Platinum(II)‐Promoted [2+3] Cycloaddition of Azide with 4‐Cyanobenzaldehyde, a Schiff Base Derivative or Dicyanobenzenes To Give Formyl‐, Amino(imino)‐ or Cyano‐Functionalized Tetrazolato Complexes

Abstract

The [2+3] cycloaddition reaction (which is greatly accelerated by microwave irradiation) of the bis(azido)platinum(II) compound cis‐[Pt(N3)2(PPh3)2] (1) with 4‐cyanobenzaldehyde (2) furnishes the N2N2‐bonded isomer of bis[5‐(4‐formylphenyl)tetrazol‐2‐ate] platinum(II) trans‐[Pt{N4CC6H4(4‐CH=O)}2(PPh3)2] (3a) as the major product, along with the N1N2‐bonded isomer 3b. Treatment of 3a with 2‐dimethylaminoethylamine (4), in refluxing methanol, gives the corresponding N2N2‐bonded bis[(E)‐5‐(4‐{[2‐(dimethylamino)ethylimino]methyl}phenyl)tetrazol‐2‐ate] platinum(II) complex trans‐[Pt{N4CC6H4(4‐CH=NCH2CH2NMe2)}2(PPh3)2] (6) in good yield. An alternative route involves the reaction of 4‐cyanobenzaldehyde (2) with diamine 4 to give the E isomer of 4‐{[2‐(dimethylamino)ethylimino]methyl}benzonitrile N≡CC6H4(4‐CH=NCH2CH2NMe2) (5), followed by the reaction of the latter with bis(azido)platinum(II) complex 1 to afford 6 in similar yield. The reaction of 6 with MCl2 (M = Pd, Ni, Zn, Cu), at room temperature for 3 h regenerates complex 3a as a result of the Schiff base hydrolysis, along with the diamine complex [MCl2(NH2CH2CH2NMe2)] (7). Treatment of 6 with ZnCl2 for 36 h affords a mixture of 3a with its substitution products [Pt{HN4CC6H4(4‐CH=O)}(NH2CH2CH2NMe2)(PPh3)]Cl2 (9; isolated in the tetrazole form) and cis‐[PtCl2(PPh3)2] (10) and diamine complex 7 (M = Zn). The [2+3] cycloaddition reactions of cis‐[Pt(N3)2(PPh3)2] (1) with unsubstituted dicyanobenzenes 11 [1,2‐C6H4(CN)2 (11a), 1,3‐C6H4(CN)2 (11b), 1,4‐C6H4(CN)2 (11c)] occur regioselectively and give the corresponding N2N2‐bonded bis[5‐(cyanophenyl)tetrazol‐2‐ate] trans‐[Pt(N4CC6H4R)2(PPh3)2] complexes 12 (R = 2‐CN 12a, 3‐CN 12b, 4‐CN 12c). The isolated compounds were characterized by IR, 1H NMR, 13C NMR and 31P{1H} NMR (metal complexes) spectroscopy, elemental analyses, ESI‐MS and X‐ray structural analyses (for 3a, 5·HCl, 7, 9 and 12a). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Pentafluorophenyl Platinum(II) Complexes of PTA and Its N-Allyl and N-Benzyl Derivatives: Synthesis, Characterization and Biological Activity

“…The pentafluorophenyl ring lies perpendicular to the plan constructed by the Pt-, P- and Cl-atoms (89.8°). The bond lengths involving the metal and the donor atoms (see Figure 1, legend), are within those found in other Pt(II) compounds [94,95,96,97,98,99]. No classical H-bond interactions could be found in 2a , but the shortest C–H⋅⋅⋅N interactions (Figure 1) expand the structure to the third dimension.…”

Microwave synthesis of bis(tetrazolato)-PdII complexes with PPh3 and water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA). The first example of C–CN bond cleavage of propionitrile by a PdII Centre

“…For example, we have shown [17] that the di(azido) complexes of the type cis-[Pt(N 3 ) 2 (PPh 3 ) 2 ] can react with nitriles NCR to give the bis(tetrazolato) compounds trans-[Pt(N 4 CR) 2 (PPh 3 ) 2 ] from which the tetrazoles can be liberated. Very recently, we have reported that [2 þ 3] cycloaddition of cis-[Pt(N 3 ) 2 (PPh 3 ) 2 ] with 4-cyanobenzaldehyde furnishes a (formylphenyl)tetrazolate complex that reacts with 2-dimethylaminoethylamine to give the corresponding Schiff base derivative, the latter undergoing hydrolysis in the presence of a metal salt, while the reactions of di(azido) complexes with dicyanobenzenes give (cyanophenyl)tetrazolate complexes [18]. In addition, the reactions of bis(tetrazolato)-Pt II compounds with propionitrile furnish mono-or dicyano-complexes, via an unusual oxidative addition involving NCeC bond cleavage of one or two propionitrile molecules, respectively [17aec].…”

Borylated Tetrazoles from Cycloaddition of Azide Anions to Nitrilium Derivatives ofcloso-Decaborate Clusters

“…This activation allows the performance of CA in water or water/alcohol mixtures, but usually prolonged heating is still necessary. Metal-mediated CA is also known, and it is typically conducted by two routes, viz., CA of free azides to coordinated nitriles (for recent works see refs − ) or metal-bound azides to uncomplexed nitriles (for recent works see refs − ). Some metal-mediated syntheses allow the generation of coordinated tetrazoles rapidly already at room temperature (RT). , Furthermore, CAs of azide ions to highly reactive alkylnitrilium salts were reported, and these reactions form 1,5-disubstituted tetrazoles at RT. , Several cases of BF 3 -catalyzed CA of azides to nitriles, except one example of intramolecular CA, require prolonged heating, and they are not recommended for synthetic purposes. − …”