Synthesis and some reactions of the heterometallic C7 complex {Cp*(dppe)Ru}C≡CC≡CC≡CC{Co3(μ-dppm)(CO) 7}

3352

Organometallics 2008, 27, 3352–3367

Synthesis and Some Reactions of the Heterometallic C₇Complex

{Cp*(dppe)Ru}Ct CCt CCt CC{Co₃(µ-dppm)(CO)₇}

Michael I. Bruce,*^,†Marcus L. Cole,^†Christian R. Parker,^†Brian W. Skelton,^‡and

Allan H. White^‡

School of Chemistry and Physics, UniVersity of Adelaide, Adelaide, South Australia 5005, and Chemistry

M313, SBBCS, UniVersity of Western Australia, Crawley, Western Australia 6009

ReceiVed October 30, 2007

The heterometallic carbon-chain complex {Cp*(dppe)Ru}Ct CCt CCt CC{Co₃(µ-dppm)(CO)₇} (1)

has been obtained by three routes that involve assembly of the C₇chain by combination of appropriate

C₁+ C₆, C₂+ C₅, or C₃+ C₄precursors. The Cp analogue 2 and Co₃(CO)₉cluster analogue 3 were

obtained via the C₂+ C₅and C₁+ C₆routes, respectively. Reaction of 1 with PPh₃gave 4 via substitution

of a Co₃cluster-bonded CO group. Addition of MeOTf to the second carbon from the Ru center in 1

afforded the vinylidene [{Cp*(dppe)Ru}dCdCMeCt CCt CC{Co₃(µ-dppm)(CO)₇}]OTf (5), while

addition of tcne or tcnq across the central Ct C bond gave {Cp*(dppe)Ru}Ct CC[dC(CN)₂]C[dC(CN)₂]-

Ct CC{Co₃(µ-dppm)(CO)₇} (6) and {Cp*(dppe)Ru}Ct CC[dC₆H₄C(CN)₂]C[dC(CN)₂]Ct CC{Co₃(µ-

dppm)(CO)₇} (7), respectively. The reaction between 1 and Fe₂(CO)₉was more complex, the major product

being {Cp*(dppe)Ru}Ct CC{Fe₃(CO)₉}CCt CC{Co₃(µ-dppm)(CO)₇} (8), accompanied by an Fe₂(CO)₆

derivative (9) of as yet undetermined structure. {Cp*(dppe)Ru}Ct CCt CCt CC{Co₂Ni(µ-dppm)(CO)₄Cp}

(10) was obtained from the reaction with NiCp₂. An unstable adduct containing two Co₂(CO)₆groups

attached to the C₇chain was formed in reactions between 1 and Co₂(CO)₈. XRD structural studies of 1,

2, 6-8, and 10 are reported. Electrochemical measurements suggest that there is some interaction between

the two end groups, although this cannot presently be quantiﬁed. It is concluded that the C₇chain is long

enough for the properties of the individual end caps to be preserved, while steric inhibition from the

phenyl groups of the dppe and dppm ligands directs addition to the central Ct C triple bond of the C₇

chain.

found to undergo several stepwise one-electron oxidations.

Theoretical calculations reveal that the HOMOs of these

complexes generally have both metal and carbon character, the

relative amounts of which depend on the nature of the end

groups and the length of the carbon chain. Consequently,

oxidation of these species can involve removal of electrons from

orbitals localized predominantly either on the carbon chain itself

(as in the Mn complexes)¹or at the metal centers (as for Fe)⁶

or from orbitals that are delocalized over all atoms of the

M-(Ct C)_x-M bridge.^4,7Calculations at various levels of

theory reveal that the HOMOs of these complexes and their

cations, although delocalized over the M-C_2x-M backbone,

are more metallic in character for examples containing ﬁrst-

row transition metals,⁹whereas they possess greater carbon

character in the examples featuring second- and third-row

transition metals.¹⁰

Introduction

Many complexes of the type {L_xM}(Ct C)_n{ML_x} (n )

1-10), containing unsaturated carbon chains end-capped by

redox-active groups such as MnX(dmpe)₂(X ) I,¹Ct CSiR₃),

2

Mn(dmpe)Cp^Me,³Re(NO)(PPh₃)Cp*,⁴Fe(CO)₂Cp*,⁵Fe(PP)Cp*

(PP ) dppe, dippe),⁶Ru(PP)Cp′ [PP ) (PPh₃)(PR₃), R ) Me,

Ph; dppm, dppe; Cp′ ) Cp, Cp*],⁷and PtAr(PR₃)₂⁸have been

* Corresponding author. Fax: + 61 8 8303 4358. E-mail: michael.bruce@

adelaide.edu.au.

^†University of Adelaide.

^‡University of Western Australia.

(1) (a) Kheradmandan, S.; Heinze, K.; Schmalle, H. W.; Berke, H.

Angew. Chem., Int. Ed. 1999, 38, 2270. (b) Fernandez, F. J.; Blacque, O.;

Alfonso, M.; Berke, H. Chem. Commun. 2001, 1266. (c) Fernandez, F. J.;

Venkatesan, K.; Blacque, O.; Alfonso, M.; Schmalle, H. W.; Berke, H.

Chem.-Eur. J. 2003, 9, 6192.

(2) Venkatesan, K.; Fox, T.; Schmalle, H. W.; Berke, H. Organometallics

2005, 24, 2834.

A

detailed study of the heterobimetallic complexes

{Cp*(dppe)Fe}Ct CCt C{Ru(dppe)Cp*}and{Cp*(dppe)Fe}Ct C-

(3) Kheradmandan, S.; Venkatesan, K.; Blacque, O.; Schmalle, H. W.;

Berke, H. Chem.-Eur. J. 2004, 10, 4872.

(4) (a) Brady, M.; Weng, W.; Zhou, Y.; Seyler, J. W.; Amoroso, A. J.;

Arif, A. M.; Bo¨hme, M.; Frenking, G.; Gladysz, J. A. J. Am. Chem. Soc.

1997, 119, 775. (b) Dembinski, R.; Lis, T.; Szafert, S.; Mayne, C. L.; Bartik,

T.; Gladysz, J. A. J. Organomet. Chem. 1999, 578, 229. (c) Dembinski,

R.; Bartik, T.; Bartik, B.; Jaeger, M.; Gladysz, J. A. J. Am. Chem. Soc.

2000, 122, 810.

(5) Akita, M.; Chung, M. C.; Sakurai, A.; Sugimoto, S.; Terada, M.;

Tanaka, M.; Moro-oka, Y. Organometallics 1997, 16, 4882.

(6) (a) Le Narvor, N.; Toupet, L.; Lapinte, C. J. Am. Chem. Soc. 1995,

117, 7129. (b) Coat, F.; Lapinte, C. Organometallics 1996, 15, 477. (c)

Coat, F.; Guillevic, M.-A.; Toupet, L.; Lapinte, C. Organometallics 1997,

16, 5988. (d) Le Narvor, N.; Lapinte, C. C. R. Acad. Sci., Paris, Ser. IIC

1998, 1, 745. (e) Guillemot, M.; Toupet, L.; Lapinte, C. Organometallics

1998, 17, 1928.

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Heath, G. A. J. Am. Chem. Soc. 2000, 122, 1949. (b) Bruce, M. I.; Ellis,

B. G.; Low, P. J.; Skelton, B. W.; White, A. H. Organometallics 2003, 22,

3184.

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2929. (b) Peters, T. B.; Bohling, J. C.; Arif, A. M.; Gladysz, J. A.

Organometallics 1999, 18, 3261. (c) Zheng, Q.; Gladysz, J. A. J. Am. Chem.

Soc. 2005, 127, 10508. (d) Owen, G. R.; Stahl, J.; Hampel, F.; Gladysz,

J. A. Organometallics 2004, 23, 5889. (e) Owen, G. R.; Hampel, F.; Gladysz,

J. A. Organometallics 2004, 23, 5893. (f) Zheng, Q.; Hampel, F.; Gladysz,

J. A. Organometallics 2004, 23, 5896. (g) Mohr, W.; Stahl, J.; Hampel, F.;

Gladysz, J. A. Inorg. Chem. 2001, 40, 3263.

(9) Paul, F.; Meyer, W. E.; Toupet, L.; Jiao, H.; Gladysz, J. A.; Lapinte,

C. J. Am. Chem. Soc. 2000, 122, 9405.

10.1021/om7010968 CCC: $40.75

2008 American Chemical Society

Publication on Web 06/14/2008

Synthesis and Chemistry of a Heterometallic C₇Complex

Organometallics, Vol. 27, No. 14, 2008 3353

Chart 1

Ct C{Ru(PPh₃)₂Cp}, which undergo stepwise oxidation with

[FeCp₂]PF₆togivethemono-anddications,[{Cp*(dppe)Fe}Ct C-

Ct C{Ru(dppe)Cp*}](PF₆)_n, and [{Cp*(dppe)Fe}Ct CCt C-

{Ru(PPh₃)₂Cp}](PF₆)_n(n ) 1, 2) has been reported.¹⁰The avail-

able X-ray structural data, together with the IR spectrum of

[{Cp*(dppe)Fe}Ct CCt C{Ru(PPh₃)₂Cp}](PF₆)₂, which shows

a decrease in the ν(CC) frequency, are consistent with the

gradual evolution of the polycarbon moiety from a diyndiyl

structure (A, Chart I) to a more cumulenic system (B or C) as

oxidation proceeds. Computational studies indicate that there

is a signiﬁcant contribution from the iron center to the highest

lying orbitals of the delocalized electronic structure. Spectro-

scopic results (⁵⁷Fe Mo¨ssbauer, ESR, IR, UV-vis, and NIR)

support these conclusions, although detailed analysis of the NIR

region, which is complicated by the overlapping of several other

transitions with the lowest energy band, suggests that the major

transition probably arises from photoinduced transfer of an

electron from iron to ruthenium. These data allow an estimation

of the relative contributions of the metal centers and ancillary

ligands to the properties of the [{M}-CC-CC-{M′}]ⁿ⁺

assemblies and clearly indicate the dominant role of ruthenium

over iron in dictating the underlying electronic structures of C₄-

bridged heterometallic complexes.¹⁰

CO)₃Cp′₃(Cp′ ) Cp, Cp^Me),¹³{Os₃(µ-H){(µ₃-C₂(Ct C)_x-

[Re(NO)(PPh₃)Cp*]}(CO)₉(x ) 1, 2),¹⁴[Cu₃(µ-dppm)₃{µ₃-

Ct CCt C[Re(Me₂bpy)(CO)₃]}₂]⁺,¹⁵Fe₂Ir{µ₃-η¹,η²-C₂Ct C-

[W(CO)₃Cp]}(CO)₇(PPh₃),¹⁶and Ru₃{µ₃-η¹,η²-CCt CC-

[Fe₂(µ-CO)(CO)₂Cp*₂]}(µ₃-CO)(CO)₉.¹⁷From studies designed

to prepare related complexes containing odd-numbered carbon

chains, we have described the compounds {(OC)₇(µ-dppm)-

Co₃}{µ₃-C(Ct C)_x[ML_n]} [e.g., x ) 1,2, ML_n) W(CO)₃Cp,

Au(PR₃) (R ) Ph, tol), Ru(dppe)Cp*, Fc, Fc′],¹⁸although no

detailed studies of their properties and reactivity have yet been

reported.

This paper describes the synthesis and some chemistry of

the complex {(OC)₇(µ-dppm)Co₃}C(Ct C)₃{Ru(dppe)Cp*} (1),

chosen because a C₇chain is long enough to avoid steric

hindrance by the phenyl groups of either of the diphosphine

ligands, but short enough to allow some electronic interaction

between the two end caps. In the course of examining the

chemistry associated with this compound, we have demonstrated

reactions of (a) the ruthenium center, (b) the tricobalt cluster,

and (c) the carbon chain.

Results and Discussion

The construction of complexes containing two different end

groups linked by carbon chains can be achieved by several

routes, of which coupling of a terminal metalla-alkyne

{ML_n}(Ct C)_xCt CH (or precursor thereof) to the second metal

center is perhaps the most convenient.^19–22An alternative

approach consists of the coupling of two shorter carbon chains,

for which we have recently developed an efﬁcient route

Consequently, the behavior of other complexes containing

dissimilar metal-ligand groups linked by unsaturated carbon

chains has evoked interest. There is a relatively small number

of complexes containing carbon chains linking two metal-ligand

groups either from different periodic groups or with differing

ligand environments. Detailed studies of {Cp*(dppe)Fe}Ct C-

C₆H₄Ct C{Re(CO)₃(bpy)} have been reported,¹¹one of the

more interesting features being the quenching of luminescence

associated with the rhenium center by addition of the iron group,

which is restored upon oxidation to the 1⁺cation.

(13) Grifﬁth, C. S.; Koutsantonis, G. A.; Skelton, B. W.; White, A. H.

J. Organomet. Chem. 2003, 672, 17.

(14) Falloon, S. B.; Szafert, S.; Arif, A. F.; Gladysz, J. A. Chem.-Eur.

J. 1998, 4, 1033.

Note that in complexes containing an odd-numbered carbon

chain, those with poly-yne formulations have both σ-bonded

and multiply bonded carbynic end groups (D), whereas the

cumulenic forms may have two identical groups (E).

(15) Yam, V. W.-W.; Lo, W.-Y.; Lam, C.-H.; Fung, K.-M.; Wong,

K. M.-C.; Lau, V. C.-Y.; Zhu, N. Coord. Chem. ReV. 2003, 245, 39.

(16) Bruce, M. I.; Ellis, B. G.; Skelton, B. W.; White, A. H. J.

Organomet. Chem. 2000, 607, 137.

(17) Akita, M.; Chung, M.-C.; Sakurai, A.; Moro-oka, Y. Chem.

Commun. 2000, 1285.

(18) (a) Bruce, M. I.; Kramarczuk, K. A; Zaitseva, N. N.; Skelton, B. W.;

White, A. H. J. Organomet. Chem. 2005, 690, 1549. (b) Antonova, A. B.;

Bruce, M. I.; Humphrey, P. A.; Gaudio, M.; Nicholson, B. K.; Scoleri, N.;

Skelton, B. W.; White, A. H.; Zaitseva, N. N. J. Organomet. Chem. 2006,

691, 4694. (c) Bruce, M. I.; Skelton, B. W.; White, A. H.; Zaitseva, N. N.

J. Organomet. Chem. 2003, 683, 398.

Several complexes containing a metal cluster acting as one

of the end caps to a carbon chain have been isolated, in which

the chain is attached via a µ- or µ₃-η¹-C atom or via a µ₃-η¹,η²-

C₂unit.¹²Examples include Ru₃{µ₃-CCt [Mo(CO)₂Cp]}(µ-

(10) Bruce, M. I.; Costuas, K.; Davin, T.; Ellis, B. G.; Halet, J.-F.;

Lapinte, C.; Low, P. J.; Smith, M. E.; Skelton, B. W.; Toupet, L.; White,

A. H. Organometallics 2005, 24, 3864.

(11) Wong, K. M.-C.; Lam, S. C.-F.; Ko, C.-C.; Zhu, N.; Yam, V. W.-

W.; Roue´, S.; Lapinte, C.; Fathallah, S.; Costuas, K.; Kahlal, S.; Halet,

J.-F. Inorg. Chem. 2003, 42, 7086.

(19) Weng, W.; Bartik, T.; Brady, M.; Bartik, B.; Ramsden, J. A.; Arif,

A. M.; Gladysz, J. A. J. Am. Chem. Soc. 1995, 117, 11922.

(20) Bruce, M. I.; Ke, M.; Low, P. J. Chem. Commun. 1996, 21, 2405.

(21) Akita, M.; Chung, M.-C.; Sakurai, A.; Sugimoto, S.; Terada, M.;

Tanaka, M.; Moro-oka, Y. Organometallics 1997, 16, 4882.

(22) Pilar Gamasa, M.; Gimeno, J.; Godefroy, I.; Lastra, E.; Mart´ın-

Vaca, B. M.; Garc´ıa-Granda, S.; Gutierrez-Rodriguez, A. J. Chem. Soc.,

Dalton Trans. 1995, 1901.

(12) For a recent review, see: Bruce, M. I.; Low, P. J. AdV. Organomet.

Chem. 2004, 50, 179.

3354 Organometallics, Vol. 27, No. 14, 2008

Bruce et al.

Scheme 1^a

a

Reagent: (i) Pd(PPh₃)₄/CuI, thf.

involving elimination of phosphine-gold(I) halides from ap-

propriate precursors.²³In seeking to make the target molecule

1 discussed above, we have employed several variants of these

reactions in order to achieve assembly of the C₇chain via C_m

+ C_nf C₇routes. Three approaches to the coupling of two

shorter carbon chains were explored (Scheme 1). Novel

intermediates were prepared by the Pd(0)/Cu(I)-catalyzed reac-

tions between Ru{Ct CCt CAu(PPh₃)}(dppe)Cp* and

Me₃SiCt CI to give Ru{(Ct C)₃SiMe₃}(dppe)Cp* (83%), fol-

lowed by treatment of the latter with AuCl(PPh₃) in the presence

of NaOMe to give Ru{(Ct C)₃Au(PPh₃)}(dppe)Cp* (94%).

The reaction of Co₃(µ₃-CBr)(µ-dppm)(CO)₇with

Ru{(Ct C)₃Au(PPh₃)}(dppe)Cp*, resulting in the coupling C₁

+ C₆f C₇, afforded 1 in 52% yield. To link C₂+ C₅f C₇,

the complex Co₃{µ₃-C(Ct C)₂Au(PPh₃)}(µ-dppm)(CO)₇was

reacted with putative Ru(Ct CI)(dppe)Cp*, prepared in situ by

deprotonation of the vinylidene [Ru(dCdCH₂)(dppe)Cp*]⁺

with 2 equiv of LiBu, followed by addition of [I(py)₂]BF₄; this

reaction afforded 1 in 26% yield. Although we have not yet

succeeded in isolating the supposed intermediate iodoalkynyl

complex Ru(Ct CI)(dppe)Cp* in a pure state, Gamasa and co-

workers have reported a similar reaction between Ru(Ct CLi)-

(PPh₃)₂(η⁵-C₉H₇) and [I(py)₂]BF₄to afford unstable Ru(Ct CI)-

(PPh₃)₂(η⁵-C₉H₇).²²A similar approach to coupling C₃+ C₄

fC₇chainswasachievedbyreactingCo₃{µ₃-CCt CAu(PPh₃)}(µ-

dppm)(CO)₇with Ru(Ct CCt CI)(dppe)Cp*,²⁴again prepared

in situ from Ru(Ct CCt CH)(dppe)Cp*, LiBu, and [I(py)₂]BF₄,

to give 1 in 57% yield. In the ES-MS, obtained from solutions

in MeOH containing NaOMe, ions at m/z 1499 ([M + Na]⁺),

1476 (M⁺), and 1448 ([M - CO]⁺) are present.

The Cp analogue of 1 was obtained from the reaction between

the supposed Ru(Ct CI)(dppe)Cp, prepared as the Cp* analogue

above, and Co₃{µ₃-CCt CAu(PPh₃)}(µ-dppm)(CO)₇, to give the

dark brown complex {Cp(dppe)Ru}Ct CCt CCt CC{Co₃(µ-

dppm)(CO)₇} (2) in 26% yield. The ES-MS, obtained from

solutions in MeOH containing NaOMe, contains ions at m/z

1429 ([M + Na]⁺) and 1406 (M⁺).

A

reaction

between

Co₃(µ₃-CBr)(CO)₉

and

Ru{(Ct C)₃Au(PPh₃)}(dppe)Cp* gave {Cp*(dppe)Ru}Ct C-

Ct CCt CC{Co₃(CO)₉} (3) in 48% yield. This maroon com-

pound is considerably less stable than either 1 or 2. The

negative-ion ES-MS contains [M + OMe]^-at m/z 1179.

Characterization of these complexes and the others described

below has been achieved by microanalysis and spectroscopically,

as well as by a single-crystal XRD study in some cases (see

below). Spectroscopic data are summarized in Table 1. The IR

and NMR spectra contain the expected absorptions; we defer

until later a discussion of the resonances of the carbon chains

in 1 and other complexes reported herein. The ³¹P NMR

spectrum contains two equal-intensity signals at δ 33.9 and 80.2

from the dppm and dppe ligands, respectively.

(23) (a) Bruce, M. I.; Smith, M. E.; Zaitseva, N. N.; Skelton, B. W.;

White, A. H. J. Organomet. Chem. 2003, 670, 170. (b) Antonova, A. B.;

Bruce, M. I.; Ellis, B. G.; Gaudio, M.; Humphrey, P. A.; Jevric, M.; Melino,

G.; Nicholson, B. K.; Perkins, G. J.; Skelton, B. W.; Stapleton, B.; White,

A. H.; Zaitseva, N. N. Chem. Commun. 2004, 960.

(24) Bruce, M. I.; Jevric M.; Parker, C. R. Unpublished results.

Synthesis and Chemistry of a Heterometallic C₇Complex

Organometallics, Vol. 27, No. 14, 2008 3355

Table 1. ¹³C NMR Chemical Shifts for Carbon Chains

complex^a

[Ru]-C₆-SiMe₃

[Ru]-C₆-Au(PPh₃)

[[Ru*]-CCMe-C₅-[Co₃]]OTf

[Ru*]-C₇-[Co₃]

#

C(1)

137.58t

154.43

357.39t

151.88

151.78

151.03

154.39/155.33

154.78

C(2)

94.07

92.01/94.15

109.04/107.56

94.88

93.27

105.56

108.56

92.90

C(4)

C(3)

C(5)

C(6)

92.19

94.15/92.01

107.56/109.04

104.01

C(7)

reference

49.43

48.99

97.32, 81.51, 91.04

48.79

51.50

69.79

51.19

77.93

64.41

this work

5

1

10

6

7

215.09

216.58

90.70, 91.49

91.85, 92.33

75.43

63.24

[Ru*]-C₇-[Co₂Ni]

107.50

[Ru*]-C₂(C₂-tcne)C₃-[Co₃]

[Ru*]-C₂(C₂-tcnq)C₃-[Co₃]

[Ru*]-C₂C[Fe₃]CC₂C-[Co₃]

83.65

82.70

80.50

8

252.61, 273.10

114.09

Me₃Si-C₃-[Co₃]

Fc-C₃-[Co₃]

Fc-C₇-[Co₃]

[Pt]-C₄-H

126.19

111.77

99.03

116.70

107.95

97.13

92.4

18b

8

63.38, 65.66, 72.73

80.95

72.3

58.9

^a[Ru] ) Ru(dppe)Cp; [Ru*] ) Ru(dppe)Cp*; [Co₃] ) Co₃(µ-dppm)(CO)₇; [Co₂Ni] ) Co₂Ni(µ-dppm)(CO)₄Cp; [Fe₃] ) Fe₃(CO)₉; [Pt] )

trans-Pt(C₆F₅)(PAr₃)₂.

Scheme 2

Ct CCt CC{Co₃(µ-dppm)(CO)₆(PPh₃)} (4) in 84% yield, sur-

prisingly considerably better that that obtained from a similar

reaction carried out in the presence of Me₃NO, which is often

used to activate cluster-bound CO groups toward substitution

(41%). The ³¹P NMR spectrum contains three resonances with

2:1:2 ratio, at δ 33.6 (d, dppm), 48.4 (broad t, PPh₃), and 80.5

(s, dppe), conﬁrming the site of PPh₃substitution to be the third

cobalt center. The ES-MS of solutions in MeOH containing

NaOMe contained [M + Na]⁺at m/z 1733.

(b) With MeOTf. A characteristic reaction of alkynyl-

ruthenium complexes is the addition of electrophiles to C_ꢀto

give vinylidene complexes.²⁵Addition of MeOTf to 1 at -78

°C, followed by warming to ambient temperature, resulted in a

slow reaction (over 5 days) to give [{Cp*(dppe)Ru}dCdCMe-

Ct CCt CC{Co₃(µ-dppm)(CO)₇}]OTf (5), isolated in 63% yield

as a brown solid. The slow rate of reaction is a surprise and not

readily explained, since addition of electrophiles to alkynyl-

ruthenium complexes is typically very fast. The presence of the

alkynyl-vinylidene ligand is indicated by the characteristic

downﬁeld triplet at δ 357.39 [J(CP) ) 16 Hz] in the ¹³C NMR

spectrum assigned to RudC, together with the Me resonance

at δ 10.15. The ³¹P NMR spectrum contains equal-intensity

singlets at δ 34.9 (dppm) and 74.0 (dppe). In the ES-MS, ions

at m/z 1491 (M⁺) and 663 ([Ru(CO)(dppe)Cp*]⁺) are found.

(c) With tetracyanoethene (tcne) and 7,7,8,8-tetra-

cyano-1,4-quinodimethane (tcnq). Reactions of tcne and tcnq

with transition metal substrates generally result in the formation

of charge transfer complexes or in oxidation reactions.²⁶These

properties result from the presence of low-lying π* orbitals in

the cyanocarbons. The products are often radical ions or

dianions, with concomitant formation of either side-on coordina-

tion, ion pairs, or nitrile-bonded complexes, such as the recently

described [{Re(CO)₃(bpy)}₄(µ₄-tcnq)]⁴⁺and [{Fe(CO)₂Cp}₄-

(tcnx)]⁴⁺(tcnx ) tcne, tcnq, tcnb), the formation of which

involves very little charge transfer from metal to the cyanocar-

bon ligand.²⁷The zwitterionic vinylidene complex

Ru⁺{dCdCPhCH(CN)(tcnq^-)}(PPh₃)₂Cp was obtained from

the reaction between tcnq and the cyclopropenyl complex

Ru{CdCPhCH(CN)}(PPh₃)₂Cp.²⁸More recently, Lapinte has

Reactions of 1. It was of interest to examine the chemistry

of 1 to determine how far the characteristic reactions of one

end group are modiﬁed by the presence of the other. To this

end, we have investigated reactions between 1 and PPh₃

[substitution of a Co(CO)₃carbonyl group], methyl triﬂate

[addition to C(2) to give a vinylidene complex], tetracyanoethene

(tcne), 7,7,8,8-tetracyanoquinonedimethane (tcnq), Co₂(CO)₈and

Fe₂(CO)₉(which are expected to add to a Ct C triple bond in

the C₇chain), and NiCp₂[either addition to a Ct C triple bond

or replacement of the Co(CO)₃group]. This chemistry is

summarized in Schemes 2–4.

(25) (a) Bruce, M. I. Chem. ReV. 1991, 91, 197. (b) Bruce, M. I.;

Swincer, A. G. AdV. Organomet. Chem. 1983, 22, 59.

(26) Kaim, W.; Moscherosch, M. Coord. Chem. ReV. 1994, 129, 157.

(27) (a) Hartmann, H.; Kaim, W.; Wanner, M.; Klein, A.; Franz, S.;

Duboc-Toia, C.; Fiedler, J.; Za´lisˇ, S. Inorg. Chem. 2003, 42, 7018. (b) Maity,

A. N.; Schwederski, B.; Sarkar, B.; Za´lisˇ, S.; Fiedler, J.; Kar, S.; Lahiri,

G. K.; Duboc, C.; Grunert, M.; Gu¨tlich, P.; Kaim, W. Inorg. Chem. 2007,

46, 7312.

(a) With PPh₃. The ready substitution of one of the CO

groups on the Co₃cluster by PPh₃was discovered serendipi-

tously during a reaction with AuI(PPh₃). The thermal reaction

between1andPPh₃inreﬂuxingthfafforded{Cp*(dppe)Ru}Ct C-

(28) Ting, P.-C.; Lin, Y.-C.; Lee, G.-H.; Cheng, M.-C.; Wang, Y. J. Am.

Chem. Soc. 1996, 118, 6433.

3356 Organometallics, Vol. 27, No. 14, 2008

Bruce et al.

and M⁺ions at m/z 1627 and 1604, respectively. A band

assigned to ν(CN) (2210 cm^-1) present in the IR spectrum is

more informative. Signals for the Cp*, CH₂, and Ph groups in

the ¹³C NMR spectrum are accompanied by weaker singlets at

δ 113.63, 113.90, 116.64, 116.83 (CN) and 201.82 (CO). The

³¹P NMR spectrum contains, in place of the usual singlets, two

AB quartets centered at δ 34.9 [J(PP) ) 47 Hz, dppm] and

80.1 [J(PP) ) 10 Hz, dppe)] arising from the nonequivalence

of the two ³¹P nuclei in the respective chelating diphosphines,

which in turn results from the marked asymmetry of the

cyanocarbon bridge. Similar coupling of the ³¹P resonances of

dppe ligands has been observed for the related complexes

{(CO)₇(µ-dppm)Co₃}CCt CCt CC[dC(CN)₂]C[dC(CN)₂]C-

{Co₃(µ-dppm)(CO)₇}^23aandRu{Ct CC[dC(CN)₂]CFcdC(CN)₂}-

(dppe)Cp,³⁴which also contain unsymmetrically coordinated

cyanocarbon ligands.

Scheme 3

As found for tcne, the reaction between 1 and tcnq proceeds

rapidly in dichloromethane, via several color changes, to give

a dark blue solution, from which the complex {Cp*(dppe)Ru}{µ-

Ct CC[dC₆H₄dC(CN)₂]C[dC(CN)₂]Ct CC}{Co₃(µ-dppm-

)(CO)₇} (7) was obtained in 86% yield. Correct microanalyses

were obtained and supported by ions at m/z 1703 and 1680 for

[M + Na]⁺and M⁺in the ES-MS obtained from a solution

containing NaOMe. The IR spectrum of a dichloromethane

solution contained a ν(CN) band at 2193 cm^-1and medium-

intensity bands at 1585 and 1369 cm^-1, which we assign to the

dC₆H₄d moiety. The ¹H NMR spectrum contains two singlets

at δ 6.18 and 6.21 (CH of C₆H₄) and aromatic protons between

δ 6.63 and 7.71. In the ¹³C NMR spectrum, the expected signals

for the Cp*, dppe, dppm, and aromatic carbons are accompanied

by four singlets between δ 114 and 118 (CN) and a multiplet

at δ 201.62 [Co-CO]. The ³¹P NMR spectrum exhibits broad

resonances at δ 33.3 (dppm) and a broad doublet at 79.6 (dppe)

[J(PP) ) 369 Hz]. The molecular structure of 7 is discussed

below.

(d) With Fe₂(CO)₉. We next examined the reactions of 1

with reactive metal complexes that might be expected to react

with either of the end groups or with the C₇chain. The reaction

of 1 with Fe₂(CO)₉, which is known to exchange CO for PPh₃

in complexes RuX(PPh₃)₂Cp,³⁵to replace Co(CO)₃groups by

FeH(CO)₃in CCo₃clusters,^36,37or to cleave Ct C triple bonds

in carbon chain complexes,^38,39afforded several products in

small yield. Optimization of reaction conditions (see Experi-

mental Section) afforded a major purple product, identiﬁed

crystallographically as {Cp*(dppe)Ru}Ct CC{Fe₃(CO)₉}CCt CC-

{Co₃(µ-dppm)(CO)₇} (8). The IR spectrum contains ν(CO)

bands between 2069 and 1913 cm^-1, although the ν(Ct C)

bands could not be positively identiﬁed. The ³¹P NMR spectrum

contains the expected dppm and dppe resonances at δ 35.2 and

78.5, respectively. In the ES-MS, [M + Na]⁺and M⁺occur at

m/z 1918 and 1896, respectively.

described the use of tcnq as an oxidizing agent, its reaction with

9,10-{[Fe(dppe)Cp*](Ct C)}₂-anthracene affording the well-

crystallized ion pair [9,10-{Cp*(dppe)Fe(Ct C)}₂C₁₄H₈](tcnq).²⁹

In contrast, the reactions of tcne and several analogous

cyanoalkenes with unsaturated hydrocarbyl systems, particularly

unsaturated C(sp) chains, attached to electron-rich metal centers,

result in initial formal [2 + 2]-cycloaddition of the cyano-alkene

to a C₂moiety. In the case of tcne, this gives a tetracyanocy-

clobutenyl group, the reaction often being followed by ring-

opening to give tetracyanobutadienyl derivatives.^30,31In some

cases, paramagnetic intermediates can be detected at the ﬁrst

stages of the reaction, suggesting the intermediacy of radical

species. Similar chemistry of tcnq is rare, the only well-

substantiated example being the reactions of trans-

Pt(Ct CR)₂(PR′₃)₂(R ) H, Me; R′ ) Me, Et), which afforded

stable, deep purple 1:1 adducts. Although initially formulated

as charge transfer complexes,³²a single-crystal XRD structure

determination of the Pt-propynyl adduct revealed that one Ct C

triple bond had formally inserted into one of the dC(CN)₂

double bonds to give trans-Pt(Ct CMe){C[dC₆H₄d-

C(CN)₂]CMedC(CN)₂}(PMe₃)₂.³³Apparently only one isomer

is formed, shown by the structural determination to be that in

which the dC(CN)₂group is attached to the outer carbon of

the Ct CMe triple bond.

The reaction between 1 and tcne in dichloromethane proceeds

rapidly through an initial dark purple coloration to black after

5 min. Workup gave black {Cp*(dppe)Ru}Ct CC[dC(CN)₂]C-

[dC(CN)₂]Ct CC{Co₃(µ-dppm)(CO)₇} (6) in 86% yield, crys-

tallographically identiﬁed (see below) as the product of formal

insertion of the central Ct C triple bond into the CdC double

bond of the alkene. The overall composition of 6 was conﬁrmed

by microanalysis and the ES-MS, which contains [M + Na]⁺

Formation of 8 involves formal cleavage of possibly one of

the strongest bonds in the molecule and results in C(3) and C(4)

capping both sides of the Fe₃triangle. This reaction has

previously been observed with other poly-ynediyl molecules

(29) de Montigny, F.; Argouarch, G.; Costuas, K.; Halet, J.-F.; Roisnel,

T.; Toupet, L.; Lapinte, C. Organometallics 2005, 24, 4558.

(30) Davison, A.; Solar, J. P. J. Organomet. Chem. 1979, 166, C13.

(31) (a) Bruce, M. I.; Hambley, T. W.; Snow, M. R.; Swincer, A. G.

Organometallics 1985, 4, 494. (b) Bruce, M. I.; Hambley, T. W.; Snow,

M. R.; Swincer, A. G. Organometallics 1985, 4, 501. (c) Bruce, M. I.;

Low, P. J.; Skelton, B. W.; White, A. H. New J. Chem. 1998, 22, 419.

(32) Masai, H.; Sonogashira, K.; Hagihara, N. J. Organomet. Chem.

1972, 34, 397.

(34) Bruce, M. I.; de Montigny, F.; Jevric, M.; Lapinte, C.; Skelton,

B. W.; Smith, M. E.; White, A. H. J. Organomet. Chem. 2004, 689, 2860.

(35) Blackmore, T.; Bruce, M. I.; Stone, F. G. A. J. Chem. Soc. A 1971,

2376.

(36) Blumhofer, R.; Vahrenkamp, H. Chem. Ber. 1986, 119, 683.

(37) Duffy, D. N.; Kassis, M. M.; Rae, A. D. J. Organomet. Chem.

1993, 460, 97.

(38) (a) Akita, M.; Sakurai, A.; Moro-oka, Y. Chem. Commun. 1999,

101. (b) Akita, M.; Sakurai, A.; Chung, M-C.; Moro-oka, Y. J. Organomet.

Chem. 2003, 670, 2.

(33) Onuma, K.-I.; Kai, Y.; Yasuoka, N.; Kasai, N. Bull. Chem. Soc.

Jpn. 1975, 48, 1696.

(39) Bruce, M. I.; Ellis, B. G. Unpublished results.

Synthesis and Chemistry of a Heterometallic C₇Complex

Organometallics, Vol. 27, No. 14, 2008 3357

Scheme 4^a

a

Reagents: (i) tcne; (ii) tcnq; (iii) Fe₂(CO)₉; (iv) Co₂(CO)₈.

such as Fp*(Ct C)_xFp*³⁸and {Ru(dppe)Cp*}(Ct C)_x-

{Ru(dppe)Cp*} (x ) 3, 4),³⁹and it has been suggested³⁸that it

proceeds via a pseudotetrahedral C₂Fe₂(CO)₆intermediate,

which then rapidly picks up a third Fe(CO)₃fragment. In these

cases, an even-numbered C_xchain is cleaved to form two odd-

numbered carbon chains, while in the reaction with 1, the C₇

chain forms C₃+ C₄chains as a result of the formation of the

bis-carbyne C₄ligand, previously found in {Co₃(µ-

dppm)_n(CO)_9-2n}₂(µ-C₄) (n ) 0,⁴⁰1⁴¹) and {MCo₂(CO)₈Cp}₂(µ-

C₄) (M ) Mo, W, Mo/W)⁴²and postulated to be related to the

structure C of the 4e-oxidized product from {Ru(PP)Cp′}₂(µ-

C₄).⁷

can be suggested, one involving coordination of the carbon chain

in a manner reminiscent of the well-known “ﬂyover” complexes

(F), while the other contains two fragments formed by cleavage

of a central C-C bond, the chain forming a µ-η¹,η²ligand to each

of two Fe(CO)₃groups (G). Although this complex does not appear

to be an intermediate en route to 8, cleavage of the carbon chain

is an attractive formulation, based on the product ratio in reactions

carried out at higher temperatures.

While several other products are formed in varying amounts in

the reactions between 1 and Fe₂(CO)₉, with one exception we have

not succeeded in isolating them in pure form. A green-brown

compound 9 has been isolated from reaction in thf and appears to

be favored over 8 at elevated temperatures. Compound 9 is thought

to be a Fe₂(CO)₆adduct from its ES-MS, m/z 1779 and 1756 for

[M + Na]⁺and M⁺obtained from a solution containing NaOMe.

To date it has not been possible to obtain X-ray quality crystals of

9. With only terminal ν(CO) bands in the IR spectrum, we may

speculate that two central Ct C triple bonds have interacted with

the Fe₂(CO)₉reagent with displacement of three CO groups; that

is, the carbon chain acts as a six-electron donor. Two structures

(40) Dellaca, R. J.; Penfold, B. R.; Robinson, B. H.; Robinson, W. T.;

Spencer, J. L. Inorg. Chem. 1970, 9, 2204.

(41) Bruce, M. I.; Skelton, B. W.; White, A. H.; Zaitseva, N. N.

Organometallics 2006, 25, 4817.

(42) Bruce, M. I.; Halet, J.-F.; Kahlal, S.; Low, P. J.; Skelton, B. W.;

White, A.H. J. Organomet. Chem. 1999, 578, 155.

(e) With NiCp₂. Reactions of CCo₃clusters with NiCp₂

or {Ni(µ-CO)Cp}₂result in replacement of a Co(CO)₃group

3358 Organometallics, Vol. 27, No. 14, 2008

Bruce et al.

by NiCp.⁴³The reaction between 1 and an equivalent amount

of NiCp₂was carried out in reﬂuxing thf and afforded brown

{Cp*(dppe)Ru}Ct CCt CCt CC{Co₂Ni(µ-dppm)(CO)₄Cp}

(10) in 41% yield. This complex was characterized spectro-

scopically and by a single-crystal XRD study. Terminal +ν(CO)

bands occur in the IR spectrum between 2076 and 1939 cm^-1

,

while in the ES-MS, M⁺and [M + Na]⁺are found at m/z 1456

1

and 1479, respectively. In the H NMR spectrum, Resonances

at δ_H1.57 (RuCp*) and 5.44 (NiCp) and δ_C10.52 and 94.50

(RuCp*) and 90.26 (NiCp) and two singlets at δ_P23.6 (dppm)

and 80.3 (dppe) support the structural assignment. In the ³¹P

NMR spectrum, there is a considerable upﬁeld shift of the dppm

resonance to δ_P23.6 resulting from replacement of the Co(CO)₃

group by NiCp.

Figure1.Projectionofamoleculeof{Cp*(dppe)Ru}(Ct C)₃C{Co₃(µ-

dppm)(CO)₇} (1) in 1 · 2thf. [In this and later ﬁgures, the projections

are normal to the Cp′(Ru) plane.]

(f) With Co₂(CO)₈. Attempted addition of a Co₂(CO)₆

fragment to the C₇chain by reacting 1 with Co₂(CO)₈gave a

dark green-brown solid, which quickly reverted to 1 during

chromatography on silica or alumina or on exposure of solutions

to air. The product is tentatively identiﬁed as the bis-adduct

{Cp*(dppe)Ru}{Ct CC₂[Co₂(CO)₆]C₂[Co₂(CO)₆]C{Co₃(µ-dpp-

m)(CO)₇} (11). Identiﬁcation of 11 rests largely on the ES-MS

([M + Na]⁺at m/z 2071), as the NMR spectra are similar (but

less well resolved) to those of 1 itself. The ³¹P NMR spectrum

contains a doublet at δ 33.8 (dppm) [J(PP) ) 24 Hz] and a

singlet at δ 81.0 (dppe), suggesting that reaction occurred on

C(3)t C(4) and C(5)t C(6). Although a mixture of 1 with Co₂(µ-

dppm)(CO)₆darkened on warming, the only isolable compounds

proved to be 1 and Co₄(µ-dppm)₂(CO)₈.⁴⁴It appears that the

steric environment about the C₇chain in 1 is too demanding to

allow this dicobalt fragment to coordinate and form a stable

complex.

CCt CR)(µ-dppm)(CO)₇(R ) Bu^t, SiMe₃, Fc), the two alkynyl

carbons resonate at δ 101.1, 116.7, 107.95 and 121.95, 126.2,

111.8, respectively, so that resonances listed here in the region

δ 105-110 probably arise from C(6). The remaining resonances

are not easily assigned: in longer carbon chains, the resonances

of the central carbons tend toward δ ca. 60.⁴⁷We note that in

the present compounds resonances in this area are not found

when the carbon chain has entered into reaction, destroying its

poly-yne nature, as in 6-8, so that in 1 and 10 we assign

resonances at δ ca. 50 to C(3). It is expected that the C(5)

resonance would be downﬁeld from C(3) and resonances in 1

and 10 at δ ca. 90 are assigned to this atom. It has not been

possible to assign the remaining resonances deﬁnitively to C(4,

5, 6).

General Comments. (a) ¹³C NMR Spectra of Carbon

Chain Nuclei. Assignment of the resonances of the C₇chain

in 1 and other compounds described herein was made by

comparison with the ¹³C NMR spectra of related compounds

(Table 1). Resonances of the chain carbons in 2 were not found,

due to poor solubility. The resonance of C(7) (numbering from

Ru to Co₃, in accord with the crystallographic numbering

schemes) was often not observed, because of the well-known

broadening of this carbon by the ⁵⁹Co quadrupole.^45,46However,

the spectra of the more soluble compounds 5 and 6 contain broad

resonances at δ 215.1 and 216.6, respectively, which are

assigned to C(7). In 8, two of the three carbyne carbon

resonances, assigned to the CFe₃carbons, are found at δ 252.61

and 273.10.

A peak at δ ca. 150 is present in most compounds, but notably

absent in the spectrum of the methylvinylidene adduct 5, and

is thus assigned to C(1) attached to the Ru center. In its place,

the spectrum of 5 contains the characteristic downﬁeld triplet

at δ 357.39 [J(CP) ) 16 Hz] assigned to RudC(1), together

with the Me resonance at δ 10.15. In related alkynyl-Ru

complexes, atom C(2) affords a resonance at δ ca. 92, and we

assign resonances in this region similarly. The cationic center

in vinylidene complexes results in a downﬁeld shift to δ ca.

100, so that one of the two resonances in this region of the

spectrum of 5 probably arises from C(2). For complexes Co₃(µ₃-

(b) Molecular Structures. The molecular structures of 1, 2,

6-8, and 10 (Figures 1–5) have been determined by XRD

studies, selected bond distances and angles being collected in

Table 2.

For 6: C(3)-C(30) 1.378(9), C(4)-C(40) 1.376(10), C(30)-

C(301, 302) 1.413, 1.427(9), C(40)-C(401, 402) 1.44, 1.42(1),

C-N1.141(9),1.145(9),1.136(12),1.119(12)Å.C(2,4)-C(3)-C(30)

126.4(6), 117.5(6), C(3, 5)-C(4)-C(40) 119.3(7), 121.9(6),

C(n01)-C(n0)-C(n02) 118.5(6), 118.3(7) (n ) 3, 4)°.

For 7: C(3)-C(301) 1.46(2), C(4)-C(8) 1.53(2), C(301)-

C(302,306)1.37(2),1.35(2),C(302)-C(303)1.32(2),C(303)-C(304)

1.42(2), C(304)-C(300, 305) 1.42(2), 1.40(2), C(305)-C(306)

1.42(2) Å; C(2, 4)-C(3)-C(301) 125.7(1), 115.1(1), C(3,

5)-C(4)-C(8) 113.4(1), 118.8(1), C(304)-C(300)-C(307,

308) 123.0(1), 122.2(1), C(307)-C(300)-C(308) 114.1(1)°.

For 8 in 8 · 2C₆H₆: [Read Co(7,5,6) for Co(2,3,4)] Fe(2)-Fe(3,

4) 2.517(1), 2.545(1), Fe(3)-Fe(4) 2.528(1), C(3)-Fe(2, 3, 4)

2.011(5), 1.976(4), 2.010(5), C(4)-Fe(2, 3, 4) 1.944(4), 1.976(5),

1.949(5) Å. C(2)-C(3)-Fe(2, 3, 4) 133.8(3), 134.4(4), 131.0(4),

C(5)-C(4)-Fe(2, 3, 4) 130.2(4), 131.6(4), 133.3(4)°.

For 8 in 8 · CH₂Cl₂: [Read Co(7,5,6) for Co(2,3,4)] Fe(2)-Fe(3,

4) 2.5228(9), 2.5189(9), Fe(3)-Fe(4) 2.5265(10), C(3)-Fe(2,

3, 4) 2.003(4), 1.966(4), 1.986(4), C(4)-Fe(2, 3, 4) 1.952(4),

1.967(4), 1.944(4) Å. C(2)-C(3)-Fe(2, 3, 4) 133.9(3), 132.3(3),

132.1(3), C(5)-C(4)-Fe(2, 3, 4) 129.2(3), 130.2(3), 135.8(3)°.

For 10: [For Co(2), read Ni(2)] Ni-C(cp) 2.093(9)-2.116(8),

av 2.104(9) Å.

(43) (a) Beurich, H.; Blumhofer, R.; Vahrenkamp, H. Chem. Ber. 1982,

115, 2409. (b) Mlekuz, M.; Bougeard, P.; McGlinchey, M. J.; Jaouen, G.

J. Organomet. Chem. 1983, 253, 117.

(44) Bruce, M. I.; Carty, A. J.; Ellis, B. G.; Low, P. J.; Skelton, B. W.;

White, A. H.; Udachin, K. A.; Zaitseva, N. N. Aust. J. Chem. 2001, 54,

277.

{Cp′(dppe)Ru}Ct CCt CCt CC{Co₃(µ-dppm)(CO)₇} (Cp′

)Cp*1,Cp2)and{Cp*(dppe)Ru}Ct CCt CCt CC{Co₂Ni(µ-

dppm)(CO)₄Cp}, 10. Two different solvates of 1, which are

(45) Aime, S.; Milone, L.; Valle, M. Inorg. Chim. Acta 1976, 18, 9.

(46) Yuan, P.; Richmond, M. G.; Schwarz, M. Inorg. Chem. 1990, 29,

679.

(47) Eisler, S.; Slepkov, A. D.; Elliott, E.; Luu, T.; McDonald, R.;

Hegmann, F. A.; Tykwinski, R. R. J. Am. Chem. Soc. 2005, 127, 2666.

Synthesis and Chemistry of a Heterometallic C₇Complex

Organometallics, Vol. 27, No. 14, 2008 3359

not isomorphous, were studied: following an initial determina-

tion on material crystallized from chloroform, yielding a result

of unsatisfactory precision, a more auspicious result was

obtained on crystals of a different solvate, obtained from thf.

A projection of the molecule in the latter is shown in Figure 1.

All compounds but 2 contain the Ru(dppe)Cp* fragment, which

hastheusualpseudo-octahedralgeometry[Ru-P2.260(2)-2.306(1),

Ru-C(cp) 2.227(4)-2.326(14) Å, angles P(1)-Ru-P(2)

79.82(6)-85.0(1), P(1,2)-Ru-C(1) 76.8(2)-90.7(1)°]. In 1 and

2, signiﬁcant differences between the two P(1,2)-Ru-C(1)

angles are found in the CHCl₃solvate of 1 [84.7, 89.2(2)°] and

2 [84.9, 92.4(2)°], while in the thf solvate of 1, these angles

are close, at 84.6, 85.6(1)°. Similar differences have been found

in most of the complexes containing Ru(PR₃)₂Cp′ groups, but

it is not clear whether they arise from a Jahn-Teller effect in

the d⁶center or from steric interactions within the crystal. The

Ru-C(1) separations are experimentally indistinguishable.

At the other end of the carbon chain is the metal cluster,

which is Co₃(µ-dppm)(CO)₇for 1, 2, and 6-8 and Co₂Ni(µ-

dppm)(CO)₄Cp for 10. The geometries of the CCo₃clusters are

similar, the dppm ligand bridging the Co(3)-Co(4) vector.

Bonds to Co are Co-Co 2.461(2)-2.4968(9), Co-P 2.188(2)-

2.241(2) Å; the Co(1,2)-C(7) bonds are shorter [1.889(5)-1.93(1)

Å] than Co(3)-C(7) [1.93(1)-1.977(4) Å], the latter showing

the usual lengthening of this bond involving a Co(CO)₃group.

These values are similar to those found in numerous related

structures.^{18,23a,48–52}In 10 (Figure 3), replacement of a Co(CO)₃

group by NiCp results in formation of two Ni-Co bonds

[2.381(1), 2.397(1) Å], shorter separations reﬂecting the different

radii of the two metal atoms. Similar differences are found in

Co₂Ni(µ₃-CPh)(µ-PPh₂CHdCHPPh₂)(CO)₄Cp [Co-Co 2.464(1),

Figure 2. Projection of a molecule of {Cp*(dppe)Ru}(Ct C)₃-

C{Co₂Ni(µ-dppm)(CO)₄Cp} (10) in 10 · 0.32C₆H₁₄.

Co-Ni

2.364(1),

2.385(1)

Å]⁵³

and

Co₂Ni(µ₃-

CCO₂Me)(CO)₆Cp [Co-Co 2.471(2), Co-Ni 2.380(2) Å].⁵⁴

The Ni-C(cp) distances range between 2.093(9) and 2.116(8)

Å [av 2.104(9) Å], and the Co₂Ni bonds to C(7) [Co(3,4)-C(7)

1.912(6), 1.895(6) Å; Ni(2)-C(7) 1.895(5) Å] are experimen-

tally indistinguishable, as found in the similar diphosphine-

substituted cluster mentioned above.⁵³

The C₇chain is a point of interest in the molecules of 1, 2,

and 10. Separations between atoms C(1)-C(7) show that a

-Ct C-Ct C-Ct C-Ct system is present. There is an

interesting alternation of the Ct C triple bonds [C(1)-C(2)

1.228(8)-1.241(6), C(3)-C(4) 1.21(1)-1.232(7), C(5)-C(6)

1.22(1)-1.226(7) Å], which is accompanied by a similar

lengthening of the C(sp)-C(sp) single bonds [C(2)-C(3)

1.33(1)-1.350(8), C(4)-C(5) 1.350(7)-1.36(1), C(6)-C(7)

1.393(7)-1.40(1) Å], consistent with an alternation in effect

of the ﬁlled Ru-C(1) π-type interaction along the C₇chain from

Ru to Co₃. To our knowledge, the molecular structure of

HCt CCt CCt CH does not appear to have been determined

so far, probably because of its explosive character, but high-

level [CCSD(T)/cc-pVTZ] computational studies have given

values of 1.212, 1.365, and 1.217 Å for the CC separations

Figure 3. Projection of a molecule of {Cp*(dppe)Ru}Ct C{C[dC-

(CN)₂]}₂Ct CC{Co₃(µ-dppm)(CO)₇} (6) in 6 · 2Me₂CO.

(outermost-innermost).⁵⁵Values for closely related compounds

include 1.198, 1.377, 1.208 Å [for (HO)CH₂(Ct C)₃CH₂(OH)],⁵⁶

1.169, 1.397, 1.184 Å [for {(Cy₃P)Au}(Ct C)₃{Au(PCy₃)}],⁵⁷

1.210, 1.383, 1.213 Å [for {Cp(Ph₃P)₂Ru}(Ct C)₃{Ru(PPh₃)₂-

Cp}]⁵⁸and 1.226, 1.345, 1.221, 1.347 Å [for {(OC)₇(µ-

dppm)Co₃}{µ₃-C(Ct C)₄-µ₃-C}{Co₃(µ-dppm)(CO)₇}].^23aThe

respective lengthening and shortening of the Ct C triple and

C-C single bonds suggest a degree of conjugation in the chain.

As shown above, however, this does not signiﬁcantly affect the

reactivity. The C₇chains are not strictly linear, with angles at

(48) Balavoine, G.; Collin, J.; Bonnet, J.-J.; Lavigne, G. J. Organomet.

Chem. 1985, 280, 429.

(49) Downard, A. J.; Robinson, B. H.; Simpson, J. Organomet. Chem.

1993, 447, 281.

(50) Duffy, D. N.; Kassis, M. M.; Rae, A. D. Acta Crystallogr., Sect. C

1991, 47, 2054.

(51) Hong, F. E.; Huang, Y.-L.; Cheng, Y.-C.; Chu, K.-M. Appl.

Organomet. Chem. 2003, 17, 458.

(52) Bruce, M. I.; Kramarczuk, K. A.; Perkins, G. J.; Skelton, B. W.;

White, A. H.; Zaitseva, N. N. J. Cluster Sci. 2004, 15, 119.

(53) Bott, S. G.; Yang, K.; Huang, D.-H.; Richmond, M. G. J. Chem.

Crystallogr. 2004, 34, 883.

(54) Blumhofer, R.; Fischer, K.; Vahrenkamp, H. Chem. Ber. 1986, 119,

194.

(55) Sattelmeyer, K. W.; Stanton, J. F. J. Am. Chem. Soc. 2000, 122,

8220.

(56) Enkelmann, V. Chem. Mater. 1994, 6, 1337.

(57) Lu, W.; Xiang, H.-F.; Zhu, N.; Che, C.-M. Organometallics 2002,

21, 2343.

(58) Bruce, M. I.; Hall, B. C.; Kelly, B. D.; Low, P. J.; Skelton, B. W.;

White, A. H. J. Chem. Soc., Dalton Trans. 1999, 3719.

3360 Organometallics, Vol. 27, No. 14, 2008

Bruce et al.

Figure5.Projectionofamoleculeof{Cp*(dppe)Ru}Ct CC{Fe₃(CO)₉}-

CCt CC{Co₃(µ-dppm)(CO)₇} (8) in 8 · 2C₆H₆.

Figure4.Projectionofamoleculeof{Cp*(dppe)Ru}Ct CC{dC₆H₄dC-

(CN)₂}C{dC(CN)₂}Ct CC{Co₃(µ-dppm)(CO)₇} (7) in 7 · 1.25thf.

{dC(CN)₂}-Ct C-Ct formulation (X ) - 6, C₆H₄7), with

two short and three longer C-C separations, the latter consistent

with C(sp)-C(sp²) (two) and C(sp²)-C(sp²) single bonds. In

6, the two dicyanomethylene groups are doubly bonded to C(3)

and C(4), while for 7, C(3) and C(4) are similarly attached to

dC₆H₄dC(CN)₂and dC(CN)₂groups, respectively. Two Ct C

triple bonds remain, while C(2)-C(3) and C(4)-C(5) are longer

than those in 1 as a result of their being C(sp²)-C(sp) bonds.

The C₇chain is no longer linear, with angles at individual carbon

atoms being between 168.1(7)° and 177.7(6)° for the C(sp)

atoms and 116.1(6)° and 118.8(6)° for C(3, 4), respectively.

The dienes adopt the s-trans conﬁguration found in the majority

of complexes containing this fragment,³¹as shown by the torsion

angles C(30)-C(3)-C(4)-C(40) [-101.5(8)° (6), 106(1)°].

individual carbon atoms ranging between 171.9(7)° and 179.0(9)°

[total bending Σ ) 15.6° (1 · thf), 23.8° (1 · CHCl₃), 27.9° (2),

31.3° (10), although this is not all in the same sense].

{Cp*(dppe)Ru}Ct CC[dXdC(CN)₂]C[dC(CN)₂]Ct C-

C{Co₃(µ-dppm)(CO)₇} (X ) - 6, C₆H₄7). Projections of these

molecules are shown in Figures 4 and 5. It is apparent that the

central C(3)-C(4) triple bond in 1 has formally inserted into

the CdC double bond of the tcne or tcnq molecule to give

tetracyano-diene fragments also attached to the remaining

C(1)-C(2) and C(5)-C(6)-C(7) fragments of the C₇chain.

The bridging ligands have the -Ct C-C{dXdC(CN)₂}-C-

Table 2. Selected Bond Distances and Angles

complex

1 · 2CHCl₃

1 · C₄H₈O

2

6 · 2C₃H₆O

7 · 1.25thf

8 · 2C₆H₆

8 · CH₂Cl₂

10 · 0.32C₆H₁₄

Bond Distances (Å)

2.273(2)

Ru-P(1)

2.260(2)

2.268(2)

2.236(8)-

2.274(7)

2.259(14)

1.971(8)

1.24(1)

1.33(1)

1.21(1)

1.36(1)

1.22(1)

2.263(1)

2.282(1)

2.227(4)-

2.277(5)

2.25(3)

2.270(2)

2.263(2)

2.306(4)

2.301(4)

2.237(14)-

2.326(14)

2.27(3)

1.88(1)

1.23(2)

1.42(2)

1.51(2)

1.48(2)

1.19(2)

1.36(2)

1.93(1)

1.81(1)

2.278(1)

2.296(1)

2.229(5)-

2.272(5)

2.26(2)

1.963(4)

1.251(6)

1.372(6)

2.263(1)

2.295(1)

2.239(4)-

2.266(5)

2.25(2)

1.946(4)

1.231(6)

1.362(6)

2.285(2)

2.283(1)

2.228(5)-

2.268(6)

2.246(15)

1.960(6)

1.239(8)

1.362(8)

1.224(8)

1.357(8)

1.227(8)

1.367(8)

1.895(6)

1.912(5)

1.895(5)

2.381(1)

2.397(1)

2.469(1)

2.214(2)

2.200(2)

Ru-P(2)

2.278(2)

Ru-C(cp)

2.23(1)-

2.272(9)

2.25(2)

2.230(6)-

2.292(6)

2.26(2)

(av.)

Ru-C(1)

1.971(4)

1.241(6)

1.348(7)

1.232(7)

1.350(7)

1.225(7)

1.398(7)

1.977(4)

1.903(4)

1.894(5)

2.4880(8)

2.4740(9)

2.4954(9)

2.208(1)

2.189(1)

1.976(7)

1.228(8)

1.350(8)

1.220(7)

1.356(7)

1.226(7)

1.393(7)

1.950(6)

1.918(5)

1.889(6)

2.469(1)

2.488(1)

2.474(1)

2.203(2)

2.199(2)

1.917(6)

1.238(8)

1.378(9)

1.492(8)

1.403(11)

1.200(11)

1.387(11)

1.936(6)

1.890(8)

1.904(6)

2.472(1)

2.463(1)

2.196(2)

2.188(2)

C(1)-C(2)

C(2)-C(3)

C(3)-C(4)

C(4)-C(5)

C(5)-C(6)

C(6)-C(7)

C(7)-Co(2)

C(7)-Co(3)

C(7)-Co(4)

Co(2)-Co(3)

Co(2)-Co(4)

Co(3)-Co(4)

Co(3)-P(3)

Co(4)-P(4)

1.402(6)

1.220(6)

1.396(6)

1.944(4)

1.895(5)

1.912(5)

2.4968(9)

2.494(1)

2.476(1)

2.199(2)

2.210(2)

1.370(6)

1.218(6)

1.370(6)

1.932(4)

1.897(4)

1.905(4)

2.4715(9)

2.4927(9)

2.4691(9)

2.185(1)

2.206(1)

1.40(1)

1.933(7)

1.898(8)

1.902(7)

2.472(2)

2.461(2)

2.470(2)

2.190(2)

2.188(2)

2.476(2)

2.465(3)

2.489(3)

2.241(4)

2.204(4)

Bond Angles (deg)

79.82(6)

85.7(2)

P(1)-Ru-P(2)

P(1)-Ru-C(1)

P(2)-Ru-C(1)

Ru-C(1)-C(2)

C(1)-C(2)-C(3)

C(2)-C(3)-C(4)

C(3)-C(4)-C(5)

C(4)-C(5)-C(6)

C(5)-C(6)-C(7)

Σ(C_n)

82.15(8)

89.2(2)

84.7(2)

171.9(7)

172.1(9)

179.0(9)

178.1(9)

178.1(8)

177.0(8)

23.8

82.90(4)

84.6(1)

85.6(1)

176.9(4)

176.8(5)

177.8(5)

177.6(5)

177.7(5)

15.6

82.11(7)

84.9(2)

92.4(2)

171.6(7)

173.1(9)

174.4(9)

175.8(8)

178.9(8)

178.3(8)

27.9

85.0(1)

84.0(4)

90.5(1)

176.8(1)

168.0(1)

119.1(1)

127.0(1)

177.6(1)

172.5(1)

82.53(5)

83.9(2)

90.7(1)

172.4(4)

179.5(5)

82.86(4)

82.7(1)

89.9(1)

174.7(4)

175.8(5)

83.89(6)

76.8(2)

89.3(2)

172.6(6)

169.3(8)

175.8(9)

175.6(6)

178.2(6)

177.2(5)

31.3

88.6(2)

174.1(6)

168.1(7)

116.1(6)

118.8(6)

176.4(6)

177.7(6)

176.5(6)

176.4(5)

175.6(5)

177.0(5)

C(6)-C(7)-Co(2)

C(6)-C(7)-Co(3)

C(6)-C(7)-Co(4)

127.1(5)

131.2(6)

136.7(6)

121.5(3)

134.9(3)

137.0(3)

125.2(5)

132.8(5)

136.7(4)

124.5(5)

139.2(5)

130.5(4)

125.5(9)

124.7(1)

140.7(1)

124.8(4)

137.4(4)

131.5(4)

124.9(3)

134.3(3)

134.9(3)

128.3(5)

132.6(5)

136.8(4)

Synthesis and Chemistry of a Heterometallic C₇Complex

Organometallics, Vol. 27, No. 14, 2008 3361

Table 3. Electrochemical Data

compound

{Ru*}(Ct C)₃SiMe₃

{Ru*}(Ct C)₃{Ru*}

{Ru*}(Ct C)₄{Ru*}

{Ru*}(Ct C)₂C{Co₃}

{Ru*}(Ct C)₃C{Co₃}

{Ru*}(Ct C)₄C{Co₃}

{Ru}(Ct C)₃C{Co₃}

{Ru′}(Ct C)₃C{Co₃}

{Ru*}(Ct C)₃C{Co₃(CO)₉}

{Ru*}(Ct C)₃C{Co₃(dppm)(CO)₆(PPh₃)}

{Ru*}(Ct C)₃C{Co₂Ni}

{Ru*}Ct C(tcne)(Ct C)₂C{Co₃}

{Ru*}Ct C(tcnq)(Ct C)₂C{Co₃}

{Ru*}Ct CC{Fe₃(CO)₉}CCt CC{Co₃}

[{Ru*}dCdCMe(Ct C)₂C{Co₃}]OTf

{Co₃}C(Ct C)₃SiMe₃

#

E¹

i_c/i_a

E²

i_c/i_a

E³

i_c/i_a

∆E^2/3

E⁴

i_c/i_a

E⁵

i_c/i_a

+0.41

-0.15

+0.08

-1.33

-1.23

- 1.14

-1.16

-1.33

-0.71

-1.26

-1.14

-1.10

-1.38

-1.13

-0.97

-1.33

-1.26

-1.03

0.4

+0.33

+0.43

+0.12

+0.28

+0.42

+0.22

+0.48

+0.17

+0.32

-0.78

-0.66

+0.38

+0.79

+0.61

-1.11

+0.71

+1.05

+1.07

+0.27

+0.39

+0.51

+1.04

+0.32

+1.16

+1.06

+0.48

+0.78

-0.51

+0.57

480

350

150

110

90

+1.33

+1.27

1

1.0

0.9

+1.13

0.4

2

0.9

0.2

100

3

4

10

6

7

8

5

0.9

0.6

1.0

0.9

1.0

0.9

0.7

0.8

irr.

0.7

890

160

+1.11

+1.16

+0.59

+1.37

0.4

irr.

0.4

0.9

0.6

0.9

+1.16

irr.

0.8

0.3

190

150

{Co₃}C(Ct C)₂C{Co₃}

{Co₃}C(Ct C)₄C{Co₃}

+0.49

Addition of tcne or tcnq to the chain occurs at C(3)-C(4),

as expected on steric grounds. However, unlike related diynyl-

and triynyl-ruthenium complexes, no isomeric products formed

by addition to either of the other Ct C triple bonds were

detected, no doubt as a result of the presence of the bulky Cp*

group. This feature contrasts with addition to the Ct C triple

bonds that are adjacent to either the Ru center^30,31or CCo₃

cluster^23athat has been observed previously.

with Ru(Ct CPh)(dppe)Cp*,⁵⁹or only one quasi-reversible

event, as with Ru{(Ct C)₃SiMe₃}(dppe)Cp*. The cobalt cluster

compounds{(OC)_7-2m(µ-dppm)_mCo₃}C(Ct C)_xC{Co₃(µ-

dppm)_m(CO)_7-2m} (m, x ) 0, 1) have less pronounced electronic

interactions between the capping clusters, each showing two

1-ereductionwaves.^40,41ThecompoundCo₃{µ₃-C(Ct C)₃SiMe₃}(µ-

dppm)(CO)₇displays one 1-e reduction (-1.33 V) and one 1-e

oxidation event (+0.61 V), which is usual for this type of cobalt

cluster.⁶⁰

{Cp*(dppe)Ru}Ct CC{Fe₃(CO)₉}CCt CC{Co₃(µ-dppm)-

(CO)₇} (8). XRD structure determinations were carried out on

benzene and dichloromethane solvates of 8. The latter used

synchrotron radiation, and values for this determination are cited

below (Figure 6). The central C(3)t C(4) triple bond in 1 has

been completely cleaved during the reaction between 1 and

Fe₂(CO)₉, which gives 8. The Ct C triple bonds between

C(1)-C(2) and C(5)-C(6) are preserved, but again are some-

what longer than normal Ct C bonds; C(4)-C(5) and C(6)-C(7)

correspond to C(sp)-C(sp) single bonds. The C(3) · · · C(4)

separation in 8 is 2.666(6) Å, too long for there to be any

residual bonding interaction through the Fe₃cluster, and the

two end groups are sufﬁciently distant from the central Fe₃

cluster to be unaffected by this part of the molecule, so that the

structural parameters are very similar to those of 1. The trigonal

bipyramidal C{Fe₃(CO)₉}C cluster contains an equilateral Fe₃

core [Fe-Fe 2.5189-2.5256(9) Å], with all Fe-C(3,4) bonds

being between 1.944 and 2.003(4) Å. Overall, the structure of

8 is similar to those determined earlier for the related complexes

{L_nM}Ct CC{Fe₃(CO)₉}C(Ct C)_x{ML_n}, values for similar

Fe-C bond lengths being between 1.942(5) and 1.981(8) (ML_n

) Fp*, n ) 1),³⁸1.93(2) and 2.01(3) [ML_n) Ru(dppe)Cp*, x

) 1], and 1.96(1) and 2.00(1) Å [ML_n) Ru(dppe)Cp*, x )

2].³⁹

In contrast, when two dissimilar end groups are present, even

qualitative analysis of the electronic communication is more

complicated than that of the homometallic species. Comparisons

of the heterometallic complexes {L_mM}(Ct C)_x{M′L′_n} with

the two homometallic series {L_mM}(Ct C)_x{ML_m} and

{L′_nM′}(Ct C)_x{M′L′_n} and the monometallic alkynyl deriva-

tives {L_mM}(Ct C)_xR and {L′_nM′}(Ct C)_xR (R ) H, Ph, or

SiR′₃, for example) may be useful in this regard. Table 3

summarizes the redox potentials that have been determined for

the complexes described above, together with other related

materials that contain only one of the redox active groups, such

as Ru{(Ct C)₃SiMe₃}(dppe)Cp* and Co₃{µ₃-C(Ct C)₃SiMe₃}(µ-

dppm)(CO)₇.^18b

The cyclic voltammogram (CV) of 1 (Figure 6) displays four

redox events, one reduction and three oxidation waves, which

might be expected from the presence of two different redox-

active metal centers. The reduction E¹(-1.23 V) was found to

be fully reversible, but the two one-electron oxidations E²

(+0.28 V) and E³(+0.39 V) start to merge, making measures

of i_A/i_Cunreliable. The third oxidation event (E⁴+1.13 V) is

quasi-reversible. Attempts to oxidize 1 to the 1+ and 2+ species

chemically were unsuccessful, presumably due to the inherent

instability of the system.

The trends observed in the parent homometallic series show

that as chain length increases, the electronic interactions between

the two Ru termini decrease and their oxidation potentials get

higher, while the reduction potential becomes lower in the Co₃

cluster series.^7b,23a,39The same changes were also observed with

{Cp*(dppe)Ru}{(Ct C)_x-µ₃-C}{Co₃(µ-dppm)(CO)₇} (x ) 2,

4).^18bEach complex shows four 1-e redox events. In general,

as x increases, the difference between the second and third

potentials (∆E^2/3) decreases until the two events merge for x )

Electrochemistry. The degree of interaction between two

redox-active metal end groups through a bridging unit can be

probed by electrochemical measurements. Where the end groups

are the same or closely related, such as found in the cases of

[Cp′(PP)Ru](Ct C)₂[Ru(PP)Cp′] [PP ) (PPh₃)(PR₃), R ) Me,

Ph; dppm, dppe; Cp′ ) Cp, Cp*],⁷electrochemical studies have

shown up to four 1-e redox events occur, rather than the

intuitively expected two 2-e processes. Computational studies

show that the two HOMOs in the neutral complexes undergo

stepwise losses of one electron at each stage. Related mono-

nuclear ruthenium complexes may display two 1-e events, as

(59) Cordiner, R. L.; Smith, M. E.; Batsanov, A. S.; Albesa-Jove, A. S.;

Hartl, F.; Howard, J. A. K.; Low, P. J. Inorg. Chim. Acta 2006, 359, 946.

(60) Bruce, M. I.; Cole, M. L.; Gaudio, M.; Skelton, B. W.; White,

A. H. J. Organomet. Chem. 2006, 691, 4601.

3362 Organometallics, Vol. 27, No. 14, 2008

Bruce et al.

Synthesis and Chemistry of a Heterometallic C₇Complex

Organometallics, Vol. 27, No. 14, 2008 3363

In complex 8 insertion of the Fe₃(CO)₉moiety in the middle

of the carbon chain appears to have an electron-withdrawing

effect on the molecule as a whole, reduction (E¹-1.13 V) being

slightly easier and oxidation (E²+0.38, E³+0.57 V) being

slightly more difﬁcult when compared to 1, with ∆E^2/3increas-

ing to 190 mV. In other homometallic Fe₃(CO)₉adducts, for

example

{Ru(dppe)Cp*}Ct CC{Fe₃(CO)₉}CCt C{Ru(dppe)Cp*}, the

Fe₃(CO)₉core slightly reduces ∆E^{1/2 39}

.

Although the degree of electronic communication between

the two metal termini in 1 cannot be quantiﬁed, the above results

show that changes in electron density in each of the end groups

and in the C₇chain are reﬂected in the CVs of the various

derivatives. In turn, this suggests that a variable degree of

electronic interaction occurs along the C₇chain. Further

quantiﬁcation of these effects must await more detailed spectro-

electrochemical and computational studies.

Figure 6. Cyclic voltammogram of {Cp*(dppe)Ru}{(Ct C)₃C}-

{Co₃(µ-dppm)(CO)₇} (1).

4. Each added Ct C unit results in an increase in E¹by ca. 100

mV. The variation in redox potential again suggests that two

termini experience a degree of interaction that is attenuated with

increasing chain length.

Conclusions

A variety of synthetic approaches is now available to construct

complexes in which carbon chains of various lengths are end-

capped by various metal-ligand moieties. We have applied

these methodologies to the syntheses of 1, 2, and 3, which

Modiﬁcation of the metal centers has an obvious effect on

the redox potentials of the molecules compared with 1.

Substitution of Cp* with the less electron donating Cp as in 2

and {Cp(PPh₃)₂Ru}(Ct C)₂C{Co₃(µ-dppm)(CO)₇} reduces

∆E^2/3to a point where the two 1-e oxidation waves overlap.

The electron density in the cobalt cluster can be tuned by

substituting electron-withdrawing carbonyl groups by electron-

donating phosphine ligands. When one of the carbonyls on the

cobalt clusters is replaced by triphenylphosphine, as in 4, there

is no signiﬁcant effect on the reduction potential (E¹-1.26, cf.

-1.23 V for 1), but the reversibility of the event is reduced.

However, the increase in electron density in the molecule results

in easier oxidation (E²+0.17 V), but this event is only quasi-

reversible. One further oxidation wave is found at +1.06 V.

Conversely, removal of all the phosphines in 3 has a more

dramatic affect by making the cobalt cluster far easier to reduce

at -0.71 V and harder to oxidize, with two events observed at

+0.48 and +1.11 V.

contain Ru(dppe)Cp′ (Cp′

)

Cp*, Cp) and Co₃(µ-

dppm)_n(CO)_9-2n(n ) 1, 0) end groups linked by C₇chains.

The reactions of 1 with several reagents give products that are

in accord with the normal reactivity of the components of this

complex, such as the formation of a substituted vinylidene

attached to the ruthenium center, addition of tcne, tcnq, or

Fe₃(CO)₉groups to the central Ct C triple bond, or Co

replacement by Ni in the Co₃cluster. This pattern of reactivity

found for 1 suggests that in this complex the C₇chain is long

enough to prevent any signiﬁcant modiﬁcation of the charac-

teristic reactions of one end group by the other. However,

direction of reactions to the central Ct C triple bond of the C₇

chain results from steric effects of the diphosphine ligand,

speciﬁcally the phenyl groups thereof, attached to the metal

centers at each end of the carbon chain.

Experimental Section

Curiously, substitution of the Co(CO)₃metal fragment in 1

with NiCp in 10 did not change the redox potential noticeably.

The second oxidation had a slightly higher potential, marginally

increasing ∆E^2/3by 50 mV to 160 mV. Conversely, reduction

of 10 is easier than 1 by 90 mV.

Changing the nature of the alkynyl bridging unit also alters

the electrochemistry of these molecules. Vinylidene-ruthenium

complexes, such as [Ru(dCdCH₂)(dppe)Cp*]⁺, have one

irreversible process at +1.68 V^7band are harder to oxidize

because the complex has a positive charge. The methylated

compound 5 displays two redox events, an easier 1-e reduction

(-0.97 V) and a more difﬁcult oxidation at +0.79 V, which

has poor reversibility.

General Comments. All reactions were carried out under dry

high-purity nitrogen using standard Schlenk techniques unless

otherwise stated, although normally no special precautions to

exclude air were taken during the subsequent workup. Common

solvents were dried, distilled under nitrogen, and degassed before

use. Separations were carried out by preparative thin-layer chro-

matography (TLC) on glass plates (20 × 20 cm) coated with silica

(Merck 60 GF254, 0.5 mm thick). Flash column chromatography

was performed using silica (Scharlau 60, 0.04-0.06 mm, 230-400

mesh) or basic alumina (Fluka, Brockmann activity II, basic, pH

10 ( 0.5).

Instruments. IR spectra were obtained on a Perkin-Elmer

Spectrum BX FT-IR infrared spectrometer. Spectra in CH₂Cl₂were

obtained using a 0.5 mm path length solution cell with NaCl

windows. Nujol mull spectra were obtained from samples mounted

between NaCl disks. NMR spectra were recorded on a Varian

Gemini 2000 (¹H at 199.98 MHz, ¹³C at 50.29 MHz), Varian

Gemini 3000 (¹H at 300.15 MHz, ¹³C at 75.47 MHz, ³¹P at 121.105

MHz), or Varian Inova 600 spectrometer (¹³C at 150.87 MHz).

Unless otherwise stated, samples were dissolved in CDCl₃or C₆D₆

(Sigma-Aldrich), contained in 5 mm sample tubes. Chemical shifts

The triyne chain is disrupted by formal replacement of one

Ct C fragment by a tetracyanobutadienediyl group in the tcne

and tcnq adducts 6 and 7. The cyanocarbon groups are redox

active, showing 1-e reductions at -0.78 V (6; limited revers-

ibility) and at -0.66, -0.51 V (7; irreversible). The latter result

from partial resolution of the effects of the dC(CN)₂and

dC₆H₄dC(CN)₂groups. Reversible reduction of the Co₃cluster

occurs at -1.10 V (6) and -1.38 V (7). Not surprisingly, the

electron-withdrawing power of the CN groups is also reﬂected

in the two higher irreversible oxidation events at +0.78 and

+1.16 V (6) and +0.59 and +1.16 V (7).

1

are given in ppm relative to internal tetramethylsilane for H and

¹³C NMR spectra and external H₃PO₄for ³¹P NMR spectra.

Electrospray mass spectra (ES-MS) were obtained from samples

3364 Organometallics, Vol. 27, No. 14, 2008

Bruce et al.

dissolved in MeOH unless otherwise indicated. Solutions were

injected into a Varian Platform II spectrometer via a 10 mL injection

loop. Ions listed are the most intense peaks in the isotopic envelope.

Nitrogen was used as the drying and nebulizing gas. Added NaOMe

was used as an aid to ionization.⁶¹

Ru{(Ct C)₃SiMe₃}(dppe)Cp* (338 mg, 0.433 mmol) was added

to the solution and allowed to stir for 15 min. AuCl(PPh₃) (214

mg, 0.433 mmol) was added, and stirring was continued for a further

3 h. The yellow precipitate was collected on a sintered ﬁlter and

washed with MeOH (2 × 5 mL) and hexane (5 mL) to afford

Ru{(Ct C)₃Au(PPh₃)}(dppe)Cp* as a yellow solid (475 mg, 94%).

Anal. Calcd (C₆₀H₅₄AuP₃Ru): C, 61.80; H, 4.67; M, 1166. Found:

C, 61.90; H, 4.59. IR (Nujol, cm^-1): ν(Ct C) 2121m, 2088w,

1965m. ¹H NMR (C₆D₆): δ 1.54 (s, 15H, Cp*), 2.01-2.25,

2.56-2.79 (2 × m, 2 × CH₂), 7.17-7.70 (m, 35H, Ph). ¹³C NMR

(CDCl₃): δ 10.19 (s, C₅Me₅), 28.98-30.05 (m, CH₂) 48.99, 51.19,

64.41, 92.01, 94.15, 154.43 (6 × s, C) 93.79 (s, C₅Me₅),

127.62-138.38 (m, Ph). ³¹P NMR (C₆D₆): δ 80.9 (s, 2P, Ru-dppe),

42.4 (s, 1P, Au-PPh₃). ES-MS (positive ion mode, MeOH-NaOMe,

m/z): 1189, [M + Na]⁺; 721, [Au(PPh₃)₂]⁺; 635, [Ru(dppe)Cp*]⁺.

Electrochemical samples (1 mM) were dissolved in CH₂Cl₂

containing 0.1 M [NBu₄]PF₆as the supporting electrolyte. Cyclic

voltammograms were recorded using a PAR model 263A poten-

tiostat, with a saturated calomel electrode. The cell contained a

Pt-mesh working electrode and Pt wire counter and pseudoreference

electrodes. Potentials are given in V vs SCE, with ferrocene as

internal calibrant (FeCp₂/[FeCp₂]⁺) +0.46 V). Microanalyses were

by CMAS, Belmont, Vic., Australia.

Reagents. The compounds Co₃(µ₃-CBr)(µ-dppm)(CO)₇,⁵²Co₃(µ₃-

CBr)(CO)₉,⁶²Co₃{µ₃-C(Ct C)_xAu(PPh₃)}(µ-dppm)(CO)₇(x ) 1,

2),¹⁸Ru{(Ct C)₂R}(dppe)Cp* [R

)

H, Au(PPh₃)],⁶³

{Cp*(dppe)Ru)}{(Ct C)₃-µ₃-C}{Co₃(µ-dppm)(CO)₇}

(1).

[Ru(dCdCH₂)(dppe)Cp′]PF₆(Cp′ ) Cp, Cp*),⁶⁴AuCl(PPh₃),⁶⁵

[I(py)₂]BF₄,⁶⁶and Pd(PPh₃)₄⁶⁷were prepared by standard literature

procedures. All other reagents were obtained as described below,

or from Sigma-Aldrich or Fluka and used without further puriﬁcation.

Me₃SiCt CI. LiBu (1.6 M solution in hexane, 9.4 mL, 15 mmol)

was added to HCt CSiMe₃(2 mL, 15 mmol) in Et₂O (40 mL) at

-40 °C, and the mixture was stirred for 5 min. A solution of I₂

(ca. 2 g) in Et₂O was added slowly until the brown color persisted,

and the mixture was stirred for a further 10 min before being washed

with aqueous Na₂S₂O₃(4 × 50 mL) and saturated aqueous NaCl

(2 × 50 mL). The organic layer was separated, dried (MgSO₄),

and evaporated (0 °C) in a Al-foil-covered ﬂask to give Me₃SiCt CI

(1.54 g, 46%), identiﬁed by ¹H NMR (CDCl₃) [δ 0.18 (s, 9H,

SiMe₃)] and ¹³C NMR [δ 0.10 (s, SiMe₃), 0.22 (s, Ct CI), 104.41

(s, Ct CSiMe₃)].

Method a. A solution of Ru{(Ct C)₃Au(PPh₃)}(dppe)Cp* (461 mg,

0.395 mmol), Co₃(µ₃-CBr)(µ-dppm)(CO)₇(335 mg, 0.395 mmol),

Pd(PPh₃)₄(40 mg, 0.032 mmol), and CuI (9 mg, 0.051 mmol) in

degassed thf (50 mL) was stirred for 16 h. The solvent was removed

underreducedpressureandpuriﬁedbypreparativeTLC(acetone-hexane,

3:7) to give a brown band (R_f) 0.55), which was further separated

by preparative TLC (CH₂Cl₂-hexane, 1:1) into three bands. The

fastest moving brown band (R_f) 0.60) contained {(CO)₇(µ-

dppm)Co₃}₂{µ₃:µ₃-C(Ct C)₂C} (12 mg, 4%), identiﬁed spectro-

scopically and by XRD (crystals from CH₂Cl₂-hexane). The middle

brown band (R_f) 0.50) afforded {Cp*(dppe)Ru)}{(Ct C)₃-µ₃-

C}{Co₃(µ-dppm)(CO)₇} (1) as a brown solid (196 mg, 34%). The

lower brown band (R_f) 0.40) contained 1 together with AuBr(PPh₃)

[³¹P NMR: δ 35.7 (C₆D₆), 36.4 (CDCl₃)], which was removed by

column chromatography (silica gel, toluene). The ﬁrst fraction

contained 1 (107 mg, 18%; total yield 303 mg, 52%). X-ray quality

crystals were grown from thf-MeOH or CHCl₃-MeOH. Anal.

Calcd (C₇₅H₆₁Co₃O₇P₄Ru): C, 61.03; H, 4.17; M, 1476. Found: C,

61.02; H, 3.98. IR (CH₂Cl₂, cm^-1): ν(CO) 2079w, 2053m, 2008m,

1941m. ¹H NMR (C₆D₆): δ 1.56 (s, 15H, Cp*), 1.75-1.98,

2.69-2.95 (2 × m, 2 × CH₂, dppe), 2.96-3.14, 4.40-4.63 (2 ×

m, CH₂, dppm), 6.70-7.82 (m, 40H, Ph). ¹³C NMR (CDCl₃): δ

9.68 (s, C₅Me₅), 28.88-29.80 (m, CH₂, dppe), 40.32-41.46 (m,

CH₂, dppm) 48.79, 90.70, 91.49, 94.85, 104.01, 151.88 (6 × s, C)

93.83 (s, C₅Me₅), 127.26-137.60 (m, Ph), 201.96 (m, CO). ³¹P

NMR (C₆D₆): δ 33.9 (s, 2P, Co₃-dppm), 80.2 (s, 2P, Ru-dppe).

ES-MS (positive ion mode, MeOH-NaOMe, m/z): 1499, [M +

Na]⁺; 1476, M⁺; 1448, [M - CO]⁺.

Method b. To a solution of [Ru(dCdCH₂)(dppe)Cp*]PF₆(80

mg, 0.10 mmol) in thf (30 mL) at -78 °C was added BuLi (0.08

mL, 2.5 M in hexane, 0.20 mmol), and the mixture was stirred for

30 min. The ﬂask was protected from light with aluminum foil,

solid [I(py)₂]BF₄(38 mg, 0.10 mmol) was then added, and stirring

was continued for a further 1 h. The solution was transferred by

cannula to a foil-wrapped Schlenk ﬂask containing Co₃{µ₃-

C(Ct C)₂Au(PPh₃)}(µ-dppm)(CO)₇(85 mg, 0.066 mmol), Pd-

(PPh₃)₄(10 mg, 0.008 mmol), and CuI (2 mg, 0.01 mmol). The

solution was left to stir at rt for 24 h, and the puriﬁcation protocol

for (a) above was employed to give 1 as a brown solid (25 mg,

26%).

Ru{(Ct C)₃SiMe₃}(dppe)Cp*. A solution of Me₃SiCt CI (268

mg, 1.20 mmol) in degassed thf (25 mL) was added to a Schlenk

ﬂask containing Ru{(Ct C)₂Au(PPh₃)}(dppe)Cp* (660 mg, 0.577

mmol), Pd(PPh₃)₄(20 mg, 0.017 mmol), and CuI (6.4 mg, 0.034

mmol), and the solution was stirred for 16 h at rt. The solvent was

removed under reduced pressure, and the resulting residue was taken

up in the minimum amount of triethylamine and puriﬁed by

chromatography (basic alumina, hexane-triethylamine, 4:1). Sol-

vent was removed from the ﬁrst yellow fraction product to afford

Ru{(Ct C)₃SiMe₃}(dppe)Cp* as a yellow solid (376 mg, 83%).

Anal. Calcd (C₄₅H₄₈P₂RuSi): C, 69.21; H, 6.20; M, 781. Found: C,

69.28; H, 6.31. IR (Nujol, cm^-1): ν(Ct C) 2110s, 1971s. ¹H NMR

(C₆D₆): δ 0.11 (s, 9H, SiMe₃), 1.50 (s, 15H, Cp*), 1.63-1.85,

2.30-2.51 (2 × m, 2 × CH₂), 7.00-7.24, 7.70-7.76 (2 × m, 20H,

Ph). ¹³C NMR (C₆D₆): δ 0.21 (s, SiMe₃), 10.05 (s, C₅Me₅),

28.78-29.94 (m, CH₂), 49.43, 69.79, 77.93, 92.19, 94.09 (5 × s,

2

C), 93.90 [t, J(CP) 2.0 Hz, C₅Me₅], 137.58 [t, J(CP) ) 23 Hz,

C(1)], 128.29-138.38 (m, Ph). ³¹P NMR (C₆D₆): δ 80.4 (s, Ru-

dppe). ES-MS (positive ion mode, MeOH, m/z): 781, M⁺; 635,

[Ru(dppe)Cp*]⁺.

Ru{(Ct C)₃Au(PPh₃)}(dppe)Cp*. A methanolic solution of

NaOMe was prepared by the addition of Na (20 mg, 0.87 mmol)

to degassed MeOH (10 mL). Once the effervescence had ceased,

(61) Henderson, W.; McIndoe, J. S.; Nicholson, B. K.; Dyson, P. J.

J. Chem. Soc., Dalton Trans. 1998, 519.

Method c (i). To a solution of Ru{(Ct C)₂H}(dppe)Cp* (231

mg, 0.305 mmol) in thf (25 mL) at -78 °C was added BuLi (0.12

mL, 2.5 M in hexane, 0.305 mmol), and the mixture was stirred

for 30 min. The ﬂask was protected from light with aluminum foil,

solid [I(py)₂]BF₄(113 mg, 0.305 mmol) was added, and stirring

was continued for a further 1 h. The solution was transferred by

cannula to a foil-wrapped Schlenk ﬂask containing Co₃{µ₃-

CCt CAu(PPh₃)}(µ-dppm)(CO)₇(301 mg, 0.240 mmol), Pd(PPh₃)₄

(30 mg, 0.024 mmol), and CuI (4 mg, 0.022 mmol). The solution

was left to stir at rt for 24 h, and the puriﬁcation protocol for (a)

above was employed to afford 1 as a brown solid (202 mg, 57%).

(62) Ercoli, R.; Santambrogio, E.; Casagrande, G. Chim. Ind. (Milan)

1962, 44, 1344.

(63) Bruce, M. I.; Ellis, B. G.; Gaudio, M.; Lapinte, C.; Melino, G.;

Paul, F.; Skelton, B. W.; Smith, M. E.; Toupet, L.; White, A. H. Dalton

Trans. 2004, 1601.

(64) Bruce, M. I.; Costuas, K.; Ellis, B. G.; Halet, J.-F.; Low, P. J.;

Moubaraki, B.; Murray, K. S.; Oudda¨ı, N.; Perkins, G. J.; Skelton, B. W.;

White, A. H. Organometallics 2007, 26, 3735.

(65) Bruce, M. I.; Nicholson, B. K.; bin Shawkataly, O. Inorg. Synth.

1989, 26, 324.

(66) Barluenga, J.; Rodriguez, M. A.; Campos, P. J. J. Org. Chem. 1990,

55, 3104.

(67) Coulson, D. R. Inorg. Synth. 1990, 28, 107.

Synthesis and Chemistry of a Heterometallic C₇Complex

Organometallics, Vol. 27, No. 14, 2008 3365

Method c (ii). To a solution of Ru{(Ct C)₂SiMe₃}(dppe)Cp*

(90 mg, 0.120 mmol) in thf (25 mL) at -78 °C was added LiMe

(0.08 mL, 1.5 M in diethyl ether, 0.120 mmol), and the mixture

was stirred for 1 h. The ﬂask was protected from light with

aluminum foil, and solid [I(py)₂]BF₄(44 mg, 0.120 mmol) was

added. Stirring was continued for a further 1 h, and the solution

was transferred by cannula to a light-protected Schlenk ﬂask

containing Co₃{µ₃-CCt CAu(PPh₃)}(µ-dppm)(CO)₇(100 mg, 0.080

mmol), Pd(PPh₃)₄(20 mg, 0.016 mmol), and CuI (4 mg, 0.022

mmol). The solution was left to stir at rt for 24 h, and the

puriﬁcation protocol for (a) above was employed to afford 1 as a

brown solid (12 mg, 10%).

) 39 Hz, 2P, Co₃-dppm], 48.4 (br, 1P, Co₃-PPh₃), 80.5 (s, 2P, Ru-

dppe). ES-MS (positive ion mode, MeOH-NaOMe, m/z): 1733,

[M + Na]⁺.

Alternatively, a stirred solution of 1 (32 mg, 0.022 mmol)

and PPh₃(11 mg, 0.041 mmol) in thf (15 mL) was heated at

reﬂux for 3 h. Solvent was removed under reduced pressure and

the crude material puriﬁed by preparative TLC (acetone-hexane,

3:7, R_f) 0.45). The reaction gave {Cp*(dppe)Ru)}{(Ct C)₃-

µ₃-C}{Co₃(µ-dppm)(PPh₃)(CO)₆} as a brown-black solid (31 mg,

84%).

(b) With methyl triﬂate. A stirred solution of 1 (100 mg,

0.0678 mmol) in CH₂Cl₂(10 mL) was cooled to -78 °C and

treated with MeOTf (11.1 mg, 0.068 mmol). After 90 min, the

solution was allowed to warm to rt. After 5 days, the reaction

mixture was run through a squat silica column, ﬁrst eluting with

acetone-hexane (1:4) to recover 1 (47 mg) and then with

acetone-hexane (4:1) to give [{Cp*(dppe)Ru)}CdCMe(Ct C)₂C-

{Co₃(µ-dppm)(CO)₇}]OTf (5) as a brown solid (37 mg, 63%

conversion). Anal. Calcd (C₇₇H₆₄Co₃O₁₀P₄RuF₃S): C, 56.39; H,

3.93; M (cation), 1491. Found: C, 56.22; H, 4.03. IR (CH₂Cl₂,

cm^-1): +ν(CO) 2060m, 2010s, ν(CdC) 1603w, 1435w. ¹H

NMR (d₆-acetone): δ 1.28 (s, 3H, Me) 1.83 (s, 15H, Cp*), 2.53,

3.10 (2 × m, 2 × CH₂, dppe), 4.17, 4.63 (2 × m, CH₂, dppm),

7.21-7.74 (m, 40H, Ph). ¹³C NMR (d₆-acetone): δ 10.15 (s,

Me) 10.52 (s, C₅Me₅), 44.96 (m, dppm), 81.51, 91.04, 97.32,

107.56, 109.04 (5 × s, C), 105.24 (s, C₅Me₅), 128.70-135.85

Extra care to exclude air, moisture, and light from reaction mixtures

involving Ru{(Ct C)_nI}(dppe)Cp′ (where n ) 1 or 2 and Cp′ ) Cp*

or Cp) was necessary, due to the sensitivity of these compounds.

{Cp(dppe)Ru)}{(Ct C)₃-µ₃-C}{Co₃(µ-dppm)(CO)₇} (2). As in

(b) above, the reaction between [Ru(dCdCH₂)(dppe)Cp]PF₆(81

mg, 0.11 mmol), BuLi (0.09 mL, 2.5 M in hexane, 0.22 mmol),

[I(py)₂]BF₄(41 mg, 0.11 mmol), Co₃{µ₃-C(Ct C)₂Au(PPh₃)}(µ-

dppm)(CO)₇(93 mg, 0.07 mmol), Pd(PPh₃)₄(10 mg, 0.008 mmol),

and CuI (2 mg, 0.01 mmol) gave a brown residue, which was

puriﬁed by preparative TLC (acetone-hexane, 3:7, R_f) 0.5 and

CH₂Cl₂-hexane, 1:1, R_f) 0.4) to give {Cp(dppe)Ru)}{(Ct C)₃-

µ₃-C}{Co₃(µ-dppm)(CO)₇} (2) as a dark brown solid (27 mg, 26%).

X-ray quality crystals were obtained from CH₂Cl₂-hexane. Anal.

Calcd (C₇₀H₅₁Co₃O₇P₄Ru): C, 59.80; H, 3.66; M, 1406. Found: C,

59.75; H, 3.65. IR (CH₂Cl₂): ν(CO) 2084w, 2054s, 2007s, 1950m

2

(m, Ph), 203.16 (br, CO), 215.09 (br, CCo₃), 357.39 [t, J(CP)

cm^-1

.

¹H NMR (C₆D₆): δ 1.98-2.26, 2.50-2.74 (2 × m, 2 ×

) 16 Hz, RudC]. ³¹P NMR (d₆-acetone): δ 34.9 (s, 2P, Co₃-

dppm), 74.0 (s, 2P, Ru-dppe). ES-MS (positive ion mode, MeOH,

m/z): 1491, M⁺; 663, [Ru(CO)(dppe)Cp*]⁺.

CH₂, dppe), 3.17, 4.51 (2 × m, CH₂, dppm), 4.18 (s, 5H, Cp),

6.86-8.04 (m, 40H, Ph). ¹³C NMR (C₆D₆): δ 27.47-31.34 (m,

dppe), 40.13-40.77 (m, dppm), 83.40 (s, Cp), 126.98-137.84 (m,

Ph). ³¹P NMR (C₆D₆): δ 34.0 (s, 2P, Co₃-dppm), 85.1 (s, 2P, Ru-

dppe). ES-MS (positive ion mode, MeOH-NaOMe, m/z): 1429,

[M + Na]⁺; 1406, M⁺.

(c) With tcne. C₂(CN)₄(5 mg, 0.034 mmol) was added to a

stirred solution of 1 (50 mg, 0.034 mmol) in CH₂Cl₂(15 mL). After

30 s the solution turned from dark brown to purple, and after 5

min the solution was black. After 30 min solvent was removed

under reduced pressure and the black residue was puriﬁed by

{Cp*(dppe)Ru)}{(Ct C)₃-µ₃-C}{Co₃(CO)₉} (3). Tetrahydrofu-

ran (20 mL) was added to

a Schlenk ﬂask containing

preparative

TLC

(CH₂Cl₂,

R_f

)

0.6),

to

give

Ru{(Ct C)₃Au(PPh₃)}(dppe)Cp* (21 mg, 0.018 mmol), Co₃(µ₃-

CBr)(CO)₉(10 mg, 0.018 mmol), Pd(PPh₃)₄(5 mg, 0.004 mmol),

and CuI (2 mg, 0.01 mmol). After 40 min the solvent was removed

under reduced pressure and the residue puriﬁed by preparative TLC

(acetone-hexane,3:7,R_f)0.75),whichgave{Cp*(dppe)Ru)}{(Ct C)₃-

µ₃-C}{Co₃(CO)₉} (3) as a dark maroon solid (15 mg, 48%). IR

{Cp*(dppe)Ru)}Ct CC[dC(CN)₂]C[dC(CN)₂]Ct C-µ₃-C{Co₃(µ-

dppm)(CO)₇} (6) as a black solid (42 mg, 77%). X-ray quality

crystals were obtained from acetone-hexane. Anal. Calcd

(C₈₁H₆₁Co₃N₄O₇P₄Ru): C, 60.65; H, 3.83; N, 3.49; M, 1604. Found:

C, 60.61; H, 3.89; N, 3.48. IR (CH₂Cl₂, cm^-1): ν(CN) 2210w,

+ν(CO) 2077m, 2043s, 2025s, 1962s, ν(CdC) 1507w, 1464w,

1436w. ¹H NMR (C₆D₆): δ 1.56 (s, 15H, Cp*), 1.97-2.21,

2.53-2.78 (2 × m, 2 × CH₂, dppe), 4.25-4.39, 4.40-4.62 (2 ×

m, CH₂, dppm), 6.66-7.88 (m, 40H, Ph). ¹³C NMR (C₆D₆): δ 9.91

(C₅Me₅), 29.31-30.12 (m, dppe), 40.13-40.77 (m, dppm), 75.43,

83.65, 105.56, 139.21, 142.90, 151.03 (6 × s, C), 96.87 (s, C₅Me₅),

113.63, 113.90, 116.64, 116.83 (4 × s, CN) 127.63-134.25 (m,

Ph), 201.82 (m, CO), 216.58 (m, CCo₃). ³¹P NMR (C₆D₆): δ 34.5,

35.3 [AB q, J(PP) ) 47 Hz, 2P, Co₃-dppm], 80.0, 80.3 [AB q,

J(PP) ) 10 Hz, 2P, Ru-dppe]. ES-MS (positive ion mode,

MeOH-NaOMe, m/z): 1627, [M + Na]⁺; 1604, M⁺.

1

(CH₂Cl₂, cm^-1): ν(CO) 2075w, 2052s, 1967w, 1922m. H NMR

(CDCl₃): δ 1.56 (s, 15H, Cp*), 1.76, 2.40 (2 × m, 2 × CH₂, dppe),

7.02-7.74 (m, 20H, Ph). ¹³C NMR (C₆D₆): δ 10.51 (C₅Me₅),

29.66-30.60 (m, dppe), 94.82 (s, C₅Me₅), 127.06-134.02 (m, Ph),

200.58 (m, CO). ³¹P NMR (CDCl₃): δ 79.7 [s, 2P, Ru(dppe)]. ES-

MS (negative ion mode, MeOH-NaOMe, m/z): 1179, [M + OMe]^-

(calcd M, 1148). Consistent microanalytical data could not be

obtained for 3.

Reactions of {Cp*(dppe)Ru)}(Ct C)₃C{Co₃(µ-dppm)(CO)₇}

(1).

(d) With tcnq. To a stirred solution of 1 (40 mg, 0.027 mmol)

in CH₂Cl₂(15 mL) was added tcnq (6 mg, 0.030 mmol). After 5

min the solution turned from dark brown to dark green and after

15 min was dark blue. After 75 min the solvent was removed under

reduced pressure and the blue residue was taken up in CH₂Cl₂and

loaded onto a silica column (10 cm). It was ﬁrst eluted with CH₂Cl₂

to remove a yellow impurity and then with acetone-hexane (3:7)

togiveabluefractioncontaining{Cp*(dppe)Ru}Ct CC[dC₆H₄dC(CN)₂]-

C[dC(CN)₂]Ct CC-µ₃}{Co₃(µ-dppm)(CO)₇} (7), obtained as a dark

blue solid (39 mg, 86%). X-ray quality crystals were obtained from

thf-MeOH. Anal. Calcd (C₈₇H₆₅Co₃N₄O₇P₄Ru.1.5CH₂Cl₂): C,

59.08; H, 3.66; N, 2.81; M, 1680. Found: C, 58.80; H, 3.79; N.

2.81. IR (cm^-1, CH₂Cl₂): ν(CN) 2193w, ν(CO) 2076w, 2044s,

(a) With triphenylphosphine and TMNO. To a stirred solution

of 1 (50 mg, 0.034 mmol) and PPh₃(9 mg, 0.034 mmol) in thf (20

mL) was added TMNO (3 mg, 0.034 mmol). After stirring for 1 h

at rt, the reaction mixture was heated at reﬂux for 16 h. Solvent

was removed under reduced pressure, and the crude material was

puriﬁed by preparative TLC (acetone-hexane, 3:7; R_f) 0.45) to

give {Cp*(dppe)Ru)}(Ct C)₃-µ₃-C{Co₃(µ-dppm)(PPh₃)(CO)₆} (4)

as

a

brown-black solid (24 mg, 41%). Anal. Calcd

(C₉₂H₇₆Co₃O₆P₅Ru): C, 64.61; H, 4.48; M, 1710. Found: C, 64.73;

H, 4.54. IR (CH₂Cl₂, cm^-1): +ν(CO) 2078w, 2020m, 1988m,

1968w, 1945m. ¹H NMR (CDCl₃): δ 1.64 (s, 15H, Cp*), 2.12-2.38,

2.69-2.95 (2 × m, 2 × CH₂, dppe), 3.21-3.42, 4.40-4.63 (2 ×

m, CH₂, dppm), 7.11-7.82 (m, 55H, Ph). ¹³C NMR (CDCl₃): δ

10.34 (C₅Me₅), 29.54 (br, dppe), 94.27 (s, C₅Me₅), 127.94-137.58

(m, Ph), 202.23 (m, CO). ³¹P NMR (CDCl₃): δ 33.6 [br d, J(PP)

1

2018vs, 1949br m, ν(CdC) 1585br m, 1369br m cm^-1. H NMR

(C₆D₆): δ 1.43 (s, 15H, Cp*), 1.95-2.19, 2.59-2.81 (2 × m, 2 ×

3366 Organometallics, Vol. 27, No. 14, 2008

Bruce et al.

CH₂, dppe), 3.23-3.37, 4.11-4.26 (2 × m, CH₂, dppm), 4.28 (s,

3H, CH₂Cl₂), 6.18, 6.21 (2 × s, dCH), 6.63-7.61 (m, 44H, Ph).

¹³C NMR (C₆D₆): δ 10.01 (C₅Me₅), 28.95-30.09 (m, PCH₂CH₂P),

39.88-40.50 (m, PCH₂P), 53.33 (s, CH₂Cl₂), 63.24, 82.70, 108.56,

154.39, 155.33 (5 × s, C), 96.62 (s, C₅Me₅), 114.24, 115.44, 117.92,

118.12 (4 × s, CN) 122.33-141.10 (m, Ph), 201.62 (2 × m, CO).

³¹P NMR (C₆D₆): δ 33.3 [br s, 2P, dppm], 79.6 [br d, J(PP) ) 369

Hz, 2P, dppe]. ES-MS (positive ion mode, MeOH-NaOMe, m/z):

1703, [M + Na]⁺; 1680, M⁺.

(e) With Fe₂(CO)₉. Solvent (thf or benzene) was added to a

ﬂask containing Fe₂(CO)₉(about 10 equiv) and {Cp*(dppe)Ru)}-

(Ct C)₃C{Co₃(µ-dppm)(CO)₇}, and the mixture was stirred for the

appropriate period. The solution was then ﬁltered though a short

column of ﬂash silica, and the crude mixture was puriﬁed by

preparative TLC (acetone-hexane, 3:7).

(g) With Co₂(CO)₈. To a mixture of 1 (40 mg, 0.027 mmol)

and Co₂(CO)₈(27 mg, 0.081 mmol) was added thf (10 mL), and

the solution was stirred for 20 min. Hexane (30 mL) was then added,

and the solution was loaded onto a silica column and eluted with

acetone-hexane (1:4). The ﬁrst fraction contained unreacted

Co₂(CO)₈. The second fraction contained the bis-Co₂(CO)₆adduct

{Cp*(dppe)Ru}{Ct CC₂[Co₂(CO)₆]C₂[Co₂(CO)₆]-µ₃-C{Co₃(µ-dpp-

m)(CO)₇} (11) (46 mg, 93%) as a dark brown-green solid. M )

2048. IR (CH₂Cl₂, cm^-1): ν(CO) 2077w, 2055s, 2045m, 2009s,

1991 (sh), 1962 (sh). ¹H NMR (C₆D₆): δ 1.64 (s, 15H, Cp*), 2.14,

2.85 (2 × m, 2 × 2H, CH₂of dppe), 3.12, 4.41 (2 × 1H, CH₂of

dppm), 6.68-8.15 (m, 55H, Ph). ¹³C NMR (C₆D₆): δ 10.63

(C₅Me₅), 94.65 (s, C₅Me₅), 126.0-135.0 (m, Ph). ³¹P NMR (C₆D₆):

δ 33.8 [br d, J(PP) ) 24 Hz, 2P], Co₃-dppm], 81.0 (s, 2P, Ru-

dppe). ES-MS (positive ion mode, MeOH-NaOMe, m/z): 2071,

[M + Na]⁺. The complex reverts to 1 if left on silica, on alumina,

or in solution in air for more than a day.

Structure Determinations. Full spheres of CCD area-detector

diffraction data were measured. N_totreﬂections were merged to

N unique (R_intcited) after “empirical”/multiscan absorption

correction (proprietary software), N_owith F > 4σ(F) considered

“observed”, with all data being used in the full matrix least-

squares reﬁnements on F². All data were measured using

monochromatic Mo KR radiation, λ ) 0.71073 Å. Anisotropic

displacement parameter forms were reﬁned for the non-hydrogen

The mixture in thf was heated to reﬂux for 80 min, the solution

turning from brown to dark green-brown. At this point, spot TLC

revealed that the starting material had been consumed. Puriﬁcation

by preparative TLC gave purple {Cp*(dppe)Ru)}Ct CC{Fe₃(CO)₉}-

CCt CC{Co₃(µ-dppm)(CO)₇} (8) (12 mg, 9%) and green-brown

{Cp*(dppe)Ru)}(Ct C)₃C{Co₃(µ-dppm)(CO)₇}{Fe₂(CO)₆} (9) (25

mg, 21%). Similar reactions carried out (a) at rt in thf for 5 h

afforded 8 (24%) and 9 (13%); (b) at rt in benzene for 3 h gave 8

(28 mg, 29%) and an unidentiﬁed ochre compound (8 mg).

{Cp*(dppe)Ru)}Ct CC{Fe₃(CO)₉}CCt CC{Co₃(µ-dppm-

)(CO)₇} (8). X-ray quality crystals were obtained from

C₆D₆-MeOH. Anal. Calcd (C₈₄H₆₁Co₃Fe₃O₁₆P₄Ru): C, 53.22; H,

3.24; M, 1896. Found: C, 53.30; H, 3.19. IR (CH₂Cl₂, cm^-1): ν(CO)

atoms, (x, y, z, U_iso

) being included, constrained at estimates.

H

Residuals R, R_won |F²| are quoted [weights: (σ2(F²) + n_wF²)^-1].

Neutral atom complex scattering factors were used; computation

used the XTAL 3.7⁶⁸or SHELXL 97⁶⁹program systems.

Pertinent results are given in the ﬁgures (which show non-

hydrogen atoms with 50% probability amplitude displacement

ellipsoids and hydrogen atoms with arbitrary radii of 0.1 Å) and

in Tables 2 and 4.

1

2069w, 2052m, 2031s, 1999m, 1913m. H NMR (C₆D₆): δ 1.63

(s, 15H, Cp*), 1.84-2.02, 2.59-2.77 (2 × m, 2 × CH₂, dppe),

3.15-3.22, 4.60-4.66 (2 × m, CH₂, dppm), 7.08-7.76 (m, 40H,

Ph). ¹³C NMR (C₆D₆): δ 11.05 (s, C₅Me₅), 29.91-30.96 (m, dppe),

38.70-39.96 (m, dppm) 80.50, 92.90, 114.09, 154.78 (4 × s, C),

96.36 (s, C₅Me₅), 126.78-142.02 (m, Ph), 203.18 (br, Co-CO),

211.95 (s, Fe-CO), 252.61, 273.10 (2 × s, CFe₃). ³¹P NMR (C₆D₆):

δ 35.2 (s, 2P, Co₃-dppm), 78.5 (s, 2P, Ru-dppe). ES-MS (positive

ion mode, MeOH-NaOMe, m/z): 1918, [M + Na]⁺; 1896, M⁺.

Variata. 1 · 2CHCl₃. One of the two solvent molecules was

modeled as rotationally disordered about the C-H bond, site

occupancies of the two sets of Cl₃components each being set at

0.5 after trial reﬁnement.

2. Phenyl ring 42 was modeled as disordered over two sets of

sites, occupancies set at 0.5 after trial reﬁnement.

{Cp*(dppe)Ru)}(Ct C)₃C{Co₃(µ-dppm)(CO)₇}{Fe₂(CO)₆} (9).

Anal. Calcd (C₈₁H₆₁Co₃Fe₂O₁₃P₄Ru.CH₂Cl₂): C, 53.50; H, 3.45; M,

1756. Found: C, 53.27; H, 4.05. IR (CH₂Cl₂, cm^-1): ν(CO) 2070w,

7 · 1.25C₄H₈O. Diffraction data were very weak, supporting

meaningful anisotropic displacement parameter reﬁnement only for

Ru, Co, and P. One of the thf solvent molecules, disposed on a

crystallographic 2-axis, was assigned site occupancy 0.5 after trial

reﬁnement; geometries of both thf components were constrained.

1

2042s, 2029m, 2011m, 1995s. H NMR (C₆D₆): δ 1.64 (s, 15H,

Cp*), 1.96-2.07, 2.68-2.85 (2 × m, 2 × CH₂, dppe), 3.08-3.15,

3.40-4.46 (2 × m, CH₂, dppm), 4.28 (s, 2H, CH₂Cl₂), 6.92-7.84

(m, 40H, Ph). ³¹P NMR (C₆D₆): major isomer (65%) δ 48.2 [br d,

J(PP) ) 121 Hz, Co₃-dppm], 81.0, 81,2 [AB quartet, J(PP) ) 23

Hz, Ru-dppe]; minor isomer (35%) 54.0 [br d, J(PP) ) 145 Hz,

Co₃-dppm], 80.2, 82.5 [AB quartet, J(PP) ) 283 Hz, Ru-dppe].

ES-MS (positive ion mode, MeOH-NaOMe, m/z): 1779, [M +

Na]⁺; 1756, M⁺.

8 · 2C₆H₆. Phenyl rings 51, 52, 61, and 62 and solvate benzene

30 were modeled as partly or fully disordered over two sets of

sites, occupancies set at 0.5 after trial reﬁnement.

8 · CH₂Cl₂. This determination was carried out using a synchro-

tron (Sector 15 of the Advanced Photon Source at the Argonne

National Laboratory, Argonne, IL). Full spheres of diffraction data

were measured at ca. 103 K with synchrotron radiation, λ ) 0.48595

Å.

(f) With NiCp₂. A mixture of 1 (50 mg, 0.034 mmol) and NiCp₂

(14 mg, 0.075 mmol) was stirred in thf (20 mL) at rt for 1 h and

at reﬂux for 16 h. Solvent was removed under reduced pressure

and the residue was puriﬁed by preparative TLC (acetone-hexane,

10 · 0.32C₆H₁₄. The (centrosymmetric) solvent residues were

modeled in terms of C₆H₁₄, site occupancies reﬁning to 0.650(18).

3:7)

to

give

{Cp*(dppe)Ru}Ct CCt CCt CC{Co₂Ni(µ-

dppm)(CO)₄Cp} (10) (24 mg, 41%) as a brown solid. Crystals

suitable for X-ray diffraction were grown from acetone-hexane.

Anal. Calcd (C₇₇H₆₆Co₂NiO₄P₄Ru): C, 63.48; H, 4.57; M, 1456.

Found: C, 63.10; H, 4.37. IR (CH₂Cl₂, cm^-1): ν(CO) 2076w,

2005w, 1983m, 1960 (sh), 1939m. ¹H NMR (C₆D₆): δ 1.57 (s, 15H,

Cp*), 2.03, 2.74 (2 × m, 2 × CH₂, dppe), 3.09, 4.25 (2 × m, CH₂,

dppm), 5.44 (s, 5H, Ni-Cp) 6.95-8.07 (m, 40H, Ph). ¹³C NMR

(C₆D₆): δ 10.52 (s, C₅Me₅), 28.82-29.60 (m, dppe), 42.29 (m,

dppm), 51.50, 91.85, 92.33, 93.27, 107.50, 151.78 (6 × s, C), 90.26

(s, Cp), 94.50 (s, C₅Me₅), 126.99-138.08 (m, Ph), 203.57 (m, Co-

CO). ³¹P NMR (C₆D₆): δ 23.6 (s, 2P, Co₃-dppm), 80.3 (s, 2P, Ru-

dppe). ES-MS (positive ion mode, MeOH-NaOMe, m/z): 1479,

[M + Na]⁺; 1456, M⁺.

Full details of the structure determinations (except structure

factors) have been deposited with the Cambridge Crystal-

lographic Data Centre as CCDC 617992-617997 and 637521.

Copies of this information may be obtained free of charge from

The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,

UK (fax: + 44 1223 336 033; e-mail: deposit@ccdc.cam.ac.uk

or www: http://www.ccdc.cam.ac.uk).

(68) Hall, S. R., du Boulay, D. J., Olthof-Hazekamp, R., Eds. The XTAL

3.7 System; University of Western Australia, 2000.

(69) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure

Determination, Universita¨t Go¨ttingen: Go¨ttingen, 1997.

Synthesis and Chemistry of a Heterometallic C₇Complex

Organometallics, Vol. 27, No. 14, 2008 3367

Acknowledgment. We thank Dr. Maryka Gaudio for

CARS Sector 15 is also supported by the National Science

Foundation/Department of Energy under Grant Nos. CHE95-

22232 and CHE0087817 and by the Illinois Board of Higher

Education. The Advanced Photon Source is supported by

the U.S. Department of Energy, Basic Energy Sciences,

Ofﬁce of Science, under Contract No. W-31-109-Eng-38.

assistance

with

the

synthesis

of

compound

Ru{(Ct C)₃SiMe₃}(dppe)Cp* and Professor Brian Nicholson

(University of Waikato, Hamilton, New Zealand) for provid-

ing the mass spectra. We gratefully acknowledge support of

this work by the ARC and by Johnson Matthey plc, Reading,

with a generous loan of RuCl₃· nH₂O. Use of the Chem-

MatCARS Sector 15 at the Advanced Photon Source was

supported by the Australian Synchrotron Research Program,

which is funded by the Commonwealth of Australia under

the Major National Research Facilities Program. ChemMat-

Supporting Information Available: This material is available

free of charge via the Internet at http://pubs.acs.org.

OM7010968

Article Doi

Synthesis and some reactions of the heterometallic C7 complex {Cp*(dppe)Ru}C≡CC≡CC≡CC{Co3(μ-dppm)(CO) 7}

DOI: 10.1021/om7010968

Source and publish data:

Authors:

Article abstract of DOI:10.1021/om7010968

Full text of DOI:10.1021/om7010968

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