Jose Pedro Sarasa

Construction of Heterometallic Cubanes [{Ti3Cp(μ3‐CMe)}(μ3‐O)3{Mo(CO)3}]

Incorporation of M(CO)(3) fragments by trinuclear Ti complexes [{Ti(3)Cp (µ(3)-CR)}(µ-O)(3)] and [{Ti(3)Cp (µ(3)-N)}(µ-NH)(3)] (Cp*=eta(5)-C(5)Me(5)) leads to the formation of an unprecedented class of heterometallic clusters with cubane structure [e.g., Eq. (a)]. Density functional calculations on these complexes indicate the existence of electron delocalization in the Ti(3)M cores (M=Cr, Mo, W).

Towards the Accurate Calculation of 183W NMR Chemical Shifts in Polyoxometalates: The Relevance of the Structure

DFT calculations were carried out to study (183)W NMR chemical shifts in the family of the Keggin anions with formula alpha-[XW(12)O(40)](q-) (X=B, Al, Si, P, Ga, Ge, As, Zn), in the beta- and gamma-[SiW(12)O(40)](4-) geometric isomers, in the derivative Dawson anion [P(2)W(18)O(62)](6-), and in the most symmetrical Lindqvist [W(6)O(19)](2-) anion and its derivative [W(10)O(32)](4-). In this article, we show that the geometry employed in the calculation of NMR chemical shifts in polyoxotungstates is extremely important if we want to be quantitative. Using very large basis sets of QZ4P quality and taking into account the conductor-like screening model (COSMO) to account for solvent effects (aqueous and organic solutions), good geometries were found for the polyoxoanions. From these optimal geometries the (183)W NMR chemical shifts were computed with the more standard basis sets of TZP quality and including spin-orbit corrections inside the zero-order regular approximation (ZORA) to describe the relativistic effects of the internal electrons. With this strategy the mean absolute error between experimental and theoretical values was found to be less than 10 ppm, which is similar to the experimental error. We also discuss how the geometry of the polyoxoanion influences on the shielding.

Rhodium/Iridium‐Titanium Azaheterometallocubanes

Treatment of [[Ti(eta5-C5Me5)(mu-NH)]3(mu3-N)] (1) with the diolefin complexes [[MCl(cod)]2] (M = Rh, Ir; cod = 1,5-cyclooctadiene) in toluene afforded the ionic complexes [M-(cod)(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)]Cl [M = Rh (2), Ir (3)]. Reaction of complexes 2 and 3 with [Ag(BPh4)] in dichloromethane leads to anion metathesis and formation of the analogous ionic derivatives [M(cod)(mu3-NH)3Ti3-(eta5-C5Me5)3(mu3-N)][BPh4] [M = Rh (4), Ir (5)]. An X-ray crystal structure determination for 5 reveals a cube-type core [IrTi3N4] for the cationic fragment, in which 1 coordinates in a tripodal fashion to the iridium atom. Reaction of the diolefin complexes [[MCl(cod))2] (M = Rh, Ir) and [[RhCl(C2H4)2]2] with the lithium derivative [[Li(mu3-NH)2(mu3-N)-Ti3(eta5-C5Me5)3(mu3-N)]2] x C7H8 (6 C7H8) in toluene gave the neutral cube-type complexes [M(cod)(mu-NH)2(mu3-N)Ti3-(eta5-C5Me5)3(mu3-N)] [M = Rh (7), Ir (8)] and [Rh(C2H4)2(mu3-NH)2(mu3-N)Ti3(eta5-C5Me5)3(mu3-N)] (9), respectively. Density functional theory calculations have been carried out on the ionic and neutral azaheterometallocubane complexes to understand their electronic structures.

Construction of Heterometallic Cubanes [{Ti3Cp*3(μ3‐CR)}(μ3‐O)3{Mo(CO)3}] (R=H, Me; Cp*=η5‐C5Me5) and [{Ti3Cp*3(μ3‐N)}(μ3‐NH)3{M(CO)3}] (M=Cr, Mo, W); Crystal Structure of [{Ti3Cp*3(μ3‐CMe)}(μ3‐O)3{Mo(CO)3}]

Der Einbau von M(CO)3-Fragmenten in die dreikernigen Ti-Komplexe [{Ti3Cp*3(μ3-CR)}(μ-O)3] und [{Ti3Cp*3(μ3-N)}(μ-NH)3] (Cp*=η5-C5Me5) fuhrt zu einer neuen Klasse von Heterometallclustern mit Cubanstruktur [z. B. Gl. (a)]. Dichtefunktionalrechungen deuten auf eine Elektronendelokalisierung in den Ti3M-Gerusten hin (M=Cr, Mo, W).

Theoretical analysis of the isomerizations and fragmentations of the C3H6O2+· radical cation

Abstract A MINDO/3 theoretical study has been performed on the potential surface of the C 3 H 6 O 2 +· radical cation. CH 2 OH · , CH 3 O · , CHO · and CH 2 O losses have been studied. Complex rearrangements occur before fragmentations. Kinetic aspects based on an RRKM analysis are discussed.

Theoretical study on the isomerization and dissociation of C4H4O+˙ radical cation

A MINDO/3 theoretical study has been performed on the potential surface of the C4H4O+˙ radical cation. Fragmentations yielding C3H4+˙(CO loss), C3H3+(CHO loss), and C2H2O+˙(C2H2 loss) ions have been studied. A wide number of pseudostable species have been found. Very complex rearrangements occur previous to the fragmentations. Kinetic aspects are discussed.