Synthesis and coordination chemistry of a novel bidentate phosphine: 6-(Diphenylphosphino)-1,3,5-triaza-7-phosphaadamantane (PTA-PPh2)

Article abstract of DOI:10.1021/ic060576a

The upper rim of 1,3,5-triaza-7-phosphaadamantane (PTA) has been modified for the first time. Lithiation of PTA, with n-butyllithium, resulted in deprotonation of an α-phosphorus methylene and the formation of 1,3,5-triaza-7-phosphaadamantane-6-yllithium (PTA-Li). The chiral chelating phosphine 6-(diphenylphosphino)-1,3,5-triaza-7-phosphaadamantane (PTA-PPh ₂) was synthesized, in racemic form, by the reaction of PTA-Li with CIPPh₂. PTA-PPh₂ has been fully characterized in solution by multinuclear NMR spectroscopy and mass spectrometry and in the solid state by X-ray crystallography. The ³¹P NMR spectrum contains a pair of doublets at -19.8 and -100.1 ppm (d, ²J_PP = 65 Hz). Unlike PTA, the new bidentate phosphine, PTA-PPh₂, is insoluble in aqueous solutions. Two group 6 metal carbonyl complexes, [M(CO)₄(PTA-PPh ₂)] (M = W and Mo), were synthesized by the addition of PTA-PPh ₂ to cis-[M(CO)₄(pip)₂] and characterized by NMR spectroscopy, IR spectroscopy, and X-ray crystallography. Also reported are the solid-state structures of cis-[W(CO)₄PTA₂], cis-[W(CO)₄(PTA)(PPh₃)], and [W(CO)₄DPPM] (DPPM = diphenylphosphinomethane). PTA-PPh₂ appears to be sterically similar to and slightly, more electron-donating than DPPM.

Full text of DOI:10.1021/ic060576a

Inorg. Chem. 2006, 45, 6748−6755
Synthesis and Coordination Chemistry of a Novel Bidentate Phosphine:
6-(Diphenylphosphino)-1,3,5-triaza-7-phosphaadamantane (PTA-PPh2)
Gene W. Wong, Jennifer L. Harkreader, Charles A. Mebi, and Brian J. Frost*
Department of Chemistry, UniVersity of NeVada, Reno, NeVada 89557
Received April 5, 2006
The upper rim of 1,3,5-triaza-7-phosphaadamantane (PTA) has been modified for the first time. Lithiation of PTA,
with n-butyllithium, resulted in deprotonation of an -phosphorus methylene and the formation of 1,3,5-triaza-7-
R
phosphaadamantane-6-yllithium (PTA-Li). The chiral chelating phosphine 6-(diphenylphosphino)-1,3,5-triaza-7-
phosphaadamantane (PTA-PPh2) was synthesized, in racemic form, by the reaction of PTA-Li with ClPPh2. PTA-
PPh2 has been fully characterized in solution by multinuclear NMR spectroscopy and mass spectrometry and in
the solid state by X-ray crystallography. The 31P NMR spectrum contains a pair of doublets at
−19.8 and −100.1
2
ppm (d, JPP
)
65 Hz). Unlike PTA, the new bidentate phosphine, PTA-PPh2, is insoluble in aqueous solutions.
W and Mo), were synthesized by the addition
Two group 6 metal carbonyl complexes, [M(CO)4(PTA-PPh2)] (M
)
of PTA-PPh2 to cis-[M(CO)4(pip)2] and characterized by NMR spectroscopy, IR spectroscopy, and X-ray
crystallography. Also reported are the solid-state structures of cis-[W(CO)4PTA2], cis-[W(CO)4(PTA)(PPh3)], and
[W(CO)4DPPM] (DPPM
) diphenylphosphinomethane). PTA-PPh2 appears to be sterically similar to and slightly
more electron-donating than DPPM.
Introduction
Progress in catalytic applications may often be correlated
with either a steric or an electronic modification to the ligand
set of the catalyst.1 Indeed, small modifications can lead to
large variation of the rate or product selectivity of a catalytic
process. We have been interested in developing methods for
the modification of 1,3,5-triaza-7-phosphaadamantane (PTA),
first reported by Daigle et al.2 in 1974 and introduced into
aqueous phase catalysis by Joo´, Darensbourg, and others.3
Recently, there has been renewed interest in this neutral,
water-soluble, and air-stable phosphine.4,5 Thus far, modi-
fication of PTA has focused on alkylation of the phosphorus6
or nitrogen7 or modification of the “lower rim” of the ligand,
i.e., the triazacyclohexane ring.8-11
Figure 1. PTA derivatives. R ) alkyl or aryl.
ligand,8 PASO2,9,10 DAPTA,11 and a “ring-opened” PTA
derivative (RO-PTA).6 With the exception of the RO-PTA
derivative, these PTA derivatives involve modification of
the triazacyclohexane ring of PTA and are reasonably distant
from phosphorus and therefore any coordinated metal center.
Prior to the submission of this entry, there have been no
reported modifications of the “upper rim” of PTA. Of interest
is that substitution at the methylene adjacent to the phos-
phorus of PTA results in chiral phosphines, with the
(1) For example, see: (a) Van Leeuwen, P. W. N. M.; Kamer, P. C. J.;
Reek, J. N. H.; Dierkes, P. Chem. ReV. 2000, 100, 2741-2770. (b)
Van Leeuwen, P. W. N. M. Homogeneous Catalysis: Understanding
the Art; Kluwer Academic Publishers: Dordrecht, The Netherlands,
2004.
(2) Daigle, D. J.; Pepperman, A. B., Jr.; Vail, S. L. J. Heterocycl. Chem.
1974, 11, 407-408.
Figure 1 depicts an arrangement of PTA derivatives that
have appeared in the literature including a ring-expanded
* To whom correspondence should be addressed. E-mail:
frost@chem.unr.edu.
6748 Inorganic Chemistry, Vol. 45, No. 17, 2006
10.1021/ic060576a CCC: $33.50
© 2006 American Chemical Society
Published on Web 07/19/2006

NoWel Bidentate Phosphine
were distilled under nitrogen from the appropriate drying agent
(sodium/benzophenone for tetrahydrofuran (THF) and hexanes;
magnesium/iodine for methanol). Water was distilled and deoxy-
genated before use. Chlorodiphenylphosphine was distilled and
stored at 5 °C under nitrogen. Anhydrous 1,2-dimethoxyethane
(DME), n-butyllithium, diethyl ether, dichloromethane, piperidine
(pip), bis(diphenylphosphino)methane (dppm), and deuterated NMR
solvents were purchased from commercial sources and used as
received. Tetrakis(hydroxymethyl)phosphonium chloride was ob-
tained from Cytec and used without further purification. 1,3,5-
Triaza-7-phosphaadamantane (PTA),12 cis-[W(CO)4(pip)2],13 cis-
[Mo(CO)4(pip)2],13 and cis-[W(CO)4(PPh3)2]13 were synthesized as
reported in the literature. All NMR spectra were recorded on either
a Varian Unity Plus 500 FT-NMR spectrometer, a Varian NMR
System 400, a GN 300 FT-NMR/Scorpio spectrometer, or a QE
300 FT-NMR/Aquarius spectrometer. 1H and 13C NMR spectra were
referenced to a residual solvent relative to tetramethylsilane.
Phosphorus chemical shifts are relative to an external reference of
85% H3PO4 in D2O with positive values downfield of the reference.
IR spectra were recorded on Perkin-Elmer 2000 FT-IR spectrometer,
in a 0.1-mm CaF2 cell for solutions or as a KBr pellet for solid
samples. X-ray crystallographic data were collected at 100((1) K
on a Bruker APEX CCD diffractometer with Mo KR radiation (λ
) 0.710 73 Å) and a detector-to-crystal distance of 4.94 cm. A
full sphere of data were collected utilizing four sets of frames, 600
frames per set with 0.3° rotation about ω between frames, and an
exposure time of 10 s/frame. Data integration, correction for Lorentz
and polarization effects, and final cell refinement were performed
using SAINTPLUS and corrected for absorption using SADABS
or TWINABS. The structures were solved using direct methods
followed by successive least-squares refinement on F 2 using the
SHELXTL 5.12 software package.14 Crystallographic data and data
collection parameters are listed in Table 1.
stereogenic carbon in close proximity to the phosphorus and,
therefore, any coordinated metal center. Herein we report
the synthesis of 1,3,5-triaza-7-phosphaadamantane-6-yllith-
ium (PTA-Li), which has allowed for the introduction of
modifications to an R-phosphorus methylene of PTA. A new
chiral bidentate phosphine based on PTA (PTA-PPh2), as
well as group 6 metal carbonyl derivatives of PTA-PPh2,
PTA, PPh3, and DPPM, are reported.
Experimental Section
Materials and Methods. Unless otherwise noted, all manipula-
tions were performed on a double-manifold Schlenk vacuum line
under nitrogen or in a nitrogen-filled glovebox. Prior to use, solvents
(3) (a) Darensbourg, D. J.; Joo´, F.; Kannisto, M.; Katho, A.; Reibenspies,
J. H.; Daigle, D. J. Inorg. Chem. 1994, 33, 200-208. (b) Darensbourg,
D. J.; Joo´, F.; Kannisto, M.; Katho, A.; Reibenspies, J. H. Organo-
metallics 1992, 11, 1990-1993. (c) Joo´, F.; Nadasdi, L.; Benyei, A.
Cs.; Darensbourg, D. J. J. Organomet. Chem. 1996, 512, 45-50. (d)
Darensbourg, D. J.; Stafford, N. W.; Joo´, F.; Reibenspies, J. H. J.
Organomet. Chem. 1995, 488, 99-108. (e) Darensbourg, D. J.; Decuir,
T. J.; Reibenspies, J. H. High Technology. In Aqueous Organometallic
Chemistry and Catalysis; Horvath, I. T., Joo, F., Eds.; Kluwer:
Dordrecht, The Netherlands, 1995; pp 61-80. (f) Laurenczy, G.; Joo´,
F.; Nadasdi, L. Inorg. Chem. 2000, 39, 5083-5088. (g) Kovacs, J.;
Todd, T. D.; Reibenspies, J. H.; Joo´, F.; Darensbourg, D. J.
Organometallics 2000, 19, 3963-3969.
(4) For an excellent review of PTA chemistry, see: Phillips, A. D.;
Gonsalvi, L.; Romerosa, A.; Vizza, F.; Peruzzini, M. Coord. Chem.
ReV. 2004, 248, 955-993.
(5) (a) Frost, B. J.; Bautista, C. M.; Huang, R.; Shearer, J. Inorg. Chem.
2006, 45, 3481-3483. (b) Frost, B. J.; Miller, S. B.; Rove, K. O.;
Pearson, D. M.; Korinek, J. D.; Harkreader, J. L.; Mebi, C. A.; Shearer,
J. Inorg. Chim. Acta 2006, 359, 283-288. (c) Frost, B. J.; Mebi, C.
A.; Gingrich, P. W. Eur. J. Inorg. Chem. 2006, 1182-1189. (d) He,
Z.; Tang, X.; Chen, Y.; He, Z. AdV. Synth. Catal. 2006, 348, 413-
417. (e) Romerosa, A.; Campos-Malpartida, T.; Lidrissi, C.; Saoud,
M.; Serrano-Ruiz, M.; Peruzzini, M.; Garrido-Ca´rdenas, J. A.; Garc´ıa-
Maroto, F. Inorg. Chem. 2006, 45, 1289-1298. (f) Krogstad, D. A.;
Cho, J.; DeBoer, A. J.; Klitzke, J. A.; Sanow, W. R.; Williams, H.
A.; Halfen, J. A. Inorg. Chim. Acta 2006, 359, 136-148. (g) Lidrissi,
C.; Romerosa, A.; Saoud, M.; Serrano-Ruiz, M.; Gonsalvi, L.;
Peruzzini, M. Angew. Chem., Int. Ed. 2005, 44, 2568-2572. (h) Mebi,
C. A.; Frost, B. J. Organometallics 2005, 24, 2339-2346. (i) Frost,
B. J.; Mebi, C. A. Organometallics 2004, 23, 5317-5323. (j) Bolano,
S.; Gonsalvi, L.; Zanobini, F.; Vizza, F.; Bertolasi, V.; Romerosa,
A.; Peruzzini, M. J. Mol. Catal. A 2004, 224, 61-70. (k) Akbayeva,
D. N.; Gonsalvi, L.; Oberhauser, W.; Peruzzini, M.; Vizza, F.;
Brueggeller, P.; Romerosa, A.; Sava, G.; Bergamo, A. Chem. Commun.
2003, 264-265.
Synthesis of 1,3,5-Triaza-7-phosphaadamantane-6-yllithium
(PTA-Li). To a suspension of dried PTA (3.10 g, 19.7 mmol) in
40 mL of THF was slowly added at room temperature n-
butyllithium (2.5 M, 11 mL, 27.5 mmol) over the course of 5 min.
The reaction was stirred at room temperature until the evolution of
butane was no longer observed (approximately 2.5-3 h). The
suspension was filtered under nitrogen and the precipitate washed
with hexanes (2 × 15 mL), resulting in 3.20 g of a fine white highly
pyrophoric powder. A yield of >90% for the synthesis of PTA-Li
was determined by quenching PTA-Li with D2O and measuring
the ratio of PTA-D/PTA by 31P NMR spectroscopy.15 PTA-D was
(6) (a) Fluck, E.; Weissgraeber, H. J. Chem.-Ztg. 1977, 101, 304. (b)
Assmann, B.; Angermaier, K.; Paul, M.; Riede, J.; Schmidbaur, H.
Chem. Ber. 1995, 128, 891-900. (c) Assmann, B.; Angermaier, K.;
Schmidbaur, H. J. Chem. Soc., Chem. Commun. 1994, 941-942.
(7) (a) Daigle, D. J.; Pepperman, A. B. J. J. Heterocycl. Chem. 1975, 12,
579-80. (b) Forward, J. M.; Staples, R. J.; Fackler, J. P., Jr. Z.
Kristallogr. 1996, 211, 129-130. (c) Forward, J. M.; Staples, R. J.;
Fackler, J. P., Jr. Z. Kristallogr. 1996, 211, 131-132. (d) Forward. J.
M.; Staples, R. J.; Liu, C. W.; Fackler, J. P., Jr. Acta Crystallogr. C
1997, 53, 195-197. (e) Pruchnik, F. P.; Smolenski, P. Appl. Orga-
nomet. Chem. 1999, 13, 829-836. (f) Pruchnik, F. P.; Smolenski, P.;
Galdecka, E.; Galdecki, Z. New J. Chem. 1998, 22, 1395-1398. (g)
Smolenski, P.; Pruchnik, F. P.; Ciunik, Z.; Lis, T. Inorg. Chem. 2003,
42, 3318-3322.
(8) (a) Navech, J.; Kraemer, R.; Majoral, J. P. Tetrahedron Lett. 1980,
21, 1449-1452. (b) Benhammou, M.; Kraemer, R.; Germa, H.;
Majoral, J. P.; Navech, J. Phosphorus Sulfur 1982, 14, 105-119.
(9) (a) Daigle, D. J.; Boudreaux, G. J.; Vail, S. L. J. Chem. Eng. Data
1976, 21, 240-241. (b) Delerno, J. R.; Majeste, R. J.; Trefonas, L.
M. J. Heterocycl. Chem. 1976, 13, 757-760. (c) Daigle, D. J.;
Pepperman, A. B., Jr.; Boudreaux, G. J. Heterocycl. Chem. 1974, 11,
1085-1086.
1
1
characterized by H, 13C, and 31P NMR spectroscopies. H NMR
(400 MHz, CDCl3): 4.602 ppm (s, 6H, NCH2N), 4.054 ppm (d,
2JPH ) 10 Hz, 5H, PCH2N, PCHDN). 13C{1H} NMR (100 MHz,
CDCl3): 73.66 ppm (vt, JPC ) 2 Hz, 3C, NCH2N), 50.60 ppm (d,
1JPC ) 20 Hz, 1C, PCH2N), 50.575 ppm (d, JPC ) 20 Hz, 1C,
PCH2N), 50.218 (vq, JPC ) 21 Hz, JDC ) 21 Hz, 1C, PCHDN).
31P{1H} NMR (162 MHz, CDCl3): -102.52 ppm (s, PTA-D),
-102.07 ppm (s, PTA).
1
1
1
Caution! PTA-Li is a highly pyrophoric solid, igniting Violently
upon exposure to air.
Synthesis of 6-(Diphenylphosphino)-1,3,5-triaza-7-phosphaada-
mantane (PTA-PPh2; 1). PTA-Li (0.5240 g, 3.21 mmol) was
suspended in 10 mL of anhydrous DME followed by the immediate
addition of chlorodiphenylphosphine (2.23 mmol, 0.49 g) at room
(10) Darensbourg, D. J.; Yarbrough, J. C.; Lewis, S. J. Organometallics
2003, 22, 2050-2056.
(11) (a) Darensbourg, D. J.; Ortiz, C. G.; Kamplain, J. W. Organometallics
2004, 23, 1747-1754. (b) Siele, V. I. J. Heterocycl. Chem. 1977, 14,
337-339.
(12) Daigle, D. J. Inorg. Synth. 1998, 3240-3245.
(13) Darensbourg, D. J.; Kump, R. L. Inorg. Chem. 1978, 17, 2680-2682.
(14) XRD Single-Crystal Software; Bruker Analytical X-ray Systems:
Madison, WI, 1999.
(15) See the Supporting Information for details.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6749

Wong et al.
Table 1. Summary of Data Collection, Solution, and Refinement Parameters for Compounds 1-4
PTA-PPh2 (1)
[W(CO)4(PTA-PPh2)] (2)
[Mo(CO)4(PTA-PPh2)] (3)
cis-[W(CO)4(PTA)(PPh3)] (4)
empirical
formula
fw
P(C6H5)2C6H11N3P
(CO)4W(P(C6H5)2C6H11N3P)
(CO)4Mo(P(C6H5)2C6H11N3P)
(CO)4W(P(C6H5)3)(PN3C6H12)
341.32
637.21
549.3
715.32
T (K)
100(2)
100(2)
100(2)
100(2)
wavelength (Å)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.710 73
monoclinic
P2(1)/n
14.357(2)
6.2457(9)
19.192(3)
90
101.598 (3)
90
1685.8(4)
4
0.710 73
monoclinic
P2(1)/n
13.989(5)
11.657(4)
14.086(5)
90
100.685(10)
90
2257.1(14)
4
0.710 73
monoclinic
P2(1)/n
14.005(7)
11.715(6)
14.060(7)
90
101.200(10)
90
2262.9(2)
4
0.710 73
monoclinic
P2(1)/m
10.015(2)
12.534(3)
11.605(2)
90
110.847(3)
90
1361.4(5)
2
Z
D
calcd (Mg/m3)
1.345
0.261
1.875
5.294
1.612
0.756
1.745
4.400
abs coeff (mm-1
cryst size (mm3)
θ range for data
collection
)
0.12 × 0.05 × 0.03
0.15 × 0.11 × 0.05
0.66 × 0.29 × 0.10
0.14 × 0.08 × 0.03
1.62-26.00
1.88-30.00
1.88-32.27
1.88-32.37
(deg)
index ranges
-17 e h e 17
-7 e k e 7
-23 e l e 23
18 907
-16 e h e 19
16 e k e 14
-19 e l e 19
17 503
-20 e h e 20
-17 e k e 17
-21 e l e 21
39 784
-15 e h e 13
-14 e k e 18
-17 e l e 17
14 622
reflns collected
independent reflns
abs correction
data/restraints/
param
3324 (Rint ) 0.0683)
6490 (Rint ) 0.0434)
7997 (Rint ) 0.0207)
5022 (Rint ) 0.0584)
SADABS
SADABS
SADABS
SADABS
3324/0/208
6490/0/289
7997/0/373
5022/0/205
GOF on F 2
final R indices
[I > 2σ(I)]
R indices
1.072
1.022
1.082
0.983
R1 ) 0.0659,
wR2 ) 0.1791
R1 ) 0.0970,
wR2 ) 0.1949
603500
R1 ) 0.0376,
wR2 ) 0.0755
R1 ) 0.0565,
wR2 ) 0.0794
603501
R1 ) 0.0253,
wR2 ) 0.0723
R1 ) 0.0278,
wR2 ) 0.0738
603502
R1 ) 0.0387,
wR2 ) 0.0721
R1 ) 0.0540,
wR2 ) 0.0766
603503
(all data)
CCDC no.
1
temperature. The reaction was stirred overnight and DME removed
under vacuum. The resulting yellow-white solid was washed with
water to remove PTA and LiCl. The remaining solid was dissolved
in a minimal amount of methanol/toluene (50:50, v/v) and purified
by column chromatography (PTA-PPh2; Rf value ) 0.55), resulting
solid in 5% overall yield (44% based on a 10% yield of 1). H
NMR (400 MHz, CD2Cl2): 3.7-4.9 ppm (m, PCH2N, NCH2N,
2
10H), 5.63 (apparent triplet, JPH ) 10 Hz, PCHP, 1H), 7.4-8.0
ppm (m, PPh2, 10H). 13C{1H} NMR (100 MHz, CD2Cl2): 55.65
1
1
ppm (d, JPC ) 10 Hz, PCH2N), 56.20 ppm (d, JPC )17 Hz,
PCH2N), 69.26 ppm (d, 3JPC ) 7 Hz, NCH2N), 73.61 ppm (d, 3JPC
) 6 Hz, NCH2N), 77.35 ppm (t, 3JPC ) 5 Hz, NCH2N), 79.67 ppm
(dd, 1JPC ) 21 and 19 Hz, PCHP), 129-132 ppm (m, Ar), 135.33
1
in 75 mg of an off-white solid (0.22 mmol, 10% yield). H NMR
(400 MHz, CD2Cl2): 7.0-7.5 ppm (m, 10H, Ar), 5.25 ppm (dt, J
) 2 and 14 Hz, 1H, P-CH-P), 3.6-4.8 ppm (m, 10H, NCH2N,
PCH2N). 13C{1H} NMR (100 MHz, CD2Cl2): 135.4 ppm (dd, JPC
) 3 Hz, JPC ) 22 Hz, Ar), 132.9 ppm (d, JPC ) 18 Hz, Ar), 129.9
ppm (s, Ar), 128.7 ppm (m, Ar), 76.6 ppm (d, JPC ) 2 Hz, NCN),
1
1
(d, JPC ) 15 Hz, Ar), 139.07 ppm (d, JPC ) 15 Hz, 1C, PCar),
1
139.39 ppm (d, JPC ) 15 Hz, 1C, PCar), 202.98 ppm (apparent
triplet, 2JPC ) 7 Hz, cis-CO), 203.77 ppm (apparent triplet, 2JPC
)
3
3
74.5 ppm (s, NCN), 68.4 ppm (dd, JPC ) 11 Hz, JPC ) 2 Hz,
N-C-N), 61.6 ppm (dd, 1JPC ) 30 Hz, 1JPC ) 14 Hz, 1C, P-CH-
P), 52.2 (dd, JPC ) 23 Hz, JPC ) 4 Hz, PCN), 47.9 ppm (dd, JPC
) 23 Hz, JPC ) 3 Hz, PCN). 31P{1H} NMR (162 MHz, CD2Cl2):
7 Hz, cis-CO), 209.37 ppm (m, two trans-CO’s). 31P{1H} NMR
(162 MHz, CD2Cl2): 21.7 ppm (d, 2JPP ) 26 Hz, 1JPW ) 201 Hz,
PPh2), -89.5 ppm (d, 2JPP ) 26 Hz, 1JPW ) 185 Hz, PTA). IR νCO
(CH2Cl2, cm-1): 2017 (s), 1917 (sh), 1899 (s), 1881 (sh). Anal.
Calcd for 2‚2(CH2Cl2): C, 35.71; H, 3.12; N, 5.21. Found: C,
35.21; H, 3.19; N, 5.28. Crystals suitable for X-ray diffraction were
obtained by slow diffusion of diethyl ether into a dichloromethane
solution of 2, resulting in yellow blocks after a few days.
2
2
-19.8 ppm (d, JPP ) 65 Hz, PPh2), -100.1 ppm (d, JPP ) 65
Hz, PTA). GC-MS (m/z): 342 (M+) 156 (major fragment
PN3C6H11). Anal. Calcd for PTA-PPh2: C, 63.34; H, 6.20; N, 12.31.
Found: C, 63.07; H, 6.23; N, 12.15. X-ray-quality crystals were
obtained by slow diffusion of diethyl ether into a methylene chloride
solution of PTA-PPh2, resulting in the formation of clear and
colorless rods over the course of 1 week.
Synthesis of [Mo(CO)4(PTA-PPh2)] (3). The synthesis of 3 was
accomplished in a manner analogous to that of 2. Crude PTA-PPh2
(230 mg) and cis-[Mo(CO)4(NHC5H10)2] (240 mg, 0.63 mmol) were
refluxed for 5 min in 20 mL of degassed dichloromethane. The
reaction mixture was filtered through Celite and the volume reduced
under vacuum to ∼5 mL. The addition of methanol and cooling to
0 °C resulted in the precipitation of 38 mg (0.07 mmol) of
crystalline 3; an 11% overall yield based on cis-[Mo(CO)4(pip)2].
1H NMR (500 MHz, CD2Cl2): 3.6-4.8 ppm (m, PCH2N, NCH2N,
10H), 5.60 ppm (apparent triplet, 2JPH ) 10 Hz, PCHP, 1H), 7.4-
8.0 ppm (m, PPh2, 10H). 31P{1H} NMR (202 MHz, CD2Cl2): 37.3
ppm (d, 2JPP ) 23 Hz, PPh2), -64.9 ppm (d, 2JPP ) 23 Hz, PTA).
Synthesis of [W(CO)4(PTA-PPh2)] (2). PTA-PPh2 was prepared
from 0.48 g of PTA-Li (2.94 mmol) and chlorodiphenylphosphine
(2.23 mmol, 0.49 g), as described above without purification by
column chromatography. The addition of the crude PTA-PPh2 to a
degassed dichloromethane solution of cis-[W(CO)4(NHC5H10)2]
(1.11 g, 2.38 mmol) under refluxing conditions afforded a yellow
solution. The solution was filtered through Celite, and the volume
was reduced under vacuum. The addition of methanol and cooling
to 0 °C resulted in the isolation of 69 mg of 2 as a yellow crystalline
6750 Inorganic Chemistry, Vol. 45, No. 17, 2006

NoWel Bidentate Phosphine
Scheme 1. Synthesis of PTA-Li and Reaction with D2O
Scheme 2. Synthesis of PTA-PPh2
by the reaction of PTA-Li with chlorodiphenylphosphine in
DME (Scheme 2). Other than PTA (resulting from proto-
nation of PTA-Li), the major byproducts of the reaction were
Ph2P-PPh2, Ph2P(O)PPh2, and Ph2P(O)-(O)PPh2, obtained
from the reductive coupling of 2 equiv of ClPPh2.16 PTA-
PPh2 is no longer water-soluble, as a result of the addition
of the large hydrophobic PPh2 group to the PTA fragment,
but is readily soluble in common organic solvents (e.g., CH2-
Cl2, CHCl3, and CH3OH). Protonation of PTA-PPh2, presum-
ably at a PTA nitrogen, in 1 M HCl(aq) results in a white
solid that is insoluble in both water and common organic
solutions. The 31P{1H} NMR spectrum of PTA-PPh2 contains
the expected pair of doublets at -19.8 and -100.1 ppm (d,
2JPP ) 65 Hz), indicating two inequivalent phosphorus nuclei.
The phenyl protons are observed as a multiplet between 7.0
and 7.5 ppm, integrating as 10 protons. The P-CH-P proton
appears as a complex multiplet (apparent triplet of doublets)
centered at 5.25 ppm, with the remaining PTA protons
observed as a complex set of peaks between 3.6 and 4.8 ppm,
integrating as 10 protons (PCH2N and NCH2N). The 13C-
{1H} NMR spectrum contains two doublet of doublets at
47.9 and 52.2 ppm (1JPC ) 23 and 4 Hz) for the unmodified
P-CH2-N carbons of the PTA fragment and a doublet of
doublets at 61.6 ppm (1JPC ) 30 and 14 Hz) for the carbon
bound to both phosphorus nuclei. The N-C-N carbons
appear in the region expected for PTA (73.5 ppm for
IR νCO (CH2Cl2, cm-1): 2022 (m), 1923 (sh), 1908 (vs), 1889 (m).
X-ray-quality crystals were obtained by layering a CH2Cl2 solution
of 3 with diethyl ether, resulting in clear pale-yellow blocks.
Synthesis of cis-[W(CO)4(PTA)(PPh3)] (4). PTA (31 mg, 0.20
mmol) was added to a suspension of cis-[W(CO)4(PPh3)2] (171 mg,
0.21 mmol) in dichloromethane. The reaction mixture was refluxed
for 22 h and monitored periodically by 31P NMR to obviate the
formation of cis-[W(CO)4(PTA)2] (5). Upon cooling to room
temperature, the solution was filtered through Celite and the solvent
volume reduced to a minimum under vacuum. The product was
isolated by column chromatography with toluene/methanol (4:1,
v/v) as the eluant (Rf ) 0.05 for 5, 0.48 for cis-[W(CO)4(PTA)-
(PPh3)], and 0.99 for cis-[W(CO)4(PPh3)2]). Removal of the solvent
under reduced pressure yielded 78 mg (0.11 mmol, 52% yield) of
1
4 as a pale-yellow powder. H NMR (300 MHz, CD2Cl2): 7.48
ppm (m, 15H, C6H5), 4.34 ppm (AB q, 6H, PCH2N), 3.75 ppm (s,
6H, NCH2N). 31P{1H} NMR (121 MHz, CD2Cl2): 22.7 ppm (d,
2JPP ) 21 Hz, 1JPW ) 236 Hz, PPh3), -80.3 ppm (d, 2JPP ) 21 Hz,
1JPW ) 218 Hz, PTA). IR νCO (CH2Cl2, cm-1): 2017 (m), 1913
(sh), 1898 (vs), 1879 (sh). X-ray-quality crystals were obtained by
the slow diffusion of diethyl ether into a dichloromethane solution
of 4, resulting in pale-yellow plates.
Results and Discussion
Synthesis of PTA-Li. The lithiation of PTA, yielding
PTA-Li, was carried out in high yield by the addition of
n-butyllithium to a suspension of PTA (Scheme 1). PTA-Li
was isolated as an off-white highly pyrophoric powder in
>90% yield. Because of its insolubility in common organic
solvents and the extreme pyrophoric nature of PTA-Li,
characterization was obtained based on the reaction of PTA-
Li with D2O. Reaction yields of PTA-Li were determined
by integration of the PTA (-102.07 ppm) and PTA-D
(-102.52 ppm) resonances obtained from the 31P NMR
spectrum of PTA-Li following reaction with D2O.15 Deu-
teration occurred regioselectively at an R-phosphorus meth-
ylene, as confirmed by 13C NMR spectroscopy.15 The 13C
NMR spectrum of PTA contains a single PCH2N methylene
resonance appearing as a doublet (1JCP ) 21 Hz) in CDCl3.
The PCH2N region (approximately 50 ppm) of the 13C NMR
spectrum of PTA-D in CDCl3 contains three sets of reso-
nances: two doublets (1JPC ) 20 Hz) centered at 50.60 and
50.575 ppm resulting from the two inequivalent PCH2N
groups and an apparent quartet for the PCHDN group
centered at 50.21 ppm. The apparent quartet arises from
3
PTA):4,12 68.4 (dd, JPC ) 11 and 2 Hz), 74.5 (s), and 76.6
3
ppm (d, JPC ) 2 Hz).
PTA is stable in air almost indefinitely; however, in
CH2Cl2, PTA-PPh2 is slowly oxidized preferentially at the
PTA phosphorus. 31P NMR spectra taken over time show
that, concomitant with the loss of the doublet at -100.1 ppm,
a doublet at -6.2 ppm (2JPP ) 40 Hz) grows in, which is
close to the chemical shift observed for oxidized PTA, Od
PTA (-2.5 ppm).12 After 1 week, ∼15% of PTA-PPh2 was
converted into OdPTA-PPh2. The PPh2 signal shifts slightly
to -19.7 ppm (2JPP ) 40 Hz) upon oxidation of the PTA
phosphorus. Oxidation of both phosphines of PTA-PPh2 with
H2O2 results in a 31P NMR spectrum containing two doublets
at -1.4 and 34.3 ppm (2JPP ) 4 Hz) for the OdPTA and
OdPPh2 phosphorus nuclei, respectively.
Structure of PTA-PPh2. The solid-state structure of PTA-
PPh2 was determined by X-ray crystallography. Compound
1 crystallized in the centrosymmetric space group P2(1)/c,
and both R and S enantiomers are present. A thermal ellipsoid
representation of 1 is shown in Figure 2 along with selected
bond lengths and angles. The P-C distances in 1 are
perturbed relative to the parent PTA ligand (P-Cave ) 1.856
1
coupling of both the 31P and D nuclei to the 13C nucleus
1
with approximately the same coupling constant (1JCD ∼ JPC
∼ 21 Hz).
Synthesis and Characterization of PTA-PPh2. The chiral
bidentate phosphine PTA-PPh2 was synthesized in low yield
(16) (a) Fluck, E.; Issleib, K. Chem. Ber. 1965, 98, 2674. (b) Russell, G.
A.; Khanna, R. K. Phosphorus Sulfur 1987, 29, 271-274.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6751

Wong et al.
Figure 3. IR spectra in the νCO region of 2 (2) and 3 (b) in
dichloromethane.
Table 2. IR νCO Stretching Frequencies of a Series of cis-[M(CO)4L2]
Complexes [M ) W and Mo; L2 ) (PTA)2, (PPh3)2, PTA-PPh2, DPPM]
Figure 2. Representation of PTA-PPh2 (1) along with the atomic
numbering scheme (thermal ellipsoids are drawn at 50% probability). Only
the S enantiomer is shown; however, both are present in the structure.
Selected bond lengths (Å) and angles (deg): P1-C1 ) 1.890(4); P1-C2
) 1.815(5); P1-C3 ) 1.832(4); P2-C1 ) 1.867(4); N1-C1 ) 1.577(5);
N1-C4 ) 1.508(5); N1-C6 ) 1.530(5); N2-C5 ) 1.477(5); P1-C1-
P2 ) 108.79(18); P2-C1-N1 ) 109.8(2).
ν
CO, cm-1
complexa
A(12)
A(11)
B1
B2
[W(CO)4(PTA-PPh2)] (2) 2018 (m) 1916 (sh) 1899 (vs) 1881 (sh)
[W(CO)4(PPh3)(PTA)] (4) 2017 (m) 1913 (sh) 1898 (vs) 1879 (sh)
[W(CO)4(PTA)2] (5)
[W(CO)4(PPh3)2]
[W(CO)4(DPPM)] (6)
[Mo(CO)4(PTA)2]b,13
[Mo(CO)4(PPh3)2]b,13
2018 (m) 1917 (sh) 1900 (vs) 1883 (sh)
2018 (m) 1939 (m) 1907 (sh) 1889 (vs)
2018 (m) 1916 (sh) 1904 (vs) 1874 (m)
2022 (m) 1930 (m) 1910 (vs) 1904 (sh)
2023 (m) 1927 (m) 1908 (vs) 1897 (m)
Scheme 3. Synthesis of 2 and 3
[Mo(CO)4(PTA-PPh2)] (3) 2022 (m) 1923 (sh) 1908 (vs) 1889 (m)
[Mo(CO)4(DPPM)]c,20
2020 (m) 1920 (s) 1907 (vs) 1879 (vs)
a Spectra determined in CH2Cl2. b Solvent: tetrachloroethylene. c Solvent:
ClCH2CH2Cl.
Å);17 P1-C1 in 1 is elongated to 1.890(4) Å, and the P1-
C2 and P1-C3 distances are slightly compressed to 1.815(5)
and 1.832(4) Å, respectively. The P-C-P angle in PTA-
PPh2 of 108.79(18)° is comparable to the P-C-P angle
observed in diphenylphosphinomethane (DPPM) of 106.2(3)°.18
Synthesis, Structure, and Spectral Properties of
[M(CO)4(PTA-PPh2)] (M ) W and Mo). The coordination
chemistry of PTA-PPh2 was explored through the synthesis
of two group 6 metal carbonyl complexes by the addition of
racemic PTA-PPh2 to cis-[M(CO)4Pip2] (M ) W and Mo)
in refluxing CH2Cl2 (Scheme 3). The 31P NMR spectrum of
2 contained the expected pair of doublets centered at +21.7
cis-CO ligands into doublet of doublets by the two phos-
phorus nuclei. IR spectra were obtained for both 2 and 3
with the expected pattern for complexes of pseudo C2V
symmetry (Figure 3); the molybdenum complex 3 appears
at higher wavenumbers. Table 2 contains a comparison of
the νCO region of the IR for a series of group 6 metal carbonyl
complexes. On the basis of the IR data for the W(CO)4L2
series, PTA-PPh2 is more electron-donating than (PPh3)2,
slightly more electron-donating than DPPM, and comparable
electronically to (PTA)2 or a mixture of PTA and PPh3.
The solid-state structures of 2 and 3 were determined by
X-ray crystallography. Pale-yellow block crystals were
obtained for both the tungsten and molybdenum analogues
by layering a dichloromethane solution of 2 or 3 with diethyl
ether. The two compounds are isostructural, with each
containing a distorted octahedral metal center with four
carbonyl ligands and the chelating PTA-PPh2 ligand coor-
dinated in a cis fashion as expected. Analogously, the solid-
state structures of 1-3 crystallized in the centrosymmetric
space group P21/n and each structure contains both the R
and S enantiomers of the chiral product. Thermal ellipsoid
representations of 2 and 3 along with the atomic numbering
scheme and selected bond lengths and angles may be found
in Figures 4 and 5, respectively. In both compounds, the PTA
phosphorus is slightly closer to the metal, P1-W1 )
2.4949(11) Å, P1-Mo1 ) 2.5040(3) Å, relative to the PPh2
phosphorus, P2-W1 ) 2.5349(12) Å, P2-Mo1 ) 2.5548-
(3) Å. The carbonyl ligands trans to phosphorus (C1 and
C2) have shorter M-C bonds than the mutually trans CO
ligands (C3 and C4): W1-C1 ) 1.986(5) Å, W1-C2 )
1.972(5) Å, W1-C3 ) 2.037(5) Å, W1-C4 ) 2.048(5) Å;
2
(PPh2) and -89.5 ppm (PTA), JPP ) 26 Hz. Tungsten
satellites were also observed, 1JPTA-W ) 185 Hz and 1JPPh -W
2
) 201 Hz. The molybdenum analogue, 3, also displayed the
expected pair of doublets in the 31P NMR spectrum centered
at +37.3 (PPh2) and -64.9 ppm (PTA), 2JPP ) 23 Hz. These
31P NMR chemical shifts are consistent with other group 6
metal carbonyl complexes containing PTA: [Mo(CO)5PTA],
-55.9 ppm;19 cis-[Mo(CO)4PTA2], -54.9 ppm;19 [W(CO)5-
PTA], -78.4 ppm.10,19 The carbonyl ligands trans to the
phosphines appear in the 13C NMR spectrum of 2 as two
apparent triplets at 202.98 (2JCP ) 7 Hz) and 203.77 ppm
(2JCP ) 7 Hz). The two CO ligands cis to phosphorus appear
as a complicated set of seven lines, centered at 209.37 ppm,
resulting from the splitting of the chemically inequivalent
(17) (a) Jogun, K. H.; Stezowski, J. J.; Fluck, E.; Weidlein, J. Phosphorus
Sulfur 1978, 4, 199-204. (b) Marsh, R. E.; Kapon, M.; Hu, S.;
Herbstein, F. H. Acta Crystallogr., Sect. B 2002, B58, 62-77.
(18) Schmidbaur, H.; Reber, G.; Schier, A.; Wagner, F. E.; Mu¨ller, G. Inorg.
Chim. Acta 1988, 147, 143-150.
(19) Alyea, E. C.; Fisher, K. J.; Foo, S.; Philip, B. Polyhedron 1993, 12,
489-492.
6752 Inorganic Chemistry, Vol. 45, No. 17, 2006

NoWel Bidentate Phosphine
Table 3. 31P NMR Chemical Shifts and Coupling Constants for 1 and
a Series of cis-[W(CO)4L2] Complexes [L2 ) (PTA)2, (PPh3)2, PTA-
PPh2, DPPM] in CD2Cl2
2JPP
Hz
,
1JPTA-W
Hz
,
1JPW
,
Hz
complex
PTA-PPh2 (1)
[W(CO)4(PTA-PPh2)] (2)
[W(CO)4(PPh3)(PTA)] (4) +22.7, -80.3
[W(CO)4(PTA)2] (5)
[W(CO)4(PPh3)2]
31P NMR
-19.8, -100.1
+21.7, -89.5
65
26
21
185
218
201
236
216
235
202
-76.5
+34.15
-21.9
[W(CO)4(DPPM)] (6)
For comparison to complex 2, we synthesized a series of
related compounds by reaction of cis-[W(CO)4(pip)2] with
PTA, PPh3, and/or dppm: 4, 5, and [W(CO)4(DPPM)] (6)
(Tables 2 and 3). 4 was synthesized in modest yields through
substitution of a triphenylphosphine ligand in cis-[W(CO)4-
(PPh3)2] by PTA. The 31P NMR spectrum of the complex
Figure 4. Thermal ellipsoid (50% probability) representation of 2 with
the atomic numbering scheme. Only the S enantiomer is shown; however,
both the R and S enantiomers are present in the structure. Selected bond
lengths (Å) and angles (deg): W1-P1 ) 2.4949(11); W1-P2 ) 2.5349-
(12); W1-C1 ) 1.986(5); W1-C2 ) 1.972(5); W1-C3 ) 2.037(5); W1-
C4 ) 2.048(5); P1-C5 ) 1.840(4); P2-C5 ) 1.870(4); P1-W1-P2 )
68.18(4); P1-C5-P2 ) 98.9(2); W1-P1-C5 ) 94.21(13); W1-P2-C5
) 92.18(14); P1-W1-C1 ) 169.02(14); P2-W1-C2 ) 166.05(13); P1-
W1-C2 ) 98.51(13); P1-W1-C3 ) 90.92(13); P2-W1-C1 ) 101.24(14);
P2-W1-C3 ) 97.71(13); C3-W1-C4 ) 174.14(17); C3-W1-C2 )
86.34(19).
exhibits a pair of doublets at +22.7 and -80.3 ppm (2JPP
)
21 Hz) for the PPh3 and PTA ligands, respectively, similar
to the 31P NMR spectrum of 2. The 2JPP of 21 Hz is indicative
of cis substitution.22 Each phosphorus in the complex also
couples to tungsten-183, giving rise to tungsten satellites,
1
1JW-PTA ) 218 Hz and JW-PPh3 ) 236 Hz. The W-P
coupling constants in 4 are ∼33 Hz larger than those
observed for 2, which are diminished because of the strain
of the four-membered chelate ring in 3 relative to 4.20 The
31P NMR resonance of the PTA ligand in 4 is shifted slightly
upfield (-80.3 ppm) relative to that in 5 (-76.5 ppm) and
may be due to steric strain, resulting in distortion of the
octahedral geometry about the tungsten center as reported
by Schenk and Buchner.22 The 31P NMR resonance resulting
from the PPh3 ligand at 22.7 ppm correlates well with that
observed for other cis-[W(CO)4(PPh3)(PR3)] complexes (e.g.,
22.9 ppm for cis-[W(CO)4(PPh3)P(OPh)3]).22 The tungsten
1
phosphorus couplings, JPW, observed for cis-[W(CO)4-
(PPh3)2] and cis-[W(CO)4(PPh3)(PTA)] are significantly
1
larger than the corresponding JPW couplings observed in 2
(Table 3). This is at least partially due to distortion of the
tungsten center from an ideal octahedron, although this likely
does not account for the entire difference. IR spectra for
compounds 2-6 (Table 2) reveal that these compounds have
similar electronic environments. PTA-PPh2 is more electron-
donating than PPh3 and DPPM and similar electronically to
PTA or a mixture of PTA and PPh3.
The solid-state structure of 4 was determined by X-ray
crystallography (Table 1). Crystals were obtained by slow
diffusion of diethyl ether into a CH2Cl2 solution of 4,
resulting in pale-yellow plates. Figure 6 contains the thermal
ellipsoid representation and atomic numbering scheme of 4.
The tungsten center is in a distorted octahedral environment
with P1-W1-P2 ) 100.60(4)°, C1-W1-P1 ) 171.36(15)°,
C3-W1-P2 ) 88.28(10)°, and C3-W1-C3A ) 165.8(2)°.
The W-P distances in 4, W1-P1 ) 2.5043(13) Å and W1-
P2 ) 2.5151(13) Å, are consistent with other tungsten
carbonyl phosphine structures. Interestingly, the W-P1
distance in 4 is slightly longer than that for [W(CO)4PTA-
Figure 5. Thermal ellipsoid (50% probability) representation of 3 along
with the atomic numbering scheme. Only the R enantiomer is shown;
however, both the R and S enantiomers are present in the structure. Selected
bond lengths (Å) and angles (deg): Mo1-P1 ) 2.5040(3); Mo1-P2 )
2.5548(3); Mo1-C1 ) 1.9881(13); Mo1-C2 ) 1.9767(12); Mo1-C3 )
2.0490(13); Mo1-C4 ) 2.0449(13); P1-C5 ) 1.8449(11); P2-C5 )
1.8671(11); P1-Mo1-P2 ) 68.370(10); P1-C5-P2 ) 99.95(5); Mo1-
P1-C5 ) 93.72(3); Mo1-P2-C5 ) 91.56(4); P1-Mo1-C1 ) 169.42-
(4); P2-Mo1-C2 ) 166.71(4); P1-Mo1-C2 ) 99.05(4); P1-Mo1-C3
) 93.98(4); P2-Mo1-C1 ) 101.42(4); P2-Mo1-C3 ) 87.10(4); C3-
Mo1-C4 ) 174.12(5); C2-Mo1-C3 ) 89.62(5).
Mo1-C1 ) 1.9881(13) Å, Mo1-C2 ) 1.9767(12) Å, Mo1-
C3 ) 2.0490(13) Å, Mo1-C4 ) 2.0449(13) Å. The bite
angle, P1-M1-P2, is 68.18(4)° for 2 and 68.370(10)° for
3, similar to the bite angle of the related dppm analogues at
67.108(16)° and 67.3(1)° for [W(CO)4dppm] (vide infra) and
[Mo(CO)4-dppm],21 respectively.
(20) Grim, S. O.; Briggs, W. L.; Barth, R. C.; Tolman, C. A.; Jesson, J. P.
Inorg. Chem. 1974, 13, 1095-1100.
(21) Cheung, K. K.; Lai, T. F.; Mok, K. S. J. Chem. Soc. A 1971, 1644-
1647.
(22) Schenk, W. A.; Buchner, W. Inorg. Chim. Acta 1983, 70, 189-196.
(23) Bernal, I.; Reisner, G. M.; Dobson, G. R.; Dobson, C. B. Inorg. Chim.
Acta 1986, 121, 199-206.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6753

Wong et al.
Figure 6. Thermal ellipsoid (50% probability) representation of 4 along
with the atomic numbering scheme. Selected bond lengths (Å) and angles
(deg): W1-P1 ) 2.5043(13); W1-P2 ) 2.5151(13); W1-C1 ) 1.995(5);
W1-C2 ) 2.009(5); W1-C3 ) 2.026(4); P1-C5 ) 1.844(4); P2-C11 )
1.823(5); P1-W1-P2 ) 100.60(4); P1-W1-C1 ) 171.36(15); P1-W1-
C2 ) 87.57(15); P1-W1-C3 ) 83.53(10); P2-W1-C1 ) 88.04(15); P2-
W1-C3 ) 88.28(10); C3-W1-C3A ) 165.8(2); C3-W1-C2 ) 92.68(10).
Figure 7. Representation of 5 with the atomic numbering scheme (thermal
ellipsoids are drawn at 50% probability). Selected bond lengths (Å) and
angles (deg): W1-P1 ) 2.4804(10); W1-C1 ) 2.003(5); W1-C2 )
2.011(8); W1-C3 ) 2.046(7); P1-C5 ) 1.841(4); P1-W1-P1A )
100.66(5); P1-W1-C1 ) 87.69(13); P1-W1-C1A ) 171.65(13); P1-
W1-C2 ) 89.09(15); P1-W1-C3 ) 83.62(11); C1-W1-C2 ) 91.1(2);
C2-W1-C3 ) 168.5(3); C1-W1-C3 ) 97.45(18).
Table 4. Comparison of Selected Bond Lengths (Å) and Angles (deg)
for cis-[M(CO)4L2] (M ) Mo and W; L ) Phosphine Ligand)
bond lengths (Å)
bond angle (deg)
compound
M1-P1
M1-P2
P1-M1-P2
[W(CO)4(PTA-PPh2)] (2) 2.4949(11) 2.5349(12)
[W(CO)4(PTA)(PPh3)] (4) 2.5043(13) 2.5151(13)
68.18(4)
100.60(4)
100.66(5)
67.108(16)
68.370(10)
67.3(1)
[W(CO)4(PTA)2] (5)
[W(CO)4(dppm)] (6)
2.4804(10) 2.4804(10)a
2.5291(5)
2.5070(5)
2.5548(3)
2.501(2)
2.495(2)
[Mo(CO)4(PTA-PPh2)] (3) 2.5040(3)
[Mo(CO)4(dppm)]21,20
[Mo(CO)4(dppe)]23
2.535(3)
2.500(2)
80.2(1)
a Generated by symmetry.
PPh2], and the W1-P2 distance in 4 is slightly shorter than
the corresponding distance in [W(CO)4PTA-PPh2] (Table 4).
The solid-state structures of the previously reported com-
plexes [W(CO)4DPPM]20 and cis-[W(CO)4PTA2]19 were also
determined by X-ray crystallography. Figures 7 and 8 contain
thermal ellipsoid representations of 5 and 6, respectively,
along with the atomic numbering scheme and selected bond
lengths and angles. Table 4 contains structural comparisons
of compounds 2-6.
Figure 8. Thermal ellipsoid representation of 6 with the atomic numbering
scheme (thermal ellipsoids are drawn at 50% probability). Selected bond
lengths (Å) and angles (deg): W1-P1 ) 2.5291(5); W1-P2 ) 2.5070(5);
W1-C1 ) 1.980(2); W1-C2 ) 1.993(2); W1-C3 ) 2.029(2); W1-C4
) 2.036(2); P1-C5 ) 1.8532(19); P2-C5 ) 1.8523(19); P1-W1-P2 )
67.108(16); P1-C5-P2 ) 97.39(9); P1-W1-C1 ) 164.76(6); P2-W1-
C2 ) 167.64(6); P1-W1-C2 ) 100.54(6); P1-W1-C3 ) 98.31(6); P2-
W1-C1 ) 97.84(6); P2-W1-C3 ) 95.22(6); C3-W1-C4 ) 167.96(8);
C3-W1-C2 ) 85.97(9).
Conclusion
We have reported here the results of lithiation of PTA
leading to PTA-Li. Utilizing this reactive synthon, we
synthesized a new chiral chelating phosphine, PTA-PPh2,
based on the PTA framework. The racemic form of PTA-
PPh2 was fully characterized in both solution and the solid
state; unfortunately, this ligand does not carry all of the
desirable properties of PTA, namely, water solubility.
However, the ability to modify PTA, through lithiation, at
an R-phosphorus methylene opens up a great deal of
possibilities in the development of new phosphine ligands
with the potential to be water-soluble. Of particular interest
is that PTA compounds modified in this manner lead to chiral
phosphine ligands, in which the stereogenic center is adjacent
to phosphorus and therefore in close proximity to a coordi-
nated metal. We are currently developing methodologies to
circumvent the low yields obtained for the PTA derivatives,
presumably, due to the bulky nature of the PTA-Li nucleo-
phile.
Acknowledgment. The authors thank Lauren Volz,
Phillip Gingrich, and Dr. Rongcai Huang for their assistance.
G.W.W. thanks the NSF-EPSCoR program (UCCSN-02-124)
for a summer fellowship and the UNR Office of Under-
graduate Research for support. The donors of the American
Chemical Society Petroleum Research Fund provided partial
support of this project. We also thank Cytec for the generous
gift of P(CH2OH)4Cl. Financial support from NSF (Grant
CHE-0226402) for the purchase of a X-ray diffractometer
is recognized.
6754 Inorganic Chemistry, Vol. 45, No. 17, 2006

NoWel Bidentate Phosphine
Supporting Information Available: Synthesis of PTA-D, cis-
[W(CO)4PTA2], and [W(CO)4DPPM]; NMR spectra of PTA-D,
PTA-PPh2, OdPTA-P(O)Ph2, and 2; IR spectra of compounds 4-6;
crystallographic details for 5 and 6; full bond lengths and angles;
and CIF files for compounds 1-6. This material is available free
of charge via the Internet at http://pubs.acs.org.
IC060576A
Inorganic Chemistry, Vol. 45, No. 17, 2006 6755