Observations on the steric impact of N- and S-donor scorpionate ligands

A comparison is made between the steric influences of a range of zinc hydrotris(pyrazolyl)borates and zinc hydrotris(thio-imidazolyl)borates ([Zn(TpR)Cl], [Zn(TmR)Cl],: R = Me, iPr, Ph tBu)) using inverse cone angle analysis. The study combines the crystallographic analysis of [Zn(TmiPr)Cl] and [Zn(TmPh)Cl] with the data previously deposited with the Cambridge Crystallographic Data Centre. The study suggests that despite efforts to manipulate the reactive pocket around the metal centre in M(TmR) complexes, the incorporation of sterically confining substituents onto the framework has a minimal effect at the metal centre unless the group attached is very large

Fluxional rhodium scorpionate complexes of the hydrotris(methimazolyl)borate (Tm) ligand and their static boratrane derivatives.

The reaction of potassium hydrotris(methimazolyl)borate {KTm = HB(mt)(3)} with [{Rh(cod)(mu-Cl)}(2)] gave [Rh(cod)Tm] while the complexes [Rh(CO)(PR(3))Tm] (R = Ph or NMe(2)) and [Rh{P(OPh)(3)}(2)Tm] were isolated from light-sensitive [Rh(CO)(2)Tm], prepared in situ from KTm and [{Rh(CO)(2)(mu-Cl)}(2)], and PR(3) or P(OPh)(3) under CO. The complexes [Rh(cod)Tm] and [Rh(CO)(PR(3))Tm] (R = Ph or NMe(2)) adopt kappa(3)-S(2)H structures in the solid state but in all cases rapid dynamic exchange processes render the three mt rings equivalent in solution. Oxidation of [Rh(CO)(PPh(3))Tm] with [Fe(eta-C(5)H(5))(2)][PF(6)] in the presence of NHPr(i)(2) gave a mixture containing two monocationic rhodaboratranes. One is assigned as [Rh(CO)(PPh(3)){B(mt)(3)}][PF(6)] on the basis of IR and NMR spectroscopy, with boron trans to the phosphine ligand. The second, structurally characterised as [Rh(PPh(3)){B(mt)(3)}][PF(6)], has boron trans to an empty coordination site, vacated by CO. Similar oxidation of [Rh(cod)Tm] gave small quantities of the boron-fluorinated bis(scorpionate) [Rh{FB(mt)(3)}(2)][PF(6)]