Syntheses of neutral iron, ruthenium and manganese half-sandwich vinylidene complexes. Crystal structure of Fe(SnPh3)(CO)(= C = CHPh)(η-C5H5)

Article abstract of DOI:10.1039/a900004f

Treatment of various anionic acyls [M(SnPh₃)(CO)(COCH₂R)(η-C₅H₅)]^- (M = Fe, Ru) and acyls [Mn(CO)₂(COCH₂R)(η-C₅H₄Me)]^- with MeCOCl affords acyl(o

Full text of DOI:10.1039/a900004f

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Syntheses of neutral iron, ruthenium and manganese half-sandwich vinylidene
complexes. Crystal structure of Fe(SnPh3)(CO)(NCNCHPh)(h-C5H5)
Harry Adams, Simon G. Broughton, Stephen J. Walters and Mark J. Winter*
Department of Chemistry, The University, Sheffield, UK S3 7HF. E-mail: Mark.Winter@Sheffield.ac.uk
Received (in Basel, Switzerland) 5th January 1999, Accepted 7th April 1999
Treatment of various anionic acyls [M(SnPh3)(CO)-
(COCH2R)(h-C5H5)]2 (M = Fe, Ru) and acyls [Mn(CO)2-
(COCH2R)(h-C5H4Me)]2 with MeCOCl affords acyl(oxy)
carbenes M(SnPh3)(CO){NC(OCOMe)CH2R}(h-C5H5) and
[Mn(CO)2{NC(OCOMe)CH2R)h-C5H4Me)] which formally
eliminate MeCO2H to form neutral half-sandwich vinyli-
dene complexes M(SnPh3)(CO)(NCNCHR)(h-C5H5) and
complexes Mn(CO)2(NCNCHR)(h-C5H4Me).
Vinylidene complexes LnM(NCNCR1R2) have attracted a great
deal of interest1 over the last 15 years, partly due to the proposed
intermediacy of vinylidene species in the Fischer–Tropsch
process,2 and also due to their ability to act as catalysts for
alkyne polymerisation3 and condensation4 reactions. These
complexes are prepared generally through either the rearrange-
ment of alk-1-ynes at a metal centre, or through alkylation or
protonation of the b-carbon of acetylide ligands. In the case of
the Group 8 transition metals, the vast majority of these
complexes are cationic. A very small number of neutral Group
7 and 8 half-sandwich vinylidene complexes are known.5–7 We
outline here a new method for the preparation of a class of
neutral iron, ruthenium and manganese vinylidene complexes,
the neutrality of which is expected to have important conse-
quences for subsequent chemistry.
Recently, we reported the isolation of a number of unusually
stable acyl(oxy) carbene species M(SnPh3)(CO){NC-
(OCOR)Ph}(h-C5H5) (M = Fe, Ru; R = Me, Ph, But).8 These
are formed through the reaction of acid chlorides RCOCl with
the anionic acyls [M(SnPh3)(CO)(COPh)(h-C5H5)]2. We now
find that the corresponding anions [M(SnPh3)(CO)-
(COCH2R)(h-C5H5)]2 3, 4 (Scheme 1) are available from the
reactions of LiCH2R with M(SnPh3)(CO)2(h-C5H5) 1, 2. These
also react with MeCOCl, but while the expected acyl(oxy)
carbenes M(SnPh3)(CO){NC(OCOMe)CH2R}(h-C5H5) 5 and 6
do indeed form, and are detectable by IR spectroscopy at low
temperatures, the products isolated at ambient temperature
are, unexpectedly, the neutral vinylidenes M(SnPh3)-
(CO)(NCNCHR)(h-C5H5) (R = H, Pr, Me, Ph) 7 and 8.† These
products correspond to the formal loss of MeCO2H from the
Scheme 1
The new complexes exhibit spectroscopic data typical for
vinylidene complexes. For example, the parent complex 7 (R =
H)§ shows a medium strength absorption [nCO(CH2Cl2) 1637
cm21] in its IR spectrum. This is attributed to the CNC stretch
and signals at dC(CDCl3) 346.2 and 105.3 in its 13C NMR
spectrum due to the vinylidene a- and b-carbons respectively.
1
The presence of a singlet for the vinylidene protons in the H
NMR of the complex indicates that vinylidene rotation is facile
at ambient temperature.
The nature of one compound 7 (R = Ph)¶ is further illustrated
by a crystallographic study (Fig. 1), carried out in order to
understand the vinylidene parameters. The FeNC bond length of
1.744(4) Å is very short, reflecting the excellent p-acceptor
properties10 of the vinylidene fragment. The CNC bond length
of 1.312(5) Å is in accord for a vinylidene complex, and reflects
a bond order of ca. two. The vinylidene fragment itself is linear
[Fe–C(7)–C(8) 179.7(3)°], and shows an orientation that
corresponds both with theoretical studies10 and with previously
intermediate
acyl(oxy)
carbenes
M(SnPh3)(CO){NC-
(OCOMe)CH2R}(h-C5H5). The presence of protons on the
carbon a to the carbene is essential for vinylidene formation, as
is the presence of the labile acyl(oxy) substituent. We note here
a previous report in which the cationic iron vinylidene
complexes [Fe(PPh3)(CO)(NCNCR2)(h-C5H5)]+ (R = H, Me)
are prepared through loss of CF3SO3H from intermediate
triflate-substituted carbenes of the form [Fe(PPh3)(CO){NC-
(OSO2CF3)CHR2}(h-C5H5)]+.9
The method for vinylidene preparation presented here is
versatile in that it allows the direct preparation of rare examples
of unsubstituted vinylidene complexes, as well as examples
bearing methyl and phenyl substituents, in a single step from
readily available starting materials. Yields are good. The
method also works for different metals. For instance, the
corresponding reactions of the manganese compound
Mn(CO)3(h-C5H4Me) 9 (Scheme 2) afford the neutral vinyli-
denes M(CO)2(NCNCHR)(h-C5H4Me) (R = Pr, Ph) 10 as red
oils.‡
Scheme 2
Chem. Commun., 1999, 1231–1232
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1630m, 1621m, 1598m, 1575m; dH(CDCl3) 7.35–7.25 (m, 2H, o-Ph),
7.20–7.05 (m, 3H, m-, p-Ph), 6.70 (s, 1H, NCNCH), 5.00 (m, 2H, h-
C5H4Me), 4.95 (m, 2H, h-C5H4Me), 2.05 (s, 3H, Me), dC(CDCl3) 380
(MnNC), 226.5 (CO), 133.3 (ipso-Ph), 128.6 (o-, m-Ph), 125.2 (p-Ph), 124.2
(o-, m-Ph), 122.4 (NCNCHPh), 88.1 (h-C5H4Me); 86.4, (h-C5H4Me), 13.7
(Me).
§ Fe(SnPh3)(CO)(NCNCH2)(h-C5H5) 7 (R = H): yellow, mp 101–103 °C
(decomp.). Found: C, 69.67; H, 4.01%; [M]+ 526; C26H22FeOSn requires C,
59.48; H, 4.22%, [M]+; 526. IR (CH2Cl2, cm21) nCO 1962s, nCNC 1633m;
dH(CDCl3) 7.65–7.54 (m, 6H, o-SnPh), 7.42–7.26 (m, 9H, m-, p-SnPh),
4.89 (s, 5H, h-C5H5), 4.57 (s, 2H, JSnH 34, FeNCNCH2); dC(CDCl3) 346.2
(FeNC), 214.4 (CO), 143.7 (ipso-SnPh), 136.7 (JSnC 37, o-SnPh), 128.2 (m-,
p-SnPh), 105.3 (FeNCNCH2), 85.4 (h-C5H5).
¶ Fe(SnPh3)(CO)(NCNCHPh)(h-C5H5) 7 (R
134–136 °C (decomp.). Found: C, 63.53; H, 4.17%; [M]+ 602;
C32H26FeOSn requires C, 63.94; H, 4.36%; [M]+ 602. IR (CH2Cl2, cm21
= Ph): red–orange, mp
)
nCO 1966s, nCNC 1650m, 1640m, 1626m, 1593m, 1574w; dH(CDCl3)
7.63–7.53 (m, 6H, o-SnPh), 7.40–7.06 (m, 14H, m-, p-SnPh with
FeNCNCHPh), 6.03 (s, 1H, JSnH 19, FeNCNCHPh), 4.99 (s, 5H, h-C5H5);
dC(CDCl3) 354.5 (FeNC), 213.7 (CO), 143.4 (JSnC 379, ipso-SnPh), 136.6
(JSnC 38, o-SnPh), 132.1 (ipso-FeNCNCHPh), 128.7 (o- or m-FeNCNCHPh),
128.2 (m-, p-SnPh), 126.8 (FeNCNCHPh), 125.9 (p-FeNCNCHPh), 124.9 (o-
or m-FeNCNCHPh), 85.6 (h-C5H5).
Fig. 1 Molecular structure of Fe(SnPh3)(CO)(NCNCHPh)(h-C5H5) 7 (R =
Ph). Selected bond lengths (Å): Fe–C(7) 1.744(4), C(7)–C(8) 1.312(5),
C(8)–C(9) 1.471(6).
Crystal data for 7 (R = Ph): monoclinic, a = 14.334(5), b = 10.318(4),
c = 19.761(10) Å, b = 111.09(4)°, U = 2727(2) Å3, Z = 4, Dc = 1.464
g cm23, space group P21/n (a non standard setting of P21/c, no. 14), Mo-Ka
radiation (l = 0.71073 Å), m(Mo-Ka) = 1.469 mm21, F(000) = 1208.
reported structures of cationic iron and ruthenium vinylidene
complexes.11,12 As expected on steric grounds, the phenyl
substituent occupies a position anti to the triphenyltin group.
The vinylidene fragment does not adopt a truly horizontal
conformation: the angle between the vinylidene plane and the
plane defined by the centroid of the cyclopentadienyl ring, iron
atom and C(7) is 73° rather than 90°. The twist is anticlockwise
as viewed along C(8)–C(7)–Fe, and presumably minimizes
steric interactions between the vinylidene hydrogen substituent
and the triphenyltin group.
Data were collected in the range 3.5
< 2q < 50° (w-scan), 4801
independent reflections (Rint = 0.0340), final R = 0.0355, with allowance
for the thermal anisotropy of all non-hydrogen atoms. CCDC 182/1225.
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Wright, J. Organomet. Chem., 1998, 565, 153.
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Rheingold, Organometallics, 1982, 1, 628.
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Whiteley, J. Chem. Soc., Dalton Trans., 1995, 2873.
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Notes and references
† Ru(SnPh3)(CO)(NCNCH2)(h-C5H5) 8 (R = H): yellow, mp 112–113 °C.
Found: C, 54.66; H, 3.81%; [M]+ 570; C32H26FeOSn requires C, 54.75; H,
3.89%; [M]+ 570. IR (CH2Cl2, cm21) nCO 1972s, nCNC 1637m; d(toluene-
d8) 7.75–7.63 (m, 6H, o-SnPh), 7.30–7.10 (m, 9H, m-, p-SnPh), 4.78 (s, 5H,
h-C5H5), 3.85 (s, 2H, JSnH 35, RuNCNCH2); dC(CDCl3) 336.3 (RuNC),
200.3 (CO), 143.5 (ipso-SnPh), 136.7 (JSnC 40, o-SnPh), 128.0 (JSnC 47, m-,
p-SnPh), 97.7 (RuNCNCH2), 88.4 (h-C5H5).
‡ Mn(CO)2(NCNCHPh)(h-C5H4Me) 10 (R = Ph): red oil. Found C, 65.26;
H, 4.29%; [M 2 2CO]+ 236; C32H26FeOSn requires C, 65.74; H, 4.42%; [M
2 2CO]+ 236. IR (light petroleum, cm21) nCO 2006s, 1952, nCNC 1647m,
Communication 9/00004F
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Chem. Commun., 1999, 1231–1232