Facile synthesis of unsymmetrical 9-phospha- and 9-arsafluorenes

Article abstract of DOI:10.1021/ic051976l

Unsymmetrical 9-chloro-9-phosphafluorenes (dibenzophospholes) and 9-chloro-9-arsafluorenes (dibenzoarsoles) have been obtained by simple thermolysis of m-terphenyldichlorophosphines and -arsines in close to quantitative yields. The reaction temperatures a

Full text of DOI:10.1021/ic051976l

Inorg. Chem. 2006, 45, 5568−5575
Facile Synthesis of Unsymmetrical 9-Phospha- and 9-Arsafluorenes
Armando A. Diaz,† Jackie D. Young,† Masood A. Khan,† and Rudolf J. Wehmschulte*,‡
Department of Chemistry and Biochemistry, UniVersity of Oklahoma, 620 Parrington OVal, Room
208, Norman, Oklahoma 73019, and Department of Chemistry, Florida Institute of Technology,
150 West UniVersity BouleVard, Melbourne, Florida 32901
Received November 15, 2005
Unsymmetrical 9-chloro-9-phosphafluorenes (dibenzophospholes) and 9-chloro-9-arsafluorenes (dibenzoarsoles) have
been obtained by simple thermolysis of m-terphenyldichlorophosphines and -arsines in close to quantitative yields.
The reaction temperatures are about 200
complete within 5 min. Alternatively, these compounds can be synthesized through an AlCl3-catalyzed Friedel
Crafts type ring-closure reaction at low temperatures, but this method suffers from difficult workup procedures. The
P(As) Cl functionality is readily alkylated. Methylation of m-xylyl derivative 4 afforded 1-(3,5-dimethylphenyl)-6,8,9-
trimethyl-9-phosphafluorene, 11. The latter compound formed the complexes 11
°C for the phosphines and 140 °C for the arsine, and the reactions are
−
−
‚
Fe(CO)4, 12, and 11
‚
RuCl2(η6
{ },
1H
-
p-cymene), 13, indicating its good donor properties. The new compounds have been characterized by H, 13C
and 31P
1
{ } NMR spectroscopy; mass spectrometry; and single-crystal X-ray crystallography in the case of 11,
1H
12, and 13.
Introduction
recent years, the applicability of the 9-phosphafluorene unit
in connection with a chiral backbone for asymmetric catalysis
has been investigated by various groups.8,9 The 9-phos-
phafluorene unit has been incorporated into polymers for the
preparation of luminescence devices,10 and unsymmetrical
9-phosphafluorene oxides are of interest for P-chiral liquid
crystals.11 Recently, a rigid bidentate ligand based on the
9-phosphafluorene framework was found to support the
palladium-catalyzed Suzuki-Miyaura reaction.12 A potential
obstacle for the more widespread use of 9-phosphafluorenes
as ligands may be found in the scarcity of simple synthetic
procedures. Typically, 9-phosphafluorenes are obtained by
the reaction of 2,2′-dilithium biphenyls with RPCl2.1,13
Disadvantages of this method include the high reactivity of
9-Phosphafluorenes (dibenzophospholes) constitute an
interesting class of compounds,1 and their transition-metal
complexes have been known for more than 30 years.2-4
Whereas the donor/acceptor properties of 9-phosphafluorenes
are very similar to those of the corresponding diarylphos-
phines, 9-phosphafluorenes are generally smaller because of
the constrained geometry of the 9-phosphafluorene unit. This
led, for instance, to the formation of five-coordinate com-
plexes L3NiX2 of 9-methyl-9-phosphafluorene with various
nickel salts,3 whereas related phosphine MePPh2 formed only
four-coordinate compounds L2NiX2.5 The coordination prop-
erties of 9-phenyl-9-phosphafluorene and its derivatives have
been studied intensively by Nelson and co-workers.6,7 In
(6) Affandi, S.; Nelson, J. H.; Alcock, N. W.; Howarth, O. W.; Alyea, E.
C.; Sheldrick, G. M. Organometallics 1988, 7, 1724-1734.
(7) Wilson, W. L.; Alcock, N. W.; Alyea, E. C.; Song, S.; Nelson, J. H.
Bull. Soc. Chim. Fr. 1993, 130, 673-682.
(8) Toth, I.; Elsevier, C. J.; de Vries, J. G.; Bakos, J.; Smeets, W. J. J.;
Spek, A. L. J. Organomet. Chem. 1997, 540, 15-25.
(9) Schenk, W. A.; Stubbe, M.; Hagel, M. J. Organomet. Chem. 1998,
560, 257-263.
(10) Makioka, Y.; Tanaka, M.; Hayashi, T. International Patent, 2002, WO
0272661.
* To whom correspondence should be addressed. Fax: 1 321 674 8951.
E-mail: rwehmsch@fit.edu.
† University of Oklahoma.
‡ Florida Institute of Technology.
(1) Aitken, R. A. In Fused FiVe-Membered Hetarenes with One Hetero-
atom; Thomas, E. J., Ed.; Thieme: New York, 2001; Vol. 10, pp 817-
838.
(2) Allen, D. W.; Mann, F. G.; Millar, I. T. Chem. Ind. 1966, 2096-
2097.
(3) Allen, D. W.; Millar, I. T.; Mann, F. G. J. Chem. Soc. A 1969, 1101-
(11) Duran, E.; Gordo, E.; Granell, J.; Velasco, D.; Lopez-Calahorra, F.
Tetrahedron Lett. 2001, 42, 7791-7793.
1109.
(4) Powell, H. M.; Watkin, D. J.; Wilford, J. B. J. Chem. Soc. A 1971,
1803-1810.
(5) Hayter, R. G. Inorg. Chem. 1963, 2, 932-935.
(12) Thoumazet, C.; Ricard, L.; Gru¨tzmacher, H.; Le Floch, P. Chem.
Commun. 2005, 1592-1594.
(13) Wittig, G.; Geissler, G. Liebigs Ann. Chem. 1953, 580, 44-57.
5568 Inorganic Chemistry, Vol. 45, No. 14, 2006
10.1021/ic051976l CCC: $33.50
© 2006 American Chemical Society
Published on Web 06/09/2006

Facile Synthesis of Unsymmetrical Fluorenes
spray mass spectra with a Micromass Q-ToF spectrometer. Melting
points were determined in Pyrex capillary tubes (sealed under
nitrogen where appropriate) with a Mel-Temp apparatus and are
uncorrected.
the dilithium species and the limited availability of 2,2′-
dibromo- or diodobiphenyl precursors. An alternative one-
pot synthesis for 9-phenyl-9-phosphafluorene starting from
Ph4PBr could not be generalized.14 Prompted by the observa-
tion by Power and co-workers that the m-terphenyl-
dichlorophosphine 2,6-Trip2C6H3PCl2 is cleanly converted
into an unsymmetrical 9-phosphafluorene, 5,7,9-triiso-
propyl-1-(2,4,6-triisopropylphenyl)-9-phosphafluorene, upon
magnesium reduction,15 we have begun to investigate the
potential of the m-terphenyldichlorophosphines as readily
available precursors for the preparation of unsymmetrical,
bulky 9-phosphafluorenes. It has since been shown that the
above-mentioned reductive approach is limited to electron-
rich m-terphenyldichlorophosphines.16 Similarly, our attempts
to generate 9-phosphafluorenes via phosphinidenes from
thermal decomposition of m-terphenylbisazidophosphines led
to dimeric and trimeric m-terphenylazidophosphazenes in-
stead.17 Here, we report (i) the preparation of unsymmetrical,
bulky 9-phosphafluorenes by simple Friedel-Crafts chem-
istry and thermolysis, (ii) the extension of this method
to 9-arsafluorenes, and (iii) the synthesis of iron and
ruthenium complexes of one of the new bulky 9-phos-
phafluorenes.
2,6-(3,5-Me2C6H3)2C6H3PCl2, 1. A suspension of 2,6-(3,5-
Me2C6H3)2C6H3I (4.40 g, 10.0 mmol) in hexanes (50 mL) was
treated with n-BuLi solution (1.6 M in hexane, 6.9 mL, 11.0 mmol)
at 0 °C. The reaction mixture was warmed to room temperature
and stirred overnight. After filtration, the solvent was distilled off
under reduced pressure, and the remaining off-white solid was
suspended in hexanes (50 mL). The suspension was cooled to -78
°C, and freshly distilled PCl3 (0.9 mL, 10.0 mmol) was added via
syringe. The dry ice/ethanol bath was removed after 10 min, and
the reaction mixture was warmed to room temperature and stirred
overnight. The fine colorless precipitate was removed by filtration,
and the clear yellow filtrate was concentrated to ca. 20 mL to induce
crystallization. Large, well-shaped crystals of 1 were obtained after
2 days at room temperature. Yield: 74%, 2.86 g. Mp: 115-122
1
°C. H NMR (400 MHz, C6D6): δ 7.19 (s, o-H(xylyl), 4H), 7.16
(dd, J ) 6.4 Hz, JPH ) 2.8 Hz, m-H, 2H), 7.09 (t, J ) 6.4 Hz, p-H,
1H), 6.85 (s, p-H(xylyl), 2H), 2.20 (s, Me, 12H). 13C{1H} NMR
(100.57 MHz, C6D6): δ 149.55 (d, JPC ) 28.3 Hz), 140.77 (d, JPC
) 8.4 Hz), 137.64, 136.02 (d, JPC ) 77.0 Hz), 131.57, 130.76,
130.07, 128.57 (d, JPC ) 3.8 Hz), 21.32 (Me). 31P{1H} NMR
(161.90 MHz, C6D6): δ 157.9 (s).
2,6-(4-t-BuC6H4)2C6H3AsCl2, 2. A suspension of 2,6-(t-
BuC6H4)2C6H3Li (generated from 2,6-(t-BuC6H4)2C6H3Br (3.94 g,
9.35 mmol) and n-BuLi) in hexanes (60 mL) was treated with
freshly distilled AsCl3 (1.85 g, 0.85 mL, 10.2 mmol) at -78 °C.
The mixture was kept at -78 °C for 1 h, slowly warmed to room
temperature, and stirred overnight. The pale yellow supernatant
solution (ca. 30 mL) was decanted, concentrated to ca. 10 mL, and
left standing at room temperature for 1 day to give large colorless
plates (0.55 g). The remaining slurry of the reaction mixture
(ca. 20 mL) was extracted with warm hexanes (50 mL) and
filtered through a medium-porosity glass frit. Concentration of the
colorless filtrate to ca. 30 mL followed by standing at room
temperature for 1 day gave a second batch of large colorless crystals
(1.25 g). The combined mother liquors were concentrated to 30
mL to afford a third batch of crystals after 3 days at room
temperature (0.82 g). Yield: 57%, 2.62 g. Mp: 133-140 °C with
gas evolution. 1H NMR (C6D6, 400 MHz): δ 7.57 (d, J ) 8.2 Hz,
o- or m-H(4-t-BuC6H4), 4H), 7.35 (d, J ) 8.2 Hz, o- or m-H(4-t-
BuC6H4), 4H), 7.18 (d, J ) 7.6 Hz, m-H, 2H), 7.08 (t, J ) 7.6 Hz,
p-H, 1H), 1.22 (s, CH3, 18H). 13C{1H} NMR (C6D6, 100.57
MHz): δ 151.74, 148.80, 142.28, 137.64, 131.43, 130.81, 130.30
(o- or m-C(4-t-BuC6H4)), 125.55 (o- or m-C(4-t-BuC6H4)), 34.62
(C(CH3)3), 31.34 (C(CH3)3).
Experimental Section
General Procedures. All work was performed under anaerobic
and anhydrous conditions by using either modified Schlenk
techniques or an Innovative Technologies drybox. Solvents were
freshly distilled under N2 from sodium, potassium, sodium/
potassium alloy, or calcium hydride and degassed twice prior
to use. PCl3, AsCl3, n-butyllithium (1.6 M in hexanes), MeLi
(1.6 M in Et2O), and MeMgBr (1.0 M in THF) were obtained
from commercial suppliers. Compounds 2,6-(4-t-BuC6H4)2C6H3-
PCl2, 3;17 2,6-Mes2C6H3PCl2, 6 (Mes ) 2,4,6-Me3C6H2);18 2,6-(2-
MeC6H4)2C6H3PCl2, 9;17 2,6-(4-t-BuC6H4)2C6H3Br;19 and 2,6-(3,5-
Me2C6H3)2C6H3I20,21 were synthesized according to literature
methods. NMR spectra were recorded on a Varian Mercury 300
MHz, a Varian Unity Plus 400 MHz, a Bruker AMX 360, or a
Bruker Avance 400 MHz spectrometer, and 1H NMR chemical shift
values were determined relative to the residual protons in C6D6
or CDCl3 as internal reference (δ ) 7.15 or 7.26). 13C NMR spectra
were referenced to the solvent signal (δ ) 128.0 or 77.0) and
31P NMR spectra to external 85% H3PO4. Infrared spectra
were recorded in the range 4000-400 cm-1 using a Nicolet
Nexus 470 FTIR spectrometer. Electron impact mass spectra were
recorded with a Finnigan MAT Polaris spectrometer and electro-
1-(3,5-Dimethylphenyl)-6,8-dimethyl-9-chloro-9-phosphafluo-
rene, 4.22 Method A: A solution of AlCl3 (0.35 g, 2.6 mmol) in
dichloromethane (20 mL) was added to a solution of 1 (1.00 g, 2.6
mmol) in dichloromethane (20 mL) at -78 °C. The yellow color
of the dichloromethane solution of 1 changed to orange upon AlCl3
addition. The reaction mixture was slowly warmed to room
temperature (ca. 45 min), and pyridine (0.42 mL, 5.2 mmol) was
added to give a pale yellow solution. After removal of the solvent
(14) Affandi, S.; Green, R. L.; Hsieh, B. T.; Holt, M. S.; Nelson, J. H.;
Alyea, E. C. Synth. React. Inorg. Met.-Org. Chem. 1987, 17, 307-
318.
(15) Twamley, B.; Sofield, C. D.; Olmstead, M. M.; Power, P. P. J. Am.
Chem. Soc. 1999, 121, 3357-3367.
(16) Smith, R. C.; Shah, S.; Protasiewicz, J. D. J. Organomet. Chem. 2002,
646, 255-261.
(17) Wehmschulte, R. J.; Khan, M. A.; Hossain, S. I. Inorg. Chem. 2001,
40, 2756-2762.
(18) Urnezius, E.; Protasiewicz, J. D. Main Group Chem. 1996, 1, 369-
372.
(22) Numbering scheme:
(19) Wehmschulte, R. J.; Khan, M. A.; Twamley, B.; Schiemenz, B.
Organometallics 2001, 20, 844-849.
(20) Lu¨ning, U.; Wangnick, C.; Peters, K.; von Schnering, H. G. Chem.
Ber. 1991, 124, 397-402.
(21) Chen, C.-T.; Gantzel, P.; Siegel, J. S.; Baldridge, K. K.; English, R.
B.; Ho, D. M. Angew. Chem., Int. Ed. Engl. 1996, 34, 2657-2660.
Inorganic Chemistry, Vol. 45, No. 14, 2006 5569

Diaz et al.
under reduced pressure, the remaining sticky solid was extracted
with hexanes (30 mL). The extract was concentrated to about half
its original volume and cooled at -40 °C for 24 h to afford colorless
crystals of 4. Yield: 29%, 0.26 g.
was identified as a mixture of 7 and silicon grease by 1H and 31P-
{1H} spectroscopy. Recrystallization from hexanes (2 mL) at -30
°C for 1 week yielded colorless crystals of 7. Yield: 14%, 0.050
g. Mp: 107-108 °C. 1H NMR (400, MHz, C6D6): δ 7.12 (m, 3H),
6.83 (m, 7H), 6.58 (s, m-H(Mes), 2H), 2.19 (s, CH3, 3H), 2.18 (s,
CH3, 3H), 1.84 (s, CH3, 3H). 13C{1H} NMR (100.57 MHz, C6D6):
δ 148.61 (d, JPC ) 22.8 Hz), 138.30 (d, JPC ) 6.1 Hz), 136.94,
136.32 (d, JPC ) 36.6 Hz), 136.28 (d, JPC ) 2.3 Hz), 134.55 (d,
JPC ) 52.7 Hz), 132.03, 131.22, 130.92, 130.45 (d, JPC ) 2.3 Hz),
128.48, 128.42, 127.56 (d, JPC ) 7.6 Hz), 21.85 (CH3), 21.23 (CH3),
21.12 (CH3). 31P{1H} NMR (161.91 MHz, C6D6): δ 79.7 (s). MS
(ESI, MeCN solution): m/z 457.1854 (calcd 457.1852).
Method B: A Schlenk flask was charged with 1 (1.78 g, 4.6
mmol) and placed into a preheated oil bath at 200 °C. After ca. 1
min, the crystals began to melt, and a gentle gas evolution
commenced. The liquid turned yellow, and the reaction was
complete after 10 min. Before cooling down the liquid, we removed
the eliminated HCl gas under reduced pressure. The yellow liquid
solidified into a pale yellow glass upon being cooled to room
temperature. Yield: >97%, >1.56 g. Mp: 152-171 °C. 1H NMR
(400 MHz, C6D6): δ 7.43 (m, 3H), 7.22 (m, 3H), 6.86 (s, br, w1/2
) 5 Hz, H-5 or H-7, 1H), 6.61 (d, br, w1/2 ) 4 Hz, JPH ) 4.8 Hz,
H-5 or H-7, 1H), 2.40 (s, CH3-6 or CH3-8, 3H), 2.22 (s, m-CH3-
(xylyl), 6H), 2.09 (s, Me-6 or Me-8, 3H). 13C{1H} NMR (100.57
MHz, C6D6): δ 147.66, 147.45, 145.65, 144.49, 142.20, 141.53,
138.14, 132.13, 130.88, 129.89, 129.39, 127.22 (d, JPC ) 3.8 Hz),
120.60, 120.28, 21.49 (CH3-6), 21.39 (CH3(xylyl)), 20.78 (d, JPC
) 15.0 Hz, CH3-8). 31P{1H} NMR (121.47 MHz, C6D6): δ 67.1
(s).
1-(4-tert-Butylphenyl)-7-tert-butyl-9-chloro-9-arsafluorene, 8.
A Schlenk flask was charged with 2 (0.81 g, 1.7 mmol) and placed
into a preheated oil bath at 145 °C. After ca. 2 min, the crystals
began to melt, and a gentle gas evolution commenced. The liquid
turned pale yellow, and the reaction was complete after three more
minutes. Before cooling down the liquid, we removed the eliminated
HCl gas under reduced pressure. The yellow liquid solidified into
a pale yellow glass upon being cooled to room temperature. Yield:
1
>95%, >0.73 g. H NMR (C6D6, 300 MHz): δ 7.83 (d, J ) 8.4
Hz, o- or m-H(4-t-BuC6H4), 2H), 7.66 (d, J ) 2.1 Hz, 1H), 7.44
(d, J ) 8.4 Hz, o- or m-H(4-t-BuC6H4), 2H), 7.43 (d, peak overlap,
J ≈ 7.8 Hz, 2H), 7.29 (dd, J ) 7.8 Hz, 1.2 Hz, 1H), 7.24 (dd, J )
8.1 Hz, 2.1 Hz, 1H), 7.21 (t, J ) 7.5 Hz, 1H), 1.22 (s, CH3, 9H),
1.12 (s, CH3, 9H). 13C{1H} NMR (C6D6, 75.45 MHz): δ 152.33,
151.00, 147.32, 147.26, 146.62, 145.32, 143.59, 139.88, 132.26,
129.12, 129.09, 128.71, 126.01, 122.34, 120.98, 35.03 (C(CH3)3),
34.76 (C(CH3)3), 31.52 (C(CH3)3), 31.37 (C(CH3)3).
1-(4-tert-Butylphenyl)-7-tert-butyl-9-chloro-9-phosphafluo-
rene, 5. Method A: AlCl3 (0.75 mmol, 0.10 g) was added via a
solids-addition funnel to a solution of 3 (0.75 mmol, 0.33 g) in
CH2Cl2 (45 mL) at -78 °C. The reaction mixture was held at that
temperature for 30 min, slowly warmed to room temperature, and
stirred overnight. The resulting clear, yellow solution was concen-
trated (2-3 mL) and cooled to -28 °C for 1 week. As no crystals
formed, the volatile materials were removed under reduced pressure.
The resulting yellow solid was suspended in hexanes (15 mL) and
treated with pyridine (0.2 mL); the colorless, cloudy mixture was
stirred for 12 h. Filtration, concentration, and subsequent cooling
to -28 °C for 4 days afforded small colorless crystals. Yield: 43%,
0.13 g.
Method B: A Schlenk flask was charged with 3 (69 mg, 0.15
mmol) and placed into a preheated oil bath at 250 °C. After ca. 1
min, the crystals began to melt, and a gentle gas evolution
commenced after two more minutes. The liquid turned yellow, and
the reaction was complete after 10 min. Before cooling the liquid
down, we removed the eliminated HCl gas under reduced pressure.
The yellow liquid solidified into a pale yellow glass upon being
cooled to room temperature and was identified as pure 5. Yield:
>95%, >0.058 g. Mp: 125-130 °C. 1H NMR (400, MHz, C6D6):
δ 7.81 (s, 1H), 7.80 (d, J ) 8.0 Hz, o- or m-H(4-t-BuC6H4), 2H),
7.43 (m, 2H), 7.41 (d, J ) 8.0 Hz, o- or m-H(4-t-BuC6H4), 2H),
7.25 (m, 2H), 7.21 (t, J ) 7.6 Hz, 1H), 1.21 (s, CH3, 9H), 1.10 (s,
CH3, 9H). 13C{1H} NMR (100.57 MHz, C6D6): δ 152.33 (d, JPC
) 5.3 Hz), 151.02, 147.33 (d, JPC ) 20.6 Hz), 145.44, 142.53 (d,
JPC ) 21.3 Hz), 141.56, 140.47 (d, JPC ) 29.0 Hz), 138.76, 132.45,
129.42 (d, JPC ) 1.5 Hz), 129.08 (d, J ) 3.8 Hz), 128.74, 128.49,
125.90, 121.60, 120.31, 34.84 (C(CH3)3), 34.58 (C(CH3)3), 31.33
(C(CH3)3), 31.17 (C(CH3)3). 31P{1H} NMR (161.91 MHz, C6D6):
δ 70.5.
1-(2-Methylphenyl)-6-methyl-9-chloro-9-phosphafluorene, 10.
A Schlenk flask was charged with 9 (0.82 g, 2.3 mmol) and placed
into a preheated oil bath at 230 °C. After ca. 2 min, the crystals
began to melt, and a gentle gas evolution commenced. The liquid
turned pale yellow, and the reaction was complete after 15 more
minutes. Before cooling down the liquid, we removed the eliminated
HCl gas under reduced pressure. The yellow liquid solidified into
a pale yellow glass upon being cooled to room temperature (0.55
g) and consisted of 10 in about 84% purity according to 31P NMR
1
spectroscopy. H NMR (300 MHz, C6D6): δ 7.63 (t, J ) 7.8 Hz,
1H), 7.49 (m, 0.5H), 7.39 (m, 1.5H), 7.14 (m, 4H), 6.98 (m, 1H),
6.85 (m, 2H), 2.25 (s, 5-CH3, 3H), 2.20 and 2.08 (s, syn and anti
2-CH3C6H4, 3H, ratio ≈ 48:52). 13C{1H} NMR (75.45 MHz,
C6D6): δ quaternary carbons 147.45, 147.12, 146.89, 146.34,
146.20, 143.32, 143.05, 142.17, 142.02, 140.81, 140.47, 137.32,
136.66, 136.34, 135.02; aromatic C-H 134.77, 132.11, 131.52,
131.24, 130.56, 130.42, 130.03, 129.64, 129.41, 128.80, 128.78,
128.56, 128.20, 126.02, 125.86, 124.62; methyl 22.37, 20.82, 20.39.
31P{1H} NMR (121.47 MHz, C6D6): δ 66.3 and 66.0 (s), syn and
anti mixture, ratio ≈ 48:52.
1-(3,5-Dimethylphenyl)-6,8,9-trimethyl-9-phosphafluorene, 11.
MeMgBr (3 M in THF, 1.5 mL, 4.5 mmol) was added to a solution
of 4 (1.37 g, 3.9 mmol) in toluene (20 mL) at -78 °C, whereupon
the yellow color faded. After warming to room temperature and
stirring overnight, the reaction mixture was filtered; the filtrate was
concentrated to ca. 5 mL and cooled to -30 °C for several days.
As no crystals had formed, the solution was concentrated further
(ca. 2 mL), and hexane was added (8 mL); the resulting solution
was concentrated to ca. 2 mL to afford large, well-shaped, colorless
crystals of 11 after 3 days at room temperature. Yield: 80%, 1.03
2,6-Mes2C6H3P(Cl)Ph, 7. AlCl3 (0.10 g, 0.75 mmol) was added
via a solids-addition funnel to a solution of 6 (0.31 g, 0.75 mmol)
in benzene (45 mL) with cooling in an ice bath. The reaction
mixture was warmed to room temperature after 30 min and stirred
overnight. Concentration to 3-4 mL followed by cooling at 4 °C
for 2 days afforded a yellow oil. The oil was isolated and suspended
in hexanes; pyridine (0.2 mL) was added to the mixture to give a
cloudy colorless solution after stirring for 24 h at room temperature.
Filtration and subsequent removal of the solvent under reduced
pressure resulted in the isolation of a viscous oily material, which
1
g. Mp: 105-108 °C. H NMR (300, MHz, C6D6): δ 7.77 (dd, J
) 7.5 Hz, 1.5 Hz, 1H), 7.55 (s, 1 H), 7.45 (s, o-H(xylyl), 2H),
7.34 (t, J ) 7.5 Hz, 1H), 7.29 (ddd, J ) 7.5 Hz, 1.5 Hz, JPH ) 3.6
Hz, 1H), 6.85 (s, 1H), 6.77 (d, JPH ) 4.2 Hz, 1H), 2.31 (s, CH3,
5570 Inorganic Chemistry, Vol. 45, No. 14, 2006

Facile Synthesis of Unsymmetrical Fluorenes
3H), 2.24 (s, Me, 3H), 2.21 (s, m-CH3, 6H), 1.04 (d, JPH ) 2.4 Hz,
PCH3, 3H). 13C{1H} NMR (75.45 MHz, C6D6): δ 144.93 (d, JPC
(d, P-CH3, JPC ) 25 Hz). 31P{1H} NMR (121.47 MHz, C6D6): δ
24.6 (s). MS (ESI, CHCl3 solution): m/z 601.14 (calcd 601.14 for
M - Cl-).
) 14.3 Hz), 144.69, 144.63 (d, JPC ) 4.3 Hz), 144.02 (d, JPC
)
2.0 Hz), 142.49, 141.48 (d, JPC ) 4.6 Hz), 139.21 (d, JPC ) 18.0
Hz), 138.61, 138.14, 129.52 (d, JPC ) 4.3 Hz), 129.35, 129.12,
127.73 (d, JPC ) 3.7 Hz), 126.84 (d, JPC ) 4.5 Hz), 120.72, 120.28,
21.73 (CH3), 21.60 (CH3 (xylyl)), 21.36 (d, JPC ) 9.1 Hz, CH3),
X-ray Crystallography. Crystals of 11 were obtained by
crystallization from a concentrated hexanes/toluene solution of 11
at room temperature, crystals of 12 from benzene solution at 3-4
°C, and crystals of 13‚CHCl3 from chloroform solution at room
temperature. The crystals (11 and 12) were removed from the
Schlenk tube under a stream of N2 gas and immediately covered
with a layer of hydrocarbon oil. A suitable crystal was selected,
attached to a glass fiber, and immediately placed in the low-
temperature nitrogen stream.23 The data for 11 were collected at
173(2) K on a Siemens P4 diffractometer and those for 12 and
13‚CHCl3 at 120(2) and 153(2) K, respectively, on a Bruker Apex
diffractometer using Mo KR (λ ) 0.71073 Å) radiation. The data
were corrected for Lorentz and polarization effects. Absorption
corrections using a multiscan method from equivalent reflections
were applied for 12 and 13‚CHCl3. The structures were solved by
direct methods using the SHELXTL program suite, version 5.1,
for 11 and version 6.124 for 12 and 13‚CHCl3; the structures were
refined by full-matrix least-squares on F2, including all reflections.
All non-hydrogen atoms were refined anisotropically, and all
hydrogen atoms were included in the refinement with idealized
parameters. Phosphafluorene 11 crystallized in the space group P1h
with two independent molecules in the symmetric unit. As both
molecules are essentially identical, the discussion in the text focuses
on one of the two molecules. The data for the second molecule
can be obtained from the Supporting Information. Some details of
the crystal data and refinement are given in Table 1, and selected
bond distances and angles are listed in Tables 2-4. Further details
are given in the Supporting Information.
1
9.63 (d, JPC ) 22.9 Hz, PCH3). 31P{1H} NMR (121.47 MHz,
C6D6): δ -28.2 (s). MS (EI, 70 eV, 120 °C): m/z 330.2 (M+, 100),
315.2 (M+ - Me, 90).
11‚Fe(CO)4, 12. Fe2(CO)9 (1.04 g, 2.9 mmol) was added via a
solid-addition funnel to a solution of 11 (0.90 g, 2.7 mmol) in
benzene (15 mL) at room temperature. After stirring for 12 h, we
removed the volatile material under reduced pressure and redis-
solved the resulting solid in benzene (20 mL). Filtration followed
by concentration to 8 mL and cooling at 3-4 °C for 1 week afforded
a fine yellow crystalline solid (0.71 g). A second batch was obtained
upon concentration of the mother liquor (0.32 g). Yield: 76%, 1.03
g. Mp: 194-202 °C. FTIR (KBr, hexane solution): 2051, 1975,
1
1952, 1942 cm-1. H NMR (300 MHz, C6D6): δ 7.52 (d, 2- or
4-H, J ) 7.2 Hz, 1H), 7.31 (s, 5-H, 1H), 7.18 (m, 3-H, 2- or 4-H,
2H), 7.06 (s, o-H, 2H), 6.92 (s, p-H, 1H), 6.68 (d, JPH ) 3.9 Hz,
1H), 2.36 (s, 8-CH3, 3H), 2.26 (s, m-CH3, 6H), 2.11 (s, 6-CH3,
3H), 1.58 (d, JPH ) 9.3 Hz, P-CH3, 3H). 13C{1H} NMR (75.45
MHz, C6D6): δ 216.81 (d, JPC ) 14.6 Hz, CO), quarternary carbons
146.41 (d, JPC ) 11.8 Hz), 141.38 (d, JPC ) 23.3 Hz), 141.42 (d,
JPC ) 1.7 Hz), 141.38, 140.49 (d, JPC ) 2.9 Hz), 139.59 (d, JPC
)
74.4 Hz), 139.53 (d, JPC ) 11.8 Hz), 137.92 (m-C), 135.96 (d, JPC
) 51.5 Hz); CH carbons 131.89 (d, JPC ) 8.6 Hz), 131.04 (d, JPC
) 1.7 Hz), 130.70 (d, JPC ) 8.1 Hz), 130.00 (p-C), 127.44 (o-C),
120.50 (d, JPC ) 19.9 Hz), 120.42 (d, JPC ) 20.1 Hz), 21.35 (6-
CH3), 21.27 (m-CH3), 20.45 (d, JPC ) 4.3 Hz, 8-CH3), 17.41 (d,
JPC ) 25.6 Hz, P-CH3). 31P{1H} NMR (121.47 MHz, C6D6): δ
37.4 (s).
Results and Discussion
Ligand Synthesis. The new terphenyldichlorophosphine
2,6-(3,5-Me2C6H3)2C6H3PCl2, 1, and the terphenyldichloro-
arsine 2,6-(4-t-BuC6H4)2C6H3AsCl2, 2, have been synthesized
in good to moderate yields by the reaction of the corre-
sponding m-terphenylithium precursor with PCl3 or AsCl3
as colorless to pale yellow crystalline solids following
established procedures.15,17,18 Contrary to dichlorophosphines,
the dichloroarsine 2 is stable toward air and moisture. After
we17 and others15,25 found that phosphinidene-based schemes
for the synthesis of unsymmetrical 9-phosphafluorenes are
limited to very few examples, we began to investigate
Friedel-Crafts type chemistry as a means for P-C bond
formation. In fact, PhPCl2 has been prepared by the reaction
of PCl3 with benzene in the presence of AlCl3.26 Test
reactions on the NMR tube scale involving the reactions of
dichlorophosphines 1 or 2,6-(4-t-BuC6H4)2C6H3PCl2, 3,17 in
C6D6 solution with 1 equiv of AlCl3 at room temperature
resulted in the rapid separation of a yellow to yellow-orange
oil at the bottom of the NMR tube. Subsequent addition of
excess pyridine led to the complete dissolution of the oil,
and the 1H NMR and 31P NMR spectra showed the formation
11‚RuCl2(η6-p-cymene), 13. A mixture of 11 (0.16 g, 0.48
mmol) and [RuCl2(η6-p-cymene)]2 (0.15 g, 0.24 mmol) was
dissolved in dichloromethane (30 mL) and stirred for 12 h at room
temperature. Concentration of the clear orange solution to 4-5 mL
and subsequent cooling at -40 °C for 2 days afforded orange
1
crystals of 13. Yield: 68%, 0.208 g. Mp: 164-168 °C (dec). H
NMR (360 MHz, CDCl3): δ 7.99 (d, 2- or 4-H, J ) 7.7 Hz, 1H),
7.70 (s, 5-H, 1H), 7.56 (td, 3-H, J ) 7.6 Hz, JHP ) 1.2 Hz, 1H),
7.29 (dd, 2- or 4-H, J ) 7.5 Hz, JHP ) 4.2 Hz, 1H), 7.07 (d, 7-H,
JPH ) 3.8 Hz, 1H), 6.96 (s, p-H, 1H), 6.85 (s, o-H, 2H), 4.74 (d,
CH(cymene), J ) 5.9 Hz, 1H), 4.68 (d, CH(cymene), J ) 5.9 Hz,
1H), 4.61 (d, CH(cymene), J ) 5.9 Hz, 1H), 4.50 (d, CH(cymene),
J ) 5.9 Hz, 1H), 2.69 (s, 6- or 8-CH3, 3H), 2.49 (s, 6- or 8-CH3,
3H), 2.32 (s, m-CH3, 6H), 2.08 (sept, CHMe2(cymene), J ) 6.9
Hz, 1H), 1.95 (d, JPH ) 12.6 Hz, P-CH3, 3H), 1.66 (s, CH3-
(cymene), 3H), 0.95 (d, CHMe2(cymene), J ) 6.9 Hz, 3H), 0.92
(d, CHMe2(cymene), J ) 6.9 Hz, 3H). 13C{1H} NMR (90.57 MHz,
CDCl3): δ 147.49 (d, JPC ) 10 Hz), 141.94 (d, JPC ) 12 Hz),
141.71 (d, JPC ) 12 Hz), 141.10 (d, JPC ) 2 Hz), 140.94 (d, JPC
)
11 Hz), 140.81 (d, JPC ) 1 Hz), 138.69 (d, JPC ) 45 Hz), 136.95,
135.45 (d, JPC ) 47 Hz), 131.85 (d, JPC ) 10 Hz), 131.58 (d, JPC
) 8 Hz), 130.44, 129.61, 128.00, 119.61 (d, JPC ) 6 Hz), 119.20
(d, JPC ) 6 Hz), 106.06 (C-Me(cymene)), 98.34 (CCHMe2-
(cymene)), 88.74 (d, CH(cymene), JPC ) 6 Hz), 86.89 (d,
CH(cymene), JPC ) 4 Hz), 85.99 (d, CH(cymene), JPC ) 5 Hz),
85.30 (d, CH(cymene), JPC ) 5 Hz), 29.87 (CHMe2(cymene)), 22.31
(CH3), 22.12 (CH3), 21.87 (CH3), 21.50 (CH3), 21.37 (m-CH3), 9.00
(23) Hope, H. In Experimental Organometallic Chemistry; Wayda, A. L.,
Darensbourg, M. Y., Eds.; ACS Symposium Series 357; American
Chemical Society: Washington, DC, 1987; Chapter 10.
(24) SHELXTL, version 6.12; Bruker ASX: Madison, WI, 1997.
(25) Shah, S.; Simpson, M. C.; Smith, R. C.; Protasiewicz, J. D. J. Am.
Chem. Soc. 2001, 123, 6925-6926.
(26) Michaelis, A. Ber. 1879, 12, 1009.
Inorganic Chemistry, Vol. 45, No. 14, 2006 5571

Diaz et al.
Table 1. Crystal Data and Structural Refinement Details for 11, 12, and 13‚CHCl3
11
12
13‚CHCl3
empirical formula
fw
C23H23P
330.38
C27H23FeO4P
498.27
C34H38Cl5PRu
755.93
T (K)
173(2)
120(2)
120(2)
wavelength (Å)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.71073
triclinic
P1h
0.71073
triclinic
P1h
0.71073
triclinic
P1h
11.069(4)
11.6728(15)
15.0716(17)
81.312(8)
69.950(18)
81.96(2)
1800.2(7)
4
1.219
0.153
704
0.52 × 0.48 × 0.46
colorless prism
50.00
6319
444
7.7148(3)
10.8237(5)
14.6848(6)
80.1070(10)
81.8550(10)
77.3020(10)
1171.53(9)
2
1.413
0.743
516
0.38 × 0.26 × 0.22
yellow prism
53.00
4759
303
11.0207(16)
12.3536(18)
12.8898(18)
79.197(2)
76.300(2)
76.714(2)
1642.8(4)
2
1.528
0.956
772
0.58 × 0.44 × 0.34
red prism
53.00
6745
378
Z
D
calcd (Mg/m3)
µ(Mo KR) (mm-1
F(000)
)
crystal size (mm3)
cryst color and habit
2θmax (deg)
no. of observations
no. of variables
R1a [I > 2σ(I)]
0.0387
0.1042
1.018
0.313
0.0777
0.0781
1.029
0.468
0.0250
0.0667
1.065
0.697
wR2b [I > 2σ(I)]
GOF on F2
largest diff. peak (e Å-3
)
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) (∑w||Fo| - |Fc|| /∑w|Fo| )1/2
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 11
.
range of 436-642 Hz have been observed for tertiary
phosphonium salts.27
P(1)-C(14)
P(1)-C(22)
P(1)-C(23)
C(13)-C(14)
C(13)-C(15)
C(15)-C(22)
1.8335(18)
1.8170(18)
1.8464(19)
1.411(2)
1.470(2)
1.403(3)
C(14)-P(1)-C(22)
C(14)-P(1)-C(23)
C(22)-P(1)-C(23)
C(13)-C(14)-P(1)
C(14)-C(13)-C(15)
C(13)-C(15)-C(22)
C(15)-C(22)-P(1)
89.99(8)
101.46(8)
102.62(8)
111.01(13)
113.49(15)
113.02(15)
112.18(13)
Table 3. Selected Bond Lengths (Å) and Angles (deg) for 12
Fe(1)-C(24)
Fe(1)-C(25)
Fe(1)-C(26)
Fe(1)-C(27)
P(1)-C(14)
P(1)-C(22)
P(1)-C(23)
1.7933(18)
1.7923(18)
1.7748(15)
1.7961(17)
1.8275(14)
1.8216(14)
1.8307(14)
C(24)-Fe(1)-C(26)
C(24)-Fe(1)-P(1)
C(26)-Fe(1)-P(1)
C(25)-Fe(1)-C(27)
C(14)-P(1)-C(22)
C(14)-P(1)-C(23)
C(22)-P(1)-C(23)
C(14)-P(1)-Fe(1)
C(22)-P(1)-Fe(1)
C(23)-P(1)-Fe(1)
122.22(7)
117.70(6)
120.07(5)
175.21(7)
91.28(6)
104.95(6)
102.19(6)
118.80(4)
117.25(5)
118.11(5)
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 13‚CHCl3
Ru(1)-P(1)
Ru(1)-Cl(1)
Ru(1)-Cl(2)
Ru(1)-Ccymene
P(1)-C(14)
P(1)-C(22)
P(1)-C(23)
2.3593(5)
2.4022(5)
2.4066(5)
2.213(29)avg.
1.8335(18)
1.8279(19)
1.8151(19)
P(1)-Ru(1)-Cl(1)
P(1)-Ru(1)-Cl(2)
Cl(1)-Ru(1)-Cl(2)
C(14)-P(1)-C(22)
C(14)-P(1)-C(23)
C(22)-P(1)-C(23)
C(14)-P(1)-Ru(1)
C(22)-P(1)-Ru(1)
C(23)-P(1)-Ru(1)
87.313(18)
88.391(19)
84.44(2)
91.61(9)
111.10(9)
105.82(9)
110.44(6)
117.09(6)
117.76(6)
Whereas the NMR scale experiments indicated selective
and essentially quantitative formation of the 9-phosphafluo-
renes, scaling to the 1-5 mmol scale was less successful.
This is mainly due to the practical difficulties in separating
the 9-phosphafluorenes from the side products, HCl‚py and
AlCl3‚py. Nevertheless, this method allowed for a relatively
convenient synthesis of unsymmetrical 9-phosphafluorenes
of corresponding 9-phosphafluorenes 4 and 5 as the only
phosphorus-containing species (eq 1). Evidence for the
formulation of the benzene insoluble oil (clathrate) being a
phosphonium salt is found in the presence of a doublet with
a P-H coupling constant of 618 Hz in the 31P NMR spectrum
(δ ) 30.1) of the oil derived from 1 and AlCl3 after isolation
(27) CRC Handbook of Phosphorus-31 Nuclear Magnetic Resonance Data;
1
and redissolution in CDCl3. JPH coupling constants in the
Tebby, J. C., Ed.; CRC Press: Boca Raton, FL, 1991.
5572 Inorganic Chemistry, Vol. 45, No. 14, 2006

Facile Synthesis of Unsymmetrical Fluorenes
from readily available m-terphenyldichlorophosphines. We
also reacted 2,6-Mes2C6H3PCl2, 6, (Mes ) 2,4,6-Me3C6H2)18
with AlCl3 in benzene solution. As 6 does not possess
hydrogen atoms in the o- or o′′-position, putative phosphe-
nium intermediate [2,6-Mes2C6H3PCl]+[AlCl4]- reacted with
the solvent, and phenyl-substituted phosphine 2,6-Mes2C6H3P-
(Cl)Ph, 7, was isolated after the addition of excess pyridine.
This reaction was also performed as an NMR scale experi-
ment using C6D6 as solvent; in this case, phosphonium salt
[2,6-Mes2C6H3P(D)(Cl)(C6D5)]+[AlCl4]- was sufficiently
soluble to allow the detection of its signal, a 1:1:1 triplet
1
with JPD ) 86 Hz at 27.2 ppm, in the 31P NMR spectrum.
Similar to the 9-phosphafluorene synthesis discussed before,
the isolated yields of 7 were low because of the difficulty in
removing the side products.
Figure 1. Thermal ellipsoid plot (40% probability level ellipsoids) showing
the molecular structure of one of the two independent molecules of 11.
Hydrogen atoms are omitted for clarity.
It has been reported that a 9-arsafluorene can be obtained
by simple refluxing of a mixture of AsCl3 and 3,3′-
dimethoxybiphenyl.28 Apparently, AsCl3 is reactive enough
to attack activated aromatic systems with As-C bond
formation. Reasoning that 2 corresponds to the AsCl2-
substituted biphenyl intermediate in the above reaction, we
investigated the thermolysis of 2. Heating of 2 to above its
melting point at ca. 140 °C caused gas evolution and a color
change to yellow. The resulting yellow solid was identified
as the 9-arsafluorene 8 (eq 2). Interestingly, the same reaction
also takes place in solution at 70 °C over a period of 3-4 h.
The analogous 9-phosphafluorene formation has not been
reported to date. However, knowing that PhPCl2 can be
prepared by the reaction of PCl3 with benzene in the gas
phase at the relatively high temperature of 600 °C,29 we then
investigated the thermolysis of the dichlorophosphines 1, 3,
and 2,6-(2-MeC6H4)2C6H3PCl2, 9. Indeed, 9-phosphafluorene
formation took place, albeit at somewhat higher temperatures
(200-230 °C) than those for the arsenic compound 2.
The P-Cl bond in the 9-phosphafluorenes is reactive and
thus easily substituted. As an initial example, we report here
the synthesis of the methyl derivative 1-(3,5-dimethylphenyl)-
6,8,9-trimethyl-9-phosphafluorene, 11, and its application as
a ligand in iron and ruthenium complexes. Reaction of 4
with MeLi or MeMgBr in toluene or hexane solution afforded
the 9-methyl-9-phosphafluorene 11 in good yield. Compound
11 was also characterized by X-ray diffraction, and the
structure is shown in Figure 1. Compound 11 features an
almost-planar (deviation from the mean plane: 0.0246 Å)
9-phosphafluorene unit with a strongly pyramidal phospho-
rus, as illustrated by the sum of the angles at P(1) with a
value of 294.1(2)° and an angle between the P(1)-C(23)
vector and the phosphafluorene plane of 69.9°. The P-CAr
bond distances of 1.8170(18) and 1.8335(18) Å are shorter
than the P-CMe distance of 1.8468(19) Å, which may be
explained by the difference in carbon radii depending on the
hybridization (here, sp2 vs sp3). Similar metric parameters
have been found for the other two m-terphenyl-derived
9-phosphafluorenes whose structures have been reported to
date: 1-(2,4,6-triisopropylphenyl)-5,7,9-triisopropyl-9-phos-
phafluorene15 and 9,9′-bis-[1-(2,6-dichlorophenyl)-5-chloro-
9-phosphafluorene].31 The flanking C(1)-C(8) aryl group
in 11 is rotated out of the 9-phosphafluorene plane by 38.2°
but is freely rotating in solution, as shown by the equivalence
of the C(1) and C(5) methyl groups and the o-hydrogens
1
(H(6A) and H(8A) in the H NMR spectra).
Complex Formation. 9-Methyl-9-phosphafluorene 11
readily reacts with Fe2(CO)9 and [(η6-cymene)RuCl2]2 at
room temperature to afford the complexes 11‚Fe(CO)4, 12,
and 11‚Ru(η6-cymene)Cl2, 13 (eq 3).
Yellow crystals of 12 were obtained by crystallization from
benzene (Figure 2). The phosphine ligand occupies an
equatorial position in the slightly distorted (CO)4FeL trigonal
bipyramid. This is rather unusual for a phosphine, because
this position tends to favor π-acids such as olefins,32
phosphaalkenes,33 and diphosphenes.34 A search of the
As was the case for the related 9-borafluorenes,30 the C-H
activation in dichlorophosphine 9 possessing flanking o-tolyl
groups requires a higher temperature (230 °C) and longer
reaction time (20 min) than those for 1 and 3, presumably
because of steric repulsion brought about by the neighboring
hydrogen in the 4-position and methyl in the 5-position in
10.
(31) Smith, R. C.; Ren, T.; Protasiewicz, J. D. Eur. J. Inorg. Chem. 2002,
2779-2783.
(28) Gottlieb-Billroth, H. J. Am. Chem. Soc. 1927, 49, 482-486.
(29) Quin, L. D. A Guide to Organophosphorus Chemistry; John Wiley &
Sons: New York, 2000.
(30) Wehmschulte, R. J.; Diaz, A. A.; Khan, M. A. Organometallics 2003,
22, 83-92.
(32) Darensbourg, D. J.; Nelson, H. H., III; Hyde, C. L. Inorg. Chem. 1974,
13, 2135-2145.
(33) Neilson, R. H.; Thoma, R. J.; Vickovic, I.; Watson, W. H. Organo-
metallics 1984, 3, 1132-1133.
Inorganic Chemistry, Vol. 45, No. 14, 2006 5573

Diaz et al.
Cambridge Structural Database resulted in only six examples
of (phosphine)Fe(CO)4 complexes in which the phosphine
ligand occupies the equatorial position, and in most of these
cases, the large size of the ligand may have favored this less-
crowded coordination site.35-38 The plane of the phos-
phafluorene unit is rotated by 57.8° out of the Fe equatorial
plane in order to minimize ligand‚‚‚CO contacts. In fact,
the shortest ligand‚‚‚CO distances are C(25)‚‚‚H(23B) and
O(2)‚‚‚H(3B), with values of 2.845 and 2.970 Å, respectively.
The Fe(1)-P(1) distance of 2.2336(4) Å is typical for this
type of complex, as are the Fe-C distances, with an average
value of 1.789 Å.35,37,39 The C(25)-Fe(1)-C(27) angle is
close to linear, with a value of 175.21(7)°, and the angles in
the equatorial plane deviate only slightly from the ideal 120°.
The observation of only one doublet at 216.65 ppm with
2JPC ) 14.9 Hz for the carbonyl carbons in the 13C{1H} NMR
spectrum of 12 at room temperature indicates structural
fluxionality in solution, a common property of this type of
complex.40 The CO stretching frequency (A1) with a value
of 2050.6 cm-1 is close to those reported for Ph3PFe(CO)4
(2050.5 cm-1), Me2PhPFe(CO)4 (2050.5 cm-1), or Bu3PFe-
(CO)4 (2046.7 cm-1),32 suggesting donor properties similar
to those of phosphafluorene 11.
Figure 2. Thermal ellipsoid plot (40% probability level ellipsoids) showing
the molecular structure of 12. Hydrogen atoms are omitted for clarity.
Figure 3. Thermal ellipsoid plot (30% probability level ellipsoids) showing
the molecular structure of 13. Hydrogen atoms are omitted for clarity.
(2.317-2.347 Å),41-43 whereas the average Ru-Cl and
Ru-C distances, with values of 2.404 and 2.213 Å, are
within the normal range (Table 4). Contrary to the structure
of 12, the phosphafluorene framework is not planar. The two
annulated aromatic rings are rotated by 3.3° around their
connecting C(13)-C(15) bond, and P(1) is displaced from
the C(14)-C(13)-C(15)-C(22) plane by 0.228 Å. In
addition, the p-cymene ring and the other ligands are in a
mutually eclipsed rather than the more commonly found
staggered conformation. These features may be due to the
steric influences of the relatively large phosphafluorene
ligand.
Ruthenium complex 13 was crystallized from chloroform.
Unlike 12, complex 13 is air stable. It is only slightly soluble
in hydrocarbons but readily dissolves in dichloromethane or
chloroform. Its solid-state structure (Figure 3) features the
piano stool arrangement typical for (η6-arene)RuCl2(phosphine)
complexes.41,42 The P(1)-Ru(1) distance with a value of
2.3593(5) Å is slightly longer than those reported previously
(34) Flynn, K. M.; Olmstead, M. M.; Power, P. P. J. Am. Chem. Soc. 1983,
105, 2085-2086.
(35) Sheldrick, W. S.; Morton, S.; Stelzer, O. Z. Anorg. Allg. Chem. 1981,
475, 232-240.
(36) DuBois, D. A.; Duesler, E. N.; Paine, R. T. Organometallics 1984, 3,
1913-1915.
Summary
(37) Howell, J. A. S.; Palin, M. G.; McArdle, P.; Cunningham, D.;
Goldschmidt, Z.; Gottlieb, H. E.; Hezroni-Langerman, D. Inorg. Chem.
1993, 32, 3493-3500.
Simple thermolysis of readily accessible m-terphenyldi-
chlorophosphines and -arsines afforded unsymmetrical 9-chlo-
ro-9-phosphafluorenes and -9-arsafluorenes in close to
quantitative yields. After methylation, resulting unsym-
(38) Howell, J. A. S.; Lovatt, J. D.; McArdle, P.; Cunningham, D.;
Maimone, E.; Gottlieb, H. E.; Goldschmidt, Z. Inorg. Chem. Commun.
1998, 1, 118-120.
(39) Bitterer, F.; Brauer, D. J.; Do¨rrenbach, F.; Gol, F.; Knu¨ppel, P. C.;
Stelzer, O.; Kru¨ger, C.; Tsay, Y. H. Z. Naturforsch., B 1991, 46, 1131-
1144.
(42) Redwine, K. D.; Hansen, H. D.; Bowley, S.; Isbell, J.; Vodak, D.;
Nelson, J. H. Synth. React. Inorg. Met.-Org. Chem. 2000, 30, 409-
431.
(40) Barnard, T. S.; Mason, M. R. Inorg. Chem. 2001, 40, 5001-5009.
(41) Bennett, M. A.; Robertson, G. B.; Smith, A. K. J. Organomet. Chem.
1972, 43, C41-C43.
(43) Hansen, H. D.; Nelson, J. H. Organometallics 2000, 19, 4740-4755.
5574 Inorganic Chemistry, Vol. 45, No. 14, 2006

Facile Synthesis of Unsymmetrical Fluorenes
metrical 9-methyl-9-phosphafluorene 11 was shown to be a
good ligand for iron and ruthenium complexes. Investigations
of the mechanism and scope of the P(As)-C bond formation
are in progress.
edged. A.A.D. and J.Y. are also grateful for summer support
from NSF-REU fellowships.
Supporting Information Available: X-ray crystallographic data
in CIF format. The material is available free of charge via the
Internet at http://pubs.acs.org.
Acknowledgment. Financial support for this work from
the donors of the Petroleum Research Fund, administered
by the American Chemical Society, is gratefully acknowl-
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Inorganic Chemistry, Vol. 45, No. 14, 2006 5575