Double DeriWatization of the Nitrido Ligand
(NCN)] (trans-[OsIVdNCN]), trans-[OsII(tpy)(Cl)2(NCNPPh3)] (trans-
[OsII-NtC-NdPPh3]), and trans-[OsII(tpy)(Cl)2(N(PPh3)CN)]
(trans-[OsII-N(sCtN)(dPPh3)]).
for junction potentials. In all cases, the auxiliary electrode was a
platinum wire. The solution in the working compartment was de-
oxygenated by N2 bubbling.
Abbreviations and formulas used in the text include the
following: TBAH ) Bu4NPF6, tetrabutylammonium hexafluoro-
phosphate; tpy ) 2,2′:6′,2′′-terpyridine; and bpy ) 2,2′-bipyridine.
The ligands are illustrated below:
Synthesis and Characterization. The following complexes and
compounds were prepared by literature procedures: trans-[OsVI-
(tpy)(Cl)2(N)]PF6,8a mer-[OsVI(bpy)(Cl)3(N)],8b trans-[OsIV(tpy)-
(Cl)2(NCN)],7c mer-Et4N[OsIV(bpy)(Cl)3(NCN)],7c and trans-[OsIV-
(tpy)(Cl)2(NPPh3)]PF6.9
trans-[OsIV(tpy)(Cl)2(NCN)]. In a 100 mL round-bottom
flask, trans-[OsVItN]+ (200 mg, 0.306 mmol) was stirred in 50
mL of CH2Cl2 under N2 atmosphere for 2 min. One equivalent of
NEt4CN (47.8 mg) in 5 mL of CH2Cl2 was bubbled with N2 for 2
min and added to the solution of trans-[OsVItN]+. The reaction
mixture was stirred continuously under N2 for 30 min. The brown
precipitate was filtered, washed thoroughly with fresh CH2Cl2, and
air-dried. Yield: 148 mg (91%). Anal. Calcd for OsC16H11N5Cl2:
C, 35.96; H, 2.07; N, 13.11. Found: C, 36.17; H, 2.15; N, 13.32.
UV-visible data (DMF) λmax, nm (ꢀ, M-1 cm-1): 867 (3.28 ×
102), 744 (7.83 × 102), 628 (2.87 × 103), 512 (6.03 × 103), 416
(8.40 × 103), 318 (3.26 × 104), and 280 (2.95 × 104). Cyclic
voltammetric data in 0.1 M TBAH/DMF (V vs SSCE): E1/2(Os-
(VI/V)) ) +1.72 V, E1/2(Os(V/IV)) ) +0.90 V, E1/2(Os(IV/III))
Materials. House water was purified with a Barnstead E-Pure
deionization system. High-purity acetonitrile was used as received
from Aldrich. Osmium tetraoxide (>99%) was purchased from the
Pressure Chemical Company. Triphenyl phosphine (PPh3) and
tetraethylammonium cyanide (Et4NCN) were purchased from
Aldrich and used without further purification. Deuterated solvents
were purchased from Cambridge Isotope Laboratories and used as
received. TBAH was recrystallized three times from boiling ethanol
and dried under vacuum at 120° for 2 days. Other chemicals
employed in the preparation of compounds were reagent grade and
used without further purification.
) -0.40 V, and E1/2(Os(III/II)) ) -1.30 V. Infrared (cm-1
,
Nujol): ν(CtNâ) ) 1938 cm-1; ν(tpy) 1466 (vs), 1456 (vs), and
1369 (vs).
Instrumentation and Measurement. Electronic absorption
spectra were acquired by using a Hewlett-Packard model 8453 diode
array UV-visible spectrophotometer in quartz cuvettes. Spectra
in the near-IR region were recorded on a Perkin-Elmer Lambda
19 spectrophotometer by using a matched pair of 10 mm path
length quartz cell. Elemental analyses were performed at Los
Alamos National Laboratory and by Atlantic Microlabs (Norcross,
GA). FT-IR spectra were recorded on a Nexus 670 FT-IR
spectrophotometer at 4 cm-1 resolution interfaced with an
IBM-compatible PC. IR measurements were made in Nujol
Mulls. 1H NMR spectra were obtained in DMSO-d6 recorded on a
JEOL-300 Fourier transform spectrometer. Organic products were
analyzed by use of a Hewlett-Packard 5890 series II gas chromato-
graph with a 12 m × 0.2 mm × 0.33 µm HP-1 column (cross-
linked methyl silicone gum) and a Hewlett-Packard 5971A mass
selective detector, both interfaced with an HP Vectra PC computer
system.
Kinetic studies by UV-visible monitoring were conducted on a
Hewlett-Packard 8453 diode array spectrophotometer interfaced
with an IBM-compatible PC. The measurements were made in
standard quartz 1 cm path length cuvettes. All kinetic studies were
performed at 25.0 ( 0.1 °C with a pseudo-first-order excess of
organic reagents. Kinetic studies of trans-[OsIV-NCN] with PPh3
and of trans-[OsIV-NPPh3]+ with Et4NCN were performed in DMF.
The concentrations of the Os(IV) solutions were 7.5 × 10-4 M for
trans-[OsIVdNCN] and 8.0 × 10-4 M for trans-[OsIV-NPPh3]+.
The concentrations of PPh3 or Et4NCN were varied from 8.15 ×
10-3 M to 9.15 × 10-2 M for PPh3 and from 5.5 × 10-4 M to 5.5
× 10-3 M for Et4NCN. The temperature of solutions during the
kinetic studies was maintained to within (0.1 °C with use of a
RTE-7 Thermo-Neslab circulating water bath.
trans-[OsII(tpy)(Cl)2(NCNPPh3)]. In a 100 mL Erlenmeyer
flask, trans-[OsIVdNCN] (300 mg, 0.561 mmol) was stirred in 30
mL of CH3CN under N2. One equivalent of PPh3 (147 mg) in 5
mL of CH3CN was added, and the reaction mixture was stirred for
1 h. The brown solution was evaporated to 5 mL by rotary
evaporation. Upon addition of 150 mL of Et2O, the brown product
was filtered, washed with fresh Et2O, and air-dried. Yield: 0.423
g (95%). Anal. Calcd for OsC34H26N5Cl2P: C, 51.26; H, 3.29; N,
8.79. Found: C, 51.40; H, 3.48; N, 8.97. Cyclic voltammetric data
in 0.1 M Bu4NPF6/DMF (V vs SSCE): E1/2(Os(IV/III)) ) +1.12
V and E1/2(Os(III/II)) ) -0.16 V. Infrared (cm-1, Nujol) for
OsII-14NCNPPh3: ν(14NRtC) ) 2235 cm-1; ν(tpy) 1467 (vs),
1447 (vs), and 1440 (vs); ν(14NâdP) ) 1116 cm-1. Infrared for
OsII-15NCNPPh3: ν(15NRtC) ) 2205 cm-1; ν(tpy) 1465 (vs),
1
1446 (vs), and 1441 (vs); ν(14NâdP) ) 1116 cm-1. H NMR (δ,
DMSO-D6): 11 H for tpy: (2 H, d) 8.32 f 8.29; (2 H, d) 8.07 f
8.04, (2 H, d) 7.99 f 7.96; (2 H, t) 7.37 f 7.33; (2 H, t) 7.23 f
7.17; (H, t) 6.29 f 6.25; 15 H for PPh3: 7.88 f 7.69. 31P NMR
(δ, DMSO-D6): 26.5 ppm. UV-visible spectra in DMF (λmax, nm
(ꢀ, M-1 cm-1): 750 (2.58 × 103), 660 (3.47 × 103), 592 (5.64 ×
103), 502 (7.03 × 103), 424 (7.95 × 103), 386 (9.56 × 103), and
330 (2.14 × 104).
trans-[OsII(tpy)(Cl)2(N(CN)PPh3)]. In a 100 mL Erlenmeyer
flask, trans-[OsIV-NPPh3]+ (400 mg, 0.519 mmol) was stirred in
40 mL of CH3CN under N2. One equivalent of Et4NCN (81.1 mg)
in 5 mL of CH3CN was added, and the reaction mixture was stirred
for 30 min. The solvent was removed by rotary evaporation. The
product was filtered, washed with Et2O, and air-dried. Yield: 0.389
g (94%). Anal. Calcd for OsC34H26N5Cl2P: C, 51.26; H, 3.29; N,
8.79. Found: C, 51.57; H, 3.38; N, 8.89. Cyclic voltammetric data
Cyclic voltammetric experiments were measured with the use
of PAR model 263 and 273 potentiostats. Bulk electrolyses were
performed with a PAR model 173 potentiostat/galvanostat. Cyclic
voltammetry measurements were conducted in a three-compartment
cell with 0.2 M TBAH as the supporting electrolyte and a 1.0 mm
platinum-working electrode for CH3CN or DMF. All potentials are
referenced to the saturated sodium chloride calomel electrode
(SSCE, 0.236 V vs NHE) at room temperature and are uncorrected
(8) (a) Pipes, D. W.; Bakir, M.; Vitols, S. E.; Hodgson, D. J.; Meyer, T.
J. J. Am. Chem. Soc. 1990, 112, 5507-5514. (b) Demadis, K. D.;
El-Samanody, El.-S.; Meyer, T. J.; White, P. S. Inorg. Chem. 1998,
37, 838-839. (c) Ware, D. C.; Taube, H. Inorg. Chem. 1991, 30 (24),
4605-4610.
(9) (a) Bakir, M.; White, P. S.; Dovletoglou, A.; Meyer, T. J. Inorg. Chem.
1991, 30, 2835-2836. (b) Demadis, K. D.; Bakir, M.; Klesczewski,
B. G.; Williams, D. S.; White, P. S.; Meyer, T. J. Inorg. Chim. Acta
1998, 270, 511-526.
Inorganic Chemistry, Vol. 44, No. 10, 2005 3659