Copper(I) complexes of fluorinated triazapentadienyl ligands: Synthesis and characterization of [N{(C3F7)C(DiPP)N}2]CuL (where L = NCCH3, CNBut, CO; Dipp = 2,6-diisopropylphenyl)

Article abstract of DOI:10.1021/ic049229w

Sterically demanding triazapentadiene [N{(C₃F ₇)C(Dipp)N}₂] H has been synthesized in good yield. It features a W-shaped ligand backbone in the solid state. [N{(C₃F ₇)C(Dipp)N}₂]H reacts wi

Full text of DOI:10.1021/ic049229w

Inorg. Chem. 2004, 43, 5786−5788
Copper(I) Complexes of Fluorinated Triazapentadienyl Ligands:
Synthesis and Characterization of [N{(C F )C(Dipp)N}2]CuL
3 7
(Where L ) NCCH , CNBut, CO; Dipp ) 2,6-Diisopropylphenyl)
3
H. V. Rasika Dias*,†,‡ and Shreeyukta Singh†
Department of Chemistry and Biochemistry, The UniVersity of Texas at Arlington,
Arlington, Texas 76019, and Institute of Fundamental Studies, Hantana Road, Kandy, Sri Lanka
Received June 14, 2004
Sterically demanding triazapentadiene [N{(C F )C(Dipp)N}2] H has
such as [H2B(3,5-(CF3)2Pz)2]-. Both types are highly flu-
3
7
orinated, monoanionic, nitrogen based donors capable of
forming six-membered metallacycles with metal ions. The
coordination chemistry of triazapentadienyl ligands is there-
fore of comparative interest. Recently, Siedle et al. described
a convenient route to these ligands starting with (C4F9)3N.9
Several metal adducts of [N{(C3F7)C(Ph)N}2]- including
copper(II) derivative [N{(C3F7)C(Ph)N}2]2Cu were also
described.9,10 Other reports in this arena prior to their work
concern the use of [N{(R)C(H)N}2]- (R ) fluoro alkyl) as
a ligand for few late transition metal ions and gallium.11 The
scarcity of information on metal triazapentadienyl complexes
and the interesting results we obtained using related fluori-
nated ligands prompted us to explore the metal coordination
chemistry of fluorinated triazapentadienes in more detail.
In this paper, we report the synthesis of a sterically
demanding, fluoroalkyl substituted, triazapentadiene ligand
[N{(C3F7)C(Dipp)N}2]H (where Dipp ) 2,6-diisopropylphen-
yl), and its utility in copper(I) chemistry. The triazapentadiene
[N{(C3F7)C(Dipp)N}2]H can be obtained in 76% yield from
the reaction of 2,6-diisopropylaniline with the perfluoro-5-
aza-4-nonene (C3F7sCFdNsC4F9)9 in ether (see Supporting
Information).12 It is a colorless, crystalline solid. The room
been synthesized in good yield. It features a W-shaped ligand
backbone in the solid state. [N{(C F )C(Dipp)N}2]H reacts with
3
7
copper(I) oxide in acetonitrile leading to [N{(C F )C(Dipp)N}2]-
3
7
CuNCCH . This copper adduct serves as an excellent precursor
3
t
to obtain thermally stable [N{(C F )C(Dipp)N}2]CuCNBu and
3
7
[N{(C F )C(Dipp)N}2]CuCO. IR spectroscopic data of these copper-
3
7
(I) isocyanide (νCN ) 2176 cm-1) and copper(I) carbonyl (νCO
2109 cm-1) complexes indicate that the [N{(C F )C(Dipp)N}2]-
)
3
7
ligand is a fairly weak donor.
Over the past few years, we have reported the chemistry
of highly fluorinated ligands such as [H2B(3,5-(CF3)2Pz)2]-
(1) and [HB(3,5-(CF3)2Pz)3]-.1-4 Their metal adducts display
very interesting properties. For example, the copper(I) car-
bonyl and ethylene adducts, [HB(3,5-(CF3)2Pz)3]CuCO5 and
[HB(3,5-(CF3)2Pz)3]Cu(η2-C2H4),6 are air and thermally sta-
ble solids. Bis(pyrazolyl)borate complexes such as [H2B(3,5-
(CF3)2Pz)2]Cu(2,4,6-collidine) show rare blue luminescence.7
Some of these copper(I) adducts also serve as excellent
oxidation8 and aziridination catalysts.6
(4) Trofimenko, S. Scorpionates: The Coordination Chemistry of Poly-
pyrazolylborate Ligands; Imperial College: London, 1999.
(5) Dias, H. V. R.; Lu, H.-L. Inorg. Chem. 1995, 34, 5380-2.
(6) Dias, H. V. R.; Lu, H.-L.; Kim, H.-J.; Polach, S. A.; Goh, T. K. H.
H.; Browning, R. G.; Lovely, C. J. Organometallics 2002, 21, 1466-
73.
(7) Omary, M. A.; Rawashdeh-Omary, M. A.; Diyabalanage, H. V. K.;
Dias, H. V. R. Inorg. Chem. 2003, 42, 8612-4.
(8) Diaconu, D.; Hu, Z.; Gorun, S. M. J. Am. Chem. Soc. 2002, 124,
1564-5.
(9) Siedle, A. R.; Webb, R. J.; Behr, F. E.; Newmark, R. A.; Weil, D. A.;
Erickson, K.; Naujok, R.; Brostrom, M.; Mueller, M.; Chou, S.-H.;
Young, V. G., Jr. Inorg. Chem. 2003, 42, 932-4.
Fluorinated triazapentadienyl ligands9 such as [N{(C3-
F7)C(Ph)N}2]- (2) may be compared to bis(pyrazolyl)borates
(10) Siedle, A. R.; Webb, R. J.; Brostrom, M.; Newmark, R. A.; Behr, F.
E.; Young, V. G., Jr. Organometallics 2004, 23, 2281-6.
(11) Hursthouse, M. B.; Mazid, M. A.; Robinson, S. D.; Sahajpal, A. J.
Chem. Soc., Dalton Trans. 1994, 3615-20. Bottrill, M.; Goddard, R.;
Green, M.; Hughes, R. P.; Lloyd, M. K.; Taylor, S. H.; Woodward,
P. J. Chem. Soc., Dalton Trans. 1975, 1150-5. Aris, D. R.; Barker,
J.; Phillips, P. R.; Alcock, N. W.; Wallbridge, M. G. H. J. Chem.
Soc., Dalton Trans. 1997, 909-10. Robinson, V.; Taylor, G. E.;
Woodward, P.; Bruce, M. I.; Wallis, R. C. J. Chem. Soc., Dalton Trans.
1981, 1169-73. Brown, H. C.; Schuman, P. D. J. Org. Chem. 1963,
28, 1122-7.
* To whom correspondence should be addressed. E-mail: dias@uta.edu.
† The University of Texas at Arlington.
‡ Institute of Fundamental Studies.
(1) Dias, H. V. R.; Gorden, J. D. Inorg. Chem. 1996, 35, 318-24.
(2) Dias, H. V. R.; Jin, W.; Kim, H.-J.; Lu, H.-L. Inorg. Chem. 1996, 35,
2317-28.
(3) Dias, H. V. R.; Kim, H.-J. Organometallics 1996, 15, 5374-79.
5786 Inorganic Chemistry, Vol. 43, No. 19, 2004
10.1021/ic049229w CCC: $27.50 © 2004 American Chemical Society
Published on Web 08/27/2004

COMMUNICATION
Figure 2. Molecular structure of [N{(C3F7)C(Dipp)N}2]CuNCCH3. Only
one of the three molecules in the asymmetric unit is shown. Selected bond
distances (Å) and angles (deg): Cu(1)-N(1) 1.864(3), Cu(1)-N(1A)
1.957(3), Cu(1)-N(3A) 1.964(2), N(1)-Cu(1)-N(1A) 135.53(11), N(1)-
Cu(1)-N(3A) 128.36(11), N(1A)-Cu(1)-N(3A) 95.74(10), C(1)-N(1)-
Cu(1) 171.5(3), N(1)-C(1)-C(2) 178.0(4).
Figure 1. Molecular structures of [N{(C3F7)C(Dipp)N}2]H. Selected bond
distances (Å) and angles (deg): N(1)-C(1) 1.3523(14), N(1)-C(9)
1.4419(14), N(2)-C(1) 1.2714(15), N(2)-C(2) 1.3868(14), N(3)-C(2)
1.2651(15), N(3)-C(21) 1.4366(15), C(1)-C(3) 1.5417(15), C(2)-C(6)
1.5382(16); C(1)-N(1)-C(9) 124.11(10), C(1)-N(2)-C(2) 129.08(10),
C(2)-N(3)-C(21) 119.90(10), N(2)-C(1)-N(1) 122.54(10), N(2)-C(1)-
C(3) 125.37(10), N(1)-C(1)-C(3) 112.05(9), N(3)-C(2)-N(2) 128.20(11),
N(3)-C(2)-C(6) 116.09(10), N(2)-C(2)-C(6) 114.55(9).
center adopts trigonal planar geometry. The average Cu-
N(CCH3) bond length of 1.867(3) Å is similar to the
corresponding distance of 1.860(3) Å observed for the
nonfluorinated diazapentadieneyl complex [PhC{HC(Dipp)-
N}2]CuNCCH3.14
temperature 1H and 19F NMR spectra of [N{(C3F7)C-
(Dipp)N}2]H in CDCl3 are fairly complex. For example, the
1H NMR signals due to the isopropyl CH(CH3)2 and
CH(CH3)2 protons appear as nine sets of doublets and four
sets of multiplets, respectively. This is likely a result of
hindered rotation of the aryl groups at room temperature, as
well as due to the presence of relatively rigid conformational
isomers (e.g., molecules with U- or W-shaped backbones).10
The X-ray crystal structure of [N{(C3F7)C(Dipp)N}2]H is
illustrated in Figure 1. It crystallizes in the form where the
acidic proton is bonded to one of the terminal nitrogen atoms.
The backbone adopts a W-shaped configuration.
The copper(I) acetonitrile complex [N{(C3F7)C(Dipp)N}2]-
CuNCCH3 is synthesized by treating the free ligand with
copper(I) oxide in acetonitrile.13 It can be isolated as an
orange, crystalline product. Solid samples and acetonitrile
solutions of [N{(C3F7)C(Dipp)N}2]CuNCCH3 can be handled
in air for short periods without any apparent signs of
decomposition. The 1H NMR spectrum of [N{(C3F7)C-
(Dipp)N}2]CuNCCH3 in CDCl3 shows just two sets of
doublets for CH(CH3)2 and a septet for CH(CH3)2. This is
in sharp contrast to the complex spectrum observed for the
free ligand. [N{(C3F7)C(Dipp)N}2]CuNCCH3 crystallizes in
the P212121 space group with three chemically similar,
crystallographically independent molecules in the crystal
lattice (Figure 2). The triazapentadienyl ligand acts as a
chelating, bidentate donor toward copper(I). The copper
Copper acetonitrile adducts are useful precursors for
various copper containing derivatives. For example, the
copper(I) isocyanide complex [N{(C3F7)C(Dipp)N}2]CuCNBut
could be obtained by reacting [N{(C3F7)C(Dipp)N}2]-
1
CuNCCH3 with tert-butyl isocyanide.15 The H NMR data
corresponding to the triazapentadienyl moiety of [N{(C3F7)C-
(Dipp)N}2]CuCNBut are similar to those observed for the
acetonitrile adduct [N{(C3F7)C(Dipp)N}2]CuNCCH3, sug-
gesting the presence of a κ2-coordinated ligand. A singlet at
1
δ 1.33 in the H NMR spectrum corresponding to the tert-
butyl group protons, as well as a strong absorption band in
the IR spectrum at 2176 cm-1 (compared to νCN of free
CNBut ) 2138 cm-1), indicates the formation of the expected
copper isocyanide adduct. The νCN band shows a shift of
about 38 cm-1 as a result of coordination to the copper(I)
center. For comparison, the νCN bands of [HB(3,5-(CF3)2-
Pz)3]CuCNBut and {[H2B(3,5-(CF3)2Pz)2]CuCNBut}2 appear
at a much higher value (2196 cm-1).16 Complexes with more
electron rich metal sites as in [HB(Pz)3]CuCNBut display
the νCN band at a relatively low frequency (2155 cm-1).17
(14) Spencer, D. J. E.; Reynolds, A. M.; Holland, P. L.; Jazdzewski, B.
A.; Duboc-Toia, C.; Le Pape, L.; Yokota, S.; Tachi, Y.; Itoh, S.;
Tolman, W. B. Inorg. Chem. 2002, 41, 6307-21.
(15) [N{(C3F7)C(Dipp)N}2]CuCNBut: yield (88%), mp 92 °C. 19F NMR
(CDCl3, 25 °C): δ -122.6 (s, â-CF2), -106.2 (s, R-CF2), -80.2 (s,
CF3). 1H NMR (CDCl3, 25 °C): δ 1.12 (d, 3JHH ) 6.5 Hz, 12H, CH-
3
(12) [N{C3F7)C(Dipp)N}2]H: yield (76%), mp 88-90 °C.
(CH3)2), 1.22 (d, JHH ) 6.5 Hz, 12H, CH(CH3)2), 1.33 (s, 9H, But),
(13) [N{(C3F7)C(Dipp)N}2]CuNCCH3: yield (69%), mp 89 °C. 19F NMR
(CDCl3, 25 °C): δ -122.5 (s, â-CF2), -106.5 (apparent quartet, JFF
) 12, 8 Hz, R-CF2), -80.3 (apparent triplet JFF ) 12, 8 Hz, CF3). 1H
3.02 (heptet, JHH ) 6.5 Hz, 4H, CH(CH3)), 7.05 (m, 6H, m- and
3
p-Ar). IR (KBr, cm-1): 2176 (CN).
(16) Dias, H. V. R.; Lu, H.-L.; Gorden, J. D.; Jin, W. Inorg. Chem. 1996,
3
NMR (CDCl3, 25 °C): δ 1.10 (d, JHH ) 5.0 Hz, 12H, CH(CH3)2),
35, 2149-51.
1.23 (d, 3JHH ) 10.5 Hz, 12H, CH(CH3)2), 1.74 (s, 3H, NCCH3), 3.03
(17) Bruce, M. I.; Ostazewski, A. P. P. J. Chem. Soc., Dalton Trans. 1973,
2433-6.
3
(heptet, JHH ) 6.7 Hz, 4H, CH(CH3)2), 7.04 (m, 6H, m- and p-Ar).
Inorganic Chemistry, Vol. 43, No. 19, 2004 5787

COMMUNICATION
The copper(I) carbonyl complex could be obtained either
by treating [N{(C3F7)C(Dipp)N}2]CuNCCH3 with CO or
from a reaction between [N{(C3F7)C(Dipp)N}2]Li and
CuOTf in the presence of CO.18 It is a thermally stable, pale
yellow solid. [N{(C3F7)C(Dipp)N}2]CuCO can be handled
in air for a few minutes without any apparent signs of
decomposition. [N{(C3F7)C(Dipp)N}2]CuCO displays a strong
absorption band in the IR at 2109 cm-1.
Figure 3. Molecular structure of [N{(C3F7)C(Dipp)N}2]CuCO. Selected
bond distances (Å) and angles (deg): C-O 1.138(2), C-Cu 1.782(2), Cu-
N(3) 1.9391(15), Cu-N(1) 1.9410(15), C(1)-N(1) 1.303(2), C(1)-N(2)
1.338(2), C(1)-C(3) 1.546(3), C(2)-N(3) 1.301(2), C(2)-N(2) 1.335(2),
C(2)-C(6) 1.551(3); O-C-Cu 178.3(2), N(1)-C(1)-N(2) 128.38(17),
N(3)-C(2)-N(2) 129.20(17), C-Cu-N(3) 133.31(8), C-Cu-N(1)
130.51(8), N(3)-Cu-N(1) 96.16(6), C(1)-N(1)-C(9) 127.56(15), C(1)-
N(1)-Cu 120.68(12), C(9)-N(1)-Cu 111.68(11), C(2)-N(2)-C(1) 125.11-
(17), C(2)-N(3)-C(21) 127.43(16), C(2)-N(3)-Cu 120.22(13), C(21)-
N(3)-Cu 112.33(12).
We have used IR data of copper carbonyl adducts
extensively to assess the donor properties of fluorinated tris-
(pyrazolyl)borate ligands.19 This high νCO suggests that the
[N{(C3F7)C(Dipp)N}2]- ligand is a fairly weak donor. It is
also a much weaker donor compared to the comparatively
substituted diazapentadineyl ligands such as [HC{(CF3)C(3,5-
(Me)2Ph)N}2]- as evident from the CO stretching frequency
of [HC{(CF3)C(3,5-(Me)2Ph)N}2]CuCO which appears at
2097 cm-1.20 For comparison, copper(I) carbonyl adducts
of the fluorinated tris(pyrazolyl)borate ligands [HB(3-(CF3),5-
(Ph)Pz)3]- and [HB(3,5-(CF3)2Pz)3]- show CO stretching
frequency bands at 2103 and 2137 cm-1, respectively.19
The X-ray structure of [N{(C3F7)C(Dipp)N}2]CuCO shows
that the copper center is three coordinate (Figure 3). The
triazapentadienyl ligand binds to the metal center in a κ2-
fashion. The Cu-C-O moiety is essentially linear with the
Cu-C-O angle of 178.3(2)°. The Cu-C distance is 1.782(2)
Å. Copper carbonyl compounds such as this three-coordinate
[N{(C3F7)C(Dipp)N}2]CuCO are rare.20-22 In most cases the
CO ligand is highly labile or compounds decompose easily
in air. For example, [HC{(CF3)C(3,5-(Me)2Ph)N}2]CuCO
and even more fluorine rich [HC{(CF3)C(3,5-(CF3)2Ph)N}2]-
CuCO (νCO ) 2110 cm-1) have not been obtained as
thermally stable solids.20 Thus far, we have not been able to
isolate copper carbonyl adducts of the highly fluorinated bis-
(pyrazolyl)borate [H2B(3,5-(CF3)2Pz)2]- either.
Overall, we report the synthesis and structural character-
ization of the first triazapentadienyl complexes of copper-
(I). In contrast to the κ1-coordinated CH3Hg[N{(C3F7)C-
(Ph)N}2],10 these adducts feature κ2-coordinated triazapenta-
dienyl moieties. The IR data of the copper carbonyl and
isocyanide adducts indicate that the fluorinated ligands such
as [N{(C3F7)C(Dipp)N}2]- are fairly weak donors. Further
studies of the coordination chemistry of this interesting class
of fluorinated ligands and the applications of their metal
adducts are presently underway.
Acknowledgment. This work has been supported by the
Robert A. Welch Foundation (Y-1289) and the National
Science Foundation (CHE 0314666). We are grateful to Dr.
A. R. Siedle (3M) and Dr. F. E. Behr (3M) for providing
useful information about the ligand synthesis, as well as for
providing us with a sample of the starting amine, N(C4F9)3.
(18) [N{(C3F7)C(Dipp)N}2]CuCO: yield (65%), mp dec 80 °C. 19F NMR
(CDCl3, 25 °C): δ -122.4 (s, â-CF2), -106.2 (s, R-CF2), -80.2 (s,
CF3). 1H NMR (CDCl3, 25 °C): δ 1.19 (d, 3JHH ) 7.0 Hz, 12H, CH-
3
3
(CH3)2), 1.28 (d, JHH ) 7.0 Hz 12H, CH(CH3)2), 3.03 (heptet, JHH
) 6.5 Hz, 4H, CH(CH3)2), 7.15 (m, 6H, m- and p-Ar). 13C NMR
2
Supporting Information Available: X-ray crystallographic data
for [N{(C3F7)C(Dipp)N}2]H and [N{(C3F7)C(Dipp)N}2]CuL (where
L ) NCCH3 and CO) (CIF), and experimental details for free ligand
and copper complexes. This material is available free of charge
via the Internet at http://pubs.acs.org.
(CDCl3, 25 °C): δ selected peaks 152.2 (t, JCF ) 23.0 Hz, NCN),
172.9 (s, CO). IR (Nujol, cm-1): 2109 (CO).
(19) Dias, H. V. R.; Goh, T. K. H. H. Polyhedron 2004, 23, 273-82.
(20) Laitar, D. S.; Mathison, C. J. N.; Davis, W. M.; Sadighi, J. P. Inorg.
Chem. 2003, 42, 7354-6.
(21) Pasquali, M.; Floriani, C.; Gaetani-Manfredotti, A. Inorg. Chem. 1980,
19, 1191-7.
(22) Villacorta, G. M.; Lippard, S. J. Inorg. Chem. 1987, 26, 3672-6.
IC049229W
5788 Inorganic Chemistry, Vol. 43, No. 19, 2004