Hemilabile orthometallated acetals: Synthesis, spectroscopic characterization and crystal and molecular structures of [RuCl{η2-C,O-C6H4-2-CH(O2C2H4)}(CO)(PPh3)2] and [HgBr{η2-C,O-C6H4-2-CH(O2C2H4)}]

Article abstract of DOI:10.1016/j.jorganchem.2007.02.029

Treatment of [RuHCl(CO)(PPh₃)₂] with [Hg{C₆H₄-2-H(O₂C₂H₄)}₂] (1) in refluxing toluene affords [RuCl{η²-C,O-C₆H₄-2-CH(O₂C₂H₄)}(CO)(PPh₃)₂] (2a). Compound 2a reacts with Ag[BF₄] followed by NaX (X = Br, I, F) to give [RuX{η²-C,O-C₆H₄-2-CH(O₂C₂H₄)}(CO)(PPh₃)₂] (2b-d). All compounds have been characterized by elemental analysis (C and H), IR, ¹H, ¹³C-{¹H} and ³¹P-{¹H} NMR spectroscopy. A crystallographic study of 2a shows the presence one pair of enantiomers and one pair of diastereoisomers in the asymmetric unit. Theoretical calculations (B3LYP using the LanL2DZ basis set) on the model compounds [RuCl(CH₃)(EH₂)(CO)(PH₃)₂] (E = O, S) (3a,b) show that for 3a a planar geometry at the OH₂ ligand and for 3b a pyramidal structure at SH₂ is favoured. The calculated electrostatic potentials for EH₂ and the acetals CH₂E₂C₂H₄ (E = O, S) are used to comment on the nature of the lone pairs at the chalcogen atoms and the coordination geometries of ether and thioether ligands. The X-ray crystallographically determined molecular structure of [BrHg(η²-C,O-C₆H₄-2-CHO₂C₂H₄)] (4) is also described and model compounds studied theoretically.

Full text of DOI:10.1016/j.jorganchem.2007.02.029

Journal of Organometallic Chemistry 692 (2007) 2519–2528
www.elsevier.com/locate/jorganchem
Hemilabile orthometallated acetals: Synthesis,
spectroscopic characterization and crystal and molecular structures
of [RuCl{g2-C,O-C6H4-2-CH(O2C2H4)}(CO)(PPh3)2] and
[HgBr{g2-C,O-C6H4-2-CH(O2C2H4)}]
a
a,
a
a
Rosalyn J. Evans , Kevin R. Flower *, Laura G. Leal , Patrick J. O’Malley ,
a
a
b
Claudia Mangold , Robin G. Pritchard , John E. Warren
a
School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK
b
CCLRC Daresbury Laboratory Daresbury, Warrington, Cheshire WA4 4NS, UK
Received 18 January 2007; received in revised form 16 February 2007
Available online 24 February 2007
Abstract
Treatment of [RuHCl(CO)(PPh3)2] with [Hg{C6H4-2-H(O2C2H4)}2] (1) in refluxing toluene affords [RuCl{g2-C,O-C6H4-2-
CH(O2C2H4)}(CO)(PPh3)2] (2a). Compound 2a reacts with Ag[BF4] followed by NaX (X = Br, I, F) to give [RuX{g2-C,O-C6H4-2-
1
CH(O2C2H4)}(CO)(PPh3)2] (2b–d). All compounds have been characterized by elemental analysis (C and H), IR, H, 13C–{1H} and
31P–{1H} NMR spectroscopy. A crystallographic study of 2a shows the presence one pair of enantiomers and one pair of diastereoisomers
in the asymmetric unit. Theoretical calculations (B3LYP using the LanL2DZ basis set) on the model compounds [RuCl-
(CH3)(EH2)(CO)(PH3)2] (E = O, S) (3a,b) show that for 3a a planar geometry at the OH2 ligand and for 3b a pyramidal structure at
SH2 is favoured. The calculated electrostatic potentials for EH2 and the acetals CH2E2C2H4 (E = O, S) are used to comment on the nature
of the lone pairs at the chalcogen atoms and the coordination geometries of ether and thioether ligands. The X-ray crystallographically
determined molecular structure of [BrHg(g2-C,O-C6H4-2-CHO2C2H4)] (4) is also described and model compounds studied theoretically.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Ruthenium; Orthometallation; Acetal; Pyramidal inversion; Crystallography; Halide
1. Introduction
and hence see if the relative magnitude of each effect be
deciphered.
Recently we reported the preparation of some cycloruth-
enated azobenzene [1] and Schiff base [2] complexes and
showed the presence of a non-conventional cis-push–pull
effect, Chart 1, that complements the normal cis-push–pull
effect observed between a halide and carbonyl ligand [3]. As
an extension to this study we were interested in synthesising
molecules in which the non-conventional cis-push–pull
effect could not be effected by the cyclometallated ligand
Several years ago we described [4] the synthesis of the
diorganomercurial Hg{o-C6H4-2-CH(O2C2H4)}2 and con-
sidered it to be an ideal candidate to act as a transfer
reagent for the hemilabile ligand {o-C6H4-2-CH(O2C2H4)}2
as it would not transmit the secondary cis-push–pull effect
observed in the related cyclometallated imine and azo-
containing systems. It was also anticipated that the acetal
ring would undergo an acetal-ring rotation similar to that
previously observed in rhenium carbonyl halide complexes
containing {pyridine-1,3-dioxan-2-yl}-based ligands and
therefore provide more information on this fluxional
process [5]. A better understanding of the nature of these
*
Corresponding author. Tel.: +44 0 1613064538; fax: +44 0 1612754598.
E-mail address: k.r.flower@manchester.ac.uk (K.R. Flower).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.02.029

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R.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 2519–2528
31P{1H} NMR spectroscopy Table 2 and 13C{1H} NMR
spectroscopy Table 3. Compound 2a was also character-
ized by a single crystal X-ray diffraction study, see Table
4 for data collection and processing parameters and the
Section 4 for additional comments on the structure solu-
tion. PLUTON [10] representations of the crystallographically
independent molecules are presented in Fig. 1 showing the
Chart 1. Non-conventional cis-push–pull effect facilitated by cylometal-
lated ligands.
˚
numbering scheme and selected bond lengths (A) and
angles (ꢁ).
Each of the independent molecules is conveniently
described as a slightly distorted octahedral with the two
PPh3 ligands mutually trans and axial with the orthoruth-
enated-2-phenylacetal, carbonyl and chloride ligands in the
equatorial plane. The four molecules can be considered as
one pair of enantiomers where the sum of the angles about
the coordinated acetal oxygen is 359.8ꢁ and one pair of
diasteroisomers where the sum of the angles about the
coordinated oxygen atom is 354.1ꢁ. These coordination
geometries at oxygen can be considered as intermediates
in the classical pyramidal inversion process [11], frequently
observed in related sulfur systems, and often investigated
by VT NMR [12]. A search of the CCDC [13] shows that
a planar oxygen environment is dominant in metal ether
complexes and on careful examination of relative ligand
orientations in these complexes there is no evidence that
oxygen planarity results from p-effects. For related thio-
ether-containing complexes pyramidal geometry at sulfur
is, as expected, normal. For example Vicente et al. have
recently reported the solid state structure of the cyclopalla-
dated thioacetal-containing complex [PdCl{g2-C,S-C6H3-
2,5-(CHS2C2H4)}(PPh3)] and the thioacetal ligand is
pyramidal at sulfur [7].
fluxional processes is useful in understanding the dynamics
of this type of ligand and the development of new hemila-
bile ligand sets for use in homogeneous catalysis [6]. Dur-
ing the course of this work Vicente et al. reported the
preparation of some analogous orthomercuriated arylace-
tals and their utility as transfer reagents in the preparation
of some orthopalladated arylacetal complexes [7]. The
number of other examples of cyclometallated (g2-C,O
coordinated) aryl acetals is limited [8].
Herein we describe the synthesis and characterization of
the cycloruthenated acetal containing complexes [RuX{g2-
C,O-C6H4-2-CH(O2C2H4)}(CO)(PPh3)2] (2a–d) (X = Cl,
Br, I, F); the fluxional nature of the acetal ring; the pres-
ence of diastereoisomers in the crystal structure of 2a which
are a result of pseudorotation of the five-membered acetal
ring; and why pyramidal inversion is readily observed in
thioether-containing complexes but not analogous ether-
containing complexes.
2. Results and discussion
2.1. Syntheses and characterization of [RuX(CO){g2-C, O-
C6H4-2-CH(O2C2H4)}(PPh3)2] (X = Cl, 2a; Br, 2b; I, 2c;
F, 2d)
In an attempt to rationalize why the ether-containing
complexes appear to prefer planar and the thioether-
containing complexes pyramidal geometries at the coordi-
nated chalcogen atom theoretical calculations (B3LYP
using the LanL2DZ basis set) [14] were carried out on the
model compounds [RuCl(CH3)(EH2)(CO)(PH3)2] (E = O,
S) (3a,b), Figs. 2 and 3 [15]. See Supplementary material
Compound 2a was prepared by modification of the
methodology reported by Roper and Wright [9], and com-
pounds 2b–d were prepared by a Ag+ mediated halogen
exchange reaction, Scheme 1.
All of the new compounds 2a–d were characterized by
˚
1
for calculated bond lengths (A) and angles (ꢁ). For 3a the
microanalysis (C, H), and IR spectroscopy Table 1, H,
structural minimum contains planar oxygen and this mini-
mized structure sits at the bottom of a single potential well.
Conversely, for 3b pyramidal geometry at sulfur is calcu-
lated to be the energetic minimum. A complex containing
planar sulfur is found to represent the transition state geom-
etry of a classical double potential well representation of a
pyramidal inversion process with a calculated activation
barrier of 44 kJ molꢀ1. Recent calculations carried out on
the [M(OH2)2]+ cations (M = Ag, Au, Cd, Hg) likewise pre-
dict a single potential well for the coordinated aquo-ligand
[16]. Structural minimization at the B3LYP LanL2DZ
level for H2E and HCE2C2H4 (E = O, S) has also been
carried out and electrostatic plots (ꢀ30 kcal molꢀ1) are
presented in Fig. 4. They show for E = O the electron
density has a banana-like appearance with the maximal
electron density found to be located in the OR2 plane. This
suggests that planar coordination is most likely in aquo and
Scheme 1. Synthetic scheme for the preparation of 2a–d. (i) C6H5CH3,
reflux, 6h; (ii) Ag[BF4], CH2Cl2/(CH3)2CO; NaX, (X = F, Br, I).

R.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 2519–2528
2521
Table 1
Physical, analyticala, and infrared datab for 2a–d
Compound
Color
Yield (%)
Microanalytical data (%). Calc in parentheses
IR m(CO) cmꢀ1
Mp (ꢁC)
C
H
2a [RuCl(CO){g2-C6H4CH(O2C2H4)}(PPh3)2]
2b [RuBr(CO){g2-C6H4CH(O2C2H4)}(PPh3)2]
2c [RuI(CO){g2-C6H4CH(O2C2H4)}(PPh3)2]
2d [RuF(CO){g2-C6H4CH(O2C2H4)}(PPh3)2]
4 [HgBr{g2-C6H4-2-CH(O2C2H4)}]
White
White
White
White
White
87
94
96
68
75
224
66.1
(65.9)
62.7
(62.6)
59.3
(59.4)
66.5
4.9
(4.7)
4.5
(4.5)
4.1
(4.2)
4.5
1921
1930
1930
1914
219
217
212
187
(67.2)
25.2
(4.8)
2.1
(25.2)
(2.1)
a
Calculated values in parentheses.
Spectra recorded as nujol mulls between KBr plates all bands strong.
b
Table 2
31P{1H} NMRa and proton datab for compounds 2a–d
Compd
31P (d)
1H (d)
2a
32.6 (AB JPP = 338)
7.75–7.12 (m, 30H aryl-H); 6.74 (d, JHH = 7.2, 1H, aryl-H); 6.62 (t, JHH = 7.2, 1H, aryl-H); 6.00 (t, JHH = 7.5,
1H, aryl-H); 5.78 (d, JHH = 7.9, 1H, aryl-H); 4.82 (s, 1H, CH); 3.66 (br s, 1H, OCH2); 3.46 (br s, 1H, OCH2);
3.30 (br s, 1H, OCH2); 2.62 (br s, 1H, OCH2)
2b
2c
2d
32.5 (AB, JPP = 301)
7.60–7.10 (m, 30H aryl-H); 6.70 (d, JHH = 7.5, 1H, aryl-H); 6.59 (t, JHH = 7.5, 1H, aryl-H); 5.99 (t, JHH = 7.6,
1H, aryl-H); 5.78 (d, JHH = 7.8, 1H, aryl-H); 4.66 (s, 1H, CH); 3.40 (br s, 1H, OCH2); 3.33 (br s, 1H, OCH2);
3.17 (br s, 1H, OCH2); 2.69 (br s, 1H, OCH2)
7.60–7.10 (m, 30H, aryl-H); 6.70 (d, JHH = 7.5, 1H, aryl-H); 6.23 (t, JHH = 7.6, 1H, aryl-H); 6.06 (t, JHH = 7.1,
1H, aryl-H); 5.90 (d, JHH = 7.8, 1H, aryl-H); 4.51 (s, 1H, CH); 3.50 (br s, 1H, OCH2); 3.30 (br s, 1H, OCH2);
3.20 (br s, 1H, OCH2); 2.85 (br s, 1H, OCH2)
7.70–7.10 (m, 30H, aryl-H); 6.70 (d, JHH = 7.6, 1H, aryl-H); 6.53 (t, JHH = 7.5, 1H, aryl-H); 6.00 (t, JHH = 7.6,
1H, aryl-H); 5.83 (d, JHH = 7.6, 1H, aryl-H); 5.04 (s, 1H, CH); 3.75–3.25 (br m, 4H, OCH2)
7.41–7.25 (m, 4H, aryl-H); 5.65 (s, JHgH = 84.4, 1H, CH); 4.27–3.94 (m, 4H, CH2)
31.9 (s)
33.0 (AB, JPP = 327,
JPF = 14.9)
4
a
Spectra recorded (162.6 MHz) in CDCl3 at 296 K; coupling constants (J) Hz, s = singlet, d = doublet, t = triplet, m = multiplet, AB = AB quartet.
Spectra recorded (200 MHz) in CDCl3 at 296 K.
b
Table 3
13C{1H} NMR dataa for compounds 2a–d
Compd
13C (d)
2a
206.6 (t, JPC = 17.4, CO); 166.0 (t, JPC = 9.6, RuC); 140.0; 136.0; 134.4; 133.5 (d, JPC = 43.5); 132.4 (d, JPC = 64.4); 129.5; 129.1; 128.7; 121.7;
120.2; 110.2; 64.8; 63.7
2b
206.7 (t, JPC = 16.4 CO); 166.0 (t, JPC = 10.6, RuC); 140.4; 136.0; 134.3; 133.5 (d, JPC = 34.8); 132.3 (d, JPC = 61.4); 129.4; 129.3; 129.1;
127.6; 121.6; 120.5; 110.2; 64.8; 63.9
2c
2d
4
207.3 (br s); 166.0 (br s); 140.8; 136.0; 135; 133.7 (br s); 132.7 (br s); 129.5; 129.4; 129.1; 127.6; 121.6; 120.7; 110.3; 65.5; 64.4
206.7 (br m); 166 (br m); 140.1; 136.0; 134.4; 133.9; 133.6; 133.0; 129.1; 128.7; 128.5; 127.8; 127.6; 121.7; 120.2; 110.2; 64.8; 63.9
151.1; 141.0; 130.9; 129.2; 130.4; 137.0; 104.2; 65.4
a
Spectra recorded (100.55 MHz) in CDCl3 at 296 K; all resonances singlets unless otherwise stated; coupling constants (J) Hz.
ether-containing complexes however, deformation from
strict planar geometry is energetically not too costly.
Whereas for E = S clear evidence of two concentrations
of electron density akin to the classical bunny-ear represen-
tation of lone pairs is visible indicating a clear preference for
pyramidal binding. These binding modes suggested by cal-
culation are also consistent with the preferred binding
modes found in the CCDC. It is also consistent with why
pyramidal inversion is readily observable for thioether-con-
taining complexes and not for ether-containing complexes
using VT NMR techniques: the transition state for the com-
plexed ether oxygen inversion is the energetic minimum
rather than the energetic maximum.
It is well known and documented that five-membered
rings are conformationally flexible [17] and that the
observed puckering can rotate easily around the ring
through 10 C2 and 10 Cs forms without the interference
of significant enthalpy barriers. This pseudorotation has
a maximum torsion angle hm and a phase angle of pseudo-
rotation P. Each can be readily calculated [17b] and utilis-
ing the crystallographic data obtained for 2a the calculated
value of hm for each acetal ring is 43.36, 42.93, 41.22, 41.04

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R.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 2519–2528
Table 4
Compounds 2a–d would be expected to give an AB
quartet resonance in their 31P{1H} NMR spectra when
the cycloruthenated acetal ligand is coordinated as a C–O
chelate, containing a planar oxygen atom. From the data
presented in Table 1 compounds 2a, b and d (which shows
additional coupling to fluorine) fit this expectation (AB
quartet), whereas 2c (singlet) does not and therefore
appears to be fluxional at room temperature. The fluxional
process that is in operation is dechelation of the acetal
oxygen with associated ring rotation about the aryl–ace-
tal–CH-bond. This process causes equilibration of the
trans-phosphine ligands and hence the appearance of a sin-
glet resonance. It also effects inversion of the chirality at
the acetal O2CH–Ph carbon atom. Inversion at the ligated
oxygen atom is also a possible fluxional process. However,
this mechanism does not equilibrate the two phosphorus
atoms as the acetal CH will always point towards the same
phosphine ligand and therefore prevent resonance equili-
bration. Cooling a CDCl3 solution of 2c caused broadening
of the spectral line consistent which is consistent with slow-
ing down the rate of ring rotation, conversely warming of a
CDCl3 solution of 2a caused broadening of the signal
indicative of speeding-up the ring rotation. In neither case
could enough data be collected to allow calculation of the
barrier to acetal ring rotation.
X-ray crystallographic data for 2a and 4
Compound
2a
4
Empirical formula
Formula weight
Temperature (K)
C188H166Cl4O13P8Ru4 C9H9BrHgO2
3427.05
120(2)
0.68630 (Synchrotron) 0.71073 (Kappa
CCD)
Monoclinic
429.66
200(2)
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
Monoclinic
P21/n
P121/c1
˚
a (A)
10.7814(13)
36.167(4)
41.839(5)
90.109(2)
16314(3)
4
9.0456(4)
4.3690(2)
25.5155(14)
90.927(2)
1008.25(8)
4
˚
b (A)
˚
c (A)
b (ꢁ)
Volume (A )
3
˚
Z
Dcalc (Mg/m3)
1.395
0.487
2.831
19.191
Absorption coefficient
(mmꢀ1
F(000)
Crystal size (mm)
h (ꢁ)
h,k,l
)
7048
0.08 · 0.02 · 0.01
2.82–26.45
ꢀ13 6 h 6 13,
ꢀ46 6 k 6 46,
ꢀ48 6 l 6 54
124375
776
0.20 · 0.06 · 0.04
3.31–25.25
0 6 h 6 10,
0 6 k 6 5,
ꢀ30 6 l 6 30
1796
Reflections collected
Independent reflections
[R(int)
Completeness to h (%)
Absorption correction
36753 [0.0802]
1796 [0.0000]
]
1
The H and 13C–{1H} NMR data, Tables 1 and 2, are
98.6
None
98.7
Semi-empirical
from equivalents
0.5140 and 0.1140
likewise indicative of the compounds 2a–d being fluxional.
1
The fluxional process for 2a was investigated by a VT H
Maximum and minimum 0.9951 and 0.9621
transmission
Refinement method
NMR study in CDCl3 at 400 MHz. The pertinent portions
of the recorded spectra are illustrated in Fig. 5. At low tem-
perature (233 K) the spectrum is consistent with a ‘static-
structure’ that contains a planar-coordinated acetal oxygen
atom. There is no evidence for the presence of an addi-
tional set of resonances that would be consistent with the
presence of a pair of diasteroisomers that would necessarily
contain pyramidally coordinated oxygen.
Full-matrix-block
least-squares on F2
36753/0/1973
Full-matrix least-
squares on F2
1796/0/119
Data/restraints/
parameters
Final R indices [I > 2r(I)] R1 = 0.0637,
wR2 = 0.1489
R1 = 0.0421,
wR2 = 0.0981
R1 = 0.0593,
wR2 = 0.1111
1.060
R indices (all data)
R1 = 0.0945,
wR2 = 0.1641
1.026
Goodness-of-fit on F2
As the temperature is elevated above room temperature
evidence for ring rotation is observed. The expected two
proton resonances for each of the OCH2 groups (proxal
and distal) to the acetal CH is not attained as coalescence
of one pair of signals occurs just below the boiling point
of the solvent; hence the presence of only one sharp signal.
The other is very broad and essentially lost in the baseline.
The barrier (DGꢀ) to ring rotation was calculated to be
62 2 kJ molꢀ1 and is consistent with other acetal ring
rotations [5]. Dechelation of the acetal oxygen atom offers
a vacant coordination site. Attempts to trap the dechelated
intermediate using the Lewis bases, CO, CNBut were car-
ried out and no evidence of ligand coordination or migra-
tory insertion observed. The non-reactivity presumably
results from the acetal ring blocking access of an incoming
ligand as it rotates. The acetal ring also seems quite stable
with respect to hydrolysis.
Extinction coefficient
0.00132(8)
0.0008(3)
1.977 and ꢀ1.850
Largest differencꢀe3in peak 1.332 and ꢀ1.452
˚
and hole (e A
)
(ꢁ) respectively with the phase angle P for each ring being
162.7, 92.0, (close to theoretical planar angles of 162 and
90 ꢁ) and 137.1, 140.6 (close to the C2 ring angle of
144 ꢁ). This pseudorotation also clearly affects the coordi-
nation geometry at the complexed oxygen atom, Fig. 1,
in each of the independent molecules in the crystal struc-
ture. Hence the presence of one pair of enantiomers, chiral
only at carbon, and one pair of diasteroisomers, chiral at
both carbon and oxygen. Therefore, based on data from
the theoretical calculations and the nature of the pseudoro-
tation observed in five-membered ring systems, the planar
and pyramidal oxygen atoms observed in the solid state
structure of 2a are unlikely to represent trapped intermedi-
ates in the classical pyramidal inversion process rather they
represent frozen intermediates on a low energy pseudorota-
tion pathway.
The IR spectra for 2a–d (Table 1) all show an expected
strong m(CO) band between 1914 and 1930 cmꢀ1
(Dm(CO) = 16 cmꢀ1), with the lowest stretch being for 2d
(X = F). This is expected as the fluoride ligand is the

R.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 2519–2528
2523
˚
Fig. 1. PLUTON representations of the independent molecules of 2a showing the atomic numbering scheme. Selected bond lengths (A) and angles (ꢁ): Ru(1)–
C(10) 1.794(6); Ru(1)–C(1) 2.062(6); Ru(1)–O(1) 2.222(4) Ru(1)–P(2) 2.3773(16); Ru(1)–P(1) 2.3775(16); Ru(1)–Cl(1) 2.4920(15); Ru(2)–C(60) 1.816(7);
Ru(2)–C(51) 2.055(6); Ru(2)–O(51) 2.208(4); Ru(2)–Cl(2) 2.4981(16); Ru(3)–C(110) 1.782(7); Ru(3)–C(101) 2.070(6); Ru(3)–O(101) 2.198(5); Ru(3)–Cl(3)
2.5172(17); Ru(4)–C(160) 1.799(7); Ru(4)–C(151) 2.077(6); Ru(4)–O(151) 2.190(5); Ru(4)–Cl(4) 2.5148(17); C(9)–O(1)–C(7)104.3(4); C(9)–O(1)–Ru(1)
134.9(4); C(7)–O(1)–Ru(1) 115.0(3); C(59)–O(51)–C(57) 104.0(5); C(59)–O(51)–Ru(2)134.9(4); C(57)–O(51)–Ru(2)115.8(4);C(109)–O(101)–C(107)
107.9(5); C(109)–O(101)–Ru(3)139.5(4); C(107)–O(101)–Ru(3) 112.6(4); C(159)–O(151)–C(157) 107.4(5); C(159)–O(151)–Ru(4) 139.5(4); C(157)–
O(151)–Ru(4) 113.1(4).
Fig. 2. SPARTAN representation of the optimized geometry of [RuCl(CH3)-
Fig. 3. SPARTAN representation of the optimized geometry of
(OH2)(CO)(PH3)2] (3a).
[RuCl(CH3)(SH2)(CO)(PH3)2] (3b).

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R.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 2519–2528
was obtained on recrystallization from hot ethanol, see
Table 4 for data collection and processing parameters
and Fig. 6 for an ORTEP [20] representation showing the
˚
atomic numbering scheme with selected bond lengths (A)
and angles (ꢁ). The most noticeable feature of this structure
is the pyramidal nature of the coordinated oxygen atom.
Theoretical calculations (B3LYP using the LanL2DZ basis
set) [13] on the model compounds [HgBr(C6H4-2-CH2EH)]
(5a,b), Figs. 7 and 8, predict, as for the ruthenium com-
pounds 3a,b, a planar oxygen atom, which differs from
the crystallographically determined structure, and pyrami-
dal sulfur. See Supplementary material for calculated bond
Fig. 4. Electrostatic contour plots at ꢀ30 kcal molꢀ1 for H2O, H2S,
˚
lengths (A) and angles (ꢁ).
CH2O2C2H4 and CH2S2C2H4.
Inspection of the extended structure for 4, Fig. 9, shows
that the coordinated acetal–oxygen atom bridges two mer-
˚
cury centres, 2.816(4) and 2.882(5) A respectively, and has
a pseudo-tetrahedral coordination geometry.
Additionally the coordination number at the mercury
centre expands to six through two additional long Hgꢁ ꢁ ꢁBr
˚
interactions at 3.652(5) and 3.395(5) A respectively which
are comfortably within the sum of the van der Waals radii
[4,21]. The differences between the calculated and solid
state geometry are a pertinent reminder of the inability of
this type of calculation to predict the presence of other
solid state interactions and how they may influence the
overall molecular geometry.
Fig. 5. VT 1H NMR spectra for 2a from 233–253 K.
strongest p-donor and has been noted previously in related
work [18] and by others [19]. Recently we reported [18] the
preparation of the related series of compounds [RuX(CO)-
(g2-C,N-C6H4CH@NC6H4-4-NO2)(PPh3)2] (X = F, Cl, Br,
I) and found the Dm(CO) = 17 cmꢀ1. The magnitude of
Dm(CO) is identical within experimental error ( 4 cmꢀ1
)
to that observed for 2a–d. It is clear that the non-conven-
tional cis-push–pull effect, Chart 1, appears to be too small
in magnitude to be effectively probed using m(CO) values
although it is amenable to measurement by 13C NMR spec-
troscopy [2].
19
Fig. 6. ORTEP
representation of 4 showing the numbering scheme.
˚
Selected bond lengths (A) and angles (ꢁ):C(1)–Hg(1) 2.041(14); Hg(1)–
Br(1) 2.4475(13); O(1)–Hg(1) 2.816(12); C(7)–O(1) 1.397(17); C(7)–O(2)
1.435(14); C(8)–O(1) 1.411(16); C(9)–O(2) 1.420(16); C(1)–Hg(1)–Br(1)
175.2(4); Hg(1)–O(1)–C(7) 97.8(3); Hg(1)–O(1)–C(8) 114.1(4); C(7)–O(1)–
C(8) 106.6(3).
2.2. Synthesis and characterization of [HgBr{g2-C6H4-2-
CH(O2C2H4)}] (4)
During the preparation of
1
[HgBr{g2-C6H4-2-
CH(O2C2H4)}] (4) was isolated as a side product. It can
be readily prepared in high yield on treatment of BrMg-
(C6H4-2-CHO2C2H4) [4] with 1 equiv. of HgBr2. Com-
pound 4 has been characterized by elemental analysis Table
1, 1H NMR Table 2 and 13C–{1H}NMR spectroscopy
Table 3. A suitable crystal for an X-ray diffraction study
Fig. 7. SPARTAN representation of the optimized geometry of [HgBr(g2-
C6H4-2-CH2OH)] (5a).

R.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 2519–2528
2525
on a Bruker DPX 200 spectrometer and 1H NMR
(400.2 MHz), 31P{1H} (162.6 MHz), 13C{1H} NMR
(100.55 MHz) were recorded on a Bruker DPX 400 spec-
trometer. 1H and 13C NMR spectra were referenced to
residual CHCl3 (d = 7.26) and CDCl3 (d = 77.0) and
31P{1H} NMR were referenced externally to 85% H3PO4
(d = 0.0). Elemental analyses were performed by the
Microanalytical Service, Department of Chemistry,
UMIST. The syntheses were carried out under a dinitrogen
atmosphere using standard Schlenk techniques. Work-ups
were generally carried out in the open unless otherwise
stated.
Fig. 8. SPARTAN representation of the optimized geometry of [HgBr(g2-
C6H4-2-CH2SH)] (5b).
4.2. Synthesis of [RuCl(CO)(g2-C6H4CHO2C2H4)-
(PPh3)2] (2a)
Caution: use of an organomercurial reagent. To
[RuHCl(CO)(PPh3)3] (1.0 g, 1.04 mmol) suspended in tolu-
ene (20 mL) was added Hg{o-C6H4-2-CH(O2C2H4)}2
(0.52 g, 1.04 mmol) and the solution heated to reflux with
continuous stirring under dinitrogen for 6 h. After cooling
the solution was filtered through Celiteꢂ to remove Hg
(caution) and the solvent removed under reduced pressure.
The crude material was then extracted with hot hexane
(3 · 25 mL) to remove PPh3 and C6H5CHO2C2H4. Recrys-
tallization from CH2Cl2/EtOH afforded 2a in good yield
(0.76 g, 87%). See Table 1 for physical and analytical data.
Fig. 9. ORTEP representation of the extended structure of 4.
3. Conclusions
The preparation and structural characterization of
[RuCl{g2-C,O-C6H4-2-(O2C2H4)}(CO)(PPh3)2] (2a), along
with theoretical calculations and searches of the CCDC
presents an explanation of the differences in the nature of
the coordination modes of ether and thioether ligands to
metal centres. It also revealed, not surprisingly, that the
nature and availability of the electron density at the chalco-
gen atom differs significantly between the oxygen and sul-
fur donor atoms. The electron density at the sulfur atom
has the classical bunny-ear like appearance, whereas at
oxygen it is more akin to a banana shape. Therefore the
favoured coordination geometry for ether ligands is
planar-at-oxygen and for thioether ligands is pyramidal-
at-sulfur. The different coordination geometries at coordi-
nated oxygen observed in the solid state structure of 2a
(planar and slightly pyramidal) which on a first look
appear to be frozen intermediates of a classical pyramidal
inversion are, in fact, frozen intermediates of a low energy
pseudorotation commonly observed for five-membered
rings.
4.3. Synthesis of [RuBr(CO)(g2-C6H4CHO2C2H4)-
(PPh3)2] (2b)
To [RuCl(CO)(g2-C6H4CHO2C2H4)(PPh3)2] (0.1 g,
0.12 mmol) dissolved in CH2Cl2/acetone (20 mL, 1:1) was
added AgBF4 (0.025 g, 0.12 mmol). After stirring for
30 min the solution was filtered through a fluted filter paper
and NaBr (0.025 g, 0.24 mmol) dissolved in water (0.5 mL)
was added along with enough ethanol to generate a homo-
geneous solution. After stirring for 30 min the solvent vol-
ume was reduced under reduced pressure affording crude
2b. Recrystallization of the crude from CH2Cl2/EtOH
afforded 2b in good yield (0.95 g, 94%). See Table 1 for
physical and analytical data. Compounds 2c and 2d were
prepared in analogous fashion.
4. Experimental
4.4. X-ray crystallography
4.1. General comments
Crystals of 2a were grown by dissolving approximately
10 mg in 0.2 mL of CH2Cl2 in a glass vial (10 mm · 25 mm)
and layering ether on top and leaving the mixture to stand
for several days.
A suitable single crystal was coated in inert perfluoro-
polyether oil and mounted on a single glass wool strand
of ca. 3 mm in length glued to a glass fibre. All measure-
ments were carried out on Station 9.8. CCLRC Daresbury
Laboratory, Daresbury, UK using a standard Bruker
SMART charge-coupled device (CCD) 1 K area-detector dif-
fractometer controlled using the SMART software package
All solvents except alcohols were dried by refluxing over
the appropriate drying agent (toluene, Na; CH2Cl2, P4O10;
hexane, NaK) and distilled prior to use. [RuHCl(CO)-
(PPh3)2] [22] and Hg{o-C6H4-2-CH(O2C2H4)}2 [4], were
prepared according to the literature procedures; all other
chemicals were obtained from commercial sources and
used as received, except for RuCl3 Æ H2O which was loaned
by Johnson Matthey. IR spectra were recorded as nujol
mulls between KBr plates on a Nicolett 5PC spectrometer,
1H NMR (200.2 MHz), 31P{1H} (81.3 MHz) were recorded

2526
R.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 2519–2528
version 5.054 [23]. This software was also used for index-
ing, cell refinement and data reduction.
these crystals was extremely poor and it was only possible
to collect data to 20ꢁ theta for Mo radiation. Nevertheless
the 4-molecule cluster seen in the current structure and the
packing anticipated above appear to be borne out.
Crystals of 4 were grown by a slow cooling of a hot 50 ꢁC
saturated solution. A suitable single crystal was attached to
a glass fibre using inert perfluoropolyether oil. The X-ray
diffraction data were collected on a Nonius Kappa CCD
4-circle diffractometer controlled using KappaCCD
Server Software [25] and COLLECT [26]. Final cell refinement
and data reduction were carried out using DENZO and
SCALEPACK from the HKLf suite of programmes [27].
The structure was solved by direct methods and sub-
jected to full-matrix least-squares refinement on F2 using
the SHELX-97 [24] program. All nonhydrogen atoms were
refined with anisotropic thermal parameters, while hydro-
gen atoms were fixed in idealized positions. Crystal data
and details of the refinement are presented in Table 4 and
a molecular image, generated using ORTEP 3 for Windows
[19], is displayed in Fig. 6.
The structure was solved by direct methods and sub-
jected to full-matrix least-squares refinement on F2 using
the SHELX-97 [24] program. All nonhydrogen atoms were
refined with anisotropic thermal parameters, while hydro-
gen atoms were fixed in idealized positions. Crystal data
and details of the refinement are presented in Table 4 and
a PLUTON [10] generated image of the asymmetric unit is dis-
played in Fig. 1.
The asymmetric unit consists of four complex molecules
and a diethylether solvate. Although the structure contains
cavities that are sufficiently large to accommodate more
diethylether molecules there is no evidence of them in the
difference maps, although a highly disordered second sol-
vate molecule cannot be ruled out. A packing diagram is
included in Supplementary material.
The current crystal structure determination was ham-
pered by two types of crystal imperfection: (i) The beta
angle is almost exactly 90ꢁ so it is not surprising that twin-
ning has occurred. Although the twin command TWIN
ꢀ100010001 defines the twin plane as the bc plane,
monoclinic symmetry means that the ab plane, a-axis or
b-axis are equally plausible twinning symmetry elements.
The ratio of the main crystal to its twin as refined with
the BASF command is 0.6022(8):0.3978(8).
Acknowledgements
K.R.F. thanks the EPSRC National Crystallographic
service, University of Southampton for a preliminary data
collection on 2a and Johnson Matthey for the loan of
RuCl3 Æ H2O.
(ii) A non-crystallographic a-glide (0.5 + x, y, 0.446 ꢀ z)
relates the enantiomeric pairs in each 4-molecule cluster
and is the most probable explanation for Ru ghost peaks
that are observed at (x, y, z + 0.11) with site occupancies
of 3% of the main Ru atoms. The crystallographic screw
axis (ꢀx, 0.5 + y, 0.5 ꢀ z), which relates the clusters down
b can be combined with the non-crystallographic a-glide
(0.5 + x, y, 0.446 ꢀ z) to create a non-crystallographic
‘‘diagonal’’ glide (0.5 ꢀ x, 0.5 + y, 0.054 + z). Although
the non-crystallographic ‘‘diagonal’’ glide is not applied a
second time as the mirror is returned to its original position
by the crystallographic 21, it is clearly an acceptable pack-
ing option. If the non-crystallographic ‘‘diagonal’’ glide
operation is applied twice a pure translation results, (x,
1 + y, 0.108 + z) c.f. (x, y, 1 + z) for a double application
of the 21 axis. Therefore occasional application of the
non-crystallographic operation as opposed to the crystallo-
graphic 21 would lead to ghost Ru peaks displaced from the
main Ru atoms by 0.108 down z*. This also suggests the
possibility of a second polymorph, in which the ‘‘diagonal’’
glide becomes the main operation. This would change the
shape of the unit cell a0 = a, and c0 = c but a0 = 180 ꢀ atan
b/0.108c and b0 = b/sin a0. This would lead to the glide
operation reflecting in the b0c0 plane and translating down
b0. Conversion to the conventional ac plane reflection and
translation down c is achieved via. a00 = c0 = c = 41.8390;
b00 = a0 = a = 10.7814; c00 = b0 = b/sin a0 = b/sin b00 =
36.448; b00 = a0 = 180 ꢀ atan b/0.108c = 97.12. A second
polymorph has been observed, which has crystallized in
space group P21/c with unit cell dimensions a = 41.9326,
b = 10.8103, c = 36.5987 and b = 97.781. The quality of
Appendix A. Supplementary material
CCDC 633950, 633951and 633952 contain the supple-
mentary crystallographic data for 2a (Synchrotron), 4
and 2a (KappaCCD). These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Histogram representations of the CCDC searches, packing
˚
diagrams for 2a, and calculated bond lengths (A) and
angles (ꢁ) for 3a–b and 5a–b are available. Supplementary
data associated with this article can be found, in the online
version, at doi:10.1016/j.jorganchem.2007.02.029.
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