Insertion reactions and catalytic hydrophosphination by triamidoamine-supported zirconium complexes

Article abstract of DOI:10.1021/om100216f

Triamidoamine-supported zirconium phosphido complexes, (N ₃N)ZrPRR′ (N₃N = N(CH₂CH ₂NSiMe₃)₃^3-; R = alkyl, aryl; R′ = R, H), have been shown to catalyze the hydrophosphination of

Full text of DOI:10.1021/om100216f

Organometallics 2010, 29, 2557–2565 2557
DOI: 10.1021/om100216f
Insertion Reactions and Catalytic Hydrophosphination by
Triamidoamine-Supported Zirconium Complexes
Andrew J. Roering,† Sarah E. Leshinski,† Stephanie M. Chan,† Tamila Shalumova,‡
Samantha N. MacMillan,‡ Joseph M. Tanski,‡ and Rory Waterman*,†
†Department of Chemistry, University of Vermont, Burlington, Vermont 05405, and
‡Department of Chemistry, Vassar College, Poughkeepsie, New York 12604
Received March 19, 2010
Triamidoamine-supported zirconium phosphido complexes, (N3N)ZrPRR0 (N3N=N(CH2CH2-
3-
NSiMe3)3 ; R=alkyl, aryl; R0 =R, H), have been shown to catalyze the hydrophosphination of
terminal alkynes as well as that of symmetric aryl and alkyl carbodiimides. A mechanism based on
insertion of the substrate into the Zr-P bond is proposed on the basis of competition experiments and
model examples of stoichiometric insertion reactions of polar, small-molecule substrates possessing
CdO, CdN, CtN, and CdS functionalities into the Zr-P bond. Molecular structures of the
insertion products (N3N)ZrNdC(PHCy)Ph (4), (N3N)ZrNdC(PPh2)Ph (5), and (N3N)ZrPhNC-
(O)PPh2 (11), as well as (N3N)Zr[η2(N,N)-(iPrN)2C(PPh2)] (9), a key intermediate in the catalytic
hydrophosphination of carbodiimides, have been determined.
Introduction
of substrate into the metal-phosphorus bond, and reductive
elimination to facilitate hydrophosphination of organic
molecules.2b,c A noteworthy exception is the nickel-based
catalyst reported by Togni, which appears to proceed via 1,4-
addition of phosphine to a coordinated substrate.5 Substrate
insertion into metal-phosphorus bonds is proposed in the
intramolecular hydrophosphination effected by lanthanide
catalysts.6 Group 2 catalysts reported by Barrett and Hill
involve insertion of unsaturated organic molecules, includ-
ing aryl alkenes and alkynes7 as well as carbodiimides,8 into
the metal-phosphorus bond. Interestingly, the only reported
early-transition-metal hydrophosphination catalyst, discov-
ered by Mindiola and co-workers,9 does not appear to
proceed via insertion into the metal-phosphorus bond;
rather, a terminal titanium-phosphinidene complex under-
goes a [2 þ 2] cycloaddition with an alkyne in a direct analogy
to early-transition-metal hydroamination catalysts.10
The synthesis of carbon-phosphorus σ bonds is an attrac-
tive transformation for chemical applications, including
the preparation of biologically active molecules, transition-
metal ligands, and polymers.1 A wide variety of preparative
routes are possible for the synthesis of P-C bonds. Hetero-
functionalization of unsaturated organic molecules is an
appealing method, given the high atom economy and effici-
ency of this type of reaction. Catalytic heterofunctionalization
reactions that form P-C bonds, including hydrophosphina-
tion,2 hydrophosphinylation,3 and hydrophosphorylation,4
have been the subject of multiple reviews.
Hydrophosphination has been well studied using late-
transition-metal, lanthanide, and group 2 catalysts. How-
ever, early-transition-metal catalysts have seen far less atten-
tion in the literature. A common mechanistic theme of many
late-metal hydrophosphination catalysts is insertion of the
unsaturated substrate into a metal-phosphorus bond. For
example, late-metal catalysts undergo a series of elementary
steps, including the oxidative addition of P-H bonds, insertion
Similar [2 þ 2] cycloaddition reactions between polar
unsaturated molecules and zirconium-phosphinidene com-
plexes to produce phosphametallacycles have been reported
by Stephan and co-workers.11 Moreover, these [2 þ 2] cyclo-
addition reactions appear to be commonplace for phosphinidene
*To whom correspondence should be addressed. E-mail: rory.waterman@
uvm.edu.
(1) (a) Herbert, D. E.; Mayer, U. F. J.; Manners, I. Angew. Chem., Int.
Ed. 2007, 46 (27), 5060–5081. (b) Clark, T. J.; Lee, K.; Manners, I. Chem.
Eur. J. 2006, 12 (34), 8634–8648. (c) Waterman, R. Curr. Org. Chem.
2008, 12, 1322–1339. (d) Masuda, J. D.; Hoskin, A. J.; Graham, T. W.;
Beddie, C.; Fermin, M. C.; Etkin, N.; Stephan, D. W. Chem. Eur. J. 2006,
12 (34), 8696–8707. (e) Gauvin, F.; Harrod, J. F.; Woo, H. G. Adv.
Organomet. Chem. 1998, 42, 363–405. (f) Waterman, R. Dalton Trans.
2009, No. 1, 18–26.
(2) (a) Glueck, D. S. Chem. Eur. J. 2008, 14 (24), 7108–7117.
(b) Glueck, D. S. Dalton Trans. 2008, No. 39, 5276–5286. (c) Glueck, D.
S. Coord. Chem. Rev. 2008, 252 (21-22), 2171–2179.
(3) (a) Coudray, L.; Montchamp, J.-L. Eur. J. Org. Chem. 2008, 2008
(21), 3601–3613. (b) Montchamp, J.-L. J. Organomet. Chem. 2005, 690
(10), 2388–2406.
(5) (a) Sadow, A. D.; Haller, I.; Fadini, L.; Togni, A. J. Am. Chem.
Soc. 2004, 126 (45), 14704–14705. (b) Sadow, A. D.; Togni, A. J. Am.
Chem. Soc. 2005, 127 (48), 17012–17024.
(6) Motta, A.; Fragala, I. L.; Marks, T. J. Organometallics 2005,
24 (21), 4995–5003.
(7) Crimmin, M. R.; Barrett, A. G. M.; Hill, M. S.; Hitchcock, P. B.;
Procopiou, P. A. Organometallics 2007, 26 (12), 2953–2956.
(8) Crimmin, M. R.; Barrett, A. G. M.; Hill, M. S.; Hitchcock, P. B.;
Procopiou, P. A. Organometallics 2008, 27 (4), 497–499.
(9) Zhao, G.; Basuli, F.; Kilgore, U. J.; Fan, H.; Aneetha, H.;
Huffman, J. C.; Wu, G.; Mindiola, D. J. J. Am. Chem. Soc. 2006, 128
(41), 13575–13585.
(10) (a) Walsh, P. J.; Hollander, F. J.; Bergman, R. G. J. Am. Chem.
Soc. 1988, 110 (26), 8729–8731. (b) Walsh, P. J.; Baranger, A. M.;
Bergman, R. G. J. Am. Chem. Soc. 1992, 114 (5), 1708–1719.
(4) Baillie, C.; Jianling Xiao, C. Curr. Org. Chem. 2003, 7 (5), 477.
r
2010 American Chemical Society
Published on Web 04/30/2010
pubs.acs.org/Organometallics

2558 Organometallics, Vol. 29, No. 11, 2010
Roering et al.
complexes of various metals.1f For example, Hillhouse and
co-workers have shown that reactions of alkenes and alkynes
with nickel phosphinidene produce phosphiranes and phos-
phirenes through a [2 þ 2] cycloaddition.12
Despite the observed cycloaddition chemistry, there is
ample precedent for insertion reactivity among early-metal
phosphido derivatives since the first such example, a 1,2-
insertion of carbon monoxide into the M-P bond of Cp*HfCl2-
(PtBu2), elucidated by Roddick and Bercaw.13 Since then, the
insertion chemistry of terminal group 4 metal-phosphido
complexes supported by cyclopentadienyl ligands has been
explored by the groups of Hey-Hawkins14 and Stephan.15
The ease with which (N3N)Zr-PRR0 derivatives are pre-
pared as part of their application for P-P16 and P-E17
bond-forming catalysis and the unlikely generation of
(N3N)Zr-phosphinidene complexes suggested that inser-
tion-based hydrophosphination may be a facile reaction
for this system.1c,18 We have explored this chemistry and
herein report the insertion reactivity of primary and secondary
zirconium phosphido complexes of the form (N3N)ZrPRR0
Figure 1. Molecular structure of 4 with thermal ellipsoids
drawn at the 35% level. Hydrogen atoms, except for H(1), are
omitted for clarity.
3-
(N3N=N(CH2CH2NSiMe3)3 ; R=Ph, Cy; R0=Ph, H) as
well as the catalytic hydrophosphination of both terminal
alkynes and carbodiimides by (N3N)ZrPPh2 (3).
˚
Table 1. Selected Bond Lengths (A) and Angles (deg) for
Complex 4
Zr-N(5)
N(5)-C(16)
C(16)-P
C(23)-P
2.059(1)
1.262(2)
1.870(1)
1.859(1)
Zr-N(2)
Zr-N(1)
Zr-N(3)
Zr-N(4)
2.084(1)
2.086(1)
2.096(1)
2.504(1)
Results and Discussion
Insertion Chemistry. The preamble to catalytic hydrophosphi-
nation by triamidoamine-supported zirconium complexes was
an investigation of stoichiometric insertion reactions of unsatu-
rated, polar small molecules into the Zr-P bond of the terminal
phosphido complexes (N3N)ZrPHCy (1), (N3N)ZrPHPh (2),
and (N3N)ZrPPh2 (3).16,19 These reactions appear to be general,
in that a variety of substrates featuring unsaturated C-N,
C-O, and C-S bonds have been shown to insert into Zr-P
bonds.
CtN Bonds. Reaction of 1 with benzonitrile afforded the
1,2-insertion product (N3N)ZrNdC(PHCy)Ph (4) as analy-
tically pure, pink microcrystals in 86% yield (eq 1). Though
the 31P{1H} NMR spectrum resonance displays the expected
singlet at δ 4.1, the 1H NMR spectrum reveals several more
diagnostic features. The first feature is the P-H proton
appearing as a doublet of doublets at δ 4.47 (JPH=224 Hz,
JHH=7 Hz). The second feature of the 1H NMR spectrum is
the unusual splitting of the methylene groups of the triami-
doamine ligand. Whereas other (N3N)ZrX complexes dis-
play pseudo-C3v symmetry, as evidenced by the apparent
Zr-N(5)-C(16)
N(5)-C(16)-P
C(23)-P-C(16)
175.3(1)
119.1(1)
107.5 (1)
N(5)-Zr-N(2)
N(5)-Zr-N(1)
N(5)-Zr-N(3)
N(5)-Zr-N(4)
105.16(4)
104.38(4)
108.12(4)
177.81(4)
equivalence of the three methylene groups each R and β to the
pseudo-apical amine nitrogen, complex 4 has lost this fea-
ture. Two sets of complex multiplets, resonating at δ 2.45 and
3.35, suggest diasterotopic methylene substituents of similar
chemical shift for the ethylene backbone. The diagnostic
vibrations νPH 2308 cm-1 and νCN 1610 cm-1 were observed
in the infrared spectrum of 4 as well. X-ray-quality single
crystals of 4 were grown from concentrated ethereal solu-
tions kept at -30 °C for extended periods. The molecular
structure of 4, shown in Figure 1, confirms the structural
assignment from spectroscopic data. Complex 4 displays
trigonal-bipyramidal-like geometry with a weak axial amine
˚
interaction: Zr-Naxial = 2.504(1) A (Table 1). The imine
carbon-nitrogen bond length (CdN = 1.262(2) A) falls
˚
within the range of other C-N bond lengths for zirconium
iminato complexes, while the metal-nitrogen bond length of
(11) Hou, Z.; Breen, T. L.; Stephan, D. W. Organometallics 1993, 12
(8), 3158–3167.
(12) (a) Waterman, R.; Hillhouse, G. L. J. Am. Chem. Soc. 2003, 125
(44), 13350–13351. (b) Waterman, R.; Hillhouse, G. L. Organometallics
2003, 22 (25), 5182–5184. (c) Aktas, H.; Slootweg, C. J.; Lammertsma,
K. Angew. Chem., Int. Ed. 2010, 49, 2–14.
˚
4, Zr-N(5)=2.059 A, is slightly longer than in previously
reported iminato ligands.11,20
(13) Roddick, D. M.; Santarsiero, B. D.; Bercaw, J. E. J. Am. Chem.
Soc. 1985, 107 (16), 4670–4678.
(14) (a) Lindenberg, F.; Sieler, J.; Hey-Hawkins, E. Polyhedron 1996,
15 (9), 1459–1464. (b) Hey, E.; Lappert, M. F.; Atwood, J. L.; Bott, S. G.
Polyhedron 1988, 7 (19-20), 2083–2086.
(15) Stephan, D. W. Angew. Chem., Int. Ed. 2000, 39 (2), 314–329.
(16) Waterman, R. Organometallics 2007, 26 (10), 2492–2494.
(17) Roering, A. J.; MacMillan, S. N.; Tanski, J. M.; Waterman, R.
Inorg. Chem. 2007, 46 (17), 6855–6857.
(18) Ghebreab, M. B.; Shalumova, T.; Tanski, J. M.; Waterman, R.
Polyhedron 2010, 29 (1), 42–45.
(19) Roering, A. J.; Maddox, A. F.; Elrod, L. T.; Chan, S. M.;
Ghebreab, M. B.; Donovan, K. L.; Davidson, J. J.; Hughes, R. P.;
Shalumova, T.; MacMillan, S. N.; Tanski, J. M.; Waterman, R.
Organometallics 2009, 28 (2), 573–581.
Reaction of 3 with benzonitrile afforded analytically pure,
orange crystals of (N3N)ZrNdC(PPh2)Ph (5) in 72% yield
(20) Segerer, U.; Blaurock, S.; Sieler, J.; Hey-Hawkins, E. Organo-
metallics 1999, 18 (15), 2838–2842.

Article
Organometallics, Vol. 29, No. 11, 2010 2559
˚
Table 2. Selected Bond Lengths (A) and Angles (deg) for
Complex 5
Zr-N(5)
N(5)-C(16)
C(16)-P
C(29)-P
C(23)-P
2.053(1)
1.257(2)
1.887(2)
1.824(2)
1.827(2)
Zr-N(1)
Zr-N(2)
Zr-N(3)
Zr-N(4)
2.092(1)
2.124(1)
2.091(1)
2.462(1)
Zr-N(5)-C(16)
C(29)-P-C(23)
C(29)-P-C(16)
C(23)-P-C(16)
172.6(1)
N(5)-Zr-N(1)
N(5)-Zr-N(2)
N(5)-Zr-N(3)
N(5)-Zr-N(4)
109.33(5)
105.69(5)
102.50(3)
173.12(5)
103.13(7)
102.40(7)
101.61(7)
seen at δ 2.35 and 3.24 as overlapping multiplets due to each
enantiomer of complex 6. To our best approximation, these
resonances appear as overlapping AA0A00BB0B00 spin sys-
tems. However, efforts to accurately simulate the 1H NMR
spectra have thus far failed. The primary phosphido hydro-
gen is clearly visible as a doublet at δ 4.61 (JPH=203 Hz) in
Figure 2. Molecular structure of 5 with thermal ellipsoids
drawn at the 35% level. Hydrogen atoms are omitted for clarity.
1
the H NMR spectrum. The 13C NMR spectrum is high-
lighted by the quaternary carbon as a doublet at δ 30.8 (JPC
=
(eq 2). The 1H NMR spectrum of 5 reveals pseudo-C3v
symmetry with respect to the triamidoamine ligand. The
13C NMR spectrum of 5 is highlighted by the imine carbon
29 Hz). Interestingly, the methyl groups of the acetone
insertion can be seen at very different peaks in the 13C
NMR spectrum at δ 80.1 and 34.2. Presumably this inequi-
valence is due to the chiral phosphine. The P-H bond can be
seen as a weak signal in the infrared at νPH 2302 cm-1. The
31P NMR spectrum was largely unremarkable but is consis-
tent with the formula given.
resonance at δ 144, which occurs as a doublet with JPC
=
39 Hz. This is similar to that of 4, which can be seen in the 13C
NMR spectrum as a doublet at δ 187 (JPC = 28 Hz).
Additional support for the structure of 5 comes from the
infrared spectrum with νCN 1630 cm-1. Confirmation of the
structure derived from spectroscopic data came from an
X-ray diffraction study. Single crystals of 5 suitable for
diffraction were prepared by cooling concentrated ethereal
solutions kept at -30 °C for extended periods. The solid-
state structure of 5, shown in Figure 2, reveals a trigonal
bipyramidal like structure with a weak axial amine interac-
˚
˚
tion (Zr-Naxial = 2.462(1) A) with Zr-N(1) = 2.059(1) A
and CdN=1.257 A (Table 2). Complex 5 is isostructural
˚
Heterocumulenes. The CdN bonds of carbodiimides read-
ily insert into the Zr-P bond. Complex 3 was treated with
N,N0-dicyclohexyl-, N,N0-diphenyl-, and N,N0-diisopropylcar-
bodiimide to afford (N3N)Zr[η2(N,N)-(CyN)2dCPPh2] (7),
(N3N)Zr[η2(N,N)-(PhN)2CPPh2] (8), and (N3N)Zr[η2(N,N)-
(iPrN)2CPPh2] (9) in 79, 93, and 96% yields, respectively
(eq 4). Phosphaguanidinate ligands have been known for
decades for a variety of metals.21 Each carbodiimide inser-
tion product displays pseudo-C3v symmetry in the 1H NMR
spectrum, and each gave diagnostic features in the IR, 13C
NMR, and 31P NMR spectra that are summarized in Table 3.
The spectral data suggested that the phosphaguanidinate
ligand engages in η2 binding through the nitrogen atoms to
the zirconium center. X-ray-quality crystals of 9 were grown
from concentrated ethereal solutions cooled to -30 °C over
extended periods. The molecular structure of 9, shown in
Figure 3, is trigonal bipyramidal like, featuring an η2 phos-
phaguanidinate ligand bound though both nitrogen atoms of
the carbodiimide as anticipated. The CdN bond lengths of
the phosphaguanidinate ligand (Table 4) suggest a deloca-
lized π bonding. This structure is consistent with known
with 4 and is highly related to other zirconium iminato
complexes.11,20
Insertion chemistry can be thwarted by more reactive
functionalities. Treatment of 3 with benzophenone imine
resulted in a ligand exchange reaction, yielding the known
iminato compound (N3N)ZrNdCPh2 as dark orange crys-
tals in 64% yield with concomitant formation of Ph2PH,
presumably due to the relatively strong Zr-N bond formed
in the ligand exchange reaction.19
CdO Bonds. Primary phosphido complexes undergo 1,2-
insertion reactions with ketones (eq 3). Reaction of 2 with
acetone resulted in the formation of (N3N)ZrOC(CH3)2-
PHPh (6) as an analytically pure, colorless powder in 95%
yield. Unlike other insertions that utilize 3 as a starting
material, reaction of acetone with complex 2 to form 6 results
in the formation of a chiral phosphorus atom. Two alkoxide
methyl resonances were well resolved as doublets at δ 1.71
(JHH=38 Hz) and δ 1.70 (JHH=49 Hz) for the enantiomers
of 6 in the 1H NMR spectrum. Both methylene groups R and
β to the apical amine nitrogen of the ligand backbone are
(21) (a) Ambrosius, H. P. M. M.; Van Der Linden, A. H. I. M.;
Steggerda, J. J. J. Organomet. Chem. 1981, 204 (2), 211–220. (b) Thewissen,
D. H. M. W.; Ambrosius, H. P. M. M.; Van Gaal, H. L. M.; Steggerda,
J. J. J. Organomet. Chem. 1980, 192 (1), 101–113. (c) Grundy, J.;
Mansfield, N. E.; Coles, M. P.; Hitchcock, P. B. Inorg. Chem. 2008, 47
(7), 2258–2260. (d) Mansfield, N. E.; Coles, M. P.; Avent, A. G.;
Hitchcock, P. B. Organometallics 2006, 25 (10), 2470–2474. (e) Mansfield,
N. E.; Coles, M. P.; Hitchcock, P. B. Dalton Trans. 2005, No. 17, 2833–
2841.

2560 Organometallics, Vol. 29, No. 11, 2010
Roering et al.
Table 3. Selected 13C and 31P NMR Signals and IR Stretches for
Carbodiimide Insertion Products 7-9
7
8
9
13C δ(CdN) (JPC, Hz)
31P δ
152.3 (32)
-18.5
1589
179.6 (63)
-18.3
1594
175.5 (75)
-9.1
1583
ν
CN (cm-1
)
Figure 4. Molecular structure of 11 with thermal ellipsoids
drawn at the 35% level. Hydrogen atoms are omitted for clarity.
isothiocyanate resulted in the formation of (N3N)Zr[η2-
(N,S)-SC(PPh2)N(C10H7)] (10) as analytically pure, yellow
microcrystals in 75% yield (eq 5). The 1H NMR spectrum is
consistent with pseudo-C3 symmetry with respect to the
triamidoamine ligand. At ambient temperature, two broad
resonances corresponding to the methylene groups of the
triamidoamine ligand are observed. This broadening sug-
gests a dynamic process in the complex on the NMR time
scale. An increase in the NMR temperature to 335 K results
in resolved peaks as triplets at δ 2.99 and 2.27, respectively.
The steric bulk of the napthyl group suggests that this
process may be partial dissociation of an η2-bound phos-
phathiourea ligand. The phosphathiourea carbon was as-
signed at δ 204 as a doublet, with JPC =55 Hz in the 13C
NMR spectrum. Both 31P NMR and infrared spectroscopy
were consistent with the formula given.
Figure 3. Molecular structure of 9 with thermal ellipsoids
drawn at the 35% level. Hydrogen atoms are omitted for clarity.
˚
Table 4. Selected Bond Lengths (A) and Angles (deg) for
Complex 9
Zr-N(5)
Zr-N(6)
C(16)-P
2.304(1)
2.346(1)
1.913(1)
Zr-N(1)
Zr-N(2)
Zr-N(3)
Zr-N(4)
2.132(1)
2.138(1)
2.112(1)
2.542(1)
N(5)-C(16)-N(6)
N(5)-C(16)-P
112.63
127.18
N(6)-C(16)-P
120.12
phosphaguanidinate complexes of zirconocene derivatives
reported by Hey-Hawkins. In those instances, insertion of a
carbodiimide into a Zr-P bond yielded the phosphaguani-
dinate product.14a,22 The phosphorus center is non-planar with
a P-C bond length that implies there is no delocalization
of the phosphorus lone pair into the N-C-N π system.
This is an important consideration, given the interest in the
interaction of the phosphorus with the N-C-N unit of a
phosphaguanidene.23 The X-ray crystal structure of 9 ap-
pears to be the first six-coordinate zirconium complex bear-
ing the N3N ligand. Six-coordinate zirconium complexes are
significant, because reported bond-forming catalysis invol-
ving the (N3N)Zr fragment has been suggested to proceed via
six-coordinate transition states.1c
Reaction of 3 with phenyl isocyanate resulted in the
formation of (N3N)Zr[η2(N,O)-OC(PPh2)N(Ph)] (11) as
analytically pure light orange crystals in 56% yield. Spectro-
scopic data were consistent with other heterocumulene in-
sertion products (vide infra). Single crystals of 11 suitable for
an X-ray diffraction study were grown from a concentrated
ethereal solution kept at -30 °C for extended periods. The
solid-state structure of 11, shown in Figure 4, reveals η2
coordination of the phosphaurea ligand featuring Zr-O=
2
˚
2.251(1) and Zr-N(5)=2.341(1) A for the η -bound phos-
phaurea ligand (Table 5). The bond lengths of both CdN
˚
˚
(1.313(2) A) and CdO (1.300(2) A) are typical of CdN and
CdO bonds, consistent with a delocalized bonding.
Carbon-sulfur double bonds have also been shown to
insert into Zr-P bonds. Reaction of 3 with carbon disulfide
resulted in the 1,2-insertion product (N3N)Zr[η2-S2C(PPh2)]
(22) Hey-Hawkins, E.; Lindenberg, F. Z. Naturforsch., B: Chem. Sci.
1993, 48, 951–957.
(23) Mansfield, N. E.; Grundy, J.; Coles, M. P.; Avent, A. G.;
Unsymmetrical heterocumulenes have also been shown to
insert into Zr-P bonds. Reaction of 3 with 1-naphthyl
Hitchcock, P. B. J. Am. Chem. Soc. 2006, 128 (42), 13879–13893.

Article
Organometallics, Vol. 29, No. 11, 2010 2561
˚
Table 5. Selected Bond Lengths (A) and Angles (deg) for
Complex 11
Table 6. Catalytic Data for the Hydrophosphination of Terminal
Alkynes and Carbodiimidesa
Zr-N(5)
Zr-O
2.341(1)
2.251(1)
1.878(2)
Zr-N(1)
Zr-N(2)
Zr-N(3)
Zr-N(4)
2.117(1)
2.108(1)
2.087(1)
2.463(1)
substrate
temp (°C)
time (h)
yield (%)b
P-C(16)
phenylacetylene
1-hexyne
CyNdCdNCy
PhNdCdNPh
iPrNdCdNiPr
100
120
120
120
120
67
72
24
24
7
66
56
75
70
53
C(29)-P-C(23)
C(29)-P-C(16)
102.02(8)
100.83(7)
C(23)-P-C(16)
103.80(7)
aAll runs at 5 mol % of complex 3 as catalyst in benzene-d6 solution in
a PTFE-valved NMR tube. bDetermined by 31P NMR spectroscopy.
1
(12) as analytically pure red crystals in 76% yield. The H
and 31P NMR and IR spectra were unremarkable. However,
the S-C-S carbon was observed at δ 144 as a doublet with
JPC=38 Hz in the 13C NMR spectrum.
previously reported alkynyl complexes (N3N)ZrCtCPh (13)
or (N3N)ZrCtCBu via H NMR spectroscopy during the
1
catalytic reactions.19 This potential of direct addition was
further implied by reports of hydrophosphination catalysis
where the metal did not participate in the P-C bond-forming
step.26 Interestingly, heterofunctionalization catalysts that
do not directly involve the metal center in key bond-forming
steps have been described for other systems.27
Thus, mechanistic insight was sought for the hydrophos-
phination of terminal alkynes. The presence of both complex
3 and terminal alkynyl complexes suggested an equilibrium
process, which seemed unusual given the large difference in
calculated bond energies between phosphido and alkynyl
complexes of the (N3N)Zr fragment.19 An attempt to mea-
sure Keq for the interconversion of 3 and 13 with phenylace-
tylene and diphenylphosphine was performed by investi-
gating each side of the equilibrium reaction (Scheme 1).
Treatment of complex 13 with 1 equiv of phenylphosphine
Catalytic Hydrophosphination. The ease with which unsatu-
rated organic molecules were able to insert into zirconium-
phosphorus bonds of 1-3 provided an opportunity to in-
vestigate hydrophosphination catalysis with these zirconium
complexes.
Terminal alkynes were converted to vinyl phosphines,
using complex 3 as a catalyst. Reaction of phenylacetylene
and diphenylphosphine in the presence of 5 mol % of
complex 3 were run at 100 °C in the dark for extended
periods, affording vinyl phosphine products in 66% yield
as a mixture of cis and trans alkenes in a 6:1 ratio, as
determined by 31P NMR spectroscopy in comparison to
literature data (Table 6).24 Similarly, 1-hexyne and diphe-
nylphosphine were reacted with 5 mol % of complex 3 at
120 °C in the dark for extended periods to afford vinyl
phosphine products in 56% yield as a mixture of the cis
and trans alkenes in a 1:5 ratio, now favoring the trans
product as compared to the literature data (Table 6).25 For
both reactions, cis and trans vinyl phosphines were formed
exclusively as anti-Markovnikov products, and no geminal
phosphine products were detected. A range of other sub-
strates possessing unsaturated C-C bonds was also tested.
Reactions with electronic-rich and -deficient alkenes and
internal alkynes failed to give hydrophosphination products
at elevated temperatures and extended reaction times. While
a number of unsaturated small molecules insert into the
Zr-P bond of this family of complexes (vide supra), attempts
at the catalytic hydrophosphination of ketones and nitriles
also failed under the conditions tested.
1
gave no obvious reaction, as observed by H or 31P NMR
spectroscopy over a period of hours at ambient temperature
in benzene-d6 solution. However, reaction of complex 3 with
1 equiv of phenylacetylene resulted in 84% conversion to 13
in with the appearance of vinyl phosphine products in 4%
1
yield according to H and 31P NMR spectroscopy. These
results suggest that reaction at the Zr-P bond is likely
important and are not consistent with direct P-H addition
across the CtC bond.
The lack of reaction between 13 and diphenylphosphine
suggested that formation of 3 is unfavorable, and deuterium
labeling experiments were undertaken to better understand
how the catalysis proceeds in the face of this apparent
substrate inhibition. Reaction of 3 with phenylacetylene-d1
resulted in formation of 13-d1, where the deuterium label had
been predominately incorporated in the trimethylsilyl sub-
stituents of the triamidoamine ligand, and a small amount
of Ph2PD was observed. When 13 was treated with Ph2PD,
13-d1 was produced with concomitant formation of Ph2PH,
as observed by 1H and 31P NMR spectroscopy in benzene-d6
solution (Scheme 2). This study implicates the existence of an
equilibrium between the metalated complex [(Me3SiNCH2)2-
NCH2CH2NSiMe2CH2-κ5(N,N,N,N,C)]Zr (14) and diphe-
nylphosphine or phenylacetylene in the formation of 3 and
13, respectively. Additionally, these labeling experiments
demonstrate a high kinetic lability of the X- ligand from
(N3N)ZrX complexes by formation of HX and 14. More
germane to this study, the summation of these indirect lines
of evidence argues for a mechanism based on insertion of
substrate into the Zr-P bond. A reviewer suggested that the
reaction could proceed via dehydrocoupling of alkyne and
The limited ability to generalize the catalysis to at least
internal alkynes suggested that two mechanisms are possible.
The first mechanism is based on insertion of the substrate
into the Zr-P bond that is due to the relative ease of this
process stoichiometrically, and the second mechanism is
based on the direct addition of the P-H bond across the
CtC bond of an activated alkyne. The latter mechanism
appeared to be possible on the basis of the observation of
(24) (a) Hayashi, M.; Matsuura, Y.; Watanabe, Y. J. Org. Chem.
2006, 71 (24), 9248–9251. (b) Takaki, K.; Koshoji, G.; Komeyama, K.;
Takeda, M.; Shishido, T.; Kitani, A.; Takehira, K. J. Org. Chem. 2003,
68 (17), 6554–6565.
(25) Semenzin, D.; Etemad-Moghadam, G.; Albouy, D.; Diallo, O.;
Koenig, M. J. Org. Chem. 1997, 62 (8), 2414–2422.
(26) Huang, J.-S.; Yu, G.-A.; Xie, J.; Wong, K.-M.; Zhu, N.; Che,
C.-M. Inorg. Chem. 2008, 47 (20), 9166–9181.
(27) Glaser, P. B.; Tilley, T. D. J. Am. Chem. Soc. 2003, 125 (45),
13640–13641.

2562 Organometallics, Vol. 29, No. 11, 2010
Roering et al.
Scheme 1. Formation of Alkynyl Complex
either the cis or trans alkene in the hydrophosphination of
terminal alkynes. Further study would be required to estab-
lish the origin of the selectivity displayed by this particular
catalyst.
Other substrates are more efficiently hydrophosphinated
by complex 3. Reactions of symmetrical carbodiimides and
diphenylphosphine in the presence of 5 mol % of 3 at 120 °C
in the dark afforded phosphaguanidine products in 53-75%
yield. Phosphaguanidines are well-known due to both the
biological relevance of the P-C-N functionality as well as
their ability to be transition-metal ligands.29 Previous re-
ports of phosphaguanidine formation from carbodiimides
has shown the need for a catalyst, as control reactions were
not facile even at elevated temperatures.30 However, the
turnover frequencies of the calcium systems by Hill and
co-workers are higher than those measured for complex 3
as a catalyst.8 It appears that carbodiimides represent a
better substrate for the hydrophosphination catalysis by
complex 3, likely because this substrate does not compete
effectively with diphenylphosphine as a ligand. It is hypothe-
sized that the hydrophosphination of carbodiimides under-
goes a similar mechanism, where the carbodiimide substrate
inserts into the Zr-P bond, as illustrated by the stoichio-
metric reactions.
Scheme 2. Deuterium Labeling Reactions
phosphine to yield Ph2PCtCR, which could then be hydro-
genated by the H2 byproduct to give the observed vinylpho-
sphine. The competition experiments do not seem to support
this mechanism, which should not depend on which ligand
(alkynyl or phosphido) is bound to zirconium. A catalytic
run was conducted under reduced pressure (to thwart hydro-
genation), which did not adversely effect the catalysis and the
same vinylphosphine products were formed at the same qua-
litative rate. While this is not strong enough evidence to
refute such a mechanism, the rarity of catalytic reactions
involving bond formation to carbon by what appears to be
σ-bond metathesis lead us to view this mechanistic sugges-
tion with caution, given the current evidence supporting
insertion (vide supra).28
With the information from the deuterium labeling studies
as well as competition experiments, a mechanism of hydro-
phosphination is proposed on the basis of insertion of
substrate into a Zr-P bond (Scheme 3). Elimination of the
vinyl phosphine product occurs by metalation of the triami-
doamine ligand to form complex 14. Reaction with diphe-
nylphosphine completes the catalytic cycle with the
formation of a phosphido complex (3). However, there is a
competitive, nonproductive path in which 14 reacts with
alkyne or complex 3 undergoes ligand exchange with alkyne
via 14. It is the formation of stable, terminal alkynyl com-
plexes that likely accounts for the sluggish overall catalysis.
Although this mechanism describes the formation of vinyl
phosphine products, it does not account for the selectivity for
Conclusion
Triamidoamine-supported zirconium phosphido com-
plexes are able to undergo a variety of insertion reactions
with small, polar unsaturated substrates. The diphenylphos-
phido complex 3 has also been found to catalyze the hydro-
phosphination of terminal alkynes as well as carbodiimides
to vinyl phosphines and phosphaguanidines, respectively. These
appear to be the first early-transition-metal complexes that
engage in insertion-based hydrophosphination catalysis, in
contrast to the cycloaddition-based hydrophosphination
catalysis with Ti reported by Mindiola.9 Despite this new
development, these Zr catalysts are not as efficient in the
hydrophosphination of carbodiimides as the calcium sys-
tems reported by Barrett and Hill.7,8 Current data support
an insertion-based mechanism for these zirconium-based
hydrophosphination catalysts.
Experimental Section
General Considerations. All manipulations were performed
under a nitrogen atmosphere with dry, oxygen-free solvents
using an M. Braun glovebox or standard Schlenk techniques.
Benzene-d6 was purchased from Cambridge Isotope Laboratory
and then degassed and dried over NaK alloy. Celite-454 was
heated to a temperature greater than 180 °C under dynamic
vacuum for at least 8 h. Elemental analyses were performed on
an Elementar Microcube. NMR spectra were recorded with
either a Bruker AXR or Varian 500 MHz spectrometer in
benzene-d6 and are reported with reference to residual solvent
resonances (δ 7.16 and 128.0) or external 85% H3PO4 (δ 0.00).
Infrared spectra were collected on a Perkin-Elmer System 2000
FT-IR spectrometer at a resolution of 1 cm-1. The starting
materials 1-3 and N,N0-diphenylcarbodiimide were prepared
(28) (a) Dagorne, S.; Rodewald, S.; Jordan, R. F. Organometallics
1997, 16 (25), 5541–5555. (b) Guram, A. S.; Jordan, R. F. Organome-
tallics 1991, 10 (10), 3470–3479. (c) Guram, A. S.; Jordan, R. F. J. Org.
Chem. 1992, 57 (22), 5994–5999. (d) Guram, A. S.; Jordan, R. F.; Taylor,
D. F. J. Am. Chem. Soc. 1991, 113 (5), 1833–1835. (e) Jordan, R. F.;
Guram, A. S. Organometallics 1990, 9 (7), 2116–2123. (f) Jordan, R. F.;
Taylor, D. F. J. Am. Chem. Soc. 1989, 111 (2), 778–779. (g) Jordan,
R. F.; Taylor, D. F.; Baenziger, N. C. Organometallics 1990, 9 (5), 1546–
1557. (h) Rodewald, S.; Jordan, R. F. J. Am. Chem. Soc. 1994, 116 (10),
4491–4492. (i) Sadow, A. D.; Tilley, T. D. J. Am. Chem. Soc. 2003, 125
(26), 7971–7977. (j) Sadow, A. D.; Tilley, T. D. Angew. Chem., Int. Ed.
2003, 42 (7), 803–805. (k) Sadow, A. D.; Tilley, T. D. J. Am. Chem. Soc.
2005, 127 (2), 643–656.
(29) (a) Grundy, J.; Coles, M. P.; Hitchcock, P. B. Dalton Trans. 2003,
No. 12, 2573–2577. (b) Mansfield, N. E.; Coles, M. P.; Avent, A. G.;
Hitchcock, P. B. Organometallics 2006, 25 (10), 2470–2474. (c) Hirai,
T.; Han, L.-B. J. Am. Chem. Soc. 2006, 128 (23), 7422–7423.
(30) Zhang, W.-X.; Nishiura, M.; Hou, Z. Chem. Commun. 2006, No.
36, 3812–3814.

Article
Organometallics, Vol. 29, No. 11, 2010 2563
Scheme 3. Proposed Catalytic Cycle for the Hydrophosphination of Terminal Alkynes with Diphenylphosphine using a Triamidoamine-
Supported Zirconium Catalyst
according to literature procedures.19,31 Diphenylphosphine-d1
was prepared by reaction of D2O with lithium diphenylphenyl-
phosphide in THF followed by distillation. Lithium diphenyl-
phosphide was prepared by the reduction of triphenylphosphine
with a copious excess of lithium metal in THF. Phenylacetylene-d1
was prepared by reaction of D2O with lithium phenylacetylide
and distilled from Et2O under a nitrogen atmosphere. The
lithium phenylacetylide was prepared by addition of 1 equiv of
n-butyllithium to phenylacetylene in Et2O. All other chemicals
were obtained from commercial suppliers and dried by conven-
tional means.
6 H), 2.43 (t, CH2, 6 H), 0.17 (s, CH3, 27 H). 13C{1H} NMR
(125.8 MHz): δ 144.9 (d, CdN, JPC=38.6 Hz), 136.5 (d, C6H5,
J
PC=10.8 Hz), 135.9 (d, C6H5, JPC=10.8 Hz), 129.5 (s, C6H5),
128.9 (s, C6H5), 128.8 (s, C6H5), 128.7 (s, C6H5), 128.6 (s, C6H5),
61.3 (s, CH2), 47.8 (s, CH2), 1.9 (s, CH3). 31P{1H} NMR
(202.4 MHz): δ 24.5 (s). IR (KBr, Nujol): 1630 s (νCN), 1460 s,
1378 m, 1261 s, 1242 s, 1192 w, 1074 s, 1054 s, 1026 m, 936 s, 920 m,
907 m, 836 s, 786 s, 772 s, 742 s, 693 s, 634 m, 600 s, 578 w, 546 w,
498 m, 447 w cm-1. Anal. Calcd for C34H54N5PSi3Zr: C, 55.24; H,
7.36; N, 9.47. Found: C, 55.34; H, 7.48, N, 9.18.
Preparation of (N3N)ZrOCMe2(PHPh) (6). A 50 mL round-
bottom flask was charged with 1 (50 mg, 0.093 mmol) and ca. 5 mL
of benzene. With stirring, acetone (9.7 mg, 0.093 mmol) in 2 mL
of benzene was added to the zirconium solution, resulting in an
instantaneous color change from red to colorless. The solution
was stirred at ambient temperature for 48 h, and then the
benzene was lyophilized, yielding colorless microcrystals of
compound 6 (42 mg, 0.057 mmol, 95%). 1H NMR (500.1 MHz):
δ 7.50 (s, 2 H, C6H5), 7.05 (s, 3 H, C6H5), 4.61 (d, JPH=206 Hz,
Preparation of (N3N)ZrNdCPh(PHCy) (4). A 50 mL round-
bottom flask was charged with 2 (370 mg, 0.44 mmol), benzoni-
trile (67 mg, 0.44 mmol), and ca. 5 mL of benzene. To the stirred
solution was added a 2 mL benzene solution containing benzo-
nitrile. An instant color change from yellow to red was observed
upon addition of benzonitrile to the zirconium solution, which
was stirred at ambient temperature for ca. 3 h. The solution was
frozen and lyophilized, yielding pink microcrystals of com-
1
pound 4 (370 mg, 0.56 mmol, 86%). H NMR (500.1 MHz):
δ 7.91 (dt, 2 H, Ph), 7.19 (d, 1 H, Ph), 7.09 (d, 2 H, Ph), 4.47 (dd,
1 H, PH), 3.24 (m, 6 H, CH2), 2.35 (m, 6 H, CH2), 1.71 (d, JHH=
39 Hz, 3 H, CH3), 1.70 (d, JHH=49 Hz, 3 H, CH3), 0.36 (s, 27 H,
CH3). 13C{1H} NMR (125.8 MHz): δ 137.6 (d, JPC =19 Hz,
C6H5), 135.8 (d, JPC=15 Hz, C6H5), one phenyl resonance was
not observed and presumed to be obstructed by benzene-d6
solvent, 80.1 (s, CH3), 63.9 (s, CH2), 46.2 (s, CH2), 34.2 (s, CH2),
31.2 (d, JPC=29 Hz, (CH3)2C-P), 1.8 (s, CH3). 31P{1H} NMR
(202.4 MHz): δ -7.3. IR (KBr, Nujol): 2302 w (νPH), 1467 s,
1374 s, 1244 s, 1180 m, 1143 m, 1026 s, 925 s, 833 s cm-1. Anal.
Calcd for C30H55N4OPSi3Zr: C, 46.60; H, 8.32; N, 9.06. Found:
C, 46.60; H, 8.55; N, 8.93.
JPH=224 Hz, JHH=7 Hz, 1 H, PH), 3.35 (m, 6 H, CH2), 2.45 (m,
6 H, CH2), 2.02 (m, 2 H, C6H11), 1.59 (m, 2 H, C6H11), 1.47 (m,
1 H, C6H11), 1.20-1.28 (m, 4 H, C6H11), 1.11 (m, 2 H, C6H11),
0.23 (s, 27 H, CH3). 13C{1H} NMR (125.8 MHz): δ 187.5
(d, CdN, JPC=28 Hz), 144.6 (d, C6H5, JPC=32 Hz), 130.0 (s,
C6H5), 128.5 (s, C6H5), 128.3 (s, C6H5), 127.1 (s, C6H5), 127.0
(s, C6H5), 62.1 (s, CH2), 47.4 (s, CH2), 35.4 (s, C6H11), 33.9 (d,
JPC = 12 Hz, C6H11), 32.7 (d, JPC = 20 Hz, C6H11), 27.5 (s,
C6H11), 27.4 (s, C6H11), 26.3 (s, C6H11), 1.8 (s, CH3). 31P{1H}
NMR (202.4 MHz): δ -4.1. IR (KBr, Nujol): 2308 m (νPH),
1610 s (νCN), 1593 m, 1575 m, 1463 s, 1448 s, 1377 m 1266 m,
1239 s, 1194 m, 1144 w, 1074 s, 1057 s, 930 s, 903 m, 836 s, 783 s,
707 w, 676 w, 565 m cm-1. Anal. Calcd for C28H56N5PSi3Zr: C,
50.25; H, 8.43; N, 10.46. Found: C, 50.49; H, 8.46; N, 10.34.
Preparation of (N3N)ZrNdCPh(PPh2) (5). A 50 mL round-
bottom flask was charged with 3 (50 mg, 0.079 mmol) and ca.
5 mL of benzene. To the stirred solution was added benzonitrile
(8.1 mg, 0.079 mmol), and the resultant red solution was stirred
at ambient temperature for 48 h; then the benzene was lyoph-
ilized, yielding purple microcrystals of compound 5 (42 mg,
0.057 mmol, 72%). 1H NMR (500.1 MHz): δ 7.99 (d, C6H5, 1 H),
7.67 (t, C6H5, 2 H), 7.06-6.93 (m, C6H5, 12 H), 3.22 (t, CH2,
Preparation of (N3N)ZrNH(PPh2)(CPh2)] (7). A 1 mL Et2O
solution of 3 (50 mg, 0.079 mmol) was cooled to -30 °C, and to
that solution was added a cold 1 mL Et2O solution of benzo-
phenone imine (14 mg, 0.079 mmol). After 1 h, the resulting dark
orange solution was dried under reduced pressure. The residue
was dissolved in Et2O, and the solution was filtered and then
concentrated under reduced pressure. The solution was then
cooled to -30 °C, yielding dark orange crystals that were col-
lected in several crops and dried under reduced pressure (41 mg,
0.050 mmol, 64%). Characterization data for 7 have already
been reported.19 1H NMR (500.1 MHz): δ 7.30 (m, C6H5, 4 H),
7.11 (m, C6H5, 6 H), 3.49 (t, C6H5, 6 H), 2.58 (t, CH2, 6 H), 0.26
(s, CH3, 27 H). 13C{1H} NMR (125.8 MHz): δ 174.8 (s, CdN),
142.1 (s, C6H5), 133.9 (s, C6H5), 129.3 (s, C6H5), 128.5 (s, C6H5),
61.4 (s, CH2), 47.1 (s, CH2), 1.4 (s, CH3). 31P{1H} NMR
(202.4 MHz): δ 47.9 (s). IR (KBr, Nujol): 1641 s (νCN), 1595 w,
1463 s, 1378 m, 1258 s, 1242 s, 1080 s, 1020 m, 931 s, 901 m, 837 s,
(31) (a) Covert, K. J.; Mayol, A.-R.; Wolczanski, P. T. Inorg. Chim.
Acta 1997, 263 (1-2), 263–278. (b) Gudat, D.; Verkade, J. G. Organo-
metallics 1989, 8 (12), 2772–2779. (c) Fell, J. B.; Coppola, G. M. Synth.
Commun. 1995, 25 (1), 43–7.
784 s, 741 m, 701 m, 631 m, 564 m, 478 w, 451 w cm-1
.

2564 Organometallics, Vol. 29, No. 11, 2010
Roering et al.
General Preparation for Carbodiimide Insertions. A 50 mL
round-bottom flask was charged with 3 (50 mg, 0.079 mmol) and
ca. 5 mL of benzene. To the stirred solution was added the cor-
responding carbodiimide N,N0-dicylohexylcarbodiimide (17 mg,
0.079 mmol), N,N0-diphenylcarbodiimide (15 mg, 0.079 mmol),
or N,N0-diisopropylcarbodiimide (10 mg, 0.079 mmol) in ca.
2 mL of benzene. A color change was observed for each insertion
product. The solutions were stirred at ambient temperature for
4-14 h when the flask was then placed in the freezer and the
benzene was lyophilized, yielding the title compound.
The residue was dissolved in Et2O, and the solution was filtered
and then concentrated under reduced pressure until incipient
crystallization. The solution was warmed to dissolve the crys-
tals, and the solution was then cooled to -30 °C. Yellow crystals
were collected in several crops and dried under vacuum (48 mg,
1
0.059 mmol, 75%). H NMR (500.1 MHz, 338 K): δ 8.38 (d,
C6H5, 1 H, JPC=8.3 Hz), 7.49 (m, C6H5, 5 H), 7.36 (m, C6H5,
2 H), 7.31 (t, C6H5, 2 H), 7.23 (m, C6H5, 3 H), 7.00 (m, C6H5,
4 H), 2.99 (t, CH2, 6 H), 2.27 (t, CH2, 6 H), 0.41 (s, CH3, 27 H).
13C{1H} NMR (125.8 MHz): δ 204.5 (d, CdN, JPC=55.5 Hz),
146.1 (d, Ar, JPC =8.8 Hz), 135.3 (s, Ar), 135.1 (s, Ar), 134.3
(s, Ar), 129.3 (s, C6H5), 128.7 (s, Ar), 126.1 (s, Ar), 125.6 (s, Ar),
125.3 (s, Ar), 125.1 (s, Ar), 121.6 (s, Ar), 121.5 (s, Ar), three
phenyl resonances obscured by benzene-d6 solvent, 63.3 (s,
CH2), 48.0 (s, CH2), 2.5 (s, CH3). 31P{1H} NMR (202.4 MHz):
δ 0.7 (s). IR (KBr, Nujol): 1592 w, 1575 w, 1480 s, 1458 s (νCN),
1378 m, 1259 m, 1069 m, 1054 m, 1028 m, 936 s, 912 m, 898 w,
839 s, 794 m, 772 s, 747 m, 724 w, 700 w, 687 w, 665 w, 548 w,
496 w, 468 w, 421 w cm-1. Anal. Calcd for C38H56N5SPSi3Zr: C,
55.56; H, 6.87; N, 8.53. Found: C, 53.85; H, 6.95; N, 7.82.
Preparation of (N3N)Zr[η2(N,O)-OC(PPh2)NPh] (12). A 1 mL
Et2O solution of 3 (50 mg, 0.079 mmol) was cooled to -30 °C, and
to that solution was added a cold 1 mL Et2O solution of phenyl
isocyanate (9.4 mg, 0.079 mmol). After 1 h, the resulting light
orange solution was dried under reduced pressure. The residue was
redissolved in Et2O, and the solution was filtered through Celite
and then concentrated under reduced pressure. The solution was
then cooled to -30 °C. Light orange crystals were collected in several
crops and dried under reduced pressure (34 mg, 0.044 mmol, 56%).
1H NMR (500.1 MHz): δ 7.73 (t, C6H5, 4 H), 7.30 (d, C6H5, 2 H,
Preparation of (N3N)Zr[η2(N,N)-(NCy)2(PPh2)] (8). A color
change from red to light yellow was seen instantly upon addition
of carbodiimide solution to the phosphido complex, and the
solution was stirred at ambient temperature for 4 h. The benzene
solution was lyophilized, yielding the title compound as a light
1
yellow powder (0.052 g, 0.044 mmol, 79%). H NMR (500.1
MHz): δ 7.68 (t, 3 H, C6H5), 7.05 (m, 2 H, Ph), 3.79 (m, 2 H,
C6H11), 3.30 (t, 6 H, CH2), 2.50 (t, 6 H, CH2), 1.86 (m, 8 H,
C6H11), 1.65 (m, 4 H, C6H11), 1.49 (m, 2 H, C6H11), 1.17 (m, 2 H,
C6H11), 1.04 (m, 4 H, C6H11), 0.40 (s, 27 H, CH3). 13C{1H}
NMR (125.8 MHz): δ 152.3 (d, JPC=31.5 Hz, CdN), 135.8 (d,
JPC =14.6 Hz, C6H5), 134.3 (d, JPC=18.6 Hz, C6H5), 129.3 (s,
C6H5), 129.0 (d, JPC=5.3 Hz, C6H5) 68.3 (s, CH2), 60.4 (d, JPC
=
32.8 Hz, C6H11), 49.3 (s, CH2), 35.8 (s, C6H11), 32.6 (s, C6H11),
26.3 (d, JPC=25.7 Hz, C6H11), 25.3 (s, C6H11), 24.6 (s, C6H11),
2.9 (s, CH3). 31P{1H} NMR (202.4 MHz): δ -18.5 (s). IR (KBr,
Nujol): 1589 (νCN) m, 1480 m, 1366 w, 1343 w, 1243 s, 1218 s,
1100 s, 1026 m, 974 m, 888 m, 846 w, 741 s, 697 s, 624 w, 523 m,
492 m, 478 m cm-1. Anal. Calcd for C40H71N6PSi3Zr: C, 57.03;
H, 8.49; N, 9.98. Found: C, 57.49; H, 8.52; N, 9.21.
Preparation of (N3N)Zr[η2(N,N)-(PhN)2C(PPh2)] (9). A color
change from red to light yellow was seen instantly upon addition
of carbodiimide solution to the phosphido complex, and the
solution was stirred at ambient temperature for 14 h. The ben-
zene solution was lyophilized, yielding the title compound as a
yellow powder (60 mg, 0.079 mmol, 93%). 1H NMR (500.1 MHz):
δ 7.51 (m, 4 H, C6H5), 7.32 (m, 4 H, C6H5), 6.90 (m, 4 H, C6H5),
6.85 (m, 4 H, C6H5), 6.80 (m, 2 H, C6H5), 6.67 (m, 2 H, C6H5),
3.32 (t, 6 H, CH2), 2.39 (t, 6 H, CH2), 0.27 (s, 27 H, CH3).
13C{1H} NMR (125.8 MHz): δ 179.6 (d, JPC=63 Hz, CdN),
147.0 (s, C6H5), 135.0 (d, JPC=22 Hz, C6H5), 134.5 (s, C6H5),
128.2 (s, C6H5), 125.6 (s, C6H5), 122.9 (s, C6H5), 63.2 (s, CH2),
47.2 (s, CH2), 1.9 (s, CH3), two phenyl resonances were not
observed and presumed to be obscured by benzene-d6 solvent.
31P{1H} NMR (202.4 MHz): δ -18.3 (s). IR (KBr, Nujol): 2849
s, 1594 (νCN) m, 1492 m, 1456 s, 1365 s, 1244 m, 1203 m, 1171 w,
1078 m, 1046 w, 1026 w, 940 m, 906 w, 837 s, 784 s, 746 m, 695 m,
676 w, 581 w, 510 w cm-1. Anal. Calcd for C40H59N6PSi3Zr: C,
57.86; H, 7.16; N, 10.12. Found: C, 57.66; H, 7.19; N, 9.91.
Preparation of (N3N)Zr[η2(N,N)-(iPrN)2C(PPh2)] (10).A gradual
color change from red to colorless was observed upon stirring for 1 h.
The solution was stirred a total of 14 h at ambient temperature. The
benzene solution was lyophilized, yielding the title compound as a
colorless powder (58 mg, 0.076 mmol, 96%). 1H NMR (500.1 MHz):
δ 7.74 (m, 4 H, C6H5), 7.16 (m, C6H5) (accurate integration could
not be obtained because of overlap with benzene-d6 solvent), 7.06 (t,
2 H, C6H5), 4.26 (m, 2 H, CH), 3.26 (t, 6 H, CH2), 2.48 (t, 6 H,
CH2), 1.24 (d, 12 H, CH3), 0.37 (s, 27 H, CH3). 13C{1H} NMR
(125.8 MHz): δ 175.5 (d, JPC=72 Hz, CdN), 135.1 (d, JPC=18 Hz,
JPC=7.5 Hz), 7.08 (t, C6H5, 4 H), 7.01 (t, C6H5, 4 H), 6.76 (t, C6H5,
1 H), 3.26 (t, CH2, 6 H), 2.39 (t, CH2, 6 H), 0.18 (s, CH3, 27 H).
13C{1H} NMR (125.8 MHz): δ 186.9 (d, CdN, JPC=43 Hz), 145.0
(s, C6H5), 132.0 (s, C6H5), 135.7 (s, C6H5), 132.8 (d, JPC=6 Hz,
C6H5), 129.4 (s, C6H5), 128.5 (s, C6H5), 128.4 (s, C6H5), 124.2 (s,
C6H5), 61.9 (s, CH2), 47.8 (s, CH2), 1.9 (s, CH3). 31P{1H} NMR
(202.4 MHz): δ -12.1 (s). IR (KBr, Nujol): 2923 s, 2854 s, 1959 w
(νCO), 1579 m, 1502 s, 1464 s, 1277 m, 1242 m, 1214 w, 1060 w,
940 m, 837 m, 693 w, 518 w, 496 w cm-1. Anal. Calcd for
C22H44N5OSi3Zr: C, 54.07; H, 7.21; N, 9.27. Found: C, 54.35; H,
7.18; N, 9.20.
Preparation of (N3N)Zr[η2-CS2(PPh2)] (13). A 1 mL Et2O
solution of 3 (50 mg, 0.079 mmol) was cooled to -30 °C, and to
that solution was added a cold 1 mL Et2O solution of carbon
disulfide (6.0 mg, 0.079 mmol). After 1 h, the resulting red
solution was dried under vacuum. The residue was dissolved in
Et2O, and the solution was filtered through Celite and concen-
trated under reduced pressure. The solution was then cooled to
-30 °C, at which point red crystals were collected in several
crops and dried under vacuum (43 mg, 0.060 mmol, 76%). 1H
NMR (500.1 MHz): δ 7.91 (t, C6H5, 2 H), 7.90 (t, C6H5, 2 H),
7.261 (t, C6H5, 3 H), 7.22 (m, C6H5, 2 H), 3.43 (t, CH2, 3 H), 3.35
(t, CH2, 3 H), 2.40-2.36 (m, CH2, 3 H), 0.43 (s, CH3, 27 H).
13C{1H} NMR (125.8 MHz): δ 144.9 (d, C-P, JPC=38.6 Hz),
136.5 (d, C6H5, JPC=10.8 Hz), 135.9 (d, C6H5, JPC=10.8 Hz),
129.5 (s, C6H5), 128.9 (s, C6H5), 128.8 (s, C6H5), 128.7 (s, C6H5),
128.6 (s, C6H5), 61.3 (s, CH2), 47.8 (s, CH2), 1.9 (s, CH3).
31P{1H} NMR (202.4 MHz): δ 45.9 (s). IR (KBr, Nujol): 2925 s,
2855 s, 1579 m, 1460 s, 1376 m, 1299 w, 1263 m, 1244 s, 1143 w,
1048 s, 1019 m, 927 s, 892 w, 837 s, 781, 743 s, 696 m, 567 w, 463 w
cm-1. Anal. Calcd for C28H50N4PS2Si3Zr: C, 47.15; H, 7.07; N,
7.85. Found: C, 46.73; H, 7.16; N, 7.81.
C6H5), 133.8 (d, JPC=20 Hz, C6H5), 128.5 (s, C6H5), 128.3 (d, JPC
=
6 Hz, C6H5), 64.5 (s, CH2), 49.8 (d, JPC=11 Hz, CH), 47.4 (s, CH2),
25.6 (d, JPC=4 Hz, CH3), 3.2 (s, CH3). 31P{1H} NMR (202.4 MHz):
δ -9.10 (s). IR (KBr, Nujol): 1946 w, 1583 (νCN) w, 1462 w, 1377 w,
1290 w, 1246 m, 1215 w, 1180 m, 1120 s, 1026 m, 936 s, 841 s, 783 w,
Catalytic Hydrophosphination. Phenylacetylene. A PFTE-
valved NMR tube was charged with 3 (10 mg, 0.016 mmol),
diphenylphosphine (59 mg, 0.31 mmol), phenylacetylene (32
mg, 0.31 mmol), and benzene-d6 (500 μL). The tube was shielded
from light and placed in a 100 °C oil bath for 67 h. The reaction
gave cis and trans vinyl phosphine products in a 4:1 mixture of
the anti-Markovnikov product on the basis of 31P NMR spec-
troscopy. The vinyl phosphines have been reported previously.24
741 m, 695 w, 585 m, 551 w cm-1
.
Preparation of (N3N)Zr[η2(N,S)-SC(PPh2)N(C10H7)] (11). A
1mLEt2Osolutionof3(50 mg, 0.079 mmol) was cooled to -30 °C,
and to that solution was added a cold 1 mL Et2O solution of
1-naphthyl isothiocyanate (15 mg, 0.079 mmol). After 1 h, the
resulting light yellow solution was dried under reduced pressure.

Article
Organometallics, Vol. 29, No. 11, 2010 2565
Table 7. Crystal Data and Structure Refinement Parameters for Complexes 4, 5, 9, and 11
4
5
9
11
formula
Mr
cryst syst
C
28H56N5PSi3Zr
C34H54N5PSi3Zr
739.28
C34H63N6PSi3Zr
762.36
C34H54N5OPSi3Zr
755.28
triclinic
669.24
monoclinic
12.3884(7)
15.0561(9)
19.166(1)
90
94.313(1)
90
3564.8(4)
P21/n
triclinic
10.1235(4)
12.0108(5)
17.5314(8)
88.382(1)
87.427(1)
69.172(1)
1990.2(1)
P1
triclinic
9.887(1)
11.625(2)
18.429(2)
99.906(2)
99.369(2)
98.168(2)
2026.9(5)
P1
˚
a/A
10.0233(4)
10.7297(5)
19.9437(9)
76.0090(1)
76.3280(1)
70.6970(1)
1935.39(2)
P1
˚
b/A
˚
c/A
R/deg
β/deg
γ/deg
3
˚
V/A
space group
Z
4
2
2
2
θ range/deg
μ/mm-1
N
1.72-30.47
0.479
49 628
1.81-28.28
0.435
26 287
1.14-28.28
0.430
26 576
2.04-28.28
0.451
25 455
Nind
Rint
10 263
9812
0.0220
0.0275
0.0689
0.588, -0.528
1.028
10 003
0.0230
0.0256
0.0615
0.424, -0.255
1.031
9553
0.0235
0.0290
0.0716
1.044, -0.601
1.036
0.0298
0.0257
0.0606
0.415, -0.197
1.044
R1a (I > 2σ(I))
wR2b (I > 2σ(I))
ΔFmax, ΔFmin/e A
GOF on R1
3
˚
P
P
P
P
a R1 = ||Fo| - |Fc||/ |Fo|. b wR2 = { [w(Fo2 - Fc2)2]/ w(Fo2)2]}1/2
.
1-Hexyne. A PFTE-valved NMR tube was charged with 3
(10 mg, 0.016 mmol), diphenylphosphine (59 mg, 0.31 mmol),
1-hexyne (25 mg, 0.031 mmol), and benzene-d6 (500 μL). The
tube was shielded from light and placed in a 120 °C oil bath for
72 h. The reaction gave cis and trans vinyl phosphine products
on the basis of 31P NMR spectroscopy. The vinyl phosphines
have been reported previously.25
from light and reacted. Both 1H and 31P NMR spectra
were taken at regular intervals to monitor the progress of the
reaction.
X-ray Structure Determinations. X-ray diffraction data were
collected on a Bruker APEX 2 CCD platform diffractometer
˚
(Mo KR, λ=0.710 73 A) at 125 K. Suitable crystals of complexes
4, 5, 9, and 11 were mounted on nylon loops with Paratone-N
cryoprotectant oil. The structures were solved using direct
methods and standard difference map techniques and were
refined by full-matrix least-squares procedures on F2 with
SHELXTL (version 6.14).32 All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms on carbon were in-
cluded in calculated positions and were refined using a riding
model. The hydrogen atom on the phosphorus of (N3N)ZrNd
CPh(PHCy) (4), H(1), was located in the Fourier difference map
and refined freely. Crystal data and structure refinement para-
meters are given in Table 7.
Carbodiimides. A PFTE-valved NMR tube was charged with
3 (10 mg, 0.016 mmol), diphenylphosphine (59 mg, 0.314 mmol),
RNdCdNR (R=Cy, 65 mg; R=Ph, 59 mg; R=iPr, 40 mg;
0.31 mmol), and benzene-d6, (500 μL). The tube was heated at
120 °C for 12-24 h. Phosphaguanidine products were observed
in 75, 84, and 53% yields for R=Cy, Ph, iPr, respectively, on the
basis of 31P NMR spectroscopy. The phosphaguanidine pro-
ducts match previously reported products.8
Competition Experiments. PTFE-valved NMR tube was
charged with (N3N)ZrCtCPh (20 mg, 0.036 mmol), diphenyl-
phosphine (6.7 mg, 0.036 mmol), and a benzene-d6 (500 μL)
solution containing ferrocene as an internal standard (0.01 M).
A second PTFE-valved NMR tube was charged with 3 (23 mg,
0.036 mmol), phenylacetylene (3.7 mg, 0.036 mmol), and ferro-
cene standard benzene-d6 (500 μL). Both NMR tubes were
shielded from light and placed in a 70 °C oil bath for a given
amount of time.
Deuterium Labeling Studies. A PTFE-valved NMR tube was
charged with 13 (0.010 g, 0.018 mmol), diphenylphosphine-d1
(0.0034 g, 0.0181 mmol), and benzene-d6 (500 μL). Ferrocene
was dissolved in the benzene-d6 and used as an internal stan-
dard. The solution was shielded from light and reacted. Both 1H
and 31P NMR spectra were taken at regular intervals to monitor
the progress of the reaction.
A second PTFE-valved NMR tube was charged with 3 (0.010 g,
0.016 mmol), phenylacetylene-d1 (0.0017 g, 0.016 mmol), and
benzene-d6 (500 μL). Ferrocene was dissolved in the benzene-d6
and used as an internal standard. The solution was shielded
Acknowledgment. This work was supported by the U.S.
National Science Foundation (Grant No. CHE-0747612)
and the donors of the Petroleum Research Fund, admi-
nistered by the American Chemical Society (No. 466669-
G3). Summer support for S.M.C. was provided by the
ACS Project SEED and the Green Mountain ACS Local
Section. X-ray crystallographic facilities were provided
by the U.S. National Science Foundation (Grant No.
CHE-0521237 to J.M.T.). R.W. is a Research Fellow of
the Alfred P. Sloan Foundation.
Supporting Information Available: CIF files giving crystal
data for 4, 5, 9, and 11. This material is available free of charge
via the Internet at http://pubs.acs.org.
(32) Sheldrick, G. M. Acta Crystallogr. 2008, A64 (1), 112–122.