New Mono- and Polynuclear Alkynyl Complexes Containing Phenylacetylide as Terminal or Bridging Ligand. X-ray Structures of the Compounds NBu4[Pt(CH2C6H4P(o-tolyl)2-κC,P)(C⋮CPh)2], [Pt(CH2C6H4P(o-tolyl)2-κC,P)(C⋮CPh)(CO)], [{Pt(CH2C6H4P(o-tolyl)2-κC,P)(μ-C⋮CPh)}2], and [{Pt(CH2C6H4P(o-tolyl)2-κC,P)(C⋮CPh)2Cu}2

Abstract

This work describes the synthesis of the compounds Q[Pt(C∧P)(C⋮CPh)2] (Q = Li+ (1), NBu4+ (2). C∧P = CH2C6H4P(o-tolyl)2-κC,P) and their use as precursors for the preparation of homo- and heteropolynuclear complexes by reactions with Lewis acid species of transition metals, M (M = Cu(I), Ag(I), Tl(I), Pd(II), Pt(II)). These reactions give rise to heteropolynuclear complexes that exhibit different bonding patterns for the bridging alkynyl ligands, depending on M. The reaction of 2 with readily available M+ (M = Cu, Ag) species affords the discrete tetranuclear clusters [{Pt(C∧P)(C⋮CPh)2M}2] (M = Cu (3), Ag (4)). The X-ray structure of 3 shows that in this complex both “Pt(C∧P)(C⋮CPh)2” fragments are connected by two d10 metal centers and are stabilized by alkynyl bridging ligands, showing the stronger preference of the MI centers (MI = Cu, Ag) for the electron-rich alkynyl units than for the basic Pt(II) center. However, the reaction of 2 with TlPF6 rendered the tentatively tetranuclear complex [{Pt(C∧P)(C⋮CPh)2Tl}2] (5), containing Pt→Tl dative bonds, which shows the higher affinity of thallium for the electron density of platinum(II) than for the alkynyl units. Moreover, the reaction of (NBu4)[Pt(C∧P)(C⋮CPh)2] (2) with the neutral complex [Pd(C6F5)2(THF)2] yields the compound (NBu4)[Pt(C∧P)(C⋮CPh)2Pd(C6F5)2] (11), in which the two alkynyl ligands are η2-bonded to Pd(II) in such a way that the “cis-Pt(C⋮CPh)2“ fragment acts as a chelate ligand toward Pd(II). Meanwhile the reactions with the cationic and neutral Pt(II) complexes [Pt(C∧P)(THF)2]+ and [Pt(C6F5)2(THF)2] produce the complexes [{Pt(C∧P)(μ-C⋮CPh)}2] (6) and (NBu4)[Pt(C∧P)(μ-C⋮CPh)2Pt(C6F5)2] (12), both containing the double μ2-η2(σ,π)-alkynyl bridging system “Pt2(μ-C⋮CPh)2” as a consequence of an alkynylating process. This bridging system “Pt2(μ-C⋮CPh)2” can be broken by neutral ligands, L, to give mono(σ-alkynyl) complexes of Pt(II). Thus, the complexes [Pt(C∧P)(C⋮CPh)L] (L = CO (7), py (8), tht (9), PPh3 (10)) have been obtained by reaction of 6 with L in a 1:2 molar ratio. When L = PPh3, the substitution reaction takes place with stereoretention, but not when L = CO, py, tht, as was conclusively established by an X-ray study on the complex [Pt(CH2C6H4P(o-tolyl)2)(CCPh)(CO)] (7). The cis or trans disposition of the two σ-C-donor ligands (C(C∧P), σ-C⋮CPh) around the Pt center in complexes 6−10 and 12 seems to depend as much on the transphobia of pairs of trans ligands (T) as on the steric requirements of those in the cis configuration.