Search

The complex [Rh([O.sub.2]Cisoq)(H)(Sn[Ph.sub.3])[(P[Ph.sub.3]).sub.2]] ([O.sub.2]Cisoq = isoquinoline-1-carboxylate), characterized by x-ray crystallography, was used as a precursor to three-center bonded complexes [Rh([O.sub.2]Cisoq)([[eta].sup.2]-HSn[Ph.sub.3])(P[Ph.sub.3])(4-Rpy)] (R = carbomethoxy, acyl, bromo, aldehyde, hydrogen, methoxy, dimethylamino), which were prepared in situ from the bis(phosphine) complex in dichloromethane by addition of the pyridine. Of two isomeric forms of [Rh([O.sub.2]Cisoq)([[eta].sup.2]-HSn[Ph.sub.3])(P[Ph.sub.3])(4-Rpy)], one, with 4-Rpy positioned trans to tin, is formed at 0[degrees]C; the other, with isoquinoline positioned trans to tin, is formed by partial (25-50%) conversion of the first isomer (in solution) upon warming to 30-35[degrees]C for a few minutes. The relative coordination geometries of the two isomers were established by using a [sup.15]N-enriched pyridine. NMR parameters ([sup.1]H, [sup.31]P, [sup.103]Rh, and [sup.119]Sn) for the pyridine-containing complexes show trends consistent with a significantly greater SnH interaction in complexes having isoquinoline lying trans to tin and a threshold of [sigma] donor strength for the pyridine below which the influence on Rh(SnH) bonding is minimal and above which the influence is to enhance the SnH interaction. Possible reasons for these effects are discussed. [sup.103]Rh NMR | [sup.119]Sn NMR | three-center bond | trans influence

Research has been conducted on the hydrotris(pyrazolyl)-borate complexes. The preparation and structural characterization of these complexes have been carried out and their reaction with PhC (sub)2 H, 4-NO (sub)2 C (sub)6 H (sub)4 -CHO and Ph (sub)3 SnH is described.

A study of the chemical shifts and coupling constants for the nuclei (super 1)H, (super 31)P, (super 103)Rh, and (super 119)Sn which are measured for over 50 compounds and influence the strength of a three-center bond is presented. The results show that the patterns of NMR data are interpreted in terms of the weakening of an Rh-(H-Sn) three-center interaction and changes in the coordination geometry of tin as the electron density on rhodium is increased.

Research was conducted to examine the interaction of triphenyltin hydride and rhodium. The structure of (Rh(NCBPh3)(H)(SnPh3)(PPh3)2) was determined by a single-crystal X-ray diffraction study which reveals the geometry to be equally well described as a distorted tetragonal pyramid with tin at the apex or a distorted trigonal bipyramid with a hydrogen of one of the phosphine phenyl groups occupying the six coordination site. The weakened interaction between Ph3SnH and rhodium is attributed to a three-center 'agostic' bond.

The N-bonded triphenylcyanoborate [Rh(NCBPh3)(PPh3)3] was produced by the reaction of the triphenylcyanoborate ion from CN- and triphenylboron in ethanol with [RhCL(PPh3)3]. The C-bonded isomer [Rh(CNBPPh3)(PPh3)3] was produced in good yields by the reaction of triphenylboron and [Rh(CN)(PPh3)3]9 in chloroform. The C-bonded isomer is composed of a trans-[Rh(CNBPh3)(PPh3)(py)] with a strong trans effect of the Ph3BNC- ligand that strongly influences the overall geometry.

The octadentate 1,4,7,10-tetrakis(acetamido)-1,4,7,10-cyclododecane is an effective ligand for larger metal ions and the resulting complexes are abnormally distorted. The Cd(II) and Zn(II) complex structures are six coordinated to four nitrogens and two oxygen atoms. A correlation exists between the helicity interchange rate and the distortion degree of the coordination geometry of the complex. The order of the rate of helicity interchange of the complexes is Zn(II) > Hg(II) > Cd(II) > Ca(II) >> Pb(II).

An analysis of diol and various minor uncharacterized by products designated P1, P2 and P3 in order of lowering Rf values, which result from 5,7-dimethylacridinone, involves a study of their structures. cis-4a,9a-dihydroxyhexahydroacridinone and hexahydro-6H-azepino(1, 2-a)-indoledione result from the reaction of tetrahydro-9(10H)-acridinone with sodium dichloroisocyanurate.

A study was conducted to examine the role of the anionic ligand in promoting oxygen binding by the complexes trans-[Rh(X)(XNC)[(P[Ph.sub.3]).sub.2] (X = Cl, Br, S[C.sub.6][F.sub.5], [C.sub.2]Ph; XNC =xylyl isocyanide). The results obtained provide insight into the influence of ligand polarizability on stabilization of [O.sub.2] binding adduct which increases in the order Cl < Br < S[C.sub.6][F.sub.5] < [C.sub.2]Ph.

H, P and Sn NMR spectroscopy techniques characterized (Rh(H) ((mu-H) SnR3)2 (PPh3)2) (R double bonds nBu, 1, Ph, 2), demonstrating that hydrogen bridging enables attachment of tin atoms to rhodium. The single terminal hydride and the hydrogens are interconverted through a dynamic process that occurs at an ambient temperature. A product (fac-Rh(H)2 - (Sn nBu3)(PPh3)3) was obtained when 1 was isolated.

The X-ray structures of the complexes [Ir(8OQ)(1,5-cod)] ( 1), [Ir(8OQd)(1,5-cod)] ( 2) and [Ir(μ-7AI)(1,5-cod)] ( 3) (where 8OQ, 8OQd and 7AI are anions derived from 8-hydroxyquinoline, 2-methyl-8-hydroxyquinoline (8-hydroxyquinaldine) and 7-azaindole, respectively) are mononuclear in the case of 1 and 2, with evidence of steric strain induced by the methyl group in 2 and dinuclear in the case of 3. The oxidative addition products [Ir(8OQd)(H)(EPh)(1,5-cod)] [E = Si ( 4), Sn ( 5)], formed by the reaction of 2 with SiHPh and SnHPh, respectively, show significant conformational differences in the solid state. Graphical Abstract: The complex cyclooctadieneiridium(I) 2-methyl-8-oxyquinolinate shows conformational isomerism as do adducts formed by its reaction with triphenylsilane and triphenyltin hydride. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Tungsten-183 NMR data are reported for the complexes cis-[W(CO)4(PPh3)(4-RC5H4N)] (R = H, Me, Ph, COMe, COPh, OMe, NMe2, Cl, NO2). The 183W chemical shift (obtained by indirect detection using 31P) is found to correlate with the Hammett σ function for the group R, with 183W shielding increasing approximately linearly with the donor strength of the pyridine over a range of 93 ppm. The X-ray structures of cis-[W(CO)4(PPh3)(4-MeOC5H4N)] and cis-[W(CO)4(PPh3)(4-PhCOC5H4N)] are also reported. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]