title: Core expansion reactions of cyanamido/carbodiimido-bridged polynuclear iridium complexes.
abstract: Core expansion reactions of di- and tetrairidium complexes [Cp*Ir(mu(2)-NCN-N,N)](2) (1; Cp* = eta(5)-C(5)Me(5)), [Cp*Ir(mu(3)-NCN-N,N,N)](4) (2), and phosphine derivatives of 1 have been investigated, and it has been revealed that cyanamido ligands in these complexes can change their coordination modes flexibly on reactions with a second transition metal complex. Treatment of diiridium complex 1 with [Cp*IrCl(2)](2) gives the tetrairidium complex [(Cp*Ir)(2)(mu(3)-NCN-N,N,N')(2)(IrCp*Cl(2))(2)] (6) with mu(3)-kappaN,kappaN,kappaN' cyanoimido(2-) ligands. On the other hand, the reaction of 1 with [PdCl(eta(3)-C(3)H(5))](2) affords the NCN-bridged Ir(2)Pd(4) hexanuclear complex [(Cp*IrCl)(2)(mu(4)-NCN-N,N,N',N')(2){Pd(2)(mu-Cl)(eta(3)-C(3)H(5))(2)}(2)] (7) and Ir(4)Pd(4) octanuclear complex [(Cp*Ir)(4)(mu(4)-NCN-N,N,N,N')(4){PdCl(eta(3)-C(3)H(5))}(4)] (8). The NCN-bridges in 7 provide the first example of the crystallographically determined mu(4)-kappaN,kappaN,kappaN',kappaN' carbodiimido(2-) ligand. Complex 8 with mu(4)-kappaN,kappaN,kappaN,kappaN' cyanoimido(2-) ligands can also be synthesized selectively by the reaction of the parent cubane complex 2 with [PdCl(eta(3)-C(3)H(5))](2). Diphosphine derivative of 1, [{Cp*Ir(mu(2)-NCN)}(2)(mu-dppm)] (4; dppm = Ph(2)PCH(2)PPh(2)), behaves differently on reactions with [PdCl(eta(3)-C(3)H(5))](2) and [MCl(cod)](2) (cod = cycloocta-1,5-diene) to form the NCN-bridged Ir(2)M(2) (M = Pd, Rh, Ir) tetranuclear complexes [(Cp*Ir)(2)(mu(3)-NCN-N,N,N')(2){PdCl(eta(3)-C(3)H(5))}(2)(mu-dppm)] (9) and [(Cp*Ir)(2)(mu(3)-NCN-N,N,N')(2){MCl(cod)}(2)(mu-dppm)] (11a, M = Rh; 11b, M = Ir), respectively. The molecular structures for 6, 7, 8, 11a, and 11b have been determined by single-crystal X-ray analyses.
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Imaji
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Tanabe
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Mutoh
authors.forename: Youichi
authors.initials: Y
authors.lastname: Ishii