Binding of Nitriles and Isonitriles to V(III) and Mo(III) Complexes: Ligand vs Metal Controlled Mechanism.

The synthesis and structures of nitrile complexes of V(N[Bu]Ar), (Ar = 3,5-MeCH), are described. Thermochemical and kinetic data for their formation were determined by variable temperature Fourier transform infrared (FTIR), calorimetry, and stopped-flow techniques. The extent of back-bonding from metal to coordinated nitrile indicates that electron donation from the metal to the nitrile plays a less prominent role for than for the related complex Mo(N[Bu]Ar), .

Dihydrogen cleavage by a dimetalloxycarbene-borane frustrated Lewis pair.

A frustrated Lewis pair of dititanoxycarbene [(Ti(N[Bu]Ar))(μ-CO)] (Ar = 3,5-MeCH) and B(CF) cleaved dihydrogen under ambient conditions to give the zwitterionic formate [(Ti(N[Bu]Ar))(μ-OCHO-ηO:ηO')(B(CF))] and the hydrido borate [Ti(N[Bu]Ar)][HB(CF)].

Countercation Effect on CO Binding to Oxo Titanate with Bulky Anilide Ligands.

This work focuses on nucleophilic activation of CO at the anionic terminal oxo titanium tris(anilide) complexes [(Solv) M][OTi(N[ Bu]Ar) ] with M=Li, Na, K, Mg, MgMe, AlCl , AlI ; Ar=3,5-Me C H ; Solv=Et O, THF, 12-crown-4, 2,2,2-cryptand; n, m=1-2. The CO binding strength to the terminal oxo ligand of [OTi(N[ Bu]Ar) ] ([1] ) and the stability of the resulting carbonate moiety [O COTi(N[ Bu]Ar) ] ([2] ) are highly dependent on the Lewis acidity of the countercation. We report herein on CO binding as a function of countercation and countercation coordination environment, and comment in this respect on the bottom and upper limits of the cation Lewis acidity.

A Dimetalloxycarbene Bonding Mode and Reductive Coupling Mechanism for Oxalate Formation from CO2.

We describe the stable and isolable dimetalloxycarbene [(TiX3 )2 (μ2 -CO2 -κ(2) C,O:κO')] 5, where X=N-(tert-butyl)-3,5-dimethylanilide, which is stabilized by fluctuating μ2 -κ(2) C,O:κ(1) O' coordination of the carbene carbon to both titanium centers of the dinuclear complex 5, as shown by variable-temperature NMR studies. Quantum chemical calculations on the unmodified molecule indicated a higher energy of only +10.5 kJ mol(-1) for the μ2 -κ(1) O:κ(1) O' bonding mode of the free dimetalloxycarbene compared to the μ2 -κ(2) C,O:κ(1) O' bonding mode of the masked dimetalloxycarbene.

Experimental and computational studies on the formation of cyanate from early metal terminal nitrido ligands and carbon monoxide.

An important challenge in the artificial fixation of N2 is to find atom efficient transformations that yield value-added products. Here we explore the coordination complex mediated conversion of ubiquitous species, CO and N2, into isocyanate. We have conceptually split the process into three steps: (1) the six-electron splitting of dinitrogen into terminal metal nitrido ligands, (2) the reduction of the complex by two electrons with CO to form an isocyanate linkage, and (3) the one electron reduction of the metal isocyanate complex to regenerate the starting metal complex and release the product.

Thermodynamic and kinetic study of cleavage of the N-O bond of N-oxides by a vanadium(III) complex: enhanced oxygen atom transfer reaction rates for adducts of nitrous oxide and mesityl nitrile oxide.

Thermodynamic, kinetic, and computational studies are reported for oxygen atom transfer (OAT) to the complex V(N[t-Bu]Ar)3 (Ar = 3,5-C6H3Me2, 1) from compounds containing N-O bonds with a range of BDEs spanning nearly 100 kcal mol(-1): PhNO (108) > SIPr/MesCNO (75) > PyO (63) > IPr/N2O (62) > MesCNO (53) > N2O (40) > dbabhNO (10) (Mes = mesityl; SIPr = 1,3-bis(diisopropyl)phenylimidazolin-2-ylidene; Py = pyridine; IPr = 1,3-bis(diisopropyl)phenylimidazol-2-ylidene; dbabh = 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene).

Facile synthesis of zero-, one-, and two-dimensional vanadyl pyrophosphates.

Crystallization of Na(2)VOP(2)O(7) from its aqueous solution results in formation of a one-dimensional inorganic polymer {Na(2)VO(H(2)O)P(2)O(7)·7H(2)O}(n) (1). When this polymer is dehydrated at elevated temperatures this polymer undergoes a phase transition to form the two-dimensional framework β-Na(2)VOP(2)O(7), which although previously reported had been difficult to access. Exchanging lithium for sodium via ion-exchange chromatography results in formation of a discrete, cyclic, tetramer species, Li(8)[VOP(2)O(7)(H(2)O)·4H(2)O](4) (2).

Ligand-based reduction of CO(2) to CO mediated by an anionic niobium nitride complex.

The terminal nitride anion complex [Na][N[triple bond]Nb(N[(t)Bu]Ar)(3)] ([Na][1], Ar = 3,5-Me(2)C(6)H(3)) reacts quantitatively with CO(2) to give the carbamate complex [Na][O(2)CN[triple bond]Nb(N[(t)Bu]Ar)(3)] ([Na][O(2)C-1]). The structure of [Na][O(2)C-1] as the bis-12-crown-4 solvate, as determined by X-ray crystallography, displays a unique N-bound carbamate ligand without any metal-oxygen interactions. When treated with organic acid anhydrides or acid chlorides, complex [Na][O(2)C-1] reacts via salt elimination to give the five-coordinate complexes (RC(O)O)(OCN)Nb(N[(t)Bu]Ar)(3) (R-2, R = Me, (t)Bu, F(3)C).

Two-electron reduction of a vanadium(V) nitride by CO to release cyanate and open a coordination site.

We report herein that the terminal nitride complex Na[NV(N[t-Bu]Ar)(3)] (Na[1-VN], Ar = 3,5-Me(2)C(6)H(3)) reacts with CO over the course of 24 h to generate V(N[t-Bu]Ar)(3) (1-V) and sodium cyanate in an isolated yield of 77%. The reaction products were identified using a combination of NMR and IR spectroscopy, and cyanate formation was further confirmed by performing a (13)C labeling experiment. In addition, we report on the synthesis and structural characterization of the isocyanate complex (OCN)V(N[t-Bu]Ar)(3) (1-V(NCO)) to compare its redox chemistry with that of (OCN)Nb(N[t-Bu]Ar)(3) (1-Nb(NCO)).

Pyridyl 'ring-flipping' in the dimers [Me2E(2-py)]2 (E=B, Al, Ga; 2-py=2-pyridyl).

The boron and aluminium dimers [Me2E(micro-py)]2 [E=B (1); Al (2)] are formed as mixtures of two isomers in which the group 13 centres are coordinated by the bridging 2-py ligands in a cis or trans manner, however, in contrast to previous studies, we find that simply heating the mixtures of these isomers of and gives the more thermodynamically stable (synthetically useful) trans isomers exclusively (the trans isomer being the only product in the case of the gallium analogue ).