Oxygen atom transfer from nitrogenous ReVO reagents to diphosphines and subsequent transformations. Rhenium(III) products and reaction models

Article abstract of DOI:10.1021/ic0005893

The concerned diphosphines are Ph₂P(CH₂)_nPPh₂ (1); abbreviated PnP, and the Re^VO reagents are ReOCl₃L (2) and ReOCl₃L′ (3), where L and L′ are the azopyridine and pyridine - imine ligands p-ClC₆H₄N=NC₅H₄N and p-MeC₆H₄N=CHC₅H₄N, respectively. One atom transfer from 2 to 1 has afforded Re(OPnP)Cl₃L (4a, n = 1; 4b, n = 2; 4c, n = 3). Of these 4b and 4c are stable, but 4a undergoes spontaneous isomerization to Re(PlPO)Cl₃L (5) in solution. Two-atom transfer studied with both 2 and 3 has afforded binuclear LCl₃Re(OPnPO)ReCl₃L (8a, n = 2; 8b, n = 3) and L′Cl₃Re(OPnPO)ReCl₃L′ (9a, n = 2; 9b, n = 3) for n = 2, 3 and mononuclear Re(OPlPO)Cl₃L (11) and Re(OPlPO)Cl₃L′ (12) for n = 1. The mixed system L′Cl₃Re(OP2PO)ReCl₃L (10) has been prepared from 3 and 4b. The complex Re(PPh₃)Cl₃L (7a) is furnished by the reaction of Re(OPPh₃)Cl₃L (6a) or 4b or 11 with PPh₃. The species have been characterized with the help of spectral, electrochemical, and X-ray structural data. All the complexes have mer geometry except 5 and 7a, which have fac geometry. The latter is best suited for concurrent Re - N and Re - P back-bonding. Variable-temperature rate data of the reaction 4a → 5 are consistent with an intramolecular strongly associative transition state (ΔS^?, -22.6 eu) in which the dangling phosphine function lies close to the metal. Two-atom transfer to PlP is believed to proceed via a transient binuclear intermediate which undergoes cleavage at one end due to steric crowding, affording 11 and 12. Crystal data for the complexes are as follows: 5·1.5 C₆H₆, empirical formula C₄₅H₃₉Cl₄N₃OP₂Re, crystal system triclinic, space group P1, a = 10.034(2) A, b = 10.737(2) A, c = 20.357(4) A, α = 89.38(3)°, β = 87.79(3)°, γ = 80.22(3)°, V = 2159.7(7) A³, Z = 2; 7a·CH₂Cl₂, empirical formula C₃₀H₂₅Cl₆N₃PRe, crystal system monoclinic, space group P2₁/n, a = 11.695(6) A, b = 17.745(7) A, c = 15.459(9) A, β = 100.94(5)°, V = 3150(3) A³, Z = 4; 9a, empirical formula C₅₂H₄₈Cl₆N₄O₂ P₂Re₂, crystal system monoclinic, space group C2/c, a = 19.769(12) A, b = 12.864(6) A, c = 22.20(2) A, β = 101.76(6)°, V = 5530(6) A³, Z = 4; 11, empirical formula C₃₆H₃₀Cl₄N₃O₂ P₂Re, crystal system monoclinic, space group I2/a, a = 16.866(6) A, b = 12.583(6) A, c = 34.78(2) A, β = 99.22(4)°, V = 7285(7) A³, Z = 8.

Full text of DOI:10.1021/ic0005893

286
Inorg. Chem. 2001, 40, 286-293
Oxygen Atom Transfer from Nitrogenous ReVO Reagents to Diphosphines and Subsequent
Transformations. Rhenium(III) Products and Reaction Models
Sibaprasad Bhattacharyya, Indranil Chakraborty, Bimal Kumar Dirghangi, and
Animesh Chakravorty*
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science,
Calcutta 700 032, India
ReceiVed June 1, 2000
The concerned diphosphines are Ph2P(CH2)nPPh2 (1), abbreviated PnP, and the ReVO reagents are ReOCl3L (2)
and ReOCl3L′ (3), where L and L′ are the azopyridine and pyridine-imine ligands p-ClC6H4NdNC5H4N and
p-MeC6H4NdCHC5H4N, respectively. One atom transfer from 2 to 1 has afforded Re(OPnP)Cl3L (4a, n ) 1; 4b,
n ) 2; 4c, n ) 3). Of these 4b and 4c are stable, but 4a undergoes spontaneous isomerization to Re(PlPO)Cl3L
(5) in solution. Two-atom transfer studied with both 2 and 3 has afforded binuclear LCl3Re(OPnPO)ReCl3L (8a,
n ) 2; 8b, n ) 3) and L′Cl3Re(OPnPO)ReCl3L′ (9a, n ) 2; 9b, n ) 3) for n ) 2, 3 and mononuclear Re-
(OP1PO)Cl3L (11) and Re(OP1PO)Cl3L′ (12) for n ) 1. The mixed system L′Cl3Re(OP2PO)ReCl3L (10) has
been prepared from 3 and 4b. The complex Re(PPh3)Cl3L (7a) is furnished by the reaction of Re(OPPh3)Cl3L
(6a) or 4b or 11 with PPh3. The species have been characterized with the help of spectral, electrochemical, and
X-ray structural data. All the complexes have mer geometry except 5 and 7a, which have fac geometry. The
latter is best suited for concurrent Re-N and Re-P back-bonding. Variable-temperature rate data of the reaction
4a f 5 are consistent with an intramolecular strongly associative transition state (∆Sq, -22.6 eu) in which the
dangling phosphine function lies close to the metal. Two-atom transfer to P1P is believed to proceed via a transient
binuclear intermediate which undergoes cleavage at one end due to steric crowding, affording 11 and 12. Crystal
data for the complexes are as follows: 5‚1.5 C6H6, empirical formula C45H39Cl4N3OP2Re, crystal system triclinic,
space group P1h, a ) 10.034(2) Å, b ) 10.737(2) Å, c ) 20.357(4) Å, R ) 89.38(3)°, â ) 87.79(3)°, γ )
80.22(3)°, V ) 2159.7(7) Å3, Z ) 2; 7a‚CH2Cl2, empirical formula C30H25Cl6N3PRe, crystal system monoclinic,
space group P21/n, a ) 11.695(6) Å, b ) 17.745(7) Å, c ) 15.459(9) Å, â ) 100.94(5)°, V ) 3150(3) Å3, Z )
4; 9a, empirical formula C52H48Cl6N4O2P2Re2, crystal system monoclinic, space group C2/c, a ) 19.769(12) Å,
b ) 12.864(6) Å, c ) 22.20(2) Å, â ) 101.76(6)°, V ) 5530(6) Å3, Z ) 4; 11, empirical formula C36H30-
Cl4N3O2P2Re, crystal system monoclinic, space group I2/a, a ) 16.866(6) Å, b ) 12.583(6) Å, c ) 34.78(2) Å,
â ) 99.22(4)°, V ) 7285(7) Å3, Z ) 8.
Introduction
π-acidic ligands to ReVO facilitates the transfer process via
electron withdrawal from the metal.1-3 The progress in the case
of monophosphines has now prompted us to explore the
reactions of such chelates with linear diphosphines of type 1,
abbreviated PnP (n ) 1-3). The serial atom transfer reactions,
This work stems from our interest in rhenium-promoted ligand
oxidations.1-8 The ReVO moiety is a potentially excellent
oxygen atom transfer reagent, as in eq 1, where the oxophilic
ReVO + PR3 f ReIIIOPR3
(1)
substrate is a tertiary phosphine.1-3,9-17 Chelation of nitrogenous
(1) Banerjee, S.; Bhattacharyya, S.; Dirghangi, B. K.; Menon, M.;
Chakravorty, A. Inorg. Chem. 2000, 39, 6.
(2) Chakraborty, I.; Bhattacharyya, S.; Banerjee, S.; Dirghangi, B. K.;
Chakravorty, A. J. Chem. Soc., Dalton Trans. 1999, 3747.
(3) Dirghangi, B. K.; Menon, M.; Pramanik, A.; Chakravorty, A. Inorg.
Chem. 1997, 36, 1095.
eq 2 and 3, have been realized. Of major interest is the
spontaneous solution reactivity of the n ) 1 products, in contrast
(4) Menon, M.; Pramanik, A.; Bag, N.; Chakravorty, A. Inorg. Chem.
1994, 33, 403.
(5) Dirghangi, B. K.; Menon, M.; Banerjee, S.; Chakravorty, A. Inorg.
Chem. 1997, 36, 3595.
(6) Banerjee, S.; Dirghangi, B. K.; Menon, M.; Pramanik, A.; Chakravorty,
A. J. Chem. Soc., Dalton Trans. 1997, 2149.
(7) Dirghangi, B. K.; Banerjee, S.; Menon, M.; Chakravorty, A. Indian
J. Chem. 1997, 36A, 249.
(8) Bhattacharyya, S.; Banerjee, S.; Dirghangi, B. K.; Menon, M.;
Chakravorty, A. J. Chem. Soc., Dalton Trans. 1999, 155.
(9) Rowbottom, J. F.; Wilkinson, G. J. Chem. Soc., Dalton Trans. 1972,
826.
(10) Rossi, R.; Duatti, A.; Magon, L.; Casellato, V.; Graziani, R.; Toniolo,
L.; J. Chem. Soc., Dalton Trans. 1982, 1949.
(11) Mayer, J. M.; Tulip, T. H. J. Am. Chem. Soc. 1984, 106, 3878.
(12) Conry, R. R.; Mayer, J. M. Inorg. Chem. 1990, 29, 4862.
(13) Battistuzzi, G.; Borsari, M.; Battistuzzi, R. Polyhedron 1997, 16, 2093.
(14) Seymore, S. B.; Brown, S. N. Inorg. Chem. 2000, 39, 325.
(15) Rouschias, G. Chem. ReV. 1974, 74, 531.
(16) Holm, R. H. Chem. ReV. 1987, 87, 1401, and references therein.
(17) Conner, K. A.; Walton, R. A. In ComprehensiVe Coordination
Compounds. The Synthesis, Reactions, Properties and Applications
of Coordination Compounds; Wilkinson, G., Gillard, R. D., McClev-
erty, J. A., Eds.; Pergamon Press: Oxford, U.K., 1987; Vol. 4, p 125.
10.1021/ic0005893 CCC: $20.00 © 2001 American Chemical Society
Published on Web 12/12/2000

Rhenium(III) Products and Reaction Models
Inorganic Chemistry, Vol. 40, No. 2, 2001 287
ReVO + PnP f ReIIIOPnP
(2)
(3)
Chart 1
ReVO + ReIIIOPnP f ReIIIOPnPOReIII
with the indefinite stability of the n > 1 species. The binuclear
complex of eq 3 could not be isolated in the n ) 1 case; instead
mononuclear ReOP1PO is afforded. On the other hand, the
ReOP1P system (eq 2, n ) 1) is found to undergo a remarkable
twin isomerization. The nature of these transformations and the
origin of the n ) 1 singularity have been scrutinized with the
help of rate data and structural models. Certain related reactions
with monophosphines have also been examined. The family of
rhenium(III) compounds defining this fascinating chemistry has
been characterized. A few reactions of ReVO species with
diphosphines leading to phosphorus-coordinated end products
have been reported in the literature.18-20
Results and Discussion
A. Isolation of Products. a. The Reactants. In most of the
reactions with PnP, the oxo complex ReOCl3L, 2, has been used
as the transfer reagent in view of its efficacy endowed by the
π-acidic azopyridine ligand (L).1 In a few studies the relatively
sluggish pyridine-2-aldimine (L′) complex3 ReOCl3L′, 3, has
oxide complex1 6 with excess PPh2R (R ) Ph, Me) in boiling
benzene. Under this drastic condition, the imide complex Re-
(NC6H4Cl)Cl3L1 is invariably formed as a byproduct.
c. Complexes 8-12. Oxygen atom transfer to both ends of
PnP has been achieved by reacting it with excess 2 or
alternatively by reacting 4 with 2. In the n ) 2, 3 cases binuclear
complexes of type 8 are isolated. However lack of solubility
and single crystals have vitiated their characterization. Fortu-
nately 9, the pyridine-2-aldimine analogue of 8, is readily formed
been employed to achieve superior product quality. The products
concerning us in this work are listed and numbered in Chart 1.
b. Complexes 4, 5, and 7. Transfer of one oxygen atom from
2 to PnP afforded 4 in good yield, eq 4. The reaction proceeded
by the reaction of eq 5, and it is soluble and crystalline. The
2 3 + PnP f 9
(5)
mixed L,L′ dimer 10 isolated by the reaction of 3 with 4b was
found to be insoluble like 8.
PnP + 2 f 4
(4)
In contrast with the n ) 2, 3 cases, successive oxygen atom
transfer from 2 to P1P afforded the mononuclear complexes 11
incorporating a dangling phosphine oxide function. Similarly 3
and P1P furnished 12.
rapidly at room temperature upon mixing 2 with excess PnP in
benzene solution. All the type 4 complexes are stable in the
solid state, and 4b and 4c are also stable in solution. In contrast
4a spontaneously isomerizes to 5, which has been isolated by
simply leaving a benzene solution of 4a for a few hours at room
temperature followed by chromatographic workup.
The monophosphine complex 7, which belongs to the same
geometrical type as 5, was furnished upon reacting the phosphine
(18) Luo, X.-L.; Crabtree, R. H. J. Am. Chem. Soc. 1990, 112, 4813.
(19) Fontaine, X. L. R.; Fowles, E. H.; Layzell, T. P.; Shaw, B. L.;
Thornton-Pett, M. J. Chem. Soc., Dalton Trans. 1991, 1519.
(20) Dilworth, J. R.; Griffiths, D. V.; Parrott, S. J.; Zheng, Y. J. Chem.
Soc., Dalton Trans. 1997, 2931.

288 Inorganic Chemistry, Vol. 40, No. 2, 2001
Bhattacharyya et al.
Table 1. Cyclic Voltammetric Potentials at 298 K in Acetonitrile
(0.1 M Et4NClO4) at a Platinum Electrodea-d
E1/2, V (∆Ep, mV)
L/L•- ReIV/ReIII compd
E1/2, V (∆Ep, mV)
compd
L/L•-
ReIV/ReIII
4a
4b
4c
5
6b
7a
-0.56e
0.96 (90)
1.01 (100)
0.99 (100)
7b
9a
9b
11
12
-0.26 (80) 1.18 (80)
0.27 (100)
-0.60e
-0.56e
0.33 (100)
-0.35 (100) 1.16 (120)
-0.55e
0.93 (70)
-0.59e
-0.27 (70) 1.20 (70)
0.99 (120)
0.30 (100)
a Scan rate 50 mV s-1 b E1/2 ) 1/2(Epa + Epc), where Epa and Epc
.
are the anodic and cathodic peak potentials, respectively. c ∆Ep ) Epc
e
- Epa. d Reference elctrode SCE. Epc.
Figure 2. Molecular view and atom-labeling scheme for Re(P1PO)-
Cl3L, 5. All non-hydrogen atoms are represented by 30% thermal
probability ellipsoids.
Figure 3. Molecular view and atom-labeling scheme for Re(PPh3)-
Cl3(L), 7a. All non-hydrogen atoms are represented by 30% thermal
probability ellipsoids.
Figure 1. Cyclic voltammograms of a 10-3 M solution of (a) 4a, (b)
9a, and (c) 5 in acetonitrile (0.1 M Et4NClO4) at a platinum electrode
response does not occur in the Re-L′ species. On going from
4a to 5 the E1/2 values of both the couples increase significantly,
suggesting better stability of the t2 as well as of azo-π* orbitals
in 5. This is consistent with bonding consideration, vide infra.
The E1/2 of the ReIV/ReIII couple in Re-L′ species is lower
than that of the corresponding Re-L species because of the
π-acidity order L . L′. Dinuclear species of type 9 display
only a single ReIV/ReIII couple, the current height being
approximately twice that for one-electron transfer as in 5 and
11 (Figure 1). There is thus little or no communication between
the two widely separated (>8 Å) metal atoms.
C. Structures. The structures of 5‚1.5 C6H6, 7a‚CH2Cl2, 9a,
and 11 have been determined. Molecular views and atom-
numbering schemes are shown in Figures 2-5, and selected
bond parameters are listed in Tables 2-4.
a. Coordination Spheres. All the complexes have severely
distorted octahedral geometries, the coordination spheres being
either RePCl3N2 (5, 7a) or ReOCl3N2 (9a, 11). In 5 the N(1),
N(3), Cl(2), and Cl(3) atoms along with the Re atom form an
excellent equatorial plane (mean deviation 0.01 Å) to which
the nearly linear P(1), Re, Cl(1) fragment is more or less
perpendicularly disposed. The coordination sphere in 7a is
similar.
with a scan rate of 50 mV s-1
.
B. Characterization. a. Spectra. Data are collected in the
Experimental Section. The complexes display Re-Cl stretches
in the range 300-340 cm-1. Coordinated O-P (4, 6, 8-12),
free P-O (5, 11, 12), azo (4-8, 10, 11), and azomethine (9,
10, 12) vibrations occur near 1120, 1200, 1330, and 1600 cm-1
,
respectively.
The 1H NMR lines of the complexes in CDCl3 are paramag-
netically (ReIII, t2g4) shifted.1,2,8,10,21 The chemical shifts of the
chelating ligands are particularly widely spread: L, +47 to -35
ppm, and L′, +30 to -33 ppm. The large difference in chemical
shifts of the proton ortho to the pyridine nitrogen is useful for
isomer identification: 4a, -9.94 ppm, and 5, -19.50 ppm. The
corresponding resonances in 4b, 4c, and 11 expectedly lie close
to that of 4a. Further, the aromatic protons of the phosphorus
ligand have distinctive spreads in the Re-OP (4, 6, 9, 11, 12)
and Re-P (5, 7) species: 1-8 and 3-21 ppm, respectively.
b. Electrochemistry. The species of Chart 1 are generally
electroactive in acetonitrile solution (8 and 10 are too insoluble).
Reduction potential data are collected in Table 1 and representa-
tive voltammograms are shown in Figure 1. The E1/2 values
and the voltammograms are diagnostic of Re-OP (4, 6, 11)
and Re-P (5, 7) species as well as of Re-L (11) and Re-L′
(12) species.
The Re-L species uniformly display two responses, one at
positive potential assigned to the ReIV/ReIII couple (redox orbital
t2g)1,3 and one at negative potential due to the L/L•- couple
(redox orbital primarily azo-π*).1,22-24 As expected, the latter
(21) Tisato, F.; Refosco, F.; Bolzati, C.; Cagnolini, A.; Gatto, S.; Bandoli,
G. J. Chem. Soc., Dalton Trans. 1997, 1421.
(22) Shivakumar, M.; Pramanik, K.; Ghosh, P.; Chakravorty, A. Inorg.
Chem. 1998, 37, 5968.
(23) Pramanik, K.; Shivakumar, M.; Ghosh, P.; Chakravorty, A. Inorg.
Chem. 2000, 39, 195.
(24) Goswami, S.; Mukherjee, R. N.; Chakravorty, A. Inorg. Chem. 1983,
22, 2825.

Rhenium(III) Products and Reaction Models
Inorganic Chemistry, Vol. 40, No. 2, 2001 289
Table 2. Selected Bond Lengths [Å] and Angles [deg] for
5‚1.5C6H6 and 7a‚CH2Cl2
5
7a
Distances
Re-N(3)
Re-N(1)
Re-Cl(2)
Re-Cl(3)
Re-Cl(1)
Re-P(1)
2.007(4)
1.994(10)
2.077(9)
2.332(3)
2.370(3)
2.375(3)
2.510(3)
1.333(13)
2.072(4)
2.345(2)
2.365(1)
2.380(2)
2.479(2)
1.322(6)
1.480(4)
N(2)-N(3)
P(2)-O(1)
Angles
N(3)-Re-N(1)
N(3)-Re-Cl(2)
N(1)-Re-Cl(2)
N(3)-Re-Cl(3)
N(1)-Re-Cl(3)
Cl(2)-Re-Cl(3)
N(3)-Re-Cl(1)
N(1)-Re-Cl(1)
Cl(2)-Re-Cl(1)
Cl(3)-Re-Cl(1)
N(3)-Re-P(1)
N(1)-Re-P(1)
Cl(2)-Re-P(1)
Cl(3)-Re-P(1)
Cl(1)-Re-P(1)
74.1(2)
103.2(1)
177.0(1)
166.0(1)
92.1(1)
90.6(1)
92.5(1)
89.9(1)
91.4(1)
89.7(1)
93.0(1)
92.5(1)
86.4(1)
85.2(1)
174.4(1)
74.2(4)
101.1(3)
175.2(3)
165.4(3)
91.5(3)
93.3(1)
88.9(3)
89.8(2)
91.1(1)
88.4(1)
94.8(3)
91.7(2)
87.7(1)
88.1(1)
176.3(1)
Figure 4. Molecular view and atom-labeling scheme for L′Cl3Re-
(OP2PO)ReCl3L′, 9a. All non-hydrogen atoms are represented by 30%
thermal probability ellipsoids
Table 3. Selected Bond Lengths [Å] and Angles [deg] for 9a
Distances
Re(1)-N(2)
Re(1)-O(1)
Re(1)-Cl(2)
N(2)-C(6)
2.020(11)
2.068(8)
2.378(4)
1.32(2)
Re(1)-N(1)
Re(1)-Cl(3)
Re(1)-Cl(1)
O(1)-P(1)
2.032(11)
2.357(4)
2.370(4)
1.506(8)
Angles
N(2)-Re(1)-N(1)
N(2)-Re(1)-O(1)
N(2)-Re(1)-Cl(3)
N(2)-Re(1)-Cl(1)
78.0(5)
94.1(4)
87.9(3)
173.0(3)
N(1)-Re(1)-O(1)
N(1)-Re(1)-Cl(3)
N(1)-Re(1)-Cl(1)
N(1)-Re(1)-Cl(2)
171.6(4)
88.5(3)
95.1(4)
94.6(3)
Figure 5. Molecular view and atom-labeling scheme for Re(OP1PO)-
Cl3L, 11. All non-hydrogen atoms are represented by 30% thermal
probability ellipsoids
Table 4. Selected Bond Lengths [Å] and Angles [deg] for 11
In 11 the N(1), N(3), O(1), and Cl(1) atoms define a good
equatorial plane (mean deviation 0.02 Å), and the Cl(2), Re,
and Cl(3) atoms constitute an approximately perpendicular axis.
The corresponding geometrical situation in 9a is very similar.
The two halves of the later molecule are related by a crystal-
lographic inversion center. The two metal atoms are widely
separated (Re‚‚‚Re, 8.222(1) Å).
b. Isomeric Geometries. The ReCl3 fragments have fac and
mer geometries in 5, 7a and 9a, 11, respectively. Tertiary
phosphines are π-accepting ligands, the acceptor orbital being
a mixture of 3dπ and P-C σ*-components.25,26 The azopyridine
ligand is also an excellent π-acid, especially at the azo site.1
Trivalent rhenium is prone to back-bonding,1,27 which can thus
have (idealized octahedral geometry assumed) both t2g(Re) f
π(P) and t2g(Re) f π*(L) components in 5 and 7a. The bonding
would be stronger in the fac geometry, in which competition
between π(P) and π*(L) for identical metal orbitals is minimal.
Back-bonding is believed to sustain the fac geometry in 5
and 7a by more than offsetting the steric and electrostatic
advantages of the mer geometry, as has been observed in related
species.2,8 Phosphine oxides are purely donor in character and
Distances
Re-N(3)
Re-O(1)
Re-Cl(3)
N(2)-N(3)
P(2)-O(2)
1.966(11)
2.030(7)
2.368(4)
1.316(13)
1.469(9)
Re-N(1)
Re-Cl(2)
Re-Cl(1)
P(1)-O(1)
2.026(10)
2.357(4)
2.382(4)
1.523(8)
Angles
N(3)-Re-N(1)
N(1)-Re-O(1)
N(1)-Re-Cl(2)
N(3)-Re-Cl(3)
O(1)-Re-Cl(3)
N(3)-Re-Cl(1)
O(1)-Re-Cl(1)
Cl(3)-Re-Cl(1)
75.3(5)
171.8(4)
93.6(3)
88.5(3)
88.4(3)
170.1(3)
93.0(2)
89.0(2)
N(3)-Re-O(1)
N(3)-Re-Cl(2)
O(1)-Re-Cl(2)
N(1)-Re-Cl(3)
Cl(2)-Re-Cl(3)
N(1)-Re-Cl(1)
Cl(2)-Re-Cl(1)
P(1)-O(1)-Re
96.5(4)
94.7(3)
87.7(3)
90.6(3)
175.2(1)
95.2(4)
88.5(2)
146.7(5)
lack accceptor properties. Hence 9a and 11 like 61 and some
related species3 have the mer geometry. The Re-N distances
in the present complexes are consistent with the above bonding
consideration, see below.
c. The Re(P1PO) and Re(OP1PO) Fragments. Two geo-
metrical features that are useful in the scrutiny of n ) 1 reactions
to be considered later will be described. First, we compare 5
and 11 (immediate environment of P atoms only) viewed down
the P‚‚‚P axis, as in 13 and 14, respectively. For angular ZP2
type species (Z ) one atom bridge; CH2 in the present case)
viewed down the P‚‚‚P axis, the staggered conformation of
substituents on the P atoms is energetically most favorable.26,28,29
On this basis the conformation 13 (in 5) is more relaxed than
(25) Cotton, F. A.; Wilkinson, G. AdVanced Inorganic Chemistry, 5th ed.;
Wiley: New York, 1988; p 64.
(26) Pramanik, A.; Bag, N.; Ray, D.; Lahiri, G. K.; Chakravorty, A. Inorg.
Chem. 1991, 30, 410.
(27) Ghosh, P.; Pramanik, A.; Bag, N.; Chakravorty, A. J. Chem. Soc.,
Dalton Trans. 1992, 1883.

290 Inorganic Chemistry, Vol. 40, No. 2, 2001
Bhattacharyya et al.
Table 5. Rate Constants and Activation Parametersa for the
Reaction 4a f 5 in Benzeneb
T, K
104[4a], M
103 k, min-1
298
303
308
313
313
313
2.54
2.54
2.54
2.54
1.89
1.27
1.92 (1)
2.68 (1)
4.53 (2)
6.27 (3)
6.32 (3)
6.30 (3)
a ∆Hq, 14.6 (1.2) kcal mol-1; ∆Sq, -22.6 (1.7) eu. b Least-squares
deviations are given in parentheses.
analogous1). In 9 the Re-N(1) and Re-N(2) lengths are nearly
equal, reflecting similar π-acidities at the two nitrogen sites
which form parts of the R-diimine fragment in L′.
D. Nature of Reactions. The primary reaction in the present
work is oxygen atom transfer (eqs 4 and 5). The nature of such
transfer has already been elaborated in the case of monophos-
phines.3 The transformations that occur after oxygen atom
transfer are scrutinized below.
a. Intramolecular Twin Isomerization of 4a. The reaction
of eq 6 embodies twin isomerization: linkage (Re-OP1P f
ReP1PO) and geometrical (mer f fac). The rate of the reaction
4a
9
k8 5
(6)
(7)
rate ) k[4a]
has been spectrophotometrically monitored in benzene solution
in the temperature range 298-313 K using the absorbance at
468 nm (decay of 4a). The time evolution spectra are character-
ized by several isosbestic points (see Supporting Information).
The reaction follows the first-order rate law of eq 7. Rate
constants and activation parameters are listed in Table 5. The
rate law and the large negative entropy of activation are
suggestive of an intramolecular pathway with strong association
of the dangling phosphine function with the metal. In effect a
septacoordinated transition state is implicated.
Although 4a did not afford single crystals, the structure of
11 provides a credible model. The pendent phosphine oxide
fragment in 11 lies relatively close to the Cl(1), Cl(3), O(1)
face from which the P(2) atom is 4.45 Å away. However a
simple rotation around the P(1)-C(24) bond can bring P(2) to
within 2.5 Å of the face as in 16, which is thus a plausible
14 (in 11). For comparison, the conformation of the Re(OP2PO)-
Re fragment in 9a, viewed down the P‚‚‚P axis, is depicted in
15: here the two P atoms are separated by two C atoms.
Second, the pendent P(1), C(24), P(2), O(2) fragment of 11
is positioned relatively close to one (Cl(1), Cl(3), O(1)) of the
four octahedral faces having O(1) as the common vertex. The
distances of the P(1), C(24), and P(2) atoms from the centroid
of this face are 2.67, 2.66, and 4.45 Å, respectively. The
corresponding distances from the other three faces lie in the
ranges 2.90-3.23, 3.47-4.17, and 5.23-5.97 Å, respectively.
d. Chelate Ring, Re-N Distances, and Back-Bonding. In
each of the four species, the five-membered chelate ring along
with the adjacent pyridine ring constitute a good plane with
mean deviation in the range 0.02-0.03 Å. The dihedral angle
of this plane with the pendent aryl group is 40.9° in 5, 49.6° in
7a, 81.3° in 9a, and 51.2° in 11.
The Re-N lengths are in general shorter than the estimated
single bond value30,31 of 2.14 Å. The double bond character is
assigned to Re-L back-bonding, especially of the t2g(Re)-π*-
(azo) type.1 Consistent with this, the Re-N(3) bond in 5, 7a,
and 11 is ∼0.06 Å shorter than the Re-N(1) bond. Further,
the NdN bond is lengthened to 1.32 Å from the free ligand
value32-34 of 1.25 Å. In 5 and 7a Re-P type back-bonding is
also present and the Re-N lengths are correspondingly longer
than those in 11, where L is the lone π-acid (the case of 6a is
(28) Powell, J. J. Chem. Soc., Chem. Commun. 1989, 200.
(29) Menon, M.; Pramanik, A.; Chakravorty, A. J. Chem. Soc., Dalton
Trans. 1995, 1417.
(30) Goeden, G. V.; Haymore, B. L. Inorg. Chem. 1983, 22, 157.
(31) Nugent, W. A.; Haymore, B. L. Coord. Chem. ReV. 1980, 31, 123.
(32) Mostad, A.; Romming, C. Acta Chem. Scand. 1971, 25, 3561.
model of the transition state. Attack by P(2) on the face with
concomitant edge displacement35,36 of a chloride ligand and Re-
OP(1) bond cleavage can afford 5, as depicted in eq 8. In 5 the

Rhenium(III) Products and Reaction Models
Inorganic Chemistry, Vol. 40, No. 2, 2001 291
ReP1PO fragment has the sterically relaxed conformation 13,
wherein the fac geometry is sustained by back-bonding.
sustaining strong Re-OP bonds until other factors destabilize
them, as in the formation of 11 and 12.
Concluding Remarks
Transfer of one and two oxygen atoms between the azopy-
ridine reagent ReOCl3L and Ph2P(CH2)nPPh2 (PnP) has been
realized via regulation of the relative ratio of the two reactants.
The products are mononuclear Re(OPnP)Cl3L, 4 (n ) 1-3),
and binuclear LCl3Re(OPnPO)ReCl3L, 8 (n ) 2, 3), respec-
tively. The latter are insoluble, but two-atom transfer and
binucleation have been authenticated with the help of pyridine-
2-aldimine dimers L′Cl3Re(OPnPO)ReCl3L′, 9 (n ) 2, 3)
generated from ReOCl3L′ and PnP.
A remarkable reactivity singularity of products occurs for n
) 1. Thus 4 (n ) 1) alone undergoes a spontaneous intramo-
lecular linkage-cum-geometrical isomerization to Re(P1PO)-
Cl3L, 5, via an associative pathway characterized by a large
negative entropy of activation. Again in the n ) 1 case alone,
two-atom transfer furnishes only mononuclear Re(OP1PO)Cl3L,
11, with a dangling phosphine oxide function, which is a vestige
of the transient binucleation that must be occurring on the
reaction path. The steric and electronic scenario promoting these
n ) 1 transformations following oxygen atom transfer has been
analyzed.
Unlike 4a, complexes 4b and 4c fail to isomerize even in
boiling benzene. The longer interphosphorus bridges evidently
make the facial approach of the pendant phosphorus site
improbable (synchronous rotation around more than one bond
required). However 4b and 4c, again unlike 4a, are reactive to
externally added phosphines.
b. Stereodynamic Substitution by External Phosphines.
We first refer to the reaction of eq 9, which is an intermolecular
analogue of that of eq 6. In 6a1 the meridional disposition of
the coordinated phosphine oxide fragment with respect to
octahedral faces is very similar to that in 11 and by inference
to that in 4a. The approach of external PPh3 to the reactive
Ongoing studies concern the effects of variation of the
chelating nitrogenous ligand on reactivity and the structure and
properties of systems incorporating fragments such as Re(PnP),
Re(PnPO) (n >1), and Re(PnPO)Re, which are not covered in
the present work.
6a + PPh3 f 7a + OPPh3
(9)
face can thus be expected to be hindered. Significantly, the
required reaction conditions of eq 9 are relatively drastic (large
PPh3 excess, boiling solvent).
As anticipated, the reaction of eq 9 works as well upon
replacing 6a by 4b or by 11 as in eqs 10 and 11. Complex 4c
Experimental Section
Materials. ReOCl3L, Re(OPPh3)Cl3L, and ReOCl3L′ were prepared
by reported methods.1,3 Dichloromethane and acetonitrile for electro-
chemical, spectral, and synthetic work were purified as before.38,39
Benzene was distilled over sodium before use. All other chemicals and
solvents were of reagent grade and were used as received.
4b + PPh3 f 7a + OP2P
11 + PPh3 f 7a + OP1PO
(10)
(11)
Physical Measurements. UV-vis spectra (CH2Cl2 solution), IR
1
spectra (KBr disk), and H NMR spectra (CDCl3) were recorded on a
Shimadzu UVPC 1601 spectrophotometer fitted with thermostated cell
compartments, a Perkin-Elmer 783 spectrophotometer, and a Bruker
FT 300 MHz spectrometer, respectively. The numbering scheme used
behaves similarly. In contrast, 4a is rapidly converted to 5 under
the same reaction conditions and no 7a is formed, implying
complete dominance of the intramolecular isomerization path-
way of eq 6.
c. Bond Cleavage Following Two-Atom Transfer. Two-
atom transfer to P1P furnishes only mononuclear 11 and 12,
and no binuclear complexes could be isolated. The dangling
phosphine oxide function in 11 and 12, however, strongly
implicates transient binucleation on the reaction pathway.
1
for H NMR is the same as in crystallography. Spin-spin structures
are abbreviated as the following: s, singlet; d, doublet; t, triplet; m,
multiplet; i, ill-resolved. Cyclic voltammetry (in MeCN, 0.1 M TEAP)
was done at a platinum working electrode under nitrogen atmosphere
on a PAR model 370-4 electrochemistry system.26 Microanalyses (C,
H, N) were performed using a Perkin-Elmer 2400 Series II elemental
analyzer.
Preparation of Complexes. Re(OP1P)Cl3L, 4a. To a solution of
P1P (220 mg, 0.57 mmol) in 10 mL of dichloromethane was added a
solution of ReOCl3L (100 mg, 0.19 mmol) in 10 mL of dichloromethane
at room temperature. The solution color rapidly turned from pink to
golden yellow. The solvent was quickly (to avoid isomerization)
removed under reduced pressure, and the yellow solid was repeatedly
washed with hexane to remove excess P1P and then dried in vacuo
over P4O10. Yield: 150 mg (87%). Anal. Calcd for C36H30Cl4N3OP2-
Re: C, 47.47; H, 3.29; N, 4.62. Found: C, 47.32; H, 3.22; N, 4.51.
UV-vis (λmax, nm (ꢀ, M-1 cm-1)): 637 (307); 473 (6340); 284 (14
The instability of such a binuclear intermediate is consistent
with the crowding near the O(2) atom of 11, as expressed in
the ReOP1PO conformation 14. The relatively short nonbonded
distances such as O(2)‚‚‚P(1), 3.55 Å, and O(2)‚‚‚C(12), 3.48
Å, reflect that stable coordination of an ReCl3L fragment to
the O(2) site is not viable. This difficulty disappears upon
lengthening the P‚‚‚P bridge as in 9a; see 15.
The dissociation of the Re-OP bond after oxygen atom
transfer from ReVO to a tertiary phosphines is a well-
documented phenomenon.11,13,16,17,19,37 However the ReCl3L and
ReCl3L′ moieties, like a few others,2,12,14 are unusual in
1
220). IR (cm-1): νRe-Cl, 310, 330; νO-P, 1120; νNdN, 1330. H NMR
(δ (J, Hz)): C5H4N, 27.12 (H(2), d, 8.4); -28.08 (H(3), t, 7.2); 39.75
(H(4), t, 6.6); -9.94 (H(5), d, 6.3); ClC6H4, 30.77 (H(7), H(11), d,
(33) Chang, C. H.; Porter, R. F.; Brauer, S. H. J. Am. Chem. Soc. 1970,
92, 5313.
(34) Ray, T.; Sengupta, S. P. Cryst. Struct. Commun. 1980, 9, 965.
(35) Serpone, N.; Bickley, D. G. Prog. Inorg. Chem. 1972, 17, 391.
(36) Goswami, S.; Chakravarty, A. R.; Chakravorty, A. Inorg. Chem. 1982,
21, 2737.
(37) Bryan, J. C.; Stenkemp, R. E.; Tulip, T. H.; Mayer, J. M. Inorg. Chem.
1987, 26, 2283.
(38) Lahiri, G. K.; Bhattacharya, S.; Ghosh, B. K.; Chakravorty, A. Inorg.
Chem. 1987, 26, 4324.
(39) Sawyer, D. T.; Roberts, J. L., Jr. Experimental Electrochemistry for
Chemists; Wiley: New York, 1974; p 167

292 Inorganic Chemistry, Vol. 40, No. 2, 2001
Bhattacharyya et al.
6.9); 10.68 (H(8), H(10), d, 7.9); P1P, -14.39 (H(24), s); 2.80 (i);
4.12 (t, 7.8); 6.74 (m); 7.08 (t, 7.5); 7.29 (m); 7.36 (m).
H(10), d, 7.5); PPh2Me, -8.35 (H(Me), s); 16.63 (H(o), d, 7.5); 20.55
(H(o), d, 7.5); 8.98 (H(m), t, 7.5); 11.11 (H(m), t, 7.2); 9.59 (H(p), t,
7.5); 10.51 (H(p), t, 7.5).
Re(OP2P)Cl3L, 4b. To a solution of P2P (227 mg; 0.57 mmol) in
10 mL of benzene was added a solution of ReOCl3L (100 mg, 0.19
mmol) in 10 mL of benzene at room temperature, leading to a change
of solution color from pink to golden yellow. The solvent was stripped
under reduced pressure. The residue was dissolved in 5 mL of
dichloromethane and then subjected to chromatography on a silica gel
column. Excess P2P was removed using benzene as the eluant, and
the golden yellow band of 4b was then eluted with a benzene-
acetonitrile (25:1) mixture. Slow evaporation of the eluate afforded 4b
as a golden yellow solid. Yield: 125 mg (71%). Anal. Calcd for C37H32-
Cl4N3OP2Re: C, 48.05; H, 3.46; N, 4.55. Found: C, 48.11; H, 3.39;
N, 4.46. UV-vis (λmax, nm (ꢀ, M-1 cm-1)): 650 (675); 475 (6390);
283 (16 365). IR (cm-1): νRe-Cl, 310, 335; νO-P, 1120; νNdN, 1330. 1H
NMR (δ (J, Hz)): C5H4N, 27.30 (H(2), d, 8.1); -27.87 (H(3), t, 7.2);
40.35 (H(4), t, 6.6); -10.45 (H(5), d, 6.8); ClC6H4, 30.45 (H(7), H(11),
d, 6.6); 10.72 (H(8), H(10), d, 7.2); P2P, -7.53 (H(24), i); -4.21
(H(25), i); 1.62 (i); 3.03 (i); 5.95 (t, 7.0); 6.82 (t, 7.2); 7.34 (m).
Re(OP3P)Cl3L, 4c, was similarly prepared from ReOCl3L and P3P.
Yield: 73%. Anal. Calcd for C38H34Cl4N3OP2Re: C, 48.61; H, 3.62;
N, 4.48. Found: C, 48.53; H, 3.55; N, 4.43. UV-vis (λmax, nm (ꢀ,
LCl3Re(OP2PO)ReCl3L, 8a. To a benzene (10 mL) solution of P2P
(40 mg, 0.10 mmol) was added ReOCl3L, 2 (160 mg, 0.30 mmol),
under stirring. The solvent was then removed under reduced pressure,
and the yellow residue was washed repeatedly with benzene, affording
8a, which was insoluble in all common organic solvents. Yield: 130
mg (85%).
8a was also synthesized by mixing a solution of 4b (100 mg, 0.11
mmol) in benzene (10 mL) with ReOCl3L, 2 (100 mg, 0.19 mmol).
Yield: 120 mg (80%). Anal. Calcd for C48H40Cl8N6O2P2Re2: C, 39.72;
H, 2.76; N, 5.79. Found: C, 39.60; H, 2.71; N, 5.69. IR (cm-1): νRe-Cl
300, 320; νO-P, 1120; νNdN, 1320.
,
LCl3Re(OP3PO)ReCl3L, 8b. It was similarly prepared from ReOCl3L
and P3P. Yield: 85%. Anal. Calcd for C49H42Cl8N6O2P2Re2: C, 40.16;
H, 2.87; N, 5.74. Found: C, 40.30; H, 2.78; N, 5.65. IR (cm-1): νRe-Cl
310, 320; νO-P, 1120; νNdN, 1325.
,
L′Cl3Re(OP2PO)ReCl3L′, 9a. A benzene solution (15 mL) contain-
ing P2P (40 mg, 0.10 mmol) and ReOCl3L′, 3 (150 mg, 0.30 mmol),
was stirred for 3 h at 40 °C. The color changed from orange to pink,
and the solvent was removed under reduced pressure. The residue thus
obtained was dissolved in 5 mL of dichloromethane and subjected to
chromatography on a silica gel column. A band containing Re(OP2P)-
Cl3L′ was first eluted out with a benzene-acetonitrile (25:1) mixture.
The pink band of 9a was then eluted with a benzene-acetonitrile (15:
1) mixture. The solvent was then stripped off under reduced pressure,
and the solid mass was dried in vacuo. Yield: 80 mg (57%). Anal.
Calcd for C52H48Cl6N4O2P2Re2: C, 44.35; H, 3.41; N, 3.98. Found:
C, 44.29; H, 3.46; N, 3.93. UV-vis (λmax, nm (ꢀ, M-1 cm-1)): 675
(3390); 525 (5700); 425sh (3370). IR (cm-1): νRe-Cl, 310; νO-P, 1120;
M-1 cm-1)): 640 (610); 475 (4940); 295 (12 300). IR (cm-1): νRe-Cl
310, 320; νO-P, 1120; νNdN, 1330.
,
Re(P1PO)Cl3L, 5. A 50 mg (0.055 mmol) sample of 4a was
dissolved in 20 mL of benzene, and the solution was kept for 8 h at
room temperature. The solvent was then removed under reduced
pressure, and the residue was dissolved in 5 mL of dichloromethane
and subjected to chromatography on a silica gel column. A yellow band
was eluted with a benzene-acetonitrile (25:2) mixture. The slow
evaporation of the eluate afforded microcrystals of 5. Yield: 42 mg
(84%). Anal. Calcd for C36H30Cl4N3OP2Re: C, 47.47; H, 3.29; N, 4.62.
Found: C, 47.52; H, 3.21; N, 4.55. UV-vis (λmax, nm (ꢀ, M-1 cm-1)):
630 (630); 477 (5465); 298 (11 305). IR (cm-1): νRe-Cl, 300, 320;
ν
CdN, 1600. 1H NMR (δ (J, Hz)): C5H4N, 12.26 (H(2), d, 7.9); -5.88
(H(3), t, 7.5); 28.73 (H(4), t, 6.6); 13.43 (H(5), i); CHdN, -32.13
(H(6), s); MeC6H4, 19.88 (H(8), H(12), d, 7.1); 10.39 (H(9), H(11), d,
7.2); 4.04 (H(p-Me), s); P2P, -11.87 (H(26, 26A), i); 5.43 (H(o), i);
8.56 (H(m), t, 7.4); 7.85 (H(p), t, 7.4).
ν
Re-P 510, 720; νP-O, 1200; νNdN, 1330. 1H NMR (δ (J, Hz)): C5H4N,
26.30 (H(2), i); -34.50 (H(3), i); 46.19 (H(4), i); -19.50 (H(5), i);
ClC6H4, 41.38 (H(7), H(11), i); 12.44 (H(8), H(10), i); P1P, 23.51
(H(24), s); 3.02 (i); 6.37 (t, 7.2); 6.85 (m); 6.95 (t, 6.9); 7.19 (m); 7.29
(i); 7.65 (t, 9.0); 7.77 (t, 6.9); 11.10 (i); 13.29 (d, 6.0); 15.97 (i).
Re(OPPh2Me)Cl3L, 6b. This was prepared from ReOCl3L and PPh2-
Me in the same way as Re(OPPh3)Cl3L1. Yield: 85%. Anal. Calcd for
C24H21Cl4N3OPRe: C, 39.67; H, 2.89; N, 5.79. Found: C, 39.61; H,
2.83; N, 5.72. UV-vis (λmax, nm (ꢀ, M-1 cm-1)): 660 (380); 467
L′Cl3Re(OP3PO)ReCl3L′, 9b. It was prepared similarly to 9a.
Yield: 65%. Anal. Calcd for C53H50Cl6N4O2P2Re2: C, 44.76; H, 3.52;
N, 3.94. Found: C, 44.69; H, 3.57; N, 3.87. UV-vis (λmax, nm (ꢀ,
M-1 cm-1)): 675 (3100); 525 (5800); 425sh (3300). IR (cm-1): νRe-Cl
,
310; νO-P, 1125; νCdN, 1600. 1H NMR (δ (J, Hz)): C5H4N, 12.63 (H(2),
i); -6.62 (H(3), t, 7.8); 29.92 (H(4), i); 12.73 (H(5), d, 9.0); CHdN,
-30.02 (H(6), s), MeC6H4, 21.13 (H(8), H(12), d, 9.0); 11.20 (H(9),
H(11), d, 6.0); 4.51 (H(p-Me), s); P3P, -9.92 (H(26, 26A), i); -6.70
(H(27), i); 5.17 (H(o), i); 7.98 (H(m), t, 7.5); 7.45 (H(p), t, 7.5).
(8145); 288 (13 540). IR (cm-1): νRe-Cl, 300, 320; νO-P, 1120; νNdN
,
1325. 1H NMR (δ (J, Hz)): C5H4N, 26.99 (H(2), d, 8.4); -27.85 (H(3),
t, 7.5); 39.61 (H(4), t, 6.3); -9.50 (H(5), d, 6.0); ClC6H4, 30.37 (H(7),
H(11), d, 7.8); 10.76 (H(8), H(10), d, 7.8); PPh2Me, -4.58 (H(Me),
s); 2.15 (H(o), i); 7.10 (H(m), t, 7.5); 6.60 (H(p), t, 7.5).
LCl3Re(OP2PO)ReCl3L′, 10. To a yellow-colored solution of 4b
(60 mg, 0.06 mmol) in 15 mL of benzene was added 3 (40 mg, 0.08
mmol). The mixture became brick red in color upon stirring for 2 h at
40 °C. The solvent was removed under reduced pressure, and the residue
was washed several times with benzene and finally dried under vacuo.
Yield: 60 mg (67%). Anal. Calcd for C50H44Cl7N5O2P2Re2: C, 42.00;
H, 3.08; N, 4.90. Found: C, 42.12; H, 3.15; N, 4.97. IR (cm-1): νRe-Cl,
310, 320; νO-P, 1140; νNdN, 1325; νCdN, 1600.
Re(PPh3)Cl3L, 7a. To a solution of 6a (100 mg, 0.13 mmol) in
benzene (15 mL) was added PPh3 (350 mg, 1.34 mmol), and the mixture
was heated to reflux under pure nitrogen for 1 h. The resulting solution
was evaporated to dryness, and the residue was washed several times
with hexane (to remove excess PPh3 ) and then subjected to chroma-
tography on a silica gel column. Benzene-acetonitrile mixtures of
compositions 50:1, 25:1, and 10:1, respectively, eluted out Re(NC6H4-
Cl)Cl3L (and OPPh3), unreacted 6a, and 7a, which was isolated by
evaporation of the solvent from last fraction. Yield: 50 mg (48%).
Anal. Calcd for C29H23Cl4N3PRe: C, 45.08; H, 2.98; N, 5.44. Found:
C, 45.19; H, 2.92; N, 5.53. UV-vis (λmax, nm (ꢀ, M-1 cm-1)): 640
Re(OP1PO)Cl3L, 11. A solution of P1P (50 mg, 0.13 mmol) and 2
(200 mg, 0.38 mmol) in 15 mL of benzene was stirred for 30 min at
room temperature. The solvent was then stripped off under reduced
pressure, and the solid mass was subjected to chromatography on a
silica gel column. The golden yellow band of 11 was eluted out with
a benzene-acetonitrile (16:1) mixture, and the microcrystalline complex
was isolated by slow evaporation. (At best 11 can account for 50% of
the total rhenium. The remaining metal remains adsorbed on the column
in the form of one or more intractable species.) Yield of 11: 90 mg
(75%). Anal. Calcd for C36H30Cl4N3O2P2Re: C, 46.65; H, 3.24; N, 4.54.
Found: C, 46.74; H, 3.29; N, 4.59. UV-vis (λmax, nm (ꢀ, M-1 cm-1)):
(610); 475 (4980); 295 (12 100). IR (cm-1): νRe-Cl, 300, 320; νRe-P
,
1
500, 710; νNdN, 1325. H NMR (δ (J, Hz)): C5H4N, 21.21 (H(2), d,
9.0); -31.66 (H(3), i); 40.08 (H(4), i); -19.80 (H(5), i); ClC6H4, 31.66
(H(7), H(11), i); 11.94 (H(8), H(10), d, 6.0); PPh3, 13.76 (H(o), i);
8.72 (H(m), i); 9.04 (H(p), i).
Re(PPh2Me)Cl3L, 7b. It was similarly prepared from Re(OPPh2-
Me)Cl3L and PPh2Me. Yield: 50%. Anal. Calcd for C24H21Cl4N3PRe:
C, 40.56; H, 2.96; N, 5.92. Found: C, 40.47; H, 2.89; N, 5.99. UV-
vis (λmax, nm (ꢀ, M-1 cm-1)): 637 (580); 470 (5020); 289 (10 500). IR
(cm-1): νRe-Cl, 310, 320; νRe-P, 500, 710; νNdN, 1330. 1H NMR (δ (J,
Hz)): C5H4N, 23.05 (H(2), d, 8.1); -33.14 (H(3), t, 6.9); 41.10 (H(4),
i); -19.16 (H(5), i); ClC6H4, 32.23 (H(7), H(11), d, 7.8); 12.20 (H(8),
650 (430); 470 (5395); 294 (11 420). IR (cm-1): νRe-Cl, 310, 330;
1
ν
O-P, 1120 (coordinated to metal); νP-O, 1200 (free) νNdN, 1325. H
NMR (δ (J, Hz)): C6H4N, 26.98 (H(2), d, 8.0); -27.40 (H(3), t, 7.2);
38.62 (H(4), t, 6.0); -9.01 (H(5), d, 7.2); ClC6H4, 30.41 (H(7), H(11),
d, 7.2); 10.64 (H(8), H(10), d, 7.6); P1P, -14.40 (H(24), s); 3.42 (i);
4.52 (t, 7.2); 6.66 (t, 7.2); 7.08 (m).

Rhenium(III) Products and Reaction Models
Inorganic Chemistry, Vol. 40, No. 2, 2001 293
Table 6. Crystallographic Data for 5‚1.5C6H6, 7a‚CH2Cl2, 9a, and 11
5‚1.5C6H6
7a‚CH2Cl2
9a
11
empirical formula
fw
cryst size, mm
cryst syst
space group
a, Å
C45H39Cl4N3OP2Re
1027.73
C30H25Cl6N3PRe
857.40
0.45 × 0.25 × 0.10
monoclinic
P21/n
11.695(6)
17.745(7)
C52H48Cl6N4O2P2Re2
1407.98
0.25 × 0.20 × 0.15
monoclinic
C2/c
19.767(12)
12.868(6)
22.20(2)
C36H30Cl4N3O2P2Re
926.57
0.4 × 0.4 × 0.2
monoclinic
I2/a
16.866(6)
12.583(6)
0.45 × 0.30 × 0.20
triclinic
P1h
10.034(2)
10.737(2)
20.357(4)
89.38(3)
87.79(3)
80.22(3)
2159.7(7)
2
b, Å
c, Å
15.459(9)
34.78(2)
R, deg
â, deg
100.94(5)
101.76(6)
99.22(4)
γ, deg
V, Å3
3150(3)
4
1.81
44.44
5.85, 14.03
5530(6)
4
1.69
47.64
6.35, 11.12
7285(7)
8
1.69
37.54
5.71, 10.19
Z
F
calcd, g cm-3
1.58
31.73
3.03, 6.90
µ, cm-1
R,a wR2b [I > 2σ(I)], %
a R ) ∑||Fo| -|Fc||/∑|Fo|. b wR2 ) [∑w(Fo - Fc2)2/∑w(Fo )2]1/2
.
2
2
Re(OP1PO)Cl3L′, 12. It was prepared in the same manner as 11
from 3 and P1P. Here stirring has to be done for 3 h at 40 °C, and the
color of the complex is pink. Yield: 70%. Anal. Calcd for C38H34-
Cl3O2P2Re: C, 50.41; H, 3.76; N, 3.10. Found: C, 50.49; H, 3.71; N,
3.16. UV-vis (λmax, nm (ꢀ, M-1 cm-1)): 675 (2300); 525 (4250); 425sh
X-ray Structure Determination. Single crystals were grown either
by slow diffusion of hexane into benzene solution (5‚1.5 C6H6, 11) or
dichloromethane solution (7a‚CH2Cl2) or by slow evaporation of
benzene solution (9a). Cell parameters were determined by a least-
squares fit of 30 machine-centered reflections (14° e 2θ e 28°). Data
were collected by the ω scan technique in the range 3° e 2θ e 47° for
5‚1.5 C6H6, 3° e 2θ e 50° for 7a‚CH2Cl2 and 9a, and 3° e 2θ e 48°
for 11 on a Siemens R3m/V four-circle diffractometer with graphite-
monochromated Mo KR (λ ) 0.710 73 Å) radiation at 25 °C. Two
check reflections after each 198 reflections showed no intensity
reduction for any of the crystals. All data were corrected for Lorentz-
polarization effects and absorption.40
The metal atoms were located from Patterson maps, and the rest of
the non-hydrogen atoms emerged from successive Fourier synthesis.
The structures were refined by full-matrix least-squares procedures on
F 2. All non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were included at calculated positions. In 5‚1.5 C6H6 the solvent
of crystallization lies on a center of symmetry and in a general position.
Calculations were performed using the SHELXTL V 5.0341 program
package. Significant crystal data are listed in Table 6.
(2790). IR (cm-1): νRe-Cl, 310; νO-P, 1120 (coordinated to metal); νP-O
,
1160 (free) νCdN, 1600. 1H NMR (δ (J, Hz)): C6H4N, 13.23 (H(2), d,
6.8); -5.42 (H(3), i); 30.30 (H(4), i); 13.88 (H(5), i); CHdN, -30.51
(H(6), s); MeC6H4, 21.23 (H(8), H(12), d, 6.0); 11.15 (H(9), H(11), d,
9.0); 4.19 (H(p-Me), s); P1P, -11.43 (H(26), s); 2.36 (i); 3.24 (t, 9.0);
6.82 (t, 7.2); 7.00 (i); 7.36 (i).
Other Reactions. a. Reaction of 4b with PPh3. To a solution of
4b (50 mg, 0.06 mmol) in dry benzene (10 mL) was added PPh3 (160
mg, 0.61 mmol). The mixture was then heated to reflux in nitrogen
atmosphere for 45 min. The complex 7a was then isolated from the
reaction mixture using the procedure described earlier. Yield: 12 mg
(28%).
b. Reaction of 11 with PPh3. The above reaction was repeated with
11 in place of 4b, affording 7a (Yield: 34%).
c. Reaction of 4a with PPh3. To a solution of 4a (50 mg, 0.06
mmol) in dry benzene (10 mL) was added PPh3 (160 mg, 0.61 mmol).
The mixture was then heated to reflux in nitrogen atmosphere for 45
min. The solvent was then removed under reduced pressure, and the
residue was washed several times with hexane and then subjected to
chromatography on a silica gel column. Benzene-acetonitrile mixtures
of compositions 50:1 and 10:1, respectively, eluted out Re(NC6H4Cl)-
Cl3L and 5 (yield: 25 mg, 50%).
Acknowledgment. We thank the Department of Science and
Technology, Indian National Science Academy, and the Council
of Scientific and Industrial Research, New Delhi, for financial
support. Affiliation with the Jawaharlal Nehru Centre for
Advanced Scientific Research, Bangalore, India, is acknowl-
edged.
Rate Measurements. Benzene solutions of 4a were used, and the
rate was followed spectrophotometrically at 468 nm. The absorbance
At was recorded as a function of time t, and A was measured when
the reaction was complete (24 h). Values of the first-order rate constants
were obtained from the slopes of the linear plots of -ln(At - A ) versus
t. The rate constant was independent of concentration (range used (1-
3) × 10-4 M) within experimental error. The activation enthalpy (∆Hq)
and entropy (∆Sq) parameters were calculated from the Eyring equation
(eq 12) utilizing rate constant data obtained over the temperature range
298-313 K.
Supporting Information Available: X-ray crystallographic files,
in CIF format, for the structure determinations of 5‚1.5 C6H6, 7a‚CH2-
Cl2, 9a, and 11, and kinetic results (time-dependent spectra, linear -ln-
(At - A ) versus t plot, Eyring plot) for 4a. These materials are available
free of charge via the Internet at http://pubs.acs.org.
IC0005893
(40) North, A. C. T.; Philips, D. C.; Mathews, F. S. Acta Crystallogr. 1968,
24A, 351.
(41) Sheldrick, G. M. SHELXTL V 5.03; Bruker Analytical X-ray Sys-
tems: Part Number 269-015900, Madison, WI, 1994.
k ) (kBT/h)[exp(-∆Hq/RT) exp(∆Sq/R)]
(12)