Synthesis and reactivity of organochalogen ester substituted η3-butadienyl complexes of Mo(II): Crystal structure of phenanthroline)].0.5 CH2Cl2

Article abstract of DOI:10.1016/S0022-328X(02)02023-5

A series of organochalcogen ester substituted η ³-butadienyl complexes of the type [MoCl(CO)₂ (η³-CH₂C(COXR)C=CH₂)(phen)] _n(phen = 1,10-phenanthroline, R = alkyl, aryl) were prepared from the acyl chloride precursor (1) and either thiols (X = S, n = 1-4), selenols (X = Se, n = 1,2) or bis(organochalcogen) mercurials, Hg[XR]₂ (X = Se, Te, n = 1,2), and the structure of the first selenoester substituted η³-butadienyl complex (4) was determined by a single-crystal X-ray diffraction analysis. Reactions of various nucleophiles or electrophiles with 1, 4 or the ester substituted complex, XR = OMe, were examined, and compared to those of related η³-allyl analogues and to their predicted behaviour based upon the structural evidence and molecular modelling calculations.

Full text of DOI:10.1016/S0022-328X(02)02023-5

Journal of Organometallic Chemistry 664 (2002) 277ꢂ287
/
www.elsevier.com/locate/jorganchem
Synthesis and reactivity of organochalogen ester substituted h3-
butadienyl complexes of Mo(II): crystal structure of [MoCl(CO)2(h3-
CH2C(COSePh)Cꢀ
/
CH2)(1,10-phenanthroline)]×
/
0.5 CH2Cl2
Annabelle G.W. Hodson a,ꢀ, Rupinder K. Thind a, Mary McPartlin b
a Faculty of Applied Sciences, University of the West of England, Frenchay, Bristol BS16 1QY, UK
b School of Applied Chemistry, University of North London, London N7 8DB, UK
Received 22 August 2002; accepted 24 September 2002
Abstract
A series of organochalcogen ester substituted h3-butadienyl complexes of the type [MoCl(CO)2(h3-CH2C(COXR)Cꢀ
CH2)(phen)]n (phenꢁ1,10-phenanthroline, Rꢁalkyl, aryl) were prepared from the acyl chloride precursor (1) and either thiols
(XꢁS, nꢁ1ꢂ4), selenols (XꢁSe, nꢁ1,2) or bis(organochalcogen) mercurials, Hg[XR]2 (XꢁSe, Te, nꢁ1,2), and the structure of
the first selenoester substituted h3-butadienyl complex (4) was determined by a single-crystal X-ray diffraction analysis. Reactions of
/
/
/
/
/
/
/
/
/
/
various nucleophiles or electrophiles with 1, 4 or the ester substituted complex, XRꢁOMe, were examined, and compared to those
/
of related h3-allyl analogues and to their predicted behaviour based upon the structural evidence and molecular modelling
calculations.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Butadienyl; Organochalcogen; Molybdenum; Reactivity studies; Selenoester
1. Introduction
data obtained for [Mo(O2CC3F7)(CO)2(h3-CH2C-
(CONHMe)CꢀCH2)(bipy)] (bipyꢁ2,2?-bipyridine) to
carry out calculations using the standard extended
/
/
In view of the recent recognition that (1,2,3-h)-trans-
butadienyl metal complexes may occur as key inter-
mediates in certain synthetic procedures [1], there is a
need to further understand the chemical behaviour of
this type of ligand. We have been investigating the
formation of complexes of general formula
Huckel molecular orbital (EHMO) method, and to
¨
predict the probable sites of nucleophilic or electrophilic
attack within the h3-butadienyl unit [6]. In principle,
isomeric forms of these complexes are possible, invol-
ving either E/Z-conformations of the two-substituent
and butadienyl double bond or rotation of bidentate L2
and ligand Y at the metal relative to the carbonyl groups
and butadienyl fragment. In view of the known synthetic
utility of organochalcogen esters of general type
[MY(CO)2(h3-CH2C(COXR)Cꢀ
W; L2ꢁ2,2?-bipyridyl, 1,10-phenanthroline; Yꢁ
from reactions of Ph4P[MCl(CO)3L2] and 1,4-dichloro-
2-butyne in chlorinated solvents (XRꢁCl) or methanol
(XRꢁOMe), and have prepared and characterised
derivatives containing amide or thioester 2-butadienyl
substitutents [2ꢂ5]. Although the general reaction
/
CH2)(L2)] (Mꢁ
/
Mo,
/
/Cl)
/
/
R?COXR (Xꢁ
/
O, S, Se, Te; R?, Rꢁalkyl, aryl) [7],
/
and our wish to test these predictions experimentally, we
herein report the formation of a series of new mono- and
polymeric chalcogenoester substituted butadienyl com-
plexes, using organomercurials as a new synthetic route,
present the crystal structure of the first selenoester
substituted h3-bonded butadienyl complex and describe
the first reactivity study of acyl chloride, ester and
selenoester substituted butadienyl complexes.
/
chemistry of these complexes has not yet been explored,
the author and others have used the X-ray diffraction
ꢀ Corresponding author. Tel.: ꢃ
3442-904
E-mail address: annabelle.hodson@uwe.ac.uk (A.G.W. Hodson).
/
44-117-3442-486; fax: ꢃ44-117-
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 2 0 2 3 - 5

278
A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ287
/
2. Experimental
(1.09 mmol). After 4 h, petrol was added to the filtered
solution, and storage at low temperature precipitated
the yellowꢂorange products. Method b: the conditions
/
2.1. General
adopted by Silveira et al. for reaction of Hg[SePh]2 or
Hg[SeCMe(H)Ph]2 with various acyl chlorides were
adapted for use as follows. To a stirred suspension of
the appropriate organochalcogen mercurial (1 mmol)
and n-tetrabutylammonium bromide (0.0129 g, 0.04
mmol) in CH2Cl2 (5 cm3) was added a solution of 1
(0.483 g, 1 mmol) in the same solvent (50 cm3), and the
mixture was stirred for 5 h. After filtration, the solvent
was removed under high vacuum. For both a and b the
Except where indicated, all reactions were carried out
under dinitrogen at room temperature (r.t.) using
degassed solvents and liquid reagents previously dried
over molecular sieves to prevent oxidation of the thiol-
and selenium-containing products. The acyl chloride (1)
and ester (11) substituted butadienyl complexes were
freshly prepared from Ph4P[MoCl(CO)3(phen)] accord-
ing to the published methods [2], and were recrystallised
from CH2Cl2-petrol mixtures before use. Infrared spec-
tra were recorded on a Perkin Elmer 781 spectrometer
using samples prepared as nujol mulls on sodium
crude solids were finally recrystallised from CH2Cl2ꢂ
/
petrol mixtures to give the title compounds 4 or 5.
Yields of each method were similar, and in the range
1
chloride discs. The H-NMR spectra were recorded at
68ꢂ71%. The dark red tellurium analogue of 4 was
/
300 MHz, with solutions in dichloromethane-d2 or
dimethylsulphoxide-d6 and referenced to tetramethylsi-
lane as internal standard. The trithiol MeC(CH2SH)3
was synthesised from the commercially available triol
via the tritosyl and trithiocyanate precursors [8]. The
selenols PhC(H)MeSeH and HSe(CH2)4SeH were ob-
tained by reduction of the appropriate selenocyanates
[9], and the bis(organochalcogenyl)mercury complexes
Hg[XR]2 were prepared [10] from reactions of mercur-
y(II) chloride and the diorganodichalcogenides, [XR]2.
Phenyl trimethylsilylselenide was prepared by the litera-
ture method [11]. Other chemicals were purchased from
commercial sources and used without further purifica-
tion.
prepared from Hg[TePh]2 using method b and a reaction
time of 2 h only.
2.4. Structure determination of [MoCl(CO)2(h3-
CH2C(COSePh)Cꢀ
/
CH2)(phen)]×/0.5 CH2Cl2
Crystals of complex 4 were grown from a CH2Cl2ꢂ
/
petrol mixture. Data were collected on a Siemens P4
diffractometer and experimental details from the struc-
ture determination are given in Table 4. Data were
corrected for Lorentz and polarisation effects, and for
absorption using R-scans. The structure was solved by
direct methods and refined by full-matrix least-squares
on F2 (SHELXTL-PLUS) [12]. Hydrogen atoms of the h3-
butadienyl group were directly located and all other
hydrogen atoms except those on the disordered dichlor-
omethane solvate molecule were included at calculated
positions. Anisotropic displacement parameters were
assigned to all full occupancy non-hydrogen atoms.
2.2. Preparation of [MoCl(CO)2(h3-
CH2C(COSCH2CO2Me)Cꢀ
/
CH2)(phen)] and
CH2)(phen)]
[MoCl(CO)2(h3-CH2C(COSCH2Ph)Cꢀ
/
Excess triethylamine (0.2 cm3) and complex 1 (0.483
g, 1.0 mmol) were stirred in dichloromethane (50 cm3),
and to this mixture methyl thioglycolate (0.2 cm3, 2.24
mmol) or benzyl mercaptan (0.12 cm3, 1.02 mmol) was
added dropwise. The orange solution darkened on
addition, and after stirring for two hours, the filtered
solution was mixed with petrol (25 cm3) and stored
overnight at low temperature. The title compounds 2
2.5. Preparation of [MoCl(CO)2(h3-CH2C-
(COSCH2CO2CH2)Cꢀ
/
CH2)(phen)]2, [MoCl-
(CO)2(h3-CH2C(COSCH2C3H2)Cꢀ
/CH2)(phen)]2 and
[MoCl(CO)2(h3-CH2C(COSe(CH2)2)Cꢀ
CH2)(phen)]2
/
and 3 were isolated as orangeꢂ
were recrystallised from CH2Cl2ꢂ
Yieldsꢁ55ꢂ65%.
/
red microcrystals that
/
petrol mixtures.
/
/
A solution of complex 1 (0.483 g, 1.00 mmol) in
dichloromethane (50 cm3) was stirred with excess
triethylamine (0.5 cm3). To this was added dropwise a
solution of the appropriate dithiol or diselenol (0.5
mmol) in dichloromethane (5 cm3), and the reaction
mixture was stirred for 2 h. After storage at low
temperature, the products were filtered from solution,
2.3. Preparation of [MoCl(CO)2(h3-
CH2C(COSePh)CꢀCH2)(phen)] and
/
[MoCl(CO)2(h3-CH2C(COSeCMe(H)Ph)Cꢀ
CH2)(phen)]
/
Method a: to a stirred mixture of 1 (0.483 g, 1.0
mmol) and excess triethylamine (0.5 cm3) in CH2Cl2 (50
cm3) was added benzeneselenol or 1-ethylbenzeneselenol
recrystallised from CH2Cl2ꢂ/petrol mixtures and dried
under vacuum to give complexes 6ꢂ
/
8. Yieldsꢁ47ꢂ64%.
/
/

A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ
/287
279
2.6. Preparation of [{MoCl(CO)2(h3-
CH2C(COSCH2)CꢀCH2)(phen)}3CMe] and of
ture. Samples of 15 produced by methods a and b gave
identical IR and NMR spectra and yields in the range
/
[{MoCl(CO)2(h3-CH2C(COSCH2CO2CH2)Cꢀ
CH2)(phen)}4C]
/
43ꢂ58%.
/
2.10. Preparation of [{Mo(pyridine)(CO)2(h3-
CH2C(CO2Me)Cꢀ
CH2)(phen)}ꢃ]
Excess triethylamine (0.21 cm3, 1.5 mmol) was added
to a stirred solution of 1 (0.386 g, 0.8 mmol) in
dichloromethane (80 cm3) at r.t., and to this was added
either 1,1,1-tris(mercaptomethyl)ethane (0.042 g, 0.25
mmol) in dichloromethane (80 cm3) or 1.0 cm3 of a
solution of pentaerythritol tetrakis(2-mercaptoacetate)
(2.5 mmol) in CH2Cl2 (10 cm3). The mixture was stirred
for 3 h. The filtered, orange product was washed first
with minimum, cold CH2Cl2 to remove any unreacted 1,
and then recrystallised as given in 2.5 to give complexes
/
Method a: excess pyridine (2.5 mmol, 0.1 cm3) was
added to a suspension of freshly prepared 11 (0.239 g,
0.5 mmol) in acetone (75 cm3), and to this a solution of
AgBF4 (0.100 g, 0.5 mmol) in acetone (15 cm3) was
added dropwise. The mixture was stirred for 6 h, filtered
and the liquor stored with petrol. Orangeꢂ
of the product precipitated at low temperature, and were
petrol mixtures. Method b:
/red crystals
recrystallised from CH2Cl2ꢂ
/
a solution of 12 (0.504 g, 0.5 mmol) in acetone (100 cm3)
was stirred with excess pyridine for 2 h. The volume was
reduced under vacuum, and addition of petrol to the
filtered solution and cooling gave the title complex.
Samples of 16 produced by methods a and b gave
identical IR and NMR spectra and yields in the range
9 or 10. Yieldsꢁ56 and 46%.
/
2.7. Preparation of [{Mo(CO)2(h3-CH2C(CO2Me)Cꢀ
/
CH2)(phen)}2(m-Cl)ꢃ]
Silver tetrafluoroborate (0.049 g, 0.25 mmol) was
added to a stirred, saturated solution of complex 11
(0.239 g, 0.5 mmol) in dichloromethane (20 cm3). After
20 min the mixture was filtered, petrol was added, and
the mixture was stored for 48 h at low temperature to
give the product 12 as a red microcrystalline solid.
32ꢂ55%.
/
2.11. Preparation of [MoCl(CO)2(h3-CH2C-
(CO2Me)C(SePh)Me)(phen)] or [MoCl(CO)2(h3-
CH2C(COSePh)C(SePh)Me)(phen)])
Yieldꢁ51%.
/
To complex 1 or 4 (0.5 mmol) in a mix of dichlor-
omethane (25 cm3) and methanol (5 cm3) was added
PhSeSiMe3 (0.227 g, 1.0 mmol), and the mixture was
stirred at r.t. for 2 h. Chromatography on silica gel using
the same solvent mix gave the products 18 and 19,
respectively.
2.8. Preparation of [{Mo(NCMe)(CO)2(h3-
CH2C(CO2Me)Cꢀ
CH2)(phen)}ꢃ] and
/
[{Mo(acetone)(CO)2(h3-CH2C(CO2Me)Cꢀ
/
CH2)(phen)}ꢃ]
A suspension of 11 (0.359 g, 0.75 mmol) in acetonitrile
or acetone (80 cm3) was stirred with silver tetrafluor-
oborate (0.156 g, 0.8 mmol) for 30 min. After filtration
of the mixture, the solvent was removed under vacuum
2.12. Reactions of 4 and methanol in the presence of
CuCl2 or HgCl2
and an orangeꢂ
quantitative yield.
/
red solid (13, 14) was isolated in
A solution of 4 (0.182 g, 0.3 mmol) in acetone (50
cm3) and methanol (10 cm3) was stirred with excess
triethylamine (0.07 cm3, 0.5 mmol) and cooled over ice.
To this mixture, a solution of copper(II) chloride or
mercury(II) chloride (0.3 mmol) in acetone (70 cm3) was
added dropwise over 0.5 h. After a further 1.5 h at
ambient temperature, excess solvent was removed under
vacuum, and the filtered solution gave the ester sub-
stituted complex 11 in 83 and 58% yield, respectively.
2.9. Preparation of [Mo(O2CC3F7)(CO)2(h3-
CH2C(CO2Me)CꢀCH2)(phen)]
/
Method a: a freshly prepared sample of 14 in acetone
was filtered into a stirred solution of excess sodium
heptafluorobutyrate (0.709 g, 3.0 mmol) in acetone (75
cm3) and the mixture was stirred for 1 h. The solvent
was removed under vacuum, and the residue was
recrystallised from acetoneꢂ/petrol to yield 15 as
2.13. Reaction of 4 with CuCl2 and n-propylamine
orangeꢂred crystals. Method b: to a stirred suspension
/
of 11 (0.479 g, 1.0 mmol) and NaO2CC3F7 (0.400 g, 1.69
mmol) in acetone (100 cm3) was added dropwise a
solution of AgBF4 (0.200 g, 1.03 mmol) in acetone (10
cm3). After 2 h, the mixture was filtered, the liquor
reduced to dryness in vacuo, and the crude product was
recrystallised from acetone and petrol at low tempera-
Excess n-propylamine (0.1 cm3) was stirred with a
solution of complex 4 (0.0385 g, 0.06 mmol) in acetone
(20 cm3), and the mixture was cooled over ice. To this,
copper(II) chloride (0.008 g, 0.06 mmol) in acetone (30
cm3) was added over 0.5 h. After stirring at r.t. for a
further 1.5 h, excess solvent was removed under reduced

280
A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ287
/
pressure to give the amide substituted butadienyl com-
plex in 70% yield.
analogue of complex 4 could be prepared in a similar
manner from Hg[TePh]2, but proved highly unstable in
air.) Addition of a solution of ethylene glycol bisthio-
glycolate, 1,4-benzenedimethanethiol or 1,4-propanedi-
selenol to a solution of 1 in exactly 1:2 mole ratio under
3. Results and discussion
basic reaction conditions afforded dimeric complexes 6ꢂ
8, respectively, having general formula [MoCl(CO)2(h3-
CH2C(COXR)CꢀCH2)(phen)]2. The trimeric complex 9
/
3.1. Preparation and spectroscopic characterisation of
h3-butadienyl complexes
/
and tetrameric 10 were prepared and characterised in a
similar manner by a combination of appropriate ratios
of complex 1 and either 1,1,1-tris(2-mercaptomethyl)-
ethane (3:1) or pentaerythritol tetrakis(2-mercaptoace-
tate) (4:1). Solid samples of the thioester and selenoester
complexes were stable in air for several days. However
prolonged storage of the latter in moist air or oxyge-
nated solvents led to the production of non-carbonyl-
containing metal species and the corresponding disele-
nides.
Addition of excess methyl thioglycolate, benzyl mer-
captan, benzeneselenol or 1-ethylbenzeneselenol (RXH)
to a basic solution of the complex [MoCl(CO)2(h3-
CH2C(COCl)Cꢀ
/
CH2)(phen)] (1) in chlorinated solvents
gave rise to a series of orangeꢂ
/
red products 2ꢂ5. These
/
were identified from their elemental analyses and infra-
red and NMR spectra (Tables 1 and 2) as thioester or
selenoester two-substituted butadienyl complexes of the
type
[MoCl(CO)2(h3-CH2C(COXR)Cꢀ
/
CH2)(phen)]
The infrared spectra of all the complexes showed a
pair of strong IR absorptions between 1893 and 1981
cmꢄ1 which were typical of a metal-cis-dicarbonyl unit,
and a band of medium intensity near 1930 or 1950 cmꢄ1
arose from the carbonyl of the thioester or selenoester
respectively. The influence of chalcogen, X, on the
position of this latter band for various compounds of
(Scheme 1). The selenoester complexes 4 and 5 were
also obtained by a second method. Silveira and co-
workers have shown that organic acyl chlorides R?COCl
can be converted to the corresponding thioester, sele-
noester or telluroester R?COXR by reaction with
bis(organochalcogenyl)mercury complexes Hg[XR]2 in
the presence of catalytic amounts of tetraalkylammo-
nium salts [10]. Following their general methodology,
Hg[SePh]2 and Hg[SeMe(H)Ph]2 were prepared by
reaction of either diphenyldiselenide and elemental
mercury or the appropriate selenol and mercury(II)
chloride. On reaction with complex 1 in the presence
of n-Bu4NBr, these mercurials gave rise to the butadie-
nyl complexes 4 and 5 in good yield. (The tellurium
the type R?COXR (R?, Rꢁalkyl, aryl) has been
/
investigated by Renson and Draguet [13], and these
results conform to their findings. An additional peak
near 1740 cmꢄ1 was also observed for complexes 2, 6
and 10, and this arose from the Cꢀ
/
O stretching mode of
the ester butadienyl substituent. Weak absorptions at
about 1675 cmꢄ1 due to the vinylic double bond could
Table 1
Selected infrared and analytical data for complexes [MoY(CO)2(h3-CH2C(COXR)CꢀCH2)(phen)]n
a
No. Butadienyl substituent, COXR
Y
Infrared data
Analysis, found (calculated) (%)
n(CꢁO))
n(CO2)
n(CꢀO)
C
H
N
2
3
COSCH2CO2Me
COSCH2Ph
COSePh
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
1893, 1970
1899, 1971
1897, 1975
1889, 1969
1901, 1977
1893, 1966
1884, 1966
1906, 1981
1904, 1979
1894, 1972
1905, 1984
1869, 1951
1885, 1960
1860, 1964
1867, 1949
1735
1637
1630
1650
1623
1631
1627
1625
1628
1640
47.70 (47.78)
54.26 (54.68)
47.21 (47.37)
48.59 (48.96)
45.36 (45.45)
46.84 (46.71)
43.01 (43.22)
47.26 (47.47)
46.40 (46.89)
49.90 (50.10)
47.27 (47.59)
2.90 (3.07)
3.31 (3.33)
2.72 (2.78)
2.98 (3.26)
3.16 (2.86)
2.62 (2.91)
2.63 (2.85)
2.98 (2.95)
2.97 (2.86)
3.20 (3.13)
4.93 (5.06)
4.88 (4.90)
4.37 (4.33)
3.97 (4.15)
4.93 (4.71)
4.50 (4.54)
4.58 (4.69)
5.02 (5.27)
4.62 (4.86)
5.60 (5.85)
5.07 (5.55)
ꢂ/
ꢂ/
ꢂ/
1752
c
c
b
4
5
COSeCMe(H)Ph
[COSCH2CO2CH2]2
[COSCH2C3H2]2
[COSe(CH2)2]2
[COSCH2]3CMe
[COSCH2CO2CH2]4C
CO2Me
6
7
ꢂ/
ꢂ/
ꢂ/
1741
1690
1698
1681
1690
1699
1692
b
b
b
8
9
10
11
12
13
14
15
16
ꢂ/
ꢂ/
ꢂ/
ꢂ/
d
CO2Me
CO2Me
2.77 (2.97)
e
MeCN
ꢂ/
ꢂ/
ꢂ
ꢂ/
/
ꢂ/
ꢂ/
e
CO2Me
CO2Me
CO2Me
Acetone
O2CC3F7
Pyridine
1642
44.15 (43.90)
1.89 (2.28)
4.47 (4.26)
c
ꢂ/
47.18 (47.04)
3.60 (3.07)
6.95 (6.45)
As nujol mulls, cmꢄ1
CH2Cl2 calculated.
.
a
b
c
0.5 CH2Cl2 calculated.
Bridging atom.
Highly unstable.
d
e

A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ
/287
281
Table 2
1H-NMR data for selected complexes 2ꢂ
a
/10
?
Hanti, Hsyn
?
ƒ
Hanti, Hsyn
ƒ
No.
Aliphatic
Aromatic
b
2
1.95 (s, H), 3.75
(s, H)
5.83 (d, 2.38, H),
6.38 (d, 2.38, H)
5.80 (d, 2.38, H),
6.35 (d, 2.38, H)
5.92 (d, 2.55, H),
6.44 (d, 2.55, H)
5.78 (d, 2.19, H),
2.28 (m, 2H), 3.46 (s,3H)
7.97 (m, 2H), 8.04 (s, 2H), 8.65 (m, 2H), 9.14 (d, 5.13, H),
9.20 (m, 5.13, H)
3
4
5
1.97 (s, H), 3.76
(s, H)
2.56 (d, 3.55, H), 2.96 (d, 3.55, H) 6.59 (m, 2H), 7.11 (m, 3H), 7.87 (m, 4H), 8.36 (d, 8.24,
H), 8.51 (d, 8.24, H), 9.10 (d, 4.94, H), 9.17 (d, 5.13, H)
6.97 (m, 2H), 7.14 (m, 3H), 8.05 (m, H), 8.17 (m, H), 8.25
1.97 (s, H), 3.76
(s, H)
1.88 (s, H), 1.91
(m, 2H), 8.87 (m, 2H), 9.27 (d, 4.78, H), 9.32 (d, 4.78, H)
0.46 (d, 7.15, 6H), 3.24 (m, 2H) 6.58 (m, 2H), 6.86 (m, 2H), 7.10 (m, 2H), 7.12 (m, 2H),
7.18 (m, H), 7.73 (m, H), 7.85 (m, 2H), 8.00 (m, H), 8.13
(m, 4H), 8.23 (s, H), 8.25 (s, H), 8.45 (m, H), 8.85 (m,
(s, H), 3.82 (s, H), 5.80 (d, 2.22, H),
6.28 (d, 2.22, H),
6.33 (d, 2.19, H)
3.85(s, H)
2H), 9.12 (m, H), 9.27 (d, 5.22, H), 9.38 (d, 4.95, H)
7.91 (m, 8H), 8.48 (m, 4H), 9.14 (m, 4H)
6
1.98 (s, 2H), 3.72 5.86 (d, 2.00, 2H), 0.85 (m, 4H), 2.16 (m, 2H),
(s, 2H) 6.41 (d, 2.00, 2H) 2.35 (m, 2H)
1.97 (s, 2H), 3.83 5.78 (d, 2.38, 2H), 2.48 (m, 2H), 2.88 (m, 2H)
(s, 2H) 6.28 (d, 2.38, 2H)
7 (1, 4)
6.34 (m, 2H), 6.76 (m, 2H), 7.98 (m,8H), 8.56 (d, 8.20,
2H), 8.78 (d, 8.20, 2H), 9.08 (d, 5.07, 2H), 9.29 (d, 5.13,
2H)
7a (1, 2)
1.95 (s, 2H), 3.80 5.83 (d, 2.38, 2H), 2.07 (d, 13.55, 2H), 2.41
(s, 2H) 6.29 (d, 2.38, 2H) (d, 13.57, 2H)
6.29 (m, 2H), 6.94 (m, 2H), 8.00 (m, 4H), 8.05 (s, 4H),
8.64 (d, 8.24, 2H), 8.77 (d, 8.24, 2H), 9.13 (d, 5.13, 2H),
9.30 (d, 4.95, 2H)
8
1.99 (s, 2H), 3.67 5.39 (d, 2.49, 2H), 1.88 (m, 4H), 3.42 (m, 4H)
(s, 2H) 5.90 (d, 2.19, 2H)
1.96 (s, 4H), 3.63 5.83 (m, 4H), 6.36 2.06 (m, 8H), 3.54 (m, 8H)
(s, 4H) (m, 4H)
7.50 (m, 4H), 7.68 (s, 4H), 8.13 (d, 1.65, 2H), 8.16 (d,
1.92, 2H), 9.03 (d, 1.92, 2H), 9.04 (d, 1.65, 2H)
7.85 (m, 16H), 8.39 (m, 8H), 9.10 (m, 8H)
10
a
Spectra recorded as solutions in dimethylsulphoxide-d6 unless otherwise stated. Data reported in ppm, multiplicity, coupling constant (Hz),
number of protons.
b
Run in dichloromethane-d2.
1
be identified for some complexes. For the polymeric
10, absorptions for n(SH) and n(SeH) near
13C-NMR spectra, however detailed H-NMR spectra
complexes 6ꢂ
/
were obtained for complexes 2ꢂ
/
8 and 10. For the
2100 and 2500 cmꢄ1, respectively were absent, and there
was no evidence to support the presence of monomeric
complexes containing pendant chalcogenol substituents.
The low solubilities of the new complexes in common
organic solvents precluded measurement of good quality
monomeric complexes 2ꢂ4, the terminal methylene
/
protons of the butadienyl gave rise to two doublets
between 5.78 and 6.44 ppm, with coupling constants of
2.38 or 2.55 Hz, and the allylic protons of the butadienyl
produced two singlets near 1.97 and 3.76 ppm. Only the
Scheme 1. Conditions: [Mo]ꢁ/MoCl(CO)2(phen) (i) excess RXH; (ii) Hg[XR]2/Bu4NCl; (iii) HXRRXH and 1 in 1:2 mole ratio; (iv) [HXR]3CMe
and 1 in 1:3 mole ratio; (v) [HXR]4C and 1 in 1:4 mole ratio.

282
A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ287
/
spectrum of complex 5 exhibited two sets of NMR
signals of approximately equal intensity across the range
3.2. Crystal structure determination of 4
A view of the molecule and the atomic labelling
scheme used are shown in Fig. 1. Crystal data for
complex 4 are given in Table 3, and important intera-
tomic parameters are given in Table 4. In accord with
the microanalytical data, each pair of molecules of 4 was
associated with one molecule of dichloromethane. The
central molybdenum atom can be described as hepta-
0ꢂ10 ppm. Reactions of achiral thiols and selenols with
the enantiomeric pair of compound 1 yielded products
in which the butadienyl substituents existed in similar
/
magnetic environments, and isomeric forms of 2ꢂ4
/
could not therefore be readily differentiated from their
1H-NMR spectra. However, a racemic mixture of either
PhC(H)MeSeH or [PhC(H)MeSe]2Hg in the synthesis of
complex 5 led to the production of four isomers, and
since enantiomeric relationships existed between two
sets of pairs, two sets of NMR signals were observed
within the spectrum.
A comparison of the integrations for 1H-NMR signals
arising from the bridging methylene and aromatic
groups of the butadienyl substituent with those due to
phen and terminal butadienyl protons within the com-
coordinate, being bonded to two carbonyl groups [Moꢂ
/
˚
˚
C(22) 1.978(10) A], two nitro-
C(21) 1.957(10) A; Moꢂ
/
˚
gens of 1,10-phenanthroline [Moꢂ
/
N(1) 2.230(7) A; Moꢂ
/
˚
˚
Cl 2.479(2) A]
N(2) 2.216(7) A], a chlorine atom [Moꢂ
and bidentate, two-substituted butadienyl unit
C11H9OSe. The metalꢂcarbon and CꢂO carbonyl
bond lengths [C(21)ꢂO(21) 1.161(11) A; C(22)ꢂO(22)
1.133(11) A] and angles [MoꢂC(21)ꢂO(21) 179.4(10)8;
MoꢂC(22)ꢂO(22) 174.9(10)8; C(21)ꢂMoꢂC(22)
/
a
/
/
˚
/
/
˚
/
/
/
/
/
/
plexes 6ꢂ8 supported a dimeric formula. For example,
/
80.5(4)8] are typical of a pair of mutually cis carbonyl
groups. The rings of the phenanthroline unit are
approximately planar within experimental error, and
the bond lengths and angles are unexceptional. The
the spectrum of 7 contained two multiplets arising from
the bridging methylene protons of the SCH2C6H4CH2S
unit at 2.48 and 2.88 ppm and two multiplets at 6.34 and
6.76 ppm due to this aromatic group. Each of these
signals, and the allylic singlets at 1.97 and 3.83 ppm,
integrated for two protons, in keeping with two
butadienyl groups per bridging unit. To assess whether
the structure of the dithioester bridge could control
monomer or dimer formation, reactions of complex 1
with 1,2- or 1,4-benzenedimethanethiol in 2:1 mole ratio
were compared. The IR spectra and elemental data for
these products (complexes 7a and 7, respectively) were
similar, and only the latter is therefore given in Table 1.
The proton NMR data for both 7a and 7 are presented
in Table 2. The spectra were consistent with dimeric
species in each case, and therefore the proximity of two
thiol functionalities in the 1,2-dithiol did not appear to
impose undue steric restriction on linkage of two
substituted butadienyl units. It is possible that flexibil-
ity, conferred by the methylene groups of the dithiol,
had permitted the aromatic linkage to orientate away
metalꢂ
tions of 1.431(12) and 1.418(12) A, a C(1)ꢂ
angle of 112.5(7)8 and MoꢂC(1) and MoꢂC(2) distances
/
butadienyl unit contains C(1)ꢂ
/
C(2)ꢂ
/
C(3) separa-
˚
/
C(2)ꢂC(3)
/
/
/
˚
of 2.300(9) and 2.228(8) A, respectively. Whilst these
results are typical of parameters found in related two-
substituted h3-allyl complexes of molybdenum [14], the
˚
C(3) distance of 2.208(9) A is noticeably shorter
Moꢂ
/
than that normally observed between molybdenum and
the terminus of an allyl system. (The fourth carbon atom
C(4) of the butadienyl system is considered non-bonded
to the metal centre.) A short bond between the metal
and quaternary carbon C(3) has been observed before in
substituted (1,2,3-h)-trans-butadienyl complexes [15],
and this carbon typically resonates at an unusually low
field in the 13C-NMR spectrum. The observed range for
this signal extends from 240 ppm, for complexes
from the two approaching metalꢂbutadienyl units.
/
Complex 9 proved too insoluble to characterise by
NMR spectroscopy, however the IR and microanaly-
tical data are in accord with a trimeric formula.
Integration of NMR signals arising from the phenan-
throline and butadienyl ligands in complex 10 showed
four metalꢂbutadienyl centres were associated with the
/
tetrathioester unit, and elemental microanalysis sup-
ported a tetrameric formula. Repeated attempts to grow
crystals of the polymeric complexes 6ꢂ10 suitable for an
/
X-ray diffraction analysis were unsuccessful. However, a
solid-state crystal structure determination of the mono-
meric, selenoester complex 4 was carried out, both to
determine the stereochemistry of the unusual h3-buta-
dienyl ligand and to assist in predicting the reactivity of
this organic fragment.
Fig. 1. Structure of [MoCl(CO)2(h3-CH2C(COSePh)Cꢀ
(4) with atom labelling scheme.
/CH2)(phen)]

A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ
/287
283
Table 3
Crystal data for complex 4×0.5 CH2Cl2
attributed to contributions from structures with either
h1-bonding at C(3) and a coordinating double bond
C(1)ꢂ
/
C(2) or with h1-bonding at C(1) and double bond
Formula
fw
C25.5H18Cl2MoN2O3Se
646.22
coordination at C(2)ꢂ
/
C(3). The 13C-NMR spectrum for
Space group
Crystal system
Unit cell dimensions
P21/n
Monoclinic
complex 4 was recorded [17], and resonances for the
butadienyl appeared at 31.2, 63.9, 173.0 and 108.9 ppm
for C(1) to C(4), respectively. However the spectroscopic
and crystallographic data do not strongly support any
one of these three structures.
˚
a (A)
11.0611(14)
7.7220(16)
30.422(4)
˚
b (A)
˚
c (A)
a (8)
b (8)
ꢂ
/
Within the substituted butadienyl system, the carbon-
yl and aromatic ring of the COSePh unit are orientated
97.081(8)
g (8)
ꢂ/
away from the terminal Cꢀ/CH2 moiety, and the phenyl
Crystal size (mm3)
0.50ꢅ0.20ꢅ0.12
2578.6(7)
3
˚
group is located well above the phen plane. At the
terminus of the butadienyl, the torsion angle between
V (A )
m(Moꢂ
/
Ka) (mmꢄ1
˚
)
2.157
0.71073
1.665
l(Moꢂ
/Ka) (A)
the C(3)ꢁ/C(4) vector and the three metal-bonded
rcalc (g cmꢄ3
)
atoms of the butadienyl was found to be 119.48.
Z
4
4887
˚
Although the C(3)ꢂ
/
C(4) bond length [1.242(13)A] is
C(terminal) separation
0.001 A in free butadiene [18] and found in
related structures, the value is within the range found for
CH2 of a ligated allene [19] and
No. of reflections collected
No. of independent reflections
Limiting indices
considerably shorter than the Cꢂ
/
3567 [Rintꢁ0.0548]
ꢄ125h 51, ꢄ85k 51,
ꢄ335l 533
1.89ꢂ
1276
˚
of 1.3449
/
2u (8)
F(000)
/
23.00
the uncoordinated Cꢀ
/
for unsubstituted h3-butadienyl complexes [20]. The
angle between the two planes defined by C(4) and its
hydrogen atoms, H(4A) and H(4B), and by C(4), C(3)
and C(2) was 1648, whilst at the opposite end of the
T (K)
198(2)
0.0699
0.0699
0.1905
0.2183
R1 [I ꢀ2F(I)]
R
Rw
TR2 (all data)
ligand, the torsion angle between the C(1)ꢂC(2) vector
/
Largest difference peak and hole 1.494, ꢄ1.306
ꢄ3
˚
(e A
)
and the plane containing C(1) and its hydrogen atoms,
H(1A) and H(1B), was found to be 1188. If the
C11H9OSe ligand is viewed as a two-substituted h3-allyl
system, with an additional double bond substituted at
one end, then the uncoordinated double bond can be
considered to be between the limits of being unconju-
gated or conjugated with the allyl unit, depending upon
the positions of the hydrogen atoms on the terminal
carbon atoms C(1) and C(4). With the C(1) hydrogen
atoms and the allyl unit non-planar, the double bond is
conjugated if the H atoms on C(4) are orthogonal to the
plane of the allyl system (Fig. 2, I), and unconjugated
with these H atoms co-planar with the allyl system (Fig.
2, II). The orthogonality of the terminal CH2 units was
shown by an improper torsion angle between the plane
C(4), H(4A), H(4B) and the plane C(1), H(1A), H(1B) of
958, and thus the double bond is not considered
conjugated to the allyl system.
Table 4
˚
Bond lengths (A) and bond angles (8) with standard deviations in
parentheses for [MoCl(CO)2(h3-CH2C(COSePh)CꢀCH2)(phen)]×0.5
CH2Cl2
Bond lengths
Moꢂ
Moꢂ
Moꢂ
Moꢂ
Moꢂ
C(2)ꢂ
C(5)ꢂ
C(5)ꢂ
/
C(21)
C(22)
N(1)
N(2)
Cl
1.957(10) Moꢂ
/
C(1)
C(2)
C(3)
2.300(9)
2.228(8)
2.208(9)
1.431(12)
1.418(12)
1.242(13)
1.161(11)
1.133(11)
/
1.978(10) Moꢂ
/
/
2.230(7)
2.216(7)
2.479(2)
Moꢂ
C(1)ꢂ
C(2)ꢂ
/
/
/
C(2)
C(3)
C(4)
/
/
/
C(5)
O(5)
Se
1.473(12) C(3)ꢂ
1.192(10) C(21)ꢂ
/
/
/O(21)
/
1.960(8)
C(22)ꢂ
/O(22)
Bond angles
C(21)ꢂMoꢂ
N(1)ꢂMoꢂN(2)
O(21)ꢂ
C(2)ꢂC(5)ꢂ
C(5)ꢂSeꢂ
/
/
C(22)
80.5(4)
74.3(2)
C(1)ꢂ
C(2)ꢂ
/C2)ꢂ
/
C(3)
C(4)
112.5(7)
141.3(9)
174.9(10)
122.0(6)
/
/
/C(3)ꢂ
/
/
C(21)ꢂ
/
Mo
179.4(10) O(22)ꢂ
/C(22)ꢂ
/
Mo
/
/
O(5)
124.0(8)
97.0(4)
O(5)ꢂ
/C(5)ꢂ
/
Se
/
/
C(51)
carrying electron-withdrawing substituents, to about
160 ppm for unsubstituted systems. It has been sug-
gested that for the former, a zwitterionic form con-
tributes a degree of carbenoid character to the Mꢂ
bond, and this further deshields the quaternary carbon
[16]. In many other cases, the short metalꢂC(3) bond
and inequivalence of carbonꢂcarbon bond lengths
within the metalꢂbound butadienyl moiety has been
/
C(3)
/
Fig. 2. Extreme orientations of the C(3) and C(4) pp orbitals in the h3-
butadienyl fragment.
/
/

284
A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ287
/
Thus whilst asymmetry at the metal centre due to
rotation of L2Y against the (allyl)M(CO)2 unit is known
23], and the putative mechanism for formation of
h3-butadienyl complex 1 from Ph4P[MCl(CO)3L2] and
1,4-dichloro-2-butyne does not preclude the formation
of isomers of this type [2], to date no evidence has been
found for this form of isomerism occurring in solid or
solution states for analogous h3-butadienyl complexes.
ciently strong Lewis acid, had competed against Agꢃ
for chloride in a second molecule of 11 to yield the
[21ꢂ
/
dimeric species [{MoCl(CO)2(h3-CH2C(CO2Me)Cꢀ
/
CH2)(phen)}2(m-Cl)]ꢃ. In contrast, chloride extraction
from 11 in the presence of acetonitrile or acetone (S)
yielded highly reactive, solvent-coordinated cations
of the type [Mo(CO)2(h3-CH2C(CO2Me)Cꢀ
/
CH2)-
(phen)S]ꢃ. Proton NMR spectra for these complexes
(13 and 14, respectively) were rather broad due to
decomposition of the samples, however peaks could be
assigned for the butadienyl and phen units, and a broad
singlet near 2.00 ppm arose from exchange of free and
coordinated solvent. On addition of excess sodium
heptafluorobutyrate to either a solution of 11 and
AgBF4 or to cationic 14 in acetone, the carboxylate
3.3. Reactivity studies
Reactions of representative complexes 1, 4 and methyl
ester 11 with various nucleophiles or electrophiles were
examined. Whilst addition of silver tetrafluoroborate to
a solution of complex 1 in chlorinated solvents in 1:2
mole ratio gave oxidation products only, a similar
reaction with 11 gave a red, crystalline product 12
(Scheme 2). Tables 1 and 2 give selected spectroscopic
data and elemental analyses of the new complexes.
Comparison of the 1H-NMR spectra of 11 and 12
showed that the peak positions for the terminal protons
of the butadienyl and phen ligand were little changed.
However, the singlet arising from the methyl ester
substituent had moved significantly downfield from
2.12 to 3.34 ppm. Curtis and Fotinos reported that a
similar reaction between silver ions and the complex
[MoCl(CO)2(h3-C3H5)(bipy)] gave rise to a dimeric
cation containing a bridging chlorine atom [24]. This
precedent, together with the elemental analyses and IR
spectra for 12, suggested that halide extraction from 11
had initially produced the coordinately unsaturated
derivative [Mo(O2CC3F7)(CO)2(h3-CH2C(CO2Me)Cꢀ
/
CH2)(phen)] (15) was isolated. Thus, in the presence of
coordinating solvents or reagents, the 16-electron inter-
mediate attains greater stability by formation of an
appropriate 18-electron complex. In support of this
observation, addition of pyridine to a mixture of 11 and
Ag(I) ions in acetone, or to a solution of 14, resulted in
the formation of the cationic species [Mo(CO)2(h3-
CH2C(CO2Me)Cꢀ
/
CH2)(phen)(pyridine)]ꢃ (16). This
behaviour shows parallels to that observed by Powell,
who similarly prepared the related cation [Mo(CO)2(h3-
C3H5)(bipy)(pyridine)]ꢃ from the chloro precursor [25].
Complex 16 could also be obtained from mixtures of
dimeric 12 and pyridine, showing the halogen bridge to
be susceptible to cleavage by bases.
Electrophilic attack on the h3-butadienyl ligand was
examined by addition of trifluoroacetic acid to a cooled
cation [Mo(CO)2(h3-CH2C(CO2Me)Cꢀ
/
CH2)(phen)]ꢃ
and that this 16-electron intermediate, being a suffi-
(ꢄ78 8C) solution of 4 in CH2Cl2. An immediate
/
Scheme 2. Key: [Mo]ꢁ
/
Mo(CO)2(phen); 1 XRꢁ
/
Cl; 4 XRꢁ
/
SePh; 11ꢂ
/
16 XRꢁ
/
OMe; 17 XRꢁ
/
SePh, Yꢁ
/
Cl; 17a XRꢁ
/
CO2CF3, YꢁCl; 17b
/
XRꢁCO2CF3, YꢁCO2CF3; 18 XRꢁ
/
/
/
OMe; 19 XRꢁ/SePh.

A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ
/287
285
reaction was apparent, as shown by the appearance of
several new peaks in the IR spectrum due to metalꢂ
from the following series of reactions. Initial protona-
tion at C(4) of the h3-butadienyl ligand in complex 4 led
to an unstable h3-vinylcarbene (17), and, since the
/
carbonyl absorptions between 1890 and 2000 cmꢄ1 and
by a significant weakening of the selenoester signal at
1650 cmꢄ1. However after warming to room tempera-
ture and chromatography on silica gel, the mixture gave
[Mo(CO)2(phen)(O2CCF3)2] as the only isolable metal-
containing species. Monitoring the reaction by 1H-
NMR spectroscopy immediately after mixing was
more informative. A sample of complex 4 (30 mg) was
shaken rapidly with a solution of CF3CO2H (ca. two
equivalents) in CDCl3 (0.5 cm3), and the mixture was
filtered into a 5 mm NMR tube. The 1H-NMR spectrum
was recorded immediately. After protonation, the two
doublets arising from terminal protons of the butadienyl
double bond in 4 were absent, and three sets of signals of
a similar pattern were present between 0.8 and 4.4 ppm.
Each set consisted of two doublets integrating for one
proton each and a singlet due to a methyl proton. The
coupling constants for the pairs of doublets were 2.73
Hz (2.97 and 3.70 ppm), 1.92 Hz (2.99 and 3.80 ppm)
and 1.08 Hz (3.02 and 4.20 ppm), and these signals were
consistent with three pairs of allylic methylene protons.
The three methyl singlets were observed at 0.87, 2.42
seleniumꢂcarbon bond of the butadienyl substituent
/
was susceptible to nucleophilic attack by trifluoroace-
tate anion, cleavage to give Ph2Se2 was accompanied by
conversion of the selenoester to COCO2CF3 (17a).
Following exchange of the metal-bound chlorine atom
for trifluoroacetate (17b), loss of the organic fragment
and capture of the resultant electron deficient species by
CF3CO2ꢄ finally yielded [Mo(CO)2(phen)(O2CCF3)2].
Low temperature NMR studies of these processes did
not yield further information.
The susceptibilities of the h3-butadienyl moiety in 1
and 4 to nucleophilic attack were investigated by
reaction of methanolic phenyl trimethylsilylselenide.
This reagent was selected both for its known potential
to deliver the anion PhSeꢄ to transition metal centres
[27,28] and its synthetic utility for the benzeneselenyla-
tion of unsaturated organic compounds [11,29]. Our
molecular modelling studies on amide substituted h3-
butadienyl complexes [6] (and related work by Curtis
and Eisenstein on h3-allyls [30]) predicted that under
frontier molecular orbital (FMO) control, nucleophilic
attack on these three-carbon units should be directed
towards the termini of the allyl function, i.e. at C(1) or
and 2.49 ppm. Although the spectrum in the region 8ꢂ
/
10 ppm was complex due to overlapping sets of peaks,
signals attributable to aromatic protons of the selenoe-
ster substituent were clearly observed at 6.30 ppm (d, 7.2
Hz, 2H), 7.02 ppm (t, 7.5 Hz, 2H) and 7.12 ppm (d, 7.1
Hz, H), and new peaks had appeared at 7.90 (m, 6H)
and 7.96 (m, 4H) due to diphenyldiselenide. The total
integration across the whole spectrum was consistent
with the presence of three h3-vinylcarbene complexes;
one containing a COSePh two-substituent and two with
non-proton containing two-substituents arising from
loss of diphenyldiselenide and formation of the CO2-
COCF3 group. Whilst Slugovc and co-workers have
demonstrated that protonation of the highly substituted
h3-butadienyl ligand in [Ru(hydrido(trispyrazolyl)bor-
ato){5,6-h:h3)-2-[2-phenyl-1-ethenylidene]-5-cycloocte-
nyl] gave rise to the corresponding h2-butadiene
complex via attack of Hꢃ at C(3) of the
C(3) of the C(1)C(2)C(3)ꢁC(4) system. However, under
/
charge control, nucleophilic attack should be directed
toward C(3) of the butadienyl, since this carbon atom
possessed the most positive net charge. The product of
stirring 1 with excess methanolic Me3SiSePh (18) gave
rise to an IR stretching absorption at 1705 cmꢄ1 and a
singlet in the 1H-NMR spectrum at 2.37 ppm (3H)
suggesting preferential reaction of the acyl chloride
substituent with methanol rather than benzeneselenol.
However, other features of the IR and 1H-NMR spectra
of 18 were inconsistent with the presence of 11. Thus,
the pair of strong IR absorptions at 1871 and 1952
cmꢄ1 attributed to the cis metalꢂ
dicarbonyl unit of 18
/
were observed at significantly lower wavenumber than
for 11 (1894 and 1972 cmꢄ1), and the 1H-NMR
spectrum of 18 showed no doublets arising from
methylene protons of a butadienyl double bond and
the appearance of a new singlet, integrating for three
protons, at 3.16 ppm. These results were consistent with
nucleophilic attack having occurred at C(3) as predicted,
and with addition of PhSeH across the double bond to
form the h3-allylic complex [MoCl(CO)2(h3-CH2C-
(CO2Me)C(Me)SePh)(phen)]. Reaction of complex 4
with methanolic Me3SiSePh under the same conditions
gave 19, which was identified from its IR and 1H-NMR
data as the selenoester two-substituted analogue to 18
[31]. There was no spectroscopic evidence for the
presence of the h3-allylic complexes of the type
[MoCl(CO)2(h3-CH2C(COXR)C(Me)OMe)(phen)] (XR
C(1)C(2)C(3)ꢁ/C(4) unit [26], the NMR data for
protonation of selenoester 4 were not consistent with
attack at this carbon atom. In contrast extended Huckel
¨
molecular orbital calculations on the complex
[Mo(CO)2(h3-CH2CHCꢀ
/
CH2)(h-C5Me5)]
predicted
that for both charge control and frontier-orbital control,
electrophilic attack should occur at the terminal carbon
of the double bond to yield an h3-vinylcarbene fragment
[20]. These results concurred with our calculations based
on the X-ray data of the (methylamido)butadienyl
complex, and predicted that electrophilic attack would
occur at C(4) of the selenoester complex 4. The pattern
of NMR signals observed for protonation of this
complex was consistent with this, and thought to arise
ꢁOMe or SePh) formed by addition of methanol across
/

286
A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ287
/
the butadienyl double bond in 1 or 4, respectively. The
former complex was previously obtained by reaction of
Ph4P[MoCl(CO)3(phen)] and 1,4-dichloro-2-butyne in
methanolic tetrahydrofuran, and the structure of the
bipyridine complex has been determined [32]. However
simple replacement of methanol by amine, thiol or
selenol in these reactions does not yield the
analogous compounds [MCl(CO)2(h3-CH2C(COXR)C-
had detached from the butadienyl ligand. No bromina-
tion products of the butadienyl could be isolated.
4. Conclusions
Thioester, selenoester or telluroester substituted h3-
butadienyl complexes were formed by reaction of the h3-
(Me)XR)(L2)] (XꢁNR, S, Se). The reaction of 1 or 4
/
CH2C(COCl)Cꢀ/CH2 moiety with either chalcogenols
with methanolic Me3SiSePh thus provides a new route
to this class of 2,3,3-trisubstituted, h3-allylic complexes.
The ability of selenoester substituted complex 4 to
perform as an acyl transfer agent was investigated. On
stirring a solution of the complex in a mixture of acetone
and either basic methanol or excess n-propylamine no
reaction occurred. However, addition of copper or
mercury(II) chlorides to these reaction mixtures gave
rise to the production of the methylester and n-
propylamide substituted complexes, respectively, in
good yield. These were identified by comparison with
the published spectroscopic data [6]. The general me-
chanism of these reactions can be expected to proceed
via initial attack of alcohol or amine on the acyl carbon
of the selenoeseter substituent to give a conventional
tetrahedral intermediate, the copper or mercuryl ion
associating with the selenium atom. Departure of the
metal selenolate then yields the ester or amide product.
Comparison of the methanolyis reaction for complex 4
with that of the thioester complex 3 showed a longer
reaction time (8 h) was required for the latter, in accord
(S, Se) or bisorganochalogen mercurials (Se, Te). The
introduction of the latter synthetic method did not lead
to significant improvement in yields, however, it pro-
vided a route to previously inaccessible tellurium
derivatives. Use of polythiols or polyselenols (nꢁ
/
2ꢂ4)
/
gave rise to polymeric complexes, in which substituted
h3-butadienyl units served as bridging ligands between
several metal centres. Substituted h3-butadienyl metal
complexes derived from achiral chalcogenols or bisor-
ganochalogen mercurials showed no spectroscopic evi-
dence for the presence of isomers in solution, and NMR
spectra were invariant over the range ꢄ
/
80 to ꢃ25 8C.
/
In the solid state, selenoester complex 4 contained a Z-
substituted, trans-butadienyl moiety, with the uncoor-
dinated double bond C(3)ꢁC(4) being unconjugated
/
with respect to p-delocalisation within the metal bound
C(1)C(2)C(3) unit. This organic fragment was therefore
expected to undergo many reactions expected for related
metal h3-allyl complexes. In agreement with this pre-
diction, halide extraction from the ester substituted
butadienyl complex gave a highly reactive 16-electron
cation, whose reactions with Lewis bases, anions and
labile solvent molecules, closely parallels those pre-
viously described for [Mo(CO)2(h3-C3H5)(bipy)]ꢃ. The
sites of electrophilic or nucleophilic attack within the
substituted butadienyl fragment (protonation at C(4) to
give a vinylcarbene moiety or attack by the phenylsele-
nide anion at C(3) to give a 2,3-disubstituted h3-allyl
unit) were in accord with predictions based on molecular
modelling techniques. The phenylselenoester two-sub-
stituted butadienyl complex 4 proved unstable to
oxidation by bromine, but readily acted as an acyl
transfer agent for methanol and propylamine in the
presence of soft, selenophilic metal cations. The poten-
tial for these complexes to serve as organic synthons is
being investigated.
with the greater carbonꢂsulphur bond strength in the
/
thioester butadienyl substituent. These results are in
accord with published observations that organochalco-
gen esters of the type R?COER (R?ꢁ
/
Me, Ph, Bz, Rꢁ
/
SeBu, TeBu [33], R?ꢁoctyl, ERꢁSeMe [7]) react with
/
/
metal halides in methanol or diethylamine to give the
corresponding ester and amide. Thus complex 4 shows
promise as an effective acyl transfer agent.
A solution of complex 4 (0.5 mmol) in dichloro-
methane (50 cm3) was brominated (0.5 mmol in 5 cm3
acetone) at low temperature (ꢄ5 8C), and the mixture
/
was monitored at different time intervals by infrared
spectroscopy. After 0.5 h a reduction in the intensity of
the n(COSe) stretching frequency at 1650 cmꢄ1 was
observed, and a new broad absorption near 1700 cmꢄ1
was assigned to formation the acyl bromide. This was in
accord with the known reaction of aryl selenoesters with
halogens to give the corresponding areneselenenyl
trihalide and acyl halide [34]. However, extended reac-
tion times, or on warming the mixture to room
temperature, the pair of strong absorptions at 1897
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 188645 for compound 4.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
and 1975 cmꢄ1 due to a cis metalꢂ
dicarbonyl unit
/
decreased in intensity. Increasing amounts of diphenyl-
diselenide and MoBr4(phen) were isolated from the
reaction, and it was apparent that the metal fragment
Cambridge CB2 1EZ, UK (Fax: ꢃ44-1223-336033; e-
/

A.G.W. Hodson et al. / Journal of Organometallic Chemistry 664 (2002) 277ꢂ
/287
287
[16] M.I. Bruce, T.W Hambley, M.J. Liddell, M.R. Snow, A.G.
Swincer, E.R.T. Tiekink, Organometallics 9 (1990) 96.
[17] For complex 4, 13C-NMR in DMSO-d6. 31.2 [C1]; 63.9 [C2]; 108.9
[C4]; 125.8, 126.2, 126.9, 127.7, 127.9, 128.8, 129.2, 130.3, 130.5,
153.1, 153.3 [aromatics]; 173.0 [C3]; 191.9 [C5]; 218.0, 219.3
[carbonyl].
mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
Acknowledgements
[18] W. Haugen, M. Trattenberg, Acta Chem. Scand. 20 (1966) 1726.
[19] S. Otsuka, A. Nakamura, Adv. Organomet. Chem. 14 (1976) 245.
[20] S.A. Benyunes, R.J. Deeth, A. Fries, M. Green, M. McPartlin,
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[21] P.K. Baker, Adv. Organomet. Chem. 40 (1996) 45 (and references
therein).
Elemental analyses were carried out by the Analytical
Services of the Universities of Bristol or Canterbury and
some NMR spectra were recorded by the University of
Portsmouth. The authors would like to thank Mr A.
Bashall for assistance with the crystallographic analysis.
[22] (a) L. Eriksson, M.P. Sjogren, B. Akermark, Acta Crystallogr.
Sect. C 52 (1996) 77;
(b) M.P.T. Sjogren, H. Frisell, B. Akermark, P.-O. Norrby, L.
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/
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