Unusually stable four-membered chelate rings in nickel(II), palladium(II), and platinum(II) complexes with the ligand 2,2-bis(diphenylphosphino)propane (2,2-dppp). Crystal and molecular structure of [PdI2(2,2-dppp)]·0.8CH2Cl2

Article abstract of DOI:10.1021/om970941t

The ligand Ph₂PC(CH₃)₂PPh₂ (2,2-dppp) reacts with Ni(II) salts to give robust squareplanar chelate complexes [NiX₂(2,2-dppp-P,?)] (X = Cl, 1; X = Br, 2) and the salt [Ni(2,2-dppp)₂](ClO₄)₂ (3). The Pd(II) analogues [PdCl₂(2,2-dppp)] (4), [PdI₂(2,2-dppp)] (5), and [Pd(2,2-dppp)₂](BF₄)₂ (6) have also been made. The crystal structure of 5 (obtained as 5·0.8CH₂Cl₂) has been determined by X-ray diffraction. The geminal C(CH₃)₂ group, when compared with related Ph₂PCH₂PPh₂ (dppm) complexes, causes a small compression of the P-C-P chelate ring angle (to 91.3(3)° for 5). With [PtCl₂(PhCN)₂], 2,2-dppp affords [PtCl₂-(2,2-dppp)] (7), which undergoes metathesis with NaI to give [PtI₂(2,2-dppp)] (8), and [Pt-(2,2-dppp)₂]Cl₂ (9) was obtained by reaction of [PtCl₂(PhCN)₂] with 2 equiv of 2,2-dppp. Reactions were then attempted with 7 and 9, which are known to result in ring-opening reactions with the corresponding complexes of dppm, but in all cases, only 2,2-dppp chelate complexes could be isolated. Thus, treatment of 7 or 9 with excess MeLi gave exclusively [PtMe₂(2,2-dppp)] (10) rather than cis,cis-[Pt₂Me₄(2,2-dppp)₂]. Attempts to ring-open 10 with excess 2,2-dppp to give cis-[PtMe₂(2,2-dppp- P)₂] were unsuccessful. Treatment of 10 with 1 equiv of HCl or, better, treatment of [PtCl(Me)(1,5-cyclooctadiene)] with 2,2-dppp gave only mononuclear [PtCl(Me)(2,2-dppp)] (11) and no dimer of the type [MePt(a-2,2-dppp)₂-(W-Cl)PtMe]Cl. Treatment of 7 with 2 equiv of NaCN in EtOH gave the chelate complex [Pt(CN)₂(2,2-dppp)] (12) rather than trans,trans-[Pt₂(CN)₄(μ-2,2-dppp)₂], and treatment of 7 with LiC≡CPh in thf or (better) H₂NNH₂·H₂O/HC≡CPh in EtOH gave [Pt(C≡CPh)₂(2,2-dppp)] (13), rather than trans trans-[Pt₂(C≡CPh)₄(μ-2,2-dppp)₂]. Reaction of 7 with LiC≡CBuⁿ in thf likewise gave [Pt(C≡CBuⁿ)₂(2,2-dppp)] (14) in low yield. The complexes were characterized by microanalyses (C, H, N and, in some cases, halide), infrared spectroscopy, ³¹P{¹H} and ¹H NMR spectroscopy, and fast atom bombardment mass spectrometry.

Full text of DOI:10.1021/om970941t

Organometallics 1998, 17, 1725-1731
1725
Un u su a lly Sta ble F ou r -Mem ber ed Ch ela te Rin gs in
Nick el(II), P a lla d iu m (II), a n d P la tin u m (II) Com p lexes
w ith th e Liga n d 2,2-Bis(d ip h en ylp h osp h in o)p r op a n e
(2,2-d p p p ). Cr ysta l a n d Molecu la r Str u ctu r e of
[P d I2(2,2-d p p p )]‚0.8CH2Cl2
J im Barkley, Melanie Ellis, Simon J . Higgins,* and Mark K. McCart
Department of Chemistry, Chemistry Buildings, University of Liverpool, Crown Street,
Liverpool L69 7ZD, United Kingdom
Received October 28, 1997
The ligand Ph2PC(CH3)2PPh2 (2,2-dppp) reacts with Ni(II) salts to give robust square-
planar chelate complexes [NiX2(2,2-dppp-P,P′)] (X ) Cl, 1; X ) Br, 2) and the salt [Ni(2,2-
dppp)2](ClO4)2 (3). The Pd(II) analogues [PdCl2(2,2-dppp)] (4), [PdI2(2,2-dppp)] (5), and
[Pd(2,2-dppp)2](BF4)2 (6) have also been made. The crystal structure of 5 (obtained as
5‚0.8CH2Cl2) has been determined by X-ray diffraction. The geminal C(CH3)2 group, when
compared with related Ph2PCH2PPh2 (dppm) complexes, causes a small compression of the
P-C-P chelate ring angle (to 91.3(3)° for 5). With [PtCl2(PhCN)2], 2,2-dppp affords [PtCl2-
(2,2-dppp)] (7), which undergoes metathesis with NaI to give [PtI2(2,2-dppp)] (8), and [Pt-
(2,2-dppp)2]Cl2 (9) was obtained by reaction of [PtCl2(PhCN)2] with 2 equiv of 2,2-dppp.
Reactions were then attempted with 7 and 9, which are known to result in ring-opening
reactions with the corresponding complexes of dppm, but in all cases, only 2,2-dppp chelate
complexes could be isolated. Thus, treatment of 7 or 9 with excess MeLi gave exclusively
[PtMe2(2,2-dppp)] (10) rather than cis,cis-[Pt2Me4(2,2-dppp)2]. Attempts to ring-open 10 with
excess 2,2-dppp to give cis-[PtMe2(2,2-dppp-P)2] were unsuccessful. Treatment of 10 with
1 equiv of HCl or, better, treatment of [PtCl(Me)(1,5-cyclooctadiene)] with 2,2-dppp gave
only mononuclear [PtCl(Me)(2,2-dppp)] (11) and no dimer of the type [MePt(µ-2,2-dppp)2-
(µ-Cl)PtMe]Cl. Treatment of 7 with 2 equiv of NaCN in EtOH gave the chelate complex
[Pt(CN)2(2,2-dppp)] (12) rather than trans,trans-[Pt2(CN)4(µ-2,2-dppp)2], and treatment of
7 with LiCtCPh in thf or (better) H2NNH2‚H2O/HCtCPh in EtOH gave [Pt(CtCPh)2(2,2-
dppp)] (13), rather than trans,trans-[Pt2(CtCPh)4(µ-2,2-dppp)2]. Reaction of 7 with LiCtCBun
in thf likewise gave [Pt(CtCBun)2(2,2-dppp)] (14) in low yield. The complexes were
characterized by microanalyses (C, H, N and, in some cases, halide), infrared spectroscopy,
1
31P{1H} and H NMR spectroscopy, and fast atom bombardment mass spectrometry.
The coordination chemistry of ligands R2PXPR2 (R )
alkyl, alkoxy, aryl; X ) CH2, NH, NR, O) has been
extensively investigated. The archetypal example
Ph2PCH2PPh2 (dppm) can chelate, but because of the
strain inherent in a four-membered chelate ring it can
also form η1 complexes or bridge two metal atoms in a
variety of coordination geometries.1,2 There is often a
fine balance between these types of behaviors. For
example, both cis,cis-[Pt2Me4(µ-dppm)2] and [PtMe2-
(dppm-P,P′)] may be prepared (the chelate is the ther-
modynamically stable form),3 and in solution at high
concentrations and low temperatures, [PtMe2(dppm-P)2]
can be generated from [PtMe2(dppm-P,P′)] and dppm.4
Routes to heterobimetallic complexes bridged by dppm
have been developed exploiting the tendency of mono-
nuclear complexes M(dppm-P)n or M(dppm-P,P′)n to
react with a labile source of a second metal ion to afford
the species M(µ-dppm)nM′,2,5,6 most notably by Shaw’s
group.4,7-11
It is clear that varying R in ligands R2PCH2PR2
causes very significant changes in their coordination
chemistry. Whereas the ligand Me2PCH2PMe2 has a
greater tendency to bridge two metal centers than does
Ph2PCH2PPh2,2,12 the use of bulkier alkyl substituents
(5) Xu, C.; Anderson, G. K.; Brammer, L.; Braddock-Wilking, J .;
Rath, N. P. Organometallics 1996, 15, 3972.
(6) Balch, A. L.; Catalano, V. J . Inorg. Chem. 1992, 31, 3934.
(7) Langrick, C. R.; McEwan, D. M.; Pringle, P. G.; Shaw, B. L. J .
Chem. Soc., Dalton Trans. 1983, 2487.
(8) Hassan, F. S. M.; Markham, D. P.; Pringle, P. G.; Shaw, B. L. J .
Chem. Soc., Dalton Trans. 1985, 279.
(9) McEwan, D. M.; Markham, D. P.; Pringle, P. G.; Shaw, B. L. J .
Chem. Soc., Dalton Trans. 1986, 1809.
(10) Fontaine, X. L. R.; Higgins, S. J .; Langrick, C. R.; Shaw, B. L.
J . Chem. Soc., Dalton Trans. 1987, 777.
(1) Anderson, G. K. Adv. Organomet. Chem. 1993, 35, 1.
(2) Chaudret, B.; Delavaux, B.; Poilblanc, R. Coord. Chem. Rev.
1988, 86, 191.
(3) Puddephatt, R. J .; Thompson, M. A.; Manojlov´ıc-Muir, L.; Muir,
K. W. J . Chem. Soc., Chem. Commun. 1981, 805.
(4) Hassan, F. S. M.; McEwan, D. M.; Pringle, P. G.; Shaw, B. L. J .
Chem. Soc., Dalton Trans. 1985, 1501.
(11) Fontaine, X. L. R.; Higgins, S. J .; Shaw, B. L.; Thornton-Pett,
M.; Yichang, W. J . Chem. Soc., Dalton Trans. 1987, 1501.
(12) McLennan, A. J .; Puddephatt, R. J . Organometallics 1985, 4,
485.
S0276-7333(97)00941-2 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 03/31/1998

1726 Organometallics, Vol. 17, No. 9, 1998
Barkley et al.
leads to ligands which are highly effective chelates and
which promote some very unusual coordination chem-
istry and homogeneous catalysis. For example, cis
hydrido alkyl complexes of Pt(II) are normally very
unstable with respect to reductive elimination of alkane,
but the complex [Pt(H)(iPr)(tBu2PCH2PtBu2)] can be
isolated, in which both the cis hydrido alkyl arrange-
ment and the four-membered chelate ring are stabilized
redox-active RuII complexes for oxide surface modifica-
tion26 and for incorporation into conjugated polymers.27
However, little has so far been reported about the
tendency of such complexes to undergo ring-opening
reactions analogous to those of chelate complexes of
dppm or 1,1-dppe.
Recently, we have shown that the ligand 2,2-bis-
(diphenylphosphino)propane (2,2-dppp) is very effective
at chelating Rh(I), reacting with [Rh2Cl2(CO)4] to give
exclusively [RhCl(CO)(2,2-dppp-P,P′)], in marked con-
trast with both dppm and 1,1-dppe.28 This work sug-
gested that complete substitution by methyl groups
for hydrogen at the methylene carbon greatly enhances
the stability of four-membered chelate rings for 2,2-
dppp over dppm or 1,1-dppe, in the same way that
substitution of But for Ph groups at phosphorus ap-
t
by the bulky exocyclic Bu groups.13 Further, on pho-
tolysis, this complex eliminates propane to give an
intermediate, postulated as the “bent”, 14 e- [Pt(tBu2-
PCH2PtBu2)], which can oxidatively add C-H bonds,13
and even C-F bonds,14 or coordinate alkenes to give the
stable complexes [Pt(tBu2PCH2PtBu2)(η2-alkene)].
Quite early in the development of dppm coordination
chemistry it was suggested that substitution at the
methylene carbon would have little effect on the coor-
dination chemistry of ligands R2PCR′2PR2 (R ) alkyl,
aryl; R′ ) H, alkyl).15 Although this conclusion was
based upon few examples, remarkably little work on this
topic has been reported since. The ligand 1,1-bis-
(diphenylphosphino)ethane (1,1-dppe) does appear largely
to mimic dppm in its coordination chemistry. For
example, with [Rh2Cl2(CO)4], both ligands react to give
the dimers trans-[Rh2Cl2(CO)2(µ-dppm)2]16,17 and [Rh2-
(µ-Cl)(CO)2(µ-1,1-dppe)2]Cl,18 respectively. Additional
steric effects may be responsible for the formation of
the chloride-bridged salt in the latter case; interestingly,
the unusual chiral 1,1-diphosphine ligand L gives a very
similar dimer, [Rh2(µ-Cl)(CO)2(µ-L)2]Cl, on treatment
with [Rh(COD)Cl]2 (COD ) cycloocta-1,5-diene) and
CO.19
t
pears to do in the chemistry of Bu2PCH2PtBu2 com-
pared with dppm. The effect is reminiscent of the
Thorpe-Ingold (gem-dimethyl) effect in small organic
ring systems, as pointed out by Shaw.29 The remark-
able chemistry observed with Pt group metal complexes
of tBu2PCH2PtBu213,14,30 has led us to begin investigating
the coordination chemistry of 2,2-dppp with Ni(II),
Pd(II), and Pt(II), and we report our initial results here.
Resu lts a n d Discu ssion
Nick el a n d P a lla d iu m Com p lexes. Reaction of
NiX2‚nH2O in EtOH with 2,2-dppp gave, regardless of
the stoichiometry employed, exclusively [NiX2(2,2-dppp-
P,P′)] (X ) Cl, 1; X ) Br, 2) as orange-red precipitates.
These were characterized by (i) microanalyses (C, H),
(ii) FAB mass spectrometry, which showed peaks cor-
responding to M+ and (M - X)+ for this formulation,
with no higher mass peaks, (iii) the 31P NMR spectra,
which showed single, temperature-invariant, sharp
resonances shifted upfield from the free ligand value,
as expected for a four-membered diphosphine chelate
ring,4 in the same chemical shift range as the corre-
1
Similar “A-frame” complexes [Pd2Cl2(µ-diphosphine)2-
(µ-CdCH2)] are obtained on treatment of [Pd(PPh3)4]
with Cl2CdCH2 and either dppm or 1,1-dppe in reflux-
ing benzene,20 and both [Pd2Cl2(µ-dppm)2](Pd-Pd) and
[Pd2Cl2(µ-1,1-dppe)2](Pd-Pd) have been synthesized by
conproportionation of labile Pd0 and PdII starting ma-
terials in the presence of dppm or 1,1-dppe.21 The
addition of nucleophiles to the double bond of chelated
(Ph2P)2CdCH2 has been demonstrated as a route to
coordinated, functionalized diphosphines of the type
(Ph2P)2CHCH2X (X ) -NHR, -NR2, -OR, -CtCR,
etc.),22-25 and we have used this reaction to prepare
sponding palladium complexes (below), and (iv) the H
NMR spectra, which showed triplets at 1.28 and 1.23
3
ppm, respectively, with J PH ) 17.4 and 16.4 Hz,
respectively.
Both 1 and 2 are robust in solution, and variable-
temperature 31P{1H} spectroscopy shows no evidence for
diphosphine ligand exchange reactions in solvents of
different polarity (CH2Cl2, CH2Cl2/CH3CN mixtures).
These results contrast with the chemistry of dppm with
NiII. In EtOH, dppm reacts with NiCl2 to give exclu-
sively [NiCl2(dppm)2] regardless of the stoichiometry
employed.31-33 Although a planar [NiCl2(dppm-P)2]
structure was proposed on the basis of electronic
(13) Hofmann, P.; Heiss, H.; Neiteler, P.; Muller, G.; Lachmann, J .
Angew. Chem., Int. Ed. Engl. 1990, 29, 880.
(14) Hofmann, P.; Unfried, G. Chem. Ber. 1992, 125, 659.
(15) Puddephatt, R. J . Chem. Soc. Rev. 1983, 12, 99.
(16) Mague, J . T.; Mitchener, J . P. Inorg. Chem. 1969, 8, 119.
(17) Cowie, M.; Dwight, S. K. Inorg. Chem. 1980, 19, 2500.
(18) van der Ploeg, A. F. M. J .; van Koten, G. Inorg. Chim. Acta
1981, 51, 225.
(24) Higgins, S. J .; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1989,
1527.
(25) Hassan, F. S. M.; Higgins, S. J .; J acobsen, G. B.; Shaw, B. L.;
Thornton-Pett, M. J . Chem. Soc., Dalton Trans. 1988, 3011.
(26) Higgins, S. J .; McCart, M. K.; McElhinney, M.; Nugent, D. C.;
Pounds, T. J . J . Chem. Soc., Chem. Commun. 1995, 2129.
(27) Higgins, S. J .; McCart, M. K.; Pounds, T. J . Chem. Commun.
1997, 1907.
(19) Marinetti, A.; Menn, C. L.; Ricard, L. Organometallics 1995,
14, 4983.
(20) Fontaine, X. L. R.; Higgins, S. J .; Shaw, B. L. J . Chem. Soc.,
Dalton Trans. 1988, 1179.
(21) Lee, C. L.; Yang, Y. P.; Rettig, S. J .; J ames, B. R.; Nelson, D.
A.; Lilga, M. A. Organometallics 1986, 5, 2220.
(22) Cooper, G. R.; McEwan, D. M.; Shaw, B. L. Inorg. Chim. Acta
1986, 122, 207.
(28) Barkley, J . V.; Grimshaw, J . C.; Higgins, S. J .; Hoare, P. B.;
McCart, M. K.; Smith, A. K. J . Chem. Soc., Dalton Trans. 1995, 2901.
(29) Shaw, B. L. J . Organomet. Chem. 1980, 200, 307.
(30) Hofmann, P.; Meier, C.; Hiller, W.; Heckel, M.; Riede, J .;
Schmidt, M. U. J . Organomet. Chem. 1995, 490, 51.
(31) Chow, K. K.; McAuliffe, C. A. Inorg. Chim. Acta 1974, 10, 197.
(32) van Hecke, G. R.; Horrocks, W. D. Inorg. Chem. 1966, 5, 1968.
(33) Booth, G.; Chatt, J . J . Chem. Soc. 1965, 3238.
(23) King, G.; Higgins, S. J .; Hopton, A. J . Chem. Soc., Dalton Trans.
1992, 3403.

Four-Membered Rings in Ni, Pd, and Pt Complexes
Organometallics, Vol. 17, No. 9, 1998 1727
spectra, it has since been shown that, at least in the
solid state, “[NiCl2(dppm)2]” is five-coordinate [NiCl2-
(dppm-P,P′)(dppm-P)].34 A firm assignment of solution
structure could not be made, although NMR and elec-
tronic spectral data were apparently not consistent with
the solid-state structure being maintained in solution,
and on recrystallization, [NiCl2(dppm-P,P′)(dppm-P)]
partially dissociates to [NiCl2(dppm-P,P′)].34 The latter
may be isolated pure by combining NiCl2 and dppm
(1:1) in anhydrous, poorly coordinating solvents,35 but
it is labile.
The additional stability conferred on the chelate rings
in 1 and 2 by the exocyclic gem-dimethyl group affects
the potential of these complexes for catalysis. For the
nickel-phosphine complex catalyzed cross-coupling of
Grignard reagents with aryl halides, known as the
Kumada coupling, [NiX2(Ph2P(CH2)3PPh2)] (X ) Cl, Br)
are the catalysts of choice. Neither [NiCl2(dppm)2]36 nor
[NiCl2(dppm)]37 act as catalysts for the coupling of
BunMgBr with C6H5Cl, the original test reaction for
Kumada coupling.36 We have shown in preliminary
studies that complex 1 does catalyze this reaction,37 with
approximately the same activity and selectivity as for
[NiCl2(dppe)].36
Treatment of an ethanol solution of [Ni(H2O)6](ClO4)2
with 2 equiv of 2,2-dppp afforded yellow [Ni(2,2-dppp)2]-
(ClO4)2 (3). The 1H NMR spectrum of 3 showed a
quintet at 1.76 ppm (apparent J PH ) 8.0 Hz), due to
the geminal methyl groups, significantly downfield of
the corresponding signals for 1 and 2. The quintet
pattern is caused by “virtual” coupling to all four 31P
nuclei; P-trans-P coupling constants in square-planar
d8 complexes are large.38
F igu r e 1. Molecular structure of [PdI2(2,2-dppp)]‚
0.8CH2Cl2 (5). Thermal ellipsoids are drawn at the 50%
probability level.
Ta ble 1. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for 5‚0.8CH2Cl2
Pd-I(1)
2.652(2)
2.643(1)
2.255(2)
2.247(2)
1.894(6)
1.805(6)
P(1)-C(10)
P(2)-C(1)
P(2)-C(16)
P(2)-C(22)
C(1)-C(2)
C(1)-C(3)
1.808(6)
1.888(6)
1.818(6)
1.812(6)
1.515(9)
1.531(9)
Pd-I(2)
Pd-P(1)
Pd-P(2)
P(1)-C(1)
P(1)-C(4)
I(1)-Pd-I(2)
93.12(5)
Pd-P(2)-C(1)
96.3(2)
I(1)-Pd-P(1)
I(1)-Pd-P(2)
I(2)-Pd-P(1)
I(2)-Pd-P(2)
P(1)-Pd-P(2)
Pd-P(1)-C(1)
C(1)-P(1)-C(4)
C(1)-P(1)-C(10)
C(4)-P(1)-C(10)
99.24(7)
171.51(4)
167.64(4)
93.84(6)
73.84(7)
95.9(2)
108.3(3)
109.6(3)
107.1(3)
C(1)-P(2)-C(16)
C(1)-P(2)-C(22)
C(16)-P(2)-C(22)
P(1)-C(1)-P(2)
P(1)-C(1)-C(2)
P(1)-C(1)-C(3)
P(2)-C(1)-C(2)
P(2)-C(1)-C(3)
C(2)-C(1)-C(3)
108.6(3)
111.2(3)
108.5(3)
91.3(3)
117.4(4)
109.8(4)
119.1(4)
107.0(4)
110.5(5)
Treatment of [PdCl2(PhCN)2] in CH2Cl2 with 2,2-dppp
gave [PdCl2(2,2-dppp)] (4). Metathesis of this with NaI
in acetone gave [PdI2(2,2-dppp)] (5); details and char-
acterizing data are in the Experimental Section. The
latter was also prepared in a one-pot reaction between
[{Pd(OAc)2}3], 2,2-dppp, and NaI in CH2Cl2/acetone. A
one-pot reaction between [PdCl2(PhCN)2], 2,2-dppp, and
AgBF4 in CH2Cl2/CH3CN gave, after recrystallization,
[Pd(2,2-dppp)2](BF4)2 (6). Characterizing data are in the
Experimental section; the FAB mass spectrum showed
peaks due to [M - BF4]+ at 1017 amu and [M - BF4 -
HBF4]+ at 930 amu, respectively. As for the NiII salt 3,
Ta ble 2. Da ta Collection , Str u ctu r e Solu tion , a n d
Refin em en t P a r a m eter s for 5‚0.8CH2Cl2
cryst habit
cryst dimens (mm)
cryst syst
space group
a (Å)
orange-yellow, needle
0.20 × 0.15 × 0.35
monoclinic
P21/c
10.705(7)
17.30(1)
b (Å)
c (Å)
16.707(9)
102.45(5)
3021(3)
1.881
153 ( 1
2.93
Rigaku AFC6S
0-25.0
5700
5389
313
â (deg)
1
the H NMR spectrum of 6 (CD3CN) showed a virtual
V (Å3)
calcd density (g/cm3)
temp (K)
quintet resonance due to the geminal methyl groups at
1.77 ppm (apparent J PH ) 8.8 Hz), significantly down-
field of the resonances for 4 and 5.
Cr ysta l Str u ctu r e of [P d I2(2,2-d p p p )]‚2CH2Cl2.
Crystals of 5 suitable for X-ray crystallography were
obtained, as [PdI2(2,2-dppp)]‚0.8CH2Cl2, on recrystalli-
zation from CH2Cl2/MeOH. The molecular structure is
shown in Figure 1, and selected bond lengths and angles
are given in Table 1; experimental details are given in
Table 2. The solvent molecules were distributed evenly
µ(Mo KR) (mm-1
diffractometer
θ range (deg)
)
no. of rflns collected
no. of indep rflns (Rint
ls params
)
R(F), Rw(F2) (F2 > 3.0σ(F2))b
0.032, 0.043
a
Graphite-monochromated X-rays, wavelength 0.710 73 Å.
R(F) ) Σ||Fo| - |Fc||/∑|Fo|; Rw ) [(Σw(|Fo| - |Fc|)2/ΣwFo2)]1/2
.
b
between two sites within the asymmetric unit and were
refined with occupancies of 0.4. The structure may be
compared with those of [PdI2({Ph2P}2CHCH2OCH2-
CH2C4H3S-3)],23 [PdI2(dppm)]39 (for which bond length
and angle data was accessed using the Cambridge
(34) Manojlov´ıc-Muir, L.; Mirza, H. A.; Sadiq, N.; Puddephatt, R. J .
Inorg. Chem. 1993, 32, 117.
(35) Ercolani, C.; Quagliano, J . V.; Vallarino, L. M. Inorg. Chim.
Acta 1973, 7, 413.
(36) Tamao, K.; Sumitani, K.; Kiso, Y.; Zembayashi, M.; Fujioka,
A.; Kodama, S.; Nakajima, I.; Minato, A.; Kumada, M. Bull. Chem.
Soc. J pn. 1976, 49, 1958.
(37) Bartley, J .; Higgins, S. J ., unpublished results.
(38) Pregosin, P. S.; Kuntz, R. W. 31P and 13C NMR of Transition
Metal-Phosphine Complexes; Springer: Berlin, 1979.
(39) Davies, J . A.; Pinkerton, A. A.; Syed, R.; Vilmer, M. J . Chem.
Soc., Chem. Commun. 1988, 47.

1728 Organometallics, Vol. 17, No. 9, 1998
Barkley et al.
Structural Database40 at the Chemical Database Ser-
vice41), and [PdCl2(dppm)].42 The metal-ligand bond
distances are typical of members of this series. The only
obvious effect of the geminal dimethyl moiety is to close
up the P-C-P chelate ring angle slightly, from 93.9°
for [PdI2(dppm)] and 93.0(1)° for [PdCl2(dppm)] to 91.3-
(3)° for 5. There is no clear trend in the other chelate
ring angles.
When [PtMe2(dppm-P,P′)] in chlorinated solvents is
treated with excess dppm, an equilibrium is established
with cis-[PtMe2(dppm-P)2]. The latter is favored by high
concentration and low temperature and can be isolated
as a pure solid.4 However, when we treated a saturated
(ca. 50 mM) solution of 10 in CDCl3/CH2Cl2 with excess
2,2-dppp and monitored the 31P{1H} NMR spectrum at
-60 °C, no trace of any species other than 10 and free
2,2-dppp could be detected. Also, whereas, depending
upon starting materials and conditions, both [PtMe2-
(dppm-P,P′)] and cis,cis-[Pt2Me4(µ-dppm)2] can be iso-
lated,3 we have been unable to make the 2,2-dppp
analogue of the latter.
P la tin u m Com p lexes. Treatment of [PtCl2(PhCN)2]
with 1 equivalent of 2,2-dppp in CH2Cl2 gave [PtCl2-
(2,2-dppp)] (7). The 31P{1H} NMR spectrum of 7 shows
a singlet resonance, shifted upfield from the free ligand,
1
with J PtP ) 3135 Hz. The upfield shift,38 and the
1
unusually low J PtP value for P-trans-Cl,43 are both as
Treatment of 10 with 1 equiv of HCl in thf gave [PtCl-
(Me)(2,2-dppp-P,P′)] (11) exclusively. That 11 is mono-
nuclear, with chelating 2,2-dppp, follows from the
spectroscopic data. In particular, the 31P{1H} NMR
spectrum shows an AX spin system to high field of the
free ligand chemical shift, with Pt satellites for the two
signals typical of P-trans-Cl and P-trans-Me. This
contrasts with the behavior of [PtMe2(dppm-P,P′)],
which reacts with HCl in benzene to give the chloride-
bridged “A-frame” complex [MePt(µ-Cl)(µ-dppm)2PtMe]-
Cl.46 A mixture of the latter and [PtCl(Me)(dppm-P,P′)]
was obtained on treatment of [PtCl(Me)(COD)] with
dppm.47 It was also observed earlier that for complexes
with the formula [PtCl(R)(dppm)]n, the chelate (n ) 1)
form is favored when R is bulky (e.g. C6H2Me3-2,4,6)
and the binuclear salt [RPt(µ-Cl)(µ-dppm)2PtR]Cl is
favored when R ) Me. For intermediate cases (e.g. R
) Ph), equilibria between these two forms were observed
in solution. We have so far been unable to synthesize
the 2,2-dppp analogue of [MePt(µ-Cl)(µ-dppm)2PtMe]Cl;
even heating 11 in ethanol with NaBPh4 did not result
in the formation of [MePt(µ-Cl)(µ-2,2-dppp)2PtMe]BPh4
or any other binuclear species (31P{1H} NMR spectro-
scopic evidence).
1
expected for a four-membered chelate ring. In the H
NMR spectrum, the ligand methyl protons resonate as
a triplet at 1.22 ppm (3J PH ) 17.2 Hz). Any coupling to
195Pt (4J PtH) is too small to be observed. Metathesis with
NaI in acetone gave [PtI2(2,2-dppp)] (8), characterized
similarly. This complex was prepared earlier, by suc-
cessive deprotonation of the ligand methylene group of
[PtI2(dppm)] with (Me3Si)2NLi and quenching with
MeI.44,45 Spectroscopically, it is very similar to 7.
Treatment of [PtCl2(PhCN)2] with 2 equiv of 2,2-dppp
in refluxing CH2Cl2/CH3CN gave the salt [Pt(2,2-dppp)2]-
Cl2 (9). The 31P{1H} NMR spectrum of 9 shows a singlet
1
at -21.6 ppm, with J PtP typical of P-trans-P in four-
membered chelate rings, 2268 Hz. In the 1H NMR
spectrum, the ligand methyl groups resonate as a
second-order quintet at 1.80 ppm (apparent J PH ) 8.4
Hz); once again no 195Pt coupling could be observed.
With complexes 7-9 in hand, we then carried out
experiments known to result in ring opening with the
analogous PtII-dppm complexes, to test the stability of
the four-membered chelate rings formed by 2,2-dppp
with PtII. We chose PtII complexes for the diagnostic
1
value of J PtP couplings in the 31P{1H} NMR spectra.
Treatment of a thf suspension of 7 or 8 with excess
MeLi gave exclusively [PtMe2(2,2-dppp)] (10), in moder-
ate yield. A better yield was obtained by the displace-
ment of 1,5-cyclooctadiene (COD) from [PtMe2(COD)].
That 10 is indeed the monomeric chelate complex is
confirmed by the FAB mass spectrum, which shows
clusters of peaks corresponding to [M - Me]+ and [M -
Me - MeH]+ for this formulation (but no higher mass
peaks), and the 31P{1H} NMR spectrum, which shows
a singlet at -2.8 ppm, upfield from the free ligand, and
We next attempted to carry out reactions known to
form “face-to-face” dimers of the type trans,trans-[Pt2R4-
(µ-dppm)2] with the dppm system. For example, whereas
treatment of [PtCl2(dppm-P,P′)] with NaCN in ethanol
gave trans,trans-[Pt2(CN)4(µ-dppm)2],8 treatment of 7
with NaCN under the same conditions gave, exclusively,
[Pt(CN)2(2,2-dppp-P,P′)] (12). Although 12 was too
1
insoluble for reliable H NMR spectra to be obtained,
and the 31P{1H} NMR spectrum was noisy, the observa-
tion of a singlet at -10.9 ppm (i.e. upfield from the free
a
1J PtP value of 1577 Hz, typical of a four-membered
1
ligand), with a J PtP of 2002 Hz (appropriate for P-trans-
1
chelate diphosphine trans to methyl ligands.4 The H
NMR spectrum showed a triplet centered at 1.29 ppm
(3J PH ) 14.4 Hz) due to the ligand methyl groups. There
CN for a four-membered chelate diphosphine, but too
small to be due to P-trans-P), is good evidence for the
mononuclear chelate structure we assign to 12. Two
bands are expected in the IR spectrum due to νCN for
the chelate complex. Although only one band was
observed, at 2130 cm-1, this was rather broad. Inter-
estingly, when we treated the salt 9 with 2 equiv of
NaCN in methanol, the product (albeit isolated in only
moderate yield) was again 12. This contrasts with the
behavior of [Pt(dppm-P,P′)2]Cl2, which reacts under
4
was no discernible J PtH, although the corresponding
3J PtH values for the methylene protons of dppm in
[PtMe2(dppm)] is 23.0 Hz.4 A triplet at 0.83 ppm (3J PH
6.7 Hz), with Pt satellites (2J PtH 72.7 Hz), was assigned
to the methyl ligands. This resonance is significantly
upfield from the corresponding resonance for [PtMe2-
(dppm)] (1.00 ppm).4
(40) Fletcher, D. A.; McMeeking, R. F.; Parkin, D., J . J . Chem. Inf.
Comput. Sci. 1996, 36, 746.
(41) Allen, F. H.; Kennard, O. Chemical Design Automation News
1993, 8, 31.
(42) Steffen, W. L.; Palenick, G. L. Inorg. Chem. 1976, 15, 2432.
(43) Braterman, P. S.; Cross, R. J .; Manojlov´ıc-Muir, L.; Young, G.
B. J . Organomet. Chem. 1975, 84, C40.
(44) Al-J ibori, S.; Shaw, B. L. Inorg. Chim. Acta 1982, 65, L123.
(45) Al-J ibori, S.; Shaw, B. L. Inorg. Chim. Acta 1983, 74, 235.
(46) Cooper, S. J .; Brown, M. P.; Puddephatt, R. J . Inorg. Chem.
1981, 20, 1374.
(47) Anderson, G. K.; Clark, H. C.; Davies, J . A. J . Organomet.
Chem. 1981, 210, 135.

Four-Membered Rings in Ni, Pd, and Pt Complexes
Organometallics, Vol. 17, No. 9, 1998 1729
these conditions to give [Pt(CN)2(dppm-P)2] in good
yield.8
The coordination chemistry of 2,2-dppp appears to
mimic that of diphosphines bearing bulky substituents
t
at phosphorus, such as Pri PCH2PPri or Bu2PCH2Pt-
Treatment of [PtCl2(dppm)] with LiCtCPh gave
trans, trans-[Pt2(CtCPh)4(µ-dppm)2],7 and although [Pt-
(CtCMe)2(dppm-P,P′)] has been prepared, from [PtCl2-
(dppm)] and HCtCMe/NaOMe/MeOH, it rearranges in
solution to the “face-to-face” dimer in the presence of
traces of free phosphine.12 In contrast, we find that
reaction of 7 with LiCtCPh gives only [Pt(CtCPh)2-
(2,2-dppp-P,P′)] (13), in moderate yield, and that 13 has
no tendency to rearrange to a dimer in solution, in the
presence of LiCtCPh, PPh3, or 2,2-dppp as catalyst.
Again, the main evidence for the structure of 13 is that
the 31P{1H} NMR spectrum shows a singlet at -15.4
2
2
Bu2. It will be interesting in the future to investigate
whether “bent 14-electron” fragments [M(2,2-dppp)]
(M ) Ni, Pd, Pt), or [Rh(2,2-dppp)Cl], analogous to
[M(tBu2PCH2PtBu2)] and [Rh(tBu2PCH2PtBu2)Cl],13,14,30
can be generated, and the stability of the four-membered
chelate rings formed by this ligand will enable investi-
gations of the role of this unusual ring size in homoge-
neous catalysis.
Exp er im en ta l Section
1
Meth od s a n d Rea gen ts. General methods were as de-
scribed in previous papers from this laboratory,23 except that
some fast atom bombardment mass spectra were run at the
EPSRC National Mass Spectrometry Service (Swansea, U.K.).
All reactions were performed under a nitrogen atmosphere.
Petroleum ether was of boiling range 40-60 °C. IR spectra
were recorded on Nujol mulls between CsI plates. The ligand
2,2-bis(diphenylphosphino)propane (2,2-dppp) was prepared
from 2,2-dichloropropane (Aldrich Chemical Co.) by the lit-
erature method,50 except that the product was recrystallized
under nitrogen from dichloromethane-ethanol. Character-
izing data were as previously reported.28 The pure, dry solid
isolated in this way is air-stable, but in an impure or wet state,
or in solution, the ligand is air-sensitive.
ppm, with a J PtP value of 2031 Hz, too small for
P-trans-P but in the right range for P-trans-CtCR.
Additionally, the infrared spectrum (Nujol mull) shows
two bands assigned to νCtC, at 2105 and 2097 cm-1. The
complex [Pt(CtCBun)2(2,2-dppp-P,P′)] (14) was also
prepared from 7 and LiCtCBun, albeit in low yield.
We found that 13 could also be prepared in better
yield by the reaction of 7 with hydrazine hydrate and
excess HCtCPh in ethanol, a reaction which has often
previously been employed to make the complexes trans-
[Pt(CtCPh)2(PR3)2].48
It is interesting that, in a study of propynylplatinum-
(II) complexes of ligands R2PCH2PR2, Puddephatt found
that various isomers of dimeric, diphosphine-bridged
complexes were favored in solution when R ) Me, Et,
or Ph but that when R ) Pri, only the chelate form
[Pt(CtCMe)2(Pri PCH2PPri )] could be isolated.12
P r ep a r a tion of [NiCl2(2,2-d p p p )] (1). A solution of [Ni-
(H2O)6]Cl2 (0.12 g, 0.5 mmol) in EtOH (10 cm3) was treated
with the ligand (0.206 g, 0.5 mmol), and the mixture was
refluxed for 10 min. Solvent volume was reduced to ca. 3 cm3,
and the red-orange microcrystalline solid that precipitated was
filtered off and dried in vacuo. Yield: 0.265 g, 84%. Selected
data for 1 are as follows. Anal. Found: C, 60.07; H, 4.86.
Calcd for C27H26Cl2NiP2: C, 59.87; H, 4.84. IR: νNi-Cl 355, 326
2
2
Clearly, the behavior of 2,2-dppp mimics that of the
latter bulky, electron-rich diphosphine.
Although trans-[Pt(CtCR)2(dppm-P)2] compounds are
readily prepared from trans,trans-[Pt2(CtCR)4(µ-dppm)2]
and additional dppm and have been used as precursors
to dppm-bridged heterobimetallic complexes,7 13 and 14
show no tendency to react with further 2,2-dppp to
afford trans-[Pt(CtCR)2(2,2-dppp-P)2] (31P{1H} NMR
spectroscopic evidence). Moreover, whereas treatment
of [Pt(dppm-P,P′)2]Cl2 with LiCtCR gave ring-opened
trans-[Pt(CtCR)2(dppm-P)2] (in low yield because of
competing deprotonation to give [Pt(Ph2PCHPPh2)2]7),
we found that treatment of the salt 9 with 2 equiv of
LiCtCPh gave only 13 and free 2,2-dppp. Moreover,
whereas the salts [Pt(dppm)2]X2 (X ) Cl, Br, I) react
with Hg(CtCR)2 to give the heterobimetallic complexes
trans-[Pt(CtCR)2(µ-dppm)2HgX2], the reaction of 9 with
Hg(CtCPh)2 again gave only a moderate yield of 13 and
free 2,2-dppp.
In summary, the coordination chemistry of 2,2-dppp
with NiII, PdII, and PtII is dominated by the strong
tendency for the formation of four-membered chelate
rings with this ligand. Reactions which, with dppm
chelate complexes, result in ring opening to give Pt(η1-
dppm)2 or Pt(µ-dppm)2Pt species, result only in ligand
metatheses with the corresponding 2,2-dppp complexes.
No evidence for chelate ring-opening reactions with PtII
or PdII complexes of the latter ligand has been found.
Moreover, the chelate complexes 1 and 2 are much more
robust than the corresponding [NiX2(dppm)] and are
catalytically active in Kumada-type coupling reactions.
cm-1
.
31P{1H} NMR (101.2 MHz; CDCl3): δ -8.1. 1H NMR
3
(200 MHz; CDCl3): 1.23, t, J PH ) 16.4 Hz (PC(CH3)2P). MS
(FAB): m/e 542 (M), 507 (M - Cl), 471 (M - HCl - Cl).
P r ep a r a tion of [NiBr 2(2,2-d p p p )] (2). Preparation was
as for 1, using [Ni(H2O)6]Br2 (0.21 g, 0.64 mmol) and 2,2-dppp
(0.26 g, 0.64 mmol) in EtOH (15 cm3). Yield: 0.24 g, 60%.
Selected data for 2 are as follows. Anal. Found: C, 51.10; H,
4.10. Calcd for C27H26Br2NiP2: C, 51.39; H, 4.15. IR: νNi-Br
287 cm-1
.
31P{1H} NMR (101.2 MHz; CDCl3): δ -1.5. 1H
NMR (200 MHz; CDCl3): 1.28, t, 3J PH ) 16.3 Hz (PC(CH3)2P).
MS (FAB): m/e 630 (M).
P r ep a r a tion of [Ni(2,2-d p p p )2](ClO4)2 (3). A solution of
[Ni(H2O)6](ClO4)2 (0.43 g, 1.20 mmol) in EtOH (20 cm3) was
treated with the ligand (1.0 g, 2.43 mmol), and the mixture
was brought to reflux. After 5 min, it was cooled to room
temperature, and the light yellow precipitate was filtered off,
washed with EtOH (2 × 5 cm3), and dried in vacuo. Yield:
1.07 g, 83%. Selected data for 3 are as follows. Anal. Found:
C, 59.69; H, 7.79. Calcd for C54H52Cl2NiO8P4: C, 59.92; H,
4.84. IR: νCl-O 1060 cm-1 (vs). 31P{1H} NMR (101.2 MHz;
CDCl3): δ -2.0. 1H NMR (200 MHz; CDCl3): 1.76, virtual
3
quintet, apparent J PH ) 8.0 Hz (PC(CH3)2P). MS (FAB): m/e
981 (M - ClO4), 881 (M - HClO4 - ClO4).
P r ep a r a tion of [P d Cl2(2,2-d p p p )] (4). The ligand (0.27
g, 0.65 mmol) was added to a solution of [PdCl2(PhCN)2] (0.25
g, 0.65 mmol) in CH2Cl2 (40 cm3), and the solution was refluxed
gently for 30 min and then cooled. The volume was reduced
to ca. 5 cm3, and addition of Et2O (30 cm3) yielded a white
precipitate, which was filtered off, dried, and recrystallized
from CH2Cl2-MeOH to afford white crystals. Yield: 0.32 g,
83%. Selected data for 4 are as follows. Anal. Found: C,
(48) Empsall, H. D.; Shaw, B. L.; Stringer, A. J . J . Organomet. Chem.
1975, 94, 131.
(49) Smith, A. K.; Tong, N., unpublished results.
(50) Hewertson, W.; Watson, H. R. J . Chem. Soc. 1962, 1490.

1730 Organometallics, Vol. 17, No. 9, 1998
Barkley et al.
54.91; H, 4.24. Calcd for C27H26Cl2P2Pd: C, 54.99; H, 4.44.
in EtOH (15 cm3) under reflux. After 2 h, the mixture was
cooled, and the solvent was removed in vacuo. The residue
was recrystallized from MeOH/Et2O. Yield: 0.35 g, 64%.
Selected data for 9 are as follows. Anal. Found: C, 59.40; H,
4.70. Calcd for C54H52Cl2P4Pt: C, 59.46; H, 4.81. 31P{1H}
NMR (101.2 MHz; CDCl3): δ -21.6, 1J Pt-P 2268 Hz. 1H NMR
IR: νPd-Cl 315, 290 cm-1
.
31P{1H} NMR (101.2 MHz; CDCl3):
3
δ -13.5. 1H NMR (200 MHz; CDCl3): 1.34, t, J PH ) 17.4 Hz
(PC(CH3)2P). MS (FAB): m/e 554 (M - Cl), 518 (M - HCl -
Cl).
P r ep a r a tion of [P d I2(2,2-d p p p )] (5). (a ) F r om 4. To a
stirred suspension of 5 (0.20 g, 0.34 mmol) in acetone (20 cm3)
was added NaI (0.51 g, 3.4 mmol). The solution turned yel-
low and the suspended solid dissolved. After 1 h, the vol-
ume was reduced to ca. 5 cm3 under reduced pressure, the
solution was filtered, and Et2O (15 cm3) was added. The yel-
low precipitate was filtered at the pump, washed successively
with water, ethanol, and diethyl ether, dried in vacuo, and
recrystallized from CH2Cl2/Et2O. Yield: 0.18 g, 69%. Orange-
yellow needle crystals of 5 suitable for X-ray crystallography
were grown from CH2Cl2/MeOH by diffusion. Selected data
for 5 are as follows. Anal. Found: C, 40.00; H, 3.22. Calcd
for C27H26I2P2Pd‚0.75CH2Cl2: C, 39.84; H, 3.31. 31P{1H} NMR
(101.2 MHz; CDCl3): δ -19.1. 1H NMR (200 MHz; CDCl3):
3
(200 MHz; CDCl3): 1.80, virtual quintet, apparent J PH ) 8.4
Hz (PC(CH3)2P). MS (FAB): m/e 1055 (M - Cl), 1020 (M -
HCl - Cl).
P r ep a r a tion of [P tMe2(2,2-d p p p )] (10). (a ) F r om 7. A
finely ground sample of 7 (0.25 g, 0.369 mmol) suspended in
dry thf (2 cm3) was treated with a solution of MeLi (1.5 cm3 of
a 1.45 M solution in Et2O; 2.18 mmol) dropwise at 0 °C with
stirring. The mixture was warmed to room temperature and
after 16 h was brought to reflux for 15 min and then cooled to
0 °C. The clear solution was worked up by the addition of
MeOH (3 drops), and the solvent was removed in vacuo. The
residue was recrystallized from CH2Cl2 and MeOH as white
microcrystals. Yield: 0.105 g, 45%. Selected data for 10 are
as follows. Anal. Found: C, 54.57; H, 5.01. Calcd for
C29H32P2Pt: C, 54.65; H, 5.06. 31P{1H} NMR (101.2 MHz;
3
1.29, t, J PH ) 16.0 Hz (PC(CH3)2P). MS (FAB): m/e 772 (M),
645 (M - I), 517 (M - I - HI).
1
CDCl3): δ -2.8, J Pt-P 1577 Hz. 1H NMR (200 MHz; CDCl3):
(b) F r om P d (OAc)2. To a solution of Pd(OAc)2 (0.20 g, 0.89
mmol) in CH2Cl2 (10 cm3) was added 2,2-dppp (0.36 g, 0.89
mmol), followed by a solution of NaI (0.39 g, 2.6 mmol) in
acetone (10 cm3). The mixture was set aside at room temper-
ature, and orange crystals separated. These were filtered off
and dried. Yield: 0.40 g, 59%. Further, less pure product was
precipitated on addition of petroleum ether (10 cm3).
3
3
1.29, t, J PH ) 14.4 Hz (PC(CH3)2P); 0.83, t, J PH ) 6.7 Hz,
2J PtH ) 72.7 Hz (Pt(CH3)2). MS (FAB): m/e 622 (M - Me),
606 (M - Me - CH4).
(b) F r om [P tMe2(COD)]. The ligand (0.260 g, 0.63 mmol)
was added to a solution of [PtMe2(COD)] (0.205 g, 0.62 mmol)
in CH2Cl2 (5 cm3). The mixture was refluxed for 15 min and
evaporated to dryness, and the residue was then triturated
with MeOH. The white product was filtered off and dried in
vacuo. Yield: 0.365 g, 92%.
P r ep a r a t ion of [P d (2,2-d p p p )2](BF 4)2 (6). To [PdCl2-
(PhCN)2] (0.46 g, 1.20 mmol) in CH2Cl2 (25 cm3) was added
sequentially AgBF4 (0.49 g, 1.2 mmol), CH3CN (35 cm3), and
2,2-dppp (1.04 g, 2.52 mmol). The mixture was stirred at
room temperature for 1 h and then filtered through a Kiesel-
guhr pad. Solvent was removed in vacuo, and the residue was
taken up in CH3CN (5 cm3) and precipitated with Et2O to give
a pale yellow solid, which was filtered off and dried in vacuo.
Yield: 1.07 g, 83%. The analytical sample was recrystallized
from CH2Cl2/Et2O. Selected data for 6 are as follows. Anal.
Found: C, 56.89; H, 4.69. Calcd for C54H52B2F8P4Pd‚0.5CH2-
Cl2: C, 57.06; H, 4.65. IR: νB-F 1058 cm-1 (vs). 31P{1H} NMR
(101.2 MHz; CDCl3): δ -2.1. 1H NMR (200 MHz; CDCl3):
P r ep a r a tion of [P tCl(Me)(2,2-d p p p )] (11). A solution of
HCl in MeOH (1.0 cm3) was generated from the methanolysis
of acetyl chloride (26 µL, 0.37 mmol) and was added to a
solution of 10 (0.237 g, 0.372 mmol) in CH2Cl2 (3 cm3). Gas
was evolved, and after 10 min, colorless crystals appeared. The
mixture was set aside for 16 h at 4 °C, and the product was
then filtered off and dried in vacuo. Yield: 0.17 g, 76%.
Selected data for 11 are as follows. Anal. Found: C, 51.20;
H, 4.41; Cl, 5.6. Calcd for C28H29ClP2Pt: C, 51.11; H, 4.44;
1
Cl, 5.39. 31P{1H} NMR (101.2 MHz; CDCl3): δ -0.7, d, J Pt-P
3
2
1
1.77, virtual quintet, apparent J PH ) 8.8 Hz (PC(CH3)2P). MS
1342 Hz, J PP 24 Hz (P-trans-CH3); -2.9, d, J Pt-P 3965 Hz,
(FAB): m/e 1017 (M - BF4), 930 (M - HBF4 - BF4).
2J PP 24 Hz (P-trans-Cl). 1H NMR (200 MHz; CDCl3): 1.30,
6H, t, J PH ) 14.7 Hz (PC(CH3)2P); 0.87, 3H, dd, J PH ) 8.1
Hz (trans), 2.5 Hz (cis), J PtH ) 59.5 Hz (PtCH3).
3
3
P r ep a r a tion of [P tCl2(2,2-d p p p )] (7). To a solution of
[PtCl2(PhCN)2] (0.472 g, 1.00 mmol) in CH2Cl2 (35 cm3) was
added the ligand (0.412 g, 1.00 mmol). The mixture was
refluxed for 10 min. White crystals separated. The solvent
volume was reduced to ca. 10 cm3, and the product was then
filtered off and dried in vacuo. Yield: 0.46 g, 68%. Further
product could be obtained by the addition of Et2O to the mother
liquor. Selected data for 7 are as follows. Anal. Found: C,
45.78; H, 3.67. Calcd for C27H26Cl2P2Pt‚0.5CH2Cl2: C, 45.82;
2
P r ep a r a tion of [P t(CN)2(2,2-d p p p )] (12). A suspension
of 7 (0.20 g, 0.29 mmol) in EtOH (25 cm3) was refluxed with
NaCN (0.029 g, 0.59 mmol) for 16 h. The colorless product
was filtered off, washed with successively water (10 cm3),
ethanol (10 cm3), and CH2Cl2 (2 cm3), and dried in vacuo.
Yield: 0.18 g, 88%. Selected data for 12 are as follows. Anal.
Found: C, 51.59; H, 3.71; N, 3.90. Calcd for C29H26N2P2Pt‚
0.25CH2Cl2: C, 51.60; H, 3.92; N, 4.11. IR: νCN 2130 cm-1
H, 3.77. IR: νPt-Cl 310, 290 cm-1
.
31P{1H} NMR (101.2 MHz;
1
CDCl3): δ -24.2, J Pt-P 3135 Hz. 1H NMR (200 MHz;
(m, broad). 31P{1H} NMR (101.2 MHz; CH2Cl2/CD2Cl2):
-10.9, J Pt-P 2002 Hz.
δ
3
1
CDCl3): 1.22, t, J PH ) 17.2 Hz (PC(CH3)2P). MS (FAB): m/e
678 (M), 643 (M - Cl).
P r ep a r a tion of [P t(CtCP h )2(2,2-d p p p )] (13). (a ) F r om
7 a n d LiCtCP h . To a suspension of finely ground 7 (0.20 g,
0.29 mmol) in thf (0.5 cm3) was added a solution of LiCtCPh
(0.79 mmol) in thf (3 cm3) at 0 °C. The mixture was stirred
for 4 h and then warmed to reflux for 10 min, cooled, and
evaporated to dryness under reduced pressure. The residue
was triturated with MeOH and filtered. The crude product
(0.12 g) was recrystallized from CH2Cl2/MeOH. Yield: 0.09
g, 42%. Selected data for 13 are as follows. Anal. Found: C,
63.70; H, 4.51. Calcd for C43H36P2Pt: C, 63.79; H, 4.48. IR:
P r ep a r a tion of [P tI2(2,2-d p p p )] (8). To 7 (0.25 g, 0.37
mmol), partially dissolved in acetone (30 cm3), was added NaI
(0.55 g, 3.7 mmol). After 1 h of stirring at room temperature,
the volume was reduced to 5 cm3 at the pump, and Et2O (10
cm3) was added. The resulting yellow precipitate was filtered
off, washed successively with water, ethanol, and diethyl
ether, and dried in vacuo. Yield: 0.22 g, 68%. Selected data
for 8 are as follows. Anal. Found: C, 37.55; H, 3.06. Calcd
for C27H26I2P2Pt: C, 37.66; H, 3.04. 31P{1H} NMR (101.2 MHz;
1
CDCl3): δ -27.9, J Pt-P 2928 Hz. 1H NMR (200 MHz;
νCtC 2105, 2097 cm-1
.
31P{1H} NMR (101.2 MHz; CDCl3): δ
3
1
CDCl3): 1.18, t, J PH ) 16.8 Hz (PC(CH3)2P). MS (FAB): m/e
-15.5, J Pt-P 2035 Hz. 1H NMR (200 MHz; CDCl3): 1.44, t,
3J PH ) 15.4 Hz (PC(CH3)2P). MS (FAB): m/e 810 (M), 708 (M
- CtCPh), 606 (M - HCtCPh - CtCPh).
861 (M), 734 (M - I).
P r ep a r a tion of [P t(2,2-d p p p )2]Cl2 (9). A solution of
[PtCl2(PhCN)2] (0.20 g, 0.5 mmol) in CH2Cl2 (15 cm3) was
added dropwise to a solution of the ligand (0.42 g, 1.0 mmol)
(b) F r om 7 a n d HCtCP h /Hyd r a zin e. To a suspension
of finely ground 7 (0.20 g, 0.29 mmol) in ethanol (1.5 cm3) was

Four-Membered Rings in Ni, Pd, and Pt Complexes
Organometallics, Vol. 17, No. 9, 1998 1731
added H2NNH2‚H2O (0.106 g, 2.10 mmol). The solution was
brought to reflux for 2 min, after which HCtCPh (0.21 g, 2.10
mmol) was added. Refluxing was continued for 10 min, during
which time a clear orange solution formed. This was set aside
for 16 h at 0 °C. The light yellow plates which crystallized
were filtered off and dried in vacuo. Yield: 0.13 g, 61%.
P r ep a r a tion of [P t(CtCBu n )2(2,2-d p p p )] (14). A solu-
tion of LiCtCBun (1.11 mmol) in thf (2 cm3) and hexane (0.7
cm3) was treated with finely ground 8 (0.25 g, 0.369 mmol) at
-78 °C. The solution was stirred, allowed to reach room
temperature, and set aside for 3 h. It was then briefly
refluxed, cooled, and evaporated to ca. 2 cm3 volume. On
addition of Et2O, a light brown precipitate was obtained. This
was filtered off and dried in vacuo. Yield: 0.043 g, 15%.
Selected data for 14 are as follows. Anal. Found: C, 60.59;
H, 5.73. Calcd for C39H44P2Pt: C, 60.82; H, 5.76. 31P{1H}
NMR (101.2 MHz; CDCl3): δ -16.6, 1J Pt-P 2024 Hz. 1H NMR
correction, using the program DIFABS,53 was applied, which
resulted in transmission factors ranging from 0.75 to 1.16. The
data were corrected for Lorentz and polarization effects. Non-
hydrogen atoms were refined anisotropically. Hydrogen atoms
were included in the structure factor calculations in idealized
positions (dC-H ) 0.95 Å) and were assigned isotropic ther-
mal parameters that were 20% greater than the Bequiv value
of the atom to which they were bonded. Details of the data
collection, structure solution, and refinement are summarized
in Table 2.
Ack n ow led gm en t. Thanks are expressed to the
EPSRC for a studentship (M.K.M.), for an allocation at
the National Mass Spectrometry Service, Swansea,
U.K., and for access to the Chemical Database Service,
Daresbury, U.K., and to J ohnson-Matthey for a gener-
ous loan of platinum metal salts.
3
(200 MHz; CDCl3): 2.42, t, J HH 7.0 Hz (CtCCH2R), 1.37, t,
3J PH ) 15.4 Hz (PC(CH3)2P), 1.33, m (CH2CH2CH2CH3), 0.72,
3
Su p p or tin g In for m a tion Ava ila ble: Tables giving posi-
tional and thermal parameters, bond distances and angles, and
torsion or conformational angles for 5‚0.8CH2Cl2 (14 pages).
Ordering information is given on any current masthead page.
t, J HH 7.0 Hz (CH2CH3). MS (FAB): m/ e 770 (M), 688 (M -
CtCBun), 606 (M - HCtCBun - CtCBun).
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of [P d I2(2,2-
d p p p -P ,P ′)]‚0.8CH2Cl2 (5‚0.8CH2Cl2). The crystal structure
was solved by direct methods.51,52 Three representative reflec-
tions, remeasured after every 150 reflections, remained un-
changed throughout data collection. An empirical absorption
OM970941T
(52) Beurskens, P. T. DIRDIF; Crystallography Laboratory, Toer-
nooiveld, 1984.
(51) Gilmore, C. J . J . Appl. Crystallogr. 1984, 17, 42.
(53) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.