New C-tetrazolato complexes of rhodium(III), palladium(II) and gold(III)

Azide Chemistry – An Inorganic Perspective, Part II[‡][3+2]‐Cycloaddition Reactions of Metal Azides and Related Systems

“…[504] Unequivocal proof of the carbodiimide nature of related products through X-ray structure analyses, however, has only recently been furnished by Y.-J. Kim and co-workers in a series of papers dealing with group 10 transition metals and, in particular, with palladium.…”

“…[62] A promising novel synthetic strategy was introduced by us in 2000. [504] Running the reaction L n M-N 3 + CNR in water allowed us to start from azido complexes generated in situ (Table 7). Analogous nickel(II) species have been obtained by metathesis from NiCl 2 (PEt 3 ) 2 and 1-alkyl-5-tetrazolyllithium already in the late sixties.…”

“…[504] [Cp*Rh(μ-N 3 )(N 3 )] 2 is a special case insofar as it entered into cycloaddition with CNCH 2 CO 2 Na, but incorporated methylisocyanide only as an additional ligand. Note that this co-existence in the same ligand sphere of potential reaction partners in compounds such as [Cp*Rh(N 3 ) 2 (CNMe)] [185] or [M(N 3 )(CO) 5 ]…”

“…chapters 1 and 3), i.e., the cycloaddition occurs the faster, the more electron-rich the isocyanide is. [36,504] However inconsistent this observation may seem in case of planar complexes, it greatly helps to understand the reactions with azidocobalt(III) chelate complexes for which the above mechanism (Equation (34)) is out of the question. Certainly, isocyanides can enter into the complex, which they frequently do by substitution of the trans-base (Table 7), but then how to approach the azide?…”

“…Though no unambiguous spectroscopic and/or structural evidence could be furnished, the authors suggested that one of the four tetrazole rings at a time was protonated at the N 4 atom to afford "normal" monocarbene species. [504] A different mechanism of ligand detachment -presumably a reductive elimination of HCN 4 Ar -takes place on treatment of trans-[Pt(H){CN 4 Ar}(PEt 3 ) 2 ] (Ar = 2,6-Me 2 C 6 H 3 ) with the diphosphine depe, even if Kim et al refrained from both an interpretation and an isolation of the organic byproduct of Pt(depe) 2 . [60] Aiming at a new type of N-heterocyclic carbene (NHC) complexes which have turned out to be suitable alternatives for phosphines in organometallic catalysis, the groups of Raubenheimer and Huynh were the first to carry out alkylation studies of C-tetrazolato complexes of gold(I) and nickel(II), successfully underlaid with X-ray structure analyses.…”