Reactions at the coordinated trichloromethyl isocyanide. Part VII. α-Chloroalkenylisocyanide versus oxazolin-2-ylidene(ato) complex formation

Article abstract of DOI:10.1016/j.jorganchem.2007.03.005

Under aprotic conditions, Cr(CO)₅CNCCl₃ (1) reacts with triphenylphosphine in the presence of aromatic aldehydes or ketones to give the α-chloroalkenylisocyanide complexes cis(Z)- and trans(E)-Cr(CO)₅CNCCl{double bond, long}CRR′ {R = H, R′ = 4-C₆H₄F (7), 4-C₆H₄-CH{double bond, long}C(Cl)NCCr(CO)₅ (8)} and Cr(CO)₅CNCCl{double bond, long}CR₂ {CR₂ = fluorenylidene (9)}. Two further representatives of this class of compounds, Cr(CO)₅CNCCl{double bond, long}CCl₂ (10) and Cr(CO)₅CN-CCl{double bond, long}CCl-NCCr(CO)₅ (11), have been obtained in low yields by reduction of 1 with zinc. Reactions with pyrrolidine of the isomeric mixtures 7 and 8 afford the alkylideneamino(pyrrolidino)carbene complexes 13 and 14. An X-ray study of 13 shows the two π-systems within the amino(imino)carbene ligand to be approximately orthogonal to one another. With tris(dimethylamino)phosphine in the place of triphenylphosphine, complex 1, 9-fluorenone plus a secondary amine combine to the 4-amino-Δ³-oxazolin-2-ylidene chromium complexes 17 and 19, the latter of which has been protonated, alkylated and subject to an X-ray structure analysis. Reasons for the different modes of reaction in the system 1/PR₃/RR′C{double bond, long}O are discussed and compared with the "dependence on the metal" of reactions in the system L_nMCN-CH-PPh₃/RR′C{double bond, long}O {L_nM = (OC)₅Cr, (OC)₅W versus Cl(Ph₃P)₂Pt⁺}.

Full text of DOI:10.1016/j.jorganchem.2007.03.005

Journal of Organometallic Chemistry 692 (2007) 2936–2948
www.elsevier.com/locate/jorganchem
Reactions at the coordinated trichloromethyl isocyanide. Part VII.
a-Chloroalkenylisocyanide versus oxazolin-2-ylidene(ato)
q
complex formation
1
Volker Langenhahn, Gerhard Beck, Gerhard Zinner, Dieter Lentz ,
1
*
Bernhard Herrschaft , Wolf Peter Fehlhammer
Institut fu¨r Anorganische und Analytische Chemie der Freien Universita¨t Berlin, Fabeckstraße 34-36, D-14195 Berlin, Germany
Received 19 January 2007; received in revised form 21 February 2007; accepted 2 March 2007
Available online 12 March 2007
Dedicated to Professor Wolfgang Beck on the occasion of his 75th birthday.
Abstract
Under aprotic conditions, Cr(CO)5CNCCl3 (1) reacts with triphenylphosphine in the presence of aromatic aldehydes or ketones to
give the a-chloroalkenylisocyanide complexes cis(Z)- and trans(E)-Cr(CO)5CNCCl@CRR0 {R = H, R0 = 4-C6H4F (7), 4-C6H4-
CH@C(Cl)NCCr(CO)5 (8)} and Cr(CO)5CNCCl@CR2 {CR2 = fluorenylidene (9)}. Two further representatives of this class of com-
pounds, Cr(CO)5CNCCl@CCl2 (10) and Cr(CO)5CN–CCl@CCl-NCCr(CO)5 (11), have been obtained in low yields by reduction of 1
with zinc. Reactions with pyrrolidine of the isomeric mixtures 7 and 8 afford the alkylideneamino(pyrrolidino)carbene complexes 13
and 14. An X-ray study of 13 shows the two p-systems within the amino(imino)carbene ligand to be approximately orthogonal to
one another. With tris(dimethylamino)phosphine in the place of triphenylphosphine, complex 1, 9-fluorenone plus a secondary amine
combine to the 4-amino-D3-oxazolin-2-ylidene chromium complexes 17 and 19, the latter of which has been protonated, alkylated
and subject to an X-ray structure analysis. Reasons for the different modes of reaction in the system 1/PR3/RR0C@O are discussed
and compared with the ‘‘dependence on the metal’’ of reactions in the system LnMCN–CH–PPh3/RR0C@O {LnM = (OC)5Cr,
(OC)5W versus Cl(Ph3P)2Pt+}.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Chromium complexes; Functional Isocyanides; Carbene ligands; Organometallic Wittig reactions; Organometallic [3+2] cycloadditions; X-ray
structures
1. Introduction
which due to the presence of two mutually reinforcing elec-
trophilic centers, the unsaturated isocyano unit and the
perchlorinated a-C atom, possesses an extremely high syn-
thetic potential [1–7]. Although most reactions occur at the
two electrophilic centers C1 and C3 jointly, affording a
broad palette of carbene, C-heterocycle, and isocyanide
complexes, it is possible, in some cases, to limit the reaction
to the trichloromethyl group of 1 and thereby obtain new
functional isocyanides.
In a series of papers we have dealt with the chemistry of
pentacarbonyl(trichloromethyl isocyanide)chromium (1)
q
For Part VI, see Ref. [7].
Corresponding author. Present address: Department Chemie und
*
Biochemie der Ludwig-Maximilians-Universita¨t Munchen, But-
¨
enandtstraße 5-13, D-81377 Munich, Germany. Tel.: +49 9466911843;
fax: +49 9466911895.
To the latter category also belong the reactions with
phosphines as nucleophiles which have turned out to be a
true bonanza for versatile organometallic/organophosphorus
E-mail address: wpfehlhammer@gmx.de (W.P. Fehlhammer).
X-ray structure determinations.
1
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.03.005

V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
2937
synthons and syntheses such as the combined isocyano-
2. Results and discussion
Wittig/metallo-nitrile-ylid reagent 2 with its carbonyl-(iso-
cyano)methyleneation and [3+2] cycloaddition reaction
patterns [6,8,9].
2.1. One-step syntheses of a-chloroalkenylisocyanide
complexes from Cr(CO)5CNCCl3
Addition at room temperature of two equivalents of tri-
phenylphosphine to a 1:1 mixture of 1 and the respective
carbonyl compound in diethylether – in the case of the dial-
dehyde a 4:2:1-stoichiometry was chosen – resulted in a
change of colour from yellow to orange and an immediate
precipitation of chlorotriphenylphosphonium chloride (Eq.
(1)). Strictly aprotic conditions were maintained during
work-up which included chromatography on silica and
finally led to the a-chloroalkenylisocyanide complexes as
microcrystalline yellow (7), orange (8) or light green mate-
rials (9) in good yields (Section 3).
C1
C3Cl3
N
(OC)5Cr
C N CH PPh3
(OC)5Cr
1
2
In an earlier report, we have demonstrated that the reac-
tion scheme established by Appel and co-workers for the
two component-system CCl4/PPh3 can be applied point
by point to exactly predict what kind of chemistry is going
on in the combination 1/PPh3 [6,10]. If we simply replace a
covalently bonded chlorine atom in Appel’s scheme by the
electronically similar pentacarbonyl(cyano)chromium radi-
cal we end up with a series of P-functionalized isocyanide
complexes of which 4, 5 (as triethylphosphonium deriva-
tive) and 6 have already been isolated and characterized
(Scheme 1) [6].
(OC)5Cr
C
N
CCl CRR´ + OPPh3
1 + 2 PPh3 + O=CRR´
-[ClPPh3]Cl
(7) R = H, R´= 4-C6H4F
8, 9
Only 3 has so far eluded isolation though in view of the
general validity of Scheme 1 there is little room for doubt
about its intermediacy. Further evidence for the existence
of 3 now comes from its trapping in Wittig-type reactions
with carbonyl compounds on which we report in the fol-
lowing. The classical analogue is the three-component sys-
tem CCl4/PPh3/O@CHPh used by Rabinowitz and Marcus
for the preparation of dichlorostyrene (Cl2C@CHPh) [11].
Furthermore, we show that replacing triphenylphosphine
by tris(dimethylamino)phosphine alters the mechanism in
a central point: now the metallo-nitrile-ylid nature of 3 or
its P(NMe2)3 derivative, respectively, comes to the fore
resulting in [3+2] cycloadditions with ketones to give chro-
mium–C bonded oxazoli(di)nes.
ð1Þ
Cl
(OC)5Cr
C N
N
C Cr(CO)5
Cl
8
Cl
(OC)5Cr
C N
9
.....
(OC)5CrCN CCl2 Cl PPh3
[(OC)5CrCN CCl2 PPh3]Cl
+ PPh3
1
PPh3
(OC)5CrCN
C
Cl
PPh3
PPh3
4
+ PPh3
(OC)5CrCN CCl PPh3
-[ClPPh3]Cl
3
HCl(H2O)
[(OC)5CrCN CHCl PPh ]
Cl
3
5
[(OC)5CrCN CH2 PPh ]
Cl
3
6
Scheme 1.

2938
V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
1
As indicated by the H and 13C NMR spectra, com-
Another approach to a-chloroalkenylisocyanide com-
plexes, e.g., cis(Z)- and trans(E)-Cr(CO)5CN–CCl@CHCl
or Cr(CO)5CN–CCl@CH2, consists in the elimination with
zinc in glacial acetic acid of chlorine from tri- and tetra-
chloroethylisocyanide(pentacarbonyl)-chromium, respec-
tively [13]. Two further representatives of this class of
compounds, viz. Cr(CO)5CN–CCl@CCl2 (10) and trans-
Cr(CO)5CN–CCl@CCl-NCCr(CO)5 (11), had very surpris-
ingly been obtained by reduction of 1 with zinc in aprotic
media; here presumably the reaction proceeds via the C3–
C3-coupled intermediate Cr(CO)5CN–CCl2–CCl2–NCCr-
(CO)5 from which again chlorine is removed to give 11
while formation of 10 requires elimination of
Cr(CO)5CNH from its partially reduced form [2]. From
the IR and Raman spectra of 11 – in particular the mutu-
ally exclusive activites of the m(C@C) and m(CCl) – a centro-
symmetric structure (overall symmetry C2h) can be inferred
which obviously also accounts for the unusual m(CO) IR
pattern (1Au + 4Bu) (Table 1).
plexes 7 and 8 form mixtures of cis(Z)- and trans(E)-iso-
mers which have so far evaded separation. In fact, the H
1
NMR spectra clearly show 7 to consist of two, and 8 to
consist of the expected three stereoisomers. This is gathered
from the vinylic protons which in the case of 7 give rise to
two singlets at d 6.80 and 6.51 having an intensity ratio of
1:2.5, while complex 8 exhibits resonances at d 7.18, 6.75
and 6.49 of relative intensities 1:2:2. Assignments of signals
to a given isomer were not possible, however. In the 13C
NMR spectra, it is particularly the carbonyl- and isocya-
nide-carbon signals of the pentacarbonyl(isocyanide)chro-
mium entity of 7 and 8 which appear doubled in number.
Some doubling of signals also occurs for the alkenyl carbon
atoms (Table 2), while there is no indication in the 13C
NMR of 8 of a third isomer. Only one set of signals, nat-
urally, is found for compound 9.
The generally small differences in the chemical shifts of
the axial- and equatorial-CO carbon atoms of the pentacar-
bonylchromium group of <2 ppm point to marked accep-
tor properties of the new ligands [12], an interpretation
which is supported by the positions at particularly low
fields of the isocyanide-carbon resonances. A range of d
values of 110–115 for the chloro(isocyano)alkenyl carbon
(ꢀC@C(Cl)NC–) agrees with earlier findings and is obvi-
ously typical for this structural element [13].
The only IR bands worth mentioning are those of the
CN stretching vibration which due to the enhanced p-
acceptor abilities of these functional isocyanides appear
at comparatively low wave numbers, and those of the
m(CO)-E mode which, consistent with bond theory, have
been shifted to higher frequencies (Table 1).
The highest lines in the mass spectra (EI) correspond
with the calculated molecular masses, and the parent peaks
of 7 and 9 as usually with CrCNR+ fragments devoid of the
carbonyl envelope (Table 3). No evidence is found in the
mass spectra for any elimination of HCl from the a-chloro-
alkenyl ligands of 7 or 8 to give the much sought-after iso-
cyanoacetylenes [14,15].
2.2. Reactions of the a-chloroalkenylisocyanide complexes 7
and 8 with pyrrolidine; X-ray structure of product 13
a-Chlorinated alkylisocyanides coordinated to pentacar-
bonylchromium are known to be highly prone to nucleo-
philic attack by amines. The absolute record holder in
this respect is the trichloromethylisocyanide ligand in 1
which consumes up to seven (!) molecules of N-nucleophile
resulting in diaminocarbene complex and free guanidine
moieties along with three equivalents of ammonium chlo-
ride [2–4]. Though markedly less electrophilic, the parent
compound of the a-chloroalkenylisocyanide complexes,
Cr(CO)5CN–CCl@CH2, still takes up two molecules of a
secondary amine HNR2 to give the imino(amino)carbene-
chromium species 12a [16].
Reactions in diethylether of 7 with three and of 8 with
six equivalents of pyrrolidine, by analogy, proceed
smoothly following the same addition–elimination mecha-
nism with migration of the double bond and formation
Table 1
Selected IR data (cmꢀ1) (KBr)
Complex
m(CN)
m(CO)
Others
7
8
2122 s
2116 s
2114 s
2118 w
2119 w
2038 s, 2000 s, sh, 1978 vs, br, 1935 s, br
2034 s, 2006 s, sh, 1975 vs, br, 1934 s, br
2044 s, 2007 s, sh, 1983 vs, br, 1942 s, br
2019 m, 1978 vs, 1949 m
2059 s, 2019 sh, 2005 sh, 1999 s, 1953 vs
2045 s, 1912 vs, br, 1888 s
2048 s, 1904 vs, br, 1875 s
2057 s, 1985 s, 1970 vs, br, 1899 s
2057 s, 1960 vs, 1923 vs, br
1597 m m(C@C)
1605 m m(C@C)
1614 m m(C@C)
1575 w m(C@C), 823 s m(CCl)
9
10a
11b,c
13
14
17
19
20
21
22
23
a
837 m m(CCl)
1626 s m(C@N), 1408 s m(N'C'N)
1624 s m(C@N), 1415 s m(N'C'N)
1644 s m(C@N), 1442 s m(N'C'O)
1638 s m(C@N), 1451 s m(N'C'O)
3206 s, br m(NH), 1626 s m(C@N), 1452 s m(N'C'O), 1083 s, br m(BF4)
1665 m m(C@N), 1453 s m(N'C'O), 1060 s, br m(BF4)
1060 vs m(BF4)
2072 s, 1997 m, 1927 vs, br
2071 s, 1998 s, 1934 vs, br
2217 s
1523 s mas(N'C'O) + mas(NO2), 1347 s ms(NO2), 1082, 1034 vs m(BF4)
In n-pentane.
b
c
Nujol mull.
Raman data of 11: 2114 w m(CN), 2049 m, 2003 s, 1956 m m(CO), 1592 vs m(C@C).

V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
2939
of the yellow crystalline substances 13 and 14 in which base
functions reside in the C1 and C3 positions. In the infrared,
accordingly, the m(CN) bands at about 2120 cmꢀ1 have dis-
appeared in favour of two strong absorptions at 1625 and
1410 cmꢀ1 which are assigned to the C@N stretching vibra-
tion of the alkylideneamino group and the m(N'C'N)
mode of the N,N0-carbene, respectively. The m(CO)-E
bands of the starting materials 7 and 8 experience a huge
drop of some 70 wavenumbers which dramatically reflects
the change from a predominant acceptor ligand, the
a-chloroalkenylisocyanide, to a strong donor, the amino-
(imino)carbene (Table 1).
about the C(carbene)–N(imine) bond providing temporary
coplanarity, respectively, would remove the so-called ‘con-
formational chirality’. Yet both possibilities are excluded
for steric (and electronic) reasons.
Quite a number of X-ray structures of alkylideneami-
nocarbene complexes is meanwhile available which unan-
imously display approximately orthogonal arrangements
of p-systems within the amino(imino)carbene ligand as
the most prominent stereochemical peculiarity [19]. Thus,
in the molecular structure of 13 (Fig. 1) an interplanar
angle of 81.4(2)ꢁ has been determined between the car-
bene plane defined by the atoms N1, C6 and N3, and
the alkylideneamino unit (N1, C7, C8) which solely serves
the purpose of orientating the ‘‘lone pair’’ on the imino
nitrogen in such a way that it interacts best with the
empty pz-orbital on the carbene carbon atom. Most of
the remaining stereochemical features in the structure of
13 are more or less mere consequences of this carbene sta-
bilizing measure:
NR2
N
(OC)5Cr
CH2X
NR2
(12a) X = H
(12b) X = Cl
ꢁ The long chromium to carbene carbon distance of
˚
2.138(3) A which equals that in complex Cr(CO)5{C(N-
˚
Me2)N@C(OMe)Ph} (d(Cr–Ccarbene) = 2.135(4) A) [20],
yet exceeds by far that in 15 (d(Cr–Ccarbene) =
N
˚
˚
2.114(3) A) [2] or in 16 (d(Cr–Ccarbene) = 2.115(2) A)
[7]; clearly, in the latter two cases the metal has to con-
tribute significantly to the overall stabilization of the
carbene as np ! pp interactions are much less favour-
able due to the reduced flexibility of the seven-mem-
bered ring in compound 15, and the presence of the
strongly electron-withdrawing imidazolyl substituents
at the imino group of 16.
N
N
(OC)5Cr
F
13
N
ꢁ The carbene-C–amino-N distance (d(C6–N3) = 1.323
˚
N
N
N
N
(4) A) which as in all structures of that type is shorter
(OC)5Cr
Cr(CO)5
than the carbene-C–imino-N bond length (d(C6–
˚
N1) = 1.367(4) A) reflecting the more efficient carbene-
N
stabilization by the amino substituents.
˚
ꢁ The C7–N2 distance of 1.352(4) A which is much shorter
14
˚
than a Csp2 –Nsp2 single bond (1.43 A) [21] and even
shorter than C6–N1 (see above) indicating some passing
on of the electron demand of the carbene carbon along
the C6–N1–C7–N2 atomic sequence. The carbene plane
(N1, C6, N3, C31) is rotated by 60.7(2)ꢁ with respect to
the meridian (Cr, C1, C3, C5), i.e., the carbene substit-
uents and the cis-CO ligands are in an almost staggered
arrangement.
The NMR spectra (Table 2) show unique sets of signals,
i.e., the mixtures of two or, respectively, three stereoiso-
mers (7, 8) have obviously been converted by these reac-
tions into single complex individuals. Their 1H NMR
data closely resemble those of 12a and, particularly, 12b
which have thoroughly been analyzed including their
´
´
dynamics [16–18]. Only a short resume will therefore be
given here: causal for the observation of only one species
each is a fast inversion at the imino nitrogen which
exchanges the cis and trans positions with respect to the
CN double bond; this kind of dynamics, however, is unable
to equilibrate the methylene hydrogens (CH2Ar) which due
to the lack of a mirror plane – the p-systems of the two car-
bene substituents are perpendicular to each other – give rise
to doublets of doublets, i.e., turn out diastereotopic (Table
2). Only coplanarity of the whole ligand or a rapid rotation
N
Cl
N
Me
N
N
N
N
(OC)5Cr
N
(OC)5Cr
N
N
Me
15
16

2940
V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
Table 2
1H, 13C{1H} and 31P{1H} NMR dataa
Compound
1H NMR
13C{1H} NMR
Solvent
CDCl3
7b
7.60 (d, 2H, C6H4, 3J(HH) = 7.2 Hz)
7.15 (d, 2H; C6H4, 3J(HH) = 7.2 Hz)
6.80, 6.51 (2s, 1H, C@CH)
215.3, 214.9 (COtrans), 213.6, 213.4 (COcis)
184.4, 179.8 (CN), 163.0 (C–F, 1J(CF) = 248 Hz)
131.4, 131.3 (C@CH), 130.3, 126.2, 116.0
(C6H4), 110.7 (C@CCl)
8c
7.60 (d, 2H, C6H4, 3J(HH) = 7.2 Hz)
7.49 (d, 2H, C6H4, 3J(HH) = 7.3 Hz)
7.18, 6.75, 6.49 (3s, 2H, C@CH)
215.7, 215.1 (COtrans), 213.5, 213.3 (COcis
185.7, 180.7 (CN), 133.0, 132.6 (C@CH)
129.9, 128.5, 126.3, 126.0 (C6H4)
113.0, 111.9 (C@CCl)
)
CDCl3
CDCl3
CDCl3
9c
8.09 (d, 1H, Ar, 3J(HH) = 7.8 Hz)
7.90 (d, 1H, Ar, 3J(HH) = 7.8 Hz)
7.57 (d, 2H, Ar, 3J(HH) = 7.2 Hz)
214.9 (COtrans), 213.3 (COcis), 187.4 (CN)
135.0 (C@CCl), 140.4, 130.1, 127.8, 126.4,
124.4, 120.0 (Ar), 109.6 (C@CCl)
7.28 (m, 4H, Ar)
13b
7.12 (m, 2H, C6H4), 7.00 (m, 2H, C6H4)
3.78 (m, 2H, N–CH2), 3.64 (d, 1H, CH2C6H4,
2J(HH) = 15 Hz), 3.47, 3.32 (2m, 6H, N–CH2)
2.35 (dt, 1H, CH2C6H4, 2J(HH) = 15 Hz)
232.6 (carbene C), 223.1 (COtrans), 219.0 (COcis)
161.6 (d, C–F, 1J(CF) = 231 Hz), 141.0 (N@C–N)
131.6–115.5 (C6H4), 54.5, 49.9, 47.5 (N–CH2)
39.9 (CH2C6H4), 25.5, 24.6 (C-CH2CH2-C)
1.92, 1.66 (2m, 8H, C-CH2CH2-C)
14b
7.12 (m, 2H, C6H4), 7.00 (m, 2H, C6H4)
3.76 (m, 4H, N–CH2), 3.64 (d, 2H, CH2C6H4,
2J(HH) = 16 Hz), 3.45, 3.35 (2m, 12H, N–CH2)
2.37 (dt, 2H, CH2C6H4, 2J(HH) = 16 Hz)
232.4 (carbene C), 223.1 (COtrans), 218.9 (COcis
141.0 (N@C–N), 134.3–126.5 (C6H4)
54.4, 49.9, 47,6 (N–CH2), 40.9 (CH2C6H4)
25.4, 24.5 (C-CH2CH2-C)
)
CDCl3
1.82, 1.65 (2m, 16H, C-CH2CH2-C)
17b
7.50 (m, 8H, Ar), 3.37 [s, 3H, N-(CH3)exo
2.35 [s, 3H, N-(CH3)endo
]
Not measured
CDCl3
CDCl3
]
19b,d
7.70, 7.49, 7.33, 7.16 (m, 8H, Ar)
3.91 [t, 2H, N-(CH2)exo], 2.62 [t, 2H,
N-(CH2)endo], 1.71 [q, 2H, C-(CH2)exo-C]
1.60 [q, 2H, C-(CH2)endo-C]
286.9 (carbene C), 224.0 (COtrans), 217.8 (COcis
175.8 (ring C4), 141.2–120.8 (Ar), 95.0
(ring C5), 51.5 [N-(CH2)exo], 45.4 [N-(CH2)endo
25.4 [C-(CH2)exo-C], 23.7 [C-(CH2)endo-C]
)
]
20c,d
10.89 (s, 1H, NH)
272.6 (carbene C), 223.5 (COtrans), 217.8 (COcis
174.8 (ring C4), 141.2–121.6 (Ar), 93.8
)
DMSO-d6
DMSO-d6
7.95, 7.60, 7.45, 7.18 (m, 8H, Ar)
4.78 [t, 2H, N-(CH2)exo], 3.82 [t, 2H,
N-(CH2)endo], 1.73 [q, 2H, C-(CH2)exo-C]
(ring C5), 51.9 [N-(CH2)exo], 46.0 [N-(CH2)endo
]
24.8 [C-(CH2)exo-C], 23.1 [C-(CH2)endo-C]
1.57 [q, 2H, C-(CH2)endo-C]
21c,d
8.02, 7.82, 7.69, 7.51 (m, 8H, Ar)
5.61 (s, 3H, Me)
268.1 (carbene C), 221.9 (COtrans), 217.8 (COcis
)
174.8 (ring C4), 141.3–121.4 (Ar), 90.6
4.65 [t, 2H, N-(CH2)exo], 4.13 [t, 2H,
N-(CH2)endo], 3.19 [q, 2H, C-(CH2)exo-C]
(ring C5), 51.9 [N-(CH2)exo], 46.1 [N-(CH2)endo]
44.9 (Me), 24.8 [C-(CH2)exo-C], 23.1 [C-(CH2)endo-C]
2.90 [q, 2H, C-(CH2)endo-C]
22b,e
8.00–7.00 (m, 45H, Ph)
MeCN-d3
4.79 (d + satellites, 2H, Ph3PCH2, 2J(PH)
= 10 Hz, 4J(195PtH) = 19 Hz)
23b,f
7.8 (m, 15H, Ph), 7.50 (m, 30H, Ph)
Acetone-d6
8.03, 6.88 (2d, 2H, C6H4, 3J(HH) = 9 Hz)
4.62 (dd, 1H, O–CHC6H4, 3J(HH) = 12 Hz,
3J(PH) = 3 Hz), 3.98 (dd, 1H, N–CH-PPh3,
3J(HH) = 12 Hz, 2J(PH) = 17 Hz)
a
Chemical shifts, d, as ppm downfield from solvent as internal standard.
1H NMR: 250 MHz, 13C{1H} NMR: 62.8 MHz.
b
c
1H NMR: 399.8 MHz, 13C{1H} NMR: 100.5 MHz.
d
3
The pyrrolidine hydrogen atoms appear as triplets (t) and quasi-quintets (q) with very similar J(HH) coupling constants of ca. 8 Hz (see, e.g., D.H.
Williams, I. Fleming, Spektroskopische Methoden zur Strukturaufkla¨rung, Georg Thieme Verlag, Stuttgart, 1979).
e
31P{1H} NMR (MeCN-d3, 36.2 MHz): 17.2 + sat. (CNCH2PPh3, 4J(195PtP) = 25 Hz), 20.2 + sat. (trans-Pt(PPh3)2, 1J(195PtP) = 2166 Hz).
31P{1H} NMR (acetone-d6, 36.2 MHz): 15.0 (ring-PPh3), 22.8 + sat. at 61.8 and -16.0 (trans-Pt(PPh3)2, 1J(195PtP) = 2822 Hz).
f

V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
2941
Table 3
Mass spectroscopic data of selected compounds [m/z (relative intensity)] (52Cr, 35Cl)
Compound
[M]+
[MꢀCO]+
[Mꢀ2CO]+
317(7)
[Mꢀ3CO]+
289(11)
549(1)
345(7)
263(9)
446(7)
395(59)
760(16)
370(7)
[Mꢀ4CO]+
261(19)
[Mꢀ5CO]+
233(100)
7a
8a,b
9a
373(6)
633(4)
429(11)
347(14)
530(54)
479(3)
521(3)
493(11)
373(3)
291(12)
474(3)
317(24)
235(21)
418(20)
367(16)
732(5)
342(51)
368(32)
368(96)f
368(14)g
289(100)
207(100)
390(100)
339(100)
704(12)
314(100)
340(100)
340(71)f
340(4)g
10a
11a,c
13d
14d
17a
19a
20d
21d
a
319(5)
451(16)
816(2)
844(1)
788(4)
398(6)
454(28)
480(11)
481(93)e
495(29)e
424(4)
396(5)
424(24)f
424(20)g
396(16)f
396(14)g
EI (80 eV).
b
c
d
e
f
Further peaks: 437(1) [Mꢀ7CO]+, 409(1) [Mꢀ8CO]+, 381(2) [Mꢀ9CO]+, 353(3) [Mꢀ10CO]+.
Further peaks: 362(38) [Mꢀ6CO]+, 334(10) [Mꢀ7CO]+, 306(11) [Mꢀ8CO]+, 278(41) [Mꢀ9CO]+, 250(50) [Mꢀ10CO]+.
+FAB, Xe, DMSO, m-NO2-benzyl alcohol.
Complex cation.
[Complex cationꢀnCOꢀH]+.
[Complex cationꢀnCOꢀMe]+.
g
2.3. Reaction of 1 with tris(dimethylamino)phosphine and
9-fluorenone in the presence of pyrrolidine. X-ray structure
of 19
P(NMe2)3, 1 and 9-fluorenone in fact reacted to give the
desired product 19 (Eq. (2)). (The emergence of 17, accord-
ingly, may be attributed to the presence of some free dim-
ethylamine in tris(dimethylamino)phosphine (see above
and 3.4); also transaminations by P(NMe2)3 definitely have
no scarcity value [24].)
In 1987, a rather unusual heterocyclic carbene complex
– 17 – had been isolated in our research group from the
reaction of pentacarbonyl(trichloromethyl isocyanide)chro-
Cl
H
NMe2
N
N
C Cr(CO)5
N
(OC)5Cr
(OC)5Cr
R´
R
O
O
18
17
N
N
O
Et2O
1
+ 2 P(NMe2)3
HN
+
O
(OC)5Cr
+
(2)
ð2Þ
19
+
[ClP(NMe2)3]Cl
+
P(NMe ) HCl
*
2 3
mium (1) with P(NMe2)3 and 9-fluorenone [22]. Later
attempts to repeat this experiment with miscellaneous car-
bonyl components O@CRR0 failed insofar, as instead of
complexes of type 17, a series of dinuclear carbene–isocya-
nide complexes (18) was obtained in the formation of
which C3–C3 coupling must have occurred [23]. Mechanis-
tic considerations in the context of the present study then
made us add an amine component explicitly. With pyrrol-
idine as a fourth component and two equivalents of
The new result can be explained by assuming an inter-
mediate – isocyano(chloro)methylene-tris(dimethylamino)
phosphorane – analogous to 3 (Scheme 1) which attacks
the carbonyl carbon of 9-fluorenone. Of the two possibili-
ties which exist for the negatively charged oxygen in A to
carry on, (1) ring closure by addition to the isocyano
group, or (2) formation of a P–O bond with elimination
of phosphine oxide to give the same a-chloroalkenylisocy-
anide complex 9 as with PPh3, now the first is verified. The

2942
V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
A host of complexes with exactly these types of ligands has
F
thus been synthesized in recent years by very versatile and
efficient three-component additions (3CC) between cyano
complexes of various metals, isocyanides and carbonyl
compounds [26]. Also notice, that there are close relations
between the two sets of synthons: thus, complex 1 is the
product of the radical alkylation of the cyano complex
[Cr(CN)(CO)5]ꢀ in chloroform, and the role of the isocya-
nide in the 3CC is clearly taken over by the trichloromethyl
side chain of complex 1, P(NMe2)3 and the amine in the
present approach (Eq. (2)).
C95
C94
C23
C96
C8
C24
C93
N2
C91
C92
C22
C7
C31
C32
N3
C21
C33
N1
C34
The wealth of information on related 3CC products we
have at our disposal makes the discussion of the spectro-
scopic and structural data of the new compounds 17 and
19 a lot easier and shorter. While in the IR, the missing
m(NC) and new absorptions about 1640 cmꢀ1 [m(ꢀC@Nꢁ)]
and 1450 cmꢀ1 [m(N'C'O)] are at least of some diagnos-
tic value, it is the exceptional low field 13C NMR shift (19:
d 286.9) of the chromium bonded carbon atom which
deserves underlining. More specific of the compounds in
question is the appearance of two (17: d 2.35, 3.37) and,
C6
O3
O4
C4
C3
Cr1
C5
O5
C2
C1
O2
O1
Fig. 1. Molecular structure of compound 13 with the crystallographic
numbering scheme (ZORTEP-plot). The thermal ellipsoids have been
drawn to include 50% probability. Selected bond lengths (A) and angles
(ꢁ): Cr1–C6 2.138(3), (Cr1–COcis av 1.889, Cr1–C1 1.863(4), C6–N1
1.367(4), C6–N3 1.323(4), N1–C7 1.279(4), C7–N2 1.352(4), C7–C8
1.517(4), C8–C91 1.518(4); (C–Cr1–C)cis 86.2(2)–96.17(13), (C–Cr1–C)trans
172.58(14)–176.0(2), Cr1–C6–N3 128.5(2), N1–C6–N3 112.6(3), C6–N1–
C7 127.6(3), N1–C7–N2 118.9(3), N2–C7–C8 118.2(3), N1–C7–C8
123.0(3).
respectively, four (19:
d
3.91, 2.62, 1.71, 1.60
˚
[AA0BB0CC0DD0-system]) markedly different 1H NMR
signals for the exocyclic amino group, the latter of which
)
O7
O8
C8
C7
O6
falling behind of the Wittig reaction appears comprehensi-
ble in view of a P atom rendered less oxygenophilic by its
electron-rich amine-substituents.
C6
C5
CR1
O5
C4
C22
O4
C1
O1
N1
C2
P(NMe2)3
[Cr0]
N21
C
N
CCl
C23
C3
C311
C31
O
C312
C322
C34
A
C24
C25
C341
C342
C32
In subsequent steps the labile phoshonio substituent in
4-position of the carbenoid oxazoline ligand is replaced
by either a second molecule of the isocyano(chloro) ylid
to give – after hydrolysis and HCl-elimination – the dinu-
clear C3–C3-coupled oxazolidin-2-ylidene/isocyanide spe-
cies 18 [23], or by the secondary amine to give – again
after HCl-elimination – 17 or 19, respectively. A similar
lability of a 4-triphenylphosphonio substituent leading to
an unexpected C3–C3 coupling has already been observed
in [3+2] cycloadditions between metallo-nitrile ylids of type
2 and triphenylketeneimine [25].
C321
C33
C331
C332
Fig. 2a. Molecular structure of compound 19 (‘ball and stick’-model) with
the crystallographic numbering scheme (DIAMOND-1.2 plot). Selected bond
˚
lengths (A) and angles (ꢁ): Cr1–C1 2.033(3), (Cr1–COcis av 1.882, Cr1–C7
1.918(11), C1–N1 1.345(4), C1–O1 1.363(4), N1–C2 1.343(4), O1–C3
1.453(4), C2–C3 1.509(4), C2–N21 1.26(2); (C–Cr1–C)cis 85.4(6)–
101.1(11), (C–Cr1–C)trans 170.2(10)–175.55(16), Cr1–C–O 169(3)–
179.3(3), Cr1–C1–N1 129.6(2), Cr1–C1–O1 118.5(2), N1–C1–O1
111.1(17), C1–N1–C2 107.7(3), C1–O1–C3 109.7(2), N1–C2–C3 111.3(3),
O1–C3–C2 99.5(2), C2–N21–C22 125.6(14), C2–N21–C25 122.2(14), C22–
N21–C25 111.1(17).
)
In this context, it is interesting to note, that in spite of
their unusual beta¨ın-like bonding situation C-bonded 4-
aminooxazolines such as 17 or 19 are stable compounds
exhibiting in fact an extremely high tendency of formation.

V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
2943
O8
O7
C8
C7
C6
O6
CR1
C5
C4
O5
C1
C3
O4
C22A
N1
C2
O1
C31
C311
C312
N21A
C341
C23A
C34
C24A
C25A
C32
C322
C342
C33
C321
C331
C332
C10
C20
C15
C30
Fig. 2b. DIAMOND-1.2 plot of 19 and the solvent molecule with special emphasis of the disorder. The atoms in question are shaded.
correspond with four lines in the 13C NMR (Table 2). This
clearly reflects an electronic situation which forces the
iminium system into a rigid coplanar orientation with
respect to the oxazoline ring thereby exposing one subs-
tituent, Me or CH2-CH2, respectively, to the magnetic
influence of the perpendicularly arranged aromatic fluor-
enediyl [27].
and Section 3). In addition we are confronted with a Cr–C1
bond (2.033(3) A) that is rather short for a carbanionic,
respectively, carbene complex stabilized by two heteroa-
˚
toms (cf., for instance, Cr(CO)5{C(NMe2)(OEt)}: d(Cr–
˚
C
carbene) = 2.133(4) A [28]), obviously a further measure
by which the entire system tries to compensate for the
strong electron deficiency introduced into the heterocycle
by the 4-ketiminium function.
The X-ray structure analysis is in full accord with this
interpretation (Figs. 2a and 2b). The interplanar angle
between the perfectly planar oxazoline ring – the maximal
deviation of an atom (O1) from its best plane amounts to
merely 6(2) pm – and the fluorene entity in fact measures
89.8(2)ꢁ. That the interaction pyrrolidine/fluorenediyl is
also a repulsive one is born out by the two external angles
about C2, N21–C2–N1 and N21–C2–C3, differing by as
much as 10ꢁ. The most striking feature common to all spe-
cies of this kind, however, is a sequence of similarly short
bond distances extending across the oxazoline ring atoms
O1, C1, N1 and C2 as well as the exo-N21. Coming up
2.4. Protonation and alkylation of complex 19
The spectroscopic and structural data collected on 19
(cf. Section 2.3) suggest its bonding to be described in terms
of an extensive p-electron delocalization of the form B with
still a considerable share of beta¨ın character. The question
arose whether the heterocyclic ligand in spite of its partially
positive charge would further react with electrophiles.
Treatment of 19 at 0 ꢁC in dichloromethane with equi-
molar amounts of (a) HBF4 and (b) Me3OþBFꢀ gave bril-
4
˚
to only 1.26(2) A the distance between the last-named is
liant yellow microcrystalline solids in an almost
quantitative yield which after workup were identified as
the cationic N,O-carbene complexes 20 and 21 (Section 3
and Tables 1–4).
particularly short and probably indicative of an isolated
Csp2 –Nsp2 double bond though this value is to be taken with
care due to some disorder in the pyrrolidine region (Fig. 2b

2944
V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
phorane had been reacted with various carbonyl
compounds to give the corresponding complex vinylisocy-
anides, a result we erroneously also assumed for a similar
reaction at platinum(II) in 22 [8]. Repeating the experiment
we now found that the [3+2] cycloaddition gets the upper
hand over the Wittig-type reaction in spite of the presence
of triphenylphosphine (Eq. (3)). What tips the balance is
the well-known activation towards nucleophilic attack
isocyanides experience when bonded to higher valent met-
als, an effect thoroughly studied in their coordination and
organometallic chemistry [30].
N
N
O
[Cr0]
B
R
N
N
1. NEt3
(OC)5Cr
[Pt(Cl)(CNCH2PPh3)(PPh3)2] (BF4)2
23 + 24
BF4
2. RCHO
O
22
ð3Þ
(20) R = H
(21) R = Me
H
N
PPh3
N
H
H
trans-[Cl(Ph3P)2Pt
]
trans-[Cl(Ph3P)2Pt
BF4
]
BF4
O
O
R
R
The increased p-acceptor ability of the N-protonated and
methylated ligands is evident from the m(CO)-A1-IR-
absorptions of the new compounds which appear some
15 wavenumbers above that of 19, and from the differences
Dd in the 13C NMR shifts of the cis- and trans-CO ligands
which decrease from 6.2 (19) to 5.7 (20) and 4.1 ppm (21),
respectively [29]. As expected both, 20 and 21 show the
same doubling of the signals of the aliphatic protons and
24
23
(23) R = 4-C6H4NO2
(24) R = 4-C6H4NO2
The resulting Pt complex 23 is sufficiently characterized
by analysis, IR, H and 31P NMR spectra as well as con-
1
ductivity measurements (Tables 1, 2 and 4, Section 3).
According to the signal pattern of the oxazolin-2-ato
hydrogens we are dealing with only one diastereoisomer,
in fact the cis-arrangement of the two hydrogens, as gath-
1
of the carbon atoms of the pyrrolidine ring in the H and
13C NMR, respectively, as 19, i.e., its free rotation about
the C–N-axis is obviously hindered (see above).
3
ered from the value of the J(H,H0) coupling constant
2.5. Oxazolin-2-ato complex formation in the system
(isocyanomethylene)triphenylphosphorane-platinum(II)
and p-nitrobenzaldehyde
(12 Hz). The other isomer might well be present in the res-
idue which makes up the bulk containing some cis-
[PtCl2(PPh3)2] along with [Pt(Cl)(CNMe)(PPh3)2]BF4 and
an impure fraction tentatively formulated as 24. Loss of
PPh3 from the heterocycle – indicated here by a higher
%N value and the lack of P-signals without 195Pt satellites
in the 31P NMR – has been observed in several cases, one
driving force being aromatization [25,31].
In the preceding sections, it has been shown that the
course of the reaction between 1, triphenylphosphine and
a carbonyl compound (aldehyde, ketone) is dramatically
changed if PPh3 is replaced by tris(dimethylamino)phos-
phine. While with the former a-chlorovinylisocyanide com-
plexes 7–9 are obtained, P(NMe2)3 gives solely rise to
oxazolin-2-ylidene(ato) species (17, 19), for which we have
put forward a reduced oxygenophilicity of the P-atom in A.
3. Experimental
All manipulations were performed under an atmosphere
of pure argon using Schlenk-tube and vacuum techniques.
The solvents were dried and distilled prior to use. Complex
1 was prepared according to a published procedure [32].
IR: Beckman IR 12 double beam infrared spectrometer
and Perkin–Elmer 983 IR-spectrometer. NMR: Bruker
AM 250, JEOL FX 90 and JEOL Lambda 400 spectrome-
ters. MS: (EI) Varian Mat 711 (excitation energy 80 eV),
(pos-FAB) Varian MAT CH 5 DF (neutral xenon source
at 3 keV). Microanalyses (C, H, N) (Table 4): Heraeus
CHN-Rapid elemental analyzer. Melting points (uncor-
rected): Gallenkamp MFB-595 apparatus. Conductivity
measurements: Knick Digital Conductometer Model 600.
PPh3
[Pt11
]
C
N
CH
O
C
Here we report on the same competition for –Oꢀ in a
slightly modified system C. Pentacarbonylchromium- and
-tungsten-coordinated (isocyanomethylene)triphenylphos-

V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
2945
N
Table 4
Analytical and other data
Complex
Chemical formula molecular mass (g/mol)
Melting point (ꢁC)
Yield (%)
72
Analyses (%)
C
H
7
C14H5ClCrFNO5
373.60
93
Calculated
Found
44.91
45.71
1.34
1.33
3.74
3.90
8
C22H6Cl2Cr2N2O10
633.15
107
63
71
4
Calculated
Found
41.69
41.61
0.94
1.57
4.41
4.95
9
C20H8ClCrNO5
429.67
115
Calculated
Found
55.89
54.02
1.86
2.13
3.25
3.21
10
11
13
14
17
19
20
21
22
C8Cl3CrNO5
348.4
85–86
174 (dec.)
88
Calculated
Found
27.58
28.27
–
–
4.02
4.15
C14Cl2Cr2N2O10
531.1
12
66
Calculated
Found
31.66
31.39
–
–
5.28
5.21
C22H22CrFN3O5
479.43
Calculated
Found
55.11
55.05
4.58
5.03
8.76
8.84
C38H40Cr2N6O10
844.45
107
59
Calculated
Found
54.04
52.95
4.73
5.39
9.95
9.32
a
C22H14CrN2O6
454.4
169 (dec.)
107
Calculated
Found
58.16
57.75
3.11
3.20
6.17
6.12
C24H16CrN2O6
77
71
77
81
18
Calculated
Found
59.96
59.67
3.33
3.66
5.83
5.82
480.27
C24H17BCrF4N2O6
568.07
173 (dec.)
188
Calculated
Found
50.07
50.30
2.99
3.51
4.92
5.07
C25H19BCrF4N2O6
582.08
Calculated
Found
51.54
49.38
3.26
3.69
4.81
5.02
C56H47B2ClF8NP3Pt + CH2Cl2
1316.00
187 (dec.)
158 (dec.)
Calculated
Found
52.02
51.86
3.75
3.91
1.06
1.14
23
C63H51BClF4N2O3P3Pt + 1/2 CH2Cl2
1336.85
Calculated
Found
57.05
57.27
3.92
4.01
2.10
2.20
a
Not determined.
3.1. Preparation of Cr(CO)5CN–CCl@CRR0 (7–9)
(general procedure)
3.2. Reduction of 1 with zinc. Complexes 10 and 11
Zinc powder (750 mg, 11.5 mmol) is suspended in a
solution of 1.50 g (4.46 mmol) of 1 in 50 ml of diethylether,
and the mixture is cooled to ꢀ40 ꢁC. Argon-saturated gla-
cial acetic acid (2 ml) is added, and the suspension is
allowed to warm to room temperature. After stirring for
16 h the yellow precipitate is filtered off and extracted with
ether (3 · 15 ml). The combined filtrate and extracts are
evaporated to dryness, and the residue is extracted with
n-pentane. Chromatography on silica gel (0.063–
0.200 mm, Merck) results in three fractions the first of
which is sublimed in high vacuum to give 30 mg of 10;
the second fraction contains traces of 11 contaminated with
10 and is disposed, while the third contains the main prod-
uct Cr(CO)5CNMe (270 mg, 45%).
Action of zinc amalgam (in excess) on 1 (504 mg,
1.50 mmol) in 40 ml of ether leads to a red-orange solution
the chromatographic work-up of which (see above) yields
two yellow phases. Only the first is collected to give after
recrystallization from dichloromethane/petrolether 50 mg
(12%) of 11 as yellow plates.
To a mixture of 336 mg (1.0 mmol) of 1 and 125 mg
(1.0 mmol) of p-fluorobenzaldehyde [respectively 67 mg
(0.5 mmol) of terephthaldehyde, respectively 180 mg
(1.0 mmol) of 9-fluorenone] in 20 ml of diethylether is
added dropwise at 0 ꢁC a solution of 524 mg (2.0 mmol)
of triphenylphosphine in 20 ml of diethylether. A precipi-
tate of [Ph3PCl]Cl forms immediately, while the superna-
tant solution turns from yellow to orange. After warming
to room temperature the solution is stirred for 24 h after
which time the precipitate is filtered off and the solution is
evaporated to dryness. The remaining residue is purified
by chromatography on
a
silica-charged column
(2 · 18 cm) with petrolether/ether (10/1) as eluent. In all
cases, the second, intensely yellow to green fraction is col-
lected. Evaporation of the solvent affords the products as
mixtures of E and Z isomers. Recrystallization from
diethylether/n-hexane (1/2) results in lemon-coloured nee-
dles (7) [respectively orange needles (8), or light green
plates (9)].

2946
V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
3.3. Reactions of 7 and 8 with pyrrolidine. Preparation of
complexes 13 and 14
3.7. Preparation of complex 23
3.7.1. trans-[Pt(Cl)(CNCH2PPh3)(PPh3)2](BF4)2 (22)
To a solution of 0.70 g (1.57 mmol) of [CNCH2PPh3]
PF6 [8] in 100 ml of dichloromethane are added 1.32 g
(0.78 mmol) of [Pt(l-Cl)(PPh3)2]2(BF4)2 [33]. After 12 h of
stirring at r.t. the first milky suspension has almost become
a clear solution which is filtered through Celite. The filtrate
is concentrated in vacuo to about 40 ml, layered with 15 ml
of ether and cooled to ꢀ15 ꢁC. The compound separates as
white crystals which are soluble in CH2Cl2 and acetonitrile.
Molar conductivity: KM (22 ꢁC, 10ꢀ7 M, nitromethane) =
145 S molꢀ1 cm2.
To 372 mg (1.0 mmol) of
7 [respectively 316 mg
(0.5 mmol) of 8] in 15 ml of diethylether are added drop-
wise 0.25 ml (3.0 mmol) of pyrrolidine in 10 ml of diethyle-
ther. A white precipitate of pyrrolidine · HCl forms. After
stirring for 4 h the precipitate is filtered off (G4-frit), and
the solvent is removed in high vacuum. The residue is dis-
solved in a minimum amount of ether and chromato-
graphed on neutral Al2O3 with n-hexane/ether (2/1) as
eluent (2 · 18 cm column). The product is in the second
fraction which is collected and taken to dryness. The pale
yellow powder is recrystallized from n-hexane/ether (2/1)
at ꢀ20 ꢁC to give pale yellow prisms (13) [respectively yel-
low needles (14)].
3.7.2. Reaction with p-nitrobenzaldehyde
The solution of 1.0 g (0.8 mmol) of 22 (see Section 3.7.1)
and 0.12 g (0.8 mmol) of p-nitrobenzaldehyde in 50 ml of
dichloromethane is mixed with ca. 0.14 ml (ꢂ1 mmol) of
triethylamine and stirred for 5 days in the dark. The sol-
vent is removed and the solid residue transferred onto a
column (2.5 · 15 cm) charged with silica/CH2Cl2. First
the residue is washed with dichloromethane until the yellow
colour of the washing liquids2 has almost disappeared.
Finally, eluation of the product is carried out with a mix-
ture of dichloromethane and acetone (1/3) resulting in a
yellow phase which is taken to dryness and recrystallized
from CH2Cl2–ether. Pale yellow microcrystals (0.19 mg)
which are soluble in polar organic solvents.
3.4. Preparation of complexes 17 and 19
A solution of 672 mg of 1(2.0 mmol) and 360 mg
(2.0 mmol) of 9-fluorenone in 40 ml of diethylether is
cooled to 0 ꢁC. To this solution is added dropwise a mix-
ture of 0.74 ml (4.0 mmol) of P(NMe2)3 and 2.0 mmol of
the secondary amine [dimethylamine (90 mg) or pyrrolidine
(0.17 ml), respectively] in 10 ml of diethylether. The colour
of the solution changes to violet, and an oily material sep-
arates. The mixture is allowed to warm to room tempera-
ture and is stirred for further 2 h. The precipitate is
filtered off and the filtrate is evaporated to dryness. The res-
idue is purified by chromatography on a silica (respectively
Al2O3-neutral: 19) charged column (2 · 15 cm) with
petrolether/ether (1/1) as eluent. The product containing
second orange-yellow fraction is collected, and the solvent
removed in vacuum. Recrystallization from toluene at
ꢀ20 ꢁC affords lemon needles (17) or intensely yellow crys-
tals (19), respectively.
3.8. X-ray structure determinations
Suitable single crystals of 13 were obtained from a solu-
tion of the complex in diethyl ether layered with n-hexane at
ꢀ20 ꢁC, those of 19 grew from a saturated toluene solution
of 19 at 0 ꢁC. The crystals were mounted on glass fibers and
all geometric and intensity data were obtained with a STOE
four circle diffractometer (compound 13) and a STOE-
IPDS 25 four circle diffractometer (compound 19),
3.5. Preparation of complex 20
˚
respectively, using Mo Ka-radiation (k = 0.71073 A) and
A solution of 480 mg (1.0 mmol) of 19 in 20 ml of dichlo-
romethane is cooled to 0 ꢁC and mixed with 0.2 ml
(1.1 mmol) of an etheral solution of HBF4 (54%). The cool-
ing device is removed and stirring continued for 12 h at r.t.
after which time the solvent is removed in high vacuum. The
residue is stirred up in 20 ml of diethylether, collected on a
frit (G4) and washed several times with 20 ml of ether each.
The remaining brilliant yellow powdery solid is dried in vac-
uum and recrystallized at 0 ꢁC from dichloromethane–
diethylether (3/1) to give yellow needle-shaped crystals.
graphite-monochromators. An absorption correction (pro-
gram DIFABS [34]) was applied to 19, however, not to 13.
Both structures were solved by direct methods and devel-
oped using alternating cycles of full-matrix least-squares
refinement and difference-Fourier synthesis (programs 13:
SHELXS-86, SHELXL-93 [35]; 19: SHELXS-97, SHELXL-97 [36]).
All non-hydrogen atoms were refined anisotropically, the
hydrogens atoms isotropically in calculated positions, or
in those suggested by the difference Fourier maps (fluor-
enediyl part of 19), respectively. In 19 half a molecule of
toluene per complex molecule was found which is
3.6. Preparation of complex 21
2
A cursory workup of the CH2Cl2-solutions yielded fractions which
From 480 mg (1.0 mmol) of 19 and 170 mg (1.1 mmol)
of trimethyloxonium tetrafluoroborate as described for
20. Before evaporating the solvent, however, an excess of
[OMe3][BF4] is quenched with methanol (1 ml) to give yel-
low needle-shaped crystals.
were clearly identified as the hydrolysis product [Pt(Cl)(CNMe)(PPh3)2]
BF4 and cis-[PtCl2(PPh3)2]. In addition there was ample evidence for an
oxazolinatoplatinum species 24 which had lost its triphenylphosphonio
substituent (see Section 2.5). Molar conductivity: KM (22 ꢁC, 10ꢀ7 M,
nitromethane) = 109 S molꢀ1 cm2.

V. Langenhahn et al. / Journal of Organometallic Chemistry 692 (2007) 2936–2948
2947
Table 5
Selected crystal and data collection details for 13 and 19
Compound
13
19
Chemical formula
C22H22CrFN3O5
479.43
0.60 · 0.32 · 0.30
Monoclinic
C24H16CrN2O6 + 1/2 C7H8
526.47
0.30 · 0.30 · 0.08
Monoclinic
Formula mass (g molꢀ1
Crystal size (mm)
Crystal system
)
Space group
P21/c (No. 14)
12.657(5)
11.645(5)
P21/n (No. 14)
12.925(2)
11.615(1)
˚
a (A)
˚
b (A)
˚
c (A)
16.102(8)
17.405(2)
b (ꢁ)
Volume (A )
106.18(4)
2279.3(2)
106.89(1)
2500.2(5)
3
˚
Z
4
4
Dcalc (g cmꢀ3
)
1.397
5.47
293
1.399
5.03
100
Absorption coefficient l (cmꢀ1
Temperature (K)
)
Scan mode
x–2h
x–2h
2h Range (ꢁ)
2.19 6 2h 6 27
2.14 6 2h 6 25.15
Reflections collected
Reflections with [I P 2r(I)]
Number of variables
Final R indices
R indices (all data)
Goodness-of-fit on F2
4968
4411
2428
289
2905
514
R1 = 0.0397, wR2 = 0.0941
R1 = 0.1411, wR2 = 0.1264
1.000
0.399/ꢀ0.274
R1 = 0.0464, wR2 = 0.1103
R1 = 0.0798, wR2 = 0.1201
0.912
0.537/ꢀ0.497
ꢀ3
˚
Residual electron density (e A
)
[3] W.P. Fehlhammer, G. Beck, J. Organomet. Chem. 369 (1989) 105–
116.
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181–191.
[6] S. Ahn, G. Beck, W.P. Fehlhammer, J. Organomet. Chem. 418 (1991)
365–376.
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(1995) 27–34.
disordered in the crystal, however; statistical disorder
between two positions each was also observed for some
atoms within the CO ligand and the pyrrolidine ring region
(Fig. 2b). Crystallographic data and selected data referring
to the data collection and refinement are summarized in
Table 5. The programs ZORTEP and DIAMOND-1.2 were used
for Figs. 1, 2a and 2b, respectively.
[8] G. Zinner, W.P. Fehlhammer, Angew. Chem., Int. Ed. Engl. 24
(1985) 979–980.
4. Supplementary material
[9] W.P. Fehlhammer, G. Zinner, M. Bakola-Christianopoulou, J.
Organomet. Chem. 331 (1987) 193–205;
Additional data for the X-ray structure analyses have
been deposited with the Cambridge Crystallographic Data
Centre. CCDC 634690 and 634691 contain the supplemen-
tary crystallographic data for 13 and 19. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk.
G. Zinner, M. Bakola-Christianopoulou, W.P. Fehlhammer, in: R.B.
King, J.J. Eisch (Eds.), Organometallic Syntheses, vol.4, Elsevier,
Amsterdam, 1988, pp. 82–86.
[10] R. Appel, F. Knoll, W. Michel, W. Morbach, H.D. Wihler, H.
Veltmann, Chem. Ber. 109 (1976) 58–70.
[11] R. Rabinowitz, R. Marcus, J. Am. Chem. Soc. 84 (1962) 1312–1313.
[12] M. Guy, J.T. Guy Jr., D.W. Bennett, Organometallics 5 (1986) 1696–
1702.
[13] W.P. Fehlhammer, G. Beck, J. Organomet. Chem. 379 (1989) 97–106.
[14] D. Lentz, D. Preugschat, J. Chem. Soc., Chem. Commun. (1992)
1523–1524.
[15] R. Kunz, W.P. Fehlhammer, Angew. Chem., Int. Ed. Engl. 33 (1995)
330–332.
Acknowledgements
[16] W.P. Fehlhammer, G. Beck, Z. Naturforsch. B 44 (1989) 1414–1420.
[17] See also: K.H. Do¨tz, Chem. Ber. 113 (1980) 3597–3604.
[18] See also: M. Oki, Applications of Dynamic NMR-Spectroscopy to
Organic Chemistry, VCH, Weinheim, 1985.
[19] H. Fischer, F.R. Kreissl, U. Schubert, P. Hoffmann, K.H. Do¨tz, K.
Weiß, Transition Metal Carbene Complexes, VCH, Weinheim, 1985.
[20] H. Fischer, U. Schubert, R. Ma¨rkl, Chem. Ber. 114 (1981) 3412–
3420.
Financial support for this work by the Fonds der Chem-
ischen Industrie and the Deutsche Forschungsgemeinschaft
is gratefully acknowledged. We also thank Professor Dr.
Robert Weiß, Erlangen, and Dr. Borislav Boyadjiev, Ber-
lin, for helpful discussions.
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