The Intramolecular Rearrangement of Phosphinohydrazides [R′2P–NR–NR–M] → [RNPR′2–NR–M]: General Rules and Exceptions. Transformations of Bulky Phosphinohydrazines (R–NH–N(PPh2)2, R = tBu, Ph2P)

Reactions of diphosphinohydrazines R–NH–N­(PPh2)2 (R = tBu (1), Ph2P (3)) with some metalation reagents (Co­[N­(SiMe3)2]2, LiN­(SiMe3)2, La­[N­(SiMe3)2]3, nBuLi, MeLi) were performed. Compound 1 was synthesized by the reaction of Ph2PCl with tert-butylhydrazine hydrochloride in 83% yield. This compound reveals temperature-dependent 31P NMR spectra due to hindered rotation about the P–N bonds. Complicated redox reaction of 1 with Co­[N­(SiMe3)2]2 proceeds with cleavage of the P–N and N–N bonds to form a binuclear cobalt complex [Co­{HN­(PPh2)2-κ2P,P′}2(μ-PPh2)]2 (2) demonstrating a short Co···Co distance of 2.3857(5) Å, which implies a formal double bond between the Co atoms. Strong nucleophiles (nBuLi, MeLi) cause fragmentation of the molecules 1 and 3, while reactions of 3 with lithium and lanthanum silylamides give products of the NNP → NPN rearrangement [Li­{Ph2P­(NPPh2)2-κ2N,N′}­(THF)2] (4) and [La­{Ph2P­(NPPh2)2-κ2N,N′}­{N­(SiMe3)2}2] (5), respectively. These complexes represent the first examples of a κ2N,N′ bonding mode for the triphosphazenide ligand [(Ph2PN)2PPh2]−. DFT calculations showed large energy gain (52.1 kcal/mol) of the [NNP]− to [NPN]− anion rearrangement.