Reaction of dichlorosilanes with diols in the presence of Et3N in toluene solution gave the monocyclic silanes S[(t-Bu)2C6H2O]2Si(Ph)Me (1), S[(t-Bu)2C6H2O]2SiPh2 (2), S[t-BuMeC6H2O]2Si(Ph)CHCH2 (3), and S[Me2C6H2O]2SiPh2 (4). X-ray structural analysis revealed that the silanes 1−3 exhibited varying degrees of sulfur−silicon donor coordination, giving geometries intermediate between a tetrahedron and a trigonal bipyramid. The eight-membered ring, common to 1−3, which contained the sulfur atom as a bridge between two aryl groups, resided in a syn or boatlike conformation. For the cyclic silane 4 having the same type of ring composition, X-ray analysis showed no sulfur−silicon interaction, and the ring in this case was in an anti or chairlike conformation. Similar to that observed with pentaoxyphosphoranes possessing the same type of sulfur-containing eight-membered ring, sulfur donor ability increased with an increase in alkyl substitution on the ring aryl components (t-Bu > Me). Sulfur coordination in the phosphorus compounds gave geometries along a coordinate from square pyramidal to octahedral. Retention of the solid state structures in solution is indicated by comparison of 29Si NMR data on 1−4 with solution state and solid state 29Si NMR data on related silanes. The ability of the sulfur atom of reduced electronegativity to promote silanes to a higher coordinate state shows that hypervalency is readily accessible for silicon. Silane 1 crystallizes in the monoclinic space group P21/n with a = 10.133(3) Å, b = 20.839(4) Å, c = 16.181(3) Å, β = 99.47(2)°, and Z = 4. Silane 2 crystallizes in the monoclinic space group Cc with a = 10.006(2) Å, b = 42.478(6) Å, c = 17.917(4) Å, β = 99.25(1)°, and Z = 8. Silane 3 crystallizes in the orthorhombic space group Pna21 with a = 20.735(2) Å, b = 12.724(1) Å, c = 10.387(1) Å, and Z = 4. Silane 4 crystallizes in the monoclinic space group P21/c with a = 10.786(2) Å, b = 26.053(7) Å, c = 8.876(1) Å, β = 100.57(1)°, and Z = 4. The final conventional unweighted residuals are 0.059 (1), 0.035 (2), 0.027 (3), and 0.050 (4).

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New nitrogen-containing phosphorus compounds 1 and 3-5 were prepared by the reaction of a nitrogen-containing phenol with PhPCl(2). Hydrolysis of 1 gave an acyclic anionic phosphinate hydrogen bonded to an ammonium component (2). Use of a nitrogen-containing diol with P(OPh)(3) resulted in oxidative addition to give hexacoordinate pentaoxyphosphorus compound 6 exhibiting P-N donor action. X-ray analyses performed on all six phosphorus compounds revealed a variety of geometries extending from three- to six-coordinate with ring sizes varying from five- to ten-membered. The structure of 3 is displaced toward a trigonal bipyramid (TBP) as a result of weak P-N donor action. As a consequence of N-C bond cleavage, 1 forms as a bicyclic phosphorane with the nitrogen atom located at an equatorial site of a TBP. In the formation of the tetracoordinate cyclic phosphinate 5, a P-C bond is formed at the expense of O-C bond cleavage of the reactant diol. (1)H and (31)P NMR spectra indicated that the basic coordination structures were retained in solution. It is concluded that the more elusive donor action found for nitrogen relative to sulfur and oxygen is a consequence of bond cleavage reactions. However, with sufficient phosphorus electrophilicity in higher valent states, P-N donor action is achievable as found in the pentaoxyphosphorane (6) in this study while more modest donor action takes place in the lower coordinate state present in 3.

The new cyclic compound 2,2'-sulfurylbis(4-methyl-6-tert-butylphenyl) methyl 2-benzoate phosphite, O(2)S[(t-Bu)MeC(6)H(4)O](2)(OC(6)H(4)CO(2)Me)P (3), containing a salicylate ligand was synthesized from 2,2'-sulfurylbis(4-methyl-6-tert-butylphenyl) chlorophosphite and methyl salicylate in the presence of triethylamine in ether solution. X-ray analyses of bis(methyl salicylate-O)phenylphosphine, (OC(6)H(4)CO(2)Me)(2)PPh (1), and bis(methylsalicylato-O)phenyl(tetrachlorophenylene-1,2-dioxy)phosphorane, (O(2)C(6)Cl(4))(OC(6)H(4)CO(2)Me)(2)PPh (2), as well as that for 3 were obtained. The phosphane 1 has a pseudo trigonal bipyramidal (TBP) structure due to coordination of a carbonyl oxygen atom at an axial site. The cyclic phosphorane 2 and the phosphite 3 lack any coordination from salicylate ligands. This results in a TBP geometry and a pyramidal geometry respectively for 2 and 3. Comparisons with X-ray structures for carboxylate-containing phosphorus compounds exhibiting oxygen coordination show the formation of four- and five-membered cyclic systems. Thus, 1 appears to be the first example of formation of a six-membered ring via carbonyl oxygen coordination. Reference is made to the tyrosyl-tRNA synthetase system where it is proposed that carbonyl oxygen atom coordination is a likely occurrence in the transition state on the basis of the analysis presented in this work.

Analogous to the formation of CH(2)[(t-Bu)(2)C(6)H(2)O](2)P(Ph)(O(2)C(6)Cl(4)) (1), the new bicyclic tetraoxyphosphoranes CH(2)[(t-Bu)(2)C(6)H(2)O](2)P(Et)(O(2)C(6)Cl(4)) (3) and CH(2)[ClC(6)H(3)O](2)P(Ph)(O(2)C(6)Cl(4)) (4) were synthesized by the oxidative addition of the appropriate cyclic phosphines with o-tetrachlorobenzoquinone. For the formation of CH(2)[(t-Bu)(2)C(6)H(2)O](2)P(Ph)(O(2)C(2)Ph(2)) (2), a similar reaction was followed with the use of benzil (PhCOCOPh) in place of o-tetrachlorobenzoquinone. X-ray analysis of 1-3 revealed trigonal bipyramidal geometries and provided evidence for the first series of complexes in the absence of ring strain in which the least electronegative group, ethyl or phenyl, is located in an axial position, in violation of the electronegativity rule. Thus, the two oxygen-containing ring systems occupied two different sets of positions in the trigonal bipyramid (TBP) with the eight-membered rings at diequatorial sites. X-ray analysis of 4 revealed a trigonal bipyramidal geometry with electron-withdrawing chlorine substituents on each ring assumed the more conventional geometry with the rings occupying axial-equatorial positions and the phenyl group located in the remaining equatorial site. The fact that molecular mechanics calculations favorably reproduced the observed geometries suggests that a steric contribution associated with the ring tert-butyl groups for 1-3 is partly responsible in favoring diequatorial ring occupancy for the eight-membered ring. NMR data supported rigid pentacoordinated structures in solution at 23 degrees C. Phosphorane 1 crystallizes in the orthorhombic space group Fdd2 with a = 44.787(5) Å, b = 34.648(8) Å, c = 10.3709(9) Å, and Z = 16. Phosphorane 2 crystallizes in the orthorhombic space group Pna2(1) with a = 20.658(8) Å, b = 10.342(2) Å, c = 19.879(6) Å, and Z = 4. Phosphorane 3 crystallizes in the orthorhombic space group Pcmn with a = 9.807(2) Å, b = 16.632(4) Å, c = 23.355(3) Å, and Z = 4. Phosphorane 4 crystallizes in the monoclinic space group C2/c with a = 35.699(5) Å, b = 12.187(2) Å, c = 14.284(3) Å, beta = 107.08(1) degrees, and Z = 8. The final conventional unweighted residuals are 0.0395 (1), 0.0518 (2), 0.0540 (3), and 0.0868 (4).