1,3‐Diphosphacyclobutene Cobalt Complexes

The synthesis and characterization of rare 1,3‐diphosphacyclobutene transition‐metal complexes is described. Reactions of the cobalt‐hydride complex [Co(P 2 C 2 t Bu 2 ) 2 H] ( G ) with n BuLi, t BuLi, or PhLi afforded [Li(solv) x {Co(η 3 ‐P 2 C 2 t Bu 2 HR)(η 4 ‐P 2 C 2 t Bu 2 )}] ( 1 : R= n Bu, (solv) x =(Et 2 O) 2 ; 2 : R= t Bu, (solv) x =(thf) 2 ; 3 : R=Ph, (solv) x =(Et 2 O)(thf) 2 ), with an η 3 ‐coordinated 1,3‐diphosphacyclobutene ligand as a result of organyl‐anion attack at one of the phosphorus atoms of the bis(1,3‐diphosphacyclobutadiene) backbone. In contrast to the reactions with PhLi, the aryl‐magnesium compounds p ‐tolyl magnesium chloride and p ‐fluorophenyl magnesium bromide deprotonate [Co(P 2 C 2 t Bu 2 ) 2 H] to give the magnesium salt [Mg(MeCN) 6 ][Co(η 4 ‐P 2 C 2 t Bu 2 ) 2 ] 2 ( 4 ), which contains a bis(1,3‐diphosphacyclobutadiene)‐cobaltate anion. The [Co(η 4 ‐P 2 C 2 t Bu 2 ) 2 ] − anions are well separated from the octahedral [Mg(MeCN) 6 ] 2+ cation in the molecular structure of 4 . Compound 1 reacts with Me 3 SiCl to give neutral [Co(η 3 ‐P 2 C 2 t Bu 2 H n Bu)(η 4 ‐P 2 C 2 t Bu 2 SiMe 3 )] ( 5 , 52 % yield) with an SiMe 3 group attached to one of the P atoms of the previously unfunctionalized backbone.