CH₃–X Reductive Elimination Reactivity of Pt^IVMe Complexes Supported by a Sulfonated CNN Pincer Ligand (X = OH, CF₃CO₂, PhNMe₂⁺)

Abstract

Three new dihydrocarbyl LPt IV Me(Y) complexes (6−8; Y = Cl, I, OCH 2 CF 3 ) supported by the sulfonated CNN pincer ligand L have been prepared and characterized. The reaction of these complexes with a number of nucleophiles (H 2 O, CF 3 CO 2 − , Me 2 SO, PhNMe 2 ) resulting in the formation of corresponding C−X coupled products CH 3 −X has been studied in 2,2,2-trifluoroethanol (TFE) and DMSO. In TFE or DMSO solutions at 22 °C, in the presence of PhNMe 2 , a quantitative formation of a C−N coupled product, PhNMe 3 + , was observed for 6−8, with the reactivity decreasing in the order 6 > 7 > 8. The use of NaO 2 CCF 3 in TFE solutions was less efficient, leading to the production of MeO 2 CCF 3 in 60% yield after 22 h at 70 °C. In DMSO the C−O coupling was high yielding when aqueous trifluoroacetic acid was used to produce methanol (87% after 3 h at 80 °C) or when NaO 2 CCF 3 was used to form MeO 2 CCF 3 (80% after 1.5 h at 80 °C), with Me 3 SO + being a minor byproduct. The kinetics study of the reaction between 6−8 and PhNMe 2 in TFE has revealed an overall second-order rate law, d[PhNMe 3 + ]/dt = k 2 [6, 7 or 8][PhNMe 2 ], consistent with the realization of an S N 2type process. A DFT modeling of several alternative pathways of reaction between 7 and PhNMe 2 in TFE supported the direct nucleophilic attack of PhNMe 2 at the methyl group carbon of 7 as the most likely mechanism of this transformation.

Oxidation of Methylplatinum(II) Complexes K[(L)PtIIMe] with O2 and C(sp3)-X (X = O and C) Reductive Elimination Reactivity of Methylplatinum(IV) Products (L)PtIVMe(OH): The Effect of Structure of Sulfonated CNN-Pincer Ligands L

“…II Me], 8, and K[(L2)Pt II Me], 9. Complex K[(L1)Pt II Me], 8, was synthesized as reported previously 17 (Scheme 4). First, a potassium salt, K[HL1], was prepared by reacting H 2 L1 17 with KO t Bu dissolved in MeOH.…”

“…Complex K[(L1)Pt II Me], 8, was synthesized as reported previously 17 (Scheme 4). First, a potassium salt, K[HL1], was prepared by reacting H 2 L1 17 with KO t Bu dissolved in MeOH. The resulting solution was combined with a stirred suspension of Pt 2 Me 4 (SMe 2 ) 2 in MeOH.…”

“…11 On the downside, similar to arylplatinum(IV) complex (dpms)Pt IV Ph(OH), 16 4 (Scheme 2, b), supported by an earlier generation of sulfonated dipyridine ligands such as di(2pyridyl)methanesulfonate (dpms), the resulting Pt(IV) aryl hydroxo complexes (L1)Pt IV Ar(OH), 2, are inert in C−O reductive elimination (compare with step c, Scheme 1). The lack of reactivity is not the case for analogous monomethylplatinum(IV) CNN-pincer complexes (L1)-Pt IV Me(Y), 5a−5c, 17 (Scheme 3, a) or a related (dpms)-Pt IV Me(OH) 2 , 6 (Scheme 3, b). 18,19 Similar to the results of prior studies of various platinum(IV) alkyls, 18−25 5a−5c can be engaged in C(sp 3 )-X bond formation reactions (X = O, N, and S) that operate the S N 2 mechanism.…”

“…18,19 Similar to the results of prior studies of various platinum(IV) alkyls, 18−25 5a−5c can be engaged in C(sp 3 )-X bond formation reactions (X = O, N, and S) that operate the S N 2 mechanism. 17 Building on these results, one of the goals of this work was to find out if hydroxo complexes (L)Pt IV Me(OH) (L = L1 and L2; Chart 1) can be generated aerobically (compare with step b, Scheme 1) from the corresponding precursors K[(L)-Pt II Me], 8 and 9.…”

Recent Progress with Pincer Transition Metal Catalysts for Sustainability

“…After the first family of PCP complexes was synthetized by Shaw in 1976 [7], numerous research groups have applied this concept for almost all types of homogeneously catalyzed chemical reactions. A myriad of novel complexes with different pincer arms have been synthetized and characterized, including a vast family of carbene pincers [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], PNP [24][25][26][27][28][29], PNN [30,31], POP [32], PCP [33][34][35][36][37][38], SNS [39,40], NCN [41], NSiN [42], CNC [43], CNN [44], NNN [45], as well as sulfur- [46][47][48], silicon- [49,50], selenium- [51,52], and boron-functionalized [53,…”