Preparation of trihydridostannyl complexes of rhenium stabilised by isocyanide ligands

Article abstract of DOI:10.1016/j.ica.2009.01.029

Mixed-ligand complexes [ReBr(CO)₂(CNR)_nL_3-n] (1-4) [R = 4-CH₃OC₆H₄, 4-CH₃C₆H₄, C(CH₃)₃; L = P(OEt)₃, PPh(OEt)₂;

Full text of DOI:10.1016/j.ica.2009.01.029

Inorganica Chimica Acta 363 (2010) 605–616
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Preparation of trihydridostannyl complexes of rhenium stabilised
by isocyanide ligands
a
b
a
Gabriele Albertin a, , Stefano Antoniutti , Jesús Castro , Gianluigi Zanardo
*
a Dipartimento di Chimica, Università Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy
b Departamento de Química Inorgánica, Universidade de Vigo, Facultade de Química, Edificio de Ciencias Experimentais, 36310 Vigo (Galicia), Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Mixed-ligand complexes [ReBr(CO)2(CNR)nL3ꢀn] (1–4) [R = 4-CH3OC6H4, 4-CH3C6H4, C(CH3)3; L = P(OEt)3,
PPh(OEt)2; n = 1, 2] were prepared by allowing carbonyl compounds [ReBr(CO)4L] and [ReBr(CO)3L2] to
react with an excess of isocyanide. Treatment of these bromocomplexes [ReBr(CO)2(CNR)nL3ꢀn] with
SnCl2 ꢁ 2H2O yielded the trichlorostannyl derivatives [Re(SnCl3)(CO)2(CNR)nL3ꢀn] (5–8). Trihydridestannyl
complexes [Re(SnH3)(CO)2(CNR)nL3ꢀn] (9–12) were prepared by allowing trichlorostannyl compounds 5–
Received 17 October 2008
Received in revised form 15 January 2009
Accepted 22 January 2009
Available online 31 January 2009
8
to react with NaBH4 in ethanol. The trimethylstannyl derivative [Re(SnMe3)(CO)2(CNC6H4-4-
CH3){PPh(OEt)2}2] (13b) was also prepared by treating [Re(SnCl3)(CO)2(CNC6H4-4-CH3){PPh(OEt)2}2] with
an excess of MgBrMe in diethylether. Reaction of the tin trihydride complexes [Re(SnH3)(CO)2(CNR)nL3ꢀn
(9–12) with CO2 (1 atm) led to dinuclear OH-bridging bis(formate) derivatives [Re{Sn(OC(H)@O)2(
Dedicated to Prof. Paul Pregosin.
]
-
Keywords:
Stannyl complexes
Rhenium
Phosphite ligands
Isocyanide ligands
Synthesis
l
OH)}(CO)2(CNR)nL3ꢀn
]
(14, 15). The complexes were characterised spectroscopically (IR, 1H, 31P, 13C,
2
119Sn NMR) and by X-ray crystal structure determination of [Re(SnH3)(CO)2{CNC(CH3)3}{PPh(OEt)2}2]
(10b).
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
but with [M(Tp)L(PPh3)] or with the [M(CO)nL5ꢀn] fragments the
dinuclear OH-bridging bis(formate) derivatives [[M]–Sn{OC(H)@
Transition metal complexes containing stannyl groups SnX3
and SnR3 as ligands have been extensively studied in recent years
[1–3], not only for the variety of reactions shown both at the me-
tal and at the tin centre, but also because the introduction of a tin
ligand into the metal fragment may modify the chemical proper-
ties of the complexes and often improve their catalytic activity
[1,4].
O}2(l-OH)]2 are always obtained [6a,6c].
These results prompted us to extend our study to include isocy-
anides (CNR) as supporting ligands in the chemistry of tin hydride
complexes, to test whether SnH3 complexes can be prepared with
such ligands, and how isocyanide may change the properties of the
tin hydride group.
The results of these studies, which include preparation and
some reactivity of unprecedented stannyl complexes of rhenium
[8] stabilised by isocyanide ligands, are reported here.
A large number of mono- and polynuclear stannyl complexes
containing halogenostannyl (SnX3) and organostannyl (SnR3) li-
gands have been synthesised [1–3]. However, despite the numer-
ous studies, only recently stable complexes containing the
simplest of the tin ligand, the trihydride SnH3, have been prepared
[5] using an osmium(II) fragment of the type [Os(Tp)L(PPh3)]
[Tp = tris(pyrazolyl)borate; L = phosphite] to stabilise the SnH3 li-
gand. Further studies from our and other laboratories have pointed
out that other d6 metal fragments, of the type [M(Cp)L(PPh3)]
(M = Ru, Os; L = phosphite), [M(CO)nL5ꢀn] (M = Mn, Re; n = 2, 3)
2. Experimental
2.1. General considerations
All synthetic work was carried out in an appropriate atmo-
sphere (Ar) using standard Schlenk techniques or an inert
atmosphere dry-box. Once isolated, the complexes were found
to be relatively stable in air, but were stored under nitrogen at
ꢀ25 °C. All solvents were dried over appropriate drying agents,
degassed on a vacuum line, and distilled into vacuum-tight stor-
age flasks. Re2(CO)10 was a Pressure Chemical Co. (USA) product
and was used as received. Phosphite PPh(OEt)2 was prepared by
the method of Rabinowitz and Pellon [9], while P(OEt)3 was an
Aldrich product, purified by distillation under nitrogen. Isocya-
nides CNC6H4-4-CH3 and CNC6H4-4-CH3O were prepared by the
[5,6] and [Os(j
2-S2CNMe2)(CO)(PPh3)2] [7], are able to stabilise
the tin trihydride ligand, and that the reactivity of the SnH3 group
strongly depends on the nature of the ancillary ligands. For exam-
ple, hydridebis(formate)stannyl complexes [M[SnH{OC(H)@O}2]-
(Cp)L(PPh3)] are stable and isolable only with the Cp ligand [6c],
* Corresponding author.
E-mail address: albertin@unive.it (G. Albertin).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.01.029

606
G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
method of Ziehn and co-workers [10], while CNC(CH3)3 was an
Aldrich product used as received. Other reagents were purchased
from commercial sources in the highest available purity and
used as received. Infrared spectra were recorded on a Perkin–El-
mer Spectrum-One FT-IR spectrophotometer. NMR spectra (1H,
31P, 13C, 119Sn) were obtained on AC200 or AVANCE 300 Bruker
spectrometers at temperatures between +20 and ꢀ90 °C, unless
otherwise noted. 1H and 13C spectra are referred to internal tet-
ramethylsilane; 31P{1H} chemical shifts are reported with respect
to 85% H3PO4, and 119Sn with respect to Sn(CH3)4, and in both
cases downfield shifts are considered positive. COSY, HMQC
and HMBC NMR experiments were performed with standard
programs. The SWAN-MR and INMR software packages [11] were
used to treat NMR data. The conductivities of 10ꢀ3 M solutions
of the complexes in CH3NO2 at 25 °C were measured with a
Radiometer CDM 83 instrument. Elemental analyses were deter-
minated in the Microanalytical Laboratory of the Dipartimento di
Scienze Farmaceutiche of the University of Padova (Italy).
2.2.4. [Re(SnCl3)(CO)2(CNR)L2] (5, 6) [R = 4-CH3OC6H4 (5), C(CH3)3
(6); L = P(OEt)3 (a), PPh(OEt)2 (b)]
In a 100-mL three-necked round-bottomed flask were placed
solid samples of [ReBr(CO)2(CNR)L2] (1, 2) (1.5 mmol), an excess
of SnCl2 ꢁ 2H2O (6 mmol, 1.35 g) and 30 mL of ethanol. The reaction
mixture was refluxed for 2 h and then the solution was concen-
trated by evaporation under reduced pressure to about 5 mL. The
yellow solid that separated out was isolated by filtration and crys-
tallised from CH2Cl2 and ethanol [1.08 g, 77% (5a), 1.18 g, 79% (5b),
1.19 g, 84% (6b)]. Anal. Calc. for C22H37Cl3NO9P2ReSn (5a) (932.75):
C, 28.33; H, 4.00; Cl, 11.40; N, 1.50. Found: C, 28.16; H, 4.11; Cl,
11.24; N, 1.62%. Anal. Calc. for C30H37Cl3NO7P2ReSn (5b) (996.84):
C, 36.15; H, 3.74; Cl, 10.67; N, 1.41. Found: C, 36.21; H, 3.85; Cl,
10.39; N, 1.27%. Anal. Calc. for C27H39Cl3NO6P2ReSn (6b) (946.83):
C, 34.25; H, 4.15; Cl, 11.23; N, 1.48. Found: C, 34.36; H, 4.02; Cl,
11.40; N, 1.32%.
2.2.5. [Re(SnCl3)(CO)2(CNR)2L] (7, 8) [R = 4-CH3OC6H4 (7), 4-CH3C6H4
(8); L = P(OEt)3 (a), PPh(OEt)2 (b)]
2.2. Synthesis of complexes
These complexes were prepared following the method used for
5, 6, starting from [ReBr(CO)2(CNR)2L] (3, 4) (1.5 mmol) [1.00 g,
74% (7a), 1.02 g, 78% (8a), 1.07 g, 79% (8b)]. Anal. Calc. for
C24H29Cl3N2O7PReSn (7a) (899.75): C, 32.04; H, 3.25; Cl, 11.82; N,
3.11. Found: C, 32.28; H, 3.41; Cl, 11.77; N, 3.28%. Anal. Calc. for
C24H29Cl3N2O5PReSn (8a) (867.75): C, 33.22; H, 3.37; Cl, 12.26; N,
3.23. Found: C, 33.05; H, 3.52; Cl, 12.03; N, 3.39%. Anal. Calc. for
C28H29Cl3N2O4PReSn (8b) (899.79): C, 37.38; H, 3.25; Cl, 11.82;
N, 3.11. Found: C, 37.16; H, 3.12; Cl, 11.97; N, 3.02%.
The complexes [ReBr(CO)5] and [ReBr(CO)3L2] [L = P(OEt)3 and
PPh(OEt)2] were prepared following the methods previously re-
ported [6a,12].
2.2.1. [ReBr(CO)4L] [L = P(OEt)3 (a) and PPh(OEt)2 (b)]
A slight excess of the appropriate phosphite (5.2 mmol) was
added to a solution of [ReBr(CO)5] (2 g, 5.0 mmol) in 30 mL of tol-
uene and the reaction mixture refluxed for 1 h. The solvent was re-
moved under reduced pressure to give an oil which was triturated
with ethanol (5 mL). A white solid separated out, which was fil-
tered and dried under vacuum [for [ReBr(CO)4{P(OEt)3}] (a)
2.42 g, 89%; for [ReBr(CO)4{PPh(OEt)2}] (b) 2.62 g, 91%]. Anal. Calc.
for C10H15BrO7PRe [ReBr(CO)4{P(OEt)3}] (a) (544.31): C, 22.07; H,
2.78. Found: C, 22.19; H, 2.90%. Anal. Calc. for C14H15BrO6PRe [Re-
Br(CO)4{PPh(OEt)2}] (b) (576.35): C, 29.17; H, 2.62. Found: C,
28.98; H, 2.51%.
2.2.6. [Re(SnH3)(CO)2(CNR)L2] (9, 10) [R = 4-CH3OC6H4 (9), C(CH3)3
(10); L = P(OEt)3 (a), PPh(OEt)2 (b)]
An excess of NaBH4 (20 mmol, 0.76 g) in ethanol (20 mL) was
added to a suspension of the appropriate trichlorostannyl complex
[Re(SnCl3)(CO)2(CNR)L2] (5, 6) (1 mmol) in ethanol (20 mL) and the
reaction mixture was stirred at room temperature for 1 h. The sol-
vent was removed under reduced pressure to give a solid, from
which the [M]–SnH3 complex was extracted with three 30-mL por-
tions of toluene. The extracts were evaporated to dryness, leaving
an oil which was triturated with ethanol (3 mL). A white solid sep-
arated out from the resulting solution cooled to ꢀ20 °C, which was
isolated by filtration and crystallised from toluene and hexane
[0.54 g, 65% (9a), 0.63 g, 71% (9b), 0.57 g, 68% (10b)]. Anal. Calc.
for C22H40NO9P2ReSn (9a) (829.42): C, 31.86; H, 4.86; N, 1.69.
Found: C, 31.71; H, 4.98; N, 1.57%. Anal. Calc. for C30H40NO7P2ReSn
(9b) (893.51): C, 40.33; H, 4.51; N, 1.57. Found: C, 40.51; H, 4.66; N,
1.51%. Anal. Calc. for C27H42NO6P2ReSn (10b) (843.49): C, 38.45; H,
5.02; N, 1.66. Found: C, 38.68; H, 4.95; N, 1.52%.
2.2.2. [ReBr(CO)2(CNR)L2] (1, 2) [R = 4-CH3OC6H4 (1), C(CH3)3 (2);
L = P(OEt)3 (a), PPh(OEt)2 (b)]
An excess of the appropriate isocyanide (4 mmol) was added to
a solution of [ReBr(CO)3L2] (2 mmol) in 20 mL of toluene and the
reaction mixture refluxed for 1 h. The solvent was removed under
reduced pressure to give an oil, which was treated with ethanol
(5 mL). The resulting solution was vigorously stirred at 0 °C until
a pale yellow solid separated out, which was filtered and dried un-
der vacuum [1.23 g, 78% (1a), 1.38 g, 81% (1b), 1.33 g, 83% (2b)].
Anal. Calc. for C22H37BrNO9P2Re (1a) (787.59): C, 33.55; H, 4.74;
Br, 10.15; N, 1.78. Found: C, 33.78; H, 4.83; Br, 10.32; N, 1.64%.
Anal. Calc. for C30H37BrNO7P2Re (1b) (851.68): C, 42.31; H, 4.38;
N, 1.64. Found: C, 42.48; H, 4.49; N, 1.57%. Anal. Calc. for
C27H39BrNO6P2Re (2b) (801.66): C, 40.45; H, 4.90; N, 1.75. Found:
C, 40.24; H, 4.95; N, 1.68%.
2.2.7. [Re(SnH3)(CO)2(CNR)2L] (11, 12) [R = 4-CH3OC6H4 (11),
4-CH3C6H4 (12); L = P(OEt)3 (a), PPh(OEt)2 (b)]
These complexes were prepared exactly like the monoisocya-
nide derivatives 9, 10, starting from [Re(SnCl3)(CO)2(CNR)2L] (7,
8) (1 mmol) [0.61 g, 77% (11a), 0.55 g, 72% (12a), 0.62 g, 78%
(12b)]. Anal. Calc. for C22H40NO9P2ReSn (11a) (796.41): C, 36.19;
H, 4.05; N, 3.52. Found: C, 36.34; H, 3.97; N, 3.70%. Anal. Calc. for
C24H32N2O5PReSn (12a) (764.41): C, 37.71; H, 4.22; N, 3.66. Found:
C, 37.52; H, 4.36; N, 3.49%. Anal. Calc. for C28H32N2O4PReSn (12b)
(796.46): C, 42.22; H, 4.05; N, 3.52. Found: C, 42.02; H, 4.18; N,
3.37%.
2.2.3. [ReBr(CO)2(CNR)2L] (3, 4) [R = 4-CH3OC6H4 (3), 4-CH3C6H4 (4);
L = P(OEt)3 (a), PPh(OEt)2 (b)]
An excess of the appropriate isocyanide (8 mmol) was added to
a solution of [ReBr(CO)4L] (2 mmol) in 20 mL of toluene and the
reaction mixture refluxed for 2 h. The solvent was removed under
reduced pressure to give an oil, which was triturated with ethanol
(5 mL). A pale yellow solid separated out, which was filtered and
dried under vacuum [1.36 g, 90% (3a), 1.39 g, 92% (4b)]. Anal. Calc.
for C24H29BrN2O7PRe (3a) (754.58): C, 38.20; H, 3.87; Br, 10.59; N,
3.71. Found: C, 38.02; H, 3.76; Br, 10.75; N, 3.84%. Anal. Calc. for
C28H29BrN2O4PRe (4b) (754.63): C, 44.57; H, 3.87; N, 3.71. Found:
C, 44.74; H, 3.75; N, 3.63%.
2.2.8. [Re(SnMe3)(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2] (13b)
An excess of MgBrMe (1.5 mmol, 0.5 mL of a 3 M solution in
diethyl ether) was added to a suspension of the trichlorostannyl
complex
[Re(SnCl3)(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2]
(5b)
(0.25 mmol, 0.25 g) in 25 mL of diethyl ether cooled to ꢀ196 °C.
The reaction mixture was brought to room temperature and stirred

G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
607
Table 1
for 2 h and then the solvent was removed under reduced pressure.
Crystal data and structure refinement for 10b.
Ethanol (10 mL) was added to the obtained solid and the resulting
suspension was stirred for 1 h. The solvent was evaporated to give
a solid, from which the trimethylstannyl complex was extracted
with three 10-mL portions of toluene. The extracts were evapo-
rated to dryness leaving an oil, which was triturated with ethanol
(3 mL). A pale yellow solid slowly separated out from the resulting
solution, which was isolated by filtration and crystallised from eth-
anol [0.12 g, 50%]. Anal. Calc. for C33H46NO7P2ReSn (935.59): C,
42.36; H, 4.96; N, 1.50. Found: C, 42.56; H, 5.13; N, 1.39%.
Empirical formula
Formula weight
T (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C27H42NO6P2ReSn
843.45
293(2)
0.71073
orthorhombic
Pbca
16.5551(15)
15.4486(14)
26.990(3)
6902.8(11)
b (Å)
c (Å)
V (Å3)
2.2.9. [Re{Sn(OC(H)@O)2(l-OH)}(CO)2(CNC6H4-4-CH3O){P(OEt)3}2]2
Z
8
Dcalc (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
1.623
4.356
3312
(14a) and [Re{Sn(OC(H)@O)2(l-OH)}(CO)2(CNC6H4-4-
)
CH3)2{P(OEt)3}]2 (15a)
A solution of the appropriate trihydridostannyl complex [Re
(SnH3)(CO)2(CNR)3ꢀn{P(OEt)3}n] (n = 1, 2) (9a, 12a) (0.1 mmol) in
toluene (5 mL) was stirred under a CO2 atmosphere (1 atm) at
room temperature for 3 h. The solvent was removed under reduced
pressure to give an oil, which was triturated with hexane (5 mL)
and ethanol (0.5 mL). A white solid slowly separated out, which
was isolated by filtration and crystallised from toluene and hexane
[0.14 g, 76% (14a), 0.13 g, 73% (15a)]. Anal. Calc. for C48H80N2O28-
P4Re2Sn2 (14a) (1866.87): C, 30.88; H, 4.32; N, 1.50. Found: C,
30.64; H, 4.44; N, 1.63%. Anal. Calc. for C52H64N4O20P2Re2Sn2
(15a) (1736.86): C, 35.96; H, 3.71; N, 3.23. Found: C, 36.18; H,
3.84; N, 3.09%.
Crystal size (mm)
Theta range for data collection (°)
Index ranges
0.44 ꢂ 0.43 ꢂ 0.10
1.51–25.03
ꢀ19 6 h 6 19; ꢀ18 6 k 6 11;
ꢀ31 6 l 6 32
22522
5511 [0.0854]
2846
Reflections collected
Independent reflections [Rint
Reflections observed (>2
Data completeness
Absorption correction
Maximum and minimum transmission
Refinement method
]
r)
0.905
semi-empirical from equivalents
1.000 and 0.484
full-matrix least-squares on F2
5511/0/361
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
0.980
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0647 wR2 = 0.1615
R1 = 0.1309 wR2 = 0.1840
1.601 and ꢀ2.168
Largest difference in peak and hole
2.2.10. X-ray crystal structure determination of
[Re(SnH3)(CO)2{CNC(CH3)3}{PPh(OEt)2}2] (10b)
(e Åꢀ3
)
Crystallographic data were collected on a Bruker Smart 1000
CCD diffractometer at CACTI (Universidade de Vigo, Spain) using
graphite monochromated Mo Ka radiation (k = 0.71073 Å), and
L
were corrected for Lorentz and polarisation effects. The software
SMART [13] was used for collecting frames of data, indexing reflec-
tions, and the determination of lattice parameters, SAINT [14] for
integration of intensity of reflections and scaling, and SADABS [15]
for empirical absorption correction. The structure was solved and
refined with the OSCAIL program [16] by direct methods and refined
by a full-matrix least-squares based on F2 [17]. Non-hydrogen
atoms were refined with anisotropic displacement parameters.
Hydrogen atoms were included in idealised positions and refined
with isotropic displacement parameters, except those bonded to
the tin atom that were found in the density map and refined iso-
tropically, although one restrain was applied to one of them in or-
der to maintain the distance Sn–H within chemically accepted
values. Details of crystal data and structural refinement are given
in Table 1.
OC
OC
Br
RNC
Re
[ReBr(CO)3L2]
CNR
L
1, 2 ( I )
CNR
Re
OC
OC
CNR
Br
RNC
[ReBr(CO)4L]
L
3, 4 ( II )
R = 4-CH3OC6H4 (1, 3), C(CH3)3 (2), 4-CH3C6H4 (4);
L = P(OEt)3 (a), PPh(OEt)2 (b).
Scheme 1.
3. Results and discussion
Good analytical data were obtained for the isocyanide com-
plexes 1–4, which were isolated as pale yellow solids stable in
air and in solution of common organic solvents, in which they be-
have as non-electrolytes [18].
3.1. Preparation of isocyanide complexes
Mixed-ligand isocyanide complexes [ReBr(CO)2(CNR)L2] (1, 2)
and [ReBr(CO)2(CNR)2L] (3, 4) were prepared by substituting car-
bonyl ligands in the [ReBr(CO)nL5ꢀn] (n = 3, 4) precursors, as shown
in Scheme 1.
Tricarbonyl complexes [ReBr(CO)3L2] react with isocyanide CNR
in refluxing toluene to give the mixed-ligand monoisocyanide
derivatives [ReBr(CO)2(CNR)L2] (1, 2) in good yields.
Under the same conditions, tetracarbonyl species [ReBr(CO)4L]
react with isocyanide CNR to give bis(isocyanide) derivatives [Re-
Br(CO)2(CNR)2L] (3, 4), which were isolated and characterised
(Scheme 1). The reaction was also carried out with a larger excess
of isocyanide and for a longer reaction time, but no further ligand
substitution was observed, as the bis(isocyanide) derivatives 3 and
4 were the only formed products.
Infrared spectra and 1H, 31P and 13C NMR data (Tables 2 and 3)
support the proposed formulations for the complexes and allow
type I and II geometries (Scheme 1) to be established in solution.
The IR spectra of the monoisocyanide derivatives 1 and 2
show only one band at 2134–2177 cmꢀ1 due to mCN of isocyanide
and two strong absorptions at 1967–1962 and at 1894–
1870 cmꢀ1 attributed to mCO of the two carbonyl ligands in a
mutually cis position. At temperatures between +20 and
ꢀ80 °C, the 31P{1H} NMR spectra display only one singlet, match-
ing the magnetic equivalence of the two phosphite ligands. Be-
sides the signals of the substituents of both phosphite and
isocyanide ligands, the 13C NMR spectra show, two triplets at

608
G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
Table 2
Selected IR and NMR data for rhenium complexes.
Compound
IRa
1H NMRb
31P{1H} NMRb,c
ppm; J, Hz
115.5 s
cmꢀ1
Assgnt
ppm; J, Hz
Assgnt
Spin syst
A2
1a [ReBr(CO)2(CNC6H4-4-CH3O){P(OEt)3}2]
2134 s
1967 s
1894 s
mCN
mCO
7.33–6.86 m
4.14
3.81 s
Ph
CH2
CH3 isocy
CH3 phos
Ph
1.30 t
1b [ReBr(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2]
2148 s
1962 s
1877 s
mCN
mCO
7.75 m
7.37 m
6.71 d
A2
131.9 s
6.51 d
4.31 m
4.08 m
3.98 m
3.85 m
3.77 m
1.35 t
CH2
CH3 isocy
CH3 phos
1.31 t
2b [ReBr(CO)2(CNtBu){PPh(OEt)2}2]
2177 s
1962 s
1870 s
mCN
mCO
7.77–7.35 m
4.25 m
4.04 m
3.92 m
3.78 m
1.33 t
Ph
A2
132.0 s
CH2
CH3 phos
1.29 t
1.02 s
CH3 isocy
Ph
CH2
CH3 isocy
CH3 phos
Ph
3a [ReBr(CO)2(CNC6H4-4-CH3O)2{P(OEt)3}]
4b [ReBr(CO)2(CNC6H4-4-CH3)2{PPh(OEt)2}]
2161 s
2122 s
1970 s
1894 s
2156 s
2118 s
1966 s
1892 s
mCN
mCO
mCN
mCO
7.40–6.90 m
4.14 m
3.82 s
A
A
117.2 s
1.33 t
7.80–6.48 md
4.30 m
4.09 m
2.38 s m
2.37 s
131.8 sd
CH2
CH3 isocy
CH3 phos
1.34 t
1.32 t
5a [Re(SnCl3)(CO)2(CNC6H4-4-CH3O){P(OEt)3}2]
5b [Re(SnCl3)(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2]
2152 s
1984 s
1940 s
mCN
mCO
7.42–6.93 me
4.09 m
3.83 s
Ph
CH2
CH3 isocy
CH3 phos
Ph
CH2
CH3 isocy
CH3 phos
A2
A2
dA 117.0e
J
¼ 286:8
31 P117 Sn
1.33 t
2151 s
1988 s
1937 s
mCN
mCO
7.75–6.78 md
4.10–3.85 m
3.80 s
dA 136.3d
¼ 248:5
J
31 P117 Sn
1.39 t
1.37 t
6b [Re(SnCl3)(CO)2(CNtBu){PPh(OEt)2}2]
2149 s
1986 s
1941 s
mCN
mCO
7.78–7.41 m
4.02 m
3.97 m
3.90 m
1.40 t
Ph
CH2
A2
dA 136.6
¼ 251:8
J
31 P117 Sn
CH3 phos
1.35 t
1.11 s
CH3 isocy
Ph
7a [Re(SnCl3)(CO)2(CNC6H4-4-CH3O)2{P(OEt)3}]
8a [Re(SnCl3)(CO)2(CNC6H4-4-CH3)2{P(OEt)3}]
2165 s
2135 s
1989 s
1952 s
mCN
mCO
7.46 m
6.93 m
4.08 q
A
A
167.5 s
J
¼ 292:5
31 P117 Sn
CH2
3.83 s
3.82 s
1.34 t
7.40–7.21
4.08 qnt
2.38 s
2.37 s
1.34 t
CH3 isocy
CH3 phos
Ph
CH2
2172 s
2142 s
1986 s
1941 s
mCN
mCO
117.0
J
¼ 295:5
¼ 248:0
31 P117 Sn
CH3 isocy
CH3 phos
Ph
CH2
CH3 isocy
CH3 phos
Ph
CH2
CH3 isocy
SnH3
8b [Re(SnCl3)(CO)2(CNC6H4-4-CH3)2{PPh(OEt)2}]
9a [Re(SnH3)(CO)2(CNC6H4-4-CH3O){P(OEt)3}2]
2166 s
2136 s
1987 s
1950 s
2118 s
1956 s
1902 s
1757 br
mCN
mCO
7.78–7.11 m
4.04 m
2.40 s
A
136.2 s
J
31 P117 Sn
1.23 t
mCN
mCO
7.36–7.01 me
4.01 m
3.84 s
A2
123.1 se
¼ 199:5
J
31 P117 Sn
mSnH
A2MX3
dX 2.85
JAX = 3.6
J
¼ 1157
1 H117 Sn
1.27 t
CH3 phos

G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
609
Table 2 (continued)
Compound
IRa
1H NMRb
31P{1H} NMRb,c
ppm; J, Hz
139.8 sd
cmꢀ1
Assgnt
ppm; J, Hz
Assgnt
Spin syst
A2
9b [Re(SnH3)(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2]
2127 s
1948 s
1188 s
1775 s
1744 s
mCN
mCO
7.84–6.31 md
3.99 m
3.75 s
A2MX3
dX 3.5
Ph
CH2
CH3 isocy
SnH3
J
¼ 168:5
31 P117 Sn
mSnH
JAX = 3.1
J
¼ 1175
1 H117 Sn
1.17 t
CH3 phos
Ph
CH2
10b [Re(SnH3)(CO)2(CNtBu){PPh(OEt)2}2]
2141 s
1956 s
1902 s
1741 br
mCN
mCO
7.83–7.02 md
4.00 m
A2
140.0 sd
¼ 175:9
J
31 P117 Sn
3.87 m
3.66 m
mSnH
A2MX3
SnH3
dX 3.33
JMX = 3.4
J
¼ 1147:5
1 H117 Sn
1.19 t
CH3 phos
1.12 t
0.74 s
CH3 isocy
Ph
CH2
CH3 isocy
SnH3
11a [Re(SnH3)(CO)2(CNC6H4-4-CH3O)2{P(OEt)3}]
12a [Re(SnH3)(CO)2(CNC6H4-4-CH3)2{P(OEt)3}]
12b [Re(SnH3)(CO)2(CNC6H4-4-CH3)2{PPh(OEt)2}]
2143 s
2105 s
1971 s
1915 s
1760 m
1736 m
mCN
mCO
mSnH
7.43–7.00 me
4.03 qnt
3.85 s
A
A
A
124.4 se
¼ 194:0
J
31 P117 Sn
AMX3
dX 2.89
JAX = 3.5
J
¼ 1143:2
1 H117 Sn
1.29 t
CH3 phos
Ph
CH2
CH3 isocy
SnH3
2139 s
2096 s
1966 s
1933 s
1739 br
mCN
mCO
mSnH
7.32 me
4.03 qnt
2.37 s
124.2 se,f
¼ 194:5
J
31 P117 Sn
AMX3
dX 2.9
JAX = 3.7
J
¼ 1164:6
1 H117 Sn
1.28 t
CH3 phos
Ph
CH2
2135 s
2092 s
1956 s
1910 s
mCN
mCO
mSnH
7.76–7.01 me
4.05 m
3.83 m
2.36 s
138.7 se
¼ 171
J
31 P117 Sn
CH3 isocy
SnH3
1756 s, br
2.34 s
AMX3
dX 2.91
JAX = 3.3
J
¼ 1162:0
1 H117 Sn
1.35 t
CH3 phos
1.33 t
13b [Re(SnMe3)(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2]
2135 s
1957 s
1902 s
mCN
mCO
7.68–6.53 me
3.98 m
3.80 m
3.70 m
3.78 s
Ph
CH2
A2
141.0 se
¼ 141:5
J
31 P117 Sn
CH3 isocy
CH3 phos
1.33 t
1.29 t
0.084 s
SnMe3
J
J
¼ 35:7
¼ 34:1
1 H119 Sn
1 H117 Sn
14a [Re{Sn(OC(H)@O)2(
l
-OH)}(CO)2(CNC6H4-4-CH3O){P(OEt)3}2]2
2148 s
1981 s
1922 s
1673 m
1602 m
mCN
mCO
8.52 se
7.64 d
7.01 d
4.14 m
3.86 s
1.32 t
8.63 sf
8.31 sf
8.49 s
HC@O
Ph
A2
118.7e
J
¼ 314:5
31 P117 Sn
mOCO
CH2
CH3 isocy
CH3 phos
OH
HC@O
HC@O
Ph
15a [Re{Sn(OC(H)@O)2(
l
-OH)}(CO)2(CNC6H4-4-CH3)2{P(OEt)3}]2
2162 s
2127 s
1984 s
1938 s
1653 m
1592 m
mCN
A
A
119.8
7.44–7.10 m
4.05 qnt
2.37 s
J
¼ 308:0
31 P117 Sn
mCO
CH2
CH3 isocy
mOCO
2.36 s
1.30 t
CH3 phos
OH
HC@O
8.61 sf
8.26 sf
a
In KBr pellets.
b
In CD2Cl2 at 20 °C, unless otherwise noted.
Positive shifts downfield from 85% H3PO4.
In CD3C6D5.
In (CD3)2CO.
At ꢀ70 °C.
c
d
e
f

610
G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
Table 3
13C{1H} and 119Sn NMR data for selected rhenium complexes.
Compounda
13C{1H} NMR
119Sn NMR
Spin syst
ppm; J, Hz
Assgnt
CO
ppm; J, Hz
1b [ReBr(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2]
196.1 t
JCP = 11.5
190.2 t
JCP = 9.75
160–114 m
153.0 t, br
63.0 t
Ph
CN
CH2
62.6 t
55.9 s
16.3 t
195.9 t
CH3O
CH3 phos
CO
2b [ReBr(CO)2(CNtBu){PPh(OEt)2}2]
JCP = 12.5
190.7 t
JCP = 11.2
141.6 br
141–128 m
62.8 t
CN
Ph
CH2
62.4 t
57.0 s
30.0 s
16.3 t
C(CH3)
C(CH3)
CH3 phos
CO
3a [ReBr(CO)2(CNC6H4-4-CH3O)2{P(OEt)3}]
192.4 d
JCP = 12.0
188.7 d
JCP = 11.3
160–114 m
148.7 d
JCP = 21
147.5 d
JCP = 96
61.7 d
Ph
CN
CH2
56.0 s
CH3O
55.9 s
16.3 d
CH3 phos
CO
4b [ReBr(CO)2(CNC6H4-4-CH3)2{PPh(OEt)2}]
5a [Re(SnCl3)(CO)2(CNC6H4-4-CH3O){P(OEt)3}2]
5b [Re(SnCl3)(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2]
6b [Re(SnCl3)(CO)2(CNtBu){PPh(OEt)2}2]
192.9 db
JCP = 11.5
189.1 d
JCP = 9.5
149.2 br
140–126 m
63.0 d
CN
Ph
CH2
21.4 s
CH3 p-tolyl
CH3 phos
CO
16.4 d
192.3 tc
JCP = 11.3
189.6 t
A2Mc
A2Mb
A2M
dM ꢀ144.7
JAM = 299.6
JCP = 11.7
160.6–115.2 m
145.2 t, br
69.6 t
Ph
CN
CH2
CH3O
CH3 phos
CO
56.1 s
16.1 t
194.1 tb
JCP = 10.9
189.9 t
dM ꢀ141.6
JAM = 259.0
JCP = 9.7
160–128 m
147.2 br
64.1 t
56.1 s
16.3 t
193.4 t
JCP = 10.9
190.2 t
Ph
CN
CH2
CH3O
CH3 phos
CO
dM ꢀ143.0
JAM = 263.7
JCP = 9.6
140.5–128.6 m
134.9 br
63.7 t
Ph
CN
CH2
58.5 s
29.8 s
16.1 t
C(CH3)
C(CH3)
CH3 phos

G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
611
Table 3 (continued)
Compounda
13C{1H} NMR
119Sn NMR
Spin syst
AM
ppm; J, Hz
Assgnt
CO
ppm; J, Hz
7a [Re(SnCl3)(CO)2(CNC6H4-4-CH3O)2{P(OEt)3}]
190.1 d
JCP = 11.6
188.4 d
JCP = 10.9
160–115 m
142.6 d
JCP = 12
140.6 d
JCP = 72
62.8 d
dM ꢀ139.5
JAM = 304.5
Ph
CN
CH2
56.1 s
CH3O
56.0
16.2 d
CH3 phos
CO
8a [Re(SnCl3)(CO)2(CNC6H4-4-CH3)2{P(OEt)3}]
8b [Re(SnCl3)(CO)2(CNC6H4-4-CH3)2{PPh(OEt)2}]
AM
AM
dM ꢀ138.3
JAM = 307.5
dM ꢀ134.3
JAM = 259.0
190.8 d
JCP = 10.6
188.2 d
JCP = 9.2
144.3 br
140–126 m
64.1 d
CN
Ph
CH2
21.5 s
16.3 d
CH3 p-tolyl
CH3 phos
CO
c
9a [Re(SnH3)(CO)2(CNC6H4-4-CH3O){P(OEt)3}2]
9b [Re(SnH3)(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2]
10b [Re(SnH3)(CO)2(CNtBu){PPh(OEt)2}2]
198.7 tc
JCP = 12
193.3 t
JCP = 10
153.8 t, br
160–115 m
61.6 t
A2MX3
dM ꢀ493.5
JAM = 207.4
JAX = 3.6
JMX = 1210.8
CN
Ph
CH2
56.0 s
16.2 t
CH3O
CH3 phos
CO
200.0 tb
JCP = 11.8
193.4 t
JCP = 9.3
156.7 t, br
159–114 m
62.3 d
A2MX3
dM ꢀ477.0
JAM = 175.0
JAX = 3.1
b
JMX = 1229.7
CN
Ph
CH2
CH3O
CH3 phos
CO
54.9 s
16.0 d
199.4 tb
JCP = 11.6
193.5 t
JCP = 9.4
143.8 br
142–124 m
61.9 t
A2MX3
dM ꢀ477.3
JAM = 183.1
JMX = 1202.9
b
CN
Ph
CH2
56.2 s
30.1 s
15.9 t
C(CH3)
C(CH3)
CH3 phos
c
11a [Re(SnH3)(CO)2(CNC6H4-4-CH3O)2{P(OEt)3}]
12a [Re(SnH3)(CO)2(CNC6H4-4-CH3)2{P(OEt)3}]
AMX3
dM ꢀ489.5
JAM = 202.0
JAX = 3.5
JMX = 1197.5
dM ꢀ501.5
JAM = 202.5
JAX = 3.7
c,d
c
196.5 d
CO
CN
AMX3
JCP = 10.5
191.7 d
JCP = 9.8
151.9 br
149.0 br
140–114 m
62.7 d
JMX = 1218.5
Ph
CH2
20.9 s
CH3 p-tolyl
20.3 s
16.1 d
CH3 phos
(continued on next page)

612
G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
Table 3 (continued)
Compounda
13C{1H} NMR
119Sn NMR
Spin syst
ppm; J, Hz
Assgnt
CO
ppm; J, Hz
197.35 dc
JCP = 11
192.4 d
JCP = 10
152.6 br
152.0 d
JCP = 37.7
142–113 m
62.9 d
AMX3
dM ꢀ479.4
JAM = 178
JAX = 3.3
c
12b [Re(SnH3)(CO)2(CNC6H4-4-CH3)2{PPh(OEt)2}]
JMX = 1201.5
CN
Ph
CH2
21.2 s
16.3 d
CH3 p-tolyl
CH3 phos
CO
c
13b [Re(SnMe3)(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2]
202.8 tc
JCP = 11.7
195.0 t
JCP = 9.8
157.5 t
JCP = 6.0
160–115 m
62.5 t
A2MX9
dM ꢀ98.0
JAM = 147.5
JMX = 35.7
CN
Ph
CH2
55.9 s
16.5 t
CH3O
CH3 phos
CH3Sn
ꢀ4.53 s
J
J
¼ 156:5
13 C119Sn
13 C117Sn
¼ 150:0
14a [Re{Sn(l-OH)(OC(H)@O)2}(CO)2(CNC6H4-4-CH3O){P(OEt)3}2]2
193.1 tc
CO
A2Mc
dM ꢀ496.0
JAM = 328
JCP = 11.5
191.0 t
JCP = 10.8
166.9 s
160–115 m
155.8 br
62.6 t
C(H)@O
Ph
CN
CH2
56.0 s
16.4 t
CH3O
CH3 phos
CO
15a [Re{Sn(
l-OH)(OC(H)@O)2}(CO)2(CNC6H4-4-CH3)2{P(OEt)3}]2
190.4 d
JCP = 12.0
189.0 d
JCP = 11.3
167.0 s
144.3 d
JCP = 15
142.7 d
JCP = 69
140–125 m
62.2 d
AM
dM ꢀ483.3
JAM = 319.5
C(H)@O
CN
Ph
CH2
21.5 s
CH3 p-tolyl
21.4 s
16.2 d
CH3 phos
a
In CD2Cl2 at 20 °C, unless otherwise noted.
b
c
In CD3C6D5.
In (CD3)2CO.
At ꢀ70 °C.
d
196.1–195.9 and at 190.7–190.2 ppm due to the carbon reso-
nances of two CO ligands which are magnetically non-equiva-
lent. The values of the two JCP also suggest that each carbonyl
is in cis position with respect to the two phosphites. In the spec-
tra, the isocyanide carbon resonance also appears as a broad sig-
nal at 153.0–141.6 ppm.
respect to phosphites. A geometry of type II (Scheme 1) is therefore
proposed for bis(isocyanide) complexes 3, 4.
3.2. Preparation of trihydridostannyl complexes
Bromo complexes [ReBr(CO)2(CNR)L2] (1, 2) and [ReBr(CO)2-
(CNR)2L] (3, 4) react with an excess of SnCl2 ꢁ 2H2O to give the tri-
chlorostannyl derivatives [Re(SnCl3)(CO)2(CNR)3ꢀnLn] (n = 1, 2)
(5–8). Treatment of these [M]–SnCl3 compounds with NaBH4 in
ethanol yielded trihydridostannyl complexes [Re(SnH3)(CO)2-
(CNR)3ꢀnLn] (n = 1, 2) (9–12), which were isolated as white or pale
yellow solids and characterised (Scheme 2).
Insertion of SnCl2 into the Re–Br bond of 1–4 may give the halo-
stannyl intermediate [Re]–SnBrCl2 which, through halide exchange
with SnCl2, may yield the final trichlorostannyl derivatives [Re
(SnCl3)(CO)2(CNR)3ꢀnLn] (5–8). However, a metathetic exchange
reaction of [ReBr(CO)2(CNR)3ꢀnLn] with SnCl2 to give the chloro
On the basis of these data, geometry I (Scheme 1) is proposed
for monoisocyanide complexes 1 and 2.
The IR spectra of bis(isocyanide) complexes 3 and 4 show two
m
CN bands at 2161–2118 cmꢀ1 of the CNR and two
mCO absorptions
at 1970–1892 cmꢀ1 of the carbonyls, indicating that both the CNR
and CO ligands are in a mutually cis position. The 13C NMR spectra
also indicate that both the two CNR and the two CO groups are not
magnetically equivalent, in agreement with the presence, in 3a, of
two well separated doublets for both the carbon signals of the iso-
cyanide and carbonyl ligands. The JCP values of the two carbonyls
are very similar and suggest that both CO are in cis position with

G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
613
L
Re
L
The IR spectra of trichlorostannyl complexes [Re(SnCl3)-
(CO)2(CNR)L2] (5, 6) show two
CO bands at 1988–1937 cmꢀ1 indi-
OC
OC
SnCl3
CNR
m
exc. SnCl2•2H2O
[ReBr(CO)2(RNC)L2]
cating the mutually cis position of the two CO ligands. One strong
band at 2152–2149 cmꢀ1 is also present and attributed to mCN of
the isocyanide ligand. The 13C NMR spectra confirm the presence
of both carbonyl and isocyanide ligands, showing one broad triplet
at 147.2–134.9 ppm of the CN carbon atom and two well separated
triplets at 194.1–189.6 (5) and 193.4–190.2 (6) ppm of the car-
bonyl carbon resonance. In addition, the two separated triplets
suggest the magnetic inequivalence of the two CO ligands, which
are also cis with respect to the two phosphites. At temperatures be-
tween +20 and ꢀ80 °C, the 31P NMR spectra appear as sharp sing-
lets, with the satellites of 119Sn and 117Sn nuclei, matching the
magnetical equivalence of the two phosphite ligands. However,
the presence of the stannyl ligand is supported by the 119Sn NMR
spectra, which show a triplet at ꢀ143.0 (6b), ꢀ144.7 (5a) or
ꢀ141.6 ppm (5b) due to coupling with the phosphorus of the
two phosphite ligands. On the basis of these data, a cis–trans
geometry of type III (Scheme 2) is proposed for trichlorostannyl
complexes 5 and 6.
EtOH, Δ
1, 2
5, 6 ( III )
H
H
L
Re
L
OC
OC
Sn
NaBH4
H
CNR
EtOH, RT
9, 10 ( V )
CNR
OC
OC
CNR
SnCl3
exc. SnCl2•2H2O
Re
L
[ReBr(CO)2(RNC)2L]
EtOH, Δ
3, 4
7, 8 ( IV )
CNR
The IR spectra of bis(isocyanide) stannyl complexes [Re(SnCl3)-
(CO)2(CNR)2L] (7, 8) indicate that both the two carbonyls and the
two isocyanides are in a mutually cis position, showing two bands
at 1989–1941 cmꢀ1 of the mCO and two bands at 2172–2135 cmꢀ1
OC
OC
CNR
NaBH4
Re
L
H
EtOH, RT
Sn
H
H
11, 12 ( VI )
of the m
CN of the isocyanides. The 13C spectra support the presence
of both the CO and CNR ligands, showing two well separated dou-
blets at 144.9–140.6 ppm of the carbon resonances of two magnet-
ically non-equivalent isocyanide ligands and two doublets at
190.8–188.2 ppm of the carbon resonances of two magnetically
non-equivalent carbonyl ligands. The JCP values of the two carbonyl
ligands are very similar (9–11 Hz), suggesting that both CO are in a
mutually cis position with the phosphite ligand. On the basis of
these data, cis–cis geometry of type IV (Scheme 2) is proposed for
stannyl complexes 7 and 8.
R = 4-CH3OC6H4 (5, 7, 9, 11), C(CH3)3 (6, 10), 4-CH3C6H4 (8, 12);
L = P(OEt)3 (a), PPh(OEt)2 (b).
Scheme 2.
intermediate [ReCl(CO)2(CNR)3ꢀnLn], followed by insertion of SnCl2
into the Re–Cl bond, may likewise explain the formation of Re–
SnCl3 complexes 5–8.
Trichlorostannyl complexes [Re]–SnCl3 (5–8) undergo substitu-
tion of all three chlorides by Hꢀ when NaBH4 is used as a reagent,
thus allowing synthesis of the first trihydridostannyl complexes
containing isocyanide as supporting ligand. These results highlight
the fact that, in this case too [6a], the introduction of isocyanide li-
gands in mixed-ligand Re(I) complexes with carbonyls and phos-
phites allows stabilisation of the tin trihydride group.
The easy synthesis of trihydridostannyl complexes 9–12 by
substituting chloride with Hꢀ in the metal-bonded SnCl3 group
prompted us to extend the substitution reaction in [Re]–SnCl3
complexes to other nucleophilic reagents, such as MgBrMe. Results
show that the reaction proceeds to give the new trimethylstannyl
complex [Re(SnMe3)(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2] (13b),
which was isolated in good yield and characterised (Scheme 3).
The new stannyl complexes 5–13 were isolated as white or yel-
low solids stable in air and in solution of the most common organic
solvents, in which they behave as non-electrolytes [18]. Their for-
mulation is supported by analytical and spectroscopic data (IR and
1H, 31P, 13C, 119Sn NMR, Tables 2 and 3) and by X-ray crystal struc-
ture determination of complex [Re(SnH3)(CO)2{CNC(CH3)3}{P-
Ph(OEt)2}2] (10b).
In addition to two
of the two carbonyl ligands and to one
m
CO bands, characteristic of a cis arrangement
m
CN band of the isocyanide,
the IR spectra of trihydridestannyl complexes [Re(SnH3)(CO)2-
(CNR)L2] (9, 10) show a broad band at 1775–1741 cmꢀ1 (two bands
at 1775 and 1744 cmꢀ1 for 9b) attributed to mSnH of the SnH3 li-
gand. Diagnostic for the presence of the tin trihydride as a ligand
are the 1H and 119Sn NMR spectra. In the proton spectra, a triplet
at 2.85 (9a), 3.5 (9b) and 3.33 (10b) ppm, with the characteristic
satellites due to coupling with 119Sn and 117Sn, was observed and
H3
H1
H2
Sn
O2
P2
C2
C35
Re
C33
C32
P1
L
C31
OC
OC
CNR
Sn
MgBrMe
N1
Me
Re
[Re(SnCl3)(CO)2(RNC)L2]
C1
5b
C34
L
Me
O1
Me
13b
R = 4-CH3OC6H4; L = PPh(OEt)2.
Fig. 1. Compound [Re(SnH3)(CO)2{CNC(CH3)3}{PPh(OEt)2}2] (10b) drawn at 20%
Scheme 3.
probability level.

614
G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
attributed to the SnH3 group. The proton- and phosphorus-coupled
119Sn NMR spectra appear as triplets of quartets at ꢀ493.6 (9a),
ꢀ477.0 (9b) and ꢀ477.3 (10b) ppm, due to coupling with the three
hydrides and two magnetically equivalent phosphorus nuclei, con-
firming the presence of the SnH3 group. At temperatures between
+20 and ꢀ80 °C, the 31P NMR spectra appear as sharp singlets, with
the 119Sn and 117Sn satellites, fitting the magnetic equivalence of
the two phosphite ligands. Instead, the 13C spectra indicate the
non-equivalence of the two CO ligands, showing two triplets at
200.0–198.7 and 193.5–193.3 ppm for the carbonyl carbon reso-
nance. On the basis of these data, cis–trans geometry of type IV
(Scheme 2) is proposed for hydridostannyl complexes 9a and 10b.
The ORTEP view of complex [Re(SnH3)(CO)2{CNC(CH3)3}{P-
Ph(OEt)2}2] (10b) is shown in Fig. 1. A selection of bond lengths
and angles are listed in Table 4. The rhenium ion is coordinated
by two carbonyl ligands in cis positions; two phosphorus atoms
of two phosphonite ligands in trans positions; a tin atom from a tri-
hydridestannyl group; and a carbon atom from a tert-butyl isocya-
nide group. The coordination polyhedron around the rhenium may
be defined as a slightly distorted octahedron. Axial angles range
from 170.8(5) to 179.2(4) in such a way that both the P–Re–P axis
and, especially, the isocyanide–Re–carbonyl axis are bent towards
the tin ligand. The cis angles range from C(31)–Re–Sn, 83.6(4) to
C(1)–Re–C(31), 97.2(5)°, highlighting this distortion.
O2
C2
O11
O1
O12
P1
Re
C1
Sn
P2
O21
O22
C31
N1
C32
C33
C35
C34
Fig. 2. Compound [Re(SnH3)(CO)2{CNC(CH3)3}{PPh(OEt)2}2] (10b) drawn at 50%
probability level. The substituents of the phosphonite groups were not drawn and
the methyl carbon atoms of the tBu group were drawn as spheres of arbitrary radii
for clarity.
Both Re–P bond lengths are almost identical
–
average
compound [6a], [Re(SnH3)(CO)2{P(OEt)3}3], but these values may
be misleading, due to the well-known restrictions of X-ray diffrac-
tometry for hydrogen atoms in the proximity of heavy metals and
the necessary restraints applied to the model.
The Re–Cisocyanide bond length is 2.056(12) Å, shorter than that
found in other Re(I) complexes with a tert-butyl isocyanide ligand
2.362(3) Å – which is the same value found for other complexes
with phosphite or phosphonite ligands in trans positions
[6b,19,20]. The substituents on the phosphorus atoms are situated
in a pseudo-staggered fashion, with torsion X–P–P–X angles
163.2(8)° (average, X = O or C) (see Fig. 2, in which the phenyl
groups were represented as spheres of arbitrary radii).
The Re–Ccarbonyl bond lengths are 2.010(15) Å in the case of the
carbonyl ligand situated trans to the tin atom, and 1.936(14) Å for
the carbonyl trans to a isocyano ligand – being longer [21] than that
trans to the stannyl ligand (vide infra) because of the strong trans
influence of the SnH3 ligand [1f,7]. However, it is difficult making
comparisons of the trans influence of the trihydridestannyl ligand
because of the lack of data. There are only four entries [5,6a,7] in
the Cambridge Structural Database version 5.29 updates (August
2008) [22] with the trihydridestannyl ligand coordinated to transi-
tion metals. The Re–C bond lengths are similar to those found in
other dicarbonyldiphosphoniterhenium(I) complexes [19,20].
The Re–Sn bond distance, 2.7543(14) Å, is slightly shorter than
that found in similar compounds such as [Re(SnH3)(CO)2-
{P(OEt)3}3], 2.7632(6) Å, and [Re(SnMe3)(CO)2{P(OEt)3}3], 2.792(1)
Å [6a], or other tin–rhenium complexes [6b]. The Sn–H bond
lengths, 1.7(1) Å (average) are similar to those found in similar
H
H
C
C
O
H
O
O
O
O
O
H
CO2
2[Re]
Sn
[Re]
Sn
Sn
[Re]
H
1 atm
O
H
H
O
H
H
9a, 12a
C
C
O
O
14a, 15a
[Re] = [Re(CO)2(CNC6H4-4-CH3O){P(OEt)3}2] (14a), [Re(CO)2(CNC6H4-4-CH3)2{P(OEt)3}] (15a).
Scheme 4.
O
H
C
H
O
H
Table 4
CO2
H2O
–H2
C
Selected bond lengths (Å) and angles (°) for 10b.
[Re]
Sn
[Re]
H
Sn
O
H
O
Re–C(2)
Re–C(31)
Re–P(2)
Sn–H(1)
1.936(14)
2.056(12)
2.363(3)
1.70(2)
1.87(10)
1.436(19)
91.4(5)
97.2(5)
91.3(4)
89.7(4)
86.9(3)
87.7(4)
83.6(4)
87.86(10)
165.6(16)
112.1(16)
177.6(14)
Re–C(1)
Re–P(1)
Re–Sn
Sn–H(2)
C(31)–N(1)
2.010(15)
2.361(3)
2.7543(14)
1.71(8)
H
H
[ A ]
H
Sn–H(3)
1.154(15)
C
C
O
H
O
O
N(1)–C(32)
C(2)–Re–C(1)
C(1)–Re–C(31)
C(1)–Re–P(1)
C(2)–Re–P(2)
C(31)–Re–P(2)
C(2)–Re–Sn
C(31)–Re–Sn
P(2)–Re–Sn
C(31)–N(1)–C(32)
N(1)–C(32)–C(33)
Re–C(1)–O(1)
O
O
O
C(2)–Re–C(31)
C(2)–Re–P(1)
C(31)–Re–P(1)
C(1)–Re–P(2)
P(1)–Re–P(2)
C(1)–Re–Sn
170.8(5)
92.9(4)
90.0(3)
[Re]
Sn
Sn
[Re]
92.2(4)
O
H
O
175.60(13)
179.2(4)
88.70(10)
178.7(13)
109.2(15)
104.9(18)
175.1(13)
H
H
C
C
P(1)–Re–Sn
N(1)–C(31)–Re
C(34)–C(32)–N(1)
N(1)–C(32)–C(35)
Re–C(2)–O(2)
O
O
14, 15
Scheme 5.

G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
615
H
O
H
O
L
CO
L
L
CO
OC
L
CNR
CNR
OC
L
CNR
CO
CNR
OC
RNC
Re
Sn
Sn
Re
CO OC
Re
Sn
Sn
Re
O
O
H
RNC
L
H
14a ( VII )
15a ( VIII )
Scheme 6.
trans to a carbonyl group [23–25]. It is known that the C–N–C bond
angle at coordinated isonitriles is a structural parameter that can
characterised as the dinuclear complexes [Re{Sn(OC(H)@O)2
(l-OH)}(CO)2(CNR)3ꢀnLn]2 (14, 15) containing an OH-bridging
be used to evaluate the extent of
p
-backbonding [23,26]. Stronger
stannyl group (Scheme 4).
backbonding increases the sp2-character at the isonitrile nitrogen
atom leading to a substantial deviation of the C–N–C bond angle
from linearity. The N(1)–C(31)–Re is 178.7(13)° but the C(31)–
N(1)–C(32) is of 165.6(16)°. This small deviation from linearity
The reaction parallels those of the mixed-ligand complexes
[Re(SnH3)(CO)nL5ꢀn] [6a] with carbonyl and phosphites, and shows
that substituting carbonyl ligands with isocyanides in the
[Re]–SnH3 fragment does not change the reactivity of the trihydride
group toward CO2 leading to OH-bridging bis(formate)stannyl
complexes 14 and 15.
suggests that the isonitrile acts mainly as a
r-donor ligands, but
some d ? p -backbonding should be considered. The C(31)–N(1)
p
bond length, 1.154(15) Å, is also slightly longer than that found
in the above complexes, but still consistent with a triple bond be-
tween both atoms.
In addition, NMR studies on the progress of the reaction of
[Re(SnH3)(CO)2(CNC6H4-4-CH3)2{P(OEt)3}] with CO2 allow us to
propose a reaction path of the type shown in Scheme 5, which is
very similar to those previously proposed for related [M]–SnH3
complexes [6a,6c].
The IR spectra of bis(isocyanide) trihydridostannyl complexes
[Re(SnH3)(CO)2(CNR)2L] (11, 12) suggest that both CO and both
CNR ligands are in a mutually cis position, owing to the presence
The 1H NMR spectra of the reaction mixture show the disap-
pearance of the multiplet near 2.9 ppm of the SnH3 group of the
precursor and the appearance of resonances attributable to the
hydridobis(formate)stannyl intermediate [Re[SnH{OC(H)@O}2]
(CO)2(CNC6H4-4-CH3)2{P(OEt)3}] (A).1 The addition of an equimolar
amount of H2O (by microsyringe) to the reaction mixture containing
A reveals the direct formation of the dinuclear OH-bridging complex
of two mCO and two m
CN absorptions. In addition, the 13C NMR spec-
tra indicate that both carbonyls and isocyanides are not magneti-
cally equivalent, because of the two well separated doublets
observed for carbonyl carbon and isocyanide carbon resonances.
The comparable values (10 and 11 Hz) of JCP observed for the two
carbonyls suggest that they should occupy the same cis position
with respect to phosphite ligands. The IR spectra also show the
[Re{Sn(OC(H)@O)2(l-OH)}(CO)2(CNC6H4-4-CH3)2{P(OEt)3}]2 (15a)
characteristic
mSnH bands of the SnH3 group, whose presence is con-
and free H2 [27], according to the path of Scheme 5.
firmed by the doublet, with 119Sn and 117Sn satellites, observed at
2.91–2.89 ppm in the proton NMR spectra and attributed to the
hydride resonance. The 119Sn NMR spectra appear as quartets of
doublets due to coupling with the three hydrides and one phos-
phite, matching the presence of the SnH3 ligand. On the basis of
these data, cis–cis geometry of type VI (Scheme 2) is reasonably
proposed for hydridostannyl complexes 11 and 12.
The initial insertion of two CO2 molecules into two Sn–H bonds
of [M]–SnH3 gives the hydridobis(formate) intermediate A, which
undergoes hydrolysis with H2O to yield the final hydroxo-bridging
complex 15. This reaction path also explains why we were not able
to isolate the intermediate A in pure form, owing to its fast reaction
even with the traces of water in common ‘‘anhydrous” solvents, to
give the final l-OH derivatives.
Besides the signals of the phosphite and isocyanide ligands, the
Dinuclear complexes 14a and 15a were obtained as pale-yellow
solids, stable in air and in solution of common organic solvents,
where they behave as non-electrolytes [18]. Analytical and spec-
troscopic data (IR and 1H, 13C, 31P and 119Sn NMR, Tables 2 and
3) support the proposed formulation and allow geometry in solu-
tion of type VII and VIII (Scheme 6) to be established.
1H NMR spectrum of the trimethylstannyl complex [Re(SnMe3)
(CO)2(CNC6H4-4-CH3O){PPh(OEt)2}2] (13b) shows
a singlet at
0.084 ppm, with the 119Sn and 117Sn satellites, attributed to the
methyl resonance of the SnMe3 group. In the 13C NMR spectrum,
a singlet at ꢀ4.53 ppm, correlated in a HMQC experiment with
the proton signal at 0.084 ppm, was attributed to the carbon reso-
nance of the SnMe3 ligand. However, indicating the presence of the
SnMe3 group is the proton- and phosphorus-coupled 119Sn NMR
spectrum, which appears as a complicated multiplet. As the 31P
spectrum is a sharp singlet, the spectrum may be simulated with
an A2MX9 model (A = 31P, M = 119Sn, X = 1H) with the parameters
listed in Section 2. The good fit between calculated and experimen-
tal patterns supports the presence of the SnMe3 ligand.
The IR spectra of monoisocyanide complex 14a show two mCO
bands of two cis carbonyl ligands and one band at 2148 cmꢀ1 of
the CNR group. Two medium-intensity absorptions at 1673 and
1602 cmꢀ1 are also present due to the mOCO asym band of the two
g
1-formate OC(H)@O groups [28]. The 1H NMR spectra show, at
ꢀ70 °C, the signal of the formate HC@ group at 8.31 ppm and the
l
-OH resonance at 8.63 ppm. The 13C NMR spectra confirm the
presence of the formate group showing a singlet at 166.9 ppm of
the (H)C@O group and support the magnetic inequivalence of the
two CO groups showing two well separated triplets for the car-
bonyl carbon atoms. At temperatures between +20 and ꢀ80 °C
the signal of the 31P NMR spectra is a sharp singlet fitting the mag-
netic equivalence of the two phosphite ligands. On the basis of
these data, cis–trans geometry VII (Scheme 6) is proposed for 14a.
The IR spectrum of the bis(isocyanide) complex 15a suggests
that both the two carbonyl and the two isocyanide ligands are in
The IR spectrum of 13b shows two mCO bands at 1957 and
1902 cmꢀ1 fitting the mutually cis position of the two CO ligands.
These ligands are not magnetically equivalent, matching the pres-
ence of two triplets at 202.8 (JCP = 11.7 Hz) and 195.0 ppm
(JCP = 9.8 Hz) for the carbon resonance of the CO ligand. On the
basis of these data, cis–trans geometry (Scheme 3) is proposed
for the trimethylstannyl complex 13b.
3.3. Reactions with CO2
1
The 1H NMR spectra show a singlet at 11.6 ppm, with the 119Sn and 117Sn
Trihydridestannyl
(9–12) (n = 1, 2) react with carbon dioxide to give white solids
complexes
[Re(SnH3)(CO)2(CNR)3ꢀnLn]
satellites, attributed to the SnH proton and a singlet at 8.61 ppm of the formate of the
intermediate [Re[SnH{OC(H)=O)2}](CO)2(CNC6H4-4-CH3)2{P(OEt)3}].

616
G. Albertin et al. / Inorganica Chimica Acta 363 (2010) 605–616
[3] (a) N.R. Neale, T.D. Tilley, J. Am. Chem. Soc. 124 (2002) 3802;
(b) M.A. Esteruelas, A. Lledos, F. Maseras, M. Oliván, E. Oñate, M.A. Tajada, J.
Tomàs, Organometallics 22 (2003) 2087;
a mutually cis position. The spectrum also shows the two mOCO asym
bands of the tin formate ligands, whose presence is confirmed by
the 1H NMR spectra, showing the HC@O resonance (ꢀ70 °C) at
8.26 ppm and OH one at 8.61 ppm. The 13C spectra support the
presence of the tin formate ligand (HC@O signal at 167.0 ppm)
and also indicate that the two carbonyl ligands are magnetically
non-equivalent owing to the presence of two well separated dou-
blets at 190.4 (JCP = 12.0 Hz) and 189.0 ppm (JCP = 11.3 Hz) for the
CO carbon resonances. cis–cis Geometry VIII (Scheme 6) is there-
fore proposed for dinuclear complex 15a.
(c) R.D. Adams, B. Captain, J.L. Smith Jr., M.B. Hall, C.L. Beddie, C.E. Webster,
Inorg. Chem. 43 (2004) 7576;
(d) N.R. Neale, T.D. Tilley, J. Am. Chem. Soc. 127 (2005) 14745;
(e) R.D. Adams, B. Captain, R.H. Herber, M. Johansson, I. Nowik, J.L. Smith, M.D.
Smith, Inorg. Chem. 44 (2005) 6346;
(f) T. Sagawa, K. Ohtsuki, T. Ishiyama, F. Ozawa, Organometallics 24 (2005)
1670;
(g) R.D. Adams, B. Captain, C.B. Hollandsworth, M. Johansson, J.L. Smith Jr.,
Organometallics 25 (2006) 3848;
(h) M.A. Alvarez, M.E. Garcia, A. Ramos, M.A. Ruiz, Organometallics 25 (2006)
5374;
(i) B. Eguillor, M.A. Esteruelas, M. Olivan, E. Oñate, Organometallics 24 (2005)
1428;
(j) H. Braunschweig, H. Bera, B. Geibel, R. Dörfler, D. Götz, F. Seeler, T. Kupfer, K.
Radacki, Eur. J. Inorg. Chem. (2007) 3416;
4. Conclusions
(k) G. Albertin, S. Antoniutti, J. Castro, S. García-Fontán, M. Noé, Dalton Trans.
(2007) 5441;
(l) L. Carlton, M.A. Fernandes, E. Sitabule, Proc. Natl. Acad. Sci. 104 (2007) 6969.
[4] (a) J.N. Coupé, E. Jordão, M.A. Fraga, M. Mendes, J. Appl. Catal. A 199 (2000) 45;
(b) S. Hermans, R. Raja, J.M. Thomas, B.F.G. Johnson, G. Sankar, D. Gleeson,
Angew. Chem., Int. Ed. 40 (2001) 1211;
In this paper we report the synthesis of mixed-ligand rhenium
complexes [ReBr(CO)2(CNR)3ꢀnLn] (n = 2, 3) with carbonyl, phos-
phite and isocyanide, allowing the preparation of unprecedented
trihydridestannyl complexes stabilised by isocyanide ligands.
Structural parameters for the tert-butyl isocyanide derivative
[Re(SnH3)(CO)2{CNC(CH3)3}{PPh(OEt)2}2] are also reported.
Trimethylstannyl complexes [Re(SnMe3)(CO)2(CNC6H4-4-CH3O)
{PPh(OEt)2}2] and dinuclear tin formate derivatives [Re{Sn(OC(H)
@O)2(l-OH)}(CO)2(CNR)3ꢀnLn]2 are also described.
(c) G.W. Huber, J.W. Shabaker, J.A. Dumesic, Science 300 (2003) 2075;
(d) R.D. Adams, B. Captain, M. Johansson, J.L. Smith Jr., J. Am. Chem. Soc. 127
(2005) 488.
[5] G. Albertin, S. Antoniutti, A. Bacchi, M. Bortoluzzi, G. Pelizzi, G. Zanardo,
Organometallics 25 (2006) 4235.
[6] (a) G. Albertin, S. Antoniutti, J. Castro, S. García-Fontán, G. Zanardo,
Organometallics 26 (2007) 2918;
(b) G. Albertin, S. Antoniutti, J. Castro, S. García-Fontán, G. Zanardo,
Organometallics 27 (2008) 2789;
(c) G. Albertin, S. Antoniutti, A. Bacchi, G. Pelizzi, G. Zanardo, Organometallics
27 (2008) 4407.
Acknowledgments
We thank Daniela Baldan for her technical assistance.
[7] M.M. Möhlen, C.E.F. Rickard, W.R. Roper, G.R. Whittell, L.J. Wright, Inorg. Chim.
Acta 360 (2007) 1287.
[8] For rhenium tin complexes see: (a) H. Preut, H.-J. Haupt, U. Florke, Acta
Crystallogr., Sect. C 40 (1984) 600;
Appendix A. Supplementary material
(b) H.-J. Haupt, P. Balsaa, B. Schwab, U. Florke, H. Preut, Z. Anorg. Allg. Chem. 22
(1984) 513;
(c) B.A. Narayanan, J.K. Kochi, Inorg. Chim. Acta 122 (1986) 85–90;
(d) D.E. Westerberg, B.E. Sutherland, J.C. Huffman, K.G. Caulton, J. Am. Chem.
Soc. 110 (1988) 1642;
(e) G.F.P. Warnock, L.C. Moodie, J.E. Ellis, J. Am. Chem. Soc. 111 (1989) 2131;
(f) J.C. Luong, R.A. Faltynek, M.S. Wrighton, J. Am. Chem. Soc. 102 (1980) 7892;
(g) B.T. Huie, S.W. Kirtley, C.B. Knobler, H.D. Kaesz, J. Organomet. Chem. 213
(1981) 45;
CCDC 705362 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.ca-
m.ac.uk/data_request/cif. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.ica.2009.01.029.
(h) M.L. Loza, R.H. Crabtree, Inorg. Chim. Acta 236 (1995) 63.
[9] R. Rabinowitz, J. Pellon, J. Org. Chem. 26 (1961) 4623.
[10] R. Appel, R. Kleinstück, K.-D. Ziehn, Angew. Chem., Int. Ed. 10 (1971) 132.
[11] G. Balacco, J. Chem. Inf. Comput. Sci. 34 (1994) 1235. http://www.inmr.net/.
[12] K.J. Reimer, A. Shaver, Inorg. Synth. 28 (1990) 155.
[13] SMART Version 5.054, Instrument Control and Data Collection Software, Bruker
Analytical X-ray Systems Inc., Madison, WI, USA, 1997.
[14] SAINT Version 6.01, Data Integration Software Package, Bruker Analytical X-ray
Systems Inc., Madison, WI, USA, 1997.
References
[1] (a) K.M. Mackay, B.K. Nicholson, in: G. Wilkinson, F.G.A. Stone, E.W. Abel (Eds.),
Comprehensive Organometallic Chemistry, vol. 2, Pergamon Press, New York,
1982, p. 1043.;
(b) M.S. Holt, W.L. Wilson, J.H. Nelson, Chem. Rev. 89 (1989) 11;
(c) M.F. Lappert, R.S. Rowe, Coord. Chem. Rev. 100 (1990) 267;
(d) A.G. Davies, in: F.G.A. Stone, E.W. Abel, G. Wilkinson (Eds.), Comprehensive
Organometallic Chemistry, vol. 2, Pergamon Press, New York, 1995, p. 218;
(e) A.G. Davies, Organotin Chemistry, Wiley-VCH, Weinheim, Germany, 2004;
(f) W.R. Roper, L.J. Wright, Organometallics 25 (2006) 4704.
[2] (a) M.L. Buil, M.A. Esteruelas, F.J. Lahoz, E. Oñate, L.A. Oro, J. Am. Chem. Soc. 117
(1995) 3619;
[15] G.M. Sheldrick, SADABS, A Computer Program for Absorption Corrections,
University of Göttingen, Germany, 1996.
[16] P. McArdle, J. Appl. Crystallogr. 28 (1995) 65.
[17] G.M. Sheldrick, SHELX-97, Program for the Solution and Refinement of Crystal
Structures, University of Göttingen, Germany, 1997.
[18] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
[19] G. Albertin, S. Antoniutti, J. Bravo, J. Castro, S. García-Fontán, M.C. Marín, M.
Noè, Eur. J. Inorg. Chem. (2006) 3451.
[20] G. Albertin, S. Antoniutti, A. Bacchi, A. Celebrin, G. Pelizzi, G. Zanardo, Dalton
Trans. (2007) 661.
[21] B.J. Coe, S.J. Glenwright, Coord. Chem. Rev. 203 (2000) 5.
[22] F.H. Allen, Acta Crystallogr. B58 (2002) 380.
[23] R. Garcia, A. Paulo, A. Domingos, I. Santos, H.-J. Pietzsch, Synth. React. Inorg.
Nano-Met. Chem. 35 (2005) 35.
[24] S. Nieto, J. Pérez, L. Riera, V. Riera, D. Miguel, J.A. Golen, A.L. Rheingold, Inorg.
Chem. 46 (2007) 3407.
[25] L. Huynh, Z. Wang, J. Yang, V. Stoeva, A. Lough, I. Manners, M.A. Winnik, Chem.
Mater. 17 (2005) 4765.
[26] H. Spies, M. Glaser, H.-J. Pietzsch, F.E. Hahn, T. Lügger, Inorg. Chim. Acta 240
(1995) 465.
(b) H. Nakazawa, Y. Yamaguchi, K. Miyoshi, Organometallics 15 (1996)
1337;
(c) U. Schubert, S. Grubert, Organometallics 15 (1996) 4707;
(d) M. Akita, R. Hua, S. Nakanishi, M. Tanaka, Y. Moro-oka, Organometallics
16 (1997) 5572;
(e) J.-P. Djukic, K.H. Dötz, M. Pfeffer, A. De Cian, J. Fischer, Organometallics
16 (1997) 5171;
(f) H. Nakazawa, Y. Yamaguchi, K. Kawamura, K. Miyoshi, Organometallics
16 (1997) 4626;
(g) B. Biswas, M. Sugimoto, S. Sakaki, Organometallics 18 (1999) 4015;
(h) M. Baya, P. Crochet, M.A. Esteruelas, E. Gutierrez-Puebla, N. Ruiz,
Organometallics 18 (1999) 5034;
(i) C.E.F. Rickard, W.R. Roper, T.J. Woodman, L.J. Wright, Chem. Commun.
(1999) 837;
(j) H. Adams, S.G. Broughton, S.J. Walters, M.J. Winter, Chem. Commun.
(1999) 1231;
(k) A.M. Clark, C.E.F. Rickard, W.R. Roper, T.J. Woodman, L.J. Wright,
Organometallics 19 (2000) 1766;
[27] A singlet near 4.6 ppm, which disappeared on shaking, was observed in the
proton NMR spectra and was attributed to free H2: R.H. Crabtree, M. Lavin, L.
Bonneviot, J. Am. Chem. Soc. 108 (1986) 4032.
[28] (a) M.K. Whittlesey, R.N. Perutz, M.H. Moore, Organometallics 25 (1996) 5166;
(b) L.D. Field, E.T. Lawrenz, W.J. Shaw, P. Turner, Inorg. Chem. 39 (2000) 5632.
and references therein.
(l) S. Hermans, B.F.G. Johnson, Chem. Commun. (2000) 1955;
(m) M. Turki, C. Daniel, S. Zális, A. Vlcek Jr., J. van Slageren, D.J. Stufkens, J.
Am. Chem. Soc. 123 (2001) 11431.