Rhodium-Mediated Dehydrogenation of Hydroboranes and Group 14 Compounds: Base-Stabilized Silylene and Germylene Complexes vs. Transmetalation.

Monocarbonyl rhodium complex LRh(CO), 1, which is stabilized by a pyrrole-based bis(phosphinimine) pincer ligand (L=κ -NNN'=2,5-[ Pr P=N(4- PrC H )] -N'(C H ) ), serves as a versatile platform for the dehydrogenation of group 14 substrates. Reaction with primary and secondary silanes and germanes (MesSiH , Et SiH , Ph GeH , BuGeH ; Mes=mesityl) liberates H and yields base-stabilized tetrylene compounds of the form κ -L(CO)Rh(ER ) (E=Si: R=Mes, H, 2; R=Et, 5; E=Ge: R=Ph, 6; R= Bu, H, 8). The ":ER " fragment in these species bridges between the rhodium center and a phosphinimine donor.

X-ray crystal structure of [ Ag][OTf]·5CD: a monoanionic bis-phosphinimine ligand supported tris-ilver complex.

The compound bis-{μ-2,5-bis-[-(4-iso-propyl-phen-yl)-,-di-phenyl-phospho-r-im-i-do-yl]pyrrol-1-ido-κ :':''}tris-ilver(I) tri-fluoro-methane-sulfonate deuterated benzene penta-solvate, [Ag(CHNP)](CFOS)·5CD, (I), was synthesized from two equivalents of Na [ = 2,5-(4- PrCHN=PPh)CHN] and three equivalents of AgOTf (OTf = OSOCF). High-quality crystals of (I) formed with five deuterated benzene solvent mol-ecules in the asymmetric unit. Notably, the bond lengths and angles between the three silver atoms are markedly different, unlike in most other reported tris-ilver complexes that tend to form three equivalent metal centers.

Reversible dehydrogenation of a primary aryl borane.

The consecutive activation of B-H bonds in mesitylborane (H2BMes; Mes = 2,4,6-(CH3)3C6H2) by a 16-electron rhodium(i) monocarbonyl complex, (iPrNNN)Rh(CO) (1-CO; iPrNNN = 2,5-[iPr2P[double bond, length as m-dash]N(4-iPrC6H4)]2N(C4H2)-) is described. Dehydrogenative extrusion of the {BMes} fragment led to the isolation of (iPrNNN)(CO)RhBMes (1-BMes). Addition of H2 gas to 1-BMes regenerated 1-CO and H2BMes, highlighting the ability of 1-CO to facilitate interconversion of {BMes} with dihydrogen.

Erratum: Di-chlorido-bis-[2-(pyridin-2-yl-κ)-1-benzimidazole-κ ]nickel(II) monohydrate. Corrigendum.

[This corrects the article DOI: 10.1107/S2414314620000401.].

Di-chlorido-bis-[2-(pyridin-2-yl-κ)-1-benzimidazole-κ ]nickel(II) monohydrate.

In the title complex, [NiCl(CHN)]·HO, a divalent nickel atom is coordinated by two 2-(pyridin-2-yl)-1-benzimidazole ligands in a slightly distorted octa-hedral environment defined by four N donors of two ,'-chelating ligands, along with two -oriented anionic chloride donors. The title complex crystallized with a water mol-ecule disordered over two positions. In the crystal, a combination of O-H⋯Cl, O-H.

Consecutive N loss from a uranium diphosphazide complex.

A new 'diphosphazidosalen' ligand was synthesized and successfully transferred to uranium using salt metathesis strategies. The resultant 8-coordinate uranium(iv) diphosphazide complex [κ6-1,2-{(N3)PPh2(2-O-C6H4)}2C6H4]UCl2 (1) is unstable to consecutive N2 loss, affording the asymmetric species [κ5-1-{(N3)PPh2(2-O-C6H4)}-2-{N=PPh2(2-O-C6H4)}C6H4)]UCl2 (2), defined by a phosphazide-phosphinimine mixed-ligand framework, and ultimately, the uranium(iv) phosphasalen complex [κ4-1,2-{N=PPh2(2-O-C6H4)}2C6H4]UCl2(THF) (3).

An H-Substituted Rhodium Silylene.

Divergent reactivity of organometallic rhodium(I) complexes, which led to the isolation of neutral rhodium silylenes, is described. Addition of PhRSiH (R=H, Ph) to the rhodium cyclooctene complex ( NNN)Rh(COE) (1-COE; NNN=2,5-[iPr P=N(4-iPrC H )] N(C H ) , COE=cyclooctene) resulted in the oxidative addition of an Si-H bond, providing rhodium(III) silyl hydride complexes ( NNN)Rh(H)SiHRPh (R=H, 2-SiH Ph; Ph, 2-SiHPh ). When the carbonyl complex ( NNN)Rh(CO) (1-CO) was treated with hydrosilanes, base-stabilized rhodium(I) silylenes κ -N,N-( NNN)(CO)Rh=SiRPh (R=H, 3-SiHPh; Ph, 3-SiPh ) were isolated and characterized using multinuclear NMR spectroscopy and X-ray crystallography.

Crystal structure of a dimeric β-diketiminate magnesium complex.

The solid-state structure of a dimeric β-diketiminate magnesium(II) complex is discussed. The compound, di-μ-iodido-bis-[(-{4-amino-1,5-bis-[2,6-bis-(propan-2-yl)phen-yl]pent-3-en-2-yl-idene}aza-nido-κ,')magnesium(II)] toluene sesquisolvate, [Mg(CHN)I]·1.5CH, crystallizes as two independent mol-ecules, each with 2/ crystallographic site symmetry, located at Wyckoff sites 2 and 2.

Elucidation of the resting state of a rhodium NNN-pincer hydrogenation catalyst that features a remarkably upfield hydride (1)H NMR chemical shift.

Rhodium(I) alkene complexes of an NNN-pincer ligand catalyze the hydrogenation of alkenes, including ethylene. The terminal or resting state of the catalyst, which exhibits an unprecedentedly upfield Rh-hydride (1)H NMR chemical shift, has been isolated and a synthetic cycle for regenerating the catalytically active species has been established.

Differences in the cyclometalation reactivity of bisphosphinimine-supported organo-rare earth complexes.

The pyrrole-based ligand N,N'-((1H-pyrrole-2,5-diyl)bis(diphenylphosphoranylylidene))bis(4-isopropylaniline) (HL(B)) can be deprotonated and coordinated to yttrium and samarium ions upon reaction with their respective trialkyl precursors. In the case of yttrium, the resulting complex [L(B)Y(CH2SiMe3)2] (1) is a Lewis base-free monomer that is remarkably resistant to cyclometalation. Conversely, the analogous samarium complex [L(B)Sm(CH2SiMe3)2] is dramatically more reactive and undergoes rapid orthometalation of one phosphinimine aryl substituent, generating an unusual 4-membered azasamaracyclic THF adduct [κ(4)-L(B)Sm(CH2SiMe3)(THF)2] (2).

A cascade reaction: ring-opening insertion of dioxaphospholane into lutetium alkyl bonds.

Geometrically constrained dioxaphospholane rings were incorporated into a bis(phosphinimine)carbazole ligand (HL) in an effort to generate an ancillary ligand system that is capable of supporting reactive lutetium alkyl functionalities and resistant to cyclometalation reactivity. This new ligand was used to prepare a lutetium dialkyl species, LLu(CH2SiMe3)2; however, the complex exhibited low thermal stability at ambient temperature. This dialkyl compound was found to be highly susceptible to a cascading inter- and intramolecular reaction that resulted in the sole formation of an asymmetric bimetallic tetraalkoxide complex.

Secondary diphosphine and diphosphido ligands: synthesis, characterisation and group 1 coordination compounds.

Two types of secondary diphosphines, 1,8-(ArPH)2C14H8 (1a: Ar = Tripp, 2,4,6-triisopropylphenyl; 1b: Ar = Mes, 2,4,6-trimethylphenyl) and 1,3-((t)BuPHCH2)2C6H4 (2), based on rigid 1,8-anthracene and flexible m-xylyl frameworks, respectively, have been synthesized using different strategies. Compounds 1a and 1b were formed by nucleophilic aromatic substitution of a potassium organophosphido salt onto 1,8-difluoroanthracene, while compound 2 was obtained by addition of the Grignard reagent [1,3-(ClMgCH2)2C6H4]x to a dichloroorganophosphine, followed by reduction to the diphosphine. These compounds were isolated as ca.

The osmium-silicon triple bond: synthesis, characterization, and reactivity of an osmium silylyne complex.

The first silylyne complex of a metal beyond group 6, [Cp*((i)Pr3P)(H)Os≡Si(Trip)][HB(C6F5)3], was prepared by a new synthetic route involving hydride abstraction from silicon. NMR and DFT computations support the presence of a silylyne ligand, and NBO and ETS-NOCV analysis revealed the nature of this Os-Si interaction as a triple bond consisting of a covalent σ bond and two strong π back-donations. The discovery of this complex allowed observations of the first cycloadditions involving a silylyne complex, and terminal alkynes are shown to react via C-H bond additions across the Os≡Si bond.

Cyclometalative C-H bond activation in rare earth and actinide metal complexes.

Cyclometalative C-H bond activation is a process that is commonly encountered in the field of organometallic chemistry. In rare earth and actinide complexes, ligand cyclometalation is most prevalent in highly reactive alkyl and hydrido species. Numerous factors promote ligand cyclometalation and influence the rate at which it occurs.

Thermally stable rare earth dialkyl complexes supported by a novel bis(phosphinimine)pyrrole ligand.

A novel bis(phosphinimine)pyrrole based ligand (HL) and its synthesis are reported. Rare earth dialkyl complexes of the ligand, LLn(CH(2)SiMe(3))(2) (Ln = Er, Lu, Sc), have been prepared and found to exhibit high thermal stability in solution. The protio-ligand and dialkyl lanthanide complexes (Ln = Er, Lu) have been characterised by single crystal X-ray diffraction studies.

Ring-opening polymerisation of rac-lactide mediated by cationic zinc complexes featuring P-stereogenic bisphosphinimine ligands.

The diastereomerically pure P-stereogenic bis(phosphinimine) ligands 4,6-(ArN[double bond, length as m-dash]PMePh)(2)dbf [Ar = 4-isopropylphenyl (Pipp): rac-4, meso-4; Ar = 2,6-diisopropylphenyl (Dipp): rac-4a; dbf = dibenzofuran] were synthesised and complexed to zinc using a protonation-alkane elimination strategy. The cationic alkylzinc complexes thus obtained, RZn[4,6-(ArN[double bond, length as m-dash]PMePh)(2)dbf][B(Ar')(4)] [Ar = Pipp, Ar' = C(6)H(3)(CF(3))(2): rac-6 (R = Et), meso-6 (R = Et), rac-7 (R = Me) meso-7 (R = Me); Ar = Dipp: rac-6a (R = Et, Ar' = C(6)H(3)(CF(3))(2)), rac-6b (R = Et, Ar' = C(6)F(5))] were investigated for their competency as initiators for the ring-opening polymerisation of rac-lactide. The formation of polylactide was achieved under relatively mild conditions (40 °C, 2-4 h) and the microstructures of the resulting polymers exhibited a slight heterotactic bias [polymer tacticity (P(r)) = 0.

Toward stereoselective lactide polymerization catalysts: cationic zinc complexes supported by a chiral phosphinimine scaffold.

The P-stereogenic phosphinimine ligands (dbf)MePhP═NAr (7: Ar = Dipp; 8: Ar = Mes; dbf = dibenzofuran, Dipp = 2,6-diisopropylphenyl, Mes = 2,4,6-trimethylphenyl) were synthesized as racemates via reactions of the parent phosphines (rac)-(dbf)MePhP (6) with organoazides. The ligands 7 and 8 were protonated by Brønsted acids to afford the aminophosphonium borate salts [(7)-H][BAr(4)] (9: Ar = C(6)F(5); 11: Ar = Ph) and [(8)-H][BAr(4)] (10: Ar = C(6)F(5); 12: Ar = Ph). The protonated ligands 9 and 10 were active toward alkane elimination reactions with diethylzinc and ethyl-[methyl-(S)-lactate]zinc to give the heteroleptic complexes [{(dbf)MePhP═NAr}ZnR][B(C(6)F(5))(4)] (Ar = Dipp, 13: R = Et; 15: R = methyl-(S)-lactate; Ar = Mes, 14: R = Et; 16: R = methyl-(S)-lactate).

Cationic zinc complexes: a new class of catalyst for living lactide polymerization at ambient temperature.

Cationic zinc complexes of a bis(phosphinimine) pincer ligand have been prepared. Methylzinc and zinc-lactate complexes have been structurally characterized, and the latter is the first cationic metal complex to promote coordination-insertion polymerization of lactide at ambient temperature. This novel catalyst system is remarkably active and also exhibits living character.

Cationic organozinc complexes of a bis(phosphinimine) pincer ligand: synthesis, structural and polymerization studies.

Cationic organozinc complexes of a neutral bis(phosphinimine) pincer ligand (L) have been prepared and structurally characterized. This recently introduced ligand was constructed from a dibenzofuran (dbf) framework with symmetric attachment of phosphinimine groups at the 4 and 6 positions. Starting from protonated derivatives [LH][B(C(6)F(5))(4)] (1a), [LH][BPh(4)] (1b), or [LH(2)][BPh(4)](2) (1c), the complexes [LZnCH(3)][B(C(6)F(5))(4)] (2a), [LZnCH(3)][BPh(4)] (2b), and [LZnOAc][BPh(4)] (3), were prepared via protonolysis of an appropriate alkylzinc precursor.

Complexes of Mg, Ca and Zn as homogeneous catalysts for lactide polymerization.

Interest in the utility of polylactide as a commodity polymer has increased significantly in recent years due to numerous environmental advantages over conventional petrochemically derived plastics. As such, the development of novel catalyst systems for the ring opening polymerization of lactide has seen tremendous progress in the past decade. In particular, divalent metals (i.

A hydrogen-substituted osmium stannylene complex: isomerization to a metallostannylene complex via an unusual alpha-hydrogen migration from tin to osmium.

An osmium complex bearing a terminal hydrogen-substituted stannylene ligand, Cp*((i)Pr(3)P)(H)Os=SnH(trip) (1) (trip = 2,4,6-triisopropylphenyl), has been prepared by stannylene extrusion, and the complex has been structurally characterized. Complex 1 coordinates Lewis bases and activates the O-H bonds of water and methanol. Most interestingly, 1 converts to the metallostannylene complex Cp*((i)Pr(3)P)(H)(2)OsSn(trip) (2) thermally or photochemically by what appears to be a radical process.

Synthetic development and chemical reactivity of transition-metal silylene complexes.

A variety of transition-metal complexes with terminal silylene ligands have become available in recent years, because of the discovery of several preparative methods. In particular, three general synthetic routes to these complexes have emerged, on the basis of anionic group abstraction, coordination of a free silylene, and alpha-hydrogen migration. The direct transformation of organosilanes to silylene ligands at a metal center (silylene extrusion) has also been observed, and this has further spurred the exploration of silylenes as ligands.

Arene complexes of beta-diketiminato supported organoscandium cations: mechanism of arene exchange and alkyne insertion in solvent separated ion pairs.

A family of isolable solvent separated organoscandium methyl cations stabilized by beta-diketiminato ligands (Ar)NC(CH3)CHC(CH3)N(Ar) (Ar=2,6-iPr-C6H3, LMe) has been prepared by reaction of LMeScR2 with [CPh3][B(C6F5)4] in the presence of an arene solvent. Arenes such as bromobenzene, benzene, toluene, para-xylene and mesitylene bind the scandium center in an eta6-bonding mode, yielding cations 1 a-e. Their solution and solid-state structures have been explored using multinuclear NMR spectroscopy and X-ray crystallography.

Hydrogen-substituted osmium silylene complexes: effect of charge localization on catalytic hydrosilation.

Addition of bulky primary silanes to the osmium benzyl compound, Cp*(iPr3P)OsCH2Ph, afforded two neutral hydrogen-substituted silylene complexes via activation of two Si-H bonds. These species have been structurally characterized, and their reactivity has been examined experimentally and computationally. Comparison of these neutral silylene complexes with their cationic analogue highlights the dramatic influence of charge distribution on the reaction chemistry of metal silylene complexes.

Cationic organoscandium beta-diketiminato chemistry: arene exchange kinetics in solvent separated ion pairs.

Abstraction of methide from the beta-diketiminato supported organoscandium complex [L1ScMe2]2 using the trityl borate activator [Ph3C][B(C6F5)4] in arene solvents gives solvent separated ion pairs in which the arene (C6H5Br, 1a; C6H6, 1b; C7H8, 1c; 1,3,5-Me3C6H3, 1d) is coordinated to the cationic scandium center in an eta6 bonding mode. L1 incorporates methyl groups in the 2,4 positions of the ligand backbone and bulky 2,6-diisopropylphenyl groups on the nitrogen atoms. The relative binding strength of the arenes is C6H5Br < C6H6 < 1,3,5-Me3C6H3 < C7H8.