Inorganic Compounds with Unusual Properties

27 Some Unusal Dimeric and Cluster Species of the Group VI Transition Metals

Downloaded by UNIV OF BATH on July 3, 2016 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/ba-1976-0150.ch027

R. E. McCARLEY, and R. J. HOXMEIER

J.

L.

TEMPLETON,

T.

J.

COLBURN,

V.

KATOVIC,

Ames Laboratory-USAEC and Department of Chemistry, Iowa State University, Ames, Iowa 50010

Several new compounds of molybdenum and tungsten that have multiple metal-metal bonds are described. It is con cluded that the compounds [Mo (O CR) ]I (R = C H , C(CH ) , or C H ), formed by reaction of Mo (O CR) with iodine in noncoordinating solvents, are I3- salts of the cations [Mo (O CR) ] with Mo-Mo bond order of 3.5. The first species containing quadruply bonded tungsten, MoW(O C(CH ) ) , was prepared in mixtures with Mo (O CR) with which it is isostructural and isomorphous. The mixtures were separated by iodination in benzene, which provided [MoW(O CC(CH ) ) ]I containing the one-electron oxi dized cation [MoW(O CC(CH ) ) ] with Mo-W bond order of 3.5. The compound [(C H ) N] W Br , prepared by reaction between [(C H ) N]W(CO) Br and dibromoethane, contains the new confacial bioctahedral anion W Br d(W-W) = 2.58(1) A, and μ(exp.) = 1.72 BM. An unusual mixed halide complex [(C H ) N] Mo I Cl is also reported. 2

3 3

6

2

4

3

5

2

2

2

5

4

+

2

2

4

2

3

3

4

2

2

2

4

3 3 4

+

2

3 3 4

3

3

9 4

7 4

2

2

9

5

92-,

2

4

9 4

2

4 10

o b j e c t i v e of o u r w o r k is t h e d e v e l o p m e n t of synthetic m e t h o d s f o r f o r m i n g strong m e t a l - m e t a l bonds, w i t h b o n d o r d e r n > 1. A l t h o u g h m a n y p u b l i s h e d reports

of t h e synthesis of d i m e r i c t r a n s i t i o n m e t a l

species h a v i n g m e t a l - m e t a l b o n d s of this k i n d h a v e a p p e a r e d (see R e f e r ences 1 a n d 2 a n d the references c i t e d t h e r e i n ) , nonetheless the r e p e r t o i r e of reactions w h i c h m a y b e c a l l e d u p o n to w e l d s u c h m e t a l - m e t a l b o n d s is q u i t e l i m i t e d . I t is a l a m e n t that reactions w h i c h d o l e a d to f o r m a t i o n of m e t a l - m e t a l b o n d s w i t h η > 1 a r e p o o r l y u n d e r s t o o d , h i g h l y specific for a p a r t i c u l a r t r a n s i t i o n m e t a l , a n d of l i t t l e use w h e n a p p l i e d to c o n 318 King; Inorganic Compounds with Unusual Properties Advances in Chemistry; American Chemical Society: Washington, DC, 1976.

27.

M C CARLEY

ET

319

Dimeric Transition Metal Species

AL.

s t r u c t i o n of n e w m o l e c u l e s w i t h specified s t r u c t u r a l features. O u t s t a n d i n g examples of these h i g h l y specific reactions are those that l e a d r e s p e c t i v e l y to the q u a d r u p l e b o n d s of the w e l l k n o w n M o

and R e

2

2

derivatives

(see

R e f e r e n c e 1 a n d the references c i t e d t h e r e i n ) . I n b o t h cases, a n i m p r e s sive list of c o m p o u n d s is n o w k n o w n , y e t the n u m b e r of reactions a c t u a l l y resulting

in

formation

of

the

metal-metal

bond

is

unfortunately

restricted. I n the case of t h e M o = M o

l i n k a g e , a l l d e r i v a t i v e s are d e r i v e d u l t i

m a t e l y f r o m the c a r b o x y l a t e d i m e r s ( 3 , 4, 5)

Mo (0 CR) 2

2

4

which, in

t u r n , are o b t a i n e d b y variants of essentially a single r o u t e , viz. b y R e a c t i o n 1 ( 3 , 4, 5, 6, 7 ) . A l t h o u g h i t w a s r e c e n t l y o b s e r v e d t h a t C r ( 0 C R )


2

2Mo(CO)

6

+

4RCOOH

Mo (0 CR) 2

2

d e r i v a t i v e s c a n be p r e p a r e d f r o m C r ( C O )

6

4

+

12CO +

2H

2

2

under similar conditions

4

(1) (8),

there has b e e n a n o t a b l e l a c k of success i n f o r m i n g the s t r u c t u r a l l y analogous

W (0 CR) 2

2

4

u s i n g s i m i l a r reactions

(9, 10).

S i n c e there is

n o reason a priori for s u p p o s i n g that alternate m e t h o d s do n o t exist, n o r

ΜΟΞΞΜΟ

that the

l i n k a g e has u n i q u e s t a b i l i t y , a search for a l t e r n a t i v e

approaches to f o r m i n g s u c h q u a d r u p l e m e t a l - m e t a l b o n d s w a s i n i t i a t e d . T h e i n i t i a l fruits of this w o r k are r e p o r t e d h e r e i n . Experimental M a t e r i a l s . T h e reagents M o ( C O ) , W ( C O ) , i o d i n e , t e t r a p r o p y l ammonium bromide, tetrabutylammonium iodide, propionic acid, ben z o i c a c i d , p i v a l i c a c i d , a n d 1,2-dibromoethane were obtained from c o m m e r c i a l sources a n d u s e d w i t h o u t p u r i f i c a t i o n . T h e solvents c h l o r o b e n z e n e , 1,2-dichloroethane, o - d i c h l o r o b e n z e n e , toluene, d e c a h y d r o n a p h thalene ( d e c a l i n ) , a n d cyclohexane were p u r g e d 10-30 m i n w i t h a stream of d r y n i t r o g e n p r i o r to use. A c e t o n i t r i l e was d r i e d o v e r m o l e c u l a r sieves ( 4 A ) a n d also p u r g e d w i t h n i t r o g e n p r i o r to use. B e n z e n e u s e d i n the p r e p a r a t i o n of M o W ( 0 C C ( C H ) ) I w a s c a r e f u l l y d r i e d a n d stored o v e r c a l c i u m h y d r i d e , t h e n v a c u u m d i s t i l l e d i n t o the r e a c t i o n vessel w h e n needed. A n a l y s e s . F o r single m e t a l analyses, samples w e r e d e c o m p o s e d w i t h n i t r i c a c i d a n d i g n i t e d to the m e t a l t r i o x i d e i n t a r e d p o r c e l a i n c r u c i b l e s . H a l o g e n analyses w e r e p e r f o r m e d b y d i s s o l v i n g the s a m p l e i n d i l u t e KOH-H 0 s o l u t i o n , b o i l i n g to d e c o m p o s e peroxides, a c i d i f y i n g w i t h acetic a c i d , a n d t h e n t i t r a t i n g p o t e n t i o m e t r i c a l l y w i t h s t a n d a r d s i l v e r nitrate s o l u t i o n . F o r m o l y b d e n u m analyses of samples c o n t a i n i n g i o d i n e , it w a s necessary to f u m e t h e samples extensively w i t h h o t s u l f u r i c a c i d to e l i m i n a t e i o d i n e ; m o l y b d e n u m was t h e n d e t e r m i n e d b y r e d u c t i o n to M o ( I I I ) i n a z i n c a m a l g a m c o l u m n f o l l o w e d b y r e a c t i o n of M o ( I I I ) w i t h excess F e ( I I I ) a n d t i t r a t i o n of the r e s u l t i n g F e ( I I ) w i t h s t a n d a r d C e ( I V ) s o l u t i o n . I n the m i x e d - m e t a l c o m p o u n d s , m o l y b d e n u m w a s separated f r o m tungsten a n d d e t e r m i n e d b y the Y a g o d a a n d F a l e s p r o c e d u r e ( 1 1 ) . 6

2

2

3

3

e

4

2

King; Inorganic Compounds with Unusual Properties Advances in Chemistry; American Chemical Society: Washington, DC, 1976.

320

INORGANIC

COMPOUNDS

WITH

UNUSUAL PROPERTIES

C a r b o n a n d h y d r o g e n analyses w e r e p e r f o r m e d b y the A m e s L a b o r a t o r y a n a l y t i c a l services a n d b y G a l b r a i t h L a b o r a t o r i e s , K n o x v i l l e , T e n n . Physical Measurements. I R spectra were recorded on nujol mulls, c a r e f u l l y sealed f r o m a i r w i t h N a C l a n d C s l w i n d o w s , o n B e c k m a n I R 1 1 , 12, a n d 4250 i n s t r u m e n t s . F r e q u e n c i e s are accurate to ± 2 c m " . E l e c t r o n s p i n resonance ( E S R ) spectra w e r e o b t a i n e d o n p o w d e r e d samples sealed i n q u a r t z a m p o u l e s u s i n g a l o c a l l y c o n s t r u c t e d c a v i t y , S t r a n d 601 spectrometer, a n d M a g n i o n m a g n e t system. D u r i n g the l i n e a r m a g n e t i c field sweep, the s p e c t r u m w a s c a l i b r a t e d w i t h p r o t o n f r e q u e n c y m a r k s at r e g u l a r i n t e r v a l s . F o r m a g n e t i c s u s c e p t i b i l i t y measurements, a F a r a d a y b a l a n c e was u s e d as d e s c r i b e d p r e v i o u s l y ( 1 2 ) . X - r a y p o w d e r d i f f r a c t i o n patterns w e r e d e t e r m i n e d w i t h samples sealed i n L i n d e m a n n glass c a p i l laries u s i n g a 114.6-mm D e B y e - S c h e r r e r c a m e r a , C u K a r a d i a t i o n , a n d a 12-hr exposure t i m e . M a s s spectra w e r e o b t a i n e d w i t h the Α Ε Ι M S 9 0 2 h i g h r e s o l u t i o n spectrometer. G e n e r a l P r o c e d u r e s . U n l e s s o t h e r w i s e n o t e d , a l l reactions a n d s a m p l e manipulations were performed under nitrogen using standard Schlenk


1

T a b l e I. Mo (0 CC H ), 2

2

2

5

t

604 s 675 s 808 s 888 s 1008 m 1075 m 1085 m 1260 w 1295 s 1301s 1380 m 1385 m 1410 sh 1430 s 1450 s 1512 s

I R A b s o r p t i o n Frequencies (cm" ) for 1

[Mo (0 CC H )JI 2

2

2

5

3

601s 695 s 810 s 890 m 1010 m 1080 m 1085 w 1248 w 1295 s

Mo (0 CC H ) 2

2

6

5 4

665 680 705 805

w s s w

—

840 m 860 w 930 m

1380 m

975 w

1410 m

1000 w 1030 m 1070 m HOOw 140 m 160 w 290 w .310 w 320 w 405 s 440 s 450 m 490 s 505 sh 590 m 600 m

1440 s 1520 w

"Relative intensities are indicated as s, strong; m, medium; w, weak; and sh,


27.

Dimeric

M C CARLEY E T A L .

Transition

Metal

321

Species

a n d d r y b o x t e c h n i q u e s or o n the v a c u u m m a n i f o l d c a p a b l e of a l i m i t i n g pressure of ca. 10" ton*. T h e samples m o s t sensitive to o x i d a t i o n , s u c h as M o W ( 0 C C ( C H ) ) , w e r e stored i n e v a c u a t e d a n d ougassed ampoules. TETRACARBOXYLATODIMOLYBDENUM ( I I ) COMPLEXES. These comp o u n d s w e r e p r e p a r e d b y m o d i f i c a t i o n of e a r l i e r p r o c e d u r e s ( 3 , 4, 5,6,7) i n o r d e r to p r o v i d e the most c o n v e n i e n t r o u t e for specific d e r i v a t i v e s . M o ( 0 2 C C o H ) 4 w a s p r e p a r e d most c o n v e n i e n t l y b y r e f l u x i n g M o ( C O ) ( t m e d ) ( w h e r e t m e d = t e t r a m e t h y l e t h y l e n e d i a m i n e ) w i t h neat p r o p i o n i c a c i d u n t i l C O e v o l u t i o n was c o m p l e t e . T h e p r o d u c t M o 2 ( 0 C C H 5 ) c r y s t a l l i z e d as l a r g e y e l l o w needles w h e n c o o l e d to 0 ° C ; it w a s t h e n filtered, w a s h e d w i t h c y c l o h e x a n e , a n d d r i e d in vacuo. I R a b s o r t p i o n frequencies are l i s t e d i n T a b l e I . L i n e s w e r e o b s e r v e d at t h e f o l l o w i n g d values ( i n A ) i n the X - r a y p o w d e r p a t t e r n : 9.80 v w , 8.72 s, 6.21 s, 4.99 s, 4.42 m , 4.10 s, 3.64 w , 2.93i w , a n d 2.87 m . M O ( 0 C C G H 5 ) 4 was prepared b y reacting M o ( C O ) w i t h a slight excess ( 5 - 1 0 % ) of b e n z o i c a c i d i n r e f l u x i n g d e c a l i n . T h e m i x t u r e w a s 6

2

3

2

3

4

5

4

2

2

4


3

2

2

6

Dimolybdenum Tetracarboxylate Derivatives" \_Mo (0 CC H )AI 2

2

e

s

665 680 710 805 810 840 845

3

w s m w w w w

935 w 975 w 985 w 1000 w 1025 m 1070 m 1095 w 1140 m 1160 w 1290 w 1310w 1320 w 1405 s 1440 s 1490 1505 1590 1595

MoJOtCCfCHsMt — — 318 340 420 450 615

w m m s s

775 m 795 895 935 975 1025 1218 1300 1362 1420 1485 1550

m m w w w s w s s s w

{Mo (0,CC(CH ) ) -\I 2

230 290 — 335 445 465 625

s s k

w w m sh s s

778 m 788 888 938 975 1022 1215 1300 1365 1420 1485 1570

m m w w w s sh s s s w

s sh sh s

shoulder.


t

322

INORGANIC COMPOUNDS W I T H UNUSUAL PROPERTIES

b r o u g h t r a p i d l y to reflux a n d a l l o w e d to reflux u n t i l gas e v o l u t i o n ceased. U p o n c o o l i n g to r o o m t e m p e r a t u r e , the orange crystals of M o ( 0 2 C C 6 H ) 4 were collected and washed w i t h benzene a n d then cyclohexane a n d then d r i e d in vacuo. I R d a t a are g i v e n i n T a b l e I. T h e f o l l o w i n g X - r a y p o w d e r p a t t e r n w a s o b s e r v e d : 11.14 s, 10.22 s, 7.53 m , 5.64 m , 5.09 m , 4.92 m , 4.63 m , 4.39 w , 4.01 w , a n d 3.49 s. 2

5

T h e pivalate derivative M o 2 ( 0 2 C C ( C H ) ) was prepared most c o n v e n i e n t l y b y r e a c t i o n of M o ( C O ) w i t h the c a l c u l a t e d a m o u n t of pivalic acid i n refluxing o-dichlorobenzene. The compound crystallized as s l e n d e r y e l l o w needles w h e n the r e a c t i o n m i x t u r e w a s c o o l e d to r o o m t e m p e r a t u r e ; i t w a s filtered, w a s h e d w i t h b e n z e n e a n d c y c l o h e x a n e , a n d d r i e d in vacuo. I R d a t a for M o 2 ( 0 2 C C ( C H ) ) 4 are i n c l u d e d i n T a b l e I. T h e f o l l o w i n g lines w e r e o b s e r v e d i n the X - r a y p o w d e r p a t t e r n : 11.49 w , 10.46 s, 9.16 s, 6.36 s, 5.69 m , 5.51 m , 5.01 s, 4.59 s, 4.26 w , a n d 4.13 m . 3

3

4

c


3

3

T E T R A P R O P I O N A T O D I M O L Y B D E N U M ( 2 . 5 ) TRHODIDE, [ M O ( 0 C C H ) 4 ] T " . I n a t y p i c a l p r e p a r a t i o n , 1.5 g (3.1 m m o l e s ) M o ( 0 C C H ) 4 > 1.3 g (5.2 m m o l e s ) I , a n d 50 m l 1,2-dichloroethane w e r e p l a c e d i n a S c h l e n k flask. T h e m i x t u r e w a s s t i r r e d 1 h r at r o o m t e m p e r a t u r e . T h e b r o w n crystals ( 8 5 % y i e l d ) w e r e c o l l e c t e d o n a f r i t i n a i r , w a s h e d t w i c e w i t h c h l o r o b e n z e n e , t w i c e w i t h c y c l o h e x a n e , a n d t h e n d r i e d in vacuo. A n a l y s i s for M o o C i H o 0 I : c a l c d : M o 22.19, I 44.02; f o u n d : M o 21.54, I 43.83, I / M o 1.54. 2

3

5

2

2

2

2

2

3

2

2

0

8

3

T h i s c o m p o u n d was m o d e r a t e l y a i r - s e n s i t i v e ; d e c o m p o s i t i o n was n o t i c e a b l e after 30 m i n i n a i r . It w a s s l i g h t l y s o l u b l e i n b e n z e n e a n d 1,2-dichloroethane a n d i n s o l u b l e i n c y c l o h e x a n e . I n a c e t o n i t r i l e i t f o r m e d a d a r k b r o w n s o l u t i o n f r o m w h i c h no s o l i d c o u l d be r e c o v e r e d . R e m o v a l of solvent in vacuo y i e l d e d a tar w h i c h w a s n o t c h a r a c t e r i z e d . I R a b s o r p t i o n f r e q u e n c i e s are l i s t e d i n T a b l e I. T h e f o l l o w i n g lines w e r e o b s e r v e d i n the X - r a y p o w d e r p a t t e r n : 10.21 v w , 7.18 s, 6.76 m , 4.62 m , 4.06 w , 3.90 w , 3.66 m , a n d 3.59 w . T E T R A B E N Z O A T O D I M O L Y B D E N U M ( 2.5) T R H O D I D E , [ M O ( 0 C C H ) ] I ~. F o r this p r e p a r a t i o n , 2.10 g (3.1 m m o l e s ) M o ( 0 C C H ) , a n d 1.3 g (5.2 m m o l e s ) i o d i n e w e r e p l a c e d i n a S c h l e n k flask, a n d 50 m l 1,2-dic h l o r o e t h a n e w a s a d d e d . T h e m i x t u r e w a s s t i r r e d at 25 ° C 1 h r , t h e n filtered. T h e b r o w n crystals ( 9 6 % y i e l d ) w e r e w a s h e d w i t h c h l o r o b e n b e n e a n d c y c l o h e x a n e , a n d d r i e d in vacuo. A n a l y s i s for M o C H O 8 l : c a l c d : M o 1 8 . 1 5 , 1 36.02; f o u n d : M o 1 7 . 9 9 , 1 36.36, I / M o 1.53. 2

3

2

2

2

6

5

6

5

4

+

4

2

2 8

2 0

3

T h i s c o m p o u n d w a s stable i n a i r for s e v e r a l d a y s ; i t w a s s p a r i n g l y s o l u b l e i n d i c h l o r o m e t h a n e a n d 1,2-dichloroethane. W h e n [ M o ( 0 C C H ) 4 ] I was stirred i n acetonitrile, a dark solution formed a n d a light colored solid material appeared almost immediately. B o t h elemental analysis a n d X - r a y p o w d e r p a t t e r n c o n f i r m e d t h a t this l i g h t m a t e r i a l w a s p u r e M O ( 0 C C G H ) 4 . T h i s p r o c e d u r e w a s r e p e a t e d s e v e r a l times o n different s a m p l e s ; the y i e l d of p r e c i p i t a t e d M o 2 ( 0 C C H ) 4 w a s a b o u t 3 3 % a n d w a s i n d e p e n d e n t of r e a c t i o n t i m e . N o s o l i d p r o d u c t c o u l d b e i s o l a t e d f r o m the m o t h e r l i q u o r ; r e m o v a l of solvent in vacuo y i e l d e d o n l y a d a r k tar. I R a b s o r p t i o n f r e q u e n c i e s for [ M o 2 ( 0 C C H ) ] I are g i v e n i n T a b l e I. T h e f o l l o w i n g lines w e r e o b s e r v e d i n the X - r a y p o w d e r p a t t e r n : 12.66 w , 10.87 s, 9.90 m , 9.35 w , 7.25 s, 6.36 m , 5.40 w , 5.04 m , 4.70 m , 4.49 m , a n d 4.25 s. 2

5

3

2

2

5

2

2

6

6

5

5

4

3


2

6

27.

M C CARLE Y

E T

Dimeric

AL.

Transition

Metal

323

Species

T E T R A P I V A L A T I D I M O L Y B D E N U M ( 2 . 5 ) TRIIODIDE, [ M O ( 0 C C ( C H ) ) ] 2

2

2

2

2

3

+

4

Table II. T°,K 10 X T°,K 6

M

X of I D = α

M

c o r r

3

Magnetic Susceptibility D a t a for 125 2714 190 1807

131 2705 200 1719

140 2466 226 1523

M

4

4

[Mo2(02CC(CH3)3) ]I 4

170 2028 300 1135

160 2174 273 1281

151 2307 250 1379

= X P — I D was used to compute the values of Z -386 Χ ΙΟ" emu/mole.

c o r r

3

2

3

2


3

I3". I n a t y p i c a l p r e p a r a t i o n , 1.0 g (1.7 m m o l e s ) M o ( 0 C C ( C H ) 3 ) a n d 0.72 g (2.83 m m o l e s ) i o d i n e w e r e p l a c e d i n a S c h l e n k flask together w i t h 40 m l of e i t h e r b e n z e n e o r 1,2-dichloroethane ( b o t h solvents w o r k e q u a l l y w e l l ) . T h e m i x t u r e w a s s t i r r e d 12 h r at 2 5 ° C , t h e n c o o l e d 2 h r at 0 ° C . R e d - b r o w n crystals of t h e p r o d u c t ( 8 0 % y i e l d ) w e r e c o l l e c t e d o n a frit i n air, washed w i t h chlorbenzene a n d cyclohexane, a n d then d r i e d in vacuo. A n a l y s i s for M o C o H 6 0 8 l 3 : c a l c d : M o 19.64, I 38.96, C 24.58, H 3.71; f o u n d : M o 19.34, I 38.85, C 24.45, H 3.89, I / M o 1.52. This c o m p o u n d was air-sensitive, slightly soluble i n benzene, chlorob e n z e n e , a n d 1,2-dichloroethane, a n d i n s o l u b l e i n c y c l o h e x a n e . I n aceto nitrile it gave a dark solution from w h i c h solid c o u l d not be recovered. I R a b s o r p t i o n frequencies for [ M o 2 ( 0 C C ( C H 3 ) ) ] l 3 are r e p o r t e d i n T a b l e I. I n the X - r a y p o w d e r p a t t e r n the f o l l o w i n g lines w e r e o b s e r v e d : 8.33 s, 7.55 s, 6.64 m , 4.78 w , 4.55 m , 4.13 m , a n d 2.89 m . M a g n e t i c s u s c e p t i b i l i t y d a t a are g i v e n i n T a b l e I I .

e x

M

c o r r

8

e

180 1916

with the value

6

T E T R A P I V A L A T O M O L Y B D E N U M ( I I ) T U N G S T E N ( I I ) . A l t h o u g h this c o m p o u n d c o u l d n e v e r be o b t a i n e d free of M o ( 0 C C ( C H ) ) , i t c o u l d b e p r e p a r e d i n concentrations as h i g h as 80 m o l e % i n the s o l i d m i x t u r e s . I n the most c o n v e n i e n t s y n t h e t i c p r o c e d u r e , the i n i t i a l W / M o r a t i o i n t h e r e a c t i o n m i x t u r e w a s ca. 3. A t ratios > 3, net y i e l d s w e r e r e d u c e d w h e r e a s ratios < 3 concentrations of the m i x e d - m e t a l c o m p o u n d i n the i s o l a t e d p r o d u c t w e r e l o w e r . I n a r e a c t i o n d e s i g n e d to m a x i m i z e t h e c o n c e n t r a t i o n of m i x e d - m e t a l c o m p o u n d i n the p r o d u c t m i x t u r e , 1.06 g ( 4 m m o l e s ) M o ( C O ) , 8.44 g (24 m m o l e s ) W ( C O ) , 5.70 g (56 m m o l e s ) p i v a l i c a c i d , a n d 30 m l o - d i c h l o r o b e n z e n e w e r e p l a c e d i n a S c h l e n k flask e q u i p p e d w i t h a c o n d e n s e r a n d c o n n e c t e d to a gas b u b b l e r . T h e m i x t u r e w a s refluxed g e n t l y ( 1 8 5 ° C ) ; C O e v o l u t i o n ceased after 5 - 6 h r , b u t r e f l u x i n g w a s c o n t i n u e d a n a d d i t i o n a l 4 h r . W h e n the b l a c k s o l u t i o n w a s c o o l e d to 25 ° C , the p r o d u c t c r y s t a l l i z e d as slender y e l l o w needles w h i c h w e r e filtered u n d e r n i t r o g e n , w a s h e d s e v e r a l times w i t h c y c l o h e x a n e , a n d t h e n d r i e d u n d e r h i g h v a c u u m . T h e p r o d u c t is v e r y sensitive to a i r a n d to m o i s t u r e ; o n exposure to a i r , i t turns b l a c k w i t h i n a f e w m i n u t e s . T h e o n l y s u i t a b l e m e t h o d for s t o r i n g this c o m p o u n d for a p e r i o d of days w a s to seal the m a t e r i a l i n c a r e f u l l y e v a c u a t e d a n d outgassed a m p o u l e s . F o r c o m p a r i s o n , M o ( 0 C C ( C H ) ) c a n b e stored i n a i r for s e v e r a l days before decomposition becomes noticeable. Analysis for 0 . 8 0 M o W ( O C C ( C H ) ) + 0 . 2 0 M o ( O C C ( C H ) 3 ) 4 : c a l c d : M o 17.65, W 21.49, C 36.14, H 5.46; f o u n d : M o 17.17, W 21.89, C 36.58, H 5.59. 2

6

2

2

3

3

4

6

2

3

3

4

2

3

3

4

2

2

3


324

INORGANIC

COMPOUNDS

WITH

UNUSUAL

PROPERTIES

T a b l e III. I R A b s o r p t i o n Frequencies MoW(0 CC(CH ) )>


2

m m m sh s

610 715 765 770 790 890

s w m m s s

- 1

[MoW(0 CC(CH )s)JI

3 s

314 338 360 420 440

(cm )

2

s

300 w 350 m 458 s 620 s 720 w 780 s 799 s 892 s

'Relative intensities are indicated as s, strong; m, medium; w, weak; and sh,

Mixtures containing 60-80 mole % M o W ( 0 C C ( C H ) ) 4 and 40-20 mole % M o ( 0 C C ( C H ) ) gave X - r a y p o w d e r patterns t h a t w e r e essentially i d e n t i c a l to t h a t of p u r e M o ( 0 C C ( C H ) ) . T h e t w o c o m p o u n d s are thus i s o m o r p h o u s a n d f o r m s o l i d solutions. B o t h c o m p o u n d s are q u i t e s o l u b l e i n b e n z e n e . I R a b s o r p t i o n f r e q u e n c i e s for M o W ( 0 C C ( C H ) ) are g i v e n i n T a b l e I I I . 2

2

2

3

3

3

3

4

2

2

3

3

4

2

3

3

4

T E T R A P I V A L A T O M O L Y B D E N U M ( 2.5) T U N G S T E N (2.5)

[MOW(0 -

IODIDE,

2

C C ( C H ) ) ] T ~ . B e c a u s e the s t a r t i n g m a t e r i a l a n d the p r o d u c t are b o t h e x t r e m e l y sensitive to a i r a n d to m o i s t u r e , m a n i p u l a t i o n s w e r e p e r f o r m e d i n a g o o d d r y box u n d e r p u r i f i e d n i t r o g e n a n d o n the h i g h v a c u u m m a n i f o l d . A Soxhlet f r i t t e d glass extractor, w i t h 3 0 0 - m l flasks at e a c h e n d a n d T e f l o n n e e d l e valves at the filter by-pass a n d the v a c u u m - l i n e c o n n e c t i o n , w a s e v a c u a t e d a n d outgassed o n the h i g h v a c u u m l i n e . T h e a p p a r a t u s was t h e n r e m o v e d to the d r y b o x w h e r e 1.15 grams of a m i x t u r e c o n t a i n i n g 70 m o l e % (0.81 g ) M o W ( 0 C C ( C H ) ) a n d 30 m o l e % M o ( 0 C C ( C H ) ) w a s p l a c e d i n the extractor. A f t e r e v a c u a t i o n o n the v a c u u m l i n e , 250 m l c a r e f u l l y p u r i f i e d b e n z e n e w a s d i s t i l l e d i n t o t h e extractor; the s t a r t i n g m a t e r i a l d i s s o l v e d i n the b e n z e n e to p r o d u c e a y e l l o w s o l u t i o n . T h e a p p a r a t u s was filled w i t h n i t r o g e n , a n d the q u a n t i t y of i o d i n e (0.149 g ) r e q u i r e d to o x i d i z e o n l y the m i x e d - m e t a l c o m p o u n d w a s p l a c e d o n the frit of the extractor. T h e extractor w a s t h e n i n v e r t e d i n o r d e r to filter the y e l l o w s o l u t i o n i n t o the o t h e r 3 0 0 - m l flask to m i x w i t h the i o d i n e . A f t e r several m i n u t e s of s t i r r i n g , the g r a y c r y s t a l l i n e p r o d u c t a p p e a r e d . S t i r r i n g w a s c o n t i n u e d for ca. 12 h r ; t h e n the p r o d u c t was filtered a n d w a s h e d s e v e r a l times w i t h b e n z e n e ( d i s t i l l e d f r o m the m o t h e r l i q u o r ) . T h e flask c o n t a i n i n g the m o t h e r l i q u o r w a s r e m o v e d u n d e r n i t r o g e n , the extractor w a s s t o p p e r e d , a n d the p r o d u c t w a s d r i e d u n d e r h i g h v a c u u m . A n a l y s i s : for [ M o W ( 0 C C ( C H ) ) ] I : c a l c d : M o 11,83, W 22.66, C 29.61, H 4.41, I 15.64; f o u n d : M o 11.45, W 22.98, C 28.22, H 4.42,1 15.42. T h i s c o m p o u n d is e x t r e m e l y a i r - s e n s i t i v e ; i n d e e d i t is p y r o p h o r i c . T h u s r e l i a b l e c a r b o n a n d h y d r o g e n analyses w e r e difficult i f n o t i m p o s sible to o b t a i n b e c a u s e of p r o b l e m s i n s a m p l e transfer a n d w e i g h i n g . F o r 3

3

4

2

2

2

3

3

3

3

4

4

2

3

3

4


27.

M C CARLEY

E T

Dimeric

AL.

Transition

Metal

325

Species

f o r the M o — W M i x e d - M e t a l D e r i v a t i v e s " MoW(0 CC


2

(CH,)

930 1024 1090 1215 1360

w m w s s

1410 1475 1480 1505 1540

s s s sh sh

)

s

k

[MoW(0 CC 2

(CH ) 3

935 1030 1090 1215 1360 1375 1410 1460 1490 1520 1558 1564

J J /

w m w s s s s s sh w w

shoulder.

the same reason, the d a t a o b t a i n e d f r o m m a g n e t i c s u s c e p t i b i l i t y m e a s u r e ments h a d m o r e scatter t h a n u s u a l ; these d a t a w i l l be r e p o r t e d elsewhere at a later date. I R a b s o r p t i o n frequencies are g i v e n i n T a b l e I I I . Bis ( TETRAPROPYLAMMONIUM )

NONABROMODITUNGSTATE,

[ ( C 3 H 7 ) 4-

N ] W B r ~ . Into a S c h l e n k flask e q u i p p e d w i t h a w a t e r - c o o l e d c o n denser w e r e p l a c e d 2.66 g ( 10 m m o l e s ) ( C H ) N B r " , 3.52 g ( 10 m m o l e s ) W ( C O ) , a n d 40 m l c h l o r o b e n z e n e . T h e m i x t u r e was b r o u g h t to reflux ( 1 3 5 ° C ) , a n d gas e v o l u t i o n w a s m o n i t o r e d . A f t e r a b o u t 20 m i n , gas e v o l u t i o n ceased a n d c o n v e r s i o n of W ( C O ) to W ( C O ) B r " was c o m plete. T h e g o l d e n y e l l o w s o l u t i o n was a l l o w e d to c o o l p r i o r to a d d i t i o n of 20 m l 1,2-dibromoethane. T h e s o l u t i o n w a s a g a i n b r o u g h t to reflux, a n d the c o l o r d a r k e n e d r a p i d l y as C O e v o l u t i o n progressed. A f t e r a f e w m i n u t e s , a b l a c k c r y s t a l l i n e s o l i d b e g a n to d e p o s i t ; the r e a c t i o n w a s c o n t i n u e d 4 - 5 h r u n t i l C O e v o l u t i o n ceased. D u r i n g this stage, the e v o l v e d gases w e r e s a m p l e d a n d a mass s p e c t r u m w a s o b t a i n e d . T h e s p e c t r u m r e v e a l e d that e t h y l e n e w a s a m a j o r c o m p o n e n t of t h e gas together w i t h C O . W h e n the r e a c t i o n w a s c o m p l e t e , the m i x t u r e w a s c o o l e d a n d filtered; the g r e e n - b l a c k s o l i d was t h e n w a s h e d w i t h c h l o r o b e n z e n e a n d a s m a l l p o r t i o n of d i c h l o r o e t h a n e . F i n a l l y , the p r o d u c t w a s r e c r y s t a l l i z e d f r o m a c e t o n i t r i l e ( i n w h i c h i t is q u i t e s o l u b l e a n d forms a d e e p green s o l u t i o n ). X - r a y p o w d e r patterns of the p r o d u c t r e c o v e r e d d i r e c t l y f r o m the r e a c t i o n m i x t u r e a n d of the r e c r y s t a l l i z e d m a t e r i a l d e m o n s t r a t e d that they w e r e i d e n t i c a l . T h e i n i t i a l y i e l d w a s 9 0 % b a s e d o n tungsten a n d 7 0 % after r e c r y s t a l l i z a t i o n . A n a l y s i s for [ ( C H ) N ] W B r : c a l c d : W 25.19, B r 49.27, C 19.75, H 3.87; f o u n d : W 25.14, B r 48.99, C 19.73, H 4.25. 2

+

2

9

2

3

7

+

4

G

6

5

3

2

7

4

2

9

BIS(TETRABUTYLAMMONIUM) CHLORODECAIODOTETRAMOLYBDATE, [ ( C H ) N ] M o I i o C l . I n a t y p i c a l r e a c t i o n , 4.89 g (13.2 m m o l e s ) t e t r a b u t y l a m m o n i u m i o d i d e a n d 3.50 g (13.2 m m o l e s ) M o ( C O ) w e r e refluxed ( 1 3 5 ° C ) 15 m i n i n 100 m l c h l o r o b e n z e n e to f o r m a g o l d e n s o l u t i o n of [ ( C H ) N ] M o ( C O ) r . T h i s s o l u t i o n w a s a l l o w e d to c o o l to r o o m t e m p e r a t u r e p r i o r to a d d i t i o n of i o d i n e (3.37 g, 13.2 m m o l e s ) w h i c h r a p i d l y o x i d i z e d t h e m o l y b d e n u m to M o ( C O ) I " w i t h l i b e r a t i o n of C O . 4

9

2

4

4

6

4

9

4

+

5

4

3


326

INORGANIC

COMPOUNDS

WITH

UNUSUAL

PROPERTIES

T h e r m a l d e c o m p o s i t i o n of the c a r b o n y l a n i o n w a s p r o m o t e d b y r e f l u x i n g t h e s o l u t i o n 1 h r ; d u r i n g this t i m e a d a r k m i c r o c r y s t a l l i n e s o l i d p r e c i p i t a t e d . T h e b l a c k s o l i d w a s i s o l a t e d b y filtration a n d p l a c e d i n a Soxhlet extractor w i t h 1,2-dichloroethane. A f t e r t w o weeks of c o n t i n u o u s extrac t i o n , v i r t u a l l y a l l of the s o l i d h a d passed t h r o u g h t h e frit; 4.87 grams of r e c r y s t a l l i z e d s o l i d w e r e i s o l a t e d f r o m the s o l u t i o n i n the e x t r a c t i o n flask by filtration. A n a l y s i s for [ ( C H ) N ] M o 4 l i o C l : c a l c d : M o 17.66, I 58.40, C I 1.63, C 17.68, H 3.34, Ν 1.29; f o u n d : M o 17.72, I 58.25, C I 1.53, C 18.08, Η 3.32, Ν 1.46. 4

9

4

2

Results and Discussion [Mo (0 CR) ]I 2

2

4

3

D e r i v a t i v e s . T h e i n i t i a l o b j e c t i v e of w o r k o n the

o x i d a t i o n of M o ( 0 C R ) Downloaded by UNIV OF BATH on July 3, 2016 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/ba-1976-0150.ch027

2

2

4

d e r i v a t i v e s w i t h halogens w a s to e x a m i n e t h e

p o s s i b i l i t y of a c h i e v i n g a d d i t i o n of h a l o g e n across the q u a d r u p l e

bond,

as i n t h e r e a c t i o n :

R

R

If s u c h reactions c o u l d be r e a l i z e d , the r e s u l t i n g p r o d u c t s e x p e c t e d to h a v e the structure analogous to the k n o w n d e r i v a t i v e s (13)

would

be

Re (0 CR) X 2

2

4

2

except that, u p o n a d d i t i o n of h a l o g e n , t h e M o - M o b o n d

w o u l d decrease i n b o n d

o r d e r f r o m 4 to 3.

H o w e v e r , reactions

with

b r o m i n e l e a d to as yet u n d e f i n e d p r o d u c t s , a n d , i n the cases e x a m i n e d , the reactions w i t h i o d i n e l e a d to t r i i o d i d e d e r i v a t i v e s

Mo (0 CR) I . 2

2

4

3

I n the reactions w i t h i o d i n e , i t w a s e s t a b l i s h e d that the t r i i o d i d e w a s the sole p r o d u c t w h e n the I / M o r a t i o w a s 0 - 1 . 5 . T h u s , n e i t h e r m o n o n o r d i i o d i d e d e r i v a t i v e s c o u l d be f o r m e d .

W h e n the I / M o r a t i o w a s

1.5, the r e a c t i o n products a p p r o a c h e d the c o m p o s i t i o n M o ( 0 C R ) I 2

2

4

5

> as

the I / M o ratio b e c a m e v e r y l a r g e ; these c o m p o u n d s a p p e a r to lose i o d i n e r e a d i l y , a n d thus t h e y are difficult to o b t a i n i n p u r e f o r m . T h e reactions r e p o r t e d here l e a d c l e a n l y to t h e t r i i o d i d e d e r i v a t i v e s w h e n n a t i n g solvents are u s e d at r o o m t e m p e r a t u r e .

noncoordi-

In coordinating


solvents

27.

Dimeric

M C CARLEY E T A L .

Transition

Metal

327

Species

s u c h as a c e t o n i t r i l e , or at e l e v a t e d t e m p e r a t u r e , the reactions p u r s u e a different course. A l l a v a i l a b l e e v i d e n c e indicates t h a t the reactions w i t h i o d i n e c o r r e s p o n d to a one-electron o x i d a t i o n of the d i m o l y b d e n u m species as i n d i c a t e d b y E q u a t i o n s 2 a n d 3.

T h e r m a l decomposition

M o ( O o C R ) + 3/2 I 2

4

Mo (0 CR) 2

2

2

+

4

+ 5 / 2 I -> [ M o ( 0 C R ) ]

4

2

[Mo (0 CR) ]

2

2

2

2

+

4

of the t r i i o d i d e + V

(2)

+ I "

(3)

5

d e r i v a t i v e s in vacuo at ca. 100 ° C liberates e l e m e n t a l i o d i n e , M o ( 0 C R ) , 2

a n d some u n i d e n t i f i e d n o n v o l a t i l e p r o d u c t .

L o s s of e l e m e n t a l

2

4

iodine

f r o m salts c o n t a i n i n g the I " a n i o n is expected at elevated temperatures. Downloaded by UNIV OF BATH on July 3, 2016 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/ba-1976-0150.ch027

3

H o w e v e r , the m o n o i o d i d e f o r m e d i n this process is e v i d e n t l y not stable, a n d i t decomposes w i t h f o r m a t i o n of M o ( 0 C R ) 2

2

as b y the s c h e m e :

4

[ M o ( 0 C R ) ] I ( s ) -> [ M o ( 0 C R ) ] I ( s ) 2

2

4

2

3

2

2[Mo (0 CR) ]I(s) ->Mo (0 CR) 2

4

2

2

2

T h e benzoate d e r i v a t i v e [ M o ( 0 C C H ) ] I 2

2

6

5

+I (g)

4

4

3

2

+

4

?

undergoes a s i m i l a r r e a c

t i o n i n a c e t o n i t r i l e , p r o b a b l y because of i n s o l u b i l i t y of M o ( 0 C C H ) 2

2

6

5

4

w h i c h precipitates a n d is r e c o v e r e d i n ca. 3 3 % y i e l d b a s e d o n the i n i t i a l q u a n t i t y of t r i i o d i d e c o m p o u n d

used.

T h e r e c o v e r y of M o ( 0 C R ) 2

2

f r o m the t h e r m a l d e c o m p o s i t i o n is a

4

strong i n d i c a t i o n that the b a s i c s t r u c t u r e of the d i m o l y b d e n u m t e t r a c a r b o x y l a t e (1,14)

is r e t a i n e d i n the t r i i o d i d e c o m p o u n d s .

T h i s is also i n d i

cated c o n v i n c i n g l y b y the I R spectra i n F i g u r e s 1 a n d 2 a n d the d a t a i n T a b l e I. T h e almost perfect b a n d for b a n d m a t c h i n g b e t w e e n the spectra of M o ( 0 C R ) 2

2

4

a n d the c o r r e s p o n d i n g [ M o ( 0 C R ) ] I 2

2

4

3

is most s t r i k i n g

i n this r e g a r d . P a r t i c u l a r l y for the p i v a l a t e d e r i v a t i v e s , the d a t a i n the 400-700 cm"

1

r e g i o n i n d i c a t e the same m o l e c u l a r f r a m e w o r k , since the

Mo—Ο stretching freqeuncies m u s t o c c u r i n this r e g i o n a n d they s h o u l d b e e s p e c i a l l y sensitive to a n y change i n m o l e c u l a r structure. T h e shift i n f r e q u e n c y of the bands at 420, 450, a n d 615 c m " for the n e u t r a l p i v a l a t e 1

to 445, 465, a n d 625 for the t r i i o d i d e d e r i v a t i v e is consistent w i t h the expected increase i n s u c h M o - O stretching freqeuncies u p o n increase i n average o x i d a t i o n state of the m e t a l atoms. F i n a l l y , the m a g n e t i c

properties r e v e a l c l e a r l y t h a t the t r i i o d i d e

derivatives are species that c o n t a i n one u n p a i r e d electron p e r d i m e r as r e q u i r e d b y o x i d a t i o n to the cations [ M o ( 0 C R ) ] . 2

b i l i t y d a t a for [ M o ( 0 C C ( C H ) ) ] I 2

2

3

3

4

3

2

4

+

M a g n e t i c suscepti

are presented i n T a b l e I I .

These

d a t a p r o v i d e a n excellent fit to the C u r i e e q u a t i o n a n d , f r o m the slope, the m a g n e t i c m o m e n t μ — 1.66 B M was f o u n d . T h e c r y s t a l l i n e t r i i o d i d e


328

INORGANIC

COMPOUNDS

WITH

UNUSUAL PROPERTIES

2 ;30


< CL " 20 10 0 1600

JL1

I

1400

Figure 1.

ι

ι

ι

ι

ι

I2D0 1000 WAVENUMBER

»

800 (CM"

1

2

I

I 400

L

200

)

IR spectrum of Μο (0 60(€Η ) ) 2

ι

600

5 8 &

in nujol mull

d e r i v a t i v e s a l l g i v e strong, r e l a t i v e l y n a r r o w E S R signals w h i c h s h o w l i t t l e e v i d e n c e of a n i s o t r o p y a n d give g values of 1.93 ± 0.01. relation μ = 2

g s(s - f 1 ) , w i t h s =

F r o m the

the c a l c u l a t e d m o m e n t , μ =

y

2

2

1.67 is

o b t a i n e d ; this is i n excellent a g r e e m e n t w i t h the m o m e n t d e r i v e d f r o m the s u s c e p t i b i l i t y measurements.

1600

1400

1200

000

800

WAVENUMBER

Figure 2 .

600

7 R spectrum of [Mo (0 CC(CH ) ) Yl ~ 2

2

400

(CM"' ) s s A

s

in nujol mull


200

27.

Dimeric

M C CARLEY E T A L . The

findings

Transition

Metal

329

Species

r e p o r t e d here for the reactions of the

dimolybdenum

carboxylates w i t h i o d i n e are consistent w i t h the r e c e n t observations

of

C o t t o n a n d P e d e r s e n ( 1 5 ) d u r i n g a s t u d y of the e l e c t r o c h e m i c a l o x i d a t i o n Mo2(02CC H )4

of

3

i n a c e t o n i t r i l e or e t h a n o l .

7

They

found

a quasi-

r e v e r s i b l e one-electron o x i d a t i o n for the i n d i c a t e d c o m p o u n d b y r o t a t i n g disc polarography a n d cyclic voltammetry, a n d g

M

=

gj_ =

1.941 for the

o x i d i z e d species b y E S R studies. F u r t h e r m o r e , the p r o p o s e d f o r m u l a t i o n of the t r i i o d i d e c o m p o u n d s as salts c o n t a i n i n g the [ M o 2 ( 0 C R ) ] 2

4

w i t h t h e same m o l e c u l a r s t r u c t u r e a n d e c l i p s e d c o n f o r m a t i o n o b s e r v e d for M o ( 0 C C H ) 2

2

3

4

3


Mo (S0 ) 2

4

is f o r m e d

(16, 1 7 ) . Mo (S0 ) 2

4

b y one-electron

" and M o ( S 0 )

4

4

2

4

4

3

2

4

(16).

4

T h e latter

o x i d a t i o n of K M o ( S 0 ) . 4

2

4

The

4

~ anions h a v e the same m o l e c u l a r s t r u c t u r e

T h e l e n g t h e n i n g of the M o - M o b o n d

from 2.111(1) A

in

" to 2 . 1 6 4 ( 2 ) A i n M o > ( S 0 ) " is e v i d e n c e t h a t the e l e c t r o n

4

4

as that

is s u p p o r t e d b y the p r e v i o u s l y p u b l i s h e d

i s o l a t i o n a n d s t r u c t u r e d e t e r m i n a t i o n of K M o ( S 0 ) compound

cation

+

L

4

4

3

was r e m o v e d f r o m the δ-bonding o r b i t a l u p o n o x i d a t i o n f r o m the 4- to 3- i o n . It thus appears that the d i m o l y b d e n u m ( I I ) species m a y b e g e n e r a l l y s u s c e p t i b l e to one-electron

o x i d a t i o n w i t h r e t e n t i o n of s t r u c t u r e .

T h e m o l e c u l a r o r b i t a l d e s c r i p t i o n of the o x i d a t i o n is best u n d e r s t o o d i n terms of

the o r b i t a l s l o c a l i z e d o n

( σ ) ( π ) ( δ ) (16). 2

4

the m e t a l a t o m s :

(σ )(π )(δ ) 2

4

2

->

I n these terms, the m e t a l - m e t a l b o n d o r d e r decreases

1

f r o m 4 to 3.5 w h e n o n e - e l e c t r o n o x i d a t i o n occurs. The M i x e d - M e t a l Compounds. pound M o W ( 0 C C ( C H ) ) 2

3

3

4

T h e successful synthesis of t h e c o m

represents the first success i n i n t r o d u c i n g

t u n g s t e n i n t o a m e t a l - m e t a l q u a d r u p l e b o n d , a n d i t is o n l y the s e c o n d successful f o r m a t i o n of a n y h e t e r o n u c l e a r q u a d r u p l e b o n d . S e n i o r (18)

CrMo(0 CCH ) . 2

3

Evidence

4

Mo (0 CC(CH ) ) 2

2

Garner and

r e p o r t e d p r e p a r a t i o n of the C r - M o m i x e d - m e t a l

3

3

4

for

the

compound

isostructural relation

and M o W ( 0 C C ( C H ) ) 2

3

3

4

between

comes m a i n l y f r o m mass

spectra, I R spectra, a n d X - r a y p o w d e r p a t t e r n d a t a . I R a b s o r p t i o n f r e quencies for the m i x e d - m e t a l species are g i v e n i n T a b l e I I I ; the v a l u e s s h o u l d be c o m p a r e d

w i t h those for the d i m o l y b d e n u m p i v a l a t e d e r i v a

tives ( T a b l e I ). T h e s e data i n d i c a t e c l e a r l y a v e r y close r e l a t i o n b e t w e e n the structures of the M o

2

a n d the M o W

compounds.

F i g u r e 3 is the mass s p e c t r u m of the m i x t u r e c o n t a i n i n g 80 m o l e MoW(O,CC(CH ) ) and20mole% 3

3

4

i o n peaks for the M o

2

Mo (0 CC(CH ) ) . 2

2

3

3

4

%

T h e parent

species are c e n t e r e d at 596 a m u , those for

the

M o W species at 683 a m u . F o r the d i m o l y b d e n u m species, the p a r e n t i o n set is i n g o o d a g r e e m e n t w i t h t h a t e x p e c t e d a c c o r d i n g to H o c h b e r g et al. ( 1 9 ) , a n d the p a r e n t i o n set for the M o W species agrees w i t h the ex pected

isotope c o m b i n a t i o n s .

H o w e v e r , t h e r e l a t i v e intensities of

the

t w o sets are n o t a n a c c u r a t e reflection of the c o m p o s i t i o n of the m i x t u r e .


330

INORGANIC

COMPOUNDS

[M02(02CCMe )4]*

UNUSUAL PROPERTIES

[Μο\^(θ2θΟΜβ ) ]

3

Figure 3.

WITH

3

4

+

Parent ion mass spectrum of a mixture containing 80 mole % MOW(0 CC(CH ) ) and 20 mole % Mo.^O CC(CH ) ) 2

3 s h

t

9 s h

T h u s , t h e r e l a t i v e i n t e n s i t y of t h e Mo > species is greater t h a n that e x Downloaded by UNIV OF BATH on July 3, 2016 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/ba-1976-0150.ch027

L

p e c t e d f r o m s a m p l e analysis. B e c a u s e of t h e extreme r e a c t i v i t y of M o W ( O o C C ( C H ) ) 4 , c h r o 3

3

m a t o g r a p h i c m e t h o d s f o r s e p a a r t i n g t h e m i x t u r e w e r e v e r y difficult to a p p l y . T h u s it w a s n o t possible to o b t a i n t h e p u r e , n e u t r a l m i x e d - m e t a l compound.

H o w e v e r , this greater r e a c t i v i t y c o u l d b e advantageous i n

preparing a pure mixed-metal compound.

It w a s n a t u r a l to investigate

the r e a c t i o n w i t h i o d i n e w i t h t h e e x p e c t a t i o n that t h e m i x e d - m e t a l c o m p o u n d w o u l d react p r e f e r e n t i a l l y i f a l i m i t e d q u a n t i t y o f o x i d a n t w a s a v a i l a b l e . T h e success of t h e m e t h o d e x c e e d e d expectations, b u t i t w a s s u r p r i s i n g t h a t a s i m p l e i o d i d e salt w a s o b t a i n e d r a t h e r t h a n t h e t r i i o d i d e salt as w i t h t h e d i m o l y b d e n u m c o m p o u n d s . facilitates

T h i s difference

probably

s e p a r a t i o n since t h e p o s s i b i l i t y of s o l i d - s o l u t i o n f o r m a t i o n

b e t w e e n o x i d i z e d p r o d u c t s is d i m i n i s h e d .

MoW(02CCMe )4l 3

Figure

4. ESR spectrum [MoW(0 CC(CH )sl]I 2

s

of

poly crystalline at 25°C


27.

M C CARLEY

E T

Dimeric

AL.

Transition

Metal

331

Species

T h e e v i d e n c e i n d i c a t e s that [ M o W ( 0 C C ( C H ) 3 ) 4 ] I 2

one-electron

2

m o l e c u l a r s t r u c t u r e (see i n the frequency

is f o r m e d

3

o x i d a t i o n of M o W ( 0 C C ( C H ) ) 3

3

w i t h r e t e n t i o n of

4

I R spectra data i n T a b l e I I I ) .

of b a n d s i n the 4 0 0 - 7 0 0 c m "

by the

A g a i n , the shift

r e g i o n reflects t h a t ex

1

p e c t e d for a n increase i n average o x i d a t i o n state of t h e m e t a l atoms.

The

E S R s p e c t r u m a n d m a g n e t i c s u s c e p t i b i l i t y d a t a also s u p p o r t r e t e n t i o n of m e t a l - m e t a l b o n d i n g . T h e E S R s p e c t r u m ( F i g u r e 4 ) d e p i c t s the n a r r o w , virtually isotropic signal w i t h g =

1.877. T h e l o w e r v a l u e of the g factor,

l o w e r t h a n that of the d i m o l y b d e n u m t r i i o d i d e salts, is e x p e c t e d b e c a u s e of the m u c h l a r g e r s p i n - o r b i t c o u p l i n g constant for t u n g s t e n .

Although

difficulty w a s e n c o u n t e r e d i n o b t a i n i n g r e p r o d u c i b l e s u s c e p t i b i l i t y d a t a ,


a n average m a g n e t i c m o m e n t of 1.58 B M w a s d e t e r m i n e d . μ=

1.61

5

T h e great r e a c t i v i t y of M o W ( 0 C C ( C H ) ) 4 a n d 2

(CH ) ) ]I 3

3

A v a l u e of

B M w a s c a l c u l a t e d f r o m the o b s e r v e d g factor. suggests that the

4

3

s t a b i l i t y of

m i n i s h e s w i t h i n t r o d u c t i o n of the t u n g s t e n a t o m . d i t u n g s t e n species m a y be

s u r m i s e d to be

[MoW(0 CC2

3

the m e t a l - m e t a l b o n d I f so,

even less

di

corresponding stable—perhaps

p r o v i d i n g a p a r t i a l e x p l a n a t i o n for the l a c k of success i n p r e p a r i n g c o m pounds

w i t h the W = = W l i n k a g e .

T h o u g h the great r e a c t i v i t y of

the

m i x e d - m e t a l c o m p o u n d s makes s y n t h e t i c w o r k difficult, it does offer the p o s s i b i l i t y that n e w reactions n o t o b s e r v e d w i t h the M o developed.

2

species c a n b e

W o r k a l o n g this l i n e is i n progress.

N e w Species f r o m R e a c t i o n s o f H a l o c a r b o n y l m e t a l l a t e A n i o n s .

The

b a s i c i d e a for this aspect of the w o r k w a s t h a t r e a c t i v e m e t a l h a l i d e fragments

m i g h t be

generated

from

the h a l o c a r b o n y l m e t a l l a t e

anions

u n d e r c o n d i t i o n s w h e r e loss of the C O l i g a n d s is p r o m o t e d i n the absence of other c o o r d i n a t i n g l i g a n d s . F o r e x a m p l e , d i n u c l e a r or cluster species m i g h t b e o b t a i n e d via t h e r m a l d e c o m p o s i t i o n of the M ( C O ) X ' anions 4

3

as i n the s c h e m e : M ( C O ) X - - > [MX ~] 4

3

3

η[ΜΧ -]->Μ Χ 3

η

3 Λ

+4CO «-

T h i s s c h e m e also presents the p o s s i b i l i t y of g e n e r a t i n g m e t a l a t o m f r a g m e n t s w h i c h m i g h t b e a d d e d to o t h e r m e t a l c l u s t e r species to b u i l d u p n e w clusters. the references

R e c e n t l y , M a t s o n a n d W e n t w o r t h (see

R e f e r e n c e 20 a n d

cited therein) have been investigating similar

reactions

b e t w e e n m e t a l h a l i d e s a n d h a l o c a r b o n y l m e t a l l a t e anions i n n o n c o o r d i n a t i n g solvents. T h e i r recent synthesis of the m i x e d - m e t a l a n i o n C r M o C l a n d t h e synthesis of the W B r 2

9

2

9

3

"

" a n d M04I10CI " salts r e p o r t e d here i l l u s 2

trate the p o w e r of this a p p r o a c h . I n the course of i n v e s t i g a t i n g the t h e r m a l d e c o m p o s i t i o n of W ( C O ) 4

B r " , a search for s u i t a b l e solvents w a s necessary. 3

A m o n g the


solvents

332

INORGANIC

COMPOUNDS WITH

c o n s i d e r e d w a s 1,2-dibromoethane.

UNUSUAL

PROPERTIES

However, a r a p i d reaction

i n this solvent b e f o r e the W ( C O ) B r " a n i o n c a n b e f o r m e d . 4

occurs

I n o r d e r to

3

c o n t r o l the r e a c t i o n , a two-step sequence i n c h l o r o b e n z e n e w a s d e v i s e d : W (CO)

+ B r " -> W ( C O ) B r +

β

5

2 W ( C O ) B r - + 7 / 2 C H B r -> W B r 5

2

4

2

2

9

2

CO

" + 7/2 C H 2

+

4

10CO

A l t h o u g h other cations w e r e t r i e d , the t e t r a p r o p y l a m m o n i u m i o n p r o v i d e d the most easily i s o l a t e d a n d c r y s t a l l i n e p r o d u c t . W ( C O ) B r " with C H B r 5

2

m a t i o n of W B r 2

of W B r Downloaded by UNIV OF BATH on July 3, 2016 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/ba-1976-0150.ch027

2

9

2

2

9

4

T h e r e a c t i o n of

proceeded virtually quantitatively w i t h for

2

" e v e n i n the presence of excess d i b r o m o e t h a n e .

Salts

" were not previously reported, although Saillant a n d W e n t -

w o r t h ( 2 1 ) r e p o r t e d p r e p a r a t i o n of the W C 1 2

T h e s t r u c t u r e a n d properties of W X 2

9

9

2

" anion. salts are of

2 _

considerable

interest since, i f i s o s t r u c t u r a l , t h e y are r e l a t e d b y one-electron o x i d a t i o n to the salts c o n t a i n i n g the c o n f a c i a l b i o c t a h e d r a l anions W X 2

Br).

C o m p o u n d s c o n t a i n i n g the W X 2

9

3

9

3

" (X = Cl,

" ions h a v e v i r t u a l l y t e m p e r a t u r e -

i n d e p e n d e n t m a g n e t i c s u s c e p t i b i l i t i e s ( 2 2 ) , a n d the b i n u c l e a r ions o b v i o u s l y have a s p i n singlet ( S = observed

in K W C 1 3

2

0 ) g r o u n d state. T h e W - W distance

is o n l y 2.41 A a n d reflects

9

b o n d i n g t h a t is best d e s c r i b e d (24) Thus, if W B r 2

9

2

(23)

strong m e t a l - m e t a l

as ( σ ) ( π ) w i t h b o n d o r d e r η = 2

3.

4

" i n the c o m p o u n d r e p o r t e d here is i s o s t r u c t u r a l , i t s h o u l d

s h o w a m a g n e t i c m o m e n t c o r r e s p o n d i n g to one u n p a i r e d e l e c t r o n ( S

=

a n d the m o m e n t s h o u l d be t e m p e r a t u r e - i n d e p e n d e n t i f the m e t a l -

y ), 2

m e t a l b o n d i n g r e m a i n s v e r y strong.

M a g n e t i c susceptibility measure

ments ( 7 7 ° - 3 0 0 ° K ) for [ ( C H ) N ] W B r 3

7

4

2

2

9

are l i s t e d i n T a b l e I V .

The

m a g n e t i c m o m e n t d e r i v e d f r o m the d a t a is i n d e e d i n d e p e n d e n t of t e m p e r a t u r e a n d is close to t h a t e x p e c t e d for S =

T h i s indicates that the

y. 2

s t r o n g m e t a l - m e t a l b o n d i n g is r e t a i n e d a n d that i t m a y b e assigned b o n d order η =

2.5.

Table I V .

M a g n e t i c C o n s t a n t s " of Salts of W B r 2

A

3

7

4

2

4

9

4

2

2

9

4

1 0

" and M o I i C l ~ 4

emu/ mole

emu/ mole

emu/ mole

-452 -867

0.370(3) 0.385(3)

-699 -1084

247 217

10'

6

W

6

° Constants were derived from least squares fit to the relation X M = =

(ID

+

ITIP)

+

CT" , 1

μ =

and

2

0

Xr/p

C 6

[(C H ) N] W Br [(C H ) N] Mo I Cl

2

emu deg/ mole

10'

Compound

9

μ, BM

1.72(1) 1.75(1) A +

CT"

:

2.8280°Λ

P r e l i m i n a r y d a t a f r o m the X - r a y c r y s t a l a n d m o l e c u l a r s t r u c t u r e d e t e r m i n a t i o n of

[(C H ) N] W Br 3

7

4

2

2

9

c a n b e r e p o r t e d here a l t h o u g h a


27.

M C CARLEY

E T

Dimeric

AL.

Transition

d e t a i l e d a c c o u n t w i l l be g i v e n elsewhere. space g r o u p C 2 / c , w i t h a = 96.10°.

36.19 A , b =

A t o t a l of 3380 reflections

Metal

333

Species

T h e crystals are m o n o c l i n i c , 11.98 a, c =

were

19.53 a, a n d β

u t i l i z e d i n refinement,

= and

a b s o r p t i o n corrections w e r e a p p l i e d because of the l a r g e l i n e a r a b s o r p t i o n coefficient ( 148.4 c m " ) for MoK

Inorganic Compounds with Unusual Properties

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