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The closely related benzylene-linked diaminophosphines PhP(CH 2 C 6 H 4 -o-NHPh) 2 (AH 2 ) and PhP(C 6 H 4 -o-CH 2 NHXyl) 2 (BH 2 with Xyl = 3,5-Me 2 C 6 H 3 ) were employed for the synthesis of tantalum(V) alkyls, which were then studied with respect to hydrogenolysis. In the case of AH 2 , the tantalum trimethyl complex [Ta(A)Me 3 ] (1) and the tantalum hydrocarbyl complex [Ta(A)(CH 2 SiMe 3 )(η 2 -EtC≡CEt)] (2) were prepared from the ligand's dilithium salt (A)Li 2 (diox). Upon hydrogenolysis of 1 and 2, the formation of methane and SiMe 4 , respectively, was observed, but well-defined tantalum hydrides could not be detected. In the case of BH 2 , the cyclometalated species [Ta(B*)(NMe 2 ) 2 ] (3 with B* = κ 4 -N,P,N,C-(PhP(C 6 H 4 -o-CH 2 NXyl)(C 6 H 4 -o-CHNXyl)) 3- ) was isolated and converted to the corresponding diiodo species [Ta(B*)I 2 ] (4). Treatment of 4 with LiCH 2 SiMe 3 resulted in the isolation of the corresponding dialkyl complex [Ta(B*)(CH 2 SiMe 3 ) 2 ] (5), which was converted to the doubly cyclometalated monoalkyl complexes [Ta(B**)(CH 2 SiMe 3 )(PMe 3 )] (6 with B** = κ 5 -C,N,P,N,C-(PhP(C 6 H 4 -o-CHNXyl) 2 ) 4- ) and [Ta(B**)(CH 2 SiMe 3 )(dmpe)] (7) via reaction with PMe 3 and dmpe, respectively. In contrast to 5 and 6, 7 was found to react cleanly with dihydrogen to afford the corresponding terminal tantalum(V) hydride [Ta(B**)(H)(dmpe)] (8). Upon reaction of 7 with D 2 , the deuteride [Ta(d 2 -B**)(D)(dmpe)] (9) was obtained and found to contain deuterium atoms in the methine positions of both tantalaaziridine subunits. The partially deuterated derivatives [Ta(B**)(D)(dmpe)] (10) and [Ta(d 2 -B**)(H)(dmpe)] (11) were generated via reaction of 8 and 9 with PhSiD 3 and PhSiH 3 , respectively. Prior to the addition of gaseous D 2 or H 2 , no H/D scrambling was observed in 10 or 11, indicating that the exchange of the methine positions proceeds via addition of D 2 or H 2 across the tantalaaziridine Ta-C bonds.

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. Triple deprotonation of 1 with n-butyllithium affords the tris-lithium salt Li3[PN3] (1-Li), which serves as a common starting material for the preparation of all the group(IV) chlorides [PN3]MCl (M = Ti, Zr, Hf) (4). Upon treatment of 4-Ti with Bn2Mg(thf)2, formation of a benzyltitanium species is observed, which is converted cleanly into a ligand-CH-activated species (5-Ti).