31P Chemical Shifts in Ru(II) Phosphine Complexes. A Computational Study of the Influence of the Coordination Sphere.

The NMR chemical shift has been the most versatile marker of chemical structures, by reflecting global and local electronic structures, and is very sensitive to any change within the chemical species. In this work, Ru(II) complexes with the same five ligands and a variable sixth ligand L (none, H2O, H2S, CH3SH, H2, N2, N2O, NO+, C═CHPh, and CO) are studied by using as the NMR reporter the phosphorus PA of a coordinated bidentate PA-N ligand (PA-N = o-diphenylphosphino-N,N'-dimethylaniline). The chemical shift of PA in RuCl2(PA-N)(PR3)(L) (R = phenyl, p-tolyl, or p-FC6H4) was shown to increase as the Ru-PA bond distance decreases, an observation that was not rationalized. This work, using density functional theory (DFT) calculations, reproduces reasonably well the observed 31P chemical shifts for these complexes and the correlation between the shifts and the Ru-PA bond distance as L varies. An interpretation of this correlation is proposed by using a natural chemical shift (NCS) analysis based on the natural bonding orbital (NBO) method. This analysis of the principal components of the chemical shift tensors shows how the σ-donating properties of L have a particularly high influence on the phosphine chemical shifts.

Binding of CO and NH3 at a five-coordinate Ru(II) centre in the solid state and in solution.

The known five-coordinate, square-pyramidal, green trans-RuCl2(P-N)(PR3) complexes (P-N = o-diphenylphosphino-N,N'-dimethylaniline; R = Ph (1a), p-tolyl), in the solid state at ambient conditions, or in CDCl3 solution at low temperatures, coordinate CO (at 1 atm) to form beige-coloured trans-monocarbonyl derivatives. In the solution reactions at room temperature, the PR3 ligand dissociates and the yellow dicarbonyl complex RuCl2(CO)2(P-N) is formed as a mixture of trans,cis- and cis,cis-isomers. With use of (13)CO, the carbonyls complexes are characterized by variable temperature NMR and IR data, and (for the monocarbonyls) elemental analyses. Similarly, 1a and the dibromo analogue (1b) in the solid state bind NH3 to form the beige trans-monoammine species RuX2(P-N)(PPh3)(NH3), trans-4a (X = Cl) and trans-4b (X = Br), with cis P-atoms. The solution NH3 reactions, however, generate a species, speculatively thought to be the unusual, tight ion-pair, bisammine species [RuX(P-N)(PPh3)(NH3)2···X], 5a (X = Cl) and 5b (X = Br), in which a halide is considered strongly H-bonded to the cis-ammine ligands, although an alternative RuX(P-N)(PPh3)(NH3)2 formulation with a monodentate P-N ligand cannot be ruled out; dissolution in CDCl3 of isolated 5a and 5b, which are characterized by NMR, elemental analysis, and conductivity data, results in a partial, reversible loss of NH3 to form some cis- and trans-4a or -4b, respectively. Treatment of 5a with one mole equivalent of NH4PF6 in acetone solution removes the H-bonded chloride to give [RuCl(P-N)(PPh3)(NH3)2]PF6 (6), and this is converted by thermal loss of NH3 to generate the extremely air-sensitive, five-coordinate, ionic species [RuCl(P-N)(PPh3)(NH3)]PF6 (7). NMR evidence is presented for formation of the tris(ammine) species [Ru(P-N)(PPh3)(NH3)3](PF6)2 (8) via treatment of trans-RuCl2(P-N)(PPh3) with an atmosphere of NH3 in the presence of 2 mole equivalents of NH4PF6.

Comparative properties of coordinated H2 and H2S at a ruthenium(II) centre.

Thermodynamic data for the reversible formation of cis-RuCl2(P-N)(PPh3)(η(2)-H2) () from trans-RuCl2(P-N)(PPh3) in C6D6 are determined by variable temperature (31)P{(1)H} and (1)H NMR spectroscopy; P-N = o-diphenylphosphino-N,N'-dimethylaniline. Values of ΔH° = -26 ± 4 kJ mol(-1), ΔS° = -40 ± 15 J mol(-1) K(-1), and ΔG° (at 25 °C) = -13.8 ± 0.2 kJ mol(-1) are compared with recently reported data for the corresponding H2S adduct (4a), where the exothermicity is greater by ~20 kJ mol(-1), but this is counteracted by a more unfavourable entropy change, and overall the K and ΔG° values at 25 °C are close. For loss of H2 from 2a in the solid state, whose X-ray structure is presented, ΔH° is 50 ± 3 kJ mol(-1) as measured by Differential Scanning Calorimetry. The pKa values of the coordinated H2 (~11) and H2S (~14) are estimated by reactions of 2a and 4a with proton sponge (1,8-bis(dimethylamino)naphthalene) in CD2Cl2 at 20 °C; the mono-hydrido and -mercapto products are identified in situ. A corresponding H2O adduct is not deprotonated under the same conditions. Related dihydrido, mercapto and hydroxy species are formed by in situ reactions of 1a with NaH, NaSH, and NaOH, respectively.

Dioxygen adducts of rhodium N-heterocyclic carbene complexes.

Rhodium complexes functionalized by N-heterocyclic carbene ligands react with dioxygen to form adducts. Depending on the specifics of the ancillary ligands, oxygen binds to Rh either as a peroxide to form a fully oxidized Rh(III) complex, or as singlet dioxygen in a Rh(I) square planar complex. We have shown through analysis of a series of compounds, some previously published and some novel, that the presence of additional ligands that would support the formation of an octahedral geometry, as typically found with Rh(III) complexes, is critical for formation of the peroxide. In addition, we have demonstrated through DFT studies, that the potential energy surface with regard to the O-O bond length is relatively shallow, which provides a rationale for the distribution of bond lengths observed for apparently similar complexes analyzed by crystallography.

Molecular recognition using ruthenium(II) porphyrin thiol complexes as probes.

In situ (1)H NMR data are reported for 106 Ru(porp)(RSH)(2) species, where porp is the dianion of ß-octaethylporphyrin (OEP), meso-tetraphenylporphyrin (TPP), and its para-substituted tetraphenyl analogues (T-p-XPP; X = OMe, Me, F, Cl, CO(2)Me, CF(3)), meso-tetrakis(3,5-dimethylphenyl)porphyrin (T-m,m'-Me(2)PP), and meso-tetramesitylporphyrin (TMP), and R = Me, Et, (n)Pr, (i)Pr, (n)Bu, (t)Bu, (n)Hex, Bn (benzyl), Ph, and p-MeOC(6)H(4). The upfield shifts in the SH resonances upon coordination of the thiol reflect changes in the porphyrin ring current and are analyzed using an empirical model that depicts quantitatively the nonbonding, electronic, and steric interactions between the thiol ligands, where steric factors dominate, and the porphyrin plane, where electronic factors dominate; such interactions are typically involved in small-molecule recognition within metalloporphyrin systems. Implications of the findings to hemethiolate proteins and surface coordination chemistry are also briefly presented.

Reversible binding of water, methanol, and ethanol to a five-coordinate ruthenium(II) complex.

The known green, five-coordinate, square-pyramidal trans-RuCl(2)(P-N)(PPh(3)) complex reversibly binds water, MeOH and EtOH in the vacant coordination site in the solid state and in CH(2)Cl(2) solution to give pink adducts (P-N = o-diphenylphosphino-N,N'-dimethylaniline). The adducts are well characterized, including X-ray analysis of the aqua complex, trans-RuCl(2)(P-N)(PPh(3))(H(2)O), which crystallizes in two different benzene-solvated forms. Comparison of the structural data with those determined previously for the binding of H(2)S, thiols, and H(2), which form cis-RuX(2)(P-N)(PPh(3))L products (X = Cl, Br; L = a S-ligand or H(2)) reveals the trans-influence trend P > H(2)S ~ thiols > H(2) > Cl ~ Br > H(2)O. Thermodynamic data for the binding of water were estimated in solution by UV-Vis spectroscopy, and ΔH(o) data for the aqua and alcohol adducts in the solid state were obtained by differential scanning calorimetry. Inclusion of published data for the S-ligand adducts reveals the thermal stability trend of the solid complexes as MeSH > MeOH > H(2)S > H(2)O > EtSH > EtOH.

Hydrogenolysis of ß-O-4 lignin model dimers by a ruthenium-xantphos catalyst.

Hydrogenolysis reactions of so-called lignin model dimers using a Ru-xantphos catalyst are presented (xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene). For example, of some nine models studied, the alcohol, 2-(2-methoxyphenoxy)-1-phenylethanol (1), with 5 mol% Ru(H)(2)(CO)(PPh(3))(xantphos) (18) in toluene-d(8) at 135 °C for 20 h under N(2), gives in ~95% yield the C-O cleavage hydrogenolysis products, acetophenone (14) and guaiacol (17), and a small amount (<5%) of the ketone, 2-(2-methoxyphenoxy)-1-phenylethanone (4), as observed by (1)H NMR spectroscopy. The in situ Ru(H)(2)(CO)(PPh(3))(3)/xantphos system gives similar findings, confirming a recent report (J. M. Nichols et al., J. Am. Chem. Soc., 2010, 132, 12554). The active catalyst is formulated 'for convenience' as 'Ru(CO)(xantphos)'. The hydrogenolysis mechanism proceeds by initial dehydrogenation to give the ketone 4, which then undergoes hydrogenolysis of the C-O bond to give 14 and 17. Hydrogenolysis of 4 to 14 and 17 also occurs using the Ru catalyst under 1 atm H(2); in contrast, use of 3-hydroxy-2-(2-methoxyphenoxy)-1-phenyl-1-propanone (7), for example, where the CH(2) of 4 has been changed to CHCH(2)OH, gives a low yield (≤15%) of hydrogenolysis products. Similarly, the diol substrate, 2-(2-methoxyphenoxy)-1-phenyl-1,3-propanediol (9), gives low yields of hydrogenolysis products. These low yields are due to formation of the catalytically inactive complexes Ru(CO)(xantphos)[C(O)C(OC(6)H(4)OMe)=C(Ph)O] (20) and/or Ru(CO)(xantphos)[C(O)CH=C(Ph)O] (21), where the organic fragments result from dehydrogenation of CH(2)OH moieties in 7 and 9. Trace amounts of Ru(CO)(xantphos)(OC(6)H(4)O), a catecholate complex, are isolated from the reaction of 18 with 1. Improved syntheses of 18 and lignin models are also presented.

Ruthenium(II) thiol and H2S complexes: synthesis, characterization, and thermodynamic properties.

The known, green, five-coordinate species trans-RuCl(2)(P-N)(PPh(3)) react with R'SH thiols to give yellow cis-RuCl(2)(P-N)(PPh(3))(R'SH) products (P-N = o-diphenylphosphino-N,N'-dimethylaniline; R' = alkyl). The MeSH and EtSH compounds are structurally characterized, with the former being the first reported for a transition metal-MeSH complex, while the thiol complexes with R' = (n)Pr, (i)Pr, (n)Pn (pentyl), (n)Hx (hexyl), and Bn (benzyl) are synthesized in situ. Other trans-RuX(2)(P-N)(PR(3)) complexes (X = Br, I; R = Ph, p-tolyl) are synthesized, and their H(2)S adducts, of a type reported earlier by our group, are also prepared. Thermodynamic data are presented for the reversible formation of the MeSH and EtSH complexes and the H(2)S analogues. The Ru(II)Cl(2)(P-N)(PPh(3)) complex in solution decomposes under O(2) to form [Ru(III)Cl(P-N)](2)(µ-O)(µ-Cl)(2).

Thiol, disulfide, and trisulfide complexes of Ru porphyrins: potential models for iron-sulfur bonds in heme proteins.

Thirty-two Ru(porp)L(2) complexes have been synthesized, where porp = the dianion of meso-tetramesitylporphyrin (TMP) or meso-tetrakis(4-methylphenyl)porphyrin (H(2)T-pMe-PP), and L = a thiol, a sulfide, a disulfide, or a trisulfide. Species studied were with RSH [R = Me, Et, (n)Pr, (i)Pr, (t)Bu, Bn (benzyl), and Ph], RSR (R = Me, Bn), RSSR (R = Me, Et, (n)Pr, Bn) and MeSS(t)Bu, and RSSSR (R = Me, Bn). All the species except two, which were the isolated Ru(T-pMe-PP)((t)BuSH)(2) and Ru(TMP)(MeSSMe)(2), were characterized in situ. The disulfide complex was characterized by X-ray analysis. (1)H NMR data for the coordinated thiols are the first reported within metalloporphyrin systems, and are especially informative because of the upfield shifts of the axial sulfur-containing ligands due to the porphyrin π-ring current effect, which is also present in the di- and trisulfide species. The disulfide in the solid state structure of Ru(TMP)(MeSSMe)(2) is η(1)(end-on) coordinated, the first example of such bonding in a nontethered, acyclic dialkyl disulfide; (1)H-(1)H EXSY NMR data in solution show that the species undergoes 1,2-S-metallotropic shifts. Stepwise formation of the bis(disulfide) complex from Ru(TMP)(MeCN)(2) in solution occurs with a cooperativity effect, resembling behavior of Fe(II)-porphyrin systems where crystal field effects dominate, but ligand trans-effects are more likely in the Ru system. The η(1)(end-on) coordination mode is also favored for the trisulfide ligand. Discussed also are the remarkable linear correlations that exist between the ring-current shielding shifts for the axial ligand C(1) protons of Ru(porp)(RS(x)R)(2) and x (the number of S atoms). The Introduction briefly reviews literature on Ru- and Fe porphyrins (including heme proteins) with sulfur-containing ligands or substrates, and relationships between our findings and this literature are discussed throughout the paper.

Reactivity of the bridged-sulfide complex Pd2Cl2(µ-S)(µ-dmpm)2 toward electrophiles.

The dipalladium(I) complex Pd(2)Cl(2)(dmpm)(2) (1a) [dmpm = bis(dimethylphosphino)methane] is known to react with elemental sulfur (S(8)) to give the bridged-sulfide complex Pd(2)Cl(2)(µ-S)(dmpm)(2) (2a) but, in the presence of excess S(8), PdCl(2)[P,S-dmpm(S)] (4a) and dmpm(S)(2) are generated. Treatment of 1a with elemental selenium (Se(8)), however, gives only Pd(2)Cl(2)(µ-Se)(dmpm)(2) (3a). Complex 4a is best made by reaction of trans-PdCl(2)(PhCN)(2) with dmpm(S). Complex 2a reacts with MeI to yield initially Pd(2)I(2)(µ-S)(dmpm)(2) and MeCl, and then Pd(2)I(2)(µ-I)(2)(dmpm)(2) and Me(2)S, whereas alkylation of 2a with MeOTf generates the cationic, bridged-methanethiolato complex [Pd(2)Cl(2)(µ-SMe)(dmpm)(2)]OTf (5). Oxidation of 2a with m-CPBA forms a mixture of Pd(2)Cl(2)(µ-SO)(dmpm)(2) and Pd(2)Cl(2)(µ-SO(2))(dmpm)(2), whereas Pd(2)Br(2)(µ-S)(dmpm)(2) reacts selectively to give Pd(2)Br(2)(µ-SO)(dmpm)(2) (6b). Treatment of the Pd(2)X(2)(µ-S)(dmpm)(2) complexes with X(2) (X = halogen) removes the bridged-sulfide as S(8), with co-production of Pd(II)(dmpm)-halide species. X-ray structures of 3a, 5 and 6b are presented. Reactions of dmpm with S(8) and Se(8) are clarified. Differences in the chemistry of the dmpm systems with that of the corresponding dppm systems [dppm = bis(diphenylphosphino)methane] are discussed.

Reactions of the bis(dialkylphosphino)methane complexes Pd2X2(µ-R2PCH2PR2)2 (X = halogen, R = Me or Et) with H2S, S8, COS, and CS2; detection of reaction intermediates.

The Pd(2)X(2)(dmpm)(2) complexes [X = Cl (1a), Br (1b), I (1c); dmpm = bis(dimethylphosphino)methane. In all the dipalladium complexes mentioned in this paper, the dmpm, depm, and dppm ligands (unless stated otherwise) are bridging, but for convenience the µ-symbol is omitted.] react with H(2)S to yield H(2) and the bridged-sulfido complexes Pd(2)X(2)(µ-S)(dmpm)(2) (2a-c), of which 2a and 2b are structurally characterized. With 1a, two rapid reversible equilibria are observed by NMR spectroscopy below -30 °C, and two reaction intermediates are detected; both are likely hydrido(mercapto) species. Reaction of 1a with 1 equiv of elemental sulfur also yields 2a. The reaction of 1a with COS results in the initial formation of Pd(2)Cl(2)(µ-COS)(dmpm)(2) (3) that undergoes decarbonylation to yield 2a and Pd(2)Cl(2)(µ-CO)(dmpm)(2) (4), which is also formed via reversible insertion of the CO into the Pd-Pd bond of 1a. The solid-state molecular structure of the previously reported complex Pd(2)Cl(2)(µ-CS(2))(dmpm)(2) (5), together with solution NMR data for 3 and 5, reveal that the bridging heterocumulene ligands coordinate in an η(2)-C,S fashion. Analogous findings were made for the corresponding Pd(2)X(2)(depm)(2) complexes [X = Cl (1a'), Br (1b'), I (1c'); depm = bis(diethylphosphino)methane], although no µ-COS species was detected. The Pd(2)X(2)(µ-S)(depm)(2) complex was structurally characterized. Differences in the chemistry of the previously studied, corresponding dppm systems (dppm = bis(diphenylphosphino)methane) are discussed.

Reactions of a phosphinoaldehyde with Pd(II), Rh(I), and Ir(I) precursors, including the formation of complexes containing a P,OH-chelated phosphinohemiacetal ligand: a new bonding mode.

The complexes trans-PdCl(2)[eta(1)-P-(Ph(2)P)CH(Ph)CH(Me)CH(OMe)(2)](2) (1) and M(H)Cl[eta(2)-P,OH-(Ph(2)P)CH(Ph)CH(Me)CH(OH)OMe][eta(2)-P,C(O)-(Ph(2)P)CH(Ph)CH(Me)C(O)], M = Rh (3) and Ir (4), are synthesized by reacting the phosphinoaldehyde [3-(diphenylphosphino)-3-phenyl-2-methyl]propionaldehyde [(Ph(2)P)(2)CH(Ph)CH(Me)CHO] with trans-PdCl(2)(PhCN)(2), [RhCl(COD)](2), and [IrCl(COD)](2), respectively, in MeOH; trans-PdCl(2)[eta(1)-P-(Ph(2)P)CH(Ph)CH(Me)CHO](2) (2) is isolated from the same reaction in CH(2)Cl(2). One diastereomer of each of the complexes 1, 3 x MeOH, and 4 x MeOH was characterized by X-ray analysis. The stereochemistry of such complexes in the solid state and in solution (MeOH and CH(2)Cl(2)) is discussed. In CD(2)Cl(2), NMR data suggest that the coordinated hemiacetal moiety of 3 (but not 4) undergoes reversible loss of MeOH; this process is associated with equilibria between various diastereomers of 3 that were investigated by (31)P{(1)H}, (13)C{(1)H}, (1)H, (1)H{(31)P}, and HSQC and HMBC (1)H/(31)P{(1)H} and (1)H/(13)C{(1)H} NMR spectroscopies. Complexes 3 and 4 reveal a new chelate bonding mode via a P atom and the hydroxyl O atom of a hemiacetal. Solvent-dependent stereochemical changes within solution species imply that such chiral phosphinoaldehydes are not likely to be useful ligands for applications in asymmetric catalysis, although conditions are suggested for testing the complexes as potential precursors for nonasymmetric catalytic processes.

Reactions of tertiary phosphines with alcohols in aqueous media.

The phosphines R(2)R'P [R = R' = Me, Et, (n)Pr, (i)Pr, (CH(2))(3)OH; Me(2)PhP and MePh(2)P] react with 2- or 4-hydroxybenzyl alcohols, including "lignin-type" vanillyl, syringyl, and alpha-methylvanillyl alcohols, in a 1:1 ratio in aqueous media, to give zwitterionic phosphobetaine products; these on treatment with aq HCl form the corresponding phosphonium chlorides in good to excellent yields. The syringyl derivative [3,5-(OMe)(2)-4-OH-C(6)H(2)CH(2)PEt(3)]Cl was structurally characterized by X-ray analysis. Kinetically, the reactivity of the benzyl alcohols, studied with the water-soluble [HO(CH(2))(3)](3)P, decreases with substituents in the order 2-hydroxy > 4-hydroxy > vanillyl > syringyl > alpha-methylvanillyl, while 3-hydroxybenzyl alcohol is unreactive; the trend is consistent with reactivity requiring the presence of an ortho- or para-OH substituent in the aromatic ring of the alcohol, and that the reactions proceed via a carbocation species stabilized as a quinone methide. Triethylphosphine reacts with coniferyl alcohol at the C=C moiety to give a zwitterionic intermediate that is again converted by aq HCl to a phosphonium chloride; no reaction was observed with cinnamyl alcohol. The effect on a phenolic pK(a) by incorporation of a phosphonium substituent is also measured.

Synthetic and mechanistic aspects of a new method for ruthenium-metalation of porphyrins and Schiff-bases.

A new method is presented for metalation of a wide range of free-base, neutral, cationic, and anionic porphyrins in refluxing dimethylformamide (DMF) using an easily prepared [Ru(DMF) 6](OTf) 3 complex, and comparisons are made with the more familiar metalation procedure using Ru 3(CO) 12. Both procedures generate Ru (II)(porp)(CO)L complexes (L = solvent); use of the Ru (III)-triflate precursor gives yields comparable to, or greater than, those obtained with the carbonyl, and generates no Ru-chlorin impurities. Mechanistic studies on the meso-tetraphenylporphyrin system reveal that the DMF furnishes the CO, which in the presence of essential water reduces the metal, and metalation likely occurs via a Ru (II)-CO species. Corresponding metalation of tetradentate Schiff-bases gives trans-[Ru (III)(Schiff- base)(DMF) 2]OTf complexes in yields of approximately 50%, a limitation being the accompanying hydrolysis of the Schiff-base through the presence of trace water.

trans-Carbonyl-chloridobis(tri-p-tolyl-phosphine)rhodium(I) acetone solvate.

The title compound, [RhCl(C(21)H(21)P)(2)(CO)]·C(3)H(6)O, was precipitated in trace yield from a reaction of RhCl(cod)(THP) with P(p-tol)(3) in a 1:1 acetone-d(6)/CD(3)OD solution under a hydrogen atmosphere [p-tol = p-tolyl, THP = tris-(hydroxy-meth-yl)phosphine, P(CH(2)OH)(3), and cod = 1,5-cyclo-octa-diene]. The complex displays a square-planar geometry around the Rh(I) atom. The complex mol-ecules and the acetone mol-ecules are linked into a chain along the a axis by inter-molecular C-H⋯Cl and C-H⋯O hydrogen bonds.

Chloridotris[tris-(4-fluoro-phen-yl)phosphine]rhodium(I) methanol solvate.

In the title compound, [RhCl{P(p-FC(6)H(4))(3)}(3)]·CH(3)OH, the Rh atom adopts a distorted square-planar geometry. Rh, Cl and one P atom lie on a mirror plane, as does the solvent molecule. There are two inter-molecular hydrogen bonds, one between the methanol O atom and an aryl H atom (2.51 Å), and one between the Cl atom and the hydr-oxy H atom of methanol [2.34 (3) Å]. The complex precipitates in trace amounts from a reaction between RhCl(cod)(thp) [cod is 1,5-cyclo-octa-diene and thp is tris-(hydroxy-meth-yl)phos-phine] and P(p-FC(6)H(4))(3) under argon in CD(3)OD. Two C(6)H(4)-F units are disordered over two positions; for one the site occupancy factors are ca. 0.53 and 0.47, for the other the values are ca. 0.64 and 0.36. The methyl H atoms of the solvent molecule are disordered across the mirror plane.

New tertiary phosphines from cinnamaldehydes and diphenylphosphine.

A 1:1 hydrophosphination of the olefinic bond of cinnamaldehyde (and substituted ones) with Ph2PH, under argon using neat reagents, gives quantitative formation of the new tertiary phosphines Ph2PCH(Ar)CH2CHO (2) as racemic mixtures (Ar = Ph, p-tol, and p-OMe-C6H4). alpha-Methylcinnamaldehyde similarly affords Ph2PCH(Ph)CH(Me)CHO, but as a mixture of diastereomers with predominantly S,S- and R,R-chirality [diastereomeric ratio (dr) approximately 20]. In a 2:1 reaction of Ph2PH with cinnamaldehyde, hydrophosphination of both the C=C and C=O bonds takes place to give the diphosphine derivative Ph2PCH(Ph)CH2CH(OH)PPh2 (3) as a diastereomeric mixture with dr approximately 2.3. In most organic solvents, the hydrophosphination of the C=O group is reversible, leading to a dynamic equilibrium between 3 and 2, but 3 is stable in coordinating solvents such as DMSO, DMF, and pyridine. X-ray analysis of a P,P-chelated PdCl2(3) complex, formed from trans-PdCl2(PhCN)2 and 3 in MeOH, reveals that the S,S/R,R-enantiomers are favored.

Interaction of tertiary phosphines with lignin-type, alpha,beta-unsaturated aldehydes in water.

To learn more about the bleaching action of pulps by (hydroxymethyl)phosphines, lignin chromophores, such as the alpha,beta-unsaturated aromatic aldehydes, sinapaldehyde, coniferylaldehyde, and coumaraldehyde, were reacted with the tertiary phosphines R2R'P [R = R' = Me, Et, (CH2)3OH, iPr, cyclo-C6H11, (CH2)2CN; R = Me or Et, R' = Ph; R = Ph, R' = Me, m-NaSO3-C6H4] in water at room temperature under argon. In all cases, initial nucleophilic attack of the phosphine occurs at the activated C=C bond to form a zwitterionic monophosphonium species. With the phosphines PR3 [R = Me, Et, (CH2)3OH] and with R2R'P (R = Me or Et, R' = Ph), the zwitterion undergoes self-condensation to give a bisphosphonium zwitterion that can react with aqueous HCl to form the corresponding dichloride salts (as a mixture of R,R- and S,S-enantiomers); X-ray structures are presented for the bisphosphonium chlorides synthesized from the Et3P and Me3P reactions with sinapaldehyde. With the more bulky phosphines, iPr3P, MePPh2, (cyclo-C6H11)3P, and Na[Ph2P(m-SO3-C6H4)], only an equilibrium of the monophosphonium zwitterion with the reactant aldehyde is observed. The weakly nucleophilic [NC(CH2)2]3P does not react with sinapaldehyde. An analysis of some exceptional 1H NMR data within the prochiral phosphorus centers of the bisphosphonium chlorides is also presented.

Formation of a phosphine-phosphinite ligand in RhCl(PRR'2)[P,P-R'(R)POCH2P(CH2OH)2] and R'H from cis-RhCl(PRR'2)2[P(CH2OH)3] via P-C bond cleavage.

Reaction of RhCl(1,5-cod)(THP), where THP = P(CH(2)OH)(3), with several PRR'2 phosphines (R = or not equal R') generates, concomitantly with R'H, the derivatives RhCl(PRR'(2))[P,P-R'(R)POCH(2)P(CH(2)OH)(2)] in two isomeric forms. The hydrogen of the hydrocarbon co-product derives from a THP hydroxyl group which becomes an 'alkoxy' group at the residual PRR' moiety, this resulting in the P,P-chelated R'(R)POCH(2)P(CH(2)OH)(2) ligand. One of the isomers of the PPh(3) system, cis-RhCl(PPh(3))[P,P-P(Ph)(2)OCH(2)P(CH(2)OH)(2)], was structurally characterized (cis refers to the disposition of the P atoms with Ph substituents).

Synthesis and X-ray structures of water-soluble tris(hydroxymethyl)phosphine complexes of rhodium(I).

The water-soluble Rh(I)-THP complexes: RhCl(1,5-cod)(THP) (), [Rh(1,5-cod)(THP)(2)]Cl (), RhCl(THP)(4) (), and trans-RhCl(CO)(THP)(2) () have been synthesized and characterized, where THP = P(CH(2)OH)(3); - are the first potentially useful entries into Rh(I)-THP chemistry, while and are the first structurally characterized Rh(I)-THP complexes.