Isaac de los Rios

The interaction of [Cp∗RuCl(dippe)] and [CpRuCl(dippe)] with alkynols: hydroxyvinylidene, allenylidene and related derivatives (dippe 1,2-bis(diisopropylphosphino)ethane)

Abstract The reactions of [Cp∗RuCl(dippe)] and [CpRuCl(dippe)] (dippe  1,2-bis(diisopropylphosphino)ethane) with several alkynols HCCC(OH)RR′ (RR′H, Me; RMe, R′Ph) have been studied. These reactions leads to the formation of the corresponding allenylidene derivatives, although in some cases hydroxyvinylidene complexes were isolated as intermediates in such process. The X-ray crystal, structure of [CpRuCCCMePh(dippe)][BPh4] was determined. In the course of the reaction of [CpRuCl(dippe)] with HCCC(OH)Me2, there is evidence for the formation of a deep bluedimeric aklynyl-carbene (or alkenyl-allenylidene) complex [{CpRu(dippe)}2(μ-C10H11)][BPh4] resulting formally from the coupling of two allenylidene moieties followed by the loss of one proton. The reaction of [Cp∗RuCCCMePh(dippe)][BPh4] with KOBu′ leads to the ene-yne derivative [Cp∗Ru(CCC(Ph)CH2)(dippe)] as result of the deprotonation of the allenylidene ligand at the δ-position. This compound was structurally characterized by single crystal X-ray crystallography. In an attempt to obtain the primary allenylidene complex [Cp∗RuCCCH2(dippe)][BPh4] by dehydration of the hydroxyvinylidene [Cp∗RuCCHCH2OH(dippe)][BPh4] using P2O5, the previously reported carbonyl complex [Cp∗Ru(CO)(dippe)][BPh4] was obtained and its crystal structure determined. This is also accessible by aerial oxidation of the hydroxy-vinylidene derivative.

Synthesis of new half-sandwich ruthenium complexes containing 1,2-bis(diisopropylphosphino)ethane (dippe); crystal structures of [Ru(C5Me5)Cl(dippe)] and [Ru(C5Me5)(O2)(dippe)][BPh4]

The complex [Ru(C5H5)Cl(PPh3)2] reacted with 1 equivalent of dippe [dippe = 1,2-bis(diisopropylphosphino)ethane] in refluxing toluene to yield [Ru(C5H5)Cl(dippe)]1. The complex [Ru(C5Me5)Cl(dippe)]2 was obtained by reaction of [{Ru(C5Me5)(µ3-Cl)}4] with a stoichiometric amount of dippe in CH2Cl2. The crystal structure of 2 has been determined. Both 1 and 2 are non-electrolytes in non-polar solvents. In alcohols, compound 2 has a strong tendency to dissociate chloride. In the presence of air, this compound binds O2 irreversibly, yielding the dioxygen complex [RuC5Me5(O2)(dippe)]+, which is isolable as the [BPh4]– salt (3). The crystal structure of this compound has also been determined. Both 1 and 2 reacted with SnCl2 in CH2Cl2 to yield the insertion derivatives [Ru(C5R5)(SnCl3)(dippe)](R = H 4 or Me 5). All compounds were characterized by NMR spectroscopy and microanalysis.

Synthesis of cationic arene complexes of iron and ruthenium with 1,2-bis(diisopropylphosphino)ethane (dippe): X-ray crystal structures of [RuCl(η6-C6H6)(dippe)][BPh4] and [RuH(η6-C6H6)(dippe)][BPh4]

Abstract The complex [FeCl2(dippe)] (dippe = 1,2-bis(diisopropylphosphino)ethane) reacts with cyclohexadienyl-lithium in tetrahydrofuran yielding a dark mixture, from which the hydrido-arene complex [FeH(C6H6)(dippe)][BPh4] (1) can be isolated in moderate yields upon treatment with MeOHNaBPh4. 1, as well as the toluene complex [FeH(C6H5Me)(dippe)][BPh4] (2), can be prepared by reaction of [FeCl2(dippe)] with LinBu in benzene or toluene respectively, followed by MeOHNaBPh4. The ruthenium complexes [RuCl(L)(dippe)]+ (L = C6H6, p-isopropylmethylbenzene (p-cymene)) are obtained by reaction of [{Ru(L)Cl2}2] wit dippe and Ag+, and isolated as the tetraphenylborate salts 3. These compounds react with NaBH4 in acetone-ethanol furnishing the hydrido-aerene derivatives [RuH(L)(dippe)][BPh4] (L = C6H6 5, p-cymene 6). All the compounds were characterized by IR, NMR and microanalysis. The X-ray crystal structures of 3 and 4 are also reported.

Metal-Assisted P−H Bond Formation: A Step towards the Hydrogenation of White Phosphorus

An overview of the chemistry of transition metal complexes containing P−H bonds is presented. Central to this microreview are those compounds in which the P−H bond is assembled by reactions entailing the transfer of one or more hydrogen atoms to white phosphorus or to Px fragments resulting from P4 activation and degradation within the coordination sphere of a transition metal complex. The relevance of these processes to the as yet unaccomplished hydrogenation of white phosphorus is briefly discussed.

Synthesis and Structural Characterization of (Carbene)ruthenium Complexes Binding Nucleobases

The new (carbene)ruthenium(II) nucleobase derivatives fac,cis-[(PNP)RuCl{C(NHC4H3N2O2)(CH2Ph)}]Cl (5) and fac,cis-[(PNP)RuCl{C(NHC5H3N4)(CH2Ph)}]Cl (6) [PNP = CH3CH2CH2N(CH2CH2PPh2)2] were synthesised by treating (vinylidene)ruthenium(II) complex fac,cis-[(PNP)RuCl2{C=C(H)Ph}] (1) with 5-aminouracil or adenine, respectively. Both complexes were characterized by spectroscopic techniques (IR and NMR) and elemental analyses, which confirmed the formation of the aminocarbene moieties incorporating 1 equiv. of the nucleobase in the complex framework. Crystal and molecular structure determination by X-ray diffraction analysis of the uracil derivative 5 revealed a very unusual O-coordination of the exocyclic C=O group on the C(4) atom of the uracil ring to the ruthenium atom leading to an unprecedented six-membered aminocarbene metallacycle. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Synthesis, Characterization, and Interconversion of the Rhenium Polyhydrides [ReH3(η4-NP3)] and [ReH4(η4-NP3)]+ {NP3 = tris[2-(diphenylphosphanyl)ethyl]amine}

The rhenium(III) dichloride complex [ReCl2(η4-NP3)]Cl (1) was prepared from [ReCl3(CH3CN)(PPh3)2] by treatment with the tripodal tetradentate ligand N(CH2CH2PPh2)3 (NP3) in ethanol. The reaction of 1 with LiAlH4 in THF gave the rhenium(III) trihydride [ReH3(η4-NP3)] (2), which was converted into the rhenium(V) tetrahydride [ReH4(η4-NP3)]BPh4 (3) by protonation in CH2Cl2 with HBF4·OMe2, followed by a metathetical reaction with NaBPh4. The classical polyhydride nature of 2 and 3, as well as the overall molecular structures in solution, were determined by NMR spectroscopy, 1H NMR relaxation, and IR spectroscopy. The polyhydride complexes 2 and 3 are stereochemically nonrigid in solution, and the thermodynamic parameters associated with the fluxional processes were determined by variable-temperature NMR studies. A single-crystal X-ray analysis of 3 has shown the complex cation [ReH4(η4-NP3)]+ to be eight-coordinated by the four donor atoms of NP3 and by four terminal hydride ligands in a distorted dodecahedral geometry. An in situ IR study in CH2Cl2 has shown that the protonation of 3 occurs regioselectively at the metal center with no formation of a dihydrogen complex. Kinetic hydrogen bond products of the formula [(η4-NP3)H3Re···HOR] (ROH = C2H5OH, CFH2CH2OH, CF3CH2OH) were intercepted by IR spectroscopy at low temperature. The thermodynamic parameters associated with the formation of the hydrogen bond adducts were determined by either IR spectroscopy applying the Iogansen equation or van’t Hoff plots of the formation constant vs. temperature.

Rhenium(III) and rhenium(V) complexes stabilized by the potentially tetradentate ligand tris(2-diphenylphosphinoethyl)amine

The reaction of the rhenium(V) nitrido complex [Re(N)Cl2(PPh3)2] with the tripodal ligand N(CH2CH2PPh2)3 (NP3 )i n THF gave [Re(N)Cl2( 2 -P,P-NP3)] (1) in which NP3 acts as a tridentate ligand using the nitrogen and two phosphorus donors for coordination. Refluxing 1 in a polar solvent such as ethanol produced [( 4 -NP3)Re(N)Cl]Cl (2) in which NP3 acts as a tetradentate ligand. Treatment of complex [Re(O)Cl3(AsPh3)2] containing the [ReO] 3 + core with NP3 in THF yielded [ReCl3{ 3 -N,P,P(N{CH2CH2Ph2}2{CH2CH2P(O)Ph2})}] (3). Complexes 1 and 3 have been characterized by single-crystal X-ray analyses.

Irreversible rearrangement of half-sandwich ruthenium hydrido-alkynyl complexes to their vinylidene isomers

The complex [(C5Me5)RuCl(dippe)](dippe = l,2-bis(diisopropylphosphino)ethane) reacts with alk-1-ynes in MeOH in the presence of NaBPh4 yielding the metastable hydrido-alkynyl derivatives [(C5Me5)Ru(H)(CCR)(dippe)][BPh4](R = CO2Me, SiMe3 or Ph), intermediates in the formation of the corresponding vinylidene complexes, to which these compounds rearrange both in solution and in the solid state.

Nucleophilic addition of phosphines to rhenium allenylidenes. Unprecedented double P–H bond activation to give an η1-P-phospha-1-butadienyl ligand

Tertiary phosphines PMe3−xPhx (x = 0–2) react with the rhenium allenylidene [(triphos)(CO)2Re(CCCPh2)]OTf (1) yielding γ-phosphonioalkynyl complexes [(triphos)(CO)2Re{CCCPh2(PMe3−xPhx)}]OTf [x = 0, (2); 1, (4); 2 (7)] which convert into the α-phosphonioallenyl derivatives [(triphos)(CO)2Re{C(PMe3−xPhx)CCPh2}]OTf [x = 0, (3); 1, (5); 2 (6)] at higher tempereature. The reactions of 1 with secondary, PHPh2, and primary, PH2CH2Fc (Fc = ferrocenyl), phosphines proceed with a similar mechanism, followed by single or double P–H bond cleavage. The γ-phosphonioalkynyl [(triphos)(CO)2Re{CCCPh2(PHPh2)}]OTf (9) and the α-phosphonioallenyl [(triphos)(CO)2Re{C(PHPh2)CCPh2}]OTf (10) have been intercepted by insitu NMR spectroscopy. On increasing the temperature, 10 undergoes a selective 1,3-P,C-H shift to give the α-phosphoniobutadienyl derivative [(triphos)(CO)2Re{C(PPh2)CHCPh2}]OTf (8). With the primary phosphine PH2CH2Fc, the initially formed α-phosphoniobutadienyl complex [(triphos)(CO)2Re{C(PHFc)CHCPh2}]OTf (11) transforms into the η1-P-phospha-1-butadienyl complex [(triphos)(CO)2Re{P(CH2Fc)CHCHCPh2}]OTf (12) upon heating at 50 °C.

1,3-Cycloaddition of pyrazole to the allenylidene ligand in [Re{CCCPh2}(CO)2{MeC(CH2PPh2)3}]+

Abstract The reaction of the allenylidene complex [Re{CCCPh 2 }(CO) 2 (triphos)]OTf ( 1 ) (triphos=MeC(CH 2 PPh 2 ) 3 ; OTf= − OSO 2 CF 3 ) with pyrazole gave the 1,2,3-diheterocyclization product [Re{CCHCPh 2 (N 2 C 3 H) 3 }(CO) 2 (triphos)]Y (Y=OTf, 2OTF ; Y=BPh 4 , 2BPh 4 ). The molecular structure of this complex was determined by a single-crystal X-ray analysis. Treatment of 2 with sodium methoxide gave the pyrazolyl-functionalized alkynyl derivative [Re{CCCPh 2 (N 2 C 3 H 3 )}(CO) 2 (triphos)] ( 3 ) via selective deprotonation of the vinylic hydrogen, followed by back opening of the metal-bound heterocycle. Protonation of 3 with triflic acid in dichloromethane re-generated 1 and free pyrazole. The overall result of this deprotonation/protonation sequence allowed us to propose a reliable mechanism for the formation of the 1,2,3-diheterocyclization product 2OTf .