the activation of white phosphorus ( p4 ) with transition metal ( tm ) complexes with the objective of generating organophosphorus compounds has been an ongoing research topic.1 for this purpose , an understanding of the p4 transformation pathway in the coordination sphere of transition metals is necessary .
thus , a variety of pn ligand moieties were stabilized to give insight into the stepwise p4 degradation and aggregation processes using wellestablished ligand systems such as the cp family ( cp = cyclopentadienyl).1 however , over the last years , diketiminato ( nacnac = l ) ligand systems have gained increasing attention in mild p4 activations using m precursors : the initial p4 fixation step of an intact p4 tetrahedron at a metal center was achieved at an electronrich cu nacnac compound.2 in reactions with transition metal complexes of groups  53 and 810,4 products with modified [ p2 ] , [ p4 ] , [ p4 ] and [ p8 ] ligands , respectively , were obtained .
so far , for nacnac systems , a [ p3 ] ligand was found solely in compound [ ( lvr)2(cyclop3 ) ] ( r = n(tolyl)2 , n=0,1 ; r = o(dipp ) , n=0 ) and [ { lv(n(tolyl)2)}2(2:,cyclop3 ) ] ( a , scheme  1).3c 
  selected examples of pntm complexes containing ligands l 
l ( l = ch[chn(2,6ipr2c6h3)]2 , l = ch[c(me)n(2,6me2c6h3)]2 , l = ch[chn(2,6me2c6h3)]2 , l = ch[c(me)n(2,6ipr2c6h3)]2 , l = ch[c(me)n(2,6et2c6h3)]2 ) .
bottom : comparison of the nacnac ligands used in this study , l , l and l.5 
  however , cyclop3 complexes of the type [ lm(2:,p3)ml ] have been structurally characterized using neutral , tridentate triphos ( 1,1,1tris(diphenylphosphinomethyl)ethane ) and etriphos ( 1,1,1tris(diethylphosphinomethyl)ethane ) ligands in different combinations with 3d metals ( fe , co , ni ) and 4d metals ( rh , pd).6 the influence of the ligand substituents in femediated p4 transformation has recently been illustrated by a comparative study using a set of ligands ll ( scheme  1).7 despite the application of the same reaction conditions , different products were obtained , which are sensitively dependent on small changes of the ligand substituents .
2,6diisopropylphenyl ( dipp ) substituents as the ligands aromatic flanking groups support the formation of the dinuclear complexes [ ( lfe)2(2:,p4 ) ] ( b)7 and [ ( lfe)2(2:,p2)2 ] ( c).4c the latter was synthesized by the driess group.4c the ligands l and l only differ in their backbone substituents . however ,
for sterically less demanding 2,6dimethylphenyl ( dmp ) substituents , the formation of the tetranuclear complexes [ ( lfe)4(4:,,,p8 ) ] [ l = l ( d1 ) , l ( d2 ) ] with dimerized p4 units was observed.7 these results demonstrate that the product formation is affected by both the aromatic flanking groups and the ligand backbone substituents .
simultaneously , we investigated the [ lco]mediated transformations of white phosphorus , which resulted in novel p4 and p3containing complexes ( vide infra ) .
in the meantime , driess and coworkers reported p4 activation by [ lco ] fragments leading to the neutral complexes [ ( lco)2(2:,p4 ) ] [ l = l ( e1 ) , l ( e2 ) ] ( scheme  1).4b oneelectron reduction led to the monoanionic products [ k(dme)4][(lco)2(2:,p4 ) ] [ l = l ( f1 ) , l ( f2 ) ] and transformed the [ p4 ] middle deck into a [ p4 ] ligand .
recently , wolf and coworkers have reported on [ ( bian)co]mediated p4 activations with a nacnacrelated bidentate redox noninnocent bian ( 1,2bis(2,6diisopropylphenylimino)acenaphthene ) ligand system yielding compounds containing [ p4 ] moieties.8 
  motivated by our first results with [ lco ] compounds , we speculated that the p4 activation outcome should be sensitive to the oxidation state of the precursor ( co versus co ) . additionally , we wanted to address the question of the ligands influence ( l  l ) in comediated p4 activations and we were intrigued by the observed patom extrusion from the initially obtained p4 middle deck to form p3 compounds .
, we report on the p4 activation by a formal co precursor yielding the monoanionic [ k(thf)6][(lco)2(2:,p4 ) ] ( 2 ) and [ k(thf)6][(lco)2(2:,p3 ) ] ( 3 ) . through a comediated p4 transformation at room temperature or under thermolytic conditions ,
the corresponding neutral relatives are obtained , which generate 2 and 3 selectively after subsequent oneelectron reduction .
the redox chemistry of the products was investigated by cyclic voltammetry ( cv ) , and their magnetic behavior was examined both in solution ( evans method ) and in the solid state ( squid ) .
the formal co precursor [ k2(lco)2(2:,n2 ) ] ( 1 ) was synthesized by a onepot reaction and was isolated as two different solvomorphs , 1solv ( solv = nhexane9 or oet2).10 the xray structures of 1solv consist of two [ lco ] fragments bridged by a n2 unit .
two potassium atoms cover the n2 moiety and are coordinated in the phenyl pockets of the dipp substituents.11 the nn distance in 1nhexane / oet2 is 1.215(3 ) and 1.220(4 )   , respectively , which is in line with the that ( 1.220(2 )   ) of the previously reported [ k2(lco)2(2:,n2 ) ] [ l = ch[c(tbu)n(2,6ipr2c6h3)]2].12 the presence of a [ n2 ] moiety in 1nhexane is supported by raman spectroscopy ( nn=1568  cm).9 the reaction of 1 with p4 proceeds by n2 evolution , showing that the formal [ n2 ] species is reoxidized and revealing 1 as a formal dicobalt(0 ) starting material . conducting the reaction in 1:1 stoichiometry leads to the complete consumption of p4 and the formation of a mixture of the monoanionic complexes [ k(thf)6][(lco)2(2:,p4 ) ] ( 2 ) and [ k(thf)6][(lco)2(2:,p3 ) ] ( 3 ) , which were detected by h  nmr spectroscopy.13 the appearance of a cyclop3 moiety in product 3 indicates that an extrusion of one p atom from the cyclop4 moiety in 2 is possible .
however , if the reaction is conducted with two equivalents of p4 , compound 2 is the only product found in the h  nmr spectrum .
the solid state structure of 22  thf reveals a salt consisting of two [ k(thf)6 ] cations and two crystallographically distinguishable [ ( lco)2(2:,p4 ) ] monoanions ( figure  1).9 each anion is a centrosymmetric dicobalt complex that consists of two [ lco ] fragments bridged by a planar cyclop4 ligand . the pp distances amount to 2.1913(10)2.1951(10 )   in anion  1 and 2.1897(10)2.2004(10 )   in anion  2 , respectively .
these values correspond well with the cyclo[p4 ] moiety ( 2.178(1 ) and 2.207(1 )   ) of the reported compound [ ( lfe)2(2:,p4 ) ] ( b).7 the central p4 ligands in 2 are almost square planar with interior angles of 86.07(3 ) and 93.92(3) in anion  1 and 86.38(3 ) and 93.62(3) in anion  2 .
the cop distances range from 2.3362(7)2.4149(7 )   in anion  1 and 2.3441(7)2.4190(7 )   in anion  2 .
minor deviations within the atomic parameters of compound 22  thf and the related compounds [ k(dme)4][(lco)2(2:,p4 ) ] [ l = l ( f1 ) , l ( f2 ) ] can be explained by small changes in the organic environment of the counter ion and the nacnac ligands of the complex monoanions .
they may affect the coco distances and their coordination geometry ( torsion angle  between the coco axis and the plane formed by the nitrogen atoms and the methine carbon in the ligand backbone ; figure  1 for graphical presentation of ).14 
  anionic part of the molecular structure of 2 .
hydrogen atoms and aromatic flanking groups are omitted for clarity ; thermal ellipsoids are drawn at 50  % probability level .
the torsion angle  is depicted spanning between the coco axis and the plane formed by the nitrogen atoms and the methine carbon in the ligand backbone .
comparison of pp and coco atomic distances and torsion angles  in anions of [ k(solv)x][(lco)2(2:,p4 ) ] ( l = l ( 2)9 , l ( f1)4b , l ( f2)4b ) .
the monoanionic [ ( lco)2(2:,p3 ) ] was obtained in two different solvomorphs [ k(dme)4][(lco)2(2:,p3)]dme ( 3  a ) and [ k(thf)6][(lco)2(2:,p3)]2  thf ( 3  b ) .
both compounds are ionic and consist of solvent ( dme or thf ) molecules , one solventsaturated potassium counter ion , and the [ ( lco)2(2:,p3 ) ] monoanion ( figures  2 and 3 ) . in both xray structures ,
the complex anions are built from two [ lco ] fragments bridged by a p3 triangle . in 3  a
, the l ligand planes are almost parallel to each other with an dihedral angle of 2.00(7) ( n1n2 versus n3n4 ) . however , in 3  b , the ligand planes are in a twisted conformation with a dihedral angel of 74.2(4) ( n1n2 versus n3n4 , figure  2 ) . 
  comparison of the anions in the molecular structures of 3  a ( left ) and 3  b ( right ) .
hydrogen atoms and aromatic flanking groups are omitted for clarity ; thermal ellipsoids of co and p atoms are drawn at 50  % probability level ; major component of disordered cyclop3 ligand is drawn in 3  a. anionic part of the molecular structure of 3  b. hydrogen atoms are omitted for clarity ; thermal ellipsoids are drawn at 50  % probability level . the different complex anion conformations may originate from packing effects directed by the unequally shaped counter cations .
the cyclop3 middle deck is disordered over two positions in 3  a ( occupancy 81:19).15 the middle deck in 3  b , however , is localized at one distinct position . as can be seen in table  2 , the pp distances in 3  a are similar to the ones in the nacnac containing compound [ { lv(n(tolyl)2)}2(2:,cyclop3 ) ] ( a),3c displaying a cyclo[p3 ] moiety . in 3  b , they compare better with the ones in [ ( triphos)co(2:,cyclop3)fe(etriphos)](pf6)2 ( g).6b overall , they are in line with pp single bonds [ for comparison : pp single bond in white phosphorus determined by xray diffraction : 2.209(5 )  ,16 electron diffraction : 2.1994(3 )  ,17 raman spectroscopy : 2.2228(5 )  ,18 and dft calculations : 2.1994(3 )  17 ] .
the cop distances in 3  a are between 2.2046(17 ) and 2.3684(8 )   and for 3  b in the range of 2.248(3 ) and 2.277(3 )  . the coco distance in 3  a is 3.7359(5 ) and amounts to 3.724(2 )   in 3  b , which is slightly elongated compared to 2 ( 3.603 and 3.625   , table  1 ) . 
 
comparison of selected atomic distances and angles in the [ ( lco)2(2:,p3 ) ] anion in 3  a ( major component ) and 3  b , [ { lv(n(tolyl)2)}2(2:,cyclop3 ) ] ( a)3c and the dication in [ ( triphos)co(2:,cyclop3)fe(etriphos)](pf6)2 ( g).6b 
  the h  nmr spectra in [ d8]thf display signals between 11.42 and 35.29  ppm for 2 
 9 and 8.15 and 12.85  ppm for 3 , respectively . except for the thf and dme signals ,
respectively , the h  nmr spectra of 3  a ,  b do not deviate from each other .
no signals are detected in the p{h }  nmr spectra for 2 and 3 due to their paramagnetic nature .
their magnetic moment ( eff ) in [ d8]thf solution ( rt ) was determined by the evans method : 3.90  b ( 2 ) and 3.51  b ( 3 ) . in the solid state ,
these values are confirmed by squid measurements displaying a gradual decrease of the magnetic moment in the temperature range from 300 to 2  k of 3.80 to 3.30  b in 2 and 3.58 to 1.70  b in 3  a. therefore , the electronic structure of 2 is best described as containing a [ p4 ] moiety bridging mixed valence co and co centers .
this is in agreement with the previously reported compounds f1 and f2.4b compound 3 , however , contains a [ p3 ] ligand , which is bridged by two co metal centers . as mentioned above , starting from the formal co precursor 1 , we obtained the compounds 2 and 3 as a mixture of products , the ratio of which is sensitively dependent on stoichiometry and reaction conditions . to discover an alternative approach , we targeted the use of the co starting material [ lco(tol ) ] ( 4  a ) , which was speculated to yield the neutral analogues of 2 and 3 .
therefore , the co compound [ lco(tol ) ] ( 4  a ) was reacted with p4 , and [ ( lco)2(2:,p4 ) ] ( 5  a ) was selectively formed .
metric parameters and the characterization of compound 5  a are discussed in detail below .
refluxing 5  a for three hours ( 110  c , toluene ) gives rise to the loss of one phosphorus atom and the formation of [ ( lco)2(2:,p3 ) ] ( 6),19 which was clearly characterized by mass spectrometry20 and h  nmr spectroscopy.21 the dinuclear compound contains two [ lco ] fragments , and the bridging middle deck exhibits a savage disorder within its cyclop3 moiety .
however , the initially localized electron density unambiguously displays triangleshaped cyclop3 constitution and enables an estimation of the pp distances in 6 ( approx .
these values are comparable with the ones found in 3  a ( 2.1674(13 ) , 2.1790(16 ) , 2.3303(17 )   ) and 3  b ( 2.217(4 ) , 2.224(4 ) and 2.237(4 )   ) and are elongated compared to the ones in a ( 2.1658(10 ) , 2.1804(9 ) and 2.2155(9 )  ).3c the coco distance in 6 is 3.747   and therefore comparable to the ones in 3  a ( 3.7359(5 )   ) and 3  b ( 3.724(2 )   ) , but elongated compared to its precursor complex 5  a ( 3.610   , vide infra ) .
the h  nmr spectrum of 6 reveals signals between 20.06 and 12.68  ppm .
the magnetic moment ( eff ) of 6 in c6d6 solution is 2.97  b at room temperature ( evans method).22 this value is confirmed in the solid state by a squid measurement .
a successive decrease from 2.7 to 2.0  b was measured in the temperature range from 300 to 2  k ( see the supporting information ) .
the electrochemical properties of the complexes 5  a and 6 were probed by cyclic voltammetry ( cv ) in thf solution containing bu4npf6 electrolyte ( 0.1  mol  l , 295  k , see supporting information for further details).20 an irreversible oxidation was detected at e 
 1/2=0.34  v for 5  a and e 
 1/2=0.11  v for 6 ( vs. cp2fe / cp2fe ) .
the compounds 5  a and 6 each reveal one reversible reduction at e 
 1/2=1.62  v ( vs. cp2fe / cp2fe ) .
the complexes 2 
 9 and 3 confirm these values by the corresponding electrochemical behavior . for 3 , an additional reduction event was monitored at 2.52  v ( vs. cp2fe / cp2fe ) .
we experimentally performed the reduction of 5  a and 6 , respectively , with one equivalent of potassium graphite in thf at room temperature .
the corresponding anionic compounds [ k(thf)6][(lco)2(2:,p4 ) ] ( 2 ) and [ k(thf)6][(lco)2(2:,p3 ) ] ( 3 ) , respectively , are selectively and quantitatively formed , which was proven by h  nmr spectroscopy of the crude reaction solution . on a preparative scale , the isolated yields obtained as single crystals are 41  % for 2 and 62  % for 3 .
consequently , regarding selectivity , this synthetic route is superior to the comediated p4 activation , which , in contrast , yielded a mixture of products .
three diketimines ( lh , lh , lh ) were synthesized to provide a comparable hybrid ligand set l 
l with backbone ( r = h , me ) and aromatic ( ph*=dmp or dipp ) substituents ( scheme  1 and scheme  2 ) , and to investigate the influence of the ligand design on the comediated p4 transformation . the [ lco(tol ) ] [ l = l ( 4  a ) , l ( 4  b ) , l ( 4  c ) ] starting materials were prepared in onepot reactions ( see the supporting information ) .
all conducted p4 activation reactions were performed under the same conditions ( [ lco(tol)]:p4=2:1 , toluene , 23  h , rt ) and yielded similar isolated products [ ( lco)2(2:,p4 ) ] [ l = l ( 5  a ) , l ( 5  b ) , l ( 5  c ) ] .
the crystals of all the new compounds 5  a  c were grown from saturated toluene solutions , and single crystal xray diffraction was performed .
c are shown in figure  s5 in the supporting information . as a representative , compound 5  a is presented in figure  4  a. its p4 moiety is rectangularly shaped , consequently spanned by two shorter and two longer pp atom distances . together with two coordinating co atoms , the [ p4co2 ] complex core builds a distorted octahedron . in 5 
a  c , the shorter pp atom distances are between 2.1256(6 ) and 2.1301(7 )   and the longer pp distances are between 2.2513(10 ) and 2.2980(7 )   . compared with a phosphorus single bond in the tetrahedral p4 , the planar rectangularshaped p4 moieties in 5 
a  c contain a pair of shorter and a pair of elongated pp bonds .
the coco distances in 5  a  c are between 3.502 and 3.610   and , therefore , any bonding interaction can be ruled out . due to the centrosymmetric molecular structure ( p21/n in 5  a 
c ) , the ligands are parallel to each other . in 5  a  c , the torsion angels  ( between the coco axis and the plane formed by the nitrogen atoms and the methine carbon in the ligand backbone ) are between 3.40(6 ) and 12.32(6). in 5  b ,  c ( and e1 ,  2 
 4b ) , the pp edges of the cyclop4 unit are nearly parallel or rectangular , respectively , compared to the nn axis of coordinating nitrogen atoms ( compare (nnppshort)= 
 1 and (nnpplong)= 
 2 , see figure  4  b ) .
the structural parameters of 5  a  c and e1 ,  2 are summarized in table  3 .
a )  molecular structure of the compound 5  a. hydrogen atoms and aromatic flanking groups are omitted for clarity ; thermal ellipsoids are drawn at 50  % probability level .
the torsion angle  is depicted , which spans between the coco axis and the plane formed by the nitrogen atoms and the methine carbon in the ligand backbone ; b )  view along co1co1 axis , revealing the angles  
 1 and  
 2 , which span between the nn axis of coordinating nitrogen atoms and the edges of the cyclop4 unit .
comparison of pp and coco atomic distances in neutral [ ( lco)2(2:,p4 ) ] [ l = l ( 5  a ) , l ( 5  b ) , l ( 5  c ) , l ( e1 ) , l ( e2 ) ] .
c display signals between 11.99 and 28.61  ppm and reveal their paramagnetic nature in solution . therefore , no signals are detected in their p{h }  nmr spectra .
their magnetic moment ( eff ) in solution ( rt ) was determined by the evans method : 3.02  b ( 5  a 
 22 in c6d6 ) , 2.42  b ( 5  b in c6d6 ) , 1.84  b ( 5  c in [ d8]thf ) . in the solid state , however , the squid measurements of 5  a and 5  b display diamagnetic behavior in the temperature range of 2300  k. their electronic structure in the solid state is best described as two antiferromagnetically coupled co centers bridged by a [ p4 ] ligand similar to the previously reported compounds e1 ,  2.4b in solution , exclusively one signal set for the ligand is observed in the h  nmr spectrum of 5  a  c , respectively , suggesting the integrity of each dinuclear compound in solution on the nmr time scale ( figure  s15 ) .
the electrochemical properties of the complexes 5  a and 6 were probed by cyclic voltammetry ( cv ) in thf solution containing bu4npf6 electrolyte ( 0.1  mol  l , 295  k , see supporting information for further details).20 an irreversible oxidation was detected at e 
 1/2=0.34  v for 5  a and e 
 1/2=0.11  v for 6 ( vs. cp2fe / cp2fe ) . the compounds 5  a and 6 each reveal one reversible reduction at e 
 1/2=1.62  v ( vs. cp2fe / cp2fe ) .
the complexes 2 
 9 and 3 confirm these values by the corresponding electrochemical behavior . for 3 , an additional reduction event was monitored at 2.52  v ( vs. cp2fe / cp2fe ) .
we experimentally performed the reduction of 5  a and 6 , respectively , with one equivalent of potassium graphite in thf at room temperature .
the corresponding anionic compounds [ k(thf)6][(lco)2(2:,p4 ) ] ( 2 ) and [ k(thf)6][(lco)2(2:,p3 ) ] ( 3 ) , respectively , are selectively and quantitatively formed , which was proven by h  nmr spectroscopy of the crude reaction solution . on a preparative scale , the isolated yields obtained as single crystals are 41  % for 2 and 62  % for 3 .
consequently , regarding selectivity , this synthetic route is superior to the comediated p4 activation , which , in contrast , yielded a mixture of products .
three diketimines ( lh , lh , lh ) were synthesized to provide a comparable hybrid ligand set l 
l with backbone ( r = h , me ) and aromatic ( ph*=dmp or dipp ) substituents ( scheme  1 and scheme  2 ) , and to investigate the influence of the ligand design on the comediated p4 transformation .
the [ lco(tol ) ] [ l = l ( 4  a ) , l ( 4  b ) , l ( 4  c ) ] starting materials were prepared in onepot reactions ( see the supporting information ) . all conducted p4 activation reactions were performed under the same conditions ( [ lco(tol)]:p4=2:1 , toluene , 23  h , rt ) and yielded similar isolated products [ ( lco)2(2:,p4 ) ] [ l = l ( 5  a ) , l ( 5  b ) , l ( 5  c ) ] . the crystals of all the new compounds 5  a  c were grown from saturated toluene solutions , and single crystal xray diffraction was performed . the molecular structures of 5  a 
c are shown in figure  s5 in the supporting information . as a representative , compound 5  a is presented in figure  4  a. its p4 moiety is rectangularly shaped , consequently spanned by two shorter and two longer pp atom distances . together with two coordinating co atoms , the [ p4co2 ] complex core builds a distorted octahedron . in 5 
a  c , the shorter pp atom distances are between 2.1256(6 ) and 2.1301(7 )   and the longer pp distances are between 2.2513(10 ) and 2.2980(7 )   . compared with a phosphorus single bond in the tetrahedral p4 , the planar rectangularshaped p4 moieties in 5 
a  c contain a pair of shorter and a pair of elongated pp bonds .
the coco distances in 5  a  c are between 3.502 and 3.610   and , therefore , any bonding interaction can be ruled out . due to the centrosymmetric molecular structure ( p21/n in 5  a 
c ) , the ligands are parallel to each other . in 5  a  c , the torsion angels  ( between the coco axis and the plane formed by the nitrogen atoms and the methine carbon in the ligand backbone ) are between 3.40(6 ) and 12.32(6). in 5  b ,  c ( and e1 ,  2 
 4b ) , the pp edges of the cyclop4 unit are nearly parallel or rectangular , respectively , compared to the nn axis of coordinating nitrogen atoms ( compare (nnppshort)= 
 1 and (nnpplong)= 
 2 , see figure  4  b ) .
the structural parameters of 5  a  c and e1 ,  2 are summarized in table  3 .
a )  molecular structure of the compound 5  a. hydrogen atoms and aromatic flanking groups are omitted for clarity ; thermal ellipsoids are drawn at 50  % probability level .
the torsion angle  is depicted , which spans between the coco axis and the plane formed by the nitrogen atoms and the methine carbon in the ligand backbone ; b )  view along co1co1 axis , revealing the angles  
 1 and  
 2 , which span between the nn axis of coordinating nitrogen atoms and the edges of the cyclop4 unit .
comparison of pp and coco atomic distances in neutral [ ( lco)2(2:,p4 ) ] [ l = l ( 5  a ) , l ( 5  b ) , l ( 5  c ) , l ( e1 ) , l ( e2 ) ] .
the h  nmr spectra of the compounds 5  a  c display signals between 11.99 and 28.61  ppm and reveal their paramagnetic nature in solution .
their magnetic moment ( eff ) in solution ( rt ) was determined by the evans method : 3.02  b ( 5  a 
 22 in c6d6 ) , 2.42  b ( 5  b in c6d6 ) , 1.84  b ( 5  c in [ d8]thf ) . in the solid state , however , the squid measurements of 5  a and 5  b display diamagnetic behavior in the temperature range of 2300  k. their electronic structure in the solid state is best described as two antiferromagnetically coupled co centers bridged by a [ p4 ] ligand similar to the previously reported compounds e1 ,  2.4b in solution , exclusively one signal set for the ligand is observed in the h  nmr spectrum of 5  a  c , respectively , suggesting the integrity of each dinuclear compound in solution on the nmr time scale ( figure  s15 ) .
we reported different [ lco]mediated p4 activations yielding neutral complexes [ ( lco)2(2:,p4 ) ] ( l = l , l , l ) , each containing a similar rectangularshaped [ p4 ] moiety .
in contrast to the p4 activation by lfe compounds , for the co system , the ligand substituents ( l  l ) do not alter the reaction outcome .
for the ligand system l , we demonstrate that one p atom can be extruded thermolytically to generate an unprecedented neutral cyclo[p3]containing compound [ ( lco)2(2:,p3 ) ] . as a novel approach
, we present the p4 transformation with a formal [ lco ] precursor , which generates corresponding monoanions with cyclo[p4 ] and cyclo[p3 ] ligands as a mixture of products .
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technical support issues arising from supporting information ( other than missing files ) should be addressed to the authors .
 abstracta comparison of p4 activations mediated by lowvalent diketiminato ( l ) cobalt complexes is presented . the formal co0 source [ k2(l3co)2(2:1,1n2 ) ] 
 ( 1 ) reacts with p4 to form a mixture of the monoanionic complexes [ k(thf)6][(l3co)2(2:4,4p4 ) ] ( 2 ) and [ k(thf)6][(l3co)2(2:3,3p3 ) ] ( 3 ) . the analogue coi precursor [ l3co(tol ) ] ( 4  a ) , however , selectively yields the corresponding neutral derivative [ ( l3co)2(2:4,4p4 ) ] ( 5  a ) . 
 compound 5  a undergoes thermal p atom loss to form the unprecedented complex [ ( l3co)2(2:3,3p3 ) ] ( 6 ) . 
 the products 2 and 3 can be obtained selectively by an oneelectron reduction of their neutral precursors 5  a and 6 , respectively . 
 the electrochemical behaviour of 2 , 3 , 5  a , and 6 is monitored by cyclic voltammetry and their magnetism is examined by squid measurements and the evans method . 
 the initial coimediated p4 activation is not influenced by applying the structurally different ligands l1 and l2 , which is proven by the formation of the isostructural products [ ( lco)2(2:4,4p4 ) ] [ l = l3 ( 5  a ) , l1 ( 5  b ) , l2 ( 5  c ) ] . 