Dynamic Titanium Phosphinoamides as Unique Bidentate Phosphorus Ligands for Platinum

Abstract

Treatment of lithium phosphinoamides, Ph2PN(Li)R [R = tBu, iPr], with TiCl4 results in formation of titanium phosphinoamides, (Ph2PNR)2TiCl2 [R = tBu (1a), iPr (1b)]. Crystallographic studies show that there are covalent bonds between the titanium and two nitrogen atoms, whereas two phosphorus atoms are coordinated to the metal center intramolecularly. Variable-temperature NMR studies suggest reversible dissociation of the phosphorus moieties from the titanium in solution. The dissociated phosphorus moieties are effectively captured by Pt(II) species; reactions of 1a with either (η4-COD)PtCl2, (η4-COD)Pt(R)(Cl) (R = Me, p-Tol), or [Me2Pt(μ-SMe2)]2 afford the corresponding Ti−Pt heterobimetallic complexes. The molecular structures of these complexes reveal that they have a six-membered dimetallacycle, in which a titanium and a platinum are connected by two bridging phosphinoamide ligands; the Pt−Ti distances indicate the existence of a Pt→Ti dative bond. The conformation of the dimetallacycle is a boat form, with two metals at the bow and the stern in the crystal; however, dynamic conformational change involving cleavage and re-formation of the Pt→Ti dative bond is indicated from variable-temperature NMR studies.

Zirconium(IV) Tris(phosphinoamide) Complexes as a Tripodal‐Type Metalloligand: A Route to Zr–M (M = Cu, Mo, Pt) Heterodimetallic Complexes

“…This was supported by the sum of the three angles at the N atom (359.3-359.9°), which is close to the theoretical value of 360°for the planar sp 2 -hybridized nitrogen atom. The shorter bond lengths of N-P were also observed in our Ti-Pt and Ti-Ru phosphinoamide complexes, [10] Zr(Ph 2 PNPh) 4 , [13] and related complexes.…”

“…[5] As shown in Figure 1, the "amphoteric ligand" reported by Labinger is a typical example, in which both the Lewis acidic R 2 Al moieties and Lewis basic R 2 P units are included in one molecule; unique reactivity of the aluminum phosphinoamide Ph 2 PNtBuAlEt 2 was discovered in the reaction with several transition-metal carbonyls. [6,7] The bi- [10] The TiPt complexes have a trigonal bipyramidal titanium and a square planar platinum center, [10a] whereas the Ti-Ru complex has titanium and ruthenium atoms with trigonal bipyramidal and tetrahedral geometries, respectively.…”

Titanium(IV) phosphinoamide as a unique bidentate ligand for late transition metals II: Ti Ru heterobimetallics bearing a bridging chlorine atom

“…This was supported by the sum of the three angles at N (358.9-359.2°), which are very close to the theoretical value of 360°f or the planar sp 2 -hybridized nitrogen atom. The shorter bond distances of NAP were also observed in our TiAPt phosphinoamide complexes [6], previously reported phosphinoamide or its related complexes [11]. The TiAN (1.969-1.983 Å ) and RuAP (2.349-2.3639 Å ) bond distances are slightly longer than those of titanium amido [8] and ruthenium phosphine [9] complexes, respectively.…”

“…Both the titanium and ruthenium centers adopt pseudo-tetrahedral coordination geometry, and the two metal centers are linked by two phosphinoamide ligands. The resulting sixmembered dimetallacycle has a boat form which is similar to that of our previously reported TiAPt phosphinoamide complexes [6]. The long TiARu distance of 3 (3.093 (2) [3.073 (2)] Å ) precludes any metal-metal interaction, because the metal-metal bonds between Ti and Ru atoms are usually shorter than 3 Å [7].…”

“…Y, Y 0 = Me) by treatment with appropriate Pt(II) precursors (Scheme 1) [6]. Crystallographic studies revealed that these new TiAPt complexes have a six-membered ring consisting of two metallic, two phosphorus, and two nitrogen atoms with a boat conformation.…”