Phosphine Phosphorus Research Articles

Amine-catalyzed substitution in CpFe(CO)2I by phosphine and bisphosphine ligands.

We have found that amines significantly accelerate iodide substitution in CpFe(CO)2I (1) (Cp = η5-cyclopentadienyl) with phosphines and allow the synthesis of new complexes that are not available through reactions carried out without an amine. The reaction of equimolar amounts of 1 and triphenylphosphine in toluene containing DIPA afforded [CpFe(CO)2PPh3]+I- within 5 min at room temperature in 72% yield (90% after 24 h). DIPA and pyrrolidine gave the highest yields of the tested amines. We performed a similar reaction using model bisphosphines 1,3-bis(diphenylphosphino)ethane (dppe) and 1,1'-bis(diphenylphosphino)ferrocene (dppf). The products depended on the reagent ratio and bore the CpFe(CO)2 moiety coordinated to one or two phosphine phosphorus atoms. Chelates [CpFe(CO)(dppe)]+I- (4) and [Cp2Fe2(CO)4(dppe)]2+2I- (5) were formed in 72% and 98% yield, respectively. We also performed the DIPA-catalyzed reaction of 1 with triethyl phosphite and obtained the product of an Michaelis-Arbuzov-like rearrangement, CpFe(CO)2[P(O)(OCH2CH3)2] (11). All complexes were characterized with spectroscopic analysis by NMR, FT-IR, and ESI-MS, and by XRD for three complexes. To clarify the reaction mechanism, we performed theoretical calculations of the intermolecular interactions between 1 and amine molecules. We propose two possible reaction mechanisms to explain the formation of products.

Structural, Theoretical, and Spectroscopic Study of Mercury(II) Complexes of two New Unsymmetric Phosphorus Ylides

The reaction of Ph2PCH2PPh2 (dppm) with 4-methylphenacyl bromide and 2-(bromoacetyl)naphthalene in chloroform produce the new phosphonium salts [Ph2PCH2PPh2CH2C(O)C6H4Me]Br (1) and [Ph2PCH2PPh2CH2C(O)C10H7]Br (2). Further, by reaction of the monophosphonium salts of dppm with the strong base Et3N the corresponding bidentate phosphorus ylides, Ph2PCH2P(Ph)2 = C(H)C(O)C6H4Me (3) and Ph2PCH2P(Ph)2 = C(H)C(O)C10H7 (4) were obtained. The reaction of these ligands with mercury(II) halides in dry methanol led to the formation of the mononuclear complexes {HgX 2[(Ph2PCH2PPh2C(H)C(O)C6H4Me)]} [X = Cl (5), Br (6), and I (7)] and {HgX 2[(Ph2PCH2PPh2C(H)C(O)C10H7)]} [X = Cl (8), Br (9), and I (10)]. Characterization of the obtained compounds was performed by elemental analysis, IR, 1H, 31P, and 13C NMR spectra. The structure of compounds 3 and 10 are unequivocally determined by single crystal X-ray diffraction techniques. X-ray analysis of 10 reveals the presence of mononuclear complex containing Hg atom in a distorted tetrahedral environment. In all complexes, the title ylides are coordinated through the ylidic carbon and the phosphine phosphorus. Computational studies on ligand 4 and complexes 8, 9, and 10 at DFT (B3LYP) level of theory are also reported. It was shown that the formation of P,C-coordinated 1+1 complex 10 is energetically more favored than corresponding P,P-coordinated 1+2 product. [Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the following free supplemental files: Additional figures]

Computational studies of complexation of nitrous oxide by borane–phosphine frustrated Lewis pairs

Computational studies of complexes Ar(3)B-ONN-PR(3) derived from reactions between borane-phosphine frustrated Lewis pairs and N(2)O reveal several interesting facets. Natural resonance theory calculations support a change in the preferred resonance structure as the Lewis acidity of the borane increases. Potential constitutional isomers where phosphorus binds to oxygen and boron to nitrogen are predicted to be unstable with respect to loss of phosphine oxide and free N(2). Other constitutional isomers represent stationary points on the potential energy surface; most are considerably less stable than the observed complexes, but one is predicted to be as stable. This arises because the dominant resonance form combines alternating charge with the presence of a stabilizing NO double bond. The relationship between Lewis acidity and complex formation for a variety of boranes was explored; the results are consistent with the idea that greater Lewis acidity stabilizes both classical and frustrated Lewis acid-base pairs, but to differing degrees such that both types can entrap N(2)O. Calculations addressing the mechanism of complex formation suggest that N(2)O binds first through the nitrogen to the phosphine phosphorus of the FLP, whereupon boron coordinates the oxygen atom. Studies of the mechanism of the degenerate exchange reaction between (4-F-H(4)C(6))(3)B-ONN-P(t-Bu)(3) and B(C(6)H(4)-4-F)(3), involves a "transition state", with relatively short B-O distances, and so resembles a classical I(a) process. The process involves two barriers, one associated with bringing the incoming borane into proximity with the oxygen, and the other associated with isomerising from a ladle-shaped cis-trans ct conformer to the observed trans-trans tt-type structure. The overall barrier for degenerate exchange was predicted to be between 65 and 110 kJ mol(-1), in fair agreement with experiment. Similar studies of the reaction between (4-F-H(4)C(6))(3)B-ONN-P(t-Bu)(3) and B(C(6)F(5))(3) indicate that this process more closely resembles a classical I(d) process, in that the "transition state" involves long B-O distances. Derivatization of the complexed NNO fragment appears possible; interaction between (F(5)C(6))(3)B-ONN-P(t-Bu)(3) and MeLi suggests stability for the ion pairs (F(5)C(6))(3)B-ON(Me)N-P(t-Bu)(3)(-)/Li(+) and (F(5)C(6))(3)B-ONN(Me)-P(t-Bu)(3)(-)/Li(+).

The First Carbodiphosphorane Complex with Two Palladium Centers Attached to the CDP Carbon: Assembly of a Single-Stranded di-Pd Helicate by the PCP Pincer ligand C(dppm)2

The reaction of the protonated PCP pincer carbodiphosphorane (CDP) complex [PdCl(CH(dppm)2)]Cl2 (1) with [PdCl2(MeCN)2] results in the opening of one ring of the pincer structure and affords the betaine [Pd2Cl5(CH(dppm)2)] (2). The [CH(dppm)2]+ ligand forms a five-membered chelate ring with the Pd(1)Cl2 moiety via the protonated CDP carbon (positively charged) and one phosphine functionality and bridges to the anionic Pd(2)Cl3 fragment via the second phosphine phosphorus. The complex is chiral due to a stereocenter at the protonated CDP carbon atom. Treatment of 2 with water effects deprotonation of the CDP carbon, C–H activation at one methylene group, and the coordination of the second Pd to the CDP carbon. The resulting tricyclic complex [Pd2Cl3(C(dppm)(Ph2CHPh2))] (3) is the first compound with two Pd centers coordinated to a CDP carbon. Compound 3 forms a single-stranded helicate structure and exhibits two interdependent carbon stereocenters, resulting in only two possible enantiomers. The complexes 2·2CH2Cl2 and 3·3CH2Cl2 crystallize in the chiral space group P21, whereby a spontaneous resolution of the enantiomers occurs in both cases.

Oxo-rhenium(V) mixed-ligand complexes with bidentate functionalized phosphines and tridentate Schiff base ligands

A series of monooxo-rhenium(V) mixed-ligand complexes containing bidentate functionalized phosphines and tridentate Schiff base (SB) ligands have been synthesized via ligand-exchange reactions starting from labile Re(V) precursors. A convenient route of synthesis is provided by the isolation of intermediate species such as [Re(O)(L n )Cl 3] − ( 1– 3), (L n =bidentate phosphino-phenolato or phosphino-carboxylato ligands). Subsequent addition of the relevant SB affords neutral mixed-ligand complexes of general formula [Re(O)(L n )(SB m )] ( 1– 3m). By reversing the addition of the two ligands, i.e. SB first followed by functionalized phosphine, the resulting mixed-ligand species do not change formulation. Conventional spectroscopic techniques and the single-crystal X-ray structure determination of the two representative compounds ([Re(O)(L 1)(SB a)] ( 1a) and [Re(O)(L 1)(SB b)] ( 1b)) reveal a distorted octahedral geometry around the rhenium center, with the phosphino-phenolato oxygen located trans to the oxo group and the equatorial sites filled by the SB donors and the phosphine phosphorus. It is worth noting that technetium chemistry works quite differently under the same reaction conditions. In fact, no intermediate species of the type [Tc(O)(L n )Cl 3] − can be isolated with [Tc(O)Cl(L 1) 2] and reduced [Tc(L n ) 3] being the major compounds.

Synthesis and characterization of novel trigonal bipyramidal technetium(III) mixed-ligand complexes with SES/S/P coordination (E = O, N(CH3), S).

Five-coordinate oxotechnetium(V) mixed-ligand complexes [TcO(SES)(S-p-C6H4-OMe)], where SES is a tridentate dithiolato fragment of the type -S(CH2)2E(CH2)2S- (E = O, 1; E = S, 2; E = NMe, 3) are converted via reduction-substitution reactions in the presence of PMe2Ph into the corresponding five-coordinate Tc(III) complexes [Tc(SES)(S-p-C6H4-OMe)(PMe2Ph)] (E = O, 4; E = S, 5; E = NMe, 6). Rearrangement of the original square pyramidal "3 + 1" oxo species to the trigonal bipyramidal "3 + 1 + 1" Tc(III) complexes occurs by placing the three thiolate donors on the basal plane, the phosphine phosphorus, and the heteroatom of the tridentate ligand at the apexes of the bipyramid. These Tc(III) complexes are diamagnetic species, thereby allowing multinuclear NMR characterization in solution, which confirm their structures to be identical to those observed in the solid state via X-ray determinations.

Gold(I) complexes with biologically active thiolate ligands

The reaction of ethanolic solutions of Na(SR) (SR=4-oxo-2-thioxopyrimidines) with [AuClL] (LPPh 3, PPh 2Me and AsPh 3) gives [Au(SR)L]; when PPN[AuCl 2] or NBu 4[AuBr(C 6F 5)] are used instead, PPN[Au(SR) 2] and NBu 4[Au(C 6F 5)(SR)] are obtained. The structure of [Au(SR 1)(PPh 3)] has been established by X-ray diffraction, and shows a linear coordination at gold involving the phosphine phosphorus and the exocyclic sulfur atom of the organic ligand.

Rhenium complexes with phosphine-containing peptides. Synthesis and characterization of oxorhenium(V) complexes with N-{N -[3-(diphenylphosphino)propionyl]glycyl}-L-S -benzylcysteine and its methyl ester

The co-ordination of dipeptides modified with a phosphine group to the ReO 3+ core has been studied, and the new donor sets PN 2 X (X = O or S) achieved. N-{N-[3-(Diphenylphosphino)propionyl]glycyl }-L-S-benzylcysteine (H 3 L 2 ) and its methyl ester derivative (H 2 L 1 ) have been used for preparing six-co-ordinated oxorhenium(V) complexes, providing a new chelating system for targeting 186/188 Re to protein bioactive molecules. The complexes have been characterized by means of UV/VIS, IR, FAB and 1 H NMR spectroscopy. The crystal structures of [ReO(L 2 )(OH 2 )]·H 2 O·MeOH and [ReO(L 1 )Cl] have been established. In both the complexes the co-ordination geometry is distorted octahedral. The ligands are tetradentate, co-ordinating the ReO 3+ moiety through the phosphine phosphorus, the two deprotonated amide nitrogens and the O or S atom from the carboxylate or thioether groups. When the cysteine carboxylic moiety is free, it can replace, in organic solvents, the thioether sulfur to give a stable complex, the fourth donor atom in the equatorial plane being a carboxylate oxygen. In basic medium [ReO(L 1 )Cl] underwent substitution of Cl - by OH - , evidence for the high stability of the PN 2 S donor set.

Hybrid ligands: synthesis, characterization and co-ordinative properties of a mixed phosphine–β-ketophosphorus ylide

Direct C-phosphination at the methyl carbon of the keto-stabilized ylide MeC(O)CHPPh 3 was achieved using 2 equivalents of LiBu and 1 equivalent of PPh 2 Cl. The structure of the resultant phosphine–phosphorus ylide, Ph 2 PCH 2 C(O)CHPPh 3 , was shown by an X-ray diffraction study to comprise a 1:1 mixture of two rotamers built around the CH 2 –C(O) axis, the C(O)CHPPh 3 moiety of both conformers adopting a cisoid form. A rotational barrier of 10 kJ mol -1 between the two isomers was found using molecular-mechanics simulation. Oxidation of the ylide with sulfur resulted in quantitative formation of the corresponding phosphine sulfide Ph 2 P(S)CH 2 C(O)CHPPh 3 . By treating 2 equivalents of Ph 3 PCHC(O)CH 2 PPh 2 (L) with [{Pd(η 3 -C 3 H 4 Me-2)Cl} 2 ], the P-monodentate complex [PdCl(η 3 -C 3 H 4 Me-2)L] 1 was formed quantitatively. Reaction of 2 equivalents of L with [{PdCl(C 6 H 4 CH 2 NMe 2 - o)} 2 ] in tetrahydrofuran afforded, in quantitative yield, the stable cationic complex [Pd(C 6 H 4 CH 2 NMe 2 -o) L]Cl 2 where the hybrid ligand is P,O-bonded to the palladium, thus illustrating the nucleophilic character of the oxygen atom of the ylide. The BF 4 - analogue of the latter complex, 3, prepared in order to exclude counter-anion effects, was obtained by treating 1 with AgBF 4 . The nickel complexes [Ni(η 5 -C 5 Ph 5 )L]X (X = I 4 or Br 5), in which the ligand is bound as in 1 and 2, were obtained by treating the corresponding [Ni(η 5 -C 5 Ph 5 )X(CO)] complexes with the ylide L.

Neutral and cationic nickel(II) complexes of phosphino-amines: [NiCl 2(PMe 2Ph) (PNMe 2)] and [NiCl(PMe 2Ph) (PNMe 2)] PF 6 (PNMe 2 = N, N′-dimethyl-2-(diphenylphosphino)aniline)

A neutral bidentate P,N-ligand combining a hard dimethylamino nitrogen and a soft phosphine phosphorus donor affords the neutral trigonal bipyramidal as well as the cationic square-planar nickel(II) complexes cis-[NiCl 2(PMe 2Ph)(PNMe 2)] and [NiCl(PMe 2Ph)(PNMe 2)]PF 6, respectively. The latter species exhibits an appreciable catalytic activity in propylene oligomerization in the presence of Et 2AlCl as co-catalyst

Crystal and Molecular Structure of a Chelating Ylide Complex of Palladium: [(Benzoylmethylene)diphenyl-2-(diphenylphosphino)ethylphosphorane]dichloropalladium(II) Toluene Solvate

Abstract The crystal structure of the title compound was solved by single-crystal X-ray diffraction techniques. Crystals are monoclinic, space group P21/c, with cell dimensions a=13.39(5), b=16.88(1), c=19.85(6) Å, β=123.54(1)°, Z=4. The final R was 0.065. The ylide ligand coordinates to palladium through the ylide carbon Pd–C, 2.115(15) Å and phosphine phosphorus Pd–P, 2.230(8) Å forming a six-membered chelate ring. The chelating ligand together with two chlorine atoms forms a square-planar geometry around the palladium. The Pd–Cl distances are discussed in terms of trans-influence of the ylide carbon.

Preparation of chelate ylide ligands and their palladium(II) and platinum(II) halide complexes

Keto-stabilized mono-ylides of 1,2-bisdiphenylphosphinoethane and bisdiphenylphosphinomethane, Ph 2P(CH 2) n P +(Ph) 2C -HC(O)R (Ph  C 6H 5; n  1 or 2; R  C 6H 5, CH 3 or OCH 3), and their palladium(II) and platinum(II) halide complexes were prepared and characterized by means of infrared, 1H and 31P NMR spectra. The chelate ylide ligands coordinate to the metal through the ylide carbon and phosphine phosphorus forming a six or five-membered chelate ring. The stability of the MC(ylide) bonding is discussed on the basis of the results of the reaction of the complexes with pyridine.

STRUCTURE OF A CHELATE YLIDE COMPLEX: DICHLORO(BENZOYLMETHYLENEDIPHENYL-2-DIPHENYLPHOSPHINOETHYLPHOSPHORANE)PALLADIUM

Abstract X-ray structure analysis of dichloro(benzoylmethylenediphenyl-2-diphenylphosphinoethylphosphorane)palladium indicates that the ylide carbon, the phosphine phosphorus and two chlorine atoms coordinate to palladium forming a square planar configuration.