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The reactions of Ni(O) phosphino complexes with carbon monoxide
INORG.
NUCL.
CHEM.
LETTERS
Vol.
7,
pp.
197-201,
1971.
Pergamon Press.
Printed in Great Britain.
THE REACTIONS OF Ni(O) PHOSPHINO COMPLEXES WITH CARBON MONOXIDE B. Corain, M. Bressan and G. Favero Istituto di Chimica Generale, II 3ezione, Centro di Stabilita' e Reattivita' di Composti di Coordinazione, C.N.R., Universita' di ?adova (Italy). ( R e c e i v e d 15 October 1970)
Several phosphino carbonyl complexes of Ni(O) have been obtained by the reaction of Ni(CO)4 with tertiary phosphines (1). The reverse reaction between complexes of the type Ni(PRs) , and CO has not been studied (2). Moreover it is known that the reaction of Pt(PPh3)4 and Pt(PPh~)a with CO at ambient conditions leads to the stepwise substitution of two PPh 3 molecules by CO (3), while the same reaction for Pd(PPh3)4 is unknown (2,4). We find that when Ni(PPh3) 4 (5) is allowed to react with CO, at 1 atm. and room temperature in benzene or dichloroethane solution, --1
Ni(CO)2(PPh3)2 in benzene)
is rapidly formed ( ~coat 1995 cm
--1
and 1940 cm
(1). The much slower appearance of a band at 2065 cm
reveals the formation of the complex Ni(CO)3(PPh3)
--I
(1,6).
We have also investigated the carbonylation of the complexes Ni(diphosph)2, where diphosph is (CeHs)2P-(CH2)n-P(CeHs)2 and n = 2(dpe)
(7), 3 (dpp), 4(dpb) at the same conditions employed
for Ni(PPh3)4.
The complex Ni(dpp)2 has been obtained by the same
method used to prepare Ni(dpb)2
(8). These compounds react
easily
with CO in benzene and dichloroethane to give complexes in which the degree of substitution of the PPh2R moiety by CO depends on the length of the alkyl chain of the ligands. Ni(dpe)2 reacts with CO in benzene (too ~
60 min.) and the IR
spectrum of the solution shows a band at 1920 cm
--I
, which is
attributed to the CO stretching frequency of the species 197
198
Ni (0) PHOSPHINO COMPLEXES WITH CARBON MONOXIDE
Vol. 7, No. 2
--I
Ni(CO)(dpe)dpe*;
a small band at 2000 cm
and a weak shoulder
--I
at 1940 cm
are attributed
to the presence
the known complex Ni(CO)2(dpe) Ni(dpp)2 and benzene
behaves
it gives
(3).
in a similar way, (t~
It appears therefore and Ni(dpp)2
bis-substituted
i.e.
in dichloroethane
90 min.) a mixture
( VCO at 1910 cm -I) and Ni(CO)2(dpp)
of Ni(dpe)2
of small amounts of
of Ni(CO)(dpp)dpp
( VCO at 2000 and 1935 cm-1).
that the solutions after the reaction with CO contain both the mono- and the
carbonyl complexes.
The stepwise
substitution
the PPh2R moieties by CO can be more easily differentiated carbonylation possible
of the complex Ni(dpb)2;
to isolate and characterise
of
in the
in this case it has been
the monocarbonyl
complex
Ni(CO)(dpb)dpb. Manometric
measurements
or dichloroethane
solutions
occurs in two separated
of carbon monoxide uptake in benzene of Ni(dpb)2
stages.
show that the absorption
The first step is fast and complete
in ca. 2 min., while the second one is slow and is complete ca.
3 hours.
in
The uptake rate and the number of moles of CO absorbed
per mole of Ni(O) do not depend appreciably
on the presence
of
free di~hosphine. At the end of the first stage, after about O. 8 moles of CO per mole of Ni(O) have been absorbed, dichloroethane attributed at 1995 cm attributed
the IR spectrum of the
solution shows a strong band at 1910 cm
to the
VCO
of the complex Ni(CO)(dpb)dpb.
and an ill-defined to the
, A weak peak
shoulder at ca. 1940 cm
are
VCO of the complex Ni(CO)2(dpb). --I
While the CO uptake continues,
the band at 1910 cm --I
decreases intensity.
in intensity and those at 1995 cm
--1
and 1940 cm
At the end of the reaction the band at 1910 cm
reduced to a small shoulder, appear completely
gain --I
is
while those at 1995 and 1940 cm
defined.
In concentrated
solutions a very pale violet product
(*) The symbols (diphosph) and diphosph indicate a diphosphine acting as a chelating and a non chelating ligand respectively.
Vol. 7, No. 2
Ni (0) P H O S P H I N O C O M P L E X E S WITH CARBON MONOXIDE
precipitates
spontaneously.
199
The IR spectrum of this compound in --1
nujol mull shows two strong bands at 1940 and 1995 cm complex Ni(CO)2(dpe)
displays two
.
The --1
~
bands at 1936 and 1997 cm CO_I and Ni(CO)2(PPh3) 2 at 1933 and 1994 cm in dichloroethylene (9).
,
These data show that the final reaction product between Ni(dpb)2 and CO must be Ni(CO)2(dpb),
although we could not isolate it in
a pure state. The carbonylation of a red orange suspension of Ni(dpb)2 n-hexaue with vigorous
in
stirring led after few hours to a lemon
yellow product, wich was filtered off under argon. is soluble in benzene and dichloroethane.
The compound
The IR spectrum in
nujol or in solution shows a strong peak at 1910 cm
--I
. This band
does not disappear when an argon current is bubbled through benzene solution of the compound.
a
This means that the CO ligand
is either coordinated irreversibly to the metal or that the loss of carbon monoxide
is kinetically unfavored.
This compound analyzes as Ni(CO)(dpb)2 Ni(CO)(P(C6Hs)2-(CH2)4-P(C6Hs)2)2: Ni, 6.24.
(Anal.
Calcd.
for
C, 72.85; H, 6.00; P, 13.18;
Found: C, 72.91; H, 6.03; P, 13. O7; Ni, 6.42).
Ni(CO)(dpb)dpb decomposes under vacuum between 190 and 200°C. The pyrolisis of the complex at 250°C leads to the liberation of O. 91 mole of CO per g. mole of Ni(O).
The solid compound is
indefinitely air stable, however it is air-sensitive when in solution. The compound can be formulated either as a tetracoordinated Ni(O)
complex with one of the d i p h o s p h i n ~ a c t i n g as a monodentate
ligand,
or as a pentacoordinated
one with two chelating diphosphines,
A tetracoordinated tetrahedral structure is more likely on the basis of the noble gas rule and of the generally admitted occurrence of this steric arrangement
in Ni(O) complexes
(3,10).
Moreover the IR spectrt~ in nujol of the complex Ni(CO)(P(CH3)3)3 --1
displays the
VC 0 band at 1917 cm
The 1910 cm
--1
(3).
band displayed by benzene solutions of the
compound is asymmetric, with a weak shoulder located at about
Ni (0) PHOSPHINO COMPLEXES WITH CARBON MONOXIDE
200
Vol. 7, No. 2
1930 cm -I. --2
A cryoscopic molecular weight determination of a 2.3 x l0 molalsolution in benzene gave 770, while the calculated one is 940. These two data, together with the ascertained scarce lability of the coordinated CO, show that the complex is partially dissociated in solution to give N1(CO)(dpb) and dpb. This result is in agreement with what has been observed for Pd(CO)(PPhs) 3 (prepared by reduction of Pd(acetylacetonate)2 with AI(C2Hs) 3 in the presence of C0 and PPhs (4)), and for Pt(C0)(PPh~) 3 ( ~ C 0 in nujol at 1908 cm-1), which in solution dissociates completely to Pt(C0)(PPh3) 2 ( ~ C 0 in benzene at 1931 cm -I) and
PPh3 (3). Ni(C0)(dpb)dpb reacts with CO in dichloroethane to give the same pale violet product obtained from Ni(dpb)2 and the same !R pattern in solution at the end of the carbon monoxide uptake.
In
conclusion, the identification of the reaction products between Ni(dpb)2 and CO in n-hexane supports the hypothesis that the first earbonylation product of Ni(dpb)2 in benzene and dichloroethane is Ni(C0)(dpb)dpb and makes reasonable the assignement of the --1
1920 and 1910 cm
bands to the tetracoordinated compounds,
Ni(CO)(dpe)dpe and Ni(C0)(dpp)dpp respectively. The behaviour of Ni(PPh3)4, Ni(dpe)2, and Ni(dpb)2 with CO seems to be rather similar, as far as the substitution of the first P P h 3 or P P h 2 R
moiety is concerned, but it becomes appreciably
different when the entrance of the second and third CO molecule is considered.
Three PPh 3 ligands can be substituted rather easily
in Ni(PPhs)4, while the complete substitution of the second PPh3R moiety in the Ni(diphosph)2 complexes appears to be possible only for Ni(dpb)2 at normal conditions.
REFERENCES
i)
See for example Gmellin's " Handbuch der Anorganischen Chemie" part B, Bol.
3, Verlag Chemie, Wenheim/Bergstr.,
8th. ed. 1966,
Vol. 7, No. 2
Ni (0) P H O S P H I N O C O M P L E X E S WITH CARBON MONOXIDE
201
p. 815 to 829. 2)
R. UGO, Coordin. Chem. Rev., 3, 319 (1968). The author reports that Ni(PPh3)4 reacts with CO to give " the well known derivatives of Ni(CO)4" , by quoting this finding as an unpublished result.
3)
~. CARIATI and R. UGO, Chim. Ind.
(Milan), 48, 1288 (1966).
4)
A. MISON0, Y. UCHIDA, M. HIDAI and K. K-UDO, J. 0rganometall. Chem., 20, 7 (1969).
5)
G. WILKE, F.W. MULLER, and H. KRONER, Angew. Chem., 73, 33 (1961).
6)
W.F. EDGELL and M.P. DUNKLE, Inorg. Chem., 4, 1629 (1965).
7)
J. CHATT, G.H. HART and H.R. WATSON, J. Chem. Soc., 2537 (1962).
8)
B. CORAIN, P. RIG0 and M. BRESSAN, Chim. Ind. (Milan), 51, 386 (1969).
9) i0)
J. CHATT and F.H. HART, J. Chem. Soc., 1378 (1960). Gmallin's'~andbuch
der Anorganischen Chemie" , Part C, Vol. l,
Verlag Chemie, Weinheim/Bergstr.,
8th ed., 1968, p. 5.
NUCL.
CHEM.
LETTERS
Vol.
7,
pp.
197-201,
1971.
Pergamon Press.
Printed in Great Britain.
THE REACTIONS OF Ni(O) PHOSPHINO COMPLEXES WITH CARBON MONOXIDE B. Corain, M. Bressan and G. Favero Istituto di Chimica Generale, II 3ezione, Centro di Stabilita' e Reattivita' di Composti di Coordinazione, C.N.R., Universita' di ?adova (Italy). ( R e c e i v e d 15 October 1970)
Several phosphino carbonyl complexes of Ni(O) have been obtained by the reaction of Ni(CO)4 with tertiary phosphines (1). The reverse reaction between complexes of the type Ni(PRs) , and CO has not been studied (2). Moreover it is known that the reaction of Pt(PPh3)4 and Pt(PPh~)a with CO at ambient conditions leads to the stepwise substitution of two PPh 3 molecules by CO (3), while the same reaction for Pd(PPh3)4 is unknown (2,4). We find that when Ni(PPh3) 4 (5) is allowed to react with CO, at 1 atm. and room temperature in benzene or dichloroethane solution, --1
Ni(CO)2(PPh3)2 in benzene)
is rapidly formed ( ~coat 1995 cm
--1
and 1940 cm
(1). The much slower appearance of a band at 2065 cm
reveals the formation of the complex Ni(CO)3(PPh3)
--I
(1,6).
We have also investigated the carbonylation of the complexes Ni(diphosph)2, where diphosph is (CeHs)2P-(CH2)n-P(CeHs)2 and n = 2(dpe)
(7), 3 (dpp), 4(dpb) at the same conditions employed
for Ni(PPh3)4.
The complex Ni(dpp)2 has been obtained by the same
method used to prepare Ni(dpb)2
(8). These compounds react
easily
with CO in benzene and dichloroethane to give complexes in which the degree of substitution of the PPh2R moiety by CO depends on the length of the alkyl chain of the ligands. Ni(dpe)2 reacts with CO in benzene (too ~
60 min.) and the IR
spectrum of the solution shows a band at 1920 cm
--I
, which is
attributed to the CO stretching frequency of the species 197
198
Ni (0) PHOSPHINO COMPLEXES WITH CARBON MONOXIDE
Vol. 7, No. 2
--I
Ni(CO)(dpe)dpe*;
a small band at 2000 cm
and a weak shoulder
--I
at 1940 cm
are attributed
to the presence
the known complex Ni(CO)2(dpe) Ni(dpp)2 and benzene
behaves
it gives
(3).
in a similar way, (t~
It appears therefore and Ni(dpp)2
bis-substituted
i.e.
in dichloroethane
90 min.) a mixture
( VCO at 1910 cm -I) and Ni(CO)2(dpp)
of Ni(dpe)2
of small amounts of
of Ni(CO)(dpp)dpp
( VCO at 2000 and 1935 cm-1).
that the solutions after the reaction with CO contain both the mono- and the
carbonyl complexes.
The stepwise
substitution
the PPh2R moieties by CO can be more easily differentiated carbonylation possible
of the complex Ni(dpb)2;
to isolate and characterise
of
in the
in this case it has been
the monocarbonyl
complex
Ni(CO)(dpb)dpb. Manometric
measurements
or dichloroethane
solutions
occurs in two separated
of carbon monoxide uptake in benzene of Ni(dpb)2
stages.
show that the absorption
The first step is fast and complete
in ca. 2 min., while the second one is slow and is complete ca.
3 hours.
in
The uptake rate and the number of moles of CO absorbed
per mole of Ni(O) do not depend appreciably
on the presence
of
free di~hosphine. At the end of the first stage, after about O. 8 moles of CO per mole of Ni(O) have been absorbed, dichloroethane attributed at 1995 cm attributed
the IR spectrum of the
solution shows a strong band at 1910 cm
to the
VCO
of the complex Ni(CO)(dpb)dpb.
and an ill-defined to the
, A weak peak
shoulder at ca. 1940 cm
are
VCO of the complex Ni(CO)2(dpb). --I
While the CO uptake continues,
the band at 1910 cm --I
decreases intensity.
in intensity and those at 1995 cm
--1
and 1940 cm
At the end of the reaction the band at 1910 cm
reduced to a small shoulder, appear completely
gain --I
is
while those at 1995 and 1940 cm
defined.
In concentrated
solutions a very pale violet product
(*) The symbols (diphosph) and diphosph indicate a diphosphine acting as a chelating and a non chelating ligand respectively.
Vol. 7, No. 2
Ni (0) P H O S P H I N O C O M P L E X E S WITH CARBON MONOXIDE
precipitates
spontaneously.
199
The IR spectrum of this compound in --1
nujol mull shows two strong bands at 1940 and 1995 cm complex Ni(CO)2(dpe)
displays two
.
The --1
~
bands at 1936 and 1997 cm CO_I and Ni(CO)2(PPh3) 2 at 1933 and 1994 cm in dichloroethylene (9).
,
These data show that the final reaction product between Ni(dpb)2 and CO must be Ni(CO)2(dpb),
although we could not isolate it in
a pure state. The carbonylation of a red orange suspension of Ni(dpb)2 n-hexaue with vigorous
in
stirring led after few hours to a lemon
yellow product, wich was filtered off under argon. is soluble in benzene and dichloroethane.
The compound
The IR spectrum in
nujol or in solution shows a strong peak at 1910 cm
--I
. This band
does not disappear when an argon current is bubbled through benzene solution of the compound.
a
This means that the CO ligand
is either coordinated irreversibly to the metal or that the loss of carbon monoxide
is kinetically unfavored.
This compound analyzes as Ni(CO)(dpb)2 Ni(CO)(P(C6Hs)2-(CH2)4-P(C6Hs)2)2: Ni, 6.24.
(Anal.
Calcd.
for
C, 72.85; H, 6.00; P, 13.18;
Found: C, 72.91; H, 6.03; P, 13. O7; Ni, 6.42).
Ni(CO)(dpb)dpb decomposes under vacuum between 190 and 200°C. The pyrolisis of the complex at 250°C leads to the liberation of O. 91 mole of CO per g. mole of Ni(O).
The solid compound is
indefinitely air stable, however it is air-sensitive when in solution. The compound can be formulated either as a tetracoordinated Ni(O)
complex with one of the d i p h o s p h i n ~ a c t i n g as a monodentate
ligand,
or as a pentacoordinated
one with two chelating diphosphines,
A tetracoordinated tetrahedral structure is more likely on the basis of the noble gas rule and of the generally admitted occurrence of this steric arrangement
in Ni(O) complexes
(3,10).
Moreover the IR spectrt~ in nujol of the complex Ni(CO)(P(CH3)3)3 --1
displays the
VC 0 band at 1917 cm
The 1910 cm
--1
(3).
band displayed by benzene solutions of the
compound is asymmetric, with a weak shoulder located at about
Ni (0) PHOSPHINO COMPLEXES WITH CARBON MONOXIDE
200
Vol. 7, No. 2
1930 cm -I. --2
A cryoscopic molecular weight determination of a 2.3 x l0 molalsolution in benzene gave 770, while the calculated one is 940. These two data, together with the ascertained scarce lability of the coordinated CO, show that the complex is partially dissociated in solution to give N1(CO)(dpb) and dpb. This result is in agreement with what has been observed for Pd(CO)(PPhs) 3 (prepared by reduction of Pd(acetylacetonate)2 with AI(C2Hs) 3 in the presence of C0 and PPhs (4)), and for Pt(C0)(PPh~) 3 ( ~ C 0 in nujol at 1908 cm-1), which in solution dissociates completely to Pt(C0)(PPh3) 2 ( ~ C 0 in benzene at 1931 cm -I) and
PPh3 (3). Ni(C0)(dpb)dpb reacts with CO in dichloroethane to give the same pale violet product obtained from Ni(dpb)2 and the same !R pattern in solution at the end of the carbon monoxide uptake.
In
conclusion, the identification of the reaction products between Ni(dpb)2 and CO in n-hexane supports the hypothesis that the first earbonylation product of Ni(dpb)2 in benzene and dichloroethane is Ni(C0)(dpb)dpb and makes reasonable the assignement of the --1
1920 and 1910 cm
bands to the tetracoordinated compounds,
Ni(CO)(dpe)dpe and Ni(C0)(dpp)dpp respectively. The behaviour of Ni(PPh3)4, Ni(dpe)2, and Ni(dpb)2 with CO seems to be rather similar, as far as the substitution of the first P P h 3 or P P h 2 R
moiety is concerned, but it becomes appreciably
different when the entrance of the second and third CO molecule is considered.
Three PPh 3 ligands can be substituted rather easily
in Ni(PPhs)4, while the complete substitution of the second PPh3R moiety in the Ni(diphosph)2 complexes appears to be possible only for Ni(dpb)2 at normal conditions.
REFERENCES
i)
See for example Gmellin's " Handbuch der Anorganischen Chemie" part B, Bol.
3, Verlag Chemie, Wenheim/Bergstr.,
8th. ed. 1966,
Vol. 7, No. 2
Ni (0) P H O S P H I N O C O M P L E X E S WITH CARBON MONOXIDE
201
p. 815 to 829. 2)
R. UGO, Coordin. Chem. Rev., 3, 319 (1968). The author reports that Ni(PPh3)4 reacts with CO to give " the well known derivatives of Ni(CO)4" , by quoting this finding as an unpublished result.
3)
~. CARIATI and R. UGO, Chim. Ind.
(Milan), 48, 1288 (1966).
4)
A. MISON0, Y. UCHIDA, M. HIDAI and K. K-UDO, J. 0rganometall. Chem., 20, 7 (1969).
5)
G. WILKE, F.W. MULLER, and H. KRONER, Angew. Chem., 73, 33 (1961).
6)
W.F. EDGELL and M.P. DUNKLE, Inorg. Chem., 4, 1629 (1965).
7)
J. CHATT, G.H. HART and H.R. WATSON, J. Chem. Soc., 2537 (1962).
8)
B. CORAIN, P. RIG0 and M. BRESSAN, Chim. Ind. (Milan), 51, 386 (1969).
9) i0)
J. CHATT and F.H. HART, J. Chem. Soc., 1378 (1960). Gmallin's'~andbuch
der Anorganischen Chemie" , Part C, Vol. l,
Verlag Chemie, Weinheim/Bergstr.,
8th ed., 1968, p. 5.