Synthesis and structural studies of phosphorus carbonyl manganacycles containing the tetraphenyldiselenoimidodiphosphinato ligand

Article abstract of DOI:10.1016/j.jorganchem.2006.03.027

The [Mn(CO)_4-x(L){Ph₂P(Se)NP(Se)Ph₂-κ ²Se}] complexes, where x = 1 for L = PPh₃ and PMePh₂, and x = 2 for L = Ph₂PCH₂CH₂PPh₂ (diphos), were synth

Full text of DOI:10.1016/j.jorganchem.2006.03.027

Journal of Organometallic Chemistry 691 (2006) 3223–3231
www.elsevier.com/locate/jorganchem
Synthesis and structural studies of phosphorus carbonyl manganacycles
containing the tetraphenyldiselenoimidodiphosphinato ligand
*
´
´
´
Juan Manuel German-Acacio, Marisol Reyes-Lezama, Noe Zuniga-Villarreal
˜
Instituto de Quı´mica, Universidad Nacional Auto´noma de Me´xico, Ciudad Universitaria, Circuito Exterior, 04510 Me´xico, D.F., Mexico
Received 24 February 2006; received in revised form 14 March 2006; accepted 14 March 2006
Available online 18 March 2006
´
Dedicated to Professor Vıctor Riera on the occassion of his 70th birthday.
Abstract
The [Mn(CO)4ꢀx(L){Ph2P(Se)NP(Se)Ph2-j2Se}] complexes, where x = 1 for L = PPh3 and PMePh2, and x = 2 for L = Ph2PCH2-
CH2PPh2 (diphos), were synthesized by two routes. The complexes were characterized by IR, mass spectrometry (FAB+), NMR (1H,
13C, 31P, 77Se) spectroscopy and/or single crystal X-ray diffraction. The X-ray diffraction analysis for [Mn(CO)3PMePh2{Ph2P(Se)NP-
(Se)Ph2-j2Se}] showed that the unit cell contains two independent mononuclear molecules with different MnSePNPSe rings’
conformations.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Manganese(I) complexes; 77Se NMR; Carbonyl substitution reactions; Tetraphenyldiselenoimidodiphosphinato complexes; Tertiary
phosphines
1. Introduction
[13a,13b], Co [14], Rh [2,12b,12c], Ir [12b,15], group 10:
Ni [16], Pd [2,12c,16,17], Pt [2,16,17], and group 11: Cu
[14,18a] Ag [18a,18b,18c] Au [18b,18d,18e]) to rare-earth
metals: Y [19], La, Gd, Er, Yb [20], and Sm [21]. Although
the list of N(SePPh2)2 [22] complexes is certainly long, it is
noteworthy the scarcity of metal carbonyl complexes with
the N(SePPh2)2 fragment (or [N(EPPh2)2]ꢀ; E = O, S for
that matter). In order to fill in this gap we have undertaken
a systematic study of reactivity of group 7 metal carbonyls
towards the [N(EPR2)2]ꢀ (E = O, S, Se; R = Me, Ph)
ligands [11a,23]. The realization that formation of the
[Mn(CO)4{Ph2P-(Se)NP(Se)Ph2-j2Se}] complex was effected
in good yield under mild reaction conditions [11a] opened
up the possibility of studying its reactivity towards Lewis
bases. This led us to the synthesis of the [Mn(CO)4ꢀx(L)-
{Ph2P(Se)NP-(Se)Ph2-j2Se}] complexes, where x = 1 for
L = PPh3, 1, and PMePh2, 2; and x = 2, for L = Ph2PCH2-
CH2PPh2 (diphos), 3, by two routes; consequently, we wish
to report in this paper on the details and assessment of
Routes A and B for the preparation of new carbonylpho-
shinotetraphenylimidodiselenodiphosphinatomanganese(I)
There are many reasons that have been invoked to study
the synthesis and structural behavior of the complexes
involving the tetraphenylimidodichalcogenodiphosphinate
ligands [N(EPPh2)2]ꢀ (E = O, S, Se); some of the principal
ones are as follows: their potential applications in several
fields (e.g. catalysis, metal extraction studies, optoelectron-
ics, NMR shift reagents, to mention a few); their capability
of joining the metal center in different fashions and, at the
same time, adopting several ring conformations in inor-
ganic metallacycles [1]. The fact is that coordination of
the [N(EPPh2)2]ꢀ (E = O, S, Se) anions has been extensively
studied over the last years. It has been found that the ligand
N(SePPh2)2 binds a wide range of atoms varying from main
group elements (K [2], group 12 [3]; Al and Ga [4], In [5], Sn
[3,6], Pb [3], Sb [7], Bi [5,7], Se [8] and Te [9]), transition met-
als (V and Cr [10], Mn [11a] and Re [11], Ru [12], Os
*
Corresponding author. Fax: +52 5616 2203.
E-mail address: zuniga@servidor.unam.mx (N. Zu´niga-Villarreal).
˜
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.03.027

3224
J.M. Germa´n-Acacio et al. / Journal of Organometallic Chemistry 691 (2006) 3223–3231
metallacycles and their characterization in solution and
solid state as well.
NMR (CDCl3, 300 MHz): d/ppm: 7.96 [dd, Ho(PNP),
3JHo–P = 14 Hz], 7.8–7.0 [m, aromatic protons: PNP and
PPh3]. 13C{1H} NMR (CDCl3, 75.6 MHz): d/ppm: 134.05
2. Experimental
[d, Co (PNP), 2JCo–P = 10 Hz]; 132.49 [d, Co (PPh3), 2JCo–P
=
11 Hz], 130.97 [d, Ci (PNP), JCi–P = 22 Hz], 130.82 [d, Ci
(PPh3), JCi–P = 22 Hz], 130.19 [s, Cp (PNP)], 129.67 [s, Cp
All preparative work was conducted in an atmosphere of
dry oxygen free nitrogen, using conventional Schlenk tech-
niques. Solvents were carefully dried; tetrahydrofuran, ethyl
ether, toluene, and hexane were dried and deoxygenated by
distillation from sodium benzophenone ketyl. [MnBr(CO)5],
chlorodiphenylphosphine, hexamethyldisilazane, and pota-
ssium tert-butoxide were acquired from Strem Chemicals,
Co. and used with no further purification except for the chlo-
rodiphenylphosphine, which was distilled under vacuum
(102 ꢁC, 1 mm Hg). Methyldiphenylphosphine, triphenyl-
phospine and diphos (1,2-bis(diphenylphosphino)ethane)
were from Aldrich, Co. Gray selenium was from Fisher Rea-
gents Scientific Company. HN(PPh2)2 [24], HN(SePPh2)2
[17], [K{(SePPh2)2N}] [2], [Mn(CO)4{Ph2P(Se)NP(Se)Ph2-
j2Se}] [11a], [MnBr(CO)4{PPh3}] [25], and [MnBr(CO)3-
{Ph2PCH2CH2PPh2-j2P}] [26] were prepared according to
literature procedures. IR spectra were obtained in solution
(4000–580 cmꢀ1) using a Nicolet FT-IR 55X spectrometer
and in KBr disk (4000–200 cmꢀ1) using a Perkin–Elmer
283B spectrometer. 1H(300 MHz), 13C(75.57 MHz),
31P(121.67 MHz), and 77Se(57.34 MHz) NMR spectra were
recorded in chloroform-d solutions at room temperature
using a Jeol GX300 instrument. The chemical shifts are
3
(PPh3)], 127.9 [d, Cm (PNP), JCm–P = 10 Hz], 127.36 [d,
3
Cm (PPh3), JCm–P = 7 Hz]. 31P{1H} NMR (CDCl3,
121.7 MHz): d/ppm: 48.45 [s(broad), PPh3], 28.3 [d, (PNP),
3JPNP–PPh3 = 21 Hz, {2JSe–PPh3 = 22 Hz1JPNP–Se = 573 Hz
(satellites)}]. 77Se{1H} NMR (CDCl3, 57.34 MHz): d/ppm:
1
2
ꢀ281.7 [dd, JPNP–Se = 573 Hz, JPPh3–Se = 22 Hz]. MS
(m/e): 888, [Mꢀ2CO]+; 598, [Mꢀ(CO)ꢀ(PPh3)]+.
2.1.3. [Mn(CO)3(PMePh2){Ph2P(Se)NP(Se)-
Ph2-j2Se}], 2
0.11 g, 89% yield; m.p. 162–164 ꢁC. IR (KBr): m(CO) 2003
vs, 1923 vs, 1904 vs cmꢀ1; m(P2N) 1177 m, 780 vw cmꢀ1
;
m(PSe) 539 m cmꢀ1. IR (CHCl3): m(CO) 2012 vs, 1938 s,
1906 s cmꢀ1. 1H NMR (CDCl3, 300 MHz): d/ppm: 8.06 [d,
3
broad, Ho(PNP), JHo–P = 11 Hz], 7.43 [m, Hm/p (PNP)],
7.92–7.13 [m, aromatic protons: PNP and PPh2Me], 2.26
2
[d, HMe, PMePh2, JPH = 8 Hz]. 13C{1H} NMR (CDCl3,
75.6 MHz): d/ppm: 138.87 [s, broad, Cp, PMePh2], 138.1
[d, broad, Ci (PNP), JCi–P = 96 Hz], 134.53 [d, broad, Ci
(PMePh2), JCi–P = 36 Hz], 132.27 [s, Cp (PNP)], 132.0 [d,
Co (PNP), JCo–P = 9 Hz], 130.67 [s, broad, Co (PMePh2)],
127.82 [s, broad, Cm (PMePh2)], 15.46 [d, CMe, PMePh2,
JC–P = 26 Hz], 220.88 [s, broad, CO], 217.12 [s, broad,
1
reported in ppm relative to TMS (for H and 13C), H3PO4
(85% aqueous solution for 31P), and Ph2Se2/CDCl3 (set to
463.5 ppm for 77Se), respectively. FAB+ mass spectra were
recorded using a JEOL SX-102A instrument. The melting
points were determined on a Fisher–Johns apparatus and
are uncorrected.
CO]. 31P{1H} NMR (CDCl3, 121.7 MHz): d/ppm: 31.6
3
[s, broad, PMePh2], 28.02 [dd, (PNP), JPNP–PPh2Me
=
22 Hz, {2JSe–PPh2Me = 23 Hz 1JPNP–Se = 578 Hz (satellites)}].
77Se{1H} NMR (CDCl3, 57.34 MHz): d/ppm: ꢀ285.0 [dd,
1JPNP–Se = 578 Hz, JPPh2MeSe = 23 Hz]. MS (m/e): 797,
2
[Mꢀ2CO]+; 597, [Mꢀ(PPh2Me)]+.
2.1. General procedures
2.1.4. [Mn(CO)2(Ph2PCH2CH2PPh2-j2P){Ph2P(Se)-
2.1.1. Route A
NP(Se)Ph2-j2Se}], 3
Synthesis of [Mn(CO)4ꢀx(L){Ph2P(Se)NP(Se)Ph2-j2Se}]
complexes, where x = 1 for L = PPh3, 1, and PMePh2, 2;
and x = 2, for L = Ph2PCH2CH2PPh2 (diphos), 3.
0.1 g (0.14 mmol) of [Mn(CO)4{Ph2(Se)NP(Se)Ph2-
j2Se}] were added to a 100 mL round bottom flask with
stirring containing 30 mL of dry toluene. An equimolar
amount of the corresponding phosphine (PPh3 0.037 g,
PMePh2 0.028 g, and diphos 0.044 g) was dissolved in
40 mL of toluene and transferred via cannula to the reac-
tion flask. After some minutes under reflux (10 min for 1,
5 for 2, and 30 min for 3) the solvent was eliminated under
reduced pressure leaving an oil (1) or a solid (2 and 3).
Crystallization was effected in hexane at 4 ꢁC for several
days yielding crystalline powders in the three cases.
0.087 g, 74% yield; mp 195–196 ꢁC. IR (KBr): m(CO) 2003
vs, 1925 s, 1859 s cmꢀ1; m(P2N) 1175 m, 738 m cmꢀ1; m(PSe)
538 m, 511 m cmꢀ1. IR (CHCl3): m(CO) 1930 vs, 1863 s cmꢀ1
.
1H NMR (CDCl3, 300 MHz): d/ppm: 8.25 [dd, broad,
Ho(PNP), diphos, 3JHH = 6 Hz, 3JHo–P = 11 Hz], 7.83–6.84
3
[m, Hm/p PNP, diphos], 2.9 [dd, CH2CH2 (diphos), JPH
=
59 Hz, JPH = 26 Hz]. 13C{1H} NMR (CDCl3, 75.6 MHz):
d/ppm: 139.67–133.63 [m, Ci, PNP, diphos], 133.21–127.0
[m, Co,m,p PNP, diphos], 28.04 [s, broad, CH2–CH2, diphos].
31P{1H} NMR (CDCl3, 121.7 MHz): d/ppm: 94.37 [s,
3
2
diphos], 66.01 [d, diphos, JPP = 20 Hz], 27.33 [t, PNP,
2
3
3
JPSe = 604 Hz, JPP = 20 Hz, JPSe = 21 Hz, JPNP-diphos
20 Hz], 26.35 [d, PNP, JPSe = 605 Hz, 3JPP = 25 Hz, 3JPSe
=
=
26 Hz]. 77Se{1H} NMR (CDCl3, 57.34 MHz): d/ppm:
ꢀ227.0 [dtd, Se(PN) trans to P(diphos), JPSe = 604 Hz,
2JPSe = 44 Hz, 2JPSe = 44 Hz, 3JPSe = 6 Hz], ꢀ328.17 [dddd,
2.1.2. [Mn(CO)3(PPh3){Ph2P(Se)NP(Se)Ph2-j2Se}], 1
0.09 g, 69% yield; m.p. 157–159 ꢁC. IR (KBr): m(CO) 2005
vs, 1902 vs cmꢀ1; m(P2N) 1177 m, 780 vw cmꢀ1; m(PSe) 540 m
cmꢀ1. IR (CHCl3): m(CO) 2010 vs, 1938 m, 1908 m cmꢀ1. 1H
2
Se(PNP) trans to CO, JPSe = 576 Hz, JPSe(cis)z = 16 Hz,
2JPSe(trans) = 40 Hz, 3JPSe = 8 Hz]. MS (m/e): 996,
[Mꢀ2CO]+; 597, [Mꢀ(diphos)]+.

J.M. Germa´n-Acacio et al. / Journal of Organometallic Chemistry 691 (2006) 3223–3231
3225
Table 2
2.1.5. Route B
Crystal data for cis-[MnBr(CO)3{PMePh2}2], b
Complexes 1, 2, and 3 were synthesized by Route B in a
similar way: in a 100 mL round bottom flask the phosphine
complex was added (0.164 g, 0.32 mmol of [MnBr(CO)4-
(PPh3)]; 0.2 g, 0.32 mmol of [MnBr(CO)3(PMePh2)2]; and
0.2 g, 0.32 mmol of [MnBr(CO)3(diphos)]) to approximately
30 mL of dry toluene. 0.187 g, 0.32 mmol of K[N(Se(PPh2)2]
in 30 mL of toluene were added via cannula and set under
reflux. Reaction times were determined by IR spectroscopy
(1 h for complex 1, 2 h for 2, and 4.5 h for 3). After the reac-
tion was completed the KBr was filtered off leaving a colored
solution (orange for 1, yellow for 2, and dark orange for 3).
Evaporation under vacuum afforded solid materials. The
yields were as follows: 76.0% for 1 (0.23 g, 0.25 mmol);
49.6% for 2 (0.141 g, 0.16 mmol); and 62% for 3 (0.211 g,
0.20 mmol).
Molecular formula
Molecular weight
Temperature (ꢁC)
Crystal size (mm)
Crystal system
C29H26BrMnO3P2 + 0.25 CH2Cl2
640.52
20
0.462 · 0.142 · 0.114
Tetragonal
Iꢀ4
Space group
˚
a (A)
26.574(1)
26.574(1)
8.583(1)
6061.1(8)
8
˚
b (A)
˚
c (A)
3
˚
V (A )
Z
h Range for data collection (ꢁ)
Reflections collected
Independent reflections
1.53–27.57
30,548
7011 (Rint = 0.1404)
Maximum and minimum transmission 0.8176 and 0.5295
Final R indices [F2 > 2r(F2)]
R indices (all data)
R1 = 0.0590, wR2 = 0.0997
R1 = 0.1110, wR2 = 0.1072
2.1.6. Synthesis of [MnBr(CO)3{PMePh2}2], b
[MnBr(CO)5] (2.0 g; 7.27 mmol) was dissolved in 25 mL
of CHCl3 in a 50 mL round bottom flask giving a yellow–
orange solution; after stirring for 10 min a solution of
methyldiphenylphosphine (1.45 g, 7.27 mmol) in 25 mL of
chloroform was added under a stream of dinitrogen. Stir-
ring for 22 h at room temperature and evaporation under
reduced pressure afforded a reddish oil. Extraction with
hexane (3 · 15 mL) and evaporation gave a yellow solid
(1.46 g, 65% yield). IR (KBr): m(CO) 2091 m, 2009 vs,
1960 s cmꢀ1. IR (nujol): m(CO) 2022 s, 1950 vs, 1904 s
2.3. Structures determination
2.3.1. Complexes 2 and 3
Suitable crystals of 2 and 3 were obtained from a
CH2Cl2/hexane 1:1 solution at 4 ꢁC for several days. Data
were collected at 20 ꢁC on a Bruker Smart Apex CCD dif-
fractometer for 62,131 (for 2) and 69,413 (for 3) reflections
of which 13,492 (2) and 18,395 (3) (F > 4.0r(F)) were inde-
pendent (Rint = 11.19% for 2 and 12.12% for 3) and used in
the full-matrix least-squares refinement. The structures
were solved by direct methods. All non-hydrogen atoms
were refined anisotropically. The residual electron densities
from a final difference Fourier synthesis were in the ranges
1
cmꢀ1. H NMR (CDCl3, 300 MHz): d/ppm: 2.26 [d, 6H,
2J(PH) = 9 Hz]; 7.48–7.64 [m, 10H]. 13C{1H} NMR
(CDCl3, 75.6): d/ppm: 128.7 [s, Cm]; 130.7 [s, Cp]; 131.5
[s, Co]; 133.8 [d, Ci, 1J(PC) = 42 Hz]; 210.6, 216.3 [bs,
CO]. 31P{1H} NMR (CDCl3, 121.7): d/ppm: 21.7 [s]. MS
(m/e): 535 [Mꢀ3CO]+, 455 [MꢀBr]+.
˚
of 0.992, ꢀ0.504 for 2 and 1.149 (0.06 A from Se(2)),
ꢀ3
˚
ꢀ0.381 eA for 3.
2.2. Crystal data
2.3.2. Complex cis-[MnBr(CO)3{PMePh2}2], b
Suitable crystals of cis-[MnBr(CO)3{PCH3Ph2}2] were
obtained from a CH2Cl2/hexane (1:1) solution at 4 ꢁC for
See Tables 1 and 2.
Table 1
Crystal data for 2 and 3
2
3
Molecular formula
Molecular weight
Temperature (ꢁC)
Crystal size (mm)
Crystal system
C40H33MnNO3P3Se2
881.44
20
0.326 · 0.298 · 0.058
Monoclinic
C52H44MnNO2P4Se2+CH2Cl2
1136.55
20
0.320 · 0.252 · 0.168
Monoclinic
Space group
P21/c
22.821(1)
17.255(1)
P21/n
17.147(1)
16.456(1)
˚
a (A)
˚
b (A)
˚
c (A)
20.776(1)
18.686(1)
b (ꢁ)
V (A )
110.518(1)
7662.1(7)
105.087(1)
5090.9(5)
3
˚
Z
8
4
h Range for data collection (ꢁ)
Reflections collected
1.58–25.00
62,131
1.67–32.57
69,413
Independent reflections
Maximum and minimum transmission
Final R indices [F2 > 2r(F2)]
R indices (all data)
13,492 (Rint = 0.1119)
0.8723 and 0.4752
R1 = 0.0576, wR2 = 0.0664
R1 = 0.1400, wR2 = 0.0766
18,395 (Rint = 0.1212)
0.76 and 0.5504
R1 = 0.0576, wR2 = 0.0641
R1 = 0.1246, wR2 = 0.0803

3226
J.M. Germa´n-Acacio et al. / Journal of Organometallic Chemistry 691 (2006) 3223–3231
several days. Data were collected at 20 ꢁC on a Bruker
Smart Apex CCD diffractometer for 30,548 reflections (h/
2h scan mode) of which 7011 (F > 4.0r(F)) were indepen-
dent (Rint = 14.04%) and used in the full-matrix least-
squares refinement. The structure was solved by direct
methods. All non-hydrogen atoms were refined anisotrop-
ically. The residual electron density from a final difference
The reaction times were established by monitoring with
IR spectroscopy in the m(CO) region. The reactions, in both
routes, were carried out at toluene reflux temperature; so, it
can be assumed that reaction times reflect the degree of
reactivity of the phosphines towards a. The longer reaction
time for formation of 3 can be accounted for by a second
CO substitution to permit diphos chelation as depicted in
Scheme 2. Variation of the phosphine concentration did
not exert any detectable effect on the reaction yields and/
or reaction times. The stereochemistry of complexes 1
and 2 was dictated by the mutually trans effect of two car-
bonyl groups: no product of labilization of the Mn–Se
bond trans to a carbonyl group was detected. For the dic-
arbonylspiro complex 3 diphos chelation was accomplished
by elimination of a CO group trans to an Mn–Se bond.
Route B (Scheme 3) involves complexes b, c, and d.
Complexes b [25] and d [26] were prepared according to lit-
erature procedures. Complex c was synthesized by mixing
equimolar amounts of [MnBr(CO)5] with PMePh2 in
CHCl3 at room temperature (see Section 2): shorter reac-
tion times led to a poor yield of c. When the reaction
was carried out with two equivalents of phosphine a mix-
ture of products resulted whose work-up turned out to be
extremely laborious rendering exiguous amounts of phos-
phine di- and trisubstitution complexes among other
unidentified products.
ꢀ3
˚
Fourier synthesis was in the range of 0.738, ꢀ0.543 eA
.
3. Results and discussion
3.1. Syntheses
The complexes [Mn(CO)4ꢀx(L){Ph2P(Se)NP(Se)Ph2-
j2Se}], where x = 1 for L = PPh3, 1, and PMePh2, 2; and
x = 2, for L = Ph2PCH2CH2PPh2 (diphos), 3, were pre-
pared by two routes: Route A consisted in the formation of
complexes 1, 2, and 3 by reaction of [Mn(CO)4{Ph2P-
(Se)NP(Se)Ph2-j2Se}] a [11a], with the corresponding phos-
phine under toluene reflux (Scheme 1). In Route B the three
complexes were obtained by reaction of the phosphine pre-
cursors [MnBr(CO)4{PPh3}] b, cis-[MnBr(CO)3{PMePh2}2]
c, and [MnBr(CO)3{diphos}] d, with K[N(Se(PPh2)2] to
afford 1, 2, and 3, respectively.
Complexes 1, 2, and 3 are unstable in solution: after 1 h at
room temperature in dichloromethane complex 1 decom-
posed into a dark precipitate (presumably MnO2) leaving
in solution Ph3P@Se, detected by 31P NMR among other
unidentified phosphine materials. A similar behavior was
detected for complexes 2 and 3 (in the case of complex 3
the monoselenophosphine compound Ph2PCH2CH2-
PPh2(Se) was identified).
Route B can be broken down into two steps: initial
attack of the tetraphenylimidodiselenophosphinate to the
metal center followed by coordination of the selenium
atom with elimination of a neutral ligand (CO or PMePh2).
The reaction times for this route are longer than those for
Route A; if nucleophilic attack of the selenium ligand to
CO
PPh3
Se
Se
OC
Mn
PMePh2
OC
Ph2PCH2CH2PPh2
K[N(Se(PPh2)2]
CO
L
Route A
Complex a
Se
Se
L'
Mn
[MnBr(CO)5]
OC
K[N(Se(PPh2)2]
Br
CO
Complex
PPh3
L
OC
Route B
Mn
1, L = PPh3; L' = CO
2, L = PMePh2, L' = CO
3, L-L' = Ph2PCH2CH2PPh2
PMePh2
L'
OC
Ph2PCH2CH2PPh2
CO
Complex
Se
Se
= Ph2P(Se)NP(Se)Ph2
b, L = PPh3; L' = CO
c, L = L' = PMePh2
d, L-L' = Ph2PCH2CH2PPh2
Scheme 1.

J.M. Germa´n-Acacio et al. / Journal of Organometallic Chemistry 691 (2006) 3223–3231
3227
P
Se
Se
OC
OC
Mn
Complex
1; P = PPh3
P
CO
2; P = PMePh2
Se
Se
CO
OC
OC
Mn
P
CO
Se
Se
P
P
P
a
Mn
OC
diphos
=
=
CO
Complex 3
P
P
Ph2P(Se)NP(Se)Ph2
Se Se
Scheme 2. Route A for formation of 1, 2, and 3.
Br
Se
L
L
L'
toluene
reflux
Se
L''
+ Ph2P(Se)NP(Se)Ph2
+
KBr
Mn
Mn
L'
OC
OC
CO
CO
Complex
Complex
b; L = PPh3, L' and L'' = CO
c; L' = CO, L and L'' = PMePh2
d; L'' = CO, L and L' = diphos
1; L = PPh3, L' = CO
2; L' = CO, L = PMePh2
3; L and L' = diphos
Se Se = Ph2P(Se)NP(Se)Ph2
Scheme 3. Route B for formation of 1, 2, and 3.
the metal center is governed by charge [27]; then, it can be
proposed that formation of intermediates A, B, and C
(shown in Fig. 1) will depend on the electron density at
the metal center. Formation of 1 (from intermediate A) will
be more favored with only one coordinated phosphine.
The second step involves displacement of a neutral two
electron donor ligand (CO or PMePh2). The stereochemis-
try of the resulting complex is governed by the trans effect
(except for complex 3 arising from intermediate C, see
below). In complex 2 the trans effect is exerted on PMePh2
leaving one phosphine in the coordination sphere; while for
complex 3 phosphine decoordination does not take place
due to stabilization of the chelated diphos. The reaction
times of Route B reflect the difficulty with which both
steps, charged and neutral nucleophilic attacks, take place,
being the longest time for the formation of complex 3
(4.5 h). In this respect it is worth mentioning that forma-
tion of complex [Mn(CO)4{Ph2P(Se)NP(Se)Ph2-j2Se}] a
starting from [MnBr(CO)5] (with a proposed intermediate
similar to the ones shown in Fig. 1 with L = L0 = CO)
requires softer reaction conditions (1 h under THF reflux)
[11a].
A comparison of the routes herein reported (both start-
ing from [MnBr(CO)5]) cannot straightforwardly be made
as preparation times of the phosphine precursors
([MnBr(CO)4{PPh3}] b, 24 h, cis-[MnBr(CO)3{PMePh2}2]
c, 22 h, and [MnBr(CO)3{diphos}] d, 10 min under toluene
reflux) drastically vary; however, it can be stated that
Route A is more efficient for the synthesis of 1, 2, and 3.
Se
Se
L
OC
OC
Mn
L'
CO
3.2. Infrared spectroscopy
Intermediate
A
B
C
L = PPh3, L' = CO
L = L' = PMePh2
L and L' = Ph2PCH2CH2PPh2
Complexes 1 and 2 present three bands (in CHCl3) in the
m(CO) carbonyl region corresponding to the 2A0 + A00
vibration modes [28] arising from the carbonyl groups’
local symmetry with a Cs point group. The carbonyl group
Fig. 1. Proposed intermediates for the formation of 1, 2, and 3 by Route B
starting from b, c, and d respectively.

3228
J.M. Germa´n-Acacio et al. / Journal of Organometallic Chemistry 691 (2006) 3223–3231
IR pattern is assigned to mononuclear complexes with fac
disposition, where the selenium PNP ligand is bound
through its two chalcogen atoms. The IR spectrum of com-
plex 3 shows two carbonyl bands derived from a Cs point
group symmetry with vibration modes A0 + A00 due to a
mononuclear complex where both the PNP and the diphos
ligands are attached to the metal center in a chelate fashion
directing the carbonyl groups to a cis arrangement in the
complex. The m(PSe) vibration in the starting material
(K[N(SePPh2)2]) appears at 545 cmꢀ1 in KBr [2]; in the case
of complexes 1–3 the corresponding bands appear around
this value (540, 539, and 538 cmꢀ1 for 1, 2 and 3,
respectively).
atom. The 77Se NMR chemical shifts do not show any
trend which can be straightforwardly accounted for; it
would be desirable to count on more data in order to
explore the governing effects on the 77Se NMR chemical
shifts in these systems; however, 77Se NMR not only
reflects the symmetry in complexes 1, 2, and 3, but also
gives insight into the interaction of the P–Se atoms through
1
the JP–Se coupling constants (Table 3).
It is readily seen from Table 3 that the P–Se coupling con-
stant values increase in the order a < 1 < 2 < 3 <
KN(SePPh2)2 < HN(SePPh2)2. The assumption that a
higher P–Se coupling constant value reflects a stronger inter-
action between both atoms makes evident, for complexes a,
1, 2, and 3, that higher electron density at the metal center
renders a stronger interaction of the P–Se atoms of the
Ph2P(Se)NP(Se)Ph2 ligand. Extrapolation of this reasoning
to compounds KN(SePPh2)2 and HN(SePPh2)2 indicates
that the P–Se strongest interaction shown in Table 3 takes
place when the selenium atom is not involved in any other
bonding apart from its interaction with the phosphorus
atom.
3.3. NMR spectroscopy
Complexes 1 and 2 show a symmetrical coordination of
the Ph2P(Se)NP(Se)Ph2 ligand in solution as evidenced by
the appearance of one signal in 31P- and 77Se NMR spectra.
In complex 3 the coordination of diphos and Ph2P(Se)NP-
(Se)Ph2 ligand in a chelate fashion originate a spiro
compound with four signals: one for each phosphorus
3.4. Structural studies
Table 3
77Se NMR shifts and coupling constants
Complexes b, 1, and 2 were each crystallized in a 1:1
mixture of CH2Cl2/hexane at 4 ꢁC giving adequate crystals
for single-crystal X-ray diffraction analyses. To the best of
our knowledge no crystal structure of complex b has ever
been reported. The geometry around the manganese center
is slightly distorted octahedral with the carbonyl groups in
fac disposition. The molecular structure of b including its
Compound
d (ppm)
1JP–Se (Hz)
Reference
a
ꢀ352.2
ꢀ281.7
ꢀ285.0
ꢀ227.0
ꢀ125.4
ꢀ156.6
562
573
578
604
687
786
[11a]
1
This work
This work
This work
[2]
2
3
KN(SePPh2)2
HN(SePPh2)2
[17]
˚
Fig. 2. Molecular structure of b including atom numbering scheme (ORTEP drawing with 50% probability ellipsoids). Selected bond lengths [A] and
angles [ꢁ]: Mn–Br(1) 2.527(1), Mn–C(1) 1.810(9), Mn–P(1) 2.387(2); P(1)–Mn–C(1) 169.8(2), P(2)–Mn–C(2) 174.5(2), Br(1)–Mn–C(3) 175.4(3).

J.M. Germa´n-Acacio et al. / Journal of Organometallic Chemistry 691 (2006) 3223–3231
3229
atom numbering scheme is shown in Fig. 2 together with
some selected bond distances and angles.
tance Se(1)–Se(2), known as the bite distance, amounts to
3.615 A in 2 and 3.637 A in 2a.
˚
˚
The unit cell of complex 2 contains two independent,
mononuclear molecules (2 and 2a). In Fig. 3 are shown
three dimensional representations of both molecules with
the corresponding atom numbering scheme and some bond
distances and angles germane to the discussion of both
complexes’ solid state structures.
The coordination geometry around the manganese
atoms in 2 and 2a is distorted octahedral.
Fig. 4 shows a three dimensional representation with
corresponding atom numbering scheme and some selected
bond lengths and angles of complex 3.
The inorganic selenium ligand binds symmetrically ren-
dering a six-membered ring manganacycle. Diphos also
coordinates in a chelate fashion to build another ring; this
one with five members to form a spiro compound. Bond
lengths and angles are similar to those in complex 2, except
for the PNP angle: in complex 3 this angle measures
The diselenoimidodiphosphinato ligand is symmetrically
coordinated to Mn through both selenium atoms; the Mn–
Se bond lengths are equivalent within experimental error
˚
(average 2.5372(1) and 2.5362(1) A in 2 and 2a, respec-
tively) indicating
Se) = 2.56 A) [29]. The P–Se and P–N bond distances in
the SePNPSe backbone are also equivalent (average P–Se
a covalent interaction (Rcov (Mn,
˚
˚
and P–N: 2.170(2) and 1.579(2) A in 2, 2.171(2) and
˚
1.584 A in 2a). In compound Ph2P(Se)NHP(Se)Ph2 neither
the P–Se nor the P–N bond lengths are symmetrical (P–
˚
˚
Se = (2.085(1), 2.101(1) A and P–N = 1.678(4), 1.686(3) A
[17]; the equivalence and lengthening of both P–Se bond
distances as well as the shortening and equivalence of both
P–N bond distances in 2 and 2a are indicative of electron
delocalization over the MnSe2P2N metallacycle. The differ-
ence in value of the PNP angle in 2, 2a (139.0(3)ꢁ and
138.4(3)ꢁ, respectively) compared with the PNP angle in a
(130.0(2)ꢁ [11a]) attests to the flexibility of the SePNPSe
backbone (in the gold complex [Au(C6F5)2{(SePPh2)2N}]
the PNP angle measures 121.37(12)ꢁ [18b]).
The MnSePNPSe ring in 2 displays a half-chair confor-
mation with the Mn(1) atom out of the plane (with a devi-
˚
ation of ꢀ1.5369 A) defined by P(2), P(1), Se(1), S(2), and
˚
N(1) (with ꢀ0.0147, 0.0147, ꢀ0.0120, 0.0120, and 0.0760 A
mean deviations, respectively). The preferred conforma-
tions of the MSePNPSe metallacycles are related to the
boat conformation (distorted, pseudo, or twisted boat),
although a half-chair conformation has been reported [9].
In 2a the MnSePNPSe ring shows a distorted boat confor-
mation with the N and Mn atoms at the apices. The dis-
Fig. 4. Molecular structure of 3 with atom numbering scheme (ORTEP
drawing with 50% probability ellipsoids). Selected bond lengths [A] and
angles [ꢁ]; Mn–Se(1) 2.5514(7), Se(1)–P(1) 2.166(1), P(1)–N 1.593(3); P(1)–
N–P(2) 133.5(2), Se(1)–Mn–Se(2) 88.60(2), N–P(1)–Se(1) 117.8(1), P(1)–
Se(1)–Mn 99.83(4).
˚
˚
Fig. 3. Molecular structures of 2 and 2a including atom numbering scheme (ORTEP drawing with 50% probability ellipsoids). Selected bond lengths [A]
and angles [ꢁ]; 2: Mn(1)–Se(1) 2.539(1), Se(1)–P(1) 2.173(2), P(1)–N(1) 1.557(5); P(1)–N(1)–P(2) 139.0(3), Se(1)–Mn(1)–Se(2) 90.87(4), N(1)–P(1)–Se(1)
119.4(2), P(1)–Se(1)–Mn(1) 103.19(6). 2a: Mn(2)–Se(3) 2.538(1), Se(3)–P(3) 2.168(2), P(3)–N(2) 1.482(5); P(3)–N(2)–P(4) 138.5(3), Se(3)–Mn(2)–Se(4)
91.63(4), N(2)–P(3)–Se(3) 118.4(2), P(3)–Se(3)–Mn(2) 101.66(6).

3230
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´
[3] V. Garcıa-Montalvo, J. Novosad, P. Kilian, J.D. Woollins, A.M.Z.
133.5(2)ꢁ which is an intermediate value between a and
2. The MnSePNPSe ring in 3 shows a twisted boat con-
formation with the Mn and N atoms at the apices and a
´
´
´
´
Slawin, P. Garcıa y Garcıa, M. Lopez-Cardoso, G. Espinosa-Perez,
R. Cea-Olivares, J. Chem. Soc., Dalton Trans. (1997) 1025–1029.
[4] M.-A. Munoz-Hernandez, A. Singer, D.A. Atwood, R. Cea-Olivares,
˜
´
˚
bite distance of 3.558 A. The five-membered ring formed
J. Organomet. Chem. 571 (1998) 15–19.
by the MnPCH2CH2P atoms adopts a pseudo-envelope
conformation.
The geometry around the manganese atom in complex 3
is pseudooctahedral. Major causes of distortion arise from
the five- and six-membered rings.
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[6] (a) L. Flores-Santos, R. Cea-Olivares, S. Hernandez-Ortega, R.A.
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(b) R. Cea-Olivares, J. Novosad, J.D. Woollins, A.M.Z. Slawin, V.
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Two routes for formation of complexes of the type
[Mn(CO)4ꢀx(L){Ph2P(Se)NP(Se)Ph2-j2Se}], where x = 1
for L = PPh3 and PMePh2; and x = 2, for L = Ph2PCH2-
CH2PPh2 have been achieved. It has been found Route A
more efficient for the preparation of the complexes herein
reported. For complex 2 the unit cell contains two indepen-
dent, mononuclear molecules (2 and 2a) with different
MnSePNPSe ring conformations. 31P–77Se coupling con-
´
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1
stants, JP–Se, are promising tools to gain insight into the
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2827–2832;
coordination of PNP ligands. An understanding of the
effects governing the 77Se NMR shifts in the imi-
dodiselenodiphosphinato systems, upon coordination, is
yet to be found.
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´
´
The authors thank Messrs E. Garcıa-Rıos, R.A. Tos-
cano, L. Velasco-Ibarra, and M.N. Zavala-Segovia for
technical assistance (Instituto de Quımica, UNAM).
N.Z.-V. gratefully acknowledges funding from PAPIIT
(DGAPA-UNAM) through grant IN217706-2 and the
CONACyT through grant P47263-Q. J.M. G.-A. and
M.R.-L. thank for CONACyT scholarships.
´
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Appendix A. Supplementary data
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Crystallographic data have been deposited for com-
pounds b, 3, and 2 in the Cambridge Crystallographic
Database, CCDC nos. 299076, 299077, and 299078, respec-
tively, in CIF format. Copies of this information may be
obtained free of charge from the Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (Fax: +44 1223
336 033; email: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk). Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2006.03.027.
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