Nucleophilic (Michael) additions to (Ph2P)2CCH2when chelated to platinum(II) dichloride or di-iodide

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Abstract
Treatment of [PtCl2(NCBut)2] with (Ph2P)2CCH2(vdpp) in dichloromethane gave [PtCl2(vdpp-PP′)](1a). Treatment of (1a) with a variety of amines or NN-dimethylhydrazine in dichloromethane gave the Michael addition products rapidly and in good yields, viz. [PtCl2{(Ph2P)2- CHCH2NHR}][R = NMe2(2a), CH2CHCH2(3), D-CHMePh (4), or CH2C6H4OMe-4 (5a)]. Complex (1a) is more reactive towards Michael addition than is [PtMe2(vdpp-PP′)]; thus it forms adducts with H2NC6H4Me-4 or H2NCH2CO2Et, i.e. [PtCl2{(Ph2P)6CHCH2NHC6H4Me-4}](7) or [PtCl2{(Ph2P)2CHCH2NHCH2CO2Et}](8). It is also remarkably reactive towards carbon nucleophiles, e.g. with 1 equivalent of ethyl acetoacetate or acetylacetone in dichloromethane in the presence of anhydrous sodium carbonate it gave [PtCl2{(Ph2P)2CHCH2CH(COMe)(CO2Et)}](10) or [PtCl2{(Ph2P)2CHCH2CH(COMe)2}](11), respectively. On prolonged treatment of (1a) with sodium iodide in acetone, acetone added to the vinylidene double bond to give [PtI2{(Ph2P)2CHCH2CH2COMe}](13a). The di-iodo-complex [PtI2(vdpp-PP′)](1b) was prepared by treating (1a) with NBun 4I in dichloromethane. Complex (1b) reacted with Me2NNH2 or amine to give adducts, e.g. [PtI2{(Ph2P)2CHCH2NHNMe2}](2b) or [PtI2{(Ph2P)2-CHCH2 NHCH2C6H4OMe-4}](5b), but not with carbon nucleophiles under conditions when the corresponding dichloro-complex (1a) underwent Michael addition. Variable-temperature n.m.r. spectroscopy was used to compare the rates of some of these reactions; 31P-{1H}, 1H-(31P), and 1H n.m.r. and i.r. data are given.

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