Synthesis, structure, and reactions of chiral rhenium vinylidene and acetylide complexes of the formula [(.eta.5-C5H5)Re(NO)(PPh3)(X)]n+. Vinylidene complexes that are formed by stereospecific C.beta. electrophilic attack, exist as two Re=C=C geometric isomers, and undergo stereospecific C.alpha. nucleophilic attack

Abstract

ChemInform Abstract The sequential reactions of the acyl complexes (I) shown in the scheme give crystalline vinylidene complexes as mixture of the geometric isomers (II) and (III). The thermodynamic synclinal isomers (II) are favored at room temperature. In CD2Cl2 these geometric isomers equilibrate. Photolysis gives (50:50) photostationary states. An X-ray structure analysis of the PF6 salt of the synclinal complex cation (IId) (space group C2/c, Z = 8) confirms the naphthyl substituent to be anti to the bulky PPh3 ligand. Reactions of (II)/(III) with base yield the acetylide complexes (IV). These react with TFA at -78 rc C (assayed by NMR) to give 98:2, > 99:1, and > 99:1 mixtures of (IIIb)/(IIb), (IIIc)/(IIc), and (IIId)/(IId). Kinetic and activation parameters for the thermal isomerization of (III) to (II) are determined. Analogous Cβ methylation reactions of (IV) are similarly stereospecific; (IVb) gives (VI). The structure of (IVb) (P1-, Z=2) is established by X-ray analysis. Reactions of (IIb), (IIIb), and its dimethyl analogue (VI) with PMe3 (IX) produce the α-phosphoniovinyl complexes (VII) indicating preferential attack on the Cα face opposite to PPh3.

Protonation of Zwitterionic Manganese and Rhenium Phosphoniostyryl Complexes (η5‐C5H5)(CO)2M––C(+PR3)=C(H)Ph: Experimental and DFT Study

“…Phosphoniostyryl complexes 3 – 7 can exist as conformationally stable E and Z isomers at room temperature, as was experimentally found for the structurally related rhenium complexes (η 5 ‐C 5 H 5 )(NO)(PPh 3 )Re–C( + PMe 3 )=C(H)CH 3 9c. According to our calculations, the most stable is the experimentally observed Z isomer of 5 , which has the phosphane and the phenyl group in a trans disposition to each other (Table 1).…”

“…The values of 3 J H,P coupling constants observed (40–44 Hz) are very close to those ( 3 J H,P( cis ) 40–43 Hz; 3 J H,P( trans ) 68–74 Hz) reported for the structurally similar manganese betaine‐type α‐phosphoniovinyl complexes (η 5 ‐C 5 Me n H 5– n )(CO) 2 Mn – –C( + PR 3 )=CH 2 (R = Me, Et; n = 0, 1, 5) 10a. The same large difference between the coupling constants of the phosphorus atom with the vinylic cis ‐ and trans ‐hydrogen atoms was observed for the related cationic rhenium [(η 5 ‐C 5 H 5 )(NO)(PPh 3 )Re–C( + PMe 3 )=C(H)Me]OTf ( 3 J H,P( cis ) 36 Hz; 3 J H,P( trans ) 61 Hz),9c iron [(η 5 ‐C 5 H 5 )(CO)(PPh 3 )Fe–C( + PR 3 )=CH 2 ]BF 4 (PR 3 = PPh 3 , PPhMe 2 ; 3 J P,H( cis ) 23 Hz, 3 J P,H( trans ) 46–53 Hz),9b and ruthenium [(η 5 ‐C 5 H 5 )(Ph 2 Me) 2 Ru–C( + PPh 2 Me)=CH 2 ]PF 6 ( 3 J P,H( cis ) 39 Hz, 3 J P,H( trans ) 73 Hz) complexes 9e. Importantly, the Z isomer of 5 was calculated to be more stable by 13–14 kJ/mol than the corresponding E isomer (see below).…”

Synthesis and Characterization of a Rhenabenzyne Complex

“…The Re-C1 bond length (1.774(4) ) is in the high end of the observed range for typical ReC bond lengths (1.672-1.802 ), [16,20] and shorter than the lengths found for typical Re = C bonds in rhenium vinylidene complexes (1.925-2.046 ). [16,21] The Re-C5 bond length (2.107 (4) ) is within the range of typical Re-C(vinyl) bond lengths (1.996-2.305 ), [16,18] and in the high end of the reported range for typical Re=CH(carbene) bonds (1.850-2.143 ). [16,17] The structural data indicate that the metallacycle of 7 has a delocalized structure with contributions from resonance structures 7 and 7 a, with 7 being more important.…”

Synthesis and Characterization of Rhenabenzyne Complexes

“…The ReÀC1 bond length (1.774 (4) ) is at the high end of those observed for typical Re C bond lengths (1.672-1.802 ) [21,28,30,31] and shorter than those found for typical Re=C bonds in rhenium vinylidene complexes (1.925-2.046 ). [30,32] The Re À C5 bond length (2.107 (4) ) is within the range of typical Re À CA C H T U N G T R E N N U N G (vinyl) bond lengths (1.996-2.305 ) [30,33] and at the high end of those reported for typical Re=CHRA C H T U N G T R E N N U N G (carbene) bonds (1.850-2.143 ). [30,34] The ring CÀC distances in 8 a are in the range of 1.367-1.457 , which are intermediate between single and double carbon À carbon bonds.…”