Rare Carbon-Bridged Bimetallic Lanthanide (Nd or Sm) and Tl(I) Geminal Carbon Derivatives of a Bis(iminophosphorano)methanediide

Abstract

i d g e d b i s -(iminophosphorano)methanediide complexes [CpNd(Tl){C-(Ph 2 PNSiMe 3 ) 2 }Cl 2 Li(THF) 2 ]•Et 2 O ( 2) and [SmCl 3 Tl{C-(Ph 2 PNSiMe 3 ) 2 }Li(THF) 2 ] 2 (3) were prepared from reactions of the dilithiated bis(iminophosphorano)methanediide [Li 2 L] (1; L = C 2− (Ph 2 PNSiMe 3 ) 2 ) with Nd and Sm chlorides and with CpTl and TlCl, respectively, in THF. Both final products contain coordinated Li linked with Cl bridges. The complexes have been structurally characterized and show that the bridging methanediide backbone carbon of the ligand is substituted with one Tl(I) and one rare-earth atom and has a tetrahedral geometry. The 31 P{ 1 H} NMR spectrum (THF-d 8 ) of 2 shows a broad signal at 13.75 ppm with a two-bond spin−spin coupling ( 2 J Tl−P = 410 Hz), indicating that the C−Tl bond is maintained in solution. The 31 P{ 1 H} NMR spectrum of 3 was less informative because the complex is more paramagnetic, and thus only a very broad single peak was observed. DFT calculations on the model compounds [CpNd(Tl){C(PhMePNSiH 3 ) 2 }Cl 2 Li(THF) 2 ] (2a) and [SmTl{C(PhMePNSiH 3 ) 2 Cl 2 ] 2 (3a), whose crystal structures are based on those for 2 and 3, were performed; the results clearly demonstrate the bonding characteristics among the metal centers (Nd(III), Sm(III), Tl(I)) and bridged carbon. In contrast to most Tl(I) compounds, 2 and 3 are reasonably stable in air; this is attributed to protection of the Tl(I) by some of the phenyl substituents on the phosphorus through π-bonding interactions. X-ray and DFT data indicate that, for 2, Tl(I) is a five-coordinate center through one strong carbene carbon bond and four weak phenyl carbon bonds, while for 3, Tl(I) is six-coordinate through strong carbene carbon and chloride bonds and four weak phenyl carbon bonds. These complexes are the first examples of a single carbon or carbene forming a bridge between the main-group heavy metal Tl(I) and another rare-earth metal.

Role of Bis(phosphinimino)methanides as Universal Ligands in the Coordination Sphere of Metals across the Periodic Table

“…Hydrogen atoms have been omitted for clarity. Reproduced from the CIF files for CCDC 1874123 and 1836724, respectively. , …”

“…Bimetallic bis­(phosphinimino)­methandiide complexes [{(Tl)­C­(Ph 2 PN­SiMe 3 ) 2 }­Nd­(Cp)­(μ-Cl) 2 ­Li­(THF) 2 ]·Et 2 O ( 168 ) and [{(Tl)­C­(Ph 2 PN­SiMe 3 ) 2 }­Sm­(μ-Cl)­Cl 2 ­Li­(THF) 2 ] 2 ( 169 ) were reported by the Zhao group as the first instances of a single carbene connecting a rare-earth metal bridge to the main-group heavy metal Tl­(I), as shown in Scheme . Complex 168 was prepared under inert oxygen-free conditions in one pot from the reaction of 6a with NdCl 3 and CpTl in THF, whereas the reaction of 6a with TlCl and SmCl 3 under similar conditions afforded complex 169 .…”

“…The solid-state structure of 169 is shown in Figure b. The authors claimed that the complexes are unusually stable in comparison to previously reported carbon-bound Tl­(I) complexes because in both cases the Tl is surrounded by the phenyl substituents of the phosphorus atoms, which provide a protective environment and prevent it from further coordination with additional donors or reaction with peripheral reagents …”

“…94 The complex 105 is monomeric in nature, in contrast with the chloride congener [{CH(Ph 2 PNSiMe 3 ) 2 }YCl 2 ] 2 , 95 which is dimeric in the solid state. The chloride complexes of yttrium and other lanthanides, [{CH(Ph 2 PNSiMe 3 ) 2 }LnCl 2 ] 2 (Ln = Y (106), Sm (107), Er (108), Dy (109), Yb (110), Lu (111)) were prepared earlier by transmetalation of the potassium methanide complex 5a′ with anhydrous yttrium or lanthanide trichlorides in a 1:1.1 molar ratio in THF followed by crystallization from hot toluene. 95 Sterically constrained lanthanum methanide complexes of the compositions [{CH(Ph 2 PNSiMe 3 ) 2 }La(I) 2 (THF)] ( 112) and [{CH(Ph 2 PNAd) 2 }La(I) 2 (THF)] (113) were also obtained using the same strategy by the reaction of the alkali metal complexes [{CH(Ph 2 PNR) 2 }M(THF) 2 ] (M = K, R = SiMe 3 (5a); M = Rb, R = Ad (7)] with [La(I) 3 (THF) 4 ] in THF, with the elimination of KI and RbI, respectively.…”

Crystal Structures of Gallium(III) Halides with Bulky Ligands

“…It is well-known that group 13 metal halides of the type MX 3 (M = B, Al, Ga, In and Tl, X = Cl − , Br − , I − ) have electron pair acceptor orbitals and can easily form donor-acceptor complexes with nitrogen, oxygen, sulfur and phosphine donor atoms [2]. We recently synthesized and structurally characterized two nitrogen donor atom complexes of group 13 elements with a bis(iminoophosphorano)methanide chelate ligand to form a (C − P 2 N 2 M + X 2 ) sixmember ring with an intramolecular ionic charge separation interaction [3,4]. There are other unusual donor-acceptor types of adducts, for example thallium (Tl(III)) platinum (Pt(II)); it has been reported that the occupied d z 2 orbital electron pairs can act as potential donor electrons to empty Tl(III) s orbitals to form Pt(II)-Tl(III) metal-metal bond complexes.…”