Dynamic titanium phosphinoamides as unique bidentate phosphorus ligands for platinum

Article abstract of DOI:10.1021/om0509600

Treatment of lithium phosphinoamides, Ph₂PN(Li)R [R = ^tBu, ⁱPr], with TiCl₄ results in formation of titanium phosphinoamides, (Ph₂PNR)₂TiCl₂ [R = ^tBu (1a), ⁱPr (1b)]. Crystallographic studies show that there are covalent bonds between the titanium and two nitrogen atoms, whereas two phosphorus atoms are coordinated to the metal center intramolecularly. Variable-temperature NMR studies suggest reversible dissociation of the phosphorus moieties from the titanium in solution. The dissociated phosphorus moieties are effectively captured by Pt(II) species; reactions of 1a with either (η⁴-COD)PtCl₂, (η⁴-COD)Pt(R)(Cl) (R = Me, p-Tol), or [Me₂Pt(μ-SMe₂)]₂ afford the corresponding Ti-Pt heterobimetallic complexes. The molecular structures of these complexes reveal that they have a six-membered dimetallacycle, in which a titanium and a platinum are connected by two bridging phosphinoamide ligands; the Pt-Ti distances indicate the existence of a Pt→Ti dative bond. The conformation of the dimetallacycle is a boat form, with two metals at the bow and the stem in the crystal; however, dynamic conformational change involving cleavage and re-formation of the Pt→Ti dative bond is indicated from variable-temperature NMR studies.

Full text of DOI:10.1021/om0509600

Organometallics 2006, 25, 1987-1994
1987
Dynamic Titanium Phosphinoamides as Unique Bidentate
Phosphorus Ligands for Platinum
Hideo Nagashima,*,†,§ Takashi Sue,§ Takashi Oda,§ Akira Kanemitsu,§ Taisuke Matsumoto,‡
Yukihiro Motoyama,†,§ and Yusuke Sunada†,§
DiVision of Applied Molecular Chemistry and Analytical Center of Institute for Materials Chemistry and
Engineering, and Graduate School of Engineering Sciences, Kyushu UniVersity, Kasuga, Fukuoka
816-8580, Japan
ReceiVed NoVember 9, 2005
Treatment of lithium phosphinoamides, Ph2PN(Li)R [R ) tBu, iPr], with TiCl4 results in formation of
titanium phosphinoamides, (Ph2PNR)2TiCl2 [R ) tBu (1a), iPr (1b)]. Crystallographic studies show that
there are covalent bonds between the titanium and two nitrogen atoms, whereas two phosphorus atoms
are coordinated to the metal center intramolecularly. Variable-temperature NMR studies suggest reversible
dissociation of the phosphorus moieties from the titanium in solution. The dissociated phosphorus moieties
are effectively captured by Pt(II) species; reactions of 1a with either (η4-COD)PtCl2, (η4-COD)Pt(R)(Cl)
(R ) Me, p-Tol), or [Me2Pt(µ-SMe2)]2 afford the corresponding Ti-Pt heterobimetallic complexes. The
molecular structures of these complexes reveal that they have a six-membered dimetallacycle, in which
a titanium and a platinum are connected by two bridging phosphinoamide ligands; the Pt-Ti distances
indicate the existence of a PtfTi dative bond. The conformation of the dimetallacycle is a boat form,
with two metals at the bow and the stern in the crystal; however, dynamic conformational change involving
cleavage and re-formation of the PtfTi dative bond is indicated from variable-temperature NMR studies.
In these earlier studies on the heterobimetallic complexes
formed by the reaction of the above metalloligand with late
transition metals, the titanium or zirconium center is considered
to act as a Lewis acidic center (electron acceptor). In fact,
Introduction
There have been numerous examples of the successful use
of phosphorus ligands for late transition metals in metal-
catalyzed organic or polymer syntheses.1 Electronic and struc-
tural properties of phosphorus ligands actually affect the rate
and selectivity of the catalytic reactions, and as control factors,
Tolman’s cone angle and ø values are generally considered
for their structural and electronic design.1a For the metal
complexes having bidentate phosphorus ligands, the importance
of the bite angle is well recognized as an additional factor for
a rational ligand design.1b Phosphorus compounds containing a
metal center in the molecule have lately been attracting the
attention of organometallic chemists as metal-containing ligands
(metalloligands) for transition metals, of which potential interac-
tion of the metal in the metalloligand with the transition metal
bound to the phosphorus atoms may provide special reactivity
of the transition metal center.2-4 In particular, several trials have
been made on the preparation of bidentate phosphorus com-
pounds containing a titanium and zirconium moiety, and their
ligation to late transition metals was studied.2,3 Examples closely
related to the present paper are Cp2M(PR2)2,2a-g Cp2Zr-
(CH2PR2)2,2h-n and Cp2M(O∼PPh2)2,2o-q (M ) Ti, Zr), which
are coordinated to late transition metals such as Rh and Pt to
give the corresponding heterobimetallic complexes of the
type Cp2M(µ-PR2)2M′Ln Cp2Zr(CH2PR2)2M′Ln, and Cp2M-
(O∼PPh2)2M′Ln (M ) Ti, Zr; M′Ln; late transition metal
fragments), respectively.
(2) (a) Baker, R. T.; Tulip, T. H. Organometallics 1986, 5, 839. (b)
Gelmini, L.; Stephan, D. W. Inorg. Chem. Acta 1986, 111, L17. (c) Yousif-
Ross, S. A.; Wojcicki, A. Inorg. Chem. Acta 1990, 171, 115. (d) Gelmini,
L.; Stephan, D. W. Organometallics 1988, 7, 849. (e) Larsonneur, A.-M.;
Choukroun, R.; Daran, J.-C.; Cuenca, T.; Flores, J. C.; Royo, P. J.
Organomet. Chem. 1993, 444, 83. (f) Lindenberg, F.; Shribman, T.; Sieler,
J.; Hey-Hawkins, E.; Eisen, M. S. J. Organomet. Chem. 1996, 515, 19. (g)
Baker, R. T.; Fultz, W. C.; Marder, T. B.; Williams, I. D. Organometallics
1990, 9, 2357. (h) Choukroun, R.; Gervais, D.; Kalck, P.; Senocq, F. J.
Organomet. Chem. 1987, 335, C9. (i) Senocq, F.; Randrianalimanana, A.;
Thorez, A.; Kalck, P.; Choukroun, R.; Gervais, D. J. Mol. Catal. 1986, 35,
213. (j) Choukroun, R.; Gervais, D.; Rifai, C. Polyhedron 1989, 8, 1760.
(k) Trzeciak, A. M.; Zio´lkowski, J. J.; Choukroun, R. J. Organomet. Chem.
1991, 420, 353. (l) Choukroun, R.; Gervais, D.; Jaud, J.; Kalck, P.; Senocq,
F. Organometallics 1986, 5, 67. (m) Choukroun, R.; Iraq, A.; Gervais, D.;
Daran, J.-C.; Jeannin, Y. Organometallics 1987, 6, 1197. (n) Choukroun,
R.; Dahan, F.; Gervais, D.; Rifai, C. Organometallics 1990, 9, 1982. (o)
Mattheis, C.; Braunstein, P.; Fischer, A. J. Chem. Soc., Dalton Trans. 2001,
800. (p) Priya, S.; Balakrishna, M. S.; Mague, J. T. J. Organomet. Chem.
2004, 689, 3335. (q) Ferguson, G. S.; Wolczanski, P. T.; Pa´rka´nyi, L.;
Zonnevylle, M. C. Organometallics 1988, 7, 1967.
(3) For other bidentate phosphorus ligands containing a titanium or
zirconium atom: (a) Delgado, E.; Fornies, J.; Hernandez, E.; Lalinde, E.;
Mansilla, N.; Moreno, M. T. J. Organomet. Chem. 1995, 494, 261. (b)
Bosch, B. E.; Bru¨mmer, I.; Kunz, K.; Erker, G.; Fro¨hlich, R.; Kotila, S.
Organometallics 2000, 19, 1255. (c) Cornelissen, C.; Erker, G.; Kehr, G.;
Fro¨hlich, R. J. Chem. Soc., Dalton Trans. 2004, 4059. (d) Cornelissen, C.;
Erker, G.; Kehr, G.; Fro¨hlich, R. Organometallics 2005, 24, 214. (e) Le
Gendre, P.; Maubrou, E.; Blacque, O.; Boni, G.; Mo¨ıse, C. Eur. J. Inorg.
Chem. 2001, 1437. (f) Comte, V.; Gendre, P. L.; Richard, P.; Mo¨ıse, C.
Organometallics 2005, 24, 1439. (g) Gendre, P. L.; Richard, P.; Mo¨ıse, C.
J. Organomet. Chem. 2000, 605, 151. (h) Pouland, C.; Boni, G.; Richard,
P.; Mo¨ıse, C. J. Chem. Soc., Dalton Trans. 1999, 2725. (i) Ara, I.; Delgado,
E.; Fornies, J.; Hernandez, E.; Lalinde, E.; Mansilla, N.; Moreno, M. T. J.
Chem. Soc., Dalton Trans. 1996, 3201.
* Corresponding author. E-mail: nagasima@cm.kyushu-u.ac.jp.
† Division of Applied Molecular Chemistry, Institute for Materials
Chemistry and Engineering, Kyushu University.
‡ Analytical Center, Institute for Materials Chemistry and Engineering,
Kyushu University.
§ Graduate School of Engineering Sciences, Kyushu University.
(1) For reviews: (a) Tolman, C. A. Chem. ReV. 1977, 77, 313. (b)
Dierkes, P.; van Leeuwen, P. W. N. M. J. Chem. Soc., Dalton Trans. 1999,
1519.
(4) For other metalloligands, see the following papers and references
therein: (a) Graham S. W.; Stephan, D. W. Organometallics 1988, 7, 903.
(b) Nadasdi, T. T.; Stephan, D. W. Organometallics 1992, 11, 116. (c)
Kuwabara, J.; Takeuchi, D.; Osakada, K. Organometallics 2004, 23, 5092.
10.1021/om0509600 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 03/07/2006

1988 Organometallics, Vol. 25, No. 8, 2006
Nagashima et al.
Scheme 1
possible contribution of the Lewis acidic zirconium center to
the cooperative reactivity with the late transition metal center
in the activation step of CO was proposed in the rhodium-
catalyzed hydroformylation of olefins with these Zr-Rh het-
erobimetallic complexes.3b-d However, it should be noted that
the titanocene or zirconocene unit is not a strong electron
acceptor, because the coordination of electron-donating Cp
ligands reduces the Lewis acidity of the titanium or zirconium
center. In this sense, replacement of the Cp2Ti or Cp2Zr unit
by a Ti or Zr moiety with stronger Lewis acidity is of interest.
If such metalloligands can be realized and successfully ligate
to transition metals, donor-acceptor interaction between the late
transition metal center and the Ti or Zr center would be more
clearly visible. However, such complexes, e.g., Cl2Ti(µ-PR2)2-
MLn and Cl2Zr(µ-CH2PR2)2MLn, have not been synthesized to
our knowledge. Part of the reason is enhanced Lewis acidity of
the Ti or Zr moiety, which causes its strong intermolecular
interaction with phosphorus atoms in the metalloligand, leading
to their self-aggregation. The self-aggregation is likely to prevent
the interaction of the phosphorus compounds containing the
TiCl2 or ZrCl2 unit with late transition metals. In fact,
compounds containing Lewis acidic R2Al and Lewis basic R2P
units in one molecule are known as “amphoteric ligands”.5 In
these compounds, self-aggregations are often seen, for example,
RnCl2-nAlCH2PR2, in which two strong PfAl bonds provide
a dimer with a six-membered ring structure.5b Although an
aluminum phosphinoamide, Ph2P(tBu)NAlEt2, was reportedly
a monomer in a benzene solution,5f this was later contradicted
by Labinger’s NMR study.5a It is interesting, however, that
Ph2P(tBu)NAlEt2 reacted with certain metal carbonyls to give
metallacyclic products, presumably due to the mechanisms
involving its dissociation to a monomeric form.
In our continuous efforts to synthesize new heterobimetallic
complexes,6,7 we were interested in the potential of (PPh2-
NR)2TiCl2 (1) as a new type of bidentate phosphorus ligand
containing a Lewis acidic TiCl2 unit. The chemistry of phos-
phinoamides has lately received considerable attention because
of two possible resonance structures, [R′2PNR]- and [R′2PdNR]-,
and detailed structural studies on the lithium phosphinoamides
have been carried out since a pioneering study by Ashby and
Li.8 Several reports were published on the phosphinoamide and
related phosphinoamide complexes of the early transition metals9
and lanthanides.10 In particular, successful preparation of (Ph2-
PNPPh2)2TiCl2 and Zr(Ph2PNPh)4 reported by Eisen and co-
workers9a strongly suggested that 1 could be synthesized by
careful treatment of TiCl4 with 2 equiv of Li[R′2PNR]. On the
other hand, it was questionable when we started this research
whether the formed 1 behaves as a bidentate phosphorus ligand;
coordination of the phosphorus moieties in 1 to a late transition
metal species should be competitive with the intramolecular
coordination of the phosphorus moieties with the titanium center.
In this paper, we wish to report that 1 can actually be
synthesized and behaves as a metalloligand to Pt(II). Thus, (Ph2-
PNR)2TiCl2 (1a, R ) tBu; 1b, R ) iPr) were prepared according
to Scheme 1, eq 1, and were characterized by spectroscopy and
crystallography. Although the crystal structures of 1a and 1b
showed coordination of the two phosphorus moieties to the
titanium center, variable-temperature NMR suggested that this
coordination was essentially reversible in solution (Scheme 1,
eq 2). The dissociated phosphorus moieties were successfully
captured by Pt(II) species to afford a series of early-late
heterobimetallic (ELHB) complexes, XX′M′(Ph2PNtBu)2TiCl2
(2a, M′ ) Pt, X, X′ ) Cl; 2b, M′ ) Pd, X, X′ ) Cl; 3a, M′ )
Pt, X ) Me, X′ ) Cl; 3a′, M′ ) Pt, X ) p-Tol, X′ ) Cl; 4a,
M′ ) Pt, X, X′ ) Me) (Scheme 1, eq 3). It is important that
interaction of the Lewis acidic titanium center and the Lewis
basic platinum center was proved by the existence of a dative
bond seen in their crystal structures. The results clearly
demonstrate the ability of 1 as a unique bidentate phosphorus
ligand containing a Lewis acidic titanium, which is capable of
interacting with platinum in the resulting Ti-Pt heterobimetallic
complexes.
(5) (a) Labinger, J. A.; Bonfiglio, J. N.; Grimmett, D. L.; Masuo, S. T.;
Shearin, E.; Miller, J. S. Organometallics 1983, 2, 733. (b) Karsch, H. H.;
Appelt, A.; Kohler, F. H.; Muller, G. Organometallics 1985, 4, 231. (c)
Beachlay Jr., O. T.; Tessier-Youngs, C. Organometallics 1983, 2, 796. (d)
Thomas, F.; Schluz, S.; Nieger, M.; Nattinen, K. Chem. Eur. J. 2002, 8,
1915. See also: (e) Thomas, S. J.; Peters, J. C. J. Am. Chem. Soc. 2001,
123, 5100. (f) Clemens, D. F.; Sisler, H. H.; Brey, W. S. Inorg. Chem.
1966, 5, 527.
(6) For reviews: (a) Stephan, D. W. Coord. Chem. ReV. 1989, 95, 41.
(b) Adams, R. D.; Cotton, F. A. Catalysis by Di- and polynuclear Metal
Cluster Complexes; Wiley-VCH: New York, 1998. (c) Braunstein, L. A.;
Oro, L. A.; Raithby P. R. Metal Clusters in Chemistry Vol. 2; Wiley-VCH:
New York, 1999. (d) Wheatley, N.; Kalck, W. Chem. ReV. 1999, 99, 3379.
(e) Gade, L. H. Angew. Chem., Int. Ed. 2000, 39, 2658.
Results and Discussion
Preparation and Characterization of Titanium Phosphi-
noamides. Treatment of Ph2PNHR (R ) tBu, iPr) with n-BuLi
in ether afforded the lithium phosphinoamide Ph2PN(Li)R. The
(7) (a) Niibayashi, S.; Mitsui, K.; Motoyama, Y.; Nagashima, H. J.
Organomet. Chem. 2005, 690, 276. (b) Niibayashi, S.; Mitsui, K.; Matsubara,
K.; Nagashima, H. Organometallics 2003, 22, 4885. (c) Matsubara, K.;
Niibayashi, S.; Nagashima, H. Organometallics 2003, 22, 1376.
(8) (a) Ashby, M. T.; Li, Z. Inorg. Chem. 1992, 31, 1322. (b) Trinquier,
G.; Ashby, M. T. Inorg. Chem. 1994, 33, 1306. (c) Poetschke, N.; Nieger,
M.; Khan, M. A.; Niecke, E.; Ashby, M. T. Inorg. Chem. 1997, 36, 4087.
(d) Eichhorn, B.; Noeth, H.; Seifert, T. Eur. J. Inorg. Chem. 1999, 2355.
(e) Fei, Z.; Scopelliti, R.; Dyson, P. J. Inorg. Chem. 2003, 42, 2125.
(9) (a) Kuhl, O.; Koch, T.; Somoza, F. B., Jr.; Junk, P. C.; Hey-Hawkins,
E.; Plat, D.; Eisen, M. S. J. Organomet. Chem. 2000, 604, 116. (b)
Smolensky, E.; Kapon, M.; Woollins, J. D.; Eisen, M. S. Organometallics
2005, 24, 3255. (c) Smolensky, E.; Kapon, M.; Eisen, M. S. Organometallics
2005, 24, 5495. (d) Qi, C.; Zhang, S.; Sun, J. J. Organomet. Chem. 2005,
690, 2941. (e) Ku¨hl, O.; Blaurock, S.; Sieler, J.; Hey-Hawkins, E.
Polyhedron 2001, 20, 111.
(10) (a) Roesky, P. W. Heteroat. Chem. 2002, 13, 514. (b) Gamer, M.
T.; Roesky, P. W. Inorg. Chem. 2004, 43, 4903.

Dynamic Titanium Phosphinoamides
Organometallics, Vol. 25, No. 8, 2006 1989
Scheme 2
Figure 1. ORTEP drawings of 1a (left) and 1b (right).
which the N-P bond distance may suggest the double-bond
nature of the N-P linkage.8 The N-P distances of 1a and 1b
are 1.640 to 1.643 Å, similar to the N-P distances of a series
of lithium phosphinoamides, which are between typical PdN
bonds and the sum of van der Waals radii of N and P. These
suggest some contribution of [R2P-dNR′], similar to the lithium
salts. The nitrogen atoms are sp2-hybridized; this suggests that
a lone pair electron of the nitrogen atom is delocalized by the
PdN and NfTi interaction.
Figure 2. Possible isomers of titanium phosphinoamides.
Table 1. Representative Bond Lengths and Angles for 1a
and 1b
As described above, two phosphorus atoms in 1a and 1b are
coordinated to the titanium center in the crystal structure. A
single 31P resonance at δ -15.8 (1a) and -19.2 (1b), which
shows a 38.4 or 53.7 ppm higher field shift compared with that
of Ph2PNHtBu (δ 22.6) or Ph2PNHiPr (δ 34.5), respectively,
1a
1b
Bond Lengths (Å)
2.3247(9)
2.3183(8)
2.4223(9)
2.4609(8)
1.980(2)
Ti-Cl(1)
Ti-Cl(2)
Ti-P(1)
2.3044(16)
2.3145(17)
2.4754(14)
2.4762(17)
1.939(3)
1.952(4)
1.642(4)
1.640(4)
1
indicates the coordination of the P atom. In contrast, H and
Ti-P(2)
13C NMR spectra of 1a and 1b did not provide clear evidence
for the coordination at room temperature. Although the coor-
dination makes two phenyl groups on the P atom inequivalent,
only the signals due to the magnetically equivalent phenyl
Ti-N(1)
Ti-N(2)
P(1)-N(1)
P(2)-N(2)
1.970(2)
1.643(2)
1.641(2)
1
groups were seen in the H and 13C NMR spectra at room
Bond Angles (deg)
94.07(3)
Cl(1)-Ti-Cl(2)
N(1)-Ti-N(2)
P(1)-Ti-P(2)
N(1)-Ti-P(1)
N(1)-Ti-P(2)
N(2)-Ti-P(1)
N(2)-Ti-P(2)
Cl(1)-Ti-P(1)
Cl(1)-Ti-P(2)
Cl(2)-Ti-P(1)
Cl(2)-Ti-P(2)
N(1)-Ti-Cl(1)
N(1)-Ti-Cl(2)
N(2)-Ti-Cl(1)
N(2)-Ti-Cl(2)
95.90(6)
112.78(18)
95.57(5)
41.49(11)
108.58(14)
127.30(13)
41.40(12)
93.34(5)
temperature. For example, the 1H NMR spectrum of 1a in CD2-
Cl2 showed a sharp singlet at δ 1.36 and three signals at δ 7.29,
7.41, and 7.53 in an integral ratio of 9:2:1:2, which are
110.05(10)
89.79(2)
42.34(7)
99.21(7)
126.09(7)
41.67(7)
t
assignable to methyl of Bu, ortho-phenyl, para-phenyl, and
meta-phenyl protons, respectively. Similarly, 13C NMR spectra
t
showed only six peaks due to the Bu and the magnetically
95.03(3)
equivalent two phenyl groups. The crystal structure of 1b
indicates an additional problem that two methyl groups due to
the isopropyl moiety should be diastereotopic; however, only
magnetically equivalent 1H and 13C resonances due to the methyl
as well as the phenyl groups are visible at room temperature.
100.93(3)
124.79(3)
140.93(3)
132.32(8)
96.71(7)
94.88(5)
125.41(5)
136.69(5)
129.21(13)
96.35(13)
114.42(11)
96.58(13)
112.74(8)
99.27(7)
A clue to the understanding of the NMR spectra was obtained
from the 1H NMR spectra at low temperature. The 1H resonances
due to the phenyl groups in 1a are significantly broadened at
-105 °C; this may result from the reversible coordination shown
resulting solution was subjected to the reaction with TiCl4 [a
half equivalent to Ph2PN(Li)R] to give the titanium phosphi-
t
i
1
noamides 1a (R ) Bu) and 1b (R ) Pr) in 84 to 81% yield.
X-ray structure determination of 1a and 1b provided the
molecular structures shown in Figure 1, and representative bond
distances and angles are summarized in Table 1. Two chlorine,
two nitrogen, and two phosphorus atoms make a distorted
octahedral arrangement, and the chlorine atoms and centers of
the N-P bonds are arranged tetrahedrally. Although there should
be two isomeric structures, Cs-symmetric A and C2-symmetric
B, shown in Figure 2, only structure A was detected in the
crystal. Two possible tautomeric structures of lithium phosphi-
noamides, [R2PN-R′]Li+ and [R2P-dNR′]Li+, were discussed
in the literature from crystal structures and MO calculations, in
in Scheme 2 (upper scheme). The H signal due to the methyl
groups of the isopropyl moiety in 1b provides more clear
evidence of the equilibrium shown in the lower scheme in
Scheme 2; the methyl resonance is a sharp doublet at room
temperature, starts to broaden at -60 °C, and turns to a broad
singlet at -90 °C. At -105 °C, broadening of the signal results
in significant decrease of the peak intensity. Similar broadening
of the 13C and 31P resonances is visible in variable-temperature
NMR measurements of 1a and 1b. The actual charts are shown
in the Supporting Information. Although a technical problem
prevents the experiment, two doublets due to the diastereotopic
methyl groups would appear at a temperature below -105 °C.

1990 Organometallics, Vol. 25, No. 8, 2006
Nagashima et al.
Table 2. Representative Bond Lengths and Angles for the
Heterobimetallic Complexes
2a
3a
4a
3a′
Bond Lengths (Å)
Pt-Ti
2.8358(8)
2.3458(16) 2.347(1)
2.3489(16)
2.7547(10) 2.6860(11) 2.7234(4)
Pt-Cl(3)
Pt-Cl(4)
Pt-C(1)
Pt-C(2)
Pt-P(1)
Pt-P(2)
Ti-Cl(1)
Ti-Cl(2)
Ti-P(1)
Ti-P(2)
Ti-N(1)
Ti-N(2)
P(1)-N(1)
P(2)-N(2)
2.3476(7)
2.154(13)
2.135(8)
2.058(2)
2.116(11)
2.2772(15) 2.3507(18) 2.325(2)
2.2868(16) 2.2632(17) 2.317(2)
2.2749(17) 2.288(2)
2.2353(15) 2.2408(18) 2.283(2)
2.7947(16) 2.728(2)
2.7823(17) 2.7795(19) 2.700(3)
1.950(4)
1.929(5)
1.664(4)
1.665(4)
2.4087(6)
2.2435(5)
2.3075(8)
2.2722(9)
2.322(2)
2.6846(19) 2.6555(8)
2.7849(7)
1.910(2)
1.998(2)
1.683(2)
1.657(2)
1.940(6)
1.965(6)
1.665(5)
1.663(5)
1.926(8)
1.957(8)
1.659(5)
1.665(6)
Bond Angles (deg)
P(1)-Pt-P(2)
102.48(5)
103.39(6)
103.39(7)
105.64(2)
85.94(2)
Cl(3)-Pt-Cl(4) 83.36(5)
P(1)-Pt-Cl(3)
P(2)-Pt-Cl(4)
C(1)-Pt-Cl(3)
C(1)-Pt-P(1)
C(1)-Pt-P(2)
C(2)-Pt-P(2)
C(1)-Pt-C(2)
86.45(5)
86.00(5)
85.90(7)
82.7(3)
168.6(3)
87.7(3)
81.34(7)
167.28(7)
86.44(7)
Figure 3. ORTEP view of 3a′.
87.4(3)
165.2(3)
88.0(2)
79.7(3)
Eisen and co-workers observed the dynamic behavior of Zr-
(Ph2PNPh)4 and proposed similar reversible dissociation of some
of the phosphorus moieties in solution.9a
are bonded to the titanium atom, whereas two phosphorus atoms
are coordinated to the platinum center. The conformation of
the six-membered ring is a boat form, with the two metal atoms
at the bow and the stern. The Ti-Pt distances indicate that there
is a possibility of a PtfTi dative bond, as discussed later in
detail. Presumably due to this dative bond, two chlorine and
two nitrogen atoms coordinated to the titanium atom are
distorted significantly from tetrahedral to pseudo-trigonal bi-
pyramidal, in which one chlorine atom and the platinum moiety
are at the apical position, whereas the other chlorine atom and
the two nitrogen ligands are at the basal position. The ligand
arrangement around the platinum atom is square planar;
however, the platinum center is somewhat out of plane due to
the Pt-Ti interaction. The phosphinoamide ligands bridge over
the PtfTi dative bond. The N-P distances around 1.66 Å are
approximately 0.1 Å shorter than the sum of the van der Waals
radii of N and P; a contribution of [R2P-dNR′] may exist
similar to those seen in titanium phosphinoamides 1a and 1b.
The nitrogen atoms are sp2-hybridized; this suggests that a lone
pair electron of the nitrogen atom is delocalized by the PdN
and NfTi interaction. The complexes bearing a bridging
Titanium Phosphinoamides as a Metalloligand: Reactions
with Organoplatinum Complexes. As described above, tita-
nium phosphinoamides were successfully prepared and char-
acterized, and the reversible dissociation of the phosphorus
moieties in solution was indicated from the variable-temperature
1H NMR. There should be a possible capture of the dissociated
phosphorus moieties in the titanium phosphinoamides by
appropriate transition metal species, leading to preparation of
new heterobimetallic complexes. In fact, treatment of 1a with
(COD)PtCl2, (COD)PtMeCl, and (COD)Pt(p-Tol)Cl actually
gave the corresponding Ti-Pt bimetallic complexes 2a, 3a, and
3a′, in 80, 84, and 65% yield, respectively. Although (COD)-
PtMe2 did not react with 1a, treatment of [Me2Pt(µ-SMe2)]2
with 1a afforded 4a in 81% yield. The molecular structures of
all four of these complexes were determined by crystallography.
Two of them, 3a and 4a, contain crystallographic problems,
which are caused by disorder of the methyl and the chloro group
in 3a, and disorder of the solvates (Et2O) in 4a. However, careful
examinations of the crystallography of 3a and 4a suggest that
there should be no problem in discussing the six-membered
dimetallacyclic structures. The ORTEP drawing of 3a′ is
depicted in Figure 3 as representative of the whole structure,
and the simplified molecular structures illustrating the six-
membered dimetallacycles of 2a, 3a, and 4a are shown in Figure
4. The representative bond distances and angles are summarized
in Table 2. All of these four complexes have a similar
dimetallacyclohexane framework, in which two nitrogen atoms
11a
phosphinoamide ligand, Cp2ZrClN(SiMe3)P(H)(tBu)Fe(CO)4
and Cp2ZrN(tBu)PR2Ir(H)Cp*,11b were synthesized by Majoral
and Bergman, respectively. Although the former was character-
ized by spectroscopic methods in the solution state, the latter
prepared from [Cp2Zr(µ-NtBu)IrCp*] with HPRR′ (R ) R′ )
Et or R ) cyclohexyl, R′ ) H) was investigated in detail by
Figure 4. Simplified molecular structures of the heterobimetallic complexes 2a (left), 3a (center), and 4a (right).

Dynamic Titanium Phosphinoamides
Organometallics, Vol. 25, No. 8, 2006 1991
Scheme 3
Figure 5.
crystallography [Zr-Ir distance: 2.642(1) Å]. The nitrogen atom
is sp2-hybridized (the sum of the three angles at N is 359.5°)
with the N-P bond length of 1.666(3) Å. These structural
features are similar to those seen in the Ti-Pt complexes
described above. (The N-P bond distance ) 1.657-1.683 Å,
and the sum of the three angles at N is 357.9-359.3°.)
Comparisons in the six-membered dimetallacyclic skeleton
among the four complexes are summarized in Figure 5. Of
particular interest is the Ti-Pt distance, which is decreased in
the order 2a [2.8358(8) Å] > 3a [2.7547(10) Å], 3a′ [2.7234-
(4) Å] > 4a [2.6860(11) Å]. Differences in electron negativity
between the chlorine and methyl or tolyl ligands suggest that
electron density of the platinum atom should be increased in
the order PtCl2 < PtMeCl, Pt(p-Tol)Cl < PtMe2. The order of
the electron density of the platinum moiety is indeed suggested
from the 195Pt-31P coupling constant: 2a (PtCl2, 2769 Hz) <
3a (PtMeCl, average ) 2384 Hz), 3a′ [Pt(p-Tol)Cl, average )
2486 Hz] < 4a (PtMe2, 1569 Hz).12,13a The above order of Ti-
Pt distance can be explained by the fact that there is a PtfTi
dative bond, and the electron-rich platinum center makes a
stronger PtfTi interaction and shorter Pt-Ti distance. As other
examples of the complexes that would have a PtfTi bond, [Cp2-
TiCH2PtX(Me)L] (X ) Cl, Me, L ) PMe3, PMe2Ph, PMePh2)
were reported by Grubbs, Lalinde, and Welter, in which the
PtfTi bond distances are similar to those of 2a-4a (2.71-
2.96 Å).14
Two instances of support for the existence of the PtfTi dative
bond were obtained from the NMR studies of Ti-Pt heterobi-
metallic complexes. First, variable-temperature NMR studies
of 4a showed the following fluxional process. Although the
molecular structure of 4a revealed that the phenyl groups bound
to the phosphorus atom are structurally not identical, these could
be independently observed in the 1H NMR. Only one set of 1H
resonances due to the phenyl groups was seen above room
temperature, but two sets were observed below -20 °C, and
broadening of the signals (coalescence) was visible between
these temperatures. Similar fluxional processes were seen in
variable-temperature 1H NMR of 2a and 3a, and it is noteworthy
that the coalescence temperature is 2a < 3a < 4a. One
explanation for this fluxional process is a conformational change
from a boat form to another boat form via the chair form
transition state, as shown in Scheme 3, which takes place by
way of breaking and re-forming of the dative bond. The order
of the coalescence temperature may reflect the order of the
dative bond strength described above. The second confirmation
by NMR spectroscopy of 4a is the coupling constant of the
195Pt satellites observed for 31P NMR. The 31P resonance due
to the Pt-P group of 4a appears at δ 15.0 ppm with the satellite
signal of JPt-P ) 1569 Hz. The JPt-P values were significantly
smaller than those of Me2Pt(dppe) (JPt-P ) 1783 Hz), Me2Pt-
(dppp) (JPt-P ) 1767 Hz),13 and Me2Pt(dppf) (JPt-P ) 1905
Hz). The data clearly demonstrate the PtMe2 species in 4a is
poorer in electron density than the others, and a plausible
explanation is the movement of electrons from the Pt species
to the Lewis acidic titanium species through the dative bond.
Concluding Remarks
As described above, we were successful in synthesizing the
titanium phosphinoamide 1 and its use as a bidentate metallo-
ligand for several organoplatinum(II) species. As often seen in
the chemistry of amphoteric ligands, the Lewis basic phosphorus
atoms of 1 interact with the Lewis acidic titanium center to
result in PfTi coordination; however, the coordination is in
an intramolecular fashion and reversible. Therefore, the dis-
sociated phosphorus atoms in 1 have the ability to react with
the Pt(II) species to afford the corresponding Ti-Pt heterobi-
metallic complexes. A striking feature of 1 as a bidentate
phosphorus ligand is its boat conformation bearing a PtfTi
dative bond. Due to this special conformation, the bite angle
(P-Pt-P) is in the range 102-106°, which is larger than the
reported data of dppp giving a six-membered chelate and rather
similar to that of EtXantphos (9,9-dimethyl-4,5-bis(diethylphos-
15b
phino)xanthene)15a and o-C6H4{CH2P(C8H14)}2 complexes.
The intramolecular donor (Pt)-acceptor (Ti) interaction through
the PtfTi dative bond results in substantial decrease in electron
density of the platinum species; this means that 1 is a relatively
less electron-donating bidentate phosphorus ligand. The boat
conformation, existence of the dative bond, and the fewer
electron-donating properties showed this titanium phosphino-
amide 1 to be a more unique bidentate phosphorus ligand than
others extensively studied in organometallic chemistry. Of
interest is how versatile the use of this ligand is for transition
metals. Preliminary results showed that 1a behaves as a ligand
for Pd(II) and Rh(I) species similar to Pt(II) as described
above: for example, treatment of (COD)PdCl2 and [(COD)-
RhCl]2 resulted in formation of insoluble organometallic
products in quantitative releasing of the COD to the solution.
The Ti-Pd product is a microcrystal, of which crystallography
gave a molecular structure closely similar to 2a, though the
quality of the crystal is inadequate to complete the structure
determination (R ) 18%). On the other hand, the reaction of
1a with [(COD)RhCl]2 afforded a product, of which elemental
analysis was consistent with “ClRh(Ph2PNtBu)2TiCl2”; however,
further attempts to carry out characterization of this Ti-Rh
compound were unsuccessful due to its poor solubility. In
contrast, attempted reactions of 1a with Pd2(dba)3‚CHCl3 or Pt-
(dba)2 resulted in complete recovery of the starting materials.
This is interesting in comparison with a metalloligand, ClTi-
(11) (a) Dufour, N.; Majoral, J.-P.; Caminade, A.-M.; Choukroun R.;
Dromzde, Y. Organometallics 1991, 10, 45. (b) Baranger, A. M.; Hollander,
F. J.; Bergman, R. G. J. Am. Chem. Soc. 1993, 115, 7890.
(12) Appleton, T. G.; Bennett, M. A. Inorg. Chem. 1978, 17, 738.
(13) (a) Hietkamp, S.; Stufkens, D. J.; Vrieze, K. J. Organomet. Chem.
1979, 169, 107. (b) Haar, C. M.; Nolan, S. P.; Marshall, W. J.; Moloy, K.
G.; Prock, A.; Giering, W. P. Organometallics 1999, 18, 474.
(14) (a) Ozawa, F.; Park, J. W.; Mackenzie, P. B.; Schaefer, W. P.;
Henling, L. M.; Grubbs, R. H. J. Am. Chem. Soc. 1989, 111, 1319. (b)
Braunstein, P.; Morise, X.; Be´nard, M.; Rohmer, M.-M.; Welter, R. Chem.
Commun. 2003, 610. (c) Berenguer, J. R.; Falvello, L. R.; Fornie´s, J.;
Lalinde, E.; Toma´s, M. Organometallics 1993, 12, 6.
(15) (a) Miedaner, A.; Raebiger, J. W.; Curtis, C. J.; Miller, S. S.; DuBuis,
D. L. Organometallics 2004, 23, 2670. (b) Eberhard, M. R.; Heslop, K.
M.; Orpen, A. G.; Pringle, P. G. Organometallics 2005, 24, 335.

1992 Organometallics, Vol. 25, No. 8, 2006
Nagashima et al.
Table 3. Crystallographic Data for Titanium
[N(SiMe3)(C6H4)PPh2]3, reported by Love,16 which has no Ti-P
intramolecular interaction and is capable of reacting with Pt(0)
precursors. This implicates that the intramolecular coordination
of phosphorus ligands to the titanium center sometimes pre-
dominates over the ligation to late transition metal species. At
present, we consider that the ligation of 1 to the transition metal
species is competitive with dissociation of 1 from the hetero-
bimetallic product, and the regeneration of 1 is more favorable
than the heterobimetallic formation in the reactions with Pd(0)
and Pt(0) precursors. In other words, a clue for the application
of 1 as the bidentate phosphorus ligand would be effective
control of the equilibrium constant, e.g., destabilization of 1 by
the substituent effect and the stabilization of the heterobimetallic
product by appropriate choice of the structure, valency, and
element of the metal species.
Phosphinoamides
1a
1b
empirical formula
fw
C32H38Cl2N2P2Ti
631.42
C30H34Cl2N2P2Ti
603.37
cryst syst
lattice type
space group
a, Å
monoclinic
primitive
P21/c (#14)
10.617(2)
16.443(4)
36.429(8)
90
94.995(2)
90
6336(2)
triclinic
primitive
P1h (#2)
14.498(5)
20.028(6)
22.641(6)
68.639(7)
88.126(9)
84.128(8)
6090(3)
b, Å
c, Å
R, deg
â, deg
γ, deg
volume, Å3
Z value
8
8
D
F(000)
calc, g/cm3
1.324
1.316
2640.00
5.638
yellow, platelet
0.18 × 0.08 × 0.07
14 501
2512.00
5.832
yellow, platelet
0.23 × 0.21 × 0.16
27 659
µ(Mo KR), cm-1
cryst color, habit
cryst dimens, mm
no. observations
(all reflns)
Experimental Section
General Procedures. Manipulation of air- and moisture-sensitive
organometallic compounds was carried out under a dry argon
atmosphere using standard Schlenk tube techniques associated with
a high-vacuum line. All solvents were distilled over appropriate
drying reagents prior to use (toluene, hexane, pentane, Et2O; Ph2-
no. variables
779
1469
refln/param ratio
R (all reflns)
18.63
0.089
0.050
0.129
0.996
0.000
18.83
0.137
0.061
0.123
1.005
0.000
R1 (I > 2.00σ(I)) a
wR2 (all reflns) b
GOF
1
CO/Na, CH2Cl2; CaH2, acetone; MS 4A). H,13C, and 31P NMR
spectra were recorded on a JEOL Lambda 600 or a Lambda 400
spectrometer at ambient temperature unless otherwise noted. H,
1
max. shift/error in final
cycle
13C, and 31P NMR chemical shifts (δ values) were given in ppm
relative to the solvent signal (1H, 13C) or standard resonances (31P;
external 85% H3PO4). Melting points were measured on a Yanaco
SMP3 micro melting point apparatus. Elemental analyses were
performed by the Elemental Analysis Center, Faculty of Science,
Kyushu University. Starting materials, phosphinoamide,17 (COD)-
PtRR′ (R, R′ ) Me, Cl, p-Tol), [Me2Pt(µ-SMe2)]2, and [(COD)-
RhCl]218 were synthesized by the method reported in the literature.
Preparation of Titanium Phosphinoamides (Ph2PNR)2TiCl2
max. peak in final diff
0.85
1.08
map, e-/Å3
min. peak in final diff
map, e-/Å3
-0.72
-1.27
2
2
2
a R1 ) ∑|Fo| - |Fc|/∑|Fo|. b wR2 ) [∑(w(Fo - Fc )2)/∑(w(Fo )2)]1/2
.
1
H, 6.11; N, 4.29. 1b: mp 140-141 °C (dec). H NMR (CD2Cl2):
δ 1.27 (d, 12H, JH-H ) 6.6 Hz, (CH3)2CH), 4.22 (m, 2H,
(CH3)2CH), 7.27 (m, 8H, meta-Ph), 7.36-7.46 (m, 12H, ortho and
para-Ph). 13C NMR (CD2Cl2): δ 25.8 ((CH3)2CH), 58.5 ((CH3)2CH),
128.8 (m, meta-Ph), 130.8 (para-Ph), 132.6 (m, ipso-Ph), 133.4
(m, ortho-Ph). 31P{1H} NMR (CD2Cl2): δ -19.2 (s). Anal. Calcd
for C30H34N2P2Cl2Ti: C, 59.72; H, 5.68; N, 4.64. Found: C, 60.03;
H, 6.01; N, 4.21.
t
i
[R ) Bu (1a), Pr (1b)]. In a 100 mL Schlenk tube, Ph2PNHtBu
(350 mg, 1.36 mmol) was dissolved in Et2O (30 mL). A hexane
solution of nBuLi (0.74 mL, 1.59 M, 1.36 mmol) was added to the
solution at -78 °C, and the solution was slowly warmed to room
temperature. After the mixture was stirred at room temperature for
3 h, it was cooled to -78 °C, and TiCl4 (0.075 mL, 0.68 mmol)
was added dropwise. The slightly yellow solution turned to dark
red, and an orange solid precipitated. After 12 h, all of the volatiles
were removed in a vacuum, and the formed crude product was
dissolved in toluene (40 mL). The insoluble materials were filtered
off through a G3 filter, and the resulting dark red filtrate was
concentrated until the volume reached 5 mL. Hexane (20 mL) was
added to this supersaturated toluene solution. The desired product
was obtained as yellow microcrystals in 84% yield (360 mg, 0.57
mmol). In a similar fashion, 1b was obtained in 81% yield. 1a:
Preparation of the Ti-Pt Heterobimetallic Complex Cl2Pt-
(Ph2PNtBu)2TiCl2 (2a). In a 20 mL Schlenk tube were placed 1a
(34 mg, 0.054 mmol) and (COD)PtCl2 (20 mg, 0.054 mmol), and
the atmosphere was replaced by argon. The mixture was dissolved
in CH2Cl2 (2 mL), and the tube was sealed by a stopcock and heated
in an oil bath, of which the temperature was controlled at 50 °C
for 5 h. The color of the solution changed from orange to red, from
which red precipitates were formed. After removal of the solvent
in vacuo, the solid was washed with hexane (2 mL × 3). The crude
product was dissolved in warm CH2Cl2, and the insoluble materials
were filtered off. The filtrate was cooled at -30 °C to form dark
red microcrystals of 2a in 80% yield (39 mg, 0.043 mmol). The
Pd homologue 2b was synthesized (87%) from 1a (30 mg, 0.042
mmol) and (COD)PdCl2 (13 mg, 0.048 mmol) in CH2Cl2 as dark
red insoluble microcrystals (34 mg, 0.042 mmol). 2a: mp 131-
133 °C (dec). 1H NMR (CD2Cl2): δ 1.43 (s, 18H, tBu), 7.13-7.18
1
t
mp 136-137 °C (dec). H NMR (CD2Cl2): δ 1.36 (s, 18H, Bu),
7.29 (m, 8H, ortho-Ph), 7.41 (m, 4H, para-Ph), 7.53 (m, 8H, meta-
Ph). 13C NMR (CD2Cl2): δ 33.1 (CMe3), 64.6 (m, CMe3), 128.6
(m, meta-Ph), 130.7 (para-Ph), 132.6 (ipso-Ph), 133.9 (m, ortho-
Ph). 31P {1H} NMR (CD2Cl2): δ -15.8 (s). Anal. Calcd for
C32H38N2P2Cl2Ti: C, 60.87; H, 6.07; N, 4.44. Found: C, 60.47;
(m, 4H, Ph), 7.32-7.53 (m, 14H, Ph), 7.67-7.72 (m, 2H, Ph). 13
C
NMR (CD2Cl2): δ 34.2 (CMe3), 71.5 (m, CMe3), 128.0, 128.7,
(16) (a) Mokuolu, Q. F.;Avent, A. G.; Hitchcock, P. B.; Love, J. B. J.
Chem. Soc., Dalton Trans. 2001, 2551. (b) Mokuolu, Q. F.; Duckmanton,
P. A.; Hitchcock, P. B.; Wilson, C.; Blake, A. J.; Shukla, L.; Love, J. B. J.
Chem. Soc., Dalton Trans. 2004, 1960. (c) Mokuolu, Q. F.; Duckmanton,
P. A.; Blake, A. J.; Willson, C.; Love, J. B. Organometallics 2003, 22,
4387.
128.8, 131.6, 131.7, 132.4 (Ph). 31P{1H} NMR (CD2Cl2): δ 6.75
(s with a satellite signal due to the coupling with 195Pt, JPt-P
)
2769 Hz). Anal. Calcd for C32H38N2P2Cl4TiPt: C, 42.83; H, 4.27;
N, 3.12. Found: C, 42.81; H, 4.30; N, 3.08.
(17) Sisler, H. H.; Smith, N. L. J. Org. Chem. 1961, 26, 611.
(18) (a) Clark, H. C.; Manzer, L. E. J. Organomet. Chem. 1973, 59,
411. (b) Peters, T. B.; Zheng, Q.; Stahl, J.; Bohling, J. C.; Arif, A. M.;
Hampel, F.; Gladysz, J. A. J. Organomet. Chem. 2002, 641, 53. (c) Scott,
J. D.; Puddephatt, R. J. Organometallics 1983, 2, 1643. (c) Giordano, G.;
Crabtree, R. H. Inorg. Synth. 1990, 28, 88.
Preparation of Ti-Pt Heterobimetallic Complexes RClPt-
(Ph2PNtBu)2TiCl2 [R ) Me (3a); R ) p-Tol (3a′)]. In a 20 mL
Schlenk tube were placed 1a (370 mg, 0.586 mmol) and (COD)-
PtMeCl (208 mg, 0.589 mmol), and the atmosphere was replaced
by argon. The mixture was dissolved in CH2Cl2 (8 mL), and the

Dynamic Titanium Phosphinoamides
Organometallics, Vol. 25, No. 8, 2006 1993
Table 4. Crystallographic Data for the Heterobimetallic Complexes
2a
3a
3a′
4a
empirical formula
fw
cryst syst
lattice type
space group
a, Å
C32H38Cl4N2P2PtTi
897.42
C33H41Cl3N2P2PtTi
877.00
C39H45Cl3N2P2PtTi‚CH2Cl2
1038.03
monoclinic
primitive
P21/n (#14)
17.861(2)
10.7169(11)
22.273(3)
96.2475(15)
4238.1(8)
4
C34H44Cl2N2P2PtTi
856.58
monoclinic
primitive
P21/c (#14)
18.131(3)
9.1326(14)
20.976(4)
105.446(3)
3347.9(10)
4
monoclinic
primitive
P21/c (#14)
18.153(3)
9.2052(13)
20.901(3)
105.6693(5)
3362.7(9)
4
monoclinic
C-centered
C2/c (#15)
28.131(5)
16.217(2)
22.080(4)
126.2680(5)
8122(2)
8
b, Å
c, Å
â, deg
volume, Å3
Z value
D
calc, g/cm3
1.780
1.732
1.627
1.401
F(000)
1768.00
48.365
red, platelet
0.05 × 0.05 × 0.04
7662
1736.00
47.362
red, platelet
0.17 × 0.16 × 0.13
7643
2064.00
38.936
red, chip
0.23 × 0.15 × 0.08
9673
3408.00
38.567
red, platelet
0.13 × 0.09 × 0.07
9061
µ(Mo KR), cm-1
cryst color, habit
cryst dimens, mm
no. observations (all reflns)
no. variables
417
411
507
423
refln/param ratio
18.37
0.061
0.037
0.088
18.60
0.034
0.031
0.089
19.08
0.028
0.025
0.071
21.42
0.065
0.049
0.168
R (all reflns)a
R1 (I > 2.00σ(I))b
wR2 (all reflns)
GOF
0.868
1.011
1.006
1.005
max. shift/error in final cycle
max. peak in final diff
map, e-/Å3
0.000
2.33
0.000
3.56
0.000
1.70
0.000
4.72
min. peak in final diff
-1.37
-1.13
-1.16
-1.00
map, e-/Å3
2
2
2
a R1 ) ∑|Fo| - |Fc|/∑|Fo|. b wR2 ) [∑(w(Fo - Fc )2)/∑(w(Fo )2)]1/2
.
solution was stirred at room temperature for 3 h. The color of the
reaction mixture changed from orange to deep red, from which red
precipitates were formed. After removal of the solvent in vacuo,
the solid was washed with pentane (5 mL). The crude product was
dissolved in a 1:1 solution of pentane and CH2Cl2, and the insoluble
materials were filtered off. The filtrate was cooled at -30 °C to
form dark red microcrystals of 3a in 84% yield (431 mg, 0.494
mmol). By a similar procedure, the p-tolyl homologue 3a′ was
(50 mg, 0.079 mmol) and [Me2Pt(µ-SMe2)]2 (23 mg, 0.04 mmol),
and the atmosphere was replaced by argon. The mixture was
dissolved in CH2Cl2 (15 mL), and the solution was stirred at room
temperature for 1 h. The color of the reaction mixture changed
from orange to deep red. After removal of the solvent in vacuo,
the solid was washed with Et2O (7 mL). The crude product was
dissolved in a 1:1 solution of Et2O and CH2Cl2, and the insoluble
materials were filtered off. The filtrate was cooled at -30 °C to
form dark red microcrystals of 4a in 81% yield (55 mg, 0.064
mmol). 4a: mp 142-143 °C (dec). 1H NMR (CD2Cl2, rt): δ 0.78
(dd with a satellite signal due to the coupling with 195Pt, 6H, JP-H
1
synthesized (65%). 3a: mp 137-138 °C (dec). H NMR (CD2-
Cl2): δ 1.19 (dd with a satellite signal due to the coupling with
195Pt, 3H, Pt-Me, JP-H ) 5.4, 5.6 Hz, JPt-H ) 54 Hz), 1.32 (s, 9H,
tBu), 1.47 (s, 9H, tBu), 6.96-7.05 (m, 2H, Ph), 7.10-7.82 (m, 18H,
Ph). 13C NMR (CD2Cl2): δ 31.6 (Pt-Me), 33.7 (CMe3), 33.8 (CMe3),
68.6 (d, JC-P ) 9.2 Hz, CMe3) 70.8 (d, JC-P ) 10.4 Hz, CMe3),
127.8, 128.3, and 128.7 (meta-Ph), 130.3, 131.0, 131.4, and 131.6
(para-Ph), 131.1, 132.4, 133.7, and 134.3 (ortho-Ph). Few ipso-
carbon resonances were assigned due to the poor solubility of 3a
to CD2Cl2. 31P{1H} NMR (CD2Cl2): δ 1.56 (s with a satellite signal
due to the coupling with 195Pt, JPt-P ) 3368 Hz, P trans to Cl),
14.7 (s with a satellite signal due to the coupling with 195Pt, JPt-P
) 1400 Hz, P trans to Me). Anal. Calcd for C33H41N2P2Cl3TiPt:
C, 45.20; H, 4.71; N, 3.19. Found: C, 45.02; H, 4.68; N, 3.13.
t
) 4.9, 8.2 Hz, JPt-H ) 66 Hz, Pt-Me), 1.39 (s, 18H, Bu), 7.03-
7.17 (m, 4H, Ph), 7.20-7.33 (m, 6H, Ph), 7.37-7.49 (m, 6H, Ph),
7.65-7.82 (m, 4H, Ph). 1H NMR (CD2Cl2, -90 °C): δ 1.39 (br s,
t
18H, Bu), 7.07 (m, 2H, meta-Ph), 7.17 (m, 2H, ortho-Ph), 7.24
(m, 1H, para-Ph), 7.27 (m, 1H, meta-Ph), 7.32 (m, 1H, ortho-Ph),
7.41 (m, 1H, para-Ph), 7.53 (m, 1H, meta-Ph), 8.02 (m, 1H, ortho-
Ph). 13C NMR (CD2Cl2, rt): δ 16.3 (dd with a satellite signal due
to the coupling with 195Pt, JP-C ) 5.8, 65.0 Hz, JPt-C ) 598 Hz,
Pt-Me), 33.6 (CMe3), 68.7 (d, JP-C ) 11.6 Hz, CMe3), 128.2, 128.3
(meta-Ph), 130.0, 130.9 (para-Ph), 131.0, 133.7 (ipso-Ph), 131.4,
134.0 (ortho-Ph). 31P{1H} NMR (CD2Cl2, rt): δ 15.0 (s with a
satellite signal due to the coupling with 195Pt, JPt-P ) 1569 Hz).
Anal. Calcd for C34H44N2P2Cl2TiPt: C, 47.68; H, 5.18; N, 3.27.
Found: C, 47.71; H, 5.21; N, 3.24.
Reaction of (Ph2PNtBu)2TiCl2 (1a) with [(COD)RhCl]2. In a
20 mL Schlenk tube were placed 1a (20 mg, 0.032 mmol) and
[(COD)RhCl]2 (8 mg, 0.016 mmol), and the atmosphere was
replaced by argon. The mixture was dissolved in CH2Cl2 (5 mL),
and the solution was stirred at 60 °C for 5 h. After filtration of the
resulting solution, the solvent was removed in vacuo, from which
a dark green powder was obtained (30 mg), mp 142-143 °C (dec).
Anal. Calcd for C32H38N2P2Cl3TiRh: C, 49.93; H, 4.98; N, 3.64.
Found: C, 50.21; H, 4.68; N, 3.54.
1
3a′: mp 181-182 °C (dec). H NMR (CD2Cl2): δ 1.22 (s, 9H,
tBu), 1.50 (s, 9H, tBu), 2.06 (s, 3H, CH3-Tol), 6.20-6.29 (m, 1H,
Ph), 6.39-6.46 (m, 2H, Ph), 6.88-7.26 (m, 8H, Ph), 7.31-7.67
(m, 10H, Ph), 7.95-8.05 (m, 3H, Ph). 13C NMR (CD2Cl2): δ 20.6
(CH3-Tol), 33.7 (d, JC-P ) 4.6 Hz, CMe3), 34.0 (d, JC-P ) 4.6 Hz,
CMe3), 68.4 (d, CMe3, JC-P ) 9.2 Hz), 70.9 (d, CMe3, JC-P
)
10.4 Hz), 127.3, 127.9, 128.0, 128.4, 129.1 (meta-Ar), 130.3, 130.3,
131.5, 131.7, 131.9 (para-Ar), 132.8, 132.9, 133.5, 135.2, 135.3
(ortho-Ar). Few ipso-carbon resonances were assigned due to the
poor solubility of 3a′ to CD2Cl2. 31P{1H} NMR (CD2Cl2): δ -2.5
(s with a satellite signal due to the coupling with 195Pt, JPt-P
)
3584 Hz, P trans to Cl), 16.7 (s with a satellite signal due to the
coupling with 195Pt, JPt-P ) 1388 Hz, P trans to Tol). Anal. Calcd
for C39H45N2P2Cl3TiPt‚CH2Cl2: C, 46.29; H, 4.56; N, 2.70.
Found: C, 46.33; H, 4.56; N, 2.69.
X-ray Data Collection and Reduction. Single crystals of all
complexes were grown from CH2Cl2/pentane. X-ray crystallography
was performed on a Rigaku Saturn CCD area detector with graphite-
monochromated Mo KR radiation (λ ) 0.71070 Å). The data were
collected at 123(2) K using ω scans in the θ range of 3.1° e θ e
Preparation of the Ti-Pt Heterobimetallic Complex Me2Pt-
(Ph2PNtBu)2TiCl2 (4a). In a 50 mL Schlenk tube were placed 1a

1994 Organometallics, Vol. 25, No. 8, 2006
Nagashima et al.
27.5° (1a), 3.0° e θ e 27.5° (1b), 3.0° e θ e 27.5° (2a), 1.2° e
θ e 31.0° (3a), 3.0° e θ e 27.5° (3a′), and 3.1° e θ e 27.5°
(4a). Data were collected and processed using Crystal-Clear
(Rigaku) on a Pentium computer. The data were corrected for
Lorentz and polarization effects. The structure was solved by heavy-
atom Patterson methods19 for 4a and by direct methods20 for 1a,
1b, 2a, 3a, and 3a′, and expanded using Fourier techniques.21 The
non-hydrogen atoms were refined anisotropically except for the Cl
and C atoms on the platinum atom in 3a. Hydrogen atoms were
refined using the riding model. The final cycle of full-matrix least-
squares refinement on F2 was based on 14 501 observed reflections
and 779 variable parameters for 1a, 27 659 observed reflections
and 1469 variable parameters for 1b, 7662 observed reflections
and 417 variable parameters for 2a, 7643 observed reflections and
411 variable parameters for 3a, 9673 observed reflections and 507
variable parameters for 3a′, and 9061 observed reflections and 423
variable parameters for 4a. Neutral atom scattering factors were
taken from Cromer and Waber.22 All calculations were performed
using the CrystalStructure23,24 crystallographic software package.
Details of final refinement are summarized in Tables 3 and 4, and
the numbering scheme employed is shown in Figures 1, 3, and 4,
which were drawn with ORTEP with 50% probability ellipsoids.
Detailed data as well as the bond distances and angles are shown
in the Supporting Information.
Acknowledgment. Financial support by a Grant-in-Aid for
Scientific Research on Priority Area (Nos. 15036253 and
16033246) “Reaction Control of Dynamic Complexes” from
Ministry of Education, Culture, Sports, Science and Technology,
Japan, is acknowledged.
Supporting Information Available: Variable-temperature NMR
1
data (1a, 1b, 2a, 3a, 4a), H, 13C, and 31P NMR data (1a, 1b, 2a,
3a, 3a′, 4a), and details of crystallographic studies (1a, 1b, 2a, 3a,
3a′, 4a). This material is available free of charge via the Internet
at http://pubs.acs.org.
(19) PATTY: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman,
W. P.; Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The
DIRDIF program system; Technical Report of the Crystallography Labora-
tory; University of Nijmegen: Nijmegen, The Netherlands, 1992.
(20) Burla, M. C.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.;
Giacovazzo, C.; Polidori, G.; Spagna, R. SIR2002; 2003.
(21) DIRDIF99: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman,
W. P.; de Gelder, R.; Israel, R.; Smits, J. M. M. The DIRDIF-99 program
system; Technical Report of the Crystallography Laboratory; University of
Nijmegen: Nijmegen, The Netherlands, 1999.
OM0509600
(22) Cromer, D. T.; Waber, J. T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol. 4.
(23) CrystalStructure 3.7.0: Crystal Structure Analysis Package; Rigaku
and Rigaku/MSC: 9009 New Trails Dr., The Woodlands, TX 77381, 2000-
2005.
(24) Watkin, D. J.; Prout, C. K.; Carruthers, J. R.; Betteridge, P. W.
CRYSTALS Issue 10; Chemical Crystallography Laboratory: Oxford, U.K.,
1996.