Photochemical reactions of Re(CO)5Br with Ph2P(S) (CH2)nP(S)Ph2 (n = 1,2,3)

Article abstract of DOI:10.1515/znb-2004-0715

The complexes fac-[Re(CO)₃Br{Ph₂P(S)(CH ₂)nP(S)Ph₂}] [1a, n = 1; 2a, n = 2; 3a, n = 3] and [Re₂(CO)₈Br₂{μ-Ph₂P(S)(CH ₂)_nP(S)Ph₂}] [1b,

Full text of DOI:10.1515/znb-2004-0715

836
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give the chelate complexes [M(CO)4{R2P(S)P(S)R2}]
(R = Me, Et, Prn, Bun) [11 – 13], where the ligand
is presumed to adopt the expected cis-chelate biden-
tate coordination. However, in certain cases, the ligand
bridges between two metals affording [M2(CO)10{µ-
R2P(S)P(S)R2}] (R = Me, Et, Prn, Bun) [14] as sec-
ondary products.
In this paper we report the preparation and charac-
terization of new complexes fac-[Re(CO)3Br{Ph2P(S)
(CH2)nP(S)Ph2}] [la, n = 1; 2a, n = 2; 3a, n = 3]
and [Re2(CO)8Br2 {µ-Ph2P(S)(CH2)nP(S)Ph2}] [1b,
n = 1; 2b, n = 2; 3b, n = 3] which were prepared
by photochemical reactions between Re(CO)5Br with
Ph2P(S)(CH2)nP(S)Ph2 (n = 1, 2, 3). The results of
suggest cis-chelate bidentate coordination of the lig-
and in fac-[Re(CO)3Br{Ph2P(S)(CH2)nP(S)Ph2}] and
bridging coordination of the ligand between two met-
als in Re2(CO)8Br2{µ-Ph2P(S)(CH2)nP(S)Ph2}] (n =
1, 2, 3).
Photochemical Reactions of Re(CO)5Br
with Ph2P(S)(CH2)nP(S)Ph2 (n = 1, 2, 3)
Elif Subasia, Ozan Sanlı Sentu¨rka,b
,
and Fadime Ugur (Sarikahya)a
a Ege University, Faculty of Science, Department of
Chemistry, Bomova, 35100, Izmir, Turkey
b Steacie Institute for Molecular Sciences, National Research
Council of Canada, 100 Sussex Drive, Ottawa, Ontario,
Canada, K1A 0R6
Reprint requests to Dr. O. S. Sentu¨rk.
Z. Naturforsch. 59b, 836 – 838 (2004);
received April 7, 2003
The complexes fac-[Re(CO)3Br{Ph2P(S)(CH2)nP(S)Ph2}]
[la, n = 1; 2a, n = 2; 3a, n = 3] and [Re2(CO)8Br2{µ-
Ph2P(S)(CH2)nP(S)Ph2}] [1b, n = 1; 2b, n = 2; 3b, n =
3] have been prepared by the photochemical reaction of
Re(CO)5Br with Ph2P(S)(CH2 )nP(S)Ph2. The products have
been characterized by elemental analysis, mass spectroscopy,
FT-IR and 31 P-[1H]-NMR spectrometry. The results suggest
cis-chelate bidentate coordination of the ligand in fac-1a –
3a and cis-bridging bidentate coordination of the ligand be-
tween two metals in 1b – 3b.
Result and Discussion
The photogenerationof M(CO)5 from M(CO)6 (M =
Cr, Mo or W) has been extensively studied. These
16-electron M(CO)5 fragments react avidly with any
available donor to form M(CO)5L species, and where
L is a chelating bidentate ligand, rapid continuation
to the chelating M(CO)4L or bridging M2(CO)10(µ-L)
products may occur [10– 14, 16]. The photochemical
reactions of Re(CO)5Br with Ph2P(S)(CH2)nP(S)Ph2
(n = 1, 2, 3) proceed in this expected manner to yield
Key words: Diphosphines, Metal Carbonyls
Introduction
The use of biphosphines, Ph2P(CH2)nPPh2, as che- the hitherto unknown series of complexes 1a – 3a and
lating or bridging ligand is well known. The chem-
istry of complexes of dppm, Ph2PCH2PPh2, was re-
viewed by Puddephatt [1], and more recently by Poil-
blanc [2, 3]. Work on related diphosphine disulfide lig-
ands has been much less extensive, but P,S-coordina-
tion has been reported for Ph2PCH2P(S)Ph2 [4, 5], and
S- or S,S-coordination for Ph2P(S)CH2P(S)Ph2 [6 – 8].
Metal complexes of phosphine and arsine sulphides
and selenides have been reviewed [9].
We have recently reported the preparation and
characterization of new complexes fac-[Re(CO)3Br
{R2P(S)P(S)R2}] and [Re2(CO)8Br2{cis-µ-R2P(S)
P(S)R2}] (R = Me, Et, Prn, Bun, Ph), which were pre-
pared by photochemical reactions between Re(CO)5Br
with Ph2P(S) P(S)Ph2 [10]. We have also previously
discovered a photochemical reaction of M(CO)6 (M =
Mo, W) with R2P(S)P(S)R2 (R = Me, Et, Prn, Bun) to
1b – 3b.
The infrared spectra of the [Re(CO)3BrL-L] com-
pounds are consistent with a fac-structure in which
ligands L-L are cis to the Br. There are three strong
carbonyl bands allowing an unequivocal assignment
of [Re(CO)3BrL-L] compounds as the fac-isomer of
CS symmetry. The three carbonyl stretching vibrations
belong to the symmetry classes of the point group as
follows (τ = 2A” + A’) [17, 18]. The infrared spectra
of the [Re2(CO)8Br2{cis-µ-L-L}] compounds are con-
sistent with a structure in which the donor centers of
L-L are cis to the Br. As expected, four bands arising
from ν(CO) vibrations are seen for each complex 1b –
3b which presumably have local C2v symmetry of the
M(CO)4 unit. The ν(CO) modes of 1a – 3a and 1b – 3b
are shifted to lower wavenumbers when compared with
the starting Re(CO)5Br molecules [19].
c
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Fig. 1. The photochemical reactions of Re(CO)5Br with Ph2P(S)(CH2)nP(S)Ph2 (n = 1, 2, 3).
The 31P-[1H] NMR spectra of complexes 1a– 3a spectra were recorded on Micromass VG Platform-II LC-
¨
MS at TUBITAK. UV irradiations were performed with a
and 1b – 3b, show only one signal in each case. The
δP values of the coordinated ligands are at higher field
than those of the free ligands, and the coordinated cis-
bridging ligands are at higher field compared to ligands
coordinated in a cis-chelating mode [20].
The mass spectral data of 1a– 3a and 1b – 3b are
given in Table 3. The mass spectra show fragmentation
via successive loss of CO groups and fragmentation of
the organic ligands.
We therefore have shown that the photochemi-
cal reactions between Re(CO)5Br and Ph2P(S)(CH2)n
P(S)Ph2 (n = 1, 2, 3) leads to two series of products,
which have the donor center in metal cis-position and
cis to the halide ligand.
medium-pressure 400 W mercury lamp through a quartz-
walled immersion well reactor. Pentane, benzene, hexane,
CH2Cl2, Me2CO, toluene and silica gel were purchased
from Merck, and Re(CO)5Br, was purchased from Aldrich.
dppm(S)2, dppe(S)2 and dppp(S)2 were prepared by litera-
ture methods [15].
The complexes, fac-[Re(CO)3Br{Ph2P(CH2)nPPh2}]
1a – 3a and [Re2(CO)8Br2{µ-R2P(S)P(S)R2}], were pre-
pared by the photochemical reactions of Re(CO)5Br with
Ph2P(CH2)nPPh2 (n = 1, dppm; 2, dppe; 3, dppp) and
obtained in 40 –60% yield by similar methods of which the
following is typical.
Syntheses
The components Re(CO)5Br (0.8 g, 2 mmol) and
dppm(S)2 (0.45 g, 1 mmol) were dissolved in tetrahydro-
furan (80 – 100 ml) and the solution was irradiated for 2 h
using a 400 W medium pressure mercury lamp through a
Experimental Section
General
Reactions were carried out under dry nitrogen by using quartz-walled immersion well reactor. During the irradiation,
Schlenk techniques. All solvents were dried and degassed the colour of the solution changed from colourless to dark
prior to use. Elemental analyses were carried out using a yellow. After the irradiation the solvent was evaporated in
LECO-CHNS-O-9320 instrument by the Technical and Sci- a vacuum resulting in a dark-yellow solid which was ex-
entific Research Council of Turkey, TUBITAK. FT-IR spec- tracted into dichloromethane (10 ml). Addition of petroleum
tra were recorded on samples in hexane at the Ege Uni- ether (50 ml) resulted in precipitation of a dark yellow solid
versity on a Mattson 1000 FT spectrophotometer. 31P[1H] which was washed with petroleum ether dried in a vacuum,
NMR spectra were recorded in CDC13/CD2C12 at UCL on and shown to be fac-[Re(CO)3Br{Ph2P(S)CH2P(S)Ph2}],
a BRUKER DPX-400 and 400 MHz High Performance Dig- 1a, (42% yield). The yellow solution was evaporated and
ital Ft-NMR instrument (TUBITAK). Electron impact mass the residue separated chromatographically through a col-
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umn packed with silica gel using n-pentane as an eluant.
A yellow fraction was isolated and dried in vacuo to give 2105 (m, C=O), 2018 (m, C=O), 1916 (m, C=O), 1876 (m,
Re2(CO)8(µ-dppeS2)Br2 2b: Yield: 40%. IR (KBr): ν =
[Re2(CO)8Br2{µ-Ph2 P(S)CH2P(S)Ph2}], 1b, (39% yield).
C=O). – 31P[1H] NMR (400 MHz, DMSO): δ = 45.86. –
Re(CO)5(dppmS2)Br,1a: Yield: 40%. IR (KBr): ν = 2018 MS (EI, 70 eV): m/z (%) = 812 (25) [M+ – ReBr(CO)4-
(m, C=O), 1916 (m, C=O), 1876 (m, C=O). – 31P[1H] NMR CO]; 784 (20) [M+ – ReBr(CO)4-2CO]; 756 (90) [M+
–
(400 MHz, DMSO): δ = 36.24. – MS (EI, 70 eV): m/z (%) = ReBr(CO)4-3CO]; 728 (90) [M+ – ReBr(CO)4-4CO]; 648
798 (35) [M+]; 770 (25) [M+–CO]; 742 (10) [M+–2CO]; (20) [M+ – ReBr(CO)4-4CO-Br]. – C34H24O8Re2P2S2Br2
714 (20) [M+ – 3CO]. −C28H22O3ReP2S2Br (798.7): calcd. (1218.4): calcd. C 33.50, H 1.98, S 5.26; found C 33.41,
C 42.11, H 2.78, S 8.03; found C 42.38, H 2.51, S 8.34.
H 1.93, S 5.34.
Re(CO)5(dppeS2)Br, 2a: Yield: 50%. IR (KBr): ν = 2008
Re2(CO)8(µ-dpppS2)Br2, 3b: Yield: 40%. IR (KBr): ν =
(m, C=O), 1914 (m, C=O), 1874 (m, C=O). – 31P[1H] NMR 2106 (m, C=O), 2010 (m, C=O), 1983 (m, C=O), 1924 (m,
(400 MHz, DMSO): δ = 32.71. – MS (EI, 70 eV): m/z (%) = C=O). – 31P[1H] NMR (400 MHz, DMSO): δ = 53.11. –
812 (15) [M+]; 784 (35) [M+- CO]; 756 (90) [M+-2CO]; MS (EI, 70 eV): m/z (%) = 854 (30) [M+ – ReBr(CO)4];
728 (75) [M+ −3CO]; 648 (20) [M+ −3CO − Br]. – 826 (5) [M+ – ReBr(CO)4-CO]; 798 (20) [M+ – ReBr(CO)4-
C29H24O3ReP2S2Br (812.7): calcd. C 42.86, H 2.98, S 7.89; 2CO]; 770 (10) [[M+ – ReBr(CO)4-3CO]; 742 (10) [M+
found: C 42.62, H 2.81, S 7.95.
–
ReBr(CO)4-4CO]; 762 (30) [M+ – ReBr(CO)4-4CO-Br)]. –
Re(CO)5(dpppS2)Br, 3a: Yield: 40%. IR (KBr): ν = 2006 C35H26O8Re2P2S2Br2 (1232.8): calcd. C 34.10, H 2.13,
(m, C=O), 1982 (m, C=O), 1925 (m, C=O). – 31P[1H] S 5.20; found C 34.19, H 2.21, S 5.29.
NMR (400 MHz, DMSO): δ = 40.25 − MS (EI, 70 eV):
For the mass spectral data relative intensities are given in
m/z (%) = 826 (10) [M+]; 798 (100) [M+-CO]; 770 (50) parentheses; probable assignments in square brackets. For all
[M+-2CO]; 662 (20) [M+-3CO-Br]. – C30H26O3ReP2S2Br assignments the most abundant isotopes of Re and Br have
(826.7): calcd. C 43.59, H 3.17, S 7.76; found C 43.33, been selected (187Re, 62.9% abundant, 79Br, 50.5% abun-
H 3.29, S 7.55.
dant).
Re2(CO)8(µ-dppmS2)Br2, 1b: Yield: 40%. IR (KBr):
ν = 2105 (m, C=O), 2018 (m, C=O), 1916 (m, C=O),
1876 (m, C=O). – 31P[1H] NMR (400 MHz, DMSO): δ =
Acknowledgements
We thank BP (Turkey) for the provision of the photochem-
ical apparatus and Research Foundation of Ege University
for funds. We thank TUBITAK for allocation of time at the
NMR, mass spectrometer and for elemental analyses.
65.25. – MS (EI, 70 eV): m/z (%) = 799 (20) [M+
–
ReBr(CO)4-CO]; 770 (40) [M+ – ReBr (CO)4-2CO)]; 742
(100) [M+ – ReBr(CO)4-3CO]; 714 (60) [M+ – ReBr(CO)4-
4CO]. – C33H22O8Re2P2S2Br2 (1204.8): calcd. C 32.90,
H 1.84, S 5.32; found C 32.87, H 1.89, S 5.39.
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