C-C bond formation between vinylidene and alkynyl ligands at ruthenium(II) leading to either enynyl or dienynyl complexes

Article abstract of DOI:10.1021/om950721k

The Ru(II) complex mer,trans-(PNP)RuCl₂(PPh₃) (1) reacts with either phenylacetylene or p-tolylacetylene to give fac,cis-(PNP)RuCl₂{C=CH(R)} (R = Ph (2), p-tolyl (3)) in refluxing tetrahydrofuran (THF) and mer,trans-(PNP)RuCl₂{C=CH(R)} (R = Ph (4), p-tolyl (5)) in a refluxing THF/EtOH mixture (1:2 v:v) [PNP = CH₃CH₂CH₂N(CH₂CH₂PPH ₂)₂]. The fac,cis vinylidene complexes 2 and 3 react with an excess of LiC≡CPh converting to the σ-alkynyl-η³-enynyl complexes anti,mer-(PNP)Ru(C≡CPh){η³-PhC₃=CH(Ph)} (8) and anti,mer-(PNP)-Ru(C≡CPh){η³-ChC₃=CH(p-tolyl)} (9), respectively. Conversely, treatment of the mer,trans vinylidene isomers with an excess of LiC≡CPh, followed by addition of a primary alcohol, exclusively gives the σ-alkynyl-η-dienynyl complexes mer-(PNP)Ru(C≡CPh){η-PhC=C-(C≡CPh)CH=CH(R)} (R = Ph, 12; R = p-tolyl, 13), Single-crystal X-ray analyses have been carried out on 8 and 13. In both compounds the coordination geometry around the Ru atom approximates an octahedron with three positions taken by a mer PNP ligand and one position taken by a phenylethynyl group. The coordination sphere around the metal center is completed by an η³-1,4-diphenylbut-3-en-1-ynyl ligand in 8 and by a 1-p-tolyl-3-(phsnyl-ethynyl)-4-phenylbuta-1(E),3(Z)-dien-4-yl ligand in 13. The latter ligand essentially uses the C₁ carbon atom to bind the metal, although a weak bonding interaction may be envisaged also with the alkynyl substituent in the 3-position. A single-crystal X-ray analysis has also been carried out on the octahedral fac,cis-(PNP)RuCl₂(CO) complex obtained by treatment of the vinylidenes 2 and 3 with molecular oxygen. The influence of the bonding mode of the PNP ligand on the different reactivity shown by the fac and mer vinylidene complexes toward LiC≡CPh is discussed in light of a multiform experimental study (X-ray structure determinations, multinuclear NMR spectroscopy, deuterium- and p-tolyl-labeling experiments, independent reactions with isolated compounds).

Full text of DOI:10.1021/om950721k

272
Organometallics 1996, 15, 272-285
C-C Bon d F or m a tion betw een Vin ylid en e a n d Alk yn yl
Liga n d s a t Ru th en iu m (II) Lea d in g to eith er En yn yl or
Dien yn yl Com p lexes†
Claudio Bianchini,* Paolo Innocenti, Maurizio Peruzzini, Antonio Romerosa, and
Fabrizio Zanobini
Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione, CNR,
Via J . Nardi 39, 50132 Firenze, Italy
Received September 8, 1995X
The Ru(II) complex mer,trans-(PNP)RuCl2(PPh3) (1) reacts with either phenylacetylene
or p-tolylacetylene to give fac,cis-(PNP)RuCl2{CdCH(R)} (R ) Ph (2), p-tolyl (3)) in refluxing
tetrahydrofuran (THF) and mer,trans-(PNP)RuCl2{CdCH(R)} (R ) Ph (4), p-tolyl (5)) in a
refluxing THF/EtOH mixture (1:2 v:v) [PNP ) CH3CH2CH2N(CH2CH2PPh2)2]. The fac,cis
vinylidene complexes 2 and 3 react with an excess of LiCtCPh converting to the σ-alkynyl-
η3-enynyl complexes anti,mer-(PNP)Ru(CtCPh){η3-PhC3dCH(Ph)} (8) and anti,mer-(PNP)-
Ru(CtCPh){η3-PhC3dCH(p-tolyl)} (9), respectively. Conversely, treatment of the mer,trans
vinylidene isomers with an excess of LiCtCPh, followed by addition of a primary alcohol,
exclusively gives the σ-alkynyl-η-dienynyl complexes mer-(PNP)Ru(CtCPh){η-PhCdC-
(CtCPh)CHdCH(R)} (R ) Ph, 12; R ) p-tolyl, 13). Single-crystal X-ray analyses have been
carried out on 8 and 13. In both compounds the coordination geometry around the Ru atom
approximates an octahedron with three positions taken by a mer PNP ligand and one position
taken by a phenylethynyl group. The coordination sphere around the metal center is
completed by an η3-1,4-diphenylbut-3-en-1-ynyl ligand in 8 and by a 1-p-tolyl-3-(phenyl-
ethynyl)-4-phenylbuta-1(E),3(Z)-dien-4-yl ligand in 13. The latter ligand essentially uses
the C1 carbon atom to bind the metal, although a weak bonding interaction may be envisaged
also with the alkynyl substituent in the 3-position. A single-crystal X-ray analysis has also
been carried out on the octahedral fac,cis-(PNP)RuCl2(CO) complex obtained by treatment
of the vinylidenes 2 and 3 with molecular oxygen. The influence of the bonding mode of the
PNP ligand on the different reactivity shown by the fac and mer vinylidene complexes toward
LiCtCPh is discussed in light of a multiform experimental study (X-ray structure
determinations, multinuclear NMR spectroscopy, deuterium- and p-tolyl-labeling experi-
ments, independent reactions with isolated compounds).
There have been several breakthroughs recently
In contrast to the mechanistic progress made in the
elucidation of the C-C bond-forming step, little is
known about the factors governing the formation of
either butenynyl or butatrienyl ligands.1b,j,2 Similarly,
the propensity of iron group metals to favor the dimer-
ization of 1-alkynes over higher oligomerization has still
eluded a detailed explanation.
regarding the mechanism by which iron group metal
complexes promote the coupling of 1-alkynes.1 The
dimerization to butenynyl complexes or, more rarely,
to butatrienyl isomers apparently occurs at iron, ruthe-
nium, and osmium by C-C bond formation between
alkynyl and vinylidene ligands.1 The C4 unsaturated
products are eventually liberated from intermediate (σ-
organyl)metal species by σ-bond metathesis with an
additional 1-alkyne molecule.
The results reported in this paper confirm that
alkynyl(vinylidene) ruthenium(II) complexes are key
intermediates to C-C coupling reactions involving
1-alkynes and show that subtle factors, such as the
bonding mode of an ancillary ligand, can tip the balance
in favor of the formation of either enynyl or dienynyl
complexes (dimerization and trimerization of 1-alkynes,
respectively).
† Dedicated to Professor Max Herberhold on the occasion of his 60th
birthday.
X Abstract published in Advance ACS Abstracts, December 1, 1995.
(1) (a) Barbaro, P.; Bianchini, C.; Peruzzini, M.; Polo, A.; Zanobini,
F.; Frediani, P. Inorg. Chim. Acta 1994, 220, 5. (b) Wakatsuki, Y.;
Yamazaki, H.; Kunegawa, N.; Satoh, J . Y.; Satoh, T. J . Am. Chem.
Soc. 1991, 113, 9604. (c) Bianchini, C.; Peruzzini, M.; Zanobini, F.;
Frediani, P.; Albinati, A. J . Am. Chem. Soc. 1991, 113, 5453. (d)
Albertin, G.; Amendola, P.; Antoniutti, S.; Ianelli, S.; Pelizzi, G.;
Bordignon, E. Organometallics 1991, 10, 2876. (e) J ia, G.; Meek, D.
W. Organometallics 1991, 10, 1444. (f) Bianchini, C.; Bohanna, C.;
Esteruelas, M. A.; Frediani, P.; Meli, A.; Oro, L. A.; Peruzzini, M.
Organometallics 1992, 11, 3837. (g) Field, L.; George, A. V.; Purches,
G. R.; Slip, I. H. M. Organometallics 1992, 11, 3019. (h) Santos, A.;
Lo´pez, J .; Matas, L.; Ros, J .; Gala`n, A.; Echavarren, A. M. Organo-
metallics 1993, 12, 4215. (i) Albertin, G.; Antoniutti, S.; Bordignon, E.
J . Chem. Soc., Dalton Trans. 1995, 719. (j) Scha¨fer, M.; Mahr, N.; Wolf,
J .; Werner, H. Angew. Chem., Int. Ed. Engl. 1993, 32, 1315. (k) Werner,
H. J . Organomet. Chem. 1994, 475, 45. (l) Wakatsuki, Y.; Koga, N.;
Yamazaki, H.; Morokuma, K. J . Am. Chem. Soc. 1994, 116, 8105.
In this work, it is also shown that a common synthetic
route to butenynyl ruthenium(II) complexes, i.e. the
metathesis reaction of chloride-vinylidene complexes
(2) (a) Heeres, H. J .; Nijhoff, J .; Teuber, J ., H.; Rogers, R. D.
Organometallics 1993, 12, 2609. (b) Corrigan, J . F.; Taylor, N. J .; Carty,
A. J . Organometallics 1994, 13, 3778. (c) Stang, P. J .; Dixit, V.;
Schiavelli, M. D.; Drees, P. J . Am. Chem. Soc. 1987, 109, 1150. (d)
Stang, P. J .; Datta, A. K.; Dixit, V.; Wistrand, L. G. Organometallics
1989, 8, 1020. (e) Stang, P. J .; Datta, A. K. Organometallics 1989, 8,
1024. (f) Wakatsuki, Y.; Yamazaki, H.; Kunnegawa, N.; J ohar, P. S.
Bull. Chem. Soc. J pn. 1993, 66, 987.
0276-7333/96/2315-0272$12.00/0 © 1996 American Chemical Society

C-C Bond Formation in Ru Complexes
Organometallics, Vol. 15, No. 1, 1996 273
stirred THF (50 mL) slurry of mer,trans-(PNP)RuCl2(PPh3) (1)
(0.46 g, 0.50 mmol), and the mixture was refluxed with stirring
for 1 h. During this time, all 1 dissolved to produce an orange
solution which, after cooling to room temperature, separated
pale orange needle crystals of 2. Yield: 92%. Anal. Calcd
for C39H41NCl2P2Ru: C, 61.83; H, 5.45; N, 1.85; Cl, 9.36.
Found: C, 61.72; H, 5.51; N, 1.69; Cl, 9.17. IR (cm-1): ν(CdC)
1644 (m), 1615 (s); phenyl reinforced vibration 1593. 31P{1H}
NMR (22 °C, CDCl3, 81.01 MHz): δ 47.92 (s). 1H NMR (22
°C, CDCl3, 200.13 MHz): δ(CdCH) 5.32 [t, 4J (HP) 3.1 Hz]. 13C-
{1H} NMR (40 °C, DMF-d7, 50.32 MHz): δ(RudCdCH) 356.31
[t, 2J (CP) 17.2 Hz], δ(RudCdCH) 113.37 [t, 3J (CP) 2.2 Hz],
δ(CH3CH2CH2N) 57.02 (s), δ(NCH2CH2P) 49.79 [vt, N ) J (CP)
+ J (CP′) ) 1.5 Hz], δ(NCH2CH2P) 31.86 [vt, N ) J (CP) +
J (CP′) ) 12.3 Hz], δ(CH3CH2CH2N) 14.52 (s), δ(CH3CH2CH2N)
11.04 (s). Compound 2 is poorly soluble in common organic
solvents, whereas it slightly dissolves in halogenated solvents.
with acetylide salts, may not mechanistically be as
simple as it appears.
Exp er im en ta l Section
Gen er a l P r oced u r es. Tetrahydrofuran (THF) and dichlo-
romethane were purified by distillation under nitrogen over
LiAlH4 and P2O5, respectively. Phenylacetylene and p-tolyl-
acetylene were purchased from Aldrich; their purity was
1
checked by H NMR spectroscopy, and when necessary, they
were distilled under nitrogen prior to use. All the other
reagents and chemicals were reagent grade and, unless
otherwise stated, were used as received by commercial sup-
pliers. All reactions and manipulations were routinely per-
formed under a dry nitrogen atmosphere by using standard
Schlenk-tube techniques. The solid complexes were collected
on sintered glass frits and washed with light petroleum ether
(bp 40-60 °C) or n-pentane before being dried in a stream of
nitrogen. The ligand CH3CH2CH2N(CH2CH2PPh2)2 (PNP)3
and the complex mer,trans-(PNP)RuCl2(PPh3)4 (1) were pre-
pared as described in the literature. Lithium phenylacetylide
(1.0 M solution in THF) was purchased from Aldrich. Lithium
p-tolylacetylide was prepared just prior to use by reacting 1
equiv of n-BuLi with p-tolylacetylene in THF at 0 °C under
nitrogen.5 Deuterated solvents for NMR measurements
(Merck) were dried over molecular sieves. 1H and 13C{1H}
NMR spectra were recorded on a Varian VXR 300, Bruker AC
200P, or Bruker AVANCE DRX 500 spectrometer operating
at 299.94, 200.13, or 500.13 MHz (1H) and 75.42, 50.32, or
125.80 MHz (13C), respectively. Peak positions are relative to
tetramethylsilane and were calibrated against the residual
solvent resonance (1H) or the deuterated solvent multiplet
(13C). 13C-DEPT experiments were run on the Bruker ACP
200 spectrometer. 1H,13C-2D HETCOR NMR experiments
were recorded on either the Bruker ACP 200 spectrometer
using the XHCORR pulse program or the Bruker AVANCE
DRX 500 spectrometer equipped with a 5-mm triple resonance
probe head for 1H detection and inverse detection of the
heteronucleus (inverse correlation mode, HMQC experiment).
The 1H,1H-2D COSY NMR experiments were routinely con-
ducted on the Bruker 200 ACP instrument in the absolute
magnitude mode using a 45 or 90° pulse after the incremental
Syn th esis of m er ,tr a n s-(P NP )Ru Cl2{CdCH(P h )} (4).
Neat phenylacetylene (0.50 mL, 4.50 mmol) was pipetted into
a well-stirred THF/EtOH (1:2 v:v, 50 mL) slurry of 1 (0.46 g,
0.50 mmol). The mixture was slowly brought to the boiling
point and then refluxed with stirring for 14 h. During this
time the orange color of 1 disappeared to give a pale solution
which, after cooling to room temperature, separated ivory
colored microcrystals of 4. Addition of ethanol (50 mL) and
concentration of the solution to half-volume under a stream
of nitrogen completed the precipitation of 4. Yield: 83%. Anal.
Calcd for
C39H41NCl2P2Ru: C, 61.83; H, 5.45; N, 1.85.
Found: C, 61.66; H, 5.39; N, 1.58. IR (cm-1): ν(CdC) 1650
(m), 1613 (s); phenyl reinforced vibration 1591. 31P{1H} NMR
(23 °C, CD2Cl2, 81.01 MHz): 26.72 (s). 1H NMR (23 °C, CD2-
Cl2, 200.13 MHz): δ(CdCH) 3.69 [t, J (HP) 3.9 Hz]. 13C{1H}
4
NMR (40 °C, DMF-d7, 50.32 MHz): δ(RudCdCH) 356.69 [t,
2J (CP) 15.4 Hz], δ(RudCdCH) 107.21 [t, 3J (CP) 4.1 Hz], δ(CH3-
CH2CH2N) 63.04 (s), δ(NCH2CH2P) 54.36 [vt, N ) J (CP) +
J (CP′) ) 3.3 Hz], δ(NCH2CH2P) 26.23 [vt, N ) J (CP) + J (CP′)
) 11.8 Hz], δ(CH3CH2CH2N) 14.04 (s), δ(CH3CH2CH2N) 9.93
(s). Compound 4 is practically unsoluble in common organic
solvents with the exception of halogenated solvents (CH2Cl2
or CHCl3) in which it readily dissolves.
Syn th esis of fa c,cis-(P NP )Ru Cl2{CdCH(p-tolyl)} (3)
a n d of m er ,tr a n s-(P NP )Ru Cl2{CdCH(p-tolyl)} (5). The
two p-tolylvinylidene complexes 3 and 5 were prepared as
described above for the corresponding phenylvinylidene com-
plexes by using p-tolylacetylene (0.50 g, 4.30 mmol) in place
of phenylacetylene.
1
delay. The H,1H-2D COSY NMR experiments on the buten-
ynyl and dienynyl complexes were acquired on the AVANCE
DRX 500 Bruker spectrometer using the phase-sensitive TPPI
mode with double quantum filter. 1H,1H-2D NOESY NMR
experiments were conducted on the same instrument in the
phase-sensitive TPPI mode in order to discriminate between
positive and negative cross peaks. 31P{1H} NMR spectra were
recorded on either the Varian VXR 300 or Bruker AC 200P
instrument operating at 121.42 or 81.01 MHz, respectively.
Chemical shifts were measured relative to external 85% H3-
PO4 with downfield values taken as positive. The proton NMR
spectra with broad-band phosphorus decoupling were recorded
on the Bruker ACP 200 instrument equipped with a 5-mm
inverse probe and a BFX-5 amplifier device using the wideband
phosphorus decoupling sequence GARP. Infrared spectra were
recorded as Nujol mulls on a Perkin-Elmer 1600 series FT-IR
spectrometer between KBr plates. A Shimadzu GC-14A/
GCMS-QP2000 instrument was employed for all GC-MS
investigations. Elemental analyses (C, H, N) were performed
using a Carlo Erba Model 1106 elemental analyzer.
fa c,cis-(P NP )Ru Cl2{CdCH(p-tolyl)} (3). Yield: 90%. Anal.
Calcd for
C40H43NCl2P2Ru: C, 62.34; H, 5.62; N, 1.82.
Found: C, 62.07; H, 5.60; N, 1.74. IR (cm-1): ν(CdC) 1632
(s), 1610 (m). 31P{1H} NMR (22 °C, CDCl3, 121.42 MHz): 48.53
(s). 1H NMR (22 °C, CDCl3, 299.94 MHz): δ(CdCH) 5.30 [t,
4J (HP) 4.0 Hz], δ[CH3(p-tolyl)] 2.40 (s). 13C{1H} NMR (22 °C,
CD2Cl2, 50.32 MHz): δ(RudCdCH) 356.90 [t, 2J (CP) 22.6 Hz],
δ(RudCdCH) 114.80 [t, 3J (CP) 2.1 Hz], δ(CH3CH2CH2N) 58.01
(s), δ(NCH2CH2P) 50.95 [vt, N ) J (CP) + J (CP′) ) 1.8 Hz],
δ(NCH2CH2P) 27.10 [vt, N ) J (CP) + J (CP′) ) 14.0 Hz, this
multiplet has been computed using the parameters J CP 28.9
Hz, J CP′ -0.6 Hz, and J PP′ 22.6 Hz], δ[CH3(p-tolyl)] 21.64 (s),
δ(CH3CH2CH2N) 15.92 (s), δ(CH3CH2CH2N) 12.33 (s).
m er ,tr a n s-(P NP )Ru Cl2{CdCH(p-tolyl)} (5). Yield: 78%.
Anal. Calcd for C40H43NCl2P2Ru: C, 62.34; H, 5.62; N, 1.82.
Found: C, 62.20; H, 5.55; N, 1.60. IR (cm-1): ν(CdC) 1621
(s), 1603 (m). 31P{1H} NMR (22 °C, CDCl3, 121.42 MHz): 26.68
(s). 1H NMR (22 °C, CD2Cl2, 299.94 MHz): δ(CdCH) 3.66 [t,
4J (HP) 3.8 Hz], δ[CH3(p-tolyl)] 2.29 (s). 13C{1H} NMR (22 °C,
CD2Cl2, 50.32 MHz): δ(RudCdCH) 359.30 [t, 2J (CP) 15.3 Hz],
δ(RudCdCH) 108.13 [t, 3J (CP) 4.0 Hz], δ(CH3CH2CH2N) 63.91
(s), δ(NCH2CH2P) 55.39 [vt, N ) J (CP) + J (CP′) ) 3.3 Hz],
δ(NCH2CH2P) 27.56 [vt, N ) J (CP) + J (CP′) ) 11.4 Hz], δ-
[CH3(p-tolyl)] 21.48 (s), δ(CH3CH2CH2N) 15.27 (s), δ(CH3CH2-
CH2N) 11.44 (s).
Syn th esis of fa c,cis-(P NP )Ru Cl2{CdCH(P h )} (2). Neat
phenylacetylene (0.50 mL, 4.50 mmol) was pipetted into a well-
(3) Sacconi, L.; Morassi, R. J . Chem. Soc. A 1969, 2904. An improved
synthesis of the PNP ligands is reported in: Bianchini, C.; Farnetti,
E.; Glendenning, L.; Graziani, M.; Nardin, G.; Peruzzini, M.; Rocchini,
E.; Zanobini, F. Organometallics 1995, 14, 1489.
(4) Bianchini, C.; Innocenti, P.; Masi, D.; Peruzzini, M.; Zanobini,
F. Gazz. Chim. Ital. 1992, 122, 461.
(5) Bianchini, C.; Frediani, P.; Masi, D.; Peruzzini, M.; Zanobini, F.
Organometallics 1994, 13, 4616.

274 Organometallics, Vol. 15, No. 1, 1996
Bianchini et al.
In Situ NMR Stu d ies. A 5-mm NMR tube was charged
under nitrogen with a solution of 1 (23 mg, 0.025 mmol) and
a 5-fold excess of phenylacetylene in THF-d8 (0.7 mL), flame
sealed, and then placed into a NMR probe at 20 °C. The
reaction was monitored by variable-temperature 31P{1H} NMR
spectroscopy. The conversion of 1 to 3 started already at ca.
40 °C with no detection of intermediate species.
Attem p ted Isom er iza tion of 2 (4) in to 3 (5). A stirred
solution of 2 (0.10 g, 0.13 mmol) in a THF/EtOH mixture (1:2
v:v, 10 mL) was heated at reflux temperature for 12 h and
then cooled to room temperature. Concentration of the result-
ing solution under nitrogen gave quantitatively the starting
compound. In a similar way, the mer-isomer 4 did not convert
to the fac-isomer 3 upon prolonged reflux (12 h) in THF. No
isomerization of either 2 or 4 was observed in refluxing
toluene.
Th er m olysis of 1. A 5-mm NMR tube was charged under
nitrogen with a solution of 1 (20 mg, 0.022 mmol) in THF-d8
(0.7 mL), flame sealed, and then placed into a NMR probe at
20 °C. The reaction was monitored by variable-temperature
31P{1H} NMR spectroscopy. The conversion of 1 to the known
face-sharing bioctahedral complex [Ru(µ-Cl)3(PNP)2]Cl4 and
free PPh3 started already at ca. 60 °C.
Syn th esis of fa c,cis-(P NP )Ru Cl2(CO) (6). A solid sample
of 2 (0.20 g, 0.26 mmol) was dissolved in dichloromethane (30
mL) saturated with dioxygen. Addition of ethanol (20 mL)
after 12 h, followed by partial removal of the solvent in vacuo,
gave pale yellow crystals of the carbonyl complex 6. Yield:
98%. GC-MS analysis of the reaction mixture showed the
formation of ca. 1 equiv of benzaldehyde. Complex 6 can be
prepared in similar yield from 5. In this case, however,
p-tolylaldehyde is formed. Anal. Calcd for C32H35NCl2OP2-
Ru: C, 56.23; H, 5.16; N, 2.05. Found: C, 56.14; H, 5.05; N,
1.90. IR (cm-1): ν(CtO) 1942 (s). 31P{1H} NMR (22 °C, CD2-
Cl2, 81.01 MHz): 58.27 (s). 13C{1H} NMR (22 °C, CD2Cl2, 50.32
MHz): δ(CtO) 203.61 [t, 2J (CP) 15.9 Hz], δ(CH3CH2CH2N)
58.60 (s), δ(NCH2CH2P) 52.69 (s), δ(NCH2CH2P) 27.08 [vt, N
) J (CP) + J (CP′) ) 12.8 Hz], δ(CH3CH2CH2N) 16.12 (s), δ(CH3-
CH2CH2N) 12.17 (s).
Syn th esis of m er ,tr a n s-(P NP )Ru Cl2(CO) (7). Meth od
A. A solution of 4 (0.20 g, 0.26 mmol) [or 5, (0.20 g, 0.26 mmol)]
in dichloromethane (30 mL) was saturated with dioxygen and
slowly heated at reflux temperature for 4 h. After cooling of
the solution to room temperature, addition of ethanol (20 mL)
and concentration of the solution under a brisk current of
nitrogen gave pale cream microcrystals of 7. Yield: 90%. GC-
MS analysis of the solution showed the formation of ca. 1 equiv
of benzaldehyde (or p-tolylaldehyde).
Meth od B. A sample of 1 (0.46 g, 0.50 mmol) was dissolved
in dichloromethane (60 mL) under a stream of carbon mon-
oxide at room temperature. The solution was then brought
to reflux temperature and refluxed under a carbon monoxide
atmosphere for 1 h during which time the starting orange color
faded to produce a pale yellow solution. After cooling of the
solution to room temperature, addition of ethanol (30 mL) and
concentration of the resulting solution under nitrogen gave
pale cream colored microcrystals of 7. Yield: 94%. Anal.
Calcd for C32H35NCl2OP2Ru: C, 56.23; H, 5.16; N, 2.05.
Found: C, 56.09; H, 5.12; N, 1.88. IR (cm-1): ν(CtO) 1955
(s). 31P{1H} NMR (22 °C, CD2Cl2, 81.01 MHz): 27.76 (s).
13C{1H} NMR (22 °C, CD2Cl2, 50.32 MHz): δ(CtO) 201.19 [t,
2J (CP) 13.5 Hz], δ(CH3CH2CH2N) 63.77 (s), δ(NCH2CH2P)
55.20 [vt, N ) J (CP) + J (CP′) ) 3.2 Hz], δ(NCH2CH2P) 27.76
[vt, N ) J (CP) + J (CP′) ) 12.0 Hz], δ(CH3CH2CH2N) 15.56
(s), δ(CH3CH2CH2N) 11.56 (s).
with no formation of other phosphorus-containing species. GC-
MS analysis of the solution showed the formation of an
equivalent amount of benzaldehyde.
Syn th esis of a n ti,m er -(P NP )Ru (CtCP h ){η3-P h C3dCH-
(P h )} (8). A 2-fold amount of LiCtCPh (1.0 M THF solution,
1.35 mL, 1.35 mmol) was added dropwise over a period of 5
min to a stirred suspension of 2 (0.50 g, 0.66 mmol) in THF
(50 mL) mantained at ca. 5 °C with an ice bath. Stirring was
continued for 30 min, during which time the color of the
solution changed from pale orange to red orange. By addition
of ethanol (30 mL) and slow evaporation of the solvent in a
stream of nitrogen at room temperature, orange microcrystals
of 8 precipitated. The crude product was recrystallized from
CH2Cl2/EtOH (1:1 v:v) to afford crystals of 8 as orange cubes.
Yield: 66%. Anal. Calcd for C55H51NP2Ru: C, 74.31; H, 5.78;
N, 1.58. Found: C, 74.08; H, 5.64; N, 1.45. IR (cm-1): ν(CtC)
2069 (s), ν(CdC) 1569 (w); phenyl reinforced vibration 1591.
31P{1H} NMR (22 °C, CD2Cl2, 81.01 MHz): 36.01 (s). 1H NMR
(22 °C, CD2Cl2, 200.13 MHz) (the numbering scheme of the
hydrogen and carbon resonances is given in footnote 6):
4
δ(CdCH) 8.28 [t, J (HP) 1.4 Hz]. 13C{1H} NMR (22 °C, CD2-
2
Cl2, 50.32 MHz): δ(C4) 154.97 [t, J (CP) 7.8 Hz], δ(C5) 135.86
[t, 2J (CP) 15.9 Hz], δ(C1) 130.50 [t, 2J (CP) 1.3 Hz], δ(C2) or
2
2
δ(C6) 115.14 [t, J (CP) 2.0 Hz] and 110.98 [t, J (CP) 1.4 Hz],
δ(CH3CH2CH2N) 62.98 (s), δ(C3) 56.88 [t, 2J (CP) 1.7 Hz],
δ(NCH2CH2P) 53.28 [vt, N ) J (CP) + J (CP′) ) 3.7 Hz],
δ(NCH2CH2P) 27.19 [vt, N ) J (CP) + J (CP′) ) 11.2 Hz], δ-
(CH3CH2CH2N) 14.75 (s), δ(CH3CH2CH2N) 10.65 (s).
Syn th esis of a n ti,m er -(P NP )Ru (CtCP h ){η3-P h C3dCH-
(p-tolyl)} (9). This compound was prepared like 8 using the
p-tolylvinylidene complex 3 in the place of 2. Yield: 72%. Anal.
Calcd for C56H53NP2Ru: C, 74.48; H, 5.92; N, 1.55. Found:
C, 74.21; H, 5.83; N, 1.50. IR (cm-1): ν(CtC) 2073 (s), ν(CdC)
1520 (w); phenyl reinforced vibration 1592. 31P{1H} NMR (22
°C, CD2Cl2, 81.01 MHz): 36.18 (s). 1H NMR (24 °C, CD2Cl2,
500.13 MHz): δ(CdCH) 8.28 (br s), δ[CH3(p-tolyl)] 2.34 (s).
13C{1H} NMR (22 °C, CD2Cl2, 50.32 MHz): δ(C4) 153.27 [t,
2
2J (CP) 7.8 Hz], δ(C5) 136.18 [t, J (CP) 14.6 Hz], δ(C1) 130.69
2
2
[t, J (CP) 1.5 Hz], δ(C2) or δ(C6) 115.33 [t, J (CP) 1.8 Hz] and
110.68 [t, 2J (CP) 1.3 Hz], δ(CH3CH2CH2N) 62.27 (s), δ(C3)
57.25 [t, 2J (CP) 1.6 Hz], δ(NCH2CH2P) 53.56 [vt, N ) J (CP) +
J (CP′) ) 3.9 Hz], δ(NCH2CH2P) 27.46 [vt, N ) J (CP) + J (CP′)
) 11.4 Hz], δ[CH3(p-tolyl)] 21.89 (s), δ(CH3CH2CH2N) 15.01
(s), δ(CH3CH2CH2N) 10.92 (s).
Syn th esis of fa c-(P NP )Ru Cl(CtCP h )(CO) (10). Meth od
A. Carbon monoxide was bubbled throughout a stirred THF
solution (50 mL) of 2 (0.20 g, 0.26 mmol) maintained at ca.
-5 °C to which 1 equiv of LiCtCPh (1.0 M THF solution, 0.26
mL, 0.26 mmol) was added dropwise over a period of 2 min.
Stirring was continued for 20 min. Addition of ethanol (20
mL) to the resulting pale yellow solution and concentration
under a brisk current of nitrogen gave yellow microcrystals of
10. Yield: 95%. Anal. Calcd for C48H46NClOP2Ru: C, 67.72;
H, 5.45; N, 1.65. Found: C, 67.63; H, 5.40; N, 1.53. IR (cm-1):
ν(CtC) 2089 (s); ν(CtO) 1968 (vs). 31P{1H} NMR (24 °C, CD2-
Cl2, 81.01 MHz); (AM spin system): δA 49.43 [d, J (PP) 27.9
Hz], δM 23.33 (d). 13C{1H} NMR (24 °C, CD2Cl2, 50.32 MHz):
2
2
δ(CtO) 200.20 [dd, J (CPtrans) 100.6 Hz, J (CPcis) 14.9 Hz], δ-
(CtC) 107.65 [t, 2J (CP) 17.1 Hz], δ(CtC) 113.70 (br s), δ(CH3-
(6) Numbering schemes for the hydrogen and carbon atoms in
complexes 8, 9 and 12, 13 are as follows:
Rea ction of 2 w ith O2 in a Sea led NMR Tu be. Solid 2
(25 mg, 0.033 mmol) was dissolved in chloroform-d1 saturated
with dioxygen (1.0 mL) and then transferred into a 5-mm NMR
tube which was flame-sealed in a liquid nitrogen bath. The
reaction was followed by 1H and 31P{1H} NMR spectroscopy
in the temperature range from 20 to 55 °C. At the latter
temperature, 2 completely disappeared within 2 h to give 6

C-C Bond Formation in Ru Complexes
Organometallics, Vol. 15, No. 1, 1996 275
CH2CH2N) 65.15 (s), δ(NCH2CH2P) 55.45 [d, J (CP) 4.0 Hz],
δ(NCH2CH2P) 52.58 (br s), δ(NCH2CH2P) 28.33 [d, J (CP) 29.7
Hz], δ(NCH2CH2P) 26.06 [d, J (CP) 22.1 Hz], δ(CH3CH2CH2N)
17.23 (s), δ(CH3CH2CH2N) 12.02 (s).
(Ph)} (12-d1) in which the selective incorporation of deuterium
into the 2-position of the butadienyl ligand was determined
1
by H NMR spectroscopy (disappearance of the signal at 6.11
ppm).
Meth od B. Compound 10 was analogously obtained by
reaction of 2 with a freshly prepared solution of lithium
p-tolylacetylide in THF.
Meth od C. NEt3 (56 µL, 0.4 mmol) was added to a stirred
solution of 2 (0.20 g, 0.26 mmol) in THF (50 mL) under a CO
atmosphere at -5 °C. Stirring was continued at room tem-
perature until a pale yellow solution was obtained. Addition
of ethanol (30 mL) and concentration of the resulting solution
under a brisk current of nitrogen gave 10 in almost quantita-
tive yield.
Syn th esis of mer -(P NP )Ru (CtCP h ){η-P h CdC(CtCP h )-
CHdCH(p-tolyl)} (13). This compound was prepared as
described above for complex 12, by replacing 2 with 3. Yield:
50%. Anal. Calcd for C64H59NP2Ru: C, 76.47; H, 5.92; N, 1.39.
Found: C, 76.31; H, 5.80; N, 1.38. IR (cm-1): ν(CtC) 2063
(s), ν(CdC) 1556 (w); phenyl reinforced vibration 1590. 31P-
{1H} NMR (22 °C, CDCl3, 81.01 MHz): 30.72 (s). 1H NMR
(24 °C, CD2Cl2, 500.13 MHz): δ(H2) 6.14 [d, 3J (H1H2) 15.7 Hz],
δ(H1) ca. 7.1 (superimposed to aromatic proton resonances, the
assignment was confirmed by a 1H,1H-2D COSY NMR experi-
ment), δ[CH3(p-tolyl)] 2.31 (s). 13C{1H} NMR (22 °C, CD2Cl2,
50.32 MHz): δ(C4) or δ(C7) 137.14 [t, 2J (CP) 16.1 Hz] and
In a separate experiment, the solvent was removed in vacuo
before adding EtOH to give a mixture of 10 and [Et3NH]Cl
(1H NMR).
1
122.75 [t, 2J (CP) 19.1 Hz], δ(C2) 128.61 (s, assigned by a H,13C-
2D HETCOR NMR experiment), δ(C1) 120.60 (s, assigned by
Isom er iza tion of fa c-(P NP )Ru Cl(CtCP h )(CO) to m er -
(P NP )Ru Cl(CtCP h )(CO) (11). NMR Rea ction . A 20 mg-
sample of 10 was dissolved in CD2Cl2 (0.7 mL) under nitrogen
in a 5-mm NMR tube which was flame sealed and introduced
into a NMR probe preheated at 50 °C. 31P{1H} NMR spectra
were acquired every 30 min. After 3 h, the AM pattern of 10
had completely disappeared, while a new singlet at 34.18 ppm
was the only signal detected. The tube was cooled to room
temperature, and 13C{1H} and 1H NMR were acquired (see
below).
1
a H,13C-2D HETCOR NMR experiment), δ(C6) or δ(C8) 116.93
(s) and 114.18 (s), δ(C3) or δ(C5) 82.77 (s) and 68.45 (s), δ(CH3-
CH2CH2N) 59.22 (s), δ(NCH2CH2P) 53.39 (s), δ(NCH2CH2P)
30.21 [vt, N ) J (CP) + J (CP′) ) 11.4 Hz], δ[CH3(p-tolyl)] 21.51
(s), δ(CH3CH2CH2N) 13.71 (s), δ(CH3CH2CH2N) 10.91 (s).
Rea ction of 4 w ith CO/NEt3. A slight excess of NEt3 was
added to stirred solution of 4 (0.25 g, 0.33 mmol) in CH2Cl2
(20 mL) saturated with CO at -5 °C. During a period of 20
min at room temperature the color of the solution changed
from cream to pale yellow. Removal of the solvent in vacuo
gave the mer carbonyl complex 11 and [HNEt3]Cl in quantita-
tive yield.
X-r a y Diffr a ction Stu d ies. A summary of crystal and
intensity data for the compounds 6, 8, and 13‚CH2Cl2, is
presented in Table 4 (6 and 8) and Table 5 (13‚CH2Cl2).
Experimental data were recorded at room temperature on
either an Enraf-Nonius CAD4 diffractometer (6 and 8) or a
Philips-PW1100 diffractometer (13‚CH2Cl2) with an upgraded
computer control (FEBO system) using graphite-monochro-
mated Mo KR radiation (6 and 8) and graphite-monochromated
Cu KR radiation (13‚CH2Cl2). A set of 25 carefully centered
reflections in the range 7° e θ e 10° (6), 8° e θ e 12° (8), and
10° e θ e 15° (13‚CH2Cl2), respectively, was used for deter-
mining the lattice constants. As a general procedure, the
intensity of three standard reflections were measured periodi-
cally every 2 h for orientation and intensity control. This
procedure did not reveal an appreciable decay of intensities.
The data were corrected for Lorentz and polarization effects.
Atomic scattering factors were those tabulated by Cromer and
Waber7 with anomalous dispersion corrections taken from ref
8. An empirical absorption correction was applied for com-
pound 13‚CH2Cl2 using the program DIFABS9 with transmis-
sion factors in the range 0.57-1.00. The computational work
was performed with a Digital Dec 5000/200 workstation using
the programs SIR92,10 SHELX-76,11 and SHELX-93.12 The
programs PARST13 and ORTEP14 were also used. Final atomic
coordinates of all atoms and structure factors are available
as Supporting Information.
P r ep a r a tive Rea ction . A sample of 200 mg of 10 (0.23
mmol) was dissolved in CH2Cl2 (40 mL) and then refluxed with
stirring for 4 h. After cooling of the sample to room temper-
ature, EtOH was added (20 mL) and the solution was
concentrated under a stream of nitrogen until pale yellow
crystals of mer-(PNP)RuCl(CtCPh)(CO) (11) precipitated
(yield >90%). Anal. Calcd for C48H46NClOP2Ru: C, 67.72; H,
5.45; N, 1.65. Found: C, 67.78; H, 5.35; N, 1.63. IR (cm-1):
ν(CtC) 2099 (s); ν(CtO) 1954 (vs). 31P{1H} NMR (23 °C,
CD2Cl2, 81.01 MHz): 34.18 (s). 13C{1H} NMR (23 °C, CD2Cl2,
50.32 MHz): δ(CtO) 200.64 [t, 2J (CP) 12.8 Hz], δ(CtC) 107.92
2
2
[t, J (CP) 13.9 Hz], δ(CtC) 112.44 [t, J (CP) 1.6 Hz], δ(CH3-
CH2CH2N) 60.62 (s), δ(NCH2CH2P) 52.57 [vt, N ) J (CP) +
J (CP′) ) 3.2 Hz], δ(NCH2CH2P) 28.55 [vt, N ) J (CP) + J (CP′)
) 12.0 Hz], δ(CH3CH2CH2N) 14.62 (s), δ(CH3CH2CH2N) 11.82
(s).
Syn th esis of mer -(P NP )Ru (CtCP h ){η-P h CdC(CtCP h )-
CHdCH(P h )} (12). A 3-fold amount of LiCtCPh (1.0 M THF
solution, 2.0 mL, 2.0 mmol) was added over a period of 5 min
to a well-stirred suspension of 4 (0.50 g, 0.66 mmol) in THF
(50 mL) at room temperature. During a period of 20 min the
color of the solution changed from cream to orange and finally
to red. On addition of ethanol (30 mL) the solution turned
deep orange and, after concentration at room temperature
under nitrogen, separated red orange crystals of 12. Yield:
58%. Anal. Calcd for C63H57NP2Ru: C, 76.34; H, 5.80; N, 1.41.
Found: C, 76.20; H, 5.69; N, 1.36. IR (cm-1): ν(CtC) 2062
(s), ν(CdC) 1514 (m); phenyl reinforced vibration 1590. 31P-
{1H} NMR (22 °C, THF-d8, 81.01 MHz): 31.06 (s). 1H NMR
(24 °C, CD2Cl2, 500.13 MHz) (the numbering scheme of the
hydrogen and carbon resonances is given in footnote 6): δ-
(H2) 6.11 [d, 3J (H1H2) 15.6 Hz], δ(H1) ca. 7.1 (obscured by
aromatic proton resonances, assigned by a 1H,1H-2D COSY
NMR experiment). 13C{1H} NMR (20 °C, CD2Cl2, 75.42
fa c,cis-(P NP )Ru Cl2(CO) (6). Pale yellow crystals (0.18 ×
0.22 × 0.16 mm) suitable for an X-ray diffraction analysis were
grown in the air by slow evaporation from a diluted dichlo-
romethane/ethanol solution of 6. The structure was solved via
2
MHz): δ(C4) or δ(C7) 139.91 [t, J (CP) 18.9 Hz] and 139.21 [t,
(7) Cromer, D. T.; Waber, J . T. Acta Crystallogr. 1965, 18, 104.
(8) International Tables of Crystallography; Kynoch Press: Bir-
mingham, U.K., 1974.
(9) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.
(10) Altomare, A.; Burla, M.; Camalli, G.; Cascarano, G.; Giacovazzo,
C.; Guagliandi, A.; Polidori, G. J . Appl. Crystallogr. 1994, 27, 435.
(11) Sheldrick, G. M. SHELX-76. A program for crystal structure
determination. University of Cambridge, 1976.
(12) Sheldrick, G. M. SHELXL93, Program for structure refinement.
University of Go¨ttingen, Germany, 1993.
(13) Nardelli, M. Comput. Chem. 1983, 7, 95.
(14) J ohnson, C. K. Report ORNL-5138; Oak Ridge National Labo-
ratory: Oak Ridge, TN, 1976.
2J (CP) 16.2 Hz], δ(C2) 130.56 (s, assigned by a 1H,13C-2D
HETCOR NMR experiment; the remaining resonance due to
the butadienyl carbon C1 could not unambiguously be as-
signed), δ(C6) or δ(C8) 118.27 [t, 2J (CP) 1.2 Hz] and 116.07 (br
s), δ(C3) or δ(C5) 84.16 (s) and 73.73 (s), δ(CH3CH2CH2N) 60.73
(s), δ(NCH2CH2P) 54.80 [vt, N ) J (CP) + J (CP′) ) 3.2 Hz],
δ(NCH2CH2P) 32.72 [vt, N ) J (CP) + J (CP′) ) 11.2 Hz], δ-
(CH3CH2CH2N) 14.92 (s), δ(CH3CH2CH2N) 12.18 (s).
Replacing EtOH with EtOD in the above reaction gave the
isotopomer mer-(PNP)Ru(CtCPh){η1-PhCdC(CtCPh)CDdCH-

276 Organometallics, Vol. 15, No. 1, 1996
Bianchini et al.
Sch em e 1
(PNP)RuCl2(PPh3)4 (1) in THF with an excess of either
phenylacetylene or p-tolylacetylene at reflux tempera-
ture results in the decoordination of triphenylphosphine
and formation of the vinylidene complexes fac,cis-(PNP)-
RuCl2{CdCH(R)} (R ) Ph (2), p-tolyl (3)).15
Patterson methods. Refinement was done by full-matrix least-
squares calculations, initially with isotropic thermal param-
eters and then with anisotropic thermal parameters for all the
atoms. All of the phenyl rings were treated as rigid bodies
with D6h symmetry and C-C distances fixed at 1.39 Å.
Hydrogen atoms were introduced in calculated positions but
not refined.
Monitoring the reaction with phenylacetylene (3
equiv) in THF-d8 by 31P{1H} NMR spectroscopy over the
temperature range from 20 to 50 °C does not show the
formation of any ruthenium intermediate species in the
course of the conversion of 1 to the vinylidene 2.
Evidently, both the 1-alkyne to vinylidene tautomer-
ization16,17 and the mer to fac isomerization18 of the
[(PNP)RuCl2] fragment are faster than the NMR time
scale. The mer to fac isomerization does not take place
when the reaction of 1 with 1-alkynes is carried out in
a 1:2 (v:v) mixture of THF and ethanol. In this case, in
fact, the mer,trans-(PNP)RuCl2{CdCH(R)} vinylidene
isomers (R ) Ph (4), p-tolyl (5)) are selectively obtained.
No isomerization of 2, 3 (4, 5) to 4, 5 (2, 3) occurs when
the compounds are refluxed in THF/ethanol (THF or
toluene).
m er -(P NP )Ru (CtCP h ){η3-P h C3dCH(P h )} (8). Crystals
suitable for an X-ray diffraction analysis were grown by slow
evaporation from a diluted THF/ethanol solution of 8. A red
parallelepiped crystal with dimensions 0.12 × 0.32 × 0.21 mm
was used for data collection. The structure was solved via
Patterson methods. Refinement was done by full-matrix least-
squares calculations, initially with isotropic thermal param-
eters and then with anisotropic thermal parameters for the
Ru, P, N, and C carbon atoms. The phenyl rings were treated
as rigid bodies with D6h symmetry (C-C ) 1.39 Å). Hydrogen
atoms were introduced in calculated positions but not refined.
m er -(P NP )R u (CtCP h ){η-P h CdC(CtCP h )CH dCH (p -
tolyl)}‚CH2Cl2 (13‚CH2Cl2). Crystals suitable for an X-ray
diffraction analysis were grown by slow evaporation from a
diluted dichloromethane/ethanol solution of 13. A red-orange
parallelepiped crystal with dimensions of 0.28 × 0.30 × 0.27
mm was used for the data collection. The structure was solved
by the heavy atom technique, and all of the non-hydrogen
atoms were found through a series of Fo Fourier maps. The
refinement was done by full-matrix least-squares calculations,
initially with isotropic thermal parameters and then with
anisotropic thermal parameters for the Ru, P, and N atoms.
All of the phenyl rings, but the p-tolyl one, were treated as
rigid bodies with D6h symmetry and C-C distances fixed at
1.39 Å. Hydrogen atoms bonded to the carbon atoms were
introduced in calculated positions using C-H bond values of
0.96 and 0.93 Å for the sp3-hybridized carbons and the phenyl
rings, respectively. A molecule of dichloromethane solvent was
found and successfully refined. The final difference map was
featureless.
Since the starting complex 1 readily loses PPh3 as a
thermal step in THF above 60 °C to give the fac dimer
[Ru(µ-Cl)3(PNP)2]Cl,4 the fac complexes 2 and 3 are
probably produced by interaction of the 1-alkyne with
the five-coordinate transient species fac-(PNP)RuCl2.
Accordingly, the role of EtOH in the formation of the
mer,trans isomers 4 and 5 might simply be that of
preventing the mer-(PNP)RuCl2 fragment from isomer-
izing to the fac arrangement prior to its interaction with
(15) The synthesis and partial characterization of 2 have already
been communicated: Bianchini, C.; Glendenning, L.; Peruzzini, M.;
Romerosa, A.; Zanobini, F. J . Chem. Soc., Chem. Commun. 1994, 2219.
(16) For leading references on the alkyne to vinylidene tautomer-
ization, see: (a) Fryzuk, M. D.; Huang, L.; McManus, N. T.; Paglia,
P.; Rettig, S. J .; White, G. S. Organometallics 1992, 11, 2979. (b)
Lumprey, J . R.; Selegue, J . P. J . Am. chem. Soc. 1992, 114, 5518. (c)
Werner, H. Angew. Chem., Int. Ed. Engl. 1990, 29, 1077. (d) Bianchini,
C.; Peruzzini, M.; Vacca, A; Zanobini, F. Organometallics 1991, 10,
3697. (e) Xiao, J .; Cowie, M. Organometallics 1993, 12, 463.
(17) For a theoretical study, see: Silvestre, J .; Hoffmann, R. Helv.
Chim. Acta 1985, 68, 1461.
Resu lts
The preparations and principal reactions described in
this paper are reported in Schemes 1-3. Selected
spectroscopic data for the new complexes are given in
the Experimental Section
(18) See, for example: (a) J ia, G.; Rheingold, A. L.; Hoggerthy, B.
S.; Meek, D. W. Inorg. Chem. 1992, 31, 900. (b) Whinnery, L. L.; Yue,
H. J .; Marsellar, J . A. Inorg. Chem. 1986, 25, 4236. (c) J ia, G.; Lee, I.;
Meek, D. W.; Gallucci, J . A. Inorg. Chim. Acta 1990, 177, 81.
Syn th esis an d Ch ar acter ization of th e Vin yliden e
Com p lexes fa c,cis- a n d m er ,tr a n s-(P NP )R u Cl2-
{CdCH(R)}. Treatment of the complex mer,trans-

C-C Bond Formation in Ru Complexes
Organometallics, Vol. 15, No. 1, 1996 277
the 1-alkyne (probably via EtOH coordination to the
unsaturated Ru(II) center).
observed triplet multiplicity, which arises from coupling
of the CR carbon to the two phosphorus atoms, shows
2J (CP) values (15.2-22.6 Hz) in line with those reported
for other Ru(II) vinylidenes containing tertiary phos-
phine ligands.24
Once formed, the fac vinylidene complexes do not
convert to the mer isomers probably because of a higher
energy barrier to isomerization than that experienced.
Indeed, meridional complexes of linear tridentate ligands
are generally favored over facial complexes due to steric
interaction.18c However, the fac geometry may be
preferred for triphosphine ligands (as well as PNP)
when there is a possibility that the phosphine atoms
are trans to weak trans-influence ligands to eliminate
the trans-phosphine interaction.18a In the PNP com-
plexes described in this work, steric effects generally
prevail over electronic effects in determining the geom-
etry of the PNP ligand. On the other hand, the selective
formation of the fac isomers 2 and 3 occurring in THF
suggests that a subtle balance of electronic and steric
effects can effectively determine the geometry of the
PNP ligand.
The IR spectra of 2-5 contain medium- to strong-
intensity bands ranging between 1650 and 1603 cm-1
which are typical of ν(CdC) of vinylidene ligands.19 Both
the fac,cis and the mer,trans complexes exhibit a singlet
resonance in the 31P{1H} NMR spectra for the two
chemically equivalent phosphorus atoms of the PNP
ligand (ca. 48 and 27 ppm, respectively). As previously
observed,20 the chemical shifts of the phosphorus atoms
are diagnostic for the coordination mode of PNP. In
particular, the phosphorus nuclei of the mer complexes,
due to the remarkable trans influence of the phosphine
ligands, resonate invariably at higher field (20-35 ppm)
than those of the fac isomers (40-60 ppm).
Oxidative Cleavage of th e Vin yliden e CdC Bon d.
Syn th esis of th e Ca r bon yl Com p lexes fa c,m er - a n d
m er ,tr a n s-(P NP )R u Cl2(CO) (6 a n d 7). The vi-
nylidene complexes 2 and 3 are air-stable in the solid
state, whereas in aerobic solutions slowly decompose
(4-5 days) to give the carbonyl complex fac,cis-(PNP)-
RuCl2(CO) (6) and aldehydes.25 This chemical trans-
formation is much faster by using pure oxygen. Under
1 atm of oxygen in CH2Cl2, 2 and 3 quantitatively
transform into the carbonyl complex 6 in 12 h at room
temperature and in ca. 30 min at reflux temperature.
1
Monitoring the reactions in CDCl3 by 31P{1H} and H
NMR spectroscopies in the temperature range from 0
to 55 °C shows only the resonances of the starting
material and of the final carbonyl product (singlet at
58.27 ppm) with no detection of any intermediate
adduct. One equivalent of either benzaldehyde or
p-tolylaldehyde is produced during the oxidative deg-
radation of the vinylidene ligands (1H NMR, GC-MS).
The mer,trans vinylidene isomers 4 and 5 in CH2Cl2
undergo analogous transformations when exposed to air.
At reflux temperature under oxygen, the complex
mer,trans-(PNP)RuCl2(CO) (7) (31P NMR: singlet at
27.76 ppm) and aldehydes are formed in quantitative
yield in ca. 4 h. Consistent with the mer,trans struc-
ture, 7 can also be prepared by refluxing 1 in THF under
a carbon monoxide atmosphere.
Strong ν(CtO) absorptions (1942 and 1955 cm-1) in
the IR spectra and low-field triplet resonances [δ 203.61,
The magnetic equivalence of the two phosphine
donors of PNP in the facial complexes 2 and 3 is
consistent with a cis structure in which the vinylidene
ligand is located trans to the nitrogen and excludes a
structure in which the vinylidene ligand and one of the
phosphorus atoms are mutually trans. The 31P NMR
spectra of all compounds are temperature invariant
down to -90 °C, consistent with a low-energy barrier
to rotation of the vinylidene group around the Ru-C-C
axis.21,22
2
2J (CP) 15.9 Hz; δ 201.19, J (CP) 13.5 Hz] in the 13C-
{1H} NMR spectra diagnose the presence of a terminal
carbonyl ligand in 6 and 7. The triplet multiplicity of
the carbonyl carbon resonances points to the equiva-
lence of the two phosphine groups in both compounds
and thus supports a trans disposition between the PNP
nitrogen and the CO ligand. In conclusion, the oxidative
cleavage of the vinylidene ligands in 2-5 promoted by
action of molecular oxygen does not change the stere-
ochemical arrangement of the PNP precursors and thus
is consistent with a regioselective attack by O2 at the
vinylidene ligand.
The 1H NMR spectra of 2-5 show the vinylidene
hydrogens to appear as triplets that transform into
1
sharp singlets in the H{31P} spectra. The vinylidene
hydrogens in the mer, trans compounds 4 and 5 are
shifted upfield by ca. 1.6 ppm as compared to those in
the fac,cis isomers 2, 3, probably because of the larger
shielding effect provided by the phenyl rings of the
mutually trans PPh2 groups.
In order to confirm the stereochemistry of 6 and
indirectly support the structures assigned to the parent
vinylidenes 2 and 3, an X-ray analysis has been carried
out on a single crystal of 6.
The molecular structure of the complex is shown in
Figure 1 with the atomic labeling scheme. A list of
selected bond distances and angles is presented in Table
1.
The crystal structure consists of discrete mononuclear
fac,cis-(PNP)RuCl2(CO) neutral molecules with no in-
The quaternary R-carbons of the RudCdC moiety in
2-5 resonate at much lower field (356.31 e δ e 359.90)
than the â-carbon atoms (ca. 110 ppm).19 The large
deshielding of the vinylidene CR carbon resonance,
which is a consequence of its electron-deficient charac-
ter, has recently been interpreted by Czech and co-
workers as being due also to changes in the paramag-
netic contribution, σp, to the nuclear shielding σ.23 The
(23) Czech, P. T.; Ye, X.-Q.; Fenske, R. F. Organometallics 1990, 9,
2016.
(24) See, for example: (a) Le Lagadec, R.; Roman, E.; Toupet, L.;
Mu¨ller, U.; Dixneuf, P. H. Organometallics 1994, 13, 5030. (b) Gamasa,
M. P.; Gimeno, J .; Ma´rtin-Vaca, B. M.; Borge, J .; Garcia´-Granda, S.;
Perez-Carren˜o, E. Organometallics 1994, 13, 4045.
(25) Several cases of oxidation of Ru(II) vinylidene complexes by
molecular oxygen have been reported, see for example: (a) Bruce, M.
I.; Swincer, A. G.; Wallis, R. C. J . Organomet. Chem. 1979, 171, C5.
(b) Oro, L. A.; Ciriano, M. A.; Foces-Foces, C.; Cano, F. M. J .
Organomet. Chem. 1985, 289, 117. (c) Mezzetti, A.; Consiglio, G.;
Morandini, F. J . Organomet. Chem. 1992, 430, C15.
(19) (a) Bruce, M. I. Chem. Rev. 1991, 91, 197. (b) Antonovas, A. B.;
Ioganson, A. A. Russ. Chem. Rev. 1989, 58, 593. (c) Bruce, M. I.;
Swincer, A. G. Adv. Organomet. Chem. 1983, 22, 59.
(20) Meek, D. W.; Mazanec, T. J . Acc. Chem. Res. 1981, 14, 266.
(21) (a) Bianchini, C.; Marchi, A.; Marvelli, L.; Peruzzini, M.;
Romerosa, A.; Rossi, R.; Vacca, A. Organometallics 1995, 14, 3203. (b)
Bianchini, C.; Meli, A.; Peruzzini, M.; Zanobini, F.; Zanello P. Orga-
nometallics 1990, 9, 241.
(22) Kostic, N. M.; Fenske, R. F. Organometallics 1982, 1, 974.

278 Organometallics, Vol. 15, No. 1, 1996
Bianchini et al.
Sch em e 2
F igu r e 1. ORTEP drawing (30% thermal ellipsoids prob-
ability) of fac,cis-(PNP)RuCl2(CO) (6). All the hydrogen
atoms are omitted for clarity.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for fa c,cis-(P NP )Ru Cl2(C)) (6)
mer,trans-(PNP)RuCl2(PPh3)29 and mer,trans-(PNP)-
RuH(Cl)(PPh3)4 complexes, but it is slightly longer than
those found in Ru(tertiary amine) complexes.28 These
data are statistically significant and indicate that the
phosphine and CO groups exhibit comparable trans
influence in the present complexes.
Ru-P1
Ru-P2
Ru-C1
Ru-Cl2
2.290(3)
2.291(3)
2.433(3)
2.446(3)
Ru-N
Ru-C8
C8-O
2.310(8)
1.814(11
1.15(1)
P1-Ru-P2
P1-Ru-C1
P2-Ru-Cl1
P1-Ru-Cl2
P2-Ru-Cl2
Cl1-Ru-Cl2
P1-Ru-N
P2-Ru-N
99.9(1)
167.7(1)
88.2(1)
85.0(1)
171.8(1)
86.0(1)
83.3(3)
83.9(2)
Cl1-Ru-N
Cl2-Ru-N
P1-Ru-C8
P2-Ru-C8
Cl1-Ru-C8
Cl2-Ru-C8
N-Ru-C8
Ru-C8-O
88.4(2)
90.2(2)
95.7(4)
93.3(4)
93.1(4)
92.8(4)
176.8(4)
178(1)
Rea ction s of th e fa c,cis-Vin ylid en e Com p lexes
w ith LiCtCP h . Syn th esis of th e σ-Alk yn yl-η3-
Bu ten yn yl Com p lexes a n ti,m er -(P NP )Ru (CtCP h )-
{η3-P h C3dCH(R)} (R ) P h , 8; R ) p-tolyl, 9).
Addition of 2 equiv of lithium phenylacetylide to a THF
solution of 2 at ca. 5 °C gives an orange solution from
which crystals of the butenynyl complex anti,mer-(PNP)-
Ru(CtCPh){η3-PhC3dCH(Ph)} (8) separate by addition
of ethanol and concentration of the resulting solution.
When the p-tolyl derivative 3 is analogously reacted
with LiCtCPh, the complex anti,mer-(PNP)Ru(CtCPh)-
{η3-PhC3dCH(p-tolyl)} (9) is obtained. The ligand set
surrounding the Ru center in 8 and 9 comprises a
meridional PNP ligand, a terminal alkynyl group, and
an η3-bonded 1,4-disubstituted butenynyl ligand.
The IR spectra show the presence of a σ-alkynyl
ligand in both complexes [ν(CtC) at ca. 2070 cm-1 (s)].
The 31P{1H} NMR spectra consist of a singlet in the
proper region of octahedral mer-PNP Ru complexes (ca.
terspersed solvent molecules in the crystal lattice. The
coordination geometry around the ruthenium center is
a distorted octahedron with the metal atom surrounded
by the two phosphorus and the nitrogen atoms of PNP,
by a carbonyl carbon atom trans to the nitrogen, and
by two mutually cis Cl atoms.
The most evident distortion from the idealized geom-
etry is the bending of the two PPh2 groups toward the
N atom [P1-Ru-N ) 83.3(2)°; P2-Ru-N ) 83.9(2)°]
and toward the two Cl atoms [P1-Ru-P2 ) 99.9(1)°].
A similar distortion, probably due to repulsion between
the four phenyl rings, has been found in (PNP)Ir(σ,η2-
C8H13) which is the only other fac-PNP complex au-
thenticated by an X-ray analysis.26 The ruthenium
atom is slightly displaced from the least-squares plane
P1-P2-Cl1-Cl2 toward the N atom by 0.155(3) Å and
from the least-squares plane P2-N-Cl2-C8 toward the
P1 atom by 0.046(8) Å.
The Ru-P distances [2.290(3) and 2.291(3) Å] fall
within the range reported in the literature for Ru(II)
phosphine complexes.27,28 These distances are shorter
[0.085(3) and 0.084(3) Å, respectively] than those found
in the starting mer,trans complex 1,29 consistent with
the greater trans influence of phosphine vs chloride. The
Ru-Cl separations [2.433(3) and 2.446(3) Å] match well
with the values reported for several Ru-Cl distances
in compounds containing the chlorine atom trans to a
phosphine.30 Finally, the Ru-N distance [2.310(8) Å]
is in excellent agreement with those found in the
1
36 ppm). The H NMR spectrum of 8 contains a triplet
at ca. 8.3 ppm [4J (CP) 1.4 Hz] which is assigned to the
vinylic hydrogen atom of the 1,4-disubstituted butenynyl
ligand (the triplet collapses to a singlet in the broad-
band 31P-decoupled 1H NMR spectrum and does not
1
show any cross-peak in the H,1H-2D COSY spectrum).
1
HMQC H,13C-2D HETCOR experiments correlate this
signal with a triplet at ca. 130.5 ppm in the 13C{1H}
NMR spectrum. The latter together with a series of
DEPT spectra and an HMQC experiment allow one to
almost completely assign the resonances of the six
carbon atoms of the alkynyl and η3-butenynyl ligands.
In particular, three resonances at 154.97 [2J (CP) 7.8
Hz], 130.50 [3J (CP) 1.3 Hz], and 56.88 ppm [2J (CP) 1.7
Hz] in the spectrum of 8 can unequivocally be assigned
to the C4, C1, and C3 carbon atoms of the butenynyl
ligand,1,6 while a triplet at 135.86 [2J (CP) 15.9 Hz] is
assigned to the CR carbon atom of the σ-phenylethynyl
ligand.31,32 Uncertainty still affects the assignment of
the quaternary C2 and C6 carbon atoms6 for which quite
(26) Bianchini, C.; Farnetti, E.; Graziani, M.; Nardin, G.; Vacca, A.;
Zanobini, F. J . Am. Chem. Soc. 1990, 112, 9190.
(27) Seddon, E. A.; Seddon, K. R. The Chemistry of Ruthenium;
Elsevier: Amsterdam, The Netherlands, 1984; Chapter 9.
(28) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J . Chem. Soc., Dalton Trans. 1989, S1.
(29) Bianchini, C.; Masi, D.; Romerosa, A.; Peruzzini, M.; Zanobini,
F. Acta Crystallogr. 1995, C51, in press.
(30) Albinati, A.; J iany, Q.; Ru¨gger, H.; Venanzi, L. M. Inorg. Chem.
1993, 32, 4940.

C-C Bond Formation in Ru Complexes
Organometallics, Vol. 15, No. 1, 1996 279
by a mer PNP ligand. A phenylethynyl ligand and an
η3-PhC3dCH(Ph) group complete the coordination sphere
about the metal center.
The largest deviation from the idealized geometry is
represented by the P1-Ru-P2 angle which closes up
to 165.0(1)° as a consequence of the bending of the two
PPh2 groups toward the N atom. The phenylethynyl
ligand, cis to the three donor atoms of PNP, is nearly
linear [Ru-C13-C12 ) 177(1)°]. The Ru-C13 bond
distance [2.00(1) Å] is appreciably shorter than those
observed for other ruthenium σ-alkynyl complexes;5,32
in particular it is shorter than a Ru-C(sp) single bond
(2.127 Å).33 The observed difference [∆ ) |dRu-C found
-
dRu-C calcd| ) 0.127(1) Å] is statistically significant and
is consistent with the high-energy ν(CtC) absorption
in the IR spectra (8, 2069 cm-1; 9, 2073 cm-1). This
experimental observable suggests a scarce dπ(metal) f
π*(ligand) back-bonding,34 and in fact, the C13-C12
separation [1.21(2) Å] does not practically differ from
the C-C distance found in disubstituted alkynes.35
F igu r e 2. ORTEP drawing (30% thermal ellipsoids prob-
ability) of the complex anti,mer-(PNP)Ru(CtCPh){η3-
PhC3dCH(Ph)} (8). Only the ipso carbons of the phenyl
rings of the PNP ligand are shown for the sake of clarity.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for
a n ti,m er -(P NP )Ru (CtCP h ){η3-P h C3dCH(P h )} (8)
The n-propyl chain on the central nitrogen donor of
PNP and the σ-phenylethynyl ligand are mutually
anti.36,37 Thus, 8 adopts an anti,mer stereochemistry
similar to that found in the related complex Ru-
(CtCPh){η3-PhC3dC(H)Ph}(Cytpp) which, however,
shows a different orientation of the butenynyl moiety
with respect to the L3Ru(CtCPh) fragment [Cyttp )
PhP{(CH2CH2CH2P(c-C6H11)2}2].38 As a consequence of
the anti stereochemistry of 8, the angle N-Ru-C8
[102.5(4)°] is larger than the angle N-Ru-C13 [86.5-
(4)°] because the n-propyl substituent can sterically
interact with the phenyl ring of the butenynyl -CtCPh
group. This part of the enynyl fragment is weakly
bound to ruthenium as shown by the long Ru-C8 and
Ru-C9 separations [2.39(1) and 2.19(1) Å, respectively]
as well as the short C8-C9 separation [1.23(2) Å].
Consequently, the bent-back angle of the phenyl sub-
stituent C9-C8-C1E is fairly large [154(1)°]. The
amplitude of this angle is commonly taken as a relevant
parameter for establishing the nature of alkyne bonding
to metal centers.39 In the case at hand, the value of
the bent-back angle, which is larger than that found for
simple η2-PhCtCPh complexes (135-140°), is consistent
with a modest perturbation of the sp character of the
alkynyl carbons and definitely agrees with a weak
Ru-P1
Ru-P2
Ru-N
Ru-C8
Ru-C9
Ru-C10
Ru-C13
2.317(3)
2.318(3)
2.271(9)
2.39(1)
2.19(1)
2.06(1)
2.00(1)
C8-C9
1.23(2)
1.46(1)
1.41(2)
1.34(2)
1.48(2)
1.21(2)
1.44(1)
C8-C1E
C9-C10
C10-C11
C11-C1F
C12-C13
C12-C1G
P1-Ru-P
165.0(1)
81.4(2)
84.1(2)
93.5(3)
93.4(3)
102.5(4)
94.5(3)
98.2(3)
133.0(4)
30.7(4)
95.9(3)
99.0(3)
171.3(4)
69.3(4)
38.6(4)
87.5(3)
87.7(3)
N-Ru-C13
C8-Ru-C13
C9-Ru-C13
C10-Ru-C13
Ru-C8-C9
Ru-C8-C1E
C9-C8-C1E
Ru-C9-C8
Ru-C9-C10
C8-C9-C10
Ru-C10-C9
Ru-C10-C11
C9-C10-C11
C10-C11-C1F
C13-C12-C1G
Ru-C13-C12
86.5(4)
171.0(4)
140.3(4)
101.7(4)
65.4(7)
140.8(8)
154(1)
83.9(8)
65.6(6)
150(1)
75.5(6)
154(1)
130(1)
125(1)
174(1)
P1-Ru-N
P2-Ru-N
P1-Ru-C8
P2-Ru-C8
N-Ru-C8
P1-Ru-C9
P2-Ru-C9
N-Ru-C9
C8-Ru-C9
P1-Ru-C10
P2-Ru-C10
N-Ru-C10
C8-Ru-C10
C9-Ru-C10
P1-Ru-C13
P2-Ru-C13
177(1)
similar magnetic parameters are found [115.14 ppm,
2J (CP) 2.0 Hz; 110.98 ppm, 1.4 Hz].
An almost identical 13C{1H} NMR spectrum is dis-
played by the p-tolyl derivative 9, the only significant
difference being the presence of a singlet resonance at
21.89 ppm, which correlates with the proton singlet at
2.34 ppm in the 1H,13C-2D HETCOR spectrum, and thus
is readily attributed to the p-tolyl CH3 group.
(33) (a) Sun, Y.; Taylor, N. J .; Carthy, A. J . J . Organomet. Chem.
1992, 423, C43. (b) Chakravarty, A. R.; Cotton, F. A. Inorg. Chim. Acta
1986, 113, 19.
(34) (a) Bianchini, C.; Meli, A.; Peruzzini, M.; Vacca, A.; Laschi, F.;
Zanello, P.; Ottaviani, M. F. Organometallics 1990, 9, 360. (b) Adams,
J . S.; Bitcon, C.; Brown, J . R.; Collison, D.; Cunningham, M.; Whiteley,
M. W. J . Chem. Soc., Dalton Trans. 1987, 3049. (c) Lichtenberger, D.
L.; Renshaw, S. K.; Bullock, R. M. J . Am. Chem. Soc. 1993, 115, 3276.
(35) (a) March, J . Advanced Organic Chemistry, 4th ed.; Wiley: New
York, 1992. (b) Gordon, A. J .; Ford, R. A. The Chemist’s Companion;
Wiley: New York, 1972; p 108.
A single-crystal X-ray analysis of 8 has confirmed the
structure assigned in solution. An ORTEP drawing of
the complex is shown in Figure 2, and selected bond
lengths and angles are reported in Table 2. The
coordination geometry around the ruthenium atom
approximates an octahedron with three positions taken
(36) Cahn, R. S.; Ingold, C.; Prelog, V. Angew. Chem., Int. Ed. Engl.
1966, 5, 385.
(37) Syn and anti stereoisomers have been previously reported for
chelated polyphosphine complexes, see: (a) Blosser, P. W.; Gallucci,
J . C.; Wojcicki, A. Inorg. Chem. 1992, 31, 2376. (b) J ia, G.; Meek, D.
W.; Gallucci, J . C. Inorg. Chem. 1991, 30, 403. (c) Letts, J . B.; Mazanec,
T. J .; Meek, D. W. J . Am. Chem. Soc. 1982, 104, 3893. (d) Yang, C.;
Socol, S. M.; Kountz, D. J .; Meek, D. W.; Glaser, R. Inorg. Chim. Acta
1986, 114, 119. (e) George, T. A.; Koczam, L. M.; Tisdale, R. C.;
Gebreyes, K.; Ma, L.; Shaick, S. N.; Zubieta, J . Polyhedron 1990, 9,
545.
(38) J ia, G.; Gallucci, J . C.; Rheingold, A. L.; Haggerty, B. S.; Meek,
D. W. Organometallics 1991, 10, 3459.
(39) Alcock, N. W.; Hill, A. F.; Melling, R. P.; Thompsett, A. R.
Organometallics 1993, 12, 641.
(31) (a) Rappert, T.; Yamamoto, A. Organometallics 1994, 13, 4984.
(b) Bruce, M. I.; Hinterding, P.; Tiekink, E. R. T.; Skelton, B. W.; White,
A. H. J . Organomet. Chem. 1993, 450, 209.
(32) (a) Helliwell, M.; Stell, K. M.; Mawby, R. J . J . Organomet. Chem.
1988, 356, C32. (b) J ia, G.; Rheingold, A. L.; Meek, D. W. Organome-
tallics 1989, 8, 1378. (c) Bruce, M. I.; Humphrey, M. G.; Snow, M. R.;
Tiekink, E. R. T. J . Organomet. Chem. 1986, 314, 213. (d) Consiglio,
G.; Morandini, F.; Sironi, A. J . Organomet. Chem. 1986, 306, C45. (e)
Wisner, J . M.; Bartczak, T. J .; Ibers, J . A. Inorg. Chim. Acta 1985,
100, 115.

280 Organometallics, Vol. 15, No. 1, 1996
Bianchini et al.
F igu r e 3. (a) Section of the phase-sensitive 2D-1H NOESY spectrum of 9 (500.13 MHz, CD2Cl2, 25 °C, τmix ) 800 ms)
showing the negative cross peak between the methyl protons and the aromatic ortho protons of the p-tolyl group. (b)
Contour plot of a section of the 2D-1H COSY spectrum of 9 (500.13 MHz, CD2Cl2, 25 °C) showing the scalar couplings for
the aromatic protons. The relevant cross peak between the protons of the p-tolyl group is marked. (c) Section of the phase-
sensitive 2D-1H NOESY spectrum of 9 (500.13 MHz, CD2Cl2, 25 °C, τmix ) 800 ms) showing the spatial relationships
between the aromatic protons. The relevant cross peak between the protons of the p-tolyl group and the butenynyl hydrogen
atom at δ 8.28 is marked.
bonding interaction of ruthenium with the CtCPh
moiety of the butenynyl ligand.
A complete assignment of the relevant hydrogen
atoms obtained by using a combination of 1H,1H-2D
COSY and NOESY NMR spectra unambiguously shows
that the p-tolyl group in 9 is bound to the â-carbon atom
of the vinyl moiety (structure I). In particular, a perusal
of the 2D-COSY NMR experiment allows one to estab-
lish the sequence of the hydrogens which are spin-spin
coupled, while, in the phase-sensitive NOESY spectrum,
the negative correlation peaks provide information on
the spatial relationships between the hydrogen atoms.
In the case at hand, the decisive feature of the NOESY
spectrum, which is presented in Figure 3a, consists of
a strong cross-peak between the p-tolyl CH3 hydrogens
(δ 2.34) and the two aromatic ortho hydrogens at ca.
7.0 ppm (partially overlapping with other aromatic
protons of the PPh2 groups). These, in turn, show a
clear correlation in the double-quantum filtered COSY
spectrum with the 2H-multiplet at δ 8.65 due to the
remaining pair of the p-tolyl hydrogen nuclei (Figure
3b). As expected, these protons do not exhibit further
scalar couplings in the COSY spectrum but display a
NOESY pattern which shows a NOE contact with the
butenynyl hydrogen at 8.28 ppm (Figure 3c).
The Ru-C and C-C bonding patterns are similar to
those found for other η3-butenynyl complexes in which
some degree of electronic delocalization in the RuC3
moiety has been suggested.1,38
NMR An a lysis of a n ti,m er -(P NP )Ru (CtCP h ){η3-
P h C3dCH(p-tolyl)} (9). Two different regioisomers (I
and II) are possible for 9, which differ from each other
in the position of the p-tolyl group in the C4 chain of
the butenynyl ligand. The question of determining the
precise structure of 9 is not of marginal importance as
the position of the p-tolyl group is evidently related to
the mechanism of formation of the butenynyl ligand
which is a central point of the present work.
These experiments clearly indicate that there is a
direct relationship between the butenynyl hydrogen and
the p-tolyl CH3 group via the four aromatic hydrogen

C-C Bond Formation in Ru Complexes
Organometallics, Vol. 15, No. 1, 1996 281
Sch em e 3
does not react with 2): the octahedral carbonyl complex
fac-(PNP)RuCl(CtCPh)(CO) (10) was quantitatively
obtained as yellow crystals (Scheme 3).
F igu r e 4. Drawing of the complex mer-(PNP)Ru(CtCPh)-
{η3-PhC3dCH(p-tolyl)} (9). All of the phenyl rings of PNP
ligand are omitted for clarity.
In order to definitely probe that a stoichiometric
amount of LiCtCPh serves to deprotonate the vi-
nylidene ligand, complex 2 in THF was reacted in the
presence of CO with either a different acetylide (LiCtC-
p-tolyl) or a base of different type (NEt3). In both
reactions, 2 is quantitatively converted to 10 (no incor-
poration of the p-tolylacetylide unit into the complex
occurs, while the conjugated acid NHEt3+, isolated as
the Cl- salt, forms in the reaction with NEt3).
atoms of the p-tolyl substituent and rule out the
alternative structure II in which there is not a geminal
disposition of the p-tolyl group and of the butenynyl
hydrogen atom.
Finally, in accord with the anti,mer stereochemistry
of 9, the NOESY spectrum does not show any contact
between the hydrogen atoms of the n-propyl chain and
those of the p-tolyl ring.
The 31P{1H} NMR spectrum of 10 in CD2Cl2 consists
of an AM spin system. On the basis of the different
trans influence exerted by the Cl and and CO ligands
on the 31P chemical shifts,20,41 the signal at 49.43 ppm
can be assigned to the PPh2 group trans to the chloride,
while the upfield signal at 23.33 ppm is assigned to the
phosphorus trans to the carbonyl ligand. The IR
spectrum shows ν(CtO) of the carbonyl ligand at 1968
A single-crystal X-ray analysis of 9 has fully con-
firmed the structural formulation determined in solu-
tion by NMR spectroscopy. Although details of the
structure of 9 will be given elsewhere, a drawing of 9 is
shown in Figure 4.40
Syn th esis a n d Ch a r a cter iza tion of fa c-(P NP )-
Ru Cl(CtCP h )(CO) (10) a n d m er -(P NP )Ru Cl(Ct
CP h )(CO) (11). Treatment of 2 in THF with 1 equiv
of LiCtCPh, followed by different workups (removal of
the solvent in vacuo, addition of either n-hexane or
EtOH), invariably gives several Ru complexes (31P
NMR). A separate experiment carried out in a sealed
NMR tube showed that a selective reaction between
stoichiometric amounts of 2 and LiCtCPh occurs in
THF-d8 with formation of a unique product (31P NMR:
singlet at 59.93 ppm) at a temperature as low as -50
°C. Above -10 °C, however, extensive decomposition
already occurs which at room temperature results in the
complete disappearance of the low-temperature com-
pound and formation of several unidentified products.
Since a similar sequence of events is observed by
treatment of 2 in THF with 1 equiv of n-BuLi (particu-
larly the selective formation of the same product at low
temperature), our conclusion is that the first 1 equiv of
LiCtCPh added to 2 deprotonates the vinylidene ligand
to give a σ-alkynyl ligand and also removes a chloride
from Ru as LiCl. As a result, the unsaturated (PNP)-
RuCl(CtCPh) complex may form which apparently
degrades at room temperature to several products by
reaction with various potential reagents in the sur-
rounding environment (HCtCPh, solvent, water). In
a successful attempt to intercept this reactive interme-
diate, the addition of LiCtCPh to 2 was carried out
under an atmosphere of carbon monoxide (which alone
cm-1 and ν(CtC) of the alkynyl group at 2089 cm-1
.
Consistent with the structure proposed in Scheme 3, the
resonance of the carbonyl carbon atom in the 13C{1H}
NMR spectrum is observed at 200.20 ppm (dd) with cis
and trans 31P-13CO coupling constants [2J (CPtrans) 100.6
2
Hz, J (CPcis) 14.9 Hz] in line with those observed for
several ruthenium carbonyl complexes.42
On standing in CH2Cl2 solution, 10 slowly converts
to the thermodynamic isomer mer-(PNP)RuCl(CtCPh)-
(CO) (11). At room temperature the complete isomer-
ization of 20 mg of 1 in 0.7 mL of CD2Cl2 occurs in 4-5
days, while at 50 °C the isomerization is complete in 3
h.
Compounds 10 and 11 exhibit very similar spectro-
scopic characteristics, the only relevant differences
being those directly connected with the coordination
mode of the PNP ligand; e.g., the 31P{1H} NMR of 11
consists of a singlet at 34.18 ppm suggestive of the mer
structure. Notably, the carbonyl carbon atom signal in
the 13C{1H} NMR spectrum of 11 falls in the same
position of the analogous resonance of 10 but appears
as a triplet [2J (CP) ) 12.8 Hz], which further supports
the structure shown in Scheme 3.
(41) Balimann, G.; Pregosin, P. S. J . Magn. Reson. 1976, 22, 235.
(42) See, for example: Hommeltoft, S. I.; Cameron, A. D.; Shack-
leton, T. A.; Fraser, M. E.; Fortier, S.; Baird, M. C. Organometallics
1986, 5, 1380.
(40) Bianchini, C.; Peruzzini, M. Unpublished results.

282 Organometallics, Vol. 15, No. 1, 1996
Bianchini et al.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for m er -[(P NP )Ru (CtCP h )-
{η1-P h CdC(CtCP h )CHdCH(p-tolyl)}]‚CH2Cl2
(13‚CH2Cl2)
Ru-P1
Ru-P2
Ru-N
Ru-C8
Ru-C14
P1-C1
P2-C3
Ru-C12
C8-C9
C8-C9
2.326(7)
2.312(7)
2.30(2)
2.04(2)
2.03(2)
1.85(2)
1.86(2)
2.48(2)
1.35(3)
1.35(3)
C9-C10
1.50(3)
1.43(3)
1.34(3)
1.22(3)
1.18(3)
1.44(3)
1.45(3)
1.43(3)
1.46(5)
2.82(2)
C9-C12
C10-C11
C12-C13
C14-C15
C11-C1,8
C13-C1,7
C15-C1,6
C4,8-C16
Ru‚‚‚C13
P1-Ru-P2
P1-Ru-N
P2-Ru-N
P1-Ru-C8
P2-Ru-C8
N-Ru-C8
P1-Ru-C12
N-Ru-C12
P1-Ru-C14
P2-Ru-C12
P2-Ru-C14
N-Ru-C14
C8-Ru-C12
164.3(2)
83.0(4)
81.4(4)
98.2(6)
97.3(6)
177.6(8)
95.0(6)
123.6(7)
89.1(7)
95.3(5)
87.0(7)
83.6(8)
58.5(8)
C8-Ru-C14
C12-Ru-C14
Ru-C8-C9
95.4(9)
153.8(8)
108(1)
132(1)
120(1)
131(2)
107(2)
121(2)
124.(2)
179(2)
164(2)
177(2)
Ru-C8-C1,5
C9-C8-C1,5
C8-C9-C10
C8-C9-C12
C9-C10-C11
C10-C11-C1,8
C9-C12-C13
C12-C13-C1,7
C14-C15-C16
F igu r e 5. ORTEP drawing (30% thermal ellipsoids prob-
ability) of the complex mer-(PNP)Ru(CtCPh){η1-PhCdC-
(CtCPh)CHdCH(p-tolyl)}] (13). All of the phenyl rings of
PNP ligand are omitted for clarity.
Rea ction s of th e m er ,tr a n s Vin ylid en e Com -
p lexes w it h LiCtCP h . Syn t h esis of t h e σ-Al-
k yn yl-η1-Hexa d ien yn yl Com p lexes m er -(P NP )Ru -
(CtCP h ){η-P h CdC(CtCP h )CHdCH(R)} (R ) P h ,
12; R ) p-tolyl, 13). Unlike the fac,cis isomers, the
mer,trans vinylidene complexes 4 and 5 in THF con-
sume 3 equiv of LiCtCPh. From the reaction mixture,
red orange crystalline complexes of the formula mer-
(PNP)Ru(CtCPh){η-PhCdC(CtCPh)CHdCH(R)} (R )
Ph, 12; R ) p-tolyl, 13) are obtained in fairly good yield
(ca. 60%) only if a primary alcohol (EtOH or MeOH) is
subsequently added. When EtOD is employed, ste-
reospecific incorporation of deuterium occurs in the
2-position of the butadienyl fragment of the C6 unsatur-
ated ligand (Scheme 2).
Both the use of 3 equiv of LiCtCPh and the addition
of alcohol are of mandatory importance for the formation
of 12 and 13 in acceptable yields. In the absence of
either reaction conditions, only trace amounts of 12 and
13 are formed together with several unidentified (PNP)-
Ru compounds.
Given the evident complexity of the underlying chemi-
cal reactions involving the addition of 3 “CtCPh” units
and one hydrogen atom to the mer-(PNP)RudCdC(H)R
fragment, a single-crystal X-ray analysis of the p-tolyl
derivative 13 has been of paramount importance for
elucidating the structure of the organyl ligands bound
to Ru. An ORTEP view of 13 is shown in Figure 5, while
selected bond angles and interatomic distances are
collected in Table 3.
center and the phenylethynyl substituent on the C9
carbon atom may be envisaged [Ru-C12 ) 2.48(2),
Ru‚‚‚C13 ) 2.82(2) Å] which is probably important for
the overall stability of the complex. Consistent with a
very weak bonding interaction, the C12-C13 separation
is 1.22(3) Å and the C9-C12-C13 sequence of carbon
atoms is practically linear [179(2)°]. Also, the value of
the bent-back angle of the phenyl substituent (164(2)°)
is intermediate between the values exhibited by η3-
(144.6-158.6°)1cd,38,43,44 and η1-butenynyl complexes
(173-175.6°).1b,39,45
In the butadiene part of the C6 ligand there is
alternation of short and long C-C bond distances.46
Double bonds are localized between the C8-C9 [1.35-
(3) Å] and C10-C11 [1.34(3) Å] carbon atoms, while the
separation C9-C10 of 1.50(3) Å corresponds to a single
bond. The “RuC6” assembly is essentially planar with
a maximum deviation of 0.062 Å for Ru from the plane.
In the alkynyl substituent, the separation C9-C12
[1.43(3) Å] although slightly shorter than a C(sp3)-C(sp)
single bond (1.47 Å)47 excludes a significative delocal-
ization of the alkyne π-electrons. Finally, the bond
angles and distances relative to the σ-alkynyl ligand are
normal and do not deserve further comments.
From a comparison of the spectroscopic and structural
data, one may readily infer that 13 exhibits the same
structure in both the solid state and solution (the 31P-
(43) Gotzig, J .; Otto, H.; Werner, H. J . Organomet. Chem. 1985, 287,
247.
(44) (a) Field, L. D.; George, A. V.; Hambley, T. W. Inorg. Chem.
1990, 29, 4565. (b) Hills, A.; Hughes, D. L.; J imenez-Tenorio, M.; Leigh,
G. J .; McGeary, C. A.; Rowley, A. T.; Bravo, M.; McKenna, M.-C. J .
Chem. Soc., Dalton Trans. 1991, 522.
(45) (a) Dobson, A.; Moore, D. S.; Robinson, S. D.; Hursthouse, M.
B.; New, L. J . Organomet. Chem. 1979, 177, C8. (b) Dobson, A.; Moore,
D. S.; Robinson, S. D.; Hursthouse, M. B.; New, L. Organometallics
1985, 4, 1119. (c) Alcock, N. A.; Hill, A. F.; Melling, R. P. Organome-
tallics 1991, 10, 3988.
(46) A similar alternation of bonds lengths has been found in [Ru-
{C(Ph)dC(Ph)C(η6-C6H5)dC(Ph)CH2CHdCH2}{P(OMe)3}2][BF4]2:
Crocker, M.; Green, M.; Nagler, K. R.; Williams, D. J . J . Chem. Soc.,
Dalton Trans. 1990, 2571. Another example is found in [(PPh3)2(CO)-
(MeO2CCtC)Ru(MeOOCCdCHCHdCHCO2Me)]: Torres, M. R.; San-
tos, A.; Ros, J .; Solans, X. Organometallics 1987, 6, 1091.
(47) March, J . Advanced Organic Chemistry, 4th ed.; Wiley: New
York, 1992; p 21.
The structure consists of discrete molecules of
mer-(PNP)Ru(CtCPh){η-PhCdC(CtCPh)CHdCH(p-
tolyl)} and clathrated CH2Cl2 molecules; the packing is
dictated by van der Waals interactions with no unusual
intramolecular contacts. The Ru atom is coordinated
by a mer-PNP ligand which shows metrical parameters
and geometrical distortions similar to those of 8 [P1-
Ru-P2 ) 164.3(2)°]. The coordination geometry around
Ru is completed by a σ-bonded phenylethynyl ligand and
by an unprecedented 1-p-tolyl-3-(phenylethynyl)-4-
phenyl-buta-1(E),3(Z)-dien-4-yl ligand which essentially
uses a carbon atom trans to the nitrogen to bind the
metal [N-Ru-C8 ) 177.6(8)°; Ru-C8 ) 2.04(2) Å].
However, a weak bonding interaction between the metal

C-C Bond Formation in Ru Complexes
Organometallics, Vol. 15, No. 1, 1996 283
Ta ble 4. Su m m a r y of Cr ysta l Da ta for
fa c,cis-(P NP )Ru Cl2(CO) (6) a n d
buried under the crowded aromatic hydrogen reso-
nances. Finally, 1H,13C-2D HMQC and DEPT NMR
experiments disclose the positions of all the carbon
atoms of the two organyl ligands bound to Ru (see
Experimental Section).
a n ti,m er -(P NP )Ru (CtCP h ){η3-P h C3dCH(P h )} (8)
6
8
formula
Mr
C32H35NCl2OP2Ru1 C56H51NP2Ru1
1
The perphenylated compound 12 exhibits H and 13C-
683.52
293(2)
888.98
293(2)
{1H} NMR spectra which are practically coincident with
those of 13 (the only difference being the resonances due
to the methyl substituent of the tolyl group in 13), and
thus, the two compounds are assigned the same struc-
ture.
Stoichiometrically, 12 and 13 differ from 8 and 9 for
containing one more “HCtCR” unit (R ) Ph, p-tolyl).
In an attempt to convert 8 and 9 to 12 and 13, the
former compounds were dissolved in THF and then
treated with excesses of either HCtCR or LiCtCR
(with or without EtOH) at different temperatures. In
no case, was a transformation of the starting compounds
observed leading to the conclusion that 8 and 9 are not
intermediates to 12 and 13.
The reaction of the vinylidene precursor 4 with 1
equiv of LiCtCPh in the presence of CO is not techni-
cally feasible due to the very poor solubility of the
complex in the solvents in which lithium acetylide can
safely be handled. However, treatment of 4 in CH2Cl2
with a slight excess of NEt3 in the presence of CO gives
the carbonyl 11 and [HNEt3]Cl suggesting that, like the
enynyl complexes 8 and 9, also the formation of the
dienynyl complexes 12 and 13 initially proceeds via
deprotonation of the vinylidene group and removal of
one chloride ligand by the first 1 equiv of LiCtCPh.
temp, K
cryst size, mm
cryst system
space group
a, Å
0.18 × 0.22 × 0.16 0.12 × 0.32 × 0.21
monoclinic
P21/c (No. 14)
11.562(2)
14.888(3)
19.403(4)
90
monoclinic
P21/c (No. 14)
12.914(3)
16.234(3)
21.737(4)
90
b, Å
c, Å
R, deg
â, deg
98.65(3)
90
92.97(3)
90
γ, deg
V, Å3
3301.9 (11)
4
1.375
0.758
1400
4551(2)
4
1.297
0.452
Z
F(calcd), g cm-3
µ(Mo KR), mm-1
F(000)
1848
radiation
graphite-
monochromated
Mo KR, λ )
0.710 69 Å
ω-2θ
graphite-
monochromated
Mo KR, λ )
0.710 69 Å
ω-2θ
scan type
θ range, deg
scan width, deg
index ranges, h, k, l
2.53-22.47
0.8 + 0.35 tan θ
2.51-22.48
0.8 + 0.35 tan θ
-12 to 12; 0 to 15; -13 to 13; 0 to 17;
0 to 20
3165
0 to 23
3610
reflcns collcd
indepdt reflcns
3056 [R(int) )
0.0367]
3506 [R(int) )
0.0313]
no. of refined params
311
1.146
250
1.075
goodness-of-fit on F2
R
0.0594 [I > 2σ(I)]
0.1891
0.0538 [I > 2σ(I)]
0.1299
Rw
largest diff peak, e Å-3 1.487
0.658
-0.445
largest diff hole, e Å-3 -0.683
Discu ssion
Ta ble 5. Su m m a r y of Cr ysta l Da ta for
Schemes 4 and 5 summarize our mechanistic inter-
pretation for the formation of the present enynyl and
dienynyl Ru(II) complexes, respectively.
m er -(P NP )Ru (CtCP h )-
{η1-P h CdC(CtCP h )C(H)dCH(p-tolyl)}‚CH2Cl2
(13‚CH2Cl2)
The stepwise mechanism proposed for the formation
of the butenynyl complex 9 (Scheme 4) is quite similar
to many others previously reported.1 However, the
position of the p-tolyl substituent in the final product
provides some interesting mechanistic information.
We have demonstrated that the first 1 equiv of
LiCtCPh serves to deprotonate the starting vinylidene
ligand. As a result, 1 equiv of HCtCPh and a free
coordination site at Ru are simultaneously generated
(step a ). The HCtCPh molecule, generated in situ, can
thus readily interact with the metal center.
Since the p-tolyl group in the final product is regio-
selectively incorporated into the vinyl portion of the C4
ligand, the interaction between the 1-alkyne and the
ruthenium center (step b) must necessarily result in a
proton transfer from the 1-alkyne to the â-carbon atom
of the alkynyl ligand. Cis σ-phenylethynyl and p-
tolylvinylidene ligands are consequently formed (step
c), and from their coupling (vinylidene migratory inser-
tion) (step e),1a,b the E-butenynyl ligand is finally
assembled (step d ).
formula
Mr
C65H62P2NCl2Ru
1090.15
293(2)
temp, K
cryst size, mm
cryst system
space group
a, Å
0.28 × 0.30 × 0.27
monoclinic
P21/n (No. 14)
13.890(4)
18.255(7)
21.857(9)
97.52(2)
5494.44
4
1.32
b, Å
c, Å
b, deg
V, Å3
Z
F(calcd), g cm-3
µ(Cu KR), mm-1
radiation
4.136
graphite-monochromated Cu KR,
λ ) 1.54 18 Å
ω-2θ
5-100
0.9 + 0.15 tan θ
0.02-0.1
6080
1824
231
0.070 [I > 3σ(I)]
0.073
scan type
2θ range, deg
scan width, deg
scan speed, deg min-1
reflcs collcd
unique data [I > 3σ(I)]
refined params
R
Rw
Notably, the structure of the butenynyl ligand ex-
cludes that the HCtCPh molecule tautomerizes to
vinylidene at step b. In this case, in fact, one would
have found the p-tolyl substituent on the alkynyl moiety
of the C4 ligand, which is not observed. A hydrogen
transfer thus occurs from an activated HCtCPh mol-
ecule (probably via π-coordination) to the Câ of the
alkynyl ligand (step c). After the C-C bond-forming
{1H} NMR spectrum shows a singlet at ca. 31 ppm). The
presence of the 1-p-tolyl-3-(phenylethynyl)-4-phenyl-
buta-1(E),3(Z)-dien-4-yl ligand is confirmed by the H
NMR spectrum. This contains a doublet (1H) at 6.14
ppm which is not coupled to the phosphorus nuclei but
is scalarly connected (1H,1H-2D COSY NMR experi-
ment) to a signal at ca. 7.1 ppm [J (HH) ) 15.7 Hz]
1

284 Organometallics, Vol. 15, No. 1, 1996
Bianchini et al.
Sch em e 4
Sch em e 5
step, the chloride ligand in intermediate D can be
replaced by a phenylethynyl group provided by the
second 1 equiv of added LiCtCPh, to give the fac-(η3-
butenynyl)alkynyl complex E. Finally, the latter com-
plex converts to the thermodynamically more stable mer
isomer 9 (in this case, the isomerization should be
favored not only by steric interaction but also by the
great trans influence of the organyl ligands).18
nylidene ligand and not before as there is selective
formation of 9. In fact, should the interaction with the
HCtCPh molecule generated in situ follow the metath-
esis reaction of compound A with LiCtCPh, a mixture
of different butenynyl ligands would form (having the
p-tolyl substituent on either the vinyl or alkynyl moiety
as a consequence of random protonation of the phenyl-
ethynyl and p-tolylethynyl ligands by HCtCPh).
In the initial stages (steps a -d ), the suggested
mechanism for the formation of the 1-p-tolyl-3-(phenyl-
The reaction with the second 1 equiv of LiCtCPh
necessarily occurs after formation of the p-tolylvi-

C-C Bond Formation in Ru Complexes
Organometallics, Vol. 15, No. 1, 1996 285
ethynyl)-4-phenyl-buta-1(E),3(Z)-dien-4-yl complex 13 is
quite similar to that proposed for 9, the only difference
being the geometry of the PNP ligand in the starting
vinylidene complex 5 as well as in the following inter-
mediates.
J ust the mer geometry of the PNP ligand in interme-
diate D may be the factor that controls the subsequent
reactivity leading to incorporation of a third “HCtCPh”
moiety into the final product.
Câ-Cγ double bond would account for the formation of
the 1-p-tolyl-3-(phenylethynyl)-4-phenyl-buta-1(E),3(Z)-
dien-4-yl ligand in 13. The HCtCPh molecule con-
sumed in this step is evidently generated in situ by
addition of ethanol to the reaction mixture which still
contains 1 equiv of unreacted LiCtCPh. In the absence
of ethanol, several unidentified products are formed
which may be consistent with the formation of a very
reactive butatrienylmetal complex.
Unlike dimerization to enynyl compounds (precursors
to disubstituted butenynes), metal-assisted trimeriza-
tion of 1-alkynes to dienynyl species (precursors to
trisubstituted hexadienynes) is a rare reaction.49 In
particular, very few ruthenium complexes, generally
polynuclear species, have been reported to promote the
trimerization of either 1-alkynes or acetylide residues.50
The major thermodynamic stability of the butenynyl
complexes vs the butatrienyl isomers may explain why
the oligomerization of 1-alkynes stops at the stage of
formation of the first C-C bond for those metals like
ruthenium that readily promote the tautomerization of
1-alkynes to vinylidenes. On the other hand, the use
of coligands with large steric hindrance, favoring the
formation of butatrienyl ligands, may provide access to
Ru complexes capable of promoting the linear trimer-
ization of 1-alkynes.
Apparently, intermediate D does not react with
LiCtCPh. In this case, in fact, complex 9 would form
which is fully stable in the presence of either LiCtCPh,
HCtCPh, or alcohols. Thus, it is suggested that
intermediate D undergoes a faster reaction than the
metathesis with LiCtCPh. The structure of the dien-
ynyl ligand in the final product 13 (particularly the
positions of the p-tolyl and deuterium labels) suggests
that D rapidly rearranges to the butatrienyl- isomer E.
Indeed, butatrienyl and butenynylmetal complexes are
known to rearrange into each other via a 1,3-metal
shift.1b In the few cases where the isomerization to the
less thermodynamically stable butatrienyl isomers has
been observed, steric factors have been invoked to
account for the transformation. In particular, it has
been proposed that bulky substituents in the 1,4-
positions of the C4 unsaturated ligands favor the
butenynyl to butatrienyl conversion at ruthenium(II).
On the basis of molecular modeling studies, Wakat-
suki and co-workers have suggested that a severe steric
repulsion between the tertiary phosphine ligands and
the alkynyl moiety of the butenynyl group promotes the
conversion of the butenynyl complex Ru(CO)(PPh3)2(Ct
CtBu)(tBuCtCCdCHtBu) to the butatrienyl isomer Ru-
(CO)(PPh3)2(CtCtBu)(tBuCdCdCdCHtBu).1b,2 A simi-
lar steric interaction (between the aromatic rings of the
butenynyl ligand and of the mutually trans PPh2 groups,
mer structure) may be the driving force for the conver-
sion of the butenynyl intermediate D to the butatrienyl
isomer E. In this eventuality, the formation of the
dienynyl complex 13 can be rationalized in terms of the
well-known capability of cumulene and cumulenyl metal
complexes to add various substrates (primary amines,
water, alcohols).48 In the case at hand, a regio- and
stereoselective trans addition of HCtCPh across the
Ack n ow led gm en t. Thanks are due to Mr. Dante
Masi for technical assistance in the X-ray structure
determinations. Thanks are also expressed to the EC
for financial support (Contract No. ERBCHRXCT930147).
Su p p or tin g In for m a tion Ava ila ble: Tables of final
positional parameters and isotropic and anisotropic displace-
ment parameters for all atoms and bond lengths and angles
for 6, 8, and 13‚CH2Cl2 (16 pages). Ordering information is
given on any current masthead page.
OM950721K
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