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Thiolate-hydride complexes of molybdenum(II)
c3 Journal of Organometallic Chemistry, 286 (1985) C3-C4 Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands
THIOLATE-HYDRIDE
(CARDUBE AFRC
COMPLEXES OF MOLYBDENUM(I1)
S)3 DR’I’MAX’ ma RAYM D1JD I, RI Cl3ARDB*
Unit of Nitrogen Fixation,
University of Sussex, Brighton BNl 9QJ (Great Britain)
(Received January 21st, 1985)
Summary The stable thiolate hydrides tram-[ MoH( SR)(dppe), ] (dppe = Ph,PCH,CH2PPh2; R = Pri, But, C6H2(C3H7)3-2,4,6; C,H,(CH,),-2,4,6 or C,H,Br-4, (C3H7)*-2,6) have been prepared by treatment of truns-[Mo(N,)2 (dppe)*] with RSH.
Although mononuclear hydride complexes of molybdenum with thiolate co-ligandshave rdevance to curren%theories of the function of the active site of njt;rogenase El}, tbejr prepzratjon has hjtierfo proved eJnsj,e. Indeed, Drily a few metal complexes of this type have been isolated [ 2,3,4,5], although they have been observed as reaction intermediates [3,4]. This appears to be a se&t ff f &e tendency bztor reductive er&ination of tlte parent tltcol, e.g. [IrH(SPh)Cl(CO)(PPh,),] loses PhSH rather easily [5]. However, during the course of our studies of the reactions of dinitrogen complexes with thiols [6], we have been able to isolate the first examples of stable mononuclear hydride-thiolate complexes of molybdenum as green crystals (A, eq. 1). THF trans-[ MoH( SR)(dppe), ] + 2N, + RSH -+ (1) 60°C (A) (R = Pri, But, C,H,(C3H7)3-2,4,6; C6Hz(CH3)3-2,4,6 or C6HzBr-4(C3H7),-2,6)
trans-[Mo(N,),(dppe),]
The use of bulky R groups is essential for the stability and isolation of compounds A. If smaller substituent groups (R’) are employed, bis(thiolate) complexes B are obtained (eq. 2) [4] . truns-[Mo(N,),(dppe),]
+ BR’SH -+ tram-[Mo( SR’)* (dppe), ] + Hz + 2Nz
(R’ = C,H4X-4 (X = H, F, Cl, CH,, 0CH3, NH,); Et, Pm or Bun) 0022-328X/85/$03.30
(B)
o 1985 Elsevier Sequoia S.A.
(2)
Reactions 2 proceed via green intermediates [ 41 which are probably thiolate hydrides, but they could not be isolated. Compounds A are assigned the &ens-configuration on the basis of their singlet ‘*P NMR spectra (Table 1). Their ‘H NMR spectra (Table 1) show the hydride resonance as a quintet in the range -3.98 to -4.98 ppm. The analogue truns-[IrH(SMe)(dppe),]PF, shows a quintet ‘El resonance at -14.8 ppm [73. TABLE
1
THIOLATO
HYDRIDE
COMPLEXES
OF
MOLYBDENL.M(Il)
v(MoH) (cm -’ ) ’ 6( ‘H) __-__~__-.-__~~~~___--___----.“---
R
~~oH(SR)(dppe):l b
(PP~)
‘J(PH)
fi( “P)
(Hz)
But
1700
-3.98
45.04t0.01
Pri
1690
-4.85
45.5
to.01
-58.0
C,H,(C,H,f_x-2.4.6
1735
-4.75
47
: 2.0
-69.5
C,H,(CH,)s-2,436
1710
-4.98
46.4
‘0.7
-61.1
C,H,Br-4(C,Hv),-2,4
1660
--4.78
46
23.0
-62.0
a Nujol
b In CD,Cl,
mulls.
solution,
rel.
SiMe,,
centre
c
--57.0
C Broad
of quintet.
ppm
resonanre
in THF
solution.
).
rel. P(OMe)
It is likely that the steric bulk of the R group in reaction 1 prevents further attack by thiol at the molybdenum. If compounds A are treated with an excess of the smaller thiol, R’SH, then they are smoothly converted into trans[WSR’h(dme)2 1. Reductive elimination of the bulky thiols is induced by treatment with neutral donors such as CO or PhNC, and gives the known compounds [Mo(XY),(dppe),] (XY = CO or PhNC) ]7] with no sign of insertion into the MO-H or MO-S bonds. References 1
C. Veeger The
Fixation, 2
T.B.
3
K.
4
J. Chatt. R.L.
and W.E.
Hague,
1984; (Eds.),
Rauchfuss Osakada, J.P.
Richards,
5
T. Gains
6
D. Povey
and
7
J. Chatt,
C.M.
Trans..
and
(1978)
Newton
(Ed%),
J. Chatt, Academic and
D.M.
Press.
and
Pina and London,
Roundhill,
T. Yamamoto Lloyd
Advances
L.M.C.
and R.L.
unpublished
A.
J. Am.
Richards,
Roundhill.
Inorg.
Richards,
3. Chem.
165
and ref.
New
Sot.;
9’7 (1975)
Research,
Trends
M.
in the
Nijhoff
Chemistry
and W. Junk, of
Nitrogen
Chem.
Inorg.
J. Chem.
Chim.
Acta.
Sot.
Dalton
13 (1974)
2521.
3386. 90
Trans.,
(1984)
L5.
(1976).
56:
C. Shortman
and
results.
R.L.
A..J.L.
Fixation
Richards
1980.
Yamamoto,
D.M.
Elson,
in Nitrogen R.L.
Pombeiro. therein.
Chem., Sot. R.L.
Dalton, Richards
Trans., and
(IQ84) G.H.D.
2585
and ref.
Royston,
therein.
J. Chem.
Sot.
Dalton
THIOLATE-HYDRIDE
(CARDUBE AFRC
COMPLEXES OF MOLYBDENUM(I1)
S)3 DR’I’MAX’ ma RAYM D1JD I, RI Cl3ARDB*
Unit of Nitrogen Fixation,
University of Sussex, Brighton BNl 9QJ (Great Britain)
(Received January 21st, 1985)
Summary The stable thiolate hydrides tram-[ MoH( SR)(dppe), ] (dppe = Ph,PCH,CH2PPh2; R = Pri, But, C6H2(C3H7)3-2,4,6; C,H,(CH,),-2,4,6 or C,H,Br-4, (C3H7)*-2,6) have been prepared by treatment of truns-[Mo(N,)2 (dppe)*] with RSH.
Although mononuclear hydride complexes of molybdenum with thiolate co-ligandshave rdevance to curren%theories of the function of the active site of njt;rogenase El}, tbejr prepzratjon has hjtierfo proved eJnsj,e. Indeed, Drily a few metal complexes of this type have been isolated [ 2,3,4,5], although they have been observed as reaction intermediates [3,4]. This appears to be a se&t ff f &e tendency bztor reductive er&ination of tlte parent tltcol, e.g. [IrH(SPh)Cl(CO)(PPh,),] loses PhSH rather easily [5]. However, during the course of our studies of the reactions of dinitrogen complexes with thiols [6], we have been able to isolate the first examples of stable mononuclear hydride-thiolate complexes of molybdenum as green crystals (A, eq. 1). THF trans-[ MoH( SR)(dppe), ] + 2N, + RSH -+ (1) 60°C (A) (R = Pri, But, C,H,(C3H7)3-2,4,6; C6Hz(CH3)3-2,4,6 or C6HzBr-4(C3H7),-2,6)
trans-[Mo(N,),(dppe),]
The use of bulky R groups is essential for the stability and isolation of compounds A. If smaller substituent groups (R’) are employed, bis(thiolate) complexes B are obtained (eq. 2) [4] . truns-[Mo(N,),(dppe),]
+ BR’SH -+ tram-[Mo( SR’)* (dppe), ] + Hz + 2Nz
(R’ = C,H4X-4 (X = H, F, Cl, CH,, 0CH3, NH,); Et, Pm or Bun) 0022-328X/85/$03.30
(B)
o 1985 Elsevier Sequoia S.A.
(2)
Reactions 2 proceed via green intermediates [ 41 which are probably thiolate hydrides, but they could not be isolated. Compounds A are assigned the &ens-configuration on the basis of their singlet ‘*P NMR spectra (Table 1). Their ‘H NMR spectra (Table 1) show the hydride resonance as a quintet in the range -3.98 to -4.98 ppm. The analogue truns-[IrH(SMe)(dppe),]PF, shows a quintet ‘El resonance at -14.8 ppm [73. TABLE
1
THIOLATO
HYDRIDE
COMPLEXES
OF
MOLYBDENL.M(Il)
v(MoH) (cm -’ ) ’ 6( ‘H) __-__~__-.-__~~~~___--___----.“---
R
~~oH(SR)(dppe):l b
(PP~)
‘J(PH)
fi( “P)
(Hz)
But
1700
-3.98
45.04t0.01
Pri
1690
-4.85
45.5
to.01
-58.0
C,H,(C,H,f_x-2.4.6
1735
-4.75
47
: 2.0
-69.5
C,H,(CH,)s-2,436
1710
-4.98
46.4
‘0.7
-61.1
C,H,Br-4(C,Hv),-2,4
1660
--4.78
46
23.0
-62.0
a Nujol
b In CD,Cl,
mulls.
solution,
rel.
SiMe,,
centre
c
--57.0
C Broad
of quintet.
ppm
resonanre
in THF
solution.
).
rel. P(OMe)
It is likely that the steric bulk of the R group in reaction 1 prevents further attack by thiol at the molybdenum. If compounds A are treated with an excess of the smaller thiol, R’SH, then they are smoothly converted into trans[WSR’h(dme)2 1. Reductive elimination of the bulky thiols is induced by treatment with neutral donors such as CO or PhNC, and gives the known compounds [Mo(XY),(dppe),] (XY = CO or PhNC) ]7] with no sign of insertion into the MO-H or MO-S bonds. References 1
C. Veeger The
Fixation, 2
T.B.
3
K.
4
J. Chatt. R.L.
and W.E.
Hague,
1984; (Eds.),
Rauchfuss Osakada, J.P.
Richards,
5
T. Gains
6
D. Povey
and
7
J. Chatt,
C.M.
Trans..
and
(1978)
Newton
(Ed%),
J. Chatt, Academic and
D.M.
Press.
and
Pina and London,
Roundhill,
T. Yamamoto Lloyd
Advances
L.M.C.
and R.L.
unpublished
A.
J. Am.
Richards,
Roundhill.
Inorg.
Richards,
3. Chem.
165
and ref.
New
Sot.;
9’7 (1975)
Research,
Trends
M.
in the
Nijhoff
Chemistry
and W. Junk, of
Nitrogen
Chem.
Inorg.
J. Chem.
Chim.
Acta.
Sot.
Dalton
13 (1974)
2521.
3386. 90
Trans.,
(1984)
L5.
(1976).
56:
C. Shortman
and
results.
R.L.
A..J.L.
Fixation
Richards
1980.
Yamamoto,
D.M.
Elson,
in Nitrogen R.L.
Pombeiro. therein.
Chem., Sot. R.L.
Dalton, Richards
Trans., and
(IQ84) G.H.D.
2585
and ref.
Royston,
therein.
J. Chem.
Sot.
Dalton