COMMUNICATION
Scheme 1. Reactions of Sterically Demanding Phosphines
similar fashion, the species (Cy2PH)B(C6F5)3 (2),7
(Bu3P)B(C6F5)3 (3), (Ph3P)B(C6F5)3 (4),8,9 (CyPH2)B(C6F5)3
(5), (Et2PH)B(C6F5)3 (6) and (Me3P)B(C6F5)3 (7)10–12 were
also prepared. All of these compounds are easily character-
ized by 1H, 11B{1H}, 13C{1H}, 19F, and 31P NMR
spectroscopy.13These data are typical for such adducts, with
each displaying a gap of the 19F NMR resonances attributable
to the m- and p-fluorine atoms and a 11B{1H} chemical shift
that are characteristic of a four-coordinate boron center.14–19
In addition, the species 1 was also characterized by X-ray
crystallography (Figure 1).20 As expected, the geometries at
B and P are both pseudotetrahedral with a P-B distance of
2.024(3) Å. This compares to 2.0270(14), 2.180(6), 2.046(8),
2.039(3), and 2.061(4) Å previously reported for the adducts
Figure 1. POV-ray drawing of 1. All H atoms except P-H are omitted
for clarity. Color code: F, pink; C, carbon; B, yellow-green; P, orange; H.
gray.
22
2,7 4,8 (H3P)B(C6F5)3,21 (PhPH2)B(C6F5)3 and 7, respec-
tively. The remaining metric parameters were unexceptional.
Heating of 1 in a Teflon-capped, sealed reaction bomb to
130 °C for 24 h in a toluene solution resulted in the formation
of a white precipitate. The addition of pentane and filtration
allowed isolation of the white solid 8 in 73% yield.13 The
11B{1H} NMR signal was observed to shift from 13.50 ppm
in the adduct to –0.21 ppm in 8, while the 31P NMR
resonance shifted downfield slightly to 11.50 ppm. Notably
this latter signal exhibits a 1JPH coupling constant of 480 Hz
typical of phosphonium salts. A new 19F NMR signal was
observed at –191.47 ppm2,6 typical of a B-F unit, while
(9) Massey, A. G.; Park, A. J. J. Organomet. Chem. 1964, 2(3), 245–50.
(10) Chase, P. A.; Parvez, M.; Piers, W. E. Acta Crystallogr., Sect. E 2006,
E62(11), o5181–o5183.
(11) Doerrer, L. H.; Graham, A. J.; Green, M. L. H. Dalton Trans. 1998,
(23), 3941–3946.
(12) Hair, G. S.; Jones, R. A.; Cowley, A. H.; Lynch, V. Organometallics
2001, 20(1), 177–181.
Figure 2. POV-ray drawing of 8. All H atoms except P-H are omitted
for clarity. COlor code: F, pink; C, carbon; B, yellow-green; P, orange; H,
gray.
(13) See the Supporting Information for full spectroscopic and analytical
characterization.
(14) Chase, P. A.; Henderson, L. D.; Piers, W. E.; Parvez, M.; Clegg, W.;
Elsegood, M. R. J. Organometallics 2006, 25, 349–357.
(15) Blackwell, J. M.; Piers, W. E.; McDonald, R. J. Am. Chem. Soc. 2002,
124, 1295–1306.
resonances at –129.22 and –131.87 ppm confirmed the
presence of a disubstituted C6F4 aryl ring. Collectively, these
(16) Blackwell, J. M.; Sonmor, E. R.; Scoccitti, T.; Piers, W. E. Org. Lett.
2000, 2, 3921–3923.
data are consistent with the formulation of
8 as
(17) Chase, P. A.; Romero, P. E.; Piers, W. E.; Parvez, M.; Patrick, B. O.
Can. J. Chem. 2005, 83, 2098–2105.
Cp2PH(C6F4)BF(C6F5)2. An X-ray crystallographic study20
of 8 (Figure 2) confirmed the zwitterionic nature, in which
a fluoroborate center is linked to a phosphonium center by
a C6F4 unit. The metric parameters are similar to those
previous reported for R2R′P(C6F4)BF(C6F5)2 (R ) R′, i-Pr,
Cy; R ) t-Bu, C6H2Me3-2,4,6, R′ ) H) derived from
sterically frustrated Lewis pairs. The molecules of 8 pack in
the solid state such that the closest approach between the
PH and BF fragments is 2.099. These head-to-tail interactions
forms an extended hydrogen-bonded structure.
(18) Horton, A. D.; With, J. d. Organometallics 1997, 16, 5424–5436.
(19) Horton, A. D.; With, J. d.; Linden, A. J. v. d.; Weg, H. v. d.
Organometallics 1996, 15, 2672–2674.
(20) X-ray data for 1: space group P21/n, a ) 9.8263(11) Å, b )
12.5957(14) Å, c ) 22.117(2) Å, ꢀ ) 96.3620(10)°, V ) 2720.5(5)
Å3, R ) 0.0431, Rw ) 0.1019, GOF ) 1.038. X-ray data for 8: space
group P21/n, a ) 11.321(4) Å, b ) 8.895(3) Å, c ) 28.018(10) Å ꢀ
) 100.216(6)°, V ) 2776.6(17) Å3, R ) 0.0812, Rw ) 0.1237, GOF
) 0.985.
(21) Bradley, D. C.; Hursthouse, M. B.; Motevalli, M.; Zheng, D. H. Chem.
Commun. 1991, 1, 7–8.
(22) Denis, J.-M.; Forintos, H.; Szelke, H.; Toupet, L.; Pham, T.-N.; Madec,
P.-J.; Gaumont, A.-C. Chem. Commun. 2003, 5, 4–55.
Inorganic Chemistry, Vol. 47, No. 6, 2008 1905