Synthesis, characterization, and reactivity of cationic molecular hydrogen complexes of manganese(I)

Article abstract of DOI:10.1021/om970226j

Hydride complexes MnH(CO)₃P₂ (1), MnH(CO)₂P₃ (2), and MnH(CO)P₄ (3) (P = P(OEt)₃ (a), PPh(OEt)₂ (b), PPh₂OEt (c), PPh(OⁱPr)₂ (d) were prepared by allowing the MnH(CO)₅ species to react with an excess of phosphine upon UV irradiation or under reflux conditions. Their formulation and geometry in solution were established by IR and ¹H, ¹³C, and ³¹P NMR spectroscopy. Protonation reactions with HBF₄·Et₂O of the monocarbonyls MnH(CO)-P₄ (3) afford isolable dihydrogen derivatives [Mn(η²-H₂)(CO)P₄]BPh₄ (5), which were characterized by variable-temperature ¹H and ³¹P NMR spectra, T₁ measurements, and J_HD values. Thermally unstable (above 0°C) [Mn(η²-H₂)(CO)₂P₃]⁺ (4) cations were also prepared by protonation of the dicarbonyl hydrides MnH(CO)₂P₃ (2) and fully characterized in solution. Evolution of H₂ from 4 and 5 results in the formation of the unsaturated complexes [Mn-(CO)₂P₃]BPh₄ (6) and [Mn(CO)P₄]BPh₄ (7), which are probably stabilized by an agostic interaction between the metal center and a C-H proton of the phosphite. Treatment of the unsaturated complexes 6 and 7 and of the triflate compounds [Mn(η¹-OSO₂CF₃)(CO)₃P ₂] (8) with Li⁺RC≡C^- gave the new acetylide derivatives [Mn(C≡CR)(CO)P₄] (9), [Mn(C≡CR)-(CO)₂P₃] (10), and [Mn(C≡CR)(CO)₃P₂] (11) (R = Ph, p-tolyl). The new series of cationic manganese compounds [Mn(CO)₂(p-tolylCN)P₃]BPh₄ (12), [Mn(CO)(p-tolylCN)P₄]BPh₄ (13), [Mn(CO)₂(p-tolylNC)P₃]BPh₄ (14), [Mn(CO)(p-tolylNC)P₄]BPh₄ (15), [Mn(CO)₃P₃]BPh₄ (16), and [Mn(CO)₂P₄]BPh₄ (17) were also obtained by reacting the unsaturated compounds 6 and 7 with the appropriate ligands.

Full text of DOI:10.1021/om970226j

Organometallics 1997, 16, 4959-4969
4959
Articles
Syn th esis, Ch a r a cter iza tion , a n d Rea ctivity of Ca tion ic
Molecu la r Hyd r ogen Com p lexes of Ma n ga n ese(I)
Gabriele Albertin,* Stefano Antoniutti, Massimo Bettiol, Emilio Bordignon, and
Fabio Busatto
Dipartimento di Chimica, Universita` Ca’ Foscari di Venezia, Dorsoduro 2137, 30123 Venezia,
Italy
Received March 31, 1997X
Hydride complexes MnH(CO)3P2 (1), MnH(CO)2P3 (2), and MnH(CO)P4 (3) (P ) P(OEt)3
(a ), PPh(OEt)2 (b), PPh2OEt (c), PPh(OiPr)2 (d ) were prepared by allowing the MnH(CO)5
species to react with an excess of phosphine upon UV irradiation or under reflux conditions.
1
Their formulation and geometry in solution were established by IR and H, 13C, and 31P
NMR spectroscopy. Protonation reactions with HBF4‚Et2O of the monocarbonyls MnH(CO)-
P4 (3) afford isolable dihydrogen derivatives [Mn(η2-H2)(CO)P4]BPh4 (5), which were
1
characterized by variable-temperature H and 31P NMR spectra, T1 measurements, and J HD
values. Thermally unstable (above 0 °C) [Mn(η2-H2)(CO)2P3]+ (4) cations were also prepared
by protonation of the dicarbonyl hydrides MnH(CO)2P3 (2) and fully characterized in solution.
Evolution of H2 from 4 and 5 results in the formation of the unsaturated complexes [Mn-
(CO)2P3]BPh4 (6) and [Mn(CO)P4]BPh4 (7), which are probably stabilized by an agostic
interaction between the metal center and a C-H proton of the phosphite. Treatment of the
unsaturated complexes 6 and 7 and of the triflate compounds [Mn(η1-OSO2CF3)(CO)3P2] (8)
with Li+RCtC- gave the new acetylide derivatives [Mn(CtCR)(CO)P4] (9), [Mn(CtCR)-
(CO)2P3] (10), and [Mn(CtCR)(CO)3P2] (11) (R ) Ph, p-tolyl). The new series of cationic
manganese compounds [Mn(CO)2(p-tolylCN)P3]BPh4 (12), [Mn(CO)(p-tolylCN)P4]BPh4 (13),
[Mn(CO)2(p-tolylNC)P3]BPh4 (14), [Mn(CO)(p-tolylNC)P4]BPh4 (15), [Mn(CO)3P3]BPh4 (16),
and [Mn(CO)2P4]BPh4 (17) were also obtained by reacting the unsaturated compounds 6
and 7 with the appropriate ligands.
In tr od u ction
few examples have been described for the first-row
transition metals and only recently have stable dihy-
drogen complexes of manganese been reported.2b,3,4
These include the trihydride3 MnH3(R2PCH2CH2PR2)2
(R ) Me, Et) which was proposed to contain a η2-H2
ligand, the compound CpMn(CO)2(η2-H2),4 and the very
recently reported derivative [Mn(η2-H2)(CO)(dppe)2]-
BAr′4 (dppe ) Ph2PCH2CH2PPh2; BAr′4 ) B{C6H3(3,5-
CF3)2}4).2b Furthermore, much work has been ad-
dressed to study the structure, the bonding, and the
reactivity of these interesting complexes1 in an attempt
to provide insight into the catalytic and stoichiometric
activation of H2 by transition metals and now it seems
certain that the stability and the chemical properties
of the η2-H2 compounds are a function not only of the
central metal but also of the nature of the ancillary
ligands and of the formal charge on the central metal.
We have previously reported5 the synthesis and some
properties of molecular hydrogen derivatives of the iron
Transition-metal dihydrogen complexes are an im-
portant class of compounds which have attracted con-
siderable interest in recent years.1,2 A large number of
isolable H2 complexes have been prepared, and the
majority of them contain metals of the second and third
row with a d6 octahedral configuration. In contrast,
although the initial focus of work in this field has been
the synthesis of new dihydrogen complexes, relatively
X Abstract published in Advance ACS Abstracts, October 1, 1997.
(1) (a) Kubas, G. J . Acc. Chem. Res. 1988, 21, 120. (b) J essop, P. G.;
Morris, R. H. Coord. Chem. Rev. 1992, 121, 155. (c) Crabtree, R. H.
Angew. Chem., Int. Ed. Engl. 1993, 92, 789. (d) Heinekey, D. M.;
Oldham, W. J ., J r. Chem. Rev. 1993, 93, 913.
(2) For recent papers see: (a) Heinekey, D. M.; Voges, M. H.;
Barnhart, D. M. J . Am. Chem. Soc. 1996, 118, 10792. (b) King, W. A.;
Luo, X.-L.; Scott, B. L.; Kubas, G. J .; Zilm, K. W. J . Am. Chem. Soc.
1996, 118, 6782. (c) Maltby, P. A.; Schlaf, M.; Steinbeck, M.; Lough,
A. J .; Morris, R. H.; Klooster, W. T.; Koetzle, T. F.; Srivastava, R. C.
J . Am. Chem. Soc. 1996, 118, 5396. (d) Kim, Y.; Deng, H.; Gallucci, J .
C.; Wojcicki, A. Inorg. Chem. 1996, 35, 7166. (e) Gusev, D. G.;
Kuhlman, R. L.; Renkema, K. B.; Eisenstein, O.; Caulton, K. G. Inorg.
Chem. 1996, 35, 6775. (f) Bacskay, G. B.; Bytheway, I.; Hush, N. S. J .
Am. Chem. Soc. 1996, 118, 3753. (g) Bullock, R. M.; Song, J .-S.; Szalda,
D. J . Organometallics 1996, 15, 2504. (h) Eckert, J .; Albinati, A.;
Bucher, U. E.; Venanzi, L. M. Inorg. Chem. 1996, 35, 1292. (i) Lee,
J r., J . C., J r.; Yao, W.; Crabtree, R. H.; Ru¨egger, H. Inorg. Chem. 1996,
35, 695. (j) Ma, B.; Collins, C. L.; Schaefer, H. F., III. J . Am. Chem.
Soc. 1996, 118, 870. (k) Li, J .; Dickson, R. M.; Ziegler, T. J . Am. Chem.
Soc. 1995, 117, 11482. (l) Moreno, B.; Sabo-Etienne, S.; Chaudret, B.;
Rodriguez, A.; J alon, F.; Trofimenko, S. J . Am. Chem. Soc. 1995, 117,
7441.
(3) Perthuisot, C.; Fan, M.; J ones, W. D. Organometallics 1992, 11,
3622.
(4) Banister, J . A.; Lee, P. D.; Poliakoff, P. D. Organometallics 1995,
14, 3876.
(5) (a) Albertin, G.; Antoniutti, S.; Bordignon, E. J . Am. Chem. Soc.
1989, 111, 2072. (b) Amendola, P.; Antoniutti, S.; Albertin, G.;
Bordignon, E. Inorg. Chem. 1990, 29, 318. (c) Albertin, G.; Amendola,
P.; Antoniutti, S.; Ianelli, S.; Pelizzi, G.; Bordignon, E. Organometallics
1991, 10, 2876. (d) Albertin, G.; Antoniutti, S.; Baldan, D.; Bordignon,
E. Inorg. Chem. 1995, 34, 6205.
S0276-7333(97)00226-4 CCC: $14.00 © 1997 American Chemical Society

4960 Organometallics, Vol. 16, No. 23, 1997
Albertin et al.
family of the type [MH(η2-H2)P4]+ containing monoden-
tate phosphite ligands PPh2(OR), PPh(OR)2, and P(OR)3
as ancillary ligands. As these ligands have shown
interesting properties in stabilizing the H2 complexes,
we have extended these studies to include the manga-
nese as a central metal, and in this paper we report the
synthesis and characterization of new isolable molecular
hydrogen complexes of this metal along with some
studies on the properties of these derivatives.
51.67; H, 5.90. Mp: 67 °C dec. IR (KBr and (n-hexane)): 2019
w (2017 w), 1941 s (1943 s), 1918 s (1926 s) νCO cm-1 1H NMR
.
(C6D6, 25 °C): δ 8.00-7.00 (m, 10H, Ph), 3.95, 3.71 (m, 8H,
CH2), 1.06 (t, 12H, CH3), -7.65 (t, 1H, Mn-H, J PH ) 40 Hz).
31P{1H} NMR (C6D6, 25 °C): δ 205.3 s. Anal. Calcd for
C31H31O5P2Mn (1c): C, 62.01; H, 5.20. Found: C, 62.17; H,
5.11. Mp: 138 °C dec. IR (KBr and (n-hexane)): 2002 w (2008
w), 1933 s (1933 s), 1919 (s) (1916 s) νCO cm-1 1H NMR (C6D6,
.
25 °C): δ 8.00-7.00 (m, 20H, Ph), 3.90 (qi, 4H, CH2), 1.10 (t,
6H, CH3), -7.36 (t, 1H, Mn-H, J PH ) 33 Hz). 31P{1H} NMR
(C6D6, 25 °C): δ 177.7 s. Anal. Calcd for C27H39O7P2Mn (1d ):
C, 54.73; H, 6.63. Found: C, 54.58; H, 6.55. Mp: 132 °C. IR
Exp er im en ta l Section
(KBr): 2023 m, 1937 s, 1901 s νCO cm-1 1H NMR (CD3C6D5,
.
All synthetic work was carried out under an appropriate
atmosphere (H2, Ar) using standard Schlenk techniques or a
Vacuum Atmospheres drybox. Once isolated, the complexes
were found to be relatively stable in air but were stored under
an inert atmosphere at -25 °C. All solvents were dried over
appropriate drying agents, degassed on a vacuum line, and
distilled into vacuumtight storage flasks. Triethyl phosphite
was an Aldrich product, purified by distillation under nitrogen;
the phosphines PPh(OEt)2, PPh2OEt, and PPh(OiPr)2 were
prepared by the method of Rabinowitz and Pellon.6 Mn2(CO)10,
HBF4‚Et2O (54% solution), triflic acid, and the alkynes were
Aldrich products, used without any further purification.
Lithium acetylides Li+RCtC- (R ) Ph, p-tolyl) were prepared
by reacting a slight excess of the appropriate acetylene (40
mmol) with lithium (35 mmol, 0.24 g) in 10 mL of THF. p-Tolyl
isocyanide was obtained by the phosgene method of Ugi et al.7
Triethylamine was dried with CaH2 and distilled before use.
Other reagents were purchased from commercial sources in
the highest available purity and used as received. The
photolysis was carried out under an argon atmosphere with a
standard 400 W medium-pressure mercury arc lamp using a
Pyrex Schlenk flask. Infrared spectra were recorded on a
Digilab Bio-Rad FTS-40 spectrophotometer. NMR spectra (1H,
13C, 31P) were obtained on a Bruker AC200 spectrometer at
temperatures varying between +30 and -90 °C, unless
otherwise noted. 1H and 13C spectra are referred to internal
tetramethylsilane, while 31P{1H} chemical shifts are reported
with respect to 85% H3PO4, with downfield shifts considered
positive. Proton T1 values were measured by the inversion-
recovery method between +30 and -90 °C with a standard
25 °C): δ 8.03-6.97 (m, 10H, Ph), 4.69 (m, 4H, CH), 1.22, 1.13
(d, 24H, CH3), -7.71 (t, 1H, Mn-H, J PH ) 38 Hz). 31P{1H}
NMR (CD3C6D5, 25 °C): δ 197.1 s.
Mn H(CO)2P 3 (2) a n d Mn H(CO)P 4 (3) (P ) P (OEt)3 (a ),
P P h (OEt)2 (b), P P h 2OEt (c), P P h (OiP r )2 (d )). A solution
of MnH(CO)5 (12.8 mmol, 2.5 g) in 30 mL of toluene was
treated under argon with 90 mmol of the appropriate phosphite
and the mixture irradiated at room temperature for 48 h in a
Pyrex Schlenk flask using a standard 400-W medium-pressure
mercury arc lamp. The solvent was then evaporated under
reduced pressure to give an oil which was triturated with
ethanol until a white solid, containing a mixture of 2 and 3,
separated out. Fractional crystallization from ethanol or
chromatographic separation on silica gel using a mixture of
petroleum ether (40-70 °C) and diethyl ether in a 10:2 ratio
as eluent allowed us to obtain pure samples of both the
hydrides 3 (25-35% yield, first eluted) and 2 (40-60% yield).
Anal. Calcd for C20H46O11P3Mn (2a ): C, 39.35; H, 7.60.
Found: C, 39.22; H, 7.67. Mp: 71 °C. IR (KBr): 1934 s, 1872
s νCO cm-1 1H NMR (C6D6, 25 °C): δ 4.10 (m, 18H, CH2), 1.23
.
(t, 27H, CH3), -8.02 (d of t, 1H, Mn-H, spin system A2BX (X
) H), J AX ) 49 Hz, J BX ) 61 Hz). 31P{1H} NMR (C6D6, 25 °C):
spin system A2B, δA 194.2, δB 186.9, J AB ) 96 Hz. Anal. Calcd
for C32H46O8P3Mn (2b): C, 54.40; H, 6.56. Found: C, 54.55;
H, 6.49. Mp: 78 °C. IR (KBr): 1933 s, 1869 s νCO cm-1 1H
.
NMR (C6D6, 25 °C): δ 7.90-7.00 (m, 15H, Ph), 4.10-3.70 (m,
12H, CH2), 1.13, 1.09, 1.05 (t, 18H, CH3), -7.45 (d of t, 1H,
Mn-H, spin system A2BX (X ) H), J AX ) 45 Hz, J BX ) 61
Hz). 31P{1H} NMR (C6D6, 25 °C): spin system A2B, δA 206.6,
δB 200.9, J AB ) 70 Hz. Anal. Calcd for C44H46O5P3Mn (2c):
C, 65.84; H, 5.78. Found: C, 65.78; H, 5.85. Mp: 137 °C. IR
180°-τ-90° pulse sequence. The conductivities of 10-3
M
solutions of the complexes in CH3NO2 at 25 °C were measured
with a Radiometer CDM 83 instrument.
Syn th esis of Com p lexes. The hydride MnH(CO)5 was
prepared from Mn2(CO)10 according to the procedure previously
reported.8
(KBr): 1922 s, 1864 s cm-1 1H NMR (CD3C6D5, -30 °C): δ
.
8.10-6.90 (m, 30H, Ph), 3.94, 3.68, 3.42 (br, 6H, CH2), 1.01 (t,
br, 9H, CH3), -6.64 (d of t, 1H, Mn-H, spin system A2BX (X
) H), J AX ) 40 Hz, J BX ) 61 Hz). 31P{1H} NMR (CD3C6D5,
-30 °C): spin system A2B, δA ) 173.8, δB ) 169.6, J AB ) 60
Hz. Anal. Calcd for C38H58O8P3Mn (2d ): C, 57.72; H, 7.39.
Found: C, 57.90; H, 7.45. Mp: 164 °C. IR (KBr): 1933 s,
Mn H(CO)3P 2 (1) (P ) P (OE t )3 (a ), P P h (OE t )2 (b ),
P P h 2OEt (c), P P h (OiP r )2 (d )). An excess of the appropriate
phosphite (80 mmol) was added to a solution of MnH(CO)5
(12.8 mmol, 2.5 g) in 30 mL of toluene and the reaction mixture
was refluxed for about 2 h. The solvent was removed under
reduced pressure, and the oil obtained was chromatographed
on a silica gel column (length 70 cm, diameter 4 cm) using a
mixture of petroleum ether (40-70 °C) and diethyl ether in a
10:1 ratio as eluent. The first eluted (300 mL) was evaporated
to dryness, leaving an oil which was treated with ethanol (5-
10 mL). A white solid slowly separated out from the resulting
stirred solution, which was filtered and dried under vacuum;
yield from 60 to 70%. Anal. Calcd for C15H31O9P2Mn (1a ):
C, 38.15; H, 6.62. Found: C, 38.24; H, 6.58. Mp: 38 °C dec.
IR (KBr and (CH3C6H5)): 2027 w (2015 w), 1941 s (1938 s),
1875 s cm-1
.
1H NMR (C6D6, 25 °C): δ 8.20-7.00 (m, 15H,
Ph), 4.78, 4.52 (m, 6H, CH), 1.33-1.11 (m, 36H, CH3), -7.17
(q, 1H, Mn-H, spin system A2BX (X ) H), J AX ) J BX ) 57
Hz). 31P{1H} NMR (C6D6, 25 °C): spin system A2B, δA 202.9,
δB 196.0, J AB ) 70 Hz. Anal. Calcd for C25H61O13P4Mn (3a ):
C, 40.11; H, 8.21. Found: C, 40.28; H, 8.17. Mp: 135 °C. IR
(KBr): 1852 s cm-1 1H NMR (C6D6, 25 °C): δ 4.20 (m, 24H,
.
CH2), 1.28 (t, 36H, CH3), -8.13 (qi, 1H, Mn-H, J PH ) 52 Hz).
31P{1H} NMR (C6D6, 25 °C): δ 194.6 s. Anal. Calcd for
C
41H61O9P4Mn (3b): C, 56.17; H, 7.01. Found: C, 56.27; H,
7.15. Mp: 169 °C. IR (KBr): 1853 s νCO cm-1 1H NMR (C6D6,
.
25 °C): δ 8.15-7.10 (m, 20H, Ph), 3.72, 3.45 (m, 16H, CH2),
1.03 (t, 24H, CH3), -7.07 (qi, 1H, Mn-H, J PH ) 52 Hz). 31P-
{1H} NMR (C6D6, 25 °C): δ 208.0 s, br.
1915 s (1921 s) νCO cm-1 1H NMR (CD3C6D5, 25 °C): δ 3.99
.
(m, 12H, CH2), 1.15 (t, 18H, CH3), -8.13 (t, 1H, Mn-H, J PH
)
-
[Mn (η2-H2)(CO)2P 3]+BF 4 (4) (P ) P (OEt)3 (a ), P P h -
43 Hz). 31P{1H} NMR (CD3C6D5, 25 °C): δ 191.0 s. Anal.
Calcd for C23H31O7P2Mn (1b): C, 51.50; H, 5.83. Found: C,
(OEt)2 (b), P P h 2OEt (c)). These complexes were prepared
in solution (CD2Cl2) at low temperature (-78 °C) by protona-
tion with HBF4‚Et2O of the hydride compounds MnH(CO)2P3
(2), but they were not isolated as solids owing to the easy loss
of hydrogen above 0 °C. A typical preparation involves the
addition by microsyringe of HBF4‚Et2O (0.02 mmol, 2.9 µL) to
(6) Rabinowitz, R.; Pellon, J . J . Org. Chem. 1961, 26, 4623.
(7) Ugi, I.; Fetzer, U.; Eholzer, W.; Knupfer, H.; Offermann, K.
Angew. Chem., Int. Ed. Engl. 1965, 4, 472.
(8) King, R. B.; Stone, F. G. A. Inorg. Synth. 1963, 7, 198.

Cationic Molecular Hydrogen Complexes of Mn(I)
Organometallics, Vol. 16, No. 23, 1997 4961
a solution of the appropriate hydride (0.2 mmol) in 0.5 mL of
CD2Cl2 placed into a 5 mm NMR tube and cooled to -78 °C.
The tube was brought to about -20 °C to complete the reaction
and then, with the temperature kept below 0 °C, the NMR
spectra (1H and 31P) were measured. The related isotopomer
1.28, 1.22, 1.18 (m, 24H, CH3). 31P{1H} NMR (CD2Cl2): 25
°C, δ 185.9 s, br; -80 °C, δ 188.8 s, br.
Mn (η1-OSO2CF 3)(CO)3[P P h (OEt)2]2 (8). An equivalent
amount of CF3SO3H (0.75 mmol, 66 µL) was added to a solution
of MnH(CO)3[PPh(OEt)2]2 (1b; 0.75 mmol, 0.5 g) in 5 mL of
diethyl ether cooled to -78 °C. The reaction mixture was
brought to room temperature, stirred for about 1 h, and then
the solvent removed under reduced pressure. The oil obtained
was triturated with n-hexane (4 mL) until a yellow solid began
to separate out (about 1 h). After cooling to -25 °C to complete
the precipitation, the solid was filtered and dried under
vacuum; yield g80%. Anal. Calcd for C24H30F3O10P2SMn: C,
42.12; H, 4.42. Found: C, 41.96; H, 4.50. IR (KBr): 2066 m,
-
[Mn(η2-HD)(CO)2{P(OEt)3}3]+CF3CO2 (4a 1) was prepared in
a NMR tube exactly like 4a using CF3COOD as the protonat-
ing agent. 4a : 1H NMR (CD2Cl2, -90 °C) δ 4.02 (m, 18H, CH2),
1.36 (t, 27H, CH3), -8.5 (br, 2H, η2-H2); 31P{1H} NMR (CD2-
Cl2, -90 °C) spin system A2B, δA 167.3, δB 159.3, J AB ) 89 Hz
4b: 1H NMR (CD2Cl2, -90 °C) δ 7.70-7.50 (m, 15H, Ph), 3.92
(br, 12H, CH2), 1.40 (br, 18H, CH3), -7.9 (br, 2H, η2-H2);
31P{1H} NMR (CD2Cl2, -90 °C) spin system A2B, δA 191.7, δB
174.7, J AB ) 72 Hz. 4c: 1H NMR (CD2Cl2, -90 °C) δ 7.51 (m,
30H, Ph), 3.90, 3.41 (m, 6H, CH2), 1.39, 1.12 (br, 9H, CH3),
-7.1 (br, 2H, η2-H2); 31P{1H} NMR (CD2Cl2, -90 °C) spin
system A2B, δA 160.4, δB 154.4, J AB ) 52 Hz.
1975 s, 1932 s νCO cm-1
.
1H NMR (CD2Cl2, 25 °C): δ 7.70,
7.50 (m, 10H, Ph), 4.05 (m, 8H, CH2), 1.36 (t, 12H, CH3).
31P{1H} NMR (CD2Cl2, 25 °C): δ 182.8 s.
[Mn (CtCP h )(CO)3P 2] (9) (P ) P (OEt)3 (a ), P P h (OEt)2
(b), P P h 2OEt (c), P P h (OiP r )2 (d )) a n d [Mn (CtC-p-tolyl)-
(CO)3P 2] (9) (P ) P P h (OEt)2 (b1), P P h 2OEt (c1)). To a
solution of the appropriate hydride MnH(CO)3P2 (1; 1.5 mmol)
in 8 mL of toluene cooled to -78 °C was added an equivalent
amount of CF3SO3H (1.5 mmol, 133 µL), and the reaction
mixture was then brought to room temperature and stirred
for 1 h. An excess of Li+[RCtC]- (4.5 mmol, 1.8 mL of a 2.5
M solution in THF) was added to the resulting solution, which
was then further stirred at room temperature for 2 h. The
solvent was removed under reduced pressure, giving an oil
which was triturated with ethanol (5 mL) at 0 °C for 2-3 h.
In some cases a pale yellow solid separated out after 2-3 h of
stirring, but often an oil remained. This oil was chromato-
graphed on a silica gel column (70 × 4 cm) using a mixture of
petroleum ether (40-60 °C), diethyl ether, and benzene in a
8:1:1 ratio as eluent. The first eluted band (about 400 mL)
was evaporated to dryness, leaving an oil which was triturated
with ethanol (5 mL) until a solid separated out (10-30 min).
This solid was filtered and dried under vacuum; yield between
30 and 55%. Anal. Calcd for C23H35O9P2Mn (9a ): C, 48.26;
[Mn (η2-H2)(CO)P 4]BP h 4 (5) (P ) P (OEt)3 (a ), P P h (OEt)2
(b)). HBF4‚Et2O (0.2 mmol, 29 µL of a 54% solution in Et2O)
was added to a solution of MnH(CO)P4 (3) (0.2 mmol) in 7 mL
of ethanol under H2 (1 atm) cooled to -78 °C. The reaction
mixture was brought to about 0 °C and after 20 min, a solution
of NaBPh4 (0.2 mmol, 0.068 g) in 3 mL of ethanol was added.
A pale yellow solid slowly separated out which was filtered,
washed with ethanol, and dried under vacuum: yield 65% (5a ),
78% (5b). Anal. Calcd for C49H82BO13P4Mn (5a ): C, 55.06;
H, 7.73. Found: C, 54.91; H, 7.81. ΛM (CH3NO2, 25 °C): 55.7
Ω-1 mol-1 cm2. IR (KBr): 1926 s νCO cm-1 1H NMR (CD2Cl2,
.
25 °C): δ 7.30-6.70 (m, 20H, Ph), 4.10 (m, 24H, CH2), 1.36 (t,
36H, CH3), -8.28 (br, 2H, η2-H2). 31P{1H} NMR (CD2Cl2, 25
°C): δ 175.7 s, br. Anal. Calcd for C65H82BO9P4Mn (5b): C,
65.22; H, 6.90. Found: C, 65.13; H, 7.06. ΛM (CH3NO2, 25
°C): 53.4 Ω-1 mol-1 cm2. IR (KBr): 1926 s νCO cm-1 1H NMR
.
(CD2Cl2, 25 °C): δ 7.50-6.80 (m, 40H, Ph), 3.56 (m, 16H, CH2),
1.56 (t, 24H, CH3), -7.22 (br, 2H, η2-H2). 31P{1H} NMR (CD2-
Cl2, 25 °C): δ 195.4 s.
[Mn (η2-HD)(CO)P 4]+CF 3CO2- (P ) P (OEt)3 (5a 1), P P h -
(OEt)2 (5b1)). These isotopomers were prepared in solution
(CD2Cl2) like the related η2-H2 compounds 5 by adding an
equimolar amount of CF3COOD to the appropriate hydrides
3 in an NMR tube.
H, 6.16. Found: C, 48.41; H, 6.24. IR (KBr): 2096 m νCtC
;
2040 m, 1959 s, 1947 s νCO cm-1 1H NMR (CD3C6D5, 25 °C):
.
δ 7.42-6.95 (m, 5H, Ph), 4.18 (m, 12H, CH2), 1.17 (t, 18H,
CH3). 31P{1H} NMR (CD3C6D5, 25 °C): δ 173.3 s. Anal. Calcd
for C31H35O7P2Mn (9b): C, 58.50; H, 5.54. Found: C, 58.28;
H, 5.65. Mp: 139 °C. IR (KBr and (CH2Cl2)): 2100 m (2094
[Mn (CO)2P 3]BP h 4 (6) a n d [Mn (CO)P 4]BP h 4 (7) (P )
P (OEt)3 (a ), P P h (OEt)2 (b)). HBF4‚Et2O (0.2 mmol, 29 µL
of a 54% solution in Et2O) was added to a solution of MnH-
(CO)2P3 (2) or MnH(CO)P4 (3; 0.2 mmol) in 7 mL of ethanol
cooled to -78 °C under argon. The reaction mixture was
slowly brought to 30 °C and stirred for 2 h. The addition of
NaBPh4 (0.2 mmol, 0.068 g) in 3 mL of ethanol caused the
precipitation of a yellow solid, which was filtered, washed with
ethanol, and dried under vacuum. Yield between 84% and
68%. Anal. Calcd for C44H65BO11P3Mn (6a ): C, 56.91; H, 7.06.
Found: C, 56.77; H, 7.12. ΛM (CH3NO2, 25 °C): 60.6 Ω-1 mol-1
1
m) νCtC; 2027 m, 1940 s (2036 m, 1958 s, 1928 s) νCO cm-1. H
NMR (C6D6, 25 °C): δ 7.95-7.00 (m, 15H, Ph), 4.22, 3.85 (m,
8H, CH2), 1.10 (t, 12H, CH3). 31P{1H} NMR (C6D6, 25 °C): δ
193.0 s. Anal. Calcd for C39H35O5P2Mn (9c): C, 66.86; H, 5.04.
Found: C, 66.71; H, 5.13. Mp: 179 °C. IR (KBr): 2094 m
ν
CtC; 2022 m, 1943 s, 1927 s νCO cm-1 1H NMR (CD2Cl2, 25
.
°C): δ 8.00-6.90 (m, 25H, Ph), 3.85 (m, 4H, CH2), 1.25 (t, 6H,
CH3). 31P{1H} NMR (CD2Cl2, 25 °C): δ 161.7 s. Anal. Calcd
for C35H43O7P2Mn (9d ): C, 60.70; H, 6.26. Found: C, 60.58;
H, 6.39. IR (KBr): 2090 m νCtC; 2038 m, 1953 s, 1924 s νCO
cm2. IR (KBr): 1983 s, 1872 s νCO cm-1 1H NMR (CD2Cl2, 25
.
cm-1 1H NMR (CD3C6D5, 25 °C): δ 8.00-6.95 (m, 15H, Ph),
.
5.00 (m, 4H, CH), 1.27, 1.20 (d, 24H, CH3). 31P{1H} NMR
(CD3C6D5, 2 °C): δ 188.8 s. Anal. Calcd for C32H37O7P2Mn
(9b1): C, 59.08; H, 5.73. Found: C, 59.24; H, 5.66. Mp: 68
°C): δ 7.30-6.80 (m, 20H, Ph), 4.09 (m, 18H, CH2), 1.30 (t,
27H, CH3). 31P{1H} NMR (CD2Cl2): 25 °C, δ 170.7 s, br; -80
°C, δ 169.9 s, br. Anal. Calcd for C56H65BO8P3Mn (6b): C,
65.63; H, 6.39. Found: C, 65.79; H, 6.26. ΛM (CH3NO2, 25
°C. IR (KBr): 2094 m νCtC; 2038 m, 1958 s, 1929 s νCO cm-1
.
°C): 57.4 Ω-1 mol-1 cm2. IR (KBr): 1970 s, 1894 s νCO cm-1
.
1H NMR (C6D6, 25 °C): δ 8.00-6.90 (m, 14H, Ph), 4.25, 3.86
(m, 8H, CH2), 2.13 (s, 3H, CH3 p-tolyl), 1.12 (t, 12H, CH3 phos).
31P{1H} NMR (C6D6, 25 °C): δ 192.9 s. Anal. Calcd for
1H NMR (CD2Cl2): 25 °C, δ 7.60-6.80 (m, 35H, Ph), 3.93 (qi,
12H, CH2), 1.35, 1.33, 1.26 (t, 18H, CH3). 31P{1H} NMR (CD2-
Cl2, -90 °C): spin system A2B, δA 187.9, δB 177.3, J AB ) 80.0
Hz. Anal. Calcd for C49H80BO13P4Mn (7a ): C, 55.17; H, 7.56.
Found: C, 55.03; H, 7.50. ΛM (CH3NO2, 25 °C): 56.0 Ω-1 mol-1
C
40H37O5P2Mn (9c1): C, 64.47; H, 4.58. Found: C, 64.64; H,
4.51. Mp: 132 °C. IR (KBr): 2092 m νCtC; 2032 m, 1945 s,
1924 s νCO cm-1 1H NMR (CD2Cl2, 25 °C): δ 7.95-6.80 (m,
.
cm2. IR (KBr): 1872 s νCO cm-1 1H NMR (CD2Cl2): 25 °C, δ
.
24H, Ph), 3.86 (m, br, 4H, CH2), 2.22 (s, 3H, CH3 p-tolyl), 1.24
(t, 6H, CH3 phos). 31P{1H} NMR (CD2Cl2, 25 °C): δ 161.7 s.
7.30-6.70 (m, 20H, Ph), 4.09 (m, br, 24H, CH2), 1.30 (t, br,
36H, CH3); -80 °C, δ 4.30, 4.09 (br, CH2), 1.56, 1.30 (br, CH3).
31P{1H} NMR (CD2Cl2): 25 °C, δ 170.0 br; -80 °C, δ 170.2 br,
168.7 s, br. Anal. Calcd for C65H80BO9P4Mn (7b): C, 65.33;
H, 6.75. Found: C, 65.52; H, 6.50. ΛM (CH3NO2, 25 °C): 58.3
[Mn (CtCP h )(CO)2P 3] (10) a n d [Mn (CtCP h )(CO)P 4]
(11) (P ) P (OEt)3 (a ), P P h (OEt)2 (b)). An equivalent
amount of HBF4‚Et2O (0.75 mmol, 108 µL of a 54% solution
in Et2O) was added to a cooled (-78 °C) solution of the
appropriate hydride MnH(CO)2P3 (2) or MnH(CO)P4 (3) in 5
mL of toluene. The reaction mixture was slowly brought to
Ω-1 mol-1 cm2. IR (KBr): 1915 s νCO cm-1 1H NMR (CD2Cl2,
.
25 °C): δ 7.80-6.80 (m, 40H, Ph), 3.71, 3.59 (m, 16H, CH2),

4962 Organometallics, Vol. 16, No. 23, 1997
Albertin et al.
30 °C and stirred for 2 h. An excess of Li+[PhCtC]- (3 mmol,
0.83 mL of a 2.5 M solution in THF) was added to the resulting
solution containing the [Mn(CO)2P3]+ and [Mn(CO)P4]+ cations,
and the stirring was continued for 2 h. Evaporation of the
solvent under reduced pressure gave an oil which was chro-
matographed on a silica gel column (70 × 4 cm) using as eluent
a mixture of petroleum ether (40-60 °C), diethyl ether, and
benzene in a 8:1:1 ratio. The first eluted band (about 400 mL)
was evaporated under reduced pressure, giving an oil which
was triturated with ethanol until a pale yellow solid separated
out. After filtration, the solid was dried under vacuum; yield
g45%. Anal. Calcd for C40H50O8P3Mn (10b): C, 59.56; H,
6.25. Found: C, 59.71; H, 6.31. IR (KBr): 2083 m νCtC; 1960
31P{1H} NMR ((CD3)2CO, 25 °C): spin system A2B, δA 168.7,
δB 159.9, J AB ) 87 Hz. Anal. Calcd for C64H72NBO8P3Mn
(14b): C, 67.32; H, 6.36; N, 1.23. Found: C, 67.50; H, 6.42;
N, 1.19. Mp: 189 °C. ΛM (CH3NO2, 25 °C): 61.7 Ω-1 mol-1
cm2. IR (KBr): 2137 s νCN; 1981 s, 1931 s νCO cm-1 1H NMR
.
((CD3)2CO, 25 °C): δ 7.70-6.60 (m, 39H, Ph), 4.01 (m, 12H,
CH2), 2.33 (s, 3H, CH3 p-tolyl), 1.37, 1.34 (t, 18H, CH3 phos).
31P{1H} NMR ((CD3)2CO, 25 °C): spin system A2B, δA 192.6,
δB 183.6, J AB ) 61 Hz. Anal. Calcd for C57H87NBO13P4Mn
(15a ): C, 57.83; H, 7.41; N, 1.18. Found: C, 57.55; H, 7.30;
N, 1.20. Mp: 183 °C. ΛM (CH3NO2, 25 °C): 53.2 Ω-1 mol-1
cm2. IR (KBr): 2116 s νCN; 1922 s νCO cm-1 1H NMR ((CD3)2-
.
CO, 25 °C): δ 7.33-6.70 (m, 24H, Ph), 4.19 (m, 24H, CH2), 2.36
(s, 3H, CH3 p-tolyl), 1.31 (t, 36H, CH3 phos). 31P{1H} NMR
((CD3)2CO, -90 °C): δ 175.2 s. Anal. Calcd for C73H87NBO9P4-
Mn (15b): C, 66.82; H, 6.68; N, 1.07. Found: C, 66.75; H,
6.59; N, 1.07. Mp: 167 °C. ΛM (CH3NO2, 25 °C): 54.3 Ω-1
s, 1885 s νCO cm-1 1H NMR (CD3C6D5, 25 °C): δ 7.90-6.80
.
(m, 20H, Ph), 4.30-3.70 (m, 12H, CH2), 1.14, 1.13, 1.09 (t, 18H,
CH3). 31P{1H} NMR (CD3C6D5, 25 °C): spin system A2B, δA
195.2, δB 188.7, J AB ) 70.0 Hz. Anal. Calcd for C33H65O13P4-
Mn (11a ): C, 46.70; H, 7.72. Found: C, 46.88; H, 7.60. Mp:
127 °C. IR (KBr and (CH2Cl2)): 2079 m (2075 m) νCtC; 1852
mol-1 cm2. IR (KBr): 2109 s νCN; 1915 s νCO cm-1 1H NMR
.
((CD3)2CO, 25 °C): δ 7.75-6.70 (m, 44H, Ph), 3.68 (m, 16H,
CH2), 2.37 (s, 3H, CH3 p-tolyl), 1.21 (t, 24H, CH3 phos).
31P{1H} NMR ((CD3)2CO, 25 °C): δ 204.7 s.
s (1862 s, 1843 s) νCO cm-1
.
1H NMR ((CD3)2CO, 25 °C): δ
7.07 m, 6.89 br (5H, Ph), 4.20 (m, 24H, CH2), 1.20 (t, 36H,
CH3). 31P{1H} NMR ((CD3)2CO, 25 °C): δ 184.5 s.
[Mn (CO)3P 3]BP h 4 (16) a n d [Mn (CO)2P 4]BP h 4 (17) (P )
P (OEt)3 (a ), P P h (OEt)2 (b)). An equivalent amount of
HBF4‚Et2O (0.4 mmol, 58 µL of a 54% solution) was added to
a suspension of the appropriate hydride MnH(CO)2P3 (2) and
MnH(CO)P4 (3) (0.4 mmol) in 4 mL of ethanol cooled to -78
°C. The reaction mixture was slowly brought to +30 °C,
stirred for 2 h, and then placed under a CO atmosphere (1
atm) for 1 h. The addition of an excess of NaBPh4 (0.8 mmol,
0.27 g) in 3 mL of ethanol caused the precipitation of a pale
yellow solid, which was filtered and crystallized from CH2Cl2
(2 mL) and ethanol (5 mL); yield g70%. Anal. Calcd for
[Mn (4-CH 3C6H 4CN)(CO)2P 3]BP h 4 (12) a n d [Mn (4-
CH3C6H4CN)(CO)P 4]BP h 4 (13) (P ) P (OEt)3 (a ), P P h -
(OEt)2 (b)). To a suspension of the appropriate hydride
MnH(CO)2P3 (2) or MnH(CO)P4 (3) (0.4 mmol) in 4 mL of
ethanol cooled to -78 °C was added an equivalent amount of
HBF4‚Et2O (0.4 mmol, 58 µL of a 54% solution). The reaction
mixture was slowly brought to about 30 °C and stirred for 2
h, and then a slight excess of p-toluonitrile (0.6 mmol, 70 µL)
was added. After 1 h of stirring an excess of NaBPh4 (0.8
mmol, 0.27 g) in 3 mL of ethanol was added and the reaction
mixture stirred until a yellow solid separated out. The
compound was filtered and crystallized from CH2Cl2 (2 mL)
C
45H65BO12P3Mn (16a ): C, 56.50; H, 6.85. Found: C, 56.43;
H, 6.88. Mp: 136 °C. ΛM (CH3NO2, 25 °C): 51.7 Ω-1 mol-1
cm2. IR (KBr): 2062 m, 1980 s, 1972 s νCO cm-1 1H NMR
and ethanol (6 mL); yield g80%. Anal. Calcd for C52H72
-
.
NBO11P3Mn (12a ): C, 59.72; H, 6.94; N, 1.34. Found: C,
((CD3)2CO, 25 °C): δ 7.35-6.00 (m, 20H, Ph), 4.25 (m, br, 18H,
CH2), 1.37 (t, br, 27H, CH3). 31P{1H} NMR ((CD3)2CO, -90
°C): δ 160 br. Anal. Calcd for C57H65BO9P3Mn (16b): C, 65.03;
H, 6.22. Found: C, 64.98; H, 6.25. Mp: 202 °C. ΛM (CH3-
NO2, 25 °C): 56.9 Ω-1 mol-1 cm2. IR (KBr): 2051 m, 1980 s,
59.88; H, 7.03; N, 1.29. Mp: 94 °C. ΛM (CH3NO2, 25 °C): 53.6
Ω-1 mol-1 cm2. IR (KBr): 2261 w νCN; 1976 s, 1916 s νCO cm-1
.
1H NMR ((CD3)2CO, 25 °C): δ 7.80-6.70 (m, 24H, Ph), 4.23
(m, 18H, CH2), 2.45 (s, 3H, CH3 p-tolyl), 1.35, 1.31 (t, 27H,
CH3 phos). 31P{1H} NMR ((CD3)2CO, -90 °C): spin system
1968 s νCO cm-1 1H NMR ((CD3)2CO, 25 °C): δ 7.61-6.70 (m,
.
A2B, δA 167.7, δB 157.4, J AB ) 99 Hz. Anal. Calcd for C64H72
-
35H, Ph), 4.01, 3.90 (m, 12H, CH2), 1.36, 1.35 (t, 18H, CH3).
31P{1H} NMR ((CD3)2CO, -90 °C): δ 186, 180 br. Anal. Calcd
for C50H80BO14P4Mn (17a ): C, 54.85; H, 7.37. Found: C, 54.81;
H, 7.39. Mp: 193 °C. ΛM (CH3NO2, 25 °C): 50.7 Ω-1 mol-1
NBO8P3Mn (12b): C, 67.32; H, 6.36; N, 1.23. Found: C, 67.15;
H, 6.23; N, 1.18. Mp: 157 °C. ΛM (CH3NO2, 25 °C): 49.7 Ω-1
mol-1 cm2. IR (KBr): 2250 w νCN; 1979 s, 1917 s νCO cm-1. 1H
NMR ((CD3)2CO, 25 °C): δ 7.70-6.70 (m, 39H, Ph), 4.05 (m,
12H, CH2), 2.36 (s, 3H, CH3 p-tolyl), 1.40, 1.37 (t, 18H, CH3
phos). 31P{1H} NMR ((CD3)2CO, -90 °C): spin system A2B,
cm2. IR (KBr): 1991 s, 1932 s νCO cm-1 1H NMR ((CD3)2CO,
.
25 °C): δ 7.30-6.70 (m, 20H, Ph), 4.18 (m, 24H, CH2), 1.34 (t,
br, 36H, CH3). 31P{1H} NMR ((CD3)2CO, -90 °C): δ 170.1 s;
167.8, 160.3 t (spin system A2B2, δA 167.8, δB 160.3, J AB ) 84
Hz). Anal. Calcd for C66H80BO10P4Mn (17b): C, 64.82; H,
6.59. Found: C, 64.76; H, 6.57. Mp: 190 °C. ΛM (CH3NO2,
25 °C): 52.5 Ω-1 mol-1 cm2. IR (KBr): 1985 s, 1922 s, br νCO
δA 197.1, δB 181.0, J AB ) 62 Hz. Anal. Calcd for C57H87
-
NBO13P4Mn (13a ): C, 57.83; H, 7.41; N, 1.18. Found: C,
57.80; H, 7.57; N, 1.10. Mp: 145 °C. ΛM (CH3NO2, 25 °C):
55.3 Ω-1 mol-1 cm2. IR (KBr): 2239 w νCN; 1894 s νCO cm-1
.
1H NMR ((CD3)2CO, 25 °C): δ 7.70-6.70 (m, 24H, Ph), 4.20
(m, 24H, CH2), 2.43 (s, 3H, CH3 p-tolyl), 1.31 (t, 36H, CH3
phos). 31P{1H} NMR ((CD3)2CO, -90 °C): δ 173.9 s. Anal.
Calcd for C73H87NBO9P4Mn (13b): C, 66.82; H, 6.68; N, 1.07.
Found: C, 66.70; H, 6.57; N, 1.11. Mp: 147 °C. ΛM (CH3-
cm-1 1H NMR ((CD3)2CO, 25 °C): δ 7.90-6.70 (m, 40H, Ph),
.
3.87, 3.68 (m, 16H, CH2), 1.35, 1.24 (t, 24H, CH3). 31P{1H}
NMR ((CD3)2CO, -90 °C): δ 194.9 s, 192 m, br.
[Mn (OH2)(CO)3P 2]BF4 (18) (P ) P P h (OEt)2 (b), P P h 2OEt
(c)). To a suspension of the appropriate hydride MnH(CO)3P2
(1) (0.4 mmol) in 3 mL of ethanol cooled to -78 °C was added
an equivalent amount of aqueous HBF4 (0.4 mmol, 52 µL of a
48% solution in water), and the reaction mixture was brought
to room temperature. After 1 h of stirring the solvent was
removed under reduced pressure, giving a yellow oil which was
triturated with diethyl ether (5 mL). A yellow solid began to
separate out after 1-2 h, which was filtered and crystallized
from ethanol (2 mL) and diethyl ether (7 mL): yield g70%.
Anal. Calcd for C23H32BF4O8P2Mn (18b): C, 43.15; H, 5.04.
Found: C, 43.12; H, 6.09. Mp: 120 °C. ΛM (CH3NO2, 25 °C):
87.6 Ω-1 mol-1 cm2. IR (KBr): 2064 m, 1978 s, 1936 s νCO
NO2, 25 °C): 57.2 Ω-1 mol-1 cm2. IR (KBr): 1886 s νCO cm-1
.
1H NMR ((CD3)2CO, 20 °C): δ 7.80-6.70 (m, 44H, Ph), 3.75
(m, 16H, CH2), 2.44 (s, 3H, CH3 p-tolyl), 1.23 (t, 24H, CH3
phos). 31P{1H} NMR ((CD3)2CO, -90 °C): δ 199.9 s.
[Mn (4-CH 3C6H 4NC)(CO)2P 3]BP h 4 (14) a n d [Mn (4-
CH3C6H4NC)(CO)P 4]BP h 4 (15) (P ) P (OEt)3 (a ), P P h -
(OEt)2 (b)). These complexes were prepared exactly like the
related nitrile compounds 12 and 13 by adding a slight excess
of p-tolyl isocyanide to a solution containing [Mn(CO)2P3]+ and
[Mn(CO)P4]+ cations in ethanol; yield g80%. Anal. Calcd for
C
52H72NBO11P3Mn (14a ): C, 59.72; H, 6.94; N, 1.34. Found:
C, 59.58; H, 6.82; N, 1.36. ΛM (CH3NO2, 25 °C): 52.9 Ω-1 mol-1
cm2. IR (KBr): 2141 s νCN; 1993 s, 1947 s νCO cm-1 1H NMR
cm-1
.
1H NMR (CD2Cl2, 25 °C): δ 7.80-7.50 (m, 10H, Ph),
.
4.10 (m, 8H, CH2), 2.53 (t, 2H, OH2, J PH ) 2.1 Hz), 1.40 (t,
12H, CH3). 31P{1H} NMR (CD2Cl2): 25 °C, δ 182.1 s, br; -90
°C, δ 183.5 s. Anal. Calcd for C31H32BF4O6P2Mn (18c): C,
((CD3)2CO, 25 °C): δ 7.45-6.70 (m, 24H, Ph), 4.23 (m, 18H,
CH2), 2.40 (s, 3H, CH3 p-tolyl), 1.35 (t, br, 27H, CH3 phos).

Cationic Molecular Hydrogen Complexes of Mn(I)
Organometallics, Vol. 16, No. 23, 1997 4963
Sch em e 1a
Two νCO bands at 1934-1864 cm-1 are instead present
in the spectra of the compounds MnH(CO)2P3 (2), in
agreement with two carbonyl ligands in mutually cis
positions. The 31P{1H} NMR spectra appear as an A2B
spin system (one doublet and one triplet), indicating that
two phosphorus nuclei are magnetically equivalent and
are different from the third. In the 1H NMR spectra
the hydride signal appears as a multiplet which can be
easily simulated as the X part of a A2BX spin system
with the parameters reported in the Experimental
Section. Finally, the 13C{1H} NMR spectra of complex
2b (Table 1) show only one multiplet, formed by a
doublet of triplets, at 225.5 ppm for the carbonyl carbon
atom, suggesting the magnetic equivalence of the two
CO ligands as in fac-cis structure II.
a
P ) P(OEt)3 (a ), PPh(OEt)2 (b), PPh2OEt (c), PPh(OiPr)2
(d ).
52.87; H, 4.58. Found: C, 52.93; H, 4.50. ΛM (CH3NO2, 25
°C): 90.2 Ω-1 mol-1 cm2. IR (Nujol): 2051 m, 1971 s, 1925 s
ν
CO cm-1 1H NMR (CD2Cl2, 25 °C): δ 7.80-7.70 (m, 20H, Ph),
.
3.66 (m, 4H, CH2), 2.48 (t, 2H, OH2), 1.22 (t, 6H, CH3). 31P{1H}
NMR (CD2Cl2): 25 °C, δ 158.4 s; -90 °C, 156.9 s.
Resu lts a n d Discu ssion
P r ep a r a t ion a n d Ch a r a ct er iza t ion of H yd r id e
Sp ecies. The manganese complexes MnH(CO)3P2 (1),
MnH(CO)2P3 (2), and MnH(CO)P4 (3) were prepared by
substituting carbonyl ligands in the hydride pentacar-
bonyl complex MnH(CO)5 with the appropriate phos-
phite, as shown in Scheme 1.
The reaction of MnH(CO)5 with an excess of phos-
phine proceeds in refluxing toluene to give exclusively
the tricarbonyl complexes 1, which were isolated as
white solids in high yield. Irradiation of MnH(CO)5
solutions containing an excess of P, instead, gives rise
to the sequential substitution of the carbonyl ligands
affording the MnH(CO)3P2 (1), MnH(CO)2P3 (2), and
MnH(CO)P4 (3) derivatives, which were isolated after
chromatographic separation and characterized. Also,
the formation of the first substitution product, the
tetracarbonyl MnH(CO)4P species was detected (IR) by
working in a low phosphite to pentacarbonyl ratio, but
the compound was not separated. Furthermore, the
substitution of all the carbonyl groups in MnH(CO)5 to
give MnHP5 species was not observed, and the pro-
tracted irradiation led only to decomposition products.
Finally, the monocarbonyls MnH(CO)P4 with PPh2OEt
(3c) and with PPh(OiPr)2 (3d ) were formed in small
amounts owing to the low substitution rates and were
not isolated.
The two monocarbonyls complexes MnH(CO)P4 (3a ,b)
show similar IR spectra, with only one νCO band at 1852
(3a ) and 1853 (3b) cm-1, but slightly different 1H and
31P NMR spectra. In the temperature range between
+30 and -90 °C the 31P{1H} spectrum of MnH(CO)-
[P(OEt)3]4 (3a ) consists of only one sharp singlet at 194.6
ppm, in agreement with a trans geometry (III). In the
1H NMR spectrum the hydride signal appears as a
quintet at -8.13 ppm with a coupling constant J HP of
52 Hz.
Good analytical data were obtained for all the hydride
complexes, which are white or pale yellow solids, air-
stable both as solids and in solution of polar and
nonpolar organic solvents, where they behave as non-
electrolytes. The infrared spectra of tricarbonyl com-
pounds MnH(CO)3P2 (1) show in the νCO region three
bands (one weak and two of strong intensity), suggesting
a mer arrangement9 of the three carbonyl ligands. In
the temperature range between +20 and -90 °C the 31P-
{1H} NMR spectra consist of only one sharp singlet at
205.3-173.3 ppm, indicating the magnetic equivalent
1
The H and 31P NMR spectra of the related complex
MnH(CO)[PPh(OEt)2]4 (3b), in contrast, are tempera-
ture dependent and the broad singlet at 208.5 ppm that
appears at room temperature in the phosphorus spectra
changes as the temperature is lowered and resolves
into a complicated multiplet at -80 °C. Also, the
hydride signal changes from a quintet (at -7.07 ppm)
at room temperature to a slightly broad multiplet at
-80 °C.
1
of the two phosphorus nuclei. In the H NMR spectra
These results implicate the presence of inequivalent
phosphorus nuclei and may suggest the presence of a
geometry with the hydride and the CO ligands in cis
positions. However, the 31P spectra may also be inter-
preted on the basis of the presence of a trans geometry
(III), in which the four PPh(OEt)2 phosphite ligands are
the hydride appears as a sharp triplet between -8.13
and -7.36 ppm. On these bases a mer-trans geometry
of type I can be proposed in solution for complexes 1.
(9) Adams, D. M. Metal-Ligand and Related Vibrations; St. Martin’s
Press: New York, 1968.

4964 Organometallics, Vol. 16, No. 23, 1997
Ta ble 1. 13C{1H} NMR Da ta for Selected Ma n ga n ese Com p ou n d s
Albertin et al.
compd
δa,b
assignt
MnH(CO)2[PPh(OEt)2]3 (2b)
225.5 d of t (2J CP ) 20 Hz)
CO
61.4, 61.2 s, br
CH2
CH3
CO
Câ
CR
CH2
CH3
CO
Ph
Câ
16.5 s, br
216.3 m
Mn(CtCPh)(CO)3[P(OEt)3]2 (9a )
Mn(CtCPh)(CO)3[PPh(OEt)2]2 (9b)
117.0 s, br
111.7 t (2J CP ) 37 Hz)
61.9 s
16.3 s
217.0 t (2J CP ) 26 Hz)
140-124 m
116.8 s, br
113.7 t (2J CP ) 32 Hz)
CR
62.8 t
16.5 t
CH2
CH3
CO
Câ
CR
CH2
CH3
CO
Câ
CR
CH2
CH3 p-tolyl
CH3 phos
CO
Câ
CR
CH2
CH3 p-tolyl
CH3 phos
CO
Mn(CtCPh)(CO)3(PPh2OEt)2 (9c)
217.8 t (2J CP ) 22 Hz), 217.3 t (2J CP ) 16 Hz)
121.8 t, br
116.4 t (2J CP ) 32 Hz)
62.6 t
16.5 t
Mn(CtC-p-tolyl)(CO)3[PPh(OEt)2]2 (9b1)
217.0 t (2J CP ) 25 Hz)
116.6 s, br
111.4 t (2J CP ) 32 Hz)
62.8 t
21.4 s
16.5 t
Mn(CtC-p-tolyl)(CO)3(PPh2OEt)2 (9c1)
217.8 t (2J CP ) 22 Hz)
121.7 s, br
114.1 t (2J CP ) 32 Hz)
62.6 s, br
21.4 s
16.5 s, br
Mn(CtCPh)(CO)2[PPh(OEt)2]3 (10b)
Mn(CtCPh)(CO)[P(OEt)3]4 (11a )
222.9 d of t (2J CP ) 24 Hz), 220.8 d of t (2J CP ) 24 Hz)
119.6 qi, br
62.4, 62.2 t
Câ
CH2
CH3
CO
16.7, 16.5 t
221.1 qi (2J CP ) 28 Hz)
119.4 qi, br
Câ
61.0 s, br
16.4 s, br
218.1 m, br
CH2
CH3
CO
[Mn(4-CH3C6H4NC)(CO)2{PPh(OEt)2}3]BPh4 (14b)
Mn(OH2)(CO)3(PPh2OEt)2]BF4 (18c)
66.7, 64.1 t
21.4 s
16.5, 16.3 t
CH2
CH3 p-tolyl
CH3 phos
CO
CH2
CH3
219.9 t (2J CP ) 18 Hz), 213.4 t (2J CP ) 22 Hz)
65.3 t
15.9 t
a
b
At 25 °C in CD2Cl2; coupling constants in Hz. Phenyl group signals are omitted.
made inequivalent by the different arrangement of the
phenyl and ethoxy groups of one phosphite with respect
to the other. Examples of inequivalent phosphorus
nuclei in octahedral complexes containing four PPhMe2
or PPh(OEt)2 ligands in a plane have recently been
monocarbonyl derivatives. Furthermore, the use of
phosphite ligands to stabilize these manganese-hydride
compounds has been restricted to P(OR)3 and P(OCH2)3-
CR, and there are no examples of phosphonite PPh-
(OEt)2 or phosphinite PPh2OEt as ancillary ligands. The
photochemical substitution of CO groups in MnH(CO)5
allows the synthesis of a rare example of manganese
hydride such as the monocarbonyl MnH(CO)P4 com-
10
reported for [IrCl2(PPhMe2)4]ClO4 and FeHCl[PPh-
11
(OEt)2]4 derivatives. Taking into account these pre-
cedents and the fact that the related MnH(CO)-
[P(OEt)3]4 (3a ) complex containing the P(OEt)3 ligands
shows, in solution, a trans geometry, we find that a
similar trans octahedral geometry can also be proposed
for the MnH(CO)[PPh(OEt)2]4 (3b) species.
(11) Albertin, G.; Antoniutti, S.; Bordignon, E. J . Organomet. Chem.
1996, 513, 147.
(12) (a) Nietlispach, D.; Bosch, H. W.; Berke, H. Chem. Ber. 1994,
127, 2403. (b) Narayanan, B. A.; Amatore, C.; Kochi, J . K. Organome-
tallics 1987, 6, 129. (c) Onaka, S.; Kondo, Y.; Furuichi, N. Bull. Chem.
Soc. J pn. 1983, 56, 2296. (d) Booth, B. L.; Haszeldine, R. N.; Reynolds,
D. M. J . Chem. Soc., Dalton Trans. 1980, 412, 407. (e) Kidd, D. R.;
Cheng, C. P.; Brown, T. L. J . Am. Chem. Soc. 1978, 100, 4103. (f)
Hayakawa, H.; Nakayama, N.; Kobayashi, A.; Sasaki, Y. Bull. Chem.
Soc. J pn. 1978, 51, 2041. (g) Onaka, S.; Yoshikawa, Y.; Yamatera, H.
J . Organomet. Chem. 1978, 157, 187. (h) Darensbourg, D. J .; Froelich,
J . A. Inorg. Chem. 1978, 17, 3300. (i) Reimann, R. H.; Singleton, E. J .
Chem. Soc., Dalton Trans. 1976, 2109. (j) Colton, C.; Commons, C. J .
Aust. J . Chem. 1975, 28, 1663. (k) Miles, W. J ., J r.; Clark, R. J . Inorg.
Chem. 1968, 7, 1801. (l) Ugo, R.; Bonati, F. J . Organomet. Chem. 1967,
8, 189. (m) Hieber, W.; Hofler, M.; Muschi, J . Chem. Ber. 1965, 98,
311.
Hydrido-carbonyl complexes of manganese have been
reported12-14in the past years, and the majority are
tricarbonyls of the type MnH(CO)3P2 containing tertiary
phosphine as coligands.12
Relatively few dicarbonyls MnH(CO)2P3 have been
described,12d,13 and only one example,14 MnH(CO)-
[P(OMe)3]4, to our knowledge, has been reported of
(10) Deeming, A. J .; Doherty, S.; Marshall, J . E.; Powell, N. I. J .
Chem. Soc., Chem. Commun. 1989, 1351.
(13) Ellermann, J .; Lindner, H. Z. Naturforsch., B 1979, 34, 799.
(14) Stuhl, L. S.; Muetterties, E. L. Inorg. Chem. 1978, 17, 2148.

Cationic Molecular Hydrogen Complexes of Mn(I)
Organometallics, Vol. 16, No. 23, 1997 4965
Ta ble 2. 1H NMR Da ta (200 MHz) in th e Hyd r id e Region for Selected Ma n ga n ese Com p lexes
compd
T, K
δ(M-H2)a
δ(M-H)a
T1(min), ms
J HD, Hz
r(H-H), Åb
MnH(CO)2[PPh(OEt)2]3 (2b)
MnH(CO)[PPh(OEt)2]4 (3b)
195
202
293
205
223
198
210
195
293
224
204
293
234
-7.91 d of t
-7.34 m, br
-7.36 qi
85
68
[Mn(η2-H2)(CO)2{P(OEt)3}3]+ (4a )
[Mn(η2-HD)(CO)2{P(OEt)3}3]+ (4a 1)
[Mn(η2-H2)(CO)2{PPh(OEt)2}3]+ (4b)
[Mn(η2-H2)(CO)2(PPh2OEt)3]+ (4c)
[Mn(η2-H2)(CO){P(OEt)3}4]+ (5a )
-8.5 br
-8.56 t
-7.9 br
-7.0 br
-8.3 br
-8.3 br
-8.41 t
-7.4 br
-7.22 br
-7.41 t
5
0.79
33
5.5
5
7
0.80
0.79
0.83
[Mn(η2-HD)(CO){P(OEt)3}4]+ (5a 1)
[Mn(η2-H2)(CO){PPh(OEt)2}4]+ (5b)
32.0
32.5
6
0.81
[Mn(η2-HD)(CO){PPh(OEt)2}4]+ (5b1)
a
b
In CD2Cl2. Fast rotation; for calculations see refs 15c and 16.
Sch em e 2a
a
P ) P(OEt)3 (a ), PPh(OEt)2 (b).
pounds together with a systematic investigation using
P(OEt)3, PPh(OR)2, or PPh2OR as a ligand.
P r ep a r a tion a n d Ch a r a cter iza tion of Dih yd r o-
gen Com p lexes. The new hydrides trans-MnH(CO)-
P4 (3) (P ) P(OEt)3 (a ), PPh(OEt)2 (b)) react under an
hydrogen atmosphere at -78 °C with HBF4‚Et2O to give
the [Mn(η2-H2)(CO)P4]+ (5a ,b) derivatives which can be
-
isolated as BPh4 salts and characterized (Scheme 2).
The compounds are pale yellow solids, diamagnetic
and 1:1 electrolytes. Under an argon atmosphere they
are relatively stable as solids, whereas in solutions of
polar organic solvents the loss of H2 at room tempera-
ture is easy for 5a , but slow for 5b, whose solution can
be handled unchanged for 1-2 h.
F igu r e 1. 1H NMR spectra of the cations (A) [Mn(η2-H2)-
(CO){PPh(OEt)2}4]+ (5b) and (B) [Mn(η2-HD)(CO){PPh-
(OEt)2}4]+ (5b1) in CD2Cl2 at 234 K in the high-field
region.
Spectroscopic data (Table 2) confirm the formulation
1
of 5 as a dihydrogen complex. The H NMR spectrum
of each compound shows, in fact, a broad resonance in
the hydride region at δ -8.3 (5a ) and at δ -7.22 (5b)
ppm. Variable-temperature T1 measurements carried
out at 200 MHz on this signal give a T1(min) value of 7
ms at 195 K for 5a and 6 ms at 204 K for 5b, in
agreement with the presence of an η2-H2 ligand.15 The
hydride precursor 3b gives a T1(min) value of 68 ms at
202 K.
between +20 and -90 °C the 31P{1H} NMR spectra of
5a appear as only one singlet, suggesting the presence
in solution of a trans geometry (IV) with the H2 ligand
trans to the CO moiety.
In order to further support these assignments, we
prepared the isotopomers [Mn(η2-HD)(CO)P4]+ (5a 1,
5b1) by protonation of 3 with an equivalent amount of
1
CF3COOD in CD2Cl2 and found by H NMR spectra a
1J HD value of 32.0 Hz for 5a 1 and of 32.5 Hz for 5b1
(Figure 1). These results strongly suggest for 5 the
presence of a true η2-H2 ligand with an estimated H-H
distance of about 0.83 (5a ) and 0.81 (5b) Å as can be
calculated15c,16 from the T1(min) value.
The related [Mn(η2-H2)(CO){PPh(OEt)2}4]BPh4 (5b)
derivative, instead, shows a broad multiplet at -90 °C
in the 31P spectra, indicating the magnetic inequivalence
of the phosphorus nuclei. However, a trans geometry
(IV) can also be proposed for this compound, as we have
proposed for the parent hydride MnH(CO)[PPh(OEt)2]4
(3b) and observed in the related 3a , attributing the
magnetic inequivalence of the P nuclei to a different
arrangement of the Ph and the OEt groups of each of
the PPh(OEt)2 ligands. A similar geometry, with the
CO and the H2 ligands in trans positions, has previously
been observed in the related [Mn(η2-H2)(CO)(dppe)2]-
The infrared spectra of both 5a and 5b show only one
νCO band at 1926 cm-1
. In the temperature range
(15) (a) Hamilton, D. G.; Crabtree, R. H. J . Am. Chem. Soc. 1988,
110, 4126. (b) Bautista, M. T.; Earl, K. A.; Maltby, P. A.; Morris, R.
H.; Schweitzer, C. T.; Sella, A. J . Am. Chem. Soc. 1988, 110, 7031. (c)
Desrosiers, P. J .; Cai, L.; Lin, Z.; Richards, R.; Halpern, J . J . Am. Chem.
Soc. 1991, 113, 4173.
(16) Earl, K. A.; J ia, G.; Maltby, P. A.; Morris, R. H. J . Am. Chem.
Soc. 1991, 113, 3027.

4966 Organometallics, Vol. 16, No. 23, 1997
Albertin et al.
Sch em e 3a
Sch em e 4a
a
P ) P(OEt)3 (a ) PPh(OEt)2 (b), PPh2OEt (c).
BAr′4 complexes,2b while for the comparable [Re(η2-H2)-
(CO){P(Me)3}4]+ cation17 a cis geometry was proposed.
A comparison of the spectroscopic data of our η2-H2
complexes with the recently reported manganese
analogues2b [Mn(η2-H2)(CO)(dppe)2]BAr′4 shows an iden-
tical value for the HD coupling constant of 32 Hz.
However, a shorter H-H distance of 0.83 or 0.81 Å was
estimated in our case from solution NMR T1 data as
compared to the 0.89(2) Å value determined by solid-
state NMR measurements in [Mn(η2-H2)(CO)(dppe)2]-
BAr′4, and these results may be attributed to the greater
π-acceptor properties of our P(OEt)3 and PPh(OEt)2
ligands as compared to that of dppe; the former ligands
in complexes 5 lower the donation of electron density
to the σ* H2 orbital. Accordingly, in the neutral
MnH3(R2PCH2CH2PR2)2 compound a H-H distance of
0.90 Å (fast H2 rotation) was calculated from T1 values.
Protonation reactions with HBF4‚Et2O at -78 °C of
the dicarbonyls fac,cis-MnH(CO)2P3 (2) also afforded
dihydrogen cations [Mn(η2-H2)(CO)2P3]+ (4) (Scheme 3),
which were fairly stable below 0 °C in solution but were
not isolated as solids owing to the easy loss of hydrogen.
a
P ) P(OEt)3 (a ), PPh(OEt)2 (b), PPh2OEt (c).
tion of the triflate ion is also observed. Furthermore,
in the temperature range from +30 to -90 °C the 31P
NMR spectrum appears as a sharp singlet near 182
ppm, in agreement with a mer-cis geometry of type V
for the compound.
1
However, the H NMR spectra of solutions containing
4 exhibit a single broad resonance in the hydride region
at δ -8.5 (4a ), -7.9 (4b), and -7.0 (4c) ppm with T1-
(min) values of 5 ms for 4a and 4c and 5.5 ms for 4b
(Table 2), in agreement with the proposed formulation,
1
which is further confirmed by the J HD value of 33 Hz
found in the isotopomer 4a 1.
The protonation reaction with HBF4‚Et2O at low
temperature (-78 °C) of the tricarbonyl MnH(CO)3P2
(1) complexes (Scheme 4) proceeds with the evolution
A mer arrangement of the CO groups in the water
complexes [Mn(OH2)(CO)3P2]BF4 (18) is also suggested
by the three characteristic νCO bands observed in the
IR spectra. Furthermore, the presence of coordinated
H2O in 18 is confirmed by its 1H NMR resonance
observed as a triplet with J PH ) 2.1 Hz at 2.53 ppm
(18b) and at 2.48 ppm (18c). Finally, a mer-trans
geometry (VI) is confirmed by the 31P spectra, which
always show, between +30 and -90 °C, a sharp singlet.
1
of H2 (by H NMR) and formation of a yellow solution
from which no stable compound was isolated. The
1
progress of the reaction was also studied by H NMR
spectra, but the presence of an η2-H2 complex was never
observed. However, using triflic acid (CF3SO3H) instead
of HBF4‚Et2O, the protonation of 1 proceeds with
evolution of H2 and formation of the triflate complexes
[Mn(η1-OSO2CF3)(CO)3P2], which, in the case P ) PPh-
(OEt)2 (8), was isolated as a solid and characterized.
Furthermore, the water complex [Mn(OH2)(CO)3P2]BF4
(18) (P ) PPh(OEt)2 (b), PPh2OEt (c)) can also be
obtained as a yellow solid by the protonation reaction
of 1 with aqueous HBF4 (Scheme 4).
The analytical and spectroscopic data of the triflate
(8) and the water (18) complexes confirm their formula-
tion. In particular, the IR spectra of the triflate
complexes [Mn(η1-OSO2CF3)(CO)3(PPh(OEt)2}2] (8) show
three νCO bands, two of which are strong at 1975 and
A comparison of the protonation reactions on the three
hydrides MnH(CO)3P2 (1), MnH(CO)2P3 (2), and MnH-
(CO)P4 (3) shows that only the dicarbonyls 2 and
monocarbonyls 3 give stable dihydrogen complexes (4,
5). Furthermore, a comparison among these η2-H2
complexes 4 and 5 shows that, although the spectro-
1932 cm-1 and one is of medium intensity at 2066 cm-1
,
suggesting a mer arrangement of the CO ligands. At
1323 cm-1 the diagnostic band18 of the η1-(O)-coordina-
1
scopic properties (T1(min) and J HD) are very similar,
the stability to the loss of H2 changes widely, according
to the carbonyl-phosphine ratio in the complexes and
to the nature of the phosphite ligands. Only the
(17) Gusev, D. G.; Nietlispach, D.; Eremenko, I. L.; Berke, H. Inorg.
Chem. 1993, 32, 3628.
(18) Lawrance, G. A. Chem. Rev. 1986, 86, 17.

Cationic Molecular Hydrogen Complexes of Mn(I)
Organometallics, Vol. 16, No. 23, 1997 4967
In the related dicarbonyl cations [Mn(CO)2P3]+ (6) this
dynamic process, in which the agostic hydrogen ex-
changes with the other methyl (or phenyl) protons of
the other phosphines, seems still very fast also at -90
°C, resulting in the 31P spectra at -90 °C being
unchanged with respect to those observed at room
temperature.
An example of an agostic bond in manganese com-
plexes has recently been demonstrated, by X-ray crys-
tallography, in the strictly comparable [Mn(CO)(dppe)]-
BAr′4 complex,2b which contains two agostic interactions
from H atoms of separate phenyl rings. Other examples
of such an interaction have been reported in related Mo-
(CO)(dppe),21 Cr(CO)3(PCy3)2,22 [Re(PR3)2(CO)3]BAr′4,23
and [{MeC(CH2PPh2)3}Re(CO)2]BF424 unsaturated com-
plexes and these precedents give further support for the
presence of an agostic interaction in our unsaturated
complexes 6 and 7.
F igu r e 2. 31P{1H} NMR spectrum (200 MHz) of the [Mn-
(CO){P(OEt)3}4]+ (7a ) cation in CD2Cl2 at 183 K.
monocarbonyl fragment [Mn(CO)P4] can in fact bind the
H2 molecule to give isolable complexes, and between
them, the PPh(OEt)2 derivative (5b) is the most stable
both in the solid state and in solution, thereby confirm-
ing the known properties of the phosphonite PPh(OEt)2
in stabilizing dihydrogen complexes.5a,b,d
It is worth noting that all the η2-H2 derivatives 4 and
5 can be deprotonated with triethylamine to give the
MnH(CO)P4 (3) and MnH(CO)2P3 (2) hydride precursors.
Evolution of H2 from 4 and 5 results in the disap-
pearance of the η2-H2 resonance at δ -8.5 to -7.22 ppm
Rea ctivity: New Ma n ga n ese Com p lexes. The
unsaturated complexes 6 and 7 and the triflate com-
pounds [Mn(η1-OSO2CF3)(CO)3P2] (8) react quickly with
a variety of ligands to give a large series of new
manganese complexes which can be isolated and char-
acterized (Scheme 5).
1
in the H NMR spectra and formation of the formally
16-electron complexes [Mn(CO)2P3]BPh4 (6) and [Mn-
(CO)P4]BPh4 (7). The compounds are yellow solids
moderately stable in air, diamagnetic, and 1:1 electro-
lytes. The diamagnetism and the reluctance of Mn(I)
to give unsaturated compounds19 seem to exclude a
pentacoordinate complex for 6 and 7 and suggest the
existence of an octahedral geometry in which an agostic
interaction20 between the electron-deficient manganese
center and a C-H bond of the ethyl (or phenyl) group
of one P(OEt)3 or PPh(OEt)2 ligand provides electronic
stabilization of the complexes.
Support for the existence of an agostic bond in 6 and
7 comes from the 31P{1H} NMR spectra of [Mn(CO)-
{P(OEt)3}4]BPh4 (7a ), which show the broad resonance
that appears at room temperature (at 170 ppm) to
resolve, at -90 °C, into two signals at δ 170.2 and 168.7
ppm and one hump as shown in Figure 2. Although
even at this temperature the spectrum is too broad to
give a fine structure, the inequivalence of the four
phosphite ligands is clear and the profile of the spectra
at -90 °C suggests that the low-exchange spectrum is
approaching an AB2C spin system. On this basis an
agostic interaction of the type shown in VII, in which
the agostic C-H interaction is interchanged from one
of the P(OEt)3 ligands to the other, may be reasonably
proposed.
The acetylide derivatives 9-11 are air-stable yellow
or orange solids that are diamagnetic and nonelectro-
lytes. The presence of the acetylide ligand is confirmed
by the IR spectra, which show the characteristic medium-
intensity ν(CtC) band at 2100-2079 cm-1, and by the
13C NMR spectra (Table 2), which exhibit the CR of the
acetylide as a well-resolved multiplet with an ap-
preciable 2J CP value and Câ as a rather broad signal due
3
to the low value of J CP. The infrared and the NMR
spectra also allow us to assign a geometry in solution
for the complexes 9-11 as reported for the related
hydrides 1-3.
The infrared spectra of the tricarbonyls Mn(CtCR)-
(CO)3P2 (9) show, in fact, two strong bands and one band
of medium intensity for νCO, while the 31P spectra,
between +30 and -90 °C, appear as a sharp singlet, in
agreement with a mer,trans geometry (VIII). The 13C
NMR spectra confirm such a structure, showing, for the
carbonyl carbon atom, two triplets of intensity ratio 2:1
2
with a J CP value of about 25 Hz due to the coupling of
the CO carbon atoms with the two equivalent phospho-
rus nuclei of the phosphite.
(21) Sato, M.; Tatsumi, T.; Kodama, T.; Hidai, M.; Uchida, T.;
Uchida, Y. J . Am. Chem. Soc. 1978, 100, 447.
(22) Zhang, K.; Gonzalez, A. A.; Mukerjee, S. L.; Chou, S.-J .; Hoff,
C. D.; Kubat-Martin, K. A.; Barnhart, D.; Kubas, G. J . J . Am. Chem.
Soc. 1991, 113, 9170.
(23) Heinekey, D. M.; Schomber, B. M.; Radzewich, C. E. J . Am.
Chem. Soc. 1994, 116, 4515.
(19) (a) Treichel, P. M. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press:
Oxford, England, 1982; Vol. 4. (b) Chiswell, B.; McKenzie, D.; Lindoy,
L. F. In Comprehensive Coordination Chemistry; Wilkinson, G., Gillard,
R. D., McCleverty, J . A., Eds.; Pergamon Press: Oxford, England, 1987;
Vol. 4.
(20) Brookhart, M.; Green, M. L. H.; Wong, L.-L. Prog. Inorg. Chem.
1988, 36, 1.
(24) Bianchini, C.; Marchi, A.; Marvelli, L.; Peruzzini, M.; Romerosa,
A.; Rossi, R.; Vacca, A. Organometallics 1995, 14, 3203.

4968 Organometallics, Vol. 16, No. 23, 1997
Albertin et al.
Sch em e 5a
7 or of the triflate 8 allows the easy synthesis of new
series of acetylide derivatives.
The alkynyl complexes 9-11 were treated with
HBF4‚Et2O or CF3SO3H in an attempt to prepare
vinylidene MndCdC(H)R or η2-alkyne Mn(η2-HCtCR)
complexes through protonation reactions of the CtCR
moiety.26 Unfortunately, no stable complexes could be
isolated, only intractable oils or mixtures of products
whose 1H and 13C NMR spectra did not reveal the
presence of any vinylidene or η2-alkyne derivative.
Studies on the progress of the reaction by IR and NMR
spectra showed that, although the protonation reaction
proceeds easily at room temperature, no evidence of a
dCdC(H)R or a η2-HCtCR complex was detected.
However, the presence of free alkyne in the reaction
mixture may suggest that the protonation reaction takes
place at the CtCR group, probably affording a vi-
nylidene27 complex, which is unstable, preventing the
isolation of stable derivatives.
New mononitrile (12, 13) and monoisocyanide (14,-
15) complexes were also prepared from the unsaturated
complexes which were isolated as air-stable pale yellow
solids that are diamagnetic and 1:1 electrolytes. The
infrared spectra show only one νCN band at 2261-2239
cm-1 for the nitrile and at 2141-2109 cm-1 for the
isocyanide. Furthermore, in the carbonyl stretching
region only one strong νCO band is present in the case
of the monocarbonyl compounds [MnL(CO)P4]BPh4 (13,
15; L ) p-tolylCN, p-tolylNC), whose 31P spectra appear
as a sharp singlet, suggesting the magnetic equivalence
of the four phosphite ligands as in the trans geometry
XI.
a
n ) 3 (9), 2 (10, 12, 14, 16), 1 (11, 13, 15, 17). P ) P(OEt)3
(a ), PPh(OEt)2 (b), PPh2OEt (c), PPh(OiPr)2 (d ), R ) Ph (a -
d ), p-tolyl (b1, c1). R1 ) p-tolyl.
In the temperature range between +30 and -90 °C
the 31P spectrum of the dicarbonyl Mn(CtCPh)(CO)2-
[PPh(OEt)2]3 (10b) is an A2B multiplet, while the IR
spectra show two νCO bands at 1960 s and 1885 s cm-1
beside the νCtC band at 2083 cm-1, indicating the cis
positions of the CO ligands. Furthermore, in the
carbonyl carbon region the 13C NMR spectra display two
doublets of triplets at 220.8 and 222.9 ppm (Table 2),
respectively. The presence of the two multiplets seems
to indicate the magnetic inequivalence of the two CO
groups, as in a cis-mer structure of the type IX. Finally,
the 13C{1H} NMR spectra of the monocarbonyl com-
pound Mn(CtCPh)(CO){P(OEt)3}4 (11a ) show only one
well-resolved quintet for the carbonyl carbon atoms at
221.1 ppm due to the coupling with four equivalent P
nuclei. The magnetic equivalence of the four phosphite
ligands is confirmed by the sharp singlet observed in
the 31P spectra, as expected for the trans geometry X.
The infrared spectra of the dicarbonyl cations [MnL-
(CO)2P3]+ (12, 14; L ) p-tolylCN, p-tolylNC) show two
νCO bands, in agreement with a mutually cis arrange-
ment of the two CO groups. The 31P{1H} NMR spectra
are A2B multiplets, while the 13C spectrum of [Mn(p-
tolylNC)(CO)2{PPh(OEt)2}3]BPh4 (14b) shows, in the
carbonyl carbon region, only one broad multiplet at
218.1 ppm, which seems to indicate the magnetic
equivalence of the two CO ligands. On this basis a fac-
cis geometry of type XII can be reasonably proposed for
the dicarbonyl compounds 12 and 14.
Relatively few manganese-alkynyl complexes have
been reported25 in comparison to other transition-metal
centers, and the use of the unsaturated complexes 6 and
The carbonyl complexes [Mn(CO)3P3]BPh4 (16) and
[Mn(CO)2P4]BPh4 (17) are air-stable pale yellow solids
whose formulation is confirmed by the elemental analy-
(25) Manna, J .; J ohn, K. D.; Hopkins, M. D. Adv. Organomet. Chem.
1995, 36, 79.
(26) Bruce, M. I. Chem. Rev. 1991, 31, 197.
(27) Kostic, N. M.; Fenske, R. F. Organometallics 1982, 1, 974.

Cationic Molecular Hydrogen Complexes of Mn(I)
Organometallics, Vol. 16, No. 23, 1997 4969
ses and IR and NMR spectra. In the νCO region the
tricarbonyls 16 show three bands between 2062 and
1968 cm-1, two of which are strong and the third of
which has medium intensity, in agreement with a mer
arrangement of the three CO ligands as in a type XIII
temperature the 31P spectra show a broad signal, which
resolves at -90 °C into a sharp singlet and an A2B2
multiplet. These results may be interpreted on the
basis of the presence of both the trans (XIV) (singlet in
the 31P spectra) and the cis (XV) (A2B2 in the 31P
spectra) isomers, whose νCO bands are in part overlap-
ping in the IR spectra.
1
geometry. The H and 31P NMR spectra indicate that
the complexes are fluxional and also at -90 °C the
spectra are still rather broad and result of difficult
simulation. However, the presence of two broad signals
of intensity ratio 2:1 seem to suggest that two phosphi-
tes are magnetically equivalent and are different from
the third, in agreement with the mer geometry XIII.
The IR spectra of the dicarbonyl derivatives [Mn-
(CO)2P4]BPh4 (17) show two νCO bands at 1991-1922
cm-1 of different intensity, i.e. one medium and sharp
and the other strong and rather broad. At room
Ack n ow led gm en t. This work was supported by the
Ministero della Ricerca Scientifica e Tecnologica
(MURST) and by the Consiglio Nazionale delle Ricerche
(CNR), Rome. We thank Daniela Baldan for technical
assistance.
OM970226J