constant + constant  (2-11) (2-12)  - 32 -  log k  , where  - log k  = a(pKa  c l  HCNS „ HC1 . pKs - pKa = 4 v  l  o  g  f n j r  a  The pKa  -pKa  H C 1  )  (2-13)  (19)  v  (2-14)  J  k _ log y- ~ CI  T  H C N S  =  =  4  (2-15)  a  a  (  0.0317  2  -  1  6  )  (2-17)  value i s an approximation, the accuracy of which determines  to a large extent the accuracy of the a v a l u e .  This approximation, has  been used to c o r r e l a t e base strength and r e a c t i v i t y i n s i m i l a r reactions and therefore, i t would seem to be an acceptable value to use here. Furthermore, the i n t e r e s t i n a l i e s not i n i t s absolute v a l u e , but i n comparisons with a values f o r s i m i l a r compounds.  Such comparisons do  show a s e n s i b l e difference between the a value of the p h o s p h o n i t r i l e and a values for compounds c o n t a i n i n g penta-valent phosphorus atoms.  a C o e f f i c i e n t s for the Reaction of Nucleophiles with Phosphoryl Compounds Compound  a  Et N(OEt)P(0)CN  0.50  2  (EtO) P(0)OP(0)(0Et) 2  PrO'(Me)'P(0)F  J  2  0.70 0.82  - 33 -  As the p o s i t i v e charge on the phosphorus atom increases, r a t e constant and the value of a should also increase. a l l other factors are constant,  the  Therefore, i f  the value of a should follow the e l e c t r o n  withdrawing effect of the l i g a n d s . The small value o f a for the p h o s p h o n i t r i l e compared with those for the phosphoryl compounds i s then an i n d i c a t i o n of the low p o s i t i v e charge on the p h o s p h o n i t r i l i c phosphorus atom.  This would be  due to e l e c t r o n donation from the lone p a i r s of the r i n g nitrogens to the phosphorus atom.  This effect i s already known; recent studies o f (22)  the i o n i z a t i o n p o t e n t i a l s of p h o s p h o n i t r i l e s  have i n d i c a t e d lone  p a i r donation. It should be observed from equation (2-15) that any factor which would increase k  would a l s o increase a.  charge on the phosphorus atom decreases a. be important a l s o .  So decreasing the p o s i t i v e  However, other factors could  In the isothiocyanate the lone p a i r on the nitrogen  could donate to the phosphorus atom.  The corresponding increase i n the  e x o c y c l i c P-N bond energy would be expected to decrease the a c t i v a t i o n energy and, thus, increase k.  Such donation would be evident (23  i n a shortened e x o c y c l i c P-N bond length; however, recent x-ray studies show only a r e l a t i v e l y small shortening and therefore  i n d i c a t e a weak  e x o c y c l i c donation. Two types of nitrogen lone p a i r donation are now evident: . (1)  donation from the r i n g nitrogen atoms which decreases a,  (2)  and donation from the isothiocyanate nitrogen atom which increases k by s t a b i l i z i n g the t r a n s i t i o n s t a t e . Because the ct value for the p h o s p h o n i t r i l e i s smaller than the  - 34 -  a values for the phosphorochloridates, appear to be dominant.  endocyclic donation would  This i s consistent with the x-ray s t r u c t u r e of  the f u l l y s u b s t i t u t e d d e r i v a t i v e , where the endocyclic shortening of the P-N bond i s greater than the e x o c y c l i c . The E value of the thiocyanate r e a c t i o n i s 15.5 ± 0.5 &  Kcal/mole.  This i s lower than the value of 18.3 Kcal/mole found by  f31 Sowerby  v  J  when using c h l o r i n e as the n u c l e o p h i l e .  The L o g ^ A or  pre-exponential factor was 10.2 ± 0.3 compared with 12.1 for the c h l o r i n e . The difference i n a c t i v a t i o n energies i s compatible w i t h the fact that s u b s t i t u t i o n by isothiocyanate i s faster than by c h l o r i n e .  The increase  i n r a t e i s then due to the s t a b i l i z a t i o n of the t r a n s i t i o n step. In conclusion i t can be stated that the work i n t h i s s e c t i o n has provided information on several c h a r a c t e r i s t i c s of p h o s p h o n i t r i l e chemistry.  • The r e a c t i o n :  N P C1 3  3  6  + 6KCNS •* N P ( N C S ) 3  3  6  + 6KC1  s t a r t s w i t h the separate and i n d i v i d u a l step:  N . P , C L + KCNS '-»• N_P,C1 NCS + KC1 o o o 5 o b C  which i s followed by a s e r i e s of other steps to give the substituted derivative.  fully  The f i r s t step i s second order, being f i r s t  order i n each reagent and i s most probably b i m o l e c u l a r . involve a penta-co-ordinate  This would  phosphorus i n the t r a n s i t i o n s t a t e .  - 35 -  Comparison of the k i n e t i c s of t h i s f i r s t step with those of the s i m i l a r c h l o r i n e exchange r e a c t i o n , enables the value of the a factor to be c a l c u l a t e d .  Further comparison of t h i s value with a  factor values for phosphoryl compounds i n d i c a t e s that the  phosphorus  atom i n the p h o s p h o n i t r i l e has a higher e l e c t r o n density than the phosphorus atom i n the phosphoryl groups.  - 36 -  C H A P T E R  THREE  METAL HALIDE DERIVATIVES OF PHOSPHONITRILES  Introduction: In the study of the chemistry of p h o s p h o n i t r i l i c d e r i v a t i v e s a major objective i s the discovery of experimental evidence relevant to t h e o r e t i c a l expectations.  . C r a i g and Paddock  f24)  and others  f25)  have,  on the b a s i s of Huckel M.O. theory, been able to explain many of the e m p i r i c a l r e s u l t s of such studies i n terms of n-electron systems covering the whole molecule. The structures of the tetrameric and hexameric p h o s p h o n i t r i l i c dimethylamide d e r i v a t i v e s are known&^>^) n d part of the object of a  the present work has been to make and study t h e i r complexes with metals, so as to throw more l i g h t on the factors i n f l u e n c i n g ir-electron d r i f t i n the p h o s p h o n i t r i l e s .  P h o s p h o n i t r i l e s are known to form a d d i t i o n . .  compounds w i t h Lewis a c i d s .  Some of the reported compounds are l i s t e d  i n Table I I I . Recent x-ray determination of the c r y s t a l stucture o f . N^P^MegH C u C l , ^ ^  shows the copper bound to only one r i n g n i t r o g e n ,  and the proton bound to the opposite nitrogen (Figure 16).  In the  f39) metal carbonyl d e r i v a t i v e , N^P^MegMo(Co)^  , i n f r a - r e d evidence suggest  a molybdenum atom co-ordinated to two opposing r i n g n i t r o g e n s .  However,  - 37 -  Table I I I  N_P_C1 "HCIO.  (28)  N_P_C1 *3S0_ j o o 6 N  3 3 6' °2 P  C 1  N  3 3  P h o s p h o n i t r i l i c Addition Compounds  N P Cl -AlBr 3  6  5  (35)  3  N  (29)  N P Br '2AlBr  6 5 6  3  6  (29,30)  3 3 V P  B  3  (28)  4  N P (NHC H ) 'HC1 3  3  3  ( 3 5 )  6  (35)  3  N P Me 'MCl (M=Sn,Ti) 3  (28)  6  3  A 1 B r  3  6  N P (NHR)  -HCl(R=Et,  3  i-Propyl, N P C1 (NHCH ) 'HC10 3  3  4  3  2  (28)  4  N P C1 (NHC H NH ) 'HC1 3  3  4  2  4  2  3  3  2  6  2  3  2  (30)  3  N,P,Me RI (R=Me, Et) N P Cl (NHP ) -HCl 3  2  r  [N P (NMe ) (NMe ) ]'2BF 3  3  2  4  N P C1 -2A1C1 3  3  6  3  3  2  (34)  4  g  N P Me Mo(C0) 4  4  4  8  4  2  g  (39)  4  2  4  4  3  (33)  4  8  N P Me RI 4  4  g  2  (40)  n  4  (41)  (R=Me, Et)  (NPF ) -2SbF 2  (30)  2  g  (N P Me H) CoCl 4  5  i-Butyl)  (28)  4  N P Me H CuCl^  (32)  4  4  n-Propyl,  n-Butyl,  N P (NH ) (C H 0 )  (31)  6  3  (28)  2  N P (NH ) -(HC H 0 )  N P Cl -2HC10 4  (36)  4  (n=3-6)  (31) (42)  - 38 /  ®• Figure 16.  The Structure of P.N.Me HCuCl 0  4 4  (Exocyclic Groups Omitted)  o  - 39 -  since i t has not been made i n c r y s t a l l i n e form, no x-ray determination of i t s structure i s a v a i l a b l e . [ (NPMe ) H] C o C l 2  to  4  2  4  , which i s s t o i c h i o m e t r i c a l l y s i m i l a r  N^P^MegH C u C l j , has an i o n i c structure composed of two s t e r i c a l l y  d i s s i m i l a r N^P^MegH" " cations and one CoCl^ 1  anion.  To date, no p h o s p h o n i t r i l e has been bonded with a t r a n s i t i o n metal h a l i d e i n such a way as to form bonds from more than one r i n g nitrogen.  A few examples e x i s t where the acceptor atom probably  bonds to one: nitrogf nitrogen, e.g. N^PjCl^'SSO^  (29,30) ' .  (Me PN) SnCl 2  3  ( M e P N ) T i C l ' ' , and (  4>  2  3  3 6  )  4  The evidence for t h i s type of bonding comes  from i n f r a - r e d and nuclear magnetic resonance  studies.  Trimeric and tetrameric d e r i v a t i v e s are probably too crowded •-• to allow the metal to s i t as c l o s e l y to the r i n g plane as would be necessary i n a multi-dentate l i g a n d .  P a r t i a l l y o f f s e t t i n g t h i s , however  i s the b a s i c i t y of the r i n g n i t r o g e n s .  The more b a s i c they are,  less important w i l l be the s t e r i c e f f e c t s .  the  The suggested s t r u c t u r e of  (39) N P MegMo(Co) 4  4  i n d i c a t e s the p o s s i b i l i t y of forming an N P R g C u C l  J 4  4  molecule with several r i n g nitrogens donating to copper.  4  2  However,  as t h i s does not happen for R = Me, a more e l e c t r o n - r e l e a s i n g e x o c y c l i c group may be necessary. Information on the b a s i c i t y of the p h o s p h o n i t r i l i c d e r i v a t i v e s i s a v a i l a b l e , and some i s presented i n Table IV. TABLE IV pKa VALUES FOR SOME PHOSPHONITRILES* Group  Trimer pKa P^ 2 6.4 a  Et  (CH )  (  4  3  '  4  4  )  Tetramer P^ P^ 2 7,6 0.2 a  a  - 40 -  Group  NMe  ( 4 5 ) 2  Trimer ^ pKa pK&2  Tetramer pKa P 2  7.6  8.3  -3.3  *  determined i n nitrobenzene  **  refers to a d d i t i o n of a second proton  K a  0.6  In none of the d e r i v a t i v e s studied d i d the pKa values change (44) by more than 1.2 u n i t s when varying r i n g s i z e from trimer to tetramer The effect of v a r i a t i o n of r i n g s i z e on base strength i s e v i d e n t l y much smaller than that of v a r i a t i o n of the e x o c y c l i c groups. I t should also be noticed that pKa values for p h o s p h o n i t r i l i c amides are very s i m i l a r to those for the free amines; dimethylamine has (45") a pKa value of 7.5  .  Knowing the ease with which amines form  complexes with a high copper c o - o r d i n a t i o n number, i t might be expected that p h o s p h o n i t r i l e s would do the same. The tetrameric p h o s p h o n i t r i l i c dimethylamide d e r i v a t i v e i s more b a s i c than the methyl d e r i v a t i v e both to f i r s t and second protonation, and therefore, w i t h copper. for  This would i n v o l v e a s t r u c t u r e s i m i l a r to that suggested  P N (Me) Mo(Co) 4  4  i t i s more l i k e l y to form a chelate complex  g  ( 3 9 ) 4  .  However, s t e r i c interference would be greater for the amide groups than the methyl groups. the increased b a s i c i t y .  This would o f f s e t some, i f not a l l , of  S t e r i c i n t e r a c t i o n s would be reduced i n the  l a r g e r r i n g s without appreciable change i n base strength.  In t h i s work  the r e a c t i o n o f copper (II) c h l o r i d e with hexameric p h o s p h o n i t r i l i c dimethylamide d e r i v a t i v e s was i n v e s t i g a t e d .  J  -  -  41  With p h o s p h o n i t r i l i c amides, a d d i t i o n reactions can occur using the lone p a i r electrons at the r i n g , or e x o c y c l i c nitrogens the molecular o r b i t a l s of the r i n g system.  or  A number of a r t i c l e s suggest  that the r i n g nitrogen atoms are the centres of b a s i c i t y .  One of  these deals with the s t r u c t u r a l determination of N ^ P ^ C ^ (NHPr*) ^HCl The proton i s bonded to a r i n g nitrogen which i n d i c a t e s that t h i s i s the centre of b a s i c i t y . supports t h i s c o n c l u s i o n .  The s t r u c t u r e of [N^P^MegHjCuCl^^ '' 0  .  site also  Never the l e s s , i t i s not inconceivable t h a t ,  i n hindered molecules, c o - o r d i n a t i o n of the e x o c y c l i c groups might (33) occur, and i n t e r a c t i o n s of t h i s s o r t have been suggested In the course of t h i s work, the tetrameric  phosphonitrilic  dimethylamide d e r i v a t i v e was made to react with copper(II) an attempt to produce a chelate complex of copper.  chloride i n  However, the  stoichiometry, N^P^(NMe )gHCuCl,j, of the r e s u l t i n g complex and i t s 2  i n f r a - r e d spectra suggest a s t r u c t u r e with only one  copper-nitrogen  covalent bond and one protonated r i n g n i t r o g e n . THE REACTION OF TETRAMERIC PHOSPHONITRILIC DIMETHYLAMIDE (T.P.D.) WITH COPPER (II) CHLORIDE.  The Preparation of T . P . D . : T . P . D . i s formed according to the P N Cl 4  4  g  + 16NHMe -*• P N ( N M e ) 2  4  4  2  equation:  g  + 8 NH Me Cl 2  2  The tetrameric p h o s p h o n i t r i l i c c h l o r i d e was prepared by the method of (47) Stokes  and the dimethylamine was the reagent grade chemical obtained  - 42 -  from Eastman Kodak. At -78°C, 80 ml (1.21 moles) of dimethylamine i n 20 ml of d i e t h y l ether were slowly mixed with 30.2 g (0.0652 moles) of p h o s p h o n i t r i l i c c h l o r i d e i n 150 ml o f d i e t h y l ether. p r e c i p i t a t e formed immediately.  tetrameric  A dense white  When t h i s formation had stopped the  r e a c t i o n mixture was allowed to reach room temperature where i t remained for two hours.  The r e a c t i o n mixture was then heated under r e f l u x for  nineteen hours. solution.  The white p r e c i p i t a t e was f i l t e r e d o f f , leaving a c l e a r  Evaporation o f t h i s s o l u t i o n l e f t a white hard powder  (m.pt. 220°C) assumed to be the crude product (A). The r e s i d u a l dimethylamine and d i e t h y l ether were removed under vacuum from the f i r s t white r e s i d u e .  C o - p r e c i p i t a t e d product was  then extracted from i t using d i e t h y l ether as the s o l v e n t .  Evaporation  of t h i s solvent l e f t a gummy white residue which was reacted for a further t h i r t y - f o u r hours with dimethylamine. The crude product r e s u l t i n g from t h i s r e a c t i o n , combined w i t h that p r e v i o u s l y obtained,  (A), weighed 16 g (40% y i e l d based on the  amount of tetrameric p h o s p h o n i t r i l i c c h l o r i d e added).  I t was p u r i f i e d  by repeated r e - c r y s t a l l i z a t i o n from d i e t h y l ether to produce white c r y s t a l l i n e needles of about 2 mm i n length, m.pt. 238°C, m.pt. 2 3 8 ° C ^ ^ ) .  (N P (NMe )g 4  4  2  The i n f r a - r e d spectrum of the sample i n a potassium  bromide p e l l e t i s shown i n Table V and Figure 17(a). A q u a l i t a t i v e c h l o r i n e a n a l y s i s showed the sample to be free from contamination by hydrogen c h l o r i d e . analysis  Quantitative micro  gave N , 31.88; C, 35.79; H, 9.55%; (formula N P ( N M e )  N, 31.60; C, 36.10; H, 9.02%.  4  4  2  g  requires  - 43 -  TABLE V Infra-red Spectra* of N P ( N M e ) 4  N P (NMe ) HCuCl 4  4  2  8  2  8  and  N P (NMe ) 4  3  Peaks i n cm"  4  4  2  (NMe ) HCuCl 2  g  3  g  •1  1  Peaks i n cm"  3100 s  3010m, 2980s, 2860s, 2780s p r  3000 - 2750 s v b  1870,  1980, 2020, 2070 p r w  2600 m  1430,  1450, 1465, 1480 p r s  1900 -,2400 p r w bands  1400 - 1230 p r s  1440,  1460, 1480, 1495 p r s  1175,  1300,  1250, 1220, 1170 s  1060 m  1060 m  1145 s  1000 - 950 b s  980 s  910 s  920 s  820 w  860 m  725 s  785 w  630 s  750s, 745m p r  520 s  660s, 665s  470 s  495 m 450 m s - strong; m - medium; w - weak; v b - very broad; b - broad; p r - p o o r l y resolved *Taken on a Perkin-Elmer 457 Grating Infra-Red  Spectrophotometer  3000  2500  2000  :  T8DTJ  (Wave Number)•(cm) • Figure 17(a).  Infra-red Spectrum, of N P (NMe_)  ft  (Wave Number)•(cm) Figure 17(a).  Continued  3000  2500  2000  TBOU  (Wave Number)•(cm) Figure 17(b).  Infra-red Spectrum of  N P (NMe ) HCuCl 4  4  2  g  3  - 48 -  The Preparation of N^P^(NMe )gHCuCl^: 2  Anhydrous copper (II) c h l o r i d e was obtained by dehydrating f49) the hydrate i n b o i l i n g butanone  .  0.3306 g (4.3 x 1 0 " moles) of T . P . D . i n 100 ml o f a c e t o n i t r i l e 4  were added to 0.0743 g (5.53 x 10" moles) of copper (II) c h l o r i d e i n 4  200 ml o f a c e t o n i t r i l e .  The brown colour of the copper (II) c h l o r i d e  s o l u t i o n immediately changed to a red-brown tea c o l o u r .  The r e a c t i o n  mixture was then heated under r e f l u x for t h i r t y minutes, cooled to - 4 ° C , and l e f t for fourteen hours. Flash evaporation of the s o l u t i o n l e f t a yellow-brown r e s i d u e . This was d i s s o l v e d i n d i e t h y l ether [copper (II) c h l o r i d e i s i n s o l u b l e i n t h i s solvent] and f i l t e r e d to give a golden wheat-coloured s o l u t i o n . Upon concentration of the s o l u t i o n and standing, there formed 0.0872 g of non-homogeneous primrose-yellow c r y s t a l s , (m.pts. 103 - 105°C, 112°C). The previous r e a c t i o n was repeated using 3.4889 g (4.55 x 10~ moles) of T . P . D . and 0.6679 g (4.97 x 1 0  - 3  3  moles) of copper (II) c h l o r i d e .  However, t h i s time the yellow-brown residue was washed i n 200 ml o f d i e t h y l ether and f i l t e r e d .  The undissolved product was extracted with  d i e t h y l ether i n a Soxhlet e x t r a c t o r for two days. yellow rhombohedral needles formed i n the f l a s k . from the solvent and d r i e d (m.pt.  During the e x t r a c t i o n , These were separated  114°C).  The amount of product recovered was: rhombohedral needles from e x t r a c t i o n  0.6980  g  m a t e r i a l d i s s o l v e d i n solvent  0.1557  g  1.2006  g  1.9543  g  residue l e f t i n thimble a f t e r e x t r a c t i o n of main product Total  - 49 -  The yellow product i n the thimble was unstable to the atmosphere, turning green upon prolonged exposure.  Except for a small amount of  i n s o l u b l e red gum the yellow product was d i s s o l v e d i n benzene.  This  was f i l t e r e d and evaporated to give a brown o i l containing some benzene and some seemingly c o l o u r l e s s c r y s t a l s .  The o i l was d i l u t e d  with 150 ml o f carbon t e t r a c h l o r i d e and the c r y s t a l s f i l t e r e d o f f as a gummy yellow powder. The c r y s t a l s formed i n the f l a s k during e x t r a c t i o n (m.pt. 114°C) were r e - c r y s t a l l i z e d from d i e t h y l ether forming yellow rhombohedral crystals,  (m.pt. 114 - 116°C); m i c r o - a n a l y s i s found N, 23.94; H, 7.04;  C, 27.3; C l , 15.45%.  Formula ( P ^ ( N M e ) H ) C u C l 2  H, 6.95; C, 27.3; C l , 15.1%.  g  3  requires N , 23.8;  The i n f r a - r e d spectrum i n potassium bromide  i s shown i n Table V and Figure 17 (b).  Discussion: N^P (NMe )gHCuCl bears an obvious s t o i c h i o m e t r i c s i m i l a r i t y 4  2  3  to N^P^MegHCuCl^, both ligands being tetrameric r i n g s with bulky electron-releasing  groups attached and each molecule having three c h l o r i n e  atoms and one copper atom.  A corresponding s t r u c t u r a l s i m i l a r i t y might  therefore be expected. The s t u r c t u r e of N^P^MegHCuCl^ has been determined by x-ray diffraction'' ^ 4 0  and the r i n g shown to be c o v a l e n t l y bonded through one  nitrogen to the copper atom o f the C u C l ^  -  group, and through  opposing nitrogen to the proton (Figure 16).  the  A s i m i l a r p o s i t i o n for  the proton i n the amide d e r i v a t i v e i s suggested by the i n f r a - r e d  spectrum.  - 50 -  Therefore, C u C l ^  -  i s most probably bound to the opposing r i n g n i t r o g e n .  The main differences i n the spectra between the octa-amino d e r i v a t i v e and i t s copper complex are the appearance of new bands at 3100, 2600, and 920 cm" , and the hypsochromic s h i f t of the peaks at 1  725 and 630 c m  - 1  to 750 and 660 c m , and the peaks at 1175 and 1145 cm" - 1  1  to 1220 and 1170 c m . - 1  Moeller and K o k a l i s ^ - * observed new bands at 2300 - 2650 c m 50  - 1  on going from the hexa-amino d e r i v a t i v e s to t h e i r h y d r o c h l o r i d e s . On the basis of s i m i l a r r e s u l t s found upon the hydrohalogenation of p y r i d i n e d e r i v a t i v e s ^ ' * ^ , he assigned these bands to  S-H s t r e t c h i n g modes.  (52") In several pyridinium d e r i v a t i v e s Evans 3374 cm" and 2800 - 2273 c m 1  assigned peaks at 3100 -  to the same s t r e t c h i n g modes.  -1  Similar  bands (at 2660 and 3080 c m ) are found i n the i n f r a - r e d spectrum o f -1  N^P^MegHCuClg, which i s known to be protonated on the nitrogen a t o m ^ " ' . 4  Peaks at 3100 and 2600 cm" i n the spectrum of N P ( N M e ) H C u C l 1  4  4  2  g  3  are  most probably due to a s i m i l a r protonation of one of the n i t r o g e n s . However, whether protonation i s e x o c y c l i c or endocyclic cannot be determined from these bands. Stahlberg *- - studied the spectrum o f N P C 1 [N(CH ) ] 54  )  3  assigned peaks at 686 and 684 c m  2  3  2  4  and  to symmetric PN (exo) s t r e t c h i n g  - 1  2  modes, and peaks at 755 and 751 c m modes.  3  -1  to asymmetric PN (exo) s t r e t c h i n g 2  S i m i l a r peaks at 630 and 725 cm" are found with N.P.(NMe_) 1  4 4  0  Z o  and may be assigned to the analogous s t r e t c h i n g modes (these may be unresolved d o u b l e t s ) . The spectrum of N P (NMe )gHCuClj shows a hypsochromic s h i f t 4  4  of these peaks to 665, 660 c m  2  - 1  and 750, 740 c m . - 1  This i s consistent  -51 -  with the presence of ir-electron withdrawing groups bonded to the r i n g . The P-N(exo) bond i n N P (NMe2)g has considerable double bond character 4  4  caused by the d e r e a l i z a t i o n of the lone p a i r electrons on nitrogen i n t o the ir-ring bonding s y s t e m .  Any bonding of the r i n g through  i t s nitrogen lone p a i r s to an e l e c t r o n withdrawing group would cause an increase i n the double bond character of the P-N(exo) bond and a r e s u l t i n g hypsochromic s h i f t of the frequency of the v i b r a t i o n a l modes. Furthermore, no difference i s noticed i n the frequency of the N-C s t r e t c h i n g mode (1060 c m ) between the two compounds.  The bonding  -1  of an acceptor to an e x o c y c l i c group would have been expected to change t h i s frequency; p a r t i c u l a r l y i f the acceptor had been a bulky copper anion.  The proton and the copper atom must, therefore, be bound to the  ring nitrogens. It seems l i k e l y t h a t , analogous to the case of N P (NMe )gHCuCl 4  the anion i s the group C u C l ^ " .  4  2  This would be expected on e l e c t r o s t a t i c  grounds to have an antipodal o r i e n t a t i o n r e l a t i v e to the proton. Evidence for t h i s i s found i n the s t r u c t u r e of N^P^MegHCuCl^. Because protonation o f the r i n g reduces the b a s i c i t y of the nitrogen atoms, t h i s o r i e n t a t i o n would eliminate any c h e l a t i o n . copper i s most probably bound to only one r i n g n i t r o g e n . involve a s t r u c t u r e analogous to that o f N.P.Me„H"CuCl_.  So the  This would  - 52 -  C H A P T E R  FOUR  THE PREPARATION OF A PHOSPHONITRILIC COMPLEX CONTAINING A CHELATED COPPER  Both s i z e and base strength should determine whether or not a p h o s p h o n i t r i l e can act as a multidentate  ligand.  The f a i l u r e of  tetrameric p h o s p h o n i t r i l i c dimethylamide to act as such a l i g a n d indicates that a p h o s p h o n i t r i l e with a larger r i n g and high b a s i c i t y i s necessary for c h e l a t i o n .  The hexameric p h o s p h o n i t r i l i c dimethylamide meets both (45 55)  these requirements  '  J  and, therefore, i t s reactions under varying  conditions w i t h copper (I) c h l o r i d e and copper (II) c h l o r i d e have been studied. In the course of t h i s work the complex N ^ P ^ ( N M e ) C u ( I I ) C l C u ( I ) C l 2  has been prepared and c h a r a c t e r i z e d .  12  I t i s the f i r s t p h o s p h o n i t r i l i c  d e r i v a t i v e to be shown to have a chelated metal atom, and also the  first  compound to contain the C u C l ~ i o n ^ ^ . 2  Several attempts were made to produce complexes containing copper i n only one o x i d a t i o n s t a t e .  However, only poorly defined s o l i d s  were obtained. THE PREPARATION OF HEXAMERIC PHOSPHONITRILIC DIMETHYLAMIDE (H.P.D.) H.P.D,  i s produced according to the  equation:  N - P . C l . ^ + 24HNMe„ + N..P,(NMe„).„ + 12NH_Me„Cl DO 12 2 6 6 2 lz 2 2  2  - 53 -  The hexameric p h o s p h o n i t r i l i c c h l o r i d e was already a v a i l a b l e and the dimethylamine was the reagent grade chemical obtained from Eastman Kodak. At -78°C 50 ml (0.75 moles) of dimethylamine were slowly added to 11.9 g (0.0171 moles) of hexameric p h o s p h o n i t r i l i c c h l o r i d e i n 75 ml of benzene.  Upon warming to room temperature,  mixture produced a dense white p r e c i p i t a t e . t h i s temperature,  the r e a c t i o n  A f t e r several hours at  the mixture was heated to r e f l u x and kept there for  ten hours. F i l t r a t i o n and evaporation of the r e a c t i o n mixture l e f t 7 g of a s t i c k y white powder which was assumed to be the desired product. Washing the f i l t r a t e with hot benzene removed several more grams of cop r e c i p i t a t e d product.  The product was r e - c r y s t a l l i z e d repeatedly from  benzene to give 6.5 g (48% of theory) of white powder, m.pt. 260 C C  ( l i t e r a t u r e 256°C  ).  A q u a l i t a t i v e c h l o r i n e a n a l y s i s was negative,  i n d i c a t i n g complete s u b s t i t u t i o n and the absence of the h y d r o c h l o r i d e , NgP^fNN^)  C l . The i n f r a - r e d spectrum, which has not as yet been  p u b l i s h e d , i s given i n Table VI and Figure 18(a).  THE REACTION OF H . P . D . WITH COPPER (II) CHLORIDE Reactions i n Butanone: The butanone used was d i s t i l l e d and the f r a c t i o n b o i l i n g between 79 - 81°C was c o l l e c t e d and passed through a column containing 400 mm of alumina and 200 mm of s i l i c a g e l . Anhydrous copper (II) c h l o r i d e was obtained from the F i s h e r S c i e n t i f i c Company.  TABLE VI  Infra-red Spectra* of H.P.D. and NgPgfNMe^  1 2  Cu Cl 2  3  3010m, 2970m, 2860bs, 2790s; p r t  3010m, 2890s, 2850s, 2800s; p r  2150 b w  1490w, 1480m, 1460m, 1455m, 1440w, 1425w; p r  1480s, 1460, 1450; s  1290 s  1400-- 1250 v b s  1250 s  1183 s  1200, 1175; p r s  1145 m  1135 s  1070, 1063; p r m  1062 m  990, 970; p r s  980 s  890 m  859 m  780 m  795 m  718, 708; p r s  768 m  650 m  743m, 730m  590 s  568 m  On  545 m 515w, 509m, 490m; p r * Taken on a Perkin-Elmer 457 Grating Infra-Red Spectrophotometer t Symbols Defined on TABLE V  (Wave Number)•(cm) Figure 18(a).  Infra-red Spectrum of N-P,(NMe_)  VI ON  (Wave Number)•(cm) Figure 18(a).  Continued  A c l e a r s o l u t i o n of 3.0054 g (3.76 x 10~ moles) of H.P.D. 3  p a r t i a l l y d i s s o l v e d i n 325 ml of butanone was added to a brown s o l u t i o n of 1.0306 g (7.66 x 10~ moles) of copper (II) c h l o r i d e . 3  colour was instantaneously  formed.  A b r i g h t red  Shaking the r e a c t i o n vessel for  several seconds d i s s o l v e d the H . P . D . leaving a c l e a r red s o l u t i o n with approximately 30 mg o f high density dark powder.  Upon standing for an  hour, none of the powder v i s i b l y went i n t o s o l u t i o n , though some of i t d i s s o l v e d on b o i l i n g . Concentrating, f i l t e r i n g , and c o o l i n g the s o l u t i o n gave 2.6758 g of r u s t - r e d f l a k e s , m.pt. 174°C.  Further c r y s t a l l i z a t i o n from  butanone y i e l d e d 2 g of flakes (m.pt. 175°C) and some i n s o l u b l e brown powder.  A second crop o f c r y s t a l s was recovered from the mother l i q u o r  of the second c r y s t a l l i z a t i o n . A f i n a l r e - c r y s t a l l i z a t i o n was accomplished by slow evaporation of a butanone s o l u t i o n with p u r i f i e d n i t r o g e n , ian  (obtained from the Canad-  L i q u i d A i r C o , ) , and 0.79 g of small red-brown f l a k e s  were obtained.  (m.pt. 180°C)  A f t e r drying i n vacuo these c r y s t a l s were analyzed;  the  r e s u l t s are shown i n Table V I I .  TABLE VII  Obtained Calculated for N P (NMe ) Cu Cl 6  6  2  1 2  2  4  C a l c u l a t e d for N P (NMe ) Cu Cl -HCl 6  6  2  1 2  2  3  Elemental A n a l y s i s of Copper Complex %N  %Cu  %C  23.3  11.40  26.8  6.80  %C1 13.21 13.25  23.62  11.90  26.99  6.75  13.29  23.59  11.88  26.96  6.83  13.28  %H  - 59 -  The i n f r a - r e d spectrum i s :  2900*, 2800*, 2750*, p . r . s , ;  1725* v . w . ; 1485*, 1460*, 1450*, p . r . s . ; 1185 , 1170 1145 ", p . r . s . ; +  f  1420* w.; 1280 s; 1250 s;  1050 m; 850 m; 795 m; 766 m; 745 m; 725 m  1  +  +  +  +  +  +  in  u n i t s of c m , ( a b b r e v i a t i o n s defined i n Table V . )  of  any peaks i n the N-H s t r e t c h i n g region i s not conclusive evidence  for  The absence  -1  the absence e i t h e r of the h y d r o c h l o r i d e , N^P^.  (NMe ) 2  1 2  Cu^l^-HCl,  or of free hydrogen c h l o r i d e . The formula, N g P ^ f N f ^ ) ^ ^ 2 4 U  p r o p e r t i e s of the compound.  C 1  w  a  s  n  o  t  c o n s  i-  s t e n  '  t  w i t h the  When a small sample was heated to 153°C i n  vacuo the c h l o r i n e analysis dropped to 10.5%, i n d i c a t i n g a loss of one c h l o r i n e atom per molecule.  This could be due to the loss of e a s i l y  removable hydrogen c h l o r i d e from a complex having the formula, N,P.. (NMe„).. _ Cu„Cl„-HCl. 6 6 2 12 2 3  Table V I I shows that the two formulas have  almost i d e n t i c a l percentage compositions and are both consistent with the a n a l y t i c a l r e s u l t s . The hydrogen c h l o r i d e could come from the o x i d a t i o n of the solvent by the copper (II) c h l o r i d e ,  e.g.:  -CH C0- + 2CuCl •> -CHC1C0- + 2CuCl + HC1 2  2  I t i s important to note that the formula, N^P^(NMe )^ 2  2  (A^CI^'HCI,  requires the presence of a copper (I) atom which i s also produced i n the redox r e a c t i o n .  Succeeding work showed that the complex does i n  fact contain two o x i d a t i o n states of copper.  I t might, therefore,  be  expected that copper (II) c h l o r i d e and H . P . D . would react d i f f e r e n t l y in.a  non-reducing s o l v e n t , a c e t o n i t r i l e , than i n the reducing solvent  *  Taken from halocarbon o i l mull  t  Taken from nujol mull  ^  - 60 -  butanone.  This r e a c t i o n and others s i m i l a r to i t are studied next.  REACTIONS IN ACETONITRILE Reaction of Copper (II) Chloride w i t h H . P . D . ; 0.98909 g (1.24 x I O  - 3  moles) H.P.D. p a r t i a l l y d i s s o l v e d i n  200 ml o f a c e t o n i t r i l e , were added to a murky green s o l u t i o n of 0.3356 g (2.49 x 1 0  - 3  moles) o f copper (II) c h l o r i d e i n 200 ml of a c e t o n i t r i l e .  One minute after mixing, a red-tea colour appeared and a l l but a small amount of H.P.D. went i n t o s o l u t i o n .  A f t e r standing for ten hours,  the  r e a c t i o n mixture was f i l t e r e d to give a c l e a r red s o l u t i o n . Removing the solvent under reduced pressure at 50°C l e f t 1.2 g of a dark red powder, m.pt. 169°C.  This was c r y s t a l l i z e d from an  a c e t o n i t r i l e - b e n z e n e mixture to produce 0.6932 g of brown c r y s t a l l o i d needles, m.pt. 170°C. wafer was:  The i n f r a - r e d spectrum taken i n potassium bromide  2950, 2900, 2850, 2825, p . r . s . ;  1500 b.m.; 1300s; 1260;  1190, 1170, 1130 p . r . m . ; 1065m; 985 b . s . ; 860s; 800m; 750m; 730m; i n u n i t s of c m , (Abbreviations defined i n Table V . ) , and i s d i f f e r e n t - 1  that o f N . P , ( N M e „ ) DO  10  Z 1Z  from  Cu Cl,. 0  Z  J  Microscopic examination showed the c r y s t a l s to be o f two types,transparent, ruby red needles and opalescent brown needles.  The former  were mechanically separated and then analyzed; (N, 22.51; H, 6.96; C, 29.42%). Further attempts at r e - c r y s t a l l i z a t i o n from a c e t o n i t r i l e f a i l e d , and produced a decomposition of the product, evident by a depressed melting p o i n t o f 153 - 156°C.  Under vacuum at 92°C, t h i s material  - 61 decomposed i n t o a white sublimate and a dark red powder. Repeated r e - c r y s t a l l i z a t i o n from chloroform and carbon t e t r a c h l o r i d e s o l u t i o n s gave a golden-yellow powder, m.pt. 171 - 173°C. The i n f r a - r e d spectrum was i d e n t i c a l to that p r e v i o u s l y obtained. A n a l y s i s of t h i s m a t e r i a l gave:  N , 20.29; P, 12.81; C, 23.88;  H, 5.82; C I , 20.97; Cu, 15.09; 0, 0.96%. Assuming a molecule having eighteen nitrogen atoms, t h i s analys corresponds t o :  N  6 S.13 12 24.72 72.2 P  ( N  C  H  ) C u  2.95 7.3°0.75 C 1  which i s most probably: N P (NMe ) HC1(CuCl ) (H 0) 6  6  2  12  2  3  2  Further p u r i f i c a t i o n by t h i n l a y e r chromatography f a i l e d owing to the decomposition of the sample.  No further p u r i f i c a t i o n was  attempted.  Reaction of Copper (I) Chloride with H . P . D . : Copper (I) c h l o r i d e was prepared by the reduction of an aqueous s o l u t i o n of copper (II) c h l o r i d e with sulphur d i o x i d e  v  .  The product  was washed with sulphurous a c i d and g l a c i a l a c e t i c a c i d , then d r i e d i n vacuo at 100°C.  The pure white powder produced by t h i s method was  stored under nitrogen i n a stoppered and wax sealed v i a l . The a c e t o n i t r i l e used i n t h i s experiment was d r i e d by the method described i n Chapter 2.  A l l oxygen was removed by heating the  - 62 s o l u t i o n under r e f l u x and bubbling i n p u r i f i e d nitrogen for two hours. The H.P.D. was heated at 90°C i n vacuo for two hours.  The  melting point was then 260°C. A l l reactions were c a r r i e d out under p u r i f i e d n i t r o g e n . A c l e a r , c o l o u r l e s s s o l u t i o n o f 1.98 g (20.0 x 1 0  - 3  moles) of  copper (I) c h l o r i d e i n 500 ml of a c e t o n i t r i l e was added to a c l e a r , c o l o u r l e s s s o l u t i o n of 4.65 g (5.82 x 1 0 d i s s o l v e d i n 100 ml of a c e t o n i t r i l e .  - 3  moles) o f H.P.D. partly-  A further 5.2 g (6.5 x 10"  of H . P . D . was added to the r e a c t i o n mixture.  3  moles)  No colour change, was  n o t i c e d during e i t h e r a d d i t i o n . Warming o f the r e a c t i o n mixture d i s s o l v e d a l l the remaining H.P.D.  During t h i s warming, the s o l u t i o n turned a pale y e l l o w .  Concentration of the s o l u t i o n produced a dark yellow s o l u t i o n and a brown-white p r e c i p i t a t e . powder.  Flash evaporation revealed 5.41 g of dark  E x t r a c t i n g t h i s powder w i t h benzene for eight hours gave a c l e a r  s o l u t i o n and l e f t i n s o l u b l e brown powder i n the Soxhlet thimble. evaporation of the s o l u t i o n gave 0.3331 g of H.P.D.  Flash  (m.pt. 243°C; i n f r a -  red spectrum as i n Table V I ) . The benzene i n s o l u b l e m a t e r i a l was washed with dry chloroform to produce a red s o l u t i o n with a green r e f l e x and leaving an i n s o l u b l e black powder. The black powder was i n s o l u b l e i n a l l the common organic s o l v e n t s , but d i s s o l v e d i n s u l p h u r i c and h y d r o c h l o r i c a c i d s , as w e l l as ammonium hydroxide.  Its i n f r a - r e d spectrum was a blank; a q u a l i t a t i v e  copper t e s t performed on i t was p o s i t i v e ; and i t s melting point was i n excess of 320°C.  A l l of t h i s i s consistent with the black powder being  - 63 m e t a l l i c copper.  T h i s , i n turn suggests d i s p r o p o r t i o n a t i o n during the  r e a c t i o n according to the equation:  2CuCl -> Cu° + C u C l  2  Because copper ( I I ) , u n l i k e copper ( I ) , forms coloured compounds, d i s p r o p o r t i o n a t i o n would also e x p l a i n  the presence of a coloured  product. When i t was cooled to -4°C, the chloroform s o l u t i o n formed 1.19 g o f c r y s t a l s having the appearance of c l o t t e d blood. a i r s e n s i t i v e , turning green upon prolonged exposure to the  These were atmosphere.  Upon drying i n vacuo, the compound had a melting point o f 191 193°C and i n n u j o l and halocarbon o i l m u l l s , i t s i n f r a - r e d spectrum was:  3012*m, 2930*s, 2900*s, 2850*s, 2810*s, 1835*w, 1800*m, 147*s,  1465*s, 1455*s, 1445*s, 1435*m, 1300* s, 1255 s, 1210 s, 1190 s, +  +  +  +  1175 s,. +  1150 s, 1070 m, 980 s, 863 m, 800 m, 773 m, 750 s, 735 s, i n u n i t s o f +  +  +  +  +  +  c m " , (abbreviations defined i n Table V ) . 1  +  +  They were soluble i n  chloroform and a c e t o n i t r i l e , but i n s o l u b l e i n p e t r o l ether, carbon t e t r a c h l o r i d e and benzene. Further attempts at r e - c r y s t a l l i z a t i o n from a c e t o n i t r i l e and chloroform r e s u l t e d i n a d u l t e r a t i o n of the product evident by a depressed melting p o i n t , 190 - 191°C.  Attempted p u r i f i c a t i o n by t h i n l a y e r  chromatography was s i m i l a r l y unsuccessful. *  Taken from halocarbon o i l mull  t  Taken from n u j o l mull  - 64 -  Reaction of Copper (I) Chloride and Copper (II) Chloride with H . P . D . : The H . P . D . , copper (I) c h l o r i d e and anhydrous, oxygen free a c e t o n i t r i l e used i n t h i s experiment were prepared i n an i d e n t i c a l manner to those used i n the previous experiment.  The anhydrous copper  c h l o r i d e was obtained from the F i s h e r S c i e n t i f i c Company. 0.1761 g (1.31 x 10~ moles) of copper (II) c h l o r i d e were 3  added to 300 ml of warm a c e t o n i t r i l e under p u r i f i e d n i t r o g e n . an immediate colour change, g i v i n g a yellow s o l u t i o n .  There was  To t h i s s o l u t i o n  0.1335 g (1.34 x 10~ moles) of copper (I) c h l o r i d e powder was added. 3  F i n a l l y , 300 ml of a c e t o n i t r i l e containing 1.0235 g (1.28 x 10 of p a r t i a l l y d i s s o l v e d H.P.D. was added.  moles)  3  There was an immediate colour  change a f t e r the f i n a l a d d i t i o n r e s u l t i n g i n a weak tea-coloured solution. The H.P.D. d i s s o l v e d completely upon b o i l i n g the r e a c t i o n mixture.  During t h i s heating, the s o l u t i o n became appreciably darker  and assumed a dark red colour . Concentration of the s o l u t i o n y i e l d e d 0.8 g of yellow f l a k e s , m.pt. 179 - 181°C.  The c r y s t a l s were reported to be c r y s t a l l o g r a p h i c a l l y  i d e n t i c a l to those of N ^ P ^ ( N M e ) . ^ C u ^ l ^ as prepared by the dehydro2  f58") halogenation of the product prepared p r e v i o u s l y i n butanone a n a l y s i s was:  .  The  N , 24.15; P, 18.22; C, 28.18; H, 6.86; Cu, 12.33; C I ,  10.28% c a l c u l a t e d for N P ( N M e ) C u C l : 6  6  2  1 2  2  3  N , 24.4; P, 18.05; C, 27.9;  H, 6.96; Cu, 12.3; C I , 10.2%. The i n f r a - r e d spectrum taken i n a potassium bromide wafer i s i d e n t i c a l to the spectrum of N P (NMe_).. „Cu»Cl_ as shown i n Table V I . fi  fi  - 65 Discussion: The r e a c t i o n between hexameric p h o s p h o n i t r i l i c dimethylamide and copper (II) c h l o r i d e i n butanone produces c r y s t a l s of  N^P^fM^)Cu  C l ^ - H C l which dehydrohalogenates upon warming to form the compound, N^P^(NMe )j2 C i ^ C l g . 2  This contains two o x i d a t i o n states o f copper and  can be produced by the r e a c t i o n of H.P.D. with a mixture of copper c h l o r i d e and copper (I) c h l o r i d e i n the non-reducing solvent,  (II)  acetonitrile  P h o s p h o n i t r i l i c amides are such strong bases that they often form hydrochlorides i n the presence of secondary amines.  However, i f a  ir-electron withdrawing group were to complex strongly to the r i n g nitrogens of such a h y d r o c h l o r i d e , there would be a considerable weakening of the forces holding the hydrogen c h l o r i d e to the molecule. i f the system: \  /  C H complexes with a n-electron  to form:  \  /  =P-N  i  H  For example,  - 66 -  there would be a reduction i n density of the lone p a i r on N(2). +  The  N(2)-H bond would be weakened and hydrogen c h l o r i d e could be more r e a d i l y removed from the molecule.  I f the complexing were strong  enough, hydrogen c h l o r i d e could be r e a d i l y removed. Hydrogen c h l o r i d e must, therefore, time during the r e a c t i o n .  have been present at some  This would occur i f copper (II) c h l o r i d e  were reduced by the s o l v e n t .  Ketones are known reducing agents,  the  following r e a c t i o n occuring for acetone: -CH -CO- + 2CuCl 2  -> -CHCl-CO- + 2CuCl + HCl  2  S i m i l a r reduction could also e x p l a i n the presence of hydrogen c h l o r i d e in N P M e H C u C l ^ \  (N P Me H)£oCl ' - , and  4 9  4  4  g  (  3  4  4  g  4 9  (NMe ) H C u C l .  )  4  2  g  3  Each  of these complexes was prepared using metal c h l o r i d e s p r e v i o u s l y dehydrated i n butanone. The formula, N^P^fNMe,,)^  C u ^ l ^ H C l suggests that copper i s  present as copper (I) and copper ( I I ) .  T h i s , and the presence of  hydrogen c h l o r i d e could be explained by a r e a c t i o n path s i m i l a r t o :  N  6 6 P  (IWe  2>12  +  C U C 1  2 *  CH CH 'CO-CH + 2CuCl 3  '  N  6 6 P  ( N M e  2  3  2 12 )  ,(N P (NMe ) 6  6  2  1 2  , C u C 1  2  Cu Cl 2  N  6 6^12 P  C  U  C  2  1  -* CH CHC1-CO-CH + 2CuCl + HCl  2  3  "  +  C U C 1  3  + HCl  N  6  3  6 ^ 1 2  P  C u  (N P (NMe ) 6  6  2  12  2  C 1  3  Cu^l^HCl  However, i t remains to be shown that the complex does i n fact contain copper (I) and copper (II) atoms.  To do t h i s , purely chemical evidence  - 67 -  i s the most s a t i s f y i n g . A c e t o n i t r i l e i s a non-reducing solvent, therefore, c h l o r i d e w i l l not be reduced i f d i s s o l v e d i n i t .  copper  (II)  I f N ^ P ^ N N ^ ) - ] ^ ^ 2^^3 U  could be produced by the r e a c t i o n o f copper (II) c h l o r i d e with H.P.D. i n a c e t o n i t r i l e , then i t must contain only copper ( I I ) .  On the other  hand, i f i t contains both o x i d a t i o n s t a t e s , then i t cannot be produced by t h i s r e a c t i o n .  The r e a c t i o n was i n v e s t i g a t e d , and while an unstable  product was i s o l a t e d , i n f r a - r e d spectroscopy and chemical a n a l y s i s showed i t was not N , P , (NMe_).. _ Cu„Cl„. 6 6 2 1 2 2 3 S i m i l a r l y i f the complex could be produced by the r e a c t i o n of copper (I) c h l o r i d e with H.P.D. i t would be p o s i t i v e evidence that i t contained only copper ( I ) .  This r e a c t i o n was i n v e s t i g a t e d , and d i d not  produce the required product.  Furthermore, ti^P^QMe^)Ch^Cl^  is a  coloured compound and there i s no known coloured complex containing only copper (I) as an acceptor, charge transfer bands)  (except when the colour r e s u l t s from  .  These experiments showed that N^P^fNMe^)^ ^ 2^3 u  c  a  n  n  o  t  be  produced from the r e a c t i o n of H.P.D. with e i t h e r copper (I) c h l o r i d e or copper (II) c h l o r i d e i n a non reducing solvent such as a c e t o n i t r i l e . This i n d i c a t e s that the metal i n the complex does not belong e x c l u s i v e l y to one o x i d a t i o n s t a t e .  And the presence of one atom each of copper  (I)  and copper (II) i n the complex was proven by the r e a c t i o n of H.P.D. with an equimolar mixture of copper (I) c h l o r i d e and copper (II) c h l o r i d e i n a c e t o n i t r i l e which produces N ^ P ^ N N ^ ) - ^ C ^ C l ^ .  Because no reduction  of the copper (II) c h l o r i d e could have occured, and because s i m i l a r s o l u t i o n s containing e i t h e r of the copper c h l o r i d e s do not produce the  - 68 -  desired product, N^P^NMe,,).^ " 2 "^3 (  u  <  m u s t  >  therefore, contain both  o x i d a t i o n states of copper. The absence of hydrogen c h l o r i d e from the product obtained from the a c e t o n i t r i l e s o l u t i o n shows that i t s presence on the product from the butanone s o l u t i o n i s a r e s u l t of a redox r e a c t i o n and i s not a necessary part of the copper.complexing process. N^P^(NMe ) 2  Cu Cl  12  2  I f i t were, then  could not be produced except through the h y d r o c h l o r i d  3  intermediate. In c o n c l u s i o n , the f o l l o w i n g facts are now known about N^P^(NMe )^ Cu^jCl^. 2  I t can be produced by the r e a c t i o n of H.P.D. with  2  e i t h e r copper (II) c h l o r i d e i n butanone or with a mixture of copper (I) c h l o r i d e and copper (II) c h l o r i d e i n a c e t o n i t r i l e . c h l o r i d e of the complex i s r e a d i l y made and heating.  The mono-hydro-  loses hydrogen c h l o r i d e upon  F i n a l l y , the complex contains both copper (I) and copper  (II).  The a c t u a l formation o f the N^P^(NMe )^ C u ^ l ^ i s , however, 2  2  s t i l l unknown, although many p o s s i b i l i t i e s are evident.  The number of  these i s somewhat l i m i t e d by the known c o - o r d i n a t i o n numbers of copper (I) and  (II)  C 5 6  '  5 9 )  .  I f the compound i s a true complex, then i t can only be: N P (NMe )  1 2  Cu(I) C u ( I I ) C l , N P ( N M e )  N P (NMe )  1 2  Cu(I)Cl  6  6  6  6  2  2  3  6  6  Cu(II)Cl.  2  a s a l t then i t can only be:  2  1 2  Cu(I)Cl C u ( I I ) C l , or 2  On the other hand, i f i t i s i n fact  N P ( N M e ) C u C u C l " , or + 2  6  6  2  1 2  2  3  N ^ P ^ ( N M e ) ^ C u C l C u C l ~ . • The choice waits upon evidence presented i n +  2  2  2  the following chapter and here no d e c i s i o n regarding the true formation of N ^ P ^ ( N M e ) C u C l 2  12  2  3  can be made.  - 69 -  C H A P T E R  F I V E  PHYSICAL STUDIES OF N,P,(NMe ),„Cu„Cl„ 0  I iZ  DO  I  5  Introduction arid Summary: An x-ray c r y s t a l s t r u c t u r e determination done on the complex shows that of the p o s s i b i l i t i e s referred to i n the previous chapter, the s t r u c t u r e i n the s o l i d i s i o n i c being N.P,(NMe„)..„CuCl CuCl ~.  The  +  I 1.1  DO  Z  c a t i o n i s the only example of a p h o s p h o n i t r i l i c d e r i v a t i v e which forms a chelate complex w i t h a t r a n s i t i o n metal.  The d e t a i l e d s t r u c t u r e found  i n the c r y s t a l does not p e r s i s t i n s o l u t i o n . The existence i n s o l u t i o n of the c a t i o n , N . P , ( N M e _ ) „ C u  ++  n  DO  l i-l  i s suggested by evidence obtained from the r e a c t i o n of the complex with silver nitrate.  This c a t i o n would have less i n t e r n a l crowding than the  corresponding N ^ P ^ ( N M e ) c a t i o n and might, therefore, 2  be favoured  in solution. Electrochemical measurements support t h i s s u p p o s i t i o n .  The  s a l t i s not a 1:1 e l e c t r o l y t e i n a c e t o n i t r i l e s o l u t i o n , the l i m i t i n g conductance being higher than has been reported for any such e l e c t r o l y t e . The existence of the anion, C u C ^ " i s proven by the molecular structure.  CuCl^" i s l i n e a r and has bond lengths corresponding to the  sum of the covalent r a d i i for Cu (I) and CI atoms.  A p o s s i b l e path for  producing anions of the type Cu(NO„) ~ i s suggested by the s i l v e r n i t r a t e  70 -  experiment. Magnetochemical studies on the s o l i d complex showed that i t contained only one copper (II) atom per molecule. The i n f r a - r e d spectrum o f the complex i s very s i m i l a r to. that o f the parent H.P.D. of the two molecules.  This i s a t t r i b u t e d to the basic s i m i l a r i t y  Due to the lack of information concerning the  i n f r a - r e d spectra of p h o s p h o n i t r i l i c d e r i v a t i v e s , very few assignments of the peaks i n e i t h e r spectrum could be made.  The C r y s t a l . S t r u c t u r e . o f  N P (NMe ) Cu Cl : 6  6  2  1 2  2  3  The c r y s t a l s t r u c t u r e of N^P^(NMe )^ C u C l 2  2  2  3  was determined  (581 i n t h i s department N^P^(NMe )j CuCl 2  2  +  J  and shown to be formed from two d i s c r e t e  and C u C l  2  .  ions,  The c a t i o n contains a chelated copper  with a d i s t o r t e d square pyramidal environment. The formula N ^ P ^ ( N M e ) ^ C u C l C u C l +  2  2  consideration of s t r u c t u r a l evidence alone,  _ 2  The anion i s l i n e a r . can be proven by  (Figures 19,20; Table V I I I .  The chelated copper, Cu(2), i s penta co-ordinate, c o - o r d i n a t i o n i s w e l l known for copper (II) atoms dimethylglyoximatocopper ( I I ) ) ,  and while such f  (for example,  t e t r a c o - o r d i n a t i o n i s the  highest observed for copper ( I ) , s i l v e r ( I ) , or gold (I) atoms  .  Thus, i t can be presumed that t h i s copper atom i s d i v a l e n t . o  Furthermore,  the Cu(2)-Cl(2) bond length (2.28A) i s b e t t e r  approximated by the sum o f the covalent r a d i i o  for Cu (II) and C l ,  o  (2.34A), than for Cu(I) and C l , (2.17A).  Thus, the p h o s p h o n i t r i l i c  d e r i v a t i v e i s far more l i k e l y to be the c a t i o n , N^P^(NMe )^ Cu(II)C1 2  2  +  Figure 19.  P h o s p h o n i t r i l i c Ring of N.P.(NMe )  CuCl  +  Anion  atom c o o r d i n a t i o n  (HMe  2  groups omitted f o r  clarity).  - 73 -  TABLE V I I I Bond l e n g t h s  o (A) and valency a n g l e s  (degrees), w i t h  standard d e v i a t i o n s i n parentheses.  (791  Cu(2)-N(l) Cu(2)-N(2) 0u(2)-Cl(2)  2.03(2) 2.11(2) 2.28(1)  Cu(l)-Cft(l) 2.06(1) [2.11(1) c o r r e c t e d f o r l i b r a t i c  N(l)-P(l) N(l)-P(3' ) N(2)-P(l) N(2)-P(2) N(3)-P(2) N(3)-P(3) P(l)-N(4) P(l)-N(5) P(2)-N(6) P(2)-N(7) P(3)-N(8) P(3)-N(9)  1 . 6 2 ( 2 ) 1 . 6 5 ( 2 ) 1 . 6 0 ( 2 ) 1.61(2) 1 . 5 1 . 5 7 ( 2 ) 1 . 6 2 ( 2 ) 1 . 6 4 ( 2 ) 1 . 6 5 ( 2 ) 1.67(2) 1.67(2) 1 . 6 8 ( 2 )  N(4) - 0 ( 1 ) N(4) -C(2) N ( 5 ) -C(3) N ( 5 ) -0(4) N2 ( 6 ) ) - C .( 5 ) N(6) - C ( 6 ) N(7) - C ( 7 ) N(7) - 0 ( 8 ) N(8) - 0 ( 9 ) N(8) - 0 ( 1 0 ) N ( 9 ) -C(ll) N(9) - 0 ( 1 2 )  1 1 1 1 1 1 1 1 1 1 1 1  N(2)-Cu(2)-N(l» ) N(2)-Cu(2)-N(2» ) N ( l )-Cu(2J-N(l» ) CH(2)-Cu(2)-N(2) CA(2)-Cu(2)-N(l)  7 9 12 16 11 9  N { 1 ) -r U ;-ra^ ; N(l) - P ( l ) - N ( 4 ) N(l)- P ( D - N ( 5 ) N(2 )- P ( l ) - N ( 4 ) N(2 )- P ( D - N ( 5 ) N(4) - P ( D - N ( 5 )  97.2(10 118.2(11 108.2(12 1 1 1 . 3 ( 1 1 1 1 7 . 9 ( 1 1 104.5(12  N(2) -P(2)-N(3) N(2) -P(2)-N(6) N(2 )- P ( 2 ) - N ( 7 ) N(3) -P(2)-N(6) N ( 3 ) -P(2)-N(7) N(6) -P(2)-K(7) N ( 3 ) -P(3)-N(l») N ( 3 ) -P(3)-N(S) N ( 3 )- P ( 3 ) - M ( 9 ) N(l» ) - P ( 3 ) - N ( 8 ) N(l» ) - P ( 3 ) - N ( 9 ) N(8) -P(3)-N(9)  1 1 1 1 1 1 1  1 9 0 0 9 9  3  (  . 2 ( 7 J .1(8) .5(11) .9(12) .8(5) . 6 ( 6 )  CA(1)-Cu(l)-Cjt(l») 1 7 9 . 5 ( 9 ) 1 3 0 . 7 ( 1 3 ) 96.9(10) 118.4(11) 1 3 7 . 6 ( 1 3 ) 9 4 . 5 ( 9 ) 127.9(11) 1 3 2 . 4 ( 1 3 )  P(l)-N(l)-P(3') p ( i j - ; j ( i j-'Ju(2j P ( 3 )-N(l J - C u ( 2 ) P(1)~N(2)-P(2) P(l)-N(2)-Cu(2) P(2)-N(2)-Cu(2) P(2)-N(3)-P(3) r  C-N-C  111-118,  mean 1  1  4  P-N-C  1  mean 1 1  22  70  1  4  ,  . . . . . . . . . . . .  4 4 4 4 4 4 5 4 4 5 5 4  6 3 5 5 6 9 5 4 6 0 0 7  ( ( ( ( ( ( ( ( ( ( ( (  3 3 3 3 3 3 3 3 3 3 3 3  ) ) ) ) ) ) ) ) ) ) ) )  1 0 . 0 ( 1 0 18.5(12 04.3(11 0 3 . 8 ( 1 2 1 5 - 5 ( 1 2 0 5 . 2 ( 1 2 1 5 . 4 ( 1 0 - 106.0(11 1 0 9 . 6 ( 1 1 110.7(10 1 0 5 . 3 ( 1 1 1 0 9 . 8 ( 1 0  74 -  than the uncharged species, N^P^. (NMe )22 " CI)C1. <  u  2  The second group found i n the c r y s t a l s t r u c t u r e i s then the anion C u C l  2  .  This anion has been postulated to e x i s t i n  solution(64,65)  but the evidence has been mainly electrochemical and i t s v a l i d i t y has been s e r i o u s l y q u e s t i o n e d ^ - ' .  S u i t a b l e analogues for C u C l ~ do  2  2  e x i s t , however, i n the anions A g C l " , A u C ^ " ^ ^ , 2  of these are l i n e a r , as i s the postulated C u C l  _ 2  and A u B r anion.  . All  _ 2  Furthermore,  a c o - o r d i n a t i o n number of two has never been found for e i t h e r Cu (II) or Ag (II) atoms.  I t should a l s o be noted that the difference between  the observed C u ( l ) - C l ( l ) bond length, and that p r e d i c t e d from the sums o f the covalent r a d i i o f the atoms  '  , i s 0.06A.  This difference  i s of the same order as those found for A g C l ~ , A u C l ~ and AuBr ~ 2  2  2  (Table I X ) .  TABLE IX ANION  .  ACTUAL AND PREDICTED BOND LENGTH CuCl "  AgCl "  AuCl -  AuBr  2.17  2.38  2.33  ,2.45  2.11  2.36  2.31  2.35  .06  .02  .01  .10  2  sum of coo v a l e n t r a d i i (A) o  bond length (A) o  d i f f e r e n c e (A)  2  2  2  A l l o f these facts p o i n t to the existence o f the anion, C u C l , , . -  T h i s , together with the evidence for the c a t i o n , N ^ P ^ N M e ^ ^ C u C l * , s u f f i c i e n t proof that the complex, N ^ P ^ ( N M e ) 2  salt, N^P (NMe ) CuCl CuCl . +  6  2  1 2  -  2  12  Cu Cl 2  3  i s i n fact  is the  I t should be noticed i n passing that  except for the s t r u c t u r e of copper (I) oxide  , there i s almost no other  - 75 -  s t r u c t u r a l evidence for the existence of the two co-ordinate copper  (I)  atom. The s t r u c t u r e and the conformation of the 'N,P,(NMe„).„CuCl o  fa  +  z 11  c a t i o n are i n t e r e s t i n g , e s p e c i a l l y when compared to those pf the (271  parent N^P^CNN^)-^  .  One of the i n t e r e s t i n g features o f the H.P.D.  s t r u c t u r e i s the effect -rr-bonding has on the e x o c y c l i c P-N bond lengths and on the p l a n a r i t y o f the P-N X  system. Me  The dimethylamide group formally has a lone p a i r of electrons on the nitrogen atom which i n the p h o s p h o n i t r i l i c system i s donated to the adjacent phosphorus atom.  This causes a shortening of the e x o c y c l i c  P-N bond length from a c a l c u l a t e d s i n g l e bond length value of 1.74A^ ' ° (27)  to 1.675 and 1.663A  k  .  The most obvious effect o f t h i s d e r e a l i z a t i o n  i s seen i n the sums o f the angles around the e x o c y c l i c nitrogen atom. In the H.P.D. molecule, they are 357.5° and 348.7°, i n d i c a t i n g a f l a t t e n i n g ^Me • of the P-N group. This i s the r e s u l t of the loss of lone p a i r e l e c t r o n  Nle  density on the nitrogen atom which allows the methyl groups and the phosphorus atom to move away from each other i n the d i r e c t i o n of the lone pair. The r i n g ir-bonding system involves the donation of the lone p a i r on the endocyclic nitrogen atom to a s u i t a b l e , vacant d - o r b i t a l on the phosphorus atom.  However, back bonding from the e x o c y c l i c nitrogen  increases the ir-electron density of the phosphorus atom.  As i t does so,  lone p a i r electrons are i n c r e a s i n g l y l o c a l i z e d on the r i n g nitrogen atoms, so lengthening the endocyclic P-N bond length. When the lone p a i r on an e x o c y c l i c nitrogen donates to the adjacent phosphorus atom, the following effects  occur:  - 76 -  1)  the e x o c y c l i c P-N bond length i s  shortened,  2)  the sum of the angles around the e x o c y c l i c nitrogen atom increases,  3)  the endocyclic P-N bond length  increases.  I d e n t i c a l effects would be n o t i c e d i f the r i n g nitrogen lone p a i r s were removed from the tT-bonding system by complexing, i . e . the r e s u l t i n g decrease i n the u - e l e c t r o n density on the phosphorus atom would r e s u l t i n a - l a r g e r n - e l e c t r o n donation from the e x o c y c l i c nitrogen atoms. In N^P^. (NMe ) . ^ C u C l * the copper atom removes -rr-electron density 2  from four r i n g nitrogen atoms, and the expected effects are a l l observed. o  o  The average endocyclic P-N bond length i s 1.60A compared to 1.563A f o r o  the parent, and the average e x o c y c l i c P-N bond length i s 1.652A as o  compared with 1.669A for the parent.  While these differences are not  large i n themselves, they are i n the correct d i r e c t i o n . Comparisons between the i n d i v i d u a l bond lengths w i t h i n the c a t i o n are also i n t e r e s t i n g . o  There are two Cu-N bond lengths, one of  o  2.03A and one of 2.11A.  This difference could e a s i l y be due to the  effect of s t e r i c factors on the alignment of the nitrogen atom lone p a i r s , i . e . as the c a t i o n i s very crowded, optimum bonding overlap cannot be expected for a l l the Cu-N bonds. The ir-electron donation from N ( l ) and N(2) atoms to the c e n t r a l copper atom lowers the bond order of the corresponding N-P bonds.  This  i s evident i n the increased bond lengths of the c a t i o n , ( P ( 3 ' ) - N ( l ) , o  o  o  o  1.65A; N ( l ) - P ( l ) , 1.62A; N ( 2 ) - P ( l ) , 1.60A; N ( 2 ) - P ( 2 ) , 1.61A), compared to o  the parent N P (NMe ) 6  6  2  (1.563A).  The l e a s t affected are the N(3 )-P(3)  o  bond l e n g t h , (1.57A), and the N(3)-P(2) bond length,  o  (1.53A).  In both  cases, the nitrogen lone p a i r electrons donate f u l l y i n t o the r i n g  - 77 -  iT-system.  It would be expected that P ( l ) have a lower -rr-electron density  than e i t h e r P ( 3 ' ) or P ( 2 ) .  In other words, P ( l ) i s joined to two  complexing nitrogen atoms and P ( 3 ' ) and P(2) to only one.  This r e s u l t s  i n the shortest e x o c y c l i c bond lengths occuring at P ( l ) - N ( 4 ) and P(l)-N(5),  (mean,  1.63(1)1).  Because the Cu(2)-N(l) bond i s shorter than the Cu(2)-N(2) bond, i t would be reasonable to assume that the lone p a i r density would be lower on N ( l ) than on N(2).  However, the sum of the angles around  N ( l ) i s 346°, w h i l e around N(2) i t i s 360°.  This apparent anomaly can  be explained by assuming that s t e r i c factors have caused a difference i n the effectiveness of the Tr-system at N ( l ) and N(2). lone p a i r electrons are more l i k e l y to form are those of N ( l ) .  Therefore, N(2)  bonds to phosphorus than  This i s evident i n the shortness of the N ( 2 ) - P ( l ) o  o  and N(2)-P(2) bonds, (1.60A and 1.61A r e s p e c t i v e l y ) , compared to the N ( l ) - P ( l ) and N ( l ) - P ( 3 « ) bonds,  (1.62A and 1.65A r e s p e c t i v e l y ) .  Again, the difference i s small but i n the correct d i r e c t i o n . The c o n f i g u r a t i o n of the r i n g i s mainly caused by c h e l a t i o n which r e s t r i c t s the s i z e of the r i n g , p u l l i n g atoms N ( l ) , N(2), N ( l ' ) and N(2') towards the centre, so g i v i n g an average endocyclic PNP angle  f 271 of  134° compared to 1 4 7 . 5 ° f o r the parent p h o s p h o n i t r i l e  .  The s t r a i n  r e s u l t i n g from t h i s crowding i s p a r t i a l l y o f f s e t by c h e l a t i o n i t s e l f which lowers the e l e c t r o n density of the r i n g bonds.  An i l l u s t r a t i o n of  t h i s i s the N ( l ) - P ( l ) and P ( l ) - N ( 2 ) bonds which are the most affected by e l e c t r o n withdrawal, and the N(1)P(1)N(2) angle which i s the lowest of t h i s type found i n p h o s p h o n i t r i l e s .  The angles at P(2) and P ( 3 ) ,  (110.0° and 1 1 5 . 4 ° ) , are also smaller than that found for the parent,  (120  - 78 The angle P(3)N(3)P(2) i s 132.4° which i s s i m i l a r to the same type o f angle i n N ^ f N M e j g ,  1 3 3 ° ^ ^ ; and N ^ M e g ,  132°  2 6  \  but  .  This large  ( 2 6  f 27)  s i g n i f i c a n t l y smaller than that i n N ^ P ^ ( N M e ) , 147.5° 2  12  »  angle i s an outstanding feature of the parent and i s a t t r i b u t e d to steric effects.  Wagner and Vos suggest that for N^P^(NMe )^ 2  2>  no angle  less than 148° could accomodate the bulky dimethylamide groups without at l e a s t one unacceptably short C . . . C d i s t a n c e .  Because a smaller angle  i s found for the N^P^ (NMe ) . ^ C u C l * c a t i o n , high s t e r i c crowding should 2  be evident i n the  intramolecular d i s t a n c e s .  In the N^P^(NMe )^ CuCl 2  2  +  c a t i o n , there are three types of  intramolecular distances of i n t e r e s t . 1)  These are:  the distance between the carbon atoms of the lower e x o c y c l i c groups and the c h l o r i n e atom, CI (2);  2)  ,  the distance between the carbons of the upper and lower e x o c y c l i c group on the same phosphorus atom; and  3)  the distance between the carbon atoms of the upper e x o c y c l i c group on d i f f e r e n t phosphorus atoms.  Some of these distances are shown i n Table X for N,P,. (NMe„), „ and o b  z  u  N P (NMe ) CuCl . +  6  6  2  1 2  TABLE X :  Type of Distance  Species  INTRAMOLECULAR DISTANCES Distance i n N P (NMe ) 6  6  2  1)  Smallest  2)  Smallest  3.52A  3)  Smallest  3.77A  1 2  Distance i n N^P^NMe^ C u C l 1 2  , o o  o  Sum o f Van der Waals +  Radii o  3.56A  3.8A  o  o  3.23A  3.8A o  3.689A  o  3.8A  - 79 In each of these types of intramolecular d i s t a n c e s , there are distances smaller than the sum of the i n d i v i d u a l Van der Waals r a d i i , which i s a d i r e c t i n d i c a t i o n of s t e r i c crowding due to the p o s i t i o n o f the c h l o r i n e atom.  This atom forces the lower e x o c y c l i c methyl' groups  to bend upwards, t h u s • i n c r e a s i n g the crowding of the e x o c y c l i c group on the same phosphorus atom, which i n t u r n , increases the crowding o f the methyl groups on d i f f e r e n t phosphorus atoms.  The c h l o r i n e has  therefore  pushed a l l the methyl groups up and away from i t s e l f , thus the smallest C . . . C bond distances are found i n the N,P,(NMe„),~CuCl o o Z 1z  +  i o n and not i n  the parent N^P^fNMe^) A further effect of crowding i s the d i s t o r t i o n of the Cu(2) atom from square pyramidal towards a t r i g o n a l bipyramidal environment. D i s t o r t i o n r a i s e s the four r i n g nitrogens out of a planar environment, pushing up the whole r i n g and the e x o c y c l i c methyl groups with i t , and i s so obvious i t becomes u n l i k e l y that any smaller p h o s p h o n i t r i l i c amide could chelate i n the same manner; a further i n d i c a t i o n that N.P.(NMe ) 4  4  c  2.  would not chelate with copper. The Infra-Red Spectrum o f N,P,(NMe„).„Cu„Cl„: O O  Z YZ  Z  o  The i n f r a - r e d spectra of H^P^(W[e^)^^Cu^Cl^ ^6^6(^ 2-' e  12  a  r  e  v e r  y s i w i l a r (Figure 18, Table V I ) .  and the parent This i s reasonable  because the complex has retained both the p h o s p h o n i t r i l i c r i n g and the e x o c y c l i c groups of the parent.  Moreover, the spectra were taken i n a  region where Cu-N or Cu-Cl v i b r a t i o n a l modes would not produce peaks, so only the r i n g and e x o c y c l i c groups would c o n t r i b u t e to the spectrum. However, differences between spectra would be expected due to e l e c t r o n  8  - 80 -  withdrawal from the r i n g i n the complex and changes i n symmetry. Unfortunately, very l i t t l e information e x i s t s about the assignment of bands i n the spectra of p h o s p h o n i t r i l i c d e r i v a t i v e s , so that a complete i n t e r p r e t a t i o n of the spectrum of NgPgCNN^).^ ^ u ^ C l j must await a b e t t e r understanding of the e n t i r e f i e l d . . (50,54) does , previous work allow some t«e. n• «t a. ,t.i•v e  However,  • <assignments.  -The peaks between 3010 and 2790 cm" i n both spectra may 1  s a f e l y be assigned to asymmetric and symmetric C-H s t r e t c h i n g modes and overtones of CH^ bonding v i b r a t i o n s .  The s i m i l a r i t y of the spectra  i n t h i s region i n d i c a t e s that there i s l i t t l e difference between the environments of the CH^ groups i n the complex and the parent.-'  This,  i n t u r n , i s consistent with c o - o r d i n a t i o n through the rings rather than the e x o c y c l i c groups. The peak at 2150 c m  -1  present i n the parent, yet absent i n  the complex, i s most probably an overtone of the peak at 1070 c m " . 1  The peaks between 1490 - 1425 c m  -1  for the complex and between  1480 - 1450 cm" for the parent can be assigned to asymmetric C-H 1  bending v i b r a t i o n s .  These are e s s e n t i a l l y s i m i l a r i n both compounds;  again i n d i c a t i v e of bonding between the copper and the endocyclic nitrogen atoms. There i s no doubt that the main v (P-N-P) band i s centered as near 1270 cm  1  i n the parent, but extensive s p l i t t i n g and reduction of  frequency occurs i n the complex i n d i c a t i n g strong i n t e r a c t i o n with the copper atom.  I t should be noticed that c h e l a t i o n of the copper w i l l  have g r e a t l y increased the r i g i d i t y of the r i n g r e s u l t i n g i n a more complex v i b r a t i o n a l p a t t e r n .  - 81 -  The doublet at 1070 and 1063 cm" i n the spectrum of the 1  parent molecule corresponds to the asymmetric band at 1062 c m  -1  in  the spectrum of the complex, and i s to be a t t r i b u t e d to C-N s t r e t c h i n g . Any further i n t e r p r e t a t i o n of the spectra past t h i s point becomes f u t i l e because of the i n c r e a s i n g number and complexity of the peaks. The main point o f i n t e r e s t i n the spectra i s the s i m i l a r i t y between the spectrum of the complex and that of the parent.  This i s  consistent with a l l the known s t r u c t u r a l information on the two molecules. v  Complexing does, however, have a large effect on the  (P-N-P) bands, causing them to s p l i t . 3-S  Therefore, the dominant features  of the spectra are due to  the various modes o f the p h o s p h o n i t r i l i c system; only as copper c h e l a t i o n a f f e c t s these does i t have any effect on the spectra. fact that only the v  Finally,  the  (P-N-P) bands are affected i s then c h a r a c t e r i s t i c  3.S  of endocyclic bonding to copper.  Studies of N,P,(NMe_)._Cu Cl_ i n S o l u t i o n : 6 6 2 12 2 3 0  The s t e r i c interference evident i n the structure of N..P,(NMe„),„oo 2 12 Q ^ C l g could be r e l i e v e d by the l o s s of the C l ( 2 ) atom from the c a t i o n . This would change the environment of Cu(2) from d i s t o r t e d square pyramidal to square p l a n a r .  The l a t t e r i s a w e l l known type of environment  for Cu(II) atoms, e.g. CuO, [ C u ( P y ) ] 4  2 + ( 5 6 )  .  I f the c h l o r i n e were l o s t as the anion C l ~ , than the double charged c a t i o n , N^P^OMe^)^2^ ^ n  +  w o u  l d be l e f t i n s o l u t i o n .  The other  - 82 -  species, C u C l ~ could also break down, though no information e x i s t s 2  concerning i t s behaviour i n s o l u t i o n .  N y h o ' l m ^ ^ used preparative  evidence to suggest the existence of the s a l t s  [Cu(AsMecj> ) ] [CuX ] . 2 4  2  These, however, were non e l e c t r o l y t e s o f undetermined molecular weight and probably do not contain the anion C u C l ^ " .  No work has been done  on a s a l t d e f i n i t e l y known to contain the anion CuCl,,"". With maximum i o n i z a t i o n t h i s anion would produce one Cu c a t i o n and two CI  anions, so that the highest p o s s i b l e degree of  d i s s o c i a t i o n which can be envisaged for NgPg(NMe )^ ^ 2^*3 * ' u  2  N P (NMe ) CuCl CuCl " +  6  6  2  12  2  > HP(NMe ) 2  1 2  Cu  + +  s  2  + Cu + 3Cl" +  I f d i s s o c i a t i o n occurs i n s o l u t i o n , then an a n a l y s i s for i o n i c c h l o r i n e w i l l show three c h l o r i n e s . p e r molecule.  Q u a n t i t a t i v e Ionic Chlorine A n a l y s i s : A gravimetric c h l o r i n e a n a l y s i s with s i l v e r n i t r a t e was employed.  The complex was d i s s o l v e d i n pure, dry a c e t o n i t r i l e and a  s o l u t i o n of s i l v e r n i t r a t e added.  The r e s u l t i n g dense white p r e c i p i t a t e  was f i l t e r e d o f f i n a tared s i n t e r e d glass f i l t e r , d r i e d , and weighed. 90.1 mg of the complex gave 0.0381 g of s i l v e r c h l o r i d e : ions would give 0.0376 g.  three c h l o r i n e  Thus, under the conditions employed, both  c a t i o n and anion d i s s o c i a t e completely.  Conductance Studies; The p o s s i b l e i o n i z a t i o n path solution i s :  of N ^ P ^ C N M e ^ ^ C u ^ l ^ i n  - 83 N P (NMe ) Cu Cl 6  6  2  1 2  2  N P (NMe ) CuCl 6  6  2  > N^P^(NMe )^CuCl* + C u C l "  3  2  2  ) N P (NMe ) Cu  +  12  6  6  2  + +  1 2  + Cl  C u C l ~ ——>CuCl + C l ' 2  CuCl  > Cu + C l +  -  The i o n i c c h l o r i n e analysis showed that a l l o f these steps do occur, but d i d not show t h e i r r e l a t i v e importance. Electrochemical measurements were done on a Wayne-Kerr U n i v e r s a l Bridge B221A.  The solvent used was a c e t o n i t r i l e d r i e d by the  method o u t l i n e d i n Chapter 2.  The c e l l used (Figure 1) had a constant,  0.19249, determined using an aqueous s o l u t i o n with a known concentration of potassium c h l o r i d e .  The complex studied had been analyzed p r e v i o u s l y  as N ^ P ^ ( N M e ) C u C l .  The constant temperature bath was held at 25°C  2  12  2  3  ± 0.02C°, A standard s o l u t i o n of N ^ P ^ ( N M e ) C u C l ^ i n 9 ml of 2  a c e t o n i t r i l e was transferred 25 ml of a c e t o n i t r i l e . taken.  12  2  i n 1 ml q u a n t i t i e s i n t o the c e l l containing  After each a d d i t i o n conductance readings were  The molecular conductance was then c a l c u l a t e d using the  formula weight of N , P , ( N M e J . _ C u C l _ . 0  D O  2 12  2  o  A l l simple e l e c t r o l y t e s ^ ' ' i n a c e t o n i t r i l e and s i m i l a r 9  solvents obey the equation:  A where:  _/\_ =  A-A/C  molecular conductance l i m i t i n g molecular conductance  t5  .  1}  - 84 -  TABLE XI L i m i t i n g Molecular Conductances of Some S a l t s i n A c e t o n i t r i l e at 25°C Salt  .(Ohms)  A  Reference  O LiC10  183.25  4  (70)  NaClO. 4  192.40  "  KCIO. 4  208.92  "  203.24  "  207.63  »  194  (71)  RbC10  4  CsCKK 4 BuNH C10 3  4  BuNH Pic.  167  "  Bu NH„C10,  185  "  Bu NH Pic.  158  "  Bu NHC10  4  177  . . "  Bu NHPic.  149  "  Et.NCIO, 4 4  189  "  Et N Salicylate  176  "  PyHC10  202  »  Et NCl  176.6  "  Et.ClO. 4 4  188.9  "  Et.NBCl. 4 4 .  180.9  "  3  o  2  2  3  3  4  4  4  (C H ) P N H SbCl 6  5  4  2  3  4  6  162.5  380  /C  x 10 -Amoles~ 2  J 2  Figure 21. Conductance Plot of NLP^fNMe 1 Cu  - 86 -  (2, = m o l a r i t y /\  = constant dependant on solvent and  The l i m i t i n g conductance, i . e . the conductance at i n f i n i t e d i l l u t i o n , i s a function of the solvent and the number and types of ions i n s o l u t i o n . For a given solvent the A very s i m i l a r .  values for any 1:1 e l e c t r o l y t e w i l l a l l be  In a c e t o n i t r i l e the A  -values for 1:1 e l e c t r o l y t e s are  between 209 - 155 Ohms" (Table X I ) . . Therefore, any A. h i g h e r than 209 1  Q  Ohms" demonstrates the presence of an e l e c t r o l y t e possessing more than 1  two univalent i o n s . t /(T for N , P , ( N M e ) . „ C u C l „ .  Figure 21 shows the p l o t of  1  0  0  The l i m i t i n g conductance i s 377 ± 10 Ohms" which i s much too large for a 1  1:1 e l e c t r o l y t e .  The r e s u l t s are compatible with various d i s s o c i a t i o n  patterns, t y p i c a l l y with: N P (NMe ) CuCl CuCl " ^ N P ( N M e ) +  6  6  2  12  2  6  6  2  1 2  Cu  + +  + C l " + CuC^"  Further studies are necessary to e s t a b l i s h t h i s pattern  definitely.  Magnetic Measurements of N ^ P ^ ( N M e ) ^ C u C l : 2  2  2  3  In the c r y s t a l s t r u c t u r e of N-P,(NMe„) „Cu-Cl_ the i n t r a 6 6 2 1 2 2 3 n  molecular distance between the two copper atoms i s too large to allow any appreciable i n t e r a c t i o n .  The c r y s t a l should therefore have a  magnetic moment corresponding to one copper (II) ion per molecule. This i s indeed the case and therefore i s further evidence that the molecule contains two o x i d a t i o n states of the copper atom. The magnetic moment, u, of a metal i o n may be approximated by  •  - 87 -  a c a l c u l a t e d value, u ' s  obtained from. y =/4s(s s  i)  +  ( 5  _  2 )  where s i s the t o t a l spin quantum number. In p r a c t i c e , however, the observed magnetic moment, u, i s u s u a l l y higher than  For the copper (II) atom  i s 1.73 B.M. (Bohr (72 73)  Magnetons), but the usual experimental value i s 1.7 - 2.2 B.M.  5  .  This i s due to incomplete o r b i t a l quenching which i n the extreme case would give a u value approximated by: y = / 4 s (s + 1) + L(L + 1) s  +  L  (5-3)  where L i s the t o t a l o r b i t a l quantum number. The experimental magnetic moment, y, i s c a l c u l a t e d from the equation: y = 2.83/X'T m  (5-4) J  where X^ = molar paramagnetic s u s c e p t i b i l i t y of the metal ion T  = temperature.  The molar s u s c e p t i b i l i t y o f the whole molecule, X , i s found by the (74) Faraday method  .  This value has to be corrected for the diamagnetism  of every species i n the molecule, which i s done using the equation: X = X' + E X m m . A A  d i a v  (5-5) J  cLxci  where X^  = diamagnetic molar s u s c e p t i b i l i t y of a l l species A. diet  Values of X^ (72,73) ions .  can be found i n the l i t e r a t u r e for various atoms and  The magnetic s u s c e p t i b i l i t y measurements were done i n t h i s  - 88 -  department  u s i n g the Faraday method  f 75")  .  An A l p h a Model 9500 water-  c o o l e d 6 i n c h e s electromagnet equipped w i t h p o l e t i p s o f Heyding d e s i g n , (1 1/2 i n c h e s i n p o l e gap), was used. suspended  Samples,  i n a q u a r t z bucket from a Cahn Rg e l e c t r o b a l a n c e .  were done under a n i t r o g e n atmosphere were f i e l d  (approx. 5 mg), were  independent.  a t 295°K.  The magnetic  X , was  m'  r  c.g.s. u n i t s .  6  susceptibilities  C a l i b r a t i o n was a c h i e v e d u s i n g HgCofCNS)^  The molar s u s c e p t i b i l i t y o f N , P , ( M N e „ ) „ C u „ C l „ , ' 6 6 2 12 2 3 845.83 x 1 0 ~  Measurements  The d i a m a g n e t i c molar s u s c e p t i b i l i t y o f  N,P, (NMe„)., „ has n o t been determined and t h e r e f o r e had t o be c a l c u l a t e d . 6 6 2 12 d is. The hexameric p h o s p h o n i t r i l i c c h l o r i d e d e r i v a t i v e has a X -300.5 x 1 0 ~  c.g.s. u n i t s (  6  atom as -20.1 x 1 0 ~  6  7 7  ^  }  t h e r e f o r e , t a k i n g X^*  c.g.s. u n i t s ^ ' " * 72  73  b  -59.3  x 10~  the x ^ m  a  a  of  m  of a chlorine  o f the P,N, r i n g i s 6 6 "  c.g.s. u n i t s . .  6  The d i a m a g n e t i c c o r r e c t i o n n e c e s s a r y f o r N.P.(NMe ).„Cu_Cl, 0  in s -573.3 x 1 0 ~ c.g.s. u n i t s . 5  T a b l e XII <  7 2  '  \ Table XII 7 3  Species N P 6  6  T h i s i s c a l c u l a t e d u s i n g the c o n s t a n t s  ring  N i n amine  Diamagnetic ^A^  X  Susceptibilities l^)  6 ,  (c.g.s. -59.3 - 5.6  C  - 6.0  H  - 2.9  CI"  - 2.6  Cu  -11  Cu  +  + +  -12  units)"  1  - 89 -  Therefore,  as: X' = X - E X ^ m m . 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