A novel methodology for the synthesis of complexes containing long carbon chains linking metal centres: Molecular structures of {Ru(dppe)Cp*} 2(μ-C14) and {Co3(μ-dppm)(CO) 7}2(μ3:μ3-C16)

Article abstract of DOI:10.1039/b315854n

Elimination of AuX(PR₃) (X = halogen, R = Ph, tol) occurs readily in reactions between compounds containing C(sp)- or C(sp²)-X bonds and alkynyl or polyynyl gold(I) complexes; this reaction has been applied to the syntheses of complexes containing a variety of metal centres linked by C_n chains (n up to 16).

Full text of DOI:10.1039/b315854n

A novel methodology for the synthesis of complexes containing long
carbon chains linking metal centres: molecular structures of
{Ru(dppe)Cp*}2(m-C14) and {Co3(m-dppm)(CO)7}2(m3:m3-C16)†
Alla B. Antonova,ab Michael I. Bruce,a Benjamin G. Ellis,a Maryka Gaudio,a Paul A. Humphrey,a
Martyn Jevric,a Giovanni Melino,a Brian K. Nicholson,c Gary J. Perkins,a Brian W. Skelton,d Bronwin
Stapleton,a Allan H. Whited and Natasha N. Zaitsevaa
a Department of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
b Institute of Chemistry and Chemical Technology, Russian Academy of Sciences, Krasnoyarsk 660049,
Russia
c
Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton, New Zealand
d Department of Chemistry, University of Western Australia, Crawley, Western Australia 6009, Australia
Received (in Cambridge, UK) 4th December 2003, Accepted 4th February 2004
First published as an Advance Article on the web 9th March 2004
15
from Co3(m3-CBr)(m-dppm)(CO)7 and 4-PhC·CC6H4C·CAu-
Elimination of AuX(PR3) (X = halogen, R = Ph, tol) occurs
readily in reactions between compounds containing C(sp)– or
(PPh3).14
C(sp2)–X bonds and alkynyl or polyynyl gold(
I
) complexes; this
This reaction is the key step in a sequence of reactions capable of
wide application to afford complexes containing odd- or even-
numbered carbon atom chains linking two end-caps that may be
either the same or different (Scheme 1). Evidently, construction of
even-numbered carbon chains requires coupling between two
smaller fragments, each bearing a s-bonded polyynyl ligand (k =
0). In contrast, the synthesis of an odd-numbered carbon ligand
with its M–C multiple bond requires a similarly multiply-bonded
precursor, such as a metal carbyne complex (k = 1).
reaction has been applied to the syntheses of complexes
containing a variety of metal centres linked by Cn chains (n up
to 16).
The chemistry of compounds containing two or more transition
metal centres linked by chains of carbon atoms has excited
researchers for a decade or more,1 both on account of their intrinsic
interest and, more recently, their potential as components or models
of nanoscale electronic and optical devices.2 In these complexes,
the M–Cn–M chain may adopt a variety of electronic configura-
tions.3
There has been little development of the chemistry of species
containing ten carbons or more in the chain, these presently being
limited to complexes of rhenium,4 iron,5 ruthenium6,7 and plati-
num.8 The longest carbon-chain complex reported is
{Pt(C6F5)[P(Tol)3]2}2{m-(C·C)12}, so far obtained only in trace
amounts.8c These symmetrical complexes contain identical metal–
ligand end-caps and have been made by either (i) oxidative
coupling using Eglinton–Glaser or the milder Hay conditions or (ii)
growth methodologies involving silylated derivatives, fluoride-
induced desilylation and subsequent coupling. Combination of two
different chains is often accompanied by competing side-reactions
which involve the basic solvent; for example, in the case of cobalt
cluster complexes, amido derivatives of the form Co3{m3-CC(O)N-
Me2}(CO)9 are formed,9,10 while in the presence of alcohols,
ruthenium complexes often afford alkoxycarbene or carbonyl
derivatives.11
We have shown that facile coupling can be achieved between
RAC·CAu(PR3) and molecules such as I(C·C)nR, I(C·C)nSiMe3 or
I(C·C)nMLx, together with organometallic mononuclear or cluster
complexes containing CX groups, such as M(·CX)(CO)2Tp (M =
Mo, W) or {MLx}3(m3-CX) [MLx
=
Co3(CO)9, Co3(m-
dppm)(CO)7, Ru3(m-H)3(CO)9, Os3(m-H)3(CO)9; X = Cl, Br, I].
Products have been isolated in high yield and characterised by the
usual analytical and spectroscopic methods and, in many cases, by
single-crystal X-ray studies. A key to this success was the finding
that symmetrical diiodopolyynes I(C·C)nI (n = 1–4)16,17 also react
rapidly and completely, allowing chain elongation by between 2
and 8 carbons.
The sequence is applicable to the synthesis of complexes
containing different end-groups and odd- or even-numbered carbon
chains. As an example of the former, the coupling of Os3(m-H)3(m3-
CBr)(CO)9 with Fc(C·C)2Au(PPh3), carried out in thf in the
presence of Pd(PPh3)4/CuI (r.t., 1 h), gave Os3(m-H)3{m3-
C(C·C)2Fc}(CO)9 (4; 86% yield). Similarly, the reaction between
Ru{(C·C)2Au[P(Tol)3]}(PPh3)2Cp and Ru3(m-H)3(m3-CBr)(CO)9
afforded red crystals of Ru3(m-H)3{m3-C(C·C)2[Ru(PPh3)2-
Cp]}(CO)9 (5; 95% yield), while Co3{m3-C(C·C)4[Ru(dppe)-
Cp*]}(m-dppm)(CO)7 [6; 61% yield, from Co3(m3-CBr)(m-
dppm)(CO)7 and Ru{(C·C)4Au(PPh3)}(dppe)Cp*] contains the
longest (to our knowledge) odd-numbered carbon chain linking two
metal centres. A further example results in the linking of three
We sought an alternative route to complexes of this type and,
guided by the isolobal analogy between H and Au(PR3),12 we have
discovered a novel elimination of AuX(PR3) (X = Cl, Br, I) in
reactions between compounds containing C(sp)–X or C(sp2)–X
bonds (X = Cl, Br, I) and alkynyl or polyynyl gold(
This elimination takes place at r.t. in Et2O or thf and is catalysed by
Pd(0)/Cu( ); in the absence of either or both of the latter, the
I) complexes.
I
reaction either did not proceed or was much slower. One-pot
syntheses of the desired gold complexes, which are generally easier
to obtain than the analogous Cu or Ag derivatives, from analogous
SiMe3 derivatives can be achieved by sequential reactions of the
latter with base (NaOEt/EtOH) and AuCl(PAr3) (Ar = Ph, Tol).
Examples of products we have characterised in initial studies of the
scope of the reaction include PhC·CC·CFc [1; 55% yield, from
PhC·CAu(PPh3) and FcC·CI13], and FcC·CC(O)Ph [2; 77% yield,
from FcC·CAu(PPh3)14 and PhC(O)Cl]. The rod-like Co3(m3-
CC·CC6H4C·CPh-4)(m-dppm)(CO)7 (3; 39% yield)13 was formed
† Electronic supplementary information (ESI) available: synthetic pro-
cedures and characterisation data for Fc(C·C)2Au(PPh3), 4 and 6–9. See
http://www.rsc.org/suppdata/cc/b3/b315854n/
Scheme 1
960
C h e m . C o m m u n . , 2 0 0 4 , 9 6 0 – 9 6 1
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4

View Article Online
Fig. 1 Plot of a molecule of {Ru(dppe)Cp*}2{m-(C·C)7} (8). Significant
bond distances and angles: Ru–C(1) 1.958(5), C(1)–C(2) 1.236(7), C(2)–
C(3) 1.354(7), C(3)–C(4) 1.226(7), C(4)–C(5) 1.351(7), C(5)–C(6)
1.218(7), C(6)–C(7) 1.357(7), C(7)–C(7A) 1.222(7) Å; Ru–C(1)–C(2)
173.8(5), C(1)–C(2)–C(3) 176.0(5), C(2)–C(3)–C(4) 178.6(6), C(3)–C(4)–
C(5) 178.5(6), C(4)–C(5)–C(6) 177.5(7), C(5)–C(6)–C(7) 178.1(6), C(6)–
C(7)–C(7A) 178.7(6)°.
Fig. 2 Plot of a molecule of {Co3(m-dppm)(CO)7}2{m3:m3-C(C·C)7C} (9).
Significant bond distances and angles: C(1)–C(2) 1.371(6), C(2)–C(3)
1.221(8), C(3)–C(4) 1.336(8), C(4)–C(5) 1.228(8), C(5)–C(6) 1.339(8),
C(6)–C(7) 1.221(8), C(7)–C(8) 1.343(9), C(8)–C(8A) 1.211(9) Å; C(1)–
C(2)–C(3) 176.4(5), C(2)–C(3)–C(4) 169.7(6), C(3)–C(4)–C(5) 176.2(6),
C(4)–C(5)–C(6) 178.9(6), C(5)–C(6)–C(7) 178.4(6), C(6)–C(7)–C(8)
178.6(6), C(7)–C(8)–C(8A) 179.6(7)°.
organometallic nuclei in the product obtained from the reaction
14
between Fe{h-C5H4C·CAu(PPh3)}2
and Co3(m-CBr)(m-
20.221(3) Å, b = 97.901(3)°, V = 3657 Å3, Z = 2; Ntot = 36 221, N =
7475 (Rint = 0.041), Nobs = 5206; R = 0.057, Rw = 0.067. CCDC 223663
and 223664. See http://www.rsc.org/suppdata/cc/b3/b315854n/ for crys-
tallographic data in CIF or other electronic format.
dppm)(CO)7, which afforded Fe{h-C5H4C·C-m3-C[Co3(m-
dppm)(CO)7]}2 (7; 96% yield). The X-ray structure of 7 will be
described elsewhere.
The Pd(0)/Cu( )-catalysed reaction of Ru{(C·C)2Au(PPh3)}(dp-
I
1 (a) M. I. Bruce and P. J. Low, Adv. Organomet. Chem., 2004, 50, 231;
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Chisholm, Angew. Chem., Int. Ed. Engl., 1991, 30, 673.
pe)Cp* with I(C·C)3I afforded {Ru(dppe)Cp*}2{m-(C·C)7} (8;
36% yield), the first C14 complex to be structurally characterised.‡
A centrosymmetric molecule of 8 is shown in Fig. 1, with selected
bond parameters given in the caption. As can be seen, the C14 chain
is essentially straight, with deviations from linearity at the carbon
atoms of between 1.3 and 6.2°; whilst the sum of deviations
amounts to 37.6° and the separation of the two Ru centres
[20.560(5) Å] is only 0.06 Å shorter than the sum of the Ru–C and
C–C distances. The C–C separations alternate [ranges
1.211–1.228(8) and 1.336–1.371(8) Å for the short (C·C) and long
(C–C) distances, respectively] as expected for a conjugated
polyyne system, with the longer bonds being in the middle of the
C
14 chain.
A sequence involving coupling of Co3(m3-CBr)(m-dppm)(CO)7
with Me3Si(C·C)2Au(PPh3) to give Co3{m3-C(C·C)2SiMe3}(m-
dppm)(CO)7, followed by a second auration as described above,
afforded Co3{m3-C(C·C)2Au(PR3)}(m-dppm)(CO)7. Reaction with
I(C·C)3I then gave the bis(cluster) C16 derivative {Co3(m-
dppm)(CO)7}2{m3:m3-C(C·C)7C} (9; 86%), also structurally char-
acterised.‡ Fig. 2 shows a plot of a centrosymmetric molecule of 9,
with selected bond parameters collected in the caption. There are no
unusual features in the Co3 clusters, while the C16 chain is also
close to linear, with a maximum deviation of 10.3° from linearity at
C(3) and a C(1)…C(1A) separation of 19.176(8) Å, which is 0.15 Å
shorter than the sum of the C–C distances.
In conclusion, we have devised and demonstrated a novel
reaction sequence with the power to generate a wide range of new
complexes containing odd- or even-numbered carbon chains with
up to (so far) 16 carbon atoms, with either identical or dissimilar
metal–ligand end-caps on the chains. These new materials have
interesting redox, optical and electronic properties, which will be
detailed elsewhere.
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We thank the Australian Research Council for support of this
work and Johnson Matthey plc, Reading, UK, for generous loans of
RuCl3·nH2O and OsO4.
11 M. I. Bruce, K. A. Kramarczuk, G. J. Perkins, B. W. Skelton, A. H.
White and N. N. Zaitseva, J. Cluster Sci., 2004, 15, in press.
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14 A. B. Antonova, M. I. Bruce and M. Jevric, unpublished work.
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Notes and references
‡ Crystal data for 8: {Ru(dppe)Cp*}2{m-(C·C)7}·7C6H6
M
¯
= 1984.04; triclinic, space group P1, a =
C86H78P4Ru2·7C6H6, M
14.108(3), b = 14.438(3), c = 15.051(3) Å, a = 75.371(3), b = 88.083(3),
g = 60.879(3)°, V = 2577 Å3, Z = 1; 22 528 ( = Ntot) absorption-corrected
CCD diffractometer reflections (monochromatic Mo-Ka radiation, l =
0.71073 Å; 2qmax = 53°, T ≈ 153 K) merged to N unique = 10 149 (Rint
= 0.057), Nobs [F > 4s(F)] = 7823; R = 0.062, Rw = 0.078. For 9:
16 H. Hopf and B. Witulski, in Modern Acetylene Chemistry, ed. P. J. Stang
and F. Diederich, VCH, Weinheim, 1995, p. 33.
17 K. Gao and N. S. Goroff, J. Am. Chem. Soc., 2000, 122, 9320.
{Co3(m-dppm)(CO)7}2{m3:m3-C(C·C)7C}
1706.71; monoclinic, space group P21/n, a = 9.170(1), b = 19.914(3), c =
M
C80H44Co6O14P4,
M
=
C h e m . C o m m u n . , 2 0 0 4 , 9 6 0 – 9 6 1
961