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Herein we describe the stoichiometric and catalytic carbene-transfer reactivity of iron(II) alkoxide complexes with iodonium ylide precursors. Treatment of PhIC(CO2Me)2 with styrene in the presence of catalytic amounts of several different Fe(OR)2(THF)2 precursors results in efficient cyclopropanation for a variety of styrenes. Computational and reactivity studies suggest a novel remote metallocarbene/vinyl radical intermediate, Fe(OR)2(κ2-(OC(OMe))2C), which could be responsible for the reactive nature of the catalyst. [ABSTRACT FROM AUTHOR]

A series of twelve second coordination sphere (SCS) functionalized manganese tricarbonyl bipyridyl complexes are investigated for their electrocatalytic CO2 reduction properties in acetonitrile. A qualitative and quantitative assessment of the SCS functional groups is discussed with respect to the catalysts' thermodynamic and kinetic efficiencies, and their product selectivities. In probing a broad scope of functional groups, it is clear that only the aprotic ortho‐arylester SCS is capable of promoting the highly desired low‐overpotential proton‐transfer electron‐transfer (PT‐ET) pathway for selective CO production. The ortho‐phenolic analogues cause an increase in overpotential with a product selectivity favoring H2 evolution, consistent with a high‐overpotential pathway via the anionic [Mn−H]− intermediate. Alternative aprotic Lewis base functional groups such as trifluoromethyl, morpholine and acetamide are shown to also be capable of intermediate manganese hydride generation. The tertiary amine substituent, 2‐morpholinophenyl, exhibits a desirable product distribution characteristic of syn‐gas (CO : H2=30 : 48) with an impressive turnover frequency, while the secondary amine group, 2‐acetamidophenyl, induces a notable shift in selectivity with a faradaic yield of 55 % for the formate (HCO2−) product. In addition to their catalytic properties, cyclic voltammetry and infrared spectroelectrochemistry (IR‐SEC) studies are presented to probe pre‐catalyst electronic properties and the two‐electron reduction activation pathway. [ABSTRACT FROM AUTHOR]

The synthesis of two chiral bulky alkoxide pro-ligands, 1-adamantyl-tert-butylphenylmethanol HOCAdtBuPh and 1-adamantylmethylphenylmethanol HOCAdMePh, is reported and their coordination chemistry with magnesium(II) is described and compared with the coordination chemistry of the previously reported achiral bulky alkoxide pro-ligand HOCtBu2Ph. Treatment of n-butyl-sec-butylmagnesium with two equivalents of the racemic mixture of HOCAdtBuPh led selectively to the formation of the mononuclear bis(alkoxide) complex Mg(OCAdtBuPh)2(THF)2. 1H NMR spectroscopy and X-ray crystallography suggested the selective formation of the C2-symmetric homochiral diastereomer Mg(OCRAdtBuPh)2(THF)2/Mg(OCSAdtBuPh)2(THF)2. In contrast, the less sterically encumbered HOCAdMePh led to the formation of dinuclear products indicating only partial alkyl group substitution. The mononuclear Mg(OCAdtBuPh)2(THF)2 complex was tested as a catalyst in different reactions for the synthesis of polyesters. In the ROP of lactide, Mg(OCAdtBuPh)2(THF)2 demonstrated very high activity, higher than that shown by Mg(OCtBu2Ph)2(THF)2, although with moderate control degrees. Both Mg(OCAdtBuPh)2(THF)2 and Mg(OCtBu2Ph)2(THF)2 were found to be very effective in the polymerization of macrolactones such as ω-pentadecalactone (PDL) and ω-6-hexadecenlactone (HDL) also under mild reaction conditions that are generally prohibitive for these substrates. The same catalysts demonstrated efficient ring-opening copolymerization (ROCOP) of propylene oxide (PO) and maleic anhydride (MA) to produce poly(propylene maleate). [ABSTRACT FROM AUTHOR]

In this study, we report the synthesis, characterization, and reactions of Cu(I) complexes of the general form Cu(L)(LigH2) (LigH2 = xanthene-based heterodinucleating ligand (E)-3-(((5-(bis(pyridin-2-ylmethyl)amino)-2,7-di-tert-butyl-9,9-dimethyl-9H-xanthen-4-yl)imino)methyl)benzene-1,2-diol); L = PMe3, PPh3, CN(2,6-Me2C6H3)). New complexes [Cu(PMe3)(LigH2)] and [CuCN(2,6-Me2C6H3)(LigH2)] were synthesized by treating [Cu(LigH2)](PF6) with trimethylphosphine and 2,6-dimethylphenyl isocyanide, respectively. These complexes were characterized by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry (HRMS), and X-ray crystallography. In contrast, attempted reactions of [Cu(LigH2)](PF6) with cyanide or styrene failed to produce isolable crystalline products. Next, the reactivity of these and previously synthesized Cu(I) phosphine and isocyanide complexes with molybdate was interrogated. IR (for isocyanide) and 31P NMR (for PPh3/PMe3) spectroscopy demonstrates the lack of oxidation reactivity. We also describe herein the first example of a structurally characterized multinuclear complex combining both Mo(VI) and Cu(I) metal ions within the same system. The heterobimetallic tetranuclear complex [Cu2Mo2O4(μ2-O)(Lig)2]·HOSiPh3 was obtained by the reaction of the silylated Mo(VI) precursor (Et4N)(MoO3(OSiPh3)) with LigH2, followed by the addition of [Cu(NCMe)4](PF6). This complex was characterized by NMR spectroscopy, high-resolution mass spectrometry, and X-ray crystallography. [ABSTRACT FROM AUTHOR]

The coordination chemistry of amine tris(phenolate) ligands around vanadium(III) and vanadium(V) is described. It is demonstrated that amine tris-(phenolate) ligands are suitable for stabilizing vanadium complexes in oxidation states of III and V.

He came to Dick's lab as a postdoc, having received a Ph.D. with Animesh Chakravorty, who himself had been a postdoc with Holm in the 1960's. Dick had moved his lab relatively recently from M.I.T., but he was well settled into lab space that would later be taken over by Ed Solomon when Dick moved once again in 1980 back to Harvard University. B My Memories of Dick Holm: a Wizard of Inorganic Synthesis, a Pioneer in Bioinorganic Chemistry, and a Connoisseur of the Written Word b by Stas Groysman I worked in the Holm laboratory at Harvard as a postdoc during the concluding part of his career. My outstanding undergraduate student at Berkeley, Mike Scott, went on to do his Ph.D. with Dick and one of my graduate students - Joel Gohdes - carried out postdoctoral research in Dick's lab. Dick's Ph.D. work with Al primarily concerned the magnetic properties of tetrahedral Co(II) complexes[[3], [5]] and the structures and properties of acetylacetonate coordination complexes.[[7], [9]] Upon finishing work in Cotton's lab in 1961, Dick took a position as instructor of inorganic chemistry at Harvard University. [Extracted from the article]

Reaction of LiOCtBu2Ph with TlPF6 forms the dimeric Tl2(OCtBu2Ph)2 complex, a rare example of a homoleptic thallium alkoxide complex demonstrating formally two-coordinate metal centers. Characterization of Tl2(OCtBu2Ph)2 by 1H and 13C NMR spectroscopy and X-ray crystallography reveals the presence of two isomers differing by the mutual conformation of the alkoxide ligands, and by the planarity of the central Tl–O–Tl–O plane. Tl2(OCtBu2Ph)2 serves as a convenient precursor to the formation of old and new [M(OCtBu2Ph)n] complexes (M = Cr, Fe, Cu, Zn), including a rare example of T-shaped Zn(OCtBu2Ph)2(THF) complex, which could not be previously synthesized using more conventional LiOR/HOR precursors. The reaction of [Ru(cymene)Cl2]2 with Tl2(OCtBu2Ph)2 results in the formation of a ruthenium(II) alkoxide complex. For ruthenium, the initial coordination of the alkoxide triggers C–H activation at the ortho-H of [OCtBu2Ph] which results in its bidentate coordination. In addition to Tl2(OCtBu2Ph)2, related Tl2(OCtBu2(3,5-Me2C6H3))2 was also synthesized, characterized, and shown to exhibit similar reactivity with iron and ruthenium precursors. Synthetic, structural, and spectroscopic characterizations are presented. [ABSTRACT FROM AUTHOR]

The status of the synthetic analogue approach as applied to the mononuclear sites in certain molybdoenzymes and the polynuclear sites in hydrogenases, nitrogenase, and carbon monoxide dehydrogenases is described. The findings from the comparison of properties of accurate analogues of these sites provide insight into the influence of protein structure and environment on intrinsic properties as represented by the analogue.

Two series of square pyramidal (SP) monodithiolene complexes and their silylated derivatives have constituted the basic molecules in a biomimetic approach to structural analogues of the oxidized states in the xanthine oxidoreductase enzyme family. The computational structural have shown that protein sites have adopted intrinsic coordination geometries rather than those dictated by protein structure and environment.

A study was conducted to investigate the synthesis and structures of bis(dithiolene)tungsten selenolate and analogous thiolate complexes of relevance to formate dehydrogenases. The findings demonstrate that bis(dithiolene) selenolate complexes of molybdenum and tungsten are synthetically accessible but are less stable than analogous thiolate complexes.

The synthesis and structure of neutral and cationic group IV metal complexes of a tetradentate amine phenolate ligand bearing two side arm donors is described. This ligand, led on the one hand, to flexible neutral complexes, in which one of the side-arm donors is not bound to the metal, and on the other hand, to exceptionally stable cationic alkoxo, and alkyl complexes, in which the two side-arm donors bind to the metal.

The synthesis of enantiomerically pure diastereotiometrically specific Salan complexes of titanium and their preliminary application in asymmetric catalysis is described. The potential of these chiral-at-metal complexes is evaluated as asymetric catalyst by employing the diastereomerically pure complexes Lig(super 1)Ti(O(super i)Pr)2 and Lig(super 3)Ti(O(super i)Pr)2 as catalysts.