(η5-cyclopentadienyl)(p-fluorophenoxo)(nitrosyl)(trimethylsi lylmethyl)molybdenum(II)

Article abstract of DOI:10.1107/S0108270101019382

A report on the synthesis of [Mo(C₅H₅)(C₆H₄FO)(C₄ H₁₁Si)(NO)] by reacting CpMo(NO)(CH₂SiMe₃)₂ where Cp denoted cyclopentadienyl, with one equivalent of p-FC₆H₄OH was presented. The piano-stool molecular structure was exhibited by the complex. A pseudo-tetrahedral geometry around the Mo atom was observed by the compound. The nitrosyl ligand was found to be involved in π-back-bonding with the Mo centre.

Full text of DOI:10.1107/S0108270101019382

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
(g5-Cyclopentadienyl)(p-fluoro-
phenoxo)(nitrosyl)(trimethylsilyl-
methyl)molybdenum(II)
Trevor W. Hayton, Peter Legzdins* and Steven J. Rettig²
Department of Chemistry, University of British Columbia, 2036 Main Mall,
Vancouver, BC, Canada V6T 1Z1
Correspondence e-mail: legzdins@chem.ubc.ca
Figure 1
The molecular structure of (I) showing 50% probability ellipsoids. H
atoms have been omitted for clarity.
Received 24 August 2001
Accepted 13 November 2001
Online 16 January 2002
Ê
and a long NÐO distance [1.207 (3) A], relative to most other
nitrosyls (Feltham & Enemark, 1981). This indicates that the
nitrosyl ligand is strongly involved in ꢀ-back-bonding with the
Ê
Mo centre. The phenoxo MoÐO distance is 1.945 (2) A,
signi®cantly longer than the WÐO distances in the related
Ê
complexes Cp*W(NO)(OCH2Ph)2 [1.910 (4) A] and Cp*
W(NO)(OCMe3)2 [Cp* is pentamethylcyclopentadienyl;
The title complex, [Mo(C5H5)(C6H4FO)(C4H11Si)(NO)], is
formed by reacting CpMo(NO)(CH2SiMe3)2, where Cp is
cyclopentadienyl, with one equivalent of p-FC6H4OH. The
complex exhibits the expected piano-stool molecular struc-
ture, with a linear nitrosyl ligand [MoÐNÐO 168.2 (2)ꢀ]
having MoÐN and NÐO distances of 1.764 (2) and
Ê
1.207 (3) A, respectively. The phenoxo MoÐO distance of
Ê
1.890 (5) and 1.903 (5) A; Legzdins et al., 1993], where
Ê
1.945 (2) A is suggestive of some multiple-bond character.
the metal±oxygen bond has de®nite multiple-bond
character. However, the phenoxo MoÐO distance is shorter
Comment
than the WÐO bonds in Cp*W(NO)(OMe)[ꢁ2-O
C
(Me)CH CPh] [2.001 (7) A; Legzdins et al., 1998] and Cp*
Ê
Many attempts to generate molybdenum± and tungsten±
alkoxo complexes in our laboratories have been unsuccessful.
The standard metathetical protocol, using a metal±halide
precursor with an alkali metal±alkoxide salt, often results in
either decomposition or the formation of NÐO bond-clea-
vage products (Legzdins et al., 1996). An alternate procedure,
namely protonation of the alkyl ligand in CpMo(NO)-
(CH2SiMe3)2 by an alcohol to generate the corresponding
alkoxo complex and SiMe4, has now been found to generate a
variety of new complexes in good yield. The title compound,
CpMo(NO)(CH2SiMe3)(p-FC6H4O), (I) (Fig. 1), has been
synthesized by this method.
W(NO)(OCMe3)[ꢁ2-N(CMe3) C(CH2CMe3)] [1.978 (4) A;
Ê
Legzdins et al., 1994]. The WÐO bonds in these two
compounds, by the nature of the ꢁ2-bound co-ligands, are
single bonds, which then suggests that the MoÐO link in (I) is
somewhat more than a single bond. Comparison with other W
and Mo complexes, namely Cp*W(MeCCMe)2(OPh) [WÐO
Ê
2.072 (7) A; O'Regan et al., 1992], [Cp*W(Me)2(OC6F5)]2(ꢂ-
Ê
N2) [WÐO 2.079 (8) A; O'Regan et al., 1990], and [Mo2-
Ê
(OPh-4-Me)7(Me2NH)2] [MoÐOterminal 2.03 A (average);
Cof®ndaffer et al., 1985], further supports this assumption.
Experimental
In a Schlenk tube, under anaerobic and anhydrous conditions,
(ꢁ5-C5H5)Mo(NO)(CH2SiMe3)2 (100 mg, 0.27 mmol) was combined
with p-¯uorophenol (31 mg, 0.27 mmol), and the mixture was
dissolved in tetrahydrofuran (THF, 20 ml). The resulting purple
solution was stirred for 3 d at room temperature, whereupon it
became deep red. The THF was removed in vacuo, and the resulting
red oil was dissolved in hexanes (30 ml) and ®ltered through a column
of celite (2 Â 2 cm). The volume of this ®ltrate was reduced to 4 ml,
and it was then cooled to 243 K overnight to induce the deposition of
(I) as a dark-red powder (64 mg, 60% yield). X-ray quality crystals
were grown from a concentrated hexanes solution at 243 K over a
Compound (I) exhibits a pseudo-tetrahedral geometry
around the Mo atom typical of this class of three-legged piano-
stool molecules. The MoÐNÐO linkage is linear [Mo1ÐN1Ð
1
period of several weeks. IR (Nujol): 1635 cm (ꢃNO). 1H NMR
ꢀ
Ê
O1 168.2 (2) ], with a short Mo1ÐN1 distance [1.764 (2) A]
(200 MHz, C6D6): ꢄ 6.81 (t, 2H, CÐHm), 7.02 (dd, 2H, CÐHo), 5.19
(s, 5H, C5H5), 2.48 (d, 1H, CH2SiMe3), 1.97 (d, 1H, CH2SiMe3), 0.17
² Deceased October 27, 1998.
m68 # 2002 International Union of Crystallography
DOI: 10.1107/S0108270101019382
Acta Cryst. (2002). C58, m68±m69

metal-organic compounds
Table 1
Selected geometric parameters (A, ).
The absorption correction was based on a three-dimensional
analysis of symmetry-equivalent data and was performed along with
batch scaling in a single step. The resulting transmission factors,
therefore, include contributions from absorption, crystal decay, and
detectable variations in beam intensity. The CÐH distances are
ꢀ
Ê
Mo1ÐO2
Mo1ÐN1
Mo1ÐC1
Mo1ÐC2
Mo1ÐC3
1.945 (2)
1.764 (2)
2.288 (3)
2.386 (3)
2.443 (3)
Mo1ÐC4
Mo1ÐC5
Mo1ÐC12
N1ÐO1
2.405 (3)
2.333 (3)
2.133 (3)
1.207 (3)
Ê
0.98 A.
Data collection: d*TREK (Molecular Structure Corporation,
1996±1998); cell re®nement: d*TREK; data reduction: d*TREK;
program(s) used to solve structure: SIR97 (Altomare et al., 1999);
program(s) used to re®ne structure: TEXSAN (Molecular Structure
Corporation, 1992±1997); software used to prepare material for
publication: TEXSAN.
O2ÐMo1ÐN1
O2ÐMo1ÐC12
N1ÐMo1ÐC12
100.84 (9)
107.86 (9)
96.0 (1)
Mo1ÐO2ÐC6
Mo1ÐN1ÐO1
Mo1ÐC12ÐSi1
128.5 (2)
168.2 (2)
129.2 (1)
(s, 9H, SiCH3). 13C NMR (200 MHz, C6D6): ꢄ 118.6 (CÐF), 116.1
(CÐHo), 115.6 (CÐHm), 104.7 (C5H5), 49.3 (CH2Si), 1.93 (SiCH3).
The authors thank NSERC and UBC for funding. They also
thank Drs W. B. Sharp and B. O. Patrick for helpful discus-
sions.
Crystal data
[Mo(C5H5)(C6H4FO)-
(C4H11Si)(NO)]
Mr = 389.35
Z = 2
Dx = 1.517 Mg m
Mo Kꢅ radiation
3
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: DA1210). Services for accessing these data are
described at the back of the journal.
Triclinic, P1
a = 7.0052 (7) A
Cell parameters from 4985
re¯ections
Ê
Ê
b = 9.0510 (9) A
ꢈ = 3.1±27.9ꢀ
ꢂ = 0.85 mm
T = 180.2 K
1
Ê
c = 14.021 (2) A
References
ꢅ = 103.510 (5)ꢀ
ꢆ = 98.776 (5)ꢀ
ꢇ = 91.830 (4)ꢀ
Altomare, A., Burla, M. C., Camalli, M., Cascarano, G., Giacovazzo, C.,
Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J.
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Irregular, red
0.25 Â 0.20 Â 0.06 mm
3
Ê
V = 852.2 (1) A
Data collection
Rigaku/ADSC CCD diffractometer
' and ! scans
Absorption correction: multi-scan
(d*TREK; Molecular Structure
Corporation, 1996±1998)
Tmin = 0.71, Tmax = 0.95
3422 independent re¯ections
2674 re¯ections with I > 3ꢉ(I)
Rint = 0.043
ꢈ
max = 27.9ꢀ
h = 7 ! 8
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2993.
k = 11 ! 10
l = 18 ! 15
7376 measured re¯ections
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3200 Research Forest Drive, The Woodlands, TX 77381, USA.
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3200 Research Forest Drive, The Woodlands, TX 77381, USA.
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J. Am. Chem. Soc. 112, 4331±4338.
Re®nement
Re®nement on F2
R(F) = 0.029
wR(F2) = 0.072
S = 0.86
3422 re¯ections
190 parameters
H-atom parameters not re®ned
w = 1/[ꢉ2(Fo2)]
(Á/ꢉ)max = 0.001
3
Ê
Áꢊmax = 0.60 e A
3
Ê
0.92 e A
Áꢊmin
=
O'Regan, M. B., Vale, M. G., Payack, J. F. & Schrock, R. R. (1992). Inorg.
Chem. 31, 1112±1115.
ꢁ
Acta Cryst. (2002). C58, m68±m69
Trevor W. Hayton et al.
[Mo(C5H5)(C6H4FO)(C4H11Si)(NO)] m69