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Readily accessible (PSi)Ni(II)‐benzyl complexes supported by bidentate phosphino(silyl) ligation were found to be effective pre‐catalysts for the direct hydrogenation of a variety of highly sterically hindered, unfunctionalized alkenes under relatively mild conditions (2.5‐5 mol% Ni, 10 atm H2, 50 °C) and without the need for additional additives or activator species. A range of substrates, including di‐, tri‐, and tetra‐substituted alkenes were evaluated in this regard and afforded good to moderate yields. Substrates featuring α,β‐unsaturated carbonyl functionality were also readily hydrogenated with no evidence for reduction of carbonyl or ester C−O functionalities. Deuteration experiments highlight the occurrence of chain walking which occurs in the background of the reported catalytic chemistry. [ABSTRACT FROM AUTHOR]

We report herein the synthesis and characterization of nickel complexes supported by tridentate and bidentate phosphino(silyl) ancillary ligands, along with the successful application of these complexes as precatalysts for the hydroboration of terminal and internal alkenes using pinacolborane (HBPin). These reactions proceeded with low nickel loadings of 2.5‐5 mol % in the absence of co‐solvent, and in some cases at room temperature. Isomerization to afford exclusively the terminal hydroboration product was obtained across a range of internal alkenes, including tri‐ and tetra‐substituted examples. This reactivity is unprecedented for nickel and offers a powerful means of achieving functionalization at a C−H position remote from the C=C double bond. Nickel‐catalyzed deuteroboration experiments using DBPin support a mechanism involving 1,2‐insertion of the alkene and subsequent chain‐walking, which results in isotopic scrambling. [ABSTRACT FROM AUTHOR]

We report herein on the synthesis and spectroscopic/crystallographic characterization of the first isolable, formally 16-electron Cp*Ru([κ.sup.2]-P~N) species, which are supported by N-phosphinoamidinate ligands. Despite the stability of such complexes, they have been shown to readily coordinate two-electron (L) donors including carbon monoxide and 2,6-xylylisocyanide, affording crystallographically characterized 18-electron Cp*Ru(L) ([κ.sup.2]-P~N) adducts. Preliminary reactivity studies confirm that such complexes are capable of extruding hydrogen from ammonia borane. Key words: N-phosphinoamidinate, ruthenium, ligand design, coordinative unsaturation. Nous decrivons la synthese et la caracterisation spectroscopique/cristallographique des premieres especes isolables Cp*Ru([κ.sup.2]-P~N) formellement a 16 electrons, qui sont supportees par des ligands N-phosphinoamidinate. Malgre leur stabilite, on a montre que ces complexes forment facilement une liaison de coordination avec des donneurs de doublet d'electrons (L), y compris le monoxyde de carbone et le 2,6-xylylisocyanure, pour donner des adduits Cp*Ru(L)([κ.sup.2]-P~N) a 18 electrons caracterises par cristallographie. Les etudes de reactivite preliminaires confirment que ces complexes sont capables d'extraire l'hydrogene de l'ammonia borane. [Traduit par la Redaction] Mots-cles: N-phosphinoamidinate, ruthenium, conception de ligands, insaturation coordinative., Introduction Coordinatively unsaturated Cp*Ru[L.sub.n] (Cp* = [η.sup.5]-[C.sub.5][Me.sub.5]) and related complexes have a well-established track record of exhibiting new and unusual metal-centered reactivity, (1, 2) with diverse applications in organic synthesis [...]

The Ir silyl pincer complexes are inserted into the N-H bonds of anilines and ammonia under mild conditions to obtain isolable [Cy-PSiP]Ir(H)(NHR) complexes. The obtained complexes are resistant to N-H bond reductive elimination at room temperature, even in the presence of arenes, alkenes, and phosphines.

The first examples of stoichiometric dehydrogenative B−H/C(sp3)−H benzylic borylation reactions, which are of relevance to catalytic methylarene (di)borylation, are reported. These unusual transformations involving a (κ2-P,N)Pt(η3-benzyl) complex, and either pinacolborane or catecholborane, proceed cleanly at room temperature. Density functional calculations suggest that borylation occurs via successive σ-bond metathesis steps, whereby a PtII−H intermediate engages in C(sp3)−H bond activation-induced dehydrogenation. [ABSTRACT FROM AUTHOR]

The synthesis of 16-electron complexes of the type (Cy-PSiP)RuX(L) (Cy-PSiP = κ3-(2-Cy2PC6H4)2SiMe) is reported. Treatment of (Cy-PSiP)H with one equiv. RuCl2(PPh3)3 in the presence of Et3N afforded a mixture of (Cy-PSiP)RuCl(PPh3) (1) and [(Cy-PSiP)RuCl]2 (2), which exists in a temperature-dependent equilibrium process involving reversible dissociation of PPh3 from 1 to form 2. While treatment of this equilibrium mixture with PMe3 afforded (Cy-PSiP)RuCl(PMe3) (3) cleanly, this product was more straightforwardly prepared by the addition of PMe3 to 2 (97% yield). Attempts to form an alkyl complex of the type (Cy-PSiP)RuMe(PMe3) via treatment of 3 with MeMgBr led to the dehydrogenation and cyclometalation of a cyclohexyl phosphino group to give the isolable 18-electron complex [MeSi(C6H4PCy2)(C6H4PCy(η3-C6H8))]RuPMe3 (4, 78% yield). The hydrido complex (Cy-PSiP)RuH(PMe3) (5) was identified as a minor by-product in this dehydrogenative process. Whereas simple 16-electron alkyl complexes of the type (Cy-PSiP)RuR(PMe3) remained elusive, the isolable allyl complex (Cy-PSiP)Ru(η3-C3H5) (9) was successfully prepared from 2 and (C3H5)MgCl (79% yield). Treatment of 3 with Me3SiN3 or NaN3 did not generate a five-coordinate azido species. However, the putative dinuclear complex [(Cy-PSiP)RuN3]2 (10) was observed to react with one equiv. of PMe3 to afford the isolable five-coordinate azido complex (Cy-PSiP)Ru(N3)(PMe3) (11; 94% yield). Crystallographic data for 3, 4, 5, 9 and 11 are presented. [ABSTRACT FROM AUTHOR]

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