Some complexes derived from zinc salicylate or 3,5-di-tert-butylsalicylate. The crystal structure of (2,2′-bipyridyl)(methanol)(O-salicylato)(O,O′-salicylato)zinc

Article abstract of DOI:10.1016/S0020-1693(98)00421-6

The aqua ligands of diaquabis(salicylato)zinc and diaquabis(3,5-di-tert-butylsalicylato)zinc are easily displaced generating related bis-pyridine and 2,2′-bipyridyl complexes. Attempts to recrystallise the tert-butylsalicylate from ethanol resulted in rep

Full text of DOI:10.1016/S0020-1693(98)00421-6

Inorganica Chimica Acta 287 (1999) 89–94
Some complexes derived from zinc salicylate or
3,5-di-tert-butylsalicylate. The crystal structure of
(2,2%-bipyridyl)(methanol)(O-salicylato)(O,O%-salicylato)zinc
Nicholas J. Brownless, Dennis A. Edwards *, Mary F. Mahon
Department of Chemistry, Uni6ersity of Bath, Bath BA2 7AY, UK
Received 2 September 1998; accepted 20 November 1998
Abstract
The aqua ligands of diaquabis(salicylato)zinc and diaquabis(3,5-di-tert-butylsalicylato)zinc are easily displaced generating
related bis-pyridine and 2,2%-bipyridyl complexes. Attempts to recrystallise the tert-butylsalicylate from ethanol resulted in
replacement of the aqua ligands by ethanol ligands. The attempted recrystallisation of (2,2%-bipyridyl)bis(salicylato)zinc from
methanol led to the isolation of octahedral [Zn(O2CC6H4OH-2)2(bipy)(MeOH)] in which one salicylato ligand is coordinated in
a monodentate fashion and the other in a bidentate chelating manner, both coordination modes involving carboxylate rather than
hydroxyl oxygen coordination. The methanol is strongly bonded trans to a nitrogen of the chelating 2,2%-bipyridyl and three
further intramolecular six-membered hydrogen bonded rings are present, generated from interactions between the carboxyl and
hydroxyl groups of the salicylate ligands and the hydroxyl group of the methanol ligand. © 1999 Elsevier Science S.A. All rights
reserved.
Keywords: Crystal structures; Zinc complexes; Salicylate complexes
of the type [Zn3(t-Bu2salH)5(CVL)]+[t-Bu2salH]− may
1. Introduction
be involved [2] (t-Bu2salHꢀ2-HO-3,5-t-Bu2C6H2CO2−).
Various zinc carboxylates are known to possess mild
antiseptic and fungistatic properties and have also been
used, for example, as catalysts, wood preservatives,
waterproofing agents, auxilliary drying agents in paints,
hardeners in varnishes and as processing lubricants and
anti-stick agents in the rubber and plastics industries
[1]. In particular, zinc salicylate has been approved by
the US Food and Drug Administration for use as an
anti-oxidant and stabiliser for polymers. Zinc salicylate
and a number of substituted salicylates have also been
employed in the coatings on paper used in carbonless
copying paper. In this application, the zinc salicylates
are known to be involved in the reactions of the
colour-formers but their detailed role is not well under-
stood. It has been suggested, for example, that with the
colour-former Crystal Violet Lactone (CVL) a species
In order to provide some more definitive information
on the nature of the products formed between zinc
salicylates and ligands we have investigated reactions of
the parent salicylate and the 3,5-di-tert-butyl derivative
with some simple neutral donor ligands. From a coordi-
nation standpoint, salicylate is a versatile ligand, dis-
playing a variety of bonding modes. For example,
mono-deprotonation of salicylic acid normally leads to
compounds containing the coordinated 2-HOC6-
H4CO2−, (salH−), anion. This anion is known to bond
to metals as a unidentate carboxylate e.g. in [Zn(-
salH)2(H2O)2] [3], as a bidentate chelating carboxylate
e.g. in [Cd(salH)2(py)3] [4], as a bidentate chelating
ligand using one carboxylate oxygen and the hydroxyl
oxygen e.g. in [Cu(salH)2] · 2H2O [5] and as a bidentate
bridging carboxylate ligand e.g. in [Rh(salH)(cod)]2 [6].
Indeed, in [Y2(salH)6(H2O)4] · 4H2O two salH− ligands
are chelating, two are bridging and two are simulta-
neously chelating and bridging [7]. Uniquely, an exam-
* Corresponding author. Tel.: +44-1225-826 826; fax: +44-1225-
826 231.
E-mail address: d.a.edwards@bath.ac.uk (D.A. Edwards)
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(98)00421-6

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N.J. Brownless et al. / Inorganica Chimica Acta 287 (1999) 89–94
ple is also known [8], [pyH][MoO2(salH)(sal)], in which
the salH− ligand arises by deprotonation of the hy-
droxyl rather than the carboxyl proton and so involves
the HO2CC6H4O− anion.
Finally both the hydroxyl and carboxyl protons can
be lost from the parent acid to generate the
[OC6H4CO2]2− anion, (sal2−) which seems to be invari-
ably chelating through the hydroxyl and one of the
carboxyl oxygens as in [Mn(sal)2(bipy)] [9] although in
at least one compound, [Mn(EtOH)4][Mn2(sal)4(py)2], it
has been established that two of the four salicylate
ligands additionally bridge to the second metal of the
complex anion [10].
sodium hydroxide solution (16.0 cm3) with heating. A
solution of anhydrous zinc chloride (2.05 g, 16 mmol)
in water (15 cm3) was then added dropwise giving a
thick gel to which was added a further 50 cm3 of water.
The crude product was filtered and purified by recrys-
tallisation from a large volume of aqueous ethanol in
which the product was slightly soluble. The resulting
crystals were filtered, washed with a little ice-cold
ethanol and diethyl ether before drying in air. Yield: 4.3
g, 45%. (Found: C, 60.5; H, 7.5. C30H46O8Zn requires:
1
C, 60.1; H, 7.7%). NMR (d6-DMSO) H l 1.28 (s, 9H,
3-t-Bu), 1.40 (s, 9H, 5-t-Bu), 7.37 (d, H4, J4,6=3.0 Hz),
7.78 (d, H6). IR (cm−1) major bands only: 3185 m,br
w(OH), 1618 m, 1560 s, 1543 s w(CC)+wasym(CO2)+
l(HOH), 1377 ms, 1364 ms wsym(CO2)+l(CH3), 812 m
(CO2 bend).
2. Experimental
2.3. Bis(ethanol)bis(3,5-di-t-butylsalicylato)zinc
IR spectra were recorded as Nujol mulls using
Perkin-Elmer 597 and Nicolet 510P spectrophotome-
ters. Microanalyses were carried out using a Carlo-Erba
microanalyser. A Jeol GX 270 spectrometer was used
to obtain 1H and 13C NMR spectra. Thermal decompo-
sitions in air were studied using a Stanton thermogravi-
metric balance with a heating rate of 4°C per minute. A
FAB mass spectrum of zinc salicylate dihydrate was
recorded on a VG 7070E spectrometer using a p-ni-
trobenzyl alcohol matrix.
Reaction of the above dihydrate with a large volume
of refluxing anhydrous ethanol followed by recrystalli-
sation from ethanol gave the bis(ethanol) product.
(Found: C, 62.4; H, 8.3. C34H54O8Zn requires: C, 62.3;
1
H, 8.2%). NMR (d6-DMSO) H l 1.08 (t, CH3CH2OH,
6H, J=6.75 Hz), 1.29 (s, 3-t-Bu, 9H), 1.39 (s, 5-t-Bu,
9H), 3.46 (q, CH3CH2OH, 4H, J=6.75 Hz), 7.37 (d,
H4, J4,6=3.0 Hz), 7.78 (d, H6); 13C{1H} l 18.7
(CH3CH2OH), 29.5, 31.6 [(CH3)3C], 34.0, 34.8
[(CH3)3C], 56.2 (CH3CH2OH), 115.6 (C1–CO2), 124.9,
127.7 (C4, C6 aryl), 135.6, 138.8 (C3, C5 aryl), 158.3
(C2–OH), 175.2 (CO2).
2.1. Diaquabis(salicylato)zinc
An aqueous solution of sodium salicylate was pre-
pared by adding salicylic acid (4.0 g, 29 mmol) to a 2 M
sodium hydroxide solution (14.5 cm3). This solution
was added dropwise with stirring to a solution of
anhydrous zinc chloride (1.97 g, 14.5 mmol) in water
(15 cm3). On standing the product precipitated and was
removed by filtration, washed with a little ice-cold
water and recrystallised from a concentrated aqueous
solution. The pure product was washed with ice-cold
ethanol then diethyl ether before drying in air. Yield:
4.1 g, 75%. (Found: C, 44.8; H, 3.7. C14H14O8Zn re-
2.4. Bis(pyridine)bis(salicylato)zinc
Pyridine (1.6 cm3, 20 mmol) was added dropwise
with stirring to a solution of diaquabis(salicylato)zinc
(3.75 g, 10 mmol) in ethanol (20 cm3). A colourless
precipitate formed over a period of 24 h and was then
filtered, washed with ice-cold ethanol and dried in air.
The product was recrystallised from hot ethanol. Yield:
1.3 g, 26%. (Found: C, 58.0; H, 3.9; N, 5.6.
C24H20N2O6Zn requires: C, 57.9; H, 4.0; N, 5.6%). IR
(cm−1) selected bands: 1632 m, 1604 s, 1580 sh, 1565 s,
1
quires: C, 44.8; H, 3.7%). NMR (CD3CN), H l 7.89
(dd, H6, J5,6=7.5 Hz, J4,6=1.5 Hz), 7.39 (dt, H4,
1540 ms w(CC)+wasym(CO2)+py bands, 1375
wsym(CO2), 585 s (CO2 bend), 420 s (py), 270, 235 m
w(ZnN).
m
J
4,5=7.5 Hz, J3,4=7.5 Hz), 6.83 (overlapping d+t, H3
and H5), (Hn are labelled around the phenyl ring from
the 2-hydroxy position); 13C{1H} l 116.4, 117.6, 118.0
and 119.3 (C3–C6 aryl), 135.4 (C1–CO2), 162.0 (C2–
OH), 175.3 (CO2). IR (cm−1) major bands only: 3290
m,br w(OH), 1619 m, 1595 s, 1570 m w(CC)+
wasym(CO2)+l(HOH), 1335 m wsym(CO2), 1232 s (OH
bend), 865 m (CO2 bend), 663 (CO2 bend).
2.5. Bis(pyridine)bis(3,5-di-t-butylsalicylato)zinc
A similar reaction to that above using the 3,5-di-t-
butylsalicylate dihydrate (6.0 g, 10 mmol) and pyridine
(1.6 cm3, 20 mmol) in ethanol gave the required
product. Yield: 6.4 g, 89%. (Found: C, 66.0; H, 7.3; N,
3.6. C40H52N2O6Zn requires: C, 66.5; H, 7.2; N, 3.9%).
IR (cm−1) selected bands: 1620 m, 1607 m, 1570 s
w(CC)+wasym(CO2)+py bands, 1379 s wsym(CO2), 562
mw, 538 m, 520 w, 426 ms (py bands).
2.2. Diaquabis(3,5-di-t-butylsalicylato)zinc
A solution of sodium 3,5-di-t-butylsalicylate was pre-
pared by dissolving the acid (8.0 g, 32 mmol) in a 2 M

N.J. Brownless et al. / Inorganica Chimica Acta 287 (1999) 89–94
91
3
˚
˚
2.6. (2,2%-Bipyridyl)bis(salicylato)zinc
16.614(5) A, i=91.99(3)°, V=2356.1 A , Z=4,
D
calc=1.49 g cm−3, v=10.9 cm−1, F(000)=1088.
Diaquabis(salicylato)zinc (3.75 g, 10 mmol) in
ethanol (20 cm3) was added to a solution of 2,2%-
bipyridyl (1.56 g, 10 mmol) in ethanol (10 cm3). The
creamy yellow precipitate, which completely formed
within 10 min, was filtered, washed with ice-cold
ethanol and recrystallised from ethanol before drying in
air. Yield: 3.3 g, 67%. (Found: C, 58.0; H, 3.6; N, 5.7.
C24H18N2O6Zn requires: C, 58.2; H, 3.6; N, 5.7%).
Data were collected at room temperature (r.t.), 293(2)
K, on a Hilger and Watts Y 290 four-circle diffrac-
tometer in the range 2.00BqB22.00° using Mo Ka
˚
(0.71069 A) radiation. A crystal of dimensions 0.3×
0.3×0.25 mm was cut from a large block and used for
data collection. The index ranges were −135h50,
−115k50 and −175l517.
The diffraction intensities were corrected for Lorentz
and polarisation effects but not for absorption. The
structure was solved by Patterson methods and refined
using the SHELX suite of programs [11]. A total of 3218
reflections were measured of which 2001 were unique
with I]2|(I). Hydrogen atoms were included at calcu-
lated positions throughout, except for the methanol
hydroxy proton which was located in the penultimate
refinement cycle. This hydrogen H(7) was refined at a
1
NMR (d6-DMSO) H l 6.77 (overlapping d+t, H3+
H5 of salicylate, J3,4=J4,5=J5,6=4.0 Hz), 7.30 (dt, H4
of salicylate, J4,6=0.7 Hz), 7.75 (t, H4 and H4% of bipy,
J
3,4=J4,5=3.7 Hz), 7.80 (dd, H6 of salicylate), 8.26 (dt,
H5 and H5% of bipy, J4,5=J5,6=3.7 Hz, J3,5=0.7 Hz),
8.65 (d, H3 and H3% of bipy, J3,4=3.7 Hz), 8.81 (d, H6
and H6% of bipy, J5,6=3.7 Hz); 13C{1H} l 116.4, 117.6,
117.8, 117.9, 122.2, 126.8, 130.8, 133.4 (C3–C6 salicy-
late, C–CO2, C3–C5 bipy), 141.1, 148.9 (C2 and C6
bipy), 161.3 (C–OH), 173.3 (CO2). IR (cm−1) selected
bands, 1628 s, 1597 s, 1551 br,s w(CC)+wasym(CO2)+
bipy bands, 560 s (CO2 bend), 471 mw, 436 m, 324 w
(bipy), 237 w(ZnN).
˚
distance of 0.82 A from O(7). In the final least-squares
cycles all atoms were allowed to vibrate anisotropically.
Final residuals after ten cycles of least-squares were
R1=0.0742, wR2=0.1887, for a weighting scheme of
w=1/[|2(Fo)2+(0.0960P)2+(12.1164)P] where P=
2
2 3
(Fo +2Fo ) . The maximum and minimum residual
densities were 0.963 and −1.256 e A−3, respectively.
2.7. (2,2%-Bipyridyl)bis(3,5-di-t-butylsalicylato)zinc
˚
Selected bond lengths and angles are given in Table 1.
The molecular structure, produced using ORTEP [11], is
shown, together with the labelling scheme in Fig. 1.
A similar reaction to that above using the di-t-butyl-
salicylate dihydrate (6.0 g, 10 mmol) and 2,2%-bipyridyl
(1.56 g, 10 mmol) in ethanol gave the desired product.
Yield: 5.7 g, 79%. (Found: C, 66.8; H, 7.0; N, 3.8.
C40H50N2O6Zn requires: C, 66.7; H, 7.0; N, 3.9%). IR
(cm−1) selected bands, 1610 sh, 1600 m, 1572 m, 1560
sh, 1551 s w(CC)+wasym(CO2)+bipy bands, 545 m
(CO2 bend), 475 w, 420 m, 410 sh (bipy).
3. Results and discussion
Although initially incorrectly formulated as a trihy-
drate [12], the hydrated form of zinc salicylate has been
shown crystallographically [3] to be the dihydrate with
a distorted tetrahedral array around the metal compris-
ing oxygens from two water ligands and two unidentate
monoanionic salicylate ligands. The salicylates are
bonded through a carboxylate oxygen, this being the
commonest mode of coordination for mono-deproto-
nated salicylic acid. The crystal structure is completed
by an extensive three-dimensional hydrogen bonded
array involving intermolecular water-2-hydroxy and
water-carboxylate O···H···O interactions, in addition to
strong intramolecular hydrogen bonding involving the
hydroxy and carboxylate groups of an individual salicy-
late ligand generating an additional six-membered ring.
The 3,5-di-t-butylsalicylate dihydrate, prepared in
this work, is thought to assume a related tetrahedral
structure as indicated by NMR and IR data [13].
Furthermore new zinc salicylate and 3,5-di-t-butylsali-
cylate complexes can be prepared by the facile displace-
ment of the water ligands from the two dihydrates. The
3,5-di-t-butylsalicylate dihydrate is simply converted
into a bis(ethanol) derivative by attempted recrystallisa-
2.8. (2,2%-Bipyridyl)(methanol)(O-salicylato)-
(O,O%-salicylato)zinc
Attempts to grow single crystals of (2,2%-
bipyridyl)bis(salicylato)zinc from ethanol for an X-ray
crystallographic study gave only hollow or twinned
crystals. Good quality crystals could, however, be
grown from methanol but analytical data and IR spec-
troscopic information indicated that a further reaction
had occurred leading to [Zn(salH)2(bipy)(MeOH)], as
was subsequently confirmed by a crystallographic
study. (Found: C, 56.5; H, 4.1; N, 5.3. C25H22N2O7Zn
requires: C, 56.8; H, 4.2; N, 5.3%). IR (cm−1) selected
bands, 1626 m, 1593 s, 1580 s, w(CC)+wasym(CO2)+
bipy bands.
2.9. X-ray crystallography
Crystal data: C25H22N2O7Zn, M 527.8, monoclinic,
space group P21/n, a=13.289(4), b=10.678(7), c=

92
N.J. Brownless et al. / Inorganica Chimica Acta 287 (1999) 89–94
Table 1
[Zn(salH)(NBA)]+ and 571, 64% [Zn2(sal)(NBA)2]+
are of high abundance, as are ions containing only
various combinations of zinc and salicylate e.g. m/z
201, 63% [Zn(salH)]+; 338, 98% [Zn(salH)2]+; 402,
65% [Zn2(salH)2]+; 539, 70% [Zn2(salH)3]+. However,
no fragments containing zinc in combination with wa-
ter are detected. Only ions with abundances of at least
40% of the most abundant metal-containing ion have
been listed above, with all m/z values relating to the
64Zn isotope.
Reactions of the salicylate and the 3,5-di-t-butylsali-
cylate dihydrates with pyridine or 2,2%-bipyridyl in
ethanol at r.t. displace the water ligands affording the
corresponding bis-pyridine or 2,2%-bipyridyl complexes
in high yields. The four compounds are most likely to
involve tetrahedral zinc with ZnO2N2 cores, the car-
boxylates being unidentate. The water ligands were not
displaced by triphenylphosphine using ethanol or iso-
propanol as reaction media.
The [Zn(salH)2(bipy)] complex was studied in a little
more depth. A thermogravimetric study carried out in
air showed that the product is stable to around 260°C
when loss of 2,2%-bipyridyl commenced, a process com-
plete by 340°C. Decomposition of the remaining anhy-
drous zinc salicylate left the oxide, a process complete
by 670°C. Attempts to recrystallise [Zn(salH)2(bipy)]
from ethanol were unsuccessful, but crystals suitable for
an X-ray crystallographic study were obtained from
methanol. However, IR spectroscopy and microanalysis
showed that methanol had reacted with the complex to
generate [Zn(salH)2(bipy)(MeOH)]. This was confirmed
by the crystallographic study which showed (Fig. 1)
that tetrahedral [Zn(salH)2(bipy)] had been converted
˚
Selected bond lengths (A) and angles (°) for [Zn(salH)2(bipy)(MeOH)]
˚
Bond lengths (A)
Zn(1)–N(1)
Zn(1)–N(2)
Zn(1)–O(1)
Zn(1)–O(2)
Zn(1)–O(4)
Zn(1)–O(7)
2.042(8)
2.147(7)
2.126(7)
2.305(7)
2.022(6)
2.146(6)
C(1)–O(1)
C(1)–O(2)
C(1)–C(2)
C(3)–O(3)
C(25)–O(7)
O(4)–C(8)
O(5)–C(8)
C(8)–C(9)
O(6)–C(10)
H(3)…O(1)
H(6)…O(5)
H(7)…O(5)
1.268(14)
1.255(14)
1.490(13)
1.367(13)
1.433(12)
1.271(11)
1.259(10)
1.480(13)
1.360(10)
1.88(7)
O(1)…O(3)
O(5)…O(6)
O(5)…O(7)
2.58(1)
2.54(1)
2.61(9)
1.85(1)
1.53(7)
Bond angles (°)
N(1)–Zn(1)–N(2)
77.3(3)
N(2)–Zn(1)–O(1)
N(2)–Zn(1)–O(2)
N(2)–Zn(1)–O(4)
N(2)–Zn(1)–O(7)
O(7)–Zn(1)–O(1)
O(7)–Zn(1)–O(4)
Zn(1)–O(1)–C(1)
Zn(1)–O(2)–C(1)
Zn(1)–O(7)–C(25)
O(4)–Zn(1)–O(2)
94.8(3)
92.3(3)
93.3(3)
171.6(3)
91.6(3)
90.2(3)
93.7(7)
86.0(6)
125.8(6)
164.2(3)
N(1)–Zn(1)–O(1) 151.2(3)
N(1)–Zn(1)–O(2) 93.1(3)
N(1)–Zn(1)–O(4) 102.6(3)
O(7)–Zn(1)–N(1)
O(1)–Zn(1)–O(2)
O(1)–C(1)–O(2)
O(4)–C(8)–O(5)
94.5(3)
59.2(3)
120.7(9)
123.3(9)
Zn(1)–O(4)–C(8) 132.8(6)
O(7)–Zn(1)–O(2)
O(3)–H(3)–O(1)
O(6)–H(6)–O(5)
O(7)–H(7)–O(5)
86.3(2)
143(7)
142(1)
159(7)
tion from refluxing ethanol. Further indication that
water is easily substituted comes from the FAB mass
spectrum of the salicylate dihydrate recorded using a
p-nitrobenzyl alcohol matrix. Metal-containing ions
which include the matrix molecule e.g. m/z 354, 100%,
Fig. 1. Molecular structure of [Zn(salH)2(bipy)(MeOH)] showing labelling scheme. Thermal ellipsoids are at the 30% probability level.

N.J. Brownless et al. / Inorganica Chimica Acta 287 (1999) 89–94
93
˚
into an octahedral product. The distorted octahedral
array has been achieved by coordination of a methanol
molecule and the conversion of one of the monodentate
salicylate ligands into a bidentate chelating carboxylate.
The core of the complex therefore involves a cis-
ZnO4N2 arrangement. The shortest Zn–O interaction is
that between the metal and oxygen O(4) of the
distance being 2.58(1) A. The intramolecular hydrogen
bonding between the carboxylate oxygen and the 2-hy-
droxy group in salicylic acid itself [19] and in zinc
salicylate dihydrate [3] results in O···O distances of 2.62
˚
and 2.51 A, respectively.
The outcome of this hydrogen bonding in the 2,2%-
bipyridyl complex is the generation of two sets of three
fused and essentially planar ring systems. The first set
comprises three six-membered rings viz. the C(9)–C(14)
phenyl ring, the hydrogen bonded ring within the
monodentate salicylate and the hydrogen bonded ring
mutually generated from the salicylate and the
methanol ligands. The second set comprises two six-
membered and one four-membered fused rings the
C(2)–C(7) phenyl ring, the hydrogen bonded ring
within the chelating salicylate and the Zn-chelating
carboxylate ring. The extensive hydrogen bonding in-
volving O(5) is undoubtedly the reason why the C(8)–
O(5) bond length (1.26(1) A) is almost identical to the
C(8)–O(4) bond length (1.27(1) A), even though the
former is formally a double bond. The internal hydro-
gen bonding leads to the essential planarity of both
salicylate ligands, irrespective of their different coordi-
nation modes.
˚
monodentate salicylate (2.022(6) A), essentially identi-
cal to that found [3] in tetrahedral [Zn(salH)2(H2O)2],
˚
(2.03 A), but slightly shorter than that found [14] in
˚
octahedral trans-[Zn(p-NO2salH)2(H2O)4], (2.047(1) A).
The Zn–O(1) and Zn–O(2) distances of 2.126(7) and
˚
2.305(7) A, respectively, show that the chelating salicy-
late ligand is bonding in a significantly asymmetric
manner. Other zinc-chelating carboxylate species dis-
play more symmetrical chelation, e.g. octahedral
[Zn(O2CMe)2(H2O)2] with Zn–O distances of 2.179(4)
˚
and 2.189(5) A, respectively [15]. The acute O(1)–Zn–
˚
O(2) angle of 59.2(3)° is as expected for a four-mem-
bered metal carboxylate ring. For example, the
corresponding angle in [Zn(O2CMe)2(H2O)2] is 59.0°
[15]. The O(1)–C(1)–O(2) angle of 120.7(9)° is also in
the expected range for a chelating carboxylate system.
The acute O(1)–Zn–O(2) and to a lesser extent the
N(1)–Zn–N(2) angles resulting from the chelating sali-
cylate and 2,2%-bipyridyl ligands are the major influ-
ences on distortion from regular octahedral geometry.
The N(1)–Zn–N(2) angle of 77.3(3)° is very much in
line with those found for other zinc-2,2%-bipyridyl com-
plexes [16–18]. Similarly, the Zn–N bond lengths of
˚
4. Supplementary material
Additional material is available from the Cambridge
Crystallographic Data Centre and comprises final frac-
tional coordinates, thermal parameters, hydrogen atom
coordinates and a complete listing of bond lengths and
angles and inter and intramolecular distances. Copies of
this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (Fax: +44-1223-336-033; e-mail: de-
posit@ccdc.cam.ac.uk or www: http://www.ccdc.
cam.ac.uk).
˚
2.042(8) and 2.147(7) A are in agreement with those
found [16–18] in zinc-2,2%-bipyridyl complexes, all be-
˚
ing in the range 2.086–2.151 A. The Zn–O(7) bond
˚
length of 2.146(6) A and the opening of the Zn–O(7)–
C(25) angle of 125.8(6)° clearly show that the methanol
is strongly coordinated to the metal and not merely
present as solvent of crystallisation. A significant struc-
tural feature is the generation of three further six-mem-
bered ring systems by intramolecular hydrogen
bonding.
References
Although the significant protons associated with the
hydroxy groups of the two salicylate anions were not
located, the presence of hydrogen bonding can be in-
ferred from the short O···O distances. The uncoordi-
nated carboxyl oxygen O(5) of the monodentate
salicylate is not only involved in a quasi-aromatic hy-
drogen bonded ring within this salicylate group utilising
C(8), C(9), C(10), O(6) and the ortho-hydroxy proton
attached to O(6), but also assists in the generation of a
second ring involving Zn, O(4), C(8) and O(5) of the
salicylate ligand and O(7) and its attached proton of the
methanol ligand. The respective O(5)···O(6) and
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˚
O(5)···O(7) distances are 2.54(1) and 2.61(9) A, respec-
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2
(1991)
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.