Bis-Acetonitrile Two-Coordinate Copper(I) Complex
for 2. It is known from various [Cu(MeCN)4]+ complexes
-63.73 ppm): δ (ppm) (s, 8F, B(C6F5)4-m-F) -134.18, (t, 4F,
B(C6F5)4-p-F) -164.34, (t, 8F, B(C6F5)4-o-F) -168.34. Anal. Calcd
for C32H12BCuF20N4: C, 42.39; H, 1.33; N, 6.18. Found: C, 42.48;
H, 1.39; N, 5.99. IR (Nujol): 2306 (MeCN, m), 2276 (MeCN, m)
- 5
- 5
that varying the counteranion (SO3Me-,5 SO3CF3 , BF4 ,
- 1
- 4
-
PF6 , ClO4 , and now B(C6F5)4 ) does not affect the
ν(CN) in these coordinately saturated tetrakis-acetonitrile
copper(I) complexes. Thus, we speculate that the discrepancy
between the ν(CN) of 2 and [Cu(MeCN)2]BF4 may be
explained by the fact that the BF4- anion may be binding or
at least interacting slightly more strongly with the copper(I)
ion than occurs with the B(C6F5)4- counteranion in 2 to lower
its ν(CN) compared to that of 2.24-26
cm-1
.
[CuI(MeCN)4]B(C6F5)4 (1). Method 2. To a 100 mL Schlenk
flask equipped with a stir bar were added [CuI(MeCN)4]PF6
(commercially available from Aldrich or Strem Chemicals) (223
mg, 0.598 mmol), LiB(C6F5)4‚Et2O (Boulder Scientific) (456 mg,
0.600 mmol), and 8 mL of deoxygenated CH3CN under an inert
atmosphere. The reaction mixture was stirred for 1 h, after which
the product (1) was precipitated with addition of 75 mL of
deoxygenated H2O. This solid was isolated via filtration through a
coarse porosity Schlenk filter frit. The product (1) was dried under
vacuum for 12 h to give 408 mg (75% yield) as an off-white solid.
19F NMR (376 MHz, CD2Cl2, 293 K; reference used was R,R,R-
trifluorotoluene, -63.73 ppm): δ (ppm) (s, 8F, B(C6F5)4-m-F)
-133.80, (t, 4F, B(C6F5)4-p-F) -164.38, (t, 8F, B(C6F5)4-o-F)
In conclusion, [CuI(MeCN)2]B(C6F5)4 (2), a linear, two-
coordinate copper(I) compound ligated by two nitrile ligands,
has been synthesized and structurally characterized. It
possesses a significantly shorter Cu-N distance than [Cu-
(MeCN)4]ClO4, and even other two-coordinate Cu(I) com-
plexes with nitrogen ligand donors, and its ν(CN) is 26 cm-1
higher than that of copper(I) tetrakis(acetonitrile) complexes.
Complex 2 may serve as a useful starting material for the
synthesis of copper(I) complexes, which can lead to solubility
in low-dielectric solvents, and where the presence of less
acetonitrile is preferred.3,27
-168.26. IR (Nujol): 2306 (MeCN, m), 2276 (MeCN, m) cm-1
.
Synthesis of [CuI(MeCN)2]B(C6F5)4 (2). In the glovebox under
N2 was dissolved [CuI(MeCN)4]B(C6F5)4 (1) (0.034 g, 0.037 mmol)
in ∼1 mL of CH2Cl2, producing a clear, colorless solution with a
minute amount of insoluble, tan-colored suspension. The mixture
was filtered through a Kimwipe-plugged pipet to remove the
insoluble solid, and the filtrate was mixed with ∼5 mL of pentane
to form a precipitate. The white precipitate was redissolved in ∼1
mL of CH2Cl2, filtered, and reprecipitated again. After the repre-
cipitation process was repeated three times to remove previously
coordinated CH3CN that had been liberated, the white solid was
dissolved in ∼2 mL of CH2Cl2, carefully layered with ∼5 mL of
pentane, and left at room temperature. After 24 h, long, white
needlelike crystals of [CuI(MeCN)2]B(C6F5)4 (2) had formed.
Yield: 0.016 g, 52%. 19F NMR (470 MHz, CD2Cl2, 293 K;
reference used was R,R,R-trifluorotoluene, -63.73 ppm): δ (ppm)
(s, 8F, B(C6F5)4-m-F) -133.78, (t, 4F, B(C6F5)4-p-F) -164.29, (t,
8F, B(C6F5)4-o-F) -168.19. IR (Nujol): 2332 (MeCN, m), 2302
(MeCN, m) cm-1. Anal. Calcd for (BC28CuF20H6N2): C, 40.78;
H, 0.73; N, 3.40. Found: C, 41.09; H, 0.63; N, 3.98.
Experimental Section
Materials and Methods. All reagents and solvents were
purchased from commercial sources and are of reagent quality
unless otherwise stated. All air-sensitive compounds were handled
under an argon atmosphere using standard Schlenk techniques or
in an MBraun Labmaster 130 inert atmosphere (<1 ppm O2, <1
ppm H2O) glovebox filled with nitrogen. Acetonitrile (CH3CN) and
methylene chloride (CH2Cl2) were distilled from calcium hydride,
and pentane was distilled from sodium/benzophenone, all under
argon. Deoxygenation of these solvents was achieved by bubbling
with argon for 30 min or by three freeze/pump/thaw cycles prior
to introduction into the glovebox. Warning: Perchorlate compounds
are potentially explosiVe! While we haVe experienced no problems,
extreme care must be taken when working with perchorlate
complexes and only small quantities should be handled.
[CuI(MeCN)4]B(C6F5)4 (1). Method 1. To a flame dried 100
mL Schlenk flask equipped with a 125 mL addition funnel and stir
bar were added [CuI(MeCN)4]ClO43 (86 mg, 0.26 mmol) and LiB-
(C6F5)4‚Et2O (Boulder Scientific) (200 mg, 0.26 mmol, 1 equiv)
under an Ar flow. In the addition funnel, 35 mL of distilled
CH3CN was added under positive Ar flow and degassed for 25
min. Addition of 3 mL of this deaerated CH3CN to the flask yielded
a clear, tan solution. After 30 min, addition of 40 mL of degassed
H2O (via Ar bubbling) to the stirring solution led to the formation
of a precipitate. This tan solid was isolated via filtration under Ar
(coarse porosity Schlenk filter frit) and placed under vacuum
overnight, and 146 mg (61% yield) of the free-flowing, off-white
solid product (1) was transferred into the glovebox for storage.
Analysis of the noncrystalline material is as follows. 19F NMR (376
MHz, CD2Cl2, 293 K; reference used was R,R,R-trifluorotoluene,
Crystallographic Structural Determination. A suitable crystal
of [CuI(MeCN)2]B(C6F5)4 (2) for data collection was selected and
mounted with epoxy cement on the tip of a fine glass fiber. Data
were collected at 173 K with a Siemens P4/CCD diffractometer
with graphite-monochromated Mo KR X-radiation (λ ) 0.71073
Å).
No evidence of symmetry higher than monoclinic was observed
in the diffraction data. The systematic absences are uniquely
consistent with the reported space group, which yielded chemically
reasonable and computationally stable results of refinement. The
structure was solved by direct methods, completed by subsequent
difference Fourier syntheses, and refined by full-matrix least-squares
procedures. The cation resides on a crystallographic inversion
center, while the anion resides on a 2-fold axis of rotation. All
non-hydrogen atoms were refined with anisotropic displacement
coefficients, and all hydrogen atoms were treated as idealized
contributions.
All software and sources of the scattering factors are contained
in the SHELXTL (5.1) program library (G. Sheldrick, Siemens
XRD, Madison, WI).
For C28H6BCuF20N2: monoclinic, C2/c, a ) 19.7183(16), b )
8.2444(7), c ) 19.8057(16) Å, â ) 118.2620(10)°, V ) 2835.9(4)
Å3, Z ) 4, Z′ ) 1/2, T ) 173(2) K, Dcalc ) 1.932 g/cm, colorless
rod, GOF ) 1.178, R(F) ) 3.43% for 3156 observed independent
reflections (4° e 2θ e 56°).
(24) Although it was long considered a “non-coordinating anion,” the
tetrafluoroborate anion has been shown in various crystal structures
to be capable of binding to electron-deficient metal centers. The
B(C6F5)4- anion, on the other hand, has not been known to coordinate
to metal centers. See ref 20.
-
(25) B(C6H3(CF3)2)4 can in fact coordinate to metal ions; see ref 26.
(26) Powell, J.; Lough, A.; Saeed, T. J. Chem. Soc., Dalton Trans. 1997,
4137-4138.
(27) The presence of even 1 equiv of MeCN per copper complex can have
a profound influence on its O2 reactivity. See ref 3.
Inorganic Chemistry, Vol. 41, No. 8, 2002 2211