Complex Formation of Lead (II) with Bromopyrogallol Red

The complex formation of lead with Bromopyragallol Red has been studied spectrophotometrically in an attempt to establish composition, stability, thermodynamic parameters and optimum condition for determining small amounts of lead. The blue complex of lead had λ_max at 630 nm (against a reagent blank). The composition as determined by different methods is 1:1 at pH 5.5±0.1. The mean value of log K, free energy (ΔG), the heat content (ΔH) and entropy change (ΔS) of the complex are found to be 6.28, ?10.46 kcal/mole and 6.31 e. u. respectively at 25°C. The molecular extinction coefficient and Sendall's sensitivity is 5000 and 0.0140 μg of lead/cm². The effect of diverse ions was examined with eighteen cations and ten anions, in the determination of lead.     

Yb2+3—xPd12—3+xP7 (x = 0.40): Different Ytterbium Species in a Substituted Structural Motif of the Zr2Fe12P7 Type

The new compound Yb_2+3—xPd_12—3+xP₇ x = 0.40(4)) was synthesized by sintering of a mixture of elemental components at 1100 °C with subsequent annealing at 800 °C. The crystal structure of Yb_2+3—xPd_12—3+xP₇ was solved and refined from X‐ray single‐crystal diffraction data: space group P6¯, a = 10.0094(4)Å, c = 3.9543(2)Å, Z = 1; R(F) = 0.022 for 814 observed unique reflections and 38 refined parameters. The atomic arrangement reproduces a structure motif of the hexagonal Zr₂Fe₁₂P₇ type in which one of the transition metal positions is substituted predominantly by ytterbium (Yb : Pd = 0.86(1) : 0.14). The ytterbium atoms are embedded in the 3D polyanion formed by palladium and phosphorus atoms. Two different environments for ytterbium atoms are present in the structure. Magnetic susceptibility measurements and XAS spectroscopy at the Yb L_III edge show the presence of ytterbium in two electronic configurations, 4?¹³ and 4?¹⁴. The following model was derived. Ytterbium atoms in the 3k site are in the 4?¹³ state, the two remaining positions contain ytterbium in intermediate‐valence states, giving totally 79 % ytterbium in the 4?¹³ electronic configuration.     

Die Konformeren des 5,5-Dimethyl-3,7-dithia-1,2-benzocycloheptens-(1) und ihre Umwandlungen Konformative Beweglichkeit flexibler Ringsysteme—XV. Untersuchungen mit Hilfe der Protonenresonanzspektroskopie

The temperature dependence of the NMR spectrum of 5,5-dimethyl-3,7-dithia-1,2-benzocyclo-heptene-( 1 ) is described and discussed. This compound occurs in two conformers with different topographies of the seven membered ring. From the chemical shift of the 2 geminal methyl groups (obtained by low-temperature spectra) it can be shown that the ring occurs in one case in the chair form and in the other case in the twist form. The free conformational energy of the twist form is only about 20 cal/mole. Two conformational changes can be distinguished: the conversion between chair and twist forms and the pseudorotation of the twist forms. The free activation enthalpies of the conversion (ΔG_V^≠) and the pseudorotation (ΔG_P^≠) are 12·6 ± 0·1 Kcal/mole (at ?12°C) and 8·3 ± 0·3 Kcal/mole (at ?95°C) respectively.     

Crystal Structures and Solution Studies of Two Novel Zinc(II) Complexes of a Proton Transfer Compound Obtained from 2, 6‐Pyridinedicarboxylic Acid and 1, 10‐Phenanthroline: Observation of Strong Intermolecular Hydrogen Bonds

The proton transfer compound LH₂ , (phenH⁺)₂(pydc^2—), has been prepared from 1, 10‐phenanthroline, phen, and 2, 6‐pyridinedicarboxylic acid, (dipicolinic acid), pydcH₂. Characterization was performed using solution and solid phase CP/MAS ¹³C NMR and IR spectroscopy. The reactions of this adduct with ZnSO₄·7H₂O and Zn(NO₃)₂·4H₂O give the complexes, [Zn(pydc)₂][Zn(phen)₂(H₂O)₂]·7H₂O (1) and [Zn(phen)₃]₄(H(Hpydc)₂)(NO₃)₇·26H₂O (2) , respectively. These complexes were characterized by ¹H and ¹³C NMR spectroscopy and single crystal X‐ray analysis. The complexes crystallize in the triclinic space group P1 with Z = 2. The unit cell dimensions for complex 1 and 2 are: a = 9.9838(9) Å, b = 14.7483(13) Å, c = 14.8365(13) Å and a = 12.640(4) Å, b = 15.855(5) Å, c = 21.830(7) Å, respectively. In complex 1 (pydc^2—) and phen, are tri‐ and bidentate ligands, respectively, and an anionic [Zn(pydc)₂]^2— and cationic [Zn(phen)₂(H₂O)₂]²⁺ complex are formed simultaneously. In complex 2 , three phen participate in complexation leaving hydrogen‐bis(pyridine‐2‐carboxylate), (H(Hpydc)₂)^— as a supramolecular anion. The fragments (H(Hpydc)₂)^—, 7 NO₃^—, and 26 H₂O in complex 2 are joined together by extensive and strong H‐bonding; therefore, the structure is composed of [Zn(phen)₃]₄⁸⁺, and an anionic hydrogen bond supramolecular assembly with the formula, {(H(Hpydc)₂(NO₃)₇)^8— · 26H₂O}_n. The anionic species (H(Hpydc)₂)^— has a special position at the inversion center, as well as one of the NO₃^— anions, which is disordered over the inversion center. Most of the hydrogen bonds in complex 2 represent strong H‐bonding. The protonation constants of the building blocks of the pydc‐phen adduct, the equilibrium constants for the reaction of (pydc^2—) with phenanthroline and the stoichiometry and stability of the Zn^II complex with LH₂ on aqueous solution were determined by potentiometric pH titration. The solution study results support self‐association between (pydc^2—) and (phenH⁺) with a stoichiometry for the Zn(II) complex similar to that observed for the isolated crystalline complex.     

A novel heterometallic dinuclear compound: rac‐pentaaqua‐1κ5O‐(μ‐2‐sulfidoacetato‐1:2κ3O:O′,S)bis(2‐sulfidoacetato‐2κ2O,S)manganese(II)tin(IV)

The title racemic heterometallic dinuclear compound, [MnSn(C₂H₂O₂S)₃(H₂O)₅], (I), contains one main group Sn^IV metal centre and one transition metal Mn^II centre, and, by design, links the Mn^II centre to the building unit of the (Δ/Λ) [SnL₃]²⁻ complex anion (L is the 2‐sulfidoacetate dianion). In this cluster, the Sn^IV centre of the (Δ/Λ) [SnL₃]²⁻ unit is coordinated by three O atoms and three S atoms from three L ligands to form an [SnO₃S₃] octahedral coordination environment. The Mn^II centre is in an [MnO₆] octahedral coordination environment, with five O atoms from five water molecules and the sixth from the μ₂‐L ligand of the (Δ/Λ) [SnL₃]²⁻ unit. Between adjacent dinuclear molecules, there are many hydrogen‐bond interactions of O—H...O, O—H...S, C—H...O and C—H...S types. Of these, eight pairs of O—H...O hydrogen bonds fuse all the dinuclear molecules into two‐dimensional supramolecular sheets along the bc plane. Adjacent supramolecular sheets are further connected through O—H...S hydrogen bonds to give a three‐dimensional supramolecular network.     

A Thermodynamic Study of Chromotropico-Titanium(III) Complex from Spectrophotometric Measurements

The formation of 1 : 2 titanium(III) complex with chromotropic acid (4, 5-dihydroxy-2, 7-naphthalene-disulfonic acid) was observed by spectrophotometric measurements at various ionic strengths. An expression, [Ti(III)]/D=1/Δ? + α_H²+/KΔ?[H₂R^2?]², was derived for the determination of the formation constant, K=7.2×10² liter² mol^?2 for the Ti(III).(HR)₂ ion in the pH range of 1.3–1.8 at constant ionic strength, I=0.2 M, at 25°C. The thermodynamic data for the reaction, Ti(III)+2H₃R^2?=Ti(III) (HR)₂+2H⁺, were calculated to be ΔG° = ?16 kJ mol^?1 ΔH° = 18 kJ mol^?1, ΔS° = 110 JK^?1 mol^?1, at 25°C.     

Kinetics of the I2-catalyzed isomerization of allyl chloride to cis- and trans-1-chloro-1-propene. The stabilization energy of the chloroallyl radical

The I₂-catalyzed isomerization of allyl chloride to cis- and trans- l-chloro-l-propene was measured in a static system in the temperature range 225–329°C. Propylene was found as a side product, mainly at the lower temperatures. The rate constant for an abstraction of a hydrogen atom from allyl chloride by an iodine atom was found to obey the equation log [k,/M^?1 sec^?1] = (10.5 ± 0.2) ?; (18.3 ± 10.4)/θ, where θ is 2.303RT in kcal/mole. Using this activation energy together with 1 ± 1 kcal/mole for the activation energy for the reaction of HI with alkyl radicals gives DH⁰ (CH₂CHCHCl? H) = 88.6 ± 1.1 kcal/mole, and 7.4 ± 1.5 kcal/mole as the stabilization energy (SE) of the chloroallyl radical. Using the results of Abell and Adolf on allyl fluoride and allyl bromide, we conclude DH⁰ (CH₂CHCHF? H) = 88.6 ± 1.1 and DH⁰ (CH₂CHCHBr? H) = 89.4 ± 1.1 kcal/ mole; the SE of the corresponding radicals are 7.4 ± 2.2 and 7.8 ± 1.5 kcal/mole. The bond dissociation energies of the C? H bonds in the allyl halides are similar to that of propene, while the SE values are about 2 kcal/mole less than in the allyl radical, resulting perhaps more from the stabilization of alkyl radicals by α-halogen atoms than from differences in the unsaturated systems.     

Novel Derivatives of the CaIn2 Type of Structure: Yb1+xMg1—xGa4 (0 ≤ x ≤ 0.058) and YLiGa4

The compounds Yb_1+xMg_1—xGa₄ (0 ≤ x ≤ 0.058) and YLiGa₄ were synthesized by direct reaction of the elements in sealed niobium crucibles. The atomic arrangement of Yb_1+xMg_1—xGa₄ (x = 0.058) represents a new structure type (space group P6¯m2, a = 4.3979(3)Å and c = 6.9671(7)Å) as evidenced by single crystal structure analysis and can be described as an ordered variant of CaIn₂. YLiGa₄ is isotypic to the ytterbium compound according to X‐ray Guinier powder data (a = 4.3168(1)Å and c = 6.8716(2)Å). Measurements of the magnetic susceptibility of both compounds reveal intrinsic diamagnetic behaviour, i.e., ytterbium in the 4f¹⁴ configuration for Yb_1+xMg_1—xGa₄ (x = 0). From electrical resistivity data both compounds can be classified as metals. The compressibility of Yb_1+xMg_1—xGa₄ (x = 0.058) as measured in diamond anvil cells by angle‐dispersive X‐ray diffraction is compatible with a valence change of the ytterbium atoms at high‐pressures and indicates a slight anisotropy which is in accordance with the structural organisation of the gallium network. X‐ray absorption spectra of the Yb L_III edge of Yb_1+xMg_1—xGa₄ (x = 0.058) at pressures up to 25.0 GPa show a two‐peak structure which reveals the presence of Yb in the 4f¹⁴ and 4f¹³ states. The amount of ytterbium in the 4f¹³ state increases in two steps with progressing compression. The bonding analysis by means of the electron localization function reveals the Zintl‐like character of both compounds and confirms the 4f¹⁴ state for the majority of ytterbium atoms.     

A Novel Proton Transfer Self‐Associated Compound from Dipicolinic Acid and Guanidine and Its Cadmium(II) Complex: Synthesis,Characterization, Crystal Structure,and Solution Studies

A novel 1:2 proton transfer self‐associated compound LH₂ , (GH⁺)₂(pydc^2—), was synthesized from the reaction of dipicolinic acid, pydcH₂, (2, 6‐pyridinedicarboxylic acid), and guanidine hydrochloride, (GH⁺)(Cl^—). The characterization was performed using IR, ¹H and ¹³C NMR spectroscopy and single‐crystal X‐ray diffraction. LH₂ · H₂O crystallizes in the space group C2/c of the monoclinic system and contains eight molecules per unit cell. The unit cell dimensions are: a = 26.480(5)Å, b = 8.055(2)Å, c = 14.068(3)Å. The first coordination complex (GH)₂[Cd(pydc)₂] · 2H₂O, was prepared using LH₂ and cadmium(II) iodide, and characterized by ¹H and ¹³C NMR spectroscopy and X‐ray crystallography. The crystal system is triclinic with space group P1¯ with one molecule per unit cell. The unit cell dimensions are: a = 8.5125(7)Å, b = 11.0731(8)Å, c = 13.2404(10)Å. The cadmium(II) atom is six‐coordinated with a distorted octahedral geometry. The two pydc^2— units are almost perpendicular to each other. The protonation constants of the building blocks of the pydc‐guanidine adduct, the equilibrium constants for the reaction of pydc^2— with guanidine and the stoichiometry and stability of the Cd²⁺ complex with LH₂ in aqueous solution were accomplished by potentiometric pH titration. The solution studies strongly support a self‐association between pydc^2— and GH⁺ with a stoichiometry for the Cd^II complex similar to that observed for the isolated crystalline complex. In fact, the [Cd(pydc)₂]^2— complex was found as the most abundant species in solution (> 90 %) at a pH >5.     

Reaction of hydrogen atoms and O2(1Δg)

The reaction of atomic hydrogen with O₂(¹Δ_g) has been investigated as a function of temperature, using a fast discharge-flow apparatus equipped for EPR detection of free radical species. The rate constant for the overall reaction was measured as (1.46 ± 0.49) × 10^?11 exp(-4000 ± 200 cal/mol/RT) cm³/s. Evidence is presented which suggests that the reaction occurs principally via abstraction, H + O₂(¹Δ_g) → OH + O, rather than via physical quenching, H + O₂(¹Δ_g) → H + O₂(X³Σ_g^?).     

Low valent tungsten reaction—Composition studies and reactions with sulfoxides and pyridine-N-oxides

Sulfoxides are converted to the corresponding sulfides in good yields by low valent tungsten agents derived from WCl₆—BuLi(1) and WCl₆—Zn (2). Pyridine-N-Oxides are also reduced easily with 1 to give the corresponding pyridines in almost quantitative yields. A yellow solid WCl₄ (THF)_n is isolated from the reaction of one mole of WCl₆ and two mole of n-BuLi in tetrahydrofuran (THF) at low temperature, and its composition is established by using ESCA. IR, ¹H and ¹²C NMR. Reaction of WCl₄ (THF)_n with excess of pyridine gives the known WCl₄(C₅H₅N)₂.     

Magnetic Investigations and 151Eu Mössbauer Spectroscopy of MYbSi4N7 with M = Sr,Ba, Eu

The isotypic nitridosilicates MYb[Si₄N₇] (M = Sr, Ba, Eu) were obtained by the reaction of the respective metals with Si(NH)₂ in a radiofrequency furnace below 1600 °C. On the basis of powder diffraction data of MYb[Si₄N₇] Rietveld refinements of the lattice constants were performed; these confirmed the previously published single‐crystal data. The compounds contain a condensed network of corner‐sharing [N(SiN₃)₄] units. The central nitrogen thus exhibits ammonium character. Magnetic susceptibility measurements of MYb[Si₄N₇] (M = Sr, Ba, Eu) show paramagnetic behavior with experimental magnetic moments of 3.03(2), (Sr), 2.73(2) (Ba), and 9.17(2) (Eu) μ_B per formula unit. In EuYbSi₄N₇ the europium and ytterbium atoms are in stable divalent and trivalent states, respectively. According to the non‐magnetic character of the alkaline earth cations, ytterbium has to be in an intermediate valence state Yb^III‐x in the strontium and barium compound. Consequently, either a partial exchange N^3—/O^2— resulting in compositions MYb^III‐x[Si₄N_7—xO_x] or an introduction of anion defects according to MYb^III‐x[Si₄N_7—x/3□_x/3] has to be assumed. The phase width 0 ≤ x ≤ 0.4 was estimated according to the magnetic measurements. ¹⁵¹Eu Mössbauer spectra of EuYb[Si₄N₇] at 78 K show a single signal at an isomer shift of δ = —12.83(3) mm s^—1 subject to quadrupole splitting of ΔE_Q = 5.7(8) mm s^—1, compatible with purely divalent europium.     

A cyano‐bridged dinuclear 4f–3d array

A cyano‐bridged bimetallic 4f–3d complex, tri­aqua‐1κ³O‐μ‐cyano‐1:2κ²N:C‐penta­cyano‐2κ⁵C‐tetrakis(2‐pyrrolidone‐1κO)­chromium(III)­dysprosium(III) dihydrate, [CrDy(C₄H₇NO)₄(CN)₆(H₂O)₃]·2H₂O, has been prepared and characterized by X‐ray crystallographic analysis. The structure consists of a neutral cyano‐bridged Dy–Cr dimer. A hydrogen‐bonded three‐dimensional architecture is formed through N—H?O, O—H?N and O—H?O hydrogen bonds.     

Bis(η5‐isopropyltetramethylcyclo­pentadienyl)(tetrahydroborato‐κ3H,H′,H′′)(tetrahydrofuran‐O)‐samarium(III): a lanthanidocene complex with a tridentate tetrahydroborato ligand

The lanthanidocene complex [Sm(BH₄)(C₁₂H₁₉)₂(C₄H₈O)], (I), shows a distorted tetrahedral arrangement around the central Sm^III atom. It consists of two η⁵‐isopropyltetramethylcyclopentadienyl ligands, one tetrahydroborato (BH₄^?) ligand bridging via H atoms to the lanthanide atom and one coordinating tetrahydrofuran (thf) molecule. The BH₄^? unit of (I) coordinates as a tridentate ligand with three bridging H atoms and one terminal H atom [Sm—B—H4 176 (2)°]. The η⁵‐isopropyl­tetra­methylcyclopentadienyl ligands of this bent‐sandwich complex [Cp1—Sm—Cp2 133.53 (1)° where Cp denotes the centroid of the cyclopentadienyl ring] adopt staggered conformations.     

Thermogravimetric investigation of the dehydration thermodynamics of amorphous silica after its hydrothermal and thermovaporous treatment

After hydrothermal and thermovaporous treatment of chemically pure amorphous aqueous silicic acid in solutions of NaOH and NH₄OH and in water vapour it is possible, using complex thermal analysis, to detect the weight loss and heat effects corresponding to evaporation of various forms of combined water, and to estimate the heats of evaporation of these forms. From the obtained data, the following water forms have been identified: (1) at 200–300° capillary-condensed water formations of the cluster type evaporate;ΔH _deh is about 8 kcal/mole H₂O; (2) at 250–400°, molecules of water linked by hydrogen bonds with hydroxyl groups on the surface and in the volume of the particles;ΔH _deh. is about 5 kcal/mole H₂O; (3) at 350 600°, molecules of water coordinated to silicon atoms in the volume of the particles;ΔH _deh is approximately 1 kcal/mole H₂O. The total evaporation heat changes from 10 kcal/mole H₂O when water of form 1 predominates, to 5 kcal/mole H₂O when forms 2 and 3 predominate.     

Novel Motif of Hydrogen Bonds in the Water-assisted Supramolecular Self-assembly of 2-acetylamino-6-methylpyridine-N-oxide and Hetero-assembly of 1:1 Co-crystal of o-Phenylenediamine with Catechol

Abstract

Water assisted supramolecular structures of 2-acetylamino-6-methylpyridine-1-oxide (1) and 1:1 complex of o-phenylenediamine with catechol (2) were determined. The crystal structure of 2-acetylamino-6-methylpyridine-1-oxide. H₂O (1), triclinic, a = 7.1276 (6), b = 7.8860 (6), c = 8.9938 (7) Å, α = 100. 143 (2), β = 91.493 (2), γ = 110.972 (1)°, V =462.47 (6) ų, Z = 2, D _calc = 1.323 mg.m^?3(293°K) reveals a novel centrosymmetric supramolecular assembly that is sustained by water molecules linking the dimers of pyridine-1-oxide through C—H…O, N—H…O, N⁺—O^? … H hydrogen bonds. The pyridine rings of the dimers are stacked at 3.473 Å apart, involving π- stacking interactions. Complex (2), C₆H₈N₂.—C₆ H₆O₂. 1/2H₂O crystallises in the monoclinic space group P2/c: a = 9.0498(2), b = 5.2275(1), c = 25.0771(2) A, β = 97.71°, V= 1175.62(4) ų, Z = 4. Refinement led to a final conventional R value of 0.041 for 2016 reflections. In these crystals (2), the water molecules lie on the twofold axis and they are linked to the pyrocatechol molecules through an O—H…O hydrogen bond.     

10‐Benzyl‐4‐oxo‐2,3,4,10‐tetrahydropyrimido[4,5‐b]quinolin‐2‐iminium chloride sesquihydrate: a polarized electronic structure within a complex hydrogen‐bonded sheet structure

In the title compound, C₁₈H₁₅N₄O⁺·Cl⁻·1.5H₂O, one water site is fully ordered with unit occupancy while the other, which lies close to an inversion centre in the space group C2/c, has only 0.5 occupancy. The cation exhibits bond fixation in the fused carbocyclic ring and electronic polarization in the terminal heterocyclic ring. The components are linked into complex sheets by a combination of N—H...O, N—H...Cl, O—H...O, O—H...Cl and C—H...O hydrogen bonds.     

3‐Nitrophenol–4,4′‐bipyridyl N,N′‐dioxide (2/1): a DFT study and CSD analysis of DPNO molecular complexes

The title 2:1 complex of 3‐nitrophenol (MNP) and 4,4′‐bipyridyl N,N′‐dioxide (DPNO), 2C₆H₅NO₃·C₁₀H₈N₂O₂ or 2MNP·DPNO, crystallizes as a centrosymmetric three‐component adduct with a dihedral angle of 59.40 (8)° between the planes of the benzene rings of MNP and DPNO (the DPNO moiety lies across a crystallographic inversion centre located at the mid‐point of the C—C bond linking its aromatic rings). The complex owes its formation to O—H...O hydrogen bonds [O...O = 2.605 (3) Å]. Molecules are linked by intermolecular C—H...O and C—H...N interactions forming R₂¹(6) and R₂²(10) rings, and R₆⁶(34) and R₄⁴(26) macro‐rings, all of which are aligned along the [01] direction, and R₂²(10) and R₂¹(7) rings aligned along the [010] direction. The combination of chains of rings along the [01] and [010] directions generates the three‐dimensional structure. A total of 27 systems containing the DNPO molecule and forming molecular complexes of an organic nature were analysed and compared with the structural characteristics of the dioxide reported here. The N—O distance [1.325 (2) Å] depends not only on the interactions involving the O atom at the N—O group, but also on the structural ordering and additional three‐dimensional interactions in the crystal structure. A density functional theory (DFT) optimized structure at the B3LYP/6‐311G(d,p) level is compared with the molecular structure in the solid state.     

Organolanthanoids: VII. The crystal and molecular structure of dibromo-η5-cyclopentadienyltris(tetrahydrofuran)ytterbium(III)

Crystals of dibromo-η⁵-cyclopentadienyltris(tetrahydrofuran)ytterbium(III) are monoclinic, P2₁/n (C_2n⁵, No. 14), with a 15.310(15), b 16.900(17), c 7.968(8) Å, β 96.66(5)° and Z = 4. The ytterbium is pseudo-octahedrally coordinated by a cyclopentadienyl ligand, trans bromines, and mer tetrahydrofuran ligands, and the ytterbium—oxygen distance trans to cyclopentadienyl is longer than the other ytterbium—oxygen bonds.     

Theoretical prediction of Ni(I)-catalyst for hydrosilylation of pyridine and quinoline

Catalytic synthesis of dihydropyridine by transition-metal complex is one of the important research targets, recently. Density functional theory calculations here demonstrate that nickel(I) hydride complex (bpy)Ni^IH (bpy = 2,2′-bipyridine) 1 is a good catalyst for hydrosilylation of both quinoline and pyridine. Two pathways are possible; in path 1, substrate reacts with 1 to form stable intermediate Int1 . After that, N³─C¹ bond of substrate inserts into Ni─H bond of 1 via TS1 to afford N-coordinated 1,2-dihydroquinoline Int2 with the Gibbs activation energy (ΔG°^‡) of 21.8 kcal mol⁻¹. Then, Int2 reacts with hydrosilane to form hydrosilane σ-complex Int3 ; this is named path 1A. In the other route (path 1B), Int1 reacts with phenylsilane in a concerted manner via hydride-shuttle transition state TS2 to afford Int3 . In TS2 , Si atom takes hypervalent trigonal bipyramidal structure. Formation of hypervalent structure is crucial for stabilization of TS2 (ΔG°^‡ = 17.3 kcal mol⁻¹). The final step of path 1 is metathesis between Ni─N³ bond of Int3 and Si─H bond of PhSiH₃ to afford N-silylated 1,2-dihydroproduct and regenerate 1 (ΔG°^‡ = 4.5 kcal mol⁻¹). In path 2, 1 reacts with hydrosilane to form Int5 , which then forms adduct Int6 with substrate through Si–N interaction between substrate and PhSiH₃. Then, N-silylated 1,2-dihydroproduct is produced via hydride-shuttle transition state TS5 (ΔG°^‡ = 18.8 kcal mol⁻¹). The absence of N-coordination of substrate to Ni^I in TS5 is the reason why path 2 is less favorable than path 1B. Quinoline hydrosilylation occurs more easily than pyridine because quinoline has the lowest unoccupied molecular orbital at lower energy than that of pyridine. © 2019 Wiley Periodicals, Inc.