Metal-phosphido and -phosphinidene complexes in P-E bond-forming reactions

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.

Phosphinidene-Bridged MoMn Derivatives of the Thiophosphinidene Complex [Mo2Cp2(μ-κ2:κ1,η6-SPMes*)(CO)2] (Mes* = 2,4,6-C6H2tBu3)

The title complex (1) reacted with [Mn₂(CO)₁₀] under visible-UV irradiation (toluene solution and quartz glassware) to give a mixture of the phosphinidene complex [MnMoCp(μ-κ¹:κ¹,η⁶-PMes*)(CO)₄], the cluster [Mn₂Mo₂Cp₂(μ-κ¹:κ¹,η⁶-PMes*)(μ₃-S)(CO)₈], and the thiophosphinidene complex [MnMoCp(μ-κ²:κ¹,η⁴-SPMes*)(CO)₅], in yields of ca. 60, 20, and 10% respectively (Mes* = 2,4,6-C₆H₂^tBu₃). The major product follows from formal replacement of the SMoCp(CO)₂ fragment in 1 with a Mn(CO)₄ fragment, and displayed multiple bonding to phosphorus (Mn-P = 2.1414(8) Å); the tetranuclear cluster results from formal insertion of a Mn₂(CO)₆ fragment in 1, with cleavage of P-S and P-Mo bonds, to render a μ₃-S bridged Mn₂Mo core bearing an exocyclic phosphinidene ligand involved in multiple bonding to one of the Mn atoms (Mn-P = 2.140(2) Å); the thiophosphinidene complex (Mn-P = 2.294(1) Å) formally results from addition of sulfur and carbon monoxide to the major MnMo product, a transformation which actually could be performed stepwise, via the MnMo thiophosphinidene complex [MnMoCp(μ-κ²:κ¹,η⁶-SPMes*)(CO)₄]. When the photolysis of 1 and [Mn₂(CO)₁₀] was performed in tetrahydrofuran solution and using conventional glassware, then the V-shaped cluster [Mn₂MoCp{μ-κ¹:κ¹:κ¹,η⁵-P(C₆H₃^tBu₃)}(CO)₈] was obtained selectively (Mo-Mn = 3.2910(5) Å, Mn-Mn = 2.9223(5) Å), which unexpectedly displays a cyclohexadienylidene-phosphinidene ligand resulting from H atom abstraction at the aryl ring of the precursor. Density functional theory calculations on the complexes [L_nM(μ-κ¹:κ¹,η⁶-PMes*)MoCp] (ML_n = MoCp(CO)₂, Mn(CO)₄, Co(CO)₃) revealed that the degree of delocalization of the metal-phosphorus π-bonding interaction over the Mo-P-M chain is significantly conditioned by the heterometal fragment ML_n, it being increased in the order Mn ≤ Mo < Co.

Visible-light and thermal driven double hydrophosphination of terminal alkynes using a commercially available iron compound

An air-stable, commercially available iron catalyst provides fast efficient double hydrophosphination of alkynes under thermal or photochemical conditions.

Imino-stabilised phosphinidene (or azaphosphole?) and some of its derivatives

Diiminophenyl (dimph) proved to be an excellent ligand platform to stabilise a low-valent phosphorus centre.

Sequential Electrophilic Substitution Reactions of Tungsten-Coordinated Phosphenium Ions and Phosphine Triflates

ion of chloride from [W(CO)₅{PPhCl₂}] with AgOSO₂CF₃ leads to the phosphine triflate complex [W(CO)₅{PPhCl(OSO₂CF₃)}] which undergoes electrophilic substitution reactions with N,N-diethylaniline, anisole, N,N-dimethyl-p-toluidine, toluene, biphenyl, naphthalene, 2,7,9,9-tetramethyl xanthene, and allyltrimethylsilane to form the chlorophosphine complexes [W(CO)₅{PPhClR}], where R = p-diethylanilinyl, p-anisyl, 2-(N,N-dimethyl-4-methylphenyl), p-tolyl, p-phenylphenyl, 1-naphthyl, 4-(2,7,9,9-tetramethylxanthyl), and allyl. Abstraction of the second chloride with AgOSO₂CF₃ leads, in most cases, to the respective phosphine triflates [W(CO)₅{PPhR(OSO₂CF₃)}], which react with ferrocene to form the ferrocenyl phosphine complexes [W(CO)₅{PPhR(C₁₀H₉Fe)}]. The W(CO)₅ unit can be removed via photolysis in the presence of bis(diphenylphosphino)ethane to form metal-free phosphines.

NI(ii) phosphine and phosphide complexes supported by a PNP-pyrrole pincer ligand

The reaction between [(PN^pyrP)NiCl] (1, PN^pyrP = 2,5-bis((di-iso-propylphosphino)-methyl)-1H-pyrrolide) and TlPF₆ in the presence of a monodentate phosphine ligand led to cationic nickel phosphine and phosphite complexes, [(PN^pyrP)Ni(PHPh₂)][PF₆] (2), [(PN^pyrP)Ni(PMe₃)][PF₆] (3), and [(PN^pyrP)Ni{P(OMe)₃}][PF₆] (4). Compound 2 can be deprotonated resulting in the generation of a terminal phosphido complex, [(PN^pyrP)Ni(PPh₂)] (5). When 3 is subjected to a base, a methyl proton of PMe₃ is abstracted to afford [(PN^pyrP)Ni(CH₂PMe₂)] (6), containing a methylene bridge between Ni and the external phosphine. Compounds 2-6 were characterized by single crystal X-ray diffraction in addition to multi-nuclear NMR spectroscopy and elemental analysis.

Terminal Parent Phosphanide and Phosphinidene Complexes of Zirconium(IV)

The reaction of [Zr(TrenDMBS )(Cl)] [Zr1; TrenDMBS =N(CH2 CH2 NSiMe2 But )3 ] with NaPH2 gave the terminal parent phosphanide complex [Zr(TrenDMBS )(PH2 )] [Zr2; Zr-P=2.690(2) Å]. Treatment of Zr2 with one equivalent of KCH2 C6 H5 and two equivalents of benzo-15-crown-5 ether (B15C5) afforded an unprecedented example (outside of matrix isolation) of a structurally authenticated transition-metal terminal parent phosphinidene complex [Zr(TrenDMBS )(PH)][K(B15C5)2 ] [Zr3; Zr=P=2.472(2) Å]. DFT calculations reveal a polarized-covalent Zr=P double bond, with a Mayer bond order of 1.48, and together with IR spectroscopic data also suggest an agostic-type Zr⋅⋅⋅HP interaction [∡ZrPH =66.7°] which is unexpectedly similar to that found in cryogenic, spectroscopically observed phosphinidene species. Surprisingly, computational data suggest that the Zr=P linkage is similarly polarized, and thus as covalent, as essentially isostructural U=P and Th=P analogues.

Phosphido complexes derived from 1,1'-ferrocenediyl-bridged secondary diphosphines

This paper focuses on ferrocene-based secondary diphosphines of the type [Fe{η⁵-C₅H₄(PHR)}₂] with P-substituents of distinctly different steric and electronic properties, namely methyl, neopentyl (Np), tert-butyl, phenyl and 3,5-bis(trifluoromethyl)phenyl (XyF). The reaction of [Fe{η⁵-C₅H₄(PHPh)}₂] (H₂1a) and [Fe{η⁵-C₅H₄(PHt-Bu)}₂] (H₂1b) with n-BuLi in the presence of TMEDA afforded lithium diphosphides of the type [Li₂(μ-1)(TMEDA)₂], which contain a cyclic non-planar Li₂P₂ core. The analogous reactions of [Fe{η⁵-C₅H₄(PHMe)}₂] (H₂1c) and [Fe{η⁵-C₅H₄(PHNp)}₂] (H₂1d) furnished dimeric aggregates exhibiting a ladder-type Li₄P₄ motif, viz. [Li₄(μ-1c)₂(TMEDA)₃] and [Li₂(μ-1d)(TMEDA)]₂. H₂1e (R = XyF) did not afford a stable lithium diphosphide. A Brønsted metathesis with Zr(NMe₂)₄ was possible with the aryl-substituted compounds H₂1a and H₂1e, leading to products of the type [{Zr(NMe₂)₃}₂(μ-1)]. In contrast, the alkyl-substituted congeners H₂1b-H₂1d were inert towards Zr(NMe₂)₄. The reaction of [Fe{η⁵-C₅H₄(PHR)}₂] with nickelocene afforded intractable mixtures of numerous products in the case of H₂1c and H₂1e. In the other three cases, compounds of the type [(NiCp)₂(μ-1)] were isolated. For H₂1b and H₂1d a two-stepped reaction via a phosphino-phosphido intermediate of the type [NiCp(H1)] was observed, which could be isolated and fully characterised in the case of [NiCp(H1b)].

Hydrophosphination-type reactivity promoted by bismuth phosphanides: scope and limitations

Phenyl isocyanate inserts into the Bi-P bond of the terminal phosphanide Bi(NON^Ar)(PCy₂) (NON^Ar = [O(SiMe₂NAr)₂]^2- Ar = 2,6-iPr₂C₆H₃) to afford the κ²N,O-phosphanylcarboxamidate complex. Liberation of the hydrophosphination product from the metal is achieved by reaction with HPPh₂. The diphenylphosphanide product, Bi(NON^Ar)(PPh₂), is however unstable and decomposes to generate reduced species, preventing catalytic turnover.

Chemistry of CS2- and SCNPh-adducts of the pyramidal phosphinidene-bridged complex [Mo2Cp(μ–κ1:κ1,η5-PC5H4)(CO)2(η6-HMes*)(PMe3)]

Heterocumulene insertion into the metallocene Mo–P bond of the title complex enables further addition of different electrophiles at the P, S or N sites.

Oxidative formation of phosphinyl radicals from a trigonal pyramidal terminal phosphide Rh(i) complex, with an unusually long Rh–P bond

A coordinatively saturated triolefinic rhodium(i) complex, bearing a terminal pyramidal phosphido ligand, generates phosphinyl radical species under oxidative conditions.

Transition-Metal-like Behavior of Main Group Elements: Ligand Exchange at a Phosphinidene

(Phosphino)phosphaketenes (>P-P═C═O) behave as (phosphino)phosphinidene-carbonyl adducts (>P-P←:C═O). CO scrambling was observed using ¹³C labeled CO, and exchange reactions with phosphines afford the corresponding (phosphino)phosphinidene-phosphine adducts (>P-P←:PR₃). The latter react with isonitriles and singlet carbenes giving (phosphino)phosphinidene-isonitrile (>P-P←:CNR) and -carbene adducts (>P-P←:C<). Based on experimental results and DFT calculations, it is shown that these "ligand" exchange reactions occur via an associative mechanism as classically observed with transition metal complexes.

The chemistry of parent phosphiranide in the coordination sphere of tungsten

2-Chloroethylphosphine W(CO)5 complex readily reacts with sodium hydride. With one equivalent of NaH, the parent phosphirane complex is obtained. With more than two equivalents, the phosphiranide complex is exclusively formed. With 1.5 equivalents, a 1 : 1 mixture of and is obtained but readily attacks at the phosphorus atom by splitting of ethylene and by the formation of the P-P complex . In turn, the P-P bond of is split by NaH to yield the phosphide complex . The phosphiranide complex is a good source for a large variety of functional phosphirane complexes . With BrCN, the 1-cyanophosphirane complex is formed. Upon heating it loses its complexing group. Upon hydrolysis, it gives the 1-hydroxyphosphirane complex which dimerizes in basic medium by opening one P-C bond of the ring to give . The reaction of with PhPCl2 yields the triphosphorus complex whose molecular structure has been established by X-ray crystal structure analysis.

Tin-catalyzed hydrophosphination of alkenes

Simple tin derivatives, Cp*2SnCl2 (1) and Ph2SnCl2 (2), catalyze the hydrophosphination of alkene substrates with diphenylphosphine. Competitive dehydrocoupling to give Ph4P2 was observed, but this side reaction can be mitigated when the catalysis is conducted under an H2 atmosphere. Efforts to prepare stable tin bis(phosphido) compounds commonly resulted in decomposition to Ph4P2. Lewis acidic inorganic tin compounds do not show dehydrocoupling reactivity. It was found that the Lewis acid, B(C6F5)3, is able to engage in the hydrophosphination of alkenes, but it is poorly effective under the conditions tested.

P-S bond cleavage in reactions of thiophosphinidene-bridged dimolybdenum complexes with [Co2(CO)8] to give phosphinidene-bridged heterometallic derivatives

The thiophosphinidene complex [Mo2Cp2(μ-κ(2):κ(1),η(6)-SPMes*)(CO)2] (Mes* = 2,4,6-C6H2(t)Bu3) reacted with [Co2(CO)8] at room temperature or below to give several of the following phosphinidene-bridged products, depending on reaction conditions: the MoCo complexes [CoMoCp(μ-κ(1):κ(1),η(6)-PMes*)(CO)3] and [CoMoCp(μ-PMes*)(CO)5] (Co-Mo = 2.972(1) Å), the MoCo3 cluster [Co3MoCp(μ3-PMes*)(CO)9] (Co-Mo = 2.664(1), 2.810(1) Å), and the sulphido-bridged tetranuclear complexes [Co2Mo2Cp2(μ-κ(1):κ(1):κ(1),η(4)-PMes*)(μ3-S)(CO)7] and [Co3MoCp(μ-κ(1):κ(1):κ(1),η(4)-PMes*)(μ3-S)(CO)8]. In contrast, the thiophosphinidene complex [Mo2Cp2(μ-κ(2):κ(1),η(4)-SPMes*)(CO)3] reacted with the same cobalt reagent selectively to give the above Mo2Co2 complex in very high yield. The latter could be decarbonylated photochemically to give [Co2Mo2Cp2(μ-κ(1):κ(1):κ(1),η(6)-PMes*)(μ3-S)(CO)6] (Co-Co = 2.435(3), Co-Mo = 2.769(2), 2.798(2) Å), after an η(4)- to η(6)-haptotropic rearrangement of the aryl ring of the phosphinidene ligand that could be reversed upon reaction with CO. The related complex [Mo2Cp2(μ-κ(2):κ(1),η(4)-SPMes*)(CO)2(CN(t)Bu)], however, displayed poor selectivity towards the cobalt dimer and yielded a mixture of CoMo complexes [CoMoCp(μ-PMes*)(CO)5] and [CoMoCp(μ-PMes*)(CO)3(CN(t)Bu)2], and the tetranuclear sulphido-bridged ones [Co2Mo2Cp2(μ-κ(1):κ(1):κ(1),η(4)-PMes*)(μ3-S)(CO)6(CN(t)Bu)] (Co-Co = 2.533(1), Co-Mo = 2.7485(9), 2.770(1) Å) and [Co3MoCp(μ-κ(1):κ(1):κ(1),η(4)-PMes*)(μ3-S)(CO)7(CN(t)Bu)] (Co-Co = 2.4120(7) to 2.5817(7) Å). This reduction in selectivity might have an electronic origin rather than a steric origin, since the related but cationic substrate [Mo2Cp2{μ-κ(2):κ(1),η(5)-SP(C6H3(t)Bu3)}(CO)2(CN(t)Bu)]BAr [Ar' = 3,5-C6H3(CF3)2] reacted with [Co2(CO)8] more selectively to give the sulphido-bridged Co2Mo2 complex [Co2Mo2Cp2{μ-κ(1):κ(1):κ(1),η(5)-P(C6H3(t)Bu3)}(μ3-S)(CO)6(CN(t)Bu)]BAr, along with small amounts of the Co3Mo complex [Co3MoCp{μ-κ(1):κ(1):κ(1),η(5)-P(C6H3(t)Bu3)}(μ3-S)(CO)7(CN(t)Bu)]BAr (Co-Co = 2.414(2) to 2.560(2) Å). The structure of the new complexes was analyzed on the basis of the corresponding X-ray diffraction and spectroscopic data, and likely reaction pathways were discussed on the basis of the above results and some additional experiments.

Spontaneous dehydrocoupling in peri-substituted phosphine-borane adducts

Bis(borane) adducts Acenap(PiPr2·BH3)(PRH·BH3) (Acenap = acenaphthene-5,6-diyl; 4a, R = Ph; 4b, R = ferrocenyl, Fc; 4c, R = H) were synthesised by the reaction of excess H3B·SMe2 with either phosphino-phosphonium salts [Acenap(PiPr2)(PR)](+)Cl(-) (1a, R = Ph; 1b, R = Fc), or bis(phosphine) Acenap(PiPr2)(PH2) (3). Bis(borane) adducts 4a-c were found to undergo dihydrogen elimination at room temperature, this spontaneous catalyst-free phosphine-borane dehydrocoupling yields BH2 bridged species Acenap(PiPr2)(μ-BH2)(PR·BH3) (5a, R = Ph; 5b, R = Fc; 5c, R = H). Thermolysis of 5c results in loss of the terminal borane moiety to afford Acenap(PiPr2)(μ-BH2)(PH) (14). Single crystal X-ray structures of 3, 4b and 5a-c are reported.

Iron- and Cobalt-Catalyzed Synthesis of Carbene Phosphinidenes

In the presence of stoichiometric or catalytic amounts of [M{N(SiMe3 )2 }2 ] (M=Fe, Co), N-heterocyclic carbenes (NHCs) react with primary phosphines to give a series of carbene phosphinidenes of the type (NHC)⋅PAr. The formation of (IMe4 )⋅PMes (Mes=mesityl) is also catalyzed by the phosphinidene-bridged complex [(IMe4 )2 Fe(μ-PMes)]2 , which provides evidence for metal-catalyzed phosphinidene transfer.

Insertion of phosphinidene complexes into the P-H bond of secondary phosphine oxides: a new version of the phospha-Wittig synthesis of P=C double bonds

Terminal phosphinidene complexes [RP-W(CO)5], as generated at 60 °C in the presence of copper chloride from the appropriate 7-phosphanorbornadiene complexes, react with secondary phosphine oxides Ar2P(O)H to give the insertion products into the P-H bonds. After metalation with NaH, these products react with aldehydes to give the corresponding phosphaalkenes which are trapped by dimethylbutadiene.

Nucleophilicity and P-C Bond Formation Reactions of a Terminal Phosphanido Iridium Complex

The diiridium complex [{Ir(ABPN2)(CO)}2(μ-CO)] (1; [ABPN2](-) = [(allyl)B(Pz)2(CH2PPh2)](-)) reacts with diphenylphosphane affording [Ir(ABPN2)(CO)(H) (PPh2)] (2), the product of the oxidative addition of the P-H bond to the metal. DFT studies revealed a large contribution of the terminal phosphanido lone pair to the HOMO of 2, indicating nucleophilic character of this ligand, which is evidenced by reactions of 2 with typical electrophiles such as H(+), Me(+), and O2. Products from the reaction of 2 with methyl chloroacetate were found to be either [Ir(ABPN2)(CO)(H)(PPh2CH2CO2Me)][PF6] ([6]PF6) or [Ir(ABPN2)(CO)(Cl)(H)] (7) and the free phosphane (PPh2CH2CO2Me), both involving P-C bond formation, depending on the reaction conditions. New complexes having iridacyclophosphapentenone and iridacyclophosphapentanone moieties result from reactions of 2 with dimethyl acetylenedicarboxylate and dimethyl maleate, respectively, as a consequence of a further incorporation of the carbonyl ligand. In this line, the terminal alkyne methyl propiolate gave a mixture of a similar iridacyclophosphapentanone complex and [Ir(ABPN2){CH═C(CO2Me)-CO}{PPh2-CH═CH(CO2Me)}] (10), which bears the functionalized phosphane PPh2-CH═CH(CO2Me) and an iridacyclobutenone fragment. Related model reactions aimed to confirm mechanistic proposals are also studied.

Synthesis and solid-state structures of gold(i) complexes of diphosphines

A series of diphosphine bis(gold) complexes were synthesised and the importance of aurophilic interactions for their structure formation was studied.

Dehydrogenative coupling involving P(O)–H bonds: a powerful way for the preparation of phosphoryl compounds

This Frontier highlights the recent progress in the preparation of organophosphorus compounds via transition metal-catalysed dehydrogenative couplings of P(O)H compounds with Z–H compounds.

A novel route to C-unsubstituted 1,2-oxaphosphetane and 1,2-oxaphospholane complexes

The synthesis of 1,2-oxaphosphetane complexes 7 and 1,2-oxaphospholane complex 12 bearing only substituents at phosphorus is reported using the reaction of Li/Cl phosphinidenoid complex 2 with 2-iodoethanol or 3-bromo-propane-1-ol and the subsequent dehydrohalogenation using KHMDS.

Zirconium-catalyzed intermolecular hydrophosphination using a chiral, air-stable primary phosphine

Catalytic hydrophosphination of alkenes using a chiral, air-stable primary phosphine, (R)-MeO-MOPH₂, proceeds under mild conditions with a zirconium catalyst to selectively furnish anti-Markovnikov, air-stable secondary phosphine or tertiary phosphine prodcuts with slight modification of the protocol.

Alkali metal catalyzed dehydro-coupling of boranes and amines leading to the formation of a B–N bond

N–H/H–B cross-dehydrogenative coupling (CDC) of boranes and amines with high conversion (>90%) and chemo-selectivity using group-1 metal salts as pre-catalysts, and under ambient conditions is presented.

Activation of A–H bonds (A = B, C, N, O, Si) by using monovalent phosphorus complexes [RP→M]

The insertion of electrophilic terminal phosphinidene complexes [RP–M] into A–H bonds (A = B, C, N, O, Si) has been reviewed and some new mechanistic proposals have been made.

Coordination chemistry of a low-coordinate non-metal element: the case of electrophilic terminal phosphinidene complexes

3-Imino-azaphosphiridine complex 1 reacts with CO to give 1,3-azaphosphetidinone complex 2, whereas with isocyanides 3a,b substitution occurred to yield the isocyanide-to-phosphinidene adducts 4a,b.

Formation of a Bridging Phosphinidene Thorium Complex

The synthesis and structural determination of the first thorium phosphinidene complex are reported. The reaction of 2 equiv of (C5Me5)2Th(CH3)2 with H2P(2,4,6-(i)Pr3C6H2) at 95 °C produces [(C5Me5)2Th]2(μ2-P[(2,6-CH2CHCH3)2-4-(i)PrC6H2] as well as 4 equiv of methane, 2 equiv from deprotonation of the phosphine and 2 equiv from C-H bond activation of one methyl group of each of the isopropyl groups at the 2- and 6-positions. Transition state calculations indicate that the steps in the mechanism are P-H, C-H, C-H, and then P-H bond activation to form the phosphinidene.

An investigation on the chemistry of the R2P = P ligand: reactions of a phosphanylphosphinidene complex of tungsten(VI) with electrophilic reagents

The nucleophilic properties of the title compound [(2,6-i-Pr2C6H3N)2(Cl)W(η(2)-t-Bu2P = P)]Li·3DME (1) were investigated in reactions with selected electrophilic reagents such as MeI, M(CO)5THF (M = Cr, Mo, W), AlCl3, and GaCl3. Methylation of 1 by MeI yields phosphanylphosphido complexes [(2,6-i-Pr2C6H3N)2W(X)(1,2-η-t-Bu2P = P-CH3)] (X = Cl, I) (2-Cl/2-I) with the formation of a new P-C bond. Moreover, 1 reacts with electrophilic compounds [(OC)5M·THF] (M = Cr, Mo, W) to yield a series of novel dinuclear phosphanylphosphinidene complexes [(2,6-i-Pr2C6H3N)2(Cl)W(1,2-η-t-Bu2P = P-M(CO)5)]Li·3DME (3, 4, 5) with very long P-M distances. Adducts [(2,6-i-Pr2C6H3N)2(Cl)W(1,2-η-t-Bu2P = P-MCl3)]Li·3DME (6, 7) formed by reaction of 1 with GaCl3 and AlCl3 are labile and dissociate into 1 and MCl3 (M = Ga, Al). The outcomes of reactions were monitored by (31)P-NMR spectroscopy. Furthermore, the structures of the isolated complexes 2-Cl/2-I, 3, 4, and [(2,6-i-Pr2C6H3N)2(Cl)W(1,2-η-t-Bu2P = P-W(t-Bu2PH)(CO)3COLi·2DME] (5-P) were confirmed unambiguously by X-ray diffraction studies.