Sulfinylamine metathesis at oxo metal species - Convenient entry into imido metal chemistry

Article abstract of DOI:10.1039/c0dt01133a

The exchange of terminal metal oxo functionalities by N-organo and N-sulfonylimido functionalities via metathesis with bent, thus very reactive sulfinyl amines R-NSO and sulfinyl sulfonylamides R-SO₂-NSO is described. It is demonstrated that in many cases sulfinyl amine metathesis offers a more convenient entry into imido complex synthesis than the much better investigated isocyanate metathesis at oxo complexes or condensation reactions with amines and silylated amines. Improved syntheses for some known key compounds and several new complexes of the type [V(NR)Cl₃] and [M(NR)₂Cl₂] (M = Cr, Mo, W) are described. Emphasis is put on the synthesis of formerly unknown base free Lewis acids with electron-withdrawing N-substituents such as haloaryl and sulfonylaryl. Surprisingly, even [CrO₂Cl₂] is selectively transformed by sulfinylamines into aryl imido derivatives without any reduction by sulfur dioxide. The molecular structures of novel haloaryl imido complexes [Cr(NAr)₂Cl₂] Ar = C₆F₅ and 2,4,6-Cl₃C₆H₂ as determined by X-ray crystallography are reported. The Royal Society of Chemistry 2011.

Full text of DOI:10.1039/c0dt01133a

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PAPER
Sulfinylamine metathesis at oxo metal species - convenient entry into imido
metal chemistry†
Konstantin A. Rufanov,a,b Jennifer Kipkea and Jo¨rg Sundermeyer*a
Received 31st August 2010, Accepted 3rd November 2010
DOI: 10.1039/c0dt01133a
The exchange of terminal metal oxo functionalities by N-organo and N-sulfonylimido functionalities
via metathesis with bent, thus very reactive sulfinyl amines R-NSO and sulfinyl sulfonylamides
R-SO2-NSO is described. It is demonstrated that in many cases sulfinyl amine metathesis offers a more
convenient entry into imido complex synthesis than the much better investigated isocyanate metathesis
at oxo complexes or condensation reactions with amines and silylated amines. Improved syntheses for
some known key compounds and several new complexes of the type [V(NR)Cl3] and [M(NR)2Cl2] (M =
Cr, Mo, W) are described. Emphasis is put on the synthesis of formerly unknown base free Lewis acids
with electron-withdrawing N-substituents such as haloaryl and sulfonylaryl. Surprisingly, even
[CrO2Cl2] is selectively transformed by sulfinylamines into aryl imido derivatives without any reduction
by sulfur dioxide. The molecular structures of novel haloaryl imido complexes [Cr(NAr)2Cl2] Ar = C6F5
and 2,4,6-Cl3C6H2 as determined by X-ray crystallography are reported.
strategy up to date, in particular if the free metal Lewis acids
Introduction
and not their ether, amine or other base adducts are the desired
Imido complex chemistry of transition metals has experienced a
products. While isocyanate metathesis is working well for vanadyl
considerable development during the last two decades.1 Formally,
the imido ligand [NR]2- coordinates to a metal by one s and up to
two p orbital interactions, similar to the cyclopentadienyl ligand.2
This so called cyclopentadienyl imido ligand analogy was first
formulated by Schrock3 and refined and developed by Gibson and
others.4 It is the fundament of the isolobal relationship of group
chloride8 it does not work at all for related chromyl chloride. As
both, chromium and vanadium imido complexes are prominent
in catalytic olefin polymerization reactions,6,5 ring opening of
epoxides,9 aziridines10 and catalytic cyclopropanation of olefins,11
we set out to develop a general and powerful method for their
direct synthesis. Metathetical transformations of oxo complexes
5
4 metallocene fragments [Ti(h -C5R5)2] and their corresponding
imido complex fragments of group 5 and 6, [V(NR)(h -C5R5)]
with sulfinyl amines RN
S
O have been observed in a handful
5
of documented examples. Slawisch reported that reaction of
VOCl3 with PhNSO gave a product with a similar IR spectrum
as the product of PhNCO metathesis.12 However there was no
further proof for the analytical purity of the product. Cenini
et al. were the first to prove, that aryl sulfinylamines ArNSO do
react metathetically with [ReOCl3(PPh3)]13 and [MoO2(chelate)2]
(chelate = acac, S2CNR2)14 to yield pure imido complexes. We
found, that the more reactive coordination polymer [MoO2Cl2]
can undergo complete metathesis with sulfonyl sulfinylamide
TosNSO, the fully characterized [Mo(NTos)2Cl2]15 was used in
oxidative nitrene [NTos] transfer reactions. Aryl sulfinylamines
ArNSO can be activated by [MoO2Cl2L2]16 and corresponding
imido complexes were used in metathetical [O]/[NAr] exchange
reactions realized in the catalytic imidation of aldehydes and
dimethylformamide.17 In our hands, sulfinylamine metathesis at
oxo metal species did work in the generation of coordinatively
unsaturated, electron poor, thus highly reactive imido species,
when standard strategies such as silyl amine condensation or
isocyanate metathesis failed. Here we report a more systematic
investigation of the scope of sulfinyl amine metathesis as an entry
and [Cr(NR)2]. While imido vanadium5 and chromium6 complexes
already have proven their catalytic activity in olefin polymeriza-
tions, there is still a need for convenient large scale syntheses for
the precursor complexes [V(NR)Cl3] and [Cr(NR)2Cl2]. There is
a wide range of synthetic methods available for introducing the
imido ligand,1,7 but only few of them are applicable in general.
Among the metathetical transformations of oxo complexes using
RN Y type reagents such as isocyanates (Y = CO), iminophos-
phoranes (Y = PR3), carbodiimides (Y = CNR), and organoimines
(Y = CHR), the isocyanate metathesis is by far the most powerful
aFachbereich Chemie der Philipps-Universita¨t Marburg, Hans-
Meerwein-Strasse, D-35032, Marburg an der Lahn, Deutschland.
E-mail: jsu@staff.uni-marburg.de; Fax: +49-6421-2825711; Tel: +49-
6421-285693
bA. N. Nesmeyanov Institute of Organoelement Compounds Russian
Academy of Sciences, Vavilov str. 28, RUS-117813, Moscow, Russia
† CCDC reference numbers 155134 (13) and 155135 (15). For crys-
tallographic data in CIF or other electronic format see DOI:
10.1039/c0dt01133a
1990 | Dalton Trans., 2011, 40, 1990–1997
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into imido complex chemistry. Emphasis is put on coordinatively
unsaturated vanadium and chromium imido complexes having
electron withdrawing N-substituents such as haloaryl and arylsul-
fonyl. For some known and important key compounds of imido
complex chemistry with electron releasing N-alkyl and N-aryl
substituents our alternative synthetic protocol is given as well.
161.45 (d, 1JCF = -264 Hz, Ar–Cpara). 19F-NMR (188 MHz, C6D6):
d/ppm = -107.3 (d, 1 H, 4JFF = 15.2 Hz, Ar–Fpara), -108.4 (d, 2 H,
4
˜
JFF = 15.2 Hz, Ar–Fortho). IR (Nujol): n = 1632 m, 1611 m, 1512
w, 1493 m, 1298 m (br), 1198 s, 1177 w, 1127 s, 1049 s, 999 m, 984
w, 870 w, 853 m, 843 s, 781 w, 741 w, 708 w cm-1. EI-MS: m/z =
193 (M+, 53%), 145 (C6H2F3N+, 100%).
[V(N-t-Bu)Cl3] (1)27. At room temperature 18.26 g (10 mL,
105.4 mmol) of VOCl3 in 20 mL of hexane were added within 5 min
to a ~50% hexane solution of t-BuNSO (12.69 g, 106.6 mmol).
The mixture was refluxed for 2 h while SO2 was driven out by
a slow stream of argon. The colour of the mixture turned dark
Experimental
Materials and methods
All synthetic procedures were performed under an atmosphere
of purified argon 99.99% using standard Schlenk techniques.
Solvents were distilled over appropriate drying agent and degassed
prior to use. NMR spectra on 1H, 13C and 19F nuclei were obtained
on Bruker ARX-200, AC-300 and on Varian VXR-400 spectrom-
eters. Mass spectra were recorded on Varian CH-7a MAT device
using electron impact with excitation energy of 70 eV. CrO2Cl2 and
VOCl3 were used as supplied (Avocado, Strem). The following
starting materials were synthesized according to the literature:
MO2Cl2 (M = Mo, W),18 t-BuNSO,19 MesNSO,20 DipNSO,21
TsNSO,22 Mes-SO2-NSO,23 2,4,6-Cl3C6H2NSO,24 C6F5NSO,25 and
2,4,6-Br3C6H2NSO.26 New sulfinyl amides and sulfinyl amines
were obtained by the standard procedure22 via interaction of
ArNH2 with excess SOCl2 in refluxing benzene.
◦
green. Volatiles were removed at 20 C and 10-2 mbar and the
residue was suspended in 20 mL of pentane with the aid of
ultrasound. For 24 h the suspension was kept at -80 ◦C, the dark-
green precipitate was separated by decanting, washed with chilled
pentane and dried in high vacuum. Yield: 22.87 g (95%) dark-
green, microcrystalline solid. Spectroscopic data in accord with
1
literature: H-NMR (CDCl3, 200 MHz): d/ppm = 1.61 (s, 18 H,
C(CH3)3). 13C-NMR (C6D6, 50 MHz): d/ppm = 28.8 (C(CH3)3),
82.3 (C(CH3)3).
General synthetic protocol toward [V(NAr)Cl3] complexes
Variant A: 1.0 equivalent of VOCl3 (~1–2 M) in n-octane and
1.1 equivalents of ArNSO were combined at room temperature
and heated at reflux for 3 h, while a slow stream of argon was
passed through the solution in order to remove SO2 released. After
removal of all volatiles in vacuo the residue was crystallized from
hot hexane by cooling the solution slowly down to -80 ◦C. Variant
B: to a 1–2 M toluene solution of 1 equiv. of VOCl3 1.1 equiv. of
ArNSO or ArSO2NSO dissolved in toluene were added at room
temperature. The reaction mixture was stirred for 1–6 h at room
temperature, while a slow stream of argon was passed through
the solution in order to remove SO2 released. After removal of
all volatiles at 20 ◦C and 10-3 mbar the residue was suspended in
pentane (20 mL) with the aid of ultrasound and the suspension was
stored at -80 ◦C for 24 h. The precipitate was separated by either
filtration at low temperature or decanting the mother liquid. The
product was washed with pre-cooled pentane and dried at 20 ◦C
and 10-3 mbar.
2,4,6-i-Pr3C6H2-SO2NSO. A mixture of 8.00 g (28.2 mmol)
of 2,4,6-i-Pr3C6H2-SO2NH2 and 4.26 g (2.60 mL, 30.0 mmol)
of SOCl2 was stirred in benzene (50 mL) for 2 h at 25 ◦C.
It was refluxed for an additional 8 h. A yellow solution was
formed while HCl was evolving. All volatiles were removed
under reduced pressure. The yellow microcrystalline residue was
spectroscopically pure and was used without further purification.
Yield: 9.02 g (97%) of the yellow solid m.p. 48 ◦C. Anal. calcd for
C15H23NO3S2 (329.47): C 54.68, H 7.04, N 4.25. Found: C 54.21,
1
H 6.98, N 4.47. H-NMR (200 MHz, CDCl3): d/ppm = 1.24 (d,
3
3
6 H, JHH = 6.7 Hz, CH(CH3)2, para), 1.27 (d, 12 H, JHH = 6.7
Hz, CH(CH3)2, ortho), 2.90 (sep, 1 H, 3JHH = 6.7 Hz, CH(CH3)2, para),
3
4.12 (sep, 2 H, JHH = 6.7 Hz, CH(CH3)2, ortho), 7.19 (s, 2 H, Har).
13C-NMR (50 MHz, CDCl3): d/ppm = 23.5 (CH(CH3)2, para), 24.5
(CH(CH3)2, ortho), 29.8 (CH(CH3)2, para), 34.3 (CH(CH3)2, ortho), 124.1
(Ar–Cmeta), 132.7 (Ar–Cpara), 150.9 (Ar–Cortho), 155.0 (Ar–Cipso). IR
[V(NDip)Cl3] (2)8e. This compound was obtained via variant
A from 6.25 g (36 mmol) of VOCl3 and 8.92 g (40 mmol) of
DipNSO. A spontaneously formed red solution turned dark-green
within 3 h. Yield of 11.4 g (95%) as dark-green needles, m.p. 28 ◦C.
Anal. calcd for C12H21Cl3NV (336.60): C 43.34, H 5.15, N 4.21.
˜
(Nujol): n = 1598 s, 1565 s, 1188 vs, 1082 vs, 1036 s, 958 w, 938
m, 888 s, 844 m, 817 w, 756 w, 685 vs, 657 vs, 628 vs, 592 s, 555
m, 541 m, 527 m, 492 w cm-1. EI-MS: m/z, 330 (M+, 45%), 268
+
+
(C15H23SO2 , 23%), 77 (C6H5 , 100%).
1
Found: C 43.14, H 5.47, N 4.39. H-NMR (C6D6, 200 MHz):
2,4,6-F3C6H2-NSO. To a solution of 10.00 g (67.98 mmol)
of 2,4,6-trifluoroaniline in benzene (100 mL) 9.70 g (5.91 mL,
81.57 mmol) of SOCl2 in benzene (30 mL) were added. The mixture
was stirred for 2 h at 25 ◦C and 8 h at reflux. After removing
3
d/ppm = 1.16 (d, 12 H, JHH = 6.8 Hz, CH(CH3)2), 4.32 (sept, 2
3
H, JHH = 6.7 Hz, CH(CH3)2), 6.64 (m, 3 H, Ph–H). 13C-NMR
(C6D6, 50 MHz): d/ppm = 24.0 (CH(CH3)2), 29.3 (CH(CH3)2),
122.8 (Ph–Cmeta), 132.7 (Ph–Cpara), 151.6 (Ph–Cortho), 171.8 (Ph–
◦
of all volatiles at 40 C and 10-2 mbar the microcrystalline
Cipso). 51V-NMR (C6D6, 105 MHz): d/ppm = 392. IR (Nujol): n =
˜
product was obtained and used without further purification. Yield:
12.74 g (97%) light-yellow solid. An analytically pure sample was
obtained by sublimation at 55 ◦C and 10-4 mbar. Anal. calcd for
C6H2F3NOS (193.14): C 37.31, H 1.04, N 7.25. Found: C 37.26,
3061 w, 1582 m, 1385 m, 1366 m, 1346 w, 1256 m, 1229 w, 1061 w,
934 w, 797 s, 752 s, 532 w, 475 s, 442 w, 280 w, 411 m cm-1. EI-MS:
m/z = 333 (M+, 18%), 175 (DipN+, 84%).
1
H 1.10, N 7.45. H-NMR (200 MHz, C6D6): d/ppm = 6.03 (t, 4
[V(NC6F5)Cl3] (3). This compound was obtained via variant B
from 4.68 g (28 mmol) of VOCl3 and 6.93 g (30 mmol) C6F5NSO.
The colour of the solution turned from yellow to dark blue.
Yield 85% (8.04 g) dark-red powder. Anal. calcd for C6Cl3F5NV
H, 3JHF = 8.0 Hz, Ph–Hmeta). 13C-NMR (50 MHz, C6D6): d/ppm =
3
3
100.8 (t, JCF = 28.0 Hz, Ar–Cmeta), 116.16 (t, JCF = 16.4 Hz,
Ar–Cipso), 154.54 (dd, 1JCF = -255 Hz, 3JCF = 15.0 Hz, Ar–Cortho),
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(338.36): C 21.37, N 4.16. Found: C 21.59, N 4.35. 13C-NMR
(CDCl3, 100 MHz): d/ppm = 136.6 (m, Arf–C), 144.2 (m, Arf–C),
145.8 (m, Arf–C) ppm. 19F-NMR (CDCl3, 188 MHz): d/ppm =
-142.2 (d, 2 F, 3JFF = 15.3 Hz, Arf–Fortho), -144.7 (t, 1 F, 3JFF = 20.4
Hz, Arf–Fpara), -160.2 (t, 2 F, 3JFF = 20.3 Hz, Arf–Fmeta). 51V-NMR
(CDCl3, 105 MHz): d/ppm = 210. IR (Nujol): n = 1632 w, 1509 s,
1306 w, 1261 m, 1071 s, 1022 m, 998 s, 801 w, 723 w, 489 m, 410 w
cm-1. EI-MS: m/z = 337 (M+ - H, 43%), 183 (C6F5N+, 100%).
Ts–Hortho). 13C-NMR (50 MHz, CDCl3): d/ppm = 21.8 (Ts–CH3),
126.5 (Ts–Cortho), 130.2 (Ts–Cmeta), 141.7 (Ts–Cpara), 146.8 (Ts–Cipso).
51
˜
V-NMR (188 MHz, CDCl3): d/ppm = -933.0. IR (Nujol): n =
2234 w, 1807 w, 1653 w, 1591 m, 1489 w, 1304 m, 1294 m, 1262 w,
1188 s, 1177 vs, 1121 m, 1080 m, 1045 w, 1017 w, 970 w, 907 w, 845
w, 810 vs, 723 w, 702 m, 654 s, 573 vs, 530 vs, 476 m cm-1. EI-MS:
˜
m/z = 327 (M+, 19%), 155 (C7H7SO2 , 100%).
+
[V(NSO2Mes)Cl3] (8). At room temperature 500 mg
(0.274 mL, 2.89 mmol) of VOCl3 in toluene (10 mL) are added to
682 mg (2.89 mmol) MesSO2NSO in toluene (10 mL). The mixture
was stirred for 24 h at 20 ◦C. After 1 h and again after 6 h SO2 was
removed together with some tolue◦ne under reduced pressure. After
24 h volatiles were removed at 40 C and 10◦-3 mbar, and the crude
product was purified by sublimation at 95 C and 3 ¥ 10-5 mbar.
Yield: 891 mg (87%) red solid. Anal. calcd for C9H11Cl3NO2SV
(354.55): C 30.46, H 3.10, N 3.95. Found: C 30.98, H 3.29, N 3.89.
1H-NMR (200 MHz, CDCl3): d/ppm = 2.37 (s, 3 H, Ar–CH3, para),
2.77 (s, 6 H, Ar–CH3, ortho), 7.11 (s, 2 H, Har). 13C-NMR (50 MHz,
CDCl3): d/ppm = 23.4 (Ar–CH3 ortho), 24.8 (Ar–CH3, para), 128.2
(Ar–Cpara), 129.0 (Ar–Cortho), 133.1 (Ar–Cmeta), 143.2 (Ar–Cipso). IR
[V(N-2,4,6-F3C6H2)Cl3] (4). This compound was obtained via
variant B from 1.28 g (7.38 mmol) VOCl3 and 1.71 g (8.85 mmol)
F3C6H2NSO (90 min). The colour of the solution turned from
yellow to dark green. Yield 83% (1.85 g) dark-green crystalline
solid. Anal. calcd for C6H2Cl3F3NV ¥ C7H8 (394.52)—crystalline
toluene solvate, according to NMR: C 30.46, H 1.36, N 4.18.
1
Found: C 30.04, H 1.55, N 4.42. H-NMR (200 MHz, C6D6):
3
d/ppm = 5.46 (t, 2 H, JHF = 8.0 Hz, Ph–Hmeta). 13C-NMR (50
2
3
MHz, C6D6): d/ppm = 100.2 (dt, JCF = 25.2 Hz, JCF = 3.7 Hz,
Ar–Cortho), 145.7 (Ar–Cmeta), 149.3 (Ar–Cipso), 165.2 (Ar–Cpara). 19F-
NMR (188 MHz, C6D6): d/ppm = -95.2 (d, 1 H, 4JFF = 15.4 Hz,
4
Ph–Fpara), -110.3 (d, 2 H, JFF = 15.4 Hz, Ph–Fortho). IR (Nujol):
˜
˜
(Nujol): n = 1807 w, 1653 w, 1592 m, 1491 w, 1304 m, 1294 m, 1260
n = 1626 s, 1601 s, 1505 w, 1493 w, 1323 w, 1181 m, 1134 s, 1049
w, 1189 s, 1178 s, 1121 m, 1081 m, 1043 w, 1017 w, 907 w, 845 w,
809 vs, 702 m, 654 s, 573 vs, 530 s, 476 m cm-1. EI-MS: m/z = 355
(M+, 5%), 199 (MesSO2N+, 37%), 118 (C9H11+, 100%).
s, 997 w, 978 w, 847 s, 737 m, 718 w, 696 w, 654 w, 619 w, 606 w,
573 w, 532 w, 509 s, 486 s, 407 s cm-1. EI-MS: m/z = 301 (M+ - H,
58%), 145 (C6H2F3N+, 100%).
[Cr(O)(N-t-Bu)Cl2] (9)28. A solution of 189 mg (1.22 mmol)
CrO2Cl2 in 10 mL of CCl4 were added at 0 ◦C to a solution of
321 mg (2.68 mmol) t-BuNSO in 10 mL of CH2Cl2. The mixture
was stirred for 10 min at 0 ◦C and 10 min at 10 ◦C while SO2 was
driven out by a stream of argon. Volatiles were removed at 20 ◦C
and 10-2 mbar, the red powder was washed with 5 mL of chilled
[V(N-2,4,6-Cl3C6H2)Cl3] (5). This compound was obtained
via variant B from 3.65 g (21.07 mmol) VOCl3 and 6.64 g
(27.39 mmol) C6H2Cl3NSO (30 min). The colour of the solution
spontaneously turned from yellow to dark green. Yield 85% (6.30
g) dark-green solid. Anal. calcd for C6H2Cl6NV (351.75): C 20.49,
1
H 0.57, N 3.98. Found: C 20.79, H 0.63, N 4.02. H-NMR (200
◦
pentane and dried at 20 C and 10-2 mbar. Yield 176 mg (69%).
MHz, C6D6): d/ppm = 6.24 (s, 2 H, Ar–Hmeta). 13C-NMR (50 MHz,
C6D6): d/ppm = 128.3 (Ar–Cmeta), 135.9, 136.7 (Ar–Cortho bzw. Ar–
Anal. calcd for C4H9Cl2CrNO (210.02): C 22.88, H 4.32, N 6.67.
1
C
˜
para). 51V-NMR (131 MHz, C6D6): d/ppm = 276.6. IR (Nujol):
Found: C 22.30, H 4.23, N 5.73. H-NMR (CDCl3, 200 MHz):
d/ppm = 1.87 (s, 9 H, C(CH3)3). 13C-NMR (CDCl3, 50 MHz):
n = 1551 vs, 1522 m, 1512 m, 1306 m, 1206 m, 1190 m, 1153 s, 1084
m, 1063 w, 972 w, 876 w, 858 s, 839 w, 820 s, 806 m, 729 w, 721 w,
710 w, 696 w, 669 w, 611 w, 575 w, 529 w, 484 w, 453 s cm-1. EI-MS:
˜
d/ppm = 28.0 (C(CH3)3), 82.5 (C(CH3)3). IR (Nujol): n = 1634
w, 1363 w, 1296 w, 1262 m, 1103 s(br), 800 m, 723 w, 665 m, 580
w cm-1. EI-MS: m/z = 210 (M+, 2%), 121 (C4H8NCr+, 49%), 56
m/z = 352 (M+, 12%), 196 (C6H2Cl3N+, 100%), 158 (VCl3 , 28%).
+
+
+
(C4H8 , 96%), 41 (C3H5 , 100%).
[V(N-2,4,6-Br3C6H2)Cl3] (6). This compound was obtained
via variant A from 3.12 g (18 mmol) of VOCl3 and 7.52 g (20 mmol)
of 2,4,6-Br3C6H2NSO in a yield of 7.42 g (85%) as dark-green
crystals. M.p. = 157 ◦C, anal. calcd for C6H2Br3Cl3NV (485.10): C
14.86, H 0.42, N 2.89. Found: C 15.09, H 0.29, N 3.15. 1H-NMR
(C6D6, 300 MHz): d/ppm = 6.75 (s, 2 H, Ph–H). 13C-NMR (C6D6,
75 MHz): d/ppm = 134.0 (Ph–Cmeta), 125.5 (Ph–Cpara), 137.5 (Ph–
[Cr(N-t-Bu)2Cl2] (10)29. The solutions of 963 mg (8.08 mmol)
t-BuNSO in and 566 mg (3.67 mmol) CrO2Cl2 in 20 mL of CCl4
were combined at room temperature and refluxed for 30 min while
a slow stream of argon was passed through the mixture. After
◦
30 min all volatiles were removed at 20 C and 5 ¥ 10-3 mbar.
The purple-red residue was washed with cold pentane and dried in
high vacuum. Yield of 585 mg (60%) purple-red microcrystalline
powder. Analytical data were identical with those reported in the
C
ortho), 141.6 (Ph–Cipso). EI-MS: m/z = 485 (M+, 11%), 450 (M+ -
Cl, 79%), 406 (M+ - Br, 10%), 328 (ArN+, 21%).
1
literature: H-NMR (CDCl3, 200 MHz): d/ppm = 1.58 (s, 18 H,
[V(NTs)Cl3] (7). To a solution of 7.94 g (34.64 mmol) TsNSO
in toluene (40 mL) another solution of 5.00 g (2.74 mL,
28.86 mmol) VOCl3 in toluene (20 mL) was slowly (10 min) added
at room temperature. The mixture was stirred for 6 h at 20 ◦C while
a slow stream of argon is passed through the solution. Volatiles
were removed at 40 ◦C and 10-◦3 mbar, and the crude product was
purified by sublimation at 80 C and 3 ¥ 10-5 mbar. Yield: 7.71
g (78%) purple crystals. Anal. calcd for C7H7Cl3NO2SV (326.50):
C(CH3)3). 13C-NMR (CDCl3, 50 MHz): d/ppm = 30.4 (C(CH3)3),
82.5 (C(CH3)3).
General procedure for the synthesis of [Cr(NAr)2Cl2]
2.2 equiv. of sulfinyl amine were added to a solution of CrO2Cl2
(1.0 equiv., 0.5–1.5 M) in CCl4. The reaction mixture was either
stirred for 24 h at room temperature (variant A) or refluxed for
30 min (variant B), while a slow stream of argon was passed trough
the solution in order to carry out SO2. After removal of all volatiles
1
C 25.75, H 2.16, N 4.29. Found: C 26.35, H 2.45, N 4.17. H-
NMR (200 MHz, CDCl3): d/ppm = 2.47 (s, 3 H, Ts–CH3), 7.39
◦
3
3
(d, 2 H, JHH = 7.7 Hz, Ts–Hmeta), 7.91 (d, 2 H, JHH = 7.7 Hz,
at 20 C and 10-3 mbar, the red-black product was washed with
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the aid of ultrasound treatment by several portions of pentane
(20 mL) and finally dried in high vacuum.
28.16, H 0.79, N 5.47. Found: C 27.89, H 0.72, N 5.83. 1H-NMR
(200 MHz, C6D6): d/ppm = 6.39 (s, 4 H, Ar–Hmeta). 13C-NMR (50
MHz, C6D6): d/ppm = 128.3 (Ar–Cmeta), 134.2 (Ar–Cortho), 137.2
[Cr(NMes)2Cl2] (11)30. This compound was obtained via vari-
ant A obtained from 1.71 g (11 mmol) of CrO2Cl2 and 4.4 g
(24.2 mmol) of MesNSO in a yield of 3.74 g (87%) as a red
microcrystalline material. Analytical data were in accord with
those reported in the literature. Anal. calcd for C18H22Cl2CrN2
(289.29): C 55.54, H 5.70, N 7.20. Found: C 55.17, H 5.38, N
˜
(Ar–Cpara), 158.5 (Ar–Cipso) ppm. IR (Nujol): n = 1545 s, 1520 w,
1188 w, 1144 m, 1082 m, 964 w, 872 w, 862 m, 822 m, 802 w, 719 w,
706 m, 621 w, 592 w, 563 w, 475 m cm-1. EI-MS: m/z = 512 (M+,
7%), 195 (C6H2Cl3N+, 36%), 36 (HCl+, 100%).
[Cr(N-2,4,6-Br3C6H2)2Cl2] (16). This compound was obtained
via variant A from 1.19 g (7.7 mmol) of CrO2Cl2 and 5.8 g
(15.4 mmol) of 2,4,6-Br3C6H2NSO. Yield: 3.95 g (89%) reddish-
brown microcrystalline powder. Anal. calcd for C12Cl2H4Br6CrN2
(634.32) C 18.51, C 0.52, N 3.60. Found: C 17.59, C 0.81, N 3.09.
1H-NMR (C6D6, 300 MHz): d/ppm = 6.77 (s, 2 H, Ph–H) ppm.
13C-NMR (C6D6, 75 MHz): d/ppm = 134.6 (Ph–CHmeta), 130.2
(Ph–Cpara), 128.5 (Ph–Cortho), 120.8 (Ph–Cipso) ppm. EI-MS: m/z =
777 (M+, 0.5%), 657 (M+ - Cl - Br, 0.6%), 577 (C+ - Cl - 2Br,
0.02%), 449 (M+ - NAr, 0.2%), 416 (M+ - NAr - Cl, 0.9%).
1
7.02. H-NMR (C6D6, 200 MHz): d/ppm = 1.84 (s, 6 H, Mes-
CH3para), 2.25 (s, 12 H, Mes-CH3ortho), 6.23 (s, 4 H, Mes-Hmeta
)
ppm. 13C-NMR (C6D6, 50 MHz): d/ppm = 19.0 (Mes-(CH3)ortho),
22.0 (Mes-(CH3)para), 129.4 (Mes-Cmeta), 138.5 (Mes-Cpara), 142.9
(Mes-Cortho), 165.0 (Mes-Cipso).
[Cr(NDip)2Cl2] (12)31. This compound was obtained via vari-
ant A from 1.71 g (11 mmol) of CrO2Cl2 and 5.4 g (24.2 mmol)
of DipNSO in a yield of 4.58 g (88%) as red–brown powder.
The compound decomposes at 320 ◦C but may be sublimed at
95 ◦C and 3 ¥ 10-3 mbar. Anal. calcd for C24H34Cl2CrN2 (473.44):
[Mo(NC6F5)2Cl2] (17). A mixture of MoO2Cl2 (2.00 g,
10 mmol) and C6F5NSO (4.08 g, 22 mmol) in toluene (25 mL)
was heated at reflux for 3 h until evolution of SO2 was finished.
After cooling the reaction mixture down to room temperature a
slow stream of an inert gas was passed trough the solution in
order to remove the traces of SO2. A red precipitate of the desired
bis-imido derivative was filtered off and washed several times by
20 mL portions of◦pentane and dried in vacuum. Yield 5.02 g
(95%). M.p. = 270 C (decomp.) Anal. calcd for C12Cl2F10MoN2
(528.98): C 27.25, N 5.30. Found: C 26.99, N 5.44. 19F-NMR
1
C 60.89, H 7.24, N 5.92. Found: C 59.44, H 6.97, N 5.75. H-
3
NMR (C6D6, 200 MHz): d/ppm = 1.08 (d, 24 H, JHH = 6.8 Hz,
CH(CH3)2), 2.96 (sept, 4 H, 3JHH = 6.7 Hz, CH(CH3)2), 7.02 (s, 6 H,
Ph–H). 13C-NMR (C6D6, 50 MHz): d/ppm = 23.1 (CH(CH3)2),
30.0 (CH(CH3)2), 123.7 (Ph–Cmeta), 128.3 (Ph–Cpara), 138.9 (Ph–
˜
ortho). IR (Nujol): n = 2855 s, 1642 w, 1582 m, 1296 m, 1262 w,
C
1221 w, 1142 w, 1080 m(br), 1022 m, br, 912 w, 799 m, 754 w, 721
w, 563 m cm-1. EI-MS: m/z = 473 (M+, 0.9%), 438 (M+ - Cl, 12%),
175 (DipN+, 57%), 160 (Dip-H, 71%), 119 (C9H12+, 25%), 36 (Cl,
100%).
3
(C6D6, 188 MHz): d/ppm = -161.9 (d, 4 F, JFF = 15.1 Hz, Arf–
3
Fortho), -165.5 (t, 2 F, JFF = 20.4 Hz, Arf–Fpara), -173.0 (t, 4 F,
3
JFF = 20.2 Hz, Arf–Fmeta). IR (Nujol): n = 1634 w, 1611 w, 1514 vs,
[Cr(NC6F5)2Cl2] (13). This compound was obtained via vari-
ant A from 1.10 g (7 mmol) of CrO2Cl2 and 3.56 g (15.4 mmol)
of C6F5NSO. Yield 2.88 g (84%) deep-red microcrystalline solid.
Anal. calcd for C12Cl2F10CrN2 (485.03): C 29.72, N 5.78. Found:
C 29.31, N 5.59. 19F-NMR (C6D6, 188 MHz): d/ppm = -130.85
˜
1344 m, 1261 w, 1231 m, 1155 w, 1067 s, 991 s, 804 m, 729 m, 494
m, 442 w cm-1. EI-MS: m/z = 530 (M+, 69%), 178 (C6F5N+, 23%),
162 (C6F4N+, 100%), 148 (C6F4, 52%).
[Mo(NSO2Mes)2Cl2] (18). 500 mg (2.51 mmol) [MoO2Cl2] and
1.19 g (5.03 mmol) MesSO2NSO were refluxed for 2 h in toluene
(40 mL). Then the mixture was cooled to room temperature while
a slow stream of argon was passed through the solution. The
yellow precipitate was separated by filtration, washed with pentane
and dried in high vacuum. Yield: 1.23 g (87%). Anal. calcd for
C18H22Cl2MoN2O4S2 (561.35): C 38.51, H 3.95, N 4.99. Found: C
3
3
(d, 4 F, JFF = 18.4 Hz, Arf–Fortho); -140.59 (t, 2 F, JFF = 24.0
Hz, Arf–Fpara); -160.88 (t, 4 F, JFF = 21.1 Hz, Arf–Fmeta) ppm.
3
EI-MS: m/z = 362 ([C6F5N NC6F5]+, 78%), 195 (C6F5N+, 79%),
+
167 (C6F5 , 67%).
[Cr(N-2,4,6-F3C6H2)2Cl2] (14). This compound was obtained
via variant B from 5.35 g (34.67 mmol) of CrO2Cl2 and 14.74
g (76.31 mmol) of 2,4,6-F3C6H2NSO. Yield: 13.61 g (95%) dark
red crystalline solid. Anal. calcd for C12H4Cl2CrF6N2 (413.07): C
34.89, H 0.98, N 6.78. Found: C 35.13, H 0.95, N 7.04. 1H-NMR
(200 MHz, C6D6): d/ppm = 5.65 (s, br, 4 H, Ar–Hmeta). 13C-NMR
(50 MHz, C6D6): d/ppm = 100.8 (Ar–Cmeta), 142.4 (Ar–Cipso), 159.0
1
38.31, H 4.06, N 5.16. H-NMR (200 MHz, CD3CN): d/ppm =
2.27 (s, 6 H, Ar–CH3 para), 2.57 (s, 12 H, Ar–CH3, ortho), 7.00 (s, 4 H,
Har) ppm. 13C-NMR (50 MHz, CD3CN): d = 20.3 (Ar–CH3 ortho),
22.4 (Ar–CH3 para), 125.8 (Ar–Cmeta), 132.0 (Ar–Cpara), 138.2 (Ar–
˜
ortho), 142.3 (Ar–Cipso). IR (Nujol): n = 1584 m, 1462 vs, 1377 s,
C
(dd, 1JCF = -265.1 Hz, 3JCF = 12.8 Hz, Ar–Cortho), 163.7 (d, 1JCF
=
1319 m, 1293 s, 1095 s, 995 m, 808 w, 684 m, 556 m, 518 w, 470 w
cm-1. EI-MS: m/z = 562 (M+, 3%), 197 (C9H11SO2N+, 100%).
-262.8 Hz, Ar–Cpara). 19F-NMR (188 MHz, C6D6): d/ppm = -94.8
(d, 2 H, 4JFF = 15.6 Hz, Ar–Fpara), -108.0 (d, 4 H, 4JFF = 15.6 Hz,
[Mo(NSO2-2,4,6-i-Pr3C6H2)2Cl2] (19). This compound was
obtained analogously to 18 from 1.50 g (7.54 mmol) [MoO2Cl2]
and 4.97 g (15.09 mmol) TripSO2NSO. Yield: 4.24 g (77%) yellow
solid. Anal. calcd for C30H46Cl2MoN2O4S2 (729.67): C 49.38, H
6.35, N 3.84. Found: C 49.19, H 6.23, N 4.02. 1H-NMR (200 MHz,
˜
Ar–Fortho). IR (Nujol): n = 1601 s, 1564 m, 1358 m, 1350 s, 1186
w, 1179 m, 1130 s, 1047 w, 1040 m, 995 w, 972 w, 959 w, 866 m,
851 w, 843 m, 729 w, 642 w, 621 w, 613 w, 598 w, 517 w, 503 w
cm-1. EI-MS: m/z = 414 (M+, 8%), 268 (M+ - C6H2F3N, 31%), 145
(C6H2F3N+, 100%).
3
CD3CN): d/ppm = 1.25 (d, 12 H, JHH = 7.4 Hz, CH(CH3)2 para),
3
[Cr(N-2,4,6-Cl3C6H2)2Cl2] (15). This compound was obtained
via variant B from 5.30 g (34.37 mmol) of CrO2Cl2 and 18.34 g
(75.61 mmol) of 2,4,6-Cl3C6H2NSO. Yield: 16.36 g (93%) dark
red crystalline solid. Anal. calcd for C12H4Cl8CrN2 (511.80): C
1.29 (d, 24 H, JHH = 7.0 Hz, CH(CH3)2 ortho), 2.97 (sep, 4 H,
3
3JHH = 6.8 Hz, CH(CH3)2 ortho), 3.48 (sep, 2 H, JHH = 6.8 Hz,
˜
CH(CH3)2 para), 7.21 (s, 4 H, Har) ppm. IR (Nujol): n = 1585 m,
1462 s, 1378 m, 1319 m, 1293 s, 1094 m, 995 m, 808 w, 684 m, 556
This journal is
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©

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m, 518 w, 468 w, 440 w cm-1. EI-MS: m/z = 449 (M+-C15H23SO2N,
Table 1 Crystal data and structure refinement for 13 and 15
+
5%), 281 (C15H23SO2N+, 89%), 77 (C6H5 , 100%).
Chemical formula
C12Cl2CrF10N2 (13) C12H4Cl8CrN2 (15)
485.04 511.77
FW/g mol-1
Crystal size/mm
Habit, colour
Diffractometer type
Radiation
T/K
[W(NC6F5)2Cl2] (20). A mixture of WO2Cl2 (2.83 g, 9.9 mmol)
and C6F5NSO (4.53 g, 19.8 mmol) in toluene (25 mL) was heated
at reflux for 10 h while a slow stream of argon was passed through
the solution. The volume of the solvent was reduced to 5 ml,
pentane (20 ml) was added and the brownish-beige precipitate was
isolated by decanting and washing by several portions of pentane
(~20 mL) under ultrasonic irradiation. The product is insoluble in
toluene and CHCl3. Yield 5.65 g (97%). M.p. = 303 ◦C (decomp.).
Anal. calcd for C12Cl2F10N2W (616.88): C 23.36, N 4.54. Found:
C 23.00, N 4.45. EI-MS: m/z = 618 (M+, 63%), 437 (M+ - C6F5N,
10%), 162 (C6F4N+, 11%), 148 (C6F4, 15%). 20 dissolves in dme
and crystallizes as base adduct [W(NC6F5)2Cl2(dme)] in close to
quantitative yield.
0.14 ¥ 0.12 ¥ 0.10 0.24 ¥ 0.21 ¥ 0.09
Prism, deep red
Stoe IPDS
Mo-Ka
Cube, deep red
Enraf Nonius CAD4
Mo-Ka
170(2)
198(2)
Cell
200
25
determination/reflections
Crystal system
Space group
a/pm
Monoclinic
P21/n, Z = 4
786.29(8)
1520.00(14)
1326.41(14)
90
101.879(12)
90
1551.3(1)
2.077
Monoclinic
C2/c, Z = 4
1421.57(6)
858.08(5)
1461.07(8)
90
96.439(5)
90
1770.99(16)
1.919
b/pm
c/pm
a/◦
b/◦
g /◦
3
˚
V/A
r
calcd/g cm-3
q-Range for data collection/◦ 2.06– 25.00
2.78–24.96
1618
Reflections collected
Independent reflections
Observed reflections
Absorption correction
Solution
Refinement
Parameters
10 478
Crystallographic study32
2735 [Rint = 0.0628] 1553 [Rint = 0.0140]
1846 [I > 2s(I)]
None
1401 [I > 2s(I)]
None
Direct methods
Intensity data for 13 and 15 were collected with graphite
monochromated Mo-Ka radiation (l = 71.073 pm). The reflec-
tions were corrected for Lorentz and polarization effects. Taking
the small crystal size and a rather small value of the absorption
coefficient into account no absorption correction was applied
to the data set. Structures were solved by direct methods and
refined by full matrix least squares methods on F2. The programs
SHELXS-9733 and SHELXL-9734 and SHELXTL35 were used.
The molecular structures are illustrated as ORTEP36 plot. A
summary of crystallographic details and the structure refinement
is given in Table 1.
Direct methods
Full-matrix at F2 Full-matrix at F2
244
105
Programs used
SHELXS-97
SHELXL-97
SHELXTL
0.0376
SHELXS-97
SHELXL-97
—
0.0258
0.0676
STOE IPDS Software
R1 (observed data), %a
wR2 (independent data), %a 0.0727
Largest diffraction peak and 0.342/-0.302
0.296/-0.574
-3
˚
hole/e A
a R1 = RꢀFo| - |Fcꢀ/R|Fo|; wR2 = R[w(Fo - Fc2)2]/R[w(Fo2)2]}
.
2
1/2
Imido vanadium(V) complexes
Results and discussion
A number of organoimidovanadylchlorides [V(NR)Cl3] have been
prepared via the sulfinyl amine metathesis in good or very good
yields. For literature known complexes with electron releasing
substituents R = t-Bu (1) and R = Dip (2) (Scheme 1) the metathesis
proceeds slowly compared to the sulfinyl amines with electron
withdrawing haloaryl substituents. The best reaction condition for
introducing electron releasing N-alkyl and donor-substituted aryl
substituents is refluxing octane (variant A) while haloaryl imido
ligands in 3–6 and sulfonyl imido ligands in 7 and 8 are better
introduced at ambient or slightly elevated temperature (variant B).
Our search for a more convenient method for the synthesis of
vanadium and of chromium imido complexes in particular having
electron-withdrawing N-substituents was initiated by the failure
to use more common strategies: Electron-poor haloaryl amines or
arylsulfonylamides and their N-silylated synthons are often not
nucleophilic enough at nitrogen to follow an addition–elimination
type of condensation reaction with VOCl3 and CrO2Cl2. On
the other hand, the high oxidizing potential of these 3d metal
acid chlorides does not allow selective reactions with electron-
rich anilines Ar–NH2. Typically, aryl ring coupling and other
oxidative aromatic side reactions are leading to many products and
intractable tars. While isocyanate metathesis is known to work well
for vanadyl chloride, isocyanates are not reactive or not selective
in their reaction with chromyl chloride. Furthermore difficulties
in the synthesis of commercially non-available isocyanates from
electron-poor primary amines and COCl2—even if generated in
situ from more convenient but expensive diphosgene—turned
out to be a restriction of the isocyanate metathesis strategy
for imido vanadium complexes. We had difficulties to convert
2,4,6-tribromophenyl aniline into the corresponding isocyanate
by reaction with phosgene or diphosgene. Contrastingly, 2,4,6-
tribromophenyl sulfinylamine as many other precursor molecules
R-NSO are readily obtained in high yields by reaction of the
primary amine with excess SOCl2.
Scheme 1 Imido vanadium(V) complex synthesis.
Taking the higher acidity of aryl sulfonylamides ArSO2NH2
compared to water into consideration the donor capability of an
aryl sulfonylimido ligand should be lower than that of an oxo
ligand.15 Due to this trend tosyl and mesyl imido complexes 7 and
8 are very Lewis acidic and highly sensitive towards hydrolysis but
they are obtained in good yields as purple crystalline and volatile
1994 | Dalton Trans., 2011, 40, 1990–1997
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compounds. Solutions of 1–8 in hydrocarbons appear dark green,
probably due to a LMCT phenomenon.
Imido chromium(VI) complexes
The prominent key compound in imido chromium chemistry is
[Cr(N-t-Bu)2Cl2] (10). It was prepared by the reaction of [CrO2Cl2]
with [t-BuNH-SiMe3] leading to [Cr(N-t-Bu)2(OSiMe3)2].37 Treat-
ment of the latter with BCl3 afforded 10 in moderate yield.29
Up to date, the only access to arylimido chromium complexes
of the type [Cr(NAr)2Cl2] were metathesis reactions using 10
as a Cr(VI) precursor compound with lower oxidation potential
than [CrO2Cl2]. Isocyanate metathesis of 10 with MesNCO led to
[Cr(NMes)2Cl2] (11),30 while sterically more demanding DipNCO
led to reduction and formation of the Cr(V) dimer [Cr(m-N-t-
Bu)(NDip)Cl]2. The desired Cr(VI) complex [Cr(NDip)2Cl2] (12)31
was synthesized by reaction of 10 with DipNH2. The isolated
intermediate [Cr(NDip)2(NH-t-Bu)Cl]31 was then treated with
BCl3 to yield 12 in four steps starting from [CrO2Cl2] in low overall
yield.
Fig. 1 Molecular structure of [Cr(NC6F5)2Cl2] (13). Representative bond
distances (pm) and angles (◦): Cr(1)–N(11) 163.7(3), Cr(1)–N(21) 164.3(3),
Cr(1)–Cl(2) 216.04(11), Cr(1)–Cl(1) 216.13(11), N(11)–C(11) 136.7(4),
N(21)–C(21) 136.6(4), N(11)–Cr(1)–N(21) 111.72(14), N(11)–Cr(1)–Cl(2)
105.81(10),
N(21)–Cr(1)–Cl(2)
107.29(11),
N(11)–Cr(1)–Cl(1)
107.80(10), N(21)–Cr(1)–Cl(1) 105.51(11), Cl(2)–Cr(1)–Cl(1) 118.80(5),
C(11)–N(11)–Cr(1) 160.4(2), C(21)–N(21)–Cr(1) 159.9(3).
The sulfinyl amine metathesis presents a new high-yield one-
pot route to 12 and related arylimido compounds. The aniline
derivative, e.g. DipNH2, is treated with excess of SOCl2 in
refluxing benzene. Typically the corresponding aryl sulfinylamines
are formed quantitatively, they may be used without further
purification by distillation. After removing the excess of SOCl2 the
straight metathesis with [CrO2Cl2] leads to 12 or new arylimido
chromium(VI) complexes 13–16 in perfect yields (Scheme 2).
Scheme 2 Imido chromium(VI) complex synthesis.
Fig. 2 Molecular structure of [Cr(N-2,4,6-Cl3C6H2)2Cl2] (15). Hy-
drogen atoms are omitted. Representative bond distances (pm) and
angles (◦): Cr–N(1) 164.8(2), N(1)–C(1) 137.0(3), Cr–Cl(4) 216.5(1),
Cr–N(1)–C(1) 149.68(15), N(1)–Cr–Cl(4) 107.49(6), N(1)–Cr–N(1A)
107.33(13), N(1)–Cr–Cl(4A) 107.83(6), Cl(4)–Cr–Cl(4A) 118.42(4). Op-
eration to generate symmetry equivalent atoms: -x + 1, y, -z + 1/2.
Mono-oxo(imido) intermediates of this reaction, such as [Cr(N-
t-Bu)(O)Cl2] (9), can be isolated when less reactive sulfinylamine t-
BuNSO is applied. 9 is a known compound. Previously it has been
synthesized in three steps from [CrO2Cl2] by treatment of [Cr(N-
t-Bu)(O)(OSiMe3)2] with PCl5.28 The spectroscopic data of 1–16
are in accord with those previously reported for literature known
compounds and the purity of all known and new compounds
was checked by elemental analyses. It is worth to mention, that
an attempt to purify [Cr(NC6F5)2Cl2] (13) by sublimation at 60–
120 ◦C and 10-4 mbar led to thermolysis: Decafluoroazobenzene
C6F5N NC6F5, the product of reductive nitrene coupling is the
highest molecular ion in the EI-mass spectrum of 13. Therefore we
expect, that oxidative nitrene-transfer chemistry will develop from
our new imido chromium complexes with electron withdrawing
N-substituents.
ranging from 105.5(1)◦ to 118.80(5)◦. Interestingly, and in accord
with the other structurally characterized complexes of this type,
the N–Cr–N angles between the two p-bound ligands tend to be
considerably smaller than the angles Cl–Cr–Cl (Table 2).
Table 2 Comparison of selected average bond distances and angles of
[Cr(NR)2Cl2]
[Cr(NR)2Cl2] av. Cr–N/pm av. Cr–N–C/◦ N–Cr–N/◦ Cl–Cr–Cl/◦
Single crystals of 13 and 15 were obtained from CCl4/hexane
and the molecular structures of 13 and 15 were determined by
an X-ray analysis. The results are shown in Fig. 1 and Fig. 2. A
comparison of characteristic average bond lengths and angles with
literature known structures of diimido chromium complexes is
drawn in Table 2. The molecular structure of 13 exhibits a distorted
tetrahedral coordination geometry with angles at chromium atom
R = t-butyla30 162.3
165.0
R = C6F5 (13) 164.0
R = 2,4,6-Cl3- 164.8
C6H2 (15)
164.3
158.6
160.2
149.7
113.3
111.0
111.7
107.3
120.4
118.8
118.8
118.4
R = Mes30
a Average values of two independent molecules.
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15 reveals crystallographically imposed C2 symmetry in the
solid state. The angle Cr–N(1)–C(1) 149.68(15)◦ in 15 shows the
strongest deviation from the linear Cr–N–C bond axes typically
found in the other comparable complexes. This could be due
to steric repulsions of the ortho-chlorine substituents. Table 2
reveals, that the strongest deviation from a linear Cr–N–C bond
axis correlates with the smallest angle N–Cr–N and the smallest
deviation from a linear Cr–N–C bond axis correlates with the
largest N–Cr–N angle.
poor sulfinyl amines and amides occur at room temperature
while a slow stream of argon is passed through the solution in
order to carry out SO2. Sufinylamines are known to be highly
reactive dienophiles in organic synthesis.22 We suggest that the first
step of these metathesis reactions is the formation of an adduct
(intermediate I). If the group R in RNSO is electron releasing, the
intermediate could be I (Scheme 4), a sulfinylmine bound via the
imino nitrogen atom.
Imido molybdenum(VI) and tungsten(VI) complexes.
Among group 6 metals the d0 oxo-chlorides MoO2Cl2 and
WO2Cl2 form coordination polymers.38 We are interested in
related sulfonylimido complexes of the type [Mo(NR)2Cl2] as
they reveal interesting metal mediated nitrene transfer reactions16
Sulfonylimido molybdenum complexes cannot be synthesized via
other strategies such as the reaction of MoO2Cl2/ArSO2N(SiMe3)2
or MoCl5/ArSO2NH2/Cl2 or Mo(CO)6/ArSO2NCl2.39
In refluxing toluene the coordination polymer of [MoO2Cl2]x is
broken up by even weak donors such as C6F5NSO or the aryl-
sulfonyl sulfinylamides MesSO2-NSO and 2,4,6-i-Pr3C6H2SO2-
NSO. Sulfur dioxide and the corresponding base free Lewis acids
[Mo(NR)2Cl2] 17–19 are obtained in almost quantitative yields
(Scheme 3).
Scheme 4 Mechanistic considerations of sulfinylamine metathesis.
If the metal oxo complex would have a considerable O-
nucleophilicity and R is highly electron withdrawing (e.g. tosyl) a
zwitterionic intermediate III and finally the cyclic intermediate II
of a 2 + 2 addition may be considered. Up to now we were not able
to isolate and characterize any intermediates of the sulfinylamine
metathesis reactions presented here. The barriers of their decay
seem to be low. This is in accord with the fact, that only few
cycloadducts of certain oxo complexes with isocyanates have been
isolated.41
Scheme 3 Imido molybdenum and tungsten(VI) complex synthesis.
Conclusions
While 17 [Mo(NC6F5)2Cl2] is soluble in benzene, indicating only
weak intermolecular interactions, the arylsulfonyl sulfinylimido
complexes 18 and 19 are insoluble in non-polar, non-donating sol-
vents. They are coordination polymers but dissolve in acetonitrile
with formation of corresponding Lewis base adducts. As expected,
[WO2Cl2]x being a coordination polymer with no terminal but only
bridging oxo ligands40 is less reactive in oxo/imido metathesis
reactions than the chromium and molybdenum homologues.
However at long reaction times, finely powdered [WO2Cl2]x
does react with C6F5NSO to yield the corresponding base free
[W(NC6F5)2Cl2]x 20, indicating that the sulfinylamine is able to
disintegrate the polymeric structure of [WO2Cl2]x by nucleophilic
attack. In contrast to the molybdenum congener, 20 is insoluble
in aromatic hydrocarbon solvents.
We have described a powerful synthetic method for the synthesis of
a wide range of organoimido vanadium, chromium, molybdenum
and tungsten complexes. The great advantage of the sulfinylamine
metathesis strategy is the direct synthesis of arylimido chromium
complexes of the type [Cr(NAr)2Cl2] from readily available
chromyl chloride. A direct approach to olefin polymerization
catalysts (V, Cr) or their precursors is described. A wide range of N-
substituents—electron releasing and withdrawing—can be intro-
duced and it is anticipated that many other molecular complexes
having terminal oxo groups will show a similar desox-imidation
pattern by reaction with R-NSO derivatives. The sulfinylamine
and sulfinyl sulfonylamide metathesis is probably the best method
for replacement of oxo ligands by imido ligands with electron-
withdrawing N-substituents, and in particular, when the imido
metal Lewis acids and not their base adducts are the desired
products.
Mechanistic considerations
The non-linear structure of sulfur(IV) cumulenes R–N
S O,
the more dipolar character of the N–S bond compared to N–
C in isocyanates, and an enhanced tendency of nucleophilic
attack at the oxophilic sulfur atom make them more reactive
than isocyanates in metathetical desox-imidations of metal oxo
complexes. The surprising result of this investigation is the kinetic
inertness of vanadyl and even chromyl chloride, a most powerful
oxidizing agent, towards reduction by sulfur dioxide at our
reaction conditions: Most reactions with more reactive, electron
Acknowledgements
The authors thank Dr Evgeni V. Avtomonov for his help in the
X-ray crystallographic study of complex 13. Financial support
by INTAS-96-1185, by DFG Priority Program 1118, and by
DAAD (Fellowship A/09/03585 for K. A. R. at the University of
Marburg) is gratefully acknowledged.
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Dalton Trans., 2011, 40, 1990–1997 | 1997
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