Zum Koordinationsverhalten von Alkinylphosphanen R n P(CC–R') 3– n

Coordination Ability of Alkynylphosphines R n P(CC – R') 3 – nAlkynylphosphines RP(CC–R') 2 ( 2 ) react with one equivalent of octacarbonyldicobalt to yield selectively the η 2 ‐μ side‐on‐coordinated alkyne complexes (R)(R' – CC)P[(η 2 ‐CC–R')Co 2 (CO) 6 ] ( 6 ); with another equivalent of Co 2 (CO) 8 the dicoordinated compounds (R)P[(η 2 ‐CC–R')Co 2 (CO) 6 ] 2 ( 7 ) are obtained. 7 may also be synthesized directly by the reaction of 2 with two equivalents of Co 2 (CO) 8 . However, P(CC–Ph) 3 yields with two equivalents of Co 2 (CO) 8 the cyclic Co 2 P 2 C 2 system {(Ph–CC)(R')P[(η 2 ‐CC–Ph)Co 2 (CO) 5 ]} 2 ( 4 ) [R' = (η 2 ‐CC–Ph)Co 2 (CO) 6 ]. Decarbonylation of 6a gives the six‐membered cyclic compound {(Ph)(Ph – C C)P[(η 2 ‐C C – Ph)Co 2 (CO) 5 ]} 2 ( 8 ), while 6b yields the cluster Co 3 (CO) 9 (μ 3 ‐P t Bu) ( 9 ). The structure of ( t Bu)P[(η 2 ‐C C – H)Co 2 )CO) 6 ] 2 ( 7b ) is elucidated by an X‐ray analysis.