A synthetic methodology has been developed for novel platinum(II) pincer complexes bearing bis((diphenyl)phosphinoxy)phenyl (PhPOCOPPh) ligand. Platinum(II) complexes of the type (PhPOCOPPh)Pt-C equivalent to CR [R = 4-(2,1,3-benzothiadiazolyl), phenyl] were synthesized via copper-catalyzed reactions in the presence of amine bases. Treatment of the chloride complex (PhPOCOPPh)PtCl with a 10%-20% excess of copper halides or cyanide in the presence of amines afforded high yields of the new complexes (PhPOCOPPh)PtX [X = I, Br, CN]. The molecular structures of complexes with the iodine and sigma-(4-benzothiadiazolylethynyl) ligands were determined by single-crystal x-ray diffraction. The IR and NMR spectroscopic data as well as the electrochemical properties of the new complexes were investigated, revealing correlations between their structures and reactivity. Electrochemical studies demonstrated that the halogen-containing complexes effectively catalyze the hydrogen evolution reaction. Based on these results, a mechanistic pathway is proposed for the platinum(II)-mediated electrochemical reduction of protons to hydrogen involving [(PhPOCOPPh)Pt] intermediates.

Pincer 1,3-bis((diphenyl)phosphinoxy)phenyl nickel(II) complexes ((POCOPPh)-P-Ph)NiX [X = I, OC(O)CH3, OC(O)CF3] were studied as potential catalysts of electrochemical hydrogen evolution reaction (HER) on a glassy carbon electrode in acetonitrile in the presence of proton donor HBF4 using cyclic voltammetry. It is shown that all the complexes can act as precatalysts for HER. A mechanism for HER involving these complexes is proposed.

The redox properties of 1,3-bis((diphenyl)phosphinoxy)phenyl nickel(II) pincer complexes ((POCOPPh)-P-Ph)NiX [X = I (1), OC(O)CH3 (2), OC(O)CF3 (3)] bearing terminal iodide, acetate and trifluoroacetate ligands were studied by electrochemical methods in acetonitrile. The redox behavior of complexes 1-3 was found to depend on both the nature of the terminal ligand and the electrode material. Complex 1 undergoes oxidation in two consecutive single - electron steps, 2-3 are oxidized in a single one- electron step, corresponding to a change in the oxidation of the metal centers Ni-II/Ni-IV and Ni-II/Ni-III, respectively. The reduction of the complexes proceeds via different mechanisms: 1 follows an & IEcy;& Scy;& IEcy;& Scy;& IEcy;, whereas 2-3 follow an EECE (E - electrochemical, C - chemical step). Schemes of their redox transformations are proposed.

The reactions of the new pincer complex bis((diphenyl)phosphinoxy)phenyl platinum [C6H3-1,3-(OPPh2)(2)]Pt- & Scy;equivalent to & Scy;-(4-C6H3N2S) (1) containing (2,1,3-benzothiadiazole-4-yl)-alkynyl ligand with transition metal substrates Pd(CH3CN)(2)X-2 (X = Cl, Br), Pt(dmso)(2)Cl-2, Pd-2(dba)(3) and CuCl were studied. The interactions of 1 with halogen-containing complexes were found to proceed through transmetalation - the transfer of the alkynyl ligand from the platinum atom of the pincer complex to the metal atom of the second reagent. The reaction of 1 with copper (I) chloride is reversible. The complexes obtained were characterized by IR- and NMR-spectroscopy

The reactions of 1,3-bis((diphenyl)phosphinoxy)benzene and PtCl2(L)(2) (L = SMe2, OSMe2, C5H5N) gave the new pincer-type 1,3-bis((diphenyl)phosphinoxy)phenyl platinum (II) complex [eta 3-kappa P:kappa C:kappa P-C6H3-1,3-(OPPh2)(2)]PtCl (1). The reaction between compound 1 and 4-ethynl-2,1,3benzothiadiazole in the presence of copper iodide lead to the new complex [C6H3-1,3-(OPPh2)(2)]Pt-CC(4-C6H3N2S) (2) containing a terminal (4-benzothiadiazol-2,1,3-yDethynyl ligand. The compounds were characterized by IR- and NMR-spectroscopy. These spectroscopy data allow us to propose the molecular structures of 1 and 2. The electrochemical properties of the new complexes were studied, the outcomes of their redox-reactions were proposed.

New binuclear MnPt µ-vinylidene complexes Cp(CO) 2 Mn(µ-C=CHPh)Pt(CN–Ad)(L) [L=PPh 3 ( 1a ), P(OPr i ) 3 ( 2a )] bearing a terminal platinum-coordinated 1-adamantyl isocyanide ligand were prepared by the treatment of Cp(CO) 2 Mn(µ-C=CHPh)Pt(CO)(L) [L=PPh 3 ( 1b ), P(OPr i ) 3 ( 2b )] with CN-Ad. At the same time the reaction between Cp(CO) 2 Mn(µ-C=CHPh)Pt(L) 2 [L=PPh 3 ( 1c ), P(OPr i ) 3 ( 2c )] and CN-Ad did not proceed. The new complexes were characterized by IR and 1 H, 13 C, 31 P NMR spectroscopy. The molecular structure of Cp(CO) 2 Mn(µ-C=CHPh)Pt(CN–Ad)[P(OPr i ) 3 ] ( 2a ) was determined by an X-ray diffraction study. The redox properties of the new complexes and their reactions of chemical oxidation were studied. An influence of the platinum-coordinated 1-adamantyl isocyanide ligand on the properties of the synthesized µ-vinylidene compounds 1a and 2a was revealed.

The known Rh(2-Me-8-Oxq)(CO)(2) complex (1) was prepared through treatment of dicarbonyl(acetylacetonate)rhodium (I) with 2-methyl-8-hydroxyquinoline for the first time. The reactions of 1 with triphenylphosphine and triphenylphosphite result in complexes Rh(2-Me-8-Oxq)(PPh3)(CO) (2) and Rh(2-Me-8-Oxq)[P(OPh)(3)](CO) (3) that were characterized by IR and NMR spectroscopy. The structures of complexes 2 and 3 were determined by single-crystal X-ray diffraction analysis. The complexes show the 2-methyl-8-quinolinolato ligand in the expected coordination mode with a slightly disordered square planar geometry at the rhodium center. In the crystal, molecules of Rh(2-Me-8-Oxq)(CO)(PPh3) (2) form centrosymmetric dimers due to pi-stacking interactions. No intermolecular contacts are observed in the crystal of 3. The UV spectroscopic and electrochemical properties of complexes 1-3 were studied. Their electronic spectra in CH3CN show three quinoline-centered absorptions. The electrochemical study revealed that the oxidation of the complexes 1-3 is two-electron and leads to the formation of dication Rh (III) species while their reduction gives radical anions, which undergoes rapid decomposition. (C) 2021 Elsevier B.V. All rights reserved.

A series of new beta-diketonate rhodium (I) complexes (acac)Rh(CO)(CNAd) (1a), (dbm)Rh(CO) (CNAd) (2a) and (hfac)Rh(CO)(CNAd) (3a) (acac = acetylacetonate, dbm = dibenzoyl methane, hfac = hexafluoroacetylacetonate, Ad = 1-adamantyl) containing adamantyl isocyanide ligand were synthesized. The new complexes were characterized by IR-and NMR-spectroscopy. These spectroscopy data allow us to propose their molecular structures. The reactions between the new complexes and diethylamine were studied.

The redox properties of new carbonyl beta- diketonate rhodium (I) complexes containing 1-adamantyl isocyanide ligand (beta- diketonato)Rh(CO)(CNAd) [beta- diketonato = acetylacetonate (acac), dibenzoylmethane (dbm), hexafluoroacetylacetonate (hfac), Ad =1-adamantyl)] were studied by electrochemical methods at platinum, glassed carbon and dropping mercury electrodes in acetonitrile. The electrochemical behaviour of the new complexes and related rhodium compounds (beta- diketonato) Rh(CO)(L) [L = CO, PPh3] were compared. The mechanism of two electron oxidation of the studied complexes was shown to depend on the nature of the chelate ligand. One electron reduction of the isocyanide complexes occurs at the E1/2 values, that are found between the reduction potentials of dicarbonyl and carbonylphosphine rhodium (I) complexes. That is consistent with the electron-donating ability of the terminal CO, CNAd and PPh3 ligands at the Rh atom.

A series of trinuclear μ3-vinylidene ReFePt clusters were synthesized by the application of two approaches: (i) reactions of the binuclear RePt μ-vinylidene complexes with Fe2(CO)9; (ii) ligand substitution or exchange reactions at the Pt atom in the synthesized ReFePt clusters. The molecular structures of CpReFePt(μ3-CCHPh)(CO)5[P(OEt)3]L [L = CO; P(OEt)3] were determined by an X-ray diffraction study. The obtained compounds were studied by IR and 1H, 13C and 31P NMR spectroscopy. The spectroscopic study revealed that the clusters CpReFePt(μ3-CCHPh)(CO)5[P(OEt)3]L [L = CO; P(OEt)3] and CpReFePt(μ3-CCHPh)(CO)6[P(OPri)3] undergo isomerization upon dissolution, resulting in three isomers with different positions of the μ3-vinylidene ligand over the ReFePt core. The redox properties of the clusters were studied by electrochemical methods. The relatively stable cation-radicals obtained by chemical oxidation of CpReFePt(μ3-CCHPh)(CO)6[P(OPri)3] and CpReFePt(μ3-CCHPh)(CO)5[P(OEt)3]2 with ferrocenium tetrafluoroborate were characterized by EPR spectroscopy.

The μ-phenylvinylidene complexes Cp(CO)2RePt(μ-C=CHPh)(PPh2H)(L) [L = PPh3 (1), P(OPri)3 (2)] were synthesized for the first time. Their IR, NMR spectroscopic and redox properties were studied. Based on IR, NMR spectroscopic data their molecular structures were proposed. The pathways of redox-reactions of the complexes were determined

A series of reactions of Cp(CO)2Mn[double bond, length as m-dash]C[double bond, length as m-dash]CHPh with different gold(i) complexes of [Au-C[triple bond, length as m-dash]C-R]n (R = 4-C5H4N, C6H5) and (tht)AuCl yielded one novel trinuclear MnAuMn cluster. The structure of this cluster can be rationalized as being formed of a vinylidene Mn-Au binuclear and Mn-acetylide fragments, and the binding between those is achieved mainly through the sharing of the electron pair of the single Mn-C σ-bond of an acetylide unit with the gold center.

The binuclear μ-vinylidene complexes containing an isocyanide ligand (1-(isocyanomethylsulfonyl)-4-methylbenzene) Cp(CO)2RePt(μ-C=CHPh)(TosMIC)(L) [L = PPh3 (1), P(OPri)3 (2)] were synthesized for the first time. The approach afforded 1 and 2 based on the substitution reactions of a platinum bound carbonyl group in Cp(CO)2RePt(μ-C=CHPh)(CO)(L) [L = PPh3 (1a), P(OPri)3 (2a)] upon addition of 1-(isocyanomethylsulfonyl)-4-methylbenzene. The complexes 1 and 2 were characterized by IR and NMR spectroscopy. Their redox properties were studied

Reactions of Cp(CO)(2)Re=C=CHPh with Pt[P(OR)(3)](4) (R = Pr-i, Et, Ph) gave binuclear mu-vinylidene complexes Cp(CO)(2)RePt(mu-C=CHPWW(OR)(3)](2). Treatment of the previously synthesized Cp(CO)(2)Re(mu-C=CHPh)Pt(PPh3)(2) with triisopropylphosphite or triethylphosphite resulted in a stepwise substitution of PPh3 ligands, leading to the disubstituted Cp(CO)(2)RePt(mu-C=CHPh)[P(OR)(3)](2) and monosubstituted Cp(CO)(2)RePt(mu-C=CHPh)[P(OR)(3)] (PPh3) (R = Pr-i or Et) species, while no triphenylphosphine ligand substitution in the reaction with P(OPh)(3) occurs at all. The monosubstituted Cp(CO)(2)RePt(mu-C=CHPh)IP(OR)(3)](PPh3) (R = Pe(i), Et, Ph) species were also obtained by reacting Cp(CO)(2)Re=C=CHPh with mixed-ligand complexes Pt(PPh3)(3)L (L = P(OPi)(3), P(OEt)(3), P (OPh)(3)). Reactions of Cp(CO)(2)RePt(mu-C=CHPh)LL' = L' = P(OPri)(3), P(OEt)(3), P(OPh)(3); L = P(OPri)(3), P(OEt)(3), P(OPh)(3), L' = PPh3) with Co-2(CO)(9) yield tricarbonyl vinylidene species Cp(CO)(2)RePt(mu-C=CHPh)IP(OR)(3)](CO) (R = Pr-i, Et, Ph). The obtained compounds were characterized by IR and H-1, C-13, P-31 NMR spectroscopy. The molecular structures of Cp(CO)(2)RePt(mu-C=CHPh)[P(OPi)(3)](2), Cp(CO)(2)RePt(mu-C=CHPh)[P(OPri)(3)](PPh3) and Cp(CO)(2)RePt(mu-C=CHPh)[P(OPri)(3)](CO) were determined by X-ray diffraction study. The redox properties of the new complexes and their reactions of chemical oxidation were studied.

The redox properties of mononuclear dicarbonyl and carbonylphosphine rhodium (I) complexes (CO)(L)Rh(RC(O)CHC(O)R’) with chelate β-diketonate ligands (L = CO, PPh3; R, R’ = Me, Ph; CF3, C4H3S) were studied by electrochemical methods at platinum, glassed carbon and dropping mercury electrodes in acetonitrile. Schemes of their redox reactions were established

The chemical oxidation of the cluster CpReFePt(μ3-C=CHPh)(CO)5(dppe) (Cp = η5-C5H5, dppe = η2- Ph2P(CH2)2PPh2) resulted in a radical cation [CpReFePt(μ3-C=CHPh)(CO)5(dppe)]+• that is sufficiently stable only at low temperature. An electronic structure of the radical cation was studied by EPR and following parameters were obtained by comparison of the experimental and model spectrum: gx = 2.070 gy = 2.0295 gz = 1.997; Ax(31P) = 17 Ay(31P) = 49 Az(31P) = 35 (Gs);Ax(195Pt) = 62 Ay(195Pt) = 45 Az(195Pt) = 105 (Gs). An unpaired electron is seen to be mainly concentrated on the iron atom (85-90%) and partially on the platinum atom (10-15%). Further transformation of the radical cation led to the formation of the binuclear complex Cp(CO)2RePt(μ-C=CHPh)(dppe) and the Fe-carbonyl fragment

The chemical oxidation of the cluster CpReFePt(mu(3)-C=CHPh)(CO)(5)(dppe) (Cp = eta(5)-C5H5, dppe = eta(2)-Ph2P(CH2)(2)PPh2) resulted in a radical cation [CpReFePt(mu(3)-C=CHPh)(CO)(5)(dppe)](+center dot) that is sufficiently stable only at low temperature. An electronic structure of the radical cation was studied by EPR and following parameters were obtained by comparison of the experimental and model spectrum: g(x) = 2.070 g(y) = 2.0295 g(z) = 1.997; A(x)(P-31) = 17 A(y)(P-31) = 49 A(z)(P-31) = 35 (Gs);A(x)(Pt-195) = 62 A(y)(Pt-195) = 45 A(z)(Pt-195) = 105 (Gs). An unpaired electron is seen to be mainly concentrated on the iron atom (85-90%) and partially on the platinum atom (10-15%). Further transformation of the radical cation led to the formation of the binuclear complex Cp(CO)(2)RePt(mu-C=CHPh)(dppe) and the Fe-carbonyl fragment.