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Lithium Tetraphenyl- and Tetramethylniccolate(II).

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Phosphorus(v) Having Trigonal Planar Coordination
By Siegfried Pohl, Edgar Niecke, and Bernt Krebs"]
The o-bond skeletons of four- to six-coordinate phosphorus
can generally be described with the aid of tetrahedra, trigonal
bipyramids, and octahedra"! Occupation of only three coordination sites leading to planar coordination has hitherto
only been postulated for unstable intermediates on the basis
of stereochemical and kinetic studiesc2!
of a phosphorus(v) derivative stabilized
by p,-p, bonds and having the composition (R,Si),NP(NSiR,), with R = C H , has now provided an opportunity to
establish, by complete X-ray structural analysis, whether trigonal planar coordination of phosphorus exists in a stable
compound. We also wished to examine to what extent the
polar resonance structures (2a) and (2b) should feature
alongside (1 ) in descriptions of the bonding in aminodiiminophosphorane.
. OlN6
Bis (trimethylsilyl) aminobis (trimethylsilylimino) phosphoranel3I, m.p. 46"C, forms monoclinic crystals of space group
C2/c having the lattice constants (at 18°C) a= 17.905,
b= 10.654, c=13.236A; p= 109.27"; V=2383A3; Z = 4 .
The structure was solved from diffractometer data by the
direct method of symbolic addition. Least squares refinement
with the structure factors of 1045 reflections observed at 18°C
converged to an R value of 4.3%.
In the solid state the molecule has C 2 symmetry. The central
phosphorus atom exhibits a planar threefold coordination
to nitrogen atoms. The uncorrected P-N bond lengths are
1.503 and 1.646A (Fig. 1). The P-Nimine distances, which
Fig. 1. Molecular structure of bis(trimethylsilyl)aminobis(trimethylsilylimino)phosphorane in the crystal (bond lenghts in A).
correspond formally to double bonds, lie at the lower limit
of all known values for PN
Apparently, planarity
favors particularly strong K bonds which probably also contribute to the stabilization of the coordinatively unsaturated
[*] Prof. Dr. B. Krebs and Dr. S . Pohl
Fakultat fur Chemie der Universitat
48 Bielefeld, Universitatsstrasse (Germany)
Dr. E. Niecke
Anorganisch-chemisches Institut der Universitlt
34 Gottingen, Tammannstrasse 4 (Germany)
A n g w . Chem. internat. Edir.
Vol. 14 ( 1 9 7 5 ) / No. 4
phosphorus. Thus any significant weight of the polar resonance
structures can be ruled out.
The P-Namine bond is significantly shorter than a single
bond (1.77A in NaP03NH3['l). The strengthening of this
bond can be explained by d,- pn interaction between phosphorus and amine nitrogen. Although the N(SiR3)zgroupis twisted
by about 32" out of the PN3 plane the participation of d
orbitals still permits this kind of overlapping. Similar effects
are probably responsible for the shortening of the Si-NImine
bonds (1.697 A) whereas the amin: nitrogen is linked to silicon
by a normal single bond (1.780A). The strengthening of the
Si-Nimine x: bond is in accord with the increase in the PNSi
angle to 148.5".
The S i x bond lengths average about 1.871 A. Successful
localization of all the H atoms shows that the methyl groups
are sterically fixed.
A supplementary low temperature study is in progress.
[Z 168 IE)
Received: November 27, 1974
German version: Angew. Chem. 87, 284 (1975)
CAS Registry numbers:
Bis(trimethylsilyl)aminobis(trimethylsilylimino)phosphorane, 521 I 1-28-1
[ 11 A square pyramidal geometry has also been observed for pentacoordinate
phosphorus in a spirocyclic structure: J. A . Howard, D. R. Russell,
and S . Tripprtt, J. C. S . Chem. Comm. 1973, 856.
[2] J. Wiseman and f . H . Wrsrhnmer, J. Amer. Chem. SOC.96, 4262 (1974);
and references cited therein.
[3] E . Nieckr and W f l i c k , Angew. Chem. 86, 128 (1974); Angew. Chem.
internat. Edit. 13, 134 (1974); 0.J. Scherrr and N . Kuhn, Chem. Ber.
107, 2123 (1974).
[4] H. R. Allcock: Phosphorus-Nitrogen Compounds. Academic Press, New
York 1972.
[ 5 ] D. 19: J . Cruickshank, Acta Crystallogr. 17, 67 I ( I 964).
Lithium Tetraphenyl- and Tetramethylniccolate(11)
By Rudolf Taube and Gerd Honymusi']
Simple binary o-organylnickel(I1) compounds NiR generally display pronounced thermal lability. Thus Ni(CH3)2
already decomposes below - l0C!'Crl1. The only stable compounds capable of isolation have so far proved to be those
containing bulky carbanions devoid of P-hydrogens, such as
Ni[C(C6H 5)3]2[21 and Ni[C6H ,(CH 3 ) 3 ] 2[31.
A considerable stabilization, regardless of the organyl group,
is known to occur on complexation, and numerous o-organyl
complexes of thegeneral type NiR2Ln,NiR(X)L,, and cpNiRL,
have been describedr4!
Our attempts to prepare chelate complex-stabilized
monoorganylnickel compounds led us to the tetraorganyl complexes Li2[NI(C2CbH5)4]-4THF (1 ), Li2[Ni(C6H5)4].4 T H F
(2), and LiZ[Ni(CH3),].2 T H F ( 3 ) , of which (2) and (3)
represent the hitherto unisolable pure phenyl- and methylnickel(11) combinations stabilized by "ate" complex formation.
For their synthesis, Ni(dpi),['] (dpi =anion of 1,3-bis(2-pyridy1imino)isoindoline) was added at -78°C to a solution of
LiC2C6H5 in THF/hexane or of LiC6H5 or LiCH3 in
THF/ether and the mixture shaken with warming to roorn
temperature until reaction was complete (ca. 1-2 h). Compounds ( I ) , (2), and ( 3 ) are deposited as small lustrous
crystals from the brown solutions; they are filtered off, washed,
and recrystallized from THF/hexane [(f )] or from T H F [(2)
and (S)] by hot extraction['l.Yield: ( I ) , 65%; ( 2 ) , 60%; and
( 3 ) , 56%.
[*] Prof. Dr. R. Taube and Dipl.-Chem. G. Honymus
Sektion Verfahrenschemie der Technischen Hochschule "Carl Schorlemmer" Leuna-Merseburg
D D R 4 2 Merseburg. Geusaer Strasse (German Democratic Republic)
Properties of ( I ) : beige crystals, decomposition with dark
discoloration above 90°C, soluble in THF. ( 2 ) : yellowish crystals, decomposition at 102-103 "C, moderately soluble in
THF. Protolysis with cyclohexanol affords (alongside THF)
benzene and biphenyl, and reaction with iodine in THF, with
consumption of 4.15 I/Ni, exclusively biphenyl. ( 3 ) : goldenyellow lustrous crystals, decomposition at 129-1 30°C. soluble
in ether, more so in THF. Protolysis with butanol affords
C H 4 (94'x). Reaction with iodine in T H F with consumption
of 4.1 I/Ni gives CH4 (35%), C2H6 (64'%,), and CZH4(1%).
The strongly air- and moisture-sensitive new complexes
are diamagnetic and therefore have planar coordination. Compared with the previously known solvate-free potassium saltLb1,
complex ( I ) is characterized by its better solubility and
enhanced stability. Complexes ( 2 ) and ( 3 ) demonstrate that
planar NiC4 coordination can be achieved not only with
sp but also with sp2 and sp3 hybridized carbon. The relatively
high thermal stability, particularly of the methyl compound,
contradicts the frequently cited Chatt-Shaw "K-bonding
effect""', whose significance for the stability of the transition
metal-carbon bond is frequently overestimated. The choice
of a suitable nickel(l1) chelate complex as starting compound
is of essential importance in the preparation of ( 2 ) and ( 3 ) .
When NiBr2.2 T H F was used only about 2% of (3) could
be isolated alongside metallic nickel. This demonstrates the
great importance of the synthetic pathway for organo-transition-metallic compounds, the success of the present method
apparently resting upon adequate complex-chemical stabilization of the nickel-carbon bond in all the intermediates of
Received: November 28, 1974 [Z 169 IE]
German version: Angew. Chem. 87, 291 (1975)
CAS Registry numbers:
( l ) , 54712-91-3; (21, 54688-82-3; (31, 54688-83-4;
Ni(dpi),, 15134-62-0; LiC,C,H,, 4440-01-1 : LiC,H,, 591-51-5;
LiCH,, 917-54-4
K ., K . Jonus, P. Mishurh, R. Sruhho. and G. Wilke. Angew.
Chem. 85, 1002 (1973): Angew. Chem. internat. Edit. l 2 . 943 (1973).
G. Wilke and H . Schorr, Angew. Chem. 78. 592 (1966): Angew. Chem.
internat. Edit. 5 , 58 I (1966).
G. Wilkc, Pure Appl. Chem. 17, 179 (1968).
D. R. Fohq. Organometal. Chem. Rev. 7. 245 ( 1972).
M. A. Rohiiisor7, S . I . Pot:. and 7: J . H u r l r r . Inorg. Chem. 6, 392
( 1 967).
R. Nusr, Angew. Chem. 72, 26 (1960).
J. Chotr and B. L. S l i m ' . J . Chem. Soc. 1960. 1718.
(2) at reduced pressure.
n-electron delocalization and fixation of the
annelated benzene ring.
bonds in the
Spectroscopic findings (Table 1 confirm the participation
of two n electrons of the benzene ring in complexation. It
follows from the marked upfield shift of the 'B-NMR signal
by 51 ppm that the boron atoms interact with the Fe(CO)3
group to a greater extent than in the previously known thiaborane-metal complexes B(SCH3).3.Cr(C0)3 (41 ~ p m ) [ ~and
(CH3)2BSCH3.Cr(CO)s(21 p ~ m ) [ ~ l .
Table I. Spectroscopic data of ( I ) and (II.Fe(CO),, and ( 2 ) and
'H-NMR. 6 [ppm] rel. to TMS
(in CDCl ,)
-0.95 Is* 6,
-0.83 (s. 6)
- 1.31 (s, 6)
-0.90 (tr, 6)
- 1.17 (tr. 6)
-7.46 (m, 2)
- 2.20 (qu, 4)
-2.10 (m, 4)
-7.63 (m. 2)
(J=7.6 H ~ )
( J = 7.6 Hz)
"6-NMR, S [ppm] rel. t o I C 2 H 5 ) ~ 0 . B F . ~
(in CDCIJ)
(in CCId
- 66.2
- 27.X
- 77.2
IR, v ( C 0 ) [cm-'] in CCl,
2060 IS)
1990 (vs)
- 1.14 (s, 6)
-7.12 (m. 2)
-7.33 (m, 2)
- 26.4
2060 (s)
1990 (vs)
The IR spectra show two bands for the Fe(C0)3 group
in the v(C0) region, and changes in the region of C=C
vibrations, on going from the free ligand to the complex.
In the 'H-NMR spectrum all signals are shifted upfield, thus
indicating an enhanced electron density on boron and a weakening of the aromatic character of the benzene ring. Owing
to relaxation effects, the two C atoms engaged in complex
bonding and the CH3-B group cannot be observed in the
I3C-NMR spectrum. The remaining signals undergo a slight
upfield shift; the I3C resonances coincide to give just one
signal: -211.1 and -210.4ppm for (2).Fe(C0)3 and
(1) .Fe(CO)3respectively (relative to TMS in CDC13).
1-59 -Benzothiadiborolenetricarbonyliron-
A Complex Having a Fixed sc-Electron System in the
Benzene Ring[
By Walter Sirbert, Gunthrr Augustin, Roland Full, Carl Kriigrr,
and %Hung TwJ[*]
1,2,5-Thiadiborolenes have both Lewis-acid and Lewis-base
character. (I)['Iand ( 2 ) L 3 ' r e a ~with
t Fe2(C0)9and Fe3(C0)12
to give red thiadiborolenecarbonyliron complexes formulated
as tricarbonyl derivatives ( I ) . Fe(C0)3 and ( 2 ) . Fe(C0)3 on
the basis of analytical and mass-spectrometric data. However,
for ( 2 ) . Fe(C0)3 this implies that the "aromatic" acts as an
unusual two-electron donor, which should lead to a loss of
Prof. Dr. W. Siebert, Dipl.-Chem. G . Augustin. and R. Full
Fachbereich Chemie der Universitat
355 Marburg, Lahnberge (Germany)
Dr. C. Kriiger and Dr. Y.-H. Tsay
Max-Planck-lnstitut fur Kohlenforschung
433 Miilheim-Ruhr, Lembkestrasse 5 (Germany)
Fig. 1. Molecular structure of benzo-1,2,5-thiadiborolenetricarbonyliron.
Maximum error + 0.004A and 0.02".
Anyrw. Chrm. inrrrnor. E d i t .
1 Vol. 14 ( 1 9 7 5 ) 1 No. 4
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tetraphenyl, tetramethylniccolate, lithium
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