Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2004
Supplementary information
Experimental details
General considerations
All compounds are air sensitive, and were synthesized and stored under N2 using standard
Schlenk and glovebox techniques. THF, Et2O, toluene and pentane were dried using
Grubbs/Dow columns.1 C6D6 was distilled from Na/benzophenone, freeze/pump/thaw
degassed and stored in a glovebox. Iodine was sublimed prior to use. Other reagents
(NaN(SiMe3)2, LiN(SiMe3)2, methylaluminoxane (10 wt. % in toluene), diethylaluminum
chloride (25 wt. %, 1.8 M, in toluene), dicumyl peroxide, anhydrous CrCl3) were
purchased from Aldrich Chemical Co., stored in a glovebox and used as received. Celite
(Aldrich) was dried overnight in a 110 C oven before being evacuated and stored in a
glovebox. 1H NMR were obtained in C6D6 solution on a Bruker Avance 300
spectrometer. Elemental analyses were performed by Guelph Chemical Laboratories
Ltd., Guelph, Ontario, Canada (Report No. 45473). Cr[N(SiMe3)2]2(THF)22 1 was
prepared from CrCl2(THF)2 and NaN(SiMe3)2 in THF, and was recrystallized from Et2O
as large light purple needles.3 Cr[N(SiMe3)2]34 2 was prepared from anhydrous CrCl3 and
LiN(SiMe3)2 in Et2O, and was recrystallized from pentane as large bright green needles.5
Synthesis of Cr[N(SiMe3)2] 2I2 3
To a blue solution of Cr[N(SiMe3)2]2(THF)2 (759 mg, 1.47 mmol) in Et2O was added
solid I2 (381 mg, 1.50 mmol). The resulting dark red-brown solution was stirred
overnight, after which time the solvent was removed in vacuo. The residue was extracted
with pentane and filtered through Celite supported on a sintered glass frit. The filtrate
was reduced in volume to ~15 mL and filtered through Celite a second time.
Recrystallization at –30 ºC for two days provided thick black plates of 3 (675 mg, 1.08
mmol). An additional 65 mg of 3 was obtained by concentrating the supernatant and
cooling to –30 ºC for several days (total yield 740 mg, 1.18 mmol, 80% yield).
Anal. C12H36CrI2N2Si4 calc C 23.00% H 5.79% N 4.47% found C 22.72% H 5.96% N
4.31%. M.p. 115–120 ºC. IR (KBr): 1403 (m), 1266 (m), 1248 (s), 843 (s), 781 (s), 692
(m), 663 (m), 639 (m).
1
H NMR (C6D6, 300 K, 300.1 MHz)  6.38 (s, ½ = 100 Hz, 4  SiMe3)
Attempted reaction of 2 and I2
To a solution of Cr[N(SiMe3)2]3 (150 mg, 0.285 mmol) in Et2O was added solid I2 (37
mg, 0.146 mmol). The resulting solution was stirred for eight days, after which time the
solvent was removed in vacuo. The residue was extracted C6D6, and a 1H NMR spectra
was obtained. The only broad signal observed was at 26 ppm, corresponding to
1
2
3
4
5
A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen and F. J. Timmers, Organometallics,
1996, 15, 1518-1520.
D. C. Bradley, M. B. Hursthouse, C. W. Newing and A. J. Welch, J. Chem. Soc., Chem. Commun.,
1972, 567–568.
A. Kayal and S. Lee. Inorg. Chem., 2002, 41, 321–330.
H. Bürger and U. Wannagat, Monatsh. Chem., 1964, 95, 1099–1102.
D. C. Bradley and R. G. Copperthwaite, Inorg. Synth., 1978, 18, 112–120.
Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2004
unreacted 2. The anticipated signal at 6.4 ppm due to 3 was not observed.
Synthesis of Cr[N(SiMe3)2](OCMe2Ph)2 4
Pentane (~6 mL) was added a mixture of Cr[N(SiMe3)2]2(THF)2 (202 mg, 0.391 mmol)
and dicumyl peroxide (107 mg, 0.396 mmol) at room temperature. The resulting solution
slowly turned from purple to green. After stirring overnight, the solvent was removed in
vacuo. The residue was extracted in a minimum amount of pentane and filtered through
Celite. Cooling the green solution at –30 C produced blue rod-shaped crystals of 4 (47
mg, 0.097 mmol, 25% yield).
Anal. C24H40CrNO2Si2 calc C 59.71% H 8.35% N 2.90% found C 59.40% H 8.45% N
2.54%. M.p. 63–65 ºC. IR (KBr): 1493 (m), 1449 (m), 1374 (w), 1356 (m), 1250 (s),
1137 (s), 1099 (m), 1075 (m), 1029 (m), 957 (s), 854 (s), 766 (m), 731 (w), 705 (m), 674
(m), 649 (m), 528 (w).
1
H NMR (C6D6, 300 K, 300.1 MHz)  53.6 (s, ½ = 1360 Hz, 18 H, 2  SiMe3), 21.2 (s,
½ = 1090 Hz, 12 H, 2  CMe2), 13.6–6.1 (broad overlapping peaks, tentatively
assigned to 2  CPh protons)
Polymerisation studies:
Black crystals of Cr[N(SiMe3)2]2I2 (11.0 mg, 0.0176 mmol) were weighed in a glovebox
in a small vial, and were quantitatively transferred to a 100 mL Schlenk flask with a
small magnetic stirbar using 40 mL of toluene. Diethylaluminum chloride (0.30 mL, 1.8
M toluene solution, 0.54 mmol) was added to the red solution from a 100 mL Sure-Seal
bottle via a 1 mL syringe, resulting in a colour change through orange to yellow. The
Schlenk was sealed, removed from the glovebox, and attached to a dual manifold
vacuum-ethylene Schlenk line. The headspace above the reaction mixture was evacuated
and replaced with ethylene. The contents were maintained under ethylene (1 bar) and
magnetically stirred for 60 min, after which time the reaction was quenched by addition
of 10 mL of 1.0 M HCl in methanol. After settling, the white solid formed was isolated
on a sintered glass crucible and washed with 5 × 10 ml of methanol and then 5 × 10 mL
of water. The solid was suction dried on the crucible before being transferred to a 20 mL
scintillation vial. The solid was dried in a 50 C vacuum oven overnight before being
weighed (0.7544 g).
Other polymerisation runs listed in Table 1 were performed in an analogous manner.