C–C σ complexes of rhodium

Brayshaw, Simon K.; Sceats, Emma L.; Green, Jennifer C.; Weller, Andrew S.

doi:10.1073/pnas.0609824104

Cited by 60 publications

(36 citation statements)

References 56 publications

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“…Protonation of platinacycles 1a and 1b.G eneration of agostic structures:C À Hbond activation and CÀCb ond-making reactions Protonation reactions of Pt II alkyl complexes have intensively been investigated [14][15][16][17][18][19] with the purpose of gaining valuableinformation on the microscopic reverse reaction, namely the activation of the CÀHb onds of alkanes. CÀHb ond activation [20][21] and subsequent functionalization [22][23][24][25] are main themes of research in organotransition-metal chemistry and require in many instances the participation of agostic structures [26] or CÀ H s-complexes [27] as reactive intermediates.…”

Section: Introductionmentioning

confidence: 59%

Reactivity of Cationic Agostic and Carbene Structures Derived from Platinum(II) Metallacycles

Campos

Ortega-Moreno

Conejero

et al. 2015

Chemistry A European J

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This paper describes the formation of new platinacyclic complexes derived from the phosphine ligands PiPr2Xyl, PMeXyl2, and PMe2Ar Xyl 2 (Xyl=2,6‐Me2C6H3 and Ar Xyl 2=2,6‐(2,6‐Me2C6H3)2‐C6H3) as well as reactivity studies of the trans‐[Pt(C^P)2] bis‐metallacyclic complex 1 a derived from PiPr2Xyl. Protonation of compound 1 a with [H(OEt2)2][BArF] (BArF=B[3,5‐(CF3)2C6H3]4) forms a cationic δ‐agostic structure 4 a, whereas α‐hydride abstraction employing [Ph3C][PF6] produces a cationic platinum carbene trans‐[Pt{PiPr2(2,6‐CH(Me)C6H3}{PiPr2(2,6‐CH2(Me)C6H3}][PF6] (8). Compounds 4 a and 8 react with H2 to yield the same 1:3 equilibrium mixture of 4 a and trans‐[PtH(PiPr2Xyl)2][BArF] (6), in which one of the phosphine ligands participates in a δ‐agostic interaction. DFT calculations reveal that H2 activation by 8 occurs at the highly electrophilic alkylidene terminus with no participation of the metal. The two compounds 4 a and 8 experience C–C coupling reactions of a different nature. Thus, 4 a gives rise to complex trans‐[PtH{(E)‐1,2‐bis(2‐(PiPr2)‐3‐MeC6H3)CHCH}] (7) that contains a tridentate diphosphine–alkene ligand, through agostic CH oxidative cleavage and C–C reductive coupling steps, whereas the C–C coupling reaction in 8 involves classical migratory insertion of its [PtCH] and [PtCH2] bonds promoted by platinum coordination of CO or CNXyl. The mechanisms of the CC bond‐forming reactions have also been investigated by computational methods.

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Section: Introductionmentioning

confidence: 59%

Reactivity of Cationic Agostic and Carbene Structures Derived from Platinum(II) Metallacycles

Campos

Ortega-Moreno

Conejero

et al. 2015

Chemistry A European J

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“…In the most important case of C-C agostic species, a very recent comprehensive review is available [44]. Notably, Weller and coworkers have identified cases where an agostic C-C is present [45][46][47]. Not only is the C-C bond close to what would otherwise be a 16e metal (dRh-C ¼ 2.352(3), 2.369(3) Å), but the C-C bond itself is significantly elongated to 1.604(4) Å, and the agostic carbons show significant J coupling to Rh in the 13 C NMR spectrum (J(Rh,C) ¼ 9 Hz).…”

Section: Silane σ Complexesmentioning

confidence: 97%

Sigma Bonds as Ligand Donor Groups in Transition Metal Complexes

Crabtree

2015

The Chemical Bond III

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Covalent X-H bonds, particularly where X is H, C, B, and Si, can act as Lewis base ligands in forming metal complexes of general type L n M(H-X), where the M-H-X angle is strongly bent so that the coordination can best be considered as side-on. The binding is greatly enhanced by back donation from the metal into the X-H σ* orbital. This elongates and eventually breaks the X-H bond, leading to characteristic structural, physicochemical characteristics and alteration of the reactivity of the ligand. The requirement for back donation means that the appropriate L n M fragment must usually have appreciable π donor character. Since the binding of the X-H bond to the metal center is relatively weak, and the binding of the deprotonated X À group left behind is much stronger, the binding also facilitates proton loss from the X-H bond. This electron redistribution results in reactivity differences which may be exploited. The case of H 2 is treated in most detail in this review, because of its central place in the field.

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“…The coordination and activation of s bonds involving Group 14 elements (E = C, Si, Ge, Sn, Pb) is at the forefront of developments in this area. An increasing variety of complexes A [3][4][5] and B [6,7] (Scheme 1) featuring side-on coordinated s(E À H) and s(E À E) bonds have been isolated, and the key factors governing the delicate balance between dissociation and oxidative addition have been progressively identified. The common feature and believed prerequisite for the coordination of saturated molecules free of lone pairs to transition metals is the superposition of ligand!metal donation (from a filled s orbital of the ligand to an empty d orbital of the metal) and metal!ligand back-donation (from a filled d orbital of the metal to an empty s* orbital of the ligand).…”

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confidence: 99%