Synthesis of 3-stannyl and 3-silyl propargyl phosphanes and the formation of a phosphinoallene

The group 14 chloropropargyls R3ECCCH2Cl (R3E = Bu3Sn, Ph3Sn, Me2PhSi, iPr3Si, nPr3Si, nBu3Si), obtained by a modified literature procedure, react with LiPPh2 to afford the novel propargyl phosphanes Ph2PCH2CCER3 in high yield, as viscous oils; (Me3Si)2PCH2CCSiPhMe2 is similarly obtained from LiP(SiMe3)2. In contrast, the reaction of PhCCCH2MgCl with ClP(NEt2)2 fails to produce a comparable propargyl phosphane, but generates preferentially (>70%) the novel phosphinoallene (Et2N)2PC(Ph)=C=CH2, which is characterised spectroscopically, and through its reaction with HCl. The coordination chemistry of representative phosphanes is explored with respect to platinum and palladium for the first time

How the sperm triggers the fertilisation calcium wave in the sea urchin egg

Fertilisation is characterised by an increase in cytosolic free calcium (Ca). This crucial event transforms the egg, releasing it from its state of cell cycle arrest and stimulating embryonic development. In the sea urchin egg the Ca1 increase is the result of increased polyphosphoinositide (PPI) hydrolysis and the production of the calcium mobilising internal messenger inositol 1,4,5-trisphosphate. I discuss the contribution of inositol polyphosphates to the calcium changes at fertilisation particularly their ability to stimulate calcium entry. I have used cortical granule exocytosis as an indicator of Ca1 and measured Ca1 in single eggs with the calcium sensitive fluorescent dye fura2. I show that, contrary to other reports, inositol phosphates activate eggs by a mechanism that is entirely independent of external calcium. A sperm activates an egg by triggering a regenerative response that involves calcium-stimulated PPI hydrolysis: in this way calcium release leads to further calcium release in an explosive manner. It has been suggested that the sperm triggers this response through a GTP-binding protein. However I show that an analogue of GDP, Guanosine-5'-O-(2-thiodiphosphate), that inhibits GTP-binding protein activation, does not prevent the sperm-induced increase in Ca or incorporation of the sperm into the egg. Also a GTP analogue, Guanosine-5'-O-thiotriphosphate, which stimulates GTP-binding proteins and causes egg activation, does so by a different mechanism than sperm. This data argues against the idea that a sperm triggers egg activation through a GTP-binding protein mechanism. The mobilisation of intracellular calcium through PPI hydrolysis and the production of inositol phosphates is a common signal transduction pathway present in many tissues. My data suggests that inositol phosphates act only to mobilise intracellular calcium and not to stimulate calcium influx. They also suggest that fertilisation in the sea urchin may involve a novel transduction pathway because the PPI hydrolysis is not linked to a GTP-binding protein as in other systems

Through-conjugation of two phosphaalkyne (‘CP’) moieties mediated by a bimetallic scaffold†

Through-conjugation of two phosphaalkyne moieties within an isolable molecule is demonstrated for the first time with the synthesis of [{Ru(dppe)2}2{μ-(CC)2C6H4-p}(CP)2], via base induced desilylation of [{Ru(dppe)2}2{μ-(CC)2C6H4 p}Cl2]. The nature of the cyaphide ligands and their influence upon the bimetallic core are studied electrochemically

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

Diphosphametacyclophanes: structural and electronic influences of substituent variation within a family of bis(diketophosphanyl) macrocycles

The condensation of MeP(SiMe3)2 with a series of 5-substituted isophthaloyl chlorides (5-R′C6H3-2,6-{C(O)Cl}2) affords the diphosphametacyclophanes m-{-C(O)-C6H3-5-R′-(C-(O)PMe)}2 (R′ = I, Me, tBu, Ph, and p-NCC6H4); the analogues m-{-C(O)-C5H3N-(C(O)PMe)}2 and m-{-C(O)-C6H4-(C(O)-PPh)}2 are similarly obtained in preference to higher oligomers, in contrast to precedent reports. The cyclophanes all adopt butterfly-like conformations in the solid state with the P-organyl substituents adopting mutually exo arrangements. Structural and computatiosnal data suggest the nature of the 5-R substituent is key in directing the inter-ring angle and the extent of LUMO stabilization about the diketophophanyl scaffold. The latter is substantiated by UV/vis pectroscopy and cyclic voltammetry, which demonstrate these cyclophanes to be appreciably comparable to the diketophosphanyl systems commonly explored in the context of organic electronic materials; intriguingly, the distinct dikeophosphanyl moieties within the macrocycles appear effectively “insulated” by the macrocycle geometry, rather than acting as a through-conjugate

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

Phosphacycloalkyldiones: synthesis and coordinative behaviour of 6- and 7-member cyclic diketophosphanyls

Glutaryl and adipoyl chlorides undergo facile condensation with the bis(silyl)phosphanes RP(SiMe3)2 (R = Me, nBu, tBu, Ph, Mes) to afford exclusively the phosphacycloalkyldiones (CH2)n(C[double bond, length as m-dash]O)2PR (n = 3, 4). Characterised spectroscopically and, for R = Ph, Mes (n = 3) crystallographically, the macrocycles are conformationally fluxional in solution and appreciably moisture sensitive. Though seemingly resistant to chemical oxidation at phosphorus, coordination is readily achieved, as illustrated by isolation of trans-[Pt(PEt3){P(Ph)(CO)2(CH2)3}Cl2] and a series of tungsten pentacarbonyl complexes, which are characterised crystallographically and by infrared and NMR spectroscopy. Together, these data suggest the macrocycles to be relatively weak σ-donors with no appreciable π-acceptor character