Organometallics
Article
Bruker Alpha Platinum ATR spectrometer with OPUS software. EPR
spectra were recorded on a Bruker EMS spectrometer in frozen
solutions at 77 K. EPR simulations used the EasySpin software
package.67
solids were washed with cold pentane (3 × 1 mL) and dissolved in
minimal Et2O. Evaporation of the saturated Et2O solution into
HMDSO gave single crystals of 1c, which were lyophilized from C6H6
to give magenta solids. Yield: 14.0 mg (0.0197 mmol), 56%. 1H NMR
(500 MHz, C6D6): δ 9.02−8.86 (m, 1H), 7.56 (d, 3JHH = 8.7 Hz, 1H),
7.47 (d, 3JHH = 7.9 Hz, 2H), 7.46 (s, 1H), 7.45−7.41 (m, 4H), 7.39 (d,
3JHH = 6.6 Hz, 2H), 7.33−7.28 (m, 4H), 7.25−7.19 (m, 4H), 7.12 (s,
X-ray Crystallography. X-ray diffraction studies were carried out
at the Caltech Division of Chemistry and Chemical Engineering X-ray
Crystallography Facility on a Bruker three-circle SMART diffrac-
tometer with a SMART 1K CCD detector, APEX CCD detector, or
Bruker D8 VENTURE Kappa Duo PHOTON 100 CMOS detector.
Data were collected at 100 K using Mo Kα radiation (λ = 0.710 73 Å)
or Cu Kα radiation (λ = 1.541 78 Å). Structures were solved by direct
or Patterson methods using SHELXS and refined against F2 on all data
by full-matrix least-squares with SHELXL-97.68 All non-hydrogen
atoms were refined anisotropically. With the exception of any μ-B−
H−M hydrides that were located on the difference map, all hydrogen
atoms were placed at geometrically calculated positions and refined
using a riding model. The isotropic displacement parameters of all
hydrogen atoms were fixed at 1.2 (1.5 for methyl groups) times the
Ueq of the atoms to which they are bonded. An A level alert is
generated by Checkcif for the structure of 1d because of a close H−H
contact between H20C (a calculated isopropyl methyl hydrogen) and
H108 (a calculated aryl H atom on the minor part of the disordered 8-
amidoquinolinyl ligand). Because the close H−H contact is between a
calculated methyl H atom and a partially occupied calculated H atom
on a highly disordered ligand, we do not anticipate that this is cause for
concern or indicative of missing symmetry or a false solution.
Preparation of (DPB)FeOPh (1a). A 62.7 mg (0.058 mmol) amount
of 1 was dissolved in ca. 10 mL of benzene to form a dark red-brown
solution. A 10.8 mg (0.115 mmol) amount of PhOH dissolved in ca. 5
mL of benzene was added to the solution of 1. Over the course of ∼1.5
h the solution turned from dark red-brown to dark yellow-brown. The
solution was allowed to stir overnight (∼16 h). GC analysis of the
headspace of the reaction mixture showed formation of H2. The
reaction mixture was lyophilized, leaving a dark residue. Crystals
suitable for X-ray diffraction studies were grown by cooling a
concentrated solution in Et2O to −30 °C in a freezer. Yield: 71.1
3
3
1H), 6.70 (d, JHH = 5.3 Hz, 1H), 6.41 (dd, JHH = 7.8, 5.4 Hz, 1H),
3
3
1.78−1.50 (m, 4H), 0.87 (d, JHH3 = 7.0 Hz, 6H), 0.73 (d, JHH = 6.3
Hz, 6H), 0.18 (s, 6H), 0.11 (d, JHH = 6.4 Hz, 6H), −22.80 (s, 1H).
11B NMR (160 MHz, C6D6): δ −7.29. 13C NMR (126 MHz, C6D6): δ
160.71, 153.81, 153.63, 147.23, 146.58, 144.03, 135.36, 132.95, 129.87,
129.67, 128.44, 126.20, 125.03, 124.62, 124.41, 122.23, 119.20, 116.80,
26.57, 23.35, 20.97, 18.75, 18.49, 18.36. 31P NMR (202 MHz, C6D6): δ
41.26. IR (thin film from C6D6, cm−1): 2279, 2270 (B−H−Fe). UV−
vis [toluene, λ(nm){ε(M−1 cm−1)}]: 287(sh){26,608}, 346(sh)
{5765}, 366{7761}, 421(sh){3548}, 498{5543}, 537(sh){5211}.
Combustion analysis for C43H50BFeNP2: calcd C 72.80, H 7.10, N
1.97; found C 72.51, H 6.84, N 1.84.
Preparation of (DPBH)Fe(8-amidoquinline) (Mixture of Two
Isomers) (1d). A solution of 1 (17.4 mg, 0.0160 mmol) and 8-
aminoquinoline (4.6 mg, 0.032 mmol) in 0.7 mL of C6D6 was allowed
to stand at RT until all 1 was consumed (∼1 h). Volatiles were
removed in vacuo, and the resulting solids were washed with cold
pentane (3 × 1 mL) and dissolved in minimal Et2O. Evaporation of
the saturated Et2O solution into hexamethyldisiloxane (HMDSO)
furnished crystals of 1d, which were lyophilized to give a red powder.
1
Yield: 18.0 mg (0.027 mmol), 83%. H NMR (300 MHz, C6D6): δ
141.88, 103.99, 85.33, 83.94, 77.91, 72.22, 68.70, 58.27, 57.69, 51.90,
24.40, 22.51, 19.91, 17.52, 17.18, 15.04, 14.47, 12.77, 11.31, 2.17, 0.74,
−1.81, −3.85, −7.08, −9.09, −9.45, −12.79, −15.24, −20.90, 25.02,
−33.79, −81.35, −83.00, −84.84, −103.43. Solution magnetic moment
(25 °C, C6D6): 5.2 μB. IR (thin film from C6D6, cm−1): 3373 (N−H),
2130 (br, s, B−H−Fe for isomer A), 2000 (B−H−Fe for isomer B).
UV−vis [toluene, λ(nm){ε(L mol−1 cm−1)}]: 297{14 527}, 368(sh)
{5188}, 415(sh){3761}, 514{2931}. Combustion analysis for
C39H49BFeN2P2: calcd C 69.45, H 7.32, N 4.15; found C 68.55, H
7.09, N 3.94.
1
mg (0.114 mmol), 99.1%. H NMR (400 MHz, C6D6): δ 142.34,
109.34, 91.02, 70.19, 5.63, 39.49, 28.01, 21.49, 21.15, 12.18, 11.02,
5.20, −0.14, −0.26, −5.69, −6.69, −11.02, −13.75, −16.56, −18.12,
−28.44, −36.17, −52.16. Solution magnetic moment (25 °C, C6D6):
3.9 μB. UV−vis [toluene, λ(nm){ε(M−1 cm−1)}]: 318(sh){5723},
393{3434}, 877{219}. Combustion analysis for C36H46BFeOP2: calcd
C 69.36, H 7.44; found C 69.25, H 7.03.
Alternative Synthesis of 1a. A 17.9 mg (0.03 mmol) sample of
(DPB)FeBr was dissolved in 10 mL of Et2O, and the mixture was
added to a solution of 3.7 mg (0.03 mmol) of NaOPh in 5 mL of Et2O
and stirred for 16 h. The resulting yellow-brown solution was filtered
through Celite and evaporated to dryness, leaving a brown residue.
This residue was extracted in benzene and lyophilized, giving a fine
brown powder, which showed identical spectroscopic features to the
product 1a prepared by the previously described method. Yield: 17.4
mg (0.028 mmol), 93.3%.
Preparation of [(DPBH)Fe(SPh)]2 (1b). A 116.3 mg (0.107 mmol)
portion of 1 was dissolved in ca. 10 mL of benzene to form a dark red-
brown solution. Then 23.6 mg (0.0.214 mmol) of PhSH dissolved in
ca. 5 mL of benzene was added to the solution of 1. Over the course of
∼1.5 h the solution turned from dark red-brown to red-orange. The
solution was allowed to stir overnight and lyophilized, leaving a fine
pale orange powder. Yield: 105.2 mg (0.0821 mmol), 76.7%. 1H NMR
(400 MHz, C6D6): δ 117.20, 52.99, 48.53, 42.05, 24.28, 13.75, 13.53,
9.11, −7.71, −8.62, −15.94, −21.91, −24.23, −25.02, −27.25, −44.97.
Solution magnetic moment (25 °C, toluene-d8): 4.77 μB per Fe center.
IR (thin film from C6D6, cm−1): 1961 (br, B−H−Fe). UV−vis
[toluene, λ(nm){ε(M−1 cm−1)}]: 324(sh){9600}, 418(sh){3200}.
Combustion analysis for C72H94B2Fe2S2P4: calcd C 67.52, H 7.40;
found C 66.85, H 6.95.
Preparation of (DPB)Co(N2) (2). A solution of 0.8483 g (1.79
mmol) of DPB and 0.2316 g (1.78 mmol) of CoCl2 in tetrahydrofuran
(ca. 80 mL) was stirred until no solids remained, leaving a deep blue
solution. Solvent was removed in vacuo, and the remaining blue
residue was triturated in Et2O for 15 min. Solvent was removed in
vacuo, and the blue residue was dissolved in benzene (80 mL). Freshly
prepared 1% sodium mercury amalgam (0.0864 g of Na, 3.76 mmol)
was added to the dark blue solution and stirred vigorously for 24 h.
The resulting dark red-orange solution was decanted and filtered
through Celite. Lyophilization afforded a fine dark brown powder.
This powder was dissolved in minimal Et2O and cooled in a freezer to
−30 °C, affording red-orange crystals of 2. Yield: 0.850 g (1.51 mmol),
1
84%. H NMR (400 MHz, C6D6): δ 17.79, 14.77, 4.04, 2.42, −2.74,
−4.04. Solution magnetic moment (25 °C, C6D6): 1.8 μB. IR (thin film
from C6D6, cm−1): 2098 (N2). UV−vis [toluene λ(nm){ε(M−1
cm−1)}]: 288{9346}. Combustion analysis for C30H41BCoN2P2 was
consistently low in nitrogen and high in carbon and hydrogen,
consistent with the labile N2 ligand; a representative analysis is shown:
calcd C 64.19, H 7.36, N 4.99; found C 64.52, H 7.57, N 4.13.
Preparation of (DPB)CoBr (2-Br). A 57.1 mg (0.12 mmol) sample
of DPB was dissolved in 10 mL of THF with 26.4 mg (0.12 mmol) of
CoBr2, giving a clear blue solution. A dark red-orange solution of 2,
67.6 mg (0.12 mmol), dissolved in 10 mL of THF was added to the
stirring solution of DPB and CoBr2 via pipet, resulting in darkening of
the reaction mixture. After stirring for 16 h the solution was yellow-
brown. The reaction mixture was filtered through Celite, and volatiles
were removed in vacuo, leaving a dark brown residue. The residue was
extracted in pentane and filtered through Celite, removing some blue
and green solids. The brown pentane extract was evaporated to
dryness and dissolved in minimal THF. Large brown crystals of 2-Br
were grown by vapor diffusion of a concentrated THF solution into
HMDSO. Crystals of suitable quality for X-ray diffraction were grown
Preparation of (DPBH)Fe(benzo[h]quinolin-10-yl) (1c). A solution
of 1 (19.1 mg, 0.0176 mmol) and benzo[h]quinoline (6.3 mg, 0.035
mmol) in 0.7 mL of C6D6 was heated at 70 °C until all of 1 was
consumed (3 h). Solvent was removed in vacuo, and the resulting
I
Organometallics XXXX, XXX, XXX−XXX