Reaction of KIn(CH2CMe3)3H with chlorodiphenylphosphine

Article abstract of DOI:10.1021/om000017q

The reaction between KIn(CH₂CMe₃)₃H and ClPPh₂ in pentane or benzene produces significant yields of two indium-phosphorus compounds, (Me₃CCH₂)₂-InPPh₂ and (Me₃CCH₂)₃In·P(CH₂CMe₃)₂. This unexpected adduct incorporates a neopentyl group that was originally a substituent on the indium reagent. The other products of the reaction are CMe₄, H₂, and KCl. The formation of all products is explained by a set of experimentally verified reactions.

Full text of DOI:10.1021/om000017q

2820
Organometallics 2000, 19, 2820-2822
Rea ction of KIn (CH2CMe3)3H w ith
Ch lor od ip h en ylp h osp h in e
O. T. Beachley, J r.* and Sun-Hua L. Chao
Department of Chemistry, State University of New York at Buffalo,
Buffalo, New York 14260-3000
Received J anuary 10, 2000
Summary: The reaction between KIn(CH2CMe3)3H and
ClPPh2 in pentane or benzene produces significant yields
of two indium-phosphorus compounds, (Me3CCH2)2-
InPPh2 and (Me3CCH2)3In‚P(CH2CMe3)Ph2. This unex-
pected adduct incorporates a neopentyl group that was
originally a substituent on the indium reagent. The other
products of the reaction are CMe4, H2, and KCl. The
formation of all products is explained by a set of
experimentally verified reactions.
not require the prior synthesis and handling of HPR′2.
Ideally, the secondary phosphine should be formed in-
situ and then be consumed by reaction with the organo-
indium compound. This goal was realized with the
synthesis of [(Me3CCH2)2InP(t-Bu)2]2 in high, if not
quantitative, yield by reacting KIn(CH2CMe3)3H6 with
ClP(t-Bu)2 in pentane (eq 2).7 In contrast, we have found
KIn(CH2CMe3)3H + ClP(t-Bu)2 pentane8
(Me3CCH2)2InP(t-Bu)2 + KCl + CMe4 (2)
In tr od u ction
The original and simplest route to compounds of the
type R2InPR′2 involves the use of the hydrocarbon
elimination reaction1-3 between InR3 and HPR′2. Even
that the reaction between KIn(CH2CMe3)3H and ClPPh2
forms a different set of products and thus involves some
reactions that were not observed for the tert-butyl
phosphine system.7
InR3 + HPR′2 hydrocarbon elimination8 R2InPR′2 + RH (1)
reaction
Resu lts a n d Discu ssion
though the metathetical reaction4 between InR2Cl and
LiPR′2 and the Me3SiCl elimination reaction5 between
InR2Cl and (Me3Si)PR′2 have also been exceedingly
useful and productive reactions to prepare R2InPR′2, the
latter reactions require the synthesis of more starting
materials than are needed for the simple hydrocarbon
elimination reaction. Therefore, a goal of our research
has been to develop a procedure for the preparation of
R2InPR′2 that would take advantage of the simplicity
of the hydrocarbon elimination reaction but that would
The reaction between KIn(CH2CMe3)3H and ClPPh2
in either pentane or benzene produces two indium-
phosphorus compounds (Me3CCH2)2InPPh22,3 and (Me3-
CCH2)3In‚P(CH2CMe3)Ph2, which account for approxi-
mately 85-90% of the initial indium and phosphorus.
The other products that were isolated from the reaction
included CMe4, H2, and KCl. The identity of the
principal product (Me3CCH2)2InPPh2 was confirmed by
1
observing that its physical properties as well as its H
and 31P NMR spectra were identical with those for
samples prepared by the elimination reaction between
In(CH2CMe3)3 with HPPh2 in pentane or benzene solu-
tion.2,3 Thus, (Me3CCH2)2InPPh2 has been synthesized
directly from the chlorophosphine without the interme-
diate preparation and isolation of HPPh2. The second
indium-phosphorus product is (Me3CCH2)3In‚P(CH2-
CMe3)Ph2, an adduct of a tertiary phosphine that
contains a neopentyl group that was a substituent on
the initial indium reagent. The 1H and 31P NMR spectra
of this adduct were identical with those of a sample
prepared from a 1:1 mixture of In(CH2CMe3)3 and
(1) (a) Coates, G. E., Graham, J . J . Chem. Soc. 1963, 233. (b)
Beachley, O. T., J r.; Coates, G. E. J . Chem. Soc. 1965, 3241. (c) Maury,
F.; Constant, G. Polyhedron 1984, 3, 581. (d) Aitchison, K. A.; Backer-
Dirks, J . D. J .; Bradley, D. C.; Faktor, M. M.; Fiegio, D. M.; Hursthouse,
M. B.; Hussain, B.; Short, R. L. J . Organomet. Chem. 1989, 366, 11.
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1990, 123, 2335. (h) Burns, J . A.; Dillingham, J . B. H.; Gripper, K. D.;
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J . D.; Banks, M. A. Rogers, R. D. Organometallics 1995, 14, 3448.
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R.; Fettinger, J . C. Organometallics 1991, 10, 1901.
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1997, 16, 3588. (h) Krannich, L. K.; Watkins, C. L.; Schauer, S. J .;
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1990, 170, 95. (b) Cowley, A. H.; J ones, R. A.; Mardonnes, M. A.; Nunn,
C. M. Organometallics 1991, 10, 1635. (c) Culp, R. D.; Cowley, A. H.;
Decken, A.; J ones, R. A.; Bond, M. R.; Mokry, L. M.; Carrano, C. J .
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10.1021/om000017q CCC: $19.00 © 2000 American Chemical Society
Publication on Web 06/06/2000

Notes
Organometallics, Vol. 19, No. 14, 2000 2821
P(CH2CMe3)Ph2 that had been prepared independently
by using the literature method.8
The occurrence of the reactions shown by eq 3-9
readily explains the formation of all products, is in
it can react with ClPPh2 to form (Me3CCH2)2InPPh2,
P(CH2CMe3)Ph2, and KCl (eq 6), as verified by an
independent experiment. Thus, K[(Me3CCH2)3InPPh2]
transferred a neopentyl group to ClPPh2 to form P(CH2-
CMe3)Ph2 rather than a PPh2 group to form P2Ph4. A
second route to P(CH2CMe3)Ph2 involves the reaction
between In(CH2CMe3)3 and ClPPh2 (eq 7), two species
likely to be present in the reaction mixture. However,
the indium product from this reaction (eq 7), In(CH2-
CMe3)2Cl,8 was not an observed product from the
reaction between KIn(CH2CMe3)3H and ClPPh2. Thus,
In(CH2CMe3)2Cl8 must have reacted with another spe-
cies such as K[(Me3CCH2)3InPPh2] if it was formed at
all. Independent experimental observations demon-
strated that In(CH2CMe3)2Cl reacts readily with K[(Me3-
CCH2)3InPPh2] to form In(CH2CMe3)3, (Me3CCH2)2-
InPPh2, and KCl (eq 8). Trisneopentylindium reacts, in
turn, with P(CH2CMe3)Ph2 to form the observed adduct
(eq 9). The availability of two different paths to P(CH2-
CMe3)Ph2 (eqs 6 and 7) permits all intermediates to be
consumed but only two indium phosphorus products to
be isolated at the end of the reaction. The overall
reaction is summarized by eq 10.
The series of equations shown by eq 3-9 accounts for
all products from the reaction between KIn(CH2-
CMe3)3H and ClPPh2. The initial reaction between KIn-
(CH2CMe3)3H and ClPPh2 (eq 3) and the hydrocarbon
elimination reaction (eq 4) are slower than the reactions
depicted by eqs 5, 6, 7, 8, and 9. The apparent slowness
of the replacement of the chlorine on phosphorus by the
hydridic hydrogen on indium and the even slower
elimination reaction between In(CH2CMe3)3 and HPPh2
provide the opportunity for the occurrence of reactions
not observed for the KIn(CH2CMe3)3H and ClP(t-Bu)2
system.7
agreement with their observed percentage yields, and
is consistent with indium and phosphorus chemistry.
All reactions in this sequence have been verified by
independent experiments. These reactions account for
the formation of (Me3CCH2)3In‚P(CH2CMe3)Ph2 and H2,
the two products that were unexpected on the basis of
the reaction between KIn(CH2CMe3)3H with ClP(t-Bu)2.7
These two products also explain why (Me3CCH2)2InPPh2
and CMe4 were not formed in equimolar amounts as
required by the balanced equation for the hydrocarbon
elimination reaction (eq 4). The percentage yield of (Me3-
CCH2)2InPPh2 (40.2%) was significantly higher than the
yield of CMe4 (27.0%). Thus, (Me3CCH2)2InPPh2 must
be formed by more reactions than only the hydrocarbon
elimination reaction.
When the original reagents KIn(CH2CMe3)3H and
ClPPh2 were combined, an insoluble solid formed. This
observation suggests the presence of KCl, whereas In-
(CH2CMe3)3 and HPPh2 (eq 3) would be soluble in
pentane and benzene and undergo the hydrocarbon
elimination reaction to form (Me3CCH2)2InPPh2 and
CMe4 (eq 4).2 However, since both the initial reaction
(eq 3) and the elimination reaction (eq 4) are relatively
slow,2 additional reactions occur to produce (Me3CCH2)2-
InPPh2. The second route to (Me3CCH2)2InPPh2 must
begin with the reaction between HPPh2 and KIn(CH2-
CMe3)3H to form H2, an observed but unexpected
product, and K[(Me3CCH2)3InPPh2] (eq 5). These ob-
servations suggest that KIn(CH2CMe3)3H reacts faster
with HPPh2 than with ClPPh2. An independent experi-
ment verified that a solution of KIn(CH2CMe3)3H re-
acted with HPPh2 within minutes of mixing to form H2
and an insoluble solid, presumably K[(Me3CCH2)3-
InPPh2] (eq 5). An additional datum in support of the
occurrence of these reactions is the observation that
96.8% of the hydridic hydrogen initially available in
KIn(CH2CMe3)3H is accounted for by the formation of
H2 (both hydrogen atoms originate with this hydride)
and CMe4. After K[(Me3CCH2)3InPPh2] has been formed,
Exp er im en ta l Section
All compounds were manipulated in a standard vacuum line
or in a purified argon atmosphere. The starting materials KH
and ClPPh2 were purchased from Aldrich Chemical Co., HPPh2
9
was purchased from Strem Chemicals, Inc., and In(CH2CMe3)3
and KIn(CH2CMe3)3H6 were prepared by using literature
methods. All solvents were dried by conventional procedures.
The 1H NMR spectra were recorded at 400 MHz by using a
Varian Unity-Inova 400 spectrometer. Proton chemical shifts
are reported in δ (ppm) units and are referenced to SiMe4 at
δ 0.00 ppm and benzene at δ 7.15 ppm. The 31P NMR spectra
are referenced to 85% H3PO4 at δ 0.00 ppm. All samples for
NMR spectra were contained in sealed NMR tubes. Infrared
spectra of solids were observed as Nujol mulls between KBr
plates and were recorded with a Perkin-Elmer 683 spectrom-
eter. Melting points were determined with a Mel-Temp by
using flame-sealed capillaries filled with purified argon and
are uncorrected.
Syn th esis of (Me3CCH2)2In P P h 2 fr om KIn (CH2CMe3)3H
a n d ClP P h 2. (a ) Mixin g Rea gen ts a t -45 °C in P en ta n e.
A tube, charged with 0.881 g (2.39 mmol) of KIn(CH2CMe3)3H
and 10 mL of pentane, was connected to a two-necked flask
that contained 0.529 g (2.40 mmol) of ClPPh2 and 20 mL of
pentane. The solution of ClPPh2 was cooled to -45 °C with a
2-propanol/dry ice bath, and then the reagents were combined.
The resulting mixture was slowly warmed to room tempera-
ture and stirred for 2 days. The noncondensable gas H2 (0.667
mmol, 55.8% based on KIn(CH2CMe3)3H, see Results and
(9) Beachley, O. T., J r.; Spiegel, E. F.; Kopasz, J . P.; Rogers, R. D.
Organometallics 1989, 8, 1915.
(8) Singh, G.; Reddy, G. S. J . Org. Chem. 1979, 44, 1057.

2822 Organometallics, Vol. 19, No. 14, 2000
Notes
Discussion) was measured with a Toepler pump-gas buret
assembly while the solution was maintained at -196 °C. Then
the product mixture was warmed to room temperature and
filtered with a medium glass frit, and the pentane was
removed by vacuum distillation. The insoluble solid (KCl) was
isolated and weighed in the drybox (0.168 g, 2.25 mmol, 94.1%
yield based on KIn(CH2CMe3)3H). The pentane-soluble solid
was transferred to a sublimator, whereupon the adduct (Me3-
CCH2)3In‚P(CH2CMe3)Ph2 (0.476 g, 0.815 mmol, 34.1% yield
based on KIn(CH2CMe3)3H) sublimed at 90-115 °C. The
residue was impure (Me3CCH2)2InPPh2 (0.566 g, 1.29 mmol,
54.0% yield based on KIn(CH2CMe3)3H). The organoindium
phosphide was purified by recrystallization from 20 mL of
pentane at -30 °C to yield 0.301 g (0.681 mmol) in the first
crop of cystals and then 0.265 g (0.598 mmol) in the second.
Thus, the total yield of (Me3CCH2)2InPPh2 was 0.566 g (1.28
mmol, 53.5% yield based on KIn(CH2CMe3)3H).
after the tube was flame sealed under vacuum, the NMR
spectrum was recorded immediately. 31P{1H} NMR (C6D6) δ:
-22.8. 1H NMR (C6D6) δ: 0.90 (s, PCCMe3, 9 H), 1.16 (s,
InCH2, 6 H), 1.19 (s, InCCMe3, 27 H), 2.08 (d, PCH2, J ) 5
Hz, 2 H).
Rea ction of KIn (CH2CMe3)3H w ith HP P h 2. A pentane
solution of HPPh2 (0.403 g, 2.16 mmol) was added to a pentane
solution of KIn(CH2CMe3)3H (0.802 g, 2.18 mmol) that had
been cooled to -50 to -60 °C. Bubbling, formation of a
precipitate, and a color change from colorless to light yellow
were observed upon mixing the reagents. After the solution
had been warmed to room temperature and stirred for 18 h,
the noncondensable gas (H2) was measured at -196 °C with
a Toepler pump-gas buret assembly (1.40 mmol H2, 64.8% H2
based on HPPh2).
NMR Sp ectr a l Stu d y of Rea ction P r od u cts a fter Mix-
in g In (CH2CMe3)3 w ith ClP P h 2. A small tube was charged
with ClPPh2 (0.182 g, 0.826 mmol), In(CH2CMe3)3 (0.271 g,
0.827 mmol), and C6D6 (1 mL). Then, a portion of the contents
was transferred to an NMR tube under vacuum and the NMR
tube was flame-sealed. The NMR spectrum was recorded 30
min after mixing of reagents. The products identified by the
NMR spectrum included In(CH2CMe3)2Cl and P(CH2CMe3)-
Ph2. 31P{1H} NMR (C6D6) δ: -41.0 (d, J ) 310 Hz, trace
HPPh2), -21.1 (s, P(CH2CMe3)Ph2), -21.2 (d, J ) 310 Hz,
trace). 31P NMR (C6D6) δ: -41.2 (d, J ) 314 Hz, trace), -21.1
(s, P(CH2CMe3)Ph2), -21.2 (d, J ) 310 Hz, trace). 1H NMR
(C6D6) δ: 0.86 (br, 0.8 H), 0.90 (s, 0.4 H), 0.94 (br, PCCMe3,
7.4 H), 1.17 (s, InCCMe3, 18 H), 1.27 (br, 1.3. H), 1.30 (s, 4.3
H), 1.56 (s, InCH2, 4 H), 7.09 (d, PPh, J ) 6 Hz, 5.3 H), 7.38
(br, 0.4 H), 7.43 (td, PPh, J ) 8 Hz, 3.2 H).
Syn th etic Sca le Rea ction betw een In (CH2CMe3)3 a n d
ClP P h 2. A pentane (5 mL) solution of ClPPh2 (0.980 g, 4.44
mmol) was added to a pentane (15 mL) solution of In(CH2-
CMe3)3 (1.46 g, 4.44 mmol) at -78 °C. The reaction mixture
was allowed to warm slowly to room temperature and was
stirred overnight. Pentane was removed by vacuum distillation
while holding the product mixture at -30 °C. Then In(CH2-
CMe3)2Cl was crystallized from fresh pentane at -20 to -30
°C and isolated by filtration. After the pentane was removed
by vacuum distillation with the flask held in an ice bath, 0.966
g of In(CH2CMe3)2Cl (3.30 mmol, 74.3% yield based on ClPPh2)
and a cloudy viscous liquid were obtained. The cloudy liquid
was purified by vacuum distillation with a short-path still by
using an oil bath at 105 °C. The phosphine P(CH2CMe3)Ph2
(0.827 g, 3.23 mmol, 72.7% based on ClPPh2) distilled at a head
temperature of 78 °C.
(Me3CCH2)2In P P h 2: mp 143-150 °C dec (lit.2,3 143-150
°C dec); 31P{1H} NMR (C6D6) δ -49.7 (s, [(Me3CCH2)2InPPh2]2),
-30.2 (s, (Me3CCH2)2InPPh2) (lit.2,3 -49.40, -29.95); 1H NMR
(C6D6) δ 1.00 (s, CMe3, 1 H), 1.06 (s, CMe3, 18 H), 1.46 (br,
PInCH2, 4 H) (lit.2,3 1.03, 1.10, 1.47 (t)).
(Me3CCH2)3In ‚P (CH2CMe3)P h 2: mp 82-84 °C; 31P{1H}
NMR (C6D6) δ -23.1 (s, (Me3CCH2)3In‚P(CH2CMe3)Ph2); 1H
NMR (C6D6) δ 0.96 (s, PCCMe3, 9 H), 1.09 (s, InCH2, 6 H),
1.14 (s, InCCMe3, 27 H), 2.07 (d, PCH2, J ) 4 Hz, 2 H).
(b) Mixin g Rea gen ts a t 0 °C in Ben zen e. The reagents
KIn(CH2CMe3)3H (1.39 g, 3.78 mmol) and ClPPh2 (0.835 g, 3.78
mmol) were combined as described previously for pentane but
by using benzene at an initial reaction temperature of 0 °C.
The isolated products included H2 (1.32 mmol, 69.8% yield
based on KIn(CH2CMe3)3H), CMe4 (separated by vacuum
fractional distillation through two -78 °C traps into a -196
°C trap, 0.0735 g, 1.02 mmol, 27.0% yield based on KIn(CH2-
CMe3)3H), KCl (0.252 g, 3.39 mmol, 89.7% yield based on KIn-
(CH2CMe3)3H), (Me3CCH2)3In‚P(CH2CMe3)Ph2 (0.784 g, 1.34
mmol, 35.4% yield based on KIn(CH2CMe3)3H), and (Me3-
CCH2)2InPPh2 (0.674 g, 1.52 mmol, 40.2% yield based on KIn-
(CH2CMe3)3H). The characterization data (mp, 31P and 1H
NMR spectra) for the two indium-phosphorus products were
identical to data given previously.
Syn th esis of P (CH2CMe3)P h 2. The Lewis base P(CH2-
CMe3)Ph2 was synthesized from ClPPh2 (10.2 g, 46.1 mmol)
and (Me3CCH2)MgCl (61.6 mmol) at 0 °C as described in the
literature.8 The phosphine (7.91 g, 30.9 mmol, 67.0% yield
based on ClPPh2) was isolated as a colorless liquid by vacuum
distillation (10-3 mm) at an oil bath temperature of 100-110
°C and a head temperature of 70-74 °C. Additional drying of
the phosphine with MgSO4 followed by short-path vacuum
distillation at a head temperature of 84-94 °C and 10-3 mm
pressure (bp lit.8 110-111 °C, 0.2 mm) gave the pure phos-
phine: 31P{1H} NMR (C6D6) δ -23.1 (lit.8 -23.3); 1H NMR
(C6D6) δ 0.99 (s, PCCMe3, 9 H), 2.07 (d, PCH2, J ) 5 Hz, 2 H),
7.04 (td, Ph, J ) 11 Hz, 10 H), 7.45 (dd, Ph, J ) 10 Hz, 10 H)
(lit.8 CDCl3: 1.00, 2.15, 7.13-7.62).
In (CH2CMe3)2Cl: 1H NMR (C6D6) δ 1.09 (s, InCCMe3, 9
H), 1.58 (s,InCH2, 2 H) (lit.6 1.09, 1.58).
P (CH2CMe3)P h 2: 1H NMR (C6D6) δ 1.01 (s, PCH2, 9 H),
1.13 (s, InCCMe3, ∼1 H), 1.51 (s, InCH2, ∼0.2 H), 2.09 (d,
PCH2C, J ) 4 Hz, 2 H), 7.08 (m, p, m-H of PPh, 6 H), 7.47 (t,
o-H of PPh, 4H); 31P{1H} NMR (C6D6) δ -21.4 (s, P(CH2CMe3)-
Ph2); 31P NMR (C6D6) δ -21.4 (br, P(CH2CMe3)Ph2).
Syn th esis a n d NMR Sp ectr a of (Me3CCH2)3In ‚P (CH2-
CMe3)P h 2. An NMR tube was charged with P(CH2CMe3)Ph2
(0.124 g, 0.482 mmol), In(CH2CMe3)3 (0.159 g, 0.483 mmol),
and C6D6. The walls of the tube were carefully rinsed with
the benzene to ensure complete mixing of the reagents. Then
Ack n ow led gm en t. This work was supported in part
by the Office of Naval Research (O.T.B.).
OM000017Q