VINYLIDENE TRANSITION-METAL COMPLEXES .35 . THE SUPPORTING ROLE OF PHOSPHINO ESTER LIGANDS FOR THE SYNTHESIS OF NEUTRAL CARBENE, VINYLIDENEAND ALLENYLIDENE RUTHENIUM(II) COMPLEXES

The reaction of [RuCl2(PPh3)3] (1) with the phosphino esters iPr2P(CH2 )nCO2R (2-4) leads to complete (n = 1; R = CH3, C2H5) or partial (n = 2; R = CH3) displacement of the PPh3 ligands and formation of the octa hedral ruthenium(II) complexes [RuCl2{kappa2(P,O)-iPr2PCH2CO2R}2] (5, 6) and -iPr2PCH2CH2CO2Me}{kappa2(P,O)-iPr2PCH2CH2-CO2Me}] (7). Treatme nt of 5 with LiBr and LiI affords the dibromo- and diiodoruthenium der ivatives 8 and 9. While compound 5 reacts with CO and SO2 by cleavage of one Ru-O bond to yield the 1:1 adducts appa(P)-iPr2PCH2CO2Me}{kappa 2(P,O)-iPr2PCH2CO2Me}] (10, 11), the reaction of the dibromo derivativ e 8 with CO in solution gives the dicarbonyl complex [RuBr2(CO)2{kappa (P)-iPr2PCH2CO2Me}2] (13). If CO is passed over 8 in the solid state, the corresponding monocarbonyl compound 14 is formed. The hydridoruthe nium(II) complex 16, which is obtained from equimolar amounts of [RuHC l(CO)(PiPr3)2] (15) and 2, reacts with HC=CMe by insertion to give the vinyl derivative l{E-CH=CHMe}(CO)(PiPr3){kappa2(P,O)-iPr2CH2CO2Me}] ( 17). Treatment of 5 with HC=CR' (R' = H, Me, tBu, Ph) and of 6, 8, 9 w ith HC=CPh affords upon photochemical activation the octahedral vinyli dene complexes {kappa(P)-iPr2PCH2CO2R}{kappa2(P,O)-iPr2PCH2CO2R}] (18- 21 and 23-25) in good to excellent yield. At room temperature, these c ompounds (with the exception of 25) are highly fluxional in solution. From P-31-NMR measurements, the free energies of activation DELTAG(not -equal) for the intramolecular rearrangement have been determined. Whe reas the reaction of 5 with HC=CCH2CH2OH leads to the carbene complex 30 containing the cyclic oxycarbene: C(CH2)3O as ligand, the functiona lized vinylidene derivatives 31 and 32 are formed on treatment of 5 wi th aryl-substituted alkynols HC=CCRR'OH (R = Ph, R' = Ph, o-Tol). Thes e react in toluene solution at 80-degrees-C by elimination of water to give the allenylidene complexes uCl2(=C=C=CRR'){kappa(P)-iPr2PCH2-CO2 Me}{kappa2(P, O)-iPr2PCH2?? CO2Me}] (33, 34). The X-ray structure anal ysis of 33 reveals a trans disposition of the chloro ligands, the phos phorus atoms as well as of one C=O oxygen and the alpha-C atom of the allenylidene unit. Compound 33 reacts with CO, CNtBu and pyridine to g ive the 1:1 adducts [RuCl2(L)(=C=C=CPh2){kappa(P)-iPr2PCH2CO2Me)2] (35 -37) and with HCl by attack on the central C=C bond to yield the vinyl carbene complex CH=CRR'){kappa(P)-iPr2-PCH2CO2Me}{kappa2(P,O)-iPr2 PCH 2CO2Me}] (38). The preparation of the phosphino ketone iPr2PCH2C(=O)CH 3 (40) and its ruthenium complexes 41 and 42 is briefly described.