REACTION OF 2,2'-BIPYRIDINE (BPY) WITH DIRHODIUM CARBOXYLATES - MONO-BPY PRODUCTS WITH VARIABLE CHELATE BINDING MODES AND INSIGHTS INTO THE REACTION-MECHANISM Academic Article uri icon

abstract

  • Synthetic procedures are described for the preparation of mono-2,2-bipyridine (bpy) complexes possessing the Rh24+ core. Reaction of Rh2(OAc)4(MeOH)2 (1) with 1 equiv of bpy in Me2CO produces Rh2(OAc)4(bpy) (3) in excellent yield. The compound crystallizes in the triclinic space group P1 with the following cell parameters at 172 C: a = 9.883(3), b = 13.078(5), c = 8.323(2) ; = 97.02(2), = 106.90(1), = 94.29(2); Z = 2; V = 1015 3. The structure was solved by direct methods (MULTAN) and refined to values of conventional indices R (Rw) of 4.72% (4.50%) using 2636 unique reflections with Fo > 3-(Fo). The two Rh2+ centers are bridged by three 1:12 AcO-groups over a Rh-Rh bond distanceof 2.475(2) . The coordination spheres of Rh(l) and Rh(2) are completed by chelating bpy and OAc- groups, respectively. The chelating OAc- is asymmetrically bound as a consequence of the axial/equatorial positioning of its two oxygen atoms O(27) and O(29). Compound 3 undergoes a reaction on dissolution in MeOH to give [Rh2(OAc)3(bpy)(MeOH)](OAc)2MeOH (4) as determined by 1H NMR (1D- and 2D-homonuclear J-resolved spectroscopy), elemental analysis, conductivity measurements, and reactivity studies. Reaction of Rh2(O2CCF3)4(Me2CO)2 (2) with 1 equiv of bpy in CH2Cl2, followed by recrystallization of the product from THF/H2O, produces crystals of Rh2(O2CCF3)4(bpy)(THF)(H2O)-THF (5). Compound 5 crystallizes in the monoclinic space group Pc with the folowing cell parameters at 105 C: a = 10.683(8), b = 9.170(8), c = 17.783(1) ; = 90.00, = 103.52(7), = 90.00; Z = 2, V = 1693 .3 The structure was solved by direct methods (MITHRIL) and refined to values of R (Rw) of 5.1% (5.8%) using 2493 unique reflections with F > 3(F). The two Rh2+ centers are bridged by two 1:1:2 O2CCF3- ligands across a Rh-Rh separation of 2.520(3) . Coordination about Rh(l) is completed by two terminal 1-O2CCF3- groups in equatorial sites with the axial site being occupied by a water molecule. Rh(2) is ligated by a chelating bpy group in the equatorial plane, with axial ligation being provided by a THF molecule. Reaction mixtures comprising [Rh2(OAc)2(MeCN)6] (BF4)2 (6) and 1 equiv of bpy in MeCN lead to isolation of [Rh2(OAc)2(bpy)(MeCN)4](BF4)2MeCN (7). Compound 7 crystallizes in the triclinic space group P1 with the following cell parameters at 170 C: a = 12.381(2), b = 14.301(2), c = 12.246(2) ; = 94.60(1), = 105.84(1), = 117.42(1); Z = 2; V = 1797 3. The structure was solved by direct methods (MULTAN) and refined to values of R (Rw) of 4.92% (5.74%) using 4723 unique reflections with F > 3(F). The two metals are bridged by two cis 1:1:2-OAc- groups that span a Rh-Rh distance of 2.5395(8) . Coordination at Rh(l) is completed by a chelating bpy in the equatorial plane and an axial MeCN ligand, while the coordination sphere of Rh(2) is completed by two equatorial MeCN molecules and an axial MeCN molecule. 1993, American Chemical Society. All rights reserved.

published proceedings

  • INORGANIC CHEMISTRY

author list (cited authors)

  • CRAWFORD, C. A., MATONIC, J. H., STREIB, W. E., HUFFMAN, J. C., DUNBAR, K. R., & CHRISTOU, G.

citation count

  • 49

complete list of authors

  • CRAWFORD, CA||MATONIC, JH||STREIB, WE||HUFFMAN, JC||DUNBAR, KR||CHRISTOU, G

publication date

  • July 1993