fac-{2-[Bis(2-amino-eth-yl)amino]-ethanaminium}trichloridorhodium(III) chloride hemihydrate.

The crystal structure of the title compound, [Rh(C(6)H(19)N(4))Cl(3)]Cl·0.5H(2)O, is isotypic with the previously reported Ru analogue. The structure contains two crystallographically independent [Rh(Htren)Cl(3)](+) cations with a facial tridentate coordination of the monoprotonated tren ligand [tren = tris-(2-amino-eth-yl)amine], leading to an overall distorted octahedral coordination environment around the Rh(III) atom. In one of the two cations, the ethyl-ene groups of the two chelate rings as well as the non-coordinating ethyl-ammonium group are disordered over two sets of sites [0.579 (3):0.421 (3) occupancy ratio]. A series of N-H⋯Cl and O-H⋯Cl hydrogen bonds stabilizes the structure.

Characteristic spin-orbit induced 1H(CH2) chemical shifts upon deprotonation of group 9 polyamine aqua and alcohol complexes.

The recently observed nonintuitive pH dependence of methylene (1)H chemical shifts in cobalt(III) polyamine complexes upon deprotonation of coordinated aqua or (poly)alcohol coligands (J. Am. Chem. Soc. 2004, 126, 6728) was attributed to differential spin-orbit effects on the (1)H shifts transmitted over three bonds from the cobalt low-spin d(6) center. These remarkably large spin-orbit effects due to the comparably light Co center have now been examined closely by comparative computations for homologous Rh and Ir complexes, as well as by NMR titrations for a Rh complex. While larger spin-orbit effects (proportional to Z(2)) would have been expected for the heavier metal centers, the characteristic (1)H deshieldings upon deprotonation of [Rh(tren)(OH(2))(2)](3+) [tren = tris(2-aminoethyl)-amine] turn out to be smaller than for the Co homologous Co complex. Systematic computational studies ranging from smaller models to the full complexes confirm these results and extend them to the Ir homologues. Closer analysis indicates that the spin-orbit shift contributions do not follow the expected Z(2) behavior but are modulated dramatically by increasing energy denominators in the perturbation expressions. This is related to the increasing ligand-field splitting from 3d to 4d to 5d system, leading to almost identical differential spin-orbit shifts for the Co and Rh complexes and to only moderately larger effects for the Ir complex (by a factor of about two). Moreover, the differential nonspin-orbit deprotonation shifts cancel the spin-orbit induced contributions largely in the Rh complex, leading to the experimentally observed inverted behavior. The full multidentate polyamine complexes studied experimentally exhibit different three- and four-bond Fermi-contact pathways for transmission of the spin-orbit (1)H shifts. The novel four-bond pathways have different conformational dependencies than the Karplus-like three-bond pathways established previously. Both types of contributions are of similar magnitude. The (1)H NMR deprotonation shift patterns of [Ir(tren)(OH(2))(2)](3+) have been predicted computationally.

Synthesis and characterization of vanadium(IV) complexes with cis-inositol in aqueous solution and in the solid-state.

The complex formation of vanadium(IV) with cis-inositol (ino) and the corresponding trimethyl ether 1,3,5-trideoxy-1,3,5-trimethoxy-cis-inositol (tmci) was studied in aqueous solution and in the solid-state. With increasing pH, the formation of [VO(H-2L)], [(VO)2L2H-5]-, [VO(H-3L)]- (L = ino) or [(VO)2L2H-6]2- (L = tmci), [V(H-3L)2]2-, and [VO(H-3L)(OH)2]3- was observed. For the vanadium(IV)/ino system, [(VO)2L2H-7]3- was observed as an additional dinuclear species. The formation constants of these complexes were determined by potentiometric titrations (25 degrees C, 0.1 M KCl). In addition, the vanadium(IV)/ino system was investigated by means of UV-vis spectrophotometric methods. EPR spectroscopy and cyclic voltammetry confirmed this complexation scheme. EPR measurements indicated the formation of three distinct isomers of the non-oxo complex [V(H-3ino)2]2- in weakly basic solution. This type of isomerism, which is not observed for the vanadium(IV)/tmci system, was assigned to the ability of ino to bind the vanadium(IV) center with three alkoxo groups having either a 1,3,5-triaxial or an 1,2,3-axial-equatorial-axial arrangement. The structures of [V(H-3ino)2][K2(ino)2].4H2O (1) and [Na6V(H-3ino)2](SO4)2.6H2O (2) were determined by single-crystal X-ray analysis. In both compounds, the coordination of each ino molecule to the vanadium(IV) center via three axial deprotonated oxygen donors was confirmed. The centrosymmetric structure of the coordination spheres corresponds to an almost regular octahedral geometry with a twist angle of 60 degrees. The crystal structure of the potassium complex 1 represents an unusual 1:1 packing of [V(H-3ino)2]2- dianions and [K2(ino)2]2+ dications, in which both K+ ions have a coordination number of nine and are bonded simultaneously to a 1,3,5-triaxial and an 1,2,3-axial-equatorial-axial site of ino. In 2, the [V(H-3ino)2]2- complexes are surrounded by six Na+ counterions that are bonded to the axial alkoxo oxygens and to the equatorial hydroxy oxygens of the cis-inositolato moieties. The six Na+ centers are further interlinked by bridging sulfate ions. According to EPR spectroscopy, the D3d symmetric structure of the [V(H-3ino)2]2- anion is retained in H2O, in dimethylformamide, and in a mixture of CHCl3/toluene 60:40 v/v.