Selenolatovinylidene complexes: Metal-mediated alkynyl selenoether rearrangements

Article abstract of DOI:10.1021/om990939x

The reactions of [RuCl₂(PPh₃)₃] and [RuCl-(PPh₃)₂(η-C₅H₅)] with PhC≡CSeⁱPr provide the selenolatovinylidene complexes [RuCl₂{=C=C(SeⁱPr)Ph}(PPh

Full text of DOI:10.1021/om990939x

Organometallics 2000, 19, 371-373
371
Selen ola tovin ylid en e Com p lexes: Meta l-Med ia ted
Alk yn yl Selen oeth er Rea r r a n gem en ts
Anthony F. Hill,* Alexander G. Hulkes, Andrew J . P. White, and
David J . Williams
Department of Chemistry, Imperial College of Science, Technology and Medicine,
South Kensington, London, U.K. SW7 2AY
Received November 29, 1999
Sch em e 1. Alk yn yl Selen oeth er /Vin ylid en e
In ter con ver sion
Summary: The reactions of [RuCl2(PPh3)3] and [RuCl-
(PPh3)2(η-C5H5)] with PhCtCSeiPr provide the seleno-
latovinylidene complexes [RuCl2{dCdC(SeiPr)Ph}(PPh3)2]
and [Ru{dCdC(SeiPr)Ph}(PPh3)2(η-C5H5)]+. The former,
being coordinatively unsaturated, readily reacts with
nitrogen and phosphorus donor ligands with retention
of the selenolatovinylidene moiety; however, π-acid ligands
induce facile elimination of PhCtCSeiPr.
By far the majority of vinylidene ligands originate
either from metal-mediated rearrangement of terminal
alkynes or electrophilic attack at the â-carbon of σ-al-
kynyl ligands;1 this is particularly true for the elements
of group 8.2 A similar intraligand mobility is displayed
by the silyl group of alkynylsilanes,1,3 and Werner has
shown that this mobility increases on descending group
14 such that alkynylstannanes serve as effective precur-
sors for group 9 stannyl-functionalized vinylidene com-
plexes.4 This migratory aptitude may be traced at least
in part to the decrease in C-element bond strength on
descending a p-block group. Silylvinylidene complexes
notwithstanding, heteroatom-functionalized vinylidene
complexes remain rare, being currently limited to (i)
halovinylidene complexes arising from â-halogenation
of the complex [Ru(CtCPh)(PPh3)2(η-C5H5)]5 or rear-
rangement of iodoalkynes,6 (ii) azovinylidenes via the
reaction of [Ru(CtCPh)(PPh3)2(η-C5H5)] with diazonium
salts,7 and (iii) the thiolatovinylidene complex [Ru{d
CdC(SMe)2}(PMe3)2(η-C5H5)]+, which is obtained upon
heating the alkynyl thioether complex [Ru{S(CtCSMe)-
Me}(PMe3)2(η-C5H5)]+. This complex, reported by An-
gelici,8 is particularly noteworthy in that it serves as a
precursor for a host of complexes of unusual organosul-
fur ligands. Herein we wish to report the confluence of
the principles of Angelici (intraligand thiolate mobility)
and Werner (increasing migratory aptitude down a
group). This has allowed the synthesis and structural
characterization of the first examples of selenolato-
functionalized vinylidene complexes, including 16- and
18-valence-electron examples. Our interest in the pos-
sibility of such an alkynyl selenoether/selenolatovi-
nylidene rearrangement process (Scheme 1) arises from
our recent reports of alkynyl selenoether and chloro-
alkyne complexes of divalent (d4) molybdenum and
tungsten,9 wherein the alkyne is required to serve as a
4-electron ligand such that rearrangement to a vi-
nylidene would be accompanied by an unfavorable
reduction in the overall valence electron count by 2
units.
Heating a tetrahydrofuran solution of [RuCl2(PPh3)3]
and PhCtCSeiPr under reflux (2 h) provides (after
chromatography) moderate yields (55%) of the vi-
nylidene complex [RuCl2{dCdC(SeiPr)Ph}(PPh3)2] (1)
(Scheme 2). Although the formulation of 1 follows
unambiguously from spectroscopic data,10 it was further
confirmed by a single-crystal structure determination.11
The molecular geometry (Figure 1) may be described as
severely distorted trigonal bipyramidal (trans bis-axial
phosphines P(1)-Ru-P(2) ) 173.07(5)°, diequatorial
chlorides Cl(1)-Ru-Cl(2) ) 148.89(6)°). This conforma-
tion is stabilized by the combination of a weak π-stack-
ing between one of the phosphine phenyl groups and
that of the vinylidene (centroid-centroid ) 3.94 Å) and
a C-H‚‚‚π interaction between the ortho hydrogen of
the adjacent phenyl group on the same phosphine and
the vinylic CdC bond (H‚‚‚π ) 2.84 Å, C-H‚‚‚π 141°,
H‚‚‚C(1) ) 2.74 Å). This is analogous to what is observed
for the isonitrile and phosphine ligands in the recently
reported complex [RuCl(CNCMe3)(PPh3){HB(pz)3}]
(pz ) pyrazol-1-yl).12 Commensurate with significant
Ru-C retrodative multiple bonding, the vinylidene
ligand occupies an equatorial site, with Ru-C(1) at
* To whom correspondence should be addressed. E-mail: a.hill@
ic.ac.uk.
(1) Bruce, M. I. Chem. Rev. 1991, 91, 197.
(2) For a review of vinylidene complexes of ruthenium and osmium
see: Hill, A. F. In Comprehensive Organometallic Chemistry II;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press:
Oxford, U.K., 1995; Vol. 7.
(3) Katayama, H.; Ozawa, F. Organometallics 1998, 17, 5190.
(4) Baum, M.; Mahr, N.; Werner, H. Chem. Ber. 1994, 127, 1877.
(5) Bruce, M. I.; Koutsantonis, G. A.; Liddell, M. J .; Nicholson, B.
K. J . Organomet. Chem. 1987, 329, 217.
(6) Berke, H.; Hund, H. U.; Lowe, C. J . Organomet. Chem. 1989,
371, 311.
(7) Bruce, M. I.; Humphrey, M. G.; Koutsantonis, G. A.; Liddell, M.
J . J . Organomet. Chem. 1987, 326, 247.
(8) Angelici, R. J .; Miller, D. C. Organometallics 1991, 10, 79.
(9) (a) Baxter, I.; Hill, A. F.; Malget, J . M.; White, A. J . P.; Williams,
D. J . Chem. Commun. 1997, 2049. (b) Hill, A. F.; Malget, J . M.; White,
A. J . P.; Williams, D. J . Chem. Commun. 1996, 721.
10.1021/om990939x CCC: $19.00 © 2000 American Chemical Society
Publication on Web 01/26/2000

372 Organometallics, Vol. 19, No. 4, 2000
Communications
Sch em e 2. Syn th esis of Selen ola tovin ylid en e
Com p lexes of Ru th en iu m (II)a
F igu r e 1. Molecular structure of 1. Selected bond lengths
(Å) and angles (deg): Ru-C(1) ) 1.769(5), Ru-Cl(1) )
2.3228(13), Ru-Cl(2) ) 2.3349(13), Ru-P(1) ) 2.3854(11),
Ru-P(2) ) 2.3985(12); C(1)-Ru-Cl(1) ) 104.7(2), C(1)-
Ru-Cl(2) ) 106.2(2), Cl(1)-Ru-Cl(2) ) 148.89(6), C(1)-
Ru-P(1) ) 90.8(2), Cl(1)-Ru-P(1) ) 86.42(4), Cl(2)-Ru-
P(1) ) 89.82(4), C(1)-Ru-P(2) ) 94.9(2), Cl(1)-Ru-
P(2) ) 88.29(5), Cl(2)-Ru-P(2) ) 92.40(5), P(1)-Ru-
P(2) ) 173.07(5).
C(2) is of primary interest, and the following points are
noted: (i) the coordination is trigonal (angle sum
359.6°); (ii) the Se-C(2) bond length of 1.917(5) Å is
significantly shorter than that to C(3) (2.017(11) Å),
indicating an appreciable degree of multiple bonding in
the former (Scheme 1). This perhaps accounts in part
for the lack of conjugation of the phenyl substituent into
the RudCdC cumulene system, which is rotated by ca.
21° out of the C(1)-C(2)-Se plane.
The coordinative unsaturation of the ruthenium
center in 1 is reflected in reactions with potential
ligands: Although simple 1:1 adducts might be expected
to arise on treatment with the simple nitrogen donor
ligands γ-picoline and tert.butylamine, these are not
observed. Rather, one phosphine is also substituted to
provide the coordinatively saturated octahedral com-
plexes [RuCl2{dCdC(SeiPr)Ph}(L)2(PPh3)] (L ) NC5H4-
Me-4 (2a ), NH2CMe3 (2b)). The picoline derivative10 is
moderately stable, while attempted isolation of the tert-
butylamine complex results primarily in reversion to 1.
In a similar manner, no tractable product resulted from
the treatment of 1 with TMEDA, although a reaction
ensued. The identity and stereochemistry of these
complexes follows unambiguously from spectroscopic
a
Legend: pic ) γ-picoline, CA ) CO, CNC6H3Me2-2,6,
bipy ) 2,2′-bipyridyl, Cp ) η-C5H5.
1.769(5) Å lying at the short end of reported ruthenium
vinylidenes,2 the majority of which are, however, cat-
ionic and/or coordinatively saturated. The vinylidene
ligand is essentially linear with Ru-C(1)-C(2) ) 175.2-
(4)°, and the C(1)-C(2) bond length at 1.329(8) Å
suggests multiple-bond character. The substitution at
(10) Selected spectroscopic data for new complexes (satisfactory
elemental microanalysis obtained unless otherwise indicated; NMR
data: δ, CDCl3, 25 °C, 13C phosphine and phenyl resonances omitted.
IR data: νRudCdC in cm-1, Nujol. FAB-MS data: m/z, nba matrix,
positive ion. 1: 1H NMR 1.10 (d, 3J ) 7.4 Hz, 6 H, CH3), 2.77 (sept, 1
H, CHMe2), 6.7-8.0 (m, 35 H, C6H5); 13C{1H} NMR 320.4 (t, 2J ) 16.2,
RudC), 111.2 (t, 3J ) 5.4, RudCdC), 34.9 (s, CHMe2), 23.7 (s, CH3);
31P{1H} NMR 30.3; IR 1600 m, 1587 s; FAB-MS 920 [M]+. 2a : 1H NMR
1.03 (d, 6 H, 3J ) 12.9 Hz, CHCH3), 2.26 (s, 6 H, CH3), 2.77 (sept, 1 H,
CHMe2), 6.7-8.6 (m, 23 H, C6H5, C5H4N); 13C{1H} NMR 328.6 (d,
2J ) 21.6 Hz, RudC), 111.5 (s, RudCdC), 35.1 (s, CHMe2), 23.6 (s,
CHCH3), 20.8 (s, NC5H4CH3); 31P{1H} NMR 41.7; IR 1618 m; FAB-
MS 658 [M - 2pic]+. 3: 1H NMR 1.31 (d, 6 H, 3J ) 6.9 Hz, CH3), 3.19
(sept, 1 H, CHMe2), 7.0-9.74 (C6H5 + bipy);13C{1H} NMR: 333.0 (d,
2J ) 24.8 Hz, RudC), 113.8 (s, RudCdC), 35.7 (s, CHMe2), 24.3 (s,
CH3); 31P{1H} NMR 39.0; IR 1620 m; FAB-MS 814 [M]+. 4: 1H NMR
1.04 (d, 6 H, 3J ) 7.4 Hz, CH3), 1.0-2.7 (m, Cy), 2.89 (sept, 1 H,
CHCH3), 6.7-7.8 (m, 5 H, C6H5); 13C{1H} NMR 320.4 (dd, 2J ) 15.3
Hz, RudC), 110.3 (dd, 3J ) 5.5 Hz, RudCdC), 34.4 (s, CHMe2), 23.7
(s, CH3); 31P{1H} NMR 29.6, 28.2 (2J ) 357.9 Hz); IR 1580, 1562 m;
FAB-MS 938 [M]+. 5a -BPh4: 1H NMR 1.31 (d, 6 H, 3J ) 7.6 Hz, CH3),
2.96 (sept, 1 H, CHMe2), 4.98 (s, 5 H, C5H5), 6.8-8.7 (m, 55 H, C6H5);
13C{1H} NMR 324.1 (t, 3J ) 15.1 Hz, RudC), 117.8 (s, RudCdC), 94.2
(s, C5H5), 35.8 (s, CHMe2), 24.0 (s, CH3); 31P{1H} NMR 41.4; IR 1621
m; FAB-MS 915 [M]+. 5b-PF6: 1H NMR 5.03 (s, 5H, C5H5), 6.7-8.0
(m, 40 H, C6H5); 13C{1H} NMR 324.2 (t, 2J ) 30.0 Hz, RudC) 117.7 (s,
RudCdC), 94.4 (C5H5); 31P{1H} NMR 41.2; IR 1625 m; FAB-MS 949
[M]+.
(11) Crystal data for 1: C47H42P2Cl2SeRu, Mr ) 919.7, triclinic, space
group P1h (No. 2), a ) 10.113(1) Å, b ) 12.296(1) Å, c ) 18.827(2) Å,
R ) 100.02(1)°, â ) 90.98(1)°, γ ) 114.05(1)°, V ) 2095.1(3) Å3, Z ) 2,
Dc ) 1.458 g cm-3, µ(Cu KR) ) 61.6 cm-1, F(000) ) 932, T ) 293 K;
deep red prisms, 0.43 × 0.43 × 0.20 mm, Siemens P4/PC diffractome-
ter, ω-scans, 6112 independent reflections. The structure was solved
by direct methods, and the major-occupancy non-hydrogen atoms were
refined anisotropically using full-matrix least squares based on F2 to
give R1 ) 0.046, wR2 ) 0.108 for 5070 independent, observed,
absorption-corrected reflections (|Fo| > 4σ(|Fo|), 2θ ) 120°) and 407
parameters.
(12) Buriez, B.; Burns, I. D.; Hill, A. F.; White, A. J . P.; Williams,
D. J .; Wilton-Ely, J . D. E. T. Organometallics 1999, 18, 1504.

Communications
Organometallics, Vol. 19, No. 4, 2000 373
data; however, their lability in solution precluded us
from obtaining structural or microanalytic data. The
more robust adduct [RuCl2{dCdC(SeiPr)Ph}(bipy)-
(PPh3)] (3) was, however, obtained with 2,2′-bipyridyl
and characterized by spectroscopy10 and by a single-
crystal X-ray structure determination.13 The reaction of
1 with the bulky and basic phosphine PCy3 is not clean,
in contrast to those of Grubbs’ alkylidene complexes
[RuCl2(CHR)(PPh3)2] (R ) Ph, CHdCPh2), where disub-
stitution occurs readily.14 Following chromatography,
moderate yields of the mixed bis(phosphine) complex
[RuCl2{dCdC(SeiPr)Ph}(PCy3)(PPh3)] (3) may be ob-
tained.10
The reactions of 1 with the carbon π-acids CO and
CNC6H3Me2-2,6 take a different and surprising course:
if we recall that the alkynyl selenoether/vinylidene
rearrangement leading to 1 required refluxing tetrahy-
drofuran, it is remarkable that treating a solution of 1
with CO (1 atm) at room temperature results in im-
mediate (2 min) and spectroscopically quantitative
formation of all-trans-[RuCl2(CO)2(PPh3)2] (4a ). A simi-
lar reaction occurs with CNC6H3Me2-2,6 to provide all-
trans-[RuCl2(CNC6H3Me2-2,6)2(PPh3)2] (4b ); however,
this proceeds more slowly and a red intermediate
(presumably the adduct [RuCl2{dCdC(SeiPr)Ph}(CN-
C6H3Me2-2,6)(PPh3)2]) may be transiently observed
(ν(CN) ) 2176 cm-1). Thus, it would appear that the
coordination of a modest (CNR) or strong (CO) π-acid
trans to the strongly π-acidic vinylidene ligand signifi-
cantly destabilizes coordination of the latter. This may
be alleviated by retroformation of the alkyne, which is
then replaced by a second equivalent of the added
ligand. In retrospect, this tallies with our previous
observations that the reaction of cct-[RuCl(CtCC6H4-
Me-4)(CO)2(PPh3)2]15 with HCl does not provide a vi-
nylidene complex but rather cct-[RuCl2(CO)2(PPh3)2].
Thus, loading a metal center with π-acidic ligands
appears to destabilize vinylidene coordination with
respect to rearrangement to a (labile) alkyne. Perusal
of the vinylidene chemistry of group 8 metals1,2 reveals
that the overwhelming majority do not involve π-acidic
co-ligands, none feature a trans disposition of vinylidene
and π-acid, and those that do possess π-acid coligands
are highly electrophilic (at CR).
The generality of the selenolatovinylidene/alkynyl
selenoether rearrangement was briefly examined: the
reaction of [RuCl(PPh3)2{HB(pz)3}] (pz ) pyrazol-1-
yl)12,16 with PhCtCSeiPr is complex, with the major
isolable product being [RuCl(CO)(PPh3){HB(pz)3}], which
presumably arises from the precedented1 hydrolysis of
a vinylidene intermediate. Similarly, no clean product
was obtained from the reaction of 1 with K[HB(pz)3].
The complex [RuCl(PPh3)2(η-C5H5)], however, reacts
with PhCtCSeiPr and Na[BPh4] to provide the isolable
salt [Ru{dCdC(SeiPr)Ph}(PPh3)2(η-C5H5)]BPh4 (5a -
BPh4) (Scheme 2).10 The related salt [Ru{dCdC(SePh)-
Ph}(PPh3)2(η-C5H5)]PF6 (5b-PF6)10 could be obtained via
a complementary strategy involving electrophilic attack
at the â-carbon of [Ru(CtCPh)(PPh3)2(η-C5H5)] by Ph-
SeCl followed by counteranion metathesis in ethanol
with [NH4]PF6.
To conclude, the conversion of alkynyl selenoethers
to selenolatovinylidenes within a transition-metal co-
ordination sphere is facile, but so is the reverse reaction,
in particular when trans π-acidic coligands are present.
The results of Angelici,8 which convincingly demonstrate
the synthetic versatility of thiolatovinylidenes, presage
a similarly rich chemistry for those based on more
mobile selenolate substituents.
Ack n ow led gm en t. We gratefully acknowledge the
financial support of the EPSRC of the U.K. in the form
of a studentship (to A.G.H.). Ruthenium salts were
generously provided by J ohnson Matthey Chemicals
Limited.
Su p p or tin g In for m a tion Ava ila ble: Tables of X-ray
structural data, including data collection parameters, posi-
tional and thermal parameters, and bond distances and angles
for the complex 1. This material is available free of charge
via the Internet at http://pubs.acs.org.
(13) Full details of this and related structures will be reported
elsewhere: White, A. J . P.; Williams, D. J . Manuscript in preparation.
(14) (a) Schwab, P.; France, M. B.; Ziller, J . W.; Grubbs, R. H. Angew.
Chem., Int. Ed. Engl. 1995, 34, 2039. (b) Cucullu, M. E.; Li, C.; Nolan,
S. P.; Nguyen, S. T.; Grubbs, R. H. Organometallics 1998, 17, 5565.
(15) Bedford, R. B.; Hill, A. F.; Thompsett, A. R.; White, A. J . P.;
Williams, D. J . Chem. Commun. 1996, 1059.
OM990939X
(16) Alcock, N. W.; Burns, I. D.; Claire, K. S.; Hill, A. F. Inorg. Chem.
1992, 31, 2906.