Chemistry of low-valent osmium

http://researchspace.auckland.ac.nz ResearchSpace@Auckland

Copyright Statement

The digital copy of this thesis is protected by the Copyright Act 1994 (New Zealand).

This thesis may be consulted by you, provided you comply with the provisions of the Act and the following conditions of use:

• Any use you make of these documents or images must be for research or private study purposes only, and you may not make them available to any other person.

• Authors control the copyright of their thesis. You will recognise the author's right to be identified as the author of this thesis, and due acknowledgement will be made to the author where appropriate.

• You will obtain the author's permission before publishing any material from their thesis.

To request permissions please use the Feedback form on our webpage.

http://researchspace.auckland.ac.nz/feedback

General copyright and disclaimer

In addition to the above conditions, authors give their consent for the digital copy of their work to be used subject to the conditions specified on the Library Thesis Consent Form.

This study concerns t h e synthesis, s t r u c t u r e and r e a c t i v i t y of

6

8

complexes of d and d osmium. The r e a c t i v i t y of c e r t a i n ligands coordinated t o l o w v a l e n t osmium has a l s o been investigated,

Various hydride complexes of osmium(11) were prepared as p o t e n t i a l precursors of osmium(0). 0sH4(pph3) r e a c t s v i t h p-tolylisocyanide (TIC) and 4-ethyl-2,6,7-trioxa-I -phosphabicyclo[2,2.2]octane (ETPO) t o y i e l d 0sH2(L) ( P P ~ ~ ) from which were derived 0sH2

(L*)

(L) ( P P ~ ~ ) ~

(L, L*

=

CO, TIC, ETPo), Attempts t o eliminate hydrogen from t h e dihydri des failed. OSHC~(CO) ( P P ~ ~ ) ~ r e a c t s with n e u t r a l l i g a n d s L

(=

TICT ETPO, ~(0Me) 3, P ( O P ~ ) 3T P P ~ ~ M ~ ) t o give O S H C ~ (CO) (I) (PPh3) which, with s i l v e r perchlorate (L

=

TIC, ETPO only) afford

O S H ( C C ~ O ~ ) (CO) ( L ) ( P P ~ ~ ) ~ . The l a b i l e perchlorate ligand can be replaced by ligands L r affording

[OSH(CO)(L)(L*)(PP~~)~]C~O~ (I

= TIC, L* = CO, TIC, PPh3; L = ETPO, I* = CO, ETPO)

.

^. O S H C ~ (CO) ( P P ~ ~ ) r e a c t s with

s i l v e r perchlorate i n a c e t o n i t r i l e t o y i e l d [OSH(CO)

( c H ~ c N ) ~ ( P P ~ ~ ) ~ ] c ~ o ~

which i n t u r n r e a c t s with n e u t r a l ligands t o give [OSH(CO) ( C X ~ C N ) (L) ( P P ~ ~ ) ~ ] c ~ o ~ (L = COT TIC, ETPO, PPh3). Cationic [OSH(CO) (PPh3) 3]+ and [OSH (TIC) 2 ( ~ ~ h 3 ) 3]+

can

be prepared from t h e a c t i o n of PPh3 on

[osH(co)~(cH~cN)(PP~~)~]+

and T I C on O . S R ( O $ C ~ ~ ~ ) ( ~ ? h ~ ) ~ respectively.

With base, [OS~I(CO) ( C H ~ C N ) ( P P ~ ~ ) 3] ~ 1a f f o r d s 0 ~ OSH(OH) (CO) (PPh3)

from

which a series of hydroxide complexes O S H ( O H ) ( C O ) ( L ) ( P P ~ ~ ) ~ (I

=

CO, T I C T ETPO) can be obtained. The hydroxide group i n OSH(OH)(CO) ( P P ~ ~ ) ~ i s cleaved by acids

HX

t o y i e l d O S B X ( C O ) ( P P ~ ~ ) ~ ( X

=

F, B r , C1, I, CH3C02, CF3C02

SC7H7, 0 ~ 1 0 ~ ) . m o s e members of the s e r i e s with X = CN, N3, OCN, SCN

I w e r e obtained from OSH ( ~ 1 0 ~ ) (CO) ( P P ~ ~ )

and

t h e appropriate anion.

I

I

From t h e values of vCO f o r t h i s s e r i e s can be gained some understanding

I

of t h e bonding properties of t h e anionic ligands.

I

The n e u t r a l omium(0) complexes OS(CO) (TIC) ( P P ~ ~ ) ~ , Os(C0) 2 ( ~( P P ~ ~ ) ~ ~2, ~os(C0) ) 2 ( ~ ~ h 3 ) and OS(CO) (TIC) (PPh3) w e r e prepared by deprotonation of t h e corresponding c a t i o n s

[ o s ~ ( ~ o ) ,(TIC) (pph3),1+, [OSH(CO) (ETPo) ( P P ~ ~ ) 2]+, [OSH(CO) 2 ( ~ ~ h 3 )

1'

and [OSH(CO) (TIC) ( P P ~ ~ )

,I+.

Q i d a t i v e addition r e a c t i o n s of t h e s e

J

d m p l e x e s have

8

been investigated. Those of O S ( C O ) ~ ( T I C ) ( P P ~ ~ ) ~ and

OS(CO) 2 ( ~ T P ~ ) (PPh3) c l o s e l y p a r a l l e l t h e r e a c t i o n s

of

OS(CO) 3 ( ~ ~ h 3 ) 2 with various oxidants, P r o t i c , a c i d s regenerate t h e hydride c a t i o n s as t h e t r a n s isomers. Halogens and mercuric h a l i d e s a l s o produce c a t i o n i c products, Dioxygen gives t h e chelated carbonate complexes

O S ( C O ~ ) ( C O ) L ( P P ~ ~ ) ~

(I =

TIC,

EZPO),

Whereas non-coordinating a c i d s with 0 s (CO) ( P P ~ ~ ) and OS(CO) (TIC) (PPh3) regenerate t h e hydride cations, h y d m h d i c acids afford OSHX(CO) ( P P ~ ~ ) 3, [OSX(CO) (TIC) ( P P ~ ~ ) 3]+ ( X

=

C1,

~ r ) and 0s12(C0) (TIC) ( P P ~ ~ ) ~ . Halogens y i e l d O S ) ~ ? ( C O ) ~ ( P P ~ ~ ) ~ (X = C1,

I),

[OsBr (CO) ( P P ~ ~ ) 3]*, [OSX(CO) (TIC) ( P P ~ ~ )

3p

(X

=

C1, B r ) and

O S I ~ (CO) (TIC) ( P P ~ ~ ) ~ . Three _isomeric f o m s of 0s1, (CO) ( P P ~ ~ ) ~ were i s o l a t e d , I n a novel reaction, sulphonyl c h l o r i d e s r e a c t with all four complexes affording [ O S C ~ ( C O ) (L) (L*) ( P P ~ ~ ) ~ ] R S O ~ (I = CO, IT

=

TIC, PPh3,

OS(CO) 2 ( ~ ~ h 3 ) 3 and OS(CO) (TIC) ( P P ~ ~ ) undergo s u b s t i t u t i o n r e a c t i o n s

and

oxidatively add I$, C2H4 and CS2,

These

r e a c t i o n s appear t o

proceed

v A

d i s s o c i a t i o n of a l a b i l e phosphine t o form a t r a n s i e n t

1 6 e l e c t r o n species:

-

^a unique process i n osmiwn(0) chemistry, Adducts with PhC2H and PhC2Ph w e r e obtained only with O S ( C O ) ~ ( P P ~ ~ ) ~ , which

a l s o r e a c t s with dioxygen t o formthe first dioxygen adduct of osmium, 0s(02)

( c o ) ~ ( P P ~ ~ ) ~ .

This complex r e a c t s with SO2 and N204 t o give sulphate and d i n i t r a t e complexes of osmiwn(11),

To study t h e s u s c e p t i b i l i t y towards nucleophilic a t t a c k of

carbon

monoxide and TIC coordinated t o osmium(11) a s e r i e s of complex c a t i o n s

(iii)

w a s chosen. OSHC~(CO) (TIC) ( P P ~ ~ ) ~ r e a c t s with perchloric acid t o give O s ~ l ( 0 ~ 1 0 ~ ) (CO) (TIC) ( P P ~ ~ ) ~ , of which two isomeric fonns were isolated, With n e u t r a l ligands, t h e perchlorate group can be displaced t o give [ O s C l (CO) (TIC) (L) ( P P ~ ~ ) 2 ] ~ 1 0 4

(I =

CO, TIC).

[OsCl (CO) 2 ( ~ ~ ~ ) (PPh3) 2]+ r e a c t s with azide ions t o give

OsCl(NC0) (CO) (TIC) ( P P ~ ~ ) ~ ~ and reversibly w i t h primary amines yielding

0sCl (CONHI?) (CO) (TIC) ( P P ~ ~ ) 2. Basic alcohols afford 0sC1 ( C O ~ R ) (CO) (TIC) ( P P ~ ~ ) (R

=

Me, ~t), and with 2-chloroethanol a heterocyclic carbene complex

[ O s C l (CO) (TIC) ( C C C ~ H ~ O )

-

( P P ~ ~ ) 2]+ results. [ O S C ~ (CO) (TIC) 2 ( ~ ~ h 3 )

r e a c t s only with methoxide ions t o give [0s(OMe) (CO) ( T I C ) ~ ( P P ~ ~ ) ~ + which, with perchloric acid, affords [0s(0ClO3) (CO) (TIC) 2 ( ~ ~ h 3 ) 2]+.

[OsC1 (CO)

,

^{(TIC) (Pph3)}

2]+

r e a c t s with hydrosulphide ions a t t h e isocyanide ligand affording a n-isothiocyanate complex ~ ~ ( n - ~ ~ ~ p - t o l ~ l ) (CO) ( P P ~ ~ ) 2.

This complex can be protonated and methylated a t nitrogen t o give

bident a t e thiocarboxamide complexes, [OS (h 4NRp-tolyl) (CO) 2 2 ~ +

(R = H, Me),

The ligand r e a c t i v i t y of ce.rtain rr-complexes has been investigated, O S ( C ~ H ~ ) (CO) 2 ( ~ ~ h 3 ) 2 r e a c t s with excess hydrochloric acid t o produce t h e hydroxycarbene complex 0sc12 (CO) (c[OH]C H

9

( P P ~ ~ ) which r e a c t s

2 5

r e v e r s i b l y with base t o give 0sc1

( c ~ H ~ )

(CO) ( P P ~ ~ ) ~ . With other acids, t h e ethyl complexes OS(C A

) x ( c o ) ~ ( P P ~ ~ ) ~

(X = I, CF3C02, 0 ~ 1 0 ~ ) r e s u l t .

2 5

O S ( C ~ H ~ ) ( 0 ~ 1 0 ~ ) (CO) 2 ( ~ ~ h 3 ) 2 r e a c t s with n e u t r a l ligands and sodium d i e t h y l d i thiocarbamate affording [ O S ( C ~ H ~ C O ) (CO)

(I)

(PPh3) 2 ] ~ 1 0 4

(I =

CO, TIC) and O S ( C ~ H ~ C O )

( s ~ c N E ~ ~ )

^(CO) ( P P ~ ~ ) respectively.

O S ( ~ = C S ~ ) ( C ~ ) ~ ( P P ~ ~ ) ~ r e a c t s with methyl iodide t o give

O S I ( C S ~ M ~ ) (CO) ( P P ~ ~ ) 2 . ~ e ~ . The m e t h y l d i t h i o e s t g ligand of t h i s complex c h e l a t e s i n polar media affording [0s(h2-C[S] m e ) (CO) 2 ( ~ ~ h 3 ) 2 ] + .

With acids 10t, 0s(n-Cs2) (CO) 2 ( ~ ~ h 3 ) y i e l d s t h e first osmium thiocarbonyl complexes, 0sx2 (CO)

(CS)

( P P ~ ~ ) ~ (X = C l ,

I).

Dibronoalkanes, B ~ ( c H ~ ) ~ B ~ , r e a c t w i t h O S ( ~ - C S ~ ) ( C O ) ~ ( P P ~ ~ ) ~ a f f o r d i n g complexes of

new

h e t e r o c y c l i c carbenes,

~ o s B ~ ( c o ) ~ ( ~ s

[CH, J ~ ~ ) ( P P ~ ~ ) ~ ] ' ( n = 1,2,3), from which can be

d e r i v e d 0sBr2(C0)

(6s [ c H ~ ] ~ ~ )

( P P ~ ~ ) ~ (n = 2,3). 0 s ( n 4 s 2 ) (CO) (TIC) (pPh3)*

behaves sirnil a r l y i n g i v i n g [0s(h 2

-c[s]

^{S M ~ )} (CO) (TIC) ( P P ~ ~ ) ~ ] ' , O S C ~ ~ ( C S ) (TIC) ( P P ~ ~ ) and [Os~r (CO) (TIC) ( C S C ~ H ~ S )

-

( P P ~ ~ ) ~ ] + .

To i n v e s t i g a t e t h e r e a c t i v i t y of a complexed functionaL isocyan.de, various complexes of tosylrnethylisocyanide (TMIC) were synthesized.

Whereas deprotonation of [ O S K ( C O ) ~ ( ~ M I C ) ( P P ~ ~ ) ~ ] ' g i v e s

O S ( C ~ ) ~ ( T M I C ) ( P P ~ ~ ) ~ , attempted deprotonation of [OSH(CO) ( T M I C ) ( P P ~ ~ ) ~ ] + results i n t h e d e a l k y l a t i o n of TMIC t o y i e l d OSH(CN)

( c o ) ( P P ~ ~ ) ~ .

' O S H C ~ ( C O ) ( T I ~ I C ) ( P P ~ ~ ) ~ r e a c t s with base and carbonyl compounds t o

-

g i v e h e t e r o c y c l i c carbene complexes

O~HC~(CO)(CMHXIO)(PP~~)~,

XY=

R1 =

Me, Et, R 2 = H, R3 = Me; R,

=

R2 =

R3 =

~ e ) . Under similar

conditions, [ O S C ~ ( C O ) ~ ( T E ~ ~ C ) ( P P ~ ~ ) ~ ] ' y i e l d s OSC~(&~TH[TOS JCH[R]~))

( c o ) ~ ( P P ~ ~ ) ~

(R = Me, Ph), which c a n be protonated a t n i t r o g e n (R

= Ne)

t o g i v e a

c a t i o n i c carbene complex, Base and acetaldehyde with ^I

I

[OSH(CO)~(TMC) ( P P ~ ~ ) ~ ] ' g i v e s trans-[~sll(C0) 2 ( h l I C ~ [ ~ ~ e

]cH[M~] b )

(Pph3) 2]+.

I

-

I

I

The a c t i o n of s i l v e r p e r c h l o r a t e a d carbon monoxide on. ^I

- -

I

O S H C ~ (CO) (CIWZO) ( P P L ~ ) ~ produces [OSR(CO) 2 ( ~(PPh3) ~ 2 ] C ~

(XI

~ = ~ ) C H ( O M ~ ) C H ( M ~ ) , C H ( O : . ~ ~ ) C ( M ~ ) ~ , C H = C ( P ~ ) )

from

which can be obtained

1- -

OSH(C=NXY~)

( c o ) , ( P P ~ ~ ) , (W

₌ C H ( ~ ? ~ ~ ) C H ( M ~ ) , C H ( O : ~ ~ ) C ( M ~ ) ~ ) by r e v e r s i b l e

-

deprotonation a t t h e ligand. Nethyl i o d i d e and O S H ( C = N X Y O ) ( C O ) ~ ( P P ~ ~ ) ~ r e a c t t o g i v e [ O S H ( C O ) ~ ( & J [ T ~ [ M ~ ] xyb) ( P P ~ ~ ) ~ ] + which do n o t deprotonate

a t t h e metal. O S H C ~ (CO) ( & M C ~ [ O M ~ J C [I-ie

j2b)

( P P ~ ~ ) ~ r e a c t s w i t h p e r c h l o r i c

1

a c i d a f f o r d i n g O S C ~ ( O C ~ O ~ ) (CO)

(&HHcI![o:.!~Jc

[ ~ e ] ~ 6 ) ( p p h 3 ) which has 'I

8 1

been used t o prepare [ O S C ~

( c o ) ~ ( ~ I I I c H [ ~ , I ~ ] c [ M ~ ] ~ ~ )

( P P ~ ~ ) ~ ] ' ,

Infrared

and

1

H

n.m.r.

spectroscopy, conductivity and elemental

analysis have been used in formulation

and

structural assignment,