bonds slightly shorter than the equatorial ones (Rh–P(2),
Rh–P(3) 2.319, 2.329 A vs. Rh–P(4), Rh–P(5), Rh–P(1)
2.330, 2.368, 2.396 A). The metrical parameters of the cation
of the pyrazolate salt [Rh(PMe3)5][3,5-(CF3)2-Pz] (3) are
similar to those found in 2 although the three equatorial
PMe3 groups are more evenly spaced with P–Rh–P angles
of 119.08, 123.03 and 117.201. The geometry of the
Ir cation in 4 is much closer to that of a perfect trigonal
bipyramid, although the Ir–P distances cover a wider range
(2.294–2.437 A). The differences in structures may be due to
packing forces.
Notes and references
z Experimental procedure: for 1: a solution of freshly prepared
Et3Si-[B(C6F5)4] (0.66 g, 0.83 mmol) in toluene (30 ml) was added to
a suspension of [Rh(PMe3)4][Cl] (0.36 g, 0.83 mmol) in toluene (60 ml)
at 25 1C. The reaction mixture was stirred (12 h) and formed an orange
oil. Cooling the tube (ꢀ10 1C) produced orange crystals of 1 which
were collected and dried under vacuum. Mp 180–183 1C (dec.). Yield:
0.78 g, 87%. 1H NMR (300 MHz, d8-toluene) d 0.79 (br s, 36H,
(PCH3)3). 19F NMR (282 MHz, d8-toluene) d ꢀ131.9 (m, Ar–F),
ꢀ163.0 (m, Ar–F), ꢀ166.7 (m, Ar–F). 31P{1H} NMR (121 MHz,
d8-toluene) d ꢀ14.15 (d, JRh–P = 131 Hz). CI-MS m/z: 407 [M+],
331 [M+ ꢀ PMe3]. IR: (ATR) 1642w, 1514m, 1463vs, 1291w, 1276w,
979s, 944s, 858m, 774m, 756m, 727w. Anal. found: C, 39.0; H, 3.1%.
Calc.: C 39.8, H 3.3%. For 2: [Rh(PMe3)4][B(C6F5)4] (1) (0.5 g,
0.046 mmol) was sealed in a glass tube with PMe3 (0.5 ml) under
vacuum. The tube was heated to 80 1C (1 h) forming an orange
solution. Cooling (room temp.) afforded crystals of 2 which were
collected and dried under vacuum. Mp 208–210 1C (dec.). Yield:
The highest Rh containing peak in the CI-MS spectrum
of 1 corresponds to the 4-coordinate cation [Rh(PMe3)4)]+
(m/z 407). For 2 the highest peak is also at m/z 407 indicating
the loss of one PMe3 ligand under the experimental conditions
employed and this is also the case for the Ir cation of 4
(m/z 497). For 3 the highest peak is at m/z 453 which
corresponds to the loss of two Me groups from the
[Rh(PMe3)5]+ cation. We have also attempted to characterise
the complexes by NMR, however these studies did not provide
any useful stereochemical information. Thus the 31P{1H}
NMR spectrum of 1 in C6D6 is a doublet at d ꢀ14.2
(JRh–P = 131 Hz) which is close to previously reported
literature values for the [Rh(PMe3)4]+ cation in other solvents.3,5
For 2 the 31P{1H} NMR spectrum (d8-PhMe room temp.)
consists of a very broad peak centered at approximately
dꢀ55 ppm (w1/2 = ca. 1000 Hz) and a sharp peak at
d ꢀ15.6. At ꢀ40 1C two very broad peaks are observed
at d ꢀ21 and ꢀ61 ppm (rel. areas 2 : 1). At ꢀ80 1C three
very broad resonances are observed at ca. d 0.0, ꢀ14 and ꢀ36
in addition to the resonance at ꢀ61 ppm which is now
considerably sharper. At this temperature 2 is not very soluble
in toluene and the low resolution data may be caused by
precipitation from solution. In contrast, 3 is considerably
more soluble than 2 in d8-toluene. The 31P{1H} NMR
spectrum at room temperature shows only a very broad peak
at ca. d ꢀ21 ppm. Cooling to ꢀ80 1C again results in the
appearance of three very broad peaks at d ꢀ4, ꢀ11 and ꢀ36 ppm.
The data suggest that the 5-coordinate Rh cation undergoes a
facile reversible loss of PMe3 in solution and that the resulting
species are stereochemically non-rigid, even at low tempera-
ture, and undergo exchange processes which are rapid on the
NMR timescale. The differences in chemical shifts for the low
temperature data for 2 and 3 suggest the possibility of weak
interactions between the different anions and the metal center.
We were unable to obtain reliable NMR data for the
iridium complex 4 due to lack of solubility and/or apparent
decomposition. In d8-toluene at room temperature the 31P{1H}
NMR spectrum shows a signal due to free PMe3 (d ꢀ61) in
addition to numerous other signals and the 1H NMR contains
numerous complex signals in the region d 0.8–1.15.
1
0.041 g, 77%. H-NMR (500 MHz, d8-toluene, ꢀ40 1C) d 0.67 (br s).
31P{H} NMR (121 MHz, d8-toluene, ꢀ40 1C) d ꢀ21.13 (br s).
CI-MS m/z: 407 [M+ ꢀ PMe3], 331 [M+ ꢀ 2PMe3]. IR: 1643w,
1513m, 1461vs, 1374vs, 1310w, 1274w, 1236vw, 1088s, 978vs, 940vs,
853vw, 774w, 756w, 709vw. Anal. found: C, 39.9; H, 3.6%. Calc.: C
40.3, H 3.9%. For 3: [Rh(PMe3)4][ 3,5-(CF3)2-Pz] (0.1 g, 0.16 mmol)
was sealed in a glass tube with PMe3 (1 ml) under vacuum. The tube
was heated to 80 1C (2 h) forming an orange oil. Cooling the tube
(room temp.) afforded crystals of 3 which were collected and dried
under vacuum. Mp o 120 1C. Yield: 0.083 g, 76%. 1H NMR
(300 MHz, C6D6, 27 1C) d 7.1 (s, 1H, Ar–H), 0.79 (m, 45H,
P(CH3)3). 19F NMR (282 MHz, C6D6) d ꢀ59.3. 31P{H} NMR
(121 MHz, C6D6) d ꢀ27.7 (br s). CI-MS m/z: 453 [M+ ꢀ 2CH3].
IR: 1516w, 1424w, 1348w, 1285w, 1256s, 1109vs, 1002m, 943vs, 858m,
799m, 719m. Anal. found: C, 34.0; H, 5.9; N, 4.3%. Calc.: C 35.0, H
6.7, N 4.1%. For 4: [Ir(m-3,5-(CF3)2-Pz)(COD)]2 (0.056 g, 0.056 mmol)
was sealed in a glass tube with PMe3 (0.5 ml) under vacuum. The tube
was heated to 80 1C (1 h) and a colorless precipitate formed. Cooling
the tube slowly to room temperature afforded colorless crystals of 4
which were collected and dried under vacuum. Mp: the compound
undergoes a color change from white to orange 75–77 1C, and appears
to melt without decomposition at 98–100 1C. Yield: 0.065 g, 75%.
1H-NMR (300 MHz, C6D6) d 7.21 (s, 1H, Ar–H), 0.80–1.15 (br m,
36H, P(CH3)). 19F NMR (282 MHz, C6D6) d ꢀ57.5 (s). 31P{1H} NMR
(121 MHz, C6D6) d ꢀ53.5 (br s). CI-MS m/z: 497 [M+ ꢀ PMe3],
421 [M+ ꢀ 2PMe3]. IR: (ATR) 2917vw, 1520vw, 1499w, 1434vw,
1326w, 1291w, 1245s, 1123m, 1095vs, 977m, 940vs, 861w, 781w, 724w.
Anal. found: C, 30.6; H, 5.9; N, 3.6%. Calc.: C 31.0, H 6.0, N 3.6%.
y Crystal data for 1: [Rh(PMe3)4][B(C6F5)4]: C36H36BF20P4Rh,
ꢀ
1086.25, triclinic, space group P1,
Mr
=
a
=
12.1222(9),
b = 12.6241(9), c = 15.8420(11) A, a = 104.7118(17)1, b =
109.8361(17)1, 98.4962(18)1, 2,
g
=
V
=
2131.6(3) A3,
Z =
T = 100(2) K, 52 101 reflections (Rint = 0.0376), 9768 unique,
R1(final) = 0.045, wR2 = 0.1020 for 8420 (I 4 2s(I)) and 571
parameters. For 2: [Rh(PMe3)5][B(C6F5)4]: C39H45BF20P5Rh,
ꢀ
Mr = 1162.32, triclinic, space group P1, a = 12.7999(7), b =
13.4422(8), c = 15.4812(9) A, a = 111.8790(14)1, b = 99.044(2)1,
g = 103.507(2)1, V = 2313.7(2) A3, Z = 2, T = 100(2) K, 47 554
reflections (Rint = 0.0760), 10580 unique, R1(final) = 0.0609, wR2 =
0.1209 for 7709 (I
[Rh(PMe3)5][(CF3)2-C5HN2]: C20H46F6N2P5Rh, Mr
triclinic, space group P1,
4
2s(I)) and 610 parameters. For 3:
686.35,
12.0818(14),
c = 14.6363(17) A, a = 88.422(4)1, b = 75.798(3)1, g = 77.305(3)1,
V = 1587.6(3) A3, Z = 2, T = 100(2) K, 27 263 reflections (Rint
=
ꢀ
a = 9.4967(11), b =
=
0.0226), 7227 unique, R1(final) = 0.00294, wR2 = 0.0703 for 6910
(I 4 2s(I)) and 486 parameters. For 4: [Ir(PMe3)5][(CF3)2-C5HN2]:
ꢀ
C20H46F6N2P5Ir, Mr = 775.66, triclinic, space group P1, a =
Further studies of these and related complexes are in
9.4552(8), b = 12.0860(10), c = 14.5150(13) A, a = 88.571(3)1, b =
75.866(2)1, g = 77.060(2)1, V = 1566.9(2) A3, Z = 2, T = 100(2) K,
43 093 reflections (Rint = 0.0741), 7160 unique, R1(final) = 0.00294,
wR2 = 0.1996 for 6381 (I 4 2s(I)) and 393 parameters. All data were
collected on a Rigaku AFC-12 with Saturn 724+CCD.
progress.
We thank the Welch Foundation (Grant F-816), Texas
Higher Education Coordinating Board (ARP 003658-
0010-2006) and the Petroleum Research Fund, administered
by the American Chemical Society (47014-AC5) for financial
support. X-Ray data were collected on instrumentation
purchased with funds from NSF grant # 0741973.
1 F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry,
John Wiley and Sons, 5th edn, 1988, pp. 900–908.
2 L. M. Haines, Inorg. Chem., 1971, 10, 1685.
ꢁc
This journal is The Royal Society of Chemistry 2010
Chem. Commun., 2010, 46, 4300–4302 | 4301