Nitrile−Amidine Coupling at Pt(IV) and Pt(II) Centers. An Easy Entry to Imidoylamidine Complexes

Abstract

Treatment of trans-[PtCl4(RCN)2] (R = Me, Et, Ph, NEt2) with 2 equiv of the amidine PhC(=NH)NHPh in a suspension of MeCN (R = Me), CHCl3 (R = Et, Ph), or in CHCl3 solution (R = NEt2) results in the formation of the imidoylamidine complexes trans-[PtCl4{NH=C(R)N=C(Ph)NHPh}2] (1-4) isolated in good yields (66-84%). The reaction of soluble complexes 3 and 4 with 2 equiv of Ph3P=CHCO2Me in CH2Cl2 (40 degrees C, 5 h) leads to dehydrochlorination resulting in a chelate ring closure to furnish the platinum(IV) chelates [PtCl2{NH=C(R)NC(Ph)=NPh}2] (R = Ph, 5; R = NEt2, 6), accordingly, and the phosphonium salt [Ph3PCH2CO2Me]Cl. Treatment of 5 with 3 equiv of Ph3P=CHCO2Me at 50 degrees C for 5 d resulted in only a 30% conversion to the corresponding Pt(II) complex [Pt{NH=C(NEt2)NC(Ph)=NPh}2] (15). The reduction can be achieved within several minutes, when Ph2PCH2CH2PPh2 in CDCl3 is used. When the platinum(II) complex trans-[PtCl2(RCN)2] is reacted with 2 equiv of the amidine, the imidoylamidinato complexes [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) and [PhC(=NH)NHPh] x HCl (7) are formed. The reaction of trans-[PtCl2(RCN)2] with 4 equiv of the amidine under a prolonged reaction time or treatment of [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) with 2 more equiv of the amidine yields the complex bearing two chelate rings [Pt{NH=C(R)NC(Ph)=NHPh}2] (12-15). The treatment of cis-[PtCl2(RCN)2] (R = Me, Et) with the amidine gives ca. 50-60% yield of [PtCl2{NH=C(R)NHC(Ph)=NHPh}] (16 and 17). All of the platinum compounds were characterized by elemental analyses; FAB mass spectrometry; IR spectroscopy; 1H, 13C{1H}, and 195Pt NMR spectroscopies, and four of them (4, 6, 8, and 15) were also characterized by X-ray crystallography. The coupling of the Pt-bound nitriles and the amidine is metal-mediated insofar as RCN and PhC(=NH)NHPh do not react in the absence of the metal centers in conditions more drastic than those of the observed reactions. The nitrile-amidine coupling reported in this work constitutes a route to the synthesis of imidoylamidine complexes, some of them exhibiting luminescent properties.

Unsymmetrical NiII–Imidoylamidine Complexes Derived from a Novel Oxime‐Mediated Single‐Pot Reaction of Nitriles

“…At the same time, following our studies on the Zn II -and Co II -ketoxime-mediated transformations of nitriles to carboxamides, carboxylic acids and amidines, [7] and applying a similar synthetic strategy to the Ni II -ketoxime system, we have achieved an easy conversion of various alkylnitriles (RCN) into imidoylamidine complexes [Ni{N(H)= C(R)NHC(R)=NH} 2 ] 2 + . [8] The family of such compounds has been recently extended [9,10] to other metals and various substituent groups (R) by using direct synthetic procedures based on nitriles, which include the solvothermal transformation of RCN [9a,b] and arylnitrile coupling with LiN-…”

Crystal structure of dichloro{[anilino(phenylimino)methyl]- (propanimidoyl)azanide}-[η2-(N,N′-diphenylguanidinato)]platinum(IV) – deuterochloroform (1:1), PtCl2(C13H12N3)(C16H17N4) · CDCl3

“…However, this interatomic distance is typical (within 3s)for this type of 1,3,5-triazapentadiene-and/or 1,3,5-triazapentadienato-containing metallacycles, and is comparable with the lengths of the corresponding C=N double bonds in the monochelated and bischelated (1,3,5-triazapentadienato)Pt II complexes [1]a nd the monochelated (1,3,5-triazapentadienato)Pt IV complex [2]. The N=C double bond lengths and the N-Csingle bond lengths in the metallacycle, in contrast to complexes of the types (1,3,5-triazapentadiene)M and/or (1,3,5-triazapentadienato)M (M =Pt II or Ni II ) [1,3,4], are indicative of ahigher degree of delocalization in the metallacycle. The N3-C7 bond distance (1.370 (2) Å)issimilar to the length of the corresponding N-Csingle bond in Pt II and Pt IV complexes containing the analogous structural fragment, i.e.…”

“…The N4-C14 and N4-C7 bond lengths (1.330(3) and 1.334(2) Å,r espectively) are close to the N-C bond lengths in Pt II and Pt IV complexes containing the Pt-N(H)=C(Et)NC(N(H)Ph)=NPh moiety [1,2]. The N1-C7 distance (1.333(2) Å)islonger than atypical N=C double bonds in the (1,3,5-triazapentadiene)M and/or (1,3,5-triazapentadienato)M (M =Pt II or Ni II )complexes [1,3,4], due to the influence of the N(H)Ph group. However, this interatomic distance is typical (within 3s)for this type of 1,3,5-triazapentadiene-and/or 1,3,5-triazapentadienato-containing metallacycles, and is comparable with the lengths of the corresponding C=N double bonds in the monochelated and bischelated (1,3,5-triazapentadienato)Pt II complexes [1]a nd the monochelated (1,3,5-triazapentadienato)Pt IV complex [2].…”

Highly luminescent imidoylamidinato platinum(ii) complexes formed by the coupling of 1H-pyrazole-1-carboxamidine with nitriles used as reaction solvents

“…12,13 Although the photophysical properties of some of them have also been reported, most of the data are limited to the solution state, in which the bis(imidoylamidinato) Pt(II) complexes exhibit weak luminescence. 13 We have succeeded in the synthesis of a series of Pt(II) complexes consisting of 2,2'-bipyridine (bpy) and imidoylamidinate {NH=C(pz)NC(R)=NH} (R = Me, Et, Ph), which exhibit drastic color change of luminescence upon grinding.…”