Synthesis and characterization of cationic [tris(pyrazolyl)methane]copper(I) carbonyl and acetonitrile complexes

Article abstract of DOI:10.1021/om960026s

The reaction of [Cu(NCMe)₄]PF₆ with equimolar amounts of the tris(substituted-pyrazolyl)methane ligands HC(3,5-Me₂pz)₃, HC(3-Phpz)₃, and HC(3-Bu^tpz)₃ yields the respective salts {[HC(3,5-Me₂pz)₃]Cu(NCMe)}PF₆, {[HC(3-Phpz)₃]Cu(NCMe)}PF₆, and {[HC(3-Bu⁴pz)₃]-Cu(NCMe)}PF₆. These complexes are unusually resistant toward reaction with dioxygen. These acetonitrile complexes react with carbon monoxide to yield the stable complexes {[HC(3,5-Me₂pz)₃]Cu(CO)}PF₆, {[HC(3-Phpz)₃]Cu(CO)}PF₆, and {[HC(3-Bu^tpz)₃]Cu(CO)}PF₆, respectively. The solid-state structures of {[HC(3-Bu^tpz)₃)]Cu(NCMe)}PF₆·CH ₂Cl₂ and ([HC(3-Bu^tpz)₃]Cu(CO)}PF₆ have been determined by X-ray crystallography. The structures are very similar, with the Cu-N distances to the donor atoms of the HC(3-Bu^tpz)₃ ligand 0.03 A? shorter in the carbonyl complex.

Full text of DOI:10.1021/om960026s

Organometallics 1996, 15, 2029-2032
2029
Syn th esis a n d Ch a r a cter iza tion of Ca tion ic
[Tr is(p yr a zolyl)m eth a n e]cop p er (I) Ca r bon yl a n d
Aceton itr ile Com p lexes
Daniel L. Reger* and J ames E. Collins
Department of Chemistry and Biochemistry, University of South Carolina,
Columbia, South Carolina 29208
Arnold L. Rheingold and Louise M. Liable-Sands
Department of Chemistry and Biochemistry, University of Delaware,
Newark, Delaware 19716
Received J anuary 17, 1996X
The reaction of [Cu(NCMe)4]PF6 with equimolar amounts of the tris(substituted-pyra-
zolyl)methane ligands HC(3,5-Me2pz)3, HC(3-Phpz)3, and HC(3-Butpz)3 yields the respective
salts {[HC(3,5-Me2pz)3]Cu(NCMe)}PF6, {[HC(3-Phpz)3]Cu(NCMe)}PF6, and {[HC(3-Butpz)3]-
Cu(NCMe)}PF6. These complexes are unusually resistant toward reaction with dioxygen.
These acetonitrile complexes react with carbon monoxide to yield the stable complexes
{[HC(3,5-Me2pz)3]Cu(CO)}PF6, {[HC(3-Phpz)3]Cu(CO)}PF6, and {[HC(3-Butpz)3]Cu(CO)}PF6,
respectively. The solid-state structures of {[HC(3-Butpz)3)]Cu(NCMe)}PF6‚CH2Cl2 and
{[HC(3-Butpz)3]Cu(CO)}PF6 have been determined by X-ray crystallography. The structures
are very similar, with the Cu-N distances to the donor atoms of the HC(3-Butpz)3 ligand
0.03 Å shorter in the carbonyl complex.
In tr od u ction
HC(3,5-Me2pz)3,7 we are studying the chemistry of the
8
9
bulkier HC(3-Phpz)3 and HC(3-Butpz)3 ligands, “rela-
tives” of the bulky second-generation poly(pyrazolyl)-
borate ligands.10 We are interested in contrasting the
chemistry of the neutral tris(pyrazolyl)methane ligands
with that previously developed for anionic tris(pyra-
zolyl)borate ligands. Reported here are the syntheses
of the cationic, four-coordinate copper(I) acetonitrile and
carbonyl complexes derived from these three tris-
(pyrazolyl)methane ligands. The solid-state structures
for the matched pair {[HC(3-Butpz)3]Cu(NCMe)}PF6‚
CH2Cl2 and {[HC(3-Butpz)3]Cu(CO)}PF6 have been de-
termined by X-ray crystallography.
Since tris(pyrazolyl)borate ligands were used by Bruce
and co-workers in the synthesis and structural charac-
terization of the first copper(I) carbonyl complex, [HB-
(pz)3]CuCO (pz ) pyrazolyl ring),1 numerous reports of
[tris(pyrazolyl)borate]CuCO complexes have appeared.2
The range of tris(pyrazolyl)borate ligands used in these
complexes includes [HB(3,5-Pri)2pz)3]CuCO,2b with bulky
substituents on the pyrazolyl ring, and a recently
reported complex with a fluorinated ligand, [HB(3,5-
(CF3)2pz)3]CuCO.2d In addition, the analogous neutral
tris(imidazolyl)phosphine ligands have been used to
prepare analogous cationic monomeric copper(I) carbo-
nyls.3 A driving force for much of the chemistry in this
area stems from its biological relevance as structural
probes for oxygen-binding enzymes4 and from recent
advances in organometallic heterogeneous catalysis.5
We have initiated a study of the coordination chem-
istry of the neutral tris(pyrazolyl)methane ligand sys-
tem with a variety of post-transition and transition
metals.6 In addition to the previously known ligand
Exp er im en ta l Section
All operations were carried out either under a nitrogen
atmosphere using standard Schlenk techniques or in a Vacuum
Atmospheres HE-493 drybox. All solvents were dried, de-
gassed, and distilled prior to use. 1H and 13C NMR chemical
shifts are reported in ppm versus TMS. [Cu(NCMe)4]PF6,11
9
HC(3,5-Me2pz)3,7b HC(3-Phpz)3,8 and HC(3-Butpz)3 were pre-
pared according to literature procedures. Clusters assigned
X Abstract published in Advance ACS Abstracts, March 15, 1996.
(1) (a) Bruce, M. I.; Ostazewski, A. P. P. J . Chem. Soc., Chem.
Commun. 1972, 1124. (b) Churchill, M. R.; DeBoer, B. G.; Rotella, F.
J .; Salah, O. M. A.; Bruce, M. I. Inorg. Chem. 1975, 14, 2051.
(2) (a) Mealli, C.; Arcus, C. S.; Wilkinson, J . L.; Marks, T. J .; Ibers,
J . A. J . Am. Chem. Soc. 1976, 98, 711. (b) Katajima, N.; Fujisawa, K.;
Fujimoto, C.; Moro-oka, Y.; Hashimoto, S.; Kitagawa, T.; Toriumi, K.;
Tatsumi, K.; Nakamura, A. J . Am. Chem. Soc. 1992, 114, 1277. (c)
Ruggiero, C. E.; Carrier, S. M.; Antholine, W. E.; Whittaker, J . W.;
Cramer, C. J .; Tolman, W. B. J . Am. Chem. Soc. 1993, 115, 11285. (d)
Dias, H. V. R.; Lu, H. L. Inorg. Chem. 1995, 34, 5380.
(3) Sorrell, T. N.; Allen, W. E.; White, P. S. Inorg. Chem. 1995, 34,
952.
(4) (a) Alben, J . O.; Moh, P. P.; Fiamingo, F. G.; Altschuld, R. A.
Proc. Natl. Acad. Sci. USA 1981, 78, 234. (b) Fager, L. Y.; Alben, J .
O. Biochemistry 1972, 11, 4786.
(5) (a) Lin, J .; J ones, P.; Guckert, J .; Solomon, E. I. J . Am. Chem.
Soc. 1991, 113, 8312. (b) Solomon, E. I.; J ones, P. M.; Maj, J . A. Chem.
Rev. 1993, 93, 2623.
(6) (a) Reger, D. L.; Collins, J . E.; Layland, R.; Adams, R. D. Inorg.
Chem. 1996, 35, 1372. (b) Reger, D. L.; Collins, J . E.; Myers, S. M.;
Liable-Sands, L. M.; Rheingold, A. L. Inorg. Chem., submitted for
publication.
(7) (a) Trofimenko, S. J . Am. Chem. Soc. 1970, 92, 5118. (b) J ulia,
S.; del Mazo, J .; Avila, L.; Elguero, J . Org. Prep. Proced. Int. 1984,
16(5), 299.
(8) This ligand has been prepared: J ameson, D. L.; Castellano, R.
K. Gettysburg College, personal communication. J ameson, D. L.;
Castellano, R. K. Inorg. Synth., submitted for publication.
(9) This ligand has been prepared by D. L. Reger and J . E. Collins
in a collaborative effort with D. L. J ameson and R. K. Castellano
(personal communication): Reger, D. L.; Collins, J . E.; J ameson, D.
L.; Castellano, R. K. Inorg. Synth., submitted for publication.
(10) (a) Trofimenko, S.; Calabrese, J . C.; Thompson, J . S. Inorg.
Chem. 1987, 26, 1507. (b) Trofimenko, S. Chem. Rev. 1993, 93, 943.
(c) Parkins, G. Adv. Inorg. Chem. 1995, 42, 291. (d) Kitajima, N.;
Tolman, W. B. Prog. Inorg. Chem. 1995, 43, 419.
(11) Kubas, G. J . Inorg. Synth. 1979, 19, 90.
0276-7333/96/2315-2029$12.00/0 © 1996 American Chemical Society

2030 Organometallics, Vol. 15, No. 8, 1996
Reger et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for
to specific ions in the mass spectra show appropriate isotopic
patterns as calculated for the atoms present. Elemental
analyses were performed by National Chemical Consulting,
Inc.
{[HC(3-Bu tp z)3]Cu (NCMe)}P F 6 (3) a n d
{[HC(3-Bu tp z)3]Cu (CO)}P F 6 (6)
3‚CH2Cl2
6
{[HC(3,5-Me2p z)3]Cu (NCMe)}P F 6 (1). A solid mixture of
[Cu(NCMe)4]PF6 (0.25 g, 0.67 mmol) and HC(3,5-Me2pz)3 (0.20
g, 0.67 mmol) was charged in a 100 mL flask and suspended
in CH2Cl2 (5 mL). After it was stirred for 24 h, the reaction
mixture was treated with hexanes (20 mL). The mixture was
filtered, and the remaining pale yellow solid was washed with
hexanes (3 × 5 mL) and dried under vacuum for several hours
(0.278 g, 0.51 mmol; 76%); mp 238-243 °C. 1H NMR (d6-
acetone; δ): 7.96 (s; 1; HC(3,5-Me2pz)3); 6.11 (s; 3; 4-H pz);
2.66, 2.29 (s, s; 9, 9; 3,5-Me pz); 2.52 (s; 3; CH3CN). Mass
spectrum (m/z): 361 {[HC(3,5-Me2pz)3]Cu}+. Anal. Calcd for
C18H25CuF6N7P: C, 39.46; H, 4.60. Found: C, 39.44; H, 4.30.
formula
fw
cryst syst
space group
a, Å
C25H39Cl2CuF6N7P
717.04
orthorhombic
Pna21
20.587(7)
17.183(5)
9.650(2)
3414(2)
4
1.395
9.03
296
3067, 2674
C23H34CuF6N6OP
619.07
orthorhombic
Pbca
17.723(3)
18.059(3)
18.260(7)
5844(3)
8
1.407
8.67
293
4727, 3820
b, Å
c, Å
V, Å3
Z
D
exptl, g cm-3
µ(Mo KR), cm-1
T, K
no. of rflns
(collctd, indpdnt)
{[HC(3-P h p z)3]Cu (NCMe)}P F 6 (2). This compound was
prepared as above using HC(3-Phpz)3 (0.30 g, 0.68 mmol) to
yield a white solid (0.415 g, 0.60 mmol; 89%); mp 210-212
°C. 1H NMR (CDCl3; δ): 8.92 (s; 1; HC(3-Phpz)3); 8.28 (br; 3;
5-H pz); 7.78, 7.40 (br, br; 6, 9; C6H5); 6.56 (br; 3; 4-H pz); 2.06
(s; 3; CH3CN). Mass spectrum (m/z): 506 {[HC(3-Phpz)3]Cu}+.
Anal. Calcd for C30H25CuF6N7P: C, 52.06; H, 3.64. Found:
C, 51.75; H, 3.75.
{[HC(3-Bu tp z)3]Cu (NCMe)}P F 6 (3). This compound was
prepared as above using HC(3-Butpz)3 (0.26 g; 0.68 mmol) to
yield a white solid (0.385 g; 0.61 mmol; 91%); mp 246-248
°C. 1H NMR (CDCl3; δ): 8.59 (s; 1; HC(3-Butpz)3); 8.02 (d, J HH
) 3 Hz; 3; 5H pz); 6.12 (d, J HH ) 3 Hz; 3; 4H pz); 2.40 (s; 3;
CH3CN); 1.36 (s; 27; C(CH3)3). 13C NMR (CDCl3; δ): 163.9 (s;
3-C pz); 131.8, 103.5 (s, s; 4,5-C’s pz); 116.0 (s; CN); 76.3 (s;
HC(3-Butpz)3); 32.1 (s; C(CH3)3); 29.9 (s; C(CH3)3); 2.6 (s; CH3-
CN). Mass spectrum (m/z): 445 {HC(3-Butpz)3]Cu}+. Crystals
suitable for an X-ray structure and the analytical sample were
grown by slow diffusion of hexanes into a saturated CH2Cl2
solution. One equivalent of CH2Cl2 is retained in the crystal
lattice. Anal. Calcd for C24H37CuF6N7P‚CH2Cl2: C, 41.88; H,
5.48. Found: C, 42.16; H, 5.57.
R(F), R(wF2),a
%
6.49, 16.36
5.57, 10.63
a
2
R(F) ) ∑||Fo| - |Fc||/∑|Fo|; R(wF2) ) [∑[w(Fo - Fc2)2]/
∑[w(Fo2)2]]1/2; w ) 1/σ2(F).
Anal. Calcd for C29H22CuF6N6OP: C, 51.30; H, 3.27. Found:
C, 51.78; H, 3.34.
{[HC(3-Bu tp z)3]Cu (CO)}P F 6 (6). This compound was
prepared as for {[HC(3,5-Me2pz)3]Cu(CO)}PF6 using HC-
(3-Butpz)3 (0.26 g, 0.68 mmol) to yield a white solid (0.35 g,
0.55 mmol; 83%); mp 248-254 °C. 1H NMR (CDCl3; δ): 8.76
(s; 1; HC(3-Butpz)3); 8.10 (d, J HH ) 3 Hz; 3; 5H pz); 6.23 (d,
J HH ) 3 Hz; 3; 4H pz); 1.42 (s; 27; C(CH3)3). 13C NMR (CDCl3;
δ): 165.2 (3C pz); 133.4, 104.9 (4,5-C’s pz); 76.0 (HC(3-
Butpz)3); 32.6 (C(CH3)3); 30.7 (C(CH3)3). The carbonyl carbon
atom resonance was not located. IR spectrum (Nujol mull;
cm-1): 2100 (CO). Low-resolution mass spectrum (m/z): 445
{HC(3-Butpz)3]Cu}+; 473 {Cu[HC(3-Butpz)3](CO)}+. Accurate
FAB high-resolution mass spectrum for {Cu[HC(3-Butpz)3]-
(CO)}+ (m/e): calcd for C23H3463CuN6O, 473.2090; found,
473.2089. Anal. Calcd for C23H34CuF6N6OP: C, 44.62; H,
5.54. Found: C, 44.63; H, 5.62.
Cr ysta llogr a p h ic Str u ctu r e Deter m in a tion . Crystals
of 3 and 6 suitable for an X-ray structural analysis were grown
by allowing hexanes to diffuse slowly into a saturated CH2Cl2
solution of each. Crystallographic data are collected in Table
1. Crystals of both samples were photographically character-
ized and determined to belong to the orthorhombic crystal
system. Systematic absences in the diffraction data were
consistent for either Pna21 or Pnam (nonstandard setting of
Pnma) for 3 and uniquely consistent for Pbca for 6. For 3,
the noncentrosymmetric space group was chosen based on Z,
the distribution of E factors, and the failure of any of the
potential molecular mirror planes to align with the crystal
axes. This choice was substantiated by the results of refine-
ment. Azimuthal scans indicated that no correction for
absorption was required; Tmax/Tmin < 1.1. The structures were
solved by direct methods and completed from difference
Fourier maps. A molecule of CH2Cl2, the recrystallization
solvent, was located in the crystal lattice for 3. The fluorine
{[HC(3,5-Me2p z)3]Cu (CO)}P F 6 (4). A solid mixture of
[Cu(NCMe)4]PF6 (0.25 g, 0.67 mmol) and HC(3,5-Me2pz)3 (0.20
g, 0.67 mmol) was charged in a 100 mL flask and suspended
in CH2Cl2 (5 mL). The mixture was degassed by the freeze-
pump-thaw method (three cycles). On the last thaw cycle,
the reaction mixture was placed under 1 atm of carbon
monoxide. After it was warmed to room temperature, the
reaction solution became homogeneous. The yellow solution
was stirred for 16 h. Hexanes (25 mL) were added, and the
yellow solid that precipitated was isolated by removing the
mother liquor via cannula filtering and drying under vacuum
(0.28 g, 0.53 mmol; 79%); mp 266-272 °C. 1H NMR (CDCl3;
δ): 7.85 (s; 1; HC(Me2pz)3); 5.99 (s; 3; 4-H pz); 2.59, 2.31 (s, s;
9, 9; 3,5-Me2pz). IR spectrum (Nujol mull; cm-1): 2113 (CO).
Low-resolution mass spectrum (m/z): 361 {[HC(3,5-Me2pz)3]-
Cu}+, 389 {[HC(3,5-Me2pz)3]Cu(CO)}+. FAB high-resolution
mass spectrum for {[HC(3,5-Me2pz)3]Cu(CO)}+ (m/e): calcd for
C17H2265CuN6O, 391.1133; found, 391.1123. Anal. Calcd for
C17H22CuF6N6OP: C, 38.17; H, 4.15. Found: C, 38.14; H, 4.09.
-
atoms in the PF6 counterion in 6 were highly disordered;
attempts to model the disorder were only partially successful.
For 3, only the Cu, N, and C atoms in CH3CN were anisotro-
pically refined, and for 6, only the Cu and CO group atoms
were refined anisotropically. Hydrogen atom contributions
were idealized. All computations used SHELXTL 5.1 software
(G. Sheldrick, Siemens XRD, Madison, WI).
{[HC(3-P h p z)3]Cu (CO)}P F 6 (5). A CH2Cl2 (5 mL) solution
of {[HC(3-Phpz)3]Cu(NCMe)}PF6 (0.40 g, 0.58 mmol) was
degassed by the freeze-pump-thaw method (three cycles).
Before the last thaw cycle, the solution was placed under an
atmosphere of CO and the reaction mixture was slowly
warmed to room temperature. After it was stirred for 18 h,
Resu lts
the reaction mixture was treated with hexanes (20 mL).
A
white solid precipitated. The mother liquor was removed by
cannula filtering, and the remaining white solid was dried
under vacuum (0.32 g, 0.47 mmol; 81%); mp 175-176 °C. 1H
NMR (CDCl3; δ): 9.10 (s; 1; HC(3-Phpz)3); 8.36 (d; J HH ) 2.5
Hz; 3; 5H pz); 7.64, 7.47 (br; br; 6, 9; C6H5); 6.61 (d; J HH ) 2.5
Hz; 3; 4H pz). IR spectrum (Nujol mull; cm-1): 2104 (CO).
Syn th eses an d P r oper ties. Reaction of [Cu(NCMe)4]-
PF6 with equimolar amounts of the neutral tris(pyra-
zolyl)methane ligands L (L ) HC(3,5-Me2pz)3, HC(3-
Phpz)3, and HC(3-Butpz)3) in CH2Cl2 yields the respective
LCu(NCMe)PF6 salts (eq 1). These complexes were

Tris(pyrazolyl)methane Cu(I) CO and CH3CN Complexes
Organometallics, Vol. 15, No. 8, 1996 2031
F igu r e 1. Diagram of {[HC(3-Butpz)3]Cu(NCMe)}+.
characterized by 1H NMR, mass spectral, and elemental
analyses. Low-resolution FAB mass analyses of each
complex showed clusters with the appropriate isotopic
pattern for the cation resulting from the loss of aceto-
nitrile. The solubility of these copper(I) monocations
in CH2Cl2 decreases in the order {[HC(3-Butpz)3]Cu-
(NCMe)}PF6 > {[HC(3-Phpz)3]Cu(NCMe)}PF6 > {[HC-
(3,5-Me2pz)3]Cu(NCMe)}PF6. All three are moderately
air stable even as solutions. Bubbling dioxygen into
CH2Cl2 solutions at -78 °C provides no color change,
though a faint green solution results upon warming to
room temperature. The complex {[HC(3-Butpz)3]Cu-
(NCMe)}PF6 was characterized in the solid state by
X-ray crystallography.
The acetonitrile in the three copper(I) cations 1-3 can
be readily substituted with carbon monoxide under mild
conditions. The respective carbon monoxide adducts
{LCu(CO)}PF6 are prepared by precipitation from CH2-
Cl2 solutions of the complexes with hexanes under an
atmosphere of carbon monoxide (eq 2). Alternatively,
F igu r e 2. Diagram of {[HC(3-Butpz)3]Cu(CO)}+.
remains associated with the copper(I) complexes in the
mass spectral analyses. These complexes are also
moderately air stable in solution. The solid-state struc-
ture of {[HC(3-Butpz)3]Cu(CO)}PF6 was determined by
X-ray crystallography.
Solid -St a t e St r u ct u r es of {[H C(3-Bu t p z)3]Cu -
(NCMe)}P F 6 (3) a n d {[H C(3-Bu t p z)3]Cu (CO)}P F 6
(6). Diagrams of the cations in 3 and 6 are provided
in Figures 1 and 2. Selected bond distances and
angles are given in Table 2. In both structures, the
coordination geometry around the copper atom is best
described as a trigonally distorted tetrahedron. The
intraligand N-Cu-N angles are restrained by the
chelate rings to 89°, and the average angles from these
nitrogen donor atoms to the CO or NCMe donor atom
open to 126°.
In the structure of 3, the Cu-N distances for the
tridentate ligand vary from 2.061(9) to 2.138(9) Å
(average 2.107 Å). The fourth Cu-N distance is much
shorter at 1.873(9) Å. These values are comparable to
those reported previously in the structure of [Cu(tris-
(1-ethyl-4-isopropylimidazolyl)phosphine)(CH3CN)]-
PF6 of 2.075(8) and 1.901(10) Å, respectively.12
Significant metrical parameters in the structure of 6
are very similar to those in 3 and in previously reported
analogous copper(I) carbonyl complexes of hydrotris-
(pyrazolyl)borate ligands1b,2b,d and the four-coordinate
complexes 4 and 6 can be prepared by mixing [Cu-
(NCMe)4]PF6 with the ligand HC(3,5-Me2pz)3 or HC(3-
Butpz)3 under CO, followed by precipitation with hex-
anes. Complex 5 forms a mixture (ca. 1/1) of the
carbonyl and acetonitrile adducts under these condi-
tions. The three CO complexes were characterized by
solid-state IR spectroscopy (Nujol mull) as well as 1H
NMR, high-resolution FAB mass analyses, and elemen-
tal analyses. Surprisingly, the carbon monoxide ligand
(12) Lynch, W. E.; Kurtz, D. M.; Wang, S.; Scott, R. A. J . Am. Chem.
Soc. 1994, 116, 11030.

2032 Organometallics, Vol. 15, No. 8, 1996
Reger et al.
Ta ble 2. Selected Bon d Dista n ces a n d An gles for
{[HC(3-Bu tp z)3]Cu (NCMe)}P F 6 (3) a n d
{[HC(3-Bu tp z)3]Cu (CO)}P F 6 (6)
Even though a CO ligand is a weak σ donor and
strong π back-bonding ligand, whereas the NCMe ligand
is viewed as a moderate σ donor and very weak π
acceptor,15 the two cations have very similar geometries
in the solid state. The average tris(pyrazolyl)methane
Cu-N bond length in 3 is 0.03 Å greater than that
observed in 6, although the shortest individual distance
is found in 3. The shortening in 6 can be attributed to
the carbonyl ligand donating less electron density than
the acetonitrile ligand to the copper, causing the nitro-
gen donor atoms from the tridentate ligand to bond more
strongly, but the effect is small.
3‚CH2Cl2
6
Bond Distances (Å)
Cu(1)-N(11)
2.138(9)
2.122(9)
2.061(9)
1.873(9)
1.105(13)
1.48(2)
Cu-N(1)
2.076(6)
2.075(5)
2.088(5)
1.778(10)
1.133(9)
Cu(1)-N(21)
Cu(1)-N(31)
Cu(1)-N(1)
C(2)-N(1)
Cu-N(3)
Cu-N(5)
Cu-C(23)
C(23)-O
C(2)-C(3)
N(11)‚‚‚N(21)
N(11)‚‚‚N(31)
N(21)‚‚‚N(31)
2.987(8)
2.968(9)
2.926(9)
N(1)‚‚‚N(3)
N(1)‚‚‚N(5)
N(3)‚‚‚N(5)
2.898(7)
2.995(6)
2.851(7)
Another feature worth noting is that in both struc-
tures there is very little tilting of the pyrazolyl rings
with respect to the C3v axis of the molecule. Thus, the
Cu-N-N-C torsion angles of the pyrazolyl rings aver-
age 172° for 3 and 174° for 6. For complexes with planar
pyrazolyl rings, as observed with these complexes, the
deviation of this angle from 180° defines the degree of
tilting of the rings. This lack of tilting contrasts with
our earlier results in thallium6a and cadmium6b struc-
tures containing the ligand HC(3,5-Me2pz)3. In the
most distorted case of {[HC(3,5-Me2pz)3]2Tl}PF6, this
M-N-N-C torsion angle is 123.2°. We attributed this
distortion to the size of the metal atom being large
in comparison to the intrinsic “bite” of the ligand. In
the present structures, no distortion is necessary be-
cause the small size of copper(I) matches the bite of the
ligand.
Bond Angles (deg)
Cu(1)-N(1)-C(2)
N(1)-Cu(1)-N(11)
N(1)-Cu(1)-N(21)
C(1)-Cu(1)-N(31)
N(11)-Cu(1)-N(21)
N(11)-Cu(1)-N(31)
N(21)-Cu(1)-N(31)
174.1(14)
122.9(4)
125.7(4)
128.7(5)
89.0(4)
Cu-C(23)-O
176.8(9)
123.7(3)
128.9(3)
125.4(3)
88.6(2)
C(23)-Cu-N(1)
C(23)-Cu-N(3)
C(23)-Cu-N(5)
N(1)-Cu-N(3)
N(1)-Cu-N(5)
N(3)-Cu-N(5)
89.9(4)
88.8(4)
92.0(2)
86.5(2)
Torsion Angles (deg)
Cu(1)N(11)-N(12)C(13) 172.6(9) CuN(1)-N(2)C(1) 172.8(2)
Cu(1)N(21)-N(22)C(23) 171.1(8) CuN(3)-N(4)C(8) 175.6(2)
Cu(1)N(31)-N(32)C(33) 172.0(9) CuN(5)-N(6)C(15) 173.6(2)
Ta ble 3. Ca r bon yl Str etch in g F r equ en cies for
[Tr is(p yr a zolyl)m eth a n e]- a n d
[Tr is(p yr a zolyl)bor a to]cop p er (I) Ca r bon yl
Com p lexes
ν(CO)
(cm-1
ν(CO)
(cm-1
)
complex
)
complex
{[HC(3,5-Me2pz)3]CuCO}+ 2113 [HB(3,5-Me2pz)3]CuCO2a 2066
Previously, Kitjima reported that addition of dioxygen
to the copper(I) species [HB(3,5-i-Pr2pz)3]Cu at low
temperatures is facile and results in a deep purple
solution.2b The product that forms is a µ-η2:η2-dioxygen
dimer, as determined by low-temperature X-ray crystal-
lography. All but the most sterically hindered cationic
copper(I) complexes of the tris(imidazolyl)phosphine
ligands also turn purple in the presence of oxygen at
low temperatures.3,12 In contrast, compounds 1-3 are
resistant toward forming this purple solution under
similar conditions and are surprisingly stable.
{[HC(3-Phpz)3]CuCO}+
{[HC(3-Butpz)3]CuCO}+
2104 [HB(3,5-Ph2pz)3]CuCO2b 2086
2100 [HB(3-Butpz)3]CuCO2c
2069
cationic complex [Cu(dien)CO]BPh4.13 Specifically, the
average Cu-N bond distance (2.080 Å) and the Cu-
CO bond distance of 1.778(10) Å fall within typical
ranges observed in the cationic and neutral copper(I)
carbonyl complexes studied previously.
Discu ssion
The complexes 1-6 are the first reported copper(I)
derivatives of the tris(pyrazolyl)methane ligands,14 and
complexes 3 and 6 are the first reported complexes on
any metal of the bulky ligand HC(3-Butpz)3. The change
from negatively charged tris(pyrazolyl)borate ligands to
these neutral analogs does not appear to change the
stability of the carbonyl complexes. Table 3 shows a
comparison of the carbonyl stretching frequencies of the
matched complexes (the substitution for the phenyl
derivative is different). As expected, the values for the
cationic complexes are higher, indicating weaker π back-
bonding with the CO ligand. A similar increase in
stretching frequency was noted previously for the
comparison of analogous neutral tris(pyrazolyl)borate
and cationic tris(imidazolyl)phosphine complexes.3
Ack n ow led gm en t is made to the National Institutes
of Health (Grant No. GM-26295) and the National
Science Foundation (Grant No. CHE-9115158 and OSR-
9108772 for D.L.R.) for support. The NSF (Grant No.
CHE-8411172 and CHE-8904942) and NIH (Grant No.
RR-02425) have supplied funds to support NMR equip-
ment, and the NIH (Grant No. RR-02849) has supplied
funds to support mass spectrometry equipment.
Su p p or tin g In for m a tion Ava ila ble: Tables of complete
data collection information, bond distances, angles, positional
parameters, and anisotropic thermal parameters for 3 and 6
(13 pages). Ordering information is given on any current
masthead page.
(13) Pasquali, M.; Marchetti, F.; Floriani, C. Inorg. Chem. 1978, 17,
1684.
OM960026S
(14) A homoleptic Cu(II) complex, {[HC(pz)3]2Cu}(NO3)2, has been
prepared and structurally characterized: Astley, T.; Gulbis, J . M.;
Hitchman, M. A.; Tiekink, E. R. T. J . Chem. Soc., Dalton Trans. 1993,
509.
(15) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; Chapter 3.