Selective ligand modification on the periphery of diruthenium compounds: Toward new metal-alkynyl scaffolds

Article abstract of DOI:10.1021/om050068t

Diruthenium compounds Ru₂(DmAniF)₃(OAc)Cl (1, DmAniF is N,N′-di(m-methoxyphenyl)-formamidinate) and cis-Ru₂(DmAniF) ₂(OAc)₂Cl (6) reacted with N,N′-dimethyl-4-iodobenz- amidine (HDMBA-I) to furnish new compounds Ru₂(DmAniF) ₃(DMBA-I)Cl (2) and cis-Ru₂(DmAniF)₂(DMBA-I) ₂Cl (7), respectively. Both compounds 2 and 7 were modified with a terminal alkyne under Sonogashira conditions. Examples reported include 2 cross-coupled with HC≡CSiⁱPr₃ or HC≡CFc to yield Ru₂(DmAniF)₃(DMBA-4-C₂Si ⁱPr₃)Cl (3a) or Ru₂-(DmAniF) ₃(DMBA-4-C₂Fc)Cl (3b), respectively, and 7 cross-coupled with HC≡CFc to yield cis-Ru₂(DmAniF)₂(DMBA-4-C ₂Fc)₂Cl (8). The peripherally modified compounds (2, 3a/3b, 7, and 8) were further alkynylated at the axial positions of the Ru ₂ core to yield a series of bis-alkynyl adducts: Ru ₂(DmAniF)₃(DMBA-4-C₂SiⁱPr ₃)(C₄SiMe₃)₂ (4a), Ru ₂(DmAniF)₃(DMBA-4-C₂Fc)(C₄SiMe ₃)₂ (4b), Ru₂(DmAniF)₃(DMBA-I) (C₄SiMe₃)₂ (5), cis-Ru₂(DmAniF) ₂(DMBA-4-C₂Fc)₂(C₂Ph)₂ (9), and cis-Ru₂(DmAniF)₂(DMBA-I)₂(C ₂Ph)₂ (10). All compounds reported were characterized with voltammetric, vis-NIR, and NMR (whenever applicable) techniques. Molecular structures of compounds 1, 4a, 5, 6, 9, and 10 were established through X-ray diffraction studies.

Full text of DOI:10.1021/om050068t

2660
Organometallics 2005, 24, 2660-2669
Selective Ligand Modification on the Periphery of
Diruthenium Compounds: Toward New Metal-Alkynyl
Scaffolds
Wei-Zhong Chen and Tong Ren*
Department of Chemistry, University of Miami, Coral Gables, Florida 33146
Received January 31, 2005
Diruthenium compounds Ru2(DmAniF)3(OAc)Cl (1, DmAniF is N,N′-di(m-methoxyphenyl)-
formamidinate) and cis-Ru2(DmAniF)2(OAc)2Cl (6) reacted with N,N′-dimethyl-4-iodobenz-
amidine (HDMBA-I) to furnish new compounds Ru2(DmAniF)3(DMBA-I)Cl (2) and cis-
Ru2(DmAniF)2(DMBA-I)2Cl (7), respectively. Both compounds 2 and 7 were modified with a
terminal alkyne under Sonogashira conditions. Examples reported include 2 cross-coupled
with HCtCSiiPr3 or HCtCFc to yield Ru2(DmAniF)3(DMBA-4-C2SiiPr3)Cl (3a) or Ru2-
(DmAniF)3(DMBA-4-C2Fc)Cl (3b), respectively, and 7 cross-coupled with HCtCFc to yield
cis-Ru2(DmAniF)2(DMBA-4-C2Fc)2Cl (8). The peripherally modified compounds (2, 3a/3b,
7, and 8) were further alkynylated at the axial positions of the Ru2 core to yield a series of
bis-alkynyl adducts: Ru2(DmAniF)3(DMBA-4-C2SiiPr3)(C4SiMe3)2 (4a), Ru2(DmAniF)3(DMBA-
4-C2Fc)(C4SiMe3)2 (4b), Ru2(DmAniF)3(DMBA-I)(C4SiMe3)2 (5), cis-Ru2(DmAniF)2(DMBA-4-
C2Fc)2(C2Ph)2 (9), and cis-Ru2(DmAniF)2(DMBA-I)2(C2Ph)2 (10). All compounds reported were
characterized with voltammetric, vis-NIR, and NMR (whenever applicable) techniques.
Molecular structures of compounds 1, 4a, 5, 6, 9, and 10 were established through X-ray
diffraction studies.
Introduction
[M]-(CtC)n-[M] type compounds with [M] as CpRuP2
and CpRu(P-P), where P and P-P stand respectively
for mono- and bisphosphines,9 CpReP(NO),10 CpFe(P-
P),11 Mn(P-P)2I and CpMn(P-P),12 and (C6F5)PtP2.13
While such 1-D systems have been studied extensively,
efforts toward 2-D and 3-D metal-alkynyl networks
remain very limited. Notable examples include the
tetra- and octanuclear platinum butadiyne squares14
Transition metal compounds containing σ-alkynyl
ligands1 are fundamentally interesting due to their
relevance to both the understanding of metal-carbon
covalent bonds2,3 and metal-assisted transformation/
interconversion among alkynes, vinylidenes, and allen-
ylidenes.4 Recent decades have witnessed significant
progress in utilizing tailored metal-alkynyl compounds
as active species for nonlinear optics,5 organic light-
emitting diodes (OLED),6 molecular sensors,7 and mo-
lecular wires.8 In the latter area, many excellent
accounts have appeared based on primarily the linear
(8) (a) Chisholm, M. H. Angew. Chem., Int. Ed. Engl. 1991, 30, 673.
(b) Bunz, U. H. F. Angew. Chem., Int. Ed. Engl. 1996, 35, 969. (c) Paul,
F.; Lapinte, C. Coord. Chem. Rev. 1998, 178-180, 431. (d) Paul, F.;
Lapinte, C. In Unusual structures and physical properties in organo-
metallic chemistry; Gielen, M., Willem, R., Wrackmeyer, B., Eds.;
Wiley: West Sussex, 2002. (e) Szafert, S.; Gladysz, J. A. Chem. Rev.
2003, 103, 4175. (f) Bruce, M. I.; Low, P. J. Adv. Organomet. Chem.
2004, 50, 179.
(9) (a) Bruce, M. I.; Low, P. J.; Costuas, K.; Halet, J.-F.; Best, S. P.;
Heath, G. A. J. Am. Chem. Soc. 2000, 122, 1949. (b) 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.
(10) (a) Dembinski, R.; Lis, T.; Szafert, S.; Mayne, C. L.; Bartik, T.;
Gladysz, J. A. J. Organomet. Chem. 1999, 578, 229. (b) Brady, M.;
Weng, W.; Zou, Y.; Seyler, J. W.; Amoroso, A. J.; Arif, A. M.; Bohme,
M.; Frenking, G.; Gladysz, J. A. J. Am. Chem. Soc. 1997, 119, 775. (c)
Batrik, T.; Bartik, B.; Brady, M.; Dembinski, R.; Gladysz, J. A. Angew.
Chem., Int. Ed. 1996, 35, 414.
(11) (a) Le Narvor, N.; Lapinte, C. J. Chem. Soc., Chem. Commun.
1993, 357. (b) Le Narvor, N.; Toupet, L.; Lapinte, C. J. Am. Chem.
Soc. 1995, 117, 7129. (c) Coat, F.; Lapinte, C. Organometallics 1996,
15, 477. (d) Coat, F.; Paul, F.; Lapinte, C.; Toupet, L.; Costuas, K.;
Halet, J.-F. J. Organomet. Chem. 2003, 683, 368.
(12) (a) Kheradmandan, S.; Venkatesan, K.; Blacque, O.; Schmalle,
H. W.; Berke, H. Chem. Eur. J. 2004, 10, 4872. (b) Kheradmandan,
S.; Heinze, K.; Schmalle, H. W.; Berke, H. Angew. Chem., Int. Ed. 1999,
38, 2270. (c) Ferna´ndez, F. J.; Blacque, O.; Alfonso, M.; Berke, H. Chem.
Commun. 2001, 1266.
* To whom correspondence should be addressed. E-mail: tren@
miami.edu. Tel: (305) 284-6617. Fax: (305) 284-1880.
(1) Modern Acetylene Chemistry; Stang, P. J.; Diederich, F., Eds.;
VCH: Weinheim, 1995.
(2) Nast, R. Coord. Chem. Rev. 1982, 47, 89.
(3) Manna, J.; John, K. D.; Hopkins, M. D. Adv. Organomet. Chem.
1995, 38, 79.
(4) (a) Bruce, M. I. Chem. Rev. 1991, 91, 197. (b) Bruce, M. I. Chem.
Rev. 1998, 98, 2797. (c) King, R. B. Coord. Chem. Rev. 2004, 248, 1531.
(d) Bruce, M. I. Coord. Chem. Rev. 2004, 248, 1603. (e) Rigaut, S.;
Touchard, D.; Dixneuf, P. H. Coord. Chem. Rev. 2004, 248, 1585.
(5) (a) Whittall, I. R.; McDonagh, A. M.; Humphrey, M. G.; Samoc,
M. Adv. Organomet. Chem. 1998, 42, 291. (b) Adv. Organomet. Chem.
1999, 43, 349. (c) Cifuentes, M. P.; Humphrey, M. G. J. Organomet.
Chem. 2004, 689, 3968. (d) Coe, B. J.; Curati, N. R. M. Comm. Inorg.
Chem. 2004, 25, 147.
(6) (a) Yam, V. W. W. Acc. Chem. Res. 2002, 35, 555. (b) Wadas, T.
J.; Lachicotte, R. J.; Eisenberg, R. Inorg. Chem. 2003, 42, 3772. (c)
Tonzetich, Z. J.; Eisenberg, R. Inorg. Chim. Acta 2003, 345, 340. (d)
Lu, W.; Mi, B.-X.; Chan, M. C. W.; Hui, Z.; Zhu, N.; Lee, S.-T.; Che,
C.-M. Chem. Commun. 2002, 206.
(7) (a) Yam, V. W. W. J. Organomet. Chem. 2004, 689, 1393. (b) Siu,
P. K. M.; Lai, S.-W.; Lu, W.; Zhu, N.; Che, C.-M. Eur. J. Inorg. Chem.
2003, 2749. (c) Lu, W.; Chan, M. C. W.; Zhu, N. Y.; Che, C. M.; He, Z.;
Wong, K. Y. Chem. Eur. J. 2003, 9, 6155. (d) Yang, Q.-Z.; Wu, L.-Z.;
Zhang, H.; Chen, B.; Wu, Z.-X.; Zhang, L.-P.; Tung, C.-H. Inorg. Chem.
2004, 43, 5195.
(13) (a) Mohr, W.; Stahl, J.; Hampel, F.; Gladysz, J. A. Inorg. Chem.
2001, 40, 3263. (b) Stahl, J.; Bohling, J. C.; Bauer, E. B.; Peters, T. B.;
Mohr, W.; Mart´ın-Alvarez, J. M.; Hampel, F.; Gladysz, J. A. Angew.
Chem., Int. Ed. 2002, 41, 1871. (c) Mohr, W.; Stahl, J.; Hampel, F.;
Gladysz, J. A. Chem. Eur. J. 2003, 9, 3324.
10.1021/om050068t CCC: $30.25 © 2005 American Chemical Society
Publication on Web 04/22/2005

New Metal-Alkynyl Scaffolds
Organometallics, Vol. 24, No. 11, 2005 2661
and Pt- and Ru-acetylide dendrimers.15 In contrast, 2-D
and 3-D architectures based on both organic polyeth-
ynylated π-systems and their metal π-complexes have
been systematically explored by a number of laborato-
ries.16 In addition to their rich structural features and
interesting physical properties displayed, organic poly-
ethynylated compounds are necessary precursors for
fused nonplanar aromatic compounds including fuller-
enes.17 Clearly, diversified topological features and
unusual physical properties should be expected from the
systematic incorporation of transition metal units into
2-D and 3-D carbon-rich networks.
Diruthenium paddlewheel compounds bearing one or
two alkynyl ligands at the axial positions, first discov-
ered by Cotton et al. in 1986,18 have been carefully
examined in recent years by the laboratories of Kadish
and Bear19 and Ren.20 Ru2-alkynyl compounds would
be of interest as building blocks for supramolecular
materials as well, since they are both intense visible-
near-infrared (vis-NIR) chromophores and excellent
electrophores with multiple reversible redox couples
over a broad potential window.21 Noteworthy recent
results from our laboratory include the demonstration
of high electron mobility across both polyyn-diyls22 and
(E)-hex-3-ene-1,5-diyn-diyl23 bridges between two Ru2
termini and facile hole transfer between two ferrocenyl
groups across a Ru2 unit along the axial direction.24 To
retain the chromophoric and electrophoric features
when incorporated into 2-D and 3-D supramolecular
assemblies, Ru2-alkynyl compounds need to be func-
tionalized in the direction(s) orthogonal to the Ru2-
σalkynyl vector.
Availability of Ru2(LL)4-n(OAc)n type compounds
(n ) 1, 2, or 3, LL is a N,N′-bidentate ligand) opens the
door to selective functionalization of diruthenium com-
plexes at their periphery. The bridging acetate is labile
and can be replaced by better donors such as a N,N′-
bidentate ligand (LL′) that is different from LL to yield
Ru2(LL)4-n(LL′)n type compounds. Recent examples of
Ru2(LL)4-n(OAc)n type compounds include LL as N,N′-
di(o-methoxyphenyl)formamidinate),25 N,N′-diphenyl-
formamidinate (DPhF),26 and N,N′-di(p-anisylformami-
dinate (DpAniF) as the LL ligand.27 Among these
examples, the synthesis of Ru2(DPhF)3(OAc)Cl by Jime´-
nez-Aparicio et al. is most attractive, where refluxing
Ru2(OAc)4Cl and 3 equiv of HDPhF in the presence of
LiCl and triethylamine afforded Ru2(DPhF)3(OAc)Cl in
84% yield after simple recrystallization.26 Very recently,
synthetic procedures for a complete series of Ru2-
(formamidinate)4-n(OAc)nCl compounds with n ) 0-3
were reported in detail, and their utility as building
blocks for polymeric architectures was postulated.27
Previously, we communicated that Ru2(DmAniF)3(OAc)-
Cl (1) reacted readily with N,N′-dimethyl-4-iodobenz-
amidine (HDMBA-I) to yield Ru2(DmAniF)3(DMBA-I)Cl,
and the latter enables the peripheral modification via
the Sonogoshira coupling reaction.28 In this contribu-
tion, we describe both the chemistry of 1 and its
surrogates in detail and analogous chemistry based on
a new synthon, cis-Ru2(DmAniF)2(OAc)2Cl.
(14) (a) Al-Qaisi, S. M.; Galat, K. J.; Chai, M.; Ray, D. G.; Rinaldi,
P. L.; Tessier, C. A.; Youngs, W. J. J. Am. Chem. Soc. 1998, 120, 12149.
(b) Bruce, M. I.; Costuas, K.; Halet, J.-F.; Hall, B. C.; Low, P. J.;
Nicholson, B. K.; Skelton, B. W.; White, A. H. J. Chem. Soc., Dalton
Trans. 2002, 383. (c) Janka, M.; Anderson, G. K.; Rath, N. P.
Organometallics 2004, 23, 4382.
(15) (a) Albinati, A.; Leoni, P.; Marchetti, L.; Rizzato, S. Angew.
Chem., Int. Ed. 2003, 42, 5990. (b) Leininger, S.; Stang, P. J.; Huang,
S. P. Organometallics 1998, 17, 3981. (c) Onitsuka, K.; Fujimoto, M.;
Ohshiro, N.; Takahashi, S. Angew. Chem., Int. Ed. 1999, 38, 689. (d)
Onitsuka, K.; Shimizu, A.; Takahashi, S. Chem. Commun. 2003, 280.
(e) Uno, M.; Dixneuf, P. H. Angew. Chem., Int. Ed. 1998, 37, 1714. (f)
Hurst, S. K.; Cifuentes, M. P.; Humphrey, M. G. Organometallics 2002,
21, 2353. (g) McDonagh, A. M.; Humphrey, M. G.; Samoc, M.; Luther-
Davies, B. Organometallics 1999, 18, 5195.
(16) (a) Bunz, U. H. F. In Carbon Rich Compounds II; De Meijere,
A., Ed.; Springer-Verlag: Berlin, 1999; Vol. 201, p 131. (b) Diederich,
F.; Gobbi, L. In Carbon Rich Compounds II; De Meijere, A., Ed.;
Springer-Verlag: Berlin, 1999; Vol. 201, p 43. (c) Bunz, U. H. F.; Rubin,
Y.; Tobe, Y. Chem. Soc. Rev. 1999, 28, 107. (d) Bunz, U. H. F. J.
Organomet. Chem. 2003, 683, 269. (e) Diederich, F. Nature 1994, 369,
199. And the earlier references therein.
(17) (a) Scott, L. T. Angew. Chem., Int. Ed. 2004, 43, 4994. (b) Hopf,
H. Classics in Hydrocarbon Chemistry; Wiley-VCH: Weinheim, 2000.
(18) Chakravarty, A. R.; Cotton, F. A. Inorg. Chim. Acta 1986, 113,
19.
(19) (a) Bear, J. L.; Han, B.; Huang, S.; Kadish, K. M. Inorg. Chem.
1996, 35, 3012. (b) Bear, J. L.; Han, B.; Huang, S. J. Am. Chem. Soc.
1993, 115, 1175.(c) Bear, J. L.; Li, Y.; Han, B.; Caemelbecke, E. V.;
Kadish, K. M. Inorg. Chem. 1997, 36, 5449. (d) Kadish, K. M.; Phan,
T. D.; Wang, L.-L.; Giribabu, L.; Thuriere, A.; Wellhoff, J.; Huang, S.;
Caemelbecke, E. V.; Bear, J. L. Inorg. Chem. 2004, 43, 4825.
(20) (a) Lin, C.; Ren, T.; Valente, E. J.; Zubkowski, J. D. J. Chem.
Soc., Dalton Trans. 1998, 571. (b) Lin, C.; Ren, T.; Valente, E. J.;
Zubkowski, J. D. J. Organomet. Chem. 1999, 579, 114. (c) Zou, G.;
Alvarez, J. C.; Ren, T. J. Organomet. Chem. 2000, 596, 152. (d) Xu,
G.-L.; Ren, T. Inorg. Chem. 2001, 40, 2925. (e) Xu, G.-L.; Ren, T.
Organometallics 2001, 20, 2400. (f) Ren, T. Organometallics 2002, 21,
732. (g) Xu, G.-L.; Campana, C.; Ren, T. Inorg. Chem. 2002, 41, 3521.
(h) Xu, G.-L.; Ren, T. J. Organomet. Chem. 2002, 655, 239. (i) Xu, G.-
L.; Jablonski, C. G.; Ren, T. J. Organomet. Chem. 2003, 683, 388. (j)
Hurst, S. K.; Xu, G.-L.; Ren, T. Organometallics 2003, 22, 4118.
(21) Ren, T.; Xu, G.-L. Comm. Inorg. Chem. 2002, 23, 355. (b) Hurst,
S. K.; Ren, T. J. Organomet. Chem. 2003, 670, 188.
Result and Discussions
Syntheses. Two important starting compounds, Ru2-
(DmAniF)3(OAc)Cl (1) and cis-Ru2(DmAniF)2(OAc)2Cl
(6), were prepared using procedures modified from
literature.26,27 Recently, Angaridis et al. reported that
refluxing Ru2(OAc)4Cl with 2 equiv of HDpAniF in the
presence of LiCl and Et3N for 18 h resulted in cis-Ru2-
(DpAniF)2(OAc)2Cl in 85% yield.27 However, our attempt
to prepare 6 under identical conditions resulted in 1 as
the major product instead. It was found that a lower
reaction temperature (e60 °C) favors the formation of
compound 6 as the major product.
As shown in Schemes 1 and 2, acetate ligands in both
compounds 1 and 6 can be readily substituted with
DMBA-I to furnish Ru2(DmAniF)3(DMBA-I)Cl (2) and
cis-Ru2(DmAniF)2(DMBA-I)2Cl (7), respectively, in sat-
isfactory yields. The iodo substituents in the resultant
compounds enable peripheral modification through a
number of Pd-catalyzed coupling reactions.29,30 Hence,
(24) (a) Xu, G.-L.; DeRosa, M. C.; Crutchley, R. J.; Ren, T. J. Am.
Chem. Soc. 2004, 126, 3728. (b) Xu, G.-L.; DeRosa, M. C.; Crutchley,
R. J.; Ren, T. J. Am. Chem. Soc. 2005, 127, manuscript in preparation.
(25) Ren, T.; DeSilva, V.; Zou, G.; Lin, C.; Daniels, L. M.; Campana,
C. F.; Alvarez, J. C. Inorg. Chem. Commun. 1999, 2, 301.
(26) Barral, M. C.; Herrero, S.; Jime´nez-Aparicio, R.; Torres, M. R.;
Urbanos, F. A. Inorg. Chem. Commun. 2004, 7, 42.
(27) (a) Angaridis, P.; Cotton, F. A.; Murillo, C. A.; Villagran, D.;
Wang, X. P. Inorg. Chem. 2004, 43, 8290. (b) Angaridis, P.; Berry, J.
F.; Cotton, F. A.; Lei, P.; Lin, C.; Murillo, C. A.; Villagran, D. Inorg.
Chem. Commun. 2004, 7, 9. (c) Angaridis, P.; Berry, J. F.; Cotton, F.
A.; Murillo, C. A.; Wang, X. P. J. Am. Chem. Soc. 2003, 125, 10327.
(28) Chen, W.-Z.; Ren, T. Organometallics 2004, 23, 3766.
(29) Brandsma, L. Preparative Acetylenic Chemistry; Elsevier: Am-
sterdam, 1988.
(22) (a) Ren, T.; Zou, G.; Alvarez, J. C. Chem. Commun. 2000, 1197.
(b) Xu, G.-L.; Zou, G.; Ni, Y.-H.; DeRosa, M. C.; Crutchley, R. J.; Ren,
T. J. Am. Chem. Soc. 2003, 125, 10057.
(23) Shi, Y.; Yee, G. T.; Wang, G.; Ren, T. J. Am. Chem. Soc. 2004,
126, 10552.

2662 Organometallics, Vol. 24, No. 11, 2005
Scheme 1. Synthesis of Ru2(LL)3(LL′) Type Compoundsa
Chen and Ren
a (i) 2 equiv N,N′-dimethyl-4-iodobenzamidine, LiCl, Et3N; 79%. (ii) HC2Y, trans-Pd(PPh3)2Cl2, CuI, iPr2NH, THF, rt; 3a: 41%,
3b: 49%. (iii) Bu4NF, THF; 57%. (iv) 3 equiv LiC4TMS, THF; 4a: 43%, 4b: 37%, 5: 46%. (v) HC2SiiPr3, trans-Pd(PPh3)2Cl2, CuI,
iPr2NH, THF, rt.
Scheme 2. Synthesis of Ru2(LL)2(LL′)2 Type Compoundsa
i
a (i) 4 equiv N,N′-dimethyl-4-iodobenzamidine, LiCl, Et3N; 75%. (ii) HC2Fc, Pd(PPh3)2Cl2,CuI, Pr2NH, THF, rt; 52%. (iii) 8
equiv LiC2Ph, THF, 9: 46%, 10, 51%.
treating 2 with terminal alkyne HCtCY under Sono-
gashira conditions furnished compounds Ru2(DmAniF)3-
(DMBA-4-C2Y)Cl (Y ) SiiPr3 (3a) and Fc (3b)), and
treating 7 with HCtCFc yielded cis-Ru2(DmAniF)2-
(DMBA-4-C2Fc)2Cl (8), all in good yields. Compounds
3a/3b reacted with 3 equiv of LiC4SiMe3 to yield trans-
bis(butadiynyl) compounds 4a/4b under conditions analo-
gous to that established early for diruthenium com-
pounds.21 Similarly, compound 8 reacted with 8 equiv
of LiCtCPh to yield compound 9. In an attempt to
explore alternative routes to compounds 4, compound
2 reacted with LiC4SiMe3 in excess to yield axial bis-
butadiynyl adduct 5. The ensuing cross-coupling reac-
tion under Sonogashira conditions, however, did not
produce the desired product due to the dissociation of
axial butadiynyls under the experimental conditions
(see Supporting Information).
All monochloro compounds, namely, 1, 2, 3a/3b, 6, 7,
and 8, are Ru2(II,III) species and paramagnetic, with
µeff ranging from 3.60 to 3.87 µB, which is consistent with
a S ) 3/2 ground state typical for Ru2(DArF)4Cl type
compounds.31 On the other hand, all axial bis-alkynyl
compounds 4a/4b, 5, 9, and 10 are Ru2(III,III) species
and diamagnetic, the latter of which enables the at-
tainment of well-resolved 1H NMR spectra. These axial
bis-alkynyl compounds also retain the feature of vis-
NIR chromophores with an intense peak at ca. 520 nm
(30) Metal-catalyzed Cross Coupling Reactions; Diederich, F., Stang,
P. J., Eds.; Wiley-VCH: Weinheim, 1998.
(31) Cotton, F. A.; Ren, T. Inorg. Chem. 1995, 34, 3190.

New Metal-Alkynyl Scaffolds
Organometallics, Vol. 24, No. 11, 2005 2663
Figure 1. ORTEP representation of molecule 1 at 30%
probability level.
Figure 3. ORTEP representation of molecule 4a at 20%
probability level.
Figure 2. ORTEP representation of molecule 6 at 30%
probability level.
and a significant peak at 910 nm. Vis-NIR spectra for
all compounds are provided in the Supporting Informa-
tion.
Molecular Structures. The structures of 1, 4a, 5,
6, 9, and 10 were determined through single-crystal
X-ray diffraction studies, and the ORTEP plots are
shown in Figures 1-6. The selected bond lengths and
angles for compounds 1, 4a, and 5 are listed in Table 1,
while those of 6, 9, and 10 are in Table 2. It is clear
that the paddlewheel arrangement of the bridging
ligands around the Ru2 core is adopted in all compounds.
In particular, structural studies of compounds 9 and 10
confirmed that the cisoid arrangement of two sets of
bridging ligands initially determined for 6 is retained,
indicating the absence of structural rearrangement
under both the ligand substitution and cross-coupling
reaction conditions.
The Ru-Ru bond lengths for compounds 1 and 6 are
2.3220(7) and 2.3219(4) Å, respectively, which are
between those reported for the chloro compounds of
Ru25+ tetracarboxylate (2.27-2.30 Å) and tetraformami-
dinate (2.34-2.39 Å) species.32 For 1, the average of the
Ru-Oeq bond lengths is 2.079[5] Å, which is slightly
longer than the average Ru-Neq distance of 2.064[5] Å.
The contrast is more significant in 6: the average Ru-
Figure 4. ORTEP representation of molecule 5 at 30%
probability level.
Oeq distance is 2.076[3] Å and the average Ru-Neq
distance is 2.036[3] Å. While compound 1 contains only
an axial chloro ligand, compound 6 has one H2O
molecule occupying the remaining axial position.
As can be seen from Figures 3-6 and Tables 1-2, all
bis-alkynyl compounds 4a, 5, 9, and 10 display similar
coordination geometry around the Ru2 core. The Ru-
Ru bond lengths, 2.5467(7), 2.5581(5), 2.5069(4), and
2.4977(6) Å, for 4a, 5, 9, and 10, respectively, are
significantly longer than those of 1 and 6, reflecting the
loss of the σ(Ru-Ru) bond upon the formation of two
σ(Ru-C) bonds.20 It is interesting to note that the Ru-
Ru bond lengths determined for 4a and 5 are close to
the average between that of Ru2(DmAniF)4(C4SiMe3)2
(2.5990(3) Å)20d and Ru2(DMBA)4(C4H)2 (2.4559(6) Å).20g
The observed variation can be rationalized on the basis
of the electron density on the Ru2 core that is deter-
mined by the donor ability of the bridging ligand: the
most donating DMBA resulted in the shortest bond
length, the least donating DmAniF resulted in the
longest, and the combination of both type ligands (4a
(32) Cotton, F. A.; Walton, R. A. Multiple Bonds Between Metal
Atoms; Oxford University Press: Oxford, 1993.

2664 Organometallics, Vol. 24, No. 11, 2005
Table 1. Selected Bond Lengths (Å) and Angles (deg) for Compounds 1, 4a, and 5
4a
Chen and Ren
1
5
Ru1-Ru2
Ru1-N1
Ru1-N3
Ru1-N5
Ru2-N2
Ru2-N4
Ru2-N6
Ru1-O1
Ru2-O2
Ru1-Cl
2.3220(7)
2.088(5)
2.103(5)
2.068(6)
2.049(5)
2.063(5)
2.013(6)
2.082(5)
2.075(5)
2.405(2)
Ru1-Ru2
Ru1-C1
Ru2-C8
Ru1-N1
Ru1-N3
Ru1-N5
Ru1-N7
Ru2-N2
Ru2-N4
Ru2-N6
Ru2-N8
C1-C2
2.5467(7)
1.976(6)
1.988(7)
2.038(1)
2.126(5)
2.054(4)
2.013(5)
2.013(4)
1.999(5)
2.054(5)
2.118(5)
1.193(8)
1.38(1)
Ru1-Ru2
Ru1-C1
Ru2-C8
Ru1-N1
Ru1-N3
Ru1-N5
Ru1-N7
Ru2-N2
Ru2-N4
Ru2-N6
Ru2-N8
C1-C2
2.5581(5)
1.949(5)
1.954(5)
2.063(3)
2.101(4)
2.049(3)
2.000(4)
1.971(3)
2.005(3)
2.110(3)
2.101(4)
1.214(6)
1.387(7)
1.189(7)
1.206(6)
1.379(6)
1.208(6)
C2-C3
C2-C3
C3-C4
C8-C9
C9-C10
C10-C11
C24-C25
1.208(9)
1.177(9)
1.379(10)
1.180(9)
1.172(8)
C3-C4
C8-C9
C9-C10
C10-C11
Ru2-Ru1-Cl
175.37(5)
Ru1-Ru2-C8
C1-Ru1-Ru2
C1-C2-C3
166.8(2)
163.0(2)
172.9(7)
176.3(9)
172.1(8)
175.0(9)
Ru1-Ru2-C8
C1-Ru1-Ru2
C1-C2-C3
163.9(1)
162.2(1)
172.7(5)
177.5(6)
176.1(5)
178.4(5)
C2-C3-C4
C2-C3-C4
C8-C9-C10
C11-C10-C9
C8-C9-C10
C11-C10-C9
Table 2. Selected Bond Lengths (Å) and Angles (deg) for Compounds 6, 9, and 10
10
6
9
Ru1-Ru2
Ru1-N1
Ru1-N3
Ru2-N2
Ru2-N4
Ru1-O1
Ru1-O3
Ru2-O2
Ru2-O4
Ru2-O11
Ru1-Cl
2.3219(4)
2.050(3)
2.033(3)
2.026(3)
2.032(3)
2.085(3)
2.080(2)
2.065(3)
2.075(2)
2.466(3)
2.457(1)
Ru1-Ru2
Ru1-C1
Ru2-C9
Ru1-N1
Ru1-N3
Ru1-N5
Ru1-N7
Ru2-N2
Ru2-N4
Ru2-N6
Ru2-N8
C1-C2
2.5069(4)
1.973 (5)
1.974(4)
2.070(3)
1.972(3)
2.043(3)
2.116(4)
1.979(3)
2.088(3)
2.115(3)
2.038(4)
1.203(6)
1.210(6)
1.195(6)
1.181(7)
Ru1-Ru2
Ru1-C1
Ru2-C9
Ru1-N1
Ru1-N3
Ru1-N5
Ru1-N7
Ru2-N2
Ru2-N4
Ru2-N6
Ru2-N8
C1-C2
2.4977(6)
1.975(5)
1.966(6)
2.026(4)
1.987(4)
2.065(4)
2.122(4)
2.035(4)
2.083(4)
2.071(4)
2.027(4)
1.187(7)
1.210(7)
C9-C10
C26-C27
C47-C48
C9-C10
Ru2-Ru1-Cl
Ru1-Ru2-O11
169.49(3)
168.40(7)
Ru1-Ru2-C9
C1-Ru1-Ru2
162.5(1)
161.6(1)
Ru1-Ru2-C9
C1-Ru1-Ru2
168.3(2)
169.1(2)
and 5) gave intermediate values. In the same vein, the
observed Ru-Ru bond lengths for the phenylethynyl
adducts (9 and 10) are shorter than those for the
butadiynyl adducts (4a and 5), since phenylethynyl is
a stronger donor than butadiynyl. In the case of 4a, the
ethynyl unit on the DMBA ligand is orthogonal to the
bis(butadiynyl) on the axial positions. There are also
significant deviations from linearity in Ru-Ru-C1
(163.0(2)°) and Ru-Ru-C8 (166.8(2)°) angles, which are
attributed to a second-order Jahn-Teller effect common
to Ru2(III,III)-alkynyl compounds.20,21
Structural features of compound 9 are worthy of
mention because of the use of ferrocenyl as peripheral
susbstituents. The C-C bond lengths of two ferrocenyl-
ethynyl moieties are 1.195(6) (C26-C27) and 1.181(7)
Å (C47-C48), which agree with the expected value of
1.20 Å within experimental error. Interestingly, the
unique axis of both ferrocenyl groups, i.e., the vector
defined by linking the centroid of Cp rings and the Fe
center (shown as a dashed line in Figure 6), parallels
the Ru2-acetylide linkage. The distance between Fe1
and Fe2 centers is 18.528 Å. Previously, a series of
Ru2II,III(O2CY)4 type compounds with Y as (CH2)nFc
(n ) 0-2), (CH)2Fc, and Rc (ruthenocenyl) were reported
Figure 5. ORTEP representation of molecule 10 at 30%
probability level.

New Metal-Alkynyl Scaffolds
Organometallics, Vol. 24, No. 11, 2005 2665
Figure 6. ORTEP representation of molecule 9 at 30%
probability level. All carbon atoms except the acetylene are
shown as unlabeled isotropic open circles for clarity.
by Aquino, where the unique axes of metallacenes are
orthogonal to the Ru-Ru vector in all three structurally
characterized compounds.33 The contrast in the align-
ment between ours and Aquino’s compounds likely
originates from the subtle difference in lattice packing:
the peripheral Fc/Rc units in Ru2II,III(O2CY)4 type
compounds are close enough to the Ru-Ru vector that
they can fill the void between adjacent bridging ligands
by being orthogonal to the Ru-Ru vector. On the other
hand, the Fc units in 9 are too far away from the Ru-
Ru vector and the void between adjacent bridging
ligands have to be filled by groups from neighboring
molecules instead.
Figure 7. Cyclic voltammograms of Ru2(DmAniF)3(OAc)
and Ru2(DmAniF)3(DMBA) type compounds recorded in a
0.20 M THF solution of Bu4NPF6 at a scan rate of 0.10 V/s.
Scheme 3. Assignments of Observed Ru2-Based
Redox Couples; X Stands for Axial Ligand
Electrochemistry. As is common to diruthenium
paddlewheel species, all compounds reported display
rich and often complex redox chemistry. Cyclic voltam-
mograms (CVs) measured for Ru2(LL)3(LL′) type com-
pounds, namely, 1-5, are shown in Figure 7. Compound
1 exhibits three Ru2-based redox couples: a one-electron
oxidation (B) and two one-electron reductions (C and
D). The first reduction (C) is irreversible due to fast
dissociation of the axial Cl- ligand upon reduction (in
Scheme 3), a phenomenon frequently observed in other
Ru2(LL)4Cl type compounds.19,34 The resultant species,
Ru2(DmAniF)3(OAc), is reoxidized at a more positive
potential (E). Unsurprisingly, these characteristics are
almost identical to that reported for Ru2(DpAniF)3(OAc)-
Cl,27 although the electrode potentials for Ru2(DpAniF)3-
(OAc)Cl are slightly shifted in the cathodic direction
since 4-MeO is a more electron-donating substituent
than 3-MeO. While the CVs of compounds 2 and 3 are
quite similar to that of 1, the electrode potentials of
corresponding couples have been cathodically shifted by
at least 100 mV, reflecting the fact that DMBA is a
much stronger donor than acetate.
Table 3. Electrode Potentials (V) of 4a, 5, and
Related Compounds
Epa(A)
E1/2(B)
E1/2(C)
Ru2(DmAniF)4(C4SiMe3)2
1.17
1.06
1.06
0.73
-0.32
-0.37
-0.39
-0.90
-1.32
-1.32
-1.39
-1.94
5
4a
Ru2(DMBA)4(C4SiMe3)2
bonds upon reduction. The electrode potentials of com-
pounds 4a and 5 are listed in Table 3 along with those
for Ru2(DmAniF)4(C4SiMe3)2 and Ru2(DMBA)4(C4Si-
Me3)2.21 Clearly, the potentials of redox couples in
compounds 4a and 5 are slightly more negative than
those of the corresponding couples in Ru2(DmAniF)4(C4-
SiMe3)2, but far more positive than those in Ru2-
(DMBA)4(C4SiMe3)2. The variation among redox poten-
tials is easily explained by the fact that DMBA is a
much stronger donor than DArF ligands. Furthermore,
compounds 4a and 5 are very similar to Ru2(DmAniF)4-
(C4SiMe3)2 in terms of the reversibility of their redox
couples.
Cyclic voltammograms (CVs) measured for several
Ru2(LL)2(LL′)2 type compounds, namely, 6, 7, and 10,
are shown in Figure 8. Ru2(DmAniF)2(OAc)2Cl (6)
displays three Ru2-based couples similar to that of 1,
but at more anodic potentials. The increased electron
deficiency at the Ru2 core is also reflected by the
irreversibility of couple B. Ru2(DpAniF)2(OAc)2Cl, the
more electron-rich analogue reported by Cotton et al.,
exhibited a reversible B.27 Upon the formation of 7 via
Cyclic voltammograms of bis(butadiynyl) adducts 4a
and 5 feature one irreversible oxidation (A) and two
reversible one-electron reductions (B and C), and the
reversibility of the latter reflects the robustness of Ru-C
(33) (a) Cooke, M. W.; Cameron, T. S.; Robertson, K. N.; Swarts, J.
C.; Aquino, M. A. S. Organometallics 2002, 21, 5962. (b) Cooke, M.
W.; Murphy, C. A.; Cameron, T. S.; Swarts, J. C.; Aquino, M. A. S.
Inorg. Chem. Commun. 2000, 3, 721.
(34) Lin, C.; Ren, T.; Valente, E. J.; Zubkowski, J. D.; Smith, E. T.
Chem. Lett. 1997, 753.

2666 Organometallics, Vol. 24, No. 11, 2005
Chen and Ren
hand, our studies of the trans-Fc(CC)2n[Ru2(DMBA)4]-
(CC)2nFc (n ) 1 and 2) family provide unambiguous
evidence of strong couplings between two Fc groups
separated by up to 11 bonds.24 It appears that the
charge transfer along the axial direction of diruthenium
paddlewheel species is far more facile than that along
the equatorial direction.
Conclusions
We presented methods for preparing Ru2-
(DmAniF)4-n(OAc)nCl (n ) 1 and 2) in excellent yields,
which complement the routes developed by Cotton and
Jime´nez-Aparicio.26,27 Further derivatization yielding
Ru2(DmAniF)4-n(DMBA-I)nCl was also demonstrated,
and the resultant compounds became a springboard for
peripheral functionalization of Ru2 species through Pd-
catalyzed cross-coupling reactions. The iodo- and alkyn-
yl-functionalized diruthenium complexes are of interest
as building blocks for both homo- and heterodimeric
supermolecular molecules, as shown in Scheme 4. Many
interesting supramolecules have been self-assembled
from dimetallic units linked by ditopic ligands at the
equatorial positions in recent years.35,36 Most of the
resultant architectures are centrosymmetric due to the
extensive use of symmetric ditopic linkers. Heterodimer-
ic assembly outlined in Scheme 4, on the other hand,
may lead to supramolecules of energy gradient or as
bulk polar materials. In addition, the presence of the
peripheral ethyne functionality should enable the for-
mation of diruthenium conjugates with biomolecules
through click reactions.37 These aspects are being vigor-
ously pursued in our laboratory.
Figure 8. Cyclic voltammograms of Ru2(LL)2(LL′)2 type
compounds 6, 7, and 10.
Figure 9. Differential pulse (solid) and cyclic (gray)
voltammograms of compounds 3b and 8.
the replacement of acetate by DMBA-I, the oxidation
couple B is shifted by -0.33 V, reflecting the extraor-
dinary donor strength of DMBA ligands. Compound 7,
however, is quite unstable toward reduction. The CV of
the bis-phenylethynyl derivative 10 is quasi-reversible
on the first reduction B, but irreversible on oxidation
(A) and second reduction (C). Clearly, Ru2(LL)2(LL′)2
type compounds are less redox-robust than Ru2(LL)3-
(LL′) type compounds, although the origin of the insta-
bility is not presently obvious.
Scheme 4. Hetero- and Homodimeric
Diruthenium Supramolecules through (i)
Sonogashira Coupling and (ii) Glaser Coupling
CVs of Ru2(DmAniF)4-n(DMBA-4-C2Fc)n (n ) 1 and
2) type compounds, i.e., 3b, 4b, 8, and 9, generally
resemble those of the corresponding Ru2(DmAniF)4-n
-
(DMBA-4-I)n compounds and are all provided in the
Supporting Information. The existence of two Fc groups
within a single molecule in both 8 and 9 presents a
unique opportunity to gauge the intramolecular elec-
tronic coupling between two Fc centers. For this reason,
both the CVs and DPVs of Ru2(DmAniF)3(DMBA-4-C2-
Fc)Cl (3b) and Ru2(DmAniF)2(DMBA-4-C2Fc)2Cl (8) in
the anodic region (0 to 1.0 V versus Ag/AgCl) are shown
in Figure 9. Voltammograms of both compounds feature
the Fc-centered oxidation (F) in addition to the Ru2-
based oxidation (B). It is immediately clear from com-
paring 8 with 3b that two Fc centers in 8 are oxidized
simultaneously and, hence, are not electronically coupled.
Previously, Aquino et al. reported a 40 mV separation
between two Fc-centered 2-e- oxidations for [Ru2-
(O2C(CH)2Fc)4](PF6), which was attributed to a weak
intramolecular electronic coupling.33 However, the ab-
sence of coupling in 8 is not surprising, considering that
two Fc units are separated by 18 bonds in 8 and only
10 bonds in [Ru2(O2C(CH)2Fc)4](PF6). On the other
Experimental Section
Copper(I) iodide and phenylacetylene were purchased from
Acros, 1,4-bis(trimethylsilyl)-1,3-butadiyne and triisopropyl-
silylacetylene were purchased from GFS Chemicals, silica gel
was purchased from Merck, and trans-Pd(PPh3)2Cl2 was
(35) (a) Cotton, F. A.; Lin, C.; Murillo, C. A. Acc. Chem. Res. 2001,
34, 759. (b) Cotton, F. A.; Lin, C.; Murillo, C. A. Proc. Nat. Acad. Sci.,
U.S.A. 2002, 99, 4810. (c) Chisholm, M. H. J. Chem. Soc., Dalton Trans.
2003, 3821.
(36) (a) Cotton, F. A.; Liu, C. Y.; Murrilo, C. A.; Villagran, D.; Wang,
X. P. J. Am. Chem. Soc. 2004, 126, 14822. (b) Cotton, F. A.; Donahue,
J. P.; Lin, C.; Murillo, C. A. Inorg. Chem. 2001, 40, 1234. (c) Bera, J.
K.; Angaridis, P.; Cotton, F. A.; Petrukhina, M. A.; Fanwick, P. E.;
Walton, R. A. J. Am. Chem. Soc. 2001, 123, 1515. (d) Kuang, S.-M.;
Fanwick, P. E.; Walton, R. A. Inorg. Chem. 2002, 41, 405. (e) Bursten,
B. E.; Chisholm, M. H.; Clark, R. J. H.; Firth, S.; Hadad, C. M.;
MacIntosh, A. M.; Wilson, P. J.; Woodward, P. M.; Zaleski, J. M. J.
Am. Chem. Soc. 2002, 124, 3050. (f) Bursten, B. E.; Chisholm, M. H.;
Clark, R. J. H.; Firth, S.; Hadad, C. M.; Wilson, P. J.; Woodward, P.
M.; Zaleski, J. M. J. Am. Chem. Soc. 2002, 124, 12244.
(37) (a) Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Angew. Chem.,
Int. Ed. 2001, 40, 2004. (b) Kolb, H. C.; Sharpless, K. B. Drug Discovery
Today 2003, 8, 1128.

New Metal-Alkynyl Scaffolds
Organometallics, Vol. 24, No. 11, 2005 2667
purchased from Strem Chemicals. Ferrocenylacetylene was
prepared according to the literature.38 1H NMR spectra were
recorded on a Bruker AVANCE300 NMR spectrometer, with
chemical shifts (δ) referenced to the residual CHCl3. Visible-
near-infrared spectra in THF were obtained with a Perkin-
Elmer Lambda-900 UV-vis-NIR spectrophotometer. Mag-
netic susceptibility was measured at 294 K with a Johnson
Matthey Mark-I magnetic susceptibility balance. Elemental
analysis was performed by Atlantic Microlab, Norcross, GA.
Cyclic and differential pulse voltammograms were recorded
in 0.2 M (n-Bu)4NPF6 solution (THF, N2-degassed) on a
CHI620A voltammetric analyzer with a glassy carbon working
electrode (diameter ) 2 mm), a Pt-wire auxiliary electrode,
and a Ag/AgCl reference electrode. The concentration of
diruthenium species was always 1.0 mM. The ferrocenium/
ferrocene couple was observed at 0.582 V (vs Ag/AgCl) under
the experimental conditions.
Preparation of Ru2(DmAniF)3(OAc)Cl (1). A round-
bottom flask was charged with Ru2(OAc)4Cl (1.0 g, 2.11 mmol),
N,N′-di(m-methoxyphenyl)formamidine (1.58 g, 6.33 mmol),
LiCl (0.50 g), Et3N (2 mL), and 40 mL of THF. The mixture
was gently refluxed for 12 h. The color changed to dark purple.
The reaction mixture was then filtered through a short silica
gel pad (2 cm). Further purification with silica column (elu-
ent: ethyl acetate/hexanes ) 1/2 to 1/1) yielded 1 as a purple
crystalline material (1.95 g, 87% based on Ru). Data for 1:
Rf(ethyl acetate/hexanes ) 1/1), 0.45. MS-FAB (m/e, based on
101Ru): 1028 [M+ - Cl]. Vis-NIR, λmax (nm, ꢀ (M-1 cm-1)):
526(3860). Anal. for C47H48ClN6O8Ru2‚THF, found(calcd): C,
53.92(53.99); H, 4.89(4.97); N, 7.46(7.41). ømol(corrected) )
5.80 × 10-3 emu, µeff ) 3.72 µB. Cyclic voltammogram [E1/2/V,
∆Ep/V, ibackward/iforward]: B, 0.743, 0.064, 0.88; D, -1.382, 0.062,
0.98; Epc(C), -0.525 V; Epa(E), -0.120 V.
at room temperature overnight. After the removal of solvent,
the residue was purified with a silica column (ethyl acetate/
hexane/triethylamine ) 3/6/1) to afford 3b as a green micro-
crystalline material. Yield: 0.55 g, 49%. Data for 3b: Rf(ethyl
acetate/hexane/triethylamine ) 3/6/1), 0.46. MS-FAB (m/e,
based on 101Ru): 1324 [M+ - Cl]. Anal. for C66H64ClN8O6Ru2-
Fe‚THF, found(calcd): C, 59.10(58.76); H, 5.34(5.07); N,
8.24(7.83). Vis-NIR, λmax (nm, ꢀ (M-1 cm-1): 464(3760).
ømol(corrected) ) 5.29 × 10-3 emu, µeff ) 3.56 µB. Cyclic
voltammogram [E1/2/V, ∆Ep/V, ibackward/iforward]: F, 0.542, 0.073,
0.87; B, 0.711, 0.066, 0.57; Epc(C), -0.733 V; Epa(E),
-0.173 V.
Preparation of Ru2(DmAniF)3(DMBA-4-C2H)Cl (3c). To
3a (0.20 g, 0.15 mmol) dissolved in 30 mL of THF was added
0.5 mL of TBAF (tetrabutylammonium fluoride, 1 M in THF),
and the mixture was stirred for ca. 20 min before being filtered
through a 2 cm silica gel pad deactivated with Et3N. After the
solvent removal, the residue was purified with chromatogra-
phy (THF/hexanes/Et3N ) 3/9/1) to yield 0.10 g of a green
microcrystalline material (57%). Anal. for C56H56ClN8O6Ru2‚
1.5C6H14, found(calcd): C, 59.83 (60.63); H, 6.02(6.29); N, 8.59-
(8.32).
Preparation of Ru2(DmAniF)3(DMBA-4-C2SiiPr3)(C4-
SiMe3)2 (4a). To a 20 mL THF solution containing 0.9 mmol
of Me3SiC4SiMe3 was added 0.9 mL of BuLi (1.0 M in hexanes)
at about -80 °C. The mixture was slowly warmed to room
temperature and stirred for another 1 h to yield a slightly
yellow solution. The solution was added to 40 mL of THF
solution containing 3a (0.30 mmol, 0.4 g) at room temperature,
and the mixture was stirred for 2 h, during which the solution
became dark red. After the solvent removal, the residue was
purified with chromatography (ethyl acetate/hexanes ) 1/6)
to yield 0.20 g of a red powder (43%). Data for 4a: Rf(ethyl
acetate/hexanes ) 1/6), 0.52. MS-FAB (m/e, based on 101Ru):
1539 [M+]. Vis-NIR, λmax (nm, ꢀ (M-1 cm-1)): 537(13 210), 911-
(1250). 1H NMR: 8.22 (s, 2H, NCHN), 7.93 (s, 2H, NCHN),
7.62-7.60 (d, 2H, aromatic), 7.19-7.08 (m, 6H, aromatic),
7.05-7.04 (d, 2H, aromatic), 6.82 (s, 2H, aromatic), 6.78 (s,
4H, aromatic), 6.69-6.68 (d, 6H, aromatic), 6.22-6.21 (d, 4H,
aromatic), 6.17-6.13 (d, 2H, aromatic), 3.66 (s, 12H, OCH3),
3.63 (s, 6H, OCH3), 3.34 (s, 6H, NCH3), 1.13 (d, 18H, SiCH-
(CH3)3), 0.28-0.17 (m, 3H, SiCH(CH3)2), 0.09 (s, 18H, Si-
(CH3)3). Anal. for C79H94N8O6Ru2Si3‚C6H14, found(calcd): C,
62.51(62.86); H, 6.68(6.70); N, 6.62(6.90). Cyclic voltammogram
[E1/2/V, ∆Ep/V, ibackward/iforward]: Epa(A), 1.070 V; B, -0.372,
0.063, 0.97; C, -1.319, 0.062, 0.98.
Preparation of Ru2(DmAniF)3(DMBA-4-C2Fc)(C4SiMe3)2
(4b). To a 20 mL THF solution containing 3.8 mmol of Me3-
SiCCCCSiMe3 was added 2.3 mL of BuLi (1.6 M in hexanes)
at about -80 °C. The mixture was slowly warmed to room
temperature and stirred for another 1 h to yield a slightly
yellow solution. The solution was added to a 40 mL THF
solution containing 3b (0.38 mmol, 0.50 g) at room tempera-
ture, and the mixture was stirred for 2 h, during which the
solution became dark red. After the solvent removal, the
residue was purified with chromatography (ethyl acetate/
hexanes ) 1/5) to yield 0.22 g of a red powder (37%). Data for
4b: Rf(ethyl acetate/hexanes ) 1/5), 0.68. MS-FAB (m/e, based
on 101Ru): 1556 [M+]. Vis-NIR, λmax (nm, ꢀ (M-1 cm-1): 538-
(16 850), 922(1280). 1H NMR: 8.11 (s, 1H, NCHN), 7.91 (s, 2H,
NCHN), 7.83-7.81 (d, 2H, aromatic), 7.12-7.03 (m, 8H,
aromatic), 6.78 (s, 2H, aromatic), 6.75 (s, 4H, aromatic), 6.70-
6.68 (d, 6H, aromatic), 6.22-6.20 (d, 4H, aromatic), 6.15-6.13
(d, 2H, aromatic), 4.54-4.51 (m, 2H, ferrocenyl), 4.33-4.28 (m,
7H, ferrocenyl), 3.85 (s, 12H, NCH3), 3.83 (s, 12H, OCH3), 3.38
(s, 6H, OCH3), 0.10 (s, 18H, Si(CH3)3). Anal. for C80H82FeN8O6-
Ru2Si2, found(calcd): C, 61.53(61.37); H, 5.29(5.28); N, 7.06-
(7.16). Cyclic voltammogram [E1/2/V, ∆Ep/V, ibackward/iforward]: F,
0.509, 0.066, 0.94; Epa(A), 1.060; B, -0.390, 0.059, 0.79; C,
-1.349, 0.081, 0.87.
Preparation of Ru2(DmAniF)3(DMBA-I)Cl (2). A mix-
ture of 1 (1.0 g, 0.94 mmol), N,N′-dimethyl-4-iodobenzamidine
(0.52 g, 1.88 mmol), LiCl (0.20 g), Et3N, (2 mL) and THF (40
mL) was refluxed overnight, with the color of the reaction
mixture changing from dark purple to green. The reaction
mixture was filtered through silica gel. After solvent removal,
the residue was purified with a silica column (ethyl acetate/
hexanes/triethylamine ) 5/10/1) to yield 2 as a green micro-
crystalline material (0.95 g, 79%). Data for 2: Rf(ethyl acetate/
hexanes/triethylamine, v/v/v: 5/10/1), 0.35. MS-FAB (m/e,
based on 101Ru): 1242 [M+ - Cl]. Vis-NIR, λmax (nm, ꢀ (M-1
cm-1)): 468(2310). Anal. for C54H55ClN8O6IRu2‚Et3N, found-
(calcd): C, 52.63(52.31); H, 4.88(5.12); N, 8.83(9.14). ømol
-
(corrected) ) 5.56 × 10-3 emu, µeff ) 3.64 µB. Cyclic voltam-
mogram [E1/2/V, ∆Ep/V, ibackward/iforward]: B, 0.551, 0.063, 0.78;
D, -1.530, 0.093, 0.61; Epc(C), -0.669 V; Epa(E), -0.200 V.
Preparation of Ru2(DmAniF)3(DMBA-4-C2SiiPr3)Cl (3a).
A mixture of 2 (1.0 g, 0.78 mmol), trans-Pd(PPh3)2Cl2 (0.2 g,
i
0.28 mmol), CuI (0.10 g, 0.52 mmol), Pr2NH (20 mL), THF
(20 mL), and triisopropylsilylacetylene (0.5 mL) was stirred
at room temperature overnight. After the removal of solvent,
the residue was purified with a silica column (ethyl acetate/
hexane/triethylamine ) 3/9/1) to afford 3a as a green micro-
crystalline material (0.43 g, 41%). Data for 3a: Rf(ethyl
acetate/hexane/triethylamine ) 3/9/1), 0.28. MS-FAB (m/e,
based on 101Ru): 1296 [M+ - Cl]. Vis-NIR, λmax (nm, ꢀ (M-1
cm-1)): 467(3730). Anal. for C65H76ClN8O6Ru2Si‚THF, found-
(calcd): C, 59.14(59.06); H, 6.03(6.03); N, 8.17(7.99). ømol
-
(corrected) ) 5.47 × 10-3 emu, µeff ) 3.60 µB. Cyclic voltam-
mogram [E1/2/V, ∆Ep/V, ibackward/iforward]: B, 0.565, 0.059, 0.83;
D, -1.494, 0.109, 0.83; Epc(C), -0.671 V; Epa(E), -0.178 V.
Preparation of Ru2(DmAniF)3(DMBA-4-C2Fc)Cl (3b).
A mixture of 2a (1.06 g, 0.83 mmol), ferrocenylacetylene (0.21
g, 1.00 mmol), trans-Pd(PPh3)Cl2 (0.30 g, 0.42 mmol), CuI (0.15
g, 0.79 mmol), iPr2NH (20 mL), and THF (20 mL) was stirred
(38) Doisneau, G.; Balavoine, G.; Fillebeen-Khan, T. J. J. Orga-
nomet. Chem. 1982, 425, 113.

2668 Organometallics, Vol. 24, No. 11, 2005
Table 4. Crystal Data for Compounds 1, 4a, 5, 6, 9, and 10
Chen and Ren
1‚H2O
4a
5
6‚H2O‚CH2Cl2
9.THF
10
formula
fw
C
47H50ClN6O9Ru2
C
79H94N8O6Ru2Si3
C
68H73IN8O6Ru2Si2
C
35H40Cl3N4O9Ru2
C
92H86N8O5Ru2Fe2
C
128H120I4N16O8Ru4
1080.50
1538.02
P1h
1483.56
967.18
P1h
1697.53
2922.28
P1h
space group P1h
P21/n
P21/c
a, Å
13.173(1)
15.375(2)
17.521(2)
18.281(3)
80.35(1)
82.95(1)
66.348(9)
4439(1)
2
21.2595(7)
10.4058(4)
33.170(1)
9.8249(4)
12.2573(5)
17.0168(7)
109.913(1)
90.523(1)
93.375(1)
1922.5(1)
2
22.1088(9)
17.0020(7)
22.1884(9)
13.9277(9)
20.2552(1)
23.247(1)
69.391(1)
83.568(1)
89.617(1)
6096.2(6)
2
b, Å
15.358(1)
16.802(1)
116.426(1)
107.284(1)
96.207(1)
2789.2(4)
2
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
107.811(1)
93.660(1)
6986.2(4)
4
27
0.71073
1.411
0.962
0.0532
0.0781
8323.5(6)
4
27
0.71073
1.355
0.754
0.0496
0.1224
T, °C
27
27
0.71073
1.150
0.429
0.0665
0.1823
27
0.71073
1.671
1.052
0.0326
0.0710
27
0.71073
1.592
1.562
0.0444
0.0989
λ(Mo KR), Å 0.71073
F
calc, g cm-3 1.284
µ, mm-1
R
0.641
0.0645
0.1896
wR2
Preparation of Ru2(DmAniF)3(DMBA-I)(C4SiMe3)2 (5).
This was synthesized using the same procedure as that for 4
with 3a replaced by 2 (0.4 g, 0.313 mmol). Compound 5 was
isolated as a dark red microcrystalline material (0.21 g, 46%).
Data for 5: Rf(ethyl acetate/hexanes ) 1/6), 0.46. MS-FAB (m/
e, based on 101Ru): 1486 [M+]. Vis-NIR, λmax (nm, ꢀ (M-1
cm-1)): 539(18 450), 910(1660). Anal. for C68H73IN8O6Ru2Si2,
found(calcd): C, 55.15(55.05); H, 5.13(4.96); N, 7.33(7.55). 1H
NMR: 8.22 (s, 1H, NCHN), 7.93 (s, 2H, NCHN), 7.87-7.86
(d, 2H, aromatic), 7.11-7.08 (m, 6H, aromatic), 7.05-6.98 (d,
2H, aromatic), 6.84 (s, 2H, aromatic), 6.73 (s, 4H, aromatic),
6.70-6.68 (d, 6H, aromatic), 6.22-6.20 (d, 4H, aromatic),
6.18-6.17 (d, 2H, aromatic), 3.32 (s, 6H, NCH3), 3.71 (s, 12H,
OCH3), 3.66 (s, 6H, OCH3), 0.10 (s, 18H, Si(CH3)3). Cyclic
voltammogram: Epa(A), 1.063 V; B, -0.371, 0.060, 0.92; C,
-1.324, 0.076, 0.73.
Preparation of cis-Ru2(DmAniF)2(OAc)2Cl (6). A round-
bottom flask was charged with Ru2(OAc)4Cl (0.474 g, 1.0
mmol), N,N′-di(m-methoxyphenyl)formamidine (0.64 g, 2.5
mmol), Et3N (2 mL), and 40 mL of THF. The mixture was
heated at ca. 60 °C and stirred under argon for 48 h. The
reaction mixture was then filtered through a short silica gel
pad (2 cm). Further purification with a silica column (flush
with ethyl acetate first, then collect product with acetone)
yielded 6 as a green crystalline material (0.42 g, 51% based
on Ru). Data for 6: Rf(CH2Cl2/acetone ) 2/1), 0.40. MS-FAB
(m/e, based on 101Ru): 832 [M+ - Cl]. Vis-NIR, λmax (nm, ꢀ
(M-1 cm-1)): 567(2970), 437(2640). Anal. for C34H36ClN4O8Ru2‚
0.5THF, found(calcd): C, 47.77(47.45); H, 4.61(4.53); N, 5.89-
(6.15). ømol(corrected) ) 6.27 × 10-3 emu, µeff ) 3.87 µB. Cyclic
voltammogram [E1/2/V, ∆Ep/V, ibackward/iforward]: Epa(B), 0.743;
D, -1.426, 0.085, 0.93; Epc(C), -0.510 V.
Preparation of cis-Ru2(DmAniF)2(DMBA-4-C2Fc)2(C2-
Ph)2 (9). This was synthesized using the same procedure as
that for 5 with the starting material 2 replaced by 8. Data for
9: yield 46%. Rf(ethyl acetate/hexanes ) 1/5), 0.38. MS-FAB
(m/e, based on 101Ru): 1628 [M+]. 1H NMR: 8.22 (s, 2H,
NCHN), 7.56-7.59 (d, 4H, aromatic), 7.05-7.11 (m, 8H,
aromatic), 6.94-6.96 (m, 8H, aromatic), 6.69-6.70 (t, 2H,
aromatic), 6.63-6.69 (m, 8H, aromatic), 6.52-6.55 (d, 4H,
aromatic), 4.52-4.53 (t, 4H, ferrocenyl), 4.23-4.27 (m, 14,
ferrocenyl), 3.36 (s, 12H, NCH3), 3.62 (s, 12H, OCH3). Cyclic
voltammogram: Vis-NIR, λmax (nm, ꢀ (M-1 cm-1)): 517-
(15 670), 908(1110). Anal. for C88H78Fe2N8O4Ru2‚C6H14, found-
(calcd.): C, 65.75(65.96); H, 5.22(5.42); N, 6.40(6.55). Cyclic
voltammogram [E1/2/V, ∆Ep/V, ibackward/iforward]: Epa(A), 1.110 V;
B, -0.673, 0.065, 0.89; Epc(C), -1.741; F, 0.756, 0.073, 0.70.
Preparation of cis-Ru2(DmAniF)2(DMBA-I)2(C2Ph)2 (10).
Compound 10 was prepared using the same procedure as that
for 5 with compound 7 (0.25 g, 0.19 mmol) instead of 2.
Compound 10 was isolated as a dark red microcrystalline
material (0.15 g, 51%). Data for 10: Rf(ethyl acetate/hexanes
) 1/5), 0.45. MS-FAB (m/e, based on 101Ru): 1463 [M+]. Vis-
NIR, λmax (nm, ꢀ (M-1 cm-1)): 521(14 720), 920(1440). Anal.
for C64H60N8O4I2Ru2‚0.5C6H14, found(calcd): C, 54.18(54.46);
H, 4.44(4.55); N, 7.09(7.44). 1H NMR: 8.20 (s, 2H, NCHN),
7.80-7.81 (d, 4H, aromatic), 7.04-7.12 (m, 8H, aromatic),
6.94-6.95 (t, 4H, aromatic), 6.73 (s, 2H, aromatic), 6.62-6.65
(d, 12H, aromatic), 6.49-6.51 (d, 4H, aromatic), 3.31 (s, 12H,
NCH3), 3.52 (s, 12H, OCH3). Cyclic voltammogram [E1/2/V, ∆Ep/
V, ibackward/iforward]: Epa(A), 0.805 V; B, -0.646, 0.065, 0.89;
Epc(C), -1.762.
X-ray Data Collection, Processing, and Structure
Analysis and Refinement. Single crystals were grown via
slow evaporation of either an ethyl acetate/hexanes solution
(1 and 10), a hexanes solution (4a and 5), a CH2Cl2 solution
(6), or a toluene/hexanes solution (9). The X-ray intensity data
were measured at 300 K on a Bruker SMART1000 CCD-based
X-ray diffractometer system using Mo KR (λ ) 0.71073 Å). Thin
plates of dimension 0.40 × 0.20 × 0.20 mm3 (1), 0.30 × 0.24 ×
0.07 mm3 (4a), 0.27 × 0.05 × 0.03 mm3 (5), 0.50 × 0.13 × 0.06
mm3 (6), 0.60 × 0.17 × 0.10 mm3 (9), and 0.48 × 0.36 × 0.20
mm3 (10) were used for X-ray crystallographic analysis.
Crystals were cemented onto a quartz fiber with epoxy glue.
Data were measured using omega scans of 0.3° per frame such
that a hemisphere (1271 frames) was collected. No decay was
indicated for any of six data sets in the re-collection of the
first 50 frames at the end of each data collection. The frames
were integrated with the Bruker SAINT software package
using a narrow-frame integration algorithm, which also cor-
rects for the Lorentz and polarization effects.39 Absorption
corrections were applied using SADABS supplied by George
Sheldrick.
Preparation of cis-Ru2(DmAniF)2(DMBA-I)2Cl (7). Syn-
thesis of 7 was analogous to that of 2 with 4 equiv of N,N′-
dimethyl-4-iodobenzamidine. Yield: 75%. Rf(ethyl acetate/
hexanes ) 1/2). MS-FAB (m/e, based on 101Ru): 1261.
ømol(corrected) ) 6.08 × 10-3 emu, µeff ) 3.81 µB. Vis-NIR,
λmax (nm, ꢀ (M-1 cm-1)): 454(5290), 559(sh). Anal. for
Ru2C48N8O4H50I2, found(calcd): C, 44.47(44.54); H, 4.00(3.89);
N, 8.46(8.66). Cyclic voltammogram [E1/2/V, ∆Ep/V, ibackward
/
iforward]: B, 0.410, 0.072, 0.89; Epc(C), -0.790 V; Epa(E),
-0.446 V.
Preparation of cis-Ru2(DmAniF)2(DMBA-4-C2Fc)2Cl
(8). Compound 8 was synthesized from treating 7 with 8 equiv
of ferrocenylacetylene using a procedure identical to that for
3b. Yield: 52%. Data for 8: Rf(ethyl acetate/hexane/triethyl-
amine ) 3/6/1), 0.51. MS-FAB (m/e, based on 101Ru): 1425
[M+ - Cl]. Vis-NIR, λmax (nm, ꢀ (M-1 cm-1): 453(7990), 650-
(sh). Anal. for Ru2C72N8O4H68Fe2Cl, found(calcd): C, 59.02-
(59.29); H, 5.05(4.70); N, 7.67(7.68). ømol(corrected) ) 5.98 ×
10-3 emu, µeff ) 3.78 µB. Cyclic voltammogram [E1/2/V, ∆Ep/V,
ibackward/iforward]: B, 0.389, 0.061, 0.49; F, 0.693, 0.066, 0.88;
Epc(C), -0.845 V; Epc(D), -1.749 V.
The structures were solved and refined using the Bruker
SHELXTL (Version 5.03) software package40 in the space

New Metal-Alkynyl Scaffolds
Organometallics, Vol. 24, No. 11, 2005 2669
groups P1hfor crystals 1, 4a, 6, and 10, P21/n for 5, and P21/c
for 9. Positions of all non-hydrogen atoms of diruthenium
moieties were revealed by the direct method. In the cases of
crystals 1, 4a, and 5, the asymmetric unit contains one
independent molecule; in the case of crystal 6, the asymmetric
unit contains one independent molecule with one H2O molecule
coordinating to its axial position and one CH2Cl2 solvate
molecule; in the case of crystal 9, the asymmetric unit contains
one independent molecule and one THF solvate molecule; in
the case of crystal 10, the asymmetric unit contains two
independent molecules. With all non-hydrogen atoms being
anisotropic and all hydrogen atoms in calculated position and
riding mode the structure was refined to convergence by the
least-squares method on F2, SHELXL-93, incorporated in
SHELXTL.PC V 5.03.
Acknowledgment. We are grateful to the National
Science Foundation (CHE0242623) and Office of Naval
Research (N00014-03-1-0531) for providing financial
support.
Supporting Information Available: Text giving details
of the attempted synthesis of 4a from 5, vis-NIR spectra of
compounds 1-10, and electrochemistry of compounds 3b, 4b,
8, and 9, and X-ray crystallographic files in CIF format for
compounds 1, 4a, 5, 6, 9, and 10. This material is available
free of charge via the Internet at http://pubs.acs.org.
(39) SAINT V 6.035 Software for the CCD Detector System; Bruker-
AXS Inc., 1999.
(40) (a) SHELXTL 5.03 (WINDOW-NT Version), Program Library
for Structure Solution and Molecular Graphics; Bruker-AXS Inc., 1998.
(b) Sheldrick, G. M. SHELXS-90, Program for the Solution of Crystal
Structures; University of Go¨ttigen: Germany, 1990. (c) Sheldrick, G.
M. SHELXL-93, Program for the Refinement of Crystal Structures;
University of Go¨ttigen: Germany, 1993.
OM050068T