Chapter 11

The Chemistry of Inorganic Ring Systems, R. Steudel (Ed.) Studies in Inorganic Chemistry, Vol. 14

© 1992 Elsevier Science Publishers B.V. All rights reserved.

Chapter 11

P

and As

UNITS AS BUILDING BLOCKS FOR METALLACYCLES, CAGES, SANDWICH AND TRIPLE-DECKER COMPLEXES

0. J . Scherer, C. Blath, J . Braun, B. Hobel, K. P f e i f f e r , B. Rink, H. Slodzyk, P. Walther, B. Werner and R. Winter Fachbereich Chemie der U n i v e r s i t a t Kaiserslautern,

Erwin-Schrddinger-StraBe, W-6750 Kaiserslautern, Germany Abstract

I n t h e c o o r d i n a t i o n s p h e r e o f s u b s t i t u t e d c y c l o p e n t a - d i e n y l t r a n s i t i o n - m e t a l complex f r a g m e n t s PO, c y c l o - P^{3 3}~ ,

open-edged Pg b e n z v a l e n e and A s ^ Dewar benzene, c y c l o - A S g a s w e l l a s open-edged E ^{1 0} d i h y d r o f u l v a l e n e s (E = P,As) have been s t a b i l i z e d f o r t h e f i r s t t i m e . S o u r c e f o r t h e P - and A sⁿ~ u n i t s a r e w h i t e phosphorus, P⁴, and y e l l o w a r s e n i c , A s⁴, r e s p e c t i v e l y .

1. INTRODUCTION

W i t h i n t h e l a s t y e a r s many n o v e l complexes w i t h

s u b s t i t u e n t - f r e e a c y c l i c and c y c l i c Eⁿ u n i t s [ 1 ] , E = P,As, S b , B i ; n = 1-8, have been s y n t h e s i z e d and c h a r a c t e r i z e d by IR, MS, NMR, and e s p e c i a l l y by X-ray a n a l y s e s . Many o f t h e s e compounds have f o r g e d b r i d g e s t o o r g a n i c c h e m i s t r y (CH i s i s o e l e c t r o n i c and i s o l o b a l [2] t o e.g. P and A s ) , t h e s o l i d - s t a t e c h e m i s t r y o f P^{n x}~ p o l y p h o s p h i d e s [3] and t o a c y c l i c and c y c l i c p o l y p h o s p h a n e s [ 4 ] . T h i s r e v i e w m a i n l y d e s c r i b e s t h e newest developments on t h e r e a c t i v i t y o f complexes w i t h Eⁿ

l i g a n d s and t h e c o o r d i n a t i v e s t a b i l i z a t i o n o f c y c l i c , e s p e c i a l l y l a r g e r E ⁿ u n i t s (E = P,As; n = 3,4,5,6 and 8) 2. RESULTS

2.1. E² Ligands (E = P,As,Sb)

I n t h e w e l l - k n o w n s e r i e s o f d i m e t a l l a - d i p h o s p h a t e t r a - h e d r a n e s [1] d e r i v a t i v e 2. [5] w i t h two d i f f e r e n t m e t a l atoms c o u l d be s y n t h e s i z e d a c c o r d i n g t o e q u a t i o n ( 1 ) :

[ C p⁴N i ( 7 )³- P³) ]

[CpW(CO)³3²,A Cp⁴Ni - CO

l a

Cp⁴ = 7 f⁵- C⁵H i P r⁴, Cp=T)⁵-C⁵H⁵

R e a c t i o n o f t h e d i n i c k e l a - d i p h o s p h a t e t r a h e d r a n e 3_ w i t h [W(CO) ⁵ ( t h f ) ] l e a d s t o f o r m a t i o n o f t h e N i²W P²- c o m p l e x 4_

w h i c h c a n be o x i d i z e d w i t h b i s ( t r i m e t h y l s i l y l ) p e r o x i d e t o g i v e 5, t h e f i r s t complex w i t h a PO l i g a n d [ 6 ] .

[Cp^{4 2}Ni²(M,»?^{2 ! 2}-P2>]

[W(CO)⁵(thf)]

- THF, - CO

Cp⁴ = T7⁵-C⁵HiPr⁴

Cp⁴Ni

F o r t h e t e t r a g o n a l - p y r a m i d a l l y s t r u c t u r e d compounds 4_ and 5 X - r a y a n a l y s e s show t h a t 4_ has a r a t h e r s h o r t P...P bond o f 2.304(4) A (2.624(5) A i n 5_) ; t h e M3-PO l i g a n d s have P-0 bond l e n g t h s o f 1.46 and 1.48 A (IR: v(P=O)=1260 cm"¹) [ 6 ] .

I n a n a l o g y t o t h e s y n t h e s i s o f 2 t h e i n t e r a c t i o n o f

[ C p⁴N i ( r j³- A s³) ] (IbJ w i t h [ C p⁴N i ( C O ) ] ² [7] a f f o r d s i n h i g h y i e l d complex 6 (d(As-As) = 2.277(6)A) [ 8 ] .

[Cp⁴Ni(M-CO)]²,A

[Cp⁴Ni ( T )³- A S³) ] 1

Cp⁴ = r?⁵-C⁵HiPr⁴

2 (d(Sb-Sb) = 2.678(1)A) was o b t a i n e d i n c a . 4 % y i e l d on h e a t i n g (180°C) [ C p M o ( C O )³]² and m e t a l l i c antimony f o r f i v e days [ 9 ] .

Cp(0C)²Mo

Cp = T)⁵-C⁵H 5"5

Mo(CO)²Cp

2.2. E³ Ligands (E = P,As)

The c o t h e r m o l y s i s o f [ C p⁴N i (/x-CO) ] ² w i t h an e x c e s s o f E (E = P,As) g i v e s i n about 60 % y i e l d t h e n i c k e l a t r i p n i c t o -

gena t e t r a h e d r a n e s 1 [ 8 ] .

Ig, E = P lfe, E = AS

A s i d e p r o d u c t o f t h e r e a c t i o n o f [ (r/^{: >}-C⁵Me⁴R)Ru(CO)² ] ² w i t h y e l l o w a r s e n i c , A s⁴, i s t h e t e t r a n u c l e a r c l u s t e r [ { ( r j⁵-

C⁵M e⁴R ) R u }³R u ( r )³- A s³) ( M³, r 7³- A s³) ( M³- A S )³ ] (g g:R =

Me,b_:R = E t ) , whose R u⁴A s⁹ s k e l e t o n i s shown i n F i g . 1 [ 1 0 ] .

F i g . 1 ( C p ' - l i g a n d s have been o m i t t e d )

I n t e r e s t i n g t o n o t e a r e t h e d i f f e r e n t d(As-As) v a l u e s o f 2.32 A (As7-9) and 2.57 A ( A s l , 4 , 6 ) f o r t h e two c y c l o - A s³ l i g a n d s .

W i t h r e s p e c t t o t h e o x i d a t i o n s t a t e o f I V , w h i c h i s a l m o s t t h e o n l y o c c u r r i n g s t a t e f o r t h o r i u m , t h e u n s u b s t i t u t e d p h o s p h o r u s l i g a n d i n | [11] i s d e s c r i b e d a s c y c l o - P^{3 3}~

(d(P-P) = 2.185 A), a f o r m u l a t i o n i s o e l e c t r o n i c w i t h c y c l o - S³.

P⁴, % M g c i²( O E t²) j "N^X^

2 [Cp»²Th(»?⁴-C⁴H⁶) ] C p "²T h - — P Th (CI)Cp»²

Cp" = r j⁵- l^/3 - t B u²C⁵H³ g

Treatment o f a d i c h l o r o m e t h a n e s o l u t i o n o f [ ( t r i p h o s ) C o( J 7³- P³)](1P⁼) w i t h [ A u C l ( P R³) ] o r RHgCl i n t h e p r e s e n c e o f T 1 P F⁶ a f f o r d s t h e complexes 11 [12] and 12 [ 1 3 ] .

[AUC1(PR³)]

10—

• (triphos)Co

R = Me or Ph

/

11

RHgCl

-HgMe

= 1

R = Me,Ph

(triphos)Co

12

X-ray s t r u c t u r e a n a l y s e s r e v e a l t h a t i n XX [12] t h e

c o o r d i n a t e d PP bond i s l e n g t h e n e d t o 2.30/2.31(2) A; t h e same h o l d s f o r 12(2.293(8) A) [ 1 3 ] .

2.3. E⁴ Ligands (E = P,As)

I n a d d i t i o n t o [Cp* (CO) ²N b ( r j⁴- E⁴) ] (X2&: E=P [ 1 4 ] , E=As [15]) XA, t h e t a n t a l u m analogue, c a n be s y t h e s i z e d p h o t o c h e m i c a l l y a c c o r d i n g t o e q u a t i o n (2) [ 1 6 ] :

[Cp»»Ta(CO)⁴]

- CO

Cp" = r ?⁵- l^/3 - t B u²C⁵H³

The X - r a y d a t a o f 11 (d(P-P) = 2.17 A, 2J£'- 2.16 A [14]) and 13a a r e n e a r l y t h e same. 2A a l s o shows a s l i g h t d i s t o r t i o n o f t h e p l a n a r P⁴ base t o a k i t e shape [ 1 6 ] . The Wade-Mingos

e l e c t r o n c o u n t i n g r u l e s [17] f o r t h e P⁴T a t e t r a g o n a l p y r a m i d i n XA l e a d t o t h e n e c e s s a r y number o f SEP (n+2 = 7 S k e l e t a l E l e c t r o n P a i r s ) f o r t h e n i d o s t r u c t u r e .

C y c l o - P⁴ as 12e donor l i g a n d ( f o u r t i m e s W ( C O )⁵- t e r m i n a l c o o r d i n a t i o n ) has been s t a b i l i z e d i n complex 15_ (d(P-P = 2.15 A) w h i c h was made from P⁴ and [ W ( C O )⁵( t h f ) ] [ 1 8 ] .

P⁴,RT

[ w ( c o )⁵( t h f ) ] [ ( o c )⁴w ( P⁴) < w ( c o )⁵>⁴] 11

T i g h t - b i n d i n g band e l e c t r o n i c s t r u c t u r e c a l c u l a t i o n s on a p r o t o t y p e s k u t t e r u d i t e L a F e⁴P^{1 2} were p e r f o r m e d i n o r d e r t o g a i n i n s i g h t i n t o t h e e l e c t r o n i c p r o p e r t i e s o f b i n a r y ( i . e .

C o A s³) and t e r n a r y s k u t t e r u d i t e compounds. The m a j o r

c o n t r i b u t i o n t o t h e h i g h e s t o c c u p i e d band o f L a F e⁴P^{1 2} comes

from t h e o r b i t a l s o f t h e P⁴ r i n g s t h a t form t h e phosphorus s u b l a t t i c e [ 1 9 ] .

2.4. E⁵ Ligands (E = P,As)

The f i r s t mixed c a r b o n y l ( p e n t a p h o s p h a c y c l o p e n t a d i e n y l ) - m e t a l complex jy6_ (and f u r t h e r examples) was o b t a i n e d by t h e

f o l l o w i n g m e t a t h e t i c r e a c t i o n [ 2 0 ] : DMF, 155°C

KP⁵ + [Mn(C0)⁵Br] ^ [<r>⁵-P⁵)Mn<CO)³] - KBr, - 2CO

i f

S t a r t i n g w i t h t h e sandwich complexes [ C p * F e ( r /⁵- E⁵) ] , E = P,As; Cp* ⁼ r j⁵- C⁵M e⁵, and [ (OC) ³Mo(NCMe) ³] t h e 30 v a l e n c e e l e c t r o n " t r i p l e d e c k e r s " XI and X§. ( F i g . 2) have been r e a l i z e d i n a s t a c k i n g r e a c t i o n [ 2 1 ] .

17 18 F i g . 2

I t i s w o r t h w h i l e t o m e n t i o n t h a t i n b o t h d i n u c l e a r complexes d(Fe...Mo) i s 3.44 A (12: d(P-P) = 2.13 A, JJL: d(As-As) =

2.35 A) [ 2 1 ] ; f o r t r i p l e d e c k e r s w i t h s h o r t e r m e t a l - m e t a l bonds, s e e r e f e r e n c e [ 1 ] ) .

2.5. Eg Ligands (E = P,As)

I n t h e t r i p l e - d e c k e r s a n d w i c h complex 1£ w i t h a r a t h e r d i s t o r t e d c y c l o - P⁶ l i g a n d [1] f u r t h e r t e r m i n a l c o o r d i n a t i o n t o a phosphorus l o n e p a i r h a s been a c h i e v e d f o r t h e f i r s t t i m e [ 1 6 ] .

[M(CO)⁵(thf)]

[<Cp"Nb)²(M,n^{3 : 3}-P⁶>] [(Cp»Nb)²(P⁶){M(CO)⁵>]

19 20 Cp" = 7 )⁵- l , 3 - t B u²C⁵H³ M = Cr,W

From t h e c l a s s i c a l ( C H )⁶~ v a l e n c e i s o m e r s A-E o f benzene i n t a c t o r open-edged E ⁶ a n a l o g u e s , E = P,As, have been s t a b i l i z e d i n t h e c o o r d i n a t i o n s p h e r e o f t r a n s i t i o n m e t a l complex f r a g m e n t s .

D E

Scheme 1

The c o t h e r m o l y s e s o f [ C p²" T h (rj *-C⁴H^g) ] w i t h P⁴ and

[ C p * C o ( C O )²] w i t h A s⁴ g i v e t h e d i - and t r i n u c l e a r complexes 11 [ 1 1 ] / 2g [22] and 2JL [22] ( F i g . 3).

F i g . 3.©sCBut

I n [Cp"²Th(M,»?^{3 : 3}-P⁶)ThCp^{, , 2}] (1£ [ 1 1 ] , Cp"=»?⁵-l^f 3 - t B u²C⁵H³) t h e b i c y c l i c P⁶ l i g a n d c a n be f o r m a l l y r e g a r d e d a s P^{6 4}~ and d e r i v e d from P⁶ b e n z v a l e n e ( c f . C_, Scheme 1) . The open-edged A s⁶ Dewar benzene ( c f . Scheme 1) has been c o o r d i n a t i v e l y

s t a b i l i z e d i n [ C p *²C o²( A s⁶) ] (2£) [ 2 2 ] . I t s As-As d i s t a n c e s v a r y from 2.33 (?r-bond c o o r d i n a t i o n ) t o 2.44 (average) and 2.59 A (7r-and a-bond c o o r d i n a t i o n ) [ 2 2 ] . B e s i d e [Cp*Co(ji-

77^{2 : 2}A s²) ] ² (22) [22] one c a n a l s o i s o l a t e [ C p *³C o³ ( A s²) ³ ] (21,

Cp =r7³-C⁵Me⁵) , whose C o³A s⁶ framework c o n s i s t s o f t h r e e Cp*CoAs² u n i t s f o r m a l l y f o r m i n g a s t r o n g l y d i s t o r t e d Cp*Co capped A s⁶ p r i s m a n e w i t h As-As bond l e n g t h s between 2.29 and 3.05 A [ 2 2 ] .

The m o l e c u l a r d y n a m i c s / d e n s i t y f u n c t i o n a l (MD/DF)

a p p r o a c h [23] shows t h a t t h e most s t a b l e P⁶ i s o m e r s a r e t h e b e n z v a l e n e and p r i s m a n e s t r u c t u r e t y p e [ 2 3 ] .

2.6. E⁸ Ligands (E = P,As)

C o n t r a r y t o t h e many E ⁶ i s o m e r s o n l y two complexes w i t h an EQ l i g a n d have been s y n t h e s i z e d so f a r .

F G

Scheme 2

On t h e one hand, t h e p h o t o l y s i s o f a P⁴/ [ C p • F e ( C O )²]² -

t o l u e n e s o l u t i o n a f f o r d s [ C p '⁴F e⁴( C O )⁶( P⁸) ]( 2 2 ) [ 2 4 ] , whose Pg cage c a n be f o r m a l l y d e r i v e d from t h e open-edged ( C H )⁸

i s o m e r cuneane [24] (see G i n Scheme 2 ) .

Cp*(OC)Fe Cp"(OC)²Fe

Cp» = »)⁵-c⁵H⁴Me

Fe(CO)²Cp*

P - Fe(CO)Cp»

23 [24]

Cp" = ?)⁵-l,3-tBU²C⁵H

X - r a y c r y s t a l l o g r a p h i c a l l y P-P d i s t a n c e s from 2.185(4) t o 2.254(4) A have been f o u n d f o r gl [24]

On t h e o t h e r hand, i n [ (Cp"Nb) ² (JLI, r j^{4 : 4}- A s⁸) ] (2A) [ 2 5 ] ,

s y n t h e s i z e d from [Cp"Nb(CO)⁴] and A s⁴ i n d e c a l i n (170°C,2h), t h e A S Q a n a l o g u e o f c y c l o o c t a t e t r a e n e ( s e e F_ i n Scheme 2) has been c o o r d i n a t i v e l y s t a b i l i z e d as a p u c k e r e d , s t r o n g l y

d i s t o r t e d eight-membered r i n g , whose As-As bond l e n g t h s v a r y between 2.355(3) and 2.530(3) A [ 2 5 ] .

T h e o r e t i c a l s t u d i e s [23] have shown t h a t , c o n t r a r y t o

w i d e s p r e a d b e l i e f , t h e most s t a b l e i s o m e r o f P^Q i s n o t c u b i c , b u t t h e "wedge" o r " c r a d l e " s t r u c t u r e ("cuneane") f o u n d as a s t r u c t u r a l m o t i f i n H i t t o r f p h o s p h o r u s .

2.7. E^{1 0} Ligands (E = P,As)

Up t o now t h e l a r g e s t Eⁿ u n i t s t h a t have been

c o o r d i n a t e d t o t r a n s i t i o n - m e t a l complex f r a g m e n t s a r e P^{1 Q} and

A s1 0 *

Scheme 3

Whereas P^{1 0}' s y n t h e s i z e d by c o t h e r m o l y s i s o f [ C p C r ( C O )³]²,

Cp=n⁵-C⁵H⁵, and P⁴, i n t h e p a r a m a g n e t i c complex 2 ^ [26] forms a p o l y c y c l i c C r ⁵P ^{1 0} s k e l e t o n ( c f . B a u d l e r ' s p o l y c l i c

phosphanes [4]) E ^{1 0} (E = P, As) can be f o r m a l l y d e r i v e d from ( C H )^{1 Q} d i h y d r o f u l v a l e n e (see Scheme 3 ) . Treatment o f

[Cp"Rh(CO)²] w i t h E⁴ a t e l e v a t e d t e m p e r a t u r e a f f o r d s t h e t e t r a n u c l e a r complexes 2_6_ (a.: M = P, b_: M = As) [ 2 7 ] .

M P M

25 [26]

X - r a y s t r u c t u r e a n a l y s e s show t h a t i n 2_5_ t h e mean v a l u e o f t h e P-P d i s t a n c e s i s 2.22 A [ 2 6 ] . F o r 26a P-P-bond l e n g t h s between 2.14 and 2.19 A a r e f o u n d . I t i s o f i n t e r e s t t o n o t e t h a t i n 26a and 26b ( i t s X - r a y s t r u c t u r e i s u n t i l now o f l o w q u a l i t y ) t h e E-E bond a t t h e "end" o f b o t h five-membered

r i n g s adds o x i d a t i v e l y (d(P...P)=2.62 A) [27] w i t h f o r m a t i o n o f d⁶ rhodium.

Acknowledgement. We t h a n k t h e Deutsche F o r s c h u n g s g e m e i n s c h a f t and t h e Fonds d e r Chemischen I n d u s t r i e f o r f i n a n c i a l s u p p o r t as w e l l a s J o h n s o n M a t t h e y f o r a generous l o a n o f R h C l³.

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