Solid/Gas Reactivity of an Ir(I) Methylidene Complex.

stabilization of known, but solution unstable, methylidene complex [Ir(Bu-PONOP)(=CH)][BAr ] allows single-crystal to single-crystal solid/gas reactivity associated with the {Ir=CH} group to be studied. Addition of H results in [Ir(Bu-PONOP)(H)][BAr ]; exposure to CO forms iridium(I) carbonyl [Ir(Bu-PONOP)(CO)][BAr ], and reaction with NH gas results in the formation of methylamine complex [(Bu-PONOP)Ir(NHMe)][BAr ] via an aminocarbene intermediate. Periodic density functional theory and electronic structure analyses confirm the Ir=CH bond character but with a very low barrier to rotation around the Ir=CH bond.

Platinum(II) Phenylpyridyl Schiff Base Complexes as Latent, Photoactivated, Alkene Hydrosilylation Catalysts.

Photoactivated catalysts for the hydrosilylation of alkenes with silanes offer temporal control in manufacturing processes that require silicone curing. We report the development of a range of air-stable Pt(II) (salicylaldimine)(phenylpyridyl), [Pt(sal)(ppy)], complexes as photoinitiated hydrosilylation catalysts. Some of these catalysts show appreciable latency in thermal catalysis and can also be rapidly (10 s) activated by a LED UV-light source (365 nm), to give systems that selectively couple trimethylvinylsilane and hexamethylsiloxymethylsilane to give the linear hydrosilylation product.

A Gold(I)-Acetylene Complex Synthesised using Single-Crystal Reactivity.

Using single-crystal to single-crystal solid/gas reactivity the gold(I) acetylene complex [Au(L1)(η-HC≡CH)][BAr ] is cleanly synthesized by addition of acetylene gas to single crystals of [Au(L1)(CO)][BAr ] [L1=tris-2-(4,4'-di-tert-butylbiphenyl)phosphine, Ar=3,5-(CF)CH]. This simplest gold-alkyne complex has been characterized by single crystal X-ray diffraction, solution and solid-state NMR spectroscopy and periodic DFT. Bonding of HC≡CH with [Au(L1)] comprises both σ-donation and π-backdonation with additional dispersion interactions within the cavity-shaped phosphine.

Controlled cluster expansion at a Zintl cluster surface.

Reaction of the tris-hypersilyl nonagermanide Zintl cluster salt, K[Ge (Hyp) ] (Hyp=Si(SiMe ) ) with [Rh(η ,η -L)Cl] (L=1,5-cyclooctadiene, COD; norbornadiene, NBD) afforded eleven- and twelve-vertex homo-multimetallic clusters by cluster core expansion. Using a stepwise procedure, starting from the Zintl cluster [Rh(COD){Ge (Hyp) }] and [Ir(COD)Cl] , this methodology was expanded for the synthesis of eleven-vertex hetero-multimetallic clusters. A mechanism for the formation of these first examples of closo eleven-vertex Zintl clusters is proposed, informed by density functional theory calculations.

lattice adaptivity triggered by solid-gas reactions of cationic group 7 pincer complexes.

The group 7 complexes [M(κ-2,6-(RPO)CHN)(CO)L][BAr] [M = Mn, R = Pr, L = THF; M = Re, R = Bu, L = vacant site] undergo solid-gas reactivity with CO to form the products of THF substitution or CO addition respectively. There is a large, local, adaptive change of [BAr] anions for M = Mn, whereas for M = Re the changes are smaller and also remote to the site of reactivity.

Dehydropolymerization of Amine-Boranes using Bis(imino)pyridine Rhodium Pre-Catalysis: σ-Amine-Borane Complexes, Nanoparticles, and Low Residual-Metal BN-Polymers that can be Chemically Repurposed.

The sigma amine-borane complexes [Rh(L1)(η :η -H B⋅NRH )][OTf] (L1=2,6-bis-[1-(2,6-diisopropylphenylimino)ethyl]pyridine, R=Me, Et, Pr) are described, alongside [Rh(L1)(NMeH )][OTf]. Using R=Me as a pre-catalyst (1 mol %) the dehydropolymerization of H B ⋅ NMeH gives [H BNMeH] selectively. Added NMeH , or the direct use of [Rh(L1)(NMeH )][OTf], is required for initiation of catalysis, which is suggested to operate through the formation of a neutral hydride complex, Rh(L1)H.

A comparison of non-covalent interactions in the crystal structures of two σ-alkane complexes of Rh exhibiting contrasting stabilities in the solid state.

Non-covalent interactions surrounding the cationic Rh σ-alkane complexes within the crystal structures of [(CyPCHCHPCy)Rh(NBA)][BAr], [1-NBA][BArF4] (NBA = norbornane, CH; Ar = 3,5-(CF)CH), and [1-propane][BArF4] are analysed using Quantum Theory of Atoms in Molecules (QTAIM) and Independent Gradient Model approaches, the latter under a Hirshfeld partitioning scheme (IGMH). In both structures the cations reside in an octahedral array of [BAr] anions within which the [1-NBA]+ cation system exhibits a greater number of C-H⋯F contacts to the anions. QTAIM and IGMH analyses indicate these include the strongest individual atom-atom non-covalent interactions between the cation and the anion in these systems.

Mechanistic Insights into Molecular Crystalline Organometallic Heterogeneous Catalysis through Parahydrogen-Based Nuclear Magnetic Resonance Studies.

The heterogeneous solid-gas reactions of crystals of [Rh(L)(propene)][BAr] (, L = BuPCHCHPBu) with H and propene, 1-butene, propyne, or 1-butyne are explored by gas-phase nuclear magnetic resonance (NMR) spectroscopy under batch conditions at 25 °C. The temporal evolution of the resulting parahydrogen-induced polarization (PHIP) effects measures catalytic flux and thus interrogates the efficiency of catalytic pairwise -H transfer, speciation changes in the crystalline catalyst at the molecular level, and allows for high-quality single-scan H, C NMR gas-phase spectra for the products to be obtained, as well as 2D-measurements. Complex reacts with H to form dimeric [Rh(L)(H)(μ-H)][BAr] (), as probed using EXAFS; meanwhile, a single-crystal of equilibrates NMR silent -H with its NMR active ortho isomer, contemporaneously converting into , and and each convert -H into -H at different rates.

Polyphosphinoborane Block Copolymer Synthesis Using Catalytic Reversible Chain-Transfer Dehydropolymerization.

An amphiphilic block copolymer of polyphosphinoborane has been prepared by a mechanism-led strategy of the sequential catalytic dehydropolymerization of precursor monomers, H B ⋅ PRH (R=Ph, n-hexyl), using the simple pre-catalyst [Rh(Ph PCH CH PPh ) ]Cl. Speciation, mechanism and polymer chain growth studies support a step-growth process where reversible chain transfer occurs, i.e.

Dehydropolymerization of HB·NMeH Mediated by Cationic Iridium(III) Precatalysts Bearing κ- Pr-PN P Pincer Ligands ( = H, Me): An Unexpected Inner-Sphere Mechanism.

The dehydropolymerization of HB·NMeH to form -methylpolyaminoborane using neutral and cationic catalysts based on the {Ir( Pr-PNP)} fragment [ Pr-PNP = κ-(CHCHP Pr)NH] is reported. Neutral Ir( Pr-PNP)H or Ir( Pr-PNP)HCl precatalysts show no, or poor and unselective, activity respectively at 298 K in 1,2-FCH solution. In contrast, addition of [NMeH][BAr ] (Ar = 3,5-(CF)CH) to Ir( Pr-PNP)H immediately starts catalysis, suggesting that a cationic catalytic manifold operates.

Zintl cluster supported low coordinate Rh(i) centers for catalytic H/D exchange between H and D.

Ligand exchange reactions of [Rh(COD){η-Ge(Hyp)}] with L-type nucleophiles such as PMe, PPh, IMe (IMe = 1,3,4,5-tetramethylimidazol-2-ylidene) or [W(Cp)H] result in the displacement of the COD ligand to afford clusters with coordinatively unsaturated trigonal pyramidal rhodium(i) centers [Rh(L){η-Ge(Hyp)}]. These species can be readily protonated allowing access to cationic rhodium-hydride complexes, [RhH(PPh){η-Ge(Hyp)}]. These clusters act as catalysts in H/D exchange between H and D and alkene isomerisation, thereby illustrating that metal-functionalized Zintl clusters are active in both H-H and C-H bond activation processes.

Inverse Isotope Effects in Single-Crystal to Single-Crystal Reactivity and the Isolation of a Rhodium Cyclooctane σ-Alkane Complex.

The sequential solid/gas single-crystal to single-crystal reaction of [Rh(CyP(CH)PCy)(COD)][BAr ] (COD = cyclooctadiene) with H or D was followed in situ by solid-state P{H} NMR spectroscopy (SSNMR) and ex situ by solution quenching and GC-MS. This was quantified using a two-step Johnson-Mehl-Avrami-Kologoromov (JMAK) model that revealed an inverse isotope effect for the second addition of H, that forms a σ-alkane complex [Rh(CyP(CH)PCy)(COA)][BAr ]. Using D, a temporal window is determined in which a structural solution for this σ-alkane complex is possible, which reveals an η,η-binding mode to the Rh(I) center, as supported by periodic density functional theory (DFT) calculations.

MicroED characterization of a robust cationic σ-alkane complex stabilized by the [B(3,5-(SF)CH)] anion, on-grid solid/gas single-crystal to single-crystal reactivity.

Microcrystalline (∼1 μm) [Rh(CyPCHCHPCy)(norbornadiene)][S-BAr], [S-BAr] = [B(3,5-(SF)CH)], reacts with H in a single-crystal to single-crystal transformation to form the σ-alkane complex [Rh(CyPCHCHPCy)(norbornane)][S-BAr], for which the structure was determined by microcrystal Electron Diffraction (microED), to 0.95 Å resolution, an on-grid hydrogenation, and a complementary single-crystal X-ray diffraction study on larger, but challenging to isolate, crystals. Comparison with the [BAr] analogue [Ar = 3,5-(CF)(CH)] shows that the [S-BAr] anion makes the σ-alkane complex robust towards decomposition both thermally and when suspended in pentane.

Controlled Synthesis of Well-Defined Polyaminoboranes on Scale Using a Robust and Efficient Catalyst.

The air tolerant precatalyst, [Rh(L)(NBD)]Cl () [L = κ-(PrPCHCH)NH, NBD = norbornadiene], mediates the selective synthesis of -methylpolyaminoborane, (HBNMeH), by dehydropolymerization of HB·NMeH. Kinetic, speciation, and DFT studies show an induction period in which the active catalyst, Rh(L)H (), forms, which sits as an outer-sphere adduct as the resting state. At the end of catalysis, dormant Rh(L)HCl () is formed.

Metathesis by Partner Interchange in σ-Bond Ligands: Expanding Applications of the σ-CAM Mechanism.

In 2007 two of us defined the σ-Complex Assisted Metathesis mechanism (Perutz and Sabo-Etienne, Angew. Chem. Int.

-aryl substituted DPEphos ligands: rhodium complexes featuring C-H anagostic interactions and B-H agostic bonds.

The synthesis of new Schrock-Osborn Rh(i) pre-catalysts with -substituted DPEphos ligands, [Rh(DPEphos-R)(NBD)][BAr ] [R = Me, OMe, Pr; Ar = 3,5-(CF)CH], is described. Along with the previously reported R = H variant, variable temperature H NMR spectroscopic and single-crystal X-ray diffraction studies show that these all have axial (C-H)⋯Rh anagostic interactions relative to the d pseudo square planar metal centres, that also result in corresponding downfield chemical shifts. Analysis by NBO, QTAIM and NCI methods shows these to be only very weak C-H⋯Rh bonding interactions, the magnitudes of which do not correlate with the observed chemical shifts.

Cluster expansion and vertex substitution pathways in nickel germanide Zintl clusters.

We describe the reactivity of the hypersilyl-functionalized Zintl cluster salt K[Ge9(Hyp)3] towards the nickel reagents Ni(COD)2 and Ni(Cp)2, which gives rise to markedly different complexes. In the case of Ni(COD)2 (COD = 1,5-cyclooctadiene), a dianionic sandwich-like cluster [Ni{Ge9(Hyp)3}2]2- (1) was obtained, in line with a simple ligand substitution reaction of COD by [Ge9(Hyp)3]-. By contrast, when an analogous reaction with Ni(Cp)2 (Cp = cyclopentadienyl) was performed, vertex substitution of the [Ge9(Hyp)3]- precursor was observed, giving rise to the nine-vertex nido-cluster (Cp)Ni[Ge8(Hyp)3] (2).

A Series of Crystallographically Characterized Linear and Branched σ-Alkane Complexes of Rhodium: From Propane to 3-Methylpentane.

Using solid-state molecular organometallic (SMOM) techniques, in particular solid/gas single-crystal to single-crystal reactivity, a series of σ-alkane complexes of the general formula [Rh(CyPCHCHPCy)(η:η-alkane)][BAr] have been prepared (alkane = propane, 2-methylbutane, hexane, 3-methylpentane; Ar = 3,5-(CF)CH). These new complexes have been characterized using single crystal X-ray diffraction, solid-state NMR spectroscopy and DFT computational techniques and present a variety of Rh(I)···H-C binding motifs at the metal coordination site: 1,2-η:η (2-methylbutane), 1,3-η:η (propane), 2,4-η:η (hexane), and 1,4-η:η (3-methylpentane). For the linear alkanes propane and hexane, some additional Rh(I)···H-C interactions with the geminal C-H bonds are also evident.

η-Alkene Complexes of [Rh(PONOP-Pr)(L)] Cations (L = COD, NBD, Ethene). Intramolecular Alkene-Assisted Hydrogenation and Dihydrogen Complex [Rh(PONOP-Pr)(η-H)].

Rhodium-alkene complexes of the pincer ligand κ-CHN-2,6-(OPPr) (PONOP-Pr) have been prepared and structurally characterized: [Rh(PONOP-Pr)(η-alkene)][BAr] [alkene = cyclooctadiene (COD), norbornadiene (NBD), ethene; Ar = 3,5-(CF)CH]. Only one of these, alkene = COD, undergoes a reaction with H (1 bar), to form [Rh(PONOP-Pr)(η-COE)][BAr] (COE = cyclooctene), while the others show no significant reactivity. This COE complex does not undergo further hydrogenation.

Selectivity of Rh⋅⋅⋅H-C Binding in a σ-Alkane Complex Controlled by the Secondary Microenvironment in the Solid State.

Single-crystal to single-crystal solid-state molecular organometallic (SMOM) techniques are used for the synthesis and structural characterization of the σ-alkane complex [Rh(tBu PCH CH CH PtBu )(η ,η -C H )][BAr ] (Ar =3,5-(CF ) C H ), in which the alkane (norbornane) binds through two exo-C-H⋅⋅⋅Rh interactions. In contrast, the bis-cyclohexyl phosphine analogue shows endo-alkane binding. A comparison of the two systems, supported by periodic DFT calculations, NCI plots and Hirshfeld surface analyses, traces this different regioselectivity to subtle changes in the local microenvironment surrounding the alkane ligand.