New palladium complexes with rigid scorpion-type ligands. Crystal structure of complexes [Pd(eta(3)-2-CH3-C3H4)(bpz*mPh)](CF3SO3) and [Pd(bpz*mpy)(2)](BF4)(2). bpz*mPh = phenyl-bis(3,5-dimethylpyrazol-1-yl)methane; bpz*mpy =pyridin-2-yl-bis(3,5-dimethylpyrazol-1-yl)methane

Two alpha-R substituted bis(3,5-dimethylpyrazol-1-yl)methane ligands (R = P h, bpz*mPh and 2-py, bpz*mpy) have been used to synthesise new palladium(II ) compounds with the general formulae PdXX'(bpz*mR) (R = Ph, X = X' = Cl; 1 a, X = X' = Me; 2a, X = Cl, X' = Me; 3a, X = X' = C6F5; 4a or R = 2-py, X = X' = Cl; 1b, X = Cl, X' = Me; 3b, X = X' = C6F5, 4b), [Pd(eta(3)-2-CH3-C3H 4)(bpz*mR)]X (X = PF6- R = Ph, 5a; X = CF3SO3-, 2-py, 5b) and [Pd(bpz*mR)(2 )](BF4)(2) (R = Ph, 6a; 2-py, 6b). In all the complexes the bpz*mR ligands adopt a rigid conformation with the R group in an axial position and, as a consequence, no boat-to-boat interconversion is observed. In Ib and 3b-5b t he pyridine group is uncoordinated. Complex 5b is present as a single isome r, while 5a exists as two isomers that are in equilibrium and differ in the orientation of the allyl group with respect to the NN ligand. For complex 6b the four possible anti isomers are observed in solution. The molecular s tructures of the major isomer of 5a and one of the isomers of 6b have been determined by X-ray structure analysis. In both structures the bpz*mR ligan ds are coordinated as bidentate. For 5a the ligand backbone confirms the st ated rigidity. For 6b a pyridine-pyrazole coordination of the two bpz*mpy l igands is observed. The fluxional behaviour implying interconversion of the two pyrazole rings in 3b, of the two isomers in 5a and the rotation of the C6F5 groups in 4a and 4b has also been studied. (C) 2000 Elsevier Science S.A. All rights reserved.