Organometallic molybdenum(V) complexes with primary phosphine ligands. Syntheses, spectroscopic properties and molecular structures of [Cp oMoCl4(PH2R)] (R = But, 1-Ad, Cy, Ph, 2,4,6-Me3C6H2, 2,4,6-Pri 3C6H2, Cpo = C5EtMe4)

Article abstract of DOI:10.1002/zaac.200300413

[Cp^oMoCl₄] (Cp^o = C₅EtMe ₄) reacts with primary phosphines PH₂R to give the paramagnetic phosphine complexes [Cp^oMoCl₄(PH ₂R)] [Cp^o = C₅

Full text of DOI:10.1002/zaac.200300413

Organometallic Molybdenum(V) Complexes with Primary Phosphine Ligands.
Syntheses, Spectroscopic Properties and Molecular Structures of
[Cp°MoCl4(PH2R)] (R ؍ But, 1-Ad, Cy, Ph, 2,4,6-Me3C6H2, 2,4,6-Pri3C6H2,
Cp° ؍ C5EtMe4)
Reinhard Felsberga, Steffen Blaurocka, 1), Peter C. Junkb, 1), Reinhard Kirmsea, Andreas Voigta, and
Evamarie Hey-Hawkins*, a
a Leipzig/Germany, Institut für Anorganische Chemie der Universität
b Clayton, Victoria/Australia, Monash University, Chemistry Department
Received December 11th, 2003.
Dedicated to Professor Werner Massa on the Occasion of his 60th Birthday
Abstract. [Cp°MoCl4] (Cp° ϭ C5EtMe4) reacts with primary phos-
phines PH2R to give the paramagnetic phosphine complexes
[Cp°MoCl4(PH2R)] [Cp° ϭ C5EtMe4, R ϭ But (1), 1-Ad (1-Ad ϭ
1-adamantyl; 2), Cy (3), Ph (4), Mes (Mes ϭ 2,4,6-Me3C6H2; 5),
Tipp (Tipp ϭ 2,4,6-Pri3C6H2; 6)]. 1Ϫ6 were characterized spectro-
scopically (IR, MS), and X-ray crystal structures were determined
for 1Ϫ4 and 6. EPR investigations in liquid and frozen solution
confirmed the presence of MoV species, and the data were used to
analyze the spin-density distribution in the first coordination
sphere. Complexes 3 and 4 react with two equivalents of NEt3 with
formation of [Cp°MoCl2(η3-P4Cy4H)] (7) and [Cp°2Mo2(µ-Cl)2(µ-
P4Ph4)] (8), respectively, in low yield. Complexes 7 and 8 were
characterized by X-ray crystallography.
Keywords: Molybdenum; Phosphorus; Phosphines; Tetraphos-
phanyl ligand; Tetraphosphine-1,4-diyl ligand
Metallorganische Molybdän(V)-Komplexe mit primären Phosphan-Liganden.
Synthese, spektroskopische Eigenschaften und Molekülstrukturen von
[Cp°MoCl4(PH2R)] (R ؍ But, 1-Ad, Cy, Ph, 2,4,6-Me3C6H2, 2,4,6-Pri3C6H2,
Cp° ؍ C5EtMe4)
Inhaltsübersicht. [Cp°MoCl4] (Cp° ϭ C5EtMe4) reagiert mit primä-
ren Phosphanen PH2R zu den paramagnetischen Phosphan-Kom-
plexen [Cp°MoCl4(PH2R)] [Cp° ϭ C5EtMe4, R ϭ But (1), 1-Ad (1-
Ad ϭ 1-Adamantyl; 2), Cy (3), Ph (4), Mes (Mes ϭ 2,4,6-
Me3C6H2; 5), Tipp (Tipp ϭ 2,4,6-Pri3C6H2; 6)]. Die Verbindungen
1Ϫ6 wurden spektroskopisch (IR, MS) charakterisiert, und von
1Ϫ4 und 6 wurden Röntgenstrukturanalysen angefertigt. EPR-Un-
tersuchungen in flüssiger und gefrorener Lösung bestätigten das
Vorliegen von MoV-Verbindungen. Die erhaltenen Daten wurden
zur Analyse der Spindichte-Verteilung in der ersten Koordinations-
sphäre der Komplexe genutzt. Die Verbindungen 3 und 4 reagieren
mit zwei Äquivalenten NEt3 in sehr geringer Ausbeute unter Bil-
dung von [Cp°MoCl2(η3-P4Cy4H)] (7) bzw. [Cp°2Mo2(µ-Cl)2(µ-
P4Ph4)] (8). Die Komplexe 7 und 8 wurden röntgenstrukturanaly-
tisch charakterisiert.
Introduction
ter can be used as starting materials for the preparation of
bridging [3a,d,e] and terminal [3c] tantalum phosphinid-
ene complexes.
Although organometallic trialkyl- and triarylphosphine
complexes of early transition metals have been studied in-
tensively, complexes derived from functionalized phos-
phines that exhibit a reactive phosphorus-substituent bond
have been largely neglected [1]. It was recently shown that
when Zr and Ta or Nb complexes react with primary phos-
phines, oxidative addition (zirconocene) [2] or formation of
stable phosphine complexes (TaV, NbV) [3] occurs. The lat-
Various substituted cyclopentadienyl molybdenum(V)
tetrachlorides are reduced on reaction with PH-func-
tionalized lithium phosphanides to give the corresponding
cyclopentadienyl molybdenum(III) dichloro complexes [4],
which can then react with further lithium reagent, yielding
terminal phosphanido, diphosphanyl, and diphosphene
complexes [5]. We attempted to prevent the reduction of
MoV by employing a primary phosphine instead of the
highly reducing lithium reagents for the introduction of a P-
functionalized ligand. While structurally characterized low-
valent molybdenum and tungsten complexes are known
with primary phosphines, e.g. [Mo(CO)6-n(PH2R)n] [6Ϫ9],
* Prof. Dr. Evamarie Hey-Hawkins
Johannisallee 29
D-04103 Leipzig, Germany
e-mail: hey@rz.uni-leipzig.de
1) X-ray structure determinations
tungsten
carbonyl
derivatives
[10Ϫ17],
[(η5-
806
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
DOI: 10.1002/zaac.200300413
Z. Anorg. Allg. Chem. 2004, 630, 806Ϫ816

Organometallic Molybdenum(V) Complexes with Primary Phosphine Ligands
C5H4Pri)WCl3(CO){PH2(CH2CHϭCH2)}]
[18]
and
converted starting material behind. Cooling gave crystals of the
phosphine complex.
[WCl4(PH2But)2] [19, 20], only a limited number of me-
tal(V) primary phosphine complexes have been described,
i.e. [CpЈMoCl4(PH2R)] (CpЈ ϭ C5H4Me, R ϭ Cy, 2,4,6-
Pri3C6H2 (Tipp)) [21], [Cp*WCl4(PH2Ph)] (Cp* ϭ C5Me5)
1: 1.62 g (4.2 mmol) [Cp°MoCl4] (in 30 mL Et2O), 0.38 g (0.38 mL,
4.2 mmol) PH2But, red-brown needles from a conc. toluene solu-
tion at 5 °C, yield: 1.46 g (73 %). Mp: 150-153 °C, ca. 165 °C (de-
comp).
Anal. Calcd for C15H28Cl4PMo (477.11): C, 37.76; H, 5.92; Cl,
29.72. Found: C, 37.40; H, 5.93; Cl, 29.00 %.
[19], and [Cp°WCl4{PH2(CH2CHϭCH2)}] (Cp°
C5Et4Me) [22].
ϭ
Here we report on the preparation, spectroscopic proper-
ties and molecular structures of organometallic molyb-
denum(V) complexes with primary phosphine ligands
[Cp°MoCl4(PH2R)] [Cp° ϭ C5EtMe4, R ϭ But (1), 1-Ad
(2), Cy (3), Ph (4), Mes (5), Tipp (6)]. Complexes 3 and 4
react with two equivalents of NEt3 with formation of
[Cp°MoCl2(η3-P4Cy4H)] (7) and [Cp°2Mo2(µ-Cl)2(µ-
P4Ph4)] (8), respectively, in low yield. The former contains
a tetraphosphanyl and the latter a tetraphosphine-1,4-diyl
ligand.
IR (cmϪ1): 2999 (m), 2975 (st), 2942 (m-st), 2917 (m-st), 2899 (st), 2857 (st),
2778 (w), 2407 (w, P-H), 2386 (w-m, P-H), 1633 (w), 1485 (st), 1457 (st),
1435 (st), 1393 (m-st), 1368 (st), 1262 (w), 1207 (m), 1181 (m), 1085 (m),
1039 (st), 1014 (st), 965 (w), 949 (w), 937 (m), 893 (st), 817 (st), 602 (w), 540
(w), 468 (w), 426 (m), 397 (w-m), 376 (st), 329 (m, δMoCl), 315 (m), 299 (m,
νasMoCl4), 240 (m, νsMoCl4), 215 (m, δMoCl), 183 (m, δMoCl), 132 (m).
2: 1.49 g (3.9 mmol) [Cp°MoCl4] (in 25 mL Et2O), 0.64 g (0.7 mL,
3.8 mmol) PH2Ad, brown prisms from toluene at Ϫ20 °C, yield:
1.6 g (75 %). Mp: 174-178 °C.
Anal. calcd for C21H34Cl4PMo (555.23): C, 45.43; H, 6.17; Cl,
25.54. Found: C, 45.30; H, 6.29; Cl, 25.11 %.
IR (cmϪ1): 2968 (m), 2899 (st), 2846 (st), 2413 (w, P-H), 2387 (w, P-H), 1627
(w), 1485 (st), 1453 (m-st), 1435 (st), 1369 (st), 1344 (m), 1317 (w), 1303 (m-
st), 1259 (m-st), 1189 (w-m), 1179 (m), 1102 (m-st), 1059 (m-st), 1043 (m-st),
1027 (st), 972 (st), 956 (w-m), 934 (st), 890 (st), 875 (st), 860 (m), 836 (m),
802 (m-st), 682 (w), 643 (w), 528 (w), 480 (w-m), 465 (w), 440 (w), 401 (m),
367 (m), 329 (m, δMoCl), 316 (m, νasMoCl4), 282 (m, νsMoCl4), 181 (m,
δMoCl), 141 (m).
Experimental
General
All experiments were carried out under purified dry argon. Solvents
were dried and freshly distilled under argon. The IR spectra were
recorded on an FT-IR spectrometer Perkin-Elmer System 2000 in
the range 4000-400 cmϪ1 (KBr) and 400-100 cmϪ1 (Nujol/poly-
ethylene). MS: VG 12-250. EPR spectra of ca. 10Ϫ3 M solutions of
1Ϫ6 in toluene were recorded with a Bruker ESP 300E at X-band
frequency (ν ഠ 9.5 GHz) at T ϭ 295 K and 130 K. The simulated
spectra were generated by using the simulation programmes “pow-
der” [23] and “SimFonia” [64]. The melting points were determined
in sealed capillaries under argon and are uncorrected. PH2R (R ϭ
But [26, 27], 1-Ad [28], Cy [26], Ph [29], Mes [27, 30], Tipp [31])
were prepared by literature procedures.
3: 1.5 g (3.9 mmol) [Cp°MoCl4] (in 30 mL Et2O), 0.5 g (0.5 mL,
4.3 mmol) PH2Cy, brown needles from toluene at Ϫ20 °C, yield:
1.6 g (82 %). Mp: 169-171 °C (decomp).
Anal. calcd for C17H30Cl4PMo (503.15): C, 40.58; H, 6.01; Cl,
28.19. Found: C, 39.94; H, 6.35; Cl, 28.28 %.
IR (cmϪ1): 2976 (m-st), 2959 (m), 2921 (st), 2854 (st), 2430 (w, P-H), 2386
(w-m, P-H), 1629 (w), 1484 (st), 1454 (st), 1435 (st), 1368 (st), 1331 (w-m),
1296 (w-m), 1277 (w), 1260 (w), 1181 (m), 1123 (w-m), 1085 (m), 1049 (m),
1038 (st), 1001 (st), 950 (w), 926 (st), 897 (st), 873 (m-st), 862 (st), 816 (m),
532 (w), 514 (w-m), 440 (w), 375 (m), 329 (st, δMoCl), 315 (m), 298 (st,
νasMoCl4), 240 (m, νsMoCl4), 215 (m, δMoCl), 183 (m, δMoCl).
4: 1.23 g (3.2 mmol) [Cp°MoCl4] (in 25 mL Et2O), 0.4 g (0.4 mL,
3.6 mmol) PH2Ph, brown prisms from toluene at Ϫ20 °C, yield:
1.5 g (94 %). Mp: 149-151 °C.
Anal. calcd for toluene-free C17H24Cl4PMo (497.11): C, 41.07; H,
4.87; Cl, 28.53. Found: C, 40.70; H, 5.03; Cl, 28.22 %.
IR (cmϪ1): 2980 (w-m), 2963 (w-m), 2934 (w), 2423 (w, P-H), 2402 (w-m, P-
H), 1571 (w), 1485 (st), 1456 (m), 1438 (st), 1431 (st), 1373 (st), 1314 (w),
1302 (w), 1262 (w), 1160 (w), 1131 (w-m), 1109 (m-st), 1043 (m-st), 1020
(m), 983 (w), 921 (m), 882 (st), 805 (w), 748 (st), 705 (w), 692 (m-st), 536
(w), 470 (m), 419 (m-st), 379 (m), 341 (sh), 330 (m, δMoCl), 295 (m, νas-
MoCl4), 257 (m, νsMoCl4) 183 (m, δMoCl).
[Cp°MoCl4]
Prepared according to the synthesis of [Cp*MoCl4] [40] and
[Cp°MoCl4(CH3CN)] [38]. PCl5 (8.1 g, 39 mmol) was slowly added
to a solution of [{Cp°Mo(CO)3}2] [38] (6.4 g, 9.7 mmol) in CH2Cl2
(30 mL). CO evolved. The solution was stirred for 12 h, the solvent
was evaporated and the remaining wine-red solid was washed with
hexane (30 mL) followed by diethyl ether (2 x 15 mL). Yield: 6.8 g
(90 %); dark red air-sensitive powder. Mp: ca. 165 °C (decomp).
Anal. calcd for C11H17Cl4Mo (387.01): C, 34.14; H, 4.43; Cl, 36.64.
Found: C, 34.29; H, 4.35; Cl, 36.42 %.
5: 1.04 g (2.7 mmol) [Cp°MoCl4] (in 30 mL Et2O), 0.4 g (0.4 mL,
2.6 mmol) PH2Mes, dark red product from toluene at Ϫ20 °C,
yield: 1.35 g (94 %). Attempts to obtain crystals suitable for X-ray
structure determination failed. Mp: 177-179 °C, 180 °C (decomp).
Anal. calcd for C20H30Cl4PMo (539.19): C, 44.55; H, 5.61; Cl,
26.30. Found: C, 43.30; H, 5.62; Cl, 26.05 %.
IR (cmϪ1): 2979, 2936, 2875 (m, C-H, CH3 and CH2); 1478 (s, C-C, Cp);
1453, 1425, 1373 (s, C-H, CH3 and CH2); 416, 352Ϫ333 (br, Mo-Cl); 279,
254 (w, Mo-Cl), 223, 201 (m, Mo-Cl).
IR (cmϪ1): 2964 (st), 2932 (m), 2873 (w), 2402 (w, P-H), 2380 (w, P-H), 1648
(w), 1483 (st), 1454 (st), 1432 (st), 1373 (st), 1307 (w), 1262 (st), 1183 (st),
1096 (st), 1028 (st), 933 (m), 872 (st), 803 (st), 702 (w), 491 (m), 454 (m),
434 (m).
General procedure for the preparation of
[Cp°MoCl4(PH2R)] [R ϭ But (1), 1-Ad (2), Cy
(3), Ph (4), Mes (5), Tipp (6)]
6: 1.44 g (3.7 mmol) [Cp°MoCl4] (in 30 mL Et2O), 0.9 g (0.9 mL,
3.8 mmol) PH2Tipp, red-brown prisms from a conc. toluene solu-
tion at 5 °C, yield: 2.1 g (91 %). Mp: 172-174 °C (decomp).
Anal. calcd for C26H42Cl4PMo (623.35): C, 50.10; H, 6.79; Cl,
22.75. Found: C, 49.10; H, 6.82; Cl, 22.43 %.
The primary phosphine was added with a pipette to a suspension
of [Cp°MoCl4] in diethyl ether. The mixture turned brown. After
stirring for 1-2 d, the solvent was removed in vacuum, giving a red-
brown (1, 4؊6) or brown (2, 3) residue. The product was washed
with hexane (10 mL) and dissolved in toluene (15 mL) leaving un-
IR (cmϪ1): 2965 (st), 2868 (m-st), 2455 (w, P-H), 2392 (w-m, P-H), 1597 (m-
st), 1557 (w-m), 1485 (st), 1459 (st), 1433 (st), 1372 (st), 1361 (st), 1321 (w),
Z. Anorg. Allg. Chem. 2004, 630, 806Ϫ816
zaac.wiley-vch.de
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
807

R. Felsberg, S. Blaurock, P. C. Junk, R. Kirmse, A. Voigt, E. Hey-Hawkins
1299 (w), 1262 (m), 1192 (w), 1170 (w-m), 1137 (m), 1103 (m), 1077 (m),
Results and Discussion
1037 (m-st), 957 (w), 937 (w), 868 (st), 842 (st), 806 (m), 747 (m-st), 653 (w),
638 (w), 476 (w), 406 (w-m), 379 (w-m), 363 (w-m), 329 (m, δMoCl), 304
(m, νasMoCl4), 258 (m, νsMoCl4), 180 (m, δMoCl).
Synthesis and properties of [Cp°MoCl4(PH2R)]
[R ϭ But (1), 1-Ad (2), Cy (3), Ph (4), Mes (5),
Tipp (6)]
Formation of [Cp°MoCl2(η3-P4Cy4H)] (7)
[Cp°MoCl4] was prepared from [{Cp°Mo(CO)3}2] and
PCl5. The air- and moisture-sensitive product is obtained
as a dark red solid which is very soluble in CH2Cl2, less
soluble in THF and almost insoluble in Et2O, toluene and
alkanes. [Cp°MoCl4] was characterized by IR and EPR
spectroscopy (vide infra).
NEt3 (0.6 ml, 0.44 g, 4.3 mmol) was added with a pipette to a sus-
pension of [Cp°MoCl4(PH2Cy)] (1.10 g, 2.2 mmol) in diethyl ether
(25 mL) at Ϫ40 °C. After stirring for 30 min. the solution was
warmed to r.t. and stirred overnight. The solid (NEt3HCl, 0.55 g)
was isolated by filtration and washed twice with Et2O (2 x 10 mL).
The combined diethyl ether solutions were concentrated and cooled
to Ϫ20 °C for 12 h, giving a mixture of solids (green, red-brown,
light brown). A crystal structure determination showed the small
amount of red-brown crystals to be 7. An IR spectrum of one crys-
tal was obtained in a diamond cell:
When an equimolar amount of PH2R [R ϭ But [26, 27],
Ad [28], Cy [26], Ph [29], Mes [27, 30] Tipp [31]] is added
to a suspension of [Cp°MoCl4] in toluene, the solution
turns red-brown with formation of the phosphine com-
plexes [Cp°MoCl4(PH2R)] (Eq. 1). Due to the low basicity
of primary phosphines, no further reaction is observed with
an excess of primary phosphine. This behaviour is in con-
trast to the reaction of [Cp*MCl4] (M ϭ Mo, W) with three
equivalents of primary amines NH2R, which yields the im-
ido complex [Cp*MCl2(NR)] and [NH3R]Cl (R ϭ But, Pri,
C6F5, 2,6-Pri2C6H3) [32].
IR (cmϪ1): 2964 (sh), 2923 (st), 2848 (st), 2605 (w-m, Cy), 2531 (w), 2498
(w-m), 2294 (m, P-H), 1447 (st), 1398 (w), 1377 (m), 1342 (w), 1295 (w),
1263 (w-m), 1174 (w), 1074 (w-m), 1024 (m), 998 (m), 921 (w), 887 (w), 849
(w), 806 (w-m), 512 (w), 466 (w).
The light brown solid was shown to be [{Cp°MoCl2}2] by 1H NMR
spectroscopy; a 31P NMR spectrum of the Et2O solution showed
signals for (PCy)4 (Ϫ68.3 ppm, s). The green solid could not be
identified.
Formation of [Cp°2Mo2(µ-Cl)2(µ-P4Ph4)] (8)
NEt3 (0.6 ml, 0.41 g, 4.0 mmol) was added with a pipette to a sus-
pension of [Cp°MoCl4(PH2Ph)] (1.0 g, 2.0 mmol) in diethyl ether
(25 mL) at Ϫ40 °C. After stirring for 30 min. the solution was
warmed to r.t. and stirred overnight. The solid (NEt3HCl) was iso-
lated by filtration and washed thrice with Et2O (3 x 15 mL). The
combined diethyl ether solutions were concentrated and cooled to
Ϫ20 °C for 12 h, giving a mixture of solids (green, light brown,
brown). A crystal structure determination showed the small
amount of brown crystals to be 8. The light brown solid was shown
to be [{Cp°MoCl2}2] by 1H NMR spectroscopy; a 31P NMR spec-
trum of the Et2O solution showed signals for (PPh)4 (Ϫ47.6 ppm,
s). The green solid could not be identified.
Scheme 1
Attempts to prepare adducts of MoV complexes often result
in reduction of the metal atom to MoIV. Thus, MoCl5 is
reduced to MoIV by nitrogen-containing ligands (e.g., ni-
triles [33, 34] etc. [35]) or oxygen-containing ligands (e.g.,
DME [36]). However, the acetonitrile adduct of
[CpRMoCl4] (CpR ϭ Cp [37], CpЈ, Cp° [38]) is stable.
Up to now, only a limited number of complexes of cyclo-
pentadienyl molybdenum(V) [or tungsten(V)] tetrachloride
with tertiary phosphine ligands are known, i.e. [Cp*
MCl4(PMe3)] [39, 40] but several cyclopentadienyl molyb-
denum(IV) [41Ϫ44] or molybdenum(III) [45Ϫ48] halide
complexes with tertiary phosphine ligands have been re-
ported. The number of molybdenum complexes with pri-
mary phosphines is limited [49Ϫ53], and only a small num-
ber of crystal structure determinations have been reported
to date [6Ϫ9, 21]. The majority are carbonyl complexes of
molybdenum(0) with primary phosphines [6Ϫ9, 50Ϫ53],
which are usually prepared by carbonyl displacement with
primary phosphines. As far as we are aware, the only known
primary phosphine complexes of molybdenum in a higher
oxidation state are [CpЈMoCl4(PH2R)] (R ϭ Cy, Tipp) [21])
and [Mo2Cl4(PH2Ph)4] [54]; theoretical calculations have
been carried out on [MoCl4-Mo(PH3)4] [55].
Data collection and structural refinement of 1 - 4 and
6 - 8
Details of the data collection and crystal structure refinement are
˚
summarized in Table 1. Data (MoKα, λ ϭ 0.71073 A) were collected
with a Siemens CCD (SMART). All observed reflections were used
for determination of the unit cell parameters. The structures were
solved by direct methods (SHELXTL PLUS [24]) and subsequent
difference Fourier syntheses and refined by full-matrix least-
squares methods on F2 (SHELXTL PLUS [24]). Restrictions for
1؊4 and 6؊8: Mo, Cl, P, and C atoms anisotropic, H atoms lo-
cated or in calculated positions and refined isotropically. Absorp-
tion correction with SADABS [25]. Crystallographic data (exclud-
ing structure factors) for the structure reported in this paper have
been deposited with the Cambridge Crystallographic Data Centre
as supplementary publication no. CCDC-221395 (1), Ϫ392 (2),
Ϫ390 (3), Ϫ391 (4), Ϫ396 (6), Ϫ394 (7), and Ϫ393 (8). Copies of
the data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, UK [fax: (ϩ44) 1223-336-
033; e-mail: deposit@ccdc.cam.ac.uk).
808
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
zaac.wiley-vch.de
Z. Anorg. Allg. Chem. 2004, 630, 806Ϫ816

Organometallic Molybdenum(V) Complexes with Primary Phosphine Ligands
Table 1 Crystal data and structure refinement for 1Ϫ4 and 6Ϫ8
Compound
1
2
3
4
empirical formula
formula weight
temperature [K]
crystal system
C15H28Cl4MoP
477.08
220(2)
orthorhombic
Pnam
C21H34Cl4MoP
555.19
223(2)
monoclinic
P21/n
C17H30Cl4MoP
503.12
220(2)
orthorhombic
P212121
C17H24Cl4MoP · 0.5 toluene
543.14
213(2)
monoclinic
C2/c
space group
unit cell dimensions
˚
a /A
15.182(1)
11.446(1)
11.626(1)
12.770(1)
14.769(1)
25.649(1)
92.563(1)
4832.7(2)
8a)
1.526
1.057
2280
11.227(1)
12.688(1)
14.776(1)
13.348(1)
13.195(1)
26.063(1)
91.567(1)
4588.8(2)
8
1.572
1.111
Ϫ
˚
b /A
˚
c /A
β /°
3
˚
V /A
2020.25(6)
4
1.569
1.250
972
2104.78(7)
4
1.588
1.204
Ϫ
Z
ρcalcd /g cmϪ3
µ(MoKα) /mmϪ1
F(000)
Θ min. Θ max. /°
2.23-27.86
Ϫ19 Յ h Յ 19
Ϫ15 Յ k Յ 14
Ϫ15 Յ l Յ 15
14282
2382
0.0722
1.59-27.77
Ϫ16 Յ h Յ 16
Ϫ7 Յ k Յ 19
Ϫ32 Յ l Յ 32
25648
10251
0.0517
2.12-27.79
Ϫ13 Յ h Յ 13
Ϫ16 Յ k Յ 16
Ϫ19 Յ l Յ 19
16667
4646
0.0270
1.56-27.89
Ϫ17 Յ h Յ 16
Ϫ17 Յ k Յ 17
Ϫ21 Յ l Յ 32
15432
4993
0.0490
index ranges
reflections collected
independent reflections
R(int)
parameters
119
1.102
0.0334
0.0545
497
1.148
0.0495
0.0979
271
1.014
0.0208
0.0536
246
1.140
0.0368
0.0773
goodness-of-fit on F2
final R indices [I2σ(I)] R1
wR2
R indices (all data) R1
wR2
largest diff. peak and hole /e A
0.0536
0.0601
0.619 and Ϫ1.108
0.0910
0.1252
0.577 and Ϫ0.867
0.0226
0.0550
0.388 and Ϫ0.450
0.0692
0.0996
0.450 and Ϫ0.690
Ϫ3
˚
a) There are two independent molecules in the asymmetric unit.
Compound
6
7
8
empirical formula
formula weight
temperature [K]
crystal system
C26H42Cl4MoP
623.31
220(2)
monoclinic
P21/c
C35H62Cl2MoP4
773.57
223(2)
monoclinic
P21/n
C46H54Cl2Mo2P4
993.55
223(2)
monoclinic
P21/n
space group
unit cell dimensions
˚
a /A
15.820(1)
16.970(1)
10.872(1)
96.411(1)
2900.7(1)
4
1.427
0.889
1292
12.331(1)
21.500(1)
15.081(1)
106.823(1)
3827.1(3)
4
1.343
0.673
1632
13.269(1)
15.465(1)
21.901(1)
104.95(1)
4342.20(8)
4
1.520
0.881
2032
˚
b /A
˚
c /A
β /°
3
˚
V /A
Z
ρcalc /g cmϪ3
µ(MoKα) /mmϪ1
F(000)
Θ min. Θ max. /°
1.30-27.93
Ϫ20 Յ h Յ 19
Ϫ19 Յ k Յ 21
Ϫ12 Յ l Յ 14
16521
6288
0.0692
1.70-27.45
Ϫ11 Յ h Յ 15
Ϫ26 Յ k Յ 25
Ϫ19 Յ l Յ 19
20405
7922
0.0777
1.63-27.26
Ϫ15 Յ h Յ 16
Ϫ14 Յ k Յ 19
Ϫ27 Յ l Յ 27
26328
8757
0.0407
index ranges
reflections collected
independent reflections
R(int)
parameters
300
0.969
0.0394
0.0818
387
1.003
0.0538
0.0951
497
1.027
0.0313
0.0768
goodness-of-fit on F2
final R indices [I2σ(I)] R1
wR2
R indices (all data) R1
wR2
largest diff. peak and hole /e A
0.0693
0.1022
1.147 and Ϫ1.359
0.1233
0.1188
0.602 and Ϫ0.839
0.0437
0.0846
0.584 and Ϫ1.366
Ϫ3
˚
For 1Ϫ6, two isomers are possible, with the cyclopen-
tadienyl ligand and the phosphine ligand in a trans or a cis
arrangement. They can be distinguished by IR spec-
troscopy. For the trans arrangement, the idealised local
symmetry of the MoCl4 fragment is C4v. Thus, 9 vibrations
(2 A1, 2 B1, 1 B2, 2 E) are expected, of which only A1
(νsMoCl4 and δMoCl4) and E (νasMoCl4 and δMoCl2) are
infrared-active [56]. For [CpMoCl4(CH3CN)], all four ab-
sorptions are observed (δMoCl 328 m, νasMoCl4 293 vst,
br, νsMoCl4 245 m, δMoCl 224 vw, 202 w) [37]. By com-
parison, the corresponding Mo-Cl bands in 1Ϫ6 can be as-
signed, as well as the Cp° and R vibrations [57]. Thus,
Z. Anorg. Allg. Chem. 2004, 630, 806Ϫ816
zaac.wiley-vch.de
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
809

R. Felsberg, S. Blaurock, P. C. Junk, R. Kirmse, A. Voigt, E. Hey-Hawkins
Table 2 Selected bond lengths and angles of compounds 1Ϫ4 and 6
Compound
Mo-P
/A
av. Mo-Cl
/A
Mo-Cen
(Cp°) /A
Cen-Mo-P
/degree
av. Cen-Mo-Cl
/degree
distance Mo
from Cl4 plane/A
P-Mo-Cl
/degree
˚
˚
˚
˚
1
2.5740(9)
2.591(1)
2.592(1)
2.5587(6)
2.567(1)
2.6169(9)
2.4207(7)
2.442(1)
2.443(1)
2.430(6)
2.425(1)
2.4232(9)
2.096
2.120
2.124
2.109
2.098
2.103
174.2
174.4
173.8
175.0
174.8
174.8
105.2
105.1
105.1
105.3
105.5
104.9
0.61
0.64
0.64
0.64
0.65
0.62
69.75(3)Ϫ80.94(3)
70.39(4)Ϫ80.07(4)
70.22(4)Ϫ80.21(4)
70.23(2)Ϫ78.97(2)
70.20(3)Ϫ79.39(3)
70.40(3)Ϫ78.77(3)
2a)
3
4
6
a) there are two independent molecules present in the unit cell
νsMoCl4 and νasMoCl4 are observed at 282-240 cmϪ1 (m)
and 316-295 cmϪ1 (m), and δMoCl in the range of 330-
329 cmϪ1 (m-st) and 215-181 cmϪ1 (m-w).
The P-H stretching vibrations in 1Ϫ6 (νsPH2 and νasPH2,
2380Ϫ2455 cmϪ1) are shifted to higher wavenumber com-
pared to the primary phosphines PH2R [νPH2 in PH2R
with R ϭ But (2282), Cy (2280) and Ph (2280 cmϪ1) [58]].
In [Mo(CO)3(PH2Ph)3], νPH is observed at 2295 cmϪ1 [50],
and the light-sensitive homoleptic yellow complex
[Mo(PH2Ph)6] exhibits several absorptions of weak to me-
dium intensity for νPH in the range 2100-2300 cmϪ1 [49].
Molecular structures of [Cp°MoCl4(PH2R)] [R ϭ
But (1), 1-Ad (2), Cy (3), Ph (4), Tipp (6)]
Only a small number of monocyclopentadienyl MoV tetra-
halide derivatives have been structurally characterized, i.e.
[Cp*MoCl4(H2O)] [59] and the phosphine complexes (η5-
pentamethylcyclopentadienyl)(1,2,3,5,6,7,7a,7b-octamethyl-
4-phenyl-7a,7b-dihydro-4H-dicyclopenta(b,d)phosphole)-
tetrachloromolybdenum ([Cp*MoCl4{PPh(C5Me4)2}]) [60]
and [CpЈMoCl4(PH2R)] (R ϭ Cy, Tipp) [21].
Fig. 1 Molecular structure of [Cp°MoCl4(PH2But)] (1) showing the
atom numbering scheme employed (ORTEP plot, 50 % probability,
SHELXTL PLUS; XP [24]). Hydrogen atoms (other than P-H) are
omitted for clarity.
Single crystals of 1Ϫ4 and 6 were obtained from toluene
solutions at 0 or Ϫ20 °C. Complex 4 crystallizes with tolu-
ene; for 2, there are two independent molecules in the asym-
metric unit (Table 1). Complex 1 lies on a crystallographic
mirror plane which passes through the atoms Mo, Cl(1),
Cl(3), P, C(1), C(3), C(5), C(10), and C(14).
In complexes 1Ϫ4 and 6, the Mo atom has a pseudo-
octahedral coordination, with the phosphine ligand located
trans to the Cp° ligand (regarded as unidentate), and the
four chlorine ligands bent away from the Cp° ligand (Figs.
1Ϫ5). Thus, the angles between the P atom and the four
chloro ligands lie between 69.75(3) and 80.94(3)° (Table 2).
The Mo atom is shifted towards the Cp° ligand and lies
˚
ca. 0.61Ϫ0.65 A above the plane defined by the four chloro
ligands, which is parallel to the plane of the Cp° ring.
The average Mo-C(Cp°) distances range from 2.096(2) to
˚
2.124(4) A and do not differ significantly from Mo-C(Cp)
distances in related complexes [41Ϫ44, 60]. The Mo-Cl
˚
bond lengths [2.4207(2) to 2.443(1) A] are longer than those
Fig. 2 Molecular structure of [Cp°MoCl4(PH2Ad)] (2) showing the
atom numbering scheme employed (ORTEP plot, 50 % probability,
SHELXTL PLUS; XP [24]). Hydrogen atoms (other than P-H) are
omitted for clarity. Only one of the two independent molecules is
shown.
˚
in [Cp*MoCl4{PPh(C5Me4)2}] [2.303(3) A] [60] but slightly
shorter than those observed in related CpMoIV compounds
(cf., [CpMoCl3L2]: L2 ϭ PMe2CH2CH2PMe2 (dmpe): av.
˚
2.493 A [41]; L2
ϭ
PPh2CH2CH2PPh2 (dppe): av.
810
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Organometallic Molybdenum(V) Complexes with Primary Phosphine Ligands
Fig. 5 Molecular structure of [Cp°MoCl4(PH2Tipp)] (6) showing
the atom numbering scheme employed (ORTEP plot, 50 % proba-
bility, SHELXTL PLUS; XP [24]). Hydrogen atoms (other than P-
H) are omitted for clarity.
Fig. 3 Molecular structure of [Cp°MoCl4(PH2Cy)] (3) showing the
atom numbering scheme employed (ORTEP plot, 50 % probability,
SHELXTL PLUS; XP [24]). Hydrogen atoms (other than P-H) are
omitted for clarity.
6 show shorter Mo(1)-P(1) bond lengths of 2.5587(6) to
˚
2.6169(9) A. In the structurally related 16-electron com-
plexes [Cp*TaCl4(PH2R)] lengthening of the metal-P bond
compared to tantalum phosphine complexes was observed
[3b].
A comparison of the corresponding CpЈ and Cp° com-
plexes [CpЈMoCl4(PH2R)] [21] and [Cp°MoCl4(PH2R)]
(R ϭ Cy, Tipp) shows that the structural data of these de-
rivatives [other than the Mo-Cen (Cen ϭ centre of the
cyclopentadienylring) distance] are hardly influenced by the
different cyclopentadienyl ligands but are affected by differ-
ent R substituents. Thus, in the Cy derivative, the Mo-P
R
˚
˚
bond lengths of 2.554(1) A (Cp ϭ CpЈ) and 2.5587(6) A
(CpR ϭ Cp°) and the mean Mo-Cl bond lengths of
2.420(1) A (Cp ϭ CpЈ) and 2.430(6) A (Cp ϭ Cp°) are
similar, while the Mo-Cen distance in the Cp° derivative is
R
R
˚
˚
Fig. 4 Molecular structure of [Cp°MoCl4(PH2Ph)] (4) showing the
atom numbering scheme employed (ORTEP plot, 50 % probability,
SHELXTL PLUS; XP [24]). Hydrogen atoms (other than P-H) are
omitted for clarity.
˚
˚
longer by ca. 0.06 A (CpЈ: av. 2.049, Cp°: av. 2.109 A). The
mean Cen-Mo-Cl angles are 105.0° (CpR ϭ CpЈ) and 105.3°
(CpR ϭ Cp°), and the mean distances of the Mo atom from
R
˚
the plane of the four Cl atoms are 0.63 A (Cp ϭ CpЈ) and
0.64 A (CpR ϭ Cp°). Similarly, these data hardly differ in
˚
the two complexes [CpRMoCl4(PH2Tipp)] (CpR ϭ CpЈ [21],
˚
˚
2.476(3) A [42]; L ϭ P(OCH2)3CEt: av. 2.46(1) A [43]; L ϭ
˚
Cp°; value for Cp° derivative in brackets: Mo-P 2.617(1) A
[2.6169(9) A], mean Mo-Cl 2.414(1) A [2.4232(9) A], Mo-
Cen 2.049 A [2.103 A], mean Cen-Mo-Cl 104.9 [104.9°],
mean distance of the Mo atom from the plane of the four
˚
PMe2Ph: av. 2.505(1) A [44]).
˚
˚
˚
While the Mo-P bond lengths of primary molybdenum(0)
carbonyl phosphine complexes are in the range of 2.41 to
˚
˚
˚
2.65 A (bulky ligands have longer Mo-P bonds) [6Ϫ9, 61],
˚
Cl atoms 0.61 [0.62 A].
and those of MoII phosphine complexes range from ca.
˚
2.539 to 2.564 A [54, 62], the Mo-P bond lengths of 18-
Intermolecular hydrogen bonding between the P-H pro-
ton and a chloro ligand of a neigboring molecule is ob-
served for 1 and 4 and results in the formation of polymeric
(for 1, Fig. 6) or dimeric (for 4, Fig. 7) arrangements in the
solid state.
electron molybdenum cyclopentadienyl complexes in which
one phosphine adopts a position trans to the cyclopen-
tadienyl ring are generally longer (2.688(4) A in
[CpMoCl3(dppe)] [42]). The 17-electron complexes 1Ϫ4 and
˚
Z. Anorg. Allg. Chem. 2004, 630, 806Ϫ816
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811

R. Felsberg, S. Blaurock, P. C. Junk, R. Kirmse, A. Voigt, E. Hey-Hawkins
ting of the hyperfine lines due to the two isotopes 95Mo and
97Mo is not observed because of the small differences in
their nuclear properties.
For determination of the exact g values and coupling
Mo
P
constants a0
and a0 , the spectra in solution and frozen
solution were simulated with the programmes “powder”
[23] and “SimFonia” [64]. The principal values obtained for
the g tensors and the [95, 97] Mo and 31P hyperfine struc-
ture tensors AMo and AP are listed in Table 3 and compared
to those determined for [Cp*MoCl4] [40], [Cp*
Fig. 6 Formation of polymeric chains by hydrogen bonding in
[Cp°MoCl4(PH2But)] (1). Hydrogen atoms (other than P-H) are
omitted for clarity. H1···Cl2Ј 2.892 A, H1Ј···Cl2Љ 2.892 A.
MoCl4(PMe3)]
[40],
[Cp*MoCl4(H2O)]
[59],
˚
˚
[CpMoCl4(CH3CN)] [37] and [CpMoBr4(CH3CN)] [37].
Unfortunately, for the cited complexes, EPR studies were
carried out only at 295 K. Furthermore, the accuracy of the
parameters determined is low, and the go values for [Cp*
MoCl4] [40] and [Cp*MoCl4(PMe3)] [40] (see Table 3) are
questionable. We earlier gave a detailed discussion of the
theoretical background of the determination of these data
[21].
The hyperfine parameters can be used to estimate the
spin density on the nuclei, and therefore allow conclusions
to be made about the nature of the M-L bonds, in particu-
lar the hybridization of the orbitals [65, 66]. For this, the
complete parameters of the hyperfine tensors are needed.
The spin densities (Cs,p,dX) can then be obtained by using
Eq. (2a, b):
Fig.
7
Formation of dimers by hydrogen bonding in
[Cp°MoCl4(PH2Ph)] (4). Hydrogen atoms (other than P-H) are
omitted for clarity. H1p···Cl1Ј 2.953 A.
˚
aoX, exp.
aoX,th.
(CsX)2 ϭ
(a)
(2)
EPR studies on [Cp°MoCl4(PH2R)] [R ϭ But (1),
1-Ad (2), Cy (3), Ph (4), Mes (5), Tipp (6)]
beXxp.
btXh.
(CpX, d)2 ϭ
with beXxp. ϭ AdXipol (b)
[Cp°MoCl4] and 1Ϫ6 are stable organometallic radicals (17-
electron species) [63]. As far as we know, the only related
MoV complexes which have been studied by EPR spec-
troscopy are [CpMoX4(CH3CN)] (with X ϭ Cl, Br) [37],
[Cp*MoCl4] [40], [Cp*MoCl4(PMe3)] [40], [Cp*MoCl4(P-
Me2Ph)] [44], and [CpЈMoCl4(PH2R] (R ϭ Cy, Tipp) [21].
However, most of these studies were performed in liquid
solution without any interpretation of the data obtained;
only for [CpЈMoCl4(PH2R] (R ϭ Cy, Tipp) [21] did we re-
port a detailed discussion.
where s, p and d represent atomic orbitals, X is the nucleus
under discussion, ao the isotropic hyperfine interaction and
bX the dipolar part of the hyperfine tensor.
Using the values for the parameters aoX,th. and btXh. calcu-
lated by Morton and Preston [66] and Eqs. (2a) and (2b),
the spin densities at the Mo and P atoms can be calculated
(see Table 4). Thus, 84.8Ϫ89.2 % of the spin density is lo-
cated in the Mo 4d orbitals, and 6.1Ϫ6.3 % was estimated
to be in the Mo 5s orbital. The latter value appears to be
questionable because of spin-polarization effects, which are
known to yield large discrepancies in the ns contributions,
especially for heavier transition metal ions [67, 68].
The 3s and 3p spin densities determined for the 31P nu-
cleus can be used to estimate the 3s, 3p hybridization of the
P atom (Eq. (3)):
A comparison of the data obtained for [Cp°MoCl4] and
those of related compounds is given in Table 3.
The primary phosphine complexes 1Ϫ6 show EPR spec-
tra which are consistent with MoV (4d1, S ϭ 1/2). EPR
spectra were obtained in toluene at 293 and 130 K. The
spectra consist of a 12-line multiplet symmetrically ar-
ranged around an intense central doublet. The doublet
arises from species which contain molybdenum isotopes
with a nuclear spin I ϭ 0 (total natural abundance 74.5 %);
the doublet splitting is due to hyperfine interaction with the
31P nucleus (I ϭ 1/2). The weaker multiplet comes from
complexes which contain the molybdenum nuclei 95Mo (I ϭ
5/2, natural abundance 15.9 %) and 97Mo (I ϭ 5/2, natural
abundance 9.6 %). These result in a sextet, which is split by
the 31P nucleus into twelve lines. Two of these lines appear
to be overlapped by the central doublet. An isotopic split-
2
(csP)2 ϭ αP2 (1-n2)
(cpP)2 ϭ αP n2
(3)
2
where αP is the overall spin density on the P atom. The
values derived with Eq. 3 are given in Table 5. The degree
of hybridization n2 of 0.72Ϫ0.78 is close to that expected
for a tetrahedrally coordinated P atom (n2 ϭ 0.75). This
result is consistent with the molecular structures (see Figs.
1Ϫ5), which show nearly tetrahedral coordination of the P
atom. After summation of the spin densities estimated for
812
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Z. Anorg. Allg. Chem. 2004, 630, 806Ϫ816

Organometallic Molybdenum(V) Complexes with Primary Phosphine Ligands
Table 3 EPR parameters for [Cp°MoCl4], 1Ϫ6, [Cp*MoCl4] (I) [40], [Cp*MoCl4(PMe3)] (II) [40], [CpMoCl4(CH3CN)] (III) [37],
[CpMoBr4(CH3CN)] (IV) [37], [Cp*MoCl4(H2O)] (V) [59], [Cp*MoCl4(PMe2Ph)][f] (VI) [44] and [CpЈMoCl4(PH2R)] [R ϭ 2,4,6-Pri3C6H2
(VII), Cy (VIII)] [21]. Hyperfine constants are given in 10Ϫ4 cmϪ1 [a]
.
1
2
3
4
5
6
[Cp°MoCl4]
1.994
I
II
III
IV
V
VI
VII
VIII
gʈ
1.960
1.996
1.985
1.984
65.4
28.8
39.5
41.2
28.5
22.3
24.4
24.3
2.06
12.2
1.963
1.998
1.986
1.986
65.6
28.4
40.8
41.0
28.3
23.1
24.9
24.8
1.74
12.4
1.961
1.998
1.985
1.986
65.9
29.4
39.5
41.7
29.8
22.9
25.2
25.2
2.30
12.2
1.962
1.999
1.986
1.987
65.6
27.2
40.8
40.1
30.2
24.1
26.2
26.1
2.05
12.8
1.964
1.998
1.985
1.986
65.3
27.9
39.5
40.5
30.1
22.9
25.3
25.3
2.41
12.5
1.964
1.998
1.986
1.987
65.3
28.0
40.8
40.6
29.6
23.5
25.6
25.5
2.04
12.4
1.975
1.968
gЌ
go
gav
1.990[d] 1.995
1.99
36.2
1.97
41.4
1.94
45.3
1.99
41.8
1.911
35.1
1.989 1.985
1.985
1.986
1.986
64.9
28.8
39.9
40.8
28.8
21.8
24.1
24.1
[b]
AʈMo
62.6
Mo
AЌ
27.9
Mo
[d]
a0
35.8
Mo [b]
aav
40.9
24.1
39.5
28.9
AʈP
P
AЌ
21.8
P
[e]
ao
P [b]
aav
24.8
24.1
AP
[c]
dipol
AMo
[c]
dipol
solvent
toluene toluene toluene toluene toluene toluene CH2Cl2
THF THF acetone acetone CH2Cl2 THF toluene toluene
Mo
P
[b]
[a] Experimental error: go, gʈ, gЌ 0.002; aoMo, AʈMo, AЌ
0.5; aoP, AʈP, AЌ
0.5.
g
av
ϭ (gʈ ϩ 2gЌ)/3 and aav ϭ (Aʈ ϩ 2AЌ)/3. Ϫ [c] AX
ϭ [(Aʈ Ϫ
dipol
AЌ)/3], X ϭ P, Mo. [d] Not resolved. [e] Perpendicular part poorly resolved Ϫ values obtained with gav ϭ go and gЌ ϭ (3go Ϫ gʈ)/2. [f] Complex was generated
in situ and not isolated.
Table 4 Spin density at phosphorus and molybdenum atoms in 1Ϫ6
and 6 with two equivalents of DBU in an attempt to pre-
pare phosphinidene complexes by elimination of HCl, anal-
ogous to the preparation of Ta phosphinidene complexes
[3c].
1
2
3
4
5
6
2
(CMo
(CMo
)
)
0.848
0.062
0.005
0.017
0.864
0.062
0.006
0.014
0.848
0.063
0.006
0.019
0.892
0.062
0.006
0.017
0.868
0.061
0.006
0.02
0.866
0.061
0.006
0.017
d
2
With DBU, the formation of [(Cp°MoCl2)2] [4] was ob-
served by 1H NMR spectroscopy. By 31P NMR spec-
troscopy, the formation of (PBut)3, (PBut)4, P2H2But2, and
PH2But (for 1), (PCy)3 and (PCy)4 (for 3), (PPh)4 (for 4)
and P2H2Tipp2 and (PTipp)3 (for 6) was observed [72]. This
indicates that deprotonation of the coordinated primary
phosphine occurs, but the phosphanide or phosphinidene
complexes formed as intermediates are unstable and re-
ductively eliminate PHR or PR [detected as P2H2R2 and
(PR)n] with formation of the observed MoIII complex,
[(Cp°MoCl2)2]. When NEt3 is employed as base, these prod-
ucts are also observed. However, small amounts of the com-
plexes [Cp°MoCl2(η3-P4Cy4H)] (7) and [Cp°2Mo2(µ-Cl)2(µ-
P4Ph4)] (8), which contain a tetraphosphanyl and tetraphos-
phine-1,4-diyl ligand, respectively, were obtained from reac-
tions of 3 and 4 with two equivalents of NEt3 and charac-
terized by X-ray crystallography.
s
2
(CP
)
(CPs
)
2
p
Table 5 Overall spin density (αP2) on phosphorus atoms and degree
of hybridization (n2) in 1Ϫ6
1
2
3
4
5
6
2
αP
0.0223
0.75
0.199
0.72
0.0245
0.77
0.0227
0.74
0.0254
0.78
0.0224
0.74
n2
Mo and P atoms (Mo s contribution neglected) and con-
sideration of the fact that, due to overlap contributions,
some terms with a negative sign are contained in the nor-
malization condition of the molecular orbital of the un-
paired electron, about 15Ϫ25 % spin density remains. This
is expected to be located on the four Cl and one Cp° ligands
in the first coordination sphere. Unfortunately, hyperfine in-
teractions with nuclei of these ligands were not observed;
therefore, the spin densities on these nuclei remain an
open question.
The reaction of 6 with two equivalents of NEt3 was also
carried out in the presence of PhNCO, which is known to
react with reactive Mo-P bonds [69, 70a, 71], to trap a reac-
tive phosphinidene complex formed as an intermediate.
Again only formation of PH2Tipp and (PTipp)4 was ob-
served by 31P NMR spectroscopy.
Molecular structures of [Cp°MoCl2(η3-P4Cy4H)]
(7) and [Cp°2Mo2(µ-Cl)2(µ-P4Ph4)] (8)
Reactivity of 1, 3, 4 and 6
As deprotonation of primary or secondary phosphines in
molybdenum carbonyl complexes can be achieved with
alkyl lithium reagents, DBU (DBU ϭ 1,8-diazabicy-
clo[5.4.0]undec-7-ene) or NEt3 [52, 69Ϫ71], we treated com-
plexes 1, 3 and 4 with two equivalents of NEt3, and 1, 3, 4
In 7, the molybdenum atom (MoIV) is coordinated in a dis-
torted octahedral fashion by the Cp° ligand, two cis-ori-
ented chloro ligands, and the phosphorus atoms P(1), P(2),
and P(4) of the tetraphosphanyl ligand, with P(1) and P(4)
trans to Cl and P(2) trans to Cp° (Cen-Mo(1)-P(2) 158.1°;
Z. Anorg. Allg. Chem. 2004, 630, 806Ϫ816
zaac.wiley-vch.de
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
813

R. Felsberg, S. Blaurock, P. C. Junk, R. Kirmse, A. Voigt, E. Hey-Hawkins
Fig. 9 Molecular structure of [Cp°2Mo2(µ-Cl)2(µ-P4Ph4)] (8) show-
ing the atom numbering scheme employed (ORTEP plot, 50 % pro-
bability, SHELXTL PLUS; XP [24]). Hydrogen atoms are omitted
Fig. 8 Molecular structure of [Cp°MoCl2(η3-P4Cy4H)] (7) showing
˚
for clarity. Selected bond lengths/A and angles/°:
the atom numbering scheme employed (ORTEP plot, 50 % proba-
bility, SHELXTL PLUS; XP [24]). Hydrogen atoms (other than P-
Mo-Mo 2.6729(3). Mo(1)-P(1) 2.4317(7), Mo(1)-P(4) 2.4554(7), Mo(2)-P(1)
2.4597(7), Mo(2)-P(4) 2.4433(7), P(1)-Mo(1)-P(4) 71.54(2), P(1)-Mo(1)-Cl(1)
75.94(2), P(1)-Mo(2)-P(4) 71.27(2), P(1)-Mo(2)-Cl(1) 75.74(2), Cl(1)-Mo(1)-
Cl(2) 71.70(2), P(4)-Mo(1)-Cl(2) 73.72(2), Cl(1)-Mo(2)-Cl(2) 71.86(2), P(4)-
Mo(2)-Cl(2) 73.81(2).
˚
H) are omitted for clarity. Selected bond lengths/A and angles/°:
Mo(1)-Cl(1) 2.509(1), Mo(1)-Cl(2) 2.505(1), Mo-P(1) 2.573(1), Mo-P(4)
2.480(1), Mo-P(2) 2.474(1), Cen-Mo 2.025; Cl(2)-Mo(1)-Cl(1) 81.23(4), Cen-
Mo(1)-Cl(1) 112.6, Cen-Mo(1)-Cl(2) 109.2, Cen-Mo(1)-P(1) 109.0, Cen-
Mo(1)-P(4) 105.1, Cen-Mo(1)-P(2) 158.1.
˚
9). In addition, a Mo-Mo bond is present (2.6729(3) A).
8 is structurally related to [Cp°2Mo2(µ-Cl)3(µ-PPh2)] and
[(Cp°MoCl2)2] [4]. These have Mo-Mo bond lengths of
˚
Fig. 8). The molybdenum atom lies 0.89 A above the plane
˚
formed by Cl(1), Cl(2), P(1) and P(4). The presence of a
monoanionic tetraphosphanyl ligand in 7 was confirmed by
X-ray structure determination and by IR spectroscopy.
Thus, the P(4)-H proton was located in the difference Four-
ier synthesis and a P-H stretching vibration was observed
in the IR spectrum at 2294 cmϪ1 (cf. 2430 and 2386 cmϪ1
in 3, and 2280 cmϪ1 in PH2Cy [58]). The Mo-Cl bonds
(2.509(1) and 2.505(1) A) are longer than in 3 (av.
2.430(6) A, Table 2). Similar bond lengths are observed in
[CpMoCl3(dmpe)] [41] [2.493(1) A]. The Mo(1)-P(1) bond
length of 2.573(1) A in 7 is similar to that of the phosphine
2.6388(8) and 2.600(2) or 2.596(2) A [4]. The Cen(1)-Mo(1)-
Mo(2)-Cen(2) moiety in 8 is almost linear (Cen(1)-Mo(1)-
Mo(2) 175.8; Mo(1)-Mo(2)-Cen(2) 176.3°). The Mo-Cl
˚
bond lengths of av. 2.5266(7) A are similar to that in
˚
[Cp°2Mo2(µ-Cl)(µ-PPh2)2] (2.519(2) A) [74], but longer than
˚
that in [(Cp°MoCl2)2] (2.487(7) A) [4] and the starting ma-
˚
terial 4 (av. 2.425(1) A). The Mo-Cl-Mo bond angles of av.
˚
63.87(2)° are similar to those in [(Cp°MoCl2)2] (av.
˚
˚
62.9(1)°). The Mo-P bond lengths (av. 2.4475(7) A) and the
˚
Mo-P-Mo bond angles (66.14(2), 66.24(2)°) are similar to
˚
˚
those in [Cp°2Mo2(µ-Cl)3(µ-PPh2)] (2.458(2) A, 64.9(1)°).
˚
complex 3 (2.5587(6) A), while the Mo(1)-P(4) bond is
shorter (2.480(1) A). This is unexpected, as the phosphine
The four bridging atoms Cl(1), Cl(2), P(1) and P(4) form
an almost perfect square with the Mo-Mo bond intersecting
this plane in the centre. The P-P bond lengths of the ter-
minal P atoms are longer than expected for single bonds
˚
moiety of the tetraphosphanyl ligand (P(4)) should exhibit
the longer and the phosphanido group (P(1)) the shorter
Mo-P bond. Presumably, formation of the two rings Mo(1)-
P(1)-P(2) and Mo(1)-P(2)-P(3)-P(4) is responsible for this
unusual behaviour. In addition, P(2) is tilted towards P(1)
and thus deviates from the ideal octahedral position by ca.
22°. In [CpMoCl3(dmpe)], an almost undistorted octa-
hedron is observed (Cen-Mo-P 178.8°) with Mo-Pax being
longer (2.614(2) A) and Mo-Peq shorter (2.481(2) A) [41].
The four Cy rings have chair conformations and, as in
cyclotetraphosphines [72], are oriented in an all-trans fa-
shion in the tetraphosphine-1-yl ligand. The P-P bond
˚
(P(1)-P(2) 2.237(1), P(3)-P(4) 2.230(1) A), while the central
P-P bond is in the range expected for P-P single bonds
˚
(2.1971(9) A). The torsion angle of the linear P4 fragment
is 13.2°.
Both 7 and 8 fulfil the 18-electron rule. Preliminary stud-
ies (by 31P NMR) [75] indicate that complexes which are
related to 8 can also be obtained from [(Cp°MoCl2)2] and
1,2,3,4-tetraorganyltetraphosphine-1,4-diides [76], while
[Cp2MCl2] (M ϭ Ti, Zr, Hf) react with potassium 1,2,3,4-
tetraorganyltetraphosphine-1,4-diides K2(PR)n (R ϭ Me,
Et, n ϭ 5; R ϭ But, Ph, n ϭ 4) with formation of
[Cp2M(PR)3] and (PR)n [77].
˚
˚
˚
lengths of av. 2.171(2) A are in the range expected for P-P
single bonds [73].
In the dimeric molybdenum(III) complex 8, each Mo
atom is coordinated by one Cp° ligand, two bridging chloro
ligands and a bridging tetraphosphine-1,4-diyl ligand (Fig.
Other cyclopentadienyl molybdenum complexes with
(PnRn)xϪ ligands include the diphosphinediyl (or diphos-
phene) complexes [Cp2Mo(P2H2)] [78], [{CpMo(CO)2}2(µ-
814
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Z. Anorg. Allg. Chem. 2004, 630, 806Ϫ816

Organometallic Molybdenum(V) Complexes with Primary Phosphine Ligands
[16] U. Vogel, A. Y. Timoshkin, M. Scheer, Angew. Chem. 2001,
P2R2)] (R ϭ Ph [79], CH(SiMe3)2 [80]) and [CpЈMo(P-
113, 4541; Angew. Chem. Int. Ed. Engl. 2001, 40, 4409.
[17] U. Vogel, M. Scheer, Z. Anorg. Allg. Chem. 2001, 627, 1593.
[18] M. L. H. Green, X. M. Morise, A. H. Hamilton, A. N. Cher-
nega, J. Organomet. Chem. 1995, 488, 73.
Me3)2(P2Mes2)] [5].
Conclusions
[19] C. J. Harlan, R. A. Jones, S. U. Koschmieder, C. M. Nunn,
Polyhedron 1990, 9, 669.
The organometallic molybdenum(V) complexes with pri-
mary phosphine ligands, [Cp°MoCl4(PH2R)] [R ϭ But (1),
1-Ad (2), Cy (3), Ph (4), Mes (5), Tipp (6)], show a trans
arrangement of the Cp° and phosphine ligands. EPR in-
vestigations confirmed the presence of MoV species, and the
data were used to analyze the spin-density distribution in
the first coordination sphere.
Complexes 3 and 4 react with triethylamine with forma-
tion of [Cp°MoCl2(η3-P4Cy4H)] (7) and [Cp°2Mo2(µ-
Cl)2(µ-P4Ph4)] (8), which respectively contain a tetraphos-
phanyl and tetraphosphine-1,4-diyl ligand.
[20] Correct space group for [WCl4(PH2But)2] [19]: R. E. Marsh,
A. L. Spek, Acta Crystallogr. 2001, 57B, 800.
[21] R. Felsberg, S. Blaurock, S. Jelonek, T. Gelbrich, R. Kirmse,
A. Voigt, E. Hey-Hawkins, Chem. Ber. 1997, 130, 807.
[22] X. Morise, M. L. H. Green, P. C. McGowan, S. J. Simpson,
J. Chem. Soc., Dalton Trans. 1994, 871.
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A modified version by K. Köhler, R. Böttcher (University
Leipzig, 1991) was used for the simulation.
[24] SHELXTL PLUS, Siemens Analyt. X-ray Inst. Inc. 1990, XS:
Program for Crystal Structure Solution, XL: Program for Crys-
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[25] R. H. Blessing, Acta Crystallogr. 1995, 51A, 33.
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Acknowledgement. P.C. Junk thanks the DAAD for a guest pro-
fessorship (316-226/röd) at the University of Leipzig.
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