Functionalized bis(pyrazol-1-yl)methanes by organotin halide on the methine carbon atom and their related reactions

Amidinatotetrylenes Donor Functionalized on Both N Atoms: Structures and Coordination Chemistry

E(hmds)(bqfam) (E = Ge (1a), Sn (1b); hmds = N(SiMe3)2, bqfam = N,N'-bis(quinol-8-yl)formamidinate), which are amidinatotetrylenes equipped with quinol-8-yl fragments on the amidinate N atoms, have been synthesized from the formamidine Hbqfam and Ge(hmds)2 or SnCl(hmds). Both 1a and 1b are fluxional in solution at room temperature, as the E atom oscillates from being attached to the two amidinate N atoms to being chelated by an amidinate N atom and its closest quinolyl N atom (both situations are similarly stable according to density functional theory calculations). The hmds group of 1a and 1b is still reactive and the deprotonation of another equivalent of Hbqfam can be achieved, allowing the formation of the homoleptic derivatives E(bqfam)2 (E = Ge, Sn). The reactions of 1a and 1b with [AuCl(tht)] (tht = tetrahydrothiophene), [PdCl2(MeCN)2], [PtCl2(cod)] (cod = cycloocta-1,5-diene), [Ru3(CO)12] and [Co2(CO)8] have been investigated. The gold(I) complexes [AuCl{κE-E(hmds)(bqfam)}] (E = Ge, Sn) have a monodentate κE-tetrylene ligand and display fluxional behavior in solution the same as that of 1a and 1b. However, the palladium(II) and platinum(II) complexes [MCl{κ3E,N,N'-ECl(hmds)(bqfam)}] (M = Pd, Pt; E = Ge, Sn) contain a κ3E,N,N'-chloridotetryl ligand that arises from the insertion of the tetrylene E atom into an M-Cl bond and the coordination of an amidinate N atom and its closest quinolyl N atom to the metal center. Finally, the binuclear ruthenium(0) and cobalt(0) complexes [Ru2{μE-κ3E,N,N'-E(hmds)(bqfam)}(CO)6] and [Co2{μE-κ3E,N,N'-E(hmds)(bqfam)}(μ-CO)(CO)4] (E = Ge, Sn) have a related κ3E,N,N'-tetrylene ligand that bridges two metal atoms through the E atom. For the κ3E,N,N'-metal complexes, the quinolyl fragment not attached to the metal is pendant in all the germanium compounds but, for the tin derivatives, is attached to (in the Pd and Pt complexes) or may interact with (in the Ru2 and Co2 complexes) the tin atom.

Bi- and tridentate stannylphosphines and their coordination to low-valent platinum

Semirigid bifunctional tin-substituted o-tolylphosphines of general formulae [Ph₂P(o-C₆H₄CH₂)SnR₃] (R = Ph, 1; R = Me, 2) and [{Ph₂P(o-C₆H₄CH₂)}₂SnPh₂] (3) were synthesized and isolated in good yields. The new compounds were fully characterized by single-crystal X-ray diffraction and multinuclear solution NMR spectroscopic techniques. The observed J(¹¹⁹Sn,³¹P) values in solution NMR spectroscopy as well as the PSn distances in the solid state and DFT calculations (B3LYP) on compounds 1 and 3 do not support the existence of intramolecular P → Sn bond interactions in either of the three compounds. 1 and 2 reacted with stoichiometric amounts of tristriphenylphosphine platinum(0) [Pt(PPh₃)₃] under toluene refluxing conditions leading to formation of Pt(ii) distorted square-planar complexes [Ph₂P(o-C₆H₄CH₂)Pt(SnR₃)(PPh₃)], (R = Ph, 4; R = Me, 5), each bearing a five-membered carbometallated ring resulting from Pt coordination to P and the benzylic C sp³ atom of the ligand architecture rather than from activation of the terminal Sn-C carbon bonds of the phenyl or methyl substituents which would have rendered six-membered rings. Additionally, the fragment SnR₃ also binds to the metal centre disposing cis to the cyclometalated carbon atom and to the single remaining PPh₃. This carbometallation takes place affecting the integrity of the ligand skeleton. NBO calculations show the Sn fragment coordinates to the metal as X-type stannyl, SnR₃. The analogous reaction of [Pt(PPh₃)₃] towards the stannyldiphosphine 3 leads to the quantitative formation of complex [(Ph₂P-o-C₆H₄CH₂)Pt(Ph₂P-o-C₆H₄CH₂SnPh₃)], 6, which exhibits five- and six-membered metallacycles at the expense of the ligand frame. All compounds were characterized exhaustively by solution spectroscopic measurements and by single crystal X-ray diffraction analysis. DFT computations corroborate the higher stability of the observed products over those resulting from preservation of the ligand backbone.