A new β-diketiminate ligand carrying a functional group on the carbon framework. Synthesis and characterization of a linear polymeric copper(I) complex

Article abstract of DOI:10.1021/ic0155535

A new β-diketiminate ligand containing a nitro group on the carbon framework has been developed, complexation of which with cuprous ion provided a novel linear polymer copper(I) complex with an extended d-pπ system.

Full text of DOI:10.1021/ic0155535

5316
Inorg. Chem. 2001, 40, 5316-5317
A New â-Diketiminate Ligand Carrying a Functional Group on the Carbon Framework. Synthesis and
Characterization of a Linear Polymeric Copper(I) Complex
Seiji Yokota,† Yoshimitsu Tachi,† Nagatoshi Nishiwaki,‡ Masahiro Ariga,‡ and Shinobu Itoh*,†
Department of Chemistry, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan,
and Department of Chemistry, Osaka Kyoiku University, Asahigaoka, Kashiwara, Osaka 582-8582, Japan
ReceiVed June 15, 2001
â-Diketiminate derivatives function as monoanionic bidentate
ligands, which have been applied for synthesis of a wide variety
of transition metal,1 main group element,2 and lanthanide com-
plexes.3 Particular attention has recently been focused on the roles
of such complexes as polymerization catalysts,1a,f,g,k,2j novel
organometallic compounds,1d,2a,b,d,g,h and models for active sites
of metalloenzymes.1j,m In most cases, sterically encumbered
â-diketiminate derivatives (R1 ) ortho-substituted aryl group in
Chart 1) have been employed to make the complexes as
mononuclear and coordinatively unsaturated. However, variation
of substituents on the carbon framework of the ligand is rather
limited (mostly R2 ) Me and R3 ) H).1-3 Thus, modification of
the ligand skeleton will provide further opportunity to add more
function to the metal complexes and to modulate their coordina-
tion chemistry.
Chart 1
Scheme 1
We report herein a new â-diketiminate ligand (2-) carrying a
nitro group on the carbon framework (R1 ) mesityl; R2 ) H; R3
) NO2).4 Complexation of the ligand with cuprous ion resulted
in formation of a linear polymeric copper(I) complex, demonstrat-
ing a possible application of the â-diketiminate ligand to the
supramolecular chemistry.
Nishiwaki and co-workers have demonstrated that aminolysis
of 1-methyl-5-nitropyrimidin-2(1H)-one (1) affords a series of
diimine derivatives of nitromalonaldehyde.5 This reaction was
applied for the preparation of ligand precursor 2H. Thus, the
reaction of 1 (3.2 mmol) and 2,4,6-trimethylaniline (6.9 mmol)
in refluxing methanol (40 mL) for 4 days gave 2H, which was
isolated by flash column chromatography in 27% (Scheme 1).6
Structural refinement of 2H in the X-ray analysis (Figure 1) has
indicated that the compound exists as a 3-imino-2-nitropropenyl-
amine derivative as shown in Scheme 1.7 Thus, the bond distances
of C(1)-C(3) (1.454(3) Å) and C(2)-N(1) (1.314(3) Å) are
longer than those of C(1)-C(2) (1.416(3) Å) and C(3)-N(2)
(1.286(3) Å), respectively.
† Osaka City University.
‡ Osaka Kyoiku University.
(1) (a) Feldman, J.; McLain, S. J.; Parthasarathy, A.; Marshall, W. J.;
Calabrese, J. C.; Arthur, S. D. Organometallics 1997, 16, 1514-1516.
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17, 1315-1323. (c) Kim, W.-K.; Fevola, M. J.; Liable-Sands, L. M.;
Rheingold, A. L.; Theopold, K. H. Organometallics 1998, 17, 4541-
4543. (d) Budzelaar, P. H. M.; de Gelder, R.; Gal, A. W. Organometallics
1998, 17, 4121-4123. (e) Budzelaar, P. H. M.; van Oort, A. B.; Orpen,
A. G. Eur. J. Inorg. Chem. 1998, 1485-1494. (f) Cheng, M.; Lobkovsky,
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Qian, B.; Scanlon, W. J.; Smith, M. R., III; Motry, D. H. Organometallics
1999, 18, 1693-1698. (i) Kakaliou, L.; Scanlon, W. J., IV; Qian, B.;
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5964-5977. (j) Holland, P. L.; Tolman, W. B. J. Am. Chem. Soc. 1999,
121, 7270-7271. (k) Lee, L. W. M.; Piers, W. E.; Elsegood, M. R. J.;
Clegg, W.; Parvez, M. Organometallics 1999, 18, 2947-2949. (l)
Budzelaar, P. H. M.; Moonen, N. N. P.; de Gelder, R.; Smits, J. M. M.;
Gal, A. W. Eur. J. Inorg. Chem. 2000, 753-769. (m) Holland, P. L.;
Tolman, W. B. J. Am. Chem. Soc. 2000, 122, 6331-6332.
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1998, 120, 9384-9385. (b) Qian, B.; Ward, D. L.; Smith, M. R., III.
Organometallics 1998, 17, 3070-3076. (c) Qian, B.; Baek, S. W.; Smith,
M. R., III. Polyhedron 1999, 18, 2405-2414. (d) Radzewich, C. E.;
Guzei, I. A.; Jordan, R. F. J. Am. Chem. Soc. 1999, 121, 8673-8674.
(e) Bailey, P. J.; Dick, C. M. E.; Fabre, S.; Parsons, S. Dalton Trans.
2000, 1655-1661. (f) Cui, C.; Roesky, H. W.; Hao, H.; Schmidt, H.-
G.; Noltemeyer, M. Angew. Chem., Int. Ed. 2000, 39, 1815-1816. (g)
Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Hao, H.;
Cimpoesu, F. Angew. Chem., Int. Ed. 2000, 39, 4274-4276. (h) Gibson,
V. C.; Segal, J. A.; White, A. J. P.; Williams, D. J. J. Am. Chem. Soc.
2000, 122, 7120-7121. (i) Hardman, N. J.; Eichler, B. E.; Power, P. P.
Chem. Commun. 2000, 1991-1992. (j) Chamberlain, B. M.; Cheng, M.;
Moore, D. R.; Ovitt, T. M.; Lobkovsky, E. B.; Coates, G. W. J. Am.
Chem. Soc. 2001, 123, 3229-3238. (k) Akkari, A.; Byrne, J. J.; Saur,
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190-198. (l) Hardman, N. J.; Power, P. P. Inorg. Chem. 2001, 40, 2474-
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Prust, J.; Noltemeyer, M.; Roesky, H. W. Inorg. Chem. 2001, 40, 2794-
2799.
Treatment of 2H (0.1 mmol) with an equimolar amount of
[CuI(MeCN)4]PF6 in the presence of Et3N (0.3 mmol) in dry
methanol (5 mL) under anaerobic conditions resulted in the
formation of dark purple microcrystals of complex 3 in 70%
(4) Related â-diketiminate type ligands having an electron-withdrawing
substituent on the carbon framework have been reported: (a) Pfaltz, A.
Acc. Chem. Res. 1993, 26, 339-345. (b) Takamura, S.; Yoshimiya, T.;
Kameyama, S.; Nishida, A.; Yamamoto, H.; Noguchi, M. Synthesis 2000,
637-639.
(5) Nishiwaki, N.; Tohda, Y.; Ariga, M. Bull. Chem. Soc. Jpn. 1996, 69,
1997-2002.
(6) Analytical data for 2H: IR (KBr) 1637 (CdN), 1573, 1311, 1289, 1270
cm-1 (NO2); 1H NMR (CDCl3, 300 MHz) δ 2.22 (s, 12H, CH3), 2.29 (s,
6H, CH3), 6.93 (s, 4H, aromatic H of Ar group), 8.75 (s, 2H, CH), 12.77
(br, 1H, NH); HRMS m/z 351.1957, calcd for C21H25N3O2 351.1947.
Anal. Calcd for C21H25N3O2: C, 71.77; H, 7.17; N, 11.96. Found: C,
71.79; H, 7.21; N, 11.75.
(7) Crystal data for 2H: M ) 351.45, C21H25N3O2, crystal dimensions 0.30
× 0.30 × 0.30 mm, triclinic, space group P1h (No. 2), a ) 8.954 (2) Å,
b ) 14.536(4) Å, c ) 8.220(2) Å, R ) 105.55(1)°, â ) 109.61(1)°, γ
) 77.70(2)°, V ) 961.9(5) Å3, Z ) 2, Fcalcd ) 1.213 g/cm3, 2θmax
)
55.0°, Mo KR ) radiation (λ ) 0.71069 Å), T ) 158 K. Data were
collected using the Rigaku RAXIS rapid imaging plate system, and the
structure was solved via direct methods. Full-matrix least-squares
refinement on F using SIR92 converged with final R ) 0.080 and Rw
)
0.103 for 5226 independent reflection with I > 1σ(I) and 3859
(3) Drees, D.; Magull, J. Z. Anorg. Allg. Chem. 1994, 620, 814-818.
parameters.
10.1021/ic0155535 CCC: $20.00 © 2001 American Chemical Society
Published on Web 09/14/2001

Communications
Inorganic Chemistry, Vol. 40, No. 21, 2001 5317
Figure 1. ORTEP drawing of 2H showing 50% probability thermal
ellipsoids. Hydrogen atoms except H(25) are omitted for clarity. Selected
bond distances (Å) and angles of least-squares planes (deg): O(1)-N(3)
1.261(2), O(2)-N(3) 1.257(2), N(1)-C(2) 1.314(3), N(1)-C(4) 1.444(3),
N(2)-C(3) 1.286(3), N(2)-C(13) 1.451(3), N(3)-C(1) 1.424(3), C(1)-
C(2) 1.416(3), C(1)-C(3) 1.454(3); plane 1 and plane 2, 49.10°; plane 1
and plane 3, 65.24°; plane 2 and plane 3, 100.64°. (Plane 1: N(1), N(2),
C(1), C(2), C(3). Plane 2: C(4), C(5), C(6), C(7), C(8), C(9). Plane 3:
C(13), C(14), C(15), C(16), C(17), C(18)).
Figure 2. A top view of the crystal packing of 3 (A) and a side view of
the linear chain of 3 (B) with 50% probability thermal ellipsoids.
Hydrogen atoms are omitted for clarity. Selected bond distances (Å) and
angles of least squares planes (deg): Cu(1)-N(1) 1.992(2), Cu(1)-N(2)
1.991(2), Cu(1)-O(1)′ 1.986(1), O(1)-N(3) 1.290(2), O(2)-N(3) 1.237(2),
N(1)-C(2) 1.295(2), N(1)-C(4) 1.438(2), N(2)-C(3) 1.291(2), N(2)-
C(13) 1.445(2), N(3)-C(1) 1.393(2), C(1)-C(2) 1.430(3), C(1)-C(3)
1.435(3); plane 1 and plane 2, 68.0; plane 1 and plane 3, 67.0. (Plane 1:
N(1), N(2), C(3), C(1), C(2). Plane 2: C(4), C(5), C(6), C(7), C(8), C(9).
Plane 3: C(13), C(14), C(15), C(16), C(17), C(18)). Atom numbering of
the ligand is the same as that indicated in Figure 1.
yield.8 When the complexation was carried out slowly at an
interface between a CH3OH solution containing [CuI(MeCN)4]-
PF6 and a CH2Cl2 solution containing 2H, single crystals of 3
were obtained, for which X-ray crystallographic analysis has been
performed (Figure 2).9,10 The neutral copper(I) unit, [CuI(2-)],
associates each other to form a head-to-tail (Cu-to-NO2) linear
chain, where the cuprous ion adopts a trigonal planar structure
and the nitro group acts as a monodentate ligand to link the
mononuclear copper(I) units (Figure 2B). The dark purple color
of 3 in the solid state may be due to the extended d-pπ interaction
through the Cu-NO2 linkage.11 In fact, the color turns to pale
yellow, when the polymer complex is converted into a monomeric
copper(I) complex such as [CuI(2-)(PPh3)].12
neighboring polymer chains.13 As a result of this arrangement,
there is a long V-shaped column along with the polymer chain.
Direction of the head-to-tail vector is the same in one column
(indicated as (I) or (II) in Figure 2A), while that in the neighboring
column is opposite; from the bottom to the top in column (I) and
from the top to the bottom in column (II). Although a great
number of self-assembled supramolecules based on copper(I) and
silver(I) complexes are known,14 the completely linear polymer
complex containing a 3-coordinate planar copper(I) complex is
rare.
In summary, a new â-diketiminate ligand containing a nitro
group on the carbon framework has been developed, complexation
of which with cuprous ion provided a novel linear polymer
copper(I) complex with an extended d-pπ system. Further studies
are now in progress to evaluate the electronic communication
between the monomer units in [CuI(2-)]n.
There seems to be no specific interaction between the neigh-
boring linear chains other than van der Waals interaction between
the aryl substituents; the mesityl groups on the polymer chain
are arranged alternately with the mesityl groups of other
(8) In the reaction of cuprous ion and other nitro-diketiminate ligands (L)
carrying different types of N-substituents such as R1 ) phenyl, 3,5-di-
tert-butylphenyl, or o-methoxyphenyl, disproportionation reaction mainly
occurred to give [CuII(L)2] and Cu0, but no linear copper(I)-polymer
complex was obtained. A 2,6-disubstituted aromatic group such as mesityl
in 2H may prevent the formation of the copper(II) complex of type
[CuII(L)2] and stabilize the copper(I) state in the polymer complex. The
copper(I) complex of a diketiminate ligand without the nitro group on
the carbon framework (R1 ) mesityl, R2 ) methyl, R3 ) H) is
significantly air-sensitive, leading to an oxidative ligand degradation.
This clearly indicates that the electron-withdrawing nature of the nitro
group is also important for stabilization of the copper(I) complex.
(9) Analytical data for 3: IR (KBr): 1598 (CdN), 1542, 1297, 1262 cm-1
(NO2). FAB-MS: m/z ) 414 ([Cu(2-)]), 828 ([Cu(2-)]2). Anal. Calcd
for C21H24N3O2Cu: C, 60.93; H, 5.84; N, 10.15. Found: C, 61.02; H,
5.85; N, 10.18.
(10) Crystal data for 3: M ) 413.99, C21H24N3O2Cu, crystal dimensions 0.30
× 0.30 × 0.30 mm, monoclinic, space group P21/a (No. 14), a )
7.2949(2) Å, b ) 15.7167(5) Å, c ) 16.6267(4) Å, â ) 100.0625(7)°,
V ) 1876.96(8) Å3, Z ) 4, Fcalcd ) 1.465 g/cm3, 2θmax ) 55.0°, Mo KR
) radiation (λ ) 0.71069 Å), T ) 93 K. Data were collected using the
Rigaku RAXIS rapid imaging plate system, and the structure was solved
via direct methods. Full-matrix least-squares refinement on F using SIR92
converged with final R ) 0.031 and Rw ) 0.046 for 8476 independent
reflection with I > 3σ(I) and 3367 parameters.
Acknowledgment. This work was partially supported by
Grants-in-Aid for Scientific Research on Priority Area (No.
11228206) and Grants-in-Aid for Scientific Research (No.
13480189) from the Ministry of Education, Science, Culture and
Sports, Japan.
Supporting Information Available: Experimental details including
synthetic procedures of the ligand and the copper complexes and X-ray
structural determination. Details of the crystallographic data supplied as
a CIF file. This material is available free of charge via the Internet at
http://pubs.acs.org.
(11) The solid sample of 3 exhibited a very broad absorption band in the
visible region (400-650 nm) in the reflectance UV-vis spectrum.
(12) [CuI(2-)(PPh3)] was obtained by treating the polymer complex 3 with
an equimolar amount of PPh3 based on the copper ion in CH2Cl2. λmax
) 365 nm (ꢀ ) 23500 M-1 cm-1). 1H NMR (600 MHz, CDCl3): δ 2.01
(s, 12H, CH3), 2.27 (s, 6H, CH3), 6.74 (s, 4H, aromatic H of Ar group),
6.79 (dd, J ) 8.0, 10.7 Hz, 6H, Ho), 7.11 (dd, J ) 7.0, 7.0 Hz, 6H, Hm),
7.30 (t, J ) 7.1 Hz, 3H, Hp), 8.89 (s, 2H, CH). HRMS (FAB, positive):
m/z 676.2170 (M+ + 1), calcd for C39H40N3O2PCu 676.2154. Anal. Calcd
for C39H39N3O2PCu: C, 69.27; H, 5.81; N, 6.21. Found: C, 69.24; H,
5.82; N, 6.03.
IC0155535
(13) The free ligand 2H itself adopts a rather similar chain structure in the
crystal, although the distance between the neighboring ligands [C(1)-
C(1)′ ) 8.22 Å] is significantly longer than that in the polymer complex
(7.29 Å). The ligand skeleton itself may promote formation of this type
of structure even in the absence of intermolecular interactions.
(14) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T. In AdVances in Inorganic
Chemistry; Sykes, A. G., Ed.; Academic Press: San Diego, 1999; Vol.
46, pp 173-303.