Formate complexes of titanium(iv) supported by a triamido-amine ligand

Abstract

The terminal formate complex [(OCHO)Ti(NN)] (3) containing the trianionic triamido-amine ligand (MeSiNCHCH)N (NN) was prepared via salt metathesis of [ClTi(NN)] (1) with sodium formate or alternatively by treatment of the alkyl complex [BuTi(NN)] (2) with ammonium formate [HNEt][OCHO]. Deprotonation of 3 with potassium hexamethyldisilazide gave a polymeric helical chain of the oxo complex {K[OTi(NN)]} (4). Reaction of 2 with the trityl salt [PhC][B(3,5-ClCH)] or the Brønsted acid [HNEt][B(CF)] gave [(EtO)Ti(NN)][BR] (6[BR]·EtO) with R = 3,5-ClCH or CF. The diethyl ether ligand was easily replaced by other L-type donor ligands such as tetrahydrofuran, pyridine, and 4-dimethylaminopyridine to give 6[BR]·L with L = thf, py, and dmap. Reaction of 6[BR]·EtO with a stoichiometric amount of CO gave the dimeric, dicationic bis(carbamate)-bridged complexes [Ti{N(CHCHNSiMe)(CHCHNSiMe(μ-CO-ηO:ηO'))}][BR] (7[BR]) through insertion of one CO into one of the titanium-amido bonds. Addition of pyridine to 7[B(CF)] formed the monomeric carbamate complex [(py)Ti{((OC-κO,O')NSiMeCHCH)N(CHCHNSiMe)}][B(CF)] (8[B(CF)]·py). The cationic formate-bridged species [(Ti(NN))(μ-OCHO-ηO:ηO')][BR] (10[BR]) readily formed when the terminal formate complex 3 was reacted with the cationic 6[BR]. The reactivity of triamido-amine stabilized titanium(iv) complexes is shown to differ considerably from that of related titanium tris(anilide) complexes.

Photo-Initiated Radical Hydrophosphination at Titanium Compounds Capable of Ti–P Insertion

“…The NMR spectra of 2 are simple, featuring an indicative methyl resonance at δ = 1.00 and methylene triplets at δ = 3.35, 2.16 in the 1 H NMR spectrum. Spectra of 2 are consistent with related derivatives. ,,, …”

Titanium(IV) Cations with Trigonal Monopyramidal Geometry: Unusual Lewis Acids Supported by a Triaryl Triamidoamine Ligand

“…The titanium atoms are markedly lifted above the equatorial plane spanned by the three amide nitrogen atoms ( 1[B(Ar Cl ) 4 ] : d (Ti1−N plane )=0.498(4) Å; 1[B(Ar F ) 4 ] : d (Ti1−N plane )=0.4906(10) Å), which resulted in an average N eq ‐Ti1‐N ax angle of 75.30°. The displacement of the titanium atoms from the equatorial plane in 1[B(Ar X ) 4 ] is even more pronounced than that in the analogous complex [Ti(OEt 2 )(TMS‐N 3 N)][B(3,5‐Cl 2 C 6 H 3 ) 4 ] ( d (Ti1−N plane )=0.381(2) Å; TMS‐N 3 N=[(Me 3 SiNCH 2 CH 2 ) 3 N] 3− ) with TBP geometry around the titanium center . The Ti−N eq bonds in both complexes ( 1[B(Ar Cl ) 4 ] : d (Ti1−N eq ) avg =1.932 Å; 1[B(Ar F ) 4 ] : d (Ti1−N eq ) avg =1.929 Å) are significantly shorter than the Ti−N ax bonds ( 1[B(Ar Cl ) 4 ] : d (Ti1−N ax )=2.309(6) Å; 1[B(Ar F ) 4 ] : d (Ti1−N ax )=2.311(2) Å); thus suggesting a significant N eq →Ti pπ–dπ bonding interaction.…”

“…with TBP geometry around the titaniumc enter. [10] The TiÀN eq bonds in both complexes (1[B(Ar Cl ) 4 ]: d(Ti1ÀN eq ) avg = 1.932 ; 1[B(Ar F ) 4 ]: d(Ti1ÀN eq ) avg = 1.929 )a re significantly shorter than the TiÀN ax bonds (1[B(Ar Cl ) 4 ]: d(Ti1ÀN ax ) = 2.309 (6) ; 1[B(Ar F ) 4 ]: d(Ti1ÀN ax ) = 2.311(2) ); thus suggesting as ignificant N eq !Ti pp-dp bonding interaction.…”

Organotitanium Complexes Supported by a Dianionic Pentadentate Ligand

“…The FT-IR spectrum features strong intensity bands at 1673 and 1244 cm -1 corresponding to the asymmetric and symmetric stretching vibrations of the CO2 unit respectively, consistent with other monodentate titanium formate complexes. 39,40 The large Δν of 429 cm -1 in 2-OC(H)O is indicative of a k 1 formate moiety, contrasting with the k 2 formato bonding mode observed in the corresponding B2Pz4Py scandium complex. 27 The difference in denticity between scandium and titanium is attributable to the lower oxophilicity and smaller ionic radius in the latter.…”