Phosphinoalkylsilyl chemistry: tripodal and mesomolecular complexation
Date
2018-07-13
Authors
Gossage, Robert Arthur
Journal Title
Journal ISSN
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Abstract
The preparation of the modified silane [special characters omitted]; a phosphinoalkylsilane or PSi) via an alkylzirconium
intermediate is reported. The synthesis of [special characters omitted]
was carried
out by the reaction of organolithium reagents with chloro-silanes
at low temperature. The PSi compounds are isolated as
air-sensitive, thermally stable and very viscous liquids.
The reactivity of two of the silanes was investigated
with the platinum group metal complex [special characters omitted] (cod =
cycloocta-1,5-diene). In both cases, square planar platinum
(II) complexes were isolated. The reactivity of
[special characters omitted] produces five coordinate M (III)
complexes which undergo stereomutation. The isomerisation of
the syn to anti forms of [special characters omitted] has
been examined at several temperatures via NMR spectroscopy and
the activation parameters determined for the conversion of the
syn to the intermediate isomer form [special characters omitted]. The implications
of the stereomutation phenomona are discussed in relation to
catalysis. None of the isomers of this complex forms a stable
six coordinate adduct when reacted with a number of common
nucleophiles. The analogous compound where M = Ir and related
complexes of the formula [special characters omitted] are reactive towards CO to form stable six coordinate
adducts containing two M-P and one M-Si, M-H, M-CO and a M-Cl
bond. Some of these adducts can be made directly by the
reaction of the PSi ligand precursor with [special characters omitted] (M =
Rh, Ir) at room temperature. The reaction of the silane
[special characters omitted] produces
six coordinate complexes directly. For M = Ir, the compound
reacts with CO to produce a six coordinate cation by
displacement of a chloride ligand, the latter of which then
acts as a non-coordinating counterion.
A series of organosilicon dendrimers of the type :
[special characters omitted] ([G-1] : x
= 3, y = 2 = q = 0; [6-2] : y = 3, x = 9 , z = q = 0; [G-3] : z
= 3, y = 9, X = 27, q = 0; [G-4] : q = 3, z = 9, y = 27, x =
81) are sythesised and examined spectroscopically. All of the
dendrimers are air stable liquids. Species G3 has a marked
tendency to undergo what appears to be self-condensation
polymerisation. End and core group substitution is presented
for a carbosilane dendrimer containing one shell of identical
exterior Si atoms. The dendrimeric end groups can be modified
by the replacement of a terminal chloride by fluoride,
hydrogen, alkyl groups or metal complexes. The selective
removal of a core phenyl group can be accomplished with the
strong acid [special characters omitted]. The resulting silyl triflate can in turn
be used as a precusor to a silyl ether, hence facilitating selective core group modification.
Description
Keywords
Silane, Complex compounds, Transition metal compounds