Synthesis, characterization and crystal structures of isothiocyanate and carbodiimide complexes derived from organomagnesium reagents: insertion into Mg–X (X = C or N) bonds
Abstract
A series of magnesium–isothiocyanate and –carbodiimide
insertion products, Mg(SCPhNBu
t
)
2
(thf)
2
1, Mg(SCPhNPh)
2
(thf)
2
2,
Mg(Pr
i
NCRNPr
i
)
2
(thf)
2
(R = Ph 3, Et 4 or Pr
i
5) and
Mg(Bu
t
NCEtNBu
t
)
2
(thf)
2
6 have been prepared by the stoichiometric reaction between
MgR
2
(R = Ph, Et or Pr
i
) and various
isothiocyanates and carbodiimides in tetrahydrofuran (thf) solution. The
1∶1 reaction between bis(diisopropylamido)magnesium and
1,3-diisopropylcarbodiimide gave a dinuclear complex
Mg
2
(µ-NPr
i
2
)
2
[(Pr
i
N)
2
CNPr
i
2
]
2
7
and a mononuclear complex
Mg[(Pr
i
N)
2
CNPr
i
2
]
2
(thf) 8 when the stoichiometry is 1∶2. The
mononuclear complexes
Mg[SC(NPh)NR
2
]
2
(thf)
2
(R = Pr
i
9 or Et 10) were
obtained using phenyl isothiocyanate and bis(diethylamido)- or
bis(diisopropylamido)-magnesium in 1∶1 stoichiometric ratio. A
plausible mechanism for the formation of 7 and 8 is
suggested. Reaction between MgEtBr and PhNCS in diethyl ether gave the
dinuclear complex
Mg
2
(SCEtNPh)
4
(OEt
2
)
2
11. All of the complexes were characterized by
1
H,
13
C NMR and IR spectroscopy as well as elemental analysis.
The crystal structures of 1, 3, 8, 9
and 11 were determined by single-crystal X-ray diffraction. The
reaction of complex 1 with an excess of PhNCO resulted in the
cyclotrimerization of phenyl isocyanate to give
(PhNCO)
3
·thf.
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