A manganese carbonyl complex derived from the P,N-bonding ligand (2-aminophenyl)diphenylphosphine

Article abstract of DOI:10.1016/j.poly.2006.06.034

Thermal reaction of [H₃Mn₃(CO)₁₂] with Ph₂PC₆H₄NH₂-2 gives good yields of [Mn₂(CO)₆(PPh₂C₆H₄NH)₂], an X-ray single crystal structure determination of which reveals a P,N-chelating ligand with each of the NH groups, formed by deprotonation of the amine groups, bridging the two metal atoms.

Full text of DOI:10.1016/j.poly.2006.06.034

Polyhedron 26 (2007) 430–433
www.elsevier.com/locate/poly
A manganese carbonyl complex derived from the P,N-bonding
ligand (2-aminophenyl)diphenylphosphine
*
Victor D. Fester, Paul J. Houghton, Lyndsay Main, Brian K Nicholson
Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton, New Zealand
Received 5 April 2006; accepted 23 June 2006
Available online 14 July 2006
Abstract
Thermal reaction of [H3Mn3(CO)12] with Ph2PC6H4NH2-2 gives good yields of [Mn2(CO)6(PPh2C6H4NH)2], an X-ray single crystal
structure determination of which reveals a P,N-chelating ligand with each of the NH groups, formed by deprotonation of the amine
groups, bridging the two metal atoms.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Manganese carbonyl; Hemilabile; X-ray crystal structure; 2-Aminophenyldiphenylphosphine
1. Introduction
Metal carbonyl complexes derived from 1 have been
reported for both mononuclear and cluster compounds
[11–18]. However, there are as yet no reports that we are
aware of where derivatives of manganese have been pre-
pared with 1. Our longer term interest stems from the pos-
sibility of controlling the reactivity of the Mn–C bond in
cyclomanganated compounds with such ancillary ligands
[19], but here we describe a novel complex (2) from initial
explorations of the reactions of 1 with simpler manganese
carbonyls.
Many bidentate hemilabile ligands have been explored
for their ability to combine a stabilising effect on the metal
centre with the possibility of readily generating a vacant
coordination site for catalysis [1–5]. The most common
ligating atom combinations are P,O or P,N which exploit
the mismatch in bonding tendencies between soft P and
hard O or N. Recent summaries giving examples are avail-
able [6–8].
One readily prepared ligand which has had some appli-
cation in organometallic chemistry is Ph2PC6H4NH2-2 (1),
which not only includes a soft-hard P,N combination but
also retains potentially reactive N–H bonds [9,10].
2. Experimental
2.1. General
Ph
Reactions were carried out under a nitrogen atmosphere
using Schlenk techniques and solvents that were distilled
under nitrogen from appropriate drying agents before
use. Electrospray mass spectra were recorded on a VG
Platform II spectrometer, operated as detailed elsewhere
[20,21]. Assignments were confirmed by simulation of the
characteristic isotope patterns using the ISOTOPE program
[22]. NMR spectra were obtained on a Bruker AC300
instrument operating under standard conditions. IR spec-
tra were recorded on a Digilab Scimitar instrument.
Ph
OC
OC
P
CO
Mn
NH
NH
CO
CO
Ph
Mn
Ph
Ph
P
NH2
OC
P
Ph
1
2
*
Corresponding author. Fax: +64 7 838 4219.
E-mail address: b.nicholson@waikato.ac.nz (B.K Nicholson).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.06.034

V.D. Fester et al. / Polyhedron 26 (2007) 430–433
431
Ph2PC6H4NH2-2 and [H3Mn3(CO)12] were prepared by the
literature methods [23,24].
2.2. Preparation of 2
C(11)
[H3Mn3(CO)12] (40 mg, 0.079 mmol) was dissolved in
heptane (5 mL ) in a Schlenk flask. (2-Aminophenyl)diphe-
nylphosphine (45 mg, 0.16 mmol) was added to the flask
and the temperature of the reaction mixture was gradually
increased to between 80 and 90 ꢁC over a period of 50 min.
During this time a colour change from orange–red to
orange–yellow was observed, with a yellow precipitate
starting to form at 80 ꢁC. After cooling to room tempera-
ture, the solvent was removed in vacuo and the residue
was redissolved in a small amount of dichloromethane. A
similar volume of diethyl ether was added and the mixture
was placed in the freezer. After one week, yellow crystals of
2 were obtained (40 mg, 61%). M.p. 110–116 ꢁC. Anal.
Calc. for C42H30N2O6P2Mn2 (Mr = 830) requires C,
60.74; H, 3.65; N, 3.37. Found: C, 59.99; H, 3.62; N,
3.38%. mCO (CH2Cl2) 2002 (s), 1923(s), 1898(s); ESI-MS,
(MeOH, added NaOMe [20,21]), positive ion m/z 853
[M+Na]+, 825 [M+NaꢀCO]+, negative ion m/z 801
[MꢀHꢀCO]ꢀ, 773 [MꢀHꢀ2CO]ꢀ. NMR (CDCl3;
P(1)
C(16)
O(2)
N(1)
Mn(1_3)
O(3)
Mn(1)
N(1_3)
O(1)
Fig. 1. The structure of the centrosymmetric dimer 2. Bond parameters
include bond lengths (A): Mn–P 2.317(1), Mn–N(1) 2.084(3), Mn–N(1)
0
˚
2.150(3), Mn. . .Mn 3.267(1); bond angles (ꢁ): Mn–P–C(11) 101.3(2), N(1)–
Mn–N(1)0 79.0(2), Mn–N(1)–Mn0 100.9(2), Mn–N(1)–C(16) 112.1(2).
1
300 MHz): H: d 7.0–8.5 (m); the NH signal was either
too broad to be observed or was amongst the aryl proton
signals and could not be assigned. 13C: owing to decompo-
sition over the period of accumulation, the spectrum was
poor and singlet signals were not resolved; doublet signals
assigned to the ring carbons ortho and para to the amino
group were at 111.0 (J = 7 Hz) and 118.9 ppm (J =
11 Hz), the remainder overlapping at 128–135 ppm. 31P:
65.4 ppm.
correction for absorption (Tmax,min = 0.7697, 0.7329).
Crystal dimensions 0.36 · 0.30 · 0.30 mm3. Refinement on
F2 gave R1 0.0563 [I > 2r(I)] and wR2 = 0.1580 (all data),
GoF = 1.027. The structure of 2 is illustrated in Fig. 1, with
selected bond parameters summarised in the caption to the
figure.
3. Results and discussion
2.3. X-ray crystallography
3.1. Synthesis and properties of 2
X-ray intensity data were collected on a Siemens
SMART CCD diffractometer using standard procedures
and software. Multiscan absorption corrections were
applied (SADABS [25]). Structures were solved by direct
methods and developed and refined on F2 using the SHELX
programmes [26] operating under WINGX [27,28]. Hydrogen
atoms were included in calculated positions, except for the
hydrogen attached to N(1), which was located as the high-
est peak in a penultimate difference map and was refined
with an isotropic temperature factor.
We were unable to isolate any new compounds from the
thermal reaction between the ligand 1 and Mn2(CO)10,
decomposition to insoluble brown residues taking place
under conditions needed for reaction. However, the trinu-
clear species H3Mn3(CO)12 underwent a smooth reaction
at 80 ꢁC with 1 to give good yields of a new species as yel-
low crystals. These were reasonably air-stable as a solid,
but solutions tended to decompose giving a green product.
1H and 13C NMR of 2 gave little useful information, while
31P NMR gave a signal at d 65.4, well-shifted from that of
the free ligand at d ꢀ19.6. This indicated that a five-mem-
bered chelate ring had formed [29], though the shift of
75 ppm is unusually large [30]. The ESI mass spectrum
suggested a mass of 830 from an [M+Na]+ ion at m/z
853, corresponding to an empirical formula of [Mn2(CO)6-
(Ph2PC6H4NH)2]. To characterise the complex a single
crystal X-ray determination was carried out. The structure
is shown in Fig. 1. This shows a centrosymmetric molecule
consisting of two Mn(CO)3 units each coordinated to a
phosphorus atom of a mono-deprotonated form of the
2.3.1. Structure of [Mn2(CO)6(Ph2PC6H4NH)2] Æ CH2Cl2
(2 Æ CH2Cl2)
Yellow crystals of 2 as the mono-solvate were obtained
from CH2Cl2.
Crystal data: C42H30N2O6P2Mn2 Æ CH2Cl2, M = 1000.36,
monoclinic,
space
group
P21/n,
a = 10.8871(1),
˚
b = 14.7066(1), c = 14.1506(2) A, b = 97.744(1)ꢁ, U =
3
2245.0(1) A , T = 190 K, Z = 2, Dcalc = 1.48 g cmꢀ3, l(Mo
˚
Ka) = 0.921 mmꢀ1, F(000) 1016; 12596 reflections collected
with 2ꢁ < h < 26ꢁ, 4520 unique (Rint = 0.0433) used after

432
V.D. Fester et al. / Polyhedron 26 (2007) 430–433
ligand 1. The two halves of the molecule are linked only by
the N atoms from the two ligands; the Mn. . .Mn distance
of 3.267 A precludes any direct metal–metalbond. The cen-
Appendix A. Supplementary material
˚
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic Data
Centre, CCDC no. 603564. Copies of this information may
be obtained free of charge from the Director, CCDC, 12
Union Rd., Cambridge CB2 1EZ, UK, fax: +44 1223 336
033, e-mail: deposit@ccdc.cam.ac.uk or http://www.ccdc.
cam.ac.uk. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.poly.2006.06.034.
tral Mn2N2 core of the molecule has strict planarity
imposed by the space group symmetry, while the five-mem-
bered metallocyclic ring formed by Mn(1)P(1)C(11)-
C(16)N(1) has a slightly folded envelope conformation,
˚
with deviations up to 0.18 A from the least-squares plane.
The Mn–N 0 bonds differ slightly with Mn(1)–N(1) and
˚
Mn(1)–N(1) being 2.084(3) and 2.150(3) A, respectively.
Deprotonation of the ligand 1 to provide a bridging
amido group has been observed before, notably in reac-
tions with [Ru3(CO)12] and [Os3(CO)12] [16–18]. However
in these cases the clusters remain intact and the amido
group bridges a formal M–M bond. A doubly bridged
Rh–Rh bond is also retained in the complex [Rh2Cl2(CO)2-
(Ph2PC6H4NH)2] [31]. Structural characterisation of two
metal carbonyl centres linked only by two amido groups
appears to be unique to compound 2, though a related rhe-
nium example derived from 2-aminopyridine has been
spectroscopically established [32].
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Acknowledgements
We thank Associate Professor Cliff Rickard, Univer-
sity of Auckland, for collection of X-ray intensity data
and Ms. Kelly Kilpin for assistance with NMR
spectroscopy.

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