Crystallographic studies of the boron–nitrogen bond in aminoboranes. Part IV. Crystal and molecular structure of (diphenylmethyleneamino)dimesitylborane

Abstract

cml, attributed t o the asymmetric stretching frequency of a cumulative BfN=C ~y s t e m . ~ By contrast a B-X=C system would be expected6 to have v(C=N) in the region of 1590-1690 cm-l. Higher stretching frequencies are characteristic of cumulative ri-systems [e.g. v,(C=C=C) a t 1920-2000,7 or v,,(C=N=C) at ca. 1845 cm-l (ref. S)]. Molecule (11) offers the possibility of a high B-N bond-order because the donor and acceptor abilities of the nitrogen and boron atoms are confined to one bond.

The crystal and molecular structure of 4-methyl-2-phenyl-(3H)-1,3,5,2-oxadiazaboroline

“…+0.011 (9) C(lO) +0.001 (lO) C(8) --0.014 (11) C(11) --0.002 (10) The B(1)--N(5) distance [1.41 (1) /~] is close to those found in aminoboranes (Bullen, 1973), in oxazaboroles (Anzenhofer, 1966) and in a cyclic tetraazenoborane (Chang, Porter & Bauer, 1969). The B(1)-O(2) distance closely resembles values found in trigonal borates (Kuribayashi, 1973;Krogh-Moe, 1974;Rettig & Trotter, 1977).…”

Structure of (di-tert-butylmethyleneamino)diphenylborane, C21H28BN

“…1 shows the molecular structure. The structure is similar to that of (mesityl)2BNCPh 2 (Bullen, 1973). In both structures, thermal motion is high for some of the substituent atoms, limiting the overall precision.…”

“…In the case of methyleneaminoboranes, (R2CNBR~)n, associated species are generally found (n = 2 or possibly more), unless the substituents R and R' are sufficiently bulky (Collier, Lappert, Snaith & Wade, 1972). For monomeric species, significant B-N n-bonding should give an allene-like structure with linear B'-N=C, as has been observed for (mesityl)EBNCPh 2 (Bullen, 1973). We report here the structure of Ph2BNCBu 2 (Bu = tertbutyl): Bu groups are particularly effective at preventing molecular association (Collier et al, 1972).…”

“…Compounds in which a methyleneamino (ketimino) group R2C=N-is bonded to a metal or metalloid atom M are of interest because of the question of z~-bonding between the N and M atoms. Such n-bonding, evidenced by high (>1700cm -1) C=N vibrational frequencies, has been conclusively demonstrated by crystal-structure determination for compounds with M=B (Bullen & Wade, 1971;Bullen, 1973), AI (Shearer, Snaith, Sowerby & Wade, 1971), and Be (Hall, Farmer, Shearer, Sowerby & Wade, 1979). In the series M(NCPh2) 4 with M = Si, Ge, or Sn, the degree of n-bonding decreases from 'substantial' (M = Si) to 'absent or very slight' (M = Sn) (Alcock, Pierce-Butler, Willey & Wade, 1975).…”

The crystal and molecular structure of 2,2,6,6-tetrachloro-4,4,8,8-tetraphenylcyclotetraphosphazatetraene, N4P4Cl4(C6H5)4

“…Studies of the structures of a number of tetrameric cyclic phosphazene molecules have shown considerable variation in the molecular geometry, in two respects: (i) variation, over a range of ca. 0.1 A, in the lengths of P-N bonds in the ring (surveyed by Wagner, 1971;Bullen & Tucker, 1972a) or of exocyclic P-CI bonds (Bullen & Dann, 1974); and (ii) differences in ring conformation [see for example Marsh & Trotter (1971a, b), Bullen & Tucker (1972b)]. The factors governing these observed differences are most likely to be found by studying isomeric molecules which differ only in the relative placing of the same exocyclic groups.…”