Synthesis and Decarbonylation Reactions of Diiron Cyclopentadienyl Complexes with Bent-Phosphinidene Bridges

Alvarez, M. Ángeles; Garcı́a, M. Esther; González, Rocío; Ramos, Alberto; Ruiz, Miguel A.

doi:10.1021/om101125g

Cited by 24 publications

(18 citation statements)

References 91 publications

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“…In particular, by using density functional theory (DFT) methods (see the Experimental Section), we have searched for isomers having either a pyramidal bridging ligand of type C or a bent terminal phosphinidene ligand. The reason for this is that recent work on the diiron complex [Fe 2 Cp 2 (PR*)(CO) 3 ] revealed that such alternative structures were of similar energy, with the one having the bent terminal PR* group remarkably reacting with H 2 under mild conditions (4 atm, 293 K), while possibly being also behind a C–H bond cleavage in the PR* ligand analogous to the one required to yield complexes 3 . Our search on the potential energy surface of our Mo 2 system actually failed to find a structure with a significantly pyramidalized bridging ligand of type C , but we found a minimum with a terminal and significantly bent phosphinidene ligand ( 1T , Mo–P–C ca.…”

Section: Resultsmentioning

confidence: 80%

Divergent Reactivity of a Phosphinidene-Bridged Dimolybdenum Complex Toward 1-Alkynes: P–C, P–H, C–C, and C–H Couplings

et al. 2017

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The ability of complex [Mo 2 Cp 2 {μ-P(2,4,6-C 6 H 2 t Bu 3 )}(CO) 4 ] to promote P−C and subsequent coupling processes has been analyzed by examining reactions with alkynes. The title compound reacted at room temperature with different terminal alkynes HCCR under visible-UV light irradiation to give, in a selective way, the corresponding phosphapropenediyl derivatives [Mo 2 Cp 2 (μ−κ 1 C :η 3 C,C,P -CRCHPR*)(CO) 4 ] for R groups of varied electron-withdrawing nature, but low to medium size, such as Pr, CO 2 Me, and p-tol. These products follow from formal insertion of the alkyne into one of the Mo-phosphinidene bonds in the parent compound, with selective P−C coupling to the terminal carbon of the alkyne. In contrast, when R was the bulky t Bu group, the corresponding photochemical reactions yielded a mixture of the cis and trans isomers of the phosphanyl-and formylalkenyl-bridged complex [Mo 2 Cp 2 {μ−κ 2 C,O :η 2 C,C -CHC( t Bu)C(O)H}{μ-P(CH 2 CMe 2 )-C 6 H 2 t Bu 2 }(CO) 2 ], which follow from a complex reaction sequence involving an H−C(sp 3 ) bond cleavage along with different P−C, P−H, C−C, and C−H bond formation steps. Density functional theory calculations were carried out to rationalize the preceding observations and suggested that an isomer of the parent complex displaying a bent terminal phosphinidene ligand might be involved in all the above photochemical reactions.

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Section: Resultsmentioning

confidence: 80%

Divergent Reactivity of a Phosphinidene-Bridged Dimolybdenum Complex Toward 1-Alkynes: P–C, P–H, C–C, and C–H Couplings

et al. 2017

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“…4 atm). While the cyclohexylphosphinidene complex 1a failed to react after 6 d in toluene solution, we found that the more congested compound 1c did react with H 2 under the same conditions, the reaction being completed in about 16 h, to give the phosphine complex [Fe 2 Cp 2 (μ-CO) 2 (CO)(PH 2 Mes*)] (actually, the synthetic precursor of 1c ) as the major compound (ca. 50% by 1 H NMR).…”

Section: Resultsmentioning

confidence: 87%

“…50% by 1 H NMR). Other products detected in the reaction mixture were free phosphine PH 2 Mes* (20%), the dimer [Fe 2 Cp 2 (CO) 4 ] (15%), the oxophosphinidene complex [Fe 2 Cp 2 (CO) 3 {P(O)Mes*}] (10%), and the phosphindole derivative [Fe 2 Cp 2 (μ-CO) 2 (CO){PH(CH 2 CMe 2 )C 6 H 2 t Bu 2 }] (5%). The presence of all these minor products can be rationalized by taking into account the known degradation processes of 1c in solution.…”

Section: Resultsmentioning

confidence: 99%

“…To examine the influence of steric factors on all this rich chemistry we later prepared the complex [Fe 2 Cp 2 (μ-PMes*)(μ-CO)(CO) 2 ] ( 1c ), with Mes* being the bulky group 2,4,6-C 6 H 2 t Bu 3 , and found that the steric pressure introduced by the Mes* group had pronounced effects concerning its synthesis, structure, thermal stability, and general reactivity . Particularly intriguing was the remarkable ability of this complex to react with dihydrogen at room temperature, to give the phosphine complex [Fe 2 Cp 2 (μ-CO) 2 (CO)(PH 2 Mes*)] as the major product .…”

Section: Introductionmentioning

confidence: 99%

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Activation of H–H and H–O Bonds at Phosphorus with Diiron Complexes Bearing Pyramidal Phosphinidene Ligands

et al. 2012

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The complex [Fe(2)Cp(2)(μ-PMes*)(μ-CO)(CO)(2)] (Mes* = 2,4,6-C(6)H(2)(t)Bu(3)), which in the solid state displays a pyramidal phosphinidene bridge, reacted at room temperature with H(2) (ca. 4 atm) to give the known phosphine complex [Fe(2)Cp(2)(μ-CO)(2)(CO)(PH(2)Mes*)] as the major product, along with small amounts of other byproducts arising from the thermal degradation of the starting material, such as the phosphindole complex [Fe(2)Cp(2)(μ-CO)(2)(CO){PH(CH(2)CMe(2))C(6)H(2)(t)Bu(2)}], the dimer [Fe(2)Cp(2)(CO)(4)], and free phosphine PH(2)Mes*. During the course of the reaction, trace amounts of the mononuclear phosphide complex [FeCp(CO)(2)(PHMes*)] were also detected, a compound later found to be the major product in the carbonylation of the parent phosphinidene complex, with this reaction also yielding the dimer [Fe(2)Cp(2)(CO)(4)] and the known diphosphene Mes*P═PMes*. The outcome of the carbonylation reactions of the title complex could be rationalized by assuming the formation of an unstable tetracarbonyl intermediate [Fe(2)Cp(2)(μ-PMes*)(CO)(4)] (undetected) that would undergo a fast homolytic cleavage of a Fe-P bond, this being followed by subsequent evolution of the radical species so generated through either dimerization or reaction with trace amounts of water present in the reaction media. A more rational synthetic procedure for the phosphide complex was accomplished through deprotonation of the phosphine compound [FeCp(CO)(2)(PH(2)Mes*)](BF(4)) with Na(OH), the latter in turn being prepared via oxidation of [Fe(2)Cp(2)(CO)(4)] with [FeCp(2)](BF(4)) in the presence of PH(2)Mes*. To account for the hydrogenation of the parent phosphinidene complex it was assumed that, in solution, small amounts of an isomer displaying a terminal phosphinidene ligand would coexist with the more stable bridged form, a proposal supported by density functional theory (DFT) calculations of both isomers, with the latter also revealing that the frontier orbitals of the terminal isomer (only 5.7 kJ mol(-1) above of the bridged isomer, in toluene solution) have the right shapes to interact with the H(2) molecule. In contrast to the above behavior, the cyclohexylphosphinidene complex [Fe(2)Cp(2)(μ-PCy)(μ-CO)(CO)(2)] failed to react with H(2) under conditions comparable to those of its PMes* analogue. Instead, it slowly reacted with HOR (R = H, Et) to give the corresponding phosphinous acid (or ethyl phosphinite) complexes [Fe(2)Cp(2)(μ-CO)(2)(CO){PH(OR)Mes*}], a behavior not observed for the PMes* complex. The presence of BEt(3) increased significantly the rate of the above reaction, thus pointing to a pathway initiated with deprotonation of an O-H bond of the reagent by the basic P center of the phosphinidene complex, this being followed by the nucleophilic attack of the OR(-) anion at the P site of the transient cationic phosphide thus formed. The solid-state structure of the cis isomer of the ethanol derivative was determined through a single crystal X-ray diffraction study (Fe-Fe = 2.5112(8) Å, Fe-P = 2.149(1) Å).

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“…120 ppm), stronger than anticipated. For instance, the 31 P chemical shifts of trigonal and pyramidal phosphinidene ligands in the iron complexes [Fe 3 Cp 3 (μ-PMes)(μ-PHMes)(μ-CO) 2 (CO)] and [Fe 2 Cp 2 (μ-PMes)(μ-CO)(CO) 2 ] differ by some 250 ppm …”

Section: Resultsmentioning

confidence: 99%

Electronic Structure and Multisite Basicity of the Pyramidal Phosphinidene-Bridged Dimolybdenum Complex [Mo₂(η⁵-C₅H₅)(μ-κ¹:κ¹,η⁵-PC₅H₄)(η⁶-C₆H₃^tBu₃)(CO)₂(PMe₃)]

et al. 2015

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The title phosphinidene complex could be sequentially protonated with HBF4·OEt2 or [H(OEt2)2](BAr'4) to give the phosphido-bridged derivatives [Mo2Cp(μ-κ(1):κ(1),η(5)-HPC5H4)(η(6)-HMes*)(CO)2(PMe3)]X and then the hydrides [Mo2Cp(H)(μ-κ(1):κ(1),η(5)-HPC5H4)(η(6)-HMes*)(CO)2(PMe3)]X2 (X = BF4, BAr'4; Ar' = 3,5-C6H3(CF3)2; Mes* = 2,4,6-C6H2(t)Bu3). Density functional theory (DFT) calculations revealed that the most favored site for initial electrophilic attack is the metallocene Mo atom, but attachment of the electrophile to the phosphinidene P atom gives more stable products. This was in agreement with all other reactions investigated, which invariably involved the attachment of the added electrophile at the P site. Thus, the title compound reacted with S8 at 223 K to give the thiophosphinidene-bridged complex [Mo2Cp{μ-κ(1):κ(1),η(5)-P(S)C5H4}(η(6)-HMes*)(CO)2(PMe3)], a poorly stable molecule which reacted with MeI at room temperature to give the corresponding thiolatophosphido derivative, isolated as [Mo2Cp{μ-κ(1):κ(1),η(5)-P(SMe)C5H4}(η(6)-HMes*)(CO)2(PMe3)](BAr'4) (P-S = 2.128(4) Å) after anion exchange with Na(BAr'4). Reaction of the title compound with MeI proceeded smoothly to give the corresponding methylphosphido derivative, isolated analogously as [Mo2Cp{μ-κ(1):κ(1),η(5)-P(Me)C5H4}(η(6)-HMes*)(CO)2(PMe3)](BAr'4). The related complex [Mo2Cp{μ-κ(1):κ(1),η(5)-P(Me)C5H4}(η(6)-HMes*)(CO)2(PMe2Ph)](BAr'4) (P-C(Me) = 1.841(5) Å) could be prepared analogously from the neutral precursor [Mo2Cp{μ-κ(1):κ(1),η(5)-PC5H4}(η(6)-HMes*)(CO)2(PMe2Ph)]. In contrast, reaction of the title complex with ethylene sulfide involved opening of the C2S ring and formation of new P-C and Mo-S bonds (1.886(7) and 2.493(2) Å, respectively), with displacement of the PMe3 ligand, to give the phosphido-thiolato complex [Mo2Cp{μ-κ(2)(P,S):κ(1)P,η(5)-P(C2H4S)C5H4}(η(6)-HMes*)(CO)2]. All these derivatives of the title complex displayed an unusual trigonal pyramidal-like environment around the bridging P atom, with the added electrophile placed in the Mo2P plane as a result of the directionality of the relevant frontier orbital of the phosphinidene complex, according to DFT calculations.

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Synthesis and Decarbonylation Reactions of Diiron Cyclopentadienyl Complexes with Bent-Phosphinidene Bridges

Cited by 24 publications

References 91 publications

Divergent Reactivity of a Phosphinidene-Bridged Dimolybdenum Complex Toward 1-Alkynes: P–C, P–H, C–C, and C–H Couplings

Divergent Reactivity of a Phosphinidene-Bridged Dimolybdenum Complex Toward 1-Alkynes: P–C, P–H, C–C, and C–H Couplings

Activation of H–H and H–O Bonds at Phosphorus with Diiron Complexes Bearing Pyramidal Phosphinidene Ligands

Electronic Structure and Multisite Basicity of the Pyramidal Phosphinidene-Bridged Dimolybdenum Complex [Mo₂(η⁵-C₅H₅)(μ-κ¹:κ¹,η⁵-PC₅H₄)(η⁶-C₆H₃^tBu₃)(CO)₂(PMe₃)]

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Synthesis and Decarbonylation Reactions of Diiron Cyclopentadienyl Complexes with Bent-Phosphinidene Bridges

Cited by 24 publications

References 91 publications

Divergent Reactivity of a Phosphinidene-Bridged Dimolybdenum Complex Toward 1-Alkynes: P–C, P–H, C–C, and C–H Couplings

Divergent Reactivity of a Phosphinidene-Bridged Dimolybdenum Complex Toward 1-Alkynes: P–C, P–H, C–C, and C–H Couplings

Activation of H–H and H–O Bonds at Phosphorus with Diiron Complexes Bearing Pyramidal Phosphinidene Ligands

Electronic Structure and Multisite Basicity of the Pyramidal Phosphinidene-Bridged Dimolybdenum Complex [Mo2(η5-C5H5)(μ-κ1:κ1,η5-PC5H4)(η6-C6H3tBu3)(CO)2(PMe3)]

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Electronic Structure and Multisite Basicity of the Pyramidal Phosphinidene-Bridged Dimolybdenum Complex [Mo₂(η⁵-C₅H₅)(μ-κ¹:κ¹,η⁵-PC₅H₄)(η⁶-C₆H₃^tBu₃)(CO)₂(PMe₃)]