766 Organometallics, Vol. 21, No. 4, 2002
Notes
IrN2P (mol wt 744.2): C, 41.96; H, 4.20; N, 3.77. Found: C,
42.21; H, 4.28; N, 3.81. 1H NMR (CD3CN): δ 1.18 (s, 15H,
CH3(C5Me5)), 2.34 (s, 6H, CH3(R)), 7.36-7.49 (m, 6H, CH(R)),
7.70 (dd, 3J ) 7.5 Hz, 2H, CH(R)), 8.96 (s, 2H, CH(imine)) ppm.
13C NMR (CD3CN): δ 8.44 (CH3(C5Me5)), 18.21 (CH3(R)), 95.39
(CCH3(C5Me5)), 123.07, 128.04, 130.45, 132.30 (CH(R)), 148.50
(CN(R)), 170.57 (CH(imine)) ppm. UV/vis (CH3CN): λmax (ꢀ)
590 (460), 408 (sh) (4260), 360 (4950), 292 (5030) nm.
pattern of reactivity was obtained by making just minor
modifications, working in a protic solvent and using
saturated cyclohexyl substituents at the 1,4-positions
of the 1,4-diaza-1,3-butadiene ligand.
Not only have the noninnocent 1,4-diaza-1,3-butadi-
ene ligands been used in complexes [(R-diimine)(η5-C5-
Me5)ClM]+ (M ) Rh, Ir), which are related to hydride
transfer catalytic schemes2,5 but they are also increas-
ingly popular as components of efficient polymerization
catalysts.6 Their reactivity as coordinated ligands of
catalytic species is therefore of some relevance.
In the following we report results from the reactions
of compounds [(RNdCHCHdNR)(η5-C5Me5)ClIr](PF6)
(1) with hydride reagents. Since these results are
compared with observations made previously for sys-
tems with R ) 2,6-dialkylphenyl,4 we chose as starting
compounds complex 1a , with the nonaromatic and
moderately bulky substituent R ) cyclohexyl, and the
structurally characterized complex 1b, with the 2-alkyl-
phenyl substituent R ) 2-methylphenyl ) o-tolyl.
[(RNCHdCHNR)(η5-C5Me5)Ir ] (R ) Cycloh exyl; 2a ). A
solution of 73 mg (0.10 mmol) 1a in 20 mL of cold (-15 °C)
acetone was treated with 136 mg (0.53 mmol) Bu4NBH4. After
a rapid color change from red to orange, the volume was
reduced to about 5 mL, and 3 mL of degassed H2O was added.
The air-sensitive orange precipitate was collected, washed with
water, and dried under vacuum. Yield: 36 mg (65%). Anal.
Calcd for C24H39IrN2 (mol wt 547.8): C, 52.62; H, 7.18; N, 5.11.
1
Found: C, 53.26; H, 7.18; N, 5.25. H NMR (C6D6): δ 1.00-
2.20 (m, 20H, CH2(R)), 1.86 (s, 15H, CH3(C5Me5)), 4.34 (m, 2H,
CHN(R)), 7.33. (s, 2H, CH(imine)) ppm. 13C NMR (C6D6): δ
10.10 (CH3(C5Me5)), 26.40, 27.10, 35.50, (CH2(R)), 72.20 (CHN-
(R)), 82.50 (CCH3(C5Me5)), 129.00 (CH(imine)) ppm. UV/vis
(CH3CN): λmax (ꢀ) 424 (15 400), 234 (sh) nm.
[(RNCHdCHNR)(η5-C5Me5)Ir ] (R ) o-Tolyl; 2b). A solu-
tion of 53.5 mg (0.072 mmol) of 1b in 10 mL of cold (-15 °C)
acetonitrile was treated with 37 mg (0.144 mmol) of Bu4NBH4.
After 1 h of stirring the solvent was removed from the dark
yellow solution and the residue extracted with n-hexane.
Removal of n-hexane produced 14 mg (35%) of a very sensitive
yellow-orange solid; an elemental analysis could not be ob-
Exp er im en ta l Section
In str u m en ta tion . 1H NMR and 13C NMR spectra were
taken on a Bruker AC 250 spectrometer, and infrared spectra
were obtained using a Perkin-Elmer PE 684 spectrometer.
Absorption spectra were recorded on a Bruins Instruments
Omega 10 spectrophotometer. Cyclic voltammetry was carried
out at a 100 mV/s standard scan rate in CH3CN/0.1 M Bu4-
NPF6 using a three-electrode configuration (glassy-carbon
working electrode, Pt counter electrode, Ag/AgCl reference) and
a PAR 273 potentiostat and function generator. The ferrocene/
ferrocenium couple served as internal reference.
[(RNdCHCHdNR)(η5-C5Me5)ClIr ](P F 6) (R ) Cycloh ex-
yl; 1a ). A suspension of 254 mg (0.318 mmol) of [Ir(C5Me5)-
Cl2]2 was obtained in 30 mL of methanol with the help of an
ultrasonic bath. Adding 175 mg (0.80 mmol) of 1,4-dicyclo-
hexyl-1,4-diaza-1,3-butadiene and stirring for 3 h at room
temperature produced a clear red solution which was reduced
to about 10 mL volume. An excess of a methanolic solution of
Bu4NPF6 was added to yield a red precipitate, which was
collected, washed with methanol and diethyl ether, and dried
1
tained. Reaction of 1b with Na[BH3(CN)] also yielded 2b. H
NMR (C6D6): δ 1.27 (s, 15H, CH3(C5Me5)), 2.05 (s, 6H, CH3-
3
5
(R)), 7.02 (dt, J ) 7.4 Hz, J ) 1.5 Hz, 2H, H(R)), 7.1, 7.2 (d,
3J ) 7.7 Hz, 4H, H(R)), 7.12 (s, 2H, H(imine)), 7.35 (d, 3J )
7.4 Hz, 2H, H(R)) ppm. 13C NMR (C6D6): δ 8.90 (CH3(C5Me5)),
16.50 (CH3(R)), 83.00 (CCH3(C5Me5)), 125.20, 125.50, 125.70,
129.80, 132.60 (CH(R)), 132.80 (CN(R)), 157.40 (CHN(imine))
ppm. UV/vis (toluene): λmax (ꢀ) 430, 285 (sh), 230 (sh) nm.
7
[(RHNCH 2CHdNR)(η5-C5Me5)HIr ](P F 6) (R ) Cyclo-
h exyl; 3). A cooled solution (-15 °C) of 54.5 mg (0.075 mmol)
of 1a in a mixture of 10 mL of ethanol and 2.5 mL of water
was treated with 23.5 mg (0.375 mmol) of Na[BH3(CN)].
Within 4 h the color changed from red to yellow; then the
volume was slowly reduced until a light yellow precipitate
began to form. This was collected, washed with degassed H2O,
and dried under vacuum. Yield: 28 mg (55%). Anal. Calcd for
under vacuum. Yield: 393 mg (85%). Anal. Calcd for C24H39
-
ClF6IrN2P (mol wt 726.2): C, 39.58; H, 5.40; N, 3.85. Found:
C, 39.08; H, 5.53; N, 3.85. 1H NMR (CD3CN): δ 1.17-2.45 (m,
20H, CH(R)), 1.70 (s, 15H, CH(C5Me5)), 4.16 (m, 2H, NCH-
(R)), 8.75 (s, 2H, CH(imine)) ppm. 13C NMR (CD3CN): δ 9.2
(CH3(C5Me5)), 25.9, 26.5, 34.1, 35.4, 49.9, 72.9 (CH(R)), 93.3
(CCH3(C5Me5)), 166.0 (CH(imine)) ppm. UV/vis (CH3CN): λmax
(ꢀ) 515 (290), 388 (3920), 277 (5650) nm.
[(R NdCH CHdNR )(η5-C5Me5)ClIr ](P F 6) (R ) o-Tolyl;
1b). A suspension of 208 mg (0.26 mmol) of [Ir(C5Me5)Cl2]2
was generated in 30 mL of methanol in an ultrasonic bath.
Addition of 154 mg (0.65 mmol) of 1,4-bis(o-tolyl)-1,4-diaza-
1,3-butadiene and stirring for 3 h at room temperature
produced a clear green solution which was reduced to about a
10 mL volume. An excess of a methanolic solution of Bu4NPF6
was added to yield a green precipitate, which was collected,
washed with methanol and diethyl ether, and dried under
vacuum. Yieldd: 346 mg (90%). Anal. Calcd for C26H31ClF6-
C
24H42F6IrN2P (mol wt 695.8): C, 41.43; H, 6.08; N, 4.03.
Found: C, 42.44; H, 6.04; N, 4.32. 1H NMR (CD3CN): δ -10.80
(s, 1H, Ir-H), 0.99-3.42 (m, 20H, CH2(R)), 1.80 (s, 15H,
CH3(C5Me5)), 3.61 (d, 2H, CHN(R)), 5.39 (s, 1H, NH(amine)),
7.81 (s, 1H, NH(imine)) ppm. 13C NMR (CD3CN): δ 10.22
(CH3(C5Me5)), 25.40, 25.70, 25.90, 26.30, 26.40, 26.50, 30.20,
31.80, 33.00, 35.30 (CH2(R)), 60.38, 66.50, (CHN(R)), 72.00
(CH2(amine)), 88.80 (CCH3(C5Me5)), 168.30 (CH(imine)) ppm.
UV/vis (CH3CN): λmax (ꢀ) 335 (sh) nm. IR (KBr): ν 2069 cm-1
(Ir-H).
[(RHNCH2CH2NHR)(η5-C5Me5)HIr ][(BH3(CN)] (R ) Cy-
cloh exyl; 4). Standing for 2 days and slow cooling of a solution
as described above for 3 gave a small amount (ca. 3 mg) of
yellowish crystals which were suitable for X-ray diffraction.
The presence of an Ir-H bond was confirmed by IR spectros-
(5) (a) Ko¨lle, U.; Gra¨tzel, M. Angew. Chem. 1987, 99, 572; Angew.
Chem., Int. Ed. Engl. 1987, 26, 568. (b) Ko¨lle, U.; Kang, B.-S.; Infelta,
P.; Compte, P.; Gra¨tzel, M. Chem. Ber. 1989, 122, 1869. (c) Reinhardt,
R.; Kaim, W. Z. Anorg. Allg. Chem. 1993, 619, 1998.
(6) (a) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am. Chem.
Soc. 1995, 117, 6414. (b) J ohnson, L. K.; Mecking, S.; Brookhart, M.
J . Am. Chem. Soc. 1996, 118, 267. (c) Ittel, S. D.; J ohnason, L. K.;
Brookhart, M. Chem. Rev. 2000, 100, 1169.
copy in KBr: ν 2059 cm-1
.
Cr ysta llogr a p h y. Single crystals of 1b were obtained
through slow cooling of a solution in CH3OH/CH2Cl2 (2/1 v/v);
single crystals of compound 4 were obtained from the reaction
solution. Crystallographic and refinement information is sum-
marized in Table 1; a Siemens P4 diffractometer was used for
data collection. The structures were solved using the programs
(7) White, C.; Thompson, S. J .; Maitlis, M. J . Chem. Soc., Dalton
Trans. 1977, 1654.