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An Aluminaphosphacubane a New Aluminum Phosphide Precursor.

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An Aluminaphosphacubane, a New Aluminum
Phosphide Precursor
By Alan H. Cowley,** Richard A . Jones,*
Miguel A . Mardones, Jerry L. Atwood,* and Simon G . Bott
There is a heightened interest in the chemistry of cubanes
and their isolobal analogues. In the context of phosphoruscontaining cubanes, salient developments include the syntheses of [rBuE(p,-P)], (E = C['], Si[']) I , [PhSn(p,-P)J,r31 2,
and several organometallic derivatives of the general type
[(L,M),(P),- J .I4]Conceptually, these novel compounds can
be regarded as derivatives of the hypothetical cubane P, .Is1
Alternatively, cubanes 1 and 2 can be viewed as tetramers of
triply-bonded monomers, RE = P. In principle, a different
class of phosphorus-containing cubane should be possible by
tetramerization of monomers of the type R M S P R ' where M
represents a group 13 element. We report the first aluminaphosphacubane.
Treatment of equimolar quantities of iBu,AlH and
Ph,SiPH,[61 in toluene at 25 "C for 12 h resulted in the evolution of H, and the formation of white, crystalline 3.
Fig. 1. View (ORTEP) of 4 showing the atom numbering scheme. Important
bond distances [A] and bond angles ["I: P-AI 2.409(4), P-AI' 2.415(4), P-AI"
2.417(4), P-Si 2.236(4), A1-C41 1.96(1), AI-P-AI' 89.0(2), AI-P-AI" 87.8(2),
AI'-P-AI" 87.7(2), AI-P-Si 127.3(2), A]'-P-Si 125.6(2), AI"-P-Si 126.8(2), PAI-P 90.9(2), P-AI-P" 92.3(2), P - A I - P 92.2(2), P-AI-C41 120.6(4), P-AI C41 127.7(4), F"'-AI-C41 123.6(4).
HL, ?SiPh,
iBu,,
p
iBu
'A,/
\A,
angles at phosphorus are less than 90" (av. 88.2(2)"). The
is slightly less
average Al-P bond distance in 4 (2.414(4)
i ?
than those observed in AI,P, dimers which span the ran e
Ph,Si
H
2.433(4) to 2.475(1)
The P-Si distance in 4 (2.236(4) )
3
is slighly shorter than that in the diphosphene 2,4,6tBu,C,H,P = PSiPh, (2.269(2)
Preliminary work indicates that an analogous gallaphosThe dimeric nature of 3 was established by mass spectromphacubane [tBuGa(p,-PSiPh,)], (6,,, = - 185) can be preetry (MS) which revealed a parent peak at m / z 864 followed
pared by treatment of [tBuGaCI,], with Ph,SiPLi, in Et,O.
by fragment ions corresponding to [MH@- iBu-Ph,Si] and
Interestingly, we have not been able to isolate cubanes when
[M@- 2iBu - Ph,Si]. Like [(Me,Si),AlP(Ph)(SiMe,)J, J71 3
phosphorus substituents other than Ph,Si are employed.
exists as a mixture of syn and anti isomers in approximately
Cubane 4 is reactive toward both electrophiles and nucleo1 :2 abundance as evidenced by the presence of two ,'Pphiles. For example, reaction of 4 with eight equivalents of
NMR peaks.['' Compound 3 starts to melt at 80 "C; howevEtOH affords Ph,SiPH,[61 and iBuAI(OEt), .[lo] Even when
er, melting is accompanied by gas evolution (MS: isobutane)
less than eight equivalents are employed, complete cage
followed by resolidification. Refluxing 3 in toluene solution
degradation occurs and a proportionate quantity of unfor 12 h, followed by concentration and cooling to - 20 "C,
changed 4 is left over. Similar results are obtained with H,O.
resulted in the isolation of white, crystalline [iBuAl(p,Treatment of 4 with four equivalents of MeLi in Et,O also
PSiPh,)], (4) in 83 % yield. Mass spectroscopy was not very
causes rupture of the AI,P, cage. The NMR data for the
useful for the characterization of 4; the highest mass peak in
MeLi reaction product correspond to those anticipated for
EI or CI experiments occurred at m / z 259 and corresponds
the anion [iBuMeAlPSiPh,]" 5.[*]This was confirmed by the
to [Ph,Si@]. The ,'P-NMR spectrum comprised a singlet at
reaction of 5 with EtOH, which produced [iBuMeAIOEt].[lo]
6 = - 213.0 and the 'H- and 13C('H}-NMR spectra were
Thermolysis studies reveal that the new Al,P, cubane 4
indicative of the presence of equal numbers of iBu and Ph,Si
represents a potentially interesting precursor to aluminum
groups. The 27A1-NMR signal for 4 was very broad
phosphide. Temperature-programmed EI or CI mass spec4700Hz) and no ,'P coupling was discernible. Elemental
trometry demonstrates that the decomposition of the cubane
analytical data corresponded to the empirical composition
starts as low as 150°C. The major volatiles are identified as
iBuAIPSiPh, . An X-ray crystallographic study"] revealed
Ph,SiH and isobutylene. XPS (X-ray Photoelectron Specthat 4 possesses a cubane structure (Fig. 1). There are no
troscopy) analysis[' ' ] and X-ray diffraction of the residue
short intermolecular contacts and each molecule resides on
that remained after heating to 500°C indicates that it is
a site of S, symmetry. As in the case of the recently isolated
aluminum phosphide.
tetraphosphacubanes, [ZBUC(&,-P)J,['~
and [ ~ B U S ~ ( ~ ~ - P ) J , [ ~ ~
the cube of 4 is distorted in the sense that the internal bond
Experimental Procedure
\
,
'
tBu'
p' '
A)
'iBu
A,[']
[*] Prof. Dr. A. H. Cowley, Prof. Dr. R. A. Jones, M. A. Mardones
Department of Chemistry
University of Texas at Austin
Austin, TX 78712 (USA)
[**I
Professor Dr. J. L. Atwood and Dr. S . G. Bott
Department of Chemistry
University of Alabama
Tuscaloosa, AL 35486 (USA)
This work was supported by the National Science Foundation, the Robert
A. Welch Foundation, and the U.S. Army Research Office.
Angew. Chem. hi.Ed. Engl. 29 (1990) No. 12
0 VCH
f
3: A toluene solution (25 wt.%) of rBu,AIH (13.4 mL, 20 mmol) was added to
5.84 g (20 mmol) of Ph,SiPHZ. The resulting clear solution, which evolved
hydrogen, was stirred for 12 h at room temperature. Solvent evaporation afforded white, crystalline 3 in virtually quantitative yield (m.p. = 80"C, decamp.). 4: A toluene solution of 3 was refluxed for 32 h. The solvent and
volatiles were removed In vacuo, following which the resulting white residue
was redissolved in toluene. After filtration and concentration of the filtrate,
colorless crystals of 4 formed in 83 % yield by cooling to - 20 "C.
Verlagsgesellschafi mbH, W-6940 Weinheim. 1990
Received: August 23, 1990 [Z 4148 IE]
German version: Angew. Chem. 102 (1990) 1504
0570-0833/90/l212-1409 $3.SOi.25/0
1409
CAS Registry numbers:
syn-3, 130149-56-3; anri-3, 130195-60-7; 4, 130149-57-4; 5, 130149-58-5;
[~BUG~(JL,-PS~P~,)],,
130149-59-6; iBu,AIH. 1191-15-7; Ph,SiPH,, 12262338-5; Ph,SiPLi,, 130149-55-2;[tBuGaCI,], ,127139-90-6; iBuAl(OEt), ,3716769-4.
intact. As possible structures the valence isomers 2 a and 2b
were proposed.“’
2a and 2b are not only aesthetically attractive, their relative stability is also of considerable interest for theoretical
studies of molecular structures, since they afford important
information about the influence of aromatic stabilization.
[l] T. Wettling, J. Schneider, 0. Wagner, C. G. Kreiter, M. Regitz, Angew.
Chem. fOf (1989) 1035; Angew. Chem. Ini. Ed. Engl. 28 (1989) 1013.
[2] M. Baudler, G. Scholz. K.-F. Tebbe, M. Fehir, Angew. Chem. 101 (1989)
352; Angew. Chem. hi.Ed. Engl. 28 (1989) 339.
[3] H. Schumann, H. Benda, Angew. Chem. 80 (1968) 846; Angew. Chem. Int.
Ed. Engl. 7 (1968) 813.
141 See, for example, G. L. Simon, L. F. Dahl, J. Am. Chem. SOC.95 (1973)
2175; 0.J. Scherer, T. Dave, J. Braun, G. Wolmershauser, J. Organomet.
Chem. 350 (1988) C20.
[5] See, for example, E. A. Halevi, H. Bock, B. Rohr, Inorg. Chem. 23 (1984)
4376. R. Ahlrichs, S . Brode. C. Ehrhardt, J: Am. Chem. SOC.107 (1985)
7260.
[6] A. H. Cowley, P. C. Knuppel, C. M. Nunn, OrganometaIl1cs8(1989)2490.
[7] J. F Janik, E. N. Duesler, W. F. McNamara, M. Westerhausen, R. T.
1
2a
2b
Paine, Organomeiallics8 (1989) 506. For additional structural information
Fig.
1.
Proposed
structures
2a
and
2b
of
C,S,
formed
from
1.
on this class of compound, see S A. Sangokoya, W. T. Pennington, G. H.
Robinson, D. C. Hrncir, J. Organomer. Chem. 385 (1990) 23.
[S] ” P NMR (121.5 MHz, C,D,, 295 K, 85% H,PO, external standard):
3: 6 = - 216.8 (anfi), - 217.6 (syn); 4. 6 = - 213.0.-’H
NMR
ring strain and the strength of the C-S double bond. We have
(300.15 MHz, C,D,, 295 K) 3: 6 = 0.36 (8H, d, broad. J = 7 . 2 Hz,
therefore calculated the geometries and energies of the C,S,
CH,AI), 0.80 (6H. d, J = 6.6 Hz, CH,), 0.94 (6H, d, J = 6.6 Hz, CH,),
0.97 (6H, d, J = 6.6 Hz, CH,), 1.07 (6H, d, J = 6.6 Hz, CH,), 1.84 (4H,
isomers 2 a and 2 b as well as of the quinoid form 2c.13*41 The
m, J = 6.6Hz, H-C(CH,),), 7.13 (18H, m, phenyl H), 7.66 (12H, m,
optimized geometries are depicted in Figure 2, and the relaphenyl H); 4: 6 = 0.23 (8H, d, broad. J =7.2 Hz, CH,AI), 0.39 (24H, d,
J=6.6Hz,C(CH3),), 1.24(4H,m,J=6.6Hz,HC(CH3),)7.13(36H,
0-p phenyl H), 7.66 (24H, m, phenyl H).-”AI NMR (78.21 MHz, C,D,,
295 K , AI(NO,), external standard) 6 = 20 (broad).
S
S
[9] 4: tetragonal, space group P 42,c (No. 114). Z = 2, u = 15.721(2),
h = 17.186(3) A; V = 4248 A3; eCAlcd
= 1.175 gcm-’; 2” < 20 < 50“
(Mo,,, 2. = 0.71069 A; p = 2.24 cm-I); T = 24°C. 8249 reflections. %I20
2a
scan mode, of these 1911 reflections with I > 6.0a(I) were used to solve
(direct methods) and refine (full-matrix, least squares) the structure of 3.
R = 0.0507, Rw = 0.0499 There is some disorder in the isobutyl groups.
1491
s//
Further details of the crystal structure investigation can be obtained from
the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische Information mbH D-7514, Eggenstein-Leopolds2.120 12.1081
hafen 2, FRG by quoting the depository number CSD-54883, the names
2\
002
of the authors, and the journal citation.
S
1.767
11.7721
[lo] Identified by comparison of ’H- and ’3C{’HJ-NMR spectra with those of
1.687
an authentic sample. See A. Alberola, R. Pedrosa. An. Quim., Ser. C 76,
2b
(1980) 21.
1366
[ l l ] XPS data were obtained on a VG Scientific Escalab Mark I instrument
with a Mg, X-ray anode.
I
1.451 11.4781s
1.397 l1.4151
1462
1.461
1.7& 11.7671
I687
Fig. 2. Calculated bond lengths [A] and angles [“I for 2a-2d. Numerical data:
3-21G* basis set, in brackets: STO-3G basis set, italics: MNDO method.
tive energies are listed in Table
In addition, we report
our results of theoretical studies on the analogous oxygen
compound C,O, in the isomeric forms 3a, 3b, and 3c.
The Structure of Cyclic c6s6 and C,06**
By Gernot Frenking*
Dedicated to Professor Karl Dimroth
on the occasion of his 80th birthday
Siilzle et al.[’l recently reported on the mass spectrometric
investigation of benzo[1,2-d: 3,4-d‘: 5,6-d”J-tri(1,3-dithiol-2one) 1, in which, after cleavage of three molecules of CO
from the radical anion leeand subsequent charge exchange
reactions, the fragments C,Sg (n = 1,0, - 1) were detected. The experimental findings provided no information
about the structure of the C,S: fragments, but, owing to the
low tendency of radical anions to rearrange,[” it was presumed that the six-membered ring structure of 1 remains
Table 1. Calculated relative energies Ere’[kcal mol- ’1 and zero point vibration
energies ZPE [kcal mol-’1 with the number of imaginary frequencies i.
Cpd. Symm. HF/STO-3G
+
[*] Prof. Dr. G. Frenking
Fachbereich Chemie der Universitdt
Hans-Meerwein-Strasse, W-3550 Marburg (FRG)
[**I This work was supported by the Fonds der Chemischen Industrie, the
Deutsche Forschungsgemeinschaft, and Convex and Silicon Graphics.
1410
0 VCH VerlagsgesellschufrmhH.
W-6940 Weinheim, 1990
Esci
2a
2b
2c
2d
3a
3b
3c
3d
D,,
D,,
D,,
D,,
D,,
D,,
D,,
Dw
136.0
0.0
48.8
130.8
0.0
88.9
64.7
-[bl
HF/
3-21G’
HF/
MP2/
MNDO
6-31G* [a] 3-21G*[a]
Ere,
NSE
i
Ere,
31.0
33.7
32.9
30.9
38.6
42.8
41.6
3
0
53.9
0.0
3.2
30.0
0.0
241.0
163.5
- [bl
0
0
0
0
0
62.3
0.0
1.1
34.7
0.0
294.1
192.4
Ere,
E,,,
i
26.5
0.0
- 10.1
3.1
0.0
233.9
148.0
78.5
0.0
28.4
66.6
6.5
316.6
205.9
0.0
3
0
0
0
3
0
0
0
[a] Energy calculation with 3-21G*-optimized geometries. [b] Optimization
leads to the structure 3a.
0570-0833~90l12~2-14ln
$3.50+.25/0
Angew. Chem. Int. Ed. Engl. 29 (1990) No. 12
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