Reactions of terminal alkynes with group 6-group 10 heterobimetallics

Article abstract of DOI:10.1021/om960379r

Reactions of PhC₂H with NiCp*M(CO)₃Cp″ [Ni-M: M = Mo, W; Cp* = η⁵-C₅Me₅; Cp″ = Cp (η⁵-C₅H₅) or Cp′ (η⁵-C₅H₄Me)] afford metallacyclic species 4, of formula NiCp*{μ-η³-(Ni),η ¹(1-M)C(H)C(Ph)C(O)}M(CO)₂Cp (Ni-M, M = Mo, W), as the principal products. These compounds are isomeric to four-membered nickelacycles obtained in similar reactions with disubstituted alkynes and contain five-membered NiC(O)C(H)C(Ph)M ring systems. Phenylacetylene also affords minor quantities of alkyne bridged complexes with dimetallatetrahedrane-type nuclear cores. Alkylation of 4 with (Me₃O)⁺BF4^- results in the methylation of the metallacyclic (acyl-like) carbonyl ligand and a structural rearrangement ensues: cationic four-membered molybdena- or tungstenacycles 6 of formula [NiCp*{μ-η³(Ni),η²( 1,3-M)C(H)C(Ph)C(OMe)}M(CO)₂Cp]⁺BF₄- (Ni-M, M = Mo, W) result. An iodide-for-carbonyl substitution reaction on 6 affords the neutral complexes 8 [NiCp*{μ-η³(Ni),η ²(1,3-M)C(H)C-(Ph)C(OMe)}MI(CO)Cp] (Ni-M), which maintain the structural core present in 6. The structure of 8b′, [NiCp*{μ-η³(Ni),η ²(1,3-W)C(H)C(Ph)C(OMe)}WI(CO)Cp′] (Ni-W) was established by X-ray diffraction.

Full text of DOI:10.1021/om960379r

Organometallics 1996, 15, 4389-4397
4389
Rea ction s of Ter m in a l Alk yn es w ith Gr ou p 6-Gr ou p 10
Heter obim eta llics
Michael J . Chetcuti,*,† Brian E. Grant,† and Philip E. Fanwick‡
Department of Chemistry and Biochemistry, University of Notre Dame,
Notre Dame, Indiana 46556, and the Department of Chemistry,
Purdue University, West Lafayette, Indiana 47907
Received J uly 20, 1996X
Reactions of PhC2H with NiCp*M(CO)3Cp′′ [Ni-M: M ) Mo, W; Cp* ) η5-C5Me5; Cp′′ )
Cp (η5-C5H5) or Cp′ (η5-C5H4Me)] afford metallacyclic species 4, of formula NiCp*{µ-η3-
(Ni),η1(1-M)C(H)C(Ph)C(O)}M(CO)2Cp (Ni-M, M ) Mo, W), as the principal products. These
compounds are isomeric to four-membered nickelacycles obtained in similar reactions with
disubstituted alkynes and contain five-membered NiC(O)C(H)C(Ph)M ring systems. Phen-
ylacetylene also affords minor quantities of alkyne bridged complexes with “dimetallatet-
rahedrane-type” nuclear cores. Alkylation of 4 with (Me3O)+BF4- results in the methylation
of the metallacyclic (acyl-like) carbonyl ligand and a structural rearrangement ensues:
cationic four-membered molybdena- or tungstenacycles 6 of formula [NiCp*{µ-η3(Ni),η2(1,3-
M)C(H)C(Ph)C(OMe)}M(CO)2Cp]+BF4- (Ni-M, M ) Mo, W) result. An iodide-for-carbonyl
substitution reaction on 6 affords the neutral complexes 8 [NiCp*{µ-η3(Ni),η2(1,3-M)C(H)C-
(Ph)C(OMe)}MI(CO)Cp] (Ni-M), which maintain the structural core present in 6. The
structure of 8b ′, [NiCp*{µ-η3(Ni),η2(1,3-W)C(H)C(Ph)C(OMe)}WI(CO)Cp′] (Ni-W) was
established by X-ray diffraction.
In tr od u ction
tions to this field described the reactions of CoxM4-x (M
) Mo, W; x ) 1-3) clusters with alkynes;19 other
research by our group has detailed the reactions of
coordinatively saturated Ni-M (M ) Mo, W) species
with alkynes.20-23
The reactions of alkynes with transition metal com-
plexes remains an active research area. The complex
nature of many of these reactions and the myriad
number of products often isolated is manifested by the
large number of publications that regularly document
new reactions in this class. Reactions of bimetallic and
heterobimetallic complexes with alkynes continue to
receive attention by many groups.1-18 Our contribu-
Most recently, we have described the chemistry of the
mixed-metal unsaturated heterobimetallic complexes
NiCp*M(CO)3Cp (Ni-M: 1, M ) Mo; 2, M ) W) with
disubstituted alkynes. The initial products obtained in
these reactions are nickelacyclic species in which a
carbonyl ligand is coupled with the alkyne as shown in
Scheme 1. The resultant NiC(R)C(R′)C(O) metallacycle
is π-complexed to the group 6 metal. Further reactions
on these species lead to “ring-flip” reactions and to the
formation of molybdenacycle or tungstenacycle species
which are π-bonded to the nickel atom.24
Terminal alkynes frequently exhibit a chemistry
different from that of their disubstituted derivatives,
presumably because some or all of the following factors
may come into play: (i) the lower steric demands of a
CH versus a CR group; (ii) the lesser electron-donating
† University of Notre Dame.
‡ Purdue University.
X Abstract published in Advance ACS Abstracts, September 15, 1996.
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1987, 6, 2298-2306.
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S0276-7333(96)00379-2 CCC: $12.00 © 1996 American Chemical Society

4390 Organometallics, Vol. 15, No. 21, 1996
Chetcuti et al.
Sch em e 1. Su m m a r y of th e Rea ction s of
Com p lexes 1, 2, a n d 2′ w ith Disu bstitu ted Alk yn es
F igu r e 1. Structure of the µ-η2,η2-PhC2H complexes 3.
3a has a “dimetallatetrahedrane” core; its structure, and
those of related species, is shown in Figure 1. Like other
bridging alkyne complexes of this type that we20-22,24
and others11,12 have isolated, this complex has a termi-
nal and a semibridging carbonyl ligand. Terminal
(semibridging) carbonyl ligand exchange is presumably
prevalent in this molecule, but as this fluxional process
cannot give this unsymmetrical molecule effective pla-
nar symmetry on the NMR time scale, two carbonyl
resonances are observed in its 13C NMR spectrum. Four
ν(CO) stretches are seen in the IR spectrum of 3a .
The major product, 4a comprises 70-80% of the
product mixture. Spectroscopic data (Tables 1-3) sug-
gest that phenylacetylene had added to 1 and indicate
that the empirical formula of 4a is NiMoCpCp*(CO)3-
(PhC2H). A plethora of isomers with this empirical
formula are possible, but these may be whittled down
to a small number of feasible structures by careful
spectroscopic analysis.
Ch a r t 1
The IR spectrum of 4a (Table 3) included a terminal
ν(CO) stretch, a semibridging ν(CO) stretch (at 1843
cm-1), and a solvent-dependent stretch that appeared
at 1690 cm-1; the latter absorption was assigned to a
MC(O) group. The downfield chemical shift of the
1
CtCH proton (7.31 ppm) in the H NMR spectrum of
4a indicated that an M-C(H) linkage was also present.
Four possible isomeric structures for the core structure
of 4a that (i) maintain an 18-electron configuration for
each metal, (ii) contain both M-C(O) and M-C(H) [or
M′-C(H)] linkages, and (iii) assume an intact C(Ph)-
C(H) linkage, are shown in Figure 2. These restrictions
still allow possible nickelacycle, molybdenacycle, and
dimetallacycle structures for 4a .
ability of a CtCH versus a CtCR group; (iii) the
possibility of CtCH activation reactions. We were
interested in investigating whether the reactions of
terminal alkynes with 1 and 2 paralleled the reactions
of disubstituted alkynes24 with the same unsaturated
heterobimetallic species. Here we describe reactions of
the terminal alkynes PhC2H and HC2H with 1 and 2,
and with their methylcyclopentadienyl analogs NiCp*M-
(CO)3Cp′ (Ni-M: 1′, M ) Mo; 2′, M ) W)25 and the
structures of the species that result from these ligand
transformations.
The acyl ν(CO) stretch seen in 4a is 30-50 cm-1
higher in energy than acyl stretches seen in four-
membered nickelacyclic species such as NiCp{µ-η2(1,3-
Ni),η2(1,2-Mo)C(Me)C(Me)C(O)}Mo(CO)2Cp (Figure 1, R
) R′ ) Me),20 whose core geometries adopt structure A
(Figure 2). Furthermore the acyl carbon resonance of
4a appears at 173 ppm in its 13C NMR spectrum, a value
∼10 ppm upfield from the acyl carbon resonances
observed for 2-butyne and 1-phenylpropyne type A
metallacycles.24 These data suggest that 4a is not
isostructural to type A metallacycles. Isomer B can be
readily dismissed as it requires a fully bridging carbonyl
(absent in 4a ) in order to satisfy the 18-electron rule.
Isomers C and D differ in their metal-acyl carbonyl
linkage. Isomer C has a Mo-C(O) acyl-type bond as
part of a four-membered ring, while D includes a Ni-
C(O) linkage within a five-membered ring. While 4a is
believed to have the structure of C or D, the available
spectroscopic data for 4a did not allow us to distinguish
between these two options. Nickel-tungsten analogs
Resu lts a n d Discu ssion
When 1 was treated with phenylacetylene, a small
amount of the µ-η2,η2-alkyne complex NiCp*(µ-η2,η2-
PhC2H)Mo(CO)2Cp (Ni-Mo, 3a ) was isolated. Complex
(25) Throughout this manuscript Cp ) η5-C5H5; Cp′ ) η5-C5H4Me;
Cp* ) η5-C5Me5. All the complexes discussed (Chart 1) have a NiCp*
group linked to either a MCp or a MCp′ group (M ) Mo, W). Primed
complexes (e.g., 1′, NiCp*Mo(CO)3Cp′) contain a MCp′ group; unprimed
complexes (e.g., 2, NiCp*W(CO)3Cp) contain a MCp group.

Group 6-Group 10 Heterobimetallics
Ta ble 1. 1H NMR Da ta for th e New Com p lexesa
Cp or Cp′ OMe
Organometallics, Vol. 15, No. 21, 1996 4391
complex
Cp*
H/Ph
H
3a
3b
3b′
3c′
4a
1.53
1.52
1.50
1.78
1.78
1.69
1.67
1.73
1.77
1.55
1.73
1.77
2.04
1.70
1.70
1.69
1.93
5.12
5.15
7.19-7.33
7.13-7.31
7.17-7.34
5.39
6.96-7.19
7.00-7.29
7.06, 7.16, 7.31
6.98, 7.10, 7.21
3.63e
7.24, 7.36, 7.56
7.40, 7.65
7.51, 7.78
6.42i
7.62, 7.42
7.38, 7.64
7.31-7.42, 7.64
6.90j
5.43
5.10
5.25
5.39
7.31
6.99
6.89
7.36e
6.73h
3.27
6.92
6.68f
6.30i
6.21g
7.67
7.24
6.19j
4.99-5.30, 1.98
5.13,b 5.23,b 2.12
5.35
4b
5.32
4b′
4b′c
4c′
5′
5.07, 5.15, 5.18, 5.21, 2.06
5.50 (2H), 5.62, 5.71, 2.13
5.20, 5.26 (2H), 5.29, 2.06
4.79, 4.98, 5.21, 5.51, 1.75d
5.39
6a
3.80
3.82
3.72
9.77 (OH)
3.64
6b′c
6c′c
7′
5.50-5.78, 2.03
5.44-5.56, 1.94
5.45-5.51, 5.16-5.23, 2.00
8a
4.98
8b′
4.56, 4.81, 4.84, 5.18, 2.01
4.73(2H), 4.89, 5.18, 1.96
3.59
3.57
8c′c
a
In CDCl3, with CHCl3 set at 7.26 ppm. δ in ppm; coupling constants in hertz. Cp′ and Ph aromatic signals are multiplets: the
multiplet center or range is given, followed (for Cp′) by the Me signal. Cp′ aromatic groups exhibit ABCD-type patterns. b AA′BB′ multiplet.
c In acetone-d6 with CHD2C(O)CD3 set at 2.04 ppm. Aromatic signals broad, down to -30 °C. J WH ) 2.9;e 4.1.f 3.9.g J HH ) 3.9;h 3.8;i
d
3.7.j
Ta ble 2. 13C NMR Da ta for New Com p lexesa
C(O)M or
C(OMe)
C(H)/C(Ph),
C(H)
complex
CO
Cp*
Cp or Cp′
Ph
3a
230.3, 240.9
222.4, 228.6
231.6, 232.4
219.2, 219.3
220.3, 220.6
222.6, 228.1
220.0
8.4, 100.7
8.8, 100.1
9.0, 102.3
9.0, 101.7
8.7, 101.5
8.2, 103.3
8.8, 105.5
92.2
75.8, 99.1
68.7, 86.6c
67.4, 127.9
53.4, 113.0
53.6, 114.0
59.7, 151.8
115.6, 127.1
126.6, 127.9, 130.6, 140.7
127.3, 128.8, 132.0, 141.6
123.4, 125.4, 128.3, 139.2
124.5, 125.7, 127.9, 138.0
124.5, 125.6, 127.6, 137.5
126.7, 127.5, 128.2, 158.3
128.6, 129.1, 130.8, ***
3b′b
4a
14.0, 88.4, 90.2, 90.8, 91.3, 109.2
91.9
89.7
13.8, 86.8, 88.8, 88.9, 91.3, 107.8
13.5, 82.7, 86.1, 91.0, 95.2, 124.
91.0
172.9
176.9
175.9
183.8
4b
4b′
5′
6a
63.3, 177.9
225.9
6b′
209.9d
64.0, 164.0f
8.5, 104.9
13.9, 83.5, 85.4, 89.0, 91.7, 110.4
99.6,g 129.7h
128.1, 128.8, 130.0, 130.4
214.5e
6c′b
7′
8a
8b′
8c′
223.1, 226.6
207.0, 213.5
245.1
238.4
244.1
63.5, 187.0
160.1
60.4, 182.2
60.7, 168.3
59.9, 187.7
9.0, 106.8
8.2, 104.2
9.3, 102.2
9.1, 101.5
9.4, 102.0
14.3, 87.7, 89.1, 92.3, 94.6, 113.1
13.9, 83.2, 85.2, 88.4, 91.9, 110.1
90.8
14.6, 82.9, 84.4, 91.9, 94.6, 104.4
14.7, 85.9, 87.3, 94.4, 94.6, 106.2
109.8, 128.5
98.6, 129.8
120.7, 130.9
119.6,i 123.0
138.4, 90.8
128.5, 129 .8, 130.3
127.8, 128.4, 128.9, 130.3
127.3, 128.1, 128.5, 133.2j
a
In chloroform-d1; δ(ppm) referenced to the CDCl3 signal set at 77.0 ppm. Unobserved signals denoted ***. Cp′, Cp* and Ph, signals
b
given in the following order: Me, other aromatic carbon atoms, ipso carbon. Coupling contants in hertz. In acetone-d6 [(CD3)2CO set at
29.8 ppm]. J WC ) 26.5;c 148.1;d 135.2;e 64.2;f 51.3;g 6.8;h 59.4;i 8.6.j
Ta ble 3. IR ν(CO) Da ta (cm -1) for New Com p lexesa
3a
1935(s), 1904(m), 1866(w), 1809(m) 5′
1970(s), 1899(s),
1653(s)
1950(s),b 1910(m), 1873(w),
1821(m)
6a d 2020(s), 1965(s)
3bb 1948(s), 1913(w), 1876(m), 1816(s) 6b′d 2013(s), 1952(s)
3b′b 1946(s), 1909 (m), 1872(w), 1810(m) 6c′d 2018(s), 1963(s)
3c′ 1910(s), 1829(m)
7
2012(s), 1962(s)
4a
1953(s), 1842(s), 1690(m)
7′d 2013(s), 1952(s)
1948(s),d 1841(s), 1670(m)
8a
1902(s)
4bc 1933(s), 1831(s), 1671(m)
4b′ 1946(s), 1835(s), 1685(m)
4c′d 1951(s), 1837(s), 1670(m)
8b′d 1885(s)
8c′ 1900(s)
a
b
In THF unless otherwise stated. In hexanes. c Nujol Mull.
d
In dichloromethane.
of 4a were therefore prepared with the hope of obtaining
good 13C NMR data. The observation of 183W-13C
couplings in the 13C NMR spectra of the Ni-W analog,
and an assessment of their magnitude, would allow us
to differentiate between options C and D.
When PhC2H was reacted with the complexes
NiCp*W(CO)3Cp′′ (Ni-W: 2, Cp′′ ) Cp; 2′, Cp′′ ) Cp′),
the µ-η2,η2-alkyne complexes NiCp*(µ-η2,η2-PhC2H)-
W(CO)2Cp′′ (Ni-W: 3b, Cp′′ ) Cp; 3b′, Cp′′ ) Cp′) were
isolated as minor reaction products (∼20-30% of the
product mixture). Spectroscopic properties of 3b and
3b′ mirror those of 3a . The only noteworthy observation
F igu r e 2. Some isomeric cores possible for complex 4a .
1
is the fact that the H NMR resonances of complex 3b′
are concentration dependent. Different concentrations
of chloroform-d1 solutions of 3b′ exhibit chemical shift
differences up to 0.17 ppm for the PhC2H proton
resonances. The Cp′ and Ph aromatic resonances also
show (smaller) concentration-dependent chemical shifts.
Higher concentrations of 3b′ led to a upfield chemical
shift for the PhC2H resonance.
The major reaction products in the reactions of 2 and
2′ with PhC2H (complexes 4b and 4b′, respectively)

4392 Organometallics, Vol. 15, No. 21, 1996
Chetcuti et al.
Sch em e 2. Rea ction s of 1, 1′, 2, a n d 2′ w ith Ter m in a l Alk yn es a n d th e P r oba ble Str u ctu r es of th e P r od u cts
featured semibridging carbonyl ligands and a methine
carbon-metal [M-C(H)] linkage. The data indicate
that these species are isostructural with 4a . If these
metallacycles were of isomeric form C, a large 183W-
13C coupling to the acyl carbon would be expected, and
a comparably large coupling to the methine carbon
should also be visible. Were isomer D the actual
structure of these species, 183W-13C coupling to the acyl
carbon would be observed.
acyl CO stretches that were familiarly observed for type
A (Figure 2) metallacycles. The physical properties of
5′ (its low solubility, very sluggish chromatographic
mobility, and orange-brown color) and its spectroscopic
features are in accord with 5′ having this structure.
However, the upfield chemical shift of the methine
proton (δCH ) 3.27 ppm) suggests that the alkyne-
derived CH proton is nested between C(O) and C(Ph)
groups (opposite to the linkage that is observed in 4b′).
This compound is therefore assigned the structure
NiCp*{µ-η2(1,3-Ni),η2(1,2-W)C(Ph)C(H)C(O)}W(CO)2-
Cp′ (Ni-W, 5′). Complex 5′ contains a nickelacyclo-
butenone ring. Reactions of phenylacetylene with the
heterobinuclear complexes and the structures of the
products obtained are summarized in Scheme 2.
It is unusual that more than one isomer with organic
bridges spanning the same bimetallic framework can
be isolated. Previously reported examples of bimetallic
metallacycles that incorporate linked alkyne and car-
bonyl moieties typically show a preference for only one
isomer. Earlier work in this laboratory showed that the
unsymmetrical alkyne 2-pentyne leads to two metalla-
cycles when reacted with Ni(CO)Cp-MoCp(CO)3. These
products were both characterized as nickelacyclobuten-
one structures, differing only in their alkyne-carbonyl
linkage but not in the bonding mode of the C(R)C(R′)C-
(O) ligand to the metals.20 Similar results were ob-
tained when 2-pentyne was reacted with 1.26
Unfortunately, 183W-13C-coupling data in the 13C
NMR spectra of both 4b and 4b′ were of limited utility
in distinguishing between possible isomers. For 4b′, the
acyl carbon resonance at δ ) 176 ppm was broad and
became broader at low temperatures; the methine
carbon resonance behaved similarly. This precluded an
accurate determination of 183W-13C coupling to either
of these carbon atoms.
More subtle arguments do suggest that isomeric form
D is the likely structure for these species. The chemical
shifts of the acyl carbonyl resonances for all three
complexes are within 3 ppm of each other despite the
change in group 6 metal between 4a (molybdenum) and
4b and 4b′ (tungsten). Were structure C adopted, a
larger chemical shift difference might have been ex-
pected between Mo-CO and W-CO resonances in 4a
and 4b , 4b ′, respectively. Furthermore the chemical
shift of the alkyne-derived CH varies significantly from
4a (67.4 ppm) to 4b and 4b′ (53.4 and 53.6 ppm,
respectively). Based on these chemical shifts data,
isomeric form D seems to be the more probable structure
for complexes 4, and this structure was tentatively
assigned to them. They may thus be represented as
NiCp*{µ-η3(Ni),η1(1-M)C(H)C(Ph)C(O)}M(CO)2Cp′′
(Ni-M: M ) Mo, Cp′′ ) Cp, 4a ; M ) W, Cp′′ ) Cp, 4b;
Cp′′ ) Cp′, 4b′). A five-membered NiMC3 ring is present
in the three species.
Previously characterized ditungsten,27 and diiron and
diruthenium metallacycles28 with C(R)C(R)C(O) ligands
spanning two metal centers have shown a preference
for one particular isomer. Furthermore, both the group
6 and the group 8 dinuclear complexes exhibit consider-
able fluxionality. The ditungsten metallacycle under-
goes a fluxional process in which reversible metal-
carbon bond cleavage occurs,27 while carbon-carbon
A third product (5′), isolated in low yields (5 -15%)
from the reaction of 2′ and phenylacetylene, clung
tenaciously to a silica gel column and could only be
eluted by using methanol as a solvent. The IR spectrum
of 5′ revealed the pattern of two terminal and one metal
(26) Chetcuti, M. J .; Grant, B. E., unpublished results.
(27) Finnimore, S. R.; Knox, S. A. R.; Taylor, G. E. J . Chem. Soc.,
Dalton Trans. 1982, 1783-1788.
(28) Dyke, A. F.; Knox, S. A. R.; Morris, N. J .; Naish, P. J . J . Chem.
Soc., Dalton Trans. 1983, 1417.

Group 6-Group 10 Heterobimetallics
Organometallics, Vol. 15, No. 21, 1996 4393
Sch em e 3. P r oton a tion or Alk yla tion of th e
Dim eta lla cyclic Sp eciesa
bond breakage is invoked to account for the dynamic
behavior of the diiron or diruthenium systems.28
Some dirhodium alkyne complexes have shown greater
flexibility. Dickson and co-workers prepared a series
of complexes by reacting the coordinatively unsaturated
Rh2(µ-CO)2Cp*2 (RhdRh) with a variety of (nontermi-
nal) alkynes.5 It was found that the products of these
reactions existed in solution as an equilibrium mixture
of metallacycle and η1,η1 parallel bridging alkyne com-
plex. Moreover, the metallacycles showed further flux-
ional behavior, independent of this equilibrium, in
which the coordination mode of the bridging organic
group jumped between the two metal sites by a mech-
anism similar to that seen in the diruthenium metal-
lacycle. The reaction of the same unsaturated dirhod-
ium complex Rh2(µ-CO)2Cp*2 (RhdRh) with ethyne led
to an equilibrium mixture of two metallacycles: both
the four-membered metallacycle and five-membered
dimetallacycle were characterized from this reaction.29
Our results of the phenylacetylene reaction with 2′
suggest that the different steric and/or electronic de-
mands of the Ph and H groups of the PhC2H ligand lead
to the formation of the two metallacycles. It is not clear
why this occurs. Possible reasons that allow the forma-
tion of 4b′ include either the presence of a relatively
bulky Ph group at C2 or the absence of a sterically
demanding group at C1.
a
The dimetallacycle species are converted to (mono)metal-
lacycles in this reaction.
literature. These include our own recent work24 and
other examples that lead to different products. Treat-
ment of the ditungsten metallacyclic species W(CO)2Cp-
{µ-η2(1,2)η2(1,3)-C(R)C(R′)C(O)}W(CO)2Cp (W-W) with
HBF4 results in the protonation of the oxygen atom of
the acyl group, yielding a compound the authors des-
ignate as a hydroxy carbene complex.27 The cationic
complex that was isolated exhibited dynamic behavior
similar to that observed for the neutral precursor.
However, the protonation of diiron metallacyclopenten-
one complexes Fe(CO)Cp{µ-η1,η3-C(R)C(R′)C(O)}(µ-CO)-
FeCp (Fe-Fe) follows a very different route. Carbon-
carbon bond cleavage occurs here, and the resultant
products are µ-alkenyl species.28
In an attempt to answer why two metallacycles were
obtained, 1′ was reacted with ethyne. Methylene chlo-
ride solutions of 1′ instantly change from blue to orange
when exposed to an ethyne atmosphere at -78 °C.
Unfortunately, the orange mixture resisted purification,
and massive decomposition ensued when chromatogra-
phy was attempted. No products could be isolated by
following this procedure. Vacuum concentration of the
1
crude reaction mixture did afford a brownish oil; H
NMR analysis of this oil showed that two main species
were present.
The minor product was formulated as the µ-η2,η2
alkyne complex NiCp*(µ-η2,η2-HC2H)Mo(CO)2Cp′ (Ni-
Mo, 3c′). The 1H NMR and IR spectra of the other
product are consistent with a metallacycle of type 4 (a
dimetallacyclopenteneone-type species). The major re-
action product is thus formulated as NiCp*{µ-η3(Ni),η1(1-
Mo)C(H)C(H)C(O)}Mo(CO)2Cp′ (Ni-Mo, 4c′). The struc-
tures of both products are shown in Scheme 2.
Using the same protocol reported earlier,24 the com-
plexes [NiCp*{µ-η3(Ni),η2(1,3-Mo)C(H)C(Ph)C(OMe)}-
-
Mo(CO)2Cp]+BF4 (Ni-Mo, 6a ) and [NiCp*{µ-η3(Ni),
η2(1,3-M)C(H)C(R)C(OMe)}M(CO)2Cp′]+BF4- (Ni-M, M
) W, R ) Ph, 6b′; M ) Mo, R ) H, 6c′) were prepared
from their neutral precursors 4a , 4b′, and 4c′ by
alkylation with (Me3O)+BF4-. Two hydroxy complexes,
the species [NiCp*{µ-η3(Ni),η2(1,3-W)C(H)C(Ph)C(OH)}-
W(CO)2Cp′]+BF4- (Ni-W, 7′) and the less well charac-
terized nickel-molybdenum complex [NiCp*{µ-η3(Ni),
η2(1,3-Mo)C(H)C(H)C(OH)}Mo(CO)2Cp]+BF4- (Ni-Mo,
7), were also prepared by treatment of 4b′ and 4a ,
respectively, with HBF4‚Et2O.
The dynamic behavior of the homobimetallic metal-
lacycles referred to earlier5,27-29 is mirrored by the
broadening of 13C NMR resonances in the spectrum of
4c′. This complex may also undergo some form of
dynamic behavior in solution and suggests that the
assignment of a dimetallacyclopentenone structure to
4c′ and other type 4 complexes may well be simplistic.
The failure to obtain low-temperature limiting spectra
precluded useful 183W-13C coupling information from
being obtained from the nickel-tungsten complexes. In
order to circumvent this problem and in an attempt to
unambiguously distinguish between possible isomeric
metallacycles, alkylation of complexes 4 was attempted.
Alkylation of metal-acyl complexes is a well-known
reaction that may lead to heteroatom-stabilized cationic
carbene complexes. Reports of electrophilic attack on
metallacyclic acyl complexes have appeared in the
The NMR data, especially 183W-13C coupling data
gleaned from the 13C NMR spectra for the Ni-W
complex 6b′, suggest that complexes 6 are cationic η2-
(M)η3(Ni)-allylic species (M ) Mo, W). The structures
of complexes 6 and 7 are shown in Scheme 3. Alkylation
or protonation of complexes 4 thus results in a rear-
rangement of the organic backbone and to the trans-
formation of what are believed to be dimetallacyclopen-
teneone species to metallacyclobutenone complexes.
Unfortunately, X-ray-quality crystals again could not
be obtained for any type 6 complex. Derivatives of
complexes 6 were isolated instead.
(29) Herrmann, W. A.; Bauer, C.; Weichmann, J . J . Organomet.
Chem. 1983, 243, C21-C26.

4394 Organometallics, Vol. 15, No. 21, 1996
Chetcuti et al.
Sch em e 4. Iod id e-for -Ca r bon yl Liga n d
Su bstitu tion on Com p lexes 6a
to unambiguously determine the structure and geo-
metrical parameters of one of these complexes, a single-
crystal X-ray diffraction study was carried out on
complex 8b′. Crystal data and data collection param-
eters and tables of key bond lengths and bond angles
are collected in Tables 4-64, respectively. A labeled
ORTEP diagram of 8b′ is shown in Figure 4.
The X-ray study confirms the formulation of complex
8b′ as NiCp*{µ-η3(Ni),η2(1,3-W)C(H)C(Ph)C(OMe)}WI-
(CO)Cp′ (Ni-W). The molecule features a tungstena-
cycle moiety bonded to a Cp*Ni group via all three
carbons atoms and the tungsten atom of the ring. The
coordination geometry about the tungsten atom, (ignor-
ing the metal-metal bond) is that of a four-legged piano
stool, with the iodide oriented in a transoid orientation
to the methoxy ring carbon (COMe-W-I ) 136.4°) and
the carbonyl ligand oriented in a transoid orientation
to the (alkyne-derived) methine carbon atom, as de-
picted in Figure 3B.
The nickel-allylic carbon bond distances differ sig-
nificantly in length, ranging from 1.967(5) Å for the Ni-
C(H) bond, to 2.042(6) for the Ni-C(Ph) bond and
2.021(6) Å for the Ni-C(OMe) bond. Significant varia-
tions in metal-carbon bond lengths between the C1, C2,
and C3 carbon atoms of the allyl ligand are not unusual.
In the cationic complex [Ni(η3,η2, η2-C12H19)]+ for ex-
ample, Ni-Callyl bond lengths range from 2.018(4) to
2.116(4) Å.30
a
Structure 8b′ was established by an X-ray diffraction
study.
The Ni-W distance of 2.6359(8) Å is consistent with
that of a Ni-W single bond.22 The W-CCO distance of
1.945(7) Å is somewhat shorter than a normal W-car-
bonyl distance, perhaps reflecting the increased dπ-
pπ backbonding, due to the factors outlined above. All
the atoms in the tungsten metallacycle are essentially
coplanar (∑ angles inside the WC3 quadrilateral )
357.6°), tallying with the treatment of the C3 unit in
the metallacycle as an allylic ligand. The MeO atom
and the ipso carbon atom of the phenyl ring are also
practically coplanar with the C3 ligand as expected for
allylic ligand substituents [∑ angles around C2 ) 358.2°;
∑ angles around C3 ) 360.1°]. The MeO and the other
phenyl carbon atoms, and the Cp* group carbon atoms
are essentially in the same plane as the WC3 ring.
Finally, the Cp′ and Cp* ligands are in a slightly
distorted trans orientation (Cp′centroid-W-Ni-Cp*centroid
torsion angle ) 154.3°).
The overall structure of 8b′ (and, presumably, those
of the other iodo complexes and their cationic precur-
sors) can be viewed as a 1,3-tungsten substituted allyl
species. Alternatively, the WC3 unit as a whole can also
be viewed as an η4-coordinated tungstenacyclobutadiene
group bonded to a Cp*Ni fragment. Parallels can be
drawn by considering the reaction of alkynes with
bimetallic bridging alkylidyne complexes. Stone and co-
workers have synthesized many µ-η2,η3-allyl complexes,
whose MM′C(R)C(R′)C(R′′) cores mirror those observed
for complexes 6-8. An alkoxy-substituted µ-η2,η3-allyl
complex has also been reported by Mathieu and co-
workers. The species Fe(CO)3{µ-η2,η3-C(R)C(R)C(OEt)}(µ-
η2,η2-PhC2Ph)Fe(CO)3 (Fe-Fe) was obtained through
F igu r e 3. Two possible isomers of complex 8b′, differing
in the relative stereochemistry of the W-I and W-CO
bonds relative to the metallacycle ring. B is the correct
structure of 8b′.
Iodide-for-carbonyl ligand substitution on complexes
6a , 6b′, and 6c′ was effected by using NBu4+I- as the
iodide source and Me3NO as the carbonyl ligand oxi-
dant. This reaction afforded the neutral iodo complexes
8a , 8b′, and 8c′, respectively, as shown in Scheme 4.
The 13C NMR spectra of all iodo compounds exhibited
a single downfield chemical shift for the terminal
carbonyl ligand; spectroscopic data indicate that they
have structures that are similar to their respective
cationic precursors 8a , 8b′, and 8c′. These complexes
all have relatively low ν(CO) stretching frequencies for
their lone carbonyl ligand (1885-1900 cm-1). They
exhibit low-field chemical shift signals for the carbonyl
carbon in the 13C NMR of the complexes.
In complexes 8, the iodide ligand may either be in a
cis or in a trans geometry relative to the C(OMe) group
of the metallacycle (Figure 3). Only one of these two
possible geometric isomers formed. Similarly, as we
reported earlier, only one isomer was observed for the
isostructural 2-butyne derivative NiCp*{µ-η3(Ni),η2(1,3-
Mo)C(Me)C(Me)C(OMe)}MoI(CO)Cp (Ni-Mo).24 To es-
tablish which of these two isomers formed, as well as
(30) Taube, R.; Wache, S.; Sieler, S.; Kempe, R. J . Organomet. Chem.
1993, 456, 131-136.

Group 6-Group 10 Heterobimetallics
Organometallics, Vol. 15, No. 21, 1996 4395
Ta ble 4. Cr ysta l Da ta a n d Da ta Collection P a r a m eter s for
NiCp *{µ-η2(W)η3(Ni)-C(H)C(P h )C(OMe)}WI(CO)Cp ′ (Ni-W, 8b′).
parameter
value
parameter
value
formula
space group
b, Å
â, °
Z
NiWC27H31IO2
P21/c (No. 14)
14.953(2)
103.126(5)
4
formula wt
757.01
a, Å
c, Å
9.3131(5)
18.617(2)
2524.8(8)
1.991
V, Å3
d
calc, g cm-3
cryst dimens, mm
radiation, λ (Å)
abs coeff µ, cm-1
transm factors
scan method
h,k,l limits
takeoff angle, deg
F000
no. of data collected
no. of data with I > 3.0σ(I)
Ra
0.35 × 0.31 × 0.28
Mo Ka, 0.71073
66.33
0.74, 1.00
ω-2θ
-10 to 9, 0-16, 0-20
2.95
1456.0
temp, °C
20
monochromator
abs corr applied
diffractometer
2θ range, deg
scan width, deg
programs used
weighing p-factor
no. of unique data
no. of variables
graphite
empirical
Enraf-Nonius CAD4
4.00-45.00
0.82 + 0.35 tan θ
Enraf-Nonius SDP
0.040
3425
289
0.027
3426
2660
0.021
b
Rw
goodness of fit
0.910
max. shift/esd in final cycle
0.18
a
b
2 1/2
R ) ∑|Fo - Fc|/∑Fo. Rw ) [∑w(|Fo - Fc|)2/∑wFo
] .
Ta ble 5. Key Bon d Dista n ces (Å) of
NiCp *{µ-η2(Mo)η3(Ni)C(H)C(P h )C(OMe)}WI(CO)Cp ′
(Ni-W, 8b′)a
atoms
distance
atoms
distance
W-I
2.8423(5)
1.945(7)
2.131(6)
2.042(6)
1.173(8)
1.431(8)
1.417(8)
W-Ni
2.6359(8)
2.136(6)
2.021(6)
1.967(5)
1.362(7)
1.434(8)
W-C(1)
W-C(2)
W-C(4)
Ni-C(3)
O(1)-C(1)
O(21)-C(22)
C(3)-C(4)
Ni-C(2)
Ni-C(4)
O(21)-C(2)
C(2)-C(3)
a
ESD’s in parentheses.
Ta ble 6. Key Bon d An gles (d eg) in
NiCp *{µ-η2(Mo)η3(Ni)C(H)C(P h )C(OMe)}WI(CO)Cp ′
(Ni-W, 8b′)a
atoms
angle
atoms
angle
I-W-Ni
89.37(2)
88.7(2)
136.3(2)
82.9(2)
48.8(2)
41.3(2)
41.4(2)
70.8(2)
116.6(5)
78.6(2)
99.1(4)
70.1(3)
68.6(3)
125.5(4)
132.7(5)
79.9(2)
72.2(3)
Ni-W-C(1)
81.1(2)
47.3(1)
60.6(2)
127.5(2)
95.1(2)
65.3(2)
52.6(2)
52.8(2)
174.3(6)
139.4(4)
123.5(4)
119.7(5)
66.5(3)
98.1(5)
129.3(5)
99.8(4)
I-W-C(1)
Ni-W-C(4)
I-W-C(2)
C(2)-W-C(4)
C(1)-W-C(4)
C(1)-W-C(2)
C(2)-Ni-C(4)
W-Ni-C(2)
I-W-C(4)
Ni-W-C(2)
C(2)-Ni-C(3)
C(3)-Ni-C(4)
W-Ni-C(3)
F igu r e 4. ORTEP diagram of NiCp*{µ-η3(Ni),η2(1,3-W)-
C(H)C(Ph)C(OMe)}WI(CO)Cp′ (8b′, Ni-W). All non-hydro-
gen atoms are shown as ellipsoids drawn at the 50%
probability level. Hydrogen atoms are shown as small
spheres of arbitrary radius.
W-Ni-C(4)
C(2)-O(21)-C(22)
W-C(2)-Ni
W-C(1)-O(1)
W-C(2)-O(21)
Ni-C(2)-O(21)
O(21)-C(2)-C(3)
Ni-C(3)-C(4)
C(2)-C(3)-C(4)
C(4)-C(3)-C(31)
W-C(4)-C(3)
W-C(2)-C(3)
Ni-C(2)-C(3)
Ni-C(3)-C(2)
Ni-C(3)-C(31)
C(2)-C(3)-C(31)
W-C(4)-Ni
higher yields than the alkyne species. The nature of
the metallacycle (four-membered or five-membered ring,
nickelacycle or molybdena- or tungstenacycle, depends
on the particular alkyne and the metallacyclic substit-
uents. Disubstituted alkynes lead to nickelacyclic prod-
ucts, as described earlier. These species rearrange to
four-membered molybdenacycle or tungstenacycle com-
plexes when alkylated or protonated.
A more complex mixture of products is obtained with
terminal alkynes. The principal products are five-
membered dimetallacycles in which the C(H)C(R)C(O)
unit is bound to the nickel via the C(H) carbon atom,
and ligated to the group 6 metal in a η1,η2-fashion [via
the C(O) and the C(H)C(R) atoms]. Alkylation or
protonation of these dimetallacycles leads to a rear-
rangement and affords four-membered molybdenacycle
or tungstenacycle cationic complexes analogous to those
observed with disubstituted alkynes. These cationic
species undergo “iodide-for-carbonyl” substitution reac-
tions to yield neutral complexes; the iodide ligand
resides on the group 6 metal.
Ni-C(4)-C(3)
a
ESDs in parentheses.
the reaction of a the bridging methoxycarbyne diiron
complex Fe(CO)3{µ-C(OEt)}(µ-η2,η2-PhC2Ph)Fe(CO)3 with
alkynes.31
Con clu sion s
The reaction of nickel-molybdenum and nickel-
tungsten complexes with alkynes leads to two main
classes of products: µ-η2,η2-alkyne complexes (with
dimetallatetrahedrane cores) and metallacyclic products
in which alkyne-carbonyl ligand coupling has occurred.
The metallacyclic species are generally obtained in
(31) Ros, J .; Commenges, G.; Mathieu, R.; Solans, X.; Font-Altaba,
M. J . Chem. Soc., Dalton Trans. 1985, 1087.

4396 Organometallics, Vol. 15, No. 21, 1996
Chetcuti et al.
The heterodinuclear species NiCp*M(CO)3(C5H4R) (Ni-M)
were prepared according to published procedures.37 The
alkynes PhC2H and HC2H were purchased from Aldrich and
were used as received. Trimethyloxonium tetrafluoroborate
(Aldrich) was stored in an oven-dried Schlenk tube under an
atmosphere of nitrogen and was rinsed with several portions
of dry CH2Cl2 immediately prior to use.
(b) Sp ectr oscop ic Mea su r em en ts. IR spectra were ob-
tained on an IBM IR-32 FT spectrometer: the solvent-subtract
function for solution spectra. Mass spectra were obtained on
J EOL J MS-AX505 HA or Finnegan-Matt mass spectrometers.
Low-resolution spectra were obtained using chemical ioniza-
tion (CI), with isobutane as the ionization source; high-
resolution spectra employed electron impact (EI) ionization and
PFK as a standard. All low-resolution spectra were compared
with calculated isotopomer patterns. The 1H and 13C NMR
spectra were recorded on a G.E. GN-300 instrument at 300
and 75 MHz, respectively, in chloroform-d1; Cr(acac)3 (∼0.01
M) was added to the 13C NMR samples as a shiftless relaxation
agent.
The diversity of molecular frameworks one sees with
C(R)C(R)C(O) ligands attached to Ni-Mo and Ni-W
frameworks is surprising. The structure of the product
depends on the nature of R and R′ and on whether the
C(O) group is alkylated or protonated. The energy
differences between the neutral metallacycle isomers
must not be large; which particular isomer obtained is
influenced by steric and electronic factors of the alkyne.
Alkylation or protonation of the C(O) group clearly
favors the molybdenacycle or tungstenacycle isomer over
nickelacycle species, irrespective of the nature of the
alkyne, but we are unable to come up with a convincing
explanation why this is so. However, some comments
on the rearrangement process are in order.
Complexes of type 5′ and those formed by disubsti-
tuted alkynes [NiCp*{µ-η2(1,3-Ni),η2(1,2-M)C(R)C(R′)-
C(O)}M(CO)2Cp′] (Ni-M), whose cores contain NiC(R)C-
(R′)C(O) metallacycles π-complexed to the group 6
metal, can be considered to be nido-octahedra with the
NiC3 ring forming the basal plane and group 6 metal
in the apical position. The molybdena- or tungstena-
cycle species of types 6- 8 can also be regarded as nido-
octahedral species with the nickel atom now in the
apical position. The rearrangement of the nido-octa-
(c) Syn th eses of Com p lexes NiCp *(µ-η2,η2-P h C2H)M-
(CO)2Cp′′ (3) an d NiCp*{µ-η1,η3-C(O)C(P h )C(H)}M(CO)2Cp′′
(4). The preparation of the Ni-Mo derivatives (3a , 4a ) and
Ni-W derivatives (3b, 3b′ and 4b, 4b′) followed similar
methods. The preparation of 3b′ and 4b′ is given as a typical
example. Complex 2′ (∼200 mg, 0.37 mmol) was dissolved in
CH2Cl2 (15 mL), and the solution was cooled to -78 °C.
Phenylacetylene (0.05 mL, 0.45 mmol) was added, and the
reaction mixture was allowed to warm to room temperature
over a 2 h period. The mixture was then separated by
chromatography. Complex NiCp*(µ-η2,η2-PhC2H)W(CO)2Cp′
(Ni-W, 3b′) eluted with a hexane/diethyl ether (14:1) mixture
and was isolated as an orange-brown solid (41 mg, ∼17%). The
metallacyclic species NiCp*{µ-η3(Ni),η1(1-W)C(H)C(Ph)C(O)}-
W(CO)2Cp′ (Ni-W, 4b′) eluted with a hexane/ether (5:1)
mixture and was isolated as dark brown crystals (90 mg,
∼37%). Elution with MeOH gave a third band. After removal
of most of the methanol, addition of diethyl ether and filtration
afforded NiCp*{µ-η2(1,3-Ni),η2(1,2-W)C(Ph)C(H)C(O)}W(CO)2-
Cp′ (Ni-W, 5′) as a brown powder (18 mg, ∼7%). Analogs to
complex 5′ were not observed with the Cp derivatives 1 or 2.
For the Ni-Mo complexes 3a and 4a , less of the bridging
alkyne compound 3a was obtained (3a :4a ) 1:8). To obtain
sufficient quantities of 3a for characterization, 4a (100 mg)
was dissolved in THF (20 mL) and the solution was brought
to reflux. After 5 h, the solvent was removed under reduced
pressure, and the product was chromatographed. A single
orange band was eluted with a hexanes/ether (5:1) mixture.
Crystallization from a concentrated hexanes solution at -20
°C afforded orange needles of (54 mg, 59%). Anal. Found
(Calcd) for 4a , NiMoC26H26O3: C, 57.71 (57.67); H, 4.84 (4.98).
MS data. 3a : 514 (M+), 486 (M - CO)+, 458 (M - 2CO)+, 356
(M - 2CO - PhC2H)+. HRMS: calcd for NiMoC25H26O2,
514.0340; found, 514.0333. 3b: 600 (M+), 572 (M - CO)+, 544
(M - 2CO)+, 442 (M - 2CO - PhC2H)+. HRMS: calcd for
NiWC25H26O2, 600.0795; found, 600.0789. 3b′. Anal. Found
(Calcd) for NiWC26H28O2: C, 50.81 (50.77); H, 4.59 (4.59). 4a :
514 (M - CO)+, 486 (M - 2CO)+, 458 (M - 3CO)+.
+
hedral species C5H5 has been predicted to take place
via a C4v f Cs f C2v f Cs f C4v pathway.32 In fact
this mechanism has been proposed to occur in various
metal alkyne cluster species with M3C2 cores.33 Indeed,
the complex OsW2(CO)7(µ-PhC2Ph)Cp2 has been crystal-
lized with either a tungsten atom or the osmium atom
as the capping apical metal;34 the orientation of the
alkyne C2 fragment relative to the OsW2 triangle has
been the subject of an extended Hu¨ckel MO investiga-
tion.35
The rearrangements on the alkylation or protonation
of nickelacycle species observed here and seen earlier24
are topologically similar to those discussed above but
involve M2C3, and not M3C2, core structures. Complexes
of type 4 can be considered to be intermediates in the
rearrangement of a group 6 metal capped nido-core
octahedral geometry to a similar nido-octahedral core
structure the nickel atom in the apical position.36
Exp er im en ta l Section
(a ) Gen er a l Tech n iqu es. All manipulations were carried
out under a nitrogen atmosphere using standard Schlenk tube
techniques and flame-dried glassware. Reagent grade chemi-
cals were used. Solvents were purified as follows: toluene,
hexanes, tetrahydrofuran (THF), and diethyl ether were
distilled from blue or purple Na/benzophenone ketyl solutions;
methylene chloride was distilled over CaH2 under a nitrogen
atmosphere, and reagent grade acetone was stored over 4 Å
molecular sieves and deoxygenated by bubbling nitrogen
through it immediately prior to use. Deuterated NMR solvents
were stored over molecular sieves under a nitrogen atmosphere
and were subjected to three freeze/thaw degassing cycles prior
to use.
Syn th esis of NiCp *{µ-η3(Ni),η1(1-Mo)C(H)C(H)C(O)}-
Mo(CO)2Cp ′ (Ni-Mo, 4c′). 1′ (∼250 mg, ∼0.55 mmol) was
dissolved in CH2Cl2 (15 mL) and chilled to -78 °C. The cold
Schlenk tube was evacuated, and an atmosphere of ethyne was
introduced. The reaction mixture was allowed to stir at this
temperature for 30 min and then slowly warmed to 0 °C. The
solvent was removed under reduced pressure at this temper-
ature leaving 4c′ as dark brown oily solid. Analysis of the
(32) Stohrer, W.-D.; Hoffmann, R., J . Am. Chem. Soc. 1972, 94,
1661-1668.
(33) Mlekuz, M.; Bougeard, P.; Sayer, B. G.; Peng, S.; McGlinchey,
M. J .; Marinetti, A.; Saillard, J .-Y.; Naceur, J . B.; Mentzen, B.; J aouen,
G. Organometallics 1985, 4, 1123-1130.
(34) (a) Churchill, M. R.; Bueno, C.; Wassermann, J . J . Inorg. Chem.
1982, 21, 640-644. (b) Busetto, L.; Green, M.; Hessner, B.; Howard,
J . A. K.; J effery, J . C.; Stone, F. G. A. J . Chem. Soc., Dalton Trans.
1983, 519-525.
(35) Halet, J .-F.; Saillard, J .-Y.; Lissillour, R.; McGlinchey, M. J .;
J aouen, G. Inorg. Chem. 1985, 24, 218-224.
(36) We wish to thank a reviewer for pointing out the topological
aspects of this rerrangement.
1
crude mixture by H NMR spectroscopy showed that, within
the experiment’s detection limits, 4c′ was the only product
detected from this reaction (>90%). Anal. Found (Calcd) for
NiMoC21H24O3: C, 52.50 (52.65); H, 5.05 (5.03).
(37) Chetcuti, M. J .; Grant, B. E.; Fanwick, P. E. Organometallics
1990, 9, 1345-1347.

Group 6-Group 10 Heterobimetallics
Organometallics, Vol. 15, No. 21, 1996 4397
Alk yla tion of Meta lla cycles. Syn th esis of [NiCp *{µ-
η2,η3-C(OMe)C(R)C(R′)}M(CO)2Cp ′′]+BF 4- (Com p lexes 6).
axis diffractometer. Cell constants and an orientation matrix
for data collection were obtained from least-squares refine-
ment, using the setting angles of 25 reflections in the range
21 < θ < 23°. Systematic absences of h0l, l ) 2n and 0k0, k
) 2n and the subsequent successful refinement indicated that
the space group was P21/c (No. 14). Lorentz, polarization
corrections, and an empirical absorption correction38 were
applied.
The structure was solved using the SHELX-86 structure
solution package. Remaining atoms were located in succeeding
Fourier syntheses. Hydrogen atoms were located and added
to the structure factor calculations, but their positions were
not refined. The structure was refined by using full-matrix
least squares: the function minimized was ∑w(|Fo| - |Fc|)2 and
the weight w was defined as per the Killean and Lawrence
method, with terms of 0.020 and 1.0.39
-
Methylation of the metallacycles with Me3O+BF4 followed
similar methods used to prepare [NiCp*{µ-η2,η3-C(OMe)-
- 24
C(R)C(R′)}M(CO)2Cp′′]+BF4
and proceed in virtually quan-
titative yield. By using 2-3 equiv of the alkylating agent, the
reaction time can be reduced to 2-3 h from the normal 5 h.
However, this necessitates a filtration step to remove unre-
-
acted Me3O+BF4
.
MS data, (m/e): 6a , 458 (M - 2CO -
MeO)+, 356 (M - 2CO - MeO - PhC2H)+. 6c′ (CI, with
isobutane): 496 (M+ and M + H+).
P r oton a tion of Syn th esis of [NiCp *{µ-η3(Ni),η1(1-W)C-
(H)C(P h )C(OH)}W(CO)2Cp ′]+BF 4- (Ni-W, 7′) a n d [NiCp *-
{µ-η3(Ni),η1(1-Mo)C(H)C(P h )C(OH)}Mo(CO)2Cp]+BF4- (Ni-
Mo, 7). Both 7′ and 7 were prepared similarly. The synthesis
of the better characterized 7′ is given here. 4b′ (150 mg, 0.23
mmol) was dissolved in ether (30 mL) and cooled to 0 °C. An
excess of HBF4 (∼3-4 equiv) was added via a pipet, prompting
immediate and complete precipitation of an dark red solid.
After allowing the precipitate to settle, the (colorless) solvent
was removed via syringe. Sequential rinsings with ether (3
× 5 mL) were also colorless. Residual ether was evaporated
Scattering factors were from Cromer and Waber.40 Anoma-
lous dispersion effects were included in Fc;41 values for δf′ and
δf′′ were those of Cromer.42 The highest peak in the final
difference Fourier had a height of 0.52 e/Å3, with an estimated
error based on δF of 0.09.43 All calculations were performed
on a VAX computer using SDP/VAX software.44
1
under reduced pressure, leaving a red-black powder. The H
NMR analysis of the product showed exclusive (>95%) forma-
tion of 7′.
Ack n ow led gm en t. We thank the University of
Notre Dame and the American Chemical Society ad-
ministered Petroleum Research Fund for financial sup-
port.
Syn th esis of NiCp *{µ-η2(1,3-Ni),η3(W)C(OMe)C(R)C-
(R′)}MI(CO)Cp ′′ (Ni-M, Com p lexes 8). The preparation of
8a , 8b′, and 8c′ followed similar procedures, and the synthesis
of 8a is given as a typical example. A Schlenk tube was
Su p p or tin g In for m a tion Ava ila ble: An ORTEP diagram
and tables of structural data, positional parameters of all
atoms, anisotropic thermal parameters for non-hydrogen
atoms, bond lengths and bond angles for all non-hydrogen
atoms for 8b′ (14 pages). Ordering information is given on
any current masthead page. Calculated and observed struc-
ture factor listings are available from the authors on request.
n
charged with 6a (105 mg, 0.18 mmol), Bu4N+I- (67 mg, 0.18
mmol), and Me3NO (17 mg, 0.22 mmol). The mixture was
dissolved in 30 mL of CH2Cl2, and the solution was allowed to
stir at reflux temperature for 30 min, during which time the
color of the solution changed from brown to red. The solution
was concentrated and the mixture was filtered and subjected
to chromatography. Elution with hexane/CH2Cl2 (2:1) gave a
single, slow-moving red band. Concentrating the solution and
cooling to -20 °C gave 8a as reddish-black crystals (yield after
crystallization 90 mg, 82%). Yields of 8b′ and 8c′ were similar,
with brownish-red 8b′ (W) differing in color from the red Mo
derivatives. Crystals of 8b′ suitable for an X-ray diffraction
study were grown from a CH2Cl2/hexane mixture at -20 °C.
MS Data for 8c′ (CI using isobutane, m/e): 795 and 794 (M +
H+, M+) (peaks overlap), 566 (M - CO)+.
OM960379R
(38) Walker, N.; Stuart, D. Acta Crystallogr. 1983, 39A, 158.
(39) Killean, R. C. G.; Lawrence, J . L. Acta Crystallogr. 1969, 25B,
1750.
(40) Cromer, D. T.; Waber, J . T. In International Tables for X-ray
Crystallography; The Kynoch Press: Birmingham, England, 1974; Vol.
IV; Table 2.2B.
(41) Ibers, J . A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(42) Cromer, D. T. In International Tables for X-ray Crystallography;
The Kynoch Press: Birmingham, England, 1974; Vol. IV; Table 2.3.1.
(43) Cruickshank, D. W. J . Acta Crystallogr. 1949, 2, 154.
(44) Frenz, B. A. In Computing in Crystallography; Schenk, H.,
Olthof-Hazelkamp, R., van Konigsveld, H., Bassi, G. C., Eds.; Delft
University Press: Delft, Holland, 1978; pp 64-71.
(d ) X-r a y Diffr a ction Stu d y of NiCp *{µ-η3(Ni),η2(1,3-
W)C(H)C(P h )C(OMe)}W(CO)ICp ′ (Ni-W, 8b′). A cube of
8b′ was mounted in a glass capillary tube in a random
orientation on a Enraf Nonius CAD4 computer controlled κ