IR (KBr, cm21) 1288m (N§N), 1925s (C°O). 1+PF62, UV–VIS (CH2Cl2):
lmax/nm (e/dm3 mol21 cm21) 524 (2940), 415 (12500), 294 (18500); IR
(KBr, cm21) 1312m (N§N), 1945s (C°O); dH (CDCl3; 300 MHz), 7.05 (s,
1H), 6.91 (d, J 8.9, 2H), 6.66 (d, J 8.9, 2H), 6.32 (s, 1H), 4.13 (s, CH3, 3H).
2+PF62, UV–VIS (CH2Cl2): lmax/nm (e/dm3 mol21 cm21) 515 (1970), 450
(2070), 380 (6600); IR (KBr, cm21) 1320m (N§N), 1960s (C°O); dH
(CDCl3; 300 MHz) 8.73 (d, J 7.8, 1H), 8.25 (t, J 7.9, 1H), 7.80 (d, J 5.4, 1H),
6.92 (t, J 8.1, 2H), 6.77 (t, J 6.0, 1H), 6.73 (d, J 8.4, 2H).
‡ Crystal data for 1: C47H39N4OP2Cl2Ru, M = 909.73, monoclinic, space
group P21/n, a = 10.029(2), b = 33.984(7), c = 12.386(3) Å, b =
97.15(3)°, U = 4189(2) Å3, Z = 4, m = 0.620 mm21, total reflections
collected 6866, unique reflections 6218, final R indices for 4109 observed
to reflux for 1 h and subsequent cooling afforded the deep green
crystalline complex [Ru(L1·2)(Cl)(CO)(PPh3)2] 1 in 85% yield
(all operations were carried out in an oxygen free environ-
ment).† A similar reaction of L2 with [Ru(H)(Br)(CO)(PPh3)3] 6
in dry heptane furnished [Ru(L2·2)(Br)(CO)(PPh3)2] 2.† The
key to our success is the use of hydridic starting materials which
provide the reducing equivalent that is necessary for anion
radical generation, eqn. (1), via Ru–H bond cleavage.
[Ru(H)(X)(CO)(PPh3)3] + L ? [Ru(L·2)(X)(CO)(PPh3)2]
1
+ ⁄2 H2 + PPh3
(1)
[I
>
2s(I)] reflections: R1
=
0.0547, wR2
=
0.1015; 2:
The solid complexes which are quite stable in dry air behave
as one-electron paramagnets (meff: 1, 1.80 mB and 2, 1.78 mB)
and display a single-line strong powder EPR signal (298 K) with
g = 2.000 for 1 and g = 1.999 for 2, the respective peak-to-
peak line-widths being 9 G and 18 G. This is consistent with the
azo anion radical description. The expected small 14N hyperfine
splitting is not resolved probably due to dominant anisotropic
contributions.2,7
C
48H39N3OP2BrRu, M = 916.74, monoclinic, space group P21/c, a =
10.226(5), b = 17.443(7), c = 22.760(8) Å, b = 97.75(3)°, U = 4023(3)
Å3, Z = 4, m = 1.506 mm21, total reflections collected 6186, unique
reflections 5703, final R indices for 3402 observed [I > 2s(I)] reflections:
R1 = 0.1010, wR2 = 0.2591. All crystallographic measurements were
performed using a Siemens R3m/V four-circle diffractometer and data were
collected by the w-scan method. The structures were solved by the Patterson
heavy-atom method (SHELXTL-Ver. 5.03) and refined on F2 by full matrix
least squares using all unique data.10 All nonhydrogen atoms for 1 and 2 are
anisotropic with H-atoms included in calculated positions (riding model).
Empirical absorption corrections for both cases were carried out on the basis
of azimuthal scans.11 One phenyl ring of P(1)Ph3 and one of P(2)Ph3
displayed two-fold disorder around C(13)–C(16) and C(31)–C(34) axes
respectively in 1. The crystal of 2 was relatively poorly diffracting and the
peaks were broad. CCDC 182/977.
The X-ray structures‡ of 1 and 2 are shown in Fig. 1 and 2;
Fig. 2 also displays the EPR spectrum of 2. In each case the L
ligand forms a planar five-membered chelate ring to which the
trans-RuII(PPh3)2 fragment lies nearly orthogonally. The halide
and carbon monoxide ligands are positioned trans to the azo and
heterocyclic nitrogen atoms respectively. The N–N distances,
1.369(8) Å in 1 and 1.341(17) Å in 2, are intermediate between
those of double ( ≈ 1.25 Å8) and single ( ≈ 1.45 Å9) bonds as
expected for the radical anion description.
1 J. L. Sadler and A. J. Bard, J. Am. Chem. Soc., 1968, 90, 1979; B. K.
Ghosh and A. Chakravorty, Coord. Chem. Rev., 1989, 95, 239.
2 C. K. Pal, S. Chattopadhyay, C. R. Sinha and A. Chakravorty, Inorg.
Chem., 1996, 35, 2442.
3 T. K. Misra, D. Das, C. R. Sinha, P. Ghosh and C. K. Pal, Inorg. Chem.,
1998, 37, 1672 and references therein.
4 S. Goswami, R. Mukherjee and A. Chakravorty, Inorg. Chem., 1983, 22,
2825.
5 R. A. Krause and K. Krause, Inorg. Chem., 1984, 23, 2195.
6 N. Ahmad, J. J. Levison, S. D. Robinson and M. F. Uttley, Inorg. Synth.,
1975, 15, 45; J. M. Jenkins, M. S. Lupin and B. L. Shaw, J. Chem. Soc.
A, 1966, 1787.
Aerial oxidation of 1 and 2 in polar solvents gives
[Ru(L1)(Cl)(CO)(PPh3)2]+ 1+ and [Ru(L2)(Br)(CO)(PPh3)2]+
2
2+ which have been isolated as diamagnetic PF6 salts.† In
+
+
1
dichloromethane solutions the E values of the 1 /1 and 2 /2
couples are respectively 20.472 V and 20.39 V vs. SCE.
Reversible coulometric recycling between 1 and 1+ and between
2 and 2+ can be repeatedly performed in an inert atmosphere. A
wider application of our synthetic procedure for anion radical
generation is under scrutiny.
7 C. K. Pal, S. Chattopadhyay, C. R. Sinha and A. Chakravorty, Inorg.
Chem., 1994, 33, 6140.
We thank the Indian National Science Academy, Department
of Science and Technology and the Council of Scientific and
Industrial Research, New Delhi for financial support. Affilia-
tion with the Jawaharlal Nehru Centre for Advanced Scientific
Research, Bangalore, India, is acknowledged.
8 A. Mostad and C. Romming, Acta Chem. Scand., 1971, 25, 3561; C. H.
Chang, R. F. Porter and S. H. Brauer, J. Am. Chem. Soc., 1970, 92, 5313;
T. Roy and S. P. Sengupta, Cryst. Struct. Commun., 1980, 9, 965.
9 Y. Morino, T. Iijima and Y. Murata, Bull. Chem. Soc. Jpn., 1960, 33,
46.
10 G. M. Sheldrick, SHELXTL, Version 5.03, Siemens Analytical X-ray
Instruments Inc., Madison, WI, 1994.
11 A. C. T. North, D. C. Phillips and F. S. Mathews, Acta Crystallogr.,
Sect. A, 1968, 24, 351.
Notes and References
† Satisfactory elemental analyses were obtained. Selected spectral data: 1,
UV–VIS (C6H6): lmax/nm (e/dm3 mol21 cm21) 568 (5000), 507 (4500),
390 (16400); IR (KBr, cm21) 1287m (N§N), 1918s (C°O). 2, UV–VIS
(C6H6): lmax/nm (e/dm3 mol21 cm21) 570 (2300), 540 (2200), 380 (7800);
Received in Cambridge, UK, 15th June 1998; 8/04480E
2104
Chem. Commun., 1998
Shivakumar, Maya
