Synthesis of Dinuclear Rhodium Complexes with 1,3-Butadiyndiyl Bridges. Coupling of the C4 and the Two C2 Units of a C2RhC4RhC2 Chain

Article abstract of DOI:10.1021/om990960y

Compounds trans-[RhF(=C=CHR)(PiPr₃)₂] (2-4), of which 2 (R = H) was prepared for the first time from [Rh{η²-O₂S(O)CF₃}(PiPr₃) ₂], C₂H₂, and KF, reacted with Ph₃SnC≡C-C≡CSnPh₃ to give the dinuclear C₄-bridged rhodium(I) complexes trans,trans-[{Rh(=C=CHR)-(PiPr₃)₂} ₂(μ-C≡C-C≡C)] (5-7) in 78-88% isolated yield. On a similar route, by using trans-[RhF(CX)(PiPr₃)₂] (8, CX = CNC₆H₃Me₂-2,6; 9, CX = CO) and Ph₃SnC≡C-C≡CSnPh₃ in the molar ratio of 2:1 as the starting materials, the diisocyanidedirhodium and dicarbonyldirhodium derivatives trans,trans-[{Rh(CX)(PiPr₃)₂} ₂(μ-C≡C-C≡C)] (12,13) were obtained. The reactions of 8 and 9 with equimolar amounts of Ph₃SnC≡C-C≡CSnPh₃ gave the mononuclear complexes trans-[Rh(C≡C-C≡CSnPh₃)(CX)(PiPr₃) ₂] (10,11), which on further treatment with 8 or 9 afforded the dinuclear compounds 12 and 13, respectively. The C-SnPh₃ bond of 10 could be cleaved both by Al₂O₃/H₂O and trans-[RhF(=C=CHPh)(PiPr₃)₂] (3) to give the butadiynyl compound trans-[Rh(C≡C-C≡CH)(CNC₆H₃Me ₂-2,6)(PiPr₃)₂] (14) and the unsymmetrical dirhodium complex trans,trans-[{Rh(=C=CHPh)(PiPr₃)₂}{Rh-(CNC ₆H₃Me₂-2,6)(PiPr₃) ₂}(μ-C≡C-C≡C)] (15). Moreover, treatment of 5 and 6 with CNC₆H₃-Me₂-2,6 or CO led to a 2-fold migratory insertion reaction to yield the novel dinuclear compounds trans,trans-[{Rh(CX)(PiPr₃)₂} ₂{μ-C(=CHR)C≡C-C≡C-C(CHR)}] (16-18), which contain a highly unsaturated eight-membered C₈ chain as a bridge. The molecular structure of 17 (CX = CO; R = Ph) was determined by X-ray crystallography.

Full text of DOI:10.1021/om990960y

Organometallics 2000, 19, 1365-1372
1365
Syn th esis of Din u clea r Rh od iu m Com p lexes w ith
1,3-Bu ta d iyn d iyl Br id ges. Cou p lin g of th e C4 a n d th e
Tw o C2 Un its of a C2Rh C4Rh C2 Ch a in †,1
J uan Gil-Rubio, Matthias Laubender, and Helmut Werner*
Institut fu¨r Anorganische Chemie der Universita¨t Wu¨rzburg, Am Hubland,
D-97074 Wu¨rzburg, Germany
Received December 6, 1999
Compounds trans-[RhF(dCdCHR)(PiPr3)2] (2-4), of which 2 (R ) H) was prepared for
the first time from [Rh{η2-O2S(O)CF3}(PiPr3)2], C2H2, and KF, reacted with Ph3SnCtC-
CtCSnPh3 to give the dinuclear C4-bridged rhodium(I) complexes trans,trans-[{Rh(dCdCHR)-
(PiPr3)2}2(µ-CtC-CtC)] (5-7) in 78-88% isolated yield. On a similar route, by using trans-
[RhF(CX)(PiPr3)2] (8, CX ) CNC6H3Me2-2,6; 9, CX ) CO) and Ph3SnCtC-CtCSnPh3 in
the molar ratio of 2:1 as the starting materials, the diisocyanidedirhodium and dicarbonyl-
dirhodium derivatives trans,trans-[{Rh(CX)(PiPr3)2}2(µ-CtC-CtC)] (12, 13) were obtained.
The reactions of 8 and 9 with equimolar amounts of Ph3SnCtC-CtCSnPh3 gave the
mononuclear complexes trans-[Rh(CtC-CtCSnPh3)(CX)(PiPr3)2] (10, 11), which on further
treatment with 8 or 9 afforded the dinuclear compounds 12 and 13, respectively. The
C-SnPh3 bond of 10 could be cleaved both by Al2O3/H2O and trans-[RhF(dCdCHPh)(PiPr3)2]
(3) to give the butadiynyl compound trans-[Rh(CtC-CtCH)(CNC6H3Me2-2,6)(PiPr3)2] (14)
and the unsymmetrical dirhodium complex trans,trans-[{Rh(dCdCHPh)(PiPr3)2}{Rh-
(CNC6H3Me2-2,6)(PiPr3)2}(µ-CtC-CtC)] (15). Moreover, treatment of 5 and 6 with CNC6H3-
Me2-2,6 or CO led to a 2-fold migratory insertion reaction to yield the novel dinuclear
compounds trans,trans-[{Rh(CX)(PiPr3)2}2{µ-C(dCHR)CtC-CtC-C(dCHR)}] (16-18), which
contain a highly unsaturated eight-membered C8 chain as a bridge. The molecular structure
of 17 (CX ) CO; R ) Ph) was determined by X-ray crystallography.
In tr od u ction
C-CtCSiMe3 to afford mono- and dinuclear rhodium(I)
complexes with a Rh-CtCPh or Rh-CtC-CtC-Rh
Following the pioneering work by Sonogashira and
Hagihara,2 and the more recent studies by Gladysz and
co-workers,3 the chemistry of di- and oligonuclear
transition metal complexes in which two neighboring
metal centers are connected by a “naked” Cn chain has
received a great deal of attention.4 Apart from the
possibility that these compounds could reveal NLO
properties,5 it appears challenging to bind the two
bond.7 Recently, this methodology has also been applied
(4) (a) Beck, W.; Niemer, B.; Wieser, M. Angew. Chem. 1993, 105,
969-996; Angew. Chem., Int. Ed. Engl. 1993, 32, 923-950. (b) Lang,
H. Angew. Chem. 1994, 106, 569-572; Angew. Chem., Int. Ed. Engl.
1994, 33, 547-550. (c) Le Narvour, N.; Toupet, L.; Lapinte, C. J . Am.
Chem. Soc. 1995, 117, 7129-7138. (d) Coat, F.; Lapinte, C. Organo-
metallics 1996, 15, 477-479. (e) Akita, M.; Chung, M.-C.; Sakurai, A.;
Terada, M.; Tanaka, M.; Moro-oka, Y. Organometallics 1997, 16, 4882-
4888. (f) Sakurai, A.; Akita, M.; Moro-oka, Y. Organometallics 1999,
18, 3241-3244. (g) Bruce, M. I.; Ke, M.; Low, P. J .; Skelton, B. W.;
White, A. H. Organometallics 1998, 17, 3539-3549. (h) Bruce, M. I.;
Kelly, B. D.; Skelton, B. W.; White, A. H. J . Chem. Soc., Dalton Trans.
1999, 847-852. (i) ALQaisi, S.; Galat, K. J .; Chai, M.; Ray, D. G.;
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120, 12149-12150.
(5) (a) Marder, S. R., Sohn, J . E., Stucky, G. D., Eds. Materials for
Nonlinear Optics: Chemical Perspectives; ACS Symposium Series 455;
American Chemical Society: Washington, DC, 1991. (b) Bruce, D. W.,
O’Hare, D., Eds. Inorganic Materials; Wiley: Chichester, U.K., 1992.
(c) Long, N. J . Angew. Chem. 1995, 107, 37-56; Angew. Chem., Int.
Ed. Engl. 1995, 34, 21-40. (d) Whittall, I. R.; McDonagh, A. M.;
Humphrey, M. G. Adv. Organomet. Chem. 1998, 42, 291-362. (e)
McDonagh, A. M.; Humphrey, M. G.; Samoc, M.; Luther-Davies, B.;
Houbrechts, S.; Wada, T.; Sasabe, H.; Persoons, A. J . Am. Chem. Soc.
1999, 121, 1405-1406. (f) Younus, M.; Ko¨hler, A.; Cron, S.; Chawdhury,
N.; Al-Mandhary, M. R. A.; Khan, M. S.; Lewis, J .; Long, N. J .; Friend,
R. H.; Raithby, P. R. Angew. Chem. 1998, 110, 3180-3183; Angew.
Chem., Int. Ed. 1998, 37, 3036-3039. (g) Kingsborough, R. P.; Swager,
T. M. Prog. Inorg. Chem. 1999, 48, 123-231.
2-
terminal carbon atoms of a Cn dianion to two redox-
active metal centers and thus to generate the precursor
of a molecular wire.6
Our own interest in this field dates back to the
observation that hydroxorhodium(I) compounds with
[Rh(PiPr3)2] as a building block react smoothly with
silylated alkynes such as PhCtCSiMe3 and Me3SiCt
† Dedicated to Professor Henri Brunner on the occasion of his 65th
birthday.
(1) Vinylidene Transition-Metal Complexes. 52. Part 51: Werner,
H.; Ilg, K.; Weberndo¨rfer, B. Organometallics 2000, 19, in press.
(2) (a) Sonogashira, K.; Fujikura, Y.; Yatake, T.; Toyoshima, N.;
Takahashi, S.; Hagihara, N. J . Organomet. Chem. 1978, 145, 101-
108. (b) Sonogashira, K.; Kataoka, S.; Takahashi, S.; Hagihara, N. J .
Organomet. Chem. 1978, 160, 319-327. (c) Sonogashira, K.; Ohga, K.;
Takahashi, S.; Hagihara, N. J . Organomet. Chem. 1980, 188, 237-
243. (d) Hagihara, N.; Sonogashira, K.; Takahashi, S. Adv. Polym. Sci.
1981, 41, 149-179.
(3) (a) Peters, T. B.; Bohling, J . C.; Arif, A. M.; Gladysz, J . A.
Organometallics 1999, 18, 3261-3263. (b) 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, 775-788, and references
therein.
(6) (a) Yam, V. W.-W.; Lau, V. C.-Y.; Cheung, K.-K. Organometallics
1996, 15, 1740-1744. (b) Colbert, M. C. B.; Lewis, J .; Long, N. J .;
Raithby, P. R.; Younus, M.; White, A. J . P.; Williams, D. J .; Payne, N.
N.; Yellowlees, L.; Beljonne, D.; Chawdhury, N.; Friend, R. H.
Organometallics 1998, 17, 3034-3045. (c) Guillemot, M.; Toupet, L.;
Lapinte, C. Organometallics 1998, 17, 1928-1930. (d) Zhu, Y.; Clot,
O.; Wolf, M.; Yap, G. P. A. J . Am. Chem. Soc. 1998, 120, 1812-1821.
10.1021/om990960y CCC: $19.00 © 2000 American Chemical Society
Publication on Web 03/08/2000

1366 Organometallics, Vol. 19, No. 7, 2000
Gil-Rubio et al.
Sch em e 1a
Sch em e 3a
a
L ) PiPr3.
Sch em e 2a
a
L ) PiPr3.
a
L ) PiPr3.
in the 31P and 19F NMR spectra, clearly indicate a trans
disposition of the two phosphine ligands.
to starting materials with vinylidenes and allenylidenes
as ligands, thus allowing the preparation of compounds
with a linear C2RhC4RhC2 and C3RhC4RhC3 chain.8,9
Since the chemistry of these compounds was almost
unexplored, we started two years ago to investigate the
reactivity of RhC4Rh derivatives toward Lewis acids and
Lewis bases. In this paper we describe the preparation
of a series of symmetrical and unsymmetrical rho-
dium(I) complexes containing a C4 bridge and report in
particular about a CO- or CNR-initiated intramolecular
C-C coupling reaction leading to products with an
eight-membered CdC-CtC-CtC-CdC moiety as a
bridge. Some preliminary results of these studies have
already been communicated.10
Treatment of the fluoro(vinylidene) complexes 2-4
with Ph3SnCtCCtCSnPh3 affords in each case a green
solution together with a white, nearly insoluble solid,
which was separated by filtration and identified by
comparison of the IR and NMR spectra as Ph3SnF.12
From the green solutions, after evaporation of the
solvent, the dinuclear complexes 5-7 were isolated in
78-88% yield (Scheme 2). The phenylvinylidene deriva-
tive 6 was already known and had been prepared in our
laboratory from trans-[Rh(OH)(dCdCHPh)(PiPr3)2] and
Ph3SnCtCCtCSnPh3.7 The new route is more favorable
insofar as workup of the reaction mixture obtained from
the hydroxorhodium compound and Ph3SnCtCCt
CSnPh3 is more tedious since it needed low-temperature
column chromatography in order to separate the soluble
byproduct Ph3SnOH from complex 6. The most typical
spectroscopic features of the new dinuclear complexes
5 and 7 are the 13C NMR resonances for the R- and
â-carbon atoms of the RhdCdC unit, which are ob-
served as doublets of triplets at δ 307.5 and 92.7 (for 5)
or 307.0 and 121.5 (for 7), respectively. The signals for
the carbon atoms of the C4 chain appear in both spectra
in the range δ 122.2-127.4. It should be noted that the
starting material 3 does not react with Me3SiCtCCt
CSiMe3 even after stirring the reaction mixture for 24
h at room temperature.
Resu lts a n d Discu ssion
Syn th esis of Din u clea r Rh od iu m Com p lexes
w ith a 1,3-Bu ta d iyn d iyl Br id ge. The preparative
route that we used to obtain the fluoro(vinylidene)-
rhodium(I) complexes trans-[RhF(dCdCHR)(PiPr3)2] (3,
R ) Ph; 4, R ) tBu)11 could also be applied for the
synthesis of the parent compound 2 with R ) H (see
Scheme 1). The reaction of the starting material 1 with
acetylene probably results in the formation of a triflato-
(vinylidene)metal intermediate, which is converted in
situ into complex 2 by treatment with potassium
fluoride. The spectroscopic data of 2 (a red-purple
crystalline solid), in particular the couplings observed
The fluoro(isocyanide) and fluoro(carbonyl) complexes
8 and 9 behave similarly to the fluoro(vinylidene)
derivatives 2-4 and give upon treatment with Ph3SnCt
CCtCSnPh3 in benzene at 60 °C the dinuclear com-
pounds 12 and 13 in moderate to good yields (Scheme
3). Since the rate of the reaction of 8 and 9 with
Ph3SnCtCCtCSnPh3 is lower than that of the related
complexes 2-4 with the distannylated butadiyne, it is
(7) Gevert, O.; Wolf, J .; Werner, H. Organometallics 1996, 15, 2806-
2809.
(8) Gil-Rubio, J .; Laubender, M.; Werner, H. Organometallics 1998,
17, 1202-1207.
(9) Gil-Rubio, J .; Weberndo¨rfer, B.; Werner, H. Angew. Chem. 2000,
112, 814-818; Angew. Chem., Int. Ed. Engl. 2000, 39, 786-789.
(10) Gil-Rubio, J .; Callejas-Gaspar, B.; Laubender, M.; Werner, H.
37th IUPAC Congress/27th GDCh General Meeting, Berlin, 1999.
(11) Gil-Rubio, J .; Weberndo¨rfer, B.; Werner, H. J . Chem. Soc.,
Dalton Trans. 1999, 1437-1444.
(12) Kriegsmann, H.; Geissler, H. Z. Anorg. Allg. Chem. 1963, 323,
170-189.

Synthesis of Dinuclear Rhodium Complexes
Organometallics, Vol. 19, No. 7, 2000 1367
Sch em e 4a
Sch em e 5a
a
L ) PiPr3.
pentane. After separation of the byproduct Ph3SnF, the
dinuclear compound 15 (see Scheme 4) containing a
different ligand sphere at both ends of the Rh-C4-Rh
chain was isolated as a green-yellow solid in 93% yield.
The 31P NMR spectrum of 15 displays two doublets with
chemical shifts and Rh-P coupling constants that are
similar to those of both the alkynyl(vinylidene) com-
plexes 5-7 and the alkynyl(isocyanide) compounds 10,
12, and 14. Regarding the 13C NMR signals of the atoms
of the C4 chain in 15, the two doublets with J (RhC) )
10.1 and 12.2 Hz are assigned to the two central carbons
and a doublet of triplets with J (RhC) ) 36.6 and J (PC)
) 20.3 Hz to one of the carbons bonded to rhodium. The
second Rh-C resonance is probably obscured by the
signal of the solvent.
A comparison of the spectroscopic data of the unsym-
metrical compound 15 with those of the symmetrical
counterpart 6 was interesting insofar as it could give a
hint how strong the mutual electronic interaction
between both metal centers through the C4 chain is.
Since the dinuclear bis(vinylidene) complexes 5-7 are
green and the bis(isocyanide) complex 12 is yellow, it
is not surprising that compound 15 is green-yellow.
However, the absorption maxima of 15 arising from the
vinylidene-metal chromophore (λmax ) 638 and 439 nm,
in hexane) are red-shifted compared to the correspond-
ing maxima of 6 (λmax ) 621 and 429 nm, in hexane).
Moreover, in the 13C NMR spectrum of 15 the signal of
the R-carbon atom of the RhdCdC fragment appears
at δ 294.4, while that of 6 is observed at δ 310.0. These
differences are probably due to the better donor ability
of the isocyanide compared with the vinylidene ligand,
indicating that there is a push-pull interaction between
the Rh(CNR)L2 and the Rh(dCdCHPh)L2 units.13
a
L ) PiPr3.
possible to observe the initial formation of the mono-
rhodium species 10 and 11. They both react slowly with
a second equivalent of the corresponding fluoro complex
8 or 9 to give the dirhodium complexes 12 and 13,
respectively.
The observed generation of the intermediates 10 and
11 prompted us to study the reactions of 8 and 9 with
equimolar amounts of Ph3SnCtCCtCSnPh3 under
milder conditions. We found that if a 1:1 mixture of the
starting materials in benzene was stirred at room
temperature for 18 h, the mononuclear compounds 10
and 11 were formed as the major products together with
small amounts (ca. 10%) of the dinuclear complexes 12
and 13. In the case of 10 we succeeded in isolating an
analytically pure sample in 43% yield by extraction of
the crude product with acetone followed by crystalliza-
tion. Attempts to isolate 10 from the reaction mixture
in better yields by using column chromatography led
to the formation of compound 14 via hydrolysis of the
Sn-C bond (Scheme 4). We were not able to obtain
complex 11 free of traces of 13 by recrystallization or
chromatography.
The most notable spectroscopic features of 10 and 14
are the 13C NMR signals of the carbon atoms of the C4
chain, which were assigned according to the different
values of the Rh-C coupling constants. Both the
resonances for the R- and â-carbon atoms appear as
doublets of triplets with J (RhC) ) 42.3 and 12.4 Hz (for
10) and 42.7 and 10.2 Hz (for 14), respectively. While
for 10 the signal of the γ-carbon atom is a doublet of
triplets (with J (RhC) ) 1.4 Hz), it is a singlet for 14.
For both compounds, the resonance of the δ-C atom
reveals no coupling with rhodium. In the case of 14, the
correct assignment of this signal could be made by
CO- a n d CNR-In itia ted C-C Cou p lin g Rea c-
tion s. The recent observation that the mononuclear
alkynyl complexes trans-[Rh(CtCR)(dCdCR′R′′)(PiPr3)2]
react with CO to give the butenynyl compounds trans-
[Rh{C(CtCR)dCR′R′′}(CO)(PiPr3)2] by migratory inser-
means of a H-13C COSY experiment.
The carbon-tin bond of the Rh-C4-SnPh3 chain in
10 could be cleaved not only by Al2O3/H2O but also upon
treatment of 10 with the fluororhodium(I) complex 3 in
1
(13) Mayr, A.; Yu, M. P. Y.; Yam, V. W.-W. J . Am. Chem. Soc. 1999,
121, 1760-1761.

1368 Organometallics, Vol. 19, No. 7, 2000
Gil-Rubio et al.
F igu r e 1. Molecular structure (ORTEP plot) of compound
17.
Ta ble 1. Selected Bon d Dista n ces a n d An gles w ith
Esd ’s for Com p ou n d 17
Bond Distances (Å)
Rh1-C2
Rh1-C70
Rh2-C7
Rh2-C71
Rh1-P1
Rh1-P2
Rh2-P3
Rh2-P4
C1-C50
C1-C2
2.103(6)
1.829(6)
2.103(5)
1.845(6)
2.343(1)
2.340(2)
2.334(2)
2.334(2)
1.453(8)
1.345(8)
C2-C3
C3-C4
C4-C5
C5-C6
C6-C7
C7-C8
C8-C60
C70-O1
C71-O2
1.420(7)
1.214(7)
1.370(7)
1.218(7)
1.409(7)
1.346(7)
1.458(7)
1.162(7)
1.143(7)
F igu r e 2. Variable-temperature 1H NMR spectra (low-
field region) of compound 17 in CDCl3. The singlets at δ
7.34 and 7.24 correspond to C6H6 and CHCl3, respectively.
Bond Angles (deg)
C70-Rh1-C2
C70-Rh1-P2
C2-Rh1-P2
C70-Rh1-P1
C2-Rh1-P1
P2-Rh1-P1
C71-Rh2-C7
C71-Rh2-P3
C7-Rh2-P3
C71-Rh2-P4
C7-Rh2-P4
P3-Rh2-P4
173.7(3)
89.7(2)
91.0(1)
89.3(2)
91.4(1)
167.02(6)
174.2(2)
89.4(2)
91.5(2)
89.5(2)
90.8(2)
167.94(5)
C2-C1-C50
C1-C2-C3
C1-C2-Rh1
C3-C2-Rh1
C4-C3-C2
C6-C5-C4
C5-C6-C7
C8-C7-C6
C8-C7-Rh2
C6-C7-Rh2
C7-C8-C60
130.0(6)
113.9(5)
128.6(4)
117.5(5)
178.1(6)
176.7(6)
176.0(6)
117.9(5)
129.0(4)
113.1(4)
129.9(5)
being 27.0(2)°. The distances Rh1-C2 and Rh2-C7
(2.103(6) and 2.103(5) Å) and the linearity of the CtC-
CtC chain suggest that there is no significant interac-
tion between the π-electrons of the CtC bonds and the
metal centers. Other noteworthy features are the pla-
narity of both CdCHPh fragments and the cis disposi-
tion of the phenyl group and the metal-ligand unit at
the CdC bonds. We assume that this configuration is
also preserved in solution since an NOE experiment
revealed a small but significant enhancement of the
signal of the phenyl proton in ortho position upon
irradiation of the resonances of the methyl protons of
the triisopropylphosphine ligands.
tion of the vinylidene ligand into the Rh-C σ-bond,14
prompted us to study also the analogous reactions of
the dinuclear complexes trans,trans-[{Rh(dCdCHR)-
(PiPr3)2}2(µ-CtC-CtC)] with carbon monoxide. The
hope was that a 2-fold migratory insertion would occur.
Passing a slow stream of CO through a solution (or
suspension) of 5 or 6 in pentane or hexane at low
temperature led indeed to a smooth conversion of the
starting materials to the dicarbonyldirhodium com-
plexes 16 and 17, which were isolated as yellow solids
in, respectively, 74% and 82% yields. The structural
proposal for 16 and 17 (Scheme 5) is supported by the
analytical and spectroscopic data as well as by an X-ray
diffraction analysis of 17. The molecular diagram (see
Figure 1) confirms the formation of an unsaturated C8
chain generated by C-C coupling of the C4 bridge and
the two vinylidene ligands. Although the central C6 unit
is nearly linear (see Table 1), the C8 chain is not planar,
the dihedral angle between the planes defined by the
carbon atoms [C60-65, C6-8] and [C50-55, C1-3]
On the basis of the result that the distances between
one of the ortho hydrogen atoms of the phenyl groups
and the metal centers are quite short (Rh1-H51 2.50(1)
and Rh2-H61 2.48(1) Å), we also took an agostic
interaction into consideration. To prove this hypothesis,
the 1H and 13C NMR spectra of compound 17 were
measured at various temperatures. We found that the
1H NMR spectrum displayed at -60 °C two different
signals at δ 9.7 and 7.1 for the phenyl protons in ortho
position (see Figure 2), indicating that the rotation of
the phenyl groups around the C-C bond is slow on the
NMR time scale. These signals coalesce at about 17 °C
to give a single resonance at δ 8.3. No coupling was
observed between the ortho hydrogens and the 103Rh or
31P nuclei. In the 13C NMR spectrum of 17 also two
signals appear for the carbon atoms in ortho position of
the phenyl rings at -60 °C but only one resonance at
room temperature. Since work by Brookhart and Green
(14) (a) Scha¨fer, M.; Mahr, N.; Wolf, J .; Werner, H. Angew. Chem.
1993, 105, 1377-1379; Angew. Chem., Int. Ed. Engl. 1993, 32, 1315-
1318. (b) Werner, H.; Wiedemann, R.; Steinert, P.; Wolf, J . Chem. Eur.
J . 1997, 3, 127-137.
1
has shown that the size of J (CH) is indicative of the

Synthesis of Dinuclear Rhodium Complexes
Organometallics, Vol. 19, No. 7, 2000 1369
1
coupling; N ) 3J (PH) + 5J (PH) or J (PC) + 3J (PC)]. IR spectra
presence of an agostic bond,15 we determined this
coupling constant from the low-temperature 13C NMR
spectrum. We found for both signals of the respective
were measured on a Bruker IFS 25 spectrometer. Decomposi-
tion temperatures were determined by DTA.
1
P r ep a r a tion of tr a n s-[Rh F (dCdCH2)(P iP r 3)2] (2). A
Schlenk flask containing a solution of compound 1 (217 mg,
0.38 mmol) in acetone (15 mL) was connected to a gastight
syringe, which was equipped with a glass stopcock and filled
with acetylene (0.4 mmol). The flask was partially evacuated
by an oil pump and cooled to liquid nitrogen temperature. The
stopcock was then opened, and the acetylene was introduced
into the flask. The mixture was slowly warmed to room
temperature with continuous stirring and stirred at 20 °C for
2.5 h. During this time the color changed initially from red-
orange to yellow-orange and then slowly to red. After KF (232
mg, 4.0 mmol) was added to the solution, the resulting
suspension was stirred for 30 min and then the solvent
removed in vacuo. The residue was extracted twice with 20
mL portions of pentane. The combined extracts were filtered,
concentrated to ca. 3 mL, and stored for 2 days at -25 °C.
Red-purple crystals precipitated, which were washed three
times with 2 mL portions of pentane (-78 °C) and dried: yield
147 mg (83%); mp 71 °C dec; IR (Nujol) ν(CdC) 1638, 1628,
ortho carbon atoms J (13C1H) values of 155.5 and 159.1
Hz, which are nearly the same. Therefore, we conclude
that the Rh‚‚‚H-C interaction is not significant and the
barrier to rotation of the phenyl groups not due to an
agostic interaction but probably to steric repulsion
between the phenyl protons in ortho position and the
isopropyl units.
Finally, we note that 2,6-dimethylphenylisocyanide
behaves analogously to CO and reacts with 6 to give
the dinuclear complex 18. The spectroscopic data of 18
are quite similar to those of 17 and also indicate a slow
rotation of the phenyl group around the C-C bond on
the NMR time scale. This finding (illustrated by the
temperature dependence of the signals of the ortho C-H
1
protons) together with a H NOE experiment suggests
that not only in 17 but also in 18 the two CdC bonds
possess a Z configuration.
ν(Rh-F) 458 cm-1; H NMR (C6D6, 200 MHz) δ 2.60 (m, 6H,
1
PCHCH3), 1.33 (dvt, N ) 13.5 Hz, J (HH) ) 6.6 Hz, 36H,
PCHCH3), 0.06 (m, 2H, RhdCdCH2); 13C{1H} NMR (C6D6,
100.6 MHz) δ 297.3 (m, Rh)C), 88.5 (m, CH2), 22.7 (vt, N )
18.5 Hz, PCHCH3), 20.1 (s, PCHCH3); 19F NMR (C6D6, 188.3
MHz) δ -219.3 (dt, J (RhF) ) 14.5 Hz, J (PF) ) 18.2 Hz);
31P{1H} NMR (C6D6, 81.0 MHz) δ 45.4 (dd, J (RhP) ) 145.0
Hz, J (PF) ) 18.2 Hz). Anal. Calcd for C20H44FP2Rh: C, 51.28;
H, 9.47. Found: C, 51.00; H, 9.33.
Con clu sion s
The work presented in this paper has shown that by
using the bisstannylated butadiyne Ph3SnCtCCt
CSnPh3 as the substrate, symmetrical as well as un-
symmetrical dinuclear rhodium(I) complexes containing
a “naked” C4 bridge can be prepared. Although a wealth
of compounds of the general composition [MLn]-C4-
[MLn] is known,2-4,7-9 only a few examples with a
different coordination sphere at the metal centers on
both sites of the C4 chain have been described.16 The
reactivity of the bis(vinylidene)dirhodium complexes 5
and 6 obtained by the SnC4Sn methodology is high-
lighted by the observation that in the presence of CO
and the isocyanide CNC6H3Me2-2,6 these compounds
undergo a 2-fold migratory insertion reaction to yield
the unusual dinuclear complexes 16-18, which contain
a highly unsaturated eight-membered C8 chain as a
bridge. We note that quite recently a related reaction
of the dinuclear ruthenium compound [{RuCl(CO)(NH3)-
(PPh3)2}(µ-CHdCH-CHdCH)] has been observed.17
This species reacts with CNtBu to afford the dicationic
complex [{Ru(CNtBu)3(PPh3)2}{µ-C(O)-CHdCH-CHd
CH-C(O)}]2+ via the intramolecular insertion of both
CO ligands into the C4H4 bridge.
P r ep a r a tion of tr a n s,tr a n s-[{Rh (dCdCH2)(P iP r 3)2}2(µ-
CtC-CtC)] (5). A solution of 2 (219 mg, 0.47 mmol) in
hexane (20 mL) was treated with Ph3SnCtCCtCSnPh3 (175
mg, 0.23 mmol) at -78 °C. Under continuous stirring, the
mixture was slowly warmed to room temperature and stirred
at 20 °C for 75 min. A change of color from red-violet to green
occurred. The solution was filtered, the filtrate was evaporated
to dryness in vacuo, and the residue was extracted 6 times
with 10 mL portions of hexane. The combined extracts were
concentrated to ca. 3 mL in vacuo, and the concentrated
solution was stored for 24 h at -25 °C. A green solid
precipitated, which was washed twice with 2 mL portions of
pentane (-40 °C) and dried: yield 187 mg (84%); mp 59 °C
1
dec; IR (Nujol) ν(CdC) 1617 cm-1; H NMR (C6D6, 400 MHz)
δ 2.80 (m, 12H, PCHCH3), 1.39 (dvt, N ) 13.2 Hz, J (HH) )
6.2 Hz, 72H, PCHCH3), -0.01 (t, J (PH) ) 3.4 Hz, 4H, Rhd
CdCH2); 13C{1H} NMR (C6D6, 100.6 MHz) δ 307.5 (dt, J (RhC)
) 47.9 Hz, J (PC) ) 15.8 Hz, RhdC), 125.0 (d, J (RhC) ) 8.7
Hz, Rh-CtC), 122.2 (dt, J (RhC) ) 38.1 Hz, J (PC) ) 19.3 Hz,
Rh-CtC), 92.7 (dt, J (RhC) ) 14.2 Hz, J (PC) ) 5.4 Hz, CH2),
25.2 (vt, N ) 20.7 Hz, PCHCH3), 20.6 (s, PCHCH3); 31P{1H}
NMR (C6D6, 162.0 MHz) δ 47.2 (d, J (RhP) ) 137.3 Hz). Anal.
Calcd for C44H88P4Rh2: C, 55.81; H, 9.37. Found: C, 55.52; H,
9.06.
P r ep a r a tion of tr a n s,tr a n s-[{Rh (dCdCHP h )(P iP r 3)2}2-
(µ-CtC-CtC)] (6). A solution of 3 (247 mg, 0.45 mmol) in
pentane (20 mL) was treated with Ph3SntCCtCSnPh3 (170
mg, 0.23 mmol) at -78 °C. Under continuous stirring, the
mixture was slowly warmed to room temperature and stirred
at 20 °C for 50 min. The green suspension was filtered, the
filtrate was evaporated to dryness in vacuo, and the residue
extracted 3 times with 20 mL portions of pentane. The
combined extracts were concentrated to ca. 4 mL in vacuo, and
the concentrated solution was stored for 2 days at -65 °C. A
green crystalline solid precipitated and was washed two times
with 2 mL portions of pentane (-78 °C) and dried: yield 195
mg (78%). The 1H, 31P NMR and IR data of the compound were
identical to those reported for 6 in the literature.7
Exp er im en ta l Section
All reactions were carried out under an atmosphere of argon
by Schlenk techniques. Solvents were dried by known proce-
dures and distilled before use. The starting materials 1,18 3,
4, 8, 9,11 and Ph3SnCtCCtCSnPh3 were prepared as de-
19
scribed in the literature. NMR spectra were recorded at room
temperature (if not otherwise indicated) on Bruker AC 200
and Bruker AMX 400 instruments [abbreviation: v ) virtual
(15) Brookhart, M.; Green, M. L. H.; Wong., L.-L. Prog. Inorg. Chem.
1988, 36, 1-124.
(16) Coat, F.; Guillevic, M.-A.; Toupet, L.; Paul, F.; Lapinte, C.
Organometallics 1997, 16, 5988-5998.
(17) Xia, H. P.; Yeung, R. C. Y.; J ia, G. Organometallics 1998, 17,
4762-4768.
(18) Werner, H.; Bosch, M.; Schneider, M. E.; Hahn, C.; Kukla, F.;
Manger, M.; Windmu¨ller, B.; Weberndo¨rfer B.; Laubender, M. J . Chem.
Soc., Dalton Trans. 1998, 3549-3558.
(19) Bre´fort, J . L.; Corriu, J . P.; Gerbier, Ph.; Gue´rin, C.; Henner,
B. J . L.; J ean, A.; Kuhlmann, Th.; Garnier, F.; Yassar, A. Organo-
metallics 1992, 11, 2500-2506.
P r epar ation of tr a n s,tr a n s-[{Rh (dCdCHtBu )(P iP r 3)2}2-
(µ-CtC-CtC)] (7). A solution of 4 (168 mg, 0.32 mmol) in

1370 Organometallics, Vol. 19, No. 7, 2000
Gil-Rubio et al.
(Nujol) ν(CtN and CtC) 2031, 2005, 1965 cm-1 1H NMR
pentane (15 mL) was treated with Ph3SnCtCCtCSnPh3 (119
mg, 0.16 mmol) at -78 °C. Under continuous stirring, the
mixture was slowly warmed to room temperature and stirred
at 20 °C for 2 h. The green suspension was filtered and the
filtrate worked up as described for 6: green crystalline solid;
yield 149 mg (88%); mp 52 °C dec; IR (Nujol) ν(CdC) 1664,
;
(C6D6, 200 MHz) δ 6.99 (s, 6H, C6H3Me2), 2.50 (m, 12H,
PCHCH3), 2.33 (s, 12H, C6H3Me2), 1.33 (dvt, N ) 13.3 Hz,
J (HH) ) 6.4 Hz, 72H, PCHCH3); 13C{1H} NMR (C6D6, 100.6
MHz) δ 133.8, 128.6, 127.8, 125.5 (all s, C6H3), 26.2 (vt, N )
19.1 Hz, PCHCH3), 20.6 (s, PCHCH3), 19.0 (s, C6H3Me2), owing
to the low solubility of 12, the signals of the Rh-CN and Ct
C carbon atoms could not be observed; 31P{1H} NMR (C6D6,
162.0 MHz) δ 51.5 (d, J (RhP) ) 135.7 Hz). Anal. Calcd for
1
1636, 1630 cm-1; H NMR (C6D6, 400 MHz) δ 2.85 (m, 12H,
PCHCH3), 1.42 (dvt, N ) 13.2 Hz, J (HH) ) 6.2 Hz, 72H,
PCHCH3), 1.06 (s, 18H, tBu), 0.05 (t, J (PH) ) 3.7 Hz, 2H, Rhd
CdCH); 13C{1H} NMR (C6D6, 100.6 MHz) δ 307.0 (dt, J (RhC)
) 48.8 Hz, J (PC) ) 15.8 Hz, RhdC), 127.4 (d, J (RhC) ) 8.1
Hz, Rh-CtC), 122.7 (dt, J (RhC) ) 37.6 Hz, J (PC) ) 19.3 Hz,
Rh-CtC), 121.5 (dt, J (RhC) ) 12.2 Hz, J (PC) ) 5.6 Hz, Rhd
C)CH), 32.4 (s, CCH3), 25.4 (vt, N ) 20.3 Hz, PCHCH3), 25.2
(s, CCH3), 20.7 (s, PCHCH3); 31P{1H} NMR (C6D6, 162.0 MHz)
δ 46.1 (d, J (RhP) ) 137.3 Hz). Anal. Calcd for C52H104P4Rh2:
C, 58.97; H, 9.90. Found: C, 58.68; H, 9.59.
C
58H102N2P4Rh2: C, 60.20; H, 8.88; N, 2.43. Found: C, 59.71;
H, 8.41; N, 2.51.
P r ep a r a tion of tr a n s,tr a n s-[{Rh (CO)(P iP r 3)2}2(µ-Ct
C-CtC)] (13). A solution of 9 (65 mg, 0.14 mmol) in benzene
(5 mL) was treated with Ph3SnCtCCtCSnPh3 (52 mg, 0.07
mmol) at room temperature. After the mixture was stirred for
15 h, its composition was examined by 31P NMR spectroscopy.
Three doublets were observed in the ratio of ca. 1:1:1 corre-
sponding to compounds 9, 13, and, probably, 11. The reaction
mixture was then stirred at 55 °C for 8.5 h, the solution was
filtered, and the filtrate was evaporated to dryness in vacuo.
The resulting yellow solid was washed twice with 2 mL
P r ep a r a tion of tr a n s-[Rh (CNC6H3Me2-2,6)(P iP r 3)2(Ct
C-CtCSn P h 3)] (10). A solution of 8 (472 mg, 0.82 mmol) in
benzene (30 mL) was added dropwise under continuous
stirring to a solution of Ph3SnCtCCtCSnPh3 (616 mg, 0.82
mmol) in benzene (10 mL) at room temperature. After the
addition was completed (ca. 1 h), the mixture was stirred at
20 °C for 18 h. A change of color from yellow to yellow-brown
occurred. The 31P NMR spectrum of the resulting solution
showed only two doublets corresponding to compounds 10 and
12 in the ratio of ca. 10:1. The suspension was filtered, the
filtrate was evaporated to dryness in vacuo, and the residue
was extracted 3 times with 10 mL portions of acetone. The
remaining yellow solid was identified by NMR spectroscopy
as 12 contaminated with small amounts of 10. The combined
acetone extracts were filtered, and the filtrate was concen-
trated in vacuo until a yellow crystalline solid started to
precipitate. After the solution was stored at -25 °C for 6 days,
a yellow-brownish crystalline solid was obtained, which was
washed three times with 5 mL portions of pentane (-20 °C)
and dried: yield 334 mg (43%); mp 106 °C dec; IR (Nujol)
ν(CtC and CtN) 2136, 2054, 2012, 1988 cm-1; 1H NMR (C6D6,
400 MHz) δ 7.72, 7.65, 7.57 (all m, 6H, ortho-H of C6H5 plus
117Sn and 119Sn satellites), 7.10 (m, 9H, meta- and para-H of
C6H5), 6.73 (m, 3H, C6H3Me2), 2.49 (m, 6H, PCHCH3), 2.28 (s,
6H, C6H3Me2), 1.35 (dvt, N ) 13.6 Hz, J (HH) ) 6.8 Hz, 36H,
PCHCH3); 13C{1H} NMR (C6D6, 100.6 MHz) δ 169.5 (dt, J (RhC)
) 55.3 Hz, J (PC) ) 15.3 Hz, Rh-CN), 138.5 (s plus two
satellite d, J (117SnC) and J (119SnC) ) 616.7 and 588.5 Hz,
ipso-C of C6H5), 137.3 (s and one satellite d, J (117SnC) )
J (119SnC) ) 42.3 Hz, meta-C of C6H5), 133.5, 130.2 (both s,
ortho- and ipso-C of C6H3Me2), 129.2 (s and one satellite d,
J (117SnC) ) J (119SnC) ) 12.1 Hz, para-C of C6H5), 128.8 (s and
two satellite d, J (117SnC) and J (119SnC) ) 59.4 and 56.3 Hz,
ortho-C of C6H5), 128.2, 126.5 (s, meta- and para-C of C6H3-
Me2), 126.1 (dt, J (RhC) ) 42.3 Hz, J (PC) ) 19.3 Hz, Rh-CtC),
102.4 (dt, J (RhC) ) 12.4 Hz, J (PC) ) 2.9 Hz, Rh-CtC), 101.1
(dt, J (RhC) ) 1.4 Hz, J (PC) ) 2.9 Hz, Rh-CtC-CtC), 71.4
(t, J (PC) ) 2.2 Hz, Rh-CtC-CtC, the 117Sn and 119Sn
satellites for the two last signals were not observed), 26.3 (vt,
N ) 19.9 Hz, PCHCH3), 20.7 (s, PCHCH3), 19.9 (s, C6H3Me2);
31P{1H} NMR (C6D6, 162.0 MHz) δ 52.0 (d, J (RhP) ) 132.0
Hz). Anal. Calcd for C49H66NP2RhSn: C, 61.78; H, 6.98; N,
1.48. Found: C, 61.48; H, 6.90; N, 1.44.
1
portions of acetone and dried: yield 55 mg (83%). The H, 31P
NMR and IR data of the compound were identical to those
reported for 13 in the literature.7
When the reaction was carried out at room temperature
using equimolar amounts of 9 and Ph3SnCtCCtCSnPh3, a
mixture of 11 and 13 in the ratio of 8:1 together with unreacted
alkyne was obtained. Attempts to isolate a pure sample of
compound 11 by recrystallization failed. Spectroscopic data for
11: 1H NMR (C6D6, 200 MHz) δ 7.8-7.4 (m, 6H, ortho-H of
C6H5 plus 117Sn and 119Sn satellites), 7.10 (m, 9H, meta- and
para-H of C6H5), 2.43 (m, 6H, PCHCH3), 1.26 (dvt, N ) 13.9
Hz, J (HH) ) 7.1 Hz, 36H, PCHCH3); 31P{1H} NMR (C6D6, 81.0
MHz) δ 54.1 (d, J (RhP) ) 125.6 Hz).
P r ep a r a t ion of tr a n s-[R h (CNC6H 3Me2-2,6)(P iP r 3)2-
(CtC-CtCH)] (14). A solution of 10 was prepared from 8
(80 mg, 0.14 mmol) and Ph3SnCtCCtCSnPh3 (104 mg, 0.14
mmol) in benzene (5 mL) at room temperature. After the
reaction was finished, the solution was concentrated to ca. 2
mL in vacuo and pentane (6 mL) was added. The resulting
suspension was chromatographed on Al2O3 (neutral, activity
grade V, column diameter 2 cm, column length 10 cm). With
pentane/benzene (10:1) a yellow fraction was eluted, which was
evaporated in vacuo to give a yellow oil. Recrystallization from
pentane at -60 °C afforded a yellow microcrystalline solid:
yield 60 mg (72%); mp 130 °C dec; IR (Nujol) ν(C-H) 3287,
ν(CtC and CtN) 2118, 2054, 2005, 1971 cm-1; 1H NMR (C6D6,
400 MHz) δ 6.72 (m, 3H, C6H3Me2), 2.47 (m, 6H, PCHCH3),
2.27 (s, 6H, C6H3Me2), 1.76 (t, J (PH) ) 1.2 Hz, 1H, C4H), 1.33
(dvt, N ) 13.6 Hz, J (HH) ) 7.2 Hz, 36H, PCHCH3); 13C{1H}
NMR (C6D6, 100.6 MHz) δ 169.7 (dt, J (RhC) ) 55.3 Hz, J (PC)
) 15.1 Hz, Rh-CN), 133.5, 130.3, 128.1, 126.4 (all s, C6H3),
122.8 (dt, J (RhC) ) 42.7 Hz, J (PC) ) 21.4 Hz, Rh-CtC), 100.9
(dt, J (RhC) ) 10.2 Hz, J (PC) ) 3.0 Hz, Rh-CtC), 73.4 (s, Rh-
CtC-CtC), 59.6 (s, Rh-CtC-CtC), 26.2 (vt, N ) 20.3 Hz,
PCHCH3), 20.6 (s, PCHCH3), 18.9 (s, C6H3Me2); 31P{1H} NMR
(C6D6, 162.0 MHz) δ 52.0 (d, J (RhP) ) 132.0 Hz). Anal. Calcd
for C31H52NP2Rh: C, 61.68; H, 8.68; N, 2.33. Found: C, 61.61;
H, 8.55; N, 2.27.
P r ep a r a tion of tr a n s,tr a n s-[{Rh (CNC6H3Me2-2,6)-
(P iP r 3)2}(µ-CtC-CtC){Rh (dCdCHP h )(P iP r 3)2}] (15). A
solution of 3 (95 mg, 0.18 mmol) in pentane (5 mL) was added
to a suspension of 10 (170 mg, 0.18 mmol) in pentane (15 mL)
at -78 °C. Under continuous stirring, the mixture was slowly
warmed to room temperature and stirred at 20 °C for 2 h. The
resulting green suspension was filtered, the solvent was
removed from the filtrate, and the residue was extracted 3
times with 8 mL portions of pentane. The combined extracts
were evaporated to dryness in vacuo, and the remaining green-
yellow solid was washed 3 times with 4 mL portions of pentane
(0 °C) and dried. The pentane washings were concentrated to
P r ep a r a tion of tr a n s,tr a n s-[{Rh (CNC6H3Me2-2,6)-
(P iP r 3)2}2(µ-CtC-CtC)] (12). A solution of 8 (247 mg, 0.43
mmol) in benzene (7 mL) was treated with Ph3SnCtCCt
CSnPh3 (161 mg, 0.22 mmol) at room temperature, and the
reaction mixture was then stirred at 60 °C for 14 h. After the
brown suspension was cooled to room temperature, it was
filtered and the filtrate was evaporated to dryness in vacuo.
Addition of acetone (2 mL) led to the precipitation of a yellow
solid, which was separated from the solution, washed 6 times
with 2 mL portions of acetone and twice with 2 mL portions
of pentane, and dried: yield 95 mg (38%); mp 95 °C dec; IR

Synthesis of Dinuclear Rhodium Complexes
Organometallics, Vol. 19, No. 7, 2000 1371
ca. 5 mL in vacuo, and after the concentrated solution was
stored at -60 °C for 11 days, a second fraction of the green-
yellow solid was obtained: overall yield 187 mg (93%); mp 82
°C dec; IR (Nujol) ν(CtC and CtN) 2030, 2004, ν(CdC) 1631,
200 MHz, 57 °C) δ 8.29 (d, J (HH) ) 7.3 Hz, 4H, ortho-H of
C6H5), 7.48 (dt, J (RhH) ) J (PH) ) 2.2 Hz, 2H, Rh-CdCH),
7.15 (t, J (HH) ) 7.3 Hz, 4H, meta-H of C6H5), 7.01 (t, J (HH)
) 7.1 Hz, 2H, para-H of C6H5), 2.39 (m, 12H, PCHCH3), 1.33
(dvt, N ) 13.9 Hz, J (HH) ) 6.9 Hz, 36H, PCHCH3), 1.16 (dvt,
N ) 13.2 Hz, J (HH) ) 6.2 Hz, 36H, PCHCH3); 13C{1H} NMR
(d8-THF, 100.6 MHz) δ 196.2 (dt, J (RhC) ) 56.3 Hz, J (PC) )
16.1 Hz, CO), 160.7 (dt, J (RhC) ) 27.2 Hz, J (PC) ) 14.1 Hz,
Rh-CdC), 147.1 (t, J (PC) ) 4.0 Hz, Rh-C)C), 144.1, 129.2,
128.0, 126.0 (all s, C6H5), 95.9, 86.5 (both s, CtC), 27.0 (vt, N
) 20.3 Hz, PCHCH3), 21.3, 20.2 (both s, PCHCH3); 31P{1H}
NMR (d8-THF, 162.0 MHz) δ 42.9 (d, J (RhP) ) 138.7 Hz).
Anal. Calcd for C58H96O2P4Rh2: C, 60.31; H, 8.38. Found: C,
59.98; H, 8.07.
1
1611 cm-1; H NMR (C6D6, 400 MHz) δ 7.27 (d, J (HH) ) 7.3
Hz, 2H, ortho-H of C6H5), 7.10 (t, J (HH) ) 7.8 Hz, 2H, meta-H
of C6H5), 6.86 (t, J (HH) ) 7.4 Hz, 1H, para-H of C6H5), 6.74
(s, 3H, C6H3Me2), 2.75, 2.52 (both m, 6H, PCHCH3), 2.33 (s,
6H, C6H3Me2), 1.54 (t, J (PH) ) 3.5 Hz, 1H, RhdCdCH), 1.42
(dvt, N ) 13.5 Hz, J (HH) ) 7.3 Hz, 36H, PCHCH3), 1.41 (dvt,
N ) 13.5 Hz, J (HH) ) 6.7 Hz, 36H, PCHCH3); 13C{1H} NMR
(C6D6, 100.6 MHz) δ 294.4 (dt, J (RhC) ) 48.8 Hz, J (PC) ) 16.3
Hz, RhdCdC), 171.0 (dt, J (RhC) ) 57.0 Hz, J (PC) ) 14.7 Hz,
Rh-CN), 131.4 (d, J (RhC) ) 10.1 Hz, Rh-CtC), 133.4, 130.9,
128.5, 128.1, 126.7, 126.2, 125.6, 124.4 (all s, C6H3 and C6H5),
116.1 (dt, J (RhC) ) 12.2 Hz, J (PC) ) 6.1 Hz, RhdCdC), 110.0
(dt, J (RhC) ) 36.6 Hz, J (PC) ) 20.3 Hz, Rh-CtC), 107.5 (d,
J (RhC) ) 12.2 Hz, Rh-CtC), 26.3, 25.7 (both vt, N ) 20.3
Hz, PCHCH3), 20.8, 20.7 (both s, PCHCH3), 19.0 (s, C6H3Me2),
one of the Rh-CtC signals obscured by the signal of the
solvent; 31P{1H} NMR (C6D6, 162.0 MHz) δ 52.6 (d, J (RhP) )
135.7 Hz, [Rh(CNC6H3Me2-2,6)(PiPr3)2]), 47.6 (d, J (RhP) )
P r ep a r a tion of tr a n s,tr a n s-[{Rh (CNC6H3Me2-2,6)-
(P iP r 3)2}2{µ2-C(dCHP h )-CtC-CtC-C(dCHP h )}] (18). A
solution of 6 (161 mg, 0.15 mmol) in pentane (12 mL) was
treated with 2,6-dimethylphenylisocyanide (43 mg, 0.33 mmol)
and stirred at room temperature for 40 min. A yellow-orange
suspension was formed, from which a microcrystalline solid
slowly precipitated. After the suspension was stored for 1 h,
the mother liquor was separated, and the yellow-orange solid
was washed 3 times with 3 mL portions of pentane and dried:
yield 156 mg (78%); mp 79 °C dec; IR (Nujol) ν(CtC and CtN)
2025, 1999 cm-1; 1H NMR (CD2Cl2, 200 MHz, - 60 °C) δ 10.62
(d, J (HH) ) 7.3 Hz, 2H, ortho-H of C6H5), 7.36 (br s, 2H, Rh-
CdCH), 7.27-7.04 (br m, 14H, C6H3 plus ortho-, meta-, and
para-H of C6H5), 2.41 (br s, 12H, C6H3Me2), 2.23 (br m, 12H,
PCHCH3), 1.28, 1.03 (both br m, 72H, PCHCH3); 1H NMR
(CD2Cl2, 200 MHz, 20 °C) δ 7.49 (dt, J (PH) ) J (RhH) ) 2.2
Hz, 2H, Rh-CdCH), 7.21 (t, J (HH) ) 7.9 Hz, 4H, meta-H of
C6H5), 7.05 (m, 8H, C6H3 plus para-H of C6H5), 2.48 (s, 12H,
C6H3Me2), 2.35 (m, 12H, PCHCH3), 1.36 (dvt, N ) 13.5 Hz,
J (HH) ) 6.6 Hz, 36H, PCHCH3), 1.15 (dvt, N ) 12.8 Hz, J (HH)
) 6.2 Hz, 36H, PCHCH3), signal for ortho-H of C6H5 extremely
broad and thus not exactly located; 1H NMR (C6D6, 400 MHz,
60 °C) δ 8.93 (br d, 4H, ortho-H of C6H5), 7.99 (dt, J (RhH) )
1.8 Hz, J (PH) ) 2.2 Hz, 2H, Rh-CdCH), 7.32 (t, J (HH) ) 7.9
Hz, 4H, meta-H of C6H5), 7.11 (t, J (HH) ) 7.0 Hz, 2H, para-H
of C6H5), 6.81 (m, 6H, C6H3Me2), 2.49 (s, 12H, C6H3Me2), 2.45
(m, 12H, PCHCH3), 1.46 (dvt, N ) 13.2 Hz, J (HH) ) 6.2 Hz,
36H, PCHCH3), 1.23 (dvt, N ) 12.8 Hz, J (HH) ) 5.8 Hz, 36H,
PCHCH3); 13C{1H} NMR (CD2Cl2, 100.6 MHz, 25 °C) δ 169.7
(dt, J (RhC) ) 57.3 Hz, J (PC) ) 16.1 Hz, Rh-CN), 165.4 (dt,
J (RhC) ) 26.2 Hz, J (PC) ) 13.6 Hz, Rh-C)C), 145.8 (dt,
J (RhC) ) 2.1 Hz, J (PC) ) 3.8 Hz, Rh-CdC), 144.7 (d, J (RhC)
) 2.0 Hz, ipso-C of C6H5), 134.2, 130.7, 129.1, 128.3, 127.3,
126.3, 124.7 (all s, C6H3 and C6H5), 97.8, 85.1 (both s, CtC),
26.6 (vt, N ) 18.2 Hz, PCHCH3), 21.1, 20.3 (both s, PCHCH3),
19.3 (s, C6H3Me2); 31P{1H} NMR (CD2Cl2, 162.0 MHz, 25 °C) δ
42.6 (d, J (RhP) ) 145.8 Hz). Anal. Calcd for C74H114N2P4Rh2:
C, 65.28; H, 8.44; N, 2.07. Found: C, 64.93; H, 8.40; N, 1.97.
137.4 Hz, [Rh(dCdCHPh)(PiPr3)2]). Anal. Calcd for C57H99
-
NP4Rh2: C, 60.68; H, 8.85; N, 1.25. Found: C, 60.67; H, 9.06;
N, 1.23.
P r ep a r a t ion of tr a n s,tr a n s-[{R h (CO)(P iP r 3)2}2{µ-C-
(dCH2)-CtC-CtC-C(dCH2)}] (16). A slow stream of CO
was passed through a suspension of 5 (109 mg, 0.23 mmol) in
pentane (12 mL) for 1 min at -78 °C. The mixture was stirred
at -78 °C for 15 min, then slowly warmed to room temperature
and stirred for 45 min at 20 °C. A very small amount of a
brown precipitate was formed, which was separated by filtra-
tion. The yellow solution was concentrated to ca. 1 mL in
vacuo. A water bath (30-40 °C) was used during the evapora-
tion to avoid a fast precipitation of a fine powder. The
concentrated solution was slowly cooled to -25 °C and stored
at this temperature for 48 h. Yellow crystals precipitated and
were washed 3 times with 1 mL portions of pentane (-60 °C)
and dried: yield 86 mg (74%); mp 58 °C dec; IR (Nujol) ν(CtC)
2134, 2067, ν(CO) 1939, 1927 cm-1; 1H NMR (C6D6, 400 MHz)
δ 6.72 (m, 2H, CH2); 5.61 (m, 2H, CH2), 2.54 (m, 12H,
PCHCH3), 1.47 (dvt, N ) 13.2 Hz, J (HH) ) 6.2 Hz, 36H,
PCHCH3), 1.43 (dvt, N ) 13.5 Hz, J (HH) ) 6.5 Hz, 36H,
PCHCH3); 13C{1H} NMR (C6D6, 100.6 MHz) δ 196.7 (dt, J (RhC)
) 56.9 Hz, J (PC) ) 14.7 Hz, CO), 160.3 (dt, J (RhC) ) 25.4
Hz, J (PC) ) 14.4 Hz, Rh-CdC), 130.5 (t, J (PC) ) 4.6 Hz, Rh-
CdC), 93.0, 84.3 (both s, CtC), 22.9 (vt, N ) 19.3 Hz,
PCHCH3), 20.7, 20.4 (both s, PCHCH3); 31P{1H} NMR (C6D6,
162.0 MHz) δ 46.3 (d, J (RhP) ) 140.7 Hz). Anal. Calcd for
C
46H88O2P4Rh2: C, 55.09; H, 8.84. Found: C, 54.96; H, 8.74.
P r ep a r a t ion of tr a n s,tr a n s-[{R h (CO)(P iP r 3)2}2{µ-C-
(dCHP h )-CtC-CtC-C(dCHP h )}] (17). A slow stream of
CO was passed through a solution of 6 (131 mg, 0.12 mmol)
in hexane (30 mL) at 0 °C until the color had changed from
green to yellow (ca. 30 s). The solution was warmed to room
temperature and stirred for 30 min at 20 °C. It was then
concentrated to ca. 4 mL in vacuo, and the concentrated
solution was stored at 0 °C for 2 h. A yellow solid precipitated,
which was washed with hexane (2 mL, 0 °C) and dried: yield
118 mg (82%); mp 88 °C dec; IR (Nujol) ν(CtC) 2064, ν(CO)
X-r a y St r u ct u r a l Det er m in a t ion of Com p ou n d 17.
Single crystals were grown at room temperature from a
concentrated solution of 17 in CH2Cl2, which was covered with
pentane. Crystal data (from 25 reflections, 10° < θ <15°):
triclinic, space group P1h (No. 2), a ) 11.220(1) Å, b ) 16.165(2)
Å, c ) 19.560(2) Å, R ) 101.383(7)°, â ) 102.456(8)°, γ )
91.781(9)°, V ) 3385.9(6) Å3, Z ) 2, dcalcd ) 1.300 g cm-3, µ(Mo
KR) ) 0.771 mm-1, crystal size 0.40 × 0.25 × 0.15 mm.
Solution details: Enraf-Nonius CAD4 diffractometer, Mo KR
radiation (0.70930 Å), graphite monochromator, zirconium
filter (factor 16.4), T ) 293(2) K, ω/θ scan, maximum 2θ )
48°, 7975 reflections scanned, 7490 independent reflections,
6337 reflections regarded as observed (I > 2σ(I)), 7490 reflec-
tions used for refinement; intensity data corrected for Lorentz
and polarization effects, empirical absorption correction (ψ-
scan method, minimum transmission 91.91%) applied; struc-
ture solved by direct methods (SHELXS-86); atomic coordi-
nates and anisotropic displacement parameters refined by full
1941 cm-1 1H NMR (CDCl3, 200 MHz, -60 °C) δ 9.67 (d,
;
J (HH) ) 8.0 Hz, 2H, ortho-H of C6H5), 7.46 (br s, 2H, Rh-Cd
CH), 7.20 (t, J (HH) ) 7.3 Hz, 4H, meta-H of C6H5), 7.10-7.03
(m, 4H, para- and ortho-H of C6H5), 2.31 (m, 12H, PCHCH3),
1
1.25, 1.03 (both br m, 72H, PCHCH3); H NMR (CDCl3, 200
MHz, 17 °C) δ 8.7-7.9 (br m, 4H, ortho-H of C6H5), 7.48 (dt,
J (RhH) ) 1.8 Hz, J (PH) ) 2.0 Hz, 2H, Rh-CdCH), 7.16 (t,
J (HH) ) 7.7 Hz, 4H, meta-H of C6H5), 7.03 (t, J (HH) ) 6.9
Hz, 2H, para-H of C6H5), 2.36 (m, 12H, PCHCH3), 1.30 (dvt,
N ) 13.9 Hz, J (HH) ) 6.6 Hz, 36H, PCHCH3), 1.09 (dvt, N )
13.2 Hz, J (HH) ) 6.2 Hz, 36H, PCHCH3); 1H NMR (CDCl3,
2
matrix least squares against Fo (SHELXL-93); R1 ) 0.0417,

1372 Organometallics, Vol. 19, No. 7, 2000
Gil-Rubio et al.
wR2 ) 0.1091; reflection/parameter ratio 11.00; residual
Mr. C. P. Kneis (DTA and elemental analysis), Mrs. M.-
L. Scha¨fer and Dr. W. Buchner (NMR measurements),
and Degussa AG for various gifts of chemicals.
electron density +0.883/-0.784 e Å-3
.
Ack n ow led gm en t . We thank the Deutsche For-
schungsgemeinschaft (Grant SFB 347) and the Fonds
der Chemischen Industrie for financial support. J .G.-
R. is grateful to the European Commission (Contract
ERBFMBICT960698) for a postdoctoral grant. We also
gratefully acknowledge support by Mrs. R. Schedl and
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and refinement parameters, bond lengths and angles, and
positional and thermal parameters for 17. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM990960Y