New tetraphosphane ligands {(X2P)2NC 6H4N(PX2)2} (X = Cl, F, OMe, OC 6H4OMe-o): Synthesis, derivatization, group 10 and 11 metal complexes and catalytic investigations. DFT calculations on intermolecular P...P interactions in halo-phosphines

Article abstract of DOI:10.1021/ic800724u

The reaction of p-phenylenediamine with excess PCl₃ in the presence of pyridine affords p-C₆H₄[N(PCl ₂)₂]₂ (1) in good yield. Fluorination of 1 with SbF₃ produces p-C₆H₄[N(PF₂) ₂]₂ (2). The aminotetra(phosphonites) p-C ₆H₄[N{P(OC₆H₄OMe-o) ₂}₂]₂ (3) and p-C₆H ₄[N{P(OMe)₂}₂]₂ (4) have been prepared by reacting 1 with appropriate amount of 2-(methoxy)phenol or methanol, respectively, in the presence of triethylamine. The reactions of 3 and 4 with H₂O₂, elemental sulfur, or selenium afforded the tetrachalcogenides, p-C₆H₄[N{P(O)(OC₆H ₄OMe-o)₂}₂]₂ (5), p-C ₆H₄[N{P(S)(OMe)₂}₂]₂ (6), and p-C₆H₄[N{P(Se)(OMe)₂}₂] ₂ (7) in good yield. Reactions of 3 with [M(COD)Cl₂] (M = Pd or Pt) (COD = cycloocta-1,5-diene) resulted in the formation of the chelate complexes, [M₂Cl₄-p-C₆H₄{N{P(OC ₆H₄OMe-o)₂}₂}₂] (8, M = Pd and 9, M = Pt). The reactions of 3 with 4 equiv of CuX (X = Br and I) produce the tetranuclear complexes, [Cu₄(μ₂-X) ₄(NCCH₃)₄-p-C₆H ₄{N(P(OC₆H₄OMe-o)₂) ₂}₂] (10, X = Br; 11, X = I). The molecular structures of 1-3, 6, 7, and 9-11 are confirmed by single-crystal X-ray diffraction studies. The weak intermolecular P...P interactions observed in 1 leads to the formation of a 2D sheetlike structure, which is also examined by DFT calculations. The catalytic activity of the Pd(II) 8 has been investigated in Suzuki-Miyaura cross-coupling reactions.

Full text of DOI:10.1021/ic800724u

Inorg. Chem. 2008, 47, 7035-7047
New Tetraphosphane Ligands {(X2P)2NC6H4N(PX2)2} (X ) Cl, F, OMe,
OC6H4OMe-o): Synthesis, Derivatization, Group 10 and 11 Metal
Complexes and Catalytic Investigations. DFT Calculations on
Intermolecular P· · · P Interactions in Halo-Phosphines
Chelladurai Ganesamoorthy,† Maravanji S. Balakrishna,*,† Joel T. Mague,‡ and Heikki M. Tuononen§
Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay,
Mumbai 400 076, India, Department of Chemistry, Tulane UniVersity,
New Orleans, Lousiana 70118, USA, and Department of Chemistry,
P.O. Box 35, FI-40014 UniVersity of JyVa¨skyla¨, Finland
Received April 23, 2008
The reaction of p-phenylenediamine with excess PCl3 in the presence of pyridine affords p-C6H4[N(PCl2)2]2 (1) in
goodyield.Fluorinationof1withSbF3 producesp-C6H4[N(PF2)2]2 (2).Theaminotetra(phosphonites)p-C6H4[N{P(OC6H4OMe-
o)2}2]2 (3) and p-C6H4[N{P(OMe)2}2]2 (4) have been prepared by reacting 1 with appropriate amount of
2-(methoxy)phenol or methanol, respectively, in the presence of triethylamine. The reactions of 3 and 4 with H2O2,
elemental sulfur, or selenium afforded the tetrachalcogenides, p-C6H4[N{P(O)(OC6H4OMe-o)2}2]2 (5),
p-C6H4[N{P(S)(OMe)2}2]2 (6), and p-C6H4[N{P(Se)(OMe)2}2]2 (7) in good yield. Reactions of 3 with [M(COD)Cl2] (M
) Pd or Pt) (COD ) cycloocta-1,5-diene) resulted in the formation of the chelate complexes, [M2Cl4-p-
C6H4{N{P(OC6H4OMe-o)2}2}2] (8, M ) Pd and 9, M ) Pt). The reactions of 3 with 4 equiv of CuX (X ) Br and I)
produce the tetranuclear complexes, [Cu4(µ2-X)4(NCCH3)4-p-C6H4{N(P(OC6H4OMe-o)2)2}2] (10, X ) Br; 11, X ) I).
The molecular structures of 1-3, 6, 7, and 9-11 are confirmed by single-crystal X-ray diffraction studies. The
weak intermolecular P · · · P interactions observed in 1 leads to the formation of a 2D sheetlike structure, which is
also examined by DFT calculations. The catalytic activity of the Pd(II) 8 has been investigated in Suzuki-Miyaura
cross-coupling reactions.
Introduction
stability, and unique physical properties.3–5 Preorganized
ligands of this class may readily form di-, tetra-, and/or
polynuclear metal complexes with metals in close proximity
The design and synthesis of polyphosphine ligands has
been an active field of research over several years1,2 as their
metal complexes show structural diversity, high thermal
(2) (a) Airey, A. L.; Swiegers, G. F.; Willis, A. C.; Wild, S. B. J. Chem.
Soc., Chem. Commun. 1995, 695–696. (b) Bianchini, C.; Meli, A.;
Peruzzini, M.; Vizza, F.; Zanobini, F. Coord. Chem. ReV. 1992, 120,
193–208. (c) Cotton, F. A.; Hong, B. Prog. Inorg. Chem. 1992, 40,
179–289. (d) Caminade, A. M.; Majoral, J. P.; Mathieu, R. Chem.
ReV. 1991, 91, 575–612. (e) Barendt, J. M.; Haltiwanger, R. C.; Squier,
C. A.; Norman, A. D. Inorg. Chem. 1991, 30, 2342–2349. (f) Meek,
D. W.; DuBois, D. L.; Tiethof, J. AdV. Chem. Ser. 1976, 150, 335–
357.
* To whom correspondence should be addressed. E-mail: krishna@
chem.iitb.ac.in. Tel.: +91 22 2576 7181. Fax: +91 22 2576 7152/2572
3480.
†
Indian Institute of Technology Bombay.
Tulane University.
University of Jyva¨skyla¨.
‡
§
(1) (a) Pei, Y.; Brule, E.; Moberg, C. Org. Biomol. Chem. 2006, 4, 544–
550. (b) Kongprakaiwoot, N.; Luck, R. L.; Urnezius, E. J. Organomet.
Chem. 2004, 689, 3350–3356. (c) Hierso, J.-C.; Fihri, A.; Ivanov,
V. V.; Hanquet, B.; Pirio, N.; Donnadieu, B.; Rebiere, B.; Amardeil,
R.; Meunier, P. J. Am. Chem. Soc. 2004, 126, 11077–11087. (d) Hierso,
J.-C.; Amardeil, R.; Bentabet, E.; Broussier, R.; Gautheron, B.;
Meunier, P.; Kalck, P. Coord. Chem. ReV. 2003, 236, 143–206. (e)
Gaw, K. G.; Smith, M. B.; Steed, J. W. J. Organomet. Chem. 2002,
664, 294–297. (f) Kuang, S.-M.; Zhang, Z.-Z.; Wang, Q.-G.; Mak,
T. C. W. Inorg. Chem. 1998, 37, 6090–6092.
(3) (a) Morisaki, Y.; Ouchi, Y.; Naka, K.; Chujo, Y. Chem. Asian J. 2007,
2, 1166–1173. (b) Menozzi, E.; Busi, M.; Massera, C.; Ugozzoli, F.;
Zuccaccia, D.; Macchioni, A.; Dalcanale, E. J. Org. Chem. 2006, 71,
2617–2624. (c) Kohl, S. W.; Heinemann, F. W.; Hummert, M.; Bauer,
W.; Grohmann, A. Dalton Trans. 2006, 5583–5592. (d) Kohl, S. W.;
Heinemann, F. W.; Hummert, M.; Bauer, W.; Grohmann, A.
Chem.sEur. J. 2006, 12, 4313–4320. (e) Schrauzer, G. N. Transition
Metals in Homogeneous Catalysis; Marcel Dekker: New York, 1971.
(f) Hierso, J.-C.; Beauperin, M.; Meunier, P. Eur. J. Inorg. Chem.
2007, 3767–3780.
10.1021/ic800724u CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 15, 2008 7035
Published on Web 07/08/2008

Ganesamoorthy et al.
Chart 1
to each other, thereby giving rise to strong cooperativity
effects in catalytic reactions.6 Incorporation of other group
5 and/or group 6 donor atoms into these system results in
mixed-multidentate phosphines, which can offer unusual
coordination geometry with remarkable chemical behavior
at the metal center.7 The conformationally rigid polyphos-
phines of good π-acceptor ligands are potential candidates
for designing conducting polymers for effective electronic
coupling through ligands.8 In addition, their chalcogenide
derivatives are more efficient cavitands for the separation
of trivalent lanthanides and actinides by solvent-extraction
processes compared to the most commonly used dithiophos-
phinic acids.9 However, the methods available for the
synthesis of conformationally rigid polyphosphines are
mostly multistep and/or low yielding.10 One of the most
commonly known polyphosphines is the tripod ligand
P(CH2CH2PR2)3 (R ) Me, Ph or cyclohexyl), whose
coordination behavior has been extensively studied.11,2b The
polyphosphines containing non-carbon spacers are less
extensive. The discovery of bis(dihalophosphino)amines,
C12P-N(R)-PC12 (R ) alkyl or aryl) has resulted in the
development of a large number of functionalized bis(phos-
phino)amines of the general formula R′2P-N(R)-PR′2 (R′
) alkoxide or amine).12 However, the same synthetic
methodology is not efficient for the preparation of analogous
tetra- and poly(dihalophosphino)amines from aromatic
polyamines. The only known tetra(dihalophosphino)amine
is p-C6H4[N(PCl2)2]2 (1), which was first synthesized in very
low yield (13%) by Haszeldine et al. in 1973, and there is
no subsequent follow-up either on its derivatization or its
transition-metal chemistry.13 Interestingly, the compounds
of type 1 can adopt several conformations depending upon
the orientation of the P-N-P skeleton with respect to the
phenylene ring. Three major idealized possibilities are: (I)
both phenylene and P-N-P skeletons can be coplanar, (II)
the phenylene ring can be perpendicular to the P-N-P
skeletons, and (III) the phenylene and one P-N-P skeleton
can be in one plane and orthogonal to the other P-N-P
skeleton. Further, the P-N-P moieties in each conformation
can adopt C2V, C2V′, and CS conformations, depending on
the mutual orientation of phosphorus lone pairs with respect
to the P-substituents as shown in Chart 1,14 so there is a
total of 18 possible conformations.
(4) (a) Bianchini, C.; Jimenez, M. V.; Meli, A.; Moneti, S.; Vizza, F.;
Herrera, V.; Sanchez-Delgado, R. A. Organometallics 1995, 14, 2342–
2352. (b) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Moneti,
S.; Herrera, V.; Sanchez-Delgado, R. A. J. Am. Chem. Soc. 1994, 116,
4370–4381.
(5) (a) Bruce, D. W. AdV. Mater. 1994, 6, 699–701. (b) Bruce, D. W.;
Holbrey, J. D.; Tajbakhsh, A. R.; Tiddy, G. J. T. J. Mater. Chem.
1993, 905–906.
(6) (a) Aubry, D. A.; Laneman, S. A.; Fronczek, F. R.; Stanley, G. G.
Inorg. Chem. 2001, 40, 5036–5041. (b) Oro, L. A.; Ciriano, M. A.;
Perez-Torrente, J.; Villarroya, B. E. Coord. Chem. ReV. 1999,
193-195, 941–975. (c) Jiang, H.; Xu, Y.; Liao, S.; Yu, D.; Chen, H.;
Li, X. J. Mol. Catal. 1999, 142, 147–152. (d) Peng, W.-J.; Train, S. G.;
Howell, D. K.; Fronczek, F. R.; Stanley, G. G. Chem. Commun. 1996,
2607–2608. (e) Suss-Fink, G. Angew. Chem., Int. Ed. Engl. 1994, 33,
67–69. (f) Broussard, M. E.; Juma, B.; Train, S. G.; Peng, W.-J.;
Laneman, S. A.; Stanley, G. G. Science 1993, 260, 1784–1788.
(7) (a) Stossel, P.; Heins, W.; Mayer, H. A.; Fawzi, R.; Steimann, M.
Organometallics 1996, 15, 3393–3403. (b) Uriarte, R.; Mazanec, T. J.;
Tau, K. D.; Meek, D. W. Inorg. Chem. 1980, 19, 79–85.
(11) (a) Field, L. D.; Messerle, B. A.; Smernik, R. J.; Hambley, T. W.;
Turner, P. Inorg. Chem. 1997, 36, 2884–2892. (b) Heinekey, D. M.;
van Roon, M. J. Am. Chem. Soc. 1996, 118, 12134–12140. (c) Mayer,
H. A.; Kaska, W. C. Chem. ReV. 1994, 94, 1239–1272. (d) Jia, G.;
Drouin, S. D.; Jessop, P. G.; Lough, A. J.; Morris, R. H. Organome-
tallics 1993, 12, 906–916. (e) Bampos, N.; Field, L. D.; Messerle,
B. A.; Smernik, R. J. Inorg. Chem. 1993, 32, 4084–4088. (f) Bianchini,
C. Pure Appl. Chem. 1991, 63, 829–834. (g) Bampos, N.; Field, L. D.
Inorg. Chem. 1990, 29, 587–588.
(8) (a) Zahavy, E.; Fox, M. A. Chem.sEur. J. 1998, 4, 1647–1652. (b)
Wang, P.-W.; Fox, M. A. Inorg. Chem. 1995, 34, 36–41. (c) Wang,
P.-W.; Fox, M. A. Inorg. Chem. 1994, 33, 2938–2945. (d) Wang, P.-
W.; Fox, M. A. Inorg. Chim. Acta 1994, 225, 15–22.
(12) (a) Mandal, S. K.; Venkatakrishnan, T. S.; Sarkar, A.; Krishnamurthy,
S. S. J. Organomet. Chem. 2006, 691, 2969–2977. (b) Veige, A. S.;
Gray, T. G.; Nocera, D. G. Inorg. Chem. 2005, 44, 17–26. (c)
Venkatakrishnan, T. S.; Krishnamurthy, S. S.; Nethaji, M. J. Orga-
nomet. Chem. 2005, 690, 4001–4017. (d) Ganesan, M.; Krishnamurthy,
S. S.; Nethaji, M. J. Organomet. Chem. 2005, 690, 1080–1091. (e)
Heyduk, A. F.; Nocera, D. G. J. Am. Chem. Soc. 2000, 122, 9415–
9426. (f) Field, J. S.; Haines, R. J.; Stewart, M. W.; Woollam, S. F.
J. Chem. Soc., Dalton Trans. 1996, 1031–1037. (g) Edwards, K. J.;
Field, J. S.; Haines, R. J.; Homann, B. D.; Stewart, M. W.;
Sundermeyer, J.; Woollam, S. F. J. Chem. Soc., Dalton Trans. 1996,
4171–4181. (h) Mague, J. T. Inorg. Chim. Acta 1995, 229, 17–25. (i)
Reddy, V. S.; Katti, K. V.; Barnes, C. L. Inorg. Chem. 1995, 34, 1273–
1277. (j) Balakrishna, M. S.; Reddy, S. V.; Krishnamurthy, S. S.;
Nixon, J. F.; St. Laurent, J. C. T. R. B. Coord. Chem. ReV. 1994,
129, 1–90. (k) King, R. B. Acc. Chem. Res. 1980, 13, 243–248.
(13) Davies, A. R.; Dronsfield, A. T.; Haszeldine, R. N.; Taylor, D. R.
J. Chem. Soc., Perkin Trans. 1 1973, 379–385.
(9) (a) Boerrigter, H.; Tomasberger, T.; Verboom, W.; Reinhoudt, D. N.
Eur. J. Org. Chem. 1999, 665–674. (b) Boerrigter, H.; Verboom, W.;
Reinhoudt, D. N. J. Org. Chem. 1997, 62, 7148–7155. (c) Lobana,
T. S. The Chemistry of Organophosphorus Compounds; Hartley, F. R.,
Ed.; Wiley: New York, 1992; Vol. 2, p 1409.
(10) (a) Gagliardo, M.; Amijs, C. H. M.; Lutz, M.; Spek, A. L.; Havenith,
R. W. A.; Hartl, F.; van Klink, G. P. M.; van Koten, G. Inorg. Chem.
2007, 46, 11133–11144. (b) Yan, Y.; Zhang, X.; Zhang, X. AdV. Synth.
Catal. 2007, 349, 1582–1586. (c) Kondolff, I.; Feuerstein, M.; Doucet,
H.; Santelli, M. Tetrahedron 2007, 63, 9514–9521. (d) Reiter, S. A.;
Nogai, S. D.; Schmidbaur, H. Z. Anorg. Allg. Chem. 2005, 631, 2595–
2600. (e) Kim, S.; Kim, J. S.; Kim, S. K.; Suh, I.-H.; Kang, S. O.;
Ko, J. Inorg. Chem. 2005, 44, 1846–1851. (f) Butler, I. R.; Drew,
M. G. B.; Caballero, A. G.; Gerner, P.; Greenwell, C. H. J. Organomet.
Chem. 2003, 679, 59–64. (g) Chatterjee, S.; Doyle, R.; Hockless,
D. C. R.; Salem, G.; Willis, A. C. J. Chem. Soc., Dalton Trans. 2000,
1829–1830. (h) Steenwinkel, P.; Kolmschot, S.; Gossage, R. A.; Dani,
P.; Veldman, N.; Spek, A. L.; van Koten, G. Eur. J. Inorg. Chem.
1998, 477–483. (i) Barney, A. A.; Fanwick, P. E.; Kubiak, C. P.
Organometallics 1997, 16, 1793–1796. (j) Fourmigue, M.; Uzelmeier,
C. E.; Boubekeur, K.; Bartley, S. L.; Dunbar, K. R. J. Organomet.
Chem. 1997, 529, 343–350. (k) Dieleman, C.; Loeber, C.; Matt, D.;
De Cian, A.; Fischer, J. J. Chem. Soc., Dalton Trans. 1995, 3097–
3100. (l) Christina, H.; McFarlane, E.; McFarlane, W. Polyhedron
1988, 7, 1875–1879, and references therein.
(14) (a) Cross, R. J.; Green, T. H.; Keat, R. J. Chem. Soc., Dalton Trans.
1976, 1424–1428. (b) Colquhoun, I. J.; McFarlane, W. J. Chem. Soc.,
Dalton Trans. 1977, 1674–1679. (c) Keat, R.; Manojlovic-Muir, L.;
Muir, K. W.; Rycroft, D. S. J. Chem. Soc., Dalton Trans. 1981, 2192–
2198. (d) Prout, T. R.; Imiolczyk, T. W.; Barthelemy, F.; Young, S. M.;
Haltiwanger, R. C.; Norman, A. D. Inorg. Chem. 1994, 33, 1783–
1790. (e) Schmidbaur, H.; Milewski-Mahrla, B.; Muller, G.; Kruger,
C. Organometallics 1984, 3, 38–43. (f) Schmidbaur, H.; Schier, A.;
Lauteschlager, S.; Riede, J.; Muller, G. Organometallics 1984, 3,
1906–1909.
7036 Inorganic Chemistry, Vol. 47, No. 15, 2008

Intermolecular P · · ·P Interactions in Halo-Phosphines
Scheme 1
These conformations can lead to the formation of different
types of oligomers and polymers such as linear sheets,
twisted chains, or cyclic structures with metals, and the nature
of which will depend on the coordination geometry of the
transition metals and the possible conformations of the
ligand. Further, 1 can also serve as a molecular synthon for
producing novel ligands with desired steric and electronic
attributes at the phosphorus centers, which may find ap-
plications in homogeneous catalysis in addition to interesting
coordination chemistry. As a part of our interest in phosphorus-
based ligands15 and their catalytic applications,16 we describe
herein the high-yield synthesis and structural characterization
of p-C6H4[N(PCl2)2]2 (1), its reactivity, and group 10 and
11 metal complexes of one of its derivatives p-C6H4[N{P(OC6-
H4OMe-o)2}2]2 (3). The utility of the palladium complex
[Pd2Cl4-p-C6H4{N{P(OC6H4OMe-o)2}2}2] (8) in Suzuki-
Miyaura cross-coupling reactions is also described. Bispal-
ladium 8 promotes one-pot multiple carbon-carbon coupling
reactions very efficiently.
and 392 Hz, respectively.14c,17 Tetraphosphine 1 reacts
smoothly with the appropriate amount of 2-(methoxy)phenol
or methanol in the presence of triethylamine to afford the
corresponding tetraphosphonites p-C6H4[N{P(OC6H4OMe-
o)2}2]2 (3) and p-C6H4[N{P(OMe)2}2]2 (4). Treatment of 1
with the sodium salt of 2-(methoxy)phenol in THF also
produces 3 in 76% yield as shown in Scheme 1. 3 is an air-
stable white crystalline solid, whereas 4 is a white solid with
a pungent smell and is moderately stable toward air. The
31P NMR spectra of 3 and 4 exhibit single resonances at
132.1 and 134.7 ppm, respectively. The 1H NMR spectra of
the 1-4 show singlets in the range of 7.03-7.79 ppm,
corresponding to the protons of the bridging phenylene group.
The o-methoxy protons in 3 show a singlet at 3.60 ppm,
whereas those in 4 resonate as a sharp triplet at 3.51 ppm
with a 3JPH coupling of 12.6 Hz. The (EI) mass spectra of 3
and 4 display the molecular ion peaks at m/z 1214.47 (M +
1) and 477.98 (M + 1), respectively. The elemental analyses
support the compositions of 1-4 and the structures of 1-3
were confirmed by X-ray structure determination.
Results and Discussion
Chalcogenide Derivatives. Treatment of 3 with aqueous
H2O2 (30% w/v) at -78 °C gives the tetra(oxide) derivative,
p-C6H4[N{P(O)(OC6H4OMe-o)2}2]2, (5). A similar oxidation
reaction of 3 with S8 or gray selenium does not proceed even
under refluxing conditions in toluene. However, the tetra-
phosphonite, p-C6H4[N{P(OMe)2}2]2 (4), reacts smoothly
with four equivalents of S8 or gray selenium in toluene under
refluxing conditions (32 h) to give the corresponding
tetra(sulfide), p-C6H4[N{P(S)(OMe)2}2]2 (6), or tetra(se-
lenide) derivative, p-C6H4[N{P(Se)(OMe)2}2]2 (7). This
difference in reactivity may be due to the steric congestion
in and the less basic nature of 3 when compared to 4.
However, the reaction of 4 with aqueous H2O2 (30% w/v)
resulted in the hydrolysis of P-N bonds. The 31P NMR
spectra of the chalcogenide derivatives 5-7 show singlets
at -12.5, 68.8, and 73.4 ppm, respectively. The selenide
derivative 7 shows characteristic selenium satellites with a
1JPSe coupling of 945 Hz. In contrast to 4, the proton NMR
spectra of 6 and 7 show broad doublets for the O-methyl
Tetraphosphanes. The reaction of p-phenylenediamine
with phosphorus trichloride in the presence of 2 equiv of
pyridine affords the tetraphosphine, p-C6H4[N(PCl2)2]2 (1)
in 75% yield. The fluorination of 1 with antimony trifluoride
produces the fluoro analogue, p-C6H4[N(PF2)2]2 (2) in 69%
yield. 1 and 2 are white crystalline solids, which readily
decompose when exposed to air or moisture. 2 is volatile
under reduced pressure even at 30 °C. The 31P NMR
spectrum of 1 consists of a single peak at 153.6 ppm, whereas
2 shows the A portion of an AA′X2X2′ multiplet centered at
1
3
2
129.7 ppm with JPF, JPF, and JPP couplings of 1248, 123,
(15) (a) Venkateswaran, R.; Balakrishna, M. S.; Mobin, S. M.; Tuononen,
H. M. Inorg. Chem. 2007, 46, 6535–6541. (b) Ganesamoorthy, C.;
Balakrishna, M. S.; Mague, J. T.; Tuononen, H. M. Inorg. Chem. 2008,
47, 2764–2776. (c) Ganesamoorthy, C.; Mague, J. T.; Balakrishna,
M. S. J. Organomet. Chem. 2007, 692, 3400–3408. (d) Suresh, D.;
Balakrishna, M. S.; Mague, J. T. Tetrahedron Lett. 2007, 48, 2283–
2285. (e) Balakrishna, M. S.; Mague, J. T. Organometallics 2007,
26, 4677–4679. (f) Chandrasekaran, P.; Mague, J. T.; Balakrishna,
M. S. Inorg. Chem. 2006, 45, 5893–5897. (g) Chandrasekaran, P.;
Mague, J. T.; Balakrishna, M. S. Organometallics 2005, 24, 3780–
3783.
3
groups at 3.51 and 3.72 ppm with JPH couplings of 14.4
and 14.7 Hz, respectively. The (EI) mass spectra of com-
pounds 5-7 display the molecular ion peaks at m/z 1278.87
(M + 1), 605.15 (M + 1), and 794.62 (M + 2), respectively,
with appropriate isotopic patterns. The structure and com-
(16) (a) Mohanty, S.; Suresh, D.; Balakrishna, M. S.; Mague, J. T. Tetrahedron
2008, 64, 240–247. (b) Punji, B.; Mague, J. T.; Balakrishna, M. S.
Inorg. Chem. 2007, 46, 11316–11327. (c) Venkateswaran, R.; Mague,
J. T.; Balakrishna, M. S. Inorg. Chem. 2007, 46, 809–817. (d)
Venkateswaran, R.; Balakrishna, M. S.; Mobin, S. M. Eur. J. Inorg.
Chem. 2007, 1930–1938. (e) Punji, B.; Ganesamoorthy, C.; Bal-
akrishna, M. S. J. Mol. Catal. A: Chem. 2006, 259, 78–83. (f) Punji,
B.; Mague, J. T.; Balakrishna, M. S. Dalton Trans. 2006, 1322–1330.
(17) (a) King, R. B.; Gimeno, J. Inorg. Chem. 1978, 17, 2390–2395. (b)
Nixon, J. F. J. Chem. Soc. A 1969, 1087–1089.
Inorganic Chemistry, Vol. 47, No. 15, 2008 7037

Ganesamoorthy et al.
Scheme 2
discrete X2P-N(R)-PX2 (1, X ) Cl; 2, X ) F and 3, X )
O) skeletons having crystallographically imposed centrosym-
metry with the C2V conformation. In 2, there are two
independent half-molecules in the asymmetric unit, which
differ only slightly in geometry and conformation. In the
X2P-N(R)-PX2 (1, X ) Cl; 2, X ) F and 3, X ) O)
skeletons, the X atoms are disposed approximately equally
above and below the P-N-P plane, whereas there is a
distorted-pyramidal geometry about the phosphorus centers
and a planar environment around the nitrogen centers with
the sum of the angles around nitrogen almost 360° in all
cases. The observed P-N bond lengths in 1-3 vary from
1.686(2) to 1.707(2) Å and are comparable with those found
in the amino bis(phosphine) derivatives, iPrN(PPh2)2 (1.710
Å),14c C6H5N{P(NHPh)2}2 (1.690 Å),19 CH3N{P(NC4H4)2}2
positions of compounds 5-7 are consistent with the analyti-
1
cal, H NMR, and mass-spectrometric data. The molecular
structures of 6 and 7 were confirmed by single-crystal X-ray
structure determinations.
Group 10 and 11 Metal Derivatives. 2-4 are potential
tetradentate ligands, and it would be interesting to explore
their coordination behavior with various transition-metal
salts. The air- and moisture-stable ligand 3 has been used
for the preparation of group 10 and 11 metal complexes.
The reactions of 3 with 2 equiv of [M(COD)Cl2] (M ) Pd
or Pt) (COD ) cycloocta-1,5-diene) in dichloromethane
yieldedthechelatecomplexes,[M2Cl4-p-C6H4{N{P(OC6H4OMe-
o)2}2}2] (8, M ) Pd and 9, M ) Pt). The 31P NMR spectra
of 8 and 9 consist of single resonances at 64.4 and 35.0 ppm,
respectively, which are considerably shielded compared to
that of the free ligand. The coordination shifts for 8 and 9
are 67.7 and 97.1 ppm, respectively, and the platinum
(1.685(1)-1.699(1) Å),20 EtN{P(OC6H3 Pr2-2,6)2}2 (1.674(5)
i
Å),EtN{P(OC6H3Me2-2,6)2}2(1.693(2)Å),21MeN{P(OC6H3Me2-
2,6)2}2 (1.672(1) Å),22 and shorter than those in C6H5-
N(PPh2)2,(1.732(2)Å),p-CNC6H4N(PPh2)2(1.723(3)-1.732(3)
Å), m-CNC6H4N(PPh2)2 (1.746(2) Å).23 In 1, the P-Cl bond
distances vary from 2.042(1) to 2.057(1) Å.24 The P-N-P
angle (109.47(6)°) subtended in 1 is smaller than those of 2
(115.43(8)°) and 3 (115.25(9)°). In 1-3, the bridging
phenylene rings are almost perpendicular to the plane of the
P-N-P skeletons with dihedral angles of 88.58(16)°
(P2-N-P1 vs C1-C3i for 1), 89.73(66)° and 87.31(66)°
(P2-N1-P1 vs C1-C3i and P3-N2-P4 vs C4-C6i for 2)
and 78.37(19)° (P1-N-P2 vs C29-C31i for 3), respectively.
In addition, 1 shows all phosphorus atoms to have intermo-
lecular P· · ·P contacts of 3.539(1) Å, which are 0.061 Å less
than the sum of the van der Waals radii and serve to generate
a slightly undulating 2D sheet structure parallel to {1,0,0}.
Although, Lewis acid-base acceptor-donor adducts between
simple phosphines are known,25 a search of the current
Cambridge Crystallographic Database shows only one
example25a of a close (3.372 Å) P · · · P contact in any of the
51 structures containing {A-PX2} (A ) N, C; X ) halogen)
moieties. A slightly shorter P · · · P separation is seen in the
solid-state structure of (C6F5)2PCH2P(C6F5)2, but here the
interactions associate the molecules into discrete pairs.25d It
is noteworthy that no discussion is given on the observed
interactions, which are of van der Waals in nature, and that
only 54 examples of close P · · · P contacts between two
tricoordinate phosphorus atoms are found in the current
version of the Cambridge Crystallographic Database.
1
complex exhibits a large JPtP coupling of 5072 Hz, which
is consistent with the proposed cis geometry around the
platinum center.18 The H NMR spectra of 8 and 9 show
1
single resonances around 3.60 ppm corresponding to the
o-methoxy groups attached to the phenyl rings. Further
evidence for the molecular composition of 8 and 9 come
from the elemental analyses, 1H NMR data, and the single-
crystal X-ray structure of the platinum derivative 9. The
reactions of 3 with 4 equiv of CuX (X ) Br and I) in
acetonitrile lead to the formation of tetranuclear complexes,
[Cu4(µ2-X)4(NCCH3)4-p-C6H4{N(P(OC6H4OMe-o)2)2}2] (10,
X ) Br; 11, X ) I) (Scheme 3). 10 and 11 are colorless, air
stable, crystalline solids, and moderately soluble in organic
solvents. The 31P NMR spectra of 10 and 11 show single
1
resonances at 103.8 and 102.6 ppm, respectively. The H
NMR spectra of 10 and 11 show single resonances at 2.07
ppm and 3.56 ppm, respectively, for coordinated CH3CN and
ortho-methoxy groups present in the phenyl rings. The
analytical data are consistent with the proposed structures
and the molecular structures of 10 and 11 are confirmed by
(19) Tarassoli, A.; Haltiwanger, R. C.; Norman, A. D. Inorg. Chem. 1982,
21, 2684–2690.
the single-crystal X-ray diffraction studies. The H and 31P
NMR spectral data for 1-11 are given in Table 1.
1
(20) Gimbert, Y.; Robert, F.; Durif, A.; Averbuch, M.-T.; Kann, N.; Greene,
A. E. J. Org. Chem. 1999, 64, 3492–3497.
(21) Prabusankar, G.; Palanisami, N.; Murugavel, R.; Butcher, R. J. Dalton
Trans. 2006, 2140–2146.
The Crystal and Molecular Structures of 1-3, 6, 7,
and 9-11. Perspective views of the molecular structures of
1-3, 6, 7, and 9-11 with atom numbering schemes are
shown in Figures 1–8, respectively. Crystal data and the
details of the structure determinations are given in Table 2,
whereas selected bond lengths and bond angles are given in
Tables 3–5. The molecular structures of 1-3 consist of
(22) Venkatakrishnan, T. S.; Mandal, S. K.; Kannan, R.; Krishnamurthy,
S. S.; Nethaji, M. J. Organomet. Chem. 2007, 692, 1875–1891.
(23) Fei, Z.; Scopelliti, R.; Dyson, P. J. Dalton Trans. 2003, 2772–2779.
(24) Chen, H. J.; Barendt, J. M.; Haltiwanger, R. C.; Hill, T. G.; Norman,
A. D. Phosphorus Sulfur 1986, 26, 155–162.
(25) (a) Kuhn, N.; Fawzi, R.; Steimann, M.; Wiethoff, J. Chem. Ber. 1996,
129, 479. (b) Holmes, R. R.; Bertaut, E. F. J. Am. Chem. Soc. 1958,
80, 2980–2983. (c) Mu¨ller, G.; Matheus, H.-J.; Winkler, M. Z.
Naturforsch. 2001, 56b, 1155–1162. (d) Marr, A. C.; Nieuwenhuyzen,
M.; Pollock, C. L.; Saunders, G. C. Organometallics 2007, 26, 2659–
2671.
(18) Balakrishna, M. S.; Santarsiero, B. D.; Cavell, R. G. Inorg. Chem.
1994, 33, 3079–3084.
7038 Inorganic Chemistry, Vol. 47, No. 15, 2008

Intermolecular P · · ·P Interactions in Halo-Phosphines
Scheme 3
Table 1. NMR Data for 1-11
1H NMR (in ppm)
31P{1H}
in analogous derivatives, 6 and 7 adopt twisted conformations
with the P ) E (E ) S, Se) vectors, making an angle of
107.6(1)° with one another.26 The two independent P ) E
bonds are virtually same [1.9191(5) Å, 1.9191(6) Å for 6
and 2.0720(4) Å, 2.0718(4) Å for 7]. The observed P ) Se
bond distances are longer than those found in compound
PhN{P(Se)(OC6H4OMe-o)2}2 (2.058(6) Å) and is reflected
in the relatively low 1JSe-P coupling of 7.27 The P-N bond
distances vary from 1.677(1) to 1.687(1) Å in both cases.
The P-N-P angles in 6 and 7 are 127.64(8)° and 127.00(6)°,
aryl
protons
compounds NMR (in ppm) CH3CN
OCH3
1
2
153.6 (s)
129.7 (m)
7.38 (s)
1JPF ) 1248 Hz
3JPF ) 123 Hz
2JPP ) 392 Hz
132.1 (s)
7.38 (s)
6.69-7.57 (m)
7.03 (s)
3
4
3.60 (s)
134.7 (s)
3.51 (t)
3JPH ) 12.6 Hz
3.57 (s)
5
6
-12.5 (s)
68.8 (s)
6.70-7.79 (m)
7.34 (s)
3.51 (d)
3JPH ) 14.4 Hz
3.72 (d)
7
73.4 (s)
7.38 (s)
1JPSe ) 945 Hz
64.4 (s)
3JPH ) 14.7 Hz
3.62 (s)
8
9
6.78-8.02 (m)
6.83-8.03 (m)
35.0 (s)
3.60 (s)
1JPtP ) 5072 Hz
103.8 (br s)
102.6 (br s)
10
11
2.07 (s) 3.57 (s)
2.07 (s) 3.55 (s)
6.75-7.66 (m)
6.75-7.74 (m)
In contrast to 1, no close P · · · P contacts are observed in
its fluoro analogue 2. Hence, as weak P · · · P contacts do not
appear to be a general feature of the solid-state structures of
phosphines bearing electronegative substituents on phospho-
rus, their occurrence suggests that a fine-tuning of the
electronic structure is necessary for this effect to be present.
To investigate the phenomenon deeper, theoretical calcula-
tions were performed for molecules 1 and 2 as well as for
some simplified model systems (below).
The packing of 3 in the solid state is surprisingly efficient,
given the bulk of the o-methoxyphenoxy substituents and is
aided by C-H · · · π and C-H · · · O interactions. Thus, H5 is
situated 2.92 Å from the center (Cg) of the phenyl ring
C15-C20 located at 2 - x, -y, 1 - z with a C-H · · · Cg
angle of 144°, whereas H12 is 3.28 Å from Cg of the ring
C1-C6 located at -0.5 + x, y, 1.5 - z with a C12-H12 · · · Cg
angle of 166°. Additionally, O4 makes an O · · · H-C
hydrogen bond with H28a located at 1.5 - x, 0.5 + y, z
(O4 · · ·H28a ) 2.56 Å; O4 · · ·H28a-C28 ) 139°), O5 makes
one with H28c located at 0.5 + x, 0.5 - y, 1 - z (O5· · ·H28c
) 2.72 Å; O5 · · · H28c-C28 ) 155°) and H21c makes one
with O7 located at 0.5+x, 0.5-y, 1-z (O7...H21c ) 2.50 Å;
O7 · · · H21c-C21 ) 162°).
Figure 1. (a) Molecular structure of 1. All hydrogen atoms have been
omitted for clarity. Displacement ellipsoids are drawn at the 50% probability
level. Symmetry operation i ) 1 - x, 1 - y, 2 - z. (b) P · · ·P interaction
in 1. All hydrogen atoms have been omitted for clarity. Displacement
ellipsoids are drawn at the 50% probability level.
6 and 7 are isomorphous and virtually isostructural with
crystallographically imposed centrosymmetry. As observed
Inorganic Chemistry, Vol. 47, No. 15, 2008 7039

Ganesamoorthy et al.
Figure 5. Molecular structure of 7. All hydrogen atoms have been omitted
for clarity. Displacement ellipsoids are drawn at the 50% probability level.
Symmetry operation i ) /2 - x, /2 - y, -z.
Figure 2. Molecular structure of 2. All hydrogen atoms have been omitted
for clarity. Displacement ellipsoids are drawn at the 50% probability level.
Symmetry operation i ) -x, -y, 1 - z.
1
3
Figure 6. Molecular structure of 9. All hydrogen atoms and lattice solvents
have been omitted for clarity. Displacement ellipsoids are drawn at the 50%
probability level. Symmetry operation i ) 1 - x, 2 - y, -z.
Figure 3. Molecular structure of 3. All hydrogen atoms have been omitted
for clarity. Displacement ellipsoids are drawn at the 50% probability level.
Symmetry operation i ) 2 - x, -y, 1 - z.
Figure 7. Molecular structure of 10. All hydrogen atoms and lattice solvents
have been omitted for clarity. Displacement ellipsoids are drawn at the 50%
probability level. Symmetry operation i ) 1 - x, 1 - y, 2 - z.
Figure 4. Molecular structure of 6. All hydrogen atoms have been omitted
for clarity. Displacement ellipsoids are drawn at the 50% probability level.
1
3
Symmetry operation i ) /2 - x, /2 - y, -z.
involves C6-H6 · · · O4 (O4 at 0.5 - x, 0.5 + y, 0.5 - z;
O4 · · ·H6)2.39Å;C6-H6 · · ·O4)159°)andC4-H4b · · ·O2
(O2 at 0.5 - x, -0.5 + y, 0.5 - z; O2· · · H4b ) 2.67 Å;
C4-H4b · · · O2 ) 156°), whereas in 7 the interactions are
C6-H6 · · · O3 (O3 at 0.5 - x, -0.5 + y, 0.5 - z; O3· · ·H6
) 2.44 Å; C6-H6 · · ·O3 ) 160°) and the weaker, bifurcated
hydrogen bond C3-H3b · · · O1,O4 (O1 and O4 at 0.5 - x,
0.5 + y, 0.5 - z); O1 · · · H3b ) 2.66 Å; O4 · · · H3b ) 2.64
Å; C3-H3b · · · O1 ) 145°; C3-H3b · · · O4 ) 142°).
respectively, and are larger than in the free ligands of the
type PhN{P(OR)2}2 (R ) alkyl or aryl groups).12j Here again,
the bridging phenylene rings are almost perpendicular to the
plane of the P-N-P skeletons of 6 and 7 with the dihedral
angles of 89.18(14)° (P2-N-C5-C6) and 92.16(12)°
(P2-N-C5-C7), respectively. For both compounds, the
molecules pack in sheets parallel to {1,0,0} with the sheets
assembled through C-H · · · O hydrogen bonding. In 6, this
7040 Inorganic Chemistry, Vol. 47, No. 15, 2008

Intermolecular P · · ·P Interactions in Halo-Phosphines
Figure 8. Molecular structure of 11. All hydrogen atoms and lattice solvent
have been omitted for clarity. Displacement ellipsoids are drawn at the 50%
probability level. Symmetry operation i ) 2 - x, -y, -z; ii ) 1 - x, 1 -
y, 1 - z.
The asymmetric unit of 9 contains half a molecule of the
metal complex and one molecule of chloroform. The
platinum adopts an approximate square-planar geometry, with
the corners occupied by two chlorines and two phosphorus
atoms of tetraphosphazane 3. In the molecular structure of
9, the two independent P-N [P1-N ) 1.684(2) Å and P2-N
) 1.686(2) Å] and P-Pt [P1-Pt ) 2.177(1) Å and P2-Pt
) 2.179(1) Å] distances are virtually the same, whereas the
P-N-P angle shrinks from 115.25(9) to 97.46(9)° due to
the formation of a strained four-membered chelate ring. The
P1-Pt-P2, Cl1-Pt-Cl2, Cl1-Pt-P1, and Cl2-Pt-P2
bond angles are 71.12(2)°, 90.92(2)°, 97.75(2)°, and
100.22(2)°, respectively, which show the distortion in the
square-planar geometry. In contrast to the molecular struc-
tures of 1-3, 6, and 7, the bridging phenylene ring is almost
parallel to the plane produced by P1-N-P2 skeleton with
the dihedral angle of 0.7(3)° (P2-N-C30-C21). Molecules
of 9 appear to be associated via C-H· · ·O hydrogen bonding
involving one phenoxy group on each side of the ligand viz.
C24-H24 · · · O1 and C25-H25 · · · O2 (O1 and O2 at 1 + x,
y, z; H24 · · · O1 ) 2.70 Å; C24-H24 · · · O1 ) 176°;
H25 · · · O2 ) 2.71 Å; C25-H25 · · · O2 ) 130°).
The molecular structures of 10 and 11 consist of discrete
Cu2X2 core (10, X ) Br and 11, X ) I) having crystallo-
graphically imposed centrosymmetry. In 11, there are two
independent half-molecules in the asymmetric unit, which
differ only slightly in geometry and conformation with both
the molecules has been held together by weak C-H· · ·I and
C-H · · · C interactions. All of the copper(I) centers are
tetrahedrally coordinated to a phosphorus atom, two bridging
halides, and a solvent molecule. As observed in complexes
Cu2(µ2-I)2(NCCH3)2{µ-PhN(P(OC6H4OMe-o)2)2} and Cu2(µ2-
I)2(C5H5N)2{µ-PhN(P(OC6H4OMe-o)2)2},28 the Cu2X2 core
adopts a butterfly shape with the halide atoms at the wingtips.
The four Cu-X bond lengths differ significantly from one
(26) Hitchcock, P. B.; Nixon, J. F.; Silaghi-Dumitrescu, I.; Haiduc, I. Inorg.
Chim. Acta 1985, 96, 77–80.
(27) Balakrishna, M. S.; George, P. P.; Mague, J. T. J. Organomet. Chem.
2004, 689, 3388–3394.
(28) Ganesamoorthy, C.; Balakrishna, M. S.; George, P. P.; Mague, J. T.
Inorg. Chem. 2007, 46, 848–858.
Inorganic Chemistry, Vol. 47, No. 15, 2008 7041

Ganesamoorthy et al.
Table 3. Selected Bond Distances and Bond Angles for 1-3
1
2
3
bond distances
(angstroms)
bond angles
(degrees)
bond distances
(angstroms)
bond angles
(degrees)
bond distances
(angstroms)
bond angles
(degrees)
Cl1-P1
Cl2-P1
Cl3-P2
Cl4-P2
P1-N
2.0457(5) Cl1-P1-Cl2 98.51(2)
2.0421(5) Cl3-P2-Cl4 98.28(2)
F1-P1 1.582(1) F1-P1-F2 94.43(6)
F2-P1 1.586(1) F3-P2-F4 94.52(7)
P1-N
P2-N
1.707(2) P1-N-P2
1.694(2) O1-P1-N
115.25(9)
94.59(7)
101.91(7)
101.83(7)
97.02(7)
2.0574(5) P1-N-P2
2.0547(5) Cl1-P1-N
109.47(6) F3-P2 1.575(1) P1-N-P2
115.43(8) P1-O1 1.639(1) O3-P1-N
101.53(4) F4-P2 1.584(1) F1-P1-N1 99.62(6)
102.31(4) P1-N1 1.689(1) F2-P1-N1 98.90(6)
101.69(4) P2-N1 1.686(2) F3-P2-N1 99.39(7)
P1-O3 1.642(1) O5-P2-N
P2-O5 1.648(1) O7-P2-N
P2-O7 1.636(1) O1-P1-O3 95.43(7)
N-C29 1.445(2) O5-P2-O7 95.04(7)
P1-N-C29 120.51(1)
1.704(1)
1.703(1)
1.445(2)
Cl2-P1-N
Cl3-P2-N
Cl4-P2-N
P1-N-C1
P2-N-C1
P2-N
N-C1
101.73(4) N-C1
124.69(9)
1.453(2) F4-P2-N1 99.88(7)
P1-N1-C1 121.3(1)
P2· · ·P1_i(inter) 3.539(1)
P2· · ·P1_i(intra) 7.620
125.82(9)
P2-N1-C1 123.3(1)
P2-N-C29 124.05(1)
P1· · ·P2
2.781
Table 4. Selected Bond Distances and Bond Angles for 6, 7, and 9
6
7
9
bond distances
(angstroms)
bond angles
(degrees)
bond distances
(angstroms)
bond angles
(degrees)
bond distances
(angstroms)
bond angles
(degrees)
P1-N
1.684(1) P1-N-P2
1.677(1) S1-P1-O1
1.919(1) S1-P1-O2
1.919(1) S2-P2-O3
127.64(8) Se1-P1 2.072(1) P1-N-P2
127.00(6) P1-N
1.684(2) P1-N-P2
97.46(9)
P2-N
S1-P1
S2-P2
114.32(4) Se2-P2 2.072(1) Se1-P1-O1 117.40(4) P2-N
1.686(2) Cl1-Pt-Cl2 90.92(2)
117.60(5) P1-N
116.67(5) P2-N
115.94(4) P1-O1
1.687(1) Se1-P1-O2 114.50(4) Pt-P1
1.680(1) Se2-P2-O3 116.02(3) Pt-P2
2.177(1) Cl1-Pt-P1
2.179(1) Cl2-Pt-P2
97.75(2)
100.22(2)
168.87(2)
171.31(2)
71.12(2)
100.30(8)
101.13(8)
119.35(6)
124.90(6)
122.35(6)
122.79(6)
P1-O1 1.579(1) S2-P2-O4
P1-O2 1.568(1) O1-P1-O2 102.34(6) P1-O2
P2-O3 1.576(1) O3-P2-O4 101.39(6) P2-O3
P2-O4 1.577(1) S1-P1-N
N-C5
1.566(1) Se2-P2-O4 116.43(4) Pt-Cl1 2.340(1) Cl1-Pt-P2
1.581(1) O1-P1-O2
1.574(1) O3-P2-O4
1.572(1) Se1-P1-N
1.454(2) Se2-P2-N
P1-N-C5
102.44(5) Pt-Cl2 2.354(1) Cl2-Pt-P1
101.49(4) P1-O1 1.596(2) P1-Pt-P2
115.94(4) P1-O3 1.579(2) O1-P1-O3
113.95(4) P2-O5 1.582(2) O5-P2-O7
114.19(8) P2-O7 1.580(2) Pt-P1-O1
118.66(8) N-C30 1.435(3) Pt-P1-O3
Pt-P2-O5
116.05(5) P2-O4
113.55(5) N-C5
113.99(9)
1.454(2) S2-P2-N
P1-N-C5
P2-N-C5
118.20(9)
P2-N-C5
Pt-P2-O7
Table 5. Selected Bond Distances and Bond Angles for 10 and 11
10
11
bond distances (angstroms)
bond angles (degrees)
bond distances (angstroms)
P1-N1 1.709(8)
bond angles (degrees)
P1-N1
1.694(13)
1.687(13)
1.626(12)
1.623(11)
1.627(11)
1.624(12)
2.191(4)
2.179(4)
2.525(3)
2.554(3)
2.582(3)
2.435(3)
1.995(14)
1.991(14)
P1-N1-P2
119.6(7)
114.8(5)
P1-N1-P2
N1-P1-Cu1
N1-P2-Cu2
P1-Cu1-I1
P1-Cu1-I2
P2-Cu2-I1
P2-Cu2-I2
P1-Cu1-N2
P2-Cu2-N3
Cu1-I1-Cu2
Cu1-I2-Cu2
I1-Cu1-I2
I1-Cu2-I2
119.0(4)
116.5(3)
116.0(3)
105.25(7)
115.80(8)
104.27(8)
116.42(8)
120.4(3)
119.7(3)
59.07(4)
61.17(4)
106.08(5)
107.59(5)
P2-N1
N1-P1-Cu1
N1-P2-Cu2
P1-Cu1-Br1
P1-Cu1-Br2
P2-Cu2-Br1
P2-Cu2-Br2
P1-Cu1-N3
P2-Cu2-N2
Cu1-Br1-Cu2
Cu1-Br2-Cu2
Br1-Cu1-Br2
Br1-Cu2-Br2
P2-N1
P1-O1
P1-O3
P2-O5
P2-O7
P1-Cu1
P2-Cu2
Cu1-I1
Cu1-I2
Cu2-I1
Cu2-I2
Cu1-N2
Cu2-N3
1.709(8)
1.626(7)
1.610(7)
1.614(7)
1.635(7)
2.194(3)
2.215(3)
2.788(2)
2.629(2)
2.688(2)
2.678(2)
1.980(10)
2.016(10)
P1-O1
118.6(5)
P1-O3
112.60(14)
110.15(13)
96.97(13)
121.43(14)
124.5(4)
P2-O5
P2-O7
P1-Cu1
P2-Cu2
Cu1-Br1
Cu1-Br2
Cu2-Br1
Cu2-Br2
Cu1-N3
Cu2-N2
116.2(4)
64.93(7)
66.63(8)
100.08(9)
101.74(9)
another but can be seen (Table 5) to fall roughly into a longer
pair and a shorter pair with each copper atom forming a long
and a short Cu-X bond. The distance between the two
copper centers in 10 and 11 are 2.742 Å and 2.700 Å (2.730
Å for another half of molecule in the asymmetric unit of
11), respectively, which indicate the presence of ligand
supported Cu · · ·Cu interactions.28 In the molecular structures
of 10 and 11, the two independent Cu-P distances differ
only slightly (Cu1-P1 ) 2.191(4) Å and Cu2-P2 )
2.179(4) Å for 10 and Cu1-P1 ) 2.194(3) Å and Cu2-P2
) 2.215(3) Å for 11), whereas the X-Cu-X angles
(Br1-Cu1-Br2 ) 100.08(9)° and Br1-Cu2-Br2 )
101.74(9)° for 10; I1-Cu1-I2 ) 106.08(5)° and I1-Cu2-I2
) 107.59(5)° for 11) show the distortion in the tetrahedral
environment around copper atoms. The angles about the
halideatoms(Cu1-Br1-Cu2)64.93(7)°andCu1-Br2-Cu2
) 66.63(8)° for 10; Cu1-I1-Cu2 ) 59.07(4)° and
Cu1-I2-Cu2 ) 61.17(4)° for 11) are considerably smaller.
The torsion angles observed between bridging phenylene ring
with P-N-P plane are 80.0(17)° (P1-N-P2 vs C34-C35)
for 10 and 77.4(10)° (P1-N-P2 vs C15-C16) for 11.
DFT Calculations on P · · · P Interactions in 1 and 2.
DFT calculations were first performed for dimers of 1 and 2
at the PBE1PBE/TZVP level of theory. The geometries were
fully optimized within C2h symmetry, and the resulting
metrical parameters are in excellent agreement with their
experimental counterparts. Selected average bond lengths and
bond angles are 1: r(P-Cl) ) 2.081 Å, r(P-N) ) 1.726 Å,
r(N-C) ) 1.429 Å, ∠PNP ) 109.6°, 2: r(P-F) ) 1.612 Å,
r(P-N) ) 1.714 Å, r(N-C) ) 1.436 Å, ∠PNP ) 115.0°.
7042 Inorganic Chemistry, Vol. 47, No. 15, 2008

Intermolecular P · · ·P Interactions in Halo-Phosphines
The calculated intermolecular P · · · P contact is 3.591 Å and
3.774 Å in 1 and 2, respectively. The calculated interaction
energy (including counterpoise correction) is only -2 kJ
mol-1 for 1 and virtually nonexistent for 2.
derivative 1 suffices to create an ordered supramolecular
assembly of molecules in the crystal lattice. The calculated
DFT and MP2 results represent upper and lower limits for
the interaction energy, respectively. Thus, the binding energy
in Cl3P· · ·PCl3 is approximated to be around 5-10 kJ mol-1.
We note that analogous short (less than sum of van der Waals
radii) contacts between tricoordinate group 15 atoms have
Taking into account the known difficulties of the standard
density functionals in modeling weak interactions and van
der Waals forces in particular,29 the geometries and energies
obtained for 1 and 2 should be compared with data from
calculations employing correlated wave function methods
such as Mo¨ller-Plesset perturbation theory (MP) or coupled
cluster (CC). Unfortunately the systems under study are
somewhat large to be treated at either above levels of theory,
which makes accurate calculations time-consuming. Hence,
we carried out MP2 calculations only for model systems for
which we used the weakly bonded PX3 dimers (X ) F, Cl)
in C2h symmetry. The smaller size of the molecules facilitates
the usage of considerably larger basis sets, which in turn
helps to remove computational errors arising from basis set
incompleteness (basis set superposition error, BSSE). Be-
cause MP2 is more prone to BSSE than DFT, counterpoise
correction was applied throughout the MP2 geometry
optimizations. For comparison purposes, the model systems
were also calculated with DFT using the PBE1PBE func-
tional in combination with the aug-cc-pVTZ basis sets.
At the MP2/aug-cc-pVTZ level of theory, the predicted
P · · · P distance for Cl3P · · · PCl3 is 3.266 Å, that is, 0.334 Å
shorter than the sum of van der Waals radii. In contrast, the
C2h symmetric structure for the fluoro derivative has a
considerably longer P · · · P separation of 3.887 Å, which
indicates the absence of any bonding interaction. Concur-
ringly, the calculated MP2 interaction energies (with coun-
terpoise correction) are -15 kJ mol-1 and -1 kJ mol-1 for
Cl3P· · · PCl3 and F3P · · · PF3, respectively. DFT calculations
for the model systems yielded intermolecular P · · ·P contacts
of 3.580 and 3.736 Å and interaction energies of -2 and
-1 kJ mol-1 for the chloro and fluoro derivatives, respec-
tively. This data is in excellent agreement with the values
obtained for systems 1 and 2 (above). Interestingly, the C2h
symmetric structure of F3P · · · PF3 is not a minimum on the
potential energy hypersurface but a first-order transition state.
Subsequent optimization following the transition state vector
gives a true minimum (all frequencies real) which is C2
symmetric and has an even longer P · · ·P separation of 3.801
Å. An analogous C2 symmetric structure with a P · · · P
distance of 3.888 Å could also be located using the MP2/
aug-cc-pVTZ Hamiltonian. However, the energy of the C2
conformer is on par with the C2h structure at both DFT and
MP2 levels of theory. Hence, we conclude that the two
monomers in the van der Waals dimer F3P · · · PF3 are
practically noninteracting.
30
been observed previously for example in Cp*AsI2 and in
the 2:1 complex between SbCl3 and 1,3,5-triacetylbenzene.31
In addition, spectroscopic studies of liquid and solid PBr3
have indicated the formation of ethane-like dimers
Br3PdPBr3 on transition to crystalline state.32 Hence, a more
exhaustive study of the nature of bonding interactions in
X3E · · · EX3 systems (E ) pnictogen, X ) halogen) using
highly accurate wave functions seems warranted.33 A full
report on the conducted computational investigations will
be given in due course.34
Suzuki-Miyaura cross-coupling reactions. The pal-
ladium-catalyzed Suzuki-Miyaura cross-coupling reaction
is one of the efficient methods for forming symmetric and
nonsymmetric biaryl compounds in organic synthesis.35
Pd(II) 8 effectively catalyzes the Suzuki-Miyaura cross-
coupling reactions of a variety of aryl halides with phenyl-
boronic acid to afford the desired biaryls in remarkably high
yields (Table 6). These reactions were studied systematically
to find the optimal conditions to afford biaryls in good yield.
It is important to achieve good yields using minimum
amounts of catalyst, therefore we examined the effect of
catalyst loading on the coupling between 4-bromobenzonitrile
and phenylboronic acid. Complete conversion of the starting
materials into biphenyl-4-carbonitrile was achieved with 0.5
mol% of catalyst in 1 h or 0.2 mol% in 4 h, therefore a
concentration of 0.2 mol% was selected as the optimal
concentration for catalytic loading. The Suzuki-Miyaura
cross-coupling reaction is strongly influenced by the solvent
and base. Whereas the reactions proceed with various bases
(K3PO4, KF, Et3N, etc.) or solvents (THF, DCM, toluene),
the best results were obtained with either potassium carbonate
or cesium carbonate as the base and methanol as the solvent.
Therefore, the catalytic reactions have been carried out in
methanol (5 mL) with potassium carbonate as a base. For
(30) Avtomonov, E. V.; Megges, K.; Wocadlo, S.; Lorberth, J. J. Orga-
nomet. Chem. 1996, 524, 253–261.
(31) Baker, W. A.; Williams, D. E. Acta Crystallogr., Sect. B. 1978, 34,
3739–3741.
(32) Kozulin, A. T.; Gogolev, A. V.; Karmanov, V. I.; Murtsovkin, V. A.
USSR. Opt. Spektrosk. 1973, 34, 1218.
(33) We are aware of only three theoretical publications discussing weak
P· · ·P interactions in phosphine dimmers (a) Del Bene, J. E.; Frisch,
M. J.; Pople, J. A. J. Phys. Chem. 1985, 89, 3669–3674. (b) Altmann,
J. A.; Govender, M. G.; Ford, T. A. Mol. Phys. 2005, 103, 949–961.
(c) Wang, W.; Zheng, W.; Pu, X.; Wong, N.-B.; Tian, A. J. Mol.
Struct. 2003, 625, 25–30.
Taken as a whole, the computational results not only
confirm the presence of weak van der Waals interactions
between two N-PX2 moieties but also demonstrate that the
interaction strength is dependent on the identity of the atoms
attached to the nuclei. The interactions are practically absent
in fluoro 2, whereas their presence in the analogous chloro
(34) Tuononen, H. M.; Balakrishna, M. S., manuscript in preparation.
(35) (a) Miyaura, N.; Suzuki, A. Chem. ReV. 1995, 95, 2457–2483. (b)
Chemler, S. R.; Trauner, D.; Danishefsky, S. J. Angew. Chem., Int.
Ed. 2001, 40, 4544–4568. (c) Hassan, J.; Sevignon, M.; Gozzi, C.;
Schulz, E.; Lemaire, M. Chem. ReV. 2002, 102, 1359–1469. (d) Kotha,
S.; Lahiri, K.; Kashinath, D. Tetrahedron 2002, 58, 9633–9695. (e)
Littke, A. F.; Fu, G. C. Angew. Chem., Int. Ed. 2002, 41, 4176–4211.
(f) Zapf, A.; Beller, M. Chem. Commun. 2005, 431–440. (g) Phan,
N. T. S.; Sluys, M. V. D.; Jones, C. W. AdV. Synth. Catal. 2006, 348,
609–679. (h) Weng, Z.; Teo, S.; Hor, T. S. A. Acc. Chem. Res. 2007,
40, 676–684.
(29) See, for example: Koch, W. ; Holthausen, M. C. A Chemist’s Guide
to Density Functional Theory; VCH: Weinheim, 2001.
Inorganic Chemistry, Vol. 47, No. 15, 2008 7043

Ganesamoorthy et al.
Table 6. Suzuki-Miyaura Cross-Coupling Reactions of Aryl Halides
with Phenylboronic Acid Catalyzed by
at room temperature with 0.2 mol% of catalyst within 1-2
h (Table 6, entries 1 and 2). 8 proved to be an active catalyst
for both the easy-to-couple substrate 4-bromoacetophenone
and the more challenging, electronically deactivated substrate
4-bromoanisole. Higher conversion rates were realized when
activated aryl bromides were used as substrates (Table 6,
entries 3 and 4). Even though good conversions were
observed with deactivated and sterically bulky aryl bromides
(Table 6, entries 7 and 8) low catalytic conversions were
observed with heterocyclic bromides (Table 6, entries 9-11).
In addition, the cross-coupling reactions of a number of di-
and tribromobenzenes with phenylboronic acid were exam-
ined. As shown in Table 6, the dibromobenzenes including
those with sterically bulky aryl bromides gave high di/
monsubstituted product ratios (entries 12-16). Coupling
reactions performed with 1,3- and 1,4-dibromobenzene
yielded 98% of disubstituted terphenyls and 2% of mono-
substituted bromobiphenyls after 2-4 h with the complete
consumption of the dibromobenzenes. A gradual increase
in the yield of terphenyl was observed with time, and a
maximum of 99.6% conversion into 1,1′:3′,1”-terphenyl was
achieved after 12 h (Table 6, entry 13). In the case of
coupling reactions with 4,4′-dibromobiphenyl and 9,10-
dibromoanthracene, 60:17 and 95:0.2 ratios of di/monosub-
stituted derivatives were obtained with in a period of 24 h
with a small amount of unreacted starting materials. The rate
of conversion of 9,10-dibromoanthracene is faster than 4,4′-
dibromobiphenyl, and no improvement in the conversions
have been observed in both the cases after attaining a
particular period of time. Also, because of the solubility
problem the reactions were carried out in toluene (Table 6,
entries 15 and 16).
[Pd2Cl4-p-C6H4{N{P(OC6H4OMe-o)2}2}2] (8)a,b,c
The catalytic activity of 8 toward aryl chlorides was also
examined and found to be relatively unreactive toward the
less expensive aryl chlorides at room temperature with low
catalyst loading. For example, the coupling reaction of
chlorobenzene with phenylboronic acid afforded only 5%
of the conversion product with 0.2 mol% of catalyst at room
temperature. However, complete conversion of chloroben-
zene into biphenyl was observed at reflux temperature with
1 mol% catalyst loading (Table 6, entry 17). In the case of
activated and deactivated aryl chlorides, the catalytic system
becomes inactive over time (30-35% conversion) and the
deposition of palladium particles is seen.
Poisoning experiments were carried out with metallic
mercury to test for the presence of a palladium colloid.36
When a drop of Hg(0) was added to the coupling reaction
of 4-bromoacetophenone with phenylboronic acid at the start,
the catalytic activity was not suppressed. This shows the
homogeneous nature of the catalyst because heterogeneous
catalysts would form an amalgam, thereby poisoning it.
Conclusion
a Aryl halide (0.5 mmol), phenylboronic acid (0.75, 1.25, and 1.75 mmol
for mono-, di- and tribromo derivatives, respectively), K2CO3 (1 mmol), MeOH
(5 mL). b Conversion to a coupled product determined by GC, based on aryl
halides; average of two runs. c Defined as mol product per mol of catalyst.
The aminotetra(phosphines) 1-4 have been prepared in
moderate to good yield from p-phenylenediamine. 1 can
(36) (a) Widegren, J. A.; Bennett, M. A.; Finke, R. G. J. Am. Chem. Soc.
2003, 125, 10301–10310. (b) Widegren, J. A.; Finke, R. G. J. Mol.
Catal. A: Chem. 2003, 198, 317–341.
example, bromo- or iodobenzene and phenylboronic acid in
the presence of K2CO3 shows 97% conversion in methanol
7044 Inorganic Chemistry, Vol. 47, No. 15, 2008

Intermolecular P · · ·P Interactions in Halo-Phosphines
refluxed for 2 days, and filtered through a frit. The insoluble residue
was extracted with hot PCl3 (2 × 15 mL). The combined extracts
were concentrated to half and kept at -30 °C for 1 day to give
analytically pure product of 1 as white crystals. Yield: 75% (14.2
g). Mp: 118-120 °C (dec). Anal. Calcd for C6H4Cl8N2P4: C, 14.08;
serve as a molecular synthon for producing large number of
tetra- and multidentate phosphines with different steric and
electronic properties based on the choice of nucleophiles.
The chloro derivative 1 shows intermolecular P · · ·P interac-
tions whose strength is estimated to be around -5 to -10
kJ mol-1 using computational methods. In agreement with
the calculated data, similar interactions are virtually absent
in the fluoro derivative 2. Hence, the results of this study
indicate that when using appropriate substituents, P · · · P
interactions - in spite of their weakness - can be utilized
for example in building supramolecular assemblies or in
crystal engineering. The oxidation behavior of 3 and 4 toward
chalcogens differ due to the difference in steric and Lewis
basic nature of the phosphorus centers. The group 10 and
11 metal complexes are moderately stable toward air and
moisture. Pd(II) 8 is an efficient catalyst for the coupling of
several activated and deactivated aryl bromides and chlorides
with phenylboronic acid and also for the one-pot multiple
carbon-carbon couplings at room temperature. The tetra-
phosphanes can show up to 18 conformational isomers. It
would be interesting to analyze the relative stabilities of these
conformers and to explore their potential ability to form
complexes with various transition-metal derivatives. Further
organometallic chemistry and catalytic reactions with this
system is under active investigation in our laboratory.
1
H, 0.79; N, 5.48. Found: C, 14.14; H, 0.77; N, 5.44%. H NMR
(300 MHz, CDCl3): δ 7.38 (s, Ph, 4H). 31P{1H} NMR (121 MHz,
CDCl3): δ 153.6 (s).
Synthesis of p-C6H4[N(PF2)2]2 (2). A mixture of 1 (1.288 g,
2.517 mmol) and SbF3 (1.350 g, 7.551 mmol) was heated to reflux
in toluene (30 mL) for 24 h. It was then cooled to room temperature,
filtered, and the solvent was removed under reduced pressure to
give a sticky residue. The residue was extracted with CH2Cl2 (3 ×
7 mL) and the combined extracts were concentrated to 5 mL. The
solution was layered with 1 mL of n-hexane and stored at -30 °C
for 2 days to afford 2 as a white crystalline material. The crystals
suitable for X-ray diffraction analysis were grown by subliming a
small quantity of 2 in a thin capillary tube at 50-52 °C under
reduced pressure (0.05 mmHg). Yield: 69% (0.660 g). Anal. Calcd
for C6H4F8N2P4: C, 18.96; H, 1.06; N, 7.37. Found: C, 19.01; H,
1
1.14; N, 7.42%. H NMR (400 MHz, CDCl3): δ 7.38 (s, Ph, 4H).
1
31P{1H} NMR (162 MHz, CDCl3): δ 129.7 (m, JPF ) 1248 Hz,
2
3JPF ) 123 Hz and JPP ) 392 Hz).
Synthesis of p-C6H4[N{P(OC6H4OMe-o)2}2]2 (3). Method 1: A
mixture of o-methoxyphenol (6.92 g, 6.2 mL, 0.056 mol) and Et3N
(5.64 g, 7.8 mL, 0.056 mol) in 20 mL of toluene was added
dropwise over 15 min to a well-stirred toluene solution (100 mL)
of 1 (3.58 g, 0.007 mol) at 0 °C. The reaction mixture was stirred
for 12 h at room temperature and refluxed for 4 h. The hot solution
was filtered through a heated frit and then stored at room
temperature for a day to afford 3 as white crystals. Additional
product could be separated from the amine hydrochloride by
washing the filter cake successively with water, methanol, and
diethylether (10 mL each). Yield: 84% (7.13 g).
Experimental Section
General Procedures. All manipulations were performed under
rigorously anaerobic conditions using Schlenk techniques. All the
solvents were purified by conventional procedures and distilled prior
to use.37 The compounds [M(COD)Cl2] (M ) Pd and Pt)38a and
CuBr38b were prepared according to the published procedures.
Pyrazine, phenylboronic acid, 2-bromo-6-methoxynaphthalene,
9,10-dibromoanthracene, 1,3-dibromobenzene, 1,4-dibromobenzene,
4,4′-dibromobiphenyl, 1,3,5-tribromobenzene, and 2,5-dibro-
mothiophene were purchased from Aldrich chemicals and used as
such. Other chemicals were obtained from commercial sources and
purified prior to use.
Instrumentation. The 1H and 31P{1H} NMR (δ in ppm) spectra
were recorded using a Varian VXR 300 or VXR 400 spectrometer
operating at the appropriate frequencies using TMS and 85% H3PO4
as internal and external references, respectively. The microanalyses
were performed using a Carlo Erba Model 1112 elemental analyzer.
Electro-spray ionization (EI) mass spectrometry experiments were
carried out using Waters Q-Tof micro-YA-105. GC analyses were
performed on a PerkinElmer Clarus 500 GC fitted with packed
column. The melting points were observed in capillary tubes and
are uncorrected.
Method 2: Freshly distilled o-methoxyphenol (7.06 g, 6.3 mL,
0.057 mol) and sodium (1.31 g, 0.057 mol) were taken in 50 mL
of THF in a two-necked flask topped with a reflux condenser and
a dropping funnel. The reaction mixture was refluxed for 6 h and
then allowed to cool to room temperature. A solution of 1 (3.64 g,
0.007 mol) in THF (60 mL) was transferred to the dropping funnel
through a cannula and was added dropwise to the reaction mixture
at 0 °C. The reaction mixture was further stirred for 12 h at room
temperature and then filtered through a frit. The filtrate was
concentrated to 30 mL under reduced pressure and stored at -30
°C to afford analytically pure product of 3 as a white crystalline
material. Yield: 76% (6.55 g). Mp: 128-130 °C. Anal. Calcd for
C62H60N2O16P4: C, 61.39; H, 4.98; N, 2.31. Found: C, 61.31; H,
1
4.99; N, 2.30%. H NMR (400 MHz, CDCl3): δ 7.57-6.69 (m,
Ph, 36H), 3.60 (s, OCH3, 24H). 31P{1H} NMR (162 MHz, CDCl3):
δ 132.1 (s). MS (EI): 1214.47 (m/z + 1).
Synthesis of p-C6H4[N{P(OMe)2}2]2 (4). A mixture of methanol
(1.01 g, 1.3 mL, 0.031 mol) and Et3N (3.17 g, 4.4 mL, 0.031 mol)
in 20 mL of toluene was added dropwise over 15 min to a well-
stirred toluene solution (40 mL) of 1 (1.95 g, 3.82 mmol) at 0 °C.
The reaction mixture was stirred for 24 h at room temperature.
The amine hydrochloride was removed by filtration through a frit
and the filtrate was concentrated to 10 mL under reduced pressure
and stored at -30 °C to afford 4 as a white crystalline material.
Yield: 52% (0.946 g). Mp: 96-98 °C. Anal. Calcd for
C14H28N2O8P4: C, 35.30; H, 5.92; N, 5.88. Found: C, 35.31; H,
Synthesis of p-C6H4[N(PCl2)2]2 (1). Pyridine (5.85 g, 0.074 mol)
was added dropwise to a mixture of p-phenylenediamine (4.0 g,
0.037 mol) and PCl3 (75 mL) at -78 °C with constant stirring.
The resultant suspension was slowly warmed to room temperature,
(37) Armarego, W. L. F.; Perrin, D. D. Purification of Laboratory
Chemicals, 4th ed.; Butterworth-Heinemann: Linacre House, Jordan
Hill, Oxford, U.K., 1996.
(38) (a) Drew, D.; Doyle, J. R. Inorg. Synth. 1990, 28, 346. (b) Furniss,
B. S.; Hannaford, A. J.; Smith, P. W. G.; Tatchell, A. R. Vogel’s
Textbook of Practical Organic Chemistry, 5th ed.; ELBS: England
1989; pp 428-429.
1
5.99; N, 5.80%. H NMR (400 MHz, CDCl3): δ 7.03 (s, Ph, 4H),
3
3.51 (t, OCH3, JPH ) 12.6 Hz, 24H). 31P{1H}NMR (162 MHz,
(39) (a) SMART, Version 5.625; Bruker-AXS: Madison, WI, 2000. (b)
APEX2, Version 2.1-4; Bruker-AXS: Madison, WI, 2007.
CDCl3): δ 134.7 (s). MS (EI): 477.98 (m/z + 1).
Inorganic Chemistry, Vol. 47, No. 15, 2008 7045

Ganesamoorthy et al.
Synthesis of p-C6H4[N{P(O)(OC6H4OMe-o)2}2]2 (5). A 30%
aqueous solution of H2O2 (0.022 g, 0.07 mL, 0.654 mmol) in THF
(7 mL) was added dropwise to a well-stirred THF solution (10 mL)
of 3 (0.189 g, 0.156 mmol) at -78 °C. The reaction mixture was
slowly warmed to room temperature and stirred for 5 h. The solvent
was removed under reduced pressure to give a sticky residue. The
residue was dissolved in 5 mL of CH2Cl2, layered with 1 mL of
n-hexane and kept at -30 °C to afford 5 as an analytically pure
brown crystalline product. Yield: 70% (0.139 g). Mp: 194-196
°C. Anal. Calcd for C62H60N2O20P4: C, 58.31; H, 4.74; N, 2.19.
Found: C, 58.25; H, 4.79; N, 2.20%. 1H NMR (400 MHz, CDCl3):
δ 7.79-6.70 (m, Ph, 36H), 3.57 (s, OCH3, 24H). 31P{1H} NMR
(162 MHz, CDCl3): δ -12.5 (s). MS (EI): 1278.87 (m/z + 1).
Synthesis of p-C6H4[N{P(S)(OMe)2}2]2 (6). A mixture of 4
(0.105 g, 0.222 mmol) and elemental sulfur (0.030 g, 0.930 mmol)
in 15 mL of toluene was refluxed for 30 h. The solution was cooled
to room temperature and filtered to remove unreacted sulfur. The
solvent was removed under reduced pressure to give a white residue.
The residue was dissolved in 4 mL of CH2Cl2, layered with 1 mL
of n-hexane and stored at -30 °C for 2 days to afford analytically
pure white crystals of 6. Yield: 77% (0.103 g). Mp: 164-166 °C.
Anal. Calcd for C14H28N2O8P4S4: C, 27.81; H, 4.67; N, 4.63; S,
Ph, 36H), 3.57 (s, OCH3, 24H), 2.07 (s, CH3CN, 12H). 31P{1H}
NMR (121 MHz, CDCl3): δ 103.8 (br s).
Synthesis of [Cu4(µ2-I)4(NCCH3)4-p-C6H4{N(P(OC6H4OMe-
o)2)2}2] (11). This was synthesized by a procedure similar to that
of 10 using 3 (0.030 g, 0.025 mmol) and cuprous iodide (0.019 g,
0.099 mmol). Yield: 82% (0.044 g). Mp: 210-212 °C (dec). Anal.
Calcd for C70H72N6O16P4Cu4I4: C, 39.30; H, 3.39; N, 3.93. Found:
C, 39.19; H, 3.30; N, 3.96%. 1H NMR (400 MHz, CDCl3): δ
7.74-6.75 (m, Ph, 36H), 3.55 (s, OCH3, 24H), 2.07 (s, CH3CN,
12H). 31P{1H} NMR (121 MHz, CDCl3): δ 102.6 (br s).
General Procedure for the Suzuki-Miyaura Cross-Coupling
Reactions of Aryl Halides with Phenylboronic Acid. In a two-
necked round-bottom flask under an atmosphere of nitrogen were
placed the appropriate amounts of aryl halides (0.5 mmol),
phenylboronic acid (0.75 mmol), K2CO3 (1 mmol), and 5 mL of
methanol. After stirring for 2 min, 0.2 mol% of the catalyst [Pd2Cl4-
p-C6H4{N{P(OC6H4OMe-o)2}2}2] (8) was added. The mixture was
stirred at room temperature or refluxed under an atmosphere of
nitrogen, and the course of the reaction was monitored by GC
analysis. After completion of the reaction, the solvent was removed
under reduced pressure. The residual mixture was diluted with H2O
(10 mL) and extracted with Et2O or toluene (2 × 6 mL). The
combined organic fractions were dried (MgSO4), stripped of the
solvent under vacuum, and the residue was redissolved in 5 mL of
dichloromethane. An aliquot was taken with a syringe and subjected
to GC analysis. Conversions were calculated versus aryl halides as
an internal standard.
X-ray Crystallography. A crystal of each of 1-3, 6, 7, and
9-11 suitable for X-ray crystal analysis was mounted in a Cryoloop
with a drop of Paratone oil and placed in the cold nitrogen stream
of the Kryoflex attachment of the Bruker APEX CCD diffracto-
meter. Full spheres of data were collected using a combination of
three sets of 400 scans in ω (0.5° per scan) at ꢁ ) 0, 90, and 180°
plus two sets of 800 scans in ꢁ (0.45° per scan) at ω ) -30 and
210° under the control of the SMART software package39a (1, 3, 6,
7, 9) or the APEX2 program suite39b (2). The crystals of 2 and 7
used for the structure determinations proved to be twinned, the
former by a 180° rotation about the a axis and the latter by a 180°
rotation about the c axis (CELL_NOW40). The raw data were
reduced to F2 values using the SAINT+ software,41 and global
refinements of unit cell parameters using 3036-9392 reflections
chosen from the full data sets were performed. Multiple measure-
ments of equivalent reflections provided the basis for empirical
absorption corrections as well as corrections for any crystal
deterioration during the data collection (SADABS42a for 1, 3, 6, 9
and TWINABS42b for 2, 7). The structures were solved by direct
methods (for 1-3, 6, 7, and 9) or the positions of the heavy atoms
were obtained from a sharpened Patterson function (for 10 and 11).
All structures were refined by full-matrix least-squares procedures
using the SHELXTL program package.43 Hydrogen atoms were
placed in calculated positions and included as riding contributions
with isotropic displacement parameters tied to those of the attached
non-hydrogen atoms.
1
21.22. Found: C, 27.75; H, 4.63; N, 4.58; S, 21.20%. H NMR
3
(400 MHz, CDCl3): δ 7.34 (s, Ph, 4H), 3.51 (d, OCH3, JPH
)
14.4 Hz, 24H). 31P{1H} NMR (162 MHz, CDCl3): δ 68.8 (s). MS
(EI): 605.15 (m/z + 1).
Synthesis of p-C6H4[N{P(Se)(OMe)2}2]2 (7). This was synthe-
sized by a procedure similar to that of 6 using 4 (0.106 g, 0.224
mmol) and elemental selenium (0.074 g, 0.941 mmol). Yield: 82%
(0.146 g). Mp: 168-170 °C. Anal. Calcd for C14H28N2O8P4Se4: C,
1
21.23; H, 3.56; N, 3.54. Found: C, 21.20; H, 3.47; N, 3.60%. H
NMR (300 MHz, CDCl3): δ 7.38 (s, Ph, 4H), 3.72 (d, OCH3, 3JPH
) 14.7 Hz, 24H). 31P{1H} NMR (121 MHz, CDCl3): δ 73.4 (s,
1JPSe ) 945 Hz). MS (EI): 794.62 (m/z + 2).
Synthesis of [Pd2Cl4-p-C6H4{N{P(OC6H4OMe-o)2}2}2] (8). A
solution of [Pd(COD)Cl2] (0.040 g, 0.139 mmol) in 10 mL of
CH2Cl2 was added dropwise to a solution of 3 (0.084 g, 0.069
mmol) also in CH2Cl2 (7 mL). The reaction mixture was allowed
to stir at room temperature for 5 h to give clear-yellow solution.
The solution was concentrated to 5 mL, saturated with 3 mL of
n-hexane, and stored at -30 °C for 1 day to give an analytically
pure yellow crystalline product 8. Yield: 70% (0.076 g). Mp:
186-188 °C (dec). Anal. Calcd for C62H60N2O16P4Pd2Cl4: C, 47.50;
1
H, 3.86; N, 1.79. Found: C, 47.56; H, 3.79; N, 1.72%. H NMR
(400 MHz, CDCl3): δ 8.02-6.78 (m, Ph, 36H), 3.62 (s, OCH3,
24H). 31P{1H} NMR (162 MHz, CDCl3): δ 64.4 (s).
Synthesis of [Pt2Cl4-p-C6H4{N{P(OC6H4OMe-o)2}2}2] (9). This
was synthesized by a procedure similar to that of 8 using
[Pt(COD)Cl2] (0.025 g, 0.067 mmol) and 3 (0.042 g, 0.033 mmol).
Yield: 81% (0.047 g). Mp: 240-244 °C. Anal. Calcd for
C62H60N2O16P4Pt2Cl4: C, 42.67; H, 3.47; N, 1.60. Found: C, 42.59;
H, 3.44; N, 1.69%. 1H NMR (400 MHz, CDCl3): δ 8.03-6.83 (m,
Ph, 36H), 3.60 (s, OCH3, 24H). 31P{1H} NMR (162 MHz, CDCl3):
1
δ 35.0 (s, JPtP ) 5072 Hz).
Synthesis of [Cu4(µ2-Br)4(NCCH3)4-p-C6H4{N(P(OC6H4OMe-
o)2)2}2] (10). A solution of cuprous bromide (0.029 g, 0.205 mmol)
in acetonitrile (5 mL) was added dropwise to a solution of 3 (0.062
g, 0.051 mmol) also in acetonitrile (5 mL). After stirring for 4 h,
the solvent was concentrated under vacuum and kept at room
temperature overnight to give analytically pure white crystals of
10. Yield: 79% (0.079 g). Mp: > 240 °C (dec). Anal. Calcd for
C70H72N6O16P4Cu4Br4: C, 43.09; H, 3.72; N, 4.31. Found: C, 43.02;
H, 3.70; N, 4.40%. 1H NMR (400 MHz, CDCl3): δ 7.66-6.75 (m,
(40) Sheldrick, G. M. CELL_NOW, University of Go¨ttingen: Go¨ttingen,
Germany, 2005.
(41) SAINT+, Versions 6.35A and 7.34A; Bruker-AXS: Madison, WI, 2002,
2006.
(42) (a) Sheldrick, G. M. SADABS, Version 2.05 and Version 2007/2;
University of Go¨ttingen: Go¨ttingen, Germany, 2002, 2007. (b)
Sheldrick, G. M. TWINABS, Version 2007/5; University of Go¨ttingen:
Go¨ttingen, Germany, 2007.
(43) (a) SHELXTL, Version 6.10; Bruker-AXS: Madison, WI, 2000. (b)
Sheldrick, G. M. SHELXS97 and SHELXL97; University of Go¨ttingen:
Go¨ttingen, Germany, 1997.
7046 Inorganic Chemistry, Vol. 47, No. 15, 2008

Intermolecular P · · ·P Interactions in Halo-Phosphines
Computational Details. The molecular structures of dimers of
1 and 2 were fully optimized using DFT. The calculations were
performed in C2h symmetry employing the PBE1PBE functional44
in combination with the TZVP basis sets.45 Full geometry optimiza-
tions were also performed for the C2h symmetric model dimers
Cl3P· · ·PCl3 and F3P· · ·PF3 at PBE1PBE and MP246 levels of theory
using Dunning’s triple-ꢂ quality basis sets augmented with polariza-
tion and diffuse functions (aug-cc-pVTZ) for all atoms.47 Frequency
calculations for the model systems were done only at the DFT level
of theory. The correction of the basis set superposition error was
done via the counterpoise procedure,48 which was applied during
geometry optimizations (MP2) and calculating binding energies
(both DFT and MP2). All calculations were performed with the
Gaussian 03 program package.49
(SRF). We also thank SAIF, Mumbai, Department of
Chemistry Instrumentation Facilities, Bombay, for spectral
and analytical data and J.T.M. thanks the Louisiana Board
of Regents through grant LEQSF(2002-03)-ENH-TR-67 for
the purchase of the CCD diffractometer and the Chemistry
Department of Tulane University for support of the X-ray
laboratory. H.M.T. thanks the Academy of Finland and the
University of Jyva¨skyla¨ for their generous financial support.
Supporting Information Available: X-ray crystallographic files
in CIF format for the structure determinations of 1-3, 6, 7, and
9-11. This material is available free of charge via the Internet at
http://pubs.acs.org.
IC800724U
Acknowledgment. We are grateful to the Department of
Science and Technology (DST), New Delhi, for financial
support of this work through grant SR/S1/IC-02/007. C.G.
thanks CSIR, New Delhi, for a Senior Research Fellowship
(49) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin,
K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone,
V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa,
J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene,
M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev,
O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala,
P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas,
O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.;
Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.;
Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen,
W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. , Gaussian 03, reVision
(44) (a) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. ReV. Lett. 1996, 77,
3865–3868. (b) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. ReV.
Lett. 1997, 78, 1396. (c) Perdew, J. P.; Ernzerhof, M.; Burke, K.
J. Chem. Phys. 1996, 105, 9982–9985. (d) Ernzerhof, M.; Scuseria,
G. E. J. Chem. Phys. 1999, 110, 5029–5036.
(45) (a) Schaefer, A.; Horn, H.; Ahlrichs, R. J. Chem. Phys. 1992, 97, 2571–
2577. (b) Schaefer, A.; Huber, C.; Ahlrichs, R. J. Chem. Phys. 1994,
100, 5829–5835.
(46) Møller, C.; Plesset, M. S. Phys. ReV. 1934, 46, 618–622.
(47) Kendall, R. A., Jr.; Harrison, R. J. J. Chem. Phys. 1992, 96, 6796–
6806.
(48) Boys, S. F.; Bernardi, F. Mol. Phys. 1970, 19, 553–566.
D.02; Gaussian, Inc.: Pittsburgh, PA, 2003.
Inorganic Chemistry, Vol. 47, No. 15, 2008 7047