High-Valent Carbamato Complexes
Synthesis and Structural Characterization of Non-Homoleptic
Carbamato Complexes of V
and Their Facile
Implantation onto Silica Surfaces
and Guido Pampaloni*
Abstract: The vanadium(V) amido-carbamato derivatives
(R = Me, 1; Et, 2) are obtained by the reaction
with preformed carbamato species (ammonium or
sodium carbamates). The synthesis of an ionic ammonium
chlorido-amide of W
, 3, is performed using WOCl
amine as precursors. Moreover, the reactivity of 3 with CO
investigated. Mixed W
chlorido-carbamato compounds, 4 and
5, are obtained by the reaction of WOCl
amounts of sodium diethylcarbamate. All of the products are
Metal-carbamato species are interesting materials that have
been investigated as suitable precursors to chemical-vapour-
and in homogeneous catalysis.
more detail, N,N-diisopropylcarbamato complexes of Ru
been found to promote the H
-hydrogenation of alkenes,
while homoleptic carbamates of group-four and group-five
transition metals have been proposed as catalytic precursors for
the polymerization reactions of cyclic esters other than alk-
There is current interest in expanding the family of high-
valent metal-carbamato complexes to mixed systems.
stance, it has been demonstrated that mixed Ti
carbamates exhibit better activities in catalytic processes, com-
pared with the corresponding homoleptic carbamates.
In the framework of our recent interest in the chemistry of
high-valent vanadium and tungsten compounds,
to exploring new synthetic pathways with the aim of obtaining
non-homoleptic carbamates of these two metal elements.
[a] University of Pisa, Dipartimento di Chimica e Chimica Industriale,
Via G. Moruzzi 13, 56124 Pisa, Italy
[b] Consorzio Interuniversitario per le Reattività Chimiche e la Catalisi (CIRCC),
Via Celso Ulpiani 27, 70126 Bari, Italy
[c] Ca' Foscari University of Venezia, Dipartimento di Scienze Molecolari e
Via Torino 155, 30170 Mestre (VE), Italy
[d] University of Bologna, Dipartimento di Chimica Industriale
Viale Risorgimento 4, 40136 Bologna, Italy
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201701260.
Eur. J. Inorg. Chem. 2018, 1176–1184
© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
characterized by analytical and spectroscopic methods (IR spec-
troscopy, multinuclear NMR spectroscopy) and by X-ray diffrac-
tion in the cases of 3 and 4. DFT calculations are useful to
elucidate the structures of the compounds and to give insight
into the various reaction pathways. The combination of 2 or 5
with amorphous silica gives solid materials, which are character-
ized by inductively coupled plasma-optical emission spectro-
scopy (ICP-OES) and energy dispersive X-ray spectroscopy (EDS)
coupled to scanning electron microscopy (SEM).
Herein, we describe the results of this work, leading to the
preparation of mixed amido-carbamato and chlorido-carbam-
ato complexes. X-ray diffraction methods and DFT calculations
have been used in several cases to elucidate the structural and
The grafting of well-defined, high-valent transition-metal
compounds onto solid surfaces, and silica in particular, has
found increasing interest in the last few years, due to possible
applications of the resulting materials in heterogeneous cataly-
The implantation of two of the new compounds onto
silica, facilitated by the disruption of the carbamato frame,
will be described too, including the solid-state characterization
of the obtained materials.
Results and Discussion
The reactions of VOF
[R=Me(1), Et (2)] were
performed to follow a feasible route recently adopted for the
synthesis of mixed fluorido-alkoxido
and mixed fluorido-
complexes. Unfortunately, we could not identify any
product from these reactions.
However, the thermally unstable vanadium(V) mixed amido/
carbamato 1 was isolated in satisfactory yield from the reaction
with an excess of [NH
] (Scheme 1).
The ethyl-substituted derivative 2 was obtained by using the
sodium salt Na(O
), produced from the reaction of NaH
in the presence of CO
at atmospheric pressure.
Such sodium salt is room-temperature stable, easy to handle
and therefore preferable to the ammonium analogue, which, in
turn, must be prepared in situ.