Randy K. Hayashi

Silylene complexes from a stable silylene and metal carbonyls: synthesis and structure of [Ni{(ButN–CHCH–NBut)Si}2(CO)2], a donor-free bis-silylene complex

[Ni(LSi)2(CO)2]3; the first silylene complex of nickel, has been obtained from the stable silylene 1,3-di-tert-2,3-dihydro-1H-1,3,2-diazasilol-2-ylidene (LSi)1 and tetracarbonylnickel; complex 3 was characterized by single crystal X-ray diffraction and NMR spectroscopy (1H, 13C, 29Si).

Reactions of the [Ni6(CO)12]2- dianion with stibine and bismuthine reagents: synthesis and stereophysical characterization of the [Ni10(SbPh)2(CO)18]2- dianion containing a noncentered icosahedral Ni10Sb2 core and Ni2(CO)4(μ2-Ph2SbOSbPh2)2 containing a centrosymmetric eight-membered (NiSbOSb)2 ring

In a further exploration of the types of high-nuclearity, mixed metal-(main-group) clusters accessible from the electron-rich [Ni6(CO)12]2- dianion (1), reactions of 1 (a direct descendent of nickel tetracarbonyl) with antimony and bismuth reagents have been carried out. The main product isolated in 50–60% yields from reactions of 1 with either chlorodiphenylstibine, Ph2SbCl, or dichlorophenylstibine, PhSbCl2, in THF solutions at room temperature is the [Ni10(SbPh)2(CO)18]2- dianion (2); its identity was unambiguously established from X-ray crystallographic determinations of four different ionic compounds, viz., [NMe4]+2 [2]2- · 2THF (2a), [NMe4]+2 [2]2- · 2Me2CO (2b), [(Ph3P)2N]+2 [2]2- · 2THF (2c), and [NMe3Ph]+2 [2]2- (2d). In each salt, the geometrically similar nickel stibinidene carbonyl dianion possesses a closo 1,12-disubsituted, icosahedral Ni10Sb2 core, (i.e., a bi-Sb-capped pentagonal-antiprismatic Ni10 configuration) of crystallographic Ci-1 site symmetry encapsulated by two antimony-attached phenyl substituents, 10 terminal carbonyl ligands (one per nickel atom), and four doubly bridging and four triply bridging carbonyl ligands. This nickel-antinomy cluster is the third member of the homologous series of [Ni10(ER)2(CO)18]2- dianions (E = P, R = Me; E = As, R = Me). A comparative geometrical analysis of their icosahedral Ni10E2 cores, which are electronically equivalent analogues of the regular 12-boron icosahedral polyhedron of the classic [B12H12]2- dianion, is given. The fact that 2 was the only nickel-stibinidene cluster isolated from a room-temperature reaction with Ph2SbCl is attributed to the facile cleavage of one of the two Sb-Ph bonds of the Ph2SbCl under the reaction conditions and to the apparent thermodynamic stability of 2. An X-ray diffraction analysis coupled with laser desorption/Fourier transform mass spectrometry (LD/FTMS) established conclusively the formulation of a side product, obtained in ∼ 5% yield from room-temperature reactions of 1 with chlorodiphenylstibine, as Ni2(CO)4(μ2-Ph2SbOSbPh2)2 (3). This molecular dimer is best viewed as a disubstituted Ni(CO)2L2 derivative of nickel tetracarbonyl in which two electron-donating SbIII atoms from two bridging Ph2SbOSbPh2 ligands have replaced two carbonyl ligands around each tetrahedrally-coordinated, zerovalent nickel atom. The resulting eight-membered cyclo-(NiSbOSb)2 complex of crystallographic Ci-1 site symmetry possesses a chair-like conformation presumably due to the bulky antimony-attached phenyl substituents. This compound (3) is the first example (to our knowledge) of a metal complex formed from bis(diphenylstibine)oxide which itself exists as a molecular compound. The origin of the bridging Ph2SbOSbPh2 ligand in 3 can be readily attributed to the partial hydrolysis of the Ph2SbCl reagent with adventitious water (i.e., “wet” solvent). The reaction of 1 with Ph2SbCl gave a third nickel-antimony compound, Ni(CO)3(SbClPh2); although not isolated from solution, the proposed existence of this monosubstituted derivative of Ni(CO)4 is based upon its infrared carbonyl frequencies being virtually identical to those previously reported for the analogous Ni(CO)3(SbClEt2) and Ni(CO)3(SbPh3). Reaction of 1 with (p-tolyl)BiBr2 in THF gave no isolatable carbonyl-containing products.

Synthesis and crystal structures of five new rhenium acetamidate complexes

Abstract Syntheses are reported of five rhenium(III) cluster complexes with acetamidate ligands: [(C 4 H 9 ) 4 N] 2 [{Re 2 Cl 6 (μ-1,2-NHCOCH 3 )} 2 ] ( 1 ), [(C 2 H 5 ) 4 N][Re 3 Cl 8 (μ-1,2-NHCOCH 3 )(μ-2,3-NHCOCH 3 )]·2.5(C 4 H 10 O) ( 2 ), [(C 4 H 9 ) 4 N] 2 [Re 3 Cl 10 (μ-1,2-NHCOCH 3 )] ( 3 ), [(C 4 H 9 ) 4 N] 2 [{Re 3 Cl 8 (μ-1,2-NHCOCH 3 )(OH)} 2 ]·1.7(C 4 H 10 O) ( 4 ), and (C 4 H 9 ) 4 N[Re 3 Cl 9 (H 2 O)(μ-1,2-NHCOCH 3 )]·C 3 H 6 O ( 5 ). The acetamidate ligands in these complexes arise via reactions of acetonitrile–rhenium halide species (either dirhenium or trirhenium chloride clusters) and water. Coordination activates the nitrile to hydrolysis; proton loss and chelation of the acetamidate ligand with displacement of chloride ion leads to the products. Initial formation of a rhenium(III) acetonitrile complex can be assisted using a halide acceptor, Ag + , to generate an open coordination site on the metal. The reaction with K 4 Mo 2 Cl 8 and Ag + ion in acetonitrile gives Mo 2 Cl 4 (NCCH 3 ) 4 ( 6 ). The use of MALDI mass spectrometry in support of synthetic efforts and as a characterization tool is described, and the molecular structures of 1 – 6 were established using X-ray crystallography.

Synthesis and X-ray crystal structures of new trirhenium nonachloride chalcogenide clusters

Abstract The acetone adduct of trirhenium nonachloride, Re 3 Cl 9 (acet) 3 , where acet=acetone, reacts in acetone solution at room temperature with tetrabutylammonium chalcogenides [N(C 4 H 9 ) 4 ] 2 E, where E=S, Se and Te, producing the tetrabutylammonium salts of the new cluster anions [Re 3 ( μ 3 -E) ( μ 2 -Cl) 3 Cl 6 ] 2 −. In the crystallographically determined structures of these compounds, triangles of rhenium atoms are capped by single chalcogen atoms, giving anions of near C 3v symmetry. The compound where E=S is also formed in the reaction of Re 3 Cl 9 with [N(C 4 H 9 ) 4 ] 2 [MoS 4 ] by sulfide transfer.

Synthetic studies toward ansatrienines: application of the Evans–Tishchenko reaction to chiral enones

Abstract Practical syntheses of the C9–C14 sterotriade 5 and the C1–C8 polyene unit 6 in ansatrienine A (mycotriene) (1a), and other ansamycin antibiotics is described. A key step for controlling the configuration of the stereogenic center at C13 involves the stereoselective reduction of enone 10 using the Evans–Tishchenko reaction.

Reaction of NO with Cp*3Co3(μ-H)4 preserves the tricobalt cluster and produces Cp*3Co3(μ3-NO)2

Abstract Cp*3Co3(μ-H)4 (4) reacts with NO to produce Cp*3Co3(μ3-NO)2 (3) which was characterized by X-ray crystallography. 3 is a diamagnetic 48 electron tricobalt cluster in which an equilateral triangular array of cobalt atoms (CoCoav=2.423(2) A) is capped on each face by a μ3-NO ligand (Co-μ3-NOav=1.863(7) A).

Reaction of Cp*(CO)2ReRe(CO)2Cp* in THF with diethyl fumarate produces Cp*Re(CO)3 and Cp*Re(CO)(η2-(E)-EtO2CCHCHCO2Et)(THF)

Abstract The rhenium dimer complex Cp*(CO)2ReRe(CO)2Cp* (1) (Cp*=C5Me5) reacted in THF with diethyl fumarate in a fragmentation reaction to form Cp*Re(CO)3 (3) and Cp*Re(CO)(η2-(E)-EtO2CCHCHCO2Et)(THF) (6). Reaction of 6 with CO resulted in substitution of the THF ligand with CO to form the alkene complex Cp*Re(CO)2(η2-(E)-EtO2CCHCHCO2Et) (7). Variable temperature 1H-NMR spectroscopy of 7 showed that rotation of the alkene ligand is slow below −50°C.

Rearrangement of Rhenium Allyl Vinyl Ketone Complexes

The isomerization of parallel−perpendicular allyl vinyl ketone complex C5H5(CO)Re(η2,η2-H2CCHCH2COCHCHCH2CMe3) (2) to the diastereomeric perpendicular−parallel complex C5H5(CO)Re(η2,η2-H2CCHCH2COCHCHCH2CMe3) (6) occurred without formation of an unsaturated intermediate trappable by either PMe3 or 13CO. The rearrangement of exo-C5H5(CO)Re[η2,η2-CH2CHCH(CH3)COCHCHCH2CMe3] (8-exo) occurred with retention of stereochemistry at rhenium and with enantioface inversion of both complexed alkenes. The kinetically formed parallel−perpendicular isomer 8-exo rearranged by sequential enantioface inversion of the vinyl π-bond to give parallel−parallel intermediate exo-C5H5(CO)Re[η2,η2-CH2CHCH(CH3)COCHCHCH2CMe3] (12-exo) and then enantioface inversion of the allyl π-bond to form the perpendicular−parallel isomer exo-C5H5(CO)Re[η2,η2-CH2CHCH(CH3)COCHCHCH2CMe3] (9-exo). Enolization of allyl vinyl ketone complexes was observed, but is not required for the isomerization. C−H insertion mechanisms involving a net hydrogen migr...