Five new organotin(IV) comp
lexes of composition [Bz
2SnL
1]
n (
href="#aoc3547-eo-0001" rel="references:#aoc3547-eo-0001">), [Bz
3SnL
1H⋅H
2O] (
href="#aoc3547-eo-0002" rel="references:#aoc3547-eo-0002">), [Me
2SnL
2⋅H
2O] (
href="#aoc3547-eo-0003" rel="references:#aoc3547-eo-0003">), [Me
2SnL
3] (
href="#aoc3547-eo-0004" rel="references:#aoc3547-eo-0004">) and [Bz
3SnL
3H]
n (
href="#aoc3547-eo-0005" rel="references:#aoc3547-eo-0005">) (w
here L
1 = (2
S)-2-{[(
E)-(4-
hydroxypentan-2-ylidene)]amino}-4-met
hylpentanoate, L
2 = (
rac)-2-{[(
E)-1-(2-
hydroxyp
henyl)met
hylidene]amino}-4-met
hylpentanoate and L
3 = (2
S)- or (
rac)-2-{[(
E)-1-(2-
hydroxyp
henyl)et
hylidene]amino}-4-met
hylpentanoate) were synt
hesized and c
haracterized using
1H NMR,
13C NMR,
119Sn NMR and infrared spectroscopic tec
hniques. T
he crystal structure of
href="#aoc3547-eo-0002" rel="references:#aoc3547-eo-0002"> reveals a distorted trigonal-bipyramidal geometry around t
he tin atom w
here t
he oxygen atoms of t
he carboxylate ligand and a water ligand occupy t
he axial positions, w
hi
le t
he t
hree benzyl ligands are located at t
he equatorial positions. On t
he ot
her
hand, t
he analogous derivative of enantiopure L
3H (
href="#aoc3547-eo-0005" rel="references:#aoc3547-eo-0005">) consists of polymeric c
hains, in w
hic
h t
he ligand-bridged tin atoms adopt t
he same
trans-Bz
3SnO
2 trigonal-bipyramidal configuration and are now coordinated to a p
henolic oxygen atom instead of H
2O. In
href="#aoc3547-eo-0002" rel="references:#aoc3547-eo-0002">, t
he OH
hydrogen of t
he ketoimine substituent
has moved to t
he nearby nitrogen atom w
hi
le in t
he salicylidene derivative
href="#aoc3547-eo-0005" rel="references:#aoc3547-eo-0005">, t
he OH is located almost midway between t
he p
henolic oxygen atom and t
he nitrogen atom of t
he CN group. For t
he dibenzyltin derivative
href="#aoc3547-eo-0001" rel="references:#aoc3547-eo-0001">, a polymeric c
hain structure is observed as a result of a long
intermolecular Sn⋅⋅⋅O bond involving t
he exocyclic carbonyl oxygen atom from t
he tridentate ligand of a neig
hbouring tin-comp
lex unit. T
he tin atom in t
his comp
lex
has distorted octa
hedral coordination geometry. In contrast, t
he racemic dimet
hyltin(IV) comp
lexes
href="#aoc3547-eo-0003" rel="references:#aoc3547-eo-0003"> and
href="#aoc3547-eo-0004" rel="references:#aoc3547-eo-0004"> display discrete monomeric structures wit
h a distorted octa
hedral- and trigonal-bipyramidal geometry, respectively. T
he structures s
how t
hat t
he coordination mode of t
he Sc
hiff base ligand depends primarily on t
he number of bulky benzyl ligands (R) at t
he tin atom, as indeed found in t
he structures of related comp
lexes w
here R = p
henyl. Wit
h t
hree bulky R groups, t
he tridentate c
helating O,N,O coordination mode is preferred, w
hereas wit
h fewer or
less bulky R ligands, only t
he carboxylate and
hydroxy groups are involved, w
hic
h leads to polymers. Larvicidal efficacies of two of t
he new tribenzyltin(IV) comp
lexes (
href="#aoc3547-eo-0002" rel="references:#aoc3547-eo-0002"> and
href="#aoc3547-eo-0005" rel="references:#aoc3547-eo-0005">) were assessed on t
he second larval instar of
Anopheles stephensi mosquito larvae and compared wit
h two trip
henyltin(IV) analogues, [P
h3SnL
1H]
n and [P
h3SnL
3H]
n. T
he results demonstrate t
hat t
he compounds containing Sn&ndas
h;P
h ligands are more effective t
han t
hose wit
h Sn&ndas
h;Bz ligands. Copyrig
ht