Transition‐Metal‐Substituted Acylphosphanes and Phosphaalkenes, 35 Unprecedented Coupling of a Transition‐Metal Carbyne and a Methylene Phosphane Moiety – Structure of [Tp'(CO) 2 W=CP=C(NEt 2 ) 2 ] [Tp = HB (3,5‐Me 2 HC 3 N 2 ) 3 ]

Condensation of [Tp](CO) 2 Mčl] [ 1 : M = Mo; 2 : W; Tp] HB (3,5‐Me 2 HC 2 N 2 ) 3 ] with the inverse phosphaalkenes Me 3 Sip=C(NR 2 ) 2 ( 3a : R = Me; 3b : Et) affords the novel phosphaalkenyl carbyne complexes [Tp](CO) 2 M.C–P=C(NR 2 ) 2 ] ( a, b ) (M = Mo; R = Me, Et) and 5a , b (M = W; R = Me, Et), which have been characterized by IR, 1 H‐, 13 C‐ and 31 P‐NMR spectroscopy. In additon, the molecular structure of 5 has been elucidated by a single‐crystal X‐ray structure determination.