Synthesis of Hf(IV) complex from cyclam (1,4,8,11-tetraazacyclotetradecane) -containing amino-amido groups

Article abstract of DOI:10.1080/00397911.2010.523337

The reactivity of cyclam (1,4,8,11-tetraazacyclcotetradecane)-containing amino-amido groups with hafnium(IV) chloride was described. Taylor & Francis Group, LLC.

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Synthesis of Hf(IV) Complex from Cyclam
(1,4,8,11-Tetraazacyclotetradecane)-
Containing Amino-Amido Groups
Munusamy Thirumavalavan a b & Jiunn-Fwu Lee b
a Departamento de Engenharia Química , Instituto Superior Técnico ,
Lisboa , Portugal
b Graduate Institute of Environmental Engineering, National Central
University , Taiwan , China
Accepted author version posted online: 26 Jul 2011.Published
online: 14 Sep 2011.
To cite this article: Munusamy Thirumavalavan & Jiunn-Fwu Lee (2012) Synthesis of Hf(IV) Complex
from Cyclam (1,4,8,11-Tetraazacyclotetradecane)-Containing Amino-Amido Groups, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
42:2, 223-226, DOI: 10.1080/00397911.2010.523337
To link to this article: http://dx.doi.org/10.1080/00397911.2010.523337
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Synthetic Communications1, 42: 223–226, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.523337
SYNTHESIS OF Hf(IV) COMPLEX FROM CYCLAM
(1,4,8,11-TETRAAZACYCLOTETRADECANE)-
CONTAINING AMINO-AMIDO GROUPS
Munusamy Thirumavalavan1,2 and Jiunn-Fwu Lee2
1
´
Departamento de Engenharia Quımica, Instituto Superior Tecnico, Lisboa,
´
Portugal
2Graduate Institute of Environmental Engineering, National Central
University, Taiwan, China
GRAPHICAL ABSTRACT
Abstract The reactivity of cyclam (1,4,8,11-tetraazacyclcotetradecane)-containing amino-
amido groups with hafnium(IV) chloride was described.
Keywords Amino-amido; cyclam; Hf(IV) complex; IR; NMR
INTRODUCTION
In coordination chemistry, polyaza macrocycles, though robust ligands, rarely
have been used in their deprotonated forms as amido ligands[1–3] or as ancilliary
ligands in organometallic chemistry for supporting organic functionalities. This
usage can be particularly addressed to the synthesis and use of amido and polyamido
ligands in early transition and transition-metal chemistry.[4–7] Such macrocyclic
polyamines have a number of basic advantages in tuning the properties of the target
complex using variants such as the number and type of donor atoms, ring size, and
structural variations. The macrocyclic effect should play an important role in the sta-
bilization of any resulting organometallic fragments. In this work, we illustrate these
principles with tetraaza macrocycle (1,4,8,11-tetraazacyclotetradecane, H4L)[8] and
Received May 19, 2010.
Address correspondence to Munusamy Thirumavalavan, Graduate Institute of Environmental
Engineering, National Central University, Chung-Li, Taoyuan County, 320 Taiwan, China. E-mail:
mtvala@yahoo.com
223

224
M. THIRUMAVALAVAN AND J.-F. LEE
Scheme 1. Synthesis of macrocyclic Hf(IV) complex.
show how in the appropriate form it can be successfully reacted with early transition
metals, illustrated here by Hf(IV). We report the synthesis of Hf(IV) complex.
Scheme 1 is the schematic representation of the reaction of the amido-amino form
of H4L with HfCl4 ꢀ 2THF. Addition of 2 equivalents of nBuLi to a tetrahydorfuran
(THF) solution of the amine gave the soluble dianionic Li2H2L. Here we illustrate its
reaction with HfCl4 ꢀ 2THF, which was best achieved in situ and led to insoluble
products. The Schlenk technique (connected with vacuum line and nitrogen) was
used to synthesize the appropriate complex.
EXPERIMENTAL
A solution of nBuLi (3.33 ml, 1.60 M in hexane) was added to a stirred slurry of
cyclam (0.5330 g, 0.0026 mol) in THF over 30 min. The solution was stirred for
60 min, and solid HfCl4 ꢀ 2THF (1.2359 g, 0.0026 mol) was added to the resulting
brown solution. The mixture was then left stirring for 4 h to finally give a red-brown
cloudy solution. The solvent was pumped off. Pyridine was added to the residue,
the brown solution was extracted, and the solvent pyridine was pumped off to get a
pale brown solid. The solid was recrystallized in pyridine to get shiny, pale brown
microcrystals (flakes), but these shiny crystalline flakes were not suitable for x-ray
analysis. Yield: ¼ 0.8336 g (70%). The synthesized Hf(IV) complex was characterized
by elemental and spectral analyses. Analytical data for C10H22N4Cl2Hf ꢀ C4H8O: Cal-
culated (%): C, 32.30; H, 5.81; N, 10.77. Found (%): C, 32.59; H, 5.89; N, 10.59. Mass
(FAB) m=z: 520 (M þ 1). Selected IR (KBr): 3135 (s) cmꢁ1 (N-H stretching).
RESULTS AND DISCUSSION
The N-H stretching of cyclam was observed at 3268 and 3186 cmꢁ1 1H
.
(300 MHz) NMR (d ppm in C5D5N): 2.84–3.89 and 1.56–2.36 (complex CH2 region).
One unpredictable peak was obtained at d ¼ 5.70, which may be due to N-H protons.
13C (75 MHz) NMR (d ppm in C5D5N): 22.50 (CCH2C), 24.88 (CCH2C), 29.63
(NCCH2), 30.66 (NCCH2), 45.67(NCH2C), 46.40 (NCH2C), 48.75 (CH2CN), 52.72
(CH2CN), 61.14 (NHCCH2), and 75.04 (NHCCH2). The 13C NMR spectra confirm
10 chemically inequivalent carbon resonances as C attached to CH2, C attached to
N, C attached to NH, C attached to N-CH2 and C attached to NH-CH2. Before
recrystallization, the NMR spectrum seems to be complex, but after fractional

SYNTHESIS OF Hf(IV) COMPLEX
225
Scheme 2. Hafnium complex–catalyzed esterification reaction.
recrystallization,[3] the NMR spectrum is simpler. Both elemental analysis and NMR
spectral analysis led to the interesting result that the complex contained one THF
molecule, either coordinated or as free lattice molecule. Although the addition of
BuLi-cyclam solutions to the metal suspensions resulted in immediate dissolution,
the formation of complex required reflux. Considering that in general the metathesis
of metal halide bonds with lithium amides occurs readily, the higher energy barriers
associated with these reactions must result from the structural features of
BuLi-cyclam. To attain the structure depicted in Scheme 1, cyclam has to undergo
structural transformation to bind the four nitrogen atoms to the same metal center.
This complex exemplifies a direction in the use of amido-amino ligands and in parti-
cular in the form of the macrocycle. To confirm the activity, we describe here highly
efficient and direct esterification of 4-phenylbutyric acid (1 mmol) and benzyl alcohol
(1 mmol) catalyzed by Hf complex (1 mol%) in toluene under reflux at inert
conditions for 10 h as shown in Scheme 2. The reaction led to 100% conversion of
ester as product. For the uncatalyzed reaction, the observed yield was only 33%.
CONCLUSION
We believe that this complex will have improved catalytic activity and we are
actively studying this.
ACKNOWLEDGMENTS
M. T. gratefully acknowledges the financial support received from FCT
ˆ
(Fundac¸a˜o Para a Ciencia e a Tecnologia, Grant No. SFRH=BPD=14985=2004),
Portugal, and the financial support by the National Science Council (NSC), Taiwan,
China.
REFERENCES
1. Lappeert, M. F.; Power, P. P.; Sagner, A. R.; Srivastava, R. C. Metal and Metalloid
Amides; Ellis Horword-Wiley: Chichester, 1980.
2. Olmstead, M. M.; Power, P. P.; Viggiano, M. A new class of a-bonded aliphatic
aza-macrocyclic complexes of transition metals: Synthesis and x-ray crystal structures of
nitrogen-bridged [(TiN4C12H24)2 and oxo-bridged [(N4C12H25) TioTi (N4C12H25)]. J. Am.
Chem. Soc. 1983, 105, 2927–2928.
3. Rogers, A. J.; Solari, E.; Floriani, C.; Villa, A. C.; Rizzoli, C. New directions in amido-
transition metal chemistry: The preparation and reaction of mixed amino-amido macrocyclic
ligands. J. Chem. Soc. Dalton Trans. 1997, 2385–2386.

226
M. THIRUMAVALAVAN AND J.-F. LEE
4. Duan, Z.; Naiini, A. A.; Lee, J.-H.; Verkade, J. G. Novel volatile azatranes of group 4
metals. Inorg. Chem. 1995, 34, 5477–5482.
5. Wan, Y.; Verkade, J. G. Hydride and fluoride transfer reactions accompanying nucleophilic
substitution at pentacoordinate silicon. J. Am. Chem. Soc. 1995, 117, 141–156.
6. Shih, K.-Y.; Shrock, R. R.; Kempe, R. Synthesis of molybdenum complexes that contain
silylated triamidoamine ligands: A m-dinitrogen complex, methyl and acetylide complexes,
and coupling of acetylides. J. Am. Chem. Soc. 1994, 116, 8804–8805.
7. Wang, E. H.; Weisman, G. R.; Hill, D. C.; Reed, D. P.; Rofers, M. E.; Condon, J. S.; Fagan,
M. A.; Calabrese, J. C.; Lam, K.-C.; Guzei, I. A.; Rheingold, A. L. Synthesis and character-
ization of cross-bridged cyclams and pendant-armed derivatives and structural studies of
their copper(II) complexes. J. Am. Chem. Soc. 2000, 122, 10561–10572.
8. Barefield, E. K.; Wagner, F.; Herlinger, A. W.; Dahl, A. R.; Holt, S. (1,4,8,11-Tetraazacy-
clotetradecane)nickel(II) perchlorate and 1,4,8,11-tetraazacyclo tetra decane. Inorg. Synth.
1976, 116, 220–225.