Nucleophilic (Michael) additions to (Ph2P)2CCH2 when chelated to dimethylplatinum(II), di(o-tolyl)platinum(II), or iodo(trimethyl)platinum(IV). Crystal structure of [PtMe3I{(PPh2)CH(PPh2)CH2NHCH2Ph}]

Abstract

Treatment of [PtMe₂(cod)](cod = cyclo-octa-1,5-diene) with (Ph₂P)₂CCH₂(vdpp) gave [PtMe₂(vdpp-PP′)](1a). Treatment of [Pt(C₆H₄Me-o)₂(cod)] with vdpp, or better, [PtCl₂(vdpp-PP′)] with o-tolylmagnesium bromide gave [Pt(C₆H₄Me-o)₂(vdpp-PP′)](1b). The vinylidene double bond in (1a) or (1b) was highly activated towards nucleophilic attack (Michael addition) by a variety of amines and hydrazines, yielding adducts of the type [PtMe₂{(PPh₂)₂CHCH₂R}] with R = NHNH₂(2), NHNHMe (3a), NHCH₂CCH (4), NMeCH₂CCH (5), NHCH₂CHCH₂(6a), NMeCH₂CHCH₂(7), L-NHCHMePh (8a), D-NHCHMePh (8b), NHCH₂Ph (9), NHCH₂C₆H₄OMe-4 (10), NHCH₂CH₂Me (11), and NHCH₂CH₂NH₂(12), or of the type [Pt(C₆H₄Me-o)₂{(PPh₂)₂CHCH₂R}] with R = NHNHMe (3b) or NHCH₂CHCH₂(6b). Some of the additions were reversible and the adducts of (1b) were not isolated pure. The platinum(II) complex (1a) reacted with Mel to give fac-[PtMe₃I(vdpp-PP′)](13) which reacted with PhCH₂NH₂ to give [PtMe₃I{(PPh₂)₂CHCH₂NHCH₂Ph}](14) which isomerised in solution to give a mixture of [[graphic omitted]HCh₂Ph}][the title compound, (15a)] and (15b) in which the H and CH₂Ph on N are interchanged. Eventually, (15b) isomerised completely to (15a). N.m.r. and i.r. data are given. Crystals of the compound (15a) are orthorhombic, space group Pca2₁ with a= 2 713.1 (5), b= 1 177.9(2), c= 2 139.6(4) pm; final R factor 0.0475 for 3 927 observed reflections.