A New Class of Oligomeric Organotin Compounds - ACS Publications

Chapter 38

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 30, 2018 | https://pubs.acs.org Publication Date: January 7, 1988 | doi: 10.1021/bk-1988-0360.ch038

A New Class of Oligomeric Organotin Compounds Robert R. Holmes, Roberta O. Day, V. Chandrasekhar, Charles G. Schmid, K. C. Kumara Swamy, and Joan M . Holmes Department of Chemistry, University of Massachusetts, Amherst, M A 01003 Oligomeric organotin oxycarboxylates based on the compositions, [R'Sn(O)O CR] and [(R'Sn(O)O CR) R'Sn(O CR) ] have "drum" and "ladder" structures, respectively. They may be prepared by condensation of a stannoic acid with the respective carboxylic acid. Reaction of RSnCl with the silver salt of the carboxylic acid also gives oxycarboxylate compositions. With the use of diphenylphosphinic acid instead of a carboxylic acid, an oxygen-capped cluster results. In addition, cubic and butterfly arrangements are obtained with dicyclohexylphosphinic acid. All of these represent new structural forms for organotin compounds. X-ray analysis shows the presence of four- and six-membered rings as a primary geometrical feature. The cluster can be viewed as a hydrolysis product of the drum just as the drum is viewed as a hydrolysis product of the ladder. Interconversion of the latter two forms has been followed by Sn NMR and is shown to be reversible. Consideration of their structural relations suggests additional forms yet to be discovered. 2

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I n 1922 Lambourne ÇL) r e p o r t e d t h a t r e a c t i o n s o f m e t h y l s t a n n o i c a c i d w i t h c a r b o x y l i c a c i d s y i e l d e d compounds whose f o r m u l a t i o n c o r r e sponded t o [MeSn(0)02CR ]3· I n a subsequent paper, Lambourne (2) reported a d d i t i o n a l oxycarboxylates of methyl stannoic a c i d , [ M e S n ( 0 ) 0 C R ] where R = E t , n - P r , i - P r h a v i n g hexameric c o m p o s i t i o n s e s t a b l i s h e d from c r y o s c o p i c m o l e c u l a r w e i g h t measurements i n benzene. Both t h e t r i m e r and hexamer d e r i v a t i v e s were a s s i g n e d c y c l i c s t r u c t u r e s c o n t a i n i n g t e t r a c o o r d i n a t e d t i n atoms. From o u r work, we know now t h a t these were erroneous assignments. The hexamer d e r i v a t i v e s of t h i s c o m p o s i t i o n t h a t we have i s o l a t e d a r e "drum" shaped m o l e c u l e s c o n t a i n i n g h e x a c o o r d i n a t e d t i n atoms. F i g u r e 1 shows a r e p r e s e n t a t i v e member, [PhSn(0)0 CCgH ι] , whose geometry was determined by a s i n g l e c r y s t a l X-ray d i f f r a c t i o n s t u d y ( 3 ) . f

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0097-6156/88/0360-0469$06.00/0 © 1988 American Chemical Society

Zeldin et al.; Inorganic and Organometallic Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1988.


INORGANIC AND ORGANOMETALLIC

POLYMERS

cyclohexyl

Ph

^cyclohexyl

cyclohexyl

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cyclohexyl'

cyclohexyl

Ph

F i g u r e 1. Schematic r e p r e s e n t a t i o n o f the drum s t r u c t u r e o f [PhSn(0)0 CC H ] . (Reproduced from R e f . 3. C o p y r i g h t 1985 American C h e m i c a l S o c i e t y . ) 2

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Oligomeric Organotin Compounds

38. HOLMES ET AL.

As o u t l i n e d elsewhere ( 4 ) , we have employed a v a r i a t i o n of t h e o r i g i n a l r e a c t i o n by Lambourne (3) i n e x p l o r i n g c o n d e n s a t i o n p r o d u c t s l e a d i n g t o t h e drum c o m p o s i t i o n as w e l l as t o a mixed o x y c a r b o x y l a t e t r i c a r b o x y l a t e f o r m u l a t i o n , [(R Sn(0)0 CR) R Sn(0 CR) ] · The l a t t e r was i d e n t i f i e d as h a v i n g an u n f o l d e d drum o r l a d d e r s t r u c t u r e ( 4 ) . The r e a c t i o n c o n s i s t s of a c o n d e n s a t i o n o f an o r g a n o s t a n n o i c a c i d with a carboxylic acid. The a p p l i c a t i o n of t h i s r e a c t i o n l e a d s t o t h e f o r m a t i o n of a s o l u b l e drum compound, [ n - B u S n ( 0 ) 0 C C 5 H g ] - C H , 1, F i g u r e 2, c o n t a i n i n g c y c l o p e n t a n e u n i t s , and t h e f o r m a t i o n o f an u n u s u a l l a d d e r compound, [ (n-BuSn(0)0 CPh) n-BuSn(Cl) ( 0 C P h ) ] , _2, F i g u r e 3 (_4 ) . I n a d d i t i o n t h e l a d d e r c o m p o s i t i o n , [ ( n - B u S n ( 0 ) 0 C C H 1 ) nB u S n ( 0 C C g H i i ) 3 ] , _3> F i g u r e 4, was p r e p a r e d from t h e r e a c t i o n o f nBuSnCl3 i t h s i l v e r c y c l o h e x a n o a t e ( 5 ) . The l a t t e r r e a c t i o n was employed by Anderson (6) i n s y n t h e s i z i n g o r g a n o t i n t r i c a r b o x y l a t e s . Both t h e drum _1 and l a d d e r _3 undergo s t r u c t u r a l changes i n s o l u t i o n i n i n t e r c o n v e r s i o n p r o c e s s e s as i n d i c a t e d by S n NMR. A mechanism a s s o c i a t e d w i t h t h i s p r o c e s s i s proposed ( 5 ) . T

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Discussion S y n t h e s i s . Both t h e c y c l o p e n t a n o a t e drum c o m p o s i t i o n , _1, and the c y c l o h e x a n o a t e drum, [ n - B u S n ( 0 ) 0 C C H i 1 3 6 » A» p r e p a r e d by a c o n d e n s a t i o n r e a c t i o n of η-butyl s t a n n o i c a c i d w i t h t h e c o r r e s p o n d i n g c a r b o x y l i c a c i d , E q u a t i o n 1. w

2

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r

e

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6 n-BuSn(0)OH + 6 RC0 H

• [n-BuSn(0)0 CR]

2

2

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+ 6 H 0

(1)

2

I n a subsequent r e a c t i o n , n-BuSnCl3 was r e a c t e d w i t h t h e s i l v e r s a l t of c y c l o h e x a n e c a r b o x y l i c a c i d i n t h e presence o f wet s o l v e n t . T h i s r e a c t i o n gave the l a d d e r f o r m u l a t i o n , _3, i d e n t i f i e d above, E q u a t i o n 2. 6 n-BuSnCl [(n-BuSn(0)0 CC H ) 2

6

n

2

+

3

+ 10 A g C H C 0 ~ 6

n

2

+ 4 H0

n-BuSnCO^CeHx ) 3 ] x

2

2

•

+ 10 A g C l + 8 HC1

(2)

Other than t h e c h l o r o d e r i v a t i v e , 2^, the drum and l a d d e r com pounds a r e p r e p a r e d i n h i g h y i e l d , > 70%. A l l a r e s o l u b l e i n o r g a n i c s o l v e n t s and show c h a r a c t e r i s t i c i n f r a r e d s p e c t r a . The drum com pounds 1^ and 4^ e x h i b i t a s y m m e t r i c a l d o u b l e t f o r t h e c a r b o x y l a t e s t r e t c h i n g f r e q u e n c y , V ^ Q Q , c e n t e r e d near 1550 cm and a s i n g l e Sn-0 s t r e t c h , V g , near 600 cm" . I n c o n t r a s t , t h e open-drum s t r u c t u r e s , 2^ and _3, snow an u n s y m m e t r i c a l V^-QQ d o u b l e t i n t h e same r e g i o n as t h a t f o r t h e drums and t h e presence of two Sn-0 s t r e t c h e s near 600 cm" . The drum compounds a r e t h e r m a l l y q u i t e s t a b l e . F o r example, the c y c l o p e n t a n e c a r b o x y l i c a c i d drum, ^L, was heated a t 300°C f o r 3 h i n vacuum. The m a t e r i a l o b t a i n e d was s o l u b l e i n CDCI3, and S n NMR showed a s i n g l e l i n e a t -491.4 ppm, compared t o t h e s t a r t i n g m a t e r i a l -485.8. The s h i f t i s presumably due t o l o s s of s o l v e n t m o l e c u l e s present i n the c r y s t a l i n the s t a r t i n g m a t e r i a l . 1

1

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1 1 9

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S n NMR Data. H y d r o l y t i c a l l y , t h e drum f o r m u l a t i o n s a r e more s t a b l e than t h e open-drum forms. The h y d r o l y s i s r e a c t i o n i n E q u a t i o n 3 illustrates this.


INORGANIC AND ORGANOMETALLIC POLYMERS


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F i g u r e 2. ORTEP p l o t of [n-BuSn(0)0 CC H ] ·ϋ Η , 1. The v i e w i s down the pseudo Sg a x i s . The t e r m i n a l carbon atoms of the n-Bu groups a r e o m i t t e d f o r purposes of c l a r i t y . (Reproduced from R e f . 5. C o p y r i g h t 1987 American Chemical S o c i e t y . ) 2

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Zeldin et al.; Inorganic and Organometallic Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1988. 2

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F i g u r e 3. 0RTEP p l o t of [ ( n - B u S n ( 0 ) 0 C P h ) n - B u S n ( C l ) ( 0 C P h ) ] , 2S i x of the e i g h t p h e n y l groups and a l l hydrogen atoms have been o m i t t e d f o r purposes of c l a r i t y . (Reproduced from Ref. 5. C o p y r i g h t 1987 American Chemical S o c i e t y . )


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HOLMES ET AL.


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Our i n v e s t i g a t i o n u s i n g S n NMR e s t a b l i s h e s the r e t e n t i o n of the drum and l a d d e r s t r u c t u r e s i n s o l u t i o n and shows t h e i r i n t e r c o n v e r s i o n a c c o r d i n g t o E q u a t i o n 3. F i g u r e 5 d i s p l a y s S n NMR s p e c t r a of a sample of the l a d d e r compound, _3, i n s l i g h t l y m o i s t CDCI3. H y d r o l y s i s i s e v i d e n t as the drum peak a t -486 ppm grows i n i n t e n s i t y r e l a t i v e to s i g n a l s a s s i g n e d t o the l a d d e r . As F i g u r e 5 emphasizes, the S n peak a t -532 ppm f o r _3 appears as a major i n t e r m e d i a t e . S i g n a l s i n t h i s r e g i o n a r e p r e s e n t i n the s p e c t r a of a l l samples except t h a t f o r the c h l o r o d e r i v a t i v e , _2, w h i c h a l s o l a c k s a h i g h f i e l d s i g n a l i n the 600-630 ppm region. The a c t i o n of excess c y c l o p e n t a n e c a r b o x y l i c a c i d on a CDCI3 s o l u t i o n of the c y c l o p e n t a n e drum, _1, causes i t s s i g n a l a t -485.8 ppm t o d i s a p p e a r and g i v e s r i s e to f o u r o t h e r peaks w h i c h c o r r e s p o n d t o f o r m a t i o n of the l a d d e r and an i n t e r m e d i a t e . These NMR e x p e r i ments have shown t h a t the h y d r o l y s i s p r o c e s s g i v e n i n E q u a t i o n 3 i s r e v e r s i b l e , i . e . , a drum forms from a l a d d e r c o m p o s i t i o n and, i n the presence of excess a c i d , the drum can be opened up to y i e l d the ladder formulation.


1 1 9

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S t r u c t u r a l D e t a i l s . F o r JL, the hexameric "drum" has i d e a l i z e d S m o l e c u l a r symmetry. The geometry of the stannoxane framework of the m o l e c u l e c o n s i s t s of six-membered r i n g s i n a c h a i r c o n f o r m a t i o n . Each Sn atom i s bonded t o t h r e e framework oxygen atoms, where the Sn0 bonds are a l l of comparable s t r e n g t h and have l e n g t h s r a n g i n g from 2.075(7)A t o 2.093(7)A. The oxygen atoms of the framework a r e t r i c o o r d i n a t e . The sum of the t h r e e Sn-O-Sn a n g l e s about these oxygen atoms range from 331.8° t o 333.9°. The Sn atoms, w h i c h are a l l c h e m i c a l l y e q u i v a l e n t , are h e x a c o o r d i n a t e d , w i t h the c o o r d i n a t i o n sphere b e i n g completed by an η-butyl group and two oxygen atoms from d i f f e r e n t c a r b o x y l a t e groups. Each of the four-membered r i n g s of the core i s spanned by a c a r b o x y l a t e group t h a t forms a s y m m e t r i c a l b r i d g e between two Sn atoms. The Sn-0 bonds t o the b r i d g i n g carboxy l a t e atoms a r e l o n g e r than the c o r e bonds and range from 2.155(8)Â t o 2.173(8)A. The "unfolded-drum" or " l a d d e r " compound _2 has c r y s t a l l o g r a p h i c C± symmetry. T h i s corresponds t o the i d e a l i z e d m o l e c u l a r symmetry and, t h e r e f o r e , t h e r e a r e t h r e e c h e m i c a l l y i n e q u i v a l e n t types of Sn atoms i n the m o l e c u l e , a l t h o u g h a l l a r e h e x a c o o r d i n a t e d . The oxygen atoms i n the open form can be s u b d i v i d e d i n t o two t y p e s , as i n the case of the drum m o l e c u l e : t r i c o o r d i n a t e framework oxygen atoms and the d i c o o r d i n a t e oxygen atoms of the b r i d g i n g c a r b o x y l a t e l i g a n d s . The geometry about the oxygen atoms of the framework of the open form tends toward p l a n a r i t y . I n t h i s case the sums of the a n g l e s about the t r i c o o r d i n a t e oxygen atoms i s 357.4° f o r 01 and 355.3° f o r 02. The geometry about the Sn atoms i s b e s t d e s c r i b e d as d i s t o r t e d octahedral. The g e n e r a l s t r u c t u r a l f e a t u r e s of the " l a d d e r " , [ ( n - B u S n ( 0 ) 0 C C H ) n - B u S n ( 0 C C H ) 3] , _3, shown i n F i g u r e 4, a r e v e r y s i m i l a r t o t h a t found f o r 2^, the p r i n c i p a l d i f f e r e n c e b e i n g a 6

2

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F i g u r e 5. T i n NMR s p e c t r a of [ ( n - B u S n ( 0 ) 0 C C H ! ) nB u S n ( 0 2 C C H ) ] , 2» CDC1 i n d i c a t i n g h y d r o l y s i s t o a "drum" form. The upper spectrum i s f o r a sample c o n t a i n i n g Ρι+Οχο» added t o reduce h y d r o l y s i s r e l a t i v e t o t h e m i d d l e spectrum w h i c h has no added d r y i n g agent. The lower spectrum i s r e c o r d e d on t h e l a t t e r sample one week l a t e r . D i d e n t i f i e s t h e l i n e due t o drum f o r m u l a t i o n and U, t h e l i n e s due t o the u n f o l d e d drum. (Reproduced from R e f . 5. C o p y r i g h t 1987 American C h e m i c a l S o c i e t y . ) 2

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38. HOLMES ET AL.


477

replacement of the C l atom i n 1_ by a pendant c y c l o h e x a n o a t e group. L i k e _2, the m o l e c u l e , _3, has c r y s t a l l o g r a p h i c C-^ symmetry. The Sn-0 bond l e n g t h s of the b r i d g i n g c a r b o x y l a t e s a r e i n g e n e r a l l o n g e r ( a v e r a g i n g 2.15(3)A) than the Sn-0 framework bonds ( a v e r a g i n g 2.06(2)A). I t i s i n t e r e s t i n g to note t h a t the bond a n g l e s a t the " p y r a m i d a l " framework oxygen atoms i n the drum, _1, average 100.4(3)° i n the distannoxane r i n g and a r e a t 133.2(3)° i n the t r i s t a n n o x a n e r i n g . T h i s compares w i t h an average bond angle a t oxygen w i t h i n the distannoxane r i n g of 102.9(1)° i n the u n f o l d e d drum, _2, which has n e a r l y p l a n a r oxygen atoms and s l i g h t l y s h o r t e r Sn-0 framework bonds, a v e r a g i n g 2.063(3)A f o r _2 compared to 2.086(7)A f o r 1. A l t h o u g h the number of bonds b r o k e n and formed i s conserved i n the h y d r o l y s i s of an u n f o l d e d drum of the type 3 t o a drum s t r u c t u r e , E q u a t i o n 3, the entropy change i s f a v o r a b l e . Ladder t o Drum C o n v e r s i o n . I t i s i n t e r e s t i n g t o s p e c u l a t e how the drum s t r u c t u r e i s formed from the l a d d e r . The i m p l i c a t i o n i s t h a t the energy d i f f e r e n c e between the two b a s i c s t r u c t u r e s i s r e l a t i v e l y s m a l l . By way of i l l u s t r a t i o n , we a p p l y the h y d r o l y s i s p r o c e s s t o the l a d d e r f o r m u l a t i o n , J3. M e c h a n i s t i c a l l y , f o r t h i s example, a c o n s e r v a t i o n i s expected i n the number of bonds t o be b r o k e n and formed i n e x e c u t i n g the h y d r o l y s i s of E q u a t i o n 3. A minimum of n i n e S n - c a r b o x y l a t e oxygen bonds are r e q u i r e d t o be c l e a v e d . D u r i n g t h i s cleavage the S n - c a r b o x y l a t e oxygen bonds must assume c i s p o s i t i o n s at the t i n atoms. These c h e l a t i n g groups are i n t r a n s p o s i t i o n s i n the open-drum s t r u c t u r e . The bonds formed i n c o m p l e t i n g the convers i o n to the drum s t r u c t u r e w i t h t h i s c o n s t r a i n t c o n s i s t of t h r e e Snc a r b o x y l a t e oxygen bonds and s i x Sn-0 bonds. F i g u r e 6 shows a p o s s i b l e i n i t i a l i n t e r m e d i a t e and F i g u r e 7 i l l u s t r a t e s a proposed form j u s t p r i o r to c l o s u r e to y i e l d the drum. P h o s p h i n i c A c i d R e a c t i o n s . R e a c t i o n of n - b u t y l s t a n n o i c a c i d w i t h diphenylphosphate i n s t e a d of a c a r b o x y l i c a c i d a l s o r e s u l t s i n the f o r m a t i o n of a drum c o m p o s i t i o n [n-BuSn(O) 0 P ( O P h ) ] 6 (Chandrasekhar, V.; Holmes, J . M.; Day, R. O.; Holmes, R. R., u n p u b l i s h e d work). However, when d i p h e n y l p h o s p h i n i c a c i d i s r e a c t e d w i t h n - b u t y l s t a n n o i c a c i d under r e f l u x i n t o l u e n e , a new s t r u c t u r a l form of t i n i s o b t a i n e d (_7) . The r e a c t i o n proceeds a c c o r d i n g t o E q u a t i o n 4 g i v i n g the s t a b l e o x i d e c o m p o s i t i o n i n 90% y i e l d , mp 198-208°C dec. 2

[ (n-BuSn(0H)0 PPh ) 0][Ph P0 ]

3 n-BuSn(0)0H + 4 P h P 0 H 2

2

2

2

+ 2

2

3

H0 2

2

2

(4)

X-ray a n a l y s i s ( F i g u r e 8) shows t i n ( I V ) p r e s e n t i n an oxygencapped c l u s t e r m o l e c u l e . The b a s i c framework c o n s i s t s of a t r i stannoxane r i n g i n a cyclohexane c h a i r arrangement. H y d r o x y l groups comprise the oxygen components of the r i n g system. A t r i c o o r d i n a t e d oxygen atom caps one s i d e of t h i s framework w h i l e t h r e e a d d i t i o n a l d i p h e n y l p h o s p h i n a t e groups b r i d g e a d j a c e n t h e x a c o o r d i n a t e d t i n atoms. I t i s noted t h a t t h r e e S n 0 r i n g u n i t s form as a consequence of the presence of the unique capping oxygen atom. These t h r e e four-membered r i n g s c o n t a i n the l a t t e r atom and form a p o r t i o n of a cube. 2

2



478


F i g u r e 6. A s u g g e s t e d i n i t i a l i n t e r m e d i a t e r e s u l t i n g i n the h y d r o l y s i s of a l a d d e r s t r u c t u r e as r e p r e s e n t e d by E q u a t i o n 3. (Reproduced f r o m R e f . 5 . C o p y r i g h t 1987 American C h e m i c a l S o c i e t y . )

Figure 7· Suggested s t r u c t u r a l r e p r e s e n t a t i o n j u s t p r i o r t o c l o s u r e t o y i e l d t h e drum. (Reproduced from R e f . 5 . C o p y r i g h t I987 American C h e m i c a l S o c i e t y . )


38. HOLMES ET AL.


479

The oxygen-capped c l u s t e r can be viewed as a h y d r o l y s i s product of the drum j u s t as the drum i s viewed as a h y d r o l y s i s product of the l a d d e r , c f . E q u a t i o n 5 (R = P h P ) . 2

!

[R Sn(0)0 R] 2

f

+ 2 R0 H 4- 2 H 0

6

2

• 2[(R Sn(OH)0 R) 0][R0 ]

2

2


drum

3

(5)

2

cluster

The schematic ( F i g u r e 9) f o r a drum i n d i c a t e s how i t i s r e l a t e d t o two c l u s t e r m o l e c u l e s . F o r m a l l y , two b r i d g i n g phosphinates r e a r r a n g e , two oxygen atoms a r e added, f o u r Sn-0 bonds are c l e a v e d , the s i x Sn-O-Sn l i n k a g e s become Sn(OH)Sn u n i t s , and two phosphinates a r e added t o hydrogen bond t o the h y d r o x y l s . The S n NMR spectrum f o r the oxygen-capped c l u s t e r e x h i b i t s a s i n g l e resonance w i t h t r i p l e t c h a r a c t e r c e n t e r e d a t -498.5 ppm ( | J ( S n - 0 - P ) I = 132.0 H z ) . T h i s o b s e r v a t i o n i s c o n s i s t e n t w i t h the presence of t h r e e e q u i v a l e n t t i n atoms p r o v i d e d by a c l u s t e r u n i t which has the hydrogen-bonded a n i o n i c phosphinate u n d e r g o i n g f a s t exchange among the t h r e e hydroxy1 groups of the t r i s t a n n o x a n e r i n g . A c u b i c arrangement, [n-BuSn(0)0 P (CgHi ι) ] i+, i s prepared (Kumara Swamy, K. C.; Day, R. O.; Holmes, R. R., accepted by JACS f o r p u b l i c a t i o n ) from a c o n d e n s a t i o n of n - b u t y l s t a n n o i c a c i d w i t h d i c y c l o h e x y l p h o s p h i n i c a c i d i n t o l u e n e s o l u t i o n ; mp 263-265°C, Sn NMR, -462.8 ppm; J ( S n - 0 - P ) = 116 Hz. As shown i n F i g u r e 10, the c o r e of the m o l e c u l e i s d e f i n e d by t i n atoms and t r i v a l e n t oxygen atoms which occupy the c o r n e r s of a d i s t o r t e d cube, each f a c e of w h i c h i s d e f i n e d by a four-membered S n 0 r i n g . The top and bottom f a c e s of the cube are open, w h i l e each of i t s f o u r s i d e s i s spanned d i a g o n a l l y by a phosphinate b r i d g e between two t i n atoms. The phos p h i n a t e b r i d g e s a r e r e q u i r e d by symmetry t o be s y m m e t r i c a l . I n a d d i t i o n , a b u t t e r f l y s t r u c t u r e ( F i g u r e 11) w h i c h c o n t a i n s two t i n atoms i n a d i m e r i c r e p r e s e n t a t i o n [n-BuSn(OH) ( 0 P ( C g H n ) ) ] a r i s e s i n the same r e a c t i o n as the cube (Kumara Swamy, K. C.; Day, R. O.; Holmes, R. R., u n p u b l i s h e d w o r k ) . The cube may be viewed as a c o n d e n s a t i o n product of the d i m e r i c c l u s t e r a c c o r d i n g t o the e x p r e s s i o n i n E q u a t i o n 6. Hence, the d i m e r i c c l u s t e r may s e r v e as a p r e c u r s o r on the way to the c u b i c form. 1 1 9

2

1 1 9

3 1

2

2

1 1 9

2

2

2

2

2[n-BuSn(0H)(0 P(C H ) ) ] 2

6

1 1

2

2

2

• [n-BuSn(0)0 P(C H χ) ]

2

2

6

1

2

2

4

+ 4(C H ) P0 H 6

n

2

2

(6)

2

The common s t r u c t u r a l u n i t i n a l l of the o l i g o m e r i c forms d i s covered so f a r i s the four-membered d i m e r i c distannoxane r i n g , S n 0 . The number of t i n atoms found i n these s t r u c t u r e s ranges from two t o s i x , e x c l u d i n g f i v e . F u r t h e r , c o n d e n s a t i o n and c o u p l i n g r e a c t i o n s a r e expected t o produce a d d i t i o n a l o l i g o m e r i c forms, r e v e a l i n g o t h e r i n t e r e s t i n g f e a t u r e s of t h i s new s t r u c t u r a l c l a s s of o r g a n o t i n compounds. 2


2


480


F i g u r e 8. ORTEP p l o t of [ ( n - B u S n ( O H ) 0 P P h ) 0 ] [ P h P 0 ] . Pendant atoms of the t h r e e η-Bu groups and of the e i g h t Ph groups a r e o m i t t e d f o r purposes of c l a r i t y . Hydrogen-bonding i n t e r a c t i o n s a r e shown as dashed l i n e s . (Reproduced from R e f . 7 · C o p y r i g h t I987 American Chemical S o c i e t y . ) 2

2

3

2

2



481


38. HOLMES ET AL.

F i g u r e 11.

ORTEP p l o t o f [n-BuSn(OH) ( 0 P ( C H ) ) ] . 2

6

n

2

2

2



482 Acknowledgments

Support o f t h i s r e s e a r c h by t h e donors o f t h e P e t r o l e u m Research Fund, a d m i n i s t e r e d by the American Chemical S o c i e t y and by t h e N a t i o n a l S c i e n c e F o u n d a t i o n (CHE 8504737) i s g r a t e f u l l y acknowledged. We thank the U n i v e r s i t y o f M a s s a c h u s e t t s Computing Center f o r generous a l l o c a t i o n o f computing time.


Literature

Cited

1. Lambourne, H. J. Chem. Soc. 1922, 121(2), 2533. 2. Lambourne, H. J. Chem. Soc. 1924, 125, 2013. 3. Chandrasekhar, V.; Day, R. O.; Holmes, R. R. Inorg. Chem. 1985, 24, 1970. 4. Holmes, R. R.; Schmid, C. G.; Chandrasekhar, V.; Day, R. O.; Holmes, J. M. J. Am. Chem. Soc. 1987, 109, 1408. 5. Chandrasekhar, V.; Schmid, C. G.; Burton, S. D.; Holmes, J. M.; Day, R. O.; Holmes, R. R. Inorg. Chem. 1987, 26, 1050. 6. Anderson, H. H. Inorg. Chem. 1964, 3, 912. 7. Day, R. O.; Holmes, J. M.; Chandrasekhar, V.; Holmes, R. R. J. Am. Chem. Soc. 1987, 109, 940. RECEIVED

September

1,

1987


A New Class of Oligomeric Organotin Compounds - ACS Publications

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