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Synthesis of Metal-Boron Coordination Compounds by Oxidative Addition.

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and then condensed the product with 3’-O-acetylthymidine
(0.5 mmole) (further 12 h at room temperature)[5]. We
were then able to isolate the triester ( l a ) 141 in 55 % yield
by preparative thin-layer chromatography of the reaction
mixture (Merck-Kieselgel P F 254, chloroformjmethanol =
93 :7 vjv).
Reduction of ( l a ) with Zn dust in 80 % acetic acid (20 min at
room temperature) and subsequent removal of the tiityl and
acetyl groups gave TpT [61 (90 % yield).
Hydrolysis of ( l a ) with concentrated ammonia (2 h) gave
tritylthymidine, thymidine, and (Zb) in the relative yields
25: 20: 55, together with phosphoric acid diesters. Acid hydrolysis (80% acetic acid, 100°C, 10 min) afforded exclusively (14.
For instance, (1) the planar complex [(C6H5)3P]2Ir(CO)C1is
converted by HCI into the octahedral iridium(1rr) complex
[(C6H5)3P]21rH(CO)C12111, and (ii) reaction of RX with the
tetrakis(triphenylphosphine)platinum(O) I31 results in loss of
2 mol. equiv. of (C&&P to give halogenoalkylbis(tripheny1phosphine)platinum(Ir) 141.
We have found that the method of oxidative addition is
eminently suited for the synthesis of covalent metal-boron
compounds. Titanocene ( I ) [51 reacts with boron halides
YzBX in ether at room temperature: the deep green of the
solution of ( I ) changing to the purple color of the compound
(2).
v
R1oo
Troo
Bis(tetraphenyldiphosphinoethane)cobalt(O) behaves similarly; for example, in benzene it is oxidized by diphenylboron
chloride to cis - diphenylborochlorobis(tetrapheny1diphosphinoethane)cobalt(rI) (47). The boron halides BC13, BBr3,
and BI3 may be used in place of diphenylboron chloride.
bI
bR2
P,h p h P\h,Ph
O=P-O-CHZCCl,
Lo
( l a ) , R1 = trityl, R2 = acetyl
( I b ) , R* = trityl, R2 = H
( l c ) , R1 = H, Rz = acetyl
T = thyminyl
Tr = trityl
+
(p\Co/p]
P’
Y2BX
-D
)P,
Ph‘Ph
P h Ph
/ \”
(3)
Ph Ph
OCOCH,
Replacing the acetylthymidine in the condensation by ( I c )
yields 55 % of the oligonucleotide ester (2) 141 (amorphous,
m.p. 143 “C). Fission of the trichloroethyl group by reduction
with Zn dust and 80% acetic acid and removal of the trityl
and acetyl groups gives TpTpT [61 (85 % yield).
Tetrakis(triphenylphosphine)platinum(O)
(5) in boiling
cyclohexane 171 reacts with diphenylboron chloride to yield
triphenylphosphine and crystalline diphenylborochlorobis(triphenylphosphine)platinum(rI) (6a).
R F values on Merck DC-prepared silica gel plates
Fz54,
chloroformlmethanol = 93:7 vlv
5’-Tritylthymidine
3’-Acetylthymidine
(2)
0.63
0.52
0.57
(la)
(Ib)
(Ic)
0.86
0.38
0.42
Sufficient Lewis-acidity on the part of the boron halide is of
decisive importance for the success of the above synthesis.
The weakly acidic compounds (C4H&BCI, [(CH~)ZN]~BCI,
B[N(CH3)2]3, and (C&)ZB-N(C~H~) d o not react.
Surprisingly, bis(tetraphenyldiphosFhinoethane)platinum(O)
181 reacts with diphenylboron chloride or bromide in boiling
cyclohexane according to :
+ 2(C6H&BX
(TPE)2Pt
-+
(TPE)P~.~(C~HS+
) ~TPE.
BX
( 7 a ) , X = C1
(761, X
=
Br
The structures of the pale yellow products (7a), m.p. 214 “C,
and (7b), m.p. 21OoC (decomp.), are not yet known. Reaction with pyridine results in loss of one mol. equiv. of
(C6Hs)zBX and formation of cis-diphenylborotetraphenyldiphosphinoethaneplatinum(1r) halides. Therefore, we classify
(70) and (7b) as diphenylboron halide adducts of the compound (8).
Synthesis of Metal-Boron Coordination
Compounds by Oxidative Addition
By G. Schmid, W. Petz, W . Arloth, and H . Noth[*l
Complex metal hydrides or metal alkyls are formed by oxidative addition of H2, HX, or RX, respectively, (X = halogen)
to d8- and dlo-metal compounds in low oxidation statesfl.21.
696
[(HSC~)~P-CHZ-CH~-P(C~H~)~~~~~[B(C~HS
(8)
Evidence for the structure of the newly prepared compounds
is provided by their chemical behavior and by elemental
analysis, molecular-weight determinations, magnetic measurements, and spectrochemical data.
Angew. Chem. internat. Edit. 1 Vol. 6 (1967) / N o . 8
1
I
X
Y
c1
C6H5
Br
C1
C6H5
Br
CI
Br
CI
c1
Br
CI
c1
Br
Br
c1
Br
M.p. ('C)
300 (decomp.)
300 (decornp.)
300 (decornp.)
115 [a1
120
1 1 5 (decomp.)
6 6 H ~ 244 (decomp.)
198-200
GHs
Br
306
208 (decomp.)
150
Color
black-violet
red-brown
red-brown
red-brown
beige
pale yellow
white
white
white
Yield
2,5-dihydro-l,6-benzod~oxocin(m.p. 30 C) as an intermediate, which is formed by reaction of ( 4 ) with 1,5-diazobicyclo[4.3.0]non-S-ene [41.
0
- aOXBr
0
Br
(3)
85
70
[a] Magpetic nioment: 4.8 BM.
Since tetrakis(triphenylphosphine)platinum(O) reacts with
SizC16 to give the compound [(CoH5)P]2Pt(SiC13):, m.p.
180 "C (decomp.), and also reacts with metal-halide complexes ofthe type L n M X , (L=phosphine,X= halogen) to give
191, i t may be predicted that not
I(C6Hj)3P]Pt(X)-MX,-1Ln
only boron halides, but also other non-metal halides, as well
as metal halide complexes, may react with the systems that we
have investigated and thus provide a simple route to numerous new metal-element compounds.
Received: May 22nd and June 7th, 1967
[ Z 5?5 IEJ
German version: Angew. Chem. 79, 683 (1967)
[*] Dr. G. Schmid, Dip[.-Chem. W. Petz, W. Arloth,
and Prof. Dr. H. Noth
lnstitut fur Anorganische Chemie der Universitat
Gutenbergstr. 18
355 Marburg (Germany)
[I] L. Vuska and J . W. Diluzi3, J . Amer. che.n. SOC.83, 2784
(1961).
[2] R. F. Heck, J . Amer. chem. Soc. 86, 2796 (1964); L. Vaska
and R . E . Rhodes, ibid. 87, 4970 (1963).
[ 3 ] L. Mufaresra and C. Cariello, J. chem. Soc. (London) 1958,
2328.
[4] C . D. Cook and G . S . Juuhal, Inorg. nucl. Chem. Letters 3 ,
31 (1967).
[5] G. W. Watt, L . J . Baye, and F. 0 . Drummond, 3 . Amer. chem.
SOC.88, 1138, (1966).
161 A. Sarco and M . Rossi, Chem. Commun. 1965, 602.
171 Reaction in aromatic hydrocarbons yields compounds with
Pt-H bonds.
[8] 1. Chaffand G . A . Rove, Nature (London) 191, 1191 (1961).
[9] A . J . Layton, R . S . Nyholnt, G . A . Pneumaricakis, and M . L .
Tobe. Chem. and Ind. 1967, 465.
1,6-Benzodioxocin: Synthesis and Properties
By W . Schroth and B. Werner[*]
Heterocyclic compounds of the type ( I ) , X = 0, N - R , S
(1,4-diheterocins) may be formally regarded as 10 x-electron
systems. We have prepared and investigated a member of
this series [ I ] , namely, 1,6-benzodioxocin (2).
The substance used as starting material was 2,5-dihydro-l,6benzodioxocin (3) [21, which was formed (along with
2-vinyl-2,3-dihydro-1,4-benzodioxin
and 2,3 :10,ll-dibenzo1,4,9,12-tetraoxacyclohexadeca-all-cis-2,6,10,14-tetraene)on
reaction of pyrocatechol with cis-l,4-dichloro-2-butene.
Double dehydrobromination of (4) [2,31, the trans dibromoadduct obtained from (3), with potassium t-butoxide does
not yield (2), but gives l-(o-hydroxyphenoxy)but-l-en-2-yne
(5) (b.p. 124 "C/lO mm). The dimination involves 3-bromoAngew. Chem. internat. Edit. / Vol. 6 (1967) No. 8
Compound (2) may be prepared by the following methods:
a) By bromination of (3) with two mol. equiv. of N-bromosuccinimide to form (6), which is not isolated but is reduced
with zinc dust in dimethylformamide. Yield approximately
10 % (with respect to (3)).
b) By monobromination of (3) with N-bromosuccinimide to
form 2-bromo-2,5-dihydro-1,6-benzodioxocin
( 7 ) , which
subsequently is treated with triethylamine.
c) By oxidation of (3) to cis- and trans-3,4-dihydroxy-2,3,4,5tetrahydro-l,6-benzodioxocin (8) [ I J (cis compound: m.p.
112OC; trnns compound: m.p. 111"C), acetylation to the
diacetoxy derivatives (9) (cis compound: m.p. 62 "C; trans
compound: m.p. 88 "C), and pyrolysis (450 "C). Yield up to
3 "/, (with respect to (3)).
R'
(S), K
=
H
(9), R
=
COCH,
Compound (2) is a colorless oil (b.p. 109 "C/13 mm) which
crystallizes on cooling (m.p. 5 "C). The 1 H - N M R signalsr51
of the heterocyclic ring protons in (2) lie in the "olefinic
range" (r = 3.05 and 4.65, both signals being split into double
doublets with J = 5 and 2 Hz, respectively); the resonance of
the benzene-ring protons lies at T = 2.40. The fact that the
uv absorption of (2) (Amax = 277, 272 nm; log Emax =
3.47, 3.49 in cyclohexane) is at shorter wavelengths than that
of (3) (Arnax = 282, 275; log E~~~ = 3.30,3.33 in cyclohexane)
indicates reduced coplanarity, i.e. hindered conjugation of
the hetero ring with the benzene ring, in compound (2).
Thus, in spite of satisfying the 4n+2 rule ( n = 2), n-electron
delocalization in the heterocyclic ring of (2) takes place to
a limited extent only, if at all [GI.
At 190°C (bath temperature), (2) reacts with maleic anhydride to give the Diels-Alder adduct (IO), m.p. 220°C;
I H - N M R : T = 3.20 (aromatic-ring protons), 3.82 (olefinic
protons), 4.86 (CH-0), and 6.07 (CH-CO-0), relative areas =
2: 1 :1 : 1. Proof of structure is provided by hydrolysis (HBr/
acetic acid) to phthalic acid. The formulated exo configuration of (10) is in agreement with the fact that no bromo-
697
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