Reactivity studies of methylzirconocene phosphide complexes

Article abstract of DOI:10.1021/om960412+

The reaction of Cp₂ZrMe(PHR) with benzophenone, cyclohexanone, acetone, benzaldehyde, and benzophenone results in the insertion of the organic substrate into the Zr-P bond. In this way, the complexes Cp₂ZrMe(OCPh₂PH(C

Full text of DOI:10.1021/om960412+

Organometallics 1996, 15, 4509-4514
4509
Rea ctivity Stu d ies of Meth ylzir con ocen e P h osp h id e
Com p lexes
Tricia L. Breen and Douglas W. Stephan*
Department of Chemistry and Biochemistry, University of Windsor,
Windsor, Ontario, Canada N9B 3P4
Received May 28, 1996X
The reaction of Cp2ZrMe(PHR) with benzophenone, cyclohexanone, acetone, benzaldehyde,
and benzophenone results in the insertion of the organic substrate into the Zr-P bond. In
this way, the complexes Cp2ZrMe(OCPh2PH(C6H2-2,4,6-t-Bu3)) (3), Cp2ZrMe(OC6H10PH(C6H2-
2,4,6-t-Bu3)) (4), Cp2ZrMe(OCMe2PHR) (R ) (C6H2-2,4,6-t-Bu3) (5), R ) (C6H2-2,4,6-Me3) (8),
and Cp2ZrMe(NC(Ph)PH(C6H2-2,4,6-t-Bu3)) (6) were prepared. The species Cp2ZrMe(PH-
(C6H2-2,4,6-Me3)) (7) was also formed in the reaction of Cp2ZrMe2 with H2P(C6H2-2,4,6-Me3);
however, 7 reacted further with Cp2ZrMe2 to give the bimetallic species (Cp2ZrMe)2(µ-P(C6H2-
2,4,6-Me3) (9). In the analogous reaction of Cp2ZrMe2 with 1 equiv of H2P(C6H2-2,4,6-Me3),
the species (Cp2Zr)(Cp2ZrPH(C6H2-2,4,6-Me3))(µ-P6H2-2,4,6-Me3))(µ-η1-η5-C5H4) (11) was
obtained. Compound 11, which results from cyclopentadienyl C-H bond activation, was
also formed directly from degradation of the unstable terminal phosphinidene species
Cp2Zr(P(C6H2-2,4,6-Me3))(PMe3) (12). The implications of this chemistry are considered and
discussed. Compound 3, 9, and 11 have been characterized crystallographically.
In tr od u ction
quired a sterically demanding substituent on P. This
view was subsequently validated by the isolation of the
first mononuclear Zr-phosphinidene complex Cp2Zr-
(PR*)(PMe3) (R* ) C6H2-2,4,6-t-Bu3) (1).5 The most
expedious path to this species involves loss of methane
from the intermediate Cp2ZrMe(PH(C6H2-2,4,6-t-Bu3))
(2) in the presence of PMe3 (eq 1).6 A wide range of
The intense study of early metal-ligand multiple
bonds is motivated not only by questions of structure
and bonding but also by issues of stability and reactiv-
ity.1 These systems offer both new reactivity patterns
and new reagents for the synthesis of compounds
incorporating heteroatoms. While landmark contribu-
tions in this area have dealt with early metal oxide,
sulfide, and imide derivatives,2 we and others3 have
focused on early metal phosphinidene species (MdPR).
Several years ago, we explored a variety of approaches
employing P-H bond activation for the synthesis of Zr-
phosphides and dimeric phosphinidene derivatives.4
These studies suggested that the stabilization of a
monometallic terminal Zr-phosphinidene complex re-
(1)
reactions in which 1 effects both intra- and intermo-
lecular phosphinidene group transfer reactions have
been examined.6
More recently, we have shown that 1 also provides
access to phosphametallacyclobutenes via [2 + 2] cyclo-
addition reactions with alkynes.7 The resulting metalla-
cycles are reactive in their own right and have been
shown to be useful synthons for a variety of cyclic
organophosphorus derivatives.8 In this paper, we ex-
amine reactions of intermediate methylzirconocene
phosphide complexes such as 2 as well as related species
with less sterically demanding substituents. The Zr-P
bonds of these species undergo insertion reactions with
* To whom correspondence should be addressed. E-mail: Stephan@
UWindsor.ca.
X Abstract published in Advance ACS Abstracts, September 15, 1996.
(1) Nugent, W. A.; Mayer, J . M. Metal-Ligand Multiple Bonds; J ohn
Wiley & Sons: New York, 1988.
(2) Lead references on oxo, sulfido, and imido complexes of the early
metals include: (a) Walsh, P. J .; Hollander, F. J .; Bergman, R. G. J .
Am. Chem. Soc. 1988, 110, 8729. (b) Walsh, P. J .; Hollander, F. J .;
Bergman, R. G. Organometallics 1993, 12, 3705. (c) Walsh, P. J .;
Carney, M. J .; Bergman, R. G. J . Am. Chem. Soc. 1991, 113, 6343. (d)
Walsh, P. J .; Hollander, F. J .; Bergman, R. G. J . Organomet. Chem.
1992, 428, 13. (e) Carney, M. J .; Walsh, P. J .; Hollander, F. J .;
Bergman, R. G. J . Am. Chem. Soc. 1989, 111, 8751. (f) Carney, M. J .;
Walsh, P. J .; Bergman, R. G. J . Am. Chem. Soc. 1990, 112, 6426. (g)
Parkin, G.; Bercaw, J . E. J . Am. Chem. Soc. 1989, 111, 391. (h)
Whinnery, L. L.; Hening, L. M.; Bercaw, J . E. J . Am. Chem. Soc. 1991,
113, 7575. (i) Bennett, J . L.; Wolczanski, P. T. J . Am. Chem. Soc. 1994,
116, 2179. (j) Schaller, C. P.; Bonanno, J . B.; Wolczanski, P. T. J . Am.
Chem. Soc. 1994, 116, 4133. (k) Cummins, C. C.; Schaller, C. P.; Van
Duyne, G. D.; Wolczanski, P. T.; Chan, A. W. E.; Hoffmann, R. J . Am.
Chem. Soc. 1991, 113, 2985. (l) Banaszak Hall, M. M.; Wolczanski, P.
T. J . Am. Chem. Soc. 1992, 114, 3854. (m) Winter, C. H.; Sheridan,
P. H.; Lewkebandara, T. S.; Heeg, M. J .; Proscia, J . W. J . Am. Chem.
Soc. 1992, 114, 1095. (n) Hill, J . E.; Fanwick, P. E.; Rothwell, I. P.
Inorg. Chem. 1989, 28, 3602. (o) Profilet, R. D.; Zambrano, C. H.;
Fanwick, P. E.; Nash, J . J .; Rothwell, I. P. Inorg. Chem. 1990, 29, 4364.
(p) Hill, J . E.; Profilet, R. D.; Fanwick, P. E.; Rothwell, I. P. Angew.
Chem., Int. Ed. Engl. 1990, 29, 664. (q) Roesky, H. W.; Voeler, H.;
Witt, M.; Noltmeyer, M. Angew. Chem., Int. Ed. Engl. 1990, 29, 669.
(r) McGrane, P. L.; J ensen, M.; Livinghouse, T. J . Am. Chem. Soc. 1992,
114, 5459. (s) Cundari, T. R. J . Am. Chem. Soc. 1992, 114, 7879.
(3) (a) Hitchcock, P. B.; Lappert, M. F.; Leung, W. P. J . Chem. Soc.,
Chem. Commun. 1987, 1282. (b) Cowley, A. H.; Pellerin, B.; Atwood,
J . L.; Bott, S. G. J . Am. Chem. Soc. 1990, 112, 6734. (c) Mathey, F.
Acc. Chem. Res. 1992, 25, 90. (d) Mathey, F. Angew. Chem., Int. Ed.
Engl. 1993, 32, 756. (e) Nakazawa, H.; Buhro, W. E.; Bertand, G.;
Gladysz, J . A. Inorg. Chem. 1984, 23, 3431. (f) Cummins, C. C.;
Schrock, R. R.; Davis, W. M. Angew. Chem., Int. Ed. Engl. 1993, 32,
756. (g) Bonanno, J . B.; Wolczanski, P. T.; Lobkovsky, E. B. J . Am.
Chem. Soc. 1994, 116, 11159.
(4) (a) Ho, J .; Stephan, D. W. Organometallics 1991, 10, 3001. (b)
Ho, J .; Stephan, D. W. Organometallics 1992, 11, 1014. (c) Ho, J .; Hou,
Z.; Drake, R. J .; Stephan, D. W. Organometallics 1993, 12, 3145.
(5) Hou, Z.; Breen, T. L.; Stephan, D. W. Organometallics 1993, 12,
3158.
(6) Breen, T. L.; Stephan, D. W. J . Am. Chem. Soc. 1995, 117, 11914.
(7) Breen, T. L.; Stephan, D. W. J . Am. Chem. Soc. 1996, 118, 4204.
(8) Breen, T. L.; Stephan, D. W., unpublished results.
S0276-7333(96)00412-8 CCC: $12.00 © 1996 American Chemical Society

4510 Organometallics, Vol. 15, No. 21, 1996
Breen and Stephan
CH), 126.7 (s, arom CH), 126.3 (s, arom CH), 125.4 (s, arom
CH), 122.3 (s, arom CH), 111.2 (s, Cp), 110.9 (s, Cp), 94.1 (d,
|J | ) 18.9 Hz, OC), 38.6 (s, C(CH3)3), 37.9 (s, C(CH3)3), 34.6 (s,
C(CH3)3), 34.3 (d, |J | ) 10.7 Hz, C(CH3)3), 33.8 (s, C(CH3)3),
31.5 (s, C(CH3)3), 22.5 (s, Me). 31P NMR (25 °C, C6D6): δ -8.6
(d, |J P-H| ) 244.1 Hz). Anal. Calcd for C42H53OPZr: C, 72.47;
H, 7.67. Found: C, 72.30; H, 7.45. (4) Yield: 72% (by 1H
NMR). 1H NMR (25 °C, C6D6): δ 7.39 (m, 2H, ArH), 5.93 (s,
5H, Cp), 5.91 (s, 5H, Cp), 4.79 (d, |J P-H| ) 222.5 Hz, 1H, PH),
organic substrates in preference to methane elimination.
Furthermore, when methane elimination is allowed to
proceed, diminished steric demands of the substituent
on P results in a highly reactive phosphinidene species
which effects cyclopentadienyl C-H bond activation.
Exp er im en ta l Section
Gen er a l Da ta . All preparations were done under an
atmosphere of dry, O2-free N2 employing either Schlenk line
techniques or a Vacuum Atmospheres inert atmosphere glove-
box. Solvents were reagent grade, distilled from the appropri-
ate drying agents under N2 and degassed by the freeze-thaw
method at least three times prior to use. All organic reagents
were purified by conventional methods. 1H and 13C{1H} NMR
spectra were recorded on a Bruker AC-300 operating at 300
and 75 MHz, respectively. 31P and 31P{1H} NMR spectra were
recorded on a Bruker AC-200 operating at 81 MHz. Trace
amounts of protonated solvents were used as references, and
chemical shifts are reported relative to SiMe4 and 85% H3PO4,
respectively. Yields obtained by 1H NMR were determined in
reference to a CH2Cl2 internal standard which was introduced
by employing a concentric NMR tube insert. Low- and high-
resolution EI mass spectral data were obtained employing a
Kratos Profile mass spectrometer outfitted with a N2 glovebag
enclosure for the inlet port. Combustion analyses were
performed by Galbraith Laboratories Inc. Knoxville, TN, or
Schwarzkopf Laboratories, Woodside, NY. Glass reaction
vessels fitted with ground glass joints and Teflon stopcocks
are referred to as “bombs”. PH2(C6H2-2,4,6-t-Bu3) and PH2-
(C6H2-2,4,6-Me3) were purchased from the Quantum Design
Chemical Co. All other reagents were purchased from the
Aldrich Chemical Co. Cp2ZrMe2,9 Cp2ZrMeCl10, Cp2Zr(P(C6H2-
2,4,6-t-Bu3))(PMe3) (1),5,6 Cp2ZrMe(PH(C6H2-2,4,6-t-Bu3)) (2),6
(Cp2ZrCl)2(µ-P(C6H2-2,4,6-Me3)) (10),4 and LiHP(C6H2-2,4,6-t-
Bu3)‚3THF11 were prepared by literature methods. The pro-
cedure of Power et al.12 was employed to prepare Li2P(C6H2-
2,4,6-Me3). In all instances, Ar refers to the (C6H2-2,4,6-t-Bu3)
group and Mes refers to the (C6H2-2,4,6-Me3) group.
t
t
2.2-1.1 (m, 10H, CyH), 1.67 (s, 9H, Bu), 1.54 (s, 9H, Bu),
1.28 (s, 9H, tBu), 0.42 (s, 3H, Me). 13C{1H} NMR (25 °C,
C6D6): δ 157.2 (br s, quat), 148.6 (s, quat), 132.2 (d, |J | ) 38.9
Hz, quat), 122.0 (s, arom CH), 110.8 (s, Cp), 110.5 (s, Cp), 87.0
(d, |J | ) 9.5 Hz, OC), 39.6 (d, |J | ) 19.0 Hz, CH2), 38.1 (d, 35.4
(d, |J | ) 11.8 Hz, C(CH3)3), 34.7 (s, C(CH3)3), 34.3 (s, C(CH3)3),
31.2 (s, C(CH3)3), 25.6 (s, CH2), 22.6 (s, CH2), 21.9 (d, |J | ) 9.7
Hz, CH2), 20.7 (s, Me). 31P NMR (25 °C, C6D6): δ -24.9 (d,
|J P-H| ) 222.3 Hz). HRMS (EI) m/e: calcd for C35H53OPZr
1
595.2642; found 595.2630 (M+ - CH3). (5) Yield: 73% (by H
NMR) 1H NMR (25 °C, C6D6): δ 7.44 (s, 2H, ArH), 5.87 (s,
5H, Cp), 5.82 (s, 5H, Cp), 5.01 (d, |J P-H| ) 228.7 Hz, 1H, PH),
t
t
t
1.69 (s, 9H, Bu), 1.53 (s, 9H, Bu), 1.29 (s, 9H, Bu), 1.04 (d,
3
3
| J P-H| ) 10.9 Hz, 3H, Me), 0.82 (d, | J P-H| ) 3.8 Hz, 3H, Me),
0.36 (s, 3H, ZrMe). 13C{1H} NMR (25 °C, C6D6): δ 156.6 (s,
quat), 154.3 (s, quat), 148.8 (s, quat), 132.9 (d, |J | ) 38.3 Hz,
quat), 121.9 (s, arom CH), 121.8 (s, arom CH), 110.5 (s, Cp),
110.4 (s, Cp), 84.7 (d, |J | ) 12.2 Hz, OC), 38.2 (s, C(CH3)3),
38.1 (s, C(CH3)3), 35.0 (d, |J | ) 11.9 Hz, C(CH3)3), 33.9 (s,
C(CH3)3), 31.3 (s, C(CH3)3), 19.9 (s, Me). 31P NMR (25 °C,
C6D6): δ -30.1 (d, |J P-H| ) 229.1 Hz). HRMS (EI) m/e: calcd
for C32H49OPZr 555.2329, found: 555.2334 (M+ - CH3). (6)
1
Yield: 56% (by H NMR). 1H NMR (25 °C, C6D6): δ 7.62 (d,
4
| J P-H| ) 2.1 Hz, 1H, ArH), 7.51 (br, 1H, ArH), 7.17-7.09 (m,
5H, PhH), 6.17 (d, |J P-H| ) 234.3 Hz, 1H, PH), 5.60 (s, 5H,
Cp), 5.58 (s, 5H, Cp), 1.73-1.49 (br, 18H, o-tBu), 1.44 (s, 9H,
p-tBu), -0.25 (br s, 3H, Me). 13C{1H} NMR (25 °C, C6D6): δ
177.9 (d, |J | ) 30.5 Hz, NdC), 150.1 (s, quat), 142.2 (d, |J | )
34.1 Hz, quat), 129.3 (s, arom CH), 128.1 (s, arom CH), 125.8
(s, arom CH), 122.3 (br s, arom CH), 108.0 (s, Cp), 107.8 (s,
Cp), 38.1 (br s, o-C(CH3)3), 35.1 (s, p-C(CH3)3), 33.5 (br s,
o-C(CH3)3), 33.4 (br s, o-C(CH3)3), 31.5 (s, p-C(CH3)3), 17.2 (br
s, Me). 31P NMR (25 °C, C6D6): δ -44.8 (d, |J P-H| ) 233.9
Hz). HMRS (EI) m/e: calcd for C36H48NPZr 615.2567, m/e
found 615.2582. (8) Yield: 73% (by 1H NMR). 1H NMR (25
°C, C6D6): δ 6.80 (s, 2H, Mes-H), 5.83 (s, 5H, Cp), 5.82 (s, 5H,
Cp), 4.42 (d, |J P-H| ) 216.5 Hz, 1H, PH), 2.50 (s, 6H, o-Me),
Syn th esis of Cp 2Zr Me(OCP h 2P H(C6H2-2,4,6-t-Bu 3)) (3),
Cp 2Zr Me(OC6H 10P H (C6H 2-2,4,6-t-Bu 3)) (4), Cp 2Zr Me-
(OCMe2P H(C6H2-2,4,6-t-Bu 3)) (5), Cp 2Zr Me(NC(P h )P H-
(C6H2-2,4,6-t-Bu 3)) (6), an d Cp2Zr Me(OCMe2P H(C6H2-2,4,6-
Me3)) (8). Compounds 3-6 and 8 were prepared through
similar routes with the appropriate substitutions of phosphide
and organic substrate; thus only one representative procedure
is given. To a benzene solution of Cp2ZrMeCl (136 mg, 0.5
mmol) and benzophenone (91 mg, 0.5 mmol) was added a
benzene solution of LiHP(C6H2-2,4,6-t-Bu3)‚THF (250 mg, 0.5
mmol). The resulting solution turned orange and then im-
mediately turned a very pale yellow. After standing for 2 h,
the solvent was removed in vacuo and the product was
extracted into pentane. Filtration was followed by a reduction
in the volume of the solution under reduced pressure. Color-
less crystals formed over 12 h at room temperature and were
isolated by filtration. (3) Yield: 289 mg (83%). 1H NMR (25
°C, C6D6): δ 7.49 (m, 2H, PhH), 7.33 (m, 1H, PhH), 7.18 (m,
1H, PhH), 7.00 (m, 6H, PhH), 6.72 (m, 2H, PhH), 5.86 (s, 5H,
Cp), 5.71 (s, 5H, Cp), 5.67 (d, |J P-H| ) 244.6 Hz, 1H, PH), 1.42
3
2.07 (s, 3H, p-Me), 1.29 (d, | J P-H| ) 5.5 Hz, 3H, Me), 1.24 (d,
3
| J P-H| ) 11.8 Hz, 3H, Me), 0.38 (s, 3H, ZrMe). 13C{1H} NMR
(25 °C, C6D6): δ 142.4 (d, |J | ) 10.4 Hz, quat), 137.8 (s, quat),
130.6 (d, |J | ) 24.1 Hz, quat), 129.3 (s, arom CH), 110.5 (s,
Cp), 83.2 (d, |J | ) 7.6 Hz, OC), 33.1 (d, |J | ) 4.1 Hz, Me)),
31.8 (s, Me), 24.1 (d, |J | ) 11.7 Hz, Me), 20.8 (s, Me), 19.2 (s,
Me). 31P NMR (25 °C, C6D6): δ -48.9 (d, |J P-H| ) 217.7 Hz).
Syn th esis of (Cp 2Zr Me)2(µ-P (C6H2-2,4,6-Me3)) (9). To a
toluene solution of Cp2ZrMe2 (503 mg, 2.0 mmol) was added a
toluene solution of H2P(C6H2-2,4,6-Me3) (152 mg, 1.0 mmol).
The colorless solution was placed in a bomb and heated at 110
°C for 5 h, during which time it became a deep indigo. After
cooling to room temperature, the volume was reduced and the
solution allowed to stand for 3 days. Large, extremely air-
sensitive dark blue crystals formed and were isolated by
filtration. Yield: 511 mg (82%). 1H NMR (25 °C, C6D6): δ
7.08 (s, 2H, ArH), 5.66 (s, 20H, Cp), 2.35 (s, 6H, o-Me), 2.27
t
t
t
(s, 9H, Bu), 1.31 (s, 9H, Bu), 1.25 (s, 9H, Bu), 0.66 (s, 3H,
Me). 13C{1H} NMR (25 °C, C6D6): δ 157.0 (s, quat), 156.6 (d,
|J | ) 17.1 Hz, quat), 149.4 (s, quat), 147.0 (d, |J | ) 21.5 Hz,
quat), 143.9 (s, quat), 130.9 (d, |J | ) 44.6 Hz, quat), 129.0 (d,
|J | ) 8.3 Hz, arom CH), 127.3 (s, arom CH), 126.8 (s, arom
3
(s, 3H, p-Me), 0.24 (d, | J P-H| ) 3.1 Hz, 6H, ZrMe). 13C{1H}
NMR (25 °C, C6D6): δ 138.1 (s, quat), 134.4 (s, quat), 128.3 (s,
arom CH), 109.8 (s, Cp), 27.9 (s, Me), 26.6 (d, |J | ) 9.0 Hz,
Me), 20.9 (s, Me). 31P NMR (25 °C, C6D6): δ 303.2 (s). Anal.
Calcd for C31H37PZr: C, 59.76; H, 5.99. Found: C, 59.67; H,
5.88.
(9) (a) Hunter, W. E.; Hrncir, D. C.; Vann Byrum, R.; Penttila, R.
A.; Atwood, J . L. Organometallics 1983, 2, 750. (b) Samuel, E.; Rausch,
M. D. J . Am. Chem. Soc. 1973, 95, 6263.
(10) J ordan, R. F. J . Organomet. Chem. 1985, 294, 321.
(11) Cowley, A. H.; Kilduff, J . E.; Newman, T. H.; Pakulski, M. J .
Am. Chem. Soc. 1982, 104, 5820.
Syn t h esis of (Cp 2Zr )(Cp 2Zr P H (C6H 2-2,4,6-Me3))(µ-
P (C6H2-2,4,6-Me3))(µ-η1:η5-C5H4) (11). (i) To a toluene solu-
tion of Cp2ZrMe2 (503 mg, 2.0 mmol) was added a toluene
(12) Hope, H.; Pestana, D. C.; Power, P. P. Angew. Chem., Int. Ed.
Engl. 1991, 30, 691.

Methylzirconocene Phosphide Complexes
Organometallics, Vol. 15, No. 21, 1996 4511
Ta ble 1. Cr ysta llogr a p h ic Da ta
3
9
11
formula
formula weight
crystal size (mm)
a, Å
b, Å
c, Å
C42H53OPZr
696.07
C31H37PZr2
623.05
C38H42P2Zr2
743.14
0.26 × 0.31 × 0.43
11.062(2)
18.456(2)
18.629(2)
97.37(1)
3771.8(8)
monoclinic
Cc
4
3.63
1.23
24
0.23 × 0.25 × 0.26
19.253(6)
7.761(2)
20.197(6)
107.88(2)
2872(1)
monoclinic
P21/n
4
7.98
1.44
24
0.35 × 0.27 × 0.33
13.310(6)
20.958(9)
13.299(3)
93.22(3)
2704(3)
monoclinic
P21/n
4
6.72
1.33
24
â, deg
vol, Å3
crystal system
space group
Z
µ (cm-1
)
d(calc) (g/cm3)
temp (°C)
λ (Å)
0.71069 Mo KR
0.71069 Mo KR
0.71069 Mo KR
scan speed (deg/min)
scan range (deg)
8
8
8
1.0 above KR1
1.0 below KR1
0.5
4.5-50, hk(l
3445
1.0 above KR1
1.0 below KR1
0.5
4.5-50, hk(l
5063
1.0 above KR1
1.0 below KR1
0.5
4.5-50, hk(l
6728
bkgd/scan time ratio
2θ, index range
data collected
unique data Fo > 3σ(Fo
variables
2
2
)
1378
194
2422
297
1907
289
transmission factors
0.889-1.000
0.916-1.000
0.659-1.000
Ra (%)a
3.50
4.65
8.10
a
Rw (%)
5.22
5.63
8.02
goodness of fit
1.51
1.81
2.04
a
2
R ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) [∑(|Fo| - |Fc|)2/∑|Fo| ]0.5
.
solution of H2P(C6H2-2,4,6-Me3) (304 mg, 2.0 mmol). The
colorless solution was placed in a bomb and heated at 110 °C
for 5 h, during which time it became dark brown. After cooling
to room temperature, the toluene was removed under reduced
pressure and the product was then dissolved in diethyl ether.
Upon standing overnight, dark brown crystals formed which
were isolated by filtration. Yield: 520 mg (70%). (ii) To a
benzene suspension of (Cp2ZrCl)2(µ-P(C6H2-2,4,6-Me3)) (10)
(322 mg, 0.5 mmol) was added excess PMe3 and a benzene
suspension of Li2P(C6H2-2,4,6-Me3) (90 mg, 0.55 mmol). The
mixture was stirred vigorously for 12 h, after which time it
was filtered. 31P NMR of the reaction mixture showed the
clean formation of Cp2Zr(P(C6H2-2,4,6-Me3))(PMe3) (12). After
filtration, the solvent was removed in vacuo and the product
dissolved in diethyl ether. Upon standing overnight, dark
brown crystals formed and were isolated by filtration. Yield:
238 mg (64%). 1H NMR (25 °C, C6D6): δ 7.03 (s, 1H, ArH),
routine. These data were used to determine the crystal
systems. Automated Laue system check routines around each
axis were consistent with the crystal system. Ultimately, 25
reflections (20° < 2θ < 25°) were used to obtain the final lattice
parameters and the orientation matrices. Crystal data are
summarized in Table 1. The observed extinctions were
consistent with the space groups. The data sets were collected
in three shells (4.5° < 2θ < 50.0°), and three standard
reflections were recorded every 197 reflections. Fixed scan
rates were employed. Up to four repetitive scans of each
reflection at the respective scan rates were averaged to ensure
meaningful statistics. The number of scans of each reflection
was determined by the intensity. The intensities of the
standards showed no statistically significant change over the
duration of the data collections. The data were processed
using the TEXSAN crystal solution package operating on a
SGI Challenger mainframe with remote X-terminals. The
reflections with Fo > 3σFo were used in the refinements.
Str u ctu r e Solu tion a n d Refin em en t. Non-hydrogen
atomic scattering factors were taken from the literature
tabulations.13,14 The Zr atom positions were determined using
direct methods employing the SHELX-86 direct methods
routines. The remaining non-hydrogen atoms were located
from successive difference Fourier map calculations. The
refinements were carried out by using full-matrix least-squares
techniques on F, minimizing the function ω(|Fo| - |Fc|)2, where
the weight ω is defined as 4Fo2/2σ(Fo2) and Fo and Fc are the
observed and calculated structure factor amplitudes. In the
final cycles of each refinement, the number of non-hydrogen
atoms that were assigned anisotropic temperature factors was
limited so as to maintain a reasonable data:variable ratio.
Empirical absorption corrections were applied to the data sets
based on ψ-scan data. Hydrogen atom positions were calcu-
lated and allowed to ride on the carbon to which they are
bonded by assuming a C-H bond length of 0.95 Å. Hydrogen
atom temperature factors were fixed at 1.10 times the isotropic
temperature factor of the carbon atom to which they are
bonded. The hydrogen atom contributions were calculated but
3
2
2
6.95 (s, 1H, ArH), 6.92 (s, 2H, Mes-H), 6.50 (br d, | J P-H| ) 7.1
Hz, 1H, CH), 6.29 (s, 5H, Cp), 5.98 (br s, 1H, CH), 5.66 (s, 5H,
Cp), 5.25 (s, 5H, Cp), 5.12 (br, 1H, CH), 4.65 (br, 1H, CH),
1
3
3.27 (dd, | J P-H| ) 203.5 Hz, | J P-H| ) 10.8 Hz, 1H, PH), 2.69
(s, 3H, Me), 2.49 (s, 6H, o-Me), 2.40 (s, 3H, Me), 2.25 (s, 3H,
Me), 2.23 (s, 3H, Me). 13C{1H} NMR (25 °C, C6D6): δ 175.1
(s, quat), 148.1 (d, |J | ) 11.9 Hz, quat), 145.3 (d, |J | ) 32.4
Hz, quat), 141.1 (d, |J | ) 9.2 Hz, quat), 138.5 (d, |J | ) 7.8 Hz,
quat), 138.0 (s, quat), 135.8 (s, quat), 132.7 (s, quat), 128.8 (s,
arom CH), 128.6 (s, arom CH), 128.1 (s, arom CH), 111.2 (s,
arom CH), 110.2 (d, |J | ) 4.5 Hz, Cp), 109.8 (s, Cp), 108.8 (s,
arom CH), 106.3 (s, Cp), 106.1 (s, arom CH), 106.0 (s, arom
CH), 25.2 (s, Me), 25.1 (s, Me), 24.1 (br s, Me), 20.9 (s, Me),
20.8 (s, Me). 31P NMR (25 °C, C6D6): δ 395.4 (d, |J P-P| ) 29.1
1
Hz), -84.2 (dd, | J P-H| ) 203.0 Hz, |J P-P| ) 29.0 Hz. Anal.
Calcd for C38H42P2Zr2: C, 61.42; H, 5.70; Found: C, 61.34; H,
5.67.
X-r a y Da ta Collection a n d Red u ction . X-ray-quality
crystals of 3, 9, and 11 were obtained directly from the
preparation as described above. The crystals were manipu-
lated and mounted in capillaries in a glovebox, thus maintain-
ing a dry, O2-free environment for each crystal. Diffraction
experiments were performed on a Rigaku AFC5 diffractometer
equipped with graphite-monochromatized Mo KR radiation.
The initial orientation matrix was obtained from 20 machine-
centered reflections selected by an automated peak search
(13) (a) Cromer, D. T.; Mann, J . B. Acta Crystallogr. Sect. A: Cryst.
Phys. Theor. Gen. Crystallogr. 1968, A24, 324. (b) Ibid. 1968, A24,
390.
(14) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Knoch Press: Birmingham, England, 1974.

4512 Organometallics, Vol. 15, No. 21, 1996
Breen and Stephan
Sch em e 1
F igu r e 1. ORTEP drawing of 3: 30% thermal ellipsoids
are shown. Zr(1)-O(1), 1.926(9) Å; Zr(1)-C(11), 2.27(2) Å;
P(1)-C(12), 1.99(1) Å; P(1)-C(25), 1.83(1) Å. O(1)-Zr(1)-
C(11), 95.9(5)°; C(12)-P(1)-C(25), 109.7(6)°; Zr(1)-O(1)-
C(12), 167.7(9)°.
not refined. In the case of 3, the hydrogen atom on P was
located and included in the final cycle of refinement and the
correct enantiomorph was determined by refinement of the
enantiomorphs of the model. The decay of the crystal of 9 was
significant (∼20%) but approximately linear during data
collection. Although a decay correction was applied to the
data, the inferior quality of the data is reflected in the poor
agreement of chemically similar Zr-C distances of the Zr-
methyl groups as well as the thermal parameters of C(31).
Nonetheless, the connectivity of 9, is affirmed by the solution.
In the case of 11, the phosphide hydrogen atom could not be
located. The final values of R, Rw, and the maximum ∆/σ on
any of the parameters in the final cycles of the refinements
are given in Table 1. The locations of the largest peaks in the
final difference Fourier map calculation as well as the mag-
nitude of the residual electron densities in each case were of
no chemical significance. Positional parameters, hydrogen
atom parameters, thermal parameters, and bond distances and
angles have been deposited as supporting information.
the NdC, while the PsC coupling constant of 30.5 Hz
confirmed the formation a PsC bond. These data verify
the formulation of 6 as Cp2ZrMe(NC(Ph)PH(C6H2-2,4,6-
t-Bu3)).
The formulation of the above insertion products was
confirmed crystallographically for compound 3 (Figure
1). The geometry about Zr is typical of zirconocene
derivatives. The Zr-methyl carbon distance is 2.27(2)
Å, while the Zr-O bond is 1.926(9) Å. The O-Zr-C
angle of 95.9(5)° is slightly less than the O-Zr-O angle
seen in the dialkoxide complex Cp2Zr(µ-OCH2CMe2-
CH2O)2ZrCp2.15 The Zr-O-C angle of 167.7(9)° is
similar to that seen in related Zr-alkoxide derivatives,
suggesting some degree of Zr-O π-bonding. Mechanis-
tically, it is noteworthy that independent generation of
2 and subsequent addition of ketone afforded the
identical products described above. As well, mixture of
LiPH(C6H2-2,4,6-t-Bu3) with ketone resulted in no reac-
tion, thus precluding formation of 3-5 from a reagent
of the form LiOCR2PH(C6H2-2,4,6-t-Bu3). These data
as well as the structural studies confirm that the above
species are formed via insertion of benzophenone into
the Zr-P bond. The result is a secondary phosphorus
center which exhibits a typical pseudopyramidal geom-
etry.
The analogous methylzirconocene phosphide complex
Cp2ZrMe(PH(C6H2-2,4,6-Me3)) (7) was generated from
the reaction of Cp2ZrMeCl with LiPH(C6H2-2,4,6-Me3),
as evidenced by the 31P NMR resonance at -6.0 ppm
(|J P-H| ) 228.5 Hz). Although this species is unstable
it too undergoes insertion of acetone yielding the mesityl
analogue of 5 (i.e., Cp2ZrMe(OCMe2PH(C6H2-2,4,6-Me3))
(8)) (Scheme 1). The instability of 7 was demonstrated
by monitoring the reaction of Cp2ZrMeCl with LiPH-
(C6H2-2,4,6-Me3) by 31P NMR spectroscopy. After 30
min at 25 °C the resonance attributable to 7 began to
diminish, and a resonance at 303 ppm along with the
resonance attributable to the free phosphine H2P(C6H2-
2,4,6-Me3) appeared concurrently. These data sug-
gested the possibility that 7 underwent a bimolecular
reaction to afford a phosphinidene bridged complex by
elimination of an equivalent of phosphine (Scheme 2).
Attempts to confirm this scenario via isolation of this
new complex were unsuccessful, as NMR data confirmed
Resu lts a n d Discu ssion
Previous work has shown that the reaction of Cp2-
ZrMeCl with LiPH(C6H2-2,4,6-t-Bu3) yields Cp2ZrMe-
(PH(C6H2-2,4,6-t-Bu3)) (2),5,6 which undergoes loss of
methane over a 3-day period and yields 1 in the
presence of PMe3. In the present study, 2 was gener-
ated in the presence of benzophenone via addition of
the phosphide to a solution of Cp2ZrMeCl and benzo-
phenone. The resulting solution turned orange, pre-
sumably a result of the formation of 2, and then
immediately became very pale yellow. After workup,
colorless crystals of the product 3 were isolated in 83%
yield. The 31P NMR spectrum of 3 showed a single
resonance at -8.6 ppm which exhibited P-H coupling
of 244.1 Hz, indicative of the phosphide moiety. The
1
observation of a H NMR singlet at 0.66 ppm suggested
the presence of a Zr-Me fragment. Furthermore, two
1
resonances in both the H and 13C NMR spectra may
be attributed to diastereotopic cyclopentadienyl groups
which result from the presence of the chiral P center.
Collectively, these data support the formulation of 3 as
Cp2ZrMe(OCPh2PH(C6H2-2,4,6-t-Bu3)). In a similar
fashion, generation of 2 in the presence of cyclohexanone
or acetone afforded the related complexes Cp2ZrMe-
(OC6H10PH(C6H2-2,4,6-t-Bu3)) (4) and Cp2ZrMe(OCMe2-
PH(C6H2-2,4,6-t-Bu3)) (5), respectively, while the pres-
ence of benzonitrile yielded the product 6 (Scheme 1).
The 31P NMR spectrum of 6 showed a single resonance
at -44.8 with a P-H coupling constant of 233.9 Hz, in
agreement with the presence of a secondary phosphide
moiety. The 13C doublet at 177.9 ppm is attributed to
(15) Stephan, D. W. Organometallics 1990, 9, 2718.

Methylzirconocene Phosphide Complexes
Organometallics, Vol. 15, No. 21, 1996 4513
Sch em e 2
further reactions had produced a complex mixture of
unidentified products. In an effort to further explore
and clarify the effect of less sterically demanding
substituents, alternative synthetic pathways were sought.
Earlier reports by Hey et al.16 described the synthesis
of Cp2Zr(PPh)3 from the reaction of Cp2ZrMe2 with
H2PPh (eq 2). In a similar fashion, heating a colorless
F igu r e 2. ORTEP drawing of 9: 30% thermal ellipsoids
are shown. Zr(1)-P(1), 2.606(3) Å; Zr(2)-P(1), 2.646(3) Å;
P(1)-C(21), 1.84(1) Å. Zr(1)-P(1)-Zr(2), 136.6(1)°; P(1)-
Zr(1)-C(31), 99.4(2)°; P(1)-Zr(2)-C(30), 98.1(3)°.
(2)
mixture of 2 equiv of Cp2ZrMe2 with H2P(C6H2-2,4,6-
Me3) at 110 °C for 5 h resulted in a color change to deep
indigo. After cooling and standing for 3 days, large dark
blue crystals of 9 were isolated in 82% yield. The 31P
NMR spectrum of 9 showed a single resonance at 303
ppm. This chemical shift together with the absence of
P-H coupling suggested a phosphinidene bridged com-
plex, while the H and 13C NMR data were consistent
1
F igu r e 3. ORTEP drawing of 11: 30% thermal ellipsoids
are shown. Zr(1)-P(1), 2.586(7) Å; Zr(1)-C(6), 2.49(3) Å;
Zr(2)-P(1), 2.576(7) Å; Zr(2)-P(2) 2.718(7) Å. P(1)-Zr(1)-
C(6), 88.9(7)°; P(1)-Zr(2)-P(2), 96.5(2)°; Zr(1)-P(1)-Zr(2),
93.3(2)°.
with the presence of two Zr-bound methyl groups.
Compound 9 was thus formulated as (Cp2ZrMe)2(µ-
P(C6H2-2,4,6-Me3) (Scheme 2). Despite the extreme air-
sensitivity of 9, as well as a problem of crystal decay
during data collection, X-ray crystallographic data did
confirm the proposed connectivity (Figure 2). Two
Cp2ZrMe units are bridged by the mesitylphosphinidene
unit with Zr-P distances of 2.606(3) and 2.646(3) Å. The
Zr-P-Zr angle is 136.6(1)°, while the sum of the angles
about P indicate its planar geometry, similar to that
observed for the closely related species (Cp2ZrCl)2(µ-
P(C6H2-2,4,6-Me3) (10).4
the 13C NMR data, were in accord with the formulation
of 11 as (Cp2Zr)(Cp2ZrPH(C6H2-2,4,6-Me3))(µ-P(C6H2-
2,4,6-Me3))(µ-η1:η5-C5H4) (Scheme 2).
The formulation of 11 was confirmed crystallographi-
cally (Figure 3). The two Zr centers are bridged by a
phosphinidene moiety as well as an η1:η5-cyclopenta-
dienyl ring. The bridging Zr-P distances at 2.586(7)
and 2.576(7) Å are slightly shorter than those seen in 9
while the Zr-P-Zr angle of 93.3(2)° is significantly
smaller than the corresponding angle in 9, consistent
with the presence of the second bridging fragment.
These parameters compare well with those previously
reported for (Cp2Zr)(Cp2ZrCl)(µ-PSiPh3)(µ-η1:η5-C5H4)
(Zr-P 2.549(6), 2.559(6) Å; Zr-P-Zr 95.2(2)°).4 The
small difference in the bridging Zr-P distances is
consistent with a π-component of the Zr(2)-P(1) bond
as described for the structurally related species (Cp2Zr)-
(Cp2ZrCl)(µ-PSiPh3)(µ-η1:η5-C5H4).4 The terminal phos-
phide ligand of 11 manifests in a dramatically longer
Zr-P distance of 2.718(7) Å, which compares well with
The corresponding reaction of Cp2ZrMe2 with 1 equiv
of H2P(C6H2-2,4,6-Me3) at 110 °C for 5 h resulted in the
formation of a dark brown product 11 which was
isolated in 70% yield. This compound exhibited 31P
NMR resonances at 395.4 and -84.2 ppm with a P-P
coupling constant of 29.0 Hz. The latter resonance also
1
exhibited a J P-H of 203.0 Hz. The H NMR spectrum
of 11 showed the resonances attributable to three
cyclopentadienyl groups at 6.29, 5.66, and 5.25 ppm. In
addition, resonances of 5.98 and 5.12 ppm were assigned
to an η1:η5-C5H4 fragment. These data, in addition to
(16) Hey, E.; Bott, S. G.; Atwood, J . L. Chem. Ber. 1988, 121, 561.

4514 Organometallics, Vol. 15, No. 21, 1996
Breen and Stephan
the longer Zr-P distance in (C5H4SiMe3)2Zr(PPh2)2
(2.694(3) Å).17 The P-Zr-P and P-Zr-C angles in 11
are 96.5(2)° and 88.9(7)°, respectively, comparable to the
corresponding angles in (Cp2Zr)(Cp2ZrCl)(µ-PSiPh3)(µ-
η1:η5-C5H4).4
(3)
An alternative synthesis of 11 has been achieved from
the unstable terminal phosphinidene species Cp2Zr-
(P(C6H2-2,4,6-Me3))(PMe3) (12) (Scheme 2). 12 was
cleanly generated by the reaction of Li2P(C6H2-2,4,6-
Me3) with 10 in the presence of PMe3, as evidenced by
31P NMR resonances consistent with data previously
reported for 12.18 This reaction is thought to proceed
through initial formation of a bis-phosphinidene bridged
dimer followed by subsequent reaction with PMe3.
However, 12 was not isolable; upon standing overnight
at 25 °C or when the solvent is removed in vacuo, 12
degraded to produce free PMe3 and 11. A plausible
mechanism involves dissociation of PMe3 from 12,
dimerization, and subsequent irreversible intramolecu-
lar cyclopentadienyl C-H bond activation (Scheme 2).
Thus, while 12 appears to be the kinetic product from
this mixture, 11 is the thermodynamic product.
We have previously described similar intramolecular
C-H bond activation in the terminal phosphinidene
species Cp*2ZrdP(C6H2-2,4,6-Me3) to produce Cp*2-
ZrPH(C6H2-(2-CH2)-4,6-Me2) (eq 3).19 Presumably the
greater steric demands of the Cp* ligands prevent
dimerization, consequently favoring intramolecular C-H
activation of the mesityl ligand. In a similar way, the
lack of cyclopentadienyl C-H bond activation in termi-
nal phosphinidene 1 may be attributed to the greater
steric demands of the supermesityl group, which pre-
clude dimerization. Owing to the fact that 11 does not
possess any sterically demanding substituents, dimer-
ization and subsequent cyclopentadienyl C-H bond
activation transpire.
In summary, mononuclear methylzirconocene phos-
phide complexes are reactive species. The chemistry
herein demonstrates the ease with which organic un-
saturates can insert into the Zr-P bond. Alternatively,
methylzirconocene phosphide complexes can react via
loss of methane to provide convenient access to Zr-
phosphinidene species. These compounds can be ob-
served and isolated only when steric demands preclude
further reaction. In the absence of such bulk, dimer-
ization and subsequent intramolecular C-H bond ac-
tivation have been observed. The potential for inter-
molecular C-H bond activation by early metal
phosphinidenes is the subject of ongoing study.
Ack n ow led gm en t . Support of this research from
the NSERC of Canada is acknowledged. T.L.B. is
grateful for the award of an NSERC postgraduate
scholarship.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic parameters, hydrogen atom parameters, and thermal
parameters for 3, 9, and 11 (30 pages). Ordering information
is given on any current masthead page.
(17) Larsonneur, A. M.; Choukroun, R.; Daran, J . C.; Cuenca, T.;
Flores, J . C.; Royo, P. J . Organomet. Chem. 1993, 444, 83.
(18) Ho, J .; Rousseau, R.; Stephan, D. W. Organometallics 1994, 13,
1918.
(19) Hou, Z.; Stephan, D. W. J . Am. Chem. Soc. 1992, 114, 10088.
OM960412+