Dinitrogen Complexes of Sulfur-Ligated Iron

We report a unique class of dinitrogen complexes of iron featuring sulfur donors in the ancillary ligand. The ligands utilized are related to the recently studied tris(phosphino)silyl ligands (2-R_2PC_6H_4)_3Si (R = Ph, iPr) but have one or two phosphine arms replaced with thioether donors. Depending on the number of phosphine arms replaced, both mononuclear and dinuclear iron complexes with dinitrogen are accessible. These complexes contribute to a desirable class of model complexes that possess both dinitrogen and sulfur ligands in the immediate iron coordination sphere

New heterodonor phosphine and bipyridine ligands

AbstractTwenty-seven phosphine and six bipyridine ligands were synthesised and characterized. Additionally, a new route to the family of phosphine ligands via o-thioanisyldichlorophosphine was found. The phosphine ligands contain thiomethylphenyl, methoxyphenyl, dimethylaminophenyl, pyridyl, naphthyl and anthracenyl groups, and the bipyridine ligands thiomorpholine and piperidine groups. Metal complexes of 3-pyridyldiphenylphosphine, 6,6'-bis(methylthiomorpholine)-2,2'-bipyridine and 4,4'-dimethyl-6,6'-bis(methylthiomorpholine)-2,2'-bipyridine were prepared.Ligands and complexes were characterized by ¹H-, ¹³C-, ³¹P- and two-dimensional HSQC-NMR spectroscopy, and crystal structures were determined for the ligands and two of the metal complexes. Tertiary phosphine ligands were prepared for catalytic purposes and tested in hydroformylation reaction at the Helsinki University of Technology and the University of Joensuu. Bipyridine ligands were designed for bimetallic coordination.The phosphine ligands cover a wide range of electronic and steric properties. The spectroscopic parameters and crystal structures were studied with the purpose of charting trends in the basicities and steric effects of the ligands.Academic Dissertation to be presented with the assent of the Faculty of Science, University of Oulu, for public discussion in Raahensali (Auditorium L 10), on May 28th, 1999, at 12 noon.Abstract Twenty-seven phosphine and six bipyridine ligands were synthesised and characterized. Additionally, a new route to the family of phosphine ligands via o-thioanisyldichlorophosphine was found. The phosphine ligands contain thiomethylphenyl, methoxyphenyl, dimethylaminophenyl, pyridyl, naphthyl and anthracenyl groups, and the bipyridine ligands thiomorpholine and piperidine groups. Metal complexes of 3-pyridyldiphenylphosphine, 6,6'-bis(methylthiomorpholine)-2,2'-bipyridine and 4,4'-dimethyl-6,6'-bis(methylthiomorpholine)-2,2'-bipyridine were prepared. Ligands and complexes were characterized by ¹H-, ¹³C-, ³¹P- and two-dimensional HSQC-NMR spectroscopy, and crystal structures were determined for the ligands and two of the metal complexes. Tertiary phosphine ligands were prepared for catalytic purposes and tested in hydroformylation reaction at the Helsinki University of Technology and the University of Joensuu. Bipyridine ligands were designed for bimetallic coordination. The phosphine ligands cover a wide range of electronic and steric properties. The spectroscopic parameters and crystal structures were studied with the purpose of charting trends in the basicities and steric effects of the ligands

Electrochemistry of ferrocenylphosphines FcCH₂PR₂ (Fc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄); R=Ph, CH₂OH and CH₂CH₂CN), and some phosphine oxide, phosphine sulfide, phosphonium and metal complex derivatives

Electrochemical studies of the free ferrocenylphosphine ligands FcCH₂PR₂ (Fc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄); R=Ph, CH₂OH and CH₂CH₂CN) and some phosphine oxide, phosphine sulfide, phosphonium and metal derivatives are described. The free ligands exhibit complex voltammetric responses due to participation of the phosphorus lone pair in the redox reactions. Uncomplicated ferrocene-based redox chemistry is observed for PV derivatives and when the ligands are coordinated in complexes cis-PtCl₂[FcCH₂P(CH₂OH)₂], PdCl₂[FcCH₂P(CH₂OH)₂], [Au{FcCH₂P(CH₂OH)₂}₂]Cl, RuCl₂(η⁶-C₁₀H₁₄)[FcCH₂P(CH₂OH)₂] and RuCl₂(η⁶-C₁₀H₁₄)(FcCH₂PPh₂). The reaction pathways of the free ligands after one-electron oxidation have been examined in detail using voltammetry, NMR spectroscopy and electrospray mass spectrometry. Direct evidence for formation of a P---P bonded product is presented

Stereoelectronic effects on the binding of neutral Lewis bases to CdSe nanocrystals

Using P-31 nuclear magnetic resonance (NMR) spectroscopy, we monitor the competition between tri-nbutylphosphine (Bu3P) and various amine and phosphine ligands for the surface of chloride terminated CdSe nanocrystals. Distinct P-31 NMR signals for free and bound phosphine ligands allow the surface ligand coverage to be measured in phosphine solution. Ligands with a small steric profile achieve higher surface coverages (Bu3P = 0.5 nm(-2), Me2P-n-octyl = 2.0 nm(-2), NH2Bu = >3 nm(-2)) and have greater relative binding affinity for the nanocrystal (binding affinity: Me3P > Me2P -n-octyl similar to Me2P -n-octadecyl > Et3P > Bu3P). Among phosphines, only Bu 3 P and Me2P-n-octyl support a colloidal dispersion, allowing a relative surface binding affinity (K-rel) to be estimated in that case (K-rel = 3.1). The affinity of the amine ligands is measured by the extent to which they displace Bu3P from the nanocrystals (K-rel: H2NBu similar to N-n-butylimidazole > 4-ethylpyridine > Bu3P similar to HNBu2 > Me2NBu > Bu3N). The affinity for the CdSe surface is greatest among soft, basic donors and depends on the number of each ligand that bind. Sterically unencumbered ligands such as imidazole, pyridine, and n-alkylamines can therefore outcompete stronger donors such as alkylphosphines. The influence of repulsive interactions between ligands on the binding affinity is a consequence of the high atom density of binary semiconductor surfaces. The observed behavior is distinct from the self-assembly of straight-chain surfactants on gold and silver where the ligands are commensurate with the underlying lattice and attractive interactions between aliphatic chains strengthen the binding

Structural studies on the interactions of a P2N tridentate ligand with copper(I) silver(I) and S : a dissertation presented in partial fulfilment of the degree of Master of Philosophy at Massey University

This thesis presents a study of the coordination chemistry, chemical reactivity, spectroscopy, structure and bonding of the hybrid polydentate ligand 2-(diphenylphosphino)-N-[2-(diphenylphosphino)benzylidene]benzeneamine (PNCP) with copper(I), silver(I) and sulfur. The hybrid polydentate (PNCP) ligand contains two inequivalent phosphorus (soft) and one nitrogen (hard) donor atoms, Chapter One is a brief overview of tertiary phosphines used as monodentate, bidentate, tridentate and polydentate ligands with transition metals. In Chapter Two, the preparation structure and characterisation of PNCP have been studied. Reactions of PNCP with sulphur have been investigated and a small site selectivity for one of the P atoms noted. Experiments have also included selective synthesis of the unsymmetrical mono-sulphide tertiary phosphine ligands SPNCP, PNCPS and of the di-sulfide SPNCPS ligand, as well as a study on the molecular structure of the 3-coordinate complex, [Cu(SPNCPS)]CIO₄. In Chapter Three the preparation of a series of copper(I) complexes of the general formula [Cu(PNCP)ClO₄] and [Cu(PNCP)L]ClO₄ (L- ligands containing S, N donor atoms) have been reported. The crystal structure of [Cu(PNCP)ClO₄] has been determined, and shows PNCP acts as a tridentate ligand coordinated to copper(I) via two phosphorus and one nitrogen donor atoms. The copper(I) atom has a distorted tetrahedral environment with two short Cu-P bonds and a slightly long Cu-N bond. In Chapter Four, studies on the preparation of the mononuclear complex [Ag(PNCP)ClO₄] and the dinuclear complex [Ag(PNCP)(SCN)]₂ are presented. Both complexes were characterized by a variety of physicochemical techniques. The tridentate behaviour of PNCP in the complex [Ag(PNCP)ClO₄] was established but the Ag-N bond was long and weak. In the complex [Ag(PNCP)(SCN)]₂ the Ag-N bond not exist and PNCP acts as a bidentate ligand

Ruthenium-Based Heterocyclic Carbene-Coordinated Olefin Metathesis Catalysts

The fascinating story of olefin (or alkene) metathesis (eq 1) began almost five decades ago, when Anderson and Merckling reported the first carbon-carbon double-bond rearrangement reaction in the titanium-catalyzed polymerization of norbornene. Nine years later, Banks and Bailey reported “a new disproportionation reaction . . . in which olefins are converted to homologues of shorter and longer carbon chains...”. In 1967, Calderon and co-workers named this metal-catalyzed redistribution of carbon-carbon double bonds olefin metathesis, from the Greek word “μετάθεση”, which means change of position. These contributions have since served as the foundation for an amazing research field, and olefin metathesis currently represents a powerful transformation in chemical synthesis, attracting a vast amount of interest both in industry and academia

Synthesis, properties, and some rhodium, iridium, and platinum complexes of a series of bulky m-terphenylphosphine ligands

A series of sterically demanding aryl phosphine ligands (L) bearing terphenyl substituents, PR2Ar′ (R = hydrocarbyl, Ar′ = 2,6-diarylphenyl radical) has been prepared and characterized. The stability of these ligands towards oxidation in the air has been tested, and theoretical and experimental studies aimed to provide information on their electronic and steric properties have been performed. Treatment of the metal dimers [MCl(COD)]2(M = Rh, Ir; COD = 1,5-cyclooctadiene) with ligands PMe2ArXyl2(L1) and PMe2ArDipp2(L5), in a 1:1 metal:ligand ratio, afforded the expected square-planar 16-electron complexes [MCl(COD)(PMe2ArXyl2)] and [MCl(COD)(PMe2ArDipp2)], respectively. These compounds were readily converted into the corresponding dicarbonyl derivatives, [MCl(CO)2(PMe2ArXyl2)] and [MCl(CO)2(PMe2ArDipp2)], respectively. While the expected κ1-P coordination mode of the PR2Ar′ ligands is found for these rhodium and iridium species, the mononuclear Pt(II) derivative obtained by reaction of PtCl2with PMe2ArDipp2has composition [PtCl2(PMe2ArDipp2)], and exhibits a bidentate κ1-P, η1-arene coordination mode involving one of the ipso carbon atoms of a flanking terphenyl aryl ring. The corresponding carbonyl compound [PtCl2(CO)(PMe2ArDipp2)], was generated under a CO atmosphere and exhibits κ1-P coordination mode.Ministerio de Ciencia CTQ2013-42501-P, CTQ2014-51912-REDC, CTQ-2014-52769-C3-3-RJunta de Andalucía FQM-119 P09-FQM-4832, FQM-2126European Union 26722

Synthesis of neutral nickel catalysts for ethylene polymerization – the influence of ligand size on catalyst stability

A facile synthesis of nickel salicylaldimine complexes with labile dissociating ligands is described. In addition to producing highly active ethylene polymerization catalysts, important insights into the effect of ligand size on catalyst stability and information on the mechanism of polymerization are provided

A homoleptic phosphine adduct of Tl(I)

A homoleptic phosphine adduct of thallium(I) supported by a tris(phosphino)borate ligand has been isolated and structurally characterized