Iridium phosphinidene complexes: A comparison with iridium imido complexes in their reaction with isocyanides

Article abstract of DOI:10.1021/ja9048509

18-Electron nucleophilic, Schrock-type phosphinidene complexes 3 [Cp*(Xy-N≡C)Ir=PAr] (Ar = Mes*, Dmp, Mes) are capable of unprecedented [1 + 2]-cycloadditions with 1 equiv of isocyanide RNC (R = Xy, Ph) to give novel iridaphosphirane complexes [Cp*(Xy-N≡C

Full text of DOI:10.1021/ja9048509

Published on Web 08/24/2009
Iridium Phosphinidene Complexes: A Comparison with
Iridium Imido Complexes in Their Reaction with Isocyanides
Halil Aktas,† Jos Mulder,† Frans J. J. de Kanter,† J. Chris Slootweg,†
Marius Schakel,† Andreas W. Ehlers,† Martin Lutz,‡ Anthony L. Spek,‡ and
Koop Lammertsma*,†
Department of Chemistry and Pharmaceutical Sciences, Vrije UniVersiteit Amsterdam,
De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands, and the BijVoet Center for
Biomolecular Research, Crystal and Structural Chemistry, Utrecht UniVersity, Padualaan 8,
3584 CH Utrecht, The Netherlands
Received July 7, 2009; E-mail: K.Lammertsma@few.vu.nl
Abstract: 18-Electron nucleophilic, Schrock-type phosphinidene complexes 3 [Cp*(XysNtC)IrdPAr] (Ar
) Mes*, Dmp, Mes) are capable of unprecedented [1 + 2]-cycloadditions with 1 equiv of isocyanide RNC
(R ) Xy, Ph) to give novel iridaphosphirane complexes [Cp*(XysNtC)IrPArCdNR]. Their structures were
ascertained by X-ray diffraction. Density functional theory investigations on model structures revealed that
the iridaphosphirane complexes are formed from the addition of the isocyanide to 16-electron species
[Cp*IrdPAr] forming first complex 3 that subsequently reacts with another isocyanide to give the products
following a different pathway than its nitrogen analogue [Cp*IrtNt-Bu] 1.
alkenes8 and alkynes,9 thereby mimicking the behavior of
Schrock-type carbenes.10 In the present study we compare the
Introduction
Ever since stable nucleophilic phosphinidenes were discov-
ered by Lappert et al. in 1987,1 the structural properties and
intriguing reactivity of these Schrock-type species continue to
fascinate.2 Exemplary valuable transfer reactions are those with
oxo- and halophilic transition metal complexes,3 such as the
phospha-Wittig reaction with carbonyl compounds that yields
phosphaalkenes4,5 and the P/O-exchange with epoxides that
gives the three-membered phosphiranes.4 Phosphaalkenes also
result on reaction with geminal dihalides,4,6,7 while other
dihalides give phosphorus heterocycles.4 Four-membered phos-
phametallocycles are accessible by [2 + 2]-cycloadditions with
behavior of phosphinidene and imido complexes.
Inspired by the reported reaction of stable, linear, 18-electron
imido complex [(η5-Cp*)IrtNt-Bu] 1 with isocyanides that
gives η2-coordinated carbodiimide complex 2,11 we targeted this
reaction for the corresponding phosphinidenes.13 At the outset
there is an intriguing difference between imido complex 1 and
its phosphorus analogue, namely bent 16-electron complex [(η5-
Cp*)IrdPsR] is not a stable species.12 Also whereas many 18-
electron [(η5-Cp*)(L)IrdP-Mes*] (L ) PR3, AsR3, dppe,
RNtC, CO, NHC) have been reported,6,14 it is not known to
be capable of [1 + 2]-cycloadditions like its well-established
Fischer-type electrophilic counterpart.15
† Vrije Universiteit Amsterdam.
Isocyanide-stabilized 18-electron [(η5-Cp*)(XysNtC)Ird
PMes*] 3a (Mes* ) 2,4,6-tri-tert-butylphenyl),6 generated by
double dehydrohalogenation6,16 of [(η5-Cp*)IrCl2(PH2Mes*)]
and concomitant ligation with 2,6-xylyl isocyanide, is an ideal
‡ Utrecht University.
(1) (a) Hitchcock, P. B.; Lappert, M. F.; Leung, W.-P. J. Chem. Soc.,
Chem. Commun. 1987, 1282–1283. (b) Bohra, R.; Hitchcock, P. B.;
Lappert, M. F.; Leung, W.-P. Polyhedron 1989, 8, 1884.
(2) (a) Slootweg, J. C.; Lammertsma, K. In Science of Synthesis; Trost,
B. M.; Mathey, F. Eds.; Georg Thieme Verlag: Stuttgart, 2009; Vol.
42, pp 15-36. (b) Mathey, F. Dalton Trans. 2007, 1861–1868.
(3) Stephan, D. W. Angew. Chem. 2000, 112, 322–338; Angew. Chem.,
Int. Ed. 2000, 39, 314-329.
(10) Schrock, R. R. Angew. Chem., Int. Ed. 2006, 45, 3748–3759.
(11) (a) Glueck, D. S.; Hollander, F. J.; Bergman, R. G. J. Am. Chem.
Soc. 1989, 111, 2719–2721. (b) Glueck, D. S.; Wu, J.; Hollander, F. J.;
Bergman, R. G. J. Am. Chem. Soc. 1991, 113, 2041–2054. (c)
Danopoulos, A. A.; Wilkinson, G.; Sweet, T. K. N.; Hursthouse, M. B.
J. Chem. Soc., Dalton Trans. 1996, 3771–3778.
(4) Breen, T. L.; Stephan, D. W. J. Am. Chem. Soc. 1995, 117, 11914–
11921.
(5) Cummins, C. C.; Schrock, R. R.; Davis, W. M. Angew. Chem. 1993,
105, 758–761; Angew. Chem., Int. Ed. Engl. 1993, 32, 756-759.
(6) Termaten, A. T.; Nijbacker, T.; Schakel, M.; Lutz, M.; Spek, A. L.;
Lammertsma, K. Organometallics 2002, 21, 3196–3202.
(7) Aktas, H.; Slootweg, J. C.; Schakel, M.; Ehlers, A. W.; Lutz, M.;
Spek, A. L.; Lammertsma, K. J. Am. Chem. Soc. 2009, 131, 6666–
6667.
(12) Termaten, A. T.; Nijbacker, T.; Ehlers, A. W.; Schakel, M.; Lutz,
M.; Spek, A. L.; McKee, M. L.; Lammertsma, K. Chem.sEur. J. 2004,
10, 4063–4072.
(13) One example is reported where a titanium phosphinidene reacts with
3 equiv of isocyanide to afford an η2-(N,C)-phosphaazaallene; see:
Basuli, F.; Watson, L. A.; Huffman, J. C.; Mindiola, D. J. Dalton
Trans. 2003, 4228–4229.
(8) Waterman, R.; Hillhouse, G. L. J. Am. Chem. Soc. 2003, 125, 13350–
13351.
(14) Termaten, A. T.; Schakel, M.; Ehlers, A. W.; Lutz, M.; Spek, A. L.;
Lammertsma, K. Chem.sEur. J. 2003, 9, 3577–3582.
(9) (a) Breen, T. L.; Stephan, D. W. J. Am. Chem. Soc. 1996, 118, 4204–
4205. (b) Breen, T. L.; Stephan, D. W. Organometallics 1996, 15,
5729–5737. (c) Zhao, G.; Basuli, F.; Kilgore, U. J.; Fan, H.; Aneetha,
H.; Huffman, J. C.; Wu, G.; Mindiola, D. J. J. Am. Chem. Soc. 2006,
128, 13575–13585.
(15) (a) Lammertsma, K. Top. Curr. Chem. 2003, 229, 95–119. (b)
Lammertsma, K.; Vlaar, M. J. M. Eur. J. Org. Chem. 2002, 1127–
1138. (c) Mathey, F.; Tran Huy, N. H.; Marinetti, A. HelV. Chim.
Acta 2001, 84, 2938–2957.
9
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J. AM. CHEM. SOC. 2009, 131, 13531–13537 13531

A R T I C L E S
Aktas et al.
starting point for the present study in which we examine the
IrdP reactivity toward isocyanides and explore the scope of
reaction for the transient, in situ generated 16-electron complex
[(η5-Cp*)IrdPsR]. We use DFT calculations to address dif-
ferences between the imido and phosphinidene complexes.
Results and Discussion
Reaction of deep pink iridium phosphinidene [(η5-Cp*)-
(XysNtC)IrdPMes*] 3a (δ 31P 757.1)6 with a 10-fold excess
of phenyl or 2,6-xylyl isocyanide at room temperature resulted
in the formation of yellow crystalline [1 + 2]-adducts 4a and
5 (R ) 4a, Xy; 5, Ph) as sole products in respectively 77%
and 87% yield after crystallization (Scheme 1). The highly
shielded resonances in the 31P NMR spectrum at δ ) -190.4
(4a) and -190.2 ppm (5) are diagnostic for three-membered
P-rings and indicate the formation of the desired iridaphos-
phiranes in analogy to iridaaziridine 2. Single-crystal X-ray
analysis of 4a and 5 established unequivocally the η2-(P,C)-
phosphaazaallene moiety17 and the linear 2,6-xylyl isocyanide,
both coordinated to iridium (Figure 1). The ca. 2.41 Å IrsP
bond of the IrPC ring is elongated from the reported 2.17-2.21
Å IrdP double bond of phosphinidene complexes like 3a
(carrying PPh3, CO, and NHC ligands instead of an iso-
cyanide),6,14 whereas the ca. 2.03 Å IrsC bond compares well
with the 2.017(9) Å reported for the IrNC ring in carbodiimide
complex 2;11c the ca. 1.80 Å PsC bond length is normal for
three-membered P-rings.
Figure 1. Displacement ellipsoid plot (50% probability) of 4a and 5.
Hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles
[deg] for 4a and 5 (in square brackets): Ir1-P1 2.4147(5) [2.4082(6)],
Ir1-C19 2.036(2) [2.029(2)], Ir1-C38[C36] 1.900(2) [1.895(2)], P1-C1
1.8766(19) [1.877(2)], P1-C19 1.805(2) [1.799(2)], N1-C19 1.267(2)
[1.265(3)], N1-C20 1.424(3) [1.424(3)], N2-C38[C36] 1.169(3) [1.168(3)],
N2-C39[C37] 1.402(3) [1.396(3)]; Ir1-P1-C19 55.46(6) [55.40(7)],
P1-Ir1-C19 46.91(6) [46.89(7)], Ir1-C38[C36]-N2 177.27(19) [178.3(2)],
C19-N1-C20 125.99(18) [123.2(2)], C38[C36]-N2-C39[C37] 171.7(2)
[175.9(2)].
Scheme 2. Synthesis of Iridaphosphiranes 4 via in situ generated
Phosphinidenes 3
Scheme 1. Synthesis of Iridaphosphiranes 4a and 5
of 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU) at -78 °C in the
presence of 10 equiv of 2,6-xylyl isocyanide resulted in an
immediate color change to deep purple, indicative of the
formation of 18-electron 3a, and upon warming to room
temperature to yellow to give after crystallization indeed
iridaphosphirane 4a in 86% isolated yield (Scheme 2). This
protocol was extended to other phosphine complexes as il-
lustrated in Scheme 2 for [(η5-Cp*)IrCl2(PH2R)] 6b (R ) Mes)
and 6c (R ) Dmp ) 2,6-dimesitylphenyl).18 Mesityl-substituted
6b undergoes a facile double dehydrohalogenation-ligation with
2 equiv of DBU and an excess of 2,6-xylyl isocyanide to afford
iridacycle 4b (δ 31P -218.7) as the sole product, which was
isolated by crystallization (60%; Scheme 2) and structurally
characterized by a single-crystal X-ray structure determination
(Figure 2). In this case, the sterically less shielded phosphinidene
intermediate [(η5-Cp*)(XysNtC)IrdPMes] 3b could not be
detected by 31P NMR spectroscopy under the reaction condi-
tions; the accordingly obtained more encumbered Dmp deriva-
tive 3c (deep purple) was observed (δ 31P 768.1) and converted
at room temperature to yellow complex 4c (64%; δ 31P -216.7).
The described reaction illustrates that different isocyanides
can be embedded in the product, something that appears not
feasible for the imido complexes.11 The question is then whether
the reaction mechanisms are the same for the two systems. Does
the distinction lie in the stability of the 16-electron intermediate
or the lack thereof? By reducing the stability of the 18-electron
phosphinidene complex and attempting to synthesize iridaphos-
phiranes directly via in situ generated 16-electron iridium
phosphinidene complexes, we examined whether the reaction
with isocyanides would mimic more closely that of imido
complex 1. The first step was to reproduce the formation of 4a.
Double dehydrohalogenation6,16 of orange colored primary
phosphine complex [(η5-Cp*)IrCl2(PH2Mes*)] (6a) with 2 equiv
Is the suggested 16-electron [(η5-Cp*)IrdPR] indeed formed
on double dehydrohalogenation of 6 in the absence of isocya-
nides (7; Scheme 2)? So far, only 16-electron zirconium
phosphinidenes have been observed in arene solvents by 31P
NMR spectroscopy (δ 31P 438-526 ppm)19 and as an unstable
Cp*2ZrdPMes*sLiCl adduct in dimethoxyethane (δ 31P 537
(16) (a) Termaten, A. T.; Aktas, H.; Schakel, M.; Ehlers, A. W.; Lutz, M.;
Spek, A. L.; Lammertsma, K. Organometallics 2003, 22, 1827–1834.
(b) Aktas, H.; Slootweg, J. C.; Ehlers, A. W.; Lutz, M.; Spek, A. L.;
Lammertsma, K. Angew. Chem. 2009, 121, 3154–3157; Angew. Chem.,
Int. Ed. 2009, 48, 3108-3111.
(17) Three platinum phosphaazaallene complexes with the general formula
PtL2-[η2-(P,C)-Mes*PCNPh] were characterized spectroscopically; see:
David, M.-A.; Alexander, J. B.; Glueck, D. S.; Yap, G. P. A.; Liable-
Sands, L. M.; Rheingold, A. L. Organometallics 1997, 16, 378–383.
(18) Base-induced double dehydrohalogenation of [(η5-Cp*)IrCl2(PH2Ph)]
(6d) in the presence of 10 equiv of 2,6-xylyl isocyanide gave a mixture
of unidentifiable products.
(19) (a) Ho, J.; Hou, Z.; Drake, R. J.; Stephan, D. W. Organometallics
1993, 12, 3145–3157. (b) Mahieu, A.; Igau, A.; Majoral, J.-P.
Phosphorus, Sulfur Silicon Relat. Elem. 1995, 104, 235–239.
9
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Iridium Phosphinidene Complexes
A R T I C L E S
Figure 2. Displacement ellipsoid plot (50% probability) of 4b. Hydrogen
atoms are omitted for clarity. Selected bond lengths [Å] and angles [deg]
for 4b: Ir1-P1 2.3952(6), Ir1-C10 2.039(2), Ir1-C29 1.888(2), P1-C1
1.837(2), P1-C10 1.799(3), N1-C10 1.267(3), N1-C11 1.429(3), N2-C29
1.172(3), N2-C30 1.398(3); Ir1-P1-C10 56.04(8), P1-Ir1-C10 47.02(7),
Ir1-C10-P1 76.94(9), Ir1-C29-N2 179.4(3), C10-N1-C11 123.8(2),
C29-N2-C30 161.9(2).
Figure 3. Intermediate E- and Z-[7c(CH2Cl2)] calculated at the BP86/TZP
level of theory. Hydrogen atoms are omitted for clarity. Selected bond
lengths [Å] and angles [deg] for E-[7c(CH2Cl2)] and Z-[7c(CH2Cl2)] (in
square brackets): Ir-P 2.192 [2.206], Ir-Cl1 2.567 [2.368]; Ir-P-Dmp
125.2 [114.6], P-Ir-Cl1 87.5 [102.9].
ppm).20 In contrast to imido analogue 1, attempted access to
Mes- and Mes*-substituted 16-electron [(η5-Cp*)IrdPR] (7a,b)
only led to dimers.12 DFT calculations have shown the imido
and phosphinidene complexes to differ with the first having a
linear IrNH arrangement with an IrtN triple bond21 and [(η5-
Cp)IrdPH] having a bent conformation (∠IrPH 126.4°) with
an IrdP double bond,12 a difference with consequences for their
reactivity. By introducing the sterically demanding Dmp sub-
stituent on phosphorus, we envisioned stabilizing the 16-electron
species by shielding the IrdP double bond. Double dehydro-
halogenation of primary phosphine complex [(η5-Cp*)-
IrCl2(PH2Dmp)] (6c) with 2 equiv of DBU in CD2Cl2 at -10
°C showed after warmup to room temperature a low-field 31P
NMR resonance at 672 ppm, suggesting indeed the formation
of a bent phosphinidene. To confirm its identity the 31P NMR
chemical shifts were calculated for the E and Z conformers of
[(η5-Cp*)IrdPDmp] 7c and their solvent adducts. Those for
“solvent-free” E-7c and Z-7c (178.9 and 418.2, respectively)
are significantly shielded from the experimental one, but those
for the solvent adducts are in the expected range (E-[7c(CH2Cl2)]
457.2, Z-[7c(CH2Cl2)] 683.6; Figure 3) with an excellent match
for the more stable Z-conformer (∆E ) 0.3 kcal·mol-1).
Therefore, we conclude that the Z-conformer is also a likely
intermediate when applying smaller donor ligands.6,16a,22
The experimental work leads us to conclude that the in situ
formed 16-electron phosphinidene coordinates with an isocya-
nide to the observable and isolable 18-electron complex 3, which
gives a [1 + 2]-cycloaddition with another isocyanide molecule
to form iridaphosphirane 4. The reaction with imido complex
1 is different in that this species is stable and that there are no
indications for an observable isocyanide coordinated 18-electron
imido complex. The question then arises whether this distinction
is due to the relative stabilities of the reactants, thus whether
the first or second isocyanide addition is rate-determining, or
to different mechanistic pathways. To answer this question we
used density functional theory at BP86/TZP to compare the
reaction of the imido and phosphinidene complexes 1′ and 7′
with isocyanide HNtC using model structures incorporating
Figure 4. Relative BP86/TZP energies (in kcal ·mol-1) for the reaction of
[(η5-Cp)IrtNH] 1′ with HNC. Selected bond lengths [Å] and angles [deg]
for 8′: Ir1-N1 1.876, Ir1-C1 1.859, C1-N2 1.210, Ir1-N1-H 105.5;
TS8′-9′: Ir1-N1 1.883, Ir1-C1 1.926, C1-N1 1.900, C1-N2 1.216,
Ir1-N1-H 120.1; 9′: Ir1-N1 1.913, Ir1-C1 2.040, C1-N1 1.352, C1-N2
1.275, Ir1-N1-H 153.1; 2′: Ir1-N1 2.124, Ir1-C1 2.076, C1-N1 1.337,
C1-N2 1.264, Ir1-C2 1.843, C2-N3 1.218, Ir1-N1-H 115.5.
only H substituents. We begin with the imido complex, [(η5-
Cp)IrtNH] 1′. The reaction starts with the addition of the
isocyanide to give bent 18-electron imido complex 8′ (∆E
) -26.1 kcal · mol-1; Figure 4),23 followed by ring closure
to 16-electron η2-carbodiimide complex 9′, requiring 18.4
kcal · mol-1 (∆E ) -10.9 kcal · mol-1), and subsequent
addition of a second isocyanide to afford the 48.3 kcal · mol-1
more stable product 2′.
The mechanism for formation of iridaphosphirane 4 is
different. Namely, addition of HNtC to [(η5-Cp)IrdPH] 7′ is
far more exothermic in giving the bent 18-electron species ([(η5-
Cp)(HNC)IrdPH] 3′ (∆E ) -58.2 kcal ·mol-1; Figure 5) that,
moreover, is energetically prohibited to undergo ring closure
to 10′ (∆E ) 27.1 kcal ·mol-1) and instead is susceptible to
attack of a second isocyanide to the phosphorus center to give
η1-(P,C)-phosphaazaallene complex 11′ (∆E ) -17.6 kcal ·
mol-1), which rearranges barrierless to the more favorable η2-
coordinated product 4′ (∆E ) -20.3 kcal ·mol-1).
(20) (a) Hou, Z.; Stephan, D. W. J. Am. Chem. Soc. 1992, 114, 10088–
10089. (b) Hou, Z.; Breen, T. L.; Stephan, D. W. Organometallics
1993, 12, 3158–3167.
(21) Jandciu, E. W.; Legzdins, P.; McNeil, W. S.; Patrick, B. O.; Smith,
K. M. Chem. Commun. 2000, 1809–1810, and references therein.
(22) Termaten, A. T.; Nijbacker, T.; Schakel, M.; Lutz, M.; Spek, A. L.;
Lammertsma, K. Chem.sEur. J. 2003, 9, 2200–2208.
(23) The alternative, direct [1 + 2]-cycloaddition of HNC to [(η5-
Cp)IrtNH] 1′ to afford η2-carbodiimide complex 9′ was not inves-
tigated in detail.
9
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A R T I C L E S
Aktas et al.
iridaazirane 2, the course of events is entirely different for the
two reactions as elucidated by DFT calculations. The imido
complex uses the first isocyanide molecule to construct a 16-
electron η2-carbodiimide complex, whereas for the phosphorus
analogue it is the second isocyanide molecule that induces the
ring closure, thereby giving the unique η2-phosphaazaallene
complex. It is further established that the sterically demanding
dimesitylphenyl substituent enables the detection of the solvent-
stabilized 16-electron phosphinidene intermediate [(η5-Cp*)Ird
PDmp] 7c, generated by double dehydrogenation of phosphine
precursor 6, prior to the reaction with isocyanides.
Experimental Section
Computations. All density functional theory calculations have
been performed with the parallelized Amsterdam density functional
(ADF) package (version 2005.01b and 2006.01).25 The Kohn-Sham
MOs were expanded in a large, uncontracted basis set of Slater-
type orbitals (STOs), of a triple-ꢀ basis set with polarization function
quality, corresponding to basis set TZP in the ADF package. The
1s core shell of carbon and nitrogen and the 1s2s2p core shells of
phosphorus were treated by the frozen core approximation. The
transition metal centers were described by a triple-ꢀ basis set for
the outer ns, np, nd, and (n + 1)s orbitals, whereas the shells of
lower energy were treated by the frozen core approximation using
a small core. All calculations were performed at the nonlocal
exchange self-consistent field (NL-SCF) level, using the local
density approximation (LDA) in the Vosko-Wilk-Nusair param-
etrization26 with nonlocal corrections for exchange (Becke88)27 and
correlation (Perdew86).28 All geometries were optimized using the
analytical gradient method implemented by Versluis and Ziegler,29
including relativistic effects by the Zeroth Order Regular Ap-
proximation (ZORA).30 The 31P NMR chemical shift tensors were
calculated with ADF’s NMR program,31 using single-point calcula-
tions with an all-electron basis for P within the ZORA approxima-
tion on the optimized frozen core structures (vide supra), using the
E-isomer of [Cp*(Me3P)IrdPMes*]6 as reference (σ -455.2 ppm)
for the total isotropic shielding tensors (δ +629.3 ppm with respect
to 85% H3PO4). All model complexes were calculated without
molecular symmetry.
Figure 5. Relative BP86/TZP energies (in kcal ·mol-1) for the reaction of
[(η5-Cp)IrdPH] 7′ with HNC. Selected bond lengths [Å] and angles [deg]
for 3′: Ir1-P1 2.223, Ir1-C1 1.858, C1-N2 1.213, Ir1-P1-H 98.9; 10′:
Ir1-P1 2.307, Ir1-C1 2.025, P1-C1 1.818, C1-N2 1.268, Ir1-P1-H
110.7; 11′: Ir1-P1 2.241, Ir1-C1 1.834, Ir1-C2 3.403, P1-C2 1.726,
C1-N1 1.229, C2-N2 1.217, Ir1-P1-H 122.9; 4′: Ir1-P1 2.439, Ir1-C1
1.850, Ir1-C2 2.066, P1-C2 1.813, C1-N1 1.216, C2-N2 1.258,
Ir1-P1-H 101.2, C2-Ir1-P1 46.6.
The higher nucleophilicity of the imido complex originates
from the lower energies of the ligand orbitals (NH -6.79 eV;
PH -5.46 eV) and is reflected in the calculated charges (-0.27
on N in 8′; -0.04 on P in 3′).24 Two differences that define the
dissimilar chemistries of the phosphinidene and imido com-
plexes are revealed by the calculated reaction pathways. First,
as noted, the initial ligand addition to the 16-electron complex
is far more exothermic for the phosphinidene than for imido
complex 8′, which suffers from distortion of the IrtNsR unit
from linearity. The second difference lies in the electronic
structure of the ring-closed structures of 9′ and 10′. An allenic,
π-conjugated NsCsN moiety is formed in Cs-symmetric 9′
that binds in a bidentate κ2-fashion to the metal, but in
phosphorus analogue 10′ π-conjugation is less favorable due
to the smaller overlap between the C(2p) and P(3p) orbitals so
that the allenic NsCsP unit binds instead to the metal in an
η2-fashion, acting as a 2-electron and not a 4-electron donor as
is the case for 9′. Therefore, nucleophilic attack of the
phosphorus of 3′ at the isocyanide is prohibited, while a modest
barrier is observed for the corresponding nitrogen attack of 8′.
As a consequence, stable 18-electron phosphinidene complexes
can be observed experimentally whereas the imido complexes
are prone to rearrangements. Formation of the final product 4′
occurs by direct attack of a second isocyanide to the phosphorus,
but this process can be hindered by steric congestion using bulky
substituents, which explains why 3a can be observed at low
temperatures by NMR spectroscopy even in an excess of
isocyanide.
General Procedures. All experiments and manipulations were
performed under an atmosphere of dry nitrogen with rigorous
exclusion of air and moisture using flame-dried glassware using
Schlenk techniques. Solvents were distilled from sodium (toluene),
CaCl2 (CH2Cl2), or LiAlH4 (pentanes, diethyl ether) and kept under
an atmosphere of dry nitrogen. Deuterated solvents were purchased
from Aldrich and dried over 4 Å molecular sieves (CD2Cl2, CDCl3,
C6D6). All solid starting materials were dried in vacuo. NMR spectra
were recorded on a Bruker Advance 250 (1H, 13C, 31P; 85% H3PO4)
or a Bruker Advance 400 (1H, 13C, 31P; 85% H3PO4) and referenced
internally to residual solvent resonances (CDCl3: 1H: δ 7.26,
1
13C{1H}: δ 77.16; CD2Cl2: H: δ 5.25, 13C{1H}: δ 54.00; C6D6:
1H: δ 7.16, 13C{1H}: δ 128.06). IR spectra were recorded on a
Mattson-6030 Galaxy FT-IR spectrophotometer, high-resolution
(25) ADF2005.01b and ADF2006.01, SCM, Theoretical Chemistry, Vrije
Universiteit, Amsterdam, The Netherlands, http://www.scm.com/.
(26) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys. 1980, 58, 1200–
1211.
(27) Becke, A. D. Phys. ReV. A 1988, 38, 3098–3100.
(28) Perdew, J. P. Phys. ReV. B 1986, 33, 8822–8824.
(29) (a) Fan, L.; Versluis, L.; Ziegler, T.; Baerends, E. J.; Raveneck, W.
Int. J. Quantum Chem. Quantum Chem. Symp. 1988, S22, 173–181.
(b) Versluis, L.; Ziegler, T. J. Chem. Phys. 1988, 88, 322–328.
(30) van Lenthe, E.; Ehlers, A. W.; Baerends, E. J. J. Chem. Phys. 1999,
110, 8943–8953.
(31) (a) Schreckenbach, G.; Ziegler, T. J. Phys. Chem. 1995, 99, 606–
611. (b) Schreckenbach, G.; Ziegler, T. J. Quantum Chem. 1997, 61,
899–918. (c) Wolff, S. K.; Ziegler, T. J. Chem. Phys. 1998, 109, 895–
905. (d) Wolff, S. K.; Ziegler, T.; van Lenthe, E.; Baerends, E. J.
J. Chem. Phys. 1999, 110, 7689–7698.
Conclusions
Imido and phosphinidene iridium complexes differ in their
properties and reactivities as established for the reaction with
isocyanides. Both isolated and in situ generated 18-electron
iridium phosphinidene [(η5-Cp*)(XysNtC)IrdPMes*] 3 afford
iridaphosphirane 4 as the sole product. Despite this apparent
resemblance with the stable imido complex 1 that gives
(24) Hirshfeld, F. L. Theor. Chim. Acta 1977, 44, 129–138.
9
13534 J. AM. CHEM. SOC. VOL. 131, NO. 37, 2009

Iridium Phosphinidene Complexes
A R T I C L E S
mass spectra (HR-MS) were recorded on a Finnigan Mat 900
spectrometer operating at an ionization potential of 70 eV, and fast
atom bombardment (FAB) mass spectrometry was carried out using
a JEOL JMS SX/SX 102A four-sector mass spectrometer (70 eV).
Melting points were measured on samples in sealed capillaries on
a Stuart Scientific SMP3 melting point apparatus and are uncor-
rected. [(η5-Cp*)IrCl2(PH2Mes*)] (6a),6 [(η5-Cp*)IrCl2(PH2Mes)]
(6b),6 [(η5-Cp*)(XysNtC)IrdPMes*] (3a),6 and Mes*PH232 were
prepared according to literature procedures. PhPH2, MesPH2, and
(s), 697.1 cm-1 (s). HR FAB-MS: calcd for C16H22Cl2PIr: 508.0451,
found 508.0459. m/z (%): 508 (8) [M]+, 473 (29) [M - Cl]+, 363
(20) [M - Cl - PhPH2]+.
[(Cp*)(XysNtC)IrPMes*CdNXy] (4a). An orange solution
of [(η5-Cp*)IrCl2(PH2Mes*)] (6a; 0.135 g, 0.20 mmol) in CH2Cl2
(2 mL) was added to a mixture of DBU (59.8 µL, 0.40 mmol) and
XysNtC (0.262 g, 2.0 mmol) in CH2Cl2 (3 mL) at -78 °C, which
resulted in a immediate color change to deep purple. After 1 h, the
reaction mixture was allowed to warm up to room temperature and
stirred for an additional hour. After evaporation to dryness, the
yellow residue was washed with pentane (2 × 1 mL) and extracted
into diethyl ether (4 × 15 mL), and the solution was filtered. After
concentration of the solution to a few milliliters, 4a (0.148 g, 0.171
mmol, 86%) was obtained as yellow crystals by crystallization at
-20 °C. Mp: 143 °C (dec). 1H NMR (400.13 MHz, C6D6, 300 K):
δ 1.11 (s, 9H; p-C(CH3)3), 1.60 (s, 15H; C5(CH3)5), 1.92 (s, 9H;
o-C(CH3)3), 1.93 (s, 6H; o-CdNXyCH3), 2.02 (s, 9H; o-C(CH3)3),
2.39 (s, 3H; o-CtNXyCH3), 2.45 (s, 3H; o-CtNXyCH3), 6.69 (d,
DmpPH2 were prepared analogously to IsPH2,34 by LiAlH4
33
reduction of respectively PhPCl2, MesPCl2, and DmpPCl2.35
PhsNtC36 was prepared by dehydration of the corresponding
formamidewithphosphorylchloride.2,6-Xylylisocyanide(XysNtC)
was purchased from Fluka and used as received.
[(η5-Cp*)IrCl2(PH2Dmp)] (6c). A mixture of freshly prepared
DmpPH2 (1.00 g, 2.89 mmol) and [(η5-Cp*)IrCl2]2 (0.59 g, 0.74
mmol) in CH2Cl2 (50 mL) was stirred for 30 min at room
temperature. Evaporation to dryness and chromatography of the
residue over silica with CHCl3 followed by CHCl3/diethyl ether
4:1 as eluent and subsequent crystallization from CH2Cl2/pentane
at -20 °C yielded [(η5-Cp*)IrCl2(PH2Dmp)] (6c) (1.08 g, 1.45
mmol, 98%) as orange crystals. Mp: 258 °C (dec). 1H NMR (400.13
MHz, CDCl3, 300 K): δ 1.32 (d, 4J(H,P) ) 3.3 Hz, 15H; C5(CH3)5),
2.15 (s, 12H; o-CH3), 2.34 (s, 6H; p-CH3), 5.49 (d, 1J(H,P) ) 378.6
Hz, 2H; PH2), 6.95 (s, 4H; m-MesH), 7.05 (dd, 3J(H,H) ) 7.5 Hz,
3
3J(H,H) ) 7.5 Hz, 2H; m-CdNXy), 6.75 (m, J(H,H) ) 7.5 Hz,
1H; p-CdNXy), 6.92 (m, 3J(H,H) ) 7.0 Hz, 1H; m-CtNXy), 6.95
3
3
(m, J(H,H) ) 7.0 Hz, 1H; p-CtNXy), 7.04 (m, J(H,H) ) 7.0
Hz, 1H; m-CtNXy), 7.06 (s, 1H; m-Mes*), 7.29 (s, 1H; m-Mes*).
13C{1H} NMR (100.64 MHz, C6D6, 300 K): δ 9.4 (s; C5(CH3)5),
19.5 (s; o-CdNXyCH3), 20.0 and 22.1 (s; o-CtNXyCH3), 31.2
4
3
4J(H,P) ) 2.9 Hz, 2H; m-PhH), 7.48 (t, J(H,H) ) 7.5 Hz, 1H;
(s; p-C(CH3)3), 33.9 (d, J(C,P) ) 11.2 Hz; o-C(CH3)3), 34.3 (s;
p-C(CH3)3), 34.6 (d, 4J(C,P) ) 6.3 Hz; o-C(CH3)3), 39.8 and 41.0
(s; o-C(CH3)3), 97.1 (s; C5(CH3)5), 121.9 (s; m-Mes*), 122.7 (s;
p-CtNXy), 123.8 (s; m-Mes*), 125.9 (s; p-CdNXy), 126.7 (s;
o-CtNXy), 127.8 (s; m-CtNXy), 127.9 (s; m-CdNXy), 128.8 (s;
m-CtNXy), 129.7 (s; o-CtNXy), 130.3 (s; o-CdNXy), 132.1 (d,
1J(C,P) ) 92.1 Hz; CdNXy), 134.1 (s; ipso-CdNXy), 141.5 (s;
p-PhH). 13C{1H} NMR (100.64 MHz, CDCl3, 300 K): δ 7.9 (s;
C5(CH3)5), 21.2 (s; p-CH3), 21.5 (s; o-CH3), 92.1 (d, 2J(C,P) ) 3.0
1
Hz; C5(CH3)5), 121.1 (d, J(C,P) ) 52.0 Hz; ipso-Ph), 128.9 (s;
3
4
m-Mes), 129.7 (d, J(C,P) ) 7.8 Hz; m-Ph), 131.1 (d, J(C,P) )
2.1 Hz; p-Ph), 136.7 (s; p-Mes), 137.3 (s; o-Mes), 138.0 (d, 3J(C,P)
) 4.3 Hz; ipso-Mes), 146.9 (d, 2J(C,P) ) 8.8 Hz; o-Ph). 31P NMR
(101.3 MHz, CDCl3, 300 K): δ -82.8 (t, 1J(P,H) ) 378.6 Hz, PH2).
IR (KBr): ν 3023.9 (w), 2988.2 (m), 2962.1 (m), 2915.9 (s), 2854.1
(w), 2383.6 (m, P-H), 2370.1 (m, P-H), 1610.3 (s), 1565.0 (s),
1448.3 (s), 1376.9 (s), 1027.9 (s), 921.8 (s), 845.6 (s), 806.1 (s),
745.4 (s), 460.9 cm-1 (s). HR FAB-MS: calcd for C34H42Cl2PIr:
744.2018, found 744.2024. m/z (%): 744 (5) [M]+, 709 (100) [M
- Cl]+, 673 (12) [M - Cl - HCl]+, 363 (95) [M - Cl -
DmpPH2]+.
4
CtNXy), 146.1 (s; p-Mes*), 150.6 (d, J(C,P) ) 12.9 Hz; ipso-
CtNXy), 156.9 (d, 2J(C,P) ) 8.4 Hz; o-Mes*), 158.4 (s; o-Mes*),
180.6 (d, 1J(C,P) ) 103.4 Hz; ipso-Mes*). 31P NMR (101.3 MHz,
C6D6, 300 K): δ -190.4 (s; PMes*). IR (KBr): ν ) 3062.4 (w),
2960.2 (s), 2948.6 (s), 2903.3 (s), 2863.8 (s), 2272.7 (very broad
w, PCdN), 2072.2 and 2020.1 (s, CtN), 1637.3 and 1586.2 (s,
CtN), 1463.7 (s, CdC), 1390.4, 1381.8 and 1359.6 (s, PsAr),
1240.0 (s), 1195.7 and 1185.1 (s, P ) C), 1124.3 (w), 1090.6 (w),
1025.0 (m, PsAr), 922.8 (w), 873.6 (w), 773.3 and 745.4 (s, PsC),
708.7 (w), 697.8 (m), 522.6 cm-1 (m). HR EI-MS: calcd for
C37H53IrNP (M - CtNXy) 735.3548, found 735.3541. m/z (%):
866 (2) [M]+, 735 (100) [M - CtNXy]+, 590 (16) [M - PMes*]+,
455 (24) [M - PMes* - Cp*]+. Alternatively, 4a can be prepared
from 3a as follows: XysNtC (0.197 g, 1.50 mmol) was added to
a dark purple solution of 3a (0.110 mg, 0.15 mmol) in pentanes
(20 mL) at room temperature. After 15 h, the yellow reaction
mixture was evaporated to dryness and the residue was washed
with pentane (2 × 1 mL) and extracted into diethyl ether. After
filtration and concentration to a few milliliters, yellow crystals of
4a (0.113 g, 0.131 mmol, 87%) were obtained at -20 °C.
[(η5-Cp*)IrCl2(PH2Ph)] (6d). A freshly prepared solution of
PhPH2 (0.6 M in Et2O, 1.05 mL, 0.63 mmol) was added to an
orange solution of [(η5-Cp*)IrCl2]2 (0.250 g, 0.314 mmol) in CH2Cl2
(20 mL) at room temperature. After 30 min, the resulting mixture
was filtered over a short silica column and eluted with CHCl3, after
which the orange fractions were combined and evaporated to
dryness. Subsequent crystallization from CH2Cl2/pentane at -20
°C yielded [(η5-Cp*)IrCl2(PH2Ph)] (6d) as yellow microcrystals,
which were washed with pentane and dried in vacuo (0.268 g, 0.528
1
mmol, 84%). Mp: 222 °C (dec). H NMR (250.13 MHz, CDCl3,
1
300 K): δ 1.63 (s, 15H; C5(CH3)5), 5.88 (d, J(H,P) ) 394.1 Hz,
2H; PH2), 7.44-7.47 (m, 3H; m- and p-PhH), 7.78-7.85 (m, 2H;
o-PhH). 13C{1H} NMR (62.90 MHz, CDCl3, 300 K): δ 8.6 (s;
C5(CH3)5), 91.9 (d, 2J(C,P) ) 3.3 Hz; C5(CH3)5), 122.6 (d, 1J(C,P)
) 53.3 Hz; ipso-Ph), 128.8 (d, 2J(C,P) ) 10.7 Hz; o-Ph), 131.5 (d,
[(Cp*)(XysNtC)IrPMes*CdNPh] (5). A freshly prepared
solution of PhsNtC (0.143 M, 10.5 mL, 1.50 mmol) in CH2Cl2
was added to a dark purple solution of 3a (0.110 mg, 0.15 mmol)
in pentane (10 mL) at room temperature. After 15 h, the yellow
reaction mixture was evaporated to dryness and the residue was
extracted into pentane. After removal of a black residue by filtration,
all volatiles were removed in vacuo. The residual yellow solid was
extracted into diethyl ether, and after concentration to a few
milliliters, yellow crystals of 5 (0.097 g, 0.116 mmol, 77%) were
3
4J(C,P) ) 2.7 Hz; p-Ph), 133.5 (d, J(C,P) ) 8.8 Hz; m-Ph). 31P
1
NMR (101.3 MHz, CDCl3, 300 K): δ -56.3 (t, J(P,H) ) 394.1
Hz, PH2). IR (KBr): ν 3051.8 (s), 2973.7 (s), 2914.9 (s), 2870.5
(m), 2412.5 (w, P-H), 2389.4 (m, P-H), 1451.2 (s), 1435.8(s),
1378.9 (s), 1156.1 (w), 1070.3 (m), 1031.7 (s), 899.6 (s), 745.4
(32) Cowley, A. H.; Kilduff, J. E.; Newman, T. H.; Pakulski, M. J. Am.
Chem. Soc. 1982, 104, 5820–5821.
1
obtained at -20 °C. Mp: 159 °C (dec). H NMR (400.13 MHz,
C6D6, 300 K): δ 0.93 (s, 9H; p-C(CH3)3), 1.62 (s, 15H; C5(CH3)5),
1.94 (s, 15H; o-C(CH3)3 and o-CtNXyCH3), 2.05 (s, 9H; o-
(33) Urnezius, E.; Protasiewicz, J. D. Main Group Chem. 1996, 1, 369–
372.
3
(34) van den Winkel, Y.; Bastiaans, H. M. M.; Bickelhaupt, F. J.
Organomet. Chem. 1991, 405, 183–194.
C(CH3)3), 6.63 (d, J(H,H) ) 7.4 Hz, 2H; m-CtNXy), 6.70 (t,
3J(H,H) ) 7.4 Hz, 1H; p-CtNXy), 7.00 (t, 3J(H,H) ) 7.3 Hz, 1H;
p-CdNPh), 7.03 (d, 4J(C,P) ) 7.8 Hz, 1H; m-Mes*), 7.18 (d,
3J(H,H) ) 7.9 Hz, 2H, m-CdNPh), 7.45 (d, 4J(C,P) ) 7.8 Hz, 1H;
(35) Overla¨nder, C.; Tirre´e, J. J.; Nieger, M.; Niecke, E.; Moser, C.; Spirk,
S.; Pietschnig, R. Appl. Organometal. Chem. 2007, 21, 46–48.
(36) (a) Ugi, I.; Meyr, R. Chem. Ber. 1960, 93, 239–248. (b) Obrecht, R.;
Hermann, R.; Ugi, I. Synthesis 1985, 400–402.
3
m-Mes*), 7.82 (d, J(H,H) ) 7.9 Hz, 2H; o-CdNPh). 13C{1H}
9
J. AM. CHEM. SOC. VOL. 131, NO. 37, 2009 13535

A R T I C L E S
Aktas et al.
NMR (100.64 MHz, C6D6, 300 K): δ 9.4 (s; C5(CH3)5), 19.0 (s;
p-MesCH3), 2.58 (s, 6H; o-CtNXyCH3), 6.77 (m, 5H; m-CdNXy,
4
3
o-CtNXyCH3), 31.0 (s; p-C(CH3)3), 33.6 (d, J(C,P) ) 11.3 Hz;
m-Mes, and p-CdNXy), 6.84 (m, J(H,H) ) 7.4 Hz, 3H; m-PhP
and p-CtNXy), 6.96 (d, 3J(H,H) ) 7.4 Hz, 2H; m-CtNXy), 6.98
o-C(CH3)3), 34.1 (s; p-C(CH3)3), 34.6 (d, 4J(C,P) ) 6.8 Hz;
o-C(CH3)3), 39.9 and 40.9 (s; o-C(CH3)3), 96.7 (s; C5(CH3)5), 119.6
(s; m-Mes*), 122.2 (s; m-Mes*), 122.6 (s; o-CdNPh), 123.8 (s;
p-CdNPh), 125.8 (s; p-CtNXy), 127.9 (s; m-CtNXy), 128.8 (s;
m-CdNPh), 129.9 (s; ipso-CtNXy), 131.6 (d, 1J(C,P) ) 80.0 Hz;
CdNPh), 133.9 (s; o-CtNXy), 140.6 (bs, CtNXy), 146.2 (s;
3
(s, 2H; m-Mes), 7.08 (t, J(H,H) ) 7.4 Hz, 1H; p-PhP). 13C{1H}
3
NMR (100.64 MHz, C6D6, 300 K): δ 9.1 (d, J(C,P) ) 2.9 Hz;
C5(CH3)5), 19.2 (s; o-CdNXyCH3), 19.8 (s; p-MesCH3), 21.0 (s;
o-MesCH3), 22.0-22.2 (bs; o-MesCH3, o-CtNXyCH3, o-CtNXy-
CH3, and p-MesCH3), 96.9 (s; C5(CH3)5), 122.4 (s; p-CtNXy),
126.0 (s, o-CtNXy), 126.1 (s; o-CtNXy), 126.2 (s; p-CdNXy),
127.1 (s; m-CtNXy), 127.2 (s; p-PhP), 128.0 (s; ipso-Mes, and
m-Mes), 128.5 (s; m-CdNXy), 128.6 (s; m-CtNXy), 129.0 (s;
m-Mes), 129.8 (s; p-Mes), 129.9 (bs; m-PhP), 130.6 (s; ipso-
CdNXy), 134.5 (s; o-CdNXy), 136.1 and 136.5 (s; o-Mes), 138.0
3
p-Mes*), 152.9 (d, J(C,P) ) 13.1 Hz; ipso-CdNPh), 156.9 (d,
2J(C,P) ) 8.2 Hz; o-Mes*), 157.7 (s; o-Mes*), 187.6 (d, 1J(C,P) )
101.4 Hz; ipso-Mes*). 31P NMR (101.3 MHz, C6D6, 300 K): δ
-190.2 (s; PMes*). IR (KBr): ν ) 3069.2 (m), 3047.0 (w), 2966.0
(m), 2945.6 (s), 2913.9 (m), 2898.5 (w), 2866.7 (w), 2851.3 (w),
2283.3 (very broad w, PCdN), 2084.7 and 2037.4 (s, CtN),
1677.8, 1644.0, 1583.3 and 1544.7 (s, CdN), 1480.1, 1462.8 and
1441.5 (s, CdC), 1390.4, 1375.0 and 1359.6 (m, PsAr), 1315.2
(m), 1261.2 (m), 1198.5 (m, PdC), 1066.4 (m), 1026.0 (m, PsAr),
898.7 (m), 875.5 (m), 789.7, 763.7, 747.3, and 735.7 (s, PsC),
692.3 and 683.6 (s), 523.6 (m), 496.6 cm-1 (w). HR EI-MS: calcd
for C37H53IrNP (M - CtNPh) 735.3548, found 735.3517. m/z (%):
838 (2) [M]+, 735 (5) [M - CtNPh]+, 707 (5) [M - CtNXy]+,
562 (6) [M - PMes*]+.
1
(d, J(C,P) ) 69.5 Hz; ipso-PhP), 140.8 (s; ipso-Mes), 144.0 (s;
2
CtNXy), 148.0 (s; ipso-CtNXy), 148.2 (d, J(C,P) ) 12.9 Hz;
o-Ph), 173.3 (d, 1J(C,P) ) 93.5 Hz; PsCdNXy). 31P NMR (101.3
MHz, C6D6, 300 K): δ -216.7 (s; PDmp). IR (KBr): ν ) 3036.4
(m), 2977.6 (m), 2949.6 (s), 2909.1 (m), 2851.3 (m), 2268.9 (very
broad w, PCdN), 2054.8 and 2012.4 (s, CtN), 1645.0 and 1586.2
(s, CdN), 1457.0 and 1443.5 (s, CdC), 1377.0 (s, PsAr), 1188.9
(m, PdC), 1088.6 (m), 1030.8 (m, PsAr), 845.6 (m), 800.3 (m),
761.7 and 745.4 (s, PsC), 672.1 (s), 546.7 (w), 520.0 cm-1 (w).
HR EI-MS: calcd for C52H58IrN2P 934.3967, found 934.3930. m/z
(%): 934 (14) [M]+, 803 (100) [M - CtNXy]+, 589 (60) [M -
DmpPH]+, 454 (16) [M - DmpPH - Cp*]+.
[(η5-Cp*)(XysNtC)IrPMesCdNXy] (4b). DBU (59.8 µL,
0.40 mmol) was added to a yellow solution of [(η5-Cp*)-
IrCl2(PH2Mes)] (6b; 0.110 g, 0.20 mmol) and XysNtC (0.262 g,
2.0 mmol) in CH2Cl2 (6 mL) at -78 °C, and the mixture was
allowed to warm up to room temperature. After evaporation to
dryness, the residue was washed with pentane (3 mL) and extracted
into diethyl ether (2 × 10 mL), and the solution was filtered. After
concentration of the solution to a few milliliters, a yellow solid
was obtained, which was recrystallized from diethyl ether at -20
°C to yield 4b (0.089 g, 0.120 mmol, 60%) as yellow crystals. Mp:
Double Dehydrohalogenation of [(η5-Cp*)IrCl2(PH2Dmp)]
(6c). DBU (2 equiv, 8.4 µL, 5.6 µmol) was added to an orange
solution of [(η5-Cp*)IrCl2(PH2Dmp)] (6c; 20.9 mg, 2.8 µmol) in
CD2Cl2 (0.4 mL) at -10 °C. After 5 min at room temperature, the
reaction mixture turned deep red of which 31P NMR spectroscopy
at 263 K showed unreacted [(η5-Cp*)IrCl2(PH2Dmp)] at δ -81.5
(9.2%) together with phosphinidene [(η5-Cp*)(CD2Cl2)IrdPDmp)]
(7c(DCM)) at δ 672.1 (11.5%), the monodehydrohalogenated
1
122 °C (dec). H NMR (400.13 MHz, C6D6, 300 K): δ 1.74 (s,
1
product [(η5-Cp*)(Cl)IrdPHDmp] at δ 105.8 (d, J(P,H) ) 369.6
15H; C5(CH3)5), 1.81 (s, 6H; o-CdNXyCH3), 1.85 (s, 3H; p-
MesCH3), 2.46 (s, 6H; o-MesCH3), 2.84 (s, 6H; o-CtNXyCH3),
6.44 (bs, 2H; m-Mes), 6.64 (d, 3J(H,H) ) 7.3 Hz, 2H; m-CdNXy),
Hz, 50.7%), and two minor products at δ -17.4 (d, 1J(P,H) ) 185.3
1
Hz, 19.3%) and -67.9 (d, J(P,H) ) 212.6 Hz, 9.3%).
Attempted Synthesis of [(η5-Cp*)(XysN′C)IrdPDmp] (3c).
An orange solution of [(η5-Cp*)IrCl2(PH2Dmp)] (6c; 75 mg, 0.10
mmol) in CH2Cl2 (1 mL) was added to a clear, colorless solution
of XysNtC (13 mg, 0.10 mmol) and DBU (29.8 µL, 0.20 mmol)
in toluene (2 mL) at room temperature. After 3 h, a color change
to dark purple was observed and the phosphinidene [(η5-
Cp*)(XysNtC)IrdPDmp] (3c) could be detected by 31P NMR
spectroscopy at δ 768.1 (50%) together with another product at
3
3
6.71 (m, J(H,H) ) 7.3 Hz, 1H; p-CdNXy), 6.99 (m, J(H,H) )
7.0 Hz, 1H; p-CtNXy), 7.06 (d, 3J(H,H) ) 7.0 Hz, 2H;
m-CtNXy). 13C{1H} NMR (100.64 MHz, C6D6, 300 K): δ 9.5 (s;
3
C5(CH3)5), 18.8 (s; o-CdNXyCH3), 20.6 (d, J(C,P) ) 16.5 Hz,
o-MesCH3), 20.8 (s; p-MesCH3), 23.8 and 23.9 (s; o-CtNXyCH3),
96.7 (s; C5(CH3)5), 122.7 (s; p-CtNXy), 125.9 (s; p-CdNXy),
127.4 (s; m-CdNXy), 127.5 (s; o-CtNXy), 128.0 (s; p-Mes), 128.1
(s; m-CtNXy), 128.7 (s; m-Mes), 130.2 (s; ipso-CdNXy), 133.7
(s; o-CdNXy), 135.4 (s; o-Mes), 143.5 (d, 2J(C,P) ) 9.7 Hz,
CtNXy), 151.9 (d, 1J(C,P) ) 70 Hz, ipso-Mes), CdNXy and ipso-
CtNXy could not be detected. 31P NMR (101.3 MHz, C6D6, 300
K): δ -218.7 (s; PMes). IR (KBr): ν ) 3034.6 (w), 2972.8 (w),
2940.0 (w), 2911.0 (m), 2886.0 (m), 2871.5 (m), 2842.6 (w), 2281.4
(very broad w, PCdN), 2057.7 and 2019.1 (s, CtN), 1638.2 and
1587.1 (s, CdN), 1459.9 and 1437.7 (s, CdC), 1376.0 (s, PsAr),
1240.0 (s), 1187.9 (m, PdC), 1025.0 (m, PsAr), 984.5 (m), 840.8
(s), 774.3 and 761.7 (s, PsC), 678.8 (s), 517.8 cm-1 (s). HR EI-
MS: calcd for C37H44IrN2P 740.2871, found 740.2896. m/z (%):
740 (<1) [M]+, 609 (1) [M - CNXy]+, 590 (20) [M - PMes]+.
1
-88.6 (d, J(P,H) ) 202 Hz, 50%).
X-ray Crystal Structure Determinations. Intensities were
measured at 150(2) K on a Nonius KappaCCD diffractometer
with a rotating anode (graphite monochromator, λ ) 0.710 73
Å) up to a resolution of (sin θ/λ)max ) 0.65 Å-1. Integration
was performed with EvalCCD37 (compounds 4a and 4b) or
HKL200038 (compound 5). The program SADABS39 was used
for absorption correction and scaling. The structures were solved
with automated Patterson methods using the program DIRDIF-
9940 and refined with SHELXL-9741 against F2 of all reflections.
Non-hydrogen atoms were refined with anisotropic displacement
parameters. All hydrogen atoms were located in difference
Fourier maps and refined with a riding model. Geometry
[(Cp*)(XysNtC)IrPDmpCdNXy] (4c). An orange solution
of [(η5-Cp*)IrCl2(PH2Dmp)] (6c; 0.075 g, 0.10 mmol) in CH2Cl2
(1.5 mL) was added to a mixture of DBU (29.9 µL, 0.20 mmol)
and XysNtC (0.131 g, 1.0 mmol) in CH2Cl2 (1 mL) at -78 °C,
and the reaction mixture was allowed to warm up to room
temperature. After evaporation to dryness, the residue was washed
with pentane (2 × 1 mL) and extracted into diethyl ether (2 × 10
mL), and the solution was filtered. After concentration of the
solution to a few milliliters, 4c (0.060 g, 0.064 mmol, 64%) was
obtained as yellow crystals by crystallization at -20 °C. Mp: 175
(37) Duisenberg, A. J. M.; Kroon-Batenburg, L. M. J.; Schreurs, A. M. M.
J. Appl. Crystallogr. 2003, 36, 220–229.
(38) Otwinowski, Z.; Minor, W. In Methods in Enzymology, Volume 276;
Carter, C. W.; Jr., Sweet, R. M., Eds.; Academic Press: 1997; pp 307-
326.
(39) Sheldrick, G. M. SADABS: Area-Detector Absorption Correction,
v2.10; Universita¨t Go¨ttingen: Germany, 1999.
(40) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; Garcia-
Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The DIRDIF99
program system, Technical Report of the Crystallography Laboratory;
University of Nijmegen: The Netherlands, 1999.
1
°C (dec). H NMR (400.13 MHz, C6D6, 346 K): δ 1.41 (s, 15H;
C5(CH3)5), 1.97 (s, 6H; o-CdNXyCH3), 2.15 (s, 6H; o-MesCH3),
2.20 (s, 6H; o-MesCH3), 2.23 (s, 3H; p-MesCH3), 2.50 (s, 3H;
(41) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
9
13536 J. AM. CHEM. SOC. VOL. 131, NO. 37, 2009

Iridium Phosphinidene Complexes
A R T I C L E S
calculations and checking for higher symmetry were performed
with the PLATON program.42 Further details are given in Table
1 in the Supporting Information.
respectively HR EI-MS and HR FAB-MS, and Mr. A.K. Mohamud
is acknowledged for his contribution at the early stage of the study.
Supporting Information Available: Cartesian coordinates (Å)
and energies (au) of all stationary points. Cif files with
crystallographic data and copies of the NMR spectra of all novel
compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
Acknowledgment. This work was supported by The Nether-
lands Foundation for Chemical Sciences (CW) with financial aid
from The Netherlands Organization for Scientific Research (NWO).
Dr. M. Smoluch and H. Peters are acknowledged for measuring
(42) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.
JA9048509
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