Nitrido Complexes of the Platinum Group Metals - Advances in

5

Nitrido Complexes of the Platinum

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G r o u p Metals M. J. CLEARE and F. M. LEVER Johnson, Matthey & Co., Ltd., Research Laboratories, Wembley, Middlesex, England W. P. GRIFFITH Inorganic Research Laboratories, Imperial College of Science & Technology, London, S.W. 7, England

A new class of binuclear nitrido complexes of tetravalent osmium and ruthenium is described in which the metal atoms are symmetrically bridged by a nitride ligand to give a linear M—N—M unit. They have the stoichiometries [MNX(HO)] and [MN(NH)Y] (M = Os, Ru; X = Cl, Br; Y = Cl, Br, etc.). Studies are reported on their vibrational spectra, structures, and bonding. Preliminary studies are reported also on trinuclear complexes of osmium and iridium. Finally, the use of vibrational spectroscopy in the study of metal-nitrido and metal—oxo complexes i discussed briefly. 3-

2

8

1

2

3+

2

2

38

2

3

'"J" he nitride ion, N ", is a strong 7r-donor ligand and, as such, one expects tofindit complexed with a metal in a relatively high oxidation state, similar to oxide andfluoridein their complexes. Of the six platinum group metals, nitrido complexes are known at present only for osmium, ruthenium, and iridium. These are shown in Table I. The terminal complexes of osmium have been known for many years, and we intend in this paper to discuss them only briefly, concentrating in more detail on the binuclear species of osmium and ruthenium, which we have been studying recently. The trinuclear complexes of iridium and osmium are discussed in the light of recent spectroscopic data. A heterometallic species, (PEt Ph) Cl ReNPtCl (PEt3), with a nitrogen bridge between a platinum and a rhenium atom has been described recently by Chart and Heaton (2), but will not be discussed here. A

2

2

2

54 In Platinum Group Metals and Compounds; Rao, U.; Advances in Chemistry; American Chemical Society: Washington, DC, 1971.

3

5.

C L E A R E

E T

Nitrido

A L .

55

Complexes

Terminal Osmium Nitrido Complexes T h e s e c o m p o u n d s h a v e b e e n k n o w n for m a n y years a n d the p r e p a r a t i v e m e t h o d s are i n d i c a t e d i n T a b l e I I . P o t a s s i u m o s m i a m a t e , K [ O s ( V I I I ) 0 N ] , is p r e p a r e d b y the a d d i t i o n 3

of aqueous a m m o n i a to a s o l u t i o n of o s m i u m tetroxide, O s 0 , i n c a u s t i c 4

potash solution (6).


Table I.

X - r a y studies s h o w t h e m o l e c u l e to b e b a s i c a l l y

N i t r i d o Complexes of the Platinum Metals Osmium

Terminal

Os(VIII) [Os0 N]Os(VI) [ O s N X ] - [ O s N X H 0 ] (X = Cl,Br,CN,l/2 X ) 3

5

2

5

4

2

0

Bridging

Os(IV) [ O s N X ( H 0 ) ] - ( X = Cl,Br) [Os N(NH )8X ] (X = Cl,Br,I,NCS,N ,N0 ) 2

8

2

2

3

2

3

2

3 +

3

Trinuclear

3

Os N 0 H i 3

7

9

2

Ruthenium Bridging only

[Ru(IV),N X (H 0) ] -(X = Cl,Br,NCS) [Ru(IV) N(N0 ) (OH) (H 0) ] " [ R u ( I V ) N ( N H ) X ] + ( X = Cl,Br,NOa) [ R u ( I V ) N ( N H ) (H O) X ] ( X = C1,NCS,N ) 8

2

2

2

2

3

2

3

2

6

2

8

3

2

2

3

3

2

6

a

3

2 +

3

Iridium Trinuclear only:

[Ι^Ν^Ο,ΜΗ,Ο);,] [Ir N(S0 ) (OH) ] [Ir N C1 (H 0) ] " 4

3

4

3

6

3

1 2

Table II.

2

3

7

4

Terminal Osmium N i t r i d o Complexes Os(VIII)

Os0

4

+

O H

9

+

N H -> [ O s 0 N ] " + 3

3

2H 0 2

P o t a s s i u m o s m i a m a t e forms pale y e l l o w c r y s t a l s . Molecular structure : distorted tetrahedral ν Os = Ν 1021 c m - . 1

Os(VI) [Os0 N]- + Χ " + 3

6 H X -> [Os Ν X ] - + X 2

5

(X =

2

+

3H 0 2

Cl,Br)

T h e s e complexes t e n d t o lose t h e l i g a n d t r a n s t o the n i t r i d e t o give (Os N X H 0 ) ~ ( X = B r , C N , y ox) i n aqueous s o l u t i o n ; ν O s = N ~ 1080 cm . 4

2

2

- 1

M o l e c u l a r s t r u c t u r e : d i s t o r t e d o c t a h e d r a l ( C ) w i t h the o s m i u m a t o m s l i g h t l y o u t of the X p l a n e t o w a r d s t h e n i t r i d e (in the case of [ O s N C l ] ) . 4r

4

In Platinum Group Metals and Compounds; Rao, U.; Advances in Chemistry; American Chemical Society: Washington, DC, 1971.

5

3 -

56

P L A T I N U M

G R O U P

M E T A L S

t e t r a h e d r a l , a l t h o u g h s o m e w h a t d i s t o r t e d (12). frequency

1

(X =

complexes

of t y p e

1 5

N substitution

[ O s ( V I ) N X ] - or 5

C O M P O U N D S

T h e Os==N s t r e t c h i n g

is at 1021 c m " , w h i c h shifts to 993 o n

Os(VI)

A N D

(16).

[Os(VI)NX4H 0]"

2

2

C l , B r , C N , ôx) are m a d e b y t h e a c t i o n of t h e a p p r o p r i a t e a c i d

H X o n p o t a s s i u m o s m i a m a t e (6, 11).

T h e t e n d e n c y to lose the l i g a n d

trans to t h e n i t r i d e a n d to substitute a w a t e r m o l e c u l e is s o m e e v i d e n c e of a trans l a b i l i z i n g effect of n~donor l i g a n d s . X - r a y studies s h o w a d i s t o r t e d o c t a h e d r a l s t r u c t u r e w i t h the o s m i u m a t o m s l i g h t l y out of the Downloaded by UNIV OF SOUTHERN CALIFORNIA on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0098.ch005

p l a n e of t h e e q u a t o r i a l X atoms t o w a r d s the n i t r i d e ( I ) . stretching

frequency

is a r o u n d 1080 c m "

T h e Os==N

i n s u c h complexes.

(11)

1

Binuclear Nitrides of Osmium and Ruthenium I n g e n e r a l , t h e r e is a s i m i l a r r a n g e of complexes

for each metal,

b o t h b e i n g i n t h e o x i d a t i o n state ( I V ) . Anionic Complexes.

T h e p r e p a r a t i o n of these c o m p o u n d s

is i n d i

c a t e d i n T a b l e I I I . T h e p r o d u c t of t h e r e a c t i o n of ( N H ) [ O s C l ] w i t h 4

2

6

c h l o r i n e gas at 4 0 0 ° C w i l l dissolve i n d i l u t e h y d r o c h l o r i c a c i d ; f r o m this Table III.

Binuclear Osmium and Ruthenium N i t r i d o Complexes Anionic

Complexes

Cli

(NH ) 4

2

[Os CI,]

+ [Os NCl (H 0) ] 400°C then H C 1 2

8

2

3

2

[Ru N C1 (H 0) ] 2

8

2

2

3

[RuN(OH) · nH 0] 6

NH

3

2

Aq./OHQ

[Ru0 ] 4

2

HBr [Ru N(OH) 2

6

5

2

2

[Ru N(OH) · n H 0 2

[Ru N Br (H 0) ] -

· nH 0]

2

8

2

3

2

HC1 + [Ru N C1 (H 0) ] 2

8

2

3

2

NC93 Ν0 θ 2

[Ru N(N0 ) (OH) (H 0) ] 2

2

6

2

2

2

3


5.

C L E A R E

E T

ΝUndo

A L .

57

Complexes

s o l u t i o n , salts of the t y p e M ( I ) [ O s ( I V ) 2 N C l ( H 0 ) 2 ] 3

tated ( 5 ) .

8

can be p r e c i p i

2

T h e analogous r u t h e n i u m complexes

m a y be prepared

by

r e a c t i o n of K [ R u ( N O ) C l ] w i t h stannous c h l o r i d e i n h y d r o c h l o r i c a c i d 2

solution (4).

5

O t h e r p r o d u c t s are f o r m e d i n this r e a c t i o n , i n p a r t i c u l a r a

n i t r o s y l c o m p l e x c o n t a i n i n g c o o r d i n a t e d S n C l " , w h i c h is s t i l l u n d e r i n 3

vestigation. A d d i t i o n of a l k a l i to a n aqueous s o l u t i o n of [ R u ( I V ) N C l ( H 0 ) ] ~ 2

y i e l d s a b r o w n gelatinous p r e c i p i t a t e of R u N ( O H ) 2

8

2

2

· n H 0 which will

5

2

redissolve i n h y d r o c h l o r i c a c i d to regenerate the o r i g i n a l c o m p l e x . Downloaded by UNIV OF SOUTHERN CALIFORNIA on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0098.ch005

3

h y d r o x y species m a y b e p r e p a r e d d i r e c t l y b y the a c t i o n of

This

formaldehyde

w i t h K [ R u ( N O ) C l ] i n a l k a l i n e s o l u t i o n , or b y r e a c t i o n of p o t a s s i u m 2

5

r u t h e n a t e , K [ R u 0 ] w i t h excess aqueous a m m o n i a . H y d r o b r o m i c a c i d 2

4

o n t h e h y d r o x y c o m p l e x y i e l d s [ R u N B r ( H 0 ) ] ~ , w h i l e the a c t i o n of 2

8

2

3

2

excess t h i o c y a n a t e o n a h y d r o c h l o r i c a c i d s o l u t i o n of the h y d r o x i d e gives [Ru N(NCS) (H 0) ] ". 2

8

2

P o t a s s i u m n i t r i t e reacts w i t h a n aqueous s o l u

3

2

t i o n of [ R u N C l ( H 0 ) ] - t o give [ R u N ( N 0 ) ( O H ) ( H 0 ) ] - . 2

8

2

3

2

2

2

6

2

2

f r a r e d s p e c t r a i n d i c a t e that b o t h of t h e l a t t e r l i g a n d s ( N 0

In

3

2

and N C S )

2

are N - b o n d e d to the m e t a l ( 5 ) . M o l a r conductances of these a n i o n i c complexes i n aqueous s o l u t i o n are i n i t i a l l y close to the values e x p e c t e d for 3:1 electrolytes, b u t o n l o n g s t a n d i n g or o n h e a t i n g t h e conductances increase g r e a t l y , a n d there is a p a r a l l e l decrease i n the p H of t h e s o l u t i o n . W e assume t h a t this results f r o m r e p l a c e m e n t of the h a l o l i g a n d s b y a q u o groups a n d loss of a p r o t o n f r o m the w a t e r l i g a n d s . T h e effect is less m a r k e d for the o s m i u m c o m plexes t h a n for r u t h e n i u m , p r e s u m a b l y because of the greater inertness of t h i r d - r o w elements t o w a r d s s u b s t i t u t i o n ( 5 ) . C a t i o n i c C o m p l e x e s . O n e series of a m m i n e complexes has b e e n f o u n d for o s m i u m ( [ O s N ( N H ) V ] 2

X ] 2

3 +

and

3

8

2

3 +

) a n d two for r u t h e n i u m ( [ R u N ( N H ) 2

[Ru N(NH ) (H 0)X ] 2

3

6

2

3

2 +

).

3

T h e preparative methods

8

are

indicated i n Table I V . R e a c t i o n of s o d i u m chloroosmate

Na [OsCl ] 2

w i t h aqueous

6

am

m o n i a at ~ 1 0 0 ° C i n a C a r i u s t u b e y i e l d s [ O s N ( N H ) C l ] C l . A n o t h e r 2

3

8

2

3

m e t h o d is the r e a c t i o n of a m m o n i a w i t h K [ O s N C l ( H 0 ) ] . T h e p r o d 3

2

u c t w i l l react w i t h excess X " i o n to g i v e

8

2

2

[Os N(NH ) X ]X 2

3

8

2

(X

3

=

B r " , I " , N C S " , N " , N 0 " ) after short r e f l u x i n g i n aqueous s o l u t i o n . Salts of 3

3

the f o r m [ O s N ( N H ) X ] Y m a y b e p r e p a r e d m e t a t h e t i c a l l y w i t h Y " i o n 2

3

8

2

3

i n the c o l d , suggesting t h a t o n l y t w o of the five X groups are c o o r d i n a t e d . T h e r e a c t i o n of aqueous a m m o n i a o n K [ R u N X ( H 0 ) ] gives a 3

m i x t u r e of Cl,Br).

[Ru N(NH ) X ]X 2

3

8

2

3

2

8

2

2

and [ R u N ( N H ) ( H 0 ) X ] X 2

3

6

2

3

(X

2

T h e f o r m e r y i e l d s species of the f o r m [ R u N ( N H ) X ] Y 2

metathesis i n the c o l d w i t h Y " i o n ( Y =

3

8

2

3

— on

B r , I , N C S , N , N 0 " ) , while boiling 3

3

w i t h a n excess of c e r t a i n l i g a n d s results i n a m m i n e r e p l a c e m e n t c o n v e r s i o n to a h e x a m m i n e species—i.e., [ R u N ( N H ) ( H 0 ) Y ] Y 2

3

6

2


3

and 2

(Y

58

P L A T I N U M

Table IV.

M E T A L S

A N D

C O M P O U N D S

Binuclear Osmium and Ruthenium Nitrido Complexes Cationic NH

[Os X ] " 6

Aq.

3

2

NH 2

Complexes

> [Os N(NH ) X J X 100°C,Carius (X = Cl,Br) tube

2

[Os NCl (H 0) ] Downloaded by UNIV OF SOUTHERN CALIFORNIA on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0098.ch005

G R O U P

8

2

[Os N(NH ) 2

3

3

2

2

8

3

Aq.

3

> [Os N(NH ) 100°C, C a r i u s tube

Cl ] +

8

3

3

2

3

Excess X ~ > [Os N(NH ) Reflux i n a q . soin 2

3

C1 ]C1

8

2

3

X ] +

8

2

3

(X = Br,I,NCS,N ,N0 ) 3

[Ru N(NH ) 2

NH [Ru N 2

3

3

3

C1 ]C1

8

2

2

Aq.

X (H 0) ] ~ 8

2

2

3

Heat [Ru N(NH ) (H 0)Cl ]Cl 2

Figure

1.

Structure

of the anion in

3

6

2

3

2

K [Ru NCl (HgO) ] 3

2

8

2

= N " , N C S " , N 0 " ) . I t appears t h a t other ligands—e.g., N 0 " — w i l l l e a v e t h e c o m p o u n d as a n o c t a m m i n e . Species of t h e t y p e [ R u N ( N H ) ( H 0 ) Y ] Z m a y b e m a d e b y metathesis w i t h Z " i n t h e c o l d ( Z = C 1 , I ) . 3

2

3

2

2

3

2


3

6

5.

C L E A R E

E T

Nitrido

A L .

59

Complexes

M o l a r c o n d u c t a n c e s for the o s m i u m a n d r u t h e n i u m o c t a m m i n e s i n aqueous s o l u t i o n w e r e close to the values e x p e c t e d f o r 3:1 (.—360 m h o s c m )

electrolytes

b u t rose o n s t a n d i n g or h e a t i n g to g i v e final values

2

nearer that e x p e c t e d for a 5:1 electrolyte ( ^ 6 0 0 m h o s c m ) .

T h i s is p r e

2

s u m a b l y because of trans a q u a t i o n ; the effect w a s a g a i n less m a r k e d for o s m i u m . S i g n i f i c a n t l y , a l l the h a l o g e n i n the h a l o species [ R u N ( N H ) 2

3

Χ 2 ] Χ δ c o u l d be p r e c i p i t a t e d w i t h silver n i t r a t e f r o m h e a t e d

8

solutions.

C o n d u c t i v i t i e s for the h e x a m m i n e s also v a r i e d s o m e w h a t w i t h t i m e , b u t Downloaded by UNIV OF SOUTHERN CALIFORNIA on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0098.ch005

i n i t i a l values w e r e l o w e r t h a n for the o c t a m m i n e s presence of a 2:1 electrolyte (240 m h o s c m )

and indicated

the

(5)

2

A n x-ray s t r u c t u r a l d e t e r m i n a t i o n has b e e n c a r r i e d out

Structure.

on K [ R u 2 N C l ( H 0 ) 2 ] 3

8

(3)

2

a n d the results are d e p i c t e d i n F i g u r e 1.

T h e a n i o n has a l i n e a r skeleton w i t h the e i g h t e q u a t o r i a l c h l o r i n e atoms e c l i p s e d so that the o v e r - a l l i d e a l i z e d s y m m e t r y of the a n i o n is D .

Each

4h

r u t h e n i u m a t o m is d i s p l a c e d 0.19 A out of the C l n i t r o g e n atom.

4

plane toward

the

S u c h a d i s p l a c e m e n t of m e t a l atoms t o w a r d s a 7r-donor

l i g a n d has b e e n o b s e r v e d i n other complexes, s u c h as K [ R e O C l i ] 4

2

(18)

0

a n d (PhÂs) [ M o O B r H 0 ] ( 7 ) , as w e l l as K [ O s N C l ] ( I ) , w h i c h has 4

2

2

5

b e e n m e n t i o n e d p r e v i o u s l y . I t has b e e n suggested that this arises m a i n l y f r o m the r e p u l s i o n b e t w e e n the n i t r o g e n a n d c h l o r i n e l i g a n d s w i t h i n t h e molecule. S p e c t r a of

Vibrational Spectra.

t y p i c a l complexes are l i s t e d i n

T a b l e s V a n d V I . T h e c o m p o u n d s e x h i b i t s i m i l a r spectra,

suggesting

that t h e y a l l h a v e the same b a s i c structure. T h e m a i n features a r e : ( a ) T h e presence of a strong sharp b a n d i n the i n f r a r e d i n the r a n g e 1 0 5 0 - 1 1 3 0 c m " , not o b s e r v e d i n t h e R a m a n . T h i s b a n d is l i t t l e c h a n g e d i n f r e q u e n c y o n d e u t e r i a t i o n , b u t shifts d o w n w a r d b y s o m e 30 c m " o n 1

1

Table V .

Vibrational Spectra of Bridging Nitrido Complexes—Anionic Species

(M NX (H 0) y2

s

K (Os N 3

2

VM N

2

2

C1 (H 0) )

2

8

2

R

2

aS

—

2

8

267(10)

J315(4) /295(2) 303s b r

185w

329(4)

J301(10) (294(4)

200w

I R 1137 v s ° I R 1135 v s K (Ru N 3

C1 (H 0) )

2

8

2

R

2

—

R — I R 1078 v s a

a

K (Ru 3

a

2

1 5

N

C1 (H 0) ) 8

2

2

%X-M-X

V MN

330(4)p (315s /289m

I R 1080 v s I R 1046 vs

—

{315s /289m

Indicates aqueous solution measurement.


60

P L A T I N U M

Table V I .

3 s

2

3

2

(Os N(ND ) C1 )C1 2

3

2

8

8

3

(Ru N(NH ) C1 )C1 2


2

3

3

2

8

a

R — I R 1104 v s

299(10)

2

3

2

8

3

C O M P O U N D S

R — I R 1101 v s

286(10)

455w 465w

267(1) 260s b r

286(3) 282m

430w 440w

254(1) 240s b r

278m 281m

J496(3) 1475(1) 465w

265w b r

280w

258m br

2 8 0 m sh

440vw 430w

250(1) 245s b r

273w 2 7 7 m sh

— — 354(1)

R

—

IR

1055

—

R — I R 1054 v s

339(10)

3

(Ru N(ND ) C1 )C1

A N D

%M—NH

VM-NH

VM N *

2

(Os N(NH ) C1 )C1

M E T A L S

Vibrational Spectra of Bridging N i t r i d o Complexes—Cationic Species

(M N(NH ) X y+ 2

GROUP

—

Figure 2. Bonding in Ο—Ru and Ru—Ν—Ru tems

Ru— sys

Diagram shows 4 d « - 2 p - 4 c L overlap. There will be a sim ilar 4 d x y - 2 p y - 4 d x y ΟΌβ^Ρ ΰ ί right angles to the plane of the paper. e

B

—

-4d =4d

x

z

y 2

EMPTY PAIRED METAL ELECTRONS PAIRED LIGAND ELECTRONS

•U

Figure

3.

Bonding

in bridging

nitride

complexes

The M.O. diagram indicates the formation of two sets of 3-center molecular orbitals with the metal d electrons paired in the nonbonding orbitals

N substitution i n [ O s N ( N H ) B r ] B r and K [ R u NCl (H 0) ]. T h i s b a n d w e h a v e assigned to v M N> the a s y m m e t r i c M — Ν — M stretch. T h i s m o d e consists almost e n t i r e l y of n i t r o g e n m o v e m e n t a n d is expected to o c c u r i n the same r e g i o n as t h e t e r m i n a l m e t a l n i t r i d e stretches. ( b ) T h e presence of a s t r o n g , s h a r p , p o l a r i z e d R a m a n b a n d near 350 c m " f o r the r u t h e n i u m complexes a n d 280 c m " for the o s m i u m c o m 1 5

2

1 5

1 5

3

as

1

8

2

3

3

2

1 5

8

2

1


2

2

5.

C L E A R E

E T

Nitrido

A L .

61

Complexes

plexes, w h i c h w e assign to t h e s y m m e t r i c M — Ν — M s t r e t c h , V M N - T h e s e bands are n o t o b s e r v e d i n t h e i n f r a r e d spectra. T h e y shift d o w n w a r d some 13 c m " o n d e u t e r i a t i o n of t h e a m m i n e complexes, b u t this is l i k e l y to b e c a u s e d b y strong c o u p l i n g of V N ( a totally symmetric m o d e ) w i t h the s y m m e t r i c m e t a l a m m i n e stretches a n d deformations h a v i n g t h e same s y m m e t r y species (A ), together w i t h a slight effect a r i s i n g f r o m t h e greater mass of d e u t e r i u m . H e r e t h e m o d e consists m a i n l y of m e t a l m o v e m e n t ; this is c l e a r l y s h o w n b y t h e effect of t h e extra mass of o s m i u m . T h e g e n e r a l l a c k of c o i n c i d e n c e b e t w e e n R a m a n a n d i n f r a r e d bands a n d , i n p a r t i c u l a r , t h e fact that t h e R a m a n - a c t i v e V M N a n d i n f r a r e d - a c t i v e v M N a r e i n a c t i v e i n the i n f r a r e d a n d R a m a n , respectively, strongly s u g gest t h e presence of a center of s y m m e t r y . T h u s , as i n [ R u N C l ( H 0 ) 2 ] ~ t h e a q u o groups l i e trans to the n i t r i d e g r o u p , i t is l i k e l y t h a t the X groups i n [ M N ( N H ) X ] w i l l b e p l a c e d s i m i l a r l y ( 5 ) . S

2

1

S

M

2

lg

S


as

2

2

2

8

3

2

2

3

8

2

3 +

E l e c t r o n i c S p e c t r a . A l l these complexes are d i a m a g n e t i c as a result of t h e 7r-bonding, w h i c h is s h o w n i n F i g u r e 2. O f t h e f o u r m e t a l d electrons o n e a c h r u t h e n i u m a t o m ( R u ( I V ) d ) , t w o {d ,d ) w i l l p a i r u p i n t h e n o n b o n d i n g m o l e c u l a r o r b i t a l of t h e set p r o d u c e d b y t h e 3-center o v e r l a p b e t w e e n t h e d a n d d orbitals o n e a c h m e t a l a t o m , a n d t h e 2p a n d 2p orbitals o n t h e n i t r i d e . T h e l o w e r energy n i t r i d e electrons w i l l p a i r i n the b o n d i n g m o l e c u l a r orbitals ( F i g ure 3 ) . T h e r e m a i n i n g t w o electrons p e r r u t h e n i u m a t o m are p a i r e d i n t h e 4 dy o r b i t a l w h i c h remains essentially n o n b o n d i n g . I t is a consequence of this b o n d i n g scheme that t h e M — Ν — M g r o u p s h o u l d b e l i n e a r a n d that t h e e q u a t o r i a l ligands s h o u l d b e i n t h e e c l i p s e d (D ) rather than the staggered ( D ) positions. 4

xy

xz

xy

y

xz

z

Z

4h

4 d

Figure

4.

Electronic

spectra of some bridging complexes

nitrido


62

P L A T I N U M

G R O U P

5 0 s 0 + 7NH (llq) I l ^ L ^ 4

M E T A L S

A N D

C O M P O U N D S

Os N 0 H |

3

3

7

9

2

ORIGINAL FORMULATION HN 3

\/

OH

HO

—Os

/\


IR. BANDS

HN

NH

\/

3

= O s = 0

/\

OH

2

OH

NH

3

AT 1087, 1025, 970cm SHIFT

1053,997, 935cm

NEW

Ν

/\

OH

3

HO

\/

0 = O s = N HN

OH

, 5

ON

N

TO

SUBSTITUTION

FORMULATION HO

OH

v

\/

H O — Os = H^N

Figure

H^l

\/

HOI

Ν — Os

\>H

5.

OH

\/

Ν =

N^^NH

3

Os

HO^

NH

3

OH ÔH

Trinuclear Os(VI) nitndo plex

com

T h e electronic spectra (350-190 τημ) of three of these complexes are s h o w n i n F i g u r e 4. Jorgensen a n d O r g e l (14)

h a v e suggested that s i m i l a r

bands observed i n K [ R u O C l i ] arise f r o m transitions f r o m the h a l o g e n 4

2

0

l i g a n d s to the a n t i b o n d i n g m o l e c u l a r o r b i t a l f r o m the 3-center b o n d . f o l l o w this assignment for the

[M NX Y2]

system, a l t h o u g h i t is n o t

8

2

We

s t r i c t l y isolectronic w i t h [ R u O X i ] " . T h e R u — O — R u a n d R u — N — R u 2

groupings

are, h o w e v e r ,

4

0

isolectronic.

The

energy

of t h e a n t i b o n d i n g

m o l e c u l a r o r b i t a l is d e t e r m i n e d l a r g e l y b y the extent of the R u — Ο — R u or R u — Ν — R u π-bonding.

T h e b a n d s are seen near 400 τημ for

O C l i o ] " a n d at 397 a n d 330 m ^ ^ ^ H ) [ O s O C l i o ] . 4

4

2

are h i g h e r i n energy (e.g., K [ O s N C l ( H 0 ) ] , 273 τημ; 3

( H 0 ) ] , 294 τημ), 2

2

2

8

2

[Ru 2

In nitride they

2

2

K [Ru NCl 3

2

8

i n d i c a t i n g that M - N ττ-bonding is stronger t h a n for

M - O i n these b i n u c l e a r systems.

Trinuclear Osmium Complex T h e final p r o d u c t of the r e a c t i o n of l i q u i d a m m o n i a w i t h O s 0 the e m p i r i c a l f o r m u l a O s N 0 H i (17,20). 3

r e d s p e c t r u m of the

15

7

9

2

4

has

W e h a v e s t u d i e d the i n f r a

N - s u b s t i t u t e d c o m p o u n d a n d p r o p o s e structure I I

( F i g u r e 5) rather t h a n structure I, w h i c h was suggested o r i g i n a l l y . B a n d s at 1087, 1025, a n d 970 c m " shift to 1053, 997, a n d 935 o n N - s u b s t i t u t i o n 1

15


5.

C L E A R E

E T

Nitrido

A L .

63

Complexes

a n d m a y b e assigned to O s — Ν — O s o r O s — Ν s t r e t c h i n g modes. T h e n e w f o r m u l a t i o n accounts f o r t h e o b s e r v a t i o n t h a t o n l y t w o molecules of a m m o n i a are released o n h e a t i n g w i t h a l k a l i , since t w o of the a m m i n e groups are i n a different e n v i r o n m e n t f r o m the other t w o (5), a n d thus p r e s u m a b l y h a v e different stabilities i n respect to m e t a l - n i t r o g e n b o n d strengths.

Trinuclear Iridium Complexes T h e reaction of ( N H ) [ I r C l ] w i t h b o i l i n g sulfuric acid yields a s o l u t i o n f r o m w h i c h green salts o f the f o r m M [ I r N ( S 0 ) e ( H 2 0 ) 3 ] c a n be p r e c i p i t a t e d ( 8 , J 5 ) . I t has b e e n suggested that t h e a n i o n has t h e structure s h o w n o n F i g u r e 6 w i t h a c o p l a n a r I r N u n i t a n d ττ-bonding b e t w e e n t h e 2 p o r b i t a l ( p e r p e n d i c u l a r to t h e I r N t r i a n g l e ) a n d t h e i r i d i u m atoms ( 1 3 , 19). T h e o x i d i z i n g p o w e r o f the species is consistent w i t h it's c o n t a i n i n g o n e I r ( I I I ) a n d t w o I r ( I V ) atoms p e r m o l e c u l e (8, 13). R e d u c t i o n w i t h v a n a d o u s i o n gives a s t r a w - y e l l o w species c o n t a i n i n g three I r ( I I I ) atoms p e r m o l e c u l e . X - r a y studies o n the s o m e w h a t s i m i l a r [ C r 3 0 ( C H C O O ) ( H 2 0 ) ] C l · 5 H 2 0 h a v e s h o w n that t h e C r O u n i t is p l a n a r w i t h a t r i a n g u l a r a r r a n g e m e n t of m e t a l atoms ( 9 ) .


4

3

6

4

3

4

3

z

3

3

6

3

s

m

Figure 6. Proposed struc ture for indium trinuclear nitrides The Ir N unit is believed to be coplanar with the iridium atoms at the corners of an equilateral triangle. A related structure has been found for [Cr 0(Aces

3

Table VII.

Trinuclear Iridium Nitrido Complexes H

S0

2

3(NH ) [Ir Cl ] 4

3

4

> (NH )4[Ir3N(S0 )6(H 0)3]

6

4

2

4

H 0 2

[Ir N(S0 ) (H 0) ] 3

4

6

2

4

3

[Ir N(S0 ) (H 0) ] ~ 3

4

6

2

3

KOH > K [Ir N(S0 ) (OH) ] Cold 7

3

4

Caustic alkali

6

Ir N(OH)

4

3

3

u

· nH 0 2

Boiling / HC1 + C s CI Cs [Ir NCl (H 0) ] 4

3

1 2

2

3


64

P L A T I N U M

G R O U P

M E T A L S

A N D

C O M P O U N D S

O t h e r reactions of [ I r a N i S O ^ e i H k O ^ ] " are s h o w n o n T a b l e V I I . 4

Cold

c a u s t i c a l k a l i e s react to r e p l a c e

the a q u o g r o u p s ,

giving

[Ir 3

N ( S 0 ) 6 ( O H ) ] " , w h i l e h o t a l k a l i appears to r e p l a c e t h e sulfate l i g a n d s 7

3

4

to g i v e

a hydroxy

precipitate w h i c h probably

Ir N(OH)u · nH 0. 3

m a y be

described

as

T h e I r N g r o u p is s t i l l i n t a c t as r e a c t i o n w i t h s u l -

2

3

f u r i c a c i d regenerates the o r i g i n a l c o m p l e x .

The hydroxy complex

dis-

solves i n H C 1 to g i v e a species w h i c h appears to b e [ I r N C l i ( H 0 ) ] ~ . 3

2

2

3

4

W e h a v e m e a s u r e d t h e i n f r a r e d s p e c t r a of these species c o n t a i n i n g


both

N and

1 4

N , a n d i n e a c h case a b a n d n e a r 780 c m " shifts d o w n w a r d

1 5

1

i n f r e q u e n c y b y some 20 c m "

1

on

to t h e a s y m m e t r i c I r N s t r e t c h . 3

1

5

N s u b s t i t u t i o n . W e assign this b a n d

T h e R a m a n s p e c t r a of the c o m p l e x e s

w e r e p o o r , o w i n g to t h e i r u n f a v o r a b l e colors, b u t w e a k b a n d s n e a r 230 cm"

m a y b e c a u s e d b y t h e s y m m e t r i c I r N stretch ( 5 ) .

1

3

s p l i t t i n g of the sulfate m o d e s is s i m i l a r to that o b s e r v e d ( S 0 ) ] (10), 4

S0

4

The

complex

in K i [ I r O 0

3

a n d p r e s u m a b l y arises f r o m the l o w site s y m m e t r y of the

9

groups w h i c h f u n c t i o n h e r e as b i d e n t a t e l i g a n d s .

Table VIII.

Vibrational Spectra of O x y and N i t r i d o Complexes X =

X = 0, cmr TERMINAL M-X 900-1060 300-400

VMX $mx

BRIDGING

N, cmr 1

1

950-1180 ca. 350

MmXn

Linear M - X - M V ¥

2

J

A

760-880 200-270

I

Linear VM x VM x 3

3

2

2

M - X - M - X - M

e

Triangular M v x* Mz

a

ca. 820 ca. 220

a e

3

1000-1160 260-370 ca. 1000

X 500-650 180-240

700-800 ca. 230

Comparison of the Vibrational Spectra of Oxy and Nitrido Complexes T a b l e V I I I shows the c h a r a c t e r i s t i c ranges of frequencies f o r s t r e t c h i n g a n d deformation modes for terminal a n d b r i d g i n g oxy a n d nitrido systems. I n e a c h case, t h e frequencies for the s t r e t c h i n g m o d e s are h i g h e r f o r n i t r i d e s t h a n f o r oxides. A l t h o u g h the n i t r o g e n a t o m is l i g h t e r t h a n o x y g e n , i t is l i k e l y t h a t this effect is c a u s e d i n l a r g e p a r t b y t h e f a c t t h a t


5. CLÉ ARE ET AL.

Nitrido Complexes

65


the nitride ligand is a more efficient ττ-donor than oxide—it is less electro negative and has more negative charge to impart to the metal atom (5).

Literature Cited (1) Bright, D., Ibers, J. Α., Inorg. Chem. 1969, 8, 709. (2) Chatt, J., Heaton, B. T., Chem. Commun. 1968, 274. (3) Ciechanowicz, M., Skapski, A.C.,Chem. Commun. 1969, 574. (4) Cleare, M. J., Griffith, W. P., Chem. Commun. 1968, 1302. (5) Cleare, M. J., Griffith, W. P.,J.Chem. Soc. 1970, A, 1117. (6) Clifford, A. F., Kobayashi, C. S., Inorg. Syn. 1960, 6, 204. (7) Cotton, F. Α., Lippard, S. J., Inorg. Chem. 1965, 4, 1621. (8) Delepine, M., Ann. Chim. (Paris) 1959, 1115, 1131. (9) Figgis, Β. N., Robertson, Ε. B., Nature 1965, 205, 695. (10) Griffith, W. P.,J.Chem. Soc. 1969, A, 2270. (11) Griffith, W. P.,J.Chem. Soc. 1965, 3694. (12) Jaeger, F. M., Zanstra, J. E., Proc. Acad. Sci. Amsterdam1932,35, 610 (13) Jorgensen, C. K., Acta Chem. Scand. 1959, 13, 196. (14) Jorgensen, C. K., Orgel, L. E., Mol. Phys. 1961, 4, 215. (15) Lecoq de Boisbaudran, Compt. Rend. 1883, 96, 1336, 1406, 1551. (16) Lewis, J., Wilkinson, G., J. Inorg. Nucl. Chem. 1958, 6, 12. (17) McCordie, W.C.,Watt, G. W., J. Inorg. Nucl. Chem. 1965, 27, 1130, 2013. (18) Morrow, J.C.,Acta Cryst. 1962, 15, 851. (19) Orgel, L. E., Nature 1960, 187, 505. (20) Potrafke, E. M., Watt, G. W., J. Inorg. Nucl. Chem. 1961, 17, 248. RECEIVED December 16, 1969.


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