Manganese(I) selenoether chemistry: Synthesis, multinuclear NMR studies and the structures of [MnCl(CO)3(MeSeCH2CH2SeMe)], [MnCl(CO)3(MeSeCH2CH2CH2SeMe)] and [MnBr(CO)3{C6H4(SeMe)2-o}]

Article abstract of DOI:10.1039/a806881j

Reaction of [Mn(CO)₅X] (X = Cl, Br or I) with RSe(CH₂)_nSeR (R = Me or Ph, n = 2; R = Me, n = 3) or C₆H₄(SeMe)₂-o in refluxing CHCl₃ yielded the neutral manganese(II) complexes [MnX(CO)₃{RSe(CH₂)_nSeR}] or [MnX(CO)₃{C₆H₄(SeMe)₂-o}] as yellow or orange solids. Infrared spectroscopic studies confirmed the factricarbonyl arrangement. Proton, ¹³C-{¹H), ⁷⁷Se-{¹H} and ⁵⁵Mn NMR spectroscopy has been used to probe the solution behaviour, and show that only those compounds involving PhSeCH₂CH₂SePh are undergoing rapid pyramidal inversion on the NMR timescale, with the individual NMR distinguishable invertomers observed for the other complexes (meso-1, meso-2 and DL) in varying ratios. X-Ray crystallographic analyses on three examples confirmed a fac-tricarbonyl arrangement, with the diselenoether ligand chelating: [MnCl(CO)₃(MeSeCH₂CH₂SeMe)] and [MnCl(CO)₃(MeSeCH₂CH₂CH₂SeMe)] adopt the DL arrangement, while [MnBr(CO)₃{C₆H₄(SeMe)₂-o}] is in the meso-2 form in the solid state. These are the first structure determinations on selenoether complexes of manganese(I) carbonyl halides. Most importantly, ⁵⁵Mn NMR spectroscopic studies show that δ(⁵⁵Mn) is to low frequency of those of the corresponding thioether compounds, lying in the range δ -175 to -702, the lowest frequencies occurring for the iodo derivatives. The CO stretching frequencies and ⁵⁵Mn NMR shifts show that, for a given X, the manganese(I) centre in [MnX(CO)₃(diselenoether)] is more shielded than in [MnX(CO)₃(dithioether)], possibly indicating increased σ donation in the former.

Full text of DOI:10.1039/a806881j

View Article Online / Journal Homepage / Table of Contents for this issue
Manganese(I) selenoether chemistry: synthesis, multinuclear NMR
studies and the structures of [MnCl(CO)3(MeSeCH2CH2SeMe)],
[MnCl(CO)3(MeSeCH2CH2CH2SeMe)] and
[MnBr(CO)3{C6H4(SeMe)2-o}]
Julie Connolly, Maxwell K. Davies and Gillian Reid*
Department of Chemistry, University of Southampton, Highfield, Southampton, UK SO17 1BJ
Received 3rd September 1998, Accepted 5th October 1998
Reaction of [Mn(CO)5X] (X = Cl, Br or I) with RSe(CH2)nSeR (R = Me or Ph, n = 2; R = Me, n = 3) or
C6H4(SeMe)2-o in refluxing CHCl3 yielded the neutral manganese() complexes [MnX(CO)3{RSe(CH2)nSeR}]
or [MnX(CO)3{C6H4(SeMe)2-o}] as yellow or orange solids. Infrared spectroscopic studies confirmed the fac-
tricarbonyl arrangement. Proton, 13C-{1H}, 77Se-{1H} and 55Mn NMR spectroscopy has been used to probe the
solution behaviour, and show that only those compounds involving PhSeCH2CH2SePh are undergoing rapid
pyramidal inversion on the NMR timescale, with the individual NMR distinguishable invertomers observed for
the other complexes (meso-1, meso-2 and ) in varying ratios. X-Ray crystallographic analyses on three examples
confirmed a fac-tricarbonyl arrangement, with the diselenoether ligand chelating: [MnCl(CO)3(MeSeCH2CH2SeMe)]
and [MnCl(CO)3(MeSeCH2CH2CH2SeMe)] adopt the  arrangement, while [MnBr(CO)3{C6H4(SeMe)2-o}] is in the
meso-2 form in the solid state. These are the first structure determinations on selenoether complexes of manganese()
carbonyl halides. Most importantly, 55Mn NMR spectroscopic studies show that δ(55Mn) is to low frequency of those
of the corresponding thioether compounds, lying in the range δ Ϫ175 to Ϫ702, the lowest frequencies occurring for
the iodo derivatives. The CO stretching frequencies and 55Mn NMR shifts show that, for a given X, the manganese()
centre in [MnX(CO)3(diselenoether)] is more shielded than in [MnX(CO)3(dithioether)], possibly indicating increased
σ donation in the former.
[Mn(CO)3X(SbPh3)2] and [Mn(CO)4X(η1-Ph2SbCH2SbPh2)]4–9
Introduction
and we have reported10 the preparation and characterisation
Recently we have been investigating the co-ordination
chemistry of macrocyclic thio- and seleno-ethers with early
transition metal centres, with particular interest in the hard
(metal)–soft (ligand) interactions in these species. In the course
of this work we have reported a range of complexes of
hard chromium() and vanadium() ions, including [CrX2-
([16]aneSe4)]PF6 (X = Cl or Br; [16]aneSe4 = 1,5,9,13-tetra-
selenacyclohexadecane), cis-[CrX2([14]aneS4)]PF6 ([14]aneS4 =
of [MnX(CO)3(L–L)] [L–L = MeSCH2CH2SMe, MeSCH2-
CH2CH2SMe, PhSCH2CH2SPh or C6H4(SMe)2-o]. These
species adopt fac-tricarbonyl arrangements with the dithio-
ether chelating. The 55Mn NMR studies showed that where
pyramidal inversion was slow on the NMR timescale the
resonances for the individual invertomers were generally well
resolved, giving δ(55Mn) in the range ϩ67 to Ϫ537. All of these
species are significantly deshielded with respect to phosphine
complexes such as [MnX(CO)3(dppe)] (X = Cl, δ Ϫ1141; X = Br,
Ϫ1254).11
1,4,8,11-tetrathiacyclotetradecane)
and
[VX3([9]aneS3)]
(X = Cl, Br or I; [9]aneS3 = 1,4,7-trithiacyclononane). EXAFS
measurements and single crystal X-ray analyses have enabled
us to establish the metal–thioether and –selenoether distances
in these compounds.1–3 More recently we have initiated a
systematic investigation of manganese() carbonyl complexes
incorporating Group 15 and 16 donor ligands. The lower
electronegativity of Se over S leads one to anticipate that R2Se
might be a better ligand than R2S to transition metal ions.
However, experimental data to substantiate this are very
limited. We proposed that 55Mn NMR and IR [ν(CO)] data on
a series of manganese() carbonyl halide adducts involving
thioether and selenoether ligands might provide experimental
evidence to support or refute this suggestion; 55Mn is 100%
I = 5/2 (Ξ = 24.840 MHz) and possesses a moderately high
quadrupole moment (0.55 × 10Ϫ28 m2), thus for complexes
with less than Oh or Td symmetry a considerable electric field
gradient is expected to result in substantial broadening of the
resonances. However, 55Mn NMR studies have been conducted
on several different classes of compound, including for example
[Mn2(CO)10] and derivatives, [Mn(CO)5X], [MnCp(CO)3],
In this paper we describe the first detailed preparations
and spectroscopic characterisation, including 1H, 13C-{1H},
55Mn and 77Se-{1H} NMR spectroscopy, of the manganese()
diselenoether complexes [MnX(CO)3(L–L)] [X = Cl, Br or I;
L–L = MeSeCH2CH2SeMe, MeSeCH2CH2CH2SeMe, PhSe-
CH2CH2SePh or C6H4(SMe)2-o] and compare the results with
those for related thioether compounds. The crystal structures
of [MnCl(CO)3(MeSeCH2CH2SeMe)], [MnCl(CO)3(MeSeCH2-
CH2CH2SeMe)] and [MnBr(CO)3{C6H4(SeMe)2-o}] are also
described. Prior to this work there were very few known
examples of selenoether complexes of MnI. The complex
[MnBr(CO)3(MeSeCH2CH2SeMe)] was first described by
Abel and Hutson12 some 30 years ago. We have resynthesized
this in order to obtain multinuclear NMR data to allow
comparisons with the other selenoether compounds and with
the thioether analogue. The only other manganese() seleno-
ether compounds reported are [Mn(NO)3(Ph2Se)2]13 and the
dinuclear [{Mn(C5H4Me)(CO)2}2(SeMe2)] for which a crystal
structure shows a bridging Me2Se ligand.14
J. Chem. Soc., Dalton Trans., 1998, 3833–3838
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Table 1 Infrared spectroscopic data (CO region) and FAB mass spectrometric data
Compound
ν(CO)a/cmϪ1
m/zb
[MnCl(CO)3(MeSeCH2CH2SeMe)]
[MnBr(CO)3(MeSeCH2CH2SeMe)]
[MnI(CO)3(MeSeCH2CH2SeMe)]
[MnCl(CO)3(MeSeCH2CH2CH2SeMe)]
[MnBr(CO)3(MeSeCH2CH2CH2SeMe)]
[MnI(CO)3(MeSeCH2CH2CH2SeMe)]
[MnCl(CO)3(PhSeCH2CH2SePh)]
[MnBr(CO)3(PhSeCH2CH2SePh)]
[MnI(CO)3(PhSeCH2CH2SePh)]
[MnCl(CO)3{C6H4(SeMe)2-o}]
2034, 1959, 1917
2031, 1955, 1917
2027, 1955, 1918
2032, 1955, 1917
2030, 1954, 1918
2025, 1951, 1918
2034, 1956, 1925
2034, 1960, 1927
2029, 1957, 1928
2037, 1964, 1924
2035, 1963, 1924
2030, 1960, 1924
392, [MnCl(CO)3(L–L)]ϩ; 357, [Mn(CO)3(L–L)]ϩ; 308, [MnCl(L–L)]ϩ
436, [MnBr(CO)3(L–L)]ϩ; 357, [Mn(CO)3(L–L)]ϩ; 352, [MnBr(L–L)]ϩ
484, [MnI(CO)3(L–L)]ϩ; 400, [MnI(L–L)]ϩ; 357, [Mn(CO)3(L–L)]ϩ
371, [Mn(CO)3(L–L)]ϩ; 322, [MnCl(L–L)]ϩ
371, [Mn(CO)3(L–L)]ϩ; 366, [MnBr(L–L)]ϩ
414, [MnI(L–L)]ϩ; 371, [Mn(CO)3(L–L)]ϩ
481, [Mn(CO)3(L–L)]ϩ; 432, [MnCl(L–L)]ϩ
481, [Mn(CO)3(L–L)]ϩ; 476, [MnBr(L–L)]ϩ
524, [MnI(L–L)]ϩ; 481, [Mn(CO)3(L–L)]ϩ
405, [Mn(CO)3(L–L)]ϩ; 356, [MnCl(L–L)]ϩ
[MnBr(CO)3{C6H4(SeMe)2-o}]
[MnI(CO)3{C6H4(SeMe)2-o}]
484, [MnBr(CO)3(L–L)]ϩ; 405, [Mn(CO)3(L–L)]ϩ; 400, [MnBr(L–L)]ϩ
532, [MnI(CO)3(L–L)]ϩ; 448, [MnI(L–L)]ϩ; 405, [Mn(CO)3(L–L)]ϩ
a Solutions in CHCl3, all CO bands were strong. b Recorded using 3-nitrobenzyl alcohol matrix; major peaks only.
compounds where inversion is slow on the NMR timescale;
Results and discussion
Syntheses
cooling the solutions sharpened the signals slightly.10
Treatment of [MnX(CO)5] (X = Cl, Br or I) with L–L
[MeSeCH2CH2SeMe, MeSeCH2CH2CH2SeMe, PhSeCH2CH2-
SePh or C6H4(SeMe)2-o] in gently refluxing CHCl3 affords the
neutral species [MnX(CO)3(L–L)] as yellow or orange solids.
In all cases the reaction flasks were wrapped with foil to
protect the manganese species from visible light. The isolated
compounds are very soluble in chlorocarbons, but poorly
soluble in hydrocarbons. The solids are reasonably stable,
although solutions of the compounds decompose rapidly when
exposed to oxygen and/or sunlight.
FAB Mass spectrometric data for these compounds are
given in Table 1. Generally, peaks with the correct isotopic dis-
tributions consistent with [MnX(L–L)]ϩ and [Mn(CO)3(L–L)]ϩ
are observed, although the parent molecule and further
peaks attributed to loss of X are also seen in a number of cases.
Solution IR spectroscopic studies show three CO stretching
vibrations, consistent with formation of fac-[MnX(CO)3(L–L)];
ν(CO) shifts to low frequency according to the series
X = Cl > Br > I, although it is virtually insensitive to changes
in the diselenoether ligand L. Importantly however, the values
of ν(CO) for these manganese selenoether compounds are
consistently slightly to low frequency of those observed for
[MnX(CO)3(dithioether)], consistent with increased occupation
of the CO π* orbitals in the former.10
For the selenoether species 1H NMR spectra were recorded at
300 K in CDCl3 solution. These were not very informative since
the broad ligand resonances made assignment of the isomers
impossible. 13C-{1H} NMR spectroscopy is rather more useful,
providing evidence that pyramidal inversion is rapid on the
NMR timescale at 300 K only for the compounds involving
PhSeCH2CH2SePh. For these systems a single resonance is
observed for the CH2 groups and this is to high frequency of
that for the ‘free’ ligand (δ 27.3). For the other compounds
several resonances are observed for the CH2 units and up to
four for the Me groups (one for each of the meso-1 and meso-2
and two for the  isomer), also to high frequency of the
corresponding resonance of the ‘free’ ligand, confirming the
presence of up to three NMR distinguishable invertomers. As
for the dithioether species, the CO resonances are very broad
even for the complexes where inversion is slow on the NMR
timescale, due to rapid quadrupolar relaxation from the directly
bonded 55Mn nucleus and hence the individual CO resonances
are not resolved.
NMR Spectroscopy
We have recorded 1H, 13C-{1H}, 77Se-{1H} and 55Mn NMR
data for the compounds in this work. The combination of
observable NMR nuclei, particularly 13C-{1H}, 55Mn and
77Se-{1H}, provides a very powerful way in which to monitor
the species present in solution. Four isomers are possible for
fac-[MnX(CO)3(diselenoether)]; meso-1, meso-2 and a pair of
NMR indistinguishable  enantiomers, with interconversion
occurring via pyramidal inversion at the co-ordinated seleno-
ether donors. Abel et al.15 have conducted detailed, quantitative
NMR spectroscopic studies on a wide range of transition metal
complexes with Group 16 donor ligands to probe inversion pro-
cesses, and, the donor atom type, the nature of the interdonor
linkage and the choice of transition metal have all been shown
to be important parameters. In this work we are concerned
with monitoring the trends in δ(55Mn) and δ(77Se) to probe the
Se–Mn co-ordination rather than with the inversion barriers.
Indeed Abel et al. have commented that the substantial quad-
rupole moment associated with 55Mn is expected to lead to
extensive broadening and hence these compounds are not
The 77Se-{1H} and 55Mn NMR data for [MnX(CO)3(L–L)]
are presented in Table 2. One 77Se resonance is expected for each
of the meso isomers and two for the  isomer. The results from
the 77Se-{1H} NMR studies are in accord with those from
the 13C-{1H} NMR studies. The rapidly inverting [MnX(CO)3-
(PhSeCH2CH2SePh)] species each show a single resonance
approximately 100 ppm to high frequency of that of free
PhSeCH2CH2SePh, confirming formation of a five-membered
chelate ring.16 Complexes involving the other diselenoether
ligands each show the presence of either all three NMR dis-
tinguishable isomers (or two of the three); in cases where we
only observe three δ(77Se) resonances we conclude that either
only two isomers are present in appreciable quantity (meso-2
and ) or the resonances are coincidental. The co-ordination
shifts [δ(complex) Ϫ δ(‘free’ ligand)] for MeSeCH2CH2SeMe
and C6H4(SeMe)2-o are approximately 120 to 170 and 170 to
200 ppm respectively. These large shifts are consistent with
the formation of a five-membered chelate ring, whereas δ(77Se-
{1H}) for the complexes of MeSeCH2CH2CH2SeMe, which
involve a six-membered chelate ring, are close to those of the
‘free’ ligand.
1
suited to detailed dynamic H NMR studies; we have shown
that this is also true for [MnX(CO)3(dithioether)], where broad
resonances were observed at room temperature even for
3834
J. Chem. Soc., Dalton Trans., 1998, 3833–3838

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Table 2 The 55Mn and 77Se-{1H} NMR spectroscopic dataa
Approximate ratio
meso-1:meso-2:
Compound
δ(55Mn) (w1/2/Hz)b
δ(77Se-{1H})c
[MnCl(CO)3(MeSeCH2CH2SeMe)]
[MnBr(CO)3(MeSeCH2CH2SeMe)]
[MnI(CO)3(MeSeCH2CH2SeMe)]
[MnCl(CO)3(MeSeCH2CH2CH2SeMe)]
[MnBr(CO)3(MeSeCH2CH2CH2SeMe)]
[MnI(CO)3(MeSeCH2CH2CH2SeMe)]
[MnCl(CO)3(PhSeCH2CH2SePh)]e
[MnBr(CO)3(PhSeCH2CH2SePh)]e
[MnI(CO)3(PhSeCH2CH2SePh)]e
[MnCl(CO)3{C6H4(SeMe)2-o}]
Ϫ277d (2000), Ϫ342 (2000), Ϫ410 (2900)
Ϫ345d (900), Ϫ428 (1500), Ϫ506 (2500)
Ϫ500d (≈1340), Ϫ607 (1220), Ϫ698 (2170)
Ϫ175 (2080), Ϫ190 (sh), Ϫ219 (sh)
Ϫ257 (2000), Ϫ317 (2000)
256, 269, 282, 290
259 (meso-2); 281, 289 ()
283 (meso-2); 239, 276 ()
75, 80, 92, 118
62, 65, 81, 109
39, 66, 73, 92
445
443
438
1:3:6
1:5:6
1:5:10
1:2:4
1:2:4
Ϫ402d (sh), Ϫ426 (1550), Ϫ499 (1760)
Ϫ249 (5200)
1:2:7
Inverting
Inverting
Inverting
1:5:4
1:10:5
1:14:4
Ϫ346 (4590)
Ϫ537 (3170)
Ϫ247d (2000), Ϫ311 (2600), Ϫ394 (4500)
Ϫ325d (1070), Ϫ414 (1860), Ϫ507 (3000)
Ϫ465,d Ϫ581 (1500), Ϫ702 (3200)
386, 400 (), 406 (meso-2)
375, 386 (), 400 (meso-2)
374, 388 (), 396 (meso-2)
[MnBr(CO)3{C6H4(SeMe)2-o}]
[MnI(CO)3{C6H4(SeMe)2-o}]
a Spectra recorded in CHCl3–CDCl3 solution at 300 K. b At 89.27 MHz and referenced to external aqueous KMnO4. c At 68.68 MHz and referenced
to neat external Me2Se. δ(77Se) for ‘free’ ligands: MeSeCH2CH2SeMe, 121; MeSeCH2CH2CH2SeMe, 74; PhSeCH2CH2SePh, 340; C6H4(SeMe)2-o,
202. d Minor isomer. e Inverting at 300 K.
this temperature. Thus, the energy barrier to inversion is higher
for the manganese() selenoether complexes than for the corre-
sponding thioethers. This is consistent with the trends observed
in other transition metal complexes of these ligands.16 As for
the thioether complexes we observe a shift in δ(55Mn) to low
frequency upon changing X from Cl to Br to I. Of greatest
significance, however, is the observation that δ(55Mn) for the
diselenoether compounds occurs to low frequency (more
shielded) of the thioether compounds by ca. 100 ppm. This is
consistent with the trend in ν(CO) discussed above, i.e. ν(CO)
for the selenoether compounds is to low frequency of ν(CO) for
the thioethers. These results indicate that there is more electron
density associated with the manganese() centre in the seleno-
ether compounds (greater occupation of the CO π* orbitals).
This can arise in three ways: greater π donation from the seleno-
ether donor, poorer π acceptance by the selenoether donor,
or increased σ donation by the selenoether donor. Since there is
little or no evidence for π bonding from thio- or seleno-ether
donors to metal centres, it is highly likely that these results
indicate an increase in L→MnI σ donation from thio- to seleno-
ether. This would also support the work of Hoffmann and co-
workers17 who predicted theoretically that R2E→M σ donation
(E = S, Se or Te) would increase in the order S < Se Ӷ Te.
Abel and co-workers18–20 have described the preparations
of the rhenium() complexes [ReX(CO)3(L–L)] [X = Cl, Br
or I; L–L = MeE(CH ) EMe or MeECH᎐CHEMe (E = S or
᎐
2
n
Se, n = 2 or 3)], including the crystal structure of fac-
[ReI(CO)3(MeSeCH2CH2SeMe)]. Detailed 1H NMR studies
revealed that the energy barrier associated with inversion at
selenium is higher than at sulfur, and that changing the halogen
has a negligible effect upon the overall energy barrier. The
results from our work on manganese() compounds are con-
sistent with these observations. Also, the relative populations of
the invertomers in solution vary with the particular system
although the meso-2 and  forms are always dominant, and
population of the meso-1 form decreases with increasing halide
size (due to unfavourable Me ؒ ؒ ؒ X or Ph ؒ ؒ ؒ X interactions).
Fig. 1 The 55Mn (89.27 MHz, CDCl3) (a) and 13C-{1H} (90.1 MHz,
CDCl3) NMR spectrum (b) of [MnBr(CO)3{C6H4(SeMe)2-o}] (methyl
region only).
The 55Mn NMR studies also confirm that at 300 K only the
complexes involving PhSeCH2CH2SePh are undergoing rapid
pyramidal inversion on the NMR timescale, showing only a
single broad resonance. For the other compounds up to three
distinct resonances attributable to the presence of up to three
NMR distinguishable stereoisomers were observed (Fig. 1).
The linewidths (<3000 Hz) are very similar to those for the
thioether analogues reported previously, and again consider-
ably smaller than for phosphine systems such as [MnX(CO)3-
(PPh2H)2] (w1/2 ca. 10 000 Hz).11 For the thioether species, 55Mn
NMR studies showed that for the compounds involving
MeSCH2CH2SMe and C6H4(SMe)2-o pyramidal inversion is
slow on the 55Mn NMR timescale at 300 K, whereas for
MeSCH2CH2CH2SMe or PhSCH2CH2SPh inversion is rapid at
X-Ray crystallography
A search of the Cambridge Crystallographic Database revealed
that there are no structurally characterised examples of seleno-
ether complexes of manganese() carbonyl halides, although
the structure of the dinuclear species [{Mn(C5H4Me)-
(CO)2}2(SeMe2)] is known.14 In order to identify the isomeric
arrangement in the solid state and to compare the Mn–Se bond
lengths with those in the Me2Se-bridged dimer [{Mn(C5H4Me)-
(CO)2}2(SeMe2)] and with d(Mn–S) in the thioether analogues,
we have conducted single crystal X-ray analyses on [MnCl-
(CO)3(MeSeCH2CH2SeMe)], [MnCl(CO)3(MeSeCH2CH2CH2-
J. Chem. Soc., Dalton Trans., 1998, 3833–3838
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Table
3
Selected bond lengths (Å) and angles (Њ) for
[MnCl(CO)3(MeSeCH2CH2SeMe)]
Se(1)–Mn(1)
Se(1)–C(2)
Se(2)–C(3)
Mn(1)–Cl(1)
Mn(1)–C(6)
O(1)–C(5)
2.481(3)
1.98(2)
1.95(1)
2.406(4)
1.79(2)
1.16(2)
1.15(2)
Se(1)–C(1)
Se(2)–Mn(1)
Se(2)–C(4)
Mn(1)–C(5)
Mn(1)–C(7)
O(2)–C(6)
C(2)–C(3)
1.96(1)
2.467(3)
1.96(1)
1.79(2)
1.80(2)
1.18(2)
1.47(2)
O(3)–C(7)
Mn(1)–Se(1)–C(1)
C(1)–Se(1)–C(2)
109.0(5)
96.6(7)
107.9(5)
88.79(8)
86.4(5)
90.2(5)
95.2(4)
175.1(5)
90.8(5)
90.4(6)
91.1(7)
Mn(1)–Se(1)–C(2)
Mn(1)–Se(2)–C(3)
C(3)–Se(2)–C(4)
Se(1)–Mn(1)–Cl(1)
Se(1)–Mn(1)–C(6)
Se(2)–Mn(1)–Cl(1)
Se(2)–Mn(1)–C(6)
Cl(1)–Mn(1)–C(5)
Cl(1)–Mn(1)–C(7)
C(5)–Mn(1)–C(7)
101.6(4)
101.2(4)
96.3(7)
92.2(1)
176.6(5)
82.7(1)
90.1(4)
177.5(5)
92.6(5)
89.5(6)
Mn(1)–Se(2)–C(4)
Se(1)–Mn(1)–Se(2)
Se(1)–Mn(1)–C(5)
Se(1)–Mn(1)–C(7)
Se(2)–Mn(1)–C(5)
Se(2)–Mn(1)–C(7)
Cl(1)–Mn(1)–C(6)
C(5)–Mn(1)–C(6)
C(6)–Mn(1)–C(7)
Table
4
Selected bond lengths (Å) and angles (Њ) for
[MnCl(CO)3(MeSeCH2CH2CH2SeMe)]
Fig. 2 View of the structure of [MnCl(CO)3(MeSeCH2CH2SeMe)]
with numbering scheme adopted. Ellipsoids are drawn at 40%
probability.
Se(1)–Mn(2)
Se(1)–C(2)
Se(2)–C(4)
Mn(2)–Cl(1)
Mn(2)–C(7)
O(1)–C(6)
O(3)–C(8)
C(2)–C(3)
2.474(2)
1.96(1)
1.961(10)
2.379(3)
1.805(10)
1.14(1)
Se(1)–C(1)
Se(2)–Mn(2)
Se(2)–C(5)
Mn(2)–C(6)
Mn(2)–C(8)
O(2)–C(7)
C(3)–C(4)
1.939(10)
2.482(2)
1.94(1)
1.792(9)
1.810(9)
1.16(1)
1.14(1)
1.53(2)
1.50(2)
Mn(2)–Se(1)–C(1)
C(1)–Se(1)–C(2)
105.4(3)
95.5(5)
107.3(3)
89.29(5)
88.0(3)
90.5(3)
89.9(3)
178.8(3)
89.8(4)
91.4(5)
90.0(4)
Mn(2)–Se(1)–C(2)
Mn(2)–Se(2)–C(4)
C(4)–Se(2)–C(5)
Se(1)–Mn(2)–Cl(1)
Se(1)–Mn(2)–C(7)
Se(2)–Mn(2)–Cl(1)
Se(2)–Mn(2)–C(7)
Cl(1)–Mn(2)–C(6)
Cl(1)–Mn(2)–C(8)
C(6)–Mn(2)–C(8)
107.4(3)
110.1(3)
97.9(5)
90.65(8)
179.2(3)
86.56(8)
90.2(3)
176.2(3)
92.3(3)
91.3(4)
Mn(2)–Se(2)–C(5)
Se(1)–Mn(2)–Se(2)
Se(1)–Mn(2)–C(6)
Se(1)–Mn(2)–C(8)
Se(2)–Mn(2)–C(6)
Se(2)–Mn(2)–C(8)
Cl(1)–Mn(2)–C(7)
C(6)–Mn(2)–C(7)
C(7)–Mn(2)–C(8)
crystals of [MnBr(CO)3{C6H4(SeMe)2-o}]† were of poorer
quality and hence the data less reliable, therefore detailed com-
parisons of the geometric parameters requires caution. How-
ever, the molecular arrangement (Fig. 4) is very similar to the
structures described above, with three mutually fac CO ligands,
a chelating diselenoether and a Br ligand completing the dis-
torted octahedron. In this case the co-ordinated diselenoether
adopts the meso-2 form with both Me groups directed to the
opposite side of the MnSe2C2 plane from the Br ligand, Mn–
Se(1) 2.454(6), Mn–Se(2) 2.468(6), Mn–Br(1) 2.562(6), Mn–
C(9) 1.79(4), Mn–C(10) 1.82(3), Mn–C(11) 1.82(3) Å. This is
also the isomer which dominates in solution at room temper-
ature. The Se–Mn–Se angle in the chelate ring is 88.3(2)Њ. As
expected on the basis of the radii of Se vs. S, the Mn–Se bond
lengths in these compounds are approximately 0.10–0.15 Å
Fig. 3 View of the structure of [MnCl(CO)3(MeSeCH2CH2CH2-
SeMe)] with numbering scheme adopted. Ellipsoids are drawn at 40%
probability.
SeMe)] and [MnBr(CO)3{C6H4(SeMe)2-o}]. Crystals of the
complexes were obtained from vapour diffusion of light
petroleum into a solution of the appropriate complex in
CH2Cl2. The crystal structures of [MnCl(CO)3(MeSeCH2CH2-
SeMe)] (Fig. 2, Table 3) and [MnCl(CO)3(MeSeCH2CH2CH2-
SeMe)] (Fig. 3, Table 4) both show a distorted octahedral
geometry at Mn, with a fac arrangement for the three CO
ligands and the chelating diselenoether adopting the 
arrangement, with one Me group on each side of the MnSe2C2
plane: [MnCl(CO)3(MeSeCH2CH2SeMe)], Mn–Se(1) 2.481(3),
Mn–Se(2) 2.467(3), Mn–Cl(1) 2.406(4), Mn–C(5) 1.79(2),
Mn–C(6) 1.79(2), Mn–C(7) 1.80(2) Å; [MnCl(CO)3(MeSeCH2-
CH2CH2SeMe)], Mn–Se(1) 2.474(2), Mn–Se(2) 2.482(2), Mn–
Cl(1) 2.379(3), Mn–C(6) 1.792(9), Mn–C(7) 1.805(10), Mn–
C(8) 1.810(9) Å. The Se–Mn–Se angles involved in the chelate
rings are 88.79(8) and 89.29(5)Њ respectively. The  isomer
was also identified in the crystal structure of [MnCl(CO)3-
(MeSCH2CH2SMe)2], suggesting that this might be the
preferred solid state arrangement for [Mn(CO)3X{MeE-
(CH2)nEMe}], E = S or Se, and indeed this is the dominant
isomer in solution at room temperature for these species. The
† Crystal data: M 482.96, orthorhombic, space group Pna21, a =
21.34(2), b = 9.50(2), c = 7.08(1) Å, V = 1448(6) Å3, Z = 4, Dc = 2.214 g
cm3, µ(Mo-Kα), 86.97 cmϪ1. 1513 unique observed reflections, 1148
with Io > 2σ(Io), R = 0.084, RЈ = 0.105. The structure was solved in
Pna21 (since the data indicated an acentric space group) by direct
methods21 and developed by iterative cycles of full-matrix least-squares
refinement and difference Fourier syntheses (an attempt to solve the
structure in Pnma yielded no solution).22 The Mn, Br, Se and O atoms
were refined anisotropically while H atoms were placed in fixed, calcu-
lated positions with d(C–H) = 0.96 Å. The weighting scheme wϪ1
=
σ2(F) gave satisfactory agreement analyses and the Flack parameter
indicated that the hand chosen was the correct enantiomorph.
3836
J. Chem. Soc., Dalton Trans., 1998, 3833–3838

View Article Online
218.4 (CO), 29.6, 29.4, 29.0 (CH2), 12.6 (Me, meso-1), 11.9 and
8.9 (Me, ).
[MnCl(CO)3(MeSeCH2CH2CH2SeMe)]. [MnCl(CO)5] (0.100
g, 0.43 mmol) and MeSeCH2CH2CH2SeMe (0.100 g, 0.43
mmol), giving a yellow precipitate (yield 0.111 g, 63%)
(Found: C, 23.4; H, 3.3. Calc. for C8H12ClMnO3Se2: C, 23.7;
H, 3.0%). 1H NMR spectrum: δ 3.25, 3.10, 2.78, 2.65 (SeCH2),
2.40, 2.18 (Me) and 1.98 (CH2CH2CH2). 13C-{1H} NMR
spectrum: δ 223.1–216.7 (CO), 26.9, 26.8, 25.3, 25.0, 24.5 (CH2),
13.4, 12.6, 11.2, 10.7 (Me).
[MnCl(CO)3(PhSeCH2CH2SePh)]. [MnCl(CO)5] (0.047 g,
0.21 mmol) and PhSeCH2CH2SePh (0.070 g, 0.21 mmol),
giving a yellow precipitate (yield 0.078 g, 75%) (Found: C, 39.4;
H, 2.8. Calc. for C17H14ClMnO3Se2: C, 39.7; H, 2.7%). 1H NMR
spectrum: δ 7.25–7.70 (Ph), 3.25–3.78 (CH2). 13C-{1H} NMR
spectrum: δ 223.2–219.6 (CO), 130.8 (sh), 130.4, 129.9 (Ph) and
30.7 (CH2).
Fig. 4 View of the structure of [MnBr(CO)3{C6H4(SeMe)2-o}] with
the numbering scheme adopted. Ellipsoids are drawn at 40% prob-
ability. Mn–Se(1) 2.454(6), Mn–Se(2) 2.468(6), Mn–Br(1) 2.562(6),
Mn–C(9) 1.79(4), Mn–C(10) 1.82(3), Mn–C(11) 1.82(3) Å.
longer than d(Mn–S) in the corresponding thioether com-
pounds. However, the increased σ bonding in the selenoethers
compared to the thioethers deduced from the spectroscopic
studies would be expected to have a very small effect on the
M–S and M–Se distances, and is therefore not expected to be
detected by X-ray crystallography. The Mn–Se bond lengths in
the selenoether compounds reported here are longer than those
observed in the SeMe2 bridged species [{Mn(C5H4Me)(CO)2}2-
(SeMe2)] [2.375(1), 2.378(1) Å].14 This may be attributed to the
repulsive effect of the second Se-based lone pair in the mono-
nuclear species, whereas in the bridged dimer there is no such
repulsion.
[MnCl(CO)3{C6H4(SeMe)2-o}]. [MnCl(CO)5] (0.024 g, 0.100
mmol) and C6H4(SeMe)2-o (0.027 g, 0.100 mmol), giving a
yellow precipitate (yield 0.031 g, 68%) (Found: C, 27.1; H,
2.3. Calc. for C11H10ClMnO3Se2ؒCH2Cl2: C, 27.5; H, 2.7%).
1H NMR spectrum: δ 7.80, 7.45 (o-C6H4), 2.70, 2.55, 2.40 (Me).
13C-{1H} NMR spectrum: δ 221.7–218.8 (CO), 134.6, 133.5,
131.1, 130.5 (o-C6H4), 20.0 (Me, meso-2), 19.5, 15.1 (Me, )
and 14.2 (Me, meso-1).
[MnBr(CO)3(MeSeCH2CH2SeMe)]. [MnBr(CO)5] (0.085 g,
0.31 mmol) and MeSeCH2CH2SeMe (0.067 g, 0.31 mmol)
giving an orange precipitate (yield 0.117 g, 87%) (Found: C,
19.8; H, 2.5. Calc. for C7H10BrMnO3Se2: C, 19.3; H, 2.3%). 1H
NMR spectrum: δ 3.36, 3.23 (sh), 3.10, 2.82 (CH2), 2.37 (sh),
2.35, 2.23 (Me). 13C-{1H} NMR spectrum: δ 124.3–116.5 (CO),
29.6, 29.3 (CH2), 15.5, 13.4, 12.9 and 10.3 (Me).
Experimental
Infrared spectra were measured as CsI discs using a Perkin-
Elmer 983 spectrometer over the range 200–4000 cmϪ1, or
in solution using NaCl plates on a Perkin-Elmer 1600 FTIR
spectrometer, mass spectra by fast-atom bombardment (FAB)
using 3-nitrobenzyl alcohol as matrix on a VG Analytical 70-
250-SE normal geometry double focusing mass spectrometer,
1H NMR spectra in CDCl3 at 300 MHz unless otherwise
stated, using a Bruker AM300 spectrometer, 13C-{1H}, 55Mn
and 77Se-{1H} NMR spectra using a Bruker AM360 spectro-
meter operating at 90.1, 89.27 or 68.68 MHz respectively and
referenced to Me4Si, external saturated, aqueous K[MnO4] and
external neat Me2Se respectively (δ 0); [Cr(acac)3] was added to
the NMR solutions prior to recording 13C-{1H} and 77Se-{1H}
spectra and a pulse delay of 2 s was employed for the 13C-{1H}
spectra to take account of the long relaxation times. The
compounds [MnX(CO)5] (X = Cl, Br or I), MeSeCH2CH2-
SeMe, MeSeCH2CH2CH2SeMe, PhSeCH2CH2SePh and C6H4-
(SeMe)2-o were prepared according to literature procedures.23,24
[MnBr(CO)3(MeSeCH2CH2CH2SeMe)].
[MnBr(CO)5]
(0.011 g, 0.40 mmol) and MeSeCH2CH2CH2SeMe (0.092 g,
0.40 mmol), giving an orange precipitate (yield 0.079 g, 44%)
(Found: C, 21.6; H, 2.9. Calc. for C8H12BrMnO3Se2: C, 21.4;
1
H, 2.7%). H NMR spectrum: δ 3.42, 3.20 (sh), 2.75, 2.62 (sh)
(SeCH2), 2.28 (Me) and 1.98 (CH2CH2CH2). 13C-{1H} NMR
spectrum: δ 223.0–216.0 (CO), 27.3, 27.2 (sh), 25.6, 24.5 (CH2),
14.2, 13.2, 12.4, 11.5 (Me).
[MnBr(CO)3(PhSeCH2CH2SePh)]. [MnBr(CO)5] (0.072 g,
0.26 mmol) and PhSeCH2CH2SePh (0.089 g, 0.26 mmol),
giving a yellow precipitate (yield 0.109 g, 74%) (Found: C, 35.9;
H, 2.3. Calc. for C17H14BrMnO3Se2: C, 36.5; H, 2.5%). 1H
NMR spectrum: δ 7.75–7.18 (Ph), 3.75–3.30 (CH2). 13C-{1H}
NMR spectrum: δ 224.5–220.1 (CO), 130.0, 129.5 (Ph) and 30.9
(CH2).
Preparations
All of the compounds were synthesized by the same general
procedure, hence only one is described in detail below.
[MnBr(CO)3{C6H4(SeMe)2-o}]. [MnBr(CO)5] (0.085 g, 0.31
mmol) and C6H4(SeMe)2-o (0.082 g, 0.31 mmol), giving an
orange precipitate (yield 0.095 g, 64%) (Found: C, 27.2; H,
1
[MnCl(CO)3(MeSeCH2CH2SeMe)]. To a degassed solution
of [MnCl(CO)5] (0.070 g, 0.30 mmol) in CHCl3 (30 ml),
MeSeCH2CH2SeMe (0.066 g, 0.305 mmol) was added. The
resulting mixture was gently refluxed for 24 h, and the solution
IR spectrum monitored until the reaction had gone to com-
pletion. The solvent volume was reduced in vacuo to ca. 2 ml
to give a yellow solution. Addition of light petroleum (bp 40–
60 ЊC) at 0 ЊC afforded a yellow solid which was filtered off,
washed with light petroleum and dried in vacuo. The compound
was recrystallised from CHCl3–light petroleum (yield 0.087 g,
73%) (Found: C, 21.3; H, 2.7. Calc. for C7H10ClMnO3Se2: C,
2.0. Calc. for C11H10BrMnO3Se2: C, 27.3; H, 2.1%). H NMR
spectrum: δ 7.85, 7.54 (o-C6H4), 2.81 (sh), 2.62 (Me). 13C-{1H}
NMR spectrum: δ 222.9–218.6 (CO), 134.9, 133.7, 131.1, 130.4
(o-C6H4), 31.0 (Me, meso-1), 21.0 (Me, meso-2), 20.4 and 17.1
(Me, ).
[MnI(CO)3(MeSeCH2CH2SeMe)]. [MnI(CO)5] (0.119 g, 0.37
mmol) and MeSeCH2CH2SeMe (0.080 g, 0.37 mmol) giving
an orange precipitate (yield 0.108 g, 61%) (Found: C, 17.7; H,
1
1.9. Calc. for C7H10IMnO3Se2: C, 17.4; H, 2.1%). H NMR
spectrum: δ 3.45, 3.12, 2.88 (CH2), 2.50, 2.31, 2.22, 2.05 (Me).
13C-{1H} NMR spectrum: δ 225.0–220.5 (CO), 30.5, 30.1
(CH2), 15.4 (Me, meso-2), 15.3, 1.3 (Me, ).
1
21.5; H, 2.6%). H NMR spectrum: δ 3.28, 3.04, 2.75 (CH2),
2.30, 2.12, 2.02 (sh) (Me). 13C-{1H} NMR spectrum: δ 222.5–
J. Chem. Soc., Dalton Trans., 1998, 3833–3838
3837

View Article Online
Table 5 Crystallographic data collection and refinement parameters
calculated positions with d(C–H) = 0.96 Å. The weighting
scheme wϪ1 = σ2(F) gave satisfactory agreement analyses and
the Flack parameter indicated that the correct enantiomorph
of [MnCl(CO)3(MeSeCH2CH2CH2SeMe)] was refined.
CCDC reference number 186/1187.
[MnCl(CO)3(MeSe-
CH2CH2SeMe)]
[MnCl(CO)3(MeSe-
CH2CH2CH2SeMe)]
Formula
M
C7H10ClMnO3Se2
390.47
C8H12ClMnO3Se2
404.49
Space group
Crystal symmetry
a/Å
b/Å
Pbca
P212121
Acknowledgements
We thank the EPSRC and the University of Southampton for
support and the Director of the Cambridge Crystallographic
Database for access.
Orthorhombic
12.283(4)
19.293(5)
10.154(4)
2406(1)
Orthorhombic
11.342(5)
12.223(7)
9.464(6)
1311(1)
c/Å
V/Å3
Z
8
4
Dc/g cmϪ3
µ(Mo-Kα)/cmϪ1
Unique observed
reflections
Observed reflections
with [Io > 2σ(Io)]
No. parameters
R
2.155
72.51
2.048
66.53
References
1 N. R. Champness, S. R. Jacob, G. Reid and C. S. Frampton, Inorg.
Chem., 1995, 34, 396; N. R. Champness, S. J. A. Pope and G. Reid,
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4 D. Rehder, Multinuclear NMR, ed. J. Mason, Plenum, New York,
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7 D. Rehder, H.-C. Bechtold, A. Kekeci, H. Schmidt and M. Z.
Siewing, Z. Naturforsch., Teil B, 1982, 37, 631.
[MnI(CO)3(MeSeCH2CH2CH2SeMe)]. [MnI(CO)5] (0.124 g,
0.38 mmol) and MeSeCH2CH2CH2SeMe (0.087 g, 0.38 mmol),
giving an orange precipitate (yield 0.126 g, 66%) (Found: C,
1
19.5; H, 2.6. Calc. for C8H12IMnO3Se2: C, 19.4; H, 2.4%). H
NMR spectrum: δ 3.30, 2.85 (SeCH2), 2.70, 2.40 (Me) and 2.00
(CH2CH2CH2). 13C-{1H} NMR spectrum: δ 226.7–217.5 (CO),
27.8, 27.5, 27.2, 26.3, 24.6, 24.3 (CH2), 15.7, 14.5, 13.9, 12.2
(Me).
8 N. J. Holmes, W. Levason and M. Webster, J. Organomet. Chem.,
1998, 568, 213.
9 A. M. Hill, W. Levason, M. Webster and I. Albers, Organometallics,
1997, 16, 5641.
10 J. Connolly, G. W. Goodban, G. Reid and A. M. Z. Slawin, J. Chem.
Soc., Dalton Trans., 1998, 2125.
[MnI(CO)3(PhSeCH2CH2SePh)]. [MnI(CO)5] (0.063 g, 0.20
mmol) and PhSeCH2CH2SePh (0.067 g, 0.20 mmol), giving
an orange precipitate (yield 0.096 g, 81%) (Found: C, 33.3; H,
1
11 S. J. A. Pope and G. Reid, unpublished work.
2.4. Calc. for C17H14IMnO3Se2: C, 33.7; H, 2.3%). H NMR
spectrum: δ 7.55–7.25 (Ph), 3.80–3.40 (CH2). 13C-{1H} NMR
spectrum: δ 226.0–220.2 (CO), 131.1, 130.3, 129.8 (Ph) and 31.3
(CH2).
12 E. W. Abel and G. V. Hutson, J. Inorg. Nucl. Chem., 1969, 31, 3333.
13 D. Rehder, K. Ihmels, D. Wenke and P. Oltmanns, Inorg. Chim.
Acta, 1985, 100, L13.
14 A. Belforte, F. Calderazzo, D. Vitali and P. F. Zanazzi, Gazz. Chim.
Ital., 1985, 115, 125.
[MnI(CO)3{C6H4(SeMe)2-o}]. [MnI(CO)5] (0.032 g, 0.098
mmol) and C6H4(SeMe)2-o (0.026 g, 0.098 mmol), giving an
orange precipitate (yield 0.043 g, 82%) (Found: C, 21.6; H, 1.9.
Calc. for C11H10IMnO3Se2ؒCHCl3: C, 22.1; H, 1.7%). 1H NMR
spectrum: δ 7.90, 7.55 (o-C6H4), 2.95, 2.60, 2.48 (sh), 2.35 (Me).
13C-{1H} NMR spectrum: δ 223.8–219.6 (CO), 134.8, 134.1,
131.0 (o-C6H4), 22.7 (Me, meso-2), 21.9, 20.7, 14.3 (Me, meso-1
and ).
15 E. W. Abel, S. K. Bhargava and K. G. Orrell, Prog. Inorg. Chem.,
1984, 33, 1.
16 E. G. Hope and W. Levason, Coord. Chem. Rev., 1993, 122, 109.
17 H. Schumann, A. M. Arif, A. L. Rheingold, C. Janiak,
R. Hoffmann and N. Kuhn, Inorg. Chem., 1991, 30, 1618.
18 E. W. Abel, S. K. Bhargava, M. M. Bhatti, K. Kite, M. A. Mazid,
K. G. Orrell, V. Sik, B. L. Williams, M. B. Hursthouse and
K. M. A. Malik, J. Chem. Soc., Dalton Trans., 1982, 2065.
19 E. W. Abel, M. M. Bhatti, K. G. Orrell and V. Sik, J. Organomet.
Chem., 1981, 208, 195.
20 E. W. Abel, S. K. Bhargava, M. M. Bhatti, M. A. Mazid, K. G.
Orrell, V. Sik, M. B. Hursthouse and K. M. A. Malik, J. Organomet.
Chem., 1983, 250, 373.
Crystal structures of [MnCl(CO)3(MeSeCH2CH2SeMe)] and
[MnCl(CO)3(MeSeCH2CH2CH2SeMe)]
21 SHELXS 86, Program for crystal structure solution, G. M.
Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
22 TEXSAN, Crystal Structure Analysis Package, Molecular Structure
Corporation, Houston, TX, 1995.
23 K. J. Reimer and A. Shaver, Inorg. Synth., 1979, 19, 159.
24 D. J. Gulliver, E. G. Hope, W. Levason, S. G. Murray, D. M. Potter
and G. L. Marshall, J. Chem. Soc., Perkin Trans. 2, 1984, 429.
25 PATTY, The DIRDIF Program System, P. T. Beurskens,
G. Admiraal, G. Beurskens, W. P. Bosman, S. Garcia-Granda,
R. O. Gould, J. M. M. Smits and C. Smykalla, Technical Report
of the Crystallography Laboratory, University of Nijmegen, 1992.
Details of the crystallographic data collection and refinement
parameters are given in Table 5. The crystals were grown by
vapour diffusion of light petroleum into solutions of the
complexes in CH2Cl2. Data collection used a Rigaku AFC7S
four-circle diffractometer operating at 150 K, with graphite-
monochromated Mo-Kα X-radiation (λ = 0.71073 Å). No
significant crystal decay or movement was observed. The
structures were solved by heavy atom Patterson methods25 and
developed by iterative cycles of full-matrix least-squares
refinement and Fourier-difference syntheses which located one
complete molecule in the asymmetric unit.22 All non-H atoms
were refined anisotropically while H atoms were placed in fixed,
Paper 8/06881J
3838
J. Chem. Soc., Dalton Trans., 1998, 3833–3838