Synthesis, characterization and structures of the novel rhenium(IV) complexes trans-[ReCl4{PPh2(OMe)}2], trans-[ReCl4{PPh2(OEt)}2] and trans-[ReCl4(OPPh3)2]

Article abstract of DOI:10.1016/S0277-5387(99)00017-0

trans-Tetrachlorobis(methyl-diphenylphosphinite)rhenium(IV) and trans-tetrachlorobis(ethyl-diphenylphosphinite)rhenium(IV) were obtained by recrystallization of the corresponding rhenium(III) phosphinite complexes, [ReCl₃L₃], in chlorinated solvents. The structures of the compounds consist of discrete molecules with trans-octahedral coordination geometry around the rhenium atom, having Re-P distances between 2.534(1) and 2.555(2) A and Re-Cl distances in the range 2.321(1)-2.336(1) A. trans-[ReCl₄(OPPh₃)₂] is formed during the reaction of triphenyloxonium tetrafluoroborate with [ReNCl₂(PPh₃)₂]. P-O bond lengths of 2.033(4) A have been found, while the Re-Cl bonds are 2.336(2) and 2.344(2) A, respectively.

Full text of DOI:10.1016/S0277-5387(99)00017-0

Polyhedron 18 (1999) 1495–1499
Synthesis, characterization and structures of the novel rhenium(IV)
complexes trans-[ReCl4hPPh2(OMe)j2], trans-[ReCl4hPPh2(OEt)j2] and
trans-[ReCl4(OPPh3)2]
a
b
b
b
´
Ulrich Abram , Rosa Carballo , Santiago Cabaleiro , Soledad Garcia-Fontan ,
b,
*
´
´
E.M. Vazquez-Lopez
aForschungszentrum Rossendorf, c/o Dresden University of Technology, Institute of Analytical Chemistry, D-01062 Dresden, Germany
b
´
Departamento de Quimica Inorganica, Facultade de Ciencias, Universidade de Vigo, E-36200 Vigo, Galicia, Spain
Received 30 October 1998; accepted 22 December 1998
Abstract
trans-Tetrachlorobis(methyl-diphenylphosphinite)rhenium(IV) and trans-tetrachlorobis(ethyl-diphenylphosphinite)rhenium(IV) were
obtained by recrystallization of the corresponding rhenium(III) phosphinite complexes, [ReCl3L3], in chlorinated solvents. The structures
of the compounds consist of discrete molecules with trans-octahedral coordination geometry around the rhenium atom, having Re–P
˚
˚
distances between 2.534(1) and 2.555(2) A and Re–Cl distances in the range 2.321(1)–2.336(1) A. trans-[ReCl4(OPPh3)2] is formed
˚
during the reaction of triphenyloxonium tetrafluoroborate with [ReNCl2(PPh3)2]. P–O bond lengths of 2.033(4) A have been found, while
the Re–Cl bonds are 2.336(2) and 2.344(2) A, respectively.
˚
1999 Elsevier Science Ltd. All rights reserved.
1. Introduction
2. Experimental
The coordination chemistry of rhenium phosphine com-
plexes is well developed. In contrast, reports of the
phosphinite and phosphine oxides derivatives are exceed-
ingly rare, despite their uneven reactivities as a conse-
quence of their different electronic and steric properties
[1].
[ReCl3hPPh2(OMe)j3],
[ReNCl2(PPh3)2] have been obtained by reported methods
[18,24]. (Ph3O)(BF4) was supplied commercially (Fluka).
[ReCl3hPPh2(OMe)j3]
and
2.1. trans-[ReCl4 hPPh2(OMe)j2 ]
[ReX4L2] derivatives (L5phosphine) have been known
for a long time and some of them have been structurally
characterized [2–8]. These Re(IV) complexes are usually
obtained by reduction of rhenium(V) chloride or oxoch-
loride precursors [5,9–11] or by oxidation of rhenium(III)
halides [12]. The latter process may be performed by the
solvents when they are chlorinated [13]. Alternative meth-
ods are ligand exchange reactions of coordinated solvent
molecules vs. phosphine ligands [14] or bond cleavage
reactions of binuclear complexes [3].
In this paper, we report the synthesis and structural
characterization of the two new rhenium(IV) phosphinite
complexes [ReCl4hPPh2(OMe)j2] and [ReCl4hPPh2-
(OEt)j2] together with those of the phosphine oxide com-
pound [ReCl4(OPPh3)2].
[ReCl3hPPh2(OMej3] (500 mg, 0.53 mmol) was dis-
solved in 10 ml of a CH2Cl2 –CCl4 mixture (1:4, v/v) and
stirred for 24 h. The resulting violet powder was filtered
off and recrystallized from CH2Cl2. Yield, 38%. M.p.:
207–2098C. Found: C, 40.7; H, 3.3%. C26H26Cl4O2P2Re
requires C, 41.1; H, 3.5%. H NMR (CD2Cl2): 18.4 (m,
8H, C6H5 ortho), 10.2 (m, 4H, C6H5 para), 8.8 (m, 8H,
C6H5 meta) and 7.2 (d, 6H, OCH3).
1
2.2. trans-[ReCl4 hPPh2(OEt)j2 ]
This compound was prepared as outlined above for the
methyl derivative starting from [ReCl3hPPh2(OMe)j3].
Yield, 47%. M.p.: 202–2088C. Found: C, 41.8; H, 3.9%.
1
C28H30Cl4O2P2Re requires C, 42.7; H, 3.8%. H NMR
(CD2Cl2): 18.4 (m, 8H, C6H5 ortho), 10.1 (m, 4H, C6H5
para), 8.8 (m, 8H, C6H5 meta), 7.4 (d, 4H, OCH2) and 3.8
(m, 6H, CH3).
*
Corresponding author.
E-mail address: ezequiel@uvigo.es (E.M. Vazquez-Lopez)
´
´
0277-5387/99/$ – see front matter
PII: S0277-5387(99)00017-0
1999 Elsevier Science Ltd. All rights reserved.

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U. Abram et al. / Polyhedron 18 (1999) 1495–1499
2.3. trans-[ReCl4(OPPh3 )2 ]
Scattering factors and anomalous dispersion terms have
been taken from reference [27]. Most calculations were
performed with the programs SHELXS97 [18] and
SHELXL97 [28].
[ReNCl2(PPh3)2] (80 mg, 0.1 mmol) was suspended in
200 ml of CH2Cl2 and (Ph3O)(BF4) (330 mg, 1 mmol)
was added. The mixture was refluxed for 24 h. During this
time, the adduct was only partially dissolved to give a
red–brown solution. The remaining solid (essentially
[ReNCl2(PPh3)2] with a few percent of [ReOCl3(PPh3)2])
was filtered off and the filtrate was reduced in volume to
about 50 ml and stored overnight in a refrigerator, which
resulted in the deposition of red plates at the glass walls.
More product could be obtained by further evaporation of
the solution. Yield, 18 mg (20%). Found: C, 48.1; H, 3.6%.
C36H30Cl4O2P2Re requires C, 48.9; H, 3.4%. IR: n(P=O)
1106 cm21. Magnetic moment (SQUID): 4.21 B.M.
3. Results and discussion
The [ReCl4L2] derivatives (L5PPh2hOMej and
PPh2hOEtj) are obtained in yields .30% by recrystalliza-
tion of the corresponding [ReCl3L3] compounds in chlori-
nated solvents. The oxidation of the rhenium(III) com-
pounds follows a reaction pattern that has previously been
found for phosphine complexes of rhenium [12] and
technetium [15]. The mechanism of this reaction has not
been elucidated. Oxygen may be ruled out as an oxidant in
the case of our reactions. No evidence has been found for
oxidation products of the readily oxidisable phosphinite
ligands that have been potentially released during the
reaction. The activation of halogenated solvents by
rhenium or molybdenum complexes, however, and their
participation in the formation of the products has also been
reported for other reactions [16,17] and suggests a remark-
able catalytic activity of the transition metal complexes
applied.
2.4. X-ray data collection, structure and refinement
Crystallographic measurements were performed on a
CAD4 Enraf-Nonius diffractometer with molybdenum Ka
radiation. Crystal data and experimental conditions are
listed in Table 3. Data were corrected for polarization and
Lorentz effects. C-scan absorption corrections were also
applied [25].
Structure analyses were carried out by the heavy atom
method [26] followed by difference Fourier techniques
until all non-hydrogen atoms were located. All non-H
atoms have been anisotropically refined. The positions of
H-atoms have been calculated geometrically and included
in structure factor calculations.
[ReCl4hPPh2(OMe)j2] and [ReCl4hPPh2(OEt)j2] are
crystalline violet products. They are air-stable and soluble
in common organic solvents such as chloroform, dichloro-
methane, alcohols, dimethylsulfoxide (DMSO), etc. The
1H NMR spectra of the paramagnetic complexes show
typical paramagnetic shifts of the signal positions with
Table 1
Crystal data and structure refinement
[ReCl4hPPh2(OMe)j2]
[ReCl4hPPh2(OEt)j2]
[ReCl4(OPPh3)2]
Empirical formula
Temperature (K)
Wavelength (A)
Crystal system/space group
Unit cell dimensions
C26H26Cl4O2P2Re
293(2)
0.71073
C28H30Cl4O2P2Re
293(2)
0.71073
C36H30Cl4O2P2Re
223(2)
˚
0.71073
Triclinic/P1
¯
Monoclinic/C2/c
Monoclinic/P21 /n
˚
˚
˚
a59.372(4) A
a515.998(3) A
a59.621(1) A
˚
˚
˚
b59.122(1) A
b515.756(2) A
b59.682(4)A
˚
˚
˚
c519.655(3) A
c510.239(2) A
c510.422(5) A
a5102.26(2)
b5108.75(2)8
g593.47(2)8
866.6(6)
b5101.54(1)8
b5104.29(1)8
3
˚
Volume (A )
2810.3(7)
1504.1(4)
Z
4
2
1
Crystal size (mm3)
u range for data collection (8)
h,k,l index range
Reflections collected
0.2530.2530.15
3–27
0,21; 0,12; 225,25
3491
0.2030.2030.15
3–27
0,11; 219,0; 212,12
3215
0.1530.1030.05
3–25
21,11; 211,11; 212,12
3893
Independent reflections (Rint
Reflections observed, criterion
Refinement method
)
3376 (0.0302)
2397, I.2s(I)
3034 (0.0371)
1949, I.2s(I)
Full-matrix least-squares on F2
3034/0/209
1.022
3057 (0.0247)
2906, I.2s (I)
Data/restraints/parameters
3376/0/160
1.023
3057/0/205
1.097
Goodness-of-fit on F2
Final R indices R1, wR2 [I.2s(I)]
wR2 [I.2s(I)]
0.0308, 0.0728
0.0307, 0.0542
0.037, 0.0754

U. Abram et al. / Polyhedron 18 (1999) 1495–1499
1497
respect to those expected for diamagnetic compounds [18].
The paramagnetism of reactives and products prevented us
from monitoring the reaction course by NMR spectros-
copy.
[ReCl4(OPPh3)2] is formed from the reaction of
[ReNCl2(PPh3)2] with (Ph3O)(BF4) in low yields. The
attempted attack of the triphenyloxonium cation at the
nucleophilic nitrido ligand of the rhenium(V) complex
could not be observed. During a refluxing period of 24 h in
CH2Cl2, however, a considerable amount of the sparingly
soluble [ReNCl2(PPh3)2] dissolved to give a red–brown
solution, from which red crystals of [ReCl4(OPPh3)2] have
been isolated. The remaining, insoluble solid contained,
besides the adduct, small amounts (approximately 5%) of
[ReOCl3(PPh3)2], which has been detected by IR spec-
troscopy.
[ReCl4(OPPh3)2] is soluble in hot CH2Cl2 and CHCl3
and can be recrystallized from those solvents to give red
plates. The compound is paramagnetic, with an effective
magnetic moment of meff54.21 B.M. The infrared spec-
trum shows the n(P=O) frequency at 1106 cm21. This
value is comparable with those that have been found for
[Re(NCS)4(PPh3)(OPPh3)] (1116 cm21) [19] and a num-
ber of ReII nitrosyl complexes containing triphenylphos-
phine oxide ligands with n(P=O) bands between 1105 and
1220 cm21 [20].
Fig. 1. ZORTEP [21] representation of the molecular structure of
[ReCl4hPPh2(OMe)j2]. Thermal ellipsoids represent 50% probability.
phosphinite derivatives, the ligands are oriented differently
with respect to the ReCl4 plane. The vector P(1)–O(1) lies
almost on the vector Re–Cl(2)i as can be seen in the value
3.1. Crystal structures
The molecular structure of the complexes trans-[Re-
Cl4hPPh2(OMe)j2] and trans-[ReCl4hPPh2(OEt)j2] are
shown in Figs. 1 and 2 and important bond distances and
angles are listed in the accompanying Table 1. A ZORTEP
representation [21] of trans-[ReCl4(OPPh3)2] is given in
Fig. 3, and the corresponding bond lengths and angles are
summarized in Table 2.
In all three structures, the rhenium atoms are situated on
symmetry centers imposing the essentially D4h symmetry
in the complexes. Therefore, all trans angles are equal to
1808 and the cis angles are all close to 908.
The Re–Cl and Re–P distances within the ReCl4P2
octahedra of the phosphinite complexes are similar to those
found in the structurally characterized tetrachlorobis(phos-
phine)rhenium(IV) derivatives trans-[ReCl4(PMe2Ph)2]
[6], trans-[ReCl4(PPh3)2] [4,5], trans-[ReCl4(PEt3)2] [3]
and trans-[ReCl4hP(m-tol)3j2] [8] and also agree with
those in the only cis-diphosphine derivative [ReCl4(dppe)]
[2]. All of these complexes, including those of the present
work, show Re–Cl distances ranging between 2.32 and
˚
˚
2.40 A and Re–P distances ranging from 2.51 to 2.55 A.
The latter, as has been reported by Engelhardt et al. ( [6],
see also ref. [22]), suggests that effects other than elec-
tronic effects should dominate the chlorine attachment to
rhenium.
Fig. 2. ZORTEP [21] representation of the molecular structure of
Although the rhenium kernel is very similar in the two
[ReCl4hPPh2(OEt)j2]. Thermal ellipsoids represent 50% probability.

1498
U. Abram et al. / Polyhedron 18 (1999) 1495–1499
Table 2
Table 3
Selected bond lengths and angles for [ReCl4(OPPh3)2]a
˚
Selected bond lengths (A) and angles (8) for [ReCl4hPPh2(OMe)j2] and
[ReCl4hPPh2(OEt)j2]
Re–O(1)
Re(1)–Cl(1)
Re(1)–Cl(2)
P(1)–O(1)
2.034(4)
P(1)–C(10)
1.777(6)
1.781(7)
1.787(7)
[ReCl4hPPh2(OMe)j2]a
[ReCl4hPPh2(OEt)j2]b
2.3438(17) P(1)–C(20)
2.3362(16) P(1)–C(30)
1.444(5)
Re–Cl(1)
Re–Cl(2)
Re–P(1)
P(1)–O(1)
P(1)–C(21)
P(1)–C(11)
O(1)–C(1)
2.3209(13)
2.3364(12)
2.5342(13)
1.598(3)
1.829(5)
1.808(5)
2.3273(14)
2.325(2)
2.555(2)
1.600(4)
1.802(6)
1.821(6)
1.441(8)
1.427(10)
90.11(6)
89.89(6)
90.63(6)
89.77(5)
89.37(6)
90.23(5)
100.6(3)
105.9(3)
104.8(3)
113.9(2)
112.8(2)
117.1(2)
123.9(4)
111.6(7)
O(1)i–Re(1)–O(1)
O(1)–Re(1)–Cl(2)i
O(1)–Re(1)–Cl(2)
O(1)–Re(1)–Cl(1)i
Cl(2)i–Re(1)–Cl(1)i
Cl(2)–Re(1)–Cl(1)i
180.0
P(1)–O(1)–Re(1)
156.2(3)
110.8(3)
106.8(3)
89.14(14)
90.86(14)
89.32(14)
90.33(6)
89.67(6)
O(1)–P(1)–C(10)
O(1)–P(1)–C(20)
C(10)–P(1)–C(20) 109.5(3)
O(1)–P(1)–C(30) 112.1(3)
C(10)–P(1)–C(30) 107.9(3)
C(20)–P(1)–C(30) 109.7(3)
1.460(6)
C(1)–C(2)
Cl(1)i–Re(1)–Cl(1) 180.0
Cl(2)–Re–Cl(1)i
Cl(2)–Re–Cl(1)
Cl(2)–Re–P(1)
Cl(1)–Re–P(1)
Cl(2)–Re–P(1)i
Cl(1)–Re–P(1)i
89.40(5)
90.60(5)
87.66(4)
90.10(5)
92.34(4)
89.90(5)
ai52x, 2y, 2z.
comparable with that of the phosphinite complexes. The
Re–O bond length of 2.033(4) A is slightly longer than
that in cis-[Re(NCS)4(PPh3)(OPPh3)], where a length of
2.018 A has been found [19] but it is similar to that in the
O(1)–P(1)–C(21) 105.4(2)
O(1)–P(1)–C(11) 100.3(2)
C(21)–P(1)–C(11) 103.0(2)
O(1)–P(1)–Re
C(21)–P(1)–Re
C(11)–P(1)–Re
˚
˚
112.7(2)
120.0(2)
113.1(2)
˚
mixed halide [ReBr2.5Cl1.5(OPPh3)2] [2.030(7) A], which
was reported recently [23]. This is surprising, since the
Re–N bond distances in the rhenium(IV) isothiocyanato
complex suggest an increase of the structural trans in-
fluence in the order OPPh3,NCS2#PPh3. Re–O dis-
C(1)–O(1)–P(1) 119.4(3)
C(2)–C(1)–O(1)
ai52x11/2, 2y11/2, 2z. bi52x, 2y, 2z.
˚
tances between 2.020 and 2.075 A have been found for a
number of rhenium(II) nitrosyl compounds with tri-
phenylphosphine oxide ligands [20]. For those complexes,
shorter bonds are also evident when PPh3 or OPPh3 are
situated in a cis-arrangement to the triphenylphosphine
oxide ligand regarded. The longest Re–OPPh3 bond has
been found in a trans position to NO1.
of the torsion angle O(1)–P(1)–Re–Cl(2)9 [1.6(2)8] in
trans-[ReCl4hPPh2(OMe)j2] (I), while the same angle is
wider
Cl4hPPh2(OEt)j2] (II).
The bonding situation in trans-[ReCl4(OPPh3)2] is
by
24.8(2)8
in
compound
trans-[Re-
Fig. 3. ZORTEP [21] representation of the molecular structure of [ReCl4(OPPh3)2]. Thermal ellipsoids represent 50% probability.

U. Abram et al. / Polyhedron 18 (1999) 1495–1499
[12] G. Rouschias, G. Wilkinson, J. Chem. Soc. A (1967) 993.
1499
Supporting information available:
[13] J. Chatt, G.J. Leigh, D.M.P. Mingos, R.J. Paske, J. Chem. Soc. A
(1968) 2636.
[14] G. Rouschias, G. Wilkinson, J. Chem. Soc. A (1968) 489.
[15] U. Amazzi, G. de Paoli, P. di Bernardo, L. Magon, J. Inorg. Nucl.
Chem. 38 (1976) 721.
More details of the crystal structure determinations
have been deposited with the Cambridge Crystallographic
Data
Center
with
the
deposition
104995
[16] D.L. Hughes, S.K. Ibrahim, C.L. Macdonald, H.M. Ali, C.J. Pickett,
J. Chem. Soc. Chem. Commun. (1992) 1762.
numbers
104994
([ReCl4hPPh2(OMe)j2]),
([ReCl4hPPh2(OEt)j2]) and 104996 ([ReCl4(OPPh3)2]).
¨
[17] S. Ritter, R. Hubener, U. Abram, J. Chem. Soc. Chem. Commun.
(1995) 2047.
´
[18] S. Garcıa-Fontan, A. Marchi, L. Marvelli, R. Rossi, S. Antoniutti, G.
References
Albertin, J. Chem. Soc. Dalton Trans. (1996) 2779.
¨
[19] R. Hubener, U. Abram, Inorg. Chim. Acta, 211 (1993) 121.
¨
[20] U. Abram, A. Voigt, R. Kirmse, K. Ortner, R. Hubener, R. Carballo,
[1] C.A. Tolman, Chem. Rev. 77 (1977) 3.
[2] J.A. Jaecker, W.R. Robinson, R.A. Walton, Inorg. Nucl. Chem. Lett.
10 (1974) 93.
[3] J. Bucknor, F.A. Cotton, L.R. Falvello, A.H. Reid, L.D. Schmul-
back, Inorg. Chem. 25 (1986) 1021.
[4] H. Kraudelt, U. Schilde, E. Uhlemann, Z. Anorg. Allg. Chem. 621
(1995) 1797.
[5] J.O. Dziegielenski, B. Machura, T.J. Bartczak, Polyhedron 15
(1996) 2913.
[6] L.M. Engelhardt, B.N. Figgis, A.N. Sobolev, P.A. Reynolds, Aust. J.
Chem. 49 (1996) 489.
[7] H. Luo, C. Orvig, S.J. Rettig, Acta Crystallogr. C52 (1996) 1377.
[8] C. Pearson, A.L. Beauchamp, Inorg. Chim. Acta 237 (1995) 13.
[9] K.V. Kotegov, G.N. Sedova, Z.A. Lorchikova, Y.N. Kabushkin, Zh.
Neorg. Khim. 24 (1979) 3301.
[10] J. Chatt, J.D. Garforth, N.P. Johnson, G.A. Rowe, J. Chem. Soc.
(1964) 601.
[11] G. Rouschia, G. Wilkinson, J. Chem. Soc. A (1966) 465.
E.M. Vazquez-Lopez, Z. Anorg. Allg. Chem. 624 (1998) 1662.
[21] L. Zsolnai, ZORTEP — a program for the ellipsoid representation of
crystal structures, University of Heidelberg, 1997.
[22] L. Aslanov, R. Mason, A.G. Wheeler, P.O. Whimp, J. Chem. Soc.
Chem. Com. (1970) 30.
[23] S.M. Harben, P.D. Smith, R.L. Beddoes, M. Helliwell, D. Collison,
C.D. Garner, Acta Crystallogr. C54 (1998) 941.
[24] U. Abram, M. Braun, S. Abram, R. Kirmse, A.Voigt, J. Chem. Soc.,
Dalton Trans. (1998) 231.
[25] A.C.T. North, D.C. Phillips, F. Scott Mathews, Acta Crystallogr.
A24 (1968) 351.
[26] G.M. Sheldrick, SHELXS97. A Program for the Solution of Crystal
Structure from X-Ray Data, University of Gottingen, 1997.
[27] International Tables for Crystallography, vol. C, Kluwer, Dordrecht,
1992.
¨
[28] G.M. Sheldrick, SHELXL97. A Program for the Refinement of
¨
Crystal Structures from X-ray Data, University of Gottingen, 1997.