Page 6 - Interaction of Multiple Bonded and Unsaturated Heavier Main Group Compounds with Hydrogen, Ammonia, Olefins, and Related Molecules

Reactivity of Multiple Bonded and Main Group Compounds Power

was observed up to 70 °C in toluene. The more crowded i
SCHEME 5. Reaction of Ar GaGaAr (Ar =C 6 H 3 -2,6-(C 6 H 3 -2,6-Pr 2 ) 2 with
0
0
0
0
0
SnAr 2 gave the symmetrically bridged Ar Sn(μ-H) 2 SnAr 0 H 2 and NH 3
which was identical to that obtained by the reaction of H 2
0
0
with Ar SnSnAr described above. Reaction with deuterium
0
0
0
afforded Ar Sn(μ-D) 2 SnAr with elimination of Ar D. The reac-
#
0
tions between NH 3 and either SnAr 2 or SnAr 2 gave the sym-
#
metrically bridged parent amido products Ar Sn(μ-NH 2 ) 2 SnAr #
#
or Ar Sn(μ-NH 2 ) 2 SnAr with Ar HorAr H elimination.
0
0
0
Density functional theory (DFT) calculations of the reac-
tions of H 2 with EAr 2 (E = Ge or Sn) showed that they initially
proceed via interaction of the σ orbital of H 2 with the 4p(Ge) 4. Reactions with Olefins and Related Unsa-
or 5p(Sn) orbital with back-donation from the Ge or Sn lone turated Molecules
pair orbital to the H 2 σ* orbital (Figure 4). 38 The subsequent
The early studies on the ditetrelynes showed that they reacted
reaction proceeds by an oxidative addition or a concerted
with several unsaturated molecules including alkynes, nitriles,
pathway. The data showed that the bond strength differ- 22,24
azides, and N 2 Oaswellassomediolefins. Wiberg et al.
ences between Ge and Sn, as well as greater nonbonded
showed that the quasi-stable disilyne R*SitSiR* (R* = SiMe-
electron pair stabilization, for tin were in general more t
(SiBu 3 ) 2 ) reacted with the parent olefin ethylene below
important than steric factors in determining the product 2e i
room temperature. ThestabledisilyneRSitSiR (R = SiPr -
#
obtained. The calculations indicated that Ar 2 GeH 2 or
{CH(SiMe 3 ) 2 } 2 ) has also been shown to react with some
Ar GeH were thermodynamically preferred with a further 25
0
mono-olefins, e.g., cis and trans butenes.
0
reaction between the latter and H 2 yielding Ar GeH 3 . For the 24
Thefacilereaction of Ar*GeGeAr* with 2,3-dimethyl-1,3-
#
reactions of NH 3 with EAr 2 (E = Ge or Sn; Ar = Ar and Ar ), the
0
butadiene suggested that reactions with olefins should be
divalent ArENH 2 products were also calculated to be the
feasible for the less bulky ditetrelynes Ar GeGeAr and
0
0
most stable for both Ge or Sn. However, the tetravalent
Ar SnSnAr . We treated a green toluene solution of Ar SnSnAr 0
0
0
0
amido species Ar 2 Ge(H)NH 2 was obtained for kinetic rea- 39
with ethylene at 25 °C and 1 atm pressure. This produced an
sons. The reactions with ammonia differed from those with
immediate color change from green to amber. To our surprise,
H 2 in that they involved two ammonia molecules in which
workup involving the reduction of the solvent volume under
the lone pair of one NH 3 becomes associated with the empty
reduced pressure (to induce product crystal growth), restored
4p or 5p orbital while a second NH 3 solvates the complexed
the original green color. Moreover, treatment of the solution
NH 3 via an intermolecular NHN interaction.
with ethylene regenerated the amber color which persisted if
Computations for the reaction of the group 13 species
the solution was stored under ethylene. Storage of the solution
M 2 H 2 (M = Al or Ga) with H 2 to give H 2 MMH 2 showed that
under ethylene at ca. 18 °C yielded crystals of the ethylene
the heats of reaction are negative which tends to support the
adduct as yellow plates. X-ray crystallography showed that the
view that the addition of H 2 to isolable dimetallenes should
also be favored. 27 We found that the H 2 reacted (Scheme 5) distannynehadcomplexedtwoethylenesasshowninFigure5.
1
1
The two CH 2 CH 2 units are η ,η :μ 2 bound to the ditin moiety in
at ca. 25 °C and 1 atm with toluene solutions of Ar GaGaAr 0
0
to produce Ar (H)Ga(μ-H) 2 Ga(H)Ar in 62% yield. 38 Structural a Z fashion in the two structurally similar, but crystallographi-
0
0
and spectroscopic data showed that the structure was cen- cally independent, molecules to afford a 1,4-distannabicyclo-
trosymmetric with two bridging and a terminally bound [2.2.0]butane core structure. It can be seen that the terphenyl
hydrogen at each gallium. Attempts to synthesize this dihy- ligands are in the Z configuration with SnSnC(ipso) angles of
0
dride by reduction of Ar GaCl 2 with hydride sources such as 163.2(1.2)° and tintin distances of 2.886(6) Å. The average
t
(Bu AlH) 2 , NaH, LiBH 4 , and LiBHEt 3 afforded a mixture of SnCH 2 bond length is 2.19(2) Å which is indistinguishable
0
products which did not contain the target dihydride species. from the SnC(Ar )distance. The CC bond distance within the
0
0
Similarly the reaction of Ar GaGaAr with liquid NH 3 at ca. CH 2 CH 2 unitsaverages1.54(5) Åwhich is typicalfor aCC
0
78 °C afforded a 73% yield of Ar (H)Ga(μ-NH 2 ) 2 Ga(H)Ar in single bond. The structure thus has CC, SnC, and SnSn
0
which gallium has inserted into an NH bond of ammonia. bond lengths in the {C(ipso)}Sn 2 (CH 2 CH 2 ) 2 cores indicated
1
The galliums are bridged symmetrically by two NH 2 moieties single bonding. Furthermore, the H, 13 C, and 119 Sn NMR data
and the hydrogens are terminally bound at each gallium. supported this conclusion. Nonetheless, both complexes
632 ’ ACCOUNTS OF CHEMICAL RESEARCH ’ 627–637 ’ 2011 ’ Vol. 44, No. 8