Remarkable spectator ligand effect on the rate constant of ligand substitution of (aqua)ruthenium(II) complexes

The influence of two different di(1-pyrazolyl)alkane ligands on the rate constant of aqua ligand substitution of ruthenium(II) complexes with the formula [Ru(H2O)(L2)(tpmm)]2+ (L2 = di(1-pyrazolyl)methane (DPMet) or 2,2-di(1-pyrazolyl)propane (DPPro)) was investigated. A 9.4 x 10(5)-fold increase in the rate constant of ligand substitution at pH = 6.86 was observed when DPMet was replaced with DPPro. This remarkable increase was unexpected, considering that these bidentate ligands appear quite similar. To help lend insight into this dramatic spectator ligand effect, the activation parameters for the ligand substitution reactions were determined, and single-crystal X-ray data were collected on the structurally analogous (chloro)ruthenium(II) complexes, [Ru(Cl)(L2)(tpmm)]+. These results are discussed in the context of a heteroscorpionate effect exerted by the DPPro ligand.     

Synthesis ofcis-[Ru{4,4′-(t-Bu)2bpy}2(PPh3)Cl+][ClO 4 − ] and the crystal structure of its disordered hemiacetonitrile,hemitoluene solvate

The complexcis-[Ru{4,4-(t-Bu)₂bpy}₂(PPh₃)Cl⁺][ClO ₄ ^– ·0.5(toluene)·0.5(MeCN), where 4,4-(t-Bu)₂bpy=4,4-di(t-butyl)-2,2-bipyridyl crystallizes with an ordered racemic mixture of the chiral cations in the centrosymmetric triclinic space group (No. 2). The structure was refined toR=4.42% for those 6426 reflections with 20=5–50^o and |F _o|>6(F). Ruthenium ligand distances are Ru–Cl=2.423(2)Å, Ru–PPh₃=2.346(2)Å and Ru–N=2.056(4)–2.098(4)Å. Both the Ru(II)-containing cation and the perchlorate anion are ordered, but the toluene and acetonitrile exhibit an interesting type of scrambled disorder about the inversion center atx=1,y=1/2,z=0.     

Synthesis and structural characterization of 2-mercapto-1-tert-butylimidazole and its Group 12 metal derivatives (HmimtBu)2MBr2 (M = Zn, Cd, Hg)

2-Mercapto-1-tert-butylimidazole (Hmim^tBu) and its Group 12 metal complexes (Hmim^tBu)₂ MBr₂ (M = Zn, Cd, Hg) have been readily prepared and structurally characterized. Whereas the former displays a dimeric structure in the solid state with two S H–N interactions linking each pair of molecules, the four-coordinate complexes exhibit distorted tetrahedral geometries with the S–M–S angles in the range 103.2–135.2. The average M–Br bond lengths are 2.401, 2.567, and 2.688 Å for M = Zn, Cd, and Hg, respectively, and the corresponding average M–S bond distances are 2.350, 2.540, and 2.467 Å. The average C–S bond length for all the complexes (1.72 Å) is only ca. 0.02 Å longer than the corresponding value in the free ligand. Hmim^tBu is orthorhombic, space group Pbca, a = 10.1571(5) Å, b = 9.7906(5) Å, c = 17.6616(9) Å, V = 1756.34(15) ų, Z = 8; (Hmim^tBu)₂ZnBr₂ is monoclinic, space group C2/c, a = 17.187(3) Å, b = 8.9908(17) Å, c = 15.560(3) Å, = 117.206(3), V = 2138.3(7) ų, Z = 4; (Hmim^tBu)₂CdBr₂ is triclinic, space group P , a = 7.4625(6) Å, b = 9.6149(9) Å, c = 31.020(3) Å, = 93.485(2), = 94.579(2), = 103.872(2), V = 2146.6(3) ų, Z = 4; (Hmim^tBu)₂HgBr₂ is monoclinic, space group P2₁/c, a = 6.8908(6) Å, b = 10.2397(9) Å, c = 29.859(3) Å, = 94.364(2), V = 2100.7(3) ų, Z = 4.     

A hydrogen-bonded dichloromethane-perchlorate-water channel in the crystal structure ofcis-[Ru(bpy)2{PPh-(o-tolyl)2}Cl+][ClO4 −]·CH2Cl2·H2O

The complexcis-[Ru(bpy)₂{PPh(o-tolyl)₂}Cl⁺][ClO₄ ^–] crystallized from a solution in dichloromethane as the dichloromethane-water solvate. The structure was refined toR=4.5% for those 2433 reflections with |F _o|>6(|F _o|). The octahedral Ru(II) cation is associated with metal-ligand distances as follows: Ru–Cl=2.434(3)Å, Ru-PPh(o-tol)₂=2.382(2)Å, and Ru–N=2.037(7)–2.088(7)Å. The structure is stabilized by a hydrogen-bonded CH₂Cl₂...ClO₄ ^–...H₂O channel which incorporates adventitious water of crystallization.     

Crystal structure ofmer,trans-[Ru(NO2)(trpy) (PPh3) 2 + ][PF 6 − ]: a “problem structure”

The complexmer,trans-[Ru(NO₂)(trpy)(PPh₃) ₂ ⁺ ][PF ₆ ^– ] crystallizes in the centrosymmetric monoclinic space groupP2₁/n withZ=4; the ruthenium atom lies close toy=1/4 and all data withh+l=2n+1 are systematically weak. The trpy ligand is not strictly planar, but has a dish-like geometry. The nitro ligand is rotated from the plane of the Ru(trpy) moiety, the N₃Ru/NO₂ interplanar angle being 32.5^o. Ruthenium-ligand distances are: Ru–PPh₃=2.418(4) Å and 2.429(4) Å, Ru–NO₂=2.063(12) Å, Ru–N(trpy, outer)=2.100(12) Å and 2.116(12) Å and Ru–N(trpy, central)=2.004(11) Å.     

Crystal structure oftrans-carbonylchlorobis-(tricyclohexylphosphine)iridium(I),trans-Ir(CO)Cl-[P(cyclo-C6H11)3]2, a disordered species

The title compound crystallizes in the centrosymmetric triclinic space group (C ₁ ^l ; No.2) witha=9.9143(10) Å,b=10.2616(11) Å,c=10.7715(10) Å, =113.887(8)°, =109.197(8)°, =90.699(9)°,V=932.78(17) ų andZ=1. A total of 4869 data were collected and merged to a set of 2450 independent reflections; the structure was solved and refined toR=1.42% andwR=1.94%. The molecule lies on a site of symmetry and is disordered, with obvious scrambling of carbonyl and chloride ligands. Resulting bond lengths include Ir–P=2.339(1) Å, Ir–Cl=2.398(4) Å and Ir–CO=1.808(15) Å.     

X-ray diffraction studies oncis-[Ru(bpy)2(PMe3)Cl+][ClO4?] andcis-[Ru(bpy)2{PMe2(o-tol)}Cl+][ClO4?]; two ordered structures in thecis-bis(bipyridyl)chloro(phosphine)-ruthenium(II) series

The complexcis-[Ru(bpy)₂(PMe₃)Cl⁺][ClO₄ ⁻] crystallizes in space group P2₁/c andcis-[Ru(bpy)₂{PMe₂(o-tol)]Cl⁺][ClO₄ ⁻] crystallizes in space group ; each is present as a racemate and neither structure suffers from disorder. The Ru−PMe₂(o-tol) bond length of 2.324(2)? is slightly longer than the simple Ru−PMe₃ bond length of 2.310(2) ?.     

Crystal structure of hexakis(tetrahydrofuran)sodium hexacarbonylvanadate(−I), [Na(THF)6 +][V(CO)6 −]

The title compound crystallizes in the space group with unit cell parameters (hexagonal setting)a=14.922(5)Å,c=14.379(9)Å,V=2773(3)ų andZ=3. The cation and the anion each lie on a site of (S₆) symmetry. Interatomic distances include Na–O(THF)=2.40(1) Å and V–C(CO)=1.91(2) Å.     

Absolute configuration of C20H30O6Si, a species with a (1R,5R)-8-oxabicyclo[3.2.1]octa-2,6-diene core produced selectivity by the rhodium(II) octanoate catalyzed decomposition of a chiral vinyldiazomethane in the presence of furan

The compound under investigation crystallizes in the noncentrosymmetric monoclinic space group P2₁ with a = 9.1798(23), b = 6.6606(18), c = 17.6591(41) Å, = 94.342(20)° and Z = 2. The C₂₀H₃₀O₆Si molecule contains three chiral centers (one of which is of known configuration, based upon an (R)-pantolactone auxiliary group). We have determined the absolute configuration of this species (via the anomalous dispersion of Si relative to C and O) and show that it is consistent with the known configuration of the (R)-pantolactone moiety