INTERACTION OF VINYL-ACETATE AND ALLYL ACETATE WITH CHLORO-BRIDGED PLATINUM(II) COMPLEXES [PT2CL4(PR3)2] - CRYSTAL-STRUCTURE OF CIS-[PTCL2(PME2PH)(CH2=CHOCOCH3)]

Five complexes of type cis-[PtCl2(PR3)Q] (PR3 =PMe3, PMe2Ph, PEt3; Q = CH2 CHOCOCH3 or CH2=CHCH2OCOCH3) have been prepared. The crystal structure of cis-[PtCl2[PME2Ph)(CH2=CHOCOCH3)] is described. Crystals of cis-[PtCl2(PME2Ph)(CH2-CHOCOCH3)] are triclinic, with a 8.441(4), b 13.660(5), c 7.697(3) Å, a 101.61(3)°, β 111.85(3)° γ 95.22(3)°, pP1, Z = 2. The structure was determined from 2011 reflections I σ 3σ (I) and refined to R = 0.037. The CH3COO grouping is syn to the cis-PMe2Ph ligand, with bond lengths of PtCl (trans to P) 2.367(3), PtCl (trans to olefin) 2.314(3), PtP 2.264(2), and PtC of 2.147(12) and 2.168(11) Å. The complexes cis-[PtCl2- (PR3)Q] were studied by variable temperature 1H and 31P NMR spectroscopy. Spectra of the vinyl acetate complexes were temperature dependent as a result of rotation about the platinum-olefin bond. The rotation was frozen out" at ca. 240 K; for cis-[PtCl2(PME2Ph)(CH2=CHOCOCH3] ΔG≠ (rotation) 15.0 ± 0.2 kcal mol-1. NMR parameters for the rotamers are reported. NMR studies of the interaction between chloro-bridged complexes of type [Pt2Cl2(PR3)2] (PR3 = P-N-Pr3 or PMe2Ph) and vinyl acetate shows that even at low temperatures (213 K) equilibrium favours the bridged complex and the proportion of trans-[PtCl2(PR3)CH2=CHOCOCH3)] is very small e.g. 2%. The allyl acetate complexes cis-[PtCl2(PR3)(CH2=CHCH2OCOCH3)] showed only one rotamer over the range 333-213 K. Reversible dissociation of cis-[PtCl2(PMe2Ph)- (CH2=CHCH2OCOCH3)] to [Pt2Cl4(PMe2Ph)2] + allyl acetate was studied at ambient temperature. At low temperatures e.g. 213-190 K addition of allyl acetate to a CDCl3 solution of [Pt2Cl2(P-n-Pr3)2] reversibly gave some olefin complex trans-[PtCl2(P-n-Pr3)(CH2=CHCH2OCOCH3)] and some O-bonded complex trans-[PtCl2(P-n-Pr3)(CH2=CHCH2OCOCH3)]. © 1979."