Synthesis and characterisation of a series of ruthenium scorpionate complexes with B-H center dot center dot center dot M agostic nteractions. Crystal structure of [RuH(kappa(2)-N,BH Tp(Tn))(PMe3)(cod)] (Tp(Tn) = hydrotris[3-(2-thienyl)pyrazol-1-yl]borate)

A series of monohydrides of Ru-II of formula RuH(Tp(R))(cod) 1-3 have been synthesized from the reaction of [RuH(NH2NMe2)(3)(cod)]BPh4 with the corres ponding Tp(R) ligand {hydrotris(7-methylindazol-2-yl)borate, Tp(Bo,7Me), 1; hydrotris[3-(2-thienyl)pyrazol-1-yl]borate, Tp(Tn), 2; tris[3-(2,4-dimetho xyphenyl)pyrazol-1-yl]hydroborate, Tp(2)((2,4(OMe))Ph), 3}. In these compou nds the Tp ligand is kappa (3) N,N',BH coordinated with a B-H . . . Ru agos tic interaction. Reactions of 1 and 2 with two-electron donor ligands, L=PM e3, PMe2Ph and CN-t-Bu, led to the formation of complexes of formula RuH(Tp (R))(L)(cod) (Tp(R)=Tp(Bo,7Me), L=PMe3 4, PMe2Ph 5 or CN-t-Bu 6; Tp(R)=Tp(T n), L=PMe3 7, PMe2Ph 8 or CN-t-Bu, 9). In this new series the incoming liga nds replace one of the coordinated pyrazole rings instead of the stated B-H . . . Ru interaction which remains and consequently the Tp(R) ligands are kappa (2) N,BH coordinated. The molecular structure of 7 was determined by an X-ray diffraction study. The ruthenium atom has a distorted octahedral e nvironment with the ligand Tp(Tn) coordinated through only one pyrazole rin g and an agostic B-H group. The two hydrides are in a mutually trans dispos ition with an angle of 166 degrees. The Ru . . .H distance is 2.07(5) and R u-H-terminal 1.33(5) Angstrom. The molecular structure of the model complex [RuH(kappa (2)-N,BH-Tp)(PH3)(H2C=CH2)(2)] has been optimised with the aid of ab initio calculations in order to compare the structural parameters wit h those of the experimentally determined structure.