Reactivity and structural patterns of phenylphosphines in acetylene and acetylide carbonyl trinuclear ruthenium clusters

Article abstract of DOI:10.1016/j.poly.2019.01.020

The acetylene [Ru₃(μ-CO)(CO)₉{μ₃-η²-(//)–HC[tbnd]C–R}] (1a: R = C(Me)[dbnd]CH₂); 1b: (Figure presented.) and the acetylide [Ru₃(μ-H)(CO)₉{μ₃-η²-(⊥)–C[tbnd]C

Full text of DOI:10.1016/j.poly.2019.01.020

Accepted Manuscript
Reactivity and structural patterns of phenylphosphines in acetylene and acety-
lide carbonyl trinuclear ruthenium clusters
Erik G. Rojo–Gómez, Abril I. Munguía–Lara, Daniel O. González–Abrego,
Gloria Sánchez–Cabrera, José G. Alvarado–Rodríguez, María G. Hernández
−Cruz, María J. Rosales–Hoz, Marco A. Leyva, Ana L. Carrasco, Noemí
Andrade–López, Francisco J. Zuno–Cruz
PII:
S0277-5387(19)30035-X
https://doi.org/10.1016/j.poly.2019.01.020
POLY 13693
DOI:
Reference:
Polyhedron
To appear in:
Received Date:
Revised Date:
Accepted Date:
28 September 2018
12 December 2018
9 January 2019
Please cite this article as: E.G. Rojo–Gómez, A.I. Munguía–Lara, D.O. González–Abrego, G. Sánchez–Cabrera,
J.G. Alvarado–Rodríguez, M.G. Hernández−Cruz, M.J. Rosales–Hoz, M.A. Leyva, A.L. Carrasco, N. Andrade–
López, F.J. Zuno–Cruz, Reactivity and structural patterns of phenylphosphines in acetylene and acetylide carbonyl
trinuclear ruthenium clusters, Polyhedron (2019), doi: https://doi.org/10.1016/j.poly.2019.01.020
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Reactivity and structural patterns of phenylphosphines in acetylene and acetylide
carbonyl trinuclear ruthenium clusters
Erik G. Rojo–Gómeza,1, Abril I. Munguía–Laraa,1, Daniel O. González–Abregoa, Gloria
Sánchez–Cabreraa*, José G. Alvarado–Rodrígueza, María G. Hernández−Cruzb, María J.
Rosales–Hozc, Marco A. Leyvac, Ana L. Carrascoc, Noemí Andrade–Lópeza, Francisco J.
Zuno–Cruza,*
a
Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Hidalgo,
Ciudad Universitaria, Carretera Pachuca−Tulancingo km 4.5. Colonia Carboneras,
Mineral de la Reforma, Hidalgo. 42184, México
b
Universidad Juárez Autónoma de Tabasco, División Académica Multidisciplinaria de
Jalpa de Méndez, Carr. Estatal Libre VHS−COM. km. 27+000 s/n Rancho, Ribera Alta,
Jalpa de Méndez, Tabasco 86205, México
c Departamento de Química, Centro de Investigación y de Estudios Avanzados, Av. Instituto
Politécnico Nacional 2508, Col. San Pedro Zacatenco, Ciudad de México 07360, México
Abstract
The acetylene [Ru3(μ–CO)(CO)9{µ3–η2–(//)–HC≡C–R}] (1a: R = C(Me)=CH2); 1b: R =
C=CH–(CH2)3–CH2) and the acetylide [Ru3(µ–H)(CO)9{µ3–η2–()–C≡C–R}] (2a: R =
C(Me)=CH2; 2b: R= C=CH–(CH2)3–CH2) clusters have been synthesized from the reaction
1 Both authors contributed equally to the work presented in this paper.
* Corresponding Authors. Phone: work +52–771–7172000 ext 2204; cell +52–1771–1625212; Fax: +52–
771–7172000 ext 6502.
E–mail address: fjzuno@uaeh.edu.mx (F. J. Zuno–Cruz).
1

of [Ru3(CO)10(NCMe)2] with 2–methyl–1–buten–3–yne and 1–ethynylcyclohexene
respectively. The reactions of the corresponding parallel acetylene 1a or 1b with
triphenylphosphine or diphenylmethylphosphine yielded four isostructural compounds
[Ru3(μ–CO)(CO)8(L){µ3–η2–(//)–HC≡C–R}] (3a1: L = PPh3, 3a2: L = PPh2Me, R =
C(Me)=CH2; 3b1: L = PPh3, 3b2: L = PPh2Me, R = C=CH–(CH2)3–CH2) where, the alkynes
are still coordinated to the metallic fragment as acetylene groups in a 3–2 parallel fashion.
Also, the isomer compounds [Ru3(µ–H)(CO)8(L){µ3–η2–()–C≡C–R}] (4a1 and 5a1: L =
PPh3, 4a2 and 5a2: L = PPh2Me, R = C(Me)=CH2; 4b1 and 5b1: L = PPh3, 4b2 and 5b2: L
= PPh2Me, R = C=CH–(CH2)3–CH2); and the disubstituted phenylphosphine clusters [Ru3(µ–
H)(CO)7(L)2{µ3–η2–()–C≡C–R}] (6a1: L = PPh3, 6a2: L = PPh2Me, R = C(Me)=CH2; 6b1:
L = PPh3, 6b2: L = PPh2Me, R = C=CH–(CH2)3–CH2) were formed during each reaction. In
these compounds, the parallel–acetylene group undergoes an oxidative addition and a
rearrangement of the coordinated organic fragment to a µ3–η2 perpendicular coordination
mode of the C–C axis by breaking acetylene C–H bond to give a hydride ligand in each case.
The synthesis of clusters [Ru3(μ–CO)(CO)8(PPh3){µ3–η2–(//)–HC≡C–C6H2–2,4,5–Me3}]
(3c1), [Ru3((µ–H)(CO)8(PPh3){µ3–η2–()–C≡C–C6H2–2,4,5–Me3}] (4c1 and 5c1) and
[Ru3(µ–H)(CO)7(PPh3)2{µ3–η2–()–C≡C–C6H2–2,4,5–Me3}] (6c1) are also described. All
compounds have been characterized in solution by infrared spectroscopy and by 1H, 13C{1H}
and 31P{1H} NMR. The molecular structures of compounds 2b, 3a1, 3b1, 4a1, 4c1, and 6b1
have been established by single crystal X–ray diffraction studies.
Keywords: Ruthenium; Clusters; Acetylenes; Acetylides, Phenylphosphines
2

1. Introduction
Carbonyl trinuclear ruthenium clusters still attract the long−standing interest on their
synthetic and reactivity features. [1-4] This interest is mainly due to the ease and straight
forward synthetic methods to yield them, helping to establish their chemical behavior,
structural patterns, and spectroscopic characteristics, obtained when they react with either
organic or inorganic ligands [5,6]. It is well known that the reaction of [Ru3(CO)12] with
2
terminal alkynes has been the source of
–
parallel coordination mode of the –C≡C–H
3
 
moiety in triruthenium clusters; these clusters subsequently undergo a facile H−migration
2
from carbon to the cluster, involving a coordination rearrangement to give the
–
3
 
acetylide–hydrido perpendicular complexes [7,8]. In addition, alkynes and phosphine ligands
are representative substrates to explore the multiple two−electron donor ligand capabilities
in cluster chemistry [5,9-11], where phosphine or phosphite ligands have been considered as
binder agents that provide stability to the metal core with potential implications in catalytic
hydrogenation reactions [12-16]. Despite the great amount of reactions between carbonyl
clusters and phosphines, the reactivity of cluster complexes with coordinated alkynes have
been less explored.
The aim of the present work is the synthesis and structural characterization of three new
2
series of
–
parallel–acetylene and perpendicular–acetylide triruthenium clusters,
3
 
obtained from ene–yne and alkyne ligands and used in phosphine substitution reactions. All
compounds were characterized in solution by Infrared and by 1H, 13C{1H} and 31P{1H} NMR
spectroscopies and by 2D–heteronuclear correlation experiments for the complete
assignment of carbon atoms. The assignment of phosphorous atoms in compounds were
determined using heteronuclear irradiation experiments. The molecular structures of
3

compounds
,
,
,
, and
in the solid state were determined by single
6b1
2b 3a1 3b1, 4a1 4c1
crystal X–ray diffraction studies.
2. Experimental Section
2.1 General procedures and materials
[Ru3(CO)10(NCMe3)2], [Ru3(–CO)(CO)9{3–2–(//)–HC≡C–C6H2–2,4,5–Me3}] (1c) and
[Ru3(–H)(CO)9{3–2–()–C≡C–C6H2–2,4,5–Me3}] (2c) were prepared by published
methods [8]. Trimethylamine N–oxide was dried and purified prior to use. All other
chemicals were purchased from Aldrich Company and used as received. All reactions were
performed under a nitrogen atmosphere by using standard Schlenk techniques. Solvents were
dried by the standard procedures prior to use. Commercial TLC plates (silica gel 60 F254)
were used to monitor the progress of the reactions. Infrared spectra were recorded as either
solid thin films in a CsI window on a GX PERKIN Elmer 2000 FT–IR spectrophotometer or
in NaCl cells on a PERKIN Elmer 16FPCFPIR spectrophotometer. Mass spectrometric
measurements were performed by direct insertion on a HR–LC 1100/MSD TOF Agilent
Technology equipment at CINVESTAV–México. NMR spectra were measured on a
VARIAN 400 and a Bruker 400 spectrometers in CDCl3, with 1H and 13C spectra relative to
1
SiMe4, and 31P spectra relative to 85% aq. H3PO4. Full assignment of H, 13C{1H} and
31P{1H} NMR for all synthesized compounds can be found in supporting information (SI)
file.
4

2.2 Single crystal X-Ray studies
Suitable crystals of 2b and 4a1 were selected and collected on an Enraf–Nonius Kappa CCD
area detector diffractometer with graphite–monochromated Mo–K radiation. Data were
integrated, scaled, sorted, and averaged using the package, HKL Scalepack by Otwinowsky
[17], the structure was solved with the SHELXS/2016 [18] structure solution program using
Direct Methods and refined with the SHELXL 2016/6 [19] refinement package using Least
Squares minimization. Data for 3b1 were collected on a Bruker D8 Venture diffractometer
using Mo–K radiation. Data collection, determination of unit cell, and integration of frames
of this compound were carried out using the Bruker APEX3 software [20,21]. A semi–
empirical absorption correction method (SADABS) [22] was applied. The structure was
solved by Direct Methods, completed by subsequent difference Fourier synthesis, and refined
by full–matrix least–squares on F2 procedures using the SHELX–2014–7 package [18].
Crystallographic programs were used under WINGX suite [23]. Suitable crystals of 3a1, 4c1,
6b1, and 6c1 were selected and collected on a Xcalibur, Atlas, Gemini diffractometer. The
crystals were kept at 294 K during data collection. Using Olex2 [24], the structure were
solved with the ShelXT [25] structure solution program using Intrinsic Phasing and refined
with the ShelXL [19] refinement package using Least Squares minimization. For all
compounds, all non–hydrogen atoms were refined anisotropically. The positions of the
hydrogen atoms were kept fixed with a common isotropic displacement parameter.
Crystallographic and other experimental data are summarized in Table 1.
5

Table 1. Crystal data and structure refinement parameters of compounds 2b, 3a1, 3b1, 4a1, 4c1 and 6b1.
Compound
Empirical formula
Formula weight
Crystal color
Crystal system
Crystal size (mm3)
Space group
a (Å)
2b
3a1
3b1
C35H25O9P1Ru3
923.75
4a1
4c1
6b1∙2CHCl3
C53H42O7P2Cl6Ru3
1368.71
Orange
Triclinic
C17H10O9Ru3
661.46
Yellow
Triclinic
0.280.150.12
P−1
9.1531(2)
9.3234(2)
14.5625(3)
76.6930(10)
81.0110(10)
63.1370(10)
1076.91(4)
2
C32H21O9P1Ru3
883.67
Yellow
Monoclinic
0.200.200.10
Cc
15.6889(8)
9.8603(4)
23.3770(14)
90.00
113.964(7)
90.00
3304.6(3)
4
C31H21O8P1Ru3
855.66
Yellow
Triclinic
0.150.080.03
P−1
9.5113(3)
10.5678(3)
16.3762(5)
81.7000(10)
77.7190(10)
84.0590(10)
1587.00(8)
2
C37H27O8P1Ru3
933.76
Yellow
Monoclinic
0.300.20.2
P21/n
9.3377(3)
32.2765(10)
12.6005(5)
90.00
109.530(4)
90.00
3579.2(2)
4
Yellow
Triclinic
0.310.210.15
P−1
0.600.500.50
P−1
9.0880(3)
10.9049(3)
18.7091(5)
75.778(10)
77.828(10)
81.345(0)
1747.36(9)
2
12.3117(2)
16.2801(3)
16.6746(3)
117.7915(18)
90.2235(13)
103.5485(15)
2849.42(10)
2
b (Å)
c (Å)
 (°)
 (°)
 (°)
V, (Å3)
Z
Dcalcd, (Mg m−3)
, (mm−1)
range (°)
Index ranges
2.040
2.120
7.40 to 54.90
−11/11, −11/12,
−18/18
1.776
1.453
5.76 to 52.108
−19/19, −12/12,
−28/28
1.7556
1.378
5.82 to 54.96
−11/11, −14/12,
−24/24
1.791
1.507
7.70 to 53.82
−11/11, −11/13,
−16/20
1.733
1.345
5.98 to 52.74
−11/11, −40/40,
−15/15
1.595
1.170
6.006 to 52.744
−15/15, −20/20,
−20/20
Reflections collected 21059
Independent
reflections
17045
27902
8027 (Rint
0.0303)
21179
6628 (Rint = 0.0500)
46279
117670
4884 (Rint = 0.0310) 6474 (Rint
=
=
7318 (Rint = 0.0514) 11640 (Rint
0.0339)
=
0.0505)
Observed reflections 4036 [I>2σ(I)]
Parameters/restraints 322/106
5663 [I>2σ(I)]
407/2
6973 [I>2σ(I)]
441/0
4895 [I>2σ(I)]
393/0
5839 [I>2σ(I)]
449/0
9653 [I>2σ(I)]
586/72
R final; R all data
0.0293, 0.0405
0.0523, 0.0625
0.1245, 0.1314 b
1.116
0.0420, 0.0491
0.1071, 0.1114 c
1.091
0.0402, 0.0696
0.0727, 0.0820 a
1.077
0.0318, 0.0507
0.0512, 0.0577 d
1.100
0.0545, 0.0702
0.1414, 0.1594 e
1.077
Rw final, Rw all data 0.0755, 0.0707 a
GOF (all data)
1.040
Max, min peaks
0.782 /−0.533
1.490 /−0.670
2.216 /−1.339
0.653 /−0.787
0.655 /−0.374
2.505 /−1.138
(eÅ−3)
2
2
2
2
2
a w−1 = 2(Fo )+(P)2 + P. b w−1 = 2(Fo )+(0.0689P)2. c w−1 = 2(Fo )+(0.0356P)2 + 5.2357P. d w−1 = 2(Fo )+(0. 0143P)2 + 2.4260P. e w−1 = 2(Fo )+(0.0729P)2 +
2
10.5499P. Where P = (Fo +2Fc2)/3.
6

2.3 Synthesis of Series 1 and 2
The ruthenium clusters Series 1a–2c were prepared according to the Scheme 1, following
four different methodologies, for further details see SI file. The numbers 1 and 2 refer to each
series of analogous compounds; a, b, and c labels are used to indicate the three terminal
alkynes used in the reactions.
Scheme 1. Synthetic methods for the preparation of ruthenium clusters Series 1 and 2.
2.4 Synthesis of Series 3 to 6
The in situ reaction of compounds 1a–1c with the corresponding phosphine (PPh3 or
PPh2Me), in a 1:1 stoichiometric ratio, gave the compounds in the Series 3 to 6. The numbers
3, 4, 5, and 6 refer to each series of analogous compounds; a, b, and c labels indicate the
terminal alkyne, and the third number in the labels of Series 3 to 6 refers to the phosphine
ligand used (1 for PPh3; 2 for PPh2Me). In Scheme 2 are summarized all the reactions carried
out, for further details see SI file.
7

Scheme 2. Structures of mono- and bis-phosphine derivatives of acetylene and acetylide ruthenium clusters.
8

3. Results and discussion
Compounds 1a, 2a, 1b, and 2b were prepared following the traditional method by using the
labile cluster [Ru3(CO)10(NCMe3)2] in the presence of an excess of the terminal alkynes 2–
methyl–1–buten–3–yne or 1–ethynylcyclohexene, respectively, at room temperature (See
Scheme 1; Method A or experimental section in SI file for details). Two compounds were
formed in each reaction, the parallel acetylene clusters of general formula [Ru3(μ–
CO)(CO)9{µ3–η2–(//)–HC≡C–R}] (1a: R = C(Me)=CH2; 1b: R = C=CH–(CH2)3–CH2) were
identified as the major products, whereas the acetylide compounds [Ru3(µ–H)(CO)9{µ3–η2–
()–C≡C–R}] (2a: R = C(Me)=CH2; 2b: R = C=CH–(CH2)3–CH2) were the minor
compounds.
The in situ reaction (See Scheme 2; Method E) of the corresponding parallel derivatives 1a
or 1b with one equivalent of triphenylphosphine (PPh3) or diphenylmethylphosphine
(PPh2Me) at room temperature for one hour yielded four different types of substituted
compounds, which were assigned on the basis of 1H and 31P NMR solution studies and they
will be discussed later. The carbonyl substitution reactions produced the analogous
compounds [Ru3(μ–CO)(CO)8(L){µ3–η2–(//)–HC≡C–R}] (3a1: L = PPh3, 3a2: L = PPh2Me,
R = C(Me)=CH2; 3b1: L = PPh3, 3b2: L = PPh2Me, R = C=CH–(CH2)3–CH2). In these
compounds, the phosphine ligand coordination takes place in the less hindered ruthenium
atom having the Ru–C) bond, maintaining the 3–2 parallel coordination mode of the
alkyne ligand to the metallic fragment. A second and a third type of compounds were also
observed; they were identified as the perpendicular acetylide phosphine substituted isomers
[Ru3(µ–H)(CO)8(L){µ3–η2–()–C≡C–R}] (4a1 and 5a1: L = PPh3, 4a2 and 5a2: L =
PPh2Me, R = C(Me)=CH2; 4b1 and 5b1: L = PPh3, 4b2 and 5b2: L = PPh2Me, R = C=CH–
9

(CH2)3–CH2). Compounds 4a1, 4b1, 4a2, and 4b2 have the coordinated phosphine attached
to one of the metals having a Ru–C() bond (which would be considered the most crowded,
but also the less electron rich metal site). On the other hand, compounds 5a1, 5b1, 5a2, and
5b2 have the phosphine coordinated to the metal having the Ru–C() bond (considered the
less hindered and the electron richest metal site). All attempts to separate these sets of isomers
were unsuccessful; the proportions for all isomeric pairs (for example, 4a1:5a1) were
1
estimated by H NMR peak integration. The ratios were different in each case, and they
depend of the used phosphine. For the PPh3 derivatives, the proportions 4a1:5a1 and 4b1:5b1
were 25:75 and 40:60, respectively, being the major isomer the one that has the phosphine
coordinated to the ruthenium atom with the C() bond from the acetylene fragment.
Reactions of perpendicular acetylide triruthenium clusters [Ru3(–H)(CO)9{µ3–η2–()–
C≡C–R}] with phosphine ligands gave exclusively compounds of type 5, where the
phosphine is coordinated to the less crowded ruthenium atom [10]. For the PPh2Me
derivatives, the ratios 4a2:5a2 and 4b2:5b2 were 54:48 and 68:32, respectively; these results
contrast with the isomers ratio observed when L = PPh3, where the major compound is the
one with the phosphine coordinated to the ruthenium with the C() bond from the acetylene
fragment. These results indicate that the more basic phosphine PPh2Me is coordinated toward
the less electron rich ruthenium (the most acidic metal) giving the major isomers 4a2 y 4b2,
and the higher steric hindrance of PPh3 ligand favors the major isomers 5a1 and 5b1.
The last compound formed in each carried out reaction were the disubstituted phosphine
compounds [Ru3(µ–H)(CO)7(L)2{µ3–η2–()–C≡C–R}] (6a1: L = PPh3, 6a2: L = PPh2Me, R
= C(Me)=CH2; 6b1: L = PPh3, 6b2: L = PPh2Me, R = C=CH–(CH2)3–CH2) . In these
10

complexes, the two phosphines are coordinated toward the two different types of ruthenium
atoms present in the trimetallic cluster (Ru–C() and Ru–C()).
In order to get a deeper insight in the course of these reactions, the following experiments
were carried out. i) The pure parallel compounds [Ru3(–CO)(CO)9{3–2–(//)–HC≡C–
C(Me3)=CH2}] (1a) or [Ru3(μ–CO)(CO)9{µ3–η2–(//)–HC≡C–C=CH–(CH2)3–CH2}] (1b)
reacts with PPh3 in a 1:1 stoichiometric ratio in dichloromethane solution at room
temperature for one hour to give the parallel derivative 3a1 or 3b1 in 44.5% or 30% yield as
the only product. ii) On the other hand, compound 3a1 or 3b1 react with PPh3 and Me3NO in
a 1:1:1 ratio to produce the isomers 4a1 and 5a1 in 25.8% yield overall, with a 29:71 ratio
respectively, or 4b1 and 5b1 in 64.0% yield overall, with a 36:64 ratio respectively. In these
reactions compound 3a1 was recovered in 13.3% and only traces of 3b1 were recuperated.
In addition, compound 3a1 or 3b1 in the presence of one equivalent of Me3NO (as
decarbonylation reagent) did not undergo a skeletal rearrangement to produce the
perpendicular derivatives (4b1 or 5b1). iii) The reactions of the isolated perpendicular
derivative 2a or 2b with PPh3 and Me3NO also in a 1:1:1 ratio yielded the disubstituted
derivative 6a1 or 6b1 in 15.6% and 14.9% yields respectively; it is interesting to note, that
in the case of compound 2b there was no evidence of 4b1 and 5b1 compound formation;
however, reaction of 2a formed compounds 4a1 and 5a1 in 28.8% yield overall, with a 22:78
ratio respectively.
These experimental results can suggest that the parallel compound 1a or 1b forms
simultaneously in the in situ reactions, compound 3a1 or 3b1 and the perpendicular
derivative 2a or 2b respectively. In addition, in two independent pathways, parallel
monophosphine compound 3a1 or 3b1 continue to react with the phosphine in the presence
11

of remaining Me3NO, to give the monosubstituted isomers 4a1:5a1 or 4b1:5b1 respectively,
meanwhile compound 2a or 2b also reacts with the phosphine to give the mixture of isomers
4a1:5a1 or 4b1:5b1, but then again when time elapse these monophosphine compounds form
the disubstituted compound 6a1 and 6b1, respectively. These separated pathways are in
agreement with the low yields obtained in these reactions by having competitive processes
in compound formation.
In further studies, the reactivity of a ruthenium derivative having an aromatic group on the
coordinated alkyne was also tested. The in situ reaction (See Scheme 2; Method E) of
compound [Ru3(–CO)(CO)9{3–2–(//)–HC≡C–C6H2–2,4,5–Me3}] (1c) with PPh3 gave
the isomeric compounds [Ru3(µ–H)(CO)8(PPh3){µ3–η2–()–C≡C–C6H2–2,4,5–Me3}] (4c1
and 5c1) in 12.0% yield. They were produced in an 80:20 ratio and all efforts to separate the
mixture were unsuccessful. The disubstituted compound [Ru3(µ–H)(CO)7(PPh3)2{µ3–η2–
()–C≡C–C6H2–2,4,5–Me3}] (6c1) was also formed in 6.0% yield. In these reaction,
compounds [Ru3(μ–CO)(CO)9{µ3–η2–(//)–HC≡C–C6H2–2,4,5–Me3}] (1c) and [Ru3(µ–
H)(CO)9{µ3–η2–()–C≡C–C6H2–2,4,5–Me3}] (2c) were also recuperated in 11.0 and 8.0 %
yields respectively. The reactivity behavior of 1c was different to the one observed for
compounds 1a or 1b; in this case the analogous compound to 3a1 was not observed under
these reaction conditions.
Compound 3c1 was obtained by changing the conditions (See Scheme 2; Method F). The
reaction of the isolated parallel derivative 1c with PPh3 in a 1:1 stoichiometric ratio in
dichloromethane at room temperature for 30 minutes, with the slowly addition of a
trimetylamine N–oxide solution gave 3c1 in 7.3% yield, being the major product of the
reaction. The isomer mixture 4c1:5c1 and the disubstituted product 6c1 were also formed in
12

6.8% and 2.7% yield respectively. This reaction mixture after 30 minutes showed a
1
60:20:7:13 ratio of compounds 3c1, 4c1, 5c1 and 6c1, determined by H NMR peak
integration. Furthermore, when the mixture reaction was monitored by NMR in CDCl3
solution for 12 hours the compounds ratio 3c1, 4c1, 5c1, and 6c1 change to 27:47:8:18
respectively. These observations indicate that phosphine parallel derivative 3c1 easily
transforms into the phosphine perpendicular derivative 4c1, because of the high reactivity of
compound 3c1. Furthermore, the isomers ratio 4c1:5c1 change from 60:40 to 72:28, which
is in agreement with the results obtained from the in situ reaction of compound 1c with PPh3
for 1 hour.
On the other hand, the reaction of isolated perpendicular cluster [Ru3(µ–H)(CO)9{µ3–η2–
()–C≡C–C6H2–2,4,5–Me3}] (2c) with PPh3 (See Scheme 2; Method G) in a 1:1
stoichiometric ratio in dichloromethane at room temperature for one hour gave the mixture
of isomers 4c1 and 5c1 in 49.8% and compound 6c1 in 20.3% yield. Compound 2c was also
recovered in 18.2% yield in the reaction.
In general, it has been observed that PR3 substitute CO ligands on the metallic centers –
bounded to the organic moiety, as the M–C() bonds are usually directed toward the less
electron rich metal [10,26,27]; however, the reactivity is ruled by the alkyne substituent.
In the cases that we have studied, a less bulky substituent on the terminal alkyne facilitate
the formation of the acetylide isomers in the order: 5a1>5b1>5c1, but it is also governed by
the basicity and the steric hindrance of the phosphine used. Furthermore, phosphine parallel
derivatives 3a1 and 3b1 are more stable than 3c1 derivative, which allow to isolate them.
This higher stabilization can be achieved by using alkenyl substituents on the alkyne ligand,
13

more than the use of an alkyne with a highly hindrance substituent and with different
electronic properties as in an aromatic ring.
IR spectrums of the parallel derivatives of Series 1 and 3 displayed absorptions between 1870
and 1895 cm−1, associated to the bridging carbonyl ligand (see SI file for full assignment).
All spectra are very similar in the terminal carbonyl region. Compound Series 4, 5 and 6
display only (CO) pattern in the terminal region, similar to those previously reported in
analogous clusters [8].
The 1H, 13C{1H} and 31P{1H} NMR spectroscopic data all compounds are summarized in the
SI file. In the 1H NMR spectra for compounds 1a and 1b, signals at high frequencies were
found at 8.21 and 8.07 ppm, respectively, and were assigned to the hydrogen attached to the
C–H. These signals are shifted to lower frequencies when compared to that observed in
compound 1c (8.44 ppm) [8], which indicates a nucleus protection by a major density in
cluster 1c than in 1a or 1b. The doublet resonances belonging to the C–H were found
between 7.67 to 7.34 ppm in Series 3, these signals are shifted to lower frequencies due to
the phosphine coordination towards the ruthenium atom directly bonded to the C, which is
consistent with a low  character of the phosphine compared with the CO ligand.
The hydride signals for 2a and 2b were observed at −20.85 and −20.80 ppm respectively, the
corresponding chemical shift of the hydride in compound 2c was reported at −20.36 ppm [8]
a rough tendency accordingly to the type of substituents on the acetylide, following the order:
2c>2a≈2b. The chemical shifts at lower frequencies indicate that the electronic density
decreases in the clusters with the presence of the alkenyl substituents.
The hydride signals in the 1H NMR spectra of Series 4 were observed from −19.53 to −20.25
ppm, meanwhile the chemical shift for the hydride of Series 5 were found between −20.50
14

and −20.97 ppm. On the other hand, the resonances for the hydride ligands in Series 6
appeared from −19.77 to −20.38 ppm, observing similar tendencies when compared to the
perpendicular acetylide cluster parent. They also showed parallel tendencies accordingly to
the type of coordination of the phosphine toward the metal atom in the cluster: M−C() or
M−C() or when two Ru atoms are phosphine substituted. The hydride signal is shifted
from higher to lower frequencies following the order: Series 4>6>5. In addition, the chemical
shifts of hydride ligands in compounds with PPh3 as substituent appear at higher frequencies
than those observed when a more basic phosphine (PPh2Me) is used. The presence of
different phosphines (PPh3 or PPh2Me) in comparable compounds, Series 4, 5, and 6, causes
a notable variation in the hydride chemical shifts (regardless the type of coordinated
acetylide: 0.32 ppm for 4a1 and 4a2; 0.43 ppm for 4b1 and 4b2; followed by those belonging
to Series 6: 0.23 ppm for 6a1 and 6a2; 0.32 ppm for 6b1 and 6b2, and finally Series 5 have
the minor : 0.11 ppm for 5a1 and 5a2; 0.16 ppm for 5b1 and 5b2.
An analysis of the (C)−(C) and (C)+(C) of the alpha and beta carbon chemical shifts
(see Table 1S in the SI file) was carried out for acetylene and acetylide compounds 1a–1c
(Series 1), 2a–2c (Series 2), and for the PPh3 derivatives of the Series 3, 4, 5 and 6. The
polarization of the C=C bond is associated to the (C)−(C), and the (C)+(C) have
been proposed to be related to the total charge alteration in the C≡C triple bond [4,28,29].
Compounds 1a and 1b have (C)−(C) absolute values of 44.2 and 54.9 ppm, respectively,
these values are larger than that reported for compound 1c ((C)−(C) = 32.3 ppm) [8] and
some other similar (//)–derivatives of general formula [Ru3(CO)10(HCCR)] (R = substituted
aryls), ((C)−(C) = 30.0 to 44.1 ppm) [8]. The value of 1b is the second largest value
reported for perpendicular alkynes triruthenium carbonyl derivatives, being the largest value
15

the one obtained for the well–known compound [Ru3(CO)10(HC≡CtBu)] ((C)−(C) = 56.9
ppm) [16]; both compounds have bulky and electrodonating alkyl groups directly attached to
the triple bond. However, the analogous phosphine derivatives 3a1, 3b1 and 3c1 have
(C)−(C) values of 49.4, 58.4 and 50.5 ppm respectively. These large values indicate a
larger polarization in the acetylene moiety when a phosphine ligand is attached to a
ruthenium atom instead of a carbonyl group. Compound 1c and its PPh3 derivative 3c1 show
the largest change in polarization going from 32.3 to 50.5 ppm with a ((C)−(C)) of 18.2
ppm.
Compounds 2a and 2b have (C)−(C) values of 74.4 and 69.9 ppm, respectively; the value
reported for compound 2c is 78.6 ppm [8]. However, the values of the phosphine
perpendicular derivatives (4a1, 4b1, 4c1; 81.8, 79.4, 84.4 ppm) are larger than those found
for the parent perpendicular clusters. These values are higher than those for the isomeric
compounds 5a1, 5b1, 5c1; 79.5, 69.8, 73.6 ppm, indicating larger polarization over the triple
bond when the phosphine is coordinated to the ruthenium atoms having Ru−C() bond. Also,
the polarization in monosubstituted phosphine compounds is dependent of the substituent on
the triple bond, following the order of the ligand: a<b<c with ((C)−(C)) data of 2.3,
9.6, and 11.2 ppm, respectively. The values for the (C)−(C) of disubstituted cluster Series
6 are similar to the one found in Series 4 and 5; however, there are no clear tendency in these
values.
The analysis of the (C)+(C) of synthesized compounds indicate that the alkyne
coordination mode, in a parallel fashion (with :: interactions) to the metal core produce
the largest charge alteration (315.2 to 334.5 ppm). On the other hand, the change in
coordination, by breaking the C–H bond, with :: interactions, reduces this alteration
16

(259.2 to 269.3 ppm). In all phosphine derivatives, the tendency observed in charge alteration
follows the order: Series 4>6>5, which indicates that the coordination of a phosphine ligand
in the ruthenium atom with a Ru−C() bond causes a higher change in triple bond charge
than the coordination on a ruthenium with a Ru−C() bond. There is certain tendency, in
both charge alteration and bond polarization related to the electronic properties on the cluster,
which increases by changing CO by PPh3 ligands, in all type of alkyne ligands and
coordination modes.
The 31P{1H} NMR data of parallel derivatives 3a1–3c1 have similar chemical shift between
40−45 ppm, while their analog compounds 3a2 and 3b2, PPh2Me derivatives, have the same
chemical shift of 23.2 ppm. The chemical shifts of the Series 4 having a P−Ru−C() bond
appears at lower frequencies than the Series 5 having a P−Ru−C() bond in both PPh3 or
PPh2Me cases. The  31P{1H} of the triphenylphosphine derivatives 4a1−4c1 are found
between 35.6−36.3 ppm and the chemical shifts of the diphenylmethylphosphine derivatives
4a2 and 4b2 are in 14.3 and 15.3 ppm respectively. Meanwhile, the chemical shifts of
compounds 5a1−5c1 are found between 50.9−54.9 ppm and the chemical shifts of the
diphenylmethylphosphine derivatives 5a2 and 5b2 are in 35.6 and 35.4 ppm. Similar
chemical shifts were found for the disubstituted PPh3, compounds 6a1–6c1. The signal
multiplicity and coupling constants for both phosphorus atoms in these compounds were
determined using heteronuclear irradiation experiments. The chemical shift of the
phosphorus atom PB attached to the ruthenium, with a C() bond, is shifted to higher
frequencies than the phosphorus atom PA attached to the ruthenium, with C() bond, due to
an increase in electron density around the metal center by the  donation of the acetylide C.
17

3.1 X−Ray Diffraction Studies.
Suitable crystals of compounds 2b, 3a1, 3b1, 4a1, 4c1, 6b1 and 6c1 for X−ray diffraction
studies were obtained from slow evaporation of chloroform solutions at low temperature (5°
C) for several days. Figs. 1–7 show the ORTEP diagrams, and selected bond distances and
angles are summarized in Table 2. The results are in good agreement with the structures
proposed in solution. The molecular structures obtained also allow us to confirm that, in
general, the structural features are practically the same among isostructural acetylide (2b,
4a1, 4c1, 6b1 and 6c1) or acetylene (3a1 and 3b1) complexes, respectively. Compound 2b
displays a positional disorder due to two different conformations in the cyclohexenyl ring,
an envelope and a fairly planar type conformations with 50−50 % probability were found, as
shown in Fig 1b.
Table 2. Selected bond lengths (Å) and angles (°) of compounds 2b, 3a1, 3b1, 4a1, 4c1
and 6b1.
Compound
Bond lengths
2b
3a1
3b1
4a1
4c1
6b1
Ru(1)–Ru(2)
Ru(2)–Ru(3)
Ru(3)–Ru(1)
Ru(1)–P(1)
Ru(3)–P(2)
C(1)–C(2)
2.7909(3)
2.7970(2)
2.8267(3)
−
2.855(1)
2.703(1)
2.790(2)
2.368(3)
−
2.8445(4) 2.8149(6) 2.8160(4)
2.6993(5) 2.8042(5) 2.8031(4)
2.7538(5) 2.8154(5) 2.8087(4)
2.8090(6)
2.8106(6)
2.8639(5)
2.3710(1) 2.3630(1) 2.3730(9) 2.3675(13)
−
−
−
−
2.3277(14)
1.322(8)
1.464(8)
1.326(3)
1.398(10)a*
1.399(10)b*
1.506(6)a*
1.39(2)
1.52 (2)
1.405(5)
1.489(5)
1.319(6)
1.450(6)
1.304(4)
1.464(4)
C(2)–C(3)
C(3)–C(4)
1.33(3)
1.335(6)
1.363(7)
1.403(4)
1.372(10)
18

1.322(7)b*
2.203(2)
2.249(13)
2.200(2)
2.306(14)
1.944(2)
−
Ru(1)–C(1)
2.10(1)
−
2.108(4)
−
2.184(5)
2.278(5)
2.216(5)
2.261(5)
1.952(4)
−
2.187(3)
2.323(3)
2.206(3)
2.269(3)
1.948(3)
−
2.163(5)
2.256(5)
2.226(5)
2.251(6)
1.946(5)
−
Ru(1)–C(2)
Ru(2)–C(1)
−
−
Ru(2)–C(2)
2.08(1)
2.19(2)
2.29(1)
2.101(4)
2.191(5)
2.283(4)
Ru(3)–C(1)
Ru(3)–C(2)
Bond angles
Ru(1)–Ru(2)–Ru(3)
Ru(2)–Ru(3)–Ru(1)
Ru(3)–Ru(1)–Ru(2)
Ru(2)–Ru(1)–P(1)
Ru(3)–Ru(1)–P(1)
Ru(1)–Ru(3)–P(2)
Ru(2) −Ru(3)–P(2)
Ru(3)–C(1)–C(2)
Ru(1)–C(1)–C(2)
Ru(2)–C(2)–C(1)
C(1)–C(2)–C(3)
60.778(7)
59.505(6)
59.718(7)
−
60.23(4)
62.52(4)
57.25(3)
59.498(1) 60.139(1) 59.979(10) 61.277(14)
62.876(1) 60.122(1) 60.239(10) 59.335(14)
57.626(1) 59.739(1) 59.782(10) 59.388(14)
142.21(9) 137.61(3) 111.22(3) 110.14(3)
132.96(9) 131.98(3) 168.85(3) 169.91(3)
110.48(4)
168.49(4)
107.71(4)
161.32(4)
155.3(5)
76.5(4)
−
−
−
−
−
−
−
−
−
−
−
155.41(17)
74.58(12)
77.30(11)
76.2(8)
111.2(9)
109.2(9)
75.3(2)
112.8(3)
107.1(3)
122.7(4)
154.6(4)
76.7(3)
71.0(3)
140.1(5)
156.7(3)
79.10(2)
70.50(2)
144.2(3)
71.7(4)
139.51(18)a* 121.4(12)
145.35(18)b*
139.2(6)
Interline and
interplane angles
C(1)–C(2)/Ru(1)–Ru(2)
89.0(2)
18.9(2)
6.7(8)
3.2(8)
−3.8(2)
88.3(3)
18.4(3)
87.8(3)
20.6(3)
87.7(5)
18.8(5)
C(1)–C(2)/Ru(1)–Ru(2)–
3.1(2)
Ru(3)
P(1)–Ru(1)/Ru(1)–
Ru(2)–Ru(3)
−
−
32.2(5)
36.2(4)
−6.8(4)
−0.5(4)
−5.7(6)
P(2)–Ru(3)/Ru(1)–
Ru(2)–Ru(3)
−
−
−
−
14.1(6)
19

Ru(1)–Ru(2)–
C(11)/Ru(1)–Ru(2)–
Ru(3)
−
22.3(5)
15.2(4)
−
−
−
*The a and b labels are due to positional (conformational) disorder of the cyclohexenyl ring
Fig. 1.a) ORTEP view of compound 2b (30% probability). b) Envelope and planar
conformations of the cyclohexenyl ring.
20

Fig. 2. ORTEP view of compound 3a1 (30% probability).
Fig. 3. ORTEP view of compound 3b1 (30% probability).
21

Fig. 4. ORTEP view of compound 4a1 (30% probability).
Fig. 5. ORTEP view of compound 4c1 (30% probability).
22

The metal–metal distances in compound 2b are similar among them, even though one is
larger than the other two, due to a slightly asymmetric coordination of the acetylide ligand
on the triangular face of the cluster. This asymmetry increases when one or two phosphine
ligands are attached to the trinuclear clusters, generating larger distances from Ru(1) to the
other two metals in compounds 4a1 and 4c1. In the case of compound 6b1 (Fig. 6), the
substitution of both PPh3 are confirmed to occurred in different metal centers, creating the
largest Ru–Ru bond (2.8639(5) Å) between the metal atoms who bear the phosphines. The
poor quality of the crystals for 6c1 [30] only permits sketch the connectivity of the heavy
atoms in the structure of this compound (Fig. 7); although, its study allowed us to identify
differences in the two coordinated phosphorous when compared to compound 6b1.
Fig. 6. ORTEP view of compound 6b1 (30% probability).
23

Fig. 7. Molecular structure of compound 6c1.
The structures of compounds 2b, 4a1, 4c1 and 6b1 show the perpendicular coordination of
the corresponding acetylide group. The cyclohexenyl group in compound 6b1 shows an
envelope ring conformation. The Ru−Ru distances are slightly larger when phosphine ligands
are coordinated to the metal framework than those in the CO derivative, changing the M−M
distances from 2.805 Å (av) in 2b to 2.810 (av) Å in monophosphine compounds 4a1, 4c1,
or to 2.816 (av) Å in all substituted compounds 4a1–6b1. These data indicate that neither
changes in electronic nor steric properties caused by the phosphine substitution are present,
leaving almost unaffected the metallic structure in the clusters.
The Ru(1)−P(1) bond distances with only  interaction with both acetylide carbons are
similar to each other in compounds 4a1−6b1. They are larger (2.3678 (av) Å) than the Ru(3)–
P(2) bond distance (2.3277(14) Å), where the C(1) of the acetylide is coordinated to the
24

metal atom. Apparently, this interaction shortens the P−Ru coordination; a similar trend has
also been reported in some other trinuclear ruthenium acetylide diphosphine clusters [8].
The C(1)−C(2) bond distances are similar for all acetylide complexes, ranging from 1.304(4)
Å in 4c1 to 1.322(8) Å in 6b1, and they are similar to several other acetylide−ruthenium
trinuclear clusters [8]. These distances are close to the normal C=C double bond distance
(Csp2–Csp2 1.34 Å [31]) reflecting the change in hybridization of these carbons upon
coordination; thus it can be observed that the bond distance increases in the order
4c1<2b<4a1<6b1, which is usually related to the polarization in the C–C bond of the
coordinated acetylide [8].
The Ru(3)–C(1)–C(2) angles of the acetylide clusters are in the 154.6(4)–156.7(3)° range,
while the C(1)–C(2)–C(3) angles are smaller (139.2(6)–144.2(3)°). In compound 2b there is
a significant difference in this angle, 139.51(18)° for C(3a) or 145.35(18)° for C(3b), that is
related to the disorder around the cyclohexenyl ring where two different conformations were
found.
The
C(1)–C(2)–C(3)
angles
increase
according
to
6b1(139.2(6)°)<4a1(140.1(4)°)<2b(139.51(18)°)<4c1(144.2(3)°); this trend can be
associated with a decrease in repulsive steric interactions between the alkenyl fragments and
the phenyl rings in the PPh3 ligands. In the case of 2b, the preferred rotational orientation of
the cyclohexenyl ring increases the repulsive forces with the CO groups, while for 4c1, the
presence of the substituted phenyl ring and its planarity find a better way to be spatially
distributed. Compound 6b1, being the most crowded complex and having a cyclohexenyl
substituent and two PPh3 ligands, has the shortest angle; however, the resemblance of values
confirms that the only important contacts that affect this structural parameters are due to the
interactions of the acetylide functional groups and the phosphine coordinated to Ru(1) atom.
25

The angles formed by the C(1)–C(2) vector and the plane formed by the three metal atoms
in the acetylide compounds have different values (18.4(6)–20.6(2)°); the order observed was
4a1<6b1≈2b<4c1. It is worth to mention that complexes coordinated to ene–yne type ligands
have smaller values (18.7° av) than that of the trimethylphenyl aromatic ring (20.6(2)°), this
situation is also associated with the inherent hindrance properties of the ligands and its spatial
distributions.
The type of substituents on C(2) does not significantly affects the perpendicular relationship
between the C(1)–C(2) and Ru(1)–Ru(2) vectors, these interlinear angles are found in the
87.7(3)–89.0(2)° range (6b1<4c1<4a1<2b) with an average of 88.2°. This value is slightly
smaller than those reported for the analogous acetylide compounds with the absence of a
coordinated phosphine, [Ru3(–H)(CO)9(3–2–()–C≡C–R}] (R = SiMe3, 89.7°; SiPh3,
89.81°) [28].
For the acetylide phosphine substituted compounds, the P(1) are roughly located below the
plane of the metal atoms (opposite to the acetylide fragment) [P(1)/triangular plane distance:
0.020 Å, 4c1; 0.234 Å, 6b1; 0.278 Å, 4a1], with angles P(1)–Ru(1)/Ru(1)–Ru(2)–Ru(3) of
−0.5(4)°, −5.7(6)°, −6.8(4)°, respectively. However, the P(2) in complex 6b1 is located above
the metal triangle plane (0.566 Å), with an angle P(1)–Ru(1)/Ru(1)–Ru(2)–Ru(3) of 14.1(6)°.
As it has been mentioned, there are differences in the orientation of the coordination of both
P atoms in compounds 6b1 and 6c1. The analysis of both structures showed, that in 6b1 both
P atoms are in the same side of an imaginary perpendicular plane bisecting the triangular Ru
plane, indicating that the phosphine ligands are found in a cisoid position to each other (see
Fig. 6); while in 6c1, the two P atoms are located in transoid position, (see Fig. 7). These two
different structures were proposed to coexist in equilibrium in solution for the reported
26

compound [Ru3(–H)(CO)7(PPh3)2(3–2–()–C≡C–tBu)][10]; however, in our case, we
have no evidence that this type of behavior is present in the bistriphenylphosphine substituted
complexes at room temperature.
It is worth to notice that in the last two decades, it has only been reported 21 structures of
analogs to compound 2b, 4a1, 4c1 or 6b1 accordingly to the CCDC database, having the
general formula [Ru3(–H)(CO)9-2x(LL)x(3–2–()–C≡C–R}] (when x = 0, R = alkyl
[26,27,32,33], aryl [8,34], SiR3 [35-38], and Fp = (5-C5H5)Fe(CO)2 [39]); when x = 1, LL
= diphosphine, R = alkyl [33,40] and R = aryl, [8,41-43]). Among them, there is no structure
described that has two monophosphines coordinated in two different ruthenium atoms,
similar to compound 6b1. In a comparative analysis, it was found that the distances C(1)–
C(2) previously reported are in the range of 1.29(1)–1.327(5) Å, and there is no tendency in
these values that can be directly associated to the R substituent (alkyl, aryl or silyl) attach to
the acetilyde fragment. However, Akita and coworker [39] have reported the only structure
of a compound where there is a metallic atom directly attach to the acetylide fragment:
[Ru3(–H)(CO)9(3–2–()–C≡C–Fp}] Fp = (5-C5H5)Fe(CO)2. In this structure, the C(1)–
C(2) bond is one of the most elongated upon coordination, consequently is the largest
distance reported (1.33(2) Å). Also, in this compound the Ru(3)–C(1)–C(2) angle of 159(1)°
is the largest reported. In general, the Ru(3)–C(1)–C(2) angle in ruthenium diphosphine
clusters have values between 150.6(1) and 156.3(3)°, with 4c1 having the second largest
value (156.7(3)°) reported. This range is smaller than the values found for the Ru(3)–C(1)–
C(2) angle in ruthenium carbonyl silyl-acetylide clusters of 152.0(3) to 157.8(6)°, the
increase is due to the hindrance properties of the acetylide silyl substituents.
27

From the same data, the Ru(1)–Ru(2) bonds bridged by the hydride ligand, in clusters with
coordinated phosphines, have values between 2.7725(6) and 2.8149(6) Å; compound 6b1 has
the largest value (2.8160(4) Å) reported. For carbonyl clusters the Ru(1)–Ru(2) distances
were found between 2.7887(3) and 2.819(2) Å, cluster 2b has one of the smallest values
(2.7909(3) Å) and compound [Ru3(–H)(CO)9(3–2–()–C≡C–Fp}] [39] the largest.
When a diphosphine (LL) is coordinated to two different ruthenium atoms (C() and C()
bonded toward the metallic fragment), the distances for Ru(1)–P(1) and Ru(2)–P(2) were
found between 2.2990(5)–2.3730(9) and 2.282(1)–2.3277(14) Å respectively. In compounds
reported here, 4a1, 4c1 and 6c1, the Ru–P distances have the largest values, these can be
attributed to the fact that they have two coordinated monophosphines, and there are more
degrees of freedom compared with the bridged diphosphine derivatives reported elsewhere.
In the case of the parallel acetylene derivatives 3a1 and 3b1, the three metal–metal distances
are significantly different to each other; the Ru(1)–Ru(2) axis parallel to the acetylene vector
C(1)–C(2), which also has a bridging CO group, is the largest, 2.8479 Å (av). The Ru(3)–
Ru(1) bond being the second largest, 2.7719 Å (av), is the one that involved the phosphine
coordination around Ru(1). Thus, the presence of the coordinated ligands (acetylene,
phosphine and bridged CO), distorts considerably the metal triangle, confirmed by the three
different bond angles around each metal center.
From the molecular structure, it can be observed that the CO substitution by the phosphine
ligand took place in the ruthenium that is the least hindered center, having the H substituent
atom in the acetylene carbon. The Ru–P bond distances are similar to each other, 2.3695 Å
(av), and are also very similar to those Ru(1)–P(1) found in the acetylide complexes, 2.3678
Å (av); apparently, the  interaction from the CH acetylene group has no influence in the
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Ru−P interaction. The C(1)–C(2) bond distances are similar for both acetylene complexes,
1.396 Å (av), and they are larger than the C–C acetylide distances here reported, 1.315 Å
(av). The acetylene distances are larger than the normal C=C double bond distance reflecting
greater changes in hybridization and polarization of these carbons upon coordination when
compared with the acetylide complexes.
The C(1)–C(2)–C(3) angles are similar for compounds 3a1 and 3b1, 122.1° (av), and are
shorter than the bond angles found in the acetylide complexes, 141.2° (av). These data
confirm significant changes in carbon hybridization, the acetylene carbons have more sp3
character, while the acetylide carbons have more sp2 character. These can be related to the
coordination mode of the alkyne type derivatives, in the parallel acetylene coordination there
are two  and one  interactions with the metal framework, meanwhile in the acetylide
complexes there is one  and two  interactions with a concomitant C−H bond breaking.
Thus, the carbon atoms changed from a sp hybridization in the alkyne free ligand to a more
sp3 resemble character in the parallel acetylene, returning to a close sp2 hybridization in the
perpendicular acetylide.
The angles formed by the C(1)–C(2) vector and the plane of the three metal atoms in the
acetylene clusters are closely parallel to each other, 3.1° (av), where the acetylene carbon
with an alkene substituent is slightly farther away from the metal triangle, as expected. The
steric effects of the propenyl or the cyclohexenyl groups also have influence in the small
distortion between the C(1)–C(2) and the Ru(1)–Ru(2) vectors, showing angles of 6.7° for
3a1 and −3.8° for 3b1; the negative sign indicates that the C(2)–(cyclohexenyl) is pointing
away from the center of the Ru triangle relative to the Ru(1)–Ru(2) axis.
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