Synthesis, spectroscopic and structural characterisation of molybdenum, tungsten and manganese carbonyl complexes of tetrathio- and tetraseleno-ether ligands

Article abstract of DOI:10.1016/j.jorganchem.2009.03.041

A range of complexes of the binucleating tetrathio- and tetraseleno-ether ligands, 1,2,4,5-C₆H₂(CH₂EMe)₄ (E = S, L³ or Se, L⁴) or C(CH₂EMe)₄ (E = S, L⁵ or Se, L⁶) and of bidentate analogues 1,2-C₆H₂(CH₂EMe)₂ (E = S, L¹ or Se = L²) with molybdenum and tungsten carbonyls and manganese carbonyl chloride have been prepared, and characterised by IR and multinuclear NMR (¹H, ¹³C{¹H}, ⁷⁷Se, ⁵⁵Mn, ⁹⁵Mo) spectroscopy and mass spectrometry. Crystal structures are reported for [Mo(CO)₄(L²)], [Mo(CO)₄(L³)], [Mo(CO)₄(μ-L³)Mo(CO)₄], [Mo(CO)₄(L⁴)], [Mn(CO)₃Cl(μ-L³)Mn(CO)₃Cl], [Mo(CO)₄(μ-L⁵)Mo(CO)₄], [Mn(CO)₃Cl(L⁵)] and two forms (containing meso and DL diastereoisomers) of [W(CO)₄(L⁵)].

Full text of DOI:10.1016/j.jorganchem.2009.03.041

Journal of Organometallic Chemistry 694 (2009) 2299–2308
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, spectroscopic and structural characterisation of molybdenum, tungsten
and manganese carbonyl complexes of tetrathio- and tetraseleno-ether ligands
*
William Levason , Luke P. Ollivere, Gillian Reid, Nikolaos Tsoureas, Michael Webster
School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 March 2009
Received in revised form 25 March 2009
Accepted 29 March 2009
Available online 5 April 2009
A range of complexes of the binucleating tetrathio- and tetraseleno-ether ligands, 1,2,4,5-C6H2(CH2EMe)4
(E = S, L3 or Se, L4) or C(CH2EMe)4 (E = S, L5 or Se, L6) and of bidentate analogues 1,2-C6H2(CH2EMe)2 (E = S,
L
1 or Se = L2) with molybdenum and tungsten carbonyls and manganese carbonyl chloride have been pre-
pared, and characterised by IR and multinuclear NMR (1H, 13C{1H}, 77Se, 55Mn, 95Mo) spectroscopy and
mass spectrometry. Crystal structures are reported for [Mo(CO)4(L2)], [Mo(CO)4(L3)], [Mo(CO)4(
L3)Mo(CO)4], [Mo(CO)4(L4)], [Mn(CO)3Cl( -L3)Mn(CO)3Cl], [Mo(CO)4( -L5)Mo(CO)4], [Mn(CO)3Cl(L5)]
and two forms (containing meso and DL diastereoisomers) of [W(CO)4(L5)].
Ó 2009 Elsevier B.V. All rights reserved.
l
-
l
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Keywords:
Manganese
Molybdenum
Tungsten
Tetrathioether
Tetraselenoether
1. Introduction
2. Experimental
The removal of sulfur compounds, mainly thiophene deriva-
tives, from natural gas and crude petroleum is one of the key
chemical industrial processes. The process, hydrodesulfurisation,
(HDS), involves hydrogen reduction of the sulfur compounds using
molybdenum catalysts often with cobalt or nickel promoters, sup-
ported on alumina. Other catalysts containing tungsten and ruthe-
nium, sometimes with a 3d metal promoter have been examined in
attempts to achieve higher activity at lower temperatures [1–4].
One approach to preparing HDS catalysts is to prepare mono- or
bi-metallic complexes with sulfur ligands, which can be absorbed
or chemically tethered to an inert support and subsequently pyrol-
ysed to yield the metallic components in a sulfur environment.
Here we report the syntheses of some sulfur and selenium ligands
based upon 1,2,4,5-tetrasubstituted aromatic or spirocyclic back-
bones, which are sterically incapable of coordinating as tetraden-
tate monometallic chelates, but which can bridge two metal
centres, and illustrate their chemistry by the preparation of mono-
and di-nuclear complexes with molybdenum, tungsten and
manganese carbonyl substrates. A small number of reports of sim-
ilar ligands have appeared along with some metal halide complex
chemistry [5]. Details of the metal carbonyl chemistry of polythio-
and polyseleno-ethers are described in recent reviews [6].
Infrared spectra were recorded as Nujol mulls between CsI
plates over the range 4000–200 cmꢀ1 or as chlorocarbon solutions
in NaCl solution cells over the range 2200–1700 cmꢀ1, using
Perkin–Elmer 983G or PE Spectrum100 instruments. 1H and
13C{1H} NMR spectra were recorded at ambient temperatures un-
less stated otherwise, using a Bruker AV300 spectrometer and ref-
erenced internally to the solvent resonance, and 13C{1H}, 77Se{1H},
55Mn and 95Mo NMR spectra on a Bruker DPX400 spectrometer and
are referenced to the solvent resonance, external neat SeMe2, aque-
ous KMnO4, aqueous Na2MoO4 at pH 11, respectively. Mass spectra
were obtained using a VG Biotech platform. Microanalyses were
undertaken by the University of Strathclyde microanalytical ser-
vice or Medac Ltd. Solvents were dried prior to use and all prepa-
rations were undertaken using standard Schlenk techniques
under a N2 atmosphere. Metal carbonyls were obtained from Al-
drich and used as received. Mn(CO)5Cl was made from Mn2(CO)10
and Cl2/CCl4 [7]. o-C6H4(CH2SMe)2 (L1), o-C6H4(CH2SeMe)2 (L2)
and C(CH2SMe)4 (L5) were made as described [8,9].
2.1. 1,2,4,5-Tetrakis(methylthiomethyl)benzene (L3)
Liquid ammonia (150 mL) was condensed into a 500 mL three
necked flask, equipped with condenser and pressure equalising
addition funnel at ꢀ78 °C using a dry-ice/acetone slush bath. So-
dium (0.76 g, 33.2 mmol) was added and the blue solution stirred
for 10 min under N2. Dimethyldisulfide (1.5 mL 17.3 mmol) was
added slowly, which discharged the blue colour. The NH3 was left
* Corresponding author. Fax: +44 023 80 593781.
E-mail address: wxl@soton.ac.uk (W. Levason).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.03.041

2300
W. Levason et al. / Journal of Organometallic Chemistry 694 (2009) 2299–2308
to evaporate under a stream of N2, and the NaSMe dissolved
in 100 mL of dry EtOH. 1,2,4,5-Tetrakis(bromomethyl)benzene
(3.0 g, 6.7 mmol) was dissolved in warm degassed EtOH
(250 mL), and added dropwise to the NaSMe solution. After half
the solution was added the flask was heated to reflux and the addi-
tion completed. The mixture was refluxed overnight. The cooled
reaction mixture was transferred to a separating funnel, and satu-
rated aqueous NaHCO3 (100 mL) added. The mixture was extracted
with CH2Cl2 (3 ꢁ 200 mL) and the organic phase was collected,
washed with 100 mL brine and dried over MgSO4. Upon removal
of most of the solvent, the product precipitated as a white solid
which was collected by filtration, washed with hexane and dried
under vacuum. A second crop of crystalline product was collected
by combining the hexane washings with the CH2Cl2 mother-liquor
and cooling at ꢀ30 °C. Overall yield: 1.85 g, 87%. Anal. Calc. for
C14H22S4: C, 52.78; H, 6.96. Found: C, 52.83; H, 6.79%. 1H NMR
(CDCl3): 2.05(s) 12[H] SMe, 3.81(s) 8[H] CH2, 7.13(s) 2[H] aromatic
CH. 13C{1H} NMR (CDCl3): 15.6 SMe, 35.2 CH2, 133.0 CH 135.2 aro-
matic quaternary. CIMS: 319 [M]+.
MgSO4, filtered and the solvent removed under vacuum to yield
pale yellow oil. Kugelröhr distillation (110 °C, 0.1 mmHg) removed
volatiles, and the residue is pure L6. Yield: 1.91 g, 55%. 1H NMR
(CDCl3): 2.07(s) 12[H] SeMe, 2.86(s) 8[H] CH2. 13C{1H} NMR
(CDCl3): 6.27 SeMe, 35.2 CH2, 44.4 quaternary C. 77Se{1H} NMR
(CH2Cl2): 24.5. CIMS: 445 [M]+.
2.5. 1,1-Bis(methylselenomethyl)cyclopropane
Freshly ground selenium powder (5.0 g, 62.5 mmol) was added
to dry THF (25 mL) and stirred in a dry three necked round-bot-
tomed flask under nitrogen. The solution was then frozen with li-
quid nitrogen. MeLi solution (39.0 mL of 1.6 M solution in diethyl
ether, 64.5 mmol) was then added via syringe to the selenium
and left to thaw for 40 min, then stirred at room temperature for
2 h. Pentaerythrityl tetrabromide (3.0 g, 8.0 mmol) in THF
(30 mL) was then added to the solution and refluxed for 1 h. The
flask was allowed to cool and then hydrolysed with NaCl solution
(25 mL). The product was then extracted via separation with
diethyl ether (3 ꢁ 20 mL) dried over MgSO4 filtered and the solvent
and Me2Se2 removed under high vacuum to leave a pale yellow oil.
Yield: 1.74 g, 87%. 1H NMR (CDCl3): 0.61(s) 4[H] CH2 cyclopropyl,
2.10(s) 8[H] SeMe, 2.82(s) 4[H] CH2. 13C{1H} NMR (CDCl3): 5.3 C-
cyclopropyl, 15.0 SeMe, 34.9 CH2. 77Se{1H} NMR (CH2Cl2): 58.6.
GC–MS: 258 (RT. 5.2) [M]+.
2.2. 1,2,4,5-Tetrakis(methylselenomethyl)benzene (L4)
Freshly ground selenium powder (3.5 g, 44.4 mmol) was
added to dry THF (25 mL) in a dry three necked round-bottomed
flask under nitrogen. The solution was then frozen (77 K) with
liquid nitrogen. MeLi solution (27.8 mL of 1.6 M solution in
diethyl ether, 44.4 mmol) was then added via syringe and the
mixture was left to thaw for 40 min, then stirred at room tem-
perature for 2 h. 1,2,4,5-Tetrakis(bromomethyl)benzene (2.5 g,
5.6 mmol) was then added and the reaction mixture was re-
fluxed for 1 h, cooled and hydrolysed with NaCl solution
(25 mL). The organic layer was then separated and the aqueous
layer was extracted with diethyl ether (3 ꢁ 20 mL). The com-
bined extracts were dried over MgSO4, filtered and the solvent
removed under high vacuum to yield a yellow powder. Yield:
2.44 g, 86%. Anal. Calc. for C14H22Se4: C, 33.22; H, 4.38. Found:
C, 33.26, H, 4.17%. 1H NMR (CDCl3): 1.96(s) 12[H] SeMe,
3.85(s) 8[H] CH2, 7.01(s) 2[H] CH. 13C{1H} NMR (CDCl3): 4.84
SeMe, 25.05 CH2, 132.8 CH 135.5 aromatic quaternary. 77Se{1H}
NMR (CH2Cl2): 150.7. CIMS: 505 [M]+. Crystals were grown by
evaporation from CH2Cl2 solution.
2.6. [Mo(CO)4(L1)]
[Mo(CO)4(nbd)] (nbd = norbornadiene), (0.085 g, 0.28 mmol)
was dissolved in toluene (10 mL) and L1 (0.055 g, 0.28 mmol) in
toluene (5 mL) added. The mixture was stirred at 75 °C for 20 h,
cooled, and the toluene removed in vacuo. The residue was dis-
solved in hot CHCl3 (5 mL), filtered through Celite and n-pentane
(5 mL) added. Refrigeration (ꢀ18°) for 3 days gave a yellow solid,
which was filtered off, rinsed with n-pentane and dried in vacuo.
Yield: 0.07 g, 62%. Anal. Calc. for C14H14MoO4S2: C, 41.38; H, 3.47.
Found: C, 41.11; H, 3.89%. 1H NMR (CDCl3): 2.56(s) 6[H] SMe,
3.84(s) 4[H] CH2, 7.1–7.3(m) 4[H] aromatic. 13C{1H} NMR
(CH2Cl2/CDCl3): 27.6 SMe, 40.7 CH2, 129.7, 132.4, 134.2 aromatic,
206.3, 215.7 CO. 95Mo NMR (CH2Cl2): ꢀ1292. APCI MS: found m/z
422; calc. [MꢀMe]+ 423. IR (Nujol):
m(CO) 2020, 1904, 1878,
1833; (CH2Cl2): m .
(CO) 2028, 1915, 1895, 1853 cmꢀ1
2.3. 1,1,1,1-Tetrakis(methylthiomethyl)methane (L5)
2.7. [W(CO)4(L1)]
This was synthesized in a way similar to that described for L3
above, starting from (5.0 g, 12.9 mmol) C(CH2Br)4, (1.42 g,
61.7 mmol) Na and (2.7 mL, 30.5 mmol) of Me2S2. After removal
of volatiles the yellow liquid was distilled to yield the product as
a colourless liquid. Yield: 3.05 g, 92%. 1H NMR (CDCl3): 2.12(s)
12[H] SMe, 2.81(s) 8[H] CH2. 13C{1H} NMR (CDCl3): 17.5 SMe,
40.8 CH2, 44.9 quaternary C. CIMS: 257 [M]+.
Was made similarly to the molybdenum complex using
[W(CO)4(tmpa)] (tmpa = Me2N(CH2)3NMe2). Yield: 65%. Anal. Calc.
for C14H14O4S2W ꢂ 1/3CHCl3: C, 32.66; H, 2.74. Found: C, 32.54; H,
2.28%. 1H NMR (CDCl3): 2.76(s) 6[H] SMe, 3.99 (s) 4[H] CH2,
7.22–7.41(m) 4[H] aromatic. 13C{1H} NMR (CDCl3): 28.8 SMe,
1
41.9 CH2, 129.1, 132.1, 134.0 aromatic, 201.9 CO, JWC = 130 Hz,
1
206.2 CO, JWC = 174 Hz. APCI MS: found m/z 494, calc. [M]+ 494.
2.4. 1,1,1,1-Tetrakis(methylselenomethyl)methane (L6)
IR (CH2Cl2):
m .
(CO) 2022, 1904, 1888, 1849 cmꢀ1
Freshly ground selenium powder (2.8 g, 3.50 mmol) was added
to dry THF (25 mL) and was stirred in a dry three necked round-
bottomed flask under nitrogen. The solution was then frozen with
liquid nitrogen. MeLi solution (21.9 mL of 1.6 M solution in diethyl
ether, 35.0 mmol) was then added via syringe and left to thaw for
40 min, then stirred at room temperature for 2 h. Pentaerythrityl
tetrabromide (3.0 g, 8.0 mmol) in THF (30 mL) was then added
dropwise and the solution was stirred for 15 h before heating to
65 °C for 30 min. After cooling, the reaction mixture was hydroly-
sed with NaCl solution (25 mL). The organic layer was separated
and the aqueous layer extracted via separation with diethyl ether
(3 ꢁ 20 mL). The combined organic solutions were dried over
2.8. [Mn(CO)3Cl(L1)]
[Mn(CO)5Cl] (0.23 g, 1.0 mmol) was dissolved in CH2Cl2 (20 mL)
and L1 (0.2 g, 1.0 mmol) in toluene (20 mL) added. The mixture was
stirred at 75 °C for 3 h, cooled, and the solvent removed in vacuo.
The residue was dissolved in hot CHCl3 (15 mL), cooled and the yel-
low solid filtered off, rinsed with CHCl3 and dried in vacuo. Yield:
0.12 g, 32%. 1H NMR (CDCl3): 2.23(s) 6[H] SMe, 4.20(s) 4[H] CH2,
7.5(m) 4[H] aromatic. 13C{1H} NMR (CH2Cl2/CDCl3): 23.2 SMe,
35.1 CH2, 129.1, 131.8, 134.0 aromatic, 208.3(vbr) CO. 55Mn NMR
(CH2Cl2): +45. IR (Nujol): m .
(CO) 2038, 1960 (vbr), 1910(sh) cmꢀ1

W. Levason et al. / Journal of Organometallic Chemistry 694 (2009) 2299–2308
2301
2.9. [Mo(CO)4(L2)]
the solution was placed at ꢀ30 °C to give a crop of the 1:1 complex.
The ether insoluble portion was taken up in THF, filtered and the
solution was layered with hexane to produce crystals of the 2:1
compound identified by an X-ray crystal structure. Yields variable
(see text). 1H NMR (CD2Cl2): 2.57(s) 12[H] SMe, 3.89(s) 8[H] CH2,
7.10(s) 2[H], aromatic. 13C{1H} NMR (CH2Cl2/CD2Cl2): 27.5 SMe,
40.7 CH2, 134.9, 137.6 aromatic, 206.4 and 215.6 CO. IR (Nujol):
[Mo(CO)4(nbd)] (0.085 g, 0.28 mmol) was dissolved in toluene
(10 mL) and L2 (0.082 g, 0.28 mmol) in toluene (5 mL) added. The
mixture was stirred at 75 °C for 24 h, cooled and the toluene re-
moved in vacuo. The residue was dissolved in hot CHCl3 (5 mL), fil-
tered through Celite and n-pentane (5 mL) added, which gave a
yellow solid, which was filtered off, rinsed with n-pentane and
dried in vacuo. Yield: 0.061 g, 53%. Anal. Calc. for C14H14MoO4Se2:
C, 33.62; H, 2.82. Found: C, 33.88; H, 2.90%. 1H NMR (CDCl3):
2.93(s) 6[H] SeMe, 3.80(s) 4[H] CH2, 7.1–7.3(m) 4[H] aromatic.
13C{1H} NMR (CH2Cl2/CDCl3): 16.8 SeMe, 31.3 CH2, 128.7, 131.6,
135.2 aromatic, 207.4, 215.5 CO. 95Mo NMR (CH2Cl2): ꢀ1393.
77Se{1H} NMR (CH2Cl2): 157.6. APCI MS: found m/z 520, calc.
m
(CO) 2023, 1907, 1876, 1828 cmꢀ1
.
2.14. [Mn(CO)3Cl(L3)]
L3 (0.32 g, 1.0 mmol) and [Mn(CO)5Cl] (0.23 g, 1.0 mmol) were
dissolved in CH2Cl2 (20 mL), the mixture was placed under partial
vacuum and heated at 55 °C. After 2½ h at this temperature the
ampoule was removed from the oil bath and the reaction mixture
was left stirring overnight at room temperature. Volatiles were re-
moved on a rotary evaporator and the yellow-brown oily residue
was re-dissolved in CH2Cl2 (15 mL) and was filtered through Celite.
The solvent from the bright yellow solution was then removed un-
der vacuum and the residue was washed with n-pentane. It was
then dissolved in a small amount of CH2Cl2 (2 mL) and n-pentane
was added (20 mL) to precipitate a microcrystalline yellow solid,
which was collected by filtration and dried under vacuum. Yield:
0.21 g, 43%. Anal. Calc. for C17H22ClMnO3S4: C, 41.42; H, 4.50.
Found: C, 42.25; H, 4.66%. 1H NMR (CDCl3): 1.96(s) 6[H] SMe unco-
ord, 2.33(s) 6[H] SMe coord, 3.71(s) 4[H] CH2 uncoord, 4.73(m)
4[H] coord, 7.05(s) 2[H] aromatic. 13C{1H} NMR (CH2Cl2/CDCl3):
15.7 SMe uncoord, 22.8 SMe coord, 34.1 CH2 uncoord, 35.1 CH2 co-
ord, 134.5, 133.1, 138.0 aromatic, 217.6(vbr) CO. 55Mn NMR
[MꢀMe]+ 519. IR (Nujol):
m(CO) 2015, 1913, 1879, 1834; (CH2Cl2):
m
(CO) 2024, 1914, 1895, 1854 cmꢀ1. Crystals were grown by cool-
ing a CHCl3 solution in a freezer.
2.10. [W(CO)4(L2)]
Was made similarly to the molybdenum complex using
[W(CO)4(tmpa)]. Yield: 53%. Anal. Calc. for C14H14O4Se2W ꢂ CHCl3:
C, 25.47; H, 2.14. Found: C, 25.07; H, 2.40%. 1H NMR (CDCl3):
2.56(s) 6[H] SeMe, 3.91(s) 4[H] CH2, 7.1–7.3(m) aromatic. 13C{1H}
NMR (CH2Cl2/CDCl3, 223 K): 17.9 SeMe, 30.6 CH2, 128.0, 131.0,
133.8 aromatic, 201.6, 205.6 CO. 77Se{1H} NMR (CH2Cl2): 115.8,
109.4 (223 K). APCI MS: found m/z 590, calc. [M]+ 590. IR (CH2Cl2):
m
(CO) 2018, 1904, 1886, 1850 cmꢀ1
.
2.11. [Mn(CO)3Cl(L2)]
(CH2Cl2): +68. IR (Nujol):
Layering a CH2Cl2 solution of [Mn(CO)3Cl(L3)] with n-pentane
produced crystals identified as [Mn(CO)3Cl(
-L3)Mn(CO)3Cl]
m .
(CO) 2027, 1941, 1906 cmꢀ1
[Mn(CO)5Cl] (0.23 g, 1.3 mmol) was dissolved in CHCl3 (50 mL)
and L2 (0.39 g, 1.3 mmol) in CHCl3 (20 mL) added. The mixture was
refluxed for 3 h, cooled, and the solvent removed in vacuo. The res-
idue was washed in hot CHCl3 (3 ꢁ 15 mL). The resulting orange
solid, was filtered and then dried in vacuo. Yield: 0.19 g, 36%. Anal.
Calc. for C13H14ClMnO3Se2 ꢂ 1/2CHCl3: C, 30.81; H, 2.78. Found: C,
30.66; H, 2.85%. 1H NMR (CDCl3): 2.2–2.5(br) 6[H] SeMe, 3.5–4.1
(br) [4H] CH2, 7.3–7.8(br) 4[H] aromatic. 13C{1H} NMR (CH2Cl2/
CDCl3): 14.8–15.9(br, overlapping) SeMe, 27.9–31.2 (br) CH2,
128.4, 129.9, 133.0, 135.2 aromatic, 217.0–220.5 (vbr) CO.
77Se{1H} NMR (CH2Cl2): 147.8, 124.1, 122.5, 120.5. 55Mn NMR
(CH2Cl2): ꢀ42(major), ꢀ77(minor), ꢀ113 (minor). IR (CH2Cl2):
l
whose structure is described below. Attempts to prepare the 2:1
complex directly gave a mixture of the 1:1 complex, ligand and
Mn2(CO)10 (identified crystallographically).
2.15. [Mo(CO)4(L4)]
[Mo(CO)4(nbd)] (0.11 g, 0.4 mmol) was dissolved in toluene
(10 mL) and L4 (0.2 g, 0.4 mmol) in toluene (5 mL) added. The mix-
ture was stirred at 75 °C for 8 h, cooled and stirred overnight, and
the toluene was removed in vacuo. The residue was dissolved in
hot CHCl3 (5 mL), filtered through Celite and n-pentane (10 mL)
added. The flask was placed in the freezer overnight which gave
a yellow solid, and crystals formed on the side of the flask (used
for the X-ray crystallography); the solid was filtered off, rinsed
with n-pentane and dried in vacuo. Yield: 0.06 g, 21%. Anal. Calc.
for C18H22MoO4Se4: C, 30.27; H, 3.11. Found: C, 30.31; H, 3.21%.
1H NMR (CDCl3): 2.02(s) 6[H] SeMe uncoord, 2.46(s) 6[H] SeMe co-
ord, 3.86(s) 4[H] CH2 uncoord, 3.87(s) 4[H] CH2 coord, 7.01(s) 2[H]
aromatic. 13C{1H} NMR (CH2Cl2/CDCl3): 6.6 SeMe uncoord, 17.4
SeMe coord, 19.1 CH2 uncoord, 29.6 CH2 coord, 133.5, 136.0,
137.9 aromatic, 211.4, 216.5 CO. 77Se{1H} NMR (CH2Cl2): 151.8
SeMe uncoord, 154.9 SeMe coord. 95Mo NMR (CH3CN): ꢀ1384. IR
m
(CO) 2030, 1949, 1921 cmꢀ1
.
2.12. [Mo(CO)4(L3)]
This complex was isolated as yellow crystals by diethyl ether
extraction of the crude produce from the attempted synthesis of
[Mo(CO)4(l
-L3)Mo(CO)4] (see Section 2.13) and identified by the
crystal structure. 1H NMR (CD2Cl2): 2.06(s) 6[H] SMe uncoord,
2.56(s) 6[H] SMe coord, 3.81(s) 4[H] CH2 uncoord, 3.83(s) 4[H]
CH2 coord, 7.13(s) 2[H] aromatic. 13C{1H} NMR (CH2Cl2/CD2Cl2):
15.56 SMe uncoord, 27.15 SMe coord, 35.25 CH2 uncoord, 40.46
CH2 coord, 133.9, 134.9 135.2 aromatic, 206.4 and 215.6 CO. IR
(CH2Cl2):
m
(CO) 2024, 1917, 1895, 1856 cmꢀ1
.
(CH2Cl2):
m
(CO) 2036, 1927, 1884 cmꢀ1
.
2.16. [Mo(CO)4(
l
-L4)Mo(CO)4]
2.13. [Mo(CO)4(
l
-L3)Mo(CO)4]
[Mn(CO)4(nbd)] (0.22 g, 0.78 mmol) was dissolved in toluene
(20 mL) and L4 (0.2 g, 0.4 mmol) in toluene (20 mL) added. The
mixture was stirred at 110 °C for 3 h. cooled and stirred overnight,
the solvent was removed in vacuo. The yellow solid was washed in
CH2Cl2 (3 ꢁ 20 mL) and dried in vacuo. Yield: 45%. Anal. Calc. for
C22H22Mo2O8Se4: C, 28.66; H, 2.40. Found: C, 29.09; H, 2.20%. 1H
NMR (CDCl3): 2.39(s) 6[H] SeMe coord, 3.80(s) 4[H] CH2 coord,
7.21(s) 2[H] aromatic. 13C{1H} NMR (MeCN): (v. poorly soluble)
In an ampoule fitted with a Young’s tap, [Mo(CO)4(nbd)] (0.10 g,
0.33 mmol) suspended in dry toluene (15 mL) was added slowly L3
(0.106 g, 0.10 mmol) in CH2Cl2 (10 mL), the ampoule partially
evacuated and placed in a thermostated oil bath at 100 °C for 3 h.
Volatiles were removed under reduced pressure and the yellow-
brown solid was extracted with dry Et2O (3 ꢁ 30 mL) and filtered
through Celite. The volume of the ether was reduced to 1/3 and

2302
W. Levason et al. / Journal of Organometallic Chemistry 694 (2009) 2299–2308
14.7 SeMe, 24.8 CH2 coord, 132.8, 136.3, 140.3 aromatic, 205.2,
217.7 CO. 77Se{1H} NMR (CH2Cl2): 151.9(s). 95Mo NMR (MeCN):
55Mn NMR (CH2Cl2): ꢀ40 w 12000 Hz. IR (Nujol):
m(CO) 2027,
½
1941, 1909 cmꢀ1. Crystals were grown by cooling a hexane solu-
ꢀ1411. IR (CH2Cl2):
m
(CO) 2025, 1914, 1893, 1829 cmꢀ1
.
tion of the compound at ꢀ30 °C.
2.17. [Mo(CO)4(L5)]
2.21. [Mo(CO)4(L6)]
[Mo(CO)4(nbd)] (0.10 g, 0.33 mmol) was placed in 20 mL
Young’s ampoule and dissolved in dry toluene (10 mL). A solution
of L5 (2.1 mL of 40 mg/mL solution) in toluene are added slowly via
syringe. The reaction mixture was placed under partial vacuum
and heated overnight at 110 °C. Volatiles were removed in vacuo
and the yellow solid was extracted in petroleum ether (60–80),
and filtered through Celite. The solution was reduced to about
4 mL and cooled to ꢀ30 °C to produce a yellow precipitate which
was isolated from the mother-liquor by filtration and dried under
vacuum. A second crop was collected by reducing the volume of
the mother-liquor and cooling at ꢀ30 °C. Overall yield: 0.10 g,
65%. Anal. Calc. for C13H20MoO4S4: C, 33.61; H, 4.34. Found: C,
33.10; H, 4.33%. 1H NMR (CDCl3): 2.19(s) 6[H] SMe uncooord,
2.51(s) 6[H] SMe coord, 2.74(s) 4[H] CH2 uncoord, 2.85(s) 4[H]
CH2 coord. 13C{1H} NMR (CH2Cl2/CDCl3): 17.8 SMe uncoord, 27.6
SMe coord, 42.2 CH2 uncoord., 43.8 C quaternary, 48.5 CH2 coord.,
[Mo(CO)4(nbd)] (0.14 g, 0.45 mmol) was dissolved in toluene
(10 mL) and L4 (0.2 g, 0.45 mmol) in toluene (5 mL) added. The
mixture was stirred at 75 °C for 3 h, cooled and stirred overnight,
when the toluene was removed in vacuo. The residue was dis-
solved in hot CHCl3 (5 mL), filtered through Celite and n-pentane
(10 mL) added. The flask was placed in the freezer overnight which
gave a dark yellow solid, which was filtered off, rinsed with n-pen-
tane and dried in vacuo. Yield 0.14 g, 48%. Anal. Calc. for
C13H20MoO4Se4: C, 23.93; H, 3.09. Found: C, 23.33; H, 3.09%. 1H
NMR (CDCl3): 2.08(s) [6H] SeMe uncoord, 2.48(s) [6H] SeMe coord,
2.85(s) [4H] CH2 uncoord, 2.89(s) [4H] CH2 coord. 13C{1H} NMR
(CH2Cl2/CDCl3): 6.2(s) MeSe uncoord, 25.3 MeSe coord, 41.0 CH2
uncoord, 44.0 C quaternary, 47.6 CH2 coord, 209.1, 215.1, CO.
95Mo NMR (CH2Cl2): ꢀ1450. 77Se{1H} NMR (CH2Cl2): 16.0(s) MeSe
coord, 23.1(s) MeSe uncoord. IR (Nujol):
1851 cmꢀ1
m(CO) 2020, 1904, 1883,
.
206.4 and 217.0 CO. 95Mo NMR (CH2Cl2): ꢀ1384. IR (Nujol):
m(CO)
2026, 1921, 1857 cmꢀ1
.
2.22. X-ray crystallography experimental
2.18. [W(CO)4(L5)]
Details of the crystallographic data collection and refinement
are given in Table 1. The crystallisation details are provided under
the section for each compound. Data collection used a Nonius
This was prepared as for the molybdenum complex from
[W(CO)4(piperidine)2] and L5 in toluene. Yield: 67%. Anal. Calc.
for C13H20O4S4W: C, 28.27; H, 3.65. Found: C, 28.54; H, 3.79%. 1H
NMR (CDCl3): 2.20(s) 6[H] SMe uncoord, 2.68(s) 6[H] SMe coord,
2.75(s) 4[H] CH2 uncoord, 3.08(s) 4[H] CH2 coord. 13C{1H} NMR
(CH2Cl2/CDCl3): 17.8 SMe uncoord, 29.5 SMe coord, 42.2 CH2 unco-
ord, 43.8 C quaternary, 48.9 CH2 coord, 202.1 and 208.0 CO. IR (Nu-
Kappa CCD diffractometer fitted with monochromated Mo K
a X-
radiation (k = 0.71073 Å), and with the crystals held at 120 K in
a dinitrogen gas stream. Structure solution and refinement were
straightforward [15–17] except as described below, and H atoms
were introduced into the model in calculated positions using the
default C–H distances. The compound [Mo(CO)4(l
-L3)Mo(CO)4]
jol):
from a CH2Cl2 solution layered with hexane and stored at ꢀ18 °C.
m
(CO) 2010, 1900(sh), 1890, 1843 cmꢀ1. Crystals were grown
had two centrosymmetric molecules in the cell, the second of
which showed disorder at S4. This was modelled as two sites
(A and B (sofs: 0.63, 0.37)) and also the bonded C(H3) was iden-
tified in the difference electron-density map (C18A/B). C16 and
C18A are on opposite sides of the Mo2/S3/S4A plane, whereas
C16 and C18B are on the same side as the Mo2/S3/S4B plane
(i.e. DL and meso isomers). The compound [Mo(CO)4(L4)] likewise
shows disorder at the uncoordinated Se3, modelled as two sites
(A/B) along with C12A/B. The compound [W(CO)4(L5)] (P21/n
form) showed a large peak ca. 1 Å away from W1. This was added
to the model as a fractional (refined) W1B atom which resulted in
a large decrease in R1 and the identification of three potential
(fractional) S atoms all about 1 Å away from S1, S2 and S3. The
geometry of these sites gave bond lengths in good agreement
with the major component, however the common refined sof
for these atoms (0.11) was such as to make identification of O
and C atoms unlikely, and this was the case. The major compo-
nent is shown in Fig. 9a. Selected bond lengths and angles are gi-
ven in Tables 2–10.
2.19. [(CO)4Mo(
-L5)Mo(CO)4]
l
A
Young’s ampoule was charged with [Mo(CO)4(nbd)]
(0.080 g, 0.26 mmol) in dry toluene (5 mL) and a solution of L5
in toluene (0.9 mL, 0.14 mmol of a 40 mg/ml solution). The am-
poule was placed under partial vacuum and the mixture left stir-
ring overnight. Volatiles were removed in vacuo, and the yellow
solid was washed with hot hexane to remove the 1:1 complex.
The residue was taken up in CH2Cl2, filtered through Celite and
volatiles were removed under vacuum. The solid was further
washed with hexane and dried under vacuum. Yield: 0.03 g,
34%. Anal. Calc. for C17H20Mo2O8S4: C, 30.36; H, 3.00. Found: C,
30.22; H, 3.09%. 1H NMR (CDCl3): 2.56(s) 12[H], SMe, 2.9(s)
8[H] CH2. 13C{1H} NMR (CH2Cl2/CDCl3): 27.6 SMe, 42.2 C quater-
nary, 48.7 CH2, 206.2 and 216.4 CO. IR (Nujol):
m(CO) 2024, 1919,
1860; (CH2Cl2):
m
(CO) 2024, 1911, 1899, 1860 cmꢀ1. Crystals are
grown by a layering a CH2Cl2 solution of the complex with
hexane.
3. Results
2.20. [Mn(CO)3Cl(L5)]
3.1. Ligands
This was prepared with a method analogous to the [W(CO)4(L5)]
complex starting from [Mn(CO)5Cl] (0.08 g, 0.35 mmol), L5 (2.2 mL
of a 40 mg/mL solution) in toluene. Yield: 0.10 g, 66%. Anal. Calc.
for C12H20ClMnO3S4: C, 33.45; H, 4.68. Found: C, 33.13; H, 4.24%.
1H NMR (CDCl3): 2.16(s) 6[H] SMe uncoord, 2.48(s) 6[H] SMe co-
ord, 2.67(s) 4[H] CH2 uncoord, 3.12(s) 4[H] CH2, coord. 13C{1H}
NMR (CH2Cl2/CDCl3): 18.0 SMe uncoord, 22.9 SMe coord, 40.6
CH2 uncoord, 41.2 CH2 coord, 43.3 C quaternary, 207.6, 217.6 CO.
The approach described in the Introduction, required tetraden-
tate ligands with architectures which would be incapable of tetra-
dentate monometallic chelation, and hence two types were chosen
(Fig. 1) based upon either a spirocyclic framework – C(CH2EMe)4
(E = S or Se) (L5, L6) or a tetrasubstituted aromatic backbone –
1,2,4,5-C6H2(CH2EMe)4 (L3, L4). We also report some compounds
of o-C6H4(CH2EMe)2 (L1, L2) [8] for comparison.

Table 1
Crystal data and structure refinement details.a
Complex
L3
L4
[Mo(CO)4(L2)]
[Mo(CO)4(L3)]
[Mo(CO)4(
l-
[Mo(CO)4(L4)]
[Mn(CO)3Cl(
l
-
[Mo(CO)4(
l
-
[W(CO)4(L5)] anti
Me (DL)
[W(CO)4(L5)] syn
Me (meso)c
[Mn(CO)3Cl(L5)]
L3)Mo(CO)4]
L3)Mn(CO)3Cl]
L5)Mo(CO)4]
Formula
M
Crystal system
Space group
a (Å)
C14H22S4
318.56
Monoclinic
P21/c (#14)
9.6553(10)
20.575(3)
9.2189(15)
90
113.249(7)
90
1682.7(4)
4
C14H22Se4
506.16
C14H14MoO4Se2
500.11
C18H22MoO4S4
526.54
C22H22Mo2O8S4
734.52
C18H22MoO4Se4
714.14
C20H22Cl2Mn2O6S4
667.40
C17H20Mo2O8S4
672.45
C13H20O4S4W
552.38
Monoclinic
Cc (#9)
10.783(2)
21.010(5)
8.7967(15)
90
106.853(10)
90
1907.2(7)
4
C13H20O4S4W
552.38
C12H20ClMnO3S4
430.91
Triclinic
Orthorhombic
Pbcn (#60)
27.939(6)
7.9549(10)
14.676(3)
90
Monoclinic
P21/n (#14)
9.5685(15)
13.647(2)
17.069(3)
90
98.572(8)
90
2203.9(6)
4
Triclinic
Monoclinic
P21/n (#14)
9.7804(10)
13.602(3)
17.285(3)
90
98.852(10)
90
2272.2(7)
4
Monoclinic
P21/c (#14)
12.772(2)
14.996(2)
14.065(2)
90
96.880(10)
90
2674.4(7)
4
Monoclinic
P21/c (#14)
14.607(2)
10.0424(15)
18.333(3)
90
111.735(5)
90
2498.1(7)
4
Monoclinic
P21/n (#14)
10.5626(10)
12.9810(15)
14.0075(15)
90
95.518(10)
90
1911.7(4)
4
Monoclinic
P21/c (#14)
11.205(3)
18.940(4)
8.8494(15)
90
91.266(6)
90
1877.6(7)
4
ꢀ
ꢀ
P 1 (#2)
P1 (#2)
9.172(3)
9.618(4)
11.742(6)
107.83(2)
91.12(3)
116.92(2)
863.9(7)
2
10.020(4)
10.040(4)
14.683(6)
74.107(15)
76.174(15)
88.089(15)
1378.8(10)
2
b (Å)
c (Å)
a
(°)
b (°)
90
90
c
(°)
U (Å3)
3261.7(10)
8
5.278
Z
(Mo
lK
a
) (mmꢀ1
)
0.547
8.477
0.994
1.255
7.005
1.490
1.376
6.506
6.491
1.294
F(0 0 0)
680
484
1920
1072
732
1360
1352
1336
1072
1072
888
Total no. of reflections
Unique
22 435
3122
9140
3647
21 685
3719
41 954
5074
24 815
6326
23 510
5186
31 146
6126
30 458
5714
8583
3923
22 551
4376
31 174
4309
reflections
[R(int)
No. of
parameters
]
0.048
168
0.086
167
0.066
192
0.040
248
0.053
349
0.057
266
0.109
311
0.044
284
0.057
204
0.030
225
0.026
194
b
R1 [I0 > 2
r(I0)]
0.075
0.106
0.224
0.059
0.114
0.099
0.038
0.056
0.082
0.027
0.037
0.064
0.053
0.083
0.113
0.054
0.085
0.090
0.055
0.092
0.088
0.029
0.046
0.060
0.035
0.040
0.080
0.029
0.032
0.064
0.022
0.028
0.049
R1 (all data)
b
wR2
[I0 > 2r(I0)]
wR2 (all data)
0.247
0.117
0.090
0.068
0.123
0.102
0.099
0.065
0.084
0.066
0.051
a
Common items: temperature = 120 K; wavelength (Mo K
a) = 0.71073 Å; h(max) = 27.5°.
.
P
P
P
P
2
1=2
R1
=
||Fo| ꢀ |Fc||/ |Fo|. wR2 ¼ ½ wðF2o ꢀ Fc2Þ = wFo4ꢃ
b
c
Ignoring disorder in the formula, M value and F(0 0 0).

2304
W. Levason et al. / Journal of Organometallic Chemistry 694 (2009) 2299–2308
Table 2
Table 7
Selected bond lengths (Å) and angles (°) for L3 and L4.
Selected bond lengths (Å) and angles (°) for [Mn(CO)3Cl(
l
-L3)Mn(CO)3Cl].
2.3709(11)
L3
S1–C7
S1–C8
S3–C11
S3–C12
C7–S1–C8
C11–S3–C12
Mn1–S1
Mn1–S2
Mn1–Cl1
Mn1–C15
Mn1–C16
Mn1–C17
2.3908(11)
2.4005(11)
2.3781(11)
1.811(4)
1.804(4)
1.806(4)
Mn2–S3
Mn2–S4
Mn2–Cl2
Mn2–C18
Mn2–C19
Mn2–C20
1.815(4)
1.801(4)
1.833(5)
1.770(8)
100.4(2)
102.7(3)
S2–C9
S2–C10
S4–C13
S4–C14
C9–S2–C10
C13–S4–C14
1.811(5)
1.787(7)
1.815(4)
1.786(4)
99.9(3)
2.3675(11)
2.3892(11)
1.810(4)
1.812(4)
1.795(4)
101.2(2)
S1–Mn1–S2
Cl1–Mn1–S1
92.69(3)
89.09(4)
S3–Mn2–S4
Cl2–Mn2–S3
103.61(4)
82.51(4)
L4
Se1–C4
Se1–C5
C4–Se1–C5
C1–C4–Se1
1.971(9)
1.940(8)
99.0(4)
Se2–C6
Se2–C7
C6–Se2–C7
C2–C6–Se2
1.974(8)
1.947(9)
97.5(4)
Cl1–Mn1–S2
90.37(4)
Cl2–Mn2–S4
81.51(4)
C15–Mn1–Cl1
C16–Mn1–Cl1
C–Mn1–C (ca. 90°)
85.75(12)
93.13(12)
87.1(2)–93.6(2)
C18–Mn2–Cl2
C19–Mn2–Cl2
C–Mn2–C (ca. 90°)
95.11(12)
95.25(12)
87.0(2)–93.2(2)
115.4(5)
112.6(6)
Table 3
Table 8
Selected bond lengths (Å) and angles (°) for [Mo(CO)4(L2)].
Selected bond lengths (Å) and angles (°) for [Mo(CO)4(l
-L5)Mo(CO)4].
Mo1–Se1
Mo1–C1
Mo1–C2
2.6670(6)
2.045(5)
1.963(5)
Mo1–Se2
Mo1–C3
Mo1–C4
2.6799(7)
1.963(4)
2.053(5)
Mo1–S1
Mo1–S2
Mo1–C1
Mo1–C2
Mo1–C3
Mo1–C4
2.5650(7)
2.5572(7)
1.972(3)
1.971(3)
2.073(3)
2.014(3)
Mo2–S3
Mo2–S4
Mo2–C5
Mo2–C6
Mo2–C7
Mo2–C8
2.5613(7)
2.5641(7)
1.980(3)
1.965(3)
2.062(3)
2.011(3)
C1–Mo1–C2
C1–Mo1–C3
C2–Mo1–C3
C6–Se1–C5
C1–Mo1–Se1
C1–Mo1–Se2
87.54(18)
86.96(18)
88.98(17)
97.1(2)
93.80(13)
93.36(12)
C2–Mo1–C4
C3–Mo1–C4
Se1–Mo1–Se2
C13–Se2–C14
C4–Mo1–Se1
C4–Mo1–Se2
87.28(18)
90.44(18)
96.059(17)
96.74(18)
91.17(12)
88.99(12)
S1–Mo1–S2
C10–S1–C14
C11–S2–C15
84.26(2)
98.06(11)
96.04(11)
S3–Mo2–S4
C12–S3–C16
C13–S4–C17
84.21(2)
97.85(11)
96.14(11)
C–Mo1–C (ca. 90°)
S–Mo1–C (ca. 90°)
86.0(1)–90.3(1)
90.7(1)–93.5(1)
C–Mo2–C (ca. 90°)
S–Mo2–C (ca. 90°)
87.7(1)–91.6(1)
87.4(1)–95.0(1)
Table 4
Selected bond lengths (Å) and angles (°) for [Mo(CO)4(L3)].
Mo1–S1
Mo1–C15
Mo1–C16
2.5955(7)
1.957(2)
1.954(2)
Mo1–S2
Mo1–C17
Mo1–C18
2.5731(7)
2.057(2)
2.044(2)
Table 9
Selected bond lengths (Å) and angles (°) for the two conformers of [W(CO)4(L5)].
(a) DL containing form
C15–Mo1–C16
C15–Mo1–C17
C15–Mo1–C18
C7–S1–C8
C17–Mo1–S1
C17–Mo1–S2
85.15(9)
90.98(9)
86.49(10)
99.63(11)
93.28(6)
93.56(6)
C16–Mo1–C17
C16–Mo1–C18
S1–Mo1–S2
C9–S2–C10
C18–Mo1–S1
C18–Mo1–S2
87.91(9)
83.03(9)
91.89(2)
99.43(10)
95.59(7)
88.71(7)
W1–S1
W1–C10
W1–C11
2.543(2)
1.963(8)
1.946(10)
W1–S2
W1–C12
W1–C13
2.554(2)
2.035(9)
2.034(8)
S1–W1–S2
83.88(6)
91.6(4)
87.7(3)
93.8(2)
89.2(2)
98.7(4)
98.3(5)
C10–W1–C13
C11–W1–C12
C11–W1–C13
C13–W1–S1
C13–W1–S2
C3–S2–C7
89.3(3)
89.3(4)
86.1(4)
89.4(2)
95.6(2)
98.7(4)
98.4(5)
C10–W1–C11
C10–W1–C12
C12–W1–S1
C12–W1–S2
C2–S1–C6
C4–S3–C8
(b) meso containing form
W1–S1
Table 5
C5–S4–C9
Selected bond lengths (Å) and angles (°) for [Mo(CO)4(
l
-L3)Mo(CO)4].
2.5394(12)
1.961(5)
1.980(5)
W1–S2
W1–C12
W1–C13
2.5367(11)
2.036(4)
2.037(5)
Mo1–S1
Mo1–C8
Mo1–C9
2.5647(16)
1.962(7)
1.942(7)
Mo1–S2
Mo1–C10
Mo1–C11
2.5939(17)
2.015(6)
2.066(6)
W1–C10
W1–C11
C8–Mo1–C9
C8–Mo1–C10
C8–Mo1–C11
C4–S1–C5
C10–Mo1–S1
C10–Mo1–S2
85.4(3)
88.4(3)
87.9(3)
97.9(3)
92.95(19)
93.40(17)
C9–Mo1–C10
C9–Mo1–C11
S1–Mo1–S2
C6–S2–C7
C11–Mo1–S1
C11–Mo1–S2
86.7(3)
88.0(3)
95.31(5)
99.9(3)
90.22(15)
91.62(16)
S1–W1–S2
86.75(4)
89.8(2)
90.6(2)
89.57(14)
90.16(13)
97.2(2)
C10–W1–C13
C11–W1–C12
C11–W1–C13
C13–W1–S1
C13–W1–S2
C3–S2–C7
88.2(2)
89.4(2)
87.4(2)
91.74(14)
93.05(13)
98.5(2)
C10–W1–C11
C10–W1–C12
C12–W1–S1
C12–W1–S2
C2–S1–C6
Table 6
Selected bond lengths (Å) and angles (°) for [Mo(CO)4(L4)].
Table 10
Selected bond lengths (Å) and angles (°) for [Mn(CO)3Cl(L5)].
Mo1–Se1
Mo1–C15
Mo1–C16
2.6715(9)
1.962(7)
1.962(7)
Mo1–Se2
Mo1–C17
Mo1–C18
2.6871(10)
2.040(7)
2.053(7)
Mn1–S1
Mn1–C1
Mn1–C2
2.3763(5)
1.7946(15)
1.8153(15)
Mn1–S2
Mn1–C3
Mn1–Cl1
2.3823(6)
1.8117(15)
2.3789(6)
C15–Mo1–C16
C15–Mo1–C17
C15–Mo1–C18
C7–Se1–C8
C17–Mo1–Se1
C17–Mo1–Se2
86.1(3)
82.6(3)
88.2(3)
96.6(3)
88.1(2)
95.6(2)
C16–Mo1–C17
C16–Mo1–C18
Se1–Mo1–Se2
C9–Se2–C10
C18–Mo1–Se1
C18–Mo1–Se2
87.2(3)
90.2(3)
90.72(3)
96.7(3)
94.4(2)
93.4(2)
S1–Mn1–S2
85.506(17)
89.775(13)
92.47(6)
S1–Mn1–Cl1
C1–Mn1–C3
C2–Mn1–C3
C6–S2–C10
91.724(16)
91.54(7)
87.67(6)
97.57(7)
S2–Mn1–Cl1
C1–Mn1–C2
C5–S1–C9
98.18(7)
C–Mn1–S (ca. 90°)
86.74(5)–93.93(5)

W. Levason et al. / Journal of Organometallic Chemistry 694 (2009) 2299–2308
2305
CH2SeMe
CH2SMe
CH2SMe
CH2SeMe
L2
MeSeCH2
MeSeCH2
L1
CH2SeMe
CH2SeMe
CH2SMe
CH2SMe
MeSCH2
MeSCH2
L4
L3
MeSeCH2
CH2SeMe
MeSCH2
MeSCH2
CH2SMe
C
C
MeSeCH2
CH2SeMe
CH2SMe
L6
L5
Fig. 1. Key to the ligands used.
Fig. 3. Structure of C6H2(CH2SeMe)4 (L4) showing the numbering scheme adopted.
Ellipsoids are drawn at the 50% probability level and H atoms have been omitted for
clarity. Symmetry operation: a = 1 ꢀ x, 2 ꢀ y, ꢀz.
L5 was made in good yield by the reaction of NaSMe with
C(CH2Br)4 in refluxing ethanol [9]. The reaction of LiSeMe with
C(CH2Br)4 in THF was reported [10] to give L6 in poor yield
(ꢄ10%). In attempts to optimise the yield we examined this reac-
tion under a variety of conditions and reactant ratios. We found
that reaction of LiSeMe with C(CH2Br)4 in a 4.5:1 molar ratio in
hot THF stirred for 15 h gave a fair yield (ꢄ55%) of L6. Increasing
the LiSeMe with C(CH2Br)4 molar ratio to 8:1 in refluxing THF pro-
3.2. Complexes of L1 and L2
The tetradentates L3 and L4 produce seven-membered rings on
chelation, and for comparison purposes, complexes of the two
bidentate xylyl backboned ligands, o-C6H4(CH2EMe)2 (L1 and L2)
were prepared. The spirocyclic L5 and L6 produce six-membered
rings and comparisons here are provided by complexes of
duced the cyclopropane derivative
in ꢄ90%
MeE(CH2)3EMe
[12,13].
The
complexes
[Mo(CO)4(L1)],
yield, and under a variety of other conditions mixtures of the
two are produced. The corresponding reaction of LiTeMe with
C(CH2Br)4 in THF affords only the cyclopropyltelluroether,
[11].
[W(CO)4(L1)], [Mo(CO)4(L2)] and [W(CO)4(L2)] were produced in
high yields by reaction of the appropriate ligands with [Mo-
(CO)4(nbd)] or [W(CO)4(tmpa)], respectively. They are air-stable
yellow crystalline solids with spectroscopic properties (Section 2)
consistent with cis-tetracarbonyls [12–14]. The only point of note
is the absence of 77Se resonances in the spectrum of [W(CO)4(L2)]
at ambient temperatures, whereas two resonances are observed
at 233 K, which reflects the rate of pyramidal inversion at E; as
usual inversion is a lower energy process in the molybdenum sys-
tem and a single (averaged) resonance is present at ambient tem-
peratures1. The structure of [Mo(CO)4(L2)] (Fig. 4 and Table 2)
confirms the geometry and shows the ligand present as the meso-1
diastereoisomer, with the Me groups and the xylyl backbone on
the same side of the MoSe2C2 plane. The Se–Mo–Se angle is
96.06(2)°, reflecting the seven-membered ring, and as usual the
Mo–CtransC are considerably longer than Mo–CtransSe [12]. The
[Mn(CO)3Cl(L)] (L = L1 or L2) were made from the appropriate ligand
and [Mn(CO)5Cl]. They have relatively poor solubilities in halocarbon
solvents, but have similar properties to those of other group 16 do-
nor examples [13]. As is always observed in complexes of this type,
the 1H NMR resonances are significantly broadened by the quadru-
polar manganese nucleus, as are the 13C carbonyl resonances,
although 55Mn NMR resonances themselves are relatively sharp. Un-
like five-membered chelate ring dithioether analogues, where the
55Mn NMR spectra show separate resonances for the various inver-
tomers [13], in the [Mn(CO)3Cl(L1)] with a seven-membered ring,
fast inversion results in a single 55Mn resonance. For [Mn(CO)3Cl(L2)]
inversion is a higher energy process and three broad overlapping
The reaction of excess NaSMe in ethanol or LiSeMe in THF with
1,2,4,5-C6H2(CH2Br)4 gave excellent yields (>85%) of the 1,2,4,5-
C6H2(CH2EMe)4, which are air-stable crystalline solids. The spec-
troscopic properties (Sections 2.1 and 2.2) are unexceptional. The
structures of both ligands were determined (Figs. 2 and 3, Table
2). The 1,2,4,5-C6H2(CH2SMe)4 has similar dimensions to those of
o-C6H4(CH2SMe)2 [8] with the sulfur atoms directed outwards pre-
sumably minimising lone pair repulsions. The tetraselenoether
although not isomorphous, has a very similar molecular structure,
and in both cases the CH2EMe groups on adjacent ring carbon
atoms are on opposite sides of the ring.
1
When neutral bidentate group 16 donor ligands chelate to a metal centre, meso
and DL diastereoisomers are generated. These interconvert (pyramidal inversion) at
varying rates depending upon the donor atom, the chelate ring size and the metal ion
involved. Fast inversion on the appropriate NMR timescales results in simple
(averaged) NMR spectra, whilst slower inverting systems may show resonances for
the individual isomers. These process have been investigated in detail elsewhere (Ref.
[12] and references therein) and were not investigated in the present work, although
they do influence the NMR spectra observed.
Fig. 2. Structure of C6H2(CH2SMe)4 (L3) showing the numbering scheme adopted.
Ellipsoids are drawn at the 50% probability level and H atoms have been omitted for
clarity.

2306
W. Levason et al. / Journal of Organometallic Chemistry 694 (2009) 2299–2308
Fig. 6. Structure of the centrosymmetric Mo1 centred molecule [Mo(CO)4(
L3)Mo(CO)4] showing the numbering scheme adopted. Ellipsoids are drawn at the
50% probability level and atoms have been omitted for clarity. Symmetry
l-
H
operation: a = ꢀx, ꢀy, 1 ꢀ z. There is a second molecule in the asymmetric unit
(Mo2 centred) with a similar structure but showing some disorder at one SMe
group.
Fig. 4. Structure of [Mo(CO)4(L2)] showing the numbering scheme adopted.
Ellipsoids are drawn at the 50% probability level and H atoms have been omitted
for clarity.
dithioether units. The only notable structural difference is the
slightly wider (ꢄ3°) S1–Mo–S2 angle of 95.31(5)° for the DL form
compared with that in the meso form in [Mo(CO)4(L3)]. There is
no significant communication between the metal centres in the
dinuclear complex as would be expected given the saturated car-
bon links in the ligand, and hence the spectroscopy reflects the fin-
gerprints of the octahedral metal centres, closely following that of
the model compounds and [Mo(CO)4(L3)] (Section 3.2). The ten-
dency to rearrange and modest solubility of [Mo(CO)4(L3)] makes
it a rather poor synthon for bimetallics. We were unable to obtain
pure samples of the corresponding tungsten complexes which are
even less soluble but seem to be prone to similar rearrangement.
In contrast to the complexes with L3, both [Mo(CO)4(L4)] and
55Mn resonances of disparate intensities, were observed at ambient
temperatures, and these correlate with several broad overlapping
features in the 77Se{1H} and 13C{1H} spectra, showing a system
approaching fast inversion at 295 K on the various energy scales.
3.3. Complexes of L3 and L4
The reaction of [Mo(CO)4(nbd)] with L3 in a 1:1 molar ratio in
toluene/CH2Cl2 gave a yellow-brown solid which was shown by
1H NMR spectroscopy to be a mixture of [Mo(CO)4(L3)] and
[Mo(CO)4(l
-L3)Mo(CO)4], the relative amounts varying from prep-
aration to preparation. Extraction of the crude product with diethyl
ether and crystallisation produced yellow [Mo(CO)4(L3)], whilst
recrystallisation of the ether insoluble residue from THF afforded
[Mo(CO)4(l
-L4)Mo(CO)4] can be prepared directly under appropri-
ate conditions (Sections 2.16 and 2.17). The structure of the former
was determined (Fig. 7 and Table 6) and like the L3 analogue, con-
tains the meso-1 isomer of the ligand. The dimensions are unexcep-
tional and the M–C(O) and C–O distances are not significantly
different from those in [Mo(CO)4(L3)] showing that the electronic
[Mo(CO)4(l
-L3)Mo(CO)4]. The spectroscopic data, especially the
1H and 13C{1H} NMR easily distinguish the two complexes,
although samples of either usually show small amounts of the
other complex and sometimes traces of free L3, suggesting that
rearrangement occurs quite readily. The structures of both
complexes were determined. The structure of [Mo(CO)4(L3)]
(Fig. 5 and Table 4) shows the Mo(CO)4 residue j2 coordinated to
L3 with the coordinated dithioether group as the meso-1 isomer,
with the <S1–Mo–S2 = 91.89(2)°, and the pattern of Mo–C(O) bond
effects of S and Se donors are similar. The dinuclear [Mo(CO)4(l-
L4)Mo(CO)4] was poorly soluble in chlorocarbons which hindered
solution spectroscopic studies.
The reaction of [Mn(CO)5Cl] with L3 in either a 1:1 or 2:1 molar
ratio in hot CH2Cl2 gave yellow crystals of [Mn(CO)3Cl(L3)], the
reaction using the higher Mn:L3 ratio also caused some decompo-
lengths similar to those in [Mo(CO)4(L2)] (above). The structure of
2
[Mo(CO)4(
l
-L3)Mo(CO)4] (Fig. 6 and Table 5) shows L3 j2j0 coor-
dinated to two Mo(CO)4 residues which adopt an anti-arrangement
with respect to the plane of the aromatic backbone. The molecule
is centrosymmetric with DL conformations for the coordinated
Fig. 7. Structure of [Mo(CO)4(L4)] showing the numbering scheme adopted.
Ellipsoids are drawn at the 50% probability level and H atoms have been omitted
for clarity. There is disorder at Se3 and C12 modelled as two sites (A and B) with
only the major A component shown.
Fig. 5. Structure of [Mo(CO)4(L3)] showing the numbering scheme adopted.
Ellipsoids are drawn at the 50% probability level and H atoms have been omitted
for clarity.

W. Levason et al. / Journal of Organometallic Chemistry 694 (2009) 2299–2308
2307
sition and significant amounts of Mn2(CO)10 (identified crystallo-
graphically) were formed. The spectroscopic data on
[Mn(CO)3Cl(L3)] mirrors that of [Mn(CO)3Cl(L1)]. Curiously in
view of the failure to synthesise it directly, a CH2Cl2 solution
of [Mn(CO)3Cl(L3)] layered with pentane, produced a few crys-
tals which were identified as the dinuclear [Mn(CO)3Cl
(l
-L3)Mn(CO)3Cl], which presumably result from rearrangement
in solution and deposit preferentially due to low solubility. The
structure (Fig. 8 and Table 7) shows the tetrathioether in a quite
different conformation to that in the dimolybdenum complex
above; the Mn residues are coordinated syn with respect to the
aromatic backbone, and whilst one Mn(CO)3Cl group is bound to
a dithioether unit in the DL form, the second is bound to a meso-
1 dithioether group. In both groups the chlorine is directed away
towards the less hindered faces of the molecule. Comparison of
the bond lengths and angles shows little differences in Mn–Cl or
Fig. 10. Structure of [Mo(CO)4(
adopted. Ellipsoids are drawn at the 50% probability level and H atoms have been
omitted for clarity.
l
-L5)Mo(CO)4] showing the numbering scheme
Mn–C(O) distances, but the Mn–S distances within the DL coordi-
nated unit are slightly longer (ꢄ0.02 Å) than in the meso, while
the <S–Mn–S is quite different (92.7(1)° for the DL versus
103.6(1)° for the meso).
3.4. Complexes of L5 and L6
The complexes of these two ligands are generally more soluble
in non-polar solvents than those of L3 and L4. For the spirocyclic
thioether L5, the complexes [Mo(CO)4(L5)], [W(CO)4(L5)], [(CO)4-
Mo(l
-L5)Mo(CO)4] and [Mn(CO)3Cl(L5)] were isolated and fully
characterised, their spectroscopic properties being much as ex-
pected. Crystal structures were obtained for two forms of
[W(CO)4(L5)], the dinuclear [(CO)4Mo( -L5)Mo(CO)4] and for
l
Fig. 8. Structure of [Mn(CO)3Cl(
adopted. Ellipsoids are drawn at the 50% probability level and H atoms have been
omitted for clarity.
l
-L3)Mn(CO)3Cl] showing the numbering scheme
[Mn(CO)3Cl(L5)] which reveal some interesting structural features.
Yellow crystals of [W(CO)4(L5)] obtained from CH2Cl2/hexane were
found to contain the DL invertomer of the j2 coordinated ligand
(Fig. 9a and Table 8) whilst a second set of crystals obtained from
the same solvent mixture showed some small amount of disorder
but contained the corresponding j2 coordinated meso invertomer
(Fig. 9b and Table 8). Although the W–C and W–S distances are
not significantly different and the axial carbonyl groups (C13–
W1–C12 ꢄ 175°) are bent away from the dithioether, the notable
difference is in the S1–W1–S2 chelate angle which is some 3°
wider in the meso form, a similar trend but smaller than in the
dinuclear manganese complex of L3. The dinuclear [(CO)4Mo
(l
-L5)Mo(CO)4] (Fig. 10 and Table 9) has both chelating S2 units
in the DL forms and the two Mo environments are very similar.
In contrast, the [Mn(CO)3Cl(L5)] (Fig. 11 and Table 10) contains a
meso-1 form of j2 coordinated ligand with both SMe groups on
the same side of the MnC2S2 plane as the chloride ligand. The
Fig. 9. Structure of two conformational isomers of [W(CO)4(L5)] showing the
numbering schemes adopted. Ellipsoids are drawn at the 50% probability level and
H atoms have been omitted for clarity. (a) C atoms C6 and C7 are anti with respect
to the WS2 plane. (b) C atoms C6 and C7 are syn with respect to the WS2 plane.
Fig. 11. Structure of [Mn(CO)3Cl(L5)] showing the numbering scheme adopted.
Ellipsoids are drawn at the 50% probability level and H atoms have been omitted for
clarity.

2308
W. Levason et al. / Journal of Organometallic Chemistry 694 (2009) 2299–2308
[Mo(CO)4(L6)] was also isolated and is little different to the thioe-
ther analogue.
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2009.03.041.
4. Conclusions
References
Several series of monometallic and homo-bimetallic carbonyl
complexes of tetrathio- and tetraseleno-ether ligands have been
prepared and characterised. The X-ray structural data reveals some
interesting comparisons, particularly in those cases where struc-
tures of units containing meso and DL forms of the same ligand
have been determined. Overall the spirocyclic ligand complexes
appear the best candidates for attempting to prepare heterobime-
tallics, since the complexes have better solubility than those based
upon 1,2,4,5-C6H2 linkages. The poor solubility of some of the latter
may contribute to the disproportionation observed in some cases,
with the equilibria driven by crystallisation of poorly soluble
forms. Work in underway to incorporate 3d or 4d metal halide
units along with the j2 coordinated metal carbonyl units from
the present work into heterobimetallics.
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Appendix A. Supplementary material
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CCDC 722298, 722299, 722300, 722301, 722302, 722303,
722304, 722305, 722306, 722307 and 722308 contains the supple-
mentary crystallographic data for [L3], [L4], [Mo(CO)4(L2)],
[Mo(CO)4(L3)], [Mo2(CO)8(L3)], [Mo(CO)4(L4)], [Mn2(CO)6Cl2(L3)],
[W(CO)4(L5)], [W(CO)4(L5)], [Mo2(CO)8(L5)], [Mn(CO)3Cl(L5)]. These
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