COMPARISON OF THE HYDROGEN BONDING IN TRANS-DICHLORO(3,3 ' -(1,3-PROPANEDIYL-DINITRILO)BIS(2-BUTANONE)DIOXIMATO) COBALT(III) AND RHODIUM(III)

Abstract

Comparison of the hydrogen bonding in the isomorphous complexes, trans-dichloro(3,3 ' -(1,3-propane-diyldinitrilo)bis(2-butanone)dioximato)-cobalt(III) and rhodium(III) provides an excellent example of the effect of metal ion size on the intramolecular 0–0 hydrogen bond(0[sbnd]0=2.448(5)Å for Co and 2.626(4)Å for Rh). The lengthening of the 0[sbnd]0 distance can be correlated with the increasing M[sbnd]N distances from Co to Rh (Co-N(imine)=1.917(4)Å; Rh-N(imine)=2.00(2)Å; Co-N(oxime)=1.887(4)Å; Rh-N(oxime)=1.976(3)Å). The hydrogen bond appears to be much more asymmetric in the rhodium case with O-H distances of 0.88(4) and 1.75(4)Å compared with 1.20(6) and 1.31(6) Å in the cobalt case. The Rh-Cl distances (av. 2.335(2) Å) are also significantly longer than the Co-Cl distances (av. 2.239(1) Å). The results obtained for the cobalt complex in this study are compared with those in an earlier study.

The compounds crystallize (Z=4) in the monoclinic space group P 2_1/n with the following parameters for Co[Rh]; a=9.846(1)[9.952(3)]; b=13.748(5)[13.751(2)]; c=11.648(2)[11.780(3)]Å; β=95.46(1)[96.43(3)]° and D_x =1.562(2)[1.713(2)]g/cm³. The structures were refined with 1643[2435] independent reflections with I > 2σ(I) to final agreement factors of 0.042[0.027].