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Kethane Activation By Photoexcited Dicopper Molecules.

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1 2 . Bondybey, V.E.;
Pimentel. G . C . ,
J. Chem. Phys..56,(1972)
Recently we demonstrated t h a t 320nm resonance e x c i t a t i o n
3832.
13. Wright, R.B.;
of copper atoms C U ( ~ P ) + C U ( ~iSn) t h e presence or methane a t
Bates, J.K.;
Gruen,D.M.,
Inorg. C h e m . , x ,
12K, causes h i g h l y e f f i c i e n t and s e l e c t i v e i n s e r t i o n of t h e
(1978) ,2275.
Cu atom i n t o a CH bond of CH4 t o form CH CuH as t h e primary
3
The a c t i v a t i o n energy and quantum y i e l d
photoproduct /l/.
Received January (7, 1982 /S 76a S/
f o r t h e chemical quenching of C U ( ~ P by
) CH,, have Since been
e s t a b l i s h e d t o be c l o s e t o zero and u n i t y r e s p e c t i v e l y /2/.
S i m i l a r experiments with e t h a n e have a l s o r e v e a l e d s e l e c t i v e
CH bcnd a c t i v a t i o n chemistry t o y i e l d C2H5CuH l e a v i n g t h e CC
bond untouched /3/.
I n both of t h e s e c a s e s , a secondary
p h o t o l y s i s channel ( i n v o l v i n g RCuH absorbing around 350nm)
l e d t o competitive fragmentation of t h e i n s e r t i o n product t o
y i e l d as t h e major p r o d u c t s CH tCuH and C2H5+CuH with only
3
t r a c e a m u n t s of CH3Cu+H and C H Cu+H r e s p e c t i v e l y ( s e l e c 2 5
t i v i t y r a t i o approximately 99:l /1,2,3/).
I n t h e c a s e of
p h o t o e x c i t e d C U ( ~ P )i n t h e presence of H a ,
only CuHtH photo-
p r o d u c t s were d e t e c t e d at 12K with no evidence f o r t h e r e a c t i v e d i h y d r i d e i n t e r m e d i a t e HCuH /4/. I n r a r e g a s
matrices
on t h e o t h e r hand, c ~ ( ’ P ) undergoes an e f f i c i e n t n o n - r a d i a t l v e
r e l a x a t i o n p r o c e s s t o t h e l o w l y i n g CU(’DI state, which by
v i r t u e of t h e e l e c t r o n i c t o v i b r a t i o n a l energy t r a n s f e r
cU(~P)+CU(~D
channeled
)
l o c a l l y t o the surrounding matrix
cage, coupled w i t h t h e long l i v e d n a t u r e of t h e C U ( ~ D s) t a t e
( n o t e 2D+2S i s p a r i t y f o r b i d d e n ) , p e r m i t s p h o t o d i f f u s i o n and
e x c i t e d s t a t e r e a c t i v e encounters with o t h e r immobilized
ground S t a t e Cu(’S)
i n t h e m a t r i x according t o :
Cu(2D)tCu(2S)*Cu2(A1nu)-Cu2(X1~~)th~400-420
-
-
797 -
I
I
Dieses Manuskript ist
zu zitieren als
Angew. Chem. Suppl.
1982,798-806
This manuscript is
to be cited as
Angew. Chem. Suppl.
1982,798-806
799
t o y i e l d Cu2 i n
-
t h e e x c i t e d A-state (Wlgner-Witmer s e p a r a t e d atom-molecule
c o r r e l a t i o n r u l e s ) which can ‘be d e t e o t e d by w e l l r e s o l v e d ,
s t r u c t u r e d A-state emission around 400-42Onm / 5 / . Relevant
a l s o t o t h e p r e s e n t s t u d y is t h e o b s e r v a t i o n t h a t photoe x c i t a t i o n of t h e 8 - s t a t e of Cu2 i n r a r e g a s m a t r i c e s (370-
0 Valag Chamie GmbH, 0-8940 Weirhim. t882
07214227/82/05050798802.50/0
400nm) r e s u l t s I n a cage-asslsted fragmentation-recombination
;.:ethane A c t i v a t i o n By Photoexcited Dlcopper Molecules
p r o c e s s ( r e c a l l t h a t both t h e A and 8-states of Cu2 are
-
bound i n t h e gas phase /6/) as seen by C U ( ~ D )s t a t e emission
(around 750 and 870nm f o r t h e 2 ~ 3 / 2 and 2 ~ 5 / 2 terms r e s -
BY
p e c t i v e l y /5/) w i t h a concomitant small (approximately 10%)
Geoffrey A. Ozin*, Steven A. M i t c h e l l
and Jamie Carsla-
b u t r e p r o d u c i b l e n e t p h o t o d i s s o c i a t i v e y i e l d /7/
Prieto
CqX)
I
%(B)
--P
according t o :
CU(2D)+Cu(2S)4CU(2S)+cxr(2S)+hm,~70
.5
Because t h e Cu(%) s t a t e cannot be d i r e c t l y p o p u l a t e d from
C U ( ~ S )in a b s o r p t i o n ( d i p o l e f o r b i d d e n p r o c e s s ) y e t i t can be
i n d i r e c t l y prepared by Cu2(B)+Cu2(X) e x c i t a t i o n , coupled with
t h e o b s e r v a t i o n t h a t t h i s kind of low energy e l e c t r o n i c t r a n s i t i o n g e n e r a l l y r e d - s h i f t s with i n c r e a s i n g c l u s t e r n u c l e a r i t y
i n t h e s i z e range n = 2
-
6 (350 t o 600nm) /4,8/, l e a d $ one
t o e n q u i r e whether CH or CC bonds i n completely s a t u r a t e d hy* P r a f e s s o r G.A.
Ozin and Dr. S.A. M i t c h e l l , Lash Miller
Czernical L a b o r a t o r i e s , 80 S t . George S t . , U n i v e r s i t y of
T x o n t o , Toronto, Ontario, Canada, M5S 1 A l
C.-. J. OarCia-Prieto,
I n s t i t u t o Nexicano d e l PetrGleo, Av.
Cisn Metros, No.152, Mexico, 14.D.F.
Mexico.
drocarbons can b e s e l e c t i v e l y a c t i v a t e d u s i n g p h o t o e x c i t e d ,
low n u c l e a r i t y metal c l u s t e r s . Experiments of t h i s t y p e a r e
novel and could y i e l d c o n s i d e r a b l e fundamental i n f o r m a t i o n
r e l e v a n t t o t h e r a p i d l y developing f i e l d of heterogeneous
p h o t o c a t a l y s i s employing oxide and z e o l i t e s u p p o r t e d m e t a l
c l u s t e r s /9/.
-
798
-
-
800
-
I n t h i s communication we would l i k e t o r e p o r t our obser-
a b i l i t y t o d e t e c t e d photochemical r e a c t i v e i n t e r m e d i a t e s and
v a t i o n u s i n g a s e l e c t i v e l y photoexcited metal c l u s t e r , namely
p r o d u c t s ) c l e a r l y r e v e a l e d s i g n i f i c a n t production of CH 3
r a d i c a l s ( F i g u r e 28, c h a r a c t e r i s t i c q u a r t e t h f s p a t t e r n
t h e m a t r i x r e a c t i o n of t h e B-state of Cu2 w i t h methane.
c e n t r e d around g = 2) following 378nm e x c i t a t i o n of Cu2 i n
v a t i o n s concerning t h e f i r s t recorded example o f a l k a n e a c t i -
Evidence for t h i s photochemical r e a c t i o n s t e m from a
number of s o u r c e s , i n c l u d i n g u v - v i s i b l e a b s o r p t i o n , f l u o r e -
CHI(. Trace amounts of H atoms ( F i g u r e 2B, c h a r a c t e r i s t i c
doublet h f s p a t t e r n c e n t r e d around g = 2)
scence e m i s s i o n / e x c i t a t i o n and e l e c t r o n s p i n resonance spectroscopy. Figure 1 shows a t g g i c a l u v - v i s i b l e a b s o r p t i o n
F i g u r e 2: E l e c t r o n s p i n resonance spectrum o b t a i n e d ( A ) on
d e p o s i t i n g Cu atoms with CH,, (Cu/CH,,=l/102) a t 12K
and (8) f o l l o w i n g 60 minutes, 378nm p h o t o e x c i t a t i o n
of t h e B'Z;
+ XIS+
a b s o r p t i o n of Cu2 molecules ( n o t e
g
t h a t t h e a b s o r p t i o n s marked with an a s t e r i s k , ob-
s e r v e d on d e p o s i t i o n and which remain unchanged
d u r i n g 378nm Cup p h o t o e x c i t a t i o n , are a t t r i b u t e d t o
paramagnetic Cun s p e c i e s /5/
and w i l l b e d e s c r i b e d
i n a forthcoming p u b l i c a t i o n ) .
Pigure 1: uv-visible a b s o r p t i o n spectrum o b t a i n e d ( A ) on dep o s i t i n g Cu atoms with CH,,(Cu/CH,,*1/103) a t 12K (B)
-
- 803 -
f o l l o w i n g 1 5 minutes, 3ZOnm p h o t o e x c i t a t i o n of t h e
were observed i n t h e s e experiments; however, no e v i d e n c e for
- 801
2 P + 2 ~ resonance a b s o r p t i o n of CU a t o m and ( c )
t c e i n s e r t l o n product CH CuH w a s o b t e i n e d at anytime d u r i n g
a f t e r 5 minutes, 378nm p h o t o e x c i t a t i o n of t h e
t z e p h o t o l y s i s treatment,although under t h e low Cu2 concen-
&+u
+ X'E;
a b s o r p t i o n of cu2 molecules.
3
t r a t i o n cmditlcns employed i n t h e s e experiments t h e i n s e r t i o n
t r a c e of a Cu/CH,,=1/103 mixture d e p o s i t e d end r e c o r d e d a t
p-sduct
could have been below t h e d e t e c t i o n l i m i t of t h e e s r
1 2 K . The f r e s h l y d e p o s i t e d sample shows t h e p r e s e n c e of Cu
measurements. This o b s e r v a t i o n should be c o n t r a s t e d w i t h t h e
atoms c o - e x i s t i n g with small amounts of Cu2 as I n d i c a t e d I n
r e a c t i o n of Cu('P)
S)
Figure 1 A . Prolonged resonance e x c i t a t i o n C U ( ~ P ) + C U ( ~of
t a t i o n of Cu('S)
t h e copper atoms (15 minutes) a t 320nm ( I n t e n s i t y a t t h e
e f f i c i e n t g e n e r a t i o n of CH CuH.
3
C o l l e c t i v e l y t h e s e r e s u l t s p o i n t t o a very e f f i c i e n t
sample roughly 80 u watt cm-')
causes r a p i d b l e a c h i n g of a l l
w i t h CHq. formed by d i r e c t resonance e x c i i n methane m a t r i c e s /l/, which leads t o
t h e Cu atom a b s o r p t i o n s , production of CH3+CuH as t h e major
p h o t o d i s s o c i a t i o n of Cup e x c i t e d at 378nm i n CH,, m a t r i c e s ,
photoproducts ( a b s o r b i n g around 200-250nm) w i t h v e r y l i t t l e
which appears t o have i t s o r i g i n i n t h e chemical quenching of
a l t e r a t i o n of t h e c o n c e n t r a t i o n of Cu2 ( F i g u r e 1B) as observed
t h e W 2 D ) photofragment according t o :
Cu('D)
p r e v i o u s l y /l/.
Subsequent p h o t o e x c i t a t i o n of Cuz a t 378nm ( 5 minutes)
t CH4
+
CH3 t CuH
I n e s s e n c e t h i s e l i m i n a t e s t h e competing c a g e - a s s i s t e d re-
r e s u l t s i n r a p i d b l e a c h i n g of t h e Cu2 a b s o r p t i o n s , w i t h a
combination pathway which predominetes i n r a r e g a s solias/5,7/.
concurrent dramatic ten-fold growth of t h e Cu atom resonance
T n i s p r o p o s a l i s e n t i r e l y c o n s i s t e n t w i t h our o b s e r v a t i o n of
absorptions (Figure 1C).
T h i s o b s e r v a t i o n s h o u l d be s h a r p l y
Contrasted w i t h t h e minor n e t p h o t o d i s s o c i a t i v e F i e l d ( % l o r )
of t r a p p e d Cu atoms following s i m i l a r p h o t o e x c i t a t i o n of Cu2
i n r a r e gas s o l i d s /7/.
Furthermore, p a r a l l e l f l u o r e s c e n c e
measurements r e v e a l t h a t t h e C U ( ~ D ) + C U ( ~eSm) i s s l o n observed
a l a r g e , n e t Cup p h o t o d i s s o c i a t i v e y i e l d of t h e Immobilized
ground s t a t e C U ( ~ S co-fragment.
)
Tnese r e s u l t s may be s i g n i f i c a n t as they p o i n t t o t h e
p s s s i b i l i t y of e x c i t e d s t a t e s e l e c t i v i t y i n t h e condensed phase
p h o t o s e n s i t i z a t i o n r e a c t i o n s of Cu atoms
f o l l o w i n g 370-400nm p h o t o e x c i t a t i o n of Cu2 i n rare g a s s o l i d s
C ~ ( ' P ) + C H+~C H ~ C ~ H ; i n s e r t i o n
/ 5 / , i s completely quenched i n methane m a t r i c e s . The c o r r e s -
Cu('D)tCHq
ponding e s r experiments (performed under h i g h e r copper con-
CU(~S)+CH,,
+ Cu+CH4
c e n t r a t i o n Cu/CH,,-1/102 c o n d i t i o n s , t o enhance t h e formation
of copper c l u s t e r s on d e p o s i t i o n , t h e r e b y i n c r e a s i n g t h e
- 802
-
t
CH3+CuH
with CH,,.
namely:
; abstraction
; immobilization
I n conclusion, metal a t o d m e t a l c l u s t e r photochemistry of
t h i s k i n d opens up t h e f a s c i n a t i n g p o s s i b i l i t y of a c t i v a t i n g
-804-
saturated hydrocarbons and performing selective alkane transformations, with small, well defined photoexcited metal
clusters, employing visible rather than uv-photons.
.
Acknowledgements:
The generous financial assistance of the Natural Sciences
I
Dieses Manuskriptist
zu zitieren als
Angew. Chem. Suppl.
1982,807-816
This manuscript is
to be cited as
Angew. Chem. Suppl.
1982,807-816
I
0 Verlag Chemie GmbH,D-6940 Weinheim,1982
M.WO
0721-4227/82/0505-0807S
and Engineering Research Council of Canada's Strategic Energy
Programme is greatly appreciated. (S.A.M.)
also acknowledges
the NSERC and Noranda for graduate scholarships at the
earlier and latter stages of his work. (J.0.P.)
Stereospezifische Synthese von Palladium(I1)-Komplexen
makrocyclischer vierztihniger Phosphan-Liganden
H
thanks the
Instituto Mexican0 del Petr6leo for financial support of his
Rainer Bartsch, Sibbele Hietkamp, Stephen Morton,
research during his leave of absence at the University of
Othrnar Stelzer
Toronto.
References :
1.
A l s Phosphoranaloga der Kronenether sind mehrztihnige
G.A. Ozin, D.F. McIntosh, S.A. Mitchell, J. Garcla-Prieto,
J. Am. Chem. SOC.
2.
3.
4.
5.
a (1981) 1574.
makrocyclische Phosphane von aktuellem Interesse /1-4/.
Die bisher in der Literatur beschriebenen Syntheseverfah-
S.A. Mitchell, Photoprocesses of Excited Metal Atoms,
ren verlaufen iiber mehrere Stufen und liefern diese
Ph.0.
Liganden bzw. ihre Komplexe als Diastereomerengemische
Thesis, University of Toronto, 1982.
G.A. Ozin, S.A. Mitchell, J. Garcla-Prieto, Angew. Chem.
nur mit MDigen Gesamtausbeuten. Unter Ausnutzung des
94 (1982) 218; Angew.
-
"Template-Effekts" /5/ gelang es uns, chirale Palladium-
Chem. Int. Ed. Engl. 21 (1982) 211.
G.A. Ozin, S.A. Mitchell, J. Garcla-Prieto, Angew. Chem.
(11)-Komplexe vierdhniger makrocyclischer Phosphanligan-
94 (19821
-
den in
No. 5; Angew. Chem. Int. Ed. Engl. 21 (1982) No.5.
G.A. Ozin, S.A. Mitchell, J. Carcla-Prieto, J. Phys. Chem.,
6.
B. Klemen,
S.
Lindkvist, Ark. f y s .
R.F. Barrow, W.G. Richqrds, D.N.
171; S.S.S.
Rao, S.V.K.
g
Syntheseschritt stereospezifisch darzustellen.
Dr. R. Bartsch, Or. S. Hietkamp, Or. S. Morton,
in press.
Prof. Dr. 0. Stelzer
(1954) 333; N. Aslund,
Travis, ibid. 30 (1965)
Rao, Ind. J. Appl. Phys.
16
(1978)
Fachbereich 9, Anorganische Chemie, Universit&tGauDstraBe 20,
Gesamthochschule-Wuppertal,
D-5600 Wuppertal 1
923..
7.
-
805 -
G.A. Ozin, H. Huber, D.F.
McIntosh, S.A. Mitchell. J.G.
Norman, Jt., L. Noodleman, J. Am. Chem. SOC.
Der Diphosphankomplex
101 (1979)
9.
G.A.
A,
-
der in einfacher Weise aus
/ 6 / zugtinglich ist, reagiert
K2PdC14 und MeHP-[CH2I2-PMeH
in Ethanol mit zwei &uivalenten Acetylaceton unter B i l -
3504.
8.
807
Ozin, S.A.
Mitchell, S. Mattar, D.P. McIntosh, J.
dung zweier isomerer Palladiwn(I1)-Komplexe
g
und
2
der
Garcla-Prieto, J. Phys. Chem., submitted for publication.
Zusammensetzung C18H40C1204P4Pd. Dabei werden in einer
L.P. Childs, D.F.
glatt verlaufenden Cyclisierungsreaktion die PH-Bindungen
Ollis, J. Catal. 66 (1980) 383 and
von
references cited therein.
A
an das Mehrfachbindungssystem in Acetylaceton
addiert. Eines der beiden Isomeren
Received February 12, 1982 /Z 76b
S/
(g)
ist in Ethanol
schwerliislich und fiIllt aus dem Reaktionsgemisch aus.
Durch Umkristallisation aus Wasser bzw. Ethanol/Tetrahydrofuran lassen sich
.
2
und
2
rein gewinnen.
2 c1-
2 c1-
1
6(P)
2
I
und
+7.6 ppm
2
20%
2,
7*
2
sind in dDriger Lllsung viillig stabil. Die
elektrischen Leitftihigkeiten verditnnter Lllsungen (ca.
m) weisen diese Komplexe als 2:1-Elektrolyte
Im Infrarotspektrum von
2
und
2
aus /7/.
treten bei ca. 3200
cm-l stark verbreiterte Banden auf, die den OH-Valenzschwingungen zugeordnet werden kiinnen.
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