ti» -OP cü û, M L, D, M VO üO •H [14
- 96 -
red u ced by 11$ t o 2.7 2S, The bond a n g le s Fe-X -Fe i n t h e s e two compounds a r e e s s e n t i a l l y i d e n t i c a l , and i f t h i s i s assumed t o be t r u e f o r Fe^Br^CNO)^ a l s o , th e n by a p p l i c a t i o n o f a r e a s o n a b le e s t i m a t e f o r th e Fe~Br bond d i s t a n c e o f 2,38%^^ a v a lu e o f ab o u t 2.8% f o r th e F e-Fe
1Q
d i s t a n c e i s o b t a i n e d . The diam agnetism o f th e d im e r ic complex has been e x p la in e d as b e in g due t o th e e x i s t e n c e o f a
22
d i r e c t Fe-Fe bond and hence th e g r e a t e r t h i s d i s t a n c e , th e more s u s c e p t i b l e th e complex w i l l be to d i s s o c i a t i o n .
A d d itio n o f t h e p seu d o h alo g en s NCO” , NCS” , and NCSe~ to DMF s o l u t i o n s o f Fe^IgCNO)^^ r e s u l t e d i n th e g e n e r a t i o n o f new e . p . r . s p e c t r a . A d d itio n o f NCS” y i e l d e d th e complex [FefNOOgfNCS)^]" i d e n t i c a l to t h a t p r e v i o u s ly o b se rv e d ^ i n Fe(II)/NCS*"/NO r e a c t i o n s .
A d d itio n o f NCO” y i e l d e d th e a n alo g o u s complex [FeCNOO^fNCOj^]" (g = 2 .0 3 0 , A(1^N)= 2.6G (2xNC0), 1.8G (2xN0) ( f i g . 5 . 6 ) . A d d itio n o f s e le n o c y a n a te (NCSe) y i e l d e d a complex weak sp ectru m which co u ld n o t be unam biguously a s s i g n e d .
5.3 . 3
1
R auchfuss and W e a t h e r i l l have shown t h a t a d d i t i o n o f a l k y l t h i o l s and a b ase to THF s o l u t i o n s o f th e yU^-iodo complex Fe^I^CNO)^ y i e l d F e2(8R)2(N0)^ i n a p r e p a r a t i v e l y u s e f u l p ro c e d u re :
FeglgCNO)^ + 2RSH + 2E t^ N S^FegCSRigCNO)^ + Et^NH+l".
Fe^IgCNO)^ i n t o FegfSRjgfNO)^ i s r e p o r t e d .
E xam in atio n o f s o l u t i o n s o f FeglgCNO)^ i n THF showed th e e x i s t e n c e o f a dimer/monomer e q u il ib r i u m ;
[FeCNOOgllg ZCFeCNO)^!]
A d d itio n o f th e b a s e , t r i e t h y lam in e , to THF s o l u t i o n s o f Fe^I^CNO)^ y i e l d e d e . p . r . s p e c t r a s i m i l a r to th o s e o f th e y i^ - io d o complex i n DMF:
[Fe(NO)gI]g 2F e(N 0)gI--- > [FeCNO)^!^]" + FeCNO)^! + [FefNOOgIg]"
E . p . r , e x a m in a tio n o f FeglgfN O )^ i n Et^N y i e l d e d a sp ectru m composed o f a s i n g l e p a ra m ag n e tic s p e c i e s , t h a t o f [FeCNOjgCNEtg)^]* ( g -2,0 3 0, A(N)=4.7G, A(N)=2.2G). The o b s e r v a t io n o f a d i s o l v o complex i s n o tew o rth y s in c e i t d e m o n s tra te s t h a t t h e n a t u r e o f th e b r id g in g l ig a n d s a f f e c t th e s o lv e com plex. I n c h a p te r f o u r i t i s shown t h a t Fe2(8R)2(N0)^ form s raono-solvo com plexes (FeCNOOgfSRjtSolv)) in a l i p h a t i c am ines. T h is o b s e r v a t io n s u g g e s ts t h a t t h e a l k y l t h i o l a t o g ro u p bonds s t r o n g e r t o [FeCNO)^]^ th a n i o d i d e .
What a p p e a rs t o happen on a d d i t i o n o f t r i e t h y lam in e t o THF s o l u t i o n s o f Fe^IgCNO)^ i s t h a t th e io d id e c o o r d in a te d t o FeCNO)^! i s d i s p l a c e d to y i e l d [Fe(NO)_]^ c o o r d in a te d t o Et_N, th e d i s p l a c e d
c 5
io d id e th e n combines w ith FefN O jgl t o y i e l d [FefN OO glg]".
Et-N
FeCNOigI --- 5--- =?» [FeCNGOgCNEt >2] + l “
- 98 - Et N
[FeC N O iglg]"- ^ [F e(N 0)2(NE tg)2]+ + 21*
C ontin u ed a d d i t i o n o f t r i e t h y l a m i n e d i s p l a c e s t h e i o d in e from t h e d i iodo complex t o y i e l d [FefN CO ^fNEt^jg]^,
A d d itio n o f a t h i o l (c h o se n th ro u g h o u t as i - p r o p y l m ercap tan f o r s i m p l i f i e d s p e c t r a l a s sig n m e n t, s in c e t h i s t h i o l c o n ta i n s o n ly a