Syntheses and molecular structure of some Rh and Ru complexes with the chelating diphenyl (2-pyridyl)phosphine ligand

Article abstract of DOI:10.1021/ic051442k

The rhodium(III) complex mer,cis-[RhCl₃(PPh₂py-P,N) (PPh₂py-P)] (1) (PPh₂py = diphenyl (2-pyridyl)phosphine) has been prepared from RhCl₃·3H₂O and PPh ₂py and converted to the trans,cis-[RhCl₂(PPh ₂py-P,N)₂]PF₆ (2) in acetone solution by treatment with Ag⁺ and PF₆^-. Ruthenium(III) and ruthenium(II) compounds with PPh₂py, mer,cis-[RuCl ₃(PPh₂Py-P,N)(PPh₂Py-P)] (3) and mer-[RuCl(PPh₂py-P,N)₂(PPh₂py-P)]Cl (5) have been obtained from DMSO precursor complexes. In a chloroform solution, complex (5) isomerizes to fac-[RuCl(PPh₂py-P,N)₂(PPh ₂py-P)]Cl (fac-5). All compounds have been characterized by MS, UV-vis, IR, and ¹H and ³¹P{¹H} NMR spectroscopy, and the Ru(III) compound has been characterized by EPR spectroscopy as well. The crystal structures of 1, 2, 3, and fac-5 have been determined. In all compounds under investigation, at least one pyridylphosphine acts as a chelate ligand. The ³¹P chemical shifts for chelating PPh₂py-P,N depend on the Ru-P bond lengths.

Full text of DOI:10.1021/ic051442k

Inorg. Chem. 2006, 45, 3369−3377
Syntheses and Molecular Structure of Some Rh and Ru Complexes with
the Chelating Diphenyl (2-Pyridyl)phosphine Ligand
Katarzyna Wajda-Hermanowicz,* Zbigniew Ciunik, and Andrzej Kochel
Faculty of Chemistry, UniVersity of Wrocław, 14 Joliot-Curie Street, 50-383 Wrocław, Poland
Received August 24, 2005
The rhodium(III) complex mer,cis-[RhCl3(PPh2py-P,N)(PPh2py-P)] (1) (PPh2py
) diphenyl (2-pyridyl)phosphine) has
been prepared from RhCl3‚3H2O and PPh2py and converted to the trans,cis-[RhCl2(PPh2py-P,N)2]PF6 (2) in acetone
solution by treatment with Ag+ and PF6-. Ruthenium(III) and ruthenium(II) compounds with PPh2py, mer,cis-
[RuCl3(PPh2py-P,N)(PPh2py-P)] (3) and mer-[RuCl(PPh2py-P,N)2(PPh2py-P)]Cl (5) have been obtained from DMSO
precursor complexes. In a chloroform solution, complex (5) isomerizes to fac-[RuCl(PPh2py-P,N)2(PPh2py-P)]Cl
1
(fac-5). All compounds have been characterized by MS, UV
−
vis, IR, and H and 31P
{
1H
}
NMR spectroscopy, and
the Ru(III) compound has been characterized by EPR spectroscopy as well. The crystal structures of 1, 2, 3, and
fac-5 have been determined. In all compounds under investigation, at least one pyridylphosphine acts as a chelate
ligand. The 31P chemical shifts for chelating PPh2py-P,N depend on the Ru
−P bond lengths.
Introduction
modes are possible with this compound: P-monodentate,6,7
N-monodentate,8 P-N bridge in homo6c,9-14 and hetero7,10,15
Tertiary phosphines form stable complexes with many
transition metals in their various oxidation states. Bidentate
ligands containing “soft” phosphorus and “hard” nitrogen
donors are extremely useful in both coordination chemistry
and homogeneous catalysis. Heterodifunctional ligands ex-
hibit very interesting properties, such as selective binding
to metal ions of different types (hard and soft), dynamic
behavior via reversible dissociation of the weaker metal-
ligand bond, or stereoelectronic control of the coordination
sphere of the metal. The P-N ligands with the π-acceptor
phosphorus atom can stabilize a low oxidation state of the
metal. The σ-donor ability of the nitrogen should help
stabilize a higher oxidation state and makes the metal more
susceptible to an oxidative addition reaction. Among the most
widely studied hemilabile1 P-N ligands, a prominent posi-
tion is occupied by the pyridyl phosphines,2-4 including chiral
derivatives.5 Diphenyl (2-pyridyl)phosphine (PPh2py) is one
of the most useful phosphine ligands applied in coordination
chemistry of the transition metals. Four different coordination
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10.1021/ic051442k CCC: $33.50
Published on Web 03/24/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 8, 2006 3369

Wajda-Hermanowicz et al.
binuclear compounds as well as in oligomers7,16 and clusters17
and the P-N chelate mode.6g,18 Diphenyl (2-pyridyl)-
phosphine in its chelating coordination mode forms four-
membered rings that are strained and relatively unstable.
However, this coordination mode plays a key role in
catalysis, e.g., in the carbonylation of alkynes by palladium
complexes.19-21 A detailed knowledge of the ground-state
geometry of the metal complexes facilitates a discussion of
structure-reactivity relationships. To establish the steric
demand of the chelate-coordinated PPh2py ligand, we
prepared and structurally characterized some new rhodium
and ruthenium complexes.
Experimental Section
Synthesis. All reactions were performed under an inert atmo-
sphere using standard Schlenk techniques.
The starting complexes cis-RuCl2(DMSO-S)3(DMSO-O)22,23 and
mer-RuCl3(DMSO-S)2(DMSO-O)24,25 were prepared according to
the literature procedures. RhCl3‚3H2O and PPh2py (Aldrich) were
used as received.
mer,cis-[RhCl3(PPh2py-P,N) (PPh2py-P)] (1). PPh2py (0.3 g,
1.14 mmol) in CH2Cl2 (15 cm3) was added with stirring to a warm
solution of RhCl3‚3H2O (0.15 g, 0.57 mmol) in anhydrous ethanol
(10 cm3). The mixture was refluxed for 2 h. The resulting orange
solution was reduced in volume to about 5 cm3.The orange complex
1 that deposited was filtered off, washed with diethyl ether, and
dried under vacuum (yield: 0.37 g, 88%). Anal. Calcd. for C34H28-
Cl3N2P2Rh (fw 735.8): C, 55.5; H, 3.8; N, 3.8; Cl, 14.5; P, 8.4.
Found: C, 55.1; H, 3.8; N, 3.7; Cl, 14.4; P, 8.0. MS-ESI m/z
(%): 699 (100), [RhCl2(PPh2py)2]+; 664 (58), [RhCl(PPh2py)2]+;
627 (10), [Rh(PPh2py)2]+. IR (cm-1, KBr): 3058 vw, 1582 vw
(νCN), 1572 w (νCN), 1482 w, 1449 w, 1434 vs, 1187 vw, 1162
vw, 1020 vw, 998 vw, 766 w, 743 m, 691 vs, 645 vw, 617 vw,
534 s, 521 vs, 505 vs; (Nujol) 495 w, 458 w (δCN), 443 m (δCN),
434 m (δCN), 424 w (δCN), 417 w, 401 w, 349 vs (νRh-Cl), 328 s
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1
(νRh-Cl), 284 vs (νRh-Cl), 258 w, 231 w, 221 s, 210 vw. H NMR
(CD2Cl2, 500 MHz, 298 K): δ 9.17 (t, 1H, H6 py(P,N)), 8.26 (d,
1H, H6 py(P)), 7.99 (m, 1H, H3 py(P)), 7.92-7.85 (m, 4H, H2
Ph(P)), 7.72 (m, 1H, H5 py(P,N)), 7.54-7.40 (m, 10H, H3 py-
(P,N), H4 py(P), H2 Ph(P,N), H4 Ph(P,N), H4 Ph(P)), 7.33-7.22
(m, 9H, H4 py(P,N), H3 Ph(P,N), H3 Ph(P)), 7.10 (m, 1H, H5
py(P)). 31P{1H} NMR (CD2Cl2, 500 MHz, 298 K): δ 31.19 (dd,
JRh-P ) 113.2 Hz, JP-P ) 9.6 Hz, P(P)), -31.97 (dd, JRh-P ) 100.4
Hz, JP-P ) 9.6 Hz, P(P,N)). UV-vis (CH2Cl2, nm (ꢀ, cm-1 M-1)):
289 (17 240), 366 (1430), 451 (350).
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DeCian, A.; Fischer, J. Inorg. Chem. 1993, 32, 1656. (b) Lo Schiavo,
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Zuber, M.; Rusek, G.; Gałdecka, E.; Gałdecki, Z. Inorg. Chim. Acta
1995, 232, 207. (e) Gałdecka, E.; Gałdecki, Z.; Wajda-Hermanowicz,
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1996, 508, 75. (g) Belletti, D.; Graiff, C.; Massera, C.; Predieri, G.;
Tiripicchio, A. Inorg. Chim. Acta 2003, 350, 421. (h) Choi, Y.-Y.;
Wong, W.-T. J. Organomet. Chem. 1999, 573, 189. (i) Hong, F.-E.;
Chang, Y.-C.; Chang, R.-E.; Lin, C.-C.; Wang, S.-L.; Liao, F.-L. J.
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Tripicchio, A. Inorg. Chem. 2002, 41, 1372.
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455, 247.
X-ray diffraction quality orange crystals of 1 were isolated from
a CH2Cl2 solution of the complex that had been layered with EtOH.
trans-[RhCl2(PPh2py-P,N)2]PF6 (2). AgNO3 (0.021 g, 0.12
mmol) was added to an acetone (10 cm3) suspension of 1 (0.09 g,
0.12 mmol), and the mixture was stirred in the dark for 20 min.
The AgCl was filtered off through a small Celite plug, and NaPF6
(0.021 g, 0.12 mmol) in acetone (10 cm3) was added to the resulting
yellow solution. After being stirred for ca. 10 min, the solution
was concentrated to 5 cm3 under reduced pressure, and Et2O (10
cm3) was added. The yellow solid was collected by suction filtration,
washed with Et2O, and dried under vacuum (yield: 0.0613 g, 60%).
Anal. Calcd. for C34H28Cl2FN2P3Rh (fw 845.3): C, 48.3; H, 3.3;
N, 3.3. Found: C, 47.9; H, 3.3; N, 3.2. MS-ESI m/z (%): 699
(100), [RhCl2(Ph2py)2]+; 664 (40), [RhCl(Ph2py)2]+. IR (cm-1
,
KBr): 3443 br/w, 3050 vw, 1584 w (νCN), 1482 w, 1452 w, 1436
s, 1384 s, 1332 vw, 1281 vw, 1262 vw, 1186 vw, 1162 vw, 1134
vw, 1100 m, 1018 w, 999 vw, 840 vs (νPF), 767 vw, 741 w, 712
vw, 687 m, 645 vw, 616 vw, 558 s (δPF), 537 s, 525 m, 513 s;
(Nujol) 495 s, 429 m (δCN), 361 s (νRh-Cl), 338 vw, 325 vw, 292
vw, 276 vw, 266 vw, 220 w, 201 m, 160 w.1H NMR ((CD3)2CO,
300 MHz, 298 K): δ 9.41 (t, 1H, H6 py), 8.58-8.47(m, 3H, H4
Ph + H4 py), 8.18 (m, 1H, H5 py), 7.73-7.65 (m, 4H, H2 Ph),
7.49-7.42 (m, 5H, H3 py + H3 Ph). 31P{1H} NMR ((CD3)2CO,
(22) Evans, I. P.; Spencer, A.; Wilkinson, G. J. Chem. Soc., Dalton Trans.
1973, 204.
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Dalton Trans. 1975, 1006.
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Mestroni, G. Inorg. Chem. 1991, 30, 609.
3370 Inorganic Chemistry, Vol. 45, No. 8, 2006

Chelating Diphenyl (2-Pyridyl)phosphine Ligand
300 MHz, 298 K): δ -15.1 (d, JRh-P ) 93.9 Hz), -144.27 (sep,
JP-F ) 713 Hz). UV-vis (acetone, nm (ꢀ, cm-1 M-1)): 295
(60 200), 328 (1880), 424 (280).
Yellow crystals of 2-(CH3)2CO were grown by freezing an
acetone solution of 2 into which Et2O had been added.
fac-[RuCl(PPh2py-P,N)2(PPh2py-P)]Cl (fac-5).18h X-ray dif-
fraction quality orange crystals of fac-5‚2CHCl3 were isolated from
a CHCl3 solution of complex 5 that had been layered with Et2O.
Physical Measurements. IR spectra were recorded on a Bruker
IFS113v; UV-vis spectra were recorded on Bruker DU 7500 and
Cary 5 spectrometers. Electrospray mass spectra were recorded on
a Finnigan MAT TSQ 700 triple stage quadrupole mass spectrom-
eter equipped with an electrospray ion source. EPR spectra were
measured on a Bruker ESP 300E spectrometer equipped with a
variable-temperature accessory and a liquid N2 Dewar insert. The
1H and 31P{1H} NMR spectra were recorded on Bruker AMX 300
and Avance 500 spectrometers. The chemical shifts in the 1H NMR
spectra were referenced to the residual proton impurities in the
deuterated solvents and 31P{1H} NMR spectra to external 85% H3-
PO4. Conductivity measurement was made at 25 °C on freshly made
0.5 mM solution of a complex in acetone, using an electrochemical
meter universal instrument (Technical University Wrocław, Poland).
The magnetic susceptibility was measured using a Quantum Design
SQUID magnetometer (type MPMS-5). The magnetic moment
values were calculated after considering the appropriate diamagnetic
corrections.
X-ray Structural Determination. The studied crystals were
mounted onto a glass fiber and then flash-frozen to 100 K (Oxford
Cryosystem cooler). Preliminary examination and intensity data
collection were carried out on a Kuma KM4CCD κ-axis diffrac-
tometer with graphite-monochromated Mo KR radiation (λ )
0.71073 Å). Crystals were positioned at 65 mm from the CCD
camera. A total of 612 frames were measured at 0.75° intervals
with a counting time of 15-20 s. Accurate cell parameters were
determined and refined by least-squares fit of 3900-7000 of the
strongest reflections. The data were corrected for Lorentz and
polarization effects, and the analytical absorption corrections were
also applied. Data reduction and analysis were carried out with the
Oxford Diffraction (Poland) programs. Structures were solved by
the heavy atom method (program SHELXS9726) and refined by
the full-matrix least-squares method on all F2 data using the
SHELXL9727 programs. Non-hydrogen atoms were refined with
anisotropic displacement parameters; hydrogen atoms were included
from geometry of molecules and ∆F maps. They were treated as
riding groups during the refinement process. The absolute structures
of chiral crystals were determined by Flack’s method.28 Crystal
data are given in Table 1, together with refinement details.
mer,cis-[RuCl3(PPh2py-P,N)(Ph2py-P)] (3). mer-[RuCl3(DMSO-
S)2(DMSO-O)] (0.0442 g, 0.1 mmol) was dissolved in CH2Cl2 (5
cm3). Ph2py (0.0526 g, 0.2 mmol) in the same solvent (5 cm3) was
added, and the resulting mixture was stirred at room temperature
for 3 h. The resulting red-orange solution was reduced in volume
to about 5 cm3 and Et2O (25 cm3) was added, giving an orange
solid. This precipitate was filtered off, washed with diethyl ether,
and dried under vacuum (yield: 0.0624 g, 85%). Anal. Calcd. for
C34H28Cl3N2P2Ru (fw 734.0): C, 55.6; H, 3.9; N, 3.8; Cl, 14.5; P,
8.4. Found: C, 55.2; H, 3.8; N, 3.7; Cl, 14.3; P, 8.0. MS-ESI m/z
(%): 697 (50), [RuCl2(Ph2py)2]+; 662 (100), [RuCl(Ph2py)2]+; 626
(10), [Ru(Ph2py)2]+. IR (cm-1, KBr): 3440 m, 3057 vw, 1582 vw
(νCN), 1571 w (νCN), 1481 m, 1448 w, 1434 vs, 1330 vw, 1309
vw, 1270 vw, 1186 vw, 1162 vw, 1131 vw, 1092 m, 1017 w, 998
vw, 986 vw, 765 m, 743 m, 727 w, 691 vs, 642 vw, 617 vw, 568
vw, 531 vs, 516 vs; (Nujol) 497 vs, 455 m (δCN), 443 m (δCN),
431 m (δCN), 424 m (δCN), 416 w, 400 w, 339 vs (νRu-Cl), 323 s
(νRu-Cl), 282 vs (νRu-Cl), 255 w, 230 w, 214 w. UV-vis (CHCl3,
nm (ꢀ, cm-1 M-1)): 248 (12 850), 364 (2510), 447 (1040), 504
(690).
Orange single crystals of 3 appropriate for X-ray measurements
were grown from chloroform/ether via the slow vapor diffusion
technique.
[NBu4][mer-RuCl3(DMSO-S)3] (4). Cis-RuCl2(DMSO-S)3-
(DMSO-O) (0.024 g, 0.05 mmol) was dissolved in 10 cm-3 of a
1:1 mixture of CH2Cl2 and CH3OH, and 0.015 g of [NBu4]Cl‚H2O
(0.05 mmol) was then added. The yellow solution was refluxed
for 15 min and vacuum-evaporated to 2 cm3. Et2O (10 cm3) was
then added. The yellow solid was collected by filtration, washed
several times with Et2O, and dried in a vacuum (yield: 0.024 g,
68%). Anal. Calcd. for C22H54Cl3NRuS3O3 (fw 684.3): C, 38.6; H,
8.0; N, 2.1; S, 14.1. Found: C, 38.4; H, 8.0; N, 2.1; S, 14.0. MS-
ESI m/z (%): 441 (75), [RuCl3(DMSO)3]-; 363 (100), [RuCl3-
(DMSO)2]-. IR (cm-1, KBr): 3405 br/vs, 2960 vs (cation), 2874
vs (cation), 1634 m, 1487 vs (cation), 1382 s (cation), 1307 w,
1287 vw, 1151 w, 1105 s (νS-O), 1081 s (νS-O), 1028 s, 973 w,
925 vw, 882 m (cation), 800 vw, 739 w, 709 vw, 676 w; (Nujol)
425 s (νRu-S), 384 m (δCSO), 345 m (νRu-Cl), 334 sh/m (νRu-Cl),
297 w (νRu-Cl), 266 w, 241 w.
Results and Discussion
mer-[Ru Cl(PPh2py-P,N)2(PPh2py-P)]Cl (5). A solution of
PPh2py in acetone (10 cm3) was added dropwise (0.0237 g, 0.09
mmol) to an acetone (5 cm3) solution of 4 (0.0205 g, 0.03 mmol).
The mixture was stirred at room temperature for 3 h. The solution
was concentrated and Et2O (20 cm3) was added, giving an orange
solid. This was filtered off, washed with diethyl ether, and dried
under vacuum (yield: 0.0066 g, 23%). Anal. Calcd. for C51H42-
Cl2N3P3Ru (fw 961.8): C, 63.7; H, 4.4; N, 4.4; Cl, 7.4. Found: C,
63.5; H, 4.4; N, 4.4; Cl, 7.2. MS-ESI m/z (%): 926 (8), [RuCl-
Rhodium Complexes. Diphenyl (2-pyridyl)phosphine is
a potentially P-N chelating ligand, but the rhodium(I) metal
center seems to favor a bidentate bridging coordination.9,12,29
Up to now, the P-N chelation to rhodium(I) was postulated
only by Faraone for cationic complex [Rh(COD)(PPh2py)]X
(X ) ClO4, PF6). The P-N chelate coordination was sup-
ported only by chemical analysis, IR spectra, and conductiv-
ity measurements; NMR spectra and X-ray structure were
not investigated.7 It is well-known that rhodium(II) com-
plexes are binuclear with a PPh2py molecule coordinated as
a bidentate bridging ligand.13,14 The compound [Cp*RhCl-
(Ph2py)3]+; 663 (100), [RuCl(Ph2py) ]+. IR (cm-1, KBr): 3434
2
br/s, 3049 w, 1583 vw (νCN), 1571 w (νCN), 1482 w, 1444 w, 1435
vs, 1309 vw, 1262 w, 1186 w, 1158 w, 1119 m, 1096 s, 1022 w,
998 vw, 802 vw, 772 w, 766 w, 745 m, 724 w, 697 s, 618 vw, 522
s, 514 s; (Nujol) 493 s, 466 m (δCN), 445 m (δCN), 433 m (δCN),
424 m (δCN), 279 m (νRu-Cl), 264 vw, 254 vw, 229 vw, 203 vw.
1H NMR ((CD3)2CO, 300 MHz, 298 K): δ 9.07 (t, H6 py(P,N)),
8.4-6.45 (m, H py + H Ph phosphine ligands). 31P{1H} NMR
((CD3)2CO, 300 MHz, 298 K): δ 53.05 (t, JP-P ) 30.5 Hz, Pterminal),
-2.80 (d, Pchelate).
18k
(PPh2py-P,N)]ClO4 is the only known example of P-N
(26) Sheldrick, G. M. SHELXS97: Program for Solution of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(27) Sheldrick, G. M SHELXL97: Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(28) Flack, H. D. Acta Crystallogr., Sect. A 1983, 39, 876.
(29) Mague, J. T. Orgamometallics 1986, 5, 918.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3371

Wajda-Hermanowicz et al.
Table 1. Crystal Data and Structure Refinement for RhCl3(PPh2py-P,N)(PPh2py-P) (1), [RhCl2(PPh2py-P,N)2]PF6 (2), RuCl3(PPh2py-P,N)(PPh2py-P)
(3), and [RuCl(PPh2py-P,N)2(PPh2py-P)]Cl (fac-5)
1
2
3
fac-5
empirical formula
fw
C34H28N2Cl3P2Rh
735.78
C37H34F6N2OCl2P3Rh
903.38
C34H28N2Cl3P2Ru
733.94
C53H44N3Cl8P3Ru
1200.49
T (K)
100(2)
100(2)
100(2)
100(2)
λ (Å)
0.71073
orthorhombic
P212121
11.0841(8)
14.9184(12
18.5128(14
90
90
90
3061.2(4)
4
1.596
0.71073
orthorhombic
P21212
13.2352(9)
11.0135(9)
13.1525(12)
90
90
90
1917.2(3)
2
1.565
0.71073
monoclinic
P21/n
0.71073
triclinic
P1h
11.781(2)
15.449(3)
17.961(4)
67.72(3)
85.64(3)
76.35(3)
2939.2(10)
2
1.356
0.748
1216
0.15 × 0.15 × 0.10
2.88-27.00
-15 < h < 15,
-19 < k < 19,
-22 < l < 16
38 268
cryst syst
space group
a (Å)
9.046(2)
b (Å)
c (Å)
21.331(4)
16.040(3)
90
90.21(3)
90
3095.1(11)
4
1.575
0.897
1484
0.12 × 0.08 × 0.06
3.22-27.00
-11 < h < 8,
-27 < k < 27,
-20 < l < 20
30 232
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
Dc (mg m-3
)
µ (mm-1
F(000)
)
0.953
1488
0.772
912
cryst size (mm3)
0.16 × 0.12 × 0.09
3.29-27.00
-14 < h < 8,
-19 < k < 19,
-23 < l < 23
20 492
0.22 × 0.18 × 0.15
3.45-27.00
-16 < h < 16,
-12 < k < 14,
-13 < l < 16
12 782
θ range for data collection (deg)
ranges of h,k,l
no. of reflns collected
no. of independent reflns (Rint
data/params
)
6566 (0.0711)
6566/380
0.863/0.919
0.920
4144 (0.0350)
4144/239
0.848/0.893
1.082
6755 (0.1240)
6755/379
0.900/0.948
1.201
12798 (0.0980)
12798/613
0.896/0.929
1.123
abs coeff min/max
GOF (F2)
final R1/wR2 indices (I > 2σI)
0.0475/0.0484
0.00050(9)
0.408/-0.454
-0.06(3)
0.0342/0.0749
0.0009(4)
0.801/-0.914
-0.01(3)
0.0762/0.1693
0.0883/0.1810
extinction coeff
largest diff peak/hole (e Å-3
Flack’s param
)
1.548/-0.936
1.304/-1.387
2
chelate coordination to rhodium. For this reason, the rho-
dium(III) metal center should be a good candidate for
preparation of such complexes with a PPh2py molecule.
The reaction of two moles of PPh2py with one mole of
RhCl3‚3H2O in ethanolic solution at room temperature gave
an air-stable, orange solid of formula [RhCl3(PPh2py)2]. The
ESI(+) MS shows no parent ion but does show fragments
[RhCl2(Ph2py)2]+, [RhCl(Ph2py)2]+, and [Rh(Ph2py)2]+ (with
the correct isotopic distributions) that correspond to the peaks
at m/z 699, 664, and 627, respectively. Two different
was formed. The small JPP value (9.6 Hz) indicates that
phosphine ligands occupy cis coordination sites. The trans
2Jpp is usually large, a few hundred Hz, whereas the cis
coupling constant is small.32 Of the two 31P NMR resonances,
the one at lower frequency with a smaller 1JRh-P is assigned
to the phosphorus trans to the chlorine atom. The other
1
resonance at higher frequency with JRh-P ) 113.2 Hz is
assigned to the phosphine ligand trans to the nitrogen atom.
The JRh-P value (100.4 Hz) for the phosphine trans to the
1
chlorine is smaller than the values reported for rhodium(III)
complexes of the type mer-[RhCl3(PR3)3], in which the
phosphine ligand is trans to chlorine.32 The lower value of
1JRh-P indicates a longer Rh-P distance, probably because
of the strain in the four-membered chelating ring. Coordina-
tion of the N atom of PPh2py to a metal ion is expected to
shift the IR bands of the pyridine ring to higher frequencies
by 10-30 cm-1.33 The band located at 1582 cm-1 is assigned
to the ν(CdN) stretching vibration. The energy of this band
is lower in comparison with that of the free PPh2py ligand
and indicates the presence of N-coordinated pyridyl. The far-
IR spectrum shows three ν(Rh-Cl) bands in the region 350-
280 cm-1 (349, 328, and 284 cm-1), which are expected for
the mer geometry.34 All above results allow us to concluded
that complex 1 is the mononuclear mer,cis isomer (Figure
1) with monodentate and bidentate pyridylphosphine ligands.
1
pyridylphosphine moieties are detected by NMR. In the H
NMR spectrum, the H6 atoms of pyridyl appear as two
signals, a doublet at 8.26 ppm and a triplet at 9.17 ppm.
The downfield-shifted resonance is assigned to the chelating
3
ligand coupling also with Rh (3JH-H ) JRh-H ) 4.3 Hz).
Two doublets of doublets are observed in the 31P{1H} NMR
spectrum. The low-field signal at δ 31.19 ppm is assigned
to the terminal pyridylphosphine ligand and the second one
at δ -31.97 ppm to the chelating phosphine ligand. An
upfield shift in the 31P NMR spectrum (relative to the
monodentate coordination) is known to be diagnostic of a
four-membered chelating ring.30,31 This indicates that the one
PPh2py molecule is coordinated as a terminal ligand and the
second one as a chelating ligand through P and N atoms.
For this type of coordination, as seen in Figure 1, there are
three possible geometrical isomers for an octahedral com-
pound of general formula [RhCl3(PPh2py-P,N)(PPh2py-P)].
(32) Pregosin, P. S.; Kunz, R. W. 31P and 13C NMR of Transition Metal
Phosphine Complexes; Springer-Verlag: Berlin, 1979.
(33) Dahlhoff, W. V.; Dick, T. R.; Ford, G. H.; Neoson, S. M. J. Inorg.
Nucl. Chem. 1971, 33, 1799.
(34) Mann, B. E.; Masters, C.; Shaw, B. L. J. Chem. Soc., Dalton Trans
1973, 1489.
1
The H and 31P NMR spectra showed that only one isomer
(30) Garrou, P. E. Chem. ReV. 1981, 81, 229.
(31) Hietkamp, S.; Stufkens, D. J.; Vrieze, K. J. Organomet. Chem. 1979,
169, 107.
3372 Inorganic Chemistry, Vol. 45, No. 8, 2006

Chelating Diphenyl (2-Pyridyl)phosphine Ligand
Figure 2. Molecular structure of [RhCl3(PPh2py-P)(PPh2py-P,N)] (1) with
crystallographic numbering.
Figure 1. Possible isomers for compounds of general formula [RhCl3(PPh2-
py-P,N)(PPh2py-P)] and [RhCl2(PPh2py-P,N)2}+.
central Rh(III) has a distorted octahedral coordination due
to the presence of a four-membered chelating ligand with
the bite angle substantially reduced from the regular cis angle
of 90° to N(1)-Rh-P(1) ) 69.21(10)°, which is similar to
that observed for the rhodium(III) compound containing
orthometalated triphenylphosphine [Rh(C6H4PPh2-C,P)3] (68-
69°).38 The Rh-Cl bond lengths are 2.3534(11), 2.3605(11),
and 2.3852(10) Å. The Rh-Cl bond trans to the phosphine
ligand is longer than other bonds. The Rh-P bond trans to
Cl is longer (2.3184(12) Å) than that trans to the N atom of
the pyridyl ring (2.3045(12) Å). Similar trends were also
observed for similar compounds of Tc(III) and Ru(III) (Table
2).
The electronic spectra of Rh(III) octahedral complexes are
expected to contain two d-d transitions from the 1A1g ground
1
1
state to T1g and T2g (for Oh symmetry), but the higher-
1
energy transition to T2g is rarely detectable because it is
hidden beneath the intense CT transitions.35 The absorption
spectrum of complex 1 in dichloromethane solution exhibits
three bands at 289 nm (ꢀ ) 17 240), 366 nm (ꢀ ) 1430),
and 451 nm (ꢀ ) 350). The band observed at 289 nm is
considered to be due to intraligand nπ* transition.36 The low-
energy band at 451 nm should be assigned to the spin-
1
1
allowed T1g r A1g transition. This transition in complex
[RhCl3(tpy)] (tpy ) 2,2′:6′,2′′-terpyridine) is observed at
similar energy (421 nm).37 The band at 366 nm is assigned
to the MLCT transition.
Coordination of the second pyridine nitrogen ligand to
rhodium in 1 has been achieved by removing the chloride
with AgNO3 in an acetone solution (Figure 1). In the
presence of NH4PF6, cationic complex [RhCl2(PPh2py)2]PF6
2 was isolated as a yellow solid. Conductivity measurements
in an acetone solution (Λ ) 119 Ω-1 cm2 mol-1 in 1 ×
10-4 M solution) indicated that 2 is a 1:1 electrolyte.39 The
electrospray mass spectra of 2 revealed peaks with the correct
isotopic distributions at m/z ) 699 and 664, corresponding
to the [RhCl2(PPh2py)2]+ and [RhCl(PPh2py)2]+ ions, re-
spectively. The IR spectrum of 2 shows the characteristic
Crystallization of complex 1 from CH2Cl2 after layering
with EtOH yielded crystals suitable for a crystal-structure
determination. The crystal structure of 1 (Figure 2) shows
the rhodium center to be approximately octahedral, with three
chlorine ligands occupying meridional positions. The two
PPh2py ligands are cis to one another and adopt two different
bonding modes, chelating and monodentate. Selected bond
lengths and angles are listed in Table 2. The mer,cis isomer
(Figure 1) of complex 1 can exist only as one achiral
stereoisomer. The single-crystal X-ray analyses revealed that
compound 1 crystallizes in isomorphous space group P212121,
which is indicative of the spontaneous resolution of the
enantiomeric pair. The chirality occurs at the metal center,
but 1 is not chiral in solution because of the fluxionality of
the arms of PPh2py. One can note that under crystallization
conditions, two enantiomorphic crystals were formed. The
-
strong absorption of the PF6 anion at 840 and 558 cm-1.
The ν(CdN) band (1584 cm-1) can be assigned to the
coordinated pyridyl groups. A single Rh-Cl stretching
vibration at 361 cm-1 indicated that two chloride ligands
are in the trans positions. The 1H and 31P{1H} NMR spectra
show that both phosphine molecules are equivalent chelating
ligands. This is confirmed by the presence of a triplet at 9.41
ppm, assigned to the H6 protons of pyridyl rings (3JH5-H6
)
3JRh-H6 ) 3 Hz) in the 1H NMR spectrum, and a doublet at
δ ) -15.1 (1JRh-P ) 93.9 Hz) in 31P{1H} NMR. A septet
(35) Lever, A. B. P. Inorganic Electronic Spectroscopy, 2nd ed.; Elsevier:
Amsterdam, 1984.
(36) Vogler, A.; Kunkely, H. Coord. Chem. ReV. 2002, 230, 243.
(37) Pruchnik, F. P.; Jakimowicz, P.; Ciunik, Z.; Zakrzewska-Czerwin˜ska,
J.; Opolski, A.; Wietrzyk, J.; Wojdat, E. Inorg. Chim. Acta 2002, 334,
59.
(38) Bennett, M. A.; Bhargava, S. K.; Ke, M.; Willis, A. C. J. Chem. Soc.,
Dalton Trans. 2000, 3537.
(39) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3373

Wajda-Hermanowicz et al.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for RhCl3(PPh2py-P)(PPh2py-P,N) (1), RuCl3(PPh2py-P)(PPh2py-P,N) (3), and
TcCl3(PPh2py-P)(PPh2py-P,N)18j
TcCl3(PPh2py)2 d4
RuCl3(PPh2py)2 d5
RhCl3(PPh2py)2 d6
Tc-N(1)
Tc-P(1)
Tc-P(2)
Tc-Cl(1)
Tc-Cl(2)
Tc-Cl(3)
2.150(4)
Ru-N(1)
Ru-P(1)
Ru-P(2)
Ru-Cl(1)
Ru-Cl(2)
Ru-Cl(3)
2.172(5)
Rh-N(1)
Rh-P(1)
Rh-P(2)
Rh-Cl(1)
Rh-Cl(2)
Rh-Cl(3)
2.085(3)
2.4554(15)
2.4325(15)
2.4174(140
2.3403(15)
2.3338(14)
2.4152(17)
2.3192(18)
2.3728(15)
2.3330(14)
2.3386(15)
2.3184(12)
2.3045(12)
2.3852(10)
2.3534(11)
2.3605(11)
N(1)-Tc-P(2)
N(1)-Tc-P(1)
P(2)-Tc-P(1)
N(1)-Tc-Cl(2)
P(2)-Tc-Cl(2)
P(1)-Tc-Cl(2)
N(1)-Tc-Cl(3)
P(2)-Tc-Cl(3)
P(1)-Tc-Cl(3)
Cl(2)-Tc-Cl(3)
173.599(13)
66.36(12)
107.24(5)
87.21(12)
92.13(6)
86.16(5)
87.57(12)
92.60(5)
N(1)-Ru-P(2)
N(1)-Ru-P(1)
P(2)-Ru-P(1)
N(1)-Ru-Cl(2)
P(2)-Ru-Cl(2)
P(1)-Ru-Cl(2)
N(1)-Ru-Cl(3)
P(2)-Ru-Cl(3)
P(1)-Ru-Cl(3)
Cl(2)-Ru-Cl(3)
172.64(13)
66.62(13)
107.51(5)
82.68(12)
92.84(5)
87.78(5)
92.43(12)
91.37(6)
N(1)-Rh-P(2)
N(1)-Rh-P(1)
P(2)-Rh-P(1)
N(1)-Rh-Cl(2)
P(2)-Rh-Cl(2)
P(1)-Rh-Cl(2)
N(1)-Rh-Cl(3)
P(2)-Rh-Cl(3)
P(1)-Rh-Cl(3)
Cl(2)-Rh-Cl(3)
175.717(10)
69.21(10)
106.56(4)
86.57(10)
93.72(4)
90.24(4)
86.83(9)
92.84(4)
87.17(4)
88.00(5)
173.36(5)
84.57(5)
172.10(5)
173.40(4)
typical of the PF6- anion was observed at -144.27 ppm. As
expected, the PPh2py:PF6- signal ratio is 2:1. The absorption
spectrum of complex 2 in acetone solution is similar to that
of 1 and exhibits three bands at 295 (60 200), 328 (1880),
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
trans-[RhCl2(PPh2py-P,N)2]PF6 (2)
Rh(1)-N(1)
Rh(1)-P(1)
Rh(1)-Cl(1)
2.149(3)
2.2731(10)
2.3361(7)
and 424 (280) nm, which are assigned to intraligand nπ*,
MLCT, and the spin-allowed T1g
respectively.
N(1)-Rh(1)-N(1)#1 110.73(15)
N(1)-Rh(1)-P(1)#1 178.79(8)
P(1)-Rh(1)-Cl(1)#1
N(1)-Rh(1)-Cl(1)
P(1)#1-Rh(1)-Cl(1)
P(1)-Rh(1)-Cl(1)
92.41(3)
88.71(7)
92.41(3)
90.70(3)
1
r
1A1g transitions,
N(1)-Rh(1)-P(1)
68.86(8)
P(1)#1-Rh(1)-P(1) 111.57(5)
N(1)-Rh(1)-Cl(1)#1 88.15(7)
Compound 2 crystallized in the chiral space group P21212
Cl(1)#1-Rh(1)-Cl(1) 174.48(4)
with two molecules in the unit cell. The crystal structure
-
consists of [RhCl2(PPh2py)2]+ cations, PF6 anions, and
P)2]+ type complexes41 for about 0.05 and 0.02 Å, respec-
tively. However, the Rh-N bond lengths found in 2 are
longer (by at least 0.06 Å) than that in 1. The N-Rh-N
and P-Rh-P angles are in the range 110.73-111.57°,
whereas P-Rh-N angles are smaller (68.86°) because of
strain in the four-membered rings.
Ruthenium Complexes. The DMSO ruthenium com-
pounds are useful precursors for the syntheses of ruthenium
complexes with P-N chelating ligands. Replacement of all
the DMSO ligands was obtained upon treatment of the
ruthenium complexes with P or N donor ligands under mild
conditions.22
A paramagnetic complex of formula [RuCl3(PPh2py)2] (3)
was obtained from mer-[RuCl3(DMSO-S)2(DMSO-O)] and
PPh2py in a CH2Cl2 solution at room temperature. The
ESI(+) MS spectrum of 3 is similar to that of mer,cis-
[RhCl3(PPh2py-P,N)(PPh2py-P)] (1). The ions [RuCl2(PPh2-
py)2]+ (m/z ) 697), [RuCl(PPh2py)2]+ (m/z ) 662), and
[Ru(PPh2py)2]+ (m/z ) 626) were observed. As expected,
the IR spectrum of 3 is also very similar to that observed
for 1 and contains weak bands at 1582 and 1571 cm-1
assigned to the ν(CdN) vibration of N-coordinated and non-
coordinated pyridyl rings, respectively. Three ν(Ru-Cl)
bands at 339, 323, and 282 cm-1 reveal a mer arrangement
of chlorides.42 Solid-state magnetic moment measurement
at 290 K suggests that complex 3 is paramagnetic with a
magnetic moment (µ ) 1.92 µB) corresponding to one
unpaired electron.42 A powdered sample of 3 at 77 K exhibits
solvate (CH3)2CO molecules, held together by electronic and
-
van der Waals interactions. The rhodium, PF6 anions, and
acetone molecules are situated on a 2-fold axis. Rh(III) in
the cation is situated in a distorted octahedral coordination
environment, with two chloride ligands in the trans positions
and two chelated P-N ligands in cis positions (Figure 3).
The five atoms Rh, P1, P1*, N1, and N1* and two pyridyl
rings are coplanar. The selected bond distances and angles
for 2 are listed in Table 3. The crystals of 2 are an example
of the chiral crystallization of achiral compounds, which is
common for inorganic, organic, and organometallic com-
pounds.40 The Rh-P and Rh-Cl distances are shorter than
those observed in 1 (Table 2) or in Rh(III) trans-[RhCl2(P-
(40) Matsuura, T.; Koshima, H. J. Photochem. Photobiol., C 2005, 6, 7-24.
(41) Hill, A. M.; Levason, W.; Preece, S. R.; Webster, M. Polyhedron 1997,
16, 1307.
(42) Ruiz-Ramirez, L.; Stephenson, T. A.; Switkes, E. S. J Chem. Soc.,
Dalton Trans. 1973, 1770.
Figure 3. Molecular structure of [RhCl2(PPh2py-P,N)2]PF6 (2) with
crystallographic numbering.
3374 Inorganic Chemistry, Vol. 45, No. 8, 2006

Chelating Diphenyl (2-Pyridyl)phosphine Ligand
Figure 5. Molecular structure of [RuCl((PPh2py-P)(PPh2py-P,N)2]Cl (fac-
5) with crystallographic numbering.
Figure 4. Molecular structure of [RuCl3(PPh2py-P)(PPh2py-P,N)] (3) with
crystallographic numbering.
of M out of the plane N1C1C2C3C4C5 are 0.127 Å for Tc,
0.198(5) Å for Rh, and 0.640(7) Å for Ru compounds.
an EPR spectrum with three g values (g1 ) 2.69, g2 ) 2.15,
and g3 ) 1.72), typical of rhombic low-spin d5 Ru(III)
complexes.43 The complex absorbs strongly in the 248-504
nm region {248 (ꢀ ) 12850), 364 (ꢀ ) 2510), 447 (ꢀ )
1040), 504 (ꢀ ) 690) nm, presumably due to the intraligand
and charge-transfer transitions. The spectrum is similar to
that observed for the d5 ruthenium(III) compounds containing
PPh3, N-donors (pyridine, bipyridine, or phenanthroline), and
Cl ligands.42
Compound 4, the meridional isomer of well-known
complex fac-[RuCl3(DMSO-S)3]-,24 was obtained from cis-
RuCl2(DMSO-S)3(DMSO-O) and [NBu4]Cl in a 1:1 mixture
of CH2Cl2 and CH3OH. As expected for the mer isomer, three
Ru-Cl bands in the IR spectrum were observed (345, 334,
and 297 cm-1). Unlike the fac isomer (one ν(SdO) band at
1100 cm-1), two ν(SdO) bands at 1105 and 1081 cm-1 were
observed for 4. The position of these bands indicate that all
three DMSO ligands are coordinated through S. The ESI-
(-) MS spectrum of compound 4 shows the [RuCl3-
(DMSO)3]- (m/z ) 441) and [RuCl3(DMSO)2]- (m/z ) 363)
ions.
The molecular structure of 3 (Figure 4) was determined
by X-ray crystallography. As expected, the compound is a
monomeric six-coordinate complex with mer chloride ligands
and two cis PPh2py molecules in two different bonding
modes, monodentate and chelating. Selected bond lengths
and angles are listed in Table 2. Table 2 also shows that the
molecular structures of Tc, Ru, and Rh compounds are nearly
identical. The P-M-N bite angles of a four-membered
metallacycle for Tc(d4), Ru(d5), and Rh(d6) species are equal
to 66.36(12), 66.62(13), and 69.21(10)°, respectively. The
M-P distances, for both chelating and nonchelating phos-
phine, diminish with an increase in the number of d electrons
from d4 to d6 (2.4554(15), 2.4152(17), and 2.3184(12) Å for
M-Pchelate and 2.4325(15), 2.3192(18), and 2.3045(12) Å for
M-Pterminal). On the other hand, the Ru-N(1) distance is
longer (2.172(5) Å) than that in Tc (2.150(4) Å) and in Rh
(2.085(3) Å). In contrast to the technetium18j and rhodium
(Figure 2), where the nitrogen atom of the uncoordinated
pyridyl ring is located almost close to the P(1) atom, in
ruthenium complex 3, the uncoordinated pyridyl ring is
located between two chlorine atoms (Figure 4) and the Cl-
(2)-Ru-Cl(3) angle (172.10(5)°) is smaller than those for
Tc and Rh (173.36(5) and 173.40(4)°, respectively). The
deviation of the coordinated pyridyl ring from the coordina-
tion plane is larger for the Ru compound. The displacements
The reaction of 4 with PPh2py (Ru:P ) 1:3) in an acetone
solution leads to the substitution of DMSO and Cl ligands
and the formation of complex [RuCl(PPh2py-P,N)2(PPh2py-
P)]Cl (5), which contains two chelating phosphine ligands.
Complex 5 displays in the IR spectrum only one ν(Ru-Cl)
band at 279 cm-1 and, characteristic for the chelate PPh2py
ligand, a ν(CdN) band at 1583 cm-1. In the 31P{1H} NMR
spectrum in acetone-d6 solution, two signals were observed,
a triplet centered at δ 53.05 and a doublet at δ -2.80 with
intensity 1:2 and coupling constant 30.5 Hz. These data
indicate that complex 5 has the mer structure, in which two
P atoms in the trans position are part of chelating rings and
a third P atom (cis to the trans P atoms) acts as a monodentate
ligand. A compound with the same formula as 5 obtained
by Faraone18h has the fac structure, in which one PPh2py
molecule is coordinated via a P atom while the remaining
two act as chelating ligands. Its 31P{1H} NMR spectrum
2
exhibits three signals at δ 47.31 (dd, J(PP) 33.6 and 27.7
2
Hz), -6.53 (dd, J(PP) 33.6 and 27.7 Hz), and -7.72 (t,
2J(PP) 27.7 Hz). The structural data for this compound were
not given. Compound 5 in CHCl3 solution is quickly
converted into a fac isomer, as proved by 31P{1H} NMR.
(43) Medhi, O. K.; Agarwala, U. Inorg. Chem. 1980, 19, 1381.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3375

Wajda-Hermanowicz et al.
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
fac-[RuCl(PPh2py-P,N)2(PPh2py-P)]Cl (fac-5)
in fac-5 and very similar to that observed in 6 (2.13(1), 2.063-
(8) Å). The Ru-P bond lengths are equal to 2.2963(17),
2.3077(18), and 2.3218(17) Å. The longest Ru-P value is
for the nonchelated phosphine in the trans position to the
nitrogen atom; the two remaining values are slightly longer
than the corresponding distances observed in 6 (2.265(4),
2.270(3) Å). The two intermolecular weak hydrogen bonds
linking C52-H52‚‚‚Cl8 and C53-H53‚‚‚Cl8 atoms of two
molecules of chloroform and the Cl- anion are observed
(D‚‚‚A distances are 3.310(8) and 3.341(10) Å; D-H‚‚‚A
angles are 166 and 165° for C52 and C53, respectively).
Ru-N(2)
Ru-N(3)
Ru-P(3)
2.118(5)
2.122(5)
2.2964(17)
Ru-P(2)
Ru-P(1)
Ru-Cl(1)
2.3081(18)
2.3220(17)
2.4218(16)
N(2)-Ru-N(3)
N(2)-Ru-P(3)
N(3)-Ru-P(3)
N(2)-Ru-P(2)
N(3)-Ru-P(2)
P(3)-Ru-P(2)
N(2)-Ru-P(1)
N(3)-Ru-P(1)
92.77(18)
161.48(14)
69.24(14)
68.33(13)
89.32(13)
105.81(6)
98.28(14)
166.62(13)
P(3)-Ru-P(1)
P(2)-Ru-P(1)
N(2)-Ru-Cl(1)
N(3)-Ru-Cl(1)
P(3)-Ru-Cl(1)
P(2)-Ru-Cl(1)
P(1)-Ru-Cl(1)
100.15(7)
101.74(6)
88.52(13)
83.87(13)
93.68(6)
155.55(6)
88.87(6)
Structural and Spectroscopic Correlation between
Complexes with Chelating Coordinated PPh2py-P,N
Ligands. Crystallographic and 31P{1H} NMR data for all
known metal complexes with one or two P-N chelates are
given in Tables 5 and 6. The literature reports on the PPh2-
py ligand acting as a P-N chelate are rather scarce. Four-
membered chelate rings are very strained, and small P-M-N
bite angles are expected. An increase of the P-M-N angle
in complexes with one (63.2-70.68°) and two (64.13-
71.26°) chelating ligands is observed. The extent of the
compression of the chelate angle follows the order W >
Re > Tc > Ru ≈ Rh > Pt and W > Ru ≈ Rh > Fe in
compounds with one and two P-N ligands, respectively. It
is also seen from Tables 5 and 6 that the shortening of the
M-N and M-P bond lengths followed in the same direction.
This trend shows the effect of the relative size of the
coordinating metal on the bite angle and bond lengths.
Furthermore, it was found that the symmetric deformation
A solution of 5 in CHCl3 layered with Et2O gives crystals
of fac-[RuCl(PPh2py-P,N)2(PPh2py-P)]Cl (fac-5) suitable for
X-ray analysis. Figure 5 shows a perspective view of the
crystal structure of fac-5. The coordination geometry of the
ruthenium atom is octahedral with very large distortions
caused mainly by the small bite angles of the two chelating
ligands (see Table 5). The coordination sphere in fac-5 is
similar to that found for cis,cis-[RuCl2(PPh2py-P,N)2] (6)18h
by Faraone et al. Both complexes fac-5 and 6 have N-Ru-P
bite angles for two chelating ligands markedly smaller than
90° (68,33(13) and 69.24(14)° for fac-5; 68.7(3) and 69.6-
(3)° for 6). In complex fac-5, analogous to the case of
compound 6, the two pyridine rings coordinated to ruthenium
are arranged orthogonally around the metal center. The Ru-
Cl bond length of 2.4218(16) Å is comparable to the
ruthenium-chlorine bond reported for 6 (2.420(3) Å) and
for cis,cis-[RuCl2(CO)2(PPh2py-PN)]18g (2.417(2) Å). The
ruthenium-nitrogen bond lengths are the same (2.118(5) Å)
Table 5. Comparison of Structural and 31P NMR Data for Metal Complexes with One Chelating PPh2py-P,N Liganda
d
M
W
complex
S4′ b (deg)
P-M-N (deg)
M-N (Å)
M-PCH (Å)
Lc
δ(PCH
)
ref
[W(CO)4(PN)]
10.1
12.21
1.9
17.29
18.02
17.32
3.88
4.34
6.1
8.39
8.47
32.6
7.7
18.20
2.86
17.6
63.2
2.256
2.240
2.280
2.198
2.150
2.1171
2.104
2.106
2.092
2.107
2.119
2.146
2.132
2.083
2.07
2.543
2.537
2.423
2.400
2.4554
2.415
2.3311
2.332
2.3038
2.412
2.321
2.348
2.338
2.322
2.223
2.327
CO
CO
Cl
Cl
Cl
-11
-18.3
18b
18m
18e
18f
18j
TW
18d
18n
18o
18c
18g
18a
18k
TW
18l
[W(CO)2NO(PN)(P)]+
[ReCl3O(PN)]
64.49
63.57
66.09
66.36
66.63
67.47
67.26
68.37
67.72
68.678
68.0
Re
Tc
[TcCl2(NO)(PN)(P)]
[TcCl3(PN)(P)]
Ru
[RuCl3(PN)(P)]
Cl
aren
[Ru(cymene)Cl(PN)]+
-11.72
-17.4
43.86
-11.25
-6.84
-20.9
-11.6
-31.97
-50.3
-17.6
[Ru(bipy)2(PN)]2+
[C6Me6RuCl(PN)]+
[RuCl2(CO)2(PN)]
[RuCl2(dppb)(PN)]
[RhCp*Cl(PN)]+
[RhCl3(PN)(P)]
Npy
aren
Cl
Cl
Cp*
Cl
Rh
Pt
67.3
69.116
70.76
70.68
[PtCl(PN)(P)]
Cl
CH3
[PtCH3(PN)(P)]+
2.07
6g
a (PN) ) chelating PPh2py-PN, (P) ) terminal coordinated PPh2py-P, TW ) this work. b Angular symmetric deformation coordinate S4′,44 defined as the
sum of the M-P-C angles minus the sum of the C-P-C angles. c Ligand trans to PCH d δ(PCH) is a 31P chemical shift for a chelating phosphine.
.
Table 6. Comparison of Structural and 31P NMR Data for Metal Complexes with Two Chelating PPh2py-P,N Ligandsa
d
M
W
complex
S4′ b (deg)
P-M-N (deg)
M-N (Å)
M-PCH (Å)
Lc
δ(PCH
)
ref
[W(CO)(NO)(PN)2]+
11.6
15.38
16.33
21.69
22.6
24.39
4.51
-8.49
3.56
64.13
65.50
69.57
68,65
69.26
68.34
68.86
69.72
71.26
2.210
2.258
2.063
2.13
2.122
2.119
2.149
2.004
2.015
2.556
2.449
2.270
2.265
2.2964
2.3077
2.2731
2.345
2.253
CO
Npy
Npy
Cl
Npy
Cl
Npy
CO
Npy
2.3
-12.8
18m
Ru
[RuCl2(PN)2]
2.64
-4.49
-6.53
-7.72
-15.1
18h
[RuCl(PN)2(P)]+
TW
18h
TW
18i
Rh
Fe
[RhCl2(PN)2]+
[Fe(CO)2(PN)2]2+
a (PN) ) chelating PPh2py-P,N, (P) ) terminal coordinated PPh2py-P, TW ) this work. b Angular symmetric deformation coordinate S4′,44 defined as
.
the sum of the M-P-C angles minus the sum of the C-P-C angles. c Ligand trans to PCH d δ(PCH) is a 31P chemical shift for a chelating phosphine.
3376 Inorganic Chemistry, Vol. 45, No. 8, 2006

Chelating Diphenyl (2-Pyridyl)phosphine Ligand
data is shown in Figure 6. It is interesting that, as for Ru(II)
complexes with triphenylphosphine and 1,4-bis(diphenylphos-
phino)butane (dppb),45 complexes with PPh2py chelating
ligands show a pronounced negative correlation between
31P{1H} chemical shift and Ru-P bond length. The negative
slope (-0.0040 Å ppm-1) of the line drawn in Figure 6 is
very similar to that of the plot for PPh3 and dppb systems
(-0.0029 Å ppm-1), whereas the intercept (2.2828 Å) is
substantially different from that for the PPh3 (2.465 Å) and
dppb (2.423Å) systems.45 The explanation of this fact seems
rather simple. It is well-known that the 31P{1H} chemical
shift for phosphine ligands depends on the C-P-C angle.33
When the C-P-C angle opens, the 31P NMR shift moves
to a lower field. This is true when phosphine is monodentate
or part of a five-or-more-membered chelating ligand, but in
the case of four-membered chelating phosphines, the C-P-C
increase and 31P{1H} chemical shift moves to a higher field.
Thus changes in the 31P chemical shifts in comparison with
the data for monodentate coordination provide a good
diagnostic tool for identifying the mode of coordination of
PPh2py ligands. It is also seen from Figure 6 that in the case
of [Ru(bipy)2(PPh2py-P,N)]2+, the chemical shift is much
higher than expected (43.86 ppm).18o This is most probably
caused by transformation in solution of the chelating phos-
phine into a monohapto ligand coordinated only via a P atom.
The correlation between structural and spectroscopic param-
eters for PPh2py-P,N could be expected for the complexes
of other metals, but there are not yet sufficient experimental
data to discuss this dependence.
Figure 6. Graph of Ru-P bond length (Å) vs31P{1H} NMR chemical
shift (ppm) for a series of ruthenium(II) complexes containing PPh2py-
P,N. (a and b) cis-[RuCl2(PPh2py-P,N)2],18h (c and d) fac-[RuCl(PPh2py-
P,N)2(PPh2py-P)]+,18h (e) [Ru(cymene)Cl(PPh2py-P,N)]+,18d (f) [Ru(cymene)-
Cl(PPh2py-P,N)]+,18n (g) [Ru(bipy)2(PPh2py-P,N)]2+ 18o
(h) [C6Me6RuCl-
,
(PPh2py-P,N)]+;18c (i) cis, cis-[RuCl2(CO)2(PPh2py-P,N)];18g (j) [RuCl2(dppb)-
(PPh2py-P,N)].18a 31P{1H} NMR data in CDCl3 (a-f, h, j), CD2Cl2 (i), and
CD3CN (g).
coordinates S4′ 44 depend on the trans influence of ligands
occupying trans-to-P coordination sites and on the M-N
bond length. The mean S4′ values are small, and phosphine
ligands are considerably flattened in complexes with CO,
arene, and Npy ligands. The smallest S4′ value (-8.49°) was
found in the [Fe(CO)2(Pph2py-P,N)2]2+ compound with CO
trans to P and the smallest M-N bond length value (2.004
Å).18i
Acknowledgment. This work was supported by the KBN
(Committee of Scientific Research), Grant 4 T09A 00224.
Supporting Information Available: Crystallographic data files
of 1, 2, 3, and fac-5 in CIF format. This material is available free
of charge via the Internet at http://pubs.acs.org.
IC051442K
A plot of the Ru-P bond lengths for Ru(II)(PPh2py-P,N)-
(45) (a) Jessop, P. G.; Rettig, S. J.; Lee, C.-L.; James, B. R. Inorg. Chem.
1991, 30, 4617. (b) MacFarlane, K. S.; Joshi, A. M.; Rettig, S. J.;
James, B. R. Inorg. Chem. 1996, 35, 7304. (c) Queiroz, S. L.; Batista,
A. A.; Oliva, G.; Gambardella, M. T.; Santos, R. H. A.; MacFarlane,
K. S.; Rettig, S. J.; James, B. R. Inorg. Chim. Acta 1998, 267, 209.
containing complexes versus their 31P{1H} chemical shift
(44) Dunne, B. J.; Morris, R. B.; Orpen, A. G J. Chem. Soc., Dalton Trans.
1991, 653.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3377