Preparation and Characterization of Cobalt(III)-Dimethyldithiocarbamato Complexes Containing R2P(CH2)nPR2 (R=CH3, C6H5; n=1,2,3,4) and PR3 (R=C2H5, C6H5). Crystal Structure of [Co{(CH3)2NCS2}{(CH3)2PCH2P(CH3)2}2](BF4)2

Twelve new cobalt(III)-phosphine complexes, [Co(dtc)x{(CH3)2P(CH2)nP(CH3)}2}3−x](3−x)+ (x=1, 2; n=1,2,3), [Co(dtc)2{(C6H5)2P(CH2)nP(C6H5)2}]+ (n=1,2,3,4), and trans-[Co(dtc)2(PR3)2]+ (R=C2H5, C6H5) were prepared, where dtc denotes dimethyldithiocarbamate(1–). The molecular structure of [Co(dtc){(CH3)2PCH2P(CH3)2}2](BF4)2 was determined by X-ray analysis. Crystal data are: monoclinic, space group Cc, a=15.927(4), b=11.726(2), c=14.422(7) Å, β=91.38(3)°, V=2692.6(15) Å3, Z=4, R=0.058 for 2251 reflections. The complex ion forms a distorted octahedron with the small P–Co–P (73.1(2) and 75.5(2)°) and S–Co–S (75.97(9)°) chelate angles. The mean Co–P and Co–S distances are 2.238(5) and 2.285(3) Å, respectively. On the basis of the angular overlap model(AOM) treatment, the ligand field bands were assigned and the effect of ring size of diphosphine chelates on these bands were examined. Positive eπ(P) values were necessary to satisfy the observed data, and the result indicates that the Co-dπ orbitals are destabilized by coordination of the phosphine ligand.