Homo- and hetero-dinuclear complexes of palladium and platinum containing phosphinoacetylene and/or chloride as bridging ligands

Ethynyltolan Platinum Complexes with (Arylalkynyl)phosphane Ligands

“…Thus, complexes 4 and 5 show one strong ν(CϵC) absorption at 2173 (4) and 2172 cm -1 (5), which confirms that the alkynyl units of the PPh 2 CϵCR ligands remain uncoordinated. The expected ν(CϵC) absorptions at lower frequencies, assignable to the bridging Pt(µ-CϵCR) 2 Pt entity, are not observed, although this structural feature has been found previously in other alkynyl-bridged complexes. [57] However, both complexes show an additional very weak ν(CϵC) absorption (2216 cm -1 ) that is clearly due to the outer C 5 ϵC 6 alkyne entity of these bridging alkynyl groups.…”

“…[4,8] However, when X is a group with a greater tendency to act as a bridging ligand (X = Cl, CϵCRЈ) these groups compete with the η 2 -bonding capacity of the PPh 2 CϵCR group to coordinate the "Pt(C 6 F 5 ) 2 " fragment and only polymetallic species with X or mixed X/PPh 2 CϵCR bridging systems are obtained. [2,3] In particular, several homo-and heterodimetallic complexes stabilized by double alkynyl bridging systems, such as cis-[{Pt(PPh 2 CϵCR) 2 (µ-η 1 :η 2 -CϵCRЈ) 2 (RЈ, R = Ph, tBu) using 1:1 or 1:2 molar ratios, respectively, thereby indicating the following order of bonding capability: CϵCRЈ Ͼ P-bonded PPh 2 CϵCR and CϵCPh Ͼ CϵCtBu fragments. [3] As an extension of this work to ethynyltolan systems {when referring to ethynyltolan as ligand, its deprotonated anion [(phenylethynyl)phenyl]ethynide is meant}, we report here the preparation and characterisation of the neutral complexes cis-[Pt(CϵCC 6 H 4 CϵCPh) 2 -(PPh 2 CϵCR) 2 ] [R = tol (2), C 6 H 4 CϵCPh (3)], which are stabilized by (arylalkynyl)phosphanes.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Furthermore, these ligands have revealed an interesting reactivity in transition-metal chemistry, such as insertion into reactive M-H or M-C bonds, [17][18][19][20][21][22][23][24][25] intramolecular coupling reactions [10,[26][27][28][29] or P-C bond cleavage to afford alkynide (CϵCR) and phosphide (PPh 2 ) fragments, [6,12,[30][31][32][33][34][35] which are often involved in subsequent coupling or insertion reactions. [36][37][38][39] In addition, simple P-coordination of alkynylphosphanes polarizes the electron density of the alkyne function by concentrating it on the C α atom, which favours its interaction with electrophilic and nucleophilic substrates such as water, [40,41] ethanol, [42,43] HX, …”

“…(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) form bridges, the η 2 -alkyne adducts [{Pt(C 6 F 5 ) 2 (µ-κP:η 2 -PPh 2 CϵCR) 2 }{Pt(C 6 F 5 ) 2 }] (R = Ph, tol), which are generated at low temperature, evolve through an unexpectedly easy sequential insertion of both PPh 2 CϵCR molecules into a Pt-C 6 F 5 bond to form unusual µ-2,3-bis(diphenylphosphanyl)-1,3-butadien-1-yl dinuclear complexes. [4,8] However, when X is a group with a greater tendency to act as a bridging ligand (X = Cl, CϵCRЈ) these groups compete with the η 2 -bonding capacity of the PPh 2 CϵCR group to coordinate the "Pt(C 6 F 5 ) 2 " fragment and only polymetallic species with X or mixed X/PPh 2 CϵCR bridging systems are obtained.…”

“…However, they have only been used as precursors of polymetallic complexes [10,15,[49][50][51][52] and in P-C bond activation or intramolecular coupling reactions [51,[53][54][55] on a few occasions. With the aim of exploring the η 2 -bonding capability of two P-coordinated diphenylphosphane ligands towards a second metal centre as a way of inducing alkyne coupling, we have previously studied the reactivity of cis-[MX 2 (PPh 2 CϵCR) 2 ] (M = Pd, Pt; X = Cl, [2] C 6 F 5 , [4,8,11] CϵCRЈ; [3] R = Ph, tol, tBu; RЈ = Ph, tBu) towards the solvate complex cis-[Pt(C 6 F 5 ) 2 (thf) 2 ] (thf = tetrahydrofuran). When X is a C 6 F 5 group with a low tendency to [R = tol (6), C 6 H 4 CϵCPh (7)], which are stabilized by a double ethynyltolan bridging system or a mixed ethynyltolan/alkynylphosphane bridging system, respectively.…”