Reductive Elimination from Metal Phosphonate Complexes
Organometallics, Vol. 23, No. 4, 2004 655
J ) 7.7, -C6H5), 6.94 (t, 2H, J ) 7.3, -C6H5), 6.77 (d, 4H, J )
8.2, -C6H5), 2.42 (m, 2H, -CH2-), 2.29 (m, 2H, -CH2-), 1.92
(m, 2H, -CH2-), 0.55 (ddd, 3H, J ) 8.2, 6.0, 4.1, PdMe). 31P-
{1H} NMR (CDCl3, 25 °C): δ 89.3 (dd, J ) 582.7, 47.3, -P(O)-
(OPh)2), 11.0 (dd, J ) 583.5, 47.5, trans-PPh2), -0.8 (dd, J )
46.9, 47.1, cis-PPh2).
solid (0.052 g, 81%). Anal. Calcd for C50H44O6P4Pd: C, 61.83;
H, 4.53. Found: C, 61.56; H, 4.88. H NMR (CDCl3, 25 °C): δ
7.60-6.88 (m, 40H, -C6H5), 2.19-2.12 (m, 4H, -CH2PPh2).
31P{1H} NMR (CDCl3, 25 °C, AA′XX′ pattern): δ 66.5 (-P(O)-
(OPh)2), 43.37 (-PPh2); J AA′ ) (29.0, J AX ) 555, J AX′ ) -29.0,
J XX′ ) (51.0.28
1
P r ep a r a tion of (d p p b)P d Me(P (O)(OP h )2) (7). The gen-
eral method was followed with 1 (0.11 g, 0.18 mmol) and dppb
(0.075 g, 0.18 mmol) to afford the title compound as a colorless
solid (0.13 g, 94%). Anal. Calcd for C41H41O3P3Pd: C, 63.04;
P r ep a r a tion of (d p p p )P d (P (O)(OP h )2)2 (16). A round-
bottom flask was charged with (dppp)PdMe(P(O)(OPh)2) (0.05
g, 0.065 mmol), HP(O)(OPh)2 (12.5 µL, 0.065 mmol), and
benzene (5 mL). After the mixture was stirred for 12 h at 80
°C, the solvent was evaporated and the solid washed with 10
mL of diethyl ether to afford the title compound as a white
solid (0.029 g, 45%). Anal. Calcd for C51H46O6P4Pd: C, 62.17;
1
H, 5.25. Found: C, 62.44; H, 5.55. H NMR (CDCl3, 25 °C): δ
7.65-7.20 (m, 20H, -C6H5), 6.95 (m, 6H, m-, p-C6H5), 6.59 (d,
4H, J ) 7.9, o-C6H5), 2.53 (m, 2H, -CH2-), 2.23 (m, 2H,
-CH2-), 2.07 (m, 2H, -CH2-), 1.51 (m, 2H, -CH2-), 0.43
(ddd, 3H, J ) 8.9, 6.2, 3.1, PdMe). 31P{1H} NMR (CDCl3, 25
°C): δ 88.4 (dd, 1P, J ) 573.3, 51.7, -P(O)(OPh2), 30.6 (dd,
1P, J ) 573.3, 35.6, trans-CH2PPh2), 7.6 (dd, 1P, J ) 51.7,
35.7, cis-CH2PPh2).
1
H, 4.67. Found: C, 62.13; H, 4.74. H NMR (CDCl3, 25 °C): δ
7.55-6.80 (m, 40 H, -C6H5), 2.19 (m, 2H, -CH2-), 1.86-1.70
(m, 4H, -CH2-). 31P{1H} NMR (CDCl3, 25 °C, AA′XX′ pat-
tern): δ 63.2 (-P(O)(OPh)2), -0.8 (-PPh2); J AA′ ) (76, J AX
563, J AX′ ) -31.0, J XX′ ) (54.0.28
)
Rea ction of Tr ia r ylp h osp h in es w ith 1. An NMR tube
was charged with 1, an appropriate amount of triarylphos-
phine, solvent (0.5 mL), and P(O)Ph3 (0.003 g, 0.011 mmol,
internal standard for reactions carried out in protonated
toluene) or C6Me6 (0.001 g, 0.012 mmol). Two drops of C6D6
were added to reaction mixtures when protonated toluene was
used as the solvent. A comparison of the integrals for the metal
complex, internal standard, and MeP(O)(OPh)2 before and
after stirring at the desired temperature gave the percent
conversion of the reaction.
Th er m olysis Rea ction s of 2-8. An NMR tube was
charged with the palladium complex (0.005 g), P(O)Ph3 (0.003
g, 0.011 mmol, internal standard for reactions carried out in
protonated toluene) or C6Me6 (0.001 g, 0.012 mmol), and the
appropriate solvent (0.5 mL). Two drops of C6D6 were added
to reaction mixtures when protonated toluene was used as the
solvent. After heating in an oil bath for the desired amount of
time, the amount of MeP(O)(OPh)2 formed in the reaction was
determined by a comparison of the integrals for the metal
complex, internal standard, and MeP(O)(OPh)2 before and
after stirring at the desired temperature.
P r ep a r a tion of (d p p f)P d Me(P (O)(OP h )2) (8). A round-
bottom flask was charged with 1 (0.11 g, 0.18 mmol), dppf
(0.098 g, 0.18 mmol), and CH2Cl2 (3 mL). After the mixture
was stirred at -43 °C for 24 h, Et2O (20 mL; precooled to -43
°C) was added. After standing at - 43 °C for 24 h, a colorless
solid formed and was separated by filtration. The residue was
washed with chilled (-45 °C) ether and hexane and dried
under vacuum (0.01 g, 63%). Anal. Calcd for C47H41O3P3Pd:
1
C, 62.10; H, 4.51. Found: C, 61.91; H, 4.84. H NMR (CDCl3,
3
25 °C): δ 7.60-7.20 (m, 20H, -C6H5), 6.92 (t, 4H, J HH ) 7.9,
3
3
m-C6H5), 6.84 (t, 2H, J HH ) 7.0, p-C6H5), 6.73 (d, 4H, J HH
)
8.0, o-C6H5), 4.35-4.0 (m, 6H, -C5H4), 3.64 (m, 2H, -C5H4),
0.69 (m, 3H, PdMe). 31P{1H} NMR (CDCl3, 25 °C): δ 85.4 (dd,
1P, J ) 602.8, 58.8, -P(O)(OPh)2), 25.8 (dd, 1P, J ) 602.8,
32.6, trans-PPh2), 14.9 (dd, 1P, J ) 58.9, 32.8, cis-PPh2).
P r ep a r a tion of (bip y)P d (P (O)(OP h )2)2 (13). A round-
bottom flask was charged with (bipy)PdMe(P(O)(OPh)2) (0.050
g, 0.098 mmol), HP(O)(OPh)2 (18.8 µL, 0.098 mmol), and CH2-
Cl2 (5 mL). After the mixture was stirred for 48 h at 75 °C,
the solvent was evaporated and the solid washed with diethyl
ether (10 mL) to afford the title compound as a white solid
(0.057 g, 45%). Anal. Calcd for C34H28N2O6P2Pd: C, 56.01; H,
3.87. Found: C, 55.65; H, 3.87. 1H NMR (CDCl3, 25 °C): δ
9.68 (dt, 2H, J ) 3.0, J ) 5.5, H6, H6′), 7.93 (d, 2H, J ) 7.8,
H3, H3′), 7.86 (t, 2H, J ) 7.9, H4, H4′), 7.27 (m, 2H, H5, H5′),
7.25 (d, 8H, J ) 8.2, o-C6H5), 7.11 (t, 8H, J ) 8.2, m-C6H5),
6.94 (t, 4H, J ) 7.3, p-C6H5). 13C NMR (CDCl3, 25 °C): δ 154.5
(s, quat), 154.0 (s, C6, C6′), 151.8 (t, J ) 4.8, ipso-C6H5), 139.9
(s, C4 and C4′), 129.2 (s, m-C6H5), 126.1 (t, J ) 2.5, C5, C5′),
123.7 (s, p-C6H5), 122.2 (s, C3, C3′), 121.7 (t, J ) 2.4, o-C6H5).
31P NMR (CDCl3, 25 °C): δ 53.1.
Kin etic An a lysis of th e Red u ctive Elim in a tion fr om
8. Since compound 8 readily eliminates MeP(O)(OPh)2 at room
temperature in solution, it was generated in situ from the
reaction of 1 with dppf. Monitoring the reaction by NMR
revealed that the displacement reaction was complete within
a few minutes at 25 °C, and control reactions demonstrated
t
that free Bu2bipy does not affect the rate of the reaction. An
NMR tube was charged with 1 (0.005 g, 8.0 µmol), appropriate
amount of dppf (2-6 equiv), P(O)Ph3 (0.003 g, 0.011 mmol,
internal standard when reactions were carried out in proto-
nated toluene) or C6Me6 (0.001 g, 0.012 mmol), and the
appropriate solvent (0.5 mL). Two drops of C6D6 were added
to reaction mixtures for a spectrometer lock when reactions
were carried out in protonated toluene. NMR data were
collected at regular intervals over 3 half-lives. The concentra-
tions of 8, excess dppf, MeP(O)(OPh)2, and Pd(dppf)2 were
determined by comparison of the integrals of the species
relative to the internal standard. The rate of MeP(O)(OPh)2
formation varied by less than 5% between reactions with 2-6
equiv of dppf. Similar results were obtained using PPh3 as the
trapping agent.
P r epar ation of (tBu 2bipy)P d(P (O)(OP h )2)2 (14). A round-
bottom flask was charged with (tBu2bipy)PdMe(P(O)(OPh)2)
(0.05 g, 0.08 mmol), HP(O)(OPh)2 (15.4 µL, 0.08 mmol), and
benzene (5 mL). After the mixture was stirred for 12 h at 75
°C, the solvent was evaporated and the solid washed with 10
mL of diethyl ether to afford the title compound as a white
solid (0.062 g, 91%). Anal. Calcd for C42H44N2O6P2Pd: C, 59.97;
1
H, 5.23. Found: C, 59.58; H, 5.29. H NMR (CDCl3, 25 °C): δ
9.80 (dt, 2H, J ) 3.0, 5.9, H6, H6′), 7.90 (s, 2H, H3, H3′), 7.41
(d, 2H, J ) 5.9, H5, H5′), 7.33 (d, 8H, J ) 8.1, o-C6H5), 7.19 (t,
8H, J ) 7.9, m-C6H5), 7.01 (t, 4H, J ) 7.4, p-C6H5), 1.39 (s,
18H, -CMe3). 13C{1H} NMR (CDCl3, 25 °C): δ 164.2 (s, quat),
155.0 (s, quat), 153.9 (s, C6, C6′), 152.1 (t, J ) 4.8, ipso-C6H5),
129.1 (s, m-C6H5), 123.5 (s, p-C6H5), 123.4 (s, C5, C5′), 121.8
(t, J ) 2.4, o-C6H5), 118.1, (s, C3, C3′), 35.5 (s, -CMe3), 30.3
(s, -CMe3). 31P{1H} NMR (CDCl3, 25 °C): δ 54.0.
Red u ctive Elim in a tion vs P r oton olysis Rea ction s. An
NMR tube was charged with the appropriate metal complex,
HP(O)(OPh)2 (1 equiv), solvent, P(O)Ph3 (0.003 g, 0.011 mmol,
internal standard when reactions were carried out in proto-
nated toluene) or C6Me6 (0.001 g, 0.012 mmol), and the
P r ep a r a tion of (d p p e)P d (P (O)(OP h )2)2 (15). A round-
bottom flask was charged with (dppe)PdMe(P(O)(OPh)2) (0.05
g, 0.066 mmol), HP(O)(OPh)2 (12.7 µL, 0.066 mmol), and
benzene (3 mL). After the mixture was stirred for 12 h at 120
°C, the solvent was evaporated and the solid washed with 10
mL of diethyl ether to afford the title compound as an off-white
(28) To simulate the spectrum, the cis couplings between the
phosphonate groups and between the phosphorus atoms of the diphos-
phine (J XX′ and J AA′) must have opposite signs. For further explanation
and discussion of AA′XX′ NMR spectral patterns see: Becker, E. D.
High-Resolution NMR: Theory and Chemical Applications, 3rd ed.;
Academic Press: San Diego, CA, 2000; pp 176-177.