Oxidation of fac-[M(CO)3(NCME)3] (M = Mo or W) with I2Cl6. Reactions of the seven-coordinate complex [WCl(ClICl)(CO)3(NCME)2]

Article abstract of DOI:10.1016/S0277-5387(01)00853-1

Reaction of fac-[Mo(CO)₃(NCMe)₃] (prepared in situ) with I₂Cl₆ resulted in a large amount of effervescence and the formation of a dark red-brown solution, and a yellow precipitate. Both the yellow precipitate and the orange solid resulting from work-up of the dark red-brown solution were found to be the Mo-Mo bonded non-carbonyl containing tetracationic complex [Mo₂(NCMe)₈][Cl]₂[ClICl]₂ (1). Oxidation of fac-[W(CO)₃(NCMe)₃] (prepared in situ) with I₂Cl₆ gave the seven-coordinate complex [WCl(ClICl)(CO)₃(NCMe)₂] (2). Treatment of 2 with an equimolar amount of L {L = PPh₃ [stirred for 1 min], AsPh₃ [stirred for 3 min] and SbPh₃ [stirred for 5 min]} in CH₂Cl₂ at room temperature gave [WCl(ClICl)(CO)₃(NCMe)L] (3-5). Reaction of [WCl(ClICl)(CO)₃(NCMe)₂] with an equimolar amount of L {L = PPh₃, AsPh₃ and SbPh₃} in CH₂Cl₂ at room temperature for 24 h gave the chloro-bridged complexes [{W(μ-Cl)(ClICl)(CO)₃L}₂] (6-8). Reaction of [WCl(ClICl)(CO)₃-(NCMe)₂] with 2 equiv. of RC₂R (R= Me or Ph) in CH₂Cl₂ at room temperature gave the bis(alkyne) complexes [WCl(ClICl)(CO)(NCMe)(η²-RC₂R)₂] (9 and 10). The reactions of [WCl(ClICl)(CO)(NCMe)(η²-PhC₂Ph)₂] with 1 equiv. of L ∧ L {L ∧ L = Ph₂P(CH₂)_nPPh₂ (n= 1-4, 6) or 2,2′-bipyridine} in CH₂Cl₂ at room temperature afforded the complexes [WCl(ClICl)(CO)(L ∧ L)(η²-PhC₂Ph)] (11-16). Treatment of [WCl(ClICl)(CO)(NCMe)(η²-RC²R)₂] (R = Me or Ph) with 2 equiv. of L ∧ L {L ∧ L = Ph₂P(CH₂)_nPPh₂ (n= 1-4, 6) in CH₂Cl₂ at room temperature afforded the dicationic complexes [W(CO)(L ∧ L)₂(η²-RC₂R)][Cl][ClICl]·CH ₂Cl₂ (17-26). All the new complexes described in this paper were characterised by elemental analysis, IR and ¹H NMR spectroscopy.

Full text of DOI:10.1016/S0277-5387(01)00853-1

Polyhedron 20 (2001) 2559–2566
www.elsevier.com/locate/poly
Oxidation of fac-[M(CO)3(NCMe)3] (M=Mo or W) with I2Cl6.
Reactions of the seven-coordinate complex
[WCl(ClICl)(CO)3(NCMe)2]
Paul K. Baker *, Craig T. Brown
Department of Chemistry, Uni6ersity of Wales, Bangor, Gwynedd, LL57 2UW, UK
Received 28 February 2001; accepted 22 May 2001
Abstract
Reaction of fac-[Mo(CO)3(NCMe)3] (prepared in situ) with I2Cl6 resulted in a large amount of effervescence and the formation
of a dark red–brown solution, and a yellow precipitate. Both the yellow precipitate and the orange solid resulting from work-up
of the dark red–brown solution were found to be the MoꢀMo bonded non-carbonyl containing tetracationic complex
[Mo2(NCMe)8][Cl]2[ClICl]2 (1). Oxidation of fac-[W(CO)3(NCMe)3] (prepared in situ) with I2Cl6 gave the seven-coordinate
complex [WCl(ClICl)(CO)3(NCMe)2] (2). Treatment of 2 with an equimolar amount of L {L=PPh3 [stirred for 1 min], AsPh3
[stirred for 3 min] and SbPh3 [stirred for 5 min]} in CH2Cl2 at room temperature gave [WCl(ClICl)(CO)3(NCMe)L] (3–5).
Reaction of [WCl(ClICl)(CO)3(NCMe)2] with an equimolar amount of L {L=PPh3, AsPh3 and SbPh3} in CH2Cl2 at room
temperature for 24 h gave the chloro-bridged complexes [{W(m-Cl)(ClICl)(CO)3L}2] (6–8). Reaction of [WCl(ClICl)(CO)3-
(NCMe)2] with 2 equiv. of RC2R (R=Me or Ph) in CH2Cl2 at room temperature gave the bis(alkyne) complexes
‚
[WCl(ClICl)(CO)(NCMe)(h2-RC2R)2] (9 and 10). The reactions of [WCl(ClICl)(CO)(NCMe)(h2-PhC2Ph)2] with 1 equiv. of L
L
‚
{L L=Ph2P(CH2)nPPh2 (n=1–4, 6) or 2,2%-bipyridine} in CH2Cl2 at room temperature afforded the complexes
[WCl(ClICl)(CO)(L L)(h2-PhC2Ph)] (11–16). Treatment of [WCl(ClICl)(CO)(NCMe)(h2-RC2R)2] (R=Me or Ph) with 2 equiv.
‚
‚
‚
of
L L {L L=Ph2P(CH2)nPPh2 (n=1–4, 6) in CH2Cl2 at room temperature afforded the dicationic complexes
[W(CO)(L L)2(h2-RC2R)][Cl][ClICl]·CH2Cl2 (17–26). All the new complexes described in this paper were characterised by
‚
1
elemental analysis, IR and H NMR spectroscopy. © 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Seven-coordinate complexes; I2Cl6; Molybdenum(II); Tungsten(II); Acetonitrile
[30], SnCl3R (R=Bun, Ph) [31–36], HgX2 [37–42] and
1. Introduction
XeF2 [43] with zero-valent carbonyl complexes
[M(CO)6−nLn] (M=Mo or W) to give halocarbonyl
complexes have also been investigated. Hitherto, until
our work described herein, no examples of the oxida-
tion of [M(CO)6−nLn] with the interhalogen com-
pound, I2Cl6 have been reported.
In 1986 [44], we described the oxidation of the zero-
valent complexes fac-[M(CO)3(NCMe)3] (M=Mo or
W) (prepared in situ) with 1 equiv. of X2 (X=Br, I) to
give the seven-coordinate complexes [MX2(CO)3-
(NCMe)2]. The chemistry of the diiodo-complexes
[MI2(CO)3(NCMe)2] has been extensively investigated
with neutral and anionic ligands [45,46]. We have also
described the oxidation of fac-[Mo(CO)3(NCMe)3]
(prepared in situ) with other oxidising agents, namely
XY (XY=ICl [47], IBr [48], GeCl4 [49], or SnCl4 [50])
The oxidation of zero-valent Group VI metal car-
bonyls [M(CO)6] (M=Mo or W), and their ligand
substituted complexes [M(CO)6−nLn] (L=neutral
donor ligands; M=Mo or W) with halogens, X2 has
been extensively studied over the past 44 years [1–22],
since the first report by Nigam and Nyholm [23] in
1957, describing the oxidation of [Mo(CO)4(diars)] with
I2 to give [MoI2(CO)2(diars)]. The use of other oxidising
agents such as ClN3 [24], CCl4 [25], SnCl4 [26,27], ICN
[28], SiHClR2 [29], MX4 (M=Ge, Sn; X=Cl, Br)
* Corresponding author. Tel.: +44-1248-351151; fax: +44-1248-
370528.
E-mail address: chs018@bangor.ac.uk (P.K. Baker).
0277-5387/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(01)00853-1

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P.K. Baker, C.T. Brown / Polyhedron 20 (2001) 2559–2566
to afford [MoXY(CO)3(NCMe)2], which also display
interesting reaction chemistry [45,46]. In this paper, we
describe the oxidation of fac-[M(CO)3(NCMe)3] (M=
Mo or W) (prepared in situ [51]), with I2Cl6 to give the
metal–metal bonded complex [Mo2(NCMe)8][Cl]2-
[ClICl]2 (1) or the seven-coordinate mixed halide com-
plex [WCl(ClICl)(CO)3(NCMe)2] (2). The reaction
chemistry of 2 with neutral monodentate donor ligands
and alkynes is described. The chemistry of the
bis(alkyne) complexes [WCl(ClICl)(CO)(NCMe)(h2-
RC2R)2] (M=Me or Ph) is also discussed.
(2), which was recrystallised from NCMe. Yield of pure
product=6.48 g, 78%.
2.2.3. [WCl(ClICl)(CO)3(NCMe)(PPh3)] (3)
To [WCl(ClICl)(CO)3(NCMe)2] (2) (0.3 g, 5.14×
10−4 mol) dissolved in CH2Cl2 (20 cm3) with continu-
ous stirring was added PPh3 (0.121 g, 5.14×10−4 mol).
The solution was stirred at r.t. for 1 min. Removal of
the solvent in vacuo gave the dark green complex
[WCl(ClICl)(CO)3(NCMe)2] (3), which was recrys-
tallised from CH2Cl2/Et2O. Yield=0.324 g, 78%.
Similar reactions of [WCl(ClICl)(CO)3(NCMe)2] (2)
with 1 equiv. of L (L=AsPh3, stirred for 3 min or
SbPh3, stirred for 5 min) gave the analogous complexes:
[WCl(ClICl)(CO)3(NCMe)(AsPh3)] (4) (yield=78%)
and [WCl(ClICl)(CO)3(NCMe)(SbPh3)] (5) (yield=
65%).
2. Experimental
2.1. General
The preparation and purification of all complexes
described in this paper were carried out using standard
vacuum/Schlenk line techniques under an atmosphere
of dry nitrogen. All chemicals used were purchased
from commercial sources. Dichloromethane was dried
and distilled over P2O5 before use. Elemental analyses
were recorded on a Carlo Erba MOD 1108 Elemental
Analyser (using helium as a carrier gas). Infrared spec-
tra were recorded on a Perkin–Elmer 1600 FT IR
spectrophotometer. Proton NMR spectra were
recorded on a Bruker AC 250 MHz NMR spectrometer
and were referenced to tetramethylsilane.
2.2.4. [{W(v-Cl)(ClICl)(CO)3(PPh3)}2] (6)
To [WCl(ClICl)(CO)3(NCMe)2] (2) (0.3 g, 5.14×
10−4 mol) dissolved in CH2Cl2 (20 cm3) with continu-
ous stirring was added PPh3 (0.121 g, 5.14×10−4 mol).
The solution was stirred at r.t. for 24 h. Removal of the
solvent in vacuo gave the dark green complex [{W(m-
Cl)(ClICl)(CO)3(PPh3)}2] (6), which was recrystallised
from CH2Cl2/Et2O. Yield=0.481 g, 61%.
Similar reactions of [WCl(ClICl)(CO)3(NCMe)2] with
1 equiv. of L {L=AsPh3 or SbPh3} in CH2Cl2 for 24 h
gave the analogous complexes: [{W(m-Cl)(ClICl)-
(CO)3(AsPh3)}2] (7) (yield=63%) and [{W(m-Cl)-
(ClICl)(CO)3(SbPh3)}2] (8) (yield=56%).
2.2. Preparations
2.2.1. [Mo2(NCMe)8][Cl]2[ClICl]2 (1a, 1b)
2.2.5. [WCl(ClICl)(CO)(NCMe)(p2-MeC2Me)2] (9)
To [WCl(ClICl)(CO)3(NCMe)2] (2) (2.0 g, 3.43×
10−3 mol) dissolved in CH2Cl2 (20 cm3) with continu-
ous stirring was added MeC2Me (0.537 cm3, 0.37 g,
6.86×10−3 mol). The solution was stirred at r.t. for 24
h. Removal of the solvent in vacuo gave the dark blue
complex [WCl(ClICl)(CO)(NCMe)(h2-MeC2Me)2] (9),
which was recrystallised from CH2Cl2/Et2O. Yield of
pure product=1.65 g, 80%.
A suspension of [Mo(CO)6] (5 g, 0.019 mol) was
refluxed in acetonitrile (150 cm3) for 24 h. The resultant
yellow solution was cooled in an ice bath to 0 °C. I2Cl6
(4.43 g, 0.0095 mol) was added to the yellow solution
resulting in a large amount of effervescence, the forma-
tion of a dark red–brown solution and the formation
of a yellow precipitate 1a. This mixture was allowed to
return to room temperature (r.t.) and stirred for 1 h.
The solution was filtered to remove the precipitate. The
remaining solution was cooled to −17 °C for 3 days,
and an orange precipitate 1b, formed. The mixture was
again filtered to remove the precipitate. Yield: 1a=
0.778 g, 4%; 1b=2.736 g, 15%.
2.2.6. [WCl(ClICl)(CO)(NCMe)(p2-PhC2Ph)2] (10)
To [WCl(ClICl)(CO)3(NCMe)2] (2) (2.0 g, 2.43×
10−3 mol) dissolved in CH2Cl2 (20 cm3) with continu-
ous stirring was added PhC2Ph (1.22 g, 6.86×10−3
mol). The solution was stirred at r.t. for 24 h. Removal
of the solvent in vacuo gave the dark green complex
[WCl(ClICl)(CO)(NCMe)(h2-PhC2Ph)2] (10), which
was recrystallised from CH2Cl2/Et2O. Yield of pure
product=2.53 g, 72%.
2.2.2. [WCl(ClICl)(CO)3(NCMe)2] (2)
A suspension of [W(CO)6] (5 g, 0.014 mol) was
refluxed in acetonitrile (150 cm3) for 72 h. The resultant
yellow solution was cooled in an ice bath to 0 °C. I2Cl6
(3.27 g, 0.007 mol) was added to the yellow solution
resulting in the formation of a dark red–brown solu-
tion. The solution was allowed to return to r.t. and
stirred for 1 h. Removal of the solvent in vacuo gave
the red–brown complex [WCl(ClICl)(CO)3(NCMe)2]
2.2.7. [WCl(ClICl)(CO){Ph2P(CH2)PPh2}(p2-PhC2Ph)]
(11)
To [WCl(ClICl)(CO)(NCMe)(h2-PhC2Ph)2] (10) (0.3
g, 2.936×10−4 mol) dissolved in CH2Cl2 (20 cm3) with

P.K. Baker, C.T. Brown / Polyhedron 20 (2001) 2559–2566
2561
continuous stirring was added Ph2P(CH2)PPh2 (0.113 g,
2.936×10−1 mol). The solution was stirred at r.t. for
24 h. Removal of the solvent in vacuo gave the
green complex [WCl(ClICl)(CO){Ph2P(CH2)PPh2}(h2-
PhC2Ph)] (11), which was recrystallised from CH2Cl2/
Et2O. Yield=0.238 g, 81%.
PPh2}2(h2-PhC2Ph)][Cl][ClICl]·CH2Cl2 (24) (yield=
88%),
[ClICl]·CH2Cl2 (26) (yield=89%).
[W(CO){Ph2P(CH2)6PPh2}2(h2-PhC2Ph)][Cl]-
3. Results and discussion
Similar reactions of [WCl(ClICl)(CO)(NCMe)(h2-
‚
‚
PhC2Ph)2] with
1
equiv. of L L {L L=Ph2P-
3.1. Oxidation of fac-[Mo(CO)3(NCMe)3] (prepared in
situ) [51] with I2Cl6
(CH2)nPPh2 (n=2–4, 6) and 2,2-bipyridine (bipy)} in
CH2Cl2 at r.t., gave the analogous complexes
[WCl(ClICl)(CO){Ph2P(CH2)2PPh2}(h2-PhC2Ph)] (12)
(yield=71%), [WCl(ClICl)(CO){Ph2P(CH2)3PPh2}(h2-
PhC2Ph)] (13) (yield=82%), [WCl(ClICl)(CO){Ph2P-
(CH2)4PPh2}(h2-PhC2Ph)] (14) (yield=65%), [WCl-
(ClICl)(CO){Ph2P(CH2)6PPh2}(h2 - PhC2Ph)] (15)
(yield=65%), and [WCl(ClICl)(CO)(bipy)(h2-PhC2Ph)]
(16) (yield=55%).
Reaction of fac-[Mo(CO)3(NCMe)3] (prepared in situ
[51]) with I2Cl6 resulted initially in much effervescence
of carbon monoxide, followed by the formation of a
yellow precipitate (1a). The solution was then sealed in
a nitrogen-filled Schlenk tube and placed in a freezer in
an attempt to grow single crystals; while the solution
was in the freezer an orange precipitate (1b) was
formed. These compounds were characterised by IR
spectroscopy and elemental analysis (C, H and N). The
IR spectra for both powders are very similar and show
no carbonyl bands, however they do give NCMe bands
at 2400, 2315 and 2285 cm−1 (see Table 2). The calcu-
lated percentages for the formula [Mo2(NCMe)8]-
[Cl]2[ClICl]2 are C, 19.5; H, 2.5 and N, 11.4%. The
values found for 1a are C, 19.9; H, 2.9 and N 11.8%.
The values found for 1b are C, 19.4; H, 2.5 and N
11.2% (see Table 1).
The infrared spectra results for 1a and 1b are all
consistent with the predicted formula for the com-
pounds as they only show nitrile stretching bands and
no carbonyl bands. The elemental analysis results for
both 1a and 1b are both consistent for the values
calculated for the formula [Mo2(NCMe)8][Cl]2[ClICl]2.
The complexes 1a and 1b are insoluble in CDCl3.
Several unsuccessful attempts have been made to grow
single crystals of 1a and 1b in several solvents such as
NCMe for X-ray crystallography.
The formula of the products from oxidation of fac-
[Mo(CO)3(NCMe)3] with I2Cl6, namely [Mo2(NCMe)8]-
[Cl]2[ClICl]2 is similar to structures previously reported
by Cotton and Weisinger [52,53] and by Mayer and
Abbott [54]. Mayer and Abbott [54] described the
preparation of [Mo2(NCMe)8](TFMS)4 (TMFS=trifl-
uoromethanesulphonate) from reaction of [Mo2(H2O)4-
(TMFS)2](TFMS)2 with acetonitrile. The colour and
spectral properties of [Mo2(NCMe)8][Cl]2[ClICl]2
(1a,1b) are identical to the tetrakis(BF4−) complex
[Mo2(NCMe)8][BF4]4, described by Cotton and
Weisinger [52,53], and the structure of this complex has
been crystallographically determined [52]. The structure
of 1a, b will be identical except for the mixed counteri-
ons in our complex. It is likely these reactions of
fac-[Mo(CO)3(NCMe)3] with I2Cl6 proceed with initial
formation of the seven-coordinate complex [Mo-
Cl(ClICl)(CO)3(NCMe)2] (see next section). The greater
lability of molybdenum compared to tungsten is well
2.2.8. [W(CO){Ph2P(CH2)PPh2}2(p2-MeC2Me)]-
[Cl][ClICl]·CH2Cl2(17)
To WCl(ClICl)(CO)(NCMe)(h2-MeC2Me)2] (9) (0.3
g, 5.05×10−4 mol) dissolved in CH2Cl2 (20 cm3) with
continuous stirring was added Ph2P(CH2)PPh2 (0.388 g,
1.01×10−3 mol). The solution was stirred at r.t. for 24
h. Removal of the solvent in vacuo gave the blue
complex [W(CO){Ph2P(CH2)PPh2}2(h2-MeC2Me)][Cl]-
[ClICl]·CH2Cl2 (17), which was recrystallised from
CH2Cl2/Et2O. Yield=0.321 g, 50%.
Similar reactions of [WCl(ClICl)(CO)(NCMe)(h2-
‚
‚
MeC2Me)2] with 2 equiv. of L L {L L=Ph2P-
(CH2)nPPh2 (n=2–4, 6)} in CH2Cl2 at r.t., gave the
analogous
complexes
[W(CO){Ph2P(CH2)2PPh2}2-
(h2-MeC2Me)][Cl][ClICl]·CH2Cl2 (19) (yield=46%),
[W(CO){Ph2P(CH2)3PPh2}2(h2-MeC2Me)][Cl][ClICl]·
CH2Cl2 (21) (yield=52%), [W(CO){Ph2P(CH2)4-
PPh2}2(h2-MeC2Me)][Cl][ClICl]·CH2Cl2 (23) (yield=
61%),
[W(CO){Ph2P(CH2)6PPh2}2(h2-MeC2Me)][Cl]-
[ClICl]·CH2Cl2 (25) (yield=56%).
2.2.9. Preparation of [W(CO){Ph2P(CH2)PPh2}2-
(p2-PhC2Ph)][Cl][ClICl]·CH2Cl2 (18)
To [WCl(ClICl)(CO)(NCMe)(h2-PhC2Ph)2] (10) (0.3
g, 2.936×10−1mol) dissolved in CH2Cl2 (20 cm3) with
continuous stirring was added Ph2P(CH2)PPh2 (0.226 g,
5.872×10−4 mol). The solution was stirred at r.t. for
24 h. Removal of the solvent in vacuo gave the blue
complex [W(CO){Ph2P(CH2)2PPh2}2(h2-PhC2Ph)][Cl]-
[ClICl]·CH2Cl2 (18), which was recrystallised from
CH2Cl2/Et2O. Yield=0.256 g, 63%.
Similar reactions of [WCl(ClICl)(CO)(NCMe)(h2-
‚
‚
PhC2Ph)2] with
2 equiv. of L L {L L=Ph2P-
(CH2)nPPh2 (n=2–4, 6)}in CH2Cl2 at r.t., gave the
analogous complexes [W(CO){Ph2P(CH2)2PPh2}2(h2-
PhC2Ph)][Cl][ClICl]·CH2Cl2
(20)
(yield=78%),
[W(CO){Ph2P(CH2)3PPh2}2(h2-PhC2Ph)][Cl][ClICl]·
CH2Cl2 (22) (yield=73%), [W(CO){Ph2P(CH2)4-

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P.K. Baker, C.T. Brown / Polyhedron 20 (2001) 2559–2566
known, and hence in the presence of acetonitrile, the
carbonyl ligands are displaced, and the Cl− and ClICl−
groups to eventually give the stable tetracationic com-
plex [Mo2(NCMe)8][Cl]2[ClICl]2 (1a, b), which is proba-
bly a thermodynamic well for this type of reaction.
Several attempts at low temperature reactions of fac-
[Mo(CO)3(NCMe)3] (prepared in situ [51]) with I2Cl6 to
try and synthesise [MoCl(ClICl)(CO)3(NCMe)2] were
made without success.
The chemistry of the important complex
[Mo2(NCMe)8][BF4]4, has been studied, for example,
Whelan et al. [55] have described the reaction of
[Mo2(NCMe)8][BF4]4 with a,v-dicarboxylic acids,
HO2C(CH2)nCO2H (n=1–8) to give salts with empiri-
cal formula [Mo2{O2C(CH2)nCO2}(NCMe)x][BF4]2.
Hence, it is useful to have another synthetic route to
this type of complex.
Tables 1–3). Although in the dimer, I2Cl6, each iodine
atom is in a square-planar environment, bonded to four
chlorine atoms, it has been found [56], that I2Cl6 readily
dissociates to ICl and Cl2. Hence it may be that initially
oxidation by Cl2 occurs followed by attachment of the
ICl to one of the chlorine atoms. We have previously
observed this type of behaviour in rhenium chemistry
[57]. The linear anion is likely to be ClICl−, since the
least electronegative iodine atom should attack the
coordinated chloride ligand. It is interesting to note
that the more labile molybdenum complex reacts in a
very different manner with I2Cl6 to the tungsten com-
plex (see previous section). The tungsten mixed-halide
complex, 2, is considerably less stable and less soluble
in chlorinated solvents such as CH2Cl2 and CHCl3 than
its diiodo-analogue [WI2(CO)3(NCMe)2] [44]. It was
difficult to obtain satisfactory elemental analysis data
for this complex. Complex 2 is stable when stored in
the solid state under nitrogen for several hours, but is
very air-sensitive in solution. The IR spectrum of 2
(CHCl3) has three strong carbonyl bands at 2016, 1933
and 1917 cm−1, as well as two NCMe bands at 2314
and 2276 cm−1 (see Table 2).
3.2. Reaction of fac-[W(CO)3(NCMe)3] (prepared in
situ [51]) with I2Cl6
Reaction of fac-[W(CO)3(NCMe)3] (prepared in situ
[51]) with I2Cl6 afforded the seven-coordinate complex
[WCl(ClICl)(CO)3(NCMe)2] (2) in high yield. This com-
pound was characterised by IR spectroscopy, elemental
Since the X-ray crystal structure of several of the
diiodo complexes [MI2(CO)3(NCR)2] (M=Mo, R=
1
analysis (C, H and N) and H NMR spectroscopy (see
Table 1
Physical and analytical data for complexes 1–26
Complex
Colour
Yield (%)
C (%)
H (%)
N (%)
[Mo2(NCMe)8][Cl]2[ClICl]2 (1a)
[Mo2(NCMe)8][Cl]2[ClICl]2 (1b)
[WCl(ClICl)(CO)3(NCMe)2] (2)
[WCl(ClICl)(CO)3(NCMe)(PPh3)] (3)
[WCl(ClICl)(CO)3(NCMe)(AsPh3)] (4)
[WCl(ClICl)(CO)3(NCMe)(SbPh3)] (5)
yellow
orange
red–brown
green
green
green
green
brown
green
blue
green
green
green
green
green
green
green
blue
green
blue
green
blue
green
blue
green
blue
4
15
78
78
78
65
61
63
56
80
72
81
71
82
65
65
55
50
63
46
78
52
73
61
88
56
89
19.9 (19.5)
19.4 (19.5)
13.4 (14.4)
33.8 (34.3)
31.8 (32.5)
31.7 (30.9)
33.2 (33.0)
30.5 (31.2)
29.9 (29.5)
23.0 (22.2)
43.8 (44.2)
46.8 (47.7)
49.0 (48.2)
48.9 (48.7)
49.3 (49.2)
50.0 (50.1)
37.8 (38.5)
49.6 (49.7)
53.1 (53.7)
50.7 (50.4)
54.9 (54.3)
50.9 (51.2)
54.7 (54.8)
51.7 (51.8)
55.1 (55.4)
53.4 (53.1)
56.1 (56.4)
2.9 (2.5)
2.5 (2.5)
1.3 (1.2)
1.9 (2.3)
3.0 (2.1)
2.4 (2.0)
2.5 (2.0)
2.3 (1.9)
1.7 (1.8)
3.1 (2.5)
3.0 (2.8)
2.5 (3.2)
4.1 (3.4)
3.6 (3.5)
3.9 (3.7)
3.9 (3.9)
1.9 (2.3)
3.4 (3.9)
3.4 (3.8)
4.7 (4.1)
4.3 (4.0)
4.5 (4.3)
4.9 (4.2)
4.5 (4.5)
5.3 (4.4)
5.4 (4.9)
4.3 (4.7)
11.8 (11.4)
11.2 (11.4)
4.0 (4.8)
1.4 (1.7)
2.3 (1.7)
0.8 (1.6)
[{W(m-Cl)(ClICl)(CO)3(PPh3)}2] (6)
[{W(m-Cl)(ClICl)(CO)3(AsPh3)}2] (7)
[{W(m-Cl)(ClICl)(CO)3(SbPh3)}2] (8)
[WCl(ClICl)(CO)(NCMe)(h2-MeC2Me)2] (9)
2.6 (2.4)
2.0 (2.8)
[WCl(ClICl)(CO)(NCMe)(h2-PhC2Ph)2] (10)
[WCl(ClICl)(CO){Ph2P(CH2)PPh2}(h2-PhC2Ph)] (11)
[WCl(ClICl)(CO){Ph2P(CH2)2PPh2}(h2-PhC2Ph)] (12)
[WCl(ClICl)(CO){Ph2P(CH2)3PPh2}(h2-PhC2Ph)] (13)
[WCl(ClICl)(CO){Ph2P(CH2)4PPh2}(h2-PhC2Ph)] (14)
[WCl(ClICl)(CO){Ph2P(CH2)6PPh2}(h2-PhC2Ph)] (15)
[WCl(ClICl)(CO)(bipy)(h2-PhC2Ph)] (16)
3.4 (3.6)
[W(CO){Ph2P(CH2)PPh2}2(h2-MeC2Me)][Cl][ClICl]·CH2Cl2 (17)
[W(CO){Ph2P(CH2)PPh2}2(h2-PhC2Ph)][Cl][ClICl]·CH2Cl2 (18)
[W(CO){Ph2P(CH2)2PPh2}2(h2-MeC2Me)][Cl][ClICl]·CH2Cl2 (19)
[W(CO){Ph2P(CH2)2PPh2}2(h2-PhC2Ph)][Cl][ClICl]·CH2Cl2 (20)
[W(CO){Ph2P(CH2)3PPh2}2(h2-MeC2Me)][Cl][ClICl]·CH2Cl2 (21)
[W(CO){Ph2P(CH2)3PPh2}2(h2-PhC2Ph)][Cl][ClICl]·CH2Cl2 (22)
[W(CO){Ph2P(CH2)4PPh2}2(h2-MeC2Me)][Cl][ClICl]·CH2Cl2 (23)
[W(CO){Ph2P(CH2)4PPh2}2(h2-PhC2Ph)][Cl][ClICl]·CH2Cl2 (24)
[W(CO){Ph2P(CH2)6PPh2}2(h2-MeC2Me)][Cl][ClICl]·CH2Cl2 (25)
[W(CO){Ph2P(CH2)6PPh2}2(h2-PhC2Ph)][Cl][ClICl]·CH2Cl2 (26)
green
Calculated values in parentheses.

P.K. Baker, C.T. Brown / Polyhedron 20 (2001) 2559–2566
2563
Table 2
IR data for complexes 1–26
Complex
w(CꢁC) (cm−1
)
w(CꢁO) (cm−1
)
w(CꢁN) (cm−1
)
1a
1b
2
3
4
5
6
7
8
2400(w); 2315(w); 2285(w)
2400(w); 2315(w); 2285(w)
2314(w); 2276(w)
2397(w)
2400(w)
2400(w)
2016(s); 1933(s); 1917(s)
2018(s); 2013(s); 1957(s)
2016(s); 1946(s); 1912(s)
2075(s); 2031(s); 1948(s)
2074(s); 2010(s); 1922(s)
2017(s); 1945(s); 1911(s)
2007(s); 1938(s); 1900(s)
2065(s)
2095(s)
1947(s)
1963(s)
1975(s)
1950(s)
1958(s)
1943(s)
1953(s)
1948(s)
1958(s)
1972(s)
1934(s)
9
1783(w)
1750(w)
1627(w)
1652(w)
1660(w)
1629(w)
1632(w)
1662(w)
1690(w)
1682(w)
1692(w)
1680(w)
1691(w)
1627(w)
1695(w)
1620(w)
1698(w)
1630(w)
2276(w)
2296(w)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
1953(s)
1935(s)
1954(s)
1951(s)
1950(s)
Spectra recorded in CHCl3 as thin films between NaCl plates; s=strong; w=weak.
Me [58]; M=W, R=Me, Et [59]; M=W, R=Ph [60])
have been determined, and since the IR spectral proper-
ties of 2 are similar to [MI2(CO)3(NCR)2], then it is
likely they will have a similar structure as shown in Fig.
1, which is a capped octahedron, with the larger ClICl
group in the uncapped position. Several unsuccessful
attempts at growing suitable single crystals of 2 were
made, probably due to the greater instability of this
complex in solution compared to [MI2(CO)3(NCR)2].
3 and 5 min, respectively) in CH2Cl2 at room tempera-
ture affords the complexes [WCl(ClICl)(CO)3(NCMe)L]
(3–5). Complexes 3–5 have been characterised by ele-
1
mental analysis (C, H and N), IR spectroscopy and H
NMR spectroscopy (see Tables 1–3). Complexes 3–5
are considerably more stable, but less soluble in CH2Cl2
and CHCl3 than complex 2, and as with complex 2 are
only slightly soluble in diethyl ether and hydrocarbon
solvents.
1
The infrared spectra (Table 2) of 3–5, as expected for
their proposed formulae display three carbonyl bands,
and a single band for the nitrile {w(NꢁC)} group. The
1H NMR spectra of 3–5, as expected, give resonances
(Table 3) for the phenyl and NCMe groups present
according to the proposed formula. Several unsuccess-
ful attempts to grow suitable single crystals of 3–5 were
made. However, the X-ray crystal structures of related
mixed ligand complexes [WI2(CO)3(NCR)(AsPh3)]
(R=Et or Ph) [61] and [WI2(CO)3(NCMe)(PPh3)] [62]
have been determined, and in view of the similar IR
properties, the structure of the capped trigonal pris-
matic geometry for 3–5 is likely.
The H NMR spectrum of 2 has, as expected, a single
methyl resonance at l=2.5 ppm, which is shifted
downfield from uncoordinated NCMe. Several unsuc-
cessful attempts to obtain mass spectroscopic data for
this complex were made and no parent ion was ob-
served. In view of our previous success investigating the
chemistry of the diiodo complexes [MI2(CO)3(NCMe)2]
[45,46], the rest of this paper describes the reactions of
[WCl(ClICl)(CO)3(NCMe)2] (2), with monodentate
donor ligands and alkynes, and also the reaction of the
bis(alkyne) complexes [WCl(ClICl)(CO)(NCMe)(h2-
RC2R)2] with neutral bidentate ligands.
In view of the previous studies involving the reac-
tions of [MI2(CO)3(NCMe)2] with 1 equiv. of L (L=
PPh3, AsPh3 or SbPh3) for prolonged periods of time,
the iodo-bridged dimers [{M(m-I)I(CO)3L}2] were iso-
lated [63], we decided to carry out the reactions of
3.3. Reactions of [WCl(ClICl)(CO)3(NCMe)2] (2) with
1 equi6. of PPh3, AsPh3 and SbPh3
Treatment of [WCl(ClICl)(CO)3(NCMe)2] with 1
equiv. of L (L=PPh3, AsPh3 and SbPh3; stirred for 1,

2564
P.K. Baker, C.T. Brown / Polyhedron 20 (2001) 2559–2566
Table 3
[WCl(ClICl)(CO)3(NCMe)2]
with
an
equimolar
1H NMR data for complexes 2–26
amount of L (PPh3, AsPh3 or SbPh3) for 24 h at room
temperature. Treatment of [WCl(ClICl)(CO)3(NCMe)2]
with 1 equiv. of L (L=PPh3, AsPh3 and SbPh3) in
CH2Cl2 at room temperature for 24 h affords the
complexes [{W(m-Cl)(ClICl)(CO)3L}2] (6–8). Com-
plexes 6–8 have been characterised by elemental anal-
Complex
1H NMR l (ppm)
2
3
4
5
2.5 (s, Me)
2.5 (s, 3H, Me); 7.0–7.7 (m, 15H, Ph)
2.4 (s, 3H, Me); 7.1–7.6 (m, 15H, Ph)
2.1 (s, 3H, Me); 7.2–7.8 (m, 15H, Ph)
7.3–7.0 (m, Ph)
1
ysis (C, H and N), IR and H NMR spectroscopy (see
6
Tables 1–3). Complexes 6–8 are all very air-sensitive
in solution, but are relatively stable in the solid state
when stored under nitrogen. The complexes are only
slightly soluble in CH2Cl2 and CHCl3.
7
8
9
10
11
12
13
7.3–7.7 (m, Ph)
7.2–7.8 (m, Ph)
2.3 (s, 3H, Me); 2.5, 2.7 (m, 12H, ꢁCMe)
2.2 (s, 3H, NCMe); 7.3–7.6 (m, 20H, Ph)
4.8 (br m, 2H, PCH2); 7.2–7.8 (br m, 30H, Ph)
2.8 (br m, 4H, PCH2); 7.3–7.8 (br m, 30H, Ph)
2.7 (br m, 4H, PCH2); 1.8 (m, 2H, CH2CH2CH2);
7.1–7.8 (br m, 30H, Ph)
2.6 (m, 4H, PCH2); 1.7 (m, 4H, CH2CH2CH2CH2);
7.2–7.8 (br m, 30H, Ph)
2.5 (m, 4H, PCH2); 1.7 (m, 4H, PCH2CH2); 1.2 (br
m, 4H, PCH2CH2CH2); 7.3–7.7 (br m, 30H, Ph)
7.2–9.8 (m, Ph+bipy)
2.2, 2.5 (2s, 6H, ꢁCMe); 4.7 (br m, 4H, PCH2); 5.3
(s, 2H, CH2Cl2); 7.3–7.8 (m, 40H, Ph)
4.8 (br, m, 4H, PCH2); 5.3 (s, 2H, CH2Cl2);
7.2–7.8 (br, m, 50H, Ph)
2.1, 2.4 (2s, 6H, ꢁCMe), 2.9 (br, m, 8H, PCH2);
5.3 (s, 2H, CH2Cl2); 7.1–7.7 (m, 40H, Ph)
3.0 (br, m, 8H, PCH2); 5.3 (s, 2H, CH2Cl2);
7.2–7.9 (m, 50H, Ph)
The infrared spectra of 6–8 have three carbonyl
1
bands. The H NMR spectra of 6–8 gave multiplets of
peaks for the phenyl groups as predicted for their
proposed formulae. Several attempts have been made
to grow single crystals of 6–8 for X-ray crystallogra-
phy without any success. Since Cotton et al. [64] have
described the structure of the bromo-bridged dimer
[{W(m-Br)Br(CO)4}2] it may be the structure of [{W(m-
Cl)(ClICl)(CO)3L}2] (6–8) is similar with each of half
of the molecule in a capped octahedral geometry, with
a carbonyl group in the capping position.
14
15
16
17
18
19
20
21
3.4. Reactions of [WCl(ClICl)(CO)3(NCMe)2] (2) with
alkynes
2.0 (m, 4H, PCH2CH2); 2.6 (m, 14H,
PCH2+ꢁCMe); 5.3 (s, 2H, CH2Cl2); 7.3–7.6 (br,
m, 40H, Ph)
22
23
1.9 (m, 4H, PCH2CH2); 2.5 (m, 8H, PCH2); 5.3 (s,
2H, CH2Cl2); 7.1–7.8 (br, m, 50H, Ph)
1.8 (m, 8H, PCH2CH2); 2.0–2.5 (m, 14H,
PCH2+ꢁCMe); 5.3 (s, 2H, CH2Cl2); 7.0–7.4 (m,
40H, Ph)
1.6 (m, 8H, PCH2CH2); 2.0–2.5 (m, 14H,
PCH2+ꢁCMe); 5.3 (s, 2H, CH2Cl2); 7.2–7.7 (m,
50H, Ph)
1.1 (m, 8H, PCH2CH2CH2); 1.5 (m, 8H,
PCH2CH2); 2.2–2.6 (m, 14H, PCH2+ꢁCMe); 5.3
(s, 2H, CH2Cl2); 7.4–7.6 (m, 40H, Ph)
1.2 (m, 8H, PCH2CH2CH2); 1.6 (m, 8H,
PCH2CH2); 1.8 (m, 8H, PCH2CH2); 2.5 (m, 8H,
PCH2); 5.3 (s, 2H, CH2Cl2); 7.3–7.9 (m, 50H, Ph)
Treatment of [WCl(ClICl)(CO)3(NCMe)2] (2) with 2
equiv. of RC2R (R=Me or Ph) in CH2Cl2 at room
temperature affords the complexes [WCl(ClICl)-
(CO)(NCMe)(h2-RC2R)2] (9 and 10). Complexes 9 and
10 were characterised by elemental analysis (C, H and
24
25
26
1
N), IR spectroscopy and H NMR spectroscopy (see
Tables 1–3). Complexes 9 and 10 are more stable and
more soluble than the seven-coordinate starting mate-
rial, 2, however they should still be stored under a
nitrogen atmosphere in the solid state.
The IR spectra for 9 and 10 showed strong single
carbonyl bands at w(CO)=2065 and 2095 cm−1 re-
spectively. As expected the more electron-rich but-2-
yne complex, 9, has a lower carbonyl stretching band
than the diphenylacetylene complex, 10. The com-
plexes 9 and 10 also have weak alkyne {w(CꢁC)}
stretching bands at 1783 and 1750 cm−1, respectively.
The IR spectral properties are also related to their
diiodo analogues [WI2(CO)(NCMe)(h2-RC2R)2] [65].
Since the X-ray crystal structures of the related diiodo
complexes [WI2(CO)(NCR%)(h2-RC2R)2] (R%=Me,
R=Me or Ph [65]; R%=But, R=Me [66]; R=Me,
R%=CH2(3-C4H3S) [67]) have been crystallographically
determined, the structures of 9 and 10 are likely to be
very similar, as shown in Fig. 2. Several unsuccessful
attempts to grow single crystals of 9 and 10 were
made.
Spectrum recorded in CDCl3 (+25 °C) using SiMe4 as a reference;
s=singlet; m=multiplet; br m=broad multiplet.
Fig. 1. Proposed structure of [WCl(ClICl)(CO)3(NCMe)2] (2).

P.K. Baker, C.T. Brown / Polyhedron 20 (2001) 2559–2566
2565
these structural types. The 1H NMR data (Table 3)
confirms with the formulation of complexes 11–16 as
mono(alkyne) complexes of the type [WCl(ClICl)-
‚
(CO)(L L)(h2-PhC2Ph)].
Treatment of [WCl(ClICl)(CO)(NCMe)(h2-RC2R)2]
‚
‚
(R=Me or Ph) with 2 equiv. of L L {L L=
Ph2P(CH2)nPPh2 (n=1–4, 6)} in CH2Cl2 at room tem-
‚
perature affords the complexes [W(CO)(L L)2-
(h2-RC2R)][Cl][ClICl]·CH2Cl2 (17–26). Complexes 17–
26 have been characterised by elemental analysis (C, H
and N), IR and 1H NMR spectroscopy (see Tables
1–3).
Fig. 2. Proposed structure of [WCl(ClICl)(CO)(NCMe)(h2-RC2R)2]
(R=Me, Ph) (9 and 10).
Complexes 17–26 are all confirmed as CH2Cl2 sol-
1
vates from repeated elemental analysis results and H
3.5. Reactions of [WCl(ClICl)(CO)(NCMe)(p2-RC2R)2]
with neutral bidentate ligands, L L
NMR spectroscopy (see Table 3). It may be that com-
plexes 17–26 might be monocationic with one of the
bidentate phosphine ligands attached in a monodentate
manner. Previous studies [71] of the reactions of
equimolar amounts of [WI(CO)(NCMe){Ph2P(CH2)-
‚
Reaction of [WCl(ClICl)(CO)(NCMe)(h2-PhC2Ph)2]
‚
‚
(10), with 1 equiv. of L L {L L=Ph2P(CH2)nPPh2
(n=1–4, 6) and 2,2%-bipy} in CH2Cl2 at room tempera-
‚
‚
PPh2}(h2-MeC2Me)]I and L L {L L=bipy, phen,
‚
ture affords the complexes [WCl(ClICl)(CO)(L L)(h2-
5,6-Me2-phen, (R=Cy,
RNꢂCHCHꢂNR
But,
PhC2Ph)] (11–16) in good yield. Complexes 11–16 were
characterised by elemental analysis (C, H and N), IR
spectroscopy and 1H NMR spectroscopy (see Tables
1–3). Complexes 11–16 were all the most stable of the
complexes described so far, and were even stable in air
in the solid state for several hours without significant
decomposition. However, they decompose in solution
when exposed to air. Complexes 11–16 were much less
soluble in CH2Cl2 and CHCl3, and hence attempts to
both grow single crystals for X-ray analysis were
unsuccessful.
C6H4OMe-p)} give the dicationic complexes [W(CO)-
‚
{Ph2P(CH2)PPh2}(L L)]2I, hence it is more likely that
the complexes 17–26 are dicationic in nature. Attempts
to obtain suitable mass spectra were unsuccessful as no
parent ions were observed. Complexes 17–26 are again
stable in air for several hours, but only moderately
soluble in CHCl3 and CH2Cl2, hence it was difficult to
obtain satisfactory NMR spectra for these complexes,
and no definitive 31P NMR spectra could be obtained.
The IR spectra for 17–26 all have single carbonyl
bands as expected slightly shifted from the neutral
mono(alkyne) complexes 11–16. Complexes 17–26 all
have alkyne stretching bands {w(CꢁC)} (see Table 2) in
the expected range for this type of complex [45]. The
bands are in similar positions to the previously reported
The IR spectra (Table 2) of complexes 11–16 all had
bands at approximately 1950 cm−1, which were in the
same region as the diiodo complexes of the type
[WI2(CO)L2(h2-RC2R)] [68]. Complexes 11–16 all have
weak alkyne stretching bands (Table 2) at considerably
lower wavenumbers than the uncoordinated alkynes
which is usual for such complexes [45], due to back
donation from filled metal orbitals to empty p*-orbitals
on the alkyne ligands. It is interesting to note that
reaction of equimolar amounts of [WCl(ClICl)(CO)-
(NCMe)(h2-PhC2Ph)2] and the more electron rich lig-
and 2,2%-bipyridine (bipy) also gives the neutral
mono(alkyne) complex [WCl(ClICl)(CO)(bipy)(h2-
PhC2Ph)] (16), which has a carbonyl band at 1943
cm−1. This is in contrast with reaction of [WI2(CO)-
(NCMe)(h2-PhC2Ph)2] with 1 equiv. of 2,2%-bipyridine
[69], which gives the cationic complex [WI(CO)-
(bipy)(h2-PhC2Ph)2]I, which has w(CO) (CHCl3)=2052
cm−1. In view of the different geometries of the related
‚
[71] complexes [W(CO){Ph2P(CH2)PPh2}2(L L)(h2-
MeC2Me)]2I. The most likely structure for these com-
plexes is with the alkyne and carbonyl group cis to each
other which is expected on electronic grounds as previ-
ously described [71].
4. Conclusions
In conclusion, we have described the different reac-
tivity of fac-[M(CO)3(NCMe)3] (M=Mo or W) to-
wards I2Cl6 to give either [Mo2(NCMe)8][Cl]2[ClICl]2 or
the seven-coordinate complex [WCl(ClICl)(CO)3-
(NCMe)2]. The chemistry of [WCl(ClICl)(CO)3-
(NCMe)2] with donor ligands and alkynes is also de-
scribed, and is generally similar to other [MXY(CO)3-
(NCMe)2] complexes we have previously described
[45,46].
complexes
[WI2(CO){Ph2P(CH2)PPh2}(h2-MeC2Me)]
[68] and [WI2(CO){Ph2P(CH2)3PPh2}(h2-EtC2Et)] [70]
without 31P NMR data due to the poor solubility of
complexes 11–16 it was not possible to decide between

2566
P.K. Baker, C.T. Brown / Polyhedron 20 (2001) 2559–2566
[36] J.T. Wang, Y.W. Zhang, Y.M. Xu, C.M. Cui, Chin. Chem. Lett.
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