Reactions of sodium bis(N-aryliminophosphoranyl)alkanides with halide-bridged platinum(II) and palladimn(II) phosphine dimers affording four-membered M-N-P-C metallacycles and orthometalated platinum(II) and palladium(II) complexes

Article abstract of DOI:10.1021/om950635k

Reaction of the sodium bis(iminophosphoranyl)alkanide compounds Na[CR″(PPh₂=NC₆H₄R′-4)2] (1a, R″ = H, R′ = CH₃; 1b, R″ = H, R′ = OCH₃; 1c, R″ = CH₃, R′ = CH₃) with M₂X

Full text of DOI:10.1021/om950635k

2376
Organometallics 1996, 15, 2376-2392
Rea ction s of Sod iu m
Bis(N-a r ylim in op h osp h or a n yl)a lk a n id es w ith
Ha lid e-Br id ged P la tin u m (II) a n d P a lla d iu m (II)
P h osp h in e Dim er s Affor d in g F ou r -Mem ber ed M-N-P -C
Meta lla cycles a n d Or th om eta la ted P la tin u m (II) a n d
P a lla d iu m (II) Com p lexes
Mandy W. Avis, Kees Vrieze, J an M. Ernsting, and Cornelis J . Elsevier*
Van ’t Hoff Research Institute, Anorganisch Chemisch Laboratorium, Universiteit van
Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands
Nora Veldman and Anthony L. Spek†
Bijvoet Center for Biomolecular Research, Vakgroep Kristal- en Struktuurchemie,
Universiteit Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands
Kattesh V. Katti and Charles L. Barnes‡
Departments of Radiology and Chemistry, University of MissourisColumbia, 409 Lewis Hall,
Columbia, Missouri 65211
Received August 10, 1995X
Reaction of the sodium bis(iminophosphoranyl)alkanide compounds Na[CR′′(PPh2dNC6H4R′-
4)2] (1a , R′′ ) H, R′ ) CH3; 1b, R′′ ) H, R′ ) OCH3; 1c, R′′ ) CH3, R′ ) CH3) with M2X4-
(PR3)2 (M ) Pt, Pd; X ) Cl, Br; PR3 ) PEt3, PMe2Ph) yields the four-membered metallacycles
MX(PR3){CR′′(PPh2dNC6H4R′-4)2} (2a -f, M ) Pt; 3a -c, M ) Pd), containing the bis-
(iminophosphoranyl)alkanide ligand coordinated in a σ-C,σ-N chelating fashion. The
molecular structure of 2e (X ) Cl, PR3 ) PMe2Ph, R′′ ) CH3, R′ ) CH3) has been determined
by X-ray crystallography. The 1,1-bis(iminophosphoranyl)ethanide ligand (1c) in 2e is σ-C,σ-
N-chelated toward the square-planar-surrounded Pt, with N coordinated trans to PMe2Ph
(Pt-N ) 2.132(4) Å) and C trans to Cl (Pt-C ) 2.116(4) Å), resulting in a puckered M-N-
P-C metallacycle and one noncoordinated phosphinimine moiety. In solution the complexes
2 and 3 undergo a dynamic process, involving an intermediate (for 2) or fast (for 3) N,N′
exchange of coordinated and noncoordinated PdN groups. Heating (to 60-80 °C) or
prolonged stirring of solutions of the kinetically obtained four-membered metallacycles 2
and 3 gives the orthometalated complexes PtX(PR3){2-C6H4PPh(NHC6H4R′-4)CHPPh2d
NC6H4R′-4} (4a -d ,f) and PdCl(PR3){2-C6H4PPh(dNC6H4Me-4)CHPPh2NHC6H4Me-4} (5a ,c).
The X-ray crystal structure of 4a (X ) Cl, PR3 ) PEt3, R′ ) CH3) has been determined. The
new mononuclear orthometalated Pt complexes 4 contain a σ-C,σ-C′ coordinated [2-C6H4-
PPh(NHC6H4R-4′)CR′′PPh2dNC6H4R′-4]- ligand, in which the ortho-H (Ph) has shifted to a
bridge position between the two noncoordinating nitrogen atoms. The four-membered
platinacycles 2a ,b and the orthometalated platinacycles 4a ,b react with 1 equiv of HBF4 or
CF3COOH to give 6a ,b and 7a ,b, respectively, by protonation of the noncoordinated
PdNC6H4R′-4 groups only. Addition of CO2 to 2a ,d and 4c,f results in an aza-Wittig reaction,
giving PtCl(PR3){CH(PPh2dNC6H4R′-4)(PPh2dO)} (8a ,d ) and PtX(PR3){2-C6H4PPh(dO)-
CHPPh2NHC6H4R′-4} (9c,f), respectively, together with aryl isocyanate and bis(aryl)-
carbodiimide.
In tr od u ction
compounds of I, which are easily obtained via deproto-
nation reactions of their neutral derivatives [CH2-
(PR2dX)2] by LDA, NaH, BuLi, or other strong bases,
are convenient precursors for transmetalation reactions.
The coordination chemistry of phosphorus-containing
monoanions I (Chart 1), that are structurally related
to acetylacetonate (II) has been the subject of several
studies these last decades.1-3 The lithium or sodium
(1) (a) Schmidbaur, H.; Gasser, O. Angew. Chem. 1976, 88, 542. (b)
Schmidbaur, H.; Gasser, O.; Kru¨ger, C.; Sekutowski, J . C. Chem. Ber.
1977, 110, 3517. (c) Schmidbaur, H.; Deschler, U.; Zimmer-Gasser,
B.; Neugebauer, D.; Schubert, U. Chem. Ber. 1980, 113, 902.
(2) (a) Browning, J .; Dixon, K. R.; Hilts, D. W. Organometallics 1989,
8, 552. (b) Wheatland, D. A.; Clapp, C. H.; Waldron, R. W. Inorg. Chem.
1972, 11, 2340.
(3) (a) Browning, J .; Bushnell, G. W.; Dixon, K. R.; Pidcock, A. Inorg.
Chem. 1983, 22, 16, 2226. (b) Berry, D. E.; Browning, J .; Dixon, K.
R.; Hilts, R. W.; Pidcock, A. Inorg. Chem. 1992, 31, 1479.
* To whom correspondence should be addressed. E-mail: inorg.
chem@sara.nl.
† To whom correspondence on the crystallography of compound 4a
should be addressed. E-mail: spea@xray.chem.ruu.nl.
‡ To whom correspondence on the crystallography of compound 2e
should be addressed. E-mail: chemclb@mizzou1.missouri.edu.
X Abstract published in Advance ACS Abstracts, April 1, 1996.
S0276-7333(95)00635-2 CCC: $12.00 © 1996 American Chemical Society

M-N-P-C Metallacycles
Ch a r t 1
Organometallics, Vol. 15, No. 9, 1996 2377
Ch a r t 3
Ch a r t 2
Recently, we reported several new coordination com-
plexes containing a ligand of this type I, bis(N-arylimi-
nophosphoranyl)methanide, [CH(PR2dN-aryl)2]-.4 In
that case Li+[CH(PR2dN-aryl)2]- reacted with [MCl-
(L)2]2 to give the four-membered metallacycles III (M
) Rh, Ir; L2 ) COD, NBD, (CO)2; Ar ) p-tolyl, p-
nitrophenyl) (Chart 2) in which the ligand is C,N
chelated.4
Such a coordination mode was rather peculiar since
the closely related bis(chalcogenophosphoranyl)methanide
ligands [CH(PR2dX)(PR2dY)]- (X, Y ) O, S, Se) coor-
dinate exclusively as X, Y chelates to Rh and Ir,2a but
C, X and X, Y coordination was observed for these
ligands with Pt3a,b and Au.5 Furthermore, an entirely
different reactivity has been observed for the related
N-SiMe3-substituted bis(iminophosphoranyl)methanide
ligand [CH(PR2dNSiMe3)2]-, forming planar six-mem-
bered metallacycles with WCl6 or WF6 under elimina-
tion of Me3Si-halide.6
It was therefore interesting to examine whether the
bis(N-aryliminophosphoranyl)methanide ligands would
coordinate to Pt and Pd similarly as found for Rh and
Ir,4 especially since only a few phosphinimine complexes
of Pt7 and Pd8 have been reported previously, although
some related Pt-phosphazene compounds are known.9-11
In a recent report we have already demonstrated that
the neutral bis(iminophosphoranyl)methane ligands
(BIPM), CH2(PR2dN-aryl)2, react with Pt2X4(PR3)2 to
give cationic or neutral four-membered platinacycles
(IV) (Chart 3), depending on the metal-to-ligand ratio,
in which the ligand is σ-N,σ-C coordinated.12 Analogous
palladium comlexes could not be obtained due to insta-
bility.12 Similar reactions with the modified ligand 1,1-
bis(iminophosphoranyl)ethane (1,1-BIPE), which has a
1,1-ethanediyl bridge instead of a methylene bridge
between the two PdN moieties, resulted in the forma-
tion of σ-N,σ-N′-coordinated Pt(II) complexes (V).13
In view of the ring strain in the above mentioned four-
membered M-X-P-C metallacycles (M ) Rh, Ir, Pt;
X ) S, Se, N-aryl)3b,4,12 one might expect that ring
enlargements via orthometalation, involving metal-
carbon bond formation at the ortho position of an
aromatic group (on P or N in our case) with concomitant
M-X bond dissociation, would be favorable. Such
reactivity has not been found for these types of four-
membered metallacycles so far, but orthometalations of
end-on coordinated phosphinimines8d and structurally
related phosphorus ylides14 are known.
In this article we report on the coordination chemistry
of the monoanions [CH(PR2dN-aryl)2]- and [CMe-
(PR2dN-aryl)2]- toward Pt2X4(PR3)2 and Pd2Cl4(PR3)2.
We will show that the kinetically obtained products, the
four-membered M-N-P-C metallacycles, readily un-
dergo orthometalation reactions to yield thermodynami-
cally more stable compounds. The reactivity and sta-
bility of the kinetic and thermodynamic platinum
complexes toward CO2 and acids will also be described.
(4) Imhoff, P.; van Asselt, R.; Ernsting, J . M.; Vrieze, K.; Elsevier,
C. J . Organometallics 1993, 12, 1523.
(5) Laguna, A.; Laguna, M.; Rojo, A.; Fraile, M. N. J . Organomet.
Chem. 1986, 315, 269.
Exp er im en ta l Section
Gen er a l Com m en ts. All manipulations were carried out
under an atmosphere of dry nitrogen using standard Schlenk
techniques at 20 °C, unless stated otherwise. The solvents
were dried and distilled prior to use. 1H and 31P{1H} NMR
spectra were recorded on Bruker AC 100 and AMX 300
instruments (operating at 100.13/300.13 and 40.53/121.50
MHz, respectively), using SiMe4 and 85% H3PO4 as the
(6) Katti, K. V.; Seseke, U.; Roesky, H. W. Inorg. Chem. 1987, 26,
814.
(7) Vicente, J .; Chicote, M.-T.; Ferna´ndez-Baeza, J .; Lahoz, F. J .;
Lo´pez, J . A. Inorg. Chem. 1991, 30, 3617.
(8) (a) Fukui, M.; Itoh, K.; Ishii, Y. Bull. Chem. Soc. J pn. 1975, 48,
2044. (b) Kiji, J .; Matsumura, A.; Okazaki, S.; Haishi, T.; Fukukawa,
J . J . Chem. Soc., Chem. Commun. 1975, 751. (c) Kiji, J .; Matsumura,
A.; Haishi, T.; Okazaki, S.; Fukukawa, J . Bull. Chem. Soc. J pn. 1977,
50, 2731. (d) Alper, H. J . Organomet. Chem. 1977, 127, 385. (e) Abel,
E. W.; Mucklejohn, S. A. Inorg. Chim. Acta 1979, 37, 107. (f) Katti,
K. V.; Batchelor, R. J .; Einstein, F. W. B.; Cavell, R. G. Inorg. Chem.
1990, 291, 808. (g) Katti, K. V.; Cavell, R. G. Organometallics 1991,
10, 539. (h) Liu, C.-H.; Chen, D.-Y.; Cheng, M.-C.; Peng, S.-M.; Liu,
S.-T. Organometallics 1995, 14, 1983.
(12) Avis, M. W.; Vrieze, K.; Kooijman, H.; Veldman, N.; Spek, A.
L.; Elsevier, C. J . Inorg. Chem. 1995, 34, 4093.
(13) Avis, M. W.; Elsevier, C. J .; Veldman, N.; Kooijman, H.; Spek,
A. L. Inorg. Chem., in press.
(9) Scherer, O. J .; Nahrstedt, A. J . Organomet. Chem. 1979, 166,
C1.
(10) Roesky, H. W.; Scholz, U.; Noltemeijer, M. Z. Anorg. Allg. Chem.
1989, 576, 255.
(11) (a) Balakrishna, M. S.; Santarsiero, B. D.; Cavell, R. G. Inorg.
Chem. 1994, 33, 3079. (b) Chandrasekaran, A.; Krishnamurthy, S.
S.; Nethji, M. Inorg. Chem. 1994, 33, 3085.
(14) (a) Baldwin, J . C.; Kaska, W. C. Inorg. Chem. 1979, 18, 686.
(b) Illingsworth, M. L.; Teagle, J . A.; Burmeister, J . L.; Flutz, W. C.;
Rheingold, A. L. Organometallics 1983, 2, 1364. (c) Teagle, J . A.;
Burmeister, J . L. Inorg. Chim. Acta 1986, 118, 65. (d) Vicente, J .;
Chicote, M. T.; Fernandez-Baeza, J . J . Organomet. Chem. 1989, 364,
407. (e) Vicente, J .; Chicote, M. T.; Lagunas, M.-C.; J ones, P. G.;
Bembenek, E. Organometallics 1994, 13, 1243.

2378 Organometallics, Vol. 15, No. 9, 1996
Avis et al.
external standards, respectively, positive shifts to high fre-
quency of the standard in all cases. 13C NMR data were
obtained from Bruker AMX 300 and ARX 400 spectrometers
(operating at 75.48/100.62 MHz, respectively), using SiMe4 as
the external standard. Elemental analyses were carried out
by Dornis and Kolbe Mikroanalytisches Laboratorium, Mu¨l-
heim a.d. Ruhr, Germany. Pt2X4(PR3)2, Pd2Cl4(PR3)2 (with PR3
) PEt3, PMe2Ph; X ) Cl, Br),15 the bis(iminophosphoranyl)-
methanes (BIPM) CH2(PPh2dNC6H4R′-4)2 (R′ ) Me, OMe),16,17
and 1,1-bis(iminophosphoranyl)ethane (1,1-BIPE) CHCH3-
P tCl(P Et3){CH(P P h 2dNC6H4OCH3-4)2} (2b). Anal. Cal-
cd for C45H50ClN2O2P3Pt: C, 55.47; H, 5.18; N, 2.87; P, 9.53.
Found: C, 55.29; H, 5.28; N, 2.78; P, 8.56. 13C NMR (CD2Cl2,
253 K, 75.48 MHz): δ 1.49 (dd, Pt-C, 1J (P,C) ) 59, 95 Hz,
2
1J (Pt,C) ) n.r.); δ 8.24 (d, PCH2CH3, J (P,C) ) 3 Hz); δ 15.50
(d, PCH2CH3, 1J (P,C) ) 38 Hz); C6H4OCH3-4, δ 55.58 and 55.63
(s, OCH3); δ 138.40 and 145.58 (vs, Cipso); δ 122.92 and 125.07
3
(d, Cortho, J (P,C) ) 19 and 13 Hz, respectively); δ 113.13 and
114.08 (s, Cmeta); δ 151.11 and 154.86 (s, Cpara); phenyls, δ 127-
134.
13
(PPh2dNC6H4CH3-4)2 were synthesized according to litera-
P t Cl(P Me2P h ){CH (P P h 2dNC6H 4CH 3-4)2} (2c). FAB
MS: found, m/z ) 963 (M, calcd for C47H46ClN2P3Pt, m/z 962.4).
13C NMR (CDCl3, 253 K, 75.48 MHz); δ 2.02 (dd, Pt-C, 1J (P,C)
ture procedures. The deprotonation of these ligands was
preferably performed as described previously;17 e.g. to a
solution of 0.45 mmol BIPM in 20 mL of THF was added a
5-fold excess of NaH (washed with ether, dried in vacuo, and
stored under nitrogen). After 2 h, during which H2 gas slowly
evolved, the light yellow solution was filtered and the residue
washed with THF (2 × 5 mL). The clear filtrate, containing
only sodium bis(iminophosphoranyl)methanide, Na+[CH-
(PPh2dNC6H4R′-4)2]- (1a , R′ ) Me; 1b, R′ ) OMe)17 in
quantitative amount, was used directly for the preparations
described below. For deprotonated 1,1-BIPE, Na+[CCH3-
(PPh2dNC6H4CH3-4)2]- (1c), a different procedure was used;
NaH was added to a solution of 1,1-BIPE in THF, and the new
solution was stirred for 2.5 h. The orange solution, still
containing excess of NaH, was directly used for reaction with
Pt2Cl4(PMe2Ph)2 (see 2e), as removal of NaH by filtration
resulted in back-reaction into the neutral ligand.
1
1
) 58, 71 Hz, J (Pt,C) ) n.r.); δ 14.48 (d, PCH3, J (P,C) ) 30
1
Hz); δ 15.05 (d, PCH3, J (P,C) ) 31 Hz); C6H4CH3-4, δ 21.24
and 21.34 (s, CH3); δ 142.36 (vs, Cipso) and 149.34 (d, Cipso
,
2J (P,C) ) 3 Hz); δ 123.63 and 123.86 (d, Cortho 3J (P,C) ) 18
,
and 18 Hz, respectively); δ(Cmeta) and δ(Cpara) obscured; phen-
yls, δ 125-135.
P t Cl(P Me2P h ){CH (P P h 2dNC6H 4OCH3-4)2} (2d ). FAB
MS: found, m/z ) 995 (M, calcd for C47H46ClN2O2P3Pt, m/z
1
994.4). Further characterization is based on H and 31P NMR
spectroscopy.
P tCl(P Me2P h ){P P h 2dNC6H4CH3-4)2} (2e). Anal. Calcd
for C48H48ClN2P3Pt: C, 59.05; H, 4.96; N, 2.87; P, 9.52.
Found: C, 59.15; H, 5.00; N, 2.94; P, 9.60. Crystals suitable
for X-ray diffraction study were obtained by slow evaporation
of a solution of 2e in a 20:1:1 mixture of Et2O/THF/hexane at
room temperature for 1 week. 13C NMR (CDCl3, 293 K, 125.77
MHz): δ 4.82 (dd, Pt-C, 1J (P,C) ) 57, 86 Hz, 1J (Pt,C) ) n.r.);
Na +[CMe(P P h 2dNC6H4Me-4)2]- (1c). Compound 1c was
isolated by careful removal of the clear orange supernatant
by a syringe and subsequent evaporation of the solvent in
vacuo for 24 h, yielding a yellow powder. Sampling 1c, e.g.
for NMR purposes, has to be done in extremely dry C6D6, since
traces of H2O result in the formation of 1,1-BIPE. 1H NMR
(C6D6): phenyl rings, δ 8.0, 7.1 (m, 20H); NC6H4, δ 6.90, 6.63
(d, 8H, 3J (H,H) ) 8.1 Hz); CCH3, δ 1.94 (t, 3H, 3J (P,H) ) 15.5
Hz); C6H4CH3-4, δ 2.20 (s, 6H). 31P NMR (C6D6): δ(P) ) 23.4
ppm (s). 13C NMR (C6D6, 75.5 MHz, 293 K): CCH3, δ 16.97
(t, 2J (P,C) ) 8.8 Hz); CCH3, δ not resolved; C6H4CH3-4, δ 21.23
1
δ 15.27 (s, Pt-CCH3); δ 13.50 (d, PCH3, J (P,C) ) 37 Hz); δ
13.93 (d, PCH3, 1J (P,C) ) 42 Hz); C6H4CH3-4, δ 20.20 and 20.47
(s, CH3); δ 141.76 and 149.62 (vs, Cipso); δ 122.79 and 124.48
3
(d, Cortho, J (P,C) ) 17 and 14 Hz, respectively); δ(Cmeta) and
δ(Cpara) obscured; phenyls, δ 126-136.
P tBr (P Et3){CH(P P h 2dNC6H4CH3-4)2} (2f) is character-
1
ized by H and 31P NMR spectroscopy only.
Syn th esis of 3a -c, P d Cl(P R3){CH(P P h 2dNC6H4R′-4)2-
C,N} (P R3 ) P Et3, P Me2P h ; R′ ) CH3, OCH3). A solution
of Pd2Cl4(PR3)2 (0.23 mmol) in 10 mL of THF was added to a
stirred solution of freshly prepared Na[CH(PPh2dNC6H4R′-
4)2] (0.45 mmol) in 30 mL of THF. The reaction mixture
immediately changes color from yellow to brownish-red and
after 30 min into orange. The cloudy solution was stirred for
at least 4 h before filtration through a glass filter (G4). The
residue (precipitated NaCl) was washed with 10 mL of THF.
The combined clear orange filtrates were evaporated to 5 mL.
The product was precipitated by the addition of pentane (60
mL) at -30 °C, washed with pentane (2 × 20 mL), and dried
in vacuo, yielding a yellow powder (87-92%).
(s); C6H4, δ 124.25 (d, Cortho
,
3J (P,C) ) 19.7 Hz); δ 130.48 (s,
meta); δ 125.14 (s, Cpara); δ 153.99 (vs, Cipso); phenyls, δ 138.4
C
(dd, Cipso
,
1J (P,C) ) 105.7 Hz, 3J (P,C) ) 11.6 Hz); δ 133.88
(vs, Cortho); δ ∼ 128.5 (obscured by C6D6, Cmeta); δ 130.61 (s,
C
para).
Syn th esis of 2a -f, P tX(P R3){CR′′(P P h 2dNC6H4R′-4)2-
C,N} (P R3 ) P Et3, P Me2P h ; X ) Cl, Br ; R′ ) CH3, OCH3,
R′′ ) H, Me). To a stirred solution of freshly prepared Na-
[CR′′(PPh2dNC6H4R′-4)2] (0.45 mmol) in 30 mL of THF was
added a solution of Pt2X4(PR3)2 (0.23 mmol) in 10 mL of THF.
After 4 h the cloudy yellow solution was filtered through a
glass filter (G4), and the residue (precipitated NaX) was
washed with 10 mL of THF. The combined clear yellow
filtrates were evaporated to dryness, leaving an oily residue.
Addition of cold pentane (40 mL) resulted in the solidification
of the product, which was washed with pentane (2 × 20 mL)
and dried in vacuo, yielding a yellow powder (84-95%).
P d Cl(P Et3){CH(P P h 2dNC6H4CH3-4)2} (3a ). Anal. Calcd
for C45H50ClN2P3Pd: C, 63.31; H, 5.90; N, 3.28; P, 10.88.
Found: C, 63.19; H, 5.95; N, 3.20; P, 10.93. FAB MS: found,
m/z ) 853 (M, calcd for C45H50ClN2P3Pd, m/z 853.7). 13C NMR
(CD2Cl2, 293 K, 75.48 MHz); δ 9.20 (vt, Pd-C, 1J (P,C) ) 82
2
Hz); δ 8.66 (d, PCH2CH3, J (P,C) ) 3 Hz); δ 17.24 (d, PCH2-
1
CH3, J (P,C) ) 30 Hz); C6H4CH3-4, δ 20.93 (s, CH3); δ 146.62
P tCl(P Et3){CH(P P h 2dNC6H4CH3-4)2} (2a ). Anal. Calcd
for C45H50ClN2P3Pt: C, 57.34; H, 5.35; N, 2.97; P, 9.86.
Found: C, 57.28; H, 5.55; N, 2.85; P, 9.81. 13C NMR (CD2Cl2,
253 K, 75.48 MHz): δ 1.67 (dd, Pt-C, 1J (P,C) ) 70, 93 Hz,
1J (Pt,C) ) n.r.); δ 8.28 (vs PCH2CH3); δ 15.50 (d, PCH2CH3,
1J (P,C) ) 38 Hz); C6H4CH3-4, δ 20.65 and 20.89 (s, CH3); δ
(s, Cipso); δ 123.89 (d, Cortho, 3J (P,C) ) 17 Hz); δ 129.34 (s, Cmeta);
δ 127.83 (s, Cpar); phenyls, δ(Cipso) obscured; δ 132.7 and 133.6
(d, Cortho, 2J (P,C) ) 9.8 Hz); δ 128.8 and 129.3 (d, Cmeta, 3J (P,C)
) 12.1 Hz); δ 132.1 and 132.4 (s, Cpara).
P d Cl(P Et3){CH(P P h 2dNC6H4OCH3-4)2} (3b). FAB MS:
found, m/z ) 885 (M, calcd for C45H50ClN2O2P3Pd, m/z 885.7).
13C NMR (CD2Cl2, 293 K, 75.48 MHz): δ 9.01 (vt, Pd-C,
1J (P,C) ) 82 Hz); δ 8.70 (d, PCH2CH3, 2J (P,C) ) 2 Hz); δ 17.25
(d, PCH2CH3, 1J (P,C) ) 30 Hz); C6H4OCH3-4, δ 56.06 (s,
OCH3); δ 142.68 (s, Cipso); δ 124.57 (d, Cortho, 3J (P,C) ) 16 Hz);
δ 114.27 (s, Cmeta); δ 153.17 (s, Cpara); phenyls, δ(Cipso) obscured;
142.64 and 149.47 (vs, Cipso); δ 122.56 and 124.14 (d, Cortho
,
3J (P,C) ) 19 and 14 Hz, respectively); δ(Cmeta) and δ(Cpara
obscured; phenyls, δ 125-135.
)
(15) Goodfellow, R. J .; Venanzi, L. M. J . Chem. Soc. 1965, 7533.
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K.; van Malssen, K. F.; Stam, C. H. Phosphorus Sulfur 1990, 47, 401.
2
δ 132.62 and 132.75 (d, Cortho, J (P,C) ) 9.8 Hz); δ 128.7 and
129.3 (d, Cmeta, 3J (P,C) ) 11.5 Hz); δ 132.1 and 132.3 (s, Cpara).
P d Cl(P Me2P h ){CH (P P h 2dNC6H 4CH 3-4)2} (3c). FAB
MS: found, m/z ) 873 (M, calcd for C47H46ClN2P3Pd, m/z

M-N-P-C Metallacycles
Organometallics, Vol. 15, No. 9, 1996 2379
1
873.7). Further characterization is based on H and 31P NMR
spectroscopy.
solution was filtered and evaporated to dryness. The residue
was washed with pentane (2 × 20 mL) and dried in vacuo,
giving a yellow solid in 76-80% yield. The washings contained
compound 3a or 3c.
P dCl(P Et3){2-C6H4P (P h )(dNC6H4Me-4)CHP P h 2N′HC6H4-
Me-4} (5a ). Anal. Calcd for C45H50ClN2P3Pd: C, 63.31; H,
5.91; N, 3.28; P, 10.88. Found: C, 62.49; H, 5.51; N, 3.53; P,
9.95. FAB MS: found, m/z ) 853 (5a ), 817 (5a - Cl) (M, calcd
for C45H50ClN2P3Pd, m/z 853.7). 13C NMR (C6D6, 293 K, 75.48
MHz): δ 35.0 (ddd, Pd-C, nJ (P,C) ) 49, 58, 72 Hz, with n )
1, 2); δ 9.3 (s, PCH2CH3); δ 17.0 (d, PCH2CH3, 1J (P,C) ) 24
Syn th esis of Or th op la tin a ted Com p lexes 4a -d ,f, [P tX-
(P R 3){2-C6H 4-P (P h )(NH C6H 4R ′-4)CH P P h 2dN′C6H 4R ′-4}-
C,C′] (P R3 ) P Et3, P Me2P h ; X ) Cl, Br ; R′ ) CH3, OCH3).
To a solution of freshly prepared Na[CR′′(PPh2dNC6H4R′-4)2]
(0.32 mmol) in 30 mL of THF was added a solution of Pt2X4-
(PR3)2 (0.16 mmol) in 10 mL of THF, and the solution was
stirred at 70-80 °C. After 6 h the cloudy yellow solution was
filtered through a glass filter (G4) filter, and the residue
(precipitated NaX) was washed with 10 mL of THF. The clear
yellow filtrate was evaporated to 5 mL. Addition of ether (40
mL) resulted in a white precipitation, which was washed with
diethyl ether (20 mL) and pentane (20 mL) and dried in vacuo,
yielding a white powder in all cases (39-61%). The washings
contained compound 2, according to 1H and 31P NMR spec-
troscopy.
Hz); C6H4CH3-4, δ 21.4 (s, CH3); δ 141.2 and 148.4 (d, Cipso
,
2J (P,C) e 2 Hz); δ 120.4, 122.9 (d, Cortho 3J (P,C) ) 9.3, 17.1
,
Hz); δ 129-131 (Cmeta); δ 126.3 and 130.6 (s, Cpara); phenyls, δ
126.3 (d, 1Cipso, 1J (P,C) ) 95 Hz); remaining δ(Cipso) obscured;
2
δ 133.4, 134.8 (d, Cortho, J (P,C) ) 8 and 11 Hz, respectively);
δ 129-131 (Cmeta); δ 131.4, 131.9, 132.0, 132.7 (s, Cpara); δ 135.7
(dd, Cipso, 1J (P,C) ) 83 Hz, 3J (P,C) ) 11 Hz); δ 137.5 (dd, Cortho
,
P t C l(P E t 3 ){2-C 6 H 4 P (P h )(N H C 6 H 4 M e -4)C H P P h 2 d
N′C6H4M-4e} (4a ). FAB MS: found, m/z ) 943 (M, calcd for
45H50ClN2P3Pt, m/z 942.6). Crystals suitable for X-ray dif-
2J (P,C) ) 18 Hz, 4J (P,C) ) 13 Hz); δ 157.9 (dd, Corthomet, 2J (P,C)
) 27 and 3 Hz).
C
P d Cl(P Me 2P h ){2-C6H 4P (P h )(dNC6H 4Me -4)CH P P h 2-
N′HC6H4Me-4] (5c). FAB MS: found, m/z ) 873 (5c), 837
(5c - Cl) (M, calcd for C47H46ClN2P3Pd, m/z 873.7). Further
characterization is based on 1H and 31P NMR spectroscopy.
F ollow in g th e Rea ction Sequ en ce in th e F or m a tion
of 5c. Compound 3c was dissolved in 0.5 mL of toluene-d8 in
a 5 mm NMR tube, and the reactions were monitored by 1H
and 31P NMR. At 20 °C, the first conversion of 3c into 5ci
took place as evidenced by the appearance of three new 31P
resonances. The solution was then heated shortly, which
resulted in some yellow precipitation. The 31P NMR showed
complete conversion of both 3c and 5ci into 5c.
fraction study were obtained by slow diffusion of pentane into
a solution of 4a in toluene at 20 °C for 3 weeks. 13C NMR
1
(CDCl3, 293 K, 75.48 MHz): δ 13.4 (ddd, Pt-C, J (P,C) ) 45,
70 Hz, 2J (P,C) ) 2 Hz, 1J (Pt,C) ≈ 736 Hz); δ 8.15 (vs,
1
PCH2CH3); δ 15.0 (d, PCH2CH3, J (P,C) ) 27 Hz); C6H4CH3-
2
4, δ 21.0 and 21.1 (s, CH3); δ 140.0 and 147.4 (d, Cipso, J (P,C)
) 5 and 7 Hz, respectively); δ 122.1, 124.3, and 136.1 (d, 2:1:1
3
C
ortho, J (P,C) ) 17 Hz, 13 Hz, and n.r., respectively); δ(Cmeta
obscured; δ 127.1 and 130.5 (s, Cpara); phenyls, δ 125.6 (d, 1
Cipso
,
1J (P,C) ) 91 Hz), remaining δ(Cipso) obscured; δ 120-
136 (Co,m,p); δ 167.8 (dd, Corthomet
,
2J (P,C) ) 36 and 125 Hz,
1J (Pt,C) ) n.r.).
P t C l(P E t 3){2-C 6H 4P (P h )(N H C 6H 4O Me -4)C H P P h 2d
N′C6H6H4OMe-4} (4b). Anal. Calcd for C45H50ClN2O2P3Pt:
C, 55.46; H, 5.17; N, 2.87; P, 9.53. Found: C, 55.38; H, 5.24;
N, 2.95; P, 9.39. 13C NMR (CD2Cl2, 293 K, 75.48 MHz): δ 13.6
P d Cl(P Me2P h ){2-C6H 4P (P h )(NH C6H 4Me-4)CH P P h 2d
N′C6H4Me-4} (5ci). 31P NMR (121.5 MHz; tol-d8): δ -10.0
(d, PMe2Ph, 3J (P,P) ) 36.4 Hz); δ 24.7 (dd, PNH, 3J (P,P) )
36.4 Hz, 2J (P,P) ) 19.8 Hz); δ 20.0 (d, PdN, 2J (P,P) ) 19.8
Hz).
Rea ction of 2a ,b w ith HBF 4 or CF 3COOH. To a solution
of 0.10 mmol of PtCl(PEt3){CH(PPh2dNC6H4R′-4)2} (2a ,b) in
20 mL of CH2Cl2 or toluene was added 14 µL (0.10 mmol) of a
54% (by weight) HBF4 solution in diethyl ether or 7.6 µL (0.10
mmol) of CF3COOH. After 5-30 min of stirring, the yellow
solution was evaporated to dryness. The solid residue was
washed with pentane (2 × 20 mL) and dried in vacuo, giving
[P t Cl(P E t 3 ){CH (P P h 2 dN C6 H 4 R′-4)(P P h 2 N ′H C6 H 4 R′-4)-
C,N}]+Y- (6a , R′ ) Me, Y ) BF4; 6b′, R′ ) OMe, Y ) CF3-
COO) in quantitative yield. Complexes 6a ,b′ are identical to
earlier reported complexes.12
Rea ction of 4a ,b w ith HBF 4 or CF 3COOH. The reactions
were performed similar as described above for the reactions
with 2a ,b , giving [PtCl(PEt3){2-C6H4P(Ph)(NHC6H4R′-4)-
CHPPh2(N′HC6H4R′-4)]-C,C′]+Y- (7a , R′ ) Me, Y ) BF4; 7a ′,
R′ ) Me, Y ) CF3COO; 7b′, R′ ) OMe, Y ) CF3COO) in almost
quantitative amounts. Anal. Calcd for C45H51BClF4N2P3Pt
(7a ): C, 52.64; H, 4.99; N, 2.72; P, 9.02. Found: C, 52.63; H,
5.07; N, 2.67; P, 8.89. FAB MS: found, m/z ) 943 (M+, calcd
for C45H51ClN2P3Pt (7a ), m/z 943.4).
R ea ct ion of 2a ,d w it h CO2. Dry CO2 gas, obtained by
evaporation of solid CO2 and led through CaCl2, was bubbled
through a solution of 0.10 mmol of PtCl(PEt3){CH(PPh2d
NC6H4R′-4)2} (2a ,d ) in 10 mL of CH2Cl2 (or benzene). After
2.5 h (or 3.5 h) stirring, the solution was evaporated to dryness.
The residue contained compound PtCl(PR3){CH(PPh2d
NC6H4R′′-4)(PPh2dO)-C,N} (8a , PR3 ) PEt3, R′′ ) Me; 8d , PR3
) PMe2Ph, R′′ ) OMe) (99.9%), aryl isocyanate (86%), and bis-
(aryl)carbodiimide (14%) according to 1H and 31P NMR. FAB
MS: found for 8a , m/z ) 853 (8a ) and 817 (8a - Cl) (M, calcd
for C38H43ClNOP3Pt, m/z 853.27).
1
2
1
(ddd, Pt-C, J (P,C) ) 46, 70 Hz, J (P,C) ) 2 Hz, J (Pt,C) )
1
n.r.); δ 8.04 (vs, PCH2CH3); δ 15.1 (d, PCH2CH3, J (P,C) ) 27
Hz); C6H4OCH3-4, δ 56.0 and 56.1 (s, OCH3); δ 136.5 and 143.5
(d, Cipso
and 136.5 (d, 2:1:1 Cortho
respectively); δ 114.8 and 115.1 (s, Cmeta); δ 152.7 and 154.8
(s, Cpara); phenyls, δ 126.4 (d, 1Cipso
1J (P,C) ) 94 Hz);
,
2J (P,C) ) 6 and 7 Hz, respectively); δ 122.7, 124.2,
,
3J (P,C) ) 17, 14 Hz and 19 Hz,
,
remaining δ(Cipso) obscured; δ 120-136 (Co,m,p); δ 168.2 (dd,
2
1
C
orthomet, J (P,C) ) 37 and 125 Hz, J (Pt,C) ) n.r.).
P t Cl(P Me2P h ){2-C6H 4-P (P h )(NH C6H 4Me-4)CH P P h 2d
N′C6H4Me-4} (4c). Anal. Calcd for C47H46ClN2P3Pt: C, 58.66;
H, 4.82; N, 2.91; P, 9.66. Found: C, 58.46; H, 4.90; N, 2.96;
P, 9.78. 13C NMR (CDCl3, 293 K, 100.62 MHz): δ 15.4 (br dd,
1
2
1
Pt-C, J (P,C) ) 47, 67 Hz, J (P,C) ) n.r., J (Pt,C) ) n.r.); δ
11.4 (d, PCH3, 1J (P,C) ) 28 Hz); δ 14.0 (d, PCH3, 1J (P,C) ) 33
Hz); C6H4CH3-4, δ 20.4 and 20.6 (s, CH3); δ 139.5 and 146.4
(d, Cipso
and 135.5 (d, 2:1:1 Cortho
respectively); δ(Cmeta) obscured; δ 126.7 and 130.0 (s, Cpara);
,
2J (P,C) ) 5 and 6 Hz, respectively); δ 121.7, 124.0,
,
3J (P,C) ) 17, 13 Hz and 19 Hz,
phenyls, δ 126.1 (d, 1 Cipso,
1J (P,C) ) 91 Hz); remaining δ-
(Cipso) obscured; δ 118-135 (Co,m,p); δ 166.2 (dd, Corthomet, 2J (P,C)
1
) 34 and 129 Hz, J (Pt,C) ) n.r.).
P t C l (P M e 2 P h ){2 -C 6 H 4 P (P h )(N H C 6 H 4 O M e -4 )C H -
1
P P h 2dN′C6H4OMe-4} (4d ). Characterization is based on H
and 31P NMR spectroscopy only.
P tBr (P Et3){2-C6H4P (P h )(NHC6H4Me-4)CHP P h 2dN′C6H4-
Me-4} (4f). Characterization is based on 1H and 31P NMR
spectroscopy only.
Syn th esis of Or th op a lla d a ted Com p ou n d s 5a ,c, [P d Cl-
(P R3){2-C6H4P (P h )(dNC6H4Me-4)CHP P h 2N′HC6H4Me-4}-
C,C′] (P R3 ) P Et3, P Me2P h ). To a solution of freshly
prepared Na[CH(PPh2dNC6H4CH3-4)2] (1a ) (0.48 mmol) in 30
mL of THF was added a solution of Pd2Cl4(PR3)2 (0.24 mmol)
in 10 mL of THF, and the mixture was stirred for 30 min at
20 °C. The cloudy orange solution was then stirred for 7 h at
90 °C, resulting in a color change to yellow. The cloudy yellow
Rea ction of 4c,f w ith CO2. Dry CO2 gas was bubbled
through a solution of 0.10 mmol of 4c,f in 10 mL of benzene.
After 3 h the solution was evaporated to 5 mL. The product
was precipitated by the addition of 20 mL of cold diethyl ether,

2380 Organometallics, Vol. 15, No. 9, 1996
Avis et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for 2e a n d 4a
> 2.0σ(I). Hydrogen atoms were introduced in the last step
of the refinement procedure on calculated positions. Weights
based on counting statistics were used. The weight modifier
compounds
2e
4a
2
K in KF0 is 0.0005. The final difference Fourier showed no
residual density outside -0.28 and 0.53 e Å-3, close to Pt. Atom
scattering factors, which include anomalous scattering con-
tributions, were taken from ref 18. Positional parameters are
listed in Table 2 for 2e. The programs used for the crystal-
lographic computations are listed under ref 19.
Crystal Data
C48H48ClN2P3Pt
976.37
P1h
triclinic
formula
Mr
space group
cryst system
Z
C45H50ClN2P3Pt
942.36
P1h
triclinic
2
2
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 4a . A color-
less, transparent crystal (0.12 × 0.12 × 0.25 mm) was mounted
on a Lindemann-glass capillary and transferred into the cold
nitrogen stream on an Enraf-Nonius CAD4-T diffractometer
on a rotating anode. Accurate unit-cell parameters and an
orientation matrix were determined from the setting angles
of 25 reflections (SET4) in the range 11.5° < θ < 14.0°.20 The
unit-cell parameters were checked for the presence of higher
lattice symmetry.21 Crystal data and details on data collection
and refinement are shown in Table 1. Data were corrected
for Lp effects. An empirical absorption/extinction correction
a, Å
b, Å
c, Å
10.1320(10)
13.880(2)
15.456(2)
103.665(6)
91.399(7)
93.898(7)
2105.4(5)
1.540
9.4085(8)
11.050(2)
19.916(2)
91.732(11)
102.509(9)
93.374(11)
2015.9(5)
1.552
R, deg
â, deg
γ, deg
V, Å3
D
calcd, g cm-3
F(000)
980
35.8
948
37.0
µ
Mo KR, cm-1
cryst size, mm
0.13 × 0.20 × 0.26
Data Collection
295
0.12 × 0.12 × 0.25
22
was applied (DIFABS as implemented in PLATON23). The
T, K
150
structure was solved by automatic Patterson methods and
subsequent difference Fourier techniques (DIRDIF-92).24 Refine-
ment on F2 was carried out by full-matrix least-squares
techniques (SHELXL-93);25 no observance criterion was applied
during refinement. All non-hydrogen atoms were refined with
anisotropic thermal parameters. The hydrogen atoms were
refined with a fixed isotropic thermal parameter amounting
to 1.5 or 1.2 times the value of the equivalent isotropic thermal
parameter of the carrier atoms, for the sp3 and sp2 hydrogen
atoms, respectively. Weights were optimized in the final
refinement cycles. Positional parameters are listed in Table
6 for 4a . The structure contains a small void of 13.7 Å3 at
0.425, 0.136, 0.646. However, no residual density was found
in that area (PLATON/SQUEEZE).26 Neutral atom scattering
factors and anomalous dispersion corrections were taken from
ref 27.
θ
min, θmax, deg
1.0-23.0
1.8, 27.5
λ(Mo KR), Å
0.710 69 (mon)
0.710 73 (graphite
monochr)
ω/2θ
scan type
∆ω, deg
hor and ver apert,
mm
X-ray exposure, h
linear decay, %
ref reflcns
ω/2θ
0.90 + 0.35 tan θ
0.84 + 0.35 tan θ
3.0 + 0.86 tan θ, 4.00 3.53, 4.00
54
3
46
2
1h71, 3h5h5h, 3h5h2h
-11:11, 0:15, -16:16 -11:12, -14:14,
-25:17
6234
5842
0.009
0.768-0.999
230, 33h2h, 22h3h
data set
tot. data
tot. unique data
R(int)
10862
9231
DIFABS corr range
0.951-1.061
Refinement
no. of refined params 496
474
Geometrical calculations and illustrations were performed
with PLATON;23 all calculations were performed on a DEC-
station 5000/125.
final Ra
0.024 [for 5322,
Fo > 4.0σ(Fo)]
0.040
0.059 [for 602,
Fo > 4σ(Fo)]
b
final Rw
final wR2c
S
0.141 (9231 data)
1.00
Resu lts
1.47
w-1 d
σ2(Fo)2 + 0.0005(Fo
0.000, 0.001
-0.28, 0.53
)
σ2(F2) + (0.0824P)2
0.000, 0.003
-4.78, 2.62
2
Syn th esis of P t- a n d P d -Bis(im in op h osp h or a -
n yl)a lk a n id e Com p lexes 2 a n d 3. Reactions of
sodium bis(iminophosphoranyl)alkanide, Na[R′′C-
(PPh2dNC6H4R′-4)2] (1a , R′ ) Me, R′′ ) H; 1b, R′ )
OMe, R′′ ) H; 1c, R′ ) Me, R′′ ) Me), with the dimeric
(∆/σ)av, (∆/σ)max
min and max res
density, e Å-3
(close to Pt)
a
R1 ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑[w(||Fo| - |Fc||)2]/∑[w(Fo2)]]1/2
.
c wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]]1/2
.
P ) (max(Fo2,0) + 2Fc2)/
d
3.
(18) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, England, 1974; Vol. IV.
washed with diethyl ether (2 × 20 mL), and dried in vacuo,
giving the white compound [PtX(PR3){2-C6H4P(Ph)(dO)CHPPh2-
(19) The following references are relevant to the NRCVAX system:
(a) Gabe, E. J .; Le Page, Y.; Charland, J .-P.; Lee, F. L.; White, P. S. J .
Appl. Crystallogr. 1989, 22, 384. (b) Flack, H. Acta Crystallogr. 1983,
A39, 876. (c) J ohnson, C. K. ORTEP-A Fortran Thermal Ellipsoid Plot
Program; Technical report ORNL-5138; Oak Ridge National Labora-
tory: Oak Ridge, TN, 1976. (d) Larson, A. C. Crystallographic
Computing; Munksgaard: Copenhagen, 1970; p 293. (e) Le Page, Y.
L. J . Appl. Crystallogr. 1988, 21, 983. (f) Le Page, Y.; Gabe, E. J . J .
Appl. Crystallogr. 1979, 12, 464. (g) Rogers, D. Acta Crystallogr., Sect.
A 1981, 37, 7.
(20) de Boer, J . L.; Duisenberg, A. J . M. Acta Crystallogr. 1984, A40,
C410.
(21) Spek, A. L. J . Appl. Crystallogr. 1988, 21, 578.
(22) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.
(23) Spek, A. L. Acta Crystallogr. 1990, A46, C34.
(24) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garc´ıa-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF program system; Technical report of the Crystallography
Laboratory, University of Nijmegen: Nijmegen, The Netherlands,
1992.
(25) Sheldrick, G. M. SHELXL-93 Program for crystal structure refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1993.
(26) Spek, A. L. Am. Crystallogr. Assoc. Abstr. 1994, 22, 66.
(27) Wilson, A. J . C., Ed. International Tables for Crystallography;
Kluwer Academic Publishers: Dordrecht, The Netherlands, 1992; Vol.
C.
NHC6H4CH3-4}-C,C′] (9c, PR3 ) PMe2Ph, X ) Cl; 9f, PR3
)
PEt3, X ) Br) in 95-99% yield. The washings contained,
according to 1H NMR, p-tolyl isocyanate and bis(p-tolyl)-
carbodiimide. A similar small-scale experiment was performed
in CDCl3 in 5 mm NMR tube and showed a complete conver-
sion within 10 min. FAB MS: found for 9c, m/z ) 873 (9c),
837 (9c - Cl) (M, calcd for C40H39ClNOP3Pt, m/z 873.3).
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 2e. Crystal
data and experimental procedures on 2e are collected in Table
1. The X-ray data were collected by using an Enraf-Nonius
CAD-4 diffractometer with Mo KR radiation and a graphite
monochromator at 22(1) °C. Unit-cell dimensions were ob-
tained from a least-squares fit to setting angles of 25 reflec-
tions with the 2θ angle in the range 20.0-30.0°. Absorption
corrections were made (µ ) 3.58 mm-1); the minimum and
maximum transmission factors are 0.767 and 0.998. Structure
2e was solved by direct methods and refined by full-matrix
least-squares techniques. The final cycle of the least-squares
refinement gave an agreement factor R of 0.024, wR ) 0.040,
and S ) 1.47, for 496 parameters and 5322 reflections with I

M-N-P-C Metallacycles
Organometallics, Vol. 15, No. 9, 1996 2381
Ta ble 2. F in a l Coor d in a tes a n d Equ iva len t
Isotr op ic Th er m a l P a r a m eter s for th e
Non -Hyd r ogen Atom s for 2e
atom
x
y
z
B(eq), Å2
Pt
Cl
0.243891(17)
0.43363(14)
0.298232(12)
0.40554(11)
0.34532(9)
0.15955(9)
0.18969(10)
0.4042(3)
0.1227(3)
0.2231(3)
0.5076(3)
0.5766(4)
0.6758(4)
0.7170(4)
0.6420(4)
0.5421(4)
0.8211(5)
0.3766(3)
0.3603(3)
0.3849(4)
0.4266(4)
0.4461(4)
0.4211(4)
0.3579(4)
0.4051(4)
-0.4036(4)
0.3590(6)
0.3125(6)
0.3111(5)
0.0570(4)
0.0626(4)
-0.0225(5)
-0.1119(5)
-0.1184(4)
-0.0350(4)
0.2392(3)
0.2902(4)
0.3512(4)
0.3578(5)
0.3076(5)
0.2483(4)
0.0635(4)
0.0121(4)
-0.0423(4)
-0.0471(4)
0.0028(5)
0.0558(5)
-0.1023(5)
0.2320(4)
0.2986(5)
0.3312(5)
0.2965(7)
0.2326(9)
0.1976(6)
0.0609(4)
0.1729(5)
0.1528(4)
0.142432(11) 2.454(9)
0.14099(10)
0.19777(8)
0.25359(8)
0.03562(9)
0.23222(24)
0.2644(3)
0.1623(3)
0.2692(3)
0.2693(3)
0.3073(4)
0.3476(3)
0.3468(3)
0.3093(3)
0.3933(5)
0.1017(3)
0.0228(3)
-0.0523(3)
-0.0484(4)
0.0308(4)
0.1057(4)
0.2827(3)
0.3699(3)
0.4375(4)
0.4186(4)
0.3315(4)
0.2647(4)
0.2193(3)
0.2322(4)
0.2051(4)
0.1690(4)
0.1570(4)
0.1810(4)
0.3550(3)
0.3593(3)
0.4394(4)
0.5160(4)
0.5128(4)
0.4323(4)
0.3168(4)
0.3691(4)
0.4209(4)
0.4237(4)
0.3708(5)
0.3181(4)
0.4833(5)
-0.0680(3)
-0.0840(4)
-0.1616(5)
-0.2240(5)
-0.2102(5)
-0.1325(4)
-0.0019(4)
-0.0582(4)
0.0851(3)
4.41(6)
2.36(5)
2.78(5)
3.08(5)
2.29(15)
3.99(22)
2.42(19)
2.58(19)
3.19(21)
3.9(3)
P(1) -0.00253(11)
P(2)
P(3)
N(1)
0.07067(12)
0.33637(14)
0.1387(4)
N(2) -0.0750(4)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
0.0265(4)
0.1653(5)
0.0721(5)
0.1040(6)
0.2263(7)
0.3192(6)
0.2901(5)
0.2584(9)
4.1(3)
3.81(23)
3.13(22)
6.7(4)
2.57(19)
2.87(21)
3.60(24)
3.9(3)
C(9) -0.0806(5)
C(10) -0.0146(5)
C(11) -0.0691(6)
C(12) -0.1881(6)
C(13) -0.2516(5)
C(14) -0.1999(5)
C(15) -0.1222(4)
C(16) -0.0839(5)
C(17) -0.1720(6)
C(18) -0.2944(6)
C(19) -0.3367(6)
C(20) -0.2499(5)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33) -0.1329(5)
C(34) -0.0676(5)
C(35) -0.1369(6)
C(36) -0.2702(5)
C(37) -0.3366(6)
C(38) -0.2708(6)
C(39) -0.3448(7)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
4.2(3)
3.68(24)
2.79(20)
3.31(22)
4.1(3)
5.1(3)
5.6(4)
4.5(3)
3.15(22)
4.0(3)
5.3(3)
5.9(4)
5.5(4)
4.3(3)
2.80(20)
3.20(23)
4.3(3)
5.0(3)
4.9(3)
3.85(25)
3.78(24)
3.7(3)
3.9(3)
4.0(3)
4.8(3)
4.8(3)
5.3(3)
3.37(23)
5.2(3)
6.6(4)
7.0(5)
8.6(6)
6.5(4)
5.0(3)
4.6(3)
cycles 2a -f, however, are stable in CH2Cl2 and CHCl3,
whereas the palladium compounds 3a -c decompose in
these solvents after 1 day at 20 °C. The products 2 and
3 are soluble and stable in THF, benzene, and toluene
and slightly soluble in Et2O and pentane. In solution
they are unstable in air, due to reactivity with CO2 (vide
infra) and probably also H2O; however, they are quite
air-stable in the solid state.
0.1752(5)
0.3127(6)
0.3818(7)
0.3140(9)
0.1799(8)
0.1107(6)
0.1513(5)
0.2745(5)
0.3273(6)
0.2559(8)
0.1343(8)
0.0818(6)
The use of Li+[HC(PPh2dNAr)2]-, as reported earlier
by Imhoff et al. for the synthesis of related Rh- and
Ir-bis(iminophosphoranyl)methanide complexes,4 also
resulted in the formation of 2 and 3 but proved less
suitable for these reactions as a result of LiX formation
instead of NaX, due to the fact that LiX is more finely
dispersed, which makes filtration difficult. The com-
plexes 2 and 3 are thermally unstable; at higher
temperatures (30-80 °C) they undergo orthometalation
reactions resulting in the complexes 4 and 5, respec-
tively (vide infra). The four-membered metallacycles 2
and 3 were analyzed by X-ray crystallography (2e),
0.3368(5)
0.4354(7)
0.4328(9)
0.3342(10)
0.2406(10)
0.2389(7)
0.2695(7)
0.5093(6)
1
elemental analysis or mass spectroscopy, and H NMR
(selected data in Table 4 and complete data in Support-
ing Information), 31P, and 13C NMR spectroscopy (Table
5 and Experimental Section).
X-r a y Cr ysta l Str u ctu r e of P tCl(P Me2P h ){C(Me)-
(P P h 2dNC6H4Me-4)2} (2e). The molecular structure
of 2e with the adopted atomic labeling scheme is shown
in Figure 1. Selected bond distances and bond angles
have been compiled in Table 3. Figure 1 shows a
distorted monomeric square-planar Pt(II) complex, with
N(1) and C(1) of the C,N chelated 1,1-bis(iminophos-
phoranyl)ethanide ligand, [CMe(PPh2dN-p-tolyl)2]-, po-
sitioned trans to P(3) and Cl, respectively. The resulting
small N(1)-Pt-C(1) angle, 73.74(16)°, and folding angle
within the four-membered Pt-N(1)-P(1)-C(1) ring
around the N(1)‚‚‚C(1) axis, 34.75(19)°, are character-
istic features for such metallacyclic systems. For in-
stance, the two related cationic four-membered plati-
nacycles [PtCl(PMe2Ph){CH(PPh2dN-p-tolyl)(PPh2NH-
p-tolyl)}-C,N]+[Cl]- (A)12 and [PtCl(PEt3){CH(PPh2dN-
p-tolyl)(PPh2NH-p-tolyl)}-C,N]+[Pt(PEt3)Cl3]- (B)12 have
similar N-Pt-C angles (73.2(3) and 73.1(4)°) and are
folded by 32.7(4) and 36.4(4)°. Other C,N-chelated
C(48) -0.0198(5)
3.38(22)
platinum and palladium precursors M2X4(PR3)2 (M )
Pt(II), Pd(II); PR3 ) PEt3, PMe2Ph; X ) Cl, Br) resulted
in the formation of new four-membered metallacycles
2 and 3. The ligand is σ-C,σ-N coordinated to the metal
in all cases, leaving one of the -PPh2dN-aryl entities
noncoordinated (eq 1).
The bridge-splitting transmetalation reactions are
best performed in THF at 20 °C giving good yields (84-
95%); other solvents like toluene or CH2Cl2 are unsuit-
able for this purpose. In toluene no precipitation of NaX
occurs, which suggests that the reaction proceeds much
slower or stops at an intermediate stage. The trans-
metalation reaction continues after redissolving the
intermediate in THF, as visualized by the precipitation
of NaX. In CH2Cl2 or CHCl3 decomposition takes place,
due to instability of the anionic ligands. The platina-

2382 Organometallics, Vol. 15, No. 9, 1996
Avis et al.
respectively. Although 2e contains an C,N-coordinated
1,1-bis(iminophosphoranyl)ethanide ligand, having a
methyl group instead of an hydrogen atom on the
coordinating C(1), the Pt-C(1) bond length of 2.116(4)
Å is within the range found for other related compounds
containing a Pt-C(sp3) bond in a four-membered
ring.3a,12,32
Comparison of the phosphinimine bond lengths within
the complex 2e clearly shows that the P(1)-N(1) bond,
1.612(4) Å, is significantly elongated due to coordination
to Pt. A value between 1.60 and 1.64 Å is normal for
this type of coordinated phosphinimine.4,7,8f,12,13,29-31,33
The much shorter P(2)-N(2) distance in 2e, 1.555(4) Å,
is indicative for a P-N double bond, since it is compa-
rable to the PdN bonds in the free 1,1-bis(iminophos-
phoranyl)ethanide ligand (1,1-BIPE) (d(P-N) ) 1.559(3)
and 1.553(3) Å).13
One striking difference between the crystal structures
of the neutral complex 2e and its closely related Ir-
bis(iminophosphoranyl)methanide complex4 is the ori-
entation of the noncoordinated PPh2dN-p-tolyl entity.
In 2e, it is pointed away from the platinum center
(torsion angles P(1)-C(1)-P(2)-N(2) ) 75.4(2)° and Pt-
C(1)-P(2)-N(2) ) 172.5(3)°), whereas in the Ir complex
this group is directed toward the Ir center (torsion
angles P-C-P-N ) -42.9(9)° and Ir-C-P-N ) 55.4-
(8)°).4 A similar phenomenon has also been found for
the related complex [PtCl(PEt3){CH(PPh2dS)2}], wherein
the noncoordinated PdS group of the C,S-coordinated
ligand is pointed toward the Pt center.3a Probably, the
steric influence of the methyl group on C(1) is respon-
sible for the unusual orientation of the noncoordinated
PdN group in complex 2e.
F igu r e 1. ORTEP plot of 2e at the 30% probability level.
Ta ble 3. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for 2e
Distances around Pt
Pt-P(3)
Pt-Cl
2.2283(13)
2.3544(13)
Pt-C(1)
Pt-N(1)
2.116(4)
2.132(4)
Distances within Phosphine
P(3)-C(40)
P(3)-C(46)
1.831(5)
1.821(6)
P(3)-C(47)
1.819(6)
Distances within Ligand
Sp ectr oscop ic Ch a r a cter iza tion of th e F ou r -
1
P(1)-N(1)
N(1)-C(2)
P(1)-C(1)
P(1)-C(9)
P(1)-C(15)
1.612(4)
1.418(6)
1.829(5)
1.820(5)
1.795(5)
P(2)-N(2)
N(2)-C(33)
P(2)-C(1)
P(2)-C(21)
P(2)-C(27)
1.555(4)
1.396(7)
1.834(5)
1.818(5)
1.828(5)
Mem ber ed Meta lla cycles 2 a n d 3. The H and 31P-
{1H} NMR data for the four-membered metallacycles 2
and 3 are listed in Tables 4 and 5. 13C{1H} NMR data
(only for 2a ,b,c,e and 3a ,b) are given in the Experi-
1
mental Section. The H NMR spectra of Pt-bis(imino-
Angles around Pt
phosphoranyl)methanides 2a -d and 2f show the CH
resonance in the region 2.44-2.64 ppm as a broad
multiplet due to coupling with three different phospho-
Cl-Pt-P(3)
Cl-Pt-C(1)
Cl-Pt-N(1)
86.20(5)
169.58(13)
95.93(10)
N(1)-Pt-C(1)
P(3)-Pt-N(1)
P(3)-Pt-C(1)
73.74(16)
172.98(10)
104.22(13)
2
rus atoms and J (Pt,H) of about 60 Hz,34 which estab-
Angles within Ligand
92.58(17) P(1)-N(1)-C(2)
132.2(3) P(2)-N(2)-C(33)
lishes the presence of a Pt-C linkage, and agrees with
earlier reported NMR data for compound 2a obtained
from a reaction of Pt2Cl4(PEt3)2 with 4 equimolar
amounts of CH2(PPh2dNC6H4Me-4)2.12 The 13C NMR
spectra of 2a -c show methine carbon resonances be-
tween 1.5 and 2.0 ppm (dd, 1J (P,C) ) 58-95 Hz; 1J (Pt,C)
was not observed). The corresponding 13C resonance for
2e lies somewhat higher, 4.82 ppm (dd), whereas the
Me group on this coordinated C atom is found at 15.27
ppm. The Pt-bis(iminophosphoranyl)ethanide complex
2e has a characteristic doublet of doublet resonance in
Pt-N(1)-P(1)
Pt-N(1)-C(2)
N(1)-P(1)-C(1)
N(1)-P(1)-C(9)
127.6(3)
133.0(4)
95.41(20) N(2)-P(2)-C(1)
115.69(20) N(2)-P(2)-C(21)
104.91(22)
112.07(25)
114.3(3)
107.37(22)
112.31(21)
N(1)-P(1)-C(15) 113.39(21) N(2)-P(2)-C(27)
C(1)-P(1)-C(9)
108.96(21) C(1)-P(2)-C(21)
C(1)-P(1)-C(15) 116.22(22) C(1)-P(2)-C(27)
C(9)-P(1)-C(15) 107.10(21) C(21)-P(2)-C(27) 105.78(22)
Pt-C(1)-P(1)
Pt-C(1)-P(2)
P(1)-C(1)-P(2)
87.26(18) Pt-C(1)-C(48)
113.89(22) P(1)-C(1)-C(48)
112.01(24) P(2)-C(1)-C(48)
122.2(3)
113.2(3)
107.1(3)
(iminophosphoranyl)methanides show comparable
N-M-C angles and ring puckering, i.e. for [Ir{CH-
(PPh2dN-p-tolyl)2}COD] a N-Ir-C angle of 73.4(4)°
and folding of 35.1°,4,28 for [Rh(COD){CH2PPh2dN-p-
tolyl}] a N-Rh-C angle of 74.2(2)° and folding of
30.4°,29 and for [Rh(COD){CH(PPh2dN-p-tolyl)(PPh2-
NH-p-tolyl)}]+ values of 73.1(1) and 33.6°,28,30 respec-
tively.
(28) Folding angles are unpublished results by P. Imhoff.
(29) Imhoff, P.; Nefkens, S. C. A.; Elsevier, C. J .; Vrieze, K.; Goubitz,
K.; Stam, C. H. Organometallics 1991, 10, 1421.
(30) Imhoff, P.; Elsevier, C. J . J . Organomet. Chem. 1989, 361, C61.
(31) Allen, C. W. Coord. Chem. Rev. 1994, 130, 137.
(32) Kemmitt, R. D. W.; Mason, S.; Moore, M. R.; Fawcett, J .;
Russell, D. R. J . Chem. Soc., Dalton Trans. 1990, 1535.
(33) Imhoff, P.; van Asselt, R.; Elsevier, C. J .; Zoutberg, M. C.; Stam,
C. H. Inorg. Chim. Acta 1991, 184, 73.
(34) 2J (Pt,H) is determined by 1H{31P} NMR spectroscopy in all
cases. A coupling between 40 and 80 Hz is normal of Pt-CH σ-bond
interactions. See e.g.: Henderson, W.; Kemmitt, R. D. W.; Prouse, L.
J . S.; Russell, D. R. J . Chem. Soc., Dalton Trans. 1990, 1853 and ref
12.
The Pt-N(1) distance of 2.132(4) Å for complex 2e is
somewhat longer than the corresponding Pt-N bonds
in the cations A and B, i.e. 2.099(6) and 2.124(8) Å),12

M-N-P-C Metallacycles
Organometallics, Vol. 15, No. 9, 1996 2383
Ta ble 4. Selected 1H NMR Da ta (p p m ) for th e Com p lexes 2-9a
typeb
solvent/T (K)
P-alkylc
δ(M-CH)d
2.47 (m)
2.44 (m)
2.52 (m; 2.5, nr, 12.8)
2.64 (m)
2J (Pt,H), Hz
δ(NH)d
2a
2b
2c
2d
2ee
2f
3a
3b
3c
FMP
FMP
FMP
FMP
FMP
FMP
FMP
FMP
FMP
OM
OM
OM
OM
OM
OM
OM
FMP
FMP
OM
CD2Cl2
CD2Cl2/233
CDCl3/253
C6D6/283
CDCl3
CDCl3
CD2Cl2
C6D6
tol-d8
CDCl3
C6D6
CDCl3
tol-d8
CDCl3
C6D6
0.99 (dt), 1.66 (m), 1.93 (m)
1.05 (dt), 1.65 (m), 2.01 (m)
1.35 (d), 1.49 (d)
1.16 (d), 1.41 (d)
0.73 (d), 1.65 (d)
59
58
67
nr
f
0.95 (dt), 1.6-1.9 (m)
1.03 (dt), 1.9 (m)
2.6 (m)
obs
2.02 (dt; 1.9, 7.7)
obs
3.25 (dt; 6.9, 16.6)
nr
2.88 (dt; 7.5, 15.0)
2.84 (m)
3.35 (dt; 6.8, 15.7)
4.24 (ddd; 7.0, 11.2, 16.0)
4.09 (ddd; 7.4, 11.7, 15.4)
3.37 (m)
nr
0.92 (dt), 1.93 (m)
1.3 (br)
0.61 (dt), 1.14 (m)
0.56 (dt), 1.11 (m)
1.12 (d), 1.22 (d)
4a
86
nr
86
75
nr
nr
4bg
4c
11.2 (br)
10.7 (br)
11.2 (br)
4d g
4fg
5a
1.11 (d), 1.19 (d)
0.56 (dt), 1.17 (m)
0.75 (dt), 1.49 (m)
0.93 (d), 1.42 (d)
0.86 (dt), 1.12 (m), 1.39 (m)
0.91 (dt), 1.12 (m), 1.40 (m)
0.56 (dt), 1.11 (m)
0.61 (dt), 1.15 (m)
0.63 (dt), 1.15 (m)
0.99 (dt), 1.68 (m), 1.95 (m)
1.32 (d), 1.48 (d)
nr
10.2 (br)
5c
6a
tol-d8
nr
CD2Cl2
CD2Cl2
C6D6
C6D6
C6D6
CDCl3
C6D6
CDCl3
CDCl3
60
63
70
94
nr
nr
nr
91
88
obsh
6b
7a g
7a ′
7b′
8a
3.88 (m)
4.51 (m)
10.5 (br d; 7)
nr
9.4 (br), 11.7 (d; 8.3)
9.2 (br), 11.5 (d; 7.9)
OM
OM
FMP
FMP
OM
4.98 (ddd; 6.8, 12.2, 13.9)
4.96 (dt; 6.6, ∼14)
∼2.3 (obs)i
g
8d
9c
2.31 (m)
1.24 (d), 1.34 (d)
0.64 (dt), 1.22 (m)
2.61 (dt; 7.4, 13.0)
3.22 (dt; 6.7, 13.3)
8.9 (d; 6.3)
10.0 (d; 7.2)
9fg
OM
a
Recorded at 300.13 MHz at 293 K, unless noted otherwise. Complete 1H NMR data are listed in the Supporting Information. Multiplets
and abbreviations: d ) doublet, dd ) doublet of doublet, dt ) doublet of triplet, ddd ) doublet of double doublet, m ) multiplet, br )
b
broad; nr ) not resolved, obs ) obscured. FMP ) four-membered platina- or palladacycle, OM ) orthometalated compound. c For Et3P:
δ(P-CH2-CH3) (dt) and δ(P-CH2-CH3) (m) are given successively, with coupling constants 3J (H,H) ) 7.5 Hz, 3J (P,H) ) 15.0 Hz, and
d
2J (P,H) ) n.r. For Me2PhP: δ(P-CH3) (d) with 2J (P,H) ≈ 8.7-9.0 Hz. Multiplicity and nJ (P,H) (with n ) 2 or 3) are given succesively.
g
h
e Measured at 500 MHz. f δ(Pt-CMe) ) 1.68 ppm (dd, 3J (P,H) ) 19.1, 17.9 Hz). Measured at 100.13 MHz. δ(NH) is obscured by phenyl
i
proton resonances. δ(CH) is obscured by the methyl resonance of the p-tolyl group on N.
Ta ble 5. 31P NMR Da ta for th e F ou r -Mem ber ed Meta lla cycles 2, 3, 6 a n d 8a
solvent/T (K)
δ(PA)
δ(PB)
δ(PC)
1J (Pt,PA)
2J (Pt,PB)
2J (Pt,PC)
2J (PB,PC)
2a
2b
2c
2d
2e
2f
CD2Cl2/253
CD2Cl2/253
CDCl3/253
tol-d8/293
CDCl3/293
CDCl3/293
CD2Cl2/293
CD2Cl2/183
CDCl3/293
CD2Cl2/190
tol-d8/293
d/184
0.7 (s)
0.8 (s)
32.5 (d)
32.1 (d)
35.2 (d)
29.8 (br)
45.0 (br)
30.5 (br)
15.7 (br)c
25.8 (d)
15.5 (br)c
25.0 (d)
12.8 (br)c
27.6 (br)
27.2 (d)
28.5 (s)e
30.3 (s)
8.0 (d)
7.0 (d)
3.2 (d)
3740
3735
3784
3840
3913
3713
426
413
424
427
427
427
114
108
87
91
89
3.9
3.6
6.5
nr
nr
nr
-21.4 (s)
-21.6 (s)
-22.6 (s)
-0.7 (s)
29.1 (br)
29.9 (s)
28.7 (br)
29.7 (s)
3.5 (br)
5.0 (s)
-0.3 (s)
0.3 (s)
1.0 (s)
-21.8 (s)
-1.6 (br)
7.8 (br)
5.5 (br)
15.7 (br)c
12.1 (d)
15.5 (br)c
11.1 (d)
12.8 (br)c
7.5 (br)
29.9 (d)
28.5 (s)e
30.3 (s)
25.0 (d)
96
3a
13.9
11.8
3b
b
3c
b
6a
6b
8a
8d b
nr
CD2Cl2/293
tol-d8/293
CDCl3/293
C6D6/293
3576
3616
3733
3821
400
402
425
429
117
103
129
110
10.2
9.4
nr
30.2 (d)
3.9
a
Recorded at 40.53 MHz, unless noted otherwise. J values in Hz. Multiplicity labels and abbreviations: br ) broad, s ) singlet, d )
doublet, dd ) doublet of doublet, nr ) not resolved. Recorded at 121.48 MHz. c Italicized values are averages by exchange. CD2Cl2
b
d
mixed with CDCl3. e δ(PB) ) δ(PC). In CD2Cl2 two separate signals at δ(PB) ) 32.1 (d) and δ(PC) ) 29.5 (d) are found.12
1
the H NMR at 1.68 ppm (3J (P,H) ) 19.1 and 17.9 Hz)
belonging to the methyl group on the coordinated C.
This signal is slightly shifted to lower frequency, when
compared to Na+[MeC(PPh2dNC6H4Me-4)2]- (1c) (see
Experimental Section). Support for the C,N coordina-
tion of the ligand to Pt and Pd was also provided by
2c,d , containing a prochiral phosphine PMe2Ph. As C,N
coordination induces chirality on the coordinated sp3-
carbon atom, two sets of signals are observed for the
complexes in solution is similar to the solid-state
structure, which has been established for 2e (Figure 1).
As reported earlier for complex 2a ,12 the platinacycles
1
2a -f show broadening of most H, 31P, and 13C signals
at 293 K, which has been attributed to a dynamic
process involving slow N,N′ exchange of the C,N-
coordinated ligand at 293 K. For 2a -f broad resonances
are found in 31P NMR at 293 K for PB (29.8-45.0 ppm)
and PC (-1.6 to 8.0 ppm), whereas the peak due to PAR3
is hardly broadened and shows characteristic 1J (Pt,PA)
coupling of 3713-3913 Hz for trans P-Pt-N com-
diastereotopic PMe groups in the H and 13C NMR. All
data indicate that the molecular structure of the Pt
1

2384 Organometallics, Vol. 15, No. 9, 1996
Avis et al.
plexes.12,35 The 2J (Pt,PB) value, ranging from 413 to 427
Hz, is characteristic for these types of four-membered
platinacycles.12 Similar two-bond Pt,P couplings have
been reported for related C,X-coordinated Pt com-
pounds, i.e. PtCl(PR3){CH(PPh2dX)(PPh2dY)} (X, Y )
S, O, Se).3 Cooling the solution to 253 K (2a -c) resulted
in sharpening of the PB and PC signals into doublets
(2J (PB,PC) ) 3.6-6.5 Hz).
For the palladium complexes 3a -c the CH resonance
is found at about 2 ppm, although it is obscured for 3a ,c
by the 4-CH3C6H4 signal, and is evident from the 13C
NMR CH signal at 9.01 ppm (vt, 1J (P,C) ) 82 Hz). The
Pd complexes 3a -c, in contrast to their Pt analogues,
are in the fast exchange mode relative to the NMR time
scale. In the 1H NMR and 13C NMR at ambient
temperature only a single set of resonances is found for
the NC6H4R′-4 groups, whereas the Pt complexes show
two sets of resonances for each group. For compound
3c, containing a prochiral PMe2Ph ligand, only one
broad PMe signal at 1.3 ppm is observed at 293 K, which
resolves into two broad signals (“doublets”) at 185 K,36
similar to what has been observed for the Pt complexes
2c,d . Evidently, the exchange process results in inver-
sion of configuration at the sp3-carbon.
were synthesized in fairly good yield (39-80%) by
reaction of M2X4(PR3)2 (M ) Pt(II), Pd(II); PR3 ) PEt3,
PMe2Ph; X ) Cl, Br) with
2 equiv of Na[HC-
(PPh2dNC6H4R′-4)2] at elevated temperatures (70-90
°C). Also, when the neutral C,N-coordinated four-
membered metallacycles 2 and 3 were heated in THF
or toluene solution, orthometalation of one of the phenyl
-
groups of the CH(PPh2dNC6R′-4)2 ligand took place
(eqs 2 and 3). Unfortunately, 2e could not be converted
into an orthometalated product due to decomposition
during prolonged stirring or heating, visible by the
formation of Pt(0).
The same phenomenon is found in the 31P NMR for
the signals of the two PdN-aryl groups of the coordi-
nated ligand, implying equivalence of these groups on
the NMR time scale at 293 K. At 183-190 K the slow-
exchange regime is reached for 3a ,b.36a The initially
broad 31P resonance at approximately 12.8-15.7 ppm
splits into two doublets, one in the region 25.0-27.6
ppm and the other around 7.5-12.1 ppm, with mutual
PB,PC coupling of 11.8-13.9 Hz. The latter is assigned
to the noncoordinated PCdN function, since it shows the
strongest resemblance with the frequency of a free
R3PdNR′ ligand.13,17
From the fact that the palladium complexes 3 show
similar fluxional behavior as observed for their platinum
analogues 2, like in PtCl(PEt3){CH(PPh2dS)2}3 and
PtCl(PEt3){C(PPh2dS)3}37 with S trans to PEt3, it is
deduced that the complexes 3 have N trans to the
phosphine, i.e. the trans influence of the phosphine is
causing the relative weakness of the M-N (M ) Pt, Pd)
and Pt-S bonds. A complex with the opposite geometry
would not show such dynamic behavior, which has been
established for the “rigid” complex PtCl(PEt3){CH-
(PPh2dS)2} with S trans to Cl.3
For both 2 as 3, the broadness of the 1H and 31P
signals at room temperature does not change signifi-
cantly upon variation of the complex concentration,
which means that the N,N′ exchange takes place via
an intramolecular process.
The ligand in 4 is σ-C,σ-C′ coordinated to the platinum
center by the methanide-C, bridging the two phosphin-
imine functions of the ligand, and by the ortho-C of the
metalated phenyl group on P, resulting in a five-
membered ring. The sp3-carbon atom is still coordi-
nated trans to the Pt-X bond, as in the neutral four-
membered platinacycles 2. The original ortho-H of the
phenyl group has shifted to the noncoordinated N atoms
forming a H-bridge between them. Its exact position
has been determined by means of a crystal structure
1
determination of 4a and has been corroborated by H
and 31P NMR spectroscopy (Tables 4 and 8). The
orthometalated Pd complex 5 shows much resemblance
to its Pt analogue but has the opposite geometry; i.e.
the sp3-carbon atom is coordinated trans to the Pd-PR3
bond. In eq 3 two structural proposals are given for 5,
either of which is consistent with the data (see spec-
troscopic characterization). Complexes 4 and 5 repre-
sent rare examples of orthometalated complexes with
a C,C′-coordinating ligand.14,38a,39
Syn th esis of Or th om eta la ted P la tin u m a n d P a l-
la d iu m Com p lexes 4 a n d 5. New orthometalated
platinum(II) and palladium(II) complexes 4 and 5
containing the bis(iminophosphoranyl)methanide ligand
[HC(PPh2dNC6H4R′-4)2]- (1a , R′ ) Me; 1b, R′ ) OMe)
(35) (a) Van der Poel, H.; Van Koten, G.; Vrieze, K. Inorg. Chem.
1980, 19, 1145. (b) Chivers, T.; Doxsee, D. D.; Hilts, R. W.; Meetsma,
A.; Parvez, M.; Van de Grampel, J . C. J . Chem. Soc., Chem. Commun.
1992, 1330. (c) Pregosin, P. S. 31P and 13C NMR of Transition Metal
Phosphorus Compounds; Springer Verlag: New York, 1979.
(36) (a) The slow-exchange limit for 3c, which lies just below 185
K, was not reached. (b) Recording of 13C NMR was impossible due to
the low solubility of the complexes at low temperatures.
For the (PMe2Ph)-Pt and -Pd complexes 2c,d and
3c, the reaction to 4c,d and 5c already proceeds at room
(38) (a) Liu, C.-H.; Li, C.-L.; Cheng, C.-H. Organometallics 1994,
13, 18. (b) Vicente, J .; Saura-Llamas, I.; J ones, P. G. J . Chem. Soc.,
Dalton Trans. 1993, 3619.
(37) Browning, J .; Beveridge, K. A.; Bushnell, G. W.; Dixon, K. R.
Inorg. Chem. 1986, 25, 1987.
(39) Avis, M. W.; van der Boom, M. E.; Elsevier, C. J .; Smeets, W.
J . J .; Spek, A. L. To be published.

M-N-P-C Metallacycles
Organometallics, Vol. 15, No. 9, 1996 2385
Ta ble 6. F in a l Coor d in a tes a n d Equ iva len t
Isotr op ic Th er m a l P a r a m eter s for th e
Non -Hyd r ogen Atom s for 4a
atoma
x
y
z
U(eq), Å2
Pt(1)
Cl(1)
P(1)
P(2)
P(3)
N(1)
N(2)
C(1)
C(2)
-0.10216(3)
-0.3286(2)
-0.0137(2)
0.0893(2)
0.0903(2)
0.2194(7)
0.1996(7)
0.1771(9)
0.2821(11)
0.24179(3) 0.24718(2)
0.0214(1)
0.1294(2)
0.0656(2)
0.4242(2)
0.4586(2)
0.5332(6)
0.5722(6)
0.0535(9)
0.22929(11) 0.0358(6)
0.21123(12) 0.0343(7)
0.34300(10) 0.0207(5)
0.19278(10) 0.0224(6)
0.3609(3)
0.2243(3)
0.2084(5)
0.0260(17)
0.029(2)
0.040(3)
0.057(4)
0.036(4)
0.033(6)
0.078(7)
0.042(7)
0.025(4)
0.030(5)
0.032(5)
0.048(6)
0.025(2)
0.030(2)
0.030(3)
0.026(2)
0.028(2)
0.024(2)
0.042(3)
0.020(2)
0.027(2)
0.043(3)
0.039(3)
0.029(3)
0.028(2)
0.027(2)
0.034(3)
0.040(3)
0.042(3)
0.028(2)
0.026(2)
0.0213(19)
0.023(2)
0.026(2)
0.036(3)
0.034(3)
0.028(2)
0.027(2)
0.024(2)
0.032(3)
0.038(3)
0.039(3)
0.038(3)
0.029(3)
0.024(2)
0.025(2)
0.030(3)
0.028(3)
0.031(3)
0.029(2)
0.052(4)
0.0616(10) 0.2782(6)
*C(3A) -0.1053(16) -0.0196(14) 0.1337(7)
*C(3B) -0.093(2)
*C(4A) -0.103(3)
*C(4B) -0.070(3)
0.064(2)
0.053(2)
-0.050(2)
0.1159(12)
0.0738(14)
0.0773(13)
*C(5A) -0.0355(18) -0.0668(14) 0.2707(9)
*C(5B) -0.081(2)
-0.0613(16) 0.2374(11)
*C(6A) -0.0142(19) -0.0289(16) 0.3459(9)
23
F igu r e 2. ORTEP plot of 4a at 50% probability level.
*C(6B) -0.077(3)
C(7)
C(8)
C(9)
-0.060(2)
0.6185(7)
0.5836(7)
0.6684(8)
0.7908(7)
0.8255(7)
0.7408(7)
0.8817(9)
0.3151(6)
0.2650(7)
0.1812(9)
0.1509(9)
0.2003(8)
0.2827(8)
0.4678(7)
0.5677(8)
0.5937(9)
0.5170(9)
0.4161(7)
0.3876(7)
0.3545(7)
0.4985(7)
0.6144(7)
0.6488(8)
0.5744(8)
0.4606(7)
0.4236(7)
0.3744(7)
0.3286(8)
0.2705(9)
0.2606(9)
0.3102(9)
0.3667(8)
0.6597(7)
0.7417(7)
0.8286(7)
0.8393(7)
0.7606(7)
0.6724(7)
0.9336(9)
0.3147(12)
0.4178(4)
0.4859(4)
0.5394(4)
0.5279(4)
0.4595(4)
0.4059(4)
0.5878(5)
0.4086(4)
0.4351(4)
0.4863(5)
0.5111(5)
0.4839(4)
0.4333(4)
0.3331(4)
0.3646(4)
0.3468(5)
0.3014(5)
0.2709(4)
0.2860(4)
0.2618(3)
0.1556(4)
0.1741(4)
0.1524(5)
0.1096(4)
0.0897(4)
0.1139(4)
0.1272(4)
0.1487(4)
0.1031(5)
0.0346(5)
0.0124(5)
0.0577(4)
0.1852(4)
0.2186(4)
0.1835(5)
0.1130(4)
0.0801(4)
0.1153(4)
0.0743(5)
Hydrogen atoms were left out for clarity. Only the major
disorder from the triethylphosphine is shown.
0.2561(8)
0.2849(8)
0.3265(8)
0.3397(8)
0.3099(8)
0.2682(8)
0.3870(10)
0.1272(7)
0.0142(8)
0.0425(9)
0.1814(9)
0.2947(8)
0.2671(8)
-0.0926(8)
-0.1350(9)
-0.2830(10)
-0.3800(9)
-0.3348(8)
-0.1885(8)
0.0868(7)
-0.0934(7)
-0.1287(8)
-0.2695(9)
-0.3737(8)
-0.3380(8)
-0.1988(8)
0.1582(8)
0.2929(8)
0.3595(9)
0.2931(9)
0.1590(10)
0.0904(8)
0.2546(8)
0.3690(8)
0.4284(9)
0.3806(9)
0.2666(9)
0.2043(8)
0.4474(12)
temperature, which contrasts with their PEt3 analogues.
For the (PMe2Ph)Pd compound 3c, the reaction to 5c is
completed within 24 h at 20 °C, whereas for Pt com-
pounds 2c,d it takes about 3-7 days to convert into 4c,d
at 20 °C.
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
The reason for the moderate yield of 4 is not clear.
When a small-scale reaction is carried out in toluene-
d8 in a NMR tube, 100% conversion of 2 into 4 is
observed. At larger scale a significant amount of the
neutral C,N-coordinated complex 2 is still present,
which is washed out with Et2O or pentane. The
platinum compounds 4 are highly soluble in CH2Cl2,
CHCl3, and THF, are less soluble in toluene or benzene,
and are insoluble in Et2O or pentane, whereas the
palladium compounds 5 are more soluble in toluene and
are slightly soluble in pentane also. In solution they
are unstable in air, due to the aza-Wittig reactivity with
CO2 (vide infra). However when pure oxygen was
bubbled through a CH2Cl2 solution of 4b, or H2O was
added, no reaction took place. An attempt to increase
the rate of the reaction or the conversion by further
increase of the temperature (120 °C in toluene) or longer
reaction time (10 h) failed. Blackening of the solution
occurs as a result of decomposition into Pt(0) and Pd-
(0), which lowers the yield.
X-r a y Cr ysta l Str u ctu r e of [P tCl(P Et3){2-C6H4P -
(P h )(NH C6H 4CH 3-4)CH P P h 2dNC6H 4CH 3-4]-C,C′]
(4a ). The molecular structure of 4a with the adopted
atomic labeling scheme is shown in Figure 2. Selected
bond distances and angles have been compiled in Table
7. The structure of 4a shows a monomeric neutral
complex in which the Pt(II) center is square-planar-
surrounded by P(1), Cl(1), C(25), and C(26); the latter
carbons belong to the orthometalated bis(iminophos-
phoranyl)methanide ligand. Complex 4a represents one
of the few examples of orthometalated complexes of Pt
and Pd, containing C,C′-chelated ligands, that have been
characterized crystallographically.14be,39
a
The asterisks indicate disordered atoms.
the strong trans influence caused by sp2-C(25), when
compared to the Pt-P bond in 2e (2.2283(13) Å) trans
to N or d(Pt-P) of 2.245(4) Å trans to S in [PtCl(PEt3)-
{CH(PPh2dS)2}].3a
The ortho sp2-carbon atom, C(25), of the orthometa-
lated phenyl group on P(2), is directly attached to the
Pt center, resulting in a Pt-C(25) distance of 2.050(8)
Å, which is in the range of d(Pt-C) values (1.975-2.051
Å) found for other orthometalated Pt complexes.14b,40
The five-membered metallacycle in 4a also strongly
An isotropic refinement has been carried out for the
Et3P ligand, since it is considerably distorted. The
relatively long Pt-P(1) bond (2.315(2) Å) directly reflects
resembles the C,C′-chelate ring in [PdCl{2-(4-Me-
(40) (a) Stoccoro, S.; Cinellu, M. A.; Zucca, A.; Minghetti, G.;
Demartin, F. Inorg. Chim. Acta 1994, 215, 17. (b) Crespo, M.; Solans,
X.; Font-Bard´ıa, M. Organometallics 1995, 14, 355. (c) Mdleleni, M.
M.; Bridgewater, J . S.; Watts, R. J .; Ford, P. C. Inorg. Chem. 1995,
34, 2334.
14e
C6H3)P(pTol)2CHPy}-C,C′]2
and [PdCl2{2-C6H4PPh-
(NHpTol)CHPPh2NHpTol}-C,C′].39 The H atom that
originated from the ortho position of the phenyl group

2386 Organometallics, Vol. 15, No. 9, 1996
Avis et al.
and 13C{1H} NMR data of the orthometalated complexes
4 and 5 are listed in Table 8 and the Experimental
Section, respectively. Direct evidence for orthometala-
tion in 4 was obtained from the 13C NMR spectra of 4a -
c, showing a characteristic sp2-C resonance at ca. 167
ppm, a doublet of doublets as a consequence of coupling
with PAR3 trans to it (2J (PA,Com) ) 125-129 Hz) and
PB (2J (PB,Com) ) 34-36 Hz). This corresponds well with
the values reported for other orthometalated Pt and Pd
complexes of the same geometry, with δ(Com) ranging
from 155 to 164 ppm and 2J (Ptrans,C) values of 112-
115 Hz, respectively.38 Unfortunately, 1J (Pt,Com) could
not be resolved. The methine-C resonance is found
Ta ble 7. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for Com p ou n d 4a
Distances around Pt(1)
Pt(1)-P(1)
Pt(1)-Cl(1)
2.315(2)
2.354(2)
Pt(1)-C(25)
Pt(1)-C(26)
2.050(8)
2.071(7)
Distances within Ligand
P(2)-N(1)
N(1)-C(7)
P(2)-C(26)
P(2)-C(14)
P(2)-C(20)
1.639(7)
1.421(10)
1.765(7)
1.798(8)
1.777(8)
P(3)-N(2)
N(2)-C(39)
P(3)-C(26)
P(3)-C(27)
P(3)-C(33)
1.596(7)
1.404(10)
1.823(7)
1.812(7)
1.827(8)
Angles around Pt(1)
Cl(1)-Pt(1)-P(1)
Cl(1)-Pt(1)-C(25)
85.76(7) C(25)-Pt(1)-C(26)
84.7(3)
174.3(2)
98.9(2)
1
between 13.4 and 15.4 ppm (ddd, J (P,C) ≈ 46 and 70
90.7(2)
P(1)-Pt(1)-C(25)
P(1)-Pt(1)-C(26)
1
Cl(1)-Pt(1)-C(26) 174.9(2)
Hz, J (Pt,C) ≈ 736 Hz (4a )). Due to the multiplicity
and resulting low intensity of the signals it was impos-
Angles within Ligand
1
sible to obtain all J (Pt,C) values.
Pt-C(25)-C(20)
Pt-C(25)-C(24)
P(2)-C(26)-P(3)
P(2)-N(1)-C(7)
N(1)-P(2)-C(26)
N(1)-P(2)-C(14)
N(1)-P(2)-C(20)
C(14)-P(2)-C(26)
C(20)-P(2)-C(26)
C(14)-P(2)-C(20)
P(2)-C(20)-C(21)
117.4(6) Pt-C(26)-P(2)
126.9(6) Pt-C(26)-P(3)
115.2(4)
101.0(3)
114.0(3)
The 1H NMR of the orthometalated Pt complexes 4a -
d ,f (Table 4) show characteristic multiplets for the CH
resonance in the range 2.84-3.57 ppm, resulting from
coupling with three different P atoms (J (P,H) is ap-
proximately 7, 15, and 16 Hz). Its coupling with 195Pt
(86 Hz) is larger than that of the four-membered
platinacycle 2 (60 Hz), which agrees with the crystal-
lographically observed shorter Pt-C bond of 4a com-
pared to 2e (vide supra). The H atom, originating from
the orthometalated Com, is positioned between the two
PdN groups as evidenced by X-ray structure determi-
nation of 4a (vide supra) and by the extremely broad
NH resonance for 4b-d between 10.7 and 11.2 ppm (σ1/2
> 200 Hz in the case of 4c), which resembles the NH
frequency found in the cationic four-membered plati-
nacycle [PtCl(PEt3){CH(PPh2dN-pAn)(PPh2NH-pAn)-
C,N}]+(CF3CO2)- (6b′) (vide infra) and analogous com-
plexes.12,33
129.8(5) P(3)-N(2)-C(39)
109.8(3) N(2)-P(3)-C(26)
107.7(3) N(2)-P(3)-C(27)
116.8(4) N(2)-P(3)-C(33)
109.8(4) C(26)-P(3)-C(27)
102.3(3) C(26)-P(3)-C(33)
110.3(3) C(27)-P(3)-C(33)
125.7(6) P(2)-C(20)-C(25)
124.7(5)
107.5(3)
113.8(4)
111.1(4)
109.8(3)
105.9(3)
108.5(4)
110.2(6)
C(20)-C(21)-C(22) 118.1(8) C(20)-C(25)-C(24) 115.7(7)
C(21)-C(22)-C(23) 119.5(9) C(23)-C(24)-C(25) 121.4(7)
C(22)-C(23)-C(24) 121.3(8)
concerned is shifted to N(1) and forms an intramolecular
hydrogen bridge with N(2), resulting in a N-H‚‚‚N
angle of 125.3(7)°. The coordination position of the sp3-
carbon atom C(26), bridging the two P-N entities of the
ligand, is still trans to the Pt-Cl bond, similar to 2e.
The Pt-C(26) bond (2.071(7) Å), however, is signifi-
cantly shorter than the Pt-C bond in 2e (2.116(4) Å)
or in other four-membered platinacycles with a similar
trans Cl-Pt-C geometry (d(Pt-C) of ca. 2.10 Å).3a,12
This is probably due to the diminished constraints in
the five-membered ring as comparison to four-mem-
bered rings. As can be seen in Figure 2, the five-
membered platinacycle is puckered. A least-squares
plane analysis of the ring defined by Pt(1), C(25), C(20),
P(2), and C(26) shows deviations of 0.283(1), -0.160-
(8), -0.067(8), 0.335(2), and -0.390(7) Å, respectively.
In general, the P-C bond distances around P(2)
(average P-C ) 1.780(8) Å) are shorter than around
P(3) (P-Cav ) 1.821(8) Å), which is presumably the
result of a positive charge on P(2), being part of the
protonated P(2)-N(1) function. The differences in
character of the two P atoms of the ligand is supported
by the P(2)-N(1) and P(3)-N(2) distances of 1.639(7)
and 1.596(7) Å, respectively. The p-tolyl group on N(2)
is, in contrast to the one on N(1), practically in plane
with its PdN bond (torsion angles P(3)-N(2)-C(39)-
C(40) ) 168.7(6)°, whereas P(2)-N(1)-C(7)-C(12) )
-127.1(7)°). The planarity could be explained by elec-
tron delocalization which occurs as a result of the
interactions of the 2pπ-orbitals of the sp2-N with the 3dπ-
orbitals of P, which is extended to the π-system of the
aryl group on N, as evidenced by the widening of the
P-N-C angle (>120°).17
The 31P NMR spectra for 4a -d ,f (Table 8) show three
signals. The doublet resonance with the largest 195Pt
coupling is assigned to PAR3; the 1J (Pt,PA) value (1913-
1941 Hz) proves that PA is trans to C,41 instead of N,
and confirms that the structure in solution is similar
to that in the solid state. The remaining two 31P signals,
3
a doublet of doublet at about 30 ppm (PB, J (PA,PB) )
34.3-36.3 Hz and 2J (PB,PC) ) 14.8-15.8 Hz) and a
doublet at 17 ppm (PC), are assigned to the aminophos-
phonium entity and the remote phosphiminine group
in 4, respectively, since they resemble the frequencies
of the corresponding groups in other complexes12,33 (see
also 2 and 3). The coupling patterns for PB (dd) and PC
(d) might be explained by the dihedral angles PA-Pt-
C-PB (-133.54°) and PA-Pt-C-PC (102.39°) obtained
from the X-ray crystal structure determination of 4a ,
3
which indicates that J (PA,PC) coupling will, according
to the Karplus relations, indeed be small or zero, since
the dihedral angle is approaching 90°.
Comparison of the NMR data of 4 and 5 (Tables 4
and 8 and Experimental Section) indicate that the
molecular structure of the palladium complexes 5a ,c
differs from the platinum complexes 4a -d ,f. First of
all, in the 13C NMR of 5a the signal belonging to the
orthometalated carbon atom (Com) is found at 157.9 ppm
2
(dd), with rather small J (P,C) values of 27 and 3 Hz,
Sp ectr oscop ic Ch a r a cter iza tion of Or th om eta -
(41) (a) Allen, F. H.; Pidcock, A. J . Chem. Soc. 1968, 2700. (b)
Lukehart, C. M.; McPhail, A. T.; McPhail, D. R.; Meyers, J . B., J r.;
Soni, H. K. Organometallics 1989, 8, 1007. (c) Dema, A. C.; Li, X.;
Lukehart, C. M.; Owen, M. D. Organometallics 1991, 10, 1197. (d)
Romeo, R.; Arena, G.; Scolaro, L. M. Inorg. Chem. 1992, 31, 4879.
1
la ted Com p lexes 4 a n d 5. Selected H NMR data are
compiled in Table 4. Complete 1H NMR data are
available from the Supporting Information. 31P{1H}

M-N-P-C Metallacycles
Organometallics, Vol. 15, No. 9, 1996 2387
Ta ble 8. 31P NMR Da ta for th e Or th om eta la ted Com p lexes 4, 5, 7, a n d 9a
δ(PA)
δ(PB)
δ(PC)
1J (Pt,PA)
2J (Pt,PB)
2J (Pt,PC)
3J (PA,PB)
2J (PB,PC)
4a
5.5 (d)
5.5 (d)
30.8 (dd)
31.1 (dd)
30.2 (dd)
30.0 (dd)
29.5 (dd)
34.0 (d)
17.9 (d)
17.9 (d)
16.1 (d)
15.6 (d)
17.6 (d)
11.0 (d)e
11.6 (d)f
24.9 (d)
21.0 (d)
21.0 (d)
29.9 (d)
29.8 (d)
1941
1939
1914
1913
1929
nr
20
nr
16
20
80
80
88
86
73
34.5
34.3
35.5
36.3
33.4
12.0
12.1
30.5
30.9
30.6
34.0
31.8
15.0
14.8
15.5
15.8
15.5
4bb
4c
-7.8 (d)
-8.3 (d)
2.8 (d)
4d c,d
4f
5a b
5cc
7a b
22.3 (dd)e
-1.6 (dd)f
5.5 (d)
33.7 (d)
23.0 (dd)
23.2 (dd)
23.9 (dd)
45.0 (dd)
45.6 (dd)
1988
1973
1972
1870
1884
nr
63
62
nr
18
137
140
140
120
99
12.2
12.4
12.8
10.7
10.2
b
7a ′
7b′
9c
9f
3.6 (d)
3.6 (d)
-6.5 (d)
3.8 (d)
b
a
Recorded at 40.53 MHz in CDCl3 at 293 K, unless stated otherwise. J values in Hz. Multiplicity labels and abbreviations: s )
singlet, d ) doublet, dd ) doublet of doublet, nr ) not resolved. In C6D6. c In toluene-d8. Recorded at 121.48 MHz. e 3J (PA,PC) ) 16.0
b
d
Hz. f 3J (PA,PC) ) 17.0 Hz.
which indicates that Com is cis to PAR3,38 instead of trans
as in 4. Second, the methine-carbon resonance lies at
a much higher frequency (35.0 ppm) and shows spin-
spin coupling with all three phosphorus atoms, which
implies that CH is coordinated trans to PAR3. The CH
group is probably more weakly coordinated due to the
trans influence of the phosphine as compared to CH in
the complexes 2, 3, or 4, and its chemical shift resembles
the frequency for ylide carbon atoms.14b,c In the 1H
NMR of 5, a CH resonance is found at about 4.1 ppm
(ddd, J (P,H) ≈ 7, 12, and 15 Hz), also at a higher
frequency than their Pt analogues 4. Furthermore, a
broad signal is observed for 5a at approximately 10
ppm, characteristic for a NH group.12,33
signals belonging to the intermediate 5ci disappear
when the three 31P resonance signals of complex 5c
show up. The sequence of formation of 5c is shown in
Scheme 3 and will be discussed at the end of this paper.
Rea ctivity of th e P la tin a cycles 2 a n d 4 w ith HY
(Y ) BF 4, CF 3COO). The cationic platinacycles 6a ,b′
and 7a ,a ′,b were readily obtained by quantitative pro-
tonation of the noncoordinated PdN groups in 2a ,b and
4a ,b, respectively, with 1 molar equiv of HBF4 or CF3-
COOH (eqs 4 and 5), at 20 °C in CH2Cl2, benzene, or
toluene, analogous to the earlier reported protonation
reactions of Rh- and Ir-bis(iminophosphranyl)metha-
nide complexes.4
A comparison of the 31P NMR data of 5a with 5c with
the results described above shows that the doublet
resonance at about 34 ppm should be assigned to an
aminophosphonium entity. The doublet at ca. 11 ppm
agrees well with the value found in 3 for a noncoordi-
nated PdN group. The remaining signal, a doublet of
doublet, belongs to PAR3 (5a , PEt3; 5c, PMe2Ph), as
confirmed for 5c by selective irradiation in the 31PA
resonance frequency at -1.6 ppm resulting in a collapse
1
of the doublet PMe resonances into singlets in the H
NMR. These data are consistent with either of the two
structural proposals for 5 given at the top of Table 8
and in eq 3.
An in situ 31P NMR experiment, following the reaction
sequence of 3c into 5c, revealed an intermediate 5ci,
which shows striking resemblance to the 31P NMR data
3
for 4c,d , a doublet at -10 ppm (δ(PA), J (PA,PB) ) 36.4
3
Hz), a doublet of doublet at 24.7 ppm (δ(PB), J (PA,PB)
) 36.4 Hz, 2J (PB,PC) ) 19.8 Hz), and the 31PC resonance
at 20.0 ppm (d). The last two resonance relate to the
remote PdN groups, which are presumably connected
via an H-bridge, similar to 4. The coupling pattern
suggests that 5ci has a trans PA-Pd-C(sp2) geometry,
like in 4, since the multiplicity of the 31P signals changes
drastically upon isomerization of 5ci into 5c. The
The new cationic orthometalated compounds 7 are
fairly stable in solution when stored under nitrogen;
however, decomposition is observed when they are held
in solution for 2-3 weeks. In general, the solubility of
the cationic complexes 7, in for instance benzene, is
better than its neutral counterparts (4).

2388 Organometallics, Vol. 15, No. 9, 1996
Avis et al.
The NMR spectroscopic data for the cationic four-
membered platinacycles 6, which show a characteristic
NH resonance in the 1H NMR (Table 4) and a high-
frequency shift for PC (Table 5), are identical to the data
that have been reported previously for the products
obtained from the bridge-splitting reactions of neutral
bis(iminophosphoranyl)methanes CH2(PPh2dNAr)2 (Ar
) p-tolyl, p-anisyl) with Pt2Cl4(PEt3)2 in the presence
of NaY.12 The protonation reaction is reversible as the
neutral complexes 2a ,b, are regenerated upon reaction
of the cationic complexes 6a ,b with an appropriate base
(LDA, NaH, DBU, or 1 equiv of BIPM12).
time scale in solution at room temperature, in contrast
to the fluxional complexes 2 and 3.
The identification of the aza-Wittig products 9c,f was
more complicated, since the 31P NMR (Table 8) shows
that both PB and PC have shifted to higher frequencies
when compared to the corresponding signals of 4c,f,
which indicates that both PN functions have changed
in character. The signal at 45.3 ppm resembles the
PdO resonance frequency as reported for the four-
membered platinacycles [Pt(L2){NPhP(dO)PhNPh}, δ-
(PdO) ) 38.9-46.5 ppm,44 and is therefore assigned to
a PBdO moiety contained in a five-membered ring in
our case. The 31P signal at 29.9 ppm is characteristic
for a PPh2NH-aryl moiety,12,33 like in 6, which is in
agreement with the observation of NH and C6H4R′-4
resonances in the 1H NMR (Table 4 and Supporting
Information) and confirms that only one PdN group has
reacted with CO2. Comparison of these data with the
structure analysis of 4c,f, shows that an H-shift from
the original PBNHAr group to the previous PCdNAr
group must have taken place upon reaction with CO2
(eq 7).
The NMR data for 4 and 7 (see Tables 4 and 8) are
quite similar, except for the occurrence of two NH
1
resonances in the H NMR for 7 and shifts due to the
ionic character of 7, which indicates that the basic
structure of the orthoplatinated complexes hardly
changes upon protonation of 4.
Rea ctivity of th e P la tin a cycles 2 a n d 4 w ith CO2.
The complexes 2a ,d and 4c,f reacted with 1 molar equiv
of CO2 to give the new platinum complexes 8a ,d and
9c,f, respectively, in high yields (95-100%) together
with aryl isocyanate and bis(aryl)carbodiimide in an
approximate 6:1 ratio (eqs 6 and 7).
Discu ssion
F or m a tion of th e F ou r -Mem ber ed Meta lla cycles
2 a n d 3. In principle there are two possible reaction
pathways (Scheme 1, routes a and b) in which the
anionic ligand [CR(PPh2dNAr)2]- (1) might attack the
precursor M2X4(PR3)2 (M ) Pt, Pd): (a) nucleophilic
attack by one of the nitrogen atoms; (b) nucleophilic
attack by the methine carbon atom. Considering what
is known about these types of bridge-splitting reactions
by σ-donor ligands,3,12,13,45 a preliminary conclusion can
be drawn that the N atoms of the [CR′(PPh2dNC6H4R′′-
4)2]- ligand have the strongest σ-donor capacity, since
the products 2 and 3 both have a trans N-M-PR3
geometry. For instance, the recently investigated bridge-
splitting reaction of Pt2Cl4(PEt3)2 by the neutral BIPM
ligand CH2(PPh2dN-pTol)2 gave a cationic four-mem-
bered platinacycle of similar geometry, which was
formed via initial nucleophilic attack by N as evidenced
by the observation of the monodentate intermediate
trans-PtCl2(PEt3){N(pTol)dPPh2CH2PPh2dN-pTol}.12 We
therefore assume that a similar reaction path (route a)
also accounts for the reactions with the anionic deriva-
tive. If the methine-C would have initiated the bridge-
splitting reaction (route b), the other geometric isomer
with C trans to PR3 would have been formed, which is
never observed (Scheme 1).
Complexes 8a ,d could not be separated from the
organic byproducts, since they are all soluble in diethyl
ether or petroleum ether (40/60). Other apolar solvents
(pentane, hexane) were unsuitable for washing out the
byproducts. The reactions proceeded much faster in
CH2Cl2 (2.5 h for 2, 15 min for 4) than in benzene or
toluene (3.5 h for 2, 3 h for 4). Continued stirring under
an atmosphere of CO2 for another 20 h did not lead to
reaction with the second PN group; decomposition was
observed instead, presumably due to traces of H2O.
The structure of the complexes 8 is directly deduced
from the characteristic high-frequency shift of the PC
resonance (Table 5), which establishes the conversion
of the remote PdN group in 2 into a PdO function,42
similar to the earlier reported reactions of analogous
Rh- and Ir-bis(iminophosphoranyl)methanide com-
plexes,4 the BIPM ligand,17 and other phosphinimines
with CO2.43 The sharp doublets in the 31P NMR indicate
that complexes 8a ,d have a rigid structure on the NMR
The preference for nucleophilic attack by N (route a)
instead of C (route b) of the anionic ligand (1) is
supported by earlier reported reactions of Li[CH2-
PPh2dNC6H4R-4]29 and Li[CH(PPh2dNC6H4R-4)2]4 with
[ML2Cl]2 (M ) Rh, Ir; L2 ) COD, NBD, (CO)2). For
these ligands a strong dependence of the product forma-
tion on the nucleophilicity of the nitrogen atom, as a
(43) (a) Schmidbaur, H. Adv. Organomet. Chem. 1970, 9, 259. (b)
Abel, E. W.; Mucklejohn, S. A. Phosphorus Sulfur 1981, 9, 253. (c)
Singh, G.; Zimmer, H. Organomet. Chem. Rev. 1967, 2, 279. (d)
Gololobov, Y. G.; Kasukhin, L. F. Tetrahedron 1992, 48, 1353.
(44) Kemmitt, R. D. W.; Mason, S.; Moore, M. R.; Russell, D. R. J .
Chem. Soc., Dalton Trans. 1992, 409.
(45) (a) Chatt, J .; Venanzi, L. M. J . Chem. Soc. 1955, 3858. (b)
Kaufmann, W.; Venanzi, L. M.; Albinati, A. Inorg. Chem. 1988, 27,
1178. (c) Clark, H. C.; Ferguson, G.; J ain, V. K.; Parvez, M. Inorg.
Chem. 1986, 25, 3808.
(42) (a) Higgins, S. J .; Taylor, R.; Shaw, B. L. J . Organomet. Chem.
1987, 525, 285. (b) Grim, S. O.; Kettler, P. B.; Thoden, J . B.
Organometallics 1991, 30, 2399.

M-N-P-C Metallacycles
Sch em e 1. Differ en t Rou tes for th e
Organometallics, Vol. 15, No. 9, 1996 2389
Sch em e 2. N,N′ Exch a n ge in 2 a n d 3
Br id ge-Sp littin g Rea ction w ith
Bis(im in op h osp h or a n yl)m eth a n id e
Ch a r t 4
For several related compounds a N-M linkage has
been established,48 and from the high-frequency shift
in the 31P NMR and the Me group in the H NMR for
Ch a r t 5
1
Na[CMe(PPh2dN-p-tolyl)2] (1c) in comparison to the
neutral ligand, 1,1-BIPE,13 it is also deduced that Na+
is probably strongly coordinated to both N atoms, as
strong polarization of the PdN bonds has occurred (IX).
So, as compared to other ligands (with X ) S, O) the
electron density in [CR′(PPh2dNR-aryl)2]- is expected
to be localized on the N atoms instead of being delocal-
ized.
function of the substituent 4-RC6H4, has been observed;
e.g. for R ) NO2, no reaction or decomposition took
place.4,29 These findings differ considerably with the
results reported by Dixon and co-workers, wherein
bridge-splitting reactions of Pt2Cl4(PEt3)2 by the ligands
Li[CH(PPh2dS)2]3 and Li[CH(PPh2dO)2]46 have led to
the formation of the initial products VI and VII,
respectively (Chart 4), by nucleophilic attack of the
carbanion on the Pt-Cl bond trans to the labilizing
phosphine,3b as demonstrated by route b in Scheme 1.
The overall conclusion that can be drawn from this
comparison is that the nucleophilicity of the σ-donor
atoms play a significant role in the initial product
formation in case of these multifunctional ligands and
determines the preference for the initial attack of N >
C > S > O of the [CH(PPh2dX)2]- ligands (with X )
NAr, S, O) to Pt2X4(PR3)2. Whether or not ring closure
takes place is strongly dependent on the nucleophilicity
of the remaining two potential σ-donor atoms.
The differences in product formation could also de-
pend on the structural differences within the ligand
itself (in solution), e.g. bonding of M+ to the anion [CR′-
(PPh2dN-aryl)2]- (M ) Na, Li), in comparison to
[CH(PPh2dX)2]- (with X ) S, O). For the [CH-
(PPh2dX)2]- ligands (X ) CR2, S, O) it is generally
accepted that the negative charge is completely delo-
calized over the π-system and that M+ is situated
between the two X functions (VIII)1c,3b,47 (Chart 5),
which probably makes these σ-donor atoms less nucleo-
philic than the methine carbon.
F lu xion a lity of 2 a n d 3. Variable-temperature
NMR spectroscopy of the neutral four-membered met-
allacycles [MX(PR3){CR′(PPh2dN-aryl)2}-C,N] (2, M )
Pt, X ) Cl, Br; 3, M ) Pd, X ) Cl) has established that
an intermediate (for 2) or fast (for 3) N,N′ exchange
process occurs on the NMR time scale at 293 K, which
can be brought into slow exchange by cooling to 253 K
(2) or 183-190 K (3). In view of the structural similari-
ties between the Pt complexes 2 and the Pd complexes
3 we gather that their fluxional processes probably
follow the same exchange mechanism, which will be
elaborated only for the four-membered palladacycles 3.
We have shown that the two halves of the bis-
(iminophosphoranyl)methanide ligand in 3a -c become
magnetically equivalent on the NMR time scale (1H, 300
MHz) at 293 K. For complex 3c we have also found that
the diastereotopic PMe groups become equivalent, in-
dicating that inversion of configuration at the methine
carbon atom occurs. Since the bis(iminophosphoranyl)-
methanide ligands in the complexes 2 and 3 are
1
coordinated by a strong M-C bond, as evidenced by H
and 13C NMR, the dynamic process must involve a net
rotation of the [CH(PPh2dN-aryl)2]- ligand around the
M-C axis, whereby PdN and PdN′ exchange positions
as indicated in Scheme 2. As the fluxional processes
are concentration independent, they must proceed in-
tramolecularly.
Two possible mechanisms could account for the N,N′
exchange processes in 2 and 3, an associative mecha-
(46) Browning, J .; Bushnell, G. W.; Dixon, K. R. Inorg. Chem. 1981,
20, 3912.
(47) Cotton, F. A.; Schunn, R. A. J . Am. Chem. Soc. 1963, 85, 2394.
(48) (a) Ashby, M. T.; Li, Z. Inorg. Chem. 1992, 31, 1321. (b)
Hasselbring, R.; Pandey, S. K.; Roesky, H. W.; Stalke, D.; Steiner, A.
J . Chem. Soc., Dalton Trans. 1993, 3447.

2390 Organometallics, Vol. 15, No. 9, 1996
Avis et al.
nism, involving five-coordinated intermediates, or a
dissociative mechanism, in which the M-N bond is
broken and a T-shaped intermediate is formed. Earlier
investigations in our laboratory concerning the fluxional
processes of analogous complexes [ML2{CH(PPh2dN-
aryl)2)}-C,N] (with M ) Rh, Ir; L2 ) COD, NBD, (CO)2)
pointed to an associative N,N′ exchange process in
which geometric isomerizations via five-coordinated
intermediates are involved.4 Only such an isomeriza-
tion step could account for the equivalence of the two
halves of the bis(iminophosphoranyl)methanide ligand
as well as for the coligands (L2) in the Rh and Ir
complexes.4
Clearly, such an associative mechanism is not operat-
ing for the Pt- and Pd-bis(iminophosphoranyl)meth-
anide complexes 2 and 3, since this would have led to
geometric isomerization around the metal center, re-
sulting in a C,N-coordinated species with opposite trans
ligands, which is not observed. An associative mecha-
nism involving only exchange of the pendant and bound
σ-donor groups via D (Scheme 2) explains the observed
phenomena for the metallacycles 2 and 3. However, a
dissociative route through C cannot be excluded. One
may argue that an associative process is favored over a
dissociative one, since (i) N′ is a good nucleophile and
(ii) the X-ray crystal structures of the [Ir(COD){CH-
(PPh2dN-pTol)2}-C,N] complex4 and [PtCl(PEt3){CH-
(PPh2dS)2}-C,S]3 have shown that the noncoordinated
PdX functions (X ) N or S) are already in close
proximity of the metal centers. The fact that the X-ray
crystal structure of complex 2e (Figure 1) shows a
different picture, i.e. the noncoordinated PdN group
pointing away from the metal, is probably an exception
caused by the steric effect of the Me group on the
coordinated methine carbon.
Also, for several other d8-transition metal complexes,
i.e. [Pt(PEt3)Cl{CH(PPh2dS)2}],3 [Pt(PEt3)Cl{C(PPh2d
S)3}],37 [M{PPh(C6H4SMe-o)2}X2], and [M{P(C6H4SMe-
o)3}2][ClO4]2 (M ) Pt, Pd, X ) halide),48 the observed
S,S′-exchange processes within the bidentate ligands are
assumed to operate via associative mechanisms, involv-
ing short-lived 18-electron five-coordinated intermedi-
ates.3,37,49 Other closely related complexes, i.e. [Rh-
(COD){(OdPPh2)2C(PPh2dS)}],42b [Ir(COD){(SdPPh2)3-
C}],50a and [M(COD){(OdPPh2)3C}] (M ) Rh, Ir),50bc
exhibit similar fluxional behavior of the tris(phosphine-
chalcogenide) ligand.
Rea ctivity of th e P la tin a cycles 2 a n d 4. The
reactions with 1 equiv of CF3COOH and HBF4, giving
the cationic complexes 6a ,b′ (eq 4)12 and 7a ,a ′,b′ (eq 5),
have most likely proceeded via direct protonation of the
noncoordinated nitrogen atom. The same type of reac-
tivity has been proposed for the reactions of Rh- and
Ir-bis(iminophosphoranyl)methanide complexes with
CF3COOH.4 The stability of the orthometalated plati-
num complexes 4a ,b toward protonation is remarkable.
Protonation of the orthometalated aryl group does not
occur, whereas this type of reactivity has been observed
for other orthometalated compounds.38a,51a
The aza-Wittig product 8, obtained from the reaction
of 2 with CO2, has proved that this type of reaction is a
suitable method to investigate the reactivity or kinetic
stability of coordinated phosphiminines.8b,c We found
that CO2 only reacts with the pendant iminophospho-
ranyl group of the complexes 2a ,d (eq 6), which means
that one PdN function is kinetically stabilized within
the metallacycle by coordination to platinum. A similar
nonreactivity toward CO2 has been reported earlier for
Rh and Ir complexes containing a single C,N-coordinat-
ed iminophosphoranylmethanide moiety, e.g. RhL2{N-
(Ar)dPPh2CH2}.4,29 The rigidity of the product 8, PtCl-
(PR3){CH(PPh2dNAr)(PPh2dO)}, in contrast to the
fluxionality of the complexes 2, is a direct consequence
of the weak σ-donor capacity of the noncoordinated PdO
group and is in agreement with the nonfluxional be-
havior of analogous Rh and Ir complexes.4
The orthometalated complexes 4c,f also react with
only 1 equiv of CO2, but this reaction is not as straight-
forward as described above for the complexes 2. The
structure of the products 9c,f (eq 7) points to the fact
that PBdNAr attacks CO2 and becomes PBdO, concomi-
tant with or after a shift of H to PCdNAr to become PC-
NHAr. The latter is not nucleophilic enough to undergo
another aza-Wittig reaction with excess CO2, which
explains why only one PdO moiety is formed. The
preference for reaction of CO2 with PBdNAr stems from
the fact that this group is more polarized than PCdNAr
because of the stabilizing effect of the formally anionic
orthometalated aryl group on the developing positive
charge on phosphorus during an aza-Wittig reaction.
F or m a tion of th e Or th om eta la ted Com p lexes 4
a n d 5. Factors that contribute to orthometalation have
been summarized in several reviews51,52 and generally
imply the following: (a) Metalation requires a certain
flexibility of the ligand. (b) The presence of bulky
groups on the donor group (the methine carbon atom
in our case) is of importance. Bulky groups have less
rotational entropy than smaller ones, and the internal
entropy loss on cyclization will therefore be correspond-
ingly lower. (c) Where four-membered rings are in-
volved, orthometalation could occur, since their internal
entropy is already small and also greater ring strain
exists. These factors will promote orthometalation to
energetically more favorable five-membered rings.
The most important driving force for orthometalation
of the four-membered metallacycles 2 and 3 is probably
the ring strain. The bulky phenyl groups on both P
atoms of the C,N-coordinated bis(iminophosphoranyl)-
methanide ligands also supply a significant contribution
to the promotion of orthometalation, which is clearly
evident by looking at the X-ray crystal structure of 2e.
Figure 1 shows that the ortho H atom of the Ph group
on the P within the four-membered platinacycle is in
close proximity of the Pt center and is most likely to
orthometalate.
(49) Abel, E. W.; Dormer, J . C.; Ellis, D.; Orrell, K. G.; Sik, V.;
Hursthouse, M. B.; Mazid, M. A. J . Chem. Soc., Dalton Trans. 1992,
1073.
(50) (a) Grim, S. O.; Kettler, P. B.; Merola, J . S. Inorg. Chim. Acta
1991, 85, 57. (b) Tanke, R. S.; Crabtree, R. H. J . Chem. Soc., Chem.
Commun. 1990, 1056. (c) Tanke, R. S.; Crabtree, R. H. J . Am. Chem.
Soc. 1990, 112, 7984.
(51) (a) Hartley, F. R. Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. A. G., Abel, E. W., Eds.; Pergamon Press:
London, 1982; Vol. 6, Chapter 39, pp 592-606. (b) Shaw, B. L. J .
Organomet. Chem. 1980, 200, 311-314. (c) Bruce, M. I. Angew. Chem.
1977, 89, 75. (d) Dehand, J .; Pfeffer, M. Coord. Chem. Rev. 1976, 18,
344-346. (e) Omae, I. Coord. Chem. Rev. 1988, 83, 137. (f) Evans,
D. W.; Baker, G. R.; Newkome, G. R. Coord. Chem. Rev. 1989, 93, 155.
There are two generally accepted mechanisms for CH
bond cleavage by Pt and Pd: an oxidative addition by
nucleophilic attack of the metal center on the aromatic
(52) Ryabov, A. D. Chem. Rev. 1990, 90, 403.

M-N-P-C Metallacycles
Organometallics, Vol. 15, No. 9, 1996 2391
aromatic substitutions for Pd in particular53 but also
for Pt.53b These electrophilic substitutions are also often
nucleophilically assisted by coordinated or free bases
(e.g. base catalyzed), which certainly could account for
the orthometalation reactions of 2 and 3, where the
C-H bond cleavage probably proceeds easily because
an internal base is present in the form of two N atoms
of the coordinated ligand, which entrap the proton.
Similar features have been reported for other ortho-
metalation reactions involving nitrogen-donor ligands,
where pendant N atoms act as intramolecular proton
acceptors and thus lead to acceleration of orthometala-
tion reactions.54 This also explains why for the PtCl-
(PEt3){CH(PPh2dS)2} complex, which closely resembles
2 and 3, orthometalation has not been found even at
higher temperatures.3b
Sch em e 3. P r op osed Rea ction Mech a n ism for
Or th om eta la tion
The fact that for analogous Rh- and Ir{CH(PPh2dN-
aryl)2} complexes no orthometalation reactions have
been found, but show extreme thermal stability in-
stead,4 indicates that an electrophilic mechanism is
indeed favored over an nucleophilic pathway, as Rh(I)
and Ir(I) are less electrophilic in nature than Pt(II) and
Pd(II). It must be noted that for the earlier reported
cationic four-membered platinacycles (identical to 6)
orthometalation has not been observed either (at higher
temperatures), but decomposition is observed instead.12,55
As shown by the X-ray crystal structure of 2e, one of
the phenyl groups on P is in close proximity of the metal
center, which is most favorable for an electrophilic
attack of the metal on the phenyl. Possibly, the flex-
ibility of the C,N-coordinated bis(iminophosphorayl)-
methanide ligand in the complexes 2 and 3, involved in
an N,N′ exchange process, facilitates the approach of
the metal.
In contrast to the orthometalation reactions involving
platinum, the conversion of the four-membered palla-
dacycles 3a ,c into the orthopalladated complexes 5a ,c
requires an isomerization step (Scheme 3). Fortunately,
the conversion of the PMe2Ph derivative 3c already
takes place at room temperature, which made it possible
to observe an initial product 5ci which has the same
trans R3PA-Pd-C(sp2) geometry as found for the final
orthoplatinated products 4. In keeping with recent
results by Vicente and co-workers,14d where the PR3
ligand in orthopalladated compounds [PdCl(PR3){2-
C6H3RP(Ar)2C′HR′′}-C,C′] is positioned trans to the Pd-
C(sp3) bond instead of trans to Pd-C(sp2), the isomer-
ization of complex 5ci is probably driven by the fact that
the trans influence of sp2-C > sp3-C, giving the ther-
modynamically more stable trans R3P-Pd-C(sp3) iso-
mer 5c. No geometric isomerization has been observed
for the platinum complexes 4, probably due to the
ring or by an electrophilic substitution reaction.52
Distinction between the two mechanisms is rather
complicated, especially when the H atom is eliminated
in the process, as is the case for 2 and 3 where it is
abstracted by N. Usually the observation of metal-
hydride species provides sufficient evidence for a nu-
cleophilic pathway. Altering the electron density on the
aromatic ring or the metal center, introducing electron-
donating or -withdrawing substituents, has in many
cases revealed the mechanism of orthometalation.52
In our case, the rates of orthometalation seem to be
largely dependent on the phosphine bound to the metal.
For both the Pt as the Pd complexes, the PMe2Ph
derivatives (2c,d and 3c) orthometalated much faster
than their PEt3 analogues (2a ,b and 3a ,b), whereas no
significant difference is observed for the rate of N,N′
exchange in the Pt complexes (2a -f) or the Pd com-
plexes (3a -c). We have therefore eliminated the pos-
sibility that this effect is caused by the difference in cone
angles of the phosphines and have attributed it to the
difference in electron-donating capacity, PEt3 > PMe2-
Ph, which indicates that a diminished electron density
is favorable for orthometalation, supporting an electro-
philic substitution mechanism (Scheme 3).
(53) (a) Takahashi, H.; Tsuji, J . J . Organomet. Chem. 1967, 10, 511.
(b) Parshall, G. W. Acc. Chem. Res. 1970, 3, 135. (c) Bruce, M. I.;
Goodall, B. L.; Stone, F. G. A. J . Chem. Soc., Chem. Commun. 1973,
558.
(54) (a) Wehman-Ooyevaar, I. C. M.; Grove, D. M.; Kooijman, H.;
van der Sluis, P.; Spek, A. L.; van Koten, G. J . Am. Chem. Soc. 1992,
114, 9916. (b) Markies, B. A.; Wijkens, P.; Kooijman, H.; Spek, A. L.;
Boersma, J .; van Koten, G. J . Chem. Soc., Chem. Commun. 1992, 1420.
(c) Valk, J .-M.; Maassarani, F.; van der Sluis, P.; Spek, A. L.; Boersma,
J .; van Koten, G. Organometallics 1994, 13, 2320.
(55) One would expect that if orthometalation takes place via an
electrophilic pathway, the reaction should proceed more readily for
these cationic derivatives in view of the more positive character of the
metal center. The fact that this is not the case is probably due to the
relatively strong Pt-N bonds in the cationic complexes as compared
to the relatively weak M-N bonds in 2 and 3.
Others have already established in a similar way that
orthometalation reactions usually occur via electrophilic

2392 Organometallics, Vol. 15, No. 9, 1996
Avis et al.
Su ppor tin g In for m ation Available: Two 1H NMR tables,
containing the complete data for the four-membered metalla-
cycles 2, 3, 6, and 8 and the orthometalated compounds 4, 5,
7, and 9, respectively, and further details of the structure
determinations, including tables of hydrogen coordinates and
U values, bond lengths and angles, and anisotropic thermal
parameters for 2e and 4a (17 pages). This material is
contained in many libraries on microfiche, immediately follows
this article in the microfilm version of the journal, can be
ordered from ACS, and can be downloaded from the Internet;
see any current masthead page for ordering information and
Internet access instructions.
overall higher thermal stability of the platinum com-
plexes as compared to their palladium analogues 5i.
Ack n ow led gm en t. This work was supported in part
(A.L.S and N.V) by the Netherlands Foundation of
Chemical Research (SON) with financial aid from the
Netherlands Organization for Scientific Research (NWO).
Furthermore, the collaboration (K.V.K, C.L.B, and
M.W.A) was made possible by funds provided by the
NWO, the Chemistry Department of the University of
Amsterdam, and the Departments of Chemistry and
Radiology and Research Reactor of the University of
MissourisColumbia.
OM950635K