Mono-hydride complexes

Consequently, in the absence of NEtz, the main catalytic species should be H2RhCl(PPh3)2(solv), whereas, in the presence of NEt3, RhH(PPh3)3 should be formed. We are aware that such a conclusion is somewhat speculative however, it seems the most likely if we look at all the experimental data reported on the subject. Table 1 reports experimental results concerning both activity and product distribution, determined in different conditions. Since the Rh(I) mono hydride complex is a catalytic species, it is reformed in every step of the reaction and its concentration remains constant. Therefore, rate data are calculated by the ratio of slopes of plots of organic substrate concentration, divided by the Rh(I) concentration, versus reaction time. The slope of these curves is obtained at about 70 % conversion of the substrate. 

Insertion of mono- or bis(aryldiazonium) cations into the Re—bonds of the hydride complexes [ReH(CO)5 (PR3)J (PR3 = P(OEt)3, PPh(OEt)2, PPh2(OEt) =1 ) results in the formation of cationic aryldiazene complexes of the compositions [Re(HNNAr)(CO)5 (PR3) ]" or [ Re(CO)5 (PR3) 2(/r-HNNArNNH)] +. " Bifunctional diazene/diazonium derivatives which can be prepared in this way are excellent building blocks for heterobinuclear and heterotrinuclear compounds with bis(aryldiazene) bridging ligands as has been demonstrated for Re-Ru, Re-Os,... 

Reactions of the silene hydride complex Cp Ru(P(Pr-/)3)(I I)(r 2-C.I I2=SiPh2) with hydrosilanes proceed via an initial migration of the hydride to the silene ligand, affording as the final products either the disilyl hydride or the mono silyl dihydrido ruthenium(IV) complexes as described in Scheme 21. Similar reductive elimination and... 

SCF and CAS SCF calculations on mono and bimetallic transition metal hydride complexes are reported. The importance of including the non dynamical correlation elTects for the study of the cis-trans isomerism in dihydrido complexes and for the study of the CO insertion reaction into the metal hydride bond is stressed. The metal to metal hydrogen transfer in a class of bimetallic d — d hydride complexes is analyzed and the feasibility of the transfer discussed as a function of the coordination pattern around the two metal centers. 

The dual function of the precatalysts 4 opened the way to well-controlled block polymerization of ethylene and MMA (eq. (5)) [89, 90]. Homopolymerization of ethylene (Mn = 10000) and subsequent copolymerization with MAA (Mn 20000) yielded the desired linear AB block copolymers. Mono and bis(alkyl/silyl)-substituted flyover metallocene hydride complexes of type 8 gave the first well-controlled block copoymerization of higher a-olefins with polar monomers such as MMA or CL [91]. In contast to the rapid formation of polyethylene [92], the polymerization of 1-pentene and 1-hexene proceeded rather slowly. For example, AB block copolymers featuring poly( 1-pentene) blocks (M 14000, PDI = 1.41) and polar PMMA blocks (M 34000, PDI = 1.77) were obtained. Due to the bis-initiating action of samarocene(II) complexes (Scheme 4), type 13-15 precatalysts are capable of producing ABA block copolymers of type poly(MMA-co-ethylene-co-MMA), poly(CL-co-ethylene-co-CL), and poly(DTC-co-ethylene-co-DTC DTC = 2,2-dimethyltrimethylene carbonate) [90]. 

Although group 5 organometallic systems have been found to be of relevance in transition-metal catalyzed hydroboration reactions, structurally authenticated group 5 boryl complexes remain relatively few in number. Smith and co-workers, for example, have probed the mechanisms for the formation of niobium and tantalum mono- and bis(boryls) from propylene complex precursors, with concomitant formation of propyl boronate esters [31,32]. Of particular interest from a structural viewpoint are the relative merits of alternative bonding descriptions for metal(V) boryl bis(hydrides) as borohydride complexes or as mono(hydride) a-borane systems [31-34]. 

Trls(diphenylthiophosphinoyl)nethanide (C(P(S)Ph2)3 ) complexes of rhodium and Iridium have been prepared and the crystal structure of the iridium complex [Ir(co) 2 T)2-C(P(S)Ph2> 3-S,S ] reveals a bidentate S,S ligand-iridium interaction. The trihydride complex [IrHa(CO)(dppe)] reacts with primary, secondary, and tertiary silanes to yield mono- and bis(silyl)hydride complexes of the formulae [IrH2(SiRR 2) (CO)(dppe)] and [IrH(SiRR 2)2(CO)(dppe)] (SiRR 2 = SiPhs,... 

Treatment of [Ru(GOD)Gl2]2 with Tr2P(GH2) PTr2 in refluxing ethanol followed by addition of GH2=GHGH2MgGl affords [Ru(Tr2P(GH2)nP Pt2)( "C3H5)2] n = Z, 3), which act as precursors for mono- and dinuclear hydride complexes. 

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