Tungsten-183 NMR study of cis-[W(CO)4(PPh3)(4-RC5H4N)]; effect of varying the σ donor strength of the pyridine.

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 (183)W chemical shift (obtained by indirect detection using (31)P) is found to correlate with the Hammett σ function for the group R, with (183)W 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.

A tungsten-183NMR study of cis and trans isomers of [W(CO)4(PPh3)(PR3)](PR3 = phosphine, phosphite).

Tungsten-183 NMR data are reported for the complexes cis- and trans-[W(CO)4(PPh3)(PR3)] (PR3 = PnBu3, PMe3, PMe2Ph, PMePh2, PPh3, P(4-C6H4OMe)3, P(4-C6H4Me)3, P(4-C6H4F)3, P(OMe)3, P(OEt)3, P(OPh)3 and for PCy3, P(NMe2)3(trans isomer only). The 183W chemical shift (obtained by indirect detection using 31P) is found to be related to the PR3 ligand parameters nu and theta (Tolman electronic factor and cone angle, respectively) for the cis isomers and to nu (but only poorly to theta) for the trans isomers. The 183W-31P spin coupling constant is also related, less clearly for P-C than for P-N and P-O bonded ligands, to nu.

Influence of ligand polarizability on the reversible binding of O2 by trans-[Rh(X)(XNC)(PPh3)2] (X = Cl, Br, SC6F5, C2Ph; XNC = xylyl isocyanide). Structures and a kinetic study.

The complexes trans-[Rh(X)(XNC)(PPh 3) 2] (X = Cl, 1; Br, 2; SC 6F 5, 3; C 2Ph, 4; XNC = xylyl isocyanide) combine reversibly with molecular oxygen to give [Rh(X)(O 2)(XNC)(PPh 3) 2] of which [Rh(SC 6F 5)(O 2)(XNC)(PPh 3) 2] ( 7) and [Rh(C 2Ph)(O 2)(XNC)(PPh 3) 2] ( 8) are sufficiently stable to be isolated in crystalline form. Complexes 2, 3, 4, and 7 have been structurally characterized. Kinetic data for the dissociation of O 2 from the dioxygen adducts of 1- 4 were obtained using (31)P NMR to monitor changes in the concentration of [Rh(X)(O 2)(XNC)(PPh 3) 2] (X = Cl, Br, SC 6F 5, C 2Ph) resulting from the bubbling of argon through the respective warmed solutions (solvent chlorobenzene).

An NMR study of trans ligand influence in rhodium eta2 triphenyltin hydride complexes.

The complex [Rh(O(2)Cisoq)(H)(SnPh(3))(PPh(3))(2)] (O(2)Cisoq = isoquinoline-1-carboxylate), characterized by x-ray crystallography, was used as a precursor to three-center bonded complexes [Rh(O(2)Cisoq)(eta(2)-HSnPh(3))(PPh(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(2)Cisoq)(eta(2)-HSnPh(3))(PPh(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 (15)N-enriched pyridine.

A nitrogen-15 NMR study of hydrogen bonding in 1-alkyl-4-imino-1,4-dihydro-3-quinolinecarboxylic acids and related compounds.

The title compounds contain groups (amine, amide, imine, carboxylic acid) that are capable of forming intramolecular hydrogen bonds involving a six-membered ring. In compounds where the two interacting functional groups are imine and carboxylic acid, the imine is protonated to give a zwitterion; where the two groups are imine and amide, the amide remains intact and forms a hydrogen bond to the imine nitrogen. The former is confirmed by the iminium 15N signal, which shows the coupling of 1J(15N,1H) -85 to -86.

Rhodium-103 NMR of [Rh(X)(PPh3)3] [X = Cl, N3, NCO, NCS, N(CN)2, NCBPh3, CNBPh3, CN] and derivatives containing CO, isocyanide, pyridine, H2 and O2. Ligand, solvent and temperature effects.

Rhodium-103 chemical shifts are reported for 62 compounds, namely [Rh(X)(PPh3)3] [X = Cl, N3, NCO, NCS, N(CN)2, NCBPh3, CNBPh3, CN] and derivatives formed by replacement of a phosphine by CO, xylyl isocyanide (XNC) and pyridine and/or by oxidative addition of H2 or O2 to give trans-[Rh(X)(PPh3)2(CO)] (delta in the range -816 to -368 ppm) trans-[Rh(X)(PPh3)2(XNC)] (delta -817 to -250 ppm), cis-[Rh(X)(PPh3)2(py)] (the trans isomer is formed with X = CN, CNBPh3) (delta -233 to 170 ppm), [Rh(X)(H)2(PPh3)3] (delta -611 to 119), trans-[Rh(X)(H)2(PPh3)2(py)] (delta -30 to 566 ppm), [Rh(X)(O2)(PPh3)3] (delta 1393 to 3273 ppm) and cis-[Rh(X)(O2)(PPh3)2(py)] (delta 1949 to 3374 ppm). For the majority of these compounds data were obtained from solutions in chloroform and in toluene at temperatures of 247 and 300 K; for [Rh(X)(PPh3)3] (delta -562 to -4 ppm) data are reported at a number of temperatures in the range 195-300 K for solutions in chloroform, toluene and dichloromethane and at 300 K for solutions in DMSO. The expected trend to lower delta(103Rh) with decreasing temperature (vibrational shielding) is observed for the dichloromethane data, but data from solutions {of [Rh(X)(PPh3)3]} in chloroform and toluene show a number of features which diverge from this pattern, i.

Reaction of bis(phosphine)(hydrotris(3,5-dimethylpyrazolyl)borato)rhodium(I) with phenylacetylene, p-nitrobenzaldehyde, and triphenyltin hydride: structures of [Rh(Tp)(PPh(3))(2)], [Rh(Tp)(H)(C(2)Ph)(P(4-C(6)H(4)F)(3))], [Rh(Tp)(H)(COC(6)H(4)-4-NO(2))(PPh(3))], and [Rh(Tp)(H)(SnPh(3))(PPh(3))].

The complexes [Rh(Tp)(PPh(3))(2)] (1a) and [Rh(Tp)(P(4-C(6)H(4)F)(3))(2)] (1b) combine with PhC(2)H, 4-NO(2)-C(6)H(4)CHO and Ph(3)SnH to give [Rh(Tp)(H)(C(2)Ph)(PR(3))] (R = Ph, 2a; R = 4-C(6)H(4)F, 2b), [Rh(Tp)(H)(COC(6)H(4)-4-NO(2))(PR(3))] (R = Ph, 3a), and [Rh(Tp)(H)(SnPh(3))(PR(3))] (R = Ph, 4a; R = 4-C(6)H(4)F, 4b) in moderate to good yield. Complexes 1a, 2b, 3a, and 4a have been structurally characterized. In 1a the Tp ligand is bidentate, in 2b, 3a, and 4a it is tridentate.

Interaction of Triphenyltin Hydride and Rhodium. Structure of [Rh(NCBPh(3))(H)(SnPh(3))(PPh(3))(2)] and NMR ((1)H, (15)N, (31)P, (103)Rh, (119)Sn) Study of Pyridine-Containing Derivatives.

The structure of [Rh(NCBPh(3))(H)(SnPh(3))(PPh(3))(2)] (1) (formed from [Rh(NCBPh(3))(PPh(3))(3)] and Ph(3)SnH) was determined by a single-crystal X-ray diffraction study which shows 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 sixth coordination site. The tin-hydride distance of 2.31(5) Å is consistent with a weak interaction.