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

Aromative Dephosphinidenation of a Bisphosphirane-Fused Anthracene toward E-H (E=H, Si, N and P) Bond Activation

A bisphosphirane-fused anthracene (5) was prepared by treatment of a sterically encumbered amino phosphorus dichloride (3) with MgA ⋅ THF3 (A=anthracene). X-ray diffraction analysis revealed a pentacyclic framework consisting of 5 with two phosphirane rings fused to the anthracene in a trans-fashion. Compound 5 has been shown to be an efficient phosphinidene synthon, readily liberating two transient phosphinidene units for subsequent downstream bond activation via the reductive elimination of anthracene under mild conditions. The formal oxidative addition of H2 and E-H (E=Si, N, P) bonds by the liberated phosphinidene provided diphosphine and substituted phosphines. Furthermore, phosphinidene transfer to alkenes and alkynes smoothly yielded the corresponding phosphiranes and phosphirenes. The mechanism of the H2 activation by 5 was investigated by density functional theory (DFT) calculations.

Decarbonylation Products of Binuclear Methylphosphinidene Complexes of Cyclopentadienyliron Carbonyls: Triplet and Quintet Structures Are Favored Energetically over Singlet Structures with Iron-Iron Multiple Bonding

The structures, energetics, and energetically preferred spin states of methylphosphinidene-bridged binuclear cyclopentadienyliron carbonyl complexes MePFe2(CO)nCp2 (n = 4, 3, 2, and 1) related to the experimentally known (μ-RP)Fe2(μ-CO)(CO)2Cp2 (R = cyclohexyl, phenyl, mesityl, and 2,4,6-tBu3C6H2) complexes have been investigated by density functional theory. Singlet structures having a pyramidal pseudotetrahedral phosphorus environment with 18-electron iron configurations are energetically preferred in the tricarbonyl and tetracarbonyl systems MePFe2(CO)nCp2 (n = 4 and 3) with the lowest energy structures of the tricarbonyl very closely resembling the experimentally determined structures. For the more unsaturated dicarbonyl and monocarbonyl systems MePFe2(CO)nCp2 (n = 2 and 1), higher spin state triplet and quintet structures are energetically preferred over singlet structures. These more highly unsaturated structures can be derived from the lowest energy singlet MePFe2(CO)nCp2 (n = 4, 3) by the removal of carbonyl groups. The iron atoms giving up carbonyl groups in their 16- and 14-electron configurations bear the spin density of the unpaired electrons in the higher spin states. The lowest energy singlet structure of the monocarbonyl MePFe2(CO)Cp2, although a relatively high energy isomer, is unusual among the collection of MePFe2(CO)nCp2 (n = 4, 3, 2, and 1) structures by having both the formal Fe=Fe double bond and the four-electron donor MeP unit with the planar phosphorus coordination required to allow each of its iron atoms to attain the favored 18-electron configuration.

E-H Bond Cleavage Processes in Reactions of Heterometallic Phosphinidene-Bridged MoRe and MoMn Complexes with Hydrogen and p-Block Element Hydrides

Reactions of complexes [MoMCp(μ-PMes*)(CO)6] with H2 and several p-block element (E) hydrides mostly resulted in the cleavage of E-H bonds under mild conditions [M = Re (1a) and Mn (1b); Mes* = 2,4,6-C6H2tBu3]. The reaction with H2 (ca. 4 atm) proceeded even at 295 K to give the hydrides [MoMCp(μ-H)(μ-PHMes*)(CO)6]. The same result was obtained in the reactions with H3SiPh and, for 1a, upon reduction with Na(Hg) followed by protonation of the resulting anion [MoReCp(μ-PHMes*)(CO)6]-. The latter reacted with [AuCl{P(p-tol)3}] to yield the related heterotrimetallic cluster [MoReAuCp(μ-PHMes*)(CO)6{P(p-tol)3}]. The reaction of 1a with thiophenol gave the thiolate-bridged complex [MoReCp(μ-PHMes*)(μ-SPh)(CO)6], which evolved readily to the pentacarbonyl derivative [MoReCp(μ-PHMes*)(μ-SPh)(CO)5]. In contrast, no P-H bond cleavage was observed in reactions of complexes 1a,b with PHCy2, which just yielded the substituted derivatives [MoMCp(μ-PMes*)(CO)5(PHCy2)]. Reactions with HSnPh3 again resulted in E-H bond cleavage, but now with the stannyl group terminally bound to M, while 1a reacted with BH3·PPh3 to give the hydride-bridged derivatives [MoReCp(μ-H)(μ-PHMes*)(CO)5(PPh3)] and [MoReCp(μ-H){μ-P(CH2CMe2)C6H2tBu2}(CO)5(PPh3)], which follow from hydrogenation, C-H cleavage, and CO/PPh3 substitution steps. Density functional theory calculations on the PPh-bridged analogue of 1a revealed that hydrogenation likely proceeds through the addition of H2 to the Mo=P double bond of the complex, followed by rearrangement of the Mo fragment to drive the resulting terminal hydride into a bridging position.

Oxidation and chalcogenylative disproportionation of anionic phosphide ligands in yttrium complexes with elemental sulfur and selenium

The oxidation and disproportionation of anionic phosphide ligands in yttrium complexes with elemental sulfur and selenium are reported. The mixed TpMe2/Cp supported yttrium phosphide complex TpMe2CpYPPh2(THF) (1) reacted with one equiv. of elemental S or Se in THF at room temperature to deliver two structurally characterized yttrium dithio- or monoseleno-phosphinates TpMe2CpYS2PPh2(THF) (2) and TpMe2CpYSePPh2(THF) (4Se), respectively. Further investigations showed that the yttrium thiophosphinate TpMe2CpYSPPh2(THF) (4S) can be isolated from the reactions of 2 and 1 or 1 and elemental S in a short reaction time. Moreover, after keeping 4S or 4Se in THF solution for some days, 2 or [(TpMe2)2Y]+[Se2PPh2]- (5) was obtained by a disproportionation process. The mechanism for the construction of the Ph2PE- and Ph2PE2- (E = S, Se) ligands has been discussed based on the in situ NMR experiments and some designed reactions.

Increasing steric demand through flexible bulk - primary phosphanes with 2,6-bis(benzhydryl)phenyl backbones

Sterically demanding primary phosphanes of the type RBhp-PH2 (Bhp = 2,6-bis(benzhydryl)-4-R-phenyl; R = Me, tBu) could be prepared in high yields by modification of synthetic protocols of established bulky phosphanes. The Bhp substituents simultaneously exhibit extensive steric expansiveness and high degrees of flexibility compared to other 2,6-substituted phenyl backbones, enabling a range of different-sized atoms and functionalities to be located between the flanking benzhydryl moieties. Therefore, it was also possible to isolate and fully characterize several halogenated precursors, a diazonium intermediate, as well as a dihalostibane.

Evidence for Iron-Catalyzed α-Phosphinidene Elimination with Phenylphosphine

The ubiquitous half-sandwich iron complex [CpFe(CO)₂ Me] (Cp=η⁵ -C₅ H₅ ) appears to be a catalyst for α-phosphinidene elimination from primary phosphines. Dehydrocoupling reactions provided initial insight into this unusual reaction mechanism, and trapping reactions with organic substrates gave products consistent with an α elimination mechanism, including a rare example of a three-component reaction. The substrate scope of this reaction is consistent with generation of a triplet phosphinidene. In all, this study presents catalytic phosphinidene transfer to unsaturated organic substrates.

Sn–H bond additions to asymmetric trigonal phosphinidene-bridged dimolybdenum complexes

Organotin hydrides add across the Mo–P double bond of binuclear phosphinidene complexes, sometimes undergoing dehydrogenation involving a cyclopentadienyl ring.

Insight into the Reaction of a Dinuclear Phosphinidene Complex with Nitriles

The phosphinidene complex [Cp*P{W(CO)5}2] (1; Cp*=C5 Me5 ) reacted with malononitrile to give the 1,2-dihydro-1,3,2-diazaphosphinine derivative 2. The reaction of 1 with 1,4-benzodinitrile gave [1,4-{{W(CO)5}2 P-N=C(Cp*)}2 (C6 H4)] (3), the first example of a cumulene-like aminophosphinidene complex. The reaction of 1 with aniline gave the aminophosphinidene complex [(Ph)N(H)P{W(CO)5}2] (4). To compare the reactivity of benzonitrile and aniline with 1, the phosphinidene complex 1 was reacted with three different isomers of aminobenzonitrile (2-, 3-, and 4-aminobenzonitrile). These reactions gave an insight into the reaction pathway of 1 with benzonitrile derivatives. Compounds 5, 6 a, 6 b, and 7, which are derivatives of 1,2-dihydro-1,3,2-diazaphosphinine or benzo-2H-1,2-azaphospholes, were, as well as all other products, characterized by mass spectrometry, NMR and IR spectroscopy, and X-ray structure analysis.

E-H Bond Activation of Ammonia and Water by a Geometrically Constrained Phosphorus(III) Compound

The synthesis of a phosphorus(III) compound bearing a N,N-bis(3,5-di-tert-butyl-2-phenoxy)amide ligand is reported. This species has been found to react with ammonia and water, activating the E–H bonds in both substrates by formal oxidative addition to afford the corresponding phosphorus(V) compounds. In the case of water, both O–H bonds can be activated, splitting the molecule into its constituent elements. To our knowledge, this is the first example of a compound based on main group elements that sequentially activates water in this manner.