UBC Theses and Dissertations

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UBC Theses and Dissertations

Structure determination of some di-(tertiary arsine) derivatives of metal carbonyls Roberts, Paul J. 1970

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THE STRUCTURE DETERMINATION OF SOME DI-(TERTIARY ARSINE) DERIVATIVES OF METAL CARBONYLS by PAIIL J . -ROBERTS B . S c . ( H o n . ) , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1967 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTQR OF PHILOSOPHY i n t h e D e p a r t m e n t o f C h e m i s t r y We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA November, 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 f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree t h a t permiss ion f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . It i s understood that copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l ga in s h a l l not be a l lowed without my w r i t t e n p e r m i s s i o n . Department of Chemistry  The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, Canada Date November l$t 1970 ABSTRACT S u p e r v i s o r : P r o f e s s o r James T r o t t e r The s t r u c t u r e s o f f o u r d i - ( t e r t i a r y a r s i n e ) d e r i -v a t i v e s o f m e t a l c a r b o n y l s have been d e t e r m i n e d by a s e -l e c t i o n o f d i r e c t , P a t t e r s o n , and F o u r i e r methods, a p p l i e d t o Mo-K d i f f T a c t o m e t e r d a t a , —a 1,2- b i s ( d i m e t h y l a r s i n o ) t e t r a f l u o r o c y c l o b u t e n e -t r i - i r o n d e c a c a r b o n y l , Me 2AsC=C (AsMe.2 ) C F 2 C F 2 . F e 3 (CO) 1 0 , c r y s t a l l i z e s i n t h e m o n o c l i n i c s p a c e g r o u p P ^ / c , w i t h a = 11.60, b = 20.04, c = 22.11 A, 3 = 9 3 . 7 ° , Z = 8 (two m o l e c u l e s p e r a s y m m e t r i c u n i t ) . The s t r u c t u r e was r e f i n e d by l e a s t - s q u a r e s p r o c e d u r e s (a t o t a l o f 74 atoms) t o a f i n a l R o f 0.09 f o r 2524 o b s e r v e d (of a t o t a l o f 3234) r e f l e c t i o n s . The m o l e c u l e i s b e s t d e s c r i b e d as a d e r i v a t i v e o f F e 3 ( C O ) i 2 , i n w h i c h one t e r m i n a l c a r b o n y l g r o u p on e a c h o f t h e two e q u i v a l e n t i r o n atoms i s r e p l a c e d by an a r s e n i c atom o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d . The c e n t r a l F e 3 A s 2 c l u s t e r i s s i g n i f i c a n t l y b e n t i n one o f t h e m o l e c u l e s o f t h e a s y m m e t r i c u n i t , b u t i s more n e a r l y p l a n a r i n t h e o t h e r m o l e c u l e . The F e - F e bond d i s t a n c e s i n t h e i r o n t r i a n g l e o (2.53,2.65,2.65 A) do n o t d i f f e r s i g n i f i c a n t l y f r o m t h o s e i n t h e p a r e n t compound. C r y s t a l s o f b i s ( 1 , 2 - b i s ( d i m e t h y l a r s i n o ) t e t r a f l u o r o c y c l o b u t e n e ) t r i r u t h e n i u m o c t a c a r b o n y l , ( M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 ) R u 3 ( C O ) 8 / a r e o r t h o r h o m b i c , s p a c e g r o u p P b c n , a = 9.07, b = 1 8 . 5 3 , c = 21.81 A, Z = 4 ( o n e - h a l f m o l e c u l e p e r a s y m m e t r i c u n i t ) . The s t r u c t u r e was r e f i n e d by l e a s t -s q u a r e s p r o c e d u r e s t o a f i n a l R o f 0.078 f o r 1507 o b s e r v e d ( o f a t o t a l o f 1712) r e f l e c t i o n s . The m o l e c u l e l i e s on a c r y s t a l l o g r a p h i c t w o - f o l d a x i s , and i s b e s t d e s c r i b e d as a d e r i v a t i v e o f R u 3 ( C O ) i 2 i n w h i c h two c a r b o n y l s on one r u t h e n i u m and one c a r b o n y l on e a c h o f t h e o t h e r r u t h e n i u m atoms a r e r e p l a c e d by t h e a r s e n i c atoms o f t h e b i d e n t a t e d i - ( t e r t i a r y a r s i n e ) l i g a n d s , i n s u c h a way t h a t e a c h l i g a n d b r i d g e s two r u t h e n i u m a t o m s , and one Ru-Ru bond o r e m a i n s u n b r i d g e d . T h i s u n b r i d g e d Ru-Ru bond (2.785 A) o i s s i g n i f i c a n t l y s h o r t e r t h a n t h e b r i d g e d ones (2.853 A) o and t h a n t h o s e o f t h e p a r e n t R u 3 ( C O ) i 2 ( a v e r a g e 2 . 8 4 8 A ) . The s k e l e t o n s o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d s do n o t d e v i a t e s i g n i f i c a n t l y f r o m e x a c t p l a n a r i t y , t h e p l a n e o f e a c h l i g a n d b e i n g t w i s t e d 18° w i t h r e s p e c t t o t h e p l a n e o f t h e r u t h e n i u m t r i a n g l e . The mean Ru-As bond l e n g t h i s 2.407 A. 1,2- b i s ( d i m e t h y l a r s i n o ) t e t r a f l u o r o c y c l o b u t e n e -t r i r u t h e n i u m d e c a c a r b o n y 1 , M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 . R u 3 ( C O ) i 0 , c r y s t a l l i z e s i n o r t h o r h o m b i c s p a c e group. P2 i 2 12 i , a = 8.594, b = 1 8 . 7 9 5 , c = 16.69 A, Z = 4. The s t r u c t u r e was r e f i n e d by l e a s t - s q u a r e s p r o c e d u r e s .to a f i n a l R o f 0.076 f o r 1828 o b s e r v e d ( o f a t o t a l o f 2028) r e f l e c t i o n s . The compound i s a d e r i v a t i v e o f R u 3 ( C O ) i 2 i n w h i c h one e q u a t o r i a l c a r b o n y l g r o u p on e a c h o f two r u t h e n i u m atoms i s r e p l a c e d by an a r s e n i c atom o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d i n s u c h a way t h a t t h e p l a n e o f t h e l i g a n d i s t w i s t e d 0 18 w i t h r e s p e c t t o t h e p l a n e o f t h e r u t h e n i u m t r i a n g l e . Ru-Ru bond d i s t a n c e s a r e 2.831, 2.831, and 2.858 A, t h e d i f -f e r e n c e between t h e s h o r t and l o n g bond l e n g t h s b e i n g s t a t i s -t i c a l l y s i g n i f i c a n t and e x p l i c a b l e i n terms o f t h e b o n d i n g c h a r a c t e r i s t i c s o f t h e l i g a n d . 1,2- b i s ( d i m e t h y l a r s i n o ) h e x a f l u o r o p r o p a n e m o l y b d e n u m t e t r a c a r b o n y l , M e 2 A s C F ( C F 3 ) C F 2 A s M e 2 . M o ( C O ) 4 , c r y s t a l l i z e s : i n t h e m o n o c l i n i c s p a c e g r o u p C2/c, a = 25.06, b = 13.27, c = 11.56 A, 6 = 102.8°, Z = 8. The s t r u c t u r e was r e f i n e d by l e a s t s q u a r e s methods t o a f i n a l R o f 0.073 f o r 1510 , o b s e r v e d (of a t o t a l o f 1750) r e f l e c t i o n s . The m o l e c u l e i s d e r i v e d f r o m Mo(CO)6 by r e p l a c i n g two c a r b o n y l g r o u p s w i t h t h e a r s e n i c atoms o f t h e c h e l a t i n g d i - ( t e r t i a r y a r s i n e ) l i g a n d . Two o f t h e c a r b o n - f l u o r i n e bond d i s t a n c e s (mean o o 1.505 A) a r e s i g n i f i c a n t l y l o n g e r t h a n t h e o t h e r s (mean 1.30 A) and t h e d i s t a n c e between t h e c a r b o n atoms o f t h e l i g a n d s k e -o l e t o n i s r e m a r k a b l y s h o r t (1.40 A ) . The w e i g h t e d mean Mo-As bond l e n g t h i s 2,572 A. V TABLE OF CONTENTS PAGE T I T L E PAGE i ABSTRACT i i TABLE OF CONTENTS V L I S T OF TABLES v i i L I S T OF FIGURES x ACKNOWLEDGEMENTS x i i I . INTRODUCTION 1 A. THE TECHNIQUE OF X-RAY CRYSTAL ANALYSIS 2 B. CHARACTERISTICS OF METAL CARBONYLS AND THEIR DERIVATIVES 8 C. RESULTS OF PRELIMINARY EXPERIMENTS 11 I I . EXPERIMENTAL SECTION 16 I I I . THE STRUCTURE DETERMINATION OF M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • F e 3 ( C O ) i 0 . 21 STRUCTURE ANALYSIS 22 DISCUSSION 36 IV. THE STRUCTURE DETERMINATION OF ( M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 ) 2 • R u 3 ( C O ) 8 . 46 STRUCTURE ANALYSIS 47 DISCUSSION 56 V. THE STRUCTURE DETERMINATION OF M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • R u 3 (CO) io. 6 4 STRUCTURE ANALYSIS 65 DISCUSSION 74 V I . THE STRUCTURE DETERMINATION OF M e 2 A s C F 2 C F ( C F 3 ) A s M e 2 • Mo (CO) it.. 79 STRUCTURE ANALYSIS 80 v i DISCUSSION 86 V I I . COMPUTER PROGRAMMING 97 A. THE WEIGHTING SCHEME PROGRAM "UPDATE". 98 B. IMPLEMENTATION OF THE THERMAL PLOT PROGRAM "ORTEP". 103 V I I I . REFERENCES 106 v i i L I S T OF TABLES PAGE I . INTRODUCTION I I . EXPERIMENTAL SECTION I I . I C r y s t a l and e x p e r i m e n t a l d a t a f o r a l l s t r u c t u r e s . . 1 9 I I I . THE STRUCTURE DETERMINATION OF M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • F e 3 ( C O ) i 0 . I I I . I C o m p a r i s o n o f 51 p o s s i b l e s o l u t i o n s g e n e r a t e d by Hoge's s i g n d e t e r m i n a t i o n p r o g r a m . 25 I I I . I I F i n a l m e a s u r e d a nd c a l c u l a t e d s t r u c t u r e f a c t o r s . 29 I I I . I l l F i n a l p o s i t i o n a l a n d t h e r m a l p a r a m e t e r s w i t h t h e i r s t a n d a r d d e v i a t i o n s . 31 I I I . I V E q u a t i o n s o f w e i g h t e d mean p l a n e s f o r i r o n t r i a n g l e a n d d i - ( t e r t i a r y a r s i n e ) . 33 I I I . V Bond d i s t a n c e s a n d v a l e n c y a n g l e s . 34 I I I . V I M a g n i t u d e s o f t h e p r i n c i p a l a x e s o f t h e r m a l v i b r a t i o n e l l i p s o i d s o f i r o n a n d a r s e n i c a t o m s . 42 I V . THE STRUCTURE DETERMINATION O F ( M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 ) 2 « R u 3 ( C O ) 8 . I V . I C o m p a r i s o n o f 16 p o s s i b l e s o l u t i o n s g e n e r a t e d by L o n g ' s s i g n d e t e r m i n a t i o n p r o g r a m . 49 I V . I I F i n a l m e a s u r e d a nd c a l c u l a t e d s t r u c t u r e f a c t o r s . 51 I V . I l l F i n a l p o s i t i o n a l and t h e r m a l p a r a m e t e r s w i t h t h e i r s t a n d a r d d e v i a t i o n s . 53 I V . I V Bond d i s t a n c e s and v a l e n c e a n g l e s . 54 IV . V E q u a t i o n s o f w e i g h t e d mean p l a n e s f o r r u t h e n i u m t r i a n g l e a n d d i - ( t e r t i a r y a r s i n e ) . 55 I V . V I M a g n i t u d e s o f p r i n c i p a l a x e s o f t h e r m a l v i b r a t i o n f o r atoms r e f i n e d a n i s o -t r o p i c a l l y . 55 V. THE STRUCTURE DETERMINATION OF M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • R u 3 ( C O ) i o • V . I F i n a l m e a s u r e d and c a l c u l a t e d s t r u c t u r e f a c t o r s . 67 V . I I F i n a l p o s i t i o n a l and t h e r m a l p a r a m e t e r s w i t h t h e i r s t a n d a r d d e v i a t i o n s . 69 V . I I I Bond d i s t a n c e s a n d v a l e n c e a n g l e s . 71 V . I V E q u a t i o n s o f w e i g h t e d mean p l a n e s f o r r u t h e n i u m t r i a n g l e a n d d i - ( t e r t i a r y a r s i n e ) . 73 V.V M a g n i t u d e s o f p r i n c i p a l a x e s o f t h e r m a l v i b r a t i o n f o r r u t h e n i u m a n d a r s e n i c a t o m s . 73 V I . THE STRUCTURE DETERMINATION OF M e 2 A s C F 2 C F ( C F 3 ) A s M e 2 • Mo ( C O ) 4 . V I . I F i n a l m e a s u r e d a nd c a l c u l a t e d s t r u c t u r e f a c t o r s . 82 V I . I I F i n a l p o s i t i o n a l and t h e r m a l p a r a m e t e r s w i t h t h e i r s t a n d a r d d e v i a t i o n s . 83 V I . I l l Bond d i s t a n c e s a n d v a l e n c e a n g l e s . 84 V I . I V M a g n i t u d e s o f p r i n c i p a l a x e s o f t h e r m a l v i b r a t i o n o f atoms r e f i n e d a n i s o t r o p i c a l l y . 85 V I . V E q u a t i o n s o f w e i g h t e d mean p l a n e o f molybdenum o c t a h e d r o n and d i r e c t i o n c o s i n e s o f v e c t o r C ( 5 ) - C ( 6 ) . 8 8 ix V I I . COMPUTER PROGRAMMING V I I . I F o r t r a n l i s t i n g o f p r o g r a m "UPDATE". 101 L I S T OF FIGURES PAGE INTRODUCTION 1.1 E x p e c t e d s t r u c t u r e f o r M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • F e 3 ( C O ) i 0 . 12 1.2 Two p o s s i b l e s t r u c t u r e s f o r ( M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 ) 2 R u 3 ( C O ) 8 . 14 1.3 Two p o s s i b l e s t r u c t u r e s f o r M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 ' R u 3 ( C O ) i o • 15 I I . EXPERIMENTAL SECTION I I I . THE STRUCTURE DETERMINATION OF M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • F e 3 (CO) io. I I I . l E-map w i t h heavy atom p o s i t i o n s s u p e r i m p o s e d . 27 111.2 M o l e c u l a r s t r u c t u r e o f M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • F e 3 ( C O ) 1 0 . 37 111.3 View o f a s y m m e t r i c c a r b o n y l b r i d g e s . 39 111.4 C o - o r d i n a t i o n a b o u t a r s e n i c atoms, s h o w i n g a n g l e s a v e r a g e d o v e r t h e f o u r a r s e n i c atoms i n t h e a s y m m e t r i c u n i t . 41 111.5 I n t e r m o l e c u l a r c o n t a c t s i n g e n e r a l v i e w . 43 111.6 P r o j e c t i o n o f u n i t c e l l down a - a x i s . 45 IV. THE STRUCTURE DETERMINATION OF ( M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 ) 2 R u 3 ( C O ) 8 . IV. 1 M o l e c u l a r s t r u c t u r e o f (Me 2AsC=C ( A s M e 2 ) C F 2 . C F 2 ) 2 • R u 3 ( C O ) 8 . 57 IV.2 C o m p a r i s o n o f ( M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 ) 2 R u 3 ( C O ) 8 and ( C 8 H 8 ) 2 R u 3 ( C O ) h . 59 IV.3 D i s t o r t i o n o f c o - o r d i n a t i o n a b o u t r u t h e n i u m . 60 x i I V . 4 P r o j e c t i o n o f t h e u n i t c e l l down a - a x i s . 63 V. THE STRUCTURE DETERMINATION OF M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • R u 3 ( C O ) i o • V . l M o l e c u l a r s t r u c t u r e o f M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • R u 3 ( C O ) i 0 . 75 V.2 D i s t o r t i o n o f c o - o r d i n a t i o n a b o u t r u t h e n i u m . 77 V.3 P r o j e c t i o n o f u n i t c e l l down a - a x i s . 78 V I . THE STRUCTURE DETERMINATION OF M e 2 A s C F 2 C F ( C F 3 ) A s M e 2 • Mo(CO)„. V I . 1 M o l e c u l a r s t r u c t u r e o f Me 2 A s C F 2 C F ( C F 3 ) A s M e 2 • Mo (CO) i j . 87 V I . 2 V i e w o f bond d i s t a n c e s and d i h e d r a l a n g l e s a r o u n d C ( 5 ) - C ( 6 ) b o n d . 90 V I . 3 P o s t u l a t e d b o n d i n g scheme t o a c c o u n t f o r a n o m a l o u s o b s e r v a t i o n s . 92 V I . 4 P r o j e c t i o n o f u n i t c e l l down c - a x i s . 96 V I I . COMPUTER PROGRAMMING V I I . l S t e r e o d i a g r a m s o f a l l f o u r d i - ( t e r t i a r y a r s i n e ) d e r i v a t i v e s . 104 ACKNOWLEDGEMENTS I w i s h t o e x p r e s s my g r a t i t u d e t o P r o f e s s o r T r o t t e r f o r h i s c o n t i n u o u s g u i d a n c e a n d t o P r o f e s s o r B. R. P e n f o l d and D r . F. H. A l l e n f o r a s s i s t a n c e w i t h v a r i o u s a s p e c t s o f c r y s t a l l o g r a p h i c c o m p u t i n g . I w o u l d l i k e t o t h a n k P r o f e s s o r s W. R. C u l l e n and N. L. P a d d o c k f o r r e a d i n g t h e p r e l i m i n a r y d r a f t o f t h i s t h e s i s and f o r m a k i n g many h e l p f u l s u g g e s t i o n s . P r o f e s s o r C u l l e n a l s o s u p p l i e d t h e c r y s t a l s a m p l e s u s e d i n t h i s w o r k . The c o - o p e r a t i o n o f Mr. T. V. T a y l o r o f t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a C o m p u t i n g C e n t r e i n p r e -p a r i n g t a b l e s o f s t r u c t u r e f a c t o r s and l i s t i n g s o f p r o -grams i s a l s o g r e a t l y a p p r e c i a t e d . I am i n d e b t e d t o t h e N a t i o n a l R e s e a r c h C o u n c i l o f C a n a d a f o r f i n a n c i a l s u p p o r t d u r i n g t h e e n t i r e t e r m o f t h i s w o r k . I . INTRODUCTION A. THE TECHNIQUE OF X-RAY CRYSTAL ANALYSIS As r e v e a l e d by t h e i n n u m e r a b l e o r g a n i c and i n -o r g a n i c compounds, n a t u r a l p r o d u c t s , b i o l o g i c a l l y i m p o r -t a n t m o l e c u l e s , and a l l o y s w h i c h have been examined i n t h e s i x t y y e a r s s i n c e i t s d i s c o v e r y , t h e t e c h n i q u e o f x - r c r y s t a l a n a l y s i s has become an e x t r e m e l y p o w e r f u l method o f s t r u c t u r e d e t e r m i n a t i o n f o r c h e m i s t s , b i o c h e m i s t s , phy s i c i s t s and m e t a l l u r g i s t s . The a p p l i c a t i o n o f t h e t e c h -n i q u e has been t r e m e n d o u s l y f a c i l i t a t e d by t h e a d v e n t o f e l e c t r o n i c c o m p uters and m e c h a n i z e d d a t a c o l l e c t i o n . However, t h e r e r e m a i n s one o b s t a c l e i n t h e way o f com-p l e t e l y u n i v e r s a l a p p l i c a b i l i t y o f t h e method. A l t h o u g h t h e a m p l i t u d e o f t h e wave d i f f r a c t e d by t h e c r y s t a l l a t -t i c e c a n be m easured, i t s p h a s e c a n n o t . To overcome t h i s d i f f i c u l t y , s e v e r a l methods have been d e v i s e d , o f w h i c h t h e P a t t e r s o n f u n c t i o n , w h i c h u s e s t h e s q u a r e s o f t h e a m p l i t u d e s (F's) o f t h e d i f f r a c t e d waves, and d i r e c t methods, i n w h i c h t h e p h a s e s a r e d e t e r m i n e d f r o m t h e mag-n i t u d e s o f n o r m a l i z e d s t r u c t u r e f a c t o r s ( E ' s ) , a r e two o f t h e most i m p o r t a n t , and o u g h t t o be d i s c u s s e d h e r e i n s u f f i c i e n t d e t a i l t o c l a r i f y t h e e n s u i n g d e s c r i p t i o n s o f s t r u c t u r e d e t e r m i n a t i o n . S i n c e t h e s t r u c t u r e a m p l i t u d e s a r e F o u r i e r t r a n s f o r m s o f t h e p e r i o d i c e l e c t r o n d e n s i t y o f t h e c r y s -t a l l a t t i c e , (eq. 1.1)., i t f o l l o w s t h a t t h e e l e c t r o n d e n s i t y must t h e r e f o r e be t h e F o u r i e r t r a n s f o r m o f t h e 3 s t r u c t u r e a m p l i t u d e s and c a n be w r i t t e n i n t e r m s o f a F o u r i e r s e r i e s o f w h i c h t h e s t r u c t u r e a m p l i t u d e s a r e c o -e f f i c i e n t s ( e q . 1 . 2 ) . -hk£ = fP(Z'X'Z) e x p { 2 i r i ( h x + k y + £z)}dv. (1.1) p ( x , y , z ) = ~ EZZ Fhkl e x p { - 2 7 r i ( h x + ky_ + Zz) } (1.2) However, e a c h s t r u c t u r e a m p l i t u d e h a s an a s s o c i a t e d unknown p h a s e , and t h e e l e c t r o n d e n s i t y c a n n o t be c a l c u l a t e d d i r e c t l y f r o m e x p e r i m e n t a l l y o b s e r v e d q u a n t i t i e s . H o wever, i f p a r t o f t h e s t r u c t u r e i s known, s t r u c t u r e f a c t o r s b a s e d on t h e p o s i t i o n s o f t h e s e known atoms c a n be c a l c u l a t e d and t h e p h a s e s o f t h e s e c a l c u l a t e d s t r u c t u r e f a c t o r s c a n be assumed t o be a p p r o x i m a t i o n s t o t h e c o r r e c t p h a s e s . An e l e c t r o n d e n s i t y map c a l c u l a t e d u s i n g t h e s e a p p r o x i m a t e p h a s e s i s e x p e c t e d t o r e v e a l a d d i t i o n a l e l e m e n t s o f t h e s t r u c t u r e and new s t r u c t u r e f a c t o r s , whose p h a s e s w i l l be c l o s e r t o t h e c o r r e c t v a l u e s , c a n be c a l c u l a t e d . The i t e r a t i v e a p p l i c a t i o n o f t h i s p r o c e s s r e s u l t s i n a c o m p l e t e s t r u c t u r e , t h e a p p r o x i m a t e a t o m i c p o s i t i o n s o f w h i c h a r e t h e n r e f i n e d by l e a s t - s q u a r e s methods t o y i e l d f i n a l r e -f i n e d p a r a m e t e r s w i t h a. f i n a l s e t o f p h a s e s . T h i s m e thod i s p a r t i c u l a r l y s u c c e s s f u l i f t h e atoms o f t h e known p o r t i o n o f t h e m o l e c u l e c o n s t i t u t e a l a r g e f r a c t i o n o f t h e s c a t t e r i n g m a t t e r i n t h e u n i t c e l l . A p p a r e n t l y t h e s o l e o b s t a c l e o f s t r u c t u r e d e t e r m i n a t i o n i s t h e i n a b i l i t y t o l o c a t e a s t a r t i n g 4 segment i n t h e u n i t c e l l and i t i s t o t h i s p r o b l e m t h a t we now t u r n o u r a t t e n t i o n . E a r l y i n t h e h i s t o r y o f x - r a y c r y s t a l l o g r a p h y ' ' " , i t was shown t h a t a F o u r i e r s e r i e s ( e q . 1.3) o f w h i c h t h e c o e f f i c i e n t s w e r e t h e p h a s e l e s s s q u a r e s o f t h e a m p l i t u d e s o f t h e d i f f r a c t e d w a v e s , p r o d u c e d a map w h i c h c o n t a i n e d p e a k s a t p o s i t i o n s c o r r e s p o n d i n g t o t h e ends o f v e c t o r s b e t w e e n a t o m i c p o s i t i o n s . P ( x , y , z ) = I E £ £ | F h k £ | 2 c o s 2rr(hx + k y + Iz) (1.3) By c o n s i d e r i n g t h e symmetry r e q u i r e m e n t s o f t h e s p a c e g r o u p o f c r y s t a l l i z a t i o n , i t w o u l d t h e n seem a s t r a i g h t -f o r w a r d m a t t e r t o l o c a t e t h e m o l e c u l e i n t h e u n i t c e l l . T h e r e a r e , h o w e v e r , s e v e r a l d r a w b a c k s t o t h e m e t h o d . P e a k s i n t h e v e c t o r d i s t r i b u t i o n t e n d t o be v e r y much b r o a d e r t h a n i n t h e e l e c t r o n d i s t r i b u t i o n and t h e v e c t o r map c a n become d i f f u s e and c o m p l i c a t e d i f t h e m o l e c u l e c o n t a i n s more t h a n a few a t o m s . S i n c e t h e i n t e n s i t y o f t h e v e c t o r p e a k i s p r o p o r t i o n a l t o t h e p r o d u c t o f t h e a t o m i c numbers o f t h e atoms t o w h i c h i t c o r r e s p o n d s , i t i s o b v i o u s t h a t v e c t o r s b e t w e e n r e l a t i v e l y h e a v y atoms w i l l a p p e a r much more i n t e n s e t h a n v e c t o r s b e t w e e n t h e l i g h t e r a t o m s . P r o -v i d e d t h a t t h e s t r u c t u r e i s d o m i n a t e d by a r e l a t i v e l y s m a l l number o f h e a v y a t o m s , t h e v e c t o r map c a n u s u a l l y be u n -r a v e l l e d and . a t o m i c p o s i t i o n s a s s i g n e d t o t h e s e a t o m s . We h a v e s e e n t h a t t h e p r e s e n c e o f a l a r g e number of atoms of s i m i l a r atomic number i s d e t r i m e n t a l to the ease with which a s o l u t i o n can be e x t r a c t e d from the Pat-t e r s o n map, but t h a t a s m a l l number of r e l a t i v e l y heavy atoms makes t h i s a powerful method. The r e v e r s e i s t r u e f o r d i r e c t methods, by which process phases are assigned from a s t a t i s t i c a l a n a l y s i s of the s t r u c t u r e amplitudes. The 2 3 theory i s formulated ' on a random arrangement of s i m i l a r atoms but has been s u c c e s s f u l l y a p p l i e d to many c r y s t a l s t r u c t u r e s which c o n t a i n atoms of extremely d i f f e r e n t atomic numbers. The cornerstone of d i r e c t methods i n c e n t r o -symmetric space groups i s the r e l a t i o n g h k l = ^ h k l h l k I £ , ~ k . , £ , £ , * -h-h'k-k 1 l-V (1.4) where , i s a simple s c a l i n g term. Although i t appears t h a t one F can be determined o n l y i f the magnitudes and phases of a l l others are known, the s e r i e s must tend s t r o n g l y i n one d i r e c t i o n (+ or -) i f F ^ ] ^ i s s u f f i c i e n t l y l a r g e , and t h i s d i r e c t i o n i s determined by the agreement i n 3 s i g n s among products of l a r g e F's . We can t h e r e f o r e w r i t e the f o l l o w i n g r e l a t i o n . S ( £ h k £ } ~ S ( f h ' k ' £ | ) ' S ( - h - h ' k-k- l - V ] ( 1 ' 5 ) where S means "the s i g n o f " and ~ means " i s probably equal 4 t o " . The p r o b a b i l i t y w i t h which t h i s equation holds depends 6 on the magnitudes of the three r e f l e c t i o n s and i s given by P = h + htanh{os/al/2 |E.., . E, , , , . E, , , . , , , P,\} -hk£ * -h' k' V - -h-h' k-k' l - V (1.6) where a 3 / a | / / 2 i s a parameter dependent on the contents of the unit c e l l and independent of th e i r location and where E's are defined by % k £ = IW2/£| fi (1-7) where e i s an integer which takes on d i f f e r e n t values for di f f e r e n t classes of r e f l e c t i o n s . A s l i g h t l y more rigourous treatment of eq. 1.4. results i n the most commonly used form of Sayre's equation. S ( - h k l } ~ h-k'I'^-h'k'i'* ' S ( I h - h ' k-k' l - V ^ ( 1 * 8 ) with corresponding p r o b a b i l i t y ; P+( W : = h + ^ t a n h ( a 3/^ / 2^hk£lg,|,|,%'k'£- • Vh'k-k'H' 1 ( 1 ' 9 ) where P + i s the prob a b i l i t y that the sign of i s p o s i t i v e . If the value, of the summation i n eq. 1.9 i s negative, P + w i l l be less than h and w i l l imply that the sign of ^^ikt i s negative with a pro b a b i l i t y P_ = 1 - P + In practice, phases are assigned to a small number of r e f l e c t i o n s and Sayre's equations are applied. 7 to determine others. This can be achieved i n several ways. An i n i t i a l set of ten very large r e f l e c t i o n s can be allowed to take on a l l possible combinations of plus and minus signs. This would r e s u l t i n 2 1 0 p o s s i b i l i t i e s , of which several w i l l be more consistent ( i . e . have higher, p r o b a b i l i t i e s ) than the others. Each of these highly pro-bable combinations i s then taken as a s t a r t i n g set and phases are generated for the remaining r e f l e c t i o n s by applying Sayre's equations. An alternative approach arises as a consequence of the fact that the o r i g i n of a centrosymmetric unit c e l l can be a r b i t r a r i l y located at any centre of symmetry. Three or sometimes fewer r e f l e c t i o n s , depending on the space group, can be assigned arbitrary phases, corresponding to the choice of o r i g i n . Three or four other r e f l e c t i o n s are allowed to take a l l possible combinations of plus and minus signs, r e s u l t i n g i n 8 or 16 possible solutions. Either method i s completed by c a l c u l a t i n g an electron density map using the phases of those solutions of highest p r o b a b i l i t y . B. CHARACTERISTICS OF METAL CARBONYLS AND THEIR DERIVATIVES Numerous r e v i e w s h a v e a p p e a r e d r e c e n t l y d e s c r i -5-7 b i n g m e t a l - c a r b o n b o n d i n g , p r e p a r a t i o n , p r o p e r t i e s , a n d 8 9 10 s t r u c t u r e o f m e t a l c a r b o n y l s , ' m e t a l atom c l u s t e r s a n d 11-14 L e w i s b a s e s u b s t i t u t e d c a r b o n y l c o m p l e x e s . The p r i n -c i p a l c o n c l u s i o n s o f t h e s e s t u d i e s o u g h t ' t o be r e v i e w e d b r i e f l y as b a c k g r o u n d t o t h e m a t e r i a l t o be p r e s e n t e d i n f o l l o w i n g p a r t s o f t h i s t h e s i s . The m o s t r e g u l a r f e a t u r e o f t h e m e t a l c a r b o n y l s and t h e i r d e r i v a t i v e s i s t h e a d h e r e n c e o f mos t o f t h e s e compounds t o t h e " e f f e c t i v e a t o m i c number" o r " i n e r t g a s " 15 l a w w h i c h r e q u i r e s t h a t t h e c e n t r a l atom a c c e p t f r o m t h e l i g a n d s s u f f i c i e n t e l e c t r o n s t h a t t h e t o t a l number o f e l e c t r o n s a r o u n d t h e m e t a l atom r e s u l t s i n a c l o s e d s h e l l c o n f i g u r a t i o n . F o r e x a m p l e , t h e compound F e ( C O ) 2 ( N O ) 2 c a n be c o n s i d e r e d t o c o n s i s t o f F e ( 0 ) (26 e l e c t r o n s ) , two c a r b o n y l g r o u p s (2x2 e l e c t r o n s ) and two n i t r o s y l g r o u p s (2x3 e l e c t r o n s ) , f o r a t o t a l o f 36 e l e c t r o n s , t h e k r y p t o n c o n f i g u r a t i o n . S i n c e , v a r i o u s l i g a n d s d o n a t e f r o m one t o a d o z e n e l e c t r o n s , t h e c o - o r d i n a t i o n number f o r a g i v e n m e t a l atom w i l l v a r y f r o m one compound t o a n o t h e r d e p e n d i n g on t h e c o m b i n a t i o n o f l i g a n d s u s e d t o c o m p l e t e t h e i n e r t g as c o n f i g u r a t i o n . F o r i n s t a n c e , i n e r t g a s c o n f i g u r a t i o n s p e c i e s e x i s t f o r i r o n -w i t h c o - o r d i n a t i o n numbers o f f o u r ( d i c a r b o n y l d i n i t r o s y l i r o n ) , f i v e ( p e n t a c a r b o n y l i r o n ) and s i x ( d i - i o d o t e t r a c a r b o n y l i r p n ) . 9 It i s obvious that an i n t e g r a l number of pair-donating ligands can complete the valence s h e l l of a metal of even atomic number, whereas metal atoms of odd atomic number must receive an additional single electron. This require-ment can be accommodated i n several ways. A ligand which donates an odd number of electrons can be employed, r e s u l t i n g i n compounds exemplified by Co (NO) (CO) 3 and HCo(COK, or the odd electron on each atom can be shared with another such atom, r e s u l t i n g i n a metal-metal bond, as i n Co2(CO) 8. Besides this regularity i n stoichiometry, metal carbonyls and t h e i r derivatives are characterized by the actual nature of the metal-ligand bond. The carbon atom of carbon monoxide possesses an sp hybridized lone pair of electrons which forms a a-bond by overlap with a vacant t r a n s i t i o n metal o r b i t a l of the proper symmetry. The carbon monoxide group also has vacant 7T-antibonding o r b i t a l s which form a TT-bond by overlap with f i l l e d non-bonding d o r b i t a l s on the metal atom. The metal-carbon bond order i n these complexes must thereby be greater than unity, requiring a concurrent decrease i n carbon-oxygen bond order. The presence of multiple bonding between metal and carbon atoms i s r e f l e c t e d by the fact that x-ray studies show that the metal-carbon bond length i s d i s t i n c t l y shorter than the sum of the single bond r a d i i . ^ Other ligands found i n stable substitution com-plexes of metal carbonyls also possess both a-donor and i r - a c c e p t o r p r o p e r t i e s . On l i g a n d s s u c h as s u b s t i t u t e d p h o s -p h i n e s and a r s i n e s , t h e a c c e p t o r p r o p e r t i e s a r i s e f r o m empty d o r b i t a l s o n t h e p h o s p h o r u s o r a r s e n i c a t o m s . I t h a s b e e n f o u n d t h a t m o s t c o m p l e x e s o f i r - b o n d i n g l i g a n d s c o n t a i n m e t a l s i n l o w o x i d a t i o n s t a t e s . T h i s c a n be e x p l a i n e d i n t e r m s o f t h e d e s c r i p t i o n o f b o n d i n g p r e s e n t e d a b o v e , s i n c e a p o s i t i v e c h a r g e o n a m e t a l atom e n h a n c e s i t s a c c e p t o r p r o p e r t i e s b u t d e c r e a s e s i t s b a c k - b o n d i n g c a p a b i l i t y w h e r e a s t h e p r e s e n c e o f a n e g a t i v e c h a r g e p r o d u c e s t h e o p p o -s i t e e f f e c t s . S i n c e b o t h a - and i r - b o n d i n g a p p e a r t o be r e q u i r e d f o r s t a b l e c o m p l e x e s , t h e p r e s e n c e o f an e l e c t r o n i c c h a r g e , e i t h e r p o s i t i v e o r n e g a t i v e , w i l l i n h i b i t t h i s t y p e o f c o m p l e x f o r m a t i o n . , The f o u r s t r u c t u r e s i n c l u d e d i n t h i s t h e s i s h a v e b e e n c h o s e n s i n c e , as d i - ( t e r t i a r y a r s i n e ) d e r i v a t i v e s o f m e t a l c a r b o n y l s , t h e y r e p r e s e n t a u n i f i e d t o p i c f o r s t u d y and d i s c u s s i o n i n t e r m s o f t h e p r i n c i p l e s e s t a b l i s h e d i n t h i s i n t r o d u c t i o n . B e c a u s e o f t h e c o m p l e x i t y o f t h e i r s y s t e m a t i c names, t h e l i g a n d s M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 and; M e 2 A s C F ( C F 3 ) C F 2 A s M e 2 w i l l o f t e n be d e n o t e d by t h e s y m b o l s L and L 1 r e s p e c t i v e l y . C. RESULTS OF PRELIMINARY EXPERIMENTS B e f o r e an x - r a y a n a l y s i s i s u n d e r t a k e n , s e v e r a l o t h e r e x p e r i m e n t s a r e o f t e n c a r r i e d o u t , and t h e r e s u l t s o f t h e s e e x p e r i m e n t s c a n l e a d t o some i d e a o f t h e s t r u c t u r e o f t h e compound u n d e r i n v e s t i g a t i o n . T h i s i s t h e c a s e f o r t h r e e o f -the compounds i n t h i s t h e s i s and t h e s e s t r u c t u r a l i n d i -c a t i o n s w i l l now be d i s c u s s e d . 17 The i n f r a - r e d , n.m.r. and M o s s b a u e r s p e c t r a o f L F e 3 ( C O ) i o s u g g e s t a s t r u c t u r e i n w h i c h two t e r m i n a l c a r -18 b o n y l g r o u p s o f t h e two e q u i v a l e n t i r o n atoms o f F e 3 ( C O ) i 2 a r e r e p l a c e d by t h e a r s e n i c s o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d ( F i g u r e I . l ) . The p r e s e n c e o f o n l y one 1 9 F r e s o n a n c e i n t h e n.m.r. s p e c t r u m i n d i c a t e s t h a t a l l t h e f l u o r i n e atoms a r e e q u i v a l e n t , s o t h a t t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d w o u l d be e x p e c t e d t o be p l a n a r , i n c o n t r a s t t o t h e p r e -v i o u s l y d e t e r m i n e d s t r u c t u r e o f L F e 2 ( C O ) 6 , i n w h i c h t h e l i g a n d i s b e n t as a r e s u l t o f t h e f o r m a t i o n o f a T r-bond 19 f r o m t h e c y c l o b u t e n e s y s t e m t o one o f t h e i r o n a t o m s . The XH n.m.r. s p e c t r u m o f L 2 R u 3 ( C O ) s c o n t a i n s two s i n g l e t s , i n d i c a t i n g a m o d e r a t e l y s y m m e t r i c a l s t r u c t u r e 2 0 f o r t h e l i g a n d . The 1 9 F n.m.r. s p e c t r u m i s a c o m p l e x a r r a n g e m e n t o f f o u r t e e n p e a k s w i t h some s i m i l a r i t y t o t h e s p e c t r u m o f L F e ( C O ) i ( , w h e r e o n l y one a r s e n i c atom o f t h e 21 l i g a n d i s b o n d e d t o t h e i r o n atom. T h e s e two p i e c e s - o f e v i d e n c e , and t h e o b s e r v a t i o n t h a t t h e l i g a n d i s n o r m a l l y r e l u c t a n t t o c h e l a t e , f a v o u r t h e s t r u c t u r e shown i n F i g u r e F i g u r e I . l S t r u c t u r e o f M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 « F e 3 (CO) i 0 e x p e c t e d on t h e b a s i s o f p r e l i m i n a r y e x p e r i m e n t s . I . 2a r a t h e r t h a n t h a t o f F i g u r e I . 2 b . The 1 9 F and 1U n.m.r. s p e c t r a o f L R u 3 ( C O ) i 0 b o t h c o n s i s t o f s i n g l e t s , i n d i c a t i n g a h i g h l y s y m m e t r i c a l s t r u c t u r e f o r t h i s c o m p l e x . T h i s c o u l d be a c c o m p l i s h e d by h a v i n g t h e l i g a n d e i t h e r c h e l a t i n g ( F i g u r e I . 3 a ) o r b r i d g i n g ( F i g u r e I.3b) i n a n e q u a t o r i a l p o s i t i o n . The l a t t e r i s f a v o u r e d b e c a u s e o f t h e s i m i l a r i t y o f t h e i n f r a - r e d s p e c t r a o f L F e 3 ( C O ) i 0 and L R u 3 ( C O ) i o i n t h e t e r m i n a l c a r b o n y l r e g i o n and b e c a u s e o f t h e known r e l u c t a n c e o f t h e l i g a n d t o c h e l a t e w i t h o u t a l s o i n v o l v i n g t h e d o u b l e b o n d o f t h e c y c l o b u t e n e r i n g . F i g u r e 1.2 Two p o s s i b l e s t r u c t u r e s f o r (Me 2 As C=C(AsMe 2 ) C F 2 CF 2 ) 2 • R u 3(CO) F i g u r e T.3 Two p o s s i b l e s t r u c t u r e s f o r M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • R u 3 (CO) 1 0 . EXPERIMENTAL SECTION L F e 3 ( C O ) i 0 i s o b t a i n e d by c h r o m a t o g r a p h y o f t h e m i x t u r e o f p r o d u c t s f o r m e d by u l t r a v i o l e t i r r a d i a t i o n o f 17 F e 3 ( C O ) i 2 and t h e d i - ( t e r t i a r y a r s i n e ) . The c r y s t a l s a r e b l a c k n e e d l e s e l o n g a t e d a l o n g a. The i n t e n s i t y d a t a w e r e c o l l e c t e d u s i n g a s a m p l e o f d i m e n s i o n s 0.3 xp.03 x, 0.04 mm. L 2 R u 3 ( C O ) 8 i s p r e p a r e d by c h r o m a t o g r a p h y o f t h e p r o d u c t s o f t h e r e a c t i o n o f R u 3 ( C O ) i 2 w i t h t h e l i g a n d 20 r e f l u x e d xn h e x a n e . The c r y s t a l u s e d t o r e c o r d t h e d a t a was an i r r e g u l a r p l a t e w i t h {001} d e v e l o p e d . I t s d i m e n s i o n s w e r e 0.05 mm. p a r a l l e l t o c and a b o u t 0.2 mm. a c r o s s . ; U l t r a v i o l e t i r r a d i a t i o n o f e q u i m o l a r q u a n t i t i e s o f R u 3 ( C O ) i 2 w i t h t h e d i - ( t e r t i a r y a r s i n e ) r e s u l t s i n t h e 20 f o r m a t i o n o f L R u 3 ( C O ) i 0 . A s i n g l e f l a k e o f t h e compound o f d i m e n s i o n s 0.07 x0.44 x0.25 mm. was r e c r y s t a l l i z e d f r o m d i e t h y l e t h e r f o r u s e i n i n t e n s i t y m e a s u r e m e n t s . L'Mo(CO)q. i s p r e p a r e d by r e c r y s t a l l i z a t i o n f r o m p e t r o l e u m e t h e r - b e n z e n e o f t h e p r o d u c t s f o r m e d by r e f l u x i n g 22 M o ( C O ) 6 w i t h t h e l i g a n d i n t o l u e n e . The c r y s t a l s a r e ; c o l o u r l e s s n e e d l e s e l o n g a t e d a l o n g c. I n t e n s i t y d a t a w e r e r e c o r d e d u s i n g a s p e c i m e n o f d i m e n s i o n s 0.16 xo.07 xo.57 mm. U n i t c e l l a n d s p a c e g r o u p d a t a f o r e a c h compound w e r e o b t a i n e d by p h o t o g r a p h i c methods and a c c u r a t e l a t t i c e p a r a m e t e r s f o r e a c h w e r e d e t e r m i n e d by l e a s t - s q u a r e s t r e a t -ment o f s i n z 8 / A 2 v a l u e s f o r t h i r t y r e f l e c t i o n s m e a s u r e d on 23 a d i f f r a c t o m e t e r w i t h Mo-K r a d i a t i o n . —a R e f l e c t i o n i n t e n s i t i e s were measured on a Datex-automated General E l e c t r i c XRD 6 d i f f r a c t o m e t e r , with a s c i n t i l l a t i o n counter, Mo-K r a d i a t i o n (Zr f i l t e r and p u l s e -—a ^ h e i g h t a n a l y s e r ) , and a 9-20 scan. The scan range i n 20 was (1.80 + 0.86 tan8) degrees and backgrounds were measured at both ends of each scan. The standard d e v i a t i o n of an i n t e n s i t y was c a l - . c u l a t e d from the counting s t a t i s t i c s u s i n g a 2 ( I ) = S + B + ( d S ) 2 where S- = scan count B = background, c o r r e c t e d to time of scan I = S - B d = an e m p i r i c a l constant which allows f o r unknown experimental e r r o r s ; values used f o r each s t r u c t u r e are given i n Table I I . I R e f l e c t i o n s whose i n t e n s i t i e s were l e s s than l a were c l a s s i f i e d as unobserved. Lorentz and p o l a r i z a t i o n f a c t o r s were a p p l i e d and the s t r u c t u r e amplitudes were d e r i v e d . A b s o r p t i o n c o r r e c t i o n s were not a p p l i e d . C r y s t a l data and parameters of data c o l l e c t i o n are g i v e n i n Table I I . I . T a b l e I I . I C r y s t a l and e x p e r i m e n t a l d a t a . L F e 3 ( C O ) i o f o r m u l a C i 8 H i 2 A s 2F i ^ F e . 301 0 m o l e c u l a r w e i g h t (gm.) 781.2 c r y s t a l s y s t e m m o n o c l i n i c o c e l l d i m e n s i o n s (A,deg.) a = 11.60(2) b = 20.04 (2) c = 22.11(2) B = 93.7(2) volume ( A 3 ) 5129 m e a s u r e d d e n s i t y (gm./cm3.) 2 . 01±0 . 02 f l o t a t i o n i n C C £ 4 / C H 3 I Z 8 c a l c u l a t e d d e n s i t y (gm./cm3.) 2.02 F( 0 0 0 ) 3040 a b s o r p t i o n c o e f f i c i e n t y 45 ( c m . - 1 ) (Mo-K^) s p a c e g r o u p F_ 2i/£ ^ 2 h ^ L 2 R u 3 ( C O ) 8 C 2 itH 2 itAsijFsRusOs 1195.3 o r t h o r h o m b i c a = 9.07(1) b = 18.53(1) c = 21.81(1) 3666 2.14±0.02 C C £ 4 / C H B r 3 4 2.17 2272 51 Pbcn (D*£) L R u 3 (CO) i o L ' M o ( C O K t C i 8 H i 2 A s 2 F l t R u 3 O i o C i 1H1 2 A s 2 F 6 M o 0 l t 917.3 o r t h o r h o m b i c a = 8.594(3) b = 18.795(5) c = 16.69(5) • 2696 2.22±0.02 C C ^ / C H B r 3 4 2.26 1736 43 P 2 i 2 i 2 i (Dj) 567.7 m o n o c l i n i c a = 25.06(2) b = 13.27(2) c = 11.56(2) 3 = 102.8(2) 3749 2. 0 4±0.02 CC^^/CHBrs 8 2.01 2096 45 C2/c ( C j h ) KD a b s e n t s p e c t r a T a b l e I I . I ( c o n t i n u e d ) hOl I = 2n+l Okl k = 2n+l OkO k = 2n+l 26 (Mo-K_a) max. (deg.) minimum i n t e r p l a n a r s p a c i n g (A) number o f r e f l e c t i o n s w i t h 26 < 26 max. number o f u n o b s e r v e d s d i n a 2 e x p r e s s i o n a x i s mounted p a r a l l e l t o ct a x i s o f d i f f r a c t o m e t e r s c a n s p e e d (deg./min.) t i m e f o r b a c k g r o u n d (sec.) 35 1.18 3234 710 0.04 4 10 h O l I = 2n+l hkO h+k = 2n+l 40 1.04 1712 205 0.02 2 20 hOO OkO 001 h = 2n+l k = 2n+l I = 2n+l 45 0.93 2028 200 0.02 2 20 h k l h+k = 2n+l hOl I = 2n+l 40 1.04 1750 240 0.02 2 20 L and L' r e p r e s e n t t h e l i g a n d s M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 and M e 2 A s C F ( C F 3 ) C F 2 A s M e 2 r e s p e c t i v e I I I . THE STRUCTURE DETERMINATION OF M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 • F e 3 (CO) i 0 1 STRUCTURE ANALYSIS The a s y m m e t r i c u n i t c o n t a i n s two m o l e c u l e s , s o t h a t , w i t h t e n h e a v y a t o m s , t h e P a t t e r s o n f u n c t i o n was c o m p l i c a t e d . Two p o s s i b l e o r i e n t a t i o n s a p p e a r e d i n t h e o r i g i n r e g i o n , b u t as a r e s u l t o f t h e l a r g e number o f p e a k s , i t was n o t i m m e d i a t e l y p o s s i b l e t o d e r i v e any f u r t h e r i n f o r m a t i o n . An a t t e m p t was t h e n made t o s o l v e t h e s t r u c t u r e 24 by d i r e c t methods u s i n g Hoge's s e r i e s o f f o u r p r o g r a m s w h i c h a p p l y S a y r e r e l a t i o n s h i p s i n two d i m e n s i o n s i n t h e 25a V and a nd P e p i n s k y v e r s i o n o f t h e C o c h r a n and D o u g l a s 25b p r o c e d u r e . The i n i t i a l p r o g r a m f i r s t c a l c u l a t e s a 2 W i l s o n p l o t f o r t h e d a t a and o u t p u t s a n o v e r a l l s c a l e and an o v e r a l l t e m p e r a t u r e f a c t o r a n d t h e n c a l c u l a t e s and o u t p u t s n o r m a l i z e d s t r u c t u r e f a c t o r s ( E ' s ) . A v e r a g e v a l u e s o f | E | and | E 2 | a r e t h e n c a l c u l a t e d t o i n d i c a t e t h e p r e s e n c e o r a b s e n c e o f a c e n t r o s y m m e t r i c e l e c t r o n d i s -t r i b u t i o n . The s e c o n d p r o g r a m r e a d s t h e t a p e o u t p u t o f t h e f i r s t and s o r t s t h e d a t a i n t o p a r i t y g r o u p s , i n c l u d i n g o n l y t h o s e r e f l e c t i o n s f o r w h i c h | E | e x c e e d s a s p e c i f i e d v a l u e . The n e x t s t a g e o f t h i s p r o g r a m i n v o l v e s t h e d e -t e r m i n a t i o n o f a l l S a y r e r e l a t i o n s h i p s a n d t h e c a l c u l a t i o n o f t h e p r o b a b i l i t y w i t h w h i c h e a c h h o l d s . The t h i r d p r o -gram o f t h e s e r i e s u s e s t h e s e S a y r e r e l a t i o n s h i p s t o d e t e r m i n e p o s s i b l e s o l u t i o n s , r e j e c t i n g t h o s e f o r w h i c h , f o r any i i SMAX = I | Eg-1 " | | - | EJJ_ | O . D h (where ri i s a r e f l e c t i o n c o n t a i n e d i n a S a y r e r e l a t i o n s h i p w h i c h f a i l s ) e x c e e d s a p r e s e t v a l u e . S i n c e t h e p r o b a b i l i t y t h a t t h e s i g n o f Eg i s c o r r e c t l y g i v e n by t h e S a y r e r e l a t i o n s h i p s i n w h i c h i t i s i n v o l v e d i s c a l c u l a t e d f r o m t h e e x p r e s s i o n P ( S ) = % + J 2 t a n h ( o - 3 / o - ! / 2 £ |Eg| • |Ej^ | • |Eg_j>| ) (3.2) Jc t h e n i f o n l y S a y r e r e l a t i o n s h i p s w h i c h f a i l a r e i n c l u d e d i n t h e s u m m a t i o n , e q . 3.2 becomes t h e p r o b a b i l i t y t h a t t h e s i g n o f i i i s o p p o s i t e t o t h a t g i v e n i n t h e s o l u t i o n . Hence by s e t t i n g a v a l u e o f SMAX c o r r e s p o n d i n g t o a p r o b a b i l i t y o f 0.985, a l l s o l u t i o n s f o r w h i c h any s i g n i s i n c o r r e c t t o t h e e x t e n t o f t h i s p r o b a b i l i t y c a n be r e j e c t e d . T h o s e s o l u t i o n s w h i c h a r e w i t h i n t h e l i m i t s o f SMAX a r e p r i n t e d o u t w i t h t h e maximum v a l u e o f t h i s q u a n -t i t y a t t a i n e d f o r any r e f l e c t i o n i n e a c h s o l u t i o n , as w e l l as t h e number o f p l u s s i g n s i n t h e s o l u t i o n a n d t h e v a l u e o f t h e f o l l o w i n g e x p r e s s i o n SEEE**2 = Z(^|Ejv|.|E^|.|Eg_j>|)2 (3.3) h k w h e r e S i s a r e f l e c t i o n c o n t a i n e d i n a S a y r e r e l a t i o n s h i p w h i c h f a i l s . The m o s t p r o b a b l e s o l u t i o n w o u l d t h e n be e x p e c t e d t o be t h a t w h i c h h a s a p p r o x i m a t e l y e q u a l numbers o f p l u s a nd m i n u s s i g n s and t h e minimum v a l u e s f o r SMAX and SEEE**2. 24 The f o u r t h p r o g r a m u s e s t h e E ' s f r o m t h e f i r s t p r o g r a m and t h e s i g n s f r o m t h e t h i r d t o p r o d u c e a t a p e s u i t a b l e f o r i n p u t t o a F o u r i e r c a l c u l a t i o n p r o g r a m c o n -t a i n i n g up t o s i x s o l u t i o n s a t o n c e , s p e c i f i e d o n l y by t h e number o f t h e s o l u t i o n a s i t i s g e n e r a t e d . I n t h e p r e s e n t w o r k , t h e a - a x i s p r o j e c t i o n was e x a m i n e d and t h e s i g n s o f 34 O k l r e f l e c t i o n s w i t h n o r -m a l i z e d s t r u c t u r e f a c t o r | E | > 1.4 w e r e d e t e r m i n e d . T a b l e I I I . l c o n t a i n s a c o m p a r i s o n o f t h e 51 s o l u t i o n s w h i c h meet t h e a c c e p t a n c e c r i t e r i a m e n t i o n e d a b o v e . S e t s 1 7 , 1 8 , 2 4 , 2 6 , 29, and 33 w e r e u s e d as i n p u t t o a F o u r i e r c a l c u l a t i o n . S e t 29 was o u t s t a n d i n g i n h a v i n g t h e l o w e s t p r o b a b i l i t y i n t h e o p p o s i t e - i n d i c a t i o n - o f - s i g n t e s t , a nd t h e E-map ( F i g u r e I I I . l ) c o m p u t e d w i t h t h i s s e t o f s i g n s r e v e a l e d t h e p o s i t i o n s , . i n p r o j e c t i o n , o f t h e t e n h e a v y atoms i n t h e a s y m m e t r i c u n i t . W i t h t h i s i n f o r m a t i o n on t h e y- and z - p a r a m e t e r s o f t h e h e a v y a t o m s , a t t e n t i o n was r e f o c u s s e d o n t h e P a t -t e r s o n f u n c t i o n , and t h e t h r e e - d i m e n s i o n a l s t r u c t u r e o f t h e two h e a v y atom u n i t s was d e r i v e d . S i x t y - o n e o f t h e s i x t y - f o u r c a r b o n , o x y g e n , and f l u o r i n e atoms w e r e l o c a t e d f r o m a F o u r i e r s u m m a t i o n w i t h p h a s e s b a s e d on t h e i r o n a nd a r s e n i c a t o m s , and t h e t h r e e r e m a i n i n g atoms w e r e f o u n d on a s u b s e q u e n t e l e c t r o n d e n s i t y map. P r e l i m i n a r y l e a s t - s q u a r e s r e f i n e m e n t o f t h e p a r a -m e t e r s u t i l i z e d t h e b l o c k - d i a g o n a l a p p r o x i m a t i o n , and r e -T a b l e I I I . I C o m p a r i s o n o f 51 s o l u t i o n s f r o m Hoge's s i g n d e t e r m i n a t i o n p r o g r a m S e t Number o f p l u s e s SMAX SEEE**2 S e t Number o f p l u s e s SMAX SEEE** 1 21 12.4 1026 22 18 12. 4 1525 2 22 12. 8 985 23 20 12.8 1449 3 20 12.4 992 24 16 12. 3 710 4 21 12. 8 951 25 17 12.3 1192 5 23 12.9 1450 26 16 12.0 587 6 20 12.4 1355 27 17 12.0 1005 7 21 12.8 1275 28 25 11.9 1269 8 20 12.4 1072 29 17 10.2 686 9 22 12. 4 1200 30 21 12. 8 1409 10 17 12.4 1196 31 22 12.9 1612 11 21 12. 8 1159 32 20 12. 8 169,0 12 21 12.4 1213 33 20 12.8 878 13 16 12.4 1578 34 21 12.8 1380 14 20 12. 8 1173 35 24 12. 8 1437 15 19 12.3 1204 36 23 12.3 1239 16 22 12. 3 1069 37 24 12.8 1342 17 21 11. 8 541 38 19 11.3 1091 18 20 11.3 969 39 18 12. 8 1194 19 23 12.8 1147 40 18 12.9 1254 20 22 12.9 1671 41 17 12.3 1080 21 21 12.4 1529 42 17 12.8 924 2 Table I I I . l (continued) Set Number of pluses SMAX SEEE**2 Set Number of pluses SMAX SEEE** 43 16 12. 8 1416 48 19 12. 8 1415 44 24 12.8 1606 49 16 12.0 1241 45 16 11.2 940 50 15 12. 8 1275 46 22 12.8 1773 51 18 12.7 1084 47 18 12.3 1381 duced R to 0.11. At this stage, a three-dimensional d i f -ference map showed electron density fluctuations around the iron and arsenic atoms which indicated anisotropic thermal motion. Refinement was continued using a modified f u l l - m a t r i x procedure. The function minimized was Zw(F Q-kF c) with w = {A + B | F | + Q | F | 2 + D | F | 3}- 1 for the observed r e f l e c t i o n s . Unobserved r e f l e c t i o n s were excluded from the refinement but included i n the f i n a l structure factor c a l -culation. The c o e f f i c i e n t s A, B, C, and D were adjusted by a short least-squares program written by the author (see Section VII) to achieve best constancy of l o c a l averages of £w(F -kF ) 2 over the f u l l range of I F I , the f i n a l values o c J 1 - o 1 being 600, 0.3, -0.06, and 0.00027 respectively. Scattering factors were from ref. 26 and included the r e a l part of the dispersion correction. The variables refined were the po s i t i o n a l parameters, anisotropic thermal parameters for . the ten heavy atoms, i s o t r o p i c thermal parameters for the other atoms, and a single o v e r a l l scale factor, a t o t a l of. F i g u r e I I I . l E-map w i t h f i n a l r e f i n e d p o s i t i o n s o f h e a v y atoms s u p e r i m p o s e d . 347 variables. Since the dimensions of the computer pro-gram used were limited to 249 variables, i t was necessary to vary d i f f e r e n t combinations of parameters i n successive cycles. No parameter c o r r e l a t i o n c o e f f i c i e n t s greater than 0.35 were observed, and f u l l convergence was reached aft e r six cycles. F i n a l values of R and R ^ were 0.090 and 0.096 1 — —w respectively for the 2524 observed r e f l e c t i o n s and 0.131 and 0.117 respectively for a l l data. A f i n a l difference; synthesis showed maximum fluctuations of +0.8 e/A 3. F i n a l observed and calculated structure factors are given i n i Table I I I . I I . F i n a l p o s i t i o n a l and thermal parameters are given i n Table I I I . I l l , together with t h e i r standard deviations calculated from the inverse matrix of the l a s t refinement cycle. The weighted mean planes of the iron t r i a n g l e and d i - ( t e r t i a r y arsine) ligand of each molecule are given i n Table I I I . I V , and the bond distances and valency angles are in Table I I I . V . t ^ R = £ IF -F I/I|F I; R = {Ew(F -F )2/2wF 2 } l / z — '-o - c " '-o1 -w - -o -c / — o T a b l e I I I . I I 29 F i n a l m e a s u r e d and c a l c u l a t e d s t r u c t u r e f a c t o r s . U n o b s e r v e d r e f l e c t i o n s h a v e an a s t e r i s k a f t e r t h e F -o v a l u e . t im r.Air i nss c u e L nss C*LC l OBS CAIC o 1* 107 114 10 1"»T 117 i 1*1 m ^ is* 11 !«•> 1 Z6<1 0 - 1 ? ZOI 2QT I ? I "* 157 Z" 1 ' 10 101 10* 30 T a b l e I I I . I I ( c o n t i n u e d ) i cm CMT, t nos C»L<" -1 iza 111 • -4 1*0 1*9 -I 111 IJ* T a b l e I I I . I l l F i n a l p o s i t i o n a l ( f r a c t i o n a l , x 10h) and t h e r m a l p a r a m e t e r s . S t a n d a r d d e v i a t i o n s a r e g i v e n i n p a r e n t h e s e s . M o l e c u l e 1 M o l e c u l e 2 ATOM X y z B ( A 2 ) X y z B ( A 2 ) F e d ) 3759 (. 3) 0773 ( 2) 1986 ( 2) 8370 ( 4) 2441 ( 3 ) 0695 ( 2) F e ( 2 ) 1932 ( 3) 0822 ( 2) 2646 ( 2) 6462 ( 4) 3155 ( 2) 0738 ( 2) F e ( 3 ) 1871 ( 4) 0053 ( 2) 1738 ( 2) 6492 ( 4) 2248 ( 2) -0048 ( 2) As (4) 0196 ( 3 ) 0762 ( 2) 3092 ( 1) 4616 ( 3) 3527 ( 2) 0792 ( 1) As (5) 012 3 ( 3) -0490 ( 2) 1633 ( 1) 4683 ( 3) 2109 ( 2) -0529 ( 1) C ( 6) 4694 (31) 1330 (18) 2313 (16) 5 .7 ( 8) 9362 (36) 2764 (20) 1247 (19) 7 .5 ( 10) C( 7) 4249 (33) 0122 (20) 2501 (18) 6 .7 (10) 7881 (31) 1830 (19) 1184 (17) 6 .3 ( 9) C( 8) 3046 (30) 1380 (19) 1537 (17) 6 .2 ( 9) 8602 (28) 3035 (18) 0172 (16) 5 .4 ( 8) C( 9) 4546 (25) 0498 (15) 1421 (14) 4 .0 ( 7) 9233 (33) 1892 (20) 0354 (17) 6 .7 ( 10) C (10) 1994 (27) 1685 (17) 2609 (14) 4 .5 ( 8) 7087 (25) 3905 (16) 0714 (13) 3 .9 ( 7) C (11) 2881 (25) 0779 (15) 329 2 (14) 4 .1 ( 7 ) 6759 (29) 3031 (18) 1546 (18) 6 .3 ( 9) C (12) 2732 (26) -0627 (15) 1691 (13) 3 .6 ( 7) 6756 (29) 1425 (20) 0014 (15) 5 .6 ( 9) C (13) 1908 (27) 0271 (16) 0975 (16) 4 .9 ( 8) 7265 (34) 2323 (20) -0694 (19) 7 .4 ( 10) C(14) 1945 (29) -0133 (18) 2620 (16) 5 .2 [ 8) 5772 (27) 2228 (16) 0699 (15) 4 .7 ( 8) C (15) 0999 (27) 0868 (16) 1849 (14) 4 .6 ( 7) 6281 (27) 3266 (17) -0138 (15) 4 .6 ( 8) C (16) 0063 (31) -1445 (19) 1706 (17) 7 .1 (10) 3993 (31) 1239 (18) -0461 (16) 6 .6 ( 9) C (17) -0819 (30) -0300 (18) 0884 (16) 6 .4 ( 9) 4406 (33) 2319 (19) -1404 (17) 7 .2 ( 10) C (18) 0165 (29) 0405 (17) 3903 (16) 5 .8 ( 9) 3900 (27) 3356 (16) 1546 (14) 5 • K 8) C(19) -0710 (32) 1564 (19) 3118 (17) 7 .3 (10) 4256 (29) 4471 (17) 0625 (15) 5 .7 ( 9) C (20) -0903 (21) 0172 (12) 2681 (12) 2 .3 ( 6) 3474 (29) 3127 (18) 0239 (16) 5 .9 ( 9) C (21) -0919 (25) -0222 (14) 2224 (13) 3 .9 ( 7) 3508 (24) 2691 (15) -0202 (13) 3 .7 ( 7) C (22) -2184 (29) -0009 (18) 2810 (16) 5 .3 ( 8) 2143 (31) 3240 (19) 0099 (17) 6 . 1 ( 9) C (23) -2172 (35) -0456 (21) 2266 (18) 7 .2 (10) 2195 (28)" 2755 (18) -0377 (16) 5 • K 8) F (24) -2237 (19) -0284 (11) 3355 (11) 8 .5 ( 6) 1544 (17) 3078 (10) 0555 ( 9) 7 .6 ( 5) F (25) -2908 (19) 0507 (ID 2770 (10) 8 .6 ( 6 ) 1874 (18) 3854 (ID -0066 (10) 8 . 1 ( 6) F (26) -2951 (19) -0304 (ID 1840 (10) 8 .5 ( 6) 1897 (17) 2950 (10) -0961 (10) 7 .6 ( 5) F (27) --2341 (17) -109 8 (11) 2398 ( 9) 7 .7 ( 5) - 1612 (18) 2176 (ID -0322 (10) 8 .2 ( 6) h-1 T a b l e I I I . I l l ( c o n t i n u e d ) M o l e c u l e 1 M o l e c u l e 2 ATOM x y z B ( A 2 ) X y z B ( A 2 ) 0( 2 8 ) 5359 (21) 1724 (12) 2543 (11) 6 .9( 6) 9953 (25) 3063 (15) 1584 (13) 9 • 3( 8) 0 (29) 4592 (21) -0263 (.13) 2820 (12) 7 .1 ( 6) 7668 (22) 1444 (14) 1560 (12) 8 • 2( 7) 0(30 ) 2664 (19) 1789 (12) 1218 (10) 5 .8 ( 5) 8924 (22) 3447 (14) -0155 (12) 8 • 0( 7) 0(31 ) 5040 (20) 0279(11) 1018 (11) 6 .2( 6) 9753 (21) 1455 (14) 0158 (11) 7 • 5( 6) 0 (32) 3328 (21) -1087(13) 1590 (11) 7 . 1 ( 6) 6905 (21.) 0838 (14) 0083 ( I D 7 .4( 6) 0 (33) 1875 (20) 0403 (12) 0464 (12) 6 • 8( 6) 7665 (25) 2401 (14) -1167 (14) 9 . 2 ( 8) 0(34 ) 3426 (20) 0789 (12) 3745 (11) 6 • 6( 6) 6826 (20) 2973 (12) 2062 (12) 7 • 2 ( .6) 0(35 ) 1945 (20) 2253 (13) 2615 (10) 6 .6( 6) 7446(21) 4475 (13) 0667 (11) 7 • K 6) 0(36 ) 1916 (19) -0608 (12) 2926 (10) 6 . 1 ( 6) 5238 (18) 1911 (11) 1023 (10) 5 .3( 5) 0(3 7 ) 0301(18) 1215( 9) 1602 ( 9) 4 .8( 5) 6110(19) 3625 (12) -0531(11) 6 .3( 6) b 11 k_2 2 b_3 3 b i 2 b 13 b 2 3 * M o l e c u l e 1 F e d ) 53 26 22 -4 4 0 F e ( 2 ) 44 27 21 -6 4 -10 F e ( 3 ) 56 30 17 -6 4 - 5 As (4) 48 21 20 -4 5 - 6 As (5) 59 24 21 -10 0 - 7 M o l e c u l e 2 F e ( l ) 48 41 26 0 -1 3 F e ( 2 ) 66 27 31 -1 -6 -8 F e ( 3 ) 54 30 26 3 2 -6 As (4) 65 21 23 1 5 -3 As (5) 71 26 19 -2 -4 -3 Mean -a .4 1 1 2 2 1 COEFFICIENTS IN THE TEMPERATURE EXPRESSION:, exp-10" (b i i h 2 + b 2 2 k 2 + b 3 3 l 2 + 2b i 2 h k + 2 b i 3 h £ + 2 b 2 3 k £ ) T a b l e I I I . IV E q u a t i o n s o f w e i g h t e d mean p l a n e s E q u a t i o n s o f p l a n e s i n t h e f o r m IX' + mY + n_Z' = p_, where X', Y, Z_' a r e c o o r d i n a t e s i n A, r e f e r r e d t o o r t h o g o n a l a x e s a , b , c * I r o n t r i a n g l e (3 Fe atoms) M o l e c u l e 1 M o l e c u l e 2 0.3477 0.3921 m •0.7384 0.6 513 n Maximum d i s p l a c e m e n t (A) 0.5778 2.8059 0 •0.6497 5.9574 0 D i - ( t e r t i a r y a r s i n e ) (2 As and 4 C atoms) M o l e c u l e 1 M o l e c u l e 2 0.2872 0.2296 -0.7502 0.5956 2.8559 0.009 0.7076 -0.6683 5.0354 0.037 34 Table I I I . V Bond d i s t a n c e s (A) and vale n c y angles (degrees). Unless otherwise s p e c i f i e d , standard d e v i a t i o n s of bond lengths are 0.03-0.04 A; of angles at Fe and As, 0.7-1.8° ; and of angles a t C, 2.2-3.4°. Molecule 1 Molecule 2 Molecule 1 Molecule 2 Fe (1) -Fe (2) 2. 652 (8) 2. 643 (7) As (4)-C (20) 1. 92 1. 92 Fe (1) -Fe(3) 2. 651(7) 2, 671 (9) As (5)-C(21) 1. 91 . 1. 97 Fe (2) -Fe(3) 2. 527 (6) 2. 517(7) Fe (2) -As(4) 2. 301 (7) 2. 278 (6) C (20)-C(21) 1. 28 1. 31 Fe (3) -As(5) 2. 300 (6) 2. 307 (7) C (20)-C(22) 1. 58 1. 57 C(21)-C(23) 1. 54 1. 55 Fe (1) -C(6) 1. 69 1. 75 C(22)-C (23) 1. 50 ; 1. 44 F e d ) -C(7) 1. 80 1. 75 F e d ) -C(8) . 1. 74 1. 69 C(22).-F(24) 1. 33 1. 30 Fe (1) -C(9) 1. 69 1. 70 C (22)-F (25) 1. 33 1. 32 Fe (2) -C(10) -.1. 73 1. 67 C (23)-F (26) 1. 30 1. 37 Fe (2) - c d i ) 1. 75 1. 81 C (23)-F (27) 1. 34 1. 35 Fe (3) -C(12) . 1. 70 1. 68 Fe (3) -C(13) 1. 75 1. 74 AVERAGE C-F 1. 33 AVERAGE Fe-G 1.73 C(6)-0(28) 1. 19 1. 15 term C (7)-0(29) 1. 10 1. 17 Fe(2) -C(14) • 1. 91 2. 02 C (8)-0 (30) 1. 15 1. 17 Fe(2) -C(15) 2. 01 1. 95 C (9)-0 (31) 1. 18 1. 16 Fe (3) -C(14) 1. 98 1. 90 C(10)-O (35) 1. 14 1. 22 Fe(3) -C(15) 1. 94 2. 06 C ( l l ) - 0 ( 3 4 ) 1. 15 1. 14 C(12)-0(32) 1. 18 1. 20 As (4) -C(18) 1. 93 1. 94 C (13)-0(33) 1. 16 1. 18 As (4) -C(19) 1. 92 1. 97 C(14)-0(36) 1. 17 1. 17 As (5) -C(16) 1. 92 1. 93 C(15)-0 (37) 1. 18 1. 13 As (5) -C(17) 1. 96 1. 98 AVERAGE C-0 1.16 AVERAGE As-Me 1.94 35 T a b l e I I I . V ( c o n t i n u e d ) M o l e c u l e M o l e c u l e 1 2 1 2 C ( 6 ) -F e ( l ) - C ( 7 ) 92 93 Fe (2) - A s ( 4 ) -C (18) 119 116 C ( 6 ) -F e ( 1 ) - C ( 8 ) 93 95 Fe (2) - A s ( 4 ) - C ( 1 9 ) 118 120 C ( 6 ) - F e ( 1 ) - C ( 9 ) 100 100 F e ( 2 ) - A s ( 4 ) - C ( 2 0 ) 114 116 C ( 6 ) - F e ( l ) - Fe (2) 105 107 C(18) -As (4) - C ( 1 9 ) 104 104 C ( 7 ) - F e ( 1 ) - C ( 9 ) 94 93 C(18) - A s ( 4 ) - C ( 2 0 ) 99 99 C ( 7 ) - F e ( 1 ) - Fe (2) 85 93 C(19) -As (4) -C (20) 100 99 C ( 7 ) - F e ( 1 ) - F e ( 3 ) 88 90 Fe (3) -As (5) -C (16) 120 116 C ( 8 ) - F e ( 1 ) - C ( 9 ) 94 92 Fe (3) - A s ( 5 ) - C ( 1 7 ) 116 121 C ( 8 ) -F e ( 1 ) - Fe (2) 86 79 Fe (3) -As (5) - C ( 2 1 ) 113 113 C ( 8 ) -F e ( l ) - F e ( 3 ) 85 81 C (16) - A s ( 5 ) - C ( 1 7 ) 104 103 C ( 9 ) - F e ( l ) - Fe (3) 96 97 C(16) - A s ( 5 ) - C ( 2 1 ) 101 99 F e ( 2 ) - F e ( l ) - F e ( 3 ) 5 6 . 9 ( 2 ) 5 6 . 5 ( 2 ) C(17) - A s ( 5 ) - C ( 2 1 ) 100 102 C (10) -Fe (2) - C d l ) 94 96 As (4) -C (20) - C ( 2 1 ) 137 134 C (10) - F e ( 2 ) - C ( 1 5 ) 86 83 As (4) - C ( 2 0 ) -C (22) 131 134 C (10) - F e ( 2 ) - A s ( 4 ) 97 97 C (21) -C (20) - C ( 2 2 ) 92 92 C ( l l ) -Fe (2) - C ( 1 4 ) 88 88 As (5) -C (21) - C ( 2 0 ) 137 136 C (11) -Fe (2) - A s ( 4 ) 100 96 As (5) -C (21) -C (23) 127 130 C ( 1 4 ) -Fe (2) - F e ( 3 ) 51 48 C (20) -C (21) - C ( 2 3 ) 96 9 3 C (14) -Fe (2) - A s ( 4 ) 88 86 C (15) -Fe (2) -Fe (3) 49 53 C(20) - C ( 2 2 ) -F (24) 111 112 C (15) -Fe (2) - A s ( 4 ) 87 89 C (20) -C (22) -F (25) 114 114 Fe (1) - F e ( 2 ) - C ( 1 0 ) 89 97 C(20) -C (22) -C (23) 86 88 F e ( l ) - F e ( 2 ) - C ( l l ) 88 82 F (24) - C ( 2 2 ) - C ( 2 3 ) 119 117 Fe (1) -Fe (2) - C ( 1 4 ) 87 80 F (24) - C ( 2 2 ) - F ( 2 5 ) 109 109 Fe (1) -Fe (2) - C ( 1 5 ) 86 94 F (25) - C ( 2 2 ) - C ( 2 3 ) 117 117 Fe (1) -Fe (2) - F e ( 3 ) 61.5 (2) 6 2 . 3 ( 2 ) Fe (3) - F e ( 2 ) - A s ( 4 ) 1 0 9 . 1 ( 2 ) 1 0 9 . 1 ( 2 ) C(21) - C ( 2 3 ) - F ( 2 6 ) 120 116 C ( 2 1 ) - C ( 2 3 ) - F ( 2 7 ) 118 113 C ( 1 2 ) -Fe (3) - C ( 1 3 ) 95 93 C (21) -C (23) -C (22) 86 88 C ( 1 2 ) -Fe (3) - C ( 1 4 ) 86 90 F (26) - C ( 2 3 ) -C (22) 114 119 C ( 1 2 ) -Fe (3) - A s ( 5 ) 97 94 F (26) - C ( 2 3 ) - F ( 2 7 ) 106 103 C (13) -Fe (3) - C ( 1 5 ) 88 84 F (27) - C ( 2 3 ) -C (22) 113 118 C ( 1 3 ) -Fe (3) - A s ( 5 ) 96 98 C (14) -Fe (3) - F e ( 2 ) 48 52 Fe (1) -C ( 6 ) -0 ( 2 8 ) 180 170 C (14) -Fe (3) - A s ( 5 ) 90 88 Fe (1) - C ( 7 ) - 0 ( 2 9 ) 177 172 C (15) -Fe (3) - F e ( 2 ) 51 49 Fe (1) - C ( 8 ) - O(30) 174 170 C (15) - F e ( 3 ) - A s ( 5 ) 87 89 Fe (1) - C ( 9 ) - 0 ( 3 1 ) 176 171 Fe (1) - F e ( 3 ) - C ( 1 2 ) 88 87 Fe (2) - C ( 1 0 ) - 0 ( 3 5 ) 174 174 Fe (1) - F e ( 3 ) - C ( 1 3 ) 90 93 .Fe (2) - C ( l l ) - 0 ( 3 4 ) 173 173 Fe (1) -Fe (3) - C ( 1 4 ) 85 82 F e ( 3 ) - C ( 1 2 ) - 0 ( 3 2 ) 173 177 F e d ) -Fe (3) - C ( 1 5 ) 87 90 Fe (3) -C (13) - 0 ( 3 3 ) 176 172 Fe (1) -Fe (3) - F e ( 2 ) 6 1 . 6 ( 2 ) 6 1 . 2 ( 2 ) Fe (2) -Fe (3) - A s ( 5 ) 1 1 0 . 4 ( 3 ) 1 1 0 . 7 ( 2 ) Fe (2) -C (14) - 0 ( 3 6 ) 143 134 Fe (3) - C ( 1 4 ) - 0 ( 3 6 ) 136 146 Fe (2) - C ( 1 5 ) - 0 ( 3 7 ) 139 147 Fe (3) - C ( 1 5 ) - 0 ( 3 7 ) 142 136 DISCUSSION The m o l e c u l e ( F i g u r e I I I . 2) i s b e s t d e s c r i b e d as 18 a d e r i v a t i v e o f F e 3 ( C O ) i 2 / w i t h one e q u a t o r i a l c a r b o n y l g r o u p on e a c h o f t h e two e q u i v a l e n t i r o n atoms r e p l a c e d by t h e a r s e n i c atoms o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d . I n e a c h o f t h e two m o l e c u l e s i n t h e a s y m m e t r i c u n i t , t h e a r s e n i c and c a r b o n atoms o f t h e l i g a n d a r e c o p l a n a r ( T a b l e 19 I I I , I V ) i n c o n t r a s t t o t h e n o n - p l a n a r i t y i n L F e 2 ( C O ) 6 . P r e s u m a b l y t h e d e v i a t i o n f r o m p l a n a r i t y i n t h e l a t t e r compound i s a s s o c i a t e d w i t h t h e i n v o l v e m e n t o f t h e c y c l o -b u t e n e i T - e l e c t r o n s i n b o n d i n g t o one o f t h e i r o n a t o m s ; . t h i s b o n d i n g i s n o t p r e s e n t i n L F e 3 ( C O ) i 0 , s o t h a t p l a n a r i t y o f t h e l i g a n d i s n o t u n e x p e c t e d . The d i f f e r e n c e i n b o n d i n g i n t h e two compounds i s f u r t h e r i n d i c a t e d by t h e C=C b o n d l e n g t h s ; t h e d i s t a n c e ( T a b l e I I I . V ) i n L F e 3 ( C O ) i 0 i s 1.30(3) A ( s t a n d a r d d e v i a t i o n i n p a r e n t h e s e s ) , i n d i c a t i n g r r e t e n t i o n o f d o u b l e - b o n d c h a r a c t e r , w h i l e t h e c o r r e s p o n d i n g o l e n g t h i n L F e 2 ( C O ) 6 i s 1.51(4) A, c o n s i s t e n t w i t h t h e i n v o l v e m e n t o f t h e i T - e l e c t r o n s i n b o n d i n g t o an i r o n atom. I n e a c h o f t h e two L F e 3 ( C O ) i o m o l e c u l e s i n t h e a s y m m e t r i c u n i t , t h e l i g a n d i s n o t q u i t e c o p l a n a r w i t h t h e i r o n t r i a n g l e , and t h e amount o f b e n d i n g i s s l i g h t l y d i f f e r e n t i n t h e two m o l e c u l e s . I n m o l e c u l e 1 t h e a n g l e b e t w e e n t h e - t r i a n g l e and l i g a n d p l a n e s i s o n l y 3.7°, b u t m o l e c u l e 2 i s more s i g n i f i c a n t l y b e n t , t h e a n g l e b e i n g 9.9°. S i n c e t h e a n g l e i s d i f f e r e n t i n t h e two m o l e c u l e s , t h e to 38 small deviations from planarity are probably a r e s u l t of c r y s t a l packing forces. The bond lengths and valency angles i n the two LFe 3(CO)io molecules i n the asymmetric unit are not s i g -n i f i c a n t l y d i f f e r e n t (Table III.V). The Fe-Fe distances i n the isosceles iron t r i a n g l e are 2.65(1) A for the o equivalent bonds, and 2.53(1) A for the carbonyl-bridged bond. These lengths are close to the distances of 2.67(1) A o T O and 2.56(1) A for the parent F e 3 ( C O ) i 2 molecule, so that replacement of two terminal carbonyl groups by the d i -(t e r t i a r y arsine) ligand has apparently proceeded with l i t t l e disturbance of the bonding i n the iron t r i a n g l e . The mean Fe-C(terminal) distance i s 1.73 A, close 27-30 to the distance found m related compounds, and a l l 31 the Fe-C-0 are close to l i n e a r , as expected. The Fe-C (bridging) distances are considerably longer, and the bridges appear to be s l i g h t l y asymmetric (Figure III.3). The mean of the four longer Fe-C(bridging) bonds (with standard deviation of the mean) i s 2.02(2) A, while the : a average of the shorter bonds i s 1.93(2) A, the difference being greater than 3a and probably s i g n i f i c a n t . This asymmetry i s sim i l a r to, although not as pronounced as that found i n P h 3 P F e 3 ( C O ) i i (average Fe-C(bridging), 2.04 0 '27 27 and 1.87 A).. As Dahm and Jacobson point out, this asymmetry need not be the r e s u l t of c r y s t a l packing forces, but could be inherent i n the bonding of the parent F e 3 ( C O ) i 2 , F i g u r e I I I . 3 View o f a s y m m e t r i c c a r b o n y l b r i d g e s . oo i n w h i c h t h e r e i s some e v i d e n c e f o r u n s y m m e t r i c a l b r i d g i n g 18 ° c a r b o n y l g r o u p s . The C-0 bond l e n g t h s a v e r a g e 1.17 A, and t h e d i s t a n c e s i n t h e b r i d g i n g c a r b o n y l s a r e n o t s i g -n i f i c a n t l y l o n g e r t h a n t h e a v e r a g e . A l l t h e o t h e r bond l e n g t h s and v a l e n c y a n g l e s ( T a b l e I I I . V ) a r e q u i t e s i m i l a r t o t h o s e i n r e l a t e d com-pounds. The a n g l e s i n t h e F e 3 ( C O ) i o m o i e t y a r e s i m i l a r 27 t o t h o s e i n Ph 3 P F e 3 ( C O ) 1 1 and t h e d i m e n s i o n s o f t h e • d i - ( t e r t i a r y a r s i n e ) l i g a n d a r e c l o s e t o t h o s e i n L C o 2 ( C O ) 6 ^ 19 and L F e 2 ( C O ) 6 a p a r t f r o m t h e d i f f e r e n c e s c a u s e d by t h e n o n - p l a n a r i t y o f t h e l i g a n d i n t h e l a t t e r compound. The v a l e n c y a n g l e s a t a r s e n i c show d e v i a t i o n s f r o m t h e e x a c t t e t r a h e d r a l v a l u e ( F i g u r e I I I . 4 ) , t h e Fe-As-C a n g l e s (113-. 121°) b e i n g l a r g e r t h a n t h e C-As-C a n g l e s ( 9 9 - 1 0 4 ° ) . o Fe-As bond l e n g t h s (mean 2.297 A) c o r r e s p o n d t o t h o s e f o u n d i n L F e 2 ( C O ) 6 1 9 and { F e ( C O ) 3 } 2 ( A s M e 3 ) * . 3 3 The m a g n i t u d e s o f t h e p r i n c i p a l axes o f t h e t h e r m a l v i b r a t i o n e l l i p s o i d s o f t h e i r o n and a r s e n i c atoms a r e g i v e n i n T a b l e I I I . V I . The l a r g e s t v i b r a t i o n s a r e a p p r o x i m a t e l y p e r p e n d i c u l a r t o t h e p l a n e o f t h e i r o n t r i -a n g l e . A l l t h e i n t e r m o l e c u l a r d i s t a n c e s c o r r e s p o n d t o n o r m a l v a n d e r Waals i n t e r a c t i o n s , t h e c l o s e s t a p p r o a c h e s D b e i n g a b o u t 3.1 A. The m o l e c u l e s a r e a r r a n g e d ( F i g u r e I I I . 5 ) so t h a t an o x y g e n atom o f a b r i d g i n g c a r b o n y l g r o u p o f e a c h m o l e c u l e i n t h e a s y m m e t r i c u n i t i s a p p r o x i m a t e l y e q u i d i s t a n t 42 T a b l e I I I . V I M a g n i t u d e s (A, a = 0.005-0.008 A) o f t h e p r i n c i p a l a x e s o f t h e t h e r m a l v i b r a t i o n e l l i p s o i d s o f t h e i r o n a n d a r s e n i c atoms M o l e c u l e 1 M o l e c u l e 2 A x i s 1 A x i s 2 A x i s 3 A x i s 1 A x i s 2 A x i s F e ( l ) 0.186 0.233 0.235 0.179 0.249 0.292 Fe (2) 0.165 0.175 0.277 0.195 0.223 0.298 F e O ) 0.190 0.192 0.261 0.190 0.222 0.273 As (4) 0.177 0.179 0.249 0.194 0.212 0.243 As (5) 0.166 0.218 0.260 0.193 0.232 0.240 43 a F i g u r e I I I . 5 I n t e r m o l e c u l a r c o n t a c t s i n g e n e r a l v i e w . f r o m t h r e e o f t h e f o u r t e r m i n a l c a r b o n y l g r o u p s o f t h e u n i q u e i r o n atom o f t h e o t h e r m o l e c u l e . A n o t h e r , s i m p l i f i e d v i e w o f t h e m o l e c u l a r p a c k i n g i s shown i n F i g u r e I I I . 6 . IV. THE STRUCTURE DETERMINATION OF { M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 } 2 - R u 3 ( C O ) 8 STRUCTURE ANALYSIS The a s y m m e t r i c u n i t c o n t a i n s h a l f a m o l e c u l e , r e q u i r i n g t h a t t h e m o l e c u l e be l o c a t e d on a c r y s t a l l o -g r a p h i c symmetry e l e m e n t . S i n c e t h e m o l e c u l e i s n o t c e n t r o s y m m e t r i c ( i t c o n t a i n s t h r e e r u t h e n i u m atoms i n a t r i a n g l e ) , i t was e x p e c t e d t o l i e on t h e t w o - f o l d a x i s a t (0,y_,%) o f P b c n . The s t r u c t u r e was s o l v e d by t h e u s e o f t h r e e d i m e n s i o n a l d i r e c t methods. S i x t e e n s e t s o f s i g n s f o r 219 r e f l e c t i o n s h a v i n g n o r m a l i z e d s t r u c t u r e f a c t o r |E| > 1.50 were d e t e r m i n e d by L o n g ' s computer p r o -gram, i n w h i c h S a y r e r e l a t i o n s h i p s were a p p l i e d i n an 34 i t e r a t i v e p r o c e d u r e . The p r o g r a m u s e s a s t a r t i n g s e t o f s e v e n s i g n s and a p p l i e s S a y r e ' s e q u a t i o n i n c o n j u n c t i o n w i t h o t h e r c o n d i t i o n s i m p o s e d on t h e E ' s by s p a c e g r o u p symmetry. The f i r s t t h r e e E's a r e c h o s e n t o s p e c i f y t h e o r i g i n and c a n be a r b i t r a r i l y a s s i g n e d p o s i t i v e s i g n s . The o t h e r f o u r a r e a l l o w e d t o t a k e on b o t h p o s i t i v e and n e g a t i v e s i g n s i n t u r n . The E ' s a r e o r d e r e d i n s u c h a way t h a t t h e s t a r t i n g s e t i s a t t h e b e g i n n i n g , f o l l o w e d by t h e r e m a i n d e r , s o r t e d i n o r d e r o f d e c r e a s i n g | E | . From e a c h o f t h e s t a r t i n g s e t s , t h e p r o g r a m p r e d i c t s t h e s i g n s f o r r e f l e c t i o n s b e l o w on t h e l i s t . E a c h new p r e -d i c t i o n i s u s e d t o d e t e r m i n e s i g n s f u r t h e r down t h e l i s t . When t h e b o t t o m o f t h e l i s t i s r e a c h e d , t h e i t e r a t i o n i s r e p e a t e d , s t a r t i n g w i t h t h e e i g h t h r e f l e c t i o n ( t h e s i g n s o f t h e s t a r t i n g s e t a r e n o t a l l o w e d t o c h a n g e ) . The number o f s i g n changes and t h e number o f s i g n s newly d e t e r m i n e d 48 a r e c o u n t e d f o r e a c h c y c l e and t h e i t e r a t i o n i s s a i d t o have c o n v e r g e d when t h e r e a r e no a d d i t i o n s t o o r ch a n g e s i n t h e l i s t o f s i g n s . 34 A c o n s i s t e n c y i n d e x , U, i s d e f i n e d as U = J _ J l i _ J l 2 J l 3 i _ (4.1) <|ES1I=IEKJ |Ega|> where t h e sums a r e o v e r a l l p a i r s n"2 and ia 3 f o r w h i c h ri2+ri3=Fii and where <> means " a v e r a g e o v e r a l l v a l u e s o f h i " . The t r u e s o l u t i o n w i l l u s u a l l y be t h e most c o n s i s t e n t one, i.e. i t w i l l have t h e h i g h e s t c o n s i s t e n c y i n d e x . U s u a l l y t h e c o r r e c t s o l u t i o n r e q u i r e s f e w e r i t e r a t i v e c y c l e s and con-, v e r g e s t o a s e t o f s i g n s w h i c h a r e a p p r o x i m a t e l y e q u a l l y d i s t r i b u t e d between p o s i t i v e and n e g a t i v e . T a b l e I V . I g i v e s a c o m p a r i s o n o f t h e s i x t e e n p o s s i b l e s o l u t i o n s g e n e r a t e d f o r t h e p r e s e n t s t r u c t u r e . S o l u t i o n 9 was o u t s t a n d i n g i n t h a t t h e i t e r a t i o n p r o c e d u r e c o n v e r g e d i n t h r e e c y c l e s t o a s e t o f s i g n s h a v i n g t h e h i g h e s t c o n s i s t e n c y i n d e x (0.95) and e q u a l numbers o f p o s i t i v e and n e g a t i v e s i g n s . An E-map c a l c u l a t e d w i t h t h i s s e t o f s i g n s i n d i c a t e d t h e p o s i t i o n s o f f o u r i n d e p e n d e n t atoms, one o f w h i c h was i s i t u a t e d on t h e t w o - f o l d r o t a t i o n a x i s as e x p e c t e d . The p o s i t i o n s and t h e r m a l p a r a m e t e r s o f t h e s e f o u r atoms ( a s s i g n e d as two As and two Ru) were i m p r o v e d by two c y c l e s o f f u l l - m a t r i x l e a s t - s q u a r e s r e f i n e m e n t , w i t h u s e o f t h e s c a t t e r i n g f a c t o r s o f r e f . 26. The r e a l p a r t o f t h e d i s -p e r s i o n c o r r e c t i o n was a p p l i e d . A d i f f e r e n c e s y n t h e s i s T a b l e I V . I C o m p a r i s o n o f t h e 16 s o l u t i o n s f r o m L o n g ' s s i g n d e t e r m i n a t i o n p r o g r a m S e t S i g n s o f s t a r t i n g s e t Number o f c y c l e s Number o f p l u s e s Number o f m i n u s e s C o n s i s t ! i n d e : U 1 +++++++ 7 109 110 0.539 2 ++++++- 8 103 116 0.464 3 +++++-+ 12 112 107 0 ;.641 4 +++++— 5 117 102 0. 896 5 ++++-++ 12 116 103 0.588 6 ++++-+- 6 108 111 0.638 7 ++++—+ 5 108 111 0.691 8 ++++ 8 103 116 0.543 9 +++-+++ 3 109 110 0.954 10 +++-++- 6 109 110 0.909 11 +++-+-+ 5 110 . 109 0.684 12 +++-+— 10 108 111 0.481 13 +++—++ 7 106 113 0. 899 14 + + + — + - 8 102 117 0.557 15 +++ + 7 110 109 0.680 16 +++ 12 105 114 0.424 p h a s e d on t h e r e f i n e d p a r a m e t e r s r e v e a l e d t h e p o s i t i o n s o f a l l t w e n t y c a r b o n , o x y g e n , and f l u o r i n e a t o m s . Two c y c l e s o f f u l l - m a t r i x r e f i n e m e n t , w i t h m i n i -m i z a t i o n o f Ew(F -F ) 2 , w = {A + B l F I + C|F I2 + D l F I 3 } - 1 f o r o b s e r v e d r e f l e c t i o n s ( u n o b s e r v e d s w e r e e x c l u d e d f r o m r e f i n e m e n t b u t i n c l u d e d i n f i n a l s t r u c t u r e f a c t o r c a l -c u l a t i o n ) , r e d u c e d R t o 0.124. A, B, C, and D w e r e a d j u s t e d t o g i v e c o n s t a n t a v e r a g e v a l u e s o f w ( F Q - F c ) 2 o v e r t h e w h o l e r a n g e o f I f | , t h e f i n a l v a l u e s b e i n g 3 7 . 3 2 , 1.09, - 0 . 0 1 5 9 , and 0.00008 r e s p e c t i v e l y . A t t h i s s t a g e a d i f f e r e n c e map showed s m a l l p e a k s and t r o u g h s a r o u n d t h e p o s i t i o n s o f t h e r u t h e n i u m and a r s e n i c a t o m s . Two f u r t h e r c y c l e s o f f u l l -m a t r i x r e f i n e m e n t u s i n g a n i s o t r o p i c t h e r m a l p a r a m e t e r s f o r t h e h e a v y atoms r e d u c e d R t o 0.089. A d i f f e r e n c e map c o m p uted a t t h i s s t a g e i n d i c a t e d t h e n e c e s s i t y o f a l s o t r e a t i n g t h e f l u o r i n e atoms a n i s o t r o p i c a l l y . Two f i n a l , c y c l e s o f f u l l - m a t r i x r e f i n e m e n t w e r e c a r r i e d o u t v a r y i n g t h e p o s i t i o n a l p a r a m e t e r s , a n i s o t r o p i c t h e r m a l p a r a m e t e r s f o r t h e r u t h e n i u m , a r s e n i c , and f l u o r i n e a t o m s , i s o t r o p i c t h e r m a l p a r a m e t e r s f o r t h e o t h e r a t o m s , and a s i n g l e o v e r a l l s c a l e f a c t o r , f o r a t o t a l o f 133 v a r i a b l e s . A t f i n a l c o n v e r g e n c e o f t h e r e f i n e m e n t , R and R w e r e 0.078 — —w and 0.098 r e s p e c t i v e l y , f o r t h e 1507 o b s e r v e d r e f l e c t i o n s , and 0.088 and 0.114 r e s p e c t i v e l y , f o r a l l d a t a . M e a s u r e d and c a l c u l a t e d s t r u c t u r e f a c t o r s a r e l i s t e d i n T a b l e I V . I I . A f i n a l d i f f e r e n c e map showed f l u c t u a t i o n s a r o u n d t h e h e a v y T a b l e I V . I I F i n a l m e a s u r e d a n d c a l c u l a t e d s t r u c t u r e f a c t o r s . U n o b s e r v e d 51 r e f l e c t i o n s h a v e an a s t e r i s k a f t e r t h e F 1 —o v a l u e , L OBS C«LC L OBS CALC t OBS C»LC L OBS CALC L OBS C*LC 0 * D» 37 0 6 1*5 159 0 « 94 109 C 10 51 *S 0 12 111 UT 14 111 »s* 1* 121 121 IB 4* •> 10 112 101 0 456 4 31 1 216 191 2 10) 10* 0 153 14* 1* 102 I0B 15 51 51 16 109 |09 5 1*4 13T 6 290 30T I 224 231 • 91 48 9 161 192 10 266 291 11 215 227 12 1B9 Z07 11 159 ITT 14 159 ISM 14 *• IB 16 152 152 IT 0* ' 1 11 102 91 l l 11* III It IB0 |T4 2 106 Ml 1 195 190 10 146 lfcT B 116 121 2 211 21T 0 11* 111 11 142 142 11 101 It 1 116 504 2 199 192 15 14) 114 I IT0 I TO |0 105 11* 0 IS 102 11 122 114 120 126 • B 191 1*7 0* 14 40 4T 144 150 t l 11T 12* 10 1* 112 110 2 121 112 0 10 15 ** 0 IB 23 16 0 20 44 41 O 594 4U 1> 111 121 16 102 106 IB 200 140 5 ?45 226 12 MS HI 5 120 120 I 116 169 S 26 31 6 111 111 B 142 16T I 162 14B atoms o f +1.5 e/A, w h i c h c o u l d n o t be a t t r i b u t e d t o any e l e m e n t s o f t h e s t r u c t u r e and w e r e assumed t o be a r e s u l t o f random e x p e r i m e n t a l e r r o r . T a b l e I V . I l l g i v e s t h e f i n a l p o s i t i o n a l and t h e r -m a l p a r a m e t e r s , w i t h s t a n d a r d d e v i a t i o n s c a l c u l a t e d f r o m t h e i n v e r s e m a t r i x o f t h e l a s t c y c l e o f r e f i n e m e n t . Bond d i s t a n c e s and v a l e n c e a n g l e s a r e g i v e n i n T a b l e I V . I V . S t a n d a r d d e v i a t i o n s f o r t h e s e q u a n t i t i e s i n c l u d e a c o n -t r i b u t i o n f r o m t h e s t a n d a r d d e v i a t i o n s o f t h e l a t t i c e p a r a m e t e r s . T a b l e I V . V g i v e s t h e e q u a t i o n s o f t h e w e i g h t e d mean p l a n e s o f t h e r u t h e n i u m t r i a n g l e and t h e a r s e n i c and c a r b o n atoms o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d . The m a g n i t u d e s o f t h e p r i n c i p a l a x e s o f a n i s o t r o p i c t h e r m a l , v i b r a t i o n e l l i p s o i d s a r e i n T a b l e I V . V I . . T a b l e I V . I l l F i n a l p o s i t i o n a l ( f r a c t i o n a l , x 1 0 4 ) and t h e r m a l p a r a m e t e r s , w i t h s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s . ATOM X y z B o r b i i b 2 2 b_33 b i 2 b i 3 _2 3 R u ( l ) 0 1014 ( 1) 2500 1014( 39) 101( 8) 189 ( 7) 0 - 68( 12) 0 Ru(2) 0686 ( 2) -0329 ( 1) 3071 ( 1) 1013 ( 29) 113 ( 6) 187 ( 5) 28 ( 9) - 44( 9) 8( 4) AS (1) 0189 ( 3) 1847 ( 1) 3340 ( 1) 1386( 41) 110( 7) 245( 7) 72 (13) -125( 13) - 35( 5) As (2) 2288 ( 2) 0000 ( 1) 3909 ( 1) 1003 ( 35) 162 ( 8) 188( 6) 66(13) - 61( 11) - 15( 5) F ( l ) 2657 (22) 2546 (10) 4549 ( 8) 3493(319) 267 (79) 463 (53) -298(130) -637(111) - 7 ( 5 3 ) F ( 2 ) 0652 (23) 2200 (12) 4981 (10) 3799(392) 623 (94) 396 (66) 617 (163) -107(136) -158 (66) F ( 3 ) 1952 (19) 1013 (10) 5378 ( 8) 4149(310) 414(72) 210(51) 181 (120) -122(100) - 10(51) F ( 4 ) 3968 (22) 1332 (11) 4931 ( 9) 2783 (363) 294 (83) 571(58) 128(140) -691(111) - 91(56) C ( l ) 2102 (29) 0973 (14) 2434 (12) 4.5 (6) C(2) 2281 (25) -0586 (12) 2560 (10) 3.6(5) C(3) 0225 (28) -1266 (1.4) 3311 (11) 4.3(5) C(4) -0948 (26) 0081 (13) 3505 (11) 3.8(5) C(5) 1275 (25) 1560 (12) 4054 (10) 3.3(5) C(6) 1734 (32) 1978 (15) 4623 (12) 5.4(6) C(7) 2003 (23) 0956 (12) 4265 (10) 3.2(4) C(8) 2448 (31) 1294 (14) 4843 (12) 5.2(5) Me (1) 1250 (35) 2780 (17) 3192 (13) 6.2(7) Me (2) -1618 (39) 2147 (20) 3771 (16) 7.4(8) Me (3) 2171 (29) -0563 (14) 4650 (12) 4.6 (6) Me (4) 4427 (33) 0051 (17) 3766 (13) 6.0 (7) 0(1 ) 3360 (22) 1028 (10) 2400 ( 8) 5.7(4) 0( 2 ) 3278 (19) -0782 ( 9) 2276 ( 8) 5.1(4) 0( 3 ) -0111 (22) -1861 (11) 3432 ( 9) 6.5(5) 0(4 ) -1890 (19) 0271 (10) 3810 ( 8) 5.2(4) c o e f f i c i e n t s i n t h e t e m p e r a t u r e e x p r e s s i o n : exp - 1 0 ~ 5 ( b i i h 2 + b 2 2 ] S 2 + b 3 3 : £ 2 + 2 b 1 2 h k + 2 b i 3 h £ + 2 b 2 3 k £ ) 54 T a b l e I V . I V o Bond d i s t a n c e s (A) and v a l e n c e a n g l e s ( d e g r e e s ) , w i t h s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s . R u ( l ) -Ru(2) 2.853 (3) C ( 5 ) - C(7) 1.39(3) Ru CD- -As(1) 2.401(3) C ( 5 ) - C(6) 1.52(3) Rut 1) - C ( l ) 1.91(3) C(6)- C(8) 1.46 (3) C(7)- C(8) 1.46 (3) Ru (2) -Ru(2' ) 2.785 (4) Ru (2) -C(2) 1.89 (2) C(6)- F ( l ) 1.35 (3) Ru (2) -C(3) 1.86 (3) C(6)- F(2) 1.32 (3) Ru (2) -C(4) 1.92(2) C(8)- F(3) 1.36(3) Ru (2) -As (2) 2.413 (3) C(8)- F ( 4 ) 1.39 (3) As (1) -Me(1) 2.00 (3) C ( l ) - 0(1) 1.15 (3) As (1) -Me(2) 1.97 (4) C(2)- 0(2) 1.15 (2) As (1) -C(5) 1.92 (2) C ( 3 ) - 0(3) 1.17 (3) C(4)- 0(4) 1.14 (3) As (2) -Me(3) 1.93 (3) As (2) -Me(4) 1.97 (3) As (2) -C(7) 1.95 (2) c ( l ) - R u ( l ) - R u ( 2 ) 77.3(8) Ru(2) -As (2)-C(7) 116.8 (6) C ( l ) - R u ( l ) - R u ( 2 ' ) 98.6(8) Me (3) -As (2)-Me(4) 102.3 (12) c ( D - R u ( l ) - A s (1) ' 90.7 (8) Me (3) -As(2)-C(7) 98.6(10) c ( D - R u ( l ) - A s (ID 92.3 (8) Me (4) -As(2)-C(7) 98:7.(H) c ( D - Ru ( l ) - C ( l ' ) 175.4 (16) As (1) - R u ( l ) - A s (ID 100.0(1) As (1) -C(5)-C (7 ) 137.9(17) As (1) -R u ( 1 ) - R u ( 2 ) 102.3(1) As (1) - C ( 5 ) - C ( 6 ) 131.5(17) Ru(2) - R u ( l ) - R u ( 2 ' ) 58.42 (9) C(7)- C(5)-C (6 ) 90.6(18) C ( 2 ) - R u ( 2 ) - R u (2') 79.3 (7) As (2) - C ( 7 ) - C ( 5 ) 131.9(17) C ( 2 ) - R u ( 2 ) - R u ( 1 ) 97.4 (7) As (2) - C ( 7 ) - C ( 8 ) 134.0 (17) C ( 2 ) - Ru (2) - A s ( 2 ) 92.8(7) C ( 5 ) - C ( 7 ) - C ( 8 ) 94.1(19) C ( 2 ) - R u ( 2 ) - C ( 3 ) 95.9(10) Ru (2 1 ) - R u ( 2 ) - R u ( l ) 60.79 (4) C ( 5 ) - C ( 6 ) - F ( l ) 117.8 (23) R u ( 2 ' ) - R u ( 2 ) - C ( 3 ) 98.7 (8) C ( 5 ) -C(6)-F(2) 116.0(24) Ru(2' )-Ru(2)-C (4 ) 95.5(7) C (5) -C(6)-C(8) 87.K19) C ( 3 ) - Ru (2.) -As (2) 99.1(8) F (1) -C ( 6 ) - C ( 8 ) 115.3(23) C ( 3 ) - R u ( 2 ) - C (4) 93.3 (11) F (1) -C ( 6 ) - F ( 2 ) 106.8(23) C ( 4 ) - R u ( 2 ) - A s (2) 89.5 (7) F (2)-C(6)-C(8) 113.3(24) C ( 4 ) - R u ( 2 ) - R u (1) 72.6 (7) i R u ( l ) - R u ( 2 ) - A s ( 2 ) 104.0(1) C(7)- C ( 8)-F(3) 119.0 (22) C(7)- C ( 8 ) - F ( 4 ) 114.4(22) R u ( l ) - As(1)-Me (1) 117.8 (8) C(7)- C ( 8 ) - C ( 6 ) 88.2 (19) R u ( l ) - A s ( 1 ) - M e ( 2 ) 119.0(10) F (3) -C ( 8 ) - C ( 6 ) 117.1(23) R u ( l ) -As ( 1 ) - C ( 5 ) 118.5 (7) F ( 3 ) -C(8) -F (4) 103.2 (21) Me (1) - A s ( 1 ) - M e ( 2 ) 103.5(14) C (6) -C ( 8 ) - F (4) 115.4(23) Me (1) -As (1)-C(5) 97.1(11) Me (2) - A s ( 1 ) - C ( 5 ) 96.8(12) 0(1)- C d ) - R u ( l ) 172.5 (23) 0 (2) -C ( 2 ) - R u ( 2 ) 175.1(20) Ru(2) - A s ( 2 ) - M e ( 3 ) 117.8 (8) 0(3)- C(3)-Ru(2) 176.1 (23) Ru(2) - A s ( 2 ) - M e ( 4 ) 119.1(9) 0(4)- C ( 4 ) - R u ( 2 ) 172.6(21) 55 T a b l e I V . V E q u a t i o n s o f p l a n e s i n t h e f o r m ZX + mY + nZ_ = p_, w h e r e o X, Y, Z_ a r e c o o r d i n a t e s i n A, r e f e r r e d t o o r t h o g o n a l a x e s a, b, c. maximum Z m n p d i s p l a c e m e n t (A) R u t h e n i u m t r i a n g l e (3 Ru atoms) 0.8945 0 -0.4471 -2.4377 0 D i - ( t e r t i a r y a r s i n e ) (2 As a n d 4C atoms) 0.8442 0.3112 -0.4364 -1.9683 0.04 T a b l e I V . V I M a g n i t u d e s (A) o f t h e p r i n c i p a l a x e s o f t h e t h e r m a l v i b r a t i o n e l l i p s o i d s A x i s 1 A x i s 2 A x i s 3 R u ( l ) 0.13 0.19 0.22 Ru(2) 0.14 0.20 0.22 A s ( l ) 0.13 0.21 0. 27 As (2) 0.16 0.19 0.23 F ( l ) 0.19 0.27 0.44 F ( 2 ) 0.24 0.32 0. 45 F ( 3 ) 0.22 , 0.26 0. 42 F ( 4 ) 0.22 0.24. 0.45 DISCUSSION The m o l e c u l a r s t e r e o c h e m i s t r y i s shown i n F i g u r e I V . 1 . The m o l e c u l e i s s i t u a t e d on a c r y s t a l l o g r a p h i c two-f o l d a x i s , and i s c o n v e n i e n t l y d e s c r i b e d as a d e r i v a t i v e 35 o f R u 3 ( C O ) i 2 i n w h i c h two c a r b o n y l g r o u p s on one r u t h e n i u m and one c a r b o n y l on e a c h o f t h e o t h e r two r u t h e n i u m atoms a r e r e p l a c e d by t h e two b i d e n t a t e d i - ( t e r t i a r y a r s i n e ) , l i g a n d s , i n s u c h a way t h a t e a c h l i g a n d b r i d g e s two r u t h e n i u m atoms, and one Ru-Ru bond r e m a i n s u n b r i d g e d . The r e p l a c e m e n t o f f o u r c a r b o n y l g r o u p s f r o m R u 3 ( C O ) i 2 t o f o r m L 2 R u 3 ( C O ) 8 c a u s e s s e v e r a l s t r u c t u r a l c h a n g e s . A l l Ru-Ru bond l e n g t h s a r e no l o n g e r e q u a l . The d i s t a n c e between two r u t h e n i u m atoms w h i c h a r e l i n k e d by t h e four-membered b r i d g e o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d i s 2.853(3) A ( s t a n d a r d d e v i a t i o n i n p a r e n t h e s e s ) , o compared w i t h 2.785(4) A f o r t h e u n b r i d g e d Ru-Ru d i s t a n c e and 2.849, 2.859, and 2.837 A. ( e a c h a = 0.006 A.) f o r t h e 35 t h r e e Ru-Ru d i s t a n c e s i n t h e p a r e n t m o l e c u l e . T h i s s i g n i f i c a n t s h o r t e n i n g p r o b a b l y a r i s e s f r o m d i f f e r e n c e s : i n u - a c c e p t o r c h a r a c t e r o f t h e d i - ( t e r t i a r y a r s i n e ) r e l a t i v e t o c a r b o n y l g r o u p s . T h i s e l e c t r o n i c d i f f e r e n c e has b e en u s e d p r e v i o u s l y t o e x p l a i n t h e i n c r e a s e i n i s o m e r 17 s h i f t o f L F e 3 ( C O ) i 0 r e l a t i v e t o F e 3 ( C O ) i 2 . S e v e r a l o t h e r r u t h e n i u m c l u s t e r compounds have been s t u d i e d " ^ ^ i n w h i c h Ru-Ru bond l e n g t h s r a n g e d f r o m 2.853 t o 2.956 A, w i t h one s h o r t d i s t a n c e o f 2.782 r e p o r t e d f o r t h e R u ( 2 ) -57 [(CH3)2AsC=C(As(CH3)2)CF2CF2]2 RU 3 (CO )Q 0 1 2 3 4 A F i g u r e I V . 1 M o l e c u l a r s t r u c t u r e o f L 2 R u 3 ( C O ) Ru(3) bond d i s t a n c e i n b i s ( c y c l o - o c t a t e t r a e n e ) t r i r u t h e n i u m 40 t e t r a c a r b o n y l ( F i g u r e I V . 2 a ) . The marked s i m i l a r i t y b etween F i g u r e s I V . 2 a and IV.2b w o u l d s u g g e s t t h a t C 8 H 8 and t h e d i - ( t e r t i a r y a r s i n e ) a r e e x e r t i n g t h e same e f f e c t on t h e b o n d i n g p r o p e r t i e s i n t h e c l u s t e r . I n b o t h c a s e s , Ru-Ru bonds i n v o l v i n g t h e r u t h e n i u m atoms w i t h t h e g r e a t e s t number o f c a r b o n y l l i g a n d s a r e t h e s h o r t e s t , r e f l e c t i n g t h e s u p e r i o r i t y o f t h e c a r b o n y l r e l a t i v e t o t h e o t h e r l i g a n d s as an e x t r a c t o r o f e l e c t r o n d e n s i t y f r o m non- ( b o n d i n g d o r b i t a l s on t h e m e t a l atom. I n o t h e r w o rds, t h e d i - ( t e r t i a r y a r s i n e ) and c y c l o - o c t a t e t r a e n e l i g a n d s a r e weaker T r - a c c e p t o r s t h a n t h e c a r b o n y l g r o u p . As e x p e c t e d f r o m n.m.r. o b s e r v a t i o n s and from, t h e s t r u c t u r e o f L F e 3 ( C O ) i o / t h e s k e l e t o n o f t h e l i g a n d does n o t d i f f e r s i g n i f i c a n t l y f r o m e x a c t p l a n a r i t y . The p l a n e o f t h e l i g a n d i s t w i s t e d 18.2° w i t h r e s p e c t t o t h e p l a n e o f t h e r u t h e n i u m t r i a n g l e and t h i s t w i s t i n g c a u s e s s i g n i f i c a n t d i s p l a c e m e n t s o f t h e c a r b o n y l g r o u p s f r o m 35 t h e i r p o s i t i o n s i n t h e p a r e n t c a r b o n y l . I n R u 3 ( C O ) i 2 a x i a l c a r b o n y l g r o u p s a r e v e r y n e a r l y p e r p e n d i c u l a r t o t h e p l a n e o f t h e r u t h e n i u m t r i a n g l e ( a n g l e s v a r y f r o m 88.0 t o 8 9 . 9 ° ) , whereas i n L 2 R U 3 ( C O ) 8 t h e t w i s t i n g o f t h e l i g a n d c a u s e s t h e c a r b o n y l g r o u p s t o be b e n t f r o m a x i a l p o s i t i o n s , as shown i n F i g u r e I V . 3 . N e v e r t h e l e s s , r u t h e n i u m d o e s ' r e t a i n an a p p r o x i m a t e l y o c t a h e d r a l c o - o r d i n a t i o n i n the, complex. The a r s e n i c atoms a l s o s u f f e r m i n o r d i s t o r t i o n s Ru As C F i g u r e IV.3 C o - o r d i n a t i o n a b o u t r u t h e n i u m atoms (a) i n p a r e n t compound and (b) R u ( l ) and (e) Ru(2) o f d i - ( t e r t i a r y a r s i n e ) c o m p l e x . o o f t h e i r c o - o r d i n a t i o n . As i n L F e 3 ( C O ) i 0 , t h e l a r g e s i z e o f t h e m e t a l atom c a u s e s Ru-As-C a n g l e s t o be l a r g e r t h a n O A s - C a n g l e s ( a v e r a g e s 118.1 and 99.5° r e s p e c t i v e l y ; of. F i g u r e I I I . 4 ) . Ru-As b o n d d i s t a n c e s a r e w i t h i n t h e r a n g e 2.308 - 2.472 A r e p o r t e d f o r Ru{ (PhzAsCeHi,) 3 A s } B r 2 . 4 1 Our o mean v a l u e (2.407 A) i s i n a c c o r d w i t h t h e d i s t a n c e w h i c h w o u l d be p r e d i c t e d f r o m t h e Fe - A s b o n d l e n g t h , and f r o m t h e d i f f e r e n c e o f a t o m i c r a d i i o f Ru and F e ; e.g. t h e , Fe- A s b o n d d i s t a n c e i n L F e 3 ( C 0 ) i p i s 2.30 A, t h e Ru-Ru ° 35 d i s t a n c e i n R u 3 ( C O ) i 2 i s 2.85 A , and t h e u n b r i d g e d F e - F e ° 18 d i s t a n c e i n F e 3 ( C O ) i 2 i s 2.65 A g i v i n g a p r e d i c t e d Ru-As b o n d l e n g t h o f {2.30 + ^ ( 2 . 8 5 - 2.65)} = 2.40 A. None o f t h e o t h e r s t r u c t u r a l p a r a m e t e r s i s p a r t i c u l a r l y s u r p r i s i n g . A v e r a g e Ru-C and C-0 d i s t a n c e s © a r e 1.89 and 1.15 A, as i n t h e p a r e n t compound, a n d t h e Ru-C-0 a n g l e s show t h e same s l i g h t d e v i a t i o n s f r o m l i n e a r i t y 31 w h i c h a r e f o u n d m a l l t h e m e t a l c a r b o n y l s . The r e t e n t i o n o f t h e d o u b l e b o n d i n t h e l i g a n d b e t w e e n C ( 5 ) and C ( 7 ) i s i n d i c a t e d by t h e s h o r t b o n d l e n g t h o f 1.39(3) A., n o t s i g -n i f i c a n t l y d i f f e r e n t f r o m t h e v a l u e f o r t h e s p 2 h y b r i d i z a t i o n scheme. The compound L R u 2 ( C O ) 6 w h i c h f o r m s d u r i n g t h e 20 p r e p a r a t i o n o f t h e p r e s e n t d e r i v a t i v e , i s assumed t o be 19 a n a l o g o u s t o L F e 2 ( C O ) 6 i n w h i c h t h i s d o u b l e b o n d i s b r o k e n t o a l l o w t h e i n v o l v e m e n t o f t h e i r - e l e c t r o n s i n b o n d i n g t o one o f t h e i r o n a t o m s . I n t e r m o l e c u l a r c o n t a c t s r a n g e f r o m 2.9 t o 3.5 A 62 and are normal van der Waals interactions. The most important of these are shown i n a projection of the structure (Figure IV.4). 63 V. THE STRUCTURE DETERMINATION M e 2 A s C = C ( A s M e 2 ) C F 2 C F 2 « R u 3 ( C O ) 1 0 STRUCTURE ANALYSIS The p o s i t i o n s o f t h e t h r e e r u t h e n i u m a nd two a r s e n i c atoms i n t h e a s y m m e t r i c u n i t w e r e d e t e r m i n e d f r o m t h e P a t t e r s o n f u n c t i o n and i m p r o v e d w i t h two c y c l e s o f f u l l - m a t r i x l e a s t - s q u a r e s r e f i n e m e n t u s i n g s c a t t e r i n g f a c t o r s f r o m r e f . 26. A d i f f e r e n c e s y n t h e s i s p h a s e d o n t h e s e r e f i n e d p a r a m e t e r s r e v e a l e d t h e p o s i t i o n s o f a l l t h i r t y - t w o c a r b o n , o x y g e n , and f l u o r i n e a t o m s . One c y c l e o f f u l l - m a t r i x r e f i n e m e n t , v a r y i n g an i s o t r o p i c t h e r m a l p a r a m e t e r and t h r e e p o s i t i o n a l p a r a m e t e r s f o r e a c h o f t h e t h i r t y - t w o l i g h t atoms r e d u c e d R t o 0.126. A t t h i s p o i n t , a l l atoms w e r e g i v e n a n i s o t r o p i c t e m p e r a t u r e f a c t o r s w h i c h , a l o n g w i t h p o s i t i o n a l p a r a m e t e r s , w e r e i m p r o v e d by s i x c y c l e s o f b l o c k - d i a g o n a l l e a s t - s q u a r e s r e f i n e m e n t , m i n i m i z i n g E w ( F o ~ F c ) 2 . R e f l e c t i o n s w e r e g i v e n w e i g h t s a c c o r d i n g t o t h e f o l l o w i n g scheme. /w = 1 i f |F I < F* o /w = F * / | F q | i f | F Q | > F * and /w = 0.5 f o r u n o b s e r v e d s F o r t h i s d a t a , a c h o i c e o f F* = 70 r e s u l t s i n a p p r o x i m a t e l y c o n s t a n t v a l u e s f o r w ( F o ~ F c ) 2 o v e r t h e w h o l e r a n g e o f |F | . A t f i n a l c o n v e r g e n c e , p a r a m e t e r s h i f t s w e r e s m a l l f r a c t i o n s o f t h e i r c o r r e s p o n d i n g s t a n d a r d d e v i a t i o n s and R and R^ w e r e 0.076 and 0.096 r e s p e c t i v e l y f o r t h e 1828 o b s e r v e d r e f l e c t i o n s and 0.088 and 0.100 f o r a l l d a t a . Measured and c a l c u l a t e d s t r u c t u r e f a c t o r s are g i v e n i n Table V . I . A f i n a l d i f f e r e n c e map showed f l u c -t u a t i o n s around the heavy atoms of ±1.8 e/A 3 which have been assumed to a r i s e from random experimental e r r o r . Table V.II l i s t s the f i n a l p o s i t i o n a l and thermal parameters with standard d e v i a t i o n s c a l c u l a t e d from the i n v e r s e s of the d i a g o n a l terms of the matrix of the f i n a l refinement c y c l e . Bond d i s t a n c e s and valence angles are g i v e n i n Table V . I I I . Standard d e v i a t i o n s of these q u a n t i t i e s c o n t a i n a c o n t r i b u t i o n from the standard d e v i a t i o n s of the u n i t c e l l parameters. Table V.IV g i v e s the equations of the weighted mean planes of the ruthenium t r i a n g l e and of the a r s e n i c and carbon atoms of the d i - ( t e r t i a r y a r s i n e ) l i g a n d . The magnitudes of the p r i n -c i p a l axes of a n i s o t r o p i c thermal v i b r a t i o n are g i v e n i n Table V.V f o r the three ruthenium and two a r s e n i c atoms. T a b l e V . I F i n a l m e asured and c a l c u l a t e d s t r u c t u r e f a c t o r s . U n o b s e r v e d r e f l e c t i o n s have an a s t e r i s k a f t e r t h e I F | v a l u e . o K OBS C» IX * 16 19 K OBS C*LC II 13 26 9 211 221 12 102 108 0 12 100 9 0 11 *9 5* 0 14 J> 11 0 16 55 56 0 II SJ 52 1 156 140 0 311 2 72 U U l 1 SB 2 243 210 11 10 7 109 0 18 21 21 0 a 2>B 219 0 9 106 101 0 13 121 l i s 0 11 150 136 5 261 2 78 10 UB 112 ] 124 LIB i 117 125 1 1*1 (45 3 U l 142 4 160 162 5 112 11S 10 161 162 2 171 171 1 226 214 6 107 106 I 151 160 1 110 116 1 I IS 126 12 131 101 1 206 198 1 112 48 5 1)6 110 I 116 129 5 106 101 12 105 109 2 125 19 11 104 102 15 10* 11 17 10 1) 159 111 68 T a b l e V . I ( c o n t i n u e d ) 3 14* 127 K OBS CALC K OBS CAI T a b l e V . I I F i n a l p o s i t i o n a l ( f r a c t i o n a l x 10k) and t h e r m a l p a r a m e t e r s w i t h s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s ATOM jx Y z b l l b 2 2 b 3 3 b 1 2 b 1 3 b 2 3 + RU(1) 2495 ( 3) 1378 ( 1) 0800 ( 2) 120 ( 3) 23 ( 1) 52 ( 1) -13 ( 1) - 4 ( 2) 0 ( 1) Ru ( 2 ) 2190 ( 2) -0011 ( 1) 1438 ( 1) 72 ( 2) 25 ( 1) 43 ( 1) - 7 ( 1) - 1 ( 2) 1 ( 1) Ru ( 3 ) 0295 ( 2) 0432 ( 1) 0121 ( 1) 72 ( 2) 21 ( 1) 44 ( 1) - 3 ( 1) - 1 ( 2) 0 ( 1) As (1) -0713 ( 3) -0690 ( 1) -0359 ( 2) 72 ( 3) 22 ( 1) 45 ( 1) - 1 ( 1) - 6 ( 2) - 1 ( 1) As (2) 0934 ( 3) -1098 ( 2) 1860 ( 2) 92 ( 3) 29 ( 1) 46 ( 1) -13 ( 1) - 6 ( 2) - 6 ( 1) F ( l ) -3672 (20) -1923 (11) 0440 (15) 104 (24) 53 ( 7) 100 (12) -38 (12) -22 (16) 5 ( 9) F ( 2 ) - 1 9 4 1 (23) -2541 ( 9) -0158 (10) 239 (33) 35 ( 5) 53 ( 7) -19 (11) 6 (15) - 5 (11) F ( 3 ) -2339 (30) -2315 (12) 1849 (16) 292 (44) 53 ( 7) 93 (12) -64 (16) 11 (24) 15 ( 9) F ( 4 ) -0567 (27) -2873 ( 9) 1204 (14) 341 (41) 37 ( 5) 103 ( I D -28 (13) -50 (19) 9 ( 7) 0 ( 1 ) -0400 (35) 1991 (14) 1631 (20) 280 (49) 61 ( 9) 129 (18) 73 (17) 22 (28) -22 (11) 0 ( 2 ) 2162 (38) 2506 (14) -0515 (15) 339 (56) 67 ( 9) 84 (11) -40 (21) -16 (23) 41 ( 7) 0 ( 3 ) 5391 (22) 0701 (12) 0031 (12) 128 (26) 70 ( 8) 62 ( 8) -16 (26) 11 (28) -16 (14) 0 ( 4 ) 4618 (32) 2079 (15) 1975 (16) 285 (45) 82 (10) 74 (12) -57 (18) 11 (23) -14 (10) 0 ( 5 ) 2703 (26) 0368 (18) -1206 (15) 127 (30) 118 (14) 63 (10) -48 (20) 49 (16) -13 (11) 0 ( 6 ) -1672 (35) 1406 (12) -0908 (15) 343 (56) 43 ( 7) 69 (11) 34 (19) -48 (22) 13 ( 9) 0 ( 7 ) -2148 (25) 0464 (16) 1452 (14) 120 (30) 88 (12) 62 (10) 12 (19) 35 (16) -13 (11) 0 ( 8 ) 0550 (32) 0784 (13) 2740 (15) 276 (51) 43 ( 8) 61 (11) - 1 (18) 26 (22) - 4 ( 9) 0 ( 9 ) 3814 (26) -0830 (11) 0052 (14) 214 (35) 39 ( 6) 94 (11) 8 (13) 25 (18) -22 (14) 0 ( 1 0 ) 5086 (24) -0163 (16) 2460 (16) 69 (24) 102 (13) 71 (10) 11 (18) -43 (14) - 1 (11) C ( l ) 0631 (59) 1713 (18) 1350 (26) 296 (93) 15 (10) 65 (20) 47 (27) 54 (41) - 1 (13) C ( 2 ) 2240 (34) 2083 (19) -0043 (17) 129 (39) 82 (14) 39 (11) -29 (21) -30 (20) -11 (11) C ( 3 ) 4218 (35) 0904 (16) 0355 (18) 138 (43) 39 ( 9) 46 (12) -10 (18) -10 (21) 14 ( 9) C ( 4 ) 3816 (42) 1816 (15) 1561 (19) 285 (54) 41 ( 8) 48 (13) - 9 1 (16) -21 (26) 5 ( 9) C ( 5 ) 1905 (31) 0391 (16) -0682 (18) 56 (35) 35 ( 9 ) 44 (13) -24 (17) 23 (19) - 5 (10) C ( 6 ) -0834 (30) 1053 (13) -0487 (19) 202 (35) 28 ( 7) 106 (14) -19 (13) -56 (18) 13 ( 9) G(7) -1124. (.38). .'. 0 470 (17J. . 1068 (17). ,176 (48) 63 (11) 4 4 (10.) - r l 8 (22) 28 (20) -16 ( 9) T a b l e V . I I ( c o n t i n u e d ) ATOM X y z b l l b_2 2 b 3 3 b i 2 b i 3 b 2 3 C(8) 1163 (41) 0506(14) 2233 (18) 284 (56) 27 ( 7) 55 (12) - 5(19) 2(25) - 4( 8) C(9) 3080 (35) -0520(15) 0569 (18) 163 (43) 30 ( 8) 57 (12) -42 (18) -71 (19) 1 ( 9) C (10) 4002 (42) -0089(21) 2096 (27) 100 (51) 44 (13) 60 (21) -59 (25) -19(31) - 4(16) C ( l l ) -1048 (29) -1417 (14) 0429 (16) 80 (32) 35( 8) 36 (10) - 8(32) -13(33) -24(16) C(12) -0510 (29) -1577(13) 1125 (20) 68 (32) 23( 7) 76 (14) -21(13) -21(19) - 2( 9) C(13) -2106 (38) -2062(14) -0439 (22) 157 (47) 21( 7) 84 (16) -12 (17) 13 (26) 15 ( 9) C(14) -1443 (45) -2249(19) 1196 (27) 166 (57) 38 (11) 98 (22) -23 (24) 13 (34) 34(14) Me (1) -0484 (44) -1033(20) 2796 (18) 254 (60) 71(13) 36 (12) -36 (25) 29(25) -13(11) Me (2) 2253 (40) -1881(18) 2084 (26) 125 (46) 40 (11) 86 (21) 3 (22) -13(31) 22(14) Me (3) -2629 (33) -0711(14) -0924 (23) 44 (36) 37(12) 73 (19) -11(20) -52 (25) 6 (14) Me (4) 0547 (35) -1257(14) -1083 (19) 278 (44) 29 ( 7) 100 (14) 10(17) 63 (19) 0( 9) ^ C o e f f i c i e n t s i n t h e t e m p e r a t u r e > e x p r e s s i o n : exp - 1 0 - , t ( b i i h 2 - 4- b 2 2 k 2 + b 3 3 £ 2 + 2b_i 2hk + 2 b i 3 h £ + 2 b 2 3 k £ ) T a b l e V . I I I o Bond d i s t a n c e s (A) and v a l e n c e a n g l e s ( d e g r e e s ) , w i t h s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s Ru (1) -Ru(2) 2.831(3) C(13) - F ( l ) 1.37(4) Ru (1) -Ru(3) 2.831 (3) C(13) - F ( 2 ) 1.35(4) Ru (1) - C ( l ) 1.95(5) C(14) - F ( 3 ) 1.34 (5) R u ( l ) -C(2) 1.95 (3) C(14) - F ( 4 ) 1. 39(4) Ru (1) -C(3) 1.88(3) Ru (1) -C(4) 1.89 (3) C ( l ) - 0 ( 1) 1.13(6) C ( 2 ) - 0(2) 1.12(4) Ru (2) -Ru(3) 2.858 (6) C ( 3 ) - 0(3) 1.21(4) Ru (2) - A s ( 2 ) 2.417 (4) C ( 4 ) - 0(4) 1.09 (4) Ru(2) -C(8) 1.87(3) C ( 5 ) - 0(5) 1.11(4) Ru (2) -C(9) 1.90(3) C ( 6 ) ~ 0 ( 6 ) 1.21(4) Ru (2) -C(10) 1.91(4) C ( 7 ) - 0(7) 1.09(4) C ( 8 ) - 0(8) 1.13(4) Ru (3) - A s ( 1 ) 2.417 (3) C ( 9 ) - 0(9) 1.22(4) Ru (3) -C(5) 1.93 (3) C(10) -0(10) 1.12 (5) Ru (3) -C(6) 1.83(3) Ru (3) -C(7) 2.00 (.3) C ( l l ) -C(12) 1.29 (4) C ( l l ) -C(13) 1.52 (4) As (1) - C ( l l ) 1.92 (3) C(12) -C(14) 1.50(4) As (1) -Me(3) 1.90 (3) C(13) -C(14) 1.43 (6) As (1) -Me(4) 1.94 (3) As (2) -C(12) 1.96(3) As (2) -Me(1) 1.98(3) As (2) -Me(2) 1.90 (3) Ru (2) - R u ( l ) -Ru(3) 60.64(11) Ru (3) - A s ( 1 ) - C ( l l ) 117 (1) Ru (2) - R u ( l ) - C ( l ) 93(1) Ru (3) - A s ( 1 ) -Me(3) 120(1) Ru (2) - R u ( l ) -C(3) 78(1) Ru (3) - A s ( 1 ) -Me(4) 119(1) Ru (2) - R u ( l ) -C(4) 102(1) C ( l l ) - A s ( 1 ) -Me(3) 101(1) Ru (3) - R u ( l ) - C ( l ) 81(1) C (11) - A s ( 1 ) -Me(4) 97 (1) Ru (3) - R u ( l ) -C(2) 94(1) Me (3) - A s ( 1 ) -Me(4) 99 (1) Ru (3) - R u ( l ) -C(3) 94 (1) C ( l ) - R u ( l ) - C(2) 92(1) Ru (2) - A s ( 2 ) -C(12) 119(1) C ( l ) - R u ( l ) - C(4) 92 (2) Ru (2) - A s ( 2 ) -Me(1) 117(1) C ( 2 ) - R u ( l ) - C(3) 97(1) Ru (2) - A s ( 2 ) -Me(2) 117(1) C ( 2 ) - R u ( l ) - C(4) 105(1) C(12) - A s ( 2 ) -Me(1) 98(1) C ( 3 ) - R u ( l ) - C(4) 90 (1) C(12) - A s ( 2 ) -Me(2) 98 (1) Me (1) - A s ( 2 ) -Me(2) 105 (2) R u ( l ) -Ru(2) -Ru(3) 59.68 (9) R u ( l ) -Ru(2) -C(8) 80 (1) As (1) - C ( l l ) -C(12) 137(2) R u ( l ) -Ru(2) -C(9) 98(1) As (1) -C (11) -C(13) 132(2) R u ( l ) -Ru(2) -C(10) 102(1) C(12) - c ( i i ) -C(13) 91(2) Ru(3) -Ru (2) - A s ( 2 ) 102.48(11) i 72 T a b l e V . I I I R u(3) - R u ( 2 ) - C ( 8 ) 9 7 ( 1 ) Ru(3) -Ru(2) - C ( 9 ) 7 8 ( 1 ) As (2) -R u ( 2 ) - C ( 8 ) 9 1 ( 1 ) As (2) -Ru(2) - C ( 9 ) 8 9 ( 1 ) As (2) -R u ( 2 ) - C ( 1 0 ) 9 7 ( 1 ) C ( 8 ) - R u ( 2 ) - C ( 1 0 ) 9 1 ( 2 ) C ( 9 ) - R u ( 2 ) - C ( 1 0 ) 94 (2) R u ( l ) - R u(3) - R u ( 2 ) 59.67 (9) Ru (1) -Ru (3) - C ( 5 ) 80 ( 1 ) R u ( l ) -Ru (3) -C ( 6 ) 1 0 0 ( 1 ) R u ( l ) - R u ( 3 ) - C ( 7 ) 9 4 ( 1 ) Ru (2) -Ru (3) - A s ( l ) 1 0 1 . 8 0 ( 1 2 ) Ru (2) -R u ( 3 ) - C ( 5 ) 9 7 ( 1 ) Ru (2) -R u ( 3 ) - C ( 7 ) 7 6 ( 1 ) As (1) -R u ( 3 ) - C ( 5 ) 90 (1) As (1) -Ru(3) - C ( 6 ) 1 0 1 ( 1 ) As (1) - R u ( 3 ) - C ( 7 ) 9 4 ( 1 ) C ( 5 ) - R u ( 3 ) - C ( 6 ) 9 1 ( 1 ) C ( 6 ) - R u ( 3 ) - C(7.) 9 5 ( 1 ) ( c o n t i n u e d ) As (2) - C ( 1 2 ) - C ( l l ) 133 (2) As (2) - C ( 1 2 ) - C ( 1 4 ) 132 (3) C ( l l ) - C ( 1 2 ) - C ( 1 4 ) 9 4 ( 3 ) F (1) -C ( 1 3 ) - F ( 2 ) 103 (3) F (1) -C ( 1 3 ) - C ( l l ) 1 1 6 ( 2 ) F (1) -C ( 1 3 ) - C ( 1 4 ) 1 1 6 ( 3 ) F ( 2 ) - C ( 1 3 ) - C ( l l ) 118 (3) F ( 2 ) - C ( 1 3 ) - C ( 1 4 ) 116 (3) C ( l l ) - C ( 1 3 ) - C ( 1 4 ) 88 (2) F ( 3 ) - C ( 1 4 ) - F ( 4 ) 103 (3) F ( 3 ) - C ( 1 4 ) - C ( 1 2 ) 1 1 7 ( 3 ) F ( 3 ) - C ( 1 4 ) - C ( 1 3 ) 121 (3) F ( 4 ) - C ( 1 4 ) - C ( 1 2 ) 1 1 5 ( 3 ) F ( 4 ) - C ( 1 4 ) - C ( 1 3 ) 116 (3) C ( 1 2 ) - C ( 1 4 ) - C ( 1 3 ) 86 (3) Mean Ru-C-0 173 1 73 T a b l e V . I V E q u a t i o n s o f p l a n e s i n t h e f o r m iX + mY + nZ = p_, w h e r e o X, Y, Z_ a r e c o o r d i n a t e s i n A, r e f e r r e d t o o r t h o g o n a l a x e s a, b , c. R u t h e n i u m t r i a n g l e (3 Ru atoms) maximum I m n p d i s p l a c e m e n t (A) 0.6940 -0.3306 -0.6396 -0.2223 0 D i - ( t e r t i a r y a r s i n e ) (2 As and 4 C atoms) 0.7490 -0.5311 - 0 . 3 9 6 1 0.4677 0.06 T a b l e V.V o M a g n i t u d e s (A) o f t h e p r i n c i p a l a x e s o f t h e t h e r m a l v i b r a t i o n e l l i p s o i d s o f t h e h e a v y a t o m s . A x i s 1 A x i s 2 A x i s 3 R u ( l ) 0.18 0.23 0.27 Ru(2) 0.16 0.21 0.25 Ru(3) 0.16 0.20 0.25 A s ( 1 ) 0.16 0.20 0.25 A s ( 2 ) 0.17 0.22 0.27 DISCUSSION I n t h e same way t h a t L F e 3 ( C O ) i 0 i s r e l a t e d t o 18 F e 3 ( C O ) i 2 , t h e complex L R u 3 ( C O ) i 0 i s r e l a t e d t o R u 3 ( C O ) i 2 . As shown i n F i g u r e V . l , one c a r b o n y l g r o u p on e a c h o f two r u t h e n i u m atoms i s r e p l a c e d by t h e a r s e n i c atoms o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d . S i n c e l i g a n d s o f l o w e r a c c e p t o r s t r e n g t h s t h a n t h e c a r b o n y l g r o u p a r e l e s s e f f i c i e n t a t r e m o v i n g i r - a n t i b o n d i n g e l e c t r o n d e n s i t y f r o m t h e m e t a l c l u s t e r , m e t a l - m e t a l bonds between atoms h a v i n g c a r b o n y l g r o u p s r e p l a c e d by t h e s e l i g a n d s w o u l d be e x p e c t e d t o be l o n g e r t h a n m e t a l - m e t a l bonds i n v o l v i n g atoms h a v i n g o n l y c a r b o n y l g r o u p s . T h i s e f f e c t h as b e e n o b s e r v e d p r e v i o u s l y , and i s i n e v i d e n c e i n t h e p r e s e n t s t r u c t u r e . The bond i d i s t a n c e s R u ( l ) - R u ( 2 ) and R u ( l ) - R u ( 3 ) , ( b o t h 2.831(3) A) a r e s i g n i f i c a n t l y s h o r t e r t h a n R u ( 2 ) - R u ( 3 ) , (2.858(6) A ) . A l t h o u g h b o t h JH and 1 9 F n.m.r. s p e c t r a c o n s i s t o f s i n g l e t r e s o n a n c e s , t h e mean p l a n e o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d i s i n f a c t t w i s t e d 18.4° w i t h r e s p e c t t o ; t h e p l a n e o f t h e r u t h e n i u m t r i a n g l e . T h i s i m p l i e s e i t h e r t h a t t h i s t w i s t i s a r e s u l t o f p a c k i n g f o r c e s ( t h e p l a n e o f t h e l i g a n d b e i n g c o - p l a n a r w i t h t h e r u t h e n i u m t r i a n g l e i n s o l u t i o n ) , o r t h a t t h e l i g a n d i s f l e x i n g i n s o l u t i o n and assumes a s t a t i o n a r y c o n f i g u r a t i o n upon c r y s t a l l i z a t i o n . As i n L 2 R u 3 ( C O ) 8 , t h e t w i s t i n g o f t h e l i g a n d a g a i n c a u s e s Ru-Ru-C a n g l e s f o r a x i a l c a r b o n y l s t o change f r o m n e a r l y 90° i n R u 3 ( C O ) i 2 t o t h e s e v e r e l y skewed c o n f i g u r a t i o n s shown F i g u r e V . l M o l e c u l a r s t r u c t u r e o f L R u 3 ( C O ) i 0 . 76 i n Figure V.2. Mean Ru-C and C-0 bond distances are i n excellent agreement with previously reported v a l u e s 3 ^ - ^ ' ^ ' 4 3 and Ru-C-0 angles (mean 172.8°, a(mean) 1.3°))are s i g n i f i c a n t l y non-linear as i n most carbonyl complexes. Ru-As bond distances (both 2.417 A) are i n good agreement with the values 2.401 and 2.413 A found for L 2Ru3(CO) 8 and are within the range 2.308 to 2.472 A reported for Ru((Ph 2AsC6EU) 3As)Br 2. 4 1 Ru-As-C angles are again larger than C-As-C angles (averages 118.2 and 99.7° respectively) due to the s t e r i c e f f e c t of the ruthenium atom (of. Figure III.4). The dimensions of the d i - ( t e r t i a r y arsine) ligand 32 are e s s e n t i a l l y i d e n t i c a l to those i n other s i m i l a r structures. The double bond i n the cyclobutene r i n g (1.29 A) i s retained and other carbon-carbon distances are reasonable. Carbon-fluorine bond distances (mean 1.36 A) are also as expected.; The extent of anisotropy of the thermal vibrations of the heavy atoms i s shown i n Table V.V. The p r i n c i p a l axes of v i b r a t i o n show no r e g u l a r i t i e s i n orientation with respect to intramolecular vectors. Intermolecular van der Waals contacts ranging from 2.96 to 3.48 A are shown i n the a-axis projection of the structure i n Figure V.3. 98 F i g u r e V.2 C o - o r d i n a t i o n a r o u n d 80 ( b ) o C Ru(2) and (b) Ru(3) o f L R u 3 ( C O ) i 0 THE STRUCTURE DETERMINATION M e 2 A s C F 2 C F (CF 3 ) AsMe 2 'Mo (CO) i, STRUCTURE ANALYSIS The c o o r d i n a t e s o f t h e molybdenum and a r s e n i c atoms i n s p a c e g r o u p C2/c w e r e d e r i v e d f r o m t h e P a t t e r s o n f u n c t i o n a n d i m p r o v e d w i t h two c y c l e s o f f u l l - m a t r i x r e f i n e m e n t , u s i n g s c a t t e r i n g f a c t o r s f r o m r e f . 2 6 . A d i f f e r e n c e s y n t h e s i s p h a s e d on t h e r e f i n e d p a r a m e t e r s r e v e a l e d t h e p o s i t i o n s o f a l l t w e n t y - o n e c a r b o n , o x y g e n , and f l u o r i n e a t o m s . One c y c l e o f f u l l - m a t r i x l e a s t - s q u a r e s r e f i n e m e n t w i t h m i n i m i z a t i o n o f EwA2 u s i n g u n i t w e i g h t s f o r a l l o b -s e r v e d r e f l e c t i o n s a n d i s o t r o p i c t h e r m a l p a r e m e t e r s f o r a l l atoms r e d u c e d R t o 0.116. C o n v e r t i n g t o a n i s o t r o p i c t e m p e r a t u r e f a c t o r s f o r molybdenum, a r s e n i c , a nd f l u o r i n e atoms and r e f i n i n g f o r one c y c l e r e d u c e d R t o 0.083. A t t h i s p o i n t , o b s e r v e d r e f l e c t i o n s w e r e a s s i g n e d w e i g h t s f r o m t h e f o l l o w i n g scheme. w = {A + B|F | + c | f o | 2 + D | F Q | 3 } ~ 1 w h e r e A, B, C, and D a r e c a l c u l a t e d by l e a s t - s q u a r e s t r e a t m e n t t o g i v e b e s t f i t t o c o n s t a n t wA 2 o v e r a l l | F 0 | . Two c y c l e s o f r e f i n e m e n t (142 v a r i a b l e s ) u s i n g t h i s w e i g h t i n g scheme w i t h A, B, C, and D e q u a l t o 7.1341, 1.5458, -0.0186 and 0.00008 r e s p e c t i v e l y ( u n o b s e r v e d r e f l e c t i o n s a r e e x -c l u d e d f r o m r e f i n e m e n t b u t i n c l u d e d i n f i n a l s t r u c t u r e f a c t o r c a l c u l a t i o n ) , r e d u c e d R and R t o 0.073 and 0.094 — —w f o r o b s e r v e d r e f l e c t i o n s and 0.085 and 0.148 f o r a l l d a t a . A t f i n a l c o n v e r g e n c e , a l l p a r a m e t e r s h i f t s w e r e s m a l l f r a c t i o n s o f t h e i r s t a n d a r d d e v i a t i o n s . A f i n a l d i f f e r e n c e F o u r i e r r e v e a l e d r e s i d u a l s o f ±1.5 e/A 3 a r o u n d t h e h e a v y atoms w h i c h c a n o n l y be e x p l a i n e d as random e x p e r i m e n t a l e r r o r . M e a s u r e d and c a l c u l a t e d s t r u c t u r e f a c t o r s a r e g i v e n i n T a b l e V I . I . T a b l e V I . I I g i v e s t h e f i n a l p o s i t i o n a l and t h e r m a l p a r a m e t e r s w i t h s t a n d a r d d e v i a t i o n s c a l c u l a t e d f r o m t h e i n v e r s e m a t r i x o f t h e l a s t r e f i n e m e n t c y c l e . Bond d i s t a n c e s and v a l e n c e a n g l e s a r e i n T a b l e . V I . I l l ; s t a n d a r d d e v i a t i o n s o f t h e s e q u a n t i t i e s t a k e i n t o a c c o u n t t h e s t a n -d a r d d e v i a t i o n s o f t h e u n i t c e l l p a r a m e t e r s . T a b l e V I . I V i shows t h e e x t e n t o f a n i s o t r p p y o f t h e t h e r m a l m o t i o n o f t h e molybdenum, a r s e n i c , a n d f l u o r i n e a t o m s . The a n i s o t r o p y i s l a r g e f o r t h e f l u o r i n e a t o m s , p a r t i c u l a r l y t h o s e o f t h e t r i f l u o r o m e t h y l g r o u p , and t h e b o n d d i s t a n c e s s h o u l d be i n c r e a s e d somewhat by c o r r e c t i o n s f o r l i b r a t i o n . However,, s i n c e t h e c a r b o n and o x y g e n atoms w e r e r e f i n e d i s o t r o - • p i c a l l y , no c o r r e c t i o n s w e r e made. A l t h o u g h b o n d l e n g t h c o m p a r i s o n s w i t h i n t h e p r e s e n t m o l e c u l e a r e v a l i d , d e -t a i l e d c o m p a r i s o n s w i t h d i s t a n c e s i n o t h e r m o l e c u l e s s h o u l d t a k e a c c o u n t o f p o s s i b l e l i b r a t i o n c o r r e c t i o n s . T a b l e V I . I 82 F i n a l m e a s u r e d and c a l c u l a t e d s t r u c t u r e r e f l e c t i o n s h a v e an a s t e r i s k a f t e r t h e . f a c t o r s . U n o b s e r v e d F I v a l u e . -I 10 20 17 K OBI C4LC K DBS C»IC 10 0 »1T S71 12 3 2Z» 2*0 I* 0 21* 7)1 I* 0 21) 24' 11 lt>B |B0 11 *1 35 11 U l 120 107 200 190 17B J74 249 o m i n 0 227 258 0 9B 105 0 2)« 25B 0 108 115 U l 12* -*l 15* |4» -»£ « 10 - H 2B 21 - 1 ! 120 1 10 111 Ul 247 261 0 200 225 0 27b 298 0 204 lis 0 25B 27* 11 i'. 40 55 -18 17* i) -ia 12 B7 -i< 251 244 -2 ! t.6 69 - i ; 107 104 - H T a b l e V I . I I F i n a l p o s i t i o n a l ( f r a c t i o n a l x IO1*) and t h e r m a l p a r a m e t e r s , w i t h s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s ATOM X Y. z B o r b i i b_2 2 b 3 3 bi 2 bi 3 K t £ 2 3 Mo 1503 ( 1) 1128 ( 2) 1863 ( 2) 22( 1) 66 ( 2) 77 ( 2) 0( 1) 8( 1) K 1) As (1) 1563 ( 1) 2939 ( 2) 2675 ( 2) 28( 1) 63 ( 2) 83( 3) - 1( 1) 6( 1) - 3 ( 2 ) As (2) 0840 ( 1) 1960 ( 2) 0112 ( 2) 24( 1) 81( 2) 73( 3) 0( 1) 4( 1) 7( 2) F ( l ) 0328 ( 9) 3159 (16) 1540 (21) 47( 6) 159(20) 299 (32) 19( 8) 78 (12) 25 (20) F ( 2 ) 0396 ( 9) 3916 (15) -0236 (17) 59( 6) 139(17) 171(21) 46 ( 9) - 27(10) 39(15) F ( 3 ) 1460 ( 7) 3969 (13) 0505 (17) 36( 4) 113 (14) 216(23) 6( 6) 35( 8) 71(15) F ( 4 ) 1441 (10) 5343 (14) 2357 (29) 50 .( 7) 81(13) 512 (56) 14( 9) 2(15) -48 (22) F ( 5 ) 0775 (13) 5515 (17) 0955 (24) 86(10) 118(18) 286(35) 29(11) 17(15) 42(21) F ( 6 ) 0680 (13) 4909 (17) 2533 (28) 102(11) 115 (18) 455 (51) 24 (12) 156(22) - 5(25) C ( l ) 2134 (12) 1379 (22) 1161 (25) 6.9 (6) C(2) 2014 (ID 0691 (21) 3245 (25) 6.3 (6) C(3) 1430 ( 9) -0220 (19) 1193 (20) 5.1(6) C(4) 0917 (ID 0826 (21) 2679 (24) 6.3 (6) C(5) 0682 (15) 3327 (28) 0663 (32) 8.8(8) C(6) 1109 (13) 3859 (23) 1399 (28) 7.6 (7) C(7) 1010 (16) 4916 (29) 1860 (33) 8.5(8) Me (1) 0073 (14) 1565 (27) -0416 (29) 8.7(8) Me (2) 1055 (13) 2251 (25) -1364 (29) 8.4(8) Me (3) 1333 (15) 3248 (29) 4113 (34) 9.9 (9) Me (4) 2249 (14) 36 45 (26) 2903 (31) 8.9 (8) 0(1 ) 2529 ( 9 ) 1517 (18) 0749 (20) 9.4(6) 0(2 ) 2331 ( 9) 0453 (18) 4112 (21) 9.5(6) 0(3 ) 1372 ( 8) -1066 (16) 0848 (19) 8.2 (5) 0 ( 4 ) 0572 (10) 0590 (18) 3206 (21) 9.8 (6) C o e f f i c i e n t s i n t h e t e m p e r a t u r e e x p r e s s i o n : exp - 1 0 - l + (b_i i h 2 + b 2 2 k 2 + b_3 3|-2 + 2b1 2hk + 2b_! 3 h J + 2 b 2 3kJ.) 00 LO T a b l e V I . I l l B ond d i s t a n c e s (A) and v a l e n c e a n g l e s ( d e g r e e s ) , w i t h s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s Mo-C(1) 1.96 (3) C ( l ) - 0 ( 1 ) 1.20 (3) Mo-C (2) 1.90 (3) C ( 2 ) - 0 ( 2 ) 1.18 (3) Mo-C(3) 1.94 (3) C ( 3 ) - 0 ( 3 ) 1.19 (3) Mo-C (4) 1.96(3) C ( 4 ) - 0 ( 4 ) 1.20(3) Mo-As(1) 2.573(4) Mo-As (2) 2.569(7) C ( 5 ) - C ( 6 ) 1.40 (4) C ( 6 ) - C ( 7 ) 1.54(4) A s ( l ) - M e ( 3 ) 1.92 (4) C ( 5 ) - F ( l ) 1.50 (4) A s ( 1 ) - M e ( 4 ) 1.92(3) C ( 5 ) - F (2) 1.37(4) As ( l ) ' - C (6) 2.06 (3) C ( 6 ) - F ( 3 ) 1.51(4) A s ( 2 ) - M e ( 1 ) 1.95(3) C ( 7 ) - F (4) 1.24 (4) A s ( 2 ) - M e ( 2 ) 1.94(3) C ( 7 ) - F ( 5 ) 1.34 (4) A s ( 2 ) - C ( 5 ) 1.99(4) C ( 7 ) - F ( 6 ) 1.26 (4) C (1)-Mo-As (1) 9 0 ( 1 ) As ( 2 ) - C ( 5 ) - F ( l ) 1 0 6 ( 2 ) C (1)-Mo-As (2) 9 2 ( 1 ) As ( 2 ) - C ( 5 ) - F ( 2 ) 1 1 3 ( 2 ) C ( l ) - M o - C (2) 87 (1) As ( 2 ) - C ( 5 ) - C ( 6 ) 1 1 8 ( 3 ) C ( l ) - M o - C ( 3 ) 9 0 ( 1 ) F ( l ) - C ( 5 ) - F ( 2 ) 108 (3) C (4)-Mo-As (1) 90 (1) F ( l ) - C ( 5 ) - C ( 6 ) 99 (3) C (4)-Mo-As (2) 93 (1) F ( 2 ) - C ( 5 ) - C ( 6 ) 112 (3) C(4)-Mo-C (2) 8 8 ( 1 ) C ( 4 ) - M o-C (3) 89( 1 ) As ( 1 ) - C ( 6 ) - C ( 7 ) 113 (2) A s ( 1 ) - M o - C ( 2 ) 9 0 ( 1 ) A s ( l ) - C ( 6 ) - F ( 3 ) 1 0 4 ( 2 ) A s ( 1 ) - M o - A s ( 2 ) 82.1 (2) As ( 1 ) - C ( 6 ) - C ( 5 ) 1 1 1 ( 2 ) A s ( 2 ) - M o - C ( 3 ) 9 5 ( 1 ) C ( 7 ) - C ( 6 ) - F ( 3 ) 108 (3) 0 ( 3 ) - M o - C (2) 9 2 ( 1 ) C ( 7 ) - C ( 6 ) - C ( 5 ) 121 (3) F ( 3 ) - C ( 6 ) - C ( 5 ) 97 (3) Mo-As ( 1 ) - M e ( 3 ) 1 2 1 ( 1 ) M o - A s ( 1 ) - M e ( 4 ) 1 1 9 ( 1 ) C ( 6 ) - C ( 7 ) - F ( 4 ) 113 (3) M o - A s ( 1 ) - C ( 6 ) 1 0 8 ( 1 ) C ( 6 ) - C ( 7 ) - F ( 5 ) 1 1 0 ( 3 ) Me ( 3 ) - A s (D-C (6) 1 0 6 ( 1 ) C ( 6 ) - C ( 7 ) - F ( 6 ) 113 (3) Me ( 3 ) - A s ( l ) - M e (4) 1 0 2 ( 2 ) F ( 4 ) - C ( 7 ) - F ( 5 ) 106 (3) M e ( 4 ) - A s ( 1 ) - C ( 6 ) 9 8 ( 1 ) F ( 4 ) - C ( 7 ) - F ( 6 ) 110 (3) F . ( 5 ) - C ( 7 ) - F ( 6 ) 1 0 5 ( 3 ) Mo-As (2)-Me (1) 12 3 ( 1 ) M o - A s ( 2 ) - M e ( 2 ) 1 2 2 ( 1 ) Mo-C (1) - 0 ( 1 ) 1 7 8 ( 3 ) Mo-As (2) -C (5) 106 (1) M o - C ( 2 ) - 0 ( 2 ) 178 (3) M e ( l ) - A s ( 2 ) - C ( 5 ) 9 5 ( 1 ) M o - C ( 3 ) - 0 (3) 176 (2) M e ( l ) - A s ( 2 ) - M e ( 2 ) 1 0 3 ( 1 ) M o - C ( 4 ) - 0 (4) 176 (2) M e ( 2 ) - A s ( 2 ) - C ( 5 ) 1 0 2 ( 1 ) 85 T a b l e V I . I V o M a g n i t u d e s (A) o f t h e p r i n c i p a l a x e s o f t h e t h e r m a l v i b r a t i o n e l l i p s o i d s o f a n i s o t r o p i c a t o m s . A x i s 1 A x i s 2 A x i s 3 MO 0.22 0.24 0 . 26 A S ( 1 ) 0.23 0,24 0,30 As (2) 0.21 0.27 0.28 F ( l ) 0.26 0.37 0.49 F ( 2 ) 0.19 0.38 0.51 F ( 3 ) 0.24 0.32 0.42 F ( 4 ) 0.25 0.39 0.61 F ( 5 ) 0.29 0.44 0.53 F ( 6 ) 0.26 0.37 0.65 . ..DISCUSSION The molecule 1,2-bis(dimethylarsino)hexafluoro-propanemolybdenum tetracarbonyl (Figure VI.1) i s derived from 44 45 molybdenum hexacarbonyl ' by replacement of two carbonyl groups by the arsenic atoms of the chelating d i - ( t e r t i a r y arsine) ligand. The co-ordination around molybdenum remains e s s e n t i a l l y octahedral. The f i v e atoms C(2), C(3), Mo, As(l) and As(2) are situated i n the least-squares plane given, i n Table VI.V with C(l) and C(4) equally spaced above and below this plane. The As-Mo-As angle i s 82.1°, and the other,, angles at molybdenum are i n the range 87-95° (Table V I . I I I ) . The Mo-C bond distances, 1.90-1.96(3), mean 1.94 A, and the C-0 bond lengths, 1.18-1,20(3), mean 1.19 A, are s i m i l a r to values reported p r e v i o u s l y . 4 ^ ^ 2 The Mo-C-0 groupings are almost exactly l i n e a r , 176-178(3)°. The Mo-As bond distance appears to be measured for the f i r s t time, the mean value being 2.572(4) A. This distance i s close to that which would be predicted from; a knowledge of other metal-arsenic bond lengths, and from differences i n covalent r a d i i ; e.g. the Fe-As bond distance o 49-52 i s 2.30 A, the Mo-Mo distances i n various compounds o average 3.25 A, and the unbridged Fe-Fe distance i n F e 3 ( C O ) i 2  0 18 i s 2.65 A, giving a predicted Mo-As bond length of (2.30 + h (3.25 - 2.65)) = 2.60 A. The As-Me bond lengths are 1.92-1.95(3), mean o 1.93 A, and the As-C (fluorocarbon) bond distances are 1.99(4) 00 T a b l e V I . V (a.) E q u a t i o n p f w e i g h t e d mean p l a n e o f Mo, A s ( l ) , A s ( 2 ) , C ( 2 ) and C ( 3 ) i n t h e f o r m £X' + mY + n Z 1 = p_ w h e r e X',Y, Z/ a r e c o o r d i n a t e s i n A, r e f e r r e d t o t h e o r t h o g o n a l a x e s a, b, c * . maximum £ m n p_ d i s p l a c e m e n t (A) 0.8801 0.1876 - 0 . 4 3 6 1 2.2605 0.03 (b.) D i r e c t i o n c o s i n e s o f t h e v e c t o r C ( 5 ) - C ( 6 ) r e f e r r e d t o t h e o r t h o g o n a l a x e s a, h , c * , ( 0 . 6 3 3 3 , 0.5014, 0.5895) and 2 . 0 6 ( 3 ) , mean 2.03 A; t h e mean v a l u e s o f t h e two t y p e s o f As-C b o nd a r e s i g n i f i c a n t l y d i f f e r e n t . The a n g l e s a t a r s e n i c w h i c h i n v o l v e t h e molybdenum atom a r e l a r g e r t h a n t h e a n g l e s i n v o l v i n g o n l y c a r b o n a t o m s . The M o - A s - C ( f l u o r o -c a r b o n ) a n g l e s , 106 and 108(1)° , a r e p r o b a b l y i n f l u e n c e d by t h e i r p r e s e n c e i n t h e f i v e - m e m b e r e d r i n g , b u t t h e Mo-AsrMe a n g l e s , 119-123 mean 121°, a r e a l l s i g n i f i c a n t l y l a r g e r t h a n t h e t e t r a h e d r a l a n g l e , p r e s u m a b l y as a r e s u l t o f t h e s t e r i c i n f l u e n c e o f t h e Mo(CO)i+ g r o u p . T h e r e a r e two d i s t i n c t M e - A s - C ( f l u o r o c a r b o n ) a n g l e s a t e a c h a r s e n i c atom, 98 and 106(1)° a t A s ( l ) , and 95 and 102(1)° a t As (2) , p r o b a b l y as a r e s u l t o f d i f f e r i n g s t e r i c i n t e r a c t i o n s b e t w e e n t h e two m e t h y l g r o u p s a t e a c h a r s e n i c and t h e f l u o r o c a r b o n . A t a b l e o f a ( t h e d i h e d r a l a n g l e b e t w e e n t h e p l a n e containing the r i n g carbon atoms and the metal atom and the plane containing the r i n g nitrogen atoms and the metal atom) and 8 (the angle between the nitrogen atoms as one looks down the carbon-carbon bond) has been compiled for a number of M(en>3 complexes. Average values of a and 3 are 24.8 and 48.6° respectively. The five-membered ring i n L'Mo (CO) i s non-planar with C(5) and C(6) d i s -placed by -0.40 and 0.14 A respectively from the As-Mo-As plane, so that the C-C bond i s twisted 23.2° with respect to the central plane of the molybdenum octahedron ( cf. 24.8° average of values from ref.53), A view along the C-C bond i s shown i n Figure VI.2. The arrangement i s staggered, with the than* dihedral angles a l l being close to 180° (178, 175, and 179°). The As-C-C-As dihedral angle (47°, cf. 48.6°, average from r e f . 53) i s reduced from an i d e a l 60° as a. r e s u l t of the formation of the chelate r i n g . The one trifluoromethyl and three f l u o r i n e substituents of the C-C bond may be c l a s s i f i e d as a x i a l or equatorial with respect to the chelate ring; the bulkier trifluoromethyl group occupies a less s t e r i c a l l y - h i n d e r e d equatorial p o s i t i o n (Figures VI.1 and VI.2). The bond distances and valence angles i n the fluorocarbon group (Table VI,III) show some unusual and i n t e r e s t i n g features. The C-F(axial) bond distances are 1.50 and 1.51(4), mean 1.51(3) A, the C-F(equatorial) bond o length i s 1.37(4) A, and the C-F(trifluoromethyl) bonds measure 1.24, 1.26, and 1.34(4), mean 1.28(2) A. The normal 54 ° C-F bond distance i s 1.33 A. The equatorial and t r i f l u o r o -methyl C-F bond lengths do not d i f f e r s i g n i f i c a n t l y from the normal value; the equatorial C-F bond cannot be claimed to be s i g n i f i c a n t l y longer than the trifluoromethyl bonds,; as i t d i f f e r s from the mean trifluoromethyl length by only 2a and from the longest observed trifluoromethyl bond by only 0.5a. The C-F(axial) bonds are however very s i g n i f i c a n t l y longer than a normal C-F bond (by 6a), than the C-F(equa-; t o r i a l ) bond ( by 2.8a), and than the mean of the C - F ( t r i -fluoromethyl) bonds (by 6a). a The C-C bond distance i s 1.40(4) A, s i g n i f i c a n t l y shorter (by 3.5a) than a normal C-C single bond (1.54 A). The valence angles at C(5) and C(6) are also informative. Those angles not involving the a x i a l f l u o r i n e atoms are a l l greater than the tetrahedral value, range 111-121(3), mean 115°; the angles involving the a x i a l fluorines are cor-respondingly less than the tetrahedral value, with the C-C-F(axial) angles being 97 and 99(3)°. A l l of these unusual features are explicable i n •. terms of a bonding system which, i n valence bond language, contains a contribution not only from the normal structure Ia (Figure VI.3), but also from the structure l b , which involves donation of molybdenum non-bonding d-electrons, via the arsenic 4d o r b i t a l s , into o r b i t a l s of the fluoro-carbon group. The molecular dimensions are best explained by an equal contribution of the two canonical forms Ia and 92 F i g u r e V I . 3 P r o p o s e d b o n d i n g scheme t o a c c o u n t f o r anomalous o b s e r v a t i o n s . 93 l b t o t h e r e s o n a n c e h y b r i d ; t h e C-C b o n d t h u s h a s 50% d o u b l e b o n d c h a r a c t e r , i n a g r e e m e n t w i t h t h e o b s e r v e d d i s t a n c e o f 1.40 A, and t h e a n g l e s n o t i n v o l v i n g F ( a x i a l ) w o u l d be e x -p e c t e d t o be a b o u t midway b e t w e e n t h e t e t r a h e d r a l (110°) and t r i g o n a l (120°) v a l u e s , as o b s e r v e d (mean 115°). The C - F ( a x i a l ) b o n d d i s t a n c e w o u l d be p r e d i c t e d t o be c o n s i d e r a b l y l o n g e r t h a n a n o r m a l s i n g l e b o n d (1.33 A) as a r e s u l t o f t h e c o n -t r i b u t i o n o f t h e n o - b o n d s t r u c t u r e , l b , a g a i n as o b s e r v e d o (1.51 A ) . I n m o l e c u l a r o r b i t a l t e r m i n o l o g y , t h e c h e l a t e r i n g c o n t a i n s a d e l o c a l i z e d i r-bond s y s t e m , w h i c h i n v o l v e s a f i l l e d m olybdenum 4d o r b i t a l , empty a r s e n i c 4d o r b i t a l s , a n d an o r b i t a l on e a c h c a r b o n atom w h i c h a p p r o x i m a t e s a p o r b i t a l , n o r m a l t o an a p p r o x i m a t e s p 2 a - b o n d i n g s y s t e m . I t i s d i f f i c u l t t o p r e d i c t w h a t d i s t a n c e w o u l d be e x p e c t e d f o r t h e C - F ( a x i a l ) b o n d s on t h e b a s i s o f t h e a b o v e b o n d i n g scheme. However, s i n c e t h e b o n d s h a v e a p r e d i c t e d t o t a l b o n d o r d e r o f 0.5, t h e d i s t a n c e w o u l d be l o n g e r t h a n o o t h e s i n g l e b o n d d i s t a n c e (1.33 A) by a p p r o x i m a t e l y 0.14 A, w h i c h i s t h e s h o r t e n i n g n o t e d i n t h e C-C b o n d f o r a r e l a t e d c h a n g e i n bond o r d e r . T h i s i s i n a g r e e m e n t w i t h t h e o b s e r v e d v a l u e o f 1.51 A. ; More r e l i a b l e c o m p a r i s o n may be made w i t h CHF=CF*Mn(CO)5 o 55 i n w h i c h l o n g C-F b o n d s , 1.48(2) A, h a v e b e e n o b s e r v e d . ; T h e s e l o n g b o n d s h a v e b e e n r a t i o n a l i z e d i n t e r r a s o f s t r u c t u r e s + 11 i n v o l v i n g Mn =C F . A n o t h e r c o m p a r a b l e s t r u c t u r e i s Mn(CO)sCF3 w h e r e i . r . s p e c t r a h a v e b e e n i n t e r p r e t e d ^ i n t e r m s o f weak C-F bonds r e s u l t i n g f r o m r e s o n a n c e s t r u c t u r e s o f t h e t y p e Mn +=CF 2 F . C o n t r i b u t i o n s f r o m s t r u c t u r e s o f t h i s t y p e have been s u p p o r t e d by t h e o b s e r v a n c e o f a s h o r t M o - C 3 F 7 47 i n 7T-C 5H 5Mo (CO) 3C 3F7 , a l t h o u g h no r e l a t e d a b n o r m a l i t i e s were f o u n d i n t h e C-F b o n d s . The s i t u a t i o n i n t h e p r e s e n t compound i s s i m i l a r , b u t w i t h t h e added f e a t u r e t h a t t h e c a r b o n atom i s n o t d i r e c t l y bonded t o t h e m e t a l , s o t h a t any e f f e c t must be t r a n s m i t t e d t h r o u g h t h e a r s e n i c atoms. I t i s w e l l known t h a t i n a m e t a l complex, t h e m e t a l atom t e n d s t o r e d u c e a h i g h f o r m a l n e g a t i v e c h a r g e by b a c k - d o n a t i o n o f e l e c t r o n s i n t o n o n - b o n d i n g o r a n t i -b o n d i n g o r b i t a l s o f t h e l i g a n d s . I t w o u l d a p p e a r t h a t t h e l i g a n d i n t h e p r e s e n t compound i s a b l e t o f u n c t i o n i n t h i s b a c k - d o n a t i o n by v i r t u e o f t h e p r e s e n c e o f t h e C-F bonds i n t h e a x i a l p o s i t i o n s . Such b o n d i n g a p p e a r s t o be a b l e t o f o r c e C-F bonds i n t o a f a v o u r a b l e a x i a l p o s i t i o n e v e n i n compounds where s t e r i c f a c t o r s f a v o u r an e q u a t o r i a l p o s i t i o n f o r t h e f l u o r i n e atom. I n Me 2AsCHFCH 2AsMe 2 «Cr (CO) it 57 f o r example, n.m.r. s t u d i e s i n d i c a t e an a x i a l f l u o r i n e atom. A t f i r s t g l a n c e , t h i s model a p p e a r s t o have t h e u n d e s i r a b l e f e a t u r e t h a t t h e p o s i t i v e c h a r g e on t h e m o l y b -denum m i g h t be e x p e c t e d t o c a u s e Mo-C bonds t o be l o n g e r and C-0 bonds t o be s h o r t e r t h a n t h o s e o f M o ( C O ) 6 as a r e s u l t o f t h e u n a v a i l a b i l i t y o f non-bonded m e t a l e l e c t r o n s f o r b a c k - b o n d i n g . C o r r e s p o n d i n g s h i f t s o f C-0 s t r e t c h i n g . f r e q u e n c i e s t o h i g h e r wavenumbers m i g h t a l s o be e x p e c t e d . However, t h e c h a r g e d i s t r i b u t i o n p i c t u r e d i n F i g u r e V I . 3 . 1 b c a n a l s o be i n t e r p r e t e d as a mechanism f o r i n c r e a s i n g t h e - r r - a c c e p t o r s t r e n g t h o f t h e d i - ( t e r t i a r y a r s i n e ) l i g a n d t o t h e l e v e l o f t h e c a r b o n y l g r o u p , i n w h i c h c a s e , no d i f f e r e n c e between t h e Mo-C and C-0 bond l e n g t h s i n M o ( C O ) 6 and t h o s e i n L'Mo(CO ) i t w o u l d be e x p e c t e d . o The C - C F 3 bond i n t h e p r e s e n t compound, 1.54 (4) A, i s a n o r m a l s i n g l e bond, t h e C-C-F a n g l e s , 110-113(3)° , a r e s l i g h t l y l a r g e r , and t h e F-C-F a n g l e s , 105-110(3)° s l i g h t l y s m a l l e r t h a n t h e t e t r a h e d r a l v a l u e . The t h e r m a l v i b r a t i o n e l l i p s o i d s f o r t h o s e atoms t r e a t e d a n i s o t r o p i c a l l y ( T a b l e V I . I V ) a r e i n g e n e r a l o r i e n t e d s o t h a t t h e maximum v i b r a t i o n s a r e i n d i r e c t i o n s o f l e a s t s t e r i c r e s t r a i n t , i.e. between o r p e r p e n d i c u l a r t o b o n d s . The i n t e r m o l e c u l a r p a c k i n g a p p e a r s t o be g o v e r n e d s o l e l y by v a n d e r Waals i n t e r a c t i o n s . A p r o j e c t i o n o f t h e s t r u c t u r e , w i t h t h e s h o r t e r i n t e r m o l e c u l a r d i s t a n c e s , i s shown i n F i g u r e V I . 4 . V I I . COMPUTER PROGRAMMING A . P R O G R A M " U P D A T E " D u r i n g r e f i n e m e n t by o u r f u l l - m a t r i x l e a s t -s q u a r e s p r o g r a m , t h e r e s i d u a l q u a n t i t y b e i n g m i n i m i z e d i s EwA 2 where A = I f ^ - F ^ J and w = k/a 2 (k i s a c o n s t a n t and o"F i s t h e s t a n d a r d d e v i a t i o n i n F ) . The p r o g r a m c a n be made t o a s s i g n s t a n d a r d d e v i a t i o n s i n F ' s f r o m 5 8 ° C r u i c k s h a n k ' s e q u a t i o n a 2 = A - > , \ B I F I + C | F 1 2 + D 1 F | 3 (7.1) F — 1 —o ' — 1 —o 1 — 1 —o 1j l ~ ~ ~ A c o r r e c t w e i g h t i n g scheme r e q u i r e s t h a t EwA 2 be c o n s t a n t o v e r l o c a l r a n g e s o f | | . S i n c e a l l r a n g e s c a n be made t o have e q u a l numbers o f r e f l e c t i o n s , £ w A 2 f o r a r a n g e i s p r o p o r t i o n a l t o t h e mean wA 2 , <wA2>, o f t h e r a n g e and we c a n s a y t h a t t h e <wA2> f o r a l l r a n g e must be e q u a l and make them a l l e q u a l t o <A 2> o f t h e f i r r a n g e . <wA 2> i = <A 2>i (7.2) b u t s i n c e w = k/a 2 (7.3) — r where a 2 i s c a l c u l a t e d f o r t h e mean F I o f t h e r a n g e . F I—oI ^ T h e r e f o r e , by t r a n s p o s i n g , (a*y = k <A 2> i/<A 2> 1 (7.5) and we must c a l c u l a t e A , B , C, and D f o r t h e b e s t l e a s t -s q u a r e s f i t o f °F^i t o k < A 2 > i / < A 2 > i o v e r NGRP r a n g e s , where NGRP i s i n p u t t o t h e p r o g r a m f r o m c a r d s . T h i s l e a d s t o t h e f a m i l i a r n o r m a l e q u a t i o n s NGRP •3 A _ r n z { A + B < | F | > . + C < | F | > .2 + D < | F | > . 3 - l i i A i l i } 2 = o , B , C , D i — — '—o 1 l — '-o 1 l — '-o 1 x <A >i (7.6) o r i n m a t r i x n o t a t i o n , / NGRP E < I F |>. Z < I F |>2 i "~2 1 i ~~2 1 E < I F I>2 z < I F I > 3 . 1 — o 1 i . 1 — o 1 1 X — x — Z< I F -|>? Z < | F |>f . 1 — O 1 1 . 1 — O 1 X E < I F I>. i '-o' i E< F i ~ ° E < I F | > ? i 2. 1 z< I F \ > K . . 1 - O 1 X X — z < IF | > ? . 1 —o 1 1 x — z< I F | > ? ^ i x 1 E < I F |>f i ~2. 1 E < I F | > ? i 2 1 A B C Z<A 2>./<A 2>i i x' E < I F I >.<A 2>./<A 2>i i '—o' x x' 1 E< | F |>. 2<A 2>./<A 2>i i '—o 1 x \' 1 E < | F |>. 3<A 2>./<A 2>J (7.7) \ o r T W/k = S (7.8) and W/k = T " 1 S (7.9) .and we s o l v e f o r A/k, B/k, C/k, and D/k by i n v e r t i n g T and m u l t i p l y i n g by S. The b e s t c h o i c e o f w e i g h t s , w h i c h g i v e s t h e l o w e s t s t a n d a r d d e v i a t i o n s i n t h e d e r i v e d p a r a m e t e r s i s w = 1/a 2 — r so t h a t i f we c a n e v a l u a t e t h e c o n s t a n t k i n (7.3) we c a n a c h i e v e t h e b e s t w e i g h t i n g scheme by m u l t i p l y i n g t h e s o l u t i o n o f t h e n o r m a l e q u a t i o n s by k. I t c a n be shown t h e o r e t i c a l l y t h a t t h e c o n s t a n t k i s ERROR = ZwA 2/(NREF-NV) (7.10) where NREF i s t h e number o f r e f l e c t i o n s and NV i s t h e number o f v a r i a b l e s i n t h e l e a s t - s q u a r e s c r y s t a l s t r u c t u r e r e f i n e m e n t . The p r o g r a m "UPDATE" c a n now be f o r m u l a t e d i n s i x s t a g e s (of. T a b l e V I I . I ) . i ) r e a d s t r u c t u r e f a c t o r d a t a and s o r t i n o r d e r o f i n c r e a s i n g m a g n i t u d e o f F . S u b r o u t i n e ASORT(A,I,N,M,K) i s an a s s e m b l e r - l a n g u a g e r o u t i n e w h i c h s o r t s t h e M by K f r a g m e n t o f t h e a r r a y A (which i s d i m e n s i o n e d N by K) a c c o r d i n g t o one-word k e y s l o c a t e d i n t h e f i r s t column o f t h e a r r a y . E a c h row i s moved w i t h i t s f i r s t e l e m e n t . ;For a d a p t a t i o n t o t h i s p r o g r a m , A i s d i m e n s i o n e d 10,000 by ;2 and M i s s e t t o NREF, t h e number o f r e f l e c t i o n s r e a d f r o m t h e s t r u c t u r e f a c t o r d a t a . The a r r a y e l e m e n t s A ( J , 1 ) and A ( J , 2 ) c o n t a i n I F ^ J and |F_ c|, r e s p e c t i v e l y , f o r t h e J t h , r e f l e c t i o n . A t t h e c o m p l e t i o n o f t h i s s t a g e o f t h e p r o -gram, we have an a r r a y A(NREF,2) w h i c h i s s o r t e d i n o r d e r o f i n c r e a s i n g I F ^ J . i i ) d e t e r m i n e t h e number o f r e f l e c t i o n s i n e a c h r a n g e . The number o f r a n g e s d e s i r e d (NGRP) i s i n p u t t o t h e p r o -gram f r o m c a r d s . E a c h r a n g e i s g i v e n NREF/NGRP r e f l e c t i o n s w i t h a d d i t i o n a l s i n g l e r e f l e c t i o n s added t o t h e f i r s t few r a n g e s i f NREF/NGRP i s n o t an i n t e g e r . T a b l e V I I . I L i s t i n g o f t h e p r o g r a m "UPDATE" OF At MOL SO. HE ANFO.I INFO • HA XFU iM tinLSQ , M Nl)LS PEAL MID' -C- : ,? l , VtM [T t. SIGII^l,YCI K I tSILl 1)1, AC ( 10|,ASI I'll PIWFNSISN S l l - U ' l .NU-Mflt I , * ( « . .41 Df'ENST.CN HJ11?),HKU<-'J .Hit .FSCALf I 171 ,ktr N|lt<) .1110) ,VI4) 9E*L*» X ,V ,SU - . T INT[i;rR-2 HJ.HR ,HL .F SCALF ,RFFN 6 FORMAT I ix , 'THIS l)A!A SF T t.ANUCT HE M M F O TO a FOUR P A^ AMFIE K CURV l t ' l 7 FORMAT( 1 K,'BY LEAST SUUAffS METHODS WITMIH1T NEGATIVE WEIGHTS') F0f iW*T(///» A = ' . F 1 S . C , ' R . >,F15.1,' C > • »F 15. "3, ' Q • ' .F11.9 I FCIkHAl | / / ' F SIT, SO SU« IM • , / I F0RMAT(3X,F4..",?Fir.,4l * FCrt «AT(> ',///) OK.MH4FI:>. :,2I5» FRI At I I H , M . 1 , 3 M - ,F f . 1.3*.Fft. i, 2X.F*,, 1.2X.F6. 3 .2X.F5.2 ,2X ,F6 . * I ,2X,IS| ,Ft-. J ,2X ,Fh . 1FIS.3,?X,I5> • f (]RWAT( * ' , 2 U ' R I K. 'WDKLSOVI f U F » " A T ( / / / « W C I G H T l N READ(5,3R1 F INLFLI RNGRP-NGRP JKP." nri ?ir [ j . i , t r. SU*< IJ 1 = 0. NRF F =~ iM) i jnn = i , ucri-OEADI ?,END=Q^) CYDIKl, S1GIK I , YC|K I, STL IK) .AC) K I t H J U l .MRU) ,HLIL| ,FSC4LHLt .REFHIL) ,1 -1 , ll ) DO 1 1=1,R 1H HJ( 11 »t';E1 r,n T:J qo I F I YCII I t I 1,1,4234 4 NHEF'NRFF*! ft(N^Er ,1 I=Y n( I ) A ( N » E F ,2|*YCI I I CONT 1NUE CALL A SORT t A, 1. lr-:";-.' ,NW rf , ? ) >?X,Fo ,3 ,2X , F 5 . Z , ?x , FKRC1H NREF V 4 6 : SCJUARED'I , A 5 ( K ) , 1 " Of-TfMUNF MOTHER TF •< CFLFC TICNS [h T-ACH Ri XNREf-NKFF 1NHFF=NRFF/NCHP J F = NH FF-C^GRP" INRFf I nn iJ=I,NGP°IFIJ- IFI 4 , 4 , 5 NHrMJlmlNRtr Gil TO 4 MJM|JI=INWrF*l CONTINUE C ALCUl AT F WEIGHT INC. ANALYSIS IN FIJRM A T III S SiriLTA - O.r iiUMFtl-* .f 00 6 J = l , NGPP su«*rn=>-, SOt(.TA=;-. • • OLSO- 1 - . KP=NU"IJ) III) 7 I > 1 . 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F L l * I r,o TC F•F «FINI GOTO 22 F»F»f|N2 GDHI 22 C:NT I N U C r,n D 3CC ' KH I IE « tt 31 f,) H"I If I 6,3'. 7 ( STO°FNO DO H JOfl = l t NGBP P.FA013,ENIJ» 161 E,F,H,G,AN T <1)=R su"i 1»- sum 11 *T( 11 DO 15 J-2,h J « 1 = J - 1 T)Jl = T(JM11 *B S11M)JI-SU>-IJI*T(JI CONTINUE T(7 LAN SUM< 7 I=SUMl7 I*T(7 I no u L=fl,ic LM1=L-1 ICLI -T ILMl l 'H SUM(L)=S1JV. (L|*T(L» CUNTINUE CONTINUF CONTINUE BEWIND 3 K(1.11=RNGRP no 19 K*2,^  K«1=K-1 XII .Kl -SUMlKHll 00 f K*2,<. X(2 . M =SU» ( Kl XI3,3)>SUMIH Xt 3, t)-SUMI •>) = S"H(6) t>0 11 1-2,4 IK l -1 -1 20? 2C-3 2G6 224 22S 226 127 22B 229 SUHRITUT INE SHI.TNI A.U, N.x.OCT, ' 1 SUPfiOllTlNE TO SOI VF H A T ° t t C0UAT1CN TIMEnsicN AM, PEAL'P A,r  "ULT OP <>>'. r>ET-i)fT-A(i,ii IFtArtSlDf TI .1. T HI J 1 "P 1 J) -B I I 1 «Mi'LT CCNTINUE CON'IMUF 00 < 1=1. BtI l-EU ll/AlI,Ll flFTURN MftlTEIAil?) FORMAT(•DETCPMINANI RETURN 1 FNfl Nn tlNIOl'F SOLO 102 i i i ) t h e f o l l o w i n g f i v e q u a n t i t i e s a r e c a l c u l a t e d f o r e a c h r a n g e and s t o r e d t e m p o r a r i l y on a d a t a f i l e . MINFO, MAXFO, and MEANFO, t h e minimum, maximum and mean |F^| i n t h e r a n g e . R, t h e d i s c r e p a n c y i n d e x E | A . | / E | F ^ | f o r t h e r a n g e . MDLSQ, t h e r a t i o < A 2 > I / < A 2 > i i v ) t h e q u a n t i t i e s MEANFO and MDLSQ a r e u s e d t o s e t up t h e m a t r i x o f n o r m a l e q u a t i o n s and t h e s y s t e m i s s o l v e d f o r A/k, B/k, C/k, and D/k. SOLTN i s a s u b r o u t i n e f o r s o l v i n g m a t r i x e q u a t i o n s . v) u s i n g t h e s e v a l u e s f o r A, B, C, and D, t h e c o n s t a n t ERROR i s e v a l u a t e d and e a c h o f t h e f o u r w e i g h t i n g scheme p a r a m e t e r s i s m u l t i p l i e d by t h i s v a l u e . U s i n g t h e s e c o r r e c t e d v a l u e s o f A, B, C, and D, a t a b l e o f MINFO, MAXFO, R, MEANFO, WTDR, MWDLSQ, ERROR, and NUM(J) i s c o m p i l e d and p r i n t e d f o r e a c h r a n g e . WTDR = {EwA 2/ZwF^} 1 / 2 " MWDLSQ = <wA2> NUM(J) = number o f r e f l e c t i o n s i n t h e , J t h range, v i ) w and a2 a r e c a l c u l a t e d and p r i n t e d as a f u n c t i o n o f F^ i n s t e p s o f F I N l f r o m FIN1 t o FLIM and i n s t e p s o f FIN2 f r o m FLIM t o FMAX where F I N l , FLIM, FIN2, and FMAX a r e i n p u t t o t h e p r o g r a m f r o m c a r d s . Sometimes b e c a u s e o f bad f i t , t h e v a l u e s o f a 2 a r e n e g a t i v e and s h o u l d be a d -j u s t e d by s m a l l changes t o t h e w e i g h t i n g p a r a m e t e r s b e f o r e b e i n g u s e d i n . s t r u c t u r e r e f i n e m e n t . B. PROGRAM "ORTEP" D u r i n g t h e c o u r s e o f t h e w o r k f o r t h i s t h e s i s , t h e Oak R i d g e N a t i o n a l L a b o r a t o r y t h e r m a l e l l i p s o i d p l o t 59 p r o g r a m , ORTEP, was made c o m p a t i b l e w i t h o u r e x i s t i n g p r o g r a m s and i m p l e m e n t e d on t h e IBM 360/67 by t h e a u t h o r . S t e r e o v i e w s o f t h e f o u r s t r u c t u r e s i n t h i s t h e s i s a r e g i v e n i n F i g u r e V I I . l as p l o t t e d by ORTEP. Atoms a r e r e p r e s e n t e d by 50% p r o b a b i l i t y e l l i p s o i d s o f t h e r m a l v i b r a t i o n . Figure V I i . l S t e r e o v i e w s o f L F e 3 ( C O ) i o (c) L R u 3 ( C O ) L 2 R u 3 ( C O ) 8 (d) L'Mo(CO) (a) (b) 105 (d) V I I I . REFERENCES 107 1. A. L. P a t t e r s o n , Z. K r i s t . , 1 9 3 5 , A 9 0 , 517. 2. A. J . C. W i l s o n , N a t u r e , 1 9 4 2 , 150, 152. 3. D. S a y r e , A c t a C r y s t . , 1 9 5 2 , 5, 60. 4. J . K a r l e and H. Hauptmann, A c t a C r y s t . , 1950, 3, 1 8 1 , 5. E. W. A b e l , Q u a r t . R e v . , 1 9 6 3 , 17, 133. 6. E. W. A b e l a n d F. G. A. S t o n e , Q u a r t . Rev. , 1969, 2_3, 325. 7. J . W. R i c h a r d s o n , i n " O r g a n o m e t a l l i c C h e m i s t r y " , H. Z e i s s e d . , R e i n h o l d , 1960, p . l . 8. J . C h a t t , P. L. P a u s o n , a n d L. M. V e n a n z i , i b i d . , p. 468. 9. F. C a l d e r a z z o , R. E r c o l i , a n d G. N a t t a , i n " O r g a n i c S y n t h e s e s v i a M e t a l C a r b o n y l s " , I . Wender and P. P i n o e d s , , I n t e r s c i e n c e , 1968, p. 1. 10. B. R. P e n f o l d , i n " P e r s p e c t i v e s i n S t r u c t u r a l C h e m i s t r y " , J . E>, D u n i t z a n d J . A. I b e r s e d s . , W i l e y , 1968, 2, 7 1 . 11. L. M. Bower and M. H. B. S t i d d a r d , I n o r g . C h im. A c t a , 1 9 6 7 , 1, 2 3 1 . 12. G. R. D o b s o n , I . W. S t o l z , a n d R. K. S h e l i n e , Advan.? I n o r g . Chem. R a d i o c h e m . , 1966, 8:, 1. 13. G. B o o t h , i b i d . , 1964, 6, 1. 14. T. A. M a n u e l , A d v a n . O r g a n o m e t a l l i c Chem. , 1 9 65, 3_, 181. 15. N. V. S i d g w i c k and R. W. B a i l e y , P r o c . Roy. S o c . , ,1934, 144, 5 21. 16. F. A. C o t t o n and R. M. W i n g , I n o r g . Chem. , 1 9 65, _4, 314. 17. W. R. C u l l e n , D. A. H a r b o u r n e , B. V. L i e n g m e , and . J . R. Sams, J . Amer. Chem. S o c . , 1968, 9_0, 3293. 18. C. H. Wei and L. F. D a h l , J . Amer. Chem. S o c , 1966, 88 108 1821; 1969, 91, 1351. 19. F. W. B. E i n s t e i n and J . T r o t t e r , J . Chem. S o c . ( A ) , 1967, 824. 20. W. R. C u l l e n and D. A. H a r b o u r n e , I n o r g . Chem., 1970, 9, 1839. 21. W. R. C u l l e n , D. A. H a r b o u r n e , B. V. Liengme, a n d ; J . R. Sams, I n o r g . Chem. , 1969, 8_, 1469. 22. J . E. H. Ward and W. R. C u l l e n , u n p u b l i s h e d r e s u l t s . 23. S. H. W h i t l o w , Ph. D. T h e s i s , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1969. 24. a) R. Hoge, Ph. D. T h e s i s , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1969. b) R. Hoge and J . T r o t t e r , J . Chem. S oc. ( A ) , 1969, 2165. 25. M.M. W o o l f s o n , " D i r e c t Methods i n C r y s t a l l o g r a p h y " , C l a r e n d o n P r e s s , 1961, (a) pp. 101-106, (b) pp 94-100. 26. " I n t e r n a t i o n a l T a b l e s f o r X - r a y C r y s t a l l o g r a p h y " , Kynoch P r e s s , 1962, v o l . I I I . 27. D. J . Dahm and R, A. J a c o b s o n , J . Amer. Chem. Soc., 1968, 90, 5106. 28. W. S. McDonald et. al. , Chem. Comm. , 1969, 1295. 29. E . H. B r a y e et. al. , J . Amer. Chem. Soc. , 1962, ET4, 4633. 30. J . F. B l o u n t et. al. , J . Amer. Chem. Soc. , 1966, _8_8, 292. 31. S. F. A. K e t t l e , I n o r g . Chem., 1965, 4, 1661. 32. J . P. Crow et. al. , i n p r e s s , J . Amer. Chem. S o c . , 1970. 33. B. M. G a t e h o u s e , Chem. Comm., 1969, 948. j 34. R. E. Long, Ph. D. T h e s i s , U n i v e r s i t y o f C a l i f o r n i a , Los A n g e l e s , 196 5. 109 35. R. Mason and A. I. M. Rae, J . Chem. Soc. ( A ) , 1968, 778. 36. R. Mason and W. R. R o b i n s o n , ibid., 1968, 468. 37. F. A. C o t t o n and W. T. Edwards, J . Amer. Chem. S o c . , 1968, 9p_, 5412. 38. F. A. C o t t o n , A. D a v i s o n and A. Musco, ibid., 1967, 89^, 6796. 39. M. J . B e n n e t t , F. A. C o t t o n and P. L e g z d i n s , ibid.-, 1967, 89_, 6797. 40. M. J . B e n n e t t , F. A. C o t t o n and P. L e g z d i n s , ibid ., 1968, 9_0, 6335. 41. R. H. B. M a i s and H. M. P o w e l l , J . Chem. S o c . , 1965, 7471. 42. L. F. D a h l and D. L. Wampler, A c t a C r y s t . , 1962, 15_, 946. 43. F. A. C o t t o n and R. E i s s , J . Amer. Chem. S o c . , 1969, 91, 6593. 44. W. R u d o r f f and U. Hofmann, Z_. P h y s i k . Chem. (B) , 1935, 28, 351. 45. L. D. Brockway, R. V. G. Ewens and M. W. L i s t e r , T r a n s . F a r a d a y S o c . , 1938, 3_4, 1350. 46. M. J . B e n n e t t and R. Mason, P r o c . Chem. S o c . , 1963, 273. 47. M. R. C h u r c h i l l and J . P. F e n n e s s e y , I n o r g . Chem., 1967, 6, 1213. 48. P. B i r d and M. R. C h u r c h i l l , Chem. Comm., 1967, 705. 49. F. C. W i l s o n and D. P. Shoemaker, J . Chem. P h y s . , 1957, 27, 809. 50. R. J . Doedens and L. F. D a h l , J . Amer. Chem. S o c . , 1965, 87, 2576. 110 51. M. R. C h u r c h i l l and P. B i r d , Chem. Comm., 1967, 746. 52. J . S. M c K e c h n i e and I . C. P a u l , Chem. Comm., 1967, 747. 53. K. N. Raymond, P. W. R. C o r f i e l d , J . A . I b e r s , I n o r g . Chem., 1968, 7, 842. 54. " T a b l e s o f I n t e r a t o m i c D i s t a n c e s and C o n f i g u r a t i o n * i n M o l e c u l e s and I o n s " , Chem. S oc. S p e c i a l P u b l . Nos. 11 and 18, 1958 and 1965. 55. F. W. B. E i n s t e i n , H. L u t h , and J . T r o t t e r , J . Chem. S o c . , 1967, 89. 56. F. A. C o t t o n and J . A. M c C l e v e r t y , J . O r g a n o m e t a l l i c Chem., 1965, 4, 490. 57. W. R. C u l l e n , L. D. H a l l , and J . E . H. Ward, Chem. Comm., 1970, 625. 58. a) D. W. J . C r u i c k s h a n k et. al. , i n "Computing Methods and t h e Phase P r o b l e m i n X - r a y C r y s t a l l o g r a p h y " , R. P e p i n s k y , J . M. R o b e r t s o n , and J . C. Speakman e d s . , Pergamon, 1961, p. 45. b) D. W. J . C r u i c k s h a n k i n "Computing Methods i n C r y s -t a l l o g r a p h y " , J . S. R o l l e t t e d . , Pergamon, 1965, p. 114. 59. C. K. J o h n s o n , ORTEP, ORNL-3794, Oak R i d g e N a t i o n a l L a b o r a t o r y , Oak R i d g e , T e n n e s s e e , U. S. A. 

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