Coupling between 3-Iminoisoindolin-1-ones and Complexed Isonitriles as a Metal-Mediated Route to a Novel Type of Palladium and Platinum Iminocarbene Species

Abstract

The reaction between isonitrile in cis-[MCl2(CNR)2] [M = Pd, R = Cy 1, Bu t 2, C6H3(2,6-Me2) 3; M = Pt, R = Cy 4, Bu t 5, C6H3(2,6-Me2) 6] and various unsubstituted or substituted iminoisoindolin-1-ones HNCC6R1R2R3R4CONH [R1−R4 = H 7; R1, R3, R4 = H, R2 = Me/R1, R2, R4 = H, R3 = Me 8 (isomeric mixture); R1, R4 = H, R2, R3 = Cl 9] proceeds under reflux conditions in CHCl3 for 2 h. The subsequent workup provides complexes [MCl{C(NC(C6R1R2R3R4CON))N(H)R}(CNR)] (M = Pd, 10−18; M = Pt, 19−27), bearing a novel type of carbene ligands, which were isolated in good (80−85% for the PdII complexes) to moderate (60−65% for the PtII species) yields. The addition of the iminoisoindolin-1-one to isonitriles is metal-mediated and has a general character. The reaction of cis-[PtCl2(CNC6H4OMe-4)2] (28) with 7 affords a mixture of PtII-containing species including the monoadduct [PtCl{C(NC(C6H4CON))N(H)C6H4OMe-4}(CNC6H4OMe-4)] (29), the unusual binuclear compound [Pt2{C(NC(C6H4CON))N(H)C6H4OMe-4}2(CNC6H4OMe-4)2(μ-HNCC6H4CON)](Cl) (30) with a bridging monodeprotonated 3-iminoisoindolin-1-one, and [Pt(C6H4CONCNH){C(NC(C6H4CON))N(H)C6H4OMe-4}(CNC6H4OMe-4)] (31), the latter resulting from the replacement of the chloro ligand in 29 by the deprotonated iminoisoindolin-1-one. Complexes 10−27 were characterized by elemental analyses (C, H, N), ESI+-MS, IR, and 1D (1H, 13C{1H}) and 2D (1H,1H-COSY, 1H,13C-HMQC/1H,13C-HSQC, 1H,13C-HMBC) NMR spectroscopies, while 29−31 by ESI+-MS, IR, and 1H NMR. In addition, the structures of three carbene complexes (10, 27, and 30) were elucidated by single-crystal X-ray diffraction analysis.

Carbene Complexes Derived from Metal‐Bound Isocyanides: Recent Advances

“…of the Isocyanide Ligand with an Imine or Amidine 539 ture, and leads to the diaminocarbene cis -[PtCl 2 (CNXyl){C(NH 2 )N(H)Xyl}], which is formally the product of the addition of ammonia to one isocyanide ligand in cis -[PtCl 2 (CNXyl) 2 ][41] .The coupling between isocyanide in cis -[MCl 2 (C ≡ NR) 2 ] (M = Pd, Pt; R = Cy, t Bu, Xyl) and various unsubstituted or substituted 3 -iminoisoindolin -1 -ones HN = CC 6 R 1 R 2 R 3 R 4 CONH (R 1 − R 4 = H; R 1 , R 3 , R 4 = H, R 2 = Me; R 1 , R 4 = H; R 2 , R 3 = Cl) affords complexes [MCl{ C (N = C(C 6 R 1 R 2 R 3 R 4 CO N )) = N(H)R}(C ≡ NR)] bearing a novel type of carbene ligands (Scheme 15.12 ), as also shown by the present authors[42] .Kukushkinet al have described the metal -mediated coupling between one or two isocyanide ligands in cis -[MCl 2 (C ≡ NR) 2 ] (M = Pd, Pt) and N -phenylbenzamidine, HN = C(Ph)NHPh (Scheme 15.13 ) [43] . The coupling proceeds with different regioselectivities upon varying the R group.…”

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

“…The crystallographic data and processing parameters for 38 are listed in (2.001(3) Å) [27], and cis-[PdCl{C(N@ C(C 6 H 4 CNHN))@N(H)Xyl}(CNXyl)] (2.015(9) Å) [28]. In 38, the carbene moiety is roughly planar and the angles around the carbene C1 atoms range from 113.1°to 129.3°therefore sustaining the sp 2 hybridization of this atom.…”

Reactivity of bulky tris(phenylpyrazolyl)methanesulfonate copper(I) complexes towards small unsaturated molecules

“…2135 and 2124 cm À1 , correspondingly), thus indicating that their activation upon coordination to the Cu centre should not be extensive [38,39]. Accordingly, the isocyanide ligand in 2 or 3 does not undergo attack by a nucleophile such as methylamine or 3-iminoisoindolin-1-one [31,42,56,58]. In fact, the unreacted starting compounds were isolated upon attempted reaction of 2 or 3 with methylamine, whereas isocyanide ligand displacement occurred with the iminoisoindolinone to give [Cu(Tpms Ph )(3-iminoisoindolin-1-one)] (5, Scheme 1).…”

“…The same product can also be obtained upon direct reaction of the acetonitrile complex 1 with 3-iminoisoindolin-1-one. It is worthwhile to point out that examples of complexes containing ligated 3-iminoisoindolin-1-ones are scarce, and up to date were represented only by Pt(II) [31], Pd(II) [31] and Zn(II) [57] species, reported recently by some of us. Hence, within the current study, we succeed to extend such a type of complexes to copper(I).…”