Chasing the agostic interaction in ligand assisted cyclometallation reactions of palladium(ii).

A 500 MHz NMR study of the reaction between 1-tetralone oxime and PdCl in CDOD shows resonances attributable to a potential agostic intermediate prior to the formation of the insoluble cyclopalladated product which itself was characterised by X-ray crystallography. Calculated structural, spectroscopic, QTAIM, NBO and NCI analysis results obtained from density functional theory (DFT) calculations give a full description of the putative agostic intermediate [PdCl(1-tetralone oxime)] (1) which is shown to include a previously unrecognised π-electron density donation from the aromatic ring to the metal in close proximity to the agostic carbon atom. Changing the (N)-OH donor to (N)-OMe does not effect the magnitude of these interactions.

New complexity for aromatic ring agostic interactions.

Density functional theory (DFT) calculations reveal that for ligand directed aromatic ring C-H bond activation, the agostic donation can share the same antibonding acceptor orbitals as a previously unrecognised π-donation from the aromatic ring of the ligand. The recognition of carbon based orbitals assisting the agostic interaction has significant implication for C-H bond activation chemistry.

4-tert-Butyl-pyridinium chloride-4,4'-(propane-2,2-di-yl)bis-(2,6-di-methyl-phenol)-toluene (2/2/1).

In the title solvated salt, C9H14N(+)·Cl(-)·C19H24O2·0.5C7H7, two mol-ecules of 4,4'-(propane-2,2-di-yl)bis-(2,6-di-methyl-phenol) are linked via O-H⋯Cl hydrogen bonds to two chloride ions, each of which is also engaged in N-H⋯Cl hydrogen bonding to a 4-tert-butyl-pyridinium cation, giving a cyclic hydrogen-bonded entity centred at 1/2, 1/2, 1/2. The toluene solvent mol-ecule resides in the lattice and resides on an inversion centre; the disorder of the methyl group requires it to have a site-occupancy factor of 0.

Bis(μ-2-hy-droxy-methyl-2-methyl-propane-1,3-diolato)bis-[di-chlorido-titanium(IV)] diethyl ether disolvate.

The title complex, [Ti2Cl4{CH3C(CH2O)2(CH2OH)}2], lies across a centre of symmetry with a diethyl ether solvent mol-ecule hydrogen bonded to the -CH2OH groups on either side of it. The Ti(IV) atom is coordinated in a distorted octa-hedral geometry by a tripodal ligand and two terminal chloride atoms. There are three coordination modes for the tripodal ligand distinguishable on the basis of their very different Ti-O bond lengths.

[6,6'-Bis(1,1-di-methyl-eth-yl)-4,4'-dimethyl-2,2'-methyl-enediphenolato-κ(2) O,O']di-chlorido-(9H-fluoren-9-ol-κO)titanium(IV)-fluorene-diethyl ether (1/0.5/1).

The title adduct, [TiCl2(C23H30O2)(C13H10O]·0.5C13H10·C4H10O, is a monomer with a trigonal-bypyramidal coordination sphere of the Ti(IV) atom in which the ligand O atoms of the bidentate diphenolate anion are located in both apical and equatorial positions. Chloride ligands occupy the remaining two equatorial sites of the trigonal bypyramid with the fluoren-9-ol O atom occupying the other apical site.

Di-μ-methanolato-bis[(2-tert-butyl-6-methylphenolato-κO)methyl-titanium(IV)].

The molecule of the title compound, [Ti2(CH3)2(CH3O)2(C11H15O)4] or {[Ti(Me)(μ-OCH3)(OC6H3CMe3-2-Me-6)]2}, has a centrosymmetric, dimeric structure with a distorted square pyramidal array about each titanium atom. The methoxide ligands form an asymmetric bridge between the two Ti(IV) atoms [Ti-O bond lengths of 1.9794 (12) and 2.

Identification of non-classical C-H···M interactions in early and late transition metal complexes containing the CH(ArO)3 ligand.

The fully optimised DFT structure of the d(0) complex [{CH(ArO)3}Ti(NEt2)] (2) at the B3LYP level compares well with the distorted tetrahedral geometry shown by the X-ray crystal structure. QTAIM analysis of the electron density associated with the C-H···Ti interaction shows a well defined bond critical point, a bond path between the hydrogen and titanium centres and a negative value for the energy density indicative of covalency. A natural bond orbital (NBO) picture of the interaction shows that the C-H σ bond electron density donates to a d hybrid orbital on the metal in a linear fashion.

Analysis of M···H-Si interactions in [{M(CpSiMe2H)Cl3}2], (M = Zr, Hf, Ti and Mo) complexes.

For the d(0) complex [{Zr(CpSiMe(2)H)Cl(3)}(2)] which contains a linear Si-H···Zr interaction across the dimer, DFT calculations are in good agreement with X-ray structures. The BP86 functional shows a slightly stronger interaction than B3LYP but for qualitative purposes either functional is sufficient. QTAIM analysis shows a bond critical point (bcp) for the interaction, a small negative value for the total energy density [H((r))] and the H atomic basin decreases in energy, E(H), and atomic volume compared to the free ligand.

(2,2'-Bipyridine-κN,N')[2-tert-butyl-anilinato(2-)]dichloridooxido-molybdenum(VI) dichloro-methane hemisolvate.

The Mo(VI) atom in the title structure, [Mo(C(10)H(13)N)Cl(2)O(C(10)H(8)N(2))]·0.5CH(2)Cl(2), has a distorted octa-hedral coord-ination sphere with cis-orientated oxide and imide ligands, trans-chloride ligands and the 2,2'-bipyridine (bipy) ligand N atoms lying trans to the oxide and imide ligands. An imide-ligand tert-butyl-methyl-group H atom makes a close approach with the oxide ligand (distance = 2.

A case for linear agostic interactions: identification by DFT calculation in a complex of Ta containing a uniquely caged triphenylmethyl C-H hydrogen.

Reaction of one equivalent of tris(3,5-di-tert-butyl-2-hydroxy)methane with TaCl5 in CH2Cl2 along with Et3N gave a solid which on prolonged crystallisation led to a small quantity of crystalline material. An X-ray crystal structure determination showed one crystal was [TaCl3[[OC6H2(CMe3)2-2,4]3CH]]- Et2NH2+.3C6H6.

A zirconium zwitterion containing a caged amine H atom.

The crystallographically centrosymmetric zwitterion bis[tris(3,5-dimethyl-2-oxidobenzyl-kappaO)ammonium]zirconium(IV) crystallizes as the chloroform disolvate, [Zr(C(27)H(31)NO(3))(2)].2CHCl(3), with the two molecules of chloroform closely associated with two of the aromatic rings. The Zr atom has a distorted octahedral geometry with three phenoxy O atoms from each of the two ligands coordinated to it.