Design, synthesis, and chemistry of sterically nondemanding primary bisphosphines

Article abstract of DOI:10.1021/ja047238y

Design and synthesis of chelating bisphosphines functionalized with the smallest chemical unit "H" on the P^III centers ((PH ₂CH₂)₂CHCH₂NHPh (4) and (PH ₂CH₂)₂CHCONHPh

Full text of DOI:10.1021/ja047238y

Published on Web 12/07/2004
Design, Synthesis, and Chemistry of Sterically Nondemanding
Primary Bisphosphines1
Nagavarakishore Pillarsetty,† Kannan Raghuraman,‡ Charles L. Barnes,† and
Kattesh V. Katti*,‡,§
Contribution from the Departments of Radiology, Chemistry, and Physics, Room 106,
Alton Building Laboratories, 301 Business Loop 70W, UniVersity of Missouri-Columbia,
Columbia, Missouri 65211
Received May 11, 2004; E-mail: kattik@health.missouri.edu
Abstract: Design and synthesis of chelating bisphosphines functionalized with the smallest chemical unit
“H” on the PIII centers ((PH2CH2)2CHCH2NHPh (4) and (PH2CH2)2CHCONHPh (5)) are described. Studies
demonstrating that no bulky chemical substituents are necessary to offer thermal/oxidative stability to the
-PH2 groups in 4 and 5 are described. The H atoms around the PIII centers in 5 (or 4) concur limited/no
steric influence, but yet the phosphines manifest high nucleophilicity to coordinate strongly with W(0) and
Re(I). The studies include synthesis and X-ray structural characterization of an air-stable primary
bisphosphine (5) and its transition-metal chemistry with W(CO)6 and Re(CO)5Br to produce the complexes
(η2-(PH2CH2)2CHCONHPh)W(CO)4 (6) and (η2-(PH2CH2)2CHCONHPh)Re(CO)3Br (7), respectively.
Introduction
in the overall design and development of phosphine ligands for
transition-metal-based homogeneous catalysts.8-11 A vast major-
Transition-metal compounds derived from functionalized
phosphine ligands have attained ubiquitous prominence in
homogeneous catalysis.2-4 The spatial disposition of substituents
around the PIII center plays a pivotal role in providing such
important properties as chirality and geometrical/steric con-
straints. Indeed, systematic variations of substituents on PIII
centers is an effective tool for tuning of electronic effects in
phosphine ligands and in their corresponding transition-metal
complexes. The chemical architecture of substituents defines
the cone angle around the PIII center, and such properties play
important roles in the catalytic activity of coordinated metal
complexes.5-7 Therefore, functionalization and fine-tuning of
substituents around PIII centers is an activity of continued interest
ity of studies toward functionalized monophosphine or chelating
bisphosphine ligands have involved functionalization with alkyl,
aryl, alkoxy, aryloxy, or chiral functionalities. Despite extensive
transition-metal chemistry and catalytic investigations on a
plethora of functionalized bisphosphines, the corresponding
studies of the primary bisphosphines (e.g., H2PXPH2, X ) alkyl
or aryl) has remained largely unexplored.12,13 This may be in
part be due to difficulties associated with the synthesis and
oxidative/thermal instability of functionalized primary bisphos-
phines.14 Design and development of “user-friendly” 15 primary
bisphosphines and their coordination chemistry with transition-
metal precursors would be of paramount importance because
the hydrogen substituents on the PIII centers provide “minimal”
sterical hindrance. Indeed, our knowledge base on the transition-
metal/organometallic chemistry of chelating phosphine ligands
with less bulky substituents and their consequent influence in
catalytic transformations is yet limited. In this context, the
development of primary bisphosphines that exhibit optimum
oxidative/thermal stability will aid in their utility as chelating
† Department of Chemistry.
‡ Department of Radiology.
§ Department of Physics.
(1) A preliminary report on this work has been presented at three conferences:
(a) Pillarsetty, N.; Kannan, R.; Katti, K. V.; Barnes, C. L. Coordination
chemistry of Mo(0), W(0), and Re(I) carbonyls with an air-stable primary
bis-phosphine. 225th ACS National Meeting, New Orleans, LA, Mar 23927,
2003; American Chemical Society: Washington, DC, 2003; INOR-216. (b)
Prabhu, K. R.; Pillarsetty, N.; Gali, H.; Katti, K. V. Curr. Sci. 2000, 78,
431-439. (c) Pillarsetty, N.; Ramaiah, K. P.; Gali, H.; Katti, K. V.; Barnes,
C. L. Abstracts of Papers, 222nd ACS National Meeting, Chicago, IL, Aug
26-30, 2001; American Chemical Society: Washington, DC, 2001; INOR-
089.
(8) RajanBabu, T. V.; Yan, Y. Y.; Shin, S. J. Am. Chem. Soc. 2001, 123,
10207-10213.
(2) Noyori, R. Asymmetric Catalysis in Organic Synthesis; John Wiley and
Sons: New York, 1994.
(9) Burk, M. J. J. Am. Chem. Soc. 1991, 113, 8518-8519.
(10) Marinetti, A.; Jus, S.; Labrue, F.; Lemarchand, A.; Genet, J.-P.; Ricard, L.
Synthesis 2001, 14, 2095-2104.
(3) Collman, J. P.; Finke, R. G.; Norton, J. R.; Hegedus, L. S. Principles and
Applications of Organotransition Metal Chemistry; University Science
Books: Washington, DC, 1997.
(11) Landis, C. R.; Jin, W.; Owen, J. S.; Clark, T. P. Angew. Chem., Int. Ed.
2001, 40, 3432-3434.
(4) Pignolet, L. H., Ed. Homogeneous Catalysis with Metal Phosphine
Complexes; Plenum Press: New York, 1983.
(12) Katti, K. V.; Pillarsetty, N.; Raghuraman, K. Top. Curr. Chem. 2003, 229
(New Aspects in Phosphorus Chemistry III), 121-141.
(13) Katti, K. V.; Gali, H.; Berning, D. E.; Smith, C. J. Acc. Chem. Res. 1999,
32, 9-17.
(5) Tolman, C. A. Chem. ReV. 1977, 77, 313-348.
(6) Gilheany, D. G. In The Chemistry of Organophosphorus Compounds;
Hartley, F. R., Ed.; John Wiley and Sons: Chichester, England, 1990; Vol.
1, Chapter 2, pp 9-49.
(14) Gilheany, D. G.; Mitchell, C. M. In The chemistry of organophosphorus
Compounds; Hartley, F. R., Ed.; John Wiley and Sons: Chichester, England,
1990; Vol. 1, Chapter 7, pp 151-190.
(7) Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Acc. Chem.
Res. 2001, 34, 895-904.
(15) Henderson, W.; Alley, S. R. J. Organomet. Chem. 2002, 656, 120-128.
9
10.1021/ja047238y CCC: $30.25 © 2005 American Chemical Society
J. AM. CHEM. SOC. 2005, 127, 331-336
331

A R T I C L E S
Pillarsetty et al.
Scheme 1. Synthesis of 4 and 5
agents and consequently expand our understanding of the nature
of their interaction with transition metals.
As part of our ongoing studies12,13,16-20 on the main-group
and transition-metal chemistry of functionalized phosphines, we
herein report the synthesis, characterization, and X-ray crystal
structure of an air-stable primary bisphosphine, N-phenyl-3-
phosphanyl-2-(phosphanylmethyl)propionamide (5). In an effort
to elucidate the σ versus the π bonding capabilities of 5, in this
paper we also report the reaction chemistry of 5 with W(CO)6
and Re(CO)5Br compounds, including the X-ray crystal struc-
tures of (η2-(PH2CH2)2CHCONHPh)W(CO)4 (6) and (η2-(PH2-
CH2)2CHCONHPh)Re(CO)3Br (7).
Figure 1. ORTEP diagram of 5.
primary bisphosphines 4 and 5 were characterized by NMR
spectroscopy (1H, 31P, and 13C) and mass spectrometry. Com-
pound 5, which exhibits remarkable air stability, has been
characterized by elemental analysis. The high-field signals at
-149.6 and -142.9 ppm for 4 and 5, respectively, were attrib-
uted to the primary phosphine moiety.21 The amide group (in
5) versus the amine group (in 4) exerted minimal influence on
Results and Discussion
1
1
the JP-H values (1JP-H in 5, 197.0 Hz; JP-H in 4, 196.7 Hz).
Our rationale for the chemical architecture of primary
bisphosphines included two motives: (a) that the primary
bisphosphine framework display optimum oxidative stability to
perform transition-metal chemistry studies; and (b) that the
transition-metal centers “strictly” interact with the two PIII
primary phosphine centers with no interference from any
ancillary coordinating units within the ligand backbone. The
second criterion stems from our overall objective of trying to
understand the coordinating chemistries of the primary phos-
phine within chelating environments.
The air-stable primary bisphosphine (PH2CH2)2CHCONHPh
(5) was synthesized via synthetic routes as shown in Scheme
1. The dibromo acid 1 was converted to its corresponding acid
chloride by treatment with oxalyl chloride, which upon treatment
with aniline produced the corresponding amide 2. The dibromo
amide 2 was converted to the bisphosphonate 3 by refluxing in
triethyl phosphite. The reduction of 3 always resulted in two
products, aminobisphosphine 4 and amidobisphosphine 5,
despite varying the reaction conditions. The yield of amide 5
was increased to 18% upon reduction of 3 at 0 °C in diethyl
ether followed by quenching the reaction mixture after 15 min.
31P NMR spectroscopic analysis of the reaction products
indicated the presence of the unreacted phosphonate 3. Higher
yields of the amine 4, with concomitant consumption of 3, were
isolated upon increasing the duration of this reaction. These two
products (4 and 5) were separated using silica gel column
chromatography. Compound 4 is a liquid, whereas compound
5 is an air-stable crystalline solid at room temperature. The new
The amine- and amide-functionalized primary phosphine
analogues 4 and 5 are remarkably stable in air and in organic
solvents (THF, CH2Cl2, toluene, etc.). In fact, no detectable
oxidation was noted upon storing crystalline 5 for over 12
months in glass vials. It is important to recognize that the alkyl-
and aromatic-functionalized primary bisphosphines H2P-X-
PH2 (X ) alkyl or aryl) are so unstable that they instantaneously
ignite upon exposure to air. Recent studies have demonstrated
that bulky groups around the PIII centers render oxidative
inertness to primary phosphines.22-28 Examples of primary
phosphines with sterically demanding substituents include
compounds with triptcyl, 2,4,6-tri-tert-butylphenyl, anthracyl,
and dibenzobarllenyl groups on the P(III) center.22-28 The
unusual oxidative stability demonstrated by the primary bis-
phosphine 5 is particularly significant as it provides a rare
example of achieving oxidative inertness without the size-
dominating effects of a bulky functional group. To address
if any intermolecular interactions influence the high oxi-
dative stability of the primary phosphine units in 5, we have
undertaken an X-ray crystal structure investigation of this
compound.
Crystals suitable for single-crystal X-ray diffraction studies
of 5 were obtained from a dichloromethane solution of 5. The
(21) Maier, L.; Diel, P. J.; Tebby, J. C. In CRC handbook of Phosphorus 31
Nuclear Magnetic Resonance Data; Tebby, J. C., Ed.; CRC Press: Boca
Raton, FL, 1991; Chapter 6.
(22) Brynda, M.; Geoffroy, M.; Bernardinelli, G. Chem. Commun. 1999, 961-
962.
(23) Goodwin, N. J.; Henderson, W.; Nicholson, B. K.; Fawcett, J.; Russell, D.
R. J. Chem. Soc., Dalton Trans. 1999, 1785-1794.
(24) Ramakrishnan, G.; Jouaiti, A.; Geoffroy, M.; Bernardinelli, G. J. Phys.
Chem. 1996, 100, 10861-10868.
(16) Gali, H.; Hoffman, T. J.; Sieckman, G. L.; Owen, N. K.; Katti, K. V.;
Volkert, W. A. Bioconjugate Chem. 2001, 12, 354-363.
(17) Raghurman, K.; Pillarsetty, N.; Volkert, W. A.; Barnes, C. L.; Jurisson,
S.; Katti, K. V. J. Am. Chem. Soc. 2002, 124, 7276-7277.
(18) Gali, H.; Karra, S. R.; Reddy, V. S.; Katti, K. V. Angew Chem., Int. Ed.
1999, 38, 2020-2023.
(19) Berning, D. E.; Katti, K. V.; Barnes, C. L.; Volkert, W. A. J. Am. Chem.
Soc. 1999, 121, 1658-1664.
(20) Prabhu, K. R.; Pillarsetty, N.; Gali, H.; Katti, K. V. J. Am. Chem. Soc.
2000, 122, 1554-1555.
(25) Brauer, D. J.; Fischer, J.; Kuchen, S.; Langhans, K. P.; Stelzer, O. Z.
Naturforsch., Teil B 1994, 49, 1511-1524.
(26) Heuer, L.; Schomborg, D.; Schmutzler, R. Chem. Ber. 1989, 122, 1473-
1476.
(27) Bartlett, R. A.; Olmstead, M. M.; Power, P. P.; Sigel, G. A. Inorg. Chem.
1987, 26, 1941-1946.
(28) Reiter, S. A.; Assmann, B.; Nogai, S. D.; Mitzel, N. W.; Schmidbaur, H.
HelV. Chim. Acta 2002, 85, 1140-1150.
9
332 J. AM. CHEM. SOC. VOL. 127, NO. 1, 2005

Sterically Nondemanding Primary Bisphosphines
A R T I C L E S
Figure 2. H-bonding in 5.
Scheme 2. Interactions of 5 with W(CO)6 or Re(CO)5Br
PH2CH2CH(CONHPh)CH2PH2}] (6) complex. The bisphos-
phine 5 reacts with Re(CO)5Br in acetonitrile under refluxing
conditions to yield two products, with resonances at δ ) -108.5
(major) and δ ) 115.2 (minor) ppm, as indicated by the 31P
NMR spectrum of the crude reaction mixture. Only one product,
fac-[Re(CO)3{η2-PH2CH2CH(CONHPh)CH2PH2}Br] (7), was
isolable upon column chromatographic purification. Com-
primary phosphine 5 crystallized in the rhombohedral crystal
system with a molecule of the solvent of crystallization. The
ORTEP plot of 5, as shown in Figure 1, confirms the molec-
ular constitution of the primary bisphosphine. The structure
reveals P-C bond lengths in 5 (1.839(4) and 1.835(4) Å)
comparable to those observed in primary phosphines, (ferroce-
nylmethyl)phosphine (1.850(3) Å), and dibenzobarallenylphos-
phine (1.859(4) Å)), which are functionalized with sterically
demanding ancillary substituents.22-28 The structure of 5 further
consisted of intermolecular hydrogen-bonding interactions
between the amide (N-H) and carbonyl (CdO) groups of the
adjacent molecule, producing an infinite linear chain as shown
in Figure 2. It may be noted that there were no direct hydrogen
bonds with the hydrogens of the primary phosphine centers.
Therefore, the oxidative inertness of 5 as a consequence of any
hydrogen-bonding interactions with the -PH2 may be dis-
counted.
Almost all of the reported crystal structures of free primary
monophosphines contain a bulky group attached to the phos-
phorus, to sterically crowd the phosphorus atom and thereby
render stability to P-H bonds.22-28 In this context, the amide-
functionalized primary bisphosphine 5 is a rare example of its
kind demonstrating excellent oxidative stability in the absence
of any bulky substituent. The reason for the unusual oxidative
stability of primary bisphosphine 5 is unclear. However,
observations from our earlier work18,20 and also as noted by
Stelzer and co-workers25 suggest that electronegative hetero-
atoms such as nitrogen or sulfur, two or three carbons away
from the phosphorus, may have negative hyperconjugative
electronic influence on the P(III) centers and thus render the
primary phosphine oxidatively stable.18,20
1
plexes 6 and 7 have been characterized by 31P and H NMR
spectroscopy, elemental analysis, and single-crystal X-ray
diffraction.
The 31P{1H} NMR spectrum of 6 showed a singlet at δ )
-111.0 ppm with tungsten satellites (1JP-W ) 206.0 Hz). The
proton-coupled 31P NMR spectrum of 6 showed a triplet, with
1JP-H coupling of 328.0 Hz, indicating that the bisphosphine
binds to the metal center without deprotonation of the PH2
centers. Similarly, the 31P{1H} NMR spectrum of 7 showed a
singlet at δ ) -108.5 ppm, and the proton-coupled spectrum
showed a triplet with 1JP-H coupling of 355.9 Hz. The 31P NMR
resonances of 6 and 7 shifted downfield with respect to the
parent primary phosphine ligand.23,29-31
The molecular structures of 6 and 7 were determined by
single-crystal X-ray diffraction analysis. Single crystals of 6
were obtained from dichloromethane/ethanol solution, and the
crystals of 7 were obtained from slow evaporation of ethyl
acetate solution. The tungsten (6) and rhenium (7) complexes
of 5 crystallized in the orthorhombic crystal system (Table 1).
The ORTEP plots for 6 and 7 are depicted in Figures 3 and 4,
respectively. Important bond lengths and bond angles for 5-7
are listed in Table 2, and a complete list of bond distances and
angles are included in the Supporting Information. The crystal
structures of 6 and 7 establish the cis-η2 coordination of ligand
5. The tungsten and rhenium atoms in complexes 6 and 7 exhibit
distorted octahedral geometry. The P-M-P bond angles in 6
and 7 are 85.49(6)° and 85.86(5)°, respectively. A closer
examination of the crystal packing diagram and intermolecular
distances in compounds 6 and 7 reveals no intermolecular
(29) Hessler, A.; Kucken, S.; Stlzer, O.; Sheldrick, W. S. J. Organomet. Chem.
1998, 553, 39-52.
Interaction of 5 with Transition Metals. The user-friendly
properties of the primary bisphosphine 5 provided an important
rationale to explore the reactivity of “sterically nondemanding”
“PH2” groups in 5 toward organometallic precursors W(CO)6
and Re(CO)5Br. The complexation reactions of 5 with metal
carbonyls are shown in Scheme 2. Primary bisphosphine 5 reacts
with tungsten hexacarbonyl in the presence of decarbonylating
agent trimethylamine N-oxide to produce the cis-[W(CO)4{η2-
(30) Campbell, T.; Gibson, A. M.; Hardt, R.; Orchard, S. D.; Pope, S. J. A.;
Reid, G. J. Organomet. Chem. 1999, 592, 296-305.
(31) Edwards, P. G.; Fleming, J. S.; Liyanage, S. S.; Coles, S. J.; Hursthouse,
M. B. J. Chem. Soc., Dalton Trans. 1996, 1801-1807.
(32) Scheper, J. T.; Jayaratne, K. C.; Liable-Sands, L. M.; Yap, G. P.; Rheingold,
A. L.; Winter, C. H. Inorg. Chem. 1999, 38, 4354-4360.
(33) Lewkebandara, T. S.; Proscia, J. W.; Winter, C. H. Chem. Mater. 1995, 7,
1053-1054.
(34) Watson, I. M.; Connor, J. A.; Whyman, R. Thin Solid Films 1991, 201,
337-349.
9
J. AM. CHEM. SOC. VOL. 127, NO. 1, 2005 333

A R T I C L E S
Pillarsetty et al.
Table 1. Crystallographic Data for 5-7
5
6
7
empirical formula
C
10.17H11Cl0.25NOP2
C14H15NO5P2W
C13H15BrNO4P2Re
fw
234.03
523.06
577.31
cryst size (mm)
cryst syst, space group
a (Å)
b (Å)
0.4 × 0.15 × 0.10
rhombohedral, R3
21.5254 (13)
21.5254 (13)
14.1730(12)
90
90
120
5687.2 (7)
18
0.40 × 0.20 × 0.02
0.40 × 0.30 × 0.15
orthorhombic, Pbca
orthorhombic, P212121
8.6521(8)
17.2931(15)
23.187(2)
90
90
90
6.5297 (4)
13.6202(9)
19.8064(13)
90
90
90
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
3469.3(5)
8
1761.5(2)
4
λ (Å)
0.71073
1.230
173(2)
0.71073
2.003
173(2)
0.71073
2.177
173(2)
Dc (Mg/m3)
T (K)
Ra (obsd data)
R1
wR2
0.0628
0.1682
0.0453
0.0898
0.0273
0.0651
Table 2. Bond Lengths (Å) and Bond Angles (deg) for 5-7
atoms
distance
atoms
angle
Compound 5
P1-C4
P2-C3
C2-C4
C2-C3
C1-O1
C1-N1
1.839(4)
1.835(4)
1.535(5)
1.532(5)
1.230(3)
1.353(4)
P1-C4-C2
P2-C3-C2
C4-C2-C3
C2-C1-O1
C2-C1-N1
118.3(2)
117.0(2)
110.2(3)
121.2(3)
115.7(2)
Compound 6
W1-P1
W1-P2
W1-C11
W1-C12
W1-C13
W1-C14
P1-C1
2.502(2)
2.472(2)
2.024(9)
1.988(8)
1.985(9)
2.018(8)
1.842(7)
1.833(7)
1.242(8)
P1-W2-P2
85.49(6)
173.2(2)
175.4(2)
176.1(3)
92.9(3)
177.1(8)
113.5(6)
121.7(6)
P1-W1-C12
P2-W1-C13
C11-W1-C14
C12-W1-C13
W1-C11-O2
C1-C2-C3
P2-C3
C2-C4-O1
C4-O1
Compound 7
Re1-P1
Re1-P2
Re1-Br1
Re1-C11
Re1-C12
Re1-C13
P1-C1
2.4346(16)
2.4332(16)
2.6434(6)
1.938(7)
1.929(7)
1.910(6)
1.825(6)
1.836(6)
1.219(7)
P1-Re1-P2
P1-Re1-C12
P2-Re1-C11
C13-Re1-Br1
C11-Re1-C12
Re1-C11-O2
C1-C2-C3
85.86(5)
92.58(19)
90.64(19)
176.9(2)
90.7(3)
178.8(6)
115.5(5)
120.7(5)
Figure 3. ORTEP diagram of 6.
P2-C3
C2-C4-O1
C4-O1
that the six-membered rings in 6 and 7 are nonplanar. The metal-
lacycles adopt an energetically (thermodynamically) favored
chair conformation, similar to the favorable conformation ob-
served in cyclohexane and its derivatives. It is striking to note
that 6 and 7 adopt a chair conformation despite the fact that
P-M-P bond angles in these complexes are 85.49(6)° and
85.85(5)°, respectively. Indeed, these angles represent a sig-
nificant deviation from the regular bond angle (111.5°) found
in cyclohexane.
The average metalphosphine bond lengths in 6 and 7 (W-P
) 2.487 Å and Re-P ) 2.4339 Å) are strikingly similar to
those observed for the W(0)/Re(I) complexes derived from alkyl-
or aryl-substituted phosphines.22-28 This finding suggests that
σ donation, being the dominant electronic contribution in
complexes derived from the primary phosphines (e.g., 6 and
7), may indeed account for the sole electronic factor providing
kinetic stability. This unique electronic effect complemented
Figure 4. ORTEP diagram of 7.
hydrogen bonding between primary phosphine hydrogens and
CdO or N-H groups.
Stereochemical and Electronic Implications. The crystal-
lographic data for the W(0) and Re(I) metallacycles suggests
9
334 J. AM. CHEM. SOC. VOL. 127, NO. 1, 2005

Sterically Nondemanding Primary Bisphosphines
A R T I C L E S
Synthesis of ((EtO)2P(O)CH2)2CHCONHPh (3). Amide 2 (12.1
g, 38.0 mmol) was refluxed for 16 h in excess triethyl phosphite, which
also served as the solvent. Volatile products were distilled off at reduced
pressure to afford the crude product as a yellow viscous oil. The crude
product upon purification on a silica gel column (ethyl acetate/hexane,
30%) yielded 13.91 g (85% yield) pure bisphosphonate 3. HRMS
(ionized with LiCl) (m/z): for C18H31NO7P2Li, calcd 442.1736, obsd
by the chemical architecture of the smallest substituents in the
primary bisphosphine framework 5 and its metal complexes 6
and 7 may be of paramount importance in catalytic applications.
The small size of “H” substituents in 6 and 7 is expected to
facilitate easy access of substrate molecules around metal
centers. The juxtaposition of minimum steric hindrance may
provide high degrees of freedom and proximity, particularly for
the sterically demanding substrates.
1
442.1746. H NMR (CDCl3, 300 MHz, δ): 9.17 (br s, 1H), 7.59 (d,
2H, J ) 8.40 Hz), 7.35-7.25 (m, 2H), 7.07 (t, 1H, J ) 7.20 Hz),
4.14-3.98 (m, 8H), 3.21-3.05 (m, 1H), 2.38-2.07 (m, 4H), 1.31-
Conclusions
3
1.18 (m, 12H). 13C NMR (CDCl3, 75 MHz, δ): 170.6 (t, JP-C ) 7.5
Hydrogen substituents of the PIII centers in 5 and in the
corresponding W(0) and Re(I) metal complexes 6 and 7,
respectively, exert important electronic influence on the coor-
dinating metals. The presence of H substituents on the PIII
centers in 5 decreases their π-back-bonding capabilities. This
electronic effect concomitantly increases the electron densities
of the primary-phosphine-bound metals. It is well-known that
an increase in the electron density of metals will lead to efficient
oxidative addition processes across the metal-catalyzed organic
transformations.4 Therefore, transition-metal/organometallic com-
pounds derived from chelating primary bisphosphines will play
important roles in catalytic processes.
1
Hz), 138.3, 128.8, 123.9, 119.5, 62.1-61.9 (m), 36.2, 28.9 (dd, JP-C
) 140.7 Hz, 3JP-C ) 13.1 Hz), 16.3-16.2 (m). 31P{1H} NMR (CDCl3,
121 MHz, δ): 30.4.
Synthesis of (PH2CH2)2CHCH2NHPh (4) and (PH2CH2)2CH-
CONHPh (5). To a cold (0 °C) solution of 3 (1.39 g, 32.0 mmol) in
diethyl ether (250 mL) was added dropwise a 1 M solution of LiAlH4
in ether (80 mL), and stirring was continued for 20 min. The excess
LAH was quenched by wet ether, and the ethereal layer was washed
with 2 N HCl (2 × 75 mL) followed by brine (2 × 100 mL). The
organic layer was separated and dried with anhydrous sodium sulfate
to yield a mixture of 4 and 5, which were separated on a silica gel
column (ethyl acetate/hexane, 15%) to yield amine 4 (40% isolated
yield) (Rf ) 0.5) and amide 5 (18% isolated yield) (Rf ) 0.17). The
following are data for 4. HRMS (m/z): (M+ + H) calcd 213.0836,
Experimental Section
1
obsd 213.0832. H NMR (CDCl3, 300 MHz, δ): 7.25-7.16 (m, 2H),
6.76-6.68 (m, 1H), 6.65 (br d, 2H, J ) 8.62 Hz), 3.2 (d, 2H, J ) 6.5
Hz), 2.72 (dt, 4H, 1JP-H ) 196.7 Hz, 1JH-H ) 7.3 Hz), 2.05-1.88 (m,
1H), 1.85-1.7 (m, 4H). 13C NMR (CDCl3, 75 MHz, δ): 148.0, 129.4,
117.5, 112.8, 47.8, 40.7, 16. 31P{1H} NMR (CDCl3, 121 MHz, δ):
-149.6. The following are data for 5. Anal. Calcd for C10H15NOP2: C,
52.87; H, 6.66; N, 6.17. Found: C, 53.13; H, 6.51; N, 5.98. HRMS
(m/z): (M+ + H) calcd 228.0707, obsd 228.0712. IR (KBr pellet, cm-1):
All reactions were carried out under nitrogen by standard Schlenk
techniques. All chemicals were obtained from Aldrich Chemical Co.
and were used without further purification. NMR spectra were re-
corded on a Bruker ARX-300 spectrometer using the specified sol-
vent. 1H and 13C chemical shifts are reported in parts per million,
downfield from internal standard SiMe4. 31P NMR (121.5 MHz) spec-
tra were recorded with 85% H3PO4 as an external standard and pos-
itive chemical shifts downfield of the standard. Mass spectra were
recorded at Washington University, St. Louis, MO, and combus-
tion analysis was done by Oneida Research Services, Whitesboro,
NY.
1
νP-H 2298 (sh, s), νCO 1657 (sh, s). H NMR (CDCl3, 300 MHz, δ):
7.52 (d, 2H, J ) 8.10 Hz), 7.32 (t, 2H, J ) 7.80 Hz), 7.12 (t, 1H, J )
7.20 Hz), 3.08-3.00 (m, 2H), 2.39-2.29 (m, 3H), 2.20-1.97 (m, 2H),
1.82-1.76 (m, 2H). 13C NMR (CDCl3, 75 MHz, δ): 171.9, 137.2,
1
129.0, 124.7, 120.3, 53.5, 18.2 (d, JP-C ) 12.1 Hz). 31P{1H} NMR
Crystallographic Data Collection and Refinement of Structure.
A suitable crystal was chosen and mounted on a glass fiber with epoxy
resin. The crystal data and refinement results were given in Table 1.
See the Supporting Information for CIF files. Data reduction and
processing followed routine procedures. Structures were solved by direct
(CDCl3, 121 MHz, δ): -142.9.
Synthesis of W(CO)4{η2-(H2PCH2)2CHCONHC6H5} (6). To a
slurry of W(CO)6 (200 mg, 0.56 mmol) in CH3CN (5 mL) was added
dropwise a solution of trimethylamine N-oxide (132.9 mg, 1.12 mmol)
in CH3CN (15 mL). The resulting yellow-colored solution was stirred
for 20 min. To this solution was slowly added compound 5 (127 mg,
0.56 mmol) in CH3CN (10 mL), and the resulting solution was refluxed
for 4 h, followed by removal of solvent under reduced pressure to give
crude product 6 as a pasty mass. The crude compound was purified on
a silica gel column (methanol/dichloromethane, 2%) to give 176 mg
(60% yield) of pure product 6 (isolated yield 60%). 1H NMR (CDCl3/
DMSO, 300 MHz, δ): 7.37(br d, 2H, J ) 8.1 Hz), 7.12 (br t, 2H, J )
8.1 Hz), 6.90 (br t, 1H, J ) 7.42 Hz), 4.60 (md, 4H, 1JP-H ) 328 Hz)
2.84 (m, 1H), 2.32 (m, 2H), 1.98 (m, 2H). 13C NMR (CD2Cl2, 75 MHz,
δ): 171.2, 137.6, 129.4, 125.2, 120.3, 44.2, 19.0 (t, JC-P ) 16.6 Hz).
31P{1H} NMR (CD2Cl2, 121 MHz, δ): -111 (s, 1JP-W ) 206 Hz). EI-
MS (m/z): [M+] for (CO)4WP2, calcd 523, obsd 523. IR (KBr pellet,
cm-1): νCO 1866 (br s), 2018 (sh, s), νPH 2336 (sh, w). Anal. Calcd for
C14H15NO5P2W: C, 32.15; H, 2.89; N, 2.68. Found: C, 32.69; H, 2.96;
N, 2.51.
2
methods and refined on Fo . Absorption corrections were done by
semiempirical equivalents.
Synthesis of (BrCH2)2CHCONHPh (2). To a vigorously stirring,
cold (0 °C) solution of 3-bromo-2-(bromomethyl)propionic acid (1)
(10.0 g, 40.6 mmol) in benzene (100 mL) was slowly added oxalyl
chloride (6.0 mL, 69.7 mmol), followed by dimethylformamide (0.2
mL). The reaction mixture was stirred at room temperature for 14 h,
and solvent was removed under vacuum to afford the corresponding
acid chloride (10.6 g, 40.0 mmol). The acid chloride was dissolved in
anhydrous CH2Cl2 (40 mL) and added to an ice cold stirring solution
of aniline (8.1 g, 88.0 mmol) in CH2Cl2 (100 mL) over a period of 20
min, and the resulting mixture was stirred for 14 h. The reaction mixture
was diluted with CH2Cl2 (600 mL) and washed with 2 N HCl (2 × 75
mL), followed by brine (100 mL), and then with saturated NaHCO3 (2
× 75 mL). The organic layer was further washed with brine (2 × 100
mL) and dried with anhydrous sodium sulfate. Removal of solvent under
reduced pressure gave the crude amide product 2. Compound 2 was
purified on a silica gel column (ethyl acetate/hexane, 4%) to give 12.1
g of 2 (91% yield) in 98% purity. HRMS (m/z): (M+ + H) for C10H11-
Synthesis of ReBr(CO)3{η2-(H2PCH2)2CHCONHC6H5} (7). A
solution of 5 (60 mg, 0.26 mmol) and rhenium pentacarbonyl bromide
(107 mg, 0.26 mmol) in anhydrous acetonitrile (10 mL) was refluxed
for 17 h. The solvent was removed to obtain the crude product. The
crude product was purified on a silica gel column (50% ethyl acetate,
hexane) to yield 83 mg (55% yield) of pure product 8 (isolated yield
1
Br2NO, calcd 319.9286, obsd 319.9295. H NMR (CDCl3, 300 MHz,
δ): 7.53 (d, 2H, J ) 7.80 Hz), 7.35 (t, 2H, J ) 8.10 Hz), 7.16 (t, 1H,
7.20 Hz), 3.73-3.67 (m, 2H), 3.60-3.55 (m, 2H), 3.12-3.09 (m, 1H).
13C NMR (CDCl3, 75 MHz, δ): 168.5, 137.1, 129.3, 125.4, 120.7, 53.2,
31.1.
1
52%). H NMR (CD3CN, 300 MHz, δ): 7.53-7.58 (m, 2H), 7.32-
7.39 (m, 2H), 7.14 (m, 1H), 5.42-5.50 (m, 1H), 5.12-5.20 (m, 1H),
9
J. AM. CHEM. SOC. VOL. 127, NO. 1, 2005 335

A R T I C L E S
Pillarsetty et al.
4.15-4.26 (m, 1H), 3.94-4.09 (m, 1H), 3.45-3.71 (m, 1H), 2.38-
2.59 (m, 2H) 2.31-2.37 (m, 2H). 31P{1H} NMR (CDCl3, 121 MHz,
δ): -108.50. IR (KBr pellet, cm-1) νCO 1903 (sh, s), 1953 (sh, s), 2033
(sh,s), νPH 2415 (s, w). Anal. Calcd for C13H15BrNO4P2Re: C, 27.05;
H, 2.62; N, 2.43. Found: C, 28.20; H, 2.53; N, 2.08.
CA103130-02), Departments of Radiology and Physics, and the
University of Missouri Research Reactor.
Supporting Information Available: Crystallographic data of
5-7 in CIF format. This material is available free of charge
via the Internet at http://pubs.acs.org.
Acknowledgment. This work was supported by the U.S.
Department of Energy, National Institutes of Health (1P50
JA047238Y
9
336 J. AM. CHEM. SOC. VOL. 127, NO. 1, 2005