Two Different Pathways in the Reduction of [(S=)PCl(μ‐NtBu)]₂ with Na

Abstract

Reduction of the cyclodiphosphazane [(S=)ClP(μ-NtBu)]2 (1) with sodium metal in refluxing toluene proceeds via two different pathways. One is a Wurtz-type pathway involving elimination of NaCl from 1 followed by head-to-tail cyclization to give the hexameric macrocycle [(μ-S)P(μ-NtBu)2 P(=S)]6 (2). The other pathway involves reduction of the P=S bonds of 1 to generate colorless singlet biradicaloid dianion trans-[S-P(Cl)(μ-NtBu)]2 (2-) , which is observed in the polymeric structures of three-dimensional [{(S-)ClP(μ-NtBu)2 PCl(S)}Na(Na⋅THF2 )]n (3) and two dimensional [{(S-)ClP(μ-NtBu)2 PCl(S)} (Na⋅THF)2 ]n (4).

A Modular Approach to Inorganic Phosphazane Macrocycles

“…[36,37] Significantly, our new method improves the yields of this type of macrocycle dramatically from approximately 10-45 % using the previous Wurtz-type approach [29,30] to over 80 % for the related macrocyles. This approach also allows a large range of achiral and chiral R-groups to be introduced into these arrangements (apart from t Bu alone, as in all previous examples), as well as all P V derivatives (which are air stable).…”

“…10 %). [29,30] A recently developed approach involves the incoporation of the well established building block…”

“…The resulting hexameric macrocycle 3-t Bu, although closely related to previously reported D (Scheme 2), contains a unique alternating (P III ) 2 (P V ) 2 backbone (Scheme 3). [30] The formation of the macrocycle 3-t Bu was monitored by 31 P NMR and found to be quantitative after a few minutes at room temperature. Interestingly, the P III and P V atoms within each of the phosph(III)azane and phosph(V)azane P 2 N 2 ring units are magnetically inequivalent, giving rise to two double-doublets in the 31 P{ 1 H} NMR spectrum at d = 56.1 ppm (P V ) and d = 225.2 ppm (P III ).…”

“…6.5 in depth (i.e., t Bu to t Bu) which is very similar to [S=P(m-N t Bu) 2 P(m-S)] 6 , the only other S-bridged phosphazane macrocycle of this type. [30] The dianion 2 is a building block for other heteroleptic (P V ) 2 (P III ) 2 macrocycles of the type [{S = P(m-N t Bu)} 2 (m-S)-{P(m-NR)} 2 ] 3 , closely related to 3-t Bu, which are readily obtained from in situ reactions of 2 with different chlorodiphosphazanes ([ClP(m-NR)] 2 ). [19] Employing this synthetic procedure allows the introduction of R groups with varying steric bulk (i.e., R = neo-pentyl, 3-CH 2 t Bu) and chirality (R = R-1-(2-naphthyl)ethyl, 3-R-naphEt).…”

“…7.66 in diameter). [30] The heteroleptic macrocycles 3-CH 2 t Bu and 3-R-naphEt are the first examples of phosphazane macrocycles containing organic substituents other than t Bu, and 3-R-naphEt is the first chiral macrocycle of this type. The ability to change the R-group provides the potential for tuning or modifying behavior such as solubility, as seen for 3-CH 2 t Bu which (unlike 3-t Bu) is highly soluble in n-hexane.…”