Preparation and crystal structure analysis of a vinyl ether chelate, dichloro[4-methoxy-2,2,N,N-tetramethylbut-(Z)-3-enylamine]palladium(II), and its conversion into di-µ-chloro-bis[3-(dimethylamino)-1-formyl-2,2-dimethylpropyl-C,N]dipalladium(II)

Abstract

Reaction of either cis-(1a) or trans-4-methoxy-2,2,N,N-tetramethylbut-3-enylamine (1b) with PdCl₂·2PhCN afforded only the cis-vinyl ether chelate [PdCl₂(NMe₂CH₂CMe₂CHCHOMe)], (6). Crystals of (6) are monoclinic, space group P2₁/n, with eight molecules in a unit cell of dimensions a= 14.241 (3), b 14.744(2), c= 13.508(1)Å, and β= 111.53(1)°. The structure was solved by the heavy-atom method and refined by full-matrix least-squares calculations to R= 0.024 8 for 3 981 reflections with I > 3σ(I). The two independent molecules have essentially the same conformation and dimensions. In each molecule, the Pd co-ordination is close to square planar with cis Cl atoms. The five-membered chelate rings have envelope conformations with quaternary carbon C(2) at the flap. The olefin configuration is cis. Principal bond lengths are Pd–Cl (trans to olefin) 2.321(1) and 2.330(1), Pd–Cl (cis to olefin) 2.298(1) and 2.296(1), Pd–N 2.082(2) and 2.089(2), Pd–C(3) 2.135(3) and 2.139(3), Pd–C(4) 2.266(3) and 2.249(3), CC 1.363(5) and 1.378(4), C(sp²)–O 1.336(4) and 1.341(4), O–CH₃ 1.436(5) and 1.442(4)Å. It has been shown that (6) is also formed, along with di-µ-chloro-bis[4-(dimethylamino)-3,3-dimethylbut-2-yl-C,N]dipalladium(II)(3), when dichloro[2,2,N,N-tetramethylbut-3-enylamine]palladium(II)(2) is allowed to react with di-µ-chloro-bis[4-(dimethylamino)-3,3-dimethyl-1 -methoxybut-2-yl-C,N]dipalladium(II)(9). The last, (9) was generated by reaction of (2) with sodium methoxide. The conversion of (6) into di-µ-chloro-bis[3-(dimethylamino)-1-formyl-2,2-dimethylpropyl-C,N]dipalladium(II)(4) was investigated and found to proceed via a vinyl alcohol complex (8).