Encapsulated Iron and Cobalt Metallocenes
Organometallics, Vol. 16, No. 7, 1997 1467
flask; to this was added NH4PF6 (90 mg, 0.55 mmol) in small
portions. The dark brown reaction mixture was stirred for 8
h, during which time it slowly turned yellow. The reaction
mixture was concentrated under vacuum to a volume of 5 mL,
and hexanes (15 mL) was added, which led to the formation
of a yellow precipitate. This solid was collected by filtration
in air, washed twice with hexanes (20 mL), and then twice
with H2O (15 mL). The solid was then dissolved in 10 mL of
acetone; centrifugation of the solution removed a small amount
of black material. Evaporation of the acetone under vacuum
and recrystallization of the residue from acetone/Et2O (5:1) at
-20 °C gave 0.22 g (81% yield) of [(Cp3i)2Co]PF6 as a bright
yellow, microcrystalline solid. When heated to 250 °C, [(Cp3i)2-
Co]PF6 darkens to an orange color, but does not melt. 1H NMR
(acetone-d6): δ 5.63 (s, 4 H, ring-CH), 2.78-2.88 (two overlap-
ping septets, 6 H, CHMe2), 1.45 (d, J ) 6.7 Hz, 12 H, CH3),
1.25 (d, J ) 6.9 Hz, 12 H, CH3), 1.13 (d, J ) 6.6 Hz, 12 H,
CH3). 13C NMR (acetone-d6): δ 111.3 (ring-CCHMe2), 78.1
(ring-CH), 27.4 (CHMe2), 25.5 (CHMe2), 25.3 (CH3), 23.1 (CH3),
22.7 (CH3). Principal IR bands (KBr, cm-1): 3115 (w), 2974
(s), 2875 (sh), 1488 (s), 1402 (sh), 1388 (m), 1367 (m), 1321
(w), 1268 (m), 1199 (w), 1181 (w), 1154 (w), 1129 (w), 1101
(w), 1062 (m), 1014 (m), 927 (m), 912 (m), 836 (s, br, P-F), 726
(w), 558 (s), 481 (w).
(KBr, cm-1): 3130 (w), 2979 (s, br), 2881 (sh), 1461 (s, br), 1402
(s), 1386 (s), 1368 (s), 1338 (m), 1316 (m), 1296 (m), 1266 (m),
1194 (m), 1169 (w), 1150 (w), 1102 (m), 1085 (m), 1069 (m),
1057 (m), 1034 (w), 972 (w), 934 (w), 898 (sh), 846 (s, br, P-F),
760 (w), 739 (w), 681 (w), 558 (s), 480 (w).
Syn th esis of [(Cp 4i)2Co]BP h 4. (Cp4i)2Co (0.12 g, 0.22
mmol) was dissolved in 15 mL of THF in an Erlenmeyer flask;
to this was added NH4BPh4 (85 mg, 0.25 mmol) in small
portions. The dark brown reaction mixture was then stirred
for 24 h, during which time it slowly turned yellow. Workup
of the reaction following the same procedure used for [(Cp3i)2-
Co]BPh4 gave 0.14 g (77% yield) of [(Cp4i)2Co]BPh4 as an
orange-yellow, microcrystalline solid (mp 200-215 °C). Anal.
Calcd for C58H78BCo: C, 82.44; H, 9.30; Co, 6.97. Found: C,
82.33; H, 9.48; Co, 7.04. 1H NMR (DMSO-d6, 60 °C): δ 7.17
(br m, 8 H, o-Ph), 6.90 (t, J ) 7.2 Hz, 8 H, m-Ph), 6.76 (t, J )
7.1 Hz, 4 H, p-Ph), 5.53 (s, 2 H, ring-CH), 2.92 (septet, J ) 6.9
Hz, 8 H, CHMe2), 1.47 (d, J ) 7.0 Hz, 12 H, CH3), 1.37 (d, J )
6.6 Hz, 12 H, CH3), 1.29 (d, J ) 6.9 Hz, 12 H, CH3), 1.06 (d, J
) 6.5 Hz, 12 H, CH3). 1H NMR (acetone-d6): δ 7.34 (br m, 8
H, o-Ph), 6.92 (t, J ) 7.3 Hz, 8 H, m-Ph), 6.78 (t, J ) 7.1 Hz,
4 H, p-Ph), 5.63 (s, 2 H, ring-CH), 3.07 (septet, J ) 6.9 Hz, 8
H, CHMe2), 1.58 (br d, 12 H, CH3), 1.46 (br d, 12 H, CH3),
1.40 (br d, 12 H, CH3), 1.15 (d, J ) 6.6 Hz, 12 H, CH3). 13C
NMR (acetone-d6): δ 164.9 (q, 1J (B-C) ) 49.5 Hz, B-C(Ph)),
137.0 (m-Ph), 125.90 (q, 2J (B-C) ) 2.6 Hz, o-Ph), 122.1 (p-Ph),
111.4 (vbr, ring-CCHMe2), 108.0 (vbr, ring-CCHMe2), 7.40 (br,
ring-CH), 27.2 (br, CHMe2), 26.9 (CHMe2), 26.8 (CH3), 24.6
(br, CH3), 23.9 (br, CH3), 22.0 (br, CH3). Principal IR bands
(KBr, cm-1): 3055 (s), 2999 (s), 2982 (sh), 2879 (sh), 1579 (m),
1479 (s), 1458 (s), 1426 (w), 1385 (m), 1367 (m), 1311 (w), 1264
(w), 1232 (w), 1185 (m), 1153 (m), 1086 (w), 1062 (w), 1052
(w), 1032 (m), 972 (w), 883 (w), 845 (w), 744 (s), 733 (s), 705
(s), 624 (w), 613 (s), 602 (m), 534 (w), 490 (w), 465 (w).
Syn th esis of [(Cp 3i)2Co]BP h 4. (Cp3i)2Co (0.15 g, 0.34
mmol) was dissolved in 20 mL of THF in an Erlenmeyer flask;
to this was added NH4BPh4 (0.13 g, 0.39 mmol) in small
portions. After 8 h, the now yellow reaction mixture was
concentrated (5 mL) and a yellow solid was precipitated by
the addition of hexanes (15 mL). The precipitate was collected
by filtration in air, washed twice with 5 mL of hexanes,
extracted into chloroform (15 mL), and filtered to remove
excess NH4BPh4. The chloroform was removed under vacuum,
and the residue was dissolved in 10 mL of acetone. The
solution was then centrifuged to remove a small amount of
black material. The acetone solution was subsequently con-
centrated to a volume of 2 mL and carefully layered with 5
mL of Et2O. After 24 h at -20 °C, golden yellow crystals of
[(Cp3i)2Co]BPh4 (mp 200-212 °C) precipitated from solution;
decantation of the remaining solution followed by drying the
crystals briefly under vacuum yielded 0.24 g (90% yield) of
product. Anal. Calcd for C52H66BCo: C, 82.09; H, 8.74; Co,
7.75. Found: C, 81.72; H, 8.51; Co, 7.51. 1H NMR (acetone-
d6): δ 7.33 (br m, 8 H, o-Ph), 6.92 (m, 8 H, m-Ph), 6.77 (m, 4
H, p-Ph), 5.65 (s, 4 H, ring-CH), 2.76-2.90 (two overlapping
septets, 6 H, CHMe2), 1.47 (d, J ) 6.6 Hz, 12 H, CH3), 1.27 (d,
J ) 6.8 Hz, 12 H, CH3), 1.15 (d, J ) 6.6 Hz, 12 H, CH3). 13C
NMR (acetone-d6): δ 164.9 (q, 1J (B-C) ) 49.4 Hz, B-C(Ph)),
Gen er a l P r oced u r es for X-r a y Cr ysta llogr a p h y.
A
suitable crystal of each compound was located and either
sealed in a glass capillary (for (Cp3i)2Co) or mounted on a glass
fiber in air. All measurements were performed at 20 °C on a
Rigaku AFC6S diffractometer at Vanderbilt University with
graphite-monochromated Mo KR (λ ) 0.710 69 Å) or Cu KR
radiation (λ ) 1.541 78 Å). Relevant crystal and data collection
parameters for the compounds are given in Table 1.
Cell constants and orientation matrices for data collection
were obtained from systematic searches of limited hemispheres
of reciprocal space; sets of diffraction maxima were located
whose setting angles were refined by least squares. The space
groups were determined from consideration of the unit cell
parameters, statistical analyses of intensity distributions, and,
where appropriate, systematic absences. Subsequent solution
and refinement of the structures confirmed the choice in each
case.
Data collection was performed using continuous ω-2θ scans
with stationary backgrounds (peak/background counting time
) 2:1). Data were reduced to a unique set of intensities and
associated σ values in the usual manner. The structures were
solved by direct methods (SHELXS-86, DIRDIF) and Fourier
techniques and refined using the full-matrix, least-squares
method of TEXSAN.14 All non-hydrogen atoms were refined
anisotropically, except when prohibited by a low number of
observed reflections. Except as noted below, hydrogen atoms
were inserted in calculated positions based on packing con-
siderations and d(C-H) ) 0.95 Å; the positions were fixed for
the final cycles of refinement. Final difference maps were
featureless. Special considerations given to the individual
structures are detailed below.
2
137.0 (m-Ph), 125.9 (q, J (B-C) ) 2.6 Hz, o-Ph), 122.2 (p-Ph),
111.3 (ring-CCHMe2), 78.1 (ring-CH), 27.4 (CHMe2), 25.5
(CHMe2), 25.3 (CH3), 23.1 (CH3), 22.7 (CH3). Principal IR
bands (KBr, cm-1): 3052 (s), 2976 (s), 2875 (sh), 1581 (m), 1480
(s), 1460 (s), 1427 (s), 1383 (m), 1366 (m), 1267 (m), 1182 (m),
1151 (m), 1126 (w), 1054 (m), 1032 (m), 1015 (w), 937 (w), 926
(w), 900 (m), 849 (m), 743 (s), 732 (s), 704 (s), 626 (w), 605 (s),
481 (w), 465 (w).
Syn th esis of [(Cp 4i)2Co]P F 6. (Cp4i)2Co (0.10 g, 0.19 mmol)
was dissolved in 10 mL of THF in an Erlenmeyer flask; to this
was added NH4PF6 (55 mg, 0.34 mmol) in small portions. The
dark brown reaction mixture was then stirred for 24 h, during
which time it slowly turned yellow. Workup of the reaction
following the same procedure used for [(Cp3i)2Co]PF6 gave 0.10
g (79% yield) of [(Cp4i)2Co]PF6 as amber crystals. When heated
to 250 °C, [(Cp4i)2Co]PF6 darkens to an orange color, but does
not melt. Anal. Calcd for C34H58CoF6P: C, 60.86; H, 8.72; Co,
8.79. Found: C, 60.03; H, 8.70; Co, 8.63. 1H NMR (acetone-
d6): δ 5.65 (s, 2 H, ring-CH), 3.09 (septet, J ) 6.8 Hz, 8 H,
CHMe2), 1.60 (br, 12 H, CH3), 1.47 (br d, 12 H, CH3), 1.42 (br,
12 H, CH3), 1.16 (br d, 12 H, CH3). 13C NMR (acetone-d6): δ
111.5 (vbr, ring-CCHMe2), 108.0 (vbr, ring-CCHMe2), 74.0 (br,
ring-CH), 27.2 (br, CHMe2), 27.0 (CHMe2), 26.8 (CH3), 24.5
(br, CH3), 23.9 (br, CH3), 22.0 (br, CH3). Principal IR bands
(Cp 3i)2F e. Only needlelike crystals of (Cp3i)2Fe could be
grown from any solvent; the most regular in shape were
obtained from acetone. The iron atom in the metallocene was
located on an inversion center. Although the absorption
(14) TEXSAN. TEXRAY Structure Analysis Package. TEXSAN
Molecular Structure Corporation: The Woodlands, TX, 1985.
Burkey, David J.
