Synthesis and structure of diamine bis(phenolate) complexes containing the Ti(OEt)-O-Ti(OEt) function

Article abstract of DOI:10.1016/j.poly.2010.02.006

Reaction of diamine-bis(phenol) ligands containing a mixture of N-methyl and N,N′-dimethyl-N,N-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine , H₂L¹ and H₂L³, with [Ti(OCHMe₂)₄ in absolut

Full text of DOI:10.1016/j.poly.2010.02.006

Polyhedron 29 (2010) 1715–1726
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Polyhedron
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Synthesis and structure of diamine bis(phenolate) complexes containing
the Ti(OEt)–O–Ti(OEt) function
*
Alastair J. Nielson , Joyce M. Waters
Chemistry, Institute of Natural Sciences, Massey University at Albany, Private Bag 102904, North Shore Mail Centre, Auckland, New Zealand
a r t i c l e i n f o
a b s t r a c t
Reaction of diamine-bis(phenol) ligands containing a mixture of N-methyl and N,N0-dimethyl-N,N-bis(2-
hydroxy-3,5-dimethylbenzyl)ethylenediamine, H2L1 and H2L3, with [Ti(OCHMe2)4 in absolute ethanol
under reflux without exclusion of air and moisture gives [(L1)Ti (OEt–O–Ti(OEt)(L1)] (1). [(L3)Ti(OEt)–
O–Ti(OEt)(L3)] (2) forms when the remaining solution containing [(L3)Ti(OEt)2] (3) (characterised by X-
ray crystallography) is hydrolysed with H2O. For the N-methyl and N,N0-dimethyl ligand mixture H2L2
and H2L4, which contain tert-butyl groups on the ortho-positions of the aryl rings, [(L2)Ti(OEt)–O–
Ti(OEt)(L2)] (4) forms much more slowly and [(L4)Ti(OEt)2] (5) does not hydrolyse when H2O is added.
When the N-protonated ligand N,N-bis(2-hydroxy-3-methyl-5-tert-butylbenzyl)ethylenediamine, H2L5,
is used, rapid hydrolysis to two isomers of [(L5)Ti(OEt–O–Ti(OEt)(L5)] (6) occurs without addition of
water. For N,N-bis(2-hydroxy-3,5-di-tert-butylbenzyl)ethylenediamine, H2L6, hydrolysis to [(L6)Ti(OEt)–
O–Ti(OEt)(L6)] (7) occurs slowly when H2O is added. For pendant NMe2 ligand N,N-dimethyl-N0,N0-
bis(2-hydroxy-3-methyl-5-tert-butylbenzyl)ethylenediamine, H2L7, the hydrolysis reaction readily gives
[(L7)Ti(OEt)–O–Ti(OEt)(L7)] (8) for which an X-ray crystal structure was obtained. The ortho-tert-butyl
ligand derivative H2L8 formed a complex analysing as [(L8)Ti(OEt)–O–Ti(OEt)(L8)] (9) which could not
be studied further due to insolubility. Pendant pyridine ligand N-(2-pyridylmethyl)-N,N-bis(20-
hydroxy-30-methyl-50-tert-butylbenzyl)amine, H2L9, apparently forms isomers of [(L9)Ti(OEt)–O–
Ti(OEt)(L9)] and possibly [{(L9)Ti(O)}2] from [(L9)Ti(OEt)2] (10). The ortho-tert-butyl ligand derivative
H2L10 formed [(L10)Ti(OEt)–O–Ti(OEt)(L10)] (11) for which an X-ray crystal structure was obtained.
Ó 2010 Elsevier Ltd. All rights reserved.
Article history:
Received 30 September 2009
Accepted 2 February 2010
Available online 10 February 2010
Keywords:
Synthesis
X-ray structures
Titanium complexes
Diaminebis(phenolate) ligands
1. Introduction
Me2)3Cl] [1]. This gives rise to the oxo-bridged complex [Ti(OCH-
Me2)3–O–Ti(OCHMe2)3] which can then be used to attach other
At present, little is known about complexes of titanium which
contain the Ti(OR–O–Ti(OR) (R = alkyl) functionality. The system
does however have potential in both catalytic and materials chem-
istry applications which makes it worthy of further consideration.
In this regard, a recent report has indicated that the system gives
rise to an active catalyst for organic reactions [1]. Further, alkoxo
complexes of titanium are efficient catalysts for ring opening poly-
merisations of cyclic esters [2] of which lactide polymerisation is at
present of particular interest [3] and this oxo-bridged system may
have potential in this field. The relevance of the system to materi-
als chemistry is that there is potential for the bridging Ti–O–Ti sys-
tem to be transformed into more complex frameworks via the
alkoxo ligands [4].
ligands by alkoxo ligand replacement. Alternatively, the oxo bridge
can be formed by this method after other ligands have been at-
tached [1]. Not only must the reactants be easily available, it is also
desirable to use procedures that do not involve complicated rou-
tines. A potentially viable strategy for the preparation of the
Ti(OR)–O–Ti(OR) system using these ideas would then appear to
be the formation of a bis-alkoxo complex (Eq. (1)) followed by par-
tial hydrolysis to give a single oxo bridge (Eq. (2)):
½TiðORÞ4 þ L ! ½LTiðORÞ2ꢀ
ð1Þ
2½LTiðORÞ2 þ H2O ! ½LTiðORÞ ꢁ O ꢁ LTiðORÞLꢀ þ 2ROH
ð2Þ
This is an attractive proposition for large scale preparations gi-
ven the ready availability of [Ti(OR)4] starting materials from com-
mercial sources. However, the method would only be viable if the
hydrolysis was incomplete and the remaining alkoxo ligands did
not hydrolyse and give an [{LTi(O)}2] type complex.
We report here the results of work aimed at preparing diamine-
bis-(phenolate) complexes containing the Ti(OR)–O–Ti(OR) func-
tionality using this hydrolysis method which is carried out in a
‘single pot’ process.
Before any catalytic or materials chemistry can be realised, effi-
cient low-cost preparative methods need to be developed that give
rise to realistic quantities of useable products. To date, the only
preparative method reported involves preforming the oxo bridge
by the relatively expensive method of adding Ag2O to [Ti(OCH-
* Corresponding author.
E-mail address: a.j.nielson@massey.ac.nz (A.J. Nielson).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.02.006

1716
A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
2.3. [(L3)Ti(OEt)–O–Ti(OEt)(L3)] (2)
2. Experimental
2.1. General
H2O (0.6 g, 0.033 mol) in absolute ethanol (1 mL) was added to
the filtrate from the preparation of complex (1) and the solution
was refluxed for 18 h, the cooled solution stood in air for two days
to reduce the solvent volume and the yellow complex (2) filtered
off. Yield: 0.89 g, 59%. C48H70N4O7Ti2 requires C, 63.35; H, 7.75; N,
All preparations and manipulations were performed without
the exclusion of air and moisture. Reaction glassware was well
dried just prior to being used. Absolute ethanol was bulk Polychem
Marketing product supplied in 200 L drums with a maximum
water content of 0.15% w/w. Winchester bottles of this product
were filled in air and kept tightly closed. If a colourless precipitate
developed on the addition of this ethanol to the [Ti(OCHMe2)4] be-
fore the ligand was added (usually when the winchester contents
were low), the reaction was aborted and a new winchester of the
solvent was used. [Ti(OCHMe2)4] was the 95% product from Alfa
Aesar. The weighed liquid was adjusted by this figure to give the
correct molar amount. N,N0-dimethylethylenediamine was the Al-
drich 85% product containing N-methylethylenediamine as the
remainder. The ligand mixtures containing H2L1 and H2L3 and
H2L2 and H2L4 were prepared using the literature methods for
the H2L2 and H2L4 preparations.16 The ligands H2L7–H2L10 were
prepared by literature methods [5,6]. 1H and 13C {1H} NMR spectra
were recorded at 500.13 MHz on a Bruker AM500 spectrometer
(bt = broad triplet, d = doublet, dq = doublet of quartets, ob-
sq = obscured, p = pentet, qd = quartet of doublets, s = singlet,
t = triplet, td = triplet of doublets). IR spectra were recorded on a
Perkin–Elmer Paragon 1000 FT-IR spectrometer (bs broad strong,
m = medium, s = strong, vw = very weak, w = weak). C, H and N
analyses were determined by Dr A Cunninghame and associates,
University of Otago, New Zealand.
6.16. Found: 63.08; H, 7.71; N, 6.16%. IR spectrum (nujol)
m :
cmꢁ1
1609w; 1423m; 1377m; 1313s; 1270s; 1259s; 1234w; 1212vw;
1186vw; 1161m; 1143vw; 1104m; 1066m; 1002w; 992vw;
958vw; 950vw; 915w; 853m; 838s; 808vw; 775vw; 721bs; 676w;
513m; 587s; 570w; 555m; 538w; 510w; 498w; 462w; 446w;
410s. The complex was insufficiently soluble to obtain NMR spectra.
Me
Me
Me
Me
Me
OEt
Me
O
Ti
O
O
Ti
O
N
Me
N
N
O
Me
N
EtO
Me
Me
Me
Me
(2)
2.2. [(L1)Ti(OEt)–O–Ti(OEt)(L1)] (1)
2.4. [(L3)Ti(OEt2] (3)
Absolute ethanol (30 mL) was added to titanium isopropoxide
(0.992 g, 3.32 mmol) and the mixture was stirred vigorously while
the mixture of ligands containing N-methyl-N,N0-bis(2-hydroxy-
3,5-dimethylbenzyl)ethylene diamine, [H2L1], and N,N0-dimethyl-
N,N0-bis(2-hydroxy-3,5-dimethylbenzyl)ethylene diamine, [H2L3],
(1.18 g, 3.31 mmol based on H2L3) was added in batches. The mix-
ture was refluxed for 2 h, cooled to room temperature and the yel-
low complex (1) filtered off. Yield: 0.080 g, 5.5%. C46H66N4O7Ti2
requires C, 62.64; H, 7.54; N, 6.35. Found: C, 62.59; H, 7.44; N,
The filtrate from the preparation of complex (2) was allowed to
stand in air for several days and the volume reduced by evaporation
to ca one-third giving bis-ethoxo complex (3) as a yellow solid.
Yield: 0.391 g, 23%. C26H40N2O4Ti requires C, 63.45; H, 8.19; N,
5.69. Found: C, 63.30; H, 8.58; N, 5.74%. IR spectrum (nujol) m :
cmꢁ1
1610w; 1422m; 1376m; 1351w; 1313s; 1262s; 1212vw; 1186vw;
1162m; 1144m; 1103s; 1060s; 1001m; 969w; 950w; 912m; 903m;
882vw; 856m; 838s; 807w; 776m; 745m; 677w; 614m; 588s;
556s; 488w; 464w; 446w. 1H NMR, d (CD2Cl2): 1.29 (t, 6H, 2Me);
1.80 (d, 2JHH 9.4 Hz, 2H, 2CHs); 2.25 (s, 6H, 2 Me); 2.27 (s, 6H, 2
Me); 2.42 (s, 6H, 2 Me); 3.02 (d, 2JHH 9.4 Hz, 2H, 2CHs); 3.13 (d,
2JHH 13.2 Hz, 2H, 2CHs); 4.58 (dq, obsq, 2JHH 10. Hz, 3JHH 7. Hz,
2H. 2OCHs); 4.59 (d, 2JHH 13.2 Hz, 2H, 2CHs); 4.76 (dq, 2JHH
10.8 Hz, 3JHH 7.0 Hz, 2H. 2OCHs); 6.67 (s, 2H, m-Hs); 6.94 (s, 2H,
m-Hs). 13C NMR d (CD2Cl2): 17.32 (Me); 19.83 (Me); 20.75 (Me);
47.24 (NMe); 51.91 (CH2); 64.87 (CH2); 71.38 (OCH2); 124.27 (C);
125.20 (C); 127.09 (C); 128.34 (CH); 131.41 (CH); 158 05 (ipso-C).
6.37%. IR spectrum (nujol)
m : 1610w; 1421m; 1376m;
cmꢁ1
1315s; 1300m; 1274s, 1262s; 1211vw; 1184vw; 1162m;
1139vw; 1126vw; 1102vw; 1063w; 1002w; 968w; 950vw;
912vw; 855m; 839s; 812m; 757s; 739bs; 678w; 614m; 589m;
560m; 537; 607w; 460w; 443w; 417m. The complex was insuffi-
ciently soluble to obtain NMR spectra.
Me
Me
Me
Me
Me
Me
Me
OEt
Me
O
Ti
O
O
Ti
O
N
H
OEt
OEt
O
Ti
O
N
N
O
Me
H
N
N
EtO
N
Me
Me
Me
Me
Me
Me
Me
(3)
(1)

A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
1717
2.5. [(L2)Ti(OEt)–O–Ti(OEt)(L2)] (4)
845s; 811m; 787w; 763w; 751m; 646w; 614m; 556s; 482m;
471m. 1H NMR d (CDCl3): 1.26 (t, 6.98 Hz, 6H, 2 Me); 1.39 (s, 18H,
CMe3); 1.62 (s, 18H, CMe3); 1.98 (d, 2JHH 9.4 Hz, 2H, 2CHs); 2.57
(s, 6H, 2NMe); 3.25 (d, 2JHH 9.4 Hz, 2H, 2CHs); 3.27 (d, 2JHH
13.5 Hz, 2H, 2CHs); 4.46 (dq, 2JHH 10.8 Hz, 3JHH 6.9 Hz, 2H,
2OCHs); 4.47 (d, 2JHH 13.5 Hz, 2H, 2CHs); 4.63 (dq, 2JHH 10.8 Hz,
3JHH 6.9 Hz, 2H, 2OCHs); 6.93 (d, 4JHH 2.6 Hz, 2H, m-Hs); 7.33 (d,
4JHH 2.6 Hz, 2H, m-Hs). 13C NMR d (CDCl3): 20.1 (Me); 30.76
(CMe3); 32.23 (CMe3); 34.67 (C); 35.71 (C); 49.12 (NMe); 53.05
(CH2); 65.85 (CH2); 71.49 (CH2); 123.89 (CH); 123.96 (C); 124.83
(CH); 136.47 (C); 139.42 (C); 159.55 (ipso-C).
Absolute ethanol (30 mL) was added to titanium isopropoxide
(0.731 g, 2.44 mmol) and the finely powdered ligand mixture of
N-methyl- N,N0-bis(2-hydroxy-3,5-di-tert-butyl benzyl)ethylene
diamine, [H2L2], and N,N0-dimethyl-N,N0-bis(2-hydroxy-3,5-di-
tert-butyl benzyl)ethylene diamine, [H2L4], (1.29 g, 2.47 mmol
based on H2L4) was added as for the preparation of complex
(1).The mixture was refluxed for 3 h, and the clear yellow solution
cooled to room temperature quickly and H2O (0.0463 g, 2.57 mmol)
in absolute ethanol (1 mL) added dropwise to the rapidly stirred
solution. The mixture was then refluxed for a further 17 h giving
the complex as a yellow precipitate which was removed by centri-
fuging. Yield: 0.14 g, 10%. C70H114N4O7Ti2 requires C, 68.99; H, 9.42;
N, 4.60. Found: C, 69.12; H, 9.46; N, 4.63%. IR spectrum (nujol),
Me3C
CMe3
m
cmꢁ1
: 1602ww; 1413w; 1376m; 1362m; 1299m; 1266m;
O
Ti
O
OEt
OEt
1299m; 1239m; 1203w; 1164w; 1132w; 1092s; 1062s; 1006vw;
979vw; 958vw; 909w; 875w; 850m; 848m; 846vw; 804w;
771vw; 758m; 721w; 684bs; 612w; 583m; 572m; 550m; 533m.
489m; 464s. 1H NMR d (CD2Cl2): 1.278 (s, 18H, 2CMe3); 1.281 (t,
6H, 2Me); 1.33 (s, 18H, 2CMe3); 1.38 (s, 18H, 2CMe3); 1.60 (s,
18H, 2CMe3); 1.94 (s, 6H, 2NMe); 2.14 (d, 2JHH 12.0 Hz, 2H,
2CHs); 2.65 (d, 2JHH 13.7 Hz, 2H, 2CHs); 2.80 (m, 4H, 2CHs and
2CHs); 3.76 (m, 4H, 2CHs and 2CHs); 4.35 (dq, 2JHH 11.0 Hz, 3JHH
7.0 Hz 2H, 2OCHs); 4.43 (dd, 2JHH 13.5 Hz and JHH 1.7 Hz, 2H,
2CHs); 4.53 (d, 2JHH 14.2 Hz, 2H, 2CHs); 4.72 (dq, 2JHH 11.0 Hz,
3JHH 7.0 Hz, 2H, 2OCHs); 6.46 (d, 4JHH 2.4 Hz, 2H, m-CHs); 6.98
(d, 4JHH 2.4 Hz, 2H, m-CHs); 7.23 (2 overlapping d, 4JHH 2.8 Hz,
4H, m-CHs); 8.45 (bt, 3JHH 8.0 Hz, 2H, 2NHs). 13C NMR d (CD2Cl2):
20.83 (Mealkoxo); 30.85 (CMe3); 30.89 (CMe3); 32.07 (CMe3); 32.11
(CMe3); 34.52 (C); 34.56 (C); 35.64 (C); 35.77 (C); 43.9 (NMe);
44.32 (CH2); 53.28 (CH2); 60.42 (CH2);65.30 (CH2); 68.90 (OCH2);
123.43 (CH); 123.83 (CH); 124.27 (C); 124.34 (CH); 124.42 (C);
125.42 (CH); 135.48 (C); 135.93 (C); 139.11 (C); 140.41 (C);
158.38 (ipso-C); 158.86 (ipso-C).
Me
N
N
Me
CMe3
Me3C
(5)
2.7. N,N-Bis(2-hydroxy-3-methyl-5-tert-butylbenzyl)ethylenediamine,
H2L5
Ethanol (60 mL) was added to ethylenediamine (2.91 g,
0.049 mol) and the mixture cooled to 0 °C and stirred rapidly while
aqueous formaldehyde (7.86 cm3) was added dropwise. After stir-
ring for 15 min with the ice bath removed, 2-methyl-4-tert-butyl-
phenol (15.93 g, 0.097 mol) was added in batches and the mixture
was refluxed for 17 h. After cooling and standing the product
deposited as colourless flakes. Yield: 3.14 g, 16%. C26H40N2O2 re-
quires C, 75.68; H, 9.77; N, 6.79. Found: C, 75.90; H, 10.18; N,
6.87%. 1H NMR d (CDCl3): 1.32 (s, 18H, CMe3); 2.27 (s, 6H, 2Me);
2.90 (s, 4H, 2CH2); 4.00 (s, 4H, 2CH2); 6.88 (d, 3JHH 2.1 Hz, 2H,
m-Hs); 7.12 (d, 3JHH 2.1 Hz, 2H, m-Hs); NHs and OHs not observed.
13C NMR d (CDCl3): 16.00 (Me); 31.66 (CMe3); 33.90 (C); 48.07
(CH2); 53.14 (CH2); 120.86 (C); 122.86 (CH); 124.47 (C); 127.02
(CH); 141.42 (C); 153.67 ipso-C.
CMe3
Me3C
CMe3
Me3C
Me
OEt
O
Ti
O
O
Ti
O
N
H
N
N
O
H
N
EtO
Me
CMe3
2.8. [(L5)Ti(OEt)-O-Ti(OEt)(L5)] (6)
Me3C
CMe3
Absolute ethanol (30 mL) was added to [Ti(OCHMe2)4] (0.985 g,
3.77 mmol) and N,N-bis(2-hydroxy-3-methyl-5-tert-butylben-
zyl)ethylenediamine, [H2L5], (1.56 g, 3.78 mmol) added as for the
preparation of complex (1). The solution was refluxed for 2 h and
the cooled solution filtered, giving the complex as a yellow solid.
Yield: 1.26 g, 65%. C56H86N4O7Ti2 requires C, 65.80; H, 8.48; N,
Me3C
(4)
5.58. Found: C, 66.01; H, 8.85; N, 5.58%. IR spectrum (nujol), m :
cmꢁ1
2.6. [(L4)Ti(OEt)2] (5)
3101w; 1605w; 1481s; 1376m; 1362m; 1315m; 1274m; 1230w;
1218m; 1200m; 1157w; 1124w; 1102m; 1080w; 1070w; 1058m;
994vw; 972vw; 962vw; 916w; 892w; 875m; 843m; 828w; 784m;
753m; 714bs; 634vw; 610m; 585m; 574w; 546m; 528m; 507w;
468m; 456w; 434m; 416m. 1H NMR d (CDCl3), isomer 1, (70%):
1.298 (s, 18H, 2CMe3); 1.302 (s, 18H, 2CMe3); 1.32 (t, 3JHH 7.2 Hz,
6H, 2Mealkoxo); 1.63 (s, 6H, 2Mearyl); 1.97 (t, 2JHH 12.2 Hz, 2H,
2CHs); 2.38 (s, 6H, 2Mearyl); 2.51–2.67 (m, 2H, 2CHs); 2.67–2.78
(m, 2H, 2CHs); 3.15 (p, 3JHH 5.8 Hz, 2H, 2NHs); 3.30 (d, 2JHH
The filtrate from the preparation of complex (4) was allowed to
stand in air for several days giving the product as a yellow crystal-
line solid after the solvent volume had reduced. Yield: 1.01 g, (63%).
C38H64N2O4Ti requires C, 69.11; H, 9.78; N, 4.24. Found: C, 69.56; H,
9.81; H, 4.29%. IR spectrum (nujol),
1368m; 1301m; 1270s;1255s; 1237m;1202m; 1166m; 1132m;
m
cmꢁ1: 1468s; 1444s; 1420m;
1106s; 1063s;1016w;992w; 966w; 953w; 914m; 904m; 876m;

1718
A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
10.4 Hz, 2H, 2CHs); 3.64 (d, 2JHH 12.8 Hz, 2H, 2CHs); 4.08 (qd, 2JHH
12.8 Hz, 3JHH 4.6 Hz, 2H, 2CHs); 4.27 (m, obsc, 2JHH 12.8 Hz, 2H,
2CHs); 4.30 (dq, obsq, 2JHH 12.8 Hz, 3JHH 7.3 Hz, 2H, 2OCHs); 4.36
(d, 2JHH 12.5 Hz, 2H, 2CHs); 4.68 (dq, 2JHH 12.8 Hz, 3JHH 6.9 Hz,
2H, 2OCHs); 6.82 (d, 4JHH 2.3 Hz, 2H, m-CHs); 6.91 (d, 4JHH
2.3 Hz, 2H, m-CHs); 7.00 (d, 4JHH 2.3 Hz, 2H, m-CHs); 7.17 (d,
4JHH 2.3 Hz, 2H, m-CHs); 7.90 (bt, 3JHH 7.8 Hz, 2H, 2NHs). 13C
NMR d (CDCl3): 15.61 (Me); 19.80 (Mealkoxo); 31.68 (CMe3); 31.71
CMe3); 33.75 (C); 33.81 (C); 45.94 (CH2); 49.27 (CH2); 52.28
(CH2); 52.83 (CH2); 68.41 (OCH2); 122.69 (C); 122.71 (CH); 124.10
(C); 124.51 (C); 124.55 (CH); 124.93 (C); 126.46 (CH); 127.00
(CH); 138 82 (C); 140.30 (C); 157.97 (ipso-C); 160.43 (ipso-C). 1H
NMR d (CDCl3), isomer 2, (30%): 1.28 (s, 18H, 2CMe3); 1.29–1.31
(obsc, 6H, 2Mealkoxo); 1.34 (s, 18H, 2CMe3); 1.69 (s, 6H, 2Mearyl);
2.07 (t, 2JHH 12.2 Hz, 2H, 2CHs); 2.42 (s, 6H, 2Mearyl); 2.51–2.65
(obsc, 2H, 2CHs); 2.67–2.77 (obsc, 2H, 2CHs); 3.04 (p, 3JHH 6.7 Hz,
4JHH 2.3 Hz, 2H, 2CHs); 3.42 (d, 2JHH 11.0 Hz, 2H, 2CHs); 3.44 (m,
2JHH 13.3 Hz, 2H, 2CHs); 3.75 (dq, 2JHH 12.8 Hz, 3JHH 7.0 Hz, 2H,
2OCHs); 4.22–4.39 (obsc, 2H, 2CHs); 4.79 (d, 2JHH 13.0 Hz, 2H,
2CHs); 5.29 (bt, 3JHH 7.5 Hz, 2H, 2NHs); 6.86 (d, 4JHH 2.3 Hz, 2H,
m-CHs); 6.92 (d, 4JHH 2.3 Hz, 2H, m-CHs); 6.97 (d, 4JHH 2.3 Hz,
2H, m-CHs); 7.25 (d, 4JHH 2.3 Hz, 2H, m-CHs). 13C NMR d (CDCl3):
16.78 (2Me); 18.42 (Mealkoxo); 31.68 (obsc,CMe3); 31.71 (ob-
sc,CMe3); 33.75 (C); 33.90 (C); 45.61 (CH2); 48.46 (CH2); 52.53
(CH2); 52.83 (CH2); 58.42 (OCH2); 122.84 (CH); 123.8 (CH); 124.43
(CH); 124.51 (C); 125.12 (C); 125.75 (C); 126.61 (CH); 127.51
(CH); 139.32 (C); 140.80 (C); 157.40 (ipso-C); 159.52 (ipso-C). H2O
(0.06 g, 3.33 mmol) in absolute ethanol (1 mL) was added to the fil-
trate and the solution refluxed for a 1 h giving a further sample of
complex (6). Yield; 0.194 g, 10%. Total yield: 75%. NMR spectroscopy
showed the presence of 78% isomer 1 and 22% isomer 2.
NMR d (CDCl3): 29.62 (CMe3); 31.66 (CMe3); 31.14 (C); 34.88 (C);
51.73 (CH2); 59.23 (CH2); 120.81 (C); 123.04 (CH); 123.26 (CH);
135.69 (C); 140.69 (C); 154.10 (ipso-C).
2.10. [(L6)Ti(OEt)-O-Ti(OEt)(L6)] (7)
Absolute ethanol (30 mL) was added to [Ti(OCHMe2)4] (0.817 g,
2.73 mmol) then N,N-bis(2-hydroxy-3,5-di-tert-butylbenzyl)ethy-
lenediamine, [H2L6], (1.36 g, 2.9 mmol) as for the preparation of
complex (1). The solution was refluxed for 2 h giving a clear yellow
solution to which was added H2O (0.10 g, 5.56 mmol) in absolute
ethanol (1 mL) and the solution refluxed for a further 17 h. On
cooling and standing the complex formed as a yellow solid. Yield:
0.77 g, 47%. C68H110N4O7Ti2 requires C, 68.60; H, 9.31; N, 4.71.
Found: C, 68.55; H, 9.50; N, 4.55%. IR spectrum (nujol),
m :
cmꢁ1
3087w; 1603w; 1441s; 1414m; 1388m; 1375m; 1361m; 1303m;
1274s; 1262s; 1242s; 1203m; 1165m; 1132m; 1097m; 1060m;
1025vw; 1004w; 972vw; 959vw; 932vw; 911w; 886vw; 874w;
869w; 854m; 842m; 804w; 758m; 702bs; 668m; 646vw; 609w;
581m; 569m; 552m; 536m; 488m; 468m; 426m.
CMe3
Me3C
CMe3
Me3C
H
OEt
O
Ti
O
O
Ti
O
N
H
N
N
O
H
N
EtO
H
CMe3
Me3C
CMe3
CMe3
Me3C
Me3C
Me
(7)
Me
H
OEt
Me
O
Ti
O
O
Ti
O
N
2.11. N,N-Dimethyl-N0,N0-bis(2-hydroxy-3-methyl-5-tert-butylbenzyl)
ethylenediamine, H2L7
H
N
N
O
H
N
Methanol (35 mL) was added to N,N-dimethylethylenediamine
(4.38 g. 0.05 mol) and the rapidly stirred solution cooled to 0 °C
after which aqueous formaldehyde solution (8 mL, 0.1 mol) was
added dropwise. The mixture was stirred for 2 h, then 4-tert-bu-
tyl-2-methylphenol (16.31 g, 0.1 mol) was added and the mixture
was refluxed for 23 h. On cooling the product separated as an oil
which solidified on standing at ꢁ20 °C. Yield: 13.7 g, 63%.
C28H44N2O2 requires C, 76.32; H, 10.07; N, 6.36. Found: C, 76.67;
EtO
H
Me
CMe3
Me3C
(6)
H, 10.45; N, 6.36%. IR spectrum (nujol)
m
cmꢁ1: 3056bs; 1608w;
1487s; 1462s; 1376s; 1362s; 1341m; 1310m; 1288m; 1254m;
1235s; 1217s; 1169; 1117m; 1104m; 1058w; 1044w; 1019w;
989m; 962w; 933w; 917w; 876m; 814m; 784m; 748w; 734w;
681w; 666w; 630w; 609w; 578w; 514w; 500w; 414w. 1H NMR d
(CDCl3): 1.37 (s, 18H, CMe3); 2.32 (s, 6H, 2Me); 2.39 (s, 6H,
2Me); 2.65 (s, 4H, 2CH2); 3.70 (s, 4H, 2CH2); 7.00 (d, 4JHH 2.4 Hz,
2H, m-Hs); 7.18 (d, 4JHH 2.4 Hz, 2H, m-Hs); 9.30 (b, 2H, 2OH).
13C NMR d (CDCl3): 16.82 (Me); 32.19 (CMe3); 34.50 (C); 45.52
(NMe); 49.74 (CH2); 57.01 (CH2); 122.01 (C); 125.09 (C); 125.31
(CH); 127.96 (CH); 141.49 (C); 153.18 (ipso-C).
2.9. N,N-Bis(2-hydroxy-3,5-di-tert-butylbenzyl)ethylenediamine, H2L6
Ethanol (60 cm3) was added to ethylenediamine (2.91 g,
0.049 mol) and the mixture cooled to 0 °C and stirred rapidly while
aqueous formaldehyde (7.86 cm3) was added dropwise. After stir-
ring for 15 min with the ice bath removed, 2,4-di-tert-butylphenol
(20.0 g, 0.097 mol) was added in batches and the mixture was re-
fluxed for 18 h. On cooling and standing for several days a white
solid was formed which were repeatedly recrystallised from hot
ethanol until NMR spectroscopy indicated a pure product was ob-
tained. Yield: 4.37 g, 18%. C32H52N2O2 requires C, 77.36; H, 10.55;
N, 5.64. Found: C, 77.98; H, 10.80; N, 5.60%. 1H NMR d (CDCl3):
1.36 (s, 18H, 2CMe3); 1.51 (s, 18H, 2CMe3); 3.08 (s, 4H, 2CH2);
3.99 (s, 4H, 2CH2); 6.92 (d, 3JHH 2.4 Hz, 2H, m-Hs); 7.31 (d, 3JHH
2.4 Hz, 2H, m-Hs); 10.78 (b, 2H, NHs), OHs not observed. 13C
2.12. [(L7)Ti(OEt)–O–Ti(OEt)(L7)] (8)
Absolute ethanol (30 mL) was added to titanium isopropoxide
(1.048 g, 3.56 mmol) then finely powdered N,N-dimethyl-N0,
N0-bis(2-hydroxy-3-methyl-5-tert-butylbenzyl)ethylenediamine,

A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
1719
[H2L7], (1.54 g, 3.56 mmol) added as for the preparation of complex
(1).The mixture was refluxed for 3 h, cooled to room temperature
quickly and H2O (0.063 g, 3.56 mmol) in absolute ethanol (1 mL)
added dropwise to the rapidly stirred solution. The mixture was
then refluxed for a further 17 h giving a yellow solution from which
the crystalline complex was obtained after evaporation of the sol-
vent by about one-third. Yield:1.58 g, 95%. C60H94N4O9Ti2 requires:
C, 66.83; H, 8.79; N, 5.20. Found: C, 66.88; H, 8.78; N, 5.20%. IR spec-
mixed as for the preparation of complex (8).The mixture was re-
fluxed for 3 h, cooled to room temperature quickly and H2O
(0.07 g, 6.7 mmol) in absolute ethanol (1 mL) added dropwise to
the rapidly stirred solution. The mixture was then refluxed for a fur-
ther 17 h giving the complex as a yellow insoluble solid. Yield:
2.138 g, 99%. C72H118N4O7Ti2 requires C, 69.36; H, 9.54; N, 4.49.
Found: C, 69.00; H, 9.69; N, 4.51%. IR spectrum (nujol)
m :
cmꢁ1
1601w; 1462s; 1412w; 1377w; 1360w; 1332w; 1296m; 1276m;
1239w; 1203w; 1166w; 1128s; 1070m; 1029w; 996vw; 966w;
944vw; 923w; 912w; 876w; 845m; 807w; 756m; 694bs; 623w;
576m; 559m; 536w; 507w; 472m; 450m. The compound is insolu-
ble which precluded further characterisation by NMR spectroscopy.
trum (nujol)
m
cmꢁ1: 1603w; 1464s; 1376m, 1361w; 1334w;
1312m; 1294w; 1275m; 1221m; 1126w; 1112w; 1095w; 1056m;
1021w; 991w; 974w; 945w; 904w; 872w; 844w; 793w; 775m;
720bs; 634w; 612w; 590m; 572m; 550m; 527w; 508w; 478w;
441m; 413m. 1H NMR d (CD2Cl2): 1.05 (t, 3JHH 6.8 Hz, 6H, Me);
1.31 (s, 36H, 4CMe3); 2.13 (s, 12H, 4Me); 2.23 (s, 12H, 4NMe);
2.30 (t, 3JHH 6.1 Hz, 4H, 2CH2); 2.31 (t, 3JHH 6.4 Hz, 4H, 2CH2);
3.05 (d, 2JHH 13.4 Hz, 4H, 4CHs); 4.55 (q, 3JHH 6.8 Hz, 4H,
2OCH2); 5.02 (d, 2JHH 13.6 Hz, 4H, 4CHs); 6.81 (d, 4JHH 2.4 Hz,
4H, m-Hs); 7.05 (d, 4JHH 2.49 Hz, 4H, m-Hs). 13C NMR d (CD2Cl2):
17.39 (Me); 19.48 (Me); 32.10 (CMe3); 34.23 (C); 48.73 (NMe2);
52.16 (CH2); 59.23 CH2); 65.59 (CH2); 71.28 (CH2); 123.35 (C);
124.37 (CH); 124.83 (C); 127.58 (CH); 139.69 (C);159.55 (ipso-C).
2.14. N-(2-Pyridylmethyl)-N,N-bis(20-hydroxy-30-methyl-50-tert-
butylbenzyl)amine, H2L9
Methanol (35 mL) was added to 2-aminomethylpyridine
(5.05 g, 0.047 mol), the solution cooled to 0 °C and aqueous form-
aldehyde (7.6 mL, 0.095 mol) added dropwise to the stirred solu-
tion. 4-tert-Butyl-2-methylphenol (15.3 g, 0.095 mol) was then
added and the mixture was refluxed for 23 h giving a gummy solid
on cooling. The product was dissolved in hot methanol (15 mL) and
the solution cooled to ꢁ20 °C giving colourless crystals. Yield:
8.02 g, 37%. C30H4N2O2 requires C, 78.22; H, 8.75; N, 6.08. Found:
2.13. [(L8)Ti(OEt)-O-Ti(OEt)(L8)] (9)
C, 78.54; H, 9.17; N, 6.15%. IR spectrum (nujol)
m
cmꢁ1: 3002m;
Absolute ethanol (30 mL), [Ti(OCHMe2)4] (1.10 g, 3.68 mmol)
and finely powdered N,N-Dimethyl-N0,N0-bis(2-hydroxy-3,5-di-tert
butylbenzyl)ethylenediamine, [H2L8], (1.94 g, 3.70 mmol) were
2703m; 2596m; 1600s; 1572w; 1489s; 1460s; 1431s; 1381s;
1364s; 1309m; 1292m; 1269w; 1244m; 1234m; 1217s; 1152w;
1122w; 1110w; 1100m; 1090w; 1055w; 1028w; 1010m; 975m;
960w; 951w; 922vw; 899w; 878m; 862m; 819w; 762m; 748m;
737w; 683w; 670w; 640w; 632w; 579vw; 516w; 502vw; 467w;
452w; 421w. 1H NMR d (CDCl3): 1.36 (s, 18H, 2CMe3); 2.30 (s,
6H, 2Me); 3.85 (s, 4H, 2CH2); 3.95 (s, 2H, CH2); 7.02 (d, 4JHH
2.5 Hz, 2H, m-Hs); 7.17 (d, 4JHH 2.5 Hz, 2H, m-Hs); 7.20 (d, 3JHH
8.2 Hz, 1H, CH); 7.34 (t, 3JHH 6.3 Hz, 1H, CH); 7.76 (td, 3JHH
7.7 Hz, 4JHH 1.8 Hz, 1H, CH); 8.74 (d, 3JHH 4.8 Hz, 1H, CH); 10.58
(b, 2H, 2OH). 13C NMR d (CDCl3): 16.76 (Me); 32.01 (CMe3);
34.30 (C); 56.70 (CH2); 57.47 (CH2); 121.06 (C); 123.10 (CH);
124.04 (CH);125.12 (C); 125.45 (CH); 128.11 (CH); 138.12 (CH);
141.74 (C); 148.65 (CH);153.61 (C); 157.16 (C).
CMe3
R
Me
R
Me3C
OEt
N
O
O
Me
O
O
N
N
Ti
Ti
N
Me
O
OEt
R
Me
CMe3
R
2.15. Reaction of H2L9 with [Ti(OCHMe2)4] and H2O
CMe3
Absolute ethanol (30 mL), [Ti(OCHMe2)4] (1.023 g, 3.42 mmol)
and finely powdered N-(2-pyridylmethyl)-N,N-bis(20-hydroxy-30-
Me-50-tert-butylbenzyl)amine, [H2L9], (1.58 g, 3.43 mmol) were
mixed as for the preparation of complex (8).The mixture was re-
fluxed for 3 h, cooled to room temperature quickly and H2O
(0.123 g, 6.67 mmol) in absolute ethanol (1 mL) added dropwise
to the rapidly stirred solution. The mixture was then refluxed for
a further 17 h giving the product as a yellow insoluble solid. Yield:
0.534 g, 28%. C64H86N4O7Ti2 requires C, 68.73; H, 7.75; N, 5.01.
(8a) R = Me
(9a) R = CMe3
CMe3
CMe3
R
R
Found: C, 68.26; H, 7.53; N,5.39%. IR spectrum (nujol)
m :
cmꢁ1
EtO
O
1606w; 1481vs; 1377m; 1371m; 1325w; 1311m; 1275m;
1220m; 1151w; 1127w; 1100w; 1086w; 1052w; 1025w; 978w;
945w; 868m; 854w; 839m; 814bs; 773s; 760m; 732w; 696w;
662vw; 649w; 625w; 603w; 595w; 546w; 525w; 479m; 425s.The
NMR spectra are very complicated and are not reported here.
N
O
Me
Me
N
N
O
Ti
O
Ti
O
Me
Me
OEt
R
N
2.16. [(L9)Ti(OEt)2] (10)
R
The solvent was removed from the filtrate of the above reaction
giving the bis-ethoxo complex (10).Yield: 1.29 g, 63%. C34H48N2O4Ti
requires C, 68.49; H, 8.12; N, 4.71. Found: C, 68.70; H, 8.31; N, 4.85%.
Me3C
CMe3
IR spectrum (nujol) m
cmꢁ1: 1604m; 1473s; 1442s; 1390m; 1375m;
(8b) R = Me
(9b) R = CMe3
1381m; 1331m; 1309s; 1276s; 1219s; 1464m; 1447m; 1118s;
1102s; 1068s; 1018w; 978w; 947; 907w; 876w; 852m; 838m;

1720
A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
811w; 774s; 763m; 752m; 730m; 696vw; 668vw; 647vw; 639w;
624w; 594s; 554m; 531m; 474w; 444m. 1H NMR d (CD2Cl2): 1.29
(s and t, 21H, CMe3 and Meethoxo); 1.53 (t, 3H, Meethoxo); 2.07 (s,
6H, 2Me); 3.42 (d, 2JHH 12.7 Hz, 2H, 2CHs); 3.71 (s, 2H, CH2); 4.53
(q, 3JHH 6.9 Hz, 2H, OCH2); 4.67 (d, 2JHH 12.7 Hz, 2H, 2CHs); 4.94,
(q, 3JHH 6.9 Hz, 2H, OCH2); 6.43 (d, 3JHH 7.1 Hz, 1H, CHpy); 6.82–
7.14 (m, 5H, CH and CHpy); 7.30 (td, 3JHH 7.6 Hz, 4JHH 1.7 Hz, 1H,
CHpy); 8.64 ((d, 3JHH 4.9 Hz 1H, CHpy). 13C NMR d (CD2CL2): 17.09
(Me); 19.81 (Me); 20.08 (Me); 32.03 (CMe3); 34.20 (C); 59.05
(CH2); 64.32 (CH2); 71.03 (CH2); 71.57 (CH2); 120.82 (CH); 122.59
(CH); 123.10 (C); 124.19 (C); 124.42 (CH); 127.66 (CH); 138.24
(CH); 140.59 (C); 148.90 (CH); 157.13 (C); 160.70 (ipso-C).
CMe3
CMe3
Me3C
Me3C
OEt
N
O
N
O
O
N
Ti
Ti
N
O
O
OEt
Me3C
CMe3
Me3C
CMe3
Me
(11a)
Me3C
N
O
CMe3
CMe3
OEt
N
Ti
O
Me3C
CMe3
Me
OEt
EtO
O
N
N
O
O
N
Ti
O
Ti
O
CMe3
OEt
(10)
N
CMe3
Me3C
Me3C
CMe3
(11b)
2.17. [(L10)Ti(OEt)-O-Ti(OEt)(L10)] (11)
Absolute ethanol (30 mL), [Ti(OCHMe2)4] (1.10 g, 3.58 mmol)
and finely powdered N-(2-pyridylmethyl)-N,N-bis(20-hydroxy-
30,50-di-tert-butylbenzyl)amine, [H2L10], (1.94 g, 3.56 mmol) were
mixed as for the preparation of complex (8).The mixture was re-
fluxed for 3 h, cooled to room temperature quickly and H2O
(0.07 g, 3.9 mmol) in absolute ethanol (1 mL) added dropwise to
the rapidly stirred solution. The mixture was then refluxed for a
further 17 h giving the complex as a yellow insoluble solid. Yield:
2.18. X-ray crystallography
Diffraction intensities for the three complexes were collected on
a Bruker SMART APEX2 CCD diffractometer equipped with graph-
ite-monochromated Mo
Ka radiation (wavelength 0.71073 Å)
using the -scan technique. Lorentz polarisation and absorption
x
1.27 g, 55%. IR spectrum (nujol)
m
cmꢁ1: 1606w; 1422s; 1415m;
corrections were applied using the programme SAINT [7]. The struc-
ture of 3 was solved by the Patterson method those of 8b and 11b
by direct methods [8]. All three structures were refined by a full-
matrix least-squares technique [9] based on F2. Anisotropic ther-
mal parameters were assigned to all non-hydrogen atoms. Hydro-
gen atoms were in calculated positions refined riding on the
carbons to which they were attached. In compound 3 relatively
high thermal motion was observed with the carbon atoms of the
two bound ethoxo groups. In compound 8b disorder was noted
for three of the four tertiary butyl groups and site occupancy fac-
tors were refined for two of them. For the third the disorder was
not resolved. Further disorder was also observed for one of the
bound ethoxy groups and these site occupancy factors were re-
fined. For compound 11b disorder was not resolved for either ter-
tiary butyl or bound ethoxo groups.
1391w; 1376w; 1360w; 1352w; 1337vw; 1291s; 1274s; 1254s;
1239m; 1201w; 1169m; 1153vw; 1130m; 1100s; 1057s; 1020w;
978w; 934w; 914m; 888vw; 877m; 856m; 841s; 808m; 781vw;
771w; 756m; 722bs; 693w; 647w; 633w; 615m; 596m; 566m;
554s; 537m; 505m; 475m; 448w; 427w. 1H NMR d (CD2Cl2):
0.89 (t, 3JHH 7.0 Hz, 6H, 2Me); 1.27 (s, 36H, 4CMe3); 1.36 (s, 36H,
4CMe3); 3.28 (d, 2JHH 12.6 Hz, 4H, 4CH); 3.81 (s, 4H, 2CH2); 4.52
(q, 3JHH 7.0 Hz, 4H, 2OCH2); 5.43 (d, 2JHH 12.6 Hz, 4H, 2CH);
6.44 (d, 3JHH 7.9 Hz, 2H, 2CHpy); 6.89 (d, 4JHH 2.5 Hz, 4H, 4CH);
6.91 (t, 3JHH 6.6 Hz, 2H, 2CHpy); 7.03 (d, 4JHH 2.5 Hz, 4H, 4CH);
7.28 (td, 3JHH 7.7 Hz, 4JHH 1.7 Hz, 2H, 2CHpy); 8.64 (d, 3JHH
5.3 Hz 2H, 2CHpy). 13C NMR d 19.61 (Me); 30.49 (CMe3); 32.15
(CMe3); 34.22 (C); 35.34 (C); 58.69 (CH2); 64.85 (CH2); 72.04
(CH2); 120.01 (CH); 121.65 (CH); 123.23 (CH); 124.96 (CH);
125.15 (C); 135.61 (C); 137 87 (CH); 138.74 (C); 150.49 (CH);
157.49 (C); 161.72 (C). Reduction of the solvent to small volume
gave further yellow solid (1.027 g) which NMR spectroscopy
showed to consist of complex 11b (41%, total yield: 71%) and other
3. Results and discussion
In developing a method for hydrolysing alkoxide complexes it
was found to be convenient to carry out the reactions using
[Ti(OCHMe2)4] in commercial grade absolute ethanol since our ini-
tial attempts at carrying out the hydrolysis in isopropanol often
complexes [doublets in the 1H NMR spectrum for the pyridine a-
C–H hydrogen at d 8.39 (25%), 8.43 (3%), 8.51 (25%), 8.64 (com-
plex(11b), 41%), 8.70 (4%) and 8.81 (2%).

A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
1721
R1
R1
gave mixtures which were difficult to separate. Thus adding
[Ti(OCHMe2)4] to a well dried reaction vessel in the air and imme-
diately adding commercial grade absolute ethanol gave a clear
solution to which the ligand was added as a solid in small batches.
This solution was then refluxed without protection from air or
moisture for about 2 h to attach the phenoxy-amine ligand in order
to form a bis-alkoxo complex without isolating it, after which the
appropriate amount of H2O in absolute ethanol was added. The
mixture was then refluxed for about 18 h to effect the alkoxide
hydrolysis reaction and complete alkoxide exchange [10].
OH
HO
N
Me
N
H
R2
R2
H2L1 R1 = R2 = Me
H2L2 R1 = R2 = CMe3
R1
R1
The diamine-bis(phenol) ligands used in this work are shown in
Chart 1. Modified Mannich reactions reported in the literature [11]
were used for the preparations rather than the imine reduction/
alkylation sequence [12]. Although not used in the present work,
a microwave assisted Mannich reaction is now available which
supplies these ligands in very high yield [13]. For the preparation
of H2L3 and H2L4, commercially available 99% N,N0-dimethylethyl-
enediamine is expensive for large scale applications hence the less
pure compound (85%) was used which also contains N-methyle-
thylenediamine (15%). The Mannich ligand synthesis method thus
provided the N-methyl and N,N0-dimethyl phenoxy-amine ligands,
H2L1 mixed with H2L3 and H2L2 mixed with H2L4. These mixtures
proved fortuitous since the N-methylethylenediamine bis-alkoxo
complexes invariably formed an insoluble hydrolysis product be-
fore the N,N0-dimethyl analogue. Thus when the mixed ligand sys-
tem containing H2L1 and H2L3 was reacted in absolute ethanol with
[Ti(OCHMe2)4], a small quantity of an insoluble solid identified as
[(L1)Ti(OEt)–O–Ti(OEt)(L1)] (1) was formed during the 2 h reflux
period used to attach the phenoxy-amine ligand. When 10 equiva-
lents of H2O were added after the removal of (1) and the solution
was refluxed for 18 h, insoluble [(L3)Ti(OEt)–O–Ti(OEt)(L3)] (2)
formed in 59% yield. The remaining solubles were identified as
the bis-ethoxo complex [(L3)Ti(OEt)2] (3) which is expected to have
trans-phenoxo and cis-ethoxo ligands based on the single set of
resonances observed in the NMR spectra. These features are similar
to those found for bis-isopropoxo complexes of group 4 metals
where this type of ligand wraps in a fac–fac mode giving C2- sym-
metric octahedral complexes [2b,2c,14,15].
OH
HO
R2
N
Me
N
Me
R2
H2L3 R1 = R2 = Me
H2L4 R1 = R2 = CMe3
R1
R1
OH
HO
N
H
N
R2
R2
H
H2L5 R1 = Me, R2 = CMe3
H2L6 R1 = R2 = CMe3
R1
R1
OH
HO
N
R2
R2
N
Me
Me
When only 1 or 2 equivalents of H2O were used in the reaction,
complex (1) precipitated initially but after the 18 h reflux period
no hydrolysis took place and only the bis-ethoxo complex (3)
was found to be present in the reaction solution. In line with this
result, complex (3) is air stable, does not appear to change on stor-
age in humid air and is apparently only converted to the hydrolysis
product under forcing conditions of excess water. Both bridging
oxo complexes (1) and (2) were insoluble in organic solvents which
precluded characterisation by NMR spectroscopy but they were
identified by precise analytical data and the presence of an asym-
metric Ti–O–Ti stretch [16–18] in the IR spectra [739 cmꢁ1 for
complex (1) and 721 cmꢁ1 for complex (2)]. These bands are easily
identified in the spectra as they are very strong and are consider-
ably broadened which distinguishes them from the rest. The
trans-phenoxo structures for (1) and (2) are preferred since molec-
ular models indicate that the position of the aryl rings for a cis-
arrangement would leave little scope for the Ti–O–Ti system to
form.
Using the ligand mixture with the ortho-tert-butyl groups on
the aryl rings (H2L2 and H2L4) no precipitate was formed during
the initial reflux period whereas addition of one equivalent of
H2O and refluxing the solution for 17 h gave [(L2)Ti(OEt)–O–
Ti(OEt)(L2)] (4). The IR spectrum is nearly identical to that found
for methyl complex (1) but has a Ti–O–Ti stretch at lower wave-
length (684 versus 721 cmꢁ1). The complex was soluble and
showed NMR spectral characteristics of the asymmetric L2 ligand
being equivalent at both ends of the Ti–O–Ti system. Thus the 1H
NMR spectrum showed single NH and NMe resonances, 4 AX sys-
H2L7 R1 = Me, R2 = CMe3
H2L8 R1 = R2 = CMe3
R1
R1
OH
HO
N
R2
R2
N
H2L9 R1 = Me, R2 = CMe3
H2L10 R1 = R2 = CMe3
Chart 1. Phenoxy-amine ligands.
tem doublets for the 2 diastereotopic CH2 group hydrogens, 4
CMe3 group resonances and two well separated sets of doublets
of quartets for the ethoxo group methylene hydrogens. The 13C
NMR spectrum shows a single set of resonances for each of the

1722
A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
different carbon atoms so that there are 12 aryl ring, 4 CH2 group
resonances and one resonance for the ethoxo ligand methylene
carbon. Evaporation of ethanol solvent from the complex (4) fil-
trate gave only the bis-ethoxo complex [(L4)Ti(OEt)2] (5) which
has C2 symmetry features in the 1H NMR spectrum similar to that
found for complex (3). The complex remains unchanged on stand-
ing for long periods in the air in the ethanol solvent and the solid is
also not air or moisture sensitive.
The use of 10 equivalents of water in the reaction mixture after
the removal of complex (4) and vigorous refluxing for 18 h or long-
er produced a similar result to the low water content reaction
where no hydrolysis of the bis-ethoxo complex occurred. Further
vigorous refluxing of bis-ethoxo complex (5) with water using
THF as solvent also did not give a hydrolysis product with only
the starting material being returned. The results thus show that
for the ortho-methyl substituted bis-ethoxo complexes, the N-
methyl phenoxy ligand compound is easily hydrolysed and the
N,N0-dimethyl compound less easily so. For the tert-butyl ligand
analogue, the N-methyl phenoxo ligand complex is only hydroly-
sed under forcing conditions whereas the N,N0-dimethyl complex
is not hydrolysed at all.
been obtained hence the complex has not been studied further. It is
interesting to note in passing however that the asymmetry only
appears in this type of complex where there are hydrogens at-
tached to the ethylenediamine system which suggests the N-
methyl groups are important in determining the trans phenolate
coordination.
The hydrolysis reactions using the N-protonated ethylenedia-
mine ligand backbones thus indicate a rapid rate enhancement
compared with the N-methyl analogues and a reduced rate when
an ortho-tert-butyl substituent is present on the phenoxo ligand
aryl ring. Suitable crystals of the N-protonated complexes have
not been obtained but an X-ray crystal structure of the N,N0-di-
methyl bis-ethoxo complex (3) was undertaken in an attempt to
identify features that might prevent the hydrolysis reaction occur-
ring easily. The structure (Fig. 1, bond lengths and angles Table 1,
Crystallographic data, Table 3) shows a C2 symmetry distorted
octahedral structure with trans-phenoxo ligands and cis-ethoxo
ligands each one of which lies trans to the cis-coordinated nitro-
gens of the ethylenediamine section.
The Ti–O bond lengths for the ethoxo ligands [1.829(2) and
1.832(2) Å] are significantly shorter than Ti–O bond lengths for
the phenoxo ligands [1.894(2) and 1.900(2) Å] indicating that the
In addressing the rapid hydrolysis of the bis-ethoxo complexes
containing the N-methyl phenoxy ligands L1 and L2, the fully N-
protonated ligands H2L5 and H2L6 were prepared. They were re-
acted with [Ti(OCHMe2)4] to establish whether the presence of
two N–H groups on the ethylenediamine section of the ligand
would allow both alkoxo ligands to be hydrolysed and thus form
[(L)Ti(O)]2 complexes rather than the [(L)Ti(OR)–O–Ti(OR)(L)] type.
A transformation of this type has been observed for a Ti complex
containing linked salicylaldimine ligands [4]. Otherwise,
[(L)Ti(O)]2 type complexes are relatively rare with apparently only
two other complexes being reported in which the diamine portion
of the ligand is made up from 1,4-diazacycloheptane [19] or 1,2-
diaminocyclohexane [20]. When refluxing of the reaction mixture
containing H2L5 and [Ti(OCHMe2)4] was initiated in the air, a pre-
cipitate was immediately formed without the addition of H2O
and further precipitate was produced as the refluxing in air contin-
ued. After 2 h the reaction was stopped and the solid formed was
characterised as [(L5)Ti(OEt)–O–Ti(OEt)(L5)] (6) based on the ana-
lytical data and spectral characteristics. The IR spectrum shows a
strong band at 714 cmꢁ1 similar to that observed for the other
complexes containing the Ti–O–Ti system. The NMR spectra show
the presence of two isomers (ratio 7:3). The 1H NMR spectrum is
very complicated showing asymmetry is present in both the iso-
mers. The asymmetry is represented per isomer by four sets of
meta-aryl CH resonances, a single set of resonances for each of
the methylene group hydrogens and two resonances for the aryl
ring ortho-methyl groups. In the 13C NMR spectrum there are per
isomer two sets of resonances for the aryl ring carbons of the li-
gand and 4 sets of methylene carbons along with a single ethoxo
ligand methylene. Asymmetry can arise for this ligand system
when the phenolate oxygens bind in a cis-fashion [11a] and there
is also the possibility of different coordination modes at both ends
of the Ti–O–Ti system. Although complicated, the spectra clearly
show that none of the [(L5)Ti(O)]2 type complex is present. Further
complex could be obtained by adding 2 equivalents of H2O to the
reaction and refluxing the solution.
p
-donation for the alkoxo ligands is more pronounced. The overall
geometry and bond lengths and angles are similar to those found
for the isopropoxo analogue [(L3)Ti(OCHMe2)2] [2b]. The Ti–O bond
lengths for the phenoxo ligand in (3) are however shorter than
those found in the isopropoxo analogue [(L0)Ti(OCHMe2)2]
{L0 = N,N0-dimethyl-N,N0-bis(2-hydroxy-4-nitrobenzyl)ethylenedia-
mine} in which there is a p-nitro substituent on the aryl ring [Ti–O
When the ortho-tert-butyl ligand H2L6 was used, no precipitate
was formed during the 2 h of reflux used to attach the ligand but a
precipitate did form after 2 equivalents of H2O were added and the
refluxing continued for 18 h. The analytical data suggest this com-
plex is [(L6)Ti(OEt)–O–Ti(OEt)(L6)] (7) and there is a strong but
broad band in the IR spectrum at 702 cmꢁ1 indicative of several
Ti–O–Ti systems. The NMR spectra are very complicated indicating
isomers and there is asymmetry attributable to at least one isomer
with cis-phenoxo group coordination. Crystalline material has not
Fig. 1. Ortep diagram [22] showing the molecular structure of [(L3)Ti(OEt)2] (3).
Hydrogen atoms have been omitted for clarity.

A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
1723
nearly quantitative yield of [(L7)(OEt)–O–Ti(OEt)(L7)] (8). The com-
plex shows a strong band in the IR spectrum at 720 cmꢁ1 consis-
tent with the Ti–O–Ti system. The 1H NMR spectrum showed
single resonances for the aryl ring methyl and tert-butyl groups,
two triplets for the NCH2CH2N section of the ligand, an AX spin sys-
tem doublet for each of the benzylic CH hydrogens, two doublets
for the meta-hydrogens of the aryl ring and a single quartet for
the ethoxo ligand methylene hydrogens. The 13C NMR spectrum
showed a single set of resonances for each of the different carbons.
The NMR features are characteristic of a symmetric environment
for the L7 ligand which indicate a trans geometry for the phenolate
rings and a twofold symmetry for the NCH2CH2NMe2 section of the
ligand. However two possible structures can give rise to these NMR
spectral features, one in which the pendant NMe2 group lies trans
to a terminal OEt ligand (Structure 8a) or where the group lies
trans to the bridging oxygen atom (Structure 8b).
Table 1
Selected bond distances (Å) and Angles (°) for 3.
Ti–O1
Ti–O2
Ti–O3
Ti–O4
Ti–N1
Ti–N2
O1–C1
O2–C20
O3–C23
O4–C25
1.894(2)
1.900(2)
1.829(2)
1.832(2)
2.342(2)
2.339(2)
1.341(2)
1.346(2)
1.423(3)
1.417(3)
Ti–O1–C1
Ti–O2–C20
Ti–O3–C23
Ti–O4–C25
141.8(1)
142.5(1)
130.6(2)
130.4(1)
An X-ray crystal structure determination of (8) (Fig. 3) con-
firmed the presence of the Ti(OEt–O–Ti(OEt) system and the sym-
metrical nature of the L7 ligand shown by the NMR spectra. Bond
length and angles are contained in Table 2 (Crystallographic data,
Table 3). The two sides of the molecule are structurally related
across a near-linear symmetric oxo bridge [Ti–O–Ti bond angle
176.8(1); Ti(1)–O(1) and Ti(2)–O(1) bond lengths 1.811(2) and
1.813(2) Å] but the ends are rotated about the oxo bridge by
approximately 90°. Each end of the molecule has a distorted octa-
hedral geometry about the titanium atom where the phenoxo li-
gands lie trans to each other, the pendant NMe2 group lies trans
to the oxo bridge and the central nitrogen lies trans to a terminal
ethoxo ligand. The geometry is thus shown to be consistent with
structure 8b rather than 8a. The coordination mode for the L7 li-
gand is similar to that generally found for other group 4 complexes
containing this ligand [5].
bond lengths 1.921(1) and 1.939(1) Å] [2b]. This represents a loos-
ening of the Ti-O -donation in the phenoxo ligand when the elec-
tron withdrawing p-nitro group is present. In turn, the alkoxo
ligand Ti–O bond lengths are shorter in the p-nitro compound than
in (3) {1.806(1) and 1.819(1) Å cf. 1.829(2) and 1.832(2) Å}. This
p
represents a tightening of the
p-donation in the alkoxo ligand
when the electron withdrawing p-nitro group is present on the
phenoxo ligand aryl ring and a loosening when the mildly electron
donating methyl group is present.
The structure of complex (3) shows that one of the N-methyl
groups point up and the other down, each one in the direction of
one of the two trans-orientated phenoxo ligands. Along with the
ortho-Me group on the phenoxo ligand aryl ring and the alkyl
group of the ethoxo ligand it is clear that entry of H2O towards
the titanium centre and ethoxo ligand oxygen atom is somewhat
hindered and this could result in the observed air-stability and
sluggish hydrolysis shown by the complex. If an aryl ring ortho-
tert-butyl substituent were present, the entry of H2O would be
highly restricted and hydrolysis would be very difficult, as was ob-
served. Assuming that when the methyl groups on nitrogen are re-
placed by hydrogen, these atoms also point in different directions,
there is then an opening up of the local environment. In addition,
coordination of nitrogen would increase the dipole of the N–H
bond allowing increased hydrogen bonding to an H2O molecule
which would hold it in an ideal situation for hydrolysis to occur
(see Fig. 2). There is then potentially a hydrogen bonding rate
enhancement mechanism available for the hydrolysis. However
the steric effect of a tert-butyl group in close proximity would ste-
rically encumber the metal centre again and slow the hydrolysis, as
was observed.
Carrying out the reaction of the pendant NMe2 ligand H2L7 with
[Ti(OCHMe2)4] in ethanol and adding one equivalent of H2O gave a
H
O
O
O
H
O
H
N
N
Ti
O
Fig. 3. Ortep diagram [22] showing the molecular structure of [(L7)Ti(OEt)–O–
Ti(OEt)(L7)] (8b). Hydrogen atoms have been omitted for clarity. Where site
occupancy factors were refined only one of the disordered groups is shown.
Fig. 2. Potential hydrogen bonding system for H2O in complexes (6) and (7).

1724
A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
Table 2
2.367(2) Å] suggesting that the oxo bridge oxygen has a stronger
Selected bond distances (Å) and angles (°) for 8b and 11b.
trans effect. However this may not be correct since the central
nitrogen may be forced closer to the metal by constraints of the
rings made with the rest of the phenoxo ligand and titanium atom
which is forced to adopt a boat-like conformation. In comparison,
the Ti–N bond lengths for the nitrogen atom trans to the ethoxo li-
gand in bis-ethoxo complex (3) [2.342(2) and 2.339(2) Å] are inter-
mediate to the above values.
8b
11b
Ti1–O1
1.811(2)
1.892(2)
1.907(2)
1.829(2)
2.320(2)
2.367(2)
1.813(2)
1.897(2)
1.900(2)
1.828(2)
2.318(3)
2.377(2)
1.354(4)
1.339(3)
1.443(11)
1.348(4)
1.337(4)
1.417(3)
Ti1–O1
1.824 (1)
1.899(1)
1.904(1)
1.808(1)
2.324(2)
2.282 (2)
1.811 (1)
1.920(1)
1.895(1)
1.823(1)
2.322(2)
2.284(2)
1.330(2)
1.342(2)
1.411(2)
1.350(2)
1.338(2)
1.412(2)
Ti1–O11
Ti1–O12
Ti1–O13
Ti1–N11
Ti1–N12
Ti2–O1
Ti2–O21
Ti2–O22
Ti2–O23
Ti2–N21
Ti2–N22
O11–C1
O12-C23
O13–C29
O21–C31
O22–C53
O23–C59
Ti1–O11
Ti1–O12
Ti1–O13
Ti1–N11
Ti1–N12
Ti2–O1
Ti2–O21
Ti2–O22
Ti2–O23
Ti2–N21
Ti2–N22
O11–C1
O12–C28
O13–C37
O21–C41
O22–C68
O23–C77
When the pendant NMe2 ligand H2L8 was reacted with [Ti(OCH-
Me2)4] and the water added, the refluxing period produced a com-
plex analysing as [(L8)Ti(OEt–O–Ti(OEt)(L8)] (9) in nearly
quantitative yield. The IR spectrum showed the usual strong Ti–
O–Ti band (694 cmꢁ1) but the complex was found to be insoluble
in organic solvents which is unusual for a ligand with tert-butyl
substituents on the aryl ring and thus further characterisation
was precluded. However, based on the crystal structure determina-
tion for complex (8), structure 9b is preferred to 9a if indeed the
complex does have an [(L8)Ti(OEt)–O–Ti(OEt)(L8)] structure.
Reaction of pendant pyridine ligand H2L9 with [Ti(OCHMe2)4] in
ethanol and addition of water in the usual manner gave a precipi-
tate which NMR spectroscopy showed to contain 3 products. The IR
spectrum shows a very broad Ti–O band at 814 cmꢁ1 but the NMR
spectra show that one product is apparently of the [(L9)Ti(O)] type.
Overall the spectra are very complicated suggesting asymmetry
associated with cis coordination of the phenoxo ligands but no sep-
aration of the 3 complexes has yet been achieved, nor has crystal-
line material been obtained hence the mixture has not been
studied further. Both cis and trans coordination modes have been
identified for the phenolato sections of this type of ligand in other
group 4 complexes [21]. The filtrate from the reaction was found to
contain [(L9)Ti(OEt)2] (10) for which the NMR spectra showed for
the L9 ligand two widely separated doublets indicating diastero-
topic aryl CH2 hydrogens, a singlet indicating equivalent py-CH2
hydrogens and two ethoxo ligand OCH2 quartets. These features
are consistent with a trans-phenoxo structure and ethoxo ligands
trans to the two different nitrogen ligands. This type of structure
has been determined by X-ray crystallography for isopropoxo ana-
logues of the group 4 metals [2a,b].
Ti1–O1–Ti2
176.8(1)
142.0(2)
141.8(2)
125.3(3)
141.5(2)
142.3(2)
132.1(2)
Ti1–O1–Ti2
177.3(1)
142.3(1)
137.9(1)
142.3(1)
134.1(1)
141.5(1)
136.7(1)
Ti1–O11–C1
Ti1–O12–C23
Ti1–O13–C29
Ti2–O21–C31
Ti2–O22–C53
Ti2–O23–C59
Ti1–O11–C1
Ti1–O12–C28
Ti1–O13–C37
Ti2–O21–C41
Ti2–O22–C68
Ti2–O23–C77
The closeness of the phenoxy-amine ligands across the oxo
bridge is such that the phenoxo ligands push back towards each
end of the molecule so that they end up centrosymmetrically re-
lated to each other. This feature then gives rise to the diastereotop-
ic aryl CH2 hydrogens and other symmetry related features in the
1H NMR spectrum. The Ti–O bond lengths for the phenoxo ligands
[range 1.892(2) to 1.907(2) Å] and ethoxo ligands [1.829(2) and
1.828(2) Å] are similar to those in bis-ethoxo complex (3)
[1.894(2) and 1.900(2) Å and 1.829(2) and 1.832(2) Å, respec-
tively]. The Ti–N bond length for the central nitrogen atom lying
trans to the ethoxo ligand [e.g. 2.320(3) Å] is shorter than for the
pendant NMe2 ligand which lies trans to the oxo bridge [e.g.
Table 3
Crystallographic data for 3, 8b and 11b.
3
8b
11b
Empirical Formula
Mr
C26H40N2O4Ti
492.50
C60H94N4O7Ti2
1079.19
C76H110N4O7Ti2
1287.48
T (K)
293(2)
90(2)
296(2)
Crystal size (mm)
Crystal system
Space Group
a (Å)
b (Å)
c (Å)
0.23, 0.11, 0.09
monoclinic
P21/c
11.7849(3)
16.9176(4)
13.1917(3)
90.0
0.30, 0.20, 0.09
orthorhombic
Pbca
26.7721(5)
15.0118(2)
29.5107(6)
90.0
0.23, 0.12, 0.12
monoclinic
P21/c
23.8582(3)
16.3286(2)
19.4977(3)
90.0
a
(°)
b (°)
105.621(1)
90.0
2533.1(9)
4
1.291
0.392
90.0
90.0
11860.3(4)
8
1.209
96.396(1)
90.0
7548.5(2)
4
1.133
0.263
c
(°)
V (Å3)
Z
Dcalc (mg mmꢁ3
)
Absorption coefficient (mmꢁ1
)
0.322
F(0 0 0)
1056
4656
2776
h Range for data collection (°)
Reflections collected
2, 28.08
31 018
1.38, 27.45
69 798
1.51, 28.10
93 720
Unique reflections (Rint
Reflections with [I > 2r(I)]
)
61 43 (0.086)
4121
12 408 (0.0928)
6671
18 263 (0.0834)
11 677
Refined parameters
306
0.9673, 0.7620
1.008
0.0453, 0.0867
0.0860, 0.1004
0.313, ꢁ0.377
Patterson methods
762
0.9716, 0.8216
0.994
0.0664, 0.1249
0.1451, 1451
0.653, ꢁ0.424
direct methods
828
0.9691, 0.7961
1.001
0.0492, 0.0978
0.0979, 0.1148
0.367, ꢁ0.445
direct methods
17
Absorption correction Tmax, Tmin
Goodness-of-fit (GOF) on F2 (all data)
Final R indices [I > 2 (I)] (R1,wR2)
R indices (all data) (R1,wR2)
Maximum, minimum
(e Åꢁ3
Method of structure solution
r
D
q
)

A.J. Nielson, J.M. Waters / Polyhedron 29 (2010) 1715–1726
1725
group is present [125.3(3)° in (8b), 142.3(1)° in (11b)] but the
remainder are relatively similar. The phenoxo ligands push back
towards each end of the molecule and the boat conformations
made by the O and central N sections of the ligand and Ti are sim-
ilar in both complexes.
Slow evaporation of the solvent from the reaction mixture gave
further precipitate which NMR spectroscopy showed to contain
mostly complex (11b) (41%) and some other complexes including
[L10Ti(OEt)2] which were not studied further. [(L10)Ti(OEt)–O–
Ti(OEt)(L10)] (11b) was refluxed vigorously with two equivalents
of H2O in THF solution for 24 h in an attempt to transform it to
an [(L10)Ti(O)]2 complex but NMR spectroscopy showed only the
starting complex was present after this process.
4. Conclusion
The work shows that phenoxy-amine complexes containing
the Ti(OEt)–O–Ti(OEt) system can be prepared using [Ti(OCH-
Me2)4] in ethanol solution by first attaching the ligand to give
an [(L)Ti(OEt)2] complex which can then be hydrolysed to the
bridging oxo system. The hydrolysis appears to terminate at this
point and there is little evidence that the ethoxo ligands in the
Ti(OEt)–O–Ti(OEt) system hydrolyse further to give complexes
of the [{(L)Ti(O)}2] type. Hydrolysis of the bis-ethoxo complexes
[(L)Ti(OEt)2] is not particularly facile but for the N,N-disubsti-
tuted ethylendiamine complexes there appears to be a rate
enhancement of the hydrolysis reaction if there is a hydrogen
atom present on the nitrogen rather than a methyl group. In
both these cases there is a slowing down of the hydrolysis if
the ortho-substituent on the phenoxo ligand is changed from a
methyl group to a tert-butyl group. In the case where both nitro-
gen atoms contain methyl groups and the ortho-substituents on
the phenoxo ligands are tert-butyl groups the hydrolysis is com-
pletely inhibited. When ligands containing phenoxy-amine
groups and pendant NMe2 or pyridine groups are used the
hydrolysis reaction can lead to the formation of isomers which
can be hard to separate. Overall, the hydrolysis reaction does
give a facile synthetic method for formation of [(L)Ti(OEt)–O–
Ti(OEt)(L)] type complexes which have potential as catalysts
and material synthesis. This potential may be even greater given
that the ligands used are now available in high yield via micro-
wave assisted synthesis [13].
Fig. 4. Ortep diagram diagram [22] showing the molecular structure of
[(L10)Ti(OEt)–O–Ti(OEt)(L10)] (11b). Hydrogen atoms have been omitted for clarity.
Reaction of the pendant pyridine ligand H2L10 using the usual
reaction conditions gave
a
55% yield of [(L10)Ti(OEt)–O–
Ti(OEt)(L10)] (11) which was identified on the basis of spectral data
and an X-ray crystal structure. The IR spectrum shows an absorp-
tion for the Ti–O–Ti system at 722 cmꢁ1 and the NMR spectra show
a single set of resonances for the L10 and ethoxo ligands. These fea-
tures and in particular the observed singlet for the Py- attached
CH2 group hydrogens and two doublets for the aryl C–H hydrogens
in the 1H NMR spectrum indicate a symmetric structure for the L10
ligand with the phenoxo ligands lying trans to each other [21].
However the spectra do not distinguish between the pendant lying
trans to the terminal ethoxo ligand (structure 11a) or the Ti–O–Ti
bridging system (Structure 11b).
The overall geometry was shown by an X-ray crystal structure
determination to be (11b) (Fig. 4). Bond lengths and angles are
contained in Table 2 (Crystallographic data, Table 3) where they
are compared with the values obtained for complex (8b) The mol-
ecule has a similar overall geometry to complex (8b). The two sides
of the molecule are structurally related across a near-linear oxo
bridge [Ti–O–Ti bond angle 177.3(1)° cf. 176.8(1) in (8b)] but the
bridge is slightly asymmetric [Ti(1)–O(1) and Ti(2)–O(1) bond
lengths 1.824(1) and 1.811(1) Å]. Each end of the molecule has a
distorted octahedral geometry about the titanium atom with
trans-phenoxo ligands, the pendant pyridine ligand nitrogen trans
to the oxo bridge and the central nitrogen atom of the ligand trans
to the terminal ethoxo ligand. The ends of the molecule are rotated
by approximately 90° with respect to each other as was also found
in (8b).
By comparing the data for 8b and 11b in Table 2 it can be seen
that overall the bond lengths are very similar indicating that
changing the ortho-substituent from Me in (8b) to tert-butyl in
(11b) has very little effect. Differences appear in the ethoxo ligand
Ti–O bond lengths for one side of the molecules [1.829(2) Å for
(8b), 1.808(1) Å for (11b)] but not the other side [[1.828(2) Å for
(8b), 1.823(1) Å for (11b)]. The Ti–N bond lengths for the NMe2
and pyridine pendant arms [2.367(2) Å in (8b), 2.282(2) Å in
(11)] also show differences. For the bond angles, the ethoxo ligand
Ti–O–C straighten out significantly when the ortho-tert-butyl
5. Supplementary data
CCDC 732091, 732092, and 732093 contain the supplementary
crystallographic data for complexes (3), (8b) and (11b). These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Acknowledgements
We thank Mr Graham Freeman for running the IR and NMR
spectra. We are grateful to Ms Tania Groutso of the University of
Auckland for the X-ray data collections.
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