Iridium(III) Complex Containing a Unique Bifurcated Hydrogen Bond Interaction Involving Ir-H?H(N)?F-B atoms. Crystal and Molecular Structure of [IrH(η1-SC5H4NH)(η2-SC 5H4N)(PPh3)2](BF 4)·0.5C6H6

Article abstract of DOI:10.1021/ic950438d

A synthetic route to a new iridium(III) complex containing a novel proton hydride bonding interaction has been established. fac-IrH₃(PPh₃)₃ reacts with 2-mercaptopyridine HSpy (Spy = 2-SC₅H₄N) to give the known dihydride Ir(H)₂(η₂-Spy)(PPh₃)₂ 8. Ir(H)₂(η²-Spy)(PPh₃)₂ reacts with HSpy· HBF₄ to give [IrH(η¹-SC₅H₄NH)(η²-SC ₅H₄N)-(PPh₃)₂](BF₄) 9 which possesses a unique bifurcated hydrogen bonding interaction involving Ir-H?H(N)?F-B atoms with the distances of 2.0(1) A? for the H?H unit and of 2.0(1) A? for the F?H unit in the crystalline state. In solution the N-H?H-Ir interaction is maintained according to ¹H T₁(min) and nOe measurements. Isotope shifts in the chemical shifts of the hydride and one phosphorus of 9 have been observed in ¹H and ³¹P{¹H} NMR spectra of [IrH(η¹-SC₅H₄ND)(η²-SC ₅H₄N)(PPh₃)₂](BF₄), 9-d₁, prepared by the reaction of 9 with MeOD or CF₃-CO₂D. The crystal and molecular structure of [IrH(η¹-SC₅H₄NH)(η²-SC ₅H₄N)(PPh₃)₂](BF ₄)·0.5C₆H₆ 9 has been solved by X-ray analysis: monoclinic space group P2₁/c with a = 17.723(3) A?, b = 10.408(1) A?, c = 26.073(4) A?, β= 108.08(1)°, V = 4572.0(11) A?³, and Z = 4. The known complex fac-IrH₃(PPh₃)₃, 7, is made by a new and improved method by reacting mer-IrHCl₂(PPh₃)₃ with NaOEt and H₂(g). VT-¹H NMR spectra (+90 to -80 °C) of the hydrides of 7 reveal that the J_AA and J_AX couplings change in the AA'A''XX'X'' pattern (A = ¹H, X = ³¹P) but that the complex is not fluxional. The T₁(min) value of 0.144 s for the hydrides of 7 at -60 °C (300 MHz) indicates that the shortest H-H distances are about 1.8 A?.

Full text of DOI:10.1021/ic950438d

Inorg. Chem. 1996, 35, 3001-3006
3001
Iridium(III) Complex Containing a Unique Bifurcated Hydrogen Bond Interaction
Involving Ir-H‚‚‚H(N)‚‚‚F-B atoms. Crystal and Molecular Structure of
[IrH(η1-SC5H4NH)(η2-SC5H4N)(PPh3)2](BF4)‚0.5C6H6
Sunghan Park, Alan J. Lough, and Robert H. Morris*
Department of Chemistry, University of Toronto, 80 St. George Street,
Toronto, Ontario M5S 1A1, Canada
ReceiVed April 14, 1995X
A synthetic route to a new iridium(III) complex containing a novel proton hydride bonding interaction has been
established. fac-IrH3(PPh3)3 reacts with 2-mercaptopyridine HSpy (Spy ) 2-SC5H4N) to give the known dihydride
Ir(H)2(η2-Spy)(PPh3)2 8. Ir(H)2(η2-Spy)(PPh3)2 reacts with HSpy.HBF4 to give [IrH(η1-SC5H4NH)(η2-SC5H4N)-
(PPh3)2](BF4) 9 which possesses a unique bifurcated hydrogen bonding interaction involving Ir-H‚‚‚H(N)‚‚‚F-B
atoms with the distances of 2.0(1) Å for the H‚‚‚H unit and of 2.0(1) Å for the F‚‚‚H unit in the crystalline state.
In solution the N-H‚‚‚H-Ir interaction is maintained according to 1H T1(min) and nOe measurements. Isotope
shifts in the chemical shifts of the hydride and one phosphorus of 9 have been observed in 1H and 31P{1H} NMR
spectra of [IrH(η1-SC5H4ND)(η2-SC5H4N)(PPh3)2](BF4), 9-d1, prepared by the reaction of 9 with MeOD or CF3-
CO2D. The crystal and molecular structure of [IrH(η1-SC5H4NH)(η2-SC5H4N)(PPh3)2](BF4)‚0.5C6H6 9 has been
solved by X-ray analysis: monoclinic space group P21/c with a ) 17.723(3) Å, b ) 10.408(1) Å, c ) 26.073(4)
Å, â ) 108.08(1)°, V ) 4572.0(11) Å3, and Z ) 4. The known complex fac-IrH3(PPh3)3, 7, is made by a new
and improved method by reacting mer-IrHCl2(PPh3)3 with NaOEt and H2(g). VT-1H NMR spectra (+90 to -80
1
°C) of the hydrides of 7 reveal that the JAA and JAX couplings change in the AA′A′′XX′X′′ pattern (A ) H, X
)
31P) but that the complex is not fluxional. The T1(min) value of 0.144 s for the hydrides of 7 at -60 °C (300
MHz) indicates that the shortest H-H distances are about 1.8 Å.
Introduction
A new intramolecular proton-hydride interaction was dis-
covered recently by Crabtree’s group1 and us.2 Such H‚‚‚H
interactions are potentially important as intermediates in the
base-promoted heterolytic splitting of dihydrogen.3
So far complexes of the types 1, 2, 4, and 5 have proton-
hydride interactions at about 1.7-1.9 Å in solution as well as
in the solid state. An iridium hydroxy complex 3 has been
proposed to contain an Ir-H‚‚‚H-O interaction at the longer
H-H distance of 2.40(1) Å as determined in a single crystal
neutron diffraction study.4
Here we report the preparation and characterization of an
iridium(III) complex 9 containing a unique bifurcated hydrogen
bonding interaction involving hydride, proton, nitrogen, and a
fluorine atom of tetrafluoroborate anion.
We have suggested2a that the H/D exchange between 1 and
D2 gas occurs via the intramolecular proton (NH) transfer to
hydride to give a dihydrogen tautomer. In the presence of the
H-bond acceptor THF, the NH groups of 1 are not correctly
positioned for formation of such a dihydrogen tautomer and no
H/D exchange is possible.
X Abstract published in AdVance ACS Abstracts, April 1, 1996.
(1) (a) Lee, J. C.; Rheingold, A. L.; Muller, B.; Pregosin, P. S.; Crabtree,
R. H. J. Chem. Soc., Chem. Commun. 1994, 1021. (b) Lee, J. C.;
Rheingold, A. L.; Peris, E.; Crabtree, R. H. J. Am. Chem. Soc. 1994,
116, 11014.
(2) (a) Lough, A. J.; Park, S. H.; Ramachandran, R.; Morris, R. H. J. Am.
Chem. Soc. 1994, 116, 8356. (b) Park, S. H.; Ramachandran, R.;
Lough, A. J.; Morris, R. H. J. Chem. Soc., Chem. Commun. 1994,
2201.
(3) Morris, R. H.; Jessop, P. G. Coord. Chem. ReV. 1992, 121, 155.
(4) (a) Milstein, D.; Calabrese, J. C.; Williams, I. D. J. Am. Chem. Soc.
1990, 108, 6387. (b) Milstein, D.; Stevens, R. C.; Bau, R.; Blum, O.;
Koetzle, T. F. J. Chem. Soc., Dalton Trans. 1990, 1429.
Experimental Section
All preparations were carried out under an atmosphere of dry argon
using conventional Schlenk techniques. All the solvents were distilled
under argon over appropriate drying agents prior to use. Tetrahydro-
furan (THF), diethyl ether (Et2O), and n-hexane were dried over and
distilled from sodium benzophenone ketyl. Ethanol (EtOH) and
dichloromethane were distilled from magnesium ethoxide and calcium
hydride, respectively. Deuterated solvents were dried over Linde type
4 Å molecular sieves and degassed prior to use. Triphenylphosphine,
2-mercaptopyridine, and an 85% solution of HBF4‚Et2O complex were
S0020-1669(95)00438-1 CCC: $12.00 © 1996 American Chemical Society

3002 Inorganic Chemistry, Vol. 35, No. 10, 1996
Park et al.
Table 1. Summary of Crystal Data, Details of Intensity Collection,
and Least-Squares Refinement Parameters for 9
empirical formula
Mr
cryst class
space group
a, Å
C49H43BF4IrN2P2S2‚0.5C6H6
1064.92
monoclinic
P21/c
17.723(3)
10.408(1)
26.073(4)
108.08(1)
4572.0(11)
4
b, Å
c, Å
â, deg
V, Å3
Z
D
calc, M gm-3
1.547
3.134
2124
µ(Mo KR), mm-1
F(000)
θ range for data collcn, deg
2.56-27.00
T, K
173(2)
min., max. transma
no. of reflcns collcd
no. of indep reflcns
Rint
0.5297, 0.7937
10290
9964
Figure 1. Structure of the cation and anion of 9 which also shows the
N-H‚‚‚F-B interaction. The hydrogen on the nitrogen of the pyri-
diniumthiolate and the hydride ligand are well defined in Fourier
difference maps.
0.0453
no. of obsd. data [I > 2σ(I)]
R1 [I > 2σ(I)]b
wR2 (all data)c
params refined
6153
0.0468
0.1156
556
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 9
Ir-N(1)
2.080(6)
2.304(2)
2.535(2)
1.730(8)
1.828(7)
1.843(7)
1.827(7)
1.352(10)
1.354(10)
2.778(8)
1.393(11)
1.412(10)
1.370(11)
1.383(10)
1.316(13)
1.326(14)
2.30(11)
2.05(13)
Ir-P(2)
2.291(2)
2.394(2)
1.72(11)
1.741(7)
1.831(7)
1.826(7)
1.833(7)
1.320(9)
1.349(10)
0.94(8)
1.374(10)
1.391(11)
1.344(11)
1.381(12)
1.36(2)
Ir-P(1)
Ir-S(2)
a Absorption correction using SHELXA-90 in SHELXL-93.6 b R1
Ir-S(1)
Ir-H(1Ir)
) ∑(Fo - Fc)/∑Fo. c wR2 ) {∑[w(Fo - Fc2)2/∑[w(Fo )2]}1/2
.
2
2
S(2)-C(10)
P(1)-C(11)
P(1)-C(31)
P(2)-C(61)
N(1)-C(5)
N(2)-C(10)
N(2)‚‚‚F(4)
C(2)-C(3)
C(4)-C(5)
C(7)-C(8)
C(9)-C(10)
B(1)-F(4)
B(1)-F(1)
F(4)‚‚‚H(1Ir)
H(1Ir)‚‚‚H(2A)
S(1)-C(5)
P(1)-C(21)
P(2)-C(41)
P(2)-C(51)
N(1)-C(1)
N(2)-C(6)
N(2)-H(2A)
C(1)-C(2)
C(3)-C(4)
C(6)-C(7)
C(8)-C(9)
B(1)-F(3)
B(1)-F(2)
F(4)‚‚‚H(2A)
purchased from Aldrich Chemical Co., Inc. Iridium trichloride hydrate
was obtained from Johnson-Matthey Co. Sodium ethoxide was
generated in the reaction of sodium metal with water-free ethanol under
argon and dried to white powder before use.
NMR spectra were obtained on a Varian Unity-400, operating at
1
400.0 MHz for H and 161.98 MHz for 31P, or on a Varian Gemini-
300, operating at 300.0 MHz for 1H and 121.45 MHz for 31P. All 31
P
NMR spectra were obtained with proton decoupling unless otherwise
stated. 31P NMR chemical shifts were measured relative to H3PO4 as
external reference. 1H NMR chemical shifts were measured relative
to deuterated solvent peaks or tetramethylsilane. Variable temperature
T1 measurements were made at 400 MHz using the inversion recovery
method. Second order spectra were simulated using the program
LAOCN-5.5 IR spectra were recorded on a Nicolet 550 Magna-IR
spectrometer. Fast atom bombardment mass spectrometry (FAB MS)
was carried out with a VG 70-250S instrument using a 3-nitrobenzyl
alcohol (NBA) matrix. All FAB MS samples were dissolved in acetone
and placed in the matrix under a blanket of nitrogen. Microanalyses
were performed by Guelph Chemical Laboratories Ltd., Ontario,
Canada.
X-ray Structural Determination. Intensity data for 9 were
collected on an Siemens P4 diffractometer, using graphite-monochro-
mated Mo KR radiation (λ ) 0.710 73 Å). The ω scan technique was
applied with variable scan speeds. Intensities of three standards
measured every 97 reflections showed no decay. Data were corrected
for Lorentz and polarization effects and for absorption.6 The Ir atom
position was solved by the Patterson method, and other non-hydrogen
atoms were located by successive difference Fourier syntheses. Non-
hydrogen atoms were refined anisotropically by full-matrix least-squares
methods on F2 (negative intensities included). Hydrogen atoms were
positioned on geometric grounds (C-H 0.96 Å, Uiso ) 0.029(3) Å2).
The N-H hydrogen and the Ir-hydride hydrogen were refined with
isotropic thermal parameters. Crystal data, data collection, and least-
squares parameters are listed in Table 1. All calculations were done
and diagrams created using SHELXL-936 and SHELXTL/PC7 on a
486-66 personal computer. A view of complex 9, including the
crystallographic labeling scheme is shown in Figure 1.
1.48(2)
1.96(8)
N(1)-Ir-P(2)
P(2)-Ir-P(1)
P(2)-Ir-S(2)
N(1)-Ir-S(1)
P(1)-Ir-S(1)
N(1)-Ir-H(1Ir)
P(1)-Ir-H(1Ir)
S(1)-Ir-H(1Ir)
C(5)-S(1)-Ir
90.1(2) N(1)-Ir-P(1)
99.07(7) N(1)-Ir-S(2)
175.03(7) P(1)-Ir-S(2)
66.4(2) P(2)-Ir-S(1)
114.26(6) S(2)-Ir-S(1)
170.7(2)
85.2(2)
85.2(2)
93.87(7)
82.95(7)
82(4)
69(4)
111(4)
135(4)
P(2)-Ir-H(1Ir)
S(2)-Ir-H(1Ir)
F(4)‚‚‚H(1Ir)-Ir
98(4)
164(6)
77.7(3) C(10)-S(2)-Ir
114.4(3)
104.1(3)
116.5(2)
107.7(2)
112.3(2)
119.0(2)
134.9(5)
123.5(7)
110(5)
117.8(7)
116.1(8)
110.9(5)
121.3(6)
114.1(11)
99.6(10)
100.4(11)
C(11)-P(1)-C(21) 100.3(3) C(11)-P(1)-C(31)
C(21)-P(1)-C(31) 104.4(3) C(11)-P(1)-Ir
C(21)-P(1)-Ir
C(51)-P(2)-Ir
C(1)-N(1)-C(5)
C(5)-N(1)-Ir
122.0(2) C(31)-P(1)-Ir
114.7(2) C(41)-P(2)-Ir
120.2(6) C(61)-P(2)-Ir
104.7(5) C(1)-N(1)-Ir
C(10)-N(2)-H(2A) 127(5)
C(6)-N(2)-C(10)
N(1)-C(1)-C(2)
C(4)-C(3)-C(2)
N(1)-C(5)-C(4)
C(4)-C(5)-S(1)
N(2)-C(10)-S(2)
F(4)-B(1)-F(1)
F(1)-B(1)-F(3)
F(1)-B(1)-F(2)
122.6(7) C(6)-N(2)-H(2A)
121.5(7) C(1)-C(2)-C(3)
121.8(7) C(3)-C(4)-C(5)
127.3(6) N(1)-C(5)-S(1)
122.7(6) C(9)-C(10)-S(2)
118.9(12) F(4)-B(1)-F(3)
116.4(10) F(4)-B(1)-F(2)
102.7(11) F(3)-B(1)-F(2)
H(1Ir)‚‚‚F(4)-B(1) 149(3)
F(4)‚‚‚H(2A)-N(2) 144(7)
H(1Ir)‚‚‚F(4)‚‚‚H(2A) 57(3)
H(2A)‚‚‚F(4)-B(1) 148.1(24)
Synthesis of crude mer-IrHCl2(PPh3)3, 6. IrCl3‚3H2O (1.0 g, 2.84
mmol) was suspended in EtOH (15 mL) in a Schlenk flask containing
a stirring bar under argon. To this was slowly added concentrated
hydrochloric acid (1.8 mL) while the suspension was stirred. Heating
at reflux for 5 h produced a dark greenish yellow solution. This was
then cooled to room temperature, and then 3 equiv of triphenylphos-
phine (1.49 g, 5.68 mmol) was added. The solution was again refluxed
for a further 12 h to produce a pale yellow precipitate. After the
solution was cooled to 0 °C, the product was filtered in air and washed
(5) Cassidei, L.; Sciacovelli, O. Quantum Chemistry Program Exchange,
No. 458, LAOCN-5.
(6) Sheldrick, G. M. SHELXL-93, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1994.
(7) Sheldrick, G. M. SHELXTL/PC; Siemens Analytical X-ray Instruments
Inc.: Madison, WI, 1990.

A Unique Bifurcated Hydrogen Bond
Inorganic Chemistry, Vol. 35, No. 10, 1996 3003
Table 3. Atomic Coordinates [×104] and Equivalent Isotropic
Displacement Parameters [Å2 × 103] for 9a
x
y
z
U(eq)
Ir
S(1)
S(2)
P(1)
P(2)
N(1)
N(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
C(61)
C(62)
C(63)
C(64)
C(65)
C(66)
B(1)
2404(1)
1808(1)
1253(1)
3117(1)
3434(1)
1606(3)
1249(4)
1325(4)
741(5)
430(5)
707(5)
1320(4)
1016(5)
426(5)
1468(1)
-760(2)
2066(2)
2108(2)
803(2)
1035(6)
4385(7)
1658(8)
1161(8)
-38(9)
-725(9)
-139(8)
5607(8)
6119(8)
5375(9)
4124(9)
3616(8)
1208(7)
212(8)
788(1)
735(1)
1027(1)
1648(1)
497(1)
36(2)
551(3)
-425(3)
-858(3)
-796(3)
-316(3)
98(3)
418(3)
574(3)
16(1)
24(1)
22(1)
17(1)
17(1)
20(1)
27(2)
25(2)
29(2)
34(2)
32(2)
24(2)
30(2)
32(2)
34(2)
32(2)
23(2)
20(2)
27(2)
38(2)
36(2)
28(2)
23(2)
20(2)
26(2)
29(2)
29(2)
30(2)
24(2)
19(2)
26(2)
39(2)
40(2)
36(2)
29(2)
17(2)
25(2)
32(2)
42(2)
43(2)
34(2)
16(2)
20(2)
27(2)
27(2)
29(2)
22(2)
17(2)
22(2)
29(2)
30(2)
28(2)
27(2)
59(4)
86(3)
126(3)
100(3)
68(2)
50(11)
26(7)
49(10)
4(5)
43(5)
288(5)
924(4)
849(3)
978(3)
845(3)
2942(4)
2408(5)
2250(6)
2656(6)
3186(5)
3341(4)
4203(4)
4622(5)
5458(5)
5878(5)
5467(5)
4634(4)
2811(4)
2937(5)
2632(5)
2187(5)
2068(5)
2373(5)
3114(4)
2758(4)
2492(5)
2585(6)
2921(6)
3196(5)
4217(4)
3986(4)
4540(5)
5353(5)
5594(5)
5027(4)
3959(4)
3864(4)
4291(5)
4776(5)
4869(5)
4461(5)
2210(9)
2891(3)
1797(6)
1686(4)
2212(4)
659(12)
-45(14)
-568(11)
-386(11)
319(13)
842(11)
40(15)
2203(3)
2110(3)
2528(3)
3060(3)
3157(3)
2740(3)
1876(3)
2064(3)
2213(3)
2191(3)
2024(3)
1861(3)
1742(3)
1417(3)
1432(4)
1759(3)
2098(3)
2086(3)
-224(3)
-389(3)
-927(3)
-1310(3)
-1162(3)
-616(3)
566(3)
413(3)
445(3)
640(3)
795(3)
762(3)
771(3)
1232(3)
1447(3)
1195(3)
732(3)
-459(9)
-74(8)
906(8)
1573(8)
2167(7)
1038(7)
1021(8)
2110(9)
3240(8)
3287(7)
3761(7)
4733(8)
5960(8)
6222(8)
5253(9)
4052(8)
435(7)
Figure 2. 1H NMR spectra at 500 MHz of the hydride resonance of
fac-Ir(H)3(PPh3)3 in toluene-d8: (a) spectrum at 90 °C; (b) spectrum at
25 °C; (c) simulation of b; (d) spectrum at -40 °C; (e) simulation of
d.
with two portions of cold ethanol and dried in Vacuo. The product
was a pale yellow powder containing a mixture of a major (mer-IrHCl2-
(PPh3)3 6) and minor species. Yield: 2.3 g (77% based on mer-IrHCl2-
(PPh3)3). This was used without further purification as indicated below.
Spectroscopic data for mer-IrHCl2(PPh3)3 follow. NMR (CD2Cl2, δ):
31P{1H}, -8.9 (d, JPP ) 13.3 Hz), -29.1 (t, JPP ) 13.3 Hz); 1H, -13.88
2
2
(dt, 1H, JPH(cis) ) 16.4 Hz, JPH(trans) ) 162 Hz, Ir-H), 6.8-8.0 {m,
45H, P(C6H5)3}. NMR (CDCl3, δ) for the minor species: 31P{1H},
6.7 (d, J ) 13.5 Hz, Int. ) 0.02 relative to total intensity of 3 in complex
6), -1.8 (d, J ) 16.4 Hz, Int. ) 0.1), -6.8 (t, J ) 16.4 Hz, Int. )
0.04); 1H, -19.16 (quartet, J ) 14.1 Hz, Int. ) 0.14 relative to intensity
of one hydride in complex 6). MS(FAB), m/z: calculated for
C54H4635Cl2193IrP3, 1050; observed, 1049 (M+ - H), 1015 (M+ - Cl),
979 (M+ - 2Cl).
-754(8)
-1089(8)
-244(9)
948(9)
1284(8)
2003(7)
3267(7)
4204(8)
3909(8)
2676(8)
1729(7)
-678(7)
-1248(7)
-2340(8)
-2893(8)
-2355(8)
-1253(8)
5303(13)
5504(8)
4386(10)
6290(7)
4626(6)
1218(22)
778(18)
1641(22)
2943(21)
3382(18)
2520(24)
1503(19)
2379(22)
3677(20)
4099(19)
3224(25)
1926(23)
2675(108)
4188(74)
Synthesis of fac-Ir(H)3(PPh3)3, 7. The crude mer-IrHCl2(PPh3)3
(1.0 g, ca. 0.63 mmol) and a large excess of dried sodium ethoxide
(0.8 g, 12 mmol) were suspended in THF (15 mL) in a Schlenk flask
containing a stirring bar under dihydrogen gas. After 30 min the stirred
solution became orange-yellow and over a period of 24 h slowly turned
pale yellow. All the solvent was then evaporated to dryness. To the
residue obtained was added a sufficient amount (ca. 20 mL) of degassed
distilled water to dissolve up sodium salts and this was stirred for 30
min before filtering under argon. The product was washed under argon
twice with water (ca. 5 mL) and then cold ethanol (ca. 1 mL) and
dried in Vacuo. Finally the pale yellow powder was similarly washed
with ether several times (3 × 5 mL) until filtrate was clear and the
product was gray-white (0.95 g, 76%). NMR (CDCl3, δ): 31P{1H},
30.05 (s); 1H, -12.25 (AA′A′′XX′X′′, simulated, see Figure 2, Ir-H),
6.8-7.8 (m, 45H, P(C6H5)3). MS(FAB), m/z: calculated for C54H48193IrP3,
982; observed, 982 (M+), 979 (M+ - 3H).
521(3)
-532(6)
-630(2)
-963(3)
-643(3)
-105(2)
-2236(9)
-2599(9)
-2936(8)
-2911(8)
-2547(9)
-2210(9)
-2683(10)
-2972(7)
-2841(8)
-2421(9)
-2132(8)
-2263(9)
333(42)
429(29)
F(1)
F(2)
F(3)
F(4)
C(1S)
C(2S)
C(3S)
C(4S)
C(5S)
C(6S)
C(7S)
C(8S)
C(9S)
C(10S)
C(11S)
C(12S)
H(1IR)
H(2A)
Synthesis of Ir(H)2(η2-SC5H4N)(PPh3)2, 8. fac-Ir(H)3(PPh3)3 (1.0
g, 1.02 mmol) and excess 2-mercaptopyridine (0.218 g, 1.96 mmol) in
benzene (15 mL) were placed in a Schlenk flask containing a magnetic
stirring bar under argon. This was stirred and refluxed for 12 h and
then the solvent was evaporated in Vacuo to dryness. The residue was
redissolved in CHCl3 and filtered through Celite. Following removal
of the solvent, the resulting powder was stirred for ca. 15 min with
ether (ca. 5 mL) several times until the filtrate turned from yellow to
colorless and then dried to give a yellowish white powder. Yield: 0.75
g, 89% based on mer-Ir(H)3(PPh3)3. Anal. Calcd for C41H36IrNP2S +
CHCl3: C, 53.22; H, 3.94; N, 1.48. Found: C, 53.78; H, 4.11; N,
1.74. IR(Nujol): ν(Ir-H) 2157 (w), 2111 (m) cm-1. NMR: 31P{1H}
85(16)
26(7)
89(17)
9(5)
25(7)
40(9)
38(9)
33(8)
94(39)
22(21)
-525(11)
-441(11)
207(13)
772(11)
688(13)
2367(64)
1682(45)
a U(eq) is defined as one-third of the trace of the orthogonalized Uij
tensor.

3004 Inorganic Chemistry, Vol. 35, No. 10, 1996
Park et al.
Scheme 1a
three hydrides based on the characteristic FAB mass spectrum.
The singlet at δ 30.05 in the 31P{1H} NMR spectrum (25 °C)
and the AA′A′′XX′X′′ pattern of the hydride resonances indicate
that this complex has facial arrangement of hydrides and has
the formula fac-IrH3(PPh3)3, 7. Therefore in the process of
hydride addition, a rearrangement of the phosphine groups
occurs from mer-[Ir] to fac-[Ir] under mild conditions. Even
though this type of complex is known,8,9,13,14 NMR data have
not been completely reported. The observed variable temper-
ature 1H NMR spectra of 7 in the hydride region are shown in
Figure 2. Approximate simulations of both the spectrum (500
MHz) of 7 in toluene-d8 at 25 °C by use of parameters JPH(trans)
) +120 Hz, JPH(cis) ) -18 Hz, JHH(cis) ) -3.5 Hz, and JPP(cis)
Key: (i) HCl/EtOH/L1; (ii) HCl/EtOH/L2; (iii) HCl/EtOH/L3; (iv)
LiAlH4/THF; (v) EtONa/THF; L1 ) PiPr3, L2 ) PCy3, L3 ) PPh2Me.
Scheme 2
) -3.2 Hz and the spectrum of -40 °C, by use of JPH(trans)
)
+120 Hz, JPH(cis) ) -14 Hz, JHH(cis) ) 0 Hz, and JPP(cis) ) -3.2
Hz are also shown in Figure 2; the signs of these J values might
all be reversed because no absolute sign determination has been
done. The same spectrum was obtained at 300 MHz. This fact
along with the lack of significant change of pattern when the
sample is warmed to 90 °C suggests that this is not a fluxional
process. Instead it can be interpreted as a change in structure
of the molecule with increasing temperature which results in
an increase in JPH and JHH coupling constants. Large increases
in JHH of hydride with temperature have been attributed to a
quantum exchange coupling phenomenon.15 However the small
change in JHH with temperature in the present system is not
consistent with this. The T1 at room temperature was reported
previously.14b The T1(min) value for the hydride was 0.144 s at
-60 °C (300 MHz). This is consistent with a trihydride
structure with H-H distances of about 1.83 Å.16
In general, preparation of iridium polyhydrides (i.e., trihy-
dride, or pentahydride) involves one step,8,13 two steps,9,11,12,14a
or several steps18 with commercially available appropriate
iridium precursors. It normally requires reaction with a large
excess of NaBH4 or LiAlH4 as hydride source and the yield is
often low. In the case of iridium trihydrides there is the
possibility of obtaining isomeric mixtures (i.e., mer-[Ir] and fac-
[Ir]).8,13,14a The method of Scheme 2 has several advantages:
convenience of making and handling sodium ethoxide, the
relatively high yield, and the production of a single isomer under
mild conditions.
(C6D6, δ), 21.3 (s); 1H (CD2Cl2, δ), -21.0 (td, 1H, JPH ) 16.6 Hz, JHH
) 6.8 Hz, IrH), -21.17 (td, 1H, JPH ) 17.5 Hz, JHH ) 6.8 Hz, IrH),
5.80 (br t, 1H, J ) 6.4 Hz, SC5H4N), 5.98 (br d, 1H, J ) 8.2 Hz,
SC5H4N), 6.51 (br d, 1H, J ) 5.5 Hz, SC5H4N), 6.65 (br t, 1H, J ) 7.7
Hz, SC5H4N), 7.0-7.9 {m, 30H, PPh3}, MS(FAB), m/z: calculated
for C41H36193IrNP2S, 829; observed, 829 (M+), 827 (M+ - 2H).
Synthesis of cis-[IrH(η1-SC5H4NH)(η2-SC5H4N)(PPh3)2](BF4), 9.
Ir(H)2(η2-SC5H4N)(PPh3)2 (100 mg, 0.12 mmol) and 1.5 equiv of
2-mercaptopyridine (20 mg, 0.18 mmol) were dissolved in dichlo-
romethane (5 mL) in a Schlenk flask under argon. While the solution
was being stirred, 85% HBF4‚Et2O (ca. 80 µL) was slowly added
through a septum using a syringe. After 10 min the solution was filtered
through Celite under Ar. The solvent was then evaporated in Vacuo
to dryness. To the residue was added 5 mL of ether, and this mixture
was swirled until the precipitation of a pale yellow powder. The powder
was washed with ether (ca. 3 mL) twice more before drying to give a
pale yellow powder. Yield: (110 mg, 89%). Anal. Calcd for C46H40-
BF4IrN2P2S2 + CH2Cl2: C, 50.8; H, 3.81; N, 2.52. Found: C, 49.45;
H, 3.96; N, 2.88. IR(Nujol): ν(N-H) 3236 (m), ν(Ir-H) 2214 (m)
cm-1. NMR (CD2Cl2, δ): 31P{1H}, -11.4 (d, JPP ) 16.3 Hz), 10.6 (d,
JPP ) 16.3 Hz); 1H, -17.82 (dd, 1H, JHP ) 14.3 Hz, IrH), 6.3-8.8 (m,
overlapping, 9H, SC5H4N and SC5H4NH), 7.0-7.6 (m, overlapping,
30H, PPh3), 12.03 (br s, 1H, NH). MS(FAB), m/z: calculated for
C46H40193IrN2P2S2, 939; observed, 939 (M+), 828 (M+ - HSC5H4N).
Results and Discussion
Crude mer-IrHCl2(PPh3)3 6,8,9 has been prepared from the
reaction of a refluxing ethanolic solution of iridium trichloride
with concentrated hydrochloric acid and triphenylphosphine
under argon. The major product is mer-IrHCl2(PPh3)3 6 with
three mer-phosphine ligands and two trans chlorides, based on
the 31P{1H} and proton NMR spectra. In fact, this type of
reaction has been used before,10-12 but the products depended
on the kind of phosphine ligand. For example, iridium(III)
complexes [IrCl4(PiPr3)2][HPiPr3], 10,10 IrHCl2(PCy3)2, 11,11 and
IrCl3(PPh2Me)3, 12,12 have been obtained in such reactions. All
of these complexes have been used as precursors to iridium
pentahydrides according to Scheme 1. However, the reaction
of 6 under reducing condition (NaOEt/THF/H2) produced the
trihydride 7 instead of the pentahydride complex IrH5(PPh3)2,
13 (Scheme 2). This product has been assigned as an iridium-
(III) complex possessing three triphenylphosphine ligands and
Complex 7 reacts readily with 2-mercaptopyridine (HSpy)
in boiling benzene to give the dihydride complex possessing a
chelating Spy ligand, Ir(H)2(η2-SC5H4N)(PPh3)2, 8 (eq 1). This
fac- or mer-IrH3(PPh3)3 + HSpy f
7
Ir(H)2(η2-Spy)(PPh3)2 + PPh3 + H2 (1)
8
was formulated on the basis of the two characteristic hydride
resonances of two doublets of triplets {-21.0, -21.17 ppm (td,
(13) (a) Malatesta, L.; Angoletta, M.; Araneo, A.; Canziani, F. Angew.
Chem. 1961, 73, 273. (b) Angoletta, M. Gazz. Chim. Ital. 1962, 92,
811.
(14) (a) Chatt, J.; Coffey, R. S.; Shaw, B. L. J. Chem. Soc. 1965, 7391.
(b) Ammann, C.; Isaia, F.; Pregosin, P. S. Magn. Reson. Chem. 1988,
26, 236.
(8) (a) Levison, J. J.; Robinson, S. D. J. Chem. Soc. A 1970, 2947. (b)
Ahmad, N.; Robinson, S. D.; Uttley, M. F. J. Chem. Soc., Dalton
Trans. 1972, 843. (c) Geoffroy, G. L.; Pierantozzi, R. J. Am. Chem.
Soc. 1976, 98, 8054.
(9) (a) Vaska, L. J. Am. Chem. Soc. 1961, 83, 756. (b) Hayter, R. G. J.
Am. Chem. Soc. 1961, 83, 1259.
(10) Clerici, M. G.; Gioacchino, S. Di; Maspero, F.; Perrotti, E.; Zanobi,
A. J. Organomet. Chem. 1975, 84, 379.
(11) Brinkmann, S.; Morris, R. H.; Ramachandran, R. Unpublished data.
(12) Bau, R.; Schwerdtfeger, C. J.; Garlaschelli, L.; Koetzle, T. F. J. Chem.
Soc., Dalton Trans. 1993, 3359.
(15) (a) Heinekey, D. M.; Payne, N. G.; Sofield, C. D. Organometallics
1990, 9, 2643. (b) Heinekey, D. M. J. Am. Chem. Soc. 1991, 113,
6074.
(16) To obtain this distance the T1(min) value is corrected for the
contributions by other hydrogens on the PPh3 groups.17 Then it is
assumed that two hydride nuclei on an equilateral triangle relax the
third by the dipolar mechanism.
(17) Desrosiers, P. J.; Cai, L.; Lin, Z.; Richards, R.; Halpern, J. J. Am.
Chem. Soc. 1991, 113, 4173.
(18) Crabtree, R. H.; Felkin, H.; Morris, G. E. J. Organomet. Chem. 1977,
141, 205.

A Unique Bifurcated Hydrogen Bond
Inorganic Chemistry, Vol. 35, No. 10, 1996 3005
JPH ) 17.5 Hz, JHH ) 6.8 Hz)} in the 1H NMR spectrum (CD2-
Cl2) and a singlet (21.3 ppm) in the 31P{1H} NMR (C6D6), along
with microanalysis and FAB mass spectrum. This complex has
been previously prepared from mer-Ir(H)3(PPh3)3 and character-
ized by X-ray analysis.19 An analogous complex of 7 containing
bis(tricyclohexylphosphine) ligands has been conveniently
prepared from the corresponding iridium(V) pentahydride
complex.20
1
IrH5(PCy3)2 + HSpy f Ir(H)2(η2-Spy)(PCy3)2 + 2H2 (2)
Figure 3. NMR spectra (25 °C): (a) H (400 MHz, hydride region),
and (b) 31P{1H} (300 MHz), of 9 in CD2Cl2 (left) and 9-d1 in CD2Cl2
with MeOD (right).
Complex 8 reacts with 1 equiv of 2-mercaptopyridine and a
strong acid (HBF4‚Et2O) in CH2Cl2 for 15 min at 20 °C to form
after isolation a pale yellow, air stable microcrystalline solid
(89%). This is identified as an iridium(III) monocationic
complex 9 containing two cis phosphine ligands, which are cis
to the hydride according to the spectroscopic studies: the
hydride resonance at -17.82 ppm as a doublet of a doublet
and the phosphorus resonances at -11.4 and 10.6 ppm as two
doublets with a coupling constant of 16.3 Hz. The proton NMR
spectrum of 9 in CD2Cl2 also contains a broad singlet at 12.03
ppm due to the proton on the pyridinium ring which is bound
to iridium in a monodentate fashion via a sulfur atom. The
proposed structure of 9 in solution is consistent with that
obtained by X-ray analysis.
Scheme 3
sulfur atom. Thus the requirement for an octahedral iridium-
(III) center is completed by a hydride ligand trans to S(1). The
hydrogen on the nitrogen of the pyridiniumthiolate is well
defined in Fourier difference maps, and the hydride ligand could
be located. The presence of the hydride is also indicated
indirectly by the presence of its trans-influence on S(1): 2.535-
(2) Å for the (trans)S-Ir bond length is significantly longer
than 2.394(2)
Å
for the (cis)S-Ir distance. The
P(2)IrS(2)C(10)N(2) units are in a plane with a maximum
deviation of 0.037 Å for the iridium atom. In this plane the
hydride ligand is positioned at 1.72(11) Å from iridium, at 82-
(4) and 98(4)° to cis-P(2) and S(2), respectively, and at 111(4)
and 69(4)° to cis-P(1) and chelate nitrogen atom (N1), respec-
tively, and 2.05(13) Å from the proton of the pyridinium ligand.
The hydride is also 2.1 Å away from H1A on the η2-SC5H4N
ligand and also from H52A, an ortho phenyl hydrogen. The
structure also shows that the H on the nitrogen has a close
contact of 1.96(8) Å with one of the fluorines in the tetrafluo-
roborate anion. A similar type of hydrogen-bonding interaction
between an anion (Cl-) and protons on the nitrogens of two
pyridine-2-thiolate rings has been reported for a rhodium(III)
complex with the Cl‚‚‚N distance of 3.156 Å.21
H/D Exchange Studies. Complex 9 undergoes H/D ex-
change upon reaction with D2 gas (1 atm), but only a very slow
reaction has been observed (less than 50% deuteration of the
NH group and IrH group in 24 h). However, a much faster
reaction of 9 with MeOD in CD2Cl2 solution at 20 °C is
observed (Scheme 3).
The 1H NMR spectrum of the CD2Cl2 solution of 9 containing
a small excess of MeOD or CF3CO2D shows after 1 h a
significant decrease (37%) in the intensity of the resonance of
the pyridinium proton. The hydride resonances (a doublet of
doublets in CD2Cl2 alone) become broad and overlapping with
another set of two doublets (0.009 ppm upfield from the first
set). It is interesting to note that in 31P{1H} NMR spectrum of
this solution, the downfield doublet at 10.65 ppm is isotopically
shifted by 0.018 ppm while the upfield doublet at -11.40 ppm
remains unchanged (see Figure 3). Therefore when complex 9
is deuterated at the NH group, there is an isotopic perturbation
in the chemical shifts of the hydride and of one of the
phosphorus groups. However, it is not clear why one phosphine
group has an isotopic shift while the other does not.
The presence of the Ir-H‚‚‚H-N interaction in 9 in solution
was deduced by use of the powerful NMR tools of VT-T1 and
NOE measurements. The proton on the pyridinium ring has a
minimum T1 of 0.235 s and the hydride of 0.266 s at 233 K
(400 MHz). The Ir-H‚‚‚H-N distance is calculated by use of
these T1(min) values and the method reported previously1 to be
1.82 ( 0.05 Å which is close to the one (2.05(13) Å) obtained
from the X-ray derived structure (see later). In an NOE
experiment, a 12% enhancement for the resonance of the
pyridinium proton in CD2Cl2 is achieved by selective irradiation
at hydride. An attempt to disrupt the Ir-H‚‚‚H-N interaction
by introducing the H-bond acceptor OPPh3 failed. In this
attempt a CD2Cl2 solution of 9 containing excess OPPh3 gave
a similar enhancement (14%) for the NH resonance when the
hydride is irradiated in a similar NOE experiment. Perhaps an
H‚‚‚F hydrogen bond between the NH group of the pyridinium
-
ring and one of the fluorines of the BF4 group as seen in the
solid state (Figure 1) prevents the OPPh3 from approaching the
NH group. The N-H and Ir-H vibrational modes of 9 in Nujol
appear as broad peaks at 3236 and 2214 cm-1, respectively.
The vibrations of the BF4 anion are those expected for a
symmetrical tetrahedral geometry, apparently unperturbed by
the F‚‚‚H interaction.
X-ray Structural Analysis of Complex 9. The structure of
9 (Figure 1) as determined at 173 K reveals that the iridium
atom is surrounded by cis-PPh3 groups, a chelating 2-pyridine-
thiolate ligand, and a 2-pyridiniumthiolate ligand bound Via
(19) (a) Mura, P.; Robinson, S. D., Acta Crystallogr. 1984, C40, 1798. (b)
Alteparmakian, V.; Mura, P.; Olby, B. G.; Robinson, S. D. Inorg.
Chim. Acta 1985, 104, L5.
(20) The reaction of Ir(H)2(η2-SC5H4N)(PCy3)2 with HSC5H4NH+ has been
used as an alternative to the reported reaction of IrH5(PCy3)2 with
HSC5H4NH+ to give the hydrogen-bonded species [Ir{H(η1-SC5H4-
NH)}2(PCy3)2](BF4) 1.2a This will be discussed elsewhere.
(21) Deeming, A. J.; Hardcastle, K. E.; Meah, M. N.; Bates, P. A.; Dawes,
H. M.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1988, 227.

3006 Inorganic Chemistry, Vol. 35, No. 10, 1996
Park et al.
Conclusion
Acknowledgment. This work was supported by grants to
R.H.M. from the NSERC (Canada) and the donors of the
Petroleum Research Fund, as administrated by the American
Chemical Society. We thank Nick Plavac and Dr. Wei Xu for
The trihydride fac-IrH3(PPh3)3 has an unusual AA′A′′XX′X′′
pattern which changes with temperature. A synthetic route to
the novel iridium(III) complex [IrH(η1-SC5H4NH)(η2-SC5H4N)-
(PPh3)2](BF4), 9, has been established from the complex Ir-
(H)2(η2-Spy)(PPh3)2, 8. Complex 8 can be obtained from the
fac- or mer-isomers of IrH3(PPh3)3. [IrH(η1-SC5H4NH)(η2-
SC5H4N)(PPh3)2](BF4) 9 possesses a unique hydrogen bond
interaction involving Ir-H‚‚‚H(N)‚‚‚F-B atoms with the
distances, of 2.0(1) Å for the H‚‚‚H unit and of 2.0(1) Å for
the F‚‚‚H unit. Isotopic shifts have been observed in 31P{1H}
and 1H NMR spectra of [IrH(η1-SC5H4ND)(η2-SC5H4N)(PPh3)2]-
(BF4), 9-d1 produced by the reaction of 9 with MeOD or CF3-
CO2D. The reaction of iridium polyhydride complexes with
mercaptopyridinium seems to be a general method of generating
complexes containing novel Ir-H‚‚‚H-N interactions.
1
making T1 measurements and obtaining low temperature H
NMR spectra and Alex Young for measuring the FAB MS
spectra. We also thank Johnson Matthey Co. for the loan of
iridium trichloride.
Supporting Information Available: A difference electron density
contour map in the plane of the P(2)IrS(2)C(10)N(2)H(2) unit and tables
of X-ray structure refinement, fractional atomic coordinates, bond
lengths and angles, and thermal parameters (7 pages). Ordering
information is given on any current masthead page.
IC950438D