Howard Einspahr

Synthesis and characterization of a series of trans-[Mo(CO)5(R2PNHCH2CH2NCHC6H4-o-O)]2M (R2 Ph2, OCH2CMe2CH2O; M Co, Ni, Cu) complexes and the crystal structure of trans-[Mo(CO)5(Ph2PNHCH2-CH2-NCHC6H4-o-O)]2Ni · 2Et2O

Abstract A series of heterotrinuclear complexes of the type trans -[Mo(CO) 5 (R 2 PNHCH 2 CH 2 Nue5fbCHC 6 H 4 - o -O)] 2 M (R 2 ue5fb Ph 2 , OCH 2 CMe 2 CH 2 O; M ue5fb Co, Ni, Cu) have been synthesized and characterized by multinuclear NMR, IR and VIS-NIR spectroscopy and by measurement of solution magnetic susceptibilities. These studies indicate that the coordination environment of the high spin Co 2+ ion is octahedral while that of the diamagnetic Ni 2+ ion is square planar. Coordination of the Ni 2+ ion to the mononuclear Mo(CO) 5 (R 2 PNHCH 2 CH 2 Nue5fbCHC 6 H 4 - o -OH) complexes causes quite different effects in the spectra of the diphenylphosphino and dioxaphosphorinane complexes. These differences appear to be due to differences in the intramolecular interactions between the P substituents and bis(salicyladiminato)M groups. The molecular structure of trans -[Mo(CO) 5 (R 2 PNHCH 2 CH 2 Nue5fbCHC 6 H 4 - o -O)] 2 Ni · 2Et 2 O has been determined. The complex cystallizes from an HOAc/THF/Et 2 O mixture in the monoclinic space group C 2/ c (crystal data: a 37.71(1), b 9.822(1), c 17.91(1) A; α = γ = 90.00(0)°, β 105.45(6)°; Z = 4). The Ni 2+ ion is coordinated to two salicylaldiminato groups in a non-tetrahedrally distorted square planar geometry while the Mo is coordinated to five COs and a P in a slightly distorted octahedral geometry. An interesting feature of the structure is the nearly planar stacking of a phenyl ring on each P with the bis(salicylaldiminato)Ni group.

Branched-chain halo- and animo-cyclitols: synthesis and an x-ray crystallographic study ☆

Abstract The base-catalyzed cyclizations of tri- O -acetyl-1,7-dibromo-1,7-dideoxy- xylo -2,6-heptodiulose ( 2 ), tri- O -acetyl-1,7-dichloro-1,7-dideoxy- xylo -2,6-heptodiulose ( 3 ), and tri- O -acetyl-1,7-di- C -azido-1,7-dideoxy- xylo -2,6-heptodiulose ( 4 ), to dL -4,5,6-tri- O -acetyl-2- C -bromo-3-C-(bromomethyl)- 2 , 3 , 4 , 6 / 5 -tetrahydroxycyclohexanone ( 5 ), dL -4,5,6-tri- O -acetyl-2-chloro-3- C -(chloromethyl)- 2 , 3 , 4 , 6 / 5 -tetrahydroxycyclohexanone ( 6 ), and dL -4,5,6-tri- O -acetyl-2- C -azido-3- C -(azidomethyl)- 2 , 3 , 4 , 6 / 5 -tetrahydroxycyclohexanone ( 7 ), respectively, are described. Reduction of the acetylated cycloses 5–7 by sodium borohydride proceeded with considerable stereoselectivity in producing branched epi -inositols, isolated as the tetraacetates 12 , 13 , and 18 . These latter compounds were used to prepare the corresponding unprotected cyclitols 24 , 25 , and 31 , and the branched amino- epi -inositols 27 , 29 , 30 , and 32 . The stereochemistry of the branched-chain cyclitols described appears to be the same as that of dL -1,4,5,6-tetra- O -acetyl-3-chloro-2- C -(chloromethyl)- epi -inositol ( 13 ), whose structure was confirmed by an X-ray crystallographic study.