Sandra Bolaño

Iridium‐EDTA as an Efficient and Readily Available Catalyst for Water Oxidation

It′s so easy: The readily available and highly water‐soluble [IrCl(Hedta)]Na complex is an efficient and robust catalyst for water oxidation to molecular oxygen. The reaction is driven by the reduction of Ce4+ to Ce3+. Its performances (TOF=6.8 min−1 and TON>12 000) are derived by UV/Vis spectroscopic, volumetric and electrochemical measurements, and compare favorably with those of the best catalysts reported so far.

SYNTHESIS AND CHARACTERIZATION OF THE BROMIDE AND HYDRIDE DERIVATIVES OF RHENIUM(I) 1,2-BIS(DIPHENYLPHOSPHINITE)ETHANE COMPLEXES

Abstract The reaction of [ReX(CO)5] (X=Br, H) with the bidentate phosphinite ligand 1,2-bis(diphenylphosphinite)ethane (L–L), synthesized by reaction of PPh2Cl and ethylene glycol in a 2:1 ratio in the presence of NEt3, at room temperature, affords the mononuclear rhenium(I) complexes fac-[ReBr(CO)3(L–L)] (1) and fac-[ReH(CO)3(L–L)] (2). The coordination geometry of the complexes was established by diffraction studies and confirmed by spectroscopic data of both complexes. Compound 1 crystallizes in the P21/c (No. 14) monoclinic space group while the hydride complex does so in P21 (No. 4). The coordination polyhedron around the rhenium atom in both cases is a slightly distorted octahedron with three carbonyl groups in facial positions. The link of the bidentate ligand to the metal atom leads to a seven-membered ReP2O2C2 ring, adopting a conformation better described as a twisted chair.

Oxorhenium(V) complexes with bis-phosphinite chelating coligands. The crystal structure of [ReOCl2(OMe)L1], [ReOCl3L2], [ReOCl2(OEt)L2] and [ReOCl2{Ph2PO(CH2)2O}{PPh2(OEt)}] [L1=Cy2PO(CH2)2OPCy2, L2=Ph2PO(CH2)2OPPh2]

Abstract The new ligand 1,2-bis(dicyclohexylphosphinite)ethane (L1) was prepared by reaction of ethylenglycol with dicyclohexylphosphine in the presence of triethylamine. By treating this ligand with the arsine complex [ReOCl3(AsPh3)2] and trituring the formed oil with methanol, the complex [ReOCl2(OMe)L1] (1) was isolated and its crystal structure was studied by X-ray diffractometry. The coordination sphere around the Re atom is a pseudo-octahedron. The crystal structure of the previously reported complex [ReOCl3L2] (2) (L2=1,2-bis[diphenylphosphinite]ethane) was solved by X-ray diffractometry. When Complex 2 was refluxed in EtOH, the oxo-alkoxide complex [ReOCl2(EtO)L2] (3) was formed by a metathesis reaction. X-ray diffraction studies of Complex 3 show a pseudo-octahedral geometry around the Re atom with the oxo and ethoxy groups mutually trans. Finally, reaction of 2 with the monodentate phosphinite PPh2(OEt) ligand yielded the paramagnetic Re(III) compound [ReCl3L2{PPh2(OEt)}] (previously reported) and the new unexpected Re(V) by-product [ReOCl2(Ph2POCH2CH2O){PPh2(OEt)}] (4). On the contrary, compounds 1 and 3 did not react with PPh2(OEt) under the same conditions.

Polyhydride complexes of rhenium with the chelating ligand 1,2-bis(diphenylphosphinite)ethane

The reaction of [ReOCl3(AsPh3)2] with Ph2POCH2CH2OPPh2 (L) in refluxing THF yielded the complex [ReOCl3L] (1). The new polyhydride [ReH7L] (2) was obtained by treating 1 with NaBH4 in absolute ethanol. The heptahydride 2 is stable in the solid state but in solution dimerises, giving [Re2H8L2] (3). Polyhydrides 2 and 3 were characterised as classical species by variable-temperature NMR spectroscopy (1H and 31P) and T1 measurements. The protonation of [ReH7L] and [Re2H8L2] in CH2Cl2-d2 with HBF4·Et2O gave the hydride cations [ReH6(η-H2)L]+ and [Re2H9L2]+, which were characterised as non-classical and classical, respectively, on the basis of T1(min) measurements. The reaction of 1 with PPhn(OR)3−n (L′; n=1, 2; R=Me, Et) in refluxing THF gave [ReCl3LL′] (4) in excellent yield. The complex [ReCl3L{PPh(OEt)2}] was converted to the pentahydride [ReH5L{PPh(OEt)2}] by treatment with NaBH4 at room temperature.

Rhenium pentahydride complexes: characterisation and protonation reactions. Crystal structure of ReH5L1L2 (L1 = Ph2PO(CH2)2OPPh2; L2 = P(OCH3)3, P(OCH2CH3)3)

Abstract Variable temperature NMR studies of the rhenium pentahydrides [ReH5L1L2] (L1=Ph2POCH2CH2OPPh2; L2=PPhn(OR)3−n, n=0–2; R=Me, Et) show a fluxional behaviour at all accessible temperatures. The coalescence events observed in the hydride region of the 1H-NMR spectra have coalescence temperatures increasing as the number of OR groups of L2 increases. Longitudinal T1(min) values (∼120 ms at 400 MHz) suggest a classical nature for these compounds. The crystal structure of compounds with L2=P(OR)3 has been determined by X-ray diffraction techniques at low temperature. Both compounds show a dodecahedral co-ordination geometry with the three phosphorus nuclei and one hydride in B sites and the remaining four hydrides in A sites. The protonation of pentahydrides with HBF4·Et2O yielded the non-classical cations [Re(η2-H2)H4L1L2]+ (T1(min)∼20 ms at 400 MHz) that slowly decompose between 253 and 273 K being more stable as the number of OR groups increases.

Counterion-dependent deuteration of pentamethylcyclopentadiene in water-soluble cationic Rh(III) complexes assisted by PTA

[Cp(*)RhCl(PTA)(2)]X (PTA = 7-phospha-1,3,5-triazaadamantane) undergoes an H/D exchange process between the methyl groups of Cp(*) and D(2)O whose rate depends on the coordinating ability of the counterion X(-). Kinetic studies and DFT calculations indicate that deuteration involves the abstraction of a Me-Cp(*) proton by a coordinated OH(-); the formation of the latter seems to be facilitated by the presence of the N-basic centers of PTA.

Reactions of [1,2-bis(diphenylphosphinite)ethane]bromotricarbonylrhenium(I) with phosphites, phosphonites and phosphinites. The crystal structure of [ReBr(CO)2{Ph2PO(CH2)2OPPh2}L′] [L′=P(OCH3)3, P(OC2H5)3 and PPh(OC2H5)2]

Abstract The rhenium carbonyl complexes cis , mer -[ReBr(CO) 2 ( L )( L ′)] [ L =1,2-bis(diphenylphosphinite)ethane, L ′ = P(OMe) 3 ( 1 ), P(OEt) 3 ( 2 ), PPh(OMe) 2 ( 3 ), PPh(OEt) 2 ( 4 ), PPh 2 (OMe) ( 5 ), PPh 2 (OEt) ( 6 )] were synthesised by reaction of [ReBr(CO) 3 L ] with 1 equiv. of the appropriate phosphite, phosphonite or phosphinite. The coordination geometry has been established by NMR, IR and, for compounds 1 , 2 and 4 , X-ray crystallography. These compounds consist of slightly distorted octahedral monomers. The conformation of the seven-membered ReP 2 O 2 C 2 chelate ring is a twist–chair for compound 1 and a twist–boat for compounds 2 and 4 .

NMR studies on the novel heterobimetallic complexes [M(dppm)(Ph2PCH2PPh2PPPP) {Pt(PPh3)2}]OTf (M = Rh, Ir) derived from the stepwise activation of white phosphorus

The solution structures of the novel heterobimetallic complexes [Ir(dppm)(Ph2PCH2PPh2PPPP){Pt(PPh3)2}]OTf (1) and [Rh(dppm)(Ph2PCH2PPh2PPPP){Pt(PPh3)2}]OTf (2) derived from the reaction of Rh and IrP5 precursors with [Pt(C2H4)(PPh3)2] have been unambiguously assigned on the basis of 1H NMR and 31P{1H} NMR data. The results are in agreement with the regio‐selective insertion of the {Pt(PPh3)2} moiety resulting in a new pentaphosphorus topology which agrees with the formal formation of a unique phosphonium(+)–tetraphosphabutadienide(2−) ligand. Copyright

Electronic effects of substituents on the stability of the iridanaphthalene compound [Ir[upper bond 1 start]Cp*{=C(OMe)CH=C(o-C6[upper bond 1 end]H4)(Ph)}(PMe3)]PF6.

Iridanaphthalene complexes are synthesized from the corresponding methoxy(alkenyl)carbeneiridium compounds. The electronic character of the substituents on the 6-position of the metallanaphthalene ring is crucial from the point of view of the stability of the iridanaphthalene, [Ir[upper bond 1 start]Cp*{=C(OMe)CH=C(o-C[upper bond 1 end]6H4)(Ph)}(PMe3)]PF6, vs. its transformation to the corresponding indanone derivatives. Stability studies of the iridanaphthalene compounds revealed that strong electron donor substituents (-OMe) stabilize the iridanaphthalene, while weak electron donor (-Me) and electron withdrawing (-NO2) groups favor the formation of indanone derivatives. Two possible indanone isomers can be obtained in the conversion of the unstable iridanaphthalene complexes and a mechanism for the formation of these isomers is proposed.