Aromatic 1H-[1,2]Diphosphole with a Planar Tricoordinated Phosphorus, Plus η²-Coordination Mode between Ruthenium(0) and a Phosphaalkene

Abstract

Tri-tert-butylphenyl)-1H-[1,2]diphosphole (12) was isolated from the unintentional and unexpected dehydrohalogenation of 1,3-bis(chloro(2,4,6-tri-tert-butylphenyl)phosphino)propane ( 5) with DBN. 1H-[1,2]Diphosphole 12 has substantial bond delocalization within the diphosphole system. Remarkably, the shortest P-C bond in the ring (1.725(4) Å) is observed for a nominal P-C single bond with the tricoordinated phosphorus atom. The P-P distance (2.0750(18) Å) in 12 is closer to the value for a PdP bond than for a P-P bond. The sum of the bond angles at the tricoordinated phosphorus atom in 12 is 351.3°, making 12 the most planar 1H-[1,2]diphosphole known to date. The 31 P NMR spectrum of 12 contains very similar chemical shifts for the tri-and dicoordinated phosphorus atoms (90.83 and 133.80 ppm), with a large P-P coupling constant ( 2 J PP ) 528.2 Hz). This is further evidence of significant delocalization of the lone pair electrons of the tricoordinated phosphorus into the ring system and is consistent with the aromaticity of the 1H-[1,2]diphosphole ring in 12. The reaction between ruthenium carbonyl and 8-{(2,4,6-tri-tert-butylphenyl)-[3-(2,4,6-tri-tert-butylphenylphosphanylidene)propyl]phosphanyl}-2,3,4,6,7,8-hexahydropyrrolo[1,2-a]pyrimidine (8), which is the second product from the unexpected dehydrohalogenation, resulted in the formation of complex 27, with a novel η 2 -coordination mode between ruthenium and the phosphaalkene. The P-C bond in the three-membered ring of 27 is substantially lengthened by η 2 -coordination, from 1.650(3) Å in the parent ligand to 1.775(3) Å in complex 27.

Ruthenaphosphaalkenyls: Synthesis, Structures, and Their Conversion to η2-Phosphaalkene Complexes

“…Thus, 32 which also exhibited a significantly lowfrequency resonance for P alkene (δ P 23). More recently, Ionkin described a similar situation (δ P 54) for his chelated phosphaalkene complex (Chart 3), 33 the significant shift from the free ligand (δ P 248), which was mirrored in the 13 C data (δ C 67, cf. 181 for the free ligand), being deemed consistent with an η 2 -coordination mode.…”

Analogy between sulfuryl and phosphino groups: the aromaticity of thiophene-oxide

“…Accordingly, combining all these planarizing effects 1-bis(trimethylsilyl)methyl-3,5-trimethylsilyl-1H-1,2,4-triphosphole [45] is fully planar. Less substituted phospholes, such as 3-methyl-1-supermesitylphosphole [42] and 1-supermesityl-1H-1,2-diphosphole [46] (Fig. 3) are not planar, although the phosphorus pyramid is quite flattened (bond angle sums about the phosphorus are 330°and 348°, respectively).…”

“…Moreover, the similarity of the electronic structure of thiophene-oxide to that of phosphole indicates that the inversion barrier of Fig. 3 The structure of 3-methyl-1-(2,4,6-tri-tert-buthylphenyl)phosphole [42], 1-bis(trimethylsilyl)methyl-3,5-trimethylsilyl-1H-1,2,4-triphosphole [45], and 1-(2,4,6-tri-tert-butylphenyl)-1H-1,2-diphosphole [46] this compound can also be reduced by proper substitution, and planar thiophene-oxide derivatives might be designed. In this study the comprehensive characterization of the aromaticity of thiophene-oxide is aimed, in the light of the structural analogy between the phosphino and the sulfuryl group.…”

Synthesis of rhodium–carbonyl complexes bearing a novel P,N-chelating ligand of Schiff-base type

“…Although Mindiola et al have postulated the existence of an intermediary titanium complex 3 bearing a P,N-chelating Schiff-base ligand (Scheme 3) [9], there has been no example for the isolation of a transition metal complex bearing such phosphorus analogue of a -diketiminato ligand [10]. On the other hand, Ionkin et al have reported the attempted synthesis of a phosphorus analogue of -diketiminate 6 bearing 2,4,6-tri-tert-butylphenyl (denoted as Mes*) group [11]. However, it was suggested that 6 undergoes ready intramolecular cyclization to afford 1H- [1,2]diphosphole derivative 5 along with the elimination of Mes*H (Scheme 3).…”