Chiral phosphine ligands in asymmetric synthesis. IV. Hydrosilation of ketones, and the structure of (bicyclo[2.2.1]hepta-2,5-diene)[N,N-dimethyl-1(R)-(o-(bis(tert-butyl)phosphino)phenyl)ethylamine]rhodium(I) perchlorate

Abstract

. Can. J. Chem. 64, 1930Chem. 64, (1986. The crystal structure and absolute configuration of (bicyclo[2.2.1]hepta-2,5-diene)[N,N-dimethyl-1(R)-(o-(bis(tertbutyl)phosphino)phenyl)ethylamine]rhodium(I) perchlorate, [Rh(R-dibutphos)(C7H8)]C104, have been determined from threedimensional X-ray data collected by counter methods. The complex crystallizes in the orthorh~~mbic space group P212121 with four formula units in a cell of dimensions a = 15.773(3), b = 18.660(4), and c = 8.990(3) A. Full-matrix least-squares techniques on F, using 2257 reflections with F > 1.5u(F), were used to refine the structure to a final agreement factor of R1 = 0.042. The cation displays a small tetrahedral distortion from :quare planar geometry (if the diene is viewed as a bidentate ligand) with Rh-P and Rh-N distances of 2.398(2) and 2.212(6) A, respectively. The absolute configuration of the aminophosphine ligand was determined to be R by the Bijvoet method. The six-membered chelate ring adopts a 6 twist-boat conformation with the methyl substituent of the chiral C atom axially disposed. Rh complexes of the aminophosphine ligand were shown to catalyze the homogeneous hydrosilation of prochiral ketones, but failed to produce an optical bias in any of systems investigated. (3) A. On a rCsolu la structure par la mCthode des moindres carr6s (matrice entibre sur F) et on l'a affinCe jusqu'a une valeur de R, = 0.042 en se basant sur 2257 rkflexions avec F > 1,5u(F). Le cation existe dans un forme tCtraCdrique 16gbrement dCformCe de la gComCtrie plan carrC (si l'on consjdkre le dikne comme un ligand bidentate) et les distances Rh-P et Rh-N sont respectivement Cgales a 2,398(2) et 2,212(6) A. Utilisant la mCthode de Bijvoet, on a determink que la configuration absolue du ligand aminophosphie est R. Le chClate a six chainons adopte une conformation 6 bateau deform6 dans lequel le substituant mCthyle de I'atome de carbone chiral est disposC dans la position axiale. On a dCmontrC que les complexes de Rh avec I'aminophosphine catalysent I'hydrosilation homogbne des cttones prochirales; toutefois, dans les systbmes CtudiCs, il n'y a pas de formation prCfCrentielle de l'un des isomkres optiques.[Traduit par la revue]

A New Class of Rhodium(I) κ1-Pand κ2-P,NComplexes with Rigid PTN(R) Ligands (PTN = 7-Phospha-3-methyl-1,3,5-triazabicyclo[3.3.1]nonane)

“…During the past decade, ligand design for homogeneous catalysts has advanced from simple bidentate diphosphines and diamines to mixed donor atom moieties, such as phosphino-ethers, phosphino-thioethers, and aminophosphines . These catalytic systems have been applied to hydroformylation, hydrogenation, and hydrosilylation reactions. − Numerous configurations of phosphorus−nitrogen ( P , N ) ligands have been reported and can be generically divided into two categories, namely, those based on structurally rigid sp 2 nitrogen centers, e.g., unsaturated pyridine and imine groups, or sp 3 nitrogen centers, which constitute saturated amine functionalities. , For sp 3 N-based ligands, rigidity is enforced either using a short (e.g., four atom) chain chelate 8 or usually by inserting a phenyl, pyridyl, ferrocenyl, or other functionalities containing π-bonding into the ligand backbone…”

Conformational Preferences Driven by theC-Methyl Substituent in Chelatedo-Diphenylphosphino-α-methyl-N,N-dimethylbenzylamine Rhodium Complexes

“…On the contrary, when the configuration of the carbon stereocenter is S , the P,N-chelate ring presents a twisted-boat conformation with an absolute configuration λ and an axial C -methyl group. This is observed in the Rh complexes with ( S,S )-bis[2-(1- N , N -dimethylaminoethyl)phenyl]phenyl)phosphine or ( S )-[2-(1- N , N -dimethylaminoethyl)phenyl]diphenylarsine, and in the structure of cis -dichloro[(1 S )- N,N -dimethyl-1-{2-[( S )- tert -butylphenylphosphino]phenyl}ethylamine- N,P ]platinum(II) . In conclusion, for R α-carbon stereocenters the six-membered ring adopts the conformation δ, and for S α-carbon stereocenters the conformation will be λ.…”

“…Solid state structures of transition metal complexes (e.g., Rh, Pd, Pt, Ni) with ligands closely related to ours have been reported and confirm that the preferred conformation is related to the configuration of the α-carbon stereocenter. For example, this is observed in Rh complexes with ( R )- N , N -dimethyl-1-phenylethylamine, [(1 R )- N,N -dimethyl{ o -[bis- tert -butylphosphino]phenyl}ethylamine- N,P ], or ( R,S )-α-(2-diphenylphosphinoferrocenyl)ethyldimethylamine, and in the Ni complex [Ni{( R )- o -(C 6 H 11 ) 2 PC 6 H 4 CHCH 3 N(CH 3 ) 2 }(NCS) 2 ] . On the contrary, when the configuration of the carbon stereocenter is S , the P,N-chelate ring presents a twisted-boat conformation with an absolute configuration λ and an axial C -methyl group.…”

Chiral P,N-bidentate ligands in coordination chemistry and organic catalysis involving rhodium and palladium

“…It should be noted that close analogues of (S)-AMPHOS 48 containing a di(tert-butyl)phosphine group in the benzene ring, instead of the diphenylphosphine group, are known, 107 namely, (S)-(70a) and (R)-DIBUTPHOS 70b. According to X-ray diffraction analysis, 107 in the rhodium complex 71, the ligand (R)-DIBUTPHOS 70b forms a metal chelate.…”