88 Organometallics, Vol. 18, No. 1, 1999
Gusev et al.
RI-J approximation.46 For Re, effective core potentials (ECP-
formed, which was filtered off hot, washed with hot ethanol
(3 × 10 mL, 70 °C), and dried under vacuum, leaving 0.99 g of
a brown solid (ca. 88%).
60) were applied, which include relativistic corrections.47
A
triple-ú valence basis plus polarization (TZVP) was employed
for the heavy metal;48a the remaining elements were treated
with a split valence plus polarization basis set (SVP).48b For
the numerical integration, the grid of accuracy “m3” was
used.46c All calculations were performed in Cs symmetry.
P r ep a r a tion of th e Com p lexes. [Re(H)2(NO)(P P h 3)3].
A mixture of 1 (1 g, 1.14 mmol) and PPh3 (1.5 g, 5.72 mmol)
suspended in ethanol (30 mL) was refluxed for 25 min. NaBH4
(250 mg, 6.608 mmol) was then added in small portions over
a period of 45 min while still refluxing. Gradually, a pale
yellow solid formed in a reaction accompanied by gas evolution.
When addition of NaBH4 was complete the liquid was filtered
off and the solid washed with hot ethanol (70 °C, 3 × 15 mL).
The product was dissolved in C6H6 (20 mL), filtered, and
precipitated with ethanol. A pale yellow solid was collected,
recrystallized in C6H6/ethanol, and subsequently dried under
vacuum, leaving 0.81 g (ca. 70.6%) of [Re(H)2(NO)(PPh3)3]. 1H
[Re(H)(η2-BH4)(NO)(P iP r 3)2] (3a ). A mixture of 2a (1.06
g, 1.52 mmol) and [NBu4]BH4 (1.03 g, 4.00 mmol) in Et2O (25
mL) was stirred for 21 h. After this time the orange solution
was filtered and dried under vacuum to yield 0.82 g (98%) of
3a contaminated with ca. 6-10 mol % of PiPr3‚BH3. Slow
cooling to -65 °C of a solution of 1.06 g of 3a in ether/pentane
(20/10 mL) afforded large crystals, which were separated by
removing the mother liquor via cannula and dried under
vacuum, yielding 0.81 g (76%). Alternatively, 3a can be isolated
in similar yield; washing with CH3CN (3 × 5 mL) the solid
was obtained after evaporation of the diethyl ether. Anal. (%).
Calc for C18H47BNOP2Re: C, 39.13; H, 8.57; N, 2.53. Found:
C, 39.39; H, 8.48; N, 2.54.
[Re(H)(η2-BH4)(NO)(P Cy3)2] (3b). The mixture containing
2b and [Re(Br)3(NO)(PCy3)2] isolated as described above (0.96
g, ca. 1 mmol) was stirred in 25 mL of ether with [NBu4]BH4
(0.810 g, 3.15 mmol) for 48 h. The resulting orange solid was
filtered off, well washed with acetonitrile (4 × 10 mL), and
dried under vacuum. Yield: 0.72 g (81.3%, calculated on
[NEt4]2[Re(Br)5(NO)] used for the preparation of 2b and [Re-
(Br)3(NO)(PCy3)2]). Anal. (%). Calc for C36H71BNOP2Re: C,
54.53; H, 9.03; N, 1.77. Found: C, 54.58; H, 8.92; N, 1.76.
[Re(H)(η2-BH4)(NO)(P P h 3)2] (3c). A mixture of [Re(H)2-
(NO)(PPh3)3] (1 g, 0.995 mmol) and 1 M THF‚BH3 (3.5 mL,
3.5 mmol) was stirred for 12 h. Over this period of time, the
starting yellow compound disappeared and an orange precipi-
tate gradually formed. The residue was washed with CH3CN
(4 × 10 mL) and dried under vacuum, leaving 650 mg (ca.
86.4%) of 3c as a bright-yellow orange solid, which can be used
without further purification for subsequent chemistry. Recrys-
tallization in THF/pentane afforded analytically pure material.
Anal. (%). Calc for C36H35BNOP2Re: C, 57.15; H, 4.66; N, 1.85.
Found: C, 56.79; H, 4.82; N, 1.85.
[Re(H)(NO)2(P iP r 3)2] (5a ). A mixture of 3a (300 mg, 0.542
mmol) and NOBF4 (100 mg, 0856 mmol) was stirred in THF
(40 mL) for 1 h. The resulting solution was concentrated under
vacuum until 15 mL of the solvent was left. Then 15 mL of
diethyl ether and KOtBu (95 mg, 0.847 mmol) were added, and
the heterogeneous mixture was stirred for an additional hour.
The solvent was removed under vacuum and the residue
extracted with pentane (2 × 15 mL). The red-orange solution
was concentrated until approximately 4 mL of the solvent was
left and then placed for 10 h at -35 °C. Red crystals were
collected and dried under vacuum, affording 216 mg of 5a (ca.
70.1%). Anal. (%). Calc for C18H43N2O2P2Re: C, 38.08; H, 7.63;
N, 4.93. Found: C, 37.76; H, 7.48; N, 4.84.
[Re(H)(NO)2(P Cy3)2] (5b). A mixture of 3b (300 mg, 0.372
mmol) and NOBF4 (68 mg, 0.582 mmol) was stirred in THF
(50 mL) for 1 h. KOtBu was then added (65.4 mg, 0.582 mmol)
and the heterogeneous mixture stirred for an additional hour.
The solvent was removed under vacuum and the residue
extracted with pentane (3 × 25 mL). Removal of the solvent
left a light orange solid, which was washed with O(SiMe3)2 (2
× 5 mL) and dried under vacuum, affording 220 mg of [Re-
(H)(NO)2(PCy3)2] (5b) (ca. 72.0%). Anal. (%). Calc for C36H67N2-
O2P2Re: C, 53.51; H, 8.36; N, 3.47. Found: C, 53.68; H, 8.12;
N, 3.26.
[Re(H)(NO)2(P P h 3)2] (5c). A mixture of 3c (135 mg, 0.179
mmol) and NOBF4 (41 mg, 0.351 mmol) was stirred in THF
(40 mL) for 1 h. KtOBu was then added (39.8 mg, 0.355 mmol)
and the mixture stirred for an additional hour. The resulting
red-brown solution was filtered and the solvent removed under
vacuum, leaving a dark red solid, which was washed with THF
(2 × 2 mL). A pink-red powder was collected and dried under
vacuum, leaving 60 mg of 5c. Pentane was layered over the
THF solution and the mixture cooled at -35 °C. After 24 h a
red microcrystalline solid formed, which was washed with
diethyl ether (3 × 10 mL), affording an additional 40 mg of 5c
NMR (C6D6): -1.93 (dtd, 1H, 2J (H-Pcis) ) 2J (H-Ptrans) ) 30.3 Hz),
2
-0.55 (dtd, 1Htrans
,
2J (H-H) ) 6.0 Hz, J (H-Peq.) ) 34.2 Hz,
NO
2J (H-Pap.) ) 32.4 Hz), 6.81-7.57 (m, 45H, P(C6H5)3). 31P{1H}
2
NMR (C6D6): 28.3 (d, 2P), 20.2 (t, 1P, J (P-P) ) 8 Hz). IR
(Nujol): 1640 (νN-O), 1950, 1800 (νRe-H). Anal. (%). Calc for
C
54H47NOP3Re: C, 64.53; H, 4.71; N, 1.39. Found: C, 64.75;
H, 4.39; N, 1.30.
[NEt4]2[Re(Br )5(NO)] (1). This preparation can be carried
out under air and does not require dry solvents.
H2O2 (10 mL, 30%) was added dropwise to Re powder (3.0
g, 16.11 mmol) at 0 °C. [NEt4]Br (4.0 g, 19.03 mmol) was added
to this solution without a further treatment. After drying the
mixture by rotary evaporation (25 mbar, 80 °C) additional
[NEt4]Br (4.0 g, 19.0 mmol) was added, and the solid dissolved
in a 70:5 mL mixture of HBr (49%) and H3PO2 (50%). NO gas
was bubbled through the solution at 110 °C, which turned dark
green in 24 h. The reaction mixture was filtered and dried by
rotary evaporation (25 mbar, 80 °C) to give a viscous dark
green semisolid. This residue was well washed with THF (3
× 30 mL), suspended in ethanol, filtered off, and additionally
washed with ethanol (2 × 25 mL) and acetone (2 × 25 mL).
The resulting apple green powder was dried under vacuum to
yield 12.76 g (ca. 90.4%) of [NEt4]2[Re(Br)5(NO)]. IR (KBr):
1732 (νN-O). Anal. (%). Calc for C16H40Br5N3ORe: C, 21.93; H,
4.60; N, 4.80. Found: C, 22.04; H, 4.60; N, 4.78.
[Re(NO)(η2-H2)(Br )2(P iP r 3)2] (2a ). A mixture of 1 (1.25 g,
1.43 mmol) and PiPr3 (0.79 g, 4.93 mmol) suspended in ethanol
(10 mL) was stirred for 48 h at 70 °C. The reaction mixture
was then left at -30 °C for 2 h and filtered cold. The residue
was then washed with ethanol (2 × 5 mL) and dried under
vacuum for 0.5 h to yield 0.75 g (ca. 75%) of a light brown
powder. The mother liquor and washings collected after the
treatment of 5 g of [NEt4]2[Re(Br)5(NO)] were reduced in
volume to ca. 10 mL, leaving additional 0.53 g of solid. This
amount was recrystallized from ethanol at 70 °C (15 mL) and
afforded 0.25 g of microcrystalline [Re(Br)2(NO)(η2-H2)(PiPr3)2],
increasing the overall yield to 80%. Anal. (%). Calc for C18H44
-
Br2NOP2Re: C, 30.95; H, 6.35; N, 2.01. Found: C, 31.10; H,
6.28; N, 2.03.
Mixtu r e Con ta in in g [Re(Br )2(NO)(η2-H2)(P Cy3)2] (2b)
a n d [Re(Br )3(NO)(P Cy3)2]. A mixture of 1 (1.0 g, 1.14 mmol)
and PCy3 (1.04 g, 3.71 mmol) suspended in ethanol (25 mL)
was stirred for 48 h at 70 °C. A brown precipitate gradually
(46) (a)Eichkorn, K.; Treutler, O.; O¨ hm, H.; Ha¨ser, M.; Ahlrichs, R.
Chem. Phys. Lett. 1995, 240, 283. (b) Eichkorn, K.; Treutler, O.; O¨ hm,
H.; Ha¨ser, M.; Ahlrichs, R. Chem. Phys. Lett. 1995, 242, 652. (c)
Eichkorn, K.; Weigend, F.; Treutler, O.; Ahlrichs, R. Theor. Chem. Acc.
1997, 97, 119.
(47) Andrae, D.; Ha¨ussermann, U.; Dolg, M.; Stoll, H.; Preuss, H.
Theor. Chim. Acta 1990, 77, 123.
(48) (a) Scha¨fer, A.; Huber, C.; Ahlrichs, R. J . Chem. Phys. 1994,
100, 5829. (b) Scha¨fer, A.; Horn, H.; Ahlrichs, R. J . Chem. Phys. 1992,
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Gusev, Dimitri
