C/s-Tetracarbonylbis(tricyclohexyl-phosphine)moIybdenum(O) and pentacarbonyl(tricyclohexylphos-phine)molybdenum(O)

Article abstract of DOI:10.1107/S0108270100013111

In the present redetermination of the complex m-tetracarbonylbis(tricyclohexylphosphine)molybdenum(0) (I) [Mo(C18H33P)2(CO)4] or m-{?1-[P(C6H1,)3]2}Mo(CO)4 the Mo atom has a distorted octahedral geometry with a large P-Mo-P angle of 104.8 (1)°. A strong trans influence on the carbonyls in (I) is seen in a shortening of the Mo-C and a lengthening of the C-O distances opposite the phosphines compared with those that are cis. This influence is greatly diminished in the complex pentacarbonyl(tricyclohexyl-phosphine)molybdenum(O) (II) [Mo(C18H33P)(CO)5] or (η1-[P(C6Hn)3])Mo(CO)5 the core of which has a slightly distorted C4v geometry.

Full text of DOI:10.1107/S0108270100013111

metal-organic compounds
and L0 have cone angles greater than 45ꢀ (Tolman, 1977). The
lability of the MoÐP(cy)3 bond in such complexes may arise,
in part, from the ligand cone angle of 170ꢀ and may account
for the dif®culty in preparation of the analogous complex cis-
{[ꢀ1-P(cy)3]2}W(CO)4 by Boyles et al. (1985). Rates of ligand
dissociation reactions from cis-(ꢀ1-L)(ꢀ1-L0)Mo(CO)4 also
point to the type of metal ion and the size of the ligand as
important kinetic controlling factors (Laboy et al., 1995;
Cortes-Figueroa et al., 1997). As part of a systematic study
testing the relationships between structure and reactivity in
these complexes, the synthesis and structures of the title
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
cis-Tetracarbonylbis(tricyclohexyl-
phosphine)molybdenum(0) and
pentacarbonyl(tricyclohexylphos-
phine)molybdenum(0)
compounds,
cis-tetracarbonylbis(tricyclohexylphosphine)-
molybdenum(0), (I), and pentacarbonyl(tricyclohexyl-
phosphine)molybdenum(0), (II), are reported. The structure
of (I) is a redetermination of that reported by Watson et al.
(1994), which was based on a very limited data set.
Jose E. Cortes-Figueroa,a Madeline S. Leon-Velazquez,a
Johanna Ramos,a Jerry P. Jasinski,b David A. Keene,b
Jeffrey D. Zubkowskic and Edward J. Valented*
The structures of (I) and (II) are shown in Figs. 1 and 2,
respectively. In (I), the Mo atom has a considerably distorted
octahedral coordination geometry, as indicated by the P1Ð
MoÐP2 bond angle of 104.8 (1)ꢀ (ideal value 90ꢀ) and the
molecular distortion from C2v symmetry. This is accompanied
by a contraction of the opposite C2ÐMoÐC3 angle to
84.2 (2)ꢀ, and of the adjacent P1ÐMoÐC3 and P2ÐMoÐC2
angles to 86.5 (2) and 84.8 (2)ꢀ, respectively. The sterically
crowded environment at the Mo atom is further indicated by
the distortions of the equatorial trans bond angles for P1Ð
MoÐC2 [169.9 (2)ꢀ], P2ÐMoÐC3 [167.6 (2)ꢀ] and C4ÐMoÐ
C1 [171.8 (3)ꢀ] from the 180ꢀ ideal. The MoÐCax bond
aOrganometallic Chemistry Research Laboratory, Department of Chemistry, Univer-
sity of Puerto Rico, Mayaguez, PR 00681, Puerto Rico, bDepartment of Chemistry,
Keene State College, Keene, NH 03435-2001, USA, cDepartment of Chemistry,
Jackson State University, Jackson, MS 39217, USA, and dDepartment of Chemistry,
Mississippi College, Clinton, MS 39058-4036, USA
Correspondence e-mail: valente@mc.edu
Received 30 May 2000
Accepted 2 October 2000
In the present redetermination of the complex cis-tetra-
carbonylbis(tricyclohexylphosphine)molybdenum(0),
(I),
[Mo(C18H33P)2(CO)4] or cis-{ꢀ1-[P(C6H11)3]2}Mo(CO)4, the
Mo atom has a distorted octahedral geometry with a large PÐ
MoÐP angle of 104.8 (1)ꢀ. A strong trans in¯uence on the
carbonyls in (I) is seen in a shortening of the MoÐC and a
lengthening of the CÐO distances opposite the phosphines
compared with those that are cis. This in¯uence is greatly
diminished in the complex pentacarbonyl(tricyclohexyl-
phosphine)molybdenum(0), (II), [Mo(C18H33P)(CO)5] or
{ꢀ1-[P(C6H11)3]}Mo(CO)5, the core of which has a slightly
distorted C4v geometry.
Ê
lengths, averaging 2.040 (8) A, are trans to each other and are
signi®cantly (about 10 s.u.'s) longer than the MoÐCeq
Ê
distances, which average 1.924 (8) A and are both trans to P.
Both MoÐP bond distances are similar and average
Ê
2.655 (2) A, which is signi®cantly longer than the average
MoÐP distance in phosphine±pentacarbonyl±molybdenum
1
Ê
complexes such as (II) [2.594 (1) A], [ꢀ -PPh3]Mo(CO)5
Comment
Tricyclohexylphoshine dissociates from cis-{ꢀ1-[P(cy)3]2}tetra-
carbonylmolybdenum(0) (cy is cyclohexyl) to produce a
mixture of {ꢀ2-[P(cy)3]2}tetracarbonylmolybdenum(0) and [ꢀ1-
P(cy)3]pentacarbonylmolybdenum(0) (Cortes-Figueroa et al.,
Figure 1
1997). Ligand dissociation from cis-(ꢀ1-L)(ꢀ1-L0)Mo(CO)4
produces (ꢀ2-L0)Mo(CO)4, for L = P(cy)3, triphenylphosphine
or piperidine and L0 = P(cy)3 or triphenylphosphine, where L
The molecular structure of complex (I) showing the atom-numbering
scheme. Displacement ellipsoids are at the 50% probability level and H
atoms have been omitted for clarity.
ꢁ
Acta Cryst. (2000). C56, 1435±1437
# 2000 International Union of Crystallography Printed in Great Britain ± all rights reserved 1435

metal-organic compounds
1
Ê
Compound (I)
[2.560 (1) A; Cotton et al., 1981], [ꢀ -P(CH2CH2CN)3]-
1
Ê
Mo(CO)5 [2.506 (1) A; Cotton et al., 1981], and trans-{bis[ꢀ -
Ê
P(cy)3]}Mo(CO)4 [2.544 (1) A; Alyea et al., 1996]. The trans
in¯uence extends to the carbonyl groups in (I), such that those
opposite the shorter MoÐP distances, C2ÐO2 and C3ÐO3,
average 1.185 (8) A, while those cis to P, C1ÐO1 and C4ÐO4,
Ê
average 1.133 (8) A. This observation is consistent with the
larger ꢁ-acceptor ability of carbonyls (Cotton & Wilkinson,
1988; Cortes-Figueroa et al., 1998).
Crystal data
3
[Mo(C18H33P)2(CO)4]
Mr = 768.81
Monoclinic, P21/n
Dx = 1.260 Mg m
Mo Kꢃ radiation
Cell parameters from 50
re¯ections
Ê
Ê
Ê
a = 10.856 (3) A
b = 25.323 (8) A
ꢄ = 7.5±18.0ꢀ
ꢅ = 0.439 mm
T = 293 (2) K
1
Ê
c = 14.795 (7) A
ꢂ = 94.68 (3)ꢀ
V = 4054 (3) A
Z = 4
3
Ê
Prism, light yellow
0.40 Â 0.20 Â 0.05 mm
Data collection
Siemens P3 diffractometer
! scans
Rint = 0.092
ꢄmax = 27.51ꢀ
Absorption correction: semi-zempi-
rical via scans (XEMP;
Siemens, 1989)
Tmin = 0.844, Tmax = 0.978
12 628 measured re¯ections
9302 independent re¯ections
3635 re¯ections with I > 2ꢆ(I)
h = 0 ! 14
k = 0 ! 32
l = 19 ! 19
3 standard re¯ections
every 197 re¯ections
frequency: 150 min
intensity decay: 3.0 (3)%
Re®nement
Re®nement on F2
R[F2 > 2ꢆ(F2)] = 0.055
wR(F2) = 0.080
S = 0.931
9302 re¯ections
424 parameters
H-atom parameters constrained
w = 1/[ꢆ2(Fo2) + (0.048P)2]
where P = (Fo2 + 2Fc2)/3
(Á/ꢆ)max = 0.001
3
Ê
Áꢇmax = 0.59 e A
3
Ê
0.70 e A
Áꢇmin
=
Table 1
Selected geometric parameters (A, ) for (I).
ꢀ
Ê
Figure 2
The molecular structure of the major conformer of complex (II) showing
the atom-numbering scheme. Displacement ellipsoids are at the 50%
probability level and H atoms have been omitted for clarity.
MoÐC2
MoÐC3
MoÐC1
MoÐC4
MoÐP2
1.921 (6)
1.927 (6)
2.039 (5)
2.042 (6)
2.6529 (16)
MoÐP1
O1ÐC1
O2ÐC2
O3ÐC3
O4ÐC4
2.6569 (17)
1.123 (6)
1.211 (6)
1.159 (6)
1.143 (6)
In the pentacarbonyl complex, (II), the Mo geometry is only
slightly distorted from the octahedral ideal and is nearly C4v.
The trans in¯uence is present in (II) but greatly diminished
compared with (I). The MoÐC5 distance, trans to P and to the
shorter MoÐP distance mentioned above, is shorter
C2ÐMoÐC3
C2ÐMoÐC1
C3ÐMoÐC1
C2ÐMoÐC4
C3ÐMoÐC4
C1ÐMoÐC4
C2ÐMoÐP2
C3ÐMoÐP2
84.2 (2)
85.8 (2)
87.7 (2)
87.8 (2)
86.6 (2)
171.8 (3)
84.81 (17)
167.64 (16)
C1ÐMoÐP2
C4ÐMoÐP2
C2ÐMoÐP1
C3ÐMoÐP1
C1ÐMoÐP1
C4ÐMoÐP1
P2ÐMoÐP1
97.26 (16)
87.27 (16)
169.87 (16)
86.47 (17)
89.77 (16)
95.73 (16)
104.81 (5)
Ê
[1.97 (1) A] than the average of the remaining MoÐC
Ê
distances [2.03 (1) A]. At the carbonyl groups, however, the
in¯uence is very weak, with the trans C5ÐO5 distance of
Ê
1.154 (6) A being larger but not statistically distinguishable
Ê
from the other four [average 1.149 (12) A]. Disorder in one
Compound (II)
cyclohexyl ring, between alternate chair conformers, was
modelled with the major conformer having an occupancy of
0.64 (1).
Crystal data
3
[Mo(C18H33P)(CO)5]
Mr = 516.40
Monoclinic, P21/n
a = 11.785 (3) A
b = 16.760 (7) A
Ê
c = 12.779 (4) A
ꢂ = 92.15 (2)ꢀ
V = 2522.3 (14) A
Z = 4
Dx = 1.360 Mg m
Mo Kꢃ radiation
Cell parameters from 42
re¯ections
Ê
Ê
ꢄ = 12±16ꢀ
ꢅ = 0.612 mm
T = 293 (2) K
1
Experimental
3
Ê
Rod, colorless
0.40 Â 0.20 Â 0.18 mm
Complex (I) was prepared from cis-[bis(piperidine)]tetracarbonyl-
molybdenum(0) following the procedure of Darensbourg & Kump
(1978); a 2.5 mol excess of tricyclohexylphosphine to the piperidine
complex was used, in dichloromethane. Light-yellow crystals of (I)
were obtained by recrystallization from dichloromethane±methanol
solution. Complex (II) was prepared by re¯uxing Mo(CO)6 and
P(cy)3 in bis(2-methoxyethyl) ether under dinitrogen. Upon cooling
to 277 K, colorless crystals of (II) formed in low yield.
Data collection
Siemens P3 diffractometer
! scans
h = 0 ! 14
k = 0 ! 19
4655 measured re¯ections
4435 independent re¯ections
2498 re¯ections with I > 2ꢆ(I)
Rint = 0.089
l = 15 ! 15
3 standard re¯ections
every 197 re¯ections
frequency: 180 min
ꢄmax = 25.01ꢀ
intensity increase: 3.2 (4)%
ꢁ
1436 Jose Cortes-Figueroa et al. [Mo(C18H33P)2(CO)4] and [Mo(C18H33P)(CO)5]
Acta Cryst. (2000). C56, 1435±1437

metal-organic compounds
Re®nement
We thank the Of®ce of Naval Research for support of
instrumentation (EJV and JDZ), the National Science Foun-
dation (HRD-9550705) and the Puerto Rico alliance for
Minority Participation (PR-AMP).
Re®nement on F2
R[F2 > 2ꢆ(F2)] = 0.045
wR(F2) = 0.091
S = 0.901
4435 re¯ections
308 parameters
H-atom parameters constrained
w = 1/[ꢆ2(Fo2) + (0.0499P)2]
where P = (Fo2 + 2Fc2)/3
(Á/ꢆ)max < 0.001
3
Ê
Áꢇmax = 0.77 e A
3
Ê
0.52 e A
Áꢇmin
=
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: FR1291). Services for accessing these data are
described at the back of the journal.
Table 2
Selected geometric parameters (A, ) for (II).
ꢀ
Ê
MoÐC5
MoÐC3
MoÐC4
MoÐC2
MoÐC1
1.972 (6)
2.009 (7)
2.020 (6)
2.038 (7)
2.046 (7)
MoÐP
2.5938 (14)
1.136 (6)
1.140 (6)
1.163 (6)
1.151 (6)
O1ÐC1
O2ÐC2
O3ÐC3
O4ÐC4
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Ê
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È
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ꢁ
Acta Cryst. (2000). C56, 1435±1437
Jose Cortes-Figueroa et al. [Mo(C18H33P)2(CO)4] and [Mo(C18H33P)(CO)5] 1437