Synthesis of a Library of Iridium-Containing Dinuclear Complexes with Bridging PNNN and PNNP Ligands (BL),[LM(mu-BL)M'L']BF_4.1.Specific Synthesis of Isomeric Heterodinuclear Complexes with Switched Metal Arrangements

摘要

Specific synthesis of a series of Ir-containing homo- and heterodinuclear complexes with the PNNP (3,5-bis((diphenylphosphino)methyl)pyrazolato) and PNNN ligands (3-(diphenylphosphino)methyl-5-pyridylpyrazolato) is reported.Reaction of the PNNX-H precursors (X = P,N) with [Ir(cod)_2]BF_4 gives pale yellow precipitates,which are characterized as the cyclic dimers of the 1:1 adduct,[(MU-KAPPA~1(P):KAPPA~2(N,X-PNNX-H)Ir(cod)]_2(BF_4)_2 (X = P,N).In the case of the PNNN system,subsequent sequential treatment of the 1:1 adduct with NEt_3 and a second metal reagent ([M(L)(cod)]BF_4:M(L) = Rh(cod),Pd(allyl)) (reaction 1) gives [(cod)Ir(PNNN)M(L)]BF_4,whereas the reversed addition of the reagents (reaction 2) furnishes [(L)M(PNNN)Ir(cod)]BF_4,the regioisomer with the switched metal arrangement.Selective preparation of the heterodinuclear PNNP complexes [(cod)Ir(PNNP)M(L)]BF_4 requires the addition according to reaction 1.In reaction 1 of the 1:1 dinuclear adduct of the PNNN system,depro-tonation of the N-H part triggers interligand migration of the Ir(cod) fragment from the N,N site of one ligand to the P,N site of the other ligand to give [(cod)Ir(PNNN)]BF_4,which reacts with the second metal fragment at the N,N site to furnish [(cod)Ir(PNNN)M(L)]BF_4.On the other hand,reaction 2 involves dissociation of the dinuclear species into the mononuclear N,N-coordinated one,[(PNNN-H)Ir(cod)]BF_4,and subsequent interaction at the free P moiety followed by deprotonation and coordination gives the other regioisomer.These intriguing transformations result from the unique coordination properties of Ir (cationic vs neutral,hard vs soft,5- vs 4-coordination,N,N vs P,N chelation),which are controlled by the deprotonation-protonation procedure.As a result of the present study,a library for Ir-containing homo- and heterodinuclear Ir(I) complexes with the PNNP and PNNN ligands has been constructed.