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The synthesis of a new bis‐NHP complex (NHP=N‐heterocyclic phosphenium) of chromium via salt metathesis and studies of its reactivity are reported. Photochemical reactions with H2 and selected olefins give rise to non‐isolable H2‐ and π‐alkene complexes identified spectroscopically, while internal alkynes react via activation of the triple bond to yield isolable metalla‐phospha‐cyclobutenes characterized by spectroscopic and XRD data. DFT studies give a preliminary account of the bonding in H2‐ and alkene‐complexes and explain the different reactivity towards alkenes and alkynes as the consequence of kinetic effects. Photolysis of the bis‐NHP‐complex in the presence of H2 and olefins or alkenes enables the catalytic hydrogenation of the organic substrates, while the π‐ethene complex mediates the catalytic hydrogenation of ethene in a dark reaction. The similarities and differences between both catalytic processes are shortly discussed. [ABSTRACT FROM AUTHOR]

The article titled "Cover Feature: The Noble Addendum of a Phosphenium Ligand to a Base Metal: Coordination, Activation, and Hydrogenation of Alkenes and Alkynes on a Chromium Complex" explores the chemical diversity and reactivity of a bis‐phosphenium complex of chromium. The research focuses on the catalytic hydrogenation of alkenes through two molecular pathways: a photochemical route and a dark reaction. The dark reaction involves a ligand exchange reaction with alkynes, resulting in the production of metallacycles. The article provides further details on these processes and their implications. [Extracted from the article]

Boryl‐substituted phosphines NHB–P(R)Ph (R = H, Ph, NHB = N‐heterocyclic boryl substituent) react with Fe2(CO)9 to give isolable Fe(CO)4 complexes, two of which were characterized by single‐crystal XRD studies. The electronic and steric properties for a series of the boryl phosphines were further assessed by evaluation of TEPs for in‐situ formed complexes [RhCl(NHB–PR1R2)(CO)2] (R1, R2 = H, Ph, Me, NMe2), and calculations of buried volumes for Fe(CO)4 complexes. The results imply that the NHB‐phosphines exhibit due to their conformational flexibility some variability in their steric bulk, and that some specimens may exhibit similar electron releasing power and steric demand as tBu3P. Studies of the amination of bromobenzene with 2,6‐diisopropylaniline confirmed that these properties can be exploited to promote Pd‐catalyzed C–N cross coupling reactions, and that formal replacement of a phenyl by a NHB substituent in the auxiliary phosphine has a beneficial effect on catalyst performance. Phosphines with an N‐heterocyclic boryl substituent at phosphorus behave as strongly electron releasing ligands that may impart despite their conformational flexibility sizeable steric shielding to a transition metal atom. This makes them suitable candidates for application as ligands in cross‐coupling chemistry. [ABSTRACT FROM AUTHOR]

tBu2P-P(SiMe3)Li reacted with [(η6-C6H6)RuCl2]2 at -40 °C in the presence of PR3 (PR3 = PEt3, PEt2Ph, PEtPh2) by the nucleophilic addition of the tBu2P-P(SiMe3) moiety to the benzene ring to yield solely the complexes [(R3P)2Ru(Cl){η5-C6H6(Me3SiP-P tBu2)}] ( 1). These products decomposed slowly at ambient temperature to yield benzene, Ru clusters, and small amounts of the dinuclear ruthenium complexes [{(R3P)2Ru}2(µ,η2:2-P2)2Ru(PR3)2] ( Ru-Ru) ( 6). Single-crystal X-ray diffraction studies of [(PhEt2P)2Ru(Cl){η5-C6H6(Me3SiP-P tBu2)}] ( 1b) and [(Ph2EtP)2Ru(Cl){η5-C6H6(Me3SiP-P tBu2)}] ( 1c) revealed that the addition of the tBu2P-P(SiMe3) group occurred through an exo pathway. Complex 6a (R = Et) displays a planar rectangular P4 system consisting of two P2 units and a Ru-Ru distance that lies in the range of a single bond. [ABSTRACT FROM AUTHOR]

The parent tris(pyrazolyl)phosphine and its 3,5-Me2, 3-Ph, and 3-t-Bu derivatives have been prepared by a simple procedure and show modest Lewis basicity of the phosphorus apex as was established by the magnitude of the 1JP,Se coupling constant of the phosphine selenides. Because of the chelating properties of both the N- and P-sites, neutral phosphorus-centered scorpion ligands allow coordination modes that are unavailable to the abundantly used anionic tris(pyrazolyl)borate scorpionates as we established for Cu(i)-complexation. The substituted P-scorpion ligands only allow for N-coordination, as the P-apex is presumably less accessible. Two X-ray crystal structures were obtained for the Cu-complex of tris(3,5-dimethylpyrazolyl)-phosphine with acetonitrile and triphenylphosphine in the fourth coordination site. The parent P-scorpion ligand can chelate with both its pyrazolyl groups and its P-apex with the product depending on the ratio in which it is mixed with the Cu(i) complex. Reacting two equivalents of the ligand with [Cu(MeCN)4][PF6] resulted in a complex in which Cu is coordinated to the three pyrazolyl groups of one ligand and to the P-apex of the other ligand as confirmed by an X-ray crystal structure determination and a DFT computational analysis. Reacting the ligand and the Cu(i) complex in an equimolar ratio resulted in a remarkable one-dimensional P-scorpion coordination polymer for which a single crystal X-ray structure could be determined. A detailed analysis of the structural features is presented. [ABSTRACT FROM AUTHOR]

The nucleophilic properties of the title compound [(2,6-i-Pr2C6H3N)2(Cl)W(η2-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 31P-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. [ABSTRACT FROM AUTHOR]

The reaction of symmetrical bis(diazaphospholenyl) compounds with [MCl2(cod)] (M = Pd, Pt; cod = 1,5-cyclooctadiene) has been used to prepare N-heterocyclic phosphenium (NHP) metal(0) halides [M(NHP)Cl]n with diverse N substituents. Characterisation by ESI-MS and NMR spectroscopy revealed that N-tBu- and N-aryl-substituted NHP precursors yield trimeric (n = 3) and dimeric (n = 2) products, respectively; the degree of aggregation is presumably controlled by the different steric requirements of the NHP moiety. A single-crystal XRD study of a trimeric Pd complex confirmed the proposed constitution of the complexes with μ2- bridging NHP and terminal chlorido ligands and allowed their metrical parameters to be analysed for the first time un- disturbed by crystallographic disorder. Studies of ligand substitution and redistribution processes revealed that the complexes withstand exchange of the μ-bridging NHP units but tolerate substitution of the terminal chlorido ligands by other strong nucleophiles (SCN-, I-) with conservation of the oligomeric framework. Attempts to replace chlorido by thiolato ligands led to the discovery of a reaction between a phosphenium metal thiolate [Pd(NHP)(SR)]3 and CH2Cl2 to give a formaldehyde dithioacetal H2C(SR) 2 (R = benzyl). This reaction could be developed into a protocol for a C--S crosscoupling reaction in the presence of a catalytic amount of the phosphenium complex. [ABSTRACT FROM AUTHOR]

Benzofused 1H-1,3-azaphospholes are lithiated at the N-atom by tBuLi but phosphinylation takes place at either the N- or the P-atom. Smaller chlorophosphines react at nitrogen, bulkier react at phosphorus. Substituents at C2 promote the latter mode. N-Substituted 2H-1,3-benzazaphospholes undergo CH-metalation or addition at the P=C bond, depending on the conditions, and allow access to 2-functionally substituted benzazaphospholes or their 2,3-dihydro derivatives, new σ2P,X or σ3P,X hybrid ligands (X=O,P). [ABSTRACT FROM AUTHOR]

Abstract: The dissociation properties of several phosphorus heterocycles and cages (complexes of phosphinidenes with P-donor ligands) were investigated using DFT methods. Good correlations have been found between the dissociation energies of the complexes with P and N ligands. The comparison with N-donor complexes revealed that the stability of complexes with pyrido-annelation(s) is very similar. The trends in dissociation energies for the benzannelated complexes are identical; however, the complexes with P ligands are much more stable than those with N ligands. The major reason for the different behavior is the pyramidality of the bridgehead P/N atoms in these complexes. [Copyright &y& Elsevier]

Quaternization of a phosphane-functionalized benzene-dithiol gave a phosphonio-decorated product, which was reacted with copper and nickel salts to yield cationic metal-bis(benzenedithiolene) complexes. Both the ligand and its complexes were fully characterized. The properties of the complexes were compared with those of previously known anionic complexes featuring identical metal coordination environments. UV/Vis and EPR studies indicate that the charge inversion induces only minor perturbations of the electronic structure of the complexes. Electrochemical studies indicated that the cationic species are more easily reducible and allowed to establish an unprecedented three-membered electron transfer series involving +3/+2/+1 metal oxidation states of a copper bis-dithiolene complex. [ABSTRACT FROM AUTHOR]

The reactivity of an anionic phosphanylphosphinidene complex of tungsten(VI), [(2,6-i-Pr2C6H3N)2(Cl)W(η²-t-Bu2PP)]Li·3DME toward PMe3, halogenophosphines, and iodine was investigated. Reaction of the starting complex with Me3P led to formation of a new neutral phosphanylphosphinidene complex, [(2,6-i-Pr2C6H3N)2(Me3P)W(η²-t-Bu2PP)]. Reactions with halogenophosphines yielded new catena-phosphorus complexes. From reaction with Ph2PCl and Ph2PBr, a complex with an anionic triphosphorus ligand t-Bu2P-P(−)-PPh2 was isolated. The main product of reaction with PhPCl2 was a tungsten(VI) complex with a pentaphosphorus ligand, t-Bu2P-P(−)-P(Ph)-P(−)-P-t-Bu2. Iodine reacted with the starting complex as an electrophile under splitting of the P-P bond in the t-Bu2PP unit to yield [(1,2-η-t-Bu2P-P-P-t-Bu2)W(2,6-i-Pr2C6H3N)2Cl], t-Bu2PI, and phosphorus polymers. The molecular structures of the isolated products in the solid state and in solution were established by single crystal X-ray diffraction and NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Base-assisted reaction of catechol phosphane 2 (H2L) with [M′Cl2(cod)] (cod = 1, 5-cyclooctadiene, M′ = Pd, Pt) yielded chelate complexes [M′(HL)2] ( 7a, b). Spectroscopic and single-crystal X-ray diffraction studies revealed that both complexes feature cis-configuration of the P- and O-donor atoms in solution and in the solid state. Reaction of 7a, b with acetylacetonato or alkoxide complexes [MO2(acac)2] (M = Mo, W), [VO(acac)2], [{Ti(μ-O)(acac)2}2], or Ti(O iPr)4 gave good to excellent yields of early-late heterometallic complexes [MO n(μ-L)2M′] (MO n = MoO2, WO2, VO; 8a, b- 10a, b) or [Ti(RO-1κ O)2(μ- L-1κ2 O, O'-2κ2 P, O)2Pd] (R = Me, iPr; 11a, b), which were inaccessible via other synthetic routes. Spectroscopic and single-crystal X-ray diffraction studies revealed that the early metal centres in 8a, b, 9b and in 11b feature distorted octahedral coordination spheres with rigid transoid alignment of the catechol ring planes. Vanadium complexes 10a, b exhibit a square-pyramidal coordination sphere with cisoid alignment of the catechol ring planes and evidence for intermolecular pairing via weak VO ···Pd contacts in the solid state; complexes 8, 9 do not undergo conformational inversion on the NMR time-scale. The molecular structure of Ti complex 11a is characterized by a different orientation of the catechol moieties, which can be envisaged to picture an intermediate state during a configuration inversion process, and a strong hydrogen bridge between a terminally coordinated catecholato-oxygen atom and a solvent molecule (MeOH). Solution NMR studies indicate that the (MeO)2Ti(μ-L)2M' framework is in this case conformationally labile and that the MeO ligands undergo intermolecular dynamic exchange with the solvent. [ABSTRACT FROM AUTHOR]

Reactions of (cod)MCl2 (cod = 1,5 cyclooctadiene, M = Pd, Pt) with N-heterocyclic secondary phosphines or diphosphines produced complexes [(NHP)MCl] 2 (NHP = N-heterocyclic phosphenium). The Pd complex was also accessible from a chlorophosphine precursor and Pd2 (dba)3. Single-crystal X-ray diffraction studies established the presence of dinuclear complexes that contain μ-bridging NHP ligands in an unsymmetrical binding mode and display a surprising change in metal coordination geometry from distorted trigonal (M = Pd) to T-shaped (M = Pt). DFT calculations on model compounds reproduced these structural features for the Pt complex but predicted an unusual C2v-symmetric molecular structure with two different metal coordination environments for the Pd species. The deviation between this structure and the actual centrosymmetric geometry is accounted for by the prediction of a flat energy hypersurface, which permits large distortions in the orientation of the NHP ligands at very low energetic cost. The DFT results and spectroscopic studies suggest that the title compounds should be described as phosphenium--metal(0)--halides rather than conventional phosphido complexes of divalent metal cations and indicate that the NHP ligands receive net charge donation from the metals but retain a distinct cationic character. The unsymmetric NHP binding mode is associated with an unequal distribution of σ-donor/π-acceptor contributions in the two M--P bonds. Preliminary studies indicate that reactions of the Pd complex with phosphine donors provide a viable source of ligand-stabilized, zerovalent metal atoms and metal(0)--halide fragments. [ABSTRACT FROM AUTHOR]

Abstract: Sulfurization of 3-[(diphenylphosphinyl)methyl]benzene-1,2-diol 1 produced phosphine sulfide 3. Both ligands reacted easily to form gold(I) and rhodium(I) complexes which were characterized by analytical and spectroscopic data, and single-crystal X-ray diffraction studies. Whereas the phosphine prefers to form complexes with a metal-to-ligand ratio of 1:2 with both metals, the phosphine sulfide exhibits a reduced donor power and yields only a 1:1 complex with AuCl. With rhodium(I), formation of a homobimetallic complex with a metal-to-ligand ratio of 2:1 was found. This complex displays an unusual coordination of both metal atoms to the catechol moiety whereas the phosphine sulfide moiety remains inactive. [Copyright &y& Elsevier]