_P.-Powell-auth.-Principles-of-Organometallic-Chemistry-Springer-Netherlands-1988

Organotransition metal chemistry
M eli or
L=
postulated
(16e)
pos tuloted ( 18 e )
+L -L
+L -L
+
CH2 PMe2 Ph
+/
Cp2W~H
thermally mosi
s table produci
(C)
second produci ( 8 )
Fig. 7.1 Reversible a-hydrogen transfer.
product (C). This experiment indicates that in this case a-hydrogen transfer is the
first step in the decomposition of the methyl complex and that like [3-hydrogen
transfer the process is reversible.
The molecular structures of the complexes (dmpe)TiCl 3 R (R = Me, Et),
determined by X-ray diffraction, shed light on pathways which lead to a- and [3-
hydrogen transfer (dmpe = Me 2 PCH 2 CH 2 PMeJ (Fig. 7.2). In the ethyl complex
one of the [3-hydrogen atoms is situated within bonding distance of the
metal atom. The structure thus models the incipient formation of a
metal(alkene)hydride envisaged in {3-hydrogen transfer. The methyl compound
similarly reflects the commencement of a-hydrogen transfer. The hydrogen atom
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