Synthesis, coordination chemistry and reactivity of cyano-functionalised N-pyrrolyl phosphines

Article abstract of DOI:10.1016/S0020-1693(02)01537-2

The cyano-functionalised N-pyrrolyl phosphines PPh₂(NC ₄H₃CN-2) (L¹) and P(NC₄H ₄)₂(NC₄H₃CN-2) (L²) have been prepared from the reaction of PClR₂ (R=Ph, NC₄H ₄) with lithium 2-cyanopyrrolide, itself generated in situ from 2-cyanopyrrole and BuLi. The reaction of L¹ or L² with [MCl₂(cod)] gives [MCl₂(L-κ¹P) ₂] (1, M=Pt, L=L¹; 2, M=Pd, L=L¹; 3, M=Pt, L=L²; 4, M=Pd, L=L²) and both cis-1 and trans-4 have been structurally characterised. The crystal structure of cis-1 reveals the presence of an unusually wide P-Pt-P angle [107.22(5)°], which has its origin in an intramolecular interaction between the two 2-cyanopyrrole rings. The reaction of L¹ with [M(dmba)(μ-Cl)]₂ (Hdmba=N,N- dimethylbenzylamine) results in formation of [MCl(dmba)(L¹- κ¹P)] (5, M=Pt; 6, M=Pd). Compounds 5 and 6 react with TlPF₆ to give oligomeric P,N-coordinated compounds of empirical formula [M(dmba)(L¹)][PF₆]. The dimeric compound [Pt(dmba)(μ-L¹-κ¹P,κ¹N)] ₂(PF₆)₂ (7), has been isolated and structurally characterised, and coordination of the cyano groups leads to formation of a 12-membered ring. Compound 6 reacts with PhCH₂ CH(NH₂)CH₂OH in the presence of TlPF₆ to yield [Pd(dmba)(PPh₂NC₄H₃{C=NCH(CH ₂Ph)CH₂O-2})]PF₆ (8) in which the cyano group has been transformed into an oxazoline group. The molybdenum complex [MoCl(CO)₃(η⁵-C₅H₅)] reacts with L¹ to give [MoCl(CO)₂(L¹-κ ¹P)(η⁵-C₅H₅)] (9) which has been structurally characterised. In contrast to the reaction of 5 or 6, compound 9 does not react with TlPF₆ or AgBF₄ to give tractable oligomeric products. Reaction of the rhodium complex [Rh(acac)(CO)₂] with L¹ occurs to give [Rh(acac)(CO)(L¹-κ¹P)] (10). The infrared spectrum of 10 indicates the electronic properties of L¹ are very similar to those for PPh₂(NC₄H₄).

Full text of DOI:10.1016/S0020-1693(02)01537-2

Inorganica Chimica Acta 350 (2003) 152ꢂ162
/
www.elsevier.com/locate/ica
Synthesis, coordination chemistry and reactivity of
cyano-functionalised N-pyrrolyl phosphines
Andrew D. Burrows *, Mary F. Mahon, Maurizio Varrone
Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
Received 6 June 2002; accepted 12 September 2002
Dedicated to Professor Pierre Braunstein.
Abstract
The cyano-functionalised N-pyrrolyl phosphines PPh2(NC4H3CN-2) (L1) and P(NC4H4)2(NC4H3CN-2) (L2) have been prepared
from the reaction of PClR2 (RꢀPh, NC4H4) with lithium 2-cyanopyrrolide, itself generated in situ from 2-cyanopyrrole and BuLi.
The reaction of L1 or L2 with [MCl2(cod)] gives [MCl2(L-k1P)2] (1, Mꢀ L1; 2, Mꢀ L1; 3, Mꢀ L2; 4, Mꢀ
Pt, Lꢀ Pd, Lꢀ Pt, Lꢀ
Pd, Lꢀ
L2) and both cis-1 and trans-4 have been structurally characterised. The crystal structure of cis-1 reveals the presence of an
unusually wide PÃPtÃP angle [107.22(5)8], which has its origin in an intramolecular interaction between the two 2-cyanopyrrole
rings. The reaction of L1 with [M(dmba)(m-Cl)]2 (HdmbaꢀN,N-dimethylbenzylamine) results in formation of [MCl(dmba)(L1-
/
/
/
/
/
/
/
/
/
/
/
/
k1P)] (5, Mꢀ
/
Pt; 6, MꢀPd). Compounds 5 and 6 react with TlPF6 to give oligomeric P,N-coordinated compounds of empirical
/
formula [M(dmba)(L1)][PF6]. The dimeric compound [Pt(dmba)(m-L1-k1P,k1N)]2(PF6)2 (7), has been isolated and structurally
characterised, and coordination of the cyano groups leads to formation of a 12-membered ring. Compound 6 reacts with
PhCH2CH(NH2)CH2OH in the presence of TlPF6 to yield [Pd(dmba)(PPh2NC4H3{CÄ
/
NCH(CH2Ph)CH2O-2})]PF6 (8) in which the
cyano group has been transformed into an oxazoline group. The molybdenum complex [MoCl(CO)3(h5-C5H5)] reacts with L1 to
give [MoCl(CO)2(L1-k1P)(h5-C5H5)] (9) which has been structurally characterised. In contrast to the reaction of 5 or 6, compound 9
does not react with TlPF6 or AgBF4 to give tractable oligomeric products. Reaction of the rhodium complex [Rh(acac)(CO)2] with
L1 occurs to give [Rh(acac)(CO)(L1-k1P)] (10). The infrared spectrum of 10 indicates the electronic properties of L1 are very similar
to those for PPh2(NC4H4).
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Phosphines; Functionalised ligands; X-ray crystal structures; Coordination; Pyrrolyl phosphines; Cyanophosphines
1. Introduction
[4]. For N-pyrrolyl phosphines, the nitrogen merely acts
as an electronegative substituent, making the ligand a
poor s-donor. The p-acidity of the ligands has been
demonstrated structurally [2], computationally [5] and
through quantitative analysis of ligand effects [6] and is
primarily a consequence of the LUMO energy.
While functionalities have been added with a view to
enhancing the electronic properties of N-pyrrolyl phos-
phines [7], very little use has been made of the pyrrolyl
ring as a skeleton for phosphines bearing additional
donor groups [8]. Recently we reported the synthesis of
the ketophosphine ligands (2-acetyl-N-pyrrolyl)diphe-
nylphosphine (L3) [9] and (2-acetyl-N-pyrrolyl)di-N-
pyrrolylphosphine (L4) [10] and showed they could act
as either P-donor or P,O-donor ligands, with the
coordination modes readily interconverted. In this paper
we report the synthesis of (2-cyano-N-pyrrolyl)diphe-
N-pyrrolyl phosphines have been known for over 25
years [1], but it is only recently that interest in these
ligands has taken off due to recognition of their
behaviour as good p-acceptors [2] and the catalytic
implications of this electronic character [3]. As a
consequence of involvement of the filled nitrogen p-
orbital in the aromatic pyrrole ring, the PÃ
no double bond character. This is in contrast to most
ligands containing PÃN bonds, which are typically good
s-donors due to the enhanced electron density this
partial delocalisation imparts on the phosphorus atom
/
N bond has
/
* Corresponding author. Fax: ꢁ
E-mail address: a.d.burrows@bath.ac.uk (A.D. Burrows).
/44-1225-82 6231.
0020-1693/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(02)01537-2

A.D. Burrows et al. / Inorganica Chimica Acta 350 (2003) 152ꢂ
/162
153
nylphosphine (L1) and (2-cyano-N-pyrrolyl)di-N-pyrro-
lylphosphine (L2), and the coordination of these ligands
to palladium, platinum, molybdenum and rhodium
centres.
was dissolved in toluene, filtered and stored at ꢃ
/
25 8C
for 24 h after which a colourless oil separated out. The
oil was washed with small amounts of cold hexane and
dried in vacuo. Yield 2.03 g (60%). d (1H) (ppm) (C6D6,
270.2 MHz) 6.43 (ps.qn, 4H, NC4H4), 6.35 (m, 1H, pyr),
6.17 (ps.t, 4H, NC4H4), 6.05 (m, 1H, pyr), 5.71 (m, 1H,
pyr). d (13C) (ppm) (C6D6, 67.9 MHz) 124.7 (s), 122.9
(d, JCP 15), 122.5 (s), 114.2 (d, JCP 5), 114.0 (d, JCP 5),
113.2 (s), 112.3 (s). d (31P) (ppm) (C6D6, 109.4 MHz)
80.1 (s). n(CN) (cmꢃ1) (CH2Cl2) 2221m.
2. Experimental
Reactions were routinely carried out using Schlenk-
line techniques under pure dry dinitrogen using dry
dioxygen-free solvents. Microanalyses (C, H and N)
were carried out by Mr. Alan Carver (University of Bath
Microanalytical Service). Infrared spectra were recorded
on a Nicolet 510P spectrometer as KBr pellets or
solutions. 1H, 13C{1H} and 31P{1H} NMR spectra
were recorded on JEOL EX270, Bruker Avance 300 or
Varian Mercury 400 spectrometers referenced to TMS
or 85% H3PO4. Coupling constants are reported in Hz.
The complexes [PtCl2(cod)] [31], [PdCl2(cod)] [32],
2.1.3. cis-[PtCl2(L1-k1P)2] (1)
[PtCl2(cod)] (0.272 g, 0.7 mmol) was added to a stirred
solution of L1 (0.386 g, 1.5 mmol) in dichloromethane
(20 cm3), and the mixture stirred overnight. The volume
of the solution was reduced by two-thirds and hexane
added to precipitate 1 as a colourless powder. This was
washed with hexane, dried in vacuo and crystallised
[M(dmba)(m-Cl)]2 (Mꢀ
Pt, Pd) [33], [MoCl(CO)3(h5-
/
from dichloromethaneꢂ
Found: C, 43.7; H, 3.00; N, 5.52. C34H26Cl2N4P2Pt×
2CH2Cl2 requires C, 43.7; H, 3.06; N, 5.67%. d (1H)
(ppm) (CD2Cl2, 399.8 MHz) 7.70ꢂ7.65 (4H, m, Ph),
/hexane. Yield 0.50 g (87%).
/
C5H5)] [34] and [Rh(acac)(CO)2] [35] were prepared by
standard literature methods. 2-Cyanopyrrole (Lancas-
ter) was dried over molecular sieves and distilled prior to
use.
/
7.57ꢂ
/
7.53 (2H, m, Ph), 7.43ꢂ7.38 (4H, m, Ph), 7.00 (1H,
/
m, pyr), 6.66 (1H, m, pyr) and 6.16 (1H, m, pyr). d (31P)
1
(ppm) (CD2Cl2, 109.4 MHz) 54.3 (s, JPtP 4021). n(CN)
(cmꢃ1) (KBr) 2215m.
2.1. Syntheses
2.1.1. PPh2(NC4H3CN-2) (L1)
A 2.5 M hexane solution of BuLi (4.3 cm3, 10.8 mmol)
was added dropwise to a solution of 2-cyanopyrrole
2.1.4. trans-[PdCl2(L1-k1P)2] (2)
[PdCl2(cod)] (0.100 g, 0.35 mmol) was added to a
stirred solution of L1 (0.193 g, 0.70 mmol) in dichlor-
omethane (10 cm3), and the mixture stirred overnight.
The resulting yellow precipitate was isolated by filtra-
tion, washed with hexane and dichloromethane and
dried in vacuo. Yield 0.150 g (59%). Found: C, 56.2; H,
3.75; N, 7.52. C34H26Cl2N4P2Pd requires C, 56.0; H,
3.59; N, 7.68%. d (1H) (ppm) (CD2Cl2, 399.8 MHz) 7.76
(m, 4H, Ph), 7.65 (m, 2H, Ph), 7.53 (m, 4H, Ph), 7.08 (m,
1H, pyr), 6.95 (m, 1H, pyr), 6.33 (m, 1H, pyr). d (31P)
(1.00 g, 10.8 mmol) in THF (10 cm3) at ꢃ
78 8C. The
/
reaction mixture was allowed to warm to ambient
temperature and added to a solution of PClPh2 (2.40
g, 10.8 mmol) in THF (5 cm3). After stirring for 4 h, the
solvent was removed in vacuo to give a yellow oil, which
was triturated with cold hexane to give a white powder.
Recrystallisation from THFꢂ
/
hexane at ꢃ25 8C af-
/
forded L1 as colourless needles. Yield 1.88 g (63%).
Found: C, 73.9; H, 4.80; N, 10.2. C17H13N2P requires C,
73.9; H, 4.74; N, 10.1%. d (1H) (ppm) (CDCl3, 399.8
(ppm) (CD2Cl2, 109.4 MHz) 68.0 (s). n(CN) (cmꢃ1
(KBr) 2211m.
)
MHz) 7.48ꢂ
/
7.40 (m, 6H, Ph), 7.34ꢂ7.30 (m, 4H, Ph),
/
6.99 (m, 1H, pyr), 6.75 (m, 1H, pyr), 6.34 (m, 1H, pyr). d
(13C) (ppm) (CDCl3, 100.5 MHz): 133.8 (d, JCP 12),
132.1 (d, JCP 21), 132.2 (s), 130.7 (s), 129.0 (d, JCP 8),
126.5 (s), 114.3 (s), 113.6 (s), 106.7 (d, JCP 23). d (31P)
2.1.5. cis-[PtCl2(L2-k1P)2] (3)
[PtCl2(cod)] (0.334 g, 0.89 mmol) was added to a
solution of L2 (0.504 g, 1.98 mmol) in dichloromethane
and the mixture stirred overnight. Addition of hexane
led to the formation of a colourless powder, which was
separated by filtration, washed with hexane and dried in
vacuo. Yield 0.605 g (88%). Found: C, 37.6; H, 2.85; N,
(ppm) (CDCl3, 161.8 MHz) 51.8 (s). n(CN) (cmꢃ1
)
(KBr) 2218m.
2.1.2. P(NC4H4)2(NC4H3CN-2) (L2)
A 2.5 M hexane solution of BuLi (5.3 cm3, 13.2 mmol)
was added dropwise to a solution of 2-cyanopyrrole
13.0. C26H22Cl2N8P2Pt×
/
CH2Cl2 requires C, 37.7; H,
(1.22 g, 13.2 mmol) in THF at ꢃ
mixture was allowed to warm to ambient temperature
and added to a THFꢂhexane solution of PCl(NC4H4)2
/
78 8C. The reaction
2.81; N, 13.0%. d (1H) (ppm) (CD2Cl2, 270.2 MHz)
7.39 (m, 4H, NC4H4), 7.04 (m, 1H, pyr), 6.54 (m, 4H,
NC4H4), 6.33 (m, 1H, pyr), 6.19 (m, 1H, pyr). d (31P)
/
1
(2.62 g, 13.2 mmol). After 3 h stirring, the solution was
filtered and the solvent removed in vacuo. The residue
(ppm) (CD2Cl2, 109.4 MHz) 69.2 (s, JPtP 3915). n(CN)
(cmꢃ1) (KBr) 2227m.

154
A.D. Burrows et al. / Inorganica Chimica Acta 350 (2003) 152ꢂ162
/
2.1.6. trans-[PdCl2(L2-k1P)2] (4)
0.1 mmol) in dichloromethane. After stirring for 24 h,
TlCl was removed by filtration and the filtrate recrys-
[PdCl2(cod)] (0.314 g, 1.1 mmol) was added to a
solution of L2 (0.550 g, 2.2 mmol) in dichloromethane
and the mixture stirred overnight. Addition of hexane
led to the formation of a yellow powder which was
separated by filtration, washed with hexane, dried in
tallised from dichloromethaneꢂ
less crystals of 7. Yield 0.056 g (80%). Found: C, 40.0;
H, 3.30; N, 5.30. C52H50F12N6P4Pt2×CH2Cl2 requires C,
40.1; H, 3.30; N, 5.30%. d (1H) (ppm) (CD2Cl2, 399.8
MHz) 7.91ꢂ7.76 (m, 12H, Ph), 7.58ꢂ7.40 (m, 8H, Ph),
/
hexane to give colour-
/
vacuo and crystallised from dichloromethaneꢂ
/hexane.
/
/
Yield 0.445 g (59%). Found: C, 45.3; H, 3.14; N, 16.3.
C26H22Cl2N8P2Pd requires C, 45.5; H, 3.23; N, 16.3%. d
(1H) (ppm) (CD2Cl2, 270.2 MHz) 7.31 (m, 4H, NC4H4),
7.06 (m, 1H, pyr), 6.53 (m, 4H, NC4H4), 6.34 (m, 1H,
pyr), 6.20 (m, 1H, pyr). d (31P) (ppm) (CD2Cl2, 109.4
MHz) 74.4 (s). n(CN) (cmꢃ1) (KBr) 2226m.
7.11 (m, 2H, pyr), 7.05 (m, 2H, Ar), 6.85 (m, 2H, Ar),
6.41 (m, 2H, pyr) 6.36 (m, 2H, pyr), 6.31 (m, 2H, Ar),
4
6.14 (m, 2H, Ar), 4.10 (d, 4H, JPH 2.4, CH2), 2.94 (d,
4
12H, JPH 3.2, CH3). d (31P) (ppm) (CD2Cl2, 161.8
1
MHz) 70.9 (s, JPtP 4363), ꢃ
/
141.6 (sept., PF6). n(CN)
(cmꢃ1) (KBr) 2258m.
2.1.7. [PtCl(dmba)(L1-k1P)] (5)
2.1.10. [Pd(dmba)(m-L1)](PF6)
A solution of L1 (0.176 g, 0.6 mmol) in dichloro-
methane (5 cm3) was added with stirring to a solution of
[Pt(dmba)(m-Cl)]2 (0.220 g, 0.30 mmol) in dichloro-
methane (5 cm3). After 2 h, the volume of the solution
was reduced in vacuo and hexane added to give 5 as a
colourless powder. Yield 0.272 g (71%). Found: C, 48.5;
H, 3.95; N, 6.55. C26H25ClN3PPt requires C, 48.7; H,
3.93; N, 6.56%. d (1H) (ppm) (CDCl3, 399.8 MHz)
Thallium hexafluorophosphate (0.070 g, 0.20 mmol)
was added to a stirred solution of complex 6 (0.111 mg,
0.20 mmol) in dichloromethane. After stirring for 24 h,
TlCl was removed by filtration. The product slowly
precipitated out of solution as a pale yellow powder,
which was washed with dichloromethane and dried in
vacuo. Yield 0.95 g (72%). Found: C, 46.2; H, 3.66; N,
6.26. C52H50F12N6P4Pd2×
/
1/2CH2Cl2 requires C, 46.2; H,
7.86ꢂ
7.43 (m, 4H, Ph), 7.09ꢂ
2H, Ar), 6.86ꢂ6.80 (m, 1H, pyr), 6.48ꢂ
pyr), 6.32ꢂ6.28 (m, 1H, Ar), 6.24ꢂ6.22 (m, 1H, pyr),
/
7.84 (m, 4H, Ph), 7.62ꢂ
7.04 (m, 1H, Ar), 6.95ꢂ
6.42 (m, 1H,
/
7.58 (m, 2H, Ph), 7.48ꢂ
/
3.76; N, 6.15%. d (1H) (ppm) (CD2Cl2, 270.2 MHz) 7.66
(br, 6H), 7.51 (br, 4H), 6.96 (br, 3H), 6.93 (br, 1H), 6.50
(br, 1H), 6.30 (br, 1H) 6.19 (br, 1H), 4.08 (br, 2H), 2.77
(br, 6H). d (31P) (ppm) (CD2Cl2, 109.4 MHz) 89.8 (s,
/
/6.88 (m,
/
/
/
/
4
3
4
4.14 (d, 2H, JPH 3.2, JPtH 30, CH2), 2.96 (d, 6H, JPH
3
br), ꢃ
141.6 (sept., PF6). n(CN) (cmꢃ1) (KBr) 2248m.
/
3.6, JPtH 24, CH3). d (31P) (ppm) (CDCl3, 161.8 MHz)
64.1 (s, JPtP 4752). n(CN) (cmꢃ1) (KBr) 2220m.
1
2.1.11. [Pd(dmba)(PPh2NC4H3{CÄ
/
NCH(CH2Ph)CH2O-2})]PF6 (8)
2.1.8. [Pd(dmba)Cl(L1-k1P)] (6)
Thallium hexafluorophosphate (0.080 g, 0.23 mmol)
was added to a stirred dichloromethane solution of 6
(0.130 g, 0.23 mmol). After 2 h (S)-2-amino-3-phenyl-1-
propanol (0.035 g, 0.23 mmol) was added and the
suspension was refluxed for 24 h. The solution was
filtered and the solvent removed in vacuo. The resulting
oil was washed with hexane and diethyl ether, then dried
in vacuo to give a glassy white solid. Yield 0.130 g
A dichloromethane solution of L1 (0.370 g, 1.34
mmol) was added with stirring to a solution of
[Pd(dmba)(m-Cl)]2 (0.370 mg, 0.67 mmol) in dichloro-
methane. After 2 h, the volume of the solution was
reduced in vacuo and hexane added. The product
separated as a yellow oil that was recrystallised from
dichloromethaneꢂhexane. Yield 0.526 g (71%). Found:
/
C, 56.3; H, 4.57; N, 7.63. C26H25ClN3PPd requires C,
56.6; H, 4.56; N, 7.61%. d (1H) (ppm) (CDCl3, 399.8
(74%). d (1H) (ppm) (CDCl3, 399.8 MHz) 7.63ꢂ
10H, Ph), 7.18ꢂ7.11 (m, 5H, Ph), 7.02 (d, 1H, J 6.8),
6.88ꢂ6.85 (m, 1H), 6.47ꢂ6.43 (m, 1H), 6.28ꢂ6.26 (m,
1H), 6.20ꢂ6.17 (m, 1H), 5.86 (br.s, 1H), 5.75 (d, 1H, J
8.4), 4.07 (d, 1H, JHH 13.2, CH2N), 3.89 (dd/m, 2H,
/7.37 (m,
/
MHz) 7.91ꢂ
7.51ꢂ7.39 (m, 4H, Ph), 7.05ꢂ
6.87 (m, 1H, Ar), 6.85 (m, 1H, pyr), 6.75 (m, 1H, Ar),
6.49 (m, 1H, pyr), 6.21ꢂ6.15 (m, 2H, Arꢁpyr), 4.15 (d,
/
7.86 (m, 4H, Ph), 7.60ꢂ
/
7.56 (m, 2H, Ph),
/
/
/
/
/
7.03 (m, 1H, Ar), 6.91ꢂ
/
/
2
4
2
/
/
2JHH 13.2, JPH 2.7, CH2N/CHN), 3.80 (dd, 1H, JHH
2H, 4JPH 2.0, CH2), 2.87 (d, 6H, 4JPH 2.4, CH3). d (13C)
(ppm) (CDCl3, 100.5 MHz) 152.4 (s), 149.1 (s), 135.5 (s),
133.2 (s), 131.0 (d, JCP 10), 129.5 (d, JCP 11), 129.0 (s),
126.0 (m), 125.1 (m), 123.5 (m), 114.1 (s), 112.2 (m),
110.3 (d, JCP 7.7), 73.8 (d, JCP 3.8, CH2), 51.2 (s, CH3).
d (31P) (ppm) (CDCl3, 161.8 MHz) 88.2 (s). n(CN)
(cmꢃ1) (KBr) 2220m.
11.4, JHH 3.9, CH2O), 3.64 (dd, 1H, JHH 11.4, JHH
7.2, CH2O), 2.99 (dd, 1H, 2JHH 13.9, 3JHH 3.9, CH2Ph),
3
2
3
4
2.74 (d, 3H, JHP 2.4, CH3), 2.69 (dd, 1H, JHH 13.9,
2
3JHH 3.9, CH2Ph), 2.64 (d, 3H, JHP 2.4, CH3). d (13C)
(ppm) (CDCl3, 75.5 MHz) 138.9 (d, J 8), 138.1 (s),
4
134.1ꢂ
/
133.6 (m), 130.5 (d, J 6), 130.5ꢂ129.6 (m), 129.3
/
(d, J 15), 128.3 (d, J 5), 127.6 (d, J 4), 127.1 (s), 126.0 (d,
J 6), 125.1 (s), 123.4 (s), 119.5 (d, J 3), 113.8 (d, J 4),
2.1.9. [Pt(dmba)(m-L1-k1P,k1N)]2(PF6)2 (7)
Thallium hexafluorophosphate (0.048 g, 0.1 mmol)
was added to a stirred solution of complex 5 (0.080 g,
3
73.1 (d, JPC 3, CH2N), 66.1 (s, CH2O), 57.1 (s, CH),
3
3
50.4 (d, JPC 2, CH3), 50.3 (d, JPC 2, CH3), 37.7 (s,
CH2Ph). d (31P) (ppm) (CDCl3, 161.8 MHz) 86.1 (s),

A.D. Burrows et al. / Inorganica Chimica Acta 350 (2003) 152ꢂ
/162
155
ꢃ
1555s.
/
141.6 (sept. PF6). n(CÄ
/
N) (cmꢃ1) (CH2Cl2) 1607s,
milder conditions than the formation of CÃ
/
P bonds.
This fact has been exploited in the synthesis of tri(N-
pyrrolyl)phosphine [2] and of aminophosphines such as
2.1.12. [MoCl(CO)2(L1-k1P)(h5-C5H5)] (9)
PPh2NHCH2CH2OCH3
[11],
PPh2NHCH2CH2N-
[MoCl(CO)3(h5-C5H5)] (0.299 g, 0.82 mmol) was
added to a hexane solution of L1 (0.229 g, 0.82 mmol)
with stirring. The mixture was refluxed for 10 h after
which the resulting red precipitate was separated by
filtration, washed with hexane and dried in vacuo. Yield
0.394 g (91%). Found: C, 54.1; H, 3.58; N, 5.10.
C24H18ClN2O2PMo requires C, 54.5; H, 3.43; N,
(CH3)2 [12] and PPh2NHC5H4N-2 [13] which have all
been prepared from the reaction of PClPh2 with the
appropriate pyrrole or amine in the presence of triethyl-
amine. This synthesis is also successful for the N-
pyrrolyl-based ketophosphine PPh2{NC4H3C(O)CH3-
2} (L3), though in this case the yield is improved by
use of the base DBU instead of NEt3 [9]. The stronger
base also increases the rate of formation of the product.
Despite the precedence of these syntheses, the reaction
of PClPh2, 2-cyanopyrrole and triethylamine did not
provide a good route to PPh2(NC4H3CN-2) (L1).
Compound L1 was the major product observed in
31P{1H} NMR spectra of crude reaction mixtures, but
other products were also invariably present, and it
proved difficult to isolate L1 from these mixtures.
However, it did prove possible to generate L1 as a
pure compound in good yield from a two-step process.
In this method, 2-cyanopyrrole was reacted with BuLi to
give lithium 2-cyanopyrrolide, and this intermediate was
reacted, without isolation, with Ph2PCl to give L1 as
colourless crystals following recrystallisation from
5.30%. d (1H) (ppm) (CDCl3, 399.8 MHz) 7.66ꢂ
7.45
/
(m, 10H, Ph), 7.10 (m, 1H, pyr), 6.65 (m, 1H, pyr), 6.23
(m, 1H, pyr), 5.63 (s, 5H, Cp). d (31P) (ppm) (CDCl3,
161.8 MHz) 114.5 (s). n(CN) (cmꢃ1) (KBr) 2217m;
n(CO) (cmꢃ1) (KBr) 1979s, 1901s.
2.1.13. [Rh(acac)(CO)(L1-k1P)] (10)
[Rh(acac)(CO)2] (0.116 g, 0.45 mmol) was added to a
stirred solution of L1 (0.125 g, 0.45 mmol) in dichlor-
omethane. After 2 h, the volume of solvent was reduced
in vacuo and diethyl ether added to precipitate 10 as a
yellow powder. This was separated by filtration, washed
with diethyl ether and dried in vacuo. Yield 0.181 g
(79%). Found: C, 52.9; H, 3.83; N, 5.30.
C23H20N2O3PRh×
5.31%. d (1H) (ppm) (CD2Cl2, 399.8 MHz) 7.69ꢂ
(m, 4H, Ph), 7.56ꢂ7.46 (m, 7H, Ph and pyr), 7.08 (m,
/1/4CH2Cl2 requires 52.9; H, 3.92; N,
THFꢂ
hexane. L1 was characterised on the basis of
/
/
7.64
NMR and IR spectroscopy. The 31P{1H} NMR spec-
trum shows a singlet at d 51.8, which is close to value
observed previously for L3 (d 55.8). The CN stretching
/
1H, pyr), 6.34 (m, 1H, pyr), 5.50 (s, 1H, CH), 2.11 (s,
3H, CH3), 1.70 (s, 3H, CH3). d (31P) (ppm) (CD2Cl2,
frequency is observed in the IR spectrum at 2218 cmꢃ1
.
1
161.8 MHz): d 98.1 (d, JPRh 197). n(CN) (cmꢃ1
)
The functionalised tri-N-pyrrolylphosphine P(NC4-
H4)2(NC4H3CN-2) (L2) was prepared by the reaction of
PCl(NC4H4)2 [10] with lithium 2-cyanopyrrolide in an
analogous manner. The 31P{1H} NMR spectrum for L2
shows a singlet at d 80.1, whereas the CN stretching
(CH2Cl2) 2218m; n(CO) (cmꢃ1) (CH2Cl2) 1992s.
2.2. Crystallography
X-ray data for compound cis-1×
lected on an EnrafꢂNonius CAD4 automatic four-circle
diffractometer using Mo Ka radiation (lꢀ
/2CH2Cl2 was col-
frequency is observed in the IR spectrum at 2221 cmꢃ1
.
/
The higher value for the chemical shift of L2 with respect
to L1 is consistent with the reduced s-basicity of this
ligand.
˚
0.71069 A),
/
and corrected for Lorentz, polarisation and absorption
(DIFABS, max and min transmission factors 1.000 and
The cyanophosphine L1 is more sensitive to hydrolysis
and alcoholysis than the ketophosphine L3, with the
reaction with methanol to give Ph2POMe reaching
completion within minutes rather than hours. Substitu-
tion of the two phenyl groups for N-pyrrolyl groups did
not affect the stability, which is surprising given the
stability to alcoholysis of tri-N-pyrrolylphosphine [2]. In
contrast to L3, the cyanophosphines L1 and L2 are also
somewhat light sensitive, slowly decomposing with a
progressive darkening in colour to deep red.
0.476). X-ray data for compounds 4, 7×
/
CH2Cl2 and 9
were collected on a Nonius Kappa CCD diffractometer
˚
0.71070 A), and corrected
using Mo Ka radiation (lꢀ
for Lorentz, polarisation and absorption (multiscan,
max and min corrections 1.055 and 0.963 for 7×CH2Cl2).
/
/
The crystal data, data collection and refinements are
summarised in Table 4. The refinements were all full-
matrix least-squares based on F2.
3. Results and discussion
3.2. Reactions of [MCl2(cod)] with L1 and L2
3.1. Ligand synthesis
The reactions of [MCl2(cod)] (MꢀPt, Pd) with 2
/
equiv. of L1 or L2 gave rise to complexes of the general
formula [MCl2L2] in good yields. The complex
[PtCl2(L1-k1P)2] (1) was formed initially as a mixture
Since NH bonds are typically more acidic than CH
P bonds generally requires
bonds, the formation of NÃ
/

156
A.D. Burrows et al. / Inorganica Chimica Acta 350 (2003) 152ꢂ162
/
of the cis and trans isomers (Â
/
10:1) as witnessed in the
Table 1
Selected bond lengths (A) and angles (8) for complexes cis-1×
and 4
31P{1H} NMR spectra by singlets with 195Pt satellites at
d 54.3 (1JPtP 4021 Hz) and d 63.3 (1JPtP 2972 Hz),
respectively. Both the chemical shift and coupling
constant values allow the major product to be assigned
as the cis-isomer. The IR spectrum shows n(CN) at 2215
cmꢃ1, which is virtually unchanged from the free ligand.
The cis isomer of complex 1 was purified by recrystalli-
˚
/
2CH2Cl2
cis-1×
/
2CH2Cl2
4
Bond lengths
Pt(1)Ã
Pt(1)Ã
P(1)Ã
N(1)Ã
N(1)Ã
N(2)Ã
C(13)Ã
C(14)Ã
C(15)Ã
C(16)Ã
/
P(1)?
2.2451(10) Pd(1)Ã
/
P(1)
Cl(1)
2.2924(6)
2.2854(6)
1.679(2)
1.670(2)
1.703(2)
1.423(3)
1.145(3)
/Cl(1)?
2.3408(11) Pd(1)Ã
/
/
N(1)?
1.729(3)
1.386(4)
1.393(5)
1.143(6)
1.339(6)
1.404(6)
1.356(5)
1.413(5)
P(1)Ã
P(1)Ã
P(1)Ã
/
N(1)
/
C(13)
C(16)
C(17)
/N(2)
sation from dichloromethaneꢂhexane, and a single-
/
/
/N(3)
crystal X-ray analysis confirmed its identity. The com-
plex [PdCl2(L1-k1P)2] (2) proved to be only sparingly
soluble in dichloromethane, precipitating during the
reaction between [PdCl2(cod)] and L1. The 31P{1H}
NMR spectrum of the powder, dissolved in CD2Cl2,
consisted of a singlet at d 68.0, whereas that of the
filtrate contained in addition to this a singlet at d 79.3.
On the basis of the chemical shift data and solubilities
the isolated compound can be characterised as the trans
isomer, with the more soluble minor compound being
the cis isomer. As with 1, n(CN) is virtually unchanged
from L1.
In contrast to the reactions with L1, only single
isomers were observed in the reactions with L2. The
31P{1H} NMR spectrum of the compound cis-
[PtCl2(L2-k1P)2] (3) consists of a singlet with 195Pt
satellites at d 69.2 (1JPtP 3915 Hz) whereas that of the
compound trans-[PdCl2(L2-k1P)2] (4) consists of a
singlet at d 74.4. The IR spectra of 3 and 4 both show
n(CN) as being virtually unchanged from the free
phosphine. The identity of 4 as the trans isomer was
confirmed by a single crystal analysis.
/
C(12)Ã
/
C(13)
/
C(14)
C(15)
C(16)
C(17)
N(4)ÃC(13)
/
/
/
/
Bond angles
P(1)ÃPt(1)Ã
P(1)ÃPt(1)Ã
P(1)ÃPt(1)Ã
Cl(1)Ã
N(2)ÃC(17)Ã
/
/
P(1)
107.22(5)
169.99(4)
82.48(4)
87.95(6)
177.7(5)
P(1)Ã
Cl(1)Ã
Cl(1)Ã
Cl(1)Ã
N(4)ÃC(13)Ã
/
Pd(1)Ã
Pd(1)Ã
Pd(1)Ã
Pd(1)Ã
/
P(1)??
180.0
180.0
/
/
Cl(1)
Cl(1)
/
/Cl(1)??
/
/
/
/P(1)
88.59(2)
91.41(2)
178.5(3)
/
Pt(1)Ã
/
Cl(1)
C(16)
/
/P(1)??
/
/
/
/
C(12)
Primed atoms generated by the symmetry transformation ꢃ
zꢁ2 and double primed atoms by the transformation ꢃx, ꢃ
zꢁ2.
/
x, y,
ꢃ
ꢃ/
/
/
/
/y,
/
Selected bond lengths and angles are given in Table 1.
The most striking feature of this structure is the PÃPtÃ
/
/
P
angle which at 107.22(5)8 is one of the largest observed
for a cis-dichlorobis(phosphine)platinum(II) complex.
Indeed, a search of the Cambridge Structural Database
[14] revealed a mean value of 97.28 for this angle in
complexes of the general formula cis-[PtCl2P2] in which
the phosphorus donors are located on different ligands.
Only one other complex has a PÃ
/
PtÃ
/
P angle as wide as
that observed for cis-1: this is cis-[PtCl2(PPhBu2t)2],
where the angle at 107.3(4)8 is similar to that in cis-1
[15]. In cis-[PtCl2(PPhBu2t)2] the wide angle is clearly a
consequence of the steric bulk of the phosphines, but in
The crystal structure determination of the platinum
complex cis-1×
geometry to be distorted square-planar (Fig. 1) with PtÃ
Cl and PtÃP distances within the expected ranges.
/
2CH2Cl2 revealed the metal coordination
/
/
Fig. 1. Molecular structure of complex cis-1×
/2CH2Cl2 with thermal ellipsoids shown at the 30% probability level. Included CH2Cl2 molecules have
been omitted for clarity.

A.D. Burrows et al. / Inorganica Chimica Acta 350 (2003) 152ꢂ
/162
157
cis-1 the cause is not so straightforward. Indeed, the
orientation adopted by the ligand in the solid state
reveals that the 2-cyano-N-pyrrolyl group is not ex-
ceptionally sterically demanding. The crystallographic
cone angle [16] for L1 in the structure of complex cis-1 is
1698, with the 2-cyano-N-pyrrolyl ring less sterically
demanding than the two phenyl rings (u/2 82.5, vs. 85.8
and 84.98)1. Examination of the crystal structure reveals
lyl)diphenylphosphine has been previously observed
[19].
3.3. Reactions of [M(dmba)(m-Cl)]2 with L1
Although (cyanoethyl)phosphines have been well
studied [20,21], ligands with rigid spacers between the
phosphino and cyano groups, such as Ph2PC6H4CN-2
[22], have received far less attention. There is some
spectroscopic evidence [23] for h2-coordination of the
cyano groups in rhenium(I) and manganese(I) com-
plexes of Ph2PC6H4CN-2, but these compounds have
not been crystallographically characterised, and it is
more likely that the ligands bridge between metal centres
with a s-bonded cyano group [24]. In order to assess the
coordination ability of the cyano group in L1, the
the wide PÃ
/
PtÃ/P angle has its origin in an intramole-
cular offset pÁ Á Áp interaction between the two 2-cyano-
N-pyrrolyl groups. The angle between the two mean
planes defined by the carbon and nitrogen atoms in the
pyrrolyl rings is 48, with the shortest inter-plane distance
˚
being that between C(15) and C(15)? (3.18 A). If the PÃ
/
PtÃ
/
P angle were more acute, this interaction between
pyrrolyl rings would be prevented on steric grounds.
Another noteworthy point is that the sum of angles
around N(1) is close to 3608 reflecting no change in the
sp2 hybridisation of the pyrrolyl nitrogen atom on
coordination.
complexes [MCl(dmba)(L1-k1P)] (5, Mꢀ
Pd; HdmbaꢀN,N-dimethylbenzylamine) were pre-
pared and reacted with TlPF6.
/
Pt; 6, Mꢀ
/
/
Complex 5 was prepared from the reaction of
[Pt(dmba)(m-Cl)]2 with L1 and characterised on the basis
of NMR and IR spectroscopy. The 31P{1H} NMR
spectrum of 5 gave a singlet with 195Pt satellites at d 64.1
[1JPtP 4752 Hz] demonstrating that only one of the two
potential geometric isomers was formed. The high value
Structural analysis of 4 revealed the palladium atom
lies on an inversion centre with half site occupancy. The
geometry around the metal centre is distorted square-
planar, with cis angles of 88.59(2) and 91.41(2)8. The
molecular structure of 4 is shown in Fig. 2(a), and
selected bond lengths and angles are given in Table 1.
Analysis of the conformation of the phosphine ligands
revealed that L2 in 4 has the same crystallographic cone
angle (1698) as L1 in cis-1, reflecting the similar steric
requirements of phenyl and pyrrolyl groups [17]. The
sum of angles around each of the pyrrolyl nitrogen
atoms is close to 3608. Obviously the trans orientation
of the ligands in the structure prevents any intramole-
cular interaction between the cyanopyrrolyl groups. The
supramolecular structure of 4 reveals no intermolecular
1
4
of JPtP together with observation of JPH coupling in
1
the H NMR spectrum indicates that the phosphorus
atom is coordinated trans to the dmba nitrogen atom
[20]. In the IR spectrum n(CN) was observed at 2220
cmꢃ1 consistent with non-coordination of the cyano
group. Complex 6 was prepared from the analogous
reaction of [Pd(dmba)(m-Cl)]2 with L1 and also char-
acterised on the basis of NMR and IR spectroscopy.
The 31P{1H} NMR spectrum of 6 gave a singlet at d
88.2, again demonstrating formation of a single isomer.
4
1
As for complex 5, the observation of JPH in the H
NMR spectrum confirmed the trans arrangement of the
phosphorus and nitrogen atoms. In the IR spectrum of
pÁ Á Áp interaction to be present either*
molecules are linked into chains via the formation of
CÃHÁ Á ÁN hydrogen bonds involving a cyanopyrrolyl
CH group and the cyano nitrogen atom [C(10)Á Á ÁN(4)
/instead, the
6, n(CN) was observed at 2220 cmꢃ1
.
/
Reaction of complex 5 with TlPF6 gave a precipitate
of TlCl and the initial formation of three compounds,
observed in the 31P{1H} NMR spectrum with similar
˚
˚
3.392(4) A, H(10)Á Á ÁN(4) 2.51 A, C(10)Ã
/
H(10)Á Á ÁN(4)
HÁ Á ÁCl
hydrogen bonds [C(6)Á Á ÁCl(1) 3.659(3) A, H(6)Á Á ÁCl(1)
1558]. These chains are cross-linked by CÃ
/
1
values for JPtP [d 70.9 (1JPtP 4363 Hz, 55%), d 66.8
˚
(1JPtP 4654 Hz, 15%), d 58.2 (1JPtP 4448 Hz, 30%)]
˚
2.76 A, C(6)Ã
shown in Fig. 2(b).
The PÃN distances in 4 and cis-1 are longer than
/
H(6)Á Á ÁCl(1) 1628]. These interactions are
together with a septet at d ꢃ
141.6 for the PF6ꢃ ion. On
/
standing for several hours, the signal for one of these
compounds [d 70.9] increased in intensity at the expense
of the other two, and after recrystallisation from
/
those in platinum(II) complexes of PPh2NHR [7] and
tri(N-pyrrolyl)phosphine [18]. The non-involvement of
the nitrogen lone pair in an aromatic ring in aminophos-
dichloromethaneꢂhexane only this product was ob-
/
served in the spectrum of both the solid and the mother
liquor, demonstrating it to be the thermodynamic
product of the reaction. The IR spectrum of this
compound shows n(CN) at 2258 cmꢃ1. The shift to a
phines allows for greater PÃ
than in N-pyrrolyl phosphines, whereas the increase in
N distances on going from tri(N-pyrrolyl)phosphine
/
N double bond character
PÃ
/
through di(N-pyrrolyl)phenylphosphine to (N-pyrro-
higher wavenumber relative to 5 (Dnꢀ
/
38 cmꢃ1) is
consistent with coordination of the cyano group
through the nitrogen atom [25]. This compound has
1
˚
van der Waals’ radius of 1.55 A used for N(1).

158
A.D. Burrows et al. / Inorganica Chimica Acta 350 (2003) 152ꢂ162
/
Fig. 2. (a) Molecular structure of complex 4 with thermal ellipsoids shown at the 30% probability level. (b) Formation of chains in the crystal
structure of 4 through CÃHÁ Á ÁN hydrogen bonds.
/
been characterised crystallographically as the dimer
[Pt(dmba)(m-L1-k1P,k1N)]2(PF6)2 (7). The two other
compounds observed in the initial NMR spectra have
yet to be characterised. Although it is tempting to assign
these to higher cyclic oligomers on the basis of their
similar coupling constants to 7, there is no evidence in
the FAB MS of the crude reaction mixture for such
species.
The X-ray crystal structure analysis of 7×
/
CH2Cl2
revealed that the cationic complex is dimeric (Fig. 3),
with coordination of the cyano nitrogen atom to a
second platinum atom leading to the formation of a 12-
membered ring. Selected bond lengths and angles are
given in Table 2. The geometry around each of the two
independent platinum centres is distorted square-planar,
with cis angles in the range 81.7(2)ꢂ94.51(14)8 for Pt(1)
/

A.D. Burrows et al. / Inorganica Chimica Acta 350 (2003) 152ꢂ
/162
159
Fig. 3. Structure of the cation in complex 7×CH2Cl2 with thermal ellipsoids shown at the 30% probability level. Hydrogen atoms have been omitted
/
for clarity.
Reaction of complex 6 with TlPF6 also gave a
precipitate of TlCl. A compound of empirical formula
[Pd(dmba)(m-L1-k1P,k1N)](PF6) was isolated, though
the low solubility and consequently the broad nature
of the NMR spectra mean it is not possible to say
whether the product is a dimer, directly analogous to 7,
or a mixture of higher oligomers. As with 7, the shift of
Table 2
˚
Selected bond lengths (A) and angles (8) for complex 7×
/
CH2Cl2
Bond lengths
Pt(1)Ã
Pt(1)Ã
Pt(1)Ã
Pt(1)Ã
Pt(2)Ã
Pt(2)Ã
Pt(2)Ã
Pt(2)Ã
/
C(18)
N(5)
N(3)
P(1)
2.024(6)
2.055(5)
2.125(5)
2.2186(14)
2.017(5)
2.047(4)
2.124(4)
2.2188(14)
1.751(5)
1.766(5)
1.148(7)
1.151(7)
/
/
/
n(CN) to a higher wavenumber (nꢀ
/
2248 cmꢃ1, Dnꢀ
/
30
/
C(44)
N(2)
N(6)
P(2)
cmꢃ1) is indicative of coordination of the cyano group
through the nitrogen atom. Similar observations were
reported by Braunstein and co-workers following the
reaction of [PdCl(dmba)(PPh2CH2CN)] with AgPF6
[20].
/
/
/
P(1)Ã
P(2)Ã
N(2)Ã
N(5)Ã
/
N(1)
/N(4)
/
C(17)
C(43)
/
Bond angles
C(18)ÃPt(1)Ã
C(18)ÃPt(1)Ã
N(5)ÃPt(1)Ã
C(18)ÃPt(1)Ã
N(5)ÃPt(1)Ã
N(3)ÃPt(1)Ã
C(44)Ã
C(44)Ã
N(2)ÃPt(2)Ã
C(44)ÃPt(2)Ã
N(2)ÃPt(2)Ã
N(6)ÃPt(2)Ã
C(17)ÃN(2)Ã
C(43)ÃN(5)Ã
N(2)ÃC(17)Ã
N(5)ÃC(43)Ã
3.4. Preparation of phosphino-oxazolines
/
/
N(5)
N(3)
172.1(2)
81.7(2)
/
/
An important reaction of cyano groups is their
conversion, on reaction with an amino alcohol, to
oxazoline groups. Phosphino-oxazolines have been
used as chiral P,N-donor ligands in a number of
catalytic reactions [27] and have also been shown to
act as hemilabile ligands [28]. Recently Pfaltz and co-
workers demonstrated that N-pyrrolyl phosphines con-
taining oxazoline groups could be prepared from a
oxazoline-functionalised pyrrole [29].
Our approach, contemporary with this, involved pre-
formation of a P,N-coordinated complex of the cyano-
phosphine and reaction of it with an amino alcohol.
Coordination of the phosphorus atom should improve
/
/
N(3)
91.0(2)
/
/
P(1)
92.83(18)
94.51(14)
174.51(15)
173.2(2)
81.73(19)
92.09(17)
92.16(16)
93.99(12)
173.86(13)
170.8(4)
170.4(5)
172.7(6)
174.5(6)
/
/
P(1)
/
/
P(1)
/
Pt(2)Ã
/
N(2)
N(6)
/
Pt(2)Ã
/
/
/
N(6)
/
/
P(2)
/
/
P(2)
/
/
P(2)
/
/
Pt(2)
Pt(1)
C(16)
C(42)
/
/
/
/
/
/
the stability of the PÃ
/
N bond towards alcoholysis,
and 81.73(19)ꢂ93.96(12)8 for Pt(2). The angle between
/
whereas coordination of the nitrogen atom should
activate the carbon atom of the nitrile group. Initial
reactions using ZnCl2, [PdCl2(cod)] and [PdCl(CH3)-
(cod)] with 2-methyl-2-aminopropanol were all promis-
ing, as indicated by the NMR and IR spectra of the
crude reaction mixtures. However, satisfactory analyti-
the two coordination planes is 80.58. There is only one
previously reported crystal structure of a cyanophos-
phine complex in which the ligand is acting in a bridging
manner, which is the octahedral nickel(II) complex
[NiBr2{P(CH2CH2CN)3}2] [26].

160
A.D. Burrows et al. / Inorganica Chimica Acta 350 (2003) 152ꢂ162
/
cal results could not be obtained due to difficulties in
purification. In contrast, the cyanophosphine complex
[PdCl(dmba)(L1-k1P)] (6) reacts with the amino alcohol
(S)-(ꢃ
the presence of TlPF6 to give the compound
[Pd(dmba)(PPh2NC4H3{C Ä NCH(CH2Ph)CH2O-
/
)-2-amino-3-phenyl-1-propanol under reflux in
/
2})]PF6 (8), which can be isolated in good yield after
work up as a glassy colourless solid (Scheme 1). The
31P{1H} NMR spectrum for 8 showed a singlet at d 86.1
in addition to the septet for the hexafluorophosphate.
The 13C{1H}, 1H and 13CÃ
/
1H correlation NMR spectra
confirmed that the cyano group had been converted into
an oxazoline group. The IR spectrum confirmed the
absence of n(CÅ
/
N) and the presence of n(CÄ/N) at 1607
cmꢃ1
.
3.5. Molybdenum complexes of L1
Fig. 4. Molecular structure of complex 9 with thermal ellipsoids
shown at the 30% probability level.
In order to investigate the coordination behaviour of
L1 on an earlier transition metal the complex
[MoCl(CO)2(L1-k1P)(h5-C5H5)] (9) was prepared from
the reaction of [MoCl(CO)3(h5-C5H5)] with L1 in
refluxing hexane. In the 31P{1H} NMR spectrum a
singlet was observed at d 114.5, in a similar position to
the resonance observed for [MoCl(CO)2(L3-k1P)(h5-
C5H5)] (d 112.2) [9]. In the IR spectrum two carbonyl
resonances reflect the cis geometry of the carbonyls and
n(CN) is observed at 2217 cmꢃ1, close to the frequency
observed for free ligand. Further confirmation of the
identity of 9 was obtained by a single crystal X-ray
analysis. Suitable single crystals were grown by diffusion
of hexane into a dichloromethane solution. The mole-
cular structure of 9 is shown in Fig. 4, and selected bond
lengths and angles are given in Table 3. The compound
adopts a pseudo square-pyramidal geometry, with the
cis carbonyls and the phosphorus and chlorine atoms
forming the base of the pyramid and the cyclopentadie-
nyl ligand the apex. The bond lengths and angles are
Table 3
˚
Selected bond lengths (A) and angles (8) for complex 9
Bond lengths
Mo(1)Ã
Mo(1)Ã
Mo(1)Ã
Mo(1)Ã
P(1)Ã
N(2)Ã
/
C(1)
C(2)
P(1)
Cl(1)
1.987(3)
1.970(3)
2.4842(6)
2.5171(7)
1.758(2)
1.151(4)
/
/
/
/
N(1)
/
C(3)
Bond angles
C(2)ÃMo(1)Ã
C(1)ÃMo(1)Ã
C(2)ÃMo(1)Ã
C(1)ÃMo(1)Ã
C(2)ÃMo(1)Ã
P(1)ÃMo(1)Ã
N(2)ÃC(3)ÃC(4)
/
/
C(1)
P(1)
P(1)
Cl(1)
Cl(1)
76.97(11)
118.77(8)
80.04(8)
77.64(8)
131.70(8)
77.28(2)
175.2(3)
/
/
/
/
/
/
/
/
/
/Cl(1)
/
/
unremarkable, though since the MoÃ
/
P distance is longer
than the MÃP distances in cis-1, trans-4 and 7, the
/
after this time. In contrast, stirring with AgBF4 led to a
precipitate of AgCl, showing abstraction had taken
place. However, the 31P{1H} NMR spectrum contained
a large number of peaks suggesting decomposition had
occurred.
crystallographic cone angle for the ligand is less (1558).
Compound 9 was treated with both TlPF6 and AgBF4
in attempts to abstract the chloride. On stirring for 24 h
in the presence of TlPF6 no reaction was observed, the
31P{1H} NMR spectrum being essentially unchanged
Scheme 1.

A.D. Burrows et al. / Inorganica Chimica Acta 350 (2003) 152ꢂ
/162
161
Table 4
Crystal data for compounds cis-1×
/
2CH2Cl2, 4, 7×
/
CH2Cl2 and 9
Complex
Empirical formula
cis-1×
/
2CH2Cl2
36H30Cl6N4P2Pt
4
7×
/
CH2Cl2
9
C
C26H22Cl2N8P2Pd
685.76
150(2)
C53H52Cl2F12N6P4Pt2
1585.97
C24H18ClMoN2O2P
528.76
150(2)
M
988.37
293(2)
Temperature
Crystal system
170(2)
orthorhombic
P212121
monoclinic
C2/c
monoclinic
P21/c
monoclinic
P21/n
Space group
a
17.714(4)
10.435(2)
21.233(3)
100.91(2)
3853.9(13)
4
8.1320(2)
19.3020(5)
9.1750(2)
95.2340(10)
1434.14(6)
2
14.1900(1)
16.5460(1)
24.7970(3)
90
9.4160(3)
14.2570(5)
16.6620(6)
104.9120(18)
2161.44(13)
4
b
c
b
U
5822.03(9)
4
5.082
Z
m(Mo Ka) (mmꢃ1
)
4.172
4729
4179
0.977
17 059
0.829
24 188
Reflections collected
Independent reflections
Rint
99 327
13 319
0.0774
3266
0.0609
4936
0.0497
R1, wR2 [I ꢀ
R indices (all data)
/
2s(I)]
0.0290, 0.0732
0.0360, 0.0753
0.0306, 0.0735
0.0459, 0.0805
0.0317, 0.0780
0.0425, 0.0859
0.0341, 0.0846
0.0451, 0.0919
3.6. Synthesis of [Rh(acac)(CO)(L1-k1P)]
gen bonds respectively, have been shown to be impor-
tant in the solid state with the former leading to an
Carbonyl stretching frequencies can be useful indica-
tors in determining the electronic properties of a
phosphine co-ligand. A considerable body of data has
been compiled for complexes of the general formula
[Rh(acac)(CO)L], which can usually be prepared in a
straightforward manner from the reaction of [Rh(a-
cac)(CO)2] with L. Reaction of L1 with [Rh(acac)(CO)2]
in dichloromethane gave, as anticipated, [Rh(a-
cac)(CO)(L1-k1P)] (10) in good yield. The carbonyl
stretching frequency for 10 was observed at 1992
cmꢃ1, which is very similar to the value previously
reported for [Rh(acac)(CO){PPh2(NC4H4)}] (1990
cmꢃ1) [30]. This suggests that introduction of the cyano
functionality into the pyrrolyl ring has little effect on the
electronic properties of the phosphine. In the 31P{1H}
NMR spectrum of 10 a doublet was observed at d 98.1
(1JPRh 197 Hz), and in the IR spectrum n(CN) was
unusually large PÃ
/
PtÃ
/
P angle in cis-1.
5. Supplementary material
Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre as
CCDC Nos. 186630ꢂ186633. Copies of the data can be
obtained free of charge on application to The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
/
(fax: ꢁ44-1223-336-033; e-mail: deposit@ccdc.cam.ac.
/
uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
observed at 2218 cmꢃ1
.
The authors would like to thank the EPSRC for
financial support and Johnson-Matthey plc for a
generous loan of platinum metal salts.
4. Conclusions
In this paper we have demonstrated that cyano-
functionalised N-pyrrolyl phosphines can be readily
prepared, and that they can act as either P-donor or
bridging P,N-donor ligands. Infrared spectroscopic
data indicates that the 2-cyano-N-pyrrolyl group is as
electron-withdrawing as the N-pyrrolyl group, demon-
strating that functionalised N-pyrrolyl phosphines can
be prepared without destroying the useful electronic
properties of the N-pyrrolyl phosphine core. The cyano
group can also be readily converted into an oxazoline
group. Both intra- and intermolecular interactions,
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