Reactivity of Diaryliodine(III) Triflates toward Palladium(II) and Platinum(II):  Reactions of C(sp²)−I Bonds to Form Arylmetal(IV) Complexes; Access to Dialkyl(aryl)metal(IV), 1,4-Benzenediyl-Bridged Platinum(IV), and Triphenylplatinum(IV) Species; and Structural Studies of Platinum(IV) Complexes

Abstract

Diphenyliodine(III) triflate is able to transfer Ph + to Pd(II) and Pt(II) with cleavage of a phenyl-iodine bond and formation of metal(IV) species, leading to the first identified transfer of Ph + to Pd(II) from an aryl-halogen bond, and, for platinum, a methodology providing a facile route to dimethyl(aryl)platinum(IV) and 1,4-arenediyl-bridged Pt(IV) species and the first archetypal triarylplatinum(IV) complex. Thus, [IPh 2 ][OTf] reacts with PtMe 2 (bpy) (bpy ) 2,2′-bipyridine) at -50°C to form iodobenzene and the Pt(IV) complex trans-Pt IV (OTf)Me 2 -Ph(N∼N) (1b) (Ph trans to OTf), and on addition of NaI, the species PtIMe 2 Ph(bpy) (2a (Ph cis to I) and 2b (Ph trans to I) in 2:1 ratio) may be isolated at -20°C. Similarly, metalla-(II)cyclopentane complexes M(C 4 H 8 )(bpy) react with [IPh 2 ][OTf] to form trans-Pt(OTf)(C 4 H 8 )-Ph(bpy) (3b) and a 1:1 ratio of cis-(4a) and trans-Pd(OTf)(C 4 H 8 )Ph(bpy) (4b); addition of halide ion gives trans-PtI(C 4 H 8 )Ph(bpy) (5b) and a 1:3 ratio of cis and trans isomers for PdI(C 4 H 8 )Ph(bpy) (6a, 6b) and PdCl(C 4 H 8 )Ph(bpy) (7a, 7b). Complex 5b isomerizes to form a 2:1 mixture of cis-PtI(C 4 H 8 )Ph(bpy) (5a) and 5b at ambient temperature in acetone. Dimethyl(2,2′-bipyridine)palladium(II) reacts with [IPh 2 ][OTf] to form Pd(OTf)Me 2 Ph(bpy), followed by transfer of a methyl group from Pd(IV) to Pd(II), to form trimethylpalladium-(IV) species. Dimethyl(2,2′-bipyridine)platinum(II) reacts with [IPh(C 6 H 4 -4-I)][OTf], followed by addition of sodium iodide, to form a 1:1 mixture of trans-PtIMe 2 Ph(bpy) (2b) and transPtIMe 2 (C 6 H 4 -4-I)(bpy) (8b), and with [IPh(C 6 H 4 -4-IPh)][OTf] 2 to form the 1,4-arenediyl complex trans-1,4-{PtIMe 2 (bpy)} 2 C 6 H 4 (9b). Diphenyl{di(tert-butyl)-2,2′-bipyridine}platinum-(II) reacts with [IPh 2 ][OTf] at 25°C over 2 days to form the triphenylplatinum(IV) complex Pt(OTf)Ph 3 (Bu t 2 bpy) (10), and addition of iodide ion results in isolation of PtIPh 3 (Bu t 2 bpy) (11). Structural studies of trans-PtIMe 2 Ph(bpy) (2b) and trans-Pt(C 4 H 8 )Ph(bpy) (5b) reveal distorted octahedral geometry and the fac-PtC 3 configuration expected for all of the metal-(IV) complexes. The compound [IPh(C 6 H 4 -4-I)][OTf] has two sets of cation-anion pairs with a complex array of weak interactions, and the cations have C-I-C angles close to 90°.

Palladium- and Copper-Catalyzed Arylation of Carbon−Hydrogen Bonds

“…Arylations can be rendered catalytic because ArI is compatible with silver salts used for iodide removal from palladium coordination sphere. It has been shown that Pd(IV) complexes possessing hard ligands are isolable in some cases;8a hence, if arene contains a hard directing group and can be cyclopalladated, we should be able to arylate it. Palladacycles have been studied extensively;8b however, alternative mechanistic pathways for C-H activation by iridium complexes have also been proposed 8c…”

“…More interestingly, electron-rich aryl iodides react faster than electron-poor ones (Scheme 3). The aryl iodide enters the catalytic cycle at the stage of oxidative addition to Pd(II), which is most likely the rate-determining step since arylation rate depends on ArI and reductive elimination from Pd(IV) is expected to be fast 8a. Oxidative addition step must be faster for electron-rich aryl iodides which is different from the usual Pd(0)-Pd(II) coupling cycle where electron-deficient aryl halides are more reactive 15.…”

Systematic differences in electrochemical reduction of the structurally characterized anti-cancer platinum(IV) complexes [Pt{((p-HC6F4)NCH2)2}-(pyridine)2Cl2], [Pt{((p-HC6F4)NCH2)2}(pyridine)2(OH)2], and [Pt{((p-HC6F4)NCH2)2}(pyridine)2(OH)Cl]

“…An analogous oxidation of cis-[Pt(C 6 F 5 ) 2 (PhN 3 Ph)] -to the corresponding dichloride has been reported [52]. Use of iodine(III) reagents to oxidize platinum / palladium(II) complexes to tetravalent derivatives is a currently active synthetic method [53][54][55][56][57][58][59]. The trans-Cl 2 arrangement in 1b was established by X-ray crystallography (below).…”

Anilide ortho‐Arylation by Using CH Activation Methodology

“…[13] It has been shown that diaryliodonium trifluoromethanesulfonates can transfer Ar + to nitrogen-ligated Pd II , thereby leading to the formation of unstable Pd IV species that decompose through reductive elimination pathways. [14] This finding of Canty and co-workers may be relevant to the mechanism of this arylation procedure; however, at this point a s-bond metathesis pathway can not be ruled out.…”