THE SYNTHESIS AND X-RAY STRUCTURE OF TRANS-[CRCL2(NPRNH(2))(4)]BF4-CENTER-DOT-H2O AND THE THERMAL AND HG2-ASSISTED CHLORIDE RELEASE KINETICS FROM SOME TRANS-[CRCL2(N)(4)](+) COMPLEXES()

Complexes of the type trans-[CrCl2(RNH(2))(4)]Cl (R = Et, nPr, nBu) ar e readily formed from [CrCl3(thf)(3)] and four equivalents of the amin e in tetrahydrofuran (thf). The structure of trans-[CrCl2(nPrNH(2))(4) ]BF4 . H2O (triclinic, P1, a = 5.828(3), b = 10.030(10), c = 10.403(4) Angstrom, alpha = 73.34(6), beta = 89.37(3), gamma = 87.78(7), V = 58 2.1(7) Angstrom(3), Z = 1) has been determined by single crystal X-ray diffraction. The two Cr-Cl bonds are approximately equivalent (Cr-Cl( 1) = 2.325(3), Cr-Cl(2) = 2.326(3)) and two of the (cis) nPrNH(2) 'arm s' are above and two below the Cr(N)(4) plane. The rates of loss of th e first chloro ligand from trans-[CrCl(RNH(2))(4)](+) (R = Et, nPr, nB u) are about 16 times slower than that for R = H. Spectrophotometrical ly determined kinetic parameters (0.05 M HNO3, 25 degrees C) are R = H : 10(6) k (s(-1)) = 45.9, Delta H not equal (kJ mol(-1)) = 94.9, Delta S not equal (JK(-1) mol(-1)) = -10; R = Et: 10(6) k = 2.88, Delta H n ot equal = 116, Delta S not equal = + 39; R = nPr: 10(6) k = 6.70, Del ta H not equal = 101, Delta S not equal = -6; R = nBu: 10(6) k = 4.90, not equal H Delta = 116, Delta S not equal = + 43. Hg2+-assisted chlo ride release kinetics for the first step in the aquation of several tr ans- [CrCl2(N)(4)](+) systems have been measured in 50:50 dmf:aq. HClO 4 (I = 0.5 M). The activation entropy data suggest that the thermal aq uation processes for trans-[CrCl2(N)(4)](+) are more widely spread acr oss the interchange mechanistic spectrum than those for the analogous Co(III) systems.