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Chemistry of the H3B(CH3)2P Group Unusual Properties of Some Simple Reference Compounds.

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X-ray structure analysis of (3) (monoclinic, space group
b = 13.272(4), c=11.660(3)
p= 101.57(3)", 2 = 4 ; four-circle diffractometer data,
R = 3.4%) proves the spiro-linkage of the thiacyclopentane
ring to S1 of the bicyclic SN skeleton (Fig. 1).
Fig. I . Molecular structure of S5Nh(CH& in the crystal with bond lengths (aSN
and oSC = 0.003, uCC =O.OiO A) and vibrational ellipsoids (50% probability).
The eight-membered ring without S1, N1, and N4 has a
conformation analogous to that of the S4N4molecule; the
other two rings (SI- Nl---S2-N2--SLN5-S3-N4 and
S1 N1 S2-N3-S5-N6-S3-N4) have a crown shape
comparable with that of the SR molecule. The distance of
2.454(1) A between S4 and S5 corresponds to a transannular
interaction. This contact is stronger!han in S4N4(2.58
weaker than in S5N6 (2.425(2) A)['' and in S5N6(CH3)2
(2.433(3) A)["].Neglecting the S(CH2)4five-membered ring,
the molecule of (3) has C, symmetry. The bond lengths averaged over both halves of the molecule are shown in Figure 1;
bond angles S ~ N - S
- 121.1(2)-125.3(2),
N- S(trivalent) ~N 104.0(2)-111.0(2). N --S(diva1ent)-N 118.4(2)119.2(2), N -S(tetravalent) -N 124.1(2)".
of compounds. Its advantages as a protecting and leaving
group and as an inert and hydrophobic synthetic moiety having influence on the solubility, volatility and surface nature
of substances were soon recognized and rapidly led to a wide
spectrum of practical applications.
It appears inapposite at first sight to expect similar properties of the isoelectronic Me2(H3B)P-group,since the otherwise typical lability of the BH-function and the formal
charges would suggest such substances to have a completely
different character. We have found, however, that 1) all
Me2(H3B)Pcompounds analogous to the Me,Si parent compounds can exist, that these 2) are surprisingly thermally and
chemically stable and 3) open up access to a variety of derivatives by substitution reactions.
The chlorophosphaneborane (1) corresponding to chloro(trimethy1)silane is readily and quantitatively obtainable
(route a) from inexpensive starting materials; the stable, distillable liquid is only slightly sensitive to moisture[''.
The compound (2) analogous to disiloxane can be prepared from (1) by controlled hydrolysis or-better-with
Ag20 (route b); its air- and water-stable crystals, m. p. 74 "C,
are sublimable without decomposition.
MezPCl + H3B.0C4H8
A solution of (2) ( 5 mmol) in CH&N (25 ml) is added
dropwise to a cooled ( - 5 to - 10 "C) and stirred solution of
(1) ( 5 mmol) in CH3CN (50 ml). A grayish-brown precipitate
appears on slow warming of the reaction mixture to room
temperature (12 h). The product is purified by dissolving
samples of ca. 50 mg in a mixture of CH2C12 (30 ml) and
CH3CN (10 ml). After removing part of the CHzClz (25 ml)
the solution is allowed to stand in a refrigerator, whereupon
yellow crystals of (3) precipitate. The yield is 40% (before recrystallization).
Received: June 5, 1979 [ Z 295 h IE]
German version: Angew. Chem. 91, 846 (1979)
111 T. Chii1er.s.J. Proctor, J . Chem. SOC.Chem. Commun. 1Y78. 642; H. W Roesk.v, M . N. S. Rao, T. Nakajima, W. S. Sheldrick, Chem. Ber., in press.
121 H . W. Roesky, C. Craf; unpublished.
131 L. Zborilova, P. Gebauer, Z . Anorg. Allg. Chem. 448, 5 (1979).
141 W. S. Sheidrick, M. N . S. Rao, H. W.Roesky, Inorg. Chem., in press.
Chemistry of the H3B(CH&P Group[**]:
Unusual Properties of Some Simple Reference Compounds
By Hubert Schmidbaur and Erwin Weisd']
The trimethylsilyl group Me3Si- confers synthetically,
technically, and analytically valuable properties on a variety
Prof. Dr. H. Schmidbaur, DipLChem. E. Weiss
Anorganisch-chemisches Institut der Technischen Universitat Munchen
Lichtenhergstrasse 4. D-8046 Garching (Germany)
[**I Part I
A n g e w Chenm Inr Ed Engl. 18 (1479) N o I0
1. LiR
Ammonolysis of (1) with NH3 in diethyl ether or the reaction with NaNH2 (route c) leads quantitatively to the analog
of (unstable![21)amino(trimethy1)silane; the product (3) is a
deliquescent crystalline substance at room temperature
which loses neither NH3 nor Hz spontaneously and can be
distilled without decomposition. After metalation with nC4H9Liin pentane, the reaction (route d) with further (1) affords the compound (4) corresponding to disilazane; like (2)
it is air- and water-stable, can be sublimed, and can be
metalated once again at the NH group (route e), giving the
important versatile reagent (5)(31.
Reaction of (1) with NaOCH3 in diethyl ether/methanol
quantitatively affords the methoxyphosphaneborane (6),
whose aromatic odor is reminiscent of that of the corresponding silyl ether. The CH30- moiety in (6) is readily replaceable by other RO groups. On reaction with aniline in
diethyl ether, (1) is completely converted into (7) already at
room temperature. Other amines give analogous products.
The structure and composition of all the named compounds was confirmed by complete elemental analyses and
spectroscopic investigations [MS, IR, NMR, 'H, I3C, "PI.
0 Verlag Chemie, GmbH. 6940 Weinheim, 1979
0570-0~33/79/1010-0781$. 02..50/0
(7): A solution of aniline (1.45 g, 15.6 mmol) in ether (5
ml) is added to a solution of (I) (0.86 g, 7.80 mmol) in ether
(20 ml). A colorless precipitate is formed which is filtered off
and washed with redistilled solvent. The filtrate is evaporated to dryness. Yield 88%; m.p. 57 " C.
The unusual properties of these prototypes deserve comment: it is a little-known fact that the BH3group in phosphaneboranes has, for much discussed but still unclear reasons[41,
lost its hydride activity to such an extent that it is even stable
towards acids and based5]. According to our findings the
monofunctional derivatives behave similarly and thus the
H3B(CH&P group proves to be a relatively inert and readily
exchangeable substituent. It is apparent then that many of
the known reactions of (CH3)3Sicompounds can be accomplished with the corresponding H3B(CH3)*Pcompounds, but
the products have a characteristically higher polarity.
Received: June 1, 1979 [ Z 296a IE]
German version: Angew. Chem. 91, 847 (1979)
[I] Earlier data referring to a product prepared from MeZPCI and B2H6 gas
which was described as decomposable could not be confirmed; most of the
spectroscopic findings, however, correspond to our findings for ( I ) : J. D.
Odom, S. Riethmiller, J. R. Durig, J. Inorg. Nucl. Chem. 36, 1713 (1974).
[2] N . Wiberg, W. Uhlenbrock, Chem. Ber. 104, 2643 (1971).
[3] Cf. the reactivity of LiN(SiMe&: U . Wannagat, H. Niederprirm, 2. Anorg.
Allg. Chem. 308, 337 (1961).
141 A. B. Burg, R. J. Wagner, J. Am. Chem. Soc. 75, 3872 (1953); F. Hewrrr, A. K.
Holliday, J. Chem. SOC.1953, 530 F. G. A. Stone, Q. Rev. Chem. Soc. 9. 174
(19%); E. L. Muetterries: Boron Hydride Chemistry. Academic Press, New
York 1975.
151 Gmelin Handbuch der Anorganischen Chemie, Supplement to the 8th edit.,
Vol. 19, Part 3. Springer-Verlag, Berlin 1975, p. 117ff.
(I): A 1 M THF solution of BH3.C4H80(63 ml, 63 mmol)
is added to 6.0 g (62.7 mmol) Me2PCl at 0 "C. The solvent is
removed at 20 mbar/2O0C and the residue distilled at 0.1
mbar/20 "C; colorless liquid"'.
(2): To a solution of (I) (0.46 g, 4.2 mmol) in THF (15 ml)
is added Ag20 (0.48 g, 2.1 mmol) and the mixture stirred in a
sealed vessel for one week at 20 "C. All volatile components
are removed at 0.1 mbar/20 "C, and the residue washed with
pentane (5 ml) and sublimed at 60 "C/10p4 mbar. Yield 66%;
m.p. 74 "C.
(3): (I) (2.96 g, 26.8 mmol) is added to a solution of
NaNH2 (1.10 g, 20.2 mmol) in T H F (10 ml) at -78 "C. The
mixture is warmed up and stirred for 1 h. Workup as in the
case of (2) gives (3) in 68% yield.-The same product is obtained on passage of NH3 into a solution of (I) (5.00 g, 45.3
mmol) in ether (75 ml) at 0 "C. After filtration from precipitated NH4Cl and removal of solvent, (3) is obtained in 98%
yield; m. p. 29 "C.
(4): One equivalent of t-BuLi in pentane is added to a suspension of (3) (2.33 g, 25.6 mmol) in pentane (20 ml) at 0 "C
and the mixture stirred for 12 h at 20°C. (I) (2.80 g, 25.6
mmol) is then added at 0 "C and stirring continued for a further 4 h at 20 "C. Removal of solvent, washing with 2 x 10 ml
water, and crystallization from toluene affords (4) in 47%
yield; m. p. 164 "C.
(6): To a solution of CH30Na.CH30H (0.93 g, 10.8
mmol) in ether (10 ml) is added 1.19 g (10.8 mmol) of (I) at
0 "C and the mixture is stirred for 1 h. Workup as for (I) affords (6) in 73.5% yield; colorless liquid.
1.35, "d"
1.30, dq
127, br
17.2, " d
1.03, d
1.05, dq
1.19, "d"
45.5, q
58.4, br
17.2, d
17.0, "d'
1.51, d
16 lhl
118.2, q
14.8, d
41 [b]
By Hubert Schmidbaur, Erwin Weiss, and Beate ZimmerGassed'l
Phosphaneboranes R3PBH3 are relatively inert owing to
the reduction in polarity of their HB and BP structural elements by specific bonding in the H,BP group. CH, groups
(R = Me) in such compounds, however, have distinct acidic
character due to the stability of the corresponding ylide
bases"]. This effect ought to be much more pronounced in
compounds of the type [Rz(H3B)PI2CH2and thus enable
metalation at the central atom.
and the borane adStarting from the bisphosphane
duct H3B.OC4HR,we have now synthesized (2), which crystallizes in the form of stacked hexagonal scales (a crystal
structure analysis could not be carried out because of the extreme thinness of the flakes). Conversion into a metalated
derivative was accomplished by reaction with alkyllithium in
an inert solvent, and a crystalline Li-complex salt (3) could
be isolated by precipitation with tetramethylethylenediamine
47.4, q
[a] 6NH=2.86, broad. IR: u(NH)=3180, u(BH)=2380cm-'.
[b] 6CH,O=3.63, d, 'J(PH)=12; 6CH10=52.9, d, 2J(PC)=3.9.
[c] S N H = 3.70, d, 'J(PH) = 13: 6C,H5 = 5.83-6.97, m.
Synthesis and Crystal Structure of a Salt Containing
the Anion [H3B(CH3)2P-CH-.P(CH3)2BH3] ; Precursors and Related Compounds[**]
0 Verlag Chemie, GmbH, 6940 Weinheim, 1979
Prof. Dr. H. Schmidbaur, DipLChem. E. Weiss, Dipl.-Chem. B. ZimmerGasser
Anorganisch-chemisches Institut der Technischen Universitat Munchen
Lichtenbergstr. 4, D-8046 Garching (Germany)
r * ] Chemistry of the H3B(CH1)zP Group, Part 2.-Part 1: [4].
0570-0X33/79/1010-0782$ 02.50/0
Angen,. Chem. Inr. Ed. Engl. I 8 (tY79) No. 10
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