Diphenylphosphinoacetate, nicotinate and thiophenoxyacetate as bridging ligands in heterometallic complexes involving bis(η-cyclopentadienyl)titanium(IV) and group 10 or 11 metal chlorides

Article abstract of DOI:10.1016/S0277-5387(00)00305-3

Heterobi- and tri-metallic compounds containing a Cp₂Ti(IV unit linked via nicotinate, thiophenoxyacetate or diphenylphosphinoacetate ligands to Pd, Pt, Cu, Ag or Au centres have been isolated. They are of the types [ Cp₂Ti {μ-OC (O) R }₂MCl₂ ] (M = Pd, R = m-C₅H₄N, CH₂SPh and CH₂PPh₂; M=Pt, R=m-C₅H₄N or CH₂PPh₂), [Cp₂Ti{μ-OC(O)CH₂PPh₂}₂(M'Cl)₂] (M' =Cu or Au) and [Cp₂Ti{μ-OC(O)CH₂PPh₂}₂AgCl]. The diphenylphosphinoacetate products arise both from methane elimination reactions of [Cp₂TiMe₂] with either [MCl₂(Ph₂PCH₂CO₂H)2] or [M'Cl (Ph₂PCH₂CO₂H)] and from reactions of [Cp₂Ti {OC(O)CH₂PPh₂}₂] with metal complexes containing labile ligands. Crystal structures of [Cp₂Ti{OC(O)CH₂PPh₂}₂] and [Cp₂Ti{μ-OC(O) CH₂PPh₂}₂PdCl₂] are discussed. The latter compound contains diphenylphosphinoacetate groups which are O-unidentate with respect to titanium and P-unidentate with respect to palladium, the result being the formation of a ten-atom heterobimetallic ring system. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(00)00305-3

www.elsevier.nl/locate/poly
Polyhedron 19 (2000) 757–764
Diphenylphosphinoacetate, nicotinate and thiophenoxyacetate as
bridging ligands in heterometallic complexes involving
bis(h-cyclopentadienyl)titanium(IV) and group 10 or 11
metal chlorides.
Crystal structures of [(h-C5H5)2Ti{OC(O)CH2PPh2}2] and
[(h-C5H5)2Ti{m-OC(O)CH2PPh2}2PdCl2]
*
Dennis A. Edwards , Mary F. Mahon, Timothy J. Paget
Department of Chemistry, University of Bath, Bath BA2 7AY, UK
Received 1 November 1999; accepted 17 January 2000
Abstract
Heterobi- and tri-metallic compounds containing a Cp2Ti(IV) unit linked via nicotinate, thiophenoxyacetate or diphenylphosphinoacetate
ligands to Pd, Pt, Cu, Ag or Au centres have been isolated. They are of the types [Cp2Ti{m-OC(O)R}2MCl2] (MsPd, Rsm-C5H4N,
CH2SPh and CH2PPh2; MsPt, Rsm-C5H4N or CH2PPh2), [Cp2Ti{m-OC(O)CH2PPh2}2(M9Cl)2] (M9sCu or Au) and [Cp2Ti{m-
OC(O)CH2PPh2}2AgCl]. The diphenylphosphinoacetate products arise both from methane elimination reactions of [Cp2TiMe2] with either
[MCl2(Ph2PCH2CO2H)2] or [M9Cl(Ph2PCH2CO2H)] and from reactions of [Cp2Ti{OC(O)CH2PPh2}2] with metal complexes containing
labile ligands. Crystal structures of [Cp2Ti{OC(O)CH2PPh2}2] and [Cp2Ti{m-OC(O)CH2PPh2}2PdCl2] are discussed. The lattercompound
contains diphenylphosphinoacetate groups which are O-unidentate with respect to titanium and P-unidentate with respect to palladium, the
result being the formation of a ten-atom heterobimetallic ring system.
q2000 Elsevier Science Ltd All rights reserved.
Keywords: Bis(h-cyclopentadienyl)titanium(IV); Crystal structures; Diphenylphosphinoacetate; Heterometallics; Nicotinate; Thiophenoxyacetate
1. Introduction
Bridging ligands that have been employed to link the
Cp2Ti(IV) fragment to late transition metals include m-
h1:h2-carbonyl [7] and anions such as phosphino [8], thiol-
ato [9], selenolato [10] and h1,h6-benzoate [11]. Crys-
Compounds containing Cp2Ti(IV) units linked to late
transition metal centres are representatives of a broad class
of heterometallic species, interest in which has been stimu-
lated by, for example, their potential catalytic [1], biological
[2,3] or medicinal [4] applications. The combination of an
oxophilic early transition metal centre with electron-rich late
transition metal centres may lead to products with properties
considerably different than bimetallic species containing
identical or closely related metals. This topic has been com-
prehensively reviewed by Stephan [5,6], whose group has
made major advances in the application of early transition
metal complexes functionalised to act as metalloligands for
late transition metals.
¨
tallographic results and extended Huckel or Fenske–Hall
molecular orbital calculations are consistent with the pres-
ence of direct early–late transition metal interactions in a
number of such compounds, for example, in [Cp2Ti-
(SCH2CH2SCH2)2CH2Cu][PF6] [12] and [Cp2Ti(SCH2-
CH2CH2PPh2)2Ni] [13].
Of particular relevance to the results reported here, is a
recent communication [14] reporting the self-assembly of
two heterobimetallic early–late metallomacrocycles from the
iso-nicotinate [Cp2Ti{OC(O)C5H4N-p}2] [15] and the
Pt(II) triflate complexes cis-[Pt(OSO2CF3)2L2] [LsPEt3
or 0.5Ph2P(CH2)3PPh2]. The products, [Cp2Ti{m-OC-
(O)C5H4N-p}2PtL2]2[CF3SO3]4, were held to be cationic
and tetranuclear with a 28-atom ring based on NMR and, for
the PEt3 complex, liquid SIMS evidence. No X-ray crystal-
* Corresponding author. Tel.: q44-1225-826444; fax: q44-1225-
826231; e-mail: chsdae@bath.ac.uk
0277-5387/00/$ - see front matter q2000 Elsevier Science Ltd All rights reserved.
PII S0277-5387(00)00305-3
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D.A. Edwards et al. / Polyhedron 19 (2000) 757–764
lographic evidence was available but molecular modelling
was used to illustrate the shape of the complex and its cavity
based on square planar platinum and distorted tetrahedral
titanium as corner units.
2.1. Bis(cyclopentadienyl)bis(O-nicotinato)titanium(IV)(1)
Sodium nicotinate (1.00 g, 6.9 mmol), prepared by reac-
tion of the acid with sodium ethoxide in absolute alcohol, and
[Cp2TiCl2] (0.50 g, 2.0 mmol) were reacted in refluxing
tetrahydrofuran (25 cm3) under nitrogen for 1 h. After cool-
ing, sodium salts were removed by filtration and the orange
filtrate was treated with hexane to produce orange crystals on
standing in an ice-bath (0.125 g, 15%). Anal. Found (calc.
for C22H18N2O4Ti): C, 62.9 (62.6); H, 4.30 (4.30); N, 6.66
(6.63)%. IR (cmy1): 3106s, 3049w (Cp), 1634vs (nasym
CO2), 1423m (Cp), 1350vs, 1306vs (nsym CO2), 1028m
We report here on a wider variety of related heterometallic
compounds containing Cp2Ti(IV) carboxylate units linked
to late transition metals synthesised by employing function-
alised carboxylates containing additional nitrogen (nicotin-
y
ate, m-C5H4NCO2 [16]), sulfur (thiophenoxyacetate,
PhSCH2CO2y) or phosphorus (diphenylphosphinoacetate,
Ph2PCH2CO2y) donor sites. Unlike the cationic,tetranuclear
iso-nicotinate complexes [14], the products are non-ionic
and either binuclear macrocycles involving a Cp2Ti(IV) unit
assembled with one group 10 (Pd or Pt) or group 11 (Ag)
metal, or trinuclear acyclic complexes in which the
Cp2Ti(IV) unit is linked to two group 11 (Cu or Au) metals.
The majority of the investigation has employed diphenyl-
phosphinoacetate as the bridging carboxylate and it has been
shown that most of the products can be prepared equally well
either from methane elimination reactions of [Cp2TiMe2]
with our recently reported [17] complexes [MCl2(Ph2-
PCH2CO2H)2] (MsPd or Pt) and [M9Cl(Ph2PCH2-
CO2H)] (MsCu or Au) or from reactions which employ
the new O-unidentate carboxylate [Cp2Ti{OC(O)CH2-
PPh2}2] as a metalloligand in reactions with late transition
metal complexes containing labile ligands. An X-ray crystal-
lographic structure determination shows one of the products,
[Cp2Ti{OC(O)CH2PPh2}2PdCl2], to contain a ten-atom
heterobimetallocyclic ring.
1
(Cp), 824s (Cp). H NMR (CDCl3): d 6.66 (s, 5H, Cp),
7.42 (dd, 1H, pyridyl), 8.28 (dt, 1H, pyridyl), 8.76 (dd, 1H,
pyridyl), 9.21 (d, 1H, pyridyl). 13C{1H} NMR (CDCl3): d
118.8 (Cp), 123.2, 129.2, 137.2, 151.0, 152.0 (pyridyl),
170.1 (CO2). FAB-MS (m/z): 344 (50% [MyC5H4N]q),
300 (100% [MyC5H4NCO2]q).
2.2. Bis(cyclopentadienyl)bis(O-thiophenoxyacetato)-
titanium(IV) (2)
A solution of [Cp2TiMe2] (0.44 g, 2.1 mmol) in tetra-
hydrofuran (3 cm3) was added dropwise to a suspension of
thiophenoxyacetic acid (0.71 g, 4.2 mmol) in tetrahydro-
furan (12 cm3) resulting in a vigorous evolution of methane.
After stirring for 1 h, removal of the solvent gave the required
product, recrystallised from tetrahydrofuran–hexane as
bright red cubes (1.00 g, 93%). Anal. Found (calc. for
C26H24O4S2Ti): C, 60.6 (60.9); H, 4.73 (4.72)%. IR
(cmy1): 3108m (Cp), 1661s, 1632vs (nasym CO2), 1437sh
(Cp), 1337s, 1302vs (nsym CO2), 1022m (Cp), 824s (Cp).
1H NMR (CDCl3): d 3.61 (s, 2H, CH2), 6.27 (s, 5H, Cp),
7.09 (m, 1H, Ph), 7.22 (m, 2H, Ph), 7.35 (m, 2H, Ph).
13C{1H} NMR (CDCl3): d 37.8 (CH2), 118.5 (Cp), 125.8,
128.1, 128.8, 136.4 (Ph), 174.1 (CO2). FAB-MS (m/z):
447 (7% [MyCp]q), 345 (100% [MyPhSCH2CO2]q),
178 (16% [Cp2Ti]q).
2. Experimental
Diphenylphosphinoacetic acid was prepared and charac-
terised as before [17], nicotinic and thiophenoxyacetic acids
being used as supplied (Aldrich). The compound
[Cp2TiMe2] was prepared from the chloride (Aldrich) and
methyllithium in diethyl ether. Bis(benzonitrile)Pd(II) or
Pt(II) dichlorides were obtained by dissolving the metal
chlorides in hot benzonitrile and isolating the crystalline
products by filtration of the cooled solutions. Solvents were
dried by distillation from appropriate reagents (sodium–ben-
zophenone, calcium hydride or molecular sieves) before use
and all reactions and manipulations were carried out under
dry nitrogen.
Microanalyses were carried out using a Carlo-Erba micro-
analysis system. JEOL GX 270 and EX 400 spectrometers
were used to obtain 1H, 13C and 31P NMR spectra. Infrared
spectra were recorded as Nujol or hexachlorobutadienemulls
(NaCl or CsI windows) using Nicolet 510P or Perkin-Elmer
597 spectrophotometers. Only selected bands are reported
here. Positive and negative ion FAB mass spectra were
recorded in 3-nitrobenzyl alcohol matricesusingaVGAutos-
pec instrument. The m/z values reported are based on 35Cl,
48Ti, 63Cu and 197Au isotopes and intensities are expressed
relative to the strongest metal-containing fragment.
2.3. Bis(cyclopentadienyl)bis(O-diphenylphosphino-
acetato)titanium(IV) (3)
A solution of [Cp2TiMe2] (0.33 g, 1.6 mmol) in dichlo-
romethane (6 cm3) was added dropwise to a solution of
diphenylphosphinoacetic acid (0.77 g, 3.2 mmol) in di-
chloromethane (4 cm3). After evolution of methane, themix-
ture was stirred for 6 h, then the solvent was removed to
produce a solid which was recrystallised from dichlorome-
thane layered with hexane togivebrightorangecubessuitable
for an X-ray crystal structure determination (1.01 g, 95%).
Anal. Found (calc. for C38H34O4P2Ti): C, 67.6 (67.7); H,
5.13 (5.17)%. IR (cmy1): 3100w, 3056vw (Cp), 1649m,
1618s (nasym CO2), 1433w (Cp), 1325s, 1285s (nsym CO2),
1019w (Cp), 824m (Cp). 1H NMR (CDCl3): d 2.96 (s, 2H,
CH2), 6.01 (s, 5H, Cp), 7.10 (m, 6H, Ph), 7.29 (m, 4H,
1
Ph). 13C{1H} NMR (CDCl3): d 37.6 (d, JC,Ps17.6 Hz,
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CH2), 118.2 (s, Cp), 128.3 (d, 2JC,Ps6.6 Hz, Cmeta), 128.6
(s, Cpara), 132.6 (d, 1JC,Ps19.8, Cipso), 138.4 (d, 2JC,Ps15.4
dichloromethane (2 cm3). Slow evolution of methane was
observed. After 2 h the solvent was removed to giveanorange
solid. Anal. Found (calc. for C38H34Cl2O4P2PdTi): C, 52.1
(54.2); H, 3.90 (4.07)%. IR (cmy1): 3087w (Cp), 1651vs
(nasym CO2), 1435s (Cp), 1312vs (nsym CO2), 1019m (Cp),
2
Hz, Cortho), 175.4 (d, JC,Ps8.8 Hz, CO2). 31P{1H}
(CDCl3): d y17.6. FAB-MS (m/z): 599 (5%[MyCp]q),
522 (9%, [MyCpyPh]q), 421 (100%, [MyPh2PCH2-
CO2]q), 344 (29%, [MyPh2PCH2CO2yPh]q).
1
818s (Cp), 339m, 307m (n PdCl). H NMR (CDCl3): d
3.53 (t, 2H, Js4.4 Hz, CH2), 6.30 (s, 5H, Cp), 7.22 (m,
2.4. Adduct of compound 1 with PdCl2
6H, Ph), 7.59 (m, 4H, Ph). 31P{1H} (CDCl3): d q13.8.
A solution of [PdCl2(NCPh)2] (0.045 g, 0.12 mmol) in
tetrahydrofuran (5 cm3) was added dropwise with stirring to
a solution of compound 1 (0.050 g, 0.12 mmol) in tetrahy-
drofuran (10 cm3) to give an orange precipitate.Afterstirring
for 24 h the product was obtained by filtration and washed
with tetrahydrofuran (0.099 g, 69%). Anal. Found (calc. for
C22H18Cl2N2O4PdTi): C, 44.0 (44.1); H, 3.41 (3.03); N,
4.57 (4.67)%. IR (cmy1): 3108w (Cp), 1642vs (nasym
CO2), 1462m (Cp), 1319vs (nsym CO2), 1019w (Cp), 828s
(Cp), 358m (n PdCl).
2.8. Adduct of compound 3 with PtCl2
2.8.1. Method A
The desired compound was prepared as for the palladium
analogue using [Cp2TiMe2] (0.05 g, 0.24 mmol),
Ph2PCH2CO2H (0.117 g, 0.48 mmol) and [PtCl2(NCPh)2]
(0.12 g, 0.24 mmol) in dichloromethane (3 cm3).
2.8.2. Method B
A solution of [Cp2TiMe2] (0.052 g, 0.25 mmol) in di-
chloromethane (0.5 cm3) was added to a suspension of cis-
[PtCl2(Ph2PCH2CO2H)2] [17] (0.166 g, 0.25 mmol) in
toluene–dichloromethane (5:1, 6 cm3). A further 0.5 cm3 of
dichloromethane was added and the mixture stirred for 24 h.
The orange precipitate was filtered and washed with dichlo-
romethane (0.071 g, 23%). A further crop of orange crystals
was obtained by concentration of the filtrate (0.123 g, 40%).
Anal. Found (calc. for C38H34Cl2O4P2PtTi): C, 48.6 (49.1);
H, 3.60 (3.68)%. IR (cmy1): 3088w (Cp), 1647s, 1593s
(nasym CO2), 1439s (Cp), 1312s (nsym CO2), 1028w (Cp),
822w (Cp), 322m, 310m (n PtCl).
2.5. Adduct of compound 1 with PtCl2
This compound was prepared in a similar manner to the
above palladium complex using [PtCl2(NCPh)2] (0.034 g,
0.07 mmol) and compound 1 (0.030 g, 0.07 mmol) in di-
chloromethane (5 cm3). Yield: 0.018 g, 37%. Anal. Found
(calc. for C22H18Cl2N2O4PtTi): C, 37.0 (38.4); H, 2.79
(2.64); N, 4.40 (4.07)%.
2.6. Adduct of compound 2 with PdCl2
A similar method to that above using [PdCl2(NCPh)2]
(0.070 g, 0.18 mmol) dissolved in dichloromethane (5 cm3)
and compound 2 (0.089 g, 0.18 mmol) in dichloromethane
(3 cm3) gave a bright orange precipitate which was filtered
and washed with dichloromethane before drying in vacuo.
Yield: 0.090 g, 72%. Anal. Found (calc. for C26H24-
Cl2O4PdS2Ti): C, 44.2 (45.3); H, 3.46 (3.51)%. IR(cmy1):
3112m (Cp), 1626vs (nasym CO2), 1443s (Cp), 1319vs
(nsym CO2), 1024m (Cp), 828s(Cp), 358w, 324m(nPdCl).
2.9. Adduct of compound 3 with 2CuCl
2.9.1. Method A
Cu(I) chloride (0.10 g, 1.00 mmol) and complex 3 (0.34
g, 0.50 mmol) were stirred in dichloromethane (5 cm3) for
72 h to give a dark red solution. Filtration followed by con-
centration of the filtrate in vacuo gave an orange powder
(0.40 g, 93%).
2.7. Adduct of compound 3 with PdCl2
2.9.2. Method B
A solution of [Cp2TiMe2] (0.061 g, 0.29 mmol) in di-
chloromethane (2 cm3) was added with stirring to a suspen-
sion of [{CuCl(Ph2PCH2CO2H)}4] [17] in dichloro-
methane (2 cm3). Evolution of methane was observed.
After standing for 72 h, concentration of the solution gave an
orange solid (0.17 g, 68%). Anal. Found (calc. for
C38H34Cl2Cu2O4P2Ti): C, 52.4 (52.9); H, 3.93 (3.97)%. IR
(cmy1): 3050w (Cp), 1634s (nasym CO2), 1435s (Cp),
1310s (nsym CO2), 1017w (Cp), 828s (Cp). 1H NMR
(CDCl3): d 3.48 (br s, 2H, CH2), 6.23 (s, 5H, Cp), 7.40 (m,
6H, Ph), 7.68 (m, 4H, Ph). 13C{1H} NMR (CDCl3): d 37.3
(s, CH2), 118.9 (s, Cp), 128.9 (s, Ph), 130.3 (s, Ph), 132.3
(d, Js15.5 Hz, Ph), 132.7 (t, Js7.7, Ph), 172.5 (s, CO2).
31P{1H} NMR (CDCl3): d y12.4 (s). FAB-MS (m/z) 827
2.7.1. Method A
Complex 3 was generated in situ from [Cp2TiMe2] (0.19
g, 0.90 mmol) and diphenylphosphinoacetic acid (0.44 g,
1.80 mmol) in dichloromethane (6 cm3). Addition of a solu-
tion of [PdCl2(NCPh)2] (0.35 g, 0.90 mmol) in dichloro-
methane (2 cm3) gave a red solution which, on standing,
deposited large red crystals which were collected by filtration
(0.43 g, 43%).
2.7.2. Method B
A solution of [Cp2TiMe2] (0.034 g, 0.17 mmol) in di-
chloromethane (2 cm3) was added to a suspension of trans-
[PdCl2(Ph2PCH2CO2H)2] [17] (0.11 g, 0.17 mmol) in
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(16% [MyCl]q), 762 (21% [MyCuCl]q), 727 (100%
[762yCl]q), 662 (74% [727yCp]q).
2.12. X-ray crystallography
Crystal data, collection and refinement details for [Cp2Ti-
{OC(O)CH2PPh2}2] (crystals from dichloromethane solu-
tion layered with hexane) and for [Cp2Ti{m-OC(O)-
CH2PPh2}2PdCl2]P3CH2Cl2 (crystals from dichloro-
methane solution; method A above) are given in Table 1.
Selected bond lengths and angles are reported in Tables 2
and 3, respectively. Diagrams of the molecular structures
produced using ORTEX [18] are shown in Figs. 1 and 2.
Data were collected using an Enraf-Nonius CAD4 diffrac-
2.10. Adduct of compound 3 with AgCl
2.10.1. Method A
Compound 3 ( 0.050 g, 0.08 mmol) and silver chloride
(0.011 g, 0.08 mmol) were stirred in dichloromethane (4
cm3) for 72 h. Filtration followed by concentration of the
filtrate gave a bright orange solid. The same product resulted
from similar reactions employing two or four molar equiva-
lents of AgCl, but in these cases an excess of AgCl had to be
removed by filtration.
˚
tometer using graphite-monochromated Mo Ka 0.71069 A
radiation. Data for both compounds were corrected for Lor-
entz and polarisation effects and those for the PdCl2 adduct
also corrected for absorption. The structures were solved
using SHELX 86 and refined using SHELX 93 [19,20]. For
[Cp2Ti{OC(O)CH2PPh2}2], in the final least-squarescycles
all atoms were allowed to vibrate anisotropically. Hydrogen
atoms were included at calculated positions. Data for [Cp2Ti-
{m-OC(O)CH2PPh2}2PdCl2]P3CH2Cl2 were collected at
170(2) K, the crystals not being of a very high quality and
crystal mounting was not without difficulty due to solvent
loss. As a result, satisfactory anisotropic refinement of all
atoms was not achieved. In the final least-squares cycles,
atoms O(3), C(13), C(29) and C(37) were treated isotrop-
ically whereas all other atoms were allowed to vibrate ani-
sotropically. Hydrogen atoms were included at calculated
positions.
2.10.2. Method B
Silver(I) diphenylphosphinoacetate (0.60 g, 1.70 mmol),
prepared from AgNO3 and Ph2PCH2CO2Na, and [Cp2TiCl2]
(0.21 g, 0.85 mmol) were stirred in dichloromethane (10
cm3) for 24 h. Filtration removed AgCl and the orangefiltrate
was evaporated and the solid product crystallised from di-
chloromethane to give an orange crystalline solid (0.53 g,
77%). Anal. Found (calc. for C38H34AgClO4P2Ti): C, 55.3
(56.5), H, 4.49 (4.24)%. IR (cmy1): 3050w (Cp), 1642vs
(nasym CO2), 1435s, (Cp), 1310sh, 1273vs (nsym CO2),
1017m (Cp), 828s (Cp). 1H NMR (CDCl3): d 3.51 (s, 2H,
CH2), 6.10 (s, 5H, Cp), 7.37 (m, 6H, Ph), 7.66 (m, 4H,
Ph). 13C{1H} NMR (CDCl3): d 37.9 (d, JC,Ps8.3 Hz,
1
CH2), 118.9 (s, Cp), 129.0 (d, 2JC,Ps5.0 Hz, Cmeta), 130.5
1
(s, Cpara), 131.9 (d, JC,Ps12.9 Hz, Cipso), 132.8 (d,
2JC,Ps8.3 Hz, Cortho), 171.7 (s, CO2). 31P{1H} NMR
(CDCl3): d y1.84 (1J107Ag, 31Ps439.3 Hz; 1J109Ag,
31Ps506.4 Hz). FAB-MS (m/z): 773 (100% [MyCl]q),
709 (77% [MyClyCp]q).
3. Results and discussion
Two new bis(h-cyclopentadienyl)titanium(IV) bis(O-
carboxylates), [Cp2Ti{OC(O)R}2] with RsCH2SPh
(thiophenoxyacetate) and CH2PPh2 (diphenylphosphino-
acetate) and the previously known [16] analogue with
RsC5H4N-m (nicotinate) have been shown to act as S-, P-
or N-donor metalloligands to various transitionmetalcentres.
Products contain Ti(IV) linked to either group 10 d8 (Pd or
Pt) or group 11 d10 (Cu, Ag or Au) metal chlorides via
bridging carboxylate moities which are O-unidentate with
respect to titanium and S-, P- or N-unidentate with respect to
the group 10 or group 11 metal. Most of the work reported
here focuses on the use of the diphenylphosphinoacetate in
this manner.
The carboxylates have been preparedfrom[Cp2TiCl2]and
sodium nicotinate or from [Cp2TiMe2] and thiophenoxy-
acetic or diphenylphosphinoacetic acids, the latter reactions
proceeding with the smooth elimination of methane. Analyt-
ical, NMR (1H, 13C and 31P), partial IR and mass spectro-
metric data for the three compounds are given in Section 2
and, being unexceptional, are not discussed further except to
note that in the mass spectra the most abundant fragment in
each case is that of the parent ion having lost one carboxylate
group.
2.11. Adduct of compound 3 with 2AuCl
A solution of [Cp2TiMe2] (0.050 g, 0.24 mmol) in di-
chloromethane (1 cm3) was added slowly with stirring to a
suspension of [AuCl(Ph2PCH2CO2H)] [17] (0.23 g, 0.48
mmol) in dichloromethane (2 cm3). After stirring overnight,
concentration of the solution in vacuo gave an orange–
yellow solid (0.22 g, 81%). Anal. Found (calc. for
C38H34Au2Cl2O4P2Ti): C, 40.1 (40.4); H, 2.92 (3.03)%. IR
(cmy1): 3058w (Cp), 1634vs (nasym CO2), 1439s (Cp),
1325s, 1292vs (nsym CO2), 1017m (Cp), 824s (Cp), 335ms
1
2
(n AuCl). H NMR (CDCl3): d 4.11 (d, 2H, JP,Hs13.4
Hz, CH2), 6.24 (s, 5H, Cp), 7.49 (m, 6H, Ph), 7.84 (m, 4H,
Ph). 13C{1H} NMR (CDCl3): d 37.8 (d, JC,Ps33.1 Hz,
1
2
CH2), 119.0 (s, Cp), 129.1 (d, JC,Ps11.0 Hz, Ph), 129.9
(s, Ph), 131.9 (s, Ph), 133.3 (d, 1JC,Ps14.4 Hz, Ph), 170.6
(d, 2JC,Ps2.2 Hz, CO2). 31P{1H} NMR (CDCl3): d q24.9
(s). FAB-MS (m/z) 1129 (3% [M]q), 1093 (13%
[MyCl]q), 1028 (13% [MyClyCp]q), 917 (14%
[Au2Cl(Ph2PCH2CO2H)2]q), 441 (100% [Au(Ph2-
PCH2CO2H)]q).
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761
Table 1
Crystal data and data collection details for [Cp2Ti{OC(O)CH2PPh2}2] and [Cp2Ti{m-OC(O)CH2PPh2}2PdCl2]P3CH2Cl2
[Cp2Ti{OC(O)CH2PPh2}2]
PdCl2PAdductP3CH2Cl2
Empirical formula
Molecular formula
Temperature (K)
Crystal system
C38H34O4P2Ti
664.49
293(2)
C41H40Cl8O4P2PdTi
1096.57
170(2)
monoclinic
P21/n (no. 14)
12.350(3)
triclinic
¯
Space group
P1 (no. 2)
˚
a (A)
11.664(3)
11.847(3)
14.191(4)
˚
b (A)
22.037(4)
16.770(5)
˚
c (A)
a (8)
b (8)
g (8)
95.09(2)
101.18(3)
117.33(2)
1673.1(8)
102.04(2)
3
˚
U (A )
4463.7(19)
4
1.632
1.173
2208
Z
2
Dc (Mg my3
)
1.319
0.391
692
m (mmy1
F(000)
)
Crystal size (mm)
u Range for data collection (8)
hkl ranges
0.2=0.2=0.3
2.03–22.00
y13 to 0, y12 to 13, y15 to 16
4374
4123 (0.0360)
0.4=0.35=0.2
2.09–21.99
y13 to 12, 0 to 23, 0 to 17
5451
Reflections collected
Independent reflections (Rint
Data, restraints, parameters
Goodness of fit on F2
)
5451 (0.0790) a
5432, 18, 496
1.141
3967, 0, 404
1.042
Final R1, wR2 indices [I)2s(I)]
0.0656, 0.1310
0.1505, 0.1775
0.0740, 0.1221
0.1563, 0.1636
1.261 and y0.873
All data
Largest residuals (e A
Weighting scheme, w
y3
˚
)
0.601 and –0.267
1/[s2(Fo2)q(0.0610P)2q2.5766P],
1/[s2(Fo2)q(0.0000P)2q58.8248P],
2
2
2
2
where Ps(Fo q2Fc )/3
where Ps(Fo q2Fc )/3
a Pre-DIFABS Rint
.
Table 2
˚
Selected bond lengths (A) and angles (8) for [Cp2Ti{OC(O)CH2PPh2}2]
Ti(1)–O(1)
O(1)–C(11)
O(2)–C(11)
C(11)–C(12)
C(12)–P(1)
Average Ti(1)–C(1–5)
Average C–C in Cp ring C(1)–C(5)
1.972(4)
1.282(8)
1.216(8)
1.516(9)
1.856(6)
2.372(7)
1.382(10)
Ti(1)–O(3)
O(3)–C(25)
O(4)–C(25)
C(25)–C(26)
C(26)–P(2)
1.925(5)
1.300(7)
1.189(8)
1.502(9)
1.830(7)
2.360(8)
1.362(13)
Average Ti(1)–C(6–10)
Average C–C in Cp ring C(6)–C(10)
O(1)–Ti(1)–O(3)
Ti(1)–O(1)–C(11)
O(1)–C(11)–O(2)
O(1)–C(11)–C(12)
O(2)–C(11)–C(12)
C(11)–C(12)–P(1)
91.5(2)
136.1(5)
125.0(7)
115.2(7)
119.8(7)
109.5 (5)
Ti(1)–O(3)–C(25)
O(3)–C(25)–O(4)
O(3)–C(25)–C(26)
O(4)–C(25)–C(26)
C(25)–C(26)–P(2)
143.4(4)
123.3(7)
113.6(6)
122.9(7)
110.4(5)
˚
To provide a comparison with one of the metal halide
adducts, an X-ray single-crystal structure determination of
[Cp2Ti{OC(O)CH2PPh2}2] has been carried out (Fig. 1).
This confirms the presence of a distorted tetrahedral environ-
ment around the metal with two O-unidentate carboxylate
titanium, are more than 3 A from the metal, and the two
phosphorus atoms, which could potentially donate, are more
˚
than 5 A from the titanium with the phosphine units so
arranged that the lone pairsare directedawayfromeachother.
Unidentate carboxylate coordination is also indicated by the
significant differences in C–O bond lengths depending on
whether the oxygen is coordinated to titanium [1.282(8),
1.300(7) A] or not [1.216(8), 1.189(8) A]. The two
diphenylphoshinoacetate groups are bonded to the titanium
in a somewhat inequivalent manner, one carboxylate having
˚
groups [Ti–O 1.972(4) and 1.925(5) A] in accord with the
large IR [nasymynsym CO2] difference of 333 cmy1. Taking
the centroids of the cyclopentadienyl rings as Z, the distortion
from regular geometry is evident from the Z–Ti–Z angle of
132.48 and the O(1)–Ti–O(3) angle of 91.5(2)8. The two
carboxylate oxygens, O(2) and O(4), not bonded to the
˚
˚
˚
a longer Ti–O (difference 0.047 A), a smaller Ti–O–C angle
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D.A. Edwards et al. / Polyhedron 19 (2000) 757–764
Table 3
˚
Selected bond lengths (A) and angles (8) for [Cp2Ti{m-OC(O)CH2PPh2}2PdCl2]P3CH2Cl2
Ti(1)–O(1)
O(1)–C(11)
O(2)–C(11)
C(11)–C(12)
1.971(8)
1.286(14)
1.197(14)
1.53(2)
Ti(1)–O(3)
O(3)–C(13)
O(4)–C(13)
C(13)–C(14)
1.959(8)
1.291(14)
1.213(14)
1.52(2)
C(12)–P(1)
Pd(1)–P(1)
Pd(1)–Cl(1)
Average Ti(1)–C(1–5)
Average C–C in Cp ring C(1)–C(5)
1.824(13)
2.259(4)
2.348(4)
2.35(2)
C(14)–P(2)
Pd(1)–P(2)
Pd(1)–Cl(2)
Average Ti(1)–C(6–10)
Average C–C in Cp ring C(6)–C(10)
1.830(13)
2.277(4)
2.339(4)
2.37(2)
1.36(2)
1.38(2)
O(1)–Ti(1)–O(3)
Ti(1)–O(1)–C(11)
O(1)–C(11)–O(2)
O(1)–C(11)–C(12)
O(2)–C(11)–C(12)
C(11)–C(12)–P(1)
C(12)–P(1)–Pd(1)
P(1)–Pd(1)–P(2)
P(1)–Pd(1)–Cl(1)
P(1)–Pd(1)–Cl(2)
89.4(3)
143.2(8)
Ti(1)–O(3)–C(13)
O(3)–C(13)–O(4)
O(3)–C(13)–C(14)
O(4)–C(13)–C(14)
C(13)–C(14)–P(2)
C(14)–P(2)–Pd(1)
P(2)–Pd(1)–Cl(1)
P(2)–Pd(1)–Cl(2)
Cl(1)–Pd(1)–Cl(2)
142.1(8)
125.8(13)
114.3(11)
119.6(12)
116.3(10)
112.8(5)
103.93(13)
83.12(13)
170.63(13)
126.4(12)
115.0(11)
118.6(11)
116.3(9)
111.6(4)
172.36(13)
84.63(13)
88.15(12)
Fig. 1. ORTEX plot of the molecular structure of [Cp2Ti{OC(O)CH2PPh2}2] (3) showing the labelling scheme. Hydrogen atoms are omitted for clarity.
Thermal ellipsoids are at the 30% probability level.
(difference 7.38) and a shorter C–O bond length (difference
0.018 A) than the other. This may imply the presence of a
additional Ti–O p bonding for both carboxylate groups, as
indicated by EHMO calculations on the formate [25]. The
average Ti–C and C–C bond lengths and C–C–C angles of
the cyclopentadienyl groups agree well with suchvaluesfrom
structure determinations of other [Cp2TiX2] compounds
[25]. Finally, it is noted that the present structure determi-
nation appears to be the first in which the diphenylphosphi-
noacetate anion acts solely as a unidentate ligand, the usual
coordination mode being O,P-chelating as in, for example,
cis-[Pd{OC(O)CH2PPh2}2] [26].
The compound [Cp2Ti{OC(O)CH2PPh2}2] has been
used both as a P-donor chelate metalloligand to assemble
neutral bimetallic macrocyclic complexes in which the two
phosphorus atoms bond to one group 10 (Pd or Pt) or group
11 (Ag) metal centreandasaP-donorbridgingmetalloligand
˚
differing extent of Ti–O p interaction supporting the primary
s bonding for the two carboxylate ligands. Such differences
have been noted previously, for example in the orthorhombic
form of [Cp2Ti{OC(O)Ph}2] [21,22], which shows Ti–O,
Ti–O–C and C–O differences between the two benzoates of
˚
˚
0.101 A, 33.58 and 0.025 A, respectively. This has been
ascribed to the presence of a strong Ti–O p bond supple-
menting the Ti–O s bond for one of the benzoates, thusgiving
an effective 18-electron count rather than a formal 16-elec-
tron count for the valenceelectrons. However,structuredeter-
minations of some other [Cp2Ti{OC(O)R}2] compounds
show very near equivalence of the carboxylate groups, e.g.
RsH [23] or CH2CN[24], presumablyresultingfromsome
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D.A. Edwards et al. / Polyhedron 19 (2000) 757–764
763
Fig. 2. ORTEX plot of the molecular structure of the 1:1 adduct of compound 3 and PdCl2 solvated with 3CH2Cl2 showing the labelling scheme. The
dichloromethane molecules and hydrogen atoms are omitted for clarity. Thermal ellipsoids are at the 30% probability level.
forming neutral trimetallic acyclic complexes by bonding to
two group 11 (Cu or Au) metal centres. In each case, the
diphenylphosphinoacetate ligands remain O-unidentate with
respect to the titanium. These products are therefore related
to, but quite distinct in type from, the cationic tetranuclear
[Cp2Ti{m-OC(O)C5H4N-p}2PtL2]2[CF3SO3]4 complexes
(LsPEt3 or 0.5 dppp) isolated by Stang and Persky [14]
from cis-[PtL2(OSO2CF3)2] and [Cp2Ti(iso-nicotinate)2].
The binuclear complexes [Cp2Ti{m-OC(O)CH2PPh2}2-
MCl2] (MsPd or Pt) have been prepared from [MCl2-
(NCPh)2] and the trinuculear [Cp2Ti{m-OC(O)CH2-
PPh2}2(CuCl)2] directly from Cu(I) chloride. One signifi-
cant feature concerning the syntheses of these compounds is
that they can be prepared at least equally well, and often
better, from methane elimination reactions of [Cp2TiMe2]
with the neutral P-donor diphenylphosphinoacetic acid com-
plexes [MCl2(Ph2PCH2CO2H)2] (MsPd or Pt) and
[M9Cl(Ph2PCH2CO2H)] (M9sCu or Au) that we have
reported previously [17]. For the complexes involvinggroup
11 metals, the silver complex has a 1:1 Ti:Ag stoichiometry
whereas the copper and gold products both have 1:2 Ti:M9
stoichiometries. The silver complex [Cp2Ti{m-OC(O)-
CH2PPh2}2AgCl] has been prepared both from the direct
reaction of AgCl with [Cp2Ti{OC(O)CH2PPh2}2] and from
the reaction of silver diphenylphosphinoacetate with
[Cp2TiCl2].
PPh2}2Ag]q, suggest that the complex is a bimetallocyclic
three-coordinate silver species. For the copper and gold com-
plexes [Cp2Ti{m-OC(O)PPh2}2(M9Cl)2], the gold product
certainly contains linear two-coordinate PAuCl moietieswith
both an IR n(AuCl) and a 31P NMR chemical shift almost
identical to those of the structurally characterised [17]
[AuCl(Ph2PCH2CO2H)] (IR n(AuCl) 335 cmy1; 31PNMR
d q25 ppm). The mass spectrum contains a parent ion sup-
porting this proposal, other fragments involving loss of chlo-
ride and/or cyclopentadienyl units. On the other hand, the
copper complex is unlikely to contain two-coordinate Cu(I).
If it did, an IR n(CuCl) at around 400 cmy1 may be expected
but no such band could be assigned. The 31P NMR d ofy12.4
ppm is very similar to that of [CuCl(Ph2PCH2CO2H)] (d of
y13.3 ppm) which was suggested [17] to be tetramericwith
a cubane or step structure. The present complex could be
similar. The 31P NMR d values of the group 11 metal com-
plexes are all downfield of that of the parent [Cp2Ti-
{OC(O)CH2PPh2}2] as a result of the additional bonding
from phosphorus. The coordination shifts, Dd, increase sig-
nificantly on progressing from copper through to gold (Dd
values of 5.2, 15.8 and 42.5 ppm for the copper, silver and
gold complexes, respectively).
The square planar palladium and platinum complexes
[Cp2Ti{m-OC(O)CH2PPh2}2MCl2] have been isolated
from both preparative routes but are less soluble than the
group 11 metal complexes, the very low solubility of the
platinum complex in suitable solvents precluding the acqui-
sition of NMR data. For the palladium complex, the 31P NMR
chemical shift is close to that of [PdCl2(Ph2PCH2CO2H)2]
[17]. These two complexes, as confirmed by the X-ray crys-
The silver complex has a large IR (nasymynsym CO2) sep-
aration of around 370 cmy1, indicative of the expected O-
unidentate bonding of the carboxylates to Ti(IV). The single
31P NMR resonance and the magnitude of the 107Ag–31P and
109Ag–31P coupling constants are reasonable for a silver–bis-
phosphine complex [27]. These results coupled with the
mass spectrometric data, which show no significant frag-
ments of mass above that of [Cp2Ti{m-OC(O)CH2-
tal structure determination of the palladium complex, involve
–––––––––––––
o
p
cis-[MCl2P2] geometry with ten-atom
TiOCCPMPCCO
rings. The precursor [PdCl2(Ph2PCH2CO2H)2] has [17] a
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764
D.A. Edwards et al. / Polyhedron 19 (2000) 757–764
trans square planar geometry when crystallisedfromaqueous
ethanol so that in its reaction with [Cp2TiMe2] to produce
[Cp2Ti{m-OC(O)CH2PPh2}2PdCl2] a rearrangement of the
ClPdCl and PPdP arrays from trans to cis must occur. Large
IR (nasymynsym CO2) differences for both complexes con-
firm the expected O-unidentate coordination of the carboxy-
latesto titaniumand thedetectionoftwoIR(nMCl)stretches
supports the presence of cis-[MCl2P2] arrangements.
priate [Cp2Ti{OC(O)R}2] with [MCl2(NCPh)2]. These
products will similarly possess ten-atom TiOCCEMECCO
rings (EsN or S).
–––––––––––––
o
p
Supplementary data
Crystallographic data are available from CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (fax: q44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk), on request, quoting the
deposition numbers CCDC 136188 and CCDC136189.
A crystal structure determination of the palladium com-
plex, as a tris(dichloromethane) solvate, confirms that the
titanium has a distorted tetrahedral environment comprising
two cyclopentadienyl and two O-unidentate carboxylate
ligands (Fig. 2). The distortion can be assessed by consid-
ering the centroids, Z, of the cyclopentadienyl rings, the Z–
Ti–Z angle being 131.68 and the O(1)–Ti–O(3) angle
89.4(3)8. The carboxylates are also P-bonded to the palla-
dium to produce the ten-atom ring mentioned above. The
Acknowledgements
We thank EPSRC for a maintenance grant to T.J.P.
˚
Ti∆Pd distance across the ten-atom ring is 4.18 A indicating
the absence of direct metal–metal interaction, unlike, for
example, the square planar Rh(I) complex [Cp2Ti-
(SCH2CH2CH2PPh2)2Rh][BF4] in which the Ti∆Rh dis-
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˚
tance is only 3.127(2) A [28]. The cis-[PdCl2P2] square
planar arrangement is distorted, the P–Pd–P angle opening to
103.93(13)8 and the Cl–Pd–P angles closing to 83.12(13)
and 84.63(13)8. The Pd–P bond lengths [2.259(4),
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2.277(4) A] are slightly shorter than those found [17] for
the three independent molecules in trans-[PdCl2(Ph2-
PCH2CO2H)2]P0.33H2OP0.33EtOH [2.326(1), 2.309(1),
˚
2.337(2) A]. Conversely, the Pd–Cl bond lengths are longer
˚
[2.348(4), 2.339(4) A] when compared to those of the
above solvated diphenylphosphinoacetic acid complex
˚
[2.305(1), 2.303(1), 2.295(1) A]. Some comparisons and
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contrasts with the structure of the parent [Cp2Ti{OC(O)-
CH2PPh2}2] are instructive. The markedly inequivalent
diphenylphosphinoacetate ligands of [Cp2Ti{OC(O)CH2-
PPh2}2], as illustrated by Ti–O and C–O bond length and Ti–
O–C bond angle differences, become essentially equivalent
in the palladium complex with respect to the titanium centre,
˚
the Ti–O and C–O bond length differences being 0.01 A or
less and the Ti–O–C angles showing only a difference of0.78.
The average Ti–C (ring) distances of 2.35(2) and 2.37(2)
˚
¨
A are in good agreement with those of [Cp2Ti{OC(O)-
ment, University of Gottingen, 1993.
˚
[21] K. Doppert, H.-P. Klein, U. Thewalt, J. Organomet. Chem. 303
(1986) 205.
[22] C.R. Lucas, E.J. Gabe, F.L. Lee, Can. J. Chem. 66 (1988) 429.
[23] D.H. Gibson, Y. Ding, J.F. Richardson, M.S. Mashuta, Acta Crystal-
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[24] D.A. Edwards, M.F. Mahon, T.J. Paget, Polyhedron 16 (1997) 25.
[25] D.M. Hoffmann, N.D. Chester, R.C. Fay, Organometallics 2 (1983)
48.
[26] S. Civis, J. Podlahova, J. Loub, J. Jecny, Acta Crystallogr., Sect. B 36
(1980) 1395.
CH2PPh2}2], [2.372(7), 2.360(8) A], and many other
bis(cyclopentadienyl)Ti(IV) compounds [25].
Finally, we have illustrated the versatility of this type of
reaction by using the potentially N- and S-donor carboxyla-
tes, nicotinate and thiophenoxyacetate, in place of the P-
bonding diphenylphosphinoacetate but in a more restricted
range of examples. In this manner, analogous [Cp2Ti{m-
OC(O)C5H4N-m}2MCl2] (MsPd and Pt) and [Cp2Ti{m-
OC(O)CH2SPh}2PdCl2] complexes have been isolated as
orange, rather insoluble, solids from reactions of the appro-
[27] E.L. Muetterties, C.W. Alegranti, J. Am. Chem. Soc. 94 (1972) 6386.
[28] G.S. White, D.W. Stephan, Organometallics 6 (1987) 2169.
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