Alkyl and Aryl Compounds of Rhodium(III) and Iridium(III)
Organometallics, Vol. 26, No. 25, 2007 6339
trimethylphenyl,10 Rh(C6Cl5)3,11 and [Rh(C6Cl5)4]-,12), pentam-
ethylcyclopentadienyl alkyls (e.g., Cp*MMe4), and oxo alkyls/
aryls(e.g.,[Rh(CH2CMe3)3]2(µ-O),13 Ir(mes)3O,14 and[Ir(mes)3]2(µ-
O)).14,15 While Rh(III) trialkyl compounds supported by chelating
amine ligands such as Rh(R′3TACN)R3 (R′ ) H, Me; R ) Me
or Et; TACN ) 1,4,7-triazacyclononane)16 and Rh(TMEDA)-
13
(C4H8S)Me3 are known, analogous alkyl/aryl compounds
cooled mixture was added Et2O (20 mL), and the yellow precipitate
was collected, washed with Et2O, and air-dried. Yield: 195 mg
(69%). 1H NMR (300 MHz, CDCl3): δ 1.44 (s, 9H, t-Bu), 1.47 (s,
9H, t-Bu), 3.18 (s, 3H, NMe2), 3.23 (s, 3H, NMe2), 7.55 (dd, J )
6.0, 2.1 Hz, 1H, H5), 7.66 (dd, J ) 6.0, 2.0 Hz, 1H, H5), 7.96 (d,
J ) 2.1 Hz, 1H, H3), 8.03 (d, J ) 2.0 Hz, 1H, H3), 8.67 (s, 1H,
CHO), 8.98 (d, J ) 6.0 Hz, 1H, H6), 9.82 (d, J ) 6.6 Hz, 1H, H6).
MS (FAB): m/z 478.1 (M+ + 1 - DMF). Anal. Calcd for C21H31-
Cl3N3ORh‚0.5Et2O: C, 47.0; H, 6.1; N, 7.1. Found: C, 47.2; H,
6.1; N, 7.3.
containing bpy have not been synthesized.
Recently, we studied the transmetalation of Ir(dtbpy)Cl3-
(DMF) (DMF ) N,N-dimethyformamide) with Grignard re-
agents. We found that alkylation of Ir(dtbpy)Cl3(DMF) with
Me3SiCH2MgCl led to C-Si cleavage of the alkyl group and
formation of a Ir(III) silyl alkyl compound, whereas that with
PhMe2CCH2MgCl resulted in an iridacycle, illustrating some
interesting organometallic chemistry of the IrIIIbpy core.18
Herein, we describe the synthesis and crystal structures of a
dtbpy-supported rhodacycle as well as Rh(III) and Ir(III) triaryl
compounds. The isolation of an Ir/Ag polymeric compound, in
which the Ag(I) ions bind to the Ir-bound aryl ligands in an
η2-fashion, will also be reported.
Preparation of Rh(dtbpy)(CH2CMe2C6H4)(CH2CMe2Ph) (2).
To a suspension of 1 (100 mg, 0.182 mmol) in THF (25 mL) was
added PhMe2CCH2MgCl (0.91 mL of a 0.8 M solution in THF,
0.726 mmol) at -78 °C. The mixture was stirred at this temperature
for 1 h, warmed to room temperature, and stirred overnight. The
volatiles were removed in vacuo, and the residue was extracted
with hexane. The extracts were concentrated and cooled at
-40 °C to give orange crystals that were suitable for X-ray
Experimental Section
General Considerations. All manipulations were carried out
under nitrogen by standard Schlenk techniques. Solvents were
purified, distilled, and degassed prior to use. NMR spectra were
recorded on a Varian Mercury 300 spectrometer operating at 300,
121.5, and 282.4 MHz for 1H, 31P, and 19F, respectively. Chemical
shifts (δ, ppm) were reported with reference to SiMe4 (1H and 13C),
P(OMe)3 (31P), and C6H5CF3 (19F). Infrared spectra were recorded
on a Perkin-Elmer 16 PC FT-IR spectrophotometer; mass spectra,
on a Finnigan TSQ 7000 spectrometer. Cyclic voltammetry was
performed with a Princeton Applied Research (PAR) model 273A
potentiostat. The working and reference electrodes were glassy
carbon and Ag/AgNO3 (0.1 M in acetonitrile) electrodes, respec-
tively. Potentials were reported with reference to the ferrocenium-
ferrocene (Cp2Fe+/0). Elemental analyses were performed by Medac
Ltd., Surrey, UK. The ligand 4,4′-di-tert-butyl-2,2′-bipyridyl (dtbpy)
was obtained from Aldrich and used as received. [Ir(dtbpy)Cl3-
(DMF)] (DMF ) N,N-dimethylformamide) was prepared by
treatment of IrCl3 with dtbpy in refluxing DMF as described
elsewhere.18 Atom-labeling schemes for the dtbpy ligand and
rhodacyclic neophyl compounds are shown below.
1
diffraction analysis. Yield: 88 mg (76%). H NMR (300 MHz,
CDCl3): δ 0.81 (s, 3H, Me), 1.18 (s, 3H, Me), 1.22 (s, 3H, Me),
1.39 (s, 18H, t-Bu), 1.57 (s, 3H, Me), 1.89 (dd, J ) 8.1, 3.2 Hz,
1H, H7), 6.38 (t, J ) 7.6 Hz, 1H, H20), 6.61 (t, J ) 7.6 Hz, 2H,
H19), 6.79 (d, J ) 7.9 Hz, 1H, H14), 6.83 (d, J ) 7.6 Hz, 2H, H5),
6.90-6.99 (m, 2H, H12,13), 7.20 (s, 1H, H3), 7.23 (s, 1H, H3), 7.78
(d, J ) 6.7 Hz, 2H, H6), 7.87 (d, J ) 1.8 Hz, 1H, H11), 8.27 (broad,
1H, H18), 8.36 (broad, 1H, H18′). Resonances for the methylene
protons H15, H17, and H17′ were found to be hidden by intense peaks
in the δ 1-2 ppm region but could be located at δ 1.31 (H15), 1.43
(H7), and 1.78 (H15′) by means of a 1H,1H COSY experiment. MS
(FAB): m/z 637.2 (M+ + 1). Anal. Calcd for C38H49N2Rh: C, 71.7;
H, 7.8; N, 4.4. Found: C, 72.2; H, 7.9; N, 4.3.
Preparation of Rh(dtbpy)(CH2CMe2C6H4)(CH2CMe2Ph)(CO)
(3). Carbon monoxide was bubbled into a solution of 2 (50 mg,
0.079 mmol) in CH2Cl2 (25 mL) at 0 °C for 30 s. The mixture was
warmed at room temperature and stirred for 4 h. The volatiles were
removed in vacuo, and the residue was recrystallized from hexane
at -40 °C to give a yellow powder. Yield: 45 mg, 86%. IR (KBr,
1
cm-1): 1987 (νCO). H NMR (300 MHz, C6D6): δ 0.88 (s, 9H,
Preparation of Rh(dtbpy)Cl3(DMF) (1). To a solution of
RhCl3‚xH2O (100 mg) in DMF (2 mL) was added dtbpy (138 mg,
0.515 mmol), and the mixture was heated at reflux for 3 h. To the
t-Bu), 0.99 (s, 9H, t-Bu), 1.05 (s, 3H, Me), 1.74 (s, 3H, Me), 1.85
(s, 3H, Me), 1.93 (s, 3H, Me), 2.17 (d, J ) 10.9 Hz, 1H, H15), 2.20
(d, J ) 4.0 Hz, 1H, H7), 2.26 (d, J ) 4.0 Hz, 1H, H7), 3.19 (d, J
) 10.9 Hz, 1H, H15), 6.15 (dd, J ) 5.7, 1.8 Hz, 1H, H5), 6.70 (dd,
J ) 5.7, 1.8 Hz, 1H, H5), 7.02 (dd, J ) 7.5, 6.0 Hz, 1H, H14),
7.23-7.33 (m, 5H, H12,13 and H19,20), 7.63 (s, 1H, H3), 7.71 (s, 1H,
H3), 7.77 (d, J ) 8.4 Hz, 2H, H18), 7.95 (dd, J ) 7.2, 1.8 Hz, 1H,
H11), 8.21 (d, J ) 5.7 Hz, 1H, H6), 8.73 (d, J ) 5.7 Hz, 1H, H6).
MS (FAB): m/z 665.3 (M+ + 1). Anal. Calcd for C39H49N2ORh‚
0.5H2O: C, 69.5; H, 7.5; N, 4.2. Found: C, 69.5; H, 7.5; N, 3.9.
Preparation of Rh(dtbpy)(CH2SiMe3)2Cl (4). To a suspension
of 1 (100 mg, 0.182 mmol) in THF (25 mL) was added Me3-
SiCH2MgCl (0.91 mL of a 0.8 M solution in THF, 0.726 mmol) at
-78 °C. The mixture was slowly warmed to room temperature and
stirred overnight. The volatiles were removed in vacuo, and the
residue was extracted with hexane. Concentration and cooling at
-40 °C gave orange crystals. Yield: 84 mg (79%). 1H NMR (300
MHz, C6D6): δ 0.31 (s, 18H, CH2SiMe3), 0.75 (d, J ) 11.4 Hz,
2H, CH2SiMe3), 0.92 (s, 9H, t-Bu), 0.95 (s, 9H, t-Bu), 2.14 (d, J
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of the type [M(bpy)(N^C)2]+ are well documented: Ohsawa, Y.; Sprouse,
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