Palladium(II)-Mediated Addition of Benzenediamines to Isocyanides: Generation of Three Types of Diaminocarbene Ligands Depending on the Isomeric Structure of the Nucleophile

Coupling of the palladium-bis­(isocyanide) complexes <i>cis</i>-[PdCl₂(CNR)₂] (R = 2,6-Me₂C₆H₃ <b>1</b>, 2-Cl-6-MeC₆H₃ <b>2</b>) with benzene-1,3-diamine (<b>BDA1</b>) leads to the diaminocarbene species <i>cis</i>-[PdCl₂(CNR)­{C­(NHR)NH­(1,3-C₆H₄NH₂)}] (<b>5</b> and <b>6</b>, respectively). In this reaction, <b>BDA1</b> behaves as a monofunctional nucleophile that adds to one of the RNC ligands by one amino group. By contrast, the reaction of <b>1</b> and <b>2</b> with benzene-1,4-diamine (<b>BDA2</b>) involves both amino functionalities of the diamine and leads to the binuclear species [<i>cis</i>-PdCl₂(CNR)­{μ-<u>C</u>­(NHR)NH­(1,4-C₆H₄)­NH<u>C</u>­(NHR)}<i>-</i>(<i>cis</i>)-PdCl₂(CNR)] (<b>6</b> and <b>7</b>) featuring two 1,4-bifunctional diaminocarbene ligands. The reaction of <i>cis</i>-[PdCl₂(CNR)₂] (R = cyclohexyl <b>3</b>) with either <b>BDA1</b> or <b>BDA2</b> does not afford any isolable carbene derivatives. The most versatile chemistry was observed when <b>1</b>–<b>3</b> were treated with benzene-1,2-diamine (<b>BDA3</b>) and the relevant substituted 1,2-diamines, viz., 4,5-dimethylbenzene-1,2-diamine (<b>BDA4</b>) and 4,5-dichlorobenzene-1,2-diamine (<b>BDA5</b>). The addition of these diamines brings about the formation of the monocarbene cationic complexes <i>cis</i>-[PdCl­(CNR)­{<u>C</u>­(NHR)NHC₆H₂X₂<u>N</u>H₂}]Cl (X = H, Me, Cl) (<b>8</b>–<b>16</b>), the Chugaev-type <i>C,C</i>-bound bis-carbenes <i>cis</i>-[PdCl₂{<u>C</u>­(NHR)NHC₆H₂X₂NH<u>C</u>­(NHR)}] (<b>17</b>, <b>18</b>), and the bis­(<i>C,N</i>-chelated)­carbene complexes <i>cis</i>-[Pd­{<u>C</u>­(NHR)NHC₆H₂X₂<u>N</u>H₂}₂]­Cl₂ (<b>19</b>–<b>24</b>). All prepared complexes (with the exception of <b>17</b> and <b>18</b>) were isolated as colorless or pale yellow solids and characterized by elemental analyses (C, H, N), HRESI^±-MS, IR, ¹H and ¹³C­{¹H} NMR spectroscopies, and <b>4</b>, <b>7</b>, <b>13</b>, <b>16</b>, and <b>24</b> by X-ray diffraction. Complexes <b>17</b> and <b>18</b> were characterized by HRESI^±-MS and IR spectroscopy, and their structures were established by X-ray crystallography

Pd-II-mediated integration of isocyanides and azide ions might proceed via formal 1,3-dipolar cycloaddition between RNC ligands and uncomplexed azide

The generation of (tetrazolate)PdII complexes via the integration of (isocyanide)PdII precursors with uncomplexed azides and the verification of plausible reaction mechanisms.</p

Application of palladium complexes bearing acyclic amino(hydrazido)carbene ligands as catalysts for copper-free Sonogashira cross-coupling

Metal-mediated coupling of one isocyanide in cis-[PdCl2(CNR1)2] (R1 = C6H11 (Cy) 1, tBu 2, 2,6-Me2C6H3 (Xyl) 3, 2-Cl-6-MeC6H34) and various carbohydrazides R2CONHNH2 [R2 = Ph 5, 4-ClC6H46, 3-NO2C6H47, 4-NO2C6H48, 4-CH3C6H49, 3,4-(MeO)2C6H310, naphth-1-yl 11, fur-2-yl 12, 4-NO2C6H4CH213, Cy 14, 1-(4-fluorophenyl)-5-oxopyrrolidine-3-yl 15, (pyrrolidin-1-yl)C(O) 16, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propane-1-yl 17, EtNHC(O) 18] or sulfohydrazides R3SO2NHNH2 [R3 = Ph 19, 4-MeC6H420] led to a series of (hydrazido)(amino)carbene complexes cis-[PdCl2{C(NHNHX)double bond; length as m-dashN(H)R1}(CNR1)]; X = COR2, SO2R3 (21–48, isolated yields 60–96%). All prepared species were characterized by elemental analyses (C, H, N), HR ESI+-MS, IR, 1H and 13C{1H} NMR spectroscopy, and by a single-crystal X-ray diffraction for 38. Complexes 21–48 demonstrated excellent activity as catalysts in copper-free Sonogashira coupling of aryl iodides and a variety of aromatic terminal alkynes. Catalytic system runs in environmentally benign EtOH ensuring product yields of up to 75–96% and TONs of up to 104. Mechanism of the copper-free Sonogashira catalytic cycle involving 21–48 as catalysts was proposed upon identification of key intermediates using HRESI-mass

Phosphorescent Cyclometalated Palladium(II) and Platinum(II) Complexes Derived from Diaminocarbene Precursors.

Metal-mediated self-assembly of isocyanides and methyl 4-aminopyrimidine-5-carboxylate leads to luminescent PdII and PtII complexes featuring C,N-cyclometalated acyclic diaminocarbene (ADC) ligands. The solid-state luminescent properties of these diaminocarbene derivatives are attributed to their triplet-state metal/metal-to-ligand charge-transfer (3MMLCT) nature, which is driven by attractive intermolecular M···M interactions further reinforced by the intramolecular π-π interactions even in the structure of the Pd compound, which is the first Pd-ADC phosphor reported

Addition of N-nucleophiles to gold(III)-bound isocyanides leading to short-lived gold(III) acyclic diaminocarbene complexes

Addition of hydrazone to gold(iii)–isocyanides led to the generation of rare short-lived gold(iii) acyclic diaminocarbene complexes.</p

Modulation of luminescent properties for [cyclometalated]-PtII(isocyanide) complexes upon co-crystallisation with halosubstituted perfluorinated arenes

Phosphorescent PtII-based cyclometalated complexes co-crystallise with bromo- and iodosubstituted perfluorinated arenes to give 1:1 adducts. X-FArenes in these co-crystals act as both σh and πh donors forming co-operative C–X•••Cl–Pt XBs...</p