Gold derivatives of scorpionates: comparison with the other coinage metal poly(pyrazolyl)borate analogues

Gold derivatives [Au(Tp(x))(PR3)] (Tp(x) = Tp, hydrotris(pyrazol-1-yl)borate or Tp*, hydrotris(3,5-dimethylpyrazol-1-yl)borate; R = Ph or 'Bu) and [Au(pzTp)(PR3)(x)] (pzTp = tetrakis(pyrazol-1-yl)borate, x = 1 or 2, R = Ph or 'Bu) have been synthesised and characterized both in solution (H-1- and P-31{H-1}-NMR) and in the solid state (IR, single crystal X-ray structure analysis, P-31 CPMAS). P-31 {H-1}-NMR) solution data suggest greater stability of the tetrakis(pyrazolyl)-borate relative to those of tris(pyrazolyl)borate. All compounds are fluxional at room temperature. In order to compare [Au(Tp*)(PPh3)] with analogous coinage metal adducts we have synthesized and structurally characterized [Cu(Tp*)(PPh3)].PPh3 and [Ag(Tp*)(PPh3)].2MeCN. In [Au(Tp*)(PPh3)] the gold atom adopts a distorted tetrahedral geometry with <Au-P> 2.181(5) and <Au-N> 2.37(2) Angstrom (cf. <Cu-P,N> 2.166(6), 2.098(1) in [Cu(Tp*)PPh3], 2.156(2), 2.075(7) in [Cu(Tp*)(PPh3)].PPh3; and <Ag-P,N> in [Ag(Tp*)PPh3].MeCN 2.347(12), 2.35(5) Angstrom). There are three independent [Au(Tp*)(PPh3)] molecules in the asymmetric unit of the structure with their PAu...B axes lying on the cell diagonal of a cubic P2(1)3 cell, two with the same chirality aligned opposed in direction to the third which is of opposite chirality. A number of Cu, Ag and An complexes containing scorpionate ligands have also been investigated by P-31 cross-polarization magic-angle-spinning (CPMAS) NMR spectroscopy.