Theresult of this analysis is shown in Figure 2and highlights that the disposition of the phosphorus and magnesium centers within compound 9 is consistent with the coupling pattern observed in the solution - state 31 PNMR spectrum and the multiplicity of signals arising in the 1 Ha nd 13 CNMR data . Thes tructure comprises two ( Dipp BDI ) magnesium units bonded to a [ nBu 2 P 8 ] 2À cluster dianion derived from the formal reductive coupling of two neutral P 4 units . A lthough the rationality of this { P 8 } c luster synthesis from the combination of two { P 4 } f ragments appears to be unique , i ts structure may be considered as ah eptaphosphanorbornane fused to an exo - oriented cyclotriphosphane ring and ac onstitutional isomer of the { P 8 } c age within the niobium(V ) species [ Ph 2 CP 8 Nb(OC [ 2 Ad]Mes ) 3 ] , which was derived through treatment of compound 1 with benzophenone . [ 14 ] Thes ingle tris(enolato ) niobium dication and the { Ph 2 C } unit of this previously described species is replaced in the present case by two ( Dipp BDI ) magnesium monocations and two n - butyl substituents . T he magnesium centers contact the Subsequent preliminary investigations indicated that the kinetic control exerted during the syntheses of compounds 8 and 9 is an apparent consequence of the steric demands of both the supporting ( Dipp BDI ) platform and the reactive nbutyl co - ligand . Analysis by 31 PNMR spectroscopy of areaction between [ ( Dipp BDI)MgH ] 2 and half amolar equivalent of P 4 provided am ixture of several phosphorus - containing species . A lthough am inor component comprised broadened resonances at d À3.5 and À159 ppm reminiscent of those observed for compound 8,the major product of this reaction was characterized by atriplet signal observed at d À284.8 ppm ( 1 J P - H = 45 Hz ) . This latter species was identified as the trimeric primary magnesium phosphide , c ompound 10 , through afurther X - ray analysis performed on single crystals produced by fractional crystallization of the reaction mixture ( Figure 3a ) . Analytically pure samples of compound 10 , Figure 2 . ORTEP representation ( 30 % probability ellipsoids ) of compound 9 . [ 17 ] Hydrogen atoms , isopropyl methyl groups and n - butyl groups aside from the P - bonded C59 and C63 atoms were removed for clarity . S elected bond lengths [ ] and angles [ 8 8 ] : P1- P5 2.195 ( 3 ) ( 14 ) , P1 - P5 - P6 92.00 ( 12 ) , P4 - P5 - P6 , 105.80 ( 12 ) , P7 - P6 - P85 9.27 ( 11 ) , P7 - P6 - P5 106.69 ( 12 ) . . ORTEP representations ( 30 % probability ellipsoids ) of a ) compound 10 with hydrogen atoms ( except those attached to P1 , P2 , and P3 ) and isopropyl methyl groups removed for clarity , a nd b ) compound 11 with hydrogen atoms and mesityl methyl groups removed for clarity . [ 17 ] notable as the first primary phosphide of aG roup 2e lement to have been structurally characterized , were found to be unstable once redissolved in [ D 8 ] toluene . M onitoring by 1 H and 31 PNMR spectroscopy at room temperature evidenced the onset of ar edistributive process to as yet unidentified magnesium - containing species and the production of PH 3 , which was observed as abinomial quartet at d À245.0 ppm in the 31 PNMR spectrum .