Kevin A. Kreisel

A bimetallic N-heterocyclic carbene complex featuring a short Cr–Cr distance

The alkylation of a chelating bis(carbene) complex of CrCl(2) yields an unusual bimetallic complex featuring a short Cr-Cr distance, novel ligand coordination, and CH(3) ligand exchange.

A Family of Heteroleptic Titanium Guanidinates: Synthesis, Thermolysis, and Surface Reactivity

A family of new mixed-ligand titanium guanidinate compounds was synthesized as potential atomic layer deposition precursors, and the surface chemistry on silica of a promising candidate (Cp(2)Ti[(N(i)Pr)(2)CN(H)(i)Pr]) was explored. Generally, these compounds have very good thermal stability with onsets of volatility between 127 and 168 degrees C, with melting points generally ranging from 147 to 165 degrees C. The reactivity of [(i)PrN(H)C(N(i)Pr)(2)]TiCp(2) was studied with high surface area silica between 180 and 330 degrees C. The surface reactivity was found to differ if the silica was preheated to 350 or 900 degrees C; this was attributed to the hydroxyl nucleation site density of the silica, which is known to vary with the temperature. The surface reaction products were characterized by solid-state NMR, and these agreed well with a calculated model. When the silica was pretreated to 350 degrees C, the precursor appeared to chemisorb primarily through the loss of a Cp ligand, while with a 900 degrees C pretreatment, the chemisorption occurred primarily through a loss of the guanidinate ligand. The adsorption enthalpies to silica were calculated for the different surface species.

Synthesis of indenyl ruthenium triazolato complexes by [3 + 2] cycloaddition of activated nitrile and alkynes to indenyl ruthenium azido complexes: crystal structures of [( η 5-C9H7)Ru(PMe2Ph)2{N3C2(CO2Me)2}] and [( η 5-C9H7)Ru(dppe){N3C2H(CN}]

The indenyl ruthenium(II) azide complexes [(η5-C9H7)Ru(L2)N3], L2 = (PMe2Ph)2 (1), dppe (2) and dppm (3), (where dppe = Ph2PCH2CH2PPh2 and dppm = PPh2CH2PPh2) were readily prepared by the reaction of NaN3 with corresponding chloro complexes [(η5-C9H7)Ru(L2)Cl]. The azido complexes undergo [3 + 2] dipolar cycloaddition reactions with activated alkynes and nitrile (NCCH = CHCN) to yield new indenyl ruthenium triazolato complexes [(η5-C9H7)Ru(L2)(N3C2(CO2R)2)], L2 = (PMe2Ph)2, R = Me (4), Et (5); L2 = dppe, R = Et (6), L2 = dppm, R = Et (7) and [(η5-C9H7)Ru(L2)(N3C2HCN)], L2 = (PMe2Ph)2 (8), L2 = dppe (9), L2 = dppm (10). The complexes were fully characterized on the basis of microanalyses, IR and NMR spectroscopy. The structures of representative complexes 4 and 9 have been determined by single-crystal X-ray methods.

Tris(mercaptoimidazolyl)borate complexes of the coinage metals: syntheses and molecular structures of the first gold compounds and related copper and silver derivatives

The first tris(mercaptoimidazolyl)borate complexes of gold, Au(Tm(tBu)) and (Tm(tBu))Au(PPh3), have been prepared and structurally characterized. Together with their copper and silver analogues M(Tm(tBu)) and (Tm(tBu))M(PPh3)(M = Cu, Ag), these compounds constitute the first two complete series of Tm(R) derivatives to be isolated for the coinage metals. In order to evaluate the steric and electronic effects of the bulky tert-butyl substituents in these species, comparative structural analyses with the known methyl-substituted analogue Ag(Tm(Me)) and various (Tm(Me))M(PR3) derivatives (M = Cu, Ag) are also presented.

Studies of η5-cyclichydrocarbon ruthenium(II) complexes containing para-amino-N-(pyrid-2-ylmethylene)phenylamine ligand: molecular structure of [(η5-C5H5)Ru(PPh3)(C5H4NCH=N-C6H4-p-NH2)]BF4

Reaction of [(η5-Cp)Ru(PPh3)2Cl] (1) with excess para-amino-N-(pyrid-2-ylmethylene)-phenylamine ligand (app) in methanol in the presence of NH4BF4 leads to the formation of [η5-CpRu(PPh3)(aap)]BF4 (6BF4). Similarly, [(η5-ind)Ru(PPh3)2(CH3CN)]BF4 (4BF4) and [(η5-Cp*)Ru(PPh3)2(CH3CN)]BF4 (5BF4) react with app to yield the cationic complexes [(η5-ind)Ru(PPh3)(app)]BF4 (7BF4) and [(η5-Cp*)Ru(PPh3)(app)]BF4 (8BF4), respectively. The complexes were characterized by analysis and spectroscopic data. The structure of a representative complex (6BF4) was established by single-crystal X-ray methods.

Tetra-μ-chloro-1:2κ4Cl;1:3κ4Cl-di­methyl-2κC,3κC-tetra­kis(tetra­hydro­furan)-1κ2O,2κO,3κO-chromium(II)dizinc(II)

The title compound, [CrZn 2 (CH 3 ) 2 Cl 4 (C 4 H 8 O) 4 ], contains a central distorted octahedral Cr atom, located at an inversion center, bound to two tetrahydrofuran ligands and four chloro ligands that bridge to two symmetry-related tetrahedral Zn atoms. The coordination around zinc is completed by methyl and tetrahydrofuran ligands. This structure is compared with a previously reported complex of vanadium, and their differences in metric parameters are explained.