P-C versus C-H bond cleavage in coordinated bis(dimethylphosphino)methane: Controlled access to either phosphinite or functionalized diphosphine complexes

Article abstract of DOI:10.1039/b305316d

Treatment of fac-[Mn(CNPh)(CO)₃(dmpm)]ClO₄ (1) with KOH affords neutral phosphinite complex fac[Mn(PMe₂O)(CNPh)(CO)₃(PMe₃)] (2) as a result of P-C bond cleavage on the dmpm ligand, whereas when carrying out the reaction in the presence of iodine the diphosphinoketenimine derivative fac-[MnI(CO)₃-{(PMe₂)₂C=C=NPh}] (4) is obtained after deprotonation and further functionalization of the central carbon atom of the diphosphine.

Full text of DOI:10.1039/b305316d

P–C versus C–H bond cleavage in coordinated
bis(dimethylphosphino)methane: controlled access to either phosphinite
or functionalized diphosphine complexes
Roberto Quesada,a Javier Ruiz,*a Víctor Riera,a Santiago García-Grandab and M. Rosario Díazb
a Departamento de Química Orgánica e Inorgánica, Facultad de Química, Universidad de Oviedo, 33071
Oviedo, Spain. E-mail: jruiz@sauron.quimica.uniovi.es; Fax: (+34) 985103446
b Departamento de Química Física y Analítica, Facultad de Química, Universidad de Oviedo, 33071
Oviedo, Spain
Received (in Cambridge, UK) 15th May 2003, Accepted 17th June 2003
First published as an Advance Article on the web 1st July 2003
Treatment of fac-[Mn(CNPh)(CO)3(dmpm)]ClO4 (1) with
KOH affords neutral phosphinite complex fac-
[Mn(PMe2O)(CNPh)(CO)3(PMe3)] (2) as a result of P–C
bond cleavage on the dmpm ligand, whereas when carrying
out the reaction in the presence of iodine the
asymmetric unit featuring very similar structural parameters. A
view of one of them is presented in Figure 1 together with
selected bond lengths and angles
diphosphinoketenimine
derivative
fac-[MnI(CO)3-
{(PMe2)2CNCNNPh}] (4) is obtained after deprotonation
and further functionalization of the central carbon atom of
the diphosphine.
Basic treatment of complexes containing diphosphinomethane
ligands usually produces deprotonation of the central carbon
atom with formation of diphosphinomethanide derivatives,1
which are useful reagents for the synthesis of functionalized
diphosphines.2 Moreover, it has been reported that basic
treatment of [PtCl2dppm] produces the cleavage of a P–C bond
of the diphosphine leading to different polynuclear species
containing phosphinite ligands depending upon the conditions
employed.3 It is of note that P–C bond cleavage plays an
important role in deactivation pathways of phosphine com-
plexes used as homogeneous catalysts4 and is an active field of
work.5 In this communication, we report the first example of a
coordinated diphosphine in which both C–H and P–C bond
cleavages can be achieved selectively by choosing the appro-
priate reaction conditions, providing controlled access to either
phosphinite complexes or diphosphinomethanide derivatives.
Reaction of fac-[Mn(CNPh)(CO)3dmpm]ClO4 (1)6† with an
excess of KOH in CH2Cl2 produces, after 2 h of stirring at room
temperature, the scission of a P–C bond of dmpm affording
neutral phosphinite complex fac-[Mn(PMe2O)(CNPh)-
(CO)3(PMe3)] (2), a process which has no precedent in the case
of alkylic diphosphines. As shown in Scheme 1, a mechanism
can be assumed for this reaction involving nucleophilic attack
of OH2 anion to a phosphorus atom, forming a transient
complex containing hydroxydimethylphosphine and dimethyl-
phosphinomethanide ligands, followed by intramolecular pro-
ton transfer from oxygen to carbon. Alternatively, treatment of
1 with a non-nucleophilic strong base such as lithium diisopro-
pylamide (LDA) in THF instantaneously produces deprotona-
tion of dmpm to give the diphosphinomethanide derivative fac-
[Mn(CNPh)(CO)3{(PMe2)2CH}] (3). Compounds 2 and 3 were
characterised by spectroscopic methods. The 31P NMR spec-
trum of 2 displayed two signals, corresponding to dimethyl-
phosphinite (d 80.2) and trimethylphosphine (d 12.5) ligands at
usual chemical shifts, whereas the 13C NMR spectrum showed
signals for each methyl group of dimethylphosphinite ligand (d
Scheme 1
2
2
29.6, JP–C = 27 Hz; d 29.9, JP–C = 27 Hz) according with
their diasterotopic character, in addition to that of trimethyl-
2
phosphine ligand (d 18.7, JP–C = 30 Hz). Nature of 2 was
unambiguously confirmed when the structure of the closely
related fac-[Mn(PMe2O)(CNt-Bu)(CO)3(PMe3)] (2a) was de-
termined by X-ray analysis.‡ 2a was prepared in an analogous
procedure to that employed for 2 starting from fac-[Mn(CNt-
Bu)(CO)3dmpm]ClO4(1a), but, unlike 2, yields suitable crystals
for X-ray analysis. Two molecules of 2a were found in the
Fig. 1 ORTEP drawing of 2a; hydrogen atoms are omitted for clarity.
Selected bond distances [Å] and angles [°]: Mn(1)–P(1) 2.328(5), Mn(1)–
P(2) 2.341(2), P(1)–C(1) 1.795(6), P(1)–C(2) 1.799(6), P(2)–C(4) 1.794(6),
P(2)–O(1) 1.492(4); P(1)–Mn(1)–P(2) 91.3(1), O(1)–P(2)–C(4) 109.5(3),
O(1)–P(2)–C(5) 106.7(3), C(4)–P(2)–C(5) 98.8(4).
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CHEM. COMMUN., 2003, 1942–1943
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(P(CH3)2)2); 31P{1H} NMR (121.5 MHz, CD2Cl2): d
(P(CH3)2)2).
‡ Crystal data for 2a (C13H24MnNO4P2·H2O): M = 393.23, crystal size
0.46 3 0.46 3 0.20 mm, a = 10.526(2), b = 14.56(1), c = 14.59(3)Å, a
= 108.43(8), b = 98.3(1), g = 98.58(7)°, V = 2054(5) Å3, rcalcd = 1.272
g cm23, m = 0.816 mm21, Z = 4, triclinic, space group P1, l = 0.71073
Å, T = 293(2) K, qmax = 25.97, independent reflections = 8009, refined
parameters = 411, R1 = 0.0438, wR2 = 0.1103, largest diff. peak and hole
0.50 and 20.52 e Å23. CCDC 210714. See http://www.rsc.org/suppdata/cc/
b3/b305316d/ for crystallographic data in .cif or other electronic format.
Two molecules of the complex were found in the asymmetric unit. Both
molecules have very similar structural parameters, with differences arising
from the presence of two molecules of water displaying O–H…O hydrogen
bonds with the oxygen atom of the phosphinite ligand in one of them.
= 5.1 (s, br,
Complex 3 is extremely sensitive to protonation, so that
traces of water revert it to 1, avoiding the obtention of solid pure
samples of this compound. Nevertheless, the low values of the
n(CNPh) (2128 cm21) and n(CO) (2000, 1930 cm21) fre-
quencies, together with the appearance of a characteristic high
field singlet (d 227.2) in the 31P NMR spectrum, strongly
support the proposed formulation for 3. Diphosphinomethanide
ligands can be readily converted to functionalized diphosphines
by reaction with electrophiles. Thus, the treatment of 3 with
iodine in the presence of KOH afforded the diphosphinoketeni-
mine derivative fac-[MnI(CO)3{(PMe2)2CNCNNPh}] (4), after
¯
formation
of
diphosphinoiodomethanide
derivative
[Mn(CNPh)(CO)3{(PMe2)2CI}] and subsequent C–C coupling
of the coordinated isocyanide and the diphosphinocarbene
fragment [(PMe2)2C:] (Scheme 1), in a parallel process to that
described for the analogous dppm complexes.7 In fact, complex
4 is easily and quantitatively obtained by direct treatment of 1
with KOH and I2 in CH2Cl2 (10 min of stirring at room
temperature). This result clearly shows that C–H bond cleavage
in 1 by KOH may occur much faster than P–C bond cleavage,
even though in the reaction of 1 with KOH no spectroscopic
evidence was found of the presence of 3, probably due to traces
of moisture in the solvent. The IR spectrum of 4 showed a lack
of bands corresponding to coordinated isocyanide, and n(CO)
(2011, 1952, 1908 cm21) frequencies according with a neutral
fac-tricarbonyl derivative, whereas 31P NMR spectrum showed
that phosphorous atoms remain equivalents (d 5.1). To our
knowledge, the diphosphine in 4 constitutes the first example of
a P-alkyl phosphinoketenimine8 and it should be noted that the
related [(PPh2)2CNCNNPh] has proved to be a valuable reagent
for the synthesis of novel phosphaheterocycles.9 It is expected
that, owing to the high basicity of the methanide carbon atom,
the diphosphinomethanide complex 3 may allow the synthesis
of a great variety of functionalized alkylic diphosphines by
carrying out the reaction of 1 and KOH in the presence of
different electrophiles.
1 R. Usón, B. R. Manzano, P. G. Jones, A. Laguna, M. Laguna and G. M.
Sheldrick, J. Chem. Soc., Dalton Trans., 1984, 839; E. J. Fernández, M.
C. Gimeno, P. G. Jones, A. Laguna, M. Laguna and J. López de
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García-Granda and A. García-Fernández, J. Chem. Soc., Chem. Com-
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2000, 19, 5533.
2 S. Al-Jibori and B. L. Shaw, J. Chem. Soc., Chem. Commun., 1982, 286;
S. Al-Jibori and B. L. Shaw, Inorg. Chim. Acta, 1983, 12, 99; J. Forniés,
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García-Granda and M. R. Díaz, Organometallics, 1998, 17, 4562; M. E.
G. Mosquera, J. Ruiz and V. Riera, Organometallics, 2001, 20, 3821; J.
Ruiz, M. Ceroni, O. V. Quinzani, V. Riera, M. Vivanco, S. García-
Granda, F. Van der Maelen, M. Lanfranchi and A. Tiripicchio, Chem.
Eur. J., 2001, 7, 4422.
3 N. W. Alcock, P. Bergamin, T. J. Kemp and P. G. Pringle, J. Chem. Soc.,
Chem. Commun., 1987, 235; P. Bergamin, S. Cortero, O. Traverso, T. J.
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B. Lin, J. S. Lai and C. W. Liu, Organometallics, 1990, 9, 530; I. J. B.
Lin, J. S. Lai, L. K. Liu and Y. S. Wen, J. Organomet. Chem., 1990, 399,
361.
4 P. E. Garrou, Chem. Rev., 1985, 85, 171; K. C. Kong and C. H. Cheng,
J. Am. Chem. Soc., 1991, 113, 6313; D. K. Morita, J. K. Stille and J. R.
Norton, J. Am. Chem. Soc., 1995, 117, 8576; F. E. Goodson, T. I. Wallow
and B. M. Novak, J. Am. Chem. Soc., 1997, 119, 12441.
5 M. A. Álvarez, M. E. García, V. Riera, M. A. Ruiz, L. R. Falvello and C.
Bois, Organometallics, 1997, 16, 354; G. García, M. E. García, S. Melón,
V. Riera, M. A. Ruiz and F. Villafañe, Organometallics, 1997, 16, 624;
C. Álvarez, M. E. García, V. Riera and M. A. Ruiz, Organometallics,
1997, 16, 1378; C. J. Reijer, H. Riegger and P. S. Pregosin,
Organometallics, 1998, 17, 5213; C. J. Reijer, M. Worle and P. S.
Pregosin, Organometallics, 2000, 19, 309; T. J. Gedelbach and P. S.
Pregosin, Eur. J. Inorg. Chem., 2002, 8, 1907; R. H. Heyn and C. H.
Görbitz, Organometallics, 2002, 21, 2781; S. G. Bott, K. Yang, M. G.
Richmond and K. A. Talafuse, Organometallics, 2003, 22, 1383.
6 Compound 1 was prepared in a similar procedure to that employed for the
closely related [Mn(CNR)(CO)3dppm]ClO4 (see: J. Ruiz, V. Riera, M.
Vivanco, S. García-Granda and M. R. Díaz, Organometallics, 1998, 17,
4562).
7 J. Ruiz, V. Riera, M. Vivanco, S. García-Granda and M. R. Díaz,
Organometallics, 1998, 17, 3835.
8 For other examples of phosphinoketenimines see: A. Igau, A. Baceiredo,
G. Trinquier and G. Bertrand, Angew. Chem., Int. Ed. Engl., 1989, 28,
621; G. Gillette, A. Igau, A. Baceiredo and G. Bertrand, Angew. Chem.,
Int. Ed. Engl., 1990, 29, 1429.
In summary, coordinated dmpm can be an appropiate entry to
either phosphinite or functionalized diphosphine complexes,
mediated by selective P–C or C–H bond cleavage, depending
upon the reaction conditions chosen.
This work was supported by the Spanish Ministerio de
Ciencia y Tecnología (Project BQU2000-0220) and by the
Principado de Asturias (Project PR-01-GE-7).
Notes and references
†
Satisfactory elemental analyses were obtained for 1, 2 and 4.
Data for 1: IR (CH2Cl2, cm21): 2150 (m) n(CNPh), 2037 (vs), 1977 (s)
n(CO); 1H NMR (300 MHz, CD2Cl2): d = 7.54 (br, 5H, Ph), 3.85 (dt, 1 H,
2JHH = 19, JPH = 12, P2CH2), 3.56 (dt, 1 H, JHH = 19, JPH = 12,
P2CH2), 1.86 (m, 12H, (P(CH3)2)2); 31P{1H} NMR (121.5 MHz, CD2Cl2):
d = 22.0 (s, br, (P(CH3)2)2).
3
2
3
Data for 2: IR (CH2Cl2, cm21): 2130 (m) n(CNPh), 2009 (vs), 1937 (s)
n(CO); 1H NMR (300 MHz, CD2Cl2): d = 7.45 (m, 5H), 1.71–1.60 (m,
15H); 31P{1H} NMR (121.5 MHz, CD2Cl2): d = 80.2 (s, br, P(CH3)2O),
12.5 (s, br, P(CH3)3); 13C{1H} NMR (75.47 MHz, CH2Cl2/D2O): d = 219.2
1
(br, CO), 178.9 (s, CNPh), 130.1–126.2 (m, Ph), 29.9 (d, JPC = 27,
P(CH3)2O), 29.6 (d, JPC
1
1
= 27, P(CH3)2O), 18.7 (d, JPC = 30,
P(CH3)3).
Data for 3: IR (THF, cm21): 2128 (m) n(CNPh), 2000 (vs), 1930 (s)
n(CO); 31P{1H} NMR (121.5 MHz, THF/D2O): d
P(CH3)2).
=
227.2 (s, br,
9 J. Ruiz, F. Marquínez, V. Riera, M. Vivanco, S. García-Granda and M. R.
Díaz, Angew. Chem., Int. Ed. Engl., 2000, 39, 1821; J. Ruiz, F.
Marquínez, V. Riera, M. Vivanco, S. García-Granda and M. R. Díaz,
Chem. Eur. J., 2002, 8, 38.
Data for 4: IR (CH2Cl2, cm21): 2011 (vs), 1952 (s), 1908 (m) n(CO); 1H
NMR (300 MHz, CD2Cl2): d = 7.47–7.32 (m, 5H, Ph), 2.00–1.86 (m, 12H,
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