Reactions of a chelated cyclopentadienylcobalt(I) complex with 3,3-disubstituted cyclopropenes: Formation of isoprene, vinylcarbene, and 1-phosphadiene ligands at the metal

Article abstract of DOI:10.1021/om970851o

(Di-tert-butylphosphanyl-P-ethyl)cyclopentadienylcobalt(I) complexes 1 and 2 were treated with 3,3-disubstituted cyclopropenes to give isoprene and vinylcarbene complexes. The diphenylvinylcarbene complex reacted with tert-butylphosphaethyne to give unusual coupling products.

Full text of DOI:10.1021/om970851o

Organometallics 1998, 17, 893-896
893
Rea ction s of a Ch ela ted Cyclop en ta d ien ylcoba lt(I)
Com p lex w ith 3,3-Disu bstitu ted Cyclop r op en es:
F or m a tion of Isop r en e, Vin ylca r ben e, a n d
1-P h osp h a d ien e Liga n d s a t th e Meta l
J an Foerstner, Alf Kakoschke, Dirk Stellfeldt, and Holger Butenscho¨n*
Institut fu¨r Organische Chemie, Universita¨t Hannover, Schneiderberg 1B,
D-30167 Hannover, Germany
Rudolf Wartchow
Institut fu¨r Anorganische Chemie, Universita¨t Hannover, Callinstrasse 9,
D-30167 Hannover, Germany
Received September 30, 1997
(Di-tert-butylphosphanyl-P-ethyl)cyclopentadienylcobalt(I) complexes 1 and 2 were treated
with 3,3-disubstituted cyclopropenes to give isoprene and vinylcarbene complexes. The
diphenylvinylcarbene complex reacted with tert-butylphosphaethyne to give unusual coupling
products.
We have investigated the chemistry of (di-tert-bu-
tylphosphanyl-P-ethyl)cyclopentadienylcobalt(I) (Cp#Co)
complexes for some time1,2 and are particularly inter-
ested in reactions which are not observed with the
unsubstituted cyclopentadienylcobalt(I) system (CpCo).
As the Cp#Co system, in contrast to CpCo, does not
facilitate cyclooligomerization reactions of alkynes, alkyne
complexes are easily obtained with Cp#Co.2 Recently,
we reported the formation of Cp#Co vinylidene com-
plexes.3,4 Reactions with tert-butylphosphaethyne re-
sulted in complete cleavage of the PtC bond with
formation of a phosphido cluster, whose phosphido
ligand could be oxidized to a PO or PS ligand.5 Cyclo-
propenes form complexes with transition metals or react
with transition metal complexes to form oligomers6-8
or vinylcarbene complexes.9,10 Because only a few
vinylcarbene complexes of cobalt are known11,12 and in
light of the role of vinylcarbene complexes in catalysis,13
we undertook the preparation of such species by treat-
ment of Cp#Co complexes such as 1 or 2 with cyclopro-
penes.
Treatment of cobalt chloride complex 1 with 3,3-
dimethylcyclopropene14,15 in the presence of sodium
amalgam4 gave 3,3-dimethylcyclopropene complex 3,16
which was characterized spectroscopically, in 71% yield.
As a consequence of a DTA measurement (DTA )
differential thermal analysis), 3 was heated at 65 °C in
THF for 2 h to give isoprene complex 6 in 97% yield.16
Although isoprene formation from 3,3-dimethylcyclo-
propene has been observed under pyrolytic conditions
in up to 10% yield,17,18 it is unprecedented in a metal-
induced reaction under comparatively mild conditions.
We rationalize this reaction in terms of an insertion
of the reduced cobalt species into one of the strained
C-C single bonds of the cyclopropene with formation
of a cobaltacyclobutene 4 as shown in Scheme 1. An
intramolecular oxidative addition of one of the six
equivalent C-H bonds (C-H activation) yields Co(III)
complex 5 with a free phosphane arm. Subsequent
reductive elimination gives isoprene complex 6.
In contrast to the reaction with 3,3-dimethylcyclopro-
pene, treatment of 2 with 3,3-diphenylcyclopropene,15,19
which lacks C-H bonds at a carbon atom adjacent to
the cyclopropene ring, resulted in the formation of
diphenylvinylcarbene complex 7 in 91% yield, which was
characterized spectroscopically.20 We have been unable
to isolate the 3,3-diphenylcyclopropene complex to date.
However, in some experiments, a small amount of the
(1) Kettenbach, R. T.; Butenscho¨n, H. New J . Chem. 1990, 14, 599.
(2) Kettenbach, R. T.; Bonrath, W.; Butenscho¨n, H. Chem. Ber. 1993,
126, 1657.
(3) Kettenbach, R. T.; Kru¨ger, C.; Butenscho¨n, H. Angew. Chem.
1992, 104, 1052; Angew. Chem., Int. Ed. Engl. 1992, 31, 1066.
(4) Foerstner, J .; Kettenbach, R.; Goddard, R.; Butenscho¨n, H. Chem.
Ber. 1996, 129, 319.
(5) Foerstner, J .; Olbrich, F.; Butenscho¨n, H. Angew. Chem. 1996,
108, 1323; Angew. Chem., Int. Ed. Engl. 1996, 35, 1234.
(6) Binger, P.; Schroth, G.; McMeeking, J . Angew. Chem. 1974, 86,
518; Angew. Chem., Int. Ed. Engl. 1974, 13, 465.
(7) Binger, P.; McMeeking, J . Angew. Chem. 1974, 86, 518; Angew.
Chem., Int. Ed. Engl. 1974, 13, 466.
(8) Binger, P.; Mu¨ller, P.; Benn, R.; Mynott, R. Angew. Chem. 1989,
101, 647; Angew. Chem., Int. Ed. Engl. 1989, 28, 610.
(9) Binger, P.; Bu¨ch, H. M. Top. Curr. Chem. 1987, 135, 77.
(10) Fischer, H.; Hofmann, J .; Mauz, E. Angew. Chem. 1991, 103,
1013; Angew. Chem., Int. Ed. Engl. 1991, 30, 998.
(13) Grubbs, R. H.; Miller, S. J .; Fu, G. C. Acc. Chem. Res. 1995,
28, 446.
(11) Wadepohl, H.; Pritzkow, H. Angew. Chem. 1987, 99, 132;
Angew. Chem., Int. Ed. Engl. 1987, 26, 127.
(12) Vale´ri, T.; Meier, F.; Weiss, E. Chem. Ber. 1988, 121, 1093.
(14) A sample of 3,3-dimethylcyclopropene was kindly provided by
Prof. Dr. P. Binger, Universita¨t Kaiserslautern.
(15) Binger, P. Synthesis 1974, 190.
S0276-7333(97)00851-0 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 02/06/1998

894 Organometallics, Vol. 17, No. 5, 1998
Foerstner et al.
cobaltacyclobutene leading to 7 was isolated and identi-
fied by inspection of its spectroscopic data.
ture (5:1) of 3,3-dimethoxycyclopropene complex 8 and
a not completely characterized side product was ob-
tained in 93% yield. Presumably, the latter is the
Reaction of cobalt chloride complex 1 with 3,3-
cobaltacyclobutene that might lead to the corresponding
vinylcarbene complex. We are currently investigating
this possibility and the chemistry of vinylcarbene com-
plex 7.
The first result in this context was obtained when 7
was treated with tert-butylphosphaethyne. Instead of
a cobaltaphosphacyclobutene,22 a mixture (3:1) was
obtained in 65% overall yield, which consisted of cou-
pling products 9 and 10, Scheme 2. These were sepa-
rated by column chromatography and subsequent crys-
tallization.23
9 was characterized spectroscopically on the basis of
the following considerations: The formula C35H47CoP2
is confirmed by the mass spectrum showing the molec-
ular ion peak at m/z 588 as well as by the high-
resolution mass spectrum of this peak. The peak at m/z
296 confirms the existence of the Cp#Co fragment. In
the 31P NMR spectrum, the signal at δ ) 29.2 corre-
sponds to an uncoordinated phosphane arm.2,4 The 31P
NMR signal at δ -66.5 is assigned to the phosphorus
atom in the coordinated CdP double bond, which is in
the same range as the corresponding value of the
conjugated system 10 (δ -11.5) and provides evidence
against a cobaltaphosphacyclobutene substructure which
should give rise to a signal at δ > 300.24,25 The 1H NMR
spectrum shows signals for all protons of 9 at reasonable
dimethoxycyclopropene21 gave a similar result; a mix-
(16) 3: 3,3-Dimethylcyclopropene (245 mg, 3.60 mmol) was con-
densed into a -50 °C cold solution of 1 (301 mg, 0.90 mmol) in THF
(50 mL). After 5 min, sodium amalgam (26.0 g, 2%) was added dropwise
via pipet. The temperature was allowed to raise to -45 °C, causing
the amalgam to melt. The mixture was stirred at this temperature for
10 min and was then allowed to warm to 20 °C. After the mixture was
stirred for 1 h, the THF was condensed into a cold trap and the residue
taken up with a small amount of diethyl ether and filtered through a
P4 frit covered with a layer of Celite (3 cm). The Celite was washed
with diethyl ether until the ether remained colorless. The diethyl ether
was condensed into a cold trap, and the residue was crystallized from
diethyl ether giving 3 (233 mg, 0.64 mmol, 71%) as brown crystals,
mp 88 °C (DTA/TG), exothermic reaction. 1H NMR (200 MHz, benzene-
3
d6): δ 1.14 (s, 3H, C(CH3)2), 1.22 (d, 18H, C(CH3)3, J C,P ) 11.5 Hz),
1.38 (s, 3H, C(CH3)2), 1.6-1.9 (m, 6H, CH2CH2, HCdCH), 4.44 + 5.35
(AA′BB′ line system, 2 × 2H, Cp#-CH). 13C NMR (50 MHz, benzene-
d6, APT): δ 24.61 (+, d, PCH2CH2, 2J C,P ) 6.5 Hz), 24.62 (-, s, C(CH3)2),
2
2
26.8 (-, br d, dCH, J C,P ) 8.0 Hz), 30.5 (-, d, C(CH3)3, J C,P ) 3.9
4
1
Hz), 34.8 (-, d, C(CH3)2, J C,P ) 1.4 Hz), 35.1 (+, d, C(CH3)3, J C,P
)
1
6.3 Hz), 37.3 (+, d, PCH2CH2, J C,P ) 20.7 Hz), 48.28 (+, d, C(CH3)2,
3J C,P ) 4.0 Hz), 78.06 (-, d, Cp#-CH, J C,P ) 6.3 Hz), 79.6 (-, s, Cp#-
2
CH), 112.6 (+, d, Cp#-CCH2, J C,P ) 7.8 Hz). 31P NMR (81 MHz,
3
benzene-d6): δ 88.1. 6: A solution of 3 (174 mg, 0.48 mmol) in toluene
(5 mL) was heated at 65 °C for 2 h. The color changed from brown to
red. The solvent was condensed into a cold trap, and the viscous residue
was taken up with diethyl ether and filtered through a P4 frit covered
with a layer of Celite (3 cm). The Celite was washed with diethyl ether
until the ether remained colorless. The ether was condensed into a
cold trap to give 6 (169 mg, 0.47, 97%) as a red oil. 1H NMR (200 MHz,
benzene-d6): δ -0.26 (dd, 1H, CHdCHH, 3J ) 9 Hz, 2J ) 1.5 Hz),
3
-0.16 (br s, 1H, C(CH3)dCHH), 1.20 (d, 18H, C(CH3)3, J P,H ) 10.5
Hz), 1.81 (m, 2H, PCH2CH2), 1.82 (m, 1H, CHdCHH), 1.85 (m, 1H,
C(CH3)dCHH), 2.11 (s, 3H, C(CH3)dCH2), 2.65 (ddd, 2H, PCH2CH2,
2
2J ) 6.0 Hz, 3J ) 7.0 Hz, J P,H ) 18.0 Hz), 4.48 (m, 1H, Cp#-CH), 4.57
(m, 1H, Cp#-CH), 4.70 (m, 1H, Cp#-CH), 4.77 (m, 1H, Cp#-CH), 4.93
(br m, 1H, CHdCH2). 13C NMR (100 MHz, benzene-d6, BB): δ 23.1 (s,
(21) Baucom, K. B.; Butler, G. B. J . Org. Chem. 1972, 37, 1730.
(22) Mu¨ller, P. Dissertation, Universita¨t Kaiserslautern, 1989.
(23) Reaction of 7 wih tert-butylphosphaethyne: tert-Butylphospha-
ethyne (2.6 mg, 0.26 mmol) was added to a solution of 7 (120 mg, 0.26
mmol) in THF (5 mL). After 3 days of stirring, a color change from
green to brown was completed. The THF was condensed into a cold
trap, and the residue was taken up with petroleum ether/diethyl ether
(3:1) and chromatographed (SiO2). The isolated material was crystal-
lized from diethyl ether to give the first fraction of 9 (74 mg, 0.13 mmol,
49%) as red crystals, mp 159 °C (DSC). 1H NMR (400 MHz, benzene-
2
C(CH3)dCH2), 23.6 (d, PCH2CH2, J C,P ) 23.3 Hz), 29.8 (d, C(CH3)3,
2J C,P ) 13.9 Hz), 30.2 (d, PCH2CH2, 1J C,P ) 30.1 Hz), 31.3 (d, C(CH3)3,
1J C,P ) 22.9 Hz), 31.5 (br s, dCH2), 34.8 (br s, dCH2), 78.6 (s, CHdCH2),
78.9 (s, Cp#-CH), 79.0 (s, Cp#-CH), 79.9 (s, Cp#-CH), 80.2 (s, Cp#-CH),
3
93.7 (C(CH3)dCH2), 101.3 (d, Cp#-CCH2, J C,P ) 15.7 Hz). 31P NMR
(81 MHz, benzene-d6): δ 29.3.
(17) Walsh, R.; Untiedt, S.; Stohlmeier, M.; de Meijere, A. Chem.
Ber. 1989, 122, 637.
3
3
(18) Srinivasan, R. J . Chem. Soc. D 1971, 1041.
(19) Binger, P. Personal communication.
d6): δ 1.18 (d, 9H, C(CH)3, J C,P ) 10.6 Hz), 1.19 (d, C(CH)3, J C,P )
10.7 Hz), 1.37 (s, 9H, C(CH3)3), 1.61 (m, 2H, CH2), 2.50 (m, 2H, CH2),
3.43 (m, 1H, phosphirene-CH, J ) 3.3 Hz), 4.23 (m, 1H, Cp#-CH), 4.63
(m, 1H, Cp#-CH), 4.78 (m, 2H, Cp#-CH), 5.37 (m, 1H, dCH, J ) 3.3
Hz), 6.94 (m, 1H, arom. H), 7.10-7.25 (4H, arom. H), 7.30-7.44 (m,
3H, arom. H), 7.72 (m, 2H, arom. H). 13C NMR (100 MHz, benzene-
(20) 7: A solution of 3,3-diphenylcyclopropene (2.12 g, 11.0 mmol)
and 2 (3.60 g, 11.0 mmol) in THF (750 mL) was stirred at 20 °C for 12
h. The color changed from red-brown to deep green. The solvent was
condensed into a cold trap, and the residue was taken up with a small
amount of THF, filtered through a P4 frit covered with a layer of Celite
(3 cm). The Celite was washed with THF until the filtrate remained
colorless. The solvent was condensed into a cold trap, and 7 (4.88 g,
10.0 mmol, 91%) was obtained as green-black crystals, mp 154.2 °C
2
2
d6): δ 23.2 (d, PCH2CH2, J C,P ) 23.5 Hz), 23.3 (d, PCH2CH2, J C,P
)
2
2
23.5 Hz), 29.8 (d, PC(CH3)3, J C,P ) 14.0 Hz), 29.9 (d, PC(CH3)3, J C,P
1
) 14.0 Hz), 30.7 (d, CC(C3)3, J C,P ) 1.5 Hz), 31.3 (d, PC(CH3)3, J C,P
)
)
22.3 Hz), 32.1 (d, CC(CH3)3, 3J C,P ) 5.1 Hz), 34.0 (d, PC(CH3)3, 1J C,P
1
(DTA/TG), exothermic reaction. 1H NMR (200 MHz, benzene-d6):
δ
9.5 Hz), 39.1 (dCH), 51.3 (d, PCH, J C,P ) 3.2 Hz), 66.3 (d, PdC, J C,P
1.07 (d, 18H, C(CH3)3, 3J P,H ) 12.0 Hz), 1.82-2.15 (m, 2H, PCH2CH2),
) 27.0 Hz), 78.2 (d, Cp#-CH, 2J C,P ) 2.4 Hz), 79.6 (d, Cp#-CH), 79.8 (d,
2.65 (dt, 2H, PCH2CH2, 3J ) 8 Hz, J P,H ) 8 Hz), 3.85 (m, 2H, Cp#-
Cp#-CH, J C,P ) 1.9 Hz), 81.3 (d, Cp#-CH, J C,P ) 6.4), 103.4 (d, Cp#-
2
2
2
3
CH), 5.80 (m, 2H, Cp#-CH), 6.95-7.52 (m, 8H, arom. CH), 8.14 (br d,
2H, arom. CH), 8.32 (br d, 1H, CodCH-CHd, 3J ) 14.0 Hz), 11.62
(dd, 1H, CodCH-CHd, 3J ) 14.0 Hz, 2J P,H ) 29.0 Hz). 13C NMR (100
C-CH2, J C,P ) 15.0 Hz), 113.3 (Ph2CdC), 124.9 (arom. CH), 125.92
(arom. CH), 125.95 (arom. CH), 126.1 (arom. CH), 127.9 (arom. CH),
128.0 (arom. CH), 128.7 (arom. CH), 128.8 (arom. CH), 129.4 (arom.
2
3
MHz, benzene-d6): δ 25.1 (d, PCH2CH2, J P,C ) 6.0 Hz), 29.5 (d,
CH), 129.5 (arom. CH), 131.6 (arom. CH), 147.5 (ipso-C, J C,P ) 12.7
C(CH3)3, J P,C ) 4.4 Hz), 34.7 (d, C(CH3)3, J P,C ) 10.9 Hz), 40.15 (d,
Hz), 151.7 (ipso-C, J C,P ) 1.9 Hz). 31P NMR (162 MHz, benzene-d6):
2
1
3
PCH2CH2, J P,C ) 19.6 Hz), 78.5 (Cp#-CH), 81.2 (d, Cp#-CH, J C,P ) 6
δ 29.2 (P(CCH3)3), -66.5 (phosphirene-P). Second crystal fraction: 10
(29 mg, 0.04 mmol, 16%).
1
2
Hz), 107.6 (d, Cp#-CCH2, J P,C ) 7.1 Hz), 123.6 (d, CPh2, J C,P ) 8.2
3
4
Hz), 125.4 (arom. CH), 125.7 (arom. CH), 125.8 (arom. CH), 146.6 (d,
(24) Haas, J . Dissertation, Universita¨t Kaiserslautern, 1990.
(25) Binger, P.; Haas, J .; Herrmann, A. T.; Langhauser, F.; Kru¨ger,
C. Angew. Chem. 1991, 103, 316; Angew. Chem., Int. Ed. Engl. 30,
1991, 310.
5
5
arom. ipso-C, J C,P ) 2, 2 Hz), 148.6 (d, arom. ipso-C, J C,P ) 2.2 Hz),
155.9 (d, CodCHdCH, J C,P ) 2.7 Hz), 199.5 (d, CodCHdCH, J C,P
33.8 Hz). 31P NMR (81 MHz, benzene-d6): δ 89.9.
3
2
)

Chelated Cyclopentadienylcobalt(I)
Organometallics, Vol. 17, No. 5, 1998 895
Sch em e 1
chemical shifts. In addition to the usual signals of the
Cp#Co fragment, the signals of the coordinated dCH at
δ 5.37 (J ) 3.3 Hz) and one of the adjacent tertiary
phosphirene CH at δ 4.43 (J ) 3.3 Hz) are diagnostic.
In the 13C NMR spectrum, the signals for all carbon
atoms are found and assigned on the basis of DEPT
spectra. The assignment of the coordinated olefinic
dCH (δ 39.1) and the phosphirene CH (δ 51.3) is based
on the observation of a C,P coupling (J ) 3.2 Hz) at the
latter signal.
The structure of 10 was determined by a crystal
structure analysis (Figure 1).26 Complex 10 is a 1,2-
cis-disubstituted 1-phosphadiene. The PdC bond dis-
tance (1.781(4) Å) is between the average values of P-C
single (1.85 Å) and PdC double bonds (1.67 Å).27 There
is one preliminary communication describing a bimetal-
lic η2 (PdC) platinum complex of a 1-phosphadiene with
F igu r e 1. Crystal structure of 10. Selected bond lengths
(Å) and angles (deg): Co1-P1 2.221(1), Co1-P2 2.257(1),
P2-P3 2.237(1), P2-C16 1.781(4), P3-C31 1.848(4), P3-
C36 1.836(4), C16-C17 1.454(5), C17-C18 1.351(5), C31-
C36 1.282(5); P1-Co1-P2 102.4(1), P2-Co1-C16 48.5(1),
Co1-P2-P3 105.4(1), Co1-P2-C16 59.9(1), P3-P2-C16
105.4(1), P2-C16-C17 125.3(3), Co1-C16-C17 118.3(3),
C16-C17-C18 127.9(3), C31-P3-C36 40.74(16), P3-
C31-C36 69.1(2), P3-C36-C31 70.1(2).
(26) Crystal structure analysis of 10: Crystal size 0.13 × 0.74 ×
0.28 mm, crystal system monoclinic, space group P21/c (No. 14), a )
18.589(3) Å, b ) 11.606(2), c ) 18.457(3) Å, â ) 103.57(2)°, V )
3870.8(12) Å3, Z ) 4, Fcalc ) 1.182 g/cm3, 2θmax ) 48.2°, Mo KR radiation,
λ ) 0.710 73 Å, 159 imaging plates, ∆φ ) 1.0°, T ) 300 K, 19 351
measured reflections, 5711 independent reflections, 5711 reflections
used for refinement, σ-limit 0 for refinement, no absorption correction,
structure solution with direct methods with SHELXS-86, refinement
with SHELXL-93, 401 free parameters, hydrogen atoms in geo-
metrically calculated positions, H27 (bound at C16) independently
refined, R1 ) 0.0413 [I > 2σ(I)], wR2 ) 0.0944 (all data), refinement
on F2, minimal and maximal residual eletron density -0.26, 0.26 e/Å3.
The crystallographic data (without structure factors) of the structure
described in this publication were deposited as supplementary publica-
tion no. CCDC 100140 at the Cambridge Crystallography Data Centre.
Copies of the data can be obtained with no charge from the following
address in Great Britain: The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ (Telefax Int. +1223/336-033. E-mail: deposit@
ccdc.cam.ac.uk).
the phosphorus atom coordinated to tungsten.28 The
additional coordination of the ligand to tungsten makes
this structure and that of 10 only partly comparable.
The PdC double bond in the platinum complex is 1.833-
(8) Å, as compared to 1.781(4) Å in 10. This is in accord
(28) Ajulu, F. A.; Al-J uaid, S. S.; Carmichael, D.; Hitchcock, P. B.;
Meidine, M. F.; Nixon, J . F.; Mathey, F.; Huy, N. H. T. J . Organomet.
Chem. 1991, 406, C20. We thank one of the reviewers for drawing our
attention to this publication.
(27) Multiple Bonds and Low Coordination in Phosphorous Chem-
istry; Regitz, M., Scherer, O. J ., Ed.; Georg Thieme Verlag: Stuttgart,
1990.

896 Organometallics, Vol. 17, No. 5, 1998
Foerstner et al.
Sch em e 2
with the fact that the ethene CdC double bond in
(Ph3P)2Pt(C2H4) is somewhat longer (1.434(13) Å)29 than
that in 2 (1.396(5) Å);3 however, the large estimated
standard deviation of the analysis of (Ph3P)2Pt(C2H4)
limits the meaning of such a comparison.
The formation of main product 9 can be explained by
assuming a cycloaddition of the vinylcarbene in 7 and
the PtC triple bond.27 To explain the formation of
1-phosphadiene 10, which is a 1:2 adduct of 7 and tert-
butylphosphaethyne, we envisage a dimerization of the
phosphaethyne to complex 11.27,30 From 11, the forma-
tion of 12 with recomplexation of the phosphane arm
can be explained as shown. A stepwise mechanism via
a phosphinidene complex 12 would be in accord with
observations of Mathey et al. with chromium and
tungsten complexes.31
Ack n ow led gm en t. This work was supported by the
Deutsche Forschungsgemeinschaft (Grant No. Bu 814/
3-1) and the Fonds der Chemischen Industrie. We thank
BASF AG, Bayer AG, Chemetall GmbH, Hu¨ls AG,
Phenolchemie GmbH, and Riedel de Hae¨n AG for
donations of chemicals.
Su p p or tin g In for m a tion Ava ila ble: Text giving the
analytical data of the new compounds, tables of crystal data,
final coordinates, hydrogen atom positions, anisotropic thermal
parameters, bond distances, bond angles, and torsion angles,
and NMR spectra (52 pages). Ordering information is given
on any current masthead page.
(29) Cheng, P.-T.; Nyburg, S. C. Can. J . Chem. 1972, 50, 912.
(30) Nixon, J . F. Chem. Soc. Rev. 1995, 319.
(31) Huy, N. H. T.; Ricard, L.; Mathey, F. Organometallics 1988, 7,
1791.
OM970851O