Supplementary material from Malcolm Harold Chisholm 15 October 1945 - 20 November 2015

Malcolm Harold Chisholm - Bibliograph

A Diphosphine Ligand with Amide Functionality and Its Complexes with Gold(I) and Silver(I): Self-Assembly of Sheet Structures

A new diphosphine ligand, <i>N</i>,<i>N</i>′-bis­(2-diphenylphosphinoethyl)­terephthalamide, dppeta, containing two amide groups, has been synthesized and shown to form complexes [Au₂Cl₂(μ-dppeta)]·2Me₂SO, <b>1</b>, with gold­(I) and [Ag₂(O₂CCF₃)₂(μ-dppeta)], <b>2</b>, and [Ag₂(OTf)₂(OH₂)₂(μ-dppeta)], <b>3</b>, with silver­(I). The ligand dppeta undergoes self-association by NH···OC hydrogen bonding in a classical way, but the complexes <b>1</b>, <b>2</b>, and <b>3</b> undergo self-association through a combination of hydrogen bonding and either aurophilic bonding (complex <b>1</b>) or secondary coordination (complexes <b>2</b> and <b>3</b>). In all cases, sheet structures are formed by self-assembly, in which the bonding interactions occur in the interior, with the outer faces containing mostly phenyl groups. In contrast, the bis­(phosphine oxide) derivative, dppetaO₂, forms a ribbon polymer using the PO groups as hydrogen bond acceptors

The Platinum Center is a Stronger Nucleophile than the Free Nitrogen Donors in a Dimethylplatinum Complex with a Dipyridylpyridazine Ligand

The ligand 1,4-di-2-pyridyl-5,6,7,8,9,10-hexahydrocycloocta­[<i>d</i>]­pyridazine (6-dppd) contains two potential chelate groups, but it coordinates to only one dimethylplatinum group in forming the complex [PtMe₂(6-dppd)], <b>1</b>. Complex <b>1</b> contains a free pyridyl and a free pyridazine nitrogen donor, but it fails to coordinate to ZnCl₂ or to CuCl to give a bimetallic complex. Complex <b>1</b> reacted with mercury­(II) salts HgX₂ (X = Cl, Br, OAc), not by coordination but by oxidative addition to the dimethylplatinum­(II) center to give the platinum­(IV) complexes [PtX­(HgX)­Me₂(6-dppd)]. Complex <b>1</b> reacted with bromine or iodine by <i>trans</i> oxidative addition to give [PtX₂Me₂(6-dppd)], X = Br or I, but, when X = I, a more complex sequence of reactions also gave rise to products of <i>cis</i> oxidative addition and to the products [PtIMe₃(6-dppd)] and [PtI₃Me­(6-dppd)], which arise through a methyl group transfer reaction. Complex <b>1</b> reacted with alkyl halides RX by <i>trans</i> oxidative addition to give [PtXRMe₂(6-dppd)], R = Me, X = I; R = CH₂Ph, X = Br; R = CH₂-4-C₆H₄-CH₂Br, X = Br. The cleavage of methyl groups from complex <b>1</b> by DCl gave a mixture of all isotopomers of methane, CH_4–<i>n</i>D_<i>n</i>, indicating ready equilibration between hydrido­(methyl)­platinum­(IV) and methaneplatinum­(II) complex intermediates

Activation of Dioxygen by Dimethylplatinum(II) Complexes

The ligands RN­(CH₂-2-C₅H₄N)₂ (<b>L1</b>, R = CH₂CH₂OH; <b>L2</b>, R = CH₂CH₂CH₂OH; <b>L3</b>, R = 2-C₆H₄OH) have been designed to give dimethylplatinum­(II) complexes that can activate dioxygen in the absence of a protic solvent. The ligands react with [Pt₂Me₄(SMe₂)₂] to give an equilibrium mixture, with the major constituent being [PtMe₂(κ²-N,N′-<b>L</b>)] (<b>1a</b>, <b>L</b> = <b>L1</b>; <b>1b</b>, <b>L</b> = <b>L2</b>; <b>1c</b>, <b>L</b> = <b>L3</b>). In the absence of air, <b>1a</b> reacts with solvent CH₂Cl₂ to give [PtMe₂(CH₂Cl)­(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L1</b>]­Cl, while <b>1c</b> decomposes with loss of methane to give [PtMe­(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L3</b>-H)] and then, by reaction with solvent, the binuclear complex [{PtMe­(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L3</b>-H)}₂(μ-H)]­Cl. In the presence of oxygen the complexes <b>1</b> in CH₂Cl₂ solution react to give [Pt­(OH)­Me₂(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L</b>)]­Cl, when <b>L</b> = <b>L1</b> or <b>L2</b>, or [Pt­(OH)­Me₂(κ³-<i>N</i>,<i>N</i>′,<i>O</i>-<b>L</b>-H)], when <b>L</b> = <b>L3</b>. The complex [Pt­(OH)­Me₂(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L2</b>)]Cl decomposed in the presence of air to give the binuclear complex [{PtMe₂(2-C₅H₄NCO₂)­(μ-OH)}₂]. The factors influencing reactivity and mechanism in these reactions are elucidated, and the presence of both a free pyridyl donor (push group) and a free hydroxyl (pull group) is suggested to give a synergy for dioxygen activation by dimethylplatinum­(II) complexes

Activation of Dioxygen by Dimethylplatinum(II) Complexes

The ligands RN­(CH₂-2-C₅H₄N)₂ (<b>L1</b>, R = CH₂CH₂OH; <b>L2</b>, R = CH₂CH₂CH₂OH; <b>L3</b>, R = 2-C₆H₄OH) have been designed to give dimethylplatinum­(II) complexes that can activate dioxygen in the absence of a protic solvent. The ligands react with [Pt₂Me₄(SMe₂)₂] to give an equilibrium mixture, with the major constituent being [PtMe₂(κ²-N,N′-<b>L</b>)] (<b>1a</b>, <b>L</b> = <b>L1</b>; <b>1b</b>, <b>L</b> = <b>L2</b>; <b>1c</b>, <b>L</b> = <b>L3</b>). In the absence of air, <b>1a</b> reacts with solvent CH₂Cl₂ to give [PtMe₂(CH₂Cl)­(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L1</b>]­Cl, while <b>1c</b> decomposes with loss of methane to give [PtMe­(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L3</b>-H)] and then, by reaction with solvent, the binuclear complex [{PtMe­(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L3</b>-H)}₂(μ-H)]­Cl. In the presence of oxygen the complexes <b>1</b> in CH₂Cl₂ solution react to give [Pt­(OH)­Me₂(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L</b>)]­Cl, when <b>L</b> = <b>L1</b> or <b>L2</b>, or [Pt­(OH)­Me₂(κ³-<i>N</i>,<i>N</i>′,<i>O</i>-<b>L</b>-H)], when <b>L</b> = <b>L3</b>. The complex [Pt­(OH)­Me₂(κ³-<i>N</i>,<i>N</i>′,<i>N</i>″-<b>L2</b>)]Cl decomposed in the presence of air to give the binuclear complex [{PtMe₂(2-C₅H₄NCO₂)­(μ-OH)}₂]. The factors influencing reactivity and mechanism in these reactions are elucidated, and the presence of both a free pyridyl donor (push group) and a free hydroxyl (pull group) is suggested to give a synergy for dioxygen activation by dimethylplatinum­(II) complexes

Organoplatinum Chemistry with a Dicarboxamide–Diphosphine Ligand: Hydrogen Bonding, Cyclometalation, and a Complex with Two Metal–Metal Donor–Acceptor Bonds

The chemistry of the ligand bis­(2-diphenylphosphinoethyl)­phthalamide, dpppa, with platinum­(II) is described. The reaction of dpppa with [Pt₂Me₄(μ-SMe₂)₂], <b>1</b>, in a 2:1 ratio gave a mixture of [PtMe₂(dpppa)] and [Pt₂Me₄(μ-dpppa)₂], both of which contain Pt···H–N hydrogen bonds. However, reaction in a 1:1 ratio gave a remarkable tetraplatinum complex, [Pt₄Me₆(μ-dpppa-H)₂], which is shown to contain two Pt–Pt donor–acceptor bonds and in which one arm of the dpppa ligand has been cyclometalated. The reaction of [PtCl₂(dpppa)] with silver trifluoroacetate, to abstract chloride, and triethylamine as base has given the bis­(cyclometalated) complex [Pt­(dpppa-2H)], and this has been crystallized in three different forms, in which one or both of the carbonyl groups act as donors to a proton or to silver­(I). The complex [Pt­(dpppa-2H)]·AgO₂CCF₃·dmso forms a dimer and [Pt­(dpppa-2H)]·(AgO₂CCF₃)₂ forms a coordination polymer in the solid state

Reactivity of a Dimethylplatinum(II) Complex with the Bis(2-pyridyl)dimethylsilane Ligand: Easy Silicon–Carbon Bond Activation

The compound [PtMe₂(bps)] (<b>1</b>; bps = bis­(2-pyridyl)­dimethylsilane) undergoes easy oxidative addition with bromine, iodine, methyl iodide, or methyl triflate to give [PtBr₂Me₂(bps)], [PtI₂Me₂(bps)], [PtIMe₃(bps)], or [PtMe₃(OH₂)­(bps)]­[OTf], respectively. The complex [PtIMe₃(bps)] is slowly hydrolyzed in solution, with cleavage of the pyridyl–silicon bonds, to give [PtIMe₃(py)₂] and (Me₂SiO)_<i>n</i>. In contrast, oxidation of <b>1</b> with oxygen/CF₃CH₂OH, hydrogen peroxide, or dibenzoyl peroxide/H₂O occurs with cleavage of a methyl–silicon bond to give [PtMe­(bps)-μ-{κ³<i>N</i>,<i>N</i>,<i>O</i>-OSiMe­(2-C₅H₄N)₂PtMe₃]­[CF₃CH₂OB­(C₆F₅)₃], [PtMe₃{κ³<i>N</i>,<i>N</i>,<i>O</i>-(2-C₅H₄N)₂SiMeO}], or [PtMe₃{κ³<i>N</i>,<i>N</i>,<i>O</i>-(2-C₅H₄N)₂SiMeOH}]­[PhCOO], respectively. Mechanistic studies indicate that this methyl transfer from silicon to platinum occurs after oxidation to platinum­(IV) and is induced by hydroxide attack at silicon

Oxidation of Dimethylplatinum(II) Complexes with a Dioxirane: The Viability of Oxoplatinum(IV) Intermediates

The complexes [PtMe₂(NN)] (NN = 2,2′-bipyridine = bipy, <b>1a</b>; NN = di-2-pyridylamine = dpa, <b>1b</b>; NN = di-2-pyridyl ketone = dpk, <b>1c</b>) react with dimethyldioxirane in moist acetone to give the hydroxoplatinum­(IV) complexes [Pt­(OH)₂Me₂(NN)] (NN = bipy, <b>2a</b>; NN = dpa, <b>2b</b>, or [Pt­(OH)­Me₂(dpkOH)], <b>3</b>). Complex <b>2a</b> crystallizes as the hydrate <b>2a</b>·7H₂O, which has a complex supramolecular network structure formed through hydrogen bonding between PtOH groups and water molecules. Attempts to trap a potential oxoplatinum­(IV) intermediate in these reactions were unsuccessful, and computational studies suggest that oxoplatinum­(IV) intermediates are improbable. It is suggested that oxygen atom transfer from the dioxirane to platinum is coupled to proton addition to give the hydroxoplatinum group directly

Switching by Photochemical <i>trans–cis</i> Isomerization of Azobenzene Substituents in Organoplatinum Complexes

A diimine ligand, LL = 2-C₅H₄NCHN-4-C₆H₄NNPh, which carries a <i>trans</i>-azobenzene substituent, forms the dimethylplatinum­(II) complex [PtMe₂(LL)], which undergoes <i>trans</i> oxidative addition with MeI, PhCH₂Br, Br₂, and I₂ to give the corresponding organoplatinum­(IV) complexes [PtIMe₃(LL)], [PtBrMe₂(CH₂Ph)­(LL)], [PtBr₂Me₂(LL)], and [PtI₂Me₂(LL)], respectively. The ligand and the platinum­(II) and platinum­(IV) complexes are shown to undergo <i>trans–cis</i> isomerization of the azobenzene substituent upon irradiation, and the <i>cis</i> isomers then underwent slow thermal isomerization back to the more stable <i>trans</i> isomers

Carbon–Hydrogen versus Nitrogen–Oxygen Bond Activation in Reactions of N‑Oxide Derivatives of 2,2′-Bipyridine and 1,10-Phenanthroline with a Dimethylplatinum(II) Complex

The reactions of the potential oxygen atom donor ligands 1,10-phenanthroline <i>N</i>-oxide (phenO) and 2,2′-bipyridine <i>N</i>-oxide (bipyO) with the dimethylplatinum­(II) complex [Pt₂Me₄(μ-SMe₂)₂] are reported. The reaction with the more rigid ligand phenO gave [PtMe₂(κ²<i>N</i>,<i>O</i>-phenO)], which underwent oxidative addition with 4-<i>t</i>-Bu-C₆H₄CH₂Br to give the platinum­(IV) complex [PtBrMe₂(CH₂C₆H₄-4-<i>t</i>-Bu)­(phenO)]. The complex [PtMe₂(phenO)] reacted with methanol in air to give [Pt­(OH)­(OMe)­Me₂(phenO)], but under an inert atmosphere it gave [Pt­(OH)­(OMe)­Me₂(phen)], in a reaction involving N–O bond activation. In contrast, the reaction of [Pt₂Me₄(μ-SMe₂)₂] with bipyO occurred by C–H bond activation to give methane and [PtMe­(κ²<i>N</i>,<i>C</i>-C₅H₄N-C₅H₃NO)­(SMe₂)], which underwent ligand substitution with pyridine, triphenylphosphine, or bis­(diphenylphosphino)­methane (dppm) to give [PtMe­(κ²<i>N</i>,<i>C</i>-C₅H₄N-C₅H₃NO)­(NC₅H₅)], [PtMe­(κ²<i>N</i>,<i>C</i>-C₅H₄N-C₅H₃NO)­(PPh₃)], or the binuclear [{PtMe­(κ²<i>N</i>,<i>C</i>-C₅H₄N-C₅H₃NO)}₂(μ-dppm)], respectively. With bis­(diphenylphosphino)­ethane (dppe), ligand substitution gave [PtMe­(κ¹<i>C</i>-C₅H₄N-C₅H₃NO)­(dppe)], which contains a monodentate metalated bipyO ligand. The mechanisms of the key reactions are discussed