Photoreactions of chromium cyclodienyl complexes with alkynes: Double [5 + 2],homo[5 + 2] cycloaddition reactions

Article abstract of DOI:10.1021/om960183r

UV irradiation of the cycloheptadienyl complexes [(η⁵-C₇H₈R)Cr(CO)₃SnPh ₃] (1a, R = H; 1b, R = C(Me)S(CH₂)₃S; 1c, R = CHPh₂) or cyclohexadienyl complexes [(η⁵

Full text of DOI:10.1021/om960183r

Organometallics 1996, 15, 3337-3344
3337
P h otor ea ction s of Ch r om iu m Cyclod ien yl Com p lexes
w ith Alk yn es: Dou ble [5 + 2],h om o[5 + 2]
Cycloa d d ition Rea ction s
Weichun Chen, Hyei-J ha Chung, Chenjie Wang, J ohn B. Sheridan,*
Marie L. Cote´, and Roger A. Lalancette
Department of Chemistry, Rutgers, The State University of New J ersey,
University Heights, Newark, New J ersey 07102
Received March 8, 1996X
UV irradiation of the cycloheptadienyl complexes [(η5-C7H8R)Cr(CO)3SnPh3] (1a , R ) H;
1b, R ) C(Me)S(CH2)3S; 1c, R ) CHPh2) or cyclohexadienyl complexes [(η5-C6H6R)Cr(CO)2-
(NO)] (7, R ) C(Me)S(CH2)3S) and 2 equiv of 2-butyne or 3-hexyne in toluene or n-hexane
gave new tricyclic complexes 2, 5, and 8. These complexes arise from sequential [5 + 2]
and homo[5 + 2] cycloadditions of two alkyne molecules to the η5-dienyl manifold forming
11-alkylidenetricyclo[5.3.1.04,10]undeca-2,5-diene or tricyclo[5.2.1.04,9]deca-2,5-dien-10-yl ligands,
respectively. Heating 2 in acetonitrile gave [Cr(CO)3(CH3CN)3] and the tricyclic organic
compounds 3. UV irradiation of 1a and 1-phenyl-1-propyne or 1c and 2-butyne directly
gave the organic compounds 4a ,b and 5c, 6a ,b, respectively, as mixtures of isomers. The
adduct resulting from 1a and two molecules of 3-hexyne has been characterized by an X-ray
diffraction study.
Sch em e 1. [5 + 2],h om o[5 + 2] Dou ble Alk yn e
Ad d ition to [Mn (CO)3(η5-C6H7)]
In tr od u ction
Transition metal-mediated cycloaddition reactions
continue to attract interest as a means of generating a
variety of ring systems both efficiently and stereoselec-
tively.1 Within this field, significant advances have
been made in the construction of medium-size carbo-
and heterocyclic rings through transition metal-medi-
ated higher-order cycloaddition processes.2-4 For ex-
ample, Rigby and co-workers have extensively investi-
gated photoinduced [6 + 2] and [6 + 4] cycloadditions
using [(η6-triene)Cr(CO)3] complexes and olefins,4
dienes,5,6 heterocumulenes,7 or even transition metal
carbene complexes.8 Likewise, we9,10 and others11 have
demonstrated the related chromium-mediated [6 + 2]
cycloadditions of alkynes to trienes.
Photoassisted higher-order cycloadditions of alkynes
to η5-dienyl ligands have also been reported by us,12
as well as by Kreiter and co-workers,13 using tricar-
bonyl(η5-cyclohexadienyl)manganese(0). In these stud-
ies, sequential [5 + 2],homo[5 + 2] double alkyne
additions to the dienyl ligand gave new tricyclic species,
(Scheme 1).
More recently, Kreiter has reported a [5 + 2] coupling
of alkynes and pentadienylmanganese complexes,14,15 as
well as [5 + 2],homo[5 + 2] double alkyne addition to
tricarbonyl(η5-cycloheptadienyl)manganese(0),16 again
promoted by UV light. The [5 + 4] coupling of dienyl
ligands and dienes at a manganese center is also
known,17-21 and it appears [5 + 2] or [5 + 4] cycload-
ditions of dienyl ligands to appropriate dienylophiles
X Abstract published in Advance ACS Abstracts, J une 1, 1996.
(1) Lautens, M.; Klute, W.; Tam, W. Chem. Rev. 1996, 96, 49.
(2) Rigby, J . H.; Ateeq, H. S.; Charles, N. R.; Henshilwood, J . A.;
Short, K. M.; Sugathapala, P. M. Tetrahedron 1993, 49, 5495.
(3) Rigby, J . H. Acc. Chem. Res. 1993, 26, 579.
(4) Rigby, J . H.; Henshilwood, J . A. J . Am. Chem. Soc. 1991, 113,
5122.
(5) Rigby, J . H.; Ateeq, H. S.; Charles, N. R.; Cuisiat, S. V.; Ferguson,
M. D.; Henshilwood, J . A.; Krueger, A. C.; Ogbu, C. O.; Short, K. M.;
Heeg, M. J . J . Am. Chem. Soc. 1993, 115, 1382.
(6) Rigby, J . H.; Scribner, S.; Heeg, M. J . Tetrahedron Lett. 1995,
36, 8569.
(7) Rigby, J . H.; Ahmed, G.; Ferguson, M. D. Tetrahedron Lett. 1993,
34, 5397.
(8) Rigby, J . H.; Pigge, F. C.; Ferguson, M. D. Tetrahedron Lett.
1994, 35, 8131.
(9) Chaffee, K.; Huo, P.; Sheridan, J . B.; Barbieri, A.; Aistars, A.;
Lalancette, R. A.; Ostrander, R. L.; Rheingold, A. L. J . Am. Chem. Soc.
1995, 117, 1900.
(13) Kreiter, C. G.; Fiedler, C.; Frank, W.; Reiss, G. J . J . Organomet.
Chem. 1995, 490, 133.
(14) Kreiter, C. G.; Koch, E.-C.; Frank, W.; Reiss, G. J . J . Organomet.
Chem. 1995, 490, 125.
(15) Kreiter, C. G.; Koch, E.-C.; Frank, W.; Reiss, G. J . Inorg. Chim.
Acta 1994, 220, 77.
(10) Chaffee, K.; Sheridan, J . B.; Aistars, A. Organometallics 1992,
11, 18.
(11) Fischler, I.; Grevels, F.; Leitich, J .; O¨ zkar, S. Chem. Ber. 1991,
124, 2857.
(16) Kreiter, C. G.; Fiedler, C.; Frank, W.; Reiss, G. J . Chem. Ber.
1995, 128, 515.
(17) Kreiter, C. G.; Lehr, K. J . Organomet. Chem. 1993, 454,
199.
(12) Wang, C.; Sheridan, J . B.; Chung, H.-J .; Cote, M.; Lalancette,
R. A.; Rheingold, A. L. J . Am. Chem. Soc. 1994, 116, 8966.
(18) Kreiter, C. G.; Lehr, K.; Leyendecker, M.; Sheldrick, W. S.;
Exner, R. Chem. Ber. 1991, 124, 3.
S0276-7333(96)00183-5 CCC: $12.00 © 1996 American Chemical Society
+
+

3338 Organometallics, Vol. 15, No. 15, 1996
Chen et al.
Sch em e 2. [5 + 2],h om o[5 + 2] Dou ble Alk yn e
may be quite general. The potential of metal-mediated
higher-order cycloaddition reactions is further exempli-
fied by a complementary catalytic [5 + 2] cycloaddi-
tion protocol between alkynes and vinylcyclopropanes
that has recently been reported by Wender and asso-
ciates.22
Ad d ition to a Cycloh ep ta d ien yl Rin g
In continuing our studies on the photoreactions of
dienyl complexes with alkynes, we now present de-
tails of a [5 + 2],homo[5 + 2] double cycloaddition to
both cycloheptadienyl(triarylstannyl)- and cyclohexadi-
enyl(nitrosyl)chromium manifolds. A schematic repre-
sentation of the coupling reaction for the seven-
membered ring is shown in Scheme 2. The final
products from the tin precursors contain an 11-alkyli-
dene-tricyclo[5.3.1.04,10]undeca-2,5-diene ring coordi-
nated to a Cr(CO)3 group, with an exocyclic alkylidene
that is generated by elimination of Ph3SnH. Subse-
quent reaction of these species with acetonitrile gives
the functionalized tricyclic compounds in good to excel-
lent yields.
The new ligand is a tricyclic triene that results from
the coupling of two alkynes with the cycloheptadienyl
ring via sequential [5 + 2] and homo[5 + 2] cycloaddi-
tions. Elimination of a hydrogen atom adjacent to C(11)
of the newly formed ring forms an exocyclic double bond
at this site. The ligand consists of three fused rings (C5,
C6, C7) with four of the ring carbon atoms, C(1), C(2),
C(3) and C(11), derived from added alkynes. It is
bonded to a chromium tricarbonyl group through all
three double bonds, i.e. C(2)dC(3), C(5)dC(6), and
C(11)dC(12), each trans to a CO ligand.
The 1H NMR spectrum of 2a shows nine distinct
resonances for the C7 ring as well as two singlets at δ
3.94 and 3.87 assigned to the exocyclic methylene
protons at C(12). Only three methyl group signals
are observed at δ 1.18, 1.55, and 2.06 since one of the
former alkyne methyl groups has been converted to the
methylene moiety. Likewise, the 13C{1H} NMR spec-
trum shows a signals at δ 74.3 {C(12)} and δ 63.6 {C-
(11)} for the coordinated exocyclic methylene and a
further 10 signals associated with the ring as well as
three distinct CO resonances at δ 233.4, 234.8, and
235.6 (Table 1).
Resu lts a n d Discu ssion
Ch r om iu m -Med ia ted Cycloh ep ta d ien yl-Alk yn e
Cou p lin g. Irradiation of toluene or n-hexane solutions
of tricarbonyl(η5-cycloheptadienyl)(triphenylstannyl)-
chromium(II) (1a ) and 2-butyne or 3-hexyne (2 equiv)
with UV light at room temperature for 0.5-4 h re-
sulted in a gradual disappearance of 1a , as monitored
by IR spectroscopy, and the formation of new neutral
tricarbonyl species 2a ,b, respectively (eq 1). Analysis
Complex 2b is analogous to 2a and was similarly
characterized. However, for 2b there exists the pos-
sibility of two isomers (E/ Z) for the exocyclic alkylidene
group, since either of the two disatereoselective meth-
ylene hydrogens adjacent to the ring can be eliminated
with the Ph3Sn moiety. Remarkably, a single isomer
is formed as observed by NMR spectroscopy, which
contrasts with the related manganese complexes gener-
ated by hydride abstraction with [CPh3]+. In those
species both E and Z isomers were formed.12 The
molecular structure of 2b was confirmed by an X-ray
diffraction study (Figure 1; Tables 2 and 3). The
structure is essentially octahedral at chromium with the
three coordinated olefins of the tricyclic ligand trans to
carbonyls. The structure shows the stereochemistry of
the C(11)dC(12) bond is E.
(1)
of the reaction solutions by gas chromatography-
mass spectrometry (GCMS) showed the presence of
triphenyltin hydride as a byproduct of the reaction.
Workup of the reaction by column chromatography
allowed the isolation of pure 2a ,b as moderately air
stable yellow solids in 75% and 88% yields (based on
1a ), respectively.
Double alkyne addition to 1a includes the elimination
of Ph3SnH and thus necessitates the use of alkynes with
hydrogen atoms adjacent to the CtC bond. Conse-
quently, attempts to induce coupling reactions with
diphenylacetylene and bis(trimethylsilyl)acetylene failed
to yield any tractable products. On the other hand, the
efficiency of the coupling reaction is not affected by the
nature of the stannyl substituent, with the trimethyl-
stannyl derivative [(η5-C7H9)Cr(CO)3SnMe3]23 yielding
Both 2a and 2b were fully characterized by elemental
analysis, H, 13C, and H-1H (2D COSY) NMR, and IR
1
1
spectroscopy (see Table 1 and Experimental Section).
(19) Kreiter, C. G.; Lehr, K. J . Organomet. Chem. 1991, 406,
159.
(20) Kreiter, C. G.; Lehr, K.; Exner, R. J . Organomet. Chem. 1991,
411, 225.
(21) Kreiter, C. G.; Lehr, K. Z. Naturforsch. 1991, 46b, 1377.
(22) Wender, P. A.; Takahashi, H.; Witulski, B. J . Am. Chem. Soc.
1995, 117, 4720.
(23) Wang, C.; Sheridan, J . B. Organometallics 1994, 13, 3639.
+
+

Chromium Cyclodienyl Complexes
Organometallics, Vol. 15, No. 15, 1996 3339
Ta ble 1. 1H a n d 13C{1H} NMR Sp ectr a l Da ta a
δ(1H)
complex
δ(13C{1H})
2a
2b
1.18 (3H, s, Me), 1.55 (3H, s, Me), 1.62 (1H, m, H9), 1.66
(1H, m, H8), 1.72 (1H, m, H8′), 1.90 (1H, m, H9′), 2.06 (3H, s,
Me), 2.07 (1H, dd, H7), 2.36 (1H, dd, H10), 3.11 (1H, dd, H4),
3.45 (1H, dd, H6), 3.87 (1H, s, H12), 3.94 (1H, s, H12′),
4.34 (1H, dd, H5)b
13.0, 16.1, 16.7 (Me), 26.0, 26.4 (C8,9), 38.9 (C10),
46.8 (C7), 47.0 (C1), 52.4 (C4), 62.9 (C5), 63.6 (C11),
67.3 (C6), 71.9 (C12), 82.0 (C2), 105.5 (C3),
233.4, 234.8, 235.6 (CO)
0.91 (3H, t, Me), 0.93 (3H, t, Me), 1.12 (3H, t, Me), 1.35 (2H, m,
CH2Me), 1.55 (2H, m, CH2Me), 1.62 (2H, m, H8,9), 1.90 (2H, m,
9.5, 13.7, 16.6, 17.2 (Me), 18.5, 22.7, 23.3 (CH2Me),
26.3 (C9), 31.5 (C8), 33.6 (C10), 47.1 (C7), 50.2 (C4),
52.7 (C1), 65.7 (C11), 66.3 (C5), 69.1 (C6), 92.5 (C12),
93.7 (C2), 107.5 (C3), 232.0, 233.7, 233.8 (CO)
H
7,8′), 2.08 (3H, d, Me), 2.17 (2H, m, H9′, CH2Me), 2.78 (1H, m,
CH2Me), 2.99 (1H, m, H10), 3.29 (1H, t, H4), 3.66 (1H, t, H6),
4.08 (1H, t, H5), 4.68 (1H, q, H12
)
3a
3b
1.28 (3H, s, Me), 1.61 (3H, s, Me), 1.65 (3H, s, Me), 1.87-2.00
(5H, m, H8,8′,9,9′,10), 2.78 (2H, m, H7,4), 4.67 (2H, s, H12′), 5.72
(1H, dd, H6), 5.74 (1H, dd, H5)
9.1 (Me), 13.1 (Me), 18.2 (Me), 25.1 (C8), 27.8 (C9),
45.1 (C7), 48.2 (C10), 51.4 (C1), 56.2 (C4),
105.3 (C12), 130.4 (C6), 132.2 (C5), 135.0 (C2),
137.4 (C3), 157 (C11)
9.7 (Me), 13.0 (Me), 13.1 (Me), 15.6 (Me), 17.9,
19.6, 20.7 (CH2), 26.9 (C8), 30.3 (C9), 35.5 (C7),
43.5 (C10), 53.2 (C4), 55.8 (C1), 113.0 (C12),
129.4 (C6), 133.2 (C5), 141.8 (C2), 143.0 (C3),
146.5 (C11)
0.86 (3H, t, Me), 0.98 (3H, t, Me), 0.99 (3H, t, Me), 1.49 (1H, m,
H8), 1.58 (3H, d, Me), 1.68-1.78 (2H, m, CH2), 1.84 (1H, m, H8′),
1.86 (1H, m, H9), 1.94 (1H, m, H9′), 2.0-2.2 (5H, m, CH2, H10),
2.94 (1H, t, H4), 3.24 (1H, m, H7), 5.20 (2H, q, H12), 5.68 (1H,
dd, H6), 5.72(1H, dd, H5)
4a
4b
5a
1.64 (1H, m, H8), 1.78 (3H, s, Me), 1.79 (1H, m, H8′), 1.83 (1H,
m, H9), 1.97 (1H, m, H9′), 2.42 (1H, t, H10), 3.08 (1H, dd,
H7), 3.52 (1H, t, H4), 4.68 (1H, s, H12), 5.07 (1H, s, H12′),
5.71 (1H, dd, H6), 5.83 (1H, t, H5), 7.20-7.44 (10H, m, Ph)
1.61 (1H, m, H8), 1.71 (3H, s, Me), 1.76 (1H, m, H8′), 1.82 (1H,
m, H9), 1.92 (1H, m, H9′), 2.64 (1H, t, H10), 3.06 (1H, dd, H7),
3.11 (1H, t, H4), 4.00 (1H, s, H12), 5.00 (1H, s, H12′), 5.84 (1H,
dd, H6), 5.88 (1H, t, H5), 7.02-7.67 (10H, m, Ph)
1.11 (s, Me), 1.53 (s, Me), 1.77 (s, Me), 1.82 (t, H9), 1.91 (m, H9′),
2.06 (s, Me), 2.10 (m, H7,10), 2.20, (m, H15), 2.40 (m, H15′),
2.65-3.00 (m, H14,14′,16,16′,8), 3.04 (t, H4), 3.78 (s, H12), 3.81
(s, H12′), 3.84 (d, H6), 4.15 (t, H5)
12.7 (Me), 18.0 (C8), 26.8 (C9), 45.1 (C7), 53.0 (C10),
56.0 (C4), 64.3 (C1), 110.7 (C12), 126.0, 127.0,
128.2, 128.5, 128.8, 129.0 (Ph), 131.5, 132.2 (C5,6),
138.0 (C2), 140.5, 142.0 (Ph), 147.0 (C3), 151.9 (C11)
13.5, 13.7, 16.6, 16.7, 20.5, 20.6 (Me), 25.5-29.2
(C8, C9, C14-16, Me-13), 39.2, 41.5 (C10), 47,
47.3, 48.2, 48.7, 49.8 (C4, C7, C13), 52.3, 53.5, 54.1,
(C13, C1), 61.0, 62.2 (C5), 63.7, 64.4 (C11), 66.3,
68.0 (C6), 71.5, 73.0 (C12), 83.5 (C2), 95, 98.2 (C3),
232.2, 234.4, 235.1, 236.0 (CO)c
5b
5c
1.14 (s, Me), 1.48 (s, Me), 1.74 (s, Me), 1.81 (t, H8), 1.93 (m, H8′),
2.05 (s, Me), 2.10 (m, H7,10), 2.20, (m, H15), 2.40 (m, H15′),
2.65-3.00 (m, H14,14′,16,16′,4,9), 3.52 (d, H6), 3.74 (s, H12),
3.76 (s, H12′), 4.09 (t, H5)
1.11 (3H, s, Me), 1.18 (1H, m, H8), 1.44 (3H, s, Me), 1.71 (1H,
m, H8′), 1.94 (1H, m, H7), 2.03 (3H, s, Me), 2.07 (1H,
dd, H10), 2.58 (1H, dd, H9), 3.29 (1H, t, H4), 3.45 (1H, t,
H6), 3.63 (1H, s, H12), 3.72 (1H, s, H12′), 3.83 (1H, d, CHPh2),
4.21 (1H, t, H5), 7.18-7.35 (10H, m, Ph)
1.30, (s, Me), 1.31 (s, Me), 1.40 (m, H9′), 1.44 (s, Me), 1.57 (s, Me),
1.58 (s, Me), 1.60 (s, Me), 1.72-2.00 (m, H8,9,10,8′), 2.55 (dd, H7),
2.68-2.78 (m, H4,7), 3.17 (m, H4), 3.75 (d, CHPh2), 4.00 (d,
CHPh2), 4.50 (s, H12′), 4.62 (s, H12′), 4.74 (s, H12), 4.76 (s,
13.2, 17.0, 24.3 (Me), 26.5 (C8), 41.7, 42.0 (C9, C10),
47.2 (C1), 47.2 (C7), 52.5 (C4), 55.2 (CHPh2),
61.0 (C5), 64.0 (C11), 68.5 (C6), 72.2 (C12), 82.2 (C2),
98.5 (C3), 126.2, 126.8, 127.5, 128.1, 128.7, 129.1,
143.1, 143.4 (Ph), 232.2, 234.0, 234.5 (CO)
6a ,b
H
12), 5.50 (t, H6), 5.78 (t, H5), 5.88-5.91 (m, H5,6),
7.1-7.4 (m, Ph)d
8a
8b
0.93 (3H, s, 10-Me), 1.18 (3H, s, 1-Me), 1.81 (1H, m, H13),
1.88 (3H, s), 1.89, (3H, s), 1.93 (3H, s, 2-Me, 3-Me, 11-Me),
2.00 (2H, m, H8, H13′), 2.37 (1H, m, brd, H7), 2.51 (1H, m,
brd, H9), 2.70 (2H, m, H12, H14), 2.96 (2H, m, H12′, H14′),
3.72 (1H, t, H5), 4.20 (1H, t, H4), 4.94 (1H, t, H6)
0.71 (3H, t), 0.95 (3H, t), 1.04 (3H, t), 1.16 (3H, t, 1-Me, 2-Me,
3-Me, 10-Me), 1.47, 1.55 (4H, m, CH2), 1.77 (1H, m, H13),
1.86 (3H, s, 11-Me), 1.94 (2H, m, brd, H8, H13′), 2.32,
2.40 (4H, m, CH2), 2.55 (1H, s, brd, H7), 2.67 (2H, m,
-1.7 (C10), 13.7, 14.1 (1-Me, 10-Me), 20.4, 23.2,
25.3 (2-Me, 3-Me, 11-Me), 26.7, 26.8, 28.6 (C12,
C13, C14), 46.2 (C9), 46.7 (C8), 49.9 (C7), 54.8
(C4), 60.7 (C1), 68.8 (C5), 79.3 (C6), 86.6 (C3),
99.9 (C2), 236.2, 239.6 (CO)
7.1 (C10), 10.3, 12.9, 14.7, 15.9 (Me), 21.2, 22.3,
22.5 (CH2), 25.3 (Me), 26.6, 26.8 (C12, C14), 28.3,
28.5 (CH2, C13), 42.0 (C9), 43.4 (C8), 47.6 (C7),
49.8 (C11), 51.0 (C4), 65.8 (C1), 71.5 (C5),
81.1 (C6), 96.2 (C3), 105.4 (C2), 235.8, 240.4 (CO)
H
12, H14), 2.75 (1H, s, brd, H9), 2.92 (2H, m, H12′, H14′),
3.63 (1H, t, H5), 4.27 (1H, t, H4), 4.88 (1H, t, H6)
a
b
d
See eqs 2, 4, and 6 for labeling; in CDCl3 unless stated otherwise. In CD3NO2. c Spectrum of the mixture of 5a ,b. Spectrum of the
mixture of 6a ,b.
2a in yield similar to that obtained from 1a 24 along with
trimethyltin hydride as the byproduct.25
Decom p lexa t ion of t h e Or ga n ic Liga n d fr om
2a ,b. When acetonitrile solutions of 2a ,b are heated
to reflux for 15-30 min, the tricyclic organic ligands are
cleanly decomplexed from the metal with concomitant
formation of [Cr(CO)3(CH3CN)3] (eq 2). Evaporation of
the solvent in vacuo and extraction of the residue with
hexane gave crude 3a ,b as colorless oils. Pure samples
were isolated in good yield following chromatography
on silica gel. The new organic compound 3a is 1,2,3-
trimethyl-11-methylenetricyclo[5.3.1.04,10]undeca-2,5-di-
ene, whereas 3b is 1,2,3-triethyl-11-(E-ethylidene)-
tricyclo[5.3.1.04,10]undeca-2,5-diene.
The isolation of the bis(alkyne)-dienyl cycloadducts
as Cr(CO)3 complexes rather than the free organic
species is dependent upon the alkyne used as well as
the nature of the substituents on the C7 ring. In some
(24) Wang, C. Ph.D. Thesis, Rutgers University, 1993.
(25) GCMS analysis of the reaction mixture showed Me3SnH was
present as well as species of molecular mass consistent with products
derived from the insertion of excess 2-butyne into the SnH bond, e.g.
Me3SnC(Me)dCHMe.
+
+

3340 Organometallics, Vol. 15, No. 15, 1996
Chen et al.
Ta ble 3. Selected Bon d Dista n ces a n d An gles
for 2b
(a) Bond Distances (Å)
Cr-C(2)
2.447(3)
2.374(4)
2.322(3)
1.830(4)
1.824(4)
1.164(5)
1.552(4)
1.540(5)
1.352(5)
1.531(5)
1.498(5)
1.352(5)
1.534(5)
1.514(5)
1.360(5)
Cr-C(3)
2.466 (4)
2.368(4)
2.445(3)
1.817(4)
1.155(5)
1.160(4)
1.556(5)
1.532(5)
1.515(5)
1.512(4)
1.543(4)
1.514(5)
1.514(5)
1.540(5)
Cr-C(5)
Cr-C(6)
Cr-C(11)
Cr-C(20)
Cr-C(22)
C(21)-O(2)
C(1)-C(2)
C(1)-C(11)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(7)-C(8)
C(8)-C(9)
C(11)-C(12)
Cr-C(12)
Cr-C(21)
C(20)-O(1)
C(22)-O(3)
C(1)-C(10)
C(1)-C(14)
C(2)-C(16)
C(3)-C(18)
C(4)-C(10)
C(6)-C(7)
C(7)-C(11)
C(9)-C(10)
(b) Bond Angles (deg)
Cr-C(20)-O(1)
Cr-C(22)-O(3)
C(6)-Cr-C(22)
C(2)-Cr-C(22)
C(5)-Cr-C(21)
C(11)-Cr-C(21)
C(2)-Cr-C(21)
C(3)-Cr-C(20)
C(6)-Cr-C(20)
C(2)-Cr-C(3)
174.6(3)
177.4(4)
103.2(2)
111.3(1)
107.9(2)
103.8(1)
162.1(2)
106.1(1)
162.7(1)
31.9(1)
98.9(1)
75.8(1)
88.5(1)
105.2(1)
77.7(1)
Cr-C(21)-O(2)
174.7(3)
83.4(2)
84.7(1)
160.8(2)
83.4(2)
165.2(2)
89.4(1)
164.1(1)
110.1(1)
81.9(1)
62.9(1)
60.2(1)
82.9(1)
33.1(1)
61.8(1)
33.0(1)
119.4(3)
111.1(3)
117.6(3)
128.5(3)
102.1(3)
124.3(3)
111.8(3)
114.1(3)
C(5)-Cr-C(22)
C(3)-Cr-C(22)
C(11)-Cr-C(22)
C(6)-Cr-C(21)
C(3)-Cr-C(21)
C(2)-Cr-C(20)
C(5)-Cr-C(20)
C(1)-Cr-C(20)
C(2)-Cr-C(5)
F igu r e 1. Molecular structure of 2b showing the atom
labeling and 30% thermal ellipsoids for all non-hydrogen
atoms. Hydrogen atoms have been omitted for clarity.
Ta ble 2. Cr ysta l Da ta for Com p ou n d 2b
C(2)-Cr-C(6)
C(2)-Cr-C(11)
C(3)-Cr-C(5)
C(3)-Cr-C(11)
C(5)-Cr-C(6)
C(6)-Cr-C(11)
C(11)-Cr-C(12)
C(1)-C(11)-C(12)
C(1)-C(2)-C(3)
C(1)-C(10)-C(9)
C(2)-C(3)-C(18)
C(3)-C(4)-C(10)
C(5)-C(6)-C(7)
C(7)-C(8)-C(9)
C(8)-C(9)-C(10)
formula
fw
C22H28CrO3
392.46
C(2)-Cr-C(12)
C(3)-Cr-C(6)
space group
a, Å
b, Å
P1h (No. 2)
7.615(2)
9.094(1)
14.816(2)
92.86(1)
97.64(1)
109.565(9)
953.4(4)
2
C(3)-Cr-C(12)
C(5)-Cr-C(11)
C(6)-Cr-C(12)
C(7)-C(11)-C(12)
C(1)-C(11)-C(7)
C(1)-C(2)-C(16)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(4)-C(5)-C(6)
C(6)-C(7)-C(8)
C(8)-C(7)-C(11)
86.9(1)
c, Å
123.3(3)
117.3(3)
123.5(3)
109.5(3)
106.5(3)
127.3(3)
112.0(3)
112.9(3)
R, deg
â, deg
γ, deg
V, Å3
Z
D(calc), g cm-3
µ(Mo KR), cm-1
radiation
R(F), %a
Rw(F), %a
1.367
6.2
Mo KR (λ ) 0.710 73 Å)
5.35
6.36
propyne gave the organic material as two isomers 4a ,b
in a 4:1 ratio (eq 3). Compounds 4a ,b were separated
a
R(F) ) ∑(|Fo| - |Fc|)/∑|Fo|; Rw(F) ) ∑(w1/2(|Fo| - |Fc|))/w1/2(|Fo|).
by TLC and spectroscopically characterized (Table 1).
The major product (4a ) is the 1,3-diphenyl-substituted
isomer with the minor product (4b) that with phenyl
groups at C(1) and C(2). This regioselectivity is similar
to that observed for the manganese-mediated cyclohexa-
dienyl-alkyne coupling mentioned earlier and arises
because of insertion preferences of the alkyne during
the homo[5 + 2] addition (see mechanistic discussion).
Compounds 4a ,b show distinctly different 1H NMR
cases, decomposition of the organometallic adducts to
the organic compounds prevented isolation of the pure
complexes. In these instances, a one-pot strategy was
employed involving irradiation of the alkynes and 1
until all of 1 had been consumed, followed by heating
in acetonitrile. Thus, 1a and 2 equiv of 1-phenyl-1-
+
+

Chromium Cyclodienyl Complexes
Organometallics, Vol. 15, No. 15, 1996 3341
spectral data with the methylene signals (H12 and H12′)
appearing as two singlets at δ 4.68 and 5.07 for 4a and
δ 4.00 and 5.00 for 4b. We attribute this difference to
the closer proximity of the phenyl substituent at C(2)
in 4b causing a greater chemical shift difference in the
methylene protons. The facile decomplexation of 4a ,b
from the metal precursors may be due to the formation
of an η6-phenyl-coordinated intermediate. Indeed, we
have previously observed facile migration of Cr(CO)3
from an η2,4-coordinated bicyclic ring to a pendant
phenyl group,9 and the η2,2,2- interaction in 2 might be
expected to be weaker still.
by GCMS) (eq 5). Two of these are the decomplexed 9-
An important consideration in these double cycload-
dition reactions is the regiochemistry of the second
addition. As observed above (eq 3), unsymmetrical
alkynes gave two regioisomers in which the groups at
C(2) and C(3) of the organic ligand are different. An
alternative probe into the regioselectivity of the double
addition involves functionalization of the cycloheptadi-
enyl ligand at C(6). In this case, the cycloheptadienyl
complex is unsymmetrical and the second addition may
occur either adjacent to, or remote from, the ring
substituent. Thus, solutions of the complexes [(η5-
C7H8R)Cr(CO)3SnPh3] (1b, R ) 6-exo-C(Me)S(CH2)3S;
1c, R ) 6-exo-CHPh2)26 were irradiated with 2 equiv of
2-butyne and the products analyzed (eqs 4 and 5).
Complex 1b gave two isomeric products 5a ,b in an
approximate 2:1 ratio (eq 4). These species could not
and 8-substituted tricyclic ligands 6a ,b, respectively,
and are isolated as a mixture. The third is the 9-(diphen-
ylmethyl)-substituted complex 5c which elutes from the
column after 6a ,b. No evidence for the 8-substituted
complex was obtained, presumably due to its decompo-
sition to 6b. As was observed for 4a ,b decomplexation
of the tricyclic ligand bearing phenyl substituents is
quite facile, and this may be the reason why a mixture
of decomplexed and complexed products is observed in
this case. From the above results it appears that the
6-substituent on 1b,c exerts little effect on the second
cycloaddition, which is not surprising since this group
is on the opposite side of the molecule from the metal
center and hence on the opposite side to the bond-
forming event.
Mech a n ism for P h 3Sn -Cr -Med ia ted Cycloh ep -
ta d ien yl-Alk yn e Cou p lin g. The formation of com-
plexes 2 and 5 as well as the organic species 4 and 6
can be viewed as occurring through sequential [5 + 2]
and homo[5 + 2] cycloadditions of two alkyne molecules
to a cycloheptadienyl manifold followed by elimination
of Ph3SnH. It should be stressed that C-C bond
formation does not occur via a traditional concerted
cycloaddition but rather through a series of stepwise
insertions at the metal center. A proposed mechanism
for the formation for 2a is shown in Scheme 3 and is
similar to the pathway by which other metal-mediated
higher-order cycloadditions have been proposed to oc-
cur.2,9,12,27 The reaction absolutely requires UV light
since the products are not observed when solutions of 1
and alkynes are heated for prolonged periods. The exact
role of the UV light is however unclear, but we propose
that irradiation of 1 generates a coordinatively unsatur-
ated intermediate by ejection of a CO ligand. As shown,
one molecule of alkyne then adds to the metal prior to
insertion into the dienyl-chromium bond. Following
be separated by column chromatography but were
1
characterized as a mixture by elemental analysis, H,
1
13C, and H-1H (2D COSY) NMR, and IR spectroscopy
(Table 1 and Experimental Section). From these data
the major isomer was determined to be that in which
the 2-methyldithiane substituent is at C(8) of the
tricyclic ring or furthest from the five-membered ring
formed in the homo[5 + 2] coupling. The other isomer
1
(5b) has this substituent at C(9). The H NMR signals
for the two isomers are very similar, and only those for
the protons closest to the 2-methyldithiane moiety show
significant differences in chemical shift.
In contrast to 1b, the reaction of 1c with 2-butyne
gave three isolable products as well as Ph3SnH (detected
(26) Chen, W.; Sheridan, J . B.; Cote´, M. L.; Lalancette, R. A.
Organometallics 1996, 15, 2700.
(27) van Houwelingen, T.; Stufkens, D. J .; Oskam, A. Organome-
tallics 1992, 11, 1146.
+
+

3342 Organometallics, Vol. 15, No. 15, 1996
Chen et al.
Sch em e 3
In the case of unsymmetrical alkynes (e.g. PhCtCMe),
the formation of the two isomers 4a ,b arises because
the second alkyne insertion can occur in a number of
ways as outlined in Scheme 4. The four possible routes
shown involve insertion of either methyl- or phenyl-
substituted alkyne termini into the Cr-allyl or Cr-
alkene bonds of intermediate Z. The isolation of both
4a ,b indicates either (a) both the phenyl and methyl
alkyne termini insert into either of the allyl- or olefin-
chromium bonds of Z (shown as (i) in Scheme 4) or (b)
if one alkyne terminus preferentially inserts over the
other, it must occur into both the allyl or olefin bound
groups. Some combination of (a) and (b) would also give
4a ,b. However, insertion into the Cr-allyl bond is
considered more likely and since there is a preference
for formation of 4a , it appears that the phenyl- rather
than methyl-substituted alkyne carbon initially inserts
into the bicyclic ligand of Z. As mentioned above,
substitution at the methylene carbons of the C7 ring
does not greatly affect the regiochemistry of 5a -c or
6a ,b, although few conclusions can be drawn from these
latter results given the rather low yields and instability
of the organometallic adducts.
Ch r om iu m -Med ia ted Cycloh exa d ien yl-Alk yn e
Cou p lin g. Irradiation of toluene or n-hexane solutions
of dicarbonyl(nitrosyl)(η5-cyclohexadienyl)chromium(0)
(7) and 2-butyne or 3-hexyne (2 equiv) at room temper-
ature for 2-6 h resulted in a gradual disappearance of
7, as monitored by IR spectroscopy, and the formation
of the neutral dicarbonyl-nitrosyl species 8a ,b (eq 6).
this step, the former alkyne is now a vinyl ligand which
can undergo further insertion into the metal-diene
bond to give a [5 + 2] cycloadduct X. A second homo[5
+ 2] addition follows in like fashion as a series of
stepwise alkyne-olefin or alkyne-allyl insertions giving
the penultimate intermediate Y.28 This species is similar
to those isolated for the related manganese-mediated
cyclohexadienyl-alkyne [5 + 2],homo[5 + 2] double
additions,12,13 but unlike those complexes it is coordi-
natively unsaturated and eliminates a hydrogen atom
adjacent to C(11) with the SnPh3 ligand giving the Cr-
(CO)3 triene complexes and Ph3SnH. This latter step
most probably occurs via â-elimination of hydride from
the methyl group at C(11) to the metal followed by
reductive elimination of Ph3SnH and coordination of a
molecule of CO from the reaction medium. There is
precedent for abstraction of hydride by trityl cation from
this position in the related manganese complexes,12 as
well as in a recent report by Kreiter in which irradiation
of 2 equiv of 3-hexyne and [(η5-cyclohexadienyl)Mn-
(CO)3] with UV light gave a product containing an
exocyclic alkylidene at C(10) of the related tricyclic ring.
This latter species arose via a 1-5 shift of a hydrogen
atom from a methylene group to C(5).13 One interesting
aspect of the Cr system is that the stereochemistry of
the newly formed double bond is exclusively E as a
result of the intramolecular elimination of Ph3SnH. If
this process were to involve the homolytic cleavage of
the Cr-Sn bond and elimination of Ph3Sn•, followed by
abstraction of H• from the remaining organometallic
fragment, both E and Z isomers might be expected. The
1-5 shift described in ref 13 is stereoselective and
presumably also proceeds via a metal-hydride inter-
mediate. No stable tin-containing double cycloadducts
are observed, probably because this would involve
intermediate Y accepting a CO ligand and forming a
7-coordinate Cr center.
Complexes 8a ,b were isolated in 44 and 51% yield,
respectively (based on 7), as red-orange powders and
1
were characterized using elemental analysis, H, 13C,
and 1H-1H (2D COSY) NMR, and IR spectroscopy
(Table 1). The polycyclic ligand in 8 is a tricyclic system
that results from sequential [5 + 2] and homo[5 + 2]
cycloadditions of two alkyne molecules to a cyclohexa-
dienyl ring. As was observed for the related Mn(CO)3
system,12,13 the ligand has three fused rings, in this case
(C5, C5, C6), with C(1), C(2), C(3), and C(10) derived from
added alkynes and C(2), C(3), C(5), C(6), and C(10)
coordinated to chromium. The 13C{1H} NMR spectrum
of 8a is particularly diagnostic of the structure and
shows two distinct carbonyl signals at δ 236 and 240,
as well as a distinctive signal at -1.7 ppm assigned to
C(10). The upfield shift of this resonance is typical of
σ-bonded carbon atoms in these types of complexes.12,13
Interestingly, the 13C NMR shifts of most signals of 8a
are further downfield than those for the Mn(CO)3
counterpart shown in Scheme 1 (C(10) is at δ -19.2),12
indicating the Cr(CO)2(NO) group is more electrophilic.
(28) In Scheme 3, initial insertion of the second alkyne into the allyl
fragment is depicted. However, the alternative insertion into the Cr-
olefin bond is also possible (see Scheme 4).
The IR spectrum of 8a (νmax(CO) 2000, 1944 and νmax
-
+
+

Chromium Cyclodienyl Complexes
Organometallics, Vol. 15, No. 15, 1996 3343
Sch em e 4. P ossible P a th w a ys to Isom er s 4a ,ba
atmosphere of dry nitrogen using standard Schlenk tech-
niques. Manipulations of air-sensitive solids were performed
inside a Braun MB 150 inert-atmosphere glovebox containing
a nitrogen atmosphere. Solvents were dried over Na/ben-
zophenone (toluene, benzene, THF, diethyl ether), CaH2 (n-
hexane, n-pentane, CH2Cl2) or K2CO3 (acetone) and were
freshly distilled prior to use. Reagents were used as supplied
by either the Aldrich Chemical Co. (Milwaukee, WI) or
Farchan Laboratories (Gainesville, FL). Infrared spectra were
recorded on a Nicolet 5ZDX FT instrument operated in the
transmittance mode, and all NMR spectra were recorded on a
Varian VXR-400S NMR Fourier transform spectrometer. Gas
chromatography-mass spectrometry (GCMS) was performed
using a Hewlett Packard HP5890 gas chromatograph con-
nected to a Finnegan Mat Incos 50 mass spectrometer (70 eV).
High-resolution mass spectra were obtained at Hoffman La
Roche (Nutley, NJ ). Microanalyses were carried out by
Robertson Microlit Laboratories (Madison, NJ ). Chromatog-
raphy was performed on Alumina (150 mesh, standard grade,
activated, neutral, purchased from Aldrich) or silica gel (230-
425 mesh, purchased from Fisher Scientific). Tricarbonyl-
(triphenylstannyl)(η5-cycloheptadienyl)chromium(II) deriva-
tives (1a -c) and dicarbonyl(nitrosyl)(η5-cyclohexadienyl)-
chromium(0) (7) were prepared using the literature proce-
dures.23,26 Photolyses were conducted through Pyrex or quartz
glassware placed approx 5 cm from a 450 W Hanovia medium-
pressure Hg broadband UV lamp.
Tr ica r b on yl(η2,η2,η2-1,2,3-t r im e t h yl-11-m e t h yle n e -
t r icyclo[5.3.1.04,10]u n d eca -2,5-d ien e)ch r om iu m (0) (2a ).
2-Butyne (0.12 mL, 1.52 mmol, 2 equiv) was added to a stirred
orange solution of [Ph3SnCr(CO)3(η5-C7H9)] (0.300 g, 0.76
mmol) in n-hexane (40 mL) at room temperature. The mixture
was photolyzed for 2 h at room temperature and monitored
by IR spectroscopy until completion. Removal of the solvent
in vacuo and chromatography of the residue on alumina (30
cm × 2.5 cm), loading with CH2Cl2 (3 mL), and eluting with
n-hexane first and then CH2Cl2/n-hexane (1:1), followed by
evaporation to dryness, gave 2a as an orange powder. Yield:
0.192 g, 75%. νmax(CO)/cm-1 (hex): 1959 (vs), 1878 (vs), and
1874 (vs). Anal. Calcd for C18H20CrO3: C, 64.29; H, 5.95.
Found: C, 64.41; H, 5.95.
a
Key: (i) alkyne insertion into the Cr-allyl bond; (ii) alkyne
insertion into the Cr-alkene bond; (iii) ring closure, -Ph3SnH,
-Cr(CO)x.
(NO) 1677 cm-1) indicates one nitrosyl and two carbonyl
ligands are present in the complex and rules out any
structure that might arise via alkyne/CO substitution,
e.g. [(MeCtCMe)2(NO)Cr(η5-C6H6R)]. In comparison to
the isostructural and isoelectronic Mn(CO)3 derivatives,
the chromium species 8a ,b are less stable, again pre-
sumably due to the more electrophilic Cr(CO)2(NO)
fragment.
Con clu sion s
We have demonstrated that chromium cyclohepta-
and cyclohexadienyl complexes undergo photoassisted
double [5 + 2],homo[5 + 2] cycloadditions with alkynes
giving tricyclo[5.3.1.04,10]undeca-2,5,-diene and tricyclo-
[5.2.1.04,9]deca-2,5-dien-10-yl species, respectively. When
the triphenyltin-cycloheptadienyl precursor complexes
were used, elimination of Ph3SnH led to an exocyclic
alkylidene in the organic ligand which had exclusively
E stereochemistry. In contrast, the nitrosyl-cyclohexa-
dienyl species gave adducts in which no hydrogen atom
abstraction occurred. The role of UV light in these
reactions is to generate an unsaturated transition-metal
intermediate which initiates a cascade of insertion
processes leading to the final adducts. The organic
products were isolated following reflux of the tricarbonyl
complexes in acetonitrile. An identical coupling reaction
has been described for the related manganese system,12
and it appears that metal-mediated [5 + 2],homo[5 +
2] double additions may be quite general for metal-η5-
dienyl manifolds, allowing the generation of four new
carbon-carbon bonds with a high degree of regio- and
stereocontrol. The development of this multiple cy-
cloaddition methodology for other coordinated polyene
manifolds, in order to access new polycyclic systems, is
in progress and will be reported in due course.
T r i c a r b o n y l(η2 ,η2 ,η2 -1,2,3-t r i e t h y l-11-(E )-e t h y li -
den etr icyclo[5.3.1.04,10]u n deca-2,5-dien e)ch r om iu m (0) (2b).
3-Hexyne (0.039 mL, 0.345 mmol, 2 equiv) was added to a
stirred orange solution of [Ph3SnCr(CO)3(η5-C7H9)] (0.10 g,
0.173 mmol) in n-hexane (150 mL) at room temperature. The
mixture was photolyzed for 2 h at room temperature and
monitored by IR spectroscopy until completion. Removal of
the solvent in vacuo and chromatography of the residue on
alumina (30 cm × 2.5 cm), loading with CH2Cl2 (2 mL), and
eluting with CH2Cl2-n-hexane (1:1), followed by evaporation
to dryness, gave 2b as an orange powder. Yield: 0.060 g, 88%.
ν
max(CO)/cm-1 (hex): 1954 (vs), 1872 (vs), and 1864 (vs). Anal.
Calcd for C22H28CrO3: C, 67.35; H, 7.14. Found: C, 67.10; H,
7.22.
1,2,3-Tr im eth yl-11-m eth ylen etr icyclo[5.3.1.04,10]u n deca-
2,5-d ien e (3a ). A solution of complex 2a (0.10 g, 0.30 mmol)
in acetonitrile (20 mL) was stirred under reflux for 30 min.
Evaporation of the solvent in vacuo and extraction of the
residue with n-hexane gave crude 3a as a pale yellow oil. Pure
3a was isolated following TLC on silica gel eluting with
n-hexane. Yield: 0.055 g (92%). GCMS (m/z for 3a ): 200 (M+),
185 (M+ - Me), 171, 157, 143, 129, 115, 105, 91, 77. The
presence of [Cr(CO)3(CH3CN)3] was confirmed by IR spectros-
copy of the reaction solution, νmax(CO)/cm-1 (CH3CN), 2074 (vs),
1950 (vs), and 1927 (vs), but this complex was not isolated.
1,2,3-Tr ie t h yl-11-(E )-e t h ylid e n e t r icyclo[5.3.1.04,10]-
u n d eca -2,5-d ien e (3b). A solution of complex 2b (0.07 g,
0.179 mmol) in acetonitrile (20 mL) was stirred under reflux
for 30 min. Evaporation of the solvent in vacuo and extraction
of the residue with hexane gave crude 3b as a pale yellow oil.
Pure 3b was isolated following TLC on silica gel eluting with
Exp er im en ta l Section
Gen er a l Meth od s. The preparation, purification, and
reactions of all complexes described were performed under an
+
+

3344 Organometallics, Vol. 15, No. 15, 1996
Chen et al.
n-hexane. Yield: 0.045 g (98%). GCMS (m/z for 3b): 256 (M+),
227 (M+ - Et), 199, 185, 171, 157, 143, 128, 115, 105, 91, 79.
2-Meth yl-1,3-d ip h en yl-11-m eth ylen etr icyclo[5.3.1.04,10]-
u n d eca -2,5-d ien e (4a ) a n d 3-Met h yl-2,3-d ip h en yl-11-
irradiated (quartz) with UV light for 6 h. Complex 8b was
isolated as a red orange powder following chromatography on
silica gel eluting with diethyl ether/n-hexane (1:49) for 2-3
min, followed by n-hexane. Yield (based on 7): 75 mg, 51%.
m et h ylen et r icyclo[5.3.1.04,10]u n d eca -2,5-d ien e
(4b ).
ν
max(CO) (hex): 1998 (vs), 1942 (vs). νmax(NO): 1677 (vs) cm-1
.
1-Phenyl-1-propyne (0.087 mL, 0.69 mmol) was added to a
stirred orange solution of [Ph3SnCr(CO)3(η5-C7H9)] (1a , 0.200
g, 0.345 mmol) in n-hexane (100 mL) at room temperature.
The mixture was photolyzed for 4 h at room temperature and
monitored by IR spectroscopy until 1a had been completely
consumed. The solvent was removed in vacuo, acetonitrile (20
mL) was added, and the solution was heated to reflux for 30
min. Filtration through Celite, removal of the acetonitrile in
vacuo, and purification (TLC, silica, eluate 1:3 hexane/CH2-
Cl2) gave 4a (0.085 g, 76%) and 4b (0.015 g, 13%) as colorless
oils, combined yield 0.100 g, 89%. 4a : m/z ) 324.1882. 4b:
m/z ) 324.1892; calcd for C25H24, m/z ) 324.1878.
5a ,b. 2-Butyne (0.02 g, 0.37 mmol) was added to a stirred
orange solution of [Ph3SnCr(CO)3(η5-C7H8R)] (1b , R ) 2-
methyldithiane, 0.130 g, 0.183 mmol) in n-hexane (150 mL)
at room temperature. The mixture was photolyzed for 4 h at
room temperature and monitored by IR spectroscopy until all
of 1b had been consumed. Removal of the solvent in vacuo,
chromatography of the residue on an alumina column (30 cm
× 2.5 cm), loading with CH2Cl2 (2 mL), and eluting initially
with n-hexane and then CH2Cl2/n-hexane (1:1), followed by
evaporation to dryness, gave the mixture of isomers 5a ,b as
an orange powder. Yield: 0.03 g, 35%. νmax(CO)/cm-1 (hex):
Anal. Calcd for C25H35CrNS2O3: C, 58.46; H, 6.87; N, 2.73.
Found: C, 58.71; H, 6.96; N, 2.66.
X-r a y Diffr a ction Stu d y. Crystallographic data are col-
lected in Table 2. An orange-red parallelepiped (0.48 × 0.28
× 0.24 mm) of 2b was mounted on a glass fiber with epoxy.
Twenty-nine automatically centered reflections (8.0 < θ <
19.7°) were used to refine the cell parameters using graphite-
monochromated Mo KR (0.710 73 Å) radiation on a Siemens
P4 diffractometer. Data were collected using the θ-2θ mode
with θ scan width ) 0.76° + KR separation and θ scan speed
3-60° min-1. A total of 4663 reflections were measured (1.5
< θ < 30°, (h,(k,+l), of which 4334 were unique (merging R
) 0.046) after absorption correction (face-indexed numerical)
(max, min transmission factors ) 0.870, 0.830)], giving 2890
with F > 4σ(F). The selected crystal had a linear absorption
coefficient µ(Mo KR) ) 6.2 cm-1. A Patterson map was used
to find the Cr and some of the light atoms, followed by
difference maps to find all other non-hydrogen atoms. Full-
matrix least-squares refinement proceeded with all non-
hydrogen atoms anisotropic and hydrogens in calculated
positions and riding on the atoms to which they are bound,
with Uiso for the exocyclic methine H (0.045 Å2), Uiso for the
ethyl-group methylene H’s (0.055 Å2), Uiso for the four methyl
groups’ H’s (0.076 Å2), and Uiso for the H’s on the cyclic ring
system (0.08 Å2). The weighting scheme w ) 1/[σ2(F) +
0.0007F2], with σ(Fo) from counting statistics gave satisfactory
agreement analyses. Final R and R′ values are 0.0535 and
0.0636, respectively, goodness of fit ) 1.13, maximum ∆/σ )
0.032, largest difference peak ) 0.37 e Å3, and largest
difference hole ) -0.44 e Å3. Data collection, cell refinement,
data reduction, structure solution, structure refinement, mo-
lecular graphics, and preparation of material for publication
used SHELXTL/PC.29,30
1959 (vs), 1876 (vs), and 1875 (vs). Anal. Calcd for C23H28
-
CrO3S2: C, 58.97; H, 5.98. Found: C, 59.07; H, 6.04.
5c a n d 6a ,b. 2-Butyne (0.036 g, 0.672 mmol) was added to
a stirred orange solution of [Ph3SnCr(CO)3(η5-C7H8CHPh2)]
(1c, 0.250 g, 0.336 mmol) in n-hexane (200 mL) at room
temperature. The mixture was photolyzed for 3 h at room
temperature and monitored by IR spectroscopy until all of 1c
had been consumed. Removal of the solvent in vacuo, chro-
matography of the residue on alumina (30 cm × 2.5 cm),
loading with CH2Cl2 (2 mL), and eluting with n-hexane gave
a mixture of the two organic isomeric products 6a ,b, 0.044 g,
yield 37%, following evaporation of solvent. Subsequent
elution with 1:1 n-hexane/CH2Cl2 and evaporation to dryness
gave a small amount of complex 5c as an orange powder.
Yield: 0.035 g, 21%. νmax(CO)/cm-1 (hex): 1959 (vs), 1876 (vs),
and 1874 (vs).
Ack n ow led gm en t. We are grateful to the Rutgers
Research Council for financial support.
Su p p or tin g In for m a tion Ava ila ble: Complete tables of
X-ray structural data, including positional and U parameters,
anisotropic thermal parameters, and bond lengths and angles
for 2b (5 pages). Ordering information is given on any current
masthead page.
8a . 2-Butyne (47 µL, 0.6 mmol) was added to a solution of
7 (0.105 g, 0.30 mmol) in toluene (50 mL) and the mixture
irradiated (quartz) with UV light for 2 h. Complex 8a was
isolated as
phy on silica gel eluting with diethyl ether/n-hexane (1:40).
Yield (based on 7): 60 mg, 44%.
max(CO) (hex): 2000 (vs),
1944 (vs) cm-1 max(NO): 1677 (vs) cm-1
Anal. Calcd for
21H27CrNS2O3: C, 55.14; H, 5.95; N, 3.06. Found: C, 55.39;
H, 6.07; N, 2.93.
a red-orange powder following chromatogra-
ν
OM960183R
.
ν
.
C
(29) Sheldrick, G. M. SHELXTL/ PC User’s Manual; Siemens
Analytical X-ray Instruments Inc.: Madison, WI, 1990.
(30) International Tables for X-Ray Crystallography; Kynoch
Press: Birmingham, U.K., 1974; Vol. 4.
8b. 3-Hexyne (64 µL, 0.58 mmol) was added to a solution
of 7 (0.100 g, 0.29 mmol) in toluene (50 mL) and the mixture
+
+