CH2), 3.1 (sbr, 4H, ethene CH2) 3.7 (2H, cyclohexyl CH), 6.9 (s,
Copper(I)-butadiene complex: [(Cu2L2(l-1,3-C4H6)]·2PF6
4H, aryl CH), 8.8 (s, 2H, CH N). H NMR (-80 ◦C, CD2Cl2):
1
=
L (0.03 g, 0.08 mmol) was dried under vacuum for 15 min in
a ‘two-arm’ crystallisation chamber. [Cu(NCCH3)4]·PF6 (0.03 g,
0.08 mmol) was added to the tube and the contents shaken
whilst adding dichloromethane (5 cm3) via cannula. Diethyl ether
(10 cm3) was transferred to the other side of the chamber via
cannula, and this side was immersed in an acetone/ice bath.
Butadiene (CAUTION) was introduced via a needle through a
septum in a side arm of the tube, and was condensed into the
diethyl ether until a total volume of ~20 cm3 was obtained (10 cm3
liquid butadiene). The system was then sealed, wrapped in plastic
netting and removed from the acetone/ice bath. After ~3 d the
solutions had equilibrated and a crop of crystals of [Cu2L2(m-1,3-
C4H6)]·2PF6 had formed.
dH (ppm); 1.4 (m, 4H, cyclohexyl CH2), 2.0 (d J = 5.31 Hz, 2H,
cyclohexyl CH2), 2.1 (s, 12H, o-mesityl CH3), 2.2 (s, 6H, p-mesityl
CH3), 2.5 (d J = 10.1 Hz, 2H, cyclohexyl CH2), 2.6 (d J = 9.7 Hz,
2H, ethene CH2), 3.1 (d J = 9.7 Hz, 2H, ethene CH2), 3.5 (2H,
cyclohexyl CH), 6.8 (s, 4H, aryl CH), 8.7 (s, 2H, CH N). 13C
=
NMR (CD2Cl2): dC (ppm); 20.0, 21.5, 30.3, 69.7, 84.5, 129.4, 133.1,
135.6, 141.1, 170.9. 1H NMR (400 MHz, silica matrix): Unresolved
spectrum; assignment of signals impossible. CP-MAS 13C NMR
(100 MHz, silica matrix): dC (ppm); 17.0, 17.9, 18.4, 20.5, 24.1,
26.7, 31.1, 67.2, 79.3, 85.0, 127.8, 128.9, 133.2, 134.8, 139.1, 162.6,
169.7.
MS (ES +ve ion): m/z 439 (65CuIL), 375 (L). IR (KBr disc) nmax
-1
=
=
(cm ): 2943 s (CH) 2868 m (CH), 1647 s (C N), 1611 m (C C
A few crystals were taken for X-ray analysis and the remaining
solutions were removed using cannula filtration. The crystals
were washed with diethyl ether (~2 cm3) and dried in vacuo for
30 min. Whilst in solution the complex is very air sensitive, but
it demonstrates remarkable stability in the solid state when dried.
No yield data were recorded for [Cu2L2(m-1,3-C4H6)]·2PF6 when
synthesised by this method.
=
aromatic), 1523 w (C C ethene), 1450 m, 1385 w, 1258 m, 943 m,
842 s (PF), 557 s (PF). Anal: Calc. for C28H38N2CuPF6: C, 55.05;
H, 6.30; N, 4.60; Found: C, 54.45; H, 6.30; N, 4.55.
UV/vis Studies on [Cu(C2H4)L]·PF6
[Cu(NCCH3)4]·PF6 (0.07 g, 0.19 mmol) and diimine ligand L
(0.07 g, 0.19 mmol) were placed in a Schlenk tube and dissolved
in dichloromethane (~10 cm3) added via cannula. The resulting
yellow solution was transferred via cannula to a specially adapted
UV/vis cell fitted with a Young’s tap. A spectrum was then
recorded between 200 and 800 nm at 298 K, which contained a
broad absorbance at ~360 nm. Ethene was then bubbled through
the cell (ca. 5 min), and a spectrum was recorded of the resulting
colourless solution. The absorbance at 360 nm was observed to
disappear. The cell was then purged with argon (bubbled through
the solution, ca. 45 min) to remove all traces of dissolved ethene,
which resulted in a yellow solution of the original acetonitrile
adduct. A UV/vis spectrum was recorded which showed the
band at 360 nm. The process of ethene addition was repeated
once more to confirm that the process was fully reversible
(Fig. 1).
Crystal data. C56H74Cu2F12N4P2, M = 1220.23, triclinic, a =
˚
9.234(10), b = 11.342(13), c = 13.985(7) A, a = 82.61(6), b =
◦
3
˚
93.35(7), c = 98.11(10) , U = 1437(2) A , T = 150(2) K, space
¯
group P1, Z = 1, 5067 reflections measured, 3258 unique (Rint
=
0.1310) which were used in all calculations. The final wR(F2) was
0.2678 (all data).
1H NMR (400 MHz, silica matrix): Second order spectrum; no
assignment of signals was possible. CP-MAS 13C NMR (100 MHz,
silica matrix): dC (ppm); 17.3, 18.0, 19.5, 20.9, 23.3, 24.2, 27.4, 30.9,
67.9, 117.5, 127.7, 129.2, 130.3, 131.8, 133.7, 134.8, 139.6, 140.5,
161.8, 171.0, 173.1. MS (ES +ve ion): m/z 439 (65CuI-L), 375 (L).
IR (KBr disc) nmax (cm-1): 2940 m (CH), 2859 w (CH), 1646 s
=
=
=
(C N), 1611 m (C C aromatic), 1559 w (C C butadiene), 1506
=
w (C C butadiene), 1456 m, 1382 w, 1018 w, 839 vs (PF), 557 s
(PF) Anal: Calc for C56H74N4Cu2P2F12: C, 55.15; H, 6.10; N, 4.60;
Found: C, 54.55; H, 6.15; N, 4.65.
Limited solubility in CD2Cl2 or CDCl3 restricted NMR studies
of [Cu2L2(m-1,3-C4H6)]·2PF6. Addition of CD3CN to a suspension
of crystals in CD2Cl2 (1:9 v/v CD3CN:CD2Cl2) resulted in the
formation of a yellow solution, believed to be due to the formation
of the monomeric acetonitrile adduct [CuL(NCCH3)]·PF6. 1H
NMR data quoted below are of poor quality, but when coupled
with 13C DEPT NMR information there is sufficient evidence
to imply that the decomposition of [Cu2L2(m-1,3-C4H6)]·2PF6 to
the acetonitrile adduct occurs in acetonitrile solution at room
temperature.
1H NMR [(CD2Cl2:CD3CN (9:1 v/v))]: dH (ppm); 1.4-1.6
(m, 4H, cyclohexyl CH2), 1.8 (m, 2H, cyclohexyl CH2), 2.0-2.2
(envelope containing o/p-mesityl CH3 and cyclohexyl CH2), 3.4
=
(2H, cyclohexyl CH), 6.8 (s, 4H, aryl CH), 8.5 (s, 2H, CH N)
[evidence of free C4H6: 5.1-5.2 (m, CH2), 6.3-6.4 (m, CH)] 13C
NMR [(CD2Cl2:CD3CN (9:1 v/v))]: dC (ppm); 18.9, 20.0, 24.0,
31.0, 70.8, 128.1, 131.9, 135.7, 137.2, 138.3, 162.9.
A procedure similar to that used in the synthesis of the cor-
responding ethene complex was followed, substituting butadiene
in place of ethene, although the ice bath was removed to avoid
condensation of butadiene. This resulted in the instantaneous
Fig. 1 UV/visible spectra of [CuL(NCCH3)]·PF6 in CH3CN, upon
repeated addition/removal of ethene (298 K).
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3143–3152 | 3145
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