Synthesis and Reactions of a Hybrid Tristibine Ligand

The tripodal tristibine N­(CH2-2-C6H4SbMe2)3 (L) has been prepared in high yield
and characterized by 1H and 13C­{1H} NMR spectroscopy and elemental analysis. A range of reactions
with transition-metal acceptors were carried out to probe the coordinative
properties of L. The 3/1 M/L complex [{FeCp­(CO)2}3(L)-κSb:κSb′:κSb″]­[BF4]3 involves tridentate
bridging coordination of L to three CpFe­(CO)2 fragments.
In [Mn­(CO)3(L)]­[CF3SO3] the ligand
adopts a tridentate chelating mode via a Sb3 donor set;
treatment of this complex with Me3NO in MeCN solution gave
crystals of [Mn­(CO)2(L)­(MeCN)]­[CF3SO3], which lost MeCN in vacuo, probably resulting in coordination of
CF3SO3– coordination of the
[CF3SO3]− anion. [M­(L)]­[BF4] (M = Ag, Cu) were also prepared. The reaction of L with
CuBr leads to isolation of [Cu4Br4(L)2] in the solid state, which contains a Cu2Br4 core with a short central Cu···Cu distance, capped
with Cu­(L) units at each end. The transition-metal complexes of L
were characterized by elemental analysis, ESI+ mass spectrometry,
IR spectroscopy, and 1H, 13C­{1H},
and (where appropriate) 55Mn or 63Cu NMR spectroscopy.
Solid-state X-ray structures were determined for [Mn­(CO)3(L)]­[CF3SO3], [Mn­(CO)2(L)­(MeCN)]­[CF3SO3], [Cu4Br4(L)2], and [Cu3Br2(L)2]­[BF4]. In each of these structures the chelating ligand adopts a twisted,
propeller-like conformation. NMR spectroscopic analysis suggests that
the ligand also adopts this rigid conformation in solution.