Structure and reactivity of mono(cyclopentadienyl)vanadium alkynyl and aryne complexes

Article abstract of DOI:10.1021/om950902m

Starting from CpVCl₂(PMe₃)₂ (1) the paramagnetic mono- and bis(phenylethynyl) complexes CpVCl_2-n(C=CPh)_n(PMe₃)₂ [n = 1 (2), 2 (3)] have been synthesized. Both compounds were characterized by X-ray diffraction and were found to be thermally more stable than other CpV^III hydrocarbyl complexes. The CpV^III bis(phenyl) complex CpVPh₂(PMe₃)₂ (5) decomposes at ambient temperature through β-hydrogen abstraction to give the first isolated vanadium benzyne complex, CpV(η²-C₆H₄)(PMe₃)₂ (6). The molecular structure of 6 indicates that this compound can best be described as a high-spin d² vanadium(III) benzometallacyclopropene. The cyclopropene character is expressed in the reactivity of 6, showing insertion of unsaturated substrates. Insertion of diphenylacetylene gives CpV(η²-PhC=CPhC₆H₄)(PMe₃) ₂ (7), with a planar vanadaindene structure, whereas terminal alkenes CH₂=CRR′ (R = H, Me; R′ = H, Me) insert regioselectively to give β-substituted metallaindanes CpV(η²-CH₂-CRR′C₆H ₄)PMe₃ (R and R′ = H, 8a; R = H, R′ = Me, 8b; R and R′ = Me, 8c), which show a low thermal stability in case one of the β-substituents is a hydrogen. With t-BuCN double insertion followed by rearrangement of the intermediate diazametallacycle gives the isoindolenine-substituted vanadium(III) imido complex CpV[NC(t-Bu)N=C(t-Bu)C₆H₄](PMe₃)₂ (9). The benzyne complex 6 reacts with dihydrogen to form the known triple-decker CpV(C₆H₆)VCp through partial hydrogenation of the benzyne ligand.

Full text of DOI:10.1021/om950902m

Organometallics 1996, 15, 2523-2533
2523
Str u ctu r e a n d Rea ctivity of
Mon o(cyclop en ta d ien yl)va n a d iu m Alk yn yl a n d Ar yn e
Com p lexes
J an Karel F. Buijink, K. Richard Kloetstra, Auke Meetsma, and J an H. Teuben*
Groningen Center for Catalysis and Synthesis, Department of Chemistry, University of
Groningen, Nijenborgh 4, NL-9747 AG Groningen, The Netherlands
Wilberth J . J . Smeets and Anthony L. Spek
Bijvoet Center for Biomolecular Research, Department of Crystal and Structural Chemistry,
University of Utrecht, Padualaan 8, NL-3584 CH Utrecht, The Netherlands
Received November 22, 1995X
Starting from CpVCl2(PMe3)2 (1) the paramagnetic mono- and bis(phenylethynyl) complexes
CpVCl2-n(CtCPh)n(PMe3)2 [n ) 1 (2), 2 (3)] have been synthesized. Both compounds were
characterized by X-ray diffraction and were found to be thermally more stable than other
CpVIII hydrocarbyl complexes. The CpVIII bis(phenyl) complex CpVPh2(PMe3)2 (5) decomposes
at ambient temperature through â-hydrogen abstraction to give the first isolated vanadium
benzyne complex, CpV(η2-C6H4)(PMe3)2 (6). The molecular structure of 6 indicates that this
compound can best be described as a high-spin d2 vanadium(III) benzometallacyclopropene.
The cyclopropene character is expressed in the reactivity of 6, showing insertion of
unsaturated substrates. Insertion of diphenylacetylene gives CpV(η2-PhCdCPhC6H4)(PMe3)2
(7), with a planar vanadaindene structure, whereas terminal alkenes CH2dCRR′ (R ) H,
Me; R′ ) H, Me) insert regioselectively to give â-substituted metallaindanes CpV(η2-CH2-
CRR′C6H4)PMe3 (R and R′ ) H, 8a ; R ) H, R′ ) Me, 8b; R and R′ ) Me, 8c), which show a
low thermal stability in case one of the â-substituents is a hydrogen. With t-BuCN double
insertion followed by rearrangement of the intermediate diazametallacycle gives the
isoindolenine-substituted vanadium(III) imido complex CpV[NC(t-Bu)N)C(t-Bu)C6H4](PMe3)2
(9). The benzyne complex 6 reacts with dihydrogen to form the known triple-decker
CpV(C6H6)VCp through partial hydrogenation of the benzyne ligand.
In tr od u ction
recently been subject of an extensive reactivity study
by Floriani et al.1g-l
Recent years brought increased interest in hydrocar-
byl complexes of trivalent vanadium.1 Traditionally,
studies in this area have dealt with (substituted) bis-
(cyclopentadienyl) systems Cp′2VR (Cp′ ) Cp or per-
alkylated Cp; R ) alkyl, aryl, allyl, alkynyl),2 although
a number of homoleptic complexes, such as V[CH-
A major contribution in this area has originated from
the study of the mono(cyclopentadienyl)vanadium(III)
dichloride complex CpVCl2(PMe3)2,5 which led to a range
of organovanadium derivatives, not only of V(III) but
also of V(II) and V(I). Important examples of the last
two categories include hydride complexes of V(II)1e and
the V(I) ethylene complex CpV(η2-C2H4)(PMe3)2.6
Depending upon the steric demands of the alkyl
group, V(III) dialkyl complexes1b-d with a varying
3
(SiMe3)2]3 and VMes3‚THF (Mes ) 2,4,6-trimethyl-
phenyl),4 have been reported. The last compound has
X Abstract published in Advance ACS Abstracts, April 15, 1996.
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S0276-7333(95)00902-2 CCC: $12.00 © 1996 American Chemical Society

2524 Organometallics, Vol. 15, No. 10, 1996
Buijink et al.
Sch em e 1. 1-Alk yn e to Vin ylid en e
Ta u tom er iza tion
centers. Dependent on the arrangement of the alkynyl
ligands, bis(alkynyl) complexes of vanadium(III) might
display similar behavior.
In this paper we describe the syntheses and molecular
structures of 16-electron CpVIII mono- and bis(alkynyl)
complexes, as well as thermal decomposition studies of
the diphenyl complex CpVPh2(PMe3)2, which resulted
in the formation of the first vanadium-benzyne com-
plex. The molecular structure and some aspects of the
reactivity of this CpV-benzyne complex will be dis-
cussed.
degree of electron deficiency have been synthesized,
1b,c
ranging from 16-electron CpVMe2(PMe3)2
to 12-
electron CpV[CH(SiMe3)2]2.1d CpVR2 complexes with
alkyl groups containing â-hydrogens could however not
be isolated, due to facile â-hydrogen transfer.6 Hydro-
gen abstraction is important in the thermolysis of V(III)
alkyl complexes, leading to interesting new species like
metallacycles and alkylidenes.1d,7 The 14-electron com-
plex CpV(CH2-t-Bu)2PMe3, for example, decomposes in
the presence of dmpe through R-hydrogen transfer to
give the first vanadium alkylidene CpV(dCH-t-Bu)-
(dmpe).1d Thermolysis of mono(cyclopentadienyl)vana-
dium(III) aryl complexes has however not been studied
in detail yet.
Resu lts a n d Discu ssion
Syn th eses a n d Molecu la r Str u ctu r es of Mon o-
(cyclop en ta d ien yl)va n a d iu m Alk yn yl Com p lexes.
Reaction of CpVCl2(PMe3)2 (1)5 with 1 or 2 equiv of
(phenylethynyl)lithium in diethyl ether affords the
mono- and bis(phenylethynyl) complexes CpVCl2-n
-
(CtCPh)n(PMe3)2 (2, n ) 1; 3, n ) 2), respectively (eq
1).
Transition metal alkynyl complexes have received
much attention in recent years, largely due to the
various bonding possibilities of acetylide anions and the
ability of the ligands to react with both nucleophilic and
electrophilic agents.8 For vanadium, however, only the
synthesis and characterization of several bis(cyclopen-
tadienyl)vanadium(III) alkynyls have been reported.2h,i,k
In this system, the stability of the V-C bond seems to
depend largely on the steric and electronic nature of
both the cyclopentadienyl and the alkynyl substituent:
the simple cyclopentadienyl complexes Cp2VCtCPh2h
Both are crystalline paramagnetic 16-electron com-
pounds, which are thermally quite stable in hydrocarbon
solvents. Solutions of 3 (benzene-d6) can be kept at 100
1
2i
°C for 16 h without significant decomposition. The H
and Cp2VCtCC6H4CtCVCp2 were found to be ther-
NMR spectra of 2 and 3 show 2 broad resonances in
each case. The resonances of the PMe3 protons (δ -11.9
ppm for 2 and δ -8.8 ppm for 3) follow the characteristic
downfield trend upon progressive displacement of chlo-
rine in 1 by hydrocarbyl ligands.1c Low-field resonances
at δ 28.3 ppm for 2 and δ 23.9 ppm for 3 probably
originate from some of the phenyl protons. No reso-
nances for the cyclopentadienyl protons were observed,
but this is normal for this type of CpVIII complex.1c The
IR spectra of 2 and 3 show characteristic νCtC vibrations
at 2043 and 2041 cm-1, respectively.2g-k Mixing of
equimolar amounts of 1 and 3 in benzene-d6 (1 week at
25 °C) does not result in the formation of 2 but leaves
unreacted starting material, which is in marked con-
trast with the observed easy comproportionation of 1
and CpVMe2(PMe3)2 to give the mono(methyl) complex
CpV(Me)Cl(PMe3)2 (4-5 h at 25 °C).1b,c Alternatively,
mally too unstable to be isolated chemically pure,
whereas both the corresponding peralkylated cyclo-
pentadienyl (C5Me4Et) derivatives2h,i as well as
2k
Cp2VCtCCMe3 were found to be stable.
The synthesis of mono- and bis(alkynyl) complexes of
mono(cyclopentadienyl)vanadium(III) might lead to in-
teresting starting materials for further reactivity stud-
ies, whereas their characterization could provide more
structural information about the V-C single bond in
low-valent vanadium complexes. For mono(alkynyl)
complexes possible equilibria among metal-alkyne,
metal-hydride alkynyl, and metal-vinylidene (Scheme
1), which have been shown to exist for several late
transition-metal complexes,9 could provide synthetic
pathways to vanadium(III) vinylidene complexes. Bis-
(alkynyl)titanocene(IV) derivatives have been used as
organometallic bidentate chelate ligands10 in the prepa-
ration of homo- and heterobinuclear complexes contain-
ing bridging σ-π-alkynyl groups between the metal
2 could not be synthesized by σ-bond metathesis of
1b,c
CpV(Me)Cl(PMe3)2
and phenylacetylene. In this
experiment the acetylene is slowly polymerized to an
insoluble polymer in a reaction reminiscent of the
catalytic polymerization of ethyne by CpVMe2(PMe3)2.1c
(7) Hessen, B. Ph.D. Thesis, Groningen, The Netherlands, 1989.
(8) Gamasa, M. P.; Gimeno, J .; Lastra, E.; Lanfranchi, M.; Tiripic-
chio, A. J . Organomet. Chem. 1991, 405, 333.
(9) Bianchini, C.; Peruzini, M.; Vacca, A.; Zanobini, F. Organo-
metallics 1991, 10, 3697 and references therein.
To elucidate the molecular structures of the two new
vanadium alkynyl compounds, X-ray structure deter-
minations were carried out. The crystal structure of the
mono(phenylethynyl) compound 2 shows 4 molecules in
the triclinic unit cell. The asymmetric unit contains two
crystallographically independent, nearly identical mol-
ecules. The molecular structure of 2 is depicted in
Figure 1 (one residue shown). Selected bond lengths
and angles are given in Table 1.
(10) (a) Ciriano, M. A.; Howard, J . A. K.; Spencer, J . L.; Stone, F.
G. A.; Wadepohl, H. J . Chem. Soc., Dalton Trans. 1979, 1749. (b) Lang,
H.; Zsolnai, L. J . Organomet. Chem. 1991, 406, C5. (c) Lang, H.; Herres,
M.; Zsolnai, L.; Imhof, W. J . Organomet. Chem. 1991, 409, C7. (d) Lang,
H.; Herres, M.; Ko¨hler, K.; Blau, S.; Weinmann, S.; Rheinwald, G.;
Imhof, W. J . Organomet. Chem. 1995, 505, 85. (e) J anssen, M. D.;
Smeets, W. J . J .; Spek, A. L.; Grove, D. M.; Lang, H.; Van Koten, G. J .
Organomet. Chem. 1995, 505, 123. (f) Lang, H.; Blau, S.; Nuber, B.;
Zsolnai, L. Organometallics 1995, 14, 3216. (g) Lang, H.; Weber, C.
Organometallics 1995, 14, 4415.

Mono(cyclopentadienyl)vanadium Complexes
Organometallics, Vol. 15, No. 10, 1996 2525
Ta ble 2. Selected Geom etr ica l Da ta for
Cp V(CtCP h )2(P Me3)2 (3)a
Bond Lengths (Å)
V(1)-P(1)
V(1)-C(1)
V(1)-C(12)
V(1)-C(13)
V(1)-C(14)
2.4447(15)
2.081(6)
2.281(13)
2.279(13)
2.306(12)
V(1)-C(15)
V(1)-C(16)
C(1)-C(2)
C(2)-C(3)
2.297(14)
2.294(13)
1.208(8)
1.425(8)
Bond Angles (deg)
P(1)-V(1)-P(1)′
P(1)-V(1)-C(1)
122.57(7)
77.06(13) V(1)-C(1)-C(2)
C(1)-V(1)-C(1)′ 129.4(2)
C(1)-V(1)-P(1)′
79.25(14)
175.3(4)
177.1(5)
C(1)-C(2)-C(3)
a
1
A prime indicates symmetry operation -x, y,
/
- z.
2
F igu r e 1. Molecular structure of CpVCl(CtCPh)(PMe3)2
(2). Only one of the two very similar but crystallographi-
cally independent molecules is shown. Thermal ellipsoids
are drawn at the 50% probability level.
Ta ble 1. Selected Geom etr ica l Da ta for
Cp VCl(CtCP h )(P Me3)2 (2)
residue 1
residue 2
Bond Lengths (Å)
2.4164(12) V(2)-Cl(2)
2.4720(11) V(2)-P(3)
2.4777(12) V(2)-P(4)
V(1)-Cl(1)
2.4037(12)
2.4683(11)
2.4724(11)
2.080(4)
2.286(3)
2.265(3)
2.294(3)
2.317(4)
2.310(4)
1.202(5)
1.443(5)
V(1)-P(1)
V(1)-P(2)
V(1)-C(1)
V(1)-C(9)
V(1)-C(10)
V(1)-C(11)
V(1)-C(12)
V(1)-C(13)
C(1)-C(2)
C(2)-C(3)
2.060(4)
2.276(3)
2.266(5)
2.295(5)
2.325(4)
2.307(4)
1.214(5)
1.437(5)
V(2)-C(20)
V(2)-C(28)
V(2)-C(29)
V(2)-C(30)
V(2)-C(31)
V(2)-C(32)
F igu r e 2. Molecular structure of CpV(CtCPh)2(PMe3)2
(3). Thermal ellipsoids are drawn at the 50% probability
level.
expected there is a clear elongation of the vanadium-
carbon bond in mono(cyclopentadienyl)vanadium com-
plexes with σ-bonded hydrocarbyl ligands on going from
an sp-hybridized carbon (as in 2, 2.060(4) Å) through
an sp2-hybridized carbon (as in CpV(η2-PhCdCPhC6H4)-
(PMe3)2 (7), 2.110(2) Å; vide infra) to an sp3-hybridized
carbon (as in CpV(η2-CH2CMe2C6H4)(PMe3)2, 2.194(3)
Å).1d
C(20)-C(21)
C(21)-C(22)
124.76(10)
80.26(4)
80.74(4)
76.75(10)
77.53(10)
130.40(4)
175.1(3)
The bis(phenylethynyl) compound 3 crystallizes with
4 molecules in a monoclinic unit cell. Selected bond
lengths and angles are given in Table 2.
The molecular structure of 3 (Figure 2) is very similar
to that of 2 and can also best be described as distorted
square-pyramidal,12 with the cyclopentadienyl ligand in
the apical position and the two phosphine ligands trans
in the square plane. Due to crystallographic C2 sym-
metry, with the 2-fold axis through the Cpcentroid and the
vanadium atom, only the bond distances and angles in
half of the molecule are listed in Table 2. The cyclo-
pentadienyl ring is disordered by the 2-fold axis in a
50:50 ratio. One of the two possible positions is shown
in Figure 2. The V-P and V-Calkynyl bond distances of
2.4447(15) and 2.081(6) Å, respectively, are similar to
those observed for 2. The trans arrangement of the
alkynyl ligands and the large C(1)-V(1)-C(1)′ bond
angle of 129.4(2)° make the use of 3 as an organo-
metallic bidentate chelate ligand unlikely.
The molecular structure of 2 can best be described as
distorted square-pyramidal with the cyclopentadienyl
function at the apical position.11 The phosphine ligands
are trans in the base plane. The V-Cl bond distances
(2.416(1) and 2.404(1) Å for residues 1 and 2, respec-
tively) are comparable to those found in the parent
dichloride 1 (mean value of 2.403 Å).1b,c The V-P
distances are in the range of those reported for other
mono(cyclopentadienyl)vanadium bis(phosphine) com-
pounds in medium to low oxidation states.1b-e The bond
angles between the ligands in the square plane are
unexceptional and show no sign of steric strain in the
molecule.
The V-Calkynyl distances (2.060(4) and 2.080(4) Å for
residues 1 and 2, respectively) and the CtCalkynyl
distances (1.214(5), 1.202(5) Å) are comparable to those
observed in bis(cyclopentadienyl)vanadium(III) alkynyl
complexes,2j,k whereas the V-C-Calkynyl bond angles
(171.8(3), 175.1(3)°) are only slightly smaller than the
corresponding angles in those complexes. As can be
Alkylation of 2 could provide alkyl-alkynyl com-
plexes, which after hydrogenolysis of the V-alkyl bond
might lead to vanadium hydride-alkynyl species. Un-
fortunately, salt metathesis of 2 and LiR [R ) Me, Ph,
CH2-t-Bu, CH2SiMe3, CH(SiMe3)2] produces intractable
(11) Percentage along Berry pseudorotation coordinate (trigonal
bipyramid to square pyramid): 80.1% for residue 1 and 78.6% for
residue 2. See: Holmes, R. R. Prog. Inorg. Chem. 1984, 32, 119.
(12) Percentage along Berry pseudorotation coordinate (trigonal
bipyramid to square pyramid): 76.5%. See ref 11.

2526 Organometallics, Vol. 15, No. 10, 1996
Buijink et al.
materials. A more defined compound is observed in the
reaction of 2 with 1 equiv of LiBH4 (eq 2), where
according to IR spectroscopy the vanadium(III) borohy-
dride CpV(η2-BH4)(CtCPh)PMe3 (4) is produced.
The IR spectrum of 4 shows characteristic borohy-
dride vibrations at 2363, 2342, and 2257 cm-1, which
correspond well with those observed for CpV(η2-BH4)-
dmpe1c and suggest η2-coordination in 4 as well. Com-
plex 4 is diamagnetic (by NMR spectroscopy) and
represents one of the few examples of low-spin vana-
dium d2 complexes.1d Formation of a low-spin η2-BH4
complex was also observed for the d3 complex CpV(BH4)-
dmpe.1c In the 1H NMR spectrum four broadened
doublets are observed for the BH4 protons (J BH ) 96
Hz, J PH ) 15 Hz) and one doublet for the PMe3 protons
of 4. However, multiple resonances in the cyclopenta-
dienyl region indicate that this compound is not pure,
as can also be seen from the elemental analysis.
Repeated recrystallizations from pentane neither im-
proved the elemental analysis nor gave less complicated
1H NMR spectra.
Syn th esis a n d Molecu la r Str u ctu r e of Cp V(η2-
C6H4)(P Me3)2. Formation of monomeric η2-benzyne
species has been observed in a number of early13 and
late14 transition metal systems. Given the instability
of free aryne, benzyne complexes are generally synthe-
sized by thermally induced elimination of alkanes or
arenes from transition metal aryl complexes (eq 3).
F igu r e 3. Molecular structure of CpV(η2-C6H4)(PMe3)2 (6).
Thermal ellipsoids are drawn at the 50% probability level.
Ta ble 3. Selected Geom etr ica l Da ta for
Cp V(η2-C6H4)(P Me3)2 (6)
Bond Lengths (Å)
V(1)-P(1)
V(1)-P(2)
V(1)-C(1)
V(1)-C(2)
V(1)-C(7)
V(1)-C(8)
V(1)-C(9)
V(1)-C(10)
2.4348(11)
2.4272(11)
2.055(3)
2.049(3)
2.291(4)
2.292(4)
2.303(3)
2.302(3)
V(1)-C(11)
C(1)-C(2)
C(1)-C(6)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
2.297(4)
1.368(5)
1.384(5)
1.385(5)
1.404(5)
1.382(5)
1.398(5)
Bond Angles (deg)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(4)-C(5)-C(6)
C(1)-C(6)-C(5)
P(1)-V(1)-P(2)
121.2(3)
118.1(3)
120.5(3)
120.7(3)
118.1(3)
95.79(4)
P(1)-V(1)-C(1)
P(1)-V(1)-C(2)
P(2)-V(1)-C(1)
P(2)-V(1)-C(2)
C(1)-V(1)-C(2)
V(1)-C(1)-C(2)
81.72(9)
109.89(9)
110.69(10)
81.29(9)
38.95(13)
70.28(18)
moderate yield (50%) after recrystallization from pen-
tane (eq 4).
Erker15 has shown that the formation of aryne
complexes during thermolysis of diarylzirconocenes
follows a concerted elimination of arene. Zirconocene
complexes with substituted benzynes have been used
extensively by Buchwald et al. for selective transforma-
tions of use in organic synthesis.13b
Bis(aryl) CpVPh2(PMe3)2 (5)1b,c was used as the start-
ing material for the synthesis of an η2-benzyne contain-
ing mono(cyclopentadienyl)vanadium complex. Ac-
cording to 1H NMR spectroscopy, 5 is stable in benzene-
d6 at 25 °C for a period of over 2 weeks but decomposes
at 50 °C (t1/2 ) 3-4 h) through elimination of benzene
to give CpV(η2-C6H4)(PMe3)2 (6), formally a vanadium(I)
complex, which could be isolated as green crystals in
The absorption at 1547 cm-1 in the IR spectrum of 6
is characteristic for a νCtC vibration in η2-benzyne
complexes.14 It is at lower energy than in the vana-
6b
dium(I) η2-alkyne complex CpV(η2-PhCtCPh)(PMe3)2
(1600 cm-1), indicating more pronounced π-back-dona-
tion in case of the benzyne ligand, as can be expected
for an alkyne system with substituents more bent away
from the metal.
To further elucidate the bonding in 6 an X-ray
structure determination was carried out. The molecular
structure is depicted in Figure 3, and selected bond
lengths and angles are given in Table 3.
(13) (a) Buchwald, S. L.; Watson, B. T. J . Am. Chem. Soc. 1986,
108, 7411. (b) Buchwald, S. L.; Nielsen, R. B. Chem. Rev. 1988, 88,
1047 and references cited therein. (c) Cockscroft, J . K.; Gibson, V. C.;
Howard, A. K.; Poole, A. D.; Siemeling, U.; Wilson, C. J . Chem. Soc.,
Chem. Commun. 1992, 1668. (d) McLain, S. J .; Schrock, R. R.; Sharp,
P. R.; Churchill, M. R.; Youngs, W. J . J . Am. Chem. Soc. 1979, 101,
262. (e) Churchill, M. R.; Youngs, W. J . Inorg. Chem. 1979, 18, 1697.
(14) (a) Hartwig, J . F.; Bergman, R. G.; Andersen, R. A. J . Am.
Chem. Soc. 1991, 113, 3403. (b) Bennet, M. A.; Hambley, T. W.;
Roberts, N. K.; Robertson, G. B. Organometallics 1985, 4, 1992.
(15) Erker, G. J . Organomet. Chem. 1977, 134, 189.
Compound 6 exhibits a simple piano-stool geometry
with a regular η5-cyclopentadienyl and two phosphine
ligands in an eclipsed geometry. The η2-benzyne ligand
is perpendicular to the plane through the Cp centroid
and the metal center that bisects the P(1)-V(1)-P(2)
angle. A similar orientation of the η2-ligand has been
observed in CpV(η2-ethene)(PMe3)2,6 but in the diphen-
6b
ylacetylene complex CpV(η2-PhCtCPh)(PMe3)2 the

Mono(cyclopentadienyl)vanadium Complexes
Organometallics, Vol. 15, No. 10, 1996 2527
Ta ble 4. Selected Geom etr ica l Da ta for
Cp V(η2-P h CdCP h C6H4)(P Me3)2 (7)
Bond Lengths (Å)
V(1)-P(1)
V(1)-P(2)
V(1)-C(1)
V(1)-C(2)
V(1)-C(3)
V(1)-C(4)
V(1)-C(5)
V(1)-C(6)
V(1)-C(19)
2.5163(7)
2.5077(8)
2.317(3)
2.317(3)
2.342(2)
2.366(2)
2.334(2)
2.143(2)
2.110(2)
C(6)-C(11)
1.432(3)
1.395(3)
1.391(3)
1.387(3)
1.402(3)
1.474(3)
1.370(3)
1.477(3)
1.500(3)
C(7)-C(8)
C(8)-C(9)
C(9)-C(10)
C(10)-C(11)
C(11)-C(12)
C(12)-C(19)
C(19)-C(20)
C(12)-C(13)
Bond Angles (deg)
P(1)-V(1)-P(2)
P(1)-V(1)-C(6)
P(2)-V(1)-C(6)
P(1)-V(1)-C(19)
P(2)-V(1)-C(19)
146.56(3) V(1)-C(6)-C(11)
73.53(6) C(6)-V(1)-C(19)
73.43(6) C(6)-C(11)-C(12)
111.94(14)
79.77(8)
116.37(17)
85.47(6) C(11)-C(12)-C(19) 116.78(18)
83.73(6) Cpcentroid-V(1)-C(6) 150.22(18)
V(1)-C(19)-C(12) 115.12(15) Cpcentroid-V(1)-C(19) 129.99(18)
F igu r e 4. Molecular structure of CpV(η2-PhCdCPhC6H4)-
(PMe3)2 (7). Thermal ellipsoids are drawn at the 50%
probability level.
trum shows a broad resonance at δ -12.2 ppm for the
â-deuterons, which corresponds to a resonance in the
1H NMR spectrum of 6, and a narrow resonance for the
γ-deuterons at δ 7.46 ppm, which is overlapped by the
alkyne is oriented halfway between perpendicular and
parallel, probably as a result of steric hindrance between
the ligands in the complex. In Cp*TaMe2(η2-C6H4)13d,e
a parallel orientation of the benzyne ligand and the
plane through the Cp* centroid and the metal center
that bisects the Me-Ta-Me angle has been found.
1
PMe3 signal in the H NMR spectrum of 6.
Rea ctivity of Cp V(η2-C6H4)(P Me3)2. Reactions of
CpV(η2-C6H4)(PMe3)2 resemble those of CpV(η2-
PhCtCPh)(PMe3)2.6b With unsaturated substrates like
alkynes, alkenes, and nitriles, C,C-coupled products are
obtained.
The V-C(benzyne) distances of 2.055(3) and 2.049(3)
Å in 6 are in between the longer V-C(ethene) distances
in CpV(η2-ethene)(PMe3)26 (2.153(3) and 2.173(3) Å) and
the shorter V-C(alkyne) distances in CpV(η2-PhCtCPh)-
(PMe3)26b (1.932(2) and 1.996(2) Å). The benzyne C(1)-
C(2) distance of 1.368(5) Å is similar to the distances
observed for other structurally characterized η2-benzyne
complexes13,14 (ranging from 1.32(6) to 1.364(8) Å). Like
in other η2-benzyne complexes, except for Schrock's
tantalum complex,13d,e no alternation of short and long
C-C bonds corresponding to “frozen out” single and
double bonds is found in the benzyne ligand of 6. All
C-C distances within the benzyne ring are identical
within experimental error and vary little from the C-C
bond in free benzene (1.392 Å),16 while the angle
between the benzyne plane and the plane containing
V1, C1, and C2 is small (3.2(2)°). These data are
consistent with a delocalized aromatic structure arising
from electron pair donation from the in-plane π-orbital
of the C6 ring coupled with a high degree of back-
donation from the metal to the benzyne π* orbital. The
benzyne in 6 may therefore be regarded as a 2-electron
ligand resulting in an overall 16-electron count for the
complex. This is in contrast with the alkyne ligand in
CpV(η2-PhCtCPh)(PMe3)2,6b which acts as a 4-electron
donor, thereby allowing a formal 18-electron configu-
ration. Complex 6 can best be regarded as a high-spin
d2 vanadium(III) benzometallacyclopropene.
Dip h en yla cetylen e. In an NMR-tube experiment
6 reacts selectively with 1 equiv of diphenylacetylene.
In this reaction a paramagnetic red-brown crystalline
compound is formed, which was identified by X-ray
diffraction as CpV(η2-PhCdCPhC6H4)(PMe3)2 (7), a
vanadaindene complex (eq 5).
Complex 7 is thought to be formed by initial loss of a
phosphine ligand, as indicated by the decrease of the
rate of formation of 7 by the addition of extra PMe3.
The CpV(η2-C6H4)PMe3 fragment, formed under mild
conditions (20 °C), then coordinates diphenylacetylene,
whereupon the alkyne and benzyne ligand couple.
Finally, trimethyl phosphine recoordinates to give 7.
During the reaction no intermediates could be detected
by NMR spectroscopy.
1
The H NMR spectrum of 7 shows several broad and
shifted resonances. The aromatic indene ring protons
give two broad resonances at δ -3.4 and -16.4 ppm.
The high-spin character of 6 manifests itself in its
1
1
The assignment was made by comparing the H NMR
paramagnetism (by NMR spectroscopy). The H NMR
spectrum of 7 with that of the reaction product of
CpV(η2-C6D4)(PMe3)2 (6-d 4) and diphenylacetylene, in
which these resonances were absent. The IR spectrum
of 7 shows characteristic strong vibrations for the
cyclopentadienyl and phosphine ligands at 793 and 945
cm-1, respectively, as well as characteristic vibrations
for the phenyl groups of the former diphenylacetylene
spectrum shows several broad and shifted resonances.
Resonances for the Cp and PMe3 protons in a ratio of
5:18 are found at δ 158 and 7.13 ppm, respectively. The
resonances due to the â- and γ-protons of the benzyne
ligand were identified with the help of a 2H NMR
spectrum of CpV(η2-C6D4)(PMe3)2 (6-d 4), prepared by
thermolysis of CpV(C6D5)2(PMe3)2 (5-d 10). This spec-
moiety at 700, 721, and 1589 cm-1
.
The X-ray structure of 7 (Figure 4, selected geo-
metrical data in Table 4) shows a distorted trigonal
(16) J effrey, G. A.; Ruble, J . R.; Mc Mullan, R. K.; Pople, J . A. Proc.
R. Soc. London, A 1987, 414, 47.

2528 Organometallics, Vol. 15, No. 10, 1996
Buijink et al.
Sch em e 2. P r op osed Mech a n ism for Th er m a l
bipyramidal geometry around vanadium. The Cpcentroid
and the vanadaindene ring lie in the equatorial plane,
the sum of the angles Cpcentroid-V(1)-C(6) (150.23(6)°),
Cpcentroid-V(1)-C(19) (129.99(6)°), and C(6)-V(1)-C(19)
(79.77(8)°) being 360°. The axial PMe3 ligands exhibit
angles smaller than 90° with the vanadaindene ring
(72.77(3) and 73.76(4)°), probably due to steric reasons.
The coordination geometry around vanadium contrasts
markedly with the square-pyramidal geometry observed
for the vanadaindane CpV(η2-CH2CMe2C6H4)(PMe3)2, in
which the phosphine ligands are in a cis-position.1d The
bond angles in the vanadaindene fragment, all close to
120°, indicate sp2-hybridization of the vanadium-bound
C(6) and C(19). The more pronounced sp2-character of
the former acetylene carbon C(19) (V(1)-C(19)-C(12)
) 115.12(15)°) compared to the former benzyne carbon
C(6) (V(1)-C(6)-C(11) ) 111.94(14)°) is expressed in
the shorter V-C distance of the first (2.110(2) and
2.143(2) Å, respectively). Both V-C bonds are shorter
Decom p osition of 8a
Only the bis(â-methyl substituted) complex 8c is ther-
mally stable enough to allow isolation. It shows broad,
shifted resonances in the 1H NMR spectrum for the
PMe3 and vanadaindane methyl substituents (δ -2.1
and -4.7 ppm, respectively). The IR spectrum of 8c
shows the characteristic Cp C-H out of plane vibration
at 795 cm-1 and a typical, strong PMe3 absorption at
3
than the V-Csp bond (2.194(3) Å) in the vanadaindane
CpV(η2-CH2CMe2C6H4)(PMe3)21d but considerably longer
than those in the metallacycle CpV(η2-C4Me2Ph2)PMe3
(1.883(3) and 1.891(3) Å).6b This complex is the product
of C,C-coupling of 2-butyne and diphenylacetylene on a
CpVIPMe3 center, a coupling similar to the one which
generates 7. On the basis of the molecular structure
and the 13C NMR data of the metallacycle, it is however
clear that this complex is not a metallacyclopentadiene
but rather a bent metallacyclopentatriene. The V-C
bonds are formally VdC bonds, and therefore their bond
distances are much shorter than those of the V-C single
bonds in 7. In 7, retaining aromaticity of the former
benzyne fragment apparently prevails over formation
of a more extended, but bent, π-system in a metalla-
cyclopentatriene structure.
1
947 cm-1. The H NMR and the IR data of 8c match
exactly those of the thermolysis product of the bis-
(neophyl) complex CpV(CH2CMe2Ph)2PMe3 in the
presence of excess phosphine (eq 7).
1d
Insertion of alkynes in metal-benzyne bonds to form
metallaindenes has been observed for a number of η2-
benzyne complexes, both of early13b and late14a transi-
tion metals. The nickel-benzyne complex Ni(η2-
C6H4)(Cy2PCH2CH2PCy2)14b (Cy ) cyclohexyl) reacts
with diphenylacetylene through displacement of the
benzyne ligand to give the corresponding η2-alkyne
complex, but with other unsaturated substrates like
alkenes even this complex displays the common inser-
tion chemistry, reflecting the high σ-bond character of
the metal-benzyne bond in η2-benzyne complexes in
general.
Ter m in a l Alk en es. With terminal alkenes
CH2dCRR′ (R ) H, Me; R′ ) H, Me) 6 reacts through
regioselective insertion in one of the V-Cbenzyne bonds
to give the corresponding â-substituted metallaindanes
8 (eq 6).
This thermolysis proceeds through δ-hydrogen ab-
straction to give the vanadaindane complex CpV(η2-
CH2CMe2C6H4)PMe3, which can be trapped by excess
PMe3 to give 8c. We recently reported the synthesis
and full characterization of this complex.1d The mo-
lecular structure shows an essentially square pyrami-
dally coordinated metal atom, with the PMe3 ligands
in a cis-position and a puckered vanadaindane ring
structure.
The low thermal stability of the vanadaindanes 8a ,b
can be ascribed to the presence of â-hydrogens in the
alkyl and aryl fragments. Attempts to prepare CpVR2
species with alkyl groups containing â-CH bonds have
been unsuccessful so far. â-Hydrogen elimination was
found to be facile in these systems.1d For instance,
reaction of the mixed methyl chloride complex CpV(Me)-
1b,c
Cl(PMe3)2
with n-BuLi produces the V(I) 1-butene
complex CpV(η2-CH2dCHEt)(PMe3)2, even at low tem-
peratures, with no traces of intermediate mixed dialkyl
CpV(Me)(n-Bu)(PMe3)2. For 8a â-hydrogen transfer and
reductive elimination would yield styrene (Scheme 2).
The styrene is probably at first complexed by the CpVI
fragment but then replaced by ethene (present in excess)
to give the known V(I) ethene compound CpV(η2-C2H4)-
(PMe3)2.6 Indeed, after 1 h at room temperature this
compound is observed in the thermolyzing mixture
1
1
These paramagnetic complexes show in the H NMR
(characteristic broad PMe3 proton resonance in the H
spectra high-field chemical shifts for the PMe3 protons,
NMR spectrum at δ 14.4 ppm). Simultaneously, reso-
nances of free styrene are present (although partially
characteristic for CpVIII bis(hydrocarbyl) complexes.1b,c

Mono(cyclopentadienyl)vanadium Complexes
Organometallics, Vol. 15, No. 10, 1996 2529
hidden by excess ethene and solvent). However, the
thermal decomposition is not clean, and at least two
other CpVI-containing species are formed, as can be seen
by the characteristic low-field chemical shifts of the
PMe3 protons. The anticipated styrene complex CpV-
(η2-CH2dCHPh)(PMe3)2 is not present, as was estab-
lished by a separate experiment in which it was made
in situ from the ethene compound CpV(η2-C2H4)(PMe3)2
with 1 mol of styrene. A new resonance at δ 11.4 ppm,
assigned to the protons of complexed PMe3 in CpV(η2-
styrene)(PMe3)2, appeared in the 1H NMR spectrum
within minutes after mixing, but it has not been
observed during the thermal decomposition of 8a .
Furthermore, the products formed initially (CpV(η2-
C2H4)(PMe3)2 and styrene) disappear slowly (days), to
give as yet unidentified products. The total ethene
uptake during formation and thermal decomposition of
8a was found to be 1.5 mol/mol of 6 (To¨pler experiment,
24 h at room temperature). A similar thermal decom-
position was observed for the â-methyl substituted
vanadaindane 8b, albeit this decomposition occurs at a
slower rate compared to that of 8a . Attempts to
elucidate the nature of these thermal decompositions
are severely hampered by the fact that paramagnetic
intermediates are involved.
Metallaindanes are formed from η2-benzyne com-
plexes and terminal olefins.13abd,17-19 Their formation
and thermal stability vary however with the metal.
Erker et al.18a established that zirconaindanes Cp2Zr-
(η2-CH2CHRC6H4) are in equilibrium with the corre-
sponding Cp2Zr(η2-benzyne)(η2-CH2dCHR) compounds,
whereas even the unsubstituted zirconaindane (R ) H)
only shows appreciable thermal decomposition at tem-
peratures above 100 °C. The ultimate products of these
thermal decompositions are phenylalkanes, reflecting
both â-hydrogen elimination and C-H activation of
solvent and cyclopentadienyl rings to occur. The ru-
thenium η2-benzyne complex (PMe3)4Ru(η2-C6H4)14a gives
with ethene an irreversible insertion to yield the ruth-
enaindane complex, which decomposes at 85 °C within
several hours through â-hydrogen transfer and reduc-
tive elimination to give styrene and (PMe3)3Ru(η2-
C2H4)2.
F igu r e 5. Molecular structure pf CpV[NC(t-Bu)NdC(t-
Bu)C6H4](PMe3)2 (9). Thermal ellipsoids are drawn at the
50% probability level.
Ta ble 5. Selected Geom etr ica l Da ta for
Cp V[NC(t-Bu )NdC(t-Bu )C6H4](P Me3)2 (9)
Bond Lengths (Å)
V(1)-P(1)
V(1)-P(2)
V(1)-C(17)
V(1)-C(18)
V(1)-C(19)
V(1)-C(20)
V(1)-C(21)
V(1)-N(2)
2.3559(12)
2.3630(13)
2.234(5)
2.304(5)
2.338(4)
2.306(4)
2.246(5)
1.696(3)
N(2)-C(8)
N(1)-C(8)
N(1)-C(1)
C(1)-C(2)
C(2)-C(7)
C(7)-C(8)
C(8)-C(9)
C(1)-C(13)
1.433(5)
1.483(4)
1.269(5)
1.507(6)
1.392(4)
1.537(6)
1.576(5)
1.511(5)
Bond Angles (deg)
P(1)-V(1)-P(2)
P(1)-V(1)-N(2)
P(2)-V(1)-N(2)
V(1)-N(2)-C(8)
N(2)-C(8)-C(7)
N(2)-C(8)-N(1)
N(2)-C(8)-C(9)
96.58(5)
93.22(10)
96.40(10)
177.3(2)
110.3(3)
110.5(3)
111.3(3)
C(1)-N(1)-C(8)
N(1)-C(8)-C(7)
N(1)-C(1)-C(2)
C(1)-C(2)-C(7)
C(2)-C(7)-C(8)
N(1)-C(1)-C(13)
110.4(3)
103.6(2)
112.6(3)
105.5(3)
107.7(3)
122.7(4)
Nitr iles. When 6 is reacted with t-BuCN, 2 equiv of
nitrile is consumed, and the green crystalline vana-
dium(III) imido complex 9 is produced in good yield (eq
8).
J udging from the initial products, thermal decomposi-
tion of vanadaindanes resembles that of late transition
metal indanes (i.e. Ru). The vanadaindanes with
â-hydrogens are much less stable than comparable
zircona- or ruthenaindanes and even less stable than
the vanadacyclopent-2-ene formed in the reaction of
CpV(η2-PhCtCPh)(PMe3)2 and excess ethene.6b This
vanadacyclopent-2-ene inserts ethene before â-hydrogen
elimination takes place, yielding a vanadacyclohept-4-
ene, which in turn undergoes a â-hydrogen elimination/
reductive elimination sequence to give a substituted
CpVI η4-hexadiene complex. Multiple insertion of ethene
in 6 might play an important role in the reaction of 6
with ethene.
The compound was characterized by X-ray diffraction.
The crystal structure of 9 involves the packing of 4
molecules in the orthorombic unit cell. The molecular
structure of 9 is depicted in Figure 5. Selected bond
lengths and angles are given in Table 5.
The molecular structure of 9 shows a simple piano-
stool geometry, with the two phosphine ligands in an
eclipsed position. The cyclopentadienyl ligand is not
regularly pentahapto bonded, presumably as a result
of competition for the metal-centered π-orbitals by the
strongly π-donating imido and cyclopentadienyl ligands.20
A distinct ring-slippage, leading to allyl-ene type cyclo-
pentadienyl bonding, as observed for several half-
(17) Erker, G. Korek, U. Petrenz, R. J . Organomet. Chem. 1991, 421,
215.
(18) (a) Erker, G.; Kropp, K. J . Am. Chem. Soc. 1979, 101, 3659. (b)
Kropp, K.; Erker, G. Organometallics 1982, 1, 1246. (c) Cuny, G. D.;
Gutie´rrez, A.; Buchwald, S. L. Organometallics 1991, 10, 537.
(19) (a) Buchwald, S. L.; Watson, B. T.; Lum, R. T.; Nugent, W. A.
J . Am. Chem. Soc. 1987, 109, 7137. (b) Buchwald, S. L.; Sayers, A.;
Watson, B. T.; Dewan, J . C. Tetrahedron Lett. 1987, 28, 3245.
(20) Gibson, V. C. J . Chem. Soc., Dalton Trans. 1994, 1607.

2530 Organometallics, Vol. 15, No. 10, 1996
Buijink et al.
sandwich niobium,21 molybdenum,22 rhenium,23 and
vanadium24 imido complexes, is clearly present in 9
(ene, V(1)-C(17) ) 2.234(5) Å, V(1)-C(21) ) 2.246(5)
Å; allyl, V(1)-C(18) ) 2.304(5) Å, V(1)-C(19) ) 2.338(4)
Å, V(1)-C(20) ) 2.306(4) Å). The V(1)-N(2) distance
of 1.696(3) Å is characteristic of V-N multiple bonding,
as is the nearly linear V(1)-N(2)-C(8) angle of 177.3(2)°.
The V-N distance is relatively long compared to most
known VdN bonds in V(IV) or V(V) systems (usually
1.60-1.68 Å)25 and similar to those found in the
relatively electron-rich V(IV) bis(pentamethylcyclopen-
Sch em e 3. P r op osed Mech a n ism for F or m a tion
of 9
tadienyl) systems Cp*2VdNR (R ) Ph, 1.730(5) Å;26
R
) C6Me2H3, 1.707(6) Å27 ). The imido substituent is a
flat, heterocyclic 1,3-disubstituted isoindolenine frag-
ment, bonded at the 1-position, C(8), to the imido
nitrogen. The isoindolenine character is clearly visible
in the short N(1)-C(1) bond length of 1.269(5) Å.
Except for CpV[dN-C(t-Bu)dCH(t-Bu)][Me2PCH2CH2-
PMe2],1d no other vanadium(III) imido complexes are
known. Compound 9 represents the first example of a
transition metal imido complex bearing a 1-isoindole-
nine substituent. Due to this unsymmetrical ligand, the
methyl protons of the two phosphine ligands exhibit
different chemical shifts in the 1H NMR spectrum of
diamagnetic 9. In the 51V NMR spectrum a broad
resonance is observed at δ 34 ppm (∆ν1/2 ) 1790 Hz),
lacking the V-P coupling observed for CpV(CH-t-Bu)-
dmpe,1d probably as a result of the low symmetry28 in
9, induced by the imido substituent. In addition to the
characteristic Cp and PMe3 absorptions at 791 and 941
cm-1, the IR spectrum of 9 shows a V-N stretching
vibration at 951 cm-1, which compares well to other
vanadium imido complexes.26,27
cycle by reaction of 6 with 1 mol of t-BuCN led to
equimolar amounts of 9 and 6, indicating that the first
nitrile insertion is rate-limiting.
Hydrolysis of 9 with HCl gas in benzene requires 3
equiv of HCl (To¨pler pump) and produces the hydro-
chloride salt of the 1-amine-substituted isoindolenine
10 in an instantaneous reaction (eq 9).
Regioselective monoinsertion of nitriles in metal-
benzyne bonds to give azametallacycles has been ob-
served for both zirconocene13a,b,19 and ruthenium14a
benzyne complexes. Presumably, this is also the first
step (A) in the reaction that produces 9 (Scheme 3).
The formed azavanadacycle is subject to further
insertion of a nitrile in the V-C bond (B) to give a
diazavanadacycle, which then rearranges (C) to the
thermodynamically more stable 1-isoindolenine imido
group. Double insertion of nitriles is not observed in
the zirconocene and ruthenium cases. The high reactiv-
ity of the azavanadacycle toward nitriles compared to
the azazircona and -ruthena cycles could be explained
by the increased strain in the azametallacycle due to
the smaller size of V(III) compared to the 4d metals Zr
and Ru. During the reaction, which is complete in 1 h
at 25 °C, no intermediates could be observed by 1H NMR
spectroscopy. Attempted synthesis of the azavanada-
Dih yd r ogen . Cyclohexane-d12 solutions of 6 react
slowly (7 days at 25 °C for completion) with dihydrogen
to form an insoluble, green crystalline material (eq 10).
(21) (a) Gibson, V. C.; Williams, D. N.; Clegg, W.; Hockless, D. C.
R. Polyhedron 1989, 8, 1819. (b) Williams, D. N.; Mitchell, J . P.; Poole,
A. D.; Siemeling, U.; Clegg, W.; Hockless, D. C. R., O’Neil, P. A.; Gibson,
V. C. J . Chem. Soc., Dalton Trans. 1992, 739.
(22) Green, M. L. H.; Konidaris, P. C.; Mountford, P.; Simpson, S.
J . J . Chem. Soc., Chem. Commun. 1992, 256.
(23) Herrmann, W. A.; Weichselbaumer, G.; Paciello, R. A.; Fischer,
R. A.; Herdtweck, E.; Okuda, J .; Marz, D. W. Organometallics 1990,
9, 489.
(24) Preuss, F.; Becker, H.; Ha¨usler, H.-J . Z. Naturforsch. 1987, 42B,
881.
(25) Nugent, W. A.; Mayer, J . M. Metal-Ligand Multiple Bonds;
Wiley: New York, 1988; p 179.
1
The H NMR spectrum of the colorless, clear solution
shows only resonances for PMe3 and C6H6 (4:1 ratio).
The green, crystalline material was identified as the V(I)
triple-decker CpV(C6H6)VCp, which has previously been
reported by Duff, J onas, et al.29 and is also formed in
the reaction of CpVMe2(PMe3)2 with H2 in benzene.1c
Formation of the triple-decker indicates generation
of CpVI fragments during the reaction. They are
probably formed through initial σ-bond metathesis of
the benzyne complex 6 with H2, followed by reductive
elimination of benzene from the unstable phenyl-
(26) Gambarotta, S.; Chiesi-Villa, A.; Guastini, C. J . Organomet.
Chem. 1984, 270, C49.
(27) Osborne, J . H.; Rheingold, A. L.; Trogler, W. C. J . Am. Chem.
Soc. 1985, 107, 7945.
(28) Devore, D. D.; Lichtenhan, J . D.; Takusagawa, F.; Maatta, E.
A. J . Am. Chem. Soc. 1987, 109, 7408.
(29) Duff, A. W.; J onas, K.; Goddard, R.; Kraus, H.-J .; Kru¨ger, C. J .
Am. Chem. Soc. 1983, 105, 5479.

Mono(cyclopentadienyl)vanadium Complexes
Organometallics, Vol. 15, No. 10, 1996 2531
according to an adapted literature procedure,31 using MeMgI
instead of MeMgBr.
hydride intermediate. Other types of σ-bond metathesis
reactions, like activation of benzene to give a bis(phenyl)
complex, have so far not been found for 6. Benzene-d6
solutions of 6 can be kept at 100 °C for days without
any sign of formation of 6-d 4 and C6H6. Likewise, no
C-H activation was observed for 6-d 4 in benzene at 100
°C. In this respect 6 contrasts strongly with ruthenium
and zirconocene η2-benzyne complexes, which both show
activation of aromatic C-H bonds.14a,15
Cp VCl(CtCP h )(P Me3)2 (2). A suspension of 1 (1.77 g,
5.22 mmol) and LiCtCPh (0.59 g, 5.46 mmol) in 35 mL of
diethyl ether was stirred for 1.5 h at 0 °C. After removal of
the solvent in vacuo the residue was extracted twice with 30
mL of pentane. Concentrating and cooling of the extract to
-25 °C yielded 0.77 g (1.19 mmol, 36%) of dark-green crystals
in two crops: 1H NMR δ 28.0 (2H, aryl, ∆ν1/2 ) 1400), -11.8
(18H, PMe3, ∆ν1/2 ) 3600); IR 3069 (w), 3057 (w), 2043 (m),
1591 (m), 1564 (m), 1481 (s), 1439 (s), 1418 (m), 1308 (m), 1294
(m), 1277 (m), 1202 (m), 1171 (m), 1121 (w), 1067 (m), 1015
(s), 945 (vs, PMe3), 909 (m), 841 (w), 824 (m), 799 (s), 758 (s),
727 (s), 694 (s), 669 (m), 529 (m), 519 (w). Anal. Calcd for
Con clu sion s
Starting from CpVCl2(PMe3)2, paramagnetic phenyl-
ethynyl complexes CpVCl2-n(CtCPh)n(PMe3)2 (n ) 1,
2) have been synthesized. Both compounds were char-
acterized by X-ray diffraction and were found to be
thermally more stable than other CpVIII hydrocarbyl
complexes. The bis(phenyl) complex CpVPh2(PMe3)2
decomposes thermally through â-hydrogen abstraction
to give the first isolated vanadium benzyne complex
CpV(η2-C6H4)(PMe3)2. The molecular structure of this
complex indicates that it is best described as a high-
spin d2 vanadium(III) benzometallacyclopropene. The
cyclopropene character is expressed in its reactivity,
showing insertion of unsaturated substrates. With
diphenylacetylene a vanadaindene complex with a
planar metallacyclic structure is obtained, and terminal
alkenes insert regioselectively to give â-substituted
metallaindanes, which show a low thermal stability in
case the â-substituent is hydrogen. With t-BuCN double
insertion followed by rearrangement of the diaza-
metallacycle to give an isoindolenine-substituted vana-
dium(III) imido complex is observed. The benzyne
complex also reacts with dihydrogen to form a known
triple-decker complex CpV(C6H6)VCp through partial
hydrogenation of the benzyne ligand.
C
19H28ClP2V: C, 56.38; H, 6.97; Cl, 8.76; V, 12.59. Found: C,
56.54; H, 7.07; Cl, 8.54; V, 12.48.
Cp V(CtCP h )2(P Me3)2 (3). A suspension of 1 (1.13 g, 3.33
mmol) and LiCtCPh (0.80 g, 7.40 mmol) in 30 mL of diethyl
ether was stirred for 1.5 h at 0 °C. After removal of the solvent
in vacuo the residue was extracted twice with 30 mL of
pentane. Concentrating and cooling of the extract to -25 °C
yielded 0.36 g (0.77 mmol, 23%) of brown crystals in three
crops: 1H NMR δ 23.9 (4H, aryl, ∆ν1/2 ) 4300), -8.8 (18H,
PMe3, ∆ν1/2 ) 5500); IR 3069 (w), 3041 (w), 2041 (s), 1589 (m),
1571 (w), 1479 (s), 1420 (m), 1292 (w), 1277 (m), 1200 (m),
1171 (w), 1121 (vw), 1067 (m), 1024 (m), 945 (vs, PMe3), 907
(w), 843 (w), 799 (s), 777 (w), 756 (s), 727 (m), 694 (s), 671 (w),
529 (m), 519 (w). Anal. Calcd for C27H33P2V: C, 68.93; H,
7.07; V, 10.83. Found: C, 68.90; H, 7.11; V, 10.65.
Cp V(η2-BH4)(CtCP h )P Me3 (4). A mixture of 3 (0.45 g,
1.13 mmol) and LiBH4 (0.08 g, 1.43 mmol) in 20 mL of diethyl
ether was stirred for 2.5 h at 25 °C. After removal of the
organic volatiles in vacuo the residue was extracted with 40
mL of pentane. Concentrating and cooling of the extract to
-80 °C gave 0.19 g (0.62 mmol, 55%) of brown microcrystals:
1H NMR δ 1.97, 1.50, 1.16, 0.84 (4 d, each 1H, J BH ) 96, J PH
) 15), 0.66 (d, 9H, J PH ) 10.7); IR 2363 (s), 2344 (s), 2257 (w),
2047 (w), 2029 (w), 1588 (m), 1481 (m), 1429 (m), 1294 (m),
1136 (w), 1117 (w), 1071 (m), 1011 (m), 974 (s), 949 (s), 889
(w), 793 (m), 758 (m), 708 (m), 669 (w), 569 (w). Anal. Calcd
for C16H23BPV: C, 62.38; H, 7.52;V, 16.53. Found: C, 62.68;
H, 7.69; V, 14.28.
Exp er im en ta l Section
Cp V(η2-C6H4)(P Me3)2 (6). A solution of 5 (0.55 g, 1.30
mmol) in 20 mL of benzene was stirred for 17 h at 50 °C. After
removal of the solvent in vacuo the residue was extracted with
60 mL of pentane. Concentrating and cooling of the extract
to -25 °C yielded 0.22 g (0.65 mmol, 50%) of dark-green
crystals: 1H NMR δ 157.0 (5H, Cp, ∆ν1/2 ) 4500), 7.13 (20H,
Gen er a l Con sid er a tion s. All manipulations were per-
formed under nitrogen (using Schlenk techniques or a glove-
box) or using vacuum line techniques. Gas uptakes were
determined with a To¨pler pump connected to a vacuum line.
NMR spectra were recorded on a Varian VXR-300 (1H, 300
MHz; 2D, 46.044 MHz; 13C, 75.4 MHz; 51V, 78.9 MHz) spec-
trometer in benzene-d6 at 25 °C (unless stated otherwise), and
PMe3 and â-C6H4, ∆ν1/2 ) 460), -12.22 (2H, γ-C6H4, ∆ν1/2
)
240); 1H NMR (THF-d8) δ 157 (5H, Cp, ∆ν1/2 ) 4500), 7.30
(20H, PMe3 and â-C6H4, ∆ν1/2 ) 340), -15.3 (2H, γ-C6H4, ∆ν1/2
) 460); IR 3092 (w), 3013 (w), 1547 (w), 1420 (m), 1406 (m),
1325 (m), 1296 (m), 1279 (s), 1235 (w), 1142 (m), 1117 (w),
1092 (w), 1057 (w), 1009 (m), 990 (m), 941 (s), 835 (w), 799
(m), 781 (s), 727 (s), 718 (s), 665 (m), 654 (m). Anal. Calcd
for C17H27P2V: C, 59.31; H, 7.90; V, 14.80. Found: C, 59.09;
H, 7.79; V, 14.91.
1
chemical shifts are in ppm, downfield from TMS (δ 0.00, H,
2D, 13C) or VOCl3 (δ 0.00, 51V) positive. Coupling constants
and half-width values, ∆ν1/2, are reported in Hz. IR spectra
were recorded on a Pye-Unicam SP3-300 or a Mattson-4020
Galaxy FT-IR spectrophotometer, from Nujol mulls between
KBr disks (unless stated otherwise). Wavenumbers are
reported in cm-1. Elemental analyses were performed at the
Microanalytical Department of the University of Groningen.
Values given are the average of at least two independent
determinations.
Cp V(C6D5)2(P Me3)2 (5-d 10). To a suspension of 1 (0.66 g,
1.95 mmol) in 20 mL of diethyl ether cooled to -55 °C, 7.1 mL
of a 0.55 M C6D5MgBr solution in diethyl ether was added
dropwise. The mixture was allowed to warm to 0 °C and
stirred for 1.5 h at this temperature. After removal of the
solvent in vacuo the residue was extracted with 60 mL of
pentane. Concentrating and cooling of the extract to -25 °C
yielded 0.57 g (1.32 mmol, 68%) of red-brown crystals: 1H
NMR δ -11.10 (18H, PMe3, ∆ν1/2 ) 1680).
Compounds 1,5 5,1b,c and LiCtCPh30 were prepared accord-
ing to published procedures. Solvents (diethyl ether, pentane
(mixed isomers), n-hexane, benzene, and deuterated solvents
except CDCl3) were distilled from Na/K alloy before use.
n-BuLi, diphenylacetylene, LiBH4 (J anssen), ethene, propene
(Matheson), isobutene (Aldrich), and HCl (Ucar) were used as
received. Grignard reagents were prepared from the corre-
sponding alkyl halides. t-BuCN was vacuum transferred and
stored over molecular sieves (4 Å). PMe3 was prepared
Cp V(η2-C6D4)(P Me3)2 (6-d 4). A solution of 5-d 10 (0.515 g,
1.214 mmol) in 20 mL of benzene was stirred for 25 h at 50
°C. After removal of the solvent in vacuo the residue was
(30) Brandsma, L. Preparative Acetylenic Chemistry; Elsevier: Am-
sterdam, The Netherlands, 1971; p 25.
(31) Luetkens, M. L., J r.; Sattelberger, A. P.; Murray, H. H.; Basil,
J . D.; Fackler, J . P., J r. Inorg. Synth. 1984, 26, 7.

2532 Organometallics, Vol. 15, No. 10, 1996
Buijink et al.
extracted with 35 mL of pentane. Concentrating and cooling
of the extract to -25 °C yielded 0.019 g (0.055 mmol, 5%) of
dark-green crystals: 1H NMR δ 158 (5H, Cp, ∆ν1/2 ) 2500),
7.13 (18H, PMe3, ∆ν1/2 ) 175); 2H NMR (C6H6) δ 7.46 (2H,
â-C6H4, ∆ν1/2 ) 2.2), -12.38 (2H, γ-C6H4, ∆ν1/2 ) 11).
â-H’s), 4.87 (br s, 5H, Cp), 1.50 (s, 9H, CMe3), 1.19 (d, 9H, 2J PH
) 4.7, PMe3), 1.15 (s, 9H, CMe3), 0.57 (d, 9H, 2J PH ) 3.9, PMe3);
13C NMR δ 174.2 (NdC-(t-Bu)), 138.0 (N-C-N), 129.6 (C6H4,
R-C), 126.9 (C6H4, â-C), 126.6 (C6H4, R-C), 126.3 (C6H4, â-C),
125.2 (C6H4, γ-C), 122.4 (C6H4, γ-C), 93.7 (Cp), 36.2 (CMe3),
28.6 (CMe3), 26.8 (CMe3), 24.2 (PMe3); 51V NMR δ 34.0 (∆ν1/2
) 1790); 31P NMR δ 45.2 (∆ν1/2 ) 8730); IR 3082 (w), 3065
(w), 3032 (w), 1595 (m), 1566 (m), 1424 (m), 1364 (m), 1333
(w), 1306 (w), 1294 (m), 1269 (m), 1248 (s), 1215 (s), 1200 (m),
1171 (w), 1155 (w), 1107 (m), 1051 (m), 1011 (m), 995 (w), 972
(w), 951 (vs), 941 (vs), 891 (w), 872 (w), 843 (w), 791 (s), 750
(s), 718 (m), 704 (m), 656 (s). Anal. Calcd for C27H45N2P2V:
C, 63.52; H, 8.88; N, 5.49; V, 9.98. Found: C, 63.65; H, 8.97;
N, 5.52; V, 9.88.
Cp V(η2-P h CdCP h C6H4)(P Me3)2 (7). A suspension of 6
(0.31 g, 0.90 mmol) and PhCtCPh (0.18 g, 1.01 mmol) in 20
mL of pentane was stirred for 19 h at 25 °C. After removal of
the solvent in vacuo the residue was extracted with 30 mL of
diethyl ether. Concentrating and cooling of the extract to -80
°C yielded 0.27 g (0.52 mmol, 57%) of red-brown crystals: 1H
NMR δ 154 (5H, Cp, ∆ν1/2 ) 3750), 18.30 (Ph, ∆ν1/2 ) 75), 16.44
(Ph, ∆ν1/2 ) 75), -3.43 (â-C6H4, ∆ν1/2 ) 600), -5.72 (Ph, ∆ν1/2
) 100), -9.53 (18H, PMe3, ∆ν1/2 ) 500), -16.43 (γ-C6H4, ∆ν1/2
) 600); IR 3067 (w), 3032 (w), 1589 (s), 1564 (w), 1547 (w),
1505 (w), 1487 (m), 1424 (s), 1325 (w), 1298 (m), 1279 (s), 1242
(w), 1200 (w), 1171 (vw), 1136 (w), 1119 (vw), 1092 (vw), 1067
(w), 1022 (m), 1007 (m), 945 (vs), 903 (m), 837 (w), 793 (vs),
758 (m), 721 (vs), 700 (s), 664 (m), 600 (m). Anal. Calcd for
H 2NC(t-Bu )NdC(t-Bu )C6H 4 (10). On
a vacuum line
equipped with a To¨pler pump a solution of 11 (45.7 mg, 90
µmol) in 4 mL of benzene was degassed by repeated freeze-
thaw cycles and then allowed to react with 0.47 mmol of HCl
gas. The solution turned dark-red, and a solid precipitated
immediately. After 10 min the mixture was cooled to -80 °C
and the excess HCl was pumped off with the To¨pler pump.
The total HCl uptake was 270 µmol (3.0 equiv). After removal
of the solvent in vacuo the residue was dissolved in 0.1 N
NaOH/H2O. Extraction with diethyl ether and removal of the
solvent in vacuo yielded a yellow oil, which was dissolved in
chloroform-d1: 1H NMR δ 7.63 (2H, m, C6H4 R-H’s), 7.32 (2H,
m, C6H4 â-H’s), 1.45 (9H, s, CMe3), 1.00 (9H, s, CMe3).
C
31H37P2V: C, 71.26; H, 7.14; V, 9.75. Found: C, 71.62; H,
7.12; V, 9.89.
Cp V(η2-CP h dCP h C6D4)(P Me3)2 (7-d 4). A green solution
of 6-d 4 (26 mg, 74 µmol) and PhCtCPh (13 mg, 74 µmol) in
0.4 mL of C6D6 in a sealed NMR tube was kept at 25 °C for 20
h: 1H NMR δ 157 (5H, Cp, ∆ν1/2 ) 3750), 18.27 (Ph, ∆ν1/2
)
79), 16.38 (Ph, ∆ν1/2 ) 68), -5.84 (Ph, ∆ν1/2 ) 90), -8.8 (PMe3,
∆ν1/2 ) 675).
Cp V(η2-CH2CH2C6H4)(P Me3)2 (8a ). A 5 mm NMR tube
equipped with a Teflon needle valve was charged with a
solution of 6 (15 mg, 0.048 mmol) in 0.5 mL of benzene-d6. On
a vacuum line ethene (0.094 mmol) was condensed into the
NMR tube at -196 °C. After warming of the sample to 25 °C
Rea ction of 6 w ith H2. A 5 mm NMR tube equipped with
a Teflon needle valve was charged with a solution of 6 (14 mg,
0.04 mmol) in 0.5 mL of cyclohexane-d12. On a vacuum line
the inert atmosphere was replaced by 1 atm of H2. After 7
1
days a green crystalline material had separated and a H NMR
a
1H NMR spectrum was taken immediately: δ 0.26 (PMe3,
spectrum was taken: δ 7.13 (6H, C6H6), 0.84 (36H, PMe3). The
volatile compounds were removed in vacuo after which an IR
spectrum of the green material was taken: IR 1422 (w), 1364
(m), 1103 (s), 1069 (w), 1053 (w), 1001 (s), 968 (w), 937 (s),
841 (w), 789 (s), 762 (vs), 675 (w). An identical spectrum was
reported for the product of the reaction of CpVMe2(PMe3)2 with
H2 in benzene.1c
∆ν1/2 ) 460). The decomposition of 8a was then monitored by
taking 1H NMR spectra periodically: CpV(C2H4)(PMe3)2, δ 14.4
(PMe3, ∆ν1/2 ) 260); styrene (resonances partially overlapped
by reaction byproducts), δ 7.1 (m, Ph), 6.6 (dd, PhCHd), 5.6
(d, dCHH), 5.1 (d, dCHH).
The corresponding propene derivative 8b was prepared
similarly: δ -0.11 (PMe3, ∆ν1/2 ) 225), -7.24 (Me, ∆ν1/2 ) 450).
Deter m in a tion of Eth en e Up ta k e by 6. On a vacuum
line equipped with a To¨pler pump a solution of 6 (137 mg, 397
µmol) in 4 mL of benzene was degassed by repeated freeze-
thaw cycles. Ethene (1.05 mmol) was condensed onto the
solution, which was then stirred for 24 h at 25 °C. After
cooling of the solution to -80 °C, the excess ethene was
pumped off (0.46 mmol) with the To¨pler pump, resulting in a
total ethene uptake of 0.58 mmol (1.5 equiv).
X-r a y St r u ct u r e Det er m in a t ion s of 2, 3, 6, 7, a n d 9.
Pertinent crystal data and data collection parameters can be
found in Table 6. Crystals suitable for X-ray diffraction were
grown by cooling a saturated solution from +20 to -30 °C at
3 °C/h (2, pentane, greenish block-shaped crystals; 3, pentane,
brown-yellow rod-shaped crystals; 6, diethyl ether, greenish
plate-shaped crystals; 7, diethyl ether, red-brown parallel-
epiped-shaped crystals; 9, pentane, dark-green block-shaped
crystals).
Cp V(η2-CH2CMe2C6H4)(P Me3)2 (8c). A solution of 6 (0.038
g, 0.11 mmol) in 0.6 mL of benzene-d6 was stirred under 1
atm of isobutene in a 15 mL vessel at 25 °C for 3 h. Part of
the resulting brown solution (0.4 mL) was transferred to a 5
mm NMR tube: 1H NMR δ 4.72 (s, 2H, dCH2, isobutene), 1.60
(s, 6H, dCMe2, isobutene), -2.1 (18H, PMe3, ∆ν1/2 ) 420), -4.7
(6H, CMe2, ∆ν1/2 ) 110). Removal of the organic volatiles in
vacuo from the rest of the brown solution gave a brown
residue: IR 3090 (vw), 3025 (m), 2775 (vw), 1560 (vw), 1418
(m), 1358 (w), 1340 (w), 1300 (mw), 1282 (m), 1009 (mw), 945
(vs), 817 (mw), 795 (s), 728 (s), 715 (m), 662 (w). The obtained
spectra are identical to those reported for the complex obtained
by thermolysis of CpV(CH2CMe2Ph)2PMe3 in the presence of
extra PMe3.1d The material obtained this way was also
characterized by elemental analysis and X-ray diffraction.
Cp V(NC(t-Bu )NdC(t-Bu )C6H4)(P Me3)2 (9). To a suspen-
sion of 6 (0.24 g, 0.69 mmol) in 20 mL of pentane cooled to
-55 °C, t-BuCN (152 µL, 1.38 mmol) was added dropwise. The
mixture was allowed to warm to 25 °C and stirred for 18 h.
After filtration the residue was extracted with 20 mL of
pentane. Concentrating and cooling of the combined filtrate
and extract to -80 °C yielded 0.21 g (0.40 mmol, 59%) of green
Crystals were mounted on top of a glass fiber (except for 9,
which was introduced in a Lindemann glass capillary) and
transferred to the cold nitrogen stream of either an Enraf-
Nonius CAD4T diffractometer (2, 3, and 9) or an Enraf-Nonius
CAD-4F diffractometer on a rotating anode, interfaced to a
VAX-11/730 (6 and 7) for data collection.
Unit cell parameters were determined from a least-squares
treatment of the SET432 setting angles of 25 reflections with
high θ (around 15°). The unit-cell parameters were checked
for the presence of higher lattice symmetry;33 examination of
the final atomic coordinates of the structure of 6 and 7 did
not yield extrametric symmetry elements.34
Intensity data were corrected for Lorentz and polarization
effects, for a linear decay (8.4% over 24.5 h for 2, 1.2% over
8.6 h for 3, 1.9% over 21 h for 9) of the three intensity control
reflections during the X-ray exposure time, and for absorption
in the case of 2 and 9 (using the DIFABS method;35 correction
(32) De Boer, J . L.; Duisenberg, A. J . M. Acta Crystallogr. 1984,
A40, C410.
(33) Spek, A. L. J . Appl. Crystallogr. 1988, 21, 578.
(34) (a) Le Page, Y. J . Appl. Crystallogr. 1987, 20, 264. (b) Le Page,
Y. J . Appl. Crystallogr. 1988, 21, 983.
3
crystals: 1H NMR δ 7.49 (q, 1H, J HH ) 2.8, C6H4 R-H), 7.37
3
3
(q, 1H, J HH ) 3.0, C6H4 R-H), 7.05 (q, 2H, J HH ) 1.5, C6H4
(35) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.

Mono(cyclopentadienyl)vanadium Complexes
Organometallics, Vol. 15, No. 10, 1996 2533
Ta ble 6. Cr ysta llogr a p h ic Da ta for 2, 3, 6, 7, a n d 9
2
3
6
7
9
formula
fw
C19H28ClP2V
404.77
C27H33P2V
470.45
C17H27P2V
344.29
C31H37P2V
522.52
C27H45N2P2V
510.56
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
triclinic
P1h
monoclinic
C2/c
17.8100(12)
16.5034(11)
9.8384(5)
monoclinic
P21/n
8.805(1)
14.049(2)
14.610(1)
monoclinic
P21/n
9.191(1)
19.909(1)
15.072(1)
orthorhombic
Pna21
14.7216(7)
19.1511(14)
9.9347(4)
11.0992(10)
11.7098(10)
16.990(2)
105.977(10)
96.562(10)
93.918(10)
2097.4(4)
4
117.515(10)
90.143(8)
98.687(7)
2564.7(3)
4
1.2184(2)
992.0
1807.3(4)
4
1.265
728
2726.3(4)
4
1.273
1104
4.8
2800.9(3)
4
1.2107(1)
1096.0
4.7
Z
d
calcd, g cm-3
1.2819(2)
848.0
7.3
F(000), e
µ(Mo KR), cm-1
cryst size, mm
T, K
5.2
7.0
0.20 × 0.20 × 0.23
0.08 × 0.10 × 0.25
0.07 × 0.30 × 0.37 0.12 × 0.28 × 0.35 0.13 × 0.25 × 0.50
150
100
130
130
150
no. of data collcd
no. unique data
no. reflns obsd
12 524
9632
6161 [I > 2.5σ(I)]
3225
2950
1717 [I > 2.5σ(I)]
144
0.058
0.064
4435
3536
2964 [I > 2.5σ(I)]
290
0.038
0.047
1
7247
5912
4733 [I > 2.5σ(I)]
456
0.033
0.037
1
4939
3381
2630 [I > 2.5σ(I)]
326
no. of params refined 453
R(F)
Rw(F)
w
0.043
0.046
0.039
0.026
{σ2(F) + 0.000285F2}-1 {σ2(F) + 0.000297F2}-1
1/σ2(Fo)
range 0.862-1.133 for 2, 0.91-1.08 for 9). The intensities of
the three standard reflections of 6 showed no statistically
significant change over the 96.3 h of data collection; those of
7 showed some decay (5%) over the 107.0 h of data collection.
secondary extinction for which the Fc values were corrected
by refinement of an empirical isotropic extinction parameter.40
One reflection for 6 with (w(||Fo| - |Fc||) > 20) was excluded
from the final refinement cycle. Final refinement on Fo by full-
matrix least-squares techniques with anisotropic thermal
displacement parameters for the non-hydrogen atoms and
isotropic thermal displacement parameters for the hydrogen
atoms converged at R ) 0.038 for 6 and R ) 0.033 for 7. One
peak in the final difference Fourier map of 6, showing a
residual electron density of 1.01 e/Å3, was located in the
vicinity of the V position but was of no chemical significance:
the rest of the difference Fourier map did not show residual
peaks outside the range (0.57 e/Å3 ((0.42 e/Å3 for 7).
For 2, 3, and 9, the structures were solved by direct methods
(2, 3, SHELXS86;36 9, SIR9237) and subsequent difference
Fourier analyses. Refinement on F was carried out by full-
matrix least-squares techniques. Hydrogen atoms were in-
troduced on calculated positions (C-H ) 0.98 Å) and included
in the refinement riding on their carrier atoms. All non-
hydrogen atoms (except the atoms of the disordered Cp rings
of 3 and 9) were refined with anisotropic thermal parameters;
hydrogen atoms of 2 and 3 were refined with one common
isotropic thermal parameter [U ) 0.053(2) Å2 for 2, 0.057(5)
Å2 for 3], and hydrogen atoms of 9 were refined with two
common isotropic thermal parameters [U ) 0.023(4) and U )
0.044(2) Å2 for CH and CH3 groups, respectively]. Weights
were introduced in the final refinement cycles; convergence
was reached at R ) 0.0425 for 2, 0.0582 for 3, and 0.0392 for
9. The absolute structure of 9 was checked by refinement with
opposite anomalous dispersion factors (-if ′′) resulting in R )
0.0405. A final difference Fourier map showed no features
outside the range -0.36 to 0.42 e/Å3 for 2, -0.55 to 0.58 e/Å3
for 3, and -0.55 to 0.58 e/Å3 for 9.
For 6 and 7, the structures were solved by Patterson
methods and extension of the model was accomplished by
direct methods applied to the difference structure factors using
the program DIRDIF.38 The positional and anisotropic ther-
mal displacement parameters for the non-hydrogen atoms
were refined with block-diagonal least-squares procedures
(CRYLSQ)39 minimizing the function Q ) ∑h [w(|Fo| - k|Fc|)2].
A subsequent difference Fourier synthesis gave all the hydro-
gen atoms, which coordinates and isotropic thermal displace-
ment parameters were refined. The crystals exhibited some
Neutral atom scattering factors were taken from ref 41 and
corrected for anomalous dispersion.42 For 2, 3, and 9, all
calculations were performed with SHELX7643 and the PLA-
TON package44 (geometrical calculations and illustrations) on
a DEC-5000 cluster at the University of Utrecht. For 6 and
7, all calculations were performed with XTAL,45 the PLATON
package (calculation of geometric data), and ORTEP46 on the
CDC-Cyber 962-31 computer at the University of Groningen.
Ack n ow led gm en t . This investigation was sup-
ported by the Netherlands Foundation for Chemical
Research (SON) with finacial aid from the Netherlands
Organization for Scientific Research (NWO).
Su p p or tin g In for m a tion Ava ila ble: Details of the struc-
ture determinations, including tables of atomic coordinates,
bond lengths and angles, and thermal parameters for 2, 3, 6,
7, and 9 (38 pages). Ordering information is given on any
current masthead page.
OM950902M
(36) Sheldrick, G. M. SHELXS86. Program for crystal structure
determination. University of Go¨ttingen, Germany, 1986.
(37) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J .
Appl. Crystallogr. 1993, 26, 343.
(40) Zachariasen, W. H. Acta Crystallogr. 1967, 23, 558.
(41) Cromer, D. T.; Mann, J . B. Acta Crystallogr. 1986, A24, 321.
(42) Cromer, D. T.; Libermann, D. J . Chem. Phys. 1970, 53, 1891.
(43) Sheldrick, G. M. SHELX76. Crystal structure analysis package.
University of Cambridge, England, 1976.
(44) Spek, A. L. Acta Crystallogr. 1990, A46, C34.
(45) XTAL3.0 Reference Manual; Hall, S. R., Stewart, J . M., Eds.;
Universities of Western Australia and Maryland: Lamb, Perth,
Australia, 1990.
(38) Beurskens, P. T.; Bosman, W. P.; Doesburg, H. M.; Van den
Hark, Th. E. M.; Prick, P. A. J .; Noordik, J . H.; Beurskens, G.;
Parthasarathi, V.; Bruins-Slot, H. J .; Haltiwanger, R. C.; Strumpel,
M. K.; Smits, J . M. M.; Garc´ıa-Granda, S.; Smykalla, C.; Behm, H. J .
J .; Scha¨fer, G.; Admiraal, G. Program system DIRDIF, Technical report
of the Crystallography Laboratory, University of Nijmegen, The
Netherlands, 1991.
(39) Olthof-Hazekamp, R. "CRYLSQ" XTAL3.0 Reference Manual;
Hall, S. R., Stewart, J . M., Eds; Universities of Western Australia and
Maryland: Lamb, Perth, Australia, 1990.
(46) J ohnson, C. K. ORTEP; Report ORNL-3794; Oak Ridge Na-
tional Laboratory: Oak Ridge, TN.