Phosphine-Based Dinuclear Platinum(II) Diamido, Amido−Hydroxo, Oxo−Amido, Oxo−Imido, Diimido, and Dihydrazido Complexes1

Two-Electron Reduction of a U(VI) Complex with Al(C5Me5)

The reduction of U(VI) to U(IV) is rare, especially in one step, and not observed electrochemically as a one-wave, two-electron couple. Here, we demonstrate that reduction of the uranium(VI) bis(imido) complex, (C₅Me₅)₂U[═N(4-OⁱPrC₆H₄)]₂, is readily accomplished with Al(C₅Me₅), forming the bridging uranium(IV)/aluminum(III) imido complex (C₅Me₅)₂U[μ₂-N(4-OⁱPrC₆H₄)]₂Al(C₅Me₅). The structure and bonding of the bridging imido complex is examined with electrochemical measurements in tandem with density functional theory calculations.

Reactivity of hemi-labile pyridyl and pyrimidyl derived chalcogen ligands towards group 10 metal phosphine precursors

The reactivity of N-heterocyclic dichalcogenides and their sodium salts towards group 10 metal phosphine precursors has been investigated.

Redox-state dependent activation of silanes and ammonia with reverse polarity (PCcarbeneP)Ni complexes: electrophilic vs. nucleophilic carbenes

A rigidified PC_alkylP ligand allowed for the synthesis and characterization of cationic and radical PC_CarbeneP nickel complexes in which the carbene anchor of the pincer framework is electrophilic rather than nucleophilic.

Three-coordinate terminal imidoiron(III) complexes: structure, spectroscopy, and mechanism of formation

Reaction of 1-adamantyl azide with iron(I) diketiminate precursors gives metastable but isolable imidoiron(III) complexes LFe=NAd (L = bulky beta-diketiminate ligand; Ad = 1-adamantyl). This paper addresses (1) the spectroscopic and structural characterization of the Fe=N multiple bond in these interesting three-coordinate iron imido complexes, and (2) the mechanism through which the imido complexes form. The iron(III) imido complexes have been examined by (1)H NMR and electron paramagnetic resonance (EPR) spectroscopies and temperature-dependent magnetic susceptibility (SQUID), and structurally characterized by crystallography and/or extended X-ray absorption fine structure (EXAFS) measurements. These data show that the imido complexes have quartet ground states and short (1.68 +/- 0.01 A) iron-nitrogen bonds. The formation of the imido complexes proceeds through unobserved iron-N(3)R intermediates, which are indicated by QM/MM computations to be best described as iron(II) with an N(3)R radical anion. The radical character on the organoazide bends its NNN linkage to enable easy N(2) loss and imido complex formation. The product distribution between imidoiron(III) products and hexazene-bridged diiron(II) products is solvent-dependent, and the solvent dependence can be explained by coordination of certain solvents to the iron(I) precursor prior to interaction with the organoazide.

Diimine supported group 10 hydroxo, oxo, amido, and imido complexes

A series of L(2) = diimine (Bian = bis(3,5-diisopropylphenylimino)acenapthene, Bu(t)(2)bpy = 4,4'-di-tert-butyl-2,2'-bipyridine) supported aqua, hydroxo, oxo, amido, imido, and mixed complexes have been prepared. Deprotonation of [L(2)Pt(mu-OH)](2)(2+) with 1,8-bis(dimethylamino)naphthalene, NaH, or KOH yields [(L(2)Pt)(2)(mu-OH)(mu-O)](+) as purple (Bian) or red (Bu(t)(2)bpy) solids. Excess KOH gives dark blue [(Bian)Pt(mu-O)](2). MeOTf addition to [(Bu(t)(2)bpy)(2)Pt(2)(mu-OH)(mu-O)](+) gives [(Bu(t)(2)bpy)(2)Pt(2)(mu-OH)(mu-OMe)](2+) while [(Bian)Pt(mu-O)](2) yields [(Bian)(2)Pt(2)(mu-OMe)(mu-O)](+). Treatment of [(Bian)Pt(mu-O)](2) with "(Ph(3)P)Au(+)" gives deep purple [(Bian)(2)Pt(2)(mu-O)(mu-OAuPPh(3))](+) while (COD)Pt(OTf)(2) gives a low yield of [(Bian)Pt(3)(mu-OH)(3)(COD)(2)](OTf)(3). Ni(Bu(t)(2)bpy)Cl(2) and [(Ph(3)PAu)(3)(mu-O)](+) in a 3 : 2 ratio yield red [Ni(3)(Bu(t)(2)bpy)(3)(mu-O)(2)](2+). M(Bu(t)(2)bpy)Cl(2) (M = Pd, Pt) and [(Ph(3)PAu)(3)(mu-O)](+) give [M(Bu(t)(2)bpy)(mu-OAuPPh(3))](2)(2+) and [Pd(4)(Bu(t)(2)bpy)(4)(mu-OAuPPh(3))](3+). Addition of ArNH(2) to [M(Bu(t)(2)bpy)(mu-OH)](2)(2+) (M = Pd, Pt) gives [Pt(2)(Bu(t)(2)bpy)(2)(mu-NHAr)(mu-OH)](2+) (Ar = Ph, 4-tol, 4-C(6)H(4)NO(2)) and [M(Bu(t)(2)bpy)(mu-NHAr)](2)(2+) (Ar = Ph, tol). Deprotonation of [Pt(2)(Bu(t)(2)bpy)(2)(mu-NH-tol)(mu-OH)](2+) with 1,8-bis(dimethylamino)naphthalene or NaH gives [Pt(2)(Bu(t)(2)bpy)(2)(mu-NH-tol)(mu-O)](+). Deprotonation of [Pt(Bu(t)(2)bpy)(mu-NH-tol)](2)(2+) with KOBu(t) gives deep green [Pt(Bu(t)(2)bpy)(mu-N-tol)](2). The triflate complexes M(Bu(t)(2)bpy)(OTf)(2) (M = Pd, Pt) are obtained from M(Bu(t)(2)bpy)Cl(2) and AgOTf. Treatment of Pt(Bu(t)(2)bpy)(OTf)(2) with water gives the aqua complex [Pt(Bu(t)(2)bpy)(H(2)O)(2)](OTf)(2).

Alkyl Carbon−Nitrogen Reductive Elimination from Platinum(IV)−Sulfonamide Complexes

Platinum(IV) complexes containing monodentate sulfonamide ligands, fac-(dppbz)PtMe(3)(NHSO(2)R) (dppbz = o-bis(diphenylphosphino)benzene; R = p-C(6)H(4)(CH2)(3)CH(3) (1a), p-C(6)H(4)CH(3) (1b), CH(3) (1c)), have been synthesized and characterized, and their thermal reactivity has been explored. Compounds 1a-c undergo competitive C-N and C-C reductive elimination upon thermolysis to form N-methylsulfonamides and ethane, respectively. Selectivity for either C-N or C-C bond formation can be achieved by altering the reaction conditions. Good yields of the C-N-coupled products were observed when the thermolyses of 1a-c were conducted in benzene-d(6). In contrast, exclusive C-C reductive elimination occurred upon themolysis of 1a,b in nitrobenzene-d(5). When the thermolyses of 1a were performed in the presence of sulfonamide anion NHSO2R- in benzene-d(6), ethane elimination was completely inhibited and C-N reductive elimination products were formed in high yield. Mechanistic studies support a two-step reaction pathway involving initial dissociation of NHSO(2)R(-) from the platinum center, followed by nucleophilic attack of this anion on a methyl group of the resulting five-coordinate platinum(IV) cation to form MeNHSO(2)R and (dppbz)PtMe(2). C-C reductive elimination to form ethane occurs directly from the five-coordinate Pt(IV) cation.

Dinuclear rhodium and iridium complexes with mixed amido/methoxo and amido/hydroxo bridges

The reactions of [[M(mu-OMe)(cod)](2)] (M = Rh, Ir; cod = 1,5- cyclooctadiene) with p-tolylamine, alpha-naphthylamine, and p-nitroaniline gave complexes with mixed-bridging ligands, [[M(cod)](2)(mu-NHAr)(mu-OMe)]. Similarly, the related complexes [[Rh(cod)](2)(mu-NHAr)(mu-OH)] were prepared from the reactions of [[Rh(mu-OH)(cod)](2)] with p-tolylamine, alpha-naphthylamine, and p-nitroaniline. The reactions of [[Rh(mu-OR)(cod)](2)] (R = H, Me) with o-nitroaniline gave the mononuclear complex [Rh(o-NO(2)C(6)H(4)NH)(cod)]. The syntheses of the amido complexes involve a proton exchange reaction from the amines to the methoxo or hydroxo ligands and the coordination of the amide ligand. These reactions were found to be reversible for the dinuclear complexes. The structure of [[Rh(cod)](2)(mu-NH[p-NO(2)C(6)H(4)])(mu-OMe)] shows two edge-shared square-planar rhodium centers folded at the edge with an anti configuration of the bridging ligands. The complex [[Rh(cod)](2)(mu-NH[alpha-naphthyl])(mu-OH)] cocrystallizes with [[Rh(mu-OH)(cod)](2)] and THF, forming a supramolecular aggregate supported by five hydrogen bridges in the solid state. In the mononuclear [Rh(o-NO(2)C(6)H(4)NH)(cod)] complex the o-nitroamido ligand chelates the rhodium center through the amido nitrogen and an oxygen of the nitro group.

A comprehensive investigation of the chemistry and basicity of a parent amidoruthenium complex

trans-(DMPE)(2)Ru(H)(NH(2)) (1) dehydrogenates cyclohexadiene and 9,10-dihydroanthracene to yield benzene (or anthracene), (DMPE)(2)Ru(H)(2), and ammonia. Addition of fluorene to 1 results in the formation of the ion pair [trans-(DMPE)(2)Ru(H)(NH(3))(+)][A(-)] (A(-) = fluorenide, 4a). Complex 1 also reacts with weak acids A-H (A-H = phenylacetylene, 1,2-propadiene, phenylacetonitrile, 4-(alpha,alpha,alpha-trifluoromethyl)phenylacetonitrile, cyclobutanone, phenol, p-cresol, aniline) to form ammonia and trans-(DMPE)(2)Ru(H)(A) (7, 8, 9a, 9b, 10, 11b, 11c, 12, respectively). In the cases where A-H = phenylacetylene, cyclobutanone, aniline, phenol, and p-cresol, the reaction was observed to proceed via ion pairs analogous to 4a. Compound 1 is reactive toward even weaker acids such as toluene, propylene, ammonia, cycloheptatriene, and dihydrogen, but in these cases deuterium labeling studies revealed that only H/D exchange between A-H and the ND(2) group is observed, rather than detectable formation of ion pairs or displacement products. Addition of triphenylmethane to 1 results in the formation of an equilibrium mixture of 1, triphenylmethane, and the ruthenium/triphenylmethide ion pair 4h. If the energetics of ion-pair association are ignored, this result indicates that the basicity of 1 is similar to that of triphenylmethide. All these observations support the conclusion that the NH(2) group in amido complex 1 is exceptionally basic and as a result prefers to abstract a proton rather than a hydrogen atom from a reactive C-H bond. The energetics and mechanism of these proton-transfer and -exchange reactions are analyzed with the help of DFT calculations.

Structural correlations and conformational preference in edge-sharing binuclear d8 complexes with XR2 bridges. A theoretical study

The binuclear complexes of d8 transition metal ions of the type [M2(mu-XR2)2L4] (where M = RhI, IrI, NiII, PdII, PtII, or AuIII; X = S, N, P, or As) appear in a variety of molecular conformations in which the coordination planes around the two metal atoms are sometimes coplanar, sometimes bent. For the bent compounds with asymmetric bridges, XR1R2, the substituents adopt different orientations relative to the metal framework and to each other. Ab initio theoretical studies on the different conformers of 30 representative complexes, complemented with a structural database analysis, have allowed the establishment of structural correlations in this family of compounds. The conformational choice results from a delicate balance of different interactions which are qualitatively analyzed, such as the changes in bond angles around the bridging atoms, the existence of weak metal...metal bonding in the bent structures, and steric interactions involving the terminal ligands and the substituents at the bridging atoms.