Synthesis and structures of chiral halo mercury(II) complexes

Article abstract of DOI:10.1016/S0022-2860(98)00509-2

HgCl2 reacts with enantiomerically pure 3-lithio-(S)-(-) or (R)-(+)-N,N-dimethyl-α-(2-naphthyl)ethylamine, (S) or (R)-LiTMNA, to produce (S)_C(R)_Hg-(HgCl), 2a', or (S)_C(R)_Hg-(HgCl), 2a, in fair yields. The bromide (2b) and iodide (2c) analogs were prepared in good yields by reaction of 2a with NaBr and NaI, respectively. The crystal structures of 2a', 2b and 2c show that the Hg atom in each compound is three-coordinate, T-shaped, and slightly pyramidal in the solid state. These three compounds form exclusively as the (S)_C(R)_Hg or (R)_C(S)_Hg diastereomers with average Hg-C and Hg-N distances of 2.08 (2) Angstroem and 2.65 (2) Angstroem, respectively. The Hg-N bond is weak and is easily cleaved in solution to form temperature-dependent equilibrium mixtures of two- and three-coordinate species as deduced from variable temperature NMR spectroscopy. - Keywords: Orthometallation; Mercury; Chiral complexes; CD spectroscopy; X-ray crystallography

Full text of DOI:10.1016/S0022-2860(98)00509-2

Journal of Molecular Structure 475 (1999) 121–130
Synthesis and structures of chiral halo[N,N-dimethyl-a-
(2-naphthyl)ethylamine-3,C,N] mercury (II) complexes
Nizamettin G u¨ l, John H. Nelson*
Department of Chemistry, University of Nevada, Reno, NV 89557-0020, USA
Received 26 February 1998; accepted 24 March 1998
Abstract
HgCl
2
reacts with enantiomerically pure 3-lithio-(S)-( − ) or (R)-( + )-N,N-dimethyl-a-(2-naphthyl)ethylamine, (S) or (R)-
LiTMNA, to produce (S) (R) -{HgCl[C H CH(Me)NMe ]}, 2aЈ, or (S) (R) -{HgCl[C H CH(Me)NMe ]}, 2a, in fair
c
Hg
10
6
2
c
Hg
10
6
2
yields. The bromide (2b) and iodide (2c) analogs were prepared in good yields by reaction of 2a with NaBr and NaI,
respectively. The crystal structures of 2aЈ, 2b and 2c show that the Hg atom in each compound is three-coordinate, T-shaped,
and slightly pyramidal in the solid state. These three compounds form exclusively as the (S) (R) or (R) (S) diastereomers
c
Hg
c
Hg
˚
˚
with average Hg–C and Hg–N distances of 2.08 (2) A and 2.65 (2) A, respectively. The Hg–N bond is weak and is easily
cleaved in solution to form temperature-dependent equilibrium mixtures of two- and three-coordinate species as deduced from
variable temperature NMR spectroscopy. ᭧ 1999 Elsevier Science B.V. All rights reserved.
Keywords: Orthometallation; Mercury; Chiral complexes; CD spectroscopy; X-ray crystallography
1
. Introduction
organometallic mercury (II) complexes. They are
also the first examples where Hg could be considered
to be a stereocenter [2] in the solid state. The mercury
(II) chloride complex (1a) is a useful reagent for the
synthesis of chiral ruthenium (II) half-sandwich com-
plexes (Scheme 1) [3]. As an extension of these earlier
studies, we have prepared the chiral napthyl amine
analogs, [(R)-(TMNA)HgX] (2a–2c) and report
herein their synthesis, characterization and structures
in solution and in the solid state.
We recently reported the synthesis and characteri-
zation of the chiral halo {2-[1-(S)-(dimethylamino)-
ethyl]phenyl-C ,N} mercury (II) complexes (1a–1c)
1
[1]. These complexes are
among the few examples of three-coordinate
*
Corresponding author. Tel.: +00-1-702-7846588; Fax: +00-1-
7
02-7846804; E-mail: jhnelson@equinox.unr.edu
0
022-2860/99/$ - see front matter ᭧ 1999 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(98)00509-2

1
22
N. G u¨ l, J.H. Nelson / Journal of Molecular Structure 475 (1999) 121–130
Scheme 1.
2. Experimental section
rotations were measured on a Perkin-Elmer model
41 polarimeter. Melting points were obtained on a
1
2
.1. Physical measurements
Mel-Temp apparatus and are uncorrected. Elemental
analyses were performed by Galbraith Laboratories,
Knoxville, TN.
NMR spectra of CDCl solutions, unless stated
3
otherwise, were recorded on a Varian Unity Plus
1
5
1
00 spectrometer operating at 500 MHz for H and
2.2. Preparation of racemic a-(2-naphthyl)-
ethylamine
13
25 MHz for C. Chemical shifts are downfield from
internal Me Si. UV-visible spectra were recorded on
4
Jasco J-600 and/or J-40 spectropolarimeters. Optical
Racemic a-(2-naphthyl)ethylamine was prepared

N. G u¨ l, J.H. Nelson / Journal of Molecular Structure 475 (1999) 121–130
123
by a slight modification to the method in the literature
4]. Commercial 88% formic acid (154.6 mL) was
added slowly via an addition funnel to 62.1 g of
solid ammonium carbonate. After the reaction
moderated, the mixture was heated continuously and
then slowly distilled until the temperature was about
the filtrate was obtained the (S)-( + ) ammonium
hydrogen tartrate salt. Liberation of the free amine
as above afforded 11.77 g (0.069 moles, 69.2%) of
the enantiomerically pure (S)-( − ) amine. The (R)-
( + ) amine was obtained in a similar yield by analo-
gous treatment of the material obtained from the fil-
trate from the methanol solution; [a]D = Ϯ 19.1Њ;
m.p. 53ЊC (literature [5] 53ЊC). (S)-( − ) ammonium
(R,R)-hydrogen tartrate m.p. 195–197ЊC; (R)-( − )
ammonium (R,R)-hydrogen tartrate m.p. 188–189ЊC.
[
2
0
170ЊC. Then, over a period of 15 min, 2Ј-aceto-
naphthone (Acros, 50.0 g, 0.29 moles) was added.
The mixture was then heated further to 183ЊC and
maintained at that temperature for 8 h while being
magnetically stirred. The heat was then removed
and the mixture cooled. At 50ЊC distilled water
(200 mL) was added to the mixture and the resulting
mixture was stirred for 2 h. The water was removed by
decantation. Concentrated HCl (120 mL) was added
and the resulting mixture was refluxed at 110ЊC for
1
h. After cooling to ambient temperature, the light-
yellow solid that formed was isolated by filtration and
recrystallized from hot water. To an aqueous solution
of the recrystallized colorless solid, 50% aqueous
NaOH was added until the pH of the solution reached
(R)-( − ) ammonium (R,R)-hydrogen tartrate NMR:
1
4
10. The mixture was extracted with five 50 mL por-
H (500 MHz, DMSO-d ) d 8.00 (d, J(H H ) =
6 1 7
3
tions of CH Cl and the combined CH Cl extracts
1.25 Hz, 1H, H ), 7.96 (d, J(H H ) = 8.5 Hz, 1H,
2
2
2
2
1
6
7
were dried over anhydrous MgSO . The solvent was
removed by rotoevaporation to afford 38.8 g (77.1%)
of a pale-orange colored oil.
H ), 7.93 (m, 1H, H ), 7.92 (m, 1H, H ), 7.66 (dd,
4
6 2 5
3
4
J(H H ) = 8.5 Hz, J(H , H ) = 1.25 Hz, 1H, H ),
6 7 1 7 7
+
7.54 (m, 2H, H ), 4.68 (bs, 3H, NH ), 4.55 (q,
3
,4
3
3
J(HH) = 6.5 Hz, 1H, CH), 3.98 (s, 2H, OH), 1.59
(d, J(HH) = 6.5 Hz, 3H, CH ). C{ H} (125 MHz,
DMSO-d ) d 174.90 (CO , COOH), 137.45 (C ),
3
13
1
2.3. Resolution of the racemic a-(2-naphthyl)-
3
−
2
ethylamine
6
10
1
32.74 (C ), 132.65 (C ), 128.41 (C ), 127.94 (C ),
8 3 2 4
Racemic a-(2-naphthyl)ethylamine was resolved
by a slight modification of the procedure in the litera-
ture [5]. To a solution of 34.0 g (0.23 moles) of (R,R)-
tartaric acid in 400 mL of methanol was added 38.8 g
127.64 (C ) 126.60 (C ), 126.48 (C ), 125.65 (C ),
7 5 6 9
124.68 (C ), 72.02 (COH), 50.06 (CH), 20.96
1
−3
(CH ). UV-Vis data (c = 3.3 × 10 M in EtOH
25ЊC). lmax (nm)/␧ (L mol cm ). 317/1.45 × 10 ,
312/2.21 × 10 , 303/3.45 × 10 , 301/3.24 × 10 ,
229/1.25 × 10 , 227/1.29 × 10 . Circular dichroism
(CD) data: molecular ellipticity [v] (deg cm
dmol ), where [v] = 3300 × (D␧) and (D␧ ) is the
measured CD quantity (in units of L mol cm ) at a
given wavelength; c = 3.3 × 10 M in EtOH at 25ЊC:
[v] = 0, [v]315 = − 66, [v]302 = − 40, c = 1.98 ×
3
−1
−1
2
2
2
2
(0.23 moles) of a-(2-naphthyl)ethylamine and the
3
3
mixture was heated to 50ЊC to bring everything into
solution. The solution was cooled to ambient tempera-
ture and left standing for 2 days. The solid that formed
was isolated by filtration, dissolved in a minimum
amount of water and 50% aqueous NaOH was
added to pH = 10. This solution was extracted with
CH Cl , the extracts were dried over anhydrous
2
l
−1
l
l
l
−
1
−1
−3
3
50
−
4
10 M in EtOH at 25ЊC: [v]276 = + 3960, [v]225 = +
3300, [v]233 = − 19140, [v]221 = − 3168.
2
2
MgSO , and the solvent was removed by rotoevapora-
4
2
0
tion to afford a colorless oil, [a] = − 13.4Њ. Treat-
(S)-( + )-ammonium (R; R)-hydrogen tartrate (3).
D
1
ment of the partially resolved amine with one
equivalent of (R,R)-tartaric acid in hot water afforded
a small amount of the solid (R)-( − ) ammonium
hydrogen tartrate salt which precipitated first. From
NMR: H (500 MHz, DMSO-d ) 7.98 (s, 1H, H ),
6
1
3
7.96 (d, J(H H ) = 8.5 Hz, 1H, H ) 7.92 (m, 1H,
H ), 7.91 (m, 1H, H ), 7.63 (d, J(H H ) = 8.5 Hz,
6
7
6
3
2
5
6
7
+
3
1H, H ), 7.54 (m, 2H, H ), 4.58 (bs, 3H, NH ),
7
3,4

1
24
N. G u¨ l, J.H. Nelson / Journal of Molecular Structure 475 (1999) 121–130
3
4
1
(
1
1
1
.54 (q, J(HH) = 6.5 Hz, 1H, CH), 3.95 (s, 2H, OH),
HCl was added. The mixture was then taken to dry-
ness on a rotary evaporator using a hot water bath. To
the residue was added 40 mL of distilled water and
20 mL of 18 M NaOH solution. The mixture was
extracted with five-40 mL portions of CH Cl . The
3
13
1
.60 (d, J(HH) = 6.5 Hz, 3H, CH ). C{ H}
125 MHz, DMSO-d ) d 174.02 (CO , COOH),
37.54 (C ), 132.53 (C ), 132.41 (C ), 128.04 (C ),
10 8 3 2
27.56 (C ), 127.28 (C ), 126.20 (C ), 125.18 (C ),
24.29 (C ), 71.29 (COH), 49.99 (CH), 20.83 (CH ).
R)-( + ) amine NMR: H: d 7.83 (d, J(H H ) =
.5 Hz, 1H, H ), 7.83 (dd, J(H H ) = 7.0 Hz,
J(H H ) = 1.5 Hz, 1H, H ), 7.83 (dd, J(H H ) =
.0 Hz, J(H H ) = 1.5 Hz, 1H, H ), 7.78 (d,
J(H H ) = 1.5 Hz, 1H, H ), 7.49 (dd, J(H H ) =
.5 Hz, J(H H = 1.5 Hz, 1H, H ), 7.47 (m,
J(H H ) = J(H H ) = 7.0 Hz, J(H H ) = 1.5 Hz,
H, H ), 7.46 (m, J(H H ) = J(H H ) = 7.0 Hz,
J(H H ) = 1.5 Hz, 1H, H ), 4.29 (q, J(HH) =
.5 Hz, 1H, CH), 1.75 (s, 2H, NH ), 1.48 (d, J(HH) =
.5 Hz, 3H, CH3). C{ H} d 145.00 (C ), 133.43
3
−
6
2
4
7
5
9
2
2
combined extracts were dried over anhydrous
1
3
1
3
(
MgSO and the MgSO ·nH O was removed by filtra-
6
7
4
4
2
3
8
tion. The CH Cl was removed on a rotary evaporator
6
2
3
2 2
4
3
to afford a pale-yellow oil. Vacuum distillation (b.p.
2
4
2
4
5
4
7
105ЊC, 0.15 to 0.2 mm Hg) afforded 10.6 g (0.053
3
5
5
4
3
1
mole, 99%) of a colorless oil. NMR: H: d 7.82 (d,
1
7
1
6
7
4
3
3
8
J(H H ) = 8.5 Hz, 1H, H ), 7.82 (dd, J(H H ) =
6 7 6 2 3
1
7
7
3
3
4
4
7.0 Hz, J(H H ) = 1.5 Hz, 1H, H ), 7.82 (dd,
2 4 2
2
3
3
4
3
5
3
3
3
4
1
J(H H ) = 7.0 Hz, J(H H ) = 1.5 Hz, 1H, H ),
4 5 3 5 5
3
3
4
4
5
4
3
4
7.72 (d, J(H H ) = 1.5 Hz, 1H, H ), 7.50 (dd,
1 7 1
2
4
4
3
3
4
6
6
(
J(H H ) = 8.5 Hz, J(H H ) = 1.5 Hz, 1H, H ),
2
6 7 1 7 7
1
3
1
3
3
4
7.47 (m, J(H H ) = J(H H ) = 7.0 Hz, J(H H ) =
1.5 Hz, 1H, H ), 7.44 (m, J(H H ) = J(H H ) =
7.0 Hz, J(H H ) = 1.5 Hz, 1H, H ), 3.40 (q, J(HH)
10
2
3
3
4
3
3
5
3
C ), 132.58 (C ), 128.14 (C ), 127.72 (C ), 127.55
C ), 125.96 (C ), 125.43 (C ), 124.46 (C ), 123.70
8
3
2
5
3
3
4
4
3
5
4
(
6
4
7
9
2
4
4
(
C ), 51.36 (CH), 25.51 (CH ). UV-Vis data (c = 3.3 ×
= 6.5 Hz, 1H, CH), 2.26 (s, 6H, NMe ), 1.46 (d,
2
J(HH) = 6.5 Hz, 3H, CH3). C{ H} d 141.98 (C ),
10
133.35 (C ), 132.76 (C ), 127.94 (C ), 127.76 (C ),
8 3 2 4
1
3
−
3
−1
−1
3
13
1
1
3
1
0
M in EtOH, 25ЊC). lmax (nm)/␧ (L mol cm ).
2
17/24, 315/18, 303/29, 301/36, 274/5.6 × 10 , 230/
.16 × 10 , 228/1.22 × 10 . CD data (c = 3.3 10 M in
3
3
−3
127.58 (C ), 125.92 (C ), 125.85 (C ), 125.83 (C ),
7 5 6 9
2
−1
EtOH, 25ЊC) [v]l (in units of deg cm dmol ),
[
1
−
125.44 (C ), 66.22 (CH), 43.44 (NMe ), 20.32 (CH ).
1
2
3
−2
v] = 0, [v]315 = + 86, [v]302 = + 53 (C = 1.98 ×
UV-Vis data (c = 3 × 10 M in EtOH, 25ЊC) l
(nm)/␧(L mol cm ). 332/1.16 × 10 , 319/1.9 ×
10 , 306/2 × 10 , 303/1.97 × 10 , 294/1.94 × 10 ,
88/2.1 × 10 , 250/2.2 × 10 . CD data (c = 3.3 ×
M in EtOH at 25ЊC) [v] (in units of deg cm
dmol ), [v] = 0, [v]321 = + 211, [v]314 = + 178
350
(c = 6.6 × 10 M in EtOH at 25ЊC) [v]303 = + 5940,
[v]270 = − 30030, [v]240 = + 58080, [v]229 = − 20790,
3
50
max
−
4
−1
−1
2
0
M in EtOH, 25ЊC), [v]276 = − 4620, [v]255
=
2
3
3
2
3630, [v]233 = + 19470, [v]221 = + 3234.
3
3
2
1
−
3
2
0
l
−1
2
(
.4. Preparation of (R)-( + )-N,N-dimethyl-a-
2-naphthyl)ethylamine, and (S)-( − )-N,N-dimethyl-
−5
a-(2-napthyl)ethylamine (R)- and (S)-TMNA
[
v]215 = + 6600.
These two compounds [6] were prepared by
Eschweiler–Clarke [7] methylation of the enantio-
merically pure (R)- and (S)-a-(2-naphthyl)ethyla-
mines. (R)-( + )-a-(2-naphthyl)ethylamine (9.15 g,
2.5. Preparation of 3-lithio-(R)-( + )N,N-dimethyl-a-
(2-naphthyl)ethylamine, (R)-[Li(TMNA)]
0.053 mole) was dissolved, with cooling, in 13 mL
of 90% formic acid and 10.9 mL of 37% aqueous
formaldehyde was added all at once to the magneti-
cally stirred mixture. Upon addition of all the
reagents, a white cloud formed above a pale-yellow
solution. Within a few minutes, the white cloud dis-
appeared and the mixture began to bubble vigorously
Under a dry nitrogen atmosphere and utilizing stan-
dard Schlenk techniques, tert-butyl lithium (48.5 mL
of a 1.7 M solution in pentane) was added slowly via
an addition funnel to (R)-( + )-TMNA (14.86 g,
75 mmol) in freshly distilled hexane (80 mL), all at
room temperature. The mixture was stirred for 18 h
at room temperature. The orange-colored solid that
formed was collected on a filter stick under a dry
nitrogen atmosphere and washed with several por-
tions of freshly distilled hexane to remove t-BuLi
as CO was formed. After the gas production sub-
2
sided, the reaction mixture was heated up to 80ЊC
and then refluxed gently for 15 h. The reaction mix-
ture was then cooled in an ice bath and 40 mL of 4 M

N. G u¨ l, J.H. Nelson / Journal of Molecular Structure 475 (1999) 121–130
125
(
until the orange-colored solid became a very pale
2.7. Preparation of (R)-[(TMNA)HgX] Compounds,
2b,c
orange) and stored in the filter stick under nitrogen
until it was used for the preparation of (R)-( + )-
Hg(TMNA)Cl.
2.7.1. Synthesis and characterization of 2b (X = Br)
To a stirred solution of 2a (0.512 g, 1.18 mmol) in
methanol (100 mL) was added solid NaBr (1.22 g,
2
.6. Preparation of (R) (S) -(TMNA)HgCl, 2a
c Hg
1
1.78 mmol), and the resulting cloudy mixture was
To a stirred solution of 13.51 g (65.5 mmol) of (R)-
Li(TMNA)] in 80 mL of anhydrous Et O at − 77ЊC
was slowly added 17.86 g (66 mmol) of powdered
stirred for 2.5 h at room temperature. The solvent
was removed by rotary evaporation and the residual
solid was extracted with CH Cl . The extracts were
[
2
2
2
HgCl over the course of 1 h. After the addition of
filtered and the solvent was removed from the filtrate
by rotoevaporation to afford 2b as a colorless
microcrystalline solid: yield 0.478 g (85.3%); m.p.
73–75ЊC. Analysis calculated for C H BrHgN·
2
HgCl2 was complete, the mixture was gradually
warmed to room temperature and was stirred for an
additional 10 h. The cream-colored suspension was
then filtered through celite to remove LiCl. The sol-
vent was removed from the filtrate by rotoevaporation
and the resulting colorless microcrystalline product
1
4
16
0.5CH OH: C, 36.74; H, 3.55; N, 2.76. Found: C,
3
1
36.58; H, 3.37; N, 2.81. NMR: H (25ЊC) d 7.92
(s, 1H, H ), 7.80 (m, 2H, H ), 7.70 (s, 1H, H ),
6
2,5
3
1
was recrystallized from a hot hexane/Et O solution:
7.49 (m, 2H, H ), 3.72 (q, J(HH) = 6.5 Hz, 1H,
CH), 2.32 (s, 6H, NMe ), 1.43 (d, J(HH) = 6.5 Hz,
3H, CH ); H ( − 60ЊC) spectrum similar to that at
2
3,4
3
yield 10.1 g (35.6%); m.p. 134–136ЊC. Analysis cal-
2
1
culated for C H C1HgN: C, 38.72; H, 3.68; N, 3.22.
1
4
16
3
1
Found: C, 38.63; H, 3.74; N, 3.15. NMR: H (25ЊC) d
25ЊC except that the singlet at d 2.32 is split into two
1
3
1
7
7
2
.93 (s, 1H, H ), 7.91 (m, 2H, H ), 7.69 (s, 1H, H ),
singlets at d 2.44 and 2.17. C{ H} (25ЊC): 149.71
6
2,5
1
3
1
2
.48 (m, 2H, H ), 3.70 (q, J(HH) = 6.5 Hz, 1H, CH),
(C , J(HgC) = 2445.1 Hz), 146.99 (C , J(HgC) =
3
,4
1
1
0
3
2
.32 (s, 6H, NMe ), 1.43 (d, J(HH) = 6.5 Hz, 3H,
56.3 Hz), 137.22 (C , J(HgC) = 136.6 Hz), 133.14
(C ), 132.74 (C , J(HgC) = 227.3 Hz), 127.66 (C ),
127.38 (C ), 126.43 (C ), 126.24 (C , J(HgC) =
4 5 9
156.6Hz), 125.89 (C ), 65.69 ( J(HgC) = 80.3 Hz,
6
2
2
1
3
CH ); H ( − 60ЊC) spectrum similar to that at 25ЊC
3
8
3
7
3
except that the singlet at d 2.23 is split into two sing-
1
3
1
3
lets at d 2.44 and 2.17; C{ H} (25ЊC): d 146.52 (C ,
1
0
2
1
13
1
J(HgC) = 57.7 (Hz), 145.24 (C , J(HgC) =
484.6 Hz), 137.46 (C2, J(HgC) = 132.8 Hz),
33.27 (C ), 132.85 (C , J (HgC) = 228.7 Hz),
CH), 42.16 (NMe ), 19.92 (CH ); C{ H} ( − 60ЊC)
2 3
1
2
2
1
spectrum similar to that at 25ЊC except for two singlets
3
at d 44.27 and 40.25 due to splitting of the NMe singlet
8
3
2
−3
1
27.67 (C ), 127.42 (C ), 126.56 (C ), 126.38 (C ,
at d 42.16. UV-Vis data (c = 2.67 × 10 M in EtOH,
7
4
5
9
3
−1
−1
2
J(HgC) = 158.0 Hz), 125.98 (C ), 65.85 (CH,
25ЊC) l (nm)/␧ (L mol cm ): 323/2.7 × 10 , 320/
6
max
3
1
2
2
2
3
J(HgC) = 82.4 Hz), 42.29 (NMe ), 20.13 (CH );
2 × 10 , 308/4.6 × 10 , 305/4 × 10 , 296/1.3 × 10 ,
290/1.6 × 10 , 252/1.7 × 10 . CD data: (c = 3.3 ×
10 M in EtOH, 25ЊC) [v] (in units of deg cm
dmol ), [v] = 0, [v]321 = − 340, [v]314 = − 297.
2
3
3
1
3
3
C{ H} ( − 60ЊC) spectrum similar to that at 25ЊC
−3
2
except for two singlets at d 44.50 and d 40.38 due to
l
−1
splitting of the NMe singlet at d 42.29. UV-Vis data
2
350
−6
−3
(
c = 2.68 × 10 M in EtOH, 25ЊC) l
(nm)/␧
(c = 6.6 × 10 M in EtOH, 25ЊC) [v]285 = + 4950,
max
−1
−1
2
2
(L mol cm ) 323/2.8 × 10 , 320/2.1 × 10 , 308/
[v]273 = + 12210, [v]266 = − 13530, [v]240 = − 29370,
[v]227 = + 11880, [v]214 = − 14520.
2
2
3
4
1
.7 × 10 , 305/4.3 × 10 , 296/1.3 × 10 , 290/1.5 ×
3
3
0 , 259/2.1 × 10 . CD data: since CD curves of
enantiomeric pairs agreed to within 2% (Fig. 4),
only those of [(R)-(TMNA)HgCl] are reported as
2.7.2. Synthesis and characterization of 2c (X = I)
The preparation was similar to that of 2b except
that NaI was used in place of NaBr. Compound 2c
was obtained as a pale yellow microcrystalline solid:
yield 0.496 g (75%): m.p. 53–55ЊC. Analysis calcu-
lated for C H HgIN·H O: C, 30.93; H, 3.31; N,
2
molecular ellipticity [v] (in units of deg cm
l
−1
−3
dmol ): (c = 3.31 × 10 M in EtOH, 25ЊC),
‰
vŠ = 0, [v]320 = − 257, [v]313 = − 224, (c = 6.6 ×
3
50
−
6
1
9
9
0 M in EtOH, 25ЊC), [v]283 = + 3696, [v]276 = +
240, [v]266 = + 15510, [v]239 = − 32340, [v]219 = +
570.
14
16
2
1
2.58. Found: C, 30.98; H, 3.27; N, 2.43. NMR: H

1
26
N. G u¨ l, J.H. Nelson / Journal of Molecular Structure 475 (1999) 121–130
(
25ЊC) 7.95 (s, 1H, H ), 7.81 (m, 1H, H ), 7.80 (m,
2.8. X-ray data collection and processing
6
2
1
H, H ), 7.72 (s, 1H, H ), 7.47 (m, 2H, H ), 3.77 (q,
5 1 3,4
3
J(HH) = 6.5 Hz, 1H, CH), 2.31 (s, 6H, NMe ), 1.43
Colorless crystals of (S)-( + )-(a)-(2-naphthyl)ethyl-
ammonium (R,R)-hydrogen tartrate (3), 2aЈ, 2b and
2c) were obtained by slow evaporation of methanol
(tartrate salt) or hexane solutions (2aЈ, 2b and 2c). Crys-
tal data and details of data collection are given in Table
2. Suitable crystals were mounted on glass fibers and
placed on a Siemens P4 diffractometer. Intensity data
2
3
1
(d, J(HH) = 6.5 Hz, 3H, CH ); H ( − 60ЊC) spectrum
3
similar to that at 25ЊC except that the singlet at d 2.31
is split into two singlets at d 2.43 and 2.16; C{ H}
1
3
1
1
(
(
25ЊC) (156.57 (C , J(HgC) = 2313.8 Hz), 147.84
1
2
2
C , J(HgC) = 56.7 Hz), 137.12 (C , J(HgC) =
1
0
2
3
1
2
1
6
2
34.5 Hz), 133.09 (C ), 137.74 (C , J(HgC) =
8 3
18.5 Hz), 127.73 (C ), 127.40 (C ), 126.36 (C ),
were taken in the q-mode at 298 K with Mo-K mono-
7
4
5
a
3
˚
26.24 (C9, 3 J(HgC) = 148.8 Hz), 125.88 (C6),
chromated radiation (l = 0.71073 A). Three check
5.84 (CH, J(HgC) = 76.0 Hz), 42.24 (NMe ),
reflections monitored every 100 reflections showed
random ( Ͻ 2%) variation during the data collections.
The data were corrected for Lorentz, polarization
effects and absorption using an empirical model derived
from azimuthal data collections. Scattering factors and
corrections for anomalous dispersion were taken from a
standard source [8]. Calculations were performed with
the Siemens SHELTXL PLUS Version 5.03 software
package on a personal computer. The structures
were solved by direct methods. Anisotropic thermal
parameters were assigned to all non-hydrogen atoms.
Hydrogen atoms were refined at calculated positions
with a riding model in which the CH vector was fixed
2
1
3
1
0.31 (CH3); C{ H} ( − 60ЊC) spectrum similar to
that at 25ЊC except for two singlets at d 44.35 and
4
4
2
3
1
1
0.33 due to splitting of the NMe singlet at d
2
−
3
2.24. UV-Vis data (c = 3.3 × 10 M in EtOH,
−
1
−1
2
5ЊC) lmax2 (nm)/␧ (L mol cm ): 323/2.6 × 10 ,
2
2
20/2 × 10 , 308/4.7 × 10 , 305/4.3 × 10 , 296/1.4 ×
0 , 290/1.9 × 10 , 253/1.8 × 10 . CD data: (c = 3.3 ×
3
3
3
−3
2
−1
0
in EtOH, 25Њ) [v] (in units of deg cm dmol ),
l
[
=
+
v]350 = 0, [v] = 422, [v]315 = − 373, [v]306 = − 191 (c
322
−6
6.6 × 10 in EtOH, 25ЊC), [v]274 = + 12540, [v]267
=
10560, [v]254 = + 2640. [v]245 = − 15510, [v]228 = +
5610, [v]222 = − 25410.
Fig. 1. Structural drawing of (S)-( + )-a-(2-naphthyl)ethylammonium (R,R) hydrogen tartrate showing the atom numbering scheme (40%
˚
˚
probability ellipsoids). Hydrogen atoms have an arbitrary radius of 0.1 A. Selected bond distances (A) and angles (Њ) are: C(11)–C(12) = 1.513
3): C(11)–C(1) = 1.517 (3); C(11)–N(1) = 1.504 (3); C(1)–C(11)–N(1) = 111.5 (2), C(1)–C(11)–C(12) = 113.2 (2), N(1)–C(11)–C(12) =
08.2 (2).
(
1

N. G u¨ l, J.H. Nelson / Journal of Molecular Structure 475 (1999) 121–130
127
Table 1
Crystallographic data for compounds 2aЈ, 2b, 2c and 3
2
aЈ 2b
2c
3
e
Formula
FW
C
14
H
16ClHgN
C
14
H
16BrHgN·0.5CH
3
OH
C
14
H
16HgINO
C
16 6
H19NO
434.32
494.78
541.77
321.32
Crystal system
Orthorhombic
5.965 (1)
13.357 (1)
18.158
Orthorhombic
6.1089 (8)
13.079 (1)
39.593 (3)
–
Monoclinic
11.556 (2)
6.057 (1)
13.077 (2)
113.371 (7)
840.1 (2)
2
Orthorhombic
7.712 (4)
7.854 (4)
25.66 (2)
–
˚
a (A)
˚
b (A)
˚
c (A)
b (Њ)
V (A )
–
˚
3
1446.7 (3)
4
3116.8 (6)
1554 (2)
4
d
Z
8
Space group
P2
1.994
108.02
1
2
1
2
1
P2
2.100
124.26
1
2
1
2
1
P2
2.142
109.87
1
1 1 1
P2 2 2
1.373
10.6
−3
r Calculated (g cm
)
−1
m (cm
)
Transmission min/max
Flack parameter
0.2561/1.00
− 0.03 (3)
0.0451
0.0948
1.056
0.706/0.975
− 0.03 (2)
0.0655
0.0630
0.997
0.288/0.978
− 0.01 (2)
0.0572
0.1086
1.034
0.843/0.892
− 0.9 (10)
0.0458
0.1109
1.057
a
R(F)
Rw(F )
2
b
c
GOF
a
R(F) = SkF
o
l − lF
c
k/SlF
o
l
b
c
d
e
2
2
2
o
2
0.5
0.5
R
w
(F
2
) = [S(q[F
o
− F
c
])]/S[w(F
) ]
2
2 2
GOF = S = [S[q(F
o
− F
c
) /(n − p)]]
There are two inequivalent molecules and 0.5 CH
O solvate
3
OH in the unit cell
H
2
˚
at 0.96 A. Solvent hydrogens for 2b and 2c were not
in good (77.1%) yield [4] and resolved by a slight
modification of the literature procedures [5]. We
have consistently obtained yields of 55–69% of (R)-
included in the refinements.
(
+ )-a-(2-naphthyl)ethylamine and its (S)-( − ) enan-
3
. Results and discussion
tiomer. Freda et al. [5] reported that resolution of the
amine from a hot water (R,R)-tartaric acid solution
gave a product with [a]D = + 9Њ (ethanol) which
Racemic a-(2-naphthyl)ethylamine was prepared
Fig. 2. Circular dichroism (CD) curves of EtOH solutions of (R)-
− )-a-(2-naphthyl)ethylammonium (R,R) hydrogen tartrate (- - -)
and (R)-( + )-a-(2-naphthyl)ethylamine (——).
(
Fig. 3. Circular dichroism (CD) spectrum of (R)-TMNA in EtOH.

1
28
N. G u¨ l, J.H. Nelson / Journal of Molecular Structure 475 (1999) 121–130
Table 2
Selected structural parameters for complexes 2aЈ, 2b and 2c
˚
Bond lengths (A)
Bond angles (Њ)
Sum of angles Distance of Hg
around Hg (Њ)
from the
˚
C
1
–N–X plane (A)
X
Cl
Br
Hg–X
2.330(4)
2.451(2)
.460(2)
2.628(1)
HgC
1
HgN
2.69(1)
X–Hg–C
176.2(5)
175.8(5)
175.6(6)
174.1(5)
175.4(6)
1
X–Hg–N
106.8(3)
102.1(3)
106.6(4)
102.7(4)
104.6(4)
1
C –Hg–N
2.07(1)
74.2(6)
74.0(6)
74.4(7)
72.9(7)
73.9(7)
357.4
351.9
356.6
349.7
353.9
0.0688(6)
0.0306(6)
0.0846(7)
0.0835(7)
0.0668(7)
2.08(2)
2.10(2)
2.06(2)
2.08(2)
2.64(1)
2.65(2)
2.63(2)
2.65(2)
2
I
Average
represented less than 50% enantiomeric excess, and
enantiomerically pure amine was obtained in two
steps. We find that treatment of the racemic amine
with a hot methanol solution of (R,R)-tartaric acid
hydrogen tartrate salt and of the free amine are nearly
mirror images. From water the (R)-( − )-ammonium
(R,R)-hydrogen tartrate salt crystallizes first from
which the (R)-( + ) free amine is obtained upon treat-
ment of the salt with concentrated NaOH solution.
The enantiomerically pure (R)-( + )- and (S)-( − )-
N,N-dimethyl-a-(2-naphthyl) ethylamines [6], (R)-
( + )- and (S)-( − )-TMNA, were then prepared by
Eschweiler–Clarke [7] methylation of the (R)-( + )-
and (S)-( − )-a-(2-naphthyl) ethylamines. Their CD
spectra (Fig. 3) are indicative of their optical purity.
Complex 2aЈ and its enantiomer, 2a, were obtained by
a procedure analogous to that which we previously
used to prepare complex 1a [1]. The bromide (2b)
and iodide (2c) analogs were prepared by metathetic
reactions of 2a with NaBr and NaI respectively.
Attempts to prepare 2a via the reaction of TMNA
with mercury (II) acetate and LiCl, as reported by
Huo et al. [9], for similar amines were unsuccessful.
X-ray crystal structures of 2aЈ, 2b and 2c show
similar features (Table 1 and Table 2) except that for
2
0
gave a product with [a]D = + 13Њ (ethanol). Then
treatment of the partially resolved and liberated
amine with a hot water solution of (R,R)-tartaric
2
0
acid gave enantiomerically pure amine, [a]D
=
+19.1Њ (ethanol). On the basis of the X-ray crystal
structure of the (S)-( + )-ammonium (R,R)-hydrogen
tartrate salt (3) (Fig. 1) and a comparison of the CD
spectrum of the (R)-( − )-ammonium (R,R)-hydrogen
tartrate salt with that of the liberated free amine
(
(
Fig. 2), we conclude that the (S)-( + )-ammonium
R,R)-hydrogen tartrate salt crystallizes first from
methanol and gives the (S)-( − ) free amine upon
treatment of this salt with concentrated NaOH solu-
tion. Note that the CD spectra of the ammonium
2
b two inequivalent molecules are present in the asym-
metric unit and the crystal contains one half molecule
of methanol, 2c contains a molecule of H O, and 2aЈ
2
contains the (S)-( − ) amine. The structure of 2aЈ
(Fig. 4) is representative. All three complexes exist
as discrete molecules with no intermolecular contacts
˚
less than 3.5 A. These molecules are only the second
reported examples of diastereomeric organometallic
Hg(II) compounds. The coordination geometry is
best described as T-shaped, which is the preferred
geometry for such three-coordinate species [10]. The
five-membered chelate ring, consisting of the Hg(1)-
C(1)-C(10)-C(11)-N(1) atoms, has the expected
envelope (puckered) conformation [11] (Fig. 4) in
Fig. 4. Circular dichroism (CD) curves of EtOH solutions of
(
(
S)-( − )-[(TMNA)HgCl] (——) and (R)-( + )-[(TMNA)HgCl]
- - -).

N. G u¨ l, J.H. Nelson / Journal of Molecular Structure 475 (1999) 121–130
129
Fig. 5. Structural drawing of (S)-[(TMNA)HgCl] (2aЈ) showing the atom numbering scheme and a view of the conformation of the chelate ring
˚
illustrating the CH group locations (40% probability ellipsoids). Hydrogen atoms have an arbitrary radius of 0.1 A.
3
order to minimize steric interactions among the
methyl groups. The metrical parameters are unexcep-
tional. According to the criteria (d HgN Ͻ 3.2 A)
rapid. However, at − 60ЊC two equally intense reso-
1
3
nances are observed for both nuclei ( C d 44.50,
1
˚
40.38; H d 2.44, 2.17), indicating the diastereotopic
suggested by Canty et al., [12] the Hg–N distances
constitute bonding (albeit weak) interactions.
The lability of the Hg–N bond is evidenced by the
nature of the two N-methyl groups due to blocked
nitrogen inversion as a result of nitrogen coordination
to mercury.
temperature dependence of the NMe resonances in
The optical activities of the amines and the mercury
complexes were determined by obtaining their room
temperature UV-Vis and CD spectra in ethanol in the
210 to 350 nm region, which corresponds to p–p*
transitions of the naphthyl chromophore. With respect
to the UV-Vis spectra, all three complexes show
2
1
13
1
the H and C{ H} NMR spectra of CDCl solutions
3
of the complexes. At 25ЊC only one resonance is
observed for the C (d 42.04) and H (d 2.32) nuclei
of the NMe group which is possible only if the
2
Hg–N bond is cleaved and nitrogen inversion is

1
30
N. G u¨ l, J.H. Nelson / Journal of Molecular Structure 475 (1999) 121–130
absorption maxima with essentially the same lmax and
values. Compounds 2a–c show CD spectra with the
priority numbers [14]: 1(X = Cl, Br, I), 2(N), 3(C1)
and 4 (the apex of the pyramid).
␧
same rotational sense, i.e., negative Cotton effects are
observed at the longest wavelength (by convention)
Acknowledgements
[13] where any such effect is detectable (ϳ320 nm).
The positions of the absorption maxima are essen-
tially the same for the three compounds, but the values
We would like to thank Professor David A.
Lightner for his generous permission to use the
JASCO spectropolarimeters and also Dr. Stefan A.
Boiadjiev for helpful discussions on CD techniques
and spectra.
of the molecular ellipticity [v] increase with increas-
l
ing mass of the coordinated halide. Fig. 4 is represen-
tative; the [v] values for all three compounds are
l
summarized in Section 2. The CD spectra of the
free amine and the mercury complexes are of opposite
rotational sense (compare Figs. 3, and 4). Since the
lack of N-coordination at ambient temperature is
established for these complexes (vide supra) the
reversal in the sense of the CD curves can be
accounted for only by the asymmetric perturbation
in the electronic transitions of the naphthyl chromo-
phore caused by Hg coordination to the naphthyl ring
carbon.
References
[
1] S. Attar, J.H. Nelson, J. Fischer, Organometallics 14 (1995)
776.
2] D. Mislow, J. Siegel, J. Am. Chem. Soc. 106 (1984) 3319.
4
[
[3] (a) H.C.L. Abbenius, M. Pfeffer, J.P. Sutter, A. de Cian, J.
Fischer, H.-J. Li, J. H. Nelson, Organometallics, 12 (1993)
4
464; (b) S. Attar, V.J. Catalano, J.H. Nelson, Organometal-
lics, 15 (1996), 2932.
Finally, we suggest that the Hg atom can be con-
sidered a stereocenter in compounds 2aЈ, 2b and 2c.
Our rationale is as follows. In the solid-state structures
of 2aЈ, 2b and 2c (Table 2) the Hg atom deviates by an
[
4] M.L. Moore, in: R.A. Adams, W.E. Buchmann, A.H. Blatt,
L.F. Fieser, J.R. Johnson, H.R. Snyder (Eds.), Organic Reac-
tions, Vol. 5, Wiley, New York, 1949, p. 320.
[5] A. Freda, B. Sjoberg, R. Sandberg, Acta Chem. Scand. 11
(1957) 1609.
˚
average of 0.0668 (7) A from the mean plane defined
[
6] K. Tani, L.D. Brown, J. Ahmed, J.A. Ibers, M. Yokota, A.
Nakamura, S. Otsuka, J. Am. Chem. Soc. 99 (1977) 7876.
7] (a) C.A. Cope, E. Ciganek, L.J. Fleckenstein, M.A.P. Mei-
singer, J. Am. Chem. Soc. 82 (1960) 4651; (b) H.T. Clarke,
H.B. Gillespie, S.Z. Weishaus, J. Am. Chem. Soc. 55 (1933)
by the X(Cl, Br, I), N, and Cl atoms. The average
values for the sum of the three angles around Hg
[
[353.9 (7)Њ] is less than 360Њ (the value expected for
a planar structure). Thus, the molecules are pyramidal,
with Hg located at the apex of each pyramid and
connected to three different groups. Compounds 2aЈ,
4571.
[8] International Tables for X-ray Crystallography, vol. C, D.
Reidel Publishing Co., Boston, 1992.
2b and 2c are only slightly less pyramidal than com-
[9] S.Q. Huo, Y.J. Wu, Y. Zhu, L. Yang, J. Organomet. Chem. 470
(1994) 17; 481 (1994) 235.
pounds 1a–c [1] for which the average deviation of
Hg from the plane and the average value for the sum
of the three angles around Hg were found to be 0.12 A
[10] P.G. Eller, D.C. Bradley, M.B. Hursthouse, D.W. Meek,
Coord. Chem. Rev. 24 (1977) 1.
˚
[11] C.J. Hawkins, Absolute Configuration of Metal Complexes,
Wiley, New York, 1971.
and 353.7 (5)Њ, respectively. The absolute configura-
tion of the chiral carbon in these compounds is not
affected by coordination of Hg to the aryl ring. Thus,
we propose that compounds 2a–c like 1a–c and their
respective enantiomers be considered diastereomeric
complexes as they all contain two stereocenters in the
solid state. The absolute configuration at Hg in 2aЈ is
[
12] (a) A.J. Canty, J.B. Deacon, Inorg. Chim. Acta 45 (1980)
L225; (b) A.J. Canty, B.M. Gatehouse, J. Chem. Soc., Dalton
Trans. (1976) 2018.
[
[
13] C. Djerassi, E. Bunnenberg, Proc. Chem. Soc. 8 (1963) 299.
14] (a) R.S. Cahn, C. Ingold, V. Prelog, Angew. Chem., Int. Ed.
Engl. 5 (1966) 385; (b) K. Stanley, M.C. Baird, J. Am. Chem.
Soc. 97 (1975) 6598; (c) T.E. Sloan, Top. Stereochem. 12
(1981) 1.
(
R) and in 2b and 2c is (S) assuming the following