Synthetic, Structural, NMR, and Computational Study of a Geminally Bis(peri-substituted) Tridentate Phosphine and Its Chalcogenides and Transition-Metal Complexes

Abstract

Coupling of two acenaphthene backbones through a phosphorus atom in a geminal fashion gives the first geminally bis(peri-substituted) tridentate phosphine 1. The rigid nature of the aromatic backbone and overall crowding of the molecule result in a rather inflexible ligand, with the three phosphorus atoms forming a relatively compact triangular cluster. Phosphine 1 displays restricted dynamics on an NMR time scale, which leads to the anisochronicity of all three phosphorus nuclei at low temperatures. Strained bis- and tris(sulfides) 2 and 3 and the bis(selenide) 4 have been isolated from the reaction of 1 with sulfur and selenium, respectively. These chalcogeno derivatives display pronounced in-plane and out-of-plane distortions of the aromatic backbones, indicating the limits of their angular distortions. In addition, we report metal complexes with tetrahedral [(1)Cu(MeCN)][BF4] (5), square planar [(1)PtCl][Cl] (6), trigonal bipyramidal [(1)FeCl2] (7), and octahedral fac-[(1)Mo(CO)3] (8) geometries. In all of these complexes the tris(phosphine) backbone is distorted, however to a significantly smaller extent than that in the mentioned chalcogenides 2-4. Complexes 5 and 8 show fluxionality in (31)P and (1)H NMR. All new compounds 1-8 were fully characterized, and their crystal structures are reported. Conclusions from dynamic NMR observations were augmented by DFT calculations.

Sterically Encumbered Tin and Phosphorus peri-Substituted Acenaphthenes

“…This is aptly demonstrated by comparing the compounds of Figure 1, the only peri-substituted systems reported up until now with separations larger than 3.8 Å. [4][5][6][7][8][9][10][11] Figure 1. Severely strained peri-substituted systems incorporating non-bonded distances greater than 3.8 Å.…”

“…The distance of the former is only 6% shorter than twice the sum of van der Waals radii of Sn [4.34 Å] 12 and statistically of equal magnitude to the largest peri-separation previously reported for a geminally bis(peri-substituted) tridentate phosphine tris(sulfide) (Figure 1 A; 4.072(3) Å). 4 It is interesting to note that the Sn•••Sn distance in 2 is only marginally longer than the peri-separation reported for the naphthalene analogue [3.864 Å]. 9 Strained bis(stannanes) 1 and 2 adopt similar conformations to corresponding 1,8-bis(trimethylelement)naphthalenes G (Ge) and F (Sn) (Figure 1), 9 with the R3Sn groups aligning in each case such that a pair of Sn-C bonds, one from each Sn centre (Sn1-C3 and Sn2-C37 in 1; Sn1-C14 and Sn2-C17 in 2; Figure 5), align roughly perpendicular to the mean acenaphthene plane ( Figure 5).…”

“…[4][5][6][7][8][9][10] Interestingly, the largest separation is found between phosphorus atoms in tris(sulfide) A [4.072(3) Å], 4,11 with similar values observed for bis(phosphours) B-D, 5,6,7,11 despite compounds with much larger peri-heteroatoms having been prepared (for example E-H). 2,8,9,11 In these compounds, P•••P separations are remarkably 6-13% longer than the sum of van der Waals radii and can be explained by the increased crowding of the bay region by the introduction of bulky chalcogen atoms in A-C, [4][5][6] and the severe coulombic repulsion experienced by the closely aligned positively charged phosphorus centers in D. 7 The series of 1,8-bis(trimethylelement)naphthalenes F-H represents a set of equally strained molecules, and in spite of having larger heteroatoms at the proximal peri-positions [rvdW (Sn) 2.17 Å, (Ge) 2.11 Å;…”

Stabilization of the Elusive Antimony(I) Cation and Its Coordination Complexes with Transition Metals

“…The P1⋅⋅⋅P2 distance in 1 is 3.4642(13) Å, which is larger than the P1A⋅⋅⋅P2A (3.0563(8) Å) distance in L (Figure S73). Also, the splay angle [28] in 1 (+20.6°) is larger than that found in L (+12.4°). The P1‐C10⋅⋅⋅C1‐P2 dihedral angle is 30.80(19)°, depicting an out‐of‐plane peri ‐strain, however not hampering the integrity of the Sb I cation.…”

Stabilization of the Elusive Antimony(I) Cation and Its Coordination Complexes with Transition Metals

“…[27] TheP1•••P2 distance in 1 is 3.4642 (13) ,which is larger than the P1A•••P2A (3.0563(8) )d istance in L (Figure S73). Also,t he splay angle [28] in 1 (+ 20.68 8)i sl arger than that found in L (+ 12.48 8). TheP 1-C10•••C1-P2 dihedral angle is 30.80( 19)8 8,d epicting an out-of-plane peri-strain, however not hampering the integrity of the Sb I cation.…”