Activation of H–H, HO–H, C(sp²)–H, C(sp³)–H, and RO–H Bonds by Transition-Metal Frustrated Lewis Pairs Based on M/N (M = Rh, Ir) Couples

Abstract

Reaction of the dimers [(Cp*MCl) 2 (μ-Cl) 2 ] (Cp* = η 5 -C 5 Me 5 ) with Ph 2 PCH 2 CH 2 NC(NH( p -Tolyl)) 2 ( H 2 L ) in the presence of NaSbF 6 affords the chlorido complexes [Cp*MCl(κ 2 N , P - H 2 L )][SbF 6 ] (M = Rh, 1 ; Ir, 2 ). Upon treatment with aqueous NaOH, solutions of 1 and 2 yield the corresponding complexes [Cp*M(κ 3 N , N′ , P - HL )][SbF 6 ] (M = Rh, 3 ; Ir, 4 ) in which the ligand HL presents a fac κ 3 N , N′ , P coordination mode. Treatment of THF solutions of complexes 3 and 4 with hydrogen gas, at room temperature, results in the formation of the metal hydrido-complexes [Cp*MH(κ 2 N , P - H 2 L )][SbF 6 ] (M = Rh, 5 ; Ir, 6 ) in which the N( p -Tolyl) group has been protonated. Complexes 3 and 4 react with deuterated water in a reversible fashion resulting in the gradual deuteration of the Cp* group. Heating at 383 K THF/H 2 O solutions of the complexes 3 and 4 affords the orthometalated complexes [Cp*M(κ 3 C , N , P - H 2 L -H )][SbF 6 ] [M = Rh, 7 ; Ir, 8 , H 2 L -H = Ph 2 PCH 2 CH 2 NC(NH( p -Tolyl))(NH(4-C 6 H 3 Me))], respectively. At 333 K, complexes 3 and 4 react in THF with methanol, primary alcohols, or 2-propanol giving the metal-hydrido complexes 5 and 6 , respectively. The reaction involves the acceptorless dehydrogenation of the alcohols at a relatively low temperature, without the assistance of an...

Guanidine-centred reactivity of CNN Pd(ii) pincer complexes including carboxylate-assisted N–H activation and –CH2– → –C(O)– oxygenation

“…6,7 On the other hand, half-sandwich Os(II) and M(III) (M = Rh and Ir) complexes of unsymmetrical guanidines, [(ArN(H)) 2 CQNR] (R = 2-picolyl and -(CH 2 ) 2 PPh 2 ), were shown to act as catalysts and as scaffolds for small molecule activation. [8][9][10] We reported two types of sixmembered cyclopalladated sym N-aryl guanidinate(1À) complexes, [Pd{k 2 (C,N)(m-X)}] 2 (X = OC(O)R 0 ; R 0 = Me, CF 3 and t Bu and X = Br) and [Pd{k 2 (C,N)(L)Br}] (L = Lewis base), and some of these palladacycles were shown to be useful precursors for anion substitution and alkyne insertion chemistry. [11][12][13] Recently, we reported the reactions of guanidines I and II with Pd(OC(O)R 0 ) 2 (R 0 = CF 3 , Me and t Bu), which afforded mononuclear III-V and dinuclear VI-VIII pincer complexes depending upon the substitution pattern in the starting materials as illustrated in Fig.…”

“…6,7 On the other hand, half-sandwich Os( ii ) and M( iii ) (M = Rh and Ir) complexes of unsymmetrical guanidines, [(ArN(H)) 2 CNR] (R = 2-picolyl and –(CH 2 ) 2 PPh 2 ), were shown to act as catalysts and as scaffolds for small molecule activation. 8–10 We reported two types of six-membered cyclopalladated sym N -aryl guanidinate(1−) complexes, [Pd{κ 2 ( C , N )(μ-X)}] 2 (X = OC(O)R′; R′ = Me, CF 3 and t Bu and X = Br) and [Pd{κ 2 ( C , N )(L)Br}] (L = Lewis base), and some of these palladacycles were shown to be useful precursors for anion substitution and alkyne insertion chemistry. 11–13…”

Synthesis and characterisation of group 11 metal complexes with a guanidine-tagged triphenylphosphine and evaluation of the isolated Au(i) complexes in gold-mediated organic reactions

“…1 More recently, compound B was employed in platinum metal complexes, which were subsequently utilised in small molecule activation and indole nitroethylation. 2 Analogous phosphines bearing cyclic guanidine moieties, C and D , were evaluated as substrate-directing ligands in hydroformylation of β,γ-unsaturated carboxylic acids 3 and found to form highly active H/D-exchange iridium catalysts (type E ). 4…”

Molecular hydrogen and water activation by transition metal frustrated Lewis pairs containing ruthenium or osmium components: catalytic hydrogenation assays

“…4 In this regard, we have recently reported the preparation of masked TMFLPs based on the phosphano–guanidine H 2 L2 and pyridinyl–guanidine H 2 L3 ligands depicted in Scheme 1. 5 These are half-sandwich (ring) M-complexes ( A , B in Scheme 1) with deprotonated monoanionic HL2 or HL3 species acting as the κ 3 ligand. In these monoanionic ligands, the central nitrogen atom may adopt sp 3 hybridization allowing both the phosphorus ( HL2 ) or the pyridine nitrogen ( HL3 ) and the iminic nitrogen atom to bond with the metal in a fac κ 3 -coordination mode.…”