Preparation and properties of the halogenoalkyl compounds [(η5-C5H5)(CO)2(PPh iMe3-i)Mo{(CH2)nX}] (n=3, 4; I=0-3; X=Br, I) and [{η5-C5(CH3)5}(CO) 3Mo{(CH2)nX}] (n=3, 4; X=Br, I)

Article abstract of DOI:10.1016/S0022-328X(01)01044-0

The compounds [Cp(CO)₂(PPh_iMe_3-i)Mo{(CH₂) _nBr}] (Cp=η⁵-C₅H₅, n=3, 4; i=0-3) and [Cp*(CO)₃Mo{(CH₂)_nBr}] (Cp=η⁵-C₅(CH₃)₅, n=3, 4) were prepared in medium to high yield by the reaction of the corresponding anion ([Cp(CO)₂(PPh_iMe_3-i)Mo]^- or [Cp*(CO)₃Mo]^-) with Br(CH₂)_nBr. The bromoalkyl compounds were subsequently reacted with NaI to give the corresponding iodoalkyl compounds [Cp(CO)₂(PPh_iMe_3-i)Mo{(CH₂) _nI}] (n=3, 4; i=0-3) and [Cp*(CO)₃Mo{(CH₂)_nI}] (n=3, 4). The iodoalkyl compounds can also be prepared by the reaction of the corresponding anion and α,ω-diiodoalkane in much lower yields. These compounds have been fully characterised and their properties are discussed. The crystal and molecular structure of [Cp(CO)₂(PPh₃)Mo{(CH₂)₃I}] is reported. The compound forms crystals in the monoclinic space group P2₁/n, with a Mo-C bond length of 2.40 A? and a C-I bond length of 2.13 A?. The compounds [Cp(CO)₃W{(CH₂)_nX}] (X=Br, I; n=3-6) were also prepared in high yield and the crystal structures of [Cp(CO)₃W{(CH₂)₅I}] and [Cp(CO)₃W{(CH₂)₃Br}] are reported. The former compound forms orthorhombic crystals in the space group P2₁nb and the latter forms triclinic crystals in the space group P1?. Both have W-C bond lengths of 2.35 A?. The C-I bond length is 2.12 A?; the C-Br bond length is 1.94 A?.

Full text of DOI:10.1016/S0022-328X(01)01044-0

Journal of Organometallic Chemistry 633 (2001) 39–50
www.elsevier.com/locate/jorganchem
Preparation and properties of the halogenoalkyl compounds
[(h5-C5H5)(CO)2(PPhiMe3−i)Mo{(CH2)nX}] (n=3, 4; i=0–3;
X=Br, I) and [{h5-C5(CH3)5}(CO)3Mo{(CH2)nX}] (n=3, 4;
X=Br, I) and the crystal structures of
[(h5-C5H5)(CO)3W{(CH2)5I}], [(h5-C5H5)(CO)3W{(CH2)3Br}] and
[(h5-C5H5)(CO)2(PPh3)Mo{(CH2)3I}]
Holger B. Friedrich a,*, Martin O. Onani a, Orde Q. Munro b,*
a School of Pure and Applied Chemistry, Uni6ersity of Natal, Durban 4041, South Africa
b School of Chemical and Physical Sciences, Uni6ersity of Natal, Pietermaritzburg, Pri6ate Bag X01, Scotts6ille 3209, South Africa
Received 2 March 2001; accepted 12 May 2001
Abstract
The compounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)nBr}] (Cp=h5-C5H5, n=3, 4; i=0–3) and [Cp*(CO)3Mo{(CH2)nBr}]
(Cp*=h5-C5(CH3)5, n=3, 4) were prepared in medium to high yield by the reaction of the corresponding anion
([Cp(CO)2(PPhiMe3−i)Mo]− or [Cp*(CO)3Mo]−) with Br(CH2)nBr. The bromoalkyl compounds were subsequently reacted with
NaI to give the corresponding iodoalkyl compounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)nI}] (n=3, 4; i=0–3) and
[Cp*(CO)3Mo{(CH2)nI}] (n=3, 4). The iodoalkyl compounds can also be prepared by the reaction of the corresponding anion
and a,v-diiodoalkane in much lower yields. These compounds have been fully characterised and their properties are discussed.
The crystal and molecular structure of [Cp(CO)2(PPh3)Mo{(CH2)3I}] is reported. The compound forms crystals in the monoclinic
,
,
space group P21/n, with
a Mo–C bond length of 2.40 A and a C–I bond length of 2.13 A. The compounds
[Cp(CO)3W{(CH2)nX}] (X=Br, I; n=3–6) were also prepared in high yield and the crystal structures of [Cp(CO)3W{(CH2)5I}]
and [Cp(CO)3W{(CH2)3Br}] are reported. The former compound forms orthorhombic crystals in the space group P21nb and the
(
,
,
latter forms triclinic crystals in the space group P1. Both have W–C bond lengths of 2.35 A. The C–I bond length is 2.12 A; the
,
C–Br bond length is 1.94 A. © 2001 Published by Elsevier Science B.V.
Keywords: Haloalkyl ligand; Tungsten; Molybdenum; Carbonyl; Cyclopentadienyl
1. Introduction
pounds of the type [LyM{(CH2)nX}] (LyM=transition
metal and its associated ligands, n]1, X=halogen)
are known precursors of cyclic carbene complexes as
well as homo- and heterodinuclear compounds (which
have been proposed as models for intermediates in
several important catalytic processes). The application
of several of these compounds in organic synthesis has
also been described [1].
Whilst halogenomethyl complexes of several transi-
tion metals are fairly well known, longer-chain
halogenoalkyl compounds have been comparatively lit-
tle studied [1]. Indeed, only those of platinum [2],
ruthenium [3], iron [4] and, very recently, tungsten [5]
have been studied in any detail. Importantly, com-
Interestingly, although the halogenomethyl com-
pounds [(h5-C5R5)(CO)3MoCH2X] (R=H, CH3; X=
Cl, Br, I) are now known [6,7], very few phosphine
substituted compounds [Cp(CO)2LMoCH2X] (L=ter-
tiary phosphine or phosphite) have been reported. Only
* Corresponding authors. HBF: Tel.: +27-31-260-3107; fax: +27-
31-260-3091. OQM (crystallography): Tel.: +27-33-260-5270; fax:
+27-33-260-5009..
E-mail addresses: friedric@nu.ac.za (H.B. Friedrich), mun-
roo@nu.ac.za (O.Q. Munro).
0022-328X/01/$ - see front matter © 2001 Published by Elsevier Science B.V.
PII: S0022-328X(01)01044-0

40
H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
compounds where L=P(OPh3) and X=Cl, Br and I
are known [8]. The only previously reported long-chain
halogenoalkyl compounds of molybdenum are
[Cp(CO)3Mo{(CH2)nX}] (n=3, X=Cl, Br, I; n=4,
X=Br, I), Cp*(CO)3Mo{(CH2)3Br}] (Cp*=C5(CH3)5)
and [Cp(CO)2(PPh3)Mo{(CH2)3Br}] [9–12]. We now
report on the syntheses and properties of the com-
pounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)nX}] (n=3, 4;
i=0–3; X=Br, I) and [Cp*(CO)3Mo{(CH2)nX}] (n=
3, 4; X=Br, I) and the structure of [Cp(CO)2(PPh3)-
Mo{(CH2)3I}]. We also report on a new, high-yielding
synthetic route to the tungsten analogues, [Cp(CO)3W-
{(CH2)nBr}] (n=3–6), the crystal structure of
[Cp(CO)3W{(CH2)3Br}] and the crystal structure of
[Cp(CO)3W{(CH2)5I}]. To our knowledge, the latter is
vents in air. Remarkably, they dissolve in water in air
to give stable yellow solutions. The unchanged
halogenoalkyl compound can then be recovered. The
decomposition product in hexane appears to be the
dimer, [Cp(CO)3W]2, whilst the decomposition products
in chloroform include elemental tungsten.
The compounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)n-
Br}] (n=3, 4; i=0–3) and [Cp*(CO)3Mo{(CH2)nBr}]
(n=3, 4) were also prepared by the method shown in
Eq. (1), namely by reacting the corresponding anion
with the dihalogenoalkane.
The bromoalkyl compounds were then reacted with
NaI in acetone at room temperature to give the corre-
sponding iodo compounds, [Cp(CO)2LM{(CH2)nI}], in
high yield (Eq. (2)).
the first reported structure of
halogenoalkyl compound.
a
long-chain
[(h5-C5R5)(CO)2LM{(CH2)nBr}]+NaI
“[(h5-C5R5)(CO)2LM{(CH2)nI}]+NaBr
(2)
where M=Mo; n=3, 4; R=H; L=PPh3, PPh2Me,
PPhMe2, PMe3; R=CH3, L=CO. M=W; n=3–6;
R=H; L=CO.
2. Results and discussion
Although the bromoalkyl compounds of iron and
ruthenium, [Cp(CO)2M{(CH2)nX}] (M=Fe, Ru), have
to be prepared at low temperature to prevent the
formation of the binuclear compounds, [Cp(CO)2M-
(CH2)nM(CO)2Cp], these conditions give very low
yields for the analogous tungsten and molybdenum
compounds, regardless of reaction times. We find that
contrary to general expectations, the reaction of
Na[Cp(CO)3W] with excess Br(CH2)nBr (n=3–6) un-
der reflux in THF affords the compounds
[Cp(CO)3W{(CH2)nBr}] in high yield (Eq. (1)), confirm-
ing that the anion [Cp(CO)3W]− is a significantly
weaker nucleophile than the cyclopentadienyldicar-
bonyl anions of iron and ruthenium [13].
The bromoalkyl compound [Cp(CO)2(PPh3)Mo-
{(CH2)nBr}], where n=3, has been shown to react with
KCN or LiI in refluxing methanol or THF respectively
to form the cyclic carbene compounds [XCp(CO)-
(PPh3)Mo{CO(CH2)2CH2}], X=I, CN [14], thus
demonstrating the significant effect of temperature and
solvent on the reactions of these haloalkyl compounds,
both in terms of yield and in which product is formed.
The molybdenum bromoalkyl compounds do, however,
form cyclic carbene compounds on reaction with NaI in
acetone over longer reaction times (\24 h). The
[Cp(CO)3W{(CH2)nI}] compounds have been reported
previously [5] and we thus only report data for these
compounds, where our data differ significantly from the
literature [15].
Na[(h5-C5R5)(CO)2LM]+Br(CH2)nBr
The molybdenum iodoalkyl compounds could also
be obtained by the reaction of the respective anion with
I(CH2)nI, which, after chromatography under N2, gave
analytically pure compounds. Yields, however, are low
and the method is not viable.
“(h5-C5R5)(CO)2LM{(CH2)nBr}]+NaBr
(1)
where M=Mo; n=3, 4; R=H; L=PPh3, PPh2Me,
PPhMe2, PMe3; R=CH3; L=CO. M=W; n=3–6;
R=H; L=CO.
Clearly the halogenoalkyl compounds of tungsten are
less thermally labile than expected. The dinuclear com-
pounds, [Cp(CO)3W(CH2)nW(CO)3Cp], are not formed.
The compounds, [Cp(CO)3W{(CH2)nBr}], are obtained
in analytically pure form by recrystallisation from a
dilute CH2Cl2–hexane solution at −78°C. Analytically
pure yields in excess of 90% are obtained by this
method, which are some 20% higher than the previ-
ously reported method [5]. Chromatography of these
compounds, which is essential for the iron analogues
[4], is not needed and leads to product loss due to
decomposition. The compounds are fairly stable in air
in the solid state and are stable in solution under
nitrogen, but decompose very rapidly in organic sol-
All compounds (Scheme 1) were obtained as yellow
solids or oils. Characterisation data for the compounds
are reported in Tables 1–3. From Table 1 it can be seen
that the melting points of the compounds decrease
steadily as methyl groups sequentially replace phenyl
groups in the coordinated tertiary phosphine. The melt-
ing points thus decrease with decreasing cone angle and
increasing pKa of the phosphine. The melting points for
the compounds where n=3 are higher than those for
where n=4. This is as observed for halogenoalkyl iron
compounds, as well as for linear unsubstituted
paraffins, and can be ascribed to crystal packing factors
[16–18]. In the IR spectra, the carbonyl bands move to
slightly lower wavenumbers as the halogen changes

H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
41
the phosphines are cis and not trans to the carbonyl
groups, their effects are relatively small.
1
The H-NMR data for these compounds are shown
in Table 2. The MoCH2 peaks show a small shift with
increasing chain length from n=3 to n=4, reflecting
the weakening of the inductive effect of the halogen
with increasing chain length. An upfield shift of the
MoCH2 peaks is also observed as the pKa values of the
phosphines increase and the cone angles decrease, as
would be expected. This effect is more pronounced in
the compounds where n=4, because the electronegative
halogen is further away. The ꢀ0.2 ppm shift of the
CH2X peaks as X is changed from Br to I is as expected
from the difference in their electronegativities. For the
compounds where n=3, the peaks also shift slightly
upfield with increasing pKa of the phosphines. This is
not observed for the compounds where n=4, pre-
sumably because the phosphine is too far away.
Assignments of the 13C-NMR spectra (Table 3) were
made using COSY, HMQC and HETCOR experi-
ments. The observation of only a single carbonyl peak
(as a doublet) for all the compounds, strongly suggests
that the phosphine is trans to the alkyl chain, with the
two carbonyl groups occupying equivalent cis positions.
This is confirmed by the crystal structure. Varying the
phosphine does not appear to affect significantly the
chemical shift of the CO group. Neither the halogen
nor the chain length appears to affect greatly the posi-
tions of the Cp or carbonyl peaks. There is, however, a
trend to lower l values for the Cp peaks as the cone
angle of the phosphine increases and the pKa increases
in going from PPh3 to PMe3. This is because the
increased electron density increases the shielding of the
Cp carbons. The halogen affects the chemical shift of
the carbon a to molybdenum. As observed for the iron
analogues [4], the peaks due to the a-carbons are
shifted upfield for compounds with smaller values of n.
This is contrary to what one would expect from consid-
eration of the inductive effects of the halogens and may
imply a weak interaction between the halogen and iron,
as has been proposed previously [4,12]. The MoCH2
peaks are at significantly higher field for the iodo
compounds than the bromo compounds where n=3,
and the opposite effect is observed where n=4. The
inverse to the above is observed for the Cp*MoCH2
peaks. The MoCH2 peaks also shift to lower field
positions with increasing pKa of the phosphines where
X=Br and n=3, whilst the opposite is observed where
X=Br, I and n=4. The CH2I peaks for the com-
pounds where n=3 are at a very much higher field than
those are where n=4.
Scheme 1.
Table 1
Data for [(h5-C5R5)(CO)2(PPhiMe3−i)Mo{(CH2)n}X], i=0–3, n=3–
4
a
Compound Yield (%)
m.p. (°C)
IR (w(CO), cm−1
)
1a
1b
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
8a
8b
9a
9b
10a
10b
57
96
87
92
51
30
40
46
54
28
42
21
64
29
96
23
38
78
18
74
120–121
\124 dec.
103–105
96–110
98–101
97–99
oil
1945s, 1868vs
1943s, 1868vs
1941s, 1865vs
1940s, 1865vs
1938s, 1860vs
1938s, 1860vs
1935s, 1857vs
1935s, 1856vs
1934s, 1856vs
1934s, 1856vs
1933s, 1856vs
1931s, 1853vs
1935s, 1857vs
1935s, 1857vs
1933s, 1855vs
1931s, 1854vs
2008s, 1924vs
2007s, 1922vs
2006s, 1919vs
2007s, 1919vs
oil
72–76
74–76
oil
oil
35–39
38–40
oil
oil
84–85
80–82
32–34
34–38
a Measured in hexane.
from Br to I, presumably reflecting the weaker electron
withdrawing character of the iodine. As one would
expect, the carbonyl bands shift to lower wavenumbers
with increasing pKa of the phosphines, with this effect
being more prominent for the compounds where n=4.
This is presumably so because the electronegative halo-
gen is further from the metal centres in these latter
compounds and hence competes less for electrons. Since
The data above indicate that there are significant
differences between the compounds where n=3 and
n=4. Specifically, the functionalised ends of the alkyl
chain can exert an influence up to a chain length of
three carbons, after which negligible or no effect is

42
H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
Table 2
1H-NMR data for [(h5-C5R5)(CO)2(PPhiMe3−i)Mo{(CH2)n}X], i=0–3, n=3–4
Compound
Cp*
Cp
a-CH2
CH2X
CH2CH2X
b-CH2
P–Ph
P–CH3
1a
1b
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
8a
8b
9a
9b
10a
10b
4.73
4.70
4.72
4.72
4.71
4.71
4.71
4.72
4.70
4.71
4.71
4.71
4.89
4.88
4.88
4.89
1.44
1.48
1.49
1.49
1.38
1.36
1.46
1.46
1.33
1.33
1.36
1.32
1.22
1.33
1.32
1.32
0.81
0.83
2.37
2.37
3.37
3.15
3.40
3.24
3.35
3.14
3.46
3.25
3.34
3.12
3.46
3.24
3.32
3.10
3.44
3.22
3.37
3.14
3.40
3.17
2.00
2.18
2.10
2.08
2.11
2.10
1.89
1.93
1.81
1.84
1.90
1.92
2.10
2.12
1.70
1.75
2.04
2.04
2.01
2.01
7.37
7.40
7.39
7.39
7.48
7.40
7.49
7.39
7.41
7.42
7.39
7.39
1.93
1.90
2.09
2.10
2.11
2.11
2.15
1.83
1.80
1.82
1.52
1.52
1.52
1.52
1.99
1.99
2.01
2.05
1.88
1.86
1.85
1.85
1.84
1.84
1.77
1.76
Measured in CDCl3; peaks are externally referenced to TMS (l=0.00), a-CH2 refers to the CH2-group a to molybdenum etc.
Table 3
13H-NMR data for [(h5-C5R5)(CO)2(PPhiMe3−i)Mo{(CH2)n}X], i=0–3, n=3–4
Compound
CO
Cp
Cp*
a-CH2
CH2X
CH2CH2X
b-CH2
P–Ph
P–CH3
1a
1b
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
8a
8b
9a
9b
10a
10b
237.94
218.49
218.51
218.43
236.93
236.93
236.91
236.95
236.98
236.94
236.94
236.95
235.07
236.04
237.27
237.46
92.72
92.70
92.65
92.65
92.38
92.36
92.58
92.34
91.83
92.98
91.75
91.76
91.02
92.21
90.96
90.95
0.15
2.24
2.23
1.90
0.53
2.42
1.73
1.32
1.03
1.89
1.07
1.00
0.15
0.99
0.80
1.09
8.74
0.97
0.33
5.60
37.67
35.85
34.34
36.79
39.94
11.93
34.90
29.69
37.69
12.09
34.16
33.79
37.74
18.45
35.01
39.64
37.81
11.48
36.35
25.49
39.54
40.68
30.95
33.19
37.63
41.05
34.41
37.11
40.17
35.82
34.83
29.67
40.39
34.50
34.20
33.81
38.86
39.79
30.87
32.54
128.17
128.17
128.17
128.10
128.31
128.24
128.54
127.69
128.54
128.27
128.47
128.29
38.77
39.46
21.55
21.54
21.13
21.58
20.91
20.43
20.96
20.37
21.71
21.60
21.76
21.78
38.99
39.50
38.82
39.17
38.88
39.91
10.31
10.33
10.31
10.54
231.26
32.91
32.59
Measured in CDCl3; peaks are externally referenced to TMS (l=0.00), a-CH2 refers to the CH2-group a to molybdenum etc.
observed. Whether this effect is transmitted through the
carbon chain or merely through space is not clear.
The structure of [Cp(CO)3W{(CH2)5I}] was deter-
mined. The compound forms orthorhombic crystals in
the space group P21nb. The structure of the molecule
and packing in the crystal are shown in Figs. 1 and 2.
Selected bond lengths and angles for this compound are
given in Tables 4 and 5; listings of atomic coordinates,
anisotropic temperature factors, H atom coordinates,
and complete crystallographic details are given in the
supplementary material. In the crystal, the compound
shows the classical ‘bump in hollow’ packing, as is also
observed in the packing of paraffins (Fig. 2) [19]. The
,
following (B4 A) intermolecular contacts more quanti-
tatively reflect the close packing that is visually evident
,
,
in Fig. 2: I···O(1), 3.95(2) A; O(1)···C(8), 3.38(4) A;
,
,
O(3)···C(8), 3.64(4) A; C(p2)···C(6), 3.89(4) A;
,
,
C(p3)···C(6), 3.95(1) A; C(p3)···C(8), 3.91(2) A;

H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
43
Table 4
,
Bond distances (A) for [Cp(CO)3W{(CH2)5I}]
W–C(3)
W–C(1)
W–C(p2)
W–C(4)
W–C(p4)
O(2)–C(2)
O(3)–C(3)
C(p1)–C(p5)
C(p3)–C(p4)
C(4)–C(5)
C(6)–C(7)
1.88(3)
2.08(3)
W–C(2)
1.994(10)
2.347(12)
2.307(14)
2.349(8)
2.121(10)
1.12(4)
1.391(7)
1.391(7)
1.391(7)
1.505(11)
1.491(16)
W–C(p1)
W–C(p5)
W–C(p3)
2.373(19)
2.348(10)
2.308(19)
1.140(12)
1.14(3)
1.391(7)
1.391(7)
1.532(16)
1.507(12)
a
I–C(8)
O(1)–C(1)
C(p1)–C(p2)
C(p2)–C(p3)
C(p4)–C(p5)
C(5)–C(6)
C(7)–C(8)
The esds of the least significant digits are given in parentheses.
a Symmetry transformation used to generate equivalent atoms: x,
y−1/2, −z+5/2.
knowledge, no simple alkyl compounds of the
Cp(CO)3W moiety have been reported, but this bond
length is in the general range of reported W–C bonds
Fig. 1. ORTEP diagram of the X-ray structure of [Cp(CO)3W-
{(CH2)5I}]; selected atom labels are shown. Thermal ellipsoids are
contoured at the 35% probability level; H atoms have an arbitrary
,
,
radius of 0.1 A.
(2.18–2.36 A) [21–23], though most of these com-
pounds have different ligands bonded to the metal. The
bond length is very similar to that in [h5-C5H4CH2-n-
CH2)(CO)3W] (2.36 A), the most similar structure [23].
,
,
C(p4)···C(6), 3.86(4) A; C(p4)···C(7), 3.98(5) A;
C(p5)···C(6), 3.76(2) A. As is usual, the alkyl chain lies
,
,
in an energetically favoured extended staggered confor-
mation (Fig. 1) [20]. While this is true of the ligand
conformation, it is noteworthy that the C(2)–W–C(4)–
C(5) dihedral angle is nearly eclipsed (9.7°) rather than
staggered (180°). This apparently reflects the conforma-
tional dictates of facilitating favourable packing of the
alkyl chains (‘bump in hollow’) and the fact that the
long W–C bonds that make up the dihedral angle
permit a less strained eclipsed configuration than in a
simple C–C–C–C dihedral angle. The W–C(4) bond
The structure of [Cp(CO)3W{(CH2)3Br}] is similar to
that of the iodo compound above; bond lengths and
angles for this compound are given in Tables 6 and 7.
Complete listings of all crystallographic data for this
compound are given in the supplementary material.
There are two independent molecules per asymmetric
unit; the structure of the molecule and packing in the
crystal are shown in Figs. 3 and 4. The W–C bond
,
length of 2.35 A is identical to the iodo compound
,
above and the C–Br bond of 1.95 A is within the range
,
in the alkyl chain was found to be 2.35 A. To our
found for ‘paraffinic’ alkyl bromide compounds [24].
Fig. 2. ORTEP diagram showing the unit cell packing of [Cp(CO)3W{(CH2)5I}] viewed down the crystallographic a-axis. Thermal ellipsoids are
contoured at the 35% probability level; H atoms have been omitted for clarity.

44
H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
Table 5
Table 7
Bond angles (°) for [Cp(CO)3W{(CH2)5I}]
Bond angles (°) for [Cp(CO)3W{(CH2)3Br}]
C(3)–W–C(2)
C(2)–W–C(1)
74.6(11) C(3)–W–C(1)
82.3(11) C(3)–W–C(p1)
106.7(3)
147.7(9)
102.2(9)
128.4(8)
34.3(3)
C(3)–W(1)–C(1)
C(1)–W(1)–C(2)
C(1)–W(1)–C(10)
C(3)–W(1)–C(9)
C(2)–W(1)–C(9)
C(3)–W(1)–C(11)
C(2)–W(1)–C(11)
C(9)–W(1)–C(11)
C(1)–W(1)–C(4)
C(10)–W(1)–C(4)
C(11)–W(1)–C(4)
C(1)–W(1)–C(7)
C(10)–W(1)–C(7)
C(11)–W(1)–C(7)
C(3)–W(1)–C(8)
C(2)–W(1)–C(8)
C(9)–W(1)–C(8)
C(4)–W(1)–C(8)
O(1)–C(1)–W(1)
O(3)–C(3)–W(1)
C(4)–C(5)–C(6)
C(8)–C(7)–C(11)
C(11)–C(7)–W(1)
C(9)–C(8)–W(1)
C(8)–C(9)–C(10)
C(10)–C(9)–W(1)
C(9)–C(10)–W(1)
C(10)–C(11)–C(7)
C(7)–C(11)–W(1)
C(1b)–W(2)–C(2b)
106.7(7) C(3)–W(1)–C(2)
78.2(6) C(3)–W(1)–C(10)
104.1(7) C(2)–W(1)–C(10)
152.8(8) C(1)–W(1)–C(9)
122.6(8) C(10)–W(1)–C(9)
110.5(7) C(1)–W(1)–C(11)
89.5(7) C(10)–W(1)–C(11)
58.3(7) C(3)–W(1)–C(4)
74.6(6) C(2)–W(1)–C(4)
133.4(7) C(9)–W(1)–C(4)
136.1(7) C(3)–W(1)–C(7)
151.3(7) C(2)–W(1)–C(7)
58.3(7) C(9)–W(1)–C(7)
35.8(7) C(4)–W(1)–C(7)
118.8(8) C(1)–W(1)–C(8)
146.5(7) C(10)–W(1)–C(8)
34.1(7) C(11)–W(1)–C(8)
81.3(6) C(7)–W(1)–C(8)
176.6(14) O(2)–C(2)–W(1)
177.3(17) C(5)–C(4)–W(1)
109.0(13) C(5)–C(6)–Br(1)
107.6(17) C(8)–C(7)–W(1)
70.9(9) C(9)–C(8)–C(7)
70.6(10) C(7)–C(8)–W(1)
109.4(18) C(8)–C(9)–W(1)
72.0(10) C(9)–C(10)–C(11)
72.9(10) C(11)–C(10)–W(1)
106.2(17) C(10)–C(11)–W(1)
73.2(10) C(1b)–W(2)–C(3b)
77.6(7) C(3b)–W(2)–C(2b)
78.9(7)
144.7(7)
90.9(7)
94.9(6)
35.1(7)
137.7(7)
35.0(7)
72.4(6)
132.2(6)
98.4(7)
98.4(7)
121.1(7)
57.3(7)
100.6(7)
118.1(7)
57.8(7)
C(2)–W–C(p1)
C(3)–W–C(p2)
C(1)–W–C(p2)
C(3)–W–C(p5)
C(1)–W–C(p5)
C(p2)–W–C(p5)
C(2)–W–C(4)
C(p1)–W–C(4)
C(p5)–W–C(4)
C(2)–W–C(p3)
C(p1)–W–C(p3)
C(p5)–W–C(p3)
C(3)–W–C(p4)
C(1)–W–C(p4)
C(p2)–W–C(p4)
C(4)–W–C(p4)
95.6(6)
C(1)–W–C(p1)
150.9(10) C(2)–W–C(p2)
95.2(10) C(p1)–W–C(p2)
113.2(9)
C(2)–W–C(p5)
88.6(5)
134.9(10) C(p1)–W–C(p5)
34.76(17)
77.2(12)
71.0(12)
92.6(7)
116.6(11)
120.0(11)
34.3(2)
80.1(3)
115.9(9)
57.8(3)
57.5(3)
133.2(3)
126.8(7)
137.2(5)
146.4(4)
57.3(3)
C(3)–W–C(4)
C(1)–W–C(4)
C(p2)–W–C(4)
C(3)–W–C(p3)
C(1)–W–C(p3)
C(p2)–W–C(p3)
C(4)–W–C(p3)
57.8(3)
98.3(10) C(2)–W–C(p4)
152.5(11) C(p1)–W–C(p4)
57.5(3)
104.5(7)
C(p5)–W–C(p4)
C(p3)–W–C(p4)
C(p2)–C(p1)–W
35.1(3)
34.74(19)
73.9(5)
58.4(7)
34.3(7)
C(p2)–C(p1)–C(p5) 108.0
C(p5)–C(p1)–W
C(p1)–C(p2)–W
C(p2)–C(p3)–C(p4) 108.0
C(p4)–C(p3)–W
C(p5)–C(p4)–W
176.4(18)
116.2(10)
113.1(13)
73.1(9)
108.1(18)
72.6(10)
75.3(10)
108.6(18)
73.9(10)
71.1(9)
71.0(9)
71.9(4)
C(p1)–C(p2)–C(p3) 108.0
C(p3)–C(p2)–W
C(p2)–C(p3)–W
71.9(6)
73.8(8)
71.0(8)
72.4(4)
C(p5)–C(p4)–C(p3) 108.0
C(p3)–C(p4)–W
C(p4)–C(p5)–W
O(1)–C(1)–W
74.2(7)
72.5(5)
177(3)
179(2)
112.7(10)
114.3(9)
C(p4)–C(p5)–C(p1) 108.0
C(p1)–C(p5)–W
O(2)–C(2)–W
C(5)–C(4)–W
C(5)–C(6)–C(7)
74.2(9)
170(4)
O(3)–C(3)–W
121.0(8)
113.9(7)
113.0(9)
C(6)–C(5)–C(4)
C(8)–C(7)–C(6)
106.8(6)
77.9(7)
a
C(7)–C(8)–I
C(1b)–W(2)–C(11b) 111.0(7) C(3b)–W(2)–C(11b) 137.0(8)
C(2b)–W(2)–C(11b) 90.8(8) C(1b)–W(2)–C(10b) 144.8(7)
The esds of the least significant digits are given in parentheses.
a Symmetry transformation used to generate equivalent atoms: x,
y+1/2, −z+5/2.
C(3b)–W(2)–C(10b) 103.9(7) C(2b)–W(2)–C(10b)
C(11b)–W(2)–C(10b) 34.6(7) C(1b)–W(2)–C(9b)
92.8(8)
152.1(7)
124.7(7)
35.1(6)
C(3b)–W(2)–C(9b)
C(11b)–W(2)–C(9b)
C(1b)–W(2)–C(4b)
C(2b)–W(2)–C(4b)
95.3(6) C(2b)–W(2)–C(9b)
57.7(6) C(10b)–W(2)–C(9b)
72.2(6) C(3b)–W(2)–C(4b)
Table 6
75.0(6)
,
Bond distances (A) for [Cp(CO)3W{(CH2)3Br}]
130.8(7) C(11b)–W(2)–C(4b) 136.0(8)
C(10b)–W(2)–C(4b) 133.2(6) C(9b)–W(2)–C(4b)
98.2(6)
119.1(7)
57.5(7)
34.1(7)
97.9(7)
120.7(7)
57.9(7)
101.4(7)
177.1(17)
177.1(15)
109.2(15)
W(1)–C(3)
W(1)–C(9)
W(1)–C(4)
W(1)–C(8)
O(1)–C(1)
1.949(17)
2.304(17)
2.347(15)
2.362(16)
1.149(18)
1.17(2)
1.51(2)
1.44(3)
1.39(3)
1.964(17)
2.03(2)
2.308(17)
2.336(14)
2.364(18)
1.15(2)
1.118(19)
1.53(2)
W(1)–C(1)
W(1)–C(11)
W(1)–C(7)
Br(1)–C(6)
O(2)–C(2)
C(4)–C(5)
1.983(17)
2.326(15)
2.356(16)
1.946(17)
1.06(2)
1.48(2)
1.39(3)
1.37(3)
1.39(3)
2.013(18)
2.285(16)
2.324(17)
2.361(16)
1.941(17)
1.04(2)
1.51(2)
1.40(3)
1.37(3)
1.36(3)
C(1b)–W(2)–C(8b)
C(2b)–W(2)–C(8b)
C(10b)–W(2)–C(8b)
C(4b)–W(2)–C(8b)
C(3b)–W(2)–C(7b)
C(11b)–W(2)–C(7b)
C(9b)–W(2)–C(7b)
C(8b)–W(2)–C(7b)
O(2b)–C(2b)–W(2)
C(5b)–C(4b)–W(2)
C(5b)–C(6b)–Br(2)
C(8b)–C(7b)–W(2)
C(9b)–C(8b)–C(7b)
C(7b)–C(8b)–W(2)
C(8b)–C(9b)–W(2)
118.1(8) C(3b)–W(2)–C(8b)
147.4(7) C(11b)–W(2)–C(8b)
57.5(7) C(9b)–W(2)–C(8b)
81.7(6) C(1b)–W(2)–C(7b)
152.2(7) C(2b)–W(2)–C(7b)
35.1(8) C(10b)–W(2)–C(7b)
57.4(7) C(4b)–W(2)–C(7b)
34.4(6) O(1b)–C(1b)–W(2)
179.4(18) O(3b)–C(3b)–W(2)
116.3(10) C(4b)–C(5b)–C(6b)
111.6(13) C(8b)–C(7b)–C(11b) 105.8(18)
72.7(10) C(11b)–C(7b)–W(2)
108.8(18) C(9b)–C(8b)–W(2)
72.9(10) C(8b)–C(9b)–C(10b) 108.4(17)
74.5(10) C(10b)–C(9b)–W(2)
O(3)–C(3)
C(5)–C(6)
C(7)–C(8)
C(8)–C(9)
C(7)–C(11)
C(9)–C(10)
W(2)–C(1b)
W(2)–C(2b)
W(2)–C(10b)
W(2)–C(4b)
W(2)–C(7b)
O(1b)–C(1b)
O(3b)–C(3b)
C(5b)–C(6b)
C(7b)–C(11b)
C(9b)–C(10b)
C(10)–C(11)
W(2)–C(3b)
W(2)–C(11b)
W(2)–C(9b)
W(2)–C(8b)
Br(2)–C(6b)
O(2b)–C(2b)
C(4b)–C(5b)
C(7b)–C(8b)
C(8b)–C(9b)
C(10b)–C(11b)
69.4(10)
71.5(10)
71.9(10)
C(11b)–C(10b)–C(9b) 107(2)
C(9b)–C(10b)–W(2)
C(10b)–C(11b)–W(2) 73.6(10) C(7b)–C(11b)–W(2)
C(11b)–C(10b)–W(2) 71.8(10)
73.1(10) C(10b)–C(11b)–C(7b) 109.7(18)
75.5(11)
1.40(3)
1.40(3)
The esds of the least significant digits are given in parentheses. Atoms
belonging to the second independent molecule in the asymmetric unit
(molecule B) are W(2), Br(2), and all those listed with alphanumeric
labels containing the letter b.
The esds of the least significant digits are given in parentheses. Atoms
belonging to the second independent molecule in the asymmetric unit
(molecule B) are W(2), Br(2), and all those listed with alphanumeric
labels containing the letter b.

H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
45
Whilst the structure clearly shows that there is no
bending of the bromine towards the tungsten in the
solid state (as possibly indicated in solution), the C(4)–
,
,
C(5) bond length at 1.48 A is 0.5 A shorter than the
equivalent bond in the longer chained iodoalkyl com-
pound, which may account for the unusual spectral
characteristics of the a-carbons in halogenopropyl com-
pounds. Interestingly, the unit cell packing of
[Cp(CO)3W{(CH2)3Br}] shown in Fig. 4 reveals that the
conformation of the alkyl ligand is probably a compro-
mise between (1) minimizing an unfavourable
C(5)···C(8) intramolecular contact between the alkyl
and Cp ligands and (2) the reality that ‘bump in hollow’
packing similar to that of Fig. 2 only becomes more
favourable as the alkyl chain becomes longer. The alkyl
ligand thus exhibits a C(2)–W(1)–C(4)–C(5) dihedral
angle that is closer to 90° than 180° in both indepen-
dent molecules of the asymmetric unit (119.1 and 118.0°
for molecules A and B, respectively).
Fig. 4. ORTEP diagram showing the unit cell packing of [Cp(CO)3W-
{(CH2)3Br}] viewed down the crystallographic a-axis. Thermal ellip-
soids are contoured at the 35% probability level; H atoms have been
omitted for clarity.
Table 8
,
Selected bond distances (A) for [Cp(CO)2(PPh3)Mo{(CH2)3I}]
Mo–C(4)
Mo–C(6)
Mo–C(7)
Mo–C(8)
Mo–P
P–C(17)
P–C(11)
O(2)–C(5)
C(2)–C(3)
C(6)–C(7)
C(8)–C(9)
1.946(7)
2.318(7)
2.341(7)
2.376(7)
2.4541(17)
1.834(6)
1.840(6)
1.127(8)
1.627(10)
1.380(11)
1.376(13)
Mo–C(5)
Mo–C(10)
Mo–C(9)
Mo–C(1)
I–C(3)
1.982(7)
2.331(7)
2.342(7)
2.402(7)
2.134(9)
1.834(6)
1.132(8)
1.264(10)
1.374(11)
1.357(13)
1.402(13)
P–C(23)
O(1)–C(4)
C(1)–C(2)
C(6)–C(10)
C(7)–C(8)
C(9)–C(10)
The esds of the least significant digits are given in parentheses.
Compound 1b forms crystals in the monoclinic space
group P21/n. Selected bond distances and angles for 1b
are given in Tables 8 and 9; non-hydrogen atomic
coordinates, anisotropic temperature factors, H atom
coordinates, and complete crystallographic details are
given in the supplementary material. The structure of
the molecule and packing in the crystal are shown in
Fig. 5 and Fig. S1 (supplementary material), respec-
tively. Similar packing to that found for
[Cp(CO)3W{(CH2)3Br}] (Fig. 4) is observed in the case
of compound 1b. The halogenoalkyl ligand is trans to
PPh3 and the P–Mo–C(1)–C(2) dihedral angle is ob-
tuse (110.6°, significantly closer to 90 than 180°). As
with [Cp(CO)3W{(CH2)3Br}], the 3-carbon alkyl chain
Fig. 3. ORTEP diagrams showing the crystallographically independent
molecules (A and B) of the X-ray structure of [Cp(CO)3W-
{(CH2)3Br}]; selected atom labels are indicated. Thermal ellipsoids
are contoured at the 35% probability level; H atoms have an arbitrary
,
radius of 0.1 A.

46
H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
,
2.40 A, which is within the range reported for Mo–C
appears to be too short to favour the ‘bump in hollow’
packing observed for [Cp(CO)3W{(CH2)5I}]. The C–I
,
(alkyl) bonds (2.27–2.41 A) [11,25]. Very few structures
of molybdenum-alkyl compounds have been reported
and to our knowledge none with the Cp(CO)2(PR3)
ligand pattern. The Mo–C(alkyl) bond lengths of the
two Cp(CO)3MoR compounds previously reported are
,
bond length of 2.12 A is within the range of C–I bonds
of ‘paraffinic’ iodoalkyl compounds [24]. The molybde-
num to carbon bond in the alkyl chain was found to be
,
marginally shorter at 2.36 and 2.38 A. The Mo–C(car-
Table 9
bonyl) bond is also marginally shorter for compound
1b compared to the Mo–CO bond in the tricarbonyl
compounds, indicating the expected greater degree of
back-bonding in the PPh3 substituted compound. No
corresponding lengthening of the C–O bond is ob-
served, however, the weakening of this bond is reflected
in the comparative IR data. The bond lengths between
the alkyl carbons in [{Cp(CO)3Mo}2(CH2)4] are re-
Selected bond angles (°) for [Cp(CO)2(PPh3)Mo{(CH2)3I}]
C(4)–Mo–C(5)
C(5)–Mo–C(6)
C(5)–Mo–C(10)
C(4)–Mo–C(7)
C(6)–Mo–C(7)
C(4)–Mo–C(9)
C(6)–Mo–C(9)
C(7)–Mo–C(9)
C(5)–Mo–C(8)
C(10)–Mo–C(8)
C(9)–Mo–C(8)
C(5)–Mo–C(1)
C(10)–Mo–C(1)
C(9)–Mo–C(1)
C(4)–Mo–P
102.9(3)
153.5(3)
147.8(3)
131.9(3)
34.5(3)
127.3(3)
57.1(3)
56.3(3)
101.0(3)
57.1(3)
33.9(3)
73.1(2)
90.2(3)
81.0(3)
80.5(2)
93.1(2)
84.1(2)
109.2(3)
103.1(3)
100.7(3)
118.97(18)
115.8(5)
116.9(5)
176.8(5)
73.3(4)
108.9(7)
71.9(4)
71.8(4)
C(4)–Mo–C(6)
C(4)–Mo–C(10)
C(6)–Mo–C(10)
C(5)–Mo–C(7)
C(10)–Mo–C(7)
C(5)–Mo–C(9)
C(10)–Mo–C(9)
C(4)–Mo–C(8)
C(6)–Mo–C(8)
C(7)–Mo–C(8)
C(4)–Mo–C(1)
C(6)–Mo–C(1)
C(7)–Mo–C(1)
C(8)–Mo–C(1)
C(5)–Mo–P
C(10)–Mo–P
C(9)–Mo–P
C(1)–Mo–P
C(17)–P–C(11)
C(17)–P–Mo
C(11)–P–Mo
C(1)–C(2)–C(3)
O(1)–C(4)–Mo
101.4(3)
98.8(3)
34.4(3)
119.0(3)
57.1(3)
113.7(3)
34.9(3)
155.4(3)
56.6(3)
33.4(3)
,
ported as being 1.53 A [11]. The C(2)–C(3) bond in
compound 1b is rather longer at 1.63 A, whilst the
C(1)–C(2) bond is very short (1.26 A). However, these
values are unlikely to be real and it is likely that they
are artifacts due to the large thermal motion of the
haloalkyl ligand.
,
,
74.7(3)
124.2(3)
137.2(3)
107.3(3)
80.54(17)
126.8(2)
140.2(2)
138.20(18)
104.0(3)
109.90(19)
118.13(19)
113.2(6)
174.9(6)
C(6)–Mo–P
C(7)–Mo–P
C(8)–Mo–P
3. Experimental
C(17)–P–C(23)
C(23)–P–C(11)
C(23)–P–Mo
C(2)–C(1)–Mo
C(2)–C(3)–I
O(2)–C(5)–Mo
C(10)–C(6)–Mo
C(8)–C(7)–C(6)
C(6)–C(7)–Mo
C(7)–C(8)–Mo
All reactions were carried out under nitrogen using
standard Schlenk tube techniques. Tetrahydrofuran
(THF) was distilled from sodium and acetone from
anhydrous CaCl2. Hexane and pentamethylcyclopenta-
diene (Aldrich) were distilled prior to use. [Cp(CO)3W]2
[26], [Cp(CO)2(PPh3)Mo]2, [Cp(CO)2(PPh2Me)Mo]2,
[Cp(CO)2(PPhMe2)Mo]2 [27] and [Cp*(CO)3Mo]2] [28]
were prepared according to literature procedures with
modifications as shown below. The dihaloalkanes,
Mo(CO)6, W(CO)6 and the tertiary phosphines (all
Aldrich, PMe3 as the silver iodide salt) were used
without further purification and NaI was dried prior to
use. Alumina (Merck, active, acidic) was deactivated
with deionised water before use. Melting points were
recorded on a Kofler hot-stage microscope and are
uncorrected. Elemental analyses were performed in the
Chemistry Department of our Pietermaritzburg campus
or at the SABS in Richards Bay. Infrared spectra were
recorded on a Nicolet Impact-400 spectrometer. The
NMR spectra were recorded on Varian Unity-Inova
400 and Varian Gemini 300 MHz spectrometers, which
also were used for the COSY, HETCOR and HMQC
experiments. Solutions for NMR were prepared under
nitrogen, using nitrogen saturated solvents.
C(10)–C(6)–C(7) 108.3(7)
C(7)–C(6)–Mo
C(8)–C(7)–Mo
C(7)–C(8)–C(9)
C(9)–C(8)–Mo
C(8)–C(9)–Mo
73.7(4)
74.7(4)
107.9(8)
71.7(4)
74.4(4)
C(8)–C(9)–C(10) 108.2(7)
C(10)–C(9)–Mo
C(6)–C(10)–Mo
72.1(4)
72.3(4)
C(6)–C(10)–C(9) 106.7(7)
C(9)–C(10)–Mo 73.0(4)
The esds of the least significant digits are given in parentheses.
3.1. Preparation of [Cp(CO)3W]2
Na (8.6 mmol) was reacted with dicyclopentadiene
(11.5 mmol) in N2-saturated diglyme (34 ml) for 3 h.
When all the metal had dissolved, hexacarbonyl tung-
sten (0.1 mmol) was added and the reaction mixture
Fig. 5. ORTEP diagram of the X-ray structure of [Cp(CO)2(PPh3)Mo-
{(CH2)3I}]; selected atom labels are shown. Thermal ellipsoids are
contoured at the 35% probability level; H atoms have an arbitrary
,
radius of 0.1 A.

H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
47
refluxed under N2 (ca. 114 h). The pink solution turned
yellow at the end of the reflux. The product was
allowed to cool under N2 (ca. 45 min). A solution of
hydrated ferric sulphate was then prepared under N2 by
dissolving hydrated ferric sulphate (238 mmol) in dis-
tilled water (52.5 ml) and acetic acid (3.125 ml). The
resulting light pink solution was then slowly added to
the reaction solution under N2 to precipitate the
[Cp(CO)3W]2, which was then filtered off. The filtrate
was washed with water (10 ml), methanol (10 ml) and
pentane (10 ml) and dried under vacuum overnight.
The unreacted hexacarbonyl tungsten was sublimed off
the product at 60°C using a cold finger to leave the
pure dimer in 91% yield.
literature procedure [29]. The mixture was allowed to
cool to room temperature under N2, CH2Cl2 (10 ml)
was then added and the mixture degassed by several
freeze–thaw cycles under vacuum. The mixture was
then connected to a U-tube connected to a flask con-
taining the trimethylphosphine silver iodide complex
(18 mmol). The trimethylphosphine silver iodide com-
plex was heated slowly and carefully to release a contin-
uous flow of trimethylphosphine gas into the reaction
vessel which was maintained in liquid N2 under vac-
uum. After all the trimethylphosphine gas had been
driven into the reaction vessel, the mixture was allowed
to attain room temperature while stirring. Bright red
powdered dimer was obtained. The physical properties
of the dimers agreed with those in the literature.
3.2. Preparation of Na[Cp(CO)3W]
3.6. Preparation of
Na (108 mmol) was reacted slowly with Hg (6 ml) in
a Schlenk tube fitted with a bottom tap and the dilute
sodium amalgam left to cool to room temperature.
THF (30 ml) was added, followed by [Cp(CO)3W]2
(1.65 mmol). The dimer was reduced to the anion,
[Cp(CO)3W]− (3.3 mmol), after 2 min of stirring, as
shown by a colour change from brick red to green. The
mercury was drained off from the bottom of the
Schlenk tube.
[Cp(CO)2(PPhiMe3−i)Mo(CH2)nBr], i=0–3, n=3–4
A solution of Na[Cp(CO)2(PPhiMe3−i)Mo], i=1–3,
(0.477 mmol) in THF (25 ml) prepared by cracking the
respective dimers, [Cp(CO)2(PPhiMe3−i)Mo]2, using
Na (152 mmol)–Hg (8 ml) was added over 35 min to a
stirred solution of Br(CH2)nBr (0.477 mmol) in THF (5
ml) at −25 to −30°C. The solution was stirred for 15
min then allowed to attain room temperature (ca. 4 h),
after which the IR spectrum of a sample isolated from
the reaction solution no longer showed the w(CO)
stretching frequencies due to the Na[Cp(CO)2-
(PPhiMe3−i)Mo]. The solvent was removed under re-
duced pressure, leaving a yellow–black residue. This
was extracted with hexane (3×10 ml), and the solution
was filtered via a cannula under N2, concentrated under
reduced pressure to approximately a third of the total
volume of the hexane used, and then cooled to −78°C
under nitrogen (ca. 2 h). The yellow product separated
from the solution. The mother liquor was syringed off
and the product dried under reduced pressure. Yields
and physical properties are listed in Table 1. The
residue after the hexane extractions contained small
quantities of [Cp(CO)2(PPhiMe3−i)MoBr] and the re-
spective dimers [Cp(CO)2(PPhiMe3−i)Mo]2. Anal.
Found. (calc.): 3a C 51.52 (51.20), H 4.8 (4.49); 4a C
52.07 (52.10), H 4.97 (4.74); 5a C 44.52 (45.31), H 4.79
(4.65); 6a C 46.37 (46.46), H 5.04 (4.92); 7a C 37.98
(37.61), H 4.73 (4.86); 8a C 38.71 (39.20), H 5.31
(5.17%).
3.3. Preparation of [Cp(CO)3W{(CH2)nBr}], n=3–6
Na [Cp(CO)3W] (3.3 mmol) in THF (30 ml) was
added dropwise over 25 min to a stirred solution of
Br(CH2)nBr (8.25 mmol) in THF (30 ml) at −25 to
−30°C. The solution was then allowed to attain room
temperature (ca. 1 h). The mixture was then refluxed
under N2 (using an oil bath at 70°C) for 14 h. The
product was allowed to cool to room temperature,
filtered through a cannula, and the solvent was then
removed under reduced pressure. The product was re-
crystallised from a mixture of hexane–dichloromethane
(10:1) at −78°C. Analytically pure yellow solid was
obtained.
3.4. Preparation of [Cp(CO)3W{(CH2)nI}], n=3–6
NaI (6.02 mmol) was added to [Cp(CO)3W-
{(CH2)nBr}], n=3–6, (3.01 mmol) in dry, N2-saturated
acetone (10 ml). The solution was stirred at room
temperature for 18 h. The solution was filtered through
a cannula and the solvent removed under reduced
pressure. The yellow solid was recrystallised twice from
hexane (40 ml) at −78°C to give the analytically pure
product.
3.7. Preparation of
[Cp(CO)2(PPhiMe3−i)Mo{(CH2)nI}], i=0–3, n=3–4
NaI (0.300 mmol) was added to a solution of
[Cp(CO)2(PPhiMe3−i)Mo{(CH2)nBr}] (0.150 mmol) in
acetone (12 ml). The solution was stirred at room
temperature for 18–24 h, after which the 1H-NMR
spectrum of a sample isolated from the reaction solu-
tion no longer showed the triplet due to the CH2Br.
3.5. Preparation of dimer [Cp(CO)2(PMe3)Mo]2
[Cp2(CO)6Mo2] (9 mmol) and diglyme (12 ml) were
used to prepare [Cp2(CO)4Mo2] in situ according to the

48
H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
3.11. Preparation of
The solvent was removed under reduced pressure, leav-
ing a yellow–orange residue. This was extracted with
hexane (3×10 ml), and the solution was filtered via a
cannula under N2, concentrated under reduced pressure
to approximately a third of the total volume of hexane
used and this was then cooled to −78°C under nitro-
gen. The yellow product separated from the solution.
The mother liquor was syringed off and the product
dried under reduced pressure. Yields and physical prop-
erties are listed in Table 1. The syringed off mother
liquor was concentrated and transferred to an alumina
column. Elution with 10% CH2Cl2–hexane gave an
orange band which was identified as [Cp(CO)2-
(PPhiMe3−i)MoI] and a dark purple band which con-
tained the respective dimers. Anal. Found (calc.): 3b C
40.98 (41.24), H 4.09 (4.23); 4b C 47.16 (48.02), H 4.63
(4.37%).
[(p5-C5(CH3)5)(CO)3Mo{(CH2)nI}], i=0–3, n=3–4
These were prepared in the same way as the [(h5-
C5H5)(CO)2(PPhiMe3−i)Mo{(CH2)nI}]
above, where i=1–3, n=3–4.
compounds
3.12. Single-crystal X-ray diffraction analyses
X-ray data for single crystals of [Cp(CO)3W-
{(CH2)5I}], [Cp(CO)3W{(CH2)3Br}] and [Cp(CO)2-
(PPh3)Mo{(CH2)3I}]
Enraf–Nonius CAD4 diffractometer at 20(2)°C using
Mo–Ka wavelength radiation (0.70930 A). The data
were reduced with the program XCAD [30]. Semi-empir-
ical absorption corrections were applied to the data for
the two iodo derivatives using a minimum of four
reflections with -values \75° (azimuthal „-scan
method) with the program ABSCALC, as implemented in
OSCAIL [30]. The data for the bromo derivative were
corrected for absorption using the Fourier series
were
collected
on
an
,
3.8. Preparation of
[Cp(CO)2(PPhiMe3−i)Mo{(CH2)nI}] using I(CH2)nI,
i=0–3, n=3–4
method of
DIFABS
[31]. The structure of
A solution of Na[Cp(CO)2(PPhiMe3−i)Mo] (0.250
mmol, 25 ml THF) was added dropwise into I(CH2)nI
(0.250 mmol, 5 ml) immersed in a dry ice–acetone bath
at −25 to −30°C. The solution was stirred at this
temperature for 15 min, after which the mixture was
stirred at room temperature until the IR spectrum
showed no w(CO) bands due to the Na[Cp(CO)2-
(PPhiMe3−i)Mo]. The solvent was removed under re-
duced pressure, leaving a yellow–orange residue. This
was extracted with hexane (3×10 ml), and the solution
was filtered via a cannula, concentrated under reduced
pressure to approximately a third of the total volume of
hexane used, and this was then cooled to −78°C under
nitrogen. The yellow product separated from the solu-
tion. The mother liquor was syringed off and the
product dried under reduced pressure. Analytically pure
products in very low yields (10–30%) were obtained.
Other products observed were identified as [Cp(CO)2-
(PPhiMe3−i)MoI] and the respective dimers.
[Cp(CO)3W{(CH2)5I}] was solved in the orthorhombic
space group P21nb with the direct methods program
SHELXS-97 [32]. The structures of [Cp(CO)3W-
{(CH2)3Br}] and [Cp(CO)2(PPh3)Mo{(CH2)3I}] were
(
solved in the triclinic and monoclinic space groups P1
and P21/n, respectively, with the direct methods pro-
gram DIRDIF [33], as implemented by the crystallo-
graphic program WinGX [34]. In each case, the final
model was plotted with Farrugia’s 32-bit implementa-
tion of the program ORTEP [35]. Crystal data, lattice
constants, and least-squares refinement details for the
three compounds are listed in Table 10.
4. Supplementary material
Crystallographic data for the structural analyses
have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC nos. 158285 for
[Cp(CO)3W{(CH2)5I}], 158286 for [Cp(CO)3W{(CH2)3-
Br}] and 158287 for [Cp(CO)2(PPh3)Mo{(CH2)3I}].
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (Fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://www.
ccdc.cam.ac.uk). Full tables of crystallographic data
(crystallographic details, atomic coordinates, thermal
parameters, bond distances and bond angles) for
[Cp(CO)3W{(CH2)5I}], [Cp(CO)3W{(CH2)3Br}] and
[Cp(CO)2(PPh3)Mo{(CH2)3I}] (21 pages) are also avail-
able from the authors.
3.9. Preparation of [Cp*(CO)3Mo]2
This was prepared according to the literature [28],
except that the Cp* was distilled prior to use and all
reagents were degassed and all reactions carried out
under N2.
3.10. Preparation of [Cp*(CO)3Mo{(CH2)nBr}],
n=3–4
These were prepared using [Cp*(CO)3Mo]2 in the
same way as [(h5-C5H5)(CO)2(PPhiMe3−i)Mo{(CH2)n-
Br}] above, where i=0–3, n=3–4.

H.B. Friedrich et al. / Journal of Organometallic Chemistry 633 (2001) 39–50
49
Table 10
Crystallographic data for [Cp(CO)3W{(CH2)5I}], [Cp(CO)3W{(CH2)3Br}] and [Cp(CO)2(PPh3)Mo{(CH2)3I}]
[Cp(CO)3W{(CH2)5I}]
[Cp(CO)3W{(CH2)3Br}]
[Cp(CO)2(PPh3)Mo{(CH2)3I}]
Empirical formula
C13H15IO3W
530.00
C11H11BrO3W
454.96
C28H26IMoO2P
648.30
Formula weight (g mol−1
)
(
Crystal system, space group
Unit cell dimensions
Orthorhombic, P21nb
Triclinic, P1
Monoclinic, P21/n
,
a (A)
8.3227(9)
14.0192(16)
12.5856(13)
6.8337(14)
12.896(4)
14.355(3)
97.13(2)
89.995(18)
90.08(3)
1255.3(5), 4
2.407
17.4796(12)
9.2587(13)
17.558(3)
,
b (A)
,
c (A)
h (°) a
i (°) a
k (°) a
112.66(9)
3
,
Volume (A ), Z
1468.5(3), 4
2.397
9.966
2622.2(6), 4
1.642
1.761
Dcalc (g cm−3
)
Absorption coefficient (mm−1
)
12.374
Crystal size (mm), colour
q range for data collection (°)
0.20×0.15×0.15, yellow
2.17–22.97
0.35×0.25×0.15, orange
2.00–24.97
0.65×0.40×0.20, orange–red
2.10–22.97
Index ranges
−25h59, −55k515,
−135l513
3181, 1409 [Rint=0.0261]
1219
−85h58, −155k515,
05l517
−55h519, −45k510,
−195l518
5606, 3629 [Rint=0.0229]
3180
Reflections collected, unique
Reflections observed (\2|)
4397, 4397 [Rint=0.0000] b
3025
Maximum and minimum transmission 0.3164, 0.2405
0.2583, 0.0982
1.052
R1=0.0493, wR2=0.1236
R1=0.0851, wR2=0.1348
2.213, −1.368
0.7196, 0.3940
1.106
R1=0.0464, wR2=0.1411
R1=0.0518, wR2=0.1459
1.336, −1.596
Goodness-of-fit on F2
1.036
Final R indices [I\2|(I)] c
R1=0.0234, wR2=0.0615
R1=0.0295, wR2=0.0642
0.547, −0.893
R indices (all data) c
−3
,
Residual extrema (e A
)
The esds of the least significant digits are given in parentheses.
a Crystallographically required 90° angles are not given.
b Internal R-factor before DIFABS [31] absorption correction 0.0194.
c R1=ꢀ(ꢁFoꢁ−ꢁFcꢁ)2/ꢀꢁFoꢁ; wR2=(ꢀ[w(Fo2−F2c)2]/ꢀ[wF4o])0.5. R-factors R1 are based on F, with F set to zero for negative F2. The criterion of
F2\2|(F2) was used only for calculating R1. R-factors based on F2 (wR2) are statistically about twice as large as those based on F.
[7] R.B. King, D.M. Braitsch, J. Organomet. Chem. 54 (1973) 9.
[8] D.H. Gibson, S.K. Mandal, K. Owen, W.E. Sattich, J.O.
Franco, Organometallics 8 (1989) 1114.
Acknowledgements
We thank the University of Natal (URF), the Na-
[9] R.B. King, M.B. Bisnette, J. Organomet. Chem. 7 (1967) 311.
tional Research Foundation, Pretoria (NRF) and the
Deutscher Akademischer Austausch Dienst (DAAD)
for financial support. MOO thanks the DAAD for a
Ph.D. scholarship and the Jomo Kenyatta University of
Agriculture and Technology (Nairobi) for study leave.
OQM thanks James Ryan for mounting and taking
preliminary X-ray photographs of several crystal speci-
mens relevant to this work. Finally, we thank Professor
M. Laing for useful discussions of the crystal data.
[10] N.A. Bailey, D.A. Dunn, C.N. Foxcroft, G.R. Harris, M.J.
Winter, S. Woodward, J. Chem. Soc. Dalton Trans. (1988) 1449.
[11] H. Adams, N.A. Bailey, M.J. Winter, J. Chem. Soc. Dalton
Trans. (1984) 273.
[12] C.P. Casey, L.J. Smith, Organometallics 7 (1988) 2419.
[13] R.B. King, Acc. Chem. Res. 3 (1970) 417.
[14] N.A. Bailey, P.L. Chell, C.P. Manuel, A. Mukhopadhyay, D.
Rodgers, H.E. Tabron, M.J. Winter, J. Chem. Soc. Dalton
Trans. (1983) 2397.
[15] [Cp(CO)3W{(CH2)4Br}]: m.p.=66–67°C. [Cp(CO)3W{(CH2)4-
I}]: m.p.=109–110°C. [Cp(CO)3W{(CH2)6Br}]: m.p.=61–
63°C. [Cp(CO)3W{(CH2)6I}]: m.p.=64–66°C. 13C-NMR
(CDCl3) l=220.44 (CO), 94.32 (Cp), 39.47 (bCH2), 37.61
(gCH2), 36.44 (dCH2), 32.85 (CH2CH2I), −7.59 (CH2I).
[16] L. Pope, P. Somerville, M.J. Laing, K.J. Hindson, J.R. Moss, J.
Organomet. Chem. 112 (1976) 309.
[17] R. Boese, H.-C. Weiss, D. Bla¨ser, Angew. Chem. Int. Ed. Engl.
38 (1999) 988.
[18] A.P. Malanoski, P.A. Monson, J. Chem. Phys. 110 (1999) 664.
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[20] R.O. Hill, C.F. Marais, J.R. Moss, K.J. Naidoo, J. Organomet.
Chem. 587 (1999) 28.
[21] D.J. Darensbourg, R. Kudaroski, J. Am. Chem. Soc. 106 (1984)
3672.
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