21 Tungsten(IV) Chelates—Potential Energy
Downloaded via YORK UNIV on December 4, 2018 at 08:22:03 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
Transfer Complexes RONALD WILLIAM
D. H.
ARCHER, CRAIG J. BATSCHELET, and
DONAHUE, DAVID R .
WHITCOMB
Department of Chemistry, Graduate Research Tower A, University of Massachusetts, Amherst, MA 01003
Inert eight-coordinate W(IV) chelates have been synthesized in our laboratories and have properties analogous to the ruthenium complexes that are currently an energy-trans fer focus. Substituted tetrakis(8-quinolinolato)tungsten(IV) complexes (1), substituted tetrakis(picolinato)tungsten(IV) complexes (2), tetrakis(pyrazinecarboxylato)tungsten(IV) (3), tetrakis(isoquinoline-1-carboxylato)tungsten(IV) (4), and bis(N,N'-disalicylidene-1,2-phenylenediaminato)tungsten(IV) (5) have been synthesized. The ML chelates are substitu tion-inert d chelates with low energy metal-to-ligand charge-transfer transitions based on relative energies and photooxidation to d -W(V) analogs, which possess ligand -to-metal charge-transfer transitions in the visible region. We have initiated the synthesis of analogous polymeric com plexes as well. 4
2
1
sizable n u m b e r of l o w - s p i n inert W L complexes h a v e b e e n synthe4
s i z e d i n o u r laboratories, w h e r e L is a b i d e n t a t e l i g a n d c h e l a t i n g through a heterocyclic aromatic nitrogen donor a n d a negatively charged o x y g e n d o n o r (1,2,3,4). A n a l o g o u s m i x e d l i g a n d W L J L V n complexes also h a v e b e e n i s o l a t e d (5,6). L i g a n d a b b r e v i a t i o n s are g i v e n i n T a b l e I. T h e c h a r a c t e r i z a t i o n of the p r e v i o u s l y r e p o r t e d (1,2,4) s u b s t i t u t e d tetrakis ( 8 - q u i n o l i n o l a t o ) tungsten ( I V ) complexes ( 1 , w h e r e X = H , B r , C I , C O C H , o r C H a n d Y = H , B r , o r C I ) has i n c l u d e d a single c r y s t a l x-ray s t u d y (7) w h i c h has v e r i f i e d t h e eight c o o r d i n a t i o n of these chelates. F u r t h e r m o r e , t h e structure is o n e expected f r o m O r g e F s r u l e ( 8 ) f o r d 3
3
2
0-8412-0429-2 / 79 / 33-173-252$05.00/ 0 © 1979 American Chemical Society
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
21.
ARCHER E T AL.
Tungsten(IV) T a b l e I.
acq" bmq" bq" cnq~ cq" dbq" dcq" diq" dsp " epic" hpic" hqa" iqc" mpic" mq" mqq " nd " nq" pic" pzc" pzd ~ q" qd -
253
Chelates
Ligand Abbreviations
5-acetyl-8-quinolinolato 7-bromo-5-methyl-8-quinolinolato 5-bromo-8-quinolinolato 7-chloro-5-nitro-8-quinolinolato = 5-chloro-8-quinolinolato 5,7-dibromo-8-quinolinolato 5,7-dichloro-8-quinolinolato 5,7-diiodo-8-quinolinolato A^^-disalicylidene-l^-phenylenediaminato = 5-ethylpicolinato = 3-hydroxypicolinato 8-hydroxyquinaldinato = 1-isoquinolinecarboxylato 5-methylpicolinato = 5-methyl-8-quinolinolato = methylenebis(quinolin-8-ol-5-ylato) = 1,5-naphthyridine-4 8-diolato 5-nitro-8-quinolinolato = picolinato == 2 - p y r a z i n e c a r b o x y l a t o = 2,3-pyrazinedicarboxylato 8-quinolinolato = 5,8-quinoxalinediolato bis ( q u i n o l i n - 8 - o l - 5 - y l a t o ) = 5-^er^-butyl-8-quinolinolato = iV^A^VV'^-tetrasalicylid^ —
=
2
2
2
;
2
2
qq " tbq" tsb " 2
4
e i g h t - c o o r d i n a t e complexes; i.e., the g r o u n d state s h o u l d h a v e the f o u r TT acceptors (the u n s a t u r a t e d n i t r o g e n d o n o r s ) i n the f o r e s h o r t e n e d
tetra-
h e d r a l array or d o d e c a h e d r a l B positions a n d the TT donors ( t h e o x y g e n d o n o r s ) i n the e l o n g a t e d t e t r a h e d r a l or d o d e c a h e d r a l A positions, w h e r e A a n d B are f r o m the n o m e n c l a t u r e d e v e l o p e d b y H o a r d a n d S i l v e r t o n (9).
T h e B positions h a v e f a v o r a b l e TT o v e r l a p w i t h the filled b± o r b i t a l
(Scheme 1). such W L
4
T h i s r u l e reduces the 93 p o s s i b l e d o d e c a h e d r a l isomers f o r
systems w i t h i n e q u i v a l e n t donors (JO) to f o u r isomers
1 ) , the most s y m m e t r i c a l of w h i c h is o b s e r v e d f o r W ( b q ) considerations c a n r e d u c e this n u m b e r e v e n f u r t h e r .
(Figure
*C H .
4
6
6
Steric
( F o r example, the
N a n d O positions s h o u l d be reversed i n d° c o m p l e x e s so that the o x y g e n TT donors c a n o v e r l a p w i t h the e m p t y & i o r b i t a l (11). tions c a u s e d us to p r e d i c t (7)
that Z r ( q )
B u t steric c o n s i d e r a -
w o u l d h a v e to b e one of the
4
isomers w i t h g edges; this p r e d i c t i o n has b e e n v e r i f i e d b y L e w i s a n d Fay
(12). F o r the d
2
complexes u n d e r d i s c u s s i o n , this r u l e appears to p l a y a
v e r y d o m i n a n t role, s u c h that s l o w e x c h a n g e N M R spectra are o b s e r v e d at e l e v a t e d temperatures
f o r the W ( d c q ) ( m p i c ) . w
4
w
complexes
e v e n t h o u g h the iso-electronic a n d i s o - s t r u c t u r a l W ( C N )
8
4
(5,6),
" i o n has b e e n
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
254
INORGANIC
COMPOUNDS WITH UNUSUAL
PROPERTIES
II
Scheme 1 K
d-like
J &i •
orbitals S
7 —
bi
(ir)
r e p o r t e d to b e n o n r i g i d at v e r y l o w temperatures
(— 1 5 0 ° C )
F u r t h e r m o r e , t w o g e o m e t r i c a l isomers of W ( d c q ) ( m p i c ) 2
isolated a n d characterized
2
E x t e n s i o n of these W L (picolinato)tungsten(IV)
4
complexes to complexes n o t i n v o l v i n g 8-
complexes
(2, where Z =
3-hydroxypicolinato complex)
l i n e c a r b o x y l a t o species, W ( p z c ) spectrally supported W ( n q )
3
(3).
(3) and W ( i q c )
andW ( h q a )
4
ously reported i n c l u d e W ( t b q ) 2
4
4
4
(2).
4
tetrakis-
H , C H , or C H
reported previously include the 2-pyrazinecarboxylato
W(dsp)
been
(5,6).
q u i n o l i n o l d e r i v a t i v e s has i n c l u d e d a n u m b e r of s u b s t i t u t e d a n d t h e analogous
(13).
have
2
Other
5
species
a n d 1-isoquino-
(4)
( 3 ) , a n d the
Complexes not previ-
a n d the q u a d r i d e n t a t e Schiff base chelate
(5 ), f o r w h i c h at least t w o isomers h a v e b e e n o b s e r v e d .
T h e entire W L series a p p e a r to b e s u b s t i t u t i o n - i n e r t species, 4
with
n e g l i g i b l e l i g a n d exchange at r o o m t e m p e r a t u r e over p e r i o d s of h o u r s . H o w e v e r , at e l e v a t e d temperatures
l i g a n d exchange c a n b e o b t a i n e d .
L o w - s p i n eight-coordinate dodecahedral d
2
complexes
( S c h e m e 1 ) are
analogous to l o w - s p i n six-coordinate o c t a h e d r a l d complexes ( S c h e m e 2 ) 6
i n terms of b o n d i n g . T h a t is, t h e d orbitals that are o r t h o g o n a l to s i g m a interactions
( t h e Z?i a n d t
2g
orbitals, r e s p e c t i v e l y )
are d o u b l y o c c u p i e d
a n d t h e s i g m a a n t i b o n d i n g orbitals are e m p t y . H e n c e , analogous inertness is l o g i c a l . Intense charge-transfer visible spectrum exhibit
energy
transitions o b s e r v e d at t h e r e d e n d o f t h e
(14,000-17,000 c m " ) f o r t h e t u n g s t e n ( I V )
chelates
1
shifts
characteristic
of metal-to-ligand
charge-transfer
species a n d are analogous to those o b s e r v e d f o r o c t a h e d r a l d
6
ions w i t h
u n s a t u r a t e d n i t r o g e n d o n o r atoms; e.g., F e ( I I ) a n d R u ( I I ) d i i m i n e s . T h e W ( I V ) chelates are c a p a b l e W(V)
cations, W L
4
+
.
of b e i n g o x i d i z e d to analogous
A strong o x i d a n t s u c h as c h l o r i n e o r b r o m i n e
is r e q u i r e d to o x i d i z e t h e t u n g s t e n - p i c o l i n a t o chelates, w h e r e a s
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
excess
21.
ARCHER E T AL.
Tungsten(IV)
Chelates
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
255
256
INORGANIC
COMPOUNDS
WITH
UNUSUAL PROPERTIES
Figure 1. The positions of the chelate rings in the WL} isomers allowed by Or gel's rule (S) that acceptors should occupy the B positions in eightcoordinate complexes. The W(bq) • C H structure is the D (mmmmj isomer (7). h
6
6
2 d
Scheme 2
(-*)
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
H
21.
ARCHER E T AL.
Tungsten(IV)
257
Chelates
l i g a n d c a n o x i d i z e t h e q u i n o l i n o l a t o species at e l e v a t e d temperatures These W L
4
(14).
chelates, w h i c h are d complexes, a p p e a r to h a v e m o d e r a t e l y
+
1
intense l i g a n d - t o - m e t a l charge-transfer transitions (3,14)
(analogous t o
o c t a h e d r a l d i o n s ) as a result of t h e h o l e i n t h e l o w e s t e n e r g y dir l e v e l ; 5
i.e., t h e b
(and t )
1
level noted above.
2g
T h e quinolinolato W L
d i s p r o p o r t i o n a t e i n s t r o n g a l c o h o l i c N a O H solutions t o W L t y p e species, w i t h t h e W L hand, the W L
4
+
+
ions
and W 0 L
4
2
2
complexes inert t o t h e base. O n t h e other
4
p i c o l i n a t o ions are d e c o m p o s e d u n d e r these c o n d i t i o n s .
These eight-coordinate d
2
hedral d
4
andd
chelates are analogous t o t h e octa-
1
a n d d r u t h e n i u m d i i m i n e species that are c u r r e n t l y a focus of 5
6
c o o r d i n a t i o n c o m p o u n d energy transfer.
T h e tungsten species offer b o t h
m e t a l a n d l i g a n d c o m p o n e n t s w h i c h are a p p r e c i a b l y less expensive t h a n the r u t h e n i u m complexes.
Syntheses O u r s t a n d a r d synthetic m e t h o d f o r these chelates is the e l e v a t e d t e m p e r a t u r e d e c a r b o n y l a t i o n of W ( C O ) , either b y m e l t reactions c o n 6
t a i n i n g excess l i g a n d (2-6,14)
o r b y t h e use of h i g h b o i l i n g solvents,
u s u a l l y either 2,4,6-trimethylpyridine
o r m e s i t y l e n e (3).
(2-6,14)
dence f o r l,2,3,4-tetrahydro-8-quinolinol has b e e n o b t a i n e d (14);
Evithere-
fore, t h e r e a c t i o n has b e e n f o r m u l a t e d as:
W ( C O ) + 5 H L - » W L + H L H + 6CO 6
4
(1)
4
T h e analogous r e a c t i o n w i t h t h e W C 1 " i o n , w h i c h w e i n i t i a l l y u s e d ( I ) , 2
9
3
is f o r m u l a t e d as:
2W C1 " + 17HL 2
9
4 W L + H L H + 12HC1 + 6C1"
3
4
4
(2)
I n d i l u t e s o l u t i o n h y d r o g e n p r o d u c t i o n c a n o c c u r , as n o t e d b y D o r s e t t and W a l t o n ( 1 5 ) , w h o have independently p r o d u c e d W ( p i c ) b y a similar d e c a r b o n y l a t i o n r e a c t i o n . W e also h a v e s y n t h e s i z e d these chelates t h r o u g h a stepwise route w h i c h does n o t r e q u i r e elevated t e m p e r a t u r e s : 4
W(CO)
Cl 6
2
-78°C
> W(CO) C1 4
HL(C1 ) 2
2
0°C
> WL
(3)
4
W h e n a l l traces of c h l o r i n e are r e m o v e d f r o m t h e W ( C O ) C l ,
elevated
temperatures
Another
4
2
are r e q u i r e d f o r t h e second step of R e a c t i o n 3.
i n d i r e c t route i n v o l v e s a n i n t e r m e d i a t e p h o s p h i n e :
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
258
INORGANIC COMPOUNDS W I T H UNUSUAL PROPERTIES—II
W(C0) C1 4
P03 2
*W(C0) (P*8)2C1 8
/
2
HL
W(C0) (P^» )2C1L 2
3
HL
WL
W(CO) (Pfc)ClL 8
HL' W(CO) (P* )L 2
8
4
W L „ L ' .i-n (4)
2
W i t h s o m e l i g a n d s , f u r t h e r o x i d a t i o n to the W ( V )
ions o c c u r u n d e r
extended reaction conditions. Synthesis of t h e p r e v i o u s l y u n r e p o r t e d W ( t b q )
4
chelate
initially
i n v o l v e d a S c h r a u p synthesis of H t b q . P r e v i o u s attempts i n other l a b o r a tories h a d f a i l e d because of the a c i d c l e a v a g e of the tert-butyl the arsenic a c i d o x i d a t i o n step ( 1 6 ) .
group i n
W e have successfully used p i c r i c
a c i d a n d 4 - t e ^ b u t y l - 2 - n i t r o p h e n o l as oxidants w i t h y i e l d s of 5 - 1 0 % . p r o c e d u r e is s i m i l a r to that u s e d f o r H m q ( 3 , 6 ) . w a s p r e p a r e d b y the d e c a r b o n y l a t i o n of W ( C O )
The W ( t b q ) 6
4
The
chelate
i n mesitylene heated
u n d e r reflux, f o l l o w e d b y s u b l i m a t i o n of u n r e a c t e d m a t e r i a l a n d c r y s t a l lization f r o m chloroform. Chromatographic separation on silica gel w i t h 1:1 v / v C H C l : h e x a n e p r o d u c e d a n a n a l y t i c a l l y p u r e W ( t b q ) 3
T w o isomers o f W ( d s p )
2
4
chelate.
h a v e b e e n i s o l a t e d f r o m t h e r e a c t i o n of 1
m m o l W ( C O ) , 2 m m o l H d s p ( w h i c h h a d been prepared b y a normal 6
2
Schiff base c o n d e n s a t i o n f r o m s a l i c y l a l d e h y d e a n d 1 , 2 - d i a m i n o b e n z e n e ) , a n d 2 m m o l H p i c i n m e s i t y l e n e h e a t e d u n d e r reflux c o n d i t i o n s f o r 48 h r . E a r l i e r attempts f o r shorter t i m e p e r i o d s h a d i n d i c a t e d i n c o m p l e t e reaction.
Preparative chromatographic separation on silica gel w i t h
as b o t h solvent a n d eluant gave t w o p r o d u c t s w i t h analyses
CHC1
3
consistent
w i t h W ( d s p ) , p l u s several m i x e d c o m p l e x e s . T h e c h a r g e transfer m a x i m a 2
for the W ( d s p )
2
species are at 22,500 a n d 22,700 c m " . F u r t h e r w o r k is 1
i n progress to e l u c i d a t e the stereochemistry of these c o m p l e x e s . Low-Energy
Charge-Transfer
Transitions
S t r o n g (c > 1 0 ) e l e c t r o n i c transitions at l o w energies ( 1 3 , 0 0 0 17,000 c m " ) are o b s e r v e d f o r a l l of t h e W L t u n g s t e n ( I V ) chelates that w e h a v e s y n t h e s i z e d ( T a b l e I I ) . W e (2,3) h a v e assigned these as m e t a l t o - l i g a n d charge-transfer b a n d s because: ( 1 ) the b a n d s are too intense to 4
1
4
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
21.
ARCHER E T AL.
Tungsten(IV)
Table II.
WL4 Low-Energy Charge-Transfer Bands"
CH W(Rq)/ 13,800
Solutions W(bq) 14,100
W(dcq) 14,300
W(q) 14,300
6
W(nq) 13,400 W(cq) 14,200
4
4
G
4
W (epic) 16,900
4
' € > 10*. R = 5-methyl or
W(hqa) 14,300
4
(cm V W(pic) 16,600 f I
4
4
4
4
W(dbq) 14,200 W(pic) 16,700
4
4
W(mpic) 16,900
M o (pic) > 20,000 4
4
) J
5-tert-buty\.
b
be s i m p l e d-d
4
W(hpic) 16,900
1
Solutions W(pzc) 16,200
s
W(dcq) 14,200
4
(cm' ) W(bmq) 14,100
4
4
CHCl W(iqc) 13,600
259
Chelates
transitions; ( 2 ) t h e b a n d s are at l o w e r energy t h a n t h e
first charge-transfer transitions of t h e analogous W ( V ) complexes, w h e r e as l i g a n d - t o - m e t a l transitions are l o w e r i n e n e r g y f o r h i g h e r o x i d a t i o n states; ( 3 ) the filled foi l e v e l w o u l d r e q u i r e a ir t o « i o r e l e v e l f o r l i g a n d - t o - m e t a l transitions i n these species b u t n o t f o r t h e o x i d i z e d f o r m ; ( 4 ) t h e i n t r a - l i g a n d transitions are s t i l l o b s e r v a b l e n e a r t h e i r free m o l e c u l e energies; ( 5 ) t h e q u i n o l i n e d e r i v a t i v e s h a v e t h e transitions at l o w e r energies t h a n t h e p y r i d i n e d e r i v a t i v e s ; a n d ( 6 ) electron w i t h d r a w i n g g r o u p s t e n d to l o w e r t h e energies of the transitions. See S c h e m e 3 f o r t h e levels
thought
to b e i n v o l v e d i n t h e l o w - e n e r g y t r a n s i t i o n a n d t h e
a p p a r e n t r e l a t i v e energies of t h e h i g h e r o c c u p i e d orbitals a n d l o w e r u n o c c u p i e d orbitals.
Scheme 3 b
2
ai
!
e ,„
ligand
> filled
/
/ W
(
I
V
> ligand
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
260
INORGANIC COMPOUNDS W I T H UNUSUAL PROPERTIES
Table III.
[ W L ] C l Low-Energy Charge-Transfer Bands 4
CH Cl W (diq) 18,300 2
W(dcq) 18,300 W(cnq) 18,700
4
+
W(bq) 18,900
+
Solutions
2
4
4
+
(cm' ) W (bmq) 18,300 1
W(acq) 19,200
+
4
4
W (dbq) 18,500
+
W(pic) 23,400
+
4
4
+
+
b
10 . Acetone.
°c > b
4
H
4
T h e analogous W ( V ) chelates h a v e intense
(c >
10 ) 4
electronic
transitions at s o m e w h a t h i g h e r energies ( > 18,000 c m " ) t h a n t h e charge1
transfer transitions i n t h e W ( I V ) chelates
(Table
III).
T h e higher
energies of analogous W ( V ) chelates w i t h e l e c t r o n w i t h d r a w i n g g r o u p s , W(cnq)
4
+
> W(dcq)
4
+
and W ( a c q )
4
+
> W(bq)
4
+
, shows that e l e c t r o n
w i t h d r a w i n g groups increase t h e energies o f these transitions, i n contrast to t h e charge-transfer b a n d s f o r the W ( I V )
chelates.
A shift to l o w e r
energies f o r a l l of t h e seven-halo species suggests that t h e n o n b o n d i n g electrons o n t h e o x y g e n are i n v o l v e d i n t h e d o n a t i o n f r o m t h e q u i n o l i n o l species.
T h e h i g h e r e n e r g y of the W ( p i c )
electron
w i t h d r a w i n g nature
4
+
i o n is consistent w i t h t h e
of t h e c a r b o x y l a t e
charge-transfer n o t e d f o r t h e W ( I V )
group.
T h e inverse
chelates s h o u l d b e at a p p r e c i a b l y
h i g h e r energies i n t h e W ( V ) chelates b e c a u s e of t h e l a c k of e l e c t r o n e l e c t r o n r e p u l s i o n s i n t h e h a l f - f i l l e d b± l e v e l i n t h e W ( V ) complexes a n d of t h e g e n e r a l l o w e r i n g of t h e d orbitals ( s u c h as t h e & i l e v e l ) i n c r e a s e d m e t a l o x i d a t i o n states.
B o t h effects increase
with
the separation
b e t w e e n the b o r b i t a l a n d t h e l i g a n d ?r* orbitals. See S c h e m e 4. 1
Scheme 4
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
21.
ARCHER E T AL.
Tungsten(IV)
261
Chelates
Photosensitivity S e v e r a l of the q u i n o l i n o l a t o - t u n g s t e n ( I V ) chelates are q u i t e sensitive to o x y g e n a n d l i g h t d u r i n g c h r o m a t o g r a p h y o n s i l i c a g e l . T h e p r o d u c t is the W ( V ) chelate. T h e W ( q )
4
chelate is m o r e sensitive t h a n is W ( c q ) , 4
w h i c h is m o r e sensitive t h a n W ( d c q ) . 4
T h a t species is, i n t u r n , m o r e
sensitive t h a n a n y of the p i c o l i n a t o - d e r i v a t i v e chelates.
A l s o , the q u i n o -
l i n o l d e r i v a t i v e s are s o m e w h a t p h o t o s e n s i t i v e i n air-saturated solutions. S o m e o x i d i z e i n the dark, too, b u t at a s l o w e r rate. T h e rates also a p p e a r to b e chelate, solvent, atmosphere, a n d i m p u r i t y d e p e n d e n t .
Quantifica-
t i o n is i n progress. T h e o b s e r v e d p h o t o s e n s i t i v e o x i d a t i o n of the t u n g s t e n ( I V )
chelates
is f u r t h e r e v i d e n c e that the l o w energy b a n d s are m e t a l - t o - l i g a n d chargetransfer.
T r a n s f e r of the ?r* e l e c t r o n f r o m the p h o t o - e x c i t e d state- to
s i l i c a g e l leaves t h e W ( V )
chelate.
L i g a n d - t o - m e t a l charge
transfer
w o u l d t e n d to g i v e r e d u c e d m e t a l or o x i d i z e d l i g a n d — c o n t r a r y to e x p e r i m e n t a l observations. Polymerization A c u r r e n t emphasis is the p r e p a r a t i o n of l i n e a r p o l y m e r s w i t h eightc o o r d i n a t e t u n g s t e n centers.
T h e q d " b i h e a d e d l i g a n d (6)
has s h o w n a n
2
a b i l i t y to f o r m a p o l y m e r i c W ( I V )
m a t e r i a l w i t h a charge
transfer
b a n d at 12,600 c m " , b u t the l o w e r n u c l e o p h i l i c i t y of this l i g a n d does n o t 1
a l l o w f o r p o l y m e r i z a t i o n b y l i g a n d exchange w i t h the W L
4
chelates u n d e r
c o n d i t i o n s that a l l o w l i g a n d exchange b e t w e e n the s i m p l e r l i g a n d s . r e a c t i o n of W ( C O ) C l 4
2
The
w i t h H q d followed by H p i c produces a blue 2
p r o d u c t w i t h a n e l e c t r o n i c t r a n s i t i o n at 14,300 c m " . A s i m i l a r p r o d u c t 1
has b e e n o b t a i n e d t h r o u g h the r e a c t i o n p e r f o r m e d i n the reverse o r d e r , b u t p u r i f i c a t i o n has p r o v e n d i f f i c u l t . T h e use of W ( C O ) ( P < £ ) L 2
mediates to f o r m W L ( q d ) 2
dione
(qd°)
p o l y m e r s shows p r o m i s e .
3
The
2
inter-
analogous
p r o v i d e s the t w o electrons n e e d e d to p r o d u c e t h e t w o -
electron oxidation. T h e more nucleophilic ligands, m q q " , n d ' , a n d q q " , 2
also are b e i n g i n v e s t i g a t e d .
2
2
L o w - e n e r g y transitions h a v e b e e n o b s e r v e d
i n some of the i n c o m p l e t e l y c h a r a c t e r i z e d species.
Acknowledgment W e w i s h to a c k n o w l e d g e t h e s u p p o r t of the A r m y R e s e a r c h O f f i c e f o r m u c h of this research.
S o m e aspects w e r e s u p p o r t e d b y the N a t i o n a l
Science F o u n d a t i o n t h r o u g h the U n i v e r s i t y of Massachusetts
Materials
R e s e a r c h L a b o r a t o r y . W e a p p r e c i a t e the c o n s t r u c t i v e c o m m e n t s of t h e r e v i e w e r s a n d editors.
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
262
INORGANIC
COMPOUNDS
WITH
UNUSUAL PROPERTIES
II
Literature Cited 1. Archer, R. D., Bonds, W. D., Jr., J. Am. Chem. Soc. (1967) 89, 2236. 2. Bonds, W. D., Jr., Archer, R. D., Inorg. Chem. (1971) 10, 2057. 3. Donahue, C. J., Archer, R. D., Inorg. Chem. (1977) 16, 2903; cf. Archer, R. D., Donahue, C. J., "Abstracts of Papers," 169th National Meeting, ACS, Philadelphia, PA, 1975, INOR 056. 4. Pribush, R. A., Ph.D. dissertation, University of Massachusetts, 1972. 5. Archer, R. D., Donahue, C. J., J. Am. Chem. Soc. (1977) 99, 269. 6. Donahue, C. J., Archer, R. D.,J.Am. Chem. Soc. (1977) 99, 6613. 7. Bonds, W. D., Jr., Archer, R. D., Hamilton, W. C., Inorg. Chem. (1971) 10, 1764. 8. Orgel, L. E., J. Inorg. Nucl. Chem. (1960) 14, 136. 9. Hoard, J. L., Silverton, J. V., Inorg. Chem. (1963) 2, 235. 10. Bennett, W. E., Inorg. Chem. (1969) 8, 1325. 11. Clark, R. J. H., Lewis, J., Nyholm, R. S., Pauling, P., Robertson, G. B., Nature (London) (1961) 192, 222. 12. Lewis, D. F., Fay, R.C.,J.Chem.Soc.,Chem. Commun. (1974) 1046. 13. Muetterties, E. L., Inorg. Chem. (1973) 12, 1963. 14. Archer, R. D., Bonds, W. D., Jr., Pribush, R. A., Inorg. Chem. (1972) 11, 1550. 15. Dorsett, T. E., Walton, R. A., J. Chem.Soc.,Dalton Trans. (1976) 347. 16. Woodcock, D., J. Chem. Soc. (1955) 4391. RECEIVED February 22, 1978.
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
