Reactions square-pyramidal complexes

The coordinated macrocycle readily reacts with alkoxide ions to yield products of type (71) (Taylor, Urbach Busch, 1969). In so doing additional flexibility is imparted to the ring which may reduce ring strain and, in part, provide a driving force for the reaction. Thus the coordinated imine carbons appear predisposed to attack by such nucleophiles. Based on this knowledge, elegant template syntheses of three-dimensional derivatives have been performed. The syntheses involved the reaction of [M(taab)]2+ (M = Ni, Cu) with the dialkoxide ions derived from bis(2-hydroxyethyl)sulphide or bis(2-hydroxyethyl)methylamine (Katovic, Taylor Busch, 1969). The products were demonstrated to be monomeric square-pyramidal complexes of type (72). The condensation... 

Compared with the huge number of oxo complexes only a few rhenium(V) compound with terminal sulfldo complexes are known. The square-pyramidal complex anion [ReS(S4)2] was first isolated in pure form in 1986 by a reaction of Rc207 with (Ph4P)Br and ammonium polysulfide in acetonitrile and the structure of the Ph4P+ salt has been elucidated. Later, the same complex anion was prepared from starting materials such as [Re2Cl8] , perrhenate, ... 

The square pyramidal complexes of group 9 iridium cyclopropylbis(>/4-diene) complexes were recently synthesized in poor yields (3-5%) by metathesis reaction between (tf-diene)2 IrCl and cyclopropyllithium or cyclopropylmagnesium bromide (equation 16)45. 

Formation of Ni—CH3 species by the more likely biological route of Ni-based nucleophilic attack on a methyl electrophile has been demonstrated. The Ni complex, (40), supported by thioether and phosphine ligation, was reduced to the Ni adduct in situ. It was then oxidized to the Ni CH3 and Ni (C(0)CH3) species by reaction with CH3I and CH3C(0)C1, respectively. These low-spin, square-pyramidal complexes contain apical organic ligands and are related by CO insertion/extrusion, which was rapid even at -60 °C, precluding kinetic analysis. 

Vanadyl (acac)2 is a square pyramidal complex of two molecules of the enolate of acac (acetyl acetone, pentan-2,4-dione) and the vanadyl (V=0) dication. It can easily accept another ligand to form an octahedral complex so there is plenty of room for the alcohol to add and for the t-BuOOH to displace one of the acac ligands to give some complex with the essential ingredients for the reaction here. 

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