The complexes cis-[PtX2P(OC6H4OMe-2)32] (X = Cl, Br or I) have been prepared by treatment of the corresponding [PtX2(cod)] (cod = cycloocta-1,5-diene) with P(OC6H4OMe-2)3. That with X = Cl reacted with 1 or 2 equivalents of SnCl2to give cis-[PtCl(SnCl3)P(OC6H4OMe-2)32] or trans-[Pt(SnCl3)2P(OC6H4OMe-2)32]. The unstable hydride trans-[PtH(Cl)P(OC6H4OMe-2)32] was detected when cis-[PtCl2P(OC6H4OMe-2)32] was treated with NaBH4or [PtP(OC6H4OMe-2)33] with HCl. The organoplatinum complexes cis-[PtR2P(OC6H4OMe-2)32] and cis-[PtR(X)P(OC6H4OMe-2)32] (R = Me, X = Cl, I or CN; R = Et, X = Cl) were obtained from platinum-(II) and -(0) precursors. Addition of HBF4to cis-[PtMe2P(OC6H4OMe-2)32], in the presence of H2O or MeCN, gave the cationic species cis-[PtMe(L)P(OC6H4OMe-2)32][BF4] (L = H2O or MeCN). The significance of the observation that complexes of the type [PtMe(L)P(OC6H4OMe-2)32] are invariably cis is discussed. The crystal structures of cis-[PtCl2P(OC6H4OMe-2)32] and cis-[PtMe(OH2)P(OC6H4OMe-2)32][BF4]·CH2Cl2have been determined. These, together with those previously reported for P(OC6H4OMe-2)3and [Pt(η-C2H4)-P(OC6H4OMe-2)32], show pronounced variation in P-O lengths and O-P-O bond angles consistent with the greater importance of Pt-P π bonding in the platinum(0) species. The phosphite P(OC6H4OMe-2)3shows a range of conformations in the structures and that with anti, gauche, gauche (agg) conformation about the P-O bonds apparently favoured in general but ggg attainable in the absence of steric crowding. In cis-[PtMe(OH2)P(OC6H4OMe-2)32][BF4]·CH2Cl2, intramolecular hydrogen bonding leads to an unusual aag conformation. Weak Pt ⋯ O interactions involving the OMe groups of the phosphite ligand are observed in these structures. The correlation of P-O length and O-P-O angle variation is mirrored by similar behaviour for 133 Z-P(OPh)3(Z = O, N or metal) structures. These observations are consistent with the now conventional view of M-P π bonding.
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|Titolo:||Tris(2-methoxyphenyl) phosphite complexes of platinum(n): The cis preference of triaryl phosphite ligands and the effect of oxidation state on metal-phosphite bonding|
|Data di pubblicazione:||1996|
|Appare nelle tipologie:||1.1 Articolo in rivista|