Rapid Inversion at Phosphorus in the [η⁴-(C₆H₁₁)₃SnP₇W(CO)₃]^2-and [(en)(CO)₃W(η¹,η⁴-P₇)M(CO)₃]^3-Ions Where M = Cr, W

Abstract

Ethylenediamine (en) solutions of [eta(4)-P(7)M(CO)(3)](3)(-) ions [M = Cr (1a), W (1b)] react with (mesitylene)W(CO)(3) to form the bimetallic complexes [(en)(CO)(3)W(eta(1),eta(4)-P(7))M(CO)(3)](3)(-) where M = Cr (3a), W (3b) in good yield. Compound 3b can be prepared directly from P(7)(3)(-) and 2 equiv of (mesitylene)W(CO)(3). Compound 3a reacts with 1 equiv of P(7)(3)(-) to form 1a and 1b. En solutions of 1b react with 1 equiv of (C(6)H(11))(3)SnCl to give [eta(4)-(C(6)H(11))(3)SnP(7)W(CO)(3)](2)(-) (4) in good crystalline yield as the [K(2,2,2-crypt)](+) salt. The X-ray structure of the [K(2,2,2-crypt)](+) salt 3b revealed a norbornadiene-like P(7) cage bound eta(4) to the W(CO)(3) fragment (cf. [eta(4)-P(7)W(CO)(3)](3)(-)) and eta(1) to the (en)(CO)(3)W fragment via the long W(2)-P(1) bond of 2.643(3) Å. The structure of 4 is similar, with a (C(6)H(11))(3)Sn(+) group attached to the P(1) atom of the [eta(4)-P(7)W(CO)(3)](3)(-) complex. The coordination geometry at P(1) is distinctly pyramidal in both compounds, which leaves the ions with no crystallographic symmetry. For complexes 3a and 3b, two fluxional processes are rapid on the NMR time scale at -50 degrees C (202 MHz) that give the P(7) cages virtual C(2)(v)() symmetry in solution and AA'A"A"'MM"X spin systems. These processes are (1) a wagging of the four P atoms bound to the M(CO)(3) units and (2) rapid inversion at P(1). For 4, inversion at phosphorus becomes slow on the NMR time scale at low temperature (-50 degrees C, 83 MHz) with DeltaG() = 13 kcal/mol. Crystallographic data are as follows. [K(2,2,2-crypt)](3)3b.en: triclinic, P&onemacr;, a = 14.396(4) Å, b = 17.543(3) Å, c = 20.518(2) Å, alpha = 82.419(11) degrees, beta = 76.830(14) degrees, gamma = 69.16(2) degrees, V = 4708(2) Å(3), Z = 2, R(F) = 5.52%, R(w)(F(2)) = 14.31%. [K(2,2,2-crypt)](2)4: triclinic, P&onemacr;, a = 12.247(2) Å, b = 15.1909(14) Å, c = 21.292(3) Å, alpha = 97.374(10) degrees, beta = 93.273(13) degrees, gamma = 111.217(9) degrees, V = 3639.8(8) Å(3), Z = 2, R(F) = 10.50%, R(w)(F(2)) = 20.21%.

A Reactive Niobium Phosphinidene P8 Cluster Obtained by Reductive Coupling of White Phosphorus

“…This structure and the NMR data described above are quite reminiscent of those reported for related P 7 complexes synthesized by Eichhorn and co-workers. [22][23][24] To add further support to our structural assignment, the results of NMR shielding calculations performed using DFT methods on a model system are in agreement with the observed data and chemical-shift assignments (Supporting Information, Figure 2S, Table 1S). …”

Protonation and Hydrogen Atom Abstraction Reactions in the Synthesis of the [HP7M(CO)3]2- Ions (M = Cr, W)

“…The hydrogen was not crystallographically located. P(6)±P (7) separations (2.968(4) A Ê and 3.307(4) A Ê , respectively) are also typical for these types of compounds [11,14,15,20,22,23] but are larger than the same asymmetries in [P 7 Cr(CO) 3 ] 3± [15]. The larger distortion in the present compound presumably results from the larger size of W relative to Cr.…”

“…The four peaks correspond to the two equivalent pairs of phosphorus atoms bound to the transition metal, P(4), P(6) and P(5), P(7), the two bridging phosphorus atoms P(2) and P(3), and the protonated phosphorus atom P(1), respectively. The asymmetries in the P(4)±P(5)/ P(6)±P(7) separations observed in the solid state are time averaged in solution due to an intramolecular wagging process that is common to all members of the general class of compounds [11,15,20]. The compounds remain fluxional at ±60°C in DMF-d 7 .…”

“…The [20] and related compounds (e. g., W(CO) 4 (P 6 Me 6 )) [21]. The asymmetry observed for the P(4)±P(5) and c) N/R = no reaction, dec = unidentified decomposition products; U = unidentified product.…”

Metal-Mediated Degradation and Reaggregation of White Phosphorus

“…For example, complexes containing P 7 ligands in either norbornadiene (A) or nortricyclane (B) skeletons (Scheme 14), have never been prepared from white phosphorus. The known way to prepare P 7 -complexes starts from the Zintl anion P 7 3- [112]. Noticeably, when Li 3 P 7 is reacted with [NiCl 2 (PBu 3 ) 2 ], head-to-head dimerization of the P 7 3-ligand occurs to afford the richest P x ligand so far known, i.e., [{Ni(PBu 3 ) 2 } 4 (P 14 )] (89), where two P 7 ligands are held together by an elongated P-P bond [113].…”