27902-71-2Relevant academic research and scientific papers
Interplay of metallophilic interactions, π-π Stacking, and ligand substituent effects in the structures and luminescence properties of neutral PtII and PdII aryl isocyanide complexes
Sluch, Ilya M.,Miranda, Anthea J.,Slaughter, Legrande M.,Elbjeirami, Oussama,Omary, Mohammad A.
, p. 10728 - 10746,19 (2020/09/02)
Packing interactions in the crystal structures of a series of cis-M(CNAr)2Cl2 complexes (M = Pt, Pd; Ar = substituted phenyl) were examined and correlated with the luminescence properties of the Pt complexes. The structures of the PhNC and p-tolyl isocyanide complexes exhibit extended chains of metallophilic interactions with M...M distances of 3.24-3.25 and 3.34 A, respectively, with nearly isostructural Pt and Pd compounds. Both structure types contain void channels running parallel to the M...M chains. The channels are 3-4 A wide and vacant for the phenyl structures, while those in the p-tolyl structures are up to 7.6 A wide and contain water. These channeled structures are stabilized by a combination of metallophilic bonding and aryl π-π stacking interactions. The Pt structure with 4-F substituents also features extended Pt...Pt chains, but with longer 3.79 A distances alternating with shorter 3.37 A contacts. Structures with 4-CF3 and 4-OMe substituents exhibit mostly isolated dimers of M...M contacts. In complexes with 2,6-dimethylphenyl isocyanide, steric hindrance precludes any short M...M contacts. The primary effect of aryl substitution is to provide alternative packing motifs, such as CF 3...π and CH3...π interactions, that either augment or disrupt the combination of metallophilic contacts and π-π stacking needed to stabilize extended M...M chains. Differences in the Pt and Pd structures containing 4-F and 4-OMe substituents are consistent with a higher driving force for metallophilic interactions for Pt versus Pd. The M-C and M-Cl bond distances indicate a slightly higher trans influence for aryl isocyanides bound to Pt versus Pd. The three extended Pt...Pt chain structures display luminescence assignable to (dσ*→pσ) excited states, demonstrating the existence of substantial orbital communication along the metal-metal chains. Face-indexing shows that the preferred crystal growth axis is along the metal-metal chains for the luminescent structures. Variable temperature structural studies showed that both M...M and π-π interactions contract upon cooling. Overall, this study suggests that synergy with π-π and other interactions is necessary to stabilize extended M...M chain structures. Thus, efforts to design functional materials based on metallophilic bonding must consider the full array of available packing motifs.
Transition-metal-promoted cyclization reactions of isocyanide ligands. Synthesis of cyclic aminooxycarbene complexes of platinum(II) and X-ray structure of trans -{(PPh3)2Pt[CN(C6H4-p-Me)CH 2CH2O]Br}BF4
Michelin, Rino A.,Zanotto, Livio,Braga, Dario,Sabatino, Piera,Angelici, Robert J.
, p. 85 - 92 (2008/10/08)
Electrophilic isocyanide CNR ligands in cationic Pt(II) complexes of the type trans-[(PR′3)2Pt(CNR)Cl]BF4 (I) (PR′3 = PPh3, PMe2Ph; R = p-MeOC6H4, p-MeC6H4, p-NO2C6H4, Me, C6H11) are converted to the corresponding 5-membered cyclic aminooxycarbene derivatives trans-{(PR′3)2Pt[CN(R)CH2CH 2O]X}BF4 (II) (X = Cl, Br) by reaction in THF with 2-bromoethanol in the presence of n-BuLi. These reactions are likely to proceed by nucleophilic attack of the alkoxide on the isocyanide carbon atom to give an imidoyl intermediate, which cyclizes intramolecularly to yield the carbene products. The less sterically hindered CNMe and aryl isocyanide ligands in I are converted in a few minutes to the final products II in ca. 70-90% yield; the more bulky CNC6H11 derivative gives only a 25% yield. The t-BuNC ligand in the complex trans-[(PPh3)2Pt(CN-t-Bu)Cl]BF4 does not react at all, nor does p-MeOC6H4NC in trans-[(PCy3)2Pt(CNC6H 4-p-OMe)Cl]BF4 with bulky PCy3 ligands. Treatment of cis-Cl2Pt(CNC6H4-p-OMe)2 with 2 equiv of 2-bromoethoxide gave the bis(aminooxycarbene) Br2Pt[CN(C6H4-p-OMe)CH2CH 2O]2. The Pt(II)-cyclic aminooxycarbenes II were characterized by their elemental analysis and IR, 1H NMR, and 31P NMR spectra. An X-ray-determined structure of trans-{(PPh3)2Pt[CN(C6H 4-p-Me)CH2CH2O]Br}BF4, space group P21/a, a, = 12.175 (2) ?, b = 26.137 (3) ?, c = 13.274 (4) ?, β = 91.61 (2)°, and Z = 4, was refined to R = 0.039 (Rw = 0.044) for 5325 independent reflections. The coordination geometry around the Pt(II) atom is square planar with the carbene ligand perpendicular to the plane. The cyclic aminooxycarbene ligand is planar with C(sp2)-N and C(sp2)-O bond distances of 1.30 (1) and 1.33 (1) ?, indicating significant π-bonding between the nitrogen, oxygen, and carbene carbon.
