Reaction of a (Salen)ruthenium(VI) nitrido complex with isocyanide

Article abstract of DOI:10.1021/ic802338f

The treatment of [Ru^VI(N)(L)(MeOH)]PF₆ (1) (L=N,N′-bis(salicylidene)-o-cyclohexyldiamine dianion) with 2 equiv of RNC (R ) (a) tBu, (b) Cy) in CH₂Cl₂ affords a mixture of blue cis-β-[Ru^III(NCNR)(L)(CN

Full text of DOI:10.1021/ic802338f

Inorg. Chem. 2009, 48, 3080-3086
Reaction of a (Salen)ruthenium(VI) Nitrido Complex with Isocyanide
Hoi-Ki Kwong,† Wai-Lun Man,† Jing Xiang,† Wing-Tak Wong,‡ and Tai-Chu Lau*,†
Department of Biology and Chemistry, City UniVersity of Hong Kong, Tat Chee AVenue, Kowloon
Tong, Hong Kong, China, and Department of Chemistry, UniVersity of Hong Kong, Pokfulam
Road, Hong Kong, China
Received December 7, 2008
The treatment of [RuVI(N)(L)(MeOH)]PF6 (1) (L ) N,N′-bis(salicylidene)-o-cyclohexyldiamine dianion) with 2 equiv
t
of RNC (R ) (a) Bu, (b) Cy) in CH2Cl2 affords a mixture of blue cis-ꢀ-[RuIII(NCNR)(L)(CNR)] (2) and green
trans-[RuIII(L)(CNR)2]PF6 (3) products. The reduction of 3 with a stoichiometric amount of Cp2Co in CH3CN gives
red trans-[RuII(L)(CNR)2] (4). Refluxing 4 with 3 equiv of RNC in methanol in the presence of 5 equiv of NH4PF6
affords a yellow complex, mer-[RuII(η3-HL)(CNR)3](PF6) (5), in which the ligand is in an η3-coordination mode.
These complexes are characterized by IR, UV-vis, ESI-MS, CV, magnetic measurements, and CHN elemental
analysis. The structures of 2a, 3a, 4a, 4b, and 5a have been determined by X-ray crystallography.
Introduction
N-oxides,14 elemental sulfur and selenium,15,16 and thiols17,18
to produce the corresponding osmium species containing
N-P, N-N, N-C, or N-E (E ) O, S, Se) bonds.
We have been interested in exploring the new reactivity
of nitrido complexes of osmium19-22 and ruthenium23,24
bearing salen or 8-quinolinato ligands. For example, we
recently reported the synthesis and reactivity of a highly
electrophilic, cationic (salen)ruthenium(VI) nitrido com-
Osmium(VI) nitrido complexes containing nitrogen-based
ligands such as cis- or trans-[OsVI(N)(tpy)Cl2]+ (tpy ) 2,2′:
6′,2′′-terpyridine), [OsVI(N)(tpm)Cl2]+ (tpm ) tris(1-pyra-
zolyl)methane), [OsVI(N)(Tp)Cl2] (Tp ) hydrotris(1-pyra-
zolyl)borate), and [OsVI(N)(bpy)Cl3] (bpy ) 2,2′-bipyridine)
have been shown to exhibit novel electrophilic properties.
They react with a variety of nucleophiles such as phos-
phines,1-3 amines,4,5 azides,6 cyanide,7 alkenes,8-10 arylbo-
ranes and Grignard reagents,11,12 nitric oxide,13 amine
(12) Crevier, T. J.; Bennett, B. K.; Soper, J. D.; Bowman, J. A.; Dehestani,
A.; Hrovat, D. A.; Lovell, S.; Kaminsky, W.; Mayer, J. M. J. Am.
Chem. Soc. 2001, 123, 1059–1071.
* To whom correspondence should be addressed. E-mail: bhtclau@
cityu.edu.hk.
(13) McCarthy, M. R.; Crevier, T. J.; Bennett, B.; Dehestani, A.; Mayer,
J. M. J. Am. Chem. Soc. 2000, 122, 12391–12392.
(14) William, D. S.; Meyer, T. J.; White, P. S. J. Am. Chem. Soc. 1995,
117, 823–824.
†
City University of Hong Kong.
‡
University of Hong Kong.
(1) Demadis, K. D.; Bakir, M.; Klesczewski, B. G.; William, D. S.; Meyer,
T. J.; White, P. S. Inorg. Chim. Acta 1998, 270, 511.
(2) Bakir, M.; Dovletoglou, A.; White, P. S.; Meyer, T. J. Inorg. Chem.
1991, 30, 2835–2836.
(3) Dehestani, A.; Kaminsky, W.; Mayer, J. M. Inorg. Chem. 2003, 42,
605–611.
(15) Demadis, K. D.; El-Samanody, E. S.; Meyer, T. J.; White, P. S. Inorg.
Chem. 1998, 37, 838–839.
(16) Crevier, T. J.; Lovell, S.; Mayer, J. M. J. Am. Chem. Soc. 1998, 120,
6607–6608.
(17) Huynh, M. H. V.; White, P. S.; Meyer, T. J. Angew. Chem., Int. Ed.
2000, 39, 4101–4104.
(4) Huynh, M. H. V.; El-Samanody, E. S.; Demadis, K. D.; White, P. S.;
Meyer, T. J. J. Am. Chem. Soc. 1999, 121, 1403–1404.
(5) Huynh, M. H. V.; El-Samanody, E. S.; Demadis, K. D.; White, P. S.;
Meyer, T. J. Inorg. Chem. 2000, 39, 3075–3085.
(6) Huynh, M. H. V.; Baker, R. T.; Jameson, D. L.; Labouriau, A.; Meyer,
T. J. J. Am. Chem. Soc. 2002, 124, 4580–4582.
(18) Huynh, M. H. V.; Morris, D. E.; White, P. S.; Meyer, T. J. Angew.
Chem., Int. Ed. 2002, 41, 2330–2333.
(19) Wong, T. W.; Lau, T. C.; Wong, W. T. Inorg. Chem. 1999, 38, 6181–
6186.
(20) Chiu, S. M.; Wong, T. W.; Man, W. L.; Wong, W. T.; Peng, S. M.;
Lau, T. C. J. Am. Chem. Soc. 2001, 123, 12720–12721.
(21) Lai, S. W.; Lau, T. C.; Fung, W. K. M.; Zhu, N.; Che, C. M.
Organometallics 2003, 22, 315–320.
(7) Huynh, M. H. V.; White, P. S.; Carter, C. A.; Meyer, T. J. Angew.
Chem., Int. Ed. 2001, 40, 3037–3039.
(8) Brown, S. N. J. Am. Chem. Soc. 1999, 121, 9752–9753.
(9) Brown, S. N. Inorg. Chem. 2000, 39, 378–381.
(10) Maestri, A. G.; Cherry, K. S.; Toboni, J. J.; Brown, S. N. J. Am. Chem.
Soc. 2001, 123, 7459–7460.
(11) Crevier, T. J.; Mayer, J. M. J. Am. Chem. Soc. 1998, 120, 5595–
5596.
(22) Leung, C. F.; Wong, T. W.; Lau, T. C.; Wong, W. T. Eur. J. Inorg.
Chem. 2005, 773–778.
(23) Man, W. L.; Tang, T. M.; Wong, T. W.; Lau, T. C.; Peng, S. M.;
Wong, W. T. J. Am. Chem. Soc. 2004, 126, 478–479.
(24) Man, W. L.; Lam, W. W. Y.; Yiu, S. M.; Lau, T. C.; Peng, S. M.
J. Am. Chem. Soc. 2004, 126, 15336–15337.
3080 Inorganic Chemistry, Vol. 48, No. 7, 2009
10.1021/ic802338f CCC: $40.75  2009 American Chemical Society
Published on Web 02/25/2009

Reaction of a (Salen)ruthenium(VI) Nitrido Complex
plex.23 This species undergoes direct nitrogen atom transfer
to alkenes at room temperature to produce (salen)ruthenium
aziridine complexes.24
We report herein the reaction of a (salen)ruthenium(VI)
nitrido complex, [RuVI(N)(L)(MeOH)]PF6 (1; L ) N,N′-
bis(salicylidene)-o-cyclohexyldiamine dianion) with isocya-
nides to produce carbodiimido and isocyanide complexes of
ruthenium(III) and -(II).
H, 5.34; N, 7.86. UV-vis (CH3CN), λmax [nm] (ε [mol-1 dm3
cm-1]): 739 (4170), 482 (1190), 328 (14700), 269 (59300), 237sh
(45800), 216 (37700). ESI-MS: m/z 588 (M+). µeff ) 1.94 µB.
Conductivity in CH3CN: Λ ) 123 Ω-1 cm2 mol-1
.
cis-ꢀ-[RuIII(NCNCy)(L)(CNCy)] ·3H2O (2b) and trans-[RuIII-
(L)(CNCy)2]PF6 (3b). These two solids were prepared by a
procedure similar to that for 2a and 3a using cyclohexyl isocyanide.
For 2b, yield: (29%). IR (KBr, cm-1): ν(O-H) 3419; ν(Ct N) 2163,
2102. Anal. calcd for C34H42N5O2Ru·3H2O: C, 57.69; H, 6.83; N,
9.89. Found: C, 57.58; H, 6.72; N, 10.01. UV-vis (CH3CN), λmax
[nm] (ε [mol-1 dm3 cm-1]): 638 (3410), 525sh (2920), 377 (6520),
Experimental Section
336 (7550), 230 (38900). ESI-MS: m/z 655 ([M + H]+). µeff
)
Materials. [RuVI(N)(L)(MeOH)](PF6) (1) was prepared by a
literature procedure.23 The Schiff base ligand, H2L (L ) N,N′-
bis(salicylidene)-o-cyclohexylenediamine dianion) was synthesized
by condensation of salicylaldehyde with trans-1,2-cyclohexyl-
diamine in refluxing ethanol. tert-Butyl isocyanide (tBuNC), cy-
clohexyl isocyanide (CyNC), and cobaltocene were purchased from
Aldrich and used as received. nBu4NPF6 (Aldrich) was recrystallized
three times from boiling ethanol and dried in vacuo at 120 °C for
one day. Acetonitrile and dichloromethane used for electrochemistry
were distilled over calcium hydride. All other chemicals were of
reagent grade and used without further purification. All manipula-
tions were performed without precaution to exclude air or moisture
unless otherwise stated.
2.02 µB. For 3b, yield: (30%). IR (KBr, cm-1): ν(Ct N) 2194;
ν(P-F) 840. Anal. calcd for C34H42N4O2PF6Ru: C, 52.04; H, 5.39;
N, 7.14. Found: C, 51.85; H, 5.45; N, 7.20. UV-vis (CH3CN),
λmax [nm] (ε [mol-1 dm3 cm-1]): 748 (4280), 482 (1230), 329
(14200), 234sh (38300), 215 (36700). ESI-MS: m/z 640 (M+). µeff
) 1.98 µB. Conductivity in CH3CN: Λ ) 125 Ω-1 cm2 mol-1
.
trans-[RuII(L)(CNtBu)2] (4a). Solid cobaltocene (27 mg, 0.14
mmol) was added to a green solution of 3a (100 mg, 0.14 mmol)
in acetonitrile (3 mL) under argon, and the solution was stirred for
30 min at room temperature. The resulting deep red solid was
filtered, washed with acetonitrile, and then air-dried. Single crystals
suitable for X-ray crystallography were obtained by the slow
diffusion of diethyl ether into a CH2Cl2 solution of 4a. Yield: (90%).
1H NMR (300 MHz, CD2Cl2): δ 8.02 (s, 2H), 7.08-7.12 (t, 4H),
6.78-6.80 (d, 2H), 6.28-6.31 (t, 2H), 2.94-2.96 (d, 2H),
2.70-2.73 (d, 2H), 1.99-2.01 (d, 2H), 1.37-1.50 (m, 4H), 1.24
(s, 18H). IR (KBr, cm-1): ν(Ct N) 2099. Anal. calcd for
C30H38N4O2Ru: C, 61.31; H, 6.52; N, 9.53. Found: C, 61.09; H,
6.31; N, 9.49. UV-vis (CH3CN), λmax [nm] (ε [mol-1dm3cm-1]):
451 (3110), 376 (13200), 336 (13700), 245sh (43800), 231 (50000).
ESI-MS: m/z 588 (M+).
Physical Measurements. IR spectra were obtained as KBr discs
1
using a Nicolet 360 FT-IR spectrophotometer. H NMR spectra
were recorded on a Varian (300 MHz) FT NMR spectrometer. The
chemical shifts (δ) were reported with reference to tetramethylsilane
(TMS). UV-vis spectra were recorded with a Perkin-Elmer Lamda
19 spectrophotometer in 1 cm quartz cuvettes. Elemental analysis
was performed using an Elementar Vario EL Analyzer. Magnetic
measurements were performed at room temperature using a
Sherwood magnetic balance (Mark II). Conductivity measurements
were done with a Cole-Parmer 01481-61 conductivity meter.
Electrospray ionization mass spectrometry (ESI-MS) was performed
with a PE-SCIEX API 300 triple quadruple mass spectrometer.
Cyclic voltammetry was performed with a PAR model 273
potentiostat using a glassy carbon working electrode, a Ag/AgNO3
(0.1 M in CH3CN) reference electrode, and a Pt wire counterelec-
trode with ferrocene (FeCp2) as the internal standard.
trans-[RuII(L)(CNCy)2] (4b). This red solid was prepared by a
procedure similar to that for 4a using 3b. Single crystals suitable
for X-ray crystallography were obtained by the slow diffusion of
1
diethyl ether into a CHCl3 solution of 4b. Yield: (88%). H NMR
(300 MHz, CD2Cl2): δ 8.02 (s, 2H), 7.07-7.10 (t, 4H), 6.78-6.80
(d, 2H), 6.33-6.36 (t, 2H), 3.80-3.82 (m, 2H), 2.99-3.02 (d, 2H),
2.71-2.74 (d, 2H), 1.99-2.01 (m, 4H), 1.18-1.64 (m, 22H). IR
(KBr, cm-1): ν(Ct N) 2108. Anal. calcd for C34H42N4O2Ru: C,
63.83; H, 6.62; N, 8.76. Found: C, 63.61; H, 6.63; N, 8.66. UV-vis
(CH3CN), λmax [nm] (ε [mol-1 dm3 cm-1]): 454 (2830), 377 (11900),
338 (12500), 246sh (38000), 230 (44300). ESI-MS: m/z 640 (M+).
mer-[RuII(η3-HL)(CNtBu)3]PF6 (5a). tBuNC (47 mg, 0.56
mmol) and NH4PF6 (140 mg, 0.86 mmol) were added to a solution
of 4a (110 mg, 0.17 mmol) in CH3OH (10 mL), and the resulting
solution was refluxed for 9 h under argon. The greenish yellow
solution was filtered and evaporated to dryness, and the residue
was redissolved in a minimum amount of CH2Cl2 and loaded onto
a silica gel column. The column was first eluted with CH2Cl2/
acetone (20:1, v/v) to remove a trace amount of green species. The
yellow band eluted with acetone was evaporated to dryness and
then recrystallized from CH3CN/Et2O. Single crystals suitable for
X-ray crystallography were obtained by the slow diffusion of diethyl
Preparation. cis-ꢀ-[RuIII(NCNtBu)(L)(CNtBu)] ·3H2O (2a)
and trans-[RuIII(L)(CNtBu)2]PF6 (3a). tBuNC (27 mg, 0.33 mmol)
was added to an orange solution of 1 (100 mg, 0.16 mmol) in
CH2Cl2 (50 mL), and the mixture was stirred for 24 h at room
temperature. The green solution was evaporated to dryness; the
residue was dissolved in a minimum amount of acetone and then
loaded onto a silica gel column. The column was eluted with
acetone to give a green band and then a blue band. Complex 2a
was obtained from the blue band after evaporation and recrystal-
lization from acetone/n-pentane. Yield: (30%). Single crystals
suitable for X-ray crystallography were obtained by the slow
diffusion of n-pentane into an acetone solution of 2a. IR (KBr,
cm-1): ν(O-H) 3424; ν(Ct N) 2156, 2103. Anal. calcd for
C30H38N5O2Ru ·3H2O: C, 54.95; H, 6.76; N, 10.68. Found: C, 55.05;
H, 6.51; N, 10.83. UV-vis (CH3CN), λmax [nm] (ε [mol-1 dm3
cm-1]): 648 (6200), 526 (5100), 378 (8180), 337 (9500), 260
(57300). ESI-MS: m/z 603 ([M + H]+). µeff ) 2.07 µB. Complex
3a was obtained from the green band after evaporation and
recrystallization from acetone/Et2O. Yield: (30%). Single crystals
suitable for X-ray crystallography were obtained by the slow
diffusion of diethyl ether into an acetone solution of the compound.
IR (KBr, cm-1): ν(Ct N) 2186; ν(P-F) 845. Anal. calcd for
C30H38N4O2PF6Ru: C, 49.18; H, 5.23; N, 7.65. Found: C, 49.34;
1
ether into a CH3CN solution of 5a. Yield: (58%). H NMR (300
MHz, CD2Cl2): δ 8.76 (s, 1H), 8.30 (s, 1H), 7.95-7.97 (d, 1H +
s, 1H [OH]), 7.40-7.44 (t, 1H), 7.23-7.26 (d, 1H), 7.09-7.13 (t,
1H), 7.00-7.05 (m, 2H), 6.67-6.70 (d, 1H), 6.52-6.55 (t, 1H),
3.32-3.34 (m, 2H), 2.87-2.90 (d, 1H), 2.56-2.59 (d, 1H),
1.98-2.14 (m, 2H), 1.60-1.74 (m, 2H), 1.44 (s, 9H), 1.38-1.42
(m, 2H), 1.31 (s, 9H), 1.20 (s, 9H). IR (KBr, cm-1): ν(O-H) 3486;
ν(Ct N) 2191, 2147; ν(P-F) 841. Anal. calcd for
Inorganic Chemistry, Vol. 48, No. 7, 2009 3081

Kwong et al.
Table 1. Crystal Data and Structure Refinement Details for Complexes 2a·3H2O, 3a, 4a, 4b·CHCl3, and 5a·CH3CN
2a·3H2O
3a
4a
4b ·CHCl3
5a·CH3CN
formula
Mr
C30H44N5O5Ru
655.78
C30H38N4O2RuPF6
732.69
C30H38N4O2Ru
587.71
C35H43N4O2RuCl3
759.15
C37H51N6O2RuPF6
857.88
cryst dimensions/mm
cryst syst
space group
0.41 × 0.25 × 0.05
orthorhombic
Pbca (No. 61)
21.857(10)
13.872(7)
23.060(11)
90
6992(6)
8
1.246
2744
0.18 × 0.21 × 0.46
monoclinic
P21/c (No. 14)
15.966(2)
14.595(2)
14.252(2)
90
3320.9(8)
4
1.465
0.04 × 0.05 × 0.45
monoclinic
C2/c (No. 15)
17.100(2)
13.6041(18)
14.7986(19)
123.149(2)
2882.4(6)
4
0.24 × 0.23 × 0.08
monoclinic
C2/c (No. 15)
34.738(5)
11.2485(16)
24.606(4)
132.242(1)
7118.0(18)
8
0.20 × 0.42 × 0.45
monoclinic
P21/n (No. 14)
14.031(7)
24.925(12)
14.199(7)
116.539(7)
4442(4)
a/Å
b/Å
c/Å
ꢀ
V/ Å3
Z
4
F
calcd, mg m-3
F(000)
1.354
1224
1.417
3136
1.283
1776
1500
no. of reflns. collected
7932 (40866)
7721 (20184)
5769
3299 (9730)
2753
8116 (23684)
6392
9793 (20363)
6981
no. of obsd reflns. (I > 2σ(I)) 3335a
final R indices, I > 2σ(I) R
GOF
no. of parameters
R ) 0.0625,awR ) 0.0706a R ) 0.042, wR ) 0.049 R ) 0.0389, wR ) 0.0751 R ) 0.058, wR ) 0.170 R ) 0.079, wR ) 0.326
1.094
388
1.087
435
1.015
169
1.046
399
1.308
499
a I > 1.5σ(I).
Scheme 1. Synthesis of Compounds 2-5
C35H48N5O2PF6Ru: C, 51.47; H, 5.92; N, 8.57. Found: C, 51.63;
H, 5.69; N, 8.72. UV-vis (CH3CN), λmax [nm] (ε [mol-1 dm3
cm-1]): 422sh (2610), 303 (12200), 236sh (34000), 215 (41500)
ESI-MS: m/z 672 (M+).
or an approximation by interimage scaling were applied. The
structures were resolved by direct methods25 and expanded using
Fourier techniques.26 All calculations were performed using the
Crystal Structure or TeXsan crystallographic software package from
Molecular Structure Corporation.27
mer-[RuII(η3-HL)(CNCy)3]PF6 (5b). This yellow solid was
prepared by a similar procedure to that for 5a using 4b and
cyclohexyl isocyanide. Yield: (60%). 1H NMR (300 MHz, CD2Cl2):
δ 8.75 (s, 1H), 8.28 (s, 1H), 7.66-7.68 (d, 1H), 7.37-7.41 (t, 1H),
7.21-7.23 (d, 1H), 7.10-7.12 (t, 1H + s, 1H [OH]), 7.01-7.08
(t, 2H) 6.64-6.66 (d, 1H), 6.47-6.51 (t, 1H), 3.89-3.94 (m, 2H),
3.36-3.39 (m, 3H), 2.88-2.91 (d, 1H), 2.56-2.59 (d, 1H),
2.02-2.14 (m, 2H), 1.83-1.95 (m, 2H), 1.28-1.69 (m, 32H). IR
(KBr, cm-1): ν(O-H) 3496; ν(Ct N) 2199, 2156; ν(P-F) 841.
Anal. calcd for C41H54N5O2PF6Ru: C, 55.03; H, 6.08; N, 7.83.
Found: C, 54.85; H, 5.94; N, 7.92. UV-vis (CH3CN), λmax [nm]
(ε [mol-1 dm3 cm-1]): 415sh (3040), 300 (12800), 236sh (36800),
218 (42700). ESI-MS: m/z 750 (M+).
Results and Discussion
The preparations of the various compounds described in
this work are summarized in Scheme 1.
t
Addition of RNC (R ) (a) Bu, (b) Cy) to [RuVI-
(N)(L)(MeOH)]PF6 (1). Treatment of 1 with 2 equiv of RNC
in CH2Cl2 at ambient conditions results in a color change
from orange to dark green after 1 day. cis-ꢀ-[RuIII(NCNR)-
(25) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla,
M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435.
(26) DIRDIF 99: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman,
W. P.; de Gelder, R.; Israel, R.; Smits, J. M. M. The DIRDIF-99
Program System; Technical Report of the Crystallography Laboratory,
University of Nijmegen: Nijmegen, The Netherlands, 1999.
(27) Single crystal structure analysis software: CrystalStructure, version
3.5.1; Rigaku/MSC Corporation: The Woodlands, TX; Rigaku, Ak-
ishima: Tokyo, Japan, 2003. Watkin, D. J.; Prout, C. K.; Carruthers,
J. R.; Betteridge, P. W. Crystals; Chemical Crystallography Lab:
Oxford, U. K., 1996, issue 10.
X-Ray Crystallography. All measurements of 2a·3H2O, 3a, 4a,
4b·CHCl3, and 5a·CH3CN were made on either a Bruker Smart
1000 CCD or a Rigaku AFC7R diffractometer with graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å) in the ω-scan
mode. Details of the intensity data collection and crystal data are
given in Table 1. The data were corrected for Lorentz and
polarization effects. Absorption corrections by the Ψ-scan method
3082 Inorganic Chemistry, Vol. 48, No. 7, 2009

Reaction of a (Salen)ruthenium(VI) Nitrido Complex
Table 2. UV-Vis (CH3CN), IR (KBr), and Electrochemical Data for Complexes 2-5
a
IR (KBr, cm-1
ν(Ct N)
)
E1/2 (volts vs Cp2Fe+/0
)
RuIV/III
complex
λmax (nm (ε, M-1 cm-1))
RuIII/II
2a
648 (6200), 526 (5100), 378 (8180), 337 (9500), 260 (57300)
2156, 2103
0.28
-0.96
-1.08b
-0.94
-1.08b
-0.43
-0.47b
-0.42
-0.47b
-0.48b
-0.46b
0.43c
0.22b
0.26c
2b
3a
3b
638 (3410), 525sh (2920), 377 (6520), 336 (7550), 230 (38900)
2163, 2102
2186
0.22b c
0.87c
,
739 (4170), 482 (1190), 328 (14700), 269 (59300), 237sh (45800),
216 (37700)
748 (4280), 482 (1230), 329 (14200), 234sh (38300), 215 (36700)
0.90b c
,
2194
0.89c
0.85b c
,
0.92b c
,
4a
4b
5a
5b
451 (3110), 376 (13200), 336 (13700), 245sh (43800), 231 (50000)
454 (2830), 377 (11900), 338 (12500), 246sh (38000), 230 (44300)
422sh (2610), 303 (12200), 236sh (34000), 215 (41500)
2099
2108
2191, 2147
2199, 2156
0.85b c
,
415sh (3040), 300 (12800), 236sh (36800), 218 (42700)
0.45c
a Glassy carbon working electrode, Pt counter electrode, Ag/AgNO3 reference electrode, 0.1 M [NnBu4]PF6 in CH3CN as supporting electrode. Ferrocene
was added as an internal standard. The ∆E values for the reversible couples in CH3CN are 65-75 mV at a scan rate of 100 mVs-1. The ∆E values in CH2Cl2
are 90-100 mV at a scan rate of 100 mVs-1 and 68-74 mV at a scan rate of 20 mVs-1 b In CH2Cl2. c Irreversible.
.
Figure 1. Cyclic voltammogram of 2a in CH3CN.
(L)(CNR)] (2) and trans-[RuIII(L)(CNR)2](PF6) (3) have been
isolated as blue and green solids, respectively (each in 30%
yield), after chromatography.
Figure 2. Molecular structure of 2a·3H2O. Thermal ellipsoids are drawn
Compounds 2a and 2b have room-temperature magnetic
moments of µeff ) 2.07 and 2.02 µB (solid sample, Gouy
method), respectively, consistent with their formulation as
RuIII complexes with one unpaired electron. The cyclic
voltammogram of 2a in CH3CN shows two reversible
couples at +0.28 V and -0.96 V (vs Cp2Fe+/0), which are
assigned to RuIV/III and RuIII/II couples, respectively (Figure
1, Table 2). Similar electrochemical behavior is observed
for other (salen)ruthenium(III) complexes.28The RuIV/III couple
in 2b is irreversible with Epc ) +0.26 versus Cp2Fe+/0. The IR
spectrum (KBr) of 2a shows two sharp bands at 2156 and
2103 cm-1, which are assigned to ν(Ct N) stretches of the
RNt C and RNdCdN- ligands, respectively. These bands
occur at 2163 and 2102 cm-1 for 2b. Carbodiimido com-
plexes generally display a strong band at around 2100 cm-1.
For example, NdCdN stretches of carbodiimido complexes
of zirconium29 and palladium30 occur at 2094 and 2140 cm-1,
respectively.
at 30% probability. H atoms are omitted for clarity.
structural refinement details are given in Table 1. Selected
bond distances and angles are listed in Table 3. The Ru atom
adopts a distorted octahedral environment and is coordinated
t
t
to one tetradentate salen, one BuNCN, and one BuNC
ligand. The salen ligand is in a cis-ꢀ configuration with two
N atoms and one O atom lying on the equatorial plane, while
one O atom occupies an apical position. The tert-butylcar-
bodiimido unit has a typical diazacumulene structure
(C(21)-N(3) ) 1.194(14) Å, C(21)-N(4) ) 1.240(15) Å,
N(3)-C(21)-N(4) ) 173.1(12)°).31 The Ru-N(3) bond
distance is 1.980(7) Å, and the Ru-N(3)-C(21) angle
(154.0(8)°) is acute. cis-ꢀ-Salen complexes of Ti,32 Cr,33
Fe,34 Co,35 Mo,36,37 W,37,38 and Re39 are known. [Ru(sa-
len)(CO)2] and [Ru(salen)(NO)(cis-stilbene sulfide)]+ have
also been reported to have cis geometry, but these compounds
have not been structurally characterized.40-42
The molecular structure of 2a has been determined by
X-ray crystallography (Figure 2). The crystal data and
The formation of 2 is proposed to involve an initial
nucleophilic addition of RNC to the nitrido ligand of 1 to
give a [RuIV(NCNR)]+ intermediate, which presumably is
then rapidly reduced by RNC.43 [RuIV(NCNR)]+ is a
reasonably strong oxidant (Table 2, E1/2 of RuIV/III for 2a )
+0.28 V vs Cp2Fe+/0).
(28) Man, W. L.; Kwong, H. K.; Lam, W. W. Y.; Xiang, J.; Wong, T. W.;
Lam, W. H.; Wong, W. T.; Peng, S. M.; Lau, T. C. Inorg. Chem.
2008, 47, 5936–5944.
(29) Kim, Y. J.; Lee, K. E.; Jeon, H. T.; Huh, H. S.; Lee, S. W. Inorg.
Chim. Acta 2008, 361, 2159–2165.
(30) Herrmann, H.; Fillol, J. L.; Wadepohl, H.; Gade, L. H. Organometallics
2008, 27, 172–174.
(31) Gordon, M. S.; Fischer, H. J. Am. Chem. Soc. 1968, 90, 2471–2476.
Inorganic Chemistry, Vol. 48, No. 7, 2009 3083

Kwong et al.
Synthesis and Characterization of trans-[RuIII-
(L)(CNR)2]PF6 (3) and trans-[RuII(L)(CNR)2] (4) (R ) (a)
tBu, (b) Cy). Compound 2 does not react with excess RNC
at room temperature over a period of 24 h, indicating that 3
is not formed from 2. We have recently reported a general
method for preparing (salen)ruthenium(III) complexes via
ligand-induced N· · ·N coupling of 1.28 Compound 3 is most
likely formed from parallel N · · · N coupling in the reaction
of 1 and RNC (eq 1).
[RuVI(N)(L)(MeOH)]+ + 2RNC f [RuIII(L)(CNR)2]+ +
1/2N2 (1)
Compounds 3a and 3b have µeff ) 1.94 and 1.98 µB,
respectively (solid sample, Gouy method). Isocyanide com-
plexes of RuII are common and well-documented;43 however,
there are few examples of ruthenium(III) isocyanide com-
plexes.45-47 The IR spectrum (KBr) of 3a shows a strong
ν(Ct N) stretch at 2186 cm-1 and an intense ν(P-F) band
at 845 cm-1. The cyclic voltammogram of 3a displays an
irreversible RuIV/III wave at Epc ) +0.87 and a reversible
RuIII/II couple at E1/2 ) -0.43 V versus Cp2Fe+/0 (Table 2).
The ESI mass spectrum of 3a (+ mode) in acetone displays
a single peak at m/z ) 588, which is assigned to the parent
cation [Ru(L)(CNtBu)2]+ (Figure S1, Supporting Informa-
tion).
Figure 3. Molecular structure of the cation of 3a. Thermal ellipsoids are
drawn at 30% probability. H atoms are omitted for clarity.
Compound 3 can be readily reduced to diamagnetic
[RuII(L)(CNR)2] (4) with CoCp2 or Zn/Hg. In the IR spectra,
the ν(Ct N) stretch is shifted from 2186 and 2194 cm-1 in
3a and 3b to 2099 and 2108 cm-1 in 4a and 4b, respectively.
This shift to lower frequency is in accord with π-back-
bonding between Ru(II) and RNC.
Figure 4. Molecular structure of 4a. Thermal ellipsoids are drawn at 30%
probability. H atoms are omitted for clarity.
The structures of 3a, 4a, and 4b have been determined by
X-ray crystallography (Figure 3 and 4 and Figure S2,
Table 3. Selected Bond Distances (Å) and Angles (deg) of 2a·3H2O
Ru(1)-O(1)
2.010 (6)
2.017 (5)
2.050 (7)
2.014 (8)
1.980 (7)
87.9 (2)
93.1 (2)
169.8 (2)
91.0 (3)
92.9 (3)
93.6 (2)
84.5 (3)
178.0 (2)
89.4 (3)
Ru(1)-C(26)
N(3)-C(21)
N(4)-C(21)
N(5)-C(26)
1.979 (10)
1.194 (14)
1.240 (15)
1.155 (13)
(32) Corden, J. P.; Errington, W.; Moore, P.; Wallbridge, M. G. H. Chem.
Commun. 1999, 323–324.
(33) Lloret, F.; Julve, M.; Mollar, M.; Castro, I.; Lattore, J.; Faus, J.; Solans,
X.; Morgenstern-Badarau, I. J. Chem. Soc., Dalton. Trans. 1989,
729–738.
(34) Lauffer, R. B.; Heistand, R. H.; Que, L. Inorg. Chem. 1983, 22, 50–
55.
(35) Calligaris, M.; Manzini, G.; Nardin, G.; Randaccio, L. J. Chem. Soc.,
Dalton. Trans. 1972, 543–547.
(36) Ramnauth, R.; Al-Juaid, S.; Motevalli, M.; Parkin, B. C.; Sullivan,
A. C. Inorg. Chem. 2004, 43, 4072–4079.
(37) Motevalli, M.; Oduwole, A. D.; Parkin, B. C.; Ramnauth, R.; Sullivan,
A. C.; Kaltsoyannis, N. Dalton. Trans. 2003, 3591–3598.
(38) Motevalli, M.; Parkin, B. C.; Ramnauth, R.; Sullivan, A. C. J. Chem.
Soc., Dalton. Trans. 2000, 2661–2662.
Ru(1)-O(2)
Ru(1)-N(1)
Ru(1)-N(2)
Ru(1)-N(3)
O(1)-Ru(1)-O(2)
O(1)-Ru(1)-N(1)
O(1)-Ru(1)-N(2)
O(1)-Ru(1)-N(3)
O(1)-Ru(1)-C(26)
O(2)-Ru(1)-N(1)
O(2)-Ru(1)-N(2)
O(2)-Ru(1)-N(3)
O(2)-Ru(1)-C(26)
N(1)-Ru(1)-N(2)
N(1)-Ru(1)-N(3)
N(1)-Ru(1)-C(26)
N(2)-Ru(1)-N(3)
N(2)-Ru(1)-C(26)
N(3)-Ru(1)-C(26)
Ru(1)-N(3)-C(21)
Ru(1)-C(26)-N(5)
N(3)-C(21)-N(4)
80.7 (3)
84.8 (3)
173.4 (3)
96.3 (3)
93.9 (3)
92.3 (3)
154.0 (8)
174.5 (9)
173.1 (12)
(39) Ison, E. A.; Cessarich, J. E.; Travia, N. E.; Fanwick, P. E.; Abu-
Omar, M. M. J. Am. Chem. Soc. 2007, 129, 1167–1178.
(40) Thornback, J. R.; Wilkinson, G. J. Chem. Soc., Dalton Trans. 1978,
110–115.
(41) Leung, W. H.; Chan, E. Y. Y.; Chow, E. K. F.; Williams, I. D.; Peng,
S. M. J. Chem. Soc., Dalton Trans. 1996, 1229–1236.
(42) Sauve, A. A.; Groves, J. T. J. Am. Chem. Soc. 2002, 124, 4770–4778.
(43) Malatesta, L.; Bonati, F. Isocyanide Complexes of Transition Metal;
John Wiley and Sons Ltd.: London, 1969.
Early transition-metal or main-group carbodiimido com-
plexes are generally prepared by the reaction of metal halides
with trialkylstannyl (or trialkylsilyl) carbodiimides.44 Car-
bodiimido complexes of Ni, Pd, and Pt have been prepared
by the reaction of azido complexes with isocyanides.30,44
A
zirconium carbodiimido complex has also been prepared
from the corresponding (1-pyridinio)imido species.29 Com-
pounds 2a and 2b are the first examples of carbodiimido
complexes of ruthenium; these complexes are also prepared
by the unprecedented method of direct nucleophilic addition
of isocyanide to a metal nitride (Mt N).
(44) Kim, Y. J.; Joo, Y. S.; Han, J. T.; Han, W. S.; Lee, S. W. J. Chem.
Soc., Dalton Trans. 2002, 3611–3618, and references therein.
(45) al Dulaimi, J. P.; Clark, R. J. H.; Saavedra S., M.; Salam, M. A. Inorg.
Chim. Acta 2000, 300–302, 525-530.
(46) Galardon, E.; Le Maux, P.; Paul, C.; Poriel, C.; Simonneaux, G. J.
Organomet. Chem. 2001, 629, 145–152.
(47) Zavarine, I. S.; Kubiak, C. P.; Yamaguchi, T.; Ota, K.; Matsui, T.;
Ito, T. Inorg. Chem. 2000, 39, 2696–2698, and references therein.
3084 Inorganic Chemistry, Vol. 48, No. 7, 2009

Reaction of a (Salen)ruthenium(VI) Nitrido Complex
Table 4. Selected Bond Distances (Å) and Angles (deg) of 3a and 4a
3a
4a
3a
4a
Ru-O(1)
2.016 (2)
2.005 (3)
2.020 (3)
2.019 (3)
98.7 (1)
90.0 (1)
171.0 (1)
93.3 (1)
85.3 (1)
170.7 (1)
89.7 (1)
88.8 (1)
88.2 (1)
2.094 (1)
2.094 (1)
2.001 (1)
2.001 (1)
91.76 (8)
92.47 (7)
175.43 (6)
94.43 (7)
84.06 (7)
175.43 (6)
92.47 (7)
94.43 (7)
84.06 (7)
Ru-C(21)
2.031 (4)
2.046 (4)
1.139 (5)
1.146 (5)
81.9 (1)
94.0 (1)
89.2 (1)
83.5 (1)
98.3 (1)
170.7 (3)
170.0 (3)
176.5 (1)
2.008 (2)
2.008 (2)
1.146 (3)
1.146 (3)
83.35 (10)
93.90 (7)
87.73 (7)
87.73 (7)
93.90 (7)
171.1 (2)
171.1 (2)
177.8 (1)
Ru-O(2)
Ru-C(26)
Ru-N(1)
Ru-N(2)
C(21)-N(3)
C(26)-N(4)
O(1)-Ru-O(2)
O(1)-Ru-N(1)
O(1)-Ru-N(2)
O(1)-Ru-C(21)
O(1)-Ru-C(26)
O(2)-Ru-N(1)
O(2)-Ru-N(2)
O(2)-Ru-C(21)
O(2)-Ru-C(26)
N(1)-Ru-N(2)
N(1)-Ru-C(21)
N(1)-Ru-C(26)
N(2)-Ru-C(21)
N(2)-Ru-C(26)
N(3)-C(21)-Ru
N(4)-C(26)-Ru
C(21)-Ru-C(26)
Supporting Information). The crystal data and structural
refinement details are given in Table 1. Selected bond
distances and angles are listed in Table 4. Compounds 3a
and 4a are isostructural with distorted octahedral geometry;
each Ru center is surrounded by a planar salen and two trans
tBuNC ligands. The average Ru-Cisocyanide distances are 2.039
and 2.008 Å for 3a and 4a, respectively; the shorter
Ru-Cisocyanide distance found in 4a again demonstrates the
presence of strong π-back-bonding between Ru(II) and RNC.
The Ru-Cisocyanide distance of 4a is comparable to that of
[RuII(TPP)(CNtBu)2] (2.015(5) Å).48 The Ru-C-N units are
slightly bent (average ∠Ru-C-N are 170.4° and 171.1° for
3a and 4a respectively). To our knowledge, the trinuclear
complex, [Ru3(µ3-O)(µ-CH3CO2)6(X)3] (X ) xylyl isocya-
nide), is the only structurally characterized RuIII isocyanide
complex reported in the literature.47
Synthesis and Characterization of an η3-Coordinated
(Salen)ruthenium(II) Complex. As described above, the
reaction of 1 with 2 equiv of RNC at room temperature
produces 2 and 3. No further reaction was observed when
t
3a or 4a was refluxed with excess BuNC in methanol or
ethanol for over 3 days under argon. However, by introducing
t
5 equiv of NH4PF6 as a proton source to 4a and BuNC in
refluxing CH3OH under argon, a color change from red to
yellow was observed after 9 h. (No color change was
observed when 3a was used.) A yellow, air-stable crystalline
compound (5a) was produced after workup, which is
assigned as mer-[RuII(η3-HL)(CNtBu)3]PF6. Compound 5b
was prepared similarly using 4b. The formation of 5 is likely
initiated by protonation of a phenoxy O atom of the salen
ligand by NH4PF6, which would facilitate substitution by
RNC. The IR (KBr) spectrum of 5a shows one strong and
one medium band at 2147 and 2191 cm-1, respectively,
which are assigned to the ν(Ct N) stretches of tBuNC. There
is a broad ν(O-H) peak at 3486 cm-1 and an intense ν(P-F)
1
band at 841 cm-1 which are absent in 4a. The H NMR
spectra of 5a and 5b in CD2Cl2 display well-resolved signals
at normal field, indicating that these compounds are dia-
magnetic. Figure 5 shows the 1H NMR spectrum of 5b from
6-9 ppm. Unlike 4b, the two imine protons occur as two
distinct singlets at δ 8.75 and 8.28, indicating that they are
in different environments. In the aromatic region (δ 6-8),
there are in total nine protons, which are attributed to the
eight aromatic protons on the ligand L plus one O-H proton
(overlapped with one aromatic proton at ca. δ 7.1). Upon
the addition of 5% D2O (by volume), the integration of the
resonance at δ 7.1 changes from two to one. For 5a, the
two imine protons again occur as two singlets at δ 8.76 and
8.30. The O-H proton overlaps with one aromatic proton
1
Figure 5. H NMR spectrum of [RuII(HL)(CNCy)3]PF6 (5b) in CD2Cl2.
Insets show the change of the peak at ca. δ7.1 before (left) and after addition
of 5% (v/v) D2O (right).
t
at δ 7.95-7.97. The three BuNC groups occur as three
singlets at δ 1.44, 1.31, and 1.20. The ESI mass spectrum
(+ mode) of 5a in acetone displays a predominant peak at
m/z ) 672, which is assigned to the parent ion
{[Ru(L)(CNtBu)3]·H}+ (Figure 6). This assignment is strongly
Figure 6. ESI mass spectrum (+ mode) of 5a in acetone. Insets show the
experimental (top) and calculated (bottom) isotopic patterns.
(48) Lee, F. W.; Choi, M. Y.; Cheung, K. K.; Che, C. M. J. Organomet.
Chem. 2000, 595, 114–125.
Inorganic Chemistry, Vol. 48, No. 7, 2009 3085

Kwong et al.
t
three BuNC ligands in the mer configuration. The salen
ligand is only three-coordinated (two N atoms and one O
atom) to ruthenium, with a dangling phenol group. To our
knowledge, this is the first example of an η3-salen complex
that has been structurally characterized. The Ru-N(1),
Ru-N(2), and Ru-O(1) distances of 2.067(5), 2.084(11),
and 2.093(10) Å, respectively, are similar to those in regular
η4-(salen)ruthenium complexes. The equatorial Ru-
C(isocyanide) distance (1.959(5) Å) is similar to that of the
apical Ru-C distances (1.979(9) and 2.013(8) Å).
Summary
The electrophilic (salen)ruthenium(VI) nitrido complex
[RuVI(N)(L)(MeOH)]+ reacts rapidly with isocyanide at room
temperature to produce a mixture of cis-ꢀ-[RuIII(NCNR)(L)-
(CNR)] and trans-[RuIII(L)(CNR)2]+. cis-ꢀ-[RuIII(NCNR)-
(L)(CNR)] is the first example of a carbodiimido complex
of ruthenium, which is formed from an unprecedented
pathway involving the nucleophilic addition of isocyanide
to the nitrido ligand. The salen ligand in the carbodiimido
complex has a cis-ꢀ geometry. trans-[RuIII(L)(CNR)2]+ is
formed by a parallel ligand-induced N · · ·N coupling reaction
of the nitrido complex. This complex is readily reduced to
trans-[RuII(L)(CNR)2], which further reacts with excess RNC
in the presence of NH4PF6 to give mer-[RuII(η3-
HL)(CNR)3]PF6, in which the salen is in an unprecedented
η3-coordination mode.
Figure 7. Molecular structure of cation of 5a·CH3CN. Thermal ellipsoids
are drawn at 30% probability. H atoms (expect O(2)-H) are omitted for
clarity.
Table 5. Selected Bond Distances (Å) and Angles (deg) of 5a·CH3CN
Ru-O(1)
2.093(10)
2.067(5)
2.084(11)
2.013(8)
1.959(5)
1.979(9)
90.7(2)
171.6(2)
88.4(2)
88.3(2)
85.6(2)
81.1(2)
91.9(2)
173.3(2)
87.9(2)
N(3)-C(21)
N(4)-C(26)
N(5)-C(31)
N(1)-C(7)
N(2)-C(14)
1.157(10)
1.152(8)
1.166(12)
1.288(9)
1.285(7)
Ru-N(1)
Ru-N(2)
Ru-C(21)
Ru-C(26)
Ru-C(31)
O(1)-Ru-N(1)
O(1)-Ru-N(2)
O(1)-Ru-C(21)
O(1)-Ru-C(26)
O(1)-Ru-C(31)
N(1)-Ru-N(2)
N(1)-Ru-C(21)
N(1)-Ru-C(26)
N(1)-Ru-C(31)
N(2)-Ru-C(21)
N(2)-Ru-C(26)
N(2)-Ru-C(31)
C(21)-Ru-C(26)
C(21)-Ru-C(31)
C(26)-Ru-C(31)
Ru-N(1)-C(7)
Ru-N(2)-C(14)
Ru-C(21)-N(3)
Ru-C(26)-N(4)
Ru-C(31)-N(5)
99.4(2)
92.1(2)
94.6(2)
174.1(3)
85.4(2)
124.0(4)
131.8(4)
177.1(6)
169.6(4)
171.1(7)
Acknowledgment. The work described in this paper was
supported by the Research Grants Council of Hong Kong
(CityU 101505, CityU 2/06C).
93.6(2)
supported by the excellent agreement between the expanded
and simulated isotopic patterns.
Supporting Information Available: Crystallographic informa-
tion files for 2a·3H2O, 3a, 4a, 4b·CHCl3, and 5a·CH3CN. ESI-
MS of 3a and molecular structure of 4b·CHCl3. These materials
are available free of charge via the Internet at http://pubs.acs.org.
The molecular structure of 5a is confirmed by X-ray
crystallography; the cation is depicted in Figure 7. The crystal
data and structural refinement details are given in Table 1.
Selected bond distances and angles are listed in Table 5. The
ruthenium atom is in a distorted octahedral environment with
IC802338F
3086 Inorganic Chemistry, Vol. 48, No. 7, 2009