Synthesis and Structures of Rare Earth 3-(4′-Methylbenzoyl)-propanoate Complexes-New Corrosion Inhibitors

Article abstract of DOI:10.1071/CH16547

A series of rare earth 3-(4′-methylbenzoyl)propanoate (mbp^-) complexes [RE(mbp)₃(H₂O)] (RE≤rare earth≤Y, La, Ce, Nd, Ho, Er) have been prepared by either metathesis reactions between the corresponding rare earth chloride and Na(mbp) or protolysis of rare earth acetates by the free acid. Single-crystal X-ray diffraction studies of [RE(mbp)₃(H₂O)] (RE≤Ce, Nd) and [Ce(mbp)₃(dmso)] reveal a 1D carboxylate-bridged polymeric structure in the solid state, featuring 9-coordinate rare earth ions. X-ray powder diffraction patterns of the bulk materials indicates that all of the [RE(mbp)₃(H₂O)] complexes except RE≤La are isomorphous. Hence, there is no structural change from the complex with RE≤Ce to that with RE≤Er despite the lanthanoid contraction. The ¹H NMR spectra of the RE≤Ho or Er complexes in (CD₃)₂SO show large paramagnetic shifts and broadening of the CH2 resonances, indicating the retention of substantial carboxylate coordination in solution.

Full text of DOI:10.1071/CH16547

RESEARCH FRONT
CSIRO PUBLISHING
Aust. J. Chem.
Full Paper
http://dx.doi.org/10.1071/CH16547
Synthesis and Structures of Rare Earth
3-(49-Methylbenzoyl)-propanoate
Complexes – New Corrosion Inhibitors*
A
A D
,
A
A
Caspar N. de Bruin-Dickason, Glen. B. Deacon,
Craig M. Forsyth,
A
A
B
Schirin Hanf, Oliver B. Heilmann, Bruce R. W. Hinton,
C D
,
B
A
Peter C. Junk,
Anthony E. Somers, YuQingTan, and DavidR. Turner
A
School of Chemistry, Monash University, Clayton, Vic. 3800, Australia.
B
Institute for Frontier Materials, Deakin University, Geelong, Vic. 3220, Australia.
C
College of Science and Engineering, James Cook University, Townsville,
Qld 4811, Australia.
D
Corresponding authors. Email: glen.deacon@monash.edu; peter.junk@jcu.edu.au
A series of rare earth 3-(40-methylbenzoyl)propanoate (mbp–) complexes [RE(mbp)3(H2O)] (RE ¼ rare earth ¼ Y, La, Ce,
Nd, Ho, Er) have been prepared by either metathesis reactions between the corresponding rare earth chloride and Na(mbp)
or protolysis of rare earth acetates by the free acid. Single-crystal X-ray diffraction studies of [RE(mbp)3(H2O)] (RE ¼ Ce,
Nd) and [Ce(mbp)3(dmso)] reveal a 1D carboxylate-bridged polymeric structure in the solid state, featuring 9-coordinate
rare earth ions. X-ray powder diffraction patterns of the bulk materials indicates that all of the [RE(mbp)3(H2O)]
complexes except RE ¼ La are isomorphous. Hence, there is no structural change from the complex with RE ¼ Ce to that
with RE ¼ Er despite the lanthanoid contraction. The 1H NMR spectra of the RE ¼ Ho or Er complexes in (CD3)2SO show
large paramagnetic shifts and broadening of the CH2 resonances, indicating the retention of substantial carboxylate
coordination in solution.
Manuscript received: 29 September 2016.
Manuscript accepted: 17 October 2016.
Published online: 15 November 2016.
Introduction
developing an understanding of structural features favouring
inhibition, it has been shown that lanthanum 3-(40-hydroxyphe-
nyl)propanoate (Ligand C, Fig. 1) is much less effective than
lanthanum 4-hydroxycinnamate, thereby establishing the
importance of the cinnamate double bond in corrosion inhibi-
tion.[13] Rare earth 3-(40-methylbenzoyl)propanoate (mbp)
Chemical corrosion inhibitors play a major role in reducing the
multi-billion dollar cost of corrosion of metal (particularly steel)
infrastructure.[1] For many years, metal chromates were domi-
nant in this role.[1a,2] However, concerns over their toxicity[3] are
driving the phasing out of their use and a search for more benign
replacements.[1a,2] In this context, rare earth salts show signifi-
cant anti-corrosion activity[4] and are environmentally friendly,
as shown by their widespread use in agriculture in China[5] and
by their use as feedstock additives in Switzerland.[6] Because
arene-functionalised carboxylate ions can also show anti-
corrosion properties, albeit at higher concentrations,[7] we are
examining the inhibitor properties of rare earth carboxylate
complexes, particularly for steel (see Fig. 1 for examples of
carboxylate ions of interest).[2]
COOϪ
COOϪ
OH
(a)
(b)
HO
(d)
O
(c)
COOϪ
For example, lanthanoid salicylates (Ligand A, Fig. 1) are
effective inhibitors with the cerium complex being the best
performer.[7] Additionally, there has been success in preparing
Fe/Ce salicylate bimetallics that model the protective film on
steel.[8] From a wide range of rare earth cinnamates[9] and
substituted cinnamates,[10] lanthanum 4-hydroxycinnamate
(Ligand B, Fig. 1) is the optimum performer.[11] In certain
applications, the praseodymium complex performs well.[12] In
COOϪ
HO
Fig. 1. Carboxylate anions used in the present and previous studies:
(a) 2-hydroxybenzoate (salicylate (Hsal–)); (b) 4-hydroxycinnamate
(4-OH-cinn–); (c) 3-(40-hydroxyphenyl)propanoate (hpp–); (d) 3-(40-methyl-
benzoyl)propanoate (mbp–).
*This paper is dedicated to our colleague and friend Professor Len Lindoy on the occasion of his 80th birthday.
Journal compilation ꢀ CSIRO 2016
www.publish.csiro.au/journals/ajc

B
C. N. de Bruin-Dickason et al.
(4-(40-methylphenyl)-4-oxobutanoate) (Ligand D, Fig. 1) com-
plexes are now a current focus, as the parent acid has been a
commercial inhibitor supplied by Ciba as Irgacor 419. It is
currently available as a 2 : 1 mixture with 4-ethylmorpholine as
Irgacor1405. Iron complexes modelling the behaviour of mbp–
on an iron surface have been published.[14] We now report the
preparation and structures of rare earth (RE) 3-(40-methylben-
zoyl)propanoate complexes [RE(mbp)3(H2O)] (RE ¼ Y, La, Ce,
Nd, Ho and Er) and [Ce(mbp)3(dmso)]. Preliminary reports on
their anti-corrosion behaviour have been given.[15] The choice
of rare earth elements covers virtually the whole size range
and includes some paramagnetic ions for exploring solution
behaviour.
indicated the loss of one coordinated water in the range of
80–1308C (the mass loss was lower than 1 H2O for the complex
with RE ¼ La) and gradual decomposition after 2308C.
Structural Studies
Single crystals of [RE(mbp)3(H2O)] (RE ¼ Ce, Nd) were grown
from filtrates of the synthesis reaction mixtures after standing
for several months, single crystals of [Ho(mbp)3(H2O)] were
obtained from an H-tube synthesis (see Experimental), and
single crystals of [Ce(mbp)3(dmso)] were grown from a satu-
rated dmso solution over several weeks. In contrast, obtaining
single crystals of the other [RE(mbp)3(H2O)] complexes has
been unsuccessful thus far.
The X-ray data for [RE(mbp)3(H2O)] (RE ¼ Ce, Nd, Ho) and
[Ce(mbp)3(dmso)] were solved in P21/c (No. 14) and C2/c
(No. 15) space groups, respectively, with one formula unit in
the asymmetric unit. The structures are depicted in Fig. 2, and
selected bond lengths are presented in Table 1. Data for the
holmium complex were of sufficient quality to only establish
connectivity, and thus the bond lengths of this complex are not
discussed. These complexes have a similar 1D polymeric
structure (Fig. 2). Each structure features 9-coordinate lantha-
noid ions terminally bound by one aqua (or O-dmso, as consis-
tent with the hard acid nature of the Ce3þ ion) ligand, and
six bridging mbp ligands. In [RE(mbp)3(H2O)] and [Ce
(mbp)3(dmso)] complexes, RE1 is bound by one oxygen atom
Results and Discussion
The synthesis of [RE(mbp)3(H2O)] complexes was accom-
plished by two methods. Metathesis reactions between three
molar equivalents of the sodium salt Na(mbp) either isolated or
prepared in situ and the required hydrated rare earth chloride
yielded the desired complexes in high yields as a colourless
(RE ¼ Y, La, Ce, Nd) or light pink (RE ¼ Ho, Er) microcrys-
talline solids (Scheme 1a). These complexes could also be
prepared in similar yields through protolysis reactions between
the free carboxylic acid and the corresponding rare earth acetate
(Scheme 1b). The bulk products were obtained analytically pure
(C, H, RE). Results of the thermogravimetric analysis (TGA)
Na(mbp)
H2O/EtOH
Hmbp
H2O/EtOH
RE(Cl)3(H2O)n
[RE(mbp)3(H2O)]
RE(O2CCH3)3(H2O)n
(a)
(b)
Scheme 1. Preparation of the [RE(mbp)3(H2O)] complexes.
O5
O10
C24
(a)
O2
O1
O4
Ce1ٞ
Ce1
O4Ј
O5Ј
Ce1Ј
O8
Ce1Љ
O7Љ
C13
O7
O1Љ
O2Љ
O8Љ
(b)
O1
O2
O5
C12
O7Ј
Ce1Ј
O4
Ce1ٞ
O4Ј
O1Ј
Ce1Љ
O7
Ce1Љ
Ce1
C23
O2Ј
O10
O8
S1
Fig. 2. Extended 1D chain of (a) [Ce(mbp)3(H2O)]n and (b) [Ce(mbp)3(dmso)]n showing the coordination sphere around the
Ce3þ metal ions and connectivity to symmetrically equivalent cerium atoms. Carboxylate ligands are truncated for clarity.

Rare Earth 3-(40-Methylbenzoyl)-propanoates
C
from each of the two m-1k(O):2k(O0) ligands (O2, O100 to Ce1
(Fig. 2a)), both oxygen atoms from two m-1k(O,O0):2k(O0)
ligands (O4, O5, O7, O8 to Ce1 (Fig. 2a)), and one oxygen
atom from each of the two m-1k(O0):2k(O,O0) ligands (O700, O40
to Ce1 (Fig. 2a)). Although the dmso analogue has a similar
coordination arrangement (Fig. 2b), the two mbp ligands che-
lating to Ce1 both bridge to the same cerium atom. In contrast, in
the aqua complex, these ligands bridge to different Ce atoms.
The structural difference is best illustrated by the angle sub-
tended by the carboxylate carbons of the chelating carboxylate
groupsatRE1, namelytransoid for the aquacomplexes(169.2(1)8
(RE ¼ Ce); 169.1(2)8 (RE ¼ Nd)) and cisoid (105.545(5)8) for the
dmso complex. The benzoyl carbonyl groups do not interact with
The larger , Ce–O . bond length in the dmso complex when
compared with that in the aqua analogue may be attributed to the
greater bulk of the neutral ligand.[16] The [Nd(mbp)3(H2O)]
complex features a slightly shorter average Nd–O bond length of
˚
˚
2.49 A, when compared with the cerium analogue (2.525 A), as
consistent with the difference in the 9-coordinate ionic radii.[17]
The RE–OC(O)R bond lengths show considerable variation
˚
with the average value approximately 0.05 A greater than RE–
OH2 or Ce–OSMe2 in the respective complexes despite the
ligand charge. Overall, the , RE–O . bond lengths of the aqua
complexes are in excellent agreement with the corresponding
values of Ce or Nd atoms of the same coordination numbers in
[Ce2(hpp)6(H2O)3] and [NaNd(hpp)7(H2O)(MeOH)][13] com-
plexes, where the mbp chain can be viewed as a functionalised
hpp (Ligand C, Fig. 1).
˚
the RE atoms with RE–O(3) distances of $6.0 A. Hydrogen
bonding is observed between an aqua hydrogen and a carboxyl
oxygen with O10—O10 distances of 2.762(4) A for the
˚
Powder X-ray diffraction (XRD) data from bulk samples of
the [RE(mbp)3(H2O)] (RE ¼ Y, Ce, Nd, Ho, Er) complexes
indicate that they are isomorphous and match the calculated
patterns of the [RE(mbp)3(H2O)] (RE ¼ Ce, Nd) structures
(Fig. 3). Slight differences between the experimental and
simulated patterns are attributable to the considerable tempera-
ture difference between the powder XRD and single-crystal
measurements. The lanthanum complex shows a significantly
different pattern and thus evidently adopts a different structure
in the solid state, possibly due to the larger ionic radius of La3þ
when compared with those of the other rare earth metals.[17] For
example, a change in the coordination of a m-1k(O):2k(O0)
ligand to m-1k(O,O0):2k(O0) would enable 10-coordination to be
attained within the 1D polymer. A structural change from La to
˚
Ce complex and 2.765(6) A for Nd.
˚
Table 1. Bond lengths (A) and angles (8) in [RE(mbp)3(solv)] complexes
Ce(mbp)3(dmso) Ce(mbp)3(H2O) Nd(mbp)3(H2O)
Ln1–O10
Ln1–O2
Ln1–O40
2.457(2)
2.449(2)
2.473(2)
2.751(2)
2.516(2)
2.699(2)
2.538(2)
2.587(2)
2.513(2)
4.3450(2)
105.545(5)
–
2.537(4)
2.430(3)
2.527(3)
2.580(3)
2.656(3)
2.542(3)
2.422(3)
2.551(3)
2.490(3)
4.1305(8)
–
2.488(6)
2.392(6)
2.492(6)
2.556(6)
2.616(6)
2.505(6)
2.407(6)
2.530(6)
2.448(3)
4.0865(8)
–
Ln1–O4
Ln1–O5
Ln1–O7
Ln1–O70
[17]
Ln1–O8
˚
Ce (ionic radius difference of 0.025 A)
is unusual but not
Ln1–O10
Ln1–Ln10
C12–Ce1–C23
C1–Ln1–C12
unknown e.g. for [LnCl3(thf)2][18] and [Ln(Odpp)3] (Odpp ¼ 2,
6-diphenylphenolate).[19] The structural conformity from Ce to
Er is in stark contrast to previously synthesised lanthanoid
carboxylate corrosion inhibitors bearing anthranilate,[20]
169.235(4)
169.1(2)
La
Ce simulated
Ce
Nd simulated
Nd
Er
Y
Ho
5
10
15
20
25
30
35
40
2q [Њ]
Fig. 3. Powder XRD data of bulk samples of the [RE(mbp)3(H2O)] complexes and simulated powder XRD patterns
obtained from [RE(mbp)3(H2O)] single crystal data.

D
C. N. de Bruin-Dickason et al.
cinnamate,[9,10] and salicylate ligands,[21] which show signifi-
cant structural variation across the lanthanoid series.
and a-methylene carbon are absent in the 0–250 ppm range,
probably due to paramagnetic broadening, whereas other signals
appear at similar values observed for the diamagnetic analogues.
Isolation of [Ce(mbp)3(dmso)] from dissolution of the aqua
complex in dmso also suggests retention of mbp ligation in
solution. Paramagnetic shifting was less pronounced for the Ho
and Er complexes in D2O, implying significant displacement of
the mbp ligands by water. However, the complexes have low
solubility in D2O, necessitating ultrasonication and heating to
obtain sufficient concentration in solution for a detectable signal,
potentially assisting ligand dissociation.
Infrared (IR) Spectra
The key features of the IR spectra of the [RE(mbp)3H2O]
complexes are given in Table 2. For the isostructural series [RE
(mbp)3(H2O)] (RE ¼ Y, Ce, Nd, Ho, Er), data are given only for
RE ¼ Ce as the compounds are isospectral (Fig. S1, Supple-
mentary Material). Data for [La(mbp)3(H2O)] differ somewhat
from those of the isostructural series, as is consistent with the
structural difference indicated by X-ray powder data. All com-
plexes show the expected features with ns(C=O) of the carbonyl
not shifted significantly from the sodium salt value, as is con-
sistent with the lack of carbonyl–metal interactions in the
structures. In addition, the nas(CO2) and ns(CO2) bands of the
complexes do not differ much from the values for the sodium
salt, consistent with bridging carboxylates,[22] whereas the
splitting may reflect the two bridging modes.
Conclusions
Six new rare earth 3-(40-methylbenzoyl)propanoate complexes
have been synthesised through either metathesis or protolysis
pathways in high yields and characterised by NMR and IR
spectroscopy, powder XRD, TGA, microanalyses, and metal
1
analyses. The H and 13C NMR spectra of these complexes
suggest that coordination of the carboxylate ligands is maintained
in dmso solution. Additionally, X-ray crystallographic exami-
nation of single crystals of [RE(mbp)3(H2O)] (RE ¼ Ce, Nd, Ho)
and the dmso-coordinated analogue, [RE(mbp)3(dmso)],
revealed a 1D polymeric structure for the complexes with
9-coordinate RE3þ ions. The powder XRD and IR data suggest
that the polymeric structure of [RE(mbp)3(H2O)] complexes is
the same for RE ¼ Y, Ce, Nd, Ho, Er, but the lanthanum analogue
adopts a different structure in the solid state. Investigation of the
potential application of the prepared complexes as corrosion
inhibitors and the mechanism through which they inhibit corro-
sion is ongoing.[15] The evidence from the NMR data that car-
boxylate coordination persists in solution is particularly relevant.
To fully determine the role of the structures on inhibiting corro-
sion, a complete study is required on the influence of the RE on
the anti-corrosion behaviour of the mbp complexes.
NMR Spectra
As complexes with both diamagnetic and paramagnetic rare earth
ions are available, comparison of their 1H and 13C NMR spectra
can provide information on whether the carboxylate ligands are
displaced by donor solvents in solution. Table 3 provides chem-
ical shifts of the methylene groups, which are nearest to the RE3þ
ion, and the methyl groups, which are the most distant from the
RE3þ ion. Similar spectra of both diamagnetic and paramagnetic
analogues would be indicative of substantial carboxylate dis-
placement. In [D6]dmso, the paramagnetic Ce, Nd, Ho, and Er
complexes show major broadening and considerable shifts of the
methylene resonances from the values of the diamagnetic com-
plexes (Table 3), as is consistent with the maintenance of car-
boxylate coordination in solution. However, the methyl
resonance shows minimal broadening and smaller shifts from the
diamagnetic analogues. Additionally, in the 13C NMR spectra of
the Ce and Nd complexes, the signals for the carboxylate carbon
Experimental
General
IR spectra were collected as solid samples using an Agilent Cary
630 attenuated total reflectance (ATR-IR) spectrometer
Table 2. Selected infrared bands (cm21) of the [RE(mbp)3(H2O)]
complexes
1
between 4000 and 600 cmꢀ1. H and 13C NMR spectra were
recorded on either a Bruker DPX300 or a Bruker Avance III 400
spectrometer, and chemical shifts were referenced to the resid-
Complex
Na(mbp)
n(OH)water ns(C=O)
nas(CO2)
1559
ns(CO2)
1399
1
ual H resonances of the deuterated solvents. Melting points
3346, 3235 1683
were determined in glass capillaries and are reported uncali-
brated. Microanalyses were performed by either the Campbell
Microanalytical Service of the University of Otago (New
Zealand) or the Elemental Analysis Service of London Metro-
politan University (UK). Metal analyses were performed by
titration of HCl-digested samples against Na2H2EDTA in hex-
amine-buffered solution with Xylenol orange indicator. TGA
was performed on a Mettler Toledo TGA-DSC1 instrument
using standard 40 mL Al metal pans in the temperature range of
35–4008C (with a ramp of 58C minꢀ1) under nitrogen gas flow
(30 mL minꢀ1). Powder XRD measurements were performed at
room temperature on a Bruker D8 ADVANCE Eco fitted with a
[La(mbp)3(H2O)] 3514, 3463 1681, 1667 1576, 1550, 1526 1435, 1406
[Ce(mbp)3(H2O)] 3455 1692, 1674 1572, 1542 1423, 1400
Table 3. Selected 1H chemical shifts (ppm) of the 3-(49-methylbenzoyl)
propanoate complexes in different solvents
(CD3)2SO
D2O
CH2CO2 CH2CO CH3 CH2CO2 CH2CO CH3
˚
Lynxeye detector using Cu radiation (wavelength ¼ 1.54059 A)
Na(mbp)
2.34
2.39
3.10 2.34
3.11 2.35
3.09 2.35
3.95 2.42
4.35 2.39
17.2 2.83
ꢀ0.13 2.04
2.60
2.52
–
3.36
3.27
–
2.48
2.37
–
with a Ni filter.
[Y(mbp)3(H2O)]
[La(mbp)3(H2O)]
[Ce(mbp)3(H2O)]
[Nd(mbp)3(H2O)]
[Ho(mbp)3(H2O)]
[Er(mbp)3(H2O)]
2.39
3.95
–
–
–
Na(mbp)
4.35
–
–
–
3-(40-Methylbenzoyl)propanoic acid (0.89 g, 4.7 mmol) was
neutralised with sodium hydrogen carbonate (0.39 g, 4.7 mmol)
in a mixture of ethanol (EtOH) and water (1 : 1 v/v). Upon
29.9
3.47
2.26
3.76
3.15
2.46
2.38
ꢀ2.63

Rare Earth 3-(40-Methylbenzoyl)-propanoates
E
evaporation of solvent under a gentle stream of air, Na(mbp) was
recovered as a colourless solid (0.99 g, 99 %), mp 196–1988C.
nmax (neat)/cmꢀ1 3058wbr, 2920wbr, 1683s, 1560s, 1400s,
1357s, 1268m, 1197m, 1179m, 1151m, 982m br, 765s. dH
([D6]dmso, 400.17 MHz) 2.31 (2H, t, CH2COO), 2.34 (3H, s,
CH3), 3.10 (2H, t, CH2CO), 7.27 (2H, d, Ar m-H), 7.84 (2H, d,
Ar o-H). dH ([D2O], 400.17 MHz) 2.31 (3H, s, CH3), 2.61 (2H, t,
CH2COO), 3.36 (2H, t, CH2CO), 7.44 (2H, d, Ar m-H), 7.96
(2H, d, Ar o-H). dC([D6]dmso, 75 MHz) 32.3, 35.5, 128.0, 129.2,
134.7, 143.0, 177.0, 200.0.
400.17 MHz) 2.35 (9H, s, CH3), 2.37 (6H, t, CH2COO), 3.09
(6H, t, CH2CO), 7.28 (6H, d, Ar m-H), 7.83 (6H, d, Ar m-H).
dC([D6]dmso, 75 MHz) 21.5, 31.8, 34.3, 128.3, 129.5, 134.8,
143.5, 183.3, 199.2 ppm. Found: C 53.98, H 4.93, La 19.13.
C33H35LaO10 (730.54) requires C 54.26, H 4.83, La 19.01 %.
[Ce(mbp)3(H2O)]
Method A: Similarly to the synthesis protocol used for
[Y(mbp)3(H2O)], the reaction between Na(mbp) (0.21 m,
0.97 mmol) and CeCl3ꢁ7H2O (0.12 g, 0.32 mmol) yielded [Ce
(mbp)3(H2O)] (0.19 g, 80 %) upon drying as a colourless
powder.
K(mbp)
3-(40-Methylbenzyol)propanoic acid (0.96 g, 4.9 mmol) was
neutralised with potassium carbonate (0.34 g, 2.4 mmol) in a
mixture of EtOH and water (1 : 1 v/v). Upon evaporation of
solvent under a gentle stream of air, K(mbp) was recovered as a
colourless solid (0.99 g, 99 %). nmax (neat)/cmꢀ1 3354w br,
2920wbr, 1678s, 1562s, 1398s, 1357m, 1248m, 1182m,
970mbr, 812s, 793s. dH ([D2O], 400.17 MHz) 2.43 (3H, s,
CH3), 2.69 (2H, t, CH2COO), 3.37 (2H, t, CH2CO), 7.42 (2H,
d, Ar m-H), 7.97 (2H, d, Ar o-H).
Method B: Similarly to the synthesis protocol used for [La
(mbp)3(H2O)] (Method B), the reaction between [Ce
(O2CCH3)3]ꢁH2O (0.16 g, 0.46 mmol) and Hmbp (0.263 g,
1.37 mmol) yielded [Ce(mbp)3(H2O)] as a colourless powder
(0.25 g, 73 %), mp 146–1488C. TGA weight loss calculated for
one H2O: 2.47 %. Found in the range of 80–1308C: 2.31 %. nmax
(neat)/cmꢀ1 3455 wbr, 3068w, 3027vw, 2952vw, 2913wbr,
1695m, 1675m, 1630w, 1607m, 1572m, 1542s, 1423m, 1400s,
1356s, 1300m, 1268w, 1240m, 1203m, 1179m, 1148w, 1110w,
1078w, 1062w, 1040vw, 1011w, 991w, 970m, 894m, 884w,
855w, 842w, 810s, 789s, 728w, 677w, 657w. dH ([D6]dmso,
400.17 MHz) 2.35 (9H, s, CH3), 3.95 (12H, vbr, CH2), 7.32 (6H,
br, Ar m-H), 8.01 (br, 6H, Ar o-H). dC([D6]dmso, 75 MHz) 21.1,
34.5br, 128.0, 129.2, 134.7, 143.1, 199.3 (COOCe and CH2COO
signals were not observed). Found: C 54.06, H 4.85, Ce 19.33.
C33H35CeO10 (731.75) requires C 54.17, H 4.82, Ce 19.15 %.
Single crystals of [Ce(mbp)3(H2O)] were grown from a reaction
mixture filtrate over several months and single crystals of [Ce
(mbp)3(dmso)] were grown from a saturated solution of [Ce
(mbp)3(H2O)] in dmso.
[Y(mbp)3(H2O)]
A freshly prepared solution of Na(mbp) (0.21 g, 0.98 mmol)
in 5 mL of a 1 : 1 EtOH/H2O mixture was added to a stirred
solution of YCl3ꢁ6H2O (0.10 g, 0.33 mmol) in water (4 mL).
Instantly, a colourless precipitate was produced. Stirring was
continued for a further 2 h, then the reaction mixture was
filtered. The colourless residue was washed with H2O
(2 ꢂ 5 mL) and hot EtOH (2 ꢂ 5 mL) to yield [Y(mbp)3(H2O)]
(0.19 g, 85 %) upon drying as a colourless powder, mp
134–1368C. TGA weight loss calculated for one H2O: 2.64 %.
Found in the range of 80–1308C: 2.52 %. nmax (neat)/cmꢀ1
3486wbr, 3027vw, 2915wbr, 1695m, 1678m, 1589s, 1557s,
1433s, 1399s, 1356m, 1297m, 1256w, 1239m, 1218w, 1202m,
1179m, 1110w, 1080w, 1063w, 1038w, 1018w, 994w, 976w,
950w, 890w, 857w, 838w, 817s, 810s. dH ([D6]dmso,
400.17 MHz) 2.35 (9H, s, CH3), 2.39 (6H, t, CH2COO), 3.11
(6H, t, CH2CO), 7.28 (6H, d, Ar m-H), 7.84 (6H, d, Ar o-H). dH
(D2O, 400.17 MHz) 2.37 (9H, s, CH3), 2.52 (6H, t, CH2COO),
3.27 (6H, t, CH2CO), 7.36 (6H, d, Ar m-H), 7.87 (6H, d, Ar o-H).
dC ([D6]dmso, 75 MHz) 21.2, 30.6, 33.8, 56.1, 128.0, 129.2,
134.4, 143.3, 182.9br, 198.8. Found: C 58.12, H 5.16, Y 13.13.
C33H35YO10 (680.54) requires C 58.24, H 5.18, Y 13.06 %.
[Nd(mbp)3(H2O)]
Method A: Similarly to the synthesis protocol used of [Y
(mbp)3(H2O)], the reaction between Na(mbp) (0.12 g,
0.55 mmol) and NdCl3ꢁ6H2O (0.066 g, 0.18 mmol) yielded
[Nd(mbp)3(H2O)] (0.087 g, 65 %) upon drying as a colourless
powder.
Method B: Similarly to the synthesis protocol used for [La
(mbp)3(H2O)] (Method B), the reaction between [Nd
(O2CCH3)3]ꢁH2O (0.10 g, 0.29mmol) and Hmbp (0.17 g,
0.87mmol) yielded [Nd(mbp)3(H2O)] as a colourless powder
(0.14 g, 66%), mp 178–1808C. TGA weight loss calculated for
one H2O: 2.45%. Found in the range of 80–1308C: 2.26%. nmax
(neat)/cmꢀ1 3460wbr, 3027vw, 2915w, 2900w, 1693m, 1675m,
1631w, 1605m, 1576s, 1553s, 1428s, 1400s, 1357s, 1295s,
1264w, 1239m, 1217vw, 1202m, 1181s, 1149vw, 1109vw,
1018w, 970w, 957w, 946vw, 886w, 855w, 813m, 807s, 791m,
678w, 657m. dH ([D6]dmso, 400.17MHz) 2.35 (9H, s, CH3), 4.35
(12H, vbr, CH2), 7.37 (6H, d, Ar m-H), 8.14 (6H, br, Ar o-H). dC
([D6]dmso, 75MHz) 21.6, 38.5vbr, 128.6, 129.7, 135.2, 143.6,
199.9 (COONd and CH2COO signals were not observed). Found:
C 52.71, H 4.79, Nd 19.13. C33H35NdO10 (735.88) requires C
53.86, H 4.82, Nd 19.60 %. Single crystals of [Nd(mbp)3(H2O)]
were grown from a reaction filtrate over several months.
[La(mbp)3(H2O)]
Method A: Similarly to the synthesis protocol used for
[Y(mbp)3(H2O)], the reaction between Na(mbp) (0.21 g,
0.98 mmol) and LaCl3ꢁ6H2O (0.12 g, 0.33 mmol) yielded [La
(mbp)3(H2O)] (0.20 g, 85 %) upon drying as a colourless
powder.
Method B: [La(O2CCH3)3]ꢁH2O (0.11 g, 0.35 mmol) in 3 : 1
EtOH/H2O was treated with an EtOH solution of Hmbp (0.21 g,
1.13 mmol), resulting in formation of a colourless precipitate,
which was washed with H2O (5 mL) and EtOH (2 ꢂ 5 mL) and
dried in a desiccator to yield [La(mbp)3(H2O)] as a colourless
powder (0.20 g, 83 %), mp 194–1958C. TGA weight loss calcu-
lated for one H2O: 2.46 %. Found: 1.51 %. nmax (neat)/cmꢀ1
3514wbr, 3463wbr, 3058vw, 3026vw, 2913wbr, 1683m,
1670m, 1605m, 1572m, 1551s, 1531s, 1518m, 1431s, 1405s,
1356m, 1300w, 1240m, 1200m, 1186m, 781w, 976w, 950w,
890m, 863w, 845w, 812s, 787w, 684w, 654w. dH ([D6]dmso,
[Ho(mbp)3(H2O)]
Similarly to the synthesis protocol used for [Y(mbp)3(H2O)],
the reaction between Na(mbp) (1.68 g, 7.92 mmol) and
HoCl3ꢁ6H2O (1.00 g, 2.64 mmol) yielded [Ho(mbp)3(H2O)] as
a light pink powder (1.72 g, 86 %), mp 1548C. TGA weight loss

F
C. N. de Bruin-Dickason et al.
calculated for one H2O: 2.38 %. Found in the range of 80–
1308C: 2.04 %. nmax (neat)/cmꢀ1: 3482wbr, 2912wbr, 1692m,
1675m, 1587s, 1556s, 1432s, 1399s, 1356m, 1296m, 1239m,
1202m, 1179m, 971w, 890s, 857s. dH ([D6]dmso, 400.17 MHz)
2.83 (9H, s, CH3), 8.03 (6H, brs, m-H), 10.3 (6H, brs, o-H), 17.2
(too broad for a satisfactory integration, vbr, CH2CO), 29.9 (too
broad for satisfactory integration, v br, CH2COO). dH(D2O,
400.17 MHz) 2.46 (9H, s, CH3), 3.43 (6H, br, CH2COO), 3.76
(6H, br, CH2CO), 7.28 (6H, br, Ar m-H), 7.84 (6H, br, Ar o-H).
Found: C 51.99, H 4.96, Ho 21.70. C33H35HoO10 (756.56)
requires C 52.39, H 4.66, Ho 21.80 %. Single crystals were
grown in a H-tube, with the metathesis reactants in separate
arms.
[Nd(mbp)3(H2O)]
C33H35NdO10,
M
735.85 g molꢀ1
, colourless needle,
0.02 ꢂ 0.001 ꢂ 0.001 mm3, monoclinic, space group P21/c (no.
14), a 33.007(7), b 12.000(2), c 7.8650(16), b 92.49(3)8,
,
3
V 3112.3(11) A , Z 4, Dc 1.570 g cmꢀ3, T 100 K, m 1.726 mmꢀ1
˚
44512 reflections measured (2.468 # 2y # 52.048), 6105 unique
(Rint 0.0685, Rs 0.0335) which were used in all calculations. The
final R1 was 0.0651 (.2s(I)) and wR2 was 0.1528 (all data).
Refinement details: crystals consistently grew as twinned needles.
Even upon breaking off a very small piece for the analysis run
using a synchrotron light source, some twinning of the data was
observed leading to a large residual Q peak near the Nd site though
after partially accounting for twinning using the TWIN command
(BASF¼ 0.0146(9)), which significantly improved the model.
DFIX commands were used to model the hydrogen atoms on the
[Er(mbp)3(H2O)]
˚
Similarly to the synthesis protocol used for [Y(mbp)3(H2O)],
the reaction between Na(mbp) (1.68 g, 7.92 mmol) and
ErCl3ꢁ6H2O (1.00 g, 2.62 mmol) yielded [Er(mbp)3(H2O)]
(1.58 g, 79 %) as a light pink powder, mp 1588C. TGA weight
loss calculated for one H2O: 2.37 %. Found in the range of
80–1308C: 2.44 %. nmax (neat)/cmꢀ1 3489wbr, 2942wbr,
1693m, 1676m, 1590s, 1557s, 1433s, 1399s, 1356m, 1296m,
1238m, 1202m, 1179m, 972w, 815s, 807s. dH([D6]dmso,
400.17 MHz) ꢀ2.65 (,6H, vbr, CH2COO), ꢀ0.13 (,6H, vbr,
CH2CO), 2.04 (9H, br, CH3), 6.8–7.25 (12H, complex, Ar-H).
dH (D2O, 400.17 MHz) 2.26 (6H, br, CH2COO), 2.38 (9H, brs,
CH3), 3.15 (6H, br, CH2CO), 7.36 (6H, br, Ar m-H), 7.90 (6H,
br, Ar o-H). Found: C 51.90, H 4.96, Er 21.80. C33H35ErO10
(758.89) requires C 52.23, H 4.65, Er 22.04 %.
water, with the bond distances set to 0.86 A.
[Ce(mbp)3(dmso)]
C35H39CeO10S, M 791.84 g molꢀ1, colourless prism,
0.20 ꢂ 0.08 ꢂ 0.08 mm3, monoclinic, space group C2/c (No.
˚
15), a 44.818(2), b 8.3296(4), c 18.5763(12) A, b 105.075(6)8,
V 6696.2(6) A , Z 8, Dc 1.571 g cmꢀ3, F000 ¼ 3224, Xcalibur,
3
˚
˚
Ruby, Gemini ultra, Mo Ka radiation, l 0.71073 A, T 123(2)
K, 2ymax ¼ 55.08, 24577 reflections collected, 7666 unique
(Rint ¼ 0.0542). Final GooF 1.042, R1 0.0368, wR2 0.0707,
R indices based on 5692 reflections with I . 2s(I) (refinement
on F2), 429 parameters, 0 restraints. Lp and absorption correc-
tions applied, m 1.480 mmꢀ1
.
Supplementary material
X-Ray Crystallography Data
IR and NMR spectra are available on the Journal’s website.
All samples were coated in viscous oil and mounted in a cryo-
stream on the respective diffractometers: a Bruker APEX II
CCD diffractometer ([Ce(mbp)3(dmso)]), with integration and
absorption corrections completed using Apex II program
suite,[23] and the MX1 ([Ho(mbp)3(H2O)]) and MX2 ([Ce
(mbp)3(H2O)] and [Nd(mbp)3(H2O)]) macromolecular beam-
lines at the Australian Synchrotron, where the data and inte-
gration were completed by Blu-ice[24] and XDS[25] software
programs, respectively. Structural solutions were obtained by
Direct methods[26] and refined using full matrix least-squares
methods against F2 using SHELX97[26] within the OLEX 2[27]
interface. Collection temperatures and further details are sup-
plied in the information below. Crystallographic data (excluding
structure factors) for the structures reported in this paper have
been deposited at the Cambridge Crystallographic Data Centre
as supplementary numbers CCDC 1505758, 1505762, and
1505823. Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge, CB2 1EZ,
UK (fax: þ44 (0) 1223 336033; email: deposit@ccdc.cam.
ac.uk).
Acknowledgements
We acknowledge initial funding from the Australian Research Council
through the Centre for Green Chemistry. The authors thank Dr Finlay Shanks
for assistance with thermogravimetric analysis. Part of this work was
undertaken on the MX1 and MX2 beamlines at the Australian Synchrotron,
Victoria, Australia.[28] Powder XRD measurements were conducted using
the facilities within the Monash X-ray Platform. CdeBD thanks the Aus-
tralian government for the award of an Australian Postgraduate Award
(APA). SH acknowledges support from the DAAD and the University of
Leipzig.
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