16971-01-0Relevant articles and documents
Metallaboratranes: Bis- and tris(methimazolyl)borane complexes of group 9 metal carbonyls and thiocarbonyls
Crossley, Ian R.,Hill, Anthony F.,Willis, Anthony C.
, p. 326 - 336 (2010/03/25)
The iridium poly(methimazolayl)borane complexes [IrH(CE)(PPh3) {κ3-B,S,S-B(mt)2R}](Ir→B) (mt = methimazolyl = 2-mercapto-3-methylimidazol-l-yl; E = O, S; R = mt, H) are described in detail. For R = mt, these materials are elucidated as paradigms for the final mechanistic intermediate in metallaboratrane formation, a role illustrated through hydride abstraction to afford the cationic salts [Ir(CE)(PPh 3){κ4-B(mt)3}]X(Ir→)8 (E = O, S; X = Cl, BF4). The rhodium poly(methimazolyl)borate complexes [Rh(CO)(PPh3){κ2-S,S'-HB(mt)2R}] (R = mt, H) are also reported. These compounds are obtained in preference to the respective borane complexes (analogous to iridium); however [Rh(CO)(PPh 3){κ2-S,S'-HB(mt)3}] is observed to undergo facile solution-phase conversion to [Rh(CO)(PPh3) {κ4-B,S,S ,S"-B(mt)3}]Cl(Rh→B)8 in chlorinated solvents. The ramifications of these results, with respect to metallaboratrane formation, are discussed, substantiating previous mechanistic conjecture. In an attempt to establish an alternative route to iridaboratranes, the first isolable tris(methimazolyl)borate complex of iridium, cis,cis-[IrHCl(PPh3)2{κ2-S,S'-HB(mt)3], is reported and shown not to evolve to the iridaboratrane [IrCl(PPh 3){κ4-B(mt)3}](Ir→B)8 under conditions that lead to the corresponding rhodaboratrane. Factors are discussed that may contribute to this fine balance between the formation of methimazolylborate and methimazolylborane complexes.
Iridium(III) Complex Containing a Unique Bifurcated Hydrogen Bond Interaction Involving Ir-H?H(N)?F-B atoms. Crystal and Molecular Structure of [IrH(η1-SC5H4NH)(η2-SC 5H4N)(PPh3)2](BF 4)·0.5C6H6
Park, Sunghan,Lough, Alan J.,Morris, Robert H.
, p. 3001 - 3006 (2008/10/09)
A synthetic route to a new iridium(III) complex containing a novel proton hydride bonding interaction has been established. fac-IrH3(PPh3)3 reacts with 2-mercaptopyridine HSpy (Spy = 2-SC5H4N) to give the known dihydride Ir(H)2(η2-Spy)(PPh3)2 8. Ir(H)2(η2-Spy)(PPh3)2 reacts with HSpy· HBF4 to give [IrH(η1-SC5H4NH)(η2-SC 5H4N)-(PPh3)2](BF4) 9 which possesses a unique bifurcated hydrogen bonding interaction involving Ir-H?H(N)?F-B atoms with the distances of 2.0(1) A? for the H?H unit and of 2.0(1) A? for the F?H unit in the crystalline state. In solution the N-H?H-Ir interaction is maintained according to 1H T1(min) and nOe measurements. Isotope shifts in the chemical shifts of the hydride and one phosphorus of 9 have been observed in 1H and 31P{1H} NMR spectra of [IrH(η1-SC5H4ND)(η2-SC 5H4N)(PPh3)2](BF4), 9-d1, prepared by the reaction of 9 with MeOD or CF3-CO2D. The crystal and molecular structure of [IrH(η1-SC5H4NH)(η2-SC 5H4N)(PPh3)2](BF 4)·0.5C6H6 9 has been solved by X-ray analysis: monoclinic space group P21/c with a = 17.723(3) A?, b = 10.408(1) A?, c = 26.073(4) A?, β= 108.08(1)°, V = 4572.0(11) A?3, and Z = 4. The known complex fac-IrH3(PPh3)3, 7, is made by a new and improved method by reacting mer-IrHCl2(PPh3)3 with NaOEt and H2(g). VT-1H NMR spectra (+90 to -80 °C) of the hydrides of 7 reveal that the JAA and JAX couplings change in the AA'A''XX'X'' pattern (A = 1H, X = 31P) but that the complex is not fluxional. The T1(min) value of 0.144 s for the hydrides of 7 at -60 °C (300 MHz) indicates that the shortest H-H distances are about 1.8 A?.
