Variable-temperature 31P NMR Spectroscopy Research Articles

The evaluation of singlet-triplet separations for [W 2(μ-H)(μ-Cl)Cl 4(μ-dppm) 2] and [W 2(μ-H) 2 (μ-O 2CC 6H 5) 2(P(C 6H 5) 3) 2] based on 31P NMR and crystallographic data

The singlet-triplet separations for the edge-sharing bioctahedral (ESBO) complex W 2(μ-H)(μ-Cl)(Cl 4(μ-dppm) 2 · (THF) 3 ( II) has been studied by 31P NMR spectroscopy. The structural characterization of [W 2(μ-H) 2(μ-O 2CC 6H 5) 2Cl 2(P(C 6H 5) 3) 2] ( I) by single-crystal X-ray crystallography has allowed the comparison of the energy of the HOMOLUMO separation determined using the Fenske-Hall method for a series of ESBO complexes with two hydride bridging atoms, two chloride bridging atoms and the mixed case with a chloride and hydride bridging atom. The complex representing the mixed case, [W 2(μ-H)(μ-Cl)Cl 4(μ-dppm) 2 · (THF) 3] ( II), has been synthesized and the value of −2 J determined from variable-temperature 31P NMR spectroscopy.

Platinum metal complexes of secondary phosphines: Synthesis and NMR spectroscopic studies of [M(PCy 2H) 3Cl] +, M = Pt, Pd

Reaction of MCl 2 (M = Pd, Pt) with PCy 2H in EtOH under dinitrogen yielded the unusual tris-secondary phosphine complexes [MCl(PCy 2H) 3]X (X − = Cl −, BF − 4, PF − 6) in high yield as stable products. Retention of the secondary phosphine protons in these complexes has been confirmed by 1H, 31P and 195Pt NMR spectroscopic studies. These results confirm that the PH bond in coordinated PCy 2H is stronger than in coordinated PPh 2H. Similar reaction of NiCl 2 · 6H 2O with PCy 2H yields the bis-secondary phosphine complex [NiCl 2(PCy 2H) 2] as reported previously (R. A. Palmer, H. F. Giles and D. R. Whitcomb, J. Chem. Soc., Dalton Trans. 1978, 1671 ; R. A. Palmer and D. R. Whitcombe, J. Mag. Res. 1980, 39, 371). Variable temperature 31P NMR spectroscopy confirms that the cis isomer exists exclusively in CH 2Cl 2 solution, while the trans isomer is the dominant form in benzene solution. Addition of excess PCy 2H leads to species with higher phosphine : metal ratios at low temperature as seen by 31P NMR spectroscopy and FAB mass spectrometry.

Reaction of three-coordinate phosphorus compounds with organophosphorus pseudohalogens 3. Phosphonium and phosphorane intermediates in the desulfurization and deoxygenation of bis(phosphinoyl) disulfides. Influence of Lewis acids on the reaction chemoselectivity

The reactions of bis(phosphinoyl) disulfides RR1P(O)S–S–P(O)RR11 with PIII compounds have been investigated and various mechanistic features have been elucidated by variable-temperature 31P NMR spectroscopy. These studies show that in most cases phosphonium intermediates [[graphic omitted]P(O)–S–[graphic omitted]–O–P(S)[graphic omitted]]5 and [[graphic omitted]P(S)–O–[graphic omitted] –O–P(S)[graphic omitted]]6 are involved. In cases where ligands on PIII increase the stability of the five-coordinate structures phosphorane intermediates are observed. In the isomerization 5→6, the mode of decomposition (desulfurization, deoxygenation or dealkylation) to give stable end products is influenced by electronic and steric factors. The presence of the Lewis acid BF3 influences considerably the stability of the transient species 5 and 6 and the chemoselectivity of the reaction.

Crystal structures vibrational 31p NMR studies of complexes of tertiary phosphine ligands with mercury(II) halides

The mercury(II) phosphine complexes (R 3P) 2HgX 2 (R 3P = PPh 3, PEt 3, 1-phenyldibenzophosphole (DBP), 1-phenyl-3, 4-dimethylphosphole (DMPP); X = Cl, Br, I and PBu 3; X = Cl) have been prepared and their solution and solid state structures determined by a combination of elemental analyses, IR, Raman NMR spectroscopy. The structures of (DBP) 2HgBr 2 ( 1), (PPh 3) 2Hg 2Br 4 ( 2), (DMPP) 2Hg 2I 4 ( 3) and (Bu 3P) 2Hg 2I 4 ( 4) have been determined from three-dimensional X-ray data collected by counter methods. Compound 1 crystallizes in space group P 1 with a = 10.568(6), b = 17.390(6), c = 9.610(3) Å, α = 106.02(4), β = 100.62(4), γ = 101.41(5)° and Z = 2. Compound 2 crystallizes in space group P2 1/ a with a = 18.619(7), b = 10.938(4), c = 18.762(5) Å, β = 90.36(2)° and Z = 4. Compound 3 crystallizes in space group Pbc2 1 with a = 8.516(4), b = 19.404(7), c = 19.545(6) Å and Z = 4. Compound 4 crystallizes in space group P2 1/ c with a = 16.450(16), b = 20.609(21), c = 24.263(31) Å, β = 109.38(8)° and Z = 8. Compound 1 deviates from ideal C 2 symmetry having slightly different HgBr (2.618(2), 2.604(2) Å) and HgP (2.513(3), 2.490(3) Å bond distances. The inequivalence of the phosphines is manifested as a second order ABX CP/MAS 31P{ 1H} NMR spectrum for 1. Compound 2 is a symmetric doubly bromide bridged dimer with essentially equivalent HgP (2.40(2), 2.44(2) Å) bond distances but its CP/MAS 31P{ 1H} NMR spectrum displays two AX resonances, showing that the phosphines are not magnetically equivalent. Compound 3 is a symmetric, doubly iodide bridged dimer having slightly different HgP (2.437(7), 2.470(7) Å) bond distances displays three AX resonances in its CP/MAS 31P{ 1H} NMR spectrum. Compound 4 is an unsymmetrical doubly iodide bridged dimer [(Bu 3P) 2HgI 2HgI 2] having equivalent HgP (2.393(21), 2.391(22) Å bond lengths but its CP/MAS 31P{ 1H} NMR spectrum shows two ABX resonances arising from the two different molecules in the unit cell with the phosphines being magnetically inequivalent in each molecule. Variable temperature 31P NMR spectroscopy shows that equilibria between monomeric (R 3P) 2HgX 2 and dimeric [R 3PHgX 2] 2 occur in solution for R 3P = DMPP and Bu 3P the dimers are very easily formed from the monomers.

Reactions of tetranuclear rhodium–triruthenium clusters with di- and tri-phosphines and with alkynes

The compound [RhRu3(µ-H)2(µ-CO)(CO)9(cp)]1(cp =η5-C2H5) and an equimolar amount of diphosphine Ph2P(CH2)nPPh2[n= 1 (dppm), 2 (dppe) or 3 (dppp)] react at ambient temperature principally with cleavage of the heteronuclear cluster to form several homonuclear rhodium and ruthenium products. Isolated ruthenium clusters are simple phosphine derivatives of [Ru3(CO)12] or [Ru4(µ-H)4(CO)12], including [Ru3(µ-diphos)2(CO)8](diphos = dppm or dppe), [Ru3(µ-diphos)(CO)10] and [{Ru3(µ-diphos)(CO)9}2(µ-diphos)](diphos = dppe or dppp), and [Ru4(µ-H)4(CO)10(dppp)]. Reaction of 1 with the triphosphine MeC(CH2PPh2)3 affords hydrido-clusters [Ru3(µ-H)H(µ-triphos)(CO)8] and [Ru3(µ-H){µ-PPhCH2CMe(CH2PPh2)2(CO)8]12, the latter formed by elimination of benzene under very mild reaction conditions. The solid-state structure of cluster 12 has been determined by X-ray crystallographic analysis [monosolvate with dichloromethane, monoclinic, space group P21/n, a= 19.549(3), b= 14.2462(21), c= 16.429(4)A, β= 90.271(18)°, Z= 4, R= 0.051, R′= 0.060] and the geometrical non-rigidity of this asymmetric molecule in solution is revealed by variable-temperature 31P NMR spectroscopy. Reactions of cluster 1 with alkynes, RCCR (R = Ph or Et), give heteronuclear products, including isomers of [RhRu3(C2R2)(CO)9(cp)] and trimetallic clusters [RhRu2(C2R2)(CO)n(cp)](R = Et, n= 7; R = Ph, n= 8); from reaction of [RhRu3(µ-H)4(CO)9(η5-C5Me5)] with PhCCPh a related tetranuclear cluster [RhRu3(C2R2)(CO)9(η5-C5Me5)] is formed. A new, octahedral heteronuclear cluster [Rh2Ru4(µ-H)2(CO)12(cp)2] is also reported.

Synthesis and crystal structure of a lanthanum complex with a diphenylphosphide ligand

Reaction of a solution of [LaL3(Ph3PO)][L = N(SiMe3)2] with Ph2PH followed by Ph3PO yields [LaL2(PPh2)(Ph3PO)2], which has been isolated as highly air-sensitive orange crystals and characterised by solution NMR spectroscopy (31P and 1H) and X-ray crystallography. The structure was refined to a final R value of 0.056 and shows the complex to have a terminal PPh2– ligand with planar co-ordination at P. Variable-temperature 31P NMR spectroscopy indicates rapid exchange between free and co-ordinated Ph3PO at room temperature but at 193 K is consistent with the solid-state structure with two Ph3PO ligands.

ChemInform Abstract: Some Selenium Analogues of the Anionic Tridentate Tripodal Sulfur Ligand, Tris(diphenylthiophosphinyl)methanide.

Abstract A new potential tridentate tripodal ligand, bis (diphenylselenophosphinyl)diphenylthiophosphinylmethanide, and its neutral protonated parent have been synthesized. The stable conformations of HTrisSSe2 and its trichalcogen analogues can be determined by variable temperature 31p NMR spectroscopy because of significant differences in chemical shifts for a particular chalcogenophosphinyl group in different stereochemical orientations within the sterically hindered molecules.

SOME SELENIUM ANALOGUES OF THE ANIONIC TRIDENTATE TRIPODAL SULFUR LIGAND, TRIS(DIPHENYLTHIOPHOSPHINYL) METHANIDE

Abstract A new potential tridentate tripodal ligand, bis (diphenylselenophosphinyl)diphenylthiophosphinylmethanide, and its neutral protonated parent have been synthesized. The stable conformations of HTrisSSe2 and its trichalcogen analogues can be determined by variable temperature 31p NMR spectroscopy because of significant differences in chemical shifts for a particular chalcogenophosphinyl group in different stereochemical orientations within the sterically hindered molecules.