Synthesis of NPN-Coordinated Tantalum Alkyl Complexes and Their Hydrogenolysis: Isolation of a Terminal Tantalum Hydride Incorporating a Doubly Cyclometalated NPN Scaffold.

The closely related benzylene-linked diaminophosphines PhP(CHCH-o-NHPh) (AH) and PhP(CH-o-CHNHXyl) (BH with Xyl = 3,5-MeCH) were employed for the synthesis of tantalum(V) alkyls, which were then studied with respect to hydrogenolysis. In the case of AH, the tantalum trimethyl complex [Ta(A)Me] (1) and the tantalum hydrocarbyl complex [Ta(A)(CHSiMe)(η-EtC≡CEt)] (2) were prepared from the ligand's dilithium salt (A)Li(diox). Upon hydrogenolysis of 1 and 2, the formation of methane and SiMe, respectively, was observed, but well-defined tantalum hydrides could not be detected.

Benzylene-linked [PNP] scaffolds and their cyclometalated zirconium and hafnium complexes.

The benzylene-linked [PNP] scaffolds HN(CH-o-CHPPh) ([A]H) and HN(CH-o-CHPPh) ([B]H) have been used for the synthesis of zirconium and hafnium complexes. For both ligands, the dimethylamides [A]M(NMe) ([A]1-M) and [B]M(NMe) ([B]1-M) were prepared and converted to the iodides [A]MI ([A]2-M) and [B]MI ([B]2-M) (M = Zr, Hf). Starting from these iodides, the corresponding benzyl derivatives [A]MBn ([A]3-M) and [B]MBn ([B]3-M) (M = Zr, Hf) were obtained via reaction with BnMg(OEt).

Synthesis and reactivity of cyclometalated triamidophosphine complexes of niobium and tantalum.

The triamidophosphine protioligand 1 reacts with the homoleptic pentakis(dimethylamido) precursors of niobium and tantalum [M(NMe2)5, where M = Nb, Ta] to form cyclometalated complexes of the type [N2PCN-κ(5)-N,N,P,C,N]M(NMe2) (2-M). Apart from the three amido donors, one benzylic position of the ligand backbone is deprotonated over the course of this reaction, resulting in the formation of a new M-C bond. As a consequence, a metallaziridine substructure is formed, and the triamidophosphine moiety thus serves as a tetraanionic pentadentate ligand.

A tripodal benzylene-linked trisamidophosphine ligand scaffold: synthesis and coordination chemistry with group(IV) metals.

A new tripodal trisamidophosphine ligand (1) based on the trisbenzylphosphine backbone has been synthesized in three steps starting from NaPH2 and phthaloyl-protected 2-aminobenzyl bromide. At elevated temperatures, 1 reacts directly with M(NMe2)4 (M = Zr, Hf) to afford the dimethylamido complexes [PN3]M(NMe2) (M = Zr, Hf) (2), which are easily converted into the corresponding triflates [PN3]MOTf (M = Zr, Hf) (3) via reaction with triethylsilyl trifluoromethanesulfonate. The related titanium chloro complex [PN3]TiCl (4-Ti) is obtained from 1 and Bn3TiCl via protonolysis.