The
synthetic protocols, structural aspects, and spectroscopic
aspects of mononuclear pseudostannatranes possessing a [4.4.3.01,5]tridecane cage have been reported. A tripodal ligand N(CH2CH2OH){CH2(2-t-Bu-4-Me-C6H2OH)}2 (H3L) having unsymmetrical
arms was reacted with n-butyltrichlorostannane, phenyltrichlorostannane,
and tin tetrachloride under different solvent systems to obtain pseudostannatranes
(1–3). The reaction of n-butyltrichlorostannane and the ligand in CH3OH/Na/THF
yielded an aqua complex of pseudostannatrane [LSnBu(H2O)]
(1
a
), which was crystallized
as its acetone solvate (i.e 1
a
·Me2CO). However, the same reactants yielded methanol
complex [LSnBu(CH3OH)] (1
b
) when the reaction was carried out in the NaOCH3/C2H5OH system. Similarly, the reaction of
phenyltrichlorostannane and the ligand under these solvent systems
yielded pseudostannatranes, i.e., an aqua complex [LSnPh(H2O)] (2
a
) and a methanol complex
[LSnPh(CH3OH)] (2
b
) (where 2a
was crystallized as 2
a
·Me2CO). The reaction of
tin tetrachloride and the ligand in the Et3N/THF system
resulted in the formation of pseudostannatrane [LHSnCl2] (3). A similar product was isolated as its triethylamine
solvate (3·NEt
3
) due to the disproportion reaction when PhSnCl3 was reacted
with the ligand in the Et3N/C6H5CH3 system, which demonstrates the first report on the reverse
Kocheshkov reaction in pseudostannatranes. The experimental findings
on the formation of 3·NEt
3
due to the reverse Kocheshkov reaction have been corroborated
with 119Sn NMR spectroscopy and density functional calculations
that provide insightful information about the underlying details of
the reaction route.
Tetrel bond, a weak noncovalent interaction between the σ‐hole of a Group IV element (silicon in our case) and the cloud of an electronegative element (oxygen in our case) is the focus of this work. The percentage strengthening of tetrel bond has been investigated by optimizing 16 binary complexes of halogenated silane and water of general formula SiXnH4−n−H2O and 16 ternary complexes, of general formula NaX−SiXnH4−n−H2O, where X=F, Cl, Br and I and n=1, 2, 3 and 4 at various levels of theory defined within the formalism of density functional theory (DFT). With the addition of NaX, tetrel bond between Si and O in SiXnH4−n−H2O gets strengthened up to 49 %, owing to cooperativity effect exerted by hydrogen bonding between X and H in the ternary complex NaX−SiXnH4−n−H2O. In the series of complexes studied here, overall stabilization due to cooperativity lies between 10 kJ/mol to 170 kJ/mol. This large extent of reinforcement due to cooperativity has never been showcased before. The exceptional stabilization and reinforcement owe its genesis to the transformation of the ternary complex into a cluster orchestrated by the H‐bonding in most of the cases and covalent bonding in few of the cases.
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