Amidoximes Provide Facile Platinum(II)-Mediated Oxime–Nitrile Coupling

The nucleophilic addition of amidoximes R′C­(NH2)NOH [R′ = Me (2.Me), Ph (2.Ph)] to coordinated nitriles in the platinum­(II) complexes trans-[PtCl2(RCN)2] [R = Et (1t.Et), Ph (1t.Ph), NMe2 (1t.NMe2)] and cis-[PtCl2(RCN)2] [R = Et (1c.Et), Ph (1c.Ph), NMe2 (1c.NMe2)]
proceeds in a 1:1 molar ratio and leads to the monoaddition products trans-[PtCl­(RCN)­{HNC­(R)­ONC­(R′)­NH2}]Cl [R = NMe2;
R′ = Me ([3a]­Cl), Ph ([3b]­Cl)], cis-[PtCl2{HNC­(R)­ONC­(R′)­NH2}] [R = NMe2; R′
= Me (4a), Ph (4b)], and trans/cis-[PtCl2(RCN)­{HNC­(R)­ONC­(R′)­NH2}] [R = Et; R′ = Me
(5a, 6a), Ph (5b, 6b); R = Ph; R′ = Me (5c, 6c), Ph
(5d, 6d), correspondingly]. If the nucleophilic
addition proceeds in a 2:1 molar ratio, the reaction gives the bisaddition
species trans/cis-[Pt­{HNC­(R)­ONC­(R′)­NH2}2]­Cl2 [R = NMe2; R′
= Me ([7a]­Cl2, [8a]­Cl2), Ph ([7b]­Cl2, [8b]­Cl2)] and trans/cis-[PtCl2{HNC­(R)­ONC­(R′)­NH2}2] [R = Et; R′ = Me (10a), Ph (9b, 10b); R = Ph; R′ = Me (9c, 10c), Ph (9d, 10d), respectively].
The reaction of 1 equiv of the corresponding amidoxime and each of
[3a]­Cl, [3b]­Cl, 5b–5d, and 6a–6d leads to [7a]­Cl2, [7b]­Cl2, 9b–9d, and 10a–10d. Open-chain bisaddition species 9b–9d and 10a–10d were transformed
to corresponding chelated bisaddition complexes [7d]2+–[7f]2+ and [8c]2+–[8f]2+ by the addition
of 2 equiv AgNO3. All of the complexes synthesized bear
nitrogen-bound O-iminoacylated amidoxime groups. The obtained complexes
were characterized by elemental analyses, high-resolution ESI-MS,
IR, and 1H NMR techniques, while 4a, 4b, 5b, 6d, [7b]­(Cl)2, [7d]­(SO3CF3)2, [8b]­(Cl)2, [8f]­(NO3)2, 9b, and 10b were also characterized
by single-crystal X-ray diffraction.