Sterically encumbered terphenyl substituted primary pnictanes ArEH2 and their metallated derivatives ArE(H)Li (Ar = -C6H3-2,6-Trip2; Trip = 2,4,6-triisopropylphenyl; e = N, P, As, Sb)

Article abstract of DOI:10.1016/S0022-328X(00)00162-5

A series of sterically crowded primary pnictanes of formula ArEH₂ (Ar = C₆H₃-2,6-Trip₂; Trip = C₆H₂-2,4,6-i-Pr₃; E = N, 2; P, 4; As, 5; Sb, 6) and their lithiated pnictide salts ArE(H)Li (E = N, 7; P, 8; As, 9; Sb, 10) have been synthesized and characterized by X-ray crystallography (2-6), NMR, IR spectroscopy, and by combustion analysis. Details of the synthesis and structures of the azide derivative ArN₃ (1) and the arylphosphinic acid ArP(O)(OH)H (3) are also given. The amine compound 2 displays a planar geometry (within the limits of experimental error) at nitrogen which is attributable to interactions between the N-H moieties and the ortho-aryl rings. The antimony compound 6 is a rare instance of a stable primary stibane and its X-ray crystal structure represents the first structural determination of such a species.

Full text of DOI:10.1016/S0022-328X(00)00162-5

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 609 (2000) 152–160
Sterically encumbered terphenyl substituted primary pnictanes
ArEH and their metallated derivatives ArE(H)Li
2
(
Ar=ꢀC H -2,6-Trip ; Trip=2,4,6-triisopropylphenyl;
6
3
2
E=N, P, As, Sb)
Brendan Twamley, Cheong-Soo Hwang, Ned J. Hardman, Philip P. Power *
Department of Chemistry, Uni6ersity of California, Da6is, One Shields A6enue, Da6is, CA 95616, USA
Received 30 January 2000; received in revised form 28 February 2000
Abstract
A series of sterically crowded primary pnictanes of formula ArEH (Ar=C H -2,6-Trip ; Trip=C H -2,4,6-i-Pr ; E=N, 2; P,
2
6
3
2
6
2
3
4; As, 5; Sb, 6) and their lithiated pnictide salts ArE(H)Li (E=N, 7; P, 8; As, 9; Sb, 10) have been synthesized and characterized
by X-ray crystallography (2-6), NMR, IR spectroscopy, and by combustion analysis. Details of the synthesis and structures of the
azide derivative ArN (1) and the arylphosphinic acid ArP(O)(OH)H (3) are also given. The amine compound 2 displays a planar
3
geometry (within the limits of experimental error) at nitrogen which is attributable to interactions between the NꢀH moieties and
the ortho-aryl rings. The antimony compound 6 is a rare instance of a stable primary stibane and its X-ray crystal structure
represents the first structural determination of such a species. © 2000 Published by Elsevier Science S.A. All rights reserved.
Keywords: Pnictanes; Sterically encumbered; Lithiated pnictanes; Terphenyls; Azide; Phosphinic acid
encumbering m-terphenyl substituents are particularly
effective at stabilizing unusual bonding and coordina-
tion numbers in compounds of the pnictogens and
many other groups in the periodic table [6]. We were
therefore interested in examining the effectiveness of
these substituents in stabilizing primary pnictanes. Ac-
cordingly we have prepared the pnictane series ArEH2
1
. Introduction
The hydrogen derivatives of the Group 15 elements
(
i.e. the pnictanes EH ; E=N, P, As, Sb or Bi) display
3
–
o
increasingly positive values for DGf as the group is
descended [1], and their decreased stabilities with in-
creasing atomic number are consistent with this trend.
Nonetheless, the bond enthalpies for the EꢀH bonds
remain surprisingly large for the heavier group mem-
bers (e.g. SbꢀH=ca. 60 kcal mol ) [1,2] which sug-
gests that their stability might be kinetically enhanced
with use of large substituents. Indeed, the substitution
of one or two hydrogens by bulkier organic groups is
already known to increase the stability of pnictanes.
(
E=N (2), P (4), As (5) or Sb (6); Ar=C H -2,6-Trip ,
6
3
2
Trip=C H -2,4,6-i-Pr ) via reduction of the corre-
6
2
3
sponding azide (ArN , 1) or halides [7] with LiAlH and
−
1
3
4
characterized them spectroscopically and structurally.
Attempts to synthesize the primary bismuthane ArBiH2
via reduction of 2,6-Trip H C BiCl with LiAlH re-
2
3
6
2
4
sulted in the isolation of the previously reported dibis-
muthene 2,6-Trip H C BiBiC H -2,6-Trip [7]. In
2
3
6
6
3
2
For example, phenylstibane, PhSbH , decomposes at
room temperature [3], whereas t-BuCH SbH [4] and
Me SiCH SbH [5] are colorless liquids which are stable
for long periods under a H atmosphere at ambient
2
addition, we report the structures of the azide ArN (1),
3
2
2
the precursor of 2, and the arylphosphinic acid
ArP(O)(OH)H (3) which results from the hydrolysis of
3
2
2
2
the halide ArPCl . The generation of the monolithio
2
temperature. Recent work has shown that sterically
salts ArE(H)Li (E=N (7), P (8), As (9) or Sb (10) by
1
reaction with n-BuLi as well as the spectroscopic ( H,
13
C, NMR, IR) characterization of 1–10 and the struc-
tural characterization of 4–6 are also described.
*
Corresponding author. Fax: +1-530-7528995.
E-mail address: pppower@ucdavis.edu (P.P. Power).
0
022-328X/00/$ - see front matter © 2000 Published by Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00162-5

B. Twamley et al. / Journal of Organometallic Chemistry 609 (2000) 152–160
153
2
. Experimental
ca. −78°C. A solution of NaOH (15 ml, 0.01 M) was
added very slowly and a vigorous reaction occurred.
The mixture was warmed to room temperature where-
upon the grey precipitate became white. The mixture
was filtered and the organic filtrate was dried over
2.1. General procedures
All manipulations were carried out using modified
Schlenk techniques under an atmosphere of N or in a
MgSO . Filtration and evaporation of the ether layer
2
4
Vacuum Atmospheres HE-43 drybox. All solvents were
distilled from Na–K alloy and degassed immediately
before use. The compounds TsN3 [8], 2,6-
Trip H C Li(OEt ) [9], 2,6-Trip H C PCl [7], 2,6-
resulted in colorless crystals of 2. Yield 1.86 g, 75%.
−
1
1
M.p. 169–172°C; IR w(NꢀH) 3378, 3472 cm
vs; H
(300 MHz, CDCl ) l 1.31 (d, 12H, p-CH(CH ) )
3
3 2
3
3
JHH=6.6 Hz, 1.33 (d, 12H, o-CH(CH ) ) JHH=6.6
Hz, 1.51 (d, 12H, o-CH(CH ) ) JHH=6.6 Hz, 2.97
2
3
6
2
2
3
6
2
3 2
3
Trip H C AsCl [7], and 2,6-Trip H C SbCl [7] were
2
3
6
2
2
3
6
2
3 2
3
prepared according to literature procedures. MeLi,
(sept, 4H, o-CH(CH ) ) JHH=6.6 Hz, 3.15 (sept, 2H,
3
2
3
3 2 HH 2
nBuLi and LiAlH were purchased commercially and
p-CH(CH ) ) J =6.6 Hz, 3.36 (br s, 2H, NH ), 7.02
4
1
13
7
31
3
used as received. H-, C-, Li- and P-NMR spectra
were recorded on a Bruker 300 MHz instrument and
referenced to the deuterated solvent. Li- and P-NMR
spectra were referenced to LiCl and H PO , respec-
(t, 1H, p-C H ) J =7.2 Hz, 7.18 (d, 2H, m-C H )
6 3 HH 6 3
JHH=7.2 Hz, 7.29 (s, 4H, m-Trip); C{ H}-NMR (75
MHz, CDCl ) l 24.0 (CH(CH ) ), 24.1 (CH(CH ) ),
3
13
1
7
31
3
3 2
3 2
24.5 (CH(CH3)2), 30.5 (o-CH(CH3)2), 34.3 (p-
CH(CH ) ), 116.93 (p-C H ), 121.1 (m-Trip), 124.99
3
4
tively. Infrared data were recorded as Nujol mulls on a
Perkin–Elmer PE-1430 instrument.
3
2
6
3
(m-C H ), 129.2 (p-Trip), 133.1 (o-C H ), 142.6 (i-
6
3
6
3
C H ), 147.5 (o-Trip), 148.2 (i-Trip).
6
3
2
.2. 2,6-Trip H C N (1)
2
3
6
3
TsN3 (1.97 g, 10 mmol) was added dropwise via
syringe to a solution of 2,6-Trip H C Li(OEt ) (5.63 g,
2.4. 2,6-Trip H C P(O)(OH)H (3)
2
3
6
2
3
6
2
1
0 mmol) in Et O (50 ml) which had been cooled to ca.
A solution of 2,6-Trip H C PCl (3.80 g, 6.51 mmol)
2 3 6 2
2
−
78°C. The solution was stirred ca. 1 h and then
warmed to ca. −10°C. Further stirring (5 h) at ca.
10°C resulted in a pale yellow solution. An aqueous
in Et O (250 ml)was added to LiAlH (2.50 g, 65.10
mmol) and stirred overnight. The mixture was heated
to reflux (3 h), cooled to ca. 25°C and stirred for a
2
4
−
solution of NaOH (30 ml, 0.01 M) was then added to
decompose excess lithium reagents. The mixture was
stirred overnight at room temperature (r.t.) and the
organic layer was separated and dried over MgSO4.
Filtration and evaporation of the solvent afforded pale
yellow crystals of 1, which were suitable for X-ray
crystallographic analysis. Yield 4.24 g, 81%. M.p. 174–
further 8 h. Excess LiAlH was destroyed by the careful
addition of dil. HCl (80 ml) at ca. −8°C. The mixture
4
was warmed to r.t., and extracted with Et O (3×50
2
ml). The organic fractions were combined, dried over
MgSO , and filtered (Celite). The solvent was removed
4
under reduced pressure and the white residue was ex-
tracted with hexane (200 ml), filtered (Celite), and
concentrated under reduced pressure to 150 ml. The
precipitates were redissolved by warming, and upon
cooling while standing overnight, colorless crystals of 3
were obtained. Yield 0.24 g, 7%. M.p. turns opaque at
−
1
1
1
75°C N evolution; IR w
2085 cm
vs; H (300
2
(NꢀN)
3
MHz, CDCl ) l 1.12 (d, 12H, p-CH(CH ) ) JHH=6.9
Hz, 1.14 (d, 12H, o-CH(CH ) ) JHH=6.9 Hz, 1.29 (d,
3
3 2
3
3
2
3
12H, o-CH(CH ) ) JHH=6.9 Hz, 2.66 (sept, 4H, o-
3 2
3
CH(CH ) ) JHH=6.9 Hz, 2.94 (sept, 2H, p-
CH(CH ) ) J =6.9 Hz, 7.05 (s, 4H, m-Trip), 7.11
140°C, melts at 233–237°C. IR w
1460s,br cm , H (300 MHz, CDCl ) l 1.16 (d, 9H,
2410s, w(PꢁO)
3
2
(PH)
3
−1
1
3
2
HH
3
3
3
(
d, 2H, m-C H ) J =6.6 Hz, 7.19 (t, 1H, p-C H )
JHH=6.6 Hz; C{ H}-NMR (75 MHz, CDCl ) l 23.5
CH(CH ) ) JHH=6.3 Hz, 1.28 (d, 9H, CH(CH ) )
6
3
13
HH
1
6
3
3 2
3 2
3
3
3
JHH=6.6 Hz, 1.37 (d, 3H, CH(CH ) ) JHH=7.2 Hz,
3
3 2
3
(
CH(CH ) ), 24.0 (CH(CH ) ), 24.5 (CH(CH ) ), 30.7
1.38 (d, 9H, CH(CH ) ) JHH=7.2 Hz, 1.50 (d, 6H,
3
2
3 2
3 2
3 2
3
(
o-CH(CH ) ), 34.3 (p-CH(CH ) ), 120.6 (m-Trip),
CH(CH ) ) J =6.9 Hz, 2.66 (sept. 3H, CH(CH ) )
3
2
3 2
3 2
HH
3 2
3
3
1
1
23.98 (p-C H ), 130.44 (m-C H ), 132.61 (p-Trip),
JHH=6.9 Hz, 2.76 (sept., 1H, CH(CH ) ) JHH=6.9
Hz, 2.91 (sept., 1H, CH(CH ) ) JHH=6.9 Hz, 3.14
(sept., 1H, CH(CH ) ) JHH=6.9 Hz, 4.64 (d, 1H, PH)
6
3
6
3
3 2
3
33.8 (o-C H ), 137.0 (i-C H ), 147.0 (o-Trip), 148.99
6
3
6
3
3 2
3
(
i-Trip).
3
2
JPH=588 Hz, 7.12 (s, 4H, m-Trip), 7.22–7.64 (m, 3H,
13
1
2
.3. 2,6-Trip H C NH (2)
p,m-C H ), 10.96 (s, br, 1H, OH); C{ H}-NMR (75
2
3
6
2
6 3
MHz, CDCl ) l 22.3 (CH(CH ) ), 24.1 (CH(CH ) ),
3
3 2
3 2
A solution of 1 (2.65 g, 5.0 mmol) in Et O (50 ml)
25.4 (CH(CH3)2), 30.8 (o-CH(CH3)2), 33.7 (p-
CH(CH ) ), 120.3 (m-Trip), 128.5 (p-C H ), 130.3 (m-
2
was added dropwise to a suspension of LiAlH (1.0 g,
4
3 2
6
3
2
6.3 mmol) in Et O (20 ml) at ca. −78°C. The mixture
C H ), 133.6 (i-Trip), 143.6 (i-C H J =12 Hz), 145.9
(o-C H ), 146.7 (o-Trip), 148.0 (p-Trip); P-NMR (121
6 3
2
6 3 6 3 CP
31
was allowed to warm to ca. 25°C and stirred ca. 2 h.
The mixture was then refluxed for 5 h, and cooled to
MHz, CDCl ) l 26.77 (JPH=582 Hz, JPC=4144 Hz).
3

1
54
B. Twamley et al. / Journal of Organometallic Chemistry 609 (2000) 152–160
2
.5. 2,6-Trip H C PH (4)
2.7. 2,6-Trip H C SbH (6)
2
3
6
2
2
3
6
2
The supernatant liquid from the above synthesis of 3
This compound was prepared in a similar manner to
5 by using 2,6-Trip -H SbCl (2.90 g, 4.81 mmol) in
was isolated and concentrated to ca. 30 ml under
reduced pressure. The precipitates were redissolved
upon warming and upon cooling slowly to ca. 25°C,
colorless needles of 4 were obtained. Yield 2.03 g, 61%.
2
C
3
6
2
Et O (30 ml) and LiAlH4 (1.83 g, 48.1 mmol). It
2
crystallized as colorless needles from a concentrated
hexane solution at ca. 5°C. Yield 1.20 g, 41%. M.p.
turns yellow at 160°C and decomposes at 195°C; IR
−
1 1
M.p. 215–218°C; IR w(PꢀH) 2308, 2304 cm ; H (300
−
1
1
3
w(
1875 cm
br; H-NMR (300 MHz, CDCl ) l
SbꢀH)
3
MHz, CDCl ) l 1.09 (d, 12H, CH(CH ) ) JHH=6.9
3
3 2
3
3
1.07 (d, 12H, CH(CH ) ) JHH=6.9 Hz, 1.20 (d, 12H,
3
2
Hz, 1.18 (d, 12H, CH(CH ) ) JHH=6.9 Hz, 1.31 (d,
2H, CH(CH ) ) JHH=6.9 Hz, 2.57 (sept, 4H, o-
CH(CH ) ) JHH=6.9 Hz, 2.95 (sept, 2H, p-
3
2
3
3 2 3 2
3
CH(CH ) ) JHH=6.9 Hz, 1.30 (d, 12H, o-CH(CH ) )
1
3 2
3
3
3
J
HH=6.9 Hz, 2.60 (sept, 4H, o-CH(CH
) ) JHH=6.9
3 2
3
2
Hz, 2.66, (s, 2H, SbH ), 2.94 (sept, 2H, p-CH(CH ) )
3
3
2
3 2
CH(CH ) ) J =6.9 Hz, 3.05 (d, 2H, PH ) J 212
3
2
HH
2
PH
3
JHH=7.2 Hz, 7.04 (s, 4H, m-Trip), 7.17 (d, 2H, m-
C H ) J =7.2 Hz, 7.34 (t, br, 1H, p-C H ) JHH=
.2 Hz; C{ H}-NMR (75 MHz, CDCl ) l 23.3
3
Hz, 7.07 (s, 4H, m-Trip), 7.11 (d, 1H, m-C H ) JHH=
6
3
3
3
3
6 3 HH
6
3
HH
13
6
3
7
1
.5 Hz, 7.12 (d, 1H, m-C H ) J =7.8 Hz, 7.32 (t, br,
H, p-C H ) JHH=7.5 Hz; C{ H}-NMR (75 MHz,
1
7
3
13
1
3
6
3
(
CH(CH ) ), 24.2 (CH(CH ) ), 25.4 (CH(CH ) ), 30.6
3 2 3 2 3 2
CDCl ) l 23.4 (CH(CH ) ), 24.1 (CH(CH ) ), 25.1
3
3 2
3 2
(
o-CH(CH ) ), 34.3 (p-CH(CH ) ), 120.9 (m-Trip),
3 2 3 2
(
1
(
(
CH(CH ) ), 30.7 (o-CH(CH ) ), 34.3 (p-CH(CH ) ),
3 2 3 2 3 2
1
27.2 (p-C H ), 127.7 (m-C H ), 136.3 (i-C H ), 140.2
6 3 6 3 6 3
20.9 (m-Trip), 126.6 (p-C H ), 128.5 (m-C H ) 132.6
6 3 6 3
(
i-Trip), 145.7 (o-C H ), 148.2 (p-Trip), 148.5 (o-Trip).
6 3
d, i-C H , J =7.95 Hz), 136.9 (i-Trip), 144.4, 144.6
6 3 CP
31
o-C H ), 145.9 (o-Trip), 148.4 (p-Trip); P-NMR (121
6
3
2.8. 2,6-Trip H C N(H)Li (7)
2
3
6
MHz, CDCl ) −139.8 (t, JPH=208 Hz).
3
A solution of 2 (2.49 g, 5.0 mmol) in Et O (30 ml)
was cooled to ca. 0°C and methyllithium (3.13 ml, 1.6
2
2
.6. 2,6-Trip H C AsH (5)
2
3
6
2
M solution in Et O) was added via syringe. The solu-
2
This compound was synthesised in a similar manner
to 4. A solution of 2,6-Trip -H C AsCl (3.84 g, 6.12
tion was allowed to warm to ca. 25°C and stirred for 2
h. The yellow solution was concentrated under reduced
pressure to ca. 15 ml and placed in a −20°C freezer for
3 days. No crystals formed. The addition of hexane (20
ml) resulted in a white precipitate. The supernatant
liquid was decanted and the product was isolated as a
2
3
6
2
mmol) in Et O (100 ml) was added to a suspension of
2
LiAlH (1.39 g, 36 mmol) at 0°C. The mixture was
4
stirred overnight then heated to reflux temperature (2
h), cooled to ca. −78°C, and dilute HCl (20%, 90 ml)
added. The mixture was warmed to 25°C, stirred
1
white solid. Yield 1.60 g, 64%. H-NMR (300 MHz,
3
C D ), l 1.00 (d, 12H, o-CH(CH ) ) JHH=6.6 Hz,
overnight, and extracted with Et O (3×50 ml). The
6
6
3 2
2
3
1
.07 (12H, o-CH(CH ) ) JHH=6.6 Hz, 1.28 (12H,
p-CH(CH ) ) J =6.6 Hz, 2.06 (s, 1H, N(H)Li), 2.90
sept, 8H, CH(CH ) ) J =6.6 Hz, 6.55 (t, 1H, p-
organic fractions were combined, dried over MgSO4,
and filtered (Celite). The solvent was removed under
reduced pressure and the white residue was extracted
with hexane (50 ml), filtered (Celite), and concentrated
under reduced pressure to ca. 20 ml. The precipitates
were redissolved by warming, and on standing
overnight in a ca. 5°C refrigerator, colorless crystals of
3 2
3
3 2
HH
3
3 2 HH
(
3
3
C H ) J =7.5 Hz, 6.79 (d, 2H, m-C H ) JHH=7.5
6
3
HH
6
3
13
1
Hz, 7.11 (s, 4H, m-Trip); C{ H}-NMR (75 MHz,
C D ) l 24.3 (CH(CH ) ), 24.7 (CH(CH ) ), 25.1
6
6
3 2
3 2
(
CH(CH ) ), 30.5 (o-CH(CH ) ), 34.4 (p-CH(CH ) ),
3 2 3 2 3 2
1
12.9 (p-C H ), 122.1 (m-Trip), 126.8 (m-C H ), 130.3
6 3 6 3
5
were obtained. Yield 1.81 g, 53%. M.p. 225–226°C;
(
1
p-Trip), 138.2 (o-C H ), 146.9 (o-Trip), 147.9 (i-Trip),
57.5 (i-C H ); Li-NMR (C D ) l −9.17 s, br.
6 3 6 6
−
1
1
6 3
IR w(
AsꢀH)
2105 cm
br; H-NMR (300 MHz, CDCl )
3
7
3
l 1.09 (d, 12H, p-CH(CH ) ) JHH=6.6 Hz, 1.18 (d,
3
2
3
12H, o-CH(CH ) ) JHH=6.9 Hz, 1.31 (d, 12H, o-
3 2
2
.9. 2,6-Trip H C P(H)Li (8)
2
3
6
3
CH(CH ) ) JHH=6.9 Hz, 2.59 (sept, 4H, o-CH(CH3)2)
3
2
3
JHH=6.9 Hz, 2.63, (s, 2H, AsH ), 2.95 (sept, 2H,
2
Crystals of 4 (2.0 g, 3.89 mmol) were dissolved in
3
p-CH(CH ) ) J =6.6 Hz, 7.06 (s, 4H, m-Trip), 7.14
3
2
HH
Et O (50 ml) and cooled to ca. 0°C whereupon n-BuLi
2
3
(
d, 2H, m-C H ) J =7.5 Hz, 7.33 (t, br, 1H, p-
6
3
HH
13
(4.86 ml, 1.6 M in hexanes) was added dropwise (10
min). The colorless solution became an opaque yellow
color. The mixture was warmed to r.t. and stirred
overnight. The mixture was then heated to reflux for 0.5
h, cooled and the solvent removed under reduced pres-
sure. The orange residue was then suspended in pentane
(50 ml) and the product, a fine pale yellow powder, was
3
1
C H ) JHH=7.5 Hz; C{ H}-NMR (75 MHz, CDCl )
6
3
3
l 23.3, 23.5 (CH(CH ) ), 24.1, 24.2 (CH(CH ) ), 25.1,
3
2
3 2
2
5.2 (CH(CH ) ), 30.6 (o-CH(CH3)2), 34.2 (p-
3 2
CH(CH ) ), 120.8, 120.9 (m-Trip), 126.8 (p-C H ),
3
2
6
3
1
28.2 (m-C H ) 135.5 (i-C H ), 138.0 (i-Trip), 145.5
6 3 6 3
(
o-C H ), 145.8 (o-Trip), 148.3 (p-Trip).
6 3

B. Twamley et al. / Journal of Organometallic Chemistry 609 (2000) 152–160
155
isolated by filtration. Yield 1.40 g, 69%. M.p. 215°C
stream on the diffractometer (5 was coated with epoxy
resin and mounted at ca. 25°C) [10]. Data for 1, 2, 4
were obtained on a Siemens P4 Rotating Anode at 130
sticky, partial melt at 230°C, with a complete melt at
1
2
45–250°C while becoming an orange color. H-NMR
8
(
400 MHz, THF-d ), l 1.16 (d, 12H, p-CH(CH ) )
JHH=6.8 Hz, 1.26 (12H, o-CH(CH ) ) JHH=6.8 Hz,
.30 (12H, o-CH(CH ) ) JHH=6.8 Hz, 1.41 (d, 1H,
K using Cu–K radiation (u=1.54178 A
on a Siemens R3m/v at 130 K using Mo–K radiation
,
), those for 3
3
2
a
3
3
3 2
a
3
1
(u=0.71073 A), and data for 5,6 were measured on a
,
3
2
PH) J =178 Hz, 2.85 (sept, 2H, p-CH(CH ) )
Bruker SMART AXS 1000 at 299 and 93 K using
Mo–Ka radiation. The SHELXTL-Plus v. 5.03 and
SHELXTL v. 5.10 program suite was used for the struc-
ture solution and refinements [11]. The structures were
solved by direct methods and refined by full-matrix
least-squares procedures. Absorption corrections were
applied to 1–4 using the program XABS2 [12] and to 5,6
using the program SADABS. Hydrogen atoms bonded
directely to the pnictogen atom were located on the
Fourier difference map and refined with fixed distances.
Other hydrogen atoms were included in the refinement
at calculated positions using a riding model included in
the SHELXTL program. The structures of 1 and 4 are
subject to disorder, which could be modelled success-
fully by using partial occupancies for the disordered
atoms as described in the Supporting Information.
Crystals of 3 included disordered solvent, which could
not be successfully modelled, see the Supporting Infor-
mation. Details of the data collection and refinement
are given in Table 1. Selected bond distances and angles
for 1–6 are provided in Table 2.
HP
3 2
3
3
JHH=6.8 Hz, 3.00 (sept, 4H, o-CH(CH ) ) J =6.8
Hz, 6.43 (s, 2H), 6.95 (s, 4H), 7.11 (s, 1H); C{ H}-
NMR (75 MHz, THF-d ) d 24.7–25.6 (m, CH(CH ) ),
3 2
HH
3
1
1
8
3
2
3
1.1 (o-CH(CH ) ), 35.3 (p-CH(CH ) ), 115.3 (p-
3 2 3 2
C H ), 120.7, 120.8 (m-Trip), 127.8 (m-C H ), 139.1,
6
3
6
3
1
39.2 (i-Trip), 143.4 (o-C H ), 145.9 (p-Trip), 147.9
6 3
31
(
o-Trip), 161.1 (i-C H ) JCP=37.5 Hz; P-NMR (121
6 3
8
7
MHz, THF-d ) l −111.1 (d, J=183 Hz); Li-NMR
8
(THF-d ) l 0.50.
2
.10. 2,6-Trip H C As(H)Li (9)
2
3
6
This compound was prepared in the same manner as
8
by using 5 (1.00 g, 1.79 mmol) in Et O (60 ml) and
2
n-BuLi (1.12 ml, 1.6 M in hexanes). Yield 0.80 g, 79%.
1
8
M.p. 178–179°C, (dec). H-NMR (300 MHz, THF-d ),
3
l 0.62 (s, 1H AsH), 1.02 (d, 12H, p-CH(CH ) ) JHH=
.9 Hz, 1.26 (12H, o-CH(CH ) ) JHH=6.9 Hz, 1.32
12H, o-CH(CH ) ) JHH=6.9 Hz, 2.85 (sept, 2H, p-
CH(CH ) ) JHH=6.9 Hz, 2.99 (sept, 4H, o-
CH(CH ) ) JHH=6.9 Hz, 6.45 (d, 2H, m-C H )
JHH=6.9 Hz, 6.55 (t, 1H, p-C H ) J =6.3 Hz, 6.94
s, 4H, m-Trip); C{ H}-NMR (75 MHz, THF-d ) d
4.9, 25.1, 25.4, 25.66, 25.7 (CH(CH ) ), 31.2 (o-
3
2
3
6
(
3 2
3
3 2
3
3
2
3
3
2
6
3
3
3
6
3
HH
1
3
1
8
(
3. Discussion
2
3
2
CH(CH ) ), 35.4 (p-CH(CH ) ), 116.8 (p-C H ), 120.6
3.1. The azide ArN , 1 and the amine ArNH , 2
3
2
3 2
6
3
3
2
(
m-Trip), 127.3 (m-C H ), 141.8 (i-Trip), 143.9 (o-
6 3
C H ), 145.8 (p-Trip), 147.6 (o-Trip), 162.2 (i-C H );
Li-NMR (THF-d ) l 0.67.
The azide 1 and the primary amine 2 were synthe-
sized in a manner analogous to Yoshifuji’s scheme for
the synthesis of 2,6-dimesityl-4-methyl aniline [13]. The
compound 1 resulted from the reaction of LiC H -2,6-
6
3
6
3
7
8
2
.11. 2,6-Trip H C Sb(H)Li (10)
2
3
6
6
3
Trip with TsN (Ts=C H SO ꢀ) [8] in ether solution.
2
3
6
5
3
This compound was prepared in the same manner as
Further reduction of 1 with LiAlH afforded the target
4
8
by using 6 (1.20 g, 1.98 mmol) in Et O (50 ml) and
primary amine 2 in 75% yield. Although 1 and 2 are
members of compound classes for which numerous
examples have been structurally characterized, there are
a number of noteworthy features in both structures.
The molecule 1 (Fig. 1) has a plane of symmetry
containing the C(4), C(1) and N(1) atoms which is
perpendicular to the central aryl ring. The azide moiety
may occupy two positions (only one of which is illus-
trated in Fig. 1) on either side of this plane with equal
probability and there is an angle of 22° between the
perpendiculars to the axial ring and the coordination
plane at N(1). The C(ipso)ꢀNꢀN angle is 135.4(3)°
which is considerably wider than those seen in other
aryl azide structures (typical angles range 115–120°)
2
n-BuLi (1.24 ml, 1.6 M in hexanes). Yield 0.62 g, 51%.
M.p. 120°C darkens, 135–140°C dec. H-NMR (300
MHz, THF-d ), l −0.89 (s, 1H, SbH), 0.99 (d, 12H,
p-CH(CH ) ) JHH=6.9 Hz, 1.26 (d, 12H, o-
1
8
3
3
2
3
CH(CH ) ) J =6.9 Hz, 1.36 (d, 12H, o-CH(CH ) )
3
2
HH
3 2
3
3
JHH=6.6 Hz, 2.85 (sept, 2H, p-CH(CH ) ) JHH=6.9
3 2
3
Hz, 2.97 (sept, 4H, o-CH(CH ) ) JHH=6.9 Hz, 6.42
3
2
3
6 3 HH 6 3
(
d, 2H, m-C H ) J =7.2 Hz, 6.63 (t, 1H, p-C H )
JHH=7.2 Hz, 6.89 (s, 4H, m-Trip); C{ H}-NMR–
3
13
1
8
not obtainable due to rapid decomposition in THF-d ;
7
8
Li-NMR (THF-d ) l −0.65.
2.12. X-ray data collection, the solution and refinement
[
14,15]. The azide moiety is not quite linear and has an
N(1)ꢀN(2)ꢀN(3) angle of 173.5(7)°. The C(ipso)ꢀN(1)
distance 1.408(5) A is normal (cf. CꢀN=1.417(7) A in
Crystals of 1–4 and 6 were coated with hydrocarbon
oil, mounted on a glass fiber and placed in the N cold
,
,
2

1
56
B. Twamley et al. / Journal of Organometallic Chemistry 609 (2000) 152–160
−
1
4
-O NH C N [14]). However, both NꢀN distances,
was observed at 2085 cm
cm
which is close to the 2104
2
4
6
3
−
1
N(1)ꢀN(2) (1.047(4) A
unusually short (cf. 1.270(6) and 1.127(17) A
O NH C N [14]). We have no obvious explanation for
this shortening although we draw attention to the fact
that the use of a closely related terphenyl ligand in
diphosphenes resulted in the shortest known PP double
bond [16]. In the IR spectrum the NN stretching band
,
) and N(2)ꢀN(3) (1.144(7) A
,
), are
observed for PhSCH N [17].
2
3
,
in 4-
The most notable feature of the structure of 2 (Fig.
2) is that the sum of bond angles at the nitrogen atom
is 359°, which indicates an almost trigonal planar coor-
dination geometry at the nitrogen. Fukuyo et al. [18]
have shown that the geometry at the nitrogen in pri-
mary amines may be strongly affected by inter- or
2
4
6
3
Table 1
Crystallographic data for compounds 1–6
1
2
3
4
5
6
Empirical formula
Formula weight
Color
C36H49N3
523.78
Pale yellow
C36H51
497.78
Colorless
N
C37.75H51O2P
567.76
Colorless
C36H51
514.74
Colorless
P
C36H51As
558.69
Colorless
C36H51Sb
605.52
Colorless
Crystal dimensions
0.44×0.22×0.05 0.28×0.22×0.04 0.28×0.28×0.14 0.40×0.16×0.10 0.20×0.20×0.20 0.38×0.16×0.05
(
mm)
Crystal habit
Block
Block
Cube
Needle
Needle
Needle
Crystal system
Space group
Orthorhombic
Pbcm
Orthorhombic
Pnma
Monoclinic
P2 /n
1
Orthorhombic
Pnma
Orthorhombic
Pnma
Orthorhombic
Pnma
Unit cell dimensions
a (A
,
)
)
)
10.930(2)
12.120(2)
25.210(5)
8.586(2)
25.579(5)
14.512(3)
15.512(3)
14.376(3)
16.999(3)
8.0950(16)
25.562(5)
15.904(3)
8.167(2)
25.828(7)
16.083(5)
8.167(2)
25.828(7)
16.083(5)
b (A
,
c (A
,
h (°)
i (°)
111.42(3)
k (°)
3
V (A
Z
,
)
3339.6(12)
4
1.042
0.454
3187.1(11)
4
1.037
0.432
3528.9(12)
4
1.069
0.107
3290.9(11)
4
1.039
0.869
3392.3(16)
4
1.094
1.022
3392.3(16)
4
1.186
0.833
d (g cm−3)
Absorption coefficient
mm
F(000)
Radiation, l (A
Temperature (K)
q (°)
−
1
(
)
1144
1096
1234
1128
1200
1272
,
)
Cu–K ; 1.54178
Cu–K ; 1.54178
Mo–K ; 0.71073 Cu–K ; 1.54178
Mo–K ; 0.71073 Mo–K ; 0.71073
a
a
a
a
a
a
130
113
2576
2270
1883
130
113
2471
2155
1201
0.0730
182
130
45
130
299
93
2
56.35
2523
2222
1450
0.0000
183
52.98
23291
3591
2274
0.0482
202
63.32
11158
6066
4343
0.0438
181
Total data
5037
4595
2616
0.0497
388
Unique data
Observed data I\2|I
Rint
0.0167
191
Parameters
R /R (all data)
Difference map (e A
0.0508/0.1358
−3) 0.449/−0.252
,
0.0631/0.1999
0.189/−0.188
0.0759/0.2041
0.45/−0.334
0.0822/0.2279
0.435/−0.302
0.0469/0.1317
0.439/−0.403
0.0295/0.0774
0.605/−0.419
1
w
Table 2
Selected bond lengths (A
,
) and angles (°) for 1–6
a
Compound
EꢀC
EꢀH
CꢀEꢀH
HꢀEꢀH
CꢀC(ipso)ꢀE
CꢀC(ipso)ꢀC
ArN3 b (1)
ArNH2 (2)
1.408(5)
1.378(8)
1.813(5)
135.4(3) c
120(3)
119.24(14)
120.0(3)
120.1(5)
121.1(4)
121.4(3)
120.0(5)
1.00(5)
1.342(19) (H(2))
119(2)
118.6(4)
{
ArP(O)(OH)H}2 (3)
1
1
.552(4) (O(1))
.512(4) (O(2))
107.6(2) (O(1))
112.5(2) (O(2))
105(3)
104.0(17)
103.8 (av)
ArPH2 (4)
ArAsH2 (5)
ArSbH2 (6)
1.845(7)
1.968(3)
2.17 (av)
1.39(2)
1.484(18)
1.67 (av)
102(2)
107(1)
111 (av)
119.7(3)
119.83(13)
119.56(8) (av)
120.3(6)
120.3(3)
120.51(15)
a
E=N, P, As or Sb.
b
c
Ar=C H -2,6-Trip .
6
3
2
CꢀNꢀN angle.

B. Twamley et al. / Journal of Organometallic Chemistry 609 (2000) 152–160
157
Fig. 1. Thermal ellipsoidal plot (30%) of ArN (1). No hydrogen atoms and only one of the disordered azide moieties are shown. Important bond
3
lengths and angles are in the text and Table 2.
Fig. 2. Thermal ellipsoidal plot (30%) of ArNH (2). Hydrogen atoms except those bound to nitrogen are not shown. Important bond lengths and
2
angles are in Table 2.
intra-molecular interactions, e.g. hydrogen bonding be-
tween amine molecules. For example, p-nitro- or trini-
tro-anilines, which feature strong inter-molecular
hydrogen bonding involving the N(H)ꢀO unit, have
trigonal planar nitrogen coordination, while unsubsti-
tuted aniline has a pyramidal nitrogen geometry [19,20].
Examination of the environment of the hydrogens
bound to the nitrogen in 2 indicates that there is no
possibility of inter-molecular hydrogen bonding in the
solid state structure. However, the structure of 2 does
suggest that there is an intra-molecular interaction be-
tween the amine hydrogen atoms and the ortho phenyl
rings of the m-terphenyl ligand [21]. The N(H)-ring
3.2. The phosphinic acid ArP(O)(OH)H (3)
The phosphinic acid compound ArP(O)(OH)H (3)
results from the reaction of the halide ArPCl2 (the
precursor for 4) with trace amounts of water. Although
it is produced only in small amounts by this process in
the synthesis of ArPCl , its low solubility in comparison
2
with ArPCl ensure its ready crystallization and purifi-
2
cation. Its IR spectrum displays a PꢀH stretching band
−
1
1
at 2410 cm
and the H-NMR spectrum displays
peaks at centered 4.64 and 10.96 ppm which are at-
tributable to the PꢀH hydrogen (JPH=588 Hz) and the
31
1
O–H hydrogen. The P{ H}-NMR spectrum reveals a
peak at 26.77 ppm (JPC=4144 Hz). These spectro-
scopic parameters are very similar to those recently
observed [16] for the closely related compound 2,6-
Mes H C P(O)(OH)H. In the X-ray crystal structure
centroid distance, 3.013 A
.9–3.1 A which is predicted by from the sum of the
van der Waals radii of H and sp hybridized carbon
22]. This interaction may cause the trigonal planar
geometry at the nitrogen atom in 2.
,
; lies within the range of
2
,
2
2
3
6
[
dimerization occurs through hydrogen bonding involv-
ing the OH and PO moieties as shown in Fig. 3.

1
58
B. Twamley et al. / Journal of Organometallic Chemistry 609 (2000) 152–160
Fig. 3. Thermal ellipsoidal plot of {ArP(O)(OH)H}2 (3). Hydrogen atoms except those bound to oxygen and phosphorus are not shown.
Important bond lengths and angles are in the text and Table 2.
Surprisingly perhaps, the size of very large -C H -2,6-
ously discussed) the coordination geometries show the
expected increased pyramidal character. The IR stretch-
ing frequencies of the EꢀH bonds are of medium to
strong intensity which undergo the expected shift to
lower energy with increasing atomic number. The fre-
quencies are within the expected range. For example,
6
3
Trip substituent is insufficient to prevent aggregation.
2
The centrosymmetric dimers feature a PꢁO and PꢀOH
distances of 1.512(4) and 1.552(4) A and the OꢀH and
,
O···HO distances (H atoms located and refined) are
.84(3) and 1.71(4) A. These structural parameters re-
0
,
−
1
semble those found for the dimers in the crystal struc-
ture of {2,6-Mes H C P(O)(OH)H} [16].
the frequency of the SbꢀH band in 6, 1875 cm , is
−1
similar to the 1865 cm
[
observed in Me SiCH SbH
3 2 2
2
3
6
2
−
1
5] or the 1870 cm in t-BuCH SbH [4]. The range of
2 2
1
the chemical shifts of the EꢀH resonances in the H-
NMR spectra, 3.36–2.66 ppm, is relatively narrow.
However, the 2.66 ppm shift of 6 is somewhat
downfield of the 1.79 and 1.75 ppm values reported for
Me SiCH SbH and t-BuCH SbH . Perhaps, this is due
3
.3. The primary pnictanes ArEH (E=P (4), As (5)
2
and Sb (6)
The compounds 4–6 were synthesized by the reduc-
tion of the ArECl precursors [7] with LiAlH . The
3
2
2
2
2
2
4
to the partial shielding of the hydrogens by the ortho-
yield obtained decreased with increasing pnictogen
atomic number from ca. 60% for the phosphane to ca.
1
3
aryl rings of the terphenyl ligands. The C-NMR spec-
tra of 2, 4, 5 and 6 also display a relatively narrow
range of chemical shift values (142.6–132.6 ppm) for
the key C(ipso) atom of the central aryl ring.
40% for the stibane. Attempted reduction of ArBiCl2
with LiAlH gave ArBiBiAr [7] as the only crystalline
4
product. Presumably, the ArBiH2 species is too un-
1
As can be seen from Table 1, the crystals of 4, 5, and
6 are isomorphous. The structures of the three com-
pounds are very similar and are characterized by a
stable to isolate near room temperature. The H- and
1
3
C-NMR spectra of 4–6 displayed no unusual charac-
3
1
teristics and the P-NMR spectrum of 4 featured a
resonance at −139.8 ppm with JPꢀH=208 Hz. These
values are typical for primary phosphanes [22]. The
Table 3
Key spectroscopic and structural data for the pnictanes 2, 4, 5, and 6
3
1
P-NMR chemical shift of 4 is very similar to the
137.8 ppm in 2,6-Mes H C PH [16] but the J for
−
2
3
6
2
PꢀH
the latter (178 Hz) is somewhat lower than the coupling
in 4. The reason for the ca. 40 Hz difference in the
coupling constant is not clear at present.
The major spectroscopic features and selected struc-
tural parameters of the pnictane series 2, 4, 5, and 6 are
presented in Table 3. With the exception of 2 (previ-

B. Twamley et al. / Journal of Organometallic Chemistry 609 (2000) 152–160
159
Fig. 4. Thermal ellipsoidal plot (30%) of ArSbH (6). Hydrogen atoms except those bound to antimony are not shown. Important bond lengths
2
and angles for 6 (and the analogues 4 and 5) are given in Table 2.
plane of symmetry perpendicular to the central aryl
ring plane which incorporates the ipso and para carbon
and pnictogen atom as illustrated by the drawing of the
stibane 6 in Fig. 4. The EꢀC bonds are of normal
length and are close to those seen in the corresponding
at room temperature under an N atmosphere in the
absence of light. Thus 6 probably has similar stability
2
to the crystalline secondary stibane Mes SbH [32]. Pre-
2
sumably, the very large Ar ligands hinder the decompo-
sition, which might involve an association pathway that
would be made more difficult by the large substituent.
ArECl species [7]. The increasing lengths of the PꢀC,
2
AsꢀC and SbꢀC bonds almost exactly mirror the differ-
ences in covalent radii (P, 1.11 A
A
,
,
; As, 1.21 A
,
; Sb, 1.43
3.4. The lithium salts ArE(H)Li (E=N (7), P (8), As
(9), Sb (10))
) between these atoms [23]. In contrast to the struc-
ture of 2, the coordination of the pnictogens in 4, 5 and
is pyramidal and the amount of pyramidal character
6
The pnictanes 2, 4–6 may be readily deprotonated by
organolithium reagents. Thus the addition of LiMe to
an ether solution of 2 results in the in situ generation of
ArN(H)Li in solution. The addition of hexane results in
the precipitation of spectroscopically pure 7 as a white
increases for the P and As derivatives although in the
Sb compound it seems to decrease slightly. This is of
course consistent with the large inversion barriers in
these compounds [24]. There does not appear to be
much tendency toward flattening of the geometries as in
the nitrogen case. Presumably, the less polar nature of
the EꢀH bonds in the heavier pnictanes does not pro-
mote the existence of dipolar interactions between the
EꢀH moieties and the ortho aryl rings which might
favor a more planar geometry at E atom.
1
solid. The H-NMR spectrum of C D displays an NꢀH
6
6
hydrogen signal at 2.06 ppm which is ca. 1 ppm upfield
13
of the NꢀH hydrogens in 2. The C-NMR spectrum of
C(ipso) resonance appears at 157.5 ppm or ca. 15 ppm
downfield of the corresponding resonance in 2.
The heavier pnictanes 4, 5, 6 are readily deproto-
A few crystal structures of heavier primary pnictanes
nated by n-BuLi in a Et O–hexane solvent to afford 8,
9, 10 as yellow powders in 50–80% yield. The H-NMR
2
1
have been reported. These concern MesPH [25], 9-
2
5
5
phosphinotriptycene [26], (h -C H )Fe(h -C H PH )
in C D confirms that the compounds contain just one
5
5
5
4
2
6
6
[
27] and a dibenzobarrellene phosphane [28]. The PꢀH
distance of 1.39(2) A in 4 is comparable to the 1.36(3)
in the dibenzobarrellene [28] but is shorter than the
.42 and 1.437 A PꢀH values determined for PH [29].
The AsꢀH distance in 5, 1.484(18) A
with the ca. 0.1 A difference in covalent radii between P
and As and the 1.519 A AsꢀH bond length in AsH3
30]. Similarly the average SbꢀH bond length, 1.67 A, is
comparable to the 1.707 A distance determined for
SbH [31].
EꢀH proton, which is shifted upfield by 1.6–3.5 ppm.
,
In the case of the phosphorus derivative 8 the J is
PꢀH
13
A
1
,
178 Hz. In the C-NMR spectra, the key resonance of
the ipso-carbon of the central aryl ring appear at
161.1(8), 162.2(9), which are 18.5 and 16.7 ppm
downfield of the precursors 4 and 5. The C-NMR of
10 in THF-d was not observable due to rapid decom-
,
3
,
, is also consistent
13
,
8
,
[
,
position in solution.
,
3
The most remarkable feature of compounds 4, 5, and
is their thermal stability. Both 4 and 5 melt without
4. Supplementary material
6
decomposition at temperatures in excess of 200°C. The
stibane 6 decomposes at 195°C and is indefinitely stable
The X-ray data have been deposited with the Cam-
bridge Crystallographic Data Center as supplementary

1
60
B. Twamley et al. / Journal of Organometallic Chemistry 609 (2000) 152–160
Characterization. ACS Sym. Ser. 357, American Chemical Soci-
ety, Washington, DC, 1987, Chapter 10.
11] G.M. Sheldrick, SHELXTL-Plus. A program package for refine-
ment of crystal structures, G o¨ ttingen, 1989.
[12] XABS2: An empirical absorption connection program. S. Parkin,
B. Moezzi, H. Hope, J. Appl. Cryst. 28 (1995) 53.
publication nos. CCDC-141058-63. Copies of the data
can be obtained on application to CCDC, 12 Union
Rd., Cambridge CB2 1EZ, UK (fax: +44-1223-336-
[
033; e-mail: deposit@ccdc.cam.-ac.uk).
[
13] S. Sasaki, H. Hatsushiba, M. Yoshifuji, Chem. Commun. (1998)
221.
14] A. Mugnoli, C. Mariani, M. Simonetta, Acta Crystallogr. 19
1965) 367.
[15] R.L. Livingston, R. Rao, J. Phys. Chem. 64 (1960) 756.
2
Acknowledgements
[
(
The authors are grateful to the National Science
Foundation for financial support. The Bruker SMART
[
[
16] E. Urnezius, J.D. Protasiewicz, Main Group Chem. 1 (1996) 369.
17] C.J. Pouchert. The Aldrich Library of FT-IR Spectra, vol. 2,
The Aldrich Chemical Company, Milwaukee, 1985.
1000 diffractometer was funded in part by NSF Instru-
mentation Grant CHE-9808259.
[
[
18] M. Fuyuko, K. Hirotsu, T. Higuchi, Acta Crystallogr. Sect. B 38
(
1982) 640.
19] J.R. Holden, C. Dickinson, C.M. Bock, J. Phys. Chem. 76 (1972)
597.
3
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