2-(Diphenylphosphinoylmethyl)pyrrole-2-(diphenylphosphinomethyl)-pyrrole (0.43/0.57) and tetrachlorido-(5-diphenylphosphinomethyl-2H-pyrrole- κ2 N,P)titanium(IV)

Article abstract of DOI:10.1107/S0108270110004506

The title phosphine oxide-phosphine, 0.43C₁₇H ₁₆NOP·0.57C₁₇H₁₆NP, (I)/(II), was obtained as a 0.861 (6):1.139 (6) cocrystallized mixture. Hydrogen bonding between the two constituents leads to the formation of 2:2 solid-state assemblies. Instead of forming the expected simple N,P-chelated system via loss of the N-bound H atom, reaction of 2-(diphenyl-phosphinometh-yl)pyrrole, (II), with TiCl₄ leads to the formation of the title titanium(IV) complex, [TiCl₄(C₁₇H₁₆NP)], (IV), containing a rearranged neutral ligand in which the N-bound H atom moves to one of the pyrrole C atoms, giving a partially unsaturated ring.

Full text of DOI:10.1107/S0108270110004506

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
system. Exploring the reactivity of pyrrole–phosphine oxide
ligands with early transition metals has shown that the phos-
phine oxide acts as a well behaved ligand with these metals.
We report here on efforts to use 2-(diphenylphosphino-
methyl)pyrrole, (II), with early transition metals.
ISSN 0108-2701
2-(Diphenylphosphinoylmethyl)-
pyrrole–2-(diphenylphosphinomethyl)-
pyrrole (0.43/0.57) and tetrachlorido-
(5-diphenylphosphinomethyl-2H-
pyrrole-j2N,P)titanium(IV)
Lewis M. Broomfield, Manfred Bochmann and Joseph A.
Wright*
School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, England
Correspondence e-mail: joseph.wright@uea.ac.uk
Received 16 December 2009
Accepted 4 February 2010
Online 24 February 2010
The title phosphine oxide–phosphine, 0.43C17H16NOPꢀ-
0.57C17H16NP, (I)/(II), was obtained as a 0.861 (6):1.139 (6)
cocrystallized mixture. Hydrogen bonding between the two
constituents leads to the formation of 2:2 solid-state
assemblies. Instead of forming the expected simple N,P-
chelated system via loss of the N-bound H atom, reaction of
2-(diphenylphosphinomethyl)pyrrole, (II), with TiCl4 leads to
the formation of the title titanium(IV) complex, [TiCl4-
(C17H16NP)], (IV), containing a rearranged neutral ligand in
which the N-bound H atom moves to one of the pyrrole C
atoms, giving a partially unsaturated ring.
Comment
The desire to improve on existing catalytic processes and find
new catalytic systems continues to drive synthetic chemists to
create novel ligand systems. For example, ongoing efforts to
find post-metallocene polymerization catalysts for alkenes
(Gibson & Spitzmesser, 2003) have led to the introduction of a
large class of salicylaldiminate and pyrrolaldiminate ligands
(see, for example, Yoshida et al., 2001; Tsurugi & Mashima,
2006; Cui et al., 2003; Yang et al., 2007). The combination of an
anionic pyrrolate moiety with other donors is, however, less
common. In an effort to explore routes to new N,P- and N,O-
chelate ligands based on pyrrolates, we have recently intro-
duced the families of pyrrole–phosphine oxide [see (I) in the
scheme as an example] and pyrrole–phosphine ligands [see
(II) in the scheme as an example] (Broomfield, Boschert et al.,
2009; Broomfield, Wright et al., 2009). These ligands are
attractive as the nature of the groups on the P atom [phenyl in
both (I) and (II)] can be varied at a late stage of the synthesis
by appropriate choice of the phosphine starting material. The
introduction of other groups onto the pyrrole ring is another
potential method for tuning the properties of the ligand
Reaction of (II) with ZrCl4 in tetrahydrofuran (THF) was
carried out with the intention of forming the bis-ligand
complex (III) (see scheme). However, crystallization of the
reaction mixture led to the isolation of crystals with an
approximately stoichiometric mixture of cocrystallized (I) and
(II), denoted (I)/(II) (Fig. 1). Synthesis of (II) from (I) is
complicated by the reactivity of the phosphine with oxygen,
and it is possible that the metal complex is not involved in
formation of the cocrystals. The occupancy of O1 was refined
freely, establishing that the site is largely occupied
[occupancy = 0.861 (6)].
The molecular geometry of (I) here (Table 1) is very similar
to that observed when the same molecule crystallizes in the
absence of (II) (Broomfield, Wright et al., 2009). The geo-
metric data observed for (I) are also in the range anticipated
for this molecule. More interesting are the intermolecular
interactions between (I) and (II) (Fig. 2 and Table 2).
Hydrogen bonding between two molecules of (I) leads to
solid-state dimer formation. This is in contrast with the
Acta Cryst. (2010). C66, m79–m82
doi:10.1107/S0108270110004506
# 2010 International Union of Crystallography m79

metal-organic compounds
Figure 2
The hydrogen-bond arrangement in (I)/(II). Displacement ellipsoids are
drawn at the 50% probability level and dashed lines indicate hydrogen
bonds. Primed atoms are generated by the symmetry operation (ꢁx, 1 ꢁ y,
ꢁz).
Figure 1
The structure of (I)/(II), showing the atom-numbering scheme. Displace-
ment ellipsoids are drawn at the 50% probability level. H atoms except
H1 and H2 have been omitted for clarity. The dashed line indicates a
hydrogen bond.
supramolecular arrangement seen in crystals of (I) alone,
where infinite one-dimensional chains are formed by
hydrogen bonding between adjacent molecules (Broomfield,
Wright et al., 2009). The O1ꢀ ꢀ ꢀN1i [symmetry code: (i) ꢁx,
˚
ꢁy + 1, ꢁz] separation observed here [2.821 (4) A] is slightly
shorter than that seen in the infinite chain arrangement
˚
[2.868 (3) A]. In addition to this pairing hydrogen-bond
interaction, each molecule of (I) also hydrogen bonds to one
˚
molecule of (II), with an O1ꢀ ꢀ ꢀN2 distance of 2.790 (3) A. The
result of this hydrogen-bond framework is the formation of an
overall zero-dimensional 2:2 supramolecular structure.
A search of the Cambridge Structural Database (CSD,
Version 5.31, 20 November 2009 release; Allen, 2002) reveals
five structures which consist of independent molecules of a
phosphine and its oxide, viz. refcodes AZUDII (Atikinson et
al., 2004), EXUDAC (Mohamed et al., 2004), QEMFAP
(Chekhlov, 2000), SIXJEO (Carriedo et al., 1990) and
UJAPEA (Hitchcock et al., 2003). All show statistical inter-
spersion of the phosphine oxide in the structure, in marked
contrast with the pattern seen here. The presence of the
strongly hydrogen-bonding amine group and the resulting
hydrogen-bond network may account for the greater order
seen in the present structure.
Figure 3
The structure of (IV), showing the atom-numbering scheme. Displace-
ment ellipsoids are drawn at the 50% probability level and H atoms are
shown as small spheres of arbitrary radii.
rearrangement (see scheme). This type of rearrangement has
previously been reported when pyrroles are reacted in the
presence of the strong Lewis base B(C6F5)3 (Guidotti et al.,
2003; Focante et al., 2004; Kehr et al., 2001).
There are two structures in the CSD which contain a re-
arranged pyrrole ligand without the presence of a porphyrin
ring or secondary bonding interactions, viz. refcodes WELTIQ
(DuBois et al., 1999) and XITLES (Kreickmann et al., 2007).
WELTIQ contains rhenium, and has an Re—N bond distance
˚
In contrast with the lack of reaction between (II) and ZrCl4,
reaction of (II) with TiCl4 did lead to the formation of a metal-
containing species (see scheme). However, analysis of the
difference Fourier map following data collection revealed that
C3 carries two H atoms and the ligand is neutral overall, giving
complex (IV) (Fig. 3). The C—C distances in the nitrogen-
containing ring are fully in agreement with the locations of the
H atoms (Table 3). The coordination geometry of the metal
atom is approximately octahedral, with the N1—Ti1—P1 bite
angle significantly smaller than 90ꢂ, presumably due to the
constraint imposed by the ligand backbone. The mechanism
for the reaction is likely to involve initial coordination of (II)
to the metal, yielding (V), followed by an acid-mediated
of 2.171 (6) A, while XITLES is a tungsten complex, with a
˚
W—N distance of 2.136 (3) A. The Ti—N distance obtained in
˚
the current work, 2.174 (5) A, is therefore somewhat longer
than might initially be anticipated on the basis of the smaller
size of the Ti centre compared with Re and W. In the case of
Ti—P bonds, a search of the CSD gives a range of 2.254–
˚
2.904 A for 226 database entries, with a mean value of
˚
˚
2.584 (4) A. The value observed for (IV) [2.6428 (17) A] is
above the average but is not atypical. Presumably, the
chelating nature of the ligand in (IV) is responsible for the
length of the bonds observed here.
In summary, whilst ligand (II) shows good promise in
forming complexes with later transition metals, early metals
ꢃ
m80 Broomfield et al.
0.43C17H16NOPꢀ0.57C17H16NP and [TiCl4(C17H16NP)]
Acta Cryst. (2010). C66, m79–m82

metal-organic compounds
Table 3
Selected geometric parameters (A, ) for (IV).
reveal additional ligand reactivity which may have to be
modulated in order to obtain the desired complexes success-
fully. Efforts to control this reactivity are ongoing, for
example, by blocking the 2-position on the pyrrole ring with a
bulky alkyl to prevent ligand rearrangement.
ꢂ
˚
Ti1—N1
Ti1—Cl3
Ti1—Cl1
Ti1—Cl4
Ti1—Cl2
Ti1—P1
2.174 (5)
C2—N1
C2—C5
C3—N1
C3—C4
C4—C5
1.303 (6)
1.439 (7)
1.464 (6)
1.471 (7)
1.320 (7)
2.2293 (18)
2.2663 (19)
2.2766 (17)
2.3079 (19)
2.6428 (17)
Experimental
N1—Ti1—Cl4
Cl3—Ti1—Cl4
Cl1—Ti1—Cl2
91.10 (12)
106.38 (7)
168.17 (7)
N1—Ti1—P1
Cl1—Ti1—P1
71.36 (11)
89.10 (6)
Compound (II) was obtained as described elsewhere (Broomfield,
Wright et al., 2009). Reaction of the free ligand with ZrCl4 in THF,
followed by the addition of an equal amount of hexane and cooling to
243 K, led to the formation of crystals of (I)/(II) [0.861 (6):1.139 (6)].
Reaction of TiCl4 with the free ligand in dichloromethane, followed
by dilution with hexane and cooling to 243 K, gave crystals of (IV)
after storage for a few days.
Compound (IV)
Crystal data
[TiCl4(C17H16NP)]
Mr = 454.98
Triclinic, P1
ꢅ = 100.588 (16)ꢂ
3
˚
V = 955.6 (3) A
Z = 2
Compound (I)/(II)
˚
a = 8.1481 (17) A
Mo Kꢁ radiation
ꢂ = 1.09 mmꢁ1
T = 140 K
0.14 ꢄ 0.06 ꢄ 0.06 mm
˚
b = 8.6323 (16) A
Crystal data
˚
c = 14.202 (3) A
3
˚
0.43C17H16NOPꢀ0.57C17H16NP
V = 2941.9 (5) A
Z = 8
ꢁ = 98.159 (15)ꢂ
ꢀ = 98.727 (16)ꢂ
Mr = 272.18
Monoclinic, P21=c
Mo Kꢁ radiation
ꢂ = 0.18 mmꢁ1
T = 140 K
0.32 ꢄ 0.08 ꢄ 0.08 mm
˚
a = 9.6282 (9) A
˚
b = 15.2848 (14) A
Data collection
˚
c = 20.391 (2) A
Oxford Diffraction Xcalibur 3/CCD
diffractometer
Absorption correction: multi-scan
(ABSPACK; Oxford Diffraction,
2006)
10184 measured reflections
3347 independent reflections
1864 reflections with I > 2ꢃ(I)
Rint = 0.112
ꢀ = 101.376 (8)ꢂ
Data collection
Oxford Diffraction Xcalibur 3/CCD
diffractometer
Absorption correction: multi-scan
(ABSPACK; Oxford Diffraction,
2006)
30196 measured reflections
5167 independent reflections
3223 reflections with I > 2ꢃ(I)
Rint = 0.110
Tmin = 0.905, Tmax = 0.937
Refinement
R[F2 > 2ꢃ(F2)] = 0.057
wR(F2) = 0.098
S = 0.89
217 parameters
H-atom parameteꢁrs3 constrained
Tmin = 0.822, Tmax = 0.986
˚
Áꢄmax = 0.53 e A
ꢁ3
˚
Refinement
3347 reflections
Áꢄmin = ꢁ0.48 e A
R[F2 > 2ꢃ(F2)] = 0.065
wR(F2) = 0.095
S = 1.01
5167 reflections
361 parameters
H atoms treated by a mixture of
independent and constrained
refinement
All C-bound H atoms were refined using a riding model
(SHELXL97; Sheldrick, 2008), and with Uiso(H) = 1.2Ueq(C) for CH
and CH2 groups or 1.5Ueq(C) for methyl groups. Methyl groups were
allowed additional rotational freedom. In (I)/(II), atoms H1 and H2
(bound to N) were located in a difference Fourier map, and both
coordinates and Uiso values were freely refined. The site occupancy of
the O atom in (I)/(II) (O1) was freely refined to a value of 0.861 (6).
For both compounds, data collection: CrysAlis CCD (Oxford
Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffrac-
tion, 2006); data reduction: CrysAlis RED; program(s) used to solve
structure: SIR92 (Altomare et al., 1993); program(s) used to refine
structure: SHELXL97 (Sheldrick, 2008); molecular graphics:
ORTEP-3 (Farrugia, 1997); software used to prepare material for
publication: SHELXL97, PLATON (Spek, 2009), WinGX (Farrugia,
1999) and enCIFer (Allen et al., 2004).
ꢁ3
˚
Áꢄmax = 0.26 e A
Áꢄmin = ꢁ0.31 e A
ꢁ3
˚
Table 1
Selected geometric parameters (A, ) for (I)/(II).
ꢂ
˚
O1—P1
P1—C12
P1—C6
P1—C1
1.458 (2)
1.808 (3)
1.811 (3)
1.827 (3)
P2—C23
P2—C29
P2—C18
1.842 (3)
1.848 (3)
1.871 (3)
O1—P1—C12
O1—P1—C6
C12—P1—C6
O1—P1—C1
C12—P1—C1
112.83 (12)
112.16 (13)
106.31 (13)
111.55 (13)
106.36 (13)
C6—P1—C1
107.23 (13)
101.88 (13)
101.63 (13)
99.95 (13)
C23—P2—C29
C23—P2—C18
C29—P2—C18
JAW thanks the EPSRC for funding. LMB thanks the
University of East Anglia for funding. The authors express
their gratitude to the Chemical Database Service (Fletcher et
al., 1996) for providing access to the Cambridge Structural
Database.
Table 2
Hydrogen-bond geometry (A, ) for (I)/(II).
ꢂ
˚
D—Hꢀ ꢀ ꢀA
D—H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D—Hꢀ ꢀ ꢀA
N1—H1ꢀ ꢀ ꢀO1i
0.86 (3)
0.88 (3)
1.99 (3)
1.91 (3)
2.821 (4)
2.790 (3)
164 (3)
174 (3)
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: EM3032). Services for accessing these data are
described at the back of the journal.
N2—H2ꢀ ꢀ ꢀO1
Symmetry code: (i) ꢁx; ꢁy þ 1; ꢁz.
Acta Cryst. (2010). C66, m79–m82
ꢃ
Broomfield et al.
0.43C17H16NOPꢀ0.57C17H16NP and [TiCl4(C17H16NP)] m81

metal-organic compounds
Focante, F., Carmurati, I., Nanni, D., Leardini, R. & Resconi, L. (2004).
Organometallics, 23, 5135–5141.
References
Allen, F. H. (2002). Acta Cryst. B58, 380–388.
Allen, F. H., Johnson, O., Shields, G. P., Smith, B. R. & Towler, M. (2004). J.
Appl. Cryst. 37, 335–338.
Altomare, A., Cascarano, G., Giacovazzo, C. & Guagliardi, A. (1993). J. Appl.
Cryst. 26, 343–350.
Atkinson, R. C. J., Gibson, V. C., Long, N. J., White, A. J. P. & Williams, D. J.
(2004). Dalton Trans. pp. 1823–1826.
Broomfield, L. M., Boschert, D., Wright, J. A., Hughes, D. L. & Bochmann, M.
(2009). J. Organomet. Chem. 694, 4084–4089.
Gibson, V. C. & Spitzmesser, S. K. (2003). Chem. Rev. 103, 283–316.
Guidotti, S., Camurati, I., Focante, F., Angellini, L., Moscardi, G., Resconi, L.,
Leardini, R., Nanni, D., Mercandelli, P., Sironi, A., Beringhelli, T. &
Maggioni, D. (2003). J. Org. Chem. 68, 5445–5465.
Hitchcock, P. B., Lee, T.-H. & Leigh, G. J. (2003). Dalton Trans. pp. 2276–
2279.
¨
Kehr, G., Roesmann, R., Frohlich, R., Holst, C. & Erker, G. (2001). Eur. J.
Inorg. Chem. pp. 535–538.
¨
Kreickmann, T., Arndt, S., Schrock, R. R. & Muller, P. (2007). Organo-
metallics, 26, 5702–5711.
Mohamed, E. M., Panchanatheswaran, K., Low, J. N. & Glidewell, C. (2004).
Acta Cryst. C60, o475–o478.
Broomfield, L. M., Wright, J. A. & Bochmann, M. (2009). Dalton Trans. pp.
8269–8279.
`
Carriedo, G. A., Rodrıguez, M. L., Garcıa-Granda, S. & Aguirre, A. (1990).
`
Inorg. Chim. Acta, 178, 101–106.
Oxford Diffraction (2006). ABSPACK, CrysAlis CCD and CrysAlis RED.
Versions 1.171. Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.
Chekhlov, A. N. (2000). Zh. Strukt. Khim. 41, 788–794.
Cui, C., Shafir, A., Reeder, C. L. & Arnold, J. (2003). Organometallics, 22,
3357–3359.
Spek, A. L. (2009). Acta Cryst. D65, 148–155.
DuBois, M. R., Vasquez, L. D., Peslherbe, L. & Noll, B. C. (1999). Organo-
metallics, 18, 2230–2240.
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838.
Fletcher, D. A., McMeeking, R. F. & Parkin, D. (1996). J. Chem. Inf. Comput.
Sci. 36, 746–749.
Tsurugi, H. & Mashima, K. (2006). Organometallics, 25, 5210–5212.
Yang, Y., Li, S., Cui, D., Chen, X. & Jing, X. (2007). Organometallics, 26, 671–
678.
Yoshida, Y., Matsui, S., Takagi, Y., Mitani, M., Nakano, T., Tanaka, H.,
Kashiwa, N. & Fujita, T. (2001). Organometallics, 20, 4793–4799.
ꢃ
m82 Broomfield et al.
0.43C17H16NOPꢀ0.57C17H16NP and [TiCl4(C17H16NP)]
Acta Cryst. (2010). C66, m79–m82