Synthesis and Properties of Iridium Bis(phosphinite) Pincer Complexes (p-XPCP)IrH2, (p-XPCP)Ir(CO), (p-XPCP)Ir(H)(aryl), and {(p-XPCP)Ir}H2{μ-N2} and Their Relevance in Alkane Transfer Dehydrogenation

Article abstract of DOI:10.1021/om030670o

A series of bis(phosphinite) (p-XPCP)IrH₂ pincer complexes {[PCP = η³-5-X-C₆H₂[OP-(tBu)₂] ₂-1,3], X = MeO (6a), Me (6b), H (6c), P (6d), C₆F ₅ (6e), and Ar^F [=3,5-bis-(trifluoromethyl)phenyl] (6f)} have been synthesized by dehydrochlorination of (p-XPCP)-IrHCl precursor complexes 4a-f with NaOtBu in the presence of hydrogen. Dehydrochlorination of 4f in the presence of nitrogen yields {(p-Ar^FPCP)Ir} ₂{μ-N₂} (11f), which was analyzed by X-ray diffraction. Complexes 6a-f exhibit identical catalytic activity in the transfer dehydrogenation of cyclooctane (COA) with tert-butylethylene (TBE) when compared to mixtures of precatalysts 4a-f and NaOtBu. The electronic properties of the fragments (p-XPCP)Ir (Aa-f) are discussed on the basis of the v_CO of (p-XPCP)Ir(CO) complexes (8a-f) as well as on VHD coupling constants of monodeuterated complexes (p-XPCP)IrHD (6a-f-d₁). Reaction of 4a-f with NaOtBu in arene solvents generates (p-XPCP)Ir(aryD(H) complexes (9 and 10), which undergo rapid arene exchange on the NMR time scale. Exchange rates are zero-order in free arene, implying a dissociative exchange mechanism. More electron-deficient complexes, e.g., (p-C₆F₅PCP)Ir(m-xylyl) (H) (10e) or (p-Ar^FPCP)Ir(m-xylyl)(H) (10f), reductively eliminate m-xylene significantly faster than the more electron-rich complexes, e.g., (p-MeOPCP)Ir(m-xylyD(H) (10a), on the basis of the line widths δv _1/2(0°C) of the hydridic NMR resonances of (p-XPCP)Ir(m-xylyl)(H) complexes 10a-f. The same correlation with substituent effects applies to the catalytic activity (initial turnover frequencies) of complexes 6a-f in the transfer dehydrogenation of COA with TBE.

Full text of DOI:10.1021/om030670o

1766
Organometallics 2004, 23, 1766-1776
Syn th esis a n d P r op er ties of Ir id iu m Bis(p h osp h in ite)
P in cer Com p lexes (p-XP CP )Ir H2, (p-XP CP )Ir (CO),
(p-XP CP )Ir (H)(a r yl), a n d {(p-XP CP )Ir }2{µ-N2} a n d Th eir
Releva n ce in Alk a n e Tr a n sfer Deh yd r ogen a tion
Inigo Go¨ttker-Schnetmann, Peter S. White, and Maurice Brookhart*
Department of Chemistry, University of North Carolina at Chapel Hill,
Chapel Hill, North Carolina 27599-3290
Received November 24, 2003
A series of bis(phosphinite) (p-XPCP)IrH2 pincer complexes {[PCP ) η3-5-X-C6H2[OP-
(tBu)2]2-1,3], X ) MeO (6a ), Me (6b), H (6c), F (6d ), C6F5 (6e), and ArF [)3,5-bis-
(trifluoromethyl)phenyl] (6f)} have been synthesized by dehydrochlorination of (p-XPCP)-
IrHCl precursor complexes 4a -f with NaOtBu in the presence of hydrogen. Dehydrochlorina-
tion of 4f in the presence of nitrogen yields {(p-ArFPCP)Ir}2{µ-N2} (11f), which was analyzed
by X-ray diffraction. Complexes 6a -f exhibit identical catalytic activity in the transfer
dehydrogenation of cyclooctane (COA) with tert-butylethylene (TBE) when compared to
mixtures of precatalysts 4a -f and NaOtBu. The electronic properties of the fragments (p-
XPCP)Ir (Aa -f) are discussed on the basis of the νCO of (p-XPCP)Ir(CO) complexes (8a -f)
1
as well as on J HD coupling constants of monodeuterated complexes (p-XPCP)IrHD (6a -f-
d1). Reaction of 4a -f with NaOtBu in arene solvents generates (p-XPCP)Ir(aryl)(H) complexes
(9 and 10), which undergo rapid arene exchange on the NMR time scale. Exchange rates
are zero-order in free arene, implying a dissociative exchange mechanism. More electron-
deficient complexes, e.g., (p-C6F5PCP)Ir(m-xylyl)(H) (10e) or (p-ArFPCP)Ir(m-xylyl)(H) (10f),
reductively eliminate m-xylene significantly faster than the more electron-rich complexes,
e.g., (p-MeOPCP)Ir(m-xylyl)(H) (10a ), on the basis of the line widths ∆ν1/2(0 °C) of the hydridic
NMR resonances of (p-XPCP)Ir(m-xylyl)(H) complexes 10a -f. The same correlation with
substituent effects applies to the catalytic activity (initial turnover frequencies) of complexes
6a -f in the transfer dehydrogenation of COA with TBE.
In tr od u ction
alkane dehydrogenation6 provides access to olefins and
arenes that are valuable feedstocks for conversion to
higher value materials. Industrial alkane dehydroge-
nations are restricted to heteregenous catalysts and
operate at high temperatures (ca. 400-600 °C);7 thus
effective homogeneous alkane dehydrogenation under
relatively low-temperature conditions is a desirable
process.
The selective functionalization of unactivated alkanes
remains a challenging task in organic chemistry, espe-
cially considering homogeneous catalyzed reactions.1
Among the known alkane functionalization processes2-5
* Corresponding author. E-mail: mbrookhart@unc.edu.
(1) For recent reviews on this topic: (a) Kakiuchi, F.; Chatani, N.
Adv. Synth. Catal. 2003, 345, 1077-1101. (b) Labinger, J . A.; Bercaw,
J . E. Nature 2002, 417, 507-514. (c) Crabtree, R. H. J . Chem. Soc.,
Dalton Trans. 2001, 2437-2450. (d) J ia, C.; Kitamura, T.; Fujiwara,
Y. Acc. Chem. Res. 2001, 34, 633-639. (e) J ensen, C. M. Chem.
Commun. 1999, 2443-2449. (f) Sen, A. Acc. Chem. Res. 1998, 31, 550-
557. (g) Shilov, A. E.; Shul’pin, G. B. Chem. Rev. 1997, 97, 2879-2932.
For leading reviews on the functionalization of sp and sp2 C-H
bonds: (h) Ritleng, V.; Sirlin, C.; Pfeffer, M. Chem. Rev. 2002, 102,
1731-1769. (i) Guari, Y.; Sabo-Etienne, S. Eur. J . Inorg. Chem. 1999,
1047-1055. (j) Dyker, G. Angew. Chem., Int. Ed. 1999, 38, 1699-1712.
(2) Alkane oxidation: (a) Gol’dschleger, N. F.; Es’kova, V. V.; Shilov,
A. E.; Shteinman, A. A. Zh. Fiz. Khim 1972, 42, 1353-1354 (Engl.
transl.) 1972, 46, 785-786. A comprehensive review featuring the
mechanistic details inter alia disclosed by the Bercaw group has been
published by: (b) Stahl, S. S.; Labinger, J . A.; Bercaw, J . E. Angew.
Chem., Int. Ed. 1998, 37, 2180-2192. Further progress was disclosed
by the Catalytica and related systems: (c) Periana, R. A.; Taube, D.
J .; Gamble, S.; Taube, H.; Satoh, T.; Fujii, H. Science 1998, 280, 560-
564. (d) Matsumoto, T.; Taube, D. J .; Periana, R. A.; Taube, Yoshida,
H. J . Am. Chem. Soc. 2000, 122, 7414-7415. (e) Periana, R. A.; Liu,
X. Y.; Bhalla, G. Chem. Commun. 2002, 3000-3001.
In 1996 Kaska, J ensen, et al. reported that the {C6H3-
[CH2P(tBu)2]2-2,6}IrH2 pincer complex (1) catalyzes the
(4) Carboxylation of alkanes: (a) Fujiwara, Y.; J intoku, T.; Uchida,
Y. New J . Chem. 1989, 13, 649-650. (b) Fujiwara, Y.; Takaki, K.;
Uchida, Y.; Taniguchi, H. Chem. Lett. 1989, 1687-1688. (c) Lin, M.;
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Periana, R. A.; Mironov, O.; Taube, D.; Bhall, G.; J ones, C. J . Science
2003, 301, 814-818.
(5) Aminomethylation of alkanes: Taniguchi, Y.; Horie, S.; Takaki,
K.; Fujiwara, Y. J . Organomet. Chem. 1995, 504, 137-141.
(6) (a) Crabtree, R. H.; Mihelcic, J . M.; Quirk, J . M. J . Am. Chem.
Soc. 1979, 101, 7738-7740. (b) Baudry, M. J .; Ephritikine, M.: Felkin,
H.; Holmes-Smith, R. J . Chem. Soc., Chem. Commun. 1983, 788-789.
(c) Baudry, M. J .; Crabtree, R. H.; Parnell, C. P.; Uriarte, R. J .
Organometallics, 1984, 3, 816-817. For some further catalytic ex-
amples: (d) Burk, M. W.; Crabtree, R. H. J . Am. Chem. Soc. 1987,
109, 8025-8032. (e) Maguire, J . A.; Goldman, A. S. J . Am. Chem. Soc.
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C. N. J . Am. Chem. Soc. 1999, 121, 7696-7697. (b) Chen, H.; Schlecht,
S.; Semple, T. C.; Hartwig, J . F Science 2000, 287, 1995-1997. (c)
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(7) (a) Wieseman, P. Petrochemicals; Ellis Horwood: Chichester,
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Organic Chemistry; Wiley-VCH: Weinheim, 2003; pp 59-89.
10.1021/om030670o CCC: $27.50 © 2004 American Chemical Society
Publication on Web 03/10/2004

Iridium Bis(phosphinite) Pincer Complexes
Organometallics, Vol. 23, No. 8, 2004 1767
exploiting C-H activation in catalytic reactions,15 we
investigated the synthesis of a series of bis(phosphinite)
(p-XPCP)IrHCl complexes {4-X-C6H2-[OP(tBu)2]2-2,6}-
IrHCl {X ) MeO (4a ), Me (4b), H (4c), F (4d ), C6F5 (4e),
and ArF [)3,5-bis(trifluoromethyl)phenyl] (4f)}, which
we expected to be much more electron-deficient than
{C6H3-[CH2P(tBu)2]2-2,6}IrH2 (1). Treatment of com-
plexes 4a -f with NaOtBu results in in situ generation
of catalysts with unprecedented activity for transfer
dehydrogenation in terms of TON, TOF, and substrate
conversion.16 We now wish to report on the sequential
synthesis of the catalytically active dihydride complexes
{4-X-C6H2-[OP(tBu)2]2-2,6}IrH2 (4a -f), as well as on
some electronic features relevant to the catalytic activi-
ties of the parent fragments {4-X-C6H2-[OP(tBu)2]2-2,6}-
Ir (Aa -f).
Ch a r t 1. P CP Ir id u m P in cer Com p lexes 1-3
transfer dehydrogenation of cyclooctane (COA) with tert-
butylethylene (TBE) in neat substrate solution to form
cyclooctene (COE) and tert-butylethane (TBA). TBE is
used as hydrogen acceptor in this reaction to overcome
the thermodynamic difficulty caused by the highly
endergonic dehydrogenation of COA (ca. 23.3 kcal/mol).8
A high thermal stability of the Ir catalyst and up to 1000
turnovers (TON) have been observed at 200 °C.1e,9 In
further studies the similar {C6H3-[CH2P(iPr)2]2-2,6}IrH2
(2) derivative proved to be the first homogeneous
catalyst for the efficient thermal acceptorless dehydro-
genation of, for example, refluxing cyclodecane (ca. 1000
TON).10 Since these initial reports, extensive experi-
mental and theoretical investigations have been con-
ducted to amplify the scope and gain a better under-
standing of the acceptor and acceptorless dehydrogena-
tions using PCP iridium pincer catalysts.11 An “anthra-
phos”-based (PCP)IrH2 pincer complex (3) despite its
lower activity at 200 °C has been proven to dehydroge-
nate cyclodecane effectively without an acceptor, since
it operates at 250 °C without decomposition.12 Recently,
complex 1 was shown to catayze the transfer dehydro-
genation of secondary and tertiary amines to form
imines13a and enamines,13b respectively.
Resu lts a n d Discu ssion
(a ) Gen er a tion of Bis(p h osp h in ite) P CP Ir id u m
Tr ih yd r id es (p-XP CP )Ir H3-Na + (5a ,c,f) a n d Syn -
th esis of Ir id iu m Dih yd r id es (p-XP CP )Ir H2 (6a -f)
a n d Tetr a h yd r id es (p-XP CP )Ir H4 (7a -f). Kaska and
J ensen et al. and Goldman et al. have shown that the
iridium PCP pincer complex {C6H3-2,6-[CH2P(tBu)2]2}-
IrH2 (1) is an active dehydrogenation catalyst for several
alkanes in both the presence and absence of a hydrogen
acceptor.9-11 Complex 1 is an oxygen- and nitrogen-
sensitive compound obtained in 85% yield after treat-
ment of the {C6H3-2,6[CH2P(tBu)2]2}IrHCl precursor
with LiBHEt3 under an atmosphere of hydrogen and
removal of dihydrogen from the formed tetrahydride
{C6H3-2,6[CH2P(tBu)2]2}IrH4 at 130 °C.11l An alterna-
tive protocol for the generation of related (PCP)IrH2
pincer complexes using either KH under ca. 2 atm of
hydrogen11c or NaH under 1 atm of hydrogen has been
reported.12 Treatment of, for example, {C6H3-2,6-[OP-
(tBu)2]2}IrHCl (4c) with NaH (or KH) under an atmo-
sphere of hydrogen in THF-d8 generates the anionic
trihydride {C6H3-2,6-[OP(tBu)2]2}IrH3Na(K) [5c-Na (K)]
Electronic tuning by substitution of the original ligand
backbone in 1 has been reported, but not yet been tested
for catalytic performance.11c,14 Driven by the remarkable
reactivity of these catalysts and our ongoing interest in
(8) The dehydrogenation enthalpy of COA (23.3 kcal/mol) is among
the lowest known for alkanes, which makes it an even more suitable
substrate for alkane dehydrogenation: NIST Standard Reference
Database Number 69, March 2003 Release, http://webbook.nist.gov/
chemistry/.
(9) Gupta, M.; Hagen, C.; Flesher, R. J .; Kaska, W. C.; J ensen, C.
M. Chem. Commun. 1996, 2083-2084.
(10) (a) Xu, W.-W.; Rosini, G. P.; Gupta, M.; J ensen, C. M.; Kaska,
W. C.; Krogh-J espersen, K.; Goldman, A. S. Chem. Commun. 1997,
2273-2274. (b) Liu, F.; Goldman, A. S. Chem. Commun. 1999, 655-
656.
(11) (a) Renkema, K. B.; Kissin, Y. V.; Goldman, A. S. J . Am. Chem.
Soc. 2003, 125, 7770-7771. (b) Krogh-J espersen, K.; Czerw, M.;
Summa, N.; Renkema, K. B.; Achord, P. D.; Goldman, A. S. J . Am.
Chem. Soc. 2002, 124, 11404-11416. (c) Krogh-J espersen, K.; Czerw,
M.; Zhu, K.; Singh, B.; Kanzelberger, M.; Darji, N.; Achord, P. D.;
Renkema, K. B.; A.Goldman, A. S. J . Am. Chem. Soc. 2002, 124,
10797-10809. (d) Li, S.; Hall, M. B. Organometallics 2001, 20, 2153-
2160. (e) Morales-Morales, D.; Lee, D. W.; Wang, Z.; J ensen, C. M.
Organometallics 2001, 20, 1144-1147. (f) Krogh-J espersen, K.; Czerw,
M.; Kanzelberger, M.; Goldman, A. S. J . Chem. Inf. Comput. Sci. 2001,
41, 56-63. (g) Kanzelberger, M.; Singh, B.; Czerw, M.; Krogh-
J espersen, K.; Goldman, A. S. J . Am. Chem. Soc. 2000, 122, 11017-
11018. (h) Liu, F.; Pak, E. B.; Singh, B.; J ensen, C. M.; Goldman, A. S.
J . Am. Chem. Soc. 1999, 121, 4086-4087. (i) Niu, S.; Hall, M. B. J .
Am. Chem. Soc. 1999, 121, 3992-3999. (j) Liu, F.; Goldman, A. S.
Chem. Commun. 1999, 655-656. (k) Lee, D. W.; Kaska, W. C.; J ensen,
C. M. Organometallics 1998, 17, 1-3. (l) Gupta, M.; Hagen, C.; Kaska,
C. W.; Cramer, R. E.; J ensen, C. M. J . Am. Chem. Soc. 1997, 119, 840-
841.
1
as the major species on the basis of the H and 31P{1H}
NMR spectra. Addition of a catalytic amount of a mild
Brønsted acid such as phenol or Brønsted base such as
NaOtBu greatly accelerates the reaction, and the an-
ionic trihydrides 5 are the only Ir-containing products
formed (Scheme 1).
The most characteristic feature of complexes 5a ,c,f
is the appearance of a multiplet and a doublet of triplets
in the hydridic region of the 1H NMR spectra at δ )
-13.35 (5a ){-13.33 (5c), -13.12 (5f)} and -13.65 (5a )
{-13.55 (5c), -13.32 (5f)} in a 1:2 ratio. Upon 31P
decoupling, the hydride resonances 5a -f assigned trans
(14) (a) Mohammad, H. A. Y.; Grimm, J . C.; Eichele, K.; Mack, H.-
G.; Speiser, B.; Novak, F.; Quintan˜illa, M. G.; Kaska, W. C.; Mayer,
H. A. Organometallics 2002, 21, 5775-5784. (b) Grimm, J . C.;
Nachtigal, C.; Mack, H.-G.; Kaska, W. C.; Mayer, H. A. Inorg. Chem.
Commun. 2000, 3, 511-514.
(15) (a) Diaz-Requejo, M. M.; DiSalvo, D.; Brookhart, M. J . Am.
Chem. Soc. 2003, 125, 2038-2039. (b) Reinartz, S.; White, P. S.;
Brookhart, M.; Templeton, J . J . Am. Chem. Soc. 2001, 123, 12724-
12725. (c) Reinartz, S.; White, P. S.; Brookhart, M.; Templeton, J .
Organometallics 2001, 20, 1709-1712. (d) Lenges, C. P.; Brookhart,
M. J . Am. Chem. Soc. 1999, 121, 6616-6623. (e) Lenges, C. P.; White,
P. S.; Brookhart, M. J . Am. Chem. Soc. 1999, 121, 4385-4396. (f)
Lenges, C. P.; Brookhart, M.; Grant, B. J . Organomet. Chem. 1997,
528, 199-203.
(12) Haenel, M. W.; Oevers, S.; Angermund, K.; Kaska, W. C.; Fan,
H.-J .; Hall, M. B. Angew. Chem., Int. Ed. 2001, 40, 3596-3600.
(13) (a) Gu, X.-Q.; Chen, W.; Morales-Morales, D.; J ensen, C. M. J .
Mol. Catal. A 2002, 189, 119-124. (b) Zhang, X.; Fried, A.; Knapp, S.;
Goldman, A. S. Chem. Commun. 2003, 2060-2061.
(16) Go¨ttker-Schnetmann, I.; White, P. S.; Brookhart, M. J . Am.
Chem. Soc. 2004, 126, 1804-1811.

1768 Organometallics, Vol. 23, No. 8, 2004
Go¨ttker-Schnetmann et al.
Sch em e 1. Gen er a tion of An ion ic (p-XP CP )Ir H3- Com p lexes (5a ,c,f)
Sch em e 2. Gen er a tion of (p-XP CP )Ir H2 (6a -f) a n d (p-XP CP )Ir H4 (7a -f) by Deh yd r och lor in a tion of 4a -f in
th e P r esen ce of H2
to carbon appear as a triplet, while the two hydrides
trans to each other appear as a doublet (2J cisH-H ) 4.8
Hz for 5a ,c, 4.9 Hz for 5f).
a J . Young tube from 23 to 100 °C causes the gradual
broadening and downfield shifting of the 31P NMR
resonance of the IrH4 complex 7f at 186.0 ppm (23 °C).
Upon further temperature increases, this band broadens
into the baseline and then becomes sharper again at
ca. 203 ppm (90 °C), which is already very close to the
206.9 ppm shift observed for the pure IrH2 complex 6f.
We therefore suggest a rapid interconversion of 6a -f
with 7a -f via reductive elimination/oxidative addition
of H2 with a temperature-dependent equilibrium favor-
ing the dihydride species at higher temperatures. Even
at 23 °C nearly colorless solutions of 7f turn red-brown
after a few seconds under vacuum, indicating formation
of 6f. Finally, treatment of solid 6f with 1 atm of
hydrogen results in immediate color change from red-
brown to pale yellow, indicating formation of 7f, which
loses H2 upon purging with argon. Characteristic spec-
troscopic features of the IrH2 complexes 6 are 31P{1H}
NMR resonances in the range of 204.9 (6c) to 208.4 ppm
(6d ), and IrH2 resonances between -17.55 (6a ) and
-16.13 ppm (6f) resolved as one triplet in each case with
2J P-H ) 8.1-8.5 Hz.
On the basis of these observations we assumed that
reaction of hydridochloro complexes 4a -f with a base
rather than a hydride donor in the presence of dihy-
drogen would also be suitable for generation of the
iridium dihydrides 6a -f, via dehydrochlorination of 4a -
f, to form the respective 14e- fragment (p-XPCP)Ir (Aa -
f) followed by H2 addition.17 Indeed, reaction of com-
plexes 4 with 1.1 equiv of NaOtBu in aromatic solvents
under 1 atm of hydrogen generates mixtures of dihy-
drides 6 and tetrahydrides 718 within 30-60 min at 23
°C. In an improved procedure the reaction is carried out
in benzene: after sublimation of the frozen solvent and
formed tBuOH at 0 °C and subsequent extraction with
pentane, pure (p-XPCP)IrH2 complexes (6) are obtained
in 86-95% yield (Scheme 2). We have not been able to
isolate pure tetrahydrides 7a -f; these complexes lose
dihydrogen to form pure complexes 6a -f much easier
than complex {C6H3-2,6-[CH2P(tBu)2]2}IrH4.19 Thus heat-
ing a solution of 7f under 1.2 atm of H2 in toluene-d8 in
On the basis of the equivalency of the hydridic sites
and the tert-butyl groups of complexes 6 as well as on
calculations on d6-L2L′MH2 fragments in general,20 and
on calculations of the {C6H3-2,6-[CH2P(tBu)2]2}IrH2
geometry in particular,11c,f,i a distorted trigonal bipyra-
midal ground state geometry of complexes 6 is assumed.
(b) Electr on ic P r op er ties of th e F r a gm en ts (p-
XP CP )Ir (Aa -f). A sensitive tool for determining the
electronic influence of the p-substituent in the (p-XPCP)-
Ir fragments is the νCO stretching frequency of the
respective carbonyl complex (p-XPCP)Ir(CO) (8a -f).
(17) Several base-induced dehydrochlorination reactions of transi-
tion metal complexes have been reviewed: Grushin, V. V. Acc. Chem.
Res. 1993, 26, 279-286, and references herein.
(18) During review, one referee pointed out that complexes 7 are
probably not Ir(V) tetrahydrides but rather Ir(III) dihydride/dihydrogen
adducts. We totally agree, on the basis of the observations made for
the Ir(III) dihydride complexes 6: These complexes already exhibit
(nonclassical) dihydrogen binding character (and likewise Ir(I) char-
1
acter) due to the substantial J HD coupling constants in their 6-d1
isotopomers (vide infra). However, for the sake of simplicity and the
lack of hard experimental evidence we will refer to complexes 7 in a
“stoichiometric” way as tetrahydrides. A more detailed discussion of
the binding mode in the dihydride complexes 6 will be published
elsewhere.
(19) The {C6H3-2,6-[CH2P(tBu)2]2}IrH4 complex can easily be ob-
tained by reaction of the precursor {C6H3-2,6-[CH2P(tBu)2]2}IrHCl with
hydrogen and 1.1 equiv of NaOtBu in analogy with the procedures
described here.
(20) Riehl, J .-F.; J ean, Y.; Eisenstein, O.; Pe´llssier, M. Organome-
tallics 1992, 11, 729-737.

Iridium Bis(phosphinite) Pincer Complexes
Organometallics, Vol. 23, No. 8, 2004 1769
Sch em e 3. Gen er a tion of Ca r bon yl Com p lexes 8a -f fr om 4 or 6 a n d νCO of Com p lexes 8
Generation of complexes 8a -f was achieved in quanti-
tative yield by displacement of hydrogen in complexes
6a -f by CO. An alternative synthesis is based on
addition of CO to complexes 4a -f and subsequent
dehydrochlorination with NaOtBu at 80 °C (Scheme 3).
The νCO stretching frequencies obtained for complexes
8a -f in pentane solution (Scheme 3) compare to 1925.5
cm-1 for {4-MeO-C6H2-2,6-[CH2P(tBu)2]2}Ir(CO), 1927.7
cm-1 for {C6H3-2,6-[CH2P(tBu)2]2}Ir(CO),21 and 1930.0
cm-1 obtained for {4-[CH3O(O)C]-C6H2-2,6-[CH2P-
(tBu)2]2}Ir(CO).11c As jugded by the significant blue shift
of ca. 20 cm-1 for the bis(phosphinite) PCP complexes
8, their (p-XPCP)Ir fragments (Aa -f) are distinctively
more electron deficient than the respective methylene-
bridged {4-X-C6H2-2,6-[CH2P(tBu)2]2}Ir pincer frag-
ments.
(strong π-back-donation) through an “elongated” dihy-
drogen complex to a nonclassical dihydrogen complex
(weak π-back-donation).22 We therefore concluded that
the higher the J HD in complexes 6a -f-d1, the weaker
the π-back-donation from the (p-XPCP)Ir fragments
(Aa -f).
1
By comparing the electronic effects based on the νCO
1
of complexes 8 and the J HD of complexes 6-d1 we find
a good correlation except for the (p-FPCP)Ir fragment
(Ad ). Whereas νCO of (p-FPCP)Ir(CO) (8d ) (1953 cm-1
)
is significantly blue-shifted with respect to 8b,c (1947,
1
1949 cm-1), the 7.7 Hz J HD observed for 6d compares
to 7.7 Hz (6b) and 8.0 Hz (6c). Considering that the
observed νCO for complexes 8 reflect both the σ-acceptor
as well as the π-donor abilities of the fragments (p-
1
XPCP)Ir (A), whereas the J HD is governed by the
Further information about the electronic properties
of the (p-XPCP)Ir fragments (A) has been extracted from
isotopic labeling studies of complexes 6a -f: The isoto-
pomers 6a -f-d1 have been shown to exhibit inter alia
1J HD couplings that are sensitive to the p-X substituent
of the PCP ligand backbone. At 23 °C in pentane the
1J HD values are 6.5 Hz (6a -d1), 7.7 Hz (6b,c-d1), 8.0 Hz
π-donor abilities of A, we can qualitatively rationalize
this discrepancy on the basis of the strong σ-acceptor
and significant π-donor abilities of the F-substituent in
complexes 8d and 6d -d1.
(c) Ar om a t ic C-H Act iva t ion , Dissocia t ive
Ar en e E xch a n ge, a n d (p -XP CP )Ir -Dep en d en t
Ar en e Exch a n ge Ra tes. Generation of complexes
6a -f can be accomplished in a sequential manner
starting from complexes 4a -f and NaOtBu in aromatic
solvents. In a typical experiment after ca. 30-60 min
at 23 °C in benzene-d6 the starting complex 4f is
1
(6c-d1), and 9.0 Hz (6e,f-d1). An increasing J HD in
transition metal (poly)hydrides is indicative of a de-
creasing H-D distance, finally resulting in complete
1
reductive elimination of HD at J HD ) 43 Hz.22 While a
1
completely consumed, as judged by H and 31P NMR,
detailed report on the structural implications of the
spectroscopic properties of deuterium-labeled com-
and the appearance of one new resonance at 182.0 ppm
is observed by 31P{1H} NMR. The 1H NMR spectrum
shows one set of signals for the aromatic ligand back-
bone as well as one triplet for the tert-butyl groups of
the new reaction intermediate. Addition of hydrogen to
this reaction mixture leads to formation of 6f and 7f
within a few minutes at 23 °C. When toluene-d8 is used
as solvent, the 1H NMR spectrum looks essentially
identical at 23 °C, while the 31P NMR resonance appears
at 181.9 ppm. Considering that oxidative addition of
arenes to the {C6H3-2,6-[CH2P(tBu)2]2}Ir fragment has
been reported,11g these results are indicative of aryl
C-D oxidative addition to the respective fragment Af.
We therefore decided to monitor the reaction of 4f,
NaOtBu, and toluene-h8 by low-temperature NMR
spectroscopy. Upon cooling the reaction mixture ob-
tained after ca. 60 min at 23 °C to -30 °C, three
overlapping triplets at -43.22 ppm can be detected by
1H NMR experiments, which broaden with increasing
1
pounds 6 will be published elsewhere, the observed J HD
for 6a -f-d1 suggest rHH between 1.33 and 1.27 Å for 6f
and between 1.41 and 1.31 Å for 6a ,23 which justifies
their classification as “elongated” dihydrogen complexes.
The degree of π-back-donation from a given ligand-
metal fragment to the antibonding σ*-H2 (H-D, re-
spectively) orbital has been shown to govern the ob-
served rHH, rHD distance along a putative reaction
coordinate going from a classical dihydride complex
(21) A differing value of νCO ) 1913 cm-1 in KBr is reported by:
Morales-Morales, D.; Redo´n, R.; Wang, Z.; Lee, D. W.; Yung, C.;
Magnuson, K.; J ensen, C. M. Can. J . Chem. 2001, 79, 823-829.
(22) Kubas, G. J . J . Organomet. Chem. 2001, 635, 37-68.
(23) (a) Heinekey, D. M.; Luther, T. A. Inorg. Chem. 1996, 35, 4396-
4399. (b) Maltby, P. A.; Schlaf, M.; Steinbeck, M.; Lough, A. J .; Morris,
R. H.; Klooster, W. T.; Koetzle, T. F.; Srivastava, R. C. J . Am. Chem.
Soc. 1996, 118, 5396-5407. (c) Hush, N. S. J . Am. Chem. Soc. 1997,
119, 1717-1719. (d) Gru¨ndemann, S.; Limbach, H. H.; Buntkowsky,
G.; Sabo-Etienne, S.; Chaudret, B. J . Phys. Chem. A 1999, 103, 4752-
4754.

1770 Organometallics, Vol. 23, No. 8, 2004
Go¨ttker-Schnetmann et al.
Sch em e 4. Gen er a tion of (Tolyl)h yd r id o Com p lexes 9f fr om Com p lexes 4f a n d Na OtBu in Nea t Tolu en e
temperature and are no longer detectable above 10 °C.
A D NMR experiment in toluene-d8 at -30 °C shows
mercially available mesitylene-d12. As exemplified for
10f, two broadened singlets (7.28 and 6.43 ppm, 2:1 H)
and the hydridic resonance split into a triplet (-43.02
ppm) are observed by 1H NMR at -30 °C for the
oxidatively added m-xylene in addition to 2 equiv of free
2
one broad signal at -43.22 ppm without detectable
splitting, while three overlapping signals at 181.9-182.0
ppm are observed in in the 31P NMR spectrum. When
reaction mixtures of 4f, NaOtBu, and m-xylene (or
o-xylene) are cooled to -30 (-20) °C, the appearance of
1
m-xylene. Further temperature-dependent H{31P} NMR
experiments on this sample between 23 and -40 °C
reveal a minimum line width ∆ν1/2(min) ) 5.5 ( 0.1 Hz
of the hydridic resonance of 10f at -30 °C. At -0 °C
the 31P decoupled hydridic resonance of 10f exhibits a
line width ∆ν1/2(0 °C) ) 43 Hz in the presence of 2 equiv
of free m-xylene. In the presence of 11 and 30 equiv of
free m-xylene ∆ν1/2(0 °C) ) 42 and 41 Hz, respectively.
Finally we find ∆ν1/2(0 °C) ) 38.0 Hz in neat protio
1
one triplet at ca. -43.03 (-43.10) ppm in the H NMR
as well as one singlet at 181.6 (181.2) ppm in the 31P-
{1H} NMR can be observed. On the basis of the forma-
tion of only one C-H activation product in m- or
o-xylene we attribute the appearance of three isomers
in the case of toluene to one p-tolyl isomer (9′f) and two
m-tolyl rotamers with the tolyl-methyl group cisoid-
(9′′f) or transoid (9′′′f) to the hydride at Ir (Scheme 4).
m-xylene (ca. 330 equiv) compared with ∆ν1/2(min-30 °C
)
1
The H NMR chemical shift of the hydridic sites in the
) 3.6 ( 0.1 Hz in neat m-xylene. On the basis of these
findings the exchange of m-xylene is clearly zero-order
in m-xylene and supports a dissociative mechanism
involving a 14e- fragment Af (which could exist as the
agostic complex Bf or the oxidative addition product
derived thereof) (Scheme 5). Under identical experi-
mental conditions similar results have been obtained
for the m-xylene exchange of complexes 10a -e. Signifi-
cantly, ∆ν1/2(0 °C) of complexes 10a -f is quite p-
substituent dependent, spanning a range from ∆ν1/2(0
°C) ) 14.3 Hz (in neat m-xylene) for the most electron-
rich 10a to 38 Hz for the most electron-deficient system
10f. Using the slow exchange approximation k ) (π ×
∆(∆ν1/2))/21/2 and the lower limit ∆ν1/2 in neat m-xylene,
we have obtained p-substituent-dependent rate con-
stants kred.el(10a -f) for the reductive elimination of
m-xylene from complexes 10a -f, which translate into
range of -43 ppm for all aryl C-H activation products
suggests a square pyramidal geometry at iridium with
the hydride in the apical position.24 On the basis of
calculations this geometry was also proposed for the
analogous complex {C6H3-2,6-[CH2P(tBu)2]2}Ir(H)(Ph),
which undergoes a fast dissociative arene exchange and
shows decoalescence on the NMR time scale at low
temperatures.11c,g
To obtain more information about an associative
versus dissociative arene exchange by the (p-XPCP)Ir
fragments (Aa -f) we have reacted the respective
(p-XPCP)IrHCl precursors (4a -f) with 1.1 equiv of
NaOtBu and initially 2-3 equiv of m-xylene in mesity-
lene-d12. Generation of the respective (3,5-dimethyl-
phenyl)hydrido complexes 10a -f is complete after 30-
60 min at 23 °C. However traces of iridium dihydrides
6a -f and one uncharacterized iridum complex in each
case can be detected by 31P NMR (not by 1H NMR),
presumably formed due to impurities in the com-
free activation energies ∆Gq
between 14.2 kcal/mol
0 °C
for the most electron-rich complex 10a and 13.6 kcal/
mol for the most electron-deficient complex 10f (Table
1).
1
(24) The hydridochloro precursors 4a -f exhibit hydridic resonances
between -40.9 and -41.9 ppm. In addition an X-ray structure analysis
of 4a indicates that the hydride occupies the apical position; see ref
16.
On the basis of the J HD of complexes 6a -f and νCO
of 8a -f the reductive elimination of m-xylene is signifi-
cantly enhanced for the more electron-deficient com-

Iridium Bis(phosphinite) Pincer Complexes
Organometallics, Vol. 23, No. 8, 2004 1771
Sch em e 5. Dissocia tive Exch a n ge of m -Xylen e in Com p lexes 10a -f
Ta ble 1. Tem p er a tu r e- a n d [m -Xylen e]-Dep en d en t
Lin e Wid th (∆ν1/2) of th e 31P -Decou p led Hyd r id ic
Reson a n ce of (p-XP CP )Ir (m -xylyl)(H) (10a -f)
(COA) w ith ter t-Bu tyleth ylen e (TBE). By comparing
the catalytic activity of complexes 6a -f with the activity
of species generated from 4a -f and NaOtBu in the
benchmark transfer dehydrogenation of COA with
TBE,9 we see no advantage in using complexes 6a -f.
Neither the initial turnover frequencies (TOFs) for
entries 1-6 nor the turnover numbers (TONs) after 40
h at 200 °C differ substantially under identical condi-
tions (Table 2). We also find virtually identical product
ratios of cyclooctene to 1,3-cyclooctadiene in these
reactions. Noteworthy, the dinitrogen complex 11f
exhibits nearly the same activity as catalyst 6f or
precatalyst 4f plus NaOtBu on a per iridium basis, when
the reaction is conducted under an argon atmosphere.
Even under an atmosphere of nitrogen, however, the
catalytic activity of complex 11f is not totally quenched
(Table 2, entry 8).
equiv of free m-xylene
330
k
red.el.(0 °C),a
2-3 28-30 neat m-xylene
neat m-xylene
∆Gq
0 °C
[kcal/mol]
10
X
∆ν1/2(0 °C)/[Hz]
[s-1
]
a
b
c
d
e
f
MeO 17.2
16.7
18.1
18.2
16.1
30
14.3
17.1
17.6
15.1
28
24
31
32
26
55
77
14.2
14.1
14.1
14.2
13.8
13.6
Me
H
F
18.4
18.6
17.1
C6F5 33
ArF
43
41
38
a
Rates are based on ∆(∆ν1/2) ) ∆ν1/2(0 °C) - ∆ν1/2(min) in neat
m-xylene. The minimum line width values ∆ν1/2(min) for com-
pounds 10 are 3.4 (10a ), 3.3 (10b), 3.3 (10c), 3.6 (10d ), 3.3 (10e),
and 3.6 Hz (10f) in neat m-xylene at -30 °C in each case.
plexes 10e,f, while π-donation by the MeO and F
substituents in 10a ,d results in the lowest rates of
reductive elimination.
Su m m a r y
Catalytically active dihydride complexes 6a -f for the
transfer dehydrogenation of COA with TBE have been
synthesized by dehydrochlorination of complexes 4a -f
in arene solvents in the presence of hydrogen. In the
absence of hydrogen the formation of highly fluxional
Ir(aryl)(hydrido) complexes 9 and 10 has been observed,
which upon addition of hydrogen furnish complexes 6a -
f. The aryl hydrido moieties in complexes 9 and 10
exhibit rapid exchange with free arene. Rate measure-
ments establish this reaction is zero-order in free arene
and provide evidence either for 14e- fragments Aa -f
or for species derived from the agostic complexes Ba -f
as reaction intermediates. The substituent dependent
electronic properties of their parent 14e- fragments
Aa -f have been probed by measuring the νCO values of
their respective (CO) complexes 8a -f. Additional infor-
(d ) Gen er a tion of th e µ-N2 Ir id iu m Dim er {(p-
Ar F P CP )Ir }2{µ-N2} (11f). We have observed the for-
mation of {(p-ArFPCP)Ir}2{µ-N2} (11f) by reacting 4f
with NaOtBu in toluene-d8 saturated with N2. The
formation of the similar {C6H3-2,6(CH2PtBu2)2Ir}2{µ-
N2} dimer (12) has been reported and is known to
inhibit the catalytic activity of the {C6H3-2,6(CH2-
PtBu2)2}Ir fragment.11k However, upon exposing sus-
pensions of isolated 11f to an atmosphere of H2 in an
NMR tube, we have observed dissociation of the dimer
and quantitative formation of mixtures of the di- and
tetrahydride 6f and 7f, respectively, by 1H and 31P
NMR.
Compound 11f, even in low concentrations, crystal-
lizes as a toluene adduct out of these solutions, while a
minor uncharacterized product remains in solution. The
X-ray structure analysis of compound 11f shows a very
similar geometry at the Ir center when compared to 12.
However, the C-Ir distance is shorter in 11f [2.001(4)
Å] than in 12 [ 2.053(12) Å], as is the Ir-N distance
[1.982(3) Å (11f), 2.007(11) Å (12)] and the N-N
distance [1.119(6) Å (11f), (1.176(13) Å 12)], which is
close to the reported value in free N2 (1.098 Å).25
Additionally the P-Ir-P angle is smaller [154.86(3)°
(11f), 160.22(10)° (12)].
1
mation has been obtained from the J HD values of
isotopically labeled complexes (p-XPCP)IrHD (6a -f-d1).
Except for the F substituent both methods provide the
same order of increasing electron deficiency (ArF ≈ C6F5
> F > H > Me > MeO based on νCO, ArF > C6F5 > H >
1
F ≈ Me > MeO based on J HD). The initial TOFs in the
transfer dehydrogenation of COA with TBE catalyzed
by 6a -f as well as the rates of reductive arene elimina-
tion in complexes 10a -f correlate with the electronic
properties of the ligand, with the more electron-deficient
systems being more active.
(e) Ca ta lytic Activity of Com p lexes 6a -f a n d 11f
in th e Tr a n sfer Deh yd r ogen a tion of Cycloocta n e
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were carried
(25) Gordon, A. J .; Ford, R. A. The Chemist’s Companion; J ohn Wiley
& Sons: New York, 1972; p 107.
out using standard Schlenk, high-vacuum, and glovebox

1772 Organometallics, Vol. 23, No. 8, 2004
Go¨ttker-Schnetmann et al.
F igu r e 1. ORTEP plot of {(p-ArFPCP)Ir}2{µ-N2}‚2toluene (11f) with thermal ellipsoids at the 50% probability level (toluene
omitted for clarity). Selected bond distances (Å) and angles (deg): Ir1-P1 2.2859(11), Ir1-P2 2.2724(10), Ir1-N1 1.982-
(3), N1-N1a 1.119(6), Ir1-C20 2.001(4), C21-O2 1.388(5), O2-P1 1.665(3), C25-O3 1.389(5), O3-P2 1.6607(25), P1-
Ir1-P2 154.86(3), N1-Ir1-C20 169.84(15), Ir1-N1-N1a 172.9(3).
Ta ble 2. Ca ta lytic Activity of in Situ -Gen er a ted Sp ecies Com p a r ed to Ca ta lysts 6a -f a n d 11f in th e
Tr a n sfer Deh yd r ogen a tion of COA w ith TBE
TON per Ir
initial TOF
COE:COD
b
entry
complex
X
headspace
(40 h, 200 °C)a
per Ir [s-1
]
(40 h, 200 °C)c
1
2
3
4
5
6
7
8
4/6a
4/6b
4/6c
4/6d
4/6e
4/6f
11f
MeO
Me
H
argon
argon
argon
argon
argon
argon
argon
N2
1904d/1886
1484d/1532
1583d/1601
1530d/1519
2041d/2056
2070d/2051
2026
1.68d/1.69
1.69d/1.68
1.92d/1.88
1.75d/1.71
2.40d/2.39
2.42d/2.47
2.17
81:19d/81:19
86:14d/85:15
84:16d/84:16
84:16d/84:16
78:22d/77:23
76:24d/75:25
76:24
F
C6F5
ArF
ArF
ArF
11f
227
0.33
100:0
TONs of TBE in reaction mixtures containing 30.3 mmol of COA, 30.3 mmol of TBE, and 10 µmol of iridum, determined by 1H NMR
a
experiments. Average value over the first 8 min of the reaction. c Determined by 1H NMR experiments. Values obtained by in situ
b
d
generation of catalytically active species from hydridochloro precatalysts 4a -f and NaOtBu according to ref 16.
techniques. Argon and nitrogen were purified by passage
through columns of BASF R3-11 (Chemaolg) and 4 Å molecular
sieves. THF was distilled from sodium benzophenone ketyl
under nitrogen. Hexanes, pentane, toluene, diethyl ether, and
dichloromethane were passed through columns of activated
alumina. Solvents and reagents used in the generation of
catalytically active Ir complexes were thoroughly freed from
nitrogen by several freeze-pump-thaw cycles and stored in
an argon atmosphere glovebox if not stated otherwise. Toluene-
d8, benzene-d6, mesitylene-d12, and THF-d8 were dried over
sodium, degassed, vacuum transferred, and stored in a glove-
box. CD2Cl2 was dried over P2O5, degassed, and vacuum
transferred prior to use. Cyclooctane (COA) was stirred with
concentrated H2SO4 for several hours until it was olefin and
arene free and then distilled under vacuum prior to use.
Hydrogen and carbon monoxide were used as received from
National Speciality Gases of Durham, NC. Hydrogen deuteride
(HD) was generated by adding a solution of deuterium oxide
in THF to a suspension of sodium hydride in THF. NMR
spectra were recorded on Bruker DRX 400 and AMX 300 MHz
instruments and are referenced either to residual protio
solvent or to TMS as internal standard. Samples in neat protio
solvent were shimmed by optimizing the intensity of the FID
and referenced to the solvent chemical shift in CDCl3 or by
external standard capillaries (benzene-d6). 31P chemical shifts
are referenced to an external H3PO4 standard. 19F chemical
shifts have not been referenced. IR spectra were recorded on
an ASI ReactIR 1000 spectrometer. Elemental analyses were
carried out by Atlantic Microlab, Inc. of Norcross, GA.
Gen er a l P r oced u r e for in Situ Gen er a tion of An ion ic
Tr ih yd r id es 5a ,c,f. THF-d8 (0.25 mL) was added to 30 µmol
of the respective precursor 4a ,c,f and 2 mg of NaH (84 µmol)
in a thick walled J . Young tube in a glovebox. One small crystal
of phenol was added, and the tube was closed and shaken while
hydrogen evolution was observed. The tube was transferred
out of the box and treated for 30 min in an ultrasound bath.
1H and 31P NMR analysis indicated quantitative generation
of iridium trihydrides 5.
(p-MeOP CP )Ir H3Na (5a ). 1H NMR (300 MHz, 23 °C, THF-
d8): δ 5.91 (s, 2H, 4- and 6-H), 3.58 (s, 3H, OCH3), 1.32 (vt,
J P-H ) 6.5 Hz, 36H, 4 × tBu), -13.35 (m, 1H, IrH), -13.65
2
2
[dt, J P-H ) 15.9 Hz, J cisH-H ) 4.8 Hz, 2H, trans-IrH2]. 31P-
{1H} NMR (121.5 MHz, 23 °C, THF-d8): δ 187.4.

Iridium Bis(phosphinite) Pincer Complexes
Organometallics, Vol. 23, No. 8, 2004 1773
(p-HP CP )Ir H3Na (5c). 1H NMR (400 MHz, 23 °C, THF-
C3 and C5), 55.0 (CH3, s, OCH3), 40.0 (Cq, vt, J P-C ) 11.6 Hz,
4 × tBu), 29.0 (CH3, vt, J P-C ) 3.7 Hz, 4 × tBu). IR (pentane,
cm-1): 2105, 2086, 2003, 1997, 1946 (νIr-H). IR (CH2Cl2, cm-1):
2105, 2086, 2003, 1997, 1946 (νIr-H). Anal Calcd for C23H43O3P2-
Ir (621.76): C, 44.43; H, 6.97. Found: C, 44.68; H, 7.28.
(p-MeP CP )Ir H2 (6b). Following the general procedure 52
mg (86 µmol, 86%) of compound 6b was obtained from 64 mg
(0.1 mmol) of precursor 4b, 11.0 mg (0.11 mmol) of NaOtBu,
3
3
d8): δ 6.30 (t, J H-H ) 7.6 Hz, 1H, 4-H), 6.13 (d, J H-H ) 7.6
Hz, 2H, 3- and 5-H), 1.32 (vt, J P-H ) 4.8 Hz, 36H, 4 × tBu),
2
2
-13.33 (m, 1H, IrH), -13.55 [dt, J P-H ) 16.0 Hz, J cisH-H
)
4.8 Hz, 2H, trans-IrH2]. 1H{31P} NMR, hydridic region (400
2
MHz, 23 °C, THF-d8): δ -13.33 (t, J H-H ) 4.8 Hz, IrH),
-13.55 [d, J cisH-H ) 4.8 Hz, trans-IrH2]. 31P{1H} NMR (162
2
1
and H2 as a red-brown amorphous solid. H NMR (400 MHz,
MHz, 23 °C, THF-d8): δ 185.9. 13C{1H} NMR (100.6 MHz, 23
°C, THF-d8): δ 164.4 (Cq, vt, J P-C, ) 7.0 Hz, C2 and C6), 133.6
(Cq, t, 2J P-C ) 6.9 Hz, C1), 119.7 (CH, C4), 101.8 (CH, vt, J P-C
) 5.7 Hz, C3 and C5), 39.2 [Cq, vt, J P-C ) 12.3 Hz, 2 × P(tBu)2],
29.7 [CH3, vt, J P-C ) 3.6 Hz, 2 × P(tBu)2].
(p-Ar F P CP )Ir H3Na (5f). H NMR (400 MHz, 23 °C, THF-
1
23 °C, C6D6): δ 6.75 (s, 2H, 3- and 5-H), 2.15 (s, 3H, p-Me),
2
1.30 [vt, J P-H ) 7.1 Hz, 36H, 2 × P(tBu)2], -17.19 (t, J P-H
)
8.1 Hz, 2H, IrH2). 31P{1H} NMR (121.5 MHz, 23 °C, C6D6): δ
205.3. 13C{1H} NMR (100.6 MHz, 23 °C, C6D6): δ 170.8 (Cq,
vt, J P-C ) 7.3 Hz, C2 and C6), 152.8 (Cq, t, J P-C ) 6.9 Hz,
2
C1), 142.7 (Cq, s, C4), 104.9 (CH, vt, J P-C ) 5.8 Hz, C3 and
C5), 40.1 (Cq, vt, J P-C ) 11.8 Hz, 4 × tBu), 28.9 (CH3, vt, J P-C
) 3.7 Hz, 4 × tBu). IR (pentane, cm-1): 2087, 2004, 1955, 1948
(νIr-H). IR (CH2Cl2, cm-1): 2098, 2076, 1999, 1937 (νIr-H). Anal.
Calcd for C23H43O2P2Ir (605.76): C, 45.60; H, 7.16. Found: C,
46.23; H, 7.73.
(p-HP CP )Ir H2 (6c). Following the general procedure 113
mg (191 µmol, 95%) of compound 6c was obtained from 125
mg (0.2 mmol) of precursor 4c, 21.0 mg (0.22 mmol) of NaOtBu,
and H2 as a red amorphous solid. 1H NMR (400.1 MHz, 23 °C,
d8): δ 8.10 (s, 2H, 2′- and 6′-H), 7.67 (s, 1H, 4′-H), 6.63 (s, 2H,
4- and 6-H), 1.36 (vt, J P-H ) 6.6 Hz, 36H, 4 × tBu), -13.12
3
2
(m, 1H, IrH), -13.32 (dt, J P-H ) 16.0 Hz, J cisH-H ) 4.9 Hz,
trans-IrH2). 31P{1H} NMR (162 MHz, 23 °C, THF-d8): δ 190.3.
13C{1H} NMR (100.6 MHz, 23 °C, THF-d8): δ 165.8 (Cq, vt,
J
P-C, ) 7.1 Hz, C2 and C6), 147.0 (Cq, s, C4), 141.9 (Cq t, 2J P-C
) 7.0 Hz, C1), 132.2 (Cq, q, 2J F-C ) 32.4 Hz, C3′ and C5′), 129.8
1
(Cq, s, C1′), 126.4 (CH, s, C2′ and C6′), 125.0 (Cq, q, J C-F
272 Hz, 2 × CF3), 118.1 (CH, m, C4′), 100.5 (CH, vt, J P-C
)
)
5.5 Hz, C3 and C5), 39.5 (Cq, vt, J P-C ) 12.2 Hz, 4 × tBu),
29.7 (CH3, vt, J P-C ) 3.6 Hz, 4 × tBu).
Gen er a l P r oced u r e for th e Syn th esis of Com p lexes (p-
XP CP )Ir H2 (6a -f). One equivalent of the respective (p-
XPCP)IrHCl complex 4a -f and 1.1 equiv of NaOtBu were
dissolved in nitrogen-free benzene in an rubber septum capped
Schlenk flask while the flask was purged with hydrogen. The
solution was stirred for 0.5-1.5 h at 23 °C under a slow flow
of hydrogen while becoming nearly colorless. The reaction
mixture was then cooled to 0 °C, and the (frozen) solvent was
removed in vacuo (10-3 mbar, 3 h). The Schlenk flask was
transferred to the glovebox, argon and nitrogen-free pentane
were added, and the solution was filtered through a 0.2 µm
pore size syringe filter (Nalgene 199-2020) into another rubber
septum capped Schlenk flask. The solvent was removed in
vacuo (10-3 mbar), the residue dissolved in 3 mL of nitrogen-
free benzene, and the benzene sublimed at 0 °C for 2 h to yield
the (p-XPCP)IrH2 complexes as brown-red to red fine powders.
The respective (p-XPCP)IrH4 (7) complexes cannot be isolated
in pure form since they lose hydrogen even in the solid state
when not stored over a hydrogen atmosphere. Spectroscopic
data are exemplified for complex 7f.
C6D6): δ 7.06 (m, 1H, 4-H), 6.95 (m, 2H, 3- and 5-H), 1.25 [vt,
2
J P-H ) 7.1 Hz, 36H, 2 × P(tBu)2], -17.04 (t, J P-H ) 8.2 Hz,
2H, IrH2). 31P{1H} NMR (162 MHz, 23 °C, C6D6): δ 204.9. 13C-
{1H} NMR (100.6 MHz, 23 °C, Tol-d8): δ 170.5 (Cq, vt, J P-C
)
2
7.3 Hz, C2 and C6), 155.0 (Cq, t, J P-C ) 6.6 Hz, C1), 131.6
(CH, s, C4), 103.9 (CH, vt, J P-C ) 5.7 Hz, C3 and C5), 40.1
(Cq, vt, J P-C ) 11.7 Hz, 4 × tBu), 28.8 (CH3, vt, J P-C ) 3.7 Hz,
4 × tBu). IR (pentane, cm-1): 2111, 2101, 2005, 1950 (νIr-H).
IR (CH2Cl2, cm-1): 2111, 2000, 1934, 1899 (νIr-H). Anal. Calcd
for C22H41O2P2Ir (591.74): C, 44.65; H, 6.98. Found: C, 45.01;
H, 6.58.
(p-F P CP )Ir H2 (6d ). Following the general procedure 53 mg
(0.87 µmol, 87%) of compound 6d was obtained from 64 mg
(0.1 mmol) of precursor 4d , 11.0 mg (0.11 mmol) of NaOtBu,
and H2 as a red-brown amorphous solid. 1H NMR (400.1 MHz,
(p-MeOP CP )Ir H2 (6a ). Following the general procedure
113 mg (0.18 mmol, 91%) of compound 6a was obtained from
131 mg (0.2 mmol) of precursor 4a , 19.3 mg (0.20 mmol) of
NaOtBu, and H2 as a red-brown amorphous solid. 1H NMR
(400 MHz, 23 °C, C6D6): δ 6.62 (s, 2H, 3- and 5-H), 3.31 (s,
3H, OCH3), 1.32 [vt, J P-H ) 7.1 Hz, 36H, 2 × P(tBu)2], -17.55
2
(t, J P-H ) 8.1 Hz, 2H, IrH2). 31P{1H} NMR (162 MHz, 23 °C,
C6D6): δ 207.6. 13C{1H} NMR (100.6 MHz, 23 °C, C6D6): δ
171.9 (Cq, vt, J P-C ) 7.4 Hz, C2 and C6), 165.5 (Cq, s, C4),
2
149.4 (Cq, t, J P-C ) 7.0 Hz, C1), 90.9 (CH, vt, J P-C ) 6.0 Hz,

1774 Organometallics, Vol. 23, No. 8, 2004
Go¨ttker-Schnetmann et al.
3
23 °C, Tol-d8): δ 6.57 (d, J F-H ) 10.3 Hz, 2H, 3- and 5-H),
d8 sample to 100 °C resulted in reversible loss of hydrogen to
form 6f even under 1.2 atm of hydrogen. 1H NMR (400.1 MHz,
2
1.23 [vt, J P-H ) 7.1 Hz, 36H, 2 × P(tBu)2], -17.13 (t, J P-H
)
8.1 Hz, 2H, IrH2). 31P{1H} NMR (162 MHz, 23 °C, Tol-d8): δ
208.4. 19F NMR (376.5 MHz, 23 °C, Tol-d8): δ -109.7. 13C-
{1H} NMR (100.6 MHz, 23 °C, Tol-d8): δ 170.9 (Cq, dvt, J F-C
3
1
) 15.4 Hz, J P-C ) 7.3 Hz, C2 and C6), 166.9 (Cq, d, J F-C
)
4
2
242.9 Hz, C4), 150.9 (Cq, dt, J F-C ) 26.4 Hz, J P-C ) 7.0 Hz,
2
C1), 92.4 (CH, dvt, J F-C ) 25.8 Hz, J P-C ) 6.1 Hz, C3 and
C5), 40.2 (Cq, vt, J P-C ) 11.5 Hz, 4 × tBu), 28.7 (CH3, vt, J P-C
) 3.6 Hz). IR (pentane, cm-1): 2112, 2094, 2006, 2001, 1952
(νIr-H). IR (CH2Cl2, cm-1): 2093, 2001, 1933, 1908 (νIr-H). Anal.
Calcd for C22H40O2P2FIr (609.73): C. 43.33; H. 6.61. Found:
C. 44.12; H, 7.23.
(p-C6F 5P CP )Ir H2 (6e). Following the general procedure 68
mg (90 µmol, 90%) of compound 6e was obtained from 79 mg
(0.1 mmol) of precursor 4e, 11.0 mg (0.11 mmol) of NaOtBu,
and H2 as a orange-red amorphous solid. 1H NMR (400.1 MHz,
23 °C, C6D6): δ 7.76 (s, 2H, 2′- and 6′-H), 7.64 (s, 1H, 4′-H),
6.84 (s, 2H, 3- and 5-H), 1.30 [vt, J P-H ) 7.2 Hz, 36H, 2 ×
P(tBu)2], -8.22 (s br, 4H, IrH4). 31P{1H} NMR (162 MHz, 23
°C, C6D6): δ 186.0. 19F{1H} NMR (376.5 MHz, 23 °C, C6D6): δ
-62.8. 13C{1H} NMR (100.6 MHz, 23 °C, C6D6): δ 164.5 (Cq,
m br, C2 and C6), 144.6 (Cq, s, C1′), 136.5 and 124.3 (Cq each,
2
m br each, C1 and C4), 131.9 (Cq, q, J F-C ) 32.9 Hz, C3′ and
1
C5′), 127.3 (CH, m, C2′ and C6′), 124.1 (Cq, q, J F-C ) 273.0
Hz, 2 × CF3), 119.9 (CH, m br, C4′), 103.8 (CH, m br, C3 and
C5), 38.4 (Cq, m br, 4 × tBu), 28.4 (CH3, m br, 4 × tBu).
Gen er a l P r oced u r e for th e Syn th esis of Com p lexes (p-
XP CP )Ir (CO) (8a -f). One equivalent of the respective com-
plex (p-XPCP)IrHCl (4a -f) and 1.1 equiv of NaOtBu were
dissolved in nitrogen-free benzene in a rubber septum capped
Schlenk flask while purging the flask with hydrogen. The
solution was stirred for 0.5-1.5 h at 23 °C with hydrogen
flowing while the solutions become pale orange. Then the
hydrogen flow was replaced by a CO flow. The solution
changed color to yellow within a few seconds. The CO flow
was maintained for 2 min, the solvent was then removed under
vacuum (10-3 mbar, 23 °C), and the residue was extracted with
methanol/water (1:1), washed with small amounts of cold
pentane (-20 °C), and dried under vacuum to yield analytically
pure samples. The complexes (p-XPCP)Ir(CO) 8a -f are sensi-
tive to air and need to be handled under argon.
5
23 °C, C6D6): δ 6.99 (t br, J F-H ) 1.4 Hz, 2H, 3- and 5-H),
2
1.24 [vt, J P-H ) 7.2 Hz, 36H, 2 × P(tBu)2], -16.46 (t, J P-H
)
8.5 Hz, 2H, IrH2). 31P{1H} NMR (162 MHz, 23 °C, C6D6): δ
206.3. 13C{1H} NMR (100.6 MHz, 23 °C, Tol-d8): δ 170.0 (Cq,
2
vt, J P-C ) 7.2 Hz, C2 and C6), 155.7 (Cq, t, J P-C ) 6.3 Hz,
C1), 144.4 (Cq, dm, J C-F ) 246 Hz, C2′ and C6′), 140.1 (Cq,
1
1
1
dm, J C-F ) 252 Hz, C4′), 138.0 (Cq, dm, J C-F ) 252 Hz, C3′
and C5′), 128.4 and 116.9 (Cq each, m each, C1′ and C4), 105.9
(CH, m, C3 and C5), 40.3 (Cq, vt, J P-C ) 11.9 Hz, 4 × tBu),
28.6 (CH3, mb, 4 × tBu). 19F{1H} NMR (376.5 MHz, 23 °C,
(p-MeOP CP )Ir (CO) (8a ). By using the general procedure
61 mg (94 µmol, 94%) of (p-MeOPCP)Ir(CO) (8a ) was obtained
from 66 mg (101 µmol) of (p-MeOPCP)IrHCl (4a ) and 10.6 mg
of NaOtBu as a fine powdered yellow solid. 1H NMR (300 MHz,
3
C6D6): δ -143.18 (m, 2 F, 2′- and 6′-F), -157.27 (t, J F-F
)
21.7 Hz, 1 F, 4′-F), -163.51 (m, 2 F, 3′- and 5′-F). IR (pentane,
cm-1): 2120, 2009, 2003, 1954 (νIr-H). IR (CH2Cl2, cm-1): 2117,
2003, 1943, 1905 (νIrH). Anal. Calcd for C28H40O2P2F6Ir
(757.78): C, 44.38; H, 5.32. Found: C, 44.62; H, 5.61.
(p-Ar F P CP )Ir H2 (6f). Following the general procedure 151
mg (187 µmol, 93%) of compound 6f was obtained from 168
mg (0.2 mmol) of precursor 4f, 21.0 mg (0.22 mmol) of NaOtBu,
and H2 as a red amorphous solid. 1H NMR (400.1 MHz, 23 °C,
23 °C, C6D6): δ 6.55 (s, 2H, 3- and 5-H), 3.30 (s, 3H, OCH3),
1.33 [vt, J P-H ) 7.7 Hz, 36H, 2 × P(tBu)2]. 31P{1H} NMR (121.5
MHz, 23 °C, C6D6): δ 200.9. 13C{1H} NMR (75.5 MHz, 23 °C,
C6D6): δ 199.6 (Cq, t, 2J P-C ) 5.0 Hz, CtO), 170.7 (Cq, vt, J P-C
2
) 8.2 Hz, C2 and C6), 162.8 (Cq, s, C4), 141.2 (Cq, t, J P-C
)
8.9 Hz, C1), 91.5 (CH, vt, J P-C ) 6.3 Hz, C3 and C5), 54.9 (CH3,
OCH3), 40.9 (Cq, vt, J P-C ) 12.4 Hz, 4 × tBu), 28.4 (CH3, vt,
J P-C ) 3.2 Hz, 4 × tBu). IR (pentane, cm-1): 1947 (νCO), 1901,
1594, 1561. Anal. Calcd for C24H41O4P2Ir (647.76): C, 44.50;
H, 6.38. Found: C, 44.96; H, 6.45.
(p-MeP CP )Ir (CO) (8b). By using the general procedure 58
mg (91 µmol, 91%) of (p-MePCP)Ir(CO) (8b) was obtained from
64 mg (100 µmol) of (p-MePCP)IrHCl (4b) and 10.6 mg (110
µmol) of NaOtBu as a fine powdered yellow solid. 1H NMR
C6D6): δ 7.80 (s, 2H, 2′- and 6′-H), 7.65 (s, 1H, 4′-H), 7.00 (s,
2H, 3- and 5-H), 1.30 [vt, J P-H ) 7.2 Hz, 36H, 2 × P(tBu)2],
-16.13 (t, 2J P-H ) 8.1 Hz, 2H, IrH2). 31P{1H} NMR (162 MHz,
23 °C, C6D6): δ 206.9. 13C{1H} NMR (100.6 MHz, 23 °C, Tol-
d8): δ 170.9 (Cq, vt, J P-C ) 7.3 Hz, C2 and C6), 155.2 (Cq, t,
2J P-C ) 6.6 Hz, C1), 144.7 and 141.1 (Cq each, s each, C4 and
2
C1′), 132.2 (Cq, q, J F-C ) 32.9 Hz, C3′ and C5′), 127.5 (CH,
m, C2′ and C6′), 124.1 (Cq, q, 1J F-C ) 273.0 Hz, 2 × CF3), 120.6
(CH, m, C4′), 103.4 (CH, vt, J P-C ) 5.6 Hz, C3 and C5), 40.4
(Cq, vt, J P-C ) 11.8 Hz, 4 × tBu), 28.7 (CH3, vt, J P-C ) 3.2 Hz,
4 × tBu). 19F{1H} NMR (376.5 MHz, 23 °C, C6D6): δ -62.83.
IR (pentane, cm-1): 2119 (νIr-H), 1590, 1546, 1279, 1179, 1144.
IR (CH2Cl2, cm-1): 2118, 2010, 1954 (νIr-H). Anal. Calcd for
C
30H43O2P2F6Ir (803.83): C, 44.82; H, 5.39. Found: C, 45.03;
H, 5.03.
(p-Ar FP CP )Ir H4 (7f). Complex 7f was obtained upon treat-
ing a benzene-d6 or toluene-d8 solution of 6f with 1.2 atm of
hydrogen at 23 °C in a J . Young tube. Heating of the toluene-
(300 MHz, 23 °C, C6D6): δ 6.65 (s, 2H, 3- and 5-H), 2.13 (s,
3H, p-Me), 1.32 [s br, 36H, 2 × P(tBu)2]. 31P{1H} NMR (121.5

Iridium Bis(phosphinite) Pincer Complexes
Organometallics, Vol. 23, No. 8, 2004 1775
MHz, 23 °C, C6D6): δ 199.2. 13C{1H} NMR (75.5 MHz, 23 °C,
C6D6): δ 199.8 (Cq, t, 2J P-C ) 5.0 Hz, CtO), 170.2 (Cq, vt, J P-C
) 8.2 Hz, C2 and C6), 145.9 (Cq, vt, J P-C ) 8.8 Hz, C1), 139.7
(Cq, s, C4), 105.3 (CH, vt, J P-C ) 5.7 Hz, C3 and C5), 40.9 (Cq,
vt, J P-C ) 14.4 Hz, 4 × tBu), 28.4 (CH3, vt, J P-C ) 3.0 Hz, 4 ×
tBu). IR (pentane, cm-1): 1947 (νCO), 1903, 1598. Anal. Calcd
for C24H41O3P2Ir (631.76): C, 45.62; H, 6.54. Found: C, 45.59;
H, 6.66.
(p-HP CP )Ir (CO) (8c). By using the general procedure 58
mg (95 µmol, 95%) of (p-HPCP)Ir(CO) (8c) was obtained from
62 mg (99 µmol) of (p-HPCP)IrHCl (4c) and 10.6 mg (110 µmol)
of NaOtBu as a fine powdered yellow solid. An alternative in
situ generation of complexes 8c was accomplished reacting a
solution of 6.5 mg (0.01 mmol) of (p-HPCP)IrHCl (4c) in
benzene-d6 under 1 atm of CO [immediate change of color to
colorless to form (p-HPCP)IrHCl(CO)] and heating of this
solution after addition of 1 mg (0.011 mmol) of NaOtBu for 2
h, 80 °C. 1H NMR (300 MHz, 23 °C, C6D6): δ 6.86 (m, 3H,
(300 MHz, 23 °C, C6D6): δ 6.91 (s, 2H, 3- and 5-H), 1.30 [vt,
J P-H ) 7.3 Hz, 36H, 2 × P(tBu)2]. 31P{1H} NMR (121.5 MHz,
23 °C, C6D6): δ 201.1. 19F{1H} NMR (376.5 MHz, 23 °C,
3
C6D6): δ -143.35 (m, 2 F, 2′-and 6′-F), -157.15 (t, J F-F
)
43.3 Hz, 1 F, 4′-F), -163.46 (m, 2 F, 3′- and 5′-F). 13C{1H} NMR
2
(75.5 MHz, 23 °C, C6D6): δ 199.4 (Cq, J P-C ) 5.0 Hz, CtO),
2
170.0 (Cq, vt, J P-C ) 8.2 Hz, C2 and C6), 150.7 (Cq, J P-C
)
1
8.4 Hz, C1); 144.4, 140.2, and 137.9 (dm each, J F-C ) 247,
248, and 250 Hz, C2′-C6′), 126.7 (Cq, s, C4), 116.6 (Cq, m, C1′),
106.1 (CH, m, C3 and C5), 41.1 (Cq, vt, J P-C ) 12.3 Hz, 4 ×
tBu), 28.3 (CH3, vt, J P-C ) 3.4 Hz, 4 × tBu). IR (pentane, cm-1):
1955 (νCO), 1908, 1547, 1522. Anal. Calcd for C29H38O3P2F5Ir
(783.78): C, 44.44; H, 4.89. Found: C, 45.10; H, 5.07.
(p-Ar F P CP )Ir (CO) (8f). By using the general procedure 38
mg (46 µmol, 92%) of (p-HPCP)Ir(CO) (8f) was obtained from
42 mg (50 µmol) of (p-HPCP)IrHCl (4f) and 5.5 mg (57 µmol)
of NaOtBu as a fine powdered orange solid. 1H NMR (300 MHz,
23 °C, C6D6): δ 7.75 (s, 2H, 2′- and 6′-H) 7.64 (s, 1H, 4′-H),
6.89 (s, 2H, 3- and 5-H), 1.34 [vt, J P-H ) 7.3 Hz, 36H, 2 ×
P(tBu)2]. 31P{1H} NMR (121.5 MHz, 23 °C, C6D6): δ 201.2. 19F-
{1H} NMR (376.5 MHz, 23 °C, C6D6): δ -62.82. 13C{1H} NMR
3-5-H), 1.30 [vt, J P-H ) 7.2 Hz, 36H, 2 × P(tBu)2]. 31P{1H}
NMR (121.5 MHz, 23 °C, C6D6): δ 199.0. 13C{1H} NMR (75.5
2
MHz, 23 °C, C6D6): δ 199.7 (Cq, t, J P-C ) 5.1 Hz, CO), 170.2
2
2
(75.5 MHz, 23 °C, C6D6): δ 199.5 (Cq, J P-C ) 5.1 Hz, CtO),
(Cq, vt, J P-C ) 8.2 Hz, C2 and C6), 149.0 (Cq, t, J P-C ) 10.0
2
170.7 (Cq, vt, J P-C ) 8.1 Hz, C2 and C6), 150.0 (Cq, t, J P-C
)
Hz, C1), 129.4 (CH, s, C4), 104.3 (CH, vt, J P-C ) 6.0 Hz, C3
and C5), 41.0 (Cq, vt, J P-C ) 12.4 Hz, 4 × tBu), 28.4 (CH3, vt,
J P-C ) 3.4 Hz, 4 × tBu). IR (pentane, cm-1): 1949 (νCO), 1904.
Anal. Calcd for C23H39O3P2Ir (617.73): C, 44.72; H, 6.36.
Found: C, 45.02; H, 6.36.
8.5 Hz, C1), 144.2 and 139.5 (Cq each, s each, C4 and C1′),
131.5 (Cq, q, J F-C ) 33.0 Hz, C3′ and C5′), 127.4 (CH, s br,
C2′ and C6′), 123.9 (Cq, q, J F-C ) 273.0 Hz, 3′-CF3 and 5′-
2
1
CF3), 120.5 (CH, s br, C4′), 103.6 (CH, vt, J P-C ) 5.8 Hz, C3
and C5), 41.1 (Cq, vt, J P-C ) 12.3 Hz, 4 × tBu), 28.3 (CH3, vt,
J P-C ) 3.3 Hz, 4 × tBu). IR (pentane, cm-1): 1955 (νCO), 1908,
(p-F P CP )Ir (CO) (8d ). By using the general procedure 61
mg (96 µmol, 96%) of (p-FPCP)Ir(CO) (8d ) was obtained from
64 mg (99 µmol) of (p-FPCP)IrHCl (4d ) and 10.6 mg (110 µmol)
of NaOtBu as a fine powdered yellow solid. 1H NMR (300 MHz,
1546, 1279, 1179, 1144. Anal. Calcd for
C31H41O3P2F6Ir
(829.82): C, 44.87; H, 4.98. Found: C, 44.96; H, 4.96.
Gen er a l P r oced u r e for th e in Situ Gen er a tion of
Hyd r id o Ar yl Com p lexes (p-XP CP )Ir (a r yl)(H) (9,10). To
a mixture of 10 µmol of the respective hydrido chloro complex
4a -f and 1.1 mg of NaOtBu in a thick walled J .Young NMR
tube was added ca. 350 mg of the respective nitrogen-free
protio arene. After 30-60 min at 23 °C the starting complex
had disappeared and one new signal was observed by 31P{1H}
NMR. Cooling of the sample to -30-10 °C results in the
appearance of hydridic resonances in the 1H NMR with
3
23 °C, C6D6): δ 6.57 (d, J F-H ) 10.2 Hz, 2H, 3-H and 5-H),
strongly temperature-dependent line widths ∆ν1/2
.
1.25 [vt, J P-H ) 7.3 Hz, 36H, 2 × P(tBu)2]. 31P{1H} NMR (121.5
MHz, 23 °C, C6D6): δ 202.3. 19F{1H} NMR (376.5 MHz, 23 °C,
C6D6): δ -113.2. 13C{1H} NMR (75.5 MHz, 23 °C, C6D6): δ
199.1 (Cq, t, 2J P-C ) 5.1 Hz, CtO), 170.0 (Cq, dvt, 3J F-C ) 15.0
Hz and J P-C ) 8.1 Hz, C2 and C6), 165.0 (Cq, d, 1J F-C ) 241.0
Exemplified NMR data are given for (p-XPCP)Ir(m-xylyl)-
(H) complexes 10a -f. 1H NMR data were obtained in both
mesitylene-d12 and neat protio m-xylene by following the
described procedure. However, mesitylene-d12 as purchased
form Aldrich contains impurities, which gave rise to generation
of trace amounts of both complexes 6a -f and one other
unidentified product. In neat protio m-xylene only one product
was formed in each case on the basis of the 31P NMR spectra.
For most complexes 10a -f all 1H NMR resonances could be
observed in neat protio m-xylene at -30 °C with intensities
comparable to the solvent satellites. 1H{31P} NMR experiments
were conducted between -40 and 23 °C either in neat m-xylene
or in mesitylene-d12 solution containing variable amounts of
m-xylene with respect to complexes 10a -f. m-Xylene concen-
tration-dependent line width determinations were conducted
between -40 and 0 °C. The minimum line width ∆ν1/2(min)
for all compounds 10a -f was observed at -30 °C, while
appropriate differences ∆ν1/2 for complexes 10a -f were ob-
served at 0 °C. 10a : 1H NMR (400.1 MHz, mesitylene-d12, -30
°C): δ 7.32 (s br, 2H, 2- and 6-H of xylyl), 6.44 (s, 2H, 3- and
5-H), 6.42 (s br, 1H, 4-H of xylyl), 3.20 (s, 3H, p-MeO), 2.37 (s,
6H, 2 × CH3 of xylyl), 1.08 [s br, 36H, 2 × P(tBu)2], -43.08 (t,
Hz, C4), 144.0 (Cq, dt, 4J F-C ) 2.2 Hz and J P-C ) 8.6 Hz, C1),
2
2
92.9 (CH, dvt, J F-C ) 25.6 Hz, C3 and C5), 41.0 (Cq, vt, J P-C
) 12.2 Hz, 4 × tBu), 28.3 (CH3, vt, J P-C ) 3.4 Hz, 4 × tBu). IR
(pentane, cm-1): 1953 (νCO), 1906, 1596, 1582. Anal. Calcd for
C
23H38O3P2FIr (635.72): C, 43.45; H, 6.03. Found: C, 43.40;
H, 6.03.
(p-C6F 5P CP )Ir (CO) (8e). By using the general procedure
33 mg (42 µmol, 84%) of (p-C6F5PCP)Ir(CO) (8e) was obtained
from 40 mg (50 µmol) of (p-C6F5PCP)IrHCl (4e) and 5.8 mg
(60 µmol) of NaOtBu as a fine powdered orange solid. 1H NMR

1776 Organometallics, Vol. 23, No. 8, 2004
Go¨ttker-Schnetmann et al.
2J P-H ) 14.2 Hz, 1H, IrH). 31P{1H} NMR (162 MHz, mesity-
lene-d12, -30 °C): δ 181.6. 10b: 1H NMR (400.1 MHz,
mesitylene-d12, -30 °C): δ 7.31 (s br, 2H, 2- and 6-H of xylyl),
6.59 (s, 2H, 3- and 5-H), 6.41 (s br, 1H, 4-H of xylyl), 2.38 (s,
6H, 2 × CH3 of xylyl), 2.10 (s, 3H, p-CH3), 1.07 [s br, 36H, 2 ×
(CH, m br, C4′), 103.0 (CH, vt, J P-C ) 5.7 Hz, C2 and C4),
2
41.8 (Cq, vt, J P-C ) 11.6 Hz, 4 × tBu), 29.5 (CH3, vt, J P-C
)
3.6 Hz, 4 × tBu), 21.7 (CH3 Tol). IR (pentane, cm-1): 2118
(νN2), 1475, 1467, 1461, 1381. Anal. Calcd for C74H98N2O4P4F12
-
Ir2 (1815.92): C, 48.94; H, 5.44. Found: C, 45.75; H, 5.29.26
Crystals suitable for X-ray structure analysis precipitated
shortly after reacting 4f and NaOtBu under an atmosphere of
nitrogen in toluene-d8 solution at 23 °C. X-ray crystal structure
analysis of compound 11f (-100 °C): space group and cell
dimensions: monoclinic, C2/c, a ) 21.1998(13) Å, b ) 19.1070-
(12) Å, c ) 21.0493(13) Å, â ) 110.927(1)°, volume ) 7963.9-
(9) Å3, empirical formula IrP2C37H49F6O2N, cell dimensions
were obtained from 6048 reflections with 2θ angle in the range
5.00-56.00°. Crystal dimensions: 0.10 × 0.10 × 0.05 mm, fw
) 907.95, Z ) 8, F(000) ) 3635.47, Fcalc ) 1.515 Mg/m3, µ )
3.50 mm-1, λ ) 0.71073 Å, 2θ(max) ) 56.0°. The intensity data
were collected on a Bruker SMART 1K diffractometer, using
the ω scan mode. The h,k,l ranges used during structure
solution and refinement are hmin,max -28, 26; kmin,max 0, 25;
2
P(tBu)2], -43.35 (t, J P-H ) 14.4 Hz, 1H, IrH). 31P{1H} NMR
(162 MHz, mesitylene-d12, -30 °C): δ 179.7. 10c (sample
contained some solid material): 1H NMR (400.1 MHz, mesi-
tylene-d12, -30 °C): δ 7.28 (s br, 2H, 2- and 6-H of xylyl), 6.82
(m, 3H, 3-6-H), 2.36 (s, 6H, 2 × CH3 of xylyl), 1.07 [s br, 36H,
2
2 × P(tBu)2], -43.34 (t, J P-H ) 14.2 Hz, 1H, IrH). 31P{1H}
NMR (162 MHz, mesitylene-d12, -30 °C): δ 179.0. 10d (sample
contained some solid material): 1H NMR (400.1 MHz, mesi-
tylene-d12, -30 °C): δ 7.25 (s br, 2H, 2- and 6-H of xylyl), 6.51
3
(d, J F-H ) 10.2 Hz, 3- and 5-H), 6.40 (s br, 1H, 4-H of xylyl),
2.35 (s, 6H, 2 × CH3 of xylyl), 1.00 [s br, 36H, 2 × P(tBu)2],
-43.33 (t, 2J P-H ) 14.2 Hz, 1H, IrH). 31P{1H} NMR (162 MHz,
mesitylene-d12, -30 °C): δ 179.5. 10e: 1H NMR (400.1 MHz,
mesitylene-d12, -30 °C): δ 7.25 (s br, 2H, 2- and 6-H of xylyl),
6.89 (m, 2H, 3- and 5-H), 6.41 (s br 1H, 4-H of xylyl), 2.37 (s,
6H, 2 × CH3 of xylyl), 1.04 [m br, 36H, 2 × P(tBu)2], -43.09
l
min,max 0, 27; no. of reflections measured 30 602, no. of unique
reflections 9618, no. of reflections with Inet > 2.5σ(Inet) ) 7504,
merging R-value on intensities 0.034. Correction was made
for absorption using SADABS. Details of the last least squares
cycle: 98 atoms, 442 parameters full-matrix on Fo counter wts
(k 0.000150). The residuals are as follows: Significant reflec-
tions: 7503, RF 0.032, Rw 0.035. All reflections: 9618, RF 0.046,
Rw 0.037. Included reflections: 7503, RF 0.032, Rw 0.035, GoF
1.4825, where RF ) ∑(Fo - Fc)/∑(Fo), Rw ) [∑(w(Fo- Fc)2)/∑-
(wFo2)]-1/2 and GoF ) [∑(w(Fo - Fc)2)/(no. of reflns - no. of
params)]-1/2. The maximum shift/σ ratio was 0.000. Last
D-map: minimum density -1.070 e/Å3, maximum density
1.400 e/Å3.
2
(t, J P-H ) 14.2 Hz, 1H, IrH). 31P{1H} NMR (162 MHz,
mesitylene-d12, -30 °C): δ 181.2. 10f: 1H NMR(400.1 MHz,
mesitylene-d12, -30 °C): d 7.77 (s, 2H, 2′- and 6′-H), 7.61 (s,
1H, 4′-H), 7.27 (s br, 2H, 2- and 6-H of xylyl), 7.02 (s, 2H, 3-
and 5-H), 6.42 (s br, 1H, 4-H of xylyl), 2.39 (s, 6H, 2 × CH3 of
2
xylyl), 1.06 [s, br., 36H, 2 × P(tBu)2], -43.03 (t, J P-H ) 14.2
Hz, 1H, IrH). 31P{1H} NMR (162 MHz, mesitylene-d12, -30
°C): δ 181.6.
{(p-Ar F P CP )Ir }2{µ-N2}*(2-x)Tol (11f). A solution of 168
mg (0.2 mmol) of precursor 4f and 21.0 mg (0.22 mmol) of
NaOtBu in 3 mL of toluene under an nitrogen atmosphere was
stirred for 60 min at 23 °C, while a red crystalline material
precipitated. The solvent was removed in high vacuum (10-3
mbar), the residue extracted with 20 mL of pentane, and the
pentane extract evaporated. The resulting residue was recrys-
tallized from refluxing toluene (3 mL) under an atmosphere
of nitrogen to yield 138 mg (76 µmol, 76%) of compound 11f
after drying under high vacuum. While X-ray crystallographic
analysis of compound 11f reveals exactly two molecules of
Gen er a l P r oced u r e for th e Tr a n sfer Deh yd r ogen a tion
of COA w ith TBE. A 1.5 mL portion of a stock solution
prepared from 3.400 g of cyclooctane (30.31 mmol), 2.690 g of
tert-butylethylene (30.36 mmol based on 95% purity), and
10 µmol of the respective (p-XPCP)IrH2 (6a -f) was transferred
into 4 mL thick walled Kontes reactors closed with Teflon
screw caps, and the reactors were placed in the cavities of a
heated aluminum block at 200 °C. After the desired reaction
time (8 min and 40 h) the Kontes reactors were removed from
the aluminum block and cooled by a stream of air. Aliquots of
the reaction mixtures were then taken in the glovebox and
1
toluene in the unit cell, the integration of the H NMR spectra
in THF-d8 or benzene-d6 gives less than 1 equiv of toluene per
iridium depending on the vacuum applied on the samples. It
was not possible, however, to totally remove toluene from
either crystalline or amorphous 11f. While monitoring the
formation of 11f in toluene-d8, we have observed the formation
of a minor side product, which did not crystallize and was not
isolated. Acquisition of 13C NMR spectra of compound 11f
requires the use of THF-d8 due to low solubility in the
commonly used solvents or instability in chlorinated solvents.
1
analyzed by H NMR. An average of two runs (from the same
stock solution) were taken in order to determine the TONs
after 8 min and 40 h. TONs were extracted from the ratio of
both the integrals of the olefinic COE, 1,3-COD, and TBE
signals and the integrals of the tert-butyl resonance of TBE
(s, 9H) and the overlapping methyl resonances of TBA (s and
t, 12H). The ratio of COE and 1,3-COD was extracted from
the two overlapping olefinic signals of COE and 1,3-COD (2,3-
H) and the isolated olefinic 1,3-COD signal (1,4-H). Except for
the ca. 5% impurity in the commercially available TBE (which
was proven to be unreactive by use of a mesitylene-h12
standard capillary and therefore can be used as an internal
standard), no signals other than COA, COE, 1,3-COD, TBE,
and TBA were detected in these reaction mixtures. The
number of COE and 1,3-COD double bonds equaled the
number of produced TBA molecules within <2% deviation in
each experiment.
1H NMR (300 MHz, 23 °C, THF-d8): δ 8.19 (“s”, 2H, 4′- and
6′-H), 7.87 (s, 1H, 2′-H), 7.16 (m, 5H, Tol), 6.87 (s, 2H, 3- and
5-H), 2.30 (s, 3H, Tol), 1.44 (vt, J P-H ) 7.0 Hz, 4 × tBu). 31P-
{1H} NMR (121.5 MHz, 23 °C, Tol-d8): δ 185.5. 19F{1H} NMR
(376.5 MHz, 23 °C, C6D6): δ -63.9. 13C{1H} NMR (75.5 MHz,
23 °C, Tol-d8): δ 170.8 (Cq, vt, J P-C ) 8.3 Hz, C2 and C6), 145.2
and 136.0 (Cq each, C4 and C1′), 138.6 (Cq, i-C Tol), 136.9 (Cq,
Ackn owledgm en t. We gratefully acknowledge fund-
ing by the National Health Institutes (grant no. GM
28938) and the Deutsche Akademie der Naturforscher
Leopoldina (grant no. BMBF-LPD 9901/8-60 to I.G.S.).
2
2
t, J P-C ) 7.6 Hz, C1), 132.7 (Cq, q, J F-C ) 32.9 Hz, C3′ and
C5′); 129.8, 129.1 and 126.2 (CH each, Tol), 127.6 (CH, m br,
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data of compound 11f. This material is available free of charge
via the Internet at http://pubs.acs.org.
1
C2′ and C6′), 124.9 (Cq, q, J F-C ) 272.5 Hz, 2 × CF3), 120.6
(26) The elemental analysis probably reflects the partial loss of
toluene from compound 11f.
OM030670O