P-phenyl Groups Research Articles

Mononuclear closo-ruthenacarborane complexes containing a rare eight-membered metal-diphosphine ring

Reactions of [exo-5,6,10-{Cl(Ph3P)2Ru}-5,6,10-(μ-H)3-10-H-nido-7,8-C2B9H8] (1) with 1,5-bis(diphenylphosphino)pentane (2) in benzene either at ambient temperature for ca 2 days or under gently reflux for 30 min in anaerobic conditions both proceed with the replacement of PPh3 ligands on the ruthenium center with the diphosphine to form diamagnetic (18-electron) closo complex [3,3-{κ2-{Ph2P(CH2)5PPh2}}-3-Cl-3-H-closo-3,1,2-RuC2B9H11] (3). On heating in benzene, 3 in the presence of a small amount of CCl4 affords stable paramagnetic (17-electron) species [3,3-{κ2-{Ph2P(CH2)5PPh2}}-3-Cl-closo-3,1,2-RuC2B9H11] (5) along with traces of ortho-phenylenecycloboronated closo complex, ▪ (7). The latter complex was prepared in higher yields by thermal treatment of either 3 or 5 under more severe conditions in toluene at 110 °C. Thermolysis of 7 in boiling toluene in the presence of a small amount of CCl4 afforded the new paramagnetic complex ▪ (8), featuring bis(ortho-cycloboronation) of both P-phenyl groups located at the same phosphorus atom of the ruthenium bound dppt ligand; a minor amount of chloro-cage-substituted complex ▪ (9) was also isolated from the latter reaction as the by-product. All new closo-ruthenacarboranes obtained were characterized by a combination of analytical, multinuclear NMR (for even-electron species) or EPR (for odd-electron species) data and, in addition, by single-crystal X-ray diffraction studies of three paramagnetic complexes 5, 7 and 8.

Carborane Complexes of Ruthenium(III): Studies on Thermal Reaction Chemistry and the Catalyst Design for Atom Transfer Radical Polymerization of Methyl Methacrylate

The heating of the 18-electron complex [3,3-(dppb)-3-H-3-Cl-closo-3,1,2-RuC(2)B(9)H(11)] (3) in benzene at 80 °C in the presence of a small amount of CCl(4) as initiator afforded paramagnetic 17-electron species [3,3-(dppb)-3-Cl-closo-3,1,2-RuC(2)B(9)H(11)] (4) along with minor amounts of two P-phenylene ortho-cycloboronated derivatives [3-Cl-3,3,8-{Ph(2)P(CH(2))(4)PPh-μ-(C(6)H(4)-ortho)}-closo-3,1,2-RuC(2)B(9)H(10)] (5) and [3,7-Cl(2)-3,3,8-{Ph(2)P(CH(2))(4)PPh-μ-(C(6)H(4)-ortho)}-closo-3,1,2-RuC(2)B(9)H(10)] (6) in total yield of ca. 80%. The heating of either 3 or 4 in toluene at 95 °C in the absence of CCl(4) led to the selective formation of 5, which was isolated in 64% and 46% yield, respectively. Thermolysis of 3 at higher temperatures (boiling toluene, 110 °C) gives novel paramagnetic species [3-Cl-3,3,7,8-{Ph(2)P(CH(2))(4)P-μ-(C(6)H(4)-ortho)(2)}-closo-3,1,2-RuC(2)B(9)H(9)] (7) featuring bis(ortho-cycloboronation) of both P-phenyl groups at the same phosphorus atom of the ruthenium-bound dppb ligand. All new paramagnetic complexes 4-7, as well as starting diamagnetic species 3, were characterized by single-crystal X-ray diffraction and, in addition, by EPR spectroscopic studies of odd-electron complexes. Ruthenacarboranes 3-5 and 7 all display high efficiency as catalysts for the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). Complex 5 gave the best catalyst performance in terms of polydispersity; the PDI (M(w)/M(n)) of the polymer samples is as low as 1.15.

Kinetic and Mechanistic Investigation of Metallacycle Ring Opening in an Ortho-Metalated Lutetium Aryl Complex

Reactivity involving metallacycle ring opening of ortho-metalated bis(phosphinimine)carbazolide complexes (LPh-κ3N,κ2CP-Ph)Lu(THF) (1a) and (LPipp-κ3N,κ2CP-Ph)Lu(THF) (1b); L = [1,8-(Ph2P═NAr)2dmc]; Ar = Ph (LPh), p-isopropylphenyl (LPipp); dmc = 3,6-dimethylcarbazolide) is described. Reaction of 1a,b with bulky anilines (2,4,6-trimethylaniline, MesNH2; 2,4,6-triisopropylaniline, TripNH2) promoted metallacycle ring opening of two ortho-metalated P-phenyl groups to liberate the bis(anilide) products (LPh-κ3N)Lu(NHMes)2 (2) and (LPipp-κ3N)Lu(NHTrip)2 (3). Regardless of the quantity of TripNH2 or MesNH2 utilized, double ring opening always prevailed to afford the bis(anilide) product, rather than the mono(anilide). In contrast, reaction of complex 1b with the bulkier reagent 2,4,6-tri-tert-butylaniline (Mes*NH2) only caused metallacycle ring opening of one ortho-metalated P-phenyl group, affording the mono(anilide) complex (LPipp-κ3N,κCP-Ph)Lu(NHMes*) (4) exclusively. Complex 4 rapidly undergoes an intramole...

Reactivity of an N-mesityl bis(phosphinimino)methane with group 10 metals

In an attempt to form a group 10 ‘carbenoid’ derivative by double deprotonation of the N-mesityl substituted bis(phosphinimino)methane [CH 2(Ph 2P N-2,4,6-Me 3C 6H 2) 2], reaction with [PdCl 2(MeCN) 2] yielded a singly metallated dichloropalladate(II) complex as the only product. This was completely characterised specroscopically and by single crystal crystal X-ray diffraction. In contrast, reaction of [CH 2(Ph 2P N-2,4,6-Me 3C 6H 2) 2] with [PtMe 2(COD)] produced a bis(phosphinimino)methanide complex, which had also undergone ortho-metallation of two P-phenyl groups to effect a triple C–H activation reaction.

Resonance stabilization and gas phase protonation in phosphorus ylides: probing through MO and DFT computations

Protonation energy (PE) calculations at the MP2/6-31G* level of theory on a set of resonance stabilized model ylides reveal that, resonance effect make these ylides multi-site basic. In some cases the ylidic carbon is not the most favored site of protonation and points out to the stability of P +–C − bond. B3LYP/6-31G* calculations yield closely related PE values, indicating its validity. The protonation energy of these ylides are intermediate to those of proton sponges and super bases. PM3 calculations were used to calculate proton affinity (PA) values for a set of the most common triphenylphosphine family of ylides. The PA values of the model ylides at PM3 level bear close resemblances to those calculated at the MP2/6-31G* and B3LYP/6-31G* levels of theory, indicating the inconsiderable contribution of zero point vibration energy (ZPVE) to the PA of these ylides. The proton affinity of the metallated ylide, Ph 3PCHLi is computed to be 287.6 kcal/mol and becomes the metal-ylide upon protonation. Introduction of nine NMe 2 groups on the three P-phenyl groups of Ph 3P CH 2 increases the PA to 301.6 kcal/mol.

Picolyl Armed C-1,2 Alternate Tetrahomodioxacalix[4]arene Tetraamides

A series of benzyl, 2-picolyl, 3-picolyl armed tetrahomodioxacalix[4]arene tetraamideswith four p-phenyl groups on the upper rim were synthesized. They were found to be in the C-1,2-alternate conformation by 1H, 13C NMR, andX-ray crystal structure.The nitrogen atom of the 2-picolyl group played an important role in the metal ion complexation.

Reduction of hafnium(IV) complexes in the presence of molecular nitrogen: Attempts to form dinitrogen complexes of the heaviest group 4 element

The reaction of [P2N2]Li2(dioxane)2 with HfCl4(THF)2 (where [P2N2] = PhP(CH2SiMe2NSiMe2CH2)2PPh) results in the formation of the hafnium dichloride complex [P2N2]HfCl2 (1). The behaviour of 1 as a potential precursor in the generation of a dinitrogen coordination complex is described. Reduction of 1 with potassium-graphite (C8K), under dinitrogen, under a variety of conditions led to a number of products, one of which is the dinuclear derivative with bridging P-phenyl groups that has the general formula {[P2N2]Hf}2 (2). Reduction of the hafnium diiodide [P2N2]HfI2 (3) — prepared via the reaction of 1 with excess Me3SiI — with C8K results in the formation of ([P2N2]Hf)2(µ-η2:η2-N2) (4) as the major product of the reaction, while {[P2N2]Hf}2 (2) and [P2N2]Hf(C7H8) (5) appear to be minor products. Reaction of 1 with 2 equiv of MeMgCl gives [P2N2]HfMe2 (6), which, upon exposure to an atmosphere of H2, gives the hafnium tetrahydride {[P2N2]Hf}2(m-H)4 (7).Key words: hafnium, dinitrogen, reduction, coordination chemistry, hydride, mixed donor ligands.

Photoluminescence properties of four-coordinate gold(I)-phosphine complexes of the types [Au(diphos)2]PF6 and [Au2(tetraphos)2](PF6)2.

Numerous reports describe the photoluminescence of two- and three-coordinate gold(I)-phosphine complexes, but emission in their analogous four-coordinate complexes is almost unknown. This work examines the luminescence of tetrahedral gold(I) complexes of the types [Au(diphos)(2)]PF(6) (diphos = 1,2-bis(diphenylphosphino)ethane, 1) and [Au(2)(tetraphos)(2)](PF(6))(2) (tetraphos = (R,R)-(+/-)/(R,S)-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane, (R,R)-(+/-)/(R,S)-2). Although nonemitting in solution, these complexes luminesce with an intense yellow color (lambda(max) 580-620 nm) at 293 K in the solid state or when immobilized as molecular dispersions within solid matrixes. The excited-state lifetimes of the emissions (tau 4.1-9.4 micros) are markedly dependent on the inter- and intramolecular phenyl-phenyl pairing interactions present. At 77 K in an ethanol glass, two transitions are observed: a minor emission at lambda(max) 415-450 nm and a major emission at lambda(max) 520-595 nm. For [Au(1)(2)]PF(6), lifetimes of tau 251.0 +/- 20.5 micros were determined for the former transition and tau 14.9 +/- 4.6 micros for the latter. Density functional theory (DFT) calculations and comparative studies indicate that the former of these emissions involves triplet LMCT pi(Ph) --> Au(d)-P(p) transitions associated with individual P-phenyl groups. The latter emissions, which are the only ones observed at 293 K, are assigned to LMCT pi(Ph-Ph) --> Au(d)-P(p) transitions associated with excited P-phenyl dimers. Other tetrahedral gold(I)-phosphine complexes containing paired P-Ph substituents display similar emissions. The corresponding phosphine ligands, whether free, protonated, or bound to Ag(I), do not exhibit comparable emissions. Far from being rare, luminescence in four-coordinate Au(I)-phosphine complexes appears to be general when stacked P-phenyl groups are present.

Syntheses and conformations of tetrahomodioxacalix[4]arene tetraamides and tetrathioamides.

A series of tetrahomodioxacalix[4]arene tetraamides and tetrathioamides with four p-phenyl groups on their upper rim were synthesized. From the (1)H and (13)C NMR and crystal structure, N-butylamido homooxacalix[4]arene (4) was found to be in the 1,3-alternate conformation and has intramolecular hydrogen bonding between N-H and facing oxygen atoms of the carbonyl O=C group. This hydrogen bonding decreased the metal ion complex ability. Transformation of the 1,3-alternate N-butylamido (4) into N-butylthioamido homooxacalix[4]arene (5) using Lawesson's reagent gave a conformational change to the C-1,2-alternate.

Synthesis of a tetrahomodioxacalix[4]arene tetraamide and the crystal structure of its lead ion complex.

The 1,4-alternate tetrahomodioxacalix[4]arene tetraamide 4 with four p-phenyl groups on its upper rim was synthesized. In two-phase metal picrate extraction, 4 exhibited Pb2+ selectivity with formation of a 1:1 complex in chloroform. In the solid-state structure of the 4*Pb(Pic)2 complex, Pb2+ is bound by the carbonyl oxygens of two adjacent amide groups and an aryl-alkyl ether oxygen atom of one of these amide-containing substituents. The crystal structure and 1H NMR spectrum of the 4*Pb2+ complex reveals pi-metal ion complexation of one aromatic ring in the ligand with Pb2+.

An NMR study of the solution conformations of di(tertiary phosphine) complexes of orthopalladated 1-phenyl-1-(N,N-dimethylamino)ethane

NOE intensities derived primarily from 2-D NMR ROESY spectra were used to study the solution conformations of the chelate rings of the (R)- and (S)-[1-phenyl-1-(N,N-dimethylamino)ethane][(2R,3R)-bis(diphenylphosphino)butane]palladium(II) cations, 3 and 4. In each, the diphosphine ring adopts a conformation with both N-methyl groups equatorial owing to potential unfavourable trans-annular methyl–phenyl interactions in the alternative conformation with axial methyl groups. For the orthometallated chelate ring the population of the conformer with C-methyl equatorial is less than 10% in 4, but is close to 55% in 3. This contrasting behaviour is attributed to inter-annular steric interactions between the N-methyl and the P-phenyl groups which also lead to a weakening of the Pd–N bond in 3 and can account for the enantioselectivity of the orthopalladated 1-phenyl-1-(N,N-dimethylamino)ethane moiety when used as a resolving agent.

Quantitative ortho-cycloboronation of P-phenyl groups in metallaborane chemistry and the crystal and molecular structure of the novel iso-closo-ten-vertex metallaborane [1,1,1-H(PPh3)(Ph2P-ortho-C6H4)-iso-closo-(1-IrB9H8-2-)

High-yield ortho-cycloboronation reactions of P-phenyl groups on phosphine ligands in iridadecaboranes accompany both nido cluster expansion and nido→close cluster closing processes that are associated with changes in the formal oxidation state of the metal atom; one of the products has a novel iso-closo-ten-vertex iridium (V)netallaborane cluster structure of idealized C3vsymmetry (lrB3B3B3).

Novel Reactions of Phosphorus Ylides with Carbonyl(cyclopentadienyl)metal Complexes: Preparative Access to μ‐Alkylidene Complexes and Unexpected Acylations

[η5-CpFe(CO)2]2 undergoes a previously unknown type of reaction with phoshorus ylides Ph3PCHR (RH, Me, iPr) to give the cis- and trans-alkyli-ene complexes (1) and (2) and a small amount of the organometal-substituted ylide (3), Surprisingly, analogous manganese complexes react with methylenephosphorane with ortho-acylation of one of the P-phenyl groups.