A transition metal borylene
complex stabilized by a non-
carbonyl ligand set: formation
by spontaneous halide loss to
give an extremely short metal-
-boron bond (video).
(work by David Addy)
Transition Metal Boryl and Related Complexes
Transition metal boryl complexes (LnMBX2) are highly topical compounds, due to their implication in an number of versatile organic transformations including metal-catalysed hydro- and diboration, and most notably, the catalytic functionalization of C-H bonds in arenes and alkanes - one of the ‘Holy Grails’ of organometallic chemistry. Thus, catalytic systems involving boryl complexes as intermediates, will selectively react at the terminal C-H bonds of alkanes such as octane to give useful organic products containing C-B bonds.
We have been involved in this area principally with the aim of better understanding the fundamental issues of electronic structure which underpin this unusual reactivity. Thus, novel synthetic, spectroscopic and computational approaches have been used to investigate the role of the formally vacant boron-centred p-orbital in structural and reaction chemistry. Recent work has revealed an alternative mechanism for attack at C-H bonds by perfluoroaryl metal boryl systems.
A related project is concerned with the activation of B-H and N-H bonds by transition metal complexes, and specifically with the elucidation of fundamental steps in the dehydrogenative coupling of amine boranes BH3.NRnH3-n. Such processes are of potential importance in hydrogen storage applications, and a number of novel iridium systems synthesized as part of a new EPSRC-funded project have shown promising initial results in this area.
Metal boryl complexes
(top) Insertion of a boryl ligand
fragment into a C-H bond of an
ancillary cyclopentadienyl ligand
in the presence of CO. See:
(bottom, l to r) Ribbon-like motif of
solid methylamine borane, featuring
unconventional N-H to H-B hydrogen
bonds; crystal structure of a doubly
C-H activated Ir carbene complex
which shows interesting reactivity
New chemistry (video)
Benzyl C-H functionalization by boro-
hydride – one of intermediates iso-
lated on reaction path. Click here.
(work of Dr Christina Tang)