Intramolecular Csp-H Activation at a Platinum(IV) Center Resulting from O Activation: The Role of a Proton-Responsive Ligand and Trans Influence.

Aerobic oxidation of a dimethylplatinum(II) complex featuring 1,1-di(2-pyridyl)ethanol as a supporting ligand leads to the formation of two unexpected Pt complexes (in ∼1:1 ratio), neither of which results from direct oxidation typical for Pt centers supported by popular κ-(,) ligands. While one product features an isomerized Pt center stabilized by the κ-(,,) ligand coordination mode, surprisingly, the other product results from intramolecular activation of the ligand methyl fragment. Mechanistic studies, reactivity of model complexes, and DFT calculations reveal that the critical proton-responsive nature of the ligand allows formation of intermediates that result in a concerted metalation deprotonation (CMD)-like C-H activation at Pt.

Facile Access to Cationic Methylstannylenes and Silylenes Stabilized by E-Pt Bonding and their Methyl Group Transfer Reactivity.

We describe a family of cationic methylstannylene and chloro- and azidosilylene organoplatinum(II) complexes supported by a neutral, binucleating ligand. Methylstannylenes MeSn: are stabilized by coordination to Pt and are formed by facile Me group transfer from dimethyl or monomethyl Pt complexes, in the latter case triggered by concomitant B-H, Si-H, and H bond activation that involves hydride transfer from Sn to Pt. A cationic chlorosilylene complex was obtained by formal HCl elimination and Cl removal from HSiCl under ambient conditions.

Cp* non-innocence and the implications of (η-Cp*H)Rh intermediates in the hydrogenation of CO, NAD, amino-borane, and the Cp* framework - a computational study.

In hydrogenation mediated by half-sandwich complexes of Rh, Cp*Rh(III)-H intermediates are critical hydride-delivery agents. For bipyridine-supported complexes, a unique transformation named 'Cp* non-innocence' leads to the appearance of (Cp*H)Rh(I) intermediates, which are purported to exhibit enhanced hydride-delivery capabilities. In this work, DFT calculations performed to compare the role of these complexes in hydrogenation reveal that (Cp*H)Rh(I) intermediates compete with the conventional pathway (involving Cp*Rh(III)-H); instead they can lead to sequential hydrogenation of the Cp* framework, and potentially, catalyst degradation.

H , B-H, and Si-H Bond Activation and Facile Protonolysis Driven by Pt-Base Metal Cooperation.

We report a series of heterobimetallic Pt/Zn and Pt/Ca complexes to study the effect of proximity of a dicationic base metal on the organometallic Pt species. Varying degrees of Pt⋅⋅⋅Zn and Zn interaction with the bridging Me group are achieved, showcasing snapshots of a hypothetical process of retrotransmetalation from Pt to Zn. In contrast, only weak interactions were observed for Ca with a Pt-bound Me group.

Construction of modular Pd/Cu multimetallic chains ligand- and anion-controlled metal-metal interactions.

The presence of Pd⋯Cu and Pd⋯Pd interactions as well as the order of metal atoms in a chain held by a modular polynucleating ligand is controlled by the coordinating ability of the anions, leading to selective formation of bi- and tetranuclear Pd/Cu and Pd chains. Metal-metal cooperative reactivity in these complexes was tested in Ar-O bond formation and alkyne activation.

Reversible Pt-CH deuteration without methane loss: metal-ligand cooperation ligand-assisted Pt-protonation.

Di(2-pyridyl)ketone dimethylplatinum(ii), (dpk)Pt(CH), reacts with CDOD at 25 °C to undergo complete deuteration of Pt-CH fragments in ∼5 h without loss of methane to form (dpk)Pt(CD) in virtually quantitative yield. The deuteration can be reversed by dissolution in CHOH or CDOH. Kinetic analysis and isotope effects, together with support from density functional theory calculations indicate a metal-ligand cooperative mechanism wherein DPK enables Pt-CH deuteration by allowing non-rate-limiting protonation of Pt by CDOD.

Metal-metal cooperative bond activation by heterobimetallic alkyl, aryl, and acetylide Pt/Cu complexes.

We report the selective formation of heterobimetallic Pt/Cu complexes that demonstrate how facile bond activation processes can be achieved by altering the reactivity of common organoplatinum compounds through their interaction with another metal center. The interaction of the Cu center with the Pt center and with a Pt-bound alkyl group increases the stability of PtMe towards undesired rollover cyclometalation. The presence of the Cu center also enables facile transmetalation from an electron-deficient tetraarylborate [B(Ar)] anion and mild C-H bond cleavage of a terminal alkyne, which was not observed in the absence of an electrophilic Cu center.

Metal-ligand cooperative κ--pyrazolate Cp*Rh-catalysts for dehydrogenation of dimethylamine-borane at room temperature.

3,5-Dimethylpyrazole (Pz*H) in well-defined Cp*RhIII (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) complexes, or as an additive to [Cp*RhCl2]2 enhances catalytic activity in the dehydrogenation of dimethylamine-borane (DMAB) at room-temperature. Mechanistic studies indicate that the Lewis acidic RhIII-centre and dangling N-atom of the Pz* fragment operate cooperatively in accepting a hydride and proton from DMAB, respectively, leading directly to dimethylamino-borane and a RhIII-H complex. The rate limiting step involves protonation of the RhIII-H by the proximal NH fragment of the Pz*H moiety.

Heavy-Metal-Free Fischer-Tropsch Type Reaction: Sequential Homologation of Alkylborane Using a Combination of CO and Hydrides as Methylene Source.

Carbon homologation reactions occur within the well-known Fischer-Tropsch process, usually mediated by transition metal catalysts at high temperature. Here we report the low-temperature, heavy-metal-free homologation of a carbon chain using CO as a C-source showing for the first time that transition-metal catalysts are not required for Fischer-Tropsch-type reactivity. Reaction of an alkylborane in the presence of either LiHBEt or LiAlH resulted in multiple CO insertion/reduction events to afford elongated chains by more than two methylene (-CH-) units, affording aldehyde products upon oxidative aqueous workup.

Platinum-mediated B-H methoxylation of bis(pyrazolyl)borate.

A new bis(pyrazolyl)dihydridoborato diphenylplatinum(ii) complex was found to react with methanol to form H2 and a new diphenylplatinum(ii) complex supported by bis(pyrazolyl)dimethoxyborate. When performed in CD3OD, in addition to the expected installation of OCD3 fragments on the B-center and concomitant formation of H-D, deuteration of PtII(C6H5)2 fragments was observed. In contrast, dissolution of the bis(pyrazolyl)dimethoxyborato diphenylplatinum(ii) complex in CD3OD led to neither deuteration of PtII(C6H5)2 fragments nor substitution of B-bound methoxy fragments.

Exclusive Csp(3)-Csp(3) vs Csp(2)-Csp(3) Reductive Elimination from Pt(IV) Governed by Ligand Constraints.

Selective reductive elimination of ethane (Csp(3)-Csp(3) RE) was observed following bromide abstraction and subsequent thermolysis of a Pt(IV) complex bearing both Csp(3)- and Csp(2)-hybridized hydrocarbyl ligands. Through a comparative experimental and theoretical study with two other Pt(IV) complexes featuring greater conformational flexibility of the ligand scaffold, we show that the rigidity of a meridionally coordinating ligand raises the barrier for Csp(2)-Csp(3) RE, resulting in unprecedented reactivity.

Oxidation of dimethyldi(2-pyridyl)borato Pt(II)Me(n) complexes, n = 1, 0, with H2O2: tandem B-to-Pt methyl group migration and formation of C-O bond.

New dimethyldi(2-pyridyl)borato (dmdpb) platinum(II) complexes, (dmdpb)Pt(II)Me(SMe(2)) (1), (dmdpb)Pt(II)(L)(SMe(2))(+), L = MeOH (2), MeCN (3), supported by dimethylsulfide ligand and featuring one (1) or no hydrocarbyls at the metal (2, 3) were prepared and their oxidation with hydrogen peroxide was studied. Both complex 1 bearing the formal charge of +1 on the metal and the methanol complex 2 capable of losing the proton of the methanol ligand to form the methoxide derivative 4 charged similarly to 1, are reactive towards H(2)O(2). However, the cationic complex 3 with a formal charge of +2 on the metal does not react with H(2)O(2).

Homogeneous catalytic transfer dehydrogenation of alkanes with a group 10 metal center.

Unambiguous catalytic homogeneous alkane transfer dehydrogenation was observed with a group 10 metal complex catalyst, LPt(II)(cyclo-C6H10)H, supported by a lipophilic dimethyl-di(4-tert-butyl-2-pyridyl)borate anionic ligand and tert-butylethene as the sacrificial hydrogen acceptor.

The role of H bonding and dipole-dipole interactions on the electrical polarizations and charge mobilities in linear arrays of urea, thiourea, and their derivatives.

Computational studies using density functional theory are carried out on linear chains of urea, N,N(')-dimethyl urea and N,N,N('),N(')-tetramethyl urea, and their sulfur analogs, viz., thiourea, N,N(')-dimethyl thiourea and N,N,N('),N(')-tetramethyl thiourea with varying chain length, to understand the effect of hydrogen bonding and dipolar interactions on the optoelectronic response properties of such linear aggregates. While molecules of urea, N,N(')-dimethyl urea, and the corresponding sulfur analogs, thiourea, N,N(')-dimethyl thiourea, are stabilized in linear chains by hydrogen bonding, the molecules of N,N,N('),N(')-tetramethyl urea and N,N,N('),N(')-tetramethyl thiourea in the linear chains are stabilized by purely dipolar interactions.