Page 348 - Academic Press Encyclopedia of Physical Science and Technology 3rd InOrganic Chemistry

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Encyclopedia of Physical Science and Technology EN010K-480 July 16, 2001 17:22

458 Noble-Gas Chemistry

XeF and 1,3-C 4 F 4 NN XeF have been synthesized as day at room temperature. The compound C 6 F 5 Xe AsF −
+
+
+
6
the AsF − salts by analogy with the fluoro(perfluoro- was also prepared by displacement of (C 6 F 5 ) 2 BF from
6
−
diazine)xenon(II) salts in BrF 5 solvent. The colorless C 6 F 5 Xe (C 6 F 5 ) 2 BF using AsF 5 . The thermal stability
+
2
−
+
solid, s-C 3 F 3 N 2 N-XeF AsF , is currently the only salt of the melt (125 C) is surprisingly high. The Xe C
◦
6
in this series of compounds which is stable at room distances of 2.079(6) and 2.082(5), Xe--F distances
temperature and is prepared by the reaction of XeF + (cation–anion contacts) of 2.714(5) and 2.672(5), and
AsF − with liquid s-trifluorotriazine, s-C 3 F 3 N 3 ,at C-Xe-F angles of 170.5(3) and 174.2(3) degrees are
6
room temperature. The salts having the formulations observed in the X-ray crystal structure.
−
L XeF AsF ·2.5BrF 5 have been characterized by The reactions of XeF 2 with the boron ligand transfer
+
6
low-temperature X-ray crystallography, where L is reagents B(m-CF 3 C 6 H 4 ) 3 and B(p-FC 6 H 4 ) 3 in CH 2 Cl 2
˚
˚
s-C 3 F 3 N 2 N- [Xe F, 1.931(5) A; Xe N, 2.316(6) A], solution at −45 to −50 C result in the formation of
◦
˚
˚
C 5 F 5 N- [Xe F, 1.932(6) A; Xe N, 2.287(8) A], 1,2- the white solids [m-CF 3 C 6 H 4 Xe] [m-CF 3 C 6 H 4 BF 3 ] −
+
˚
˚
−
C 4 F 4 NN- [Xe F, 1.956(8) A; Xe N, 2.247(9) A], and and [p-FC 6 H 4 Xe] [(p-FC 6 H 4 ) 2 BF 2 ] . The former
+
˚
˚
◦
1,3-C 4 F 4 NN- [Xe F, 1.90(2) A; Xe N, 2.28(3) A]. In all compound is stable for up to1hinCH 3 C Nat −41 C,
cases, the prefluorinated heterocycle and N-coordinated whereas the latter compound decomposes below −40 C
◦
XeF group are coplanar. when an attempt is made to dissolve it in the coordinating
Other examples of xenon(II) bonded to inorganic solvent CH 3 C N. The 2,6-C 6 H 3 F 2 Xe cation has been
+
nitrogen base centers are known. The reaction of F 3 S N prepared as the BF − salt. The X-ray structure shows
4
˚
+
with L = XeF , XeOSeF , and XeOTeF + leads to the that xenon is bonded to carbon [Xe C, 2.090(6) A] and
+
5 5
+
formation of the corresponding F 3 S N L cations. The weakly coordinated to a single F atom of the tetrafluo-
˚
+
+
F 3 S N L cation is formed by reaction of XeF AsF − roborate anion [Xe--F, 3.096(4) A]. The xenonium salt
6
◦
with liquid F 3 S Nat −20 C or in HF solvent to form Xe(2,4,6-F 3 C 6 H 2 ) BF − is prepared by the reaction of
+
4
the F 3 S NXeF cation. The cation undergoes a two-step B(C 6 H 2 F 3 )·thf and XeF 2 in the presence of BF 3 ·O(CH 3 ) 2
+
fluorination in HF to yield two further cations, F 4 S NXe + in CH 2 Cl 2 solution at −40 C, is stable for up to 21 days
◦
and F 5 SN(H)Xe . The tellurium analogue of the latter at room temperature in dry air, and is hydrolyzed slowly
+
+
cation, F 5 TeN(H)Xe , is synthesized from F 5 TeNH 2 over 7 days in aqueous CH 3 C N solution. Arylxenon
−
+
and XeF AsF in HF solvent at low temperatures. The trifluoromethanesulfonates are directly prepared by
6
F 5 TeN(H)Xe + cation has been obtained as the AsF − reaction with CF 3 CO 2 XeO 3 SCF 3 . The reaction of
6
salt and has been shown to interact strongly through Xe(O 2 CCF 3 ) 2 and CF 3 SO 3 H gives the highly reactive
the Xe atom with the AsF − anion in the solid state, intermediate CF 3 CO 2 XeO 3 SCF 3 . Benzene derivatives
6
˚
forming a Xe--F As bridge [Xe N, 2.044(4) A; Xe--F, containing electron-withdrawing substituents, such as
˚
2.580(3) A]. F, CF 3 , Cl, or NO 2 , undergo electrophilic attack by
CF 3 CO 2 XeO 3 SCF 3 to yield arylxenon trifluorometh-
anesulfonate salts containing the 2,4,6-F 3 H 2 C 5 CXe ,
+
3. Xenon Bonded to Carbon
2,5-F(O 2 N)H 3 C 5 CXe , 2,5-F(CF 3 )H 3 C 5 CXe , and
+
+
A number of structurally well-characterized compounds 3,5-(CF 3 ) 2 H 3 C 5 CXe + cations. The molecular structure
+
containing Xe C bonds are known. In all cases they of 2,6-F 2 H 3 C 5 CXe O 3 SCF − has been determined by
3
˚
occur as colorless salts of xenonium cations, R Xe + X-ray crystallography [Xe C, 2.09(1) A]. The xenon
(R = a fluorophenyl or alkynyl group). The formation atom of the arylxenon unit is also weakly coordinated to
−
of the pentafluorophenylxenon(II) cation, C 6 F 5 Xe ,in one O atom of the CF 3 SO anion.
+
3
◦
◦
CH 2 Cl 2 (−30 C) and CH 3 C N(0 C) solutions with the Reaction of Me 3 SiC 6 F 5 /[Me 4 N]F with XeF 2 in propi-
−
anions B(C 6 F 5 ) 3 F , B(C 6 F 5 ) 2 F , and B(C 6 F 5 )F − has
−
2 3 onitrile, propionitrile/acetonitrile, acetonitrile, or CH 2 Cl 2
been established. The salts are formed by the reaction of yieldsXe(C 6 F 5 ) 2 ,thefirstexampleofxenonbondedtotwo
XeF 2 with the ligand transfer reagent B(C 6 F 5 ) 3 . The carbon atoms. When the same reaction is carried out in a
X-ray crystal structure of [CH 3 C N Xe C 6 F 5 ] + 1:1 stoichiometry, C 6 F 5 XeF is the predominant product.
[(C 6 F 5 ) 2 BF 2 ] − shows that the xenon atom is weakly Reaction of C 6 F 5 XeF with Me 3 SiOSO 2 CF 3 gives [C 6 F 5
−
+
+
coordinated to the nitrogen atom of a CH 3 C N Xe] OSO 2 CF . The reaction of C 6 F 5 Xe AsF − with
6
3
˚
˚
molecule [Xe N, 2.681(8) A; Xe C, 2.092(8) A]. This 4-ClC 5 H 4 N·HCl in CH 2 Cl 2 at −78 gives 85% C 6 F 5 XeCl,
◦
salt decomposes slowly at 14 C. Reaction of [CH 3 C the first example of the bulk preparation of a xenon(II)–
◦
N Xe C 6 F 5 ] [(C 6 F 5 ) 2 BF 2 ] − with AsF 5 in CH 3 C N chlorine bonded species (see Section III.A). The reac-
+
−
+
−
+
solution results in [CH 3 C N Xe C 6 F 5 ] AsF . Solu- tion of C 6 F 5 Xe AsF with Me 3 SiCl in CH 2 Cl 2 at −78 ◦
6 6
−
+
tions of this compound in CH 3 C N are stable for up to 1 gives 91% (C 6 F 5 Xe) 2 Cl AsF , which was characterized
6