Chemistry of Fischer-type rhenacyclobutadiene complexes. I. Deprotonation, addition/substitution of nucleophilic reagents at α-carbon, and insertion of heteroatoms into rhenium-carbon bonds

Article abstract of DOI:10.1016/j.jorganchem.2004.03.026

The rhenacyclobutadienes (CO)₄Re(η²-C(R) C(CO₂Me)C(OR′)) (2) undergo a number of reactions that mirror those of Fischer alkoxycarbene complexes. Thus, (CO)₄Re(η²-C(Me)C(CO₂Me)C(OEt)) (2a) can be deprotonated by LDA, Na[OBu-t], or Na[CH(CO₂Me)₂] to give the ylide-like conjugate base [(CO)₄Re(η²-C (=CH₂)C(CO₂Me)C(OEt)]^- (3), which was isolated as PPN(3). Li(3) undergoes deuteriation with DCl/D₂O and alkylation with Et₃OPF₆ at ReC=CH₂, with the latter reaction affording (CO)₄Re(η²-C (CH₂Et) C(CO₂Me)C(OEt)) (4). Repetition of the sequence deprotonation-ethylation on 4 generates (CO)₄ Re(η²-C(CHEt₂) C(CO₂Me)C(OEt)) (5). The nature of the alkoxy substituent in 2 can be varied by use of the rhenacyclobutenones Na[(CO)₄Re(η²-C(R) C(CO₂Me)C(O))] (Na(1)) in conjunction with AcCl and R′OH to produce a series of new complexes (R=Ph, R′=Et (2b); R=Me, R′=CH₂CH=CH₂ (2c), (CH₂)₃C=CH (2d), Me (2e)). Aminolysis of 2a with the primary and secondary amines PhNH₂, HO(CH₂)₂NH, p-TolNH₂, and Et₂NH yields the aminorhenacyclobutadiene complexes (CO)₄Re(η²-C(Me)C(CO₂Me) C(NHR′ or NR′₂)) (R₂′=Et₂ (6a); R′=Ph (6b), (CH₂)₂OH (6c), p-Tol (6d)). These complexes display lesser carbene-like character than their alkoxy counterparts 2, as evidenced by ¹H and ¹³C NMR spectroscopic properties and lack of reactivity toward LDA by 6a. Reactions of each 2a and 6a with PPhMe₂ at low temperature afford (CO)₄Re(η²-C(Me)(PPhMe₂) C(CO₂Me)C(OEt)) (7) and (CO)₃(PPhMe₂) Re(η²-C(Me)C(CO₂Me)C(NEt₂)) (9), respectively, further in agreement with the more carbenoid nature of 2a than 6a. 7 undergoes conversion to (CO)₃ (PPhMe₂)Re(η²-C(Me)C(CO₂Me)C(OEt)) (8) upon heating. 2a reacts with each of (NH₄)₂ [Ce(NO₃)₆], DMSO, EtNO₂/Et₃N, and Me₃NO under various conditions to afford one or both of the oxygen atom insertion products into the Re=C bonds, (CO)₄Re(κ²-OC(Me) C(CO₂Me)C(OEt)) (10) and (CO)₄ Re(κ²-C(Me)C(CO₂Me) C(OEt)O) (11). In contrast, no reaction occurred between 2a and S₈ on heating. However, 6a was converted to the NH insertion product (CO)₄Re(κ²-NHC(Me) C(CO₂Me) C(NEt₂)) (12) by the action of H₂NNH₂·H₂O at 0 °C. All new compounds were characterized by a combination of elemental analysis, mass spectrometry, and IR and NMR spectroscopy.

Full text of DOI:10.1016/j.jorganchem.2004.03.026

Journal of Organometallic Chemistry 689 (2004) 2000–2012
www.elsevier.com/locate/jorganchem
Chemistry of Fischer-type rhenacyclobutadiene complexes. I.
Deprotonation, addition/substitution of nucleophilic reagents at
a-carbon, and insertion of heteroatoms into rhenium–carbon bonds
a,
Veronique Plantevin a,1, Andrew Wojcicki
*
ꢀ
a
Department of Chemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, OH 43210-1185, USA
Received 29 December 2003; accepted 8 March 2004
Abstract
The rhenacyclobutadienes (CO)4Re(g2- C(R)C(CO2Me)C(OR0)) (2) undergo a number of reactions that mirror those of
Fischer alkoxycarbene complexes. Thus, (CO)4Re(g2-C(Me)C(CO2Me)C(OEt)) (2a) can be deprotonated by LDA, Na[OBu-t],
or Na[CH(CO2Me)2] to give the ylide-like conjugate base [(CO)4Re(g2-C(@CH2)C(CO2Me)C(OEt)]ꢀ (3), which was isolated as
PPN(3). Li(3) undergoes deuteriation with DCl/D2O and alkylation with Et3OPF6 at ReC@CH2, with the latter reaction af-
fording (CO)4Re(g2-C(CH2Et)C(CO2Me)C(OEt)) (4). Repetition of the sequence deprotonation-ethylation on 4 generates
(CO)4Re(g2-C(CHEt2)C(CO2Me)C(OEt)) (5). The nature of the alkoxy substituent in 2 can be varied by use of the rhena-
cyclobutenones Na[(CO)4Re(g2-C(R)C(CO2Me)C(O))] (Na(1)) in conjunction with AcCl and R0OH to produce a series of new
complexes (R ¼ Ph, R0 ¼ Et (2b); R ¼ Me, R0 ¼ CH2CH@CH2 (2c), (CH2)3CBCH (2d), Me (2e)). Aminolysis of 2a with the
primary and secondary amines PhNH2, HO(CH2)2NH, p-TolNH2, and Et2NH yields the aminorhenacyclobutadiene complexes
(CO)4Re(g2-C(Me)C(CO2Me)C(NHR0 or NR20 )) (R02 ¼ Et2 (6a); R0 ¼ Ph (6b), (CH2)2OH (6c), p-Tol (6d)). These complexes
display lesser carbene-like character than their alkoxy counterparts 2, as evidenced by 1H and 13C NMR spectroscopic
properties and lack of reactivity toward LDA by 6a. Reactions of each 2a and 6a with PPhMe2 at low temperature afford
(CO)4Re(g2-C(Me)(PPhMe2)C(CO2Me)C(OEt)) (7) and (CO)3(PPhMe2)Re(g2-C(Me)C(CO2Me)C(NEt2)) (9), respectively, fur-
ther in agreement with the more carbenoid nature of 2a than 6a. 7 undergoes conversion to (CO)3(PPhMe2)Re(g2-C(Me)
C(CO2Me)C(OEt)) (8) upon heating. 2a reacts with each of (NH4)2[Ce(NO3)6], DMSO, EtNO2/Et3N, and Me3NO under
various conditions to afford one or both of the oxygen atom insertion products into the Re@C bonds, (CO)4Re(j2-OC
(Me)C(CO2Me)C(OEt)) (10) and (CO)4Re(j2-C(Me)C(CO2Me)C(OEt)O) (11). In contrast, no reaction occurred between 2a and
S8 on heating. However, 6a was converted to the NH insertion product (CO)4Re(j2-NHC(Me)C(CO2Me)C(NEt2)) (12) by the
action of H2NNH2 ꢁ H2O at 0 °C. All new compounds were characterized by a combination of elemental analysis, mass
spectrometry, and IR and NMR spectroscopy.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Rhenium complexes; Metallacyclobutadiene complexes; Fischer carbene complexes; Deprotonation reactions; Aminolysis reactions;
Insertion reactions
1. Introduction
We have previously reported the synthesis of rhena-
cyclobutenone complexes Na[(CO)4Re(g2-C(R)C(CO2Me)
C(O))] (Na(1)) by reaction of Na[Re(CO)5] with the ac-
* Corresponding author. Tel.: +1-614-292-4750; fax: +1-614-292-
1685.
E-mail address: wojcicki@chemistry.ohio-state.edu (A. Wojcicki).
Present address: Celgene, Signal Research Division, 4550 Towne
Centre Court, San Diego, CA 92121, USA.
1
tivated alkynes RCBCCO2Me (R ¼ H, Me, CO2Me)
[1,2]. Alkylation of Na(1) with Et3OPF6 furnished the
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.03.026

V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
2001
corresponding rhenacyclobutadiene complexes (CO)4Re
(g2-C(R)C(CO2Me)C(OEt)) (2).
action chemistry of 2 and related rhenacyclobutadienes.
Reported in this paper are our studies directed at de-
veloping further methods of synthesis of Fischer rhe-
nacyclopentadiene complexes and at expanding the
scope of their addition/substitution reactions with nu-
cleophiles as well as insertion reactions of heteroatoms
into Re@C bonds. The accompanying paper is con-
cerned with reactions of 2 and derivatives with alkynes
and sulfonium ylides and with rearrangements induced
by nitriles and pyridine [11].
2. Experimental
Structural, spectroscopic [1,2] and limited reaction
chemistry studies on 2 [1–3] have indicated that these
complexes may be regarded as metallacyclobutadiene
analogues of Fischer-type carbenes [4], in the same sense
that Schrock metallacyclobutadienes [5] are related to
Schrock-type carbenes (alkylidenes) [6] (cf. I and II).
Fischer carbene and metallacyclobutadiene complexes
generally contain a low oxidation state transition metal
in conjunction with carbonyl ligands, are often stabi-
lized by the presence of a heteroatom bonded to carbene
carbon, and show electrophilic properties. In contrast,
Schrock alkylidene and metallacyclobutadiene com-
plexes incorporate metal in a high formal oxidation state
2.1. General procedures and measurements
Reactions and manipulations of air-sensitive com-
pounds were conducted under an atmosphere of dry
argon by use of standard procedures [12]. Solvents were
dried [13], distilled under argon, and degassed before
use. Elemental analyses were carried out by M-H-W
Laboratories, Phoenix, AZ and Guelph Chemical Lab-
oratories Ltd, London, Ont., Canada. IR and NMR
2
(1H, H, 13C, and 31P) spectra were obtained as previ-
ously described [14,15]. Mass spectra were recorded on a
Kratos VG70-250S spectrometer by using either electron
impact (EI) or fast atom bombardment (FAB) tech-
niques. All listed mass peaks are those of ions containing
187Re. Column chromatography was done on silica gel
(Merck grade 60, 230–240 mesh).
2
and behave as nucleophiles.
2.2. Materials
Reagents were procured from various commercial
sources and used as received. A solution of Na[Re(CO)5]
in THF was prepared as described previously [2].
Rhenacyclobutenone Na[(CO)4Re(g2-C(Me)C(CO2Me)
C(O)] (Na(1a))) was synthesized according to a proce-
dure reported in the literature [2], but generally on a
larger (ca. 4 times) scale, which resulted in the formation
of purer product (less polynuclear rhenium carbonyl
impurity). The complex (CO)4Re(g2-C(Me)C(CO2
Me)C(OEt)) (2a) was obtained by treatment of Na(1a)
with Et3OPF6 [2] (Method 1) or with AcCl and EtOH
(Method 2, cf. Section 2.4.1.).
Since their discovery in 1964 [8], Fischer carbene
complexes have shown extensive reaction chemistry and
are considered to be one of the most versatile reagents in
organic synthesis [9,10]. To explore chemical analogies
between Fischer carbene and metallacyclobutadiene
complexes, we have investigated several aspects of re-
2.3. Deprotonation reactions of (CO)4Re(g2-C(Me)
C(CO2Me)C(OEt)) (2a) and deuteriation or alkylation
of resultant M[(CO)4Re(g2-C(@CH2)C(CO2Me)
C(OEt))] (M(3): M ¼ Li, Na, PPN)
2.3.1. Synthesis of PPN[(CO)4Re(g2-C(@CH2)C(CO2-
Me)C(OEt))] (PPN(3): PPN@(Ph3P)2N)
A solution of 2a (0.349 g, 0.770 mmol) in 20 ml of
THF at )78 °C was treated with 1 equivalent of LDA
(lithium diisopropylamide) in hexane (0.970 ml, 0.8 M)
2
However, some metal carbene/alkylidene complexes show amphi-
philic properties [7].

2002
V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
to produce an immediate color change to orange. The
reaction mixture was stirred at )78 °C for 1 h, at which
time complete disappearance of 2a was observed by IR
spectroscopy, and new m(CO) bands were noted at 2058
(w), 1960 (s), 1901 (s), and 1630 (m) cmꢀ1. One equiv-
alent (0.442 g) of PPNCl was then added and stirring
was continued while the mixture was allowed to warm to
room temperature. Insoluble matter was removed by
filtration, and the orange filtrate was concentrated.
Addition of hexane (60 ml) with cooling to 0 °C induced
the precipitation of an orange solid which was collected,
washed with 20-ml portions of hexane, and dried in
vacuo for 24 h. The yield of PPN[(CO)4Re(g2-
C(@CH2)C(CO2Me)C(OEt))] (PPN(3)) was 0.330g
(94%). 1H NMR (THF-d8): d 7.8–7.2 (m, 30 H, Ph), 6.3
2.3.4. Synthesis of (CO)4Re(g2-C(CH2Et)C(CO2Me)
C(OEt)) (4)
A solution of 2a (0.205 g, 0.450 mmol) in 15 ml of
THF at )78 °C was treated with 1 equivalent (0.135 ml,
1.5 M) of LDA in hexane. The reaction and workup
were conducted as described in Section 2.3.1. After the
volatiles were removed under reduced pressure, the
brown oil was dissolved in 15 ml of CH2Cl2. A solution
of Et3OPF6 (0.112 g, 1 equivalent) in 5 ml of CH2Cl2
was added, and the mixture was stirred at room tem-
perature for 1 h. The solvent was evaporated, and the
residue was extracted with 10 ml of hexane. Filtration
and removal of the solvent from the filtrate afforded a
yellow oil (0.109 g) that contained 2a and the alkylated
products, mainly (CO)4Re(g2-C(CH2Et)C(CO2Me)
C(OEt)) (4). Repeated chromatography on silica gel
afforded (29% yield) pure yellow 4. 1H NMR (CDCl3): d
4.69 (q, 3J ¼ 7.2 Hz, 2 H, OCH2), 3.70 (s, 3 H, CO2Me),
3.17 (t, 3J ¼ 7.3 Hz, 2 H, CH2Et), 1.85 (sept, 3J ꢂ 7.5 Hz,
2
2
(d, J ¼ 4.5 Hz, 1 H, @CH2), 4.67 (d, J ¼ 4.5 Hz, 1 H,
@CH2), 4.02 (q, 3J ¼ 7.02 Hz, 2 H, OCH2), 3.36 (s, 3 H,
CO2Me), 1.21 (t, 3J ¼ 7.02 Hz, 3 H, OCH2Me). The
complex decomposes slowly in solution.
3
2 H, CH2CH2Me), 1.58 (t, J ¼ 7.2 Hz, 3 H, OCH2Me),
3
1.05 (t, J ¼ 7.3 Hz, 3 H, CH2CH2Me). 13C{1H} NMR
2.3.2. Reaction of 2a with LDA followed by addition of
DCl/D2O
(CDCl3): d 253.6 (s, ReCOEt), 243.1 (s, ReCCH2Et),
193.4, 191.9 (2 s, cis-CO), 190.1 (s, trans-CO), 159.2
(s, CO2Me), 155.1 (s, CCO2Me), 79.8 (s, OCH2), 50.6 (s,
CO2Me), 47.8 (s, CH2Et), 24.1 (s, CH2CH2Me), 14.8 (s,
OCH2Me), 14.4 (s, CH2CH2Me). MS (EI): m/z 482
(Mþ), 454 (Mþ ) CO), 426 (Mþ ) 2CO), 398
(Mþ ) 3CO), 370 (Mþ ) 4CO), 339 (Mþ ) 4CO ) OMe),
311 (Mþ ) 4CO ) CO2Me).
A solution of Li(3) in THF at )78 °C was prepared
from 2a (0.349 g, 0.770 mmol) and LDA as described in
Section 2.3.1. To this solution was then added ca. 5-fold
excess of DCl (20% w/w in D2O) resulting in the for-
mation of a white precipitate which was removed by
filtration. The filtrate was pumped down to dryness, and
the residue was extracted with 20-ml portions of hexane.
A bright yellow solid, obtained in yields P95%
( P0.332 g) upon evaporation of hexane, was spectro-
scopically characterized as a mixture of 2a and
(CO)4Re(g2-C(Me-d1)C(CO2Me)C(OEt)) (up to 87% D
incorporation determined by integration). 1H NMR
(CDCl3): d 4.69 (q, 3J ¼ 7.10 Hz, 2 H, OCH2), 3.69 (s, 3
2.3.5. Synthesis of (CO)4Re(g2-C(CHEt2)C(CO2Me)
C(OEt)) (5)
The sequence deprotonation of 2a (0.204 g, 0.450
mmol) in THF with 1 equivalent of LDA to generate
Li(3) followed by addition of Et3OPF6 (0.112 g, 1
equivalent) was carried out as described in Section 2.3.1.
The resultant impure 4 was then similarly subjected to
sequential treatment with LDA (0.5 equivalent) and
Et3OPF6 (0.056 g). Solvent was removed from the re-
action mixture, and the crude product was dissolved in
1–2 ml of 2:1 hexane/CH2Cl2 and loaded on top of a
silica gel column packed with the same solvent mixture.
The product was eluted off as a homogeneous yellow
band. The dialkylated complex (CO)4Re(g2-C(CHEt2)
C(CO2Me)C(OEt)) (5) was isolated as a yellow oil that
solidified when subjected to pumping. Yield: 0.060 g
(44%). IR (hexane): m(CO) 2079 (w), 1993 (s), 1948 (s),
2
H, CO2Me), 3.06 (s, 3 H, ReCMe), 3.02 (t, JDH ¼ 2.2
Hz, 2 H, ReCCH2D), 1.58 (t, 3J ¼ 7.10 Hz, 3 H,
OCH2Me). 2H NMR (CH2Cl2): d 3.04 (t, 2JDH ¼ 2.3 Hz,
CH2D). In some trials, 2a-d2 was observed in minute
amounts.
2.3.3. Reaction of 2a with Na[CH(CO2Me)2] followed
by addition of DCl/D2O
A freshly prepared solution of Na[CH(CO2Me)2]
(0.039 g, 0.300 mmol) in 5 ml of THF was slowly added
to 2a (0.113 g, 0.250 mmol) in 15 ml of THF at 0 °C. The
reaction mixture was stirred for 30 min as its color be-
came deep yellow and its IR spectrum indicated that all
starting material had reacted. The solution was con-
centrated to 2 ml, and hexane (50 ml) was added to
1
3
1719 (w) cmꢀ1. H NMR (CDCl3): d 4.71 (q, J ¼ 7.2
Hz, 2 H, OCH2), 3.70 (s, 3 H, CO2Me), 3.53 (m, 1 H,
CHEt2), 1.60 (t, 3J ¼ 7.15 Hz, 3 H, OCH2Me), 1.77–1.26
(m, 4 H, CHCH2Me), 0.87 (t, 3J ¼ 7.4 Hz, 6 H,
CHCH2Me). 13C NMR (CDCl3): d 255.7 (s, ReCOEt),
242.9 (s, ReCCHEt2), 193.4, 191.4 (2s, cis-CO), 190.3 (s,
trans-CO), 159.6 (s, CO2Me), 156.7 (s, CCO2Me), 79.6
(t, OCH2), 54.3 (d, CHEt2), 50.5 (q, CO2Me), 29.3 (t,
CHCH2Me), 14.8 (q, OCH2Me), 12.5 (q, CHCH2Me).
1
induce the precipitation of Na(3), characterized by H
NMR spectroscopy (cf. Section 2.3.1). Complex Na(3)
was then treated with DCl/D2O as described in Section
2.3.2 for Li(3). A similar workup yielded a mixture of 2a
and 2a-d1 (0.096 g).

V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
2003
MS (EI): m/z 510 (Mþ), 482 (Mþ ) CO). Anal. Found:
C, 37.64; H, 4.00%. Calc. for C16H19O7Re: C, 37.72; H,
3.76%.
NMR (CDCl3): d 243.5 (s, ReCOEt), 227.4 (s, ReCPh),
193.3, 191.5 (2s, cis-CO), 189.9 (s, trans-CO), 160.5 (s,
CO2Me), 152.1 (s, CCO2Me), 145.5 (s, ipso C of Ph),
130.6 (s, p C of Ph), 128.6, 128.1 (2s, other C of Ph), 79.7
(s, OCH2Me), 50.8 (s, CO2Me), 14.8 (s, OCH2Me). MS
(EI): m/z 516 (Mþ), 488 (Mþ ) CO), 460 (Mþ ) 2CO),
429 (Mþ ) 2CO ) OMe), 401 (Mþ ) 3CO ) OMe).
2.4. Reactions of Na[(CO)4Re(g2-C(R)C(CO2Me)
C(O))] (Na (1)) with AcCl/R0OH
2.4.1. Synthesis of (CO)4Re(g2-C(Me)C(CO2Me)
C(OEt)) (2a) (Method 2)
2.4.3. Synthesis of (CO)4Re(g2-C(Me)C(CO2Me)
C(OCH2CH@CH2)) (2c) (Method 2)
Rhenacyclobutenone Na[(CO)4Re(g2-C(Me)C(CO2
Me)C(O))] (Na(1a)), obtained by reduction of Re-
2(CO)10 (1.00 g, 1.53 mmol) with sodium (ca. 0.5 g)
followed by treatment with an excess of MeCBCCO2Me
(0.307 ml, 0.300 g, 3.06 mmol) [1,2], was added to 20 ml
of CH2Cl2, and the resulting suspension was cooled to
)15 °C and treated with AcCl (0.130 ml, 0.118 g, 1
equivalent). The mixture turned bright yellow within
minutes. After 20 min of stirring, EtOH (0.359 ml, 0.432
g, 2 equivalents) was added, and the contents were al-
lowed to warm to room temperature. Insoluble material
was removed by filtration, and the filtrate was evapo-
rated to dryness. Extraction of the residue with 20-ml
portions of hexane and removal of solvent resulted in
the isolation of (CO)4Re(g2-C(Me)C(CO2Me)C(OEt))
(2a) as a bright yellow solid in 80% yield (0.650 g).
Further purification can be achieved by chromatogra-
phy on silica gel with 1:1 hexane/CH2Cl2 as the eluent.
Spectroscopic properties of the product matched those
of 2a reported in the literature [2].
Rhenacyclobutenone Na(1a), obtained from 0.250 g
(0.385 mmol) of Re2(CO)10 and an excess of each so-
dium and MeCBCCO2Me [2], was reacted with AcCl
(0.055 ml, 0.060 g, 1.06 equivalents) and CH2@
CHCH2OH (0.055 ml, 0.045 g, 1 equivalent) as de-
scribed in Section 2.4.1 for 2a. Product (CO)4Re(g2-
C(Me)C(CO2Me)C(OCH2CH@CH2)) (2c) was isolated
as a yellow crystalline solid in 76% yield (0.270 g). IR
(hexane): m(CO) 2080 (w), 1994 (s), 1949 (s), 1717 (w)
3
cmꢀ1
.
1H NMR (CDCl3): d 6.11 (m, Jcis ¼ 10.6 Hz,
3Jtrans ¼ 17.2 Hz, Jallylic ¼ 4.7 Hz, 1 H, CH2CH@CH2),
3
3
2
5.52 (m, Jtrans ¼ 17.2 Hz, Jgem ¼ 1.5 Hz,
1 H,
CH2CH@CH2), 5.42 (m, 1 H, CH2CH@CH2), 5.13 (m,
4Jallylic ¼ 0.7 Hz, 2 H, CH2CH@CH2), 3.70 (s, CO2Me),
3.07 (s, ReCMe) (J’s determined by selective decou-
pling). 13C{1H} NMR (CDCl3): d 249.8, 244.5 (2s, Re-
COEt, ReCMe), 193.1, 192.3, 189.9 (3s, CO) 159.9 (s,
CO2Me), 155.7 (CCO2Me), 130.6 (s, OCH2CH@CH2),
120.2 (s, OCH2CH@CH2), 83.6 (s, OCH2CH@CH2),
50.6 (s, CO2Me), 35.8 (s, ReCMe). MS (FAB): m/z 467
(Mþ + 1), 452 (Mþ + 1 ) Me), 369 (Mþ + 1 ) CO )
OC3H5), 341 (Mþ + 1 ) 2CO ) OC3H5). Anal. Found: C,
33.4; H, 2.53%. Calc. for C13H11O7Re: C, 33.55; H,
2.38%.
2.4.2. Synthesis of (CO)4Re(g2-C(Ph)C(CO2Me)
C(OEt)) (2b) (Method 2)
The precursor of 2b, Na[(CO)4Re(g2-C(Ph)C
(CO2Me)(C(O))] (Na(1b)), was prepared by an adapta-
tion of the general procedure reported for Na(1a) [2],
from Re2(CO)10 (2.00 g, 3.06 mmol), sodium (ca. 1.0 g),
and PhCBCCO2Me (0.0850 ml, 0.981 g, 1 equivalent). It
was isolated as bright orange needles (2.50 g, 80% yield)
after recrystallization from Et2O/THF/hexane at room
temperature. IR (THF): m(CO) 2054 (w), 2005 (s), 1940
2.4.4. Synthesis of (CO)4Re(g2-C(Me)C(CO2Me)
C(O(CH2)3CBCH)) (2d) (Method 2)
Rhenacyclobutenone Na(1a), obtained from 0.250 g
(0.385 mmol) of Re2(CO)10 and an excess of each so-
dium and MeCBCCO2Me [2], was reacted with AcCl
(0.055 ml, 0.060 g, 1 equivalent) and 4-pentyn-1-ol
(0.070 ml, 0.065 g, 1 equivalent) as described in Section
2.4.1 for 2a. Product (CO)4Re(g2-C(Me)C(CO2Me)
C(O(CH2)3CBCH)) (2d) was isolated in 83% yield
(0.312 g) after recrystallization from hexane. IR (hex-
ane): m(CO) 2066 (w), 2011 (m), 1982 (s), 1950 (s);
1
(s), 1904 (m), 1608 (w) cmꢀ1. H NMR (acetone-d6): d
7.4–7.2 (m, 5 H, Ph), 3.63 (s, 3 H, Me). 13C{1H} NMR
(acetone-d6): 225.7 (s, ReC@O), 202.4 (s, ReCPh),
199.6, 197.4, 196.9 (3s, CO), 161.7 (s, CO2Me), 149.3 (s,
CCO2Me), 128.1, 127.8, 127.0, 126.6 (4s, Ph), 49.6 (s,
CO2Me).
1
3
The synthesis of 2b was carried out in a manner
strictly analogous to that of 2a (Section 2.4.1). By using
0.500 g (0.980 mmol) of Na(1b), 1 equivalent of AcCl
(0.070 ml, 0.052 g), and an excess of EtOH (0.200 ml),
(CO)4Re(g2-C(Ph)C(CO2Me)C(OEt)) (2b) was obtained
as a bright orange solid in 77% yield (0.387 g, 0.760
mmol). IR (hexane): m(CO) 2079 (w), 1995 (s), 1946 (s),
1725 (w) cmꢀ1. 1H NMR (CDCl3): d 7.49–7.41 (m, 5 H,
m(CBC) 1995 cmꢀ1. H NMR (CDCl3): d 4.73 (t, J ¼
6.31 Hz, 2 H, OCH2), 3.69 (s, 3 H, CO2Me), 3.06 (s, 3
3
4
H, ReCMe), 2.44 (td, J ¼ 6.8 Hz, J ¼ 2.5 Hz, 2 H,
CH2CBCH), 2.16 (quint, 3J ¼ 6.8 Hz,
2
H,
CH2CH2CH2), 2.03 (t, 3J ¼ 2.5 Hz, 1 H, CBCH).
13C{1H} NMR (CDCl3): d 249.0, 244.1 (2s, ReCOCH2,
ReCMe), 193.1, 192.1 (2s, cis-CO), 190.0 (s, trans-CO),
158.9 (s, CO2Me), 155.6 (s, CCO2Me), 82.1 (s, OCH2),
82.0 (s, CBCH), 69.9 (s, CBCH), 50.5 (s, CO2Me),
36.6 (s, ReCMe), 27.8 (s, CH2CH2CH2), 14.8 (s,
3
Ph), 4.76 (q, J ¼ 7.2 Hz, 2 H, OCH2Me), 3.64 (s, 3 H,
3
CO2Me), 1.63 (t, J ¼ 7.2 Hz, 3 H, OCH2Me). 13C{1H}

2004
V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
CH2CBCH). MS (FAB): m/z 492 (Mþ), 464 (Mþ ) CO),
436 (Mþ ) 2CO), 380 (Mþ ) 4CO).
145.8(s, CCO2Me), 140.4 (s, ipso C of Ph), 129.4, 128.0,
123.1 (3s, other C of Ph), 50.8 (s, CO2Me), 33.5 (s,
ReCMe). MS (FAB): m/z 501 (Mþ), 473 (Mþ ) CO), 417
(Mþ ) 3CO), 389 (Mþ ) 4CO).
2.4.5. Synthesis of (CO)4Re(g2-C(Me)C(CO2Me)C
(OMe)) (2e) (Method 2)
Product (CO)4Re(g2-C(Me)C(CO2Me)C(OMe)) (2e)
was obtained as a green solid in 76% yield from Na(1a),
AcCl, and MeOH by a procedure similar to that de-
scribed in Section 2.4.1 for 2a. IR (hexane): m(CO) 2081
2.5.3. Synthesis of (CO)4Re(g2-C(Me)C(CO2Me)
C(NH(CH2)2OH)) (6c)
Complex 6c was isolated as a yellow-green solid from
reaction of 2a (0.254 g, 0.560 mmol) and 2-aminoethanol
(0.034 ml, 0.034 g, 1 equivalent) by use of a procedure
similar to that described in Section 2.5.1. IR (hexane):
m(CO) 2060 (w), 2000 (s), 1975 (s), 1930 (m), 1675 (w)
cmꢀ1. 1H NMR (CDCl3): d 3.94 (t, 2 H, OCH2), 3.72 (s, 3
H, CO2Me), 3.69 (m, 2 H, NCH2), 2.92 (s, 3 H, ReCMe),
1.88 (br s, 1 H, NH). 13C{1H} NMR (CDCl3): d 224.1 (s,
ReCNHCH2), 197.8 (s, ReCMe), 193.5, 192.7 (2s, cis-
CO), 190.1 (s, trans-CO), 162.5 (s, CO2Me), 145.0 (s,
CCO2Me), 61.8 (s, OCH2), 58.9 (s, NCH2), 50.4 (s,
CO2Me), 32.7 (s, ReCMe). MS (FAB): m/z 471 (Mþ + 2),
(w), 1995 (s), 1951 (s), 1719 (w) cmꢀ1 1H NMR
.
(CDCl3): d 4.44 (s, 3 H, OMe), 3.71 (s, 3 H, CO2Me),
3.08 (s, 3 H, ReCMe). 13C{1H} NMR (CDCl3): d 249.6,
246.6 (2s, ReCOMe, ReCMe), 193.2, 192.2 (2s, cis-CO),
189.9 (s, trans-CO), 158.9 (s, CO2Me), 155.4 (s,
CCO2Me), 69.0 (s, OMe), 50.6 (s, CO2Me), 35.8 (s,
ReCMe). Anal. Found: C, 30.23; H, 2.06%. Calc. for
C11H9O7Re: C, 30.07; H, 2.06%.
2.5. Reactions of (CO)4Re(g2-C(Me)C(CO2Me)
C(OEt)) (2a) with amines
442
(Mþ ) CO + 1),
414
(Mþ ) 2CO + 1),
386
(Mþ ) 3CO + 1), 358 (Mþ ) 4CO + 1).
2.5.1. Synthesis of (CO)4Re(g2-C(Me)C(CO2Me)
C(NEt2)) (6a)
2.5.4. Synthesis of (CO)4Re(g2-C(Me)C(CO2Me)
C(NHTol-p)) (6d)
A solution of 2a (0.480 g, 1.06 mml) in 20 mol of
THF was treated with 1 equivalent of Et2NH (0.11 ml,
0.078 g), and the mixture was stirred at 0 °C. After 2 h,
the IR spectrum (m(CO)) showed that 2a had been
consumed. Evaporation of the solvent yielded a bright
yellow oil which was dissolved in 1 ml of CH2Cl2, lay-
ered with hexane, and stored at )23 °C for 2 h. The
product diffused into hexane and was obtained there-
from by evaporation. The yield of (CO)4Re(g2-
C(Me)C(CO2Me)C(NEt2)) (6a) ranged from 74% to
85% in various trials. IR (hexane): m(CO) 2066 (w), 2004
Complex 6d was isolated in 95% yield as a green solid
from reaction of 2a (0.100 g, 0.221 mmol) and p-tolui-
dine (0.024 g, 1 equivalent) by use of a procedure similar
to that described in Section 2.5.1. IR (THF): m(CO) 2052
(w), 1953 (s), 1914 (s), 1651 (w) cmꢀ1 1H NMR
.
(CDCl3): d 12.31 (br s, 1 H, NH), 7.4–7.3 (m, 4 H,
C6H4), 3.78 (s, 3 H, CO2Me), 2.99 (s, 3 H, ReCMe), 2.41
(s, 3 H, C6H4Me). 13C NMR (CDCl3): d 229.8 (s, Re-
CNTol), 196.4 (s, ReCMe), 193.7, 191.6 (2s, cis-CO),
191.0 (s, trans-CO), 162.9 (s, CO2Me), 145.8 (s,
CCO2Me), 138.0, 137.9 (2s, C of Ph), 130.0, 122.8 (2d,
CH of Ph), 50.5 (q, CO2Me), 33.4 (q, ReCMe), 21.1 (q,
C6H4Me). MS (EI): m/z 515 (Mþ). Anal. Found: C,
39.86; H, 2.95%. Calc. for C17H14NO6Re: C, 39.69; H,
2.74%.
(s), 1974 (s), 1924 (m), 1712 (w) cmꢀ1 1H NMR
.
(CDCl3): d 3.71 (s, 3 H, CO2Me), 3.70 (m, 4 H,
NCH2Me), 2.69 (s, 3 H, ReCMe), 1.37 (t, 3J ¼ 7.2 Hz, 3
H, NCH2Me), 1.26 (t, 3J ¼ 7.2 Hz, 3 H, NCH2Me). 13
C
NMR (CDCl3): d 210.1 (s, ReCNEt2), 193.7 (s, Re-
CMe), 193.2, 191.3, 191.1 (3s, CO), 163.7 (s, CO2Me),
147.9 (s, CCO2Me), 56.8 (q, CO2Me), 50.8, 47.8 (2t,
NCH2Me), 31.3 (q, ReCMe), 14.0, 13.7 (2q, NCH2Me).
MS (FAB): m/z 481 (Mþ), 453 (Mþ ) CO), 425
(Mþ ) 2CO).
2.6. Reactions of (CO)4Re(g2-C(Me)C(CO2Me)
C(X)) (X ¼ OEt (2a), NEt2 (6a)) with PPhMe2
2.6.1. Synthesis of (CO)4Re(g2-C(Me)(PPhMe2)
C(CO2Me)C(OEt)) (7)
2.5.2. Synthesis of (CO)4Re(g2-C(Me)C(CO2Me)
C(NHPh)) (6b)
To a solution of 2a (0.117 g, 0.258 mmol) in 10 ml of
CH2Cl2 at )78 °C was added by syringe PPhMe2 (0.058
ml, 0.054 g, 1 equivalent). The yellow color faded as the
solution was stirred for 1 h. The solvent was then re-
moved under reduced pressure at low temperature. The
residue was purified by dissolution in 1 ml of 1:1 Et2O/
THF, layering with hexane, and cooling at )23 °C for 3
days. The product (CO)4Re(g2-C(Me)(PPhMe2)
C(CO2Me)C(OEt)) (7) goes into solution while impuri-
ties oil out; it was isolated upon removal of the solvent.
Yield: 0.122 g (53%). IR (THF): m(CO) 2059 (m), 1969
Complex 6b was isolated in 70–86% yield as a green
solid from reaction of 2a (0.376 g, 0.83 mmol) with
PhNH2 (0.075 ml, 0.035 g, 1 equivalent) by use of a
procedure similar to that described in Section 2.5.1. IR
(hexane): m(CO) 2060 (w), 2002 (s), 1975 (s), 1935 (m),
1
1710 (w) cmꢀ1. H NMR (CDCl3): d 7.4 (m, 5 H, Ph),
3.77 (s, 3 H, CO2Me), 2.99 (s, 3 H, ReCMe). 13C{1H}
NMR (CDCl3): d 230.5 (s, ReCNHPh), 197.4 (s, Re-
CMe), 193.6, 191.4, 190.9 (3s, CO), 162.8 (s, CO2Me),

V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
2005
(s), 1943 (s), 1919 (s), 1649 (w) cmꢀ1. 1H NMR (CDCl3):
(d, 2JPH ¼ 7.8 Hz, 3 H, PMe), 1.72 (d, 2JPH ¼ 7.8 Hz, 3 H,
PMe), 1.32 (t, 3J ¼ 7.2 Hz, 3 H, NCH2Me), 1.15 (t, 3J ¼
7.2 Hz, 3 H, NCH2Me). 13C{1H} NMR (CDCl3): d 223.1
3
d 7.68–7.53 (m, 5 H, Ph), 4.01 (q, J ¼ 7.1 Hz, 2 H,
3
OCH2Me), 3.66 (s, 3 H, CO2Me), 2.28 (d, JPH ¼ 19.9
2
2
2
Hz, 3 H, ReCMe), 2.10 (d, JPH ¼ 11.8 Hz, 3 H, PMe),
(d, JPC ¼ 13.1 Hz, ReCNEt2), 201.4 (d, JPC ¼ 12.0 Hz,
ReCMe), 201.1 (d, 2JPC ¼ 7.8 Hz, CO cis to P), 200.1 (d,
2JPC ¼ 7.1 Hz, CO cis to P), 197.6 (d, 2JPC ¼ 61.6 Hz, CO
2
3
1.89 (d, JPH ¼ 12.07 Hz, 3 H, PMe), 1.36 (t, J ¼ 7.1
Hz, 3 H, OCH2Me). 13C{1H} NMR (CDCl3): d 195.1
3
3
(d, JPC ¼ 17.7 Hz, ReCOEt), 194.4, 191.1, 190.8, 189.9
trans to P), 163.9 (s, CO2Me), 145.1 (d, JPC ¼ 8.5 Hz,
(4s, CO), 164.6 (s, CO2Me), 133–129 (m, Ph), 114.0 (d,
2JPC ¼ 5.5 Hz, CCO2Me), 73.4 (s, OCH2Me), 50.3 (s,
CCO2Me), 137.9 (d, 1JPC ¼ 40.1 Hz, ipso C of Ph), 129.8–
128.1 (m, other C of Ph), 55.3 (s, NCH2Me), 50.5 (s,
CO2Me), 46.9 (s, NCH2Me), 30.6 (s, ReCMe), 16.6 (d,
2
CO2Me), 27.2 (d, JPC ¼ 6.6 Hz, ReCMe), 15.2 (s,
1
1
OCH2Me), 10.9 (d, JPC ¼ 48.3 Hz, PMe), 8.2 (d,
1JPC ¼ 30.1 Hz, PMe), 15.6 (d, JPC ¼ 29.5 Hz, PMe),
1JPC ¼ 62.2 Hz, PMe), )4.3 (d, JPC ¼ 30.5 Hz, ReCP).
13.7, 13.1 (2s, NCH2Me). 31P{1H} NMR (CDCl3): d
)25.2 (s). Anal. Found: C, 42.79; H, 4.50%. Calc. for
C21H27O5NPRe: C, 42.70; H, 4.61%.
1
31P{1H} NMR (CDCl3): d 32.34 (s). MS (FAB): m/z 592
(Mþ).
2.6.2. Conversion of
C(Me)C(CO2Me)C(OEt)) (8)
7
to (CO)3(PPhMe2)Re(g2-
2.7. Reactions of (CO)4Re(g2-C(Me)C(CO2Me)
C(OEt)) (2a) with oxygen-transfer reagents
A solution of 7 (0.122 g, 0.206 mmol) in 15 ml of THF
was maintained at reflux temperature for 1 h. The solvent
was then evaporated, and the residue was extracted with
hexane. The yellow oil obtained by evaporation of the
extracts solidified upon storage for 10 h. Yield of
(CO)3(PPhMe2)Re(g2-C(Me)C(CO2Me) C(OEt)) (8):
0.090 g (80%). IR (hexane): m(CO) 2007 (s), 1939 (s), 1904
(s), 1708 (m) cmꢀ1. 1H NMR (CDCl3): d 7.4–7.2 (m, 5 H,
2.7.1. Reaction of 2a with EtNO2/Et3N
A solution of 2a (0.250 g, 0.55 mmol) in 15 ml of
THF was treated with an equimolar mixture of
EtNO2 (0.040 ml, 0.55 mmol) and Et3N (0.084 ml,
0.55 mmol). The contents were stirred overnight at
room temperature, and the solvent was evaporated
under reduced pressure. The residue was extracted
with 10-ml portions of hexane, and the extracts were
evaporated to afford 0.211 g of a yellow oil which was
shown by 1H NMR spectroscopy to be a mixture of
unreacted 2a and known [2] (CO)4Re(j2-OC(Me)C
(CO2Me)C(OEt)) (10). The two complexes were sepa-
rated by column chromatography using hexane to
elute 2a, and CH2Cl2 to elute 10. The latter was
isolated in 43% yield (0.110 g) by evaporation of the
3
Ph), 4.37 (q, J ¼ 7.2 Hz, 2 H, OCH2Me), 3.63 (s, 3 H,
CO2Me), 2.73 (d, 4JPH ¼ 1.8 Hz, 3 H, ReCMe), 1.86–1.80
2
(overlapping 2d, 2JPH ꢂ JPH ꢂ 9 Hz, 6 H, PMe2), 1.43 (t,
3J ¼ 7.2 Hz 3 H, OCH2Me). 13C{1H } NMR (CDCl3): d
2
258.6, 252.9 (2d, JPC ¼ 2JPC ¼ 12.2 Hz, ReCOEt, Re-
2
CMe), 200.8 (d, JPC ¼ 8.2 Hz, CO cis to P), 199.3 (d,
2JPC ¼ 7.2 Hz, CO cis to P), 197.6 (d, 2JPC ¼ 58.3 Hz, CO
4
trans to P), 159.1 (d, JPC ¼ 3.8 Hz, CO2Me), 152.8 (d,
3JPC ¼ 8.4 Hz, CCO2Me), 136.7 (d, JPC ¼ 43.8 Hz, ipso
1
1
C of Ph), 130-128 (m, other C of Ph), 78.6 (s, OCH2Me),
solvent and characterized by comparison of its IR, H
and 13C{1H} NMR, and MS FAB data with those
reported earlier [2].
1
50.0 (s, CO2Me), 34.7 (s, ReCMe), 17.2 (d, JPC ¼ 31.3
1
Hz, PMe), 16.2 (d, JPC ¼ 30.9 Hz, PMe), 14.6 (s,
OCH2Me). 31P{1H} NMR (CDCl3): d )26.17 (s). MS
(FAB): m/z 564 (Mþ).
2.7.2. Reaction of 2a with (NH4)2[Ce(NO3)6] in acetone
at 0 °C
2.6.3. Synthesis of (CO)3(PPhMe2)Re(g2-C(Me)
C(CO2Me)C(NEt2)) (9)
To a solution of 2a (0.050 g, 0.11 mmol) in 5 ml of
acetone at 0 °C was added (NH4)2[Ce(NO3)6] (0.18 g,
0.33 mmol), also in 5 ml of acetone at the same tem-
perature. The reaction mixture was stirred at 0 °C for 6
h and then allowed to warm to room temperature
overnight. The solvent was removed under reduced
pressure, and the crude product was extracted with 10
ml of CH2Cl2. Column chromatography eluting with
CH2Cl2 followed by Et2O afforded a yellow oil after
To a solution of 6a (0.197 g, 0.410 mmol) in 5 ml of
CH2Cl2 at )78 °C was added by syringe 1 equivalent of
PPhMe2 (0.067 ml, 0.057 g), and the reaction mixture was
stirred at low temperature for 2 h. The solvent was then
removed under reduced pressure, and the remaining oil
was treated with 5 ml of hexane at )78 °C. Complex
(CO)3(PPhMe2)Re(g2-C(Me)C(CO2Me)C(NEt2))
(9)
precipitated out and was filtered off and washed with
hexane. Yield: 0.042 g (18%). No attempt was made to
obtain further product from the supernatant solution. IR
(hexane): m(CO) 2000 (m), 1923 (s), 1890 (s), 1680 (w)
cmꢀ1. 1H NMR (CDCl3): d 7.6–7.1 (m, 5 H, Ph), 3.68 (s, 3
H, CO2Me), 3.48 (q, 3J ¼ 7.2 Hz, 2 H, NCH2Me), 3.37 (m,
2 H, NCH2Me), 2.43 (d, 4JPH ¼ 2.0 Hz, 3 H, ReCMe), 1.78
1
removal of the solvent. A H NMR spectrum of the oil
showed it to contain 10 and (CO)4Re(j2-C(Me)C
(CO2Me)C(OEt)O) (11), also previously reported [2], in
a 7:1 ratio, respectively. A similar ratio was observed
when 1 equivalent of (NH4)2[Ce(NO3)6] was used under
the same conditions.

2006
V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
2.7.3. Reaction of 2a with (NH4)2[Ce(NO3)2] in acetone
at reflux temperature
A
solution of 2a (0.050 g, 0.11 mmol) and
(NH4)2[Ce(NO3)6] (0.18 g, 0.33 mmol) in 10 ml of ace-
tone was kept at reflux temperature for 1 h. It was then
allowed to cool to room temperature and treated as
described in Section 2.7.2. A 4:1 ratio 10/11 was shown
1
by H NMR spectroscopy.
2.7.4. Reaction of 2a with Me2SO (DMSO)
A solution of 2a (0.050 g, 0.11 mmol) in 0.5 ml of
DMSO-d6 at ambient temperature was monitored by 1H
NMR spectroscopy. After 1 h, a mixture of 2a, 10, and
11 (2.6:2.3:1.0 ratio) was observed, and after 5 h, only 10
and 11 (3:1 ratio) were noted. Solvent was then re-
moved, and the residue was extracted with hexane. A
mixture of 10 and 11 (same ratio) was isolated.
Scheme 1.
RCBCCO2Me where R ¼ H, Me, CO2Me [1,2] and, in
this study, Ph (Section 3.4.2), as well as from
Na[Re(CO5] and EtO2CCBCCO2Et [16]. Step 2, viz.,
conversion of Na(1) to 2, could be effected successfully
only by use of Et3OPF6. Weaker alkylating reagents,
e.g., MeI, are unreactive [2,16]. Thus, the preparative
route in Scheme 1 provides access to few rhenacyclo-
butadienes 2; in addition, it makes use of the hazardous
and commercially very limited oxonium salts. We
therefore sought other ways to modify the substituents
R on C(1) and OR0 on C(3).
In the context of our investigation to develop chem-
istry of Fischer rhenacyclobutadienes for comparison
with that of Fischer carbene complexes, we set out to
explore electrophilic properties of C(1) (and its Ca) and
C(3) in 2. Nucleophilic substitutions at these carbon
centers expand the range of available rhenacyclobut-
adiene complexes. Finally, of interest were further
studies on insertion of heteroatoms into the Re@C(1)
and/or Re@C(3) bonds [2,3], as similar reactions are well
established for Fischer carbene complexes [4,9a,17].
2.8. Reaction of (CO)4Re(g2-C(Me)C(CO2Me)
C(NEt2)) (6a) with hydrazine monohydrate
To a solution of 6a (0.192 g, 0.400 mmol) in 10 ml of
THF at 0 °C was added H2NNH2 ꢁ H2O (0.020 ml, 0.020
g, 0.40 mmol), and the resulting mixture was stirred for
24 h as it warmed to room temperature. After evapo-
ration of the solvent, the residue was extracted with
hexane. Removal of hexane afforded an oil, which
slowly crystallized under vacuum to give (CO)4Re(j2-
(NHC(Me)C(CO2Me)C(NEt2)) (12) as a bright yellow
solid in 84% yield (0.166 g). IR (hexane): m(NH) 3380
(w); m(CO) 2087 (s), 1990 (s), 1938 (s); m(CN) 1685 (m,
1
br) cmꢀ1. H NMR (CDCl3): d 5.85 (br s, 1 H, NH),
3.65 (s, 3 H, CO2Me), 3.63 (q, 3J ¼ 7.1 Hz, 4 H,
NCH2Me), 2.25 (s, 3 H, NCMe), 1.22 (t, 3J ¼ 7.1 Hz, 6
H, NCH2Me). (nOe: irradiation of signal at d 2.25 re-
sulted in a 4.4% enhancement of signal at d 5.85).
13C{1H} NMR (CDCl3): d 218.4 (s, ReCN), 192.4,
190.8, 187.2 (3s, CO), 186.7 (s, NCMe), 168.5 (s,
CO2Me), 113.4 (s, CCO2Me), 52.3 (s, NCH2Me), 50.5
(s, CO2Me), 26.1 (s, NCMe), 14.3 (s, NCH2Me). MS
(EI): m/z 496 (Mþ), 468 (Mþ ) CO), 440 (Mþ ) 2CO).
Anal. Found: C, 33.88; H, 3.66, N, 5.54%. Calc. for
C14H17N2O6Re: C, 33.93; H, 3.46; N, 5.65%.
3.2. Deprotonation of Me at C(1) in (CO)4Re(g2-
C(Me)C(CO2Me)C(OEt)) (2a) and related chemistry
Fischer carbene complexes are markedly acidic
[9a,18,19]. For example, complexes of the type
(CO)5M@C(Me)OR0 (M ¼ Cr, W) undergo rapid H–D
exchange in the presence of base. We find that 2a in
THF at low temperature is readily deprotonated by
LDA, Na[OBu-t], or Na[CH(CO2Me)2] (Scheme 2). The
deprotonation by LDA at )78 °C is evidenced by the
shift in m(CBO) from 2080 (w), 1991 (s), and 1937 (s)
cmꢀ1 for 2a to 2058 (w), 1960 (s), and 1901 (s) cmꢀ1 for
the product to reflect acquisition of negative charge at
rhenium (cf. III). Moreover, the appearance of the car-
boxylate m(C@O) band at 1630 cmꢀ1 for Li[(CO)4Re(g2-
C(@CH2)C(CO2Me)C(OEt))] (Li(3)) compared to 1704
cmꢀ1 for 2a indicates that stabilization of the former can
3. Results and discussion
3.1. General considerations
As stated in the Introduction, at the start of this in-
vestigation the synthetic pathway to the subject rhena-
cyclobutadiene complexes 2 consisted of the two steps
presented in Scheme 1. The first reaction requires that
the alkyne contain at least one electron-withdrawing
group. Accordingly, rhenacyclobutenone complexes
Na(1) have been obtained from Na[Re(CO)5] and

V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
2007
minute amount of 2a-d2 also observed in some runs
(87% D incorporation in the ReCMe group for the Li(3)
reaction). This behavior parallels that of metal carbene
complexes [9a]; for example, Casey reported that de-
protonation of (CO)5M@C(Me)OMe (M ¼ Cr, W) with
n-BuLi followed by acidification with DCl or DBr yiel-
ded ca. 90% (CO)5M@C(Me-d1)OMe as well as the Me-
d0, Me-d2, and Me-d3 isotopomers [19].
Advantage can be taken of the acidity of the ReCMe
protons of 2a and the thermodynamic stability of 3 by
derivatizing the former through deprotonation followed
by alkylation (Scheme 2). Accordingly, treatment of 2a
with LDA and addition of Et3OPF6 to the resulting
solution of Li(3) afforded after chromatography pure
monoethylated derivative of 2a, (CO)4Re(g2-
C(CH2Et)(C(CO2Me)C(OEt)) (4). The composition of
the product receives support from its EI mass spectrum,
1
and its structure is evidenced by the H and 13C{1H}
NMR data, which are similar to those of 2a, except for
the signals relating to the replacement of ReCMe with
ReCCH2Et. By repeating the sequence deprotonation
with LDA followed by addition of Et3OPF6 on crude 4,
the diethylated derivative of 2a, (CO)4Re(g2-
C(CHEt2)C(CO2Me)C(OEt)) (5) was obtained in 44%
isolated yield after chromatographic removal of 2a and
4. Again, its spectroscopic data are similar to those of 2a
(and 4), except for features due to a different substituent
at C(1).
Scheme 2.
be rationalized by the resonance structure IV, in addi-
tion to III. Addition of PPNCl to this solution resulted
in the isolation of PPN[(CO)4Re(g2-C(@CH2)
1
C(CO2Me)C(OEt))] (PPN(3)) in excellent yield. The H
Disappointingly, attempts at modification of the
substituent at C(1) of 2a by using Li(3) in conjunction
with reagents other than oxonium salts were fruitless.
Reactions of Li(3) with each of MeI, PhC(O)Cl, and
MeC(O)CH@CH2 either did not proceed or furnished
mixtures of inseparable compounds. In contrast, the
corresponding conjugate bases of Fischer carbene
complexes are useful reagents for the modification of the
carbene side chain. Besides the oxonium salts and flu-
orosulfonates, a number of other reagents, including
allyl and benzyl halides, a-bromoesters, aldehydes, and
epoxides, inter alia, react readily and cleanly with vari-
ous metal carbene derived anions [9,19,20].
NMR spectrum of PPN(3) shows that the ReCMe sin-
glet of 2a at d 3.07 is absent; in its place two doublets are
observed at d 6.3 and 4.7 with a 2J ¼ 4.5 Hz, consistent
with the presence of a vinyl group, ReC@CH2. The
product decomposes slowly on storage in solution.
3.3. Modification of alkoxy group at C(3) in
(CO)4Re(g2-C(R)C(CO2Me)C(OR0)) (2)
The rhenacyclobutadiene (CO)4Re(g2-C(Me)C(CO2-
Me)C(OEt)) (2a) reacts very slowly with neat methanol
at room temperature to afford only 5% conversion to
(CO)4Re(g2-C(Me)C(CO2Me)C(OMe)) (2e) in 2 days.
A much more practical route to diversification of the
alkoxy group at C(3) in 2 proved to be reaction of
Na[(CO)4Re(g2-C(R)C(CO2Me)C(O))] (Na(1)) with
AcCl followed by R0OH (Scheme 3). This approach had
been successfully applied by Connor and Jones toward
the introduction of different OR0 groups in Fischer
alkoxycarbene complexes [21].
When solutions of Na(3) and Li(3) were treated with
DCl/D2O, a yellow solid was isolated after workup.
Examination of the product by H NMR spectroscopy
revealed it to be a mixture of 2a and 2a-d1, with a
1

2008
V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
aminorhenacyclobutadiene (CO)40Re(g2-C(Me)C(CO2
Me)C(NHR0 or NR20 )) products (R2 ¼ Et2 (6a); R0 ¼ Ph
(6b), (CH2)2OH (6c), p-Tol (6d)) (Scheme 4). These
conversions are thought to follow the same mechanism
as the one implicated for Fischer carbene complexes,
viz., nucleophilic attack of the amine at C(3) to yield an
ylide-type structure (cf. Section 3.5), proton migration
from the amino to the alkoxy substituent, and irrevers-
ible elimination of alcohol [23]. Attack at C(1) is also
possible but has not been observed, possibly for ther-
modynamic reasons owing to its expected unproductive
reversibility.
Complexes 6a–6d were characterized by mass spec-
trometric/chemical analysis, and their proposed struc-
1
tures were inferred from the IR and H and 13C{1H}
NMR spectra. The IR m(CO) region resembles that of
the alkoxyrhenacyclobutadienes 2a and 2c–2e; however,
the bands are shifted to lower energy by J10 cmꢀ1 to
indicate a greater negative charge at Re in 6 than in 2.
Comparison of the 13C{1H} NMR ReCMe and ReCN
signals of 6a–6d (at d 197.8–193.7 and 230.5–210.1) with
the ReCMe and ReCOC signals of 2a and 2c–2e (at d
249.8–246.4 and 246.6–243.7) shows considerably
greater shielding in the amino-substituted complexes.
Similar differences exist between Fischer alkoxycarbene
and aminocarbene complexes, but the downfield chem-
ical shifts are much larger [4].
Scheme 3.
Treatment of Na(1)with1equivalent of AcCl at )15°C
followed by the addition of R0OH afforded after workup
76–83% yield of the appropriate rhenacyclobutadiene 2
(R ¼ Me, R0 ¼ Et (2a), CH2CH@CH2 (2c), (CH2)3CBCH
(2d), Me (2e); R ¼ Ph, R0 ¼ Et (2b)) (Method 2, cf. Section
2.4). However, this methodology could not be success-
fully applied to reactions of Na(1) with carboxylic amides
such as acetamide or less nucleophilic alcohols such as
trifluoroethanol, which yielded only intractable mixtures
of products. The new complexes 2b–2e show IR and 1H
and 13C{1H} NMR spectroscopic properties that are very
similar to those of 2a, except for the features due to the
presence of different substituents at C(1) and/or C(3). For
all complexes, the 13C{1H} NMR signals of the ReCR
and ReCOR0 nuclei occur in the low-field region d 249.8–
227.4, as expected.
Another noteworthy feature in the NMR spectra of
6a is the inequivalence of the Et groups of NEt2. In the
1H NMR spectrum, two NCH2Me signals are observed
while the NCH2Me resonance is an unresolved multi-
plet. In the 13C NMR spectrum, there are two signals for
each of CH2 and Me. The inequivalence of the Et groups
indicates restricted rotation about the ReC–N bond
owing to substantial C@N p-bonding. For Fischer am-
inocarbene complexes, such C@N bonding is significant;
in fact, geometrical isomers have been observed by H
NMR spectroscopy when the amino group is NHR or
NRR0 [22].
The aforementioned spectroscopic properties of 6
and the differences observed between 2 and 6 can be
1
3.4. Aminolysis at C(3) in (CO)4Re(g2-C(Me)C
(CO2Me)C(OEt)) (2a)
Alkoxy substituents at carbene carbon are excellent
leaving groups, and Fischer carbene complexes of the
type LnM@C(R)OR0 undergo replacement of OR0 with
NHR0 or NR02 upon respective reactions with primary
and the less crowded secondary amines [9a,22].
We find that 2a reacts with the primary amines
PhNH2, HO(CH2)2NH2, and p-TolNH2 at )78 °C fol-
lowed by warming and with the secondary amine Et2NH
at 0 °C to afford the corresponding C(3)-substituted
Scheme 4.

V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
2009
rationalized by the relative contributions of the reso-
nance structure V 0to the description of bonding. When
X ¼ NHR0 or NR2, this structure contributes more to
the overall description of bonding (that also includes the
structures depicted in I) than when X ¼ OR0. This in
turn reduces Fischer carbene character of 6 owing to
lesser M@C-bonding. It also places a higher negative
charge on Re and hence decreases m(CO) of 6 relative to
2. Similar trends hold for analogous Fischer carbene
complexes [4,9].
analogous to those reported for Fischer carbene com-
plexes (CO)5M@C(R)OMe (M ¼ Cr, W) and secondary
or tertiary phosphines, where both addition to carbene
carbon and CO substitution were observed [25].
The synthesis of aminorhenacyclobutadiene com-
plexes 6 prompted us to extend the foregoing study to
reactions of 2a and 6a with PPhMe2. The objective of
these additional experiments was to elucidate how the
nature of X in (CO)4Re(g2-C(Me)C(CO2Me)C(X)) –
OEt or NEt2 – affects outcome of reaction with
phosphine.
We find that 2a and PPhMe2 react at )78 °C with
warming to ca. 0 °C to yield the product of addition of
the phosphine to C(1), viz., (CO)4Re(g2-C(Me)(PPh-
Me2)C(CO2Me)C(OEt)) (7). Complex 7 on heating in
THF at reflux afforded the CO-substitution derivative
of 2, (CO)3(PPhMe2)Re(g2-C(Me)C(CO2Me)C(OEt))
(8). In contrast, 6a and PPhMe2 under similar low-
temperature reaction conditions gave directly the
CO-substitution product (CO)3(PPhMe2)Re(g2-C(Me)
C(CO2Me) C(NEt2)) (9) (Scheme 5). There was no
spectroscopic evidence for intermediacy of a 6aPPhMe2
adduct.
The structure of 7 was inferred with the aid of IR and
NMR spectroscopy (cf. Section 2.6.1) and by compari-
son with corresponding data for the related complexes
(CO)4Re(g2-C(R)(PR30 )C(CO2Me)C(OEt)), one of which
was characterized by X-ray diffraction techniques [2]. In
the 13C{1H } NMR spectrum, four equal-intensity ReCO
A decreased Fischer carbene character of 6 compared
to 2 also manifests itself by the lack of reactivity of 6a
toward LDA in deprotonation. Under the conditions
that mirrored those for the deprotonation followed by
reaction with DCl/D2O for 2a (Section 2.3.2), no reac-
tion was observed for 6a. This result is consistent with
the reports that Fischer aminocarbene complexes are
substantially less acidic than corresponding Fischer
alkoxycarbene complexes; for example, the pKa of
(CO)5Cr@C(Me)NMe2 in MeCN is about 10 units
higher than that of (CO)5Cr@C(Me)OMe [9a]. Never-
theless, Fischer aminocarbene complexes still can be
deprotonated [9,24].
In an attempt to extend the range of rhenacyclobut-
adiene complexes to C(3)-substituted sulfur analogues of
2, 2a was reacted with a large excess of PhSH in THF at
room temperature for 2 days. However, no reaction
occurred under these conditions.
3.5. Phosphine addition at C(1) and CO substitution in
(CO)4Re(g2-C(Me)C(CO2Me)C(X)) (X ¼ OEt (2a),
NEt2 (6a))
Reactions of rhenacyclobutadiene complexes
(CO)4Re(g2-C(R)C(CO2Me)C(OEt)) (2: R ¼ Me (2a),
CO2Me) with PR03 (R0 ¼ Et, p-Tol) at ambient temper-
ature were previously studied in our laboratory [2]. The
outcome was either addition of PR03 to C(1) to give
(CO)4Re(g2-C(R)(PR30 )C(CO2Me)C(OEt)) or replace-
ment of a trans-CO with PR03 (when R ¼ Me, R0 ¼
p-Tol). Heating (CO)4Re(g2-C(Me)(PEt3)C(CO2Me)
C(OEt)) in benzene at reflux afforded the CO substitu-
tion product (CO)3(PEt3)Re(g2-C(Me)C(CO2Me)C
(OEt)), but a similar prolonged treatment of (CO)4Re
(g2-C(CO2Me)(PR03)C(CO2Me)C(OEt)) (R0 ¼ Et, p-Tol
resulted in no chemical change. These reactions are
Scheme 5.

2010
V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
singlet resonances are observed, which is consistent with
the trans CO’s being inequivalent owing to the presence
of the chiral center ReC(Me)(PPhMe2). Also because of
this chiral center, the PPhMe2 shows diastereotopic Me
groups in both 1H and 13C{1H} NMR spectra. The
13C{1H} signal of ReCOEt is still observed at low field (d
195.1); however, that of ReC(Me)(PPhMe2), which is no
longer carbene-like in nature, is shifted dramatically
upfield to d )4.3, where it appears as a doublet
(1JPC ¼ 30.5 Hz). The coupling constants 3JPH ¼ 19.9 Hz
3.6. Insertion of oxygen atom into Re@C bond of
(CO)4Re(g2-C(Me)C(CO2Me)C(OEt)) (2a)
In a previous paper from this laboratory it was re-
ported that 2a and other alkoxyrhenacyclobutadiene
complexes 2 react with (NH4)2[Ce(NO3)6] to afford
products of insertion of oxygen atom into Re@C bonds,
(CO)4Re(j2-OC(R)C(CO2Me)C(OEt)) (R ¼ H, Me (10),
CO2Me) and (CO)4Re(j2-C(R)C(CO2Me) C(OEt)O)
(R ¼ Me (11), CO2Me) [2] (Scheme 6). The structure of
10 was ascertained by X-ray diffraction techniques. A
similar reaction was reported for (CO)4Re(g2-C3Ph3)
and Me3NO by Berke and coworkers [30]. The forego-
ing transformations are related to those of Fischer car-
bene complexes, which undergo oxidative cleavage by
the action of (NH4)2[Ce(NO3)6], DMSO, and Me3NO,
inter alia, to replace the M@C by O@C [31].
The goal of the present study was to augment the
earlier investigation of oxygen atom insertion of 2a by
examining (a) the efficacy of other oxygen transfer re-
agents and (b) relative propensity for insertion into
Re@C(1) and Re@C(3) to give 10 and 11, respectively.
In this context, further studies on reactions of 2a with
(NH4)2[Ce(NO3)6] showed that product selectivity is
affected to some extent by the temperature. Thus, by
running the reaction at 0–25 °C in acetone solution, a ca.
7:1 mixture of 10/11 was obtained regardless of whether
1 or 3 equivalents of (NH4)2[Ce(NO3)6] were employed.
However, at reflux temperature of acetone the ratio of
10/11 decreased to 4:1. The relative amounts of 10 and
11 in a mixture of products do not change upon treat-
ment with the cerium(IV) complex for several hours.
Other reagents are also effective in converting 2a to
one or both of 10 and 11 in THF solution (Scheme 6).
Use of 1:1 EtNO2/Et3N at room temperature affords 10
as the only product isolated in detectable quantity;
1
1
and JPC ¼ 6.6 Hz observed, respectively, in the H and
13C{1H} NMR spectra for ReC(Me)(PPhMe2) support
nucleophilic addition of PPhMe2 to the ReCMe carbene
center.
Complexes 8 and 9 each show three strong IR m(CO)
bands, a pattern characteristic of such a six-coordinate
fac-tricarbonyl arrangement [26]. The absorption bands
of 8 occur at a somewhat higher energy (ꢂ10 cmꢀ1) than
those of 9, as noted earlier (cf. Section 3.4) for the parent
tetracarbonyls 2a and 6a. The appearance of three equal
intensity ReCO signals at d 201–197 in the 13C{1H}
NMR spectra of 8 and 9 lends support to the assigned
structures. The CO trans to PPhMe2 resonates with a
2
much larger JPC (58.3 and 61.6 Hz, respectively) than
the two cis CO’s (2JPC ¼ 7.2–8.2 and 7.1–7.8 Hz, re-
spectively), as expected [27]. A carbene-like nature of the
two complexes is reflected in the 13C{1H} resonances of
ReC at d 258.6 and 252.9 for 8 and d 223.1 and 201.4 for
9. The alkoxyrhenacyclobutadiene 8 appears more car-
bene-like than the aminorhenacyclobutadiene 9, as ob-
served for their tetracarbonyl precursors and related
1
complexes. Because the Re center is chiral, two H and
13C{1H} signals occur for PMe2 in the spectra of each 8
and 9.
The reaction of 2a with PPhMe2 to aford 7 followed
by conversion of the latter to 8 represents transfor-
mations that are similar to those reported earlier for
alkoxyrhenacyclobutadiene complexes with other ter-
tiary phosphines [2]. In contrast, 6a yields a CO-sub-
stitution product directly upon reaction with PPhMe2.
This difference in behavior parallels that observed for
corresponding Fischer carbene complexes. Whereas
metal alkoxycarbene complexes afford addition com-
plexes with phosphines [25], metal aminocarbene
complexes fail to do so presumably owing to the re-
duced electrophilicity of their carbene carbon atoms
[28].
Finally, it is noteworthy that the productive addition
of phosphines to ReCof 2 is at C(1) whereas the pro-
ductive addition of amines to ReCof 2 is at C(3).
Possibly, both reactions are orbital (rather than charge)
controlled, as proposed for Fischer carbene complexes
[29], and favor C(1). Nevertheless, productive addition
of amines occurs at C(3), since it leads to the elimi-
nation of ethanol from ReC(OEt)(NH2R0 or NHR20 ) to
provide a driving force for that reaction.
Scheme 6.

V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
2011
however, in DMSO at room temperature, a 3:1 mixture
of 10/11 was obtained. Furthermore, with Me3NO at ca.
25 °C, 11 was found as the major product. The reason
for this unusual isomer preference is not clear.
Oxidative cleavage of the M@C bond in Fischer
carbene complexes also can be effected with elemental
sulfur [32]. However, attempts at extending this chem-
istry to 2a by using an excess of S8 in THF at reflux
temperature resulted in no reaction.
with the present data considering different metals and
substituents at C and N. It is also noteworthy that only
one signal occurs for each of the CH2 and Me of the Et
group in the 1H and 13C{1H} NMR spectra of 12, unlike
with 6a which shows two signals for each (cf. Section
3.4). Hence, there appears little multiple bonding in
ReC-NEt2, and of the canonical structures VI–VIII,
VIII seems relatively unimportant.
3.7. Insertion of NH into Re@C bond of (CO)4Re(g2-
C(Me)C(CO2Me)C(NEt2)) (6a)
The alkoxyrhenacyclobutadiene 2a reacts with
H2NNH2 ꢁ H2O in THF at 0 °C to afford (CO)4Re(g2-
C(Me)C(CO2Me)C(OEt)NH) and (CO)4Re(g2-NHC
(Me)C(CO2Me)C(OEt)) as the respective major and
minor products of NH insertion into Re@C [3]. The
structure of the latter product was elucidated, and a
possible mechanism of the reaction was addressed. Fi-
scher alkoxycarbene complexes also insert the NH from
hydrazines [33], NH2OH [17], and NH@SPh2 [34] into
their M@C bonds. Since the aminorhenacyclobutadiene
6a shows less Fischer carbene character than 2a, it was
of interest to ascertain whether it would behave similarly
to 2a toward H2NNH2 ꢁ H2O.
4. Summary
Reaction of 6a with H2NNH2 ꢁ H2O was carried out
under conditions comparable to those for 2a, and after
workup afforded (CO)4Re(j2-NHC(Me)C(CO2Me)
C(NEt2)) (12) in 84% yield (Scheme 7). Complex 12 was
characterized by 1H and 13C{1H} NMR spectroscopy in
conjunction with mass spectrometry and chemical
analysis. The proposed regiochemistry of insertion of
NH into the Re@CMe bond is based on a nOe experi-
Rhenacyclobutadiene complexes of the type
(CO)4Re(g2-C(R)C(CO2Me)C(OR0)) (2) show Fischer
carbene-like NMR spectroscopic properties and, in
many cases, parallel chemical behavior. When R ¼ alkyl
(Me, CH2Et), they undergo deprotonation by LDA,
Na[OBu-t], or Na[CH(CO2Me)2] to yield ylide-type
conjugate bases 3 that can be deuteriated with DCl/D2O
or alkylated with Et3OPF6. The alkoxy substituent in 2
can be modified by treatment of Na[(CO)4Re(g2-
C(R)C(CO2Me)C(O))] (Na(1)) first with AcCl and then
with R0OH. Aminolysis of 2a (R ¼ Me, R0 ¼ Et) with
R0NH2 or R02NH affords the aminorhenacyclobutadi-
enes (CO)4Re(g2-C(R)C(CO2Me)C(NHR0 or NR02)) (6).
Complexes 6 are less carbene-like than 2, and 6a
(R ¼ Me, R02-Et2) could not be deprotonated with LDA.
Both 2a and 6a react with PPhMe2, the former by ad-
dition to ReCMe, and the latter by replacement of a CO.
Likewise, both 2a and 6a insert oxygen atom or the
isoelectronic NH fragment into their Re@C bonds. All
of these reactions find precedence in the chemistry of
Fischer carbene complexes. However, differences in
chemical behavior have been found as well and include
lack of reactivity of 2a toward PhSH and S8.
1
ment. Thus, irradiation of the H signal of 12 at d 2.25
(ReNCMe) resulted in a 4.4% enhancement of the signal
at d 5.85 (NH) to show spatial proximity of these pro-
tons. In the 13C{1H} NMR spectrum of 12, the Re-
CNEt2 and ReNHCMe signals are observed at d 218.4
and 186.7, respectively. For comparison, the ReCOEt
and ReNHCMe carbon nuclei of (CO)4Re(j2-
NHC(Me)C(CO2Me)C(OEt)) resonate at d 239.3 and
190.4, respectively [3]. Furthermore, a complex related
to 12, (g5-C5Me5)(CO)2W(j2-N(Et)CHCHC(NHEt)),
shows the 13C resonance of WCNHEt at d 221.8 and
that of WN(Et)CH at d 166.6 [35], in good agreement
Acknowledgements
This research was supported in part by the National
Science Foundation and The Ohio State University.
Scheme 7.

2012
V. Plantevin, A. Wojcicki / Journal of Organometallic Chemistry 689 (2004) 2000–2012
[19] (a) C.P. Casey, R.L. Anderson, J. Am. Chem. Soc. 96 (1974)
1230;
References
(b) C.P. Casey, W.R. Brunsvold, J. Organomet. Chem. 118 (1976)
309.
[1] L.L. Padolik, J. Gallucci, A. Wojcicki, J. Organomet. Chem. 338
(1990) C1.
[20] (a) C.P. Casey, R.A. Boggs, R.L. Anderson, J. Am. Chem. Soc.
94 (1972) 8947;
[2] L.L. Padolik, J.C. Gallucci, A. Wojcicki, J. Am. Chem. Soc. 115
(1993) 9986.
(b) C.P. Casey, W.R. Brunsvold, J. Organomet. Chem. 102 (1975)
175;
[3] V. Plantevin, J.C. Gallucci, A. Wojcicki, Inorg. Chim. Acta 222
(1994) 199.
(c) C.P. Casey, W.R. Brunsvold, D.M. Scheck, Inorg. Chem. 16
(1977) 3059.
[4] E.O. Fischer, Adv. Organomet. Chem. 14 (1976) 1.
[5] (a) J.H. Wengrovius, J. Sancho, R.R. Schrock, J. Am. Chem. Soc.
103 (1981) 3932;
[21] (a) J.A. Connor, E.M. Jones, J. Chem. Soc. D (1971) 570;
(b) J.A. Connor, E.M. Jones, J. Chem. Soc. A (1971) 3368.
[22] (a) U. Klabunde, E.O. Fischer, J. Am. Chem. Soc. 89 (1967) 7141;
(b) J.A. Connor, E.O. Fischer, J. Chem. Soc. A (1969) 578;
(c) E. Moser, E.O. Fischer, J. Organomet. Chem. 16 (1969) 275;
(d) E.O. Fischer, H.-J. Kollmeier, Chem. Ber. 104 (1971) 1339;
(e) E.O. Fischer, B. Heckl, H. Werner, J. Organomet. Chem. 28
(1971) 359.
(b) R.R. Schrock, Acc. Chem. Res. 19 (1986) 342;
(c) I.A. Weinstock, R.R. Schrock, W.M. Davis, J. Am. Chem.
Soc. 113 (1991) 135.
[6] (a) R.R. Schrock, J. Am. Chem. Soc. 96 (1974) 9796;
(b) R.R. Schrock, Acc. Chem. Res. 12 (1979) 98.
[7] For example: C.P. Casey, P.C. Vosejpka, F.R. Askham, J. Am.
Chem. Soc. 112 (1990) 3713, and references therein.
[23] (a) B. Heckl, H. Werner, E.O. Fischer, Angew. Chem., Int. Ed.
Engl. 7 (1968) 817;
€
[8] E.O. Fischer, A. Maasbol, Angew. Chem., Int. Ed. Engl. 3 (1964)
580.
[9] Selected recent reviews: (a) C.F. Bernasconi, Adv. Phys. Org.
Chem. 37 (2002) 137;
(b) H. Werner, E.O. Fischer, B. Heckl, C.G. Kreiter, J.
Organomet. Chem. 28 (1971) 367;
(c) C.F. Bernasconi, M.W. Stronah, J. Am. Chem. Soc. 115 (1993)
1341;
(b) J. Barluenga, Pure Appl. Chem. 74 (2002) 1317;
(c) G. Bertrand (Ed.), J. Organomet. Chem. 617–618 (2001)
(special issue on transition-metal carbene complexes);
(d) A. de Meijere, H. Schirmer, M. Deutsch, Angew. Chem. Int.
Ed. Engl. 39 (2000) 3964;
(d) C.F. Bernasconi, C. Whitesell, R.A. Johnson, Tetrahedron 56
(2000) 4917.
[24] W.D. Wulff, B.A. Anderson, A.J. Toole, Y.-C. Xu, Inorg. Chim.
Acta 220 (1994) 215.
(e) J. Barluenga, F.J. Fananas, Tetrahedron 56 (2000) 4597;
(f) J.W. Herndon, Tetrahedron 56 (2000) 1257;
[25] (a) F.R. Kreissl, C.G. Kreiter, E.O. Fischer, Angew. Chem., Int.
Ed. Engl. 11 (1972) 643;
€
(g) K.H. Dotz, P. Tomuschat, Chem. Soc. Rev. 28 (1999)
(b) F.R. Kreissl, E.O. Fischer, C.G. Kreiter, H. Fischer, Chem.
Ber. 106 (1973) 1262;
187;
(h) F.Z. Dorwald, Metal Carbenes in Organic Synthesis, Wiley-
€
VCH, Weinheim, 1999;
(c) H. Fischer, E.O. Fischer, C.G. Kreiter, H. Werner, Chem. Ber.
107 (1974) 2459;
(i) W.D. Wulff, Organometallics 17 (1998) 3116;
(j) R. Aumann, H. Nienaber, Adv. Organomet. Chem. 41 (1997)
163;
(d) E.O. Fischer, T. Selmayr, F.R. Kreissl, Monatsh Chem. 108
(1977) 759;
(e) E.O. Fischer, T. Selmayr, F.R. Kreissl, Chem. Ber. 110 (1977)
2947.
(k) D.F. Harvey, D. Sigano, Chem. Rev. 96 (1996) 271;
(l) A. de Meijere, Pure Appl. Chem. 68 (1996) 61.
[10] Selected recent papers: (a) H. Wang, W.D. Wulff, A.L. Rheingold,
J. Am. Chem. Soc. 125 (2003) 8980;
[26] P.S. Braterman, Metal Carbonyl Spectra, Academic Press, New
York, 1975.
[27] C. Elschenbroich, A. Salzer, in: Organometallics – A Concise
Introduction, second ed., VCH, Weinheim, 1992, p. 302.
(b) K. Fuchibe, N. Isasawa, Chem. Eur. J. 9 (2003) 905;
(c) J. Zhang, T.B. Gunnoe, Organometallics 22 (2003) 2291;
€
[28] K.H. Dotz, in: P.S. Braterman (Ed.), Reactions of Coordinated
€
(d) H. Werner, C. Grunwald, W. Stuer, J. Wolf, Organometallics
€
Ligands, vol. 1, Plenum Press, New York, 1986 (Chapter 4).
[29] (a) W.B. Perry, T.F. Schaaf, W.L. Jolly, L.J. Todd, D.L. Cronin,
Inorg. Chem. 13 (1974) 2038;
22 (2003) 1558;
(e) C.F. Bernasconi, S. Bhattacharya, Organometallics 22 (2003)
426;
(b) T.F. Block, R.F. Fenske, C.P. Casey, J. Am. Chem. Soc. 98
(1976) 441;
(c) T.F. Block, R.F. Fenske, J. Organomet. Chem. 139 (1977) 235.
€
(f) R. Aumann, X. Fu, C. Holst, R. Frohlich, Organometallics 21
(2002) 4356;
(g) R. Stumpf, M. Jaeger, H. Fischer, Organometallics 20 (2001)
4040;
€
[30] (a) C. Lowe, V. Shklover, H. Berke, Organometallics 10 (1991)
3396;
(b) C. Lowe, V. Shklover, H.W. Bosch, H. Berke, Chem. Ber. 126
ꢀ
€
(h) J.P. Moreto, S. Ricart, K.H. Dotz, E. Molins, Organometallics
€
(1993) 1769.
20 (2001) 62.
[11] V. Plantevin, A. Wojcicki, J. Organomet. Chem., Xref
doi:10.1016/j.jorganchem.2004.03.024.
:
[31] (a) F.A. Cotton, C.M. Lukehart, J. Am. Chem. Soc. 93 (1971) 2672;
(b) C.M. Lukehart, J.V. Zeile, J. Organomet. Chem. 97 (1975) 421;
(c) C.M. Lukehart, J.V. Zeile, Inorg. Chim. Acta 17 (1976) L7;
(d) C.P. Casey, T.J. Burkhardt, C.A. Bunnell, J.C. Calabrese, J.
Am. Chem. Soc. 99 (1977) 2127;
[12] D.F. Shriver, M.A. Drezdzon, The Manipulation of Air-Sensitive
Compounds, second ed., Wiley, New York, 1986.
[13] D.D. Perrin, W.L.F. Armarego, D.R. Perrin, Purification of
Laboratory Chemicals, Pergamon, Oxford, 1991.
(e) C.P. Casey, W.R. Brunsvold, Inorg. Chem. 16 (1977) 391.
€
[14] R.R. Willis, M. Calligaris, P. Faleschini, J.C. Gallucci, A.
Wojcicki, J. Organomet. Chem. 193–194 (2000) 465.
[15] R.T. Dunsizer, V.M. Marsico, V. Plantevin, A. Wojcicki, Inorg.
Chim. Acta 342 (2003) 279.
[32] E.O. Fischer, S. Riedmuller, Chem. Ber. 107 (1974) 915.
[33] R.G. Raubenheimer, S. Lotz, G. Kruger, G. Gafner, J. Organo-
met. Chem. 173 (1979) C1.
[34] R.G. Raubenheimer, G.J. Kruger, F. Scott, R. Otte, Organomet-
allics 6 (1987) 1789.
[16] L.L. Padolik, Ph.D. Dissertation, The Ohio State University,
1990.
€
[35] A.C. Filippou, C. Volkl, P. Kiprof, J. Organomet. Chem. 415
(1991) 375.
[17] E.O. Fischer, R. Aumann, Chem. Ber. 101 (1968) 963.
[18] C.G. Kreiter, Angew. Chem., Int. Ed. Engl. 7 (1968) 147.