TRANS EFFECT AND TRANS INFLUENCE IN RUTHENIUM(II) TETRAAMMINES - IMIDAZOLE AS A PROBE LIGAND

The following substitution reactions: trans-[Ru(NH3)(4)L(1)(H2O)](2+) + L(2 k-1)reversible arrow(k1)trans-[Ru(NH3)(4)L(1)L(2)](2+)+H2O, wher e L(1) = phosphite, phosphine, AsPh(3) or SbPh(3), and L(2) = imidazol e, have been studied under pseudo-first order conditions. The reaction proceeds through an I-d dissociative mechanism. The trans effect of L (1) has been estimated based on the k(1), values: SbPh(3) < AsPh(3) < PBu(3) < P(Ph)(3) similar to dppe < P(OMe)(3) < P(OEt)(3) < P(OBu)(3) < P(OPri)(3). The trans effect series obtained with electrophilic L(2) ligands (pyrazine and isonicotinamide) for the same phosphorus(III) l igands (L(1)) were similar. The position of L(1) in these series can b e related to the alpha or pi character of L(1). The trans influence se ries has been written based on the reciprocal of K-eq = k(1)/k(-1): P( OPri)(3) congruent to P(OEt)(3) congruent to P(OBu)(3) < P(OMe)(3) < P (Ph)(3) < P(Bu)(3) < AsPh(3) < SbPh(3) < dppe.