Bis(keto‐phosphane) and Bis(enolato‐phosphane) Ruthenium Complexes − Synthesis and X‐ray Structure Determination of RuCl(NO)[η 2 ‐ (P,O) ‐Ph 2 PCH=C( t Bu)O] 2

A slow reaction consisting of a cleavage of one Ru−Cl bond occurred when a mixture of RuCl 2 [Ph 2 PCH 2 C( t Bu)=O] 2 ( 1 ) and [NH 4 ][PF 6 ] was dissolved in methanol as shown by a subsequent reaction with carbon monoxide affording the stable cationic derivative {RuCl(CO)[Ph 2 PCH 2 C( t Bu)=O] 2 }[PF 6 ] ( 2 ). By contrast, the straightforward reaction of 1 with carbon monoxide yielded RuCl 2 (CO)[Ph 2 PCH 2 C( t Bu)=O][Ph 2 PCH 2 C(=O) t Bu] ( 3 ) which contains unreactive Ru−Cl bonds. The isomerization of 2, which is induced under sun light exposure, is the preliminary step to the selective formation of the all‐cis bis(enolato‐phosphane) derivative (ccc) Ru(CO) 2 [η 2 ‐ (P,O) ‐Ph 2 PCH=C( t Bu)O] 2 ( 9 ). The isomeric bis(enolato‐phosphane) derivative (cct) ‐Ru(CO) 2 [η 2 ‐ (P,O) ‐Ph 2 PCH=C( t Bu)O] 2 ( 10 ), with trans phosphorus and cis carbonyl ligands, respectively, was selectively obtained under mild basic conditions, starting from (cct) ‐RuCl 2 (CO) 2 [Ph 2 PCH 2 C(=O) t Bu] 2 ( 4 ), which results from the reaction of 3 with carbon monoxide under thermal activation. Through an oxidative addition process, the reaction of 1 with [NO][BF 4 ] yielded {RuCl 2 (NO)[Ph 2 PCH 2 C( t Bu)=O][Ph 2 PCH 2 C(=O) t Bu]}[BF 4 ] ( 13 ) with trans phosphorus and trans chloride ligands, respectively. Simple deprotonation of 13 generated the enolato‐phosphane Ru IV complex RuCl 2 (NO)[Ph 2 PCH=C( t Bu)O][Ph 2 PCH 2 C(=O) t Bu] ( 14 ) which retains the same geometry. Under basic conditions, the bis(enolato‐phosphane) derivative RuCl(NO)[η 2 ‐ (P,O) ‐Ph 2 PCH=C( t Bu)O] 2 ( 15 ) was obtained. The formation of 15 surprisingly showed a trans to cis rearrangement of the two phosphorus coordinating atoms, as further confirmed by an X‐ray structure determination.