The organometallic chemistry of conjugated, low-coordinate phosphacarbon compounds

Organometallic complexes incorporating low-coordinate phosphorus have been synthesised with a view to better understanding the physical and electronic properties and reactivity of such compounds, along with synthetic methodologies to furnish them. Novel ruthenium complexes of the type [Ru(CO){κ3-N,C,P-P(PzR′R″)CH(R)}(PPh3)2] (Pz = pyrazolyl) have been synthesised via addition of pyrazolates to complexes of the type RuCl(CO)(PPh3)2(P=CHR). The general structure of the resultant products was elucidated, with a Ru–C–P three-membered ring and bridging pyrazolyl unit confirmed by heteronuclear NMR spectroscopy and X-ray diffraction studies. The nature of the R groups was found to affect the nature of the P–C bond, which lies between a typical single and double P–C bond. The formation of these complexes demonstrated for the first time the ambiphilic nature of the parent ruthenaphosphaalkenyl systems, which was explored by both DFT calculations and their reactivity upon addition of various nucleophiles and electrophiles. A range of extended π-systems have been sought for their potential utility in the synthesis of phosphapolyynyl fragments. Complexes of the type [Tp′M(CO)2(≡CC≡CR)] were pursued, (where R = CO2R’) via a variety of synthetic protocols including traditional Sonogashira methodologies, in situ formation of the propargylidyne moiety (M≡C≡C–) and cross-coupling reactions between a terminal alkyne and Au(PPh3)-terminated propargylidynes. Additionally, a range of metal–alkynyl complexes were pursued via vinylidene/alkyne tautomerism reactions. In particular, the successful synthesis of a range of complexes of the type [RuCl(dppe)2(=CH=CR)][OTf] and [RuCl(dppe)2(C≡CR)] is discussed with characterization of the novel compounds by IR and heteronuclear NMR spectroscopies, mass spectrometry and X-ray diffraction studies. Finally, synthesis of a novel series of cyaphide-containing compounds is demonstrated. The physical and chemical properties of this elusive ligand are discussed and the electronic properties studied computationally. Attempts were also made to furnish complexes with η1-coordination of the phosphorus lone pair to a second metal centre, i.e. complexes of the type [(dppe)2(RC≡C)Ru–C≡P–MLn]

Ruthenaphosphaalkenyls: synthesis, structures, and their conversion to η2‑phosphaalkene complexes

The ruthenaphosphaalkenyls [Ru{PCH-(SiMe2R)}Cl(CO)(PPh3)2] (R = Me, Ph, Tol) have been prepared in good yield by the facile hydroruthenation of the respective phosphaalkynes, RMe2SiCP, with [RuHCl(CO)-(PPh3)3]; all three compounds have been structurally characterized in the solid state. Complemented by DFT studies of these, and the precedent [Ru{PCH(tBu)}Cl(CO)(PPh3)2], the phosphaalkenyl moieties have been established unequivocally to behave as one-electron donors to the coordinately unsaturated, 15-electron “RuCl(CO)(PPh3)2” fragment, corroborating an earlier demonstration of nucleophilic character at phosphorus within the tert-butyl system. Notwithstanding, the ruthenaphosphaalkenyls are shown to react with the nucelophiles Lipz′ (pz′ = pz, pz*, pzH,CF3, pzMe,CF3) to afford the η1,η2-chelated pyrazolylphosphaalkene complexes [Ru{η1-N:η2-P,C-P(pz′)CH(R)}(CO)(PPh3)2], which feature a three-membered metallacyclic (Ru−C−P) core. The nature of these novel compounds is discussed, alongside preliminary insight into the process by which they are formed

Cyaphide-alkynyl complexes: metal-ligand conjugation and the influence of remote substituents

A homologous series of novel trans-cyaphide-alkynyl complexes, viz. trans-[Ru(dppe)2(CP)(CCC6H4R-p)] (R = Me, H, F, CO2Me, NO2) is prepared and comprehensively characterised, alongside their parent phosphaalkyne-complex cations trans-[Ru(dppe)2(1-PCSiMe3)(CCC6H4R-p)]+. Structural data for trans-[Ru(dppe)2(CP)(CCC6H4R-p)] (R = Me, F) and trans-[Ru(dppe)2(1-PCSiMe3)(CCC6H4R-p)]+ (R = F, CO2Me) are described, along with that for the previously reported trans-[Ru(dppe)2(CP)(CCCO2Me)]. NMR spectroscopic data indicate significant influence of the remote aromatic substituent over the properties of the cyaphide ligand, in line with the Hammett parameter (p), suggesting appreciable ‘communication’ along the through-conjugate chain. Cyclic voltammety shows irreversible oxidative behaviour, at more anodic Epa than in the respective alkynyl-chloride complexes, though apparently moderated by the remote substituent

Synthesis and electronic structure of the first cyaphide-alkynyl complexes

The novel complexes trans-[Ru(dppe)2(CCR)(CP)] (R = CO2Me, C6H4OMe), the first to incorporate cyaphide as part of a conjugated system, are obtained in facile manner. The electronic structure of these compounds is probed by X-ray, DFT and UV/Vis studies

Ambiphilic reactivity of a ruthenaphosphaalkenyl: synthesis of P-pyrazolylphosphaalkene complexes of ruthenium(0)

The novel ruthenaphosphaalkenyl complex [Ru{P═CH(SiMe3)}Cl(CO)(PPh3)2], prepared from [RuHCl(CO)(PPh3)3] and Me3SiC≡P, exhibits ambiphilic behavior, reacting at phosphorus with both nucleophiles and electrophiles. Its reaction with Li(pz′) or K[HB(pz′)3] (pz′ = pz, pz*) affords [Ru{η1-N:η2-P,C-P(pz′)═CH(SiMe3)}(CO)(PPh3)2], a rare example of a ruthenium(0) η2-phosphaalkene complex and the first example of a P-pyrazolylphosphaalkene. Conversely, reaction with the electrophilic PhHgCl leads to metalation at phosphorus, affording [Ru{η1-P(HgPh)═CH(SiMe3)}Cl2(CO)(PPh3)2]

Ruthenaphosphaalkenyls: Synthesis, Structures, and Their Conversion to η²‑Phosphaalkene Complexes

The ruthena­phospha­alkenyls [Ru­{PCH­(SiMe₂R)}­Cl­(CO)­(PPh₃)₂] (R = Me, Ph, Tol) have been prepared in good yield by the facile hydroruthenation of the respective phospha­alkynes, RMe₂SiCP, with [RuHCl­(CO)­(PPh₃)₃]; all three compounds have been structurally characterized in the solid state. Complemented by DFT studies of these, and the precedent [Ru­{PCH­(^<i>t</i>Bu)}­Cl­(CO)­(PPh₃)₂], the phospha­alkenyl moieties have been established unequivocally to behave as one-electron donors to the coordinately unsaturated, 15-electron “RuCl­(CO)­(PPh₃)₂” fragment, corroborating an earlier demonstration of nucleophilic character at phosphorus within the <i>tert-</i>butyl system. Notwithstanding, the ruthena­phospha­alkenyls are shown to react with the nucelophiles Lipz′ (pz′ = pz, pz*, pz^H,CF₃, pz^Me,CF₃) to afford the η¹,η²-chelated pyrazolyl­phospha­alkene complexes [Ru­{η¹-<i>N</i>:η²<i>-P,C-</i>P­(pz′)CH­(R)}­(CO)­(PPh₃)₂], which feature a three-membered metallacyclic (Ru–C–P) core. The nature of these novel compounds is discussed, alongside preliminary insight into the process by which they are formed

Ruthenaphosphaalkenyls: Synthesis, Structures, and Their Conversion to η²‑Phosphaalkene Complexes

The ruthena­phospha­alkenyls [Ru­{PCH­(SiMe₂R)}­Cl­(CO)­(PPh₃)₂] (R = Me, Ph, Tol) have been prepared in good yield by the facile hydroruthenation of the respective phospha­alkynes, RMe₂SiCP, with [RuHCl­(CO)­(PPh₃)₃]; all three compounds have been structurally characterized in the solid state. Complemented by DFT studies of these, and the precedent [Ru­{PCH­(^<i>t</i>Bu)}­Cl­(CO)­(PPh₃)₂], the phospha­alkenyl moieties have been established unequivocally to behave as one-electron donors to the coordinately unsaturated, 15-electron “RuCl­(CO)­(PPh₃)₂” fragment, corroborating an earlier demonstration of nucleophilic character at phosphorus within the <i>tert-</i>butyl system. Notwithstanding, the ruthena­phospha­alkenyls are shown to react with the nucelophiles Lipz′ (pz′ = pz, pz*, pz^H,CF₃, pz^Me,CF₃) to afford the η¹,η²-chelated pyrazolyl­phospha­alkene complexes [Ru­{η¹-<i>N</i>:η²<i>-P,C-</i>P­(pz′)CH­(R)}­(CO)­(PPh₃)₂], which feature a three-membered metallacyclic (Ru–C–P) core. The nature of these novel compounds is discussed, alongside preliminary insight into the process by which they are formed

Ambiphilic Reactivity of a Ruthenaphosphaalkenyl: Synthesis of <i>P</i>‑Pyrazolylphosphaalkene Complexes of Ruthenium(0)

The novel ruthenaphosphaalkenyl complex [Ru­{PCH­(SiMe₃)}­Cl­(CO)­(PPh₃)₂], prepared from [RuHCl­(CO)­(PPh₃)₃] and Me₃SiCP, exhibits ambiphilic behavior, reacting at phosphorus with both nucleophiles and electrophiles. Its reaction with Li­(pz′) or K­[HB­(pz′)₃] (pz′ = pz, pz*) affords [Ru­{η¹-<i>N</i>:η²<i>-P</i>,<i>C-</i>P­(pz′)CH­(SiMe₃)}­(CO)­(PPh₃)₂], a rare example of a ruthenium(0) η²-phosphaalkene complex and the first example of a <i>P</i>-pyrazolylphosphaalkene. Conversely, reaction with the electrophilic PhHgCl leads to metalation at phosphorus, affording [Ru­{η¹-P­(HgPh)CH­(SiMe₃)}­Cl₂(CO)­(PPh₃)₂]

Ambiphilic Reactivity of a Ruthenaphosphaalkenyl: Synthesis of <i>P</i>‑Pyrazolylphosphaalkene Complexes of Ruthenium(0)

The novel ruthenaphosphaalkenyl complex [Ru­{PCH­(SiMe₃)}­Cl­(CO)­(PPh₃)₂], prepared from [RuHCl­(CO)­(PPh₃)₃] and Me₃SiCP, exhibits ambiphilic behavior, reacting at phosphorus with both nucleophiles and electrophiles. Its reaction with Li­(pz′) or K­[HB­(pz′)₃] (pz′ = pz, pz*) affords [Ru­{η¹-<i>N</i>:η²<i>-P</i>,<i>C-</i>P­(pz′)CH­(SiMe₃)}­(CO)­(PPh₃)₂], a rare example of a ruthenium(0) η²-phosphaalkene complex and the first example of a <i>P</i>-pyrazolylphosphaalkene. Conversely, reaction with the electrophilic PhHgCl leads to metalation at phosphorus, affording [Ru­{η¹-P­(HgPh)CH­(SiMe₃)}­Cl₂(CO)­(PPh₃)₂]