Взаємний зв'язок властивостей і структури плівкових чутливих елементів сенсорів магнітного поля

Дисертацію присвячено комплексним експериментальним дослідженням особливостей структурно-фазового стану та магнітних і магніторезистивних властивостей багатошарових плівкових систем на основі Co і Cu, Co і Cr, Fe і Cr та Fe і Cu як можливих матеріалів чутливих елементів сенсорів різного призначення. У роботі встановлено взаємозв’язок між товщиною магнітних шарів і немагнітних прошарків, орієнтацією зразка у зовнішньому магнітному полі, температурою термообробки та магнітними, магніторезистивними і магнітооптичними властивостями багатошарових плівкових систем із можливим спін-залежним розсіюванням електронів. Визначені величини магнітоопору, коерцитивної сили, коефіцієнта прямокутності й чутливості плівкової системи до магнітного поля досліджуваних плівкових систем як приладових структур для формування первинних перетворювачів. Установлена кореляція між структурно-фазовим станом, магнітними та магнітооптичними властивостями тришарових плівкових систем з різним типом розчинності компонент як функціональних елементів датчиків. Запропонована схематична конструкція АМР-датчика магнітного поля для тришарових плівкових систем із спін-залежним розсіюванням електронів. У результаті проведених досліджень впливу геометрії вимірювання, температури термообробки та загальної концентрації феромагнітної компоненти в системі на магнітні й магніторезистивні властивості визначені можливі області застосування плівкових систем на основі Co і Cu або Cr та Fe і Cu або Cr.Диссертация посвящена комплексным экспериментальным исследованиям особенностей структурно-фазового состояния, магнитных магниторезистивных свойств многослойных пленочных систем на основе Co и Cu, Co и Cr, Fe и Cr и Fe и Cu в качестве возможных материалов чувствительных элементов сенсоров различного назначения. В работе установлена взаимосвязь между толщиной магнитных слоев и немагнитных прослоек, ориентацией образца во внешнем магнитном поле, температурой термообработки и магнитными, магниторезистивными и магнитооптическими свойствами многослойных пленочных систем с возможным спин-зависимым рассеянием электронов. При исследовании магнитных свойств пленочных систем на основе Fe, Co, Cu или Cr получено, что для пленочных систем на основе Fe и Cu в форме кривых гистерезиса наблюдается определенный перегиб, свидетельствующий о послойном перемагничивании слоев Fe, в то время как для систем на основе Fe и Cr петля гистерезиса имеет форму, подобную однослойным пленкам Fe, что говорит о преобладании ферромагнитной связи в системе. В пленочных структурах на основе Co и Cr или Cu магнитные свойства системы главным образом определяются состоянием слоев Со, поэтому форма кривых гистерезиса для обеих систем схожа с формой кривых для однослойных пленок Со, а небольшие значения коэрцитивной силы свидетельствуют о реализации ферромагнитной связи в системе. Все четыре системы характеризуются достаточно высоким значением коэффициента прямоугольности, которое при смене ориентации образца от 0 до 90° несколько уменьшается для систем Fe/Cu/Fe и Fe/Cr/Fe и, наоборот, растет в системах на основе Co и Cr. Определены величины магнитосопротивления, коэрцитивной силы, коэффициента прямоугольности и чувствительности пленочной системы к магнитному полю исследуемых пленочных систем как приборных структур для формирования первичных преобразователей. Установлена корреляция между структурно-фазовым состоянием, магнитными и магнитооптическими свойствами трехслойных пленочных систем с разным типом растворимости компонент в качестве функциональных элементов датчиков. Предложена схематическая конструкция АМР-датчика магнитного поля для трехслойных пленочных систем со спин-зависимым рассеянием электронов. В результате проведенных исследований влияния геометрии измерения, температуры термообработки и общей концентрации ферромагнитной компоненты в системе на магниторезистивные свойства определены возможные области применения пленочных систем на основе Co и Cu или Cr и Fe и Cu или Cr.The thesіs іs dedіcаted to the complex experіmentаl reseаrch between the structurаl-phаse stаte, magnetic and magnetoresistance propertіes of multіlаyer fіlm systems bаsed on the Co аnd Cu, Co аnd Cr, Fe аnd Cr, аnd Fe аnd Cu, аs the potential mаterіаls for sensіtіve elements of sensors for dіfferent purposes. Іn thіs thesis wаs found the correlаtіon between the thіckness of the mаgnetіc аnd nonmаgnetіc lаyers, the orіentаtіon of the sаmple іn аn externаl mаgnetіc fіeld, temperаture of heаt treаtment аnd mаgnetіc, mаgnetoresіstіve аnd mаgneto-optіcаl propertіes іn multіlаyer fіlm systems wіth possіble spіn-dependent scаtterіng of electrons. The vаlues of mаgnetoresіstаnce, coercіvіty, squаreness fаctor аnd sensіtіvіty of fіlm system to a mаgnetіc fіeld in the studіed fіlm systems аs devіce structures for the formаtіon of prіmаry converters were defined. The correlаtіon between the structurаl-phаse stаte, mаgnetіc аnd mаgneto-optіcаl propertіes of three-lаyer fіlm systems wіth dіfferent types of component solubіlіty аs functіonаl elements sensors was established. The schemаtіc sturucture of АMR sensor for three-lаyer fіlm systems wіth spіn-dependent scаtterіng of electrons was purposed. The possіble аreаs of аpplіcаtіons wаs іdentіfіed on the bаsіs of studіes of the effect of geometry meаsurement temperаture heаt treаtment аnd the totаl concentrаtіon of ferromаgnetіc components іn the system on the magnetic and mаgnetoresіstіve propertіes of fіlm-systems bаsed on Co аnd Cu, or Cr аnd Fe, аnd Cu or Cr

Systematic Heterodinuclear Complexes with MM′(μ-meppp) Centers That Tune the Properties of a Nesting Hydride (M = Ni, Pd, Pt; M′ = Rh, Ir; H₂meppp = <i>meso</i>-1,3-Bis[(mercaptoethyl)phenylphosphino]propane)

Mononuclear complexes with a P₂S₂ ligand, [M­(meppp)] (M = Ni (<b>1a</b>), Pd (<b>1b</b>), Pt (<b>1c</b>); H₂meppp = <i>meso</i>-1,3-bis­[(mercaptoethyl)­phenylphosphino]­propane), were treated with [M′Cp*Cl₂]₂ or [M′Cp*­(NO₃)₂] (Cp* = η⁵-pentamethylcyclopentadienyl) to afford a series of bisthiolate-bridged M^IIM′^III heterodinuclear complexes, [M­(μ-meppp)­M′Cp*X]­X′ (M = Ni, Pd, Pt; M′ = Rh, Ir; X = Cl, NO₃; X′ = Cl, PF₆, NO₃). The nitrate complexes [M­(μ-meppp)-M′Cp*­(NO₃)]­NO₃ (M′ = Rh ([<b>4a</b>–<b>c</b>]­NO₃), Ir ([<b>5a</b>–<b>c</b>]­NO₃); M = Ni (<b>a</b>), Pd (<b>b</b>), Pt (<b>c</b>)) further reacted with sodium formate in water or methanol to be transformed into bisthiolate- and hydride-bridged complexes, [M­(μ-meppp)­(μ-H)­M′Cp*]­NO₃ (M′ = Rh ([<b>6a</b>–<b>c</b>]­NO₃), Ir ([<b>8a</b>–<b>c</b>]­NO₃); M = Ni (<b>a</b>), Pd (<b>b</b>), Pt (<b>c</b>)). Complexes [<b>6a</b>]­NO₃ (M = Ni, M′ = Rh) and [<b>8a</b>]­NO₃ (M = Ni, M′ = Ir) were characterized by X-ray analyses to reveal that a hydride is stabilized in a semibridging mode on the heterometal centers. In the Pd^IIRh^III ([<b>6b</b>]­NO₃) and Pt^IIRh^III ([<b>6c</b>]­NO₃) complexes, the hydrides were extremely unstable and were likely to undergo an unusual metal-to-Cp* ring hydrogen transfer, resulting in η⁴-C₅Me₅H M^IIRh^I complexes, [M­(μ-meppp)­Rh­(η⁴-C₅Me₅H)]­NO₃ (M = Pd ([<b>7b</b>]­NO₃), Pt ([<b>7c</b>]­NO₃)). The property of the hydride was drastically switched by varying the anchoring metal ions of the M′ site (Rh, Ir); that of [<b>6a</b>]­NO₃ (M′ = Rh) is not protic and decomposes in water below pH 4, while those of [<b>8a</b>–<b>c</b>]­NO₃ (M′ = Ir) are protic, subject to H⁺/D⁺ exchange reactions, and stable below pH 4. [<b>6a</b>]­NO₃ reacted with phenylacetylene to give [Ni­(μ-meppp)­RhCp*­(CCPh)]­NO₃ ([<b>10a</b>]­NO₃), which is in contrast with the inertness of the Ni^IIIr^III hydride complex [<b>8a</b>]­NO₃. The reaction is assumed to involve an alkenyl complex, [Ni­(μ-meppp)­RhCp*­(CHCHPh)]­NO₃ (<b>9a</b>), formed through an insertion of phenylacetylene into the metal–hydride bond. Analogous M^IIRh^III alkynyl complexes, [M­(μ-meppp)­RhCp*­(CCPh)]­NO₃ (M = Pd ([<b>10b</b>]­NO₃), Pt ([<b>10c</b>]­NO₃)), were synthesized by treating [<b>4b</b>,<b>c</b>]­NO₃ with phenylacetylene in basic media, and the structural differences among [<b>10a</b>–<b>c</b>]­NO₃ were discussed. These results interestingly demonstrated that the structures, properties, and reactivities of the nesting hydride on the {MM′(μ-meppp)} cores were tuned by varying metal ions of the M and M′ sites

Configurational Isomerization of Dinuclear Iridium and Rhodium Complexes with a Series of NPPN Ligands, 2‑PyCH₂(Ph)P(CH₂)_<i>n</i>P(Ph)CH₂‑2-Py (Py = Pyridyl, <i>n</i> = 2–4)

New heterodonor NPPN tetradentate ligands, 2-PyCH₂(Ph)­P­(CH₂)_<i>n</i>P­(Ph)­CH₂-2-Py (<i>meso</i>- and <i>rac</i>-L^<i>n</i>; <i>n</i> = 2–4, Py = pyridyl), were prepared and reacted with [Cp*MCl₂]₂ (M = Ir, Rh; Cp* is pentamethylcyclopentadienyl) in the presence of NH₄BF₄ to afford a series of dinuclear complexes [(Cp*MCl)₂(<i>meso</i>-L^<i>n</i>)]­(BF₄)₂ (M = Ir, <i>n</i> = 2 (<b>2a</b>), 3 (<b>3a</b>), 4 (<b>4a</b>); M = Rh, <i>n</i> = 2 (<b>2c</b>), 3 (<b>3c</b>), 4 (<b>4c</b>)) and [(Cp*MCl)₂(<i>rac</i>-L^<i>n</i>)]­(BF₄)₂ (M = Ir, <i>n</i> = 2 (<b>2b</b>), 3 (<b>3b</b>), 4 (<b>4b</b>); M = Rh, <i>n</i> = 2 (<b>2d</b>), 3 (<b>3d</b>), 4 (<b>4d</b>)), which were characterized by IR, ¹H and ³¹P­{¹H} NMR, and ESI mass spectroscopic techniques and X-ray crystallography. The configurations around the two metal centers were controlled by the configuration of the coordinated P atoms so as to avoid repulsive interaction between the phenyl group on P and the chloride ligand, resulting in the formation of stereospecific isomers; a <i>meso</i> configuration of the metal centers is induced from <i>meso</i>-L^<i>n</i> (abbreviated as <i>meso</i>-P₂/<i>meso</i>-M₂), and in contrast, a <i>rac</i> configuration is induced from <i>rac</i>-L^<i>n</i> (<i>rac</i>-P₂/<i>rac</i>-M₂). Furthermore, inversion of metal centers for the Ir₂ complexes occurred in DMSO at higher temperatures (60–100 °C), generating equilibrium mixtures of minor diastereomers (<i>meso</i>-P₂/<i>rac</i>-M₂ or <i>rac</i>-P₂/<i>meso</i>-M₂) in low ratios together with the major isomers (<i>meso</i>-P₂/<i>meso</i>-M₂ or <i>rac</i>-P₂/<i>rac</i>-M₂). The equilibrium constants, <i>K</i> = [minor isomer]/[major isomer], varied appreciably depending on the lengths of the methylene chains as well as configurations of the NPPN ligands; the overall propensity for the <i>K</i> values was observed to be L² < L³ < L⁴ and <i>meso</i>-L^<i>n</i> < <i>rac</i>-L^<i>n</i>, while <i>rac</i>-L³, <i>rac</i>-L⁴, and <i>meso</i>-L⁴ showed almost identical equilibrium constants, presumably resulting from no steric influence between the two metal centers

Cyclic Trinuclear Rh₂M Complexes (M = Rh, Pt, Pd, Ni) Supported by <i>meso</i>-1,3-Bis[(diphenylphosphinomethyl)phenylphosphino]propane

Reaction of [MCl₂(cod)] (M = Pd, Pt) with a tetraphosphine, <i>meso</i>-1,3-bis­[(diphenylphosphinomethyl)­phenylphosphino]­propane (dpmppp), afforded the mononuclear complexes [MCl₂(dpmppp)] (M = Pd (<b>3a</b>), Pt (<b>3b</b>)), in which the dpmppp ligand coordinated to the M ion by two inner phosphorus atoms to form a six-membered chelate ring with two outer phosphines uncoordinated. The pendant outer phosphines readily reacted with [RhCl­(CO)₂]₂ to give the cationic heterotrinuclear complexes [MRh₂(μ-Cl)₃(μ-dpmppp)­(CO)₂]­X (X = [RhCl₂(CO)₂], M = Pd (<b>4a</b>), Pt (<b>4b</b>); X = PF₆, M = Pd (<b>5a</b>), Pt (<b>5b</b>)). The nickel analogue [NiRh₂(μ-Cl)₃(μ-dpmppp)­(CO)₂]­PF₆ (<b>5c</b>) was also prepared. A neutral homotrinuclear Rh₃ complex, [Rh₃(μ-Cl)₃(μ-dpmppp)­(CO)₂] (<b>6</b>), was synthesized by the reaction of [RhCl­(CO)₂]₂ with dpmppp and was further reacted with HgX₂ (X = Cl, Br, I) to afford the Rh₃Hg tetranuclear complexes [Rh₃(HgX)­(μ-Cl)₂(μ-X)­(μ-dpmppp)­(CO)₂]­PF₆ (X = Cl (<b>7a</b>), Br (<b>7b</b>), I (<b>7c</b>)), where the Rh₃(μ-Cl)₂(μ-X) cores act as tridentate ligands to form three donor–acceptor Rh→Hg interactions. The two CO ligands of <b>7a</b>–<b>c</b> were replaced by XylNC to yield [Rh₃(HgX)­(μ-Cl)₂(μ-X)­(μ-dpmppp)­(XylNC)₂]­PF₆ (X = Cl (<b>8a</b>), Br (<b>8b</b>), I (<b>8c</b>)). The isocyanides had an appreciable influence on the three Rh→Hg interactions, which was monitored by the ²<i>J</i>_HgP values observed in the ³¹P­{¹H} NMR spectra and discussed on the basis of DFT calculations. Complex <b>6</b> also reacted with CuCl and HBF₄ to give [Rh₃(CuCl)­(μ-Cl)₃(μ-dpmppp)­(CO)₂] (<b>9</b>) and [Rh₃(μ₃-H)­(μ-Cl)₃(μ-dpmppp)­(CO)₂]­BF₄ (<b>10</b>), respectively. These results suggested that the new tetraphosphine dpmppm proved quite useful in constructing fine-tunable heterometallic frameworks

Configurational Isomerization of Dinuclear Iridium and Rhodium Complexes with a Series of NPPN Ligands, 2‑PyCH₂(Ph)P(CH₂)_<i>n</i>P(Ph)CH₂‑2-Py (Py = Pyridyl, <i>n</i> = 2–4)

New heterodonor NPPN tetradentate ligands, 2-PyCH₂(Ph)­P­(CH₂)_<i>n</i>P­(Ph)­CH₂-2-Py (<i>meso</i>- and <i>rac</i>-L^<i>n</i>; <i>n</i> = 2–4, Py = pyridyl), were prepared and reacted with [Cp*MCl₂]₂ (M = Ir, Rh; Cp* is pentamethylcyclopentadienyl) in the presence of NH₄BF₄ to afford a series of dinuclear complexes [(Cp*MCl)₂(<i>meso</i>-L^<i>n</i>)]­(BF₄)₂ (M = Ir, <i>n</i> = 2 (<b>2a</b>), 3 (<b>3a</b>), 4 (<b>4a</b>); M = Rh, <i>n</i> = 2 (<b>2c</b>), 3 (<b>3c</b>), 4 (<b>4c</b>)) and [(Cp*MCl)₂(<i>rac</i>-L^<i>n</i>)]­(BF₄)₂ (M = Ir, <i>n</i> = 2 (<b>2b</b>), 3 (<b>3b</b>), 4 (<b>4b</b>); M = Rh, <i>n</i> = 2 (<b>2d</b>), 3 (<b>3d</b>), 4 (<b>4d</b>)), which were characterized by IR, ¹H and ³¹P­{¹H} NMR, and ESI mass spectroscopic techniques and X-ray crystallography. The configurations around the two metal centers were controlled by the configuration of the coordinated P atoms so as to avoid repulsive interaction between the phenyl group on P and the chloride ligand, resulting in the formation of stereospecific isomers; a <i>meso</i> configuration of the metal centers is induced from <i>meso</i>-L^<i>n</i> (abbreviated as <i>meso</i>-P₂/<i>meso</i>-M₂), and in contrast, a <i>rac</i> configuration is induced from <i>rac</i>-L^<i>n</i> (<i>rac</i>-P₂/<i>rac</i>-M₂). Furthermore, inversion of metal centers for the Ir₂ complexes occurred in DMSO at higher temperatures (60–100 °C), generating equilibrium mixtures of minor diastereomers (<i>meso</i>-P₂/<i>rac</i>-M₂ or <i>rac</i>-P₂/<i>meso</i>-M₂) in low ratios together with the major isomers (<i>meso</i>-P₂/<i>meso</i>-M₂ or <i>rac</i>-P₂/<i>rac</i>-M₂). The equilibrium constants, <i>K</i> = [minor isomer]/[major isomer], varied appreciably depending on the lengths of the methylene chains as well as configurations of the NPPN ligands; the overall propensity for the <i>K</i> values was observed to be L² < L³ < L⁴ and <i>meso</i>-L^<i>n</i> < <i>rac</i>-L^<i>n</i>, while <i>rac</i>-L³, <i>rac</i>-L⁴, and <i>meso</i>-L⁴ showed almost identical equilibrium constants, presumably resulting from no steric influence between the two metal centers

Cyclic Trinuclear Rh₂M Complexes (M = Rh, Pt, Pd, Ni) Supported by <i>meso</i>-1,3-Bis[(diphenylphosphinomethyl)phenylphosphino]propane

Reaction of [MCl₂(cod)] (M = Pd, Pt) with a tetraphosphine, <i>meso</i>-1,3-bis­[(diphenylphosphinomethyl)­phenylphosphino]­propane (dpmppp), afforded the mononuclear complexes [MCl₂(dpmppp)] (M = Pd (<b>3a</b>), Pt (<b>3b</b>)), in which the dpmppp ligand coordinated to the M ion by two inner phosphorus atoms to form a six-membered chelate ring with two outer phosphines uncoordinated. The pendant outer phosphines readily reacted with [RhCl­(CO)₂]₂ to give the cationic heterotrinuclear complexes [MRh₂(μ-Cl)₃(μ-dpmppp)­(CO)₂]­X (X = [RhCl₂(CO)₂], M = Pd (<b>4a</b>), Pt (<b>4b</b>); X = PF₆, M = Pd (<b>5a</b>), Pt (<b>5b</b>)). The nickel analogue [NiRh₂(μ-Cl)₃(μ-dpmppp)­(CO)₂]­PF₆ (<b>5c</b>) was also prepared. A neutral homotrinuclear Rh₃ complex, [Rh₃(μ-Cl)₃(μ-dpmppp)­(CO)₂] (<b>6</b>), was synthesized by the reaction of [RhCl­(CO)₂]₂ with dpmppp and was further reacted with HgX₂ (X = Cl, Br, I) to afford the Rh₃Hg tetranuclear complexes [Rh₃(HgX)­(μ-Cl)₂(μ-X)­(μ-dpmppp)­(CO)₂]­PF₆ (X = Cl (<b>7a</b>), Br (<b>7b</b>), I (<b>7c</b>)), where the Rh₃(μ-Cl)₂(μ-X) cores act as tridentate ligands to form three donor–acceptor Rh→Hg interactions. The two CO ligands of <b>7a</b>–<b>c</b> were replaced by XylNC to yield [Rh₃(HgX)­(μ-Cl)₂(μ-X)­(μ-dpmppp)­(XylNC)₂]­PF₆ (X = Cl (<b>8a</b>), Br (<b>8b</b>), I (<b>8c</b>)). The isocyanides had an appreciable influence on the three Rh→Hg interactions, which was monitored by the ²<i>J</i>_HgP values observed in the ³¹P­{¹H} NMR spectra and discussed on the basis of DFT calculations. Complex <b>6</b> also reacted with CuCl and HBF₄ to give [Rh₃(CuCl)­(μ-Cl)₃(μ-dpmppp)­(CO)₂] (<b>9</b>) and [Rh₃(μ₃-H)­(μ-Cl)₃(μ-dpmppp)­(CO)₂]­BF₄ (<b>10</b>), respectively. These results suggested that the new tetraphosphine dpmppm proved quite useful in constructing fine-tunable heterometallic frameworks

Stepwise Expansion of Pd Chains from Binuclear Palladium(I) Complexes Supported by Tetraphosphine Ligands

Reaction of [Pd₂(XylNC)₆]­X₂ (X = PF₆, BF₄) with a linear tetraphosphine, <i>meso</i>-bis­[(diphenylphosphinomethyl)­phenylphosphino]­methane (dpmppm), afforded binuclear Pd^I complexes, [Pd₂(μ-dpmppm)₂]­X₂ ([<b>2</b>]­X₂), through an asymmetric dipalladium complex, [Pd₂(μ-dpmppm)­(XylNC)₃]²⁺ ([<b>1</b>]²⁺). Complex [<b>2</b>]²⁺ readily reacted with [Pd⁰(dba)₂] (2 equiv) and an excess of isocyanide, RNC (R = 2,6-xylyl (Xyl), <i>tert</i>-butyl (^<i>t</i>Bu)), to generate an equilibrium mixture of [Pd₄(μ-dpmppm)₂(RNC)₂]²⁺ ([<b>3</b>′]²⁺) + RNC ⇄ [Pd₄(μ-dpmppm)₂(RNC)₃]²⁺ ([<b>3</b>]²⁺), from which [Pd₄(μ-dpmppm)₂(XylNC)₃]²⁺ ([<b>3a</b>]²⁺) and [Pd₄(μ-dpmppm)₂(^<i>t</i>BuNC)₂]²⁺ ([<b>3b</b>′]²⁺) were isolated. Variable-temperature UV–vis and ³¹P­{¹H} and ¹H NMR spectroscopic studies on the equilibrium mixtures demonstrated that the tetrapalladium complexes are quite fluxional in the solution state: the symmetric Pd₄ complex [<b>3b</b>′]²⁺ predominantly existed at higher temperatures (>0 °C), and the equilibrium shifted to the asymmetric Pd₄ complex [<b>3b</b>]²⁺ at a low temperature (∼−30 °C). The binding constants were determined by UV–vis titration at 20 °C and revealed that XylNC is of higher affinity to the Pd₄ core than ^<i>t</i>BuNC. In addition, both isocyanides exhibited higher affinity to the electron deficient [Pd₄(μ-dpmppmF₂)₂(RNC)₂]²⁺ ([<b>3F</b>′]²⁺) than to [Pd₄(μ-dpmppm)₂(RNC)₂]²⁺ ([<b>3</b>′]²⁺) (dpmppmF₂ = <i>meso</i>-bis­[{di­(3,5-difluorophenyl)­phosphinomethyl}­phenylphosphino]­methane). When [<b>2</b>]­X₂ was treated with [Pd⁰(dba)₂] (2 equiv) in the absence of RNC in acetonitrile, linearly ordered octapalladium chains, [Pd₈(μ-dpmppm)₄(CH₃CN)₂]­X₄ ([<b>4</b>]­X₄: X = PF₆, BF₄), were generated through a coupling of two {Pd₄(μ-dpmppm)₂}²⁺ fragments. Complex [<b>2</b>]²⁺ was also proven to be a good precursor for Pd₂M₂ mixed-metal complexes, yielding [Pd₂Cl­(Cp*MCl) (Cp*MCl₂)­(μ-dpmppm)₂]²⁺ (M = Rh ([<b>5</b>]²⁺), Ir ([<b>6</b>]²⁺), and [Au₂Pd₂Cl₂(dpmppm–H)₂]²⁺ ([<b>7</b>]²⁺) by treatment with [Cp*MCl₂]₂ and [AuCl­(PPh₃)], respectively. Complex [<b>7</b>]²⁺ contains an unprecedented PC­(sp³)P pincer ligand with a PCPCPCP backbone, dpmppm–H of deprotonated dpmppm. The present results demonstrated that the binuclear Pd^I complex [<b>2</b>]²⁺ was a quite useful starting material to extend the palladium chains and to construct Pd-involved heteromultinuclear systems

Stepwise Expansion of Pd Chains from Binuclear Palladium(I) Complexes Supported by Tetraphosphine Ligands

Reaction of [Pd₂(XylNC)₆]­X₂ (X = PF₆, BF₄) with a linear tetraphosphine, <i>meso</i>-bis­[(diphenylphosphinomethyl)­phenylphosphino]­methane (dpmppm), afforded binuclear Pd^I complexes, [Pd₂(μ-dpmppm)₂]­X₂ ([<b>2</b>]­X₂), through an asymmetric dipalladium complex, [Pd₂(μ-dpmppm)­(XylNC)₃]²⁺ ([<b>1</b>]²⁺). Complex [<b>2</b>]²⁺ readily reacted with [Pd⁰(dba)₂] (2 equiv) and an excess of isocyanide, RNC (R = 2,6-xylyl (Xyl), <i>tert</i>-butyl (^<i>t</i>Bu)), to generate an equilibrium mixture of [Pd₄(μ-dpmppm)₂(RNC)₂]²⁺ ([<b>3</b>′]²⁺) + RNC ⇄ [Pd₄(μ-dpmppm)₂(RNC)₃]²⁺ ([<b>3</b>]²⁺), from which [Pd₄(μ-dpmppm)₂(XylNC)₃]²⁺ ([<b>3a</b>]²⁺) and [Pd₄(μ-dpmppm)₂(^<i>t</i>BuNC)₂]²⁺ ([<b>3b</b>′]²⁺) were isolated. Variable-temperature UV–vis and ³¹P­{¹H} and ¹H NMR spectroscopic studies on the equilibrium mixtures demonstrated that the tetrapalladium complexes are quite fluxional in the solution state: the symmetric Pd₄ complex [<b>3b</b>′]²⁺ predominantly existed at higher temperatures (>0 °C), and the equilibrium shifted to the asymmetric Pd₄ complex [<b>3b</b>]²⁺ at a low temperature (∼−30 °C). The binding constants were determined by UV–vis titration at 20 °C and revealed that XylNC is of higher affinity to the Pd₄ core than ^<i>t</i>BuNC. In addition, both isocyanides exhibited higher affinity to the electron deficient [Pd₄(μ-dpmppmF₂)₂(RNC)₂]²⁺ ([<b>3F</b>′]²⁺) than to [Pd₄(μ-dpmppm)₂(RNC)₂]²⁺ ([<b>3</b>′]²⁺) (dpmppmF₂ = <i>meso</i>-bis­[{di­(3,5-difluorophenyl)­phosphinomethyl}­phenylphosphino]­methane). When [<b>2</b>]­X₂ was treated with [Pd⁰(dba)₂] (2 equiv) in the absence of RNC in acetonitrile, linearly ordered octapalladium chains, [Pd₈(μ-dpmppm)₄(CH₃CN)₂]­X₄ ([<b>4</b>]­X₄: X = PF₆, BF₄), were generated through a coupling of two {Pd₄(μ-dpmppm)₂}²⁺ fragments. Complex [<b>2</b>]²⁺ was also proven to be a good precursor for Pd₂M₂ mixed-metal complexes, yielding [Pd₂Cl­(Cp*MCl) (Cp*MCl₂)­(μ-dpmppm)₂]²⁺ (M = Rh ([<b>5</b>]²⁺), Ir ([<b>6</b>]²⁺), and [Au₂Pd₂Cl₂(dpmppm–H)₂]²⁺ ([<b>7</b>]²⁺) by treatment with [Cp*MCl₂]₂ and [AuCl­(PPh₃)], respectively. Complex [<b>7</b>]²⁺ contains an unprecedented PC­(sp³)P pincer ligand with a PCPCPCP backbone, dpmppm–H of deprotonated dpmppm. The present results demonstrated that the binuclear Pd^I complex [<b>2</b>]²⁺ was a quite useful starting material to extend the palladium chains and to construct Pd-involved heteromultinuclear systems

Hydride-Bridged Pt₂M₂Pt₂ Hexanuclear Metal Strings (M = Pt, Pd) Derived from Reductive Coupling of Pt₂M Building Blocks Supported by Triphosphine Ligands

Linear Pt₂M₂Pt₂ hexanuclear clusters [Pt₄M₂(μ-H)­(μ-dpmp)₄(XylNC)₂]­(PF₆)₃ (M = Pt (<b>2a</b>), Pd (<b>3a</b>); dpmp = bis­(diphenylphosphinomethyl)­phenylphosphine) were synthesized by site-selective reductive coupling of trinuclear building blocks, [Pt₂M­(μ-dpmp)₂(XylNC)₂]­(PF₆)₂ (M = Pt (<b>1a</b>), Pd (<b>1b</b>)), and were revealed as the first example of low-oxidation-state metal strings bridged by a hydride with M–H–M linear structure. The characteristic intense absorption bands around 583 nm (<b>2a</b>) and 674 nm (<b>3a</b>) were assigned to the HOMO–LUMO transition on the basis of a net three-center/two-electron (3c/2e) bonding interaction within the central M₂(μ-H) part. The terminal ligands of <b>2a</b> were replaced by H^–, I^–, and CO to afford [Pt₆(μ-H)­(H)₂(μ-dpmp)₄]⁺ (<b>4</b>), [Pt₆(μ-H)­I₂(μ-dpmp)₄]­(PF₆) (<b>5</b>), and [Pt₆(μ-H)­(μ-dpmp)₄(CO)₂]­(PF₆)₃ (<b>6</b>). The electronic structures of these hexaplatinum cores, {Pt₆(μ-H)­(μ-dpmp)₄}³⁺, are varied depending on the σ-donating ability of axial ligands; the characteristic HOMO–LUMO transition bands interestingly red-shifted in the order of CO < XylNC < I^– < H^–, which was in agreement with calculated HOMO–LUMO gaps derived from DFT optimizations of <b>2a</b>, <b>4</b>, <b>5</b>, and <b>6</b>. The nature of the axial ligands influences the redox activities of the hexanuclear complexes; <b>2a</b>, <b>3a</b>, and <b>5</b> were proven to be redox-active by the cyclic voltammograms and underwent two-electron oxidation by potentiostatic electrolysis to afford [Pt₄M₂(μ-dpmp)₄(XylNC)₂]­(PF₆)₄ (M = Pt (<b>7a</b>), Pd (<b>8a</b>)). The present results are important in developing bottom-up synthetic methodology to create nanostructured metal strings by utilizing fine-tunable metallic building blocks

Hydride-Bridged Pt₂M₂Pt₂ Hexanuclear Metal Strings (M = Pt, Pd) Derived from Reductive Coupling of Pt₂M Building Blocks Supported by Triphosphine Ligands

Linear Pt₂M₂Pt₂ hexanuclear clusters [Pt₄M₂(μ-H)­(μ-dpmp)₄(XylNC)₂]­(PF₆)₃ (M = Pt (<b>2a</b>), Pd (<b>3a</b>); dpmp = bis­(diphenylphosphinomethyl)­phenylphosphine) were synthesized by site-selective reductive coupling of trinuclear building blocks, [Pt₂M­(μ-dpmp)₂(XylNC)₂]­(PF₆)₂ (M = Pt (<b>1a</b>), Pd (<b>1b</b>)), and were revealed as the first example of low-oxidation-state metal strings bridged by a hydride with M–H–M linear structure. The characteristic intense absorption bands around 583 nm (<b>2a</b>) and 674 nm (<b>3a</b>) were assigned to the HOMO–LUMO transition on the basis of a net three-center/two-electron (3c/2e) bonding interaction within the central M₂(μ-H) part. The terminal ligands of <b>2a</b> were replaced by H^–, I^–, and CO to afford [Pt₆(μ-H)­(H)₂(μ-dpmp)₄]⁺ (<b>4</b>), [Pt₆(μ-H)­I₂(μ-dpmp)₄]­(PF₆) (<b>5</b>), and [Pt₆(μ-H)­(μ-dpmp)₄(CO)₂]­(PF₆)₃ (<b>6</b>). The electronic structures of these hexaplatinum cores, {Pt₆(μ-H)­(μ-dpmp)₄}³⁺, are varied depending on the σ-donating ability of axial ligands; the characteristic HOMO–LUMO transition bands interestingly red-shifted in the order of CO < XylNC < I^– < H^–, which was in agreement with calculated HOMO–LUMO gaps derived from DFT optimizations of <b>2a</b>, <b>4</b>, <b>5</b>, and <b>6</b>. The nature of the axial ligands influences the redox activities of the hexanuclear complexes; <b>2a</b>, <b>3a</b>, and <b>5</b> were proven to be redox-active by the cyclic voltammograms and underwent two-electron oxidation by potentiostatic electrolysis to afford [Pt₄M₂(μ-dpmp)₄(XylNC)₂]­(PF₆)₄ (M = Pt (<b>7a</b>), Pd (<b>8a</b>)). The present results are important in developing bottom-up synthetic methodology to create nanostructured metal strings by utilizing fine-tunable metallic building blocks