Synthesis and catalytic applications of chiral hydridoiridium(III) complexes with diamine/bis(monophosphane) and diamine/diphosphane coordination

Article abstract of DOI:10.1002/ejic.200700380

The P₂/N₂-coordinated cis-dihydridoiridium(III) chelate complexes (OC-6-13)-[IrH₂(H₂N∩NH ₂)(PR₃)₂]BF₄ [PR₃ = PPh₃, H₂N∩NH₂ = 1,2-(H₂N) ₂C₆H₄ (1a); (1R,2R)-(H₂N) ₂C₆H₁₀ {(R,R)-dach) (1b); (R)-2,2′- diamino-1,1′-binaphthyl {(R)-dabin} (1c); PR₃ = PiPr ₃, H₂N∩NH₂ = (R,R)-dach (2a), (R)-dabin (2b); PR₃ = PCy₃, H₂N∩NH₂ = (R)-dabin (3)] were obtained by treating the respective diamine ligands with labile precursors such as [IrH₂(OCMe₂) ₂(PPh₃)₂]BF₄, [(η⁴-1, 5-C₈H₁₂)Ir(PPh₃)₂]BF₄, or [IrH₅(PR₃)₂]/HBF₄ (R = iPr, Cy). While oxidative addition of HCl to [(η⁴-1,5-C₈H ₁₂)Ir{(S,S)-bdpcp}]BF₄ [(S,S)-bdpcp = (1S,2S)-(Ph ₂P)₂C₅H₈] yields the usual mononuclear adduct [(η⁴-1,5-C₈H₁₂)Ir(H)(Cl) {(S,S)-bdpcp}]BF₄ (4), similar treatment of [(η⁴-1,5- C₈H₁₂)Ir{(R)-binap}]BF₄ furnishes the triply chlorido-bridged diiridium complex [{(Ae)-binap}₂Ir ₂H₂(μ-Cl)₃]BF₄ (5). Opening of the μ-Cl bridges of 5 by N,N nucleophiles was used to synthesise the three diamine/(R)-binap complexes [Ir(H)(Cl)-(H₂N∩NH ₂){(R)-binap}]BF₄ [H₂N∩NH₂ = (1R,2R)-H₂NCH(Ph)CH(Ph)NH₂ {(R,R)-dpen} (6a), (R,R)-dach (6b), and H₂NCMe₂CMe₂NH₂ {tmen} (6c). Whereas the dihydrides [IrH₂{(R,R)-dach)(PR₃) ₂]BF₄ and [IrH₂{(R)-dabin}-(PR ₃)₂]BF₄ (R = iPr, Ph) are only poor (pre)catalysts for the enantioselective hydrogenation of acetophenone, complexes 6a-c catalyze the formation of 1-phenylethanol in good enantiomeric excess [ee_max = 82-84 % (S)] in the presence of base. The crystal structures of 1a, 4, and 5 have been determined. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700380

FULL PAPER
DOI: 10.1002/ejic.200700380
Synthesis and Catalytic Applications of Chiral Hydridoiridium(III) Complexes
with Diamine/Bis(monophosphane) and Diamine/Diphosphane Coordination
Lutz Dahlenburg,*[a] Ralf Menzel,[a] and Frank W. Heinemann[a]
Dedicated to Professor Gottfried Huttner on the occasion of his 70th birthday
Keywords: Iridium / N ligands / P ligands / Asymmetric catalysis
The P2/N2-coordinated cis-dihydridoiridium(III) chelate com- complex [{(R)-binap}2Ir2H2(µ-Cl)3]BF4 (5). Opening of the µ-
plexes (OC-6-13)-[IrH2(H2NʝNH2)(PR3)2]BF4 [PR3 = PPh3,
H2NʝNH2 1,2-(H2N)2C6H4 (1a); (1R,2R)-(H2N)2C6H10
Cl bridges of 5 by N,N nucleophiles was used to synthesise
=
the
three
diamine/(R)-binap
complexes
[Ir(H)(Cl)-
{(R,R)-dach} (1b); (R)-2,2Ј-diamino-1,1Ј-binaphthyl {(R)-
dabin} (1c); PR3 = PiPr3, H2NʝNH2 = (R,R)-dach (2a), (R)-
(H2NʝNH2){(R)-binap}]BF4
H2NCH(Ph)CH(Ph)NH2 {(R,R)-dpen} (6a), (R,R)-dach (6b),
[H2NʝNH2
=
(1R,2R)-
dabin (2b); PR3 = PCy3, H2NʝNH2 = (R)-dabin (3)] were ob- and H2NCMe2CMe2NH2 {tmen} (6c). Whereas the dihy-
tained by treating the respective diamine ligands with labile
precursors such as [IrH2(OCMe2)2(PPh3)2]BF4, [(η4-1,5-
C8H12)Ir(PPh3)2]BF4, or [IrH5(PR3)2]/HBF4 (R = iPr, Cy). While
oxidative addition of HCl to [(η4-1,5-C8H12)Ir{(S,S)-
bdpcp}]BF4 [(S,S)-bdpcp = (1S,2S)-(Ph2P)2C5H8] yields the
usual mononuclear adduct [(η4-1,5-C8H12)Ir(H)(Cl){(S,S)-
bdpcp}]BF4 (4), similar treatment of [(η4-1,5-C8H12)Ir{(R)-
drides [IrH2{(R,R)-dach}(PR3)2]BF4 and [IrH2{(R)-dabin}-
(PR3)2]BF4 (R = iPr, Ph) are only poor (pre)catalysts for the
enantioselective hydrogenation of acetophenone, complexes
6a–c catalyze the formation of 1-phenylethanol in good enan-
tiomeric excess [eemax = 82–84% (S)] in the presence of base.
The crystal structures of 1a, 4, and 5 have been determined.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
binap}]BF4 furnishes the triply chlorido-bridged diiridium Germany, 2007)
phenone, although both their activity and selectivity (eemax.
Introduction
= 71%)[1] were inferior to those of the established RuII-
based systems.[3]
We recently[1] described some 2,2Ј-bis(diphenylphos-
phanyl)-1,1Ј-binaphthyl-coordinated diamine(diphosphane)-
rhodium(I) complexes such as [Rh{(R,R)-H2NCH(Ph)CH-
(Ph)NH2}{(R)-binap}]BF4 and the like, which were made
without difficulty by treating [(η4-1,5-C8H12)Rh{(R)-
binap}]BF4 with N,N-chelate ligands under hydrogen. Oxi-
dative addition of HCl led to the rhodium(III) derivative
(OC-6-43)-[Rh(H)(Cl){(R,R)-H2NCH(Ph)CH(Ph)NH2}{(R)-
binap}]BF4. From a structural point of view, this latter
complex can be regarded as an analog of the neutral ruthe-
nium(II) compound (OC-6-43)-[Ru(H)(Cl){(R,R)-H2NCH-
(Ph)CH(Ph)NH2}{(R)-binap}], which is well known to be
an excellent (pre)catalyst for the stereoselective hydrogena-
tion of ketones and imines.[2a]
In our search for complexes of the Group 9 transition
metals with possibly improved catalytic properties we set
out to synthesize and investigate some cationic hydrido
compounds of iridium(III) with coordination spheres domi-
nated by (preferentially chiral) diamine and (di)phosphane
ligands, namely [IrH2(H2NʝNH2)(PR3)2]BF4 (R = Ph, iPr,
Cy) and [Ir(H)(X)(H2NʝNH2)(Ph2PʝPPh2)]BF4 (X = H
or Cl).
Results and Discussion
Complexes
If activated by a strong base in 2-propanol, the diamine-
(diphosphane)rhodium complexes were also found to act as
enantioselective catalysts for the reduction of aceto-
Either of the cationic IrI or IrIII complexes [(η4-1,5-
C8H12)Ir(PR3)2]+ and [IrH2(OCMe2)2(PR3)2]+ (R = Ph),[4]
respectively, or the pentahydrides [IrH5(PR3)2] (R = iPr,
Cy)[5] could be used as starting material for the preparation
of the target compounds [IrH2(H2NʝNH2)(PR3)2]+. Thus,
stoichiometric 1:1 reactions of the solvento complex [Ir-
H2(OCMe2)2(PPh3)2]BF4 with 1,2-phenylenediamine (1,2-
phdn) or (1R,2R)-1,2-diaminocyclohexane [(R,R)-dach] re-
sulted in smooth replacement of the loosely bound acetone
[a] Institut für Anorganische Chemie der Friedrich-Alexander-
Universität Erlangen-Nürnberg,
Egerlandstrasse 1, 91058 Erlangen, Germany
Fax: +49-9131-85-27387
E-mail: Lutz.Dahlenburg@chemie.uni-erlangen.de
4364
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Chiral Hydridoiridium(III) Complexes
ligands by the two diamines to give [IrH2(1,2-phdn)-
Crystals of [IrH2(1,2-phdn)(PPh3)2]BF4 (1a) suitable for
(PPh3)2]BF4 (1a)[6] and [IrH2{(R,R)-dach}(PPh3)2]BF4 (1b), an X-ray diffraction study were grown from dichlorometh-
as expected (Scheme 1). Since the weakly solvated dihy- ane. As anticipated, the structure determination revealed
drides [IrH2(solv)2(PR3)2]+ are formed in the presence of a the presence of N–H···F hydrogen-bonded ion-pairs with
coordinating solvent, either by hydrogenation of [(η4-1,5- the iridium atom in the close to octahedral coordination
C8H12)Ir(PR3)2]+ [4] or by protonation of [IrH5(PR3)2] with environment inferred from the NMR spectroscopic data
a strong acid,[4c,5b] both the dieneiridium(I) complexes and above (Figure 1). The hydride ligands could not be located
the pentahydrides could be employed as precursors as well. from the final density maps in any of the structures re-
For example, treatment of [(η4-1,5-C8H12)Ir(PPh3)2]BF4 ported in this paper but were placed, with d(Ir–H) re-
with an equimolar amount of (R)-2,2Ј-diamino-1,1Ј-bi- strained to 1.6 Å, at the positions calculated by Orpen’s
naphthyl [(R)-dabin] in CH2Cl2 under hydrogen gave HYDEX energy-minimizing procedure.[7,8] The metal-to-
[IrH2{(R)-dabin}(PPh3)2]BF4 (1c) as an additional diamine- phosphane distances of 2.292(1) and 2.302(1) Å are slightly
containing bis(triphenylphosphane) complex, whereas the shorter than, but still comparable to, the Ir–P bond lengths
triisopropyl- and tricyclohexylphosphane analogues previously reported by Crabtree for the structurally related
[IrH2{(R,R)-dach}(PiPr3)2]BF4 (2a), [IrH2{(R)-dabin}- acetone complex [IrH2(OCMe2)2(PPh3)2]BF4 [d(Ir–P) =
(PiPr3)2]BF4 (2b), and [IrH2{(R)-dabin}(PCy3)2]BF4 (3) 2.313 and 2.321 Å].[4c] A feature of interest is the coordina-
were obtained from [IrH5(PiPr3)2] or [IrH5(PCy3)2] by aci- tion of the ortho-phenylenediamine ligand, with the two Ir–
dolysis with HBF4 (54% in Et2O) and subsequent reaction NH2 distances amounting to 2.163(4) and 2.202(5) Å. The
with the required diamine in a 1:1 molar ratio (Scheme 1).
Ir–NH2 linkages of 1a tend to be longer than the iridium–
amine bond lengths of, for example, (OC-6-12)-
[IrCl2{Me2P(CH2)2NH2}2]PF6 [d(Ir–NH2) trans to Ir–N:
2.090 Å),[9a]
(OC-6-43)-[Ir(H)(Cl){Ph2P(CH2)2NH2}2]Cl
[d(Ir–N) trans to Ir–P: 2.136 and 2.137 Å),[10a] and (OC-
6-13)-[IrCl2{Ph2P(CH2)2NH2}2]BF4 [d(Ir–N) trans to Ir–P:
2.142 and 2.152 Å),[9b] which reflects the high trans-bond-
weakening influence of the two hydrides opposite to the
amine donors.
Scheme 1. Synthesis of complexes 1–3.
Figure 1. Structure of the ion-pair [IrH2(1,2-phdn)(PPh3)2]BF4
(1a); phenyl H atoms have been omitted for clarity. Selected bond
lengths [Å] and angles [°]: Ir1–P1 2.302(1), Ir–P2 2.292(1), Ir–N1
2.163(4), Ir–N2 2.202(5); P1–Ir–P2 174.37(6), P1–Ir–N1 93.5(1),
P1–Ir–N2 90.8(1); hydrogen-bonding interactions (D–H, H···A,
D···A [Å], D–H···A [°]): N1–H···F1 0.92, 2.27, 2.854(5), 121.1; N1–
H···F4 0.92, 2.42, 2.997(6), 120.5; N2–H···F2_#1 0.92, 2.17,
2.863(7), 131.2; N2–H···F3_#1 0.92, 2.37, 3.001(6), 125.3. Sym-
metry transformation used to generate equivalent atoms: #1 = x +
1/2, y + 1/2, z.
The OC-6-13 stereochemistry of compounds 1–3
(Scheme 1) follows from the observation of their IrH reso-
nances between δ = –21 and –27 ppm, which is typical for
hydridoiridium(III) complexes with hard donor ligands
trans to H.[4b] Further confirmation of the coordination ge-
ometry depicted in Scheme 1 came from the cis-2JP,H coup-
ling constants of 16–18 Hz found in all cases.
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L. Dahlenburg, R. Menzel, F. W. Heinemann
FULL PAPER
In exploratory studies aimed at synthesizing the P2/N2- ligands. The structure consists of discrete [(η4-1,5-C8H12)-
–
coordinated hydride complexes [Ir(H)(X)(H2NʝNH2)- Ir(H)(Cl){(S,S)-bdpcp}]+ cations (Figure 2) and BF4
(Ph2PʝPPh2)]BF4 (X = H, Cl), which have one chiral bi- anions. The Ir–Cl bond trans to the hydride is long at
dentate rather than two achiral monodentate phosphorus 2.490(4) Å,[12] which is entirely consistent with the strong
ligands, two diene(diphosphane) complexes [(η4-1,5-C8H12) trans influence of hydrido ligands.
Ir(Ph2PʝPPh2)]BF4 {Ph2PʝPPh2
=
(R)-binap[11] and
In contrast to the “normal” oxidative addition of HCl to
(1S,2S)-1,2-bis(diphenylphosphanyl)cyclopentane
[(S,S)- [(η4-1,5-C8H12)Ir{(S,S)-bdpcp}]BF4, the reaction of hydro-
bdpcp]} were selected as potential starting materials. As gen chloride with [(η4-1,5-C8H12)Ir{(R)-binap}]BF4 did not
mentioned by way of introduction, related rhodium chemis- lead to a mononuclear IrIII complex but instead gave the
try has shown that the bis(chelates) [Rh(H2NʝNH2){(R)- triply
binap}]BF4 {H2NʝNH2 = H2NCMe2CMe2NH2 (tmen), binap}2Ir2H2(µ-Cl)3]BF4 (5) (Scheme 2). It is well known
(1R,2R)-H2NCH(Ph)CH(Ph)NH2 [(R,R)-dpen],
or that IrIII has a pronounced tendency to form cationic[13]
chlorido-bridged
binuclear
product
[{(R)-
(1R,2R)-1,2-(H2N)2C6H10 [(R,R)-dach]} are smoothly confacial-bioctahedral structures held together by three
formed when [(η4-1,5-C8H12)Rh{(R)-binap}]BF4 is hydro- connecting mononegative donors such as halide, hydride,
genated in the presence of the required diamine ligand.[1] alkoxide, amide, and the like. Reported examples include
In view of the greater stability of the Ir–H bond than the the (R)-binap-coordinated complexes [{(R)-binap}2Ir2H2(µ-
Rh–H bond, we expected that similar treatment of the OR)2(µ-Cl)]Cl (R = H, CH3), which were obtained by oxi-
diene(diphosphane) iridium precursors [(η4-1,5-C8H12)- dative addition of the O–H bonds of water and methanol
Ir(Ph2PʝPPh2)]BF4 would result in the formation of
mixed-ligand complexes [IrH2(H2NʝNH2)(Ph2PʝPPh2)]-
BF4 by oxidative addition of dihydrogen to initially formed
[Ir(H2NʝNH2)(Ph2PʝPPh2)]BF4 intermediates. However,
only mixtures of various hydride-containing complexes
were produced, from which none of the hoped-for com-
pounds could be isolated.
Expecting that it might be easier to substitute the hard
nitrogen donors for the σ,π-bonded diolefin ligand at the
IrIII rather than the IrI oxidation stage, we prepared the
complex [(η4-1,5-C8H12)Ir(H)(Cl){(S,S)-bdpcp}]BF4 (4) by
oxidative addition of hydrogen chloride to its [(η4-1,5-
C8H12)Ir{(S,S)-bdpcp}]BF4 precursor. Compound 4 was
shown by NMR spectroscopy, together with an X-ray struc-
ture analysis, to bear trans-bonded chlorido and hydrido Scheme 2. Formation of diiridium complex 5.
Figure 2. Structure of the cation of [(η4-1,5-C8H12)Ir(H)(Cl){(S,S)-bdpcp}]BF4 (4); carbon-bonded H atoms have been omitted for clarity.
Selected bond lengths [Å] and angles [°]: Ir–Cl1 2.490(4), Ir–P1 2.332(4), Ir–P2 2.319(4); Cl1–Ir–P1 88.8(1), Cl1–Ir–P2 84.0(1), P1–Ir–P2
85.5(1).
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Chiral Hydridoiridium(III) Complexes
to [{(R)-binap}2Ir2(µ-Cl)2],[13h] as well as the recently de-
We propose that [(η4-1,5-C8H12)Ir{(R)-binap}]BF4 reacts
scribed halide salts [{(S)-binap}2Ir2H2(µ-X)3]X (X = Cl, Br, with hydrogen chloride to initially give an HCl adduct sim-
I), which were formed by sequential treatment of [(η2- ilar to 4, where the greater bulkiness of the two “Ph2Pnaph-
C8H14)4Ir2(µ-Cl)2] first with the chelate phosphane and thyl” binap building blocks than that of the two “Ph2Pal-
then with aqueous HX.[13p]
kyl” halves of the chelate ring in the mononuclear complex
Figure 3. Structures of the two crystallographically independent cations of [{(R)-binap}2Ir2H2(µ-Cl)3]BF4 (5); aryl H atoms have been
omitted for clarity. Selected bond lengths [Å] and angles [°] for cation I: Ir1–Cl1 2.470(1), Ir1–Cl2 2.534(1), Ir1–Cl3 2.428(1), Ir1–P1
2.251(1), Ir1–P2 2.257(1), Ir2–Cl1 2.436(1), Ir2–Cl2 2.532(1), Ir2–Cl3 2.458(1), Ir2–P3 2.252(1), Ir2–P4 2.245(1); Cl1–Ir1–Cl2 78.99(4),
Cl1–Ir1–Cl3 79.37(5), Cl1–Ir1–P1 94.37(5), Cl1–Ir1–P2 173.17(5), Cl2–Ir1–Cl3 79.27(4), Cl2–Ir1–P1 106.40(5), Cl2–Ir1–P2 100.72(5),
Cl3–Ir1–P1 170.74(5), Cl3–Ir1–P2 93.85(5), P1–Ir1–P2 92.26(5), Cl1–Ir2–Cl2 79.65(4), Cl1–Ir2–Cl3 79.45(5), Cl1–Ir2–P3 170.01(5), Cl1–
Ir2–P4 94.66(5), Cl2–Ir2–Cl3 78.77(4), Cl2–Ir2–P3 106.54(5), Cl2–Ir2–P4 100.37(5), Cl3–Ir2–P3 93.89(5), Cl3–Ir2–P4 174.11(5), P3–
Ir2–P4 91.94(5), Ir1–Cl1–Ir2 86.10(1), Ir1–Cl2–Ir2 82.76(1), Ir1–Cl3–Ir2 86.52(1). Selected dihedral angles, given as (plane)/(plane) [°]:
(Ir1,Cl1,Cl2)/(Ir2,Cl1,Cl2) 58.43(4), (Ir1,Cl1,Cl3)/(Ir2,Cl1,Cl3) 54.49(5), (Ir1,Cl2,Cl3)/(Ir2,Cl2,Cl3) 58.44(4), (Ir1,Cl1,Ir2)/(Ir1,Cl2,Ir2)
61.00(1), (Ir1,Cl1,Ir2)/(Ir1,Cl3,Ir2) 57.72(1), (Ir1,Cl2,Ir2)/(Ir1,Cl3,Ir2) 61.28(1), (naphthyl C1–C10)/(naphthyl C11–C20), 76.1(1); (naph-
thyl C45–C54)/(naphthyl C55–C64), 67.7(1). Corresponding parameters for cation II: Ir3–Cl4 2.530(1), Ir3–Cl5 2.426(1), Ir3–Cl6 2.463(1),
Ir3–P5 2.259(1), Ir3–P6 2.250(1), Ir4–Cl4 2.542(1), Ir4–Cl5 2.452(1), Ir4–Cl6 2.440(1), Ir4–P7 2.260(1), Ir4–P8 2.257(1); Cl4–Ir3–Cl5
79.80(4), Cl4–Ir3–Cl6 79.03(4), Cl4–Ir3–P5 107.61(5), Cl4–Ir3–P6 98.80(5), Cl5–Ir3–Cl6 79.83(4), Cl5–Ir3–P5 168.85(5), Cl5–Ir3–P6
93.89(5), Cl6–Ir3–P5 93.21(5), Cl6–Ir3–P6 173.61(5), P5–Ir3–P6 93.18(5), Cl4–Ir4–Cl5 79.10(4), Cl4–Ir4–Cl6 79.23(4), Cl4–Ir4–P7
100.53(5), Cl4–Ir4–P8 105.97(5), Cl5–Ir4–Cl6 79.78(5), Cl5–Ir4–P8 92.68(5), Cl5–Ir4–P7 174.44(5), Cl6–Ir4–P7 94.69(5), Cl6–Ir4–P8
170.00(5), P7–Ir4–P8 92.74(5), Ir3–Cl4–Ir4 82.33(1), Ir3–Cl5–Ir4 86.38(1), Ir3–Cl6–Ir4 85.83(1); (Ir3,Cl4,Cl5)/(Ir4,Cl4,Cl5) 58.37(5),
(Ir3,Cl4,Cl6)/(Ir4,Cl4,Cl6) 59.38(5), (Ir3,Cl5,Cl6)/(Ir4,Cl5,Cl6) 54.29(3), (Ir3,Cl4,Ir4)/(Ir3,Cl5,Ir4) 60.85(1), (Ir3,Cl4,Ir4)/(Ir3,Cl6,Ir4)
61.92(1), (Ir3,Cl5,Ir4)/(Ir3,Cl6,Ir4) 57.23(1), (naphthyl C89–C98)/(naphthyl C99–C108), 73.0(1); (naphthyl C133–C142)/(naphthyl C143–
C152), 72.0(1).
Eur. J. Inorg. Chem. 2007, 4364–4374
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L. Dahlenburg, R. Menzel, F. W. Heinemann
FULL PAPER
facilitates the decoordination of the cyclooctadiene ligand was observed in the reaction of the HCl adduct with the
through “steric pressure”.[14a,14b] Bridge-closing combina- stronger basic aliphatic diamine 1,2-(H2N)2C6H10.
tion of the remaining “[{(R)-binap}Ir(H)(Cl)]+ fragments Brønsted base-assisted dehydrohalogenations, as observed
would then form [{(R)-binap}2Ir2H2(µ-Cl)2]2+, which stabi- between 4 and diamines, are the infrequently encountered
lizes to 5 by the addition of an extra chloride ion provided reverse reaction of HX oxidative addition; they are compar-
by the excess of HCl.[14c]
atively common with IrIII [17]
. In fact, similar amine-induced
The bimetallic structure of 5 was confirmed by X-ray eliminations of HCl have recently been reported for some
analysis. Single crystals grown from an acetone/diethyl triply chlorido-bridged binuclear hydrides of iridium(III)
ether solvent mixture were found to have the idealized com- bearing trimethylene-linked N-heterocyclic carbenes
position [{(R)-binap}2Ir2H2(µ-Cl)3]BF4·Me2CO·1/2 H2O· (NHCs) as terminal ligands.[13o] Whereas those
1/4 Et2O and to contain, in addition to the different solvent [{(NHC)(CH2)3(NHC)}2Ir2H2(µ-Cl)3]PF6 dimers under-
molecules, two crystallographically independent ion pairs in went complete degradation in the presence of nitrogen
the asymmetric unit. Perspective views of the molecular bases, binap-chelated diiridium complex 5 reacts with sev-
models that resulted for the cationic parts are presented in eral diamines to smoothly produce the diamine(diphos-
Figure 3. The structures of the two cations are very close to phane) target compounds [Ir(H)(Cl)(H2NʝNH2){(R)-
C2-symmetric, with the twofold rotation axes passing binap}]BF4 [H2NʝNH2 = (R,R)-dpen (6a), (R,R)-dach
through the midpoints of the Ir···Ir vectors and the chlorido (6b), and tmen (6c)] by nucleophilic opening of the
ligands Cl2 and Cl4 trans to the Ir–H bonds. In solution, chlorido bridges. In order to favor the formation of these
this molecular C2 symmetry is mirrored by a deceptively three cationic species (Scheme 3), the liberated chloride was
simple AAЈBBЈ 31P{1H} NMR pattern arising from the two removed by precipitation with AgBF4, although the ad-
chiral diphosphane ligands (pairs of “doublets”, where only dition of Ag+ is not imperative with the completely ali-
4
|2JP,P + JP,P| = 20.0 Hz is resolved). The pair-wise shared phatic and, hence, more electron-rich diamines tmen and
coordination planes spanned by one metal center and two dach. Diiridium complex 5 does not undergo the bridge-
bridging chlorido ligands are inclined to each other at opening reaction upon combination with (R)-2,2Ј-diamino-
angles between 120.62° and 125.71°, with the interplanar 1,1Ј-binaphthyl, either because of too much steric pressure
angles of the Ir(µCl)Ir bridges varying from 118.08(1)° to in the resulting [Ir(H)(Cl){(R)-dabin)}{(R)-binap}]+ cation
122.77(1)° (ranges of the supplementary dihedral angles or because of a too low nucleophilicity of the aromatic (R)-
given in the legend to Figure 3: 59.38(5)–54.29(3)° and dabin ligand.
61.92(1)–57.23(1)°, respectively). The angles between the
normals to the four pairs of naphthyl least squares planes
amount to 67.7(1)° and 76.1(1)° in cation I and 72.0(1)°
and 73.0(1)° in cation II. Though much less than the dihe-
dral angle of 81.4° displayed by the pairs of naphthalene
rings in the related [{(R)-binap}2Ir2H2(µ-OCH3)2(µ-Cl)]+
cation,[13h] these values clearly fall within the limits of about
65–77° that have previously been reported for several mono-
and binuclear binap compounds of RuII, RhI, IrI, and
IrIII [13p,15]
As anticipated, the Ir–Cl bonds trans to Ir–H
.
[2.530(1)–2.534(1) Å] are significantly longer than those op-
posite to the Ir–P bonds [2.426(1)–2.470(1) Å] and are
amongst the longest IrIII–µ–Cl distances reported to
date.[16] The Ir–P bond lengths of 7 vary between 2.246(1)
and 2.260(1) Å and thus compare favorably with the metal-
to-phosphorus distances of 2.248 and 2.262 Å measured for
the aforementioned chlorido/methoxido-bridged diiridi-
um(III) complex.[13h] The obtuse P–Ir–P angles of 91.94(5)–
93.18(5)° likewise closely resemble those of other structur-
Scheme 3. Synthesis of mixed-ligand complexes 6a–c.
Complexes 6a–c proved difficult to crystallize and there-
ally characterized iridium complexes bearing (R)- or (S)- fore could only be characterized spectroscopically. Their 1H
binap ligands.[13h,13p,15g,15h]
NMR spectra were found to display hydride signals at
Completely unexpectedly, the reaction of [(η4-1,5-C8H12)- around δ = –20 ppm as doublets of doublets. Two JP,H
Ir(H)(Cl){(S,S)-bdpcp}]BF4 (4) with different H2NʝNH2 coupling constants amounting to around 16 and 18 Hz
chelate ligands did not result in diene/diamine exchange. place these hydrido ligands in a position cis to two chemi-
Depending on the reaction conditions, the less basic aro- cally inequivalent binap P atoms which, accordingly, give
matic or aliphatic amines 2,2Ј-diamino-1,1Ј-binaphthyl and rise to two 31P{1H} doublets (δ = –13 to –10 and –1 ppm;
1,2-diphenylethylenediamine either left the compound un- cis-2JP,P ≈ 22 Hz). These data indicate that the stereochemis-
changed or furnished mixtures with the dehydrochlorinated try of 6a–c is either OC-6-43 with the hydride trans to Cl,
iridium(I) precursor [(η4-1,5-C8H12)Ir{(S,S)-bdpcp}]BF4. as proposed for [Rh(H)(Cl){(R,R)-dpen}{(R)-binap}]-
Complete removal of hydrogen chloride from the IrIII center BF4,[1] or OC-6-23, where the Ir–H bond is opposite to one
2
4368
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4364–4374

Chiral Hydridoiridium(III) Complexes
of the NH2 functionalities. Although we could not corrobo- Table 1. Enantioselective hydrogenation of acetophenone in the
presence of base-modified iridium(III) precatalysts; p(H2) = 20 bar.
rate the actual structure by X-ray analysis, the geometry
with the hydride trans to chloride shown in Scheme 3 is fa-
vored over the trans-H–Ir–N alternative by comparison
with the IrH NMR spectroscopic data of some [Ir(H)(Cl)(a-
minophosphane)2]X chelate complexes having crystallo-
graphically established OC-6-43 stereochemistry, for exam-
ple [Ir(H)(Cl)(H2N(CH2)2PPh2)2]Cl[10a] and [Ir(H)(Cl){o-
HN(R)C6H4PPh2}2]X (R = Et, CH2Ph; X– = Cl–, OH–,
No.
Precatalyst
t [h]
PhCH(OH)Me ee [%] (config.)
[%]
1
2
3
4
5
6
7
8
9
10
11
12
13
6a[a]
6b[a]
1.5
1.5
2
4
1.5
2
1
2
2
3
100
100
61
42
100
51
82 (S)
75 (S)
59 (S)
38 (S)
73 (S)
24(S)
6b[b]
6b[c]
6c[a]
1b[a]
–
MeCO2 ).[18] Similar to 6a–c, all of these compounds dis-
1c[a]
37
69
37
Ͻ2 (S)
Ͻ2 (S)
9 (S)
2a[a]
play δ(IrH) in the range –22 to –20 ppm with cis-2J(P,H) ≈
2b[a]
18 Hz.[19]
6a[d]
11
62
100
100
80 (S)
66 (S)
84 (S)
71 (S)
6b[d]
3
2
2
5/(R,R)-dpen[e]
5/(R,R)-dach[e]
Catalytic Hydrogenation of Acetophenone
[a] Acetophenone (5.0 mmol), 0.01 mmol of IrIII complex, KOH
(50 equiv.), methanol (3 mL); T = 50 °C. [b] In ethanol at s:c =
500:1; T = 40 °C. [c] In 2-propanol at s:c = 200:1; T = 60 °C. [d]
33.0 mmol of acetophenone, 6.6ϫ10–3 mmol of IrIII complex, and
0.33 mmol of KOH in methanol (4 mL); T = 50 °C. [e] In situ cata-
lysts activated with 25 equiv. of KOH in methanol; s:c = 250:1, T
= 50 °C.
Both
the
chiral
chlorido-hydrido
complexes
[Ir(H)(Cl)(H2NʝNH2){(R)-binap}]BF4 [H2NʝNH2
=
(R,R)-dpen (6a), (R,R)-dach (6b), or tmen (6c)] and the di-
hydrides [IrH2{H2NʝNH2}(PR3)2]BF4 [H2NʝNH2/PR3 =
(R,R)-dach/PPh3 (1b), (R)-dabin/PPh3 (1c), (R,R)-dach/
PiPr3 (2a), or (R)-dabin/PiPr3 (2b)] were investigated for
their ability to form stereoselective ϾC=O hydrogenation
catalysts. In fact, all of them catalyzed the asymmetric hy- erolytic activation of the hydrogen molecule during reac-
drogenation of acetophenone to (S)-1-phenylethanol at sub- tion,[20] is a characteristic feature of iridium-based ϾC=O
strate-to-catalyst (s:c) ratios ranging from 200:1 to 5000:1 hydrogenation catalysts bearing ligands that, like the di-
in the presence of a strong base (typically 50 equiv. of amines used in the present study, have acidic primary or
KOH) in alcoholic solution under H2 (20 bar) at 40–60 °C secondary amine ends.
(Table 1). The success of these hydrogenation reactions de-
As compared to complexes 1b/1c and 2a/2b, where only
pends critically on the presence of extra base in the catalytic the diamine ligands can contribute to the (poor) stereoselec-
system and the use of a protic reaction medium. Thus, vir- tive outcome of the catalytic runs (Table 1, entries 6–9),
tually no catalytic ϾC=O reduction occurred in alcohols in compounds 6a–c, which possess an additional (R)-binap li-
the absence of base or in an aprotic solvent such as benzene gand, form much more enantioselective systems, as ex-
containing a basic additive. Methanol proved to be the sol- pected. Best results of 82–84% ee were obtained with the
vent of choice, as reactions in ethanol and 2-propanol pro- preformed complex [Ir(H)(Cl){(R,R)-dpen}{(R)-binap}]-
ceeded slower and resulted in reduced enantioselectivity BF4 (6a) and its in situ generated equivalent
(Table 1, entries 2–4).
[{(R)-binap}2Ir2H2(µ-Cl)3]BF4/(R,R)-dpen [5/(R,R)-dpen;
The likelihood of the ketone reduction proceeding by di- Table 1, entries 1 and 12).[21] With (R,R)-dach as the di-
rect metal-assisted transfer of Hδ–/Hδ+ equivalents from the amine co-ligand, the ee achieved with both the preformed
H2 molecule to the carbonyl dipole was substantiated by and the in situ catalysts 6b and 5/(R,R)-dach was seen to
ruling out the alternative pathway involving Hδ–/Hδ+ trans- drop to 71–75% (Table 1, entries 2 and 13). Further re-
fer from the solvent. Thus, when a solution of acetophen- placement of the (R,R)-dach chelate by the achiral diamine
one in CH3OH was hydrogenated with D2 (10 bar) em- H2NCMe2CMe2NH2 in precatalyst 6c left the optical yield
ploying the combined 6b/KOH catalyst, α-deuterated of the (S) isomer (73%; Table 1, no. 5) essentially un-
PhCD(OH)CH3 was formed as the main alcohol product, changed, thus suggesting that it is preferentially the diphos-
which was demonstrated by NMR spectroscopy as de- phane which determines the asymmetric induction. Com-
scribed previously.[10b] The observation of minor amounts parison of these results with those obtained with isoelec-
of PhCH(OH)CH3 as a by-product of the deuteration reac- tronic RuII-based catalysts reveals some interesting trends.
tion cannot be attributed to the methanol molecule serving
At first glance, the combined system [Ir(H)(Cl)(tmen)-
as a hydrogen source because no formation of PhCH(OH)- {(R)-binap}]BF4/KOH/MeOH appears to be superior in
CH3 or PhCD(OH)CH3 was observed when the reaction selectivity [73% for (S)-PhCH(OH)Me] to the [Ru(H)(Cl)-
was carried out in the absence of hydrogen gas in CH3OH (tmen){(R)-binap}]-derived dihydride [Ru(H)2(tmen){(R)-
or CD3OH. The formation of the non-deuterated isoto- binap}], which produced the (S) isomer of 1-phenylethanol
pomer rather points to “D2 + CH3OH = CH3OD + HD” in only 6–14% yield when used in 2-propanol without
and “HD + CH3OH = CH3OD + H2” exchange processes added base.[2b,2c] However, the seemingly poor performance
accompanying the catalysis. We have shown in previous of this ruthenium complex results from catalyst deactivation
work[10b] that the exchange of isotopes between a protic sol- by formation of diastereomeric alkoxides such as
vent and the hydrogen atmosphere, which is typical of het- [Ru(H){(S)-OCH(Me)Ph}(tmen){(R)-binap}] and [Ru(H)-
Eur. J. Inorg. Chem. 2007, 4364–4374
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4369

L. Dahlenburg, R. Menzel, F. W. Heinemann
FULL PAPER
{(R)-OCH(Me)Ph}(tmen){(R)-binap}] during the build up alcohol with a degree of enantioselectivity which, in the
of the acidic product alcohol. This unwanted side reaction most favorable cases, closely matches that of established iso-
can be prevented by the addition of base or by lowering the electronic RuII-based catalysts containing identical phos-
polarity of the solvent. Running the Ru-catalyzed reaction phorus and nitrogen donor ligands.
in 2-propanol in the presence of base or in benzene (where
Ir complex 6c remains completely inactive) thus established
Experimental Section
an inherent enantioselectivity of 51–68% (R) for the ruthe-
nium-based (R)-binap/tmen system,[2b,2c] which is therefore
comparable to 6c with respect to the ee values that can be
attained but yields the opposite enantiomer. In the presence
of base, the RuII complex [Ru(H)(Cl){(R,R)-dach}{(R)-
binap}] catalyzes the hydrogenation of acetophenone (neat
or dissolved in benzene) to afford (S)-PhCH(OH)Me in
88% ee,[2a,2c] which makes it a somewhat more selective cat-
alyst than [Ir(H)(Cl){(R,R)-dach}{(R)-binap}]BF4 (6b),
which gives the (S) form of the alcohol in only around 75%
ee. With base-modified [Ru(H)(Cl){(R,R)-dpen}{(R)-
binap}], the Morris group has achieved 73% ee for the for-
mation of (S)-PhCH(OH)Me,[2a] while the catalytic species
generated in basic media from the dichlorido precursor
[RuCl2{(S,S)-dpen}{(S)-tolbinap}] (tolbinap is the di-p-
tolyl analogue of binap) afforded the (R) enantiomer in 78–
83% yield, as reported independently by Noyori and co-
workers[22] and Rautenstrauch and Morris et al.[2d] Hence,
the selectivity of the corresponding iridium-based system
[Ir(H)(Cl){(R,R)-dpen}{(R)-binap}]BF4/KOH/MeOH [82%
ee for the (S) isomeric alcohol] compares favorably with
that observed for the two established ruthenium catalysts
possessing the same ligands. However, the RuII complexes,
which work very fast at substrate-to-catalyst ratios as high
as 105–106, form much more active systems: the most active
IrIII catalyst studied in this work is formed from the only
moderately selective complex 6b in the presence of 50 equiv.
of KOH. This system furnished 62% of 1-phenylethanol
within 3 h at s:c = 5000, albeit with a reduced selectivity of
66% ee for the (S) isomer (Table 1, entry 11). Under iden-
tical conditions, the most selective precatalyst 6a maintains
an optical yield of 80% ee (S) but shows poor activity,
transforming only 11% of the ketone to the product alcohol
(Table 1, entry 10).
General: All manipulations were performed under nitrogen or ar-
gon, unless stated otherwise. Solvents were distilled from the appro-
priate drying agents prior to use. NMR: Bruker DPX 300
(300.1 MHz for 1H, 75.5 MHz for 13C, and 121.5 MHz for 31P)
with SiMe4 as internal or H3PO4 as external standard (downfield
positive) at ambient temperature (“m” = deceptively simple mul-
tiplet). GC: Shimadzu GC-17A (FID). Silver tetrafluoroborate,
HBF4 (54% in Et2O), and the diphosphane and diamine ligands
(R)-2,2Ј-bis(diphenylphosphanyl)-1,1Ј-binaphthyl [(R)-binap], 1,2-
phenylenediamine (1,2-phdn), (R)-2,2Ј-diamino-1,1Ј-binaphthyl
[(R)-dabin], (1R,2R)- and (1S,2S)-1,2-diphenylethylenediamine
[(R,R)-, (S,S)-dpen], and (1R,2R)-1,2-diaminocyclohexane [(R,R)-
dach] were used as purchased. 1,1Ј,2,2Ј-Tetramethylethylenedi-
amine (tmen),[23] (1S,2S)-1,2-bis(diphenylphosphanyl)cyclopentane
[(S,S)-bdpcp],[24] [(η4-1,5-C8H12)2Ir2(µ-Cl)2],[25] [(η4-1,5-C8H12)-
Ir(PPh3)2]BF4,[4d,4e] [IrH2(OCMe2)2(PPh3)2]BF4,[4d,4e] [IrH5(P-
iPr3)2],[5d] and [IrH5(PCy3)2][5e] were prepared according to pub-
lished procedures or slight modifications thereof. The complex [(η4-
1,5-C8H12)Ir{(R)-binap}]BF4 was previously made from [(η4-1,5-
C8H12)Ir(NCMe)2]BF4 which, in turn, was synthesized from [(η4-
1,5-C8H12)2Ir2(µ-Cl)2] via [(η4-1,5-C8H12)2Ir]BF4 as a further inter-
mediate.[11] A more direct route is given here: A 1:2:2 molar mixture
of [(η4-1,5-C8H12)2Ir2(µ-Cl)2] (425 mg, 0.63 mmol), (R)-binap
(785 mg, 1.26 mmol), and AgBF4 (245 mg, 1.26 mmol) in 30 mL of
methanol was stirred for 24 h at ambient conditions with the ex-
clusion of light. Precipitated silver chloride was then removed by
filtration through diatomaceous earth (Celite® 521), which was
washed with small portions of CH2Cl2 until the residue on the filter
was colorless. Evaporation of the filtrate to a final volume of about
2 mL followed by dilution with 30 mL of diethyl ether gave the
product as a raspberry-colored solid, which was filtered off, washed
with diethyl ether (3ϫ5 mL), and dried under vacuum; yield:
1
950 mg (75%). H NMR (CD2Cl2): δ = 1.84–2.30 (m, 8 H, CH2),
4.15, 4.40 (both m, 2 H each, both CH), 6.39–7.78 (m, 32 H, aryl
H) ppm. 31P{1H} NMR (CD2Cl2): δ = 16.05 (s) ppm [ref.[11] δ =
15.1 ppm in CDCl3]. C52H44BF4IrP2 (1008.9): calcd. C 61.85, H
4.39; found C 62.08, H 4.54.
[(η4-1,5-C8H12)Ir{(S,S)-bdpcp}]BF4 was isolated in 60% yield from
a similar 1:2:2 reaction of [(η4-1,5-C8H12)2Ir2(µ-Cl)2] with AgBF4
and the diphosphane in methanol: 1H NMR (CD2Cl2): δ = 1.16,
1.70–2.36 (both m, 2 + 12 H, both CH2), 2.74 (m, 2 H, PCH), 4.00,
4.73 (both m, 2 H each, both diene CH), 7.31–7.89 (m, 20 H, aryl
δ = 20.70 (s) ppm.
C37H40BF4IrP2 (825.70): calcd. C 53.82, H 4.88; found C 53.61, H
4.71.
Conclusions
This work has shown that cationic dihydridoiridium(III)
complexes with two monodentate phosphanes and one che-
lating diamine can easily be made by treating different
H2NʝNH2 ligands with a number of readily accessible sub-
stitutionally labile precursors. The preparation of the
mixed-ligand bis(chelates) [Ir(H)(Cl)(H2NʝNH2){(R)-
binap}]BF4 [H2NʝNH2 = (R,R)-dpen (6a), (R,R)-dach
(6b), or tmen (6c)] is more involved and requires dinuclear
[{(R)-binap}2Ir2H2(µ-Cl)3]BF4 as a synthetic intermediate.
While cis-dihydrides such as [IrH2{(R,R)-dach}(PR3)2]BF4
and [IrH2{(R)-dabin}(PR3)2]BF4 (R = iPr, Ph) are only
poor (pre)catalysts for the enantioselective hydrogenation
of acetophenone to 1-phenylethanol, the combined systems
H) ppm. 31P{1H} NMR (CD2Cl2):
[IrH2(1,2-phdn)(PPh3)2]BF4 (1a): A solution of [IrH2(OCMe2)2-
(PPh3)2]BF4 (440 mg, 0.49 mmol) in 15 mL of thf was stirred with
1,2-phenylenediamine (55 mg, 0.50 mmol) at room temperature.
After a short while the product separated from the reaction mixture
as a colorless solid, which was filtered off, washed with diethyl
ether (2ϫ3 mL), and dried under vacuum. Yield: 198 mg (44%).
1H NMR (CD2Cl2): δ = –20.84 (t, 2JP,H = 16.7 Hz, 2 H, IrH2), 4.04
(br., 4 H, NH2), 6.77, 7.03 (AAЈBBЈ-type m, 4 H, phenylene H),
7.30–7.51 (m, 30 H, phenyl H) ppm. 13C{1H} NMR (CD2Cl2): δ =
(6a–c)/KOH/MeOH catalyze the formation of the product 128.58, 129.66 (both s, phenylene C-3,6 and C-4,5), 129.88 (t, 3JP,C
4370 Eur. J. Inorg. Chem. 2007, 4364–4374
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chiral Hydridoiridium(III) Complexes
= 20.2 Hz, phenyl C-3,5), 131.70 (s, phenyl C-4), 132.26 (t, JP,C
103.9 Hz, phenyl C-1), 133.99 (t, JP,C = 24.5 Hz, phenyl C-2,6),
139.81 (phenylene C-1,2) ppm. 31P{1H} NMR (CD2Cl2): δ = 24.49
(s) ppm. C42H40BF4IrN2P2 (913.71): calcd. C 55.21, H 4.41, N 3.07;
found C 54.71, H 4.25, N 2.72.
1
=
[IrH2{(R)-dabin}(PCy3)2]BF4 (3): Synthesized from [IrH5(PCy3)2]
(115 mg, 0.15 mmol), treated with HBF4 as outlined for 2a, and
the diamine (43 mg, 0.15 mmol) in 10 mL of benzene in 80% yield
2
1
2
(135 mg). H NMR (CD2Cl2): δ = –26.57 (t, JP,H = 18.1 Hz, 2 H,
IrH2), 1.15–1.87 (m, 66 H, cyclohexyl H), 2.06 (m, 6 H, PCH),
4.99, 5.21 (both br., 2 H each, both NH2), 6.82 (d, 3JH,H = 8.8 Hz,
2 H, aryl 3-H), 7.15 (“t”, Σ3JH,H = 15.0 Hz, 2 H, aryl 6-H), 7.42
[IrH2{(R,R)-dach}(PPh3)2]BF4 (1b): This complex was prepared as
described for 1a from [IrH2(OCMe2)2(PPh3)2]BF4 (200 mg,
0.22 mmol) and the diamine ligand (25 mg, 0.22 mmol) in 10 mL
of thf. Yield: 121 mg (60%) of a colorless solid. 1H NMR (CD2Cl2):
3
(m, 4 H, aryl 7,8-H), 7.98 (d, JH,H = 8.2 Hz, 2 H, aryl 5-H), 8.10
3
(d, JH,H = 8.8 Hz, 2 H, aryl 4-H) ppm. 31P{1H} NMR (CD2Cl2):
δ = 20.92 (s) ppm. C56H84BF4IrN2P2 (1126.27): calcd. C 59.72, H
2
δ = –21.07 (t, JP,H = 17.6 Hz, 2 H, IrH2), 0.33, 0.71, 1.20–1.33,
7.52,
N 2.49; found C 58.66, H 7.14, N 2.32; calcd. for
1.39, 1.75 (all m, 2 + 2 + 4 + 2 + 2 H, CH2 and NH2), 2.79 (m, 2
H, CH), 7.4–7.7 (m, 30 H, C6H5) ppm. 13C{1H} NMR: δ = 25.13
(s, C6H10 C-4,5), 36.28 (s, C6H10 C-3,6), 60.96 (s, C6H10 C-1,2),
C56H84BF4IrN2P2·CH2Cl2 (1211.2): calcd. C 56.52, H 7.16, N 2.31.
[(η4-1,5-C8H12)Ir(H)(Cl){(S,S)-bdpcp}]BF4 (4): Dropwise addition
of a saturated solution of hydrogen chloride in diethyl ether to a
suspension of [(η4-1,5-C8H12)Ir{(S,S)-bdpcp}]BF4 (204 mg,
0.25 mmol) in 20 mL of thf gave a clear yellow solution, from which
the product separated within 1 h as pale-yellow microcrystals. Yield
(after washing three times with 2 mL of Et2O and drying): 190 mg
(89%). 1H NMR (CD2Cl2): δ = –14.05 (dd, cis-2JP,H = 7.1 and
11.5 Hz, 1 H, IrH), 0.96, 1.47 (both m, 1 H each, both CH2), 1.85–
2.86 (m, 14 H, CH2 and phosphane CH), 3.89, 4.27, 5.32 (all m, 1
+ 2 + 1 H, diene CH), 7.21–7.82 (m, 20 H, aryl H) ppm. 31P{1H}
NMR (CD2Cl2): δ = 6.03, 15.30 (both d, JP,P = 15.6 Hz) ppm.
C37H41BClF4IrP2 (862.16): calcd. C 51.55, H 4.79; found C 50.98,
H 4.66.
3
129.96 (t, JP,C = 20.2 Hz, phenyl C-3,5), 131.62 (s, phenyl C-4),
133.66 (t, 1JP,C = 104.0 Hz, phenyl C-1), 134.10 (t, 2JP,C = 24.6 Hz,
phenyl C-2,6) ppm. 31P{1H} NMR (CD2Cl2): δ = 21.92 (s) ppm.
C42H46BF4IrN2P2 (919.81): calcd. C 54.84, H 5.04, N 3.05; found
C 54.45, H 5.49, N 2.91.
[IrH2{(R)-dabin}(PPh3)2]BF4 (1c): A solution of [(η4-1,5-C8H12)-
Ir(PPh3)2]BF4 (106 mg, 0.12 mmol) and an equimolar quantity of
(R)-dabin (34 mg) in 10 mL of CH2Cl2 was stirred for 20 min under
an atmosphere of hydrogen, which caused the mixture to change
color from red to pale yellow. The off-white product was isolated
by adding diethyl ether (80 mL), then washed with Et2O and dried
1
under vacuum. Yield: 109 mg (83%). H NMR ([D6]acetone): δ =
2
–23.48 (t, JP,H = 18.1 Hz, 2 H, IrH2), 3.62 (br., 4 H, NH2), 5.90,
[{(R)-binap}2Ir2H2(µ-Cl)3]BF4 (5): A solution of dry HCl gas in di-
ethyl ether was added dropwise to a stirring solution of [(η4-1,5-
C8H12)Ir{(R)-binap}]BF4 (205 mg, 0.20 mmol) in 10 mL of thf un-
der ambient conditions. The red mixture gradually became yellow
and the addition of HCl·Et2O was stopped when no further color
change was discernible. The product was precipitated after stirring
for an additional 10 min and concentration of the solution to about
1 mL by adding 20 mL of diethyl ether. It was then washed twice
with 2 mL of Et2O and dried under vacuum. Yield: 172 mg (94%).
1H NMR (CD2Cl2): δ = –22.73 (dd, 2JP,H = 15.6 and 21.5 Hz, 2 H,
IrH), 6.30–8.03 (m, 64 H, aryl H) ppm. 31P{1H} NMR (CD2Cl2):
3
6.05, 6.44 (all d, JH,H = 8.8, 10.4, and 8.2 Hz, 2 H each, all aryl
H), 7.17, 7.28, 7.37, 7.91 (all m, 44 H, aryl H) ppm. 31P{1H} NMR
([D6]acetone): δ = 24.33 (s) ppm. Complex 1c as well as its ana-
logues 2a, 2b, and 3 were found to retain varying amounts of resid-
ual CH2Cl2 solvent so that no satisfactory elemental analyses could
be obtained: C56H48BF4IrN2P2 (1090.0): calcd. C 61.71, H 4.44,
N
2.57; found
C
59.45,
H
4.38,
N
2.31; calcd. for
C56H48BF4IrN2P2·CH2Cl2 (1162.9): calcd. C 57.84, H 4.33, N 2.41.
[IrH2{(R,R)-dach}(PiPr3)2]BF4 (2a): Tetrafluoroboric acid (54% in
Et2O) was added dropwise to a solution of [IrH5(PiPr3)2] (525 mg,
1.02 mmol) in 15 mL of benzene until no further evolution of hy-
drogen was observed. The diamine ligand (116 mg, 1.02 mmol) was
then added and the resulting mixture stirred for 1 h at room tem-
perature. The residue remaining after evaporation to dryness was
redissolved in 5 mL of CH2Cl2 and the product was isolated as an
off-white solid by adding 50 mL of diethyl ether. Yield: 418 mg
(57%). 1H NMR (C6D6): δ = –23.28 (t, 2JP,H = 18.0 Hz, 2 H, IrH2),
4
δ = –6.54, 1.59 (both AAЈBBЈ-type “d”, |2JP,P + JP,P| = 20.0 Hz)
ppm. C88H66BCl3F4Ir2P4 (1825.0): calcd. C 57.89, H 3.65; found C
57.83, H 3.50.
[Ir(H)(Cl){(R,R)-dpen}{(R)-binap}]BF4 (6a): A mixture of (R,R)-
dpen (44 mg, 0.21 mmol) and AgBF4 (20 mg, 0.10 mmol) in 5 mL
of thf was added to a solution of 5 (185 mg, 0.10 mmol) in 5 mL
of thf. After stirring for 30 min under ambient conditions, the pre-
cipitate of AgCl was filtered off and the filtrate was concentrated
to about 1 mL. Precipitation with 20 mL of diethyl ether, followed
by filtration and washing with Et2O (2ϫ3 mL) gave 108 mg (47%)
3
3
0.58 (m, 4 H, CH2), 1.19 (dd, JH,H = 7.1, JP,H = 15.4 Hz, 36 H,
CH3), 1.37 (m, 4 H, CH2), 2.17 (m, 6 H, PCH), 2.46, 2.60 (both
br., 2 H each, both NH2), 3.88 (m, 2 H, NCH) ppm. 31P{1H} NMR
(C6D6): δ = 44.02 (s) ppm. C24H58BF4IrN2P2 (715.71): calcd. C
40.28, H 8.17, N 3.91; found C 39.13, H 7.90, N 3.78; calcd. for
C24H58BF4IrN2P2·CH2Cl2 (800.64): calcd. C 37.50, H 7.55, N 3.50.
Compounds 2b and 3 were obtained analogously:
1
of the product as a yellowish white solid. H NMR (CD2Cl2): δ =
2
–19.81 (dd, JP,H = 15.9 and 18.0 Hz, 1 H, IrH), 2.91, 3.00, 3.29,
3.89 (all br., 1 H each, NH2), 4.39 (m, 2 H, CH), 6.18–8.12 (m, 42
H, aryl H) ppm. 31P{1H} NMR (CD2Cl2): δ = –9.99, –0.64 (both
d, JP,P = 22.3 Hz) ppm. C58H49BClF4IrN2P2 (1150.5): calcd. C
60.55, H 4.29, N 2.43; found C 61.15, H 4.53, N 2.38. Similar
procedures were used for the preparation of complexes 6b and 6c.
[IrH2{(R)-dabin}(PiPr3)2]BF4 (2b): Synthesized from [IrH5(PiPr3)2]
(228 mg, 0.44 mmol), treated with HBF4 as described above, and
(R)-dabin (125 mg, 0.44 mmol) in 15 mL of benzene in 82% yield
1
2
(320 mg). H NMR (CD2Cl2): δ = –26.56 (t, JP,H = 18.3 Hz, 2 H,
IrH2), 0.86 (dd, 3JH,H = 6.6, JP,H = 14.8 Hz, 36 H, CH3), 2.06 (m,
[Ir(H)(Cl){(R,R)-dach}{(R)-binap}]BF4 (6b): Synthesized from 5
3
6 H, PCH), 4.98, 5.10 (both br., 2 H each, both NH2), 6.69 (d, (100 mg, 0.05 mmol) and the diamine (13 mg, 0.11 mmol) in 10 mL
3JH,H = 8.8 Hz, 2 H, aryl 3-H), 7.15 (“t”, Σ3JH,H = 15.0 Hz, 2 H,
of thf. Yield: 84 mg (73%). 1H NMR (CD2Cl2): δ = –20.35 (dd,
3
aryl 6-H), 7.35 (m, 4 H, aryl 7,8-H), 7.82 (d, JH,H = 8.2 Hz, 2 H, 2JP,H = 15.5 and 18.2 Hz, 1 H, IrH), 1.19–2.09 (m, 8 H, CH2), 2.85
3
aryl 5-H), 7.98 (d, JH,H = 8.8 Hz, 2 H, aryl 4-H) ppm. 31P{1H}
NMR (C6D6): δ = 44.35 (s) ppm. C38H60BF4IrN2P2 (885.87): calcd.
C 51.52, H 6.83, N 3.16; found C 49.73, H 6.60, N 3.08; calcd. for
C38H60BF4IrN2P2·CH2Cl2 (970.81): calcd. C 48.25, H 6.44, N 2.89.
(br., 4 H, NH2), 3.01, 4.81 (both m, 1 H each, both CH), 6.28–8.15
(m, 32 H, aryl H) ppm. 31P{1H} NMR (CD2Cl2): δ = –10.69, –1.10
(both d, JP,P = 22.3 Hz) ppm. C50H47BClF4IrN2P2 (1052.4): calcd.
C 57.07, H 4.50, N 2.66; found C 56.96, H 4.32, N 2.43.
Eur. J. Inorg. Chem. 2007, 4364–4374
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4371

L. Dahlenburg, R. Menzel, F. W. Heinemann
0.38ϫ0.30ϫ0.13 mm3,
C37H41ClIrP2·BF4·C3H6O
FULL PAPER
[Ir(H)(Cl)(tmen){(R)-binap}]BF4 (6c): Synthesized from 5 (120 mg, 4·Me2CO:
0.07 mmol) and the diamine ligand (16 mg, 0.14 mmol) in thf
(10 mL). Yield: 64 mg (48%). H NMR (CD2Cl2): δ = –20.00 (dd,
(920.18); orthorhombic, P212121, a = 10.431(1), b = 19.128(3), c =
19.438(7) Å, V = 3878(2) Å3, Z = 4, dcalcd. = 1.576 gcm–3, µ(Mo-
Kα) = 3.644 mm–1; 2.10° Յ Θ Յ 25.17°, 4928 reflections collected
(–3 Յ h Յ +12, –3 Յ k Յ +22, –3 Յ l Յ +23), 4652 unique (Rint
1
2JP,H = 15.6 and 17.4 Hz, 1 H, IrH), 1.02, 1.08, 1.12, 1.20 (all s, 3
H each, all CH3), 2.06, 2.37, 3.96, 4.85 (all br., 1 H each, all NH2),
6.23–8.12 (m, 32 H, aryl H) ppm. 31P{1H} NMR (CD2Cl2): δ =
–12.92, –1.10 (both d, JP,P = 22.4 Hz) ppm. C50H49BClF4IrN2P2
(1054.4): calcd. C 56.96, H 4.68, N 2.66; found C 56.83, H 4.58, N
2.34.
= 0.0471); wR2 = 0.1373 for all data and 454 parameters, R1
=
0.0578 for 3712 intensities I Ͼ 2σ(I); absolute structure parameter
x = –0.010(17).[33]
5·solv: 0.26ϫ0.18ϫ0.16 mm3, C88H66Cl3Ir2P4·BF4·C3H6O·HO0.5
CH2.5O0.25 (1910.5); orthorhombic, P212121, a = 21.205(2), b =
24.821(4), c = 32.830(3) Å, V = 17279(4) Å3, Z = 8, dcalcd.
·
General Procedure for Catalytic ϾC=O Hydrogenation: A 10-mL
Schlenk tube equipped with a small magnetic stirring bar was
charged with an alcoholic solution of the catalyst complex (typi-
cally 0.01 mmol in 3.0 mL of methanol). The required amounts of
potassium hydroxide and acetophenone (see Table 1) were then
added, the mixture was stirred for 10 min under ambient condi-
tions, and the tube was inserted into an argon-filled stainless steel
autoclave. The autoclave was sealed and vented several times with
H2 (Messer–Griesheim; 99.999%), subsequently pressurized to
20 bar, and the contents stirred at 40–60 °C. At the end of the reac-
tion, the pressure was vented, the solvent removed under vacuum,
and the residue was diluted with diethyl ether to precipitate the
catalyst as a brownish black solid. The solution was decanted and
chromatographed on a silica gel column using diethyl ether as the
eluent. Volatile material was distilled off and the mixture of prod-
ucts was analyzed by 1H NMR spectroscopy. Conversions and
product compositions were determined on the basis of the integra-
tions of the PhC(O)CH3 and PhCH(OH)CH3 signals. Enantio-
meric excesses were measured by GC using a Chrompack Chirasil-
Dex CB column.
=
1.469 gcm–3, µ(Mo-Kα) = 3.299 mm–1; 2.67° Յ Θ Յ 28.00°, 172715
reflections collected (–20 Յ h Յ +28, –32 Յ k Յ +32, –42 Յ l Յ
+43), 39510 unique (Rint = 0.0462); wR2 = 0.1264 for all data and
1943 parameters, R1 = 0.0427 for 32060 intensities I Ͼ 2σ(I); abso-
lute structure parameter x = 0.010(4).[33]
CCDC-640544 (for 1a), -640546 (for 4·Me2CO), and -640545 (for
5·solv) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Center via www.ccdc.cam.ac.uk/
data_request/cif.
Acknowledgments
Support of this work by the Deutsche Forschungsgemeinschaft
(SFB 583) is gratefully acknowledged. We are also indebted to Mrs.
S. Hoffmann and Mr. P. Bakatselos for their skilful assistance.
X-ray Structure Determinations: The crystal used for the structure
analysis of 1a was grown from dichloromethane. Recrystallization
of 4 and 5 from acetone/diethyl ether mixtures afforded single crys-
tals of solvent-containing addition compounds identified as [(η4-
1,5-C8H12)Ir(H)(Cl){(S,S)-bdpcp}]BF4·Me2CO and [{(R)-binap}2-
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Ir2H2(µ-Cl)3]BF4·Me2CO·1/2H2O·1/4Et2O
(“4·Me2CO”
and
“5·solv” hereafter). Diffraction measurements were made at
–173(2) °C with a Bruker-Nonius Kappa CCD instrument for com-
pounds 1a and 5·solv and at –160(2) °C with an Enraf–Nonius
CAD4 MACH3 diffractometer for 4·Me2CO, both of which used
Mo-Kα radiation (λ = 0.71073 Å); diffraction data were corrected
for absorption by appropriate numerical[26] (1a: Tmin = 0.277, Tmax
= 0.801), refined[27] (4·Me2CO: Tmin = 0.227, Tmax = 0.621), or
empirical[28] (5·solv: Tmin = 0.738, Tmax = 1.000) methods. The
structures were solved by direct methods and subsequently refined
by full-matrix (1a, 4·Me2CO) or, in view of the large dimensions
of 5·solv, by block-matrix least-squares procedures on F2 with al-
lowance for anisotropic thermal motion of all non-hydrogen atoms
employing both the SHELXTL NT 6.12[29] and the WinGX[30a]
package with some of the relevant programs (SIR-97,[31] SHELXL-
97,[32] XHYDEX,[7] ORTEP-3[30b]) implemented therein. The crys-
tal of 1a under study proved to be a pseudomerohedral twin. The
twin law used during the refinement was –1 0 0 0 –1 0 0 0 –1 and
resulted in a twin component ratio of approximately 5:1 (BASF
0.2122).
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clinic, C2, a = 9.1624(9), b = 17.197(2), c = 24.204(2) Å, β =
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4372
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4364–4374

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