New Organoplatinum(II) and -(IV) Complexes
Organometallics, Vol. 17, No. 2, 1998 239
spectra were recorded on a Bruins Instruments Omega 10
instrument. A Perkin-Elmer LS-3B fluorescence spectrometer
served to record emission spectra. Cyclic voltammetry and
differential pulse voltammetry were carried out using a three-
electrode configuration (glassy-carbon working electrode, plati-
num counter electrode, Ag/AgCl reference) and a PAR 273
potentiostat and function generator with PAR M270/250
software. As internal standard the ferrocene/ferrocenium
couple (FeCp2+/0) was used. The photochemical experiments
were effected by irradiation of cooled dilute solutions (see text)
with an HBO 50W/AC mercury vapor lamp or a 100 W halogen
lamp. The wavelength range was adjusted using cutoff filters.
Product analysis by GC was performed with Perkin-Elmer
8410 and Carlo Erba Fractovap 2150 instruments (column PS
086). GC-MS measurements were performed with a Finnigan
4500 quadrupole mass spectrometer. For spectroelectrochemi-
cal measurements we employed an optically transparent thin-
layer electrolytic (OTTLE) cell.10
ylethylenediamine in 20 mL of diethyl ether was stirred at
ambient temperature for 10 h. The reaction mixture was
concentrated to 5 mL, and 10 mL of n-hexane was added. The
mixture was kept at -30 °C to accomplish precipitation of the
colorless product. Yield: 105 mg (0.28 mmol, 71%). Anal.
Calcd for C10H28N2Pt: C, 32.34; H, 7.60; N, 7.54. Found: C,
31.67; H, 7.10; N, 7.44.
Gen er a l P r oced u r e for Dim eth ylp la tin u m Com p lexes
P tMe2(R-DAB). In typical reactions, 0.4 mmol of the R-DAB
ligand was added to a solution of 0.115 g (0.2 mmol) of [Pt2-
Me4(µ-SMe2)2] in a mixture of 15 mL of benzene and 10 mL of
diethyl ether. The solution was stirred overnight at ambient
temperature. After removal of the solvents the resulting solids
were dissolved in a sufficient amount of diethyl ether. At -30
°C microcrystalline solids precipitated from this solution (dark
green for the complex with p-Tol-DAB, greenish blue for that
with 2,6-Xyl-DAB, and dark purple for the compound with Cy-
DAB). They were collected on a microporous glass frit, washed
with 10 mL of hexane, and dried in vacuo. Yield for
PtMe2(Cy-DAB): 71.3 mg (0.16 mmol, 40%). Anal. Calcd for
Ma ter ia ls. The R-DAB ligands11 and the platinum precur-
sor complexes [Pt2Me8(µ-SMe2)2],12 [Pt2Me4(µ-SMe2)2],13 and
14
(DMSO)2PtMes2 were obtained following literature proce-
C
16H30N2Pt: C, 43.13; H, 6.79; N, 6.29. Found: C, 43.29; H,
dures. PtMe2(TMEDA) was obtained according to published
procedures.15 Other reagents were used as commercially
available. All preparations and physical measurements were
carried out in dried solvents under an argon atmosphere, using
Schlenk techniques. Furthermore, the tetramethylplatinum-
(IV) compounds had to be prepared and studied in the absence
of intense light. Solvents for photochemical experiments were
additionally degassed by three subsequent freeze-pump-thaw
cycles.
Gen er a l P r oced u r e for Tetr a m eth ylp la tin u m Com -
p lexes P tMe4(R-DAB). In a typical reaction, 0.4 mmol of the
R-DAB ligand was added to a solution of 0.127 g (0.2 mmol)
of [Pt2Me8(µ-SMe2)2] in 20 mL of diethyl ether. Within a few
minutes the solutions become intensely colored. After stirring
at ambient temperatures overnight in the absence of light the
volume of the solution was reduced to 10 mL. At -30 °C
microcrystalline solids precipitated from this solution (red for
for the complex with t-Bu-DAB, brown for those with p-Tol-
and 2,6-Xyl-DAB, and purple for PtMe4(Cy-DAB)). They were
collected on a microporous frit, washed with hexane, and dried
in vacuo. Yield for PtMe4(t-Bu-DAB): 115 mg (0.27 mmol,
68%). Anal. Calcd for C14H32N2Pt: C, 39.70; H, 7.62; N, 6.62.
Found: C, 39.32; H, 7.75; N, 6.32. PtMe4(Cy-DAB): yield 90
mg (0.19 mmol, 47%). Anal. Calcd for C18H36N2Pt: C, 45.46;
H, 7.63; N, 5.89. Found: C, 245.81; H, 7.75; N, 5.76.
PtMe4(p-Tol-DAB): yield 135 mg (0.276 mmol, 69%). Anal.
Calcd for C20H28N2Pt: C, 48.87; H, 5.74; N, 5.70. Found: C,
48.41; H, 5.67; N, 5.69. PtMe4(2,6-Xyl-DAB): yield 88 mg (0.17
mmol, 29%). Anal. Calcd for C22H32N2Pt: C, 50.85; H, 6.21;
N, 5.39. Found: C, 50.76; H, 6.09; N, 5.14.
6.60; N, 6.02. Yield for PtMe2(p-Tol-DAB): 120 mg (0.26 mmol,
65%). Anal. Calcd for C18H22N2Pt: C, 46.85; H, 4.81; N, 6.07.
Found: C, 46.66; H, 4.69; N, 6.06. Yield for PtMe2(2,6-Xyl-
DAB): 49 mg (0.1 mmol, 25%). Anal. Calcd for C20H26N2Pt:
C, 49.07; H, 5.35; N, 5.72. Found: C, 48.94; H, 5.51; N, 5.35.
With t-Bu-DAB the corresponding complex could be detected
1
by H NMR but could not be isolated.
Gen er a l P r oced u r e for Dim esitylp la tin u m Com p lexes
P tMes2(R-DAB). In typical reactions, 150 mg (0.225 mmol)
of bis(dimethyl sulfoxide)dimesitylplatinum(II) was suspended
together with 0.26 mmol of the corresponding R-DAB ligand
in 40 mL of toluene and heated under reflux for 20 h. The
reaction is complete when the IR-active νSdO vibration of the
precursor complex has vanished.16 The reaction mixture is
then left at 4 °C overnight, and the resulting dark microcrys-
talline precipitate is filtered, washed with diethyl ether, and
dried in vacuo. Yield for PtMes2(Cy-DAB): 92.7 mg (0.142
mmol, 63%) of a purple solid. Anal. Calcd for C32H46N2Pt:
C, 58.79; H, 7.09; N, 4.29. Found: C, 58.97; H, 7.05; N, 4.07.
Yield for PtMes2(p-Tol-DAB): 78.4 mg (0.117 mmol, 53%) of a
dark green solid. Anal. Calcd for C34H38N2Pt: C, 60.97; H,
5.72; N, 4.18. Found: C, 61.79; H, 5.48, N, 4.05.
P h otolysis of P tMe4(t-Bu -DAB). In preliminary experi-
ments acetone, THF, diethyl ether, toluene, benzene, and
pyridine were tested as solvents for the photolysis of PtMe4-
(t-Bu-DAB). A mixture of products resulted in each case, and
acetone was eventually chosen as the solvent with the least
complications.
A dilute solution containing 150 mg (0.36 mmol) of PtMe4-
(t-Bu-DAB) in 60 mL of dried and deaerated acetone was
irradiated in a water-cooled Schlenk vessel using a halogen
lamp (λ > 475 nm; cut-off filter GG 475). Irradiation was
stopped after about 15 min when the sample had turned
completely colorless. (Left unattended, this solution decom-
posed, forming a brown solution and a precipitate of elemental
platinum.) The colorless solution was evaporated to about 5
mL, and 10 mL of n-hexane was added. However, even after
2 days at -30 °C there was no formation of any solid. After
complete removal of the solvent under reduced pressure, a
yellowish viscous oil remained. The complex mixture of
methylplatinum-containing substances could not be separated
using either chromatographic methods or fractionated crystal-
lization. 1H-NMR (CDCl3): δ -0.47(m), 0.05 (s), 0.19 (s), 0.14,
0.30, 0.20, 0.71 (s, 2J (195Pt1H) ) 71.2 Hz), 0.89, 0.90, 0.93, 0.97,
1.04, 1.06, 1.11, 1.16, 1.17, 1.20, 1.23, 1.26, 1.30, 1.33 (s), 1.44
(s), 2.13 (s), 2.28 (s), 2.61 (s), 3.45 (m), 3.56 (m), 3.98 (s), 3.99
(d, J (HH) ) 5.1 Hz), 4.43 (s), 7.38 (d, J (HH) ) 5.4 Hz), 7.43
P tMe4(t-Bu -P yca ). The synthesis proceeded in the same
way as for the R-DAB complexes. Yield: 100 mg of an orange
solid (0.24 mmol, 60%). Anal. Calcd for C14H26N2Pt: C, 40.28;
H, 6.28; N, 6.71. Found: C, 39.85; H, 6.18; N, 6.45.
P tMe4(TMEDA). A solution of 127 mg (0.2 mmol) of Pt2-
Me8(µ-SMe2)2 and 46 mg (0.4 mmol) of N,N,N′,N′-tetrameth-
(9) (a) Polm, L. H.; van Koten, G.; Elsevier, C. J .; Vrieze, K.; van
Saften, B. F. K.; Stam, C. H. J . Organomet. Chem. 1986, 304, 353. (b)
Stahl, T.; Kasack, V.; Kaim, W. J . Chem. Soc., Perkin Trans. 2 1995,
2127.
(10) Krejcik, M.; Danek, M.; Hartl, F. J . Electroanal. Chem. Inter-
facial Electrochem. 1991, 317, 179.
(11) (a) tom Dieck, H.; Renk, I. W. Chem. Ber., 1971, 104, 92. (b)
tom Dieck, H.; Svoboda, M.; Greiser, T. Z. Naturforsch. 1981, 36B,
823.
(12) Scott, J . D.; Puddephatt, R. J . Organometallics 1983, 2, 1643.
(13) Scott, J . D.; Puddephatt, R. J . Organometallics 1986, 5, 1538.
(14) Eaborn, C.; Kundu, K.; Pidcock, A. J . Chem. Soc., Dalton Trans.
1981, 933.
(15) (a) Yang, D.-S.; Bancroft, G. M.; Dignard-Bailey, L.; Puddephatt,
R. J .; Tse, J . S. Inorg. Chem. 1990, 29, 2487. (b) Appleton, F. G.; Hall,
J . R.; Neale, D. W.; Williams, M. A. J . Organomet. Chem. 1984, 276,
C73.
(16) Cotton, F. A.; Francis, R.; Horrocks, W. D., J r. J . Phys. Chem.
1969, 64, 1534.