Sterically Encumbered Tin and Phosphorus peri-Substituted Acenaphthenes

Abstract

is distorted, but notably less so than in bis(sulfide) 4-S. All compounds were fully characterized and except for bis(phosphine) 5 crystal structures were determined.

Peri-Substituted Phosphorus–Tellurium Systems–An Experimental and Theoretical Investigation of the P···Te through-Space Interaction

“…1.846(4) Å for one of the starting materials, the peri-substituted Br, P i Pr 2 ). 26,27 The acenaphthene skeleton of the systems is mainly planar with the central acenaphthene ring torsion angles (e.g. C6-C5-C10-C1 and C4-C5-C10-C9) being close to 180°.…”

Sterically Congested 5-Diphenylphosphinoacenaphth-6-yl-silanes and -silanols

“…6,7 The 5,6-bis(triorganostannyl)-substituted acenaphthenes 5,6-(Me 3 Sn) 2 -Ace (IX) and 5,6-(Ph 3 Sn) 2 -Ace (X) possess even larger Sn−Sn peri-distances of 3.969(1) and 4.066(1) Å, which might be related to the restricted buckling of the more rigid acenaphthyl scaffold compared to the more flexible naphthyl backbone. 8,9 Among the organometallic group 14 compounds VI−X, the Si derivative VI is thermally the least stable and arguably also the most difficult to prepare. The straightforward salt metathesis of 1,8-dilithionaphthalene, 1,8-Li 2 -Nap, or 5,6-dilithioacenaphthene, 5,6-Li 2 -Ace, with Me 3 GeCl, Me 3 SnCl, and Ph 3 SnCl afforded VII−X, but the analogous reaction with Me 3 SiCl failed to provide VI.…”

Synthetic, Structural, and Spectroscopic Studies of Sterically Crowded Tin–Chalcogen Acenaphthenes

“…The increased strength of the Sn-E interaction in 5-9 causes even greater distortion to the naturally tetrahedral tin environment, with the sum of the pseudo-equatorial C-Sn-C angles increasing to between 353-357°, more in line with a trigonal bipyramidal geometry (Table 5). This is supported by looking at the geometrical goodness [∆∑(θ) = ∆∑(θ eq ) -∆∑(θ ax ); 0° (tetrahedron) ≤ ∆∑(θ) ≤ 90° (trigonal bipyramid)] 34 for each compound, which steadily increases from ∆∑(θ) = 26.5° (1), 28.5° (2), 35.5° (3), 37.4° (4) in the triphenyltin derivatives to ∆∑(θ) = 60.4°[72.7°] (5), 53.2° (6), 66.9°(7), 68.8° (8), 67.5° (9) in the triorganotin chlorides. The molecular structure of bis(peri-substituted) sulfur-tin acenaphthene [{Acenap(SPh)} 2 SnCl 2 ] 10 is constructed from two crystallographically unique acenaphthene fragments which couple through a central pseudo-hexacoordinated tin atom in a geminal fashion (Figure 7).…”

“…[4][5][6][7] Repulsion inevitably leads to deformation of the naturally rigid naphthalene geometry through in-and out-of-plane distortions of the exocyclic peri-bonds or buckling of the organic framework (angular strain) and is characteristic of much larger peri-distances. [4][5][6][7] For example, the introduction of bulky chalcogen atoms within the bay region of tris(sulfide) A (Figure 1), 8 and similarly in bis(phosphines) of type B, [9][10][11] naturally increases the steric congestion across the peri-gap resulting in non-bonding P•••P separations that are remarkably 6-13% longer than the sum of van der Waals radii, with the peri-distance for the former [4.072(3) Å] the largest ever reported. 12 Bis(stannanes) C are further examples of severely strained molecules, with repulsion imposed by the two bulky tin centers leading to equally long periseparations (~92% ∑r vdW ).…”

“…12 Bis(stannanes) C are further examples of severely strained molecules, with repulsion imposed by the two bulky tin centers leading to equally long periseparations (~92% ∑r vdW ). 9,13,14 In contrast, substituent effects in 5-(dichlorophosphino)-6-(diisopropylphosphino) acenaphthene D induce a strongly attractive donor−acceptor interaction between the two electronically disparate functional groups, leading to a notably compressed P-P bond distance of 2.257(1) Å (63% ∑r vdW ). 15 Tellurium 1,2-dications E 16 and dithiole F 17 have similarly short E-E bond lengths (58-68% ∑r vdW ) and further demonstrate the unique ability of peri-substituted systems to relieve steric strain and achieve a relaxed geometry via the formation of a direct bond between the peri-atoms.…”